JPS62294260A - Magnetic color toner - Google Patents

Abstract

PURPOSE:To improve dispersibility and to form a sharp color image by incorporating a binder resin such as polystyrene, and substantially spherical gamma-Fe2O3 into a toner, thereby obtaining the magnetic toner. CONSTITUTION:The spherical gamma-Fe2O3 is obtd. by effective reaction in two stages by an alkaline wet process. More specifically, an alkali is brought into reaction at about 0.80-0.99equiv. with the Fe<2+> of an aq. ferrous salt soln. to prepare the aq. soln. contg. the ferrous hydroxide colloid and while said soln. is heated, oxygen is passed therethrough to form the spherical gamma-Fe2O3 in the 1st stage. The alkali is brought into reaction at about >=1.00equiv. with the Fe<2+> remaining in the aq. ferrous salt soln. and the soln. is subjected to heating and oxidizing to obtain the spherical gamma-Fe2O3 in the 2nd stage. The polystyrene, polyester, etc. are used as the binder resin. The substantially spherical gamma-Fe2O3 and the binder resin are incorporated into the toner to obtain the magnetic toner. Since the spherical gamma-Fe2O3 is used, the surface condition is stabilized and the affinity to the resin, dispersibility and colorability are improved.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention The present invention relates to a magnetic toner used in electrophotography, electrostatic printing, etc., and particularly relates to a magnetic color toner.

As a conventional electrophotographic method, U.S. Patent No. 2,297,691
Specification, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 4
Many methods are known, as described in Japanese Patent No. 3-24748, etc., but in general, a photoconductive substance is used, and if necessary, after the toner image is transferred to a transfer material such as paper, , heat, pressure, etc. to obtain a copy.

Various developing methods for visualizing electrostatic latent images using toner are also known. For example, the magnetic brush method described in US Pat. No. 2,874,063, the cascade development method described in US Pat. No. 2,618,552, and US Pat.
A number of development methods are known, such as the powder cloud method, the fur brush development method, and the liquid development method described in No. 21776. Among these developing methods, in particular, a magnetic brush method using a developer mainly consisting of toner and carrier;
Cascade method, liquid development method, etc. are widely used (in practical use). All of these methods are excellent methods that can obtain good images relatively stably, but on the other hand, they suffer from deterioration of the carrier and the mixing ratio of toner and carrier. A common problem with two-component developers is fluctuation.

In order to avoid such problems, various development methods using a one-component developer consisting only of toner have been proposed.
Among them, the toner particles are made of magnetic toner particles. There are many excellent methods that use a developer.

On the other hand, recently, the purposes of use have become more diverse, and there is a desire for a color copying machine that can produce desired images as needed.

The present inventors have devised the dispersibility of the magnetic material in the toner and the affinity of the magnetic material to the binder resin, and found that in order to obtain magnetic particles with excellent dispersibility and high coloring power, It has been found that particles need to have a spherical shape with low bulk density and low oil absorption.

Fe3O4 particles exhibiting a spherical shape are generated in an aqueous solution near neutrality, and in this case, it is difficult to convert the entire amount of Fe2+ in the ferrous salt aqueous solution to Fe5O4 particles, and unreacted Fe2° The yield is low because it remains, and unreacted Fe2+ causes wastewater pollution, so countermeasures are required. From the total amount of p e2+ in the ferrous salt aqueous solution, Fe
In order to produce 3O4 particles and increase the yield, it is necessary to react an aqueous ferrous salt solution with an alkali equivalent of 1 equivalent or more with respect to the aqueous ferrous salt solution. In this case, since the alkaline reaction aqueous solution is about PHII or higher, the Fe3O4 particles produced are hexahedral or octahedral particles. Even if these Fe3O4 particles are oxidized at high temperature to obtain γ-Fe2O3 magnetic material and used to form a magnetic color toner, it has poor affinity with the resin, so the dispersion of the magnetic material is poor and a long-term side-out durability test is required. If this is done, the magnetic substance content ratio of the toner in the developing machine becomes rich in magnetic substance, resulting in a decrease in image density. Furthermore, the practical electrophotographic properties of the toner, such as developability, fixing properties, cleaning properties,
There is also room to improve environmental dependence, storage stability, etc.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bright sepia magnetic color toner that solves the above-mentioned problems and provides a clear color image with good dispersibility.

A further object of the present invention is to provide a magnetic color toner having excellent durability and stability against environmental changes.

A further object of the present invention is to provide a magnetic color toner that is stable against heat and light and does not fade or change color over a long period of time.

The object of the present invention is to create a magnetic color toner containing γ-Fe2O3 having a substantially spherical shape, which is formed by heat-treating Fe3O4 obtained by a wet method in which an alkali is added in two steps. Our goal is to provide the following.

That is, the step of forming spherical γ-Fe2O3 according to the present invention involves reacting an aqueous ferrous salt solution with an alkali equivalent to 0.80 to 0.9 g of Fe''+ in the aqueous ferrous salt solution. By passing an oxygen-containing gas through the ferrous reaction aqueous solution containing the obtained ferrous hydroxide colloid while heating it in a temperature range of 70°C to 1000°C, the ferrous hydroxide colloid took on a spherical shape. 1.00 for the first stage to generate magnetite particles and the Fe2+ remaining after the first stage reaction.
The second step includes adding an equivalent amount or more of alkali and heating and oxidizing under the same conditions as the first step reaction, and the step of obtaining spheroidized γ-Fe2O3 by further heating and oxidizing treatment.

The alkalis used in the present invention include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates; magnesium hydroxide,
Alkaline earth metal oxides such as calcium oxide; alkaline earth metal hydroxides; alkaline earth metal carbonates; ammonia gas, ammonium hydroxide and ammonium carbonate. Preferred is sodium hydroxide or potassium hydroxide.

The amount of alkali used in the first reaction of the present invention is 0.80 to 0.9 g equivalent to Fe2+ in the ferrous salt aqueous solution. When the amount is less than 0.80 equivalent or more than 0.9 g equivalent, it is difficult to produce Fe304 particles having a spherical shape.

The reaction temperature in the first stage reaction of the present invention is 70'C~1
It is 00℃. If the temperature is 708°C or lower, acicular goethite particles are mixed and the F remains spherical even at 100°C or higher.
Although e3O4 particles are produced, they are not industrially viable.

The oxidation means is carried out by passing an oxygen-containing gas into the liquid.

The amount of alkali used in the second stage reaction of the present invention is 1.00 equivalent or more with respect to the residual Fe"+ in the first stage reaction. 1. If the amount is less than OO equivalent, the entire amount of Fe:+ will not precipitate. A preferable amount is 2, which is 1.00 equivalent or more in consideration of industrial efficiency.

The reaction temperature of the second stage reaction in the present invention may be the same as that of the first stage reaction, and the oxidation means may also be the same.

The conditions for further heating and oxidation treatment to make γ-Fe2O3 are 1.0 at an appropriate temperature range of about 150°C to 500°C.
~1O is oxidized while introducing air for 10 hours to obtain γ-Fe2O3 having a spherical shape.

In a preferred embodiment of the present invention, the magnetic material is bonded to the binder resin 10.
The magnetic color toner contains 20 to 100 parts by weight (more preferably 40 to 80 parts by weight) relative to 0 parts by weight.

The spherical γ- produced through the above-mentioned heat oxidation treatment
Magnetic color toner containing Fe2O3 has a stable surface state of its magnetic material, has a large and constant affinity with resin, has good dispersibility, and has no non-uniformity in magnetic and electrical properties. It is constant, has good durability, and is excellent as a magnetic color toner. Further, the magnetic color toner containing spherical γ-Fe2O3 of the present invention has a particularly bright sepia color tone and is stable against light and heat.

The binder resin used in the toner of the present invention includes styrene and its substituted compounds such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer. Homopolymers and their copolymers: Copolymers of styrene and acrylic esters, such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, and styrene-n-butyl acrylate copolymer. Copolymers of styrene and methacrylic esters, such as styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, and styrene-n-butyl methacrylate copolymer:
Multi-component copolymers of styrene and acrylic esters and methacrylic esters: Other styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-butadiene copolymers, styrene-vinyl methyl ketone copolymers, styrene - Styrenic copolymers of styrene and other vinyl monomers such as acrylonitrile indene copolymers and styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenolic resin, aliphatic or alicyclic hydrocarbon resin,
Petroleum resin, chlorinated paraffin, etc. can be used alone or in combination. Furthermore, as binder resins for toners used in pressure fixing systems, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, higher fatty acids, polyamide resins, and polyester resins are used. etc. can be used alone or in combination.

Additives may be mixed into the toner of the present invention, if necessary. Such additives include lubricants, fixing aids such as low molecular weight polyethylene, flow agents and anti-caking agents such as colloidal silica, and conductivity imparting agents such as metal oxides such as tin oxide. .

In manufacturing this magnetic toner, the constituent materials are kneaded using a thermal kneading machine such as a hot roll, a niegu, or an extruder, and then obtained by mechanical crushing and classification.
Alternatively, a material such as magnetic powder is dispersed in a binder resin solution and then spray-dried. Alternatively, the emulsified suspension is obtained by mixing a specified material with the unit that should constitute the binder resin solution. Various methods can be applied, such as a polymerization method and a toner manufacturing method, in which a magnetic toner is obtained by polymerizing the magnetic toner.

To develop a latent image using the toner of the present invention, a method using a conductive magnetic toner described in U.S. Pat.
A method using an insulating magnetic toner described in JP-A-55-18656, JP-A-53-83630, JP-A-54-
There are known development methods such as the so-called microtoning development method consisting of magnetic toner and non-magnetic toner described in Japanese Patent Application Laid-Open No. 54-42141.
A method using an insulating toner described in Japanese Patent Publication No. 55-18656, that is, an electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic developer on its surface. are arranged with a certain gap between them, the insulating magnetic developer is supported on the developer carrier to a thickness thinner than the gap, and the insulating magnetic developer is applied to the electrostatic image holding layer under the action of a magnetic field. Particularly preferred is a method in which the material is transferred to the body and developed.

The present invention will be specifically explained below using examples. Note that all parts in the following formulations are parts by weight.

Example I An aqueous ferrous sulfate solution containing 1.5 mol/l of 2,64N Na was prepared in advance in a reactor.
OH aqueous solution 2OI! In addition to (0.88 for F e”+
corresponds to equivalent amount. ) A ferrous salt aqueous solution containing Fe(OH)2 was produced at pH 6, 9 and temperature 90°C.

The above ferrous salt aqueous solution containing Fe(OH) 2 was heated to a temperature of 90°C.
100 I/min at °C! 240 minutes to produce a ferrous salt aqueous solution containing magnetite particles.

Next, 3% of the first salt aqueous solution containing the above magnetite particles was added.
．． 78N N a O! (Add aqueous solution 21 (Fe2F
This corresponds to 1.05 equivalents. ) At a pH of 11.8 and a temperature of 90°C, 2O1 air per minute was bubbled through for 60 minutes to produce magnetite particles.

These magnetite particles were oxidized at a temperature of 200° C. for about 3 hours while introducing air to produce spherical γ-Fe2O3.

The obtained γ-Fe2O3 was analyzed using an electron microscope (JEOL JS
M-T300) According to observation, the particles had an obvious spherical shape and were uniform in particle size.

The mixture was sufficiently kneaded in a roll mill at 150° C. for 30 minutes, and then finely pulverized with a jet mill and classified with an air classifier to obtain toner particles having an average size of about 12 μm.

0 parts of hydrophobic colloidal silica powder was added to 100 parts of this powder.
．． 4 parts were mixed to prepare a developer. Using a commercially available dry copying machine (product name NP-7550 manufactured by Canon), developer 2O0
This initial toner and 1 g of the toner after durability were put into a tablet molding machine and pressed for 2000 sheets for 1 minute.
When tablets were made under a pressure of Kg/cm2 and the density was measured, the initial value was approximately 1.50 g/cc, and even after durability it was approximately 1.50 g/cc, showing no change in density and good dispersion of the magnetic material. there were. In addition, the image had a high density and a bright sepia color, and was clear and fog-free.

When this image was run through a fade meter, no fading or discoloration was observed over a long period of time.

Examples 2 to 5 The procedure was the same as in Example 1, except that the type of ferrous salt aqueous solution, the type and concentration of alkali, the amount used in the first stage, the reaction temperature, the heat oxidation treatment conditions, and the binder resin were changed. A magnetic color toner was obtained.

Comparative Example 1 Ferrous sulfate aqueous solution containing Fc”1.5 moA/A 2OA
' was prepared in advance in the reactor with 3,45-N Na
In addition to 2OA of OH aqueous solution (corresponding to 1.15 equivalents to Fe2+), Fe at PH128 temperature 90°C
An aqueous solution containing (OH)2 was produced.

The magnetite produced by blowing air at a rate of 1001/min for 220 minutes at a temperature of 90°C into the aqueous solution containing Fe(OH)2 was oxidized while blowing air at a temperature of 200°C for 3 hours. γ-Fe2O3 was obtained. The shape of this magnetic body is a hexahedron. The same procedure as in Example 1 was carried out except that this magnetic material was used, and the initial toner density was 1.50 g/cc, and the toner density after durability was 1.70 g/cc, and the toner after durability was made of magnetic material. The content ratio changed and became rich in magnetic material. In addition, the image density was good at the initial stage, but after durability testing, the density clearly decreased by 1 degree.

That is, by using the spherical γ-Fe2O3 of the present invention, the surface condition becomes stable, the affinity with the resin increases, and it has excellent dispersibility and coloring power. Furthermore, there is no non-uniformity in the magnetic and electrical properties (constant and durable,
Excellent as a magnetic color toner.

Claims (1)

[Claims] (1) Binder resin and substantially spherical γ-Fe_2O_3
A magnetic color toner characterized by containing.