JPH04345170A - Dry developer for electrostatic latent image - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an abnormal image due to the sticking of electric conductive magnetic particles to a photosensitive body in a dry developing system using insulating magnetic toner particles and the electric conductive magnetic particles and to prevent the electric conductive magnetic particles from being made visible as an abnormal image even if the particles stick to the edge of an image and is transferred to a transfer member by making the color of the electric conductive magnetic particles similar to that of the transfer paper. CONSTITUTION:In a dry developer for an electrostatic latent image made of a mixture of insulating magnetic toner particles with electric conductive magnetic particles, fine spinel ferrite powder of 5-80nm average particle diameter is used as the magnetic material of the electric conductive magnetic particles.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to electrophotography, electrostatic recording,
The present invention relates to a dry magnetic developer for developing electrostatic images in electrostatic printing and the like.

0002

2. Description of the Related Art As a means for developing an electrostatic image formed on an electrophotographic photoreceptor or an electrostatic recording medium, a toner in which pigments, magnetic substances, etc. are dispersed in a binder resin is used. A method of developing by forming a thin layer on a carrier such as a developing roller [
one-component development method], and a two-component development method (two-component development method) using a developer containing toner mixed with a magnetic carrier.
Both methods (dry development method) are generally adopted, but in recent years, as an intermediate method between both methods, a method using a developer containing an insulating magnetic toner and conductive magnetic particles smaller in diameter than the magnetic carrier in a two-component developer is used. has been developed and put into practical use.

[0003] Such a developing method uses an insulating magnetic toner as described in, for example, JP-A-53-33152, JP-A-53-33633, and JP-A-57-10150. A method using a developer made of a mixture of a binder resin and conductive magnetic particles made of a magnetic material, and JP-A No. 5
6-142540, JP-A No. 56-159653, and JP-A-56-161552, the volume average diameter is 1/5 to 4/4 of that of the insulating magnetic toner. There is a method using a developer made of a mixture with conductive magnetic particles. This development method has a wider margin for toner density than normal two-component development methods.
This has the advantage that toner density control is not required.

0004

[Problems to be Solved by the Invention] However, in the above development method, because the particle size of the conductive magnetic particles that serve as the carrier in the two-component developer is small, the adhesion of the conductive magnetic particles to the image edge portion is different from that in the normal case. It has the disadvantage that it is more common than two-component development systems. Therefore, the current situation is that abnormal images (such as dust on image edges) are likely to occur due to this, and it is difficult to reduce them.

Therefore, it is an object of the present invention to solve the above-mentioned problems, that is, to prevent the occurrence of abnormal images due to adhesion of conductive magnetic particles to a photoreceptor in a developing method using insulating magnetic toner and conductive magnetic particles. An object of the present invention is to provide a developer that can prevent the above problems. Another object of the present invention is to make the conductive magnetic particles themselves the same color as the transfer paper, so that even if the conductive magnetic particles adhere to the edge of the image and are transferred to the transfer member, the edge deposits will be the same color as the background. Therefore, it is an object of the present invention to provide a developer that can prevent the appearance of an abnormal image.

[0006]

[Means for Solving the Problem] As a result of extensive studies, the present inventors have found that a developer using spinel ferrite fine powder of a specific particle size as the magnetic material of the conductive magnetic particles is suitable for the above purpose. This discovery led to the completion of the present invention.

That is, according to the present invention, there is provided a dry developer for electrostatic latent images comprising a mixture of insulating magnetic toner particles and conductive magnetic particles, wherein the conductive magnetic particles have an average particle size as a magnetic material. A dry developer for electrostatic latent images is provided, which is characterized in that it contains spinel ferrite fine powder having a diameter of 5 to 80 nm.

A feature of the developer of the present invention is that by using spinel ferrite fine powder as the magnetic material of the conductive magnetic particles, it can be made into a light-colored, translucent magnetic material that retains magnetism. In addition, by setting the average particle size of the fine powder to 5 to 80 nm, the translucency of the magnetic particles increases and the hiding power weakens, so the coloring power of the coloring material becomes dominant, and the conductive magnetic particles This makes it possible to make the colors vivid. Further, as for the spinel structure, a reverse spinel structure is superior in terms of light transmittance.

If the average particle size of the spinel ferrite fine powder used is less than 5 nm, the proportion of paramagnetism due to thermal fluctuations will increase and the magnetic force will decrease, whereas if the average particle size exceeds 80 nm, the magnetic force will decrease. , a decrease in translucency occurs.

The spinel ferrite used in the present invention is particularly preferably one represented by the following general formula. AB2O4 [A in the formula includes at least two of 3d, 4d, 4f, and 5d transition metals/rare earth elements (however, trivalent Fe,
(excluding Co). Further, B includes at least one of Fe, Co, Mn, and Cr. ]

[0011] As a method of ensuring translucency, a method of increasing the particle size (1 μm or more) (for example, Japanese Patent Laid-Open No. 58-187
No. 951, No. 58-217945, No. 59-1708
No. 47, No. 59-170848, etc.), but
According to this method, even if uniform dispersion is achieved through kneading, the composition distribution of the magnetic particles after pulverization and classification will widen, resulting in particles with a large amount of magnetic material and particles with a small amount of magnetic material, resulting in problems such as deterioration of durability, so this method was adopted. Can not.

[0012] Furthermore, SnO2-based conductive fine powder is effective as a transparent substance that imparts conductivity to the magnetic particles. For example, they are SnO2-SbO2-based, SnO2-BaSO4-based, etc., and have a particle size of 0.01 to 1 μm.

The conductive magnetic particles in the present invention contain at least a binder resin and the spinel ferrite fine powder, and the content of the spinel ferrite fine powder is 25 to 120 parts by weight based on 100 parts by weight of the binder resin. The amount is appropriate, and 40 to 100 parts by weight is particularly preferred. If it is less than 25 parts by weight, the amount of magnetization as magnetic particles will be small, and the amount of adhesion to the image edge will be large. Conversely, if it exceeds 120 parts by weight, the spinel ferrite fine powder will be a non-fixing component, resulting in poor fixing properties. decreases.

[0014] As the binder resin constituting the conductive magnetic particles, all resins conventionally used as binder resins for toners can be used, and specific examples include the binder resins for toners described later. Examples include those similar to those exemplified as .

The spinel ferrite fine powder of the present invention is produced, for example, as follows. First, 3d, 4d, 4f
, 5d of at least two chlorides of transition metals/rare earth elements (excluding trivalent Fe, Co), and Fe, Co,
Mix metal salts selected from Mn and Cr in an appropriate ratio,
Soluble in water. The mixing ratio of the total amount of metal salts and water at this time is usually 1.0 to 4 mol per liter of water, preferably 1.0 to 3.0 mol per liter of water.
It is a mole. Next, an alkali such as caustic soda is added to this mixed solution to adjust its pH to preferably 11±1. When the pH of the mixed solution is adjusted to the value,
A mixture of the metal hydroxide and water is obtained.

This mixture is then subjected to hydrothermal synthesis. The heating temperature during hydrothermal synthesis is usually 150 to 300°C, preferably 180 to 250°C. Heating temperature is 150℃
If it is less than 300°C, the reaction may not proceed sufficiently to form an oxide, and if it exceeds 300°C, the particle size will increase. The hydrothermal synthesis time depends on the scale, but is usually 1~
5 hours, preferably 2 to 4 hours. If the reaction time is less than 1 hour, the reaction may not proceed sufficiently to form an oxide, and if it exceeds 5 hours, the particle size will increase. After cooling, the water in the mixture is removed and dried to obtain spinel ferrite fine powder.

The insulating magnetic toner particles used in the present invention are:
It contains at least a binder resin and a magnetic material, and in this case, all binder resins conventionally used as binder resins for toners can be used. Specifically, monopolymers of styrene and its substituted products, such as polystyrene, polychlorostyrene, and polyvinyltoluene;
Styrene/p-chlorostyrene copolymer, styrene/propylene copolymer, styrene/vinyltoluene copolymer, styrene/vinylnaphthalene copolymer, styrene/methyl acrylate copolymer, styrene/ethyl acrylate copolymer , styrene/butyl acrylate copolymer, styrene/octyl acrylate copolymer, styrene/methyl methacrylate copolymer, styrene/ethyl methacrylate copolymer, styrene/butyl methacrylate copolymer, styrene/α- Methyl chlormethacrylate copolymer, styrene/acrylonitrile copolymer, styrene/vinyl methyl ether copolymer, styrene/vinyl ethyl ether copolymer, styrene/vinyl methyl ketone copolymer,
Styrenic copolymers such as styrene/butadiene copolymer, styrene/isoprene copolymer, styrene/acrylonitrile/indene copolymer, styrene/maleic acid copolymer, and styrene/maleic acid ester copolymer; polymethyl methacrylate , polybutyl methacrylate,
Polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyral butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Examples include paraffin wax, which may be used alone or in combination of two or more.

[0018] As the magnetic material, all the materials conventionally used as magnetic materials for toner can be used. Specific examples include magnetite, hematite,
Metals such as iron oxide, iron, cobalt, nickel such as ferrite, or these metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, Examples include alloys of metals such as tungsten and vanadium, and mixtures thereof.

Furthermore, the toner particles used in the present invention can of course contain a colorant, and all pigments and dyes conventionally used as colorants for toners can be used. Specifically, ultramarine blue, aniline blue, calco oil blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue,
Phthalocyanine Green, Malacanite Green, Hansa Yellow G, Rhodamine 6C Lake, Quinacridone,
Examples include benzidine yellow, rose bengal, monoazo dyes and pigments, disazo dyes and pigments, trisazo dyes and pigments, and mixtures thereof.

The toner particles used in the present invention may optionally contain a charge control agent for controlling the charge of the toner, a fluidizing agent such as colloidal silica, titanium oxide,
Metal oxides such as aluminum oxide, abrasives such as silicon carbide, lubricants such as fatty acid metal salts, etc. can be contained.

[0021]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. Note that all percentages and parts shown below are based on weight.

(Production of magnetic metal oxide) Production example 1 0.7 mol of magnesium sulfate heptahydrate, 0.3 mol of zinc sulfate heptahydrate, and hydrated ferric sulfate [Fe(SO4)3.n
1.0 mol of H2O] was dissolved in 1 liter of distilled water. A caustic soda aqueous solution was added to the obtained aqueous solution until the pH of the solution became 11±1, thereby gelling the aqueous solution. The obtained gelled product was loaded into a stainless steel autoclave, and hydrothermal synthesis was performed over 3 hours while heating it to 220°C. After the reaction, the autoclave was cooled and the contents were taken out of the autoclave to obtain a slurry suspension with a solid content of approximately 10%.

The fine powder obtained by drying this at room temperature was pale red and transparent, and the average particle size determined by X-ray diffraction was 8 nm, and only spinel was recognized as the mineral. Moreover, the value of saturation magnetic moment was 31.4 emu/g. The saturation magnetic moment used here is the magnetic field of 5KO applied by a vibrating sample magnetometer (VSM-3 model) manufactured by Toei Kogyo Co., Ltd.
This is the value at e.

Production Example 2 0.5 mol of manganese sulfate tetrahydrate and 0.5 mol of zinc sulfate heptahydrate.
5 mol and hydrated ferric sulfate [Fe(SO4)3・nH2
1.0 mol of O] was dissolved in 1 liter of distilled water. A caustic soda aqueous solution was added to the obtained aqueous solution until the pH of the solution became 11±1, thereby gelling the aqueous solution. The obtained gelled product was placed in a stainless steel beaker and kept at 100° C. for 30 minutes in a water bath to perform hydrothermal synthesis. After the reaction, the contents are taken out from the stainless steel beaker after cooling, and the solid content is reduced to approximately 1.
A 0% slurry suspension was obtained.

The fine powder obtained by drying this at room temperature was pale red and transparent, and the average particle size determined by X-ray diffraction was 15 nm, and only spinel was recognized as the mineral. Moreover, the value of saturation magnetic moment was 48.4 emu/g.

Example 1 Styrene/n-butyl methacrylate copolymer 100.0 parts Spinel ferrite fine powder obtained in Production Example 1
40.0 parts SnO2-SbO2
fine powder
5.0 parts The mixture having the above composition was sufficiently stirred and mixed using a Henschel mixer, then melted by heating at 130° C. to 140° C. for 30 minutes using a roll mill, and then cooled to room temperature. This mixture was crushed and classified to obtain conductive magnetic particles with a particle size of 15 μm. The volume resistivity of the particles was 1010 Ω·cm, and the particles were light gray and transparent.

The volume resistivity was measured by the following method. Place an insulating plastic cylinder with an inner diameter of 10 mmφ on top of an electrode with a diameter of 10 mmφ, place the sample so that the height is 2 mm, level the sample, and then gently insert the 10 mmφ electrode from the top of the cylinder. do. The pressure applied to the sample was 1000 g/cm 2 , and the sample was determined from the current value, area, and thickness 1 minute after applying a DC voltage of 100 V.

Next, a mixture having the following composition was sufficiently stirred and mixed using a Henschel mixer, and then heated to 130°C or more using a roll mill.
The mixture was melted by heating at 140° C. for 30 minutes, and then cooled to room temperature. This mixture was pulverized and classified to obtain insulating magnetic toner particles with a particle size of 12 μm. Styrene/n-butyl methacrylate copolymer 100.0 parts Magnetite fine powder
100.0 copies
Metal-containing azo dye (charge control agent)
2.0 copies

The obtained conductive magnetic particles, insulating magnetic toner particles, and colloidal silica were mixed in the following amounts to prepare a developer. conductive magnetic particles

70 parts insulating magnetic toner particles

Part 30 Colloidal Silica
0.5 part

When the obtained developer was placed in FP-1530 (manufactured by Panasonic Corporation) and an image was produced, a clear image at the edge portions of the image was obtained. In addition, the image quality was sufficient to withstand up to three times of repeated image production using the image as a document.

Example 2 Styrene/n-butyl methacrylate copolymer 100.0 parts Spinel ferrite fine powder obtained in Production Example 2
100.0 parts SnO2-SbO2 fine powder
10.0 parts TiO2 fine powder
5.0
After thoroughly stirring and mixing the mixture having the above composition using a Henschel mixer, the mixture was melted by heating at 130° C. to 140° C. for 30 minutes using a roll mill, and then cooled to room temperature. This mixture was crushed and classified to obtain conductive magnetic particles with a particle size of 5 μm. The volume resistivity of the particles was 106 Ω·cm, and the particles were white and transparent.

Next, a mixture having the following composition was sufficiently stirred and mixed using a Henschel mixer, and then heated to 130°C or more using a roll mill.
The mixture was melted by heating at 140° C. for 30 minutes, and then cooled to room temperature. This mixture was pulverized and classified to obtain insulating magnetic toner particles having a particle size of 9 μm. Styrene/n-butyl methacrylate copolymer 100.0 parts Magnetite fine powder
80.0 copies
Nigrosine dye (charge control agent)
2.0
Department

The obtained conductive magnetic particles, insulating magnetic toner particles, and colloidal silica were mixed in the following amounts to prepare a developer. conductive magnetic particles

15.0 parts insulating magnetic toner particles

85.0 parts colloidal silica
0.5 part

003
4) When the obtained developer was put into LP4080 (manufactured by Ricoh) and an image was produced, a clear image was obtained. However, when black or colored transfer paper was used, dust could be seen at the edges of the image, which is due to the white conductive magnetic particles preventing abnormal images from appearing. .

Comparative Example 1 Styrene/n-butyl methacrylate copolymer 100.0 parts Magnetite fine powder
40.0 copies
SnO2-SbO2 fine powder

5.0 parts The mixture having the above composition was sufficiently stirred and mixed using a Henschel mixer, and then heated to 130°C to 140°C using a roll mill.
The mixture was melted by heating for 30 minutes, and then cooled to room temperature. This mixture was crushed and classified to obtain conductive magnetic particles with a particle size of 15 μm. The volume resistivity of the particles was 1010 Ω·cm, and the particles were black fine powder.

Next, a mixture having the following composition was sufficiently stirred and mixed with a Henschel mixer, and then heated to 130°C with a roll mill.
The mixture was melted by heating at 140° C. for 30 minutes, and then cooled to room temperature. This mixture was pulverized and classified to obtain insulating magnetic toner particles with a particle size of 12 μm. Styrene/n-butyl methacrylate copolymer 100.0 parts Magnetite fine powder
100.0 copies
Metal-containing azo dye (charge control agent)
2.0 copies

The obtained conductive magnetic particles, insulating magnetic toner particles, and colloidal silica were mixed in the following amounts to prepare a developer. conductive magnetic particles

70 parts insulating magnetic toner particles

Part 30 Colloidal Silica
0.5 part

When the obtained developer was placed in FP-1530 (manufactured by Panasonic Corporation) and an image was produced, toner dust was observed at the edges of the image and a poor image was obtained. Furthermore, when an image is used as a document, a usable image can only be obtained once.

Styrene/n-butyl methacrylate copolymer 100.0 parts γ-F
e2O3 fine powder
100.0 copies
SnO2-SbO2 fine powder
1
0.0 part TiO2 fine powder

5.0 parts The mixture having the above composition was sufficiently stirred and mixed using a Henschel mixer, then melted by heating at 130° C. to 140° C. for 30 minutes using a roll mill, and then cooled to room temperature. This mixture was crushed and classified to obtain conductive magnetic particles with a particle size of 5 μm. The volume resistivity of this particle is 10
6 Ω·cm, and the particles had a reddish-brown color even though they contained TiO2.

Next, a mixture having the following composition was sufficiently stirred and mixed with a Henschel mixer, and then heated to 130°C with a roll mill.
The mixture was melted by heating at 140° C. for 30 minutes, and then cooled to room temperature. This mixture was crushed and classified to obtain insulating magnetic toner particles having a particle size of 9 μm. Styrene/n-butyl methacrylate copolymer 100.0 parts Magnetite fine powder
80.0 copies
Nigrosine dye (charge control agent)
2.0
Department

The obtained conductive magnetic particles, insulating magnetic toner particles, and colloidal silica were mixed in the following amounts to prepare a developer. conductive magnetic particles

15.0 parts insulating magnetic toner particles

85.0 parts colloidal silica
0.5 part

004
2) When the obtained developer was placed in LP4080 (manufactured by Ricoh Co., Ltd.) and an image was produced, dust was observed at the edges of the image, and the image was poor.

[0043]

Effects of the Invention The developer of the present invention is a dry developer for electrostatic latent images consisting of a mixture of insulating magnetic toner particles and conductive magnetic particles, and moreover, the average magnetic material of the conductive magnetic particles is Since the spinel ferrite fine powder having a particle size of 5 to 80 nm is used, the following outstanding effects can be achieved in a dry development method using an insulating magnetic toner and conductive magnetic particles. b) It is possible to prevent the occurrence of abnormal images due to adhesion of conductive magnetic particles to the photoreceptor. b) Even if the conductive magnetic particles adhere to the edge of the image and are transferred to the transfer member, by making the conductive magnetic particles themselves the same color as the transfer paper, the edge deposits will be the same color as the background, resulting in an abnormal image. It is possible to prevent the manifestation of

Claims (2)

[Claims] 1. A dry developer for electrostatic latent images comprising a mixture of insulating magnetic toner particles and conductive magnetic particles, comprising:
Moreover, the conductive magnetic particles have an average particle size of 5 as a magnetic material.
A dry developer for electrostatic latent images, characterized in that it contains spinel ferrite fine powder of ~80 nm. 2. The dry developer for electrostatic latent images according to claim 1, wherein the spinel ferrite fine powder is represented by the following general formula. AB2O4 [A in the formula includes at least two of 3d, 4d, 4f, and 5d transition metals/rare earth elements (however, trivalent Fe,
(excluding Co). Further, B includes at least one of Fe, Co, Mn, and Cr. ]