JP2004279771A - Electrostatic charge image developing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner having excellent storage stability and cleanability. <P>SOLUTION: The toner contains a binder resin, a colorant, and a charge control agent, wherein a volume mode diameter (a) of toner particles is 5-10 μm, a volume average particle diameter to number average particle diameter ratio is 1.0-1.3, an average circularity is 0.97-0.995, a standard deviation of particle diameter is ≤2 μm, an average circularity on the smaller particle diameter side is equal to or slightly larger than that on the larger particle diameter side in a specified ratio, and electric conductivity of a water extracted liquid obtained by treatment under prescribed measurement conditions is in a specified range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２８】
上記式において、ｎは円形度Ｃｉを求めた粒子の個数である。
上記式においてＣｉは０．６〜４００μｍの円相当径の粒子群の各粒子について測定された円周長を元に次式により算出された各粒子の円形度である。
円形度（Ｃｉ）＝粒子の投影面積に等しい円の周囲長／粒子投影像の周囲長
上記式において、ｆｉは円形度Ｃｉの粒子の頻度である。
上記円形度及び平均円形度は、シスメックス社製フロー式粒子像分析装置「ＦＰＩＡ−１０００」又は「ＦＰＩＡ−２０００」を用いて測定することができる。
【００２９】
本発明の静電荷像現像用トナーを構成するトナー粒子の粒径の標準偏差（ｂ）は２μｍ以下であり、好ましくは１．５μｍ以下である。トナー粒子の粒径の標準偏差が２μｍを超えるとカブリが発生するなど、画質の低下が生じる。トナー粒子の標準偏差は、円形度及び平均円形度と同様、シスメックス社製フロー式粒子像分析装置「ＦＰＩＡ−１０００」又は「ＦＰＩＡ−２０００」を用いて測定することができる体積基準の値である。
【００３０】
本発明の静電荷像現像用トナーを構成するトナー粒子は、体積モード径をａとし、トナー粒子の粒径の標準偏差をｂとした場合、（ａ−２ｂ）μｍ以上ａμｍ未満の粒径を有するトナー粒子の平均円形度をＣ１とし、ａμｍ以上（ａ＋２ｂ）μｍ未満の粒径を有するトナー粒子の平均円形度をＣ２とした場合、（Ｃ１／Ｃ２）が１．００〜１．０２であり、好ましくは１．００〜１．０１であり、更に好ましくは１．００〜１．００５である。この数値はトナー粒子の合一状態を表現する意義がある。（Ｃ１／Ｃ２）が大きいと、トナー粒子が２個結合した、いわゆる合一粒子が多くなっていることを示している。（Ｃ１／Ｃ２）が上記範囲にあると、カブリの発生が少なく、ドット再現性も良好になる。
なお、上記Ｃ１及びＣ２についても、円形度及び平均円形度と同様、シスメックス社製フロー式粒子像分析装置「ＦＰＩＡ−１０００」又は「ＦＰＩＡ−２０００」を用いて測定することができる。
【００３１】
本発明の静電荷像現像用トナーは、導電率σ１が０〜１０μＳ／ｃｍのイオン交換水に、トナー濃度が６重量％になるように分散させ、加熱して１０分間煮沸した後、別途煮沸させた導電率σ１が０〜１０μＳ／ｃｍのイオン交換水を加えて蒸発水分を補充して元の容量にし、室温（２２℃程度の温度）まで冷却して得られた水抽出液の導電率σ２が２０μＳ／ｃｍ以下であり、好ましくは１０μＳ／ｃｍ以下である。また、σ２−σ１は０．１〜１０μＳ／ｃｍであり、好ましくは０．１〜６μＳ／ｃｍである。導電率σ２が２０μＳ／ｃｍを超えると、帯電量の環境に対する依存性が高くなって、環境変動（温度や湿度の変化）による画質の低下を引き起こす。σ２−σ１が１０μＳ／ｃｍを超えた場合も、帯電量の環境に対する依存性が高くなって、環境変動（温度や湿度の変化）による画質の低下を引き起こす。一方、σ２−σ１が０．１μＳ／ｃｍ未満であると印字濃度が低下し、かぶりが発生する。
【００３２】
本発明の静電荷像現像用トナーは、示差走査熱量分析計（ＤＳＣ）にて測定した融解エンタルピー（ΔＨ）が１〜１０ｍＪ／ｍｇであることが好ましく、２〜６ｍＪ／ｍｇであることが更に好ましく、３〜５ｍＪ／ｍｇであることが特に好ましい。静電荷像現像用トナーの示差走査熱量分析計にて測定した融解エンタルピー（ΔＨ）が上記範囲内であると定着性が優れる。ΔＨが１０ｍＪ／ｍｇを超えるとトナーの溶融に多大な熱量を必要とし、カラー画像の如く、多色、多層での画像形成の際に低エネルギー定着（低温定着）が達成できない場合がある。また、ΔＨが１ｍＪ／ｍｇ未満であると、定着性が劣る場合があり、十分な離型効果が得られない場合がある。なお、ΔＨは示差走査熱量分析計曲線の吸熱ピークとベースラインとに囲まれた領域の面積（ピーク面積）より算出することができる。
【００３３】
本発明の静電荷像現像用トナーは、そのままで電子写真の現像に用いることもできるが、通常は、静電荷像現像用トナーの帯電性、流動性、保存安定性等を調整するために、トナー粒子表面に、該トナー粒子よりも小さい粒径の微粒子（以下、外添剤という。）を付着又は埋設させてから用いることが好ましい。
外添剤としては、通常、流動性や帯電性を向上させる目的で使用されている無機粒子や有機樹脂粒子が挙げられる。外添剤として添加するこれらの粒子は、トナー粒子よりも平均粒径が小さい。例えば、無機粒子としては、シリカ、酸化アルミニウム、酸化チタン、酸化亜鉛、酸化錫などが挙げられ、有機樹脂粒子としては、メタクリル酸エステル重合体粒子、アクリル酸エステル重合体粒子、スチレン−メタクリル酸エステル共重合体粒子、スチレン−アクリル酸エステル共重合体粒子、コアがスチレン重合体で、シェルがメタクリル酸エステル重合体で形成されたコアシェル型粒子などが挙げられる。これらのうち、シリカ粒子や酸化チタン粒子が好適であり、この表面を疎水化処理した粒子が好ましく、疎水化処理されたシリカ粒子が特に好ましい。外添剤の量は、特に限定されないが、トナー粒子１００重量部に対して、通常、０．１〜６重量部である。
【００３４】
本発明の静電荷像現像用トナーは、前述した範囲の特性を有するものを与えることができる方法であれば、その製造方法に特に制限はないが、重合法によって製造することが好ましい。
次に、重合法により静電荷像現像用トナーを構成するトナー粒子を製造する方法について説明する。
本発明の静電荷像現像用トナーを構成するトナー粒子は、例えば、水溶性多価無機塩と水酸化アルカリとを水性分散媒中で混合して難水溶性無機化合物のコロイドを含有する水性分散媒を調製し、熟成させる工程；重合性単量体、着色剤、帯電制御剤及び重合開始剤を含有する重合性単量体組成物を、上記熟成された難水溶性無機化合物のコロイドを含有する水性分散媒に添加して、該組成物の液滴を形成させ、上記液滴を含有する水性分散媒を得る工程；及び液滴を含有する水性分散媒中にホウ素化合物を添加した後、該水性分散媒を加熱して、重合性単量体を重合してトナー粒子を形成する工程；を含むことを特徴とする、静電荷像現像用トナーの製造方法によって製造することができる。
【００３５】
本発明では、重合性単量体組成物を得るときに、予め着色剤と帯電制御樹脂を混合して製造した帯電制御樹脂組成物を得、それを離型剤等とともに重合性単量体に添加して混合してもよい。その際、着色剤の量は、帯電制御樹脂１００重量部に対して、通常１０〜２００重量部、好ましくは２０〜１５０重量部である。帯電制御樹脂組成物の製造には、有機溶剤を用いることが好ましい。有機溶剤を用いることで、帯電制御樹脂が柔らかくなり、顔料と混合し易くなる。
【００３６】
有機溶剤の量は、帯電制御樹脂１００重量部に対して、通常、０〜１００重量部、好ましくは５〜８０重量部、さらに好ましくは１０〜６０重量部であり、この範囲にあると分散性と加工性のバランスが優れる。また、このとき、有機溶剤は、一度に全量を添加しても、あるいは混合状態を確認しながら、何回かに分割して添加しても良い。
混合は、ロール、ニーダー、一軸押出機、二軸押出機、バンバリー、ブス・コニーダー等を用いて行うことができる。有機溶剤を用いる場合は、有機溶剤が外部に漏れない密閉系の混合機が好ましい。
また、混合機にはトルクメーターが設置されていることが、トルクのレベルで分散性を管理することができるので好ましい。
【００３７】
重合性単量体としては、例えば、モノビニル単量体、架橋性単量体、マクロモノマー等を挙げることができる。この重合性単量体が重合され、結着樹脂成分となる。
モノビニル単量体としては、スチレン、ビニルトルエン、α−メチルスチレン等の芳香族ビニル単量体；（メタ）アクリル酸；（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸シクロヘキシル、（メタ）アクリル酸イソボニル等の（メタ）アクリル系共重合体；エチレン、プロピレン、ブチレン等のモノオレフィン単量体；等が挙げられる。
モノビニル単量体は、単独で用いても、複数の単量体を組み合わせて用いても良い。これらモノビニル単量体のうち、芳香族ビニル単量体単独、芳香族ビニル単量体と（メタ）アクリル系単量体との併用などが好適に用いられる。
【００３８】
モノビニル単量体と共に、架橋性単量体を用いるとホットオフセットが有効に改善される。架橋性単量体は、２個以上のビニル基を有する単量体である。具体的には、ジビニルベンゼン、ジビニルナフタレン、エチレングリコールジメタクリレート、ペンタエリスリトールトリアリルエーテルやトリメチロールプロパントリアクリレート等を挙げることができる。これらの架橋性単量体は、それぞれ単独で、あるいは２種以上組み合わせて用いることができる。架橋性単量体の量は、モノビニル単量体１００重量部当たり、通常１０重量部以下、好ましくは、０．１〜２重量部である。
【００３９】
また、モノビニル単量体と共に、マクロモノマーを用いると、保存性と低温での定着性とのバランスが良好になるので好ましい。マクロモノマーは、分子鎖の末端に重合可能な炭素−炭素不飽和二重結合を有するもので、数平均分子量が、通常、１，０００〜３０，０００のオリゴマーまたはポリマーである。
マクロモノマーは、前記モノビニル単量体を重合して得られる重合体のガラス転移温度よりも、高いガラス転移温度を有する重合体を与えるものが好ましい。マクロモノマーの量は、モノビニル単量体１００重量部に対して、通常、０．０１〜１０重量部、好ましくは０．０３〜５重量部、さらに好ましくは０．０５〜１重量部である。
【００４０】
重合開始剤としては、例えば過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩；４，４’−アゾビス（４−シアノバレリック酸）、２，２’−アゾビス（２−メチル−Ｎ−（２−ヒドロキシエチル）プロピオンアミド、２，２’−アゾビス（２−アミジノプロパン）ジヒドロクロライド、２，２’−アゾビス（２，４−ジメチルバレロニトリル）、２，２’−アゾビスイソブチロニトリル等のアゾ化合物；ジ−ｔ−ブチルパーオキシド、ベンゾイルパーオキシド、ｔ−ブチルパーオキシ−２−エチルヘキサノエート、ｔ−ヘキシルパーオキシ−２−エチルヘキサノエート、ｔ−ブチルパーオキシピバレート、ジ−イソプロピルパーオキシジカーボネート、ジ−ｔ−ブチルパーオキシイソフタレート、ｔ−ブチルパーオキシイソブチレート等の過酸化物類等が挙げられる。また、上記重合開始剤と還元剤とを組み合わせたレドックス開始剤を用いてもよい。
【００４１】
重合性単量体の重合に用いられる重合開始剤の量は、重合性単量体１００重量部に対して、好ましくは０．１〜２０重量部であり、更に好ましくは０．３〜１５重量部であり、最も好ましくは０．５〜１０重量部である。重合開始剤は、重合性単量体組成物中にあらかじめ添加しておく。
【００４２】
分散安定化剤として用いられる難水溶性無機化合物のコロイドは、水溶性多価無機塩と水酸化アルカリとを水性分散媒中で混合して生成したものである。このような難水溶性無機化合物としては、例えば水酸化マグネシウム等が挙げられる。難水溶性無機化合物のコロイドを含有する水性分散媒を熟成させてからトナー製造に用いると、容易に本発明の静電荷像現像用トナーを得ることができるので好ましい。本発明で熟成とは、難水溶性無機化合物のコロイドを含有する水性分散媒を調製した後、直ちに用いず、一定時間放置することである。具体的には、１５〜３５℃の温度、好ましくは２０〜３０℃の温度で４〜１８時間、好ましくは５〜１５時間放置することである。
【００４３】
上記分散安定化剤の量は、重合性単量体１００重量部に対して、好ましくは０．１〜２０重量部である。分散安定化剤の量が０．１重量部未満であると十分な重合安定性を得ることが困難になり、重合凝集物が生成しやすくなる場合があり、一方、２０重量部を超えて使用すると、重合安定性の効果が飽和し、経済的でないことに加え、水性分散媒の粘度が高くなりすぎ、混合後の小さな液滴を形成することが困難となる場合がある。
また、重合に際しては、水溶性高分子を重合トナーの帯電特性の環境依存性や定着性の変化が大きくならない範囲で併用することができる。水溶性高分子としては、例えばポリビニルアルコール、メチルセルロース、ゼラチン等が挙げられる。
【００４４】
重合に際しては、重合性単量体の液滴を形成させた後、この液滴を含む水性分散媒中にホウ素化合物を添加する。ホウ素化合物としては、三フッ化ホウ素、三塩化ホウ素、テトラフルオロホウ酸、テトラヒドロホウ酸ナトリウム、テトラヒドロホウ酸カリウム、四ホウ酸ナトリウム、四ホウ酸ナトリウム十水和物、メタホウ酸ナトリウム、メタホウ酸ナトリウム四水和物、ペルオキソホウ酸ナトリウム四水和物、ホウ酸、メタホウ酸カリウム、四ホウ酸カリウム八水和物等が挙げられる。ホウ素化合物は水溶液の状態で添加することが好ましい。上記ホウ素化合物の量は、難水溶性化合物のコロイド１００重量部に対して、好ましくは０．１〜５重量部であり、更に好ましくは０．３〜３重量部である。
【００４５】
また、重合に際しては、分子量調整剤を使用することが好ましい。該分子量調整剤としては、例えばｔ−ドデシルメルカプタン、ｎ−ドデシルメルカプタン、ｎ−オクチルメルカプタン、２，２，４，６，６−ペンタメチルヘプタン−４−チオール等のメルカプタン類等が挙げられる。上記分子量調整剤は、重合開始前または重合途中に添加することができる。上記分子量調整剤の量は、重合性単量体１００重量部に対して、好ましくは０．０１〜１０重量部であり、更に好ましくは０．１〜５重量部である。
【００４６】
コアシェル型トナー粒子を製造する方法としては特に制限はなく、従来公知の方法によって製造することができる。例えば、スプレイドライ法、界面反応法、ｉｎ ｓｉｔｕ重合法、相分離法などの方法が挙げられる。具体的には、粉砕法、重合法、会合法又は転相乳化法により得られたトナー粒子をコア粒子として、それに、シェル層を被覆することによりコアシェル型トナー粒子が得られる。この製造方法の中でも、ｉｎ ｓｉｔｕ重合法や相分離法が、製造効率の点から好ましい。
【００４７】
ｉｎ ｓｉｔｕ重合法によるコアシェル型トナー粒子の製造方法を以下に説明する。
コア粒子が分散している水系分散媒体中に、シェルを形成するための重合性単量体（シェル用重合性単量体）と重合開始剤とを添加し、重合することでコアシェル型トナー粒子を得ることができる。
シェルを形成する具体的な方法としては、コア粒子を得るために行った重合反応の反応系にシェル用重合性単量体を添加して継続的に重合する方法、または別の反応系で得たコア粒子を仕込み、これにシェル用重合性単量体と重合開始剤を添加して重合する方法などを挙げることができる。
シェル用重合性単量体は反応系中に一括して添加しても、またはプランジャポンプなどのポンプを使用して連続的もしくは断続的に添加してもよい。
【００４８】
シェル用重合性単量体としては、スチレン、アクリロニトリル、メチルメタクリレートなどのガラス転移温度が８０℃を超える重合体を形成する単量体をそれぞれ単独で、あるいは２種以上組み合わせて使用することができる。
【００４９】
シェル用重合性単量体を添加する際に、水溶性の重合開始剤を添加することがコアシェル型トナー粒子を得やすくなるので好ましい。シェル用重合性単量体の添加の際に水溶性重合開始剤を添加すると、コア粒子の外表面近傍に水溶性重合開始剤が移動し、コア粒子表面で、シェル用重合性単量体が重合しやすくなると考えられる。
【００５０】
水溶性重合開始剤としては、過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩；２，２’−アゾビス（２−メチル−Ｎ−（２−ヒドロキシエチル）プロピオンアミド）、２，２’−アゾビス−（２−メチル−Ｎ−（１，１−ビス（ヒドロキシメチル）２−ヒドロキシエチル）プロピオンアミド）等のアゾ系開始剤などを挙げることができる。水溶性重合開始剤の量は、シェル用重合性単量体１００重量部に対して、通常、０．１〜５０重量部、好ましくは１〜３０重量部である。
【００５１】
重合の際の温度は、好ましくは５０℃以上であり、更に好ましくは８０〜９５℃である。また、反応時間は好ましくは１〜２０時間であり、更に好ましくは２〜１０時間である。重合終了後に、常法に従い、濾過、洗浄、脱水および乾燥の操作を、必要に応じて数回繰り返すことが好ましい。
【００５２】
重合によって得られるトナー粒子の水分散液のｐＨが６．５以下になるように酸を添加して、分散安定化剤である難水溶性無機化合物のコロイドを溶解させることが好ましい。添加する酸としては、硫酸、塩酸、硝酸などの無機酸、蟻酸、酢酸などの有機酸を用いることができるが、除去効率の大きいことや製造設備への負担が小さいことから、特に硫酸が好適である。トナー粒子をろ過により分取した後、３０〜４０℃の水でトナー粒子の洗浄を行い、トナー粒子を乾燥する。水性分散媒中のトナー粒子を濾過する方法は特に制限されない。例えば、遠心濾過法、真空濾過法、加圧濾過法などを挙げることができる。これらのうち遠心濾過法が好適である。トナー粒子の洗浄に用いられる水の温度は３０〜５０℃であり、好ましくは３０〜４０℃である。水の温度が３０℃より低いと洗浄効果が不十分となり、一方、５０℃より高いとトナー形状が変化する傾向がある。
トナー粒子を乾燥する方法に格別の制限はなく、真空乾燥機等を用いることができる。
【００５３】
本発明の静電荷像現像用トナーは、トナー粒子及び外添剤、また必要に応じてその他の微粒子をヘンシェルミキサー等の高速撹拌機を用いて混合することにより得られる。
【００５４】
【実施例】
以下、本発明を実施例により更に詳細に説明する。なお、本発明の範囲は、かかる実施例に限定されないことはいうまでもない。なお、以下の実施例において、部および％は、特に断りのない限り重量部又は重量％を表す。
【００５５】
本実施例では、以下の方法でトナーの評価を行った。
（１）粒径、粒径分布
トナー粒子の粒径分布、すなわち体積平均粒径と個数平均粒径（Ｄｐ）との比（Ｄｖ／Ｄｐ）は粒径測定機（ベックマン・コールター社製、機種名「マルチサイザー」）により測定した。このマルチサイザーによる測定は、アパーチャー径：１００μｍ、媒体：イソトンＩＩ、濃度１０％、測定粒子個数：５０，０００個の条件で行った。
【００５６】
（２）体積モード径、平均円形度、標準偏差
２０ｍｇのトナー粒子に分散媒として０．１％ アニオン系界面活性剤水溶液を１００μｌ加えてなじませた後、水１０ｍｌを加えて撹拌し、体積モード径、平均円形度、標準偏差の測定を行った。測定はシスメックス社製フロー式粒子像分析装置「ＦＰＩＡ−２０００」を用いて行った。解析は体積基準（１５μｍ以下の区分について）にて行った。
更に、（ａ−２ｂ）μｍ以上ａμｍ未満の粒径を有するトナー粒子の平均円形度（Ｃ１）、及びａμｍ以上（ａ＋２ｂ）μｍ未満の粒径を有するトナー粒子の平均円形度（Ｃ２）についても、上記装置により解析を行った。
【００５７】
（３）導電率
トナー６ｇを、イオン交換水（σ１が０．８μＳ／ｃｍ；ｐＨ＝７）に分散して１００ｇにする。これを加熱して、煮沸させ、煮沸状態を約１０分間保持（１０分間煮沸）した後、別途約１０分間煮沸しておいたイオン交換水（σ１が０．８μＳ／ｃｍ；ｐＨ＝７）を補充して煮沸前の容量に戻し、室温（約２２℃）に冷却し、抽出液の導電率σ２を測定した。また、用いたイオン交換水の導電率σ１を測定し、σ２−σ１を算出した。導電率は、導電率計「ＥＳ−１２」（堀場製作所製）を用いて測定した。
【００５８】
（４）融解エンタルピー
融解エンタルピーは、示差走査熱量計（ＤＳＣ ＳＳＣ５２００、セイコー電子工業社製）を用いて、ＡＳＴＭ Ｄ３４１８−８２に準拠して、昇温速度１０℃／分で測定したＤＳＣ曲線のピーク面積から算出した。
【００５９】
（５）カブリ
市販の非磁性一成分現像方式のプリンター（１８枚機）に再生紙をセットして、このプリンター装置に静電荷像現像用トナーを入れ、温度１０℃、湿度２０％の（Ｌ／Ｌ）環境、温度２３℃、湿度５０％の（Ｎ／Ｎ）環境、温度３５℃、湿度８０％の（Ｈ／Ｈ）環境下でそれぞれ、一昼夜放置した後、プリンターの印字濃度を５％に設定して印字を行い、５００枚毎に印字を一時停止させ、現像後の感光体上の非現像部のトナーを粘着テープ（住友スリーエム社製、スコッチメンディングテープ８１０−３−１８）に付着させた。それを印字用紙に貼り付け、その白色度（Ｂ）を白色度計（日本電色社製）で測定した。同時に、粘着テープだけを貼り付けた印字用紙の白色度（Ａ）を測定し、それぞれの白色度の差（Ａ−Ｂ）（％）を求めた。この価と、印字初期（１０枚印字時）の白色度の差（Ａ−Ｂ）（％）との差が１％以下である最大枚数（５００枚単位でカウント）を調べた。なお、試験は１０，０００枚で終了した。
【００６０】
（６）細線再現性
（５）で使用したプリンターを用いて、温度１０℃及び湿度２０％の（Ｌ／Ｌ）環境下、温度２３℃及び湿度５０％の（Ｎ／Ｎ）環境下、温度３５℃及び湿度８０％の（Ｈ／Ｈ）環境下で一昼夜放置した後、２×２ドットライン（幅約８５μｍ）で連続して線画像を形成し、５００枚毎に、印字評価システム「ＲＴ２０００」（ＹＡ−ＭＡ社製）によって測定し、線画像の濃度分布データを採取した。この時、その濃度の最大値の半値における全幅を線幅として、一枚目の線画像の線幅を基準として、その線幅の差が１０μｍ以下のものは１枚目の線画像を再現しているとして、線画像の線幅の差が１０μｍ以下を維持できる枚数を調べた。なお、この試験は１０，０００枚で終了した。
【００６１】
（７）印字濃度
（５）で使用したプリンターに印字用紙をセットし、現像装置にトナーを入れ、温度３５℃及び湿度８０％の（Ｈ／Ｈ）環境下で一昼夜放置後、プリンターを５％印字濃度に設定して初期から連続印字を行い、１００枚目印字（初期印字）、及び１０，０００枚目印字（連続印字）に黒ベタ印字を行い、ＭｃＢｅｔｈ社製透過式画像濃度測定機を用いて、印字濃度を測定した。
【００６２】
実施例１
スチレン９０．５部、ｎ−ブチルアクリレート９部、及び２−アクリルアミド−２−メチルプロパンスルホン酸０．５部からなる重合性単量体１００部をトルエン９００部中に投入し、アゾビスジメチルバレロニトリル４部の存在下、８０℃で８時間反応させた。反応終了後、トルエンを減圧留去して、負帯電制御樹脂であるスルホン酸基含有共重合体（Ｍｗ＝１６，０００）を得た。
上述した負帯電制御樹脂であるスルホン酸基含有共重合体６部、及びカーボンブラック（商品名「＃２５Ｂ」、三菱化学社製；一次粒径４０ｎｍ）６部を、スチレン８３部、ｎ−ブチルアクリレート１７部及びジビニルベンゼン０．６部に溶解した。次いで、ｔ−ドデシルメルカプタン１部、及びジペンタエリスリトールヘキサミリステート１０部を室温下、ビーズミルで分散させ、均一混合液を得た。この均一混合液に重合開始剤ｔ−ブチルパーオキシ２−エチルヘキサノエート（商品名「パーブチルＯ」、日本油脂社製）５部を添加し、重合性単量体組成物を得た。
一方、メタクリル酸メチル２部及び水６５部を混合し、シェル用重合性単量体の水分散液を得た。
【００６３】
他方、イオン交換水２５０部に塩化マグネシウム９．５部を溶解した水溶液に、イオン交換水５０部に水酸化ナトリウム５．５部を溶解した水溶液を撹拌下で徐々に添加して、水酸化マグネシウムコロイド分散液を製造し、２５℃に６時間放置して熟成させた。熟成した分散液に、重合性単量体組成物を投入し、連続乳化分散機であるエバラマイルダーＭＤＮ３０４型（荏原製作所社製）を用いて、１５，０００ｒｐｍの回転数で１０分間攪拌して、重合性単量体組成物（コア用単量体組成物）の液滴を形成させた。形成されたコア用単量体組成物が分散した水酸化マグネシウムコロイド分散液に、四ホウ酸ナトリウム十水和物を１部添加し、攪拌翼を装着した反応器に入れ、８５℃の温度で重合反応を開始させ、重合転化率がほぼ１００％に達した後、シェル用重合性単量体の水分散液、及び２，２’−アゾビス（２−メチル−Ｎ（２−ヒドロキシエチル）−プロピオンアミド（和光純薬社製、商品名「ＶＡ−０８６」）０．３部を反応器に入れた。重合反応を４時間継続した後、反応を停止し、コアシェル型トナー粒子の水分散液を得た。
【００６４】
上述のようにして得られたコアシェル型重合体トナー粒子の水分散液に２５℃で硫酸を添加して１０分間撹拌して、系のｐＨを４以下に調整した後、濾過により脱水した。次いで、分取したトナー粒子とイオン交換水５００部とを混合して再スラリー化し３８℃の水で洗浄を行った。その後、再度、脱水及び水洗浄を数回繰り返し行い、固形分を濾過遠心分離した後、乾燥機にて４５℃で２昼夜乾燥を行い、トナー粒子を得た。
上述のようにして得られたトナー粒子１００部に、疎水化処理されたコロイダルシリカ（日本アエロジル社製：ＲＸ−２００）０．６部を添加し、ヘンシェルミキサーを用いて混合し、負帯電性静電荷像現像用トナーを調製した。得られた静電荷像現像用トナーについて、上述した評価を行った。評価結果を表１に示す。
【００６５】
実施例２
スチレン８９部、ｎ−ブチルアクリレート９部、及びＮ−ベンジル−Ｎ，Ｎ−ジメチル−Ｎ−（２−メタクリルオキシエチル）アンモニウムクロライド２部からなる重合性単量体１００部をトルエン９００部中に投入し、アゾビスジメチルバレロニトリル４部の存在下、８０℃で８時間反応させた。反応終了後、トルエンを減圧留去して、正帯電制御樹脂である、第４級アンモニウム塩基含有共重合体（Ｍｗ＝２５，０００）を得た。
負帯電制御樹脂に代え、上述のようにして得られた正帯電制御樹脂を用いた以外は、実施例１と同様に操作を行い、静電荷像現像用トナーを得た。得られた静電荷像現像用トナーについて、実施例１と同様に評価を行った。評価結果を表１に示す。
【００６６】
比較例１
スチレン８０．５部及びｎ−ブチルアクリレート１９．５部からなるコア用重合性単量体（これらの単量体を共重合して得られた共重合体のＴｇ＝５５℃）、ポリメタクリル酸エステルマクロモノマー（東亜合成化学工業社製、商品名「ＡＡ６」、Ｔｇ＝９４℃）０．３部、ジビニルベンゼン０．５部、ｔ−ドデシルメルカプタン１．２部、カーボンブラック（三菱化学社製、商品名「＃２５Ｂ」）７部、帯電制御剤（保土ヶ谷化学社製、商品名「スピロンブラックＴＲＨ」）１部、離型剤（フィッシャートロプシュワックス、サゾール社製、商品名「パラフリント スプレイ ３０」、吸熱ピーク温度：１００℃）２部を、メディア型湿式粉砕機の撹拌槽内に投入して離型剤を湿式粉砕して、コア用重合性単量体組成物を得た。
一方、メチルメタクリレート（Ｔｇ＝１０５℃）２部と水６５部を超音波乳化機にて微分散化処理して、シェル用重合性単量体の水分散液を得た。
【００６７】
他方、イオン交換水２５０部に塩化マグネシウム１０．２部を溶解した水溶液に、イオン交換水５０部に水酸化ナトリウム６．２部を溶解した水溶液を攪拌下で徐々に添加し、次いで、５％四ホウ酸ナトリウム十水和物水溶液を２０部添加して、水酸化マグネシウムコロイド分散液を調製した。
【００６８】
得られた水酸化マグネシウムコロイド分散液に、コア用重合性単量体組成物とｔ−ブチルパーオキシ−２−エチルヘキサノエート（日本油脂社製、商品名「パーブチルＯ」）５部を添加し、１５，０００ｒｐｍで回転するエバラマイルダー（荏原製作所社製：商品名ＭＤＮ３０３Ｖ）を総滞留時間３秒で通過させ、通過させた分散液を、インナーノズルを経て、元の撹拌槽内に噴出速度０．５ｍ／ｓで戻し循環させコア用重合性単量体組成物の液滴を形成させた。次いで９０℃に加温し重合反応を開始させた。重合転化率がほぼ１００％に達した後、前記シェル用重合性単量体の水分散液に２−メチル−Ｎ−（２−ハイドロキシエチル）−プロピオンアミド（和光純薬社製、商品名「ＶＡ−０８６」）０．３部を溶解し、それを反応器に入れた。４時間重合を継続した後、反応を停止し、コアシェル型トナー粒子の水分散液を得た。このコアシェル型トナー粒子を用いた以外は実施例１と同様に操作を行い、静電荷像現像用トナーを得た。得られた静電荷像現像用トナーについて、実施例１と同様に評価を行った。評価結果を表２に示す。
【００６９】
比較例２
４つ口フラスコに環流冷却器、水分離装置、窒素ガス導入管、温度計、撹拌装置を取り付け、マントルヒーター中に設置し、ビスフェノールＡ−ＥＯ付加物５部、ビスフェノールＡ−ＰＯ付加物５部、テレフタル酸４部及フマル酸５部からなる単量体組成物を仕込み、フラスコ内に窒素を導入しながら加熱・撹拌して反応させポリエステル樹脂を得た。
次いで、上述のようにして得られたポリエステル樹脂７０部及びカーボンブラック（商品名「＃２５Ｂ」、三菱化学社製；一次粒径４０ｎｍ）３０部を加圧ニーダーに仕込み混合した。得られた混合物を冷却後、フェザーミルにより粉砕し顔料マスターバッチを得た。
【００７０】
次いで、上述のようにして得られたポリエステル樹脂９３部、顔料マスターバッチ１０部及びサリチル酸亜鉛金属錯体（オリエント化学工業社製、商品名「Ｅ８４」）２部、酸化型低分子ポリプロピレン（三洋化成工業社製、商品名「ビスコールＴＳ２００」）２部をヘンシェルミキサーで十分混合した後、混合物を２軸押出混練機で溶融混練し、得られた混練物を迅速に冷却した後、フェザーミルで粗粉砕した。その粗砕物をジェット粉砕機（日本ニューマチック工業社製、商品名「ＩＤＳ」）で粉砕粗粉分級したのち、ＤＳ分級機（日本ニューマチック工業社製）で微粉分級することによりトナー母粒子を得た。
【００７１】
得られたトナー母粒子１００部に対して疎水性シリカＴＳ５００ （キャボジル社製、ＢＥＴ比表面積２２５ｍ^２／ｇ）０．５部及び疎水性シリカＮＡＸ５０ （日本アエロジル社製、ＢＥＴ比表面積４０ｍ^２／ｇ）０．３重量部を添加し、ヘンシェルミキサーを用い周速３０ｍ／ｓｅｃで９０秒間混合処理を行った。次いで、表面改質装置（サーフュージングシステム；日本ニューマチック工業社製）を用いて、最高温度；２５０℃、滞留時間；０．５秒、粉体分散濃度；１００ｇ／ｍ^３、冷却風温度；１８℃、冷却水温度１０℃の条件でトナー母粒子の表面改質処理を行い、トナー母粒子１００部に対して、疎水性シリカＲ９７２（日本アエロジル社製、ＢＥＴ比表面積１１０ｍ^２／ｇ）０．５部及びチタン酸ストロンチウム粒子Ａ１を０．３部添加し、ヘンシェルミキサーを用いて周速３０ｍ／ｓｅｃで１８０秒間混合処理を行い、静電荷像現像用トナーを得た。得られた静電荷像現像用トナーについて、上述した評価を行った。評価結果を表２に示す。
【００７２】
比較例３
高速撹拌装置ＴＫ式ホモミキサー（特殊機化工業社製）を備えた４つ口フラスコ中に、イオン交換水６５０部及び０．１ｍｏｌ／リットルの第３リン酸ナトリウム水溶液５００部を投入し、回転数を１２０００ｒｐｍに調整し、７０℃に加温した。次いで、フラスコに１．０ｍｏｌ／リットルの塩化カルシウム水溶液７０部を徐々に添加し、微小な難水溶性の第３リン酸カルシウムコロイドを含む分散安定化剤の水性分散媒を調製した。
一方、スチレン７７部、２−エチルヘキシルアクリレート２３部、ジビニルベンゼン０．２部、カーボンブラック８部、１，１−ビス（４−ヒドロキシフェニル）シクロヘキサンポリカーボネート６部、負帯電制御剤（アゾ染料系鉄化合物）２部、及びワックス成分１０部をアトライター（三井金属社製）を用い３時間分散させた後、２，２’−アゾビス（２，４−ジメチルバレロニトリル）５部を添加し重合性単量体組成物を調製した。
【００７３】
次いで、上述した分散安定化剤の水性分散媒中に重合性単量体組成物を投入し、内温７０℃の窒素雰囲気下で、高速撹拌器の回転数を１２，０００ｒｐｍに維持しつつ、１５分間撹拌し、重合性単量体組成物の液滴を形成させた。その後、撹拌器をプロペラ撹拌羽根に換え５０ｒｐｍで撹拌しながら同温度で１０時間保持して重合を完了した。重合終了後、８０℃／４７ｋＰａ（３５０Ｔｏｒｒ）の加熱減圧下で残存モノマーを留去し、懸濁液を冷却し、次いで希塩酸を添加し分散安定化剤を除去した。更に水洗浄を数回繰り返した後、円錐型リボン乾燥機（大川原製作所製）を用い、４５℃／１．３ｋＰａ（１０Ｔｏｒｒ）の加熱減圧下で、螺旋リボン回転翼で撹拌しながら重合体粒子の球形化処理と乾燥処理を６時間行い、トナー粒子を得た。
得られたトナー粒子１００部及び疎水性オイル処理シリカ微粉体２部をヘンシェルミキサーで乾式混合して、静電荷像現像用トナーを得た。得られた静電荷像現像用トナーについて、上述した評価を行った。評価結果を表２に示す。
【００７４】
【表１】

【００７５】
【表２】

【００７６】
表１及び表２の静電荷像現像用トナーの評価結果から、以下のことがわかる。Ｃ１／Ｃ２及びσ２−σ１の値が、本発明で規定した範囲より大きい比較例１の静電荷像現像用トナーは、カブリが発生し、細線再現性が低下しており、印字濃度の低いものである。
σ２の値、及びσ２−σ１の値が、本発明で規定した範囲より大きい比較例２の静電荷像現像用トナーは、カブリが発生し、細線再現性が低下しており、印字濃度の低いものである。
体積平均粒径と個数平均粒径との比（Ｄｖ／Ｄｐ）の値、粒径標準偏差、σ２の値、及びσ２−σ１の値が、本発明で規定した範囲より大きい比較例３の静電荷像現像用トナーは、カブリが発生し、細線再現性が低下しており、印字濃度の低いものである。
これに対して、本発明の実施例１の静電荷像現像用トナーは、細線再現性が良好で印字濃度が高く、かつカブリが発生し難いものである。
【００７７】
【発明の効果】
本発明により、カブリが発生し難く、ドット再現性の向上した静電荷像現像用トナーが提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic image, and more particularly, to a toner for developing an electrostatic image with less fog and improved dot reproducibility.
[0002]
[Prior art]
Electrophotography generally means forming an electric latent image on a photoreceptor by various means, then developing the latent image with toner to form a visible image, and transferring it to a transfer material such as paper or an OHP sheet. This method refers to a method of transferring a visible image toner and then fixing the transferred toner onto a transfer material by pressure or the like to obtain a printed material.
In recent years, the functions of printers and copiers have become more sophisticated, and there has been a demand for a method of forming an electrostatic charge image with a laser to achieve high resolution and high speed at the same time. For this reason, toners are required to have a low particle size and a low-temperature fixation that can be used for high-speed models, in addition to a small particle size and a sharp distribution that can support high resolution. Further, as in the conventional case, the toner is required to have performance such as stability of charging characteristics and cleaning properties.
[0003]
Conventionally, toner is manufactured by melt-kneading and uniformly dispersing a colorant of a dye or a pigment or other additives in a binder resin such as a thermoplastic resin and then finely pulverizing with a pulverizer. , A so-called crushing method. In this pulverization method, it is difficult to reduce the particle size of the toner to about 5 to 6 μm or less, and there is a limit in narrowing the particle size distribution even in the classification operation. Further, since the additive is exposed on the surface of the toner, it is difficult to control the charge amount of the toner, which causes problems such as scattering of images and fogging. As a toner manufactured by the pulverization method, for example, Japanese Patent Application Laid-Open No. H11-202557 discloses a toner in which the particle size, the particle size distribution, the circularity, and the like are controlled. The toner disclosed in this publication is manufactured by a pulverization method, and it is difficult to remove fine powder or to eliminate the generation of fine powder. Was inadequate.
[0004]
In recent years, toners produced by a polymerization method have been used in order to achieve a smaller particle size and narrow a particle size distribution. In the case of the toner produced by the polymerization method, the charging stability can be improved by further adhering the fine particles to the surface and reducing the bleed component of the additive. The present applicant discloses, in JP-A-8-160661, a polymerization developer in which the content of metal ions derived from a poorly water-soluble metal compound is 1000 ppm or less. In the developer disclosed in the publication, image quality deterioration due to environmental fluctuation is greatly improved, but further improvement in fluidity and storage stability has been required. JP-A-11-72949 discloses a developer having a specific range of pH or a non-magnetic one-component developer having a specific range of conductivity. According to the developer disclosed in this publication, fluidity and storage stability are improved, but further improvement in print density and dot reproducibility has been required in order to cope with higher resolution.
[0005]
Japanese Patent Application Laid-Open No. 2000-3069 discloses a toner in which a volume average particle diameter, an average circularity, and a circularity standard deviation are specified. JP-A-11-344829 discloses a toner manufactured by a suspension polymerization method and having an average circularity of 0.970 to 0.995. It is disclosed that the toner disclosed in the above publication has excellent dot reproducibility and excellent fluidity. However, the above-mentioned toner has a problem that the charging characteristics easily change and storage stability is insufficient, and the toner aggregates when left in a high-temperature environment. When the toner aggregates, poor charging is apt to occur, resulting in a problem that the resolution of the developed image is deteriorated, and further, a problem that the filming is liable to occur.
[0006]
[Patent Document 1]
JP-A-11-202557
[Patent Document 2]
JP-A-8-160661
[Patent Document 3]
JP-A-11-72949
[Patent Document 4]
JP-A-2000-3069
[Patent Document 5]
JP-A-11-344829
[0007]
[Problems to be solved by the invention]
Accordingly, it is an object of the present invention to provide a toner for developing an electrostatic image in which fog hardly occurs and dot reproducibility is improved.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, in an electrostatic image developing toner containing at least a toner particle including a binder resin, a colorant and a charge control agent, the volume mode diameter of the toner particle Ratio of volume average particle diameter (Dv) to number average particle diameter (Dp) (Dv / Dp), average circularity, standard deviation of particle diameter, average circularity of toner particles having a specific particle diameter The knowledge that the above object can be achieved by setting the ratio of the average circularity of the toner particles having a specific particle size to a specific range and setting the conductivity of the aqueous extract of the toner to a specific range. Obtained.
[0009]
The present invention has been made based on the above findings, and is a toner for developing an electrostatic image containing toner particles comprising at least a binder resin, a colorant and a charge control agent, wherein the volume mode diameter of the toner particles ( a) is 5 to 10 μm, the ratio (Dv / Dp) of the volume average particle diameter (Dv) to the number average particle diameter (Dp) is 1.0 to 1.3, and the average circularity is 0.97. (A-2b) The average circularity (C1) of the toner particles having a particle size of not less than 2 μm and less than a μm is not more than 0.995, and the standard deviation (b) of the particle size of the toner particles is not more than 2 μm. An ion having a ratio (C1 / C2) to the average circularity (C2) of the toner particles having a particle diameter of less than (a + 2b) μm of 1.00 to 1.02 and a conductivity σ1 of 0 to 10 μS / cm. Disperse the toner in replacement water so that the toner concentration becomes 6% by weight, and heat. After boiling for 10 minutes, ion-exchanged water having a conductivity .sigma.1 of 0 to 10 .mu.S / cm, which has been separately boiled, is added to replenish the evaporated water to its original volume, and cooled to room temperature to obtain a water extract. An object of the present invention is to provide a toner for developing an electrostatic image, having a conductivity σ2 of 20 μS / cm or less and σ2−σ1 of 0.1 to 10 μS / cm.
The toner for developing an electrostatic image is less likely to cause fog and has improved dot reproducibility.
[0010]
The toner for developing electrostatic images preferably has an enthalpy of fusion (ΔH) of 1 to 10 mJ / mg as measured by a differential scanning calorimeter.
The charge control agent is preferably a charge control resin having a weight average molecular weight of 3,000 to 300,000.
[0011]
Further, the present invention provides a process for preparing an aqueous dispersion medium containing a colloid of a poorly water-soluble inorganic compound by mixing a water-soluble polyvalent inorganic salt and an alkali hydroxide in an aqueous dispersion medium, and aging the mixture. A polymerizable monomer composition containing a monomer, a colorant, a charge control agent and a polymerization initiator, to the aqueous dispersion medium containing a colloid of the aged hardly water-soluble inorganic compound, Forming an aqueous dispersion medium containing droplets; and adding a boron compound to the aqueous dispersion medium containing the droplets, and then heating the aqueous dispersion medium to form a polymerizable monomer. And forming a toner particle by polymerizing the monomer. 3. A method for producing a toner for developing an electrostatic image, comprising the steps of:
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the toner for developing an electrostatic image of the present invention will be described.
The toner particles constituting the electrostatic image developing toner of the present invention include at least a binder resin, a colorant, and a charge control agent.
Specific examples of the binder resin include polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin, which are conventionally used widely in toner.
[0013]
As the colorant, any pigments and dyes can be used in addition to carbon black, titanium black, magnetic powder, oil black, and titanium white. As the black carbon black, those having a primary particle diameter of 20 to 40 nm are suitably used. When the particle size is in this range, carbon black can be uniformly dispersed in the toner, and fog is reduced, which is preferable.
[0014]
When a color toner is obtained, a yellow colorant, a magenta colorant or a cyan colorant is usually used.
As the yellow colorant, for example, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185, 186, and 186.
As the magenta colorant, for example, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Red 31, 48, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251; I. Pigment Violet 19 and the like.
As the cyan coloring agent, for example, a copper phthalocyanine compound and a derivative thereof, an anthraquinone compound, and the like can be used. Specifically, C.I. I. Pigment Blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, 60 and the like.
The amount of the colorant is preferably 1 to 10 parts by weight based on 100 parts by weight of the binder resin.
In order to obtain a full-color image, development is performed by combining a toner containing three colors of cyan, magenta, and yellow and, if necessary, a black colorant.
[0015]
As the charge control agent, a charge control resin is preferable. The reason for this is that the charge control resin has high compatibility with the binder resin, is colorless, and can provide a toner for developing an electrostatic charge image with stable chargeability even in high-speed color continuous printing. Examples of the charge control resin include quaternary ammonium produced according to the description in JP-A-63-60458, JP-A-3-175456, JP-A-3-243954, JP-A-11-15192 and the like. A (salt) group-containing copolymer, a sulfonic acid (salt) group-containing copolymer produced according to the description in JP-A-1-217464, JP-A-3-15858 and the like can be used. .
The amount of the monomer unit having a quaternary ammonium (salt) group or a sulfonic acid (salt) group contained in these copolymers is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight. % By weight. When the content is within this range, the charge amount of the toner for developing an electrostatic image is easily controlled, and the occurrence of fog can be reduced.
[0016]
The charge control resin preferably has a weight average molecular weight of 3,000 to 300,000, more preferably 4,000 to 50,000, and most preferably 6,000 to 35,000. If the weight average molecular weight of the charge control resin is less than 3,000, the viscosity at the time of kneading in producing the toner for developing an electrostatic image may be too low, and the dispersion of the pigment may be insufficient.
The glass transition temperature of the charge control resin is preferably from 40 to 80 ° C, more preferably from 45 to 75 ° C, and most preferably from 45 to 70 ° C. If the glass transition temperature is lower than 40 ° C., the storage stability of the toner for developing an electrostatic image deteriorates, and if it exceeds 80 ° C., the fixability may decrease.
[0017]
The amount of the charge control agent is usually 0.01 to 30 parts by weight, preferably 0.3 to 25 parts by weight, based on 100 parts by weight of the binder resin.
[0018]
In the present invention, it is preferable that a release agent is further contained in the toner particles. Examples of the release agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; natural plant waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, microcrystalline, petrolatum, and the like. Petroleum waxes and modified waxes thereof; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, and dipentaerythritol hexamyristate;
The release agent can be used alone or in combination of two or more.
[0019]
Among the above release agents, a synthetic wax and a polyfunctional ester compound are preferable. Among these, in the DSC curve measured by the differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is preferably in the range of 30 to 150 ° C, more preferably 40 to 100 ° C, and most preferably 50 to 80 ° C. A polyfunctional ester compound is preferable because a toner having an excellent balance between fixation and releasability at the time of fixing can be obtained. In particular, those having a molecular weight of 1,000 or more, dissolving at least 5 parts by weight with respect to 100 parts by weight of styrene at 25 ° C., and having an acid value of 10 mg KOH / g or less show a remarkable effect on lowering the fixing temperature, and are therefore more preferable. . Endothermic peak temperature means the value measured by ASTM D3418-82.
The amount of the release agent is usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the binder resin.
[0020]
The toner particles can be so-called core-shell type (or also referred to as “capsule type”) particles obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. . In the core-shell type particles, by lowering the softening point substance inside (core layer) with a substance having a higher softening point, it is possible to balance between lowering the fixing temperature and preventing aggregation during storage. preferable.
Usually, the core layer of the core-shell type particles is composed of the binder resin, the colorant, the charge control resin, and the release agent, and the shell layer is composed of only the binder resin.
[0021]
The weight ratio between the core layer and the shell layer of the core-shell type particles is not particularly limited, but is usually from 80/20 to 99.9 / 0.1.
By setting the ratio of the shell layer to the above ratio, it is possible to have both the storage stability of the toner for developing an electrostatic image and the fixability at a low temperature.
[0022]
The average thickness of the shell layer of the core-shell type particles is usually 0.001 to 1.0 μm, preferably 0.003 to 0.5 μm, more preferably 0.005 to 0.2 μm. When the thickness is large, the fixability is reduced, and when the thickness is small, the storability may be reduced. The core particles forming the core-shell type toner particles do not need to have all surfaces covered with the shell layer, and may have a part of the surface of the core particles covered with the shell layer.
When the core particle diameter and the shell layer thickness of the core-shell type particles can be observed by an electron microscope, they can be obtained by directly measuring the size and shell thickness of randomly selected particles from the observation photograph, When it is difficult to observe the core and the shell in the above, it can be calculated from the particle size of the core particles and the amount of the monomer forming the shell used in the production of the toner for developing an electrostatic image.
[0023]
The toner particles constituting the electrostatic image developing toner of the present invention have a volume mode diameter (a) of 5 to 10 μm, preferably 5 to 8 μm. If the volume mode diameter (a) is less than 5 μm, the fluidity of the toner becomes small, fog may occur, transfer residue may occur, or the cleaning property may decrease. May decrease. The volume mode diameter (a) is the most frequent value in the particle size distribution on a volume basis. The volume mode diameter of the toner particles can be measured using, for example, a flow type particle image analyzer “FPIA-1000” or “FPIA-2000” manufactured by Sysmex Corporation.
[0024]
The ratio (Dv / Dp) of the volume average particle diameter (Dv) to the number average particle diameter (Dp) of the toner particles constituting the toner for developing an electrostatic image of the present invention is 1.0 to 1.3. , Preferably 1.0 to 1.2. When Dv / Dp exceeds 1.3, fog occurs.
The volume average particle diameter and the number average particle diameter of the toner particles can be measured using, for example, a Multisizer (manufactured by Beckman Coulter, Inc.).
[0025]
The toner particles constituting the electrostatic image developing toner of the present invention have an average circularity measured by a flow type particle image analyzer of 0.97 to 0.995, preferably 0.975 to 0.995. is there. When the average circularity is less than 0.97, the reproducibility of fine lines is obtained in an L / L environment (temperature: 10 ° C., humidity: 20%), in an N / N environment (temperature: 23 ° C., humidity: 50%), Inferior in any H / H environment (temperature: 35 ° C., humidity: 80%).
The average circularity can be relatively easily adjusted to the above range by manufacturing using a phase inversion emulsification method, a dissolution suspension method, a polymerization method (suspension polymerization method, emulsion polymerization method) or the like.
[0026]
In the present invention, the circularity is defined as a value obtained by dividing the perimeter of a circle having the same projected area as the particle image by the perimeter of the projected image of the particle. The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of particles, and is an index indicating the degree of unevenness of the toner. The average circularity is 1 when the toner is perfectly spherical, and becomes smaller as the surface shape of the toner particles becomes more complicated.
The average circularity (Ca) is a value obtained by the following equation.
[0027]
(Equation 1)

[0028]
In the above equation, n is the number of particles for which the circularity Ci has been determined.
In the above equation, Ci is the circularity of each particle calculated by the following equation based on the circumference measured for each particle of the particle group having a circle equivalent diameter of 0.6 to 400 μm.
Circularity (Ci) = perimeter of circle equal to projected area of particle / perimeter of projected particle image
In the above equation, fi is the frequency of particles having a circularity Ci.
The circularity and the average circularity can be measured using a flow particle image analyzer “FPIA-1000” or “FPIA-2000” manufactured by Sysmex Corporation.
[0029]
The standard deviation (b) of the particle size of the toner particles constituting the toner for developing an electrostatic image of the present invention is 2 μm or less, preferably 1.5 μm or less. If the standard deviation of the particle size of the toner particles exceeds 2 μm, the image quality is deteriorated, such as fogging. The standard deviation of the toner particles is a volume-based value that can be measured using a flow particle image analyzer “FPIA-1000” or “FPIA-2000” manufactured by Sysmex Corporation, similarly to the circularity and the average circularity. .
[0030]
Assuming that the volume mode diameter is a and the standard deviation of the toner particle diameter is b, the toner particles constituting the electrostatic image developing toner of the present invention have a particle diameter of (a−2b) μm or more and less than a μm. (C1 / C2) is 1.00 to 1.02 when the average circularity of the toner particles is C1 and the average circularity of the toner particles having a particle diameter of a μm or more and less than (a + 2b) μm is C2. , Preferably 1.00 to 1.01, and more preferably 1.00 to 1.005. This numerical value is significant in expressing the coalesced state of the toner particles. When (C1 / C2) is large, it indicates that so-called coalesced particles in which two toner particles are bonded are increased. When (C1 / C2) is within the above range, fogging is reduced and dot reproducibility is improved.
In addition, C1 and C2 can also be measured using a flow type particle image analyzer “FPIA-1000” or “FPIA-2000” manufactured by Sysmex Corporation, similarly to the circularity and the average circularity.
[0031]
The toner for developing an electrostatic image of the present invention is dispersed in ion-exchanged water having a conductivity σ1 of 0 to 10 μS / cm so that the toner concentration becomes 6% by weight, heated and boiled for 10 minutes, and then separately boiled. The conductivity of the water extract obtained by adding ion-exchanged water having a conductivity σ1 of 0 to 10 μS / cm to replenish the evaporated water to the original volume, and cooling to room temperature (about 22 ° C.) σ2 is 20 μS / cm or less, preferably 10 μS / cm or less. Further, σ2−σ1 is 0.1 to 10 μS / cm, preferably 0.1 to 6 μS / cm. When the conductivity σ2 exceeds 20 μS / cm, the dependence of the charge amount on the environment increases, and the image quality deteriorates due to environmental changes (changes in temperature and humidity). Also when σ2−σ1 exceeds 10 μS / cm, the dependence of the charge amount on the environment increases, and the image quality is reduced due to environmental fluctuations (changes in temperature and humidity). On the other hand, if σ2−σ1 is less than 0.1 μS / cm, the print density decreases and fog occurs.
[0032]
The toner for developing an electrostatic image of the present invention preferably has an enthalpy of fusion (ΔH) of 1 to 10 mJ / mg, more preferably 2 to 6 mJ / mg, measured by a differential scanning calorimeter (DSC). It is particularly preferably 3 to 5 mJ / mg. When the enthalpy of fusion (ΔH) of the toner for electrostatic image development measured by a differential scanning calorimeter is within the above range, the fixability is excellent. When ΔH exceeds 10 mJ / mg, a large amount of heat is required for melting the toner, and low energy fixing (low temperature fixing) may not be achieved when forming a multi-color, multi-layer image such as a color image. If ΔH is less than 1 mJ / mg, the fixability may be poor, and a sufficient releasing effect may not be obtained. ΔH can be calculated from the area (peak area) of the region surrounded by the endothermic peak and the baseline of the differential scanning calorimeter curve.
[0033]
The electrostatic image developing toner of the present invention can be used as it is for electrophotographic development, but usually, in order to adjust the chargeability, fluidity, storage stability, etc. of the electrostatic image developing toner, It is preferable that fine particles having a particle size smaller than the toner particles (hereinafter, referred to as an external additive) are attached or embedded on the surface of the toner particles before use.
Examples of the external additive include inorganic particles and organic resin particles that are generally used for the purpose of improving fluidity and chargeability. These particles added as external additives have a smaller average particle size than the toner particles. For example, as the inorganic particles, silica, aluminum oxide, titanium oxide, zinc oxide, tin oxide and the like can be mentioned, and as the organic resin particles, methacrylate polymer particles, acrylate polymer particles, styrene-methacrylate ester Copolymer particles, styrene-acrylate copolymer particles, core-shell type particles in which the core is a styrene polymer and the shell is formed of a methacrylate polymer, and the like. Among these, silica particles and titanium oxide particles are preferable, particles whose surface is subjected to a hydrophobic treatment are preferable, and silica particles whose surface is subjected to a hydrophobic treatment are particularly preferable. The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight based on 100 parts by weight of the toner particles.
[0034]
The method for producing the toner for developing an electrostatic image of the present invention is not particularly limited as long as it can provide a toner having the characteristics in the above-mentioned range, but is preferably produced by a polymerization method.
Next, a method for producing toner particles constituting the electrostatic image developing toner by a polymerization method will be described.
The toner particles constituting the toner for developing an electrostatic image of the present invention include, for example, an aqueous dispersion containing a colloid of a poorly water-soluble inorganic compound by mixing a water-soluble polyvalent inorganic salt and an alkali hydroxide in an aqueous dispersion medium. Preparing a medium and aging; a polymerizable monomer composition containing a polymerizable monomer, a colorant, a charge controlling agent and a polymerization initiator, containing a colloid of the aged hardly water-soluble inorganic compound. Adding the boron compound to the aqueous dispersion medium containing the droplets; and adding the boron compound to the aqueous dispersion medium containing the droplets. A step of heating the aqueous dispersion medium to polymerize the polymerizable monomer to form toner particles; and producing a toner for electrostatic image development.
[0035]
In the present invention, when obtaining a polymerizable monomer composition, to obtain a charge control resin composition manufactured by previously mixing a colorant and a charge control resin, it is converted to a polymerizable monomer together with a release agent and the like. You may add and mix. At that time, the amount of the colorant is usually 10 to 200 parts by weight, preferably 20 to 150 parts by weight, based on 100 parts by weight of the charge control resin. For the production of the charge control resin composition, it is preferable to use an organic solvent. The use of the organic solvent makes the charge control resin soft and easy to mix with the pigment.
[0036]
The amount of the organic solvent is usually from 0 to 100 parts by weight, preferably from 5 to 80 parts by weight, more preferably from 10 to 60 parts by weight, based on 100 parts by weight of the charge control resin. And the balance of workability is excellent. At this time, the organic solvent may be added all at once, or may be added in several portions while checking the mixed state.
Mixing can be carried out using a roll, a kneader, a single screw extruder, a twin screw extruder, a Banbury, a Buss co-kneader or the like. When an organic solvent is used, a closed mixer in which the organic solvent does not leak to the outside is preferable.
Further, it is preferable that a torque meter is installed in the mixer because the dispersibility can be controlled at the torque level.
[0037]
Examples of the polymerizable monomer include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component.
Monovinyl monomers include aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid. (Meth) acrylic copolymers such as propyl, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobonyl (meth) acrylate; monomers such as ethylene, propylene, and butylene Olefin monomers; and the like.
Monovinyl monomers may be used alone or in combination of a plurality of monomers. Of these monovinyl monomers, an aromatic vinyl monomer alone, or a combination of an aromatic vinyl monomer and a (meth) acrylic monomer is preferably used.
[0038]
When a crosslinkable monomer is used together with the monovinyl monomer, hot offset is effectively improved. The crosslinkable monomer is a monomer having two or more vinyl groups. Specific examples include divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate, pentaerythritol triallyl ether, and trimethylolpropane triacrylate. These crosslinkable monomers can be used alone or in combination of two or more. The amount of the crosslinkable monomer is usually 10 parts by weight or less, preferably 0.1 to 2 parts by weight, per 100 parts by weight of the monovinyl monomer.
[0039]
Further, it is preferable to use a macromonomer together with the monovinyl monomer, because the balance between the preservability and the fixing property at a low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the terminal of the molecular chain, and is usually an oligomer or polymer having a number average molecular weight of 1,000 to 30,000.
The macromonomer is preferably one that gives a polymer having a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer. The amount of the macromonomer is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the monovinyl monomer.
[0040]
Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methyl-N- (2- Hydroxyethyl) propionamide, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, etc. Azo compounds: di-t-butyl peroxide, benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-hexyl peroxy-2-ethylhexanoate, t-butyl peroxypivalate, -Isopropylperoxydicarbonate, di-t-butylperoxyisophthalate, t-butylperoxyisobutyrate, etc. Include peroxides, and the like. It is also possible to use a redox initiator which is a combination of the polymerization initiator and a reducing agent.
[0041]
The amount of the polymerization initiator used for the polymerization of the polymerizable monomer is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 15 parts by weight, based on 100 parts by weight of the polymerizable monomer. Parts, most preferably 0.5 to 10 parts by weight. The polymerization initiator is added in advance to the polymerizable monomer composition.
[0042]
The colloid of a poorly water-soluble inorganic compound used as a dispersion stabilizer is formed by mixing a water-soluble polyvalent inorganic salt and an alkali hydroxide in an aqueous dispersion medium. Examples of such poorly water-soluble inorganic compounds include magnesium hydroxide. It is preferable to use the aqueous dispersion medium containing the colloid of the poorly water-soluble inorganic compound in the production of the toner after aging, since the toner for developing an electrostatic image of the present invention can be easily obtained. In the present invention, aging means that an aqueous dispersion medium containing a colloid of a poorly water-soluble inorganic compound is prepared and then left for a certain period of time without immediate use. Specifically, it is left at a temperature of 15 to 35 ° C., preferably 20 to 30 ° C. for 4 to 18 hours, preferably 5 to 15 hours.
[0043]
The amount of the dispersion stabilizer is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer. When the amount of the dispersion stabilizer is less than 0.1 part by weight, it is difficult to obtain sufficient polymerization stability, and a polymer aggregate may be easily generated. On the other hand, when the amount exceeds 20 parts by weight, Then, the effect of the polymerization stability is saturated, and in addition to being uneconomical, the viscosity of the aqueous dispersion medium becomes too high, and it may be difficult to form small droplets after mixing.
In the polymerization, a water-soluble polymer can be used in combination as long as the environment-dependent charging characteristics of the polymerized toner and the change in fixing property do not become large. Examples of the water-soluble polymer include polyvinyl alcohol, methyl cellulose, gelatin and the like.
[0044]
In the polymerization, after forming droplets of the polymerizable monomer, a boron compound is added to an aqueous dispersion medium containing the droplets. As the boron compound, boron trifluoride, boron trichloride, tetrafluoroborate, sodium tetrahydroborate, potassium tetrahydroborate, sodium tetraborate, sodium tetraborate decahydrate, sodium metaborate, sodium metaborate Tetrahydrate, sodium peroxoborate tetrahydrate, boric acid, potassium metaborate, potassium tetraborate octahydrate and the like can be mentioned. The boron compound is preferably added in the form of an aqueous solution. The amount of the boron compound is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight, based on 100 parts by weight of the colloid of the poorly water-soluble compound.
[0045]
In the polymerization, it is preferable to use a molecular weight modifier. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol. The molecular weight modifier can be added before or during the polymerization. The amount of the molecular weight modifier is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0046]
The method for producing the core-shell toner particles is not particularly limited, and can be produced by a conventionally known method. For example, a method such as a spray drying method, an interfacial reaction method, an in situ polymerization method, and a phase separation method may be used. Specifically, core-shell type toner particles can be obtained by using a toner particle obtained by a pulverization method, a polymerization method, an association method or a phase inversion emulsification method as a core particle and coating a shell layer thereon. Among these production methods, an in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.
[0047]
A method for producing core-shell type toner particles by an in situ polymerization method will be described below.
A polymerizable monomer for forming a shell (polymerizable monomer for shell) and a polymerization initiator are added to an aqueous dispersion medium in which the core particles are dispersed, and the polymerization is performed. Can be obtained.
As a specific method of forming the shell, a method of continuously polymerizing by adding a polymerizable monomer for shell to the reaction system of the polymerization reaction performed to obtain the core particles, or a method obtained by another reaction system A method in which the core particles are charged, and a polymerizable monomer for shell and a polymerization initiator are added thereto to carry out polymerization.
The polymerizable monomer for shell may be added to the reaction system at once, or may be added continuously or intermittently using a pump such as a plunger pump.
[0048]
As the polymerizable monomer for the shell, monomers that form a polymer having a glass transition temperature exceeding 80 ° C., such as styrene, acrylonitrile, and methyl methacrylate, can be used alone or in combination of two or more. .
[0049]
When adding the polymerizable monomer for shell, it is preferable to add a water-soluble polymerization initiator since core-shell type toner particles can be easily obtained. When the water-soluble polymerization initiator is added during the addition of the shell-polymerizable monomer, the water-soluble polymerization initiator moves to the vicinity of the outer surface of the core particle, and the shell-polymerizable monomer is transferred to the surface of the core particle. It is considered that polymerization is likely to occur.
[0050]
Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) propionamide), 2,2′-azobis- An azo initiator such as (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide) and the like can be mentioned. The amount of the water-soluble polymerization initiator is usually 0.1 to 50 parts by weight, preferably 1 to 30 parts by weight, based on 100 parts by weight of the polymerizable monomer for shell.
[0051]
The temperature during the polymerization is preferably 50 ° C. or higher, more preferably 80 to 95 ° C. The reaction time is preferably from 1 to 20 hours, more preferably from 2 to 10 hours. After completion of the polymerization, it is preferable to repeat the operations of filtration, washing, dehydration and drying several times as necessary according to a conventional method.
[0052]
It is preferable to add an acid so that the pH of the aqueous dispersion of toner particles obtained by polymerization becomes 6.5 or less to dissolve the colloid of the poorly water-soluble inorganic compound as a dispersion stabilizer. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid can be used. However, sulfuric acid is particularly preferred because of high removal efficiency and a small burden on manufacturing equipment. It is. After separating the toner particles by filtration, the toner particles are washed with water at 30 to 40 ° C., and the toner particles are dried. The method for filtering the toner particles in the aqueous dispersion medium is not particularly limited. For example, a centrifugal filtration method, a vacuum filtration method, a pressure filtration method, and the like can be given. Of these, the centrifugal filtration method is preferred. The temperature of the water used for washing the toner particles is 30 to 50C, preferably 30 to 40C. If the water temperature is lower than 30 ° C., the cleaning effect becomes insufficient, while if it is higher than 50 ° C., the toner shape tends to change.
There is no particular limitation on the method for drying the toner particles, and a vacuum dryer or the like can be used.
[0053]
The toner for developing an electrostatic image of the present invention can be obtained by mixing toner particles, external additives, and, if necessary, other fine particles using a high-speed stirrer such as a Henschel mixer.
[0054]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. It goes without saying that the scope of the present invention is not limited to the examples. In the following examples, parts and% represent parts by weight or% by weight unless otherwise specified.
[0055]
In this embodiment, the toner was evaluated by the following method.
(1) Particle size, particle size distribution
The particle size distribution of the toner particles, that is, the ratio (Dv / Dp) between the volume average particle size and the number average particle size (Dp) was measured by a particle size measuring device (model name “Multisizer” manufactured by Beckman Coulter, Inc.). . The measurement by this multisizer was performed under the conditions of an aperture diameter: 100 μm, a medium: Isoton II, a concentration of 10%, and the number of particles measured: 50,000.
[0056]
(2) Volume mode diameter, average circularity, standard deviation
After adding 100 μl of a 0.1% aqueous solution of an anionic surfactant as a dispersion medium to 20 mg of the toner particles and allowing them to adjust, 10 ml of water was added and stirred, and the volume mode diameter, average circularity, and standard deviation were measured. . The measurement was performed using a flow particle image analyzer “FPIA-2000” manufactured by Sysmex Corporation. The analysis was performed on a volume basis (for a section of 15 μm or less).
Furthermore, the average circularity (C1) of toner particles having a particle diameter of (a-2b) μm or more and less than aμm and the average circularity (C2) of toner particles having a particle diameter of aμm or more and less than (a + 2b) μm are also described. The analysis was performed by the above-mentioned apparatus.
[0057]
(3) conductivity
6 g of the toner is dispersed in ion-exchanged water (σ1 is 0.8 μS / cm; pH = 7) to make 100 g. This is heated and boiled, and after maintaining the boiling state for about 10 minutes (boil for 10 minutes), ion-exchanged water (σ1 is 0.8 μS / cm; pH = 7) separately boiled for about 10 minutes is added. The volume was replenished and returned to the volume before boiling, cooled to room temperature (about 22 ° C.), and the conductivity σ2 of the extract was measured. Further, the conductivity σ1 of the used ion-exchanged water was measured, and σ2−σ1 was calculated. The conductivity was measured using a conductivity meter “ES-12” (manufactured by Horiba, Ltd.).
[0058]
(4) Enthalpy of melting
The enthalpy of fusion was calculated from the peak area of the DSC curve measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC SSC5200, manufactured by Seiko Instruments Inc.) in accordance with ASTM D3418-82.
[0059]
(5) Fog
Recycled paper is set in a commercially available non-magnetic one-component developing system printer (18-sheet machine), toner for developing an electrostatic image is put in the printer, and the temperature is 10 ° C. and the humidity is 20% (L / L). In a (N / N) environment at a temperature of 23 ° C. and a humidity of 50%, and in a (H / H) environment at a temperature of 35 ° C. and a humidity of 80%, the printing density of the printer was set to 5% Printing was performed, printing was temporarily stopped every 500 sheets, and the toner in the non-developed portion on the photoreceptor after development was adhered to an adhesive tape (Scotch Mending Tape 810-3-18, manufactured by Sumitomo 3M Limited). It was affixed to printing paper, and its whiteness (B) was measured with a whiteness meter (manufactured by Nippon Denshoku). At the same time, the whiteness (A) of the printing paper to which only the adhesive tape was stuck was measured, and the difference (AB) (%) between the whiteness was determined. The maximum number of sheets (counted in units of 500 sheets) in which the difference between this value and the difference in whiteness (AB) (%) at the beginning of printing (at the time of printing 10 sheets) was 1% or less was examined. The test was completed after 10,000 sheets.
[0060]
(6) Fine line reproducibility
Using the printer used in (5), under a (L / L) environment with a temperature of 10 ° C. and a humidity of 20%, under a (N / N) environment with a temperature of 23 ° C. and a humidity of 50%, a temperature of 35 ° C. and a humidity of 80% (H / H) environment, a line image is formed continuously with 2 × 2 dot lines (width of about 85 μm), and the print evaluation system “RT2000” (YA-MA) And the density distribution data of the line image was collected. At this time, when the full width at half the maximum value of the density is defined as the line width and the line width of the first line image is 10 μm or less, the line image of the first line image is reproduced. It was determined that the difference between the line widths of the line images was 10 μm or less. This test was completed after 10,000 sheets.
[0061]
(7) Print density
Set the printing paper in the printer used in (5), put the toner in the developing device, and leave it overnight (H / H) at a temperature of 35 ° C and a humidity of 80%, then set the printer to 5% print density. From the initial stage, and perform solid printing on the 100th sheet (initial printing) and the 10,000th sheet (continuous printing), and print density using a transmission image density measuring device manufactured by McBeth. Was measured.
[0062]
Example 1
100 parts of a polymerizable monomer composed of 90.5 parts of styrene, 9 parts of n-butyl acrylate, and 0.5 part of 2-acrylamido-2-methylpropanesulfonic acid was charged into 900 parts of toluene, and azobisdimethylvalero was added. The reaction was carried out at 80 ° C. for 8 hours in the presence of 4 parts of nitrile. After completion of the reaction, toluene was distilled off under reduced pressure to obtain a sulfonic acid group-containing copolymer (Mw = 16,000) as a negative charge control resin.
6 parts of the sulfonic acid group-containing copolymer, which is the above-described negative charge control resin, and 6 parts of carbon black (trade name “# 25B”, manufactured by Mitsubishi Chemical Corporation; primary particle size: 40 nm) were combined with 83 parts of styrene and n-butyl. Dissolved in 17 parts of acrylate and 0.6 part of divinylbenzene. Next, 1 part of t-dodecyl mercaptan and 10 parts of dipentaerythritol hexamyristate were dispersed at room temperature in a bead mill to obtain a uniform mixed solution. 5 parts of a polymerization initiator t-butyl peroxy 2-ethylhexanoate (trade name "Perbutyl O", manufactured by NOF CORPORATION) was added to the homogeneous mixture to obtain a polymerizable monomer composition.
On the other hand, 2 parts of methyl methacrylate and 65 parts of water were mixed to obtain an aqueous dispersion of a polymerizable monomer for shell.
[0063]
On the other hand, an aqueous solution obtained by dissolving 5.5 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added to an aqueous solution obtained by dissolving 9.5 parts of magnesium chloride in 250 parts of ion-exchanged water. A colloidal dispersion was prepared and aged at 25 ° C. for 6 hours. The polymerizable monomer composition is charged into the aged dispersion liquid, and the mixture is stirred at 15,000 rpm for 10 minutes using a continuous emulsifying and dispersing machine, Ebara Milder MDN304 (manufactured by Ebara Corporation). Thus, droplets of the polymerizable monomer composition (core monomer composition) were formed. One part of sodium tetraborate decahydrate is added to the magnesium hydroxide colloid dispersion in which the formed core monomer composition is dispersed, and the mixture is placed in a reactor equipped with a stirring blade, and heated at a temperature of 85 ° C. After the polymerization reaction was started and the polymerization conversion reached almost 100%, an aqueous dispersion of the polymerizable monomer for shell and 2,2′-azobis (2-methyl-N (2-hydroxyethyl)- 0.3 parts of propionamide (manufactured by Wako Pure Chemical Industries, trade name "VA-086") was placed in the reactor, and after the polymerization reaction was continued for 4 hours, the reaction was stopped and an aqueous dispersion of core-shell type toner particles was obtained. Got.
[0064]
Sulfuric acid was added to the aqueous dispersion of core-shell type polymer toner particles obtained as described above at 25 ° C., and the mixture was stirred for 10 minutes to adjust the pH of the system to 4 or less, and then dehydrated by filtration. Next, the separated toner particles and 500 parts of ion-exchanged water were mixed and reslurried, and washed with water at 38 ° C. Thereafter, dehydration and water washing were repeated several times again, and the solid content was filtered and centrifuged, followed by drying at 45 ° C. for two days and nights using a drier to obtain toner particles.
To 100 parts of the toner particles obtained as described above, 0.6 part of colloidal silica (RX-200, manufactured by Nippon Aerosil Co., Ltd.) that has been subjected to a hydrophobic treatment is added, and mixed using a Henschel mixer to obtain a negatively chargeable toner. An electrostatic image developing toner was prepared. The above-mentioned evaluation was performed on the obtained electrostatic image developing toner. Table 1 shows the evaluation results.
[0065]
Example 2
100 parts of a polymerizable monomer composed of 89 parts of styrene, 9 parts of n-butyl acrylate, and 2 parts of N-benzyl-N, N-dimethyl-N- (2-methacryloxyethyl) ammonium chloride are added to 900 parts of toluene. The mixture was charged and reacted at 80 ° C. for 8 hours in the presence of 4 parts of azobisdimethylvaleronitrile. After completion of the reaction, toluene was distilled off under reduced pressure to obtain a quaternary ammonium base-containing copolymer (Mw = 25,000), which was a positive charge control resin.
The procedure of Example 1 was repeated, except that the positive charge control resin obtained as described above was used instead of the negative charge control resin, to obtain a toner for developing an electrostatic charge image. The obtained electrostatic image developing toner was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.
[0066]
Comparative Example 1
Core polymerizable monomer composed of 80.5 parts of styrene and 19.5 parts of n-butyl acrylate (Tg of copolymer obtained by copolymerizing these monomers = 55 ° C.), polymethacrylic acid 0.3 parts of ester macromonomer (manufactured by Toa Gosei Chemical Industry Co., Ltd., trade name “AA6”, Tg = 94 ° C.), 0.5 part of divinylbenzene, 1.2 parts of t-dodecyl mercaptan, carbon black (manufactured by Mitsubishi Chemical Corporation) 7 parts of trade name "# 25B", 1 part of charge control agent (manufactured by Hodogaya Chemical Co., Ltd., trade name of "Spiron Black TRH"), mold release agent (Fisher Tropsch wax, manufactured by Sasol Co., Ltd., trade name of "paraflint spray" 30 ", endothermic peak temperature: 100 ° C.), and 2 parts were charged into a stirring tank of a media-type wet pulverizer to wet-pulverize the release agent to obtain a polymerizable monomer composition for a core.
On the other hand, 2 parts of methyl methacrylate (Tg = 105 ° C.) and 65 parts of water were finely dispersed by an ultrasonic emulsifier to obtain an aqueous dispersion of a polymerizable monomer for shell.
[0067]
On the other hand, an aqueous solution obtained by dissolving 6.2 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added to an aqueous solution obtained by dissolving 10.2 parts of magnesium chloride in 250 parts of ion-exchanged water. 20 parts of an aqueous solution of sodium tetraborate decahydrate was added to prepare a magnesium hydroxide colloid dispersion.
[0068]
To the resulting magnesium hydroxide colloidal dispersion, a polymerizable monomer composition for a core and 5 parts of t-butylperoxy-2-ethylhexanoate (trade name “Perbutyl O” manufactured by NOF Corporation) are added. Then, an Ebara Milder (trade name: MDN303V, manufactured by Ebara Corporation) rotating at 15,000 rpm is passed for a total residence time of 3 seconds, and the passed dispersion is ejected into the original stirring tank via an inner nozzle. The liquid was returned and circulated at a speed of 0.5 m / s to form droplets of the polymerizable monomer composition for the core. Then, the mixture was heated to 90 ° C. to start the polymerization reaction. After the polymerization conversion reached almost 100%, 2-methyl-N- (2-hydroxyethyl) -propionamide (trade name, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the aqueous dispersion of the polymerizable monomer for shell. 0.3 g of VA-086 ") was dissolved and placed in the reactor. After the polymerization was continued for 4 hours, the reaction was stopped to obtain an aqueous dispersion of core-shell type toner particles. The same operation as in Example 1 was performed except that the core-shell type toner particles were used, to obtain a toner for developing an electrostatic image. The obtained electrostatic image developing toner was evaluated in the same manner as in Example 1. Table 2 shows the evaluation results.
[0069]
Comparative Example 2
A four-necked flask was equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirrer, and was installed in a mantle heater. 5 parts of bisphenol A-EO adduct, 5 parts of bisphenol A-PO adduct Then, a monomer composition comprising 4 parts of terephthalic acid and 5 parts of fumaric acid was charged and heated and stirred while introducing nitrogen into the flask to obtain a polyester resin.
Next, 70 parts of the polyester resin obtained as described above and 30 parts of carbon black (trade name “# 25B”, manufactured by Mitsubishi Chemical Corporation; primary particle size: 40 nm) were charged into a pressure kneader and mixed. After cooling the obtained mixture, it was pulverized by a feather mill to obtain a pigment master batch.
[0070]
Next, 93 parts of the polyester resin obtained as described above, 10 parts of a pigment master batch, and 2 parts of a zinc salicylate metal complex (trade name “E84” manufactured by Orient Chemical Industries, Ltd.), oxidized low-molecular-weight polypropylene (Sanyo Chemical Industries, Ltd.) After 2 parts of Viscol TS200 (trade name, manufactured by the company) are sufficiently mixed with a Henschel mixer, the mixture is melt-kneaded with a twin-screw extruder, and the obtained kneaded material is rapidly cooled and coarsely pulverized with a feather mill. did. The crushed product is crushed and coarsely classified by a jet crusher (manufactured by Nippon Pneumatic Industries Co., Ltd., trade name "IDS"), and then finely sized by a DS classifier (manufactured by Nippon Pneumatic Industries Co., Ltd.) to obtain toner base particles. Obtained.
[0071]
Hydrophobic silica TS500 (manufactured by Cabosil, BET specific surface area: 225 m) was used for 100 parts of the obtained toner base particles.²/ G) 0.5 part and hydrophobic silica NAX50 (manufactured by Nippon Aerosil Co., Ltd., BET specific surface area 40 m)²/ G) 0.3 part by weight was added, and a mixing treatment was performed for 90 seconds at a peripheral speed of 30 m / sec using a Henschel mixer. Then, using a surface modification device (Surfusing system; manufactured by Nippon Pneumatic Industries, Ltd.), the maximum temperature: 250 ° C., the residence time: 0.5 seconds, the powder dispersion concentration: 100 g / m.³The surface of the toner base particles is subjected to a surface modification treatment at a cooling air temperature of 18 ° C. and a cooling water temperature of 10 ° C., and hydrophobic silica R972 (Nippon Aerosil Co., Ltd., BET specific surface area 110 m) is applied to 100 parts of the toner base particles.²/ G) 0.5 part and 0.3 part of strontium titanate particles A1 were added, and mixed for 180 seconds at a peripheral speed of 30 m / sec using a Henschel mixer to obtain a toner for developing an electrostatic image. The above-mentioned evaluation was performed on the obtained electrostatic image developing toner. Table 2 shows the evaluation results.
[0072]
Comparative Example 3
In a four-necked flask equipped with a high-speed stirrer TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), 650 parts of ion-exchanged water and 500 parts of a 0.1 mol / l sodium tertiary sodium phosphate aqueous solution are charged, and rotated. The number was adjusted to 12000 rpm and heated to 70 ° C. Next, 70 parts of a 1.0 mol / L calcium chloride aqueous solution was gradually added to the flask to prepare an aqueous dispersion medium of a dispersion stabilizer containing fine, slightly water-soluble, tribasic calcium phosphate colloid.
On the other hand, 77 parts of styrene, 23 parts of 2-ethylhexyl acrylate, 0.2 part of divinylbenzene, 8 parts of carbon black, 6 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane polycarbonate, a negative charge control agent (azo dye-based iron Compound) (2 parts) and 10 parts of a wax component were dispersed for 3 hours using an attritor (manufactured by Mitsui Kinzoku Co., Ltd.), and then 5 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) was added to polymerize. A monomer composition was prepared.
[0073]
Next, the polymerizable monomer composition is charged into the aqueous dispersion medium of the above-mentioned dispersion stabilizer, and while maintaining the rotation speed of the high-speed stirrer at 12,000 rpm under a nitrogen atmosphere at an internal temperature of 70 ° C, The mixture was stirred for 15 minutes to form droplets of the polymerizable monomer composition. Thereafter, the stirring was changed to a propeller stirring blade, and the mixture was maintained at the same temperature for 10 hours while stirring at 50 rpm to complete the polymerization. After completion of the polymerization, the remaining monomer was distilled off under heating and reduced pressure of 80 ° C./47 kPa (350 Torr), the suspension was cooled, and then dilute hydrochloric acid was added to remove the dispersion stabilizer. After repeating the water washing several times, the polymer particles were stirred using a conical ribbon drier (manufactured by Okawara Seisakusho) under a reduced pressure of 45 ° C./1.3 kPa (10 Torr) with a spiral ribbon rotating blade. The sphering treatment and the drying treatment were performed for 6 hours to obtain toner particles.
100 parts of the obtained toner particles and 2 parts of the hydrophobic oil-treated silica fine powder were dry-mixed with a Henschel mixer to obtain a toner for developing an electrostatic image. The above-mentioned evaluation was performed on the obtained electrostatic image developing toner. Table 2 shows the evaluation results.
[0074]
[Table 1]

[0075]
[Table 2]

[0076]
From the evaluation results of the electrostatic image developing toners in Tables 1 and 2, the following can be understood. The toner for developing an electrostatic image of Comparative Example 1 in which the values of C1 / C2 and σ2−σ1 are larger than the ranges specified in the present invention has fog, reduced fine line reproducibility, and low print density. It is.
The toner for developing an electrostatic charge image of Comparative Example 2 in which the value of σ2 and the value of σ2−σ1 are larger than the ranges specified in the present invention is fogged, thin line reproducibility is reduced, and printing density is low. Things.
The value of the ratio (Dv / Dp) of the volume average particle diameter to the number average particle diameter (Dv / Dp), the standard deviation of the particle diameter, the value of σ2, and the value of σ2-σ1 are larger than the ranges specified in the present invention. The charge image developing toner has fogging, reduced fine line reproducibility, and low print density.
In contrast, the electrostatic image developing toner of Example 1 of the present invention has good fine line reproducibility, high print density, and is less likely to cause fogging.
[0077]
【The invention's effect】
According to the present invention, there is provided an electrostatic image developing toner which is less likely to generate fog and has improved dot reproducibility.

Claims (4)

An electrostatic image developing toner containing toner particles comprising at least a binder resin, a colorant and a charge control agent,
The volume mode diameter (a) of the toner particles is 5 to 10 μm, and the ratio (Dv / Dp) of the volume average particle diameter (Dv) to the number average particle diameter (Dp) is 1.0 to 1.3. Has an average circularity of 0.97 to 0.995,
The standard deviation (b) of the particle diameter of the toner particles is 2 μm or less, the average circularity (C1) of the toner particles having a particle diameter of (a−2b) μm or more and less than a μm, A ratio (C1 / C2) of the average circularity (C2) of the toner particles having a particle diameter to 1.00 to 1.02,
The toner is dispersed in ion-exchanged water having a conductivity σ1 of 0 to 10 μS / cm such that the toner concentration becomes 6% by weight, heated and boiled for 10 minutes, and then separately boiled conductivity σ1 of 0 to 10 μS / cm. The water extract obtained by replenishing evaporated water by adding ion-exchanged water to the original volume and cooling to room temperature has a conductivity σ2 of 20 μS / cm or less, and σ2-σ1 of 0.1 to 10 μS. / Cm, an electrostatic image developing toner. The electrostatic image developing toner according to claim 1, wherein the enthalpy of fusion (ΔH) measured by a differential scanning calorimeter is 1 to 10 mJ / mg. The electrostatic image developing toner according to claim 1, wherein the charge control agent is a charge control resin having a weight average molecular weight of 3,000 to 300,000. Mixing a water-soluble polyvalent inorganic salt and an alkali hydroxide in an aqueous dispersion medium to prepare an aqueous dispersion medium containing a colloid of a poorly water-soluble inorganic compound, followed by aging;
Add a polymerizable monomer composition containing a polymerizable monomer, a colorant, a charge control agent and a polymerization initiator to an aqueous dispersion medium containing a colloid of the aged hardly water-soluble inorganic compound, Forming droplets of the composition to obtain an aqueous dispersion medium containing the droplets; and after adding a boron compound to the aqueous dispersion medium containing the droplets, heating the aqueous dispersion medium, Polymerizing a polymerizable monomer to form toner particles;
A method for producing a toner for developing an electrostatic image, comprising: