JP2015227268A - Ferrite particle, carrier for electrophotography and developer for electrophotography using the same - Google Patents
Ferrite particle, carrier for electrophotography and developer for electrophotography using the same Download PDFInfo
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- Developing Agents For Electrophotography (AREA)
- Compounds Of Iron (AREA)
Abstract
Description
本発明はフェライト粒子並びにそれを用いた電子写真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 ferrite particles, an electrophotographic 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ー、複写機などの画像形成装置では、静電潜像担持体（以下、「感光体」と記すことがある）の表面に形成された静電潜像を現像剤で可視像化し、この可視像を用紙等に転写した後、加熱・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、キャリアとトナーとを含むいわゆる二成分現像剤が広く使用されている。 For example, in image forming apparatuses such as facsimiles, printers, and copiers using an electrophotographic system, an electrostatic latent image formed on the surface of an electrostatic latent image carrier (hereinafter sometimes referred to as “photosensitive member”). Is visualized with a developer, and the visible image is transferred onto paper or the like, and then fixed by heating and pressing. A so-called two-component developer including a carrier and a toner is widely used as a developer from the viewpoint of high image quality and colorization.
この二成分現像剤を用いた現像は、複数の磁極を内蔵し、現像剤を表面に担持する現像剤担持体（以下、「現像スリーブ」と記すことがある）と、感光体とを所定間隔を隔てて略平行に対向配置し、感光体と現像スリーブとが対向する領域（以下、「現像領域」と記すことがある）において、キャリアが集合して穂立ちした磁気ブラシを現像スリーブ上に形成させると共に、感光体と現像スリーブとの間に現像バイアス電圧を印加し、感光体表面の静電潜像にトナーを付着させることにより行われる。 In the development using the two-component developer, a plurality of magnetic poles are built in, and a developer carrier (hereinafter sometimes referred to as a “development sleeve”) that carries the developer on the surface and a photosensitive member are spaced at a predetermined interval. In a region where the photosensitive member and the developing sleeve face each other (hereinafter referred to as a “developing region”), a magnetic brush that gathers and stands up is placed on the developing sleeve. In addition to the formation, a developing bias voltage is applied between the photosensitive member and the developing sleeve, and toner is attached to the electrostatic latent image on the surface of the photosensitive member.
特許文献１では、ＳｒＴｉＯ３を添加することで、小粒径で球形状の粒子表面に微小な凹凸を形成させ、高帯電性と長寿命などを図るキャリア芯材が提案されている。しかし、かかる提案のキャリア芯材では、局所的なＳｒフェライトの異常生成が生じた粒子が所定比率以上で存在する。 Patent Document 1 proposes a carrier core material that has SrTiO 3 added to form minute irregularities on the surface of a spherical particle having a small particle diameter, thereby achieving high chargeability and long life. However, in the proposed carrier core material, particles in which local abnormal generation of Sr ferrite occurs are present in a predetermined ratio or more.
特許文献２では、小粒径で良好な電気抵抗を有し、粒度分布や表面性の粒子間バラツキの小さいキャリア芯材が提案されている。しかし、かかる提案の小粒径のキャリアでは、現像装置内における現像剤の搬送性は十分には改善されないおそれがある。 Patent Document 2 proposes a carrier core material having a small particle size, good electrical resistance, and small particle size distribution and surface-to-particle variation. However, the carrier having such a small particle diameter may not sufficiently improve the developer transportability in the developing device.
特許文献３では、粒子表面に不均一な凹凸を形成することで流動性を低下させ、帯電立ち上がりの向上を図るキャリア芯材が提案されている。しかし、かかる提案のキャリア芯材では、粒子表面の不均一な凹凸が被覆樹脂の剥離を助長する原因となるおそれがある。 Patent Document 3 proposes a carrier core material that reduces fluidity by forming uneven unevenness on the particle surface and improves charge rising. However, in the proposed carrier core material, uneven unevenness on the particle surface may cause peeling of the coating resin.
特許文献４では、シリコーン樹脂を被覆して流動度を適正化することで、キャリア付着やトナー飛散、高画質化を図るキャリア芯材が提案されている。しかし、かかる提案のキャリア芯材は、被覆する樹脂が特定され、キャリアとしての性能を制限されるものである。 Patent Document 4 proposes a carrier core material that is coated with a silicone resin to optimize fluidity, thereby achieving carrier adhesion, toner scattering, and high image quality. However, the proposed carrier core material is one in which the resin to be coated is specified and the performance as a carrier is limited.
近年、画像形成装置における画像形成速度の高速化という市場要求に対応するため、現像スリーブの回転速度を速めて、現像領域への現像剤の単位時間当たりの供給量を増加させる傾向にある。 In recent years, in order to meet the market demand for higher image forming speed in image forming apparatuses, the rotational speed of the developing sleeve tends to be increased to increase the amount of developer supplied per unit time to the developing area.
しかし、例えば、３０μｍ以下の小粒径のキャリアを用いた場合、トナーとの十分な混合が行われないことがあった。また、現像スリーブの回転速度を速めて現像領域への現像剤供給量を増加させても、十分な画像濃度が得られないことがあった。 However, for example, when a carrier having a small particle diameter of 30 μm or less is used, sufficient mixing with the toner may not be performed. Further, even if the rotation speed of the developing sleeve is increased and the amount of developer supplied to the developing area is increased, a sufficient image density may not be obtained.
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、電子写真方式画像形成装置のキャリアとして用いた場合に、画像形成速度が速くなってもトナーとの混合が良好で十分な画像濃度が得られるフェライト粒子を提供することにある。 The present invention has been made in view of such a conventional problem, and its purpose is that when used as a carrier of an electrophotographic image forming apparatus, the mixing with toner is good even when the image forming speed is increased. An object of the present invention is to provide ferrite particles that can provide a sufficient image density.
前記目的を達成する本発明に係るフェライト粒子は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とするフェライト粒子であって、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、当該フェライト粒子の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とする。なお、本明細書における「粒子表面の結晶均一度」については後述の実施例においてその測定方法を含め説明する。また、「流動度」は、JIS Z2502に準拠し、フェライト粒子５０ｇが流れ落ちるのに要する時間（秒）である。 The ferrite particle according to the present invention that achieves the above object has the composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, and depends on Mg and Mn. It is the number of substitutions with Fe. Ferrite particles whose main component is a material represented by 0 <X <1), containing Ca element in a range of 0.05 mass% to 0.5 mass%, The crystal uniformity on the particle surface is 80% by number or more, and the difference between the fluidity of the ferrite particles and the fluidity after demagnetization is in the range of 2.5 seconds to 16.0 seconds. And The “crystal uniformity on the particle surface” in the present specification will be described in the examples described later, including the measurement method. The “fluidity” is the time (seconds) required for 50 g of ferrite particles to flow in accordance with JIS Z2502.
体積平均粒子径としては、２０μｍ〜３０μｍの範囲であるのが好ましい。 The volume average particle diameter is preferably in the range of 20 μm to 30 μm.
また本発明によれば、前記のいずれかに記載のフェライト粒子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。 In addition, according to the present invention, there is provided an electrophotographic developing carrier characterized in that the surface of the ferrite particles 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.
また、本発明に係るフェライト粒子の前駆体は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とするフェライト粒子の前駆体であって、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、１０００ガウスの磁界下で１５秒間着磁した後の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とする。この前駆体を用いて着磁処理をすれば、本発明のフェライト粒子を得られる。 Further, the precursor of the ferrite particles according to the present invention, the composition formula M X Fe 3-X O 4 ( where, M is .X is Mg and Mn is a sum of Mg and Mn, by Mg and Mn The number of substitutions with Fe, which is a precursor of ferrite particles whose main component is a material represented by 0 <X <1), and Ca element in a range of 0.05 mass% to 0.5 mass%. And the crystal surface uniformity of the particle surface is 80% by number or more, and the difference between the fluidity after magnetizing for 15 seconds under a magnetic field of 1000 gauss and the fluidity after demagnetizing treatment is 2.5 seconds. It is characterized by being in a range of ˜16.0 seconds. If this precursor is used for magnetization treatment, the ferrite particles of the present invention can be obtained.
本発明に係るフェライト粒子によれば、キャリアとして用いた場合に、画像形成速度が速くなってもトナーとの混合が十分に行われ、十分な画像濃度が得られる。 According to the ferrite particles of the present invention, when used as a carrier, even when the image forming speed is increased, the toner particles are sufficiently mixed and a sufficient image density is obtained.
本発明者等は、小粒径のフェライト粒子をキャリアとして用いた場合であっても、トナーとの混合性が低下せず、また、画像形成速度を速めても十分な画像濃度が得られるようにすべく鋭意検討を重ねた結果、粒子表面に現れている結晶の大きさの均一性及び粒子の着磁性が影響していることを突き止め本発明をなすに至った。 The inventors of the present invention do not deteriorate the mixing property with the toner even when the ferrite particles having a small particle diameter are used as the carrier, and a sufficient image density can be obtained even if the image forming speed is increased. As a result of extensive studies, the inventors have found that the uniformity of the size of crystals appearing on the particle surface and the magnetization of the particles are affecting the present invention.
すなわち、本発明に係るフェライト粒子は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とし、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、当該フェライト粒子の流動度と、脱磁処理した後の流動度との差（ＦＲ変化とも言う）が２．５秒〜１６．０秒の範囲であることが大きな特徴である。 That is, the ferrite particles according to the present invention have a composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, The number of substitutions is mainly composed of a material represented by 0 <X <1), contains Ca element in the range of 0.05% by mass to 0.5% by mass, and has 80 crystal uniformity on the particle surface. The difference between the fluidity of the ferrite particles and the fluidity after demagnetization (also referred to as FR change) is in the range of 2.5 seconds to 16.0 seconds. .
本発明のフェライト粒子では、Ｃａ元素の添加量が０．０５質量％〜０．５質量％の範囲であることが重要である。Ｃａ元素の添加量が０．０５質量％未満であると、フェライト粒子の結晶に異常成長が生じ、粒子表面の結晶の大きさが不均一となる。反対に、Ｃａ元素の添加量が０．５質量％を超えると、フェライト粒子を着磁させたときの磁力が大きくなりすぎ、粒子同士の凝集が生じて流動性が大きく低下しトナーとの混合性が悪くなる。より好ましいＣａ元素の添加量は０．１質量％〜０．３質量％の範囲である。 In the ferrite particles of the present invention, it is important that the amount of Ca element added is in the range of 0.05 mass% to 0.5 mass%. When the addition amount of the Ca element is less than 0.05% by mass, abnormal growth occurs in the ferrite particle crystal, and the crystal size on the particle surface becomes non-uniform. On the contrary, if the amount of Ca element added exceeds 0.5% by mass, the magnetic force when the ferrite particles are magnetized becomes too large, causing the particles to agglomerate, greatly reducing fluidity and mixing with the toner. Sexuality gets worse. A more preferable addition amount of Ca element is in the range of 0.1% by mass to 0.3% by mass.
また、本発明のフェライト粒子では、粒子表面の結晶均一度が８０個数％以上であることが重要である。後述の実施例で示すように、表面に５μｍ超の結晶が現れているフェライト粒子の存在割合が８０個数％よりも少ないと、流動性が悪くなりトナーとの混合性が低下する。フェライト粒子表面の結晶均一度は、Ｃａの含有量及び製造工程における焼結条件などによって調整すればよい。詳細は後述する。 In the ferrite particles of the present invention, it is important that the crystal uniformity on the particle surface is 80% by number or more. As will be described in Examples below, if the proportion of ferrite particles having crystals of more than 5 μm appearing on the surface is less than 80% by number, the fluidity is deteriorated and the mixing property with the toner is lowered. The crystal uniformity on the surface of the ferrite particles may be adjusted depending on the Ca content and the sintering conditions in the manufacturing process. Details will be described later.
そしてまた、本発明のフェライト粒子では、当該フェライト粒子の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることも重要である。かかる流動度の差が２．５秒未満であると、フェライト粒子の流動性が磁性により影響を受けていないと言え、流動性が制御できないものである。トナーとの混合が十分となるような制御ができない。逆に、前記の流動度の差が１６．０秒を超えると、粒子同士の磁力による結びつきが強くなりすぎてトナーとの混合性が低下する。前記の流動度の差のより好ましい範囲は４秒〜１４秒の範囲である。 In the ferrite particles of the present invention, it is also important that the difference between the fluidity of the ferrite particles and the fluidity after demagnetization is in the range of 2.5 seconds to 16.0 seconds. If the difference in fluidity is less than 2.5 seconds, it can be said that the fluidity of the ferrite particles is not affected by magnetism, and the fluidity cannot be controlled. It is impossible to control the mixture with the toner sufficiently. On the other hand, when the difference in fluidity exceeds 16.0 seconds, the binding between the particles is too strong and the mixing property with the toner decreases. A more preferable range of the difference in fluidity is in the range of 4 seconds to 14 seconds.
本発明のフェライト粒子の粒径に特に限定はないが、体積平均粒子径が２０μｍ〜３０μｍの範囲のいわゆる小粒径のものが好ましい。２０μｍ以上であれば、キャリア飛散による画像欠陥が発生しないので好ましい。３０μｍ以下であれば、小粒径のトナーが使用でき、画質向上が図れるので好ましい。また、その粒度分布はシャープであるのが好ましい。具体的には、１８μｍ以下の体積累積値は、１０％以下が好ましく、より好ましくは３．５％以下である。１０％以下であれば、キャリア飛散による画像欠陥が発生しないので好ましい。一方、８６μｍ以上の体積累積値は、５％以下が好ましく、より好ましくは１％以下である。５％以下であれば、画質が劣化しにくいので、好ましい。 The particle diameter of the ferrite particles of the present invention is not particularly limited, but those having a so-called small particle diameter with a volume average particle diameter in the range of 20 μm to 30 μm are preferable. If it is 20 micrometers or more, since the image defect by carrier scattering does not generate | occur | produce, it is preferable. If it is 30 μm or less, a toner having a small particle diameter can be used and image quality can be improved. The particle size distribution is preferably sharp. Specifically, the volume cumulative value of 18 μm or less is preferably 10% or less, more preferably 3.5% or less. If it is 10% or less, image defects due to carrier scattering do not occur, which is preferable. On the other hand, the volume cumulative value of 86 μm or more is preferably 5% or less, more preferably 1% or less. If it is 5% or less, the image quality is hardly deteriorated, which is preferable.
本発明のフェライト粒子は各種用途に用いることができ、例えば、電子写真現像用キャリアや電磁波吸収材、電磁波シールド材用材料粉末、ゴム、プラスチック用充填材・補強材、ペンキ、絵具・接着剤用艶消材、充填材、補強材等として用いることができる。これらの中でも特に電子写真現像用キャリアとして好適に用いられる。 The ferrite particles of the present invention can be used in various applications, for example, electrophotographic developer carriers, electromagnetic wave absorbing materials, electromagnetic shielding material powders, rubber, fillers / reinforcing materials for plastics, paints, paints / adhesives It can be used as a matting material, filler, reinforcing material and the like. Among these, it is particularly preferably used as a carrier for electrophotographic development.
本発明のフェライト粒子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 the manufacturing method of the ferrite particle of the present invention is not particularly limited, the manufacturing method described below is preferable.
まず、Ｆｅ成分原料とＭｇ成分原料、Ｍｎ成分原料、そして添加剤としてＣａ成分原料とを秤量して仮焼成する。仮焼成の温度としては７５０℃〜９００℃の範囲が好ましい。７５０℃以上であれば、仮焼による一部フェライト化が進み、焼成時のガス発生量が少なく、固体間反応が十分に進むため、好ましい。一方、９００℃以下であれば、仮焼による焼結が弱く、後のスラリー粉砕工程で原料を十分に粉砕できるので好ましい。また、仮焼成時の雰囲気としては大気雰囲気が好ましい。Ｆｅ成分原料としては、Ｆｅ２Ｏ３等が好適に使用される。Ｍｇ成分原料としてはＭｇＯ、Ｍｇ（ＯＨ）２、ＭｇＣＯ３が使用でき、Ｍｎ成分原料としてはＭｎＣＯ３、Ｍｎ３Ｏ４等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等が好適に使用される。 First, the Fe component raw material, the Mg component raw material, the Mn component raw material, and the Ca component raw material as an additive are weighed and temporarily fired. The pre-baking temperature is preferably in the range of 750 ° C to 900 ° C. If it is 750 degreeC or more, since part ferrite-ization by calcination advances, the amount of gas generation at the time of baking is small, and reaction between solids fully advances, it is preferable. On the other hand, if it is 900 degrees C or less, since sintering by calcination is weak and a raw material can fully be grind | pulverized at a later slurry grinding | pulverization process, it is preferable. Moreover, an air atmosphere is preferable as the atmosphere at the time of temporary firing. As the Fe component material, Fe 2 O 3 or the like is preferably used. MgO, Mg (OH) 2 and MgCO 3 can be used as the Mg component raw material, and MnCO 3 , Mn 3 O 4 and the like can be suitably used as the Mn component raw material. As the Ca component material, CaO, Ca (OH) 2 , CaCO 3 or the like is preferably used.
次いで、仮焼成した原料を解粒して分散媒中に投入しスラリーを作製する。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、前記仮焼成原料の他、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０．５〜２質量％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０．５〜２質量％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５０〜９０質量％の範囲が望ましい。より好ましくは６０〜８０質量％である。６０質量％以上であれば、造粒品中に粒子内細孔が少なく、焼成時の焼結不足を防ぐことができる。一方、８０質量％以下であれば、会合粒子が少なく、粒子形状による流動性悪化を防ぐことができる。 Next, the calcined raw material is pulverized and charged into a dispersion medium to prepare a slurry. Water is preferred as the dispersion medium used in the present invention. In addition to the calcined raw material, a binder, a dispersant and the like may be blended in the dispersion medium as 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% by mass 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% by mass. 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% by mass. More preferably, it is 60-80 mass%. If it is 60 mass% or more, there are few intraparticle pores in a granulated product, and it can prevent the sintering shortage at the time of baking. On the other hand, if it is 80 mass% or less, there are few associated particles and the fluidity | liquidity deterioration by particle shape can be prevented.
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。粉砕後の原材料の体積平均粒子径は１０μｍ以下が好ましく、より好ましくは２μｍ以下である。また、体積粒度分布９０％の粒子径Ｄ９０は、１．５μｍ〜４．０μｍの範囲が好ましい。１．５μｍ以上であれば、粒子表面に微細な凹凸を形成することができるので、好ましい。一方、４．０μ以下であれば、粗大粒子を十分に粉砕できており、焼成時に結晶の異常粒成長を防ぐことができる。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 volume average particle size of the raw material after pulverization is preferably 10 μm or less, more preferably 2 μm or less. Further, the particle size D 90 of the volume particle size distribution 90% is preferably in the range of 1.5 μm to 4.0 μm. If it is 1.5 micrometers or more, since a fine unevenness | corrugation can be formed in the particle | grain surface, it is preferable. On the other hand, if it is 4.0 μm or less, coarse particles can be sufficiently pulverized, and abnormal grain growth of crystals can be prevented during firing. 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、粉砕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１０〜２００μｍ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。造粒物の好ましい体積平均粒子径は２５μｍ〜３５μｍの範囲である。また、体積粒度分布１０％の好ましい粒子径Ｄ１０は１０μｍ〜３０μｍの範囲である。 Then, the pulverized slurry 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 to 300 ° C. Thereby, a spherical granulated product having a particle size of 10 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. The preferred volume average particle diameter of the granulated product is in the range of 25 μm to 35 μm. Moreover, the preferable particle diameter D10 of volume particle size distribution 10% is the range of 10 micrometers-30 micrometers.
次に、造粒物を所定温度に加熱した炉に投入して、フェライト粒子を合成するための一般的な手法で焼成する。焼成温度としては１０５０℃〜１２００℃の範囲が好ましい。焼成温度が１０５０℃以下であると、相変態が起こりにくくなるとともに焼結も進みにくくなり、粒子表面に大きな凸部が形成されず、粒子内に細孔が多くできる。また、焼結温度が１２００℃を超えると、過剰焼結による過大グレインの発生がするおそれがある。前記焼成温度に至るまでの昇温速度としては２５０℃／ｈ〜５００℃／ｈの範囲が好ましい。また、焼成雰囲気は、酸素濃度が０％〜２１％の範囲で適宜調整すればよい。好ましい酸素濃度は加熱域６％以下、冷却域２％以下の範囲である。 Next, the granulated product is put into a furnace heated to a predetermined temperature, and fired by a general method for synthesizing ferrite particles. The firing temperature is preferably in the range of 1050 ° C to 1200 ° C. When the firing temperature is 1050 ° C. or lower, phase transformation hardly occurs and sintering does not proceed easily, so that large convex portions are not formed on the particle surface and pores can be increased in the particle. Further, if the sintering temperature exceeds 1200 ° C., excessive grain may be generated due to excessive sintering. The rate of temperature increase up to the firing temperature is preferably in the range of 250 ° C / h to 500 ° C / h. Moreover, what is necessary is just to adjust a baking atmosphere suitably in the range whose oxygen concentration is 0%-21%. A preferable oxygen concentration is a heating area of 6% or less and a cooling area of 2% or less.
このようにして得られた焼成物を必要により解粒してフェライト粒子の前駆体（以下、単に「前駆体」と記すことがある）とする。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ってもよい。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。前駆体の体積平均粒子径としては２０μｍ〜３０μｍの範囲が好ましい。 The fired product thus obtained is pulverized as necessary to obtain a ferrite particle precursor (hereinafter, simply referred to as “precursor”). 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 may be performed in order to make the particle size in 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. The volume average particle diameter of the precursor is preferably in the range of 20 μm to 30 μm.
その後、必要に応じて、分級後の前駆体を酸化性雰囲気中で加熱して、前駆体の粒子表面に酸化被膜を形成して粒子の高抵抗化を図ってもよい（高抵抗化処理）。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 precursor may be heated in an oxidizing atmosphere to form an oxide film on the surface of the precursor particles to increase the resistance of the particles (high resistance 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 to 800 ° C, more preferably in the range of 250 to 600 ° C. The heating time is preferably in the range of 0.5 hours to 5 hours.
さらに、本発明では、小粒径キャリアにおいて流動性を制御し、トナーとの混合性を改善できないか鋭意検討を進めた。その結果、前駆体を一定の磁場の環境下で３秒以上磁場を印加して前駆体を磁化させて本発明に係るフェライト粒子とすると、流動性が制御され、トナーとの混合性が大幅に改善されるとの知見を得た。具体的には、磁選工程において、１０００ガウスの磁界中で３秒以上かけて前駆体を着磁及び選別する。３秒以上であれば、前駆体を十分に磁化させ、流動性を遅くすることができる。好ましい磁選時間は５秒以上であり、産業上、５秒〜２０秒の範囲である。さらには、１５秒あれば本発明の効果がより確実に発現される。これにより、キャリアとトナーを混合するときの抵抗が増え、トナーとの混合性が改善されると考えられる。すなわち、本発明に係る前駆体を用いれば、磁着状態を制御することで、優れたフェライト粒子が得られることを見出した。 Furthermore, in the present invention, diligent investigations have been made as to whether the fluidity of a small particle carrier can be controlled and the mixing property with the toner can be improved. As a result, when the precursor is magnetized by applying a magnetic field for 3 seconds or more in a constant magnetic field environment to obtain the ferrite particles according to the present invention, the fluidity is controlled and the mixing property with the toner is greatly increased. The knowledge that it is improved was obtained. Specifically, in the magnetic separation process, the precursor is magnetized and selected in a magnetic field of 1000 gauss over 3 seconds. If it is 3 seconds or more, the precursor can be sufficiently magnetized to slow down the fluidity. A preferable magnetic separation time is 5 seconds or more, and industrially ranges from 5 seconds to 20 seconds. Furthermore, if it is 15 seconds, the effect of this invention will be expressed more reliably. Thereby, it is considered that the resistance when mixing the carrier and the toner is increased, and the mixing property with the toner is improved. That is, it has been found that if the precursor according to the present invention is used, excellent ferrite particles can be obtained by controlling the magnetized state.
また、この発明の電子写真現像剤用フェライト粒子は、細孔容積の値が０．００７ｃｍ３／ｇ以上０．０２５ｃｍ３／ｇ以下であって、かつ、ＢＥＴ比表面積の値が０．１５０ｍ２／ｇ以上０．２３０ｍ２／ｇ以下である。このように、本発明の電子写真現像剤用フェライト粒子は、フェライト粒子を構成する粒子の内部の細孔容積が十分小さいにもかかわらず、従来のフェライト粒子よりも高いＢＥＴ比表面積の値を示す。そのため、フェライト粒子を構成する粒子の表面には、適度な凹凸形状が形成されており、また、フェライト粒子の粒子の内部の焼結が十分に促進されているため、フェライト粒子として強度の面においても十分に優れたものである。 The ferrite particles for an electrophotographic developer of the present invention have a pore volume value of 0.007 cm 3 / g or more and 0.025 cm 3 / g or less, and a BET specific surface area value of 0.150 m 2. / G or more and 0.230 m 2 / g or less. As described above, the ferrite particles for an electrophotographic developer of the present invention show a higher BET specific surface area value than conventional ferrite particles even though the pore volume inside the particles constituting the ferrite particles is sufficiently small. . Therefore, moderate irregularities are formed on the surface of the particles constituting the ferrite particles, and since the sintering inside the ferrite particles is sufficiently promoted, the ferrite particles are strong in terms of strength. Is also excellent enough.
以上のようにして作製した本発明のフェライト粒子を、電子写真現像用キャリアとして用いる場合、フェライト粒子を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、フェライト粒子の表面を樹脂で被覆して用いる。 When the ferrite particles of the present invention produced as described above are used as a carrier for electrophotographic development, the ferrite particles can be used as they are as a carrier for electrophotographic development. However, from the viewpoint of chargeability and the like, The surface is coated with a resin.
フェライト粒子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 covering the surface of the ferrite particles, conventionally known resins can be used, for example, polyethylene, polypropylene, polyvinyl chloride, poly-4-methylpentene-1, polyvinylidene chloride, ABS (acrylonitrile-butadiene-styrene). Examples thereof include resins, polystyrene, (meth) acrylic resins, polyvinyl alcohol resins, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, polybutadiene-based thermoplastic elastomers, fluorine silicone-based resins, and the like.
フェライト粒子の表面を樹脂で被覆するには、樹脂の溶液又は分散液をフェライト粒子に施せばよい。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質量％〜３０質量％、特に０．００１質量％〜２質量％の範囲内にあるのがよい。 In order to coat the surface of the ferrite particles with a resin, a resin solution or dispersion may be applied to the ferrite particles. 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 resin component concentration in the coating solution should generally be in the range of 0.001% to 30% by weight, particularly 0.001% to 2% by weight.
フェライト粒子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 for coating the resin on the ferrite particles, 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.
キャリアの粒子径は、一般に、体積平均粒子径で１０μｍ〜２００μｍの範囲、特に２０μｍ〜３０μｍの範囲が好ましい。 The particle diameter of the carrier is generally preferably in the range of 10 μm to 200 μm, particularly in the range of 20 μm to 30 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１質量％〜１５質量％の範囲が好ましい。トナー濃度が１質量％未満の場合、画像濃度が薄くなりすぎ、他方トナー濃度が１５質量％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３質量％〜１０質量％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. Generally, the toner concentration in the developer is preferably in the range of 1% by mass to 15% by mass. When the toner density is less than 1% by mass, the image density becomes too low, while when the toner density exceeds 15% by mass, toner scattering occurs in the developing device, and the toner adheres to the background portion such as internal dirt or transfer paper. This is because there is a risk of malfunction. A more preferable toner concentration is in the range of 3% by mass to 10% by mass.
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子径で１μｍ〜１５μｍの範囲が好ましく、５μｍ〜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 1 μm to 15 μm, more preferably in the range of 5 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。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.
（実施例１）
ＭｎＭｇ系フェライト粒子を下記方法で作製した。出発原料として、Ｆｅ２Ｏ３（体積平均粒子径：０．５μｍ）を４２．６ｍｏｌと、ＭｎＯ（体積平均粒子径：０．８μｍ）を３８．３ｍｏｌと、ＭｇＯ（体積平均粒子径：０．５μｍ）を５．７ｍｏｌと、ＣａＯを０．５ｍｏｌとなるように混合し、温度８００℃、大気雰囲気下で仮焼成した。
得られた仮焼成物１４．３ｋｇを、水４．９ｋｇ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９０ｇ添加して混合物とした。この混合物の固形分濃度は７５質量％であった。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。体積平均粒子径は１．１μｍ、体積粒度分布９０％の粒子径Ｄ９０は２．１μｍであった、
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１０〜２００μｍの乾燥造粒物を得た。この造粒物から、網目３５μｍの篩網を用いて粗粒を分離し、網目２５μｍの篩網を用いて微粒を分離し、体積平均粒子径が３３．６μｍ、体積粒度分布１０％の粒子径Ｄ１０が２６．９μｍの造粒粉とした。
この造粒粉を、電気炉に投入し、１１００℃で３時間焼成した。焼成時の酸素濃度は、加熱域を５０００ｐｐｍとし、冷却域を１５０００ｐｐｍとした。そして、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。
Example 1
MnMg ferrite particles were produced by the following method. As starting materials, 42.6 mol of Fe 2 O 3 (volume average particle size: 0.5 μm), 38.3 mol of MnO (volume average particle size: 0.8 μm), and MgO (volume average particle size: 0.00). 5 μm) was mixed with 5.7 mol and CaO to 0.5 mol, and calcined at a temperature of 800 ° C. in an air atmosphere.
14.3 kg of the obtained calcined product was dispersed in 4.9 kg of water, and 90 g of an ammonium polycarboxylate dispersant was added as a dispersant to obtain a mixture. The solid content concentration of this mixture was 75% by mass. This mixture was pulverized by a wet ball mill (media diameter 2 mm) to obtain a mixed slurry. The volume average particle size was 1.1 μm, and the particle size D90 of the volume particle size distribution 90% was 2.1 μm.
This mixed slurry was sprayed into hot air at about 130 ° C. with a spray dryer to obtain a dry granulated product having a particle size of 10 to 200 μm. From this granulated product, coarse particles are separated using a sieve mesh with a mesh size of 35 μm, fine particles are separated using a sieve mesh with a mesh size of 25 μm, and a particle size having a volume average particle size of 33.6 μm and a volume particle size distribution of 10%. A granulated powder having a D 10 of 26.9 μm was obtained.
This granulated powder was put into an electric furnace and fired at 1100 ° C. for 3 hours. The oxygen concentration during firing was set to 5000 ppm in the heating region and 15000 ppm in the cooling region. The obtained fired product was pulverized with a hammer mill and then classified using a vibration sieve.
次いで、分級した焼成物を大気雰囲気下で温度５００℃で１時間酸化処理した後、得られたフェライト粒子の前駆体を１０００ガウスの磁界中で１５秒間粒子選別を行い、体積平均粒子径２５μｍのフェライト粒子を得た。
得られたフェライト粒子の表面の結晶均一度、磁気特性、体積平均粒子径、見かけ密度、流動度、比表面積、細孔容積、組成を後述の方法でそれぞれ測定した。表２及び表３に測定結果をまとめて示す。
Next, the classified fired product was oxidized at a temperature of 500 ° C. for 1 hour in an air atmosphere, and then the obtained ferrite particle precursor was subjected to particle selection for 15 seconds in a magnetic field of 1000 gauss, and the volume average particle diameter was 25 μm. Ferrite particles were obtained.
The crystal uniformity, magnetic properties, volume average particle diameter, apparent density, fluidity, specific surface area, pore volume, and composition of the surface of the obtained ferrite particles were measured by the methods described below. Tables 2 and 3 summarize the measurement results.
（結晶均一度）
結晶均一度は、ＳＥＭ撮影を行った後、得られた画像から評価した。具体的には、サンプルをＳＥＭ（加速電圧；５ｋＶ、倍率；４００倍）で４視野、撮影した。得られた画像をもとに、視野に全体が写っている粒子数（Ａ）をカウントする。粒子全体が写っていない粒子はカウントしない。次に、カウントした粒子のうち、粒子表面の結晶サイズ（最大直径；長軸）が５μｍ以上の結晶サイズを有する粒子を粗大結晶粒子と判断し、その粒子数（Ｂ）をカウントする。得られたデータから以下の計算式で、結晶均一度を評価した。結晶均一度は均一な結晶粒子の比率を示している。図１に、粒子表面の結晶サイズが５μｍ未満のフェライト粒子を、図２に、粒子表面の結晶サイズが５μｍ以上のフェライト粒子（粗大結晶粒子）を、それぞれ示す。
結晶均一度（個数％）＝（全粒子数（Ａ）−粗大結晶粒子数（Ｂ））／全粒子数（Ａ）
(Crystal uniformity)
The crystal uniformity was evaluated from the obtained image after SEM photography. Specifically, the sample was photographed with SEM (acceleration voltage: 5 kV, magnification: 400 times) for 4 fields of view. Based on the obtained image, the number (A) of particles that are entirely visible in the field of view is counted. Particles that do not show the entire particle are not counted. Next, among the counted particles, a particle having a crystal size (maximum diameter; long axis) of 5 μm or more on the particle surface is determined as a coarse crystal particle, and the number (B) of the particles is counted. The crystal uniformity was evaluated from the obtained data by the following calculation formula. The crystal uniformity indicates a ratio of uniform crystal particles. FIG. 1 shows ferrite particles having a crystal size on the particle surface of less than 5 μm, and FIG. 2 shows ferrite particles (coarse crystal particles) having a crystal size on the particle surface of 5 μm or more.
Crystal homogeneity (number%) = (total number of particles (A) −number of coarse crystal particles (B)) / total number of particles (A)
（磁気特性）
室温専用振動試料型磁力計（ＶＳＭ）（東英工業株式会社製「VSM-P7」）を用いて磁化の測定を行い、１０００エルステッドの磁場における磁化σ１ｋ（Ａ・ｍ２／ｋｇ）、残留磁化σｒ（Ａ・ｍ２／ｋｇ）をそれぞれ測定した。
(Magnetic properties)
Magnetization is measured using a vibration sample type magnetometer (VSM) dedicated to room temperature (“VSM-P7” manufactured by Toei Kogyo Co., Ltd.). Magnetization σ 1k (A · m 2 / kg) in a 1000 oersted magnetic field, residual Magnetization σr (A · m 2 / kg) was measured.
（平均粒子径）
フェライト粒子、原料スラリーの体積平均粒子径、体積粒度分布１０％粒子径Ｄ１０、体積粒度分布９０％粒子径Ｄ９０を、レーザー回折式粒度分布測定装置（日機装社製「マイクロトラックModel9320-X100」）を用いて測定した。
(Average particle size)
Ferrite particles, volume average particle diameter of raw material slurry, volume particle size distribution 10% particle diameter D 10 , volume particle size distribution 90% particle diameter D 90 , laser diffraction particle size distribution measuring device (“Microtrack Model 9320-X100” manufactured by Nikkiso Co., Ltd.) ).
（見かけ密度ＡＤ）
見かけ密度ＡＤは、JIS Z 2504に準拠して測定した。
(Apparent density AD)
The apparent density AD was measured according to JIS Z 2504.
（流動度ＦＲ）
流動度は、JIS Z 2502に準拠して測定した。
フェライト粒子７０ｇを密閉可能な袋に入れ、その袋をトレイに乗せて、カネテック社製のテーブル形脱磁器（形式；ＫＭＤ−２０Ｃ）上で止めずに４回通過させた後、流動度を測定した。そして、下記式から脱磁前後の流動度変化を算出した。なお、流動度は、フェライト粒子５０ｇが流れ落ちるのに要する時間（ｓｅｃ／５０ｇ）で示される。
流動度変化＝（脱磁前の流動度）−（脱磁後の流動度）
(Fluidity FR)
The fluidity was measured according to JIS Z 2502.
Put 70g of ferrite particles in a sealable bag, put the bag on a tray, and pass it four times without stopping on a table-type demagnetizer (model: KMD-20C) manufactured by Kanetec, and measure the fluidity. did. The change in fluidity before and after demagnetization was calculated from the following formula. The fluidity is indicated by the time (sec / 50 g) required for 50 g of ferrite particles to flow down.
Flow rate change = (flow rate before demagnetization)-(flow rate after demagnetization)
（フェライト粒子の前駆体の流動度ＦＲ）
フェライト粒子の前駆体の流動度を評価するため、前駆体を念のため脱磁し、１０００ガウスの磁界下で１５秒間着磁する着磁を施し、着磁後の流動度と、これを脱磁処理した再脱磁後の流動度の差を原料粉の流動度変化とする。
フェライト粒子の前駆体の流動度変化＝（着磁後の流動度）−（脱磁後の流動度）
なお、フェライト粒子の前駆体の流動変化は、フェライト粉の流動変化と実質的に同一であった。
(Flow rate FR of precursor of ferrite particles)
In order to evaluate the fluidity of the precursor of the ferrite particles, the precursor is demagnetized just in case and magnetized by magnetizing for 15 seconds under a magnetic field of 1000 gauss. The difference in fluidity after re-demagnetization that has been magnetically treated is defined as the change in fluidity of the raw material powder.
Change in fluidity of ferrite particle precursor = (flow rate after magnetization) − (flow rate after demagnetization)
Note that the flow change of the ferrite particle precursor was substantially the same as the flow change of the ferrite powder.
（ＢＥＴ比表面積）
ＢＥＴ一点法比表面積測定装置（「Macsorb HM model-1208」マウンテック社製）を用いて、サンプル８．０００ｇを容積１０ｍｌのセルに充填し、２００℃で３０分間脱気して測定した。
(BET specific surface area)
Using a BET single-point method specific surface area measuring device (“Macsorb HM model-1208”, manufactured by Mountec Co., Ltd.), a cell having a volume of 10 ml was filled in a cell having a capacity of 10 ml, and deaerated at 200 ° C. for 30 minutes for measurement.
（細孔容積）
細孔容積の測定については、以下の通り行った。評価装置は、Ｑｕａｎｔａｃｈｒｏｍｅ社製のＰＯＲＥＭＡＳＴＥＲ−６０ＧＴを使用した。具体的には、測定条件としては、Ｃｅｌｌ Ｓｔｅｍ Ｖｏｌｕｍｅ：０．５ｍｌ、Ｈｅａｄｐｒｅｓｓｕｒｅ：２０ＰＳＩＡ、水銀の表面張力：４８５．００ｅｒｇ／ｃｍ２、水銀の接触角：１３０．００ｄｅｇｒｅｅｓ、高圧測定モード：Ｆｉｘｅｄ Ｒａｔｅ、Ｍｏｔｅｒ Ｓｐｅｅｄ：１、高圧測定レンジ：２０．００〜１００００．００ＰＳＩとし、サンプル１．２００ｇを秤量して０．５ｍｌ（ｃｃ）のセルに充填して測定を行った。また、１００００．００ＰＳＩ時の容積Ｂ（ｍｌ／ｇ）から１００ＰＳＩ時の容積Ａ（ｍｌ／ｇ）を差し引いた値を、細孔容積とした。
(Pore volume)
The pore volume was measured as follows. As an evaluation apparatus, POREMASTER-60GT manufactured by Quantachrome was used. Specifically, the measurement conditions include Cell Stem Volume: 0.5 ml, Headpressure: 20 PSIA, Mercury surface tension: 485.00 erg / cm 2 , Mercury contact angle: 130.00 degrees, High-pressure measurement mode: Fixed Rate, Motor Speed: 1, high pressure measurement range: 20.00 to 10000.00 PSI, 1.200 g of sample was weighed and filled in a 0.5 ml (cc) cell for measurement. The value obtained by subtracting the volume A (ml / g) at 100 PSI from the volume B (ml / g) at 10000.00 PSI was defined as the pore volume.
（組成）
（Ｆｅの分析）
鉄元素を含むフェライト粒子を秤量し、塩酸と硝酸の混酸水に溶解させた。この溶液を蒸発乾固させた後、硫酸水を添加して再溶解し過剰な塩酸と硝酸とを揮発させる。この溶液に固体Ａｌを添加して液中のＦｅ３＋を全てＦｅ２＋に還元する。続いて、この溶液中のＦｅ２＋イオンの量を過マンガン酸カリウム溶液で電位差滴定することにより定量分析し、Ｆｅ（Ｆｅ２＋）の滴定量を求めた。
（Ｍｎの分析）
フェライト粒子のＭｎ含有量は、ＪＩＳ Ｇ１３１１−１９８７記載のフェロマンガン分析方法（電位差滴定法）に準拠して定量分析を行った。本願発明に記載したフェライト粒子のＭｎ含有量は、このフェロマンガン分析方法（電位差滴定法）で定量分析し得られたＭｎ量である。
（Ｃａの分析）
フェライト粒子のＣａ含有量は、以下の方法で分析を行った。本願発明に係るフェライト粒子を酸溶液中で溶解し、ＩＣＰにて定量分析を行った。本願発明に記載したフェライト粒子のＣａ含有量は、このＩＣＰによる定量分析で得られたＣａ量である。Ｍｇ含有量も同様にＩＣＰによる定量分析で得られる。
(composition)
(Analysis of Fe)
Ferrite particles containing iron element were weighed and dissolved in a mixed acid water of hydrochloric acid and nitric acid. After evaporating this solution to dryness, sulfuric acid water is added and redissolved to volatilize excess hydrochloric acid and nitric acid. Solid Al is added to this solution to reduce all Fe 3+ in the solution to Fe 2+ . Subsequently, the amount of Fe 2+ ions in the solution was quantitatively analyzed by potentiometric titration with a potassium permanganate solution to obtain a titer of Fe (Fe 2+ ).
(Analysis of Mn)
The Mn content of the ferrite particles was quantitatively analyzed according to the ferromanganese analysis method (potentiometric titration method) described in JIS G1311-1987. The Mn content of the ferrite particles described in the present invention is the amount of Mn obtained by quantitative analysis by this ferromanganese analysis method (potentiometric titration method).
(Ca analysis)
The Ca content of the ferrite particles was analyzed by the following method. The ferrite particles according to the present invention were dissolved in an acid solution, and quantitative analysis was performed by ICP. The Ca content of the ferrite particles described in the present invention is the amount of Ca obtained by this quantitative analysis by ICP. Similarly, the Mg content can be obtained by quantitative analysis by ICP.
得られたフェライト粒子４．７５ｇと、体積平均粒子径５．０μｍの市販のフルカラー機のトナー０．２５ｇとを、温度２５℃、相対湿度５０％の環境下で２４時間調湿した後、５０ｍｌ共栓試験管に投入し、振とう機（ヤヨイ社製「ＹＳ−ＬＤ」）で振とうした後のフェライト粒子の帯電量をブローオフ法で測定した。
そして、５分間、１０分間振とうした後の帯電量（μＣ／ｇ）と、３０分間振とうした後の帯電量（μＣ／ｇ）との比を求め、混合性を以下のように評価した。評価結果を表３に合わせて示す。
「◎」：帯電量比が０．９〜１．０，トナーがフェライト粒子と分離せず、均一に混合し、現像剤として使用可能なレベル。
「○」：帯電量比が０．８〜０．９，トナーがフェライト粒子とほとんど分離せず、均一に混合し、現像剤として使用可能なレベル。
「△」：帯電量比が０．７〜０．８，トナーがフェライト粒子とほとんど分離し、現像剤として使用不可能なレベル。
「×」：帯電量比が０〜０．７，トナーがフェライト粒子と分離し、現像剤として使用不可能なレベル。
なお、帯電量比が０．８以上あれば、良好なフェライト粒子である。
After adjusting the humidity of 4.75 g of the obtained ferrite particles and 0.25 g of a commercially available full color toner having a volume average particle diameter of 5.0 μm in an environment of a temperature of 25 ° C. and a relative humidity of 50% for 24 hours, 50 ml The charged amount of the ferrite particles after being put into a stoppered test tube and shaken with a shaker (“YS-LD” manufactured by Yayoi Co., Ltd.) was measured by a blow-off method.
Then, the ratio between the charge amount after shaking for 5 minutes and 10 minutes (μC / g) and the charge amount after shaking for 30 minutes (μC / g) was determined, and the mixing property was evaluated as follows. . The evaluation results are shown in Table 3.
“A”: A charge amount ratio of 0.9 to 1.0, a level at which the toner does not separate from the ferrite particles, is uniformly mixed, and can be used as a developer.
“◯”: The charge amount ratio is 0.8 to 0.9, the toner hardly separates from the ferrite particles, and is uniformly mixed and usable as a developer.
“Δ”: The charge amount ratio is 0.7 to 0.8, the toner is almost separated from the ferrite particles, and cannot be used as a developer.
“X”: The charge amount ratio is 0 to 0.7, and the toner is separated from the ferrite particles and cannot be used as a developer.
If the charge amount ratio is 0.8 or more, the ferrite particles are good.
（実施例２〜８，参考例１，比較例１〜８）
表１に示す組成及び製造条件で実施例１と同様にしてフェライト粒子を作製し、得られたフェライト粒子の物性を実施例１と同様にして測定した。表２及び表３に測定結果をまとめて示す。次に、実施例１と同様の評価方法で、フェライト粒子とトナーとの混合性を評価した。評価結果を表３に合わせて示す。
なお、参考例１では、実施例１と同様のフェライト粒子の前駆体について、磁選(磁着)時間を２秒間とした場合である。磁着の効果の発現が不足し、トナーとの混合性が劣っていた。しかし、実施例にあるように磁着時間を５秒間以上とすることで、本発明の効果は得られる。この前駆体を用いれば、トナーの混合に優れたフェライト粒子を得る事は可能である。
(Examples 2-8, Reference Example 1, Comparative Examples 1-8)
Ferrite particles were produced in the same manner as in Example 1 with the compositions and production conditions shown in Table 1, and the physical properties of the obtained ferrite particles were measured in the same manner as in Example 1. Tables 2 and 3 summarize the measurement results. Next, the mixing method of the ferrite particles and the toner was evaluated by the same evaluation method as in Example 1. The evaluation results are shown in Table 3.
In Reference Example 1, the same ferrite particle precursor as that in Example 1 is set to have a magnetic separation (magnetization) time of 2 seconds. The effect of magnetic adhesion was insufficient, and the miscibility with the toner was poor. However, the effect of the present invention can be obtained by setting the magnetizing time to 5 seconds or longer as in the embodiment. If this precursor is used, it is possible to obtain ferrite particles excellent in toner mixing.
本発明に係るフェライト粒子をキャリアとして用いた場合には、トナーとの混合性が向上し、画像形成速度が速くなっても十分な画像濃度が得られ有用である。 When the ferrite particles according to the present invention are used as a carrier, the mixing with toner is improved, and a sufficient image density can be obtained even when the image forming speed is increased, which is useful.
前記目的を達成する本発明に係るフェライト粒子は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とするフェライト粒子であって、体積平均粒子径が２０μｍ〜３０μｍの範囲であり、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、当該フェライト粒子の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とする。なお、本明細書における「粒子表面の結晶均一度」については後述の実施例においてその測定方法を含め説明する。また、「流動度」は、JIS Z2502に準拠し、フェライト粒子５０ｇが流れ落ちるのに要する時間（秒）である。 The ferrite particle according to the present invention that achieves the above object has the composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, and depends on Mg and Mn. The number of substitution with Fe. Ferrite particles whose main component is a material represented by 0 <X <1), the volume average particle diameter is in the range of 20 μm to 30 μm, and the Ca element is 0.05 mass. The crystal surface uniformity of the particle surface is 80% by number or more, and the difference between the flow rate of the ferrite particles and the flow rate after demagnetization is 2.5. The range is from 1 second to 16.0 seconds. The “crystal uniformity on the particle surface” in the present specification will be described in the examples described later, including the measurement method. The “fluidity” is the time (seconds) required for 50 g of ferrite particles to flow in accordance with JIS Z2502.
また、本発明に係るフェライト粒子の前駆体は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とするフェライト粒子の前駆体であって、体積平均粒子径が２０μｍ〜３０μｍの範囲であり、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、１０００ガウスの磁界下で１５秒間着磁した後の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とする。この前駆体を用いて着磁処理をすれば、本発明のフェライト粒子を得られる。 Further, the precursor of the ferrite particles according to the present invention, the composition formula M X Fe 3-X O 4 ( where, M is .X is Mg and Mn is a sum of Mg and Mn, by Mg and Mn It is the number of substitutions with Fe. Precursor of ferrite particles whose main component is a material represented by 0 <X <1), the volume average particle diameter is in the range of 20 μm to 30 μm, and Ca element is 0 .05% by mass to 0.5% by mass, the crystal uniformity on the particle surface is 80% by number or more, the fluidity after magnetizing for 15 seconds under a magnetic field of 1000 gauss, and demagnetization treatment The difference from the fluidity after the treatment is in the range of 2.5 seconds to 16.0 seconds. If this precursor is used for magnetization treatment, the ferrite particles of the present invention can be obtained.
すなわち、本発明に係るフェライト粒子は、組成式ＭＸＦｅ３−ＸＯ４（但し、ＭはＭｇ及びＭｎである。ＸはＭｇとＭｎの総計であって、ＭｇとＭｎとによるＦｅとの置換数である。０＜Ｘ＜１）で表される材料を主成分とし、体積平均粒子径が２０μｍ〜３０μｍの範囲であり、Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、粒子表面の結晶均一度が８０個数％以上であり、当該フェライト粒子の流動度と、脱磁処理した後の流動度との差（ＦＲ変化とも言う）が２．５秒〜１６．０秒の範囲であることが大きな特徴である。 That is, the ferrite particles according to the present invention have a composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, The number of substitutions is based on the material represented by 0 <X <1), the volume average particle diameter is in the range of 20 μm to 30 μm, and the Ca element is in the range of 0.05 mass% to 0.5 mass%. The crystal uniformity on the particle surface is 80% by number or more, and the difference between the fluidity of the ferrite particles and the fluidity after demagnetization (also referred to as FR change) is 2.5 seconds to 16 A major feature is the range of 0.0 second.
本発明のフェライト粒子は、体積平均粒子径が２０μｍ〜３０μｍの範囲のいわゆる小粒径のものである。２０μｍ以上であれば、キャリア飛散による画像欠陥が発生しないので好ましい。３０μｍ以下であれば、小粒径のトナーが使用でき、画質向上が図れるので好ましい。また、その粒度分布はシャープであるのが好ましい。具体的には、１８μｍ以下の体積累積値は、１０％以下が好ましく、より好ましくは３．５％以下である。１０％以下であれば、キャリア飛散による画像欠陥が発生しないので好ましい。一方、８６μｍ以上の体積累積値は、５％以下が好ましく、より好ましくは１％以下である。５％以下であれば、画質が劣化しにくいので、好ましい。 Ferrite particles of the present invention is the volume average particle diameter of the so-called small particle size in the range of 20Myuemu～30myuemu. If it is 20 micrometers or more, since the image defect by carrier scattering does not generate | occur | produce, it is preferable. If it is 30 μm or less, a toner having a small particle diameter can be used and image quality can be improved. The particle size distribution is preferably sharp. Specifically, the volume cumulative value of 18 μm or less is preferably 10% or less, more preferably 3.5% or less. If it is 10% or less, image defects due to carrier scattering do not occur, which is preferable. On the other hand, the volume cumulative value of 86 μm or more is preferably 5% or less, more preferably 1% or less. If it is 5% or less, the image quality is hardly deteriorated, which is preferable.
Claims (5)
Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、
粒子表面の結晶均一度が８０個数％以上であり、
当該フェライト粒子の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とするフェライト粒子。 Composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, and is the number of substitutions of Fe with Mg and Mn. 0 <X <1 ) Ferrite particles whose main component is a material represented by
Ca element is contained in the range of 0.05% by mass to 0.5% by mass,
The crystal uniformity on the particle surface is 80% by number or more,
A ferrite particle characterized in that a difference between a fluidity of the ferrite particle and a fluidity after demagnetization is in a range of 2.5 seconds to 16.0 seconds.
Ｃａ元素を０．０５質量％〜０．５質量％の範囲で含有し、
粒子表面の結晶均一度が８０個数％以上であり、
１０００ガウスの磁界下で１５秒間着磁した後の流動度と、脱磁処理した後の流動度との差が２．５秒〜１６．０秒の範囲であることを特徴とするフェライト粒子の前駆体。 Composition formula M X Fe 3 -X O 4 (where M is Mg and Mn. X is the total of Mg and Mn, and is the number of substitutions of Fe with Mg and Mn. 0 <X <1 Is a precursor of ferrite particles whose main component is a material represented by
Ca element is contained in the range of 0.05% by mass to 0.5% by mass,
The crystal uniformity on the particle surface is 80% by number or more,
The difference between the fluidity after magnetizing for 15 seconds under a magnetic field of 1000 gauss and the fluidity after demagnetization is in the range of 2.5 seconds to 16.0 seconds. precursor.
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