JP7588992B2 - Magnetic carrier, two-component developer, replenishment developer, and image forming method - Google Patents

Description

The present invention relates to a magnetic carrier, a two-component developer, a replenishment developer, and an image forming method using the same, which are used in an image forming method for visualizing an electrostatic image using electrophotography.

Conventionally, in the electrophotographic image forming method, a method is generally used in which an electrostatic latent image is formed on an electrostatic latent image carrier by using various means, and toner is attached to the electrostatic latent image to develop it. As a developing method, a two-component developing method is widely adopted in which carrier particles called a magnetic carrier are mixed with the toner, and the toner is triboelectrically charged to give an appropriate amount of positive or negative charge to the toner, and the charge is used as a driving force for development.
The magnetic carrier can improve the stirring, transportability, and chargeability of the developer, and the functional division with the toner can be clarified. Therefore, the two-component development method has the advantage that the developer performance can be easily controlled.
On the other hand, in recent years, with the advancement of technology in the field of electrophotography, there has been an increasingly strict demand for higher speed and longer life of the apparatus as well as higher definition and stable image quality. In order to meet such demands, there is a demand for higher performance of the magnetic carrier.
As such a magnetic carrier, a magnetic carrier has been proposed in which wax is present as a domain in the resin coating layer of the magnetic carrier, and an external additive is selectively attached to the domain portion to stabilize macro-charge (see Patent Document 1). As a result, the macro-chargeability of the developer is stabilized, but further improvements are required in terms of image density stability during long-term use and density unevenness caused by the attachment of an external additive to the magnetic carrier surface to make the chargeability of the magnetic carrier surface uneven. In addition, a magnetic carrier has been proposed in which a crystalline resin is added to the resin coating layer of the magnetic carrier and is compatible with the resin coating layer to stabilize the charge (Patent Document 2). As a result, the ability to impart chargeability to the transparent toner is obtained, and long-term image quality is improved, but there is room for further improvement in the issue of obtaining a high-quality image without density unevenness in the full-color image itself.

JP 2011-70003 A JP 2010-210703 A

The magnetic carriers disclosed in Japanese Patent Application Laid-Open No. 2003-233999 and Japanese Patent Application Laid-Open No. 2003-233999 tend to improve the problem of extending the life of the developer.
However, in the market, particularly in the field of on-demand printers, there is an ever-increasing demand for high-quality images that are free of density unevenness over a long period of time, and therefore there is an urgent need to develop a magnetic carrier that maintains image density even after long-term use and has little density unevenness within the image, and an image forming method using the same.
The object of the present invention is to provide a magnetic carrier that solves the above problems. Specifically, the present invention provides a magnetic carrier, a refill developer, and an image forming method using the same that can suppress uneven density in an image surface and provide stable, even images and high-quality character images even after long-term use regardless of the usage environment.

（式中、Ｘは単結合又は炭素数１以上６以下のアルキレン基を示し、
Ｒ ¹ は、ニトリル基（－Ｃ≡Ｎ）、
アミド基（－Ｃ（＝Ｏ）ＮＨＲ ¹⁰ 、該Ｒ ¹⁰ は水素原子）、
－ＣＯＯＲ ¹¹ （該Ｒ ¹¹ は炭素数１以上６以下のアルキル基若しくは炭素数１以上６以下のヒドロキシアルキル基）、
－ＣＯＯ（ＣＨ ₂ ） ₂ ＮＨＣＯＯＲ ¹⁴ （該Ｒ ¹⁴ は炭素数１以上４以下のアルキル基）、又は
－ＣＯＯ（ＣＨ ₂ ） ₂ －ＮＨ－Ｃ（＝Ｏ）－Ｎ（Ｒ ¹⁵ ） ₂ （該Ｒ ¹⁵ はそれぞれ独立して、炭素数１以上６以下のアルキル基）
を示し、
Ｒ ² は、炭素数１以上４以下のアルキル基を示し、Ｒ ³ は、それぞれ独立して水素原子又はメチル基を示す。）
該磁性キャリアコア粒子の粉体ｐＨが、８．０以上１１．０以下であり、
該第一組成物から該第四組成物において、該第一の重合性単量体の含有割合が、各組成物中の全重合性単量体の総モル数を基準として５．０モル％以上６０．０モル％以下であり、
該組成物中の該第二の重合性単量体の含有割合が、該重合体Ａ中の全重合性単量体の総モル数を基準として２０．０モル％以上９５．０モル％以下であり、
該第一の重合性単量体のＳＰ値をＳＰ₁₂とし、該第二の重合性単量体のＳＰ値をＳＰ₂₂としたとき、下記式（３）と（４）を満たすことを特徴とする磁性キャリアに関する。
０．６０（Ｊ／ｃｍ³）^0.5≦ＳＰ₂₂－ＳＰ₁₂≦１５．００（Ｊ／ｃｍ³）^0.5 （３）
１８．３０（Ｊ／ｃｍ³）^0.5≦ＳＰ₂₂ （４）
（但し、第一の重合性単量体が複数存在する場合、ＳＰ ₁₂ は、それぞれの重合性単量体のＳＰ値の加重平均の値である。第二の重合性単量体は、算出したＳＰ ₁₂ に対して式（３）を満たすＳＰ ₂₂ を有する重合性単量体すべてが該当する。第二の重合性単量体が複数存在する場合、ＳＰ ₂₂ は、それぞれの重合性単量体のＳＰ値であり、ＳＰ ₂₂ －ＳＰ ₁₂ はそれぞれの第二の重合性単量体に対して決定される。）
また、本発明は、結着樹脂を含有するトナー粒子を有するトナーと、磁性キャリアとを含有する二成分系現像剤であって、該磁性キャリアが上記磁性キャリアである二成分系現像剤に関する。
また、本発明は、静電潜像担持体を帯電する帯電工程、該静電潜像担持体の表面に静電潜像を形成する静電潜像形成工程、該静電潜像を現像器内の二成分系現像剤を用いて現像し、トナー像を形成する現像工程、該トナー像を中間転写体を介して又は介さずに、転写材に転写する転写工程、及び転写された該トナー像を該転写材に定着する定着工程を有し、該現像器内の該二成分系現像剤のトナー濃度の低減に応じて、補給用現像剤が現像器に補給される画像形成方法に使用するための補給用現像剤であって、
該補給用現像剤は、上記二成分系現像剤に含まれる該トナーと該磁性キャリアと、を含有し、
該補給用現像剤は、該磁性キャリア１質量部に対して該トナーを２質量部以上５０質量部以下含有する補給用現像剤に関する。
また、本発明は、静電潜像担持体を帯電する帯電工程、該静電潜像担持体の表面に静電潜像を形成する静電潜像形成工程、該静電潜像を二成分系現像剤を用いて現像し、トナー像を形成する現像工程、該トナー像を中間転写体を介して又は介さずに、転写材に転写する転写工程、及び転写された該トナー像を該転写材に定着する定着工程を有する画像形成方法であって、
該二成分系現像剤が、上記二成分系現像剤である画像形成方法に関する。
さらに、本発明は、静電潜像担持体を帯電する帯電工程、該静電潜像担持体の表面に静電潜像を形成する静電潜像形成工程、該静電潜像を現像器内の二成分系現像剤を用いて現像し、トナー像を形成する現像工程、該トナー像を中間転写体を介して又は介さずに、転写材に転写する転写工程、及び転写された該トナー像を該転写材に定着する定着工程を有し、該現像器内の該二成分系現像剤のトナー濃度の低減に応じて、補給用現像剤が現像器に補給される画像形成方法であって、
該補給用現像剤は、上記二成分系現像剤に含まれる該トナーと該磁性キャリアと、を含有し、
該補給用現像剤は、該磁性キャリア１質量部に対して該トナーを２質量部以上５０質量部以下含有する画像形成方法に関する。 The present inventors have discovered that by using a two-component developer as described below, it is possible to suppress uneven density within an image surface, and to obtain stable, uniform images even after long-term use regardless of the usage environment.
That is , the present invention provides a magnetic carrier comprising magnetic carrier core particles and magnetic carrier particles having a resin coating layer on the surface of the magnetic carrier core particles,
The resin coating layer contains only polymer A as a resin ,
The polymer A is
a polymer of a first composition containing only the first polymerizable monomer and the second polymerizable monomer;
a polymer of a second composition containing only the first polymerizable monomer, the second polymerizable monomer, and styrene;
a polymer of a third composition containing only the first polymerizable monomer, the second polymerizable monomer, and methyl methacrylate; or
a polymer of a fourth composition containing only the first polymerizable monomer, the second polymerizable monomer, styrene, and methyl methacrylate;
and
the first polymerizable monomer is at least one selected from the group consisting of stearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, heneicosanyl (meth)acrylate, behenyl (meth)acrylate, lignoceryl (meth)acrylate, ceryl (meth)acrylate, octacosal (meth)acrylate, myrisyl (meth)acrylate, dodricontal (meth)acrylate, and 2-decyltetradecyl (meth)acrylate ;
The second polymerizable monomer is at least one selected from the group consisting of the following formulae (A) and (B):

(In the formula, X represents a single bond or an alkylene group having 1 to 6 carbon atoms,
R ¹ is a nitrile group (-C≡N);
an amide group (-C(=O)NHR ¹⁰ , R ¹⁰ being a hydrogen atom);
-COOR ¹¹ (wherein R ¹¹ is an alkyl group having 1 to 6 carbon atoms or a hydroxyalkyl group having 1 to 6 carbon atoms);
--COO(CH ₂ ) ₂ NHCOOR ¹⁴ (wherein R ¹⁴ is an alkyl group having 1 to 4 carbon atoms), or
--COO(CH.sub.2 ₎ .sub.2 _-- NH--C(.dbd.O)--N(R.sub.15 ⁾ .sub.2 ₍ wherein each of the ^R.sub.15 's is independently an alkyl group having 1 to 6 carbon atoms)
indicates,
R2 represents an alkyl group having 1 to 4 carbon atoms, and each R3 ^{independently represents} a hydrogen atom or a methyl group.
The powder pH of the magnetic carrier core particles is 8.0 or more and 11.0 or less,
In the first composition to the fourth composition, the content ratio of the first polymerizable monomer is 5.0 mol % or more and 60.0 mol % or less based on the total number of moles of all polymerizable monomers in each composition ,
the content ratio of the second polymerizable monomer in the composition is 20.0 mol % or more and 95.0 mol % or less based on the total number of moles of all polymerizable monomers in the polymer A,
The present invention relates to a magnetic carrier characterized in that, when the SP value of the first polymerizable monomer is SP ₁₂ and the SP value of the second polymerizable monomer is SP ₂₂ , the following formulas (3) and (4) are satisfied:
0.60 (J/cm ³ ) ^0.5 ≦SP ₂₂ -SP ₁₂ ≦15.00 (J/cm ³ ) ^0.5 (3)
18.30 (J/cm ³ ) ^0.5 ≦SP ₂₂ (4)
(However, when a plurality of first polymerizable monomers are present, SP ₁₂ is a weighted average value of the SP values of the respective polymerizable monomers. The second polymerizable monomer corresponds to all polymerizable monomers having SP ₂₂ that satisfies formula (3) for the calculated SP _12. When a plurality of second polymerizable monomers are present, SP ₂₂ is the SP value of each polymerizable monomer, and SP ₂₂ -SP ₁₂ is determined for each second polymerizable monomer.)
The present invention also relates to a two-component developer containing a toner having toner particles containing a binder resin and a magnetic carrier, the magnetic carrier being the above-mentioned magnetic carrier.
The present invention also relates to a replenishment developer for use in an image forming method, which includes a charging step of charging an electrostatic latent image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with a two-component developer in a developing device to form a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body, and a fixing step of fixing the transferred toner image to the transfer material, wherein the replenishment developer is replenished to the developing device in response to a decrease in toner concentration of the two-component developer in the developing device,
the replenishment developer contains the toner and the magnetic carrier contained in the two-component developer,
The replenishing developer relates to a replenishing developer containing 2 parts by mass or more and 50 parts by mass or less of the toner per part by mass of the magnetic carrier.
The present invention also provides an image forming method including a charging step of charging an electrostatic latent image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with a two-component developer to form a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body, and a fixing step of fixing the transferred toner image to the transfer material,
The present invention relates to an image forming method, wherein the two-component developer is the above-mentioned two-component developer.
The present invention further provides an image forming method comprising a charging step of charging an electrostatic latent image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with a two-component developer in a developing device to form a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body, and a fixing step of fixing the transferred toner image to the transfer material, wherein a replenishment developer is replenished to the developing device in response to a reduction in toner concentration of the two-component developer in the developing device,
the replenishment developer contains the toner and the magnetic carrier contained in the two-component developer,
The replenishing developer relates to an image forming method in which the toner is contained in an amount of 2 parts by mass or more and 50 parts by mass or less per part by mass of the magnetic carrier.

This invention suppresses uneven density within the image surface, and produces stable, uniform images even over long periods of use, regardless of the usage environment.

FIG. 1 is a schematic diagram of an image forming apparatus. FIG. 1 is a schematic diagram of an image forming apparatus using an intermediate transfer member.

In the present invention, the expressions "XX or more and XX or less" and "XX to XX" that express a numerical range refer to a numerical range including the lower and upper limit endpoints, unless otherwise specified.

In the present invention, (meth)acrylic acid ester means an acrylic acid ester and/or a methacrylic acid ester.

In the present invention, a "monomer unit" refers to one section of carbon-carbon bonds in the main chain of a polymer formed by polymerization of a vinyl monomer. A vinyl monomer can be represented by the following formula (Z).

［式（Ｚ）中、Ｒ_Z1は、水素原子、又はアルキル基を表し、Ｒ_Z2は、任意の置換基を表す。］

[In formula (Z), _R represents a hydrogen atom or an alkyl group, and _R represents an arbitrary substituent.]

<Magnetic Carrier>
The first magnetic carrier of the present invention is a magnetic carrier containing magnetic carrier core particles and magnetic carrier particles having a resin coating layer on the surface of the magnetic carrier core particles,
the resin coating layer contains a polymer A having a first monomer unit derived from a first polymerizable monomer and a monomer unit derived from a second polymerizable monomer different from the first polymerizable monomer;
the first polymerizable monomer is at least one selected from the group consisting of (meth)acrylic acid esters having an alkyl group having 18 to 36 carbon atoms,
a content ratio of the first monomer unit in the polymer A is 5.0 mol % or more and 60.0 mol % or less based on the total number of moles of all monomer units in the polymer A,
a content ratio of the second monomer unit in the polymer A is 20.0 mol % or more and 95.0 mol % or less based on the total number of moles of all monomer units in the polymer A,
When the SP value of the first monomer unit is SP ₁₁ (J/cm ³ ) ^0.5 and the SP value of the second monomer unit is SP ₂₁ (J/cm ³ ) ^0.5 , the following formulas (1) and (2) are satisfied:
3.00 (J/cm ³ ) ^0.5 ≦SP ₂₁ -SP ₁₁ ≦25.00 (J/cm ³ ) ^0.5 (1)
21.00 (J/cm ³ ) ^0.5 ≦SP ₂₁ (2)

The second magnetic carrier of the present invention is a magnetic carrier containing magnetic carrier core particles and magnetic carrier particles having a resin coating layer on the surface of the magnetic carrier core particles,
the resin coating layer contains a polymer A which is a polymer of a composition containing a first polymerizable monomer and a second polymerizable monomer different from the first polymerizable monomer;
the first polymerizable monomer is at least one selected from the group consisting of (meth)acrylic acid esters having an alkyl group having 18 to 36 carbon atoms,
the content of the first polymerizable monomer in the composition is 5.0 mol % or more and 60.0 mol % or less based on the total number of moles of all polymerizable monomers in the polymer A,
the content ratio of the second polymerizable monomer in the composition is 20.0 mol % or more and 95.0 mol % or less based on the total number of moles of all polymerizable monomers in the polymer A,
When the SP value of the first polymerizable monomer is SP ₁₂ and the SP value of the second polymerizable monomer is SP ₂₂ , the following formulas (3) and (4) are satisfied.
0.60 (J/cm ³ ) ^0.5 ≦SP ₂₂ -SP ₁₂ ≦15.00 (J/cm ³ ) ^0.5 (3)
18.30 (J/cm ³ ) ^0.5 ≦SP ₂₂ (4)

Here, the SP value is an abbreviation for solubility parameter, and is a value that serves as an index of solubility. The calculation method will be described later.

The inventors conducted extensive research aimed at achieving both suppression of density unevenness within an image surface and an extended lifespan of the developer over a long period of use, and as a result discovered that the magnetic carrier with the above configuration is important.

The mechanism by which the magnetic carrier of the present invention can solve the above problems is believed to be as follows.

The magnetic carrier of the present invention contains a resin having a specific structure in the resin coating layer, specifically, a resin in which two or more monomer units with significantly different polarities are polymerized in a block form. In this resin, two or more monomer units with significantly different polarities form a microphase separation state in the toner particles. It is considered that the phase of the monomer unit with a relatively high polarity (hereinafter, "polar portion") is oriented toward the polar portion present on the surface of the magnetic carrier core particle. As a result, when the resin of the present invention is used in the resin coating layer, the phase of the monomer unit with a relatively low polarity (hereinafter, also referred to as the "crystalline portion") is oriented on the surface of the magnetic carrier particle. Since this phase of the monomer unit with a relatively low polarity has crystallinity, the crystalline portion present on the magnetic carrier surface allows the external additive derived from the toner to slide, thereby making it possible to suppress contamination of the external additive on the magnetic carrier particle surface. As a result, in various environments from low humidity to high temperature and high humidity, the change in image density between the initial use and after long-term use, and the unevenness in density in the image surface over a long period of use are suppressed, and a high-quality image can be obtained.

In the present invention, the resin coating layer contains polymer A. Polymer A is a polymer of a composition containing a first polymerizable monomer and a second polymerizable monomer different from the first polymerizable monomer. In addition, polymer A has a first monomer unit derived from the first polymerizable monomer and a second monomer unit derived from the second polymerizable monomer different from the first polymerizable monomer.

The first polymerizable monomer is at least one selected from the group consisting of (meth)acrylic acid esters having an alkyl group having 18 to 36 carbon atoms. The first monomer unit is derived from the first polymerizable monomer.

The (meth)acrylic acid ester has a long-chain alkyl group, which can impart crystallinity to the resin coating layer present on the surface of the magnetic carrier particles. This increases the lubricity of the magnetic carrier particle surface, suppressing contamination by external additives. Furthermore, the (meth)acrylic acid ester is highly hydrophobic, so it also has low moisture absorption in high-temperature, high-humidity environments, contributing to excellent charge retention.

On the other hand, when the (meth)acrylic acid ester has an alkyl group with less than 18 carbon atoms, the alkyl group has a short chain length, so the resulting polymer A has low hydrophobicity and high hygroscopicity in a high-temperature, high-humidity environment, resulting in poor charge retention. Also, when the (meth)acrylic acid ester has an alkyl group with more than 36 carbon atoms, the (meth)acrylic acid ester has an alkyl group with a long chain length, so the crystallinity is increased more than necessary, resulting in poor charge retention under high-temperature, high-humidity conditions.

Examples of (meth)acrylic acid esters having an alkyl group having from 18 to 36 carbon atoms include (meth)acrylic acid esters having a linear alkyl group having from 18 to 36 carbon atoms [stearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, heneicosanyl (meth)acrylate, behenyl (meth)acrylate, lignoceryl (meth)acrylate, ceryl (meth)acrylate, octacosal (meth)acrylate, myricyl (meth)acrylate, dodriacoutal (meth)acrylate, etc.] and (meth)acrylic acid esters having a branched alkyl group having from 18 to 36 carbon atoms [2-decyltetradecyl (meth)acrylate, etc.].

Among these, from the above viewpoint, at least one selected from the group consisting of (meth)acrylic acid esters having a linear alkyl group with 18 to 36 carbon atoms is preferred, at least one selected from the group consisting of (meth)acrylic acid esters having a linear alkyl group with 18 to 30 carbon atoms is more preferred, and at least one of linear stearyl (meth)acrylate and behenyl (meth)acrylate is even more preferred.

The first polymerizable monomer may be used alone or in combination of two or more types.

The second polymerizable monomer is a polymerizable monomer different from the first polymerizable monomer and satisfies the above formulas (1) and (2), or the above formulas ( 3 ) and ( 4 ). The second monomer unit is derived from the second polymerizable monomer. The second polymerizable monomer may be used alone or in combination of two or more kinds.

The second polymerizable monomer is preferably at least one selected from the group consisting of the following formulae (A) and (B):

（式中、Ｘは単結合又は炭素数１以上６以下のアルキレン基を示し、
Ｒ¹は、ニトリル基（－Ｃ≡Ｎ）、
アミド基（－Ｃ（＝Ｏ）ＮＨＲ¹⁰（Ｒ¹⁰は水素原子、若しくは炭素数１以上４以下のアルキル基））、
ヒドロキシ基、
－ＣＯＯＲ¹¹（Ｒ¹¹は炭素数１以上６以下（好ましくは１以上４以下）のアルキル基若しくは炭素数１以上６以下（好ましくは１以上４以下）のヒドロキシアルキル基）、
ウレタン基（－ＮＨＣＯＯＲ¹²（Ｒ¹²は炭素数１以上４以下のアルキル基））、
ウレア基（－ＮＨ－Ｃ（＝Ｏ）－Ｎ（Ｒ¹³）₂（Ｒ¹³はそれぞれ独立して、水素原子若しくは炭素数１以上６以下（好ましくは１以上４以下）のアルキル基））、
－ＣＯＯ（ＣＨ₂）₂ＮＨＣＯＯＲ¹⁴（Ｒ¹⁴は炭素数１以上４以下のアルキル基）、又は
－ＣＯＯ（ＣＨ₂）₂－ＮＨ－Ｃ（＝Ｏ）－Ｎ（Ｒ¹⁵）₂（Ｒ¹⁵はそれぞれ独立して、水素原子若しくは炭素数１以上６以下（好ましくは１以上４以下）のアルキル基）
であり、
Ｒ²は、炭素数１以上４以下のアルキル基であり、Ｒ³は、それぞれ独立して水素原子又はメチル基である。）

(In the formula, X represents a single bond or an alkylene group having 1 to 6 carbon atoms,
R ¹ is a nitrile group (-C≡N);
an amide group (-C(=O) ^NHR10 ( ^R10 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms));
Hydroxy groups,
-COOR ¹¹ (R ¹¹ is an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4) or a hydroxyalkyl group having 1 to 6 carbon atoms (preferably 1 to 4);
a urethane group (-NHCOOR ¹² (R ¹² is an alkyl group having 1 to 4 carbon atoms)),
a urea group (-NH-C(=O) -N( ^R13 ) ₂ (wherein ^R13 is independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms));
-COO( _CH2 ) _2NHCOOR14 ^{( R14} is an alkyl group having 1 to 4 carbon atoms), or -COO( _CH2 ) _2- NH-C(=O) -N( ^R15 ) ₂ ( ^R15 is each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4)).
and
^R2 is an alkyl group having 1 to 4 carbon atoms, and each ^R3 is independently a hydrogen atom or a methyl group.

By using at least one selected from the group consisting of the above formulas (A) and (B) as the second polymerizable monomer, the second monomer unit has a particularly high polarity, and a microphase separation state can be preferably formed in the toner particles. In addition, the second monomer unit is preferably oriented in the polar portion present on the surface of the magnetic carrier particle, and the adhesion of the resin coating layer can be improved.

Furthermore, a compound containing at least one of a nitrile group and an amide group is highly polar yet non-ionic, and therefore can exhibit more appropriate adhesion, making it more preferable as the second polymerizable monomer. Furthermore, a compound containing at least one of a nitrile group and an amide group is non-ionic, and therefore highly hydrophobic, and has low hygroscopicity in high-temperature and high-humidity environments, making it preferable in that it can exhibit excellent charge retention.

As the second polymerizable monomer, specifically, for example, among the polymerizable monomers listed below, a polymerizable monomer satisfying the above formulas (1) and (2) or the above formulas ( 3 ) and ( 4 ) can be used.

Monomers having nitrile groups; for example, acrylonitrile, methacrylonitrile, etc.

Monomers having a hydroxy group; for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.

Monomers having an amide group; for example, acrylamide, a monomer obtained by reacting an amine having 1 to 30 carbon atoms with a carboxylic acid having 2 to 30 carbon atoms and an ethylenically unsaturated bond (such as acrylic acid and methacrylic acid) by a known method.

Monomer having a urethane group: for example, an alcohol having 2 to 22 carbon atoms having an ethylenically unsaturated bond (e.g., 2-hydroxyethyl methacrylate, vinyl alcohol, etc.) and an isocyanate having 1 to 30 carbon atoms [monoisocyanate compounds (benzenesulfonyl isocyanate, tosyl isocyanate, phenyl isocyanate, p-chlorophenyl isocyanate, butyl isocyanate, hexyl isocyanate, t-butyl isocyanate, cyclohexyl isocyanate, octyl isocyanate, 2-ethylhexyl isocyanate, dodecyl isocyanate, adamantyl isocyanate, 2,6-dimethylphenyl isocyanate, 3,5-dimethylphenyl isocyanate, 2,6-dipropylphenyl isocyanate, etc.), aliphatic diisocyanates, Cyanate compounds (such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate), alicyclic diisocyanate compounds (such as 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate), and aromatic diisocyanate compounds (such as phenyl diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenylether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, etc.) by a known method, and an alcohol having 1 to 26 carbon atoms (methanol, ethanol, propanol, isopropyl alcohol, butanol, t-butyl alcohol, pentanol, heptanol, octanol, 2-ethylhexanol, nonanol, decanol, undecyl alcohol, lauryl alcohol, dodecyl alcohol , myristyl alcohol, pentadecyl alcohol, cetanol, heptadecanol, stearyl alcohol, isostearyl alcohol, elaidyl alcohol, oleyl alcohol, linoleyl alcohol, linolenyl alcohol, nonadecyl alcohol, heneicosanol, behenyl alcohol, erucyl alcohol, etc.) with an isocyanate having an ethylenically unsaturated bond and having 2 to 30 carbon atoms [2-isocyanatoethyl (meth)acrylate, 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl (meth)acrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl (meth)acrylate, 1,1-(bis(meth)acryloyloxymethyl)ethyl isocyanate, etc.] by a known method, and the like.

Monomers having a urea group: For example, monomers obtained by reacting an amine having 3 to 22 carbon atoms [primary amines (such as normal butylamine, t-butylamine, propylamine, and isopropylamine), secondary amines (such as di-normal ethylamine, di-normal propylamine, and di-normal butylamine), aniline, and cycloxylamine] with an isocyanate having 2 to 30 carbon atoms and an ethylenically unsaturated bond by a known method.

Monomers having a carboxy group; for example, methacrylic acid, acrylic acid, 2-carboxyethyl (meth)acrylate.

Among these, it is preferable to use a monomer having a nitrile group, an amide group, a urethane group, a hydroxy group, or a urea group. More preferably, it is a monomer having at least one functional group selected from the group consisting of a nitrile group, an amide group, a urethane group, a hydroxy group, and a urea group, and an ethylenically unsaturated bond.

Also preferably used as the second polymerizable monomer are vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, and vinyl octylate.

The content of the first monomer unit in polymer A is 5.0 mol% or more and 60.0 mol% or less based on the total number of moles of all monomer units in polymer A, and the content of the second monomer unit in polymer A is 20.0 mol% or more and 95.0 mol% or less based on the total number of moles of all monomer units in polymer A. The content of the first polymerizable monomer in the composition constituting polymer A is 5.0 mol% or more and 60.0 mol% or less based on the total number of moles of all polymerizable monomers in the composition, and the content of the second polymerizable monomer in the composition is 20.0 mol% or more and 95.0 mol% or less based on the total number of moles of all polymerizable monomers in the composition.

When the content ratio of the first monomer unit and the content ratio of the first polymerizable monomer are within the above ranges, the crystallinity of the resin coating layer improves the lubricity of the magnetic carrier particle surface, and excellent spent resistance is exhibited. In addition, when the content ratio of the second monomer unit and the content ratio of the second polymerizable monomer are within the above ranges, the adhesion between the resin coating layer and the magnetic carrier core particles is enhanced, and good charging stability is obtained even with long-term use.

On the other hand, when the content of the first monomer unit or the content of the first polymerizable monomer is less than 5.0 mol%, the proportion of non-crosslinked parts having crystallinity is small, and therefore the spent resistance is poor. Also, when the content of the first monomer unit or the content of the first polymerizable monomer is more than 60.0 mol%, the proportion of polar parts is relatively small, and therefore the adhesion of the resin coating layer is reduced, and good charging stability cannot be obtained.

When polymer A has monomer units derived from (meth)acrylic acid esters having two or more alkyl groups with 18 to 36 carbon atoms, the content ratio of the first monomer unit represents the molar ratio of the total of them. Similarly, when the composition used for polymer A contains (meth)acrylic acid esters having two or more alkyl groups with 18 to 36 carbon atoms, the content ratio of the first polymerizable monomer represents the molar ratio of the total of them.

In addition, when the content of the second monomer unit in polymer A is less than 20.0 mol% based on the total number of moles of all monomer units in polymer A, the proportion of polar parts is relatively small, so the adhesion of the resin coating layer decreases and good charging stability cannot be obtained. In addition, when the content of the second monomer unit in polymer A is more than 95.0 mol% based on the total number of moles of all monomer units in polymer A, the proportion of non-crosslinked parts having crystallinity is small, so spent resistance is poor.

In addition, the content ratio of the second monomer unit in polymer A is preferably 40.0 mol% or more and 95.0 mol% or less, and even more preferably 40.0 mol% or more and 70.0 mol% or less, based on the total number of moles of all monomer units in polymer A, from the viewpoint of charge retention, since both the non-polar portion that imparts lubricity to the magnetic carrier particles and the polar portion that enhances the adhesion of the resin coating layer can be achieved. For the same reason, the content ratio of the second polymerizable monomer in the composition is preferably 40.0 mol% or more and 95.0 mol% or less, and even more preferably 40.0 mol% or more and 70.0 mol% or less, based on the total number of moles of all monomer units in the composition.

When polymer A contains two or more types of monomer units derived from a second polymerizable monomer satisfying formula (1), the proportion of the second monomer units represents the total molar ratio of those. Similarly, when the composition used for polymer A contains two or more types of second polymerizable monomers, the content ratio of the second polymerizable monomers represents the total molar ratio of those.

In the first magnetic carrier, polymer A satisfies the following formulas (1) and (2) when the SP value of the first monomer unit is _SP11 (J/ ^m3 ) ^0.5 and the SP value of the second monomer unit is _SP21 (J/ ^m3 ) ^0.5 .
3.00≦(SP ₂₁ -SP ₁₁ )≦25.00...(1)
21.00≦SP ₂₁ ...(2)

In addition, in the second magnetic carrier, when the SP value of the first polymerizable monomer is _SP12 (J/ ^cm3 ) ^0.5 and the SP value of the second polymerizable monomer is _SP22 (J/ ^cm3 ) ^0.5 , polymer A satisfies the following formulas ( 3 ) and ( 4 ).
60≦( _SP22 - _SP12 )≦15.00...( 3 )
18.30≦SP ₂₂ ...( 4 )

By satisfying the above formulas (1) and (2) or the above formulas ( 3 ) and ( 4 ), the second monomer unit has high polarity, and a polarity difference occurs between the first and second monomer units. This polarity difference can form a microphase separation state in the resin coating layer of the magnetic carrier. As a result, the non-polar part that contributes to the lubricity of the magnetic carrier particle surface and the polar part that contributes to the adhesion of the resin coating layer can be present in a domain matrix form, so that a magnetic carrier that can obtain good charging stability even when used for a long period of time can be obtained.

The mechanism by which satisfying the above formulas (1) and (2) or the above formulas ( 3 ) and ( 4 ) improves the lubricity of the magnetic carrier particle surface and the adhesion of the resin coating layer, thereby obtaining good charging stability even during long-term use, is believed to be as follows.

The first monomer unit is incorporated into polymer A, and crystallinity is expressed by the aggregation of the first monomer units. Normally, the crystallization of the first monomer unit is inhibited when other monomer units are incorporated, making it difficult for the polymer to exhibit crystallinity. This tendency becomes more pronounced when multiple types of monomer units are randomly bonded to each other within a single polymer molecule.

On the other hand, in the present invention, by using the first polymerizable monomer and the second polymerizable monomer so that the content ratio of the first monomer unit and the second monomer unit are within the range of the above formulas (1) and (2), it is believed that the first polymerizable monomer and the second polymerizable monomer do not bond randomly during polymerization, but can be bonded to a certain extent continuously. As a result, a block in which the first monomer units are assembled together is formed, and the polymer A becomes a block copolymer, and it is believed that it is possible to increase the crystallinity even if other monomer units are incorporated, and the melting point can be maintained. In other words, it is preferable that the polymer A has a crystalline portion containing the first monomer unit derived from the first polymerizable monomer. In addition, it is preferable that the polymer A has an amorphous portion containing the second monomer unit derived from the second polymerizable monomer.

On the other hand, the SP values of each monomer unit, SP ₁₁ and SP ₂₁ , are (SP ₂₁ -SP ₁₁ ) < 3.00.
In the case where the polarity difference between the monomer units is too small, it is not possible to form a microphase separation state in the resin coating layer of the magnetic carrier, the lubricity of the magnetic carrier surface decreases, and the charge retention is poor.
25.00<(SP ₂₁ -SP ₁₁ )
If this is the case, it means that the polarity difference between the units is too large, and polymer A does not have a structure similar to that of a block copolymer, causing variation in the lubricity of the magnetic carrier particle surface and poor charge retention.

In addition, the SP value of the second monomer unit, SP _{21 ,} is SP ₂₁ <21.00.
In the case of the above, the second monomer unit has low polarity, and the adhesion to the resin coating layer is reduced, resulting in poor charge retention.

The lower limit of SP ₂₁ -SP ₁₁ is preferably 4.00 or more, and more preferably 5.00 or more. The upper limit is preferably 20.00 or less, and more preferably 15.00 or less. SP ₂₁ is preferably 22.00 or more.

In the second magnetic carrier, the SP values of each polymerizable monomer, SP ₁₂ and SP ₂₂ , are (SP ₂₂ -SP ₁₂ )<0.60.
In the case where the polarity difference between the polymerizable monomers is too small, it is not possible to form a microphase separation state in the resin coating layer of the magnetic carrier, the lubricity of the magnetic carrier surface decreases, and the charge retention is poor.
15.00<(SP ₂₂ -SP ₁₂ )
If this is the case, it means that the polarity difference between the polymerizable monomers is too large, and polymer A does not have a structure similar to that of a block copolymer, causing variation in the lubricity of the magnetic carrier particle surface and poor charge retention.

In addition, the SP value of the second polymerizable monomer, SP _{22 ,} is SP ₂₂ <18.30.
In this case, the second polymerizable monomer has low polarity, and the adhesion to the resin coating layer is reduced, resulting in poor charge retention.

The lower limit of SP ₂₂ -SP ₁₂ is preferably 2.00 or more, and more preferably 3.00 or more. The upper limit is preferably 10.00 or less, and more preferably 7.00 or less. SP ₂₂ is preferably 25.00 or more, and more preferably 29.00 or more.

In the present invention, when multiple types of monomer units satisfying the requirements for the first monomer unit are present in polymer A, the value of _SP11 in formula (1) is a weighted average of the SP values of the respective monomer units. For example, when monomer unit A having an SP value of _SP111 is contained in an amount of A mol % based on the total number of moles of monomer units satisfying the requirements for the first monomer unit, and monomer unit B having an SP value of _SP112 is contained in an amount of (100-A) mol % based on the total number of moles of monomer units satisfying the requirements for the first monomer unit, the SP value ( _SP11 ) is
SP ₁₁ = (SP ₁₁₁ × A + SP ₁₁₂ × (100-A)) / 100
The calculation is similar when three or more monomer units satisfying the requirements of the first monomer unit are included. On the other hand, _SP12 also represents an average value calculated from the molar ratio of each first polymerizable monomer.

On the other hand, the monomer units derived from the second polymerizable monomer include all monomer units having _SP21 that satisfies formula (1) relative to _SP11 calculated by the above method. Similarly, the second polymerizable monomer includes all polymerizable monomers having _SP22 that satisfies formula (2) relative to _SP12 calculated by the above method.

That is, when the second polymerizable monomer is two or more kinds of polymerizable monomers, _SP21 represents the SP value of the monomer unit derived from each polymerizable monomer, and _SP21 - _SP11 is determined for each monomer unit derived from the second polymerizable monomer. Similarly, _SP22 represents the SP value of each polymerizable monomer, and _SP22 - _SP12 is determined for each second polymerizable monomer.

Next, we will explain the magnetic carrier core used in the present invention.

As the magnetic carrier core used in the magnetic carrier of the present invention, a known magnetic carrier core can be used. It is more preferable to use magnetic material-dispersed resin particles in which a magnetic material is dispersed in a resin component, or porous magnetic core particles containing resin in the voids.

These methods can reduce the true density of the magnetic carrier, thereby reducing the load on the toner. As a result, even with long-term use, there is little deterioration in image quality, and it is possible to reduce the frequency of replacing the developer, which is made up of toner and carrier. However, the above is not limiting, and the effects of the present invention can be fully achieved even if a commercially available magnetic carrier core is used.

As the magnetic material component used in the magnetic material-dispersed resin particles, various magnetic iron compound particle powders can be used, such as magnetite particle powder, maghemite particle powder, or magnetic iron oxide particle powder containing at least one selected from silicon oxide, silicon hydroxide, aluminum oxide, and aluminum hydroxide; magnetoplumbite type ferrite particle powder containing barium, strontium, or barium-strontium; and spinel type ferrite particle powder containing at least one selected from manganese, nickel, zinc, lithium, and magnesium.

Among these, magnetic iron oxide particles are preferably used.

In addition to the magnetic component, non-magnetic inorganic compound particles such as non-magnetic iron oxide particles such as hematite particles, non-magnetic ferric oxide hydrous particles such as goethite particles, titanium oxide particles, silica particles, talc particles, alumina particles, barium sulfate particles, barium carbonate particles, cadmium yellow particles, calcium carbonate particles, and zinc oxide particles may be used in combination with the magnetic iron compound particles.

When using a mixture of magnetic iron compound particles and non-magnetic inorganic compound particles, it is preferable that the mixture contains at least 30% by mass of magnetic iron compound particles.

It is preferable that the magnetic iron compound particles are all or partly treated with an oleophilic treatment agent.

The lipophilic treatment agent used in this case may be an organic compound having one or more functional groups selected from the group consisting of epoxy groups, amino groups, mercapto groups, organic acid groups, ester groups, ketone groups, halogenated alkyl groups, and aldehyde groups, or a mixture thereof.

As the organic compound having a functional group, a coupling agent is preferred, more preferably a silane coupling agent, a titanium coupling agent, or an aluminum coupling agent, and a silane coupling agent is particularly preferred.

The binder resin that constitutes the magnetic material-dispersed resin particles is preferably a thermosetting resin.

For example, there are phenolic resin, epoxy resin, unsaturated polyester resin, etc., but it is preferable to contain phenolic resin because it is inexpensive and easy to manufacture. For example, phenol-formaldehyde resin can be mentioned.

The content ratio of the binder resin and the magnetic iron compound particle powder (or a mixture of the magnetic iron compound particle powder and the non-magnetic inorganic compound particle powder) constituting the composite particles in the present invention is preferably 1 to 20 mass % of the binder resin and 80 to 99 mass % of the magnetic iron compound particle powder (or the mixture).

Next, we will describe the manufacturing method for magnetic material-dispersed resin particles.

As described in the examples below, for example, composite particles can be produced by stirring phenols and aldehydes in an aqueous medium in the presence of magnetic and non-magnetic inorganic compound particles and a basic catalyst. The phenols and aldehydes are then reacted and cured to produce composite particles containing inorganic compound particles such as magnetic iron oxide particles and a phenol resin.

It can also be produced by grinding a binder resin containing inorganic compound particles such as magnetic iron oxide particles, a so-called kneading grinding method. The former method is preferred because it is easy to control the particle size of the magnetic carrier and to obtain a sharp particle size distribution.

Next, we will explain the porous magnetic core particles.

The material of the porous magnetic core particles is preferably magnetite or ferrite. Furthermore, it is more preferable that the material of the porous magnetic core particles is ferrite, since this allows the porous structure of the porous magnetic core particles to be controlled and the resistance to be adjusted.

Ferrite is a sintered body represented by the following general formula:
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is a monovalent metal, M2 is a divalent metal, and when x+y+z=1.0, x and y are each in the range of 0≦(x,y)≦0.8, and z is in the range of 0.2<z<1.0.)

In the formula, it is preferable to use at least one metal atom selected from the group consisting of Li, Fe, Mn, Mg, Sr, Cu, Zn, and Ca as M1 and M2. In addition, Ni, Co, Ba, Y, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Si, and rare earths can also be used.

For magnetic carriers, it is preferable to control the surface irregularities of the porous magnetic core particles in order to maintain an appropriate level of magnetization and to set the pore diameter within the desired range. It is also preferable to be able to easily control the speed of the ferritization reaction and to suitably control the resistivity and magnetic force of the porous magnetic core. From these viewpoints, Mn-based ferrites, Mn-Mg-based ferrites, Mn-Mg-Sr-based ferrites, and Li-Mn-based ferrites that contain Mn element are more preferable.

The manufacturing process when using porous ferrite particles as the magnetic carrier core is described in detail below.

<Step 1 (weighing and mixing step)>
The raw materials for the ferrite are weighed and mixed.

Ferrite raw materials include metal particles of the above metal elements, or their oxides, hydroxides, oxalates, carbonates, etc.

Examples of mixing equipment include the following: ball mills, planetary mills, Giotto mills, and vibration mills. In particular, ball mills are preferred from the standpoint of mixability.

Specifically, weighed ferrite raw material and balls are placed in a ball mill, and then crushed and mixed, preferably for 0.1 to 20.0 hours.

<Step 2 (Pre-firing step)>
The pulverized and mixed ferrite raw material is pre-fired in air or nitrogen atmosphere, preferably at a firing temperature of 700° C. to 1200° C., for 0.5 to 5.0 hours, to form ferrite. For firing, the following furnaces are used, for example: burner-type incinerator, rotary-type firing furnace, electric furnace, etc.

<Step 3 (pulverization step)>
The calcined ferrite produced in step 2 is pulverized in a pulverizer.

There are no particular limitations on the type of pulverizer, so long as the desired particle size can be obtained. Examples include the following: crushers, hammer mills, ball mills, bead mills, planetary mills, and Giotto mills.

In order to obtain the desired particle size of the pulverized ferrite product, it is preferable to control the material, particle size, and operating time of the balls and beads used in a ball mill or bead mill, for example. Specifically, to reduce the particle size of the calcined ferrite slurry, balls with a heavy specific gravity can be used and the milling time can be extended. In addition, to widen the particle size distribution of the calcined ferrite, balls or beads with a heavy specific gravity can be used and the milling time can be shortened. Also, calcined ferrite with a wide distribution can be obtained by mixing multiple calcined ferrites with different particle sizes.

In addition, when using ball mills or bead mills, the wet method is more efficient than the dry method because the ground product does not fly up inside the mill. For this reason, the wet method is more preferable than the dry method.

<Step 4 (granulation step)>
To the pulverized calcined ferrite, water, a binder, and, if necessary, a pore adjusting agent, such as a foaming agent or resin particles, are added.

Examples of foaming agents include sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, ammonium bicarbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate.

Examples of resin microparticles include polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-acrylonitrile-indene copolymer as styrene copolymers; polyvinyl chloride, phenol resin, modified phenol resin, maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, and silicone resin; polyester resin having a monomer selected from aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols, and diphenols as a structural unit; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone-indene resin, petroleum resin, and hybrid resin having a polyester unit and a vinyl polymer unit.

For example, polyvinyl alcohol is used as the binder.

In step 3, if wet grinding is used, it is preferable to take into account the water contained in the ferrite slurry and add a binder and, if necessary, a pore adjuster.

The obtained ferrite slurry is dried and granulated using a spray dryer, preferably in a heated atmosphere of 100°C to 200°C. There are no particular limitations on the spray dryer as long as it can obtain the desired particle size of the porous magnetic core particles. For example, a spray dryer can be used.

<Step 5 (Main Firing Step)>
Next, the granulated product is fired preferably at 800° C. or more and 1400° C. or less, preferably for 1 hour or more and 24 hours or less.

By increasing the sintering temperature and time, the sintering of the porous magnetic core particles progresses, resulting in a smaller pore size and a reduced number of pores.

<Step 6 (sorting step)>
After the sintered particles are crushed as described above, they may be classified or sieved to remove coarse particles and fine particles, if necessary.

From the viewpoint of suppressing carrier adhesion and roughness in images, the volume distribution 50% particle size (D50) of the magnetic core particles is preferably 18.0 μm or more and 68.0 μm or less.

<Process 7 (filling process)>
The physical strength of the porous magnetic core particles may be low depending on the internal pore volume. In order to increase the physical strength as a magnetic carrier, the voids of the porous magnetic core particles are filled with resin at least in part. It is preferable to fill the porous magnetic core particles with the resin. The amount of the resin filled in the porous magnetic core particles is preferably 2% by mass or more and 15% by mass or less.

If there is little variation in the resin content of each magnetic carrier, the resin may fill only a portion of the internal voids, the resin may fill only the voids near the surface of the porous magnetic core particle with voids remaining inside, or the internal voids may be completely filled with resin.

The method of filling the voids in the porous magnetic core particles with resin is not particularly limited, but examples include a method of impregnating the porous magnetic core particles with a resin solution using a coating method such as a dipping method, a spraying method, a brushing method, or a fluidized bed, and then volatilizing the solvent. It is also possible to use a method of diluting the resin in a solvent and adding this to the voids in the porous magnetic core particles.

The solvent used here may be any solvent capable of dissolving the resin. In the case of a resin that is soluble in an organic solvent, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. In the case of a water-soluble resin or an emulsion-type resin, water may be used as the solvent.

The amount of resin solids in the resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. If it is 50% by mass or less, the viscosity is not too high and the resin solution is likely to uniformly penetrate into the voids of the porous magnetic core particles. On the other hand, if it is 1% by mass or more, the amount of resin is appropriate and the adhesion of the resin to the porous magnetic core particles is good.

The resin to be filled into the voids of the porous magnetic core particles may be either a thermoplastic resin or a thermosetting resin. It is preferable that the resin has a high affinity for the porous magnetic core particles. When a resin with high affinity is used, the surface of the porous magnetic core particles can be covered with the resin at the same time as filling the voids of the porous magnetic core particles with the resin.

The above-mentioned filling resins include the following thermoplastic resins: novolac resin, saturated alkyl polyester resin, polyarylate, polyamide resin, acrylic resin, etc.

Thermosetting resins include the following: phenolic resins, epoxy resins, unsaturated polyester resins, silicone resins, etc.

The magnetic carrier core used in the magnetic carrier of the present invention preferably has a powder pH of 8.0 or more and 11.0 or less. When the powder pH is in this range, the adhesion with the polymer A in the resin coating layer is improved, and the charge retention tends to be improved.

The magnetic carrier also has a resin coating layer on the surface of the magnetic carrier core.

Methods for coating the surfaces of magnetic carrier core particles with resin include, but are not limited to, dipping, spraying, brushing, dry coating, and coating by coating methods such as fluidized bed.

The resin coating layer may contain a resin other than the above polymer A, if necessary. As the resin other than polymer A, a vinyl resin that is a copolymer of a vinyl monomer having a cyclic hydrocarbon group in the molecular structure and another vinyl monomer is preferable. More preferable is a copolymer of a monomer including a (meth)acrylic acid ester having an alicyclic hydrocarbon group and a macromonomer. More preferable is a copolymer of a (meth)acrylic acid ester having an alicyclic hydrocarbon group, another (meth)acrylic monomer other than the (meth)acrylic acid ester having the alicyclic hydrocarbon group, and a macromonomer.

The content of the resin coating layer of the magnetic carrier in the present invention is preferably 0.5 parts by mass or more and 5.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, per 100 parts by mass of the magnetic carrier core. When the content is 0.5 parts by mass or more, the lubricity of the resin coating layer is increased and changes in image density are suppressed. On the other hand, when the content is 5.0 parts by mass or less, appropriate unevenness is generated on the surface of the magnetic carrier particles, resulting in good charging stability.

The resin coating layer may contain conductive particles or charge-controlling particles or materials. Examples of conductive particles include carbon black, magnetite, graphite, zinc oxide, and tin oxide.

The amount of conductive particles added is preferably 0.1 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of coating resin in order to adjust the resistance of the magnetic carrier.

Examples of particles with charge control properties include organic metal complex particles, organic metal salt particles, chelate compound particles, monoazo metal complex particles, acetylacetone metal complex particles, hydroxycarboxylic acid metal complex particles, polycarboxylic acid metal complex particles, polyol metal complex particles, polymethyl methacrylate resin particles, polystyrene resin particles, melamine resin particles, phenolic resin particles, nylon resin particles, silica particles, titanium oxide particles, and alumina particles.

The amount of charge-controlling particles added is preferably 0.5 parts by mass or more and 50.0 parts by mass or less per 100 parts by mass of the coating resin in order to adjust the amount of triboelectric charge.

The arithmetic mean roughness Ra (based on JIS-B0601) of the magnetic carrier used in the present invention is preferably 0.15 μm or more and 0.25 μm or less. If the arithmetic mean roughness Ra of the magnetic carrier is less than 0.15 μm, the spent resistance and charge retention may decrease. Furthermore, if the arithmetic mean roughness Ra of the magnetic carrier is greater than 0.25 μm, the resin coating layer may be scraped off at the convex parts of the magnetic carrier particles during long-term use, which may result in a decrease in charge retention.

<Toner>
Next, a preferred toner configuration will be described in detail below.

The toner has toner particles containing a binder resin and, if necessary, a colorant and a release agent. Examples of binder resins include vinyl resins, polyester resins, and epoxy resins. Among these, vinyl resins and polyester resins are more preferred in terms of chargeability and fixability. Polyester resins are particularly preferred.

Homopolymers or copolymers of vinyl monomers, polyesters, polyurethanes, epoxy resins, polyvinyl butyral, rosin, modified rosin, terpene resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, etc. can be mixed with the binder resins described above as necessary.

When two or more resins are mixed and used as a binder resin, it is more preferable to mix resins with different molecular weights in an appropriate ratio.

The glass transition temperature of the binder resin is preferably 45°C or more and 80°C or less, more preferably 55°C or more and 70°C or less. The number average molecular weight (Mn) is preferably 2500 or more and 50,000 or less. The weight average molecular weight (Mw) is preferably 10,000 or more and 1,000,000 or less.

The following polyester resins are also preferred as binder resins.

Based on the total monomer units constituting the polyester resin, it is preferable that 45 mol% to 55 mol% is an alcohol component, and 45 mol% to 55 mol% is an acid component.

The acid value of the polyester resin is preferably 0 mgKOH/g or more and 90 mgKOH/g or less, more preferably 5 mgKOH/g or more and 50 mgKOH/g or less, and the OH value is preferably 0 mgKOH/g or more and 50 mgKOH/g or less, more preferably 5 mgKOH/g or more and 30 mgKOH/g or less. This is because the charging characteristics of the toner become more environmentally dependent as the number of terminal groups in the molecular chain increases.

The glass transition temperature of the polyester resin is preferably 50°C or more and 75°C or less, more preferably 55°C or more and 65°C or less. The number average molecular weight (Mn) is preferably 1500 or more and 50,000 or less, more preferably 2000 or more and 20,000 or less. The weight average molecular weight (Mw) is preferably 6000 or more and 100,000 or less, more preferably 10,000 or more and 90,000 or less.

The colorant is preferably non-magnetic. Examples of colorants include:

Black colorants include carbon black; and those prepared by mixing a yellow colorant, a magenta colorant, and a cyan colorant to produce a black color.

Examples of color pigments for magenta toner include the following: condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specific examples include C.I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57 : 1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 150, 163, 166, 169, 177, 184, 185, 202, 206, 207, 209, 220, 221, 238, 254, 269; C.I. Pigment Violet 19, C.I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

As a colorant, a pigment may be used alone, but it is preferable to use a combination of a dye and a pigment to improve the clarity of the image in terms of the image quality of a full-color image.

Dyes for magenta toner include the following: C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. Disperse Red 9, C.I. Solvent Violet 8, 13, 14, 21, 27, C.I. Disperse Violet 1, and other oil-soluble dyes; C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, and C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28, and other basic dyes.

Color pigments for cyan toner include the following: C.I. Pigment Blue 1, 2, 3, 7, 15:2, 15:3, 15:4, 16, 17, 60, 62, 66; C.I. Bat Blue 6, C.I. Acid Blue 45, copper phthalocyanine pigments with 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

Yellow coloring pigments include the following: condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal compounds, methine compounds, and allylamide compounds.

Specific examples include C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 155, 168, 174, 180, 181, 185, 191; C.I. Bat Yellow 1, 3, 20. In addition, dyes such as C.I. Direct Green 6, C.I. Basic Green 4, C.I. Basic Green 6, and Solvent Yellow 162 can also be used.

The amount of colorant used is preferably 0.1 parts by weight to 30 parts by weight, more preferably 0.5 parts by weight to 20 parts by weight, and even more preferably 3 parts by weight to 15 parts by weight, per 100 parts by weight of binder resin.

There are no particular limitations on the method for producing the toner, and any known method can be used. Examples include the melt kneading method, suspension polymerization method, dissolution suspension method, and emulsion aggregation method.

In addition, in the above toner, it is preferable to use a toner in which a colorant is mixed in advance with a binder resin to form a master batch. Then, by melting and kneading this colorant master batch with other raw materials (binder resin, wax, etc.), the colorant can be well dispersed in the toner.

To further stabilize the chargeability of the toner, a charge control agent can be used as necessary. It is preferable to use 0.5 parts by weight or more and 10 parts by weight or less of the charge control agent per 100 parts by weight of the binder resin. If it is 0.5 parts by weight or more, sufficient charging characteristics can be obtained. On the other hand, if it is 10 parts by weight or less, compatibility with other materials becomes good and excessive charging at low humidity can be suppressed.

Examples of charge control agents include:

As an example of a negative charge control agent that controls the toner to be negatively charged, an organic metal complex or a chelate compound is effective. Examples of such a negative charge control agent include monoazo metal complexes, metal complexes of aromatic hydroxycarboxylic acids, and metal complexes of aromatic dicarboxylic acids. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, their anhydrides, or their esters, or phenol derivatives of bisphenol.

Positive charge control agents that control the toner to be positively charged include modified products of nigrosine and fatty acid metal salts, quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate, and onium salts such as phosphonium salts that are analogues of these, and chelate pigments thereof, such as triphenylmethane dyes and lake pigments thereof (lake forming agents include phosphotungstic acid, phosphomolybdic acid, phosphotungstomolybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide compounds, etc.), and metal salts of higher fatty acids, such as diorgano tin oxides such as dibutyl tin oxide, dioctyl tin oxide, and dicyclohexyl tin oxide, and diorgano tin borates such as dibutyl tin borate, dioctyl tin borate, and dicyclohexyl tin borate.

If necessary, one or more types of release agents may be contained in the toner particles. Examples of release agents include the following:

Aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, and paraffin wax are preferably used. Other examples include oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof; waxes whose main component is fatty acid esters such as carnauba wax, sazol wax, and montan acid ester wax; and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax.

The amount of release agent is preferably 0.1 parts by weight or more and 20 parts by weight or less, more preferably 0.5 parts by weight or more and 10 parts by weight or less, per 100 parts by weight of binder resin.

The melting point of the release agent, as determined by the maximum endothermic peak temperature during heating measured with a differential scanning calorimeter (DSC), is preferably 65°C or higher and 130°C or lower. It is more preferably 80°C or higher and 125°C or lower. If the melting point is 65°C or higher, the toner has a suitable viscosity, which makes it possible to suppress toner adhesion to the photoreceptor. On the other hand, if the melting point is 130°C or lower, low-temperature fixability is improved.

For the toner, a fine powder may be used as a flowability improver, which can be added externally to the toner particles to increase the flowability before and after the addition. For example, fluorine-based resin powder such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; fine silica powder such as wet-processed silica and dry-processed silica, fine titanium oxide powder, fine alumina powder, etc. are surface-treated with a silane coupling agent, titanium coupling agent, or silicone oil to make them hydrophobic, and those treated so that the hydrophobicity level measured by a methanol titration test is in the range of 30 to 80 are particularly preferred.

The inorganic fine particles are preferably used in an amount of 0.1 parts by weight to 10 parts by weight, more preferably 0.2 parts by weight to 8 parts by weight, per 100 parts by weight of toner particles.

<Two-component developer>
The two-component developer of the present invention contains a toner having toner particles containing a binder resin, and a magnetic carrier.

When toner is mixed with a magnetic carrier, the carrier mixing ratio is preferably 2% by weight or more and 15% by weight or less, more preferably 4% by weight or more and 13% by weight or less, in terms of toner concentration in the developer, and generally good results are obtained. A toner concentration of 2% by weight or more results in good image density, and a toner concentration of 15% by weight or less can suppress fogging and scattering inside the machine.

The two-component developer containing the magnetic carrier of the present invention is
a charging step of charging an electrostatic latent image carrier;
an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image bearing member;
a developing step of developing the electrostatic latent image with a two-component developer to form a toner image;
The toner image can be used in an image forming method having a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing step of fixing the transferred toner image to the transfer material.

The image forming method may also have a configuration in which a two-component developer is included in the developing device, and a replenishment developer is replenished to the developing device in response to a decrease in the toner concentration of the two-component developer in the developing device. The magnetic carrier of the present invention can be used as a replenishment developer for use in such an image forming method. The image forming method may also have a configuration in which excess magnetic carrier in the developing device is discharged from the developing device as necessary.

The replenishment developer preferably contains a magnetic carrier and a toner having toner particles containing a binder resin and, if necessary, a colorant and a release agent. The replenishment developer preferably contains 2 parts by mass or more and 50 parts by mass or less of toner per 1 part by mass of the replenishment magnetic carrier. Note that the replenishment developer may be only toner without the replenishment magnetic carrier.

Next, we will explain an example of an image forming apparatus equipped with a developing device that uses a magnetic carrier, a two-component developer, and a replenishment developer, but the present invention is not limited to this.

<Image forming method>
In Fig. 1, an electrostatic latent image carrier (photosensitive drum) 1 rotates in the direction of the arrow in the figure. The electrostatic latent image carrier 1 is charged by a charger 2, which is a charging means, and the surface of the charged electrostatic latent image carrier 1 is exposed by an exposure device 3, which is an electrostatic latent image forming means, to form an electrostatic latent image. The developing device 4 has a developing container 5 that contains a two-component developer, and the developer carrier 6 is arranged in a rotatable state, and contains a magnet 7 as a magnetic field generating means inside the developer carrier 6. At least one of the magnets 7 is disposed so as to face the latent image carrier.

The two-component developer is held on the developer carrier 6 by the magnetic field of the magnet 7, and the amount of the two-component developer is regulated by the regulating member 8 before being transported to the development section facing the electrostatic latent image carrier 1. In the development section, a magnetic brush is formed by the magnetic field generated by the magnet 7. The electrostatic latent image is then visualized as a toner image by applying a development bias consisting of an alternating electric field superimposed on a direct electric field. The toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to the recording medium 12 by the transfer charger 11.

As shown in FIG. 2, the image may be transferred from the electrostatic latent image carrier 1 to an intermediate transfer body 9, and then electrostatically transferred to a transfer material (recording medium) 12. The recording medium 12 is then transported to a fixing device 13, where the toner is fixed onto the recording medium 12 by heating and pressurizing it. The recording medium 12 is then discharged outside the device as an output image. After the transfer process, any toner remaining on the electrostatic latent image carrier 1 is removed by a cleaner 15.

After that, the electrostatic latent image carrier 1, which has been cleaned by the cleaner 15, is electrically initialized by light irradiation from the pre-exposure 16, and the above image formation operation is repeated.

Figure 2 shows an example of a full-color image forming device.

The arrangement of the image forming units K, Y, C, M, etc. in the figure and the arrows indicating the rotation direction are not limited to these in any way. Incidentally, K stands for black, Y for yellow, C for cyan, and M for magenta. In FIG. 2, electrostatic latent image carriers 1K, 1Y, 1C, and 1M rotate in the direction of the arrows in the figure. Each electrostatic latent image carrier is charged by chargers 2K, 2Y, 2C, and 2M, which are charging means, and the charged surface of each electrostatic latent image carrier is exposed by exposure devices 3K, 3Y, 3C, and 3M, which are electrostatic latent image forming means, to form an electrostatic latent image.

The electrostatic latent image is then visualized as a toner image by two-component developer carried on developer carriers 6K, 6Y, 6C, and 6M provided in developing devices 4K, 4Y, 4C, and 4M, which are developing means. It is then transferred to intermediate transfer body 9 by intermediate transfer chargers 10K, 10Y, 10C, and 10M, which are transfer means. It is then transferred to recording medium 12 by transfer charger 11, which is also transfer means, and recording medium 12 is fixed by heat and pressure by fixing device 13, which is fixing means, and output as an image. Then, intermediate transfer body cleaner 14, which is a cleaning member for intermediate transfer body 9, collects the remaining toner after transfer, etc.

Specifically, the development method is preferably to apply an AC voltage to the developer carrier to form an alternating electric field in the development area while the magnetic brush is in contact with the photosensitive member. The distance (SD distance) between the developer carrier (developing sleeve) 6 and the photosensitive drum 1 is preferably 100 μm or more and 1000 μm or less in order to prevent carrier adhesion and improve dot reproducibility. If it is 100 μm or more, the supply of developer is sufficient and the image density is good. If it is 1000 μm or less, the magnetic field lines from the magnetic pole S1 are less likely to spread, the density of the magnetic brush is good, and dot reproducibility is improved. In addition, the force that holds the magnetic coated carrier is increased, and carrier adhesion can be suppressed.

The peak-to-peak voltage (Vpp) of the alternating electric field is preferably 300 V or more and 3000 V or less, more preferably 500 V or more and 1800 V or less. The frequency is preferably 500 Hz or more and 10000 Hz or less, more preferably 1000 Hz or more and 7000 Hz or less, and each can be appropriately selected depending on the process.

In this case, the waveform of the AC bias for forming the AC electric field can be a triangular wave, a square wave, a sine wave, or a waveform with a changed duty ratio. In order to respond to changes in the toner image formation speed, it is preferable to apply a development bias voltage having a discontinuous AC bias voltage (intermittent AC superimposed voltage) to the developer carrier for development. If the applied voltage is 300V or more, sufficient image density is easily obtained, and fogging toner in non-image areas is easily collected. Also, if it is 3000V or less, disturbance of the latent image via the magnetic brush is less likely to occur, and good image quality is obtained.

By using a two-component developer with a well-charged toner, the fog removal voltage (Vback) can be lowered, and the primary charge of the photoconductor can be lowered, thereby extending the life of the photoconductor. Vback depends on the development system, but is preferably 200V or less, and more preferably 150V or less. A contrast potential of 100V or more and 400V or less is preferably used to produce sufficient image density.

Furthermore, if the frequency is lower than 500 Hz, this also has an effect on the process speed, but the configuration of the electrostatic latent image carrier may be the same as that of the photoreceptor normally used in image forming devices. For example, a photoreceptor may be configured such that a conductive layer, an undercoat layer, a charge generation layer, a charge transport layer, and optionally a charge injection layer are provided in that order on a conductive substrate such as aluminum or SUS.

The conductive layer, undercoat layer, charge generation layer, and charge transport layer may be layers that are typically used in photoreceptors. For example, a charge injection layer or a protective layer may be used as the outermost layer of the photoreceptor.

The following describes how to measure the physical properties of the present invention.

<Method for measuring the content of monomer units derived from various polymerizable monomers in polymer A>
The content of monomer units derived from various polymerizable monomers in polymer A is measured by ¹ H-NMR under the following conditions.
Measuring device: FT NMR device JNM-EX400 (manufactured by JEOL Ltd.)
Measurement frequency: 400MHz
Pulse condition: 5.0 μs
Frequency range: 10,500 Hz
Number of measurements: 64 Measurement temperature: 30°C
Sample: 50 mg of a measurement sample is placed in a sample tube with an inner diameter of 5 mm, deuterated chloroform (CDCl ₃ ) is added as a solvent, and this is dissolved in a thermostatic chamber at 40° C. to prepare a sample.

From the obtained ^1H -NMR chart, a peak independent of peaks attributable to components of the monomer unit derived from the first polymerizable monomer is selected, and an integral value _S1 of this peak is calculated.

Similarly, from the peaks attributable to the components of the monomer unit derived from the second polymerizable monomer, a peak independent of the peaks attributable to the components of the monomer units derived from the other monomer units is selected, and the integral value _S2 of this peak is calculated.

Furthermore, in the case where a third polymerizable monomer is used, a peak independent of the peaks attributable to the constituent elements of the monomer unit derived from the third polymerizable monomer is selected from the peaks attributable to the constituent elements of the monomer unit derived from the other monomer units, and the integral value _S3 of this peak is calculated.

The content ratio of the monomer unit derived from the first polymerizable monomer is determined as follows using the above integral values _S1 , _S2, and _S3 , where _n1 , _{n2, and n3} are the numbers of hydrogen atoms in the constituent elements to which the peaks of interest for each site belong.
Content (mol %) of monomer unit derived from first polymerizable monomer=
{(S ₁ /n ₁ )/((S ₁ /n ₁ )+(S ₂ /n ₂ )+(S ₃ /n ₃ ))}×100

Similarly, the content ratios of the monomer units derived from the second polymerizable monomer and the third polymerizable monomer are determined as follows.
Content (mol %) of monomer unit derived from second polymerizable monomer=
{(S ₂ /n ₂ )/((S ₁ /n ₁ )+(S ₂ /n ₂ )+(S ₃ /n ₃ ))}×100
Content (mol%) of monomer unit derived from third polymerizable monomer=
{(S ₃ /n ₃ )/((S ₁ /n ₁ )+(S ₂ /n ₂ )+(S ₃ /n ₃ ))}×100

In addition, when polymer A uses a polymerizable monomer that does not contain hydrogen atoms in any of its constituent elements other than the vinyl group, ¹³ C-NMR is used, the measurement nucleus is set to ¹³ C, and the measurement is performed in single pulse mode, and calculation is performed in the same manner using ¹ H-NMR.

<SP value calculation method>
The SP value of a polymerizable monomer and the SP value of a unit derived from a polymerizable monomer are determined as follows according to the calculation method proposed by Fedors.

For each polymerizable monomer or release agent, the evaporation energy (Δei) (cal/mol) and molar volume (Δvi) (cm ³ /mol) for the atom or atomic group in the molecular structure are obtained from the table in "Polym. Eng. Sci., 14(2), 147-154 (1974)", and (4.184 × ΣΔei/ΣΔvi) ^0.5 is defined as the SP value (J/cm ³ ) ^0.5 .

Incidentally, SP ₁₁ and SP ₂₁ are calculated in the same manner as above for the atoms or atomic groups in the molecular structure in the state in which the double bond of the polymerizable monomer is cleaved by polymerization.

SP ₁₃ is calculated by determining the evaporation energy (Δei) and molar volume (Δvi) of each monomer unit derived from the polymerizable monomer constituting the polymer A, calculating the product of each monomer unit and the molar ratio (j) of each monomer unit in the polymer A, and dividing the sum of the evaporation energies of the monomer units by the sum of the molar volumes, according to the following formula.
SP ₃ = {4.184×(Σj×ΣΔei)/(Σj×ΣΔvi)} ^0.5

<Separation of Resin Coating Layer from Magnetic Carrier and Separation of Polymer A in Resin Coating Layer>
As a method for separating the resin coating layer from the magnetic carrier, there is a method in which the magnetic carrier is placed in a cup and the coating resin is eluted with toluene.

The eluted resin is dried and then dissolved in tetrahydrofuran (THF), and separated using the following apparatus.
[Device configuration]
LC-908 (Japan Analytical Industry Co., Ltd.)
JRS-86 (same company; repeat injector)
JAR-2 (same company; autosampler)
FC-201 (Gilson; Fraction Collector)
[Column configuration]
JAIGEL-1H to 5H (20φ×600 mm: preparative column) (manufactured by Japan Analytical Industry Co., Ltd.)
[Measurement conditions]
Temperature: 40°C
Solvent: THF
Flow rate: 5ml/min.
Detector: RI

Based on the molecular weight distribution of the coating resin, the resin composition is specified by the method described below, and the elution time at which the peak molecular weight (Mp) of polymer A is reached is measured in advance, and the resin components are separated around that time. The solvent is then removed, and the polymer is dried to obtain polymer A.

The resin structure of polymer A can be identified by identifying the atomic groups from the absorption wavenumbers using a Fourier transform infrared spectrometer (Spectrum One: manufactured by PerkinElmer).

<Measurement of weight average molecular weight of polymer A and resins other than polymer A by GPC>
The molecular weight (Mw) of the THF-soluble portion of the polymer A and the resin other than the polymer A is measured by gel permeation chromatography (GPC) as follows.

First, prepare the measurement sample as follows:

The sample (the coating resin separated from the magnetic carrier, and polymer A separated using a separation device) was mixed with tetrahydrofuran (THF) at a concentration of 5 mg/ml and left to stand at room temperature for 24 hours to dissolve the sample in THF. The sample was then passed through a sample treatment filter (Myshoridisk H-25-2, Tosoh Corporation) to prepare the GPC sample.

Next, using a GPC measuring device (HLC-8120GPC manufactured by Tosoh Corporation), measurements are carried out under the following measuring conditions according to the operating manual for said device.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: 7 columns of Shodex KF-801, 802, 803, 804, 805, 806, and 807 (manufactured by Showa Denko K.K.)
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0ml/min
Oven temperature: 40.0°C
Sample injection volume: 0.10 mL

When calculating the molecular weight of the sample, a molecular weight calibration curve is used that is created using standard polystyrene resins (e.g., trade names "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500" manufactured by Tosoh Corporation).

<Method of measuring volume average particle size (D50) of magnetic carrier and porous magnetic core>
The particle size distribution is measured using a laser diffraction/scattering type particle size distribution measuring device "Microtrac MT3300EX" (manufactured by Nikkiso Co., Ltd.).

The volume average particle size (D50) of the magnetic carrier and porous magnetic core is measured using a sample supplying device for dry measurement, "One-shot dry type sample conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.). The supply conditions for the Turbotrac are a dust collector as the vacuum source, with an air volume of approximately 33 l/sec and a pressure of approximately 17 kPa. Control is performed automatically on the software. The particle size is calculated as the 50% particle size (D50), which is the cumulative value of the volume average. Control and analysis are performed using the attached software (version 10.3.3-202D). The measurement conditions are as follows:
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81%
Particle shape: Non-spherical Upper limit of measurement: 1408μm
Measurement lower limit: 0.243μm
Measurement environment: 23°C, 50% RH

<Measurement of pore size and pore volume of porous magnetic core>
The pore size distribution of the porous magnetic core is measured by mercury intrusion porosimetry.

The measurement principle is as follows:

In this measurement, the pressure applied to the mercury is changed and the amount of mercury that penetrates into the pores is measured. The conditions under which mercury can penetrate into the pores can be expressed as PD = -4σ cos θ, based on the balance of forces, where P is the pressure, D is the pore diameter, and θ and σ are the contact angle and surface tension of the mercury, respectively. If the contact angle and surface tension are constants, then the pressure P and the pore diameter D into which mercury can penetrate at that time are inversely proportional. For this reason, the pressure P and the amount of infiltrating liquid V at that time are measured by changing the pressure, and the horizontal axis P of the P-V curve is directly substituted for the pore diameter in this formula to determine the pore distribution.

Measurements can be performed using a measuring device such as the fully automatic multi-function mercury porosimeter PoreMaster series or PoreMaster-GT series manufactured by Yuasa Ionics, or the automatic porosimeter AutoPore IV 9500 series manufactured by Shimadzu Corporation.

Specifically, measurements are performed using Shimadzu Corporation's Autopore IV9520 under the following conditions and procedures.

Measurement conditions Measurement environment 20℃
Measurement cell: Sample volume 5 cm ³ , Indentation volume 1.1 cm ³ , Application: Powder Measurement range: 2.0 psia (13.8 kPa) or more, 59989.6 psia (413.7 kPa) or less Measurement steps: 80 steps
(The steps are spaced equally apart when the pore diameter is taken logarithmically.)
Pressurization parameters: Exhaust pressure 50 μmHg
Exhaust time: 5.0 min
Mercury injection pressure: 2.0 psia (13.8 kPa)
Equilibration time: 5 sec
High pressure parameters Equilibration time 5sec
Mercury parameters Advancing contact angle 130.0 degrees
Receding contact angle 130.0 degrees
Surface tension 485.0mN/m (485.0dynes/cm)
Mercury density 13.5335g/mL

Measurement procedure: (1) Approximately 1.0 g of the porous magnetic core is weighed and placed in the sample cell.
Enter the weighing value.
(2) In the low pressure section, measure the range from 2.0 psia (13.8 kPa) to 45.8 psia (315.6 kPa).
(3) In the high pressure section, the range was measured to be 45.9 psia (316.3 kPa) or more and 59,989.6 psia (413.6 kPa) or less.
(4) The pore size distribution is calculated from the mercury injection pressure and the amount of mercury injected.
Steps (2), (3), and (4) are performed automatically by the software provided with the device.

From the pore size distribution measured as described above, the pore size at which the differential pore volume is maximum in the pore size range of 0.1 μm to 3.0 μm is read, and this is taken as the pore size at which the differential pore volume is maximum.

The pore volume is calculated by integrating the differential pore volume in the pore diameter range of 0.1 μm to 3.0 μm using the attached software, and this is taken as the pore volume.

<Measurement of Surface Roughness Ra of Magnetic Carrier and Magnetic Carrier Core Particles>
In the present invention, a non-contact three-dimensional surface measuring device (Micromap 123, manufactured by Ryoka Systems Co., Ltd.) was used for the measurement. This measuring device is a high-precision laser microscope, and can convert the surface roughness within the surface being observed into three dimensions. A specific example of the measurement method is shown below.

A 20x two-beam interference objective lens was attached to the optical microscope section of the micromap. A magnetic carrier or magnetic carrier core particle was placed under the lens, and the interference image was vertically scanned using a CCD camera in Wave mode to obtain a three-dimensional image of the magnetic carrier or magnetic carrier core particle surface. The obtained image was measured for the surface roughness Ra of the cross section at the cutting line using analysis software (SX-Viewer, Ryoka Systems Co., Ltd.) attached to the measuring instrument. The surface roughness Ra is obtained by summing up and averaging the absolute values of the deviations from the average line to the cross-sectional curve in the evaluation length. In the present invention, in order to further eliminate the influence of curvature on the unevenness of the magnetic carrier or magnetic carrier core particle surface, the measurement conditions were a cutting length of 24 μm, an evaluation length of 8 μm, and a cutoff value of 8 μm, and the center of the magnetic carrier or porous magnetic core particle on the three-dimensional image was aligned with the midpoint of the cutting line to calculate the surface roughness Ra. In the present invention, the surface roughness Ra is the average value obtained by measuring 50 magnetic carriers or magnetic carrier core particles.

<Measurement of Powder pH of Magnetic Carrier Core>
The powder pH of the magnetic carrier core is measured as follows.

10 g of magnetic carrier is weighed into a beaker, the resin coating layer is removed using toluene, and then it is dried. 50 g of pure water is added to the thoroughly dried magnetic carrier from which the resin coating layer has been removed, and the mixture is stirred for 2 minutes. The pure water in which the magnetic carrier from which the resin coating layer has been removed is then dispersed is measured using a pH meter (pH METER D-51, manufactured by Horiba, Ltd.) calibrated with aqueous solutions of pH 4, pH 7, and pH 9, and the value is taken as the powder pH of the magnetic carrier core.

<Method of measuring weight average particle diameter (D4) and number average particle diameter (D1)>
The weight average particle diameter (D4) and number average particle diameter (D1) of the toner were measured using a precision particle size distribution measuring device using a pore electrical resistance method equipped with a 100 μm aperture tube, "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.), and the accompanying dedicated software for setting measurement conditions and analyzing measurement data, "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.). Measurement was performed with an effective measurement channel count of 25,000 channels, and the measurement data was analyzed and calculated.

The electrolyte solution used for the measurements is prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of approximately 1% by mass, for example "ISOTON II" (manufactured by Beckman Coulter).

Before performing measurements and analysis, the dedicated software was configured as follows:

In the "Change Standard Measurement Method (SOM) screen" of the dedicated software, set the total count number in control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard Particle 10.0 μm" (manufactured by Beckman Coulter). Press the threshold/noise level measurement button to automatically set the threshold and noise level. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the aperture tube flush after measurement.

In the dedicated software's "Pulse to particle size conversion setting screen," set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range to 2 μm to 60 μm.

The specific measurement method is as follows:

(1) Pour about 200 ml of the electrolyte solution into a 250 ml round-bottom glass beaker for use with the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "aperture tube flush" function of the dedicated software.
(2) About 30 ml of the aqueous electrolyte solution is placed in a 100 ml flat-bottom glass beaker, and about 0.3 ml of a dilution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, made of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted 3 times by mass with ion-exchanged water is added thereto as a dispersant.
(3) A predetermined amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetorara 150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electric output of 120 W. About 2 ml of the above-mentioned Contaminon N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized.
(5) In a state where the electrolyte solution in the beaker in (4) is irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolyte solution and dispersed. Then, ultrasonic dispersion treatment is continued for another 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted so as to be 10°C or higher and 40°C or lower.
(6) The electrolytic solution (5) in which the toner is dispersed is dropped using a pipette into the round-bottom beaker (1) placed in the sample stand, and the measurement concentration is adjusted to about 5%. Then, the measurement is continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using the dedicated software that comes with the device to calculate the weight average particle diameter (D4) and number average particle diameter (D1). When the dedicated software is set to graph/volume %, the "average diameter" on the analysis/volume statistics (arithmetic mean) screen is the weight average particle diameter (D4), and when the dedicated software is set to graph/number %, the "average diameter" on the analysis/number statistics (arithmetic mean) screen is the number average particle diameter (D1).

<Calculation method for fine powder amount>
The amount of fine particles in the toner based on the number of particles (percentage by number) is calculated as follows.

For example, to determine the percentage of particles in a toner that are 4.0 μm or smaller, after performing measurements using the Multisizer 3 described above, (1) set the dedicated software to Graph/Number % and display the measurement results chart as number %. (2) Check the "<" in the particle size setting section on the Format/Particle Size/Particle Size Statistics screen, and enter "4" in the particle size input section below. Then, (3) when the Analysis/Number Statistics (Arithmetic Mean) screen is displayed, the value in the "<4 μm" display section is the percentage of particles in the toner that are 4.0 μm or smaller.

<How to calculate the amount of coarse powder>
The amount of coarse powder (vol %) on a volume basis in the toner is calculated as follows.

For example, to determine the volume percentage of particles in a toner that are 10.0 μm or larger, after performing measurements using the Multisizer 3 described above, (1) set the dedicated software to Graph/Volume % and display the measurement results chart in volume %. (2) Check the ">" in the particle size setting section on the Format/Particle Size/Particle Size Statistics screen, and enter "10" in the particle size input section below. Then, (3) when the Analysis/Volume Statistics (Arithmetic Mean) screen is displayed, the value in the ">10 μm" display section is the volume percentage of particles in the toner that are 10.0 μm or larger.

<Method for measuring the acid value of resin>
The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of a sample. The acid value of a resin is measured in accordance with JIS K 0070-1992, and more specifically, is measured according to the following procedure.
(1) Preparation of Reagents 1.0 g of phenolphthalein was dissolved in 90 ml of ethyl alcohol (95% by volume), and ion-exchanged water was added to make up to 100 ml to obtain a phenolphthalein solution.
Dissolve 7 g of special grade potassium hydroxide in 5 ml of water, and add ethyl alcohol (95% by volume) to make 1 L. Place in an alkali-resistant container to avoid contact with carbon dioxide, etc., leave for 3 days, then filter to obtain a potassium hydroxide solution. Store the obtained potassium hydroxide solution in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 ml of 0.1 mol/l hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution, and titrating with the potassium hydroxide solution, from the amount of the potassium hydroxide solution required for neutralization. The 0.1 mol/l hydrochloric acid used is prepared in accordance with JIS K 8001-1998.
(2) Procedure (A) Main Test 2.0 g of the crushed resin sample is accurately weighed into a 200 ml Erlenmeyer flask, and 100 ml of a mixed solution of toluene/ethanol (2:1) is added and dissolved over 5 hours. Then, several drops of the phenolphthalein solution are added as an indicator, and titration is performed using the potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for about 30 seconds.
(B) Blank Test: A blank test is carried out in the same manner as above, except that no sample is used (i.e., only a mixed solution of toluene/ethanol (2:1) is used).
(3) The obtained result is substituted into the following formula to calculate the acid value.
A=[(CB)×f×5.61]/S
Here, A is the acid value (mg KOH/g), B is the amount of potassium hydroxide solution added for the blank test (ml), C is the amount of potassium hydroxide solution added for the main test (ml), f is the factor of the potassium hydroxide solution, and S is the mass of the sample (g).

<Method for measuring the hydroxyl value of a resin>
The hydroxyl value is the number of milligrams of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl group when 1 g of a sample is acetylated. The hydroxyl value of a resin is measured in accordance with JIS K 0070-1992, and specifically, it is measured according to the following procedure.
(1) Preparation of the reagent: Place 25 g of special grade acetic anhydride in a 100 ml measuring flask, add pyridine to make the total volume 100 ml, and shake thoroughly to obtain an acetylation reagent. Store the obtained acetylation reagent in a brown bottle to avoid contact with moisture, carbon dioxide, etc.
1.0 g of phenolphthalein was dissolved in 90 ml of ethyl alcohol (95% by volume), and ion-exchanged water was added to make up to 100 ml to obtain a phenolphthalein solution.
Dissolve 35 g of special grade potassium hydroxide in 20 ml of water, and add ethyl alcohol (95% by volume) to make 1 L. Place in an alkali-resistant container to avoid contact with carbon dioxide, etc., leave for 3 days, then filter to obtain a potassium hydroxide solution. Store the obtained potassium hydroxide solution in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 ml of 0.5 mol/l hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution, and titrating with the potassium hydroxide solution, from the amount of the potassium hydroxide solution required for neutralization. The 0.5 mol/l hydrochloric acid used is prepared in accordance with JIS K 8001-1998.
(2) Procedure (A) Main Test: 1.0 g of the crushed resin sample is accurately weighed into a 200-ml round-bottom flask, and 5.0 ml of the acetylation reagent is accurately added to the sample using a volumetric pipette. If the sample is difficult to dissolve in the acetylation reagent, add a small amount of special grade toluene to dissolve it.
A small funnel is placed on the mouth of the flask, and the flask is heated by immersing about 1 cm of the bottom in a glycerin bath at about 97° C. At this time, it is preferable to cover the base of the neck of the flask with a piece of cardboard with a round hole in it in order to prevent the temperature of the neck of the flask from rising due to the heat of the bath.
After 1 hour, remove the flask from the glycerin bath and allow it to cool. After allowing it to cool, add 1 ml of water from the funnel and shake to hydrolyze the acetic anhydride. To further complete the hydrolysis, heat the flask again in the glycerin bath for 10 minutes. After allowing it to cool, wash the funnel and the walls of the flask with 5 ml of ethyl alcohol.
Add a few drops of the phenolphthalein solution as an indicator and titrate with the potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for about 30 seconds.
(B) Blank Test The same titration as above is carried out except that no amorphous polyester sample is used.
(3) The obtained result is substituted into the following formula to calculate the hydroxyl value.
A=[{(B-C)×28.05×f}/S]+D
Here, A is the hydroxyl value (mg KOH/g), B is the amount (ml) of potassium hydroxide solution added for the blank test, C is the amount (ml) of potassium hydroxide solution added for the main test, f is the factor of the potassium hydroxide solution, S is the mass (g) of the sample, and D is the acid value (mg KOH/g) of the sample.

<Measurement of glass transition temperature (Tg) of resin>
The glass transition temperature of the resin is measured using a differential scanning calorimeter "Q2000" (manufactured by TA Instruments) in accordance with ASTM D3418-82.

The melting points of indium and zinc are used to correct the temperature of the device's detection section, and the heat of fusion of indium is used to correct the amount of heat.

Specifically, approximately 5 mg of resin is weighed out and placed in an aluminum pan. An empty aluminum pan is used as a reference, and measurements are performed at a temperature increase rate of 10°C/min in the measurement range of 30°C to 180°C.

The temperature is first raised to 180°C and held there for 10 minutes, then lowered to 30°C, and then raised again. During this second heating process, a specific heat change is obtained in the temperature range of 30°C to 100°C. The glass transition temperature (Tg:°C) of the resin is determined by the temperature at the point where a straight line equidistant in the vertical direction from a straight line extending the baseline before and after the specific heat change occurs intersects with the curve of the stepwise change in the glass transition in the DSC curve.

<Measurement of the peak temperature of the endothermic peak of wax>
The peak top temperature of the maximum endothermic peak of the wax is measured using a differential scanning calorimeter "Q1000" (manufactured by TA Instruments) in accordance with ASTM D3418-82.

The melting points of indium and zinc are used to correct the temperature of the device's detection section, and the heat of fusion of indium is used to correct the amount of heat.

Specifically, about 5 mg of a sample is precisely weighed and placed in a silver pan, and a measurement is performed once. An empty silver pan is used as a reference. The measurement conditions are as follows.
Heating rate: 10° C./min
Measurement start temperature: 20℃
Measurement end temperature: 180°C

When using toner as a sample, if the endothermic peak (the endothermic peak derived from the binder resin) does not overlap with the endothermic peaks of resins other than the wax, the maximum endothermic peak obtained is treated as the endothermic peak derived from the wax.

On the other hand, when toner is used as a sample, the endothermic peak of the wax is identified by extracting the wax from the toner by Soxhlet extraction using a hexane solvent, performing differential scanning calorimetry of the wax alone using the method described above, and comparing the endothermic peak obtained with the endothermic peak of the toner.

The maximum endothermic peak refers to the peak with the largest amount of endothermic heat when there are multiple peaks. The peak temperature of the maximum endothermic peak is the melting point.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following formulations, parts are by weight unless otherwise specified.

<Production Example of Polymer A1>
Solvent: toluene 100.0 parts Monomer composition 100.0 parts (the monomer composition is a mixture of behenyl acrylate, methacrylonitrile, and styrene in the ratio shown below)
Behenyl acrylate (first polymerizable monomer) 67.0 parts (28.9 mol%)
Methacrylonitrile (second polymerizable monomer) 22.0 parts (53.8 mol%)
Styrene (third polymerizable monomer) 11.0 parts (17.3 mol%)
Polymerization initiator t-butyl peroxypivalate (Perbutyl PV, manufactured by NOF Corp.) 0.5 parts The above materials were charged into a reaction vessel equipped with a reflux condenser, a stirrer, a thermometer, and a nitrogen inlet tube under a nitrogen atmosphere. The reaction vessel was heated to 70°C while stirring at 200 rpm to carry out a polymerization reaction for 12 hours, and a solution in which the polymer of the monomer composition was dissolved in toluene was obtained. Subsequently, the temperature of the solution was lowered to 25°C, and the solution was added to 1000.0 parts of methanol while stirring, and the methanol insoluble matter was precipitated. The obtained methanol insoluble matter was filtered, washed with methanol, and then vacuum dried at 40°C for 24 hours to obtain polymer A1. The weight average molecular weight of polymer A1 was 68,400, the melting point was 62°C, and the acid value was 0.0 mgKOH/g.

When the above polymer A1 was analyzed by NMR, it was found to contain 28.9 mol% of monomer units derived from behenyl acrylate, 53.8 mol% of monomer units derived from methacrylonitrile, and 17.3 mol% of monomer units derived from styrene. The SP values of the polymerizable monomers and the units derived from the polymerizable monomers were calculated by the above method.

<Preparation of Monomer Having Urethane Group>
50.0 parts of methanol was charged into a reaction vessel. Then, 5.0 parts of Karenz MOI [2-isocyanatoethyl methacrylate] (Showa Denko K.K.) was added dropwise at 40° C. while stirring. After the dropwise addition was completed, stirring was continued for 2 hours while maintaining the temperature at 40° C. Then, unreacted methanol was removed with an evaporator to prepare a monomer having a urethane group.

<Preparation of Monomer Having Urea Group>
50.0 parts of dibutylamine was charged into a reaction vessel. Then, 5.0 parts of Karenz MOI [2-isocyanatoethyl methacrylate] was added dropwise at room temperature while stirring. After the dropwise addition was completed, stirring was continued for 2 hours. Then, unreacted dibutylamine was removed with an evaporator to prepare a monomer having a urea group.

<Production Examples of Polymers A2 to A29>
Polymers A2 to A29 were obtained by carrying out the reaction in the same manner as in the production example of polymer A1, except that the polymerizable monomers and the parts thereof were changed as shown in Table 1. The physical properties of polymers A2 to A29 are shown in Tables 2 to 4.

表１～３中の略号は以下の通り。
ＢＥＡ：ベヘニルアクリレート
ＢＭＡ：ベヘニルメタクリレート
ＳＡ：ステアリルアクリレート
ＭＹＡ：ミリシルアクリレート
ＯＡ：オクタコサアクリレート
ＨＡ：ヘキサデシルアクリレート
ＭＮ：メタクリロニトリル
ＡＮ：アクリロニトリル
ＨＰＭＡ：メタクリル酸２‐ヒドロキシプロピル
ＡＭ：アクリルアミド
ＵＴ：ウレタン基を有する単量体
ＵＲ：ウレア基を有する単量体
ＡＡ：アクリル酸
ＶＡ：酢酸ビニル
ＭＡ：アクリル酸メチル
Ｓｔ：スチレン
ＭＭ：メタクリル酸メチル

The abbreviations in Tables 1 to 3 are as follows.
BEA: Behenyl acrylate BMA: Behenyl methacrylate SA: Stearyl acrylate MYA: Myrisil acrylate OA: Octacosaacrylate HA: Hexadecyl acrylate MN: Methacrylonitrile AN: Acrylonitrile HPMA: 2-hydroxypropyl methacrylate AM: Acrylamide UT: Monomer with urethane group UR: Monomer with urea group AA: Acrylic acid VA: Vinyl acetate MA: Methyl acrylate St: Styrene MM: Methyl methacrylate

<Production Example of Magnetic Carrier Core 1>
Process 1 (weighing and mixing process)
Fe ₂ O ₃ 68.3% by mass
MnCO ₃ 28.5% by mass
Mg(OH) ₂ 2.0% by mass
SrCO ₃ 1.2% by mass
The above ferrite raw materials were weighed, 80 parts of the ferrite raw materials were mixed with 20 parts of water, and then wet-mixed in a ball mill using zirconia having a diameter (φ) of 10 mm for 3 hours to prepare a slurry. The solid content of the slurry was 80 mass %.

Step 2 (pre-firing step)
The mixed slurry was dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) and then fired in a batch-type electric furnace in a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1,050° C. for 3.0 hours to produce calcined ferrite.

Step 3 (Crushing step)
The calcined ferrite was crushed to about 0.5 mm with a crusher, and water was added to prepare a slurry. The solid content of the slurry was set to 70 mass%. The slurry was crushed for 3 hours with a wet ball mill using 1/8 inch stainless steel beads to obtain a slurry. The slurry was further crushed for 4 hours with a wet bead mill using zirconia with a diameter of 1 mm to obtain a calcined ferrite slurry having a volume-based 50% particle size (D50) of 1.3 μm.

Step 4 (granulation step)
To 100 parts of the calcined ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 1.5 parts of polyvinyl alcohol as a binder were added, and the mixture was granulated into spherical particles and dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) The resulting granulated material was subjected to particle size adjustment, and then heated at 700° C. for 2 hours using a rotary electric furnace to remove organic substances such as the dispersant and binder.

Step 5 (firing step)
The material was fired in a nitrogen atmosphere (oxygen concentration 1.0% by volume) for 2 hours from room temperature to the firing temperature (1100° C.), and then held at 1100° C. for 4 hours. The material was then cooled to 60° C. over 8 hours, returned from the nitrogen atmosphere to the air, and taken out at a temperature of 40° C. or less.

Step 6 (sorting step)
After the agglomerated particles were crushed, the particles were sieved through a sieve with 150 μm openings to remove coarse particles, air classification to remove fine powder, and further magnetic separation to remove low magnetic force particles to obtain porous magnetic core particles 1.

100 parts of porous magnetic core particles 1 were placed in the stirring vessel of a mixer (Dalton's universal stirrer NDMV type), the temperature was kept at 60°C, and 5 parts of a filling resin consisting of 95.0% by mass of methyl silicone oligomer and 5.0% by mass of γ-aminopropyltrimethoxysilane was dripped in at normal pressure.

After the dripping was completed, stirring was continued while adjusting the time, the temperature was raised to 70°C, and the resin composition was filled into the particles of each porous magnetic core.

After cooling, the resin-filled magnetic core particles obtained were transferred to a mixer (UD-AT type drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) with a spiral blade in a rotatable mixing container, and the temperature was raised to 140°C while stirring at a rate of 2°C/min under a nitrogen atmosphere. Heating and stirring were then continued at 140°C for 50 minutes.

Then, the mixture was cooled to room temperature, and the ferrite particles filled with resin and hardened were taken out, and non-magnetic materials were removed using a magnetic separator. Furthermore, coarse particles were removed using a vibrating sieve to obtain magnetic carrier cores 1 filled with resin.

<Production Examples of Magnetic Carrier Cores 3 to 7>
Magnetic carrier cores 3 to 7 were obtained in the same manner as magnetic carrier core 1 except that the production conditions were changed as shown in Table 5.

<Production Example of Magnetic Carrier Core 2>
To 100.0 parts of magnetite powder having a number-average particle size of 0.30 μm, 4.0 parts of a silane coupling agent (3-(2-aminoethylamino)propyltrimethoxysilane) was added, and the mixture was mixed and stirred at high speed in a container at 100° C. or higher to treat the fine particles.
10 parts phenol 6 parts formaldehyde solution (40% formaldehyde, 10% methanol, 50% water)
・84 parts of treated magnetite The above material, 5 parts of 28% ammonia water, and 20 parts of water were put into a flask, and the temperature was raised to 85°C in 30 minutes while stirring and mixing, and the mixture was kept at 85°C for 3 hours to polymerize and harden the resulting phenolic resin.Then, the hardened phenolic resin was cooled to 30°C, and water was added, after which the supernatant liquid was removed, and the precipitate was washed with water and then air-dried.Then, the mixture was dried at a temperature of 60°C under reduced pressure (5 mmHg or less) to obtain a spherical magnetic carrier core 2 in which the magnetic material was dispersed.

<Production Example of Magnetic Carrier 1>
Magnetic carrier core 1 100.0 parts Polymer A1 2.00 parts Magnetic carrier core 1: For 100.0 parts, the above-mentioned number of coating resins was diluted with toluene so that the resin content was 5%, and a resin solution was prepared by stirring thoroughly. Then, magnetic carrier core 1 was placed in a planetary mixer (Nauta Mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a temperature of 60°C, and the above-mentioned resin solution was added. As a method of addition, 1/2 the amount of resin solution was added, and solvent removal and coating operation were performed for 30 minutes. Next, 1/2 the amount of resin solution was added, and solvent removal and coating operation were performed for 40 minutes.

The magnetic carrier coated with the resin coating layer was then transferred to a mixer (UD-AT type drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) with a spiral blade in a rotatable mixing container, and heat-treated at 120°C for 2 hours in a nitrogen atmosphere while stirring at 10 revolutions per minute. The magnetic carrier obtained was separated into low magnetic products by magnetic separation, passed through a sieve with 150 μm openings, and then classified with an air classifier to obtain magnetic carrier 1.

<Production Examples of Magnetic Carriers 2 to 42>
Magnetic Carriers 2 to 42 were obtained in the same manner as Magnetic Carrier 1 except that the magnetic carrier formulation was changed as shown in Table 6.

<Toner Production Example>
Binder resin: 100 parts (polyester having a Tg of 57° C., an acid value of 12 mg KOH/g, and a hydroxyl value of 15 mg KOH/g)
・C.I. Pigment Blue 15:3 5.5 parts・3,5-di-t-butyl salicylic acid aluminum compound 0.2 parts・Normal paraffin wax (melting point: 90 ° C.) 6 parts The above-mentioned materials were mixed well with a Henschel mixer (FM-75J type, manufactured by Nippon Coke & Co., Ltd.), and then kneaded at a feed rate of 10 kg / hr with a twin-screw kneader (trade name: PCM-30 type, manufactured by Ikegai Steel Co., Ltd.) set at a temperature of 130 ° C. (kneaded material temperature at the time of discharge was 150 ° C.). The kneaded material obtained was cooled, crushed with a hammer mill, and then finely pulverized with a mechanical crusher (trade name: T-250, manufactured by Turbo Kogyo Co., Ltd.) at a feed rate of 15 kg / hr. Particles were obtained that had a weight average particle size of 5.5 μm, contained 55.6% by number of particles with a particle size of 4.0 μm or less, and contained 0.8% by volume of particles with a particle size of 10.0 μm or more.

The obtained particles were classified using a rotary classifier (product name: TTSP100, manufactured by Hosokawa Micron Corporation) to remove fine and coarse particles. Cyan toner particles 1 were obtained, which had a weight average particle size of 6.0 μm, a particle content of 27.8% by number with a particle size of 4.0 μm or less, and a particle content of 2.2% by volume with a particle size of 10.0 μm or more.

Furthermore, the following materials were charged into a Henschel mixer (product name: FM-75J type, manufactured by Nippon Coke & Engineering Co., Ltd.), and mixed at a rotating blade peripheral speed of 35.0 (m/sec) for a mixing time of 3 minutes to obtain cyan toner 1.
Cyan toner particles 1: 100 parts Silica particles: 1.0 part (silica particles having a number average particle size of primary particles of 10 nm, surface-treated with hexamethyldisilazane)
Strontium titanate particles: 0.5 parts (strontium titanate particles having a number-average particle size of primary particles of 40 nm, surface-treated with an octylsilane compound)
Toner 1 and magnetic carriers 1 to 42 were used, and each material was shaken in a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) so that the toner concentration was 8% by mass, to prepare 300 g of a two-component developer. The vibration conditions of the shaker were 200 rpm and 2 minutes.

On the other hand, 92 parts of toner 1 was added to 8 parts of each of magnetic carriers 1 to 42, and mixed for 5 minutes in a V-type mixer in an environment of normal temperature and humidity of 23°C/50% RH to obtain a replenishment developer. Details of the two-component developer are shown in Table 7, and details of the replenishment developer are shown in Table 8.

[Examples 1 to 33, Comparative Examples 1 to 9]
The prepared two-component developer and replenishment developer were used to carry out the following evaluations.

A modified Canon color copier, ImagePRESS C850, was used as the image forming device.

When forming images, the developer in the cyan developer was replaced with the two-component developers 1 to 42 described above, and the replenishment developer in the cyan replenishment developer container was replaced with the replenishment developers 1 to 42 described above. The modifications were as follows:

(1) The development contrast can be adjusted to any value and the automatic correction by the main unit is prevented from operating.
(2) The AC component of the developing bias was modified to have a frequency of 2.0 kHz, and the peak-to-peak voltage (Vpp) was modified so that it could be changed in increments of 0.1 kV from 0.7 kV to 1.8 kV.
(3) It was modified so that a monochrome image could be formed.

Using the modified machine, a single cyan color image was formed using laser beam printer paper CS-814 (81.4 g/m ² ) (available from Canon Marketing Japan Inc.) as transfer paper, and the following evaluation tests were carried out.

For image formation, FFH output charts with image ratios of 1% and 40% were used. FFH is a value that expresses 256 gradations in hexadecimal, with 00h being the first gradation (white background) of 256 gradations and FFH being the 256th gradation (solid area) of 256 gradations.

(1) Image Density Change Under an H/H environment (temperature 30°C/humidity 80RH%), FFH images (toner amount on paper: 0.35 mg/ ^cm2 ) measuring 15 mm x 15 mm were printed on transfer paper (CS-814) at a total of nine locations, including the center and edges of the paper. The density of the center of each image was measured using an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A), and the average value of the image densities obtained was calculated. Furthermore, after 10,000 sheets of FFH output charts with image ratios of 1% and 40% were printed in the same environment, evaluation images were printed in the same manner as before the printing, and the average value of the image densities obtained was calculated. In the same manner, the average value of the image densities was calculated every 10,000 sheets until the total number of printed sheets reached 50,000. The difference between the maximum and minimum values among the six average values obtained was calculated and evaluated according to the following criteria. The evaluation results are shown in Table 9.

<Evaluation criteria>
A: The difference is 0.02 or less. B: The difference is greater than 0.02 and less than 0.05. C: The difference is greater than 0.05 and less than 0.08. D: The difference is greater than 0.08 and less than 0.10. E: The difference is greater than 0.10 and less than 0.13. F: The difference is greater than 0.13 and less than 0.15. G: The difference is greater than 0.15 and less than 0.20. H: The difference is greater than 0.20 and less than 0.25. I: The difference is greater than 0.25 and less than 0.30. J: The difference is greater than 0.30.

(2) Image density change when left unattended After passing 50,000 sheets of a 40% FFH output chart in (1), the image was left unattended for three nights in a H/H environment. After that, an evaluation image was output under the same conditions as before the image was left unattended, and the average image density was calculated. The difference in the average image density before and after the image was left unattended was calculated, and the image was evaluated according to the following criteria. The evaluation results are shown in Table 9.

<Evaluation criteria>
A: The difference is 0.02 or less. B: The difference is greater than 0.02 and less than 0.04. C: The difference is greater than 0.04 and less than 0.06. D: The difference is greater than 0.06 and less than 0.08. E: The difference is greater than 0.08 and less than 0.10. F: The difference is greater than 0.10 and less than 0.12. G: The difference is greater than 0.12 and less than 0.15. H: The difference is greater than 0.15 and less than 0.18. I: The difference is greater than 0.18 and less than 0.20. J: The difference is greater than 0.20.

(3) In-plane uniformity After the durability test was performed under the above-mentioned conditions, five FFH images with an image ratio of 100% were output. Furthermore, an FFH image with a size of 200 mm x 280 mm (toner amount on paper: 0.35 mg/cm ² ) was output on A4 size paper (CS-814), and the obtained image was divided into 140 pieces of 20 mm x 20 mm each. The density of the center of each image was measured using an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A). Of the obtained image densities, the standard deviation of the image density was calculated and the in-plane uniformity was evaluated according to the following criteria. The evaluation results are shown in Table 9.

<Evaluation criteria>
A: Standard deviation is 0.01 or less B: Standard deviation is greater than 0.01 and less than 0.03 C: Standard deviation is greater than 0.03 and less than 0.05 D: Standard deviation is greater than 0.05 and less than 0.07 E: Standard deviation is greater than 0.07 and less than 0.10 F: Standard deviation is greater than 0.10 and less than 0.12 G: Standard deviation is greater than 0.12 and less than 0.15 H: Standard deviation is greater than 0.15 and less than 0.17 I: Standard deviation is greater than 0.17 and less than 0.20 J: Standard deviation is greater than 0.20

(4) Overall Judgment The evaluation ranks in the above evaluation items (1) to (3) were converted into numerical values, and the total value was judged according to the following criteria.

For the evaluation items (1) to (3), the scores were A=10, B=9, C=8, D=7, E=6, F=5, G=4, H=3, I=2, and J=1.

Products with a total overall score of 25 points or more were deemed to have achieved the effects of the present invention.

The results are shown in Table 9.

1, 1K, 1Y, 1C, 1M: electrostatic latent image carrier, 2, 2K, 2Y, 2C, 2M: charger, 3, 3K, 3Y, 3C, 3M: exposure device, 4, 4K, 4Y, 4C, 4M: developer, 5: developer container, 6, 6K, 6Y, 6C, 6M: developer carrier, 7: magnet, 8: regulating member, 9: intermediate transfer body, 10K, 10Y, 10C, 10M: intermediate transfer charger, 11: transfer charger, 12: transfer material (recording medium), 13: fixing device, 14: intermediate transfer body cleaner, 15, 15K, 15Y, 15C, 15M: cleaner, 16: pre-exposure, 17: cylindrical container, 18: lower electrode, 19: support base, 20: upper electrode, 21: magnetic carrier or carrier core, 22: electrometer, 23: processing computer, d1: gap when no sample is present, d2: gap when sample is filled

Claims (10)

A magnetic carrier comprising magnetic carrier core particles and magnetic carrier particles having a resin coating layer on the surface of the magnetic carrier core particles,
The resin coating layer contains only polymer A as a resin ,
The polymer A is
a polymer of a first composition containing only the first polymerizable monomer and the second polymerizable monomer;
a polymer of a second composition containing only the first polymerizable monomer, the second polymerizable monomer, and styrene;
a polymer of a third composition containing only the first polymerizable monomer, the second polymerizable monomer, and methyl methacrylate; or
a polymer of a fourth composition containing only the first polymerizable monomer, the second polymerizable monomer, styrene, and methyl methacrylate;
and
the first polymerizable monomer is at least one selected from the group consisting of stearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, heneicosanyl (meth)acrylate, behenyl (meth)acrylate, lignoceryl (meth)acrylate, ceryl (meth)acrylate, octacosal (meth)acrylate, myrisyl (meth)acrylate, doriacontal (meth)acrylate, and 2-decyltetradecyl (meth)acrylate ;
The second polymerizable monomer is at least one selected from the group consisting of the following formulae (A) and (B):

(In the formula, X represents a single bond or an alkylene group having 1 to 6 carbon atoms,
R ¹ is a nitrile group (-C≡N);
an amide group (-C(=O)NHR ¹⁰ , R ¹⁰ being a hydrogen atom);
-COOR ¹¹ (wherein R ¹¹ is an alkyl group having 1 to 6 carbon atoms or a hydroxyalkyl group having 1 to 6 carbon atoms);
--COO(CH ₂ ) ₂ NHCOOR ¹⁴ (wherein R ¹⁴ is an alkyl group having 1 to 4 carbon atoms), or
--COO(CH.sub.2 ₎ .sub.2 _-- NH--C(.dbd.O)--N(R.sub.15 ⁾ .sub.2 ₍ wherein each of the ^R.sub.15 's is independently an alkyl group having 1 to 6 carbon atoms)
indicates,
R2 represents an alkyl group having 1 to 4 carbon atoms, and each R3 ^{independently represents} a hydrogen atom or a methyl group.
The powder pH of the magnetic carrier core particles is 8.0 or more and 11.0 or less,
In the first composition to the fourth composition, the content ratio of the first polymerizable monomer is 5.0 mol % or more and 60.0 mol % or less based on the total number of moles of all polymerizable monomers in each composition ,
the content ratio of the second polymerizable monomer in the composition is 20.0 mol % or more and 95.0 mol % or less based on the total number of moles of all polymerizable monomers in the polymer A,
A magnetic carrier characterized in that, when the SP value of the first polymerizable monomer is SP ₁₂ and the SP value of the second polymerizable monomer is SP ₂₂ , the following formulas (3) and (4) are satisfied:
0.60 (J/cm ³ ) ^0.5 ≦SP ₂₂ -SP ₁₂ ≦15.00 (J/cm ³ ) ^0.5 (3)
18.30 (J/cm ³ ) ^0.5 ≦SP ₂₂ (4)
(However, when a plurality of first polymerizable monomers are present, SP ₁₂ is a weighted average value of the SP values of the respective polymerizable monomers. The second polymerizable monomer corresponds to all polymerizable monomers having SP ₂₂ that satisfies formula (3) for the calculated SP _12. When a plurality of second polymerizable monomers are present, SP ₂₂ is the SP value of each polymerizable monomer, and SP ₂₂ -SP ₁₂ is determined for each second polymerizable monomer.) 2. The magnetic carrier according to claim 1 , wherein the content of the second polymerizable monomer in the composition is 40.0 mol % or more and 95.0 mol % or less based on the total number of moles of all polymerizable monomers in the composition. 3. The magnetic carrier according to claim 1, wherein the first polymerizable monomer is at least one selected from the group consisting of stearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, heneicosanyl (meth)acrylate, behenyl (meth)acrylate, lignoceryl (meth)acrylate, ceryl (meth)acrylate, octacosal (meth)acrylate, myrisyl (meth)acrylate, and doriacontal (meth)acrylate. A magnetic carrier according to any one of claims ₁ to ₃ , wherein the second polymerizable monomer is at least one selected from the group consisting of methacrylonitrile, acrylonitrile, 2-hydroxypropyl methacrylate, acrylamide, acrylic acid, vinyl acetate, methyl acrylate, CH2 _{= C ( -CH3} ) _-COO (CH2)2NHCOOCH3, CH2=C(-CH3) -COO ₍ CH2 ) 2 _- NH - C ₍ = _O ) _-N ( -CH2CH2CH2CH3 ₎ 2 _. 5. The magnetic carrier according to claim 1 , wherein the resin coating layer is present in an amount of 0.5 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the magnetic carrier core. 6. The magnetic carrier according to claim 1, wherein the surface roughness Ra of the magnetic carrier particles is 0.15 μm or more and 0.25 μm or less. A two-component developer containing a toner having toner particles containing a binder resin and a magnetic carrier, the magnetic carrier being the magnetic carrier according to any one of claims 1 to 6 . An image forming method comprising: a charging step of charging an electrostatic latent image carrier; an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier; a developing step of developing the electrostatic latent image with a two-component developer to form a toner image; a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body; and a fixing step of fixing the transferred toner image to the transfer material,
The image forming method, wherein the two-component developer is the two-component developer according to claim 7 . a charging step of charging an electrostatic latent image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with a two-component developer in a developing device to form a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body, and a fixing step of fixing the transferred toner image to the transfer material, wherein the replenishment developer is replenished to the developing device in response to a reduction in toner concentration of the two-component developer in the developing device,
The replenishment developer contains a magnetic carrier and a toner having toner particles containing a binder resin,
the replenishment developer contains 2 parts by mass or more and 50 parts by mass or less of the toner per part by mass of the magnetic carrier,
The magnetic carrier according to any one of claims 1 to 6 is used as a replenishing developer. an image forming method comprising: a charging step of charging an electrostatic latent image carrier; an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier; a developing step of developing the electrostatic latent image with a two-component developer in a developing device to form a toner image; a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer body; and a fixing step of fixing the transferred toner image to the transfer material, wherein a replenishment developer is replenished to the developing device in response to a reduction in toner concentration of the two-component developer in the developing device,
The replenishment developer contains a magnetic carrier and a toner having toner particles containing a binder resin,
the replenishment developer contains 2 parts by mass or more and 50 parts by mass or less of the toner per part by mass of the magnetic carrier,
The image forming method, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 6 .

Images