JPS5865442A - Developing agent - Google Patents

Abstract

PURPOSE:To obtain a magnetic developing agent having excellent shelf life, fixability and environmental stability by contg. toner particle and gamma-fe2O3 having specific pH and grain size. CONSTITUTION:A developing agent contg. toner particle and gamma-Fe2O3 of <=8.0pH and <=0.1mu grain size. More particularly preferable form is to add gamma-Fe2O3 or <=200 oersted (Oe) coercive force and <=30emu/g residual magnetization at about 0.01-10.0wt% based on the weight of the toner externally onto the surface of a magnetic toner. If the residual magnetization and coercive force of the externally added material are too large in the relation with the magnetic material in the toner, the magnetic force of the toner increases too much and gives adverse influence such as decrease in the density of pictures. If the residual alkali components are contained much in the magnetic material, the rate of moisture absorption of the externally added material in the stage of high humidity increases, thus degrading the electrostatic chargeability of the toner and decreasing the density of pictures. Therefore the preferably pH of the gamma-Fe2O3 is <=8.0.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer that develops an electric latent image in electrophotography, electrostatic printing, etc., and particularly to a developer that improves the durability of toner.

More specifically, the present invention relates to a developer that improves the heat resistance and IA durability of a magnetic toner suitable for a developing method in which a latent image is visualized by flying toner.

Conventionally, as an electrophotographic method, U.S. Patent No. 2,297,69
A number of methods are known, as described in No. 1 Specification, Bulletin of Japanese Patent Publication No. 42-23910, Publication of Japanese Patent Publication No. 24748 of 1982, etc.2, but generally, photoreceptors using photoconductive materials are used. After forming an electrical latent layer on the top of the surface by various means, then developing the latent layer with a toner and transferring the toner image to a transfer material such as paper as necessary, heat, pressure or solvent vapor is applied. It fixes using equal pressure to obtain copies. Various developing methods for visualizing electrical latent bonds using toner are also known, such as U.S. Pat. No. 2,874,063.
Magnetic brush method described in No. 2, 61
The cascade development method described in No. 8,552, the powder-cloud method and fur brush development method described in No. 2,221,776, and the nine patents previously proposed by the applicant. 1987-42141 and JP-A-55-
A large number of developing methods are known, such as the developing method described in No. 18656 and the liquid developing method.

As toners used in these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. Furthermore, it is also known to use modern mold powder to which a third substance is added for the purpose of harvesting.

The developed nine-toner image 11 is transferred and fixed on a transfer support such as paper, if necessary. Methods for fixing toner images include a method in which the toner is heated and melted using a heater or a heated roller, and then fused and solidified on the support, a method in which the binder resin of the toner is softened or dissolved with an organic solvent and then fixed on the support, and a method in which the toner is fixed on the support by applying pressure. A method of fixing toner on a support by using a method is known.

By the way, these pigment, resin, or wax binder-based toners have traditionally been improved in fixability, heat resistance,
There are contradictory factors in improving development durability. For example, in pressure fixing toners, increasing the amount of adhesive substances to improve fixing properties has an adverse effect on the toner's heat resistance (blocking resistance, contamination of the developing sleeve with pillars, etc.), and it is currently difficult to obtain durable toners. It is.

In order to avoid these drawbacks, a method of externally adding fine particles to toner has been proposed, and the main external additives include fine powders such as colloidal silica, carbon black, and tin oxide, and high-grade Examples include fine particles of lubricants such as fatty acids and metal soaps.

However, in the development method in which toner is ejected from a developing sleeve onto an electrostatic latent image to develop it, development is performed using frictional charging between the toner and the sleeve, so the amount of original charge on the toner poses a problem. For example, if a substance with low electrical resistance such as carbon black is used, the triboelectric potential of the toner decreases, resulting in problems such as low image density or no image. Furthermore, low molecular weight organic substances such as lubricants themselves cause sleeve contamination and reduce frictional electrification of the toner and sleeve, and therefore cannot be used as external additives. Colloidal silica is a material that is effective in regulating fluidity and isobaric, has low electrical resistance, and is also effective in terms of frictional charging, but it is a completely third component in the magnetic toner components, and it tends to deteriorate fixing properties. work. or,
The hydrophobized silica fine powder that is commonly used has a low ability to adsorb low molecular weight components of resins, etc., and rounding K, which improves toner storage stability, has to be externally added in large quantities. It is difficult to prevent the heat resistance from deteriorating due to low molecular weight substances in the toner resin without impairing the fixing performance using only colloidal silica.

The present invention provides an electrophotographic developer that overcomes the above-mentioned drawbacks. That is, an object of the present invention is to obtain a magnetic developer with excellent storage stability (heat-resistant blocking properties). A further object of the present invention is to obtain a magnetic developer with excellent printing durability and less sleeve contamination. A further object of the present invention is to obtain a magnetic developer with excellent fixing properties. A further object of the present invention is to obtain a magnetic developer with excellent environmental stability.

Its features include toner particles and a pH of 8. θ
The following describes a developer having γ-re and Os particles having a particle size of 0.1 μm or less.

The preferred form for magnetic fields is a coercive force of 200 oersted (OC).
) or less, γ-Fe with residual magnetization of 30 errs/f or less
, O, on the surface of the magnetic toner at 0.01 relative to the toner weight.
~io, o Weight percent is externally added.

γ-re as an external additive in the present invention, 0. has a large adsorption amount of low melting point substances, and in addition, γ-Fe20B is a magnetic material and is equivalent to magnetic particles contained in toner, so it does not impede fixing performance, and if necessary,
It is also possible to reduce the amount of magnetic material in the toner. Furthermore, it has negative electrical chargeability and has a resistance value of about 10"Ω, so it does not inhibit the charging of toner necessary for development, and it is not an insulator, so it can prevent unevenness at low humidity. There are many features such as γ-re, O,
This becomes noticeable when the particle size is set to 0.1 μ or less, but preferably the smaller the particle size, the better (,0,05
A value of 4 below μ is desirable.

In addition, if the residual magnetization or coercive force of the additive is too large in relation to the magnetic material inside the toner, the magnetic force of the toner will become too large and cause negative effects such as a decrease in image density. 3 Q erma/f or less and coercive force of 200 Qe or less are desirable.

In addition, if there is a large amount of residual alkali in the magnetic material, the amount of moisture absorbed by the external additive will be large when it is humid, and the charging properties of the toner will deteriorate, significantly reducing the image density.
is 8.0 or less (measured by JI8-5101-24)
is desirable, more preferably neutral or acidic 1-Fe with a pH of 7.0 or less, 0. is good.

In addition, as an external additive material, if it is too small, the effect of the present invention cannot be obtained, and if it is too large, it will affect the electrical and magnetic properties of the toner, so it should be 0.01 to 100% of the weight of the toner.
A range of 0% by weight (preferably 0.1 to 5.0% by weight) is preferable.

In addition, r-FetOs#'i as an external additive can be used in all ordinary magnetic toners, and examples of resins used in toner include styrene resin and styrene resin.
Acrylic acid ester copolymer resin, epoxy resin, styrene-butadiene coelectrolyte, styrene-medicrylic acid copolymer, petroleum resin, polyamide resin, silicone resin,
Examples include polyvinyl acetate resin, natural resin, polypropylene wax, polyethylene wax, paraffin wax, petroleum wax, and natural wax.

In addition, the magnetic materials used in the toner particles include iron, cobalt, such as magnetite, hematite, and ferrite.
Examples include alloys and compounds of nickel, manganese, zinc, and other ferromagnetic alloys.

FIG. 1 shows a particularly preferred embodiment in a cross-sectional view of a developing process to which the developer of the present invention can be applied. In the figure, the electrostatic image holder l moves in the direction of the arrow. The non-magnetic cylinder 3, which is a developer carrier, rotates in the developing section so as to move in the same direction as the surface of the image carrier. A multipolar permanent magnet 2 is arranged inside the non-magnetic cylinder 3 so as not to rotate. The one-component insulating magnetic developer 6 sent from the developer container 5 is applied onto the non-magnetic cylindrical surface, and due to the friction between the cylindrical surface and the toner particles, the toner particles are charged with a polarity opposite to the 11E charge. give.

Furthermore, by arranging the iron doctor blade 4 close to the cylindrical surface (with an interval of 50 μm to 500 μm) and facing one magnetic pole (S pole in the figure) of the multipolar permanent magnet 2, the thickness of the toner can be reduced to one layer. Regulate thinly (30μ to 300μ) and uniformly.

By adjusting this cylinder 30 rotation speed k, the current Rin Ai
The surface velocity and preferably the internal velocity of the + layer are made to be substantially equal to or close to the velocity of the electrostatic image holding surface. Iron glue as Doctor Blade 4 k)K
Permanent magnets may be used to form the opposing magnetic poles. Further, an alternating current bias may be applied between the developer carrier and the static support surface in the developing section. This AC bias has f of 200 to 4000Hz and Vpp of 500 to 3000.
It's good to have Vf.

As described above, in this developing step, the non-magnetic cylinder 3 containing the multipolar permanent magnet 2 was used in order to stably hold the one-component magnetic developer carrier on the developer carrier. Further, in order to form a thin and uniform developer layer, a doctor blade 4 made of a magnetic thin plate or a permanent magnet was placed close to the surface of the cylinder 3. When a magnetic doctor blade is used in this way, opposing magnetic poles are formed between the magnetic poles of the permanent magnet contained in the developer carrier, and the toner particle chains are forcibly separated between the doctor blade and the developer carrier. Other parts on the carrier of the current drug,
For example, it is advantageous for controlling the thickness of the developer layer in the developing area facing the electromagnetic surface. Further, by imparting such forced movement to the developer, the developer becomes more uniform than the development agent II#i, and thus a thin and uniform layer of toner, which could not be achieved with a non-magnetic doctor blade, can be achieved. Moreover, since the gap between the doctor blade and the sleeve can be set wide, there is also the effect of preventing the destruction and aggregation of toner particles.

When the toner particles are transferred to the developing area, they are transferred to electrostatic *@ due to the attraction action of the electrostatic image or the action of AC bias.

Hereinafter, the details of the present invention will be specifically explained using Examples, but the scope of the present invention is not limited thereby.

[Example 1] Polystyrene resin as resin; Picolastic D-1
25 (manufactured by Esso Standard Oil Co., Ltd.) 100 parts by weight, magnetic material: BPT-500 (manufactured by Toda Kogyo) 50 parts by weight, negative charge control agent; Bontron E-81 (Orient Chemical Exhibition)
Two parts by weight were heated and kneaded in a two-roll mill, cooled, and coarsely pulverized, further finely pulverized in a jet mill, and then classified in an air classifier to obtain a magnetic toner having a size of 5 to 20 μm. This toner 10
0 parts by weight, particle size 0.05μ or less, pH 7.8, coercive force 9
00e, r-FetOs with residual magnetization 15 emu/fr
(manufactured by Mitsubishi Metals) 0.8 parts by weight was mixed into powder using a Henschel Mikiner, and the above y-Fe and 0.8 parts by weight were applied to the toner surface. was added to prepare a developer.

For comparison, 100 parts by weight of the above toner and 0.8 parts by weight of colloidal silica: R-972 (manufactured by Nippon Aerosil Co., Ltd.) were powder-mixed in a Henschel mixer in the same manner as in Example 1, and externally added. It is set as Example-1. When I used a commercially available copying machine NP-200J with these two types of developers, I was able to produce good results with both of them.

Furthermore, using this developer, we conducted a storage test (50C, 1 day and night), room temperature and low humidity (25℃, 10-15 RH), and high temperature and high temperature (30℃, 85% to 90XRH) environmental tests. I got the result below.

ヮ811 Preservation test Room temperature and low temperature High temperature and high humidity Occasional concentration
Moisture unevenness Image density implementation Nu 1.3 1.3 0 1
．． 0 Comparison Ga 2 1.4 G, 8 to ×
1.1 [Example 2] The ratio of styrene, n-butyl acrylate, castor wax, and ethylene-ethyl acrylate was 30:20:
30:20 copolymer: 0RT-159 (manufactured by Fujikura Kasei) 100 parts by weight, magnetic material; BL-100 (manufactured by Titanium Industries) 50 parts by weight, negative charge control agent; Bontron H-81 (
2 parts by weight of Orient Chemical Exhibition) were made into a toner in the same manner as in Example 1, and 100 parts by weight of this toner was mixed with particle sizes O and OSμ.
Below, residual magnetization 11 emu/fr1 antimagnetic cuff 50
e.

1.0 weight of 1-re, O, (Mitsubishi Metals Department) with a pH of 7.0 was added externally in the same manner as in Example 1 to form a developer.

Similarly! r-Fe with pH 11,t, residual magnetization 9 emu/lr, coercive force 1200 e, particle size 0.05 s or less,
0. (manufactured by Mitsubishi Metals) 1.0 parts by weight was externally added as Comparative Example 2, and a companion was added as Comparative Example 3 with 1.0 parts by weight of colloidal silica R-972t. The following results were obtained using a copying machine NP-120.

Initial density Storage test, room temperature and low humidity Once after high temperature and high humidity Time unevenness Image density Example 2 1.5 1.4 Q
1.1 Comparative Example 2 1.5 1.5
Q 0.7 ratio @泗3 1.6 0.7
△ 1.2

[Brief explanation of the drawing]

FIG. 1X1 is a sectional view showing an embodiment of a development process to which the developer of the present invention can be applied. l... Electrostatic holder, 3... Non-magnetic cylinder, 4...
Doctor blade, 6... Insulating developer. Applicant: Canon Co., Ltd.

Claims (1)

[Claims] developer.