JPH0257302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic toner used in electrophotography or electrostatic recording.

<Conventional technology> Conventionally, magnetic toner has a specific resistance that uses electrostatic induction.
They can be roughly divided into conductive ones with a resistance of about 10 ⁶ to ^{10 13} Ω·cm, and insulative ones with a resistivity of 10 ¹³ Ω·cm or more that utilize frictional charging. The former has good developability, but poor transfer results in insufficient image density and poor image clarity. The latter has good transferability, but has a serious problem of poor developability. In other words, conventional insulating magnetic toners have poor triboelectric charging properties between the toners or between the toners and the developing device to obtain stable charging, so they cannot produce sharp images like those of two-component toners. do not have.

As a solution to this problem, an attempt was made to add silica to the surface of the magnetic toner as an auxiliary compound containing a highly chargeable substance, but in this case, even if it had a moderate chargeability initially, continuous copying Electric charge is accumulated due to friction between the developing sleeve and the toner, causing problems such as toner adhesion to the sleeve and decreased fluidity.

In addition, toners with electrical resistance intermediate between conductive toners and insulating toners have been developed, and toners with high developability and good transferability have been proposed, but they suffer from the problem of deterioration of transferability in high-humidity environments. It was something I had.

<Problems to be Solved by the Invention> The present invention improves the developability of insulating magnetic toner, which has been impossible with the prior art. This is intended to suitably control the frictional electrification between the blade and sleeve of the machine. Furthermore, the present invention provides a magnetic toner that ensures the fluidity required of a magnetic toner and also satisfies transferability even in a high-humidity atmosphere.

<Means for Solving the Problems> The present invention has been made in view of the above-mentioned circumstances, and as a result of intensive studies on the composition and manufacturing method of toner for the purpose, the present invention has been made to solve the following problems: A region (A) where the surface of the toner particle is covered with the external additive and a region (A) where the surface is not covered with the external additive or the coating density is low.
Region (B) is significantly lower than that of Region (B), and Region (A) and Region (B) have triboelectric charging properties of opposite polarity to each other, and both regions exist one or several times per toner particle. It has been discovered that a magnetic toner characterized by the following characteristics exhibits excellent effects.

FIGS. 1 and 2 are cross-sectional views schematically showing one example of the structure of the magnetic toner of the present invention. In other words, FIG. 1 shows a region (A) 3 of the surface of a primary pulverized toner 1 containing a positively chargeable charge control agent in which a negatively chargeable external additive is fixed to the carrier iron powder to form a negatively charged region. At the same time, a positively charged region of the primary pulverized toner itself is formed in region (B) 4. On the other hand, FIG. 2 shows that a positively chargeable external additive is fixed to region (A) 3 of the surface of the primary pulverized toner 1 containing a negatively chargeable charge control agent to form a positively charged region, and the region ( B) A negatively charged region is formed in 4. In this case, it is necessary that the region (B) is not coated with the external additive or that the coating density is significantly lower than that of the region (A). The fact that the coating density is significantly lower than that in area (A) means that the triboelectric charging properties in area (B) depend on the surface of the primary crushed toner, and a small amount of external additives are added to the extent that the charging properties are not affected by the external additives. means that it is coated with an agent. Also, area (A)
It is preferable that one toner particle and (B) exist as shown in FIGS. 1 and 2, but depending on the pulverization conditions, several, ie, 2 to 3, may be unevenly distributed.

Such a structure functions as a carrier for the two-component developer and allows suitable charge retention on the toner surface, resulting in good developability and good images.
Furthermore, it was confirmed that as a single particle, the positive and negative charges were canceled and the amount of charge was reduced, so that no adhesion to the sleeve occurred, and furthermore, the transferability was good.

The ratio of area (A)/area (B) is preferably 50/50, but
25/25 depending on the development and transfer system of the copier used
It is necessary to control it within the range of 75 to 75/25. In this case, region (A)/region (B) can be controlled by setting the particle size during the primary pulverization and secondary pulverization described below.

Next, the production of the magnetic toner of the present invention will be described. First, the essential components of magnetic toner, such as magnetic powder, thermoplastic resin, waxes, charge control agents, coloring dyes and pigments, etc., are prepared in a predetermined composition, then hot-melted and kneaded in an extrusion kneader such as an extruder, and after cooling. Primary pulverization and classification are performed to obtain a particle size approximately twice the target particle diameter of the toner of the present invention to produce a primary pulverized toner.
Next, a fine powder external additive having a polarity opposite to that of the toner or the polarity of the charge control agent in the toner is fixed to the surface of the obtained primary pulverized toner.

The external additive can be fixed on the surface of the primary crushed toner by stirring the magnetic core toner and the external additive for about 10 minutes while heating in a stirrer such as a Henschel mixer.

Next, the toner whose entire surface is covered with the external additive is subjected to a pulverizer and subjected to secondary pulverization and classification to obtain the magnetic toner of the present invention having a particle size of 10 to 20 μm. The obtained magnetic toner has a region (A) covered with an external additive through secondary pulverization and classification, and a region (B) in which the inside of the first pulverized toner is exposed as a surface. For the primary and secondary crushing and classification, a regular crushing classifier such as a jet mill is used, and the particle size after each crushing affects the strength of positive and negative chargeability and the ratio of regions (A) and (B). Therefore, it is necessary to control it appropriately.

Next, the materials of the present invention will be described.

The magnetic powder is magnetite fine particles with Fe ₃ O ₄ composition, γ
-All ferromagnetic substances such as Fe ₂ O ₃ are targeted. As the resin, thermoplastic resins such as acrylic, polyester, and epoxy, which are commonly used for toners, are used. As the charge control agent blended into the magnetic core toner, those conventionally used dispersed or melted in the toner can be used. In other words, as a material that controls positive chargeability, for example, nigrosine, carbon number 2, etc.
Azine dye containing ~16 alkyl groups, CI
Basic Violet 1, CIBasic Violet 3, CI
There are basic dyes such as Basic Blue 1 and CIBasic Blue 3, and lake pigments of these basic dyes.
Furthermore, a metal dye such as a monoazo dye is used as a material for controlling the negative chargeability. Further, instead of blending a charge control agent, chargeability may be imparted to the magnetic core toner by using a resin having a positively or negatively chargeable functional group or a magnetic powder whose surface is treated with a charge control agent. on the other hand,
External additives to be fixed on the surface of the primary crushed toner include hydrophobic alumina, positively charged silica, and fine particles of a positively charged charge control agent blended into the primary crushed toner to control positive charging. In addition, as a material for controlling negative chargeability, fine particles of silica, hydrophobic silica, and a negatively chargeable charge control agent blended in the primary pulverized toner are used.

<Examples> The present invention will be described in detail below using Examples and Comparative Examples.

Example 1 Magnetite (EPT-500 manufactured by Toda Kogyo Co., Ltd.)
50 parts by weight Styrene/acrylic resin (Priolite AC manufactured by Guttoyer) 50 parts by weight Nigrosine dye (Oil Black BY manufactured by Orient Chemical Co., Ltd.) 1 part by weight The above components were melt-kneaded, cooled, and crushed.
1.0 parts by weight of hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) is mixed with the toner that has been primarily crushed and classified to 24 μm while heating it to 65°C in a Henschel mixer for about 10 minutes, and then it is mixed on the surface of the primary crushed toner. Fixed hydrophobic silica. This toner was secondarily pulverized to 12 μm to obtain the magnetic toner of the present invention.

The blow-off charge amount of the thus obtained magnetic toner was +8 μc/g. In this case, the blow-off charge amount is calculated by mixing 100 parts by weight of carrier iron powder (TEFV200/300 manufactured by Nippon Tetsuko Co., Ltd.) with 5 parts by weight of toner, and using a blow-off powder charge amount measuring device (manufactured by Toshiba Chemical Co., Ltd.). It was measured in This magnetic toner was applied to a PPC copier equipped with a Se photoreceptor.
After making 1,000 continuous copies, I was able to obtain stable images with a Macbeth image density of 1.41 and a fog of 0.7 (reflection whiteness meter).

Furthermore, this toner can be used at 80% with the above PPC copier.
Continuous copying was performed in a high humidity atmosphere at RH 30°C, and the transferability did not deteriorate at all. In addition, when the same toner was applied to a commercially available PPC copying machine U BIX 1200 that has a negatively charged OPC photoreceptor and 1000 copies were made continuously, the Macbeth image density was 1.28 and the fog was 0.9.
(Reflection whiteness meter) We were always able to obtain stable images.

Example 2 Magnetite (EPT-500 manufactured by Toda Kogyo Co., Ltd.)
50 parts by weight Styrene/acrylic resin (Priolite AC, manufactured by Guttoyer) 50 parts by weight, metal-containing dye (Sabon First Blue HFL, manufactured by BASF) 2 parts by weight The above components were treated in the same manner as in Example 1, and the particle size was
A primary pulverized toner of 18 μm was obtained. Next, 1.0 part by weight of alumina (manufactured by Nippon Aerosil Co., Ltd.) was stirred and mixed with this toner while heating it to 65° C. in a Henschel mixer, and the mixture was fixed on the surface of the toner. Further, this toner was pulverized and classified to 12 μm to obtain a magnetic toner.
The blow-off charge amount of this magnetic toner is -12μc/
It was hot at g.

The obtained magnetic toner of the present invention is used as a negatively chargeable OPC.
When applied to a U BIX 1200 PPC copier equipped with a photoreceptor and continuously copied 1000 sheets, stable images with a Macbeth image density of 1.37 and a fog of 0.5 (reflection whiteness meter) were obtained.

Example 3 Magnetite (EPT-500 manufactured by Toda Kogyo Co., Ltd.)
50 parts by weight Styrene resin (Picolastic D-125 manufactured by Etsu Standard Co., Ltd.) 50 parts by weight Nigrosine dye (Nigrosine EX manufactured by Orient Chemical Co., Ltd.) 2 parts by weight The above components were treated in the same manner as in Example 1 to obtain particle size.
A primary pulverized toner of 30 μm was obtained. Next, add hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) to this toner.
0.8 parts by weight of the toner was stirred and mixed for about 10 minutes while heating to 65° C. in a Henschel mixer to make it adhere to the toner surface. Further, this toner was pulverized and classified to 12 μm to obtain a magnetic toner. The blow-off charge amount of this magnetic toner was +11 μc/g.

The obtained magnetic toner of the present invention is used as a negatively chargeable OPC.
When applied to a PPC copy U BIX 1200 machine equipped with a photoreceptor and continuously copied 1000 sheets, stable images with a Macbeth reflection density of 1.35 and a fog of 0.9 (reflection whiteness meter) were always obtained.

Comparative example magnetite (EPT-500 manufactured by Toda Kogyo Co., Ltd.)
50 parts by weight Styrene/acrylic resin (Priolite AC manufactured by Guttoyer) 50 parts by weight Nigrosine dye (Oil Black BY manufactured by Orient Chemical Co., Ltd.) 1 part by weight The above components were melt-kneaded, cooled, and crushed.
1.0 parts by weight of hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) was stirred and mixed in a Henschel mixer for about 10 minutes while heating to 65° C. to fix the toner on the surface of the toner. The blow-off charge amount of this magnetic toner was +8 μc/g. When the obtained comparative toner was applied to a PPC copying machine with a photoreceptor Se, the initial image density was 1.30 and the fog was 0.5 (reflection whiteness meter), but after copying several hundred copies, the image density became 0.76. This was a practical problem.

<Effects of the Invention> The third example clearly represents the effects of the present invention.
Show the diagram. That is, FIG. 3 shows Example 1 of the present invention.
A bias voltage was applied to electrostatic recording paper using the magnetic toner shown in Figure 1 and a comparison toner made using conventional technology.
This shows the relationship between the applied voltage and the image density when the electrostatic charge image formed by applying a voltage ranging from 300V to -300V is developed, and shows whether the magnetic toner of the present invention can form either a positive or negative electrostatic charge image. It can be seen that it is also a bipolar toner that can be developed satisfactorily.

On the other hand, the comparative toner has low recording density and poor developability for both positive and negative applied voltages.

Judging from the above results, the magnetic toner of the present invention is not only expected to provide high image quality, but also has no toner adhesion to the developer sleeve even after long-term continuous copying, and has good transferability in a high-humidity atmosphere. It has now become possible to achieve both developability and transferability, which have been problems with conventional magnetic toners.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views schematically showing an example of the magnetic toner of the present invention, and FIG. 3 shows the relationship between bias applied voltage and image density showing the effects of the present invention. 1...Primary crushed toner, 2...External additive, 3...
Area (A), 4... Area (B).

Claims (1)

[Claims] 1. In magnetic toner particles made of at least magnetic powder and resin, the surface of the toner particles is coated with an external additive in a region (A) and is not coated with an external additive or the coating density is in a region (A). The region (A) and the region (B) have triboelectric charging properties of opposite polarity to each other, and one or more of both regions exist per toner particle. A magnetic toner featuring: