JP6061423B2 - Carrier core material, carrier for electrophotographic development using the same and developer for electrophotography - Google Patents
Carrier core material, carrier for electrophotographic development using the same and developer for electrophotography Download PDFInfo
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- JP6061423B2 JP6061423B2 JP2013071980A JP2013071980A JP6061423B2 JP 6061423 B2 JP6061423 B2 JP 6061423B2 JP 2013071980 A JP2013071980 A JP 2013071980A JP 2013071980 A JP2013071980 A JP 2013071980A JP 6061423 B2 JP6061423 B2 JP 6061423B2
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Landscapes
- Developing Agents For Electrophotography (AREA)
Description
本発明はキャリア芯材並びにそれを用いた電子写真現像用キャリア及び電子写真用現像剤に関するものである。 The present invention relates to a carrier core material, an electrophotographic developer carrier and an electrophotographic developer using the same.
例えば、電子写真方式を用いたファクシミリやプリンタ、複写機などの画像形成装置では、感光体の表面に形成された静電潜像にトナーを付着させて可視像化し、この可視像を用紙等に転写した後、加熱及び加圧して定着させている。高画質化やカラー化の観点から、現像剤としては、電子写真現像用キャリア(以下、単に「キャリア」と記すことがある)とトナーとを含むいわゆる二成分系の電子写真用現像剤(以下、単に「現像剤」と記すことがある)が広く使用されている。 For example, in an image forming apparatus such as a facsimile, a printer, or a copier using an electrophotographic system, a toner is attached to an electrostatic latent image formed on the surface of a photosensitive member to make a visible image, and the visible image is formed on a sheet. After being transferred to, etc., it is fixed by heating and pressing. From the viewpoint of high image quality and colorization, as a developer, a so-called two-component electrophotographic developer (hereinafter referred to as “electrophotographic developer”) including a carrier for electrophotographic development (hereinafter sometimes simply referred to as “carrier”) and toner is used. Are sometimes used simply as “developer”.
二成分系の現像剤を用いた現像方式では、キャリアとトナーとを現像装置内で撹拌混合し、摩擦によってトナーを所定量まで帯電させる。そして、回転する現像ローラに現像剤を供給し、現像ローラ上で磁気ブラシを形成させて、磁気ブラシを介して感光体へトナーを電気的に移動させて感光体上の静電潜像を可視像化する。トナー移動後のキャリアは現像ローラ上に残留し、現像装置内で再びトナーと混合される。このため、キャリアの特性として、磁気ブラシを形成する磁気特性と、所望の電荷をトナーに付与する帯電特性および繰り返し使用における耐久性が要求される。 In a developing method using a two-component developer, a carrier and a toner are agitated and mixed in a developing device, and the toner is charged to a predetermined amount by friction. Then, a developer is supplied to the rotating developing roller, a magnetic brush is formed on the developing roller, and the toner is electrically moved to the photosensitive member via the magnetic brush, so that an electrostatic latent image on the photosensitive member can be formed. Visualize. The carrier after the toner movement remains on the developing roller and is mixed with the toner again in the developing device. For this reason, as the characteristics of the carrier, magnetic characteristics for forming a magnetic brush, charging characteristics for imparting a desired charge to the toner, and durability in repeated use are required.
そこで、マグネタイトや各種フェライト等のキャリア芯材の表面を樹脂で被覆したキャリアが一般に用いられているが、これまで使用されてきたキャリアは見掛け密度(比重)が高かったため、現像剤の撹拌に要する動力が大きく、また、トナーの割れやトナー外添剤のトナー粒子内への埋没などのトナー劣化も生じやすかった。そこで、近年の画像形成装置の高速化とも相俟ってキャリアの低比重化が強く望まれていた。 Therefore, a carrier in which the surface of a carrier core material such as magnetite or various ferrites is coated with a resin is generally used. However, since the carrier used so far has a high apparent density (specific gravity), it is necessary to stir the developer. Power was large, and toner degradation such as toner cracking and embedding of toner external additives in toner particles was likely to occur. Therefore, in combination with the recent increase in the speed of image forming apparatuses, a reduction in specific gravity of carriers has been strongly desired.
例えば特許文献1〜3では、粒子内に所定の大きさの空孔を形成してキャリア芯材を低比重化する技術が提案されている。 For example, Patent Documents 1 to 3 propose a technique in which pores of a predetermined size are formed in the particles to reduce the specific gravity of the carrier core material.
しかしながら、特許文献1及び特許文献2に開示されているキャリア芯材では、製造工程における炭酸塩等のガス化によって粒子内に空孔を形成しているため、作製されたキャリア芯材の空孔は細孔を介して外部と繋がっており、画像形成速度の速い装置に用いた場合、キャリア芯材の割れや欠けが発生するおそれがある。また、キャリア芯材を樹脂で被覆する際、被覆樹脂が粒子内に浸み込む量が多くなり経済性が悪くなる。さらに、キャリア芯材の製造工程において高抵抗化を目的として表面酸化処理をする場合、粒子内部まで酸化されてしまい磁気特性が大幅に低下する。 However, in the carrier core material disclosed in Patent Document 1 and Patent Document 2, since the voids are formed in the particles by gasification of carbonate or the like in the manufacturing process, the voids of the produced carrier core material Is connected to the outside through pores, and when used in an apparatus having a high image forming speed, the carrier core material may be cracked or chipped. Further, when the carrier core material is coated with a resin, the amount of the coating resin soaked into the particles increases, resulting in poor economic efficiency. Furthermore, when surface oxidation treatment is performed for the purpose of increasing the resistance in the manufacturing process of the carrier core material, the inside of the particles is oxidized and the magnetic properties are greatly reduced.
また、特許文献3で提案のキャリア芯材では、中空形状のコア材の表面を、磁性微粒子を分散させた樹脂バインダで被覆しているため、残留磁化及び保磁力が高くなり過ぎるおそれがある。 Further, in the carrier core material proposed in Patent Document 3, since the surface of the hollow core material is covered with a resin binder in which magnetic fine particles are dispersed, the residual magnetization and the coercive force may be too high.
本発明はこのような従来の問題に鑑みてなされたものであり、その目的は、低比重であって、画像形成速度が速くなっても割れや欠けが生じることがなく、また回転トルクが大きくならず、さらに所定の磁気特性を有するキャリア芯材を提供することにある。 The present invention has been made in view of the above-described conventional problems. The object of the present invention is to provide a low specific gravity, which does not cause cracking or chipping even when the image forming speed is increased, and has a large rotational torque. Furthermore, another object is to provide a carrier core material having predetermined magnetic characteristics.
本発明によれば、組成式MXFe3−XO4(但し、MはMg,Mn,Ca,Ti,Cu,Zn,Sr,Niからなる群より選択される少なくとも1種の金属元素、0<X≦1)で表される焼結粒子である第1キャリア芯材と、前記組成式で表され中空体を内包する焼結粒子である第2キャリア芯材とを含有し、前記第2キャリア芯材を20個数%以上有することを特徴とするキャリア芯材が提供される。 According to the present invention, the composition formula M X Fe 3 -X O 4 (where M is at least one metal element selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr, Ni, Containing a first carrier core material that is a sintered particle represented by 0 <X ≦ 1) and a second carrier core material that is a sintered particle represented by the composition formula and enclosing a hollow body, There is provided a carrier core material characterized by having 20 carrier % or more of two carrier core materials .
ここで、水銀圧入法で測定した、細孔径4μm以下の細孔容積は0.005mL/g以下であるのが好ましい。 Here, the pore volume with a pore diameter of 4 μm or less, measured by mercury porosimetry, is preferably 0.005 mL / g or less.
また、キャリア芯材の粒径Dに対する前記中空体の粒径dの比d/Dの平均値としては、0.10〜0.75の範囲であるのが好ましい。 The average value of the ratio d / D of the particle diameter d of the hollow body to the particle diameter D of the carrier core material is preferably in the range of 0.10 to 0.75.
見掛け密度としては2.2g/cm3以下であるのが好ましい。 The apparent density is preferably 2.2 g / cm 3 or less.
そしてまた、粒子密度としては3.0g/cm3〜4.7g/cm3の範囲であるのが好ましい。 And also, preferably as the particle density in the range of 3.0g / cm 3 ~4.7g / cm 3 .
また本発明によれば、前記のいずれかに記載のキャリア芯材の表面を樹脂で被覆したことを特徴とする電子写真現像用キャリアが提供される。 According to the present invention, there is also provided an electrophotographic developing carrier characterized in that the surface of the carrier core material described above is coated with a resin.
さらに本発明によれば、前記記載の電子写真現像用キャリアとトナーとを含む電子写真用現像剤が提供される。 Furthermore, according to the present invention, there is provided an electrophotographic developer comprising the electrophotographic developer carrier described above and a toner.
そしてまた本発明によれば、キャリア芯材原料を湿式粉砕後に、混合スラリー中に中空体を添加して撹拌し、スプレードライヤーで造粒することを特徴とする電子写真用キャリア芯材の製造方法が提供される。 And according to the present invention, a carrier core material for electrophotography is produced by wet pulverizing a carrier core material, adding a hollow body to the mixed slurry, stirring, and granulating with a spray dryer. Is provided.
本発明に係るキャリア芯材は、低比重であって、しかも現像器の撹拌速度等が速くなっても割れが効果的に抑制される。また、キャリア芯材を樹脂で被覆する場合、被覆樹脂が粒子内に浸み込む量が少なくなる。さらに、キャリア芯材を表面酸化処理した場合に粒子表面のみが酸化されるので、キャリア芯材の磁力低下を、内部に空孔を有さない中実のキャリア芯材と同程度に小さく抑えながら高抵抗化が図れる。 The carrier core material according to the present invention has a low specific gravity, and cracks are effectively suppressed even when the stirring speed of the developing device is increased. Further, when the carrier core material is coated with a resin, the amount of the coating resin soaked into the particles is reduced. Furthermore, since only the particle surface is oxidized when the carrier core material is subjected to surface oxidation treatment, the decrease in the magnetic force of the carrier core material is kept as small as that of a solid carrier core material having no voids inside. High resistance can be achieved.
また、本発明に係る電子写真現像用キャリア及び電子写真用現像剤によれば、画像形成速度の高速化及び高画質化が図れる。 In addition, according to the electrophotographic developer carrier and the electrophotographic developer according to the present invention, the image forming speed can be increased and the image quality can be improved.
本発明に係るキャリア芯材は、組成式MXFe3−XO4(但し、MはMg,Mn,Ca,Ti,Cu,Zn,Sr,Niからなる群より選択される少なくとも1種の金属元素、0<X≦1)で表される焼結粒子である第1キャリア芯材と、前記組成式で表され中空体を内包する焼結粒子である第2キャリア芯材とを含有し、前記第2キャリア芯材を20個数%以上有することを特徴とする。第2キャリア芯材が中空体を内包することにより、キャリア芯材の見掛け密度を小さくしながら、粒子強度の低下を抑えることができるようになる。なお、中空体を内包する第2キャリア芯材が20個数%未満であると、粒子強度は確保できるものの見掛け密度を小さくできない。 The carrier core material according to the present invention has a composition formula M X Fe 3-X O 4 (where M is at least one selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr, Ni). A first carrier core material which is a sintered particle represented by a metal element, 0 <X ≦ 1), and a second carrier core material which is a sintered particle represented by the above composition formula and enclosing a hollow body. The second carrier core material has at least 20% by number. By including the hollow body in the second carrier core material , a decrease in particle strength can be suppressed while reducing the apparent density of the carrier core material. If the second carrier core material containing the hollow body is less than 20% by number, the particle density can be ensured but the apparent density cannot be reduced.
本発明で使用する中空体に特に限定はなく、従来公知のものが使用できる。例えば、外殻成分がガラス、シリカ、シラスなどの無機系材料からなる無機質中空体、熱可塑性樹脂やカーボン等の有機系材料からなる有機質中空体が挙げられる。代表的なものとしては、樹脂バルーン、ガラスバルーン、フライアッシュバルーン、シリカバルーン、シラスバルーン、フェノールバルーン、カーボンバルーン、アルミナバルーン、ジルコニアバルーンなどが挙げられる。ただし、キャリア芯材が焼成することによって製造される場合は、中空体を構成する材料は融点が焼成温度以上である必要がある。この場合、シリカバルーンが好適に使用される。 There is no limitation in particular in the hollow body used by this invention, A conventionally well-known thing can be used. Examples thereof include an inorganic hollow body whose outer shell component is made of an inorganic material such as glass, silica, and shirasu, and an organic hollow body made of an organic material such as a thermoplastic resin and carbon. Typical examples include resin balloons, glass balloons, fly ash balloons, silica balloons, shirasu balloons, phenol balloons, carbon balloons, alumina balloons, zirconia balloons, and the like. However, when the carrier core material is produced by firing, the material constituting the hollow body needs to have a melting point equal to or higher than the firing temperature. In this case, a silica balloon is preferably used.
また、中空体の平均粒径は、第2キャリア芯材の平均粒径との兼ね合いから適宜決定すればよいが、一般に、5μm〜50μmの範囲が好ましい。また、第2キャリア芯材の粒径Dに対する中空体の粒径dの比d/Dの平均値は0.10〜0.75の範囲が好ましい。粒径比d/Dの平均値が0.10未満であると、第2キャリア芯材の見掛け密度を十分に小さくできない一方、粒径比d/Dの平均値が0.75を超えると第2キャリア芯材の強度が低下するおそれがある。より好ましい粒径比d/Dの平均値は0.40〜0.75の範囲である。
Moreover, the average particle diameter of the hollow body may be appropriately determined from the balance with the average particle diameter of the second carrier core material , but generally a range of 5 μm to 50 μm is preferable. The average value of the ratio d / D of the particle diameter d of the hollow body to the particle diameter D of the second carrier core material is preferably in the range of 0.10 to 0.75. If the average value of the particle size ratio d / D is less than 0.10, while unable to sufficiently reduce the apparent density of the second carrier core material, the average value of the particle size ratio d / D is more than 0.75 second 2 The strength of the carrier core material may be reduced. The average value of the particle size ratio d / D is more preferably in the range of 0.40 to 0.75.
本発明のキャリア芯材では、割れの起点となるような、外部と繋がる細孔が存在せず、キャリア芯材に内包されている中空体に位置の偏りがないので、割れが効果的に抑制される。キャリア芯材に内包される中空体の個数に限定はないが、1つのキャリア芯材に対して1つの中空体が内包されているのが好ましい。このとき、中空体はキャリア芯材の略中心に位置しているのが好ましい。また、中空体の形状は球状が好ましい。 In the carrier core material of the present invention, there are no pores connected to the outside, which are the starting points of cracks, and there is no bias in the position of the hollow body contained in the carrier core material, so cracks are effectively suppressed. Is done. Although the number of hollow bodies included in the carrier core material is not limited, it is preferable that one hollow body is included in one carrier core material. At this time, it is preferable that the hollow body is located substantially at the center of the carrier core material. The hollow body is preferably spherical.
また、本発明のキャリア芯材では、外部と繋がる細孔が存在しないので、高抵抗化を目的としてキャリア芯材に表面酸化処理をした場合に、粒子内部は酸化されず磁力低下が小さく抑えられる。また、キャリア芯材を樹脂で被覆してキャリアとする際、被覆樹脂が粒子内に浸み込むのが抑えられ、被覆樹脂が必要以上に消費されるのが防止される。本発明のキャリア芯材における、水銀圧入法で測定した、細孔径4μm以下の細孔容積は0.005mL/g以下であるのが好ましい。 Further, in the carrier core material of the present invention, since there are no pores connected to the outside, when the carrier core material is subjected to surface oxidation treatment for the purpose of increasing resistance, the inside of the particles is not oxidized and the magnetic force drop is suppressed to a small level. . Further, when the carrier core material is coated with a resin to make a carrier, the coating resin is prevented from entering the particles, and the coating resin is prevented from being consumed more than necessary. In the carrier core material of the present invention, the pore volume with a pore diameter of 4 μm or less, measured by mercury porosimetry, is preferably 0.005 mL / g or less.
本発明のキャリア芯材の好ましい電気抵抗は、印加電圧1000Vにおいて1.0×107Ω・cm〜1.0×1010Ω・cmの範囲である。電気抵抗が1.0×107Ω・cm未満であると、電荷リークの発生するおそれがある一方、電気抵抗が1.0×1010Ω・cmを超えると、エッジ効果が大きくなり画像濃度の低下を招くおそれがある。キャリア芯材のより好ましい電気抵抗は、1.0×107Ω・cm〜1.0×109Ω・cmの範囲である。 A preferable electrical resistance of the carrier core material of the present invention is in the range of 1.0 × 10 7 Ω · cm to 1.0 × 10 10 Ω · cm at an applied voltage of 1000V. If the electric resistance is less than 1.0 × 10 7 Ω · cm, charge leakage may occur. On the other hand, if the electric resistance exceeds 1.0 × 10 10 Ω · cm, the edge effect increases and the image density increases. There is a risk of lowering. The more preferable electric resistance of the carrier core material is in the range of 1.0 × 10 7 Ω · cm to 1.0 × 10 9 Ω · cm.
本発明のキャリア芯材の見掛け密度(比重)としては、2.2g/cm3以下であるのが好ましい。見掛け密度が2.2g/cm3よりも高いと撹拌に要する動力を充分には軽減できない。より好ましい見掛け密度は2.0g/cm3以下である。 The apparent density (specific gravity) of the carrier core material of the present invention is preferably 2.2 g / cm 3 or less. If the apparent density is higher than 2.2 g / cm 3 , the power required for stirring cannot be sufficiently reduced. A more preferable apparent density is 2.0 g / cm 3 or less.
また、本発明のキャリア芯材の粒子密度としては、4.7g/cm3以下であるのが好ましい。粒子密度が4.7g/cm3よりも高いと撹拌に要する動力を充分には軽減できない。より好ましい粒子密度は4.0g/cm3以下である。 Further, the particle density of the carrier core material of the present invention is preferably 4.7 g / cm 3 or less. If the particle density is higher than 4.7 g / cm 3 , the power required for stirring cannot be sufficiently reduced. A more preferable particle density is 4.0 g / cm 3 or less.
本発明のキャリア芯材の粒径に特に限定はないが、平均粒径で数十μm程度が好ましく、粒度分布はシャープであるのが好ましい。 The particle diameter of the carrier core material of the present invention is not particularly limited, but the average particle diameter is preferably about several tens of μm, and the particle size distribution is preferably sharp.
本発明のキャリア芯材の製造方法に特に限定はないが、以下に説明する製造方法が好適である。 Although there is no limitation in particular in the manufacturing method of the carrier core material of this invention, the manufacturing method demonstrated below is suitable.
まず、Fe成分原料とM成分原料、そして必要により添加剤とを秤量して分散媒中に投入し混合してスラリーを作製する。なお、MはMg、Mn、Ca、Ti、Cu、Zn、Sr、Ni等の2価の金属元素から選ばれる少なくとも1種の金属元素である。Fe成分原料としては、Fe2O3等が好適に使用される。M成分原料としては、MnであればMnCO3、Mn3O4等が使用でき、MgであればMgO、Mg(OH)2、MgCO3が好適に使用できる。また、Ca成分原料としては、CaO、Ca(OH)2、CaCO3等から選択される少なくとも1種の化合物が好適に使用される。 First, an Fe component raw material, an M component raw material, and, if necessary, an additive are weighed, put into a dispersion medium, and mixed to prepare a slurry. M is at least one metal element selected from divalent metal elements such as Mg, Mn, Ca, Ti, Cu, Zn, Sr, and Ni. As the Fe component material, Fe 2 O 3 or the like is preferably used. As the M component raw material, MnCO 3 , Mn 3 O 4 and the like can be used for Mn, and MgO, Mg (OH) 2 and MgCO 3 can be suitably used for Mg. As the Ca component raw material, at least one compound selected from CaO, Ca (OH) 2 , CaCO 3 and the like is preferably used.
本発明で使用する分散媒としては水が好適である。分散媒には、前記Fe成分原料、M成分原料の他、必要によりバインダー、分散剤等を配合してもよい。バインダーとしては、例えば、ポリビニルアルコールが好適に使用できる。バインダーの配合量としてはスラリー中の濃度が0.5〜2wt%程度とするのが好ましい。また、分散剤としては、例えば、ポリカルボン酸アンモニウム等が好適に使用できる。分散剤の配合量としてはスラリー中の濃度が0.5〜2wt%程度とするのが好ましい。その他、潤滑剤や焼結促進剤等を配合してもよい。スラリーの固形分濃度は50〜90wt%の範囲が望ましい。また、Fe成分原料、M成分原料を分散媒に投入する前に、必要により、粉砕混合の処理をしておいてもよい。 Water is preferred as the dispersion medium used in the present invention. In addition to the Fe component raw material and M component raw material, a binder, a dispersant, and the like may be blended in the dispersion medium, if necessary. For example, polyvinyl alcohol can be suitably used as the binder. The blending amount of the binder is preferably about 0.5 to 2 wt% in the slurry. Moreover, as a dispersing agent, polycarboxylate ammonium etc. can be used conveniently, for example. As the blending amount of the dispersant, the concentration in the slurry is preferably about 0.5 to 2 wt%. In addition, you may mix | blend a lubricant, a sintering accelerator, etc. The solid content concentration of the slurry is desirably in the range of 50 to 90 wt%. Further, before introducing the Fe component raw material and the M component raw material into the dispersion medium, if necessary, pulverization and mixing may be performed.
次に、以上のようにして作製されたスラリーを湿式粉砕する。例えば、ボールミルや振動ミルを用いて所定時間湿式粉砕する。粉砕後の原材料の平均粒径は50μm以下が好ましく、より好ましくは10μm以下である。振動ミルやボールミルには、所定粒径のメディアを内在させるのがよい。メディアの材質としては、鉄系のクロム鋼や酸化物系のジルコニア、チタニア、アルミナなどが挙げられる。粉砕工程の形態としては連続式及び回分式のいずれであってもよい。粉砕物の粒径は、粉砕時間や回転速度、使用するメディアの材質・粒径などによって調整される。 Next, the slurry produced as described above is wet pulverized. For example, wet grinding is performed for a predetermined time using a ball mill or a vibration mill. The average particle diameter of the raw material after pulverization is preferably 50 μm or less, more preferably 10 μm or less. The vibration mill or ball mill preferably contains a medium having a predetermined particle diameter. Examples of the material of the media include iron-based chromium steel and oxide-based zirconia, titania, and alumina. As a form of a grinding | pulverization process, any of a continuous type and a batch type may be sufficient. The particle size of the pulverized product is adjusted depending on the pulverization time and rotation speed, the material and particle size of the media used, and the like.
そして、湿式粉砕されたスラリーに所定量の中空体を配合する。キャリア芯材中の、中空体を内包した粒子の割合、及びキャリア芯材1粒子中に内包される中空体の個数が調整されるため、中空体の配合量に限定はないが、1wt%〜10wt%の範囲が望ましい。 Then, a predetermined amount of the hollow body is blended into the wet-pulverized slurry. Since the ratio of the particles including the hollow body in the carrier core material and the number of hollow bodies included in one particle of the carrier core material are adjusted, the amount of the hollow body is not limited. A range of 10 wt% is desirable.
次いで、中空体が配合されたスラリーを噴霧乾燥させて造粒する。具体的には、スプレードライヤーなどの噴霧乾燥機にスラリーを導入し、雰囲気中へ噴霧することによって球状に造粒する。噴霧乾燥時の雰囲気温度は100℃〜300℃の範囲が好ましい。これにより、粒径10μm〜200μmの球状の造粒物が得られる。なお、得られた造粒物は、振動ふるい等を用いて、粗大粒子や微粉を除去し粒度分布をシャープなものとするのが望ましい。 Next, the slurry containing the hollow body is spray-dried and granulated. Specifically, the slurry is introduced into a spray dryer such as a spray dryer, and granulated into a spherical shape by spraying into the atmosphere. The atmospheric temperature during spray drying is preferably in the range of 100 ° C to 300 ° C. Thereby, a spherical granulated product having a particle diameter of 10 μm to 200 μm is obtained. In addition, it is desirable that the obtained granulated product has a sharp particle size distribution by removing coarse particles and fine powder using a vibration sieve or the like.
次に、造粒物を800℃以上に加熱した炉に投入して、キャリア芯材を合成するための一般的な手法で焼成することにより、キャリア芯材を生成させる。焼成温度が800℃未満であると焼結が進行しない。焼成温度の好ましい上限値は1500℃である。焼成温度が1500℃以上であると、キャリア芯材同士の過剰焼結が起こり、異形粒子が発生することがあるからである。したがって、焼成温度としては800℃〜1500℃の範囲が好ましい。 Next, the granulated product is put into a furnace heated to 800 ° C. or higher and fired by a general method for synthesizing a carrier core material, thereby generating a carrier core material. When the firing temperature is less than 800 ° C., sintering does not proceed. A preferable upper limit of the firing temperature is 1500 ° C. This is because when the firing temperature is 1500 ° C. or higher, the carrier cores are excessively sintered and irregular shaped particles may be generated. Therefore, the firing temperature is preferably in the range of 800 ° C to 1500 ° C.
このようにして得られた焼成物を必要により解粒する。具体的には、例えば、ハンマーミル等によって焼成物を解粒する。解粒工程の形態としては連続式及び回分式のいずれであってもよい。そして、必要により、粒径を所定範囲に揃えるため分級を行う。分級方法としては、風力分級や篩分級など従来公知の方法を用いることができる。また、風力分級機で1次分級した後、振動篩や超音波篩で粒径を所定範囲に揃えるようにしてもよい。さらに、分級工程後に、磁場選鉱機によって非磁性粒子を除去するようにしてもよい。 The fired product thus obtained is pulverized as necessary. Specifically, for example, the fired product is pulverized by a hammer mill or the like. The form of the granulation step may be either a continuous type or a batch type. And if necessary, classification is performed in order to make the particle size within a predetermined range. As a classification method, a conventionally known method such as air classification or sieve classification can be used. In addition, after primary classification with an air classifier, the particle size may be aligned within a predetermined range with a vibration sieve or an ultrasonic sieve. Furthermore, you may make it remove a nonmagnetic particle with a magnetic field separator after a classification process.
その後、必要に応じて、分級後の粉末(焼成物)を酸化性雰囲気中で加熱して、粒子表面に酸化被膜を形成してキャリア芯材の高抵抗化を図ってもよい(表面酸化処理)。酸化性雰囲気としては大気雰囲気又は酸素と窒素の混合雰囲気のいずれでもよい。また、加熱温度は、200℃〜800℃の範囲が好ましく、250℃〜600℃の範囲がさらに好ましい。加熱時間は0.5時間〜5時間の範囲が好ましい。 Thereafter, if necessary, the classified powder (baked product) may be heated in an oxidizing atmosphere to form an oxide film on the particle surface to increase the resistance of the carrier core (surface oxidation treatment). ). The oxidizing atmosphere may be either an air atmosphere or a mixed atmosphere of oxygen and nitrogen. The heating temperature is preferably in the range of 200 ° C to 800 ° C, and more preferably in the range of 250 ° C to 600 ° C. The heating time is preferably in the range of 0.5 hours to 5 hours.
前述のように、このときキャリア芯材内部には中空体のみが存在しており細孔を持たないので、粒子内部は酸化されず粒子表面のみが酸化される。これにより、キャリア芯材の電気抵抗が高められ且つ磁力低下が小さく抑えられる。 As described above, at this time, only the hollow body exists inside the carrier core material and does not have pores, so the inside of the particle is not oxidized and only the surface of the particle is oxidized. As a result, the electrical resistance of the carrier core material is increased, and the decrease in magnetic force is kept small.
以上のようにして作製した本発明のキャリア芯材は、そのまま電子写真現像用キャリアとして用いることもできるが、帯電性等の観点からは、キャリア芯材の表面を樹脂で被覆して用いるのが好ましい。 The carrier core material of the present invention produced as described above can be used as a carrier for electrophotographic development as it is, but from the viewpoint of chargeability, the surface of the carrier core material is used by coating with a resin. preferable.
キャリア芯材の表面を被覆する樹脂としては、従来公知のものが使用でき、例えば、ポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリ−4−メチルペンテン−1、ポリ塩化ビニリデン、ABS(アクリロニトリル−ブタジエン−スチレン)樹脂、ポリスチレン、(メタ)アクリル系樹脂、ポリビニルアルコール系樹脂、並びにポリ塩化ビニル系やポリウレタン系、ポリエステル系、ポリアミド系、ポリブタジエン系等の熱可塑性エストラマー、フッ素シリコーン系樹脂などが挙げられる。 As the resin for coating the surface of the carrier core material, conventionally known resins can be used, for example, polyethylene, polypropylene, polyvinyl chloride, poly-4-methylpentene-1, polyvinylidene chloride, ABS (acrylonitrile-butadiene-styrene). ) Resin, polystyrene, (meth) acrylic resin, polyvinyl alcohol resin, polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene, and other thermoplastic elastomers, and fluorosilicone resins.
キャリア芯材の表面を樹脂で被覆するには、樹脂の溶液又は分散液をキャリア芯材に塗布すればよい。塗布溶液用の溶媒としては、トルエン、キシレン等の芳香族炭化水素系溶媒;アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン系溶媒;テトラヒドロフラン、ジオキサン等の環状エーテル類溶媒;エタノール、プロパノール、ブタノール等のアルコール系溶媒;エチルセロソルブ、ブチルセロソルブ等のセロソルブ系溶媒;酢酸エチル、酢酸ブチル等のエステル系溶媒;ジメチルホルムアミド、ジメチルアセトアミド等のアミド系溶媒などの1種又は2種以上を用いることができる。塗布溶液中の樹脂成分濃度は、一般に0.001〜30wt%、特に0.001〜2wt%の範囲内にあるのがよい。 In order to coat the surface of the carrier core material with resin, a resin solution or dispersion may be applied to the carrier core material. Solvents for the coating solution include aromatic hydrocarbon solvents such as toluene and xylene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; cyclic ether solvents such as tetrahydrofuran and dioxane; ethanol, propanol, and butanol Alcohol solvents such as ethyl cellosolve, cellosolve solvents such as butyl cellosolve; ester solvents such as ethyl acetate and butyl acetate; amide solvents such as dimethylformamide and dimethylacetamide, etc. . The concentration of the resin component in the coating solution is generally in the range of 0.001 to 30 wt%, particularly 0.001 to 2 wt%.
キャリア芯材への樹脂の被覆方法としては、例えばスプレードライ法や流動床法あるいは流動床を用いたスプレードライ法、浸漬法等を用いることができる。これらの中でも、少ない樹脂量で効率的に塗布できる点で流動床法が特に好ましい。樹脂被覆量は、例えば流動床法の場合には吹き付ける樹脂溶液量や吹き付け時間によって調整することができる。 As a method of coating the resin on the carrier core material, for example, a spray drying method, a fluidized bed method, a spray drying method using a fluidized bed, an immersion method, or the like can be used. Among these, the fluidized bed method is particularly preferable in that it can be efficiently applied with a small amount of resin. For example, in the case of the fluidized bed method, the resin coating amount can be adjusted by the amount of resin solution sprayed and the spraying time.
キャリアの平均粒子径は、一般に、体積平均粒子径で10μm〜200μmの範囲、特に10μm〜50μmの範囲が好ましい。 In general, the average particle diameter of the carrier is preferably in the range of 10 μm to 200 μm, particularly in the range of 10 μm to 50 μm, in terms of volume average particle diameter.
本発明に係る電子写真用現像剤は、以上のようにして作製したキャリアとトナーとを混合してなる。キャリアとトナーとの混合比に特に限定はなく、使用する現像装置の現像条件などから適宜決定すればよい。一般に現像剤中のトナー濃度は1wt%〜15wt%の範囲が好ましい。トナー濃度が1wt%未満の場合、画像濃度が薄くなりすぎ、他方トナー濃度が15wt%を超える場合、現像装置内でトナー飛散が発生し機内汚れや転写紙などの背景部分にトナーが付着する不具合が生じるおそれがあるからである。より好ましいトナー濃度は3wt%〜10wt%の範囲である。 The electrophotographic developer according to the present invention is obtained by mixing the carrier prepared as described above and a toner. The mixing ratio of the carrier and the toner is not particularly limited, and may be determined as appropriate based on the developing conditions of the developing device to be used. In general, the toner concentration in the developer is preferably in the range of 1 wt% to 15 wt%. When the toner density is less than 1 wt%, the image density becomes too thin, and when the toner density exceeds 15 wt%, the toner scatters in the developing device, and the toner adheres to the background portion such as in-machine dirt or transfer paper. This is because there is a risk of occurrence. A more preferable toner concentration is in the range of 3 wt% to 10 wt%.
トナーとしては、重合法、粉砕分級法、溶融造粒法、スプレー造粒法など従来公知の方法で製造したものが使用できる。具体的には、熱可塑性樹脂を主成分とする結着樹脂中に、着色剤、離型剤、帯電制御剤等を含有させたものが好適に使用できる。 As the toner, toner produced by a conventionally known method such as a polymerization method, a pulverization classification method, a melt granulation method, or a spray granulation method can be used. Specifically, a binder resin containing a thermoplastic resin as a main component and containing a colorant, a release agent, a charge control agent and the like can be suitably used.
トナーの粒径は、一般に、コールターカウンターによる体積平均粒径で5μm〜15μmの範囲が好ましく、7μm〜12μmの範囲がより好ましい。 In general, the particle diameter of the toner is preferably in the range of 5 μm to 15 μm, more preferably in the range of 7 μm to 12 μm, as a volume average particle diameter measured by a Coulter counter.
トナー表面には、必要により、改質剤を添加してもよい。改質剤としては、例えば、シリカ、アルミナ、酸化亜鉛、酸化チタン、酸化マグネシウム、ポリメチルメタクリレート等が挙げられる。これらの1種又は2種以上を組み合わせて使用できる。 If necessary, a modifier may be added to the toner surface. Examples of the modifier include silica, alumina, zinc oxide, titanium oxide, magnesium oxide, polymethyl methacrylate and the like. These 1 type (s) or 2 or more types can be used in combination.
キャリアとトナーとの混合は、従来公知の混合装置を用いることができる。例えばヘンシェルミキサー、V型混合機、タンブラーミキサー、ハイブリタイザー等を用いることができる。 A known mixing device can be used for mixing the carrier and the toner. For example, a Henschel mixer, a V-type mixer, a tumbler mixer, a hybridizer, or the like can be used.
以下、本発明を実施例によりさらに詳しく説明するが本発明はこれらの実施例に何ら限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.
実施例1
Mnフェライトからなるキャリア芯材を下記方法で作製した。出発原料として、Fe2O3(平均粒径:0.6μm)1179gと、Mn3O4(平均粒径:0.9μm)461gとを純水360g中に分散し、分散剤としてポリカルボン酸アンモニウム系分散剤を10g添加して混合物とした。この混合物を湿式ボールミル(メディア径2mm)により粉砕処理し、混合スラリーを得た。
Example 1
A carrier core material made of Mn ferrite was prepared by the following method. As starting materials, 1179 g of Fe 2 O 3 (average particle size: 0.6 μm) and 461 g of Mn 3 O 4 (average particle size: 0.9 μm) are dispersed in 360 g of pure water, and polycarboxylic acid is used as a dispersant. 10 g of an ammonium dispersant was added to form a mixture. This mixture was pulverized by a wet ball mill (media diameter 2 mm) to obtain a mixed slurry.
この混合スラリーに日本フィライト社製のシリカバルーン「フィライト200/7」を分級して平均粒径23.9μmとしたもの16.4g(1wt%)を添加し十分に撹拌した。この混合スラリーをスプレードライヤーにて約130℃の熱風中に噴霧し、粒径10μm〜100μmの乾燥造粒物を得た。この造粒物から、粒径100μmを超える粗粒は篩網を用いて除去した。 To this mixed slurry, 16.4 g (1 wt%) of a silica balloon “Philite 200/7” manufactured by Nippon Philite was classified to an average particle size of 23.9 μm was added and stirred sufficiently. This mixed slurry was sprayed into hot air of about 130 ° C. with a spray dryer to obtain a dry granulated product having a particle size of 10 μm to 100 μm. From this granulated product, coarse particles having a particle size exceeding 100 μm were removed using a sieve screen.
この造粒物を、窒素雰囲気下(酸素分圧PO2=10−3atm)の電気炉に投入し1050℃まで2時間かけて昇温し、その後1050℃で3時間保持し焼成を行った。そして、常温まで冷却した。得られた焼成物をハンマーミルで解粒した後に振動ふるいを用いて分級した。そして、さらに大気雰囲気下において温度450℃で1時間表面酸化処理を行い平均粒径35.9μmのキャリア芯材を得た。
得られたキャリア芯材の見掛け密度、粒子密度、細孔容積、磁気特性、粒子強度を下記に示す方法でそれぞれ測定した。表2に測定結果をまとめて示す。また、図1に粒子断面のSEM写真を示す。
This granulated product was put into an electric furnace under a nitrogen atmosphere (oxygen partial pressure P O2 = 10 −3 atm), heated to 1050 ° C. over 2 hours, and then held at 1050 ° C. for 3 hours for firing. . And it cooled to normal temperature. The obtained fired product was pulverized with a hammer mill and classified using a vibration sieve. Further, a surface oxidation treatment was performed for 1 hour at a temperature of 450 ° C. in an air atmosphere to obtain a carrier core material having an average particle diameter of 35.9 μm.
The apparent density, particle density, pore volume, magnetic properties, and particle strength of the obtained carrier core material were measured by the following methods. Table 2 summarizes the measurement results. FIG. 1 shows an SEM photograph of the particle cross section.
(見掛け密度)
キャリア芯材の見掛け密度はJIS Z 2504に準拠して測定した。
(Apparent density)
The apparent density of the carrier core material was measured in accordance with JIS Z 2504.
(粒子密度)
Quantachrome社製のウルトラピクノメーター「Ultrapycnometer」を用いて下記条件で粒子密度を測定した。
サンプルセル:中
サンプル量:60g
繰返し測定:10回
パージモード:Flow
パージ時間:1分
(Particle density)
The particle density was measured under the following conditions using an Ultrapycnometer manufactured by Quantachrome.
Sample cell: Medium sample amount: 60g
Repeat measurement: 10 times Purge mode: Flow
Purge time: 1 minute
(細孔容積)
Quantachrome社製のポロシメーター「PoremasterGT60」を用いて下記条件で微分細孔容積分布を測定した。そして、測定した微分細孔容積分布から細孔容積を求めた。
ガラスセル:外容積3.2cm3 浸入容積0.5cm3
サンプル量:1g
低圧側測定
・脱気
・水銀充填(0〜50psi(0〜345kPa))
高圧側測定
・水銀圧入(20psi〜30000psi(139kPa〜207MPa))
水銀の表面張力:480dyn/cm
水銀の接触角 :141.3°
(Pore volume)
The differential pore volume distribution was measured under the following conditions using a porosimeter “Poremaster GT60” manufactured by Quantachrome. And the pore volume was calculated | required from the measured differential pore volume distribution.
Glass cell: outer volume 3.2 cm 3 intrusion volume 0.5 cm 3
Sample amount: 1g
Low pressure side measurement, degassing, mercury filling (0-50 psi (0-345 kPa))
High-pressure side measurement / mercury intrusion (20 psi to 30000 psi (139 kPa to 207 MPa))
Mercury surface tension: 480 dyn / cm
Mercury contact angle: 141.3 °
(磁気特性の変化量)
室温専用振動試料型磁力計(VSM)(東英工業社製「VSM−P7」)を用いて、外部磁場を0〜79.58×104A/m(10000エルステッド)の範囲で1サイクル連続的に印加して、79.58×103A/m(1000エルステッド)の磁場における磁化σ1k(Am2/kg)を、表面酸化処理前後のキャリア芯材についてそれぞれ測定した。そして、その変化量を算出した。
(Change in magnetic properties)
Using a vibration sample type magnetometer (VSM) dedicated to room temperature (“VSM-P7” manufactured by Toei Kogyo Co., Ltd.), the external magnetic field ranges from 0 to 79.58 × 10 4 A / m (10000 Oersted) for one cycle. The magnetization σ 1k (Am 2 / kg) in a magnetic field of 79.58 × 10 3 A / m (1000 oersted) was measured for the carrier core material before and after the surface oxidation treatment. Then, the amount of change was calculated.
(粒子強度)
作製したキャリア芯材40g程度を網目25μmの篩を用いて、マイクロトラック粒度分析計(日機装社製)で測定したときの14μm以下の累積粒子頻度が0.10%以下となるように調整する。そして、調整した試料30gをサンプルミルに投入し、回転数12,500rpmで1分間撹拌する。次いで、マイクロトラック粒度分析計を用いて14μm以下の累積粒子頻度を測定する。サンプルミルによって処理した後の累積粒子頻度と処理する前の累積粒子頻度との差を算出し、これを微粉発生量として粒子強度の指標とした。評価基準は下記のとおりである。
○:0.00〜1.50%
△:1.50〜3.00%
×:3.00%以上
(Particle strength)
About 40 g of the produced carrier core material is adjusted using a sieve having a mesh size of 25 μm so that the cumulative particle frequency of 14 μm or less when measured with a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) is 0.10% or less. Then, 30 g of the adjusted sample is put into a sample mill and stirred for 1 minute at a rotational speed of 12,500 rpm. Next, the cumulative particle frequency of 14 μm or less is measured using a Microtrac particle size analyzer. The difference between the cumulative particle frequency after processing by the sample mill and the cumulative particle frequency before processing was calculated, and this was used as an index of particle strength as the amount of fine powder generated. The evaluation criteria are as follows.
○: 0.00 to 1.50%
Δ: 1.50 to 3.00%
X: 3.00% or more
(中空体を内包する粒子の割合)
得られたキャリア芯材を熱硬化性樹脂中に分散させた後、加熱により樹脂を硬化させた。この硬化物の表面を日本電子社製のクロスセクションポリッシャ「SM-09010」を用いて研磨した。研磨面を日本電子社製の走査電子顕微鏡「JSM-6510LA」を用いて観察し、粒子の断面写真を倍率250倍で複数視野について撮影した。撮影した粒子断面写真から、500粒子中に存在する中空体を内包している粒子の個数を求め、その割合を算出した。
(Percentage of particles enclosing a hollow body)
The obtained carrier core material was dispersed in a thermosetting resin, and then the resin was cured by heating. The surface of the cured product was polished using a cross section polisher “SM-09010” manufactured by JEOL. The polished surface was observed using a scanning electron microscope “JSM-6510LA” manufactured by JEOL Ltd., and cross-sectional photographs of the particles were taken for a plurality of fields of view at a magnification of 250 times. The number of particles enclosing a hollow body present in 500 particles was determined from the photographed particle cross-sectional photograph, and the ratio was calculated.
(キャリア芯材と中空体との粒径比d/D)
前記と同様に粒子の断面写真を倍率1000倍で撮影した。撮影した粒子断面写真から、中空体を内包する粒子のみランダムに100粒子選択し、Media Cybernetics社製の画像解析ソフト「Image-Pro PLUS」を用いて、キャリア芯材粒径(最大直径)Dと中空体の粒径(最大直径)dとを測定した。キャリア芯材粒径の測定時には、穴を埋めるモードを選択した。測定された値から粒径比d/Dを求め、平均値を算出した。なお、粒子断面は必ずしも芯材粒子の中心部を観察できるものではなく、中心部からずれたところを観察する可能性があるので注意が必要である。
(Particle size ratio d / D between carrier core and hollow)
Similar to the above, a cross-sectional photograph of the particles was taken at a magnification of 1000 times. From the photographed cross section of the particle, 100 particles are selected at random from the inside of the hollow body, and using the image analysis software “Image-Pro PLUS” manufactured by Media Cybernetics, the carrier core particle diameter (maximum diameter) D and The particle size (maximum diameter) d of the hollow body was measured. When measuring the particle diameter of the carrier core material, the mode for filling the holes was selected. The particle size ratio d / D was determined from the measured values, and the average value was calculated. Note that the cross section of the particles does not necessarily allow the central portion of the core particle to be observed, and there is a possibility of observing a location shifted from the central portion, so care must be taken.
実施例2〜7,比較例1〜3
表1に示す出発原料及び配合量、焼成温度で実施例1と同様にしてキャリア芯材を作製した。そして、実施例1と同様にして各物性を測定した。表2に測定結果をまとめて示す。
Examples 2-7, Comparative Examples 1-3
A carrier core material was produced in the same manner as in Example 1 with the starting materials, blending amounts, and firing temperature shown in Table 1. And each physical property was measured like Example 1. FIG. Table 2 summarizes the measurement results.
表2から明らかなように、実施例1〜7のキャリア芯材は、中空体を20個数%以上内包し、見掛け密度は2.20g/cm3以下と低かった。しかも、粒子強度は比較例1の中実のキャリア芯材と同程度の高い強度を有していた。また、表面酸化処理の前後で、磁化σ1k(Am2/kg)の低下は1.9Am2/kg以下と小さく抑えられていた。 As is apparent from Table 2, the carrier core materials of Examples 1 to 7 contained 20% by number or more of hollow bodies, and the apparent density was as low as 2.20 g / cm 3 or less. Moreover, the particle strength was as high as that of the solid carrier core material of Comparative Example 1. In addition, before and after the surface oxidation treatment, the decrease in magnetization σ 1k (Am 2 / kg) was suppressed to 1.9 Am 2 / kg or less.
これに対し、中実である比較例1のキャリア芯材、及び中空体を内包する粒子の割合が5個数%の比較例2のキャリア芯材では、粒子強度等は良好であったものの、見掛け密度が2.42g/cm3及び2.43g/cm3と高かった。また、焼成工程におけるガス発生で空孔を形成した比較例3のキャリア芯材では、見掛け密度は1.92g/cm3と低かったものの、表面酸化処理による磁化σ1k(Am2/kg)の低下が大きく、粒子強度も低かった。 In contrast, the solid carrier core material of Comparative Example 1 and the carrier core material of Comparative Example 2 in which the proportion of the particles enclosing the hollow body was 5% by number, although the particle strength and the like were good, the apparent density was as high as 2.42 g / cm 3 and 2.43 g / cm 3. Further, in the carrier core material of Comparative Example 3 in which pores were formed by gas generation in the firing process, although the apparent density was as low as 1.92 g / cm 3 , the magnetization σ 1k (Am 2 / kg) due to the surface oxidation treatment was reduced. The drop was large and the particle strength was low.
本発明に係るキャリア芯材は、見掛け密度が低く、しかも現像器の撹拌速度等が速くなっても割れなどが少ない。また、キャリア芯材を樹脂で被覆する場合、被覆樹脂が粒子内に浸み込む量が少ない。さらに、キャリア芯材を表面酸化処理した場合、キャリア芯材の磁力低下が小さく抑えられ有用である。 The carrier core material according to the present invention has a low apparent density and has few cracks even when the stirring speed of the developing device is increased. Further, when the carrier core material is coated with a resin, the amount of the coating resin soaked into the particles is small. Furthermore, when the carrier core material is subjected to surface oxidation treatment, the decrease in the magnetic force of the carrier core material is suppressed to be small, which is useful.
Claims (7)
前記組成式で表され中空体を内包する焼結粒子である第2キャリア芯材と
を含有し、
前記第2キャリア芯材を20個数%以上有することを特徴とするキャリア芯材。 Composition formula M X Fe 3-X O 4 (where M is at least one metal element selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr, Ni, 0 <X ≦ 1) A first carrier core material that is a sintered particle represented by :
A second carrier core material, which is a sintered particle represented by the composition formula and encapsulating a hollow body;
Containing
A carrier core material comprising 20% by number or more of the second carrier core material.
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