JPS59220745A - Magnetic toner - Google Patents

Abstract

PURPOSE:To obtain a magnetic toner having good triboelectricity by incorporating a fine ferromagnetic powder having specified average particle diameter and specified coercive force and controlling an agglomeration degree of a toner in a specified range. CONSTITUTION:A magnetic toner contains a fine ferromagnetic powder having an average particle diameter of 0.65-0.90mum, and a coercive force of 60-100 Oe (oersted), and an agglomeration degree of the toner is controlled to 5-25%. The fine ferromagnetic powder is added to a binder resin in a ratio of (30-100):100. As a magnetic material, iron ferrite contg. a metal or metallic oxide is especially used.

Description

[Detailed description of the invention] In the Fi electrophotographic method or electrostatic printing method of the present invention,
The present invention relates to magnetic toners used to develop latent electrical or magnetic images.

Conventionally, regarding electrophotography, U.S. Patent No. 229769
No. 1, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 36
As described in Japanese Patent Publication No. 43-24748 (US Pat. No. 4,071,361), the photoconductive layer is uniformly charged and exposed to a light image corresponding to the original. A latent image is formed by eliminating the charge in the exposed area. Development is carried out by depositing a finely powdered electrostatic substance, so-called toner, on the obtained electrostatic latent image. The toner is attracted to the electrostatic latent image depending on the amount of charge on the photoconductive layer, forming a toner image with shading. This toner image is transferred to a support surface such as paper or cloth as necessary, and permanently fixed on the support surface by heating, pressure, or the like. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed to the photoconductor layer. In addition to the fixing method described above, it is also possible to use other means such as solvent treatment and overcoating treatment.

There are many known developing methods for this electrophotography.
Until now, development methods such as the cascade development method described in US Pat. No. 2,618,552 and the magnetic brush method described in US Pat. No. 2,874,063, which are development methods in which toner is mixed with a carrier and used as a two-component toner, have been widely used.

However, in recent years, a developing method using a one-component magnetic toner that does not use a carrier has come into use. This magnetic toner development method does not require toner concentration detection and control mechanisms compared to the two-component toner described above.

The developing device can be easily downsized. It has many advantages, such as less edge effect and good reproduction of dark areas.

Currently, ferromagnetic fine powders for magnetic toner include iron, nickel, cobalt, manganese, etc. alone, magnetite (Fe2O2), γ-hematite (γ-Fe2J), etc.
, ferrite, and other alloys such as permanent alloys that exhibit ferromagnetism have been proposed.

However, single metals and alloys such as TL tend to become physically unstable during the process of pulverization for use as toner, and even have the risk of explosion during the process.

Magnetite and ferrite have almost satisfactory magnetic properties and electrical properties, and have been put into practical use.

However, even if such ferromagnetic fine powder is used, there are problems with the triboelectric charging properties as a magnetic toner and the transportability within a developing device.

In general, magnetic toner is charged by contact and friction with a cylindrical developing sleeve in which a permanent magnet rod is inserted, and the electrostatic force required during development is obtained. However, in this case as well, the important issue is how to stably and uniformly highly charge the magnetic doves that do not have carriers. uneven,
Toner having only a weak charging ability causes so-called fog, which is toner adhesion to areas other than the electrostatic latent image, during development, and weak toner adhesion to the transfer material due to the low Coulomb force of the toner during transfer. This weak toner adhesion to the transfer material is caused by an air gap, which is a minute gap created between the fixing roll, the transfer material, and the transferred toner on the fixing roll, when the transfer material enters the fixing roll, causing the copy image to appear on the copy image. This causes tailing.

In particular, the above-mentioned tailing phenomenon is remarkable under high temperature and high humidity conditions, where the volume resistivity decreases and the triboelectric charging ability decreases at the same time.

The coercive force and average particle size of the magnetic material, which is the main component of magnetic toner, have a significant influence on the physical properties and electrophotographic properties of the toner.

The coercive force of a magnetic material is one index indicating the ability of the magnetic material, in other words, the magnetic toner containing it, as a permanent magnet. The higher this coercive force is, the more strongly the magnetic toner is fixed on the above-mentioned developing tube, thereby impairing the conveyance property and lowering the charging ability. On the other hand, if the coercive force is too low, the toner will not be smoothly held and transported on the current sleeve, causing toner to fall from the developing device or toner to scatter.

Another factor that contributes to the transportability of the magnetic toner is the fluidity of the magnetic toner itself, in addition to the above-mentioned characteristics of the magnetic material. As this liquidity increases, 1. ) The movement of the toner within the developing device is preferable, as it makes it easier to charge, but on the other hand, if the toner has good fluidity, the magnetic toner moves easily during the transfer process, which tends to cause disturbances in the transferred image.

As the average particle size of the magnetic material becomes finer, the amount of magnetic material dispersed inside the produced magnetic toner or exposed on the toner surface increases, the volume resistivity and surface resistance tend to decrease, and the charging ability decreases. This worsens and becomes a cause of fogging and trailing.

In addition, if the average particle size becomes coarse, the magnetic material alone will be mixed into the magnetic toner during the toner manufacturing process, which will easily cause white streaks on the image and a decrease in density during P1 durability. Become.

In conventional technology, the physical properties and particle size of magnetic materials have been investigated individually, but after various studies on the characteristics of magnetic materials and magnetic toner, the present inventors have investigated the individual coercivity and particle size of magnetic materials. It is not possible to obtain a magnetic toner with sufficiently high performance by specifying only the diameter, but only by comprehensively specifying the coercive force, particle size, and fluidity of the toner containing a magnetic material with these characteristics. It was discovered that a magnetic toner with good conductivity and transportability could be obtained, and the present invention was completed.

The present invention provides a magnetic toner with good performance, which is different from conventional magnetic toners.

The objective is to provide a magnetic toner having extremely good triboelectric charging properties.

Another object of the present invention is to provide a magnetic toner that has favorable transportability within a developing device.

Another object of the present invention is to provide a magnetic toner with significantly improved image quality in terms of trailing and fogging.

Another object is to provide a magnetic toner with good durability.

The object of the present invention is that the average particle size and coercive force are no and 65, respectively.
This can be achieved by a magnetic toner containing ferromagnetic fine powder in the range of ~0.90μ, 60-1000e (Oersted), and the coagulation year of the magnetic toner is 5-25 inches. .

In the present invention, the values in each range are values set by combining the matrix as described in detail in the examples, and if the average particle size is less than 0.65μ, trailing and fogging will occur under high temperature and high humidity. However, if it exceeds 0.90μ, white streaks are likely to appear during durability. Further, as for the magnetic properties of the magnetic material, the optimum range is a coercive force of 60 to 1000 e, and even if it exceeds this range or is less than that, problems tend to occur in transportability.

The ferromagnetic fine powder used in the present invention includes ferromagnetic elements and alloys containing these, iron, cobalt, nickel, such as magnetite, hematite, and ferrite, which are compounds.
There are alloys and compounds such as manganese.

In particular, as a magnetic substance suitable for the present invention, a ferromagnetic hepterarite containing one or more of the following metals or metal oxides as components in iron ferrite is preferable. Its quantitative ratio is 0.001 to 20 in terms of the contained metal or metal oxide as a single metal to the total iron in the ferrite.
% is preferred. Particularly good is 0.01 to 15%.

Examples of metals and metal oxides that can be contained in iron ferrite include Mn, FIB, 00% Ni, Cu,
Zn.

? s There are other metals represented by the element symbols Li and Ba as well as Ca.

The magnetic substance contained in the magnetic toner can be contained in an amount of 30 to 100 parts, preferably 40 to 90 parts, and most preferably 50 to 85 parts, based on 100 parts of the binder resin. Further, the fluidity of the magnetic toner is desirably 5 to 25%, preferably 5.5 to 15.0% in terms of the degree of cohesion.

As the binder resin used in the present invention, all known binder resins can be used, such as polystyrene,
- Monopolymers of styrene and its substituted products such as chlorostyrene and polyvinyltoluene; styrene-P-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene co-M Copolymer% styrene-vinylnaphthalene copolymer , styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer,
Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic m copolymer, styrene-maleic acid ester copolymer Styrenic copolymers such as polymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyamide, polyacrylic resin, Rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum fat, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination.

Furthermore, the magnetic toner used in the present invention may contain various dyes and pigments such as carbon black, colloidal silica, etc. for the purpose of toning, improving fluidity, controlling charge, and the like.

A vibrating sample magnetometer (manufactured by Toei Kogyo) was used to measure the coercive force of the magnetic material. Approximately a1 to 1f of the magnetic material to be tested was weighed, an external magnetic field of 10 KOe was applied, and the coercive force was measured by recording the magnetic hysteresis on a recorder.

The measurement method is to first apply an external magnetic field of 10 KOe,
Gradually reduce the size and at the same time start recording on the recorder.

When the external magnetic field reaches QOe, a reverse magnetic field is gradually applied at 10 KOet. Regarding the coercive force, directly read the X-axis value of the hysteresis loop recorded on the recorder.

In addition, before all measurements, adjust the output with the nickel standard (standard sample arm).

Further, the average particle diameter in the present invention was measured by the Fisher method based on the air permeation method.

The fluidity of the magnetic toner was represented by the degree of aggregation.

The degree of aggregation of the magnetic toner was measured using a powder tester (manufactured by Hoiyo Micron). 2F of the toner to be tested was passed through a 71C sieve with 60, 100, and 200 meshes, and then the degree of aggregation was determined by applying the residue from each sieve to the formula below.

Cohesion degree (%) = A + B 10 The present invention will be explained in more detail with reference to Examples below.

Example 1 Comparative Examples 1 to 6 100 parts of polyethylene resin 60 parts of magnetic material 3 parts of charge control agent
A 30μ magnetic toner was obtained. Next, colloidal silica was mixed and added to the magnetic toner using a Henschel mixer, and the addition amount, mixing speed, and time were varied to obtain a magnetic toner having a desired degree of aggregation.

Magnetic l-toner was produced by the above method in which the three factors of coercive force of the magnetic material, particle size, and fluidity of the magnetic toner containing the magnetic material were changed, and the image quality under high temperature and high humidity, A comparison of durability performance is shown in the table.

Example 2 Binder resin f x f v :y″″7″υ″″7″υ″
A magnetic toner was produced in the same manner as in Example 1 except for the resin, and NP
-201 copying machine (manufactured by Canon) under high temperature and high humidity, clear and fog-free images were obtained.

Example 3 The magnetic material has a coercive force and an average particle size of 92.10e and 0.68μ
A magnetic toner with an agglomeration degree of 6.4 was obtained by manufacturing the toner in the same manner as in Example 2, and was used for continuous durability, but even after 10,000 copies, the toner transportability in the current machine was still poor. The image quality was as good as the initial one.

Example 4 An image was produced using the magnetic toner whose agglomeration degree was adjusted to 198% in Example 1 under high temperature and high humidity conditions (35° C., 85% RH), but there was no trailing.
It was even.

Patent applicant: Canon Co., Ltd. Representative Patent Attorney Kari No Yu 305-

Claims (2)

[Claims] (1) Average particle size and coercive force are each 0.65 to 0.90
μ, contains ferromagnetic fine powder in the range of 60 to 1 (IQOe (Oersted)), and the degree of agglomeration of the magnetic toner is 5 to 25.
Magnetic toner characterized by being 0% (2) 30 to 10 parts of ferromagnetic fine powder per 100 parts of binder M resin
0 parts of the magnetic toner according to claim 1.