JP2015138230A - Carrier for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrophotography that has high charge applying capacity to toner, is excellent in spent resistance, has stable chargeability even during continuous printing of a number of images, is excellent in initial charge start-up property and charge holding power, and has good adhesion to a core material and coating property; and a two-component developer for electrophotography using the carrier.SOLUTION: There is provided a carrier for electrophotography having a core material and a resin coating layer that coats the surface of the core material, where the resin coating layer contains an acrylic resin, a silicone resin, and a silicone modified acrylic resin; and when the total amount of the acrylic resin, a silicone resin, and a silicone modified acrylic resin is 100 weight%, the ratios of the acrylic resin, silicone resin, and silicone modified acrylic resin in the resin coating layer are 40 to 85 weight%, 10 to 30 weight%, and 5 to 30 weight%, respectively.

Description

  The present invention relates to an electrophotographic carrier and an electrophotographic two-component developer using the electrophotographic carrier. The carrier of the present invention is a carrier for an electrostatic latent image developer.

The electrophotographic two-component developer used in the electrophotographic system is composed of a toner and a carrier, and the carrier is mixed and stirred with the toner in the developing tank and frictionally charged to give the toner a desired charge and charge. It has a function of carrying the toner on the electrostatic latent image on the photosensitive member to form a toner image. The carrier returns to the developing tank again from the top of the magnet roll, and is again mixed and agitated with newly replenished toner and used repeatedly.
Accordingly, the carrier is required to continuously exhibit desired characteristics as a carrier in any environment during the period of use, and to give particularly stable charging characteristics.

However, the conventional two-component developer for electrophotography causes a spent phenomenon in which toner is fused to the surface of the carrier due to stress such as collision between carriers caused by stirring or friction between the developing tank and the carrier. In order to prevent such deterioration due to the spent phenomenon of the carrier, the surface of the core material has been conventionally coated with various resins. When the surface of the core material is coated with a resin, the surface of the carrier becomes smooth and the toner hardly adheres to the carrier, so that the spent phenomenon is less likely to occur. Therefore, the lifetime of the developer can be extended. Furthermore, by selecting a resin, it is possible to control the charging characteristics, electrical resistance, etc. of the carrier.
In addition, since the core material is not directly affected by the environment due to the resin coating, the physical properties of the carrier hardly change with respect to environmental resistance, for example, temperature change, humidity change and the like.
Thus, when the surface of the core material of the carrier is coated with resin, the practical characteristics are greatly improved.

Typical examples of the coating resin include acrylic resin and silicone resin, and the acrylic resin-coated carrier is highly adhesive to the core material and hardly peels off. Although it is excellent in the ability to impart charge to the toner, it has the disadvantage of poor spent resistance and charge retention.
On the other hand, silicone resin-coated carriers have low surface energy, low coefficient of friction, and excellent spent resistance, but are poor in charge imparting ability, and are susceptible to fogging when toner is replenished.

  Therefore, for the purpose of combining the characteristics of an acrylic resin-coated carrier and a silicone resin-coated carrier, a carrier using both an acrylic resin and a silicone resin has been proposed. For example, in Patent Document 1 and Patent Document 2, an acrylic resin and a silicone resin are proposed. Has been proposed that is characterized by its resin ratio. There are also proposals for grafting a silicone resin to an acrylic resin as in Patent Document 3 and proposals for producing a coating film by producing a copolymer of silanol-containing acrylic monomers as in Patent Document 4.

JP-A-11-202561 JP 2003-167389 A JP2013-003428A JP 2010-244026 A

  However, the compatibility between the acrylic resin and the silicone resin is originally poor, and it is difficult to obtain a uniform coating film that maintains the low surface energy of the silicone resin. In addition, as in Patent Documents 3 and 4, there is a concern that the characteristics of the acrylic resin may be lost by including a silicone component from the monomer.

  The object of the present invention is to provide a toner with high charge-imparting ability, excellent spent resistance, stable charging even in continuous printing of a large number of sheets, excellent initial charge start-up property and charge holding power, and core material. It is to provide a carrier for electrophotography having good adhesion and coating properties with the toner and a two-component developer for electrophotography using the carrier.

  The present invention has solved the above problems by the following technical configuration.

(1) An electrophotographic carrier having a core material and a resin coating layer covering the surface of the core material,
The resin coating layer includes an acrylic resin, a silicone resin, and a silicone-modified acrylic resin,
The ratio of the acrylic resin, silicone resin, and silicone-modified acrylic resin in the resin coating layer is 40 to 85% by weight of acrylic resin when the total amount of acrylic resin, silicone resin, and silicone-modified acrylic resin is 100% by weight. A carrier for electrophotography, wherein the silicone resin is 10 to 30% by weight and the silicone-modified acrylic resin is 5 to 30% by weight.

(2) The electrophotographic carrier as described in (1) above, wherein the glass transition temperature Tg of the acrylic resin is 80 ° C. or higher.

(3) The electrophotographic carrier as described in (1) or (2) above, wherein the acrylic resin has an acid value of 3 or less.

(4) The electrophotographic carrier according to any one of (1) to (3), wherein the resin coating layer contains carbon black and magnetite.

(5) The content of the carbon black is 1 to 15 parts by weight with respect to 100 parts by weight of the solid content of the resin in the resin coating layer, and the content of the magnetite is that of the resin in the resin coating layer. The electrophotographic carrier as described in (4) above, which is 10 to 150 parts by weight with respect to 100 parts by weight of the solid content.

(6) The resin coating layer contains an organometallic catalyst, the organometallic catalyst content X (parts by weight) with respect to 100 parts by weight of the resin solids in the resin coating layer, and the resin solids 100 in the resin coating layer Any of (1) to (5) above, wherein the content Y (parts by weight) of the silicone resin with respect to parts by weight satisfies the relational expression (Y / 5) ≦ X ≦ (Y / 2) An electrophotographic carrier as described in 1.

(7) The resin coating layer further includes a styrene-acrylic resin, and the ratio of the styrene-acrylic resin is more than 0 to 30 parts by weight with respect to 100 parts by weight in total of the acrylic resin, the silicone resin, and the silicone-modified acrylic resin. The carrier for electrophotography according to any one of (1) to (6), wherein

(8) The electron according to any one of (1) to (7), wherein the silicone-modified acrylic resin comprises methyl methacrylate and 3-methacryloxypropyltrimethoxysilane as monomer components. Photo carrier.

(9) The electrophotographic carrier according to any one of (1) to (8), wherein the silicone resin is a thermosetting silicone resin.

(10) The electrophotographic carrier according to any one of (1) to (9), wherein the dielectric breakdown voltage is 0.5 to 3.5 kV.

(11) An electrophotographic two-component developer comprising the electrophotographic carrier according to any one of (1) to (10) and a toner.

The electrophotographic carrier of the present invention has a resin coating layer made of a resin in which an acrylic resin, a silicone resin, and a silicone-modified acrylic resin are combined under specific conditions. In addition, the charging property is stable even in continuous printing of a large number of sheets, and an electrophotographic carrier having excellent initial charge rising property, excellent charge holding power in life, and good adhesion to the core material and coating property is obtained. be able to.
In particular, by combining a coating resin using an acrylic resin and a silicone resin with a silicone-modified acrylic resin, the compatibility and adhesion between the acrylic resin and the silicone resin is improved, and an electronic that takes full advantage of the characteristics of both resins. A photographic carrier can be created.

It is a circuit diagram (figure seen from the side surface direction) of a dielectric breakdown voltage measuring device.

  Hereinafter, although embodiment of this invention is described in detail, this invention is not limited to the following embodiment, In the range of the objective of this invention, it can implement by adding a change suitably. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

  The electrophotographic carrier of the present invention has a core material and a resin coating layer that covers the surface of the core material, and further has other configurations as necessary.

[Core material]
Magnetic particles are used as the core material in the present invention. The magnetic particles are not particularly limited, and include iron powder, magnetite, Mn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Mn-Mg-Sr ferrite, Mg ferrite, other alkali metals, alkaline earths, and light metals. The above ferrite group can be used according to the purpose, and can be suitably used from those subjected to oxidation treatment or the like as necessary. Among these, a ferrite core material is preferable, and a ferrite core material containing Mn and Mg is more preferable.

  Although it does not specifically limit about the average particle diameter of a core material, 10-120 micrometers is preferable, 20-90 micrometers is more preferable, 30-80 micrometers is still more preferable. If the average particle size is 120 μm or less, the gradation of the print density is good, and if it is 10 μm or more, carrier adhesion can be reduced. In addition, the average particle diameter of the core material and the carrier described later (carrier having a resin coating layer on the surface of the core material) is measured by a dry dispersion device (RODOS (SYMPATEC)) in a laser diffraction particle size distribution device (HELOS (SYMPATEC)). ))). The average particle size for the core material and the carrier is the volume average particle size.

Saturation magnetization of the core material is not particularly limited, but is preferably 20~90Am ² / kg, more preferably 30~80Am ² / kg, more preferably 35~70Am ² / kg. If the saturation magnetization is greater than 90 Am ² / kg, missing characters tend to occur, and if it is less than ²⁰ Am ² / kg, fog tends to occur. By using a core material having saturation magnetization in such a range as an electrophotographic carrier, an electrophotographic two-component developer using the core material has a severe printing durability that allows continuous printing at a low printing rate. Even under conditions, a desired image density can be obtained. The saturation magnetization in the present invention is obtained by using a vibrating sample magnetometer BHV-35H manufactured by Riken Denshi Co., Ltd., filling the sample into a measurement capsule (0.0565 cc), and applying a magnetic field of 1.1 (MA / m). Can be measured. Incidentally, the saturation magnetization is also 20~90Am ² / kg are preferred carrier (carrier having a resin coating layer on the core material surface), more preferably 30~80Am ² / kg, more preferably 35~70Am ² / kg.

(Resin coating layer)
The electrophotographic carrier of the present invention has a resin coating layer that covers the surface of the core material, and the resin coating layer contains a resin in which an acrylic resin, a silicone resin, and a silicone-modified acrylic resin are combined at a specific ratio.

  The acrylic resin that coats the core material is a polymer of one or more monomers selected from methacrylic acid ester, methacrylic acid, acrylic acid ester, acrylic acid, and acrylamide, from the viewpoint of maintaining spent resistance and chargeability. A polymer of at least one monomer selected from methyl methacrylate, methacrylic acid, and acrylic acid is preferred. The acrylic resin preferably has a glass transition point Tg of 80 ° C. or higher, more preferably 90 ° C. or higher, still more preferably 100 ° C. or higher, and still more preferably 105 ° C. or higher. The acid value of the acrylic resin is preferably 3 or less, and more preferably 2 or less from the viewpoints of environmental characteristics and yield.

  Commercially available acrylic resins include Dianal BR-52, BR-80, BR-100, LR-269, LR-1065 (more from Mitsubishi Rayon Co., Ltd.) and Acryt 0404EA-P, 0403Ka, 0502TI (more from Taisei Fine Chemical Co., Ltd.) ) And the like.

  The silicone resin that coats the core material is preferably a thermosetting silicone resin. As commercially available silicone resins, KR-212, KR-272, KR-251, KR-255 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2410, SR2440, SR2441 (manufactured by Toray Dow Corning), TSR-127B, Examples include TSR-144, TSR-160 (manufactured by Momentive Performance Materials).

  The silicone-modified acrylic resin that coats the core material is a silicone-modified acrylic resin having an acrylic acid-based polymer composed of an acrylic acid-based monomer as a main skeleton, and is distinguished from the above-mentioned acrylic resin in that it has a silicone moiety. In the silicone-modified acrylic resin, the combination of the acrylic monomer and the silicone-containing monomer or the silicone resin component is not particularly limited. As the acrylic monomer, methacrylic acid ester, methacrylic acid, acrylic ester, acrylic One or more monomers selected from acids and acrylamides are preferred. Moreover, as a silicone containing monomer, the compound chosen from the silane coupling agent containing a methacryl group, and its oligomer is preferable. As the silicone resin component, a modifying silicone resin or the like can be used. Examples of the constituent material having a commercially available silicone component include KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, X-40-2655A (manufactured by Shin-Etsu Chemical Co., Ltd.). The silicone-modified acrylic resin preferably includes methyl methacrylate and 3-methacryloxypropyltrimethoxysilane as monomer components.

  In the present invention, when the ratio of the acrylic resin, the silicone resin, and the silicone-modified acrylic resin in the resin coating layer is 100% by weight of the total amount of the acrylic resin, the silicone resin, and the silicone-modified acrylic resin, the acrylic resin is 40 to 40%. 85% by weight, preferably 60-80% by weight, silicone resin is 10-30% by weight, preferably 10-20% by weight, and silicone-modified acrylic resin is 5-30% by weight, 10-20% by weight. If the proportion of the acrylic resin is greater than 85% by weight, image deterioration due to high charge occurs, and if it is less than 40% by weight, the initial charge imparting property deteriorates. Further, when the proportion of the silicone resin is larger than 30% by weight, fogging is remarkable, and when it is smaller than 10% by weight, the spent resistance is deteriorated. On the other hand, when the proportion of the silicone-modified acrylic resin is larger than 30% by weight, the charging stability is poor, and when it is smaller than 5% by weight, the coating property is deteriorated and causes carrier adhesion. In addition, this ratio is weight% based on the weight of resin solid content conversion.

  In the present invention, the resin coating layer preferably further contains a styrene-acrylic resin. Styrene-acrylic resins are distinguished from the above acrylic resins in that they contain styrene as a monomer component. Examples of the styrene-acrylic resin that covers the core material include a copolymer of styrene and an acrylic monomer selected from methyl methacrylate, methacrylic acid, and acrylic acid. Examples of commercially available styrene-acrylic resins include SBM-73, SBM-100, and SBM-600 (manufactured by Sanyo Chemical Co., Ltd.). When the resin coating layer contains styrene-acrylic resin, the ratio of styrene-acrylic resin is more than 0 to 30 parts by weight and more than 0 to 100 parts by weight in total of acrylic resin, silicone resin, and silicone-modified acrylic resin. -20 parts by weight, more than 0 to 15 parts by weight, more preferably 5 to 15 parts by weight. In addition, this weight ratio is a weight ratio based on the weight of resin solid content conversion.

  As long as the weight percent of the acrylic resin, silicone resin, and silicone-modified acrylic resin in the resin coating layer is within the scope of the present invention, the resin coating layer further comprises a polyolefin resin (polyolefin resin and its derivatives and modified resins. This also applies to other resins such as epoxy resins, polyester resins, polyurethane resins, amino resins, and the like. In the present invention, the resin coating layer is preferably composed of an acrylic resin, a silicone resin, and a silicone-modified acrylic resin, or is preferably composed of an acrylic resin, a silicone resin, a silicone-modified acrylic resin, and a styrene-acrylic resin. That is, the resin in the resin coating layer is preferably an acrylic resin, a silicone resin, and a silicone-modified acrylic resin, or an acrylic resin, a silicone resin, a silicone-modified acrylic resin, and a styrene-acrylic resin. In the present invention, the proportion of acrylic resin, silicone resin, and silicone-modified acrylic resin in the resin coating layer is preferably 90% by weight or more, more preferably 95% by weight or more, even if it is 100% by weight. Good. Moreover, when the resin coating layer contains a styrene-acrylic resin, the ratio of the acrylic resin, the silicone resin, the silicone-modified acrylic resin, and the styrene-acrylic resin in the resin coating layer is 90% by weight or more. It is preferably 95% by weight or more, and may be 100% by weight.

  In the present invention, for the purpose of adjusting the chargeability of the carrier, a charge control agent is blended in the resin coating layer, or the outermost layer of the resin coating layer is coated with a silane coupling agent having a positively or negatively charged functional group. Can be processed. The type of the charge control agent is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from charge control agents that have been conventionally blended in a carrier coat layer. Examples of the charge control agent include a quaternary ammonium salt, an organometallic complex, and a resin charge control agent having a positively or negatively chargeable functional group. Moreover, the kind of silane coupling agent is not specifically limited in the range which does not inhibit the objective of this invention, It can select suitably from the silane coupling agent conventionally used for the process of the coat layer of a carrier. Examples of the silane coupling agent include aminosilane coupling agents, fluorine-based silane coupling agents, and epoxy silane coupling agents.

  In the present invention, the resin coating layer preferably contains conductive fine particles. Examples of the conductive fine particles include carbon black and magnetite, and it is preferable to include both carbon black and magnetite.

As the conductive fine particles, carbon black such as ketjen black, furnace black, acetylene black and channel black, metal oxide such as TiO ₂ , ZnO, Fe ₃ O ₄ and SnO ₂ are used. As the conductive fine particles, it is preferable to use one or more kinds of carbon black and one or more kinds of metal oxides and further one or more kinds of magnetite. More preferably, carbon black and magnetite are used in combination. Specific carbon blacks include VULCAN XC72R, REGAL330R, BLACK PEARLS 2000, MONARCH 120 (above, manufactured by Cabot Corporation), MA100, MA7 (above, manufactured by Mitsubishi Chemical Corporation), etc., and as magnetite, BL-100 BL-500, ABL-205 (above, manufactured by Titanium Industry Co., Ltd.), KBC-100, KBC-100-60S, KBC-100 SNW (above, manufactured by Kanto Denka Kogyo Co., Ltd.) and the like can be used. The content of carbon black is preferably 1 to 15 parts by weight with respect to 100 parts by weight of the solid content of the resin in the resin coating layer. If the carbon black content is 1 part by weight or more, the edge effect is moderate, and if it is 15 parts by weight or less, fogging is reduced. The magnetite content is preferably 10 to 150 parts by weight with respect to 100 parts by weight of the solid content of the resin in the resin coating layer. When the content of magnetite is 10 parts by weight or more, the image density is sufficient, and when it is 150 parts by weight or less, carrier adhesion decreases.

  In the present invention, the resin coating layer preferably contains an organometallic catalyst. The organometallic catalyst is preferably an organometallic catalyst that has an effect of accelerating the curing of the silicone resin. As the organic metal catalyst, an organic compound containing a metal selected from Sn, Ti, Al, Fe, and Zr, for example, an alkoxide containing the metal, a chelate compound, a metal soap, and the like can be used. An organometallic catalyst containing a metal selected from Sn, Ti, and Zr is preferred from the viewpoint of curability, and an organometallic catalyst containing a metal selected from Ti and Zr is more preferred from the viewpoint of safety and environmental impact. More preferably, the alkoxy group has 4 or less carbon atoms. Commercially available organometallic catalysts include Neostan U-200, U-100, U-810, U-820 (Nitto Kasei Co., Ltd. Sn catalyst), ORGATICS TC-100, TC-400, TC-401, TC- 750 (above Ti catalyst manufactured by Matsumoto Fine Chemical Co., Ltd.), Orugachix ZC-580, ZC-700 (above Zr catalyst produced by Matsumoto Fine Chemical Co., Ltd.). When the resin coating layer contains an organometallic catalyst, the content X (parts by weight) of the organometallic catalyst with respect to 100 parts by weight of the solid content of the resin in the resin coating layer and the solid content of 100 parts by weight of the resin in the resin coating layer It is preferable that the content Y (parts by weight) of the silicone resin satisfy the relational expression of (Y / 5) ≦ X ≦ (Y / 2). When X is Y / 2 or less, the coating properties are good, and when X is Y / 5 or more, a good cured state can be obtained.

  The means for forming the resin coating layer on the surface of the core material is not particularly limited, and an immersion method, a spray coating method using a fluidized bed, and the like can be suitably used. In addition, a step of performing a heat treatment after coating may be added, and heat treatment may be performed in the coating processing apparatus simultaneously with coating. When heat treatment is performed after coating, a fluid electric furnace, a microwave heating furnace, or the like may be used.

  The resin coating amount varies depending on the type of resin, the charging characteristics required for the carrier, and the electrical resistance characteristics, but the resin amount in the resin coating layer is 0.3 to 3.5 weights with respect to 100 parts by weight of the core material. Part is preferable, and 0.5 to 3.0 parts by weight is more preferable. When the coating amount is 0.3 parts by weight or more, it is easy to uniformly cover the core material surface with the coating resin, and the spent resistance is also improved. Further, when the coating amount is 3.5 parts by weight or less, the initial charge rising property is improved, and the occurrence of problems such as an increase in particle association can be suppressed. This resin amount is a resin amount in terms of solid content.

According to the present invention,
A method for producing an electrophotographic carrier, comprising a step of bringing a resin coating composition into contact with a core material,
The resin coating composition contains an acrylic resin, a silicone resin, a silicone-modified acrylic resin, and a liquid medium,
When the ratio of the acrylic resin, silicone resin, and silicone-modified acrylic resin in the resin coating composition is 100% by weight of the total amount of acrylic resin, silicone resin, and silicone-modified acrylic resin, the acrylic resin is 40 to 85. % By weight, 10-30% by weight of silicone resin, 5-30% by weight of silicone-modified acrylic resin,
A method for producing an electrophotographic carrier is provided. This production method is suitable as a method for producing the electrophotographic carrier of the present invention.

  In this production method, the step of bringing the resin coating composition into contact with the core material can be performed by the method described above as a means for forming the resin coating layer on the surface of the core material. Moreover, the component and preferable aspect which a resin coating composition contains can be suitably selected and applied from what was demonstrated by the resin coating layer. The resin coating composition preferably contains conductive fine particles, and more preferably contains carbon black and magnetite as the conductive fine particles. The resin coating composition contains an organometallic catalyst, and the content X (parts by weight) of the organometallic catalyst with respect to 100 parts by weight of the solid content of the resin in the resin coating composition, and the resin in the resin coating layer It is preferable that the content Y (parts by weight) of the silicone resin with respect to 100 parts by weight of the solid content satisfies the relational expression (Y / 5) ≦ X ≦ (Y / 2). The resin coating composition preferably contains 3 to 60% by weight of resin in terms of solid content. The resin coating composition can be prepared using a liquid medium such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran, diethyl ether, acetone, N-methylpyrrolidone and the like. As shown in the Examples, the resin coating composition can be used as a resin solution containing such a solvent. This manufacturing method may include a step of forming a resin coating layer that covers the surface of the core material by bringing the resin coating composition into contact with the core material. In this production method, the resin in the resin coating composition is 0.3 to 3.5 parts by weight, more preferably 0.5 to 3.0 parts by weight with respect to 100 parts by weight of the core material. It is preferable to use a coating composition.

  The electrophotographic carrier of the present invention preferably has a dielectric breakdown voltage of 0.5 to 3.5 kV, more preferably 1.0 to 3.0 kV. If the dielectric breakdown voltage is 0.5 kV or higher, carrier adhesion can be reduced, and if it is 3.5 kV or lower, the edge effect becomes moderate and image degradation can be suppressed. The dielectric breakdown voltage can be measured by the method of the example described later.

  The electrophotographic carrier of the present invention preferably has an average particle size of 20 to 90 μm, and more preferably 30 to 80 μm. If the average particle diameter is 20 μm or more, carrier adhesion is less likely to occur, and if it is 90 μm or less, the toner conveyance amount is improved and the image quality is improved.

  The present invention relates to a two-component developer for electrophotography containing the electrophotographic carrier of the present invention and a toner. As the toner, any toner such as a toner manufactured by a pulverization method and a toner manufactured by a polymerization method can be used. Depending on the image forming apparatus, a positively charged toner or a negatively charged toner is selected to constitute a developer. In the positively charged toner for an electrophotographic carrier of the present invention, a nigrosine dye or a quaternary ammonium salt is used as a charge control agent. A toner manufactured using a monoazo dye or the like is preferable as the negatively charged toner for an electrophotographic carrier of the present invention.

  As the toner used in the present invention, a toner in which a colorant, a charge control agent and the like are dispersed in a binder resin can be suitably used. There is no restriction | limiting in particular as binder resin, A polystyrene resin, a styrene-acryl resin, a polyester resin, an epoxy resin, a polyurethane resin etc. are mentioned. A conventionally well-known thing can be suitably selected as a coloring agent and a charge control agent. If necessary, wax, external additives and the like are also used. The term “two components” for a developer expresses for convenience that the developer is mainly composed of two components, a carrier and a toner, and does not exclude the inclusion of other components. Absent.

  Hereinafter, the present invention will be described in more detail based on examples. The present invention is not limited to these.

<Production example>
(Production of silicone-modified acrylic resin a)
After substituting with nitrogen using a 2 L three-necked flask equipped with a stirrer, 300 parts by weight of methyl isobutyl ketone (MIBK) and 1.5 parts by weight of dimethyl-2,2-azobis (2-methylpropionate) were charged and stirred while stirring. The temperature was raised to ° C. Next, 320 parts by weight of methyl methacrylate and 30 parts by weight of 3-methacryloxypropyltrimethoxysilane (KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.) were uniformly added to the solution in the flask over 3.5 hours. The polymerization was completed by reacting for a period of time to obtain a silicone-modified acrylic resin solution containing the silicone-modified acrylic resin a. The resulting silicone-modified acrylic resin solution had a solid content concentration of 39.8% by weight.

(Production of silicone-modified acrylic resin b)
After nitrogen substitution using a 2 L three-necked flask equipped with a stirrer, 300 parts by weight of MIBK and 1.5 parts by weight of dimethyl-2,2-azobis (2-methylpropionate) were charged, and the temperature was raised to 90 ° C. while stirring. Next, 320 parts by weight of methyl methacrylate and 30 parts by weight of 3-methacryloxypropylmethyldimethoxysilane (KBM502 manufactured by Shin-Etsu Chemical Co., Ltd.) were uniformly added to the solution in the flask over 3.5 hours. The polymerization was completed by reacting for a time to obtain a silicone-modified acrylic resin solution containing the silicone-modified acrylic resin b. The resulting silicone-modified acrylic resin solution had a solid content concentration of 40.2% by weight.

[Example 1]
Acrylic resin a (Dainar LR-1065 manufactured by Mitsubishi Rayon Co., Ltd., glass transition temperature Tg 105 ° C., acid value of 2 or less), silicone resin a (SR 2410 manufactured by Toray Dow Corning Co., Ltd.), and silicone-modified acrylic resin a manufactured by the above method Were mixed so that the weight ratio was A: B: C = 70: 20: 10 to obtain a mixture of coating resins. Here, when the total of the acrylic resin, the silicone resin and the silicone-modified acrylic resin is 100% by weight, the weight% of the acrylic resin is A, the weight% of the silicone resin is B, and the weight% of the silicone-modified acrylic resin is C. (Hereinafter, the same applies to the case where the resin has three or less components).
Next, 7 parts by weight of an organic Ti catalyst (Origatix TC-750 manufactured by Matsumoto Fine Chemical Co., Ltd., indicated as “Ti-based” in the table) is added as a silicone resin curing catalyst to 100 parts by weight of the coated resin solid content. Diluted in Next, 5 parts by weight of carbon black (VULCAN XC72R manufactured by Cabot Corporation) with respect to 100 parts by weight of the coated resin solids, and magnetite fine particles (KBC-100-60S manufactured by Kanto Denka Kogyo Co., Ltd., average particle size 0.3 μm) are coated with the solid resin. It added to the resin solution so that it might become 20 weight part with respect to 100 weight part per minute, and it stirred with the mixer, and obtained the coating resin solution.
The obtained coating resin solution is adjusted so that the resin solid content is 1.5 parts by weight with respect to 100 parts by weight of the core material (MnMg ferrite, average particle diameter 40 μm, saturation magnetization 63 Am ² / kg), and fluidized bed type coating. After spray coating using an apparatus and drying the solvent, heat treatment was performed at 120 ° C. for 2 hours in a thermal circulation oven, and coarse particles were removed with a 75 μm sieve to obtain a carrier of the present invention having an average particle diameter of 40 μm ( (See Table 1).

[Example 2]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the weight ratio of the resin in Example 1 was changed to A: B: C = 85: 10: 5.

[Example 3]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the weight ratio of the resin in Example 1 was changed to A: B: C = 40: 30: 30.

[Example 4]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the weight ratio of the resin in Example 1 was changed to A: B: C = 65: 30: 5.

[Example 5]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the silicone-modified acrylic resin a in Example 1 was changed to the silicone-modified acrylic resin b.

[Example 6]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 2 except that the silicone-modified acrylic resin a in Example 2 was changed to the silicone-modified acrylic resin b.

[Example 7]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 3 except that the silicone-modified acrylic resin a in Example 3 was changed to the silicone-modified acrylic resin b.

[Example 8]
The carrier of the present invention having an average particle size of 40 μm was obtained in the same manner as in Example 4 except that the silicone-modified acrylic resin a in Example 4 was changed to the silicone-modified acrylic resin b.

[Example 9]
The amount of carbon black added in Example 1 was 15 parts by weight with respect to 100 parts by weight of the coated resin solids, the amount of magnetite added was 150 parts by weight with respect to 100 parts by weight of the coated resin solids, and the others were the same as in Example 1. Similarly, the carrier of the present invention having an average particle diameter of 40 μm was obtained.

[Example 10]
The amount of carbon black added in Example 1 is 1 part by weight with respect to 100 parts by weight of the coated resin solids, the amount of magnetite added is 10 parts by weight with respect to 100 parts by weight of the coated resin solids, and the others are the same as in Example 1. Similarly, the carrier of the present invention having an average particle diameter of 40 μm was obtained.

[Example 11]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the amount of the organic Ti catalyst added in Example 1 was 10 parts by weight with respect to 100 parts by weight of the coating resin solid content.

[Example 12]
The carrier of the present invention having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the amount of the organic Ti catalyst added in Example 1 was 4 parts by weight with respect to 100 parts by weight of the coated resin solid content.

[Example 13]
In Example 1, styrene-acrylic resin a (SBM-100, manufactured by Sanyo Chemical Co., Ltd.) was used as the coating resin, and the weight ratio was A: B: C: D = 60: 20: 10: 10 (A + B + C total 100 parts by weight). The carrier of the present invention having an average particle diameter of 40 μm was obtained so that D was 11 parts by weight. Here, when the total of the acrylic resin, silicone resin, silicone-modified acrylic resin and styrene-acrylic resin is 100% by weight, the weight percent of the acrylic resin is A, the weight percent of the silicone resin is B, and the weight of the silicone-modified acrylic resin. % Is C, and the weight% of the styrene-acrylic resin is D (hereinafter, the same applies to the case where the resin is a four component).

[Example 14]
In Example 1, the same styrene-acrylic resin a as in Example 13 was used as the coating resin, and the weight ratio was A: B: C: D = 55: 20: 10: 15 (D for a total of 100 parts by weight of A + B + C) The carrier of the present invention having an average particle diameter of 40 μm was obtained.

[Comparative Example 1]
In Example 1, a silicone-modified acrylic resin was not used as the coating resin, and a carrier having an average particle diameter of 40 μm was obtained with a resin weight ratio of A: B: C = 85: 15: 0.

[Comparative Example 2]
In Example 1, a silicone resin was not used as the coating resin, and a carrier having an average particle diameter of 40 μm was obtained with a weight ratio of the resin of A: B: C = 85: 0: 15.

[Comparative Example 3]
In Example 6, a silicone resin was not used as the coating resin, and a carrier having an average particle diameter of 40 μm was obtained with a resin weight ratio of A: B: C = 85: 0: 15.

[Comparative Example 4]
The weight ratio of the resin in Example 1 was changed to A: B: C = 90: 5: 5, and others were obtained in the same manner as in Example 1 to obtain a carrier having an average particle diameter of 40 μm.

[Comparative Example 5]
The weight ratio of the resin in Example 1 was changed to A: B: C = 30: 40: 30, and others were obtained in the same manner as in Example 1 to obtain a carrier having an average particle diameter of 40 μm.

[Comparative Example 6]
The weight ratio of the resin in Example 1 was changed to A: B: C = 30: 30: 40 to obtain a carrier having an average particle diameter of 40 μm.

[Comparative Example 7]
The carrier having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the silicone-modified acrylic resin a in Example 1 was changed to an acrylic-modified silicone resin (KR-9706 manufactured by Shin-Etsu Chemical Co., Ltd.). The acrylic modified silicone resin has a main skeleton of silicone and is different from the silicone modified acrylic resin.

[Comparative Example 8]
A carrier having an average particle diameter of 40 μm was obtained in the same manner as in Example 1 except that the silicone-modified acrylic resin a in Example 1 was changed to an acrylic silane coupling agent (KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.).

[Comparative Example 9]
In Example 13, the weight ratio of the coating resin was A: B: C: D = 40: 30: 10: 20 to obtain a carrier having an average particle diameter of 40 μm.

[Evaluation of carrier for electrophotography]
For the carriers of Examples 1 to 14 and Comparative Examples 1 to 9, under the environment of a temperature of 22 ° C. and a humidity of 55%, the resin coating state confirmation by SEM observation, saturation magnetization, dielectric breakdown voltage measurement, electrical resistance value measurement, The following method was carried out. Table 1 shows the structure of the carrier used, and Table 2 shows the evaluation results.

<Resin coating state>
The state of resin coating on the carrier is determined by SEM observation. Carriers with many exposed cores cause a large charge leakage and a decrease in charge retention. The SEM image is observed using a scanning electron microscope (S-3400N manufactured by Hitachi High-Tech), observed in a field of view of 100 or more carrier particles, and the number of particles having a good resin coverage is counted. It was evaluated with. Here, good coverage means that each core exposed portion is 30% or less in surface observation for each particle.
○: Number of particles with good coverage is 80% or more ×: Number of particles with good coverage is less than 80%

<Dielectric breakdown voltage measurement>
The dielectric breakdown voltage was measured with a measuring instrument in which the N pole and the S pole were made to face each other and the distance between the magnetic poles was 6 mm (magnetic pole: surface magnetic flux density 1500 G, counter magnetic pole area 10 mm × 30 mm). A schematic circuit diagram of the breakdown voltage measuring instrument is shown in FIG. As shown in FIG. 1, nonmagnetic parallel plate electrodes 2 and 2 ′ (electrode area 10 mm × 40 mm, electrode interval 2 mm) are arranged between magnetic poles 3 and 3 ′, and a sample is placed between the electrodes 2 and 2 ′. 200 mg of a certain electrophotographic carrier 1 was put, and the electrophotographic carrier 1 was held between the electrodes 2 and 2 'by a magnetic force. The electrodes 2, 2 ′ are installed on an insulating support 4. An AC voltage was applied to the electrodes 2 and 2 ′ using a withstand voltage tester (TOS5051 manufactured by Kikusui Electronics Co., Ltd.), and an applied voltage value at which a leakage current value was 110 mA or more was defined as a dielectric breakdown voltage. The electrode 2 used brass. The support 4 was made of Teflon (registered trademark).

<Electric resistance value>
In the measuring instrument used in the above dielectric breakdown voltage measurement, the electrode interval is set to 2 mm, the electrophotographic carrier as a sample is held, and the electric resistance value when a DC voltage of 500 V is applied is measured as the insulation resistance measuring instrument. (TR-8601 Takeda Riken) was used. In the table, it is shown as “resistance value (500 V)”.

[Production and evaluation of two-component developer for electrophotography]
Under an environment of a temperature of 22 ° C. and a humidity of 55%, 7.0 parts by weight of negatively charged toner was mixed for 30 minutes with a V-type blender with respect to 100 parts by weight of the carrier prepared in the example or the comparative example to obtain a developer. Using this developer, a printing resistance test of 50,000 sheets was performed on a copying machine (30 sheets machine) using a chart with an image area of 5%, and the developer charge amount, image density, edge effect, fog, carrier adhesion, resistance The spent property was measured by the following method. Table 1 shows the structure of the carrier used, and Table 2 shows the evaluation results.

<Charge amount>
Using a suction-type charge measuring device (q / m-meter Epping), a 795 mesh was attached to the cell, and the charge amount before and after the test was measured. If the difference between the initial charge amount and the charge amount after 50,000-sheet printing is 5 μC / g or more, image defects and fog are likely to occur.

<Image density>
It measured using the reflection densitometer (RD-915 Macbeth company make), and evaluated with the following reference | standard.
A: The initial image density is 1.3 or more, and the change in image density after printing 50,000 sheets is 0.0 or more and less than 0.05.
A: The initial image density is 1.3 or more, and the change in image density after printing 50,000 sheets is 0.05 or more and less than 0.10.
Δ: The initial image density is 1.3 or more, and the change in image density after 50,000 sheet printing is 0.10 or more and less than 0.15.
X: The initial image density is less than 1.3, or the change in image density after 50,000 sheet printing is 0.15 or more.

<Edge effect>
A solid image chart was printed and evaluated using a reflection densitometer (RD-915 Macbeth) to compare the image density at the center of the solid image with the image density at the edge.
○: Image density difference is within 0.05.
Δ: Image density difference is more than 0.05 and within 0.10. (Usable level)
X: The image density difference is more than 0.10. (Unusable level)

<Fog>
It measured using the whiteness meter (TC-6D Tokyo Denshoku Co., Ltd.), and evaluated on the following reference | standard. The evaluation was calculated by taking the difference of the value after printing resistance from the value of the paper before printing resistance.
A: The initial fog is 0.2 or less, and the difference between the value before printing resistance and the value after printing resistance is 0.0 or more and less than 0.1.
○: Initial fog is 0.2 or less, and the difference between the value before printing resistance and the value after printing resistance is 0.1 or more and less than 0.3.
(Triangle | delta): Initial fog is 0.2 or less, and the difference of the value before printing resistance and the value after printing resistance is 0.3 or more and less than 0.5.
X: The initial fog is more than 0.2, or the difference between the value before printing resistance and the value after printing resistance is 0.5 or more.

<Carrier adhesion>
The number of carrier particles on the image during solid image printing was evaluated visually.
○: There are 3 or less carrier-adhering particles on the image.
Δ: The number of carrier-adhering particles on the image is 4 or more and 8 or less. (Usable level)
X: Nine or more carrier adhesion particles on the image. (Unusable level)

<Spent resistance>
Measure the carbon value of the carrier from which the toner has been removed from the carrier before the printing resistance test and the developer after the printing resistance test using CARBON ANALYZER (EMIA-221V HORIBA), and calculate the increase rate of the carbon value by the following formula. The spent resistance was evaluated by estimating the spent amount.
{(Carbon value of carrier after printing) − (Carbon value of carrier before printing)} / (Carbon value of carrier before printing) × 100 = Carbon value increase rate (%)
A: Carbon value increase rate is less than 15%.
○: Carbon value increase rate is 15% or more and less than 30%.
(Triangle | delta): Carbon value increase rate is 30% or more and less than 40%.
X: Carbon value increase rate is 40% or more.

* 1 Part by weight of coating resin solids with respect to 100 parts by weight of core material * 2 Part by weight with respect to 100 parts by weight of coating resin solids * 3 Figures in parentheses are A (acrylic resin), B (silicone resin), and C ( % By weight when the total amount of (silicone-modified acrylic resin) is 100% by weight.

  From Table 2, the carriers of Examples 1 to 14 prepared according to the present invention exhibited good development characteristics even after the printing resistance test. On the other hand, the carriers produced according to Comparative Examples 1 to 9 have development characteristics that are difficult to use.

  As described above with reference to the examples, in the electrophotographic carrier, the toner is formed by forming a resin coating layer made of a resin obtained by combining at least a specific weight ratio of an acrylic resin, a silicone-modified acrylic resin, and a silicone resin with the core material. High charging ability, excellent spent resistance, stable charging even in continuous printing of many sheets, excellent initial charge buildup and charge retention, adhesion to core material and coating film A good electrophotographic carrier could be obtained.

1: Electrophotographic carrier 2, 2 ′: Electrode 3, 3 ′: Magnetic pole 4: Support base

Claims (11)

An electrophotographic carrier having a core material and a resin coating layer covering the surface of the core material,
The resin coating layer includes an acrylic resin, a silicone resin, and a silicone-modified acrylic resin,
The ratio of the acrylic resin, silicone resin, and silicone-modified acrylic resin in the resin coating layer is 40 to 85% by weight of acrylic resin when the total amount of acrylic resin, silicone resin, and silicone-modified acrylic resin is 100% by weight. The silicone resin is 10 to 30% by weight, and the silicone-modified acrylic resin is 5 to 30% by weight.
Electrophotographic carrier.   The carrier for electrophotography according to claim 1, wherein the acrylic resin has a glass transition temperature Tg of 80 ° C. or higher.   The electrophotographic carrier according to claim 1, wherein the acid value of the acrylic resin is 3 or less.   The electrophotographic carrier according to claim 1, wherein the resin coating layer contains carbon black and magnetite.   The content of the carbon black is 1 to 15 parts by weight with respect to 100 parts by weight of the solid content of the resin in the resin coating layer, and the content of the magnetite is 100 solids content of the resin in the resin coating layer. The carrier for electrophotography according to claim 4, wherein the carrier is 10 to 150 parts by weight with respect to parts by weight.   The resin coating layer contains an organometallic catalyst, and the content X (parts by weight) of the organometallic catalyst with respect to 100 parts by weight of the solid content of the resin in the resin coating layer and the solid content of 100 parts by weight of the resin in the resin coating layer 6. The electrophotographic carrier according to claim 1, wherein the content Y (parts by weight) of the silicone resin satisfies a relational expression of (Y / 5) ≦ X ≦ (Y / 2).   The resin coating layer further contains a styrene-acrylic resin, and the ratio of the styrene-acrylic resin is more than 0 to 30 parts by weight with respect to 100 parts by weight in total of the acrylic resin, the silicone resin, and the silicone-modified acrylic resin. The carrier for electrophotography according to any one of claims 1 to 6.   The carrier for electrophotography according to any one of claims 1 to 7, wherein the silicone-modified acrylic resin comprises methyl methacrylate and 3-methacryloxypropyltrimethoxysilane as monomer components.   The electrophotographic carrier according to claim 1, wherein the silicone resin is a thermosetting silicone resin.   10. The electrophotographic carrier according to claim 1, wherein the dielectric breakdown voltage is 0.5 to 3.5 kV.   An electrophotographic two-component developer comprising the electrophotographic carrier according to claim 1 and a toner.

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