JP2001330997A - Electrophotographic carrier, method for manufacturing the same, and coating material for carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic carrier and a method for manufacturing the carrier which suppresses the influences of toner spent on the carrier surface by using a soft elastic resin as a coating resin, which has an ability to stably impart the optimum electrification property to the toner and which can maintain the ability for a long time. SOLUTION: The electrophotographic carrier is coated with a resin showing >=0.5 μm plastic deformation and >=0.5 μm elastic deformation by the measurement using Knoop indenter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carrier for electrophotography, and more particularly to a dry two-component developer carrier and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in electrophotography, an electrostatic latent image is formed on a photosensitive member or an electrostatic recording member by using various means,
A method is generally employed in which electrostatic fine particles called toner are attached to the electrostatic latent image to develop the electrostatic latent image. In this development, carrier particles called carriers are mixed with toner particles, and both are triboelectrically charged to impart an appropriate amount of positive or negative charge to the toner.

[0003] Carriers are generally classified into a coated carrier having a coating layer on the surface of a core material and a non-coated carrier having no coating layer on the surface of the core material. Because of the superiority of the coated carrier, various types of coated carriers have been developed and put into practical use. There are various characteristics required for the coated carrier, but it is necessary to stably impart appropriate chargeability (charge amount and charge distribution) to the toner and to maintain the appropriate and stable chargeability for a long period of time. . For that purpose, it is important that the carrier has suitable electrical properties, and has high resistance to environmental changes such as humidity and temperature, high impact resistance, high friction resistance, and the ability to impart chargeability does not change in the long term. In fact, various coated carriers have been proposed.

[0004] The magnetic brush method using a two-component developer includes:
There are problems such as lowering and unevenness of image density due to deterioration of the charge of the developer, generation of significant background stain, generation of image roughness due to carrier adhesion to the image, consumption of carrier, and generation of image density unevenness. The deterioration of the charge of the developer is likely to occur due to the adhesion of the toner component to the carrier coating layer or the peeling of the coating layer, and the carrier and the toner come into contact with each other in the developing machine, rub against each other, and are triboelectrically charged. This is caused by stress during transport.

[0005] Further, if the coating layer becomes non-uniform, the background tends to stain when the environment changes such as humidity and temperature, when toner is added, and when the toner concentration is high. In particular, the adhesion of the toner component to the carrier coating layer, together with the triboelectric charging function of the toner, causes the toner to contaminate (spent) the carrier surface, making it impossible to obtain a desired charging property.
Therefore, in order to prolong the life of the developer, it is required to completely prevent spent, to select a carrier structure which is not affected by spent, and to select a material.

In order to prevent such charge deterioration, the hardness of the coating resin is increased to make it difficult to peel off, or the surface energy of the coating resin is reduced to prevent the toner component from sticking to the carrier coating layer. Efforts have been made to prevent charge deterioration by using the same.

For example, an unreacted thermoplastic resin having a hydroxyl group and an alkoxylated melamine are used for the purpose of increasing the adhesion to the core substance and the coating strength, and improving the fluidity, moisture resistance and separation of the toner from the carrier. A carrier in which a core material is coated with a resin component obtained by curing a resin (Japanese Patent Laid-Open No. Sho 62-2)
62057), a carrier coated with a core material with a resin obtained by cross-linking an acrylic resin and a melamine resin for the purpose of improving durability and environmental resistance (see JP-A-2-79862), durability, heat resistance and Carrier coated with a core material with an acrylic resin cross-linked with a melamine formaldehyde resin composition for the purpose of improving environmental resistance (JP-A-5-21)
However, there has been a problem that a carrier containing a melamine resin has a large charge reduction at high temperature and high humidity.

As a method for preventing spent, it has been proposed to use a silicone resin or a fluorine resin (Japanese Patent Application Laid-Open Nos. 60-186844 and 64-13).
No. 560). Certainly, the silicon resin and the fluorine-based resin have an advantage that the surface energy is low and thus the toner is hardly spent, but on the other hand, they have a disadvantage that they are hardly adhered to the carrier core material and easily peeled off. In addition, in the case of silicone resin, the effect of preventing spent is not exhibited unless it is sufficiently cured. When cured sufficiently, the molecular weight increases and a hard but brittle film is formed, which is difficult to control. If the carrier is used for a long time even if it is cured appropriately, the coating on the carrier surface will wear and eventually lose the resin, the desired chargeability will not be obtained, and at the same time, the function to prevent spent will not work . Further, when the exposed portion of the carrier nucleus particles is widened, the toner component is fixed to the nucleus particles, resulting in charge deterioration. Therefore, improvement in the structure of the carrier and the material of the coating layer which are not affected by the spent are expected.

Japanese Patent Application Laid-Open No. 62-187863 discloses a carrier obtained by coating iron oxide powder with a cured product of a copolymer having a carboxyl group and / or hydroxyl and a melamine resin. With this method, both a line image and a solid image provide high image density and achieve a long life. Also, Japanese Patent Application Laid-Open No. 62-262
Japanese Patent No. 057 discloses a carrier for electrophotography, wherein the surface is coated with a material mainly composed of a resin obtained by curing an unreacted thermoplastic resin having a hydroxyl group and an alkoxylated melamine resin. By using a material having a high adhesiveness to the carrier and a high coating strength, the electric resistance of the carrier is maintained at a high level, and at the same time, the fluidity, the moisture resistance and the separation from the toner are improved. The above-mentioned publication describes that a long life and high image quality can be achieved by forming a film for curing a resin having a hydroxyl group and a melamine resin. JP-A-62-187863
Japanese Patent Application Publication No. JP-A-2005-17764 claims high durability and high image quality as compared with non-coated. JP-A-62-262057 discloses that a long life and high image quality are achieved by a high resistance carrier having a high coating strength.

However, conventional resin-coated carriers still have problems in durability, heat resistance and environmental resistance, and improvement of their properties is desired. For the purpose of improving the ability to impart triboelectric charge, guanamine, a guanamine derivative or a guanamine-based condensate is coated with the coating resin 1.
A carrier in which the core material is coated with a coating resin containing 0.1 to 20 parts by weight with respect to 00 parts by weight has been proposed (Japanese Patent Application Laid-Open No. Sho.
However, it was not possible to maintain a sufficient charge amount for a long period of time.

In order to improve these disadvantages, 40
There has been proposed a carrier coated with a thermosetting resin composed of a guanamine resin in an amount of at least% by weight and a second resin having a functional group capable of reacting and crosslinking with the guanamine resin. Although this carrier is a hard carrier that is excellent in environmental stability and is hard to be scraped, it is still difficult to say that the spent resistance has not been sufficiently solved (see JP-A-8-6307).

[0012]

SUMMARY OF THE INVENTION Accordingly, the present invention has an ability to solve the above-mentioned drawbacks, suppress the effect of toner spent on the carrier surface, and stably provide the toner with optimal chargeability. It is an object of the present invention to provide an electrophotographic carrier capable of maintaining its ability for a long period of time and a method for producing the same. In particular, the effect is remarkably exhibited by using a soft and elastic resin as the coating resin.

[0013]

The object of the present invention is to provide an electrophotographic carrier coated with a resin having a plastic deformation of at least 0.5 μm and an elastic deformation of at least 0.5 μm by a Knoop indenter. , (2) "for electrophotography comprising a core material coated with a resin which has at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or melamine derivative having a degree of polymerization of 2 or less and has been subjected to a curing reaction. Carrier ", (3)" the content ratio of the at least unreacted hydroxyl group-containing acrylic resin to the completely alkyl-substituted melamine or melamine derivative having a polymerization degree of 2 or less is 50:50 to 90:10 (weight ratio). The electrophotographic carrier according to the above (2), "
(4) The above item (2) or (3), wherein the hydroxyl value of the acrylic resin having at least an unreacted hydroxyl group is 150 (KOH mg / g) or less.
(5) The electrophotographic carrier according to (4), wherein the hydroxyl value of the acrylic resin having at least unreacted hydroxyl group is 20 to 120 (KOHmg / g). The described electrophotographic carrier ",
(6) “The electrophotographic carrier according to any one of the above (2) to (5), wherein the thickness of the resin film is 0.1 to 0.5 μm”, (7) ) "Acrylic resin having at least unreacted hydroxyl group and degree of polymerization 2
The above-mentioned (2) to (2), wherein the core substance is coated with a resin coating containing carbon black as a conductive material in a resin containing the following completely alkyl-substituted melamine or a melamine derivative. (6) The carrier for electrophotography according to any one of (6) and (8) in a resin containing an acrylic resin having at least an unreacted hydroxyl group and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less. Wherein the core material is coated with a resin coating containing carbon black as a conductive material.

[0014] The object of the present invention is to provide (9) a resin comprising a resin containing at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less, and subjected to a curing reaction; (10) A content ratio of at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or guanamine derivative having a degree of polymerization of 2 or less to 60:40 to 90. : 10
(9) The carrier for electrophotography according to the item (9), wherein the hydroxyl value of the acrylic resin having at least an unreacted hydroxyl group is 120 (KOHmg / g). (9) or (10), wherein the acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 20 to 100.
(KOH mg / g).
(1) The electrophotographic carrier according to the item (1), (13) any of the above items (9) to (12), wherein the resin film has a thickness of 0.1 to 0.5 μm. (14) "Carbon black as a conductive material in a resin containing an acrylic resin having at least an unreacted hydroxyl group and a completely alkyl-substituted guanamine or guanamine derivative having a degree of polymerization of 2 or less." (15) The electrophotographic carrier according to any one of (9) to (13), wherein the core material is coated with a resin coating containing Carbon black as a conductive material must not be contained in a resin containing an acrylic resin having a hydroxyl group in the reaction and a completely alkyl-substituted guanamine or guanamine derivative having a degree of polymerization of 2 or less. In the resin coating is achieved by the electrophotographic color carrier "which is characterized by comprising coating the core substance.

Another object of the present invention is to provide (16) an electron curable resin which contains at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a polymerization degree of 2 or less. (17) "The content ratio of at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or melamine derivative having a polymerization degree of 2 or less to 50:50 to 90:10 (weight ratio) (18) The coating material for an electrophotographic carrier according to the above (16), wherein the acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 150.
(KOH mg / g) or less, the coating material for an electrophotographic carrier according to the above (16) or (17), "(19)" an acrylic resin having at least an unreacted hydroxyl group. Has a hydroxyl value of 20 to 12
0 (KOHmg / g), the coating material for an electrophotographic carrier according to the above (18), "
(20) "A resin comprising at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, containing carbon black as a conductive material. (16) The coating material for an electrophotographic carrier according to any one of the above items (16) to (19) ", (21)" an acrylic resin having at least an unreacted hydroxyl group and a completely alkyl-substituted resin having a polymerization degree of 2 or less. It is achieved by a "color electrophotographic carrier coating material characterized by comprising carbon black as a conductive material in a resin containing melamine or a melamine derivative."

Another object of the present invention is to provide an electrophotography (22) of the present invention which comprises an acrylic resin having at least an unreacted hydroxyl group and a completely alkyl-substituted guanamine or a guanamine derivative having a polymerization degree of 2 or less, and cured by heating. "Carrier coating material", (23) "the content ratio of at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or guanamine derivative having a degree of polymerization of 2 or less to 60:40 to 90:10 (weight ratio). The coating material for an electrophotographic carrier according to the above item (22) ", (24)" the acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 1;
20 (KOHmg / g) or less, the coating material for an electrophotographic carrier according to the above (22) or (23), "(25)" an acryl having at least unreacted hydroxyl group. The hydroxyl value of the resin is 20 to
100 (KOHmg / g), the coating material for an electrophotographic carrier according to the above (24), "
(26) A resin characterized by comprising carbon black as a conductive material in a resin containing at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less. The coating material for an electrophotographic carrier according to any one of the above items (22) to (25) ", (27)" an acrylic resin having at least an unreacted hydroxyl group and a completely alkyl-substituted resin having a polymerization degree of 2 or less. A coating material for a color electrophotographic carrier, characterized by comprising carbon black as a conductive material in a resin containing guanamine or a guanamine derivative.

Further, the above object is achieved by (28) the present invention, wherein the core substance is coated with a resin containing an acrylic resin having at least unreacted hydroxyl groups and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less. rear,
The method for producing an electrophotographic carrier according to any one of the above items (2) to (8), which comprises a curing reaction ”and (29)“ polymerization with an acrylic resin having at least an unreacted hydroxyl group ”. The electron according to any one of the above items (9) to (15), wherein the core material is coated with a resin containing a completely alkyl-substituted guanamine or a guanamine derivative having a degree of 2 or less, and then subjected to a curing reaction. A method for producing a photographic carrier ".

The object of the present invention is to provide (30) a toner for electrophotography according to any one of the above items (1) to (15), wherein the toner comprises at least a binder resin and a pigment. An electrophotographic developer characterized by containing a carrier "
Achieved by

Further, the above object is achieved by (31) a "container filled with the developer for electrophotography described in (30)" of the present invention.

Further, the above object is attained by (32) an image forming apparatus characterized by mounting a container filled with the electrophotographic developer according to the above (31). .

That is, in the first invention, the plastic deformation by the Knoop indenter is 0.5 μm or more and the elastic deformation is 0.5
An electrophotographic carrier coated with a resin of not less than μm is used. In the first aspect of the present invention, the plastic deformation by the Knoop indenter is 0.5 μm or more and the elastic deformation is 0.5
By using a resin having a thickness of not less than μm, a soft and hard-to-cut resin film is formed on the carrier surface to achieve a long life. More preferably, the amount of plastic deformation is 1.5 μm or more,
The elastic deformation amount is 1.0 or more. The equipment used at this time is a Shimadzu Dynamic Ultra Micro Hardness Tester (DUH-201,
Shimadzu Corporation). The measurement conditions are shown below.

Test MODE: 2 (load-removal test) Conditions (1) Indenter: Knoop (2) Load: 5 gf (3) Load speed: 5 (coefficient) (4) Holding time: 5 seconds (at maximum load) ( 5) Measured value: average of three measurements Measured under these conditions, and measured the plastic deformation and elastic deformation at that time.

Sample Preparation Method A resin to be measured is uniformly coated on an aluminum plate to a thickness that can be measured under the above conditions. The plastic deformation amount, which is the measured value, is 0.
A carrier coated with a resin having a thickness of 5 μm or more and an elastic deformation amount of 0.5 μm or more is suitable for a long life because the film is hardly shaved. If the amount of plastic deformation is less than 0.5, the film is easily scraped, and if the amount of elastic deformation is less than 0.5, problems such as cracking and peeling of the resin due to the impact of a collision between the developers occur, resulting in a longer life. Cannot be achieved. The resin used in the first invention may be any resin, as long as the plastic deformation and the elastic deformation are 0.5 μm or more.

According to a second aspect of the present invention, there is provided a resin containing at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, as a core material of ferrite or magnetite carrier particles. Using a carrier coated with
The second invention uses a carrier in which ferrite or magnetite carrier particles are coated with a resin containing at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine having a degree of polymerization of 2 or less. .

In the second aspect of the present invention, melamine includes a complete alkyl type, a methylol group type, an imino type, and a methylol / imino type. Among these, a perfect alkyl type is preferred for crosslinking with an alkyl resin. The reason for this is that this type hardly undergoes self-condensation during the curing reaction, and the crosslinking reaction with the acrylic resin occurs, resulting in a relatively soft coating film. The second feature of the present invention resides in that the film is soft, and the spent film is hardly scraped because the film is soft. However, care must be taken when the temperature for the curing reaction is too high because of the nature of self-condensation. The imino type is more likely to undergo self-condensation and harder to form a dense crosslink than the complete alkyl type, but forms a hard coating. Although the methylol group type is almost the same as the imino type, it is not preferable in terms of safety because a formalin reaction occurs upon heating. If the reaction is not completely completed, the methylol group remains and the environmental stability is extremely deteriorated. The methylol / imino form naturally has the properties of both the methylol form and the imino form.

The completely alkyl melamine used in the second invention has the following formula.

[0027]

Embedded image (X _{1 to} X ₆ are any of methoxymethyl, ethoxymethyl, propoxymethyl, and butoxymethyl groups.)

[0028]

Embedded image

The completely alkyl melamine used in the second invention has a degree of polymerization of 2 or less in order to form a dense crosslinked structure. When a polymer having a high degree of polymerization is used, the same result as when self-condensation has proceeded is obtained. Melamine in the second invention is 2,4,6-triamino-1,3,3.
It is obtained by reacting an adduct of 5-triazine and formaldehyde with a lower alcohol such as methanol, ethanol, propanol and butanol. The use of a completely alkyl-type melamine can provide a relatively soft and dense crosslinked structure as described above, but on the other hand, it is difficult to design such as setting the mixing ratio of the acrylic resin and melamine and setting the curing temperature. Particularly, it is suitable as a carrier coating resin when the content ratio with a completely alkyl-substituted melamine or a melamine derivative is 50:50 to 90:10. If the melamine derivative is added in excess of this ratio, the rate of self-condensation increases and the film becomes hard, which is not preferable. On the other hand, if the amount is too small, the crosslinking is sparse, resulting in a film having low strength, which causes a problem in durability. As described above, the carrier particles according to the second aspect of the present invention cover at least a resin containing an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine having a degree of polymerization of 2 or less. Guanamine includes a completely alkyl type, a methylol group type, an imino type, and a methylol / imino type. Among these, a perfect alkyl type is preferred for crosslinking with an alkyl resin. The reason for this is that this type hardly undergoes self-condensation during the curing reaction, and the crosslinking reaction with the acrylic resin occurs, resulting in a relatively soft coating film.

The third feature of the present invention is that, while making use of the softness of the acrylic resin, by forming a dense crosslinked structure with guanamine, it is hard to scrape even though it is soft.
Furthermore, it is difficult to spend. However, care must be taken when the temperature for the curing reaction is too high because of the nature of self-condensation. The imino type is more likely to undergo self-condensation and harder to form a dense crosslink than the complete alkyl type, but forms a hard coating. Although the methylol group type is almost the same as the imino type, it is not preferable in terms of safety because a formalin reaction occurs upon heating. If the reaction is not completely completed, the methylol group remains and the environmental stability is extremely deteriorated. The methylol / imino form naturally has the properties of both the methylol form and the imino form.

The completely alkyl-substituted guanamine used in the third invention has the following formula.

[0032]

Embedded image (X ₁ is an alkyl group or a phenyl group, and X _{2 to} X ₅ are any of a methoxymethyl, ethoxymethyl, propoxymethyl, and butoxymethyl group.)

[0033]

Embedded image

Further, the completely alkyl-substituted guanamine used in the third aspect of the present invention has a degree of polymerization of 2 or less in order to form a dense crosslinked structure. When guanamine having a high degree of polymerization is used, a cluster structure is easily formed together with self-condensation, and the resin tends to be hard and brittle. Guanamine in the third aspect of the present invention is obtained by reacting an adduct of 4,6-diamino-1,3,5-triazine with formaldehyde and a lower alcohol such as methanol, ethanol, propanol or butanol.

When a fully alkyl-substituted guanamine is used, a relatively soft and dense crosslinked structure can be obtained as described above, but on the other hand, it is difficult to design such as the mixing ratio of the acrylic resin and guanamine and the setting of the curing temperature. In particular, it is suitable as a carrier coating resin when the content ratio with fully alkyl-substituted guanamine is 60:40 to 90:10. If guanamine is added in excess of this ratio, the rate of self-condensation increases, and the film becomes hard, which is not preferable.
On the other hand, if the amount is too small, the crosslinking is sparse, resulting in a film having low strength, which causes a problem in durability.

On the other hand, the acrylic resin used in the present invention needs a functional group reactive with melamine and a functional group reactive with completely alkyl-substituted guanamine. As a result of intensive studies, it was found that a hydroxyl group was most suitable. Acrylic resin is
Any polymer containing at least a monomer having a hydroxyl group may be used. For example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
Hydroxybutyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate, ε-caprolactone adduct of hydroxyethyl (meth) acrylate,
Examples thereof include ethylene and propylene adducts of hydroxyethyl (meth) acrylate.

Other copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
Acrylics such as tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, tridecyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and dimethylaminoethyl (meth) acrylate Esters of acids and methacrylic acid can be used. Other copolymerizable monomers include styrene, α-methylstyrene, vinyltoluene,
Acrylonitrile, methacrylonitrile, vinyl acetate,
Examples include vinyl propionate, acrylamide, methacrylamide, methylolacrylamide, vinyl chloride, propylene, ethylene and the like.

In the second aspect of the present invention, it is also preferable to use an acrylic resin having a hydroxyl value of 150 (KOH mg / g) or less in order to suppress environmental fluctuation of the charge amount. When the hydroxyl value exceeds 150 (KOHmg / g),
Inevitably, many unreacted hydroxyl groups remain. More preferably, the hydroxyl value is 20 to 120 (KOHmg /
g). When the hydroxyl value is less than 20, the crosslink density becomes low and the film strength decreases. In order to suppress environmental fluctuation, it is more effective to set the hydroxyl value to 120 or less.

In the third aspect of the present invention, it is also important to use an acrylic resin having a hydroxyl value of 120 (KOH mg / g) or less in order to suppress environmental fluctuation of the charge amount. If the hydroxyl value exceeds 120 (KOH mg / g), many unreacted hydroxyl groups remain. More preferably, the hydroxyl value is 20 to 100 (KOHmg
/ G). When the hydroxyl value is less than 20, the crosslink density becomes low and the film strength decreases. In order to suppress environmental fluctuations, it is more effective to set the hydroxyl value to 100 or less.

The acrylic resin can be synthesized by a conventional method, and can be produced by any known polymerization method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method. At that time, azobisisobutyronitrile, 4,4′-azobis (4-cyanopentanoic acid), benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, cumene hydroperoxide, Potassium persulfate, hydrogen peroxide,
2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propioamide] and the like can be used. If necessary, dodecyl mercaptan, mercaptoethanol, α-methylstyrene dimer and the like can be used as a chain transfer agent. Can be used.

Further, by using this material, it is possible to make the thickness of the coating resin 0.1 to 0.5 μm.
When the film thickness is smaller than 0.1 μm, it is natural that the resistance is extremely lowered because of the influence of the core material, which is not preferable. Since the resin is extremely less abraded than a conventionally used silicone resin, the film does not have to be thick even for a long service life. When the film is thick, not only does the material cost increase, but also problems such as agglomeration of carriers during coating and a decrease in productivity occur. Further, since the film thickness can be reduced, the fluidity of the carrier is improved, and the effect of preventing spent can be obtained.

Further, by using a completely alkyl-substituted melamine or a completely alkyl-substituted guanamine having a polymerization degree of 2 or less, it becomes easy to incorporate an additive into the resin. In particular, it becomes easy to uniformly disperse the carbon black in the coating resin. This means that when dispersing acrylic resin and melamine or guanamine and carbon black, melamine or guanamine is uniformly dispersed in the liquid,
Further, it is considered that the compound is uniformly present without a crosslinking reaction during coating. Further, this carrier can be used as a carrier for a color developer because carbon black is uniformly dispersed in the resin and the present coating resin has excellent abrasion resistance. In particular, even when used for a yellow developer carrier that is sensitive to color stain, no color stain occurs. Carbon black used as an additive may be any of commercially available furnace black, channel black, acetylene black, and the like.
What is suitable for desired charging, resistance and the like may be used.

As the magnetic core material that can be used, generally ferrite particles and magnetite particles having a substantially spherical shape can be used. The particle size of the core material is usually 20 to 100 μm.
m can be used, but the effect of using the present coating resin is particularly large when the particle diameter is small. This is because the present resin is excellent in abrasion resistance, so that a thin film coating is possible.

The method for producing the carrier according to the second and third aspects of the present invention is performed by a general coating method. For example, an immersion method, a flow method, or the like is used. Thereafter, the carrier is heated at a curing temperature or higher to produce a carrier.

The coating material for a carrier according to the present invention described in the above items (16) to (27) varies depending on the material composition and the composition ratio. For example, the carrier coating material may be in the form of a solution using a solvent or in the form of a dispersion. The core material can be easily and uniformly coated by a known coating method such as spraying, and cured by heating and drying to produce a carrier having a strong coating layer. No crosslinking reaction occurs at the time of core material coating. Therefore, there is no need to perform a heat treatment immediately after coating as in the case of a thermosetting silicone resin-coated carrier. In addition, since the thermal crosslinking can be controlled in a single step, the variation in the quality of the coated carrier can be suppressed.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner has a colorant dispersed in a binder resin. Examples of the binder resin used for the toner include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, and n- (meth) acrylate.
Α-methylene aliphatic monocarboxylic esters such as -propyl, lauryl (meth) acrylate and 2-ethylhexyl (meth) acrylate; vinyl nitriles such as (meth) acrylonitrile; 2-vinylpyridine and 4-vinylpyridine Vinyl pyridines such as vinyl methyl ether and vinyl isobutyl ether;
Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone: Monomers such as unsaturated hydrocarbons such as ethylene, propylene, isoprene, butadiene and their halides, and halogenated unsaturated hydrocarbons such as chloroprene Polymer, or a copolymer obtained by combining two or more of these monomers, further a mixture thereof, a rosin-modified phenol formalin resin, an epoxy resin, a polyester resin,
Polyurethane resin, polyamide resin, cellulose resin,
Examples thereof include non-vinyl condensation resins such as polyether resins, and mixtures of these with the above-mentioned vinyl resins.

As the colorant used in the toner, all known dyes and pigments can be used, for example, carbon black,
Nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow,
Yellow iron oxide, loess, graphite, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, R
N, R), Pigment Yellow L, Benzidine Yellow (G, GR), Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazin Yellow B
GL, Isoindolinone Yellow, Bengala, Lead Tan, Lead Zhu, Cadmium Red, Cadmium Mercury Red,
Antimony Vermilion, Permanent Red 4R, Para Red,
Faise Red, Parachlor Ortho Nitroaniline Red, Risor Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine Min BS,
Permanent red (F2R, F4R, FRL, FRL
L, F4RH), Fast Scarlet VD, Belcan Fast Rubin B, Brilliant Scarlet G, Lisor Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F
2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Museum, Eosin Lake,
Rhodamine lake B, rhodamine lake Y, alizarin lake, thioindigo red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, polyazo red, chrome vermilion, benzidine orange, perinone orange, oil orange, cobalt blue, cerulean blue , Alkaline blue lake, peacock blue lake, Victoria blue lake, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue, indanthrene blue (R
S, BC), indigo, ultramarine, navy blue, anthraquinone blue, fast violet B, methyl violet lake, cobalt violet, manganese violet, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalocyanine Green, Anthraquinone Green, Titanium Oxide, Zinc White, Lithobon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight based on 100 parts by weight of the binder resin.

The toner of the present invention may contain a charge control agent for reinforcement as required. As the charge control agent for reinforcement, any known charge control agents can be used. For example, nigrosine dye, triphenylmethane dye, chromium-containing metal complex dye, molybdate chelate pigment, rhodamine dye, alkoxy amine, quaternary ammonium Salts (including fluorinated quaternary ammonium salts), alkyl amides, simple substances or compounds of phosphorus, simple substances or compounds of tungsten, fluorine-based activators, salicylic acid metal salts, and
Metal salts of salicylic acid derivatives. More specifically, Nigrosine dye Bontron 03, quaternary ammonium salt Bontron P-51, metal-containing azo dye Bontron S-
34, E-82 of oxynaphthoic acid-based metal complex, E-84 of salicylic acid-based metal salt, E-8 of phenol-based condensate
9, TP-302 and TP-415 of quaternary ammonium salt molybdenum complex
(Above, manufactured by Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy charge PSY VP2038, triphenylmethane derivative copy blue PR, quaternary ammonium salt copy charge NEG VP2036, copy charge NX VP434 (above, Hoechst) Company), L
RA-901, LR-147 which is a boron complex (manufactured by Nippon Carlit Co., Ltd.), copper phthalocyanine, perylene, quinacridone, azo pigments, and other polymer systems having functional groups such as sulfonic acid groups, carboxyl groups, and quaternary ammonium salts. The compound of.

In the present invention, the amount of the reinforcing charge control agent used is determined by the toner production method including the amount of the main charge control agent, the type of the binder resin, the presence or absence of additives used as required, and the dispersion method. Although it is not particularly limited, it is preferably used in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin. Preferably, the range is 0.3 to 5 parts by weight. Of course, an anti-offset agent, a flow improver and the like may be appropriately added. An external additive such as a fluidizing agent such as silica, titania, and alumina, a cleaning aid such as polystyrene fine particles, polymethyl methacrylate fine particles, and polyvinylidene fluoride fine particles, or a transfer aid can be used. In particular, hydrophobic silica having a primary average particle size of 5 to 30 nm is preferably used. In addition, other known components such as low molecular weight polypropylene, low molecular weight polyethylene, and an offset preventing agent such as wax can be added as an offset preventing agent. Preferably the weight average molecular weight is 500 to 500
Zero low molecular weight polypropylene is preferred. As for the particle diameter of the toner, the smaller the diameter is, the higher the image quality is, and the better is 5 to 12 μm, preferably about 5 to 10 μm.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of an image forming apparatus in which a container filled with the electrophotographic developer of the present invention is mounted, and a developing section (1) mounted in an image forming apparatus main body; FIG. 3 is a partial cross-sectional view showing a developer container (2) filled with the electrophotographic developer of the present invention to be supplied to the developing section (1) and a developer feeding means (3) connecting the two. .

In FIG. 1, a developing section (1) is a developing housing filled with the electrophotographic developer of the present invention containing a liquid two-component developer (D) formed by mixing a toner and a carrier. (4), first and second stirring screws (5) and (6) for stirring and mixing the developer (D), and a developing roller (7).
Are arranged to face the photoconductor (8) of the latent image carrier. The photoconductor (8) is driven to rotate in the direction indicated by the arrow,
An electrostatic latent image is formed on the surface. Reference symbol (26) in the figure
Is a connecting member (2) fixed to the developer receiving port (23).
4) A cap fitted over or without a filter (25). Around the photoreceptor (8), charging means, exposure means, transfer means, and static elimination means (not shown)
Other known units such as a cleaning unit are arranged.

A first and a second stirring screw (5),
The rotation of (6) agitates the developer (D) in the developing housing (4), and the carrier is frictionally charged with the toner to the opposite polarity. Such a developer (D) is
The developer is supplied to the peripheral surface of the developing roller (7) which is driven to rotate in the direction of the arrow, and the supplied developer is carried on the peripheral surface of the developing roller (7).
It is conveyed in the rotation direction. Next, the amount of the conveyed developer is regulated by the doctor blade (9), and the regulated developer is transferred to the photoconductor (8) and the developing roller (7).
And the toner in the developer is electrostatically transferred to the electrostatic latent image on the photoreceptor surface, and the electrostatic latent image is visualized as a toner image. .

[0053]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited by these examples. In the examples, “parts” means parts by weight.

[First Resin Coated Carrier] (Toner Production Example 1) 100 parts by weight of styrene-n-butyl methacrylate resin 8 parts by weight of carbon black (MA # 8, manufactured by Mitsubishi Kasei Co., Ltd.) 8 parts by weight of charge control agent 3 parts by weight of Tsuchiya Chemical Co., Ltd .; Spiron Black TRH) 3 parts by weight of an anti-offset agent (manufactured by Sanyo Chemical Industry Co., Ltd .; VISCOL 550P) 3 parts by weight The above materials were kneaded and pulverized to obtain toner particles having an average particle size of 7.5 μm. Then, 100 parts of the toner and 0.7% of hydrophobic silica R-972 (manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer to obtain a toner for evaluation.

(Toner Production Example 2) Yellow toner formulation: 100 parts of polyester resin (Mn: 3850, Mw / Mn: 7.0, Tg: 62 ° C., softening point: 125 ° C., acid value: 15) 100 parts: Yellow pigment (Novoperm Yellow P-HG manufactured by Clariant Japan Co., Ltd.) 5 parts • Zinc salicylate (Bontron E-84 manufactured by Orient Chemical Co.) 1.5 parts After pulverizing and classifying the above material to an average particle diameter of 7.5 μm, 100 parts of toner and Toner was obtained by mixing 0.7 parts of hydrophobic silica HDK2000H (manufactured by Clariant Japan KK).

Example of First Carrier Example 1 Example of Synthesis of Acrylic Resin Having Hydroxyl Group Xylene 70 was stirred in a nitrogen stream while stirring with a stirrer.
0 g and n-butanol 300 g were added, and the temperature was raised to 100 ° C., styrene 400 g, methyl methacrylate 160
g, 110 g of i-butyl methacrylate, 200 g of n-butyl acrylate, 30 g of methacrylic acid, 100 g of 2-hydroxyethyl acrylate and 10 g of azobisisobutyronitrile as a polymerization initiator were added dropwise over 5 hours. Thereafter, the content was further reacted for 6 hours to obtain a resin having a solid content of about 50%. (Hydroxyl value: 41
(KOHmg / g), number average molecular weight 14000)

Cu—Zn ferrite (manufactured by Powder Tech, average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (the above synthetic product) 10 parts Toluene 300 parts The above methylated melamine, acrylic resin and toluene were mixed to prepare a coating solution. The temperature of the fluidized bed coating apparatus into which the ferrite was charged was maintained at about 60 ° C., and the coating liquid was sprayed. After the spraying was completed, it was dried for about 10 minutes and taken out. Next, this carrier is placed in an electric furnace for 1 hour.
Treated at 50 ° C for 1 hour, crushed after cooling, and 0.2 µm thick
Was obtained.

The carriers of Examples and Comparative Examples were manufactured in the same manner. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Comparative Example 1] Cu-Zn ferrite (manufactured by Powdertech Co., average particle size 50 μm, F-300) 1000 parts Silicon resin (Toray Dow Corning Silicone SR-2411) 150 parts Toluene 150 parts The above silicon The resin and toluene were mixed to prepare a coating solution. The temperature of the fluidized bed coating apparatus into which the ferrite was charged was maintained at about 80 ° C., and the coating liquid was sprayed. After the spraying was completed, it was dried for about 10 minutes and taken out. Next, this carrier was treated in an electric furnace at 200 ° C. for 2 hours, cooled, and crushed to obtain a resin-coated carrier having a film thickness of 0.8 μm. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Example 2] Cu-Zn ferrite (manufactured by Powder Tech Co., average particle size 50 µm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 3.5 Part Acrylic resin (hydroxyl value 41, solid content 50%) 7 parts Toluene 300 parts This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation. .

[Example 3] Cu-Zn ferrite (manufactured by Powder Tech Co., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 0.7 Part Acrylic resin (hydroxyl value 41, solid content 50%) 12.6 parts Toluene 300 parts This carrier and the toner of Production Example 1 were mixed with a turbuler mixer so that the toner concentration became 4%, and the developer for evaluation was mixed. Created.

Example 4 A resin having a hydroxyl value of 147 (KOH mg / g) was synthesized from the acrylic resin of Example 1 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (hydroxyl value 147 solid content 50) %) 10 parts Toluene 300 parts This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 5 A resin having a hydroxyl value of 116 (KOH mg / g) was synthesized from the acrylic resin of Example 1 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (hydroxyl value 116 solid content 50 %) 10 parts Toluene 300 parts This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 6 A resin having a hydroxyl value of 28 (KOH mg / g) was synthesized from the acrylic resin of Example 1 by reducing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (hydroxyl value 28 solid content 50) %) 10 parts Toluene 300 parts This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 7 A resin having a hydroxyl value of 15 (KOH mg / g) was synthesized from the acrylic resin of Example 1 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (hydroxyl value 15 solid content 50) %) 10 parts Toluene 300 parts The preparation method was the same as in Example 1. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Example 8] 1000 parts of Cu-Zn ferrite (manufactured by Powder Tech Co., average particle diameter 50 μm, F-300) 1000 parts of completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic Resin (hydroxyl value 41, solid content 50%) 10 parts Printex 90 (manufactured by Degussa) 0.1 part Toluene 300 parts Methylated melamine, acrylic resin, toluene and carbon black were dispersed for 10 minutes by a homomixer, and coating was performed. . Thereafter, the same operation as in Example 1 was performed to prepare a carrier. This carrier and the toner of Production Example 2 were mixed with a turbuler mixer to a toner concentration of 6% to prepare a developer for evaluation.

[Comparative Example 2] Cu-Zn ferrite (manufactured by Powder Tech Co., Ltd., average particle size 50 µm, F-300) 1000 parts Completely substituted methylated melamine (degree of polymerization 2.30, solid content 100%) 2 parts Acrylic Resin (hydroxyl value 41, solid content 50%) 10 parts Toluene 300 parts The production method was the same as in Example 1. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Comparative Example 3 1000 parts of Cu-Zn ferrite (manufactured by Powder Tech, average particle size 50 μm, F-300) 4 parts Acrylic completely substituted methylated melamine (degree of polymerization 1.70, solid content 100%) Resin (hydroxyl value 41, solid content 50%) 6 parts Toluene 300 parts The production method was the same as in Example 1. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Comparative Example 4 Cu-Zn Ferrite (Powdertech, average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (degree of polymerization 1.70, solid content 100%) 0.35 Part Acrylic resin (hydroxyl value 41, solid content 50%) 13.3 parts Toluene 300 parts The production method was the same as in Example 1. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Comparative Example 5 A resin having a hydroxyl value of 163 (KOH mg / g) was synthesized from the acrylic resin of Example 1 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (manufactured by Powder Tech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated melamine (polymerization degree 1.70, solid content 100%) 2 parts Acrylic resin (hydroxyl value 163 solid content 50) %) 10 parts Toluene 300 parts The preparation method was the same as in Example 1. This carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Comparative Example 6] The carrier of Example 1 and the toner of Production Example 2 were mixed with a turbuler mixer to a toner concentration of 6% to prepare a developer for evaluation.

[Evaluation Method] (Sample Preparation Method) The coating resins of Examples 1, 9 and Comparative Example 1 were applied to an aluminum plate so as to have a thickness of about 5 μm.
Each sample was subjected to a heat treatment under the same conditions as in the examples and comparative examples.

(Measurement Method) This sample is measured with a Shimadzu Dynamic Ultra Micro Hardness Tester (DUH-201, manufactured by Shimadzu Corporation). The measurement conditions are shown below. Test MODE: 2 (load-removal test) Conditions (1) Indenter: Knoop (2) Load: 5 gf (3) Load speed: 5 (coefficient) (4) Holding time: 5 seconds (at maximum load) (5) Measurement Value: average of three measurements Measured under these conditions, and measured the plastic deformation and elastic deformation at that time. Table 1 shows the results.

[0074]

[Table 1]

(Evaluation method) Image M manufactured by Ricoh Company
The durability test of 10,000 sheets was performed using the F250 modified machine,
And the state of the coating resin of the carrier was observed by SEM.
As a result, the carriers of Examples 1 and 9 were not shaved at all, but only the carrier of Comparative Example 1 was found to have shaved coat films. Examples 1 to 7 and Comparative Examples 2 to 5 are Ricoh I
A durability test was performed using a modified Magio MF250 machine, and the state of the coating resin of the carrier was observed with an SEM. The results are shown in Table 2. Example 8 and Comparative Example 6
In Table 3, a change in color tone due to desorption of carbon from the carrier was evaluated in Table 3 by taking 1,000 sheets of images using Ricoh's PRETER550. Evaluation method: L, a *, b * at ID 1.0 were measured by X-write 938.

[0076]

[Table 2] ◎: very good ○: good △: acceptable level ×: bad

The decrease in the amount of charge in 50,000 copies is caused by scraping of the carrier film or by toner spent on the carrier. Carriers having no problem in observation of the coat state and having a reduced charge amount were caused by spent. From the results of the above examples, it is possible to design a carrier that balances durability and environmental stability by using the polymerization degree of melamine, the ratio of acrylic resin / melamine, and the hydroxyl value of acrylic resin in specific ranges. Becomes

[0078]

[Table 3]

[Second Resin Coated Carrier] (Toner Production Example 3) 100 parts by weight of styrene-n-butyl methacrylate resin 8 parts by weight of carbon black (manufactured by Mitsubishi Kasei Co., Ltd., MA # 8) 8 parts by weight of charge control agent 3 parts by weight of Tsuchiya Chemical Co., Ltd .; Spiron Black TRH) 3 parts by weight of an anti-offset agent (manufactured by Sanyo Chemical Industry Co., Ltd .; VISCOL 550P) 3 parts by weight The above materials were kneaded and pulverized to obtain toner particles having an average particle size of 7.5 μm. Then, 100 parts of the toner and 0.7% of hydrophobic silica R-972 (manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer to obtain a toner for evaluation.

(Toner Production Example 4) Yellow toner formulation: 100 parts of polyester resin (Mn: 3850, Mw / Mn: 7.0, Tg: 62 ° C., softening point: 125 ° C., acid value: 15) 100 parts: Yellow pigment (Novoperm Yellow P-HG manufactured by Clariant Japan Co., Ltd.) 5 parts • Zinc salicylate (Bontron E-84 manufactured by Orient Chemical Co.) 1.5 parts After pulverizing and classifying the above material to an average particle diameter of 7.5 μm, 100 parts of toner and Toner was obtained by mixing 0.7 parts of hydrophobic silica HDK2000H (manufactured by Clariant Japan KK).

[Example of Second Carrier] [Example 9] Example of Production of Carrier Example of Synthesis of Acrylic Resin Having Hydroxyl Group Xylene 70 was stirred in a nitrogen stream while stirring with a stirrer.
0 g and n-butanol 300 g were added, and the temperature was raised to 100 ° C., styrene 400 g, methyl methacrylate 160
g, 110 g of i-butyl methacrylate, 200 g of n-butyl acrylate, 30 g of methacrylic acid, 100 g of 2-hydroxyethyl acrylate and 10 g of azobisisobutyronitrile as a polymerization initiator were added dropwise over 5 hours. Thereafter, the content was further reacted for 6 hours to obtain a resin having a solid content of about 50%. (Hydroxyl value: 41
(KOHmg / g, number average molecular weight 14000)

Cu-Zn ferrite (manufactured by Powder Tech Co., Ltd., average particle diameter 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (above) Synthetic product Solid content 50%) 10 parts Toluene 300 parts The above methylated guanamine, acrylic resin and toluene were mixed to prepare a coating solution. The temperature of the fluidized bed coating apparatus into which the ferrite was charged was maintained at about 60 ° C., and the coating liquid was sprayed. After spraying, about 10
It was dried for a minute and removed. Next, this carrier is treated in an electric furnace at 150 ° C. for 1 hour, and then cooled and crushed to obtain a film having a thickness of 0.2 μm.
m of resin-coated carriers were obtained. In the same manner, carriers of Examples and Comparative Examples were prepared in the same manner. This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 10 Cu-Zn Ferrite (Powdertech, average particle size 50 μm, F-300) 1000 parts Fully substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 3.6 Part Acrylic resin (hydroxyl value 41, solid content 50%) 8.4 parts Toluene 300 parts This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4%, and the developer for evaluation was mixed. Created.

Example 11 Cu-Zn Ferrite (Powdertech, average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 0.9 Part Acrylic resin (hydroxyl value 41, solid content 50%) 12.6 parts Toluene 300 parts This carrier and the toner of Production Example 3 were mixed with a turbuler mixer so that the toner concentration was 4%, and the developer for evaluation was mixed. Created.

Example 12 A resin having a hydroxyl value of 147 (KOH mg / g) was synthesized from the acrylic resin of Example 9 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (manufactured by Powdertech, average particle size 50 m, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (hydroxyl value 147 solid) 10 parts Toluene 300 parts A toner for evaluation was prepared by mixing the carrier and the toner of Production Example 3 with a Turbuler mixer so that the toner concentration was 4%.

Example 13 A resin having a hydroxyl value of 116 (KOH mg / g) was synthesized from the acrylic resin of Example 9 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (hydroxyl value 116 solid) 10 parts Toluene 300 parts This carrier and the toner of Production Example 4 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 14 A resin having a hydroxyl value of 28 (KOH mg / g) was synthesized from the acrylic resin of Example 9 by reducing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (hydroxyl value 28 solid) 10 parts Toluene 300 parts The carrier and the toner of Production Example 1 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 15 A resin having a hydroxyl value of 15 (KOH mg / g) was synthesized from the acrylic resin of Example 9 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (manufactured by Powder Tech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (hydroxyl value 15 solid) (50% for 10 minutes) 10 parts Toluene 300 parts The preparation method was the same as in Example 8. This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Example 16 Cu-Zn Ferrite (Powdertech, average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 Part Acrylic resin (hydroxyl value 41, solid content 50%) 10 parts Printex 90 (manufactured by Degussa) 0.1 part Toluene 300 parts Methylated melamine, acrylic resin, toluene and carbon black are dispersed by a homomixer for 10 minutes, and coating is performed. Carried out. Thereafter, the same operation as in Example 1 was performed to prepare a carrier. This carrier and the toner of Production Example 4 were mixed with a turbuler mixer to a toner concentration of 6% to prepare a developer for evaluation.

[Comparative Example 7] Cu-Zn ferrite (manufactured by Powder Tech Co., Ltd., average particle size: 50 μm, F-300) 1000 parts Completely substituted butylated benzoguanamine (polymerization degree: 3.00, solid content: 70%) 2.9 Part Acrylic resin (hydroxyl value 41, solid content 50%) 10 parts Toluene 300 parts The preparation method was the same as in Example 1. This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Comparative Example 8] Cu-Zn ferrite (manufactured by Powder Tech Co., average particle size 50 µm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 4.55 Part Acrylic resin (hydroxyl value 41, solid content 50%) 7 parts Toluene 300 parts The preparation method was the same as in Example 9. This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

[Comparative Example 9] Cu-Zn ferrite (manufactured by Powder Tech, average particle size 50 µm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 0.46 Part Acrylic resin (hydroxyl value 41, solid content 50%) 13.3 parts Toluene 300 parts The preparation method was the same as in Example 9. This carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Comparative Example 10 A resin having a hydroxyl value of 163 (KOH mg / g) was synthesized from the acrylic resin of Example 9 by increasing the amount of 2-hydroxyethyl acrylate. Cu-Zn ferrite (Powdertech Co., Ltd., average particle size 50 μm, F-300) 1000 parts Completely substituted methylated benzoguanamine (polymerization degree 1.65, solid content 77%) 2.6 parts Acrylic resin (hydroxyl value 163 solid) (50% for minutes) 10 parts Toluene 300 parts The preparation method was the same as in Example 9. The carrier and the toner of Production Example 3 were mixed with a turbuler mixer to a toner concentration of 4% to prepare a developer for evaluation.

Comparative Example 11 The evaluation developer was prepared by mixing the carrier of Example 9 and the toner of Production Example 4 with a turbuler mixer so that the toner concentration became 6%.

[Evaluation Methods] Examples 9 to 15 and Comparative Examples 7 to
For No. 10, a durability test was performed using a modified Ricoh Imagio MF250 machine, and the state of the coating resin of the carrier was observed by SEM, and the results are shown in Table 4. In Example 16 and Comparative Example 11, PRETE manufactured by Ricoh Company was used.
1000 images were taken at R550, and the change in color tone due to desorption of carbon from the carrier was evaluated in Table 5. Evaluation method: L, a *, b * at the time of ID 1.0 were measured by X-write 938.

[0096]

[Table 4] ◎: very good ○: good △: acceptable level ×: bad

The decrease in the amount of charge in 50,000 copies is caused by scraping of the carrier film or by toner spent on the carrier. Carriers having no problem in observation of the coat state and having a reduced charge amount were caused by spent. From the results of the above examples, it is possible to design a carrier that balances durability and environmental stability by using the polymerization degree of guanamine, the ratio of acrylic resin / melamine, and the hydroxyl value of acrylic resin in specific ranges. Becomes

[0098]

[Table 5]

[0099]

As is apparent from the detailed and specific description, even if carbon black is added to the carrier coating resin of the present invention, the color characteristics do not change over time, and the present resin can be used. Thus, it is possible to obtain an excellent effect that it can be used as a carrier for a color developer.

[Brief description of the drawings]

FIG. 1 is a view showing a container filled with a developer for electrophotography of the present invention and an image forming apparatus equipped with the container.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing unit 2 developer storage container 3 developer feeding means 4 developing housing 5 stirring screw 6 stirring screw 7 developing roller 8 photoreceptor 9 doctor blade 23 developer receiving port 24 connection member 25 filter 26 cap D developer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kosuke Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Tomomi Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F-term (reference) 2H005 BA06 BA07 BA11 CA02 CA15 CB18 EA07 FA02

Claims (22)

[Claims] 1. The plastic deformation by a Knoop indenter is 0.5 μm.
An electrophotographic carrier coated with a resin having an elastic deformation of at least 0.5 m and an elastic deformation of at least 0.5 m. 2. A carrier for electrophotography comprising a core material coated with a resin which has at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less and has been subjected to a curing reaction. . 3. The content ratio of at least an unreacted hydroxyl-containing acrylic resin to a completely alkyl-substituted melamine or melamine derivative having a degree of polymerization of 2 or less is 50: 5.
3. The carrier for electrophotography according to claim 2, wherein the carrier is 0 to 90:10 (weight ratio). 4. An acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 150 (KOHmg /
g) The electrophotographic carrier according to claim 2, wherein: 5. An acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 20 to 120 (KOHm
g / g). The electrophotographic carrier according to claim 4, wherein 6. The carrier for electrophotography according to claim 2, wherein the resin film has a thickness of 0.1 to 0.5 μm. 7. A resin coating comprising at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, and a resin coating comprising carbon black as a conductive material. The electrophotographic carrier according to any one of claims 2 to 6, wherein the carrier is coated with a substance. 8. A resin coating comprising at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, and a resin coating comprising carbon black as a conductive material. A color electrophotographic carrier characterized by being coated with a substance. 9. A carrier for electrophotography comprising a core material coated with a resin which has at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less and has undergone a curing reaction. . 10. The content ratio of at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or guanamine derivative having a degree of polymerization of 2 or less to 6
The electrophotographic carrier according to claim 9, wherein the carrier ratio is 0:40 to 90:10 (weight ratio). 11. An acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 120 (KOH mg / kg).
g) The electrophotographic carrier according to claim 9, wherein: 12. An acrylic resin having at least an unreacted hydroxyl group has a hydroxyl value of 20 to 100 (KOH
(mg / g). The electrophotographic carrier according to claim 11, wherein 13. The resin film has a thickness of 0.1 to 0.5 μm.
The electrophotographic carrier according to any one of claims 9 to 12, wherein: 14. A core comprising a resin film containing carbon black as a conductive material in a resin containing at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less. The electrophotographic carrier according to any one of claims 9 to 13, wherein the carrier is coated with a substance. 15. A core comprising a resin film containing carbon black as a conductive material in a resin containing at least an acrylic resin having an unreacted hydroxyl group and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less. A color electrophotographic carrier characterized by being coated with a substance. 16. A core material coated with a resin containing at least an unreacted acrylic resin having a hydroxyl group and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, followed by a curing reaction. 8. A method for producing the electrophotographic carrier according to any one of 1 to 7. 17. The core material is coated with a resin containing at least an unreacted acrylic resin having a hydroxyl group and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less, followed by a curing reaction. A method for producing the electrophotographic carrier according to any one of 9 to 15. 18. A coating material for an electrophotographic carrier, comprising at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted melamine or a melamine derivative having a degree of polymerization of 2 or less, and cured by heating. 19. A coating material for an electrophotographic carrier, comprising at least an unreacted hydroxyl group-containing acrylic resin and a completely alkyl-substituted guanamine or a guanamine derivative having a degree of polymerization of 2 or less, and cured by heating. 20. An electrophotographic developer, comprising: a toner comprising at least a binder resin and a pigment; and the electrophotographic carrier according to claim 1. Description: 21. A container filled with the electrophotographic developer according to claim 20. 22. An image forming apparatus comprising a container filled with the electrophotographic developer according to claim 21.