JPH01108553A - Production of toner for electrophotography - Google Patents

Abstract

PURPOSE:To suppress an increase in production cost by electrostatically sticking magnetic powder having the average grain size smaller than the average grain size of a nonmagnetic toner on the surface of said toner, then thermally melting the surface of the toner to stick the magnetic powder to the surface of the toner. CONSTITUTION:The toner for electrophotography formed by electrostatically sticking the magnetic toner having the average grain size smaller than the average grain size of the nonmagnetic toner to the surface of the toner, then thermally melting the surface of the toner to fix the magnetic powder to the surface of the toner is used. Any magnetic materials are usable as the magnetic powder and may be the fine powder of magnetic metals such as iron (Fe) and nickel (Ni), metal oxides such as ferrite (gamma-Fe2O3) and magnetite (Fe3O4) and magnetic alloys; above all, the iron, ferrite and magnetite are more adequate. Magnetism is thereby imparted only to the surface of the toner. Since the magnetic powder of the amt. slighter than general magnetic toners needs be used, the permissible latitude of the toner concn. is widened with a slight increase in production cost.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to provide a toner that can reduce toner scattering even when the amount of charge of the toner is low with respect to toner used in electrophotography, etc. After electrostatically adhering magnetic powder having an average particle size smaller than the average particle size of the toner, the surface of the toner is thermally melted to fix the magnetic powder to the surface of the toner, thereby producing an electrophotographic toner.

[Industrial application field]

The present invention relates to a method for producing an electrophotographic toner with an expanded allowable toner concentration range.

Electrophotographic technology is widely used in copying machines, but is also actively used in information devices such as printers and facsimile machines.

The printing process of an electrophotographic printer is to uniformly charge the surface of a photocon drum coated with a photoconductive insulator by corona discharge, etc., and then transfer the optical image to a photoconductive insulator by various means. It irradiates the body to create an electrostatic latent image, and toner is attached to this latent image to create a visible image.

In this process, the toner is a colored fine particle made by dispersing a colorant in a synthetic resin, and is supplied to a magnetic roll together with magnetic powder called a carrier, and the carrier is magnetically attracted to form a magnetic brush and rotate once. The carrier and toner rub against each other and are charged to opposite polarities, creating a magnetic developer.

Next, the ear of the magnetic brush rubs the surface of the photocondrum on which the electrostatic latent image is located, so that only the toner is separated and adhered by electric attraction, and the electrostatic latent image is developed.

The toner image created in this way is electrostatically transferred onto the recording paper by applying an electric field from the back side of the recording paper in the transfer section, and then heat and pressure are applied to the toner image in the fixing unit to transfer the toner image onto the recording paper. The record is completed by fusing it to the

Next, a magnetic developer consisting of two components, a carrier and a toner, is made of iron (Fe) with an average particle size of about 100 μm as a carrier.
powder, ferrite (γ-FezOa) powder, magnetite (
Magnetic powder such as Fe+04) powder or magnetic powder coated with resin is used.

Furthermore, as a toner, a non-magnetic insulating powder is commonly used, which is made by dispersing a coloring agent in a binder resin made of natural or synthetic resin and pulverizing the mixture to an average particle size of about 10 μm.

[Conventional technology]

As mentioned above, when development is performed using a two-component developer consisting of carrier and toner, transfer and fixing properties are excellent.
The allowable range of toner concentration, which indicates the mixing ratio of carrier and toner, is very narrow.

That is, when the toner concentration is high, the amount of charge generated by friction with the carrier becomes low, so that the toner easily separates from the carrier, causing toner scattering within the device and fogging on the printed background area.

On the other hand, when the toner concentration is low, the amount of charge of the toner becomes high and the print density becomes low.

Therefore, while the device is in use, it is necessary to appropriately replenish the consumed toner and always maintain a constant toner concentration.

This requires a highly accurate toner replenishment mechanism and toner concentration control mechanism, which poses a problem in that the device becomes expensive.

Therefore, the method of expanding the allowable range of toner density is to
This has been done for both toner and toner.

That is, the particle size of the carrier is reduced, or a resin carrier having a small particle size in which magnetic powder is dispersed in an insulating resin is used.

However, when using magnetic powder with a small particle size, it becomes difficult to sufficiently coat the resin, which results in insufficient effects in controlling electrical resistance and chargeability, and when using a resin carrier, the magnetic force There is a problem in that the magnetic brush is easily separated from the magnet roll that constitutes the magnetic brush because the magnetic brush becomes weak.

Regarding toner, magnetic toner in which magnetic powder is dispersed in the toner has been put to practical use, but there is a problem in that the cost is high because a large amount of magnetic powder is used.

[Problem that the invention seeks to solve]

As described above, it is necessary to expand the allowable range of toner concentration, and measures are being taken from both the toner and carrier perspectives, but the challenge is to achieve this without significantly increasing the manufacturing cost of toner.

[Means for solving problems]

The above problem is solved by electrostatically adhering magnetic powder with an average particle size smaller than the average particle size of the toner to the surface of a non-magnetic toner, then thermally melting the surface of the toner, and fixing the magnetic powder to the surface of the toner. This problem can be solved by using electrophotographic toner made by

[Effect]

The present invention is an improvement over conventional magnetic toners.

In other words, conventional magnetic toner is made by dispersing magnetic powder in resin spheres with a diameter of about 10 μm that contain pigments, and because it itself contains magnetic material,
Even if the toner charge amount is low at high toner concentration,
Since the toner is magnetically attracted to the magnetic roll, scattering from the developing device can be reduced.

However, the amount of magnetic powder used in the toner is 20 to 50%.
The high content (about % by weight) leads to high costs.

As a countermeasure to this problem, the present invention electrostatically adheres magnetic powder to the surface of non-magnetic toner, and then heat-fuses only the surface of the toner to fix the magnetic powder. A method is used in which magnetic toner and magnetic powder are mixed and stirred at high speed.

Next, an impact force is applied to cause the non-magnetic toner with magnetic powder attached thereto to collide with the plate at high speed, and the impact energy causes the toner surface to be thermally melted, thereby fixing the magnetic powder to the toner surface.

The magnetic powder may be any magnetic material, including magnetic metals such as iron (Fe) and nickel (Ni).

Ferrite (T-FezO+) + magnetite (pes
Fine powder of metal oxides or magnetic alloys such as o4) may be used, but
Among them, iron, ferrite, magnetite, etc. are suitable.

〔Example〕

Example 1: The composition of the non-magnetic toner was as follows: Styrene-acrylic resin (Himer SMB 600 Sanyo Chemical Industries)...95 parts by weight Azo dye (Bontron 5-37. Orient Chemical)...2 parts by weight carbon black ( Black Pearl l, Capo Soto)... After melting and kneading 3 parts by weight, it was crushed and classified, and the average particle size was 1.
A 2 μm insulating toner was made.

Next, magnetite having an average particle size of 0.1 μm was used as the magnetic powder, and 20 parts by weight of magnetite and 100 parts by weight of the non-magnetic toner were mixed in a Henschel mixer (FM-10
B type, mixed using Mitsui Miike Engineering),
It was electrostatically attached by rotating at a rotational speed of 150 rpm.

Next, this was put into a centrifugal rotary mixer (Mechano Mill 10, Kaida Seiko) and rotated at 2000 rpm to cause collision, thereby fixing the magnetite magnetic powder to the surface of the toner.

Next, the thus produced magnetic toner and resin-coated ferrite carrier (average particle size: 60 μm) were mixed and stirred using a ball mill to prepare a magnetic developer.

This magnetic developer exhibited chargeability with a toner specific charge of -5 to -15 μC/g at a toner concentration of 5 to 30% by weight.

Furthermore, as a result of a printing test using a commercially available copying machine using a heat roll fixing method, the toner specific charge was -5μ at a toner concentration of 30% by weight.
No toner scattering or fogging was observed even at C/g.
Good images were obtained at toner concentrations in the range of 5 to 30% by weight, and the allowable range of toner concentrations could be made very wide.

Next, set the initial toner concentration to 30% by weight and replenish 4g of toner for every 100 sheets of printing.
Although 0 sheets of printing were performed, the image was able to be maintained at the same level as the initial image.

Example 2: A magnetic toner was prepared in exactly the same manner as in Example 1 except that ferrite with an average particle size of 0.5 μm was used as the magnetic powder, and a magnetic developer was prepared by mixing and stirring with the same carrier as in Example 1. did.

The charging property of the magnetic developer was almost the same as that of the magnetic developer of Example 1.

Furthermore, when printing was evaluated in the same manner as in Example 1,
When the toner concentration was in the range of 5 to 30% by weight, good images with little fogging in the image background and little carrier adhesion were obtained.

Furthermore, the toner transferability and fixability were good.

Comparative Example I: A magnetic carrier was prepared in exactly the same manner as in Example 1, except that magnetic powder was not fixed on the toner surface, and mixed and stirred with the same carrier as in Example 1 to prepare a magnetic developer.

This developer had a toner specific charge of -5 to -15 μC/g at a toner concentration of 5 to 30% by weight, and the dependence of the toner specific charge on the toner concentration was the same as in Example 1.

Next, printing evaluation was performed in the same manner as in Example 1.
When the toner concentration was 30% by weight and the toner specific charge was -5 μC/g, significant toner scattering and fogging were observed.

〔Effect of the invention〕

According to the present invention, it is possible to impart magnetism only to the surface of the toner, and since it is sufficient to use a smaller amount of magnetic powder than a general magnetic toner, the allowable range of toner concentration can be expanded with a slight increase in manufacturing cost. .

Claims (1)

[Claims] After electrostatically adhering magnetic powder having an average particle size smaller than the average particle size of the toner to the surface of a non-magnetic toner, the surface of the toner is thermally melted to fix the magnetic powder to the surface of the toner. A method for producing an electrophotographic toner characterized by: