JPS63257764A - Magnetic toner - Google Patents

Abstract

PURPOSE:To obtain an image having high quality by additionally fixing the fine powder of a silicone resin on the surface of a toner particle contg. a fixing resin and a magnetic powder. CONSTITUTION:The fine particle of the silicone resin is additionally fixed on the surface of the toner particle contg. the fixing resin and the magnetic powder. The particle size of the silicone resin fine particle is 0.2-3mum, and the additional amount of said particle is 0.1-1.0wt.% based on the titled toner. Thus, even in the case that the titled toner is the magnetic toner contg. an electric charge controller and having the high electric charge property, the fluidity of the toner is high and the occurrence of the blocking phenomenon is prevented, and the image having the high quality and image density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner for visualizing an electrostatic charge image formed on the surface of an image carrier.

In particular, the present invention relates to a magnetic toner containing a fixing resin and magnetic powder.

[Conventional technology]

When developing an electrostatic charge image formed on the surface of an image carrier,
Although the magnetic brush method is generally used.

In this developing method, the developer used in magnetic brush development is often a two-component developer in which a magnetic carrier such as iron powder or ferrite powder is mixed with a non-magnetic toner made of a resin and a colorant.

1. Image quality is determined by toner density. It is complicated to control the toner concentration in the developer so that it is always constant.

On the other hand, a developing method using a single-component magnetic toner mainly composed of resin and magnetic powder is also used, and compared to the two-component developer described above, this method is said to be easier to use because there is no need to troubleshoot toner concentration management. There are advantages.

[Problem that the invention seeks to solve]

A developing method using the above magnetic toner is as follows.

D, C, resistance in an electric field of 100 V/cm is 104
A method using magnetic toner of ~10”Ω・ant (
(Refer to Japanese Patent Publication No. 56-2705) was first put into practical use, but since the magnetic toner is conductive, when applied to the so-called PPC method, which transfers the developed toner image onto plain paper, it is difficult to transfer clearly. There was a drawback that images could not be obtained. In order to eliminate such problems, Japanese Unexamined Patent Publication No. 53-3
A method using an uncharged insulating magnetic toner as described in Japanese Patent No. 1136 has been proposed and put into practical use. Such magnetic toner for PPC has a problem of low fluidity because the magnetic toner has a considerably high electrical resistance. In addition, in the above-mentioned uncharged magnetic toner, it is difficult to stably obtain the charge necessary for developing. Therefore, in recent years, charging properties have been improved by incorporating charge control agents. Charged magnetic toners (for example, see Japanese Patent Application Laid-Open No. 55-48754) have come into widespread use, which tends to cause charged agglomeration development, which further promotes a decline in fluidity and, in extreme cases, There is a problem that the developing work does not proceed smoothly.

An object of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a magnetic toner with significantly improved fluidity.

[Means to solve the problem] One aspect of the present invention is to solve the above problems.

In a magnetic toner made of toner particles containing a fixing resin and magnetic powder, fine silicone resin powder is added and fixed to the surface of the toner particles. This technical method was adopted.

In the present invention, if the average particle diameter of the silicone resin fine powder adhered to the surface of the magnetic toner particles is less than 0.2 .mu.1, it is disadvantageous because no effect of preventing the bonding between the magnetic toner particles can be expected. On the other hand, if the average particle diameter exceeds 3μ, the number of particles adhering to the toner decreases, and the effect of preventing bonding between toner particles decreases, which is undesirable. Although the weight% addition is fixed.

If it is less than 0.1% by weight, the amount fixed on the surface of the magnetic toner particles is small, resulting in insufficient binding or aggregation prevention effect between fn toner particles, while if it exceeds 1.0% by weight, excess free silicone resin particles This is disadvantageous because the powder is present and the fixing performance is deteriorated.

In the present invention, the fixing resin is appropriately selected depending on the fixing method.For example, when the fixing method is a heat roll fixing method using heat and pressure, polystyrene, styrene-acrylic copolymer, styrene-butadiene copolymer, etc. Styrenic resins such as polymers.

Epoxy resins such as bisphenol type epoxy resins and oil-modified epoxy resins, polyester resins, etc. are used. Two or more of these resins may be mixed, but in order not to reduce the fluidity of the toner.

Resins whose glass transition point exceeds 40°C can be effectively used.

In addition to iron oxides such as ferrite and magnetite, alloys or compounds containing ferromagnetic elements such as cobalt and nickel can also be effectively used as the magnetic powder. The magnetic powder preferably has an average particle size of about 0.1 to 3 μm in order to be uniformly dispersed in the toner. The content is 10
It may be within the range of 80% to 80%, and may be determined depending on usage conditions such as the type of photoreceptor and development conditions. The preferred range is 40-75% by weight.

In addition to the above, the present invention may contain known additives used in general dry developers, such as various pigments and dyes such as carbon blank, aniline blue, lamp black, rose bengal, nigrosine dye, and azo dye. Can be done. These contents depend on the toner's electrical properties (resistance,
Although it is determined depending on the amount of charge (charge amount), etc., it is usually set to 10% by weight or less in order not to reduce fixing performance.

The magnetic toner of the present invention is manufactured using the above-mentioned materials, for example, in the following manner. First, resin and magnetic powder are dry mixed, heated and kneaded, and then cooled and solidified. Next, the cooled solidified product is crushed and then classified to a predetermined particle size. Then, fine powder of silicone resin is added and mixed with the toner particles obtained by classification, and the fine powder is fixed on the surface of the toner particles.

The magnetic toner of the present invention preferably has an average particle size of 5 to 30 μm. If there are many particles less than 5 μm, capri will increase, and if there are many particles larger than 30 μm, the image will become rough. A more desirable range is 10 to 20 μm. In addition, the resistance of toner is C, 4, from the point of view of transferability to plain paper.
In an electric field of kV/cm, it is preferably 10'''Ω・cm or more (more preferably 10'5Ω・0111 or more). The absolute value of the triboelectric charge amount of the toner is 5 to 30 μc/g (more preferably 10 to 25 μc/g). The range of g) is preferable. If the amount of charge is too small, the developability will deteriorate, and if it is too large, it will tend to aggregate.

The measurement of resistance and charge amount is based on Japanese Patent Application Laid-Open No. 57-9754.
According to the method described in Public Vehicle No. 5. In other words, measure a small amount of sample (several tens of mg), and use an improved dial gauge with an inner diameter of 3.
．． 05 mm (cross-sectional area = 0.073 cm) filled into a Teflon (trade name) molded rim cylinder.

A load of 0.1 kg was applied, and the resistance of the carrier was measured in an electric field of D and C of 100 V/cm, and the resistance of the toner was measured in an electric field of D and 0.4 kV/cm to calculate the volume resistivity.

For measurement, Yokogawa Hewless Packard insulation resistance meter (4
329A type) was used. The charge amount of the toner was measured using a pro-off triboelectric charge meter (Toshiba Chemical TB-200 model) and a ferrite carrier (Hitachi Metals KBN-100).
Measurement was performed using a toner concentration of 5%.

〔Example〕

Styrene acrylic resin 47 parts by weight (MW=
140,000 MN = 6,680) 50 parts by weight of magnetite (EPT5 manufactured by Toda Kogyo)
00) Charge control agent 3 parts by weight (Bontron E81 manufactured by Orient Chemical Co., Ltd.) The above-mentioned raw materials were dry mixed and heated and kneaded at a temperature of 200° C. using a kneader. After cooling and solidifying the resulting mixture, a jet mill is used to reduce the particle size to 5.
Milled to ~20 μm particles. Next, add this crushed powder to 120
After heat treatment by introducing the magnetic toner into a hot air stream at ℃, it was classified using a zigzag classifier to obtain a magnetic toner having a particle size distribution of 5 to 20 μm.Next, this magnetic toner was mixed with fine silicone resin powder ( Tospar grains (Pk approximately 2 μm) manufactured by Toshiba Silicone were added and adhered and fixed to the surface of the magnetic toner.

The resistance of the toner is 3X10”Ω・Cl11, and the amount of charge is -
It was 12μc/g. For comparison, a sample was prepared in which 0.5 parts by weight of hydrophobic silica (Nippon Aerosil R972) was added instead of the silicone resin fine powder.

Next, developing and fixing conditions will be described. A selenium drum is used as the photosensitive drum, and the charging voltage is +720v.
And the circumferential speed was 150 mm/sec. A sleeve made of 5US304 with a built-in magnet roll (10 pole magnetized 1 surface magnetic flux density 800 G) facing the selenium drum (
The magnet roll and hollow sleeve were rotated in opposite directions at 120 Orpm and 20 Orpm, respectively, and the developing gap was 0.4 mm.
Magnetic brush development was performed with a doctor gap of 0.31. The obtained toner image was transferred to plain paper and heated at 180°C.
Heat roll fixing was performed at 1 kg/cm.

The table shows the results of the above development and fixing. In the table, the silicone resin added in the amount O indicates that 0.5 parts by weight of hydrophobic silica was added.

As is clear from the table, in No. 1, since there is no silicone resin fine powder, the fluidity is low, the second image density is low, and blocking occurs. No. 2
However, the addition of silicone resin fine powder improves the fluidity and increases the image density, which shows a tendency to prevent the blocking phenomenon from occurring. - In method No. 6, the action of the resin in the toner is diluted by the silicone resin, and the drawbacks of the silicone resin appear, and the charging property necessary for the toner is insufficient, resulting in a decrease in image density. - [Effects of the Invention] Since the present invention has the structure and operation as described above, even if it is a highly chargeable magnetic toner containing a charge control agent, it has high fluidity (and prevents the occurrence of blocking phenomenon). At the same time, it is possible to obtain a high quality image with high single image density.

Claims (2)

[Claims] (1) A magnetic toner comprising toner particles containing a fixing resin and magnetic powder, characterized in that fine silicone resin powder is added and fixed to the surface of the toner particles. (2) The particle size of the silicone resin fine powder is 0.2 to 3 μm,
The magnetic toner according to claim 1, wherein the amount added is 0.1 to 1.0% by weight.