JP2000162828A - Magnetic carrier for electrophotographic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic carrier superior in durability and having stable electrostatic charging ability by more tightly bonding a silicone resin coating layer to magnetic core material particles. SOLUTION: This magnetic carrier comprises a magnetic particulate powder having 10-200 μm average particle diameter, obtained by coating the surfaces of magnetic core material particles with a resin composition consisting of a metallic curing agent, coupling agent and a silicone resin by way of a layer comprising an oligomer of a silane coupling agent. The average particle diameter of the carrier is 10-200 μm. When the diameter is 10 μm or smaller, the carrier is liable to cause the phenomenon that electrostatic charging ability peculiar to the carrier is lost due to the tight sticking of a toner to the particulate surface of the carrier, that is, the spent of the toner. When the diameter is 200 μm or longer, a clear image will not be obtained. In order to attain high image quality and high grade, a range of preferably 10-100 μm, more preferably 10-50 μm average particle diameter is provided to the carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides an industrially and economically advantageous magnetic carrier for an electrophotographic developer having excellent durability and stable chargeability.

[0002]

2. Description of the Related Art In an electrophotographic developing method, selenium, O
A photoconductive substance such as PC (organic semiconductor) or a-Si is used as a photoreceptor, an electrostatic latent image is formed by various means, and the polarity of the latent image is formed on the latent image by using a magnetic brush developing method or the like. The oppositely charged toner adheres by electrostatic force,
A method of visualizing is adopted.

As is well known, in this developing method, carrier particles called magnetic carriers are used, and an appropriate amount of positive or negative electricity is applied to the toner by frictional charging, and a magnet is built in by utilizing a magnetic force. The toner is conveyed to a developing area near the surface of the photoconductor on which the latent image has been formed through a developing sleeve.

In recent years, this electrophotographic developing method has been widely used in copiers and printers, and is required to be able to handle various objects such as fine lines, small letters, photographs, and color originals. There is also a demand for higher quality, higher speed, and higher continuity, etc., and in particular, the demand for these various properties is expected to increase further in the future.

[0005] In order to be able to cope with various objects and to improve image quality and quality, studies have been made to reduce the particle size of each of toner particles and magnetic carrier particles. With respect to, those having an average particle diameter of 10 to 50 μm are strongly required.

On the other hand, for high speed and continuous operation, it is strongly required to improve the durability as a developer. In the case of a magnetic carrier, a mechanical pulverization method, an electrolytic method, a reduction method, Granulated and baked particles obtained by granulating and heating and firing iron powder, various ferrite fine particle powders or magnetite fine particle powders obtained by various methods such as a decomposition method and a sintering method, and a binder resin for magnetic fine particles and non-magnetic fine particles. Composite particles and the like dispersed therein are used as magnetic core particles (hereinafter, referred to as “magnetic core particles”), and the particle surfaces of the magnetic core particles are coated with various resins. It has already been put to practical use.

[0007] There is no limit to the recent improvement in characteristics, and in order to obtain a clear image, it is necessary that the magnetic carrier be stable without changing its charge amount even after long-time use. That is, there is a problem in that the coating resin layer on the surface of the magnetic core material particles is peeled off due to the use of the magnetic carrier for a long time, and as a result, the chargeability of the magnetic carrier changes and the toner cannot be properly charged. It is strongly required that the coating resin layer is prevented from peeling off from the particle surface of the magnetic core material particles to improve durability and to have stable chargeability.

Conventionally, in order to improve the durability of a magnetic carrier, a magnetic carrier in which a silicone resin is coated on the surface of a magnetic core material particle via a layer of a coupling agent (JP-A-60-19156, JP-A-62-1146
No. 3 etc.) are known.

[0009]

A magnetic carrier having excellent durability and a stable chargeability is currently being most demanded, but such a magnetic carrier has not yet been obtained.

That is, in the known magnetic carrier, the coupling agent is bonded to a hydrophilic group such as a hydroxyl group present on the surface of the magnetic core material particles and also to the silicone resin coating layer, so that the silicone resin is bonded to the magnetic core. The silicone resin coating layer is less likely to peel off than when directly coated on the particle surface of the material particles. However, as shown in the comparative example below, peeling starts after repeated use for a long time, and it is still sufficiently durable. It was hard to say that it was excellent.
Also, the chargeability was easily changed.

Accordingly, the present invention has a technical problem to obtain a magnetic carrier having excellent durability and stable chargeability by bonding a silicone resin coating layer more firmly to magnetic core particles. And

[0012]

The above technical object can be achieved by the present invention as described below.

That is, according to the present invention, a resin composition comprising a metal-based curing agent, a coupling agent and a silicone resin is coated on the surface of a magnetic core material particle via a layer comprising a silane-based coupling agent oligomer. Average particle size 10-2
A magnetic carrier for an electrophotographic developer, comprising a magnetic particle powder of 00 μm.

Next, the configuration of the present invention will be described in more detail.

First, the magnetic carrier according to the present invention will be described.

The average particle size of the magnetic carrier according to the present invention is 10 to 200 μm. When the average particle diameter is less than 10 μm, the phenomenon that toner is firmly adhered to the particle surface of the magnetic carrier and the inherent chargeability of the magnetic carrier is lost, that is, so-called toner spent tends to occur. If it exceeds 200 μm, a clear image cannot be obtained. In particular, the range is preferably from 10 to 100 μm, and more preferably from 10 to 50 μm, for higher image quality and higher quality.

As the magnetic core particles in the present invention, any of the aforementioned magnetic core particles can be used. As granulated and fired particles, lithium, manganese, magnesium,
Copper, ferrite of one or more elements selected from zinc or the like or magnetite containing these elements can be used. Specifically, lithium-manganese ferrite, lithium-magnesium ferrite, magnesium ferrite, Copper-zinc ferrite is preferred. In order to obtain a magnetic carrier having a high magnetization value, granulated and fired particles are preferable.

As the above-mentioned composite particles, resin and magnetic fine particles such as ferrite fine particles and magnetite fine particles, and, if necessary, nonmagnetic fine particles such as hematite are granulated by a kneading / grinding method or a polymerization method. Things can be used. In order to obtain a magnetic carrier with improved durability, composite particles having a low specific gravity, particularly 2 to 4, are preferred.

The ratio of the resin constituting the composite particles to the magnetic fine particles is 1 to 20% by weight of the resin and 80% by weight of the magnetic fine particles.
Preferably it is ~ 99 wt%. If necessary, 70% by weight or less of the magnetic fine particles may be replaced with nonmagnetic fine particles such as hematite.

The magnetic fine particles and the non-magnetic fine particles used in producing the composite particles as the magnetic core material particles may have any particle shape such as spherical, flat, or acicular. The average particle diameter is preferably 0.05 to 5.0 μm. In order to improve the properties such as dispersibility of the particles in the resin, if necessary, the particles may be surface-treated with a coupling agent or the like to make them lipophilic.

The particle shape of the magnetic core material particles in the present invention may be spherical, granular, or flat. As for the particle size of the magnetic core material particles, the average particle diameter is preferably from 8 to 195 μm, more preferably from 8 to 97 μm. When it is less than 8 μm, the particle size of the magnetic carrier particles obtained is less than 10 μm. When it exceeds 195 μm, the particle size of the obtained magnetic carrier particle powder exceeds 200 μm.

The oligomer of the silane coupling agent in the present invention generally has a repeating unit (degree of polymerization) of a monomer, which is a structural unit of the silane coupling agent, of 2 to 10 mer.
Preferably, it may be a low-polymer compound of 2 to 8 mer,
It may be a mixture thereof. The degree of oligomerization of the silane-based coupling agent oligomer was determined by measuring the molecular weight of the obtained oligomer with a gas chromatography mass spectrometer and determining the number of oligomers from the molecular weight of the used monomer. The monomer constituting the silane coupling agent oligomer is a silane coupling agent containing one or more of an amino group, an epoxy group, a vinyl group, a mercapto group, a halogen group and an alkyl group.

Specifically, γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, N-phenyl-
silane coupling agents having an amino group such as γ-aminopropyltrimethoxysilane; γ-glycidoxypropylmethyldiethoxysilane, β-3,4-epoxycyclohexyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane A coupling agent having a vinyl group such as vinyltrichlorosilane, vinyltriethoxysilane, and vinyl tris (β-methoxy) silane; a mercapto group such as γ-mercaptopropyltrimethoxysilane. Coupling agents having: dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Coupling agents having a halogen group such as allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane;
It is a coupling agent having an alkyl group such as trimethylsilane.

The silane coupling agent oligomer used in the present invention may be a commercially available product or a manufactured product. Examples of commercially available oligomers include amino-based silane coupling agent oligomers such as MS3201 (trade name: manufactured by Chisso Corporation), MS3301 (trade name: manufactured by Chisso Corporation), K
BP-40 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.), KB
P-41 (trade name: Shin-Etsu Chemical Co., Ltd.) and KB
P-43 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.), and as an epoxy-based silane coupling agent oligomer, MS5
101 (trade name: manufactured by Chisso Corporation) and MS5102
(Trade name: manufactured by Chisso Corporation), as mercapto-based silane coupling agent oligomers, X-12-414
(Trade name: Shin-Etsu Chemical Co., Ltd.).

The amount of the silane coupling agent oligomer is preferably 0.01 to 3% by weight, more preferably 0.01 to 2.5% by weight, based on the magnetic core particles.
If the amount is less than 0.01% by weight, it becomes difficult to bond the resin composition coating layer more firmly. When the content exceeds 3% by weight, the resin composition coating layer can be more firmly bonded, but the effect is saturated and there is no point in applying more than necessary.

The silicone resin in the magnetic carrier coating resin composition according to the present invention is a trifunctional silicone (hereinafter, referred to as T) in consideration of the durability of the magnetic carrier.
And the ratio of difunctional silicone (hereinafter referred to as D) is 9
The range is preferably from 5: 5 to 40:60, more preferably from 95: 5 to 50:50.

The amount of the coating resin composition is preferably 0.05 to 10.0% by weight based on the magnetic core particles.
If the content is less than 0.05% by weight, the coating tends to be insufficient and uneven, and it is difficult to improve the durability of the magnetic carrier particles. On the other hand, if the coating amount is more than 10% by weight, the magnetic core material particles are liable to peel off from the particle surface, and it is difficult to obtain a magnetic carrier having a stable chargeability. Preferably it is 0.1 to 10% by weight, more preferably 0.2 to 5% by weight.

The metal curing agent in the present invention includes aluminum tri-sec-butoxide, titanium tetra-n-butoxide, titanium-tetra-iso-propoxide, di-n-butyltin dilaurate, metal alkoxide and the like.

The metal alkoxide is represented by (RO) _n M
(Where R is a C ₁ -C ₁₆ alkyl group, M is Al, T
One, two or more metals selected from i, Na, K, Ca, Zn, and Fe, and n is an integer of 1 to 4). Considering practicality such as industrial efficiency and economical efficiency, R is a C ₂ -C ₈ alkyl group, more preferably C ₂ -C _{4. In} order to further improve the durability of the resin composition coating, M Is Al,
Ti metal is preferred. Specifically, aluminum-tri-n-butoxide (n = 4, M = Al), aluminum-tri-ethoxide (n = 2, M = Al), aluminum-tri-sec-butoxide (n = 4, M = A
l), aluminum tri-isopropoxide (n =
3, M = Al), titanium-tetra-n-butoxide (n = 4, M = Ti), titanium-tetraethoxide (n = 2, M = Ti) and titanium-tetra-iso-
Propoxide (n = 3, M = Ti) or the like can be used.

The amount of the metal-based curing agent is preferably 0.05 to 1.0% by weight, more preferably 0.05 to 0.5% by weight, based on the solid content of the silicone resin. 0.05% by weight
If it is less than 3, the curing rate of the silicone resin is low, and the magnetic carrier particles obtained are liable to aggregate each other, resulting in a low yield. If it exceeds 1.0% by weight, the resin composition coating layer tends to be brittle, and the durability tends to decrease.

When a metal alkoxide is used as the metal-based curing agent, the content is 0.05 to 0.5% by weight, particularly 0.05 to 0.5% by weight.
Because a silicone resin can be sufficiently cured with a small amount of about 0.3% by weight to form a uniform and sufficient resin composition coating layer, a strong resin composition coating layer can be formed. Particularly preferred.

The coupling agent in the coating resin composition of the present invention is one or more selected from silane coupling agents, titanium coupling agents, and aluminum coupling agents.

Examples of the silane coupling agent include a silane coupling agent having a mercapto group, a halogen group or an alkyl group. Specifically, γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-
Aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, N
Silane coupling agents having an amino group such as -phenyl-γ-aminopropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-3,
4-epoxycyclohexyltrimethoxysilane, γ-
Coupling agents having an epoxy group such as glycidoxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl tris (β-
One or more selected from coupling agents having a vinyl group such as methoxy) silane. When it is necessary to increase the charge amount of the negatively chargeable toner, a silane coupling agent having an amino group is preferable. When it is not desired to change the charge amount of the toner much, a coupling agent having an epoxy group is preferable.

The titanium-based coupling agent is And so on. Since isopropyloxy-titanium-stearate is excellent in water repellency, the magnetic carrier obtained is suppressed from changing in electric resistance due to moisture absorption.

The aluminum-based coupling agent is And so on.

The amount of the coupling agent is preferably 0.1 to 20.0% by weight based on the solid content of the silicone resin. 0.1
When the amount is less than 10% by weight, the curing speed of the silicone resin is slowed down, and it is difficult to form a resin coating layer having excellent durability, which is the object of the present invention, and aggregation between magnetic carrier particles occurs. It will be easier. If it exceeds 20.0% by weight, the resin composition coating layer tends to be brittle and the durability is reduced, so that the chargeability of the magnetic carrier obtained tends to be unstable.

The magnetic carrier particles according to the present invention comprise (a)
The true specific gravity is usually 2 to 7, preferably 2.5 to 5.5, and (2) the electric resistance is usually 10 ⁷ Ω. cm or more, preferably 10 ⁸ to 10 ¹⁶ Ω. cm, and (3) the saturation magnetization is 20 to 90 emu / g, preferably 25 to 90 emu / g.
and (4) durability (change in charge amount) is usually 12% or less, preferably 8% or less.

The electrophotographic developer comprises at least a magnetic carrier and a toner, and the mixing ratio is usually 80 to 97 parts by weight of the magnetic carrier and 3 to 20 parts by weight of the toner.

Next, a method for producing a magnetic carrier according to the present invention will be described.

As described above, the magnetic carrier according to the present invention is prepared by mixing and stirring the magnetic core material powder in a solution comprising a solvent containing a silane coupling agent oligomer, and then mixing the silicone resin with the metal-based material. The coating agent prepared by diluting the curing agent and the coupling agent with toluene so that the solid content becomes 5 to 30% by weight, and then adjusting the respective addition amounts so that the gelation time becomes 2 to 5 hours. It can be obtained by adding and mixing a working liquid and coating the particle surface of the magnetic core particles with the coating liquid via a layer made of a silane-based coupling agent oligomer. Almost all of the solvent containing the silane-based coupling agent oligomer is applied as a silane-based coupling agent oligomer on the particle surface of the magnetic core material particles, and almost all of the coating liquid is applied to the surface of the magnetic core material particles. It is coated via a layer made of a silane coupling agent oligomer to form a resin composition coating layer.

As described above, the silane-based coupling agent oligomer in the present invention may be a commercially available one. However, the silane-based coupling agent, which is the structural monomer described above, may be used using a known catalyst such as an acid or a base. Can be produced by oligomerization by hydrolysis and condensation. Specifically, a silane coupling agent is dissolved in a solvent at a ratio of 1 to 20% by weight and stirred at a liquid temperature of 30 to 50C.
The stirring time is preferably 2 to 3 hours. When the hydrolysis / condensation reaction of the silane coupling agent is carried out in a solvent, the magnetic core material particles can be treated as they are, which is preferable. As the solvent, isopropyl alcohol or ethanol is preferable.

When the solid content is less than 5% by weight, it takes a long time to remove a solvent such as toluene and the like.
Not economic. When the solid content concentration exceeds 30% by weight, the resin composition of the magnetic core material particles (hereinafter, referred to as “treated magnetic core material particles”) on which the layer made of the silane coupling agent oligomer is adhered. It is difficult to form a sufficient and uniform coating layer with the object. If the gelation time is less than 2 hours, the coating liquid itself will thicken, making it difficult to form a sufficient and uniform coating layer of the treated magnetic core particles with the resin composition. If the gelation time exceeds 5 hours, the treated magnetic core particles tend to agglomerate with each other.

The addition amount of the coating liquid is preferably in the range of 0.05 to 10.0% by weight as a solid content based on the treated magnetic core material powder. If the content is less than 0.05% by weight, the coating of the treated magnetic core particles with the resin composition tends to be insufficient and uneven. If the content exceeds 10.0% by weight, the resulting magnetic carrier has a high electric resistance value, causing problems such as charge-up on an image.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION

A typical embodiment of the present invention is as follows.

The average particle diameter of the particles in the following embodiments and the following examples and comparative examples is indicated by a value measured by a laser diffraction type particle size distribution meter (manufactured by Horiba, Ltd.). The morphology was observed with a scanning electron microscope (S-800, manufactured by Hitachi, Ltd.).

The saturation magnetization was measured using a vibrating sample magnetometer VSM-3.
External magnetic field 10 using S-15 (manufactured by Toei Kogyo Co., Ltd.)
It is shown as a value measured under kOe.

The true specific gravity was shown by a value measured with a multi-volume density meter (manufactured by Micromeritics).

The volume resistivity was indicated by a value measured with a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company).

The durability test was performed as follows. 50 g of the magnetic carrier particle powder is placed in a 100 cc glass sample bottle, capped, and shaken with a paint conditioner (manufactured by RED DEVIL) for 10 hours. The charge amount of each sample before and after shaking was measured.

The charge amount is determined by sufficiently mixing 95 parts by weight of the magnetic carrier particle powder and 5 parts by weight of the toner produced by the following method, and using a blow-off charge amount measuring device TB-200 (manufactured by Toshiba Chemical Co., Ltd.). It was measured. <Production of Toner> A polyester resin obtained by condensing propoxylated bisphenol with fumaric acid 100 parts by weight Phthalocyanine pigment 4 parts by weight Di-tert-butylsalicylate chromium complex 4 parts by weight was sufficiently premixed with a Henschel mixer. The mixture was melt-kneaded by a twin-screw extruder, cooled, coarsely ground by using a hammer mill, and then finely ground by an air jet-type fine mill. This finely pulverized product was classified to obtain a negatively chargeable cyan colored powder having a weight average particle size of 8 μm. To 100 parts by weight of the cyan colored powder, 10 parts by weight of titanium oxide fine powder was added and mixed by a Henschel mixer to obtain a cyan toner.

The yield of the magnetic carrier particles in which the resin composition coating is formed on the surface of the magnetic core material particles is as follows: the sieve opening corresponding to each of the magnetic core material particles A to E is 44 μm.
m, 63 μm, 63 μm, 75 μm and 75 μm The value obtained by dividing the amount of the magnetic carrier particles having the resin composition coating formed on the particle surface through the sieves by the amount before the sieve. Was shown as a percentage.

<Production of Magnetic Core Particles> 1 kg of spherical magnetite particle powder having an average particle diameter of 0.24 μm was charged into a Henschel mixer, and NB
7.5 g of -aminoethyl-γ-aminopropylmethyldimethoxysilane KBM-602 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as silane coupling agent a) is added and mixed, and the above spherical magnetite particles are mixed. Was coated with the silane coupling agent a.

Separately, 50 g of phenol, 75 g of 37% formalin, 400 g of the above-mentioned lipophilic spherical magnetite particles, 15 g of 25% aqueous ammonia, and 50 g of water were charged into a 1-liter four-necked flask, and stirred for 60 minutes. To 85 ° C., and reacted and cured at the same temperature for 120 minutes to produce a composite particle powder composed of a phenol resin and a spherical magnetite particle powder. Next, the content in the flask was cooled to 30 ° C., 0.5 l of water was added, the supernatant was removed, and the lower layer sediment was washed with water.
Air dried.

Next, this is reduced under reduced pressure (5 mmHg or less).
And dried at 150 to 180 ° C. to obtain composite particle powder (hereinafter, referred to as composite particle powder A).

The composite particle powder A is a spherical (sphericity: 1.1) particle having a magnetite particle content of 88% by weight, an average particle diameter of 18 μm, a specific gravity of 3.55, and a saturation magnetization. Is 75 emu / g and volume resistivity is 1 × 1
0 ⁸ Ωcm.

<Treatment of magnetic core material particles with silane-based coupling agent oligomer solution> γ-aminopropyltrimethoxysilane KBM-903 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane-based coupling agent
1.0 g of the silane coupling agent b was placed in a flask containing 50 g of isopropyl alcohol in advance,
After adding a small amount of an acetic acid / water mixed solution with stirring, the mixture is stirred for 3 hours while maintaining the solution temperature at 40 ° C. to cause a hydrolysis / condensation reaction to produce an isopropyl alcohol solution containing an oligomer of the silane coupling agent b. Prepared. Next, a universal stirrer (5XDML: manufactured by Dalton Co., Ltd.)
Into the mixture, 1 kg of the composite particle powder A1 was added, and the mixture was stirred until the product temperature reached 50 ° C. Then, an isopropyl alcohol solution containing an oligomer of the silane coupling agent b prepared in advance was added, followed by stirring. After stirring for 1 hour, the temperature is raised to 80 ° C., and the mixture is further stirred for 1 hour at that temperature to treat the magnetic core material particles, and the silane coupling is performed on the surface of the magnetic core material particles. A layer composed of the oligomer of the agent b was formed. The layer composed of the oligomer of the silane coupling agent b was 0.1% by weight based on the magnetic core particles.

<Coating of Magnetic Core Particles with Resin Composition> After the product temperature was lowered again to 50 ° C., the silicone resin (T /
(D unit ratio = 90/10) as a solid content, 30 g of aluminum-tri-sec-butoxide (hereinafter, referred to as a metal-based curing agent g) as a metal-based curing agent, and 0.7 g of a coupling agent b. And a solution diluted with toluene so that the solid content concentration of the silicone resin becomes 20% is added. Subsequently, after stirring at the same temperature for 1 hour, a heat treatment is performed at 200 ° C. for 2 hours under an inert atmosphere of nitrogen gas, so that the metal-based curing agent g is formed on the particle surfaces of the composite particles via a layer made of a coupling agent oligomer. And a coating layer of a resin composition consisting of a coupling agent b and a silicone resin. The yield was 97%, and the coating with the resin composition was sufficient and uniform. Table 3 shows properties of the obtained magnetic carrier.

As a result of observation with an electron microscope, coating with the resin composition was sufficient and uniform, and the coating amount was 2.5% by weight. The obtained magnetic carrier had an average particle size of 19 μm.
m, bulk density 1.72 g / ml, specific gravity 3.53, electric resistance value 5 × 10 ¹⁴ Ωcm, saturation magnetization value 74 emu / g,
The rate of change of the charge amount was 5% (initial -37 μC / g, -35 μC / g after shaking).

[0060]

The most important point in the present invention is that a resin composition comprising a metal-based curing agent, a coupling agent and a silicone resin is provided on the surface of the magnetic core material particles via a layer comprising a silane-based coupling agent oligomer. This is the fact that the coated magnetic particle powder has excellent durability and stable chargeability.

Regarding the reason why the durability of the magnetic carrier according to the present invention is excellent, the present inventor has proposed that a magnetic core material treated with a silane coupling agent oligomer in forming a resin composition coating layer on the surface of the magnetic carrier. When particles are used, the silane-based coupling agent oligomer is bonded to the particle surface of the magnetic core material particles at multiple points and is firmly fixed as compared with a conventionally known coupling agent monomer. This is considered to be because the material can be firmly bonded to the particle surface of the magnetic core material particles.

Regarding the reason why the chargeability of the magnetic carrier according to the present invention is stable, the present inventor has found that the improvement in the durability of the magnetic carrier makes it difficult for the resin composition coating to peel off and affects the charge amount. It is thought that this is because the movement of the coupling agent that exerts the effect can be suppressed. That is, in the magnetic carrier according to the present invention, the silane-based coupling agent oligomer is firmly fixed to the particle surface of the magnetic core material particles, and the silane-based coupling agent oligomer is subjected to the subsequent resin composition coating step. In the above, the dissolution into the solvent or the separation and migration into the resin composition coating layer are suppressed.

[0063]

Next, examples and comparative examples will be described. Examples 1 to 7, Comparative Examples 1 to 3

First, magnetic core material particles A to E were prepared. Table 1 shows the conditions for forming the composite particles B and C, which are the magnetic core particles, and Table 2 shows the characteristics of the magnetic core particles B to E.

[0065]

[Table 1]

[0066]

[Table 2]

Next, the type of the magnetic core material particles, the presence / absence of the treatment with the silane-based coupling agent oligomer, the type and amount, the type and amount of the silicone resin, the presence / absence, type and amount of the metal-based curing agent, and the coupling agent A magnetic carrier was obtained in the same manner as in the above embodiment, except that the type and amount of were variously changed.

Table 3 shows the main conditions at this time, and Table 4 shows various characteristics.
Shown in In Comparative Example 3, a conventionally well-known silane-based coupling agent monomer was used instead of the silane-based coupling agent oligomer.

[0069]

[Table 3]

[0070]

[Table 4]

The composite particle powder coated with the silicone resin obtained in Comparative Example 1 had its charge amount greatly changed in the durability test, and thus the coating layer was peeled off by the mechanical impact in the durability test. it is conceivable that.

In Table 3, the coupling agents a to
f and the metallic hardeners g to i are as follows, respectively.

<Coupling agent> Coupling agent a: N
-Β-aminoethyl-γ-aminopropylmethyldimethoxysilane (N-β- (aminoethyl) -γ-
aminopropylmethyldimethox
ysilane) (trade name: KBM602: manufactured by Shin-Etsu Chemical Co., Ltd.) Coupling agent b: γ-aminopropyltrimethoxysilane (γ-aminopropritrimethox)
ysilane) (trade name: KBM-903: manufactured by Shin-Etsu Chemical Co., Ltd.) Coupling agent c: N-phenyl-γ-aminopropyltrimethoxysilane (N-phenyl-γ-amin)
oppropyltrimethyoxysilane)
(Trade name: KBM573: manufactured by Shin-Etsu Chemical Co., Ltd.) Coupling agent d: γ-glycidoxypropyl trimethoxysilane (γ-glycidoxypropylpropyl)
imoxysilane) (Product name: KBM40)
3: Shin-Etsu Chemical Co., Ltd.) Coupling agent e: γ-mercaptopropyltrimethoxysilane (γ-mercaptopropyltrim)
ethoxysilane) (trade name: KBM803:
Shin-Etsu Chemical Co., Ltd.) Coupling agent f: isopropyloxy-titanium-
Tristearate (Isopropoxy-tit)
anium-tristearate) (trade name: KR
-TTS: Ajinomoto Co., Inc.)

<Metal-based curing agent> Metal-based curing agent g: aluminum tri-sec-butoxide (Aluminiu)
m tri-sec-butoxide Metal-based curing agent h: Titanium tetra-n-butoxide
e) Metal-based curing agent i: Di-n-butyltin dilaurate (Di-n-butyltin dilaurate)

[0075]

The magnetic carrier for an electrophotographic developer according to the present invention has excellent durability, so that the resin composition coating hardly peels off even when used repeatedly for a long period of time.
Further, since it has a stable chargeability due to the fact that the elution and movement of the coupling agent affecting the charge amount are suppressed, it is suitable as a magnetic carrier for an electrophotographic developer.

Claims (1)

[Claims] 1. An average particle diameter in which a resin composition comprising a metal-based curing agent, a coupling agent and a silicone resin is coated on a surface of a magnetic core material particle via a layer comprising a silane-based coupling agent oligomer. A magnetic carrier for an electrophotographic developer, comprising magnetic particle powder of 10 to 200 μm.