JP5689988B2 - Carrier core material for electrophotographic developer and method for producing the same - Google Patents
Carrier core material for electrophotographic developer and method for producing the same Download PDFInfo
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Images
Description
本発明は、電子写真現像剤用キャリア芯材およびその製造方法に関し、特に、複写機やプリンタなどの現像器において電子写真現像に使用される電子写真現像剤用キャリア芯材およびその製造方法に関する。 The present invention relates to a carrier core material for an electrophotographic developer and a manufacturing method thereof, and more particularly to a carrier core material for an electrophotographic developer used for electrophotographic development in a developing device such as a copying machine or a printer and a manufacturing method thereof.
従来、複写機やプリンタなどの現像器において、電子写真現像方法としてカスケード法や磁気ブラシ現像法などの方法が用いられている。磁気ブラシ現像法は、近年一般的に使用されている方法であり、感光体ドラム上に形成された静電潜像に磁気ブラシを介してトナー像を顕像化させた後、熱定着させて画像を得る方法である。 Conventionally, in a developing device such as a copying machine or a printer, a method such as a cascade method or a magnetic brush developing method is used as an electrophotographic developing method. The magnetic brush development method is a method that is generally used in recent years. After a toner image is visualized on an electrostatic latent image formed on a photosensitive drum via a magnetic brush, it is thermally fixed. This is a method for obtaining an image.
磁気ブラシ現像法は、磁気ブラシをトナーのみで形成する一成分系現像方式と、電子写真現像剤用キャリア（以下、「キャリア」という）の粒子上にトナーを静電的に配向させて磁気ブラシを形成する二成分系現像方式に大別される。これらの方式のうち、二成分系現像方式は、トナーの帯電特性が安定して得られ、良好な画像品質を得ることができるという利点がある。 The magnetic brush developing method includes a one-component developing method in which a magnetic brush is formed only with toner, and a magnetic brush by electrostatically orienting toner on particles of an electrophotographic developer carrier (hereinafter referred to as “carrier”). The two-component development system that forms Of these methods, the two-component development method has the advantage that the charging characteristics of the toner can be obtained stably and good image quality can be obtained.
二成分系現像方式におけるキャリアは、現像器内でトナーと混合および攪拌されることによってトナーに電荷を付与するだけでなく、トナーを感光体上に搬送する担持体として機能する。トナーを感光体に搬送した後のキャリアは、マグネットロール上に残留し、現像器内で再びトナーと混合される。そのため、キャリアは、磁気ブラシを形成する磁気特性の他、所望の電荷をトナーに付与する帯電特性や、繰り返し使用における耐久性などの特性が要求されている。 The carrier in the two-component development system not only imparts electric charge to the toner by being mixed and stirred with the toner in the developing device, but also functions as a carrier that conveys the toner onto the photoreceptor. The carrier after the toner is conveyed to the photoreceptor remains on the magnet roll and is mixed with the toner again in the developing device. Therefore, the carrier is required to have characteristics such as a charging characteristic for imparting a desired charge to the toner and a durability in repeated use, in addition to the magnetic characteristic for forming the magnetic brush.
これらの特性を満足するために、一般に、キャリアを構成する粒子として、マグネタイトや各種フェライトの磁性粒子からなる芯材（以下、「キャリア芯材」という）の表面を樹脂で被覆したキャリア粒子が用いられている。また、キャリアの耐久性を高めるためには、長期間にわたってトナーと混合および攪拌されてもキャリア粒子の割れや欠けを抑制するとともに、帯電付与能力を維持する必要がある。 In order to satisfy these characteristics, carrier particles in which the surface of a core made of magnetic particles of magnetite or various ferrites (hereinafter referred to as “carrier core”) is coated with a resin are generally used as the particles constituting the carrier. It has been. Further, in order to increase the durability of the carrier, it is necessary to suppress the cracking and chipping of the carrier particles and to maintain the charge imparting ability even when mixed and stirred with the toner for a long period of time.
キャリアの耐久性を高める方法として、フェライト用原料を調整して得られた平均粒径２０〜５０μｍの原料粉末を、大気中において、原料粉末搬送ガスとともに燃焼火炎中に投入し、溶射してフェライト化し、次いで、急冷凝固させて捕集、回収することによって、電子写真用フェライトキャリア芯材を製造する方法が提案されている（例えば、特許文献１参照）。また、フェライト原料を粉砕、混合、ペレット化した後、９００〜１２００℃で仮焼成し、次いで、粉砕、スラリー化し、スラリー粒径のＤ５０を３．０μｍ以下にし且つＤ９０を４．５μｍ以下にした後、１１５０〜１２３０℃で１〜２４時間本焼成することによって、電子写真現像剤用フェライトキャリアを製造する方法が提案されている（例えば、特許文献２参照）。 As a method for enhancing the durability of the carrier, the raw material powder having an average particle diameter of 20 to 50 μm obtained by adjusting the raw material for ferrite is introduced into the combustion flame together with the raw material powder carrier gas in the atmosphere, and sprayed to ferrite. Then, a method for producing a ferrite carrier core material for electrophotography by rapidly solidifying by rapid solidification and collecting is proposed (for example, see Patent Document 1). In addition, after pulverizing, mixing, and pelletizing the ferrite raw material, it is temporarily fired at 900 to 1200 ° C., and then pulverized and slurried to make D 50 of the slurry particle size 3.0 μm or less and D 90 4.5 μm or less. After that, a method for producing a ferrite carrier for an electrophotographic developer by subjecting to main firing at 1150 to 1230 ° C. for 1 to 24 hours has been proposed (for example, see Patent Document 2).
しかし、特許文献１の方法のように、原料粉末を燃焼火炎中で溶射する方法では、原料粉末を溶融するのに多大なエネルギーを必要とするため、経済的でない。 However, the method of spraying the raw material powder in the combustion flame as in the method of Patent Document 1 is not economical because a great amount of energy is required to melt the raw material powder.
また、特許文献２の方法のように、１０００℃より高い温度で原料を焼成すると、大きなエネルギーを必要とするだけでなく、高温で処理するために粒子同士が焼結してしまった場合に解粒することが困難になり、生産性が低下するという問題がある。また、特許文献２の方法などの従来の方法において、仮に焼成温度を１０００℃以下にした場合には、粒子を十分に焼成することができないため、粒子の強度が著しく低下し、粒子の割れや欠けを防ぐことが困難になる。 In addition, when the raw material is fired at a temperature higher than 1000 ° C. as in the method of Patent Document 2, not only a large energy is required, but also when the particles are sintered for processing at a high temperature. There is a problem that it becomes difficult to granulate and productivity decreases. Further, in the conventional method such as the method of Patent Document 2, if the firing temperature is set to 1000 ° C. or lower, the particles cannot be sufficiently fired. It becomes difficult to prevent chipping.
したがって、本発明は、このような従来の問題点に鑑み、焼成温度を１０００℃以下にしても粒子を十分に焼成することができ、長期間にわたってトナーと混合および攪拌されてもキャリア粒子の割れや欠けを抑制することができ、長期間にわたって安定した画像特性を得ることができる電子写真現像剤用キャリア芯材、およびそのキャリア芯材を安価に製造することができる電子写真現像剤用キャリア芯材の製造方法を提供することを目的とする。 Therefore, in view of such a conventional problem, the present invention can sufficiently sinter the particles even when the calcination temperature is 1000 ° C. or less, and the carrier particles are cracked even when mixed and stirred with the toner for a long period of time. Carrier core material for electrophotographic developer capable of suppressing chipping and chipping and obtaining stable image characteristics over a long period of time, and carrier core for electrophotographic developer capable of producing the carrier core material at low cost It aims at providing the manufacturing method of material.
本発明者らは、上記課題を解決するために鋭意研究した結果、酸化鉄粉末と炭酸塩との混合物を顆粒化した後、１０００℃以下の温度で熱処理することにより、焼成温度を１０００℃以下にしても粒子を十分に焼成することができ、長期間にわたってトナーと混合および攪拌されてもキャリア粒子の割れや欠けを抑制することができ、長期間にわたって安定した画像特性を得ることができる、電子写真現像剤用キャリア芯材を安価に製造することができることを見出し、本発明を完成するに至った。 As a result of intensive studies to solve the above problems, the present inventors granulated a mixture of iron oxide powder and carbonate, and then heat-treated at a temperature of 1000 ° C. or lower, thereby reducing the firing temperature to 1000 ° C. or lower. Even so, the particles can be sufficiently baked, and even when mixed and stirred with the toner for a long period of time, the carrier particles can be prevented from cracking or chipping, and stable image characteristics can be obtained over a long period of time. It has been found that a carrier core material for an electrophotographic developer can be produced at a low cost, and the present invention has been completed.
すなわち、本発明による電子写真現像剤用キャリア芯材の製造方法は、酸化鉄粉末と炭酸塩との混合物を顆粒化した後、１０００℃以下の温度で熱処理することを特徴とする。この電子写真現像剤用キャリア芯材の製造方法において、熱処理が酸素濃度１．０×１０−４ｐｐｍ以下の雰囲気において行うのが好ましい。また、酸化鉄粉末が三酸化二鉄粉末であるのが好ましい。また、炭酸塩が、炭酸リチウム、炭酸カルシウム、炭酸マグネシウム、炭酸バリウムおよび炭酸ストロンチウムからなる群から選ばれる一種以上であるのが好ましい。さらに、混合物が還元剤を含むのが好ましい。 That is, the method for producing a carrier core material for an electrophotographic developer according to the present invention is characterized in that a mixture of iron oxide powder and carbonate is granulated and then heat-treated at a temperature of 1000 ° C. or lower. In this method for producing a carrier core material for an electrophotographic developer, the heat treatment is preferably performed in an atmosphere having an oxygen concentration of 1.0 × 10 −4 ppm or less. Moreover, it is preferable that an iron oxide powder is a ferric trioxide powder. The carbonate is preferably at least one selected from the group consisting of lithium carbonate, calcium carbonate, magnesium carbonate, barium carbonate and strontium carbonate. Furthermore, the mixture preferably contains a reducing agent.
また、本発明による電子写真現像剤用キャリア芯材は、球形度が０．８以上、比表面積が０．０９ｍ２／ｇ以下であり、粒子の表面にステップ状の凹凸を有することを特徴とする。この電子写真現像剤用キャリア芯材において、ステップ状の凹凸の間隔が０．１〜５．０μｍ、高低差が０．１〜１．０μｍであるのが好ましい。また、ステップ状の凹凸が粒子の表面積の２０％以上を占めるのが好ましい。また、粒径が１０〜１００μｍであるのが好ましい。さらに、キャリア芯材が、化学式Ｆｅ３Ｏ４で表記されるマグネタイトからなるのが好ましい。 The carrier core material for an electrophotographic developer according to the present invention has a sphericity of 0.8 or more, a specific surface area of 0.09 m 2 / g or less, and has stepped irregularities on the surface of the particles. To do. In this carrier core material for an electrophotographic developer, it is preferable that the step-like unevenness interval is 0.1 to 5.0 μm and the height difference is 0.1 to 1.0 μm. Moreover, it is preferable that the step-shaped unevenness occupies 20% or more of the surface area of the particles. Moreover, it is preferable that a particle size is 10-100 micrometers. Furthermore, the carrier core material is preferably made of magnetite represented by the chemical formula Fe 3 O 4 .
さらに、本発明による電子写真現像剤用キャリアは、上記のキャリア芯材が樹脂で被覆されていることを特徴とする。 Furthermore, the carrier for an electrophotographic developer according to the present invention is characterized in that the carrier core material is coated with a resin.
本発明によれば、焼成温度を１０００℃以下にしても粒子を十分に焼成することができ、長期間にわたってトナーと混合および攪拌されてもキャリア粒子の割れや欠けを抑制することができ、長期間にわたって安定した画像特性を得ることができる、電子写真現像剤用キャリア芯材を安価に製造することができる。 According to the present invention, the particles can be sufficiently fired even when the firing temperature is 1000 ° C. or less, and even if the toner is mixed and stirred for a long period of time, the carrier particles can be prevented from cracking or chipping. A carrier core material for an electrophotographic developer that can obtain stable image characteristics over a period of time can be manufactured at low cost.
本発明による電子写真現像剤用キャリア芯材の製造方法の実施の形態は、原料としての酸化鉄（Ｆｅ２Ｏ３）粉末を副原料としての炭酸塩と混合した後に造粒（顆粒化）して、前駆体となる粒子を得る造粒工程と、この造粒工程で得られた前駆体の粒子を１０００℃以下で熱処理して、前駆体の粒子を焼成する焼成工程とを備えている。以下、これらの工程について詳細に説明する。 In the embodiment of the method for producing a carrier core material for an electrophotographic developer according to the present invention, an iron oxide (Fe 2 O 3 ) powder as a raw material is mixed with a carbonate as an auxiliary material and then granulated (granulated). A granulation step for obtaining particles to be a precursor, and a firing step for firing the precursor particles by heat-treating the precursor particles obtained in the granulation step at 1000 ° C. or lower. Hereinafter, these steps will be described in detail.
（造粒工程）
まず、キャリア芯材の原料として酸化鉄（Ｆｅ２Ｏ３）粉末を用意するとともに、副原料として炭酸塩を用意する。酸化鉄粉末は、副原料と均一に混合することができるように、１μｍ以下の粒径を有するのが好ましい。また、炭酸塩としては、炭酸リチウム、炭酸カルシウム、炭酸マグネシウム、炭酸バリウム、炭酸ストロンチウムなどを使用することができ、取り扱いの観点から炭酸カルシウムまたは炭酸マグネシウムを使用するのが好ましい。また、原料にカーボンなどの還元剤を混合してもよい。
(Granulation process)
First, iron oxide (Fe 2 O 3 ) powder is prepared as a raw material for the carrier core material, and carbonate is prepared as an auxiliary raw material. The iron oxide powder preferably has a particle size of 1 μm or less so that it can be uniformly mixed with the auxiliary material. Further, as the carbonate, lithium carbonate, calcium carbonate, magnesium carbonate, barium carbonate, strontium carbonate and the like can be used, and calcium carbonate or magnesium carbonate is preferably used from the viewpoint of handling. Moreover, you may mix reducing agents, such as carbon, with a raw material.
次に、原料としての酸化鉄粉末と副原料としての炭酸塩の混合物を造粒（顆粒化）して、前駆体となる粒子を得る。この造粒は、公知の造粒方法により行うことができるが、噴霧乾燥法により行うのが好ましい。噴霧乾燥法により造粒する場合には、原料としての酸化鉄粉末と副原料としての炭酸塩を水中に分散させてスラリーとした後、得られたスラリーを乾燥風中に噴霧することにより、所望の粒度分布の前駆体の粒子を得る。 Next, a mixture of iron oxide powder as a raw material and carbonate as an auxiliary raw material is granulated (granulated) to obtain particles as a precursor. This granulation can be performed by a known granulation method, but is preferably performed by a spray drying method. In the case of granulation by spray drying, iron oxide powder as a raw material and carbonate as an auxiliary raw material are dispersed in water to form a slurry, and then the obtained slurry is sprayed into a drying air to obtain a desired Precursor particles with a particle size distribution of
スラリー中の固形分の濃度は、５０〜９０質量％にするのが好ましい。また、造粒した前駆体の粒子の形状を維持するために、水にバインダーを添加するのが好ましい。このバインダーとしては、例えば、ポリビニルアルコールを使用することができる。水中のバインダーの濃度は、０．５〜２質量％程度でよい。また、スラリーに分散剤を添加するのが好ましい。この分散剤としては、例えば、ポリカルボン酸アンモニウム系の分散剤を使用するのが好ましい。 The concentration of the solid content in the slurry is preferably 50 to 90% by mass. In order to maintain the shape of the granulated precursor particles, it is preferable to add a binder to water. As this binder, for example, polyvinyl alcohol can be used. The concentration of the binder in water may be about 0.5 to 2% by mass. Further, it is preferable to add a dispersant to the slurry. For example, an ammonium polycarboxylate dispersant is preferably used as the dispersant.
（焼成工程）
次に、造粒工程で得られた前駆体の粒子を低酸素雰囲気において１０００℃以下で焼成することにより、磁性相を有する磁性体粒子にする。この焼成は、前駆体の粒子を加熱炉に投入して、所定時間加熱することによって行うことができる。焼成温度は、目的とする磁性相が生成する温度範囲において１０００℃以下の温度に設定すればよい。焼成温度を１０００℃以下と低くすると、エネルギーコスト面で有利であり、また、粒子同士が強く焼結することによる凝集体の発生を抑制することができるので、粉砕や解粒が容易になり、生産性の面からも優れている。焼成中の炉内の酸素濃度は、１．０×１０−４ｐｐｍ以下にするのが好ましい。このような低酸素濃度の雰囲気下では、１０００℃以下でも酸化鉄からマグネタイトを生成することができる。焼成中の炉内の酸素濃度は、炉内に高純度の不活性ガスを流したり、炉内または焼成物中にカーボンなどの還元剤を投入することによって、調整することができる。
(Baking process)
Next, the particles of the precursor obtained in the granulation step are fired at 1000 ° C. or less in a low oxygen atmosphere to obtain magnetic particles having a magnetic phase. This firing can be performed by putting the precursor particles into a heating furnace and heating them for a predetermined time. What is necessary is just to set a calcination temperature to the temperature of 1000 degrees C or less in the temperature range which the target magnetic phase produces | generates. When the firing temperature is lowered to 1000 ° C. or less, it is advantageous in terms of energy cost, and since generation of aggregates due to strong sintering between particles can be suppressed, pulverization and pulverization become easy. It is also excellent in terms of productivity. The oxygen concentration in the furnace during firing is preferably 1.0 × 10 −4 ppm or less. Under such a low oxygen concentration atmosphere, magnetite can be produced from iron oxide even at 1000 ° C. or lower. The oxygen concentration in the furnace during firing can be adjusted by flowing a high-purity inert gas into the furnace, or by introducing a reducing agent such as carbon into the furnace or the fired product.
このようにして得られた焼成物をハンマーミルなどにより解粒し、篩などを用いて分級処理を行うことにより、所望の粒度分布のキャリア芯材を得ることができる。 A carrier core material having a desired particle size distribution can be obtained by pulverizing the fired product thus obtained with a hammer mill or the like and performing classification using a sieve or the like.
（電子写真現像剤用キャリアの製造）
このようにして得られたキャリア芯材は、帯電付与能力の調整およびトナースペントを抑制するために、シリコーン系樹脂などで被覆することにより、電子写真現像剤用キャリアを得ることができる。
(Manufacture of carrier for electrophotographic developer)
The carrier core material thus obtained can be coated with a silicone resin or the like in order to adjust the charge imparting ability and suppress toner spent, thereby obtaining an electrophotographic developer carrier.
（キャリア芯材の特性）
上述したキャリア芯材の製造方法の実施の形態によって製造されたキャリア芯材は、球形度が０．８以上、比表面積が０．０９ｍ２／ｇ以下であり、粒子の表面にステップ状の凹凸を有する。
(Characteristics of carrier core material)
The carrier core material manufactured according to the embodiment of the carrier core material manufacturing method described above has a sphericity of 0.8 or more and a specific surface area of 0.09 m 2 / g or less, and stepped irregularities on the surface of the particles. Have
キャリア芯材の粒子の球形度が高く（粒子の形状が真球に近く）、比表面積が低くなると、粒子の流動性が良好になるので、攪拌ストレスが低減されることに加えて、粒子の表面に空孔や粒界または表面のキズがほとんど存在せず、割れや欠けの起点が少なくなり、粒子の割れや欠けを抑制することができる。このような表面特性を有するキャリア芯材を用いることにより、キャリア粒子同士の衝突による粒子の破壊が生じ難く、優れた強度を有する電子写真現像剤用キャリアを得ることができる。 If the carrier core particles have a high sphericity (the shape of the particles is close to a true sphere) and the specific surface area is low, the fluidity of the particles is improved. There are almost no voids, grain boundaries or surface scratches on the surface, the starting point of cracks and chips is reduced, and cracks and chips of particles can be suppressed. By using a carrier core material having such surface characteristics, it is possible to obtain a carrier for an electrophotographic developer that is less likely to be destroyed by collision of carrier particles and has excellent strength.
また、キャリア芯材の粒子の表面に微細なステップ状の凹凸が存在すると、トナーとの攪拌における摩擦帯電が生じ易くなり、凸部において電荷の受渡しが円滑に行われて、キャリア芯材の帯電付与能力が向上する。このような帯電付与能力の高い粒子をキャリア芯材として用いると、キャリアの帯電維持性能を向上させることがわかった。 Also, if there are fine step-like irregularities on the surface of the carrier core particles, triboelectric charge is likely to occur during stirring with the toner, and the charge is smoothly transferred at the convex portions, so that the carrier core material is charged. Grant ability is improved. It has been found that the use of particles having such a high charge-imparting ability as a carrier core material improves the charge maintaining performance of the carrier.
なお、本明細書中において、「ステップ状の凹凸」とは、図１Ａ〜図１ＤのＳＥＭ像から観察されるような階段状となった粒子成長の跡であり、同心円状に広がった隆起部分の集合として観察される。このステップ状の凹凸は、比表面積に影響を与えない程度に微細であるのが好ましく、ステップ状の凹凸があっても粒子の比表面積が０．０９ｍ２／ｇ以下を満たしている。
In this specification, the term "step-like unevenness", a trace of grain growth that such was stepped as observed from the SEM image of FIG 1A~ Figure 1D, the raised portion extends concentrically Is observed as a set of The step-like unevenness is preferably fine enough not to affect the specific surface area, and even if the step-like unevenness is present, the specific surface area of the particles satisfies 0.09 m 2 / g or less.
ステップ状の凹凸の高低差は、０．１〜１．０μｍであるのが好ましい。高低差が大き過ぎると、粒子の凹凸部分同士の引っ掛かりによって粒子の流動性が悪化したり、粒子の割れや欠けの起点となるので好ましくなく、一方、高低差が小さ過ぎたり、凹凸が全く存在しないと、帯電特性の長期安定性を向上させることができない。また、ステップ状の凹凸の間隔は、０．１〜５．０μｍであるのが好ましい。さらに、ステップ状の凹凸は、粒子の表面積の２０％以上を占めるのが好ましい。ステップ状の凹凸の領域が狭すぎると、粒子の表面がほとんど平滑になり、帯電特性の長期安定性を向上させることができない。 The height difference of the stepped irregularities is preferably 0.1 to 1.0 μm. If the height difference is too large, it is not preferable because the fluidity of the particles deteriorates due to the catching between the uneven portions of the particles, or it becomes the starting point of cracking or chipping of the particles, while the height difference is too small or there is no unevenness at all. Otherwise, the long-term stability of the charging characteristics cannot be improved. Moreover, it is preferable that the space | interval of a step-shaped unevenness | corrugation is 0.1-5.0 micrometers. Furthermore, it is preferable that the step-shaped unevenness occupies 20% or more of the surface area of the particles. If the step-shaped uneven region is too narrow, the surface of the particles becomes almost smooth and the long-term stability of the charging characteristics cannot be improved.
また、キャリア芯材の粒径は、１０〜１００μｍであるのが好ましい。粒径が小さ過ぎると、粒子１個当たりの磁化が減少して、キャリア粒子が現像器内で磁気ドラム上から脱落する、いわゆるキャリア飛散現象を抑制することが困難になる。一方、キャリア芯材の粒径が大き過ぎると、トナーへの帯電付与能力が低下するので好ましくない。 Moreover, it is preferable that the particle size of a carrier core material is 10-100 micrometers. If the particle size is too small, the magnetization per particle decreases, and it becomes difficult to suppress the so-called carrier scattering phenomenon in which carrier particles fall off from the magnetic drum in the developing device. On the other hand, if the particle diameter of the carrier core material is too large, the charge imparting ability to the toner is lowered, which is not preferable.
キャリア芯材の組成は、所望の磁気特性を有する組成であればよいが、化学式Ｆｅ３Ｏ４で表記されるマグネタイトであるのが好ましい。このような組成のキャリア芯材は、磁化が十分に高く且つ保磁力が低いので、電子写真現像剤用キャリア芯材として好ましい。また、純粋な鉄元素と酸素のみからなり、有害な金属元素も含まないので、環境負荷を低減できる観点からも好ましい。 The composition of the carrier core may be any composition having desired magnetic properties, but is preferably magnetite represented by the chemical formula Fe 3 O 4 . A carrier core material having such a composition is preferable as a carrier core material for an electrophotographic developer because it has sufficiently high magnetization and low coercive force. Moreover, since it consists only of pure iron element and oxygen and does not contain harmful metal elements, it is preferable from the viewpoint of reducing the environmental load.
以下、本発明による電子写真現像剤用キャリア芯材およびその製造方法の実施例について詳細に説明する。 Examples of the carrier core material for an electrophotographic developer and the production method thereof according to the present invention will be described in detail below.
［実施例１］
ポリカルボン酸アンモニウム系分散剤６０ｇを添加した純水３．０ｋｇに、原料としてのＦｅ２Ｏ３（平均粒径０．６μｍ）１０ｋｇと、副原料として炭酸カルシウム１０ｇと、還元剤としてカーボンブラック粉末（三菱化学株式会社製のＭＡ−７）１２０ｇとを分散させ、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]
3.0 kg of pure water to which 60 g of an ammonium polycarboxylate-based dispersant is added, 10 kg of Fe 2 O 3 (average particle size 0.6 μm) as a raw material, 10 g of calcium carbonate as an auxiliary material, and carbon black powder as a reducing agent (MA-7 manufactured by Mitsubishi Chemical Corporation) (120 g) was dispersed and pulverized by a wet ball mill (media diameter: 2 mm) to obtain a mixed slurry.
このようにして得られたスラリーをスプレードライヤーによって約１３０℃の熱風中に噴霧し、粒径１０〜１００μｍの乾燥造粒物を得た。 The slurry thus obtained 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 100 μm.
この造粒物を電気炉に投入して９５０℃で３時間焼成した。この焼成では、原料中に混合したカーボンブラック粉末の酸化反応によって炉内の酸素濃度が減少して、酸素計（第一熱研株式会社製の酸素計（ジルコニア式Ｏ２センサＴＢ−ＩＩＦ＋コントロールユニット）による酸素濃度は１．０×１０−８ｐｐｍになっていた。このようにして得られた焼成物を粉砕した後に篩により分級して、所望の粒径のキャリア芯材（フェライト粉末）を得た。 This granulated product was put into an electric furnace and fired at 950 ° C. for 3 hours. In this firing, the oxygen concentration in the furnace is reduced by the oxidation reaction of the carbon black powder mixed in the raw material, and an oxygen meter (an oxygen meter (Zirconia type O 2 sensor TB-IIF + control unit manufactured by Daiichi Thermal Laboratory Co., Ltd.) The oxygen concentration due to) was 1.0 × 10 −8 ppm, and the fired product thus obtained was pulverized and classified by a sieve to obtain a carrier core material (ferrite powder) having a desired particle size. Obtained.
［実施例２〜４］
副原料としてそれぞれ炭酸カルシウム５０ｇ（実施例２）、炭酸バリウム１０ｇ（実施例３）、炭酸バリウム５０ｇ（実施例４）を使用した以外は、実施例１と同様の方法によりキャリア芯材を得た。
[Examples 2 to 4]
A carrier core material was obtained in the same manner as in Example 1 except that 50 g of calcium carbonate (Example 2), 10 g of barium carbonate (Example 3), and 50 g of barium carbonate (Example 4) were used as auxiliary materials. .
［比較例１〜３］
副原料としての炭酸カルシウムを使用しなかった（比較例１）、焼成温度を１３００℃にした（比較例２）、炭酸カルシウムの代わりに水酸化カルシウム１０ｇを使用した（比較例３）以外は、実施例１と同様の方法によりキャリア芯材を得た。
[Comparative Examples 1-3]
Calcium carbonate as an auxiliary material was not used (Comparative Example 1), the firing temperature was 1300 ° C. (Comparative Example 2), and 10 g of calcium hydroxide was used instead of calcium carbonate (Comparative Example 3). A carrier core material was obtained in the same manner as in Example 1.
このようにして実施例１〜４および比較例１〜３で得られたキャリア芯材について、以下のように粒子の球形度、凹凸の間隔、凹凸の高低差、凹凸の面積率、粒径、見掛け密度、流動度、表面積、飽和磁化σｓ、強度および帯電特性の評価を行った。 Thus, for the carrier core materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3, the sphericity of the particles, the interval between the irregularities, the height difference of the irregularities, the area ratio of the irregularities, the particle size, The apparent density, fluidity, surface area, saturation magnetization σs, strength and charging characteristics were evaluated.
キャリア芯材の粒子の球形度については、コンピュータ上で画像解析ソフト（Ｓｏｆｔ Ｉｍａｇｉｎｇ Ｓｙｓｔｅｍ ＧｍｂＨ社製のａｎａｌｙＳＩＳ)を使用して、走査型電子顕微鏡（ＳＥＭ）により観察された画像（倍率５００倍のＳＥＭ写真）中の５０個の粒子の円形度の平均値を算出し、この円形度の平均値をキャリア芯材の粒子の球形度とした。その結果、キャリア芯材の粒子の球形度は、それぞれ０．９２（実施例１）、０．８８（実施例２）、０．８７（実施例３）、０．８８（実施例４）、０．９３（比較例１）、０．８８（比較例２）、０．８９（比較例３）であった。 As for the sphericity of the particles of the carrier core material, an image (SEM having a magnification of 500 times) observed by a scanning electron microscope (SEM) using image analysis software (analySIS manufactured by Soft Imaging System GmbH) on a computer. The average value of the circularity of the 50 particles in the photograph) was calculated, and the average value of the circularity was defined as the sphericity of the particles of the carrier core material. As a result, the sphericity of the carrier core particles is 0.92 (Example 1), 0.88 (Example 2), 0.87 (Example 3), 0.88 (Example 4), respectively. They were 0.93 (Comparative Example 1), 0.88 (Comparative Example 2), and 0.89 (Comparative Example 3).
キャリア芯材の粒子の表面の凹凸の間隔および高低差は、レーザー顕微鏡（オリンパス社製のＯＬＳ３０−ＬＳＵ）を使用して、粒子の表面をスキャンすることによって測定した。その結果、キャリア芯材の粒子の表面の凹凸の間隔は、それぞれ０．５〜１μｍ（実施例１）、０．５〜４μｍ（実施例２）、０．２〜３μｍ（実施例３）、０．３〜１μｍ（実施例４）であり、凹凸の高低差は、０．３μｍ（実施例１）、０．３μｍ（実施例２）、０．５μｍ（実施例３）、０．４μｍ（実施例４）であった。 The unevenness spacing and elevation difference on the surface of the carrier core material particles were measured by scanning the surface of the particles using a laser microscope (OLS30-LSU manufactured by Olympus). As a result, the irregularities on the surface of the carrier core particles are 0.5 to 1 μm (Example 1), 0.5 to 4 μm (Example 2), and 0.2 to 3 μm (Example 3), respectively. The height difference of the unevenness is 0.3 μm (Example 1), 0.3 μm (Example 2), 0.5 μm (Example 3), 0.4 μm (Example 4). Example 4).
粒子の表面における凹凸の面積率は、球形度と同様に粒子の表面に対して画像解析を行い、ステップ状の凹凸の領域とそれ以外の領域に分離して算出した。その結果、凹凸の面積率は、それぞれ６０％（実施例１）、５０％（実施例２）、５０％（実施例３）、６０％（実施例４）であった。 The area ratio of the unevenness on the surface of the particle was calculated by performing image analysis on the surface of the particle in the same manner as the sphericity, and separating into a step-shaped unevenness region and other regions. As a result, the area ratios of the irregularities were 60% (Example 1), 50% (Example 2), 50% (Example 3), and 60% (Example 4), respectively.
キャリア芯材の粒径は、マイクロトラック（日機装株式会社製のＭｏｄｅｌ：９３２０−Ｘ１００）を使用して測定し、体積率５０％までの積算粒径であるＤ５０の値を粒径とした。その結果、粒径は、それぞれ６１．２μｍ（実施例１）、６５．５μｍ（実施例２）、６２．３μｍ（実施例３）、５７．２μｍ（実施例４）、６４．６μｍ（比較例１）、５８．２μｍ（比較例２）、６０．５μｍ（比較例３）であった。 The particle size of the carrier core material, Microtrac (manufactured by Nikkiso Co., Ltd. Model: 9320-X100) measured using, was particle size values of D 50 is a cumulative particle size to a volume ratio of 50%. As a result, the particle sizes were 61.2 μm (Example 1), 65.5 μm (Example 2), 62.3 μm (Example 3), 57.2 μm (Example 4), and 64.6 μm (Comparative Example), respectively. 1), 58.2 μm (Comparative Example 2), and 60.5 μm (Comparative Example 3).
キャリア芯材の粒子の見掛け密度は、ＪＩＳ−２５０４に準ずる方法により測定した。その結果、見掛け密度は、それぞれ２．４９ｇ／ｃｃ（実施例１）、２．５１ｇ／ｃｃ（実施例２）、２．４２ｇ／ｃｃ（実施例３）、２．６２ｇ／ｃｃ（実施例４）、２．２８ｇ／ｃｃ（比較例１）、２．５４ｇ／ｃｃ（比較例２）、２．３０ｇ／ｃｃ（比較例３）であった。 The apparent density of the particles of the carrier core material was measured by a method according to JIS-2504. As a result, the apparent densities were 2.49 g / cc (Example 1), 2.51 g / cc (Example 2), 2.42 g / cc (Example 3), 2.62 g / cc (Example 4), respectively. ), 2.28 g / cc (Comparative Example 1), 2.54 g / cc (Comparative Example 2), and 2.30 g / cc (Comparative Example 3).
キャリア芯材の粒子の流動度は、ＪＩＳ−２５０２に準ずる方法により測定した。その結果、流動度は、それぞれ２４．２ｓ（実施例１）、２３．２ｓ（実施例２）、２２．９ｓ（実施例３）、２３．８ｓ（実施例４）、２６．９ｓ（比較例１）、２８．３ｓ（比較例２）、２３．３ｓ（比較例３）であった。 The fluidity of the carrier core particles was measured by a method according to JIS-2502. As a result, the fluidity was 24.2 s (Example 1), 23.2 s (Example 2), 22.9 s (Example 3), 23.8 s (Example 4), and 26.9 s (comparative example), respectively. 1), 28.3 s (Comparative Example 2), and 23.3 s (Comparative Example 3).
キャリア芯材の粒子の比表面積は、マウンテック社製のＭａｃｓｏｒｂ（Ｍｏｄｅｌ：１２０８）を使用し、吸着ガスとして窒素ガス、キャリアガスとしてヘリウムガスを使用して、ＢＥＴ法により求めた。その結果、比表面積は、それぞれ０．０５ｍ２／ｇ（実施例１）、０．０６ｍ２／ｇ（実施例２）、０．０５ｍ２／ｇ（実施例３）、０．０７ｍ２／ｇ（実施例４）、０．１８ｍ２／ｇ（比較例１）、０．０７ｍ２／ｇ（比較例２）、０．０６ｍ２／ｇ（比較例３）であった。 The specific surface area of the particles of the carrier core material was obtained by BET method using Macsorb (Model: 1208) manufactured by Mountec Co., using nitrogen gas as the adsorption gas and helium gas as the carrier gas. As a result, the specific surface area is respectively 0.05 m 2 / g (Example 1), 0.06m 2 / g (Example 2), 0.05m 2 / g (Example 3), 0.07m 2 / g (Example 4), 0.18 m 2 / g (Comparative Example 1), 0.07 m 2 / g (Comparative Example 2), and 0.06 m 2 / g (Comparative Example 3).
キャリア芯材の磁気特性として、ＶＳＭ（東英工業株式会社製のＶＳＭ−Ｐ７）を使用して磁化の測定を行い、外部磁場１００００Ｏｅにおける磁化を測定し、飽和磁化σｓ（ｅｍｕ／ｇ）を得た。その結果、飽和磁化σｓは、それぞれ８９．７ｅｍｕ／ｇ（実施例１）、９０．７ｅｍｕ／ｇ（実施例２）、９０．３ｅｍｕ／ｇ（実施例３）、８９．９ｅｍｕ／ｇ（実施例４）、９０．３ｅｍｕ／ｇ（比較例１）、９０．７ｅｍｕ／ｇ（比較例２）、９１．５ｅｍｕ／ｇ（比較例３）であった。 As the magnetic properties of the carrier core material, the magnetization is measured using VSM (VSM-P7 manufactured by Toei Kogyo Co., Ltd.), the magnetization in an external magnetic field of 10000 Oe is measured, and the saturation magnetization σs (emu / g) is obtained. It was. As a result, the saturation magnetization σs was 89.7 emu / g (Example 1), 90.7 emu / g (Example 2), 90.3 emu / g (Example 3), and 89.9 emu / g (Example), respectively. 4), 90.3 emu / g (Comparative Example 1), 90.7 emu / g (Comparative Example 2), and 91.5 emu / g (Comparative Example 3).
キャリア芯材の粒子の強度は、キャリア芯材の試料１００ｇをサンプルミル（協立理工株式会社製のＳＫ−Ｍ１０）に投入して回転数１６０００ｒｐｍで４０秒間粉砕処理した後、この処理の前後のキャリア芯材の粒径の変化を測定して評価した。具体的には、粒径変化率＝処理後の粒径Ｄ５０／処理前の粒径Ｄ５０を算出して、粒子の強度とした。この値が１．０に近いほど破砕処理によって粒子の割れや欠けによる粒径の変化が発生せず、機械的強度に優れた粒子である。その結果、粒子の強度は、それぞれ０．９５（実施例１）、０．９５（実施例２）、０．９２（実施例３）、０．９７（実施例４）、０．５７（比較例１）、０．８８（比較例２）、０．６６（比較例３）であった。 The strength of the carrier core particle was measured by putting 100 g of the carrier core sample into a sample mill (SK-M10 manufactured by Kyoritsu Riko Co., Ltd.) and grinding it at a rotational speed of 16000 rpm for 40 seconds. The change in the particle size of the carrier core material was measured and evaluated. Specifically, the particle size change rate = the particle diameter D 50 after the treatment / the particle diameter D 50 before the treatment was calculated as the particle strength. The closer this value is to 1.0, the more excellent the mechanical strength is because the particle size does not change due to cracking or chipping of the particles by the crushing treatment. As a result, the particle strengths were 0.95 (Example 1), 0.95 (Example 2), 0.92 (Example 3), 0.97 (Example 4), and 0.57 (comparative), respectively. Example 1), 0.88 (Comparative Example 2), and 0.66 (Comparative Example 3).
実施例１〜４および比較例１〜３で得られたキャリア芯材について、製造条件および特性を表１〜３に示す。 Production conditions and characteristics of the carrier core materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Tables 1 to 3.
キャリア芯材の帯電量を算出するために、実施例１〜４および比較例１〜３で得られたそれぞれのキャリア芯材３８ｇと市販のトナー（モノクロ用の粒径６μｍの一般的なトナー）２．０ｇをガラス瓶に入れ、振とう機に装填して２０分間攪拌して混合粉体を帯電量測定用試料とした。この帯電量測定用試料５００ｍｇに対して、吸引法によりキャリア芯材がトナーに与えた電荷を測定して、帯電量（μＣ／ｇ）を算出した。なお、電荷の測定は、電荷測定装置（日本パイオテク株式会社製のＳＴＣ−１−Ｃ１型）を使用し、吸引圧力を７．０ｋＰａとし、吸引用メッシュとして５００メッシュのＳＵＳ網を使用した。その結果、キャリア芯材の帯電量は、それぞれ２０．８μＣ／ｇ（実施例１）、２３．８μＣ／ｇ（実施例２）、１９．５μＣ／ｇ（実施例３）、２４．２μＣ／ｇ（実施例４）、１０．２μＣ／ｇ（比較例１）、１５．２μＣ／ｇ（比較例２）、１４．８μＣ／ｇ（比較例３）であった。 In order to calculate the charge amount of the carrier core material, each carrier core material 38g obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and a commercially available toner (a general toner having a particle size of 6 μm for monochrome) 2.0 g was put into a glass bottle, loaded into a shaker and stirred for 20 minutes, and the mixed powder was used as a charge measurement sample. The charge amount (μC / g) was calculated by measuring the charge applied to the toner by the carrier core material with respect to 500 mg of this charge amount measurement sample. The charge was measured using a charge measuring device (STC-1-C1 type manufactured by Nippon Piotech Co., Ltd.), a suction pressure of 7.0 kPa, and a 500 mesh SUS net as a suction mesh. As a result, the charge amount of the carrier core material was 20.8 μC / g (Example 1), 23.8 μC / g (Example 2), 19.5 μC / g (Example 3), and 24.2 μC / g, respectively. (Example 4) 10.2 μC / g (Comparative Example 1), 15.2 μC / g (Comparative Example 2), and 14.8 μC / g (Comparative Example 3).
また、実施例１〜４および比較例１〜３で得られたキャリア芯材に対して、以下のように樹脂被覆を行って電子写真現像剤用キャリアを得た。すなわち、シリコーン系樹脂（東レダウコーニングシリコーン株式会社製のＳＲ−２４１１）をトルエンに溶解させて濃度３０％の樹脂被覆用の樹脂溶液を用意し、この樹脂溶液と実施例１〜４および比較例１〜３で得られたキャリア芯材とを質量比１：９の割合で撹拌機に装填し、樹脂溶液にキャリア芯材を浸漬しながら、１５０〜２５０℃で３時間加熱および撹拌して、キャリア芯材に対して樹脂３．０質量％の割合でキャリア芯材を樹脂で被覆した。この樹脂で被覆されたキャリア芯材を熱風循環式加熱装置によって２５０℃で５時間加熱することにより、樹脂被覆層を硬化させてキャリアを得た。 Moreover, the carrier core material obtained in Examples 1 to 4 and Comparative Examples 1 to 3 was subjected to resin coating as follows to obtain an electrophotographic developer carrier. That is, a silicone resin (SR-2411 manufactured by Toray Dow Corning Silicone Co., Ltd.) was dissolved in toluene to prepare a resin solution for resin coating with a concentration of 30%. This resin solution, Examples 1 to 4 and Comparative Example The carrier core material obtained in 1 to 3 is charged in a stirrer at a mass ratio of 1: 9, and heated and stirred at 150 to 250 ° C. for 3 hours while immersing the carrier core material in the resin solution. The carrier core material was coated with the resin at a ratio of 3.0% by mass of the resin with respect to the carrier core material. The carrier core material coated with this resin was heated at 250 ° C. for 5 hours with a hot air circulation heating device to cure the resin coating layer to obtain a carrier.
このようにして得られた樹脂被覆後のそれぞれのキャリア３８ｇと市販のトナー２．０ｇをガラス瓶に入れ、振とう機に装填して２０分間攪拌して帯電量測定用試料とした。この帯電量測定用試料に対して、上述したキャリア芯材の帯電量の算出と同様の方法により、キャリアがトナーに与えた電荷を測定して、帯電量（μＣ／ｇ）を算出した。この帯電量をキャリアの初期帯電量とした。また、帯電量測定試料を振とう機によってさらに２４時間連続して撹拌した後、同様の方法により帯電量を算出し、この２４時間撹拌後の帯電量と初期帯電量との差（２４時間撹拌後の帯電量−初期帯電量）を帯電量の変化量（μＣ／ｇ）として、キャリアの耐久性の指標とした。この帯電量の変化量の絶対値が小さいほど、長時間にわたって攪拌しても帯電量の変化が生じないので、帯電維持性能が良好であるといえる。 Each of the thus-coated resin-coated carriers (38 g) and commercially available toner (2.0 g) were placed in a glass bottle, loaded into a shaker and stirred for 20 minutes to obtain a charge amount measurement sample. The charge amount (μC / g) was calculated by measuring the charge applied to the toner by the carrier in the same manner as the calculation of the charge amount of the carrier core material described above. This charge amount was used as the initial charge amount of the carrier. In addition, after the charge amount measurement sample was continuously stirred for 24 hours with a shaker, the charge amount was calculated by the same method, and the difference between the charge amount after the 24 hour stirring and the initial charge amount (24 hour stirring). The subsequent charge amount−initial charge amount) was defined as the change amount of charge amount (μC / g), which was used as an index of carrier durability. It can be said that the smaller the absolute value of the change amount of the charge amount, the better the charge maintaining performance because the change in the charge amount does not occur even when stirring for a long time.
その結果、初期帯電量は、それぞれ２８．３μＣ／ｇ（実施例１）、２５．４μＣ／ｇ（実施例２）、２６．２μＣ／ｇ（実施例３）、３１．４μＣ／ｇ（実施例４）、２４．２μＣ／ｇ（比較例１）、３２．５μＣ／ｇ（比較例２）、２９．５μＣ／ｇ（比較例３）、２４時間撹拌後の帯電量は、それぞれ２７．９μＣ／ｇ（実施例１）、２４．６μＣ／ｇ（実施例２）、２５．５μＣ／ｇ（実施例３）、３０．３μＣ／ｇ（実施例４）、１９．７μＣ／ｇ（比較例１）、２７．４μＣ／ｇ（比較例２）、２５．８μＣ／ｇ（比較例３）であり、帯電量の変化量は、それぞれ−０．４μＣ／ｇ（実施例１）、−０．８μＣ／ｇ（実施例２）、−０．７μＣ／ｇ（実施例３）、−１．１μＣ／ｇ（実施例４）、−４．５μＣ／ｇ（比較例１）、−５．１μＣ／ｇ（比較例２）、−３．７μＣ／ｇ（比較例３）であった。これらの結果を表４に示す。 As a result, the initial charge amounts were 28.3 μC / g (Example 1), 25.4 μC / g (Example 2), 26.2 μC / g (Example 3), and 31.4 μC / g (Example), respectively. 4), 24.2 μC / g (Comparative Example 1), 32.5 μC / g (Comparative Example 2), 29.5 μC / g (Comparative Example 3), and the charge amount after stirring for 24 hours was 27.9 μC / g, respectively. g (Example 1), 24.6 μC / g (Example 2), 25.5 μC / g (Example 3), 30.3 μC / g (Example 4), 19.7 μC / g (Comparative Example 1) 27.4 μC / g (Comparative Example 2) and 25.8 μC / g (Comparative Example 3), and the amount of change in charge amount was −0.4 μC / g (Example 1) and −0.8 μC / g, respectively. g (Example 2), -0.7 μC / g (Example 3), -1.1 μC / g (Example 4), -4.5 μC / g (Comparative Example 1), -5.1 μC / G (Comparative Example 2) and -3.7 μC / g (Comparative Example 3). These results are shown in Table 4.
実施例１で得られたキャリア芯材の任意の４つ粒子の表面のＳＥＭ像を図１Ａ〜図１Ｄに示す。これらの図からわかるように、実施例１では、１０００℃以下という比較的低温で焼成したにもかかわらず、粒子の成長が進行しており、粒子の界面はほとんど見られない。また、いずれの粒子でも、表面に結晶成長の結果生じたステップ状の凹凸があり、それ以外の領域では平滑な表面になっている。レーザー顕微鏡によりキャリア芯材の凹凸を評価した結果、この凹凸の高さは約０．３μｍであり、凹凸の間隔は、最小で０．５μｍ、最大で１．５μｍであった。なお、実施例２〜４で得られたキャリア芯材でもほぼ同様の結果が得られた。 The SEM images of the surfaces of any four particles of the carrier core material obtained in Example 1 are shown in FIGS. 1A to 1D. As can be seen from these figures, in Example 1, despite the firing at a relatively low temperature of 1000 ° C. or less, the growth of the particles progresses and the interface of the particles is hardly seen. Further, in any particle, the surface has step-like irregularities generated as a result of crystal growth, and the surface is smooth in other regions. As a result of evaluating the unevenness of the carrier core material with a laser microscope, the height of the unevenness was about 0.3 μm, and the interval between the unevenness was a minimum of 0.5 μm and a maximum of 1.5 μm. In addition, the substantially same result was obtained also with the carrier core material obtained in Examples 2-4.
また、比較例１〜３で得られたキャリア芯材の任意の粒子の表面のＳＥＭ像をそれぞれ図２〜図４に示す。図２に示すように、副原料としての炭酸カルシウムを使用しなかった以外は実施例１と同様の方法により得られた比較例１のキャリア芯材は、粒子の成長がほとんど進行しておらず、粒子の界面が多い多孔質形状の粒子になっている。図３に示すように、実施例１より高温の１３００℃で焼成した以外は実施例１と同様の方法により得られた比較例２のキャリア芯材は、粒子の全体が平滑になっており、実施例１〜４のようなステップ状の凹凸は見られない。図４に示すように、炭酸塩の代わりに同一のアルカリ金属の水酸化物を使用した以外は実施例１と同様の方法により得られた比較例３のキャリア芯材は、１０００℃以下で焼成しても粒子の成長が進行しているものの、実施例１〜４のようなステップ状の凹凸は見られない。 Moreover, the SEM image of the surface of the arbitrary particle | grains of the carrier core material obtained by Comparative Examples 1-3 is shown in FIGS. 2-4, respectively. As shown in FIG. 2, in the carrier core material of Comparative Example 1 obtained by the same method as in Example 1 except that calcium carbonate as an auxiliary material was not used, particle growth hardly progressed. The particles have a porous shape with many particle interfaces. As shown in FIG. 3, the carrier core material of Comparative Example 2 obtained by the same method as in Example 1 except that it was fired at 1300 ° C., which is higher than that in Example 1, has the entire particles smoothed. The step-like unevenness | corrugation like Examples 1-4 is not seen. As shown in FIG. 4, the carrier core material of Comparative Example 3 obtained by the same method as in Example 1 except that the same alkali metal hydroxide was used instead of carbonate was fired at 1000 ° C. or lower. Even though the growth of the particles is progressing, the step-like unevenness as in Examples 1 to 4 is not seen.
これらの結果から、実施例１〜４のように、酸化鉄粉末と炭酸塩との混合物を顆粒化した後、１０００℃以下の温度で熱処理して還元反応を行うことにより、粒子の表面にステップ状の凹凸を有するキャリア芯材が得られることがわかる。 From these results, as in Examples 1 to 4, after granulating a mixture of iron oxide powder and carbonate, heat treatment is performed at a temperature of 1000 ° C. or lower, and a reduction reaction is performed on the surface of the particles. It turns out that the carrier core material which has a shape unevenness | corrugation is obtained.
また、実施例１〜４および比較例１〜３で得られたキャリア芯材はいずれも、飽和磁化σsが８０ｅｍｕ／ｇ以上であり、キャリア芯材として好ましい磁気特性を有している。 In addition, the carrier core materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 each have a saturation magnetization σ s of 80 emu / g or more, and have preferable magnetic properties as a carrier core material.
しかし、比較例１で得られたキャリア芯材は、焼結が弱いために見掛け密度が低く、比表面積の大きな多孔質状の粒子になっている。そのため、このキャリア芯材は、粒子の強度が著しく悪化しており、電子写真現像剤用キャリアに使用すると、粒子の割れや欠けが発生して好ましくない。 However, the carrier core material obtained in Comparative Example 1 is porous particles having a low apparent density and a large specific surface area due to weak sintering. For this reason, the carrier core material is remarkably deteriorated in the strength of the particles, and when used as a carrier for an electrophotographic developer, the particles are not preferably cracked or chipped.
比較例２および３で得られたキャリア芯材は、焼結が進行して粒子の強度が改善されている。しかし、実施例１〜４で得られたキャリア芯材は、高い粒子の強度を有するとともに、キャリア芯材の帯電付与能力が高い点で、比較例２および３と異なっているため、樹脂被覆後のキャリアの帯電維持性能を向上させることができる。このように、実施例１〜４で得られたキャリア芯材が、高い帯電付与能力を有するのは、図１Ａ〜図１Ｄに見られるような微細な凹凸が摩擦時の電荷の受与に効果的に作用しているためであると考えられる。 In the carrier core materials obtained in Comparative Examples 2 and 3, sintering progresses and the strength of the particles is improved. However, since the carrier core material obtained in Examples 1 to 4 is different from Comparative Examples 2 and 3 in that the carrier core material has high particle strength and the charge imparting ability of the carrier core material is high, after the resin coating The charge maintaining performance of the carrier can be improved. As described above, the carrier core materials obtained in Examples 1 to 4 have a high charge imparting ability because the fine unevenness as seen in FIGS. 1A to 1D is effective in receiving charges during friction. This is thought to be due to the action.
実施例１〜４および比較例１〜３で得られたキャリア芯材の粒子の比表面積と強度との関係を図５に示す。この図からわかるように、実施例１〜４で得られたキャリア芯材の粒子は、比表面積が低く、強度が高いことがわかる。 FIG. 5 shows the relationship between the specific surface area of the particles of the carrier core material obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and the strength. As can be seen from the figure, the carrier core particles obtained in Examples 1 to 4 have low specific surface area and high strength.
また、実施例１〜４で得られたキャリア芯材を樹脂で被覆したキャリアは、長期間にわたってトナーとの混合攪拌を行っても、帯電付与能力の変化が起こり難く、帯電維持性能に優れている。これは、下地であるキャリア芯材の帯電付与能力の高さが有効に作用しているためであると考えられる。 Further, the carrier obtained by coating the carrier core material obtained in Examples 1 to 4 with a resin is hardly changed in charge imparting ability even when mixed and stirred with a toner for a long period of time, and has excellent charge maintaining performance. Yes. This is considered to be because the high charge imparting ability of the carrier core material as the base works effectively.
このように、実施例１〜４で得られたキャリア芯材を使用することにより、粒子の割れや欠けが生じ難く、帯電量の変化が生じ難く、長期間にわたって現像を繰り返しても、画質の変化が生じ難い電子写真現像剤用キャリアを製造することができる。 In this way, by using the carrier core material obtained in Examples 1 to 4, it is difficult for the particles to crack or chip, and the amount of charge hardly changes. A carrier for an electrophotographic developer that hardly changes can be produced.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000172017A (en) * | 1998-12-02 | 2000-06-23 | Fuji Elelctrochem Co Ltd | Production of ferrite carrier core for electrophotographic development |
| JP4590303B2 (en) * | 2004-05-13 | 2010-12-01 | キヤノン株式会社 | Magnetic material-containing resin carrier and two-component developer |
| JP4928116B2 (en) * | 2005-11-09 | 2012-05-09 | キヤノン株式会社 | Replenishment developer and development method using the same |
| JP2007279588A (en) * | 2006-04-11 | 2007-10-25 | Canon Inc | Developer for replenishment and image forming method |
| JP5300361B2 (en) * | 2008-07-29 | 2013-09-25 | キヤノン株式会社 | Developing apparatus and developing method |
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