JP2004004506A - Electrostatic charge image developing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner with negative electrostatic charging property which has small variation in electrostatic charging quantity due to environmental changes, high print density, small photoreceptor fogging in high-temperature/high-humidity environment, and small fogging during endurance and is adaptive to a high-speed printer. <P>SOLUTION: In the electrostatic charge image developing toner which contains at least a binder resin, a coloring agent and an electrostatic charging control agent, the electrostatic charging control agent contains a negative electrostatic charging control resin (A) consisting of a polymer having a structure unit with a negative charging functionality and a nigrosine dye (B). Here, a calculated value of an expression (c×100)/(a×b) is 2.0 to 7.0, where (a) is the content (wt.%) of the structure unit with the negative charging functionality in the negative charging control resin (A), (b) is the content (wt.%) of the negative charging control resin (A) for 100 wt.pts. binding resin, and (c) is the content (wt.pts.) of nigrosine dye (B) for 100 wt.pts. binding resin. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
（式中、Ｚ⁻は、スルホン酸などのアニオン種である。）
で表わされる化合物が代表的なものであるが、各種置換基を有するものであってもよい。市販のニグロシン染料としては、オリエント化学工業社製のボントロンＮ−０１、ボントロンＮ−０７などが挙げられる。
【００２７】
３．負帯電制御樹脂とニグロシン染料の使用量
本発明では、負帯電制御樹脂と正帯電制御剤のニグロシンとを併用するが、負帯電性でかつ諸特性に優れたトナーを得るために、負帯電制御樹脂中の負帯電性官能基を持つ構造単位の含有量と、結着樹脂１００重量部に対する負帯電制御樹脂の含有量と、結着樹脂１００重量部に対するニグロシン染料の含有量とが特定の関係式を満足することが必要である。
【００２８】
より具体的に、負帯電制御樹脂（Ａ）中の負帯電性官能基を持つ構造単位の含有量をａ（重量％）とし、結着樹脂１００重量部に対する負帯電制御樹脂（Ａ）の含有量をｂ（重量部）とし、結着樹脂１００重量部に対するニグロシン染料（Ｂ）の含有量をｃ（重量部）としたとき、これらが下記の関係式（Ｉ）
２．０≦（ｃ×１００）／（ａ×ｂ）≦７．０　　　…（Ｉ）
を満足することが必要である。
【００２９】
負帯電制御樹脂（Ａ）中の負帯電性官能基を持つ構造単位の含有量のａ重量％としては、負帯電性官能基を持つ構造単位を有する重合体を合成するときに使用した「負帯電性官能基を持つ単量体」の共重合割合（重量％）を使用することができる。また、結着樹脂１００重量部に対する負帯電制御樹脂の含有量ｂ重量部、及びニグロシン染料の含有量ｃ重量部としては、重合トナーの場合、それぞれ重合性単量体１００重量部に対する使用割合（重量部）を用いることができる。
【００３０】
負帯電制御樹脂（Ａ）とニグロシン染料（Ｂ）とを併用しても、ａ、ｂ、及びｃが関係式（Ｉ）を満足しない場合には、目的を達成することができない。例えば、（ｃ×１００）／（ａ×ｂ）の計算値が２．０未満と小さい場合には、低温／低湿（Ｌ／Ｌ）、常温／常湿（Ｎ／Ｎ）、及び高温／高湿（Ｈ／Ｈ）のいずれの環境条件下でも印字濃度が低くなり、高温／高湿（Ｈ／Ｈ）条件下での感光体カブリが著しくなる。一方、（ｃ×１００）／（ａ×ｂ）の計算値が７．０を超過して大きくなると、いずれの環境条件下でも印字濃度が低くなり、高温／高湿条件下での感光体カブリが著しくなり、さらには耐久性カブリが多くなる。
【００３１】
また、正帯電制御剤として、ニグロシン染料以外の正帯電制御剤を用いると、前記関係式（Ｉ）を満足する場合であっても、いずれの環境条件下でも印字濃度が低くなり、高温／高湿条件下での感光体カブリが著しくなる。通常の負帯電制御剤とニグロシン染料とを併用した場合には、いずれの環境条件下でも印字濃度が低くなり、高温／高湿条件下での感光体カブリが著しくなり、さらには耐久性カブリが多くなる。
【００３２】
本発明では、負帯電制御樹脂とニグロシン染料とを特定の範囲内で併用することにより、粒径分布がシャープで、流動性と保存性に優れ、低温／低湿下及び高温／高湿下のいずれの環境においても帯電性があまり変化せず、さらには、連続印字を行っても画質の低下が抑制される静電荷像現像用トナーを得ることができる。
【００３３】
負帯電制御樹脂（Ａ）の使用割合は、結着樹脂１００重量部に対して、通常０．１〜２０重量部、好ましくは０．５〜１０重量部である。ニグロシン染料（Ｂ）の使用割合は、結着樹脂１００重量部に対して、通常０．０５〜０．５重量部、好ましくは０．１〜０．４重量部である。この結着樹脂の重量部は、結着樹脂を形成するのに使用する重合性単量体の重量部で代替することができる。
【００３４】
負帯電制御樹脂（Ａ）とニグロシン染料（Ｂ）の合計の使用割合は、結着樹脂１００重量部に対して、好ましくは０．１５〜２０重量部、より好ましくは０．３〜１０重量部であり、特に好ましくは１〜５重量部である。負帯電制御樹脂（Ａ）とニグロシン染料（Ｂ）との使用比率（Ａ：Ｂ）は、好ましくは１０：１〜１０：５（重量比）である。
【００３５】
４．静電荷像現像用トナー
本発明のトナーは、少なくとも結着樹脂、着色剤、及び帯電制御剤（前述の負帯電制御樹脂とニグロシン染料）を含有する着色粒子であればよく、その製造法によって特に制限されない。本発明のトナーは、例えば、粉砕法や重合法により得ることができる。また、着色粒子の表面に樹脂被覆層を形成したコア・シェル型構造を有するカプセルトナーであってもよい。本発明のトナーは、重合法によって得られる重合トナーであることが好適である。
【００３６】
重合トナーは、分散安定剤を含有する水系分散媒体中で、少なくとも重合性単量体、着色剤、及び帯電制御剤を含有する重合性単量体組成物を重合することにより得ることができる。重合性単量体が重合して生成する重合体が結着樹脂となる。水系分散媒体として、イオン交換水などを用いることができ、所望によりアルコールなどの親水性溶媒を加えてもよい。
【００３７】
コア・シェル型構造を有する重合トナーは、分散安定剤を含有する水系分散媒体中で、少なくとも重合性単量体、着色剤、及び帯電制御剤を含有する単量体組成物を重合することにより得られた着色粒子をコア粒子とし、該コア粒子の存在下にシェル用重合性単量体を重合することにより得ることができる。シェル用重合性単量体が重合して形成される重合体層が樹脂被覆層（シェル）となる。
【００３８】
重合性単量体組成物には、必要に応じて、離型剤、架橋性単量体、マクロモノマー、分子量調整剤、滑剤、分散助剤などの各種添加剤を含有させることができる。
【００３９】
（１）重合性単量体
結着樹脂を形成するための重合性単量体として、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、重合体粒子中の結着樹脂成分となる。
【００４０】
モノビニル単量体としては、具体的には、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、（メタ）アクリル酸ジメチルアミノエチル、（メタ）アクリルアミド等の（メタ）アクリル酸の誘導体；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。
【００４１】
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よい。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）アクリル酸の誘導体との組み合わせなどが好適に用いられる。
【００４２】
モノビニル単量体と共に、架橋性単量体及び架橋性重合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、及びこれらの誘導体等の芳香族ジビニル化合物；エチレングリコールジメタクリレート、ジエチレングリコールジメタクリレート、１，４−ブタンジオールジアクリレート等のジエチレン性不飽和カルボン酸エステル；Ｎ，Ｎ−ジビニルアニリン、ジビニルエーテル等のビニル基を２個有する化合物、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のビニル基を３個以上有する化合物等を挙げることができる。
【００４３】
架橋性重合体は、重合体中に２個以上のビニル基を有する重合体であり、具体的には、分子内に２個以上の水酸基を有するポリエチレン、ポリプロピレン、ポリエステル、ポリエチレングリコール等の重合体と、アクリル酸やメタクリル酸等の不飽和カルボン酸単量体を縮合反応することにより得られるエステルを挙げることができる。
【００４４】
これらの架橋性単量体及び架橋性重合体は、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。使用量は、モノビニル単量体１００重量部に対して、通常１０重量部以下、好ましくは０．０１〜７重量部、より好ましくは０．０５〜５重量部、特に好ましくは０．１〜３重量部である。
【００４５】
モノビニル単量体と共にマクロモノマーを用いると、高温での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。数平均分子量が上記範囲内にあると、マクロモノマーの溶融性を損なうことなく、定着性及び保存性が維持できるので好ましい。
【００４６】
マクロモノマー分子鎖の末端にある重合可能な炭素−炭素不飽和二重結合としては、アクリロイル基、メタクリロイル基などを挙げることができ、共重合のし易さの観点からメタクリロイル基が好ましい。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。
【００４７】
マクロモノマーの具体例としては、スチレン、スチレン誘導体、メタクリル酸エステル、アクリル酸エステル、アクリロニトリル、メタクリロニトリル等を単独でまたは２種以上を重合して得られる重合体、ポリシロキサン骨格を有するマクロモノマーなどを挙げることができるが、これらの中でも、親水性のものが好ましく、特にメタクリル酸エステルまたはアクリル酸エステルを単独で、あるいはこれらを組み合わせて重合して得られる重合体が好ましい。
【００４８】
マクロモノマーを使用する場合、その使用量は、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、より好ましくは０．０５〜１重量部である。マクロモノマーの使用量が上記範囲内にあると、トナーの保存性を維持して、定着性が向上するので好ましい。
【００４９】
（２）着色剤
着色剤としては、カーボンブラックやチタンホワイトなどのトナーの分野で用いられている各種顔料及び染料を使用することができる。黒色着色剤としては、カーボンブラック、ニグロシンベースの染顔料類；コバルト、ニッケル、四三酸化鉄、酸化鉄マンガン、酸化鉄亜鉛、酸化鉄ニッケル等の磁性粒子；等を挙げることができる。カーボンブラックを用いる場合、一次粒径が２０〜４０ｎｍであるものを用いると良好な画質が得られ、また、トナーの環境への安全性も高まるので好ましい。カラートナー用着色剤としては、イエロー着色剤、マゼンタ着色剤、シアン着色剤などを使用することができる。
【００５０】
イエロー着色剤としては、縮合アゾ化合物、イソインドリノン化合物、アンスラキノン化合物、アゾ金属錯体、メチン化合物、アリルアミド化合物などが用いられる。具体的には、例えば、Ｃ．Ｉ．ピグメントイエロー３、１２、１３、１４、１５、１７、６２、６５、７３、７４、８３、９０、９３、９５、９５、９７、１０９、１１０、１１１、１２０、１２８、１２９、１３８、１４７、１５５、１６８、１８０、１８１などがある。この他、ネフトールイエローＳ、ハンザイエローＧ、Ｃ．Ｉ．バットイエロー等が挙げられる。
【００５１】
マゼンタ着色剤としては、縮合アゾ化合物、ジケトピロロピロール化合物、アンスラキノン化合物、キナクリドン化合物、塩基染料レーキ化合物、ナフトール化合物、ベンズイミダゾロン化合物、チオインジゴ化合物、ペリレン化合物などがある。具体的には、例えば、Ｃ．Ｉ．ピグメントレッド２、３、５、６、７、２３、４８、４８：２、４８：３、４８：４、５７、５７：１、５８、６０、６３、６４、６８、８１、８１：１、８３、８７、８８、８９、９０、１１２、１１４、１２２、１２３、１４４、１４６、１４９、１６３、１６６、１６９、１７０、１７７、１８４、１８５、１８７、２０２、２０６、２０７、２０９、２２０、２５１、２５４などが挙げられる。この他、Ｃ．Ｉ．ピグメントバイオレット１９等が挙げられる。
【００５２】
シアン着色剤としては、銅フタロシアニン化合物及びその誘導体、アントラキノン化合物、塩基染料レーキ化合物などが挙げられる。具体的には、例えば、Ｃ．Ｉ．ピグメントブルー１、２、３、６、７、１５、１５：１、１５：２、１５：３、１５：４、１６、１７、６０、６２、６６などがある。この他、フタロシアニンブルー、Ｃ．Ｉ．バットブルー、Ｃ．Ｉ．アシッドブルーなどが挙げられる。
【００５３】
これらの着色剤は、それぞれ単独で、あるいは２種以上を組み合わせ使用することができる。着色剤は、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１〜２０重量部の割合で用いられる。
【００５４】
（３）滑剤・分散助剤
着色剤のトナー粒子中への均一分散等を目的として、オレイン酸、ステアリン酸等の脂肪酸、脂肪酸とＮａ、Ｋ、Ｃａ、Ｍｇ、Ｚｎ等の金属とからなる脂肪酸金属塩などの滑剤；シラン系またはチタン系カップリング剤等の分散助剤；などを使用してもよい。このような滑剤や分散剤は、着色剤の重量を基準として、通常１／１０００〜１／１程度の割合で使用される。
【００５５】
（４）帯電制御剤
本発明は、帯電制御剤として、前述の負帯電制御樹脂とニグロシン染料とを併用するが、本発明の目的を損なわない少量の範囲内で、これら以外の帯電制御剤や帯電制御樹脂を含有させてもよい。
【００５６】
（５）離型剤
オフセット防止または熱ロール定着時の離型性の向上などの目的で、離型剤を重合性単量体組成物中に含有させることができる。離型剤としては、例えば、低分子量ポリエチレン、低分子量ポリプロピレン、低分子量ポリブチレンなどのポリオレフィンワックス類；キャンデリラ、カルナウバ、ライス、木ロウ、ホホバなどの植物系天然ワックス；パラフィン、マイクロクリスタリン、ペトロラクタムなどの石油系ワックスおよびその変性ワックス；フィッシャートロプシュワックスなどの合成ワックス；ペンタエリスリトールテトラミリステート、ペンタエリスリトールテトラパルミテート、ジペンタエリスリトールヘキサミリステートなどの多官能エステル化合物；などが挙げられる。これらは、１種あるいは２種以上を組み合わせて使用することができる。
【００５７】
これらのうち、合成ワックス、末端変性ポリオレフィンワックス類、石油系ワックス、多官能エステル化合物などが好ましい。多官能エステル化合物のなかでも示差走査熱量計により測定されるＤＳＣ曲線において、昇温時の吸熱ピーク温度が３０〜２００℃、好ましくは４０〜１６０℃、より好ましくは５０〜１２０℃の範囲にあるペンタエリスリトールエステルや、同吸熱ピーク温度が５０〜８０℃の範囲にあるジペンタエリスリトールエステルなどの多官能エステル化合物を使用すると、トナーの定着性と剥離性とのバランス面で特に好ましい。
【００５８】
昇温時の吸熱ピーク温度が３０〜２００℃の範囲にあるペンタエリスリトールエステルや同吸熱ピーク温度が５０〜８０℃の範囲にあるジペンタエリスリトールエステルなどの多官能エステル化合物の中でも、分子量が１，０００以上で、スチレン１００重量部に対して２５℃で５重量部以上溶解し、酸価が１０ｍｇ／ＫＯＨ以下のものは、トナーの定着温度低下に対して顕著な効果を示すのでより好ましい。吸熱ピーク温度は、ＡＳＴＭ　Ｄ３４１８−８２によって測定された値である。
【００５９】
離型剤の使用割合は、結着樹脂（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０．５〜２０重量部、より好ましくは１〜１０重量部である。
【００６０】
（６）重合開始剤
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−シアノ吉草酸）、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）二塩酸塩、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、ジクミルパーオキシド、ラウロイルパーオキシド、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、１，１′，３，３′−テトラメチルブチルパーオキシ−２−エチルヘキサノエート、ｔ−ブチルパーオキシイソブチレート等の過酸化物類などを挙げることができる。また、これら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使用することができる。
【００６１】
これらの中でも、使用される重合性単量体に可溶な油溶性の重合開始剤を選択することが好ましく、必要に応じて、水溶性の重合開始剤をこれと併用することもできる。重合開始剤は、重合性単量体１００重量部に対して、通常０．１〜２０重量部、好ましくは０．３〜１５重量部、より好ましくは０．５〜１０重量部の割合で用いる。
【００６２】
重合開始剤は、重合性単量体組成物中に予め添加することができるが、懸濁重合の場合は、液滴形成工程終了後または重合反応の途中の懸濁液、乳化重合の場合は、乳化工程終了後または重合反応の途中の乳化液に直接添加することもできる。
【００６３】
（７）分子量調整剤
重合に際して、分子量調整剤を添加することが好ましい。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；四塩化炭素、四臭化炭素等のハロゲン化炭化水素類；などを挙げることができる。分子量調整剤は、重合開始前、あるいは重合途中に添加することができる。分子量調整剤は、重合性単量体１００重量部に対して、通常０．０１〜１０重量部、好ましくは０．１〜５重量部の割合で用いられる。
【００６４】
（８）分散安定剤
本発明に用いる分散安定剤は、難水溶性金属化合物のコロイドを含有するものが好適である。難水溶性金属化合物としては、硫酸バリウム、硫酸カルシウム、などの硫酸塩；炭酸バリウム、炭酸カルシウム、炭酸マグネシウムなどの炭酸塩；りん酸カルシウムなどのりん酸塩；酸化アルミニウム、酸化チタンなどの金属酸化物；水酸化アルミニウム、水酸化マグネシウム、水酸化第二鉄の金属水酸化物；等を挙げることができる。これらのうち、難水溶性金属水酸化物のコロイドを含有する分散剤は、重合体粒子の粒径分布を狭くすることができ、画像の鮮明性が向上するので好適である。
【００６５】
難水溶性金属化合物のコロイドを含有する分散剤は、その製法による制限はないが、水溶性多価金属化合物の水溶液のｐＨを７以上に調整することによって得られる難水溶性の金属水酸化物のコロイド、特に水溶性多価金属化合物と水酸化アルカリ金属塩との水相中の反応により生成する難水溶性の金属水酸化物のコロイドを用いることが好ましい。難水溶性金属化合物のコロイドは、個数粒径分布Ｄ５０（個数粒径分布の５０％累積値）が０．５μｍ以下で、Ｄ９０（個数粒径分布の９０％累積値）が１μｍ以下であることが好ましい。
【００６６】
分散安定剤は、重合性単量体１００重量部に対して、通常０．１〜２０重量部の割合で使用する。この割合が少なすぎると、充分な重合安定性を得ることが困難であり、重合凝集物が生成しやすくなる。逆に、この割合が多すぎると、水溶液粘度が大きくなって重合安定性が低くなる。
【００６７】
本発明においては、必要に応じて、水溶性高分子を含有する分散剤を用いることができる。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、ゼラチン等を例示することができる。本発明においては、界面活性剤を使用する必要はないが、帯電特性の環境依存性が大きくならない範囲で、懸濁重合を安定に行うために使用することができる。
【００６８】
（９）重合トナーの製造方法
１．重合法
重合トナーは、重合性単量体の重合により生成した結着樹脂と着色剤と帯電制御剤などを含有する重合体粒子である。この重合トナーは、例えば、以下の工程により得ることができる。重合性単量体、着色剤、帯電制御剤、その他の添加剤などを混合機を用いて混合し、必要に応じて、メディヤ型湿式粉砕機（例えば、ビーズミル）などを用いて湿式粉砕し、重合性単量体組成物を得る。重合性単量体組成物を、分散安定剤を含有する水系分散媒体中に分散させ、撹拌し、単量体組成物の均一な液滴（体積平均粒径が５０〜１０００μｍ程度の一次液滴）を形成する。重合開始剤の添加時期は、早期重合を避けるため、水系分散媒体中で液滴の大きさが均一になってからでよい。
【００６９】
水系分散媒体中に単量体組成物の液滴が分散した懸濁液に重合開始剤を添加混合し、さらに、高速回転剪断型撹拌機を用いて、液滴の粒径が目的とするトナー粒子に近い小粒径になるまで撹拌する。このようにして形成された微小粒径の液滴（体積平均粒径が１〜１２μｍ程度程度の二次液滴）を含有する懸濁液を重合反応器に仕込み、通常５〜１２０℃、好ましくは３５〜９５℃の温度で懸濁重合を行う。重合温度が低すぎると、触媒活性が高い重合開始剤を用いなければならないので、重合反応の管理が困難になる。重合温度が高すぎると、低温で溶融する添加剤を含む場合、これがトナー表面にブリードし、保存性が悪くなることがある。
【００７０】
重合性単量体組成物の微小な液滴の体積平均粒径及び粒径分布は、重合トナーの体積平均粒径や粒径分布に影響する。液滴の粒径が大きすぎると、生成する重合トナー粒子が大きくなり、画像の解像度が低下するようになる。液滴の粒径分布が広いと、定着温度のばらつきが生じ、カブリ、トナーフィルミングの発生などの不具合が生じるようになる。したがって、液滴は、予定しているトナー粒子の大きさまで小さくするように造粒することが望ましい。
【００７１】
重合性単量体組成物の液滴の体積平均粒径は、通常１〜１２μｍ、好ましくは２〜１０μｍ、より好ましくは３〜８μｍである。重合性単量体組成物の液滴の粒径分布（体積平均粒径／数平均粒径）は、通常１〜３、好ましくは１〜２．５、より好ましくは１〜２である。特に微細な液滴を造粒する場合には、高速回転する回転子と、それを取り囲み、かつ小孔または櫛歯を有する固定子との間隙に、単量体組成物を含有する水系分散媒体を流通させる方法が好適である。
【００７２】
重合性単量体として前述のモノビニル単量体の中から１種以上を選択するが、トナーの定着温度を下げるには、ガラス転移温度（Ｔｇ）が通常８０℃以下、好ましくは４０〜８０℃、より好ましくは５０〜７０℃程度の重合体を形成し得る単量体または単量体の組み合わせを選択することが好ましい。本発明において、結着樹脂を構成する共重合体のＴｇは、使用する単量体の種類と使用割合に応じて算出される計算値（計算Ｔｇ）である。
【００７３】
懸濁重合により、重合性単量体の重合により生成した結着樹脂と着色剤と帯電制御剤などを含有する着色重合体粒子が生成する。本発明では、この着色重合体粒子をトナーとして使用することができるが、トナーの保存性（耐ブロッキング性）、低温定着性、定着時の溶融性などを改善する目的で、懸濁重合によって得られた着色重合体粒子の上に、さらに重合体層を形成して、コア・シェル型構造を有するカプセルトナーとすることができる。
【００７４】
２．コア・シェル構造を有するトナーの製造法
コア・シェル型構造の形成方法は、特に限定されないが、重合トナーの場合には、前記着色重合体粒子をコア粒子とし、該コア粒子の存在下にシェル用重合性単量体を重合して、コア粒子の表面に重合体層（シェル）を形成する方法が好ましい。シェル用重合性単量体として、コア粒子を構成する重合体成分のＴｇよりも高いＴｇを有する重合体を形成するものを使用すると、トナーの保存性を改善することができる。
【００７５】
一方、コア粒子を構成する重合体成分のＴｇを低く設定することにより、重合トナーの定着温度を下げたり、溶融特性を改善したりすることができ、それによって、印字（複写、印刷など）の高速化やフルカラー化、ＯＨＰ（オーバーヘッドプロジェクター）透過性などに好適に対応することができる。
【００７６】
コア及びシェルを形成するための重合性単量体としては、前述のモノビニル系単量体の中から好ましいものを適宜選択することができる。コア用重合性単量体とシェル用重合性単量体との重量比は、通常４０／６０〜９９．９／０．１、好ましくは６０／４０〜９９．７／０．３、より好ましくは８０／２０〜９９．５／０．５である。シェル用重合性単量体の割合が過小であると、保存性の改善効果が小さく、過大であると、定着温度の低減効果が小さくなる。
【００７７】
シェル用重合性単量体により形成される重合体のＴｇは、通常５０℃超過１２０℃以下、好ましくは６０℃超過１１０℃以下、より好ましくは８０℃超過１０５℃以下である。コア用重合性単量体から形成される重合体とシェル用重合性単量体から形成される重合体との間のＴｇの差は、好ましくは１０℃以上、より好ましくは２０℃以上、特に好ましくは３０℃以上である。多くの場合、定着温度と保存性のバランスの観点から、コア用重合性単量体として、Ｔｇが通常６０℃以下、好ましくは、４０〜６０℃の重合体を形成しうるものを選択するのが好ましい。一方、シェル用重合性単量体としては、スチレンやメチルメタクリレートなどのＴｇが８０℃を越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種以上を組み合わせて使用することが好ましい。
【００７８】
シェル用重合性単量体は、コア粒子の平均粒径よりも小さな液滴として重合反応系に添加することが好ましい。シェル用重合性単量体の液滴の粒径が大きすぎると、コア粒子の周囲に重合体層が均一に形成され難くなる。シェル用重合性単量体を小さな液滴とするには、シェル用重合性単量体と水系分散媒体との混合物を、例えば、超音波乳化機などを用いて、微分散処理を行い、得られた分散液を反応系に添加すればよい。シェル用重合性単量体が、２０℃の水に対する溶解度が０．１重量％以上の比較的水溶性の単量体（例えば、メチルメタクリレート）である場合には、コア粒子の表面に比較的速やかに移行しやすいので、微分散処理を行う必要はないが、均一なシェルを形成する上で、微分散処理を行うことが好ましい。シェル用重合性単量体が、２０℃の水に対する溶解度が０．１重量％未満の単量体（例えば、スチレン）の場合には、微分散処理を行うか、あるいは２０℃の水に対する溶解度が５重量％以上の有機溶媒（例えば、アルコール類）を反応系に加えることにより、コア粒子の表面に移行しやすくすることが好ましい。
【００７９】
シェル用重合性単量体には、帯電制御剤を加えることができる。帯電制御剤としては、前述したコア粒子製造に使用するのと同様のものが好ましく、使用する場合には、シェル用重合性単量体１００重量部に対して、通常、０．０１〜１０重量部、好ましくは０．１〜５重量部の割合で用いられる。
【００８０】
コア・シェル型構造の重合トナーを製造するには、コア粒子を含有する懸濁液中に、シェル用重合性単量体またはその水系分散液を一括的、または連続的もしくは断続的に添加する。シェル用重合性単量体を添加する際に水溶性のラジカル開始剤を添加することがシェルを形成する上で好ましい。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、シェル用重合性単量体が移行したコア粒子の外表面近傍に水溶性重合開始剤が進入し、コア粒子表面に重合体（シェル）を形成しやすくなると考えられる。
【００８１】
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）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％、好ましくは１〜２０重量％である。
【００８２】
シェルの平均厚みは、通常０．００１〜１．０μｍ、好ましくは０．００３〜０．５μｍ、よりに好ましくは０．００５〜０．２μｍである。シェル厚みが大きすぎると定着性が低下し、小さすぎると保存性が低下する。重合法トナーのコア粒子径、及びシェルの厚みは、電子顕微鏡により観察できる場合は、その観察写真から無作意に選択した粒子の大きさ及びシェル厚みを直接測ることにより得ることができ、電子顕微鏡でコアとシェルとを観察することが困難な場合は、コア粒子の粒径と、シェルを形成する重合性単量体の使用量から算定することができる。
【００８３】
（１０）トナー
本発明の静電荷像現像用トナー（コア・シェル型構造を有するカプセルトナーを含む）の体積平均粒径は、通常１〜１２μｍ、好ましくは２〜１１μｍ、より好ましくは３〜１０μｍである。解像度を高めて高精細な画像を得る場合には、トナーの体積平均粒径を好ましくは２〜９μｍ、より好ましくは３〜８μｍ、特に好ましくは３〜７μｍにまで小さくすることが特に望ましい。
【００８４】
本発明のトナーの体積平均粒径（ｄｖ）／個数平均粒径（ｄｐ）で表される粒径分布は、通常１．７以下、好ましくは１．５以下、より好ましくは１．３以下である。トナーの体積平均粒径が大きすぎると、解像度が低下しやすくなる。トナーの粒径分布が大きいと、大粒径のトナーの割合が多くなり、解像度が低下しやすくなる。
【００８５】
本発明のトナーは、長径（ｄｌ）と短径（ｄｓ）との比（ｄｌ／ｄｓ）で表される球形度が、好ましくは１〜１．３、より好ましくは１〜１．２の実質的に球形であることが好ましい。実質的に球形のトナーを非磁性一成分現像剤として用いると、感光体上のトナー像の転写材への転写効率が向上する。このような球形のトナーは、懸濁重合法により得ることができる。
【００８６】
（１１）非磁性一成分現像剤
本発明の重合トナーは、各種現像剤のトナー成分として使用することができるが、非磁性一成分現像剤として使用することが好ましい。本発明の重合トナーを非磁性一成分現像剤とする場合には、必要に応じて外添剤を混合することができる。外添剤としては、流動化剤や研磨剤などとして作用する無機粒子や有機樹脂粒子が挙げられる。
【００８７】
無機粒子としては、例えば、二酸化ケイ素（シリカ）、酸化アルミニウム（アルミナ）、酸化チタン、酸化亜鉛、酸化錫、チタン酸バリウム、チタン酸ストロンチウムなどが挙げられる。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共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。
【００８８】
これらの中でも、無機酸化物粒子が好ましく、二酸化ケイ素が特に好ましい。無機微粒子表面を疎水化処理することができ、疎水化処理された二酸化ケイ素粒子が特に好適である。外添剤は、２種以上を組み合わせて用いてもよく、外添剤を組み合わせて用いる場合には、平均粒子径の異なる無機粒子同士または無機粒子と有機樹脂粒子とを組み合わせる方法が好適である。外添剤の量は、特に限定されないが、重合トナー１００重量部に対して、通常０．１〜６重量部である。外添剤を重合トナーに付着させるには、通常、重合トナーと外添剤とをヘンシェルミキサーなどの混合機に入れて攪拌する。
【００８９】
【実施例】
以下に、合成例、実施例及び比較例を挙げて、本発明をさらに具体的に説明する。なお、部及び％は、特に断りのない限り重量基準である。物性等の測定方法は、以下のとおりである。
【００９０】
（１）粒径及び粒径分布
重合体粒子の体積平均粒径（ｄｖ）、及び体積平均粒径（ｄｖ）と個数平均粒径（ｄｐ）との比（ｄｖ／ｄｐ）で表わされる粒径分布は、マルチサイザー（ベックマン・コールター社製）により測定した。その測定条件は、アパーチャー径＝１００μｍ、媒体＝イソトンＩＩ、測定粒子個数＝１００，０００個であった。
【００９１】
（２）球形度
走査型電子顕微鏡で重合体粒子の写真を撮影し、その写真をネクサス９０００型の画像処理装置で読み込み、重合体粒子の長径（ｒｌ）と短径（ｒｓ）との比（ｒｌ／ｒｓ）を測定した。重合体粒子の測定個数を１００個とした。測定値を平均して、球形度（ｒｌ／ｒｓ）を算出した。
【００９２】
（３）ブローオフ帯電量
１００ｃｍ^３のボールミルポットにキャリア（ＴＥＦＶ１５０／２５０）５７ｇとトナー３ｇを投入して、３０分間攪拌して混合した後、ブローオフ帯電量測定装置ＴＢ−２００（東芝ケミカル製）を使用して、トナーの単位重量当たりの帯電量（μＣ／ｇ）を測定した。
【００９３】
（４）印字濃度
実施例及び比較例で得られたトナーを非磁性一成分現像方式のプリンター（沖データ社製、商品名「マイクロライン１４ｎ」）に入れて、ベタの印字を行なった。印字の環境条件は、低温／低湿（温度１０℃／相対湿度２０％；Ｌ／Ｌ）、常温／常湿（温度２３℃／相対湿度５０％；Ｎ／Ｎ）、及び高温／高湿（温度３５℃／相対湿度８０％；Ｈ／Ｈ）とした。各環境条件下で初期から１，０００枚の連続印字を行なった後、印字濃度を測定した。印字濃度は、マクベス反射濃度計ＲＤ９１４型（Ａ　Ｄｉｖｉｓｉｏｎ　Ｋｏｌｌｍｏｒｇｅｎ　Ｉｎｓｔｒｕｍｅｎｔｓ　Ｃｏｒｐ．製）を用いて、ベタ印字部の印字濃度を測定した。
【００９４】
（５）感光体カブリ
実施例及び比較例で得られたトナーを非磁性一成分現像方式のプリンター（沖データ社製、商品名「マイクロライン１４ｎ」）に入れて、５％濃度で初期から１，０００枚の連続印字を行なった。印字の環境条件は、低温／低湿（温度１０℃／相対湿度２０％；Ｌ／Ｌ）、常温／常湿（温度２３℃／相対湿度５０％；Ｎ／Ｎ）、及び高温／高湿（温度３５℃／相対湿度８０％；Ｈ／Ｈ）とした。１，０００枚の連続印字後、黒ベタで印字し、表面に有機感光体（ＯＰＣ）層が設けられている感光体ドラム上の非画像部分のトナーをメンディングテープで紙に転写し、白色度計（日本電色社製）で反射率の値（Ｒ２）を測定した。一方、メンディングテープだけを紙に貼り、白色度計で反射率の値（Ｒ１）を測定した。両者の差（Ｒ１−Ｒ２）を感光体カブリとした。
【００９５】
（６）耐久カブリ
実施例及び比較例で得られたトナーを非磁性一成分現像方式のプリンター（沖データ社製、商品名「マイクロライン１４ｎ」）に入れて、常温／常湿（温度２３℃／相対湿度５０％；Ｎ／Ｎ）環境下で、５％濃度で初期から連続印字を行なった。１，０００枚印字する毎に、黒ベタで印字し、白色度計（日本電色社製）で測定した転写紙の非画像部のカブリが１５％以下の画質を維持することができる印字枚数を調べた。カブリは、印字後の白色度をＨ２とし、印字前の白色度をＨ１とすると、カブリ＝〔（Ｈ１−Ｈ２）／Ｈ１〕×１００の式から算出することができる。耐久カブリは、以下の基準で評価した。
○：連続印字枚数が１０，０００以上、
△：連続印字枚数が１０，０００未満。
【００９６】
［合成例１］負帯電制御樹脂 （Ａ１） の合成
スチレン８２％、ｎ−ブチルアクリレート１１％、及び２−アクリルアミド−２−メチルプロパンスルホン酸７％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、スルホン酸基含有共重合体を得た。該スルホン酸基含有共重合体の重量平均分子量（Ｍｗ）は、２０，０００であった。該スルホン酸基含有共重合体を負帯電制御樹脂（Ａ１）と呼ぶ。負帯電制御樹脂（Ａ１）の「官能基を持つ構造単位の重量％」は、７％である。
【００９７】
［合成例２］負帯電制御樹脂 （Ａ２） の合成
合成例１と同様にして、スチレン９５．２％と２−アクリルアミド−２−メチルプロパンスルホン酸４．８％とを共重合させて、スルホン酸基含有共重合体を得た。該スルホン酸基含有共重合体の重量平均分子量（Ｍｗ）は、８，０００であった。該スルホン酸基含有共重合体を負帯電制御樹脂（Ａ２）と呼ぶ。負帯電制御樹脂（Ａ２）の「官能基を持つ構造単位の重量％」は、４．８％である。
【００９８】
［合成例３］負帯電制御樹脂 （Ａ３） の合成
合成例１と同様にして、スチレン８６％、ｎ−ブチルアクリレート９％、及び２−アクリルアミド−２−メチルプロパンスルホン酸５％を共重合させて、スルホン酸基含有共重合体を得た。この該スルホン酸基含有共重合体の重量平均分子量（Ｍｗ）は、２０，０００であった。該スルホン酸基含有共重合体を負帯電制御樹脂（Ａ３）と呼ぶ。負帯電制御樹脂（Ａ３）の「官能基を持つ構造単位の重量％」は、５％である。
【００９９】
［実施例１］
１．コア用重合性単量体組成物の調製
スチレン８０．５部、アクリル酸ブチル１９．５部、ジビニルベンゼン０．７部、及びポリメタクリル酸メチルマクロマー（東亜合成化学社製、商品名「ＡＡ６」）からなるコア用重合性単量体に、カーボンブラック（三菱化学社製、商品名「＃２５」７部）、負帯電制御樹脂（Ａ１）１部、ニグロシン染料（正帯電制御剤；オリエント化学工業社製、商品名「ボントロンＮ−０１」）０．４部、ｔ−ドデシルメルカプタン１．７部、及びジペンタエリスリトールヘキサミリステート１０部を加えて、攪拌、混合して、均一分散させてコア用重合性単量体組成物を調製した。
【０１００】
２．水系分散媒体の調製
イオン交換水２５０部に塩化マグネシウム９．８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６．９部を溶解した水溶液を攪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調製した。生成したコロイドの粒径分布を測定した結果、個数平均粒径Ｄ５０（個数粒径分布の５０％累積値）が０．３７μｍ、Ｄ９０（個数粒径分布の９０％累積値）が０．６８μｍであった。粒径分布は、粒径分布測定装置（ＳＡＬＤ２０００Ａ型、島津製作所株式会社製）を用いて測定した。粒径分布の測定条件は、屈折率が１．５５−０．２０ｉ、超音波照射時間が５分間であり、分散媒として１０％食塩水を使用した。
【０１０１】
３．液滴の形成工程
上記で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、及び重合開始剤としてｔ−ブチルパーオキシ−２−エチルヘキサノエート５部を投入し、プロペラ式攪拌機を用いて攪拌混合した。次いで、回転子の回転数１５，０００ｒｐｍで稼働している高速回転剪断型撹拌装置（エバラマイルダー；荏原製作所社製、商品名「ＭＤＮ３０３Ｖ」）に、ポンプを用いて混合液を供給し、コア用重合性単量体組成物の液滴を形成した。
【０１０２】
４．重合工程
コア用重合性単量体組成物の液滴を含有する水分散液を、攪拌翼を装着した反応器に移した。水分散液を加熱し、重合を開始した。反応器のジャケット温度と反応器内の液温とを測定し、カスケード制御法を用いて、反応器内の水分散液の温度が９０℃で一定になるように、ジャケット温度をコントロールした。重合転化率がほぼ１００％に達したときに、サンプリングし、生成した着色重合体粒子（コア粒子）の粒径を測定したところ、７．８１μｍであった。
【０１０３】
次に、コア粒子の水分散液を含有する反応器内に、シェル形成用重合性単量体としてメチルメタクリレート１部を添加した。さらに、２，２′−アゾビス〔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」）０．１部をイオン交換水１０部に溶解した開始剤溶液を反応器内に添加し、３時間重合を継続した。反応を停止して、ｐＨ９．５のコア・シェル型構造を有する重合体粒子の水分散液を得た。
【０１０４】
この水分散液を攪拌しながら、硫酸を添加してｐＨを５以下にすることにより酸洗浄（２５℃、１０分間）を行い、濾過により水を分離した後、新たにイオン交換水５００部を加えて再スラリー化し水洗浄を行った。その後、再度、脱水と水洗浄を数回繰り返し行って、固形分を濾過分離した後、乾燥機にて４５℃で２昼夜乾燥を行い、重合体粒子を回収した。
【０１０５】
５．重合トナー
このようにして得られた重合体粒子（コア・シェル型重合トナー）の体積平均粒径（ｄｖ）は７．８２μｍで、体積平均粒径（ｄｖ）／個数平均粒径（ｄｐ）は１．２０で、球形度（ｒｌ／ｒｓ）は１．１であった。この重合体粒子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、商品名「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て非磁性一成分現像剤（トナー）を調製した。結果を表１に示す。
【０１０６】
［実施例２］
実施例１において、ニグロシン系染料（正帯電制御剤；オリエント化学工業社製、商品名「ボントロンＮ−０１」）の添加量を０．４部から０．２部に変えたこと以外は、実施例１と同様に操作した。結果を表１に示す。
【０１０７】
［比較例１］
実施例１において、ニグロシン染料（正帯電制御剤；オリエント化学工業社製、商品名「ボントロンＮ−０１」）を添加しなかったこと以外は、実施例１と同様に操作した。結果を表１に示す。
【０１０８】
［比較例２］
実施例１において、ニグロシン染料（正帯電制御剤；オリエント化学工業社製、商品名「ボントロンＮ−０１」）の添加量を０．４部から０．６部に変えたこと以外は、実施例１と同様に操作した。結果を表１に示す。
【０１０９】
【表１】

【０１１０】
（脚注）
（１）負帯電制御樹脂（Ａ１）：スルホン酸基含有共重合体
（２）正帯電制御剤（Ｂ１）：ニグロシン染料、オリエント化学工業社製、商品名「ボントロンＮ−０１」
【０１１１】
［比較例３］
実施例１において、負帯電制御樹脂（Ａ１）１部を負帯電制御樹脂（Ａ２）２部に、ニグロシン染料（正帯電制御剤）０．４部を第４級アンモニウム塩化合物（オリエント化学工業社製、商品名「ボントロンＰ−５１）０．５部に、それぞれ代えたこと以外は、実施例１と同様に操作した。結果を表２に示す。
【０１１２】
［比較例４］
実施例１において、負帯電制御樹脂（Ａ１）をアゾ系含クロム錯塩（負帯電制御剤；保土ヶ谷化学工業社製、商品名「スピロンブラックＴＲＨ」）に代え、かつ、ニグロシン染料（正帯電制御剤）の添加量を０．４部から０．２５部に変えたこと以外は、実施例１と同様に操作した。結果を表２に示す。
【０１１３】
［比較例５］
実施例１において、負帯電制御樹脂（Ａ１）１部を負帯電制御樹脂（Ａ３）５部に代えて、かつ、ニグロシン染料（正帯電制御剤）の添加量を０．４部から０．３部に変えたこと以外は、実施例１と同様に操作した。結果を表２に示す。
【０１１４】
【表２】

【０１１５】
（脚注）
（１）負帯電制御樹脂（Ａ２）：スルホン酸基含有共重合体
（２）負帯電制御樹脂（Ａ３）：スルホン酸基含有共重合体
（３）負帯電制御剤（Ａ４）：アゾ系含クロム錯塩顔料（保土ヶ谷化学工業社製、商品名「スピロンブラックＴＲＨ」）
（４）正帯電制御剤（Ｂ１）：ニグロシン染料（オリエント化学工業社製、商品名「ボントロンＮ−０１」
（５）正帯電制御剤（Ｂ２）：第４級アンモニウム塩化合物（オリエント化学工業社製、商品名「ボントロンＰ−５１」）
【発明の効果】
本発明によれば、環境変動による帯電量の変化が小さく、印字濃度が高く、高温／高湿環境下での感光体カブリが少なく、さらには耐久時のカブリが少なく、高速プリンターに対応することができる負帯電性の静電荷像現像用トナーが提供される。本発明の負帯電性トナーは、高速プリンターなどに適用することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image, and more specifically, a change in the amount of charge due to environmental fluctuations is small, a print density is high, and a photoreceptor fog under high temperature / humidity environment is small. The present invention relates to a negatively chargeable toner for developing an electrostatic image, which has less fog and can be used for a high-speed printer.
[0002]
[Prior art]
In an electrophotographic image forming apparatus such as an electrophotographic copying machine or a laser beam printer, an electrostatic latent image formed on a photoconductor is formed by dispersing additives such as a colorant and a charge control agent in a binder resin. The toner is developed with an electrostatic image developing toner composed of colored particles (hereinafter, may be simply referred to as “toner”).
[0003]
In general, toner is roughly classified into pulverized toner and polymerized toner. The pulverized toner can be obtained by melt-kneading additives, such as a colorant and a charge controlling agent, with a binder resin synthesized in advance, pulverizing and classifying. Polymerized toner, after dispersing a polymerizable monomer composition containing a polymerizable monomer, a colorant, a charge control agent, and the like as fine droplets in an aqueous dispersion medium containing a dispersion stabilizer, It can be obtained by polymerization.
[0004]
The electrostatic latent image formed on the photoconductor is a positively charged or negatively charged electrostatic image. To develop an electrostatic latent image on a photoreceptor with toner, it is necessary to impart sufficient chargeability to the toner. Therefore, the toner contains various charge control agents having positive chargeability or negative chargeability. Representative examples of the negative charge control agent include metal-containing complex dyes such as an azo-based chromium-containing complex dye and an azo-based iron-containing complex dye. Examples of the positive charge control agent include a nigrosine dye and a quaternary ammonium salt compound.
[0005]
However, when these charge control agents are used, problems such as generation of fog and reduction in image density are likely to occur. Further, since these charge control agents have strong hydrophilicity, the stability of fine droplets composed of the polymerizable monomer composition in an aqueous dispersion medium is likely to be impaired during the production of a polymerized toner.
[0006]
Thus, various proposals have been made for a resin-type charge control agent that replaces the conventional charge control agent. For example, Japanese Unexamined Patent Publication (Kokai) No. 3-175456 discloses a positively chargeable charge control resin (i.e., "positive charge control resin") comprising a copolymer of a styrene monomer and an acrylate ester containing a quaternary ammonium salt group. ) Is disclosed. JP-A-1-217464, JP-A-3-15858 and JP-A-3-243954 disclose a negatively chargeable charge control resin comprising a sulfonic acid group-containing copolymer (that is, a negative charge control resin). Polymerized toners containing a "charge control resin") are disclosed.
[0007]
When such a positively or negatively chargeable charge control resin is used, a relatively high quality image having good toner chargeability and no fog can be obtained at the beginning of printing. However, when continuous printing is performed in a low-temperature and low-humidity environment, the toner containing the charge control resin increases the charge of the toner, and the print density is reduced at an early stage. Further, the toner containing the charge control resin has a large image quality dependency on the environment, and it is difficult to maintain a sufficiently high image quality especially in a high temperature and high humidity environment. Further, when a negative charge control resin is used, toner scattering is likely to occur due to continuous printing.
[0008]
On the other hand, in order to improve the function of the charge control agent, a method in which a positive charge control agent and a negative charge control agent are used in combination has been proposed. For example, JP-A-4-195166 discloses a negative charge control resin comprising a copolymer containing an acrylamide-based monomer having a sulfonic acid group-containing hydrocarbon group, and a charge control action having a polarity opposite to that of the negative charge control resin. There has been proposed a toner in which a charge control agent comprising a quaternary ammonium salt compound is used in combination. This publication reports that when a negative charge control resin and a quaternary ammonium salt compound are used in combination, the toner charge distribution becomes sharper when the toner is used as a two-component developer. However, when the negative charge control resin and the quaternary ammonium salt compound are used in combination, a sufficient printing density cannot be obtained, and the fog of the photoreceptor under a high temperature and high humidity environment becomes remarkable.
[0009]
JP-A-6-161156 discloses a method for producing a polymerized toner using a mixture of an azo metal-containing salt dye as a negative charge control agent and a nigrosine dye as a positive charge control agent. The publication describes that the combined use of these charge control agents can provide a polymerized toner having a small particle diameter in which the amount of charge is adjusted to an appropriate value while preventing undesirable emulsion polymerization. However, when an azo-based metal-containing salt pigment and a nigrosine dye are used in combination as a charge control agent, it is difficult to obtain a sufficient printing density, and the photoreceptor fog in a high-temperature and high-humidity environment increases, resulting in durability fog. Is also unsatisfactory.
[0010]
Japanese Patent Application Laid-Open No. 2000-347445 discloses that, by using a positive charge control resin and a negative charge control resin in combination, the particle size distribution is sharp, the fluidity and the storage stability are excellent, the environment dependence of the charge amount is small, It is disclosed that a toner with less deterioration in image quality due to continuous printing can be obtained. The publication discloses that when a positive charge control resin or a negative charge control resin is used alone, or when these charge control resins are used in combination with a charge control agent such as a nigrosine dye or an azo metal-containing salt pigment, It is shown that the image quality is largely dependent on the environment and only unsatisfactory results can be obtained.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to respond to a high-speed printer with a small change in the amount of charge due to environmental fluctuations, a high print density, less fogging of the photoreceptor in a high-temperature / high-humidity environment, and a less fog during durability. It is an object of the present invention to provide a negatively chargeable toner for developing an electrostatic image that can be used.
[0012]
The present inventor has conducted extensive studies to achieve the above object, and as a result, used a negative charge control resin and a nigrosine dye in combination as a charge control agent, and a structural unit having a negative chargeable functional group in the negative charge control resin. When the content, the content of the negative charge control resin with respect to 100 parts by weight of the binder resin, and the content of the nigrosine dye with respect to 100 parts by weight of the binder resin satisfy a specific relational expression, the object can be achieved. I found it.
[0013]
In general, the combined use of a charge control resin and a normal charge control agent is negatively controlled in Japanese Patent Application Laid-Open No. 2000-347445, from the viewpoint of the effect, and the negative charge control resin and the nigrosine dye are used in combination. It is surprising that a toner having excellent action effects can be obtained by the combined use in the above-mentioned specific selected range. The present invention has been completed based on these findings.
[0014]
[Means for Solving the Problems]
Thus, according to the present invention, at least a binder resin, a colorant, and a toner for electrostatic image development containing a charge control agent,
(1) The charge control agent contains a negative charge control resin (A) composed of a polymer having a structural unit having a negative charge functional group and a nigrosine dye (B), and
(2) The content of the structural unit having a negative charge functional group in the negative charge control resin (A) is defined as a (% by weight), and the content of the negative charge control resin (A) relative to 100 parts by weight of the binder resin is defined as b (parts by weight) and the content of the nigrosine dye (B) relative to 100 parts by weight of the binder resin is c (parts by weight).
2.0 ≦ (c × 100) / (a × b) ≦ 7.0 (I)
Satisfy
A negatively chargeable toner for developing an electrostatic image is provided.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
1.Negative charge control resin
The negative charge control resin (A) used in the present invention is a polymer having a functional group that provides negative charge (that is, a negative charge functional group). The negative charge control resin is preferably a copolymer of a vinyl monomer having a negative charge functional group and another vinyl monomer copolymerizable therewith. May be a polymer into which the functional group is introduced. From the viewpoint of compatibility with the binder resin, a copolymer containing a monomer unit having a negatively chargeable functional group, a vinyl aromatic hydrocarbon monomer unit and a (meth) acrylate monomer unit is particularly preferable. preferable. When the negative charge control resin is compatible with the binder resin in the toner, the chargeability of the toner becomes uniform. The negative charge control resin is preferably soluble in the styrene monomer from the viewpoint of dispersibility in the polymerizable monomer composition during production of the polymerized toner.
[0016]
Examples of the negatively-chargeable functional group include an acid anhydride group, a carboxyl group, a sulfuric acid residue, a sulfonic acid group, a phosphoric acid group, and salts thereof. For the production of a non-magnetic one-component developer toner, a sulfonic acid group or a sulfuric acid residue is preferable, and a sulfonic acid group is particularly preferable.
[0017]
The weight average molecular weight of the negative charge control resin is generally 1,000 to 100,000, preferably 2,000 to 50,000, and more preferably 3,000 to 30,000. If the weight average molecular weight of the negative charge control resin is too large, handling during the production of the toner may be poor, or the size of the droplets of the polymerizable monomer composition containing the same may vary, so that the particle size distribution may be reduced. It becomes difficult to obtain sharp toner. If the weight average molecular weight of the negative charge control resin is too small, the dispersibility of the colorant will decrease, and the storage stability will decrease. The weight average molecular weight of the negative charge control resin is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography using tetrahydrofuran.
[0018]
The content of the structural unit derived from the monomer having a negative chargeable functional group in the negative charge control resin is usually 0.5 to 15% by weight, preferably 1 to 10% by weight, more preferably 2 to 9% by weight. %. If the content of the structural unit having a negatively-chargeable functional group is too small, the charging ability and the charging suppression ability tend to decrease. If the number of the structural units is too large, the charge amount of the negatively charged toner becomes too high, and the print density tends to be low.
[0019]
As the negative charge control resin (A), a polymer having a sulfonic acid group is preferred from the viewpoints of dispersion stability of droplets of the polymerizable monomer composition during production of the polymerized toner, charge controllability of the toner, image quality and the like. A copolymer having a structural unit derived from a sulfonic acid group-containing (meth) acrylate monomer and a structural unit derived from another polymerizable monomer is more preferable, and a sulfonic acid group-containing (meth) acrylamide monomer is more preferable. Particularly preferred is a copolymer comprising a structural unit derived from a vinyl aromatic hydrocarbon monomer and a structural unit derived from a (meth) acrylate monomer.
[0020]
Such copolymers are prepared by emulsion polymerization and dispersion polymerization of a sulfonic acid group-containing (meth) acrylamide monomer, a vinyl aromatic hydrocarbon monomer, and a (meth) acrylate monomer using a polymerization initiator. , Suspension polymerization, or solution polymerization. Among them, the solution polymerization method is preferable in that a copolymer having a target weight average molecular weight is easily obtained. Examples of the polymerization initiator include an azo initiator and an organic peroxide. The polymerization temperature is usually from 50 to 200 ° C. The polymerization time is usually 0.5 to 20 hours.
[0021]
Examples of the vinyl aromatic hydrocarbon monomer used for producing the negative charge control resin include styrene and α-methylstyrene. Examples of the (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and n-hexyl (meth) acrylate. No.
[0022]
Examples of the sulfonic acid group-containing (meth) acrylamide monomer include 2-acrylamide-1-methylpropanesulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-acrylamide-n-butanesulfonic acid, and 2-acrylamide- n-hexanesulfonic acid, 2-acrylamide-n-octanesulfonic acid, 2-acrylamide-n-dodecanesulfonic acid, 2-acrylamide-n-tetradecanesulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-acrylamide -2-phenylpropanesulfonic acid, 2-acrylamido-2,2,4-trimethylpentanesulfonic acid, 2-acrylamido-2-methylphenylethanesulfonic acid, 2-acrylamido-2- (4-chlorophenyl) propanesulfonic acid, 3- Acrylamidoalkylsulfonic acids such as acrylamido-3-methylbutanesulfonic acid, 2-methacrylamido-n-decanesulfonic acid and 4-methacrylamidobenzenesulfonic acid; acrylamidocarboxyalkyl such as 2-acrylamido-2-carboxymethylpropanesulfonic acid Sulfonic acids; acrylamide-heterocyclic group-containing alkylsulfonic acids such as 2-acrylamide-2- (2-pyridine) propanesulfonic acid; and metal salts thereof. These sulfonic acid group-containing (meth) acrylamide monomers may be used alone or in combination of two or more.
[0023]
The usage ratio of each monomer can be arbitrarily selected, but the ratio of the structural unit derived from the vinyl aromatic hydrocarbon monomer in the copolymer is usually 70 to 98% by weight, preferably 75 to 98% by weight. It is 95% by weight, more preferably 80 to 90% by weight. The ratio of the structural unit derived from the (meth) acrylate monomer is usually 1.5 to 29.5% by weight, preferably 4 to 24% by weight, and more preferably 8 to 18%. The structural unit derived from the sulfonic acid group-containing (meth) acrylamide monomer is usually 0.5 to 20% by weight, preferably 1 to 10% by weight, more preferably 2 to 9% by weight.
[0024]
2.Nigrosine dye
In the present invention, as a charge control agent used in combination with the negative charge control resin (A), a nigrosine dye (B) which is a positive charge control agent is selected from known ones and used. Nigrosine dye has the following formula
[0025]
Embedded image

[0026]
(Where Z⁻Is an anionic species such as sulfonic acid. )
The compound represented by is a typical one, but may have various substituents. Commercially available nigrosine dyes include Bontron N-01 and Bontron N-07 manufactured by Orient Chemical Industries.
[0027]
3.Amount of negative charge control resin and nigrosine dye used
In the present invention, the negative charge control resin and the positive charge control agent nigrosine are used in combination, but in order to obtain a toner having negative chargeability and excellent properties, the negative charge control resin has a negative chargeable functional group. It is necessary that the content of the structural unit, the content of the negative charge control resin with respect to 100 parts by weight of the binder resin, and the content of the nigrosine dye with respect to 100 parts by weight of the binder resin satisfy a specific relational expression.
[0028]
More specifically, the content of the structural unit having a negative charge functional group in the negative charge control resin (A) is defined as a (% by weight), and the content of the negative charge control resin (A) relative to 100 parts by weight of the binder resin is included. When the amount is b (parts by weight) and the content of the nigrosine dye (B) relative to 100 parts by weight of the binder resin is c (parts by weight), these are represented by the following relational formula (I):
2.0 ≦ (c × 100) / (a × b) ≦ 7.0 (I)
It is necessary to satisfy
[0029]
The a weight% of the content of the structural unit having a negatively chargeable functional group in the negatively chargeable control resin (A) is defined as “a negative%” used when synthesizing a polymer having a structural unit having a negatively chargeable functional group. The copolymerization ratio (% by weight) of "a monomer having a chargeable functional group" can be used. In the case of a polymerized toner, the content b of the negative charge control resin and the content c of the nigrosine dye are 100 parts by weight of the binder resin with respect to 100 parts by weight of the binder resin. Parts by weight) can be used.
[0030]
Even if the negative charge control resin (A) and the nigrosine dye (B) are used in combination, the object cannot be achieved unless a, b, and c satisfy the relational expression (I). For example, when the calculated value of (c × 100) / (a × b) is as small as less than 2.0, low temperature / low humidity (L / L), normal temperature / normal humidity (N / N), and high temperature / high The print density is lowered under any of the environmental conditions of humidity (H / H), and the fog of the photoreceptor under the condition of high temperature / high humidity (H / H) becomes remarkable. On the other hand, when the calculated value of (c × 100) / (a × b) exceeds 7.0 and becomes large, the print density becomes low under any environmental conditions, and the photoreceptor fog under high temperature / high humidity conditions And durability fog increases.
[0031]
When a positive charge control agent other than the nigrosine dye is used as the positive charge control agent, the print density becomes low under any environmental conditions even when the above-mentioned relational formula (I) is satisfied, and the high temperature / high Photoreceptor fogging under wet conditions becomes remarkable. When a normal negative charge control agent and a nigrosine dye are used in combination, the print density becomes low under any environmental conditions, and the photoreceptor fog under high temperature / high humidity conditions becomes remarkable, and furthermore, the durability fog is reduced. More.
[0032]
In the present invention, by using a negative charge control resin and a nigrosine dye together within a specific range, the particle size distribution is sharp, the fluidity and the preservability are excellent, and any of low temperature / low humidity and high temperature / high humidity can be used. In this environment, the toner for developing an electrostatic charge image can be obtained in which the chargeability does not change much and the deterioration in image quality is suppressed even when continuous printing is performed.
[0033]
The usage ratio of the negative charge control resin (A) is usually 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the binder resin. The use ratio of the nigrosine dye (B) is usually 0.05 to 0.5 part by weight, preferably 0.1 to 0.4 part by weight, based on 100 parts by weight of the binder resin. The parts by weight of the binder resin can be replaced by the parts by weight of the polymerizable monomer used to form the binder resin.
[0034]
The total use ratio of the negative charge control resin (A) and the nigrosine dye (B) is preferably 0.15 to 20 parts by weight, more preferably 0.3 to 10 parts by weight, based on 100 parts by weight of the binder resin. And particularly preferably 1 to 5 parts by weight. The use ratio (A: B) of the negative charge control resin (A) and the nigrosine dye (B) is preferably 10: 1 to 10: 5 (weight ratio).
[0035]
4.Toner for developing electrostatic images
The toner of the present invention may be colored particles containing at least a binder resin, a colorant, and a charge control agent (the above-described negative charge control resin and nigrosine dye), and is not particularly limited by a manufacturing method. The toner of the present invention can be obtained by, for example, a pulverization method or a polymerization method. Further, a capsule toner having a core-shell type structure in which a resin coating layer is formed on the surface of a colored particle may be used. The toner of the present invention is preferably a polymerized toner obtained by a polymerization method.
[0036]
The polymerized toner can be obtained by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a charge control agent in an aqueous dispersion medium containing a dispersion stabilizer. The polymer formed by polymerizing the polymerizable monomer becomes the binder resin. As the aqueous dispersion medium, ion-exchanged water or the like can be used, and if desired, a hydrophilic solvent such as alcohol may be added.
[0037]
Polymerized toner having a core-shell type structure is obtained by polymerizing a monomer composition containing at least a polymerizable monomer, a colorant, and a charge control agent in an aqueous dispersion medium containing a dispersion stabilizer. The obtained colored particles can be used as core particles, and can be obtained by polymerizing a polymerizable monomer for shell in the presence of the core particles. The polymer layer formed by polymerizing the polymerizable monomer for shell becomes a resin coating layer (shell).
[0038]
If necessary, the polymerizable monomer composition may contain various additives such as a release agent, a crosslinkable monomer, a macromonomer, a molecular weight modifier, a lubricant, and a dispersion aid.
[0039]
(1) Polymerizable monomer
Examples of the polymerizable monomer for forming the binder resin include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized and becomes a binder resin component in the polymer particles.
[0040]
Specific examples of the monovinyl monomer include aromatic vinyl monomers such as styrene, vinyltoluene, and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobonyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acrylamide (Meth) acrylic acid derivatives; monoolefin monomers such as ethylene, propylene and butylene; and the like.
[0041]
Monovinyl monomers may be used alone or in combination of a plurality of monomers. Among these monovinyl monomers, an aromatic vinyl monomer alone, a combination of an aromatic vinyl monomer and a derivative of (meth) acrylic acid, and the like are preferably used.
[0042]
When a crosslinkable monomer and a crosslinkable polymer are used together with the monovinyl monomer, hot offset is effectively improved. The crosslinkable monomer is a monomer having two or more vinyl groups. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic esters such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and 1,4-butanediol diacrylate; , N-divinylaniline, compounds having two vinyl groups such as divinyl ether, and compounds having three or more vinyl groups such as pentaerythritol triallyl ether and trimethylolpropane triacrylate.
[0043]
The crosslinkable polymer is a polymer having two or more vinyl groups in the polymer, and specifically, a polymer having two or more hydroxyl groups in a molecule, such as polyethylene, polypropylene, polyester, or polyethylene glycol. And an ester obtained by subjecting an unsaturated carboxylic acid monomer such as acrylic acid or methacrylic acid to a condensation reaction.
[0044]
These crosslinkable monomers and crosslinkable polymers can be used alone or in combination of two or more. The amount used is usually 10 parts by weight or less, preferably 0.01 to 7 parts by weight, more preferably 0.05 to 5 parts by weight, particularly preferably 0.1 to 3 parts by weight, per 100 parts by weight of the monovinyl monomer. Parts by weight.
[0045]
It is preferable to use a macromonomer together with the monovinyl monomer, because the balance between the storage property at a high temperature 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 an oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000. When the number average molecular weight is within the above range, the fixability and the preservability can be maintained without impairing the meltability of the macromonomer, which is preferable.
[0046]
Examples of the polymerizable carbon-carbon unsaturated double bond at the terminal of the macromonomer molecular chain include an acryloyl group and a methacryloyl group, and a methacryloyl group is preferable from the viewpoint of easy copolymerization. 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.
[0047]
Specific examples of the macromonomer include styrene, a styrene derivative, a methacrylate, an acrylate, acrylonitrile, a polymer obtained by polymerizing two or more kinds of methacrylonitrile, etc., and a macromonomer having a polysiloxane skeleton. Among them, hydrophilic ones are preferable, and a polymer obtained by polymerizing methacrylic acid ester or acrylic acid ester alone or in combination thereof is particularly preferable.
[0048]
When a macromonomer is used, it is used in an amount of 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, per 100 parts by weight of the monovinyl monomer. Parts by weight. It is preferable that the amount of the macromonomer be within the above range, because the storage stability of the toner is maintained and the fixability is improved.
[0049]
(2) Colorant
As the colorant, various pigments and dyes used in the field of toner such as carbon black and titanium white can be used. Examples of the black colorant include carbon black, nigrosine-based dyes and pigments; and magnetic particles such as cobalt, nickel, triiron tetroxide, iron manganese oxide, iron zinc oxide, and iron nickel oxide. In the case of using carbon black, it is preferable to use a carbon black having a primary particle size of 20 to 40 nm because good image quality can be obtained and the safety of the toner to the environment is enhanced. As a colorant for a color toner, a yellow colorant, a magenta colorant, a cyan colorant, and the like can be used.
[0050]
As the yellow colorant, a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, an allylamide compound, or the like is used. Specifically, for example, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 90, 93, 95, 95, 97, 109, 110, 111, 120, 128, 129, 138, 147, 155, 168, 180, 181 and the like. In addition, Nephtol Yellow S, Hansa Yellow G, C.I. I. Bat yellow and the like.
[0051]
Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, perylene compounds and the like. Specifically, for example, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48, 48: 2, 48: 3, 48: 4, 57, 57: 1, 58, 60, 63, 64, 68, 81, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 163, 166, 169, 170, 177, 184, 185, 187, 202, 206, 207, 209, 220, 251 and 254. In addition, C.I. I. Pigment Violet 19 and the like.
[0052]
Examples of the cyan coloring agent include a copper phthalocyanine compound and a derivative thereof, an anthraquinone compound, and a basic dye lake compound. Specifically, for example, C.I. I. Pigment Blue 1, 2, 3, 6, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66 and the like. In addition, phthalocyanine blue, C.I. I. Bat blue, C.I. I. Acid blue and the like.
[0053]
These colorants can be used alone or in combination of two or more. The coloring agent is used in a proportion of usually 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0054]
(3) Lubricant and dispersion aid
Lubricants such as fatty acids such as oleic acid and stearic acid, fatty acid metal salts composed of fatty acids and metals such as Na, K, Ca, Mg and Zn; for the purpose of uniformly dispersing the colorant in the toner particles; Alternatively, a dispersion aid such as a titanium-based coupling agent; and the like may be used. Such a lubricant or dispersant is generally used at a ratio of about 1/1000 to 1/1 based on the weight of the colorant.
[0055]
(4) Charge control agent
In the present invention, as the charge control agent, the negative charge control resin and the nigrosine dye are used in combination, but within a small amount that does not impair the object of the present invention, a charge control agent or a charge control resin other than these is contained. May be.
[0056]
(5) Release agent
A release agent can be contained in the polymerizable monomer composition for the purpose of preventing offset or improving the releasability during hot roll fixing. 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, petrolactam, etc. And waxes modified therefrom; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, and dipentaerythritol hexamyristate; These can be used alone or in combination of two or more.
[0057]
Among these, synthetic waxes, end-modified polyolefin waxes, petroleum waxes, polyfunctional ester compounds, and the like are preferable. Among the polyfunctional ester compounds, in the DSC curve measured by the differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is in the range of 30 to 200 ° C, preferably 40 to 160 ° C, more preferably 50 to 120 ° C. It is particularly preferable to use a polyfunctional ester compound such as pentaerythritol ester or dipentaerythritol ester having the endothermic peak temperature in the range of 50 to 80 ° C. in view of the balance between the fixing property and the peeling property of the toner.
[0058]
Among polyfunctional ester compounds such as pentaerythritol ester having an endothermic peak temperature in the range of 30 to 200 ° C. and dipentaerythritol ester having the endothermic peak temperature in the range of 50 to 80 ° C., the molecular weight is 1, It is more preferable that the amount is not less than 000 and not less than 5 parts by weight at 25 ° C. with respect to 100 parts by weight of styrene, and the acid value is not more than 10 mg / KOH, because it has a remarkable effect on lowering the fixing temperature of the toner. Endothermic peak temperature is the value measured by ASTM D3418-82.
[0059]
The ratio of the release agent used is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the binder resin (polymerizable monomer). Parts by weight.
[0060]
(6) polymerization initiator
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. An azo compound of the formula: di-t-butyl peroxide, dicumyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate , T-butyl peroxypivalate, di-isopropylperoxydicarbonate, di-t-butylperoxyisophthalate, 1, And peroxides such as', 3,3'-tetramethylbutylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, etc. These polymerization initiators and reducing agents Redox initiators in combination with can be used.
[0061]
Among these, it is preferable to select an oil-soluble polymerization initiator soluble in the polymerizable monomer to be used, and if necessary, a water-soluble polymerization initiator can be used in combination therewith. The polymerization initiator is used in an amount of usually 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the polymerizable monomer. .
[0062]
The polymerization initiator can be added in advance to the polymerizable monomer composition, but in the case of suspension polymerization, after the completion of the droplet formation step or in the middle of the polymerization reaction, in the case of emulsion polymerization, It can also be added directly to the emulsion after the emulsification step or during the polymerization reaction.
[0063]
(7) Molecular weight regulator
At the time of polymerization, it is preferable to add a molecular weight modifier. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-pentamethylheptane-4-thiol; carbon tetrachloride, Halogenated hydrocarbons such as carbon bromide; and the like. The molecular weight modifier can be added before the start of the polymerization or during the polymerization. The molecular weight modifier is used in an amount of usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0064]
(8) Dispersion stabilizer
The dispersion stabilizer used in the present invention preferably contains a colloid of a poorly water-soluble metal compound. Examples of poorly water-soluble metal compounds include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; and metal oxides such as aluminum oxide and titanium oxide. Metal hydroxides of aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; and the like. Among them, a dispersant containing a colloid of a poorly water-soluble metal hydroxide is preferable because it can narrow the particle size distribution of the polymer particles and improves the sharpness of an image.
[0065]
The dispersant containing the colloid of the poorly water-soluble metal compound is not limited by the method of production, but the poorly water-soluble metal hydroxide obtained by adjusting the pH of the aqueous solution of the water-soluble polyvalent metal compound to 7 or more. In particular, a colloid of a poorly water-soluble metal hydroxide formed by a reaction of a water-soluble polyvalent metal compound with an alkali metal hydroxide in an aqueous phase is preferably used. The colloid of the poorly water-soluble metal compound has a number particle size distribution D50 (50% cumulative value of number particle size distribution) of 0.5 μm or less and a D90 (90% cumulative value of number particle size distribution) of 1 μm or less. Is preferred.
[0066]
The dispersion stabilizer is used usually in a ratio of 0.1 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer. If this ratio is too small, it is difficult to obtain sufficient polymerization stability, and polymer aggregates are likely to be generated. Conversely, if this ratio is too large, the viscosity of the aqueous solution will increase and the polymerization stability will decrease.
[0067]
In the present invention, if necessary, a dispersant containing a water-soluble polymer can be used. Examples of the water-soluble polymer include polyvinyl alcohol, methyl cellulose, and gelatin. In the present invention, it is not necessary to use a surfactant, but it can be used for stably performing suspension polymerization as long as the environment of the charging characteristics does not become large.
[0068]
(9) Method for producing polymerized toner
1. Polymerization method
The polymerized toner is a polymer particle containing a binder resin formed by polymerization of a polymerizable monomer, a colorant, a charge control agent, and the like. This polymerized toner can be obtained, for example, by the following steps. A polymerizable monomer, a colorant, a charge controlling agent, other additives, and the like are mixed using a mixer, and if necessary, wet pulverized using a media-type wet pulverizer (for example, a bead mill). A polymerizable monomer composition is obtained. The polymerizable monomer composition is dispersed in an aqueous dispersion medium containing a dispersion stabilizer, stirred, and uniformly dispersed in the monomer composition (primary droplets having a volume average particle diameter of about 50 to 1000 μm). ) Is formed. The time for adding the polymerization initiator may be after the droplet size becomes uniform in the aqueous dispersion medium in order to avoid early polymerization.
[0069]
A polymerization initiator is added to a suspension in which droplets of the monomer composition are dispersed in an aqueous dispersion medium, and the mixture is further mixed with a high-speed rotary shearing stirrer. Stir until small particle size close to particles. A suspension containing the thus formed droplets having a small particle diameter (secondary droplets having a volume average particle diameter of about 1 to 12 μm) is charged into a polymerization reactor. Performs suspension polymerization at a temperature of 35 to 95C. If the polymerization temperature is too low, a polymerization initiator having a high catalytic activity must be used, which makes it difficult to control the polymerization reaction. If the polymerization temperature is too high, when an additive that melts at a low temperature is included, it may bleed on the toner surface and the storage stability may be deteriorated.
[0070]
The volume average particle size and the particle size distribution of the fine droplets of the polymerizable monomer composition affect the volume average particle size and the particle size distribution of the polymerized toner. If the particle size of the droplet is too large, the generated polymerized toner particles become large, and the resolution of the image decreases. If the particle size distribution of the droplets is wide, a variation in fixing temperature occurs, which causes problems such as fogging and toner filming. Therefore, it is desirable that the liquid droplets are granulated so as to be reduced to a predetermined size of the toner particles.
[0071]
The volume average particle diameter of the droplets of the polymerizable monomer composition is usually 1 to 12 μm, preferably 2 to 10 μm, more preferably 3 to 8 μm. The particle size distribution (volume average particle size / number average particle size) of the droplets of the polymerizable monomer composition is usually 1 to 3, preferably 1 to 2.5, and more preferably 1 to 2. Particularly when granulating fine droplets, an aqueous dispersion medium containing a monomer composition is provided in a gap between a high-speed rotating rotor and a stator surrounding the rotor and having small holes or comb teeth. Is suitable.
[0072]
One or more of the above-mentioned monovinyl monomers are selected as the polymerizable monomer. To lower the fixing temperature of the toner, the glass transition temperature (Tg) is usually 80 ° C or lower, preferably 40 to 80 ° C. It is preferable to select a monomer or a combination of monomers capable of forming a polymer at a temperature of about 50 to 70 ° C. In the present invention, the Tg of the copolymer constituting the binder resin is a calculated value (calculated Tg) calculated according to the type of the monomer used and the usage ratio.
[0073]
By the suspension polymerization, colored polymer particles containing a binder resin produced by the polymerization of the polymerizable monomer, a colorant, a charge control agent and the like are produced. In the present invention, the colored polymer particles can be used as a toner, but are obtained by suspension polymerization for the purpose of improving the storage stability (blocking resistance), low-temperature fixability, and meltability at the time of fixing of the toner. A polymer layer can be further formed on the colored polymer particles thus obtained to obtain a capsule toner having a core-shell type structure.
[0074]
2. Method for producing toner having core-shell structure
The method for forming the core-shell type structure is not particularly limited, but in the case of a polymerized toner, the colored polymer particles are used as core particles, and the polymerizable monomer for shell is polymerized in the presence of the core particles. A method of forming a polymer layer (shell) on the surface of the core particles is preferred. When a polymerizable monomer having a higher Tg than the polymer component constituting the core particle is used as the polymerizable monomer for the shell, the storage stability of the toner can be improved.
[0075]
On the other hand, by setting the Tg of the polymer component constituting the core particles low, it is possible to lower the fixing temperature of the polymerized toner and to improve the melting characteristics, thereby making it possible to improve the printing (copying, printing, etc.). Higher speed, full color, OHP (overhead projector) transparency, and the like can be suitably handled.
[0076]
As the polymerizable monomer for forming the core and the shell, a preferable monomer can be appropriately selected from the above-mentioned monovinyl monomers. The weight ratio of the polymerizable monomer for core to the polymerizable monomer for shell is usually 40/60 to 99.9 / 0.1, preferably 60/40 to 99.7 / 0.3, more preferably. Is 80/20 to 99.5 / 0.5. If the proportion of the polymerizable monomer for shell is too small, the effect of improving the storage stability is small, and if it is too large, the effect of reducing the fixing temperature is small.
[0077]
The Tg of the polymer formed by the polymerizable monomer for the shell is usually more than 50 ° C and 120 ° C or less, preferably more than 60 ° C and 110 ° C or less, more preferably more than 80 ° C and 105 ° C or less. The difference in Tg between the polymer formed from the polymerizable monomer for the core and the polymer formed from the polymerizable monomer for the shell is preferably at least 10 ° C, more preferably at least 20 ° C, particularly Preferably it is 30 ° C. or higher. In many cases, from the viewpoint of the balance between the fixing temperature and the storage stability, the polymerizable monomer for the core is selected from those capable of forming a polymer having a Tg of usually 60 ° C or lower, preferably 40 to 60 ° C. Is preferred. On the other hand, as the polymerizable monomer for shell, it is preferable to use monomers that form a polymer having a Tg of more than 80 ° C., such as styrene and methyl methacrylate, alone or in combination of two or more. .
[0078]
The polymerizable monomer for shell is preferably added to the polymerization reaction system as droplets smaller than the average particle size of the core particles. If the particle size of the droplets of the polymerizable monomer for shell is too large, it becomes difficult to form a polymer layer uniformly around the core particles. In order to make the polymerizable monomer for shell into small droplets, a mixture of the polymerizable monomer for shell and an aqueous dispersion medium is subjected to fine dispersion treatment using, for example, an ultrasonic emulsifier, and is obtained. What is necessary is just to add the obtained dispersion liquid to a reaction system. When the polymerizable monomer for shell is a relatively water-soluble monomer (for example, methyl methacrylate) having a solubility in water at 20 ° C. of 0.1% by weight or more, the surface of the core particles has a relatively high solubility. It is not necessary to perform the fine dispersion treatment because the transition is easy, but it is preferable to perform the fine dispersion treatment to form a uniform shell. When the polymerizable monomer for the shell is a monomer (eg, styrene) having a solubility in water at 20 ° C. of less than 0.1% by weight, a fine dispersion treatment is performed, or the solubility in water at 20 ° C. It is preferable to add 5% by weight or more of an organic solvent (for example, alcohols) to the reaction system to facilitate the transfer to the surface of the core particles.
[0079]
A charge control agent can be added to the polymerizable monomer for shell. As the charge control agent, those similar to those used in the production of the core particles described above are preferable, and when used, usually 0.01 to 10 parts by weight based on 100 parts by weight of the polymerizable monomer for shell. Parts, preferably 0.1 to 5 parts by weight.
[0080]
To produce a core-shell type polymerized toner, a polymerizable monomer for shell or an aqueous dispersion thereof is added to a suspension containing core particles all at once, or continuously or intermittently. . It is preferable to add a water-soluble radical initiator when adding the polymerizable monomer for shell in order to form a shell. If the water-soluble polymerization initiator is added during the addition of the shell-forming polymerizable monomer, the water-soluble polymerization initiator enters the vicinity of the outer surface of the core particle to which the shell-forming polymerizable monomer has migrated, and It is considered that a polymer (shell) is easily formed in the polymer.
[0081]
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) ethyl] propionamide] and the like can be mentioned. The amount of the water-soluble polymerization initiator is usually 0.1 to 50% by weight, preferably 1 to 20% by weight, based on 100 parts by weight of the polymerizable monomer for shell.
[0082]
The average thickness of the shell is usually 0.001 to 1.0 μm, preferably 0.003 to 0.5 μm, and more preferably 0.005 to 0.2 μm. If the shell thickness is too large, the fixability decreases, and if it is too small, the storage stability decreases. When the core particle diameter of the polymerization method toner and the shell thickness can be observed by an electron microscope, it can be obtained by directly measuring the size and shell thickness of particles randomly selected from the observation photograph, When it is difficult to observe the core and the shell with a microscope, it can be calculated from the particle size of the core particles and the amount of the polymerizable monomer forming the shell.
[0083]
(10) Toner
The volume average particle diameter of the toner for developing an electrostatic image (including the capsule toner having a core-shell type structure) of the present invention is usually 1 to 12 μm, preferably 2 to 11 μm, more preferably 3 to 10 μm. In order to obtain a high-definition image by increasing the resolution, it is particularly desirable to reduce the volume average particle diameter of the toner to preferably 2 to 9 μm, more preferably 3 to 8 μm, and particularly preferably 3 to 7 μm.
[0084]
The particle size distribution represented by the volume average particle size (dv) / number average particle size (dp) of the toner of the present invention is usually 1.7 or less, preferably 1.5 or less, more preferably 1.3 or less. is there. If the volume average particle size of the toner is too large, the resolution tends to be reduced. If the particle size distribution of the toner is large, the ratio of the toner having a large particle size increases, and the resolution tends to decrease.
[0085]
The toner of the present invention has a sphericity expressed by a ratio (dl / ds) of a major axis (dl) to a minor axis (ds) of preferably 1 to 1.3, more preferably 1 to 1.2. It is preferably spherical. When a substantially spherical toner is used as the non-magnetic one-component developer, the transfer efficiency of the toner image on the photoconductor to the transfer material is improved. Such a spherical toner can be obtained by a suspension polymerization method.
[0086]
(11) Non-magnetic one-component developer
The polymerized toner of the present invention can be used as a toner component of various developers, but is preferably used as a non-magnetic one-component developer. When the polymerized toner of the present invention is used as a non-magnetic one-component developer, an external additive can be mixed as needed. Examples of the external additive include inorganic particles and organic resin particles that act as a fluidizing agent or an abrasive.
[0087]
Examples of the inorganic particles include silicon dioxide (silica), aluminum oxide (alumina), titanium oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. Examples of the organic resin particles include methacrylate polymer particles, acrylate polymer particles, styrene-methacrylate copolymer particles, styrene-acrylate copolymer particles, a styrene polymer core, and a methacrylic acid shell. Core-shell type particles formed of an ester copolymer are exemplified.
[0088]
Among these, inorganic oxide particles are preferred, and silicon dioxide is particularly preferred. The surface of the inorganic fine particles can be subjected to a hydrophobic treatment, and silicon dioxide particles subjected to the hydrophobic treatment are particularly preferable. The external additives may be used in combination of two or more kinds. When the external additives are used in combination, a method of combining inorganic particles having different average particle diameters or inorganic particles and organic resin particles is 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 polymerized toner. In order for the external additive to adhere to the polymerized toner, the polymerized toner and the external additive are usually put into a mixer such as a Henschel mixer and stirred.
[0089]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Synthesis Examples, Examples, and Comparative Examples. Parts and percentages are by weight unless otherwise specified. Methods for measuring physical properties and the like are as follows.
[0090]
(1) Particle size and particle size distribution
The particle size distribution represented by the volume average particle size (dv) of the polymer particles and the ratio (dv / dp) of the volume average particle size (dv) to the number average particle size (dp) is determined by using a Multisizer (Beckman Coulter). Manufactured by the company). The measurement conditions were as follows: aperture diameter = 100 μm, medium = Isothon II, number of measured particles = 100,000.
[0091]
(2) Sphericity
A photograph of the polymer particles is taken with a scanning electron microscope, and the photograph is read by an image processing apparatus of a Nexus 9000 type, and the ratio (rl / rs) between the major axis (rl) and the minor axis (rs) of the polymer particles is determined. It was measured. The measured number of the polymer particles was set to 100. The measured values were averaged to calculate sphericity (rl / rs).
[0092]
(3) Blow-off charge amount
100cm³After charging 57 g of carrier (TEFV150 / 250) and 3 g of toner into a ball mill pot, stirring and mixing for 30 minutes, the unit weight of toner is measured using a blow-off charge amount measuring device TB-200 (manufactured by Toshiba Chemical). Per charge (μC / g) was measured.
[0093]
(4) Print density
The toners obtained in Examples and Comparative Examples were placed in a non-magnetic one-component developing system printer (trade name “Microline 14n” manufactured by Oki Data Corporation) to perform solid printing. Environmental conditions for printing include low temperature / low humidity (temperature 10 ° C / relative humidity 20%; L / L), normal temperature / normal humidity (temperature 23 ° C / relative humidity 50%; N / N), and high temperature / high humidity (temperature 35 ° C./80% relative humidity; H / H). After continuous printing of 1,000 sheets from the beginning under each environmental condition, the print density was measured. The print density was measured using a Macbeth reflection densitometer RD914 (A Division, Kollmorgen Instruments, Corp.).
[0094]
(5) Photoreceptor fog
The toner obtained in each of Examples and Comparative Examples was put into a non-magnetic one-component developing system printer (trade name “Microline 14n” manufactured by Oki Data Corporation) to continuously print 1,000 sheets from the beginning at 5% density. Was performed. Environmental conditions for printing include low temperature / low humidity (temperature 10 ° C / relative humidity 20%; L / L), normal temperature / normal humidity (temperature 23 ° C / relative humidity 50%; N / N), and high temperature / high humidity (temperature 35 ° C./80% relative humidity; H / H). After continuous printing of 1,000 sheets, printing is performed in solid black, and the toner of the non-image portion on the photosensitive drum on the surface of which an organic photosensitive member (OPC) layer is provided is transferred to paper with a mending tape, and white. The reflectivity value (R2) was measured with a densitometer (manufactured by Nippon Denshoku Co., Ltd.). On the other hand, only the mending tape was applied to paper, and the value of the reflectance (R1) was measured with a whiteness meter. The difference (R1-R2) between the two was defined as the photoreceptor fog.
[0095]
(6) Durable fog
The toners obtained in Examples and Comparative Examples were put into a non-magnetic one-component developing system printer (trade name “Microline 14n” manufactured by Oki Data Corporation), and were put at normal temperature / normal humidity (temperature 23 ° C./relative humidity 50%). ; N / N), continuous printing was performed from the beginning at 5% density. Each time 1,000 sheets are printed, the number of printed sheets that can be printed with solid black and maintain an image quality of 15% or less of fog in the non-image area of the transfer paper measured by a whiteness meter (manufactured by Nippon Denshoku Co., Ltd.) Was examined. Assuming that the whiteness after printing is H2 and the whiteness before printing is H1, fog can be calculated from the following equation: fog = [(H1−H2) / H1] × 100. Durability fog was evaluated according to the following criteria.
：: 10,000 or more continuous prints
Δ: The number of continuous prints is less than 10,000.
[0096]
[Synthesis Example 1]Negative charge control resin (A1) Synthesis of
100 parts of a polymerizable monomer composed of 82% of styrene, 11% of n-butyl acrylate, and 7% of 2-acrylamido-2-methylpropanesulfonic acid were put into 900 parts of toluene, and 4 parts of azobisdimethylvaleronitrile were added. The reaction was carried out at 80 ° C. for 8 hours in the presence. After completion of the reaction, toluene was distilled off under reduced pressure to obtain a sulfonic acid group-containing copolymer. The weight average molecular weight (Mw) of the sulfonic acid group-containing copolymer was 20,000. The sulfonic acid group-containing copolymer is referred to as a negative charge control resin (A1). The “weight% of the structural unit having a functional group” of the negative charge control resin (A1) is 7%.
[0097]
[Synthesis Example 2]Negative charge control resin (A2) Synthesis of
In the same manner as in Synthesis Example 1, 95.2% of styrene and 4.8% of 2-acrylamido-2-methylpropanesulfonic acid were copolymerized to obtain a sulfonic acid group-containing copolymer. The weight average molecular weight (Mw) of the sulfonic acid group-containing copolymer was 8,000. The sulfonic acid group-containing copolymer is referred to as a negative charge control resin (A2). The “weight% of the structural unit having a functional group” of the negative charge control resin (A2) is 4.8%.
[0098]
[Synthesis Example 3]Negative charge control resin (A3) Synthesis of
In the same manner as in Synthesis Example 1, 86% of styrene, 9% of n-butyl acrylate, and 5% of 2-acrylamido-2-methylpropanesulfonic acid were copolymerized to obtain a sulfonic acid group-containing copolymer. The weight average molecular weight (Mw) of the sulfonic acid group-containing copolymer was 20,000. The sulfonic acid group-containing copolymer is referred to as negative charge control resin (A3). The “weight% of the structural unit having a functional group” of the negative charge control resin (A3) is 5%.
[0099]
[Example 1]
1.Preparation of polymerizable monomer composition for core
80.5 parts of styrene, 19.5 parts of butyl acrylate, 0.7 part of divinylbenzene, and a polymerizable monomer for core composed of polymethyl methacrylate macromer (trade name “AA6” manufactured by Toa Gosei Chemical Co., Ltd.) , Carbon black (manufactured by Mitsubishi Chemical Corporation, trade name “# 25”, 7 parts), 1 part of negative charge control resin (A1), nigrosine dye (positive charge control agent; trade name “Bontron N-01, manufactured by Orient Chemical Industry Co., Ltd.” )) 0.4 parts, 1.7 parts of t-dodecyl mercaptan, and 10 parts of dipentaerythritol hexamyristate are added, stirred, mixed and uniformly dispersed to prepare a polymerizable monomer composition for a core. did.
[0100]
2.Preparation of aqueous dispersion medium
To an aqueous solution obtained by dissolving 9.8 parts of magnesium chloride in 250 parts of ion-exchanged water, an aqueous solution obtained by dissolving 6.9 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring, and the magnesium hydroxide colloid was dispersed. A liquid was prepared. As a result of measuring the particle size distribution of the formed colloid, the number average particle size D50 (50% cumulative value of the number particle size distribution) was 0.37 μm, and D90 (90% cumulative value of the number particle size distribution) was 0.68 μm. there were. The particle size distribution was measured using a particle size distribution measuring device (SALD2000A type, manufactured by Shimadzu Corporation). The measurement conditions of the particle size distribution were as follows: the refractive index was 1.55-0.20i, the ultrasonic irradiation time was 5 minutes, and 10% saline was used as the dispersion medium.
[0101]
3.Droplet formation process
To the magnesium hydroxide colloidal dispersion obtained above, 5 parts of t-butylperoxy-2-ethylhexanoate as a polymerizable monomer composition for a core and a polymerization initiator were charged, and a propeller type stirrer was added. And mixed with stirring. Next, the mixed liquid was supplied to a high-speed rotary shearing stirrer (Ebara Milder; manufactured by Ebara Corporation, trade name "MDN303V") operating at a rotation speed of the rotor of 15,000 rpm using a pump, and the core was supplied. Drops of the polymerizable monomer composition were formed.
[0102]
4.Polymerization process
The aqueous dispersion containing the droplets of the polymerizable monomer composition for the core was transferred to a reactor equipped with a stirring blade. The aqueous dispersion was heated to initiate polymerization. The jacket temperature of the reactor and the liquid temperature in the reactor were measured, and the jacket temperature was controlled using a cascade control method so that the temperature of the aqueous dispersion in the reactor was constant at 90 ° C. When the polymerization conversion reached approximately 100%, sampling was performed, and the particle size of the produced colored polymer particles (core particles) was measured to be 7.81 μm.
[0103]
Next, 1 part of methyl methacrylate was added as a shell-forming polymerizable monomer into a reactor containing an aqueous dispersion of core particles. Further, 0.1 part of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] (trade name “VA-086”, manufactured by Wako Pure Chemical Industries, Ltd.) was replaced with 10 parts of ion-exchanged water. Was added into the reactor, and polymerization was continued for 3 hours. The reaction was stopped to obtain an aqueous dispersion of polymer particles having a core-shell structure having a pH of 9.5.
[0104]
While stirring this aqueous dispersion, sulfuric acid was added to adjust the pH to 5 or less, acid washing (25 ° C., 10 minutes) was performed, water was separated by filtration, and 500 parts of ion-exchanged water was newly added. In addition, it was reslurried and washed with water. Thereafter, dehydration and washing with water were repeated several times again, and the solid content was separated by filtration, followed by drying at 45 ° C. for two days and nights using a drier to collect polymer particles.
[0105]
5.Polymerized toner
The polymer particles (core-shell type polymerized toner) thus obtained have a volume average particle diameter (dv) of 7.82 μm, and a volume average particle diameter (dv) / number average particle diameter (dp) of 1. At 20, the sphericity (rl / rs) was 1.1. To 100 parts of the polymer particles, 0.6 part of hydrophobized colloidal silica (trade name “RX-200” manufactured by Nippon Aerosil Co., Ltd.) is added and mixed using a Henschel mixer to perform non-magnetic one-component development. An agent (toner) was prepared. Table 1 shows the results.
[0106]
[Example 2]
Example 1 was carried out in the same manner as in Example 1 except that the addition amount of the nigrosine dye (positive charge control agent; product name: Bontron N-01, manufactured by Orient Chemical Industries) was changed from 0.4 part to 0.2 part. The procedure was the same as in Example 1. Table 1 shows the results.
[0107]
[Comparative Example 1]
Example 1 was repeated except that no nigrosine dye (positive charge control agent; manufactured by Orient Chemical Industry Co., Ltd., trade name "Bontron N-01") was not added. Table 1 shows the results.
[0108]
[Comparative Example 2]
Example 1 is the same as Example 1 except that the addition amount of the nigrosine dye (positive charge control agent; product name: Bontron N-01, manufactured by Orient Chemical Industries) was changed from 0.4 part to 0.6 part. The same operation as in 1 was performed. Table 1 shows the results.
[0109]
[Table 1]

[0110]
(footnote)
(1) Negative charge control resin (A1): sulfonic acid group-containing copolymer
(2) Positive charge control agent (B1): Nigrosine dye, manufactured by Orient Chemical Industries, trade name "Bontron N-01"
[0111]
[Comparative Example 3]
In Example 1, 1 part of the negative charge control resin (A1) was replaced by 2 parts of the negative charge control resin (A2), and 0.4 part of a nigrosine dye (positive charge control agent) was replaced by a quaternary ammonium salt compound (Orient Chemical Co., Ltd.) The procedure was the same as that of Example 1 except that the product was replaced by 0.5 part of “Bontron P-51” (trade name), and the results are shown in Table 2.
[0112]
[Comparative Example 4]
In Example 1, the negative charge control resin (A1) was replaced with an azo-based chromium-containing complex salt (negative charge control agent; trade name "Spiron Black TRH" manufactured by Hodogaya Chemical Industry Co., Ltd.), and a nigrosine dye (positive charge control) The same operation as in Example 1 was carried out, except that the addition amount of the agent was changed from 0.4 part to 0.25 part. Table 2 shows the results.
[0113]
[Comparative Example 5]
In Example 1, 1 part of the negative charge control resin (A1) was replaced with 5 parts of the negative charge control resin (A3), and the addition amount of the nigrosine dye (positive charge control agent) was changed from 0.4 part to 0.3 part. The same operation as in Example 1 was performed, except that the parts were changed. Table 2 shows the results.
[0114]
[Table 2]

[0115]
(footnote)
(1) Negative charge control resin (A2): sulfonic acid group-containing copolymer
(2) negative charge control resin (A3): sulfonic acid group-containing copolymer
(3) Negative charge control agent (A4): Azo-based chromium-containing complex salt pigment (trade name "Spiron Black TRH" manufactured by Hodogaya Chemical Industry Co., Ltd.)
(4) Positive charge control agent (B1): Nigrosine dye (trade name “Bontron N-01” manufactured by Orient Chemical Industries, Ltd.)
(5) Positive charge control agent (B2): quaternary ammonium salt compound (trade name “Bontron P-51” manufactured by Orient Chemical Industries)
【The invention's effect】
According to the present invention, a change in the charge amount due to environmental fluctuation is small, the print density is high, the fog of the photoreceptor under a high temperature / high humidity environment is small, and the fog at the time of durability is small. And a negatively chargeable toner for developing an electrostatic image. The negatively chargeable toner of the present invention can be applied to high-speed printers and the like.

Claims (3)

At least a binder resin, a colorant, and a toner for electrostatic image development containing a charge control agent,
(1) The charge control agent contains a negative charge control resin (A) comprising a polymer having a structural unit having a negative charge functional group and a nigrosine dye (B), and (2) a negative charge control resin The content of the structural unit having a negatively chargeable functional group in (A) is defined as a (% by weight), and the content of the negative charge control resin (A) relative to 100 parts by weight of the binder resin is defined as b (parts by weight). When the content of the nigrosine dye (B) with respect to 100 parts by weight of the binder resin is represented by c (parts by weight), these are represented by the following formula (I).
2.0 ≦ (c × 100) / (a × b) ≦ 7.0 (I)
A negatively chargeable toner for developing electrostatic images, characterized by satisfying the following. The negative charge control resin (A) is a polymer having a weight average molecular weight of 1,000 to 100,000 having a structural unit composed of a monomer having a sulfonic acid group as a structural unit having a negative charge functional group. 2. The toner for developing an electrostatic image according to 1. A core-shell type in which a coating layer made of a resin having a glass transition temperature higher than the glass transition temperature of the binder resin is formed on the surface of colored particles containing at least a binder resin, a colorant, and a charge control agent. The electrostatic image developing toner according to claim 1, wherein the toner is a capsule toner having a structure.