JPS6361266A - Flash fixing type magnetic toner for developing magnetic latent image - Google Patents

Abstract

PURPOSE:To decrease the staining of a magnetic head and to obtain a high- density image by sticking a PE resin having mol.wt. in a specific range to the surface of toner particles contg. a thermoplastic resin and magnetic powder. CONSTITUTION:This magnetic toner is used for obtaining the final image by developing a magnetic latent image, then transferring the image and subjecting the image to flash fixing. The toner is formed by sticking the PE resin having the mol.wt. ranging 1,500-12,000 to the surface of the toner particles contg. the thermoplastic resin and the magnetic powder. The toner adheres transiently to the magnetic head when the magnetic latent image is developed by using the magnetic toner stuck with the PE resin on the surface, but the PE has the property to solidify and shrink on cooling; therefore, the PE peels easily from the magnetic head and does not longer adhere to the magnetic head. The PE is too soft and the toner is liable to flocculate if the mol.wt. of the PE resin is below 1,500. The PE is hard and is difficult to fix if the mol.wt. exceeds 12,000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic toner for developing a magnetic latent image which is used in a magnetic printing system and is capable of flash fixing.

7 [Prior Art] As one of the image reproduction methods, a magnetic printing method that applies magnetic recording technology has been developed and put into practical use. The magnetic printing method involves the steps of writing information signals onto a magnetic drum, which is a recording medium, using a magnetic head to form a magnetic latent image, and developing the magnetic latent image using a one-component magnetic toner.

The method includes a step of transferring the toner image onto a transfer sheet, a step of fixing the transferred toner image, and a step of cleaning with the magnetic toner remaining on the magnetic drum after the transfer. (Unexamined Japanese Patent Publication No. 54-32328, No. 55-10868
(See No. 1) This magnetic printing method has the advantage that it is not necessary to replace the photoreceptor every tens of thousands of copies as in the electrophotographic method, and maintenance is easy.

The fixing method in the magnetic printing method is the same as in the electrophotographic method, such as a hot roll fixing method, an oven fixing method, a flash fixing method, or a pressure fixing method. Among these, the flash fixing method that uses the emission spectrum of Xe or halogen gas irradiates a heat amount of about 200 to 300 J in a short time of about 100 μsec, so it can heat efficiently with less heat loss from the irradiated object. It has advantages such as no fear of fire and quick start. The magnetic toner used in the flash fixing method uses a thermoplastic resin with a low softening point, such as an epoxy resin, in order to obtain good fixing properties with less energy.

[Problem that the invention seeks to solve]

In the above-mentioned magnetic printing method, a part of the magnetic lines of force generated by energizing the magnetic head leaks into the recording medium from the gap portion of the magnetic head, forming a magnetization pattern (latent image). Therefore, the gap between the magnetic head and the magnetic drum should be as narrow as possible, and is generally 5 μm or less (in practice, 1 μm or less).

However, when using a flash-fixable magnetic toner that is mainly composed of a thermoplastic resin with a low softening point and magnetic powder, as described above,
A phenomenon occurs in which toner adheres to the magnetic head and is fused as it is. When performing magnetic printing, after the transfer, the cleaning blade 1 is pressed against the magnetic drum to remove residual magnetic toner, and then the cleaning blade is separated from the magnetic drum and the magnetic head is scanned to form a latent image. This is due to this.

That is, when the blade separates from the drum, the toner accumulated on the blade spills out.

If you print with toner still attached to the magnetic head in this way, the gap between the magnetic drum and the magnetic head will apparently widen, which weakens the force that attracts the magnetic toner and lowers the image density. Put it away.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a flash fixing type magnetic 1-toner that can reduce the amount of 1-toner attached to a magnetic head and thereby produce images with high density.

[Means for solving problems]

The magnetic toner of the present invention develops a magnetic latent image.

A magnetic toner used in a magnetic printing method that obtains a final image by performing flash fixing after transfer.
It is characterized by being fixed with a polyethylene resin having a molecular weight in the range of 00 to 12,000.

As a result of various studies to prevent staining of the magnetic head in a magnetic printing system, the present inventor found that it is effective to adhere a polyethylene resin to the surface of toner particles containing a fixing resin and magnetic powder.

When a magnetic latent image is developed using magnetic toner with polyethylene resin adhered to its surface, the toner temporarily adheres to the magnetic head, but since polyethylene has the property of shrinking on the cooling surface, it is easily peeled off. , the fusion to the magnetic head is eliminated.

The polyethylene resin that adheres to the surface of the toner particles is 1,
It is necessary to have a molecular weight in the range of 500 to 12,000. If the molecular weight is less than 1,500, the polyethylene is soft and the toner tends to aggregate.
This results in decreased storage stability. When the molecular weight exceeds 12,000.

Since polyethylene is hard, it is difficult to fix 1 to 3 toner.

Such polyethylene is preferably fixed to the surface of the toner particles in an amount of 0.1 to 5 parts by weight per 10 parts by weight of the toner particles. If the amount of adhesion is less than 0.1 part by weight, the effect will be small.

If the amount of adhesion exceeds 5 parts by weight, the fixing performance will decrease.

Further, polyethylene may be added inside the toner particles, thereby further preventing adhesion to the magnetic head.

The amount added is generally 5 parts by weight or less.

Next, the toner particles contain a fixing resin and magnetic powder as essential components.

The fixing resin is a thermoplastic resin with a relatively softening point, such as a bisphenol type epoxy resin, in order to enable fixing with a flash lamp.

Epoxy resins such as styrene-modified epoxy resins and oil-modified epoxy resins, and silicone-added amide waxes can be used. Among these, epoxy resins, particularly bisphenol type epoxy resins, are generally used. Among epoxy resins, those having an epoxy equivalent in the range of 700 to 4,000 are desirable. When the epoxy equivalent is less than 700,
If the resin becomes too soft, the storage stability will be reduced, and if the epoxy equivalent exceeds 4,000, the fixing performance will be reduced.

As the magnetic powder, alloys or compounds containing ferromagnetic elements such as ferrite, magnetite, iron, cobal 1-, nickel, etc. can be used, but in order to incorporate them into the toner, an average particle size of 0.1 Particles of about 3 μm are preferable.

The content of the magnetic powder is suitably 40 to 75% by weight. If it is less than 40% by weight, the magnetic force of the toner will be weakened and the toner will easily separate from the sleeve, resulting in increased fog and poor conveyance. If the weight exceeds 75 weight, fixing performance will decrease.

In addition to the above-mentioned components, the toner particles of the present invention contain a fluidity modifier (
One or more of known additives such as hydrophobic silica), conductive particles (e.g. carbon black), charge control agents (e.g. nigrosine dye, alloy metal azo dye), etc.
It may be added inside and/or on the surface of the particles. The amount added is suitably 10% by weight or less so as not to impair fixing properties.

The magnetic toner of the present invention can be manufactured, for example, as follows.

First, raw materials including fixing resin and magnetic powder are dry mixed, heated, kneaded, cooled and solidified, and then pulverized.

The obtained pulverized powder is heat treated and then classified to obtain toner particles of a predetermined particle size.

Next, by dry mixing the toner particles and granular polyethylene resin, a magnetic toner in which polyethylene resin is adhered to the surface of the toner particles is obtained.

The magnetic toner of the present invention preferably has a volume resistivity of 10 14 Ω·1 or more in order to facilitate transfer to plain paper. This resistance value was determined by weighing a small amount of the sample (several tens of square meters), filling it in a Teflon (trade name) insulating cylinder with an inner diameter of 3.05 am (cross-sectional area = 0.073 all) equipped with an improved dial gauge, and weighing O, 1 kg. Apply a load of D, C
It was measured in an electric field of 4KV/an. For the measurement, an insulation resistance meter (Model 4329A) manufactured by Yokogawa Hewlett-Packard was used.

Further, the magnetic toner of the present invention desirably has a charging voltage within ±25 V in order to reduce fog. This charging voltage (surface potential) is measured by the apparatus shown in FIG. In the same figure, 1 is a non-magnetic sleeve (outer diameter 50I)
IffiIφ), 2 is a permanent magnet member (outer diameter 46m, length 150I, 12m symmetrical magnetization, magnetic flux density on sleeve 1,
000G), 3 is a surface electrometer (Trek 344).

4 is a measuring head. After adjusting the gap g between the sleeve 1 and the probe 4 to 5 m, 3 g of toner is supplied onto the sleeve 1, and the permanent magnet member 2 is set to 1, OOOr,p,
The surface potential of the toner is measured when the toner is rotated for 1 minute at m.

〔Example〕

The details of the present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

40 parts by weight of λ1 bisphenol type epoxy resin (Epicoat 1004K manufactured by Shell Chemical Co., Ltd., epoxy equivalent weight = 950) and 60 parts by weight of magnetite (EPT500 manufactured by Toda Kogyo Co., Ltd.) were dry mixed and kneaded at a temperature of 100° C. in a panburi machine. The mixed material was cooled and solidified, then ground into particles of 20 μm or less using a jet mill, and classified to obtain toner particles with an average particle size of 15 μrn. By adding and mixing particles of medium-density ethylene wax (molecular weight 4,000) to the toner particles, 0.2% of the polyethylene wax is coated on the surface of the toner particles.
The weight part was fixed. jlFi again! In order to adjust image quality, 0.1 part by weight of carbon black (Mitsubishi Kasei 344) was added and mixed at the same time.

The volume resistivity of the obtained magnetic 1 henna is 1x1014Ω
・■, and the charging voltage on the sleeve was -12V.

Example 1 except that the amount of K-dish polyethylene wax added was changed.
Four types of magnetic toners (Nα2 to 5) were produced under the same conditions as above. The amount of polyethylene wax fixed to the Nα2 toner was 0.5 parts by weight.

The Nα3 1-toner was 1 part by weight, the Nα4 toner was 3 parts by weight, and the Nα5 toner was 5 parts by weight.

30 parts by weight of bisphenol type epoxy resin (Shell Chemical Co., Ltd. Epicoat 1007.Epoxy ff1=1920), 68 parts by weight of magnetite (Toda Kogyo ffEPT500), polyethylene wax (molecule ff18,000) 2
Parts by weight were dry mixed and kneaded at a temperature of 100°C in a panburi. After the kneaded material was cooled and solidified, it was heated in a Geno 1-mill.
Grind into particles of 0 μm or less and classify to obtain an average particle size of 15 μm.
toner particles were obtained. By adding particles of low density polyethylene wax (molecule i2,000) to the toner particles and mixing them, a magnetic toner (Nα6) in which 2 parts by weight of polyethylene wax was fixed to the surface of the toner particles was obtained.

Magnetic toner (Nα6) was obtained under the same conditions as in Example 1 except that polyethylene wax was not added to the surface of the toner particles.

Comparative Example 2 Magnetic toner (N
α8) was obtained.

Using each of the above magnetic toners, one continuous test was carried out under the following conditions.
We evaluated 10,000 images.

A magnetic drum (outer diameter 250 Trn) with o-N1r formed on an aluminum alloy drum was set at a circumferential speed of 150 nu/
It was rotated under the conditions of 1.0 sec and an image was written by a magnetic head to form a magnetic latent image. The developing device is equipped with a magnet roll that has a barium ferrite magnet with an outer diameter of 48 mm (magnetized with 4 poles, the magnetic flux density on the sleeve is 60 G for the developing m pole, and 500 G for the others) inside a stainless steel FF sleeve with an outer diameter of 50 m. , developed the magnetic latent image. Here, the doctor gap was set to 0.8 m, the developing gap was set to 0.6 m, and the sleeve was rotated 80 r, p in the same direction as the magnetic drum in the developing section.

The toner image obtained by developing 6 with rotation at J is 6KV.
Corona transfer was carried out on the shuttle paper at a transfer voltage of .

Xe lamp fixing machine (capacitor capacity 1,200μF,
Fixing was performed by irradiating energy of about 250 J with 740 V). Table 1 shows the J value results of the obtained images.

From the Margin Table 1 below, it can be seen that with magnetic toner (Nα1 to 6) in which up to 5 parts by weight of polyethylene wax having a specific molecular weight is fixed to the surface of the toner particles, the magnetic head is not contaminated even after continuous printing of 10,000 sheets. It can be seen that high image density can be obtained with extremely little amount. On the other hand, with the magnetic toner (Nα7) to which polyethylene wax is not added, stains on the magnetic head become noticeable and the image quality per image decreases. Furthermore, in the case of magnetic toner (&8) containing a large amount of polyethylene wax, the fixing performance is lowered.

〔Effect of the invention〕

As described above, one of the magnetic toners of the present invention is as follows.

Polyethylene wax is added to the surface of the 1-ner particles to prevent staining of the magnetic head.

High quality images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a toner surface potential measuring device.

Claims (2)

[Claims] (1) Magnetism for flash fixing type magnetic latent image development characterized by fixing a polyethylene resin having a molecular weight in the range of 1,500 to 12,000 on the surface of toner particles containing a thermoplastic resin and magnetic powder. toner. (2) The flash fixing type magnetic toner for developing magnetic latent images according to claim 1, wherein 0.1 to 5 parts by weight of polyethylene resin per 100 parts by weight of toner particles is fixed to the surface of the toner particles.