JPS6026351A - Magnetic toner - Google Patents

Abstract

PURPOSE:To obtain a sharp red or sepia color without changing developing characteristics in any cases of low and high humidities by incorporating gamma-Fe2O3 as an essential component, and setting the product of its specific surface area and a content of magnetic powder per 100g of a binder resin to a specified value. CONSTITUTION:A magnetic toner contains gamma-Fe2O3 as an essential component, and the product of its BET specific surface area Sm<2>/g measured by the N2 adsorption method and a content of magnetic powder Wg per 100g of a binder resin satisfies the following equation: 450>=S.W>=50. The use of such gamma-Fe2O3 as the essential component of the magnetic powder raises electric resistance of the toner and can prevent deterioration of image quality of a copy against fluctuation of the environment. The regulation of the S.W value within such a range can prevent image unevenness especially even low temps. and low humidities, deterioration of image density even under high temps. and high humidities, and can improve fixation of an image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner used in electrophotography, electrostatic printing, magnetic recording, and the like.

The electrophotographic method uses the properties of photoconductors such as cadmium sulfide, polyvinyl carbazole, selenium, and zinc oxide to form a latent image. is applied, image exposure is performed to form a static t!i mark,
Then, the electrostatic latent image is developed with toner powder charged with a polarity opposite to that of the electrostatic latent image, and if necessary, the image is transferred to a transfer sheet and fixed.

The electronic printing method, as proposed in Japanese Patent Publication No. Sho 42-14342, is a method of guiding and fixing a charged powder toner onto a recording material using an electric field for printing.

The electrostatic recording method is a method in which charges are applied to a dielectric layer in the form of an image, and charged toner powder is attached and fixed thereon. Similarly, the magnetic printing method is a method in which a magnetic latent image is formed on a recording material. In this method, the image is formed, developed with toner powder containing a magnetic material, transferred to a transfer material, and fixed.

Various developing methods are known for visualizing such electrical or magnetic 1Ill# images using toner.
Broadly speaking, there are dry development methods and wet development methods.

The former method is further divided into a method using a two-component developer using carrier particles and a method using a single-component developer that does not use any carrier particles.

Among the two-component developing methods, depending on the type of carrier for transporting the toner, a magnetic brush method using an iron powder carrier, a cascade method using a bead carrier, etc. have been widely put into practical use.

Furthermore, various developing methods using a one-component developer consisting only of toner have been proposed, and among them, many excellent methods using magnetic toner have been put into practical use. Development methods using magnetic component developers include the MagneDry method using conductive toner, the method using dielectric polarization of toner particles disclosed in JP-A No. 52-94140, and the method using dielectric polarization of toner particles disclosed in JP-A-52-94140;
31136, a method of charge transfer by toner disturbance, and developing methods recently proposed by the present applicant, such as those disclosed in Japanese Patent Laid-Open No. 54-42141 and Japanese Patent Laid-Open No. 55-18656. Conventional magnetic toners use black magnetite or ferrite, and if necessary, add carbon black.However, these magnetic toners In many cases, since the electrical resistance of the magnetic material is low, development characteristics tend to deteriorate when the copying environment becomes high humidity.

Therefore, an object of the present invention is to provide a magnetic toner whose developing characteristics hardly deteriorate even under low humidity and high humidity environments. Another object of the present invention is to provide a magnetic toner of red color [7] or sepia color.

That is, the present invention provides a magnetic toner containing at least magnetic powder and a binder resin, in which the magnetic powder is γ-Fe2O.
3 as the main component and produced by its nitrogen adsorption method.
ET specific surface area (Sm2/, 9) and the binder resin 100I in the toner! -M(W) of the magnetic powder contained in
The present invention provides a magnetic toner characterized in that g) has the following relationship.

450≧S-W≧50 preferably 400≧S-W≧10
0 In the present invention, γ-F0205 is the main component (50%
It is believed that by using magnetic powder containing 80% or more of the magnetic powder, the electrical resistance of the toner increases and the quality of copies does not deteriorate against environmental changes.

However, magnetic powder containing γ-Fe 203 as its main component has a lower saturation magnetization than black magnetite, so it is less likely to be restrained by a magnetic field, and has a high electrical resistance, which makes it difficult to use as a toner, especially in a low-humidity environment. If too much charge is accumulated, it becomes difficult to be restrained by the magnetic field, and when this is used, images may become uneven. The present invention solves this problem, and has S and W in the range of 450≧S−W≧50.
It is to control. If the S-W is less than 50, unevenness will occur in the image, especially under low temperature and low humidity;
If it exceeds 100%, the image density will decrease under high temperature and high humidity conditions, and it will be difficult to fix the image.

In the present invention, each of S and W is also 1,
It is preferable that 5≦S≦20.15≦W≦100.

The magnetic powder containing γ-Fe 203 as a main component used in the present invention preferably contains γ-Fe2O3 in an amount of 50% by weight or more, preferably 80 cents or more, and has a particle size of about 0.05 to 5μ. preferable. Further, the surface may be treated with various treatment agents.

The electrical resistance of the toner of the present invention is 1012r) crn or more (
Molding at 100 kg/cm2 pressure, applied voltage 100 V/
ctn'#L Coining It is desirable that the value is determined from the current value after the coining process has elapsed.

In addition, as the binder resin used in the present invention, 1. Homopolymers of styrene and its substituted products, such as J5 listyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, styrene-vinyltoluene co-X polymer, and copolymers thereof; styrene-acrylic Copolymers of styrene and acrylic esters such as acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer; styrene-methyl methacrylate copolymer, styrene-methacrylic acid Copolymers of styrene and methacrylic esters such as ethyl copolymers and styrene-n-butyl methacrylate copolymers; multi-component copolymers of styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, Styrene-vinyl methyl ether co-ft combination.

Styrenic copolymers of styrene and other vinyl monomers, such as styrene-butadiene copolymers, styrene-vinylmethylketone copolymers, styrene-acrylonitrile-indene copolymers, and styrene-maleic acid ester copolymers; Limethyl methacrylate, polybutyl methacrylate, poly61 vinyl 1 yJ? Polyester 1 polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin 1 petroleum resin, chlorinated/elastic rough-in, and turmeric can be used alone or in combination.

Furthermore, low molecular weight polyethylene, low molecular weight polynolopyrene, and ethylene-vinyl acetate copolymer are used as binder resins for toners used in pressure fixing systems.

Ethylene-acrylic ester copolymer, paraffin,
Higher fatty acids, polyamide resins, polyester resins, etc. can be used alone or in combination.

Additives may be mixed into the toner of the present invention as required. Such additives include dyes and pigments, lubricants, fixing aids such as low molecular weight polyethylene, lubricants such as metal salts of higher fatty acids and fluororesin powder, and abrasives such as C.
eO2, and metal oxides such as tin oxide as conductivity imparting agents.

In manufacturing this magnetic toner, a hot roll is used.

After thoroughly kneading the constituent materials using a thermal kneader such as a Ni-Goo or an extruder, the material can be obtained by mechanical crushing and classification, or by dispersing materials such as magnetic powder in a binder resin solution and then spray drying. or after mixing the specified material with the monomer that should constitute the binder resin,
Each method can be applied, such as a polymerization toner production method in which a magnetic toner is obtained by polymerizing this emulsified suspension.

Further, the toner of the present invention may have a particle size of 1 to 500, if necessary.
It is used mixed with carrier particles of about μ size.

Developing a latent image using the toner of the present invention is described in Japanese Unexamined Patent Publication No. 5
4-42141, method using insulating magnetic toner described in 55-18656, JP-A-53-83
There are developing methods using magnetic toner and non-magnetic toner as described in JP-A-54-42141 and JP-A-54-24632, and other methods using high-resistance magnetic toner. 55-18656, in which an electrostatic image holder that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic developer on its surface are separated by a certain gap. The insulating magnetic developer is supported on the developer carrier with a thickness as thin as the gap, and the insulating magnetic developer is transferred to the electrostatic image carrier under the action of a magnetic field. Particularly preferred is a method in which the film is allowed to develop.

Example 1 100 parts by weight of styrene notyl methacrylate-dimethylaminoethyl methacrylate copolymer (70:25:5), 4 parts by weight of polypropylene, and 7 parts by weight of magnetic powder composed of γ-Fe2O3 (BET specific surface area: 5 m2,151). Mix and melt-knead using a roll mill. After cooling, it is coarsely ground using a hammer mill and then finely ground using a Schett grinder. Next, 5-20μ fluorescent fine particles 1 were classified using a wind classifier.
00 parts by weight and 0.31 parts by weight of fine silicic acid powder were mixed to prepare a toner. Apply this toner to a commercially available copier (product name: P
C-20 (manufactured by Canon), and images were produced. Even under high temperature and high humidity conditions (30° C., 90% RH), clear, fog-free sepia-colored images were obtained. Also, low temperature and low humidity (15℃ 10
%RH), the image was good with no unevenness.

The electrical resistance of the toner was 10 Ωα.

Examples 2 to 5 In place of the magnetic powder of Example 1, the BET specific surface area and the amount added were (7yy+”/fl, 60 double spots), respectively.
, (3,5m2/,!/.

80 parts by weight), (15m2/f1.25 parts by weight),
(4m2#.

The same procedure as in Example 1 was conducted except that magnetic powder containing 7'-Fe2O3 (30 parts by weight) as a main component was used, and good results were obtained. The electrical resistance of this toner is 1014Ω, 11015ΩCm, respectively.
*1015 Ω, 10 r) tyn, 10 Ωan.

Example 6 Sterene-butyl methacrylate-butyl maleic acid copolymer (70:25:5) 1007 ft- parts polynolopylene 3 parts by weight, magnetic powder mainly composed of γ-Fe205 (IIET specific surface area 5 m2/g) 20 weight A toner is prepared from 7 parts by weight of Pigment Red 81, red pigment C1, and 7 parts by weight. Next, 80 parts by weight of this toner was mixed with 20 parts by weight of magnetic powder having a particle size of about 2 to 3 microns as a carrier to prepare a developer. Apply this developer to a commercially available copying machine (
It was applied to the product (trade name: N1)-30OR, manufactured by Canon). A clear red image was obtained, and the results were good.

Comparative Example 1.2 In place of the magnetic powder of Example 1, BET specific surface area and addition amount were (5 m''79, 100 parts by weight), (3,
sm” 7g.

Example 1 was carried out in almost the same manner as in Example 1, except that a magnetic powder containing γ-Fs205, which is In the latter case, the image was uneven.

The SIW and SW of the above Example toner and Comparative Example toner are shown in the following table.

Claims (1)

[Scope of Claims] A magnetic toner containing at least a magnetic powder and a binder resin, wherein the magnetic powder contains γ-Fe 205 as a main component and has a BET specific surface area (S
m27f! ) and the amount (Wg) of the magnetic powder contained with respect to the binder resin 10 (l) in the toner have the following relationship: 450≧3−w≧ 50