JPS63301965A - Preparation of magnetic carrier - Google Patents

Abstract

PURPOSE:To prevent deterioration in fluidity and electric chargeability by adding the charge regulating agent and a binder resin to a magnetic powder, melting and kneading the mixture, pulverizing and classifying it, and irradiating the obtained carrier by flash light to form it into spheres. CONSTITUTION:The carrier is formed by adding the charge regulating agent and a binder resin to a magnetic powder, melting and kneading the mixture, pulverizing and classifying it, and irradiating the obtained carrier by flash light in a state of suspended in the air to form it into spheres. The nearly spherical carrier having a small average particle diameter is formed by kneading the fine magnetic powder into the binder resin containing the charge regulating agent, then pulverizing the mixture, irradiating the obtained fine carrier powder suspended in the air with flash light to heat and melt the surface part of the carrier, and nearly sphering it by using the surface tension of the melt, thus permitting the resin coating to be executed without deteriorating fluidity and chargeability, and fluidity to be increased without deteriorating chargeability.

Description

[Detailed Description of the Invention] [Summary] As a method for obtaining a small particle size magnetic carrier with excellent fluidity and chargeability, a charge control agent and a binder resin are added to magnetic powder, melt-kneaded, and then pulverized. A manufacturing method in which the classified carrier is irradiated with flash light to make it into spheres.

[Industrial application field]

The present invention relates to a method for producing a magnetic carrier used in electrophotography,
In particular, the present invention relates to a method for producing a small particle size magnetic carrier with excellent fluidity and chargeability.

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

Now, let's talk about the printing process of an electrophotographic printer. After the surface of a photocon drum coated with a thin film of photoconductive insulator is uniformly charged by corona discharge, etc., it is charged in response to an electrical signal. ON.

An electrostatic latent image is created by irradiating the optical W electric insulator with the turned-off light, and toner is transferred to this electrostatic latent image to form a visible image.

In step 5, the toner is made up of colored fine particles with a particle size of approximately 10 μm in which a colorant is dispersed in a synthetic resin, and is electrostatically attracted to a magnetic carrier (hereinafter simply referred to as carrier) forming a magnetic brush. When the carrier that forms the magnetic brush brushes the photocon drum, only the toner separates from the carrier due to electrostatic attraction and adheres to the electrostatic latent image on the photocon drum. By doing so, development and visualization is performed.

Next, the thus generated toner image is transferred to paper and then fixed by heating and fusing to obtain a printed matter.

TECHNICAL FIELD The present invention relates to improvements in carriers used in power-based electrophotography techniques.

[Conventional technology]

The constituent material of the carrier is Rib/Fe) 403 (Here, H
is a divalent metal ion such as Mn, Fe, Co, Ni, Cu, Zn, Mg, etc.)
, Fe, and other magnetically sensitive metal oxides and metal materials were used, and initially powders with an average particle size of about 100 μm or those coated with resin to prevent toner filming were used.

The toner used is one in which a colorant is dispersed in a binder resin made of natural or synthetic resin, and then pulverized to have an average particle size of about 10 μm.

These two-component developers have excellent transfer and fixing properties because only the toner is developed, but on the other hand, in order to obtain good images, the toner density tolerance range, which is the mixing ratio of carrier and toner, is very limited. The problem was that it was too small.

Therefore, in order to obtain good images, it is necessary to appropriately replenish the consumed toner and always maintain a constant toner density.To do this, toner density control that accurately detects and controls the toner density is necessary. This method requires a mechanism and a toner replenishment mechanism, which has the disadvantage of being complicated and expensive.

As a method of alleviating such problems and widening the allowable range of toner concentration, the average particle diameter of the carrier is reduced to about 20 to 30 μm to increase the surface area per unit volume.

However, Fe powder, which is used to control electrical resistance and chargeability,
Ferrite powder, magnetite powder (iron ferrite, Pez
Because it is difficult to coat carriers such as Os ) with resin, sufficient effects have not been achieved.

As an alternative to this, there is a pulverization method in which the carrier and resin are kneaded and then pulverized, but this has the problem of reduced fluidity due to the carrier having many corners, as well as deterioration of chargeability and high cost. There is a problem that it becomes.

[Problem that the invention seeks to solve]

As mentioned above, in order to widen the toner concentration range, the average particle diameter of the carrier is reduced.
The problem is that it causes a decrease in fluidity and deterioration in chargeability.

c) Means for solving the problem] The above problem is solved by adding a charge control agent and a binder resin to magnetic powder, melting and kneading the mixture, pulverizing and classifying the mixture to create a carrier, and then adding this carrier to a gas. This problem can be solved by a method for producing magnetic carriers in which the carriers are suspended in a state of being irradiated with flash light to make the carriers spherical in shape.

[Effect]

The present invention provides a method for coating small particle carriers with resin without causing a decrease in fluidity or deterioration of chargeability by kneading fine magnetic powder into a binder resin containing a charge control agent and then pulverizing the powder. After forming carriers with a small average particle size, the floating carriers are irradiated with flash light and heated to melt the surface portion, and the surface tension at that time is used to form a nearly spherical shape.

By adopting such a method, fluidity can be increased without deteriorating charging properties.

〔Example〕

Example: The names and composition ratios of magnetic powder, binder resin, and charge control agent are as follows.

Magnetic powder: (Average particle size 2 μm, magnetization at IKOe 93
emu/g manufactured by Kanto Denka)...50 parts by weight Binder resin: (Product name P 67 modified by Kao)...47 parts by weight Charge control agent: (Product name Black Pear manufactured by Cab Black)
Is 2000 ) -3 parts by weight were melted, kneaded, crushed, and classified to produce a carrier having an average particle size of 20 μm.

This carrier was made into a sphere using an apparatus as shown in FIG.

That is, the first container 2 is filled with the carrier 1 that has been crushed and classified using a wind classifier, and compressed air of 8 atmospheres is blown through the ventilation hole 3 provided at the bottom of the glass, which is then heated by a flash lamp 5. By blowing up the inside of the tube 4, it was heated and made into a spherical shape.

The spherical carrier 1 is carried by the air flow and stored in the second container 6.

Note that a filter 7 was provided at the exhaust part of the second container 6 to prevent it from escaping to the outside.

Next, the names and composition ratios of the constituent components of the toner used in the examples are as follows.

Polyester resin (NE2150 manufactured by Kao)...9
5 parts by weight Ab-based dye (Bontron 5-34, manufactured by Orient Chemical Co., Ltd.) ... 2 parts by weight Carbon blank (former name: ack Pearls L, manufactured by Gear Black) ... 3 parts by weight were melted and kneaded, then crushed and classified. A toner having an average particle size of 12 μm was prepared.

The thus prepared carrier and toner were mixed and stirred in a ball mill to prepare a two-component developer.

The obtained developer exhibited very excellent chargeability with a toner specific charge of -10 to -15 μC/g at a toner concentration in the range of 5 to 55% by weight.

In addition, as a result of a printing test using a commercially available copying machine with a heat roll fixing method, it was possible to obtain good images with less fogging and carrier adhesion in the image background at toner concentrations in the range of 5 to 55 stars%, and the toner concentration was acceptable. I was able to make it very wide.

However, when the toner concentration was 5% by weight or less, the image density decreased, and when the toner concentration was 55% by weight or more, toner scattering increased.

Next, the initial toner concentration was set to 35% by weight, and 20,000 sheets were printed while replenishing 4 g of toner every time 100 sheets were printed, and images equivalent to the initial image could be obtained.

Comparative Example: A two-component developer was prepared in the same manner as in the example except that 4-Yaria was not spheroidized by mixing the carrier with the same toner as in the example.

The obtained developer has a toner specific charge of -10 to -15 μC/g in a toner concentration range of 5 to 50% by weight, and the dependence of the toner specific charge on the toner concentration is stronger compared to the examples, and it also depends on the individual carrier. It was found that the allowable range of toner concentration was narrower than in Examples due to variations in chargeability.

Further, when a developer with a toner concentration of 35% by weight was prepared and a printing test was conducted, a lot of fogging and carrier adhesion were observed.

Next, in order to evaluate the fluidity of the carrier, the carrier 1 was placed in the hopper 8 shown in FIG.

As a result of measuring the amount of fall per revolution of a sponge roller with a length of 200 mm, the amount of fall of a conventional carrier without spherical formation was 2.1 g, while the amount of fall of a carrier with spherical formation was 2.1 g. The weight was 7.8 g, demonstrating an improvement in fluidity.

〔Effect of the invention〕

The carrier produced by applying the present invention has excellent fluidity and has a very wide toner concentration tolerance range, so it does not require a toner concentration control mechanism, which improves workability and simplifies the equipment. can do.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a carrier spheroidization device, and FIG. 2 is a sectional view showing the configuration of a hopper. In the figure, 1 is the carrier, 5 is the flash lamp, and 8 is the carrier.
is a hopper, and 9 is a sponge roller. −＋Ha I+J4-272〉1-nilo

Claims (1)

[Claims] After adding a charge control agent and a binder resin to magnetic powder and melting and kneading the mixture, the mixture is pulverized and classified to make a carrier.
A method for producing a magnetic carrier, which comprises irradiating the carrier with flash light while suspended in a gas to make the carrier spherical in shape.