JP3962479B2 - Toner for electrostatic image development - Google Patents

Description

【００２２】
又、本発明の静電荷像現像用トナーは、１２５℃、５ｋｇ荷重におけるメルトインデックス（ＭＩ）の値が１５ｇ／１０ｍｉｎ．以下である場合に、より好ましい効果が得られる。即ち、この条件を満たす磁性酸化鉄及び結着樹脂を有するトナーは、トナー製造時における粉砕工程で、磁性酸化鉄がトナー表面にもっとも露出し易いという挙動を示す。一方、ＭＩが１５ｇ／１０ｍｉｎ．より大きい場合には、磁性酸化鉄がトナー表面に露出しにくくなるので、本発明が目的とする排紙コロ等の紙搬送部材へのトナー付着の防止効果が充分に得られにくい。
本発明において、メルトインデックス（ＭＩ）は、ＪＩＳ Ｋ７２１０記載の装置を用いて、下記の測定条件下、手動切り取り法で測定を行った。この時、測定値は１０分値に換算する。
・測定温度 ：１２５℃
・荷重 ：５ｋｇ
・試料充填量：５〜１０ｇ
【００２３】
又、本発明の静電荷像現像用トナーにおいては、本発明において使用する結着樹脂中のニトリル基と、磁性酸化鉄との密着力を適度に弱める効果が得られるため、磁性酸化鉄に、ケイ素元素が含有された磁性酸化鉄を使用することが好ましい。更に、磁性酸化鉄中のケイ素元素の含有率が、鉄元素を基準として０．１〜１０重量％、より好ましくは０．２〜４重量％のものを使用することが好ましい。即ち、本発明者らが検討した結果、このような割合でケイ素元素が含有されている磁性酸化鉄を使用することによって、結着樹脂中のニトリル基と磁性酸化鉄との密着力を適度に弱める効果がより向上し、トナー粒子表面に磁性酸化鉄をより露出させ易くできる。
【００２４】
これに対し、磁性酸化鉄中のケイ素元素の含有率が、鉄元素を基準として０．１重量％よりも少ないと、上記した磁性酸化鉄をトナー粒子表面に露出させ易くするために添加したケイ素元素の効果が充分に得られにくい。本発明においては、先に述べたように、より好ましくは、ケイ素元素の含有率を０．２重量％以上とする。一方、磁性酸化鉄中のケイ素元素の含有率が、鉄元素を基準として１０重量％よりも多いと、結着樹脂と磁性酸化鉄との密着力が弱くなり過ぎて、トナー粒子表面に露出した磁性酸化鉄がトナー粒子から外れ易くなってしまい、結果としてトナー粒子表面に露出する磁性酸化鉄の量が少なくなってしまう場合がある。本発明においては、先に述べたように、ケイ素元素の含有率を４重量％以下とすることがより好ましい。
【００２５】
本発明においては、更に、磁性酸化鉄中にケイ素元素が上記した含有量で含有され、且つ、磁性酸化鉄を表面から溶解し、鉄元素の溶解率が２０重量％となるところまでに溶解液中に存在しているケイ素元素の含有量をＢとし、磁性酸化鉄中のケイ素元素の全含有量をＡとした場合に、Ａに対するＢの比の値Ｂ／Ａと、磁性酸化鉄の表面に存在するケイ素の含有量をＣとした場合に、上記含有量Ａに対するＣの比の値Ｃ／Ａが、下記の関係を満足するものを使用することが好ましい。即ち、Ｂ／Ａの値が（Ｂ／Ａ）×１００＝４４〜１００％であって、且つ、Ｃ／Ａの値が（Ｃ／Ａ）×１００＝１０〜９５％であるもの、より好ましくは、（Ｂ／Ａ）×１００＝４４〜８４％であって、且つ（Ｃ／Ａ）×１００＝１０〜５５％であるものを使用する。
【００２６】
即ち、本発明においては、上記の条件を満たすようにケイ素元素が分布している磁性酸化鉄をトナーの構成材料として使用することによって、定着時に、トナー表面付近に存在している磁性酸化鉄が、溶融したトナー内部に更に入り込みにくくでき、先に述べた定着画像の表面に存在している磁性酸化鉄のスペーサーとしての働きをより効果的にすることができる。この結果、定着画像の排紙コロに対する接触面積が少なくなって、排紙コロへのトナー付着を抑制する効果を向上させることが可能となる。
【００２７】
これに対し、上記した磁性酸化鉄を表面から溶解し、鉄元素の溶解率が２０重量％となるところまでに存在しているケイ素元素の含有量Ｂと、磁性酸化鉄中のケイ素元素の全含有量Ａとの比（Ｂ／Ａ）が４４％よりも小さい材料を使用した場合は、定着時に、溶融したトナー内部に磁性酸化鉄が入り込み易くなる傾向があり、好ましくない。一方、本発明においては、鉄元素の溶解率が２０重量％のところ迄に全てのケイ素元素が存在する（Ｂ／Ａ）＝１００％のものを使用してもよいが、（Ｂ／Ａ）の比があまり大き過ぎると、磁性酸化鉄の表面に凹凸が増えて脆くなるのでトナー製造時の混練工程等で欠けを生じ易くなるため、磁性酸化鉄の形状を球形度（Ψ）０．８以上に維持しにくくなる場合がある。従って、本発明においては、先に述べたように、（Ｂ／Ａ）の比が８４％以内のものを使用することがより好ましい。
【００２８】
更に、上記に加えて、磁性酸化鉄の表面に存在するケイ素の含有量Ｃと、磁性酸化鉄中のケイ素元素の全含有量Ａとの比（Ｃ／Ａ）が１０％よりも小さいものを使用すると、スペーサーとしての効果が充分に得られにくくなる。一方、（Ｃ／Ａ）の比が大き過ぎると、磁性酸化鉄表面に、ケイ素元素を均一に保持することが難しくなって、安定したスペーサーとしての効果が得られにくくなり好ましくない。従って、本発明においては、先に述べたように、（Ｃ／Ａ）の比が９５％以内のもの、より好ましくは５５％以内のものを使用するとよい。
【００２９】
上記したように、本発明の静電荷像現像用トナーを形成する場合に、（Ｂ／Ａ）の比、及び（Ｃ／Ａ）の比が特定の値を満足するようにケイ素元素が分布している磁性酸化鉄を使用すれば、良好な磁性トナー特性が得られることがわかった。換言すれば、本発明のより顕著な効果を得るためには、磁性酸化鉄粒子中に存在するケイ素元素の分布が、磁性酸化鉄粒子内部から表面に向かって連続的に、又は段階的に増加していく傾向にあるものを使用し、本発明の静電荷像現像用トナーを形成することが好ましいことを示している。
【００３０】
このような本発明の静電荷像現像用トナーに好適なケイ素元素の分布を有する磁性酸化鉄粒子は、例えば、下記の方法で製造することができる。
第一鉄塩水溶液に所定量のケイ酸化合物を添加した後、鉄成分に対して当量、又は当量以上の水酸化ナトリウムの如きアルカリを加え、水酸化第一鉄を含む水溶液を調製する。調製した水溶液のｐＨを７以上、好ましくは８〜１０に維持しながら空気を吹き込み、水溶液を７０℃以上に加温しながら水酸化第一鉄の酸化反応を行って、先ず、磁性酸化鉄粒子の芯となる種晶を生成する。
次に、この種晶を含むスラリー状の液に、前に加えたアルカリの添加量を基準として、約１当量の硫酸第一鉄を含む水溶液を加える。液のｐＨを６〜１０に維持しつつ、空気を吹き込みながら水酸化第一鉄の反応を進め、種晶を芯にして磁性酸化鉄粒子を成長させる。酸化反応が進むにつれて液のｐＨは酸性側に移行していくが、液のｐＨを６未満にしないようにすることが好ましい。そして、酸化反応の終期に、液のｐＨを調整することにより、磁性酸化鉄粒子の表層及び表面にケイ酸化合物を所定量遍在させることができる。
【００３１】
上記において、第一鉄塩水溶液に所定量添加させるケイ酸化合物としては、例えば、市販のケイ酸ソーダ等のケイ酸塩類、加水分解等で生じるゾル状ケイ酸等のケイ酸が例示される。尚、本発明に悪影響を与えない限り、硫酸アルミ、アルミナ等のその他の添加剤を加えてもよい。
【００３２】
又、第一鉄塩としては、一般的に、硫酸法チタン製造の際に副生する硫酸鉄、鋼板の表面洗浄に伴って副生する硫酸鉄の利用が可能であり、更に、塩化鉄等も利用することも可能である。上記した水溶液法による磁性酸化鉄の製造方法においては、一般に、反応時の粘度の上昇を防ぐため、及び硫酸鉄の溶解度との兼ね合いから、鉄濃度が０．５〜２ｍｏｌ／ｌの硫酸鉄が用いられる。このときに採用する硫酸鉄の濃度は、一般的に、薄いほど製品の粒度が細かくなる傾向がある。又、反応に際しては、空気量が多いほど、そして反応温度が低いほど製品が微粒化し易い傾向がある。
【００３３】
本発明の静電荷像現像用トナーにおいては、上述した製造方法によって、ケイ酸成分を有し、且つケイ素元素が特定に分布する磁性酸化鉄粒子を生成し、得られた磁性酸化鉄粒子を用いてトナーを作製することが好ましい。
本発明において、磁性酸化鉄粒子表面に存在するケイ素元素の含有量Ｃは、次のような方法によって求めた。先ず、５リットルのビーカーに、約３リットルの脱イオン水を入れ、５０〜６０℃になるようにウォーターバスで加温しておく。これに、約４００ｍｌの脱イオン水でスラリーとした磁性酸化鉄粒子約２５ｇを、約３００ｍｌの脱イオン水を用いて水洗しながら入れて、脱イオン水と共に、上記５リットルビーカー中に加える。
【００３４】
次いで、温度を約６０℃、撹拌スピードを約２００ｒｐｍに保ちながら、特級水酸化ナトリウムを加えて約１規定の水酸化ナトリウム溶液とする。この結果、磁性酸化鉄粒子表面にあるケイ酸の如きケイ素化合物の溶解が開始する。溶解開始から３０分後に、ビーカー中から水酸化ナトリウム水溶液を２０ｍｌをサンプリングし、０．１μメンブランフィルターでろ過し、ろ液を採取する。そして、ろ液を測定用試料として、プラズマ発光分光（ＩＣＰ）を用いてケイ素元素の定量を行う。
この際、磁性酸化鉄粒子表面に存在するケイ素元素の含有量Ｃは、水酸化ナトリウム水溶液中の単位当たりのケイ素元素濃度（ｍｇ／ｌ）を測定し、磁性酸化鉄試料の単位重量当たりのケイ素元素含有量（ｍｇ／ｇ）として求めた。
【００３５】
更に、本発明においては、磁性酸化鉄粒子中のケイ素元素の含有率（鉄元素を基準とした場合の重量％）、鉄元素の溶解率、この鉄元素の溶解率が２０重量％になるまでに溶解液中に存在するケイ素元素の含有量Ｂ、及び磁性酸化鉄粒子中のケイ素元素の全含有量Ａは、次に述べる方法によって求めた。
先ず、５リットルのビーカーに約３リットルの脱イオン水を入れて、４５〜５０℃になるようにウォーターバスで加温する。これに、約４００ｍｌの脱イオン水でスラリーとした磁性酸化鉄粒子約２５ｇを、約３００ｍｌの脱イオン水を用いて水洗しながら入れて、脱イオン水と共に、上記５リットルビーカー中に加える。
【００３６】
次いで、温度を約５０℃、撹拌スピードを約２００ｒｐｍに保ちながら、特級塩酸を加え、磁性酸化鉄の溶解を開始する。このとき、磁性酸化鉄濃度は約５ｇ／ｌであり、塩酸水溶液は約３規定の濃度になっている。溶解開始から、全て溶解して透明になるまでの間に数回、ビーカー中から塩酸水溶液を約２０ｍｌずつサンプリングし、０．１μメンブランフィルターでろ過し、ろ液を採取する。そして、ろ液を測定用試料（各サンプル）として、プラズマ発光分光（ＩＣＰ）を用いて、塩酸水溶液中の単位当たりの鉄元素及びケイ素元素濃度（ｍｇ／ｌ）の定量を行った。
【００３７】
上記した測定結果から、次式によって、各サンプル毎の鉄元素の溶解率を算出した。
【数２】

又、鉄元素を基準としたケイ素元素の含有率は、上記のようにして磁性酸化鉄を全て溶解して得られた塩酸水溶液サンプルについて、単位当たりの鉄元素濃度及びケイ素元素濃度を夫々測定し、次式によって算出した。
【数３】

【００３８】
磁性酸化鉄粒子中のケイ素元素の全含有量Ａは、全ての磁性酸化鉄粒子が溶解された後にサンプリングしたサンプルの塩酸水溶液中の単位当たりのケイ素元素濃度を測定し、磁性酸化鉄試料の単位重量当たりのケイ素元素含有量（ｍｇ／ｇ）として求めた。更に、磁性酸化鉄粒子のケイ素元素の含有量Ｂは、溶解の度合いに応じて段階的にサンプリングした各サンプルのうち、上記で算出した鉄元素の溶解率が２０％であったサンプルについて測定した塩酸水溶液中の単位当たりのケイ素元素濃度（ｍｇ／ｌ）を用い、磁性酸化鉄試料の単位重量当たりのケイ素元素含有量（ｍｇ／ｇ）として求めた。
【００３９】
上記ケイ素元素の含有量Ａ、Ｂ及びＣを測定する具体的な方法としては、以下の２つの方法が挙げられる。先ず、第１の方法としては、使用する磁性酸化鉄を２つに分けて、一方で、上記したような操作によって、ケイ素元素濃度を測定して、上記のようにしてケイ素元素含有量Ａ及びＢを求め、２つに分けた別の磁性酸化鉄を用いて、先に述べた操作によって磁性酸化鉄粒子表面のケイ素元素含有量Ｃを別途測定する方法がある。又、第２の方法としては、先に述べた操作によって磁性酸化鉄表面のケイ素元素の含有量Ｃを測定し、測定後、ろ紙上に残った磁性酸化鉄を試料として使用し、上記したケイ素元素の含有量Ａ及びＢの測定操作に従って、鉄元素の溶解率が２０％迄のケイ素元素含有量Ｂ’（＝含有量Ｂから含有量Ｃを除いた量に相当）及び全含有量Ａ’（＝含有量Ａから含有量Ｃを除いた量に相当）を測定し、最終的に含有量Ａ及びＢを算出する方法がある。
【００４０】
上記したような構成材料からなる本発明の静電荷像現像用トナーには、必要に応じて荷電制御剤を含有させてもよい。この際に使用できる荷電制御剤としては、負帯電性トナーの場合には、例えば、モノアゾ染料の金属錯塩、サリチル酸、アルキルサリチル酸、ジアルキルサリチル酸又はナフトエ酸の金属錯塩等の負荷電制御剤が挙げられる。又、正帯電性トナーの場合には、例えば、ニグロシン系化合物、有機四級アンモニウム塩の如き正荷電制御剤が使用できる。
又、本発明では、必要に応じてトナー中にワックスが含有されていることが好ましい。この際に用いるワックスとしては、例えば、パラフィンワックス及びその誘導体、マイクロクリスタリンワックス、及びその誘導体、フィッシャートロプシュワックス及びその誘導体、ポリオレフィンワックス及びその誘導体、カルナバワックス及びその誘導体等が挙げられる。尚、上記誘導体には、酸化物やビニル系モノマーとのブロック共重合物、グラフト変性物が含まれる。
【００４１】
又、本発明の静電荷像現像用トナーには、環境安定性、帯電安定性、現像性、流動性及び保存性を向上させるために、無機微粉体又は疎水性無機微粉体が混合されていることが好ましい。具体的には、例えば、シリカ微粉末、酸化チタン微粉末、或いはそれらの疎水化物が挙げられる。これらは、単独或いは併用して用いることが好ましい。シリカ微粉体としては、ケイ素ハロゲン化物の蒸気相酸化により生成されたいわゆる乾式法又はヒュームドシリカと称される乾式シリカ、及び水ガラス等から製造される所謂湿式シリカの両者が使用可能である。特に、表面及び内部にあるシラノール基が少なく、又、Ｎａ₂Ｏ、ＳＯ₃ ^2-等の製造残渣が少ないことから、乾式シリカの方が好ましい。又、乾式シリカにおいては、製造工程において、例えば、塩化アルミニウム、塩化チタン等、他の金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによって、シリカと他の金属酸化物の複合微粉体を得ることも可能であるが、本発明においては、これらを利用することもできる。
【００４２】
更に、本発明において用いるシリカ微粉体は、疎水化処理されているものが好ましい。疎水化処理する方法としては、シリカ微粉体と反応或いは物理吸着する有機ケイ素化合物等でシリカ微粉体を化学的に処理することによって疎水性が付与される。特に好ましい疎水化処理の方法としては、例えば、ケイ素ハロゲン化合物の蒸気相酸化により生成された乾式シリカ微粉体をシランカップリング剤で処理した後、或いはシランカップリング剤で処理すると同時に、シリコーンオイルの如き有機ケイ素化合物で処理する方法が挙げられる。
【００４３】
上記の疎水化処理で使用されるシランカップリング剤としては、例えば、ヘキサメチルジシラザン、トリメチルシラン、トリメチルクロルシラン、トリメチルエトキシシラン、ジメチルジクロルシラン、メチルトリクロルシラン、アリルジメチルクロルシラン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ブロムメチルジメチルクロルシラン、α−クロルエチルトリクロルシラン、β−クロルエチルトリクロルシラン、クロルメチルジメチルクロルシラン、トリオルガノシリルメルカプタン、トリメチルシリルメルカプタン、トリオルガノシリルアクリレート、ビニルジメチルアセトキシシラン、ジメチルジエトキシシラン、ジメチルジメトキシシラン、ジフェニルジエトキシシラン、ヘキサメチルジシロキサン、１，３−ジビニルテトラメチルジシロキサン、１，３−ジフェニルテトラメチルジシロキサン、及び１分子当たり２〜１２個のシロキサン単位を有し、末端に位置する単位に夫々、１個当てのケイ素原子に結合した水酸基を有するジメチルポリシロキサン等が挙げられる。
【００４４】
又、上記の疎水化処理で使用される有機ケイ素化合物としては、シリコーンオイルが挙げられる。好ましいシリコーンオイルとしては、２５℃における粘度が、３０〜１０００センチストークスのものが挙げられ、具体的には、ジメチルシリコーンオイル、メチルフェニルシリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイル等が特に好ましい。
又、シリコーンオイル処理の方法としては、種々の方法がある。例えば、シランカップリング剤で処理されたシリカ微粉体にシリコーンオイルを加え、これらをヘンシェルミキサー等の混合機を用いて直接混合する方法を用いてもよいし、ベースとなるシリカ微粉体にシリコーンオイルを噴霧する方法を用いてもよい。或いは、適当な溶剤にシリコーンオイルを溶解或いは分散させた後、シリカ微粉体を加えて混合し、その後、溶剤を除去する方法でもよい。
【００４５】
本発明の静電荷像現像用トナーには、必要に応じて、上記したシリカ微粉体やシリカ微粉体と酸化チタン微粉体等との複合微粉体以外の外部添加剤を添加してもよい。外部添加剤としては、例えば、帯電補助剤、導電性付与剤、流動性付与剤、ケーキング防止剤、熱ロール定着時の離型剤、滑剤、研磨剤等の働きをする樹脂微粒子や無機微粒子等が挙げられる。
具体的には、例えば、テフロン、ステアリン酸亜鉛、ポリフッ化ビニリデンの如き滑剤が挙げられるが、これらの中でもポリフッ化ビニリデンが好ましい。或いは、例えば、酸化セリウム、炭化ケイ素、チタン酸ストロンチウム等の研磨剤が挙げられるが、これらの中でもチタン酸ストロンチウムが好ましい。或いは、例えば、酸化チタン、酸化アルミニウム等の流動性付与剤が挙げられるが、これらの中でも特に疎水性のものが好ましい。ケーキング防止剤や、例えば、カーボンブラック、酸化亜鉛、酸化アンチモン、酸化スズ等の導電性付与剤、或いは、逆極性の白色微粒子及び黒色微粒子を、現像性向上剤として少量用いることもできる。
【００４６】
本発明の静電荷像現像用トナーは、上記したようなトナー構成材料をボールミルの如き混合機により充分混合してから、加熱ロール、ニーダー、エクストルーダーの如き熱混練機を用いて溶融、捏和及び練肉し、冷却固化した後、粉砕及び厳密な分級を行って生成することができる。
【００４７】
【実施例】
以下、実施例、参考例及び比較例を挙げて本発明をより具体的に説明するが、本発明は何らこれに限定されない。
（結着樹脂の製造例１）
４ツ口フラスコに、脱気水１８０重量部と、ポリビニルアルコールの２重量％水溶液２０重量部とを投入した後、アクリロニトリル１５重量部、スチレン６５重量部、メタクリル酸ラウリル１５重量部、マレイン酸モノブチル５重量部、及び、ジ−ｔ−ブチルパーオキシヘキサヒドロテレフタレート２．０重量部の溶液からなる混合液を加え、撹拌して懸濁液とした。
次に、フラスコ内を充分に窒素で置換した後、８０℃まで昇温して、重合を開始した。８０℃の温度を１２時間保持した後、更に、９５℃で５時間保持して重合を完了した。これを瀘別し、水洗、乾燥し、重合体１−１を得た。
【００４８】
次に、４ツ口フラスコ内にキシレン３００重量部を投入し、撹拌しながら容器内を充分に窒素で置換した後、昇温して還流させる。この還流下で、アクリロニトリル１５重量部、スチレン７５重量部、メタクリル酸ラウリル９．５重量部、マレイン酸モノブチル０．５重量部、及び、ジ−ｔｅｒｔ−ブチルパーオキサイド３重量部の混合液を４時間かけて滴下した後、２時間保持し、重合を完了し、有機溶剤を留去し、重合体１−２を得た。
【００４９】
次に、キシレン１００重量部に、上記で得られた重合体１−１を３０重量部、及び重合体１−２を７０重量部の計１００重量部を投入し、昇温して還流下で撹拌し、１２時間保持した後、有機溶剤を留去して樹脂を得た。次に、得られた樹脂を、冷却、固化後、粉砕してトナー用結着樹脂１とした。得られたトナー用結着樹脂１の物性を表１に示した。
【００５０】
（結着樹脂の製造例２）
混合液として、アクリロニトリル２０重量部、スチレン６５重量部、アクリル酸−２エチルヘキシル１０重量部、マレイン酸モノブチル２重量部、及びジ−ｔｅｒｔ−ブチルパーオキサイド１．１重量部からなる混合液を用いること以外は、結着樹脂の製造例１の重合体１−２の作製方法の場合と同様にして重合体２−２を得た。この得られた重合体２−２を用いること以外は結着樹脂の製造例１の場合と同様にして得られた樹脂を、冷却、固化後、粉砕してトナー用結着樹脂２とした。この得られたトナー用結着樹脂２の特性を表１に示した。
【００５１】
（結着樹脂の製造例３）
４ツ口フラスコに、脱気水１８０重量部と、ポリビニルアルコールの２重量％水溶液２０重量部とを投入した後、アクリロニトリル２重量部、スチレン７０重量部、アクリル酸−ｎ−ブチル２１重量部、マレイン酸モノブチル７重量部、及び、ジ−ｔ−ブチルパーオキシヘキサヒドロテレフタレート２．４重量部の溶液からなる混合液を加えて、撹拌し懸濁液とした。
フラスコ内を充分に窒素で置換した後、８５℃まで昇温して、重合を開始した。８５℃の温度を１２時間保持した後、更に、９５℃で５時間保持して重合反応を完了した。これを瀘別して、水洗、乾燥して重合体３−１を得た。
【００５２】
次に、混合液として、モノマー組成をスチレン８５重量部、アクリル酸−ｎ−ブチル１４重量部、マレイン酸モノブチル１重量部、及び、ジ−ｔｅｒｔ−ブチルパーオキサイド２．５重量部からなる混合液を用いること以外は、結着樹脂の製造例１の重合体１−２の作製方法の場合と同様にして重合を行って、重合体３−２を得た。
キシレン１００重量部に、上記で得られた重合体３−１を１５重量部と、重合体３−２を８５重量部の計１００重量部を投入し、昇温して還流下で撹拌し、１２時間保持した後、有機溶剤を留去して樹脂を得た。得られた樹脂を、冷却、固化後、粉砕してトナー用結着樹脂３とした。この得られたトナー用結着樹脂３の特性を表１に示した。
【００５３】
（結着樹脂の製造例４）
４ツ口フラスコに、脱気水１８０重量部と、ポリビニルアルコールの２重量％水溶液２０重量部を投入した後、アクリロニトリル３５重量部、スチレン５０重量部、メタクリル酸ラウリル１２重量部、マレイン酸モノブチル３重量部、及び、ジ−ｔ−ブチルパーオキシヘキサヒドロテレフタレート３．０重量部の溶液からなる混合液を加え、撹拌し懸濁液とした。
更に、フラスコ内を充分に窒素で置換した後、９０℃まで昇温して、重合を開始した。９０℃の温度に１２時間保持した後、更に、９５℃で５時間保持して重合を完了した。これを瀘別し、水洗、乾燥して重合体４−１を得た。
【００５４】
次に、モノマー組成を、アクリロニトリル３５重量部、スチレン５５重量部、メタクリル酸ラウリル８重量部、マレイン酸モノブチル２重量部、及び、ジ−ｔｅｒｔ−ブチルパーオキサイド３．５重量部とする以外は重合体１−１を製造した場合と同様にして重合を行って、重合体４−２を得た。
キシレン１００重量部に、上記で得られた重合体４−１を３５重量部と、重合体４−２を６５重量部の計１００重量部を投入し、昇温して還流下で撹拌し、１２時間保持した後、有機溶剤を留去して樹脂を得た。そして、得られた樹脂を、冷却、固化後、粉砕してトナー用結着樹脂４とした。この得られたトナー用結着樹脂４の特性を表１に示した。
【００５５】
（結着樹脂の比較製造例）
４ツ口フラスコに、脱気水１８０重量部と、ポリビニルアルコールの２重量％水溶液２０重量部を投入した後、スチレン７２重量部、アクリル酸−ｎ−ブチル２８重量部、及び、ジ−ｔ−ブチルパーオキシヘキサヒドロテレフタレート１重量部の溶液からなる混合液を加え、撹拌し懸濁液とした。
更に、フラスコ内を充分に窒素で置換した後、７５℃まで昇温して、重合を開始した。７５℃の温度に１２時間保持した後、更に、９５℃で５時間保持して重合を完了した。これを瀘別し、水洗、乾燥し、重合体５−１を得た。
【００５６】
次に、モノマー組成を、スチレン８７重量部、アクリル酸−ｎ−ブチル１３重量部、及び、ジ−ｔｅｒｔ−ブチルパーオキサイド２重量部からなる混合液を用いること以外は、結着樹脂の製造例１における重合体１−１の場合と同様にして重合を行って、重合体５−２を得た。
キシレン１００重量部に、上記で得られた重合体５−１を２５重量部と、重合体５−２を７５重量部の計１００重量部を投入し、昇温して還流下で撹拌し、１２時間保持した後、有機溶剤を留去して樹脂を得た。得られた樹脂を、冷却、固化後、粉砕して比較トナー用結着樹脂とした。この得られた比較トナー用結着樹脂の特性を表１に示した。
【００５７】
【表１】
表１：実施例及び比較例で用いたトナー用結着樹脂の特性

【００５８】
（磁性酸化鉄の製造例１）
硫酸第一鉄水溶液中に、鉄元素に対するケイ素元素の含有率が１．６重量％となるようにケイ酸ソーダを添加した後、鉄イオンに対して１．０〜１．１当量となるように苛性ソーダ溶液を混合して、水酸化第一鉄を含む水溶液を調製した。
この水溶液のｐＨを９に維持しながら空気を吹き込み、８０〜９０℃で酸化反応を行い、種晶を生成させるためのスラリー液を調製した。次いで、このスラリー液に、当初のアルカリ量（ケイ酸ソーダのナトリウム成分及び苛性ソーダのナトリウム成分）に対して、０．９〜１．２当量となるよう硫酸第一鉄水溶液を加えた後、スラリー液のｐＨを８に維持して、空気を吹き込みながら酸化反応を進め、酸化反応の終期にｐＨを調整して、磁性酸化鉄粒子表面にケイ酸成分を遍在させた。生成した磁性酸化鉄粒子を常法により、洗浄、濾過、乾燥し、次いで凝集しているものを解砕処理し、磁性酸化鉄粒子１を得た。この得られた磁性酸化鉄粒子１について、ケイ素元素の分布状態等の特性を表２に示した。
【００５９】
（磁性酸化鉄の製造例２）
ケイ酸ソーダを添加しない以外は、磁性酸化鉄製造例１と同様にしてケイ素元素を含有しない磁性酸化鉄粒子２を得た。この得られた磁性酸化鉄粒子２について、ケイ素元素の分布状態等の特性を表２に示した。
【００６０】
（磁性酸化鉄の製造例３）
磁性酸化鉄粒子１に、更に、鉄元素に対してケイ素元素の含有率が３．３重量％となるようにケイ酸微粉体を添加し、ヘンシェルミキサーにて混合して磁性酸化鉄粒子３を得た。この得られた磁性酸化鉄粒子３のケイ素元素の分布状態等の特性を表２に示した。
【００６１】
（磁性酸化鉄の製造例４）
磁性酸化鉄粒子２に、鉄元素に対してケイ素元素の含有率が０．７重量％となるようにケイ酸微粉体を添加し、ヘンシェルミキサーにて混合して磁性酸化鉄粒子４を得た。この得られた磁性酸化鉄粒子４のケイ素元素について、分布状態等の特性を表２に示した。
【００６２】
（磁性酸化鉄の製造例５）
鉄元素に対してケイ素元素の含有率が１．０重量％となるようにケイ酸ソーダを添加した後、表面にケイ素元素が存在しないような条件とする以外は、磁性酸化鉄の製造例１と同様にして磁性酸化鉄粒子５を得た。この得られた磁性酸化鉄粒子５について、ケイ素元素の分布状態等の特性を表２に示した。
【００６３】
（磁性酸化鉄の比較製造例）
ケイ酸ソーダを添加せず、又、温度やｐＨを変更することで、八面体（球形度Ψ＝０．６９）の比較用の磁性酸化鉄粒子を得た。この得られた比較用磁性酸化鉄粒子について、ケイ素元素の分布状態等の特性を表２に示した。
【００６４】
【表２】
表２：磁性酸化鉄粒子の特性

【００６５】
実施例１
・トナー用結着樹脂１ １００重量部
・磁性酸化鉄粒子１ １００重量部
・負荷電制御剤（アゾ系鉄錯体） １．５重量部
・ポリエチレンワックス（分子量７００） ３重量部
以上の材料を混合してから、２軸押し出し機にて混練後、粗粉砕、微粉砕、分級工程を経てトナー粒子を得た。更に、このトナー粒子１００重量部に対して疎水性シリカ１．０重量部をヘンシェルミキサーにて混合し、平均粒径６．８μｍの本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは３．１（ｇ／１０ｍｉｎ．）であった。
【００６６】
実施例２
トナー用結着樹脂２を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは１．４（ｇ／１０ｍｉｎ．）であった。
【００６７】
実施例３
トナー用結着樹脂３を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは１２．０（ｇ／１０ｍｉｎ．）であった。
【００６８】
実施例４
磁性酸化鉄粒子３を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは３．３（ｇ／１０ｍｉｎ．）であった。
【００６９】
実施例５
磁性酸化鉄粒子４を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは３．０（ｇ／１０ｍｉｎ．）であった。
【００７０】
実施例６
磁性酸化鉄粒子５を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは２．９（ｇ／１０ｍｉｎ．）であった。
【００７１】
参考例１
磁性酸化鉄粒子２を１００重量部用いること以外は実施例１と同様にして、本参考例の静電荷像現像用トナーを得た。該トナーのＭＩは２．８（ｇ／１０ｍｉｎ．）であった。
【００７２】
実施例８
トナー用結着樹脂４を１００重量部用いること以外は実施例１と同様にして、本実施例の静電荷像現像用トナーを得た。該トナーのＭＩは２１．７（ｇ／１０ｍｉｎ．）であった。
【００７３】
比較例１
比較トナー用結着樹脂を１００重量部用いること以外は実施例１と同様にして、比較例の静電荷像現像用トナーを得た。該トナーのＭＩは６．８（ｇ／１０ｍｉｎ．）であった。
【００７４】
比較例２
比較トナー用結着樹脂を１００重量部と比較磁性酸化鉄粒子を１００重量部とを用いること以外は実施例１と同様にして、比較例の静電荷像現像用トナーを得た。該トナーのＭＩは７．２（ｇ／１０ｍｉｎ．）であった。
【００７５】
（評価）
上記実施例１〜６、８、参考例１、比較例１及び２で得られた各静電荷像現像用トナーについての評価を次のようにして行った。キヤノン製レーザープリンターＬＢＰ−４３０（８枚機）を１２枚機にスピードアップし、定着器の温度設定を高めに変更し、更に、排紙コロと転写紙との接触圧を強くし、排紙コロにトナー付着し易い構成に改造したものを評価機として使用した。
そして、常温常湿環境下で５千枚の画出し試験を行って、１千枚毎に、排紙コロへのトナー付着を、「画像への影響」と「排紙コロ表面へのトナー付着の観察」という２つの観点から評価した。評価は、以下のような基準で行った。尚、×はジャム（紙詰まり）が発生したことを示し、その時点で評価を終了させた。この評価結果を表３に示した。
【００７６】
１．排紙コロへのトナー付着性評価
◎：排紙コロ表面へのトナー付着が全くない。
○：排紙コロ表面へのトナー付着は少し有るが、画像への影響は全く無い。
○△：画像への影響が少しあるが、良いレベル。
△：画像欠陥が発生するが、ジャムは発生しない。
×：排紙コロへのトナー付着が原因でジャムが発生する。
【００７７】
【表３】

【００７８】
【発明の効果】
以上説明したように、本発明によれば、マシンの小型化、高速化、高耐久化に伴って、より顕著になっている排紙コロ等の紙搬送部材へのトナー付着の問題が解決された静電荷像現像用トナーが提供される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic image developing toner for revealing an electrostatic image formed by electrophotography, electrostatic printing or the like.
[0002]
[Prior art]
Conventionally, many methods are known as electrophotographic methods. In general, an electric latent image is formed on a photosensitive member by various means using a photoconductive substance, and then the latent image is formed. The toner image is developed with a toner to form a visible image. The toner image is transferred onto a transfer material such as paper as necessary, and then fixed on the transfer material with heat and pressure to obtain a copy.
[0003]
In recent years, there have been a large number of devices that use electrophotography, such as various printers and facsimiles, in addition to the conventionally known copying machines, but because of the need for miniaturization, one-component developers were used. A developing device is often used. Among these, a method using a magnetic one-component developer composed of magnetic toner particles is excellent.
However, when the magnetic one-component developer is used, there are many problems in miniaturization. In particular, with regard to paper transport, due to the downsizing of the device, the transport path often has a tight angle by design. There is a tendency that the contact time between the paper conveying member and the transfer paper increases and the contact pressure increases. For this reason, the toner on the image that cannot be sufficiently cooled after passing through the fixing device is brought into contact with a paper conveying member such as a paper discharge roller, and there is a problem that the toner easily adheres to these members. This problem becomes more prominent as the machine speeds up and durability increases.
[0004]
On the other hand, in Japanese Patent Publication No. 7-23972, a one-component magnetic toner made of a resin containing acrylonitrile has been proposed. There was little effect on the toner adhesion problem. Japanese Patent Laid-Open No. 8-305081 proposes a toner for electrophotography using a resin containing a nitrile group. Similarly to the above, only by improving the resin constituting the toner, It turns out that the problem is not fully satisfactory.
JP-A-5-72801 proposes to use magnetic iron oxide containing a large amount of silicon element on the surface as a constituent material of the toner. However, only by improving such magnetic iron oxide, It is difficult to improve the problem of toner adhesion to a paper conveying member such as a paper discharge roller.
As described above, regarding the problem of toner adhesion to a paper transport member such as a paper discharge roller, the present situation is that further improvement of the toner is required.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to solve the problem of toner adhesion to a paper conveying member such as a paper discharge roller, which has become a more prominent phenomenon as the machine becomes smaller, faster and more durable. The object is to provide a toner for image development.
[0006]
[Means for Solving the Problems]
  The above object is achieved by the present invention described below. That is, the present invention provides an electrostatic charge image developing toner containing at least a binder resin and magnetic iron oxide, wherein the binder resin has a vinyl resin containing a nitrile group, and the magnetic iron oxide has a spherical shape. The degree (Ψ) is 0.8 or more, and the content of silicon element in the magnetic iron oxide is 0.00 on the basis of the iron element.2~4The toner for developing an electrostatic charge image has a melt index (MI) of 15 g / 10 min. An electrostatic charge image developing toner characterized by the following.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.
As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that a binder resin having a vinyl resin containing a nitrile group and a magnetic oxidation having a sphericity (Ψ) of 0.8 or more. By using toner combined with iron, a particularly excellent effect can be obtained for preventing toner adhesion to a paper transport member such as a paper discharge roller (hereinafter also simply referred to as “paper discharge roller” or “paper transport member”). As a result, the present invention has been found. In view of various experimental results, the present inventors consider the mechanism by which excellent effects can be obtained by the above configuration in the present invention as follows.
[0008]
First, as described above, the problem of toner adhesion to the paper discharge roller was developed on a transfer material such as paper (hereinafter simply referred to as “transfer paper”), and then thermally fused in the fixing process. When the toner comes into contact with the paper discharge roller before it cools and hardens, the resin component in the toner adheres to the paper discharge roller. Further, once the toner starts to adhere to the discharge roller, the toner adhesion is promoted starting from that portion, and the discharge roller is covered with the toner, so that the release property between the discharge roller and the transfer paper is deteriorated. . As a result, the transfer paper may be wound around the paper discharge roller or the toner in the image area may be peeled off the paper discharge roller, causing a paper jam called image defect or jam.
[0009]
On the other hand, the magnetic iron oxide having a sphericity (Ψ) of 0.8 or more used in the present invention has a spherical shape. Therefore, if it is contained in the toner, it plays a role as a so-called spacer. It has a function capable of suppressing toner adhesion. In addition, since it is spherical, the contact area with the resin is small when dispersed in the toner and the adhesion with the resin is small. Therefore, cracks are generated at the resin / magnetic iron oxide interface during the pulverization process during toner production. It is likely to occur and the probability that the magnetic iron oxide is exposed on the toner particle surface is high. Furthermore, as a result of studies by the present inventors, if this magnetic iron oxide is combined with a binder resin having a vinyl resin containing a nitrile group, the magnetic iron oxide can be more easily exposed on the toner particle surface. I knew it was possible. The reason for this is not clear, but it is thought that the nitrile group contained in the binder resin exhibits an effect of moderately weakening the adhesion between the magnetic iron oxide surface and the binder resin.
[0010]
Further, since the binder resin has a highly polar nitrile group in the molecule, the polarity of the resin molecule is increased, the cohesive force between the resin molecules is increased, and the toner is melted at the time of fixing the toner image. A certain degree of elasticity can be maintained. Therefore, the magnetic iron oxide exposed on the surface of the toner particles does not enter the melted toner even at the time of fixing and can be present on the surface of the fixed image as it is.
As described above, a toner having a vinyl resin containing a nitrile group as a binder resin and magnetic iron oxide having a sphericity (Ψ) of 0.8 or more has a large amount of magnetic iron oxide on the surface of the fixed image. For example, even if the toner melted during the fixing process does not cool and harden, the magnetic iron oxide works like a spacer between the discharge roller and the fixed image. Since the contact area between the two can be reduced, it is considered that the toner can be effectively prevented from adhering to the paper discharge roller.
[0011]
Hereinafter, each material constituting the electrostatic image developing toner of the present invention will be briefly described.
Examples of the vinyl resin containing a nitrile group used in the binder resin in the present invention include acrylonitrile, methacrylonitrile and methyl group of methacrylonitrile, ethyl group, propyl group, isopropyl group, butyl group, isobutyl. A vinyl monomer substituted with a lower alkyl group such as a group, or a nitrile group such as cinnamic acid nitrile or a derivative thereof, α-cyano-3-hydroxycinnamic acid, α-cyano-4-hydroxy cinnamic acid, etc. Examples thereof include those containing a vinyl monomer alone or mixed and copolymerized with another vinyl monomer. Among these, particularly preferred are copolymers of acrylonitrile, methacrylonitrile and other vinyl monomers.
[0012]
Further, as a binder resin suitable for the present invention, the nitrile group is 9.4 to 943 mmol / 100 g (0.5 to 50% by weight as acrylonitrile), more preferably 94.3 to 565.8 mmol / 100 g (acrylonitrile). As a vinyl resin contained in the range of 5 to 30% by weight. That is, if the content of the nitrile group in the binder resin is less than 9.4 mmol / 100 g, the effect of exposing the magnetic iron oxide to the toner particle surface is reduced, whereas if it is more than 943 mmol / 100 g, the magnetic oxidation is reduced. It becomes difficult to uniformly disperse iron in the toner, and it becomes difficult to expose magnetic iron oxide uniformly on the surface of the toner particles.
[0013]
Specific examples of the other vinyl monomers that can be used for the copolymerization with the vinyl monomer containing a nitrile group as described above include the following. For example, styrene such as styrene, p-chlorostyrene, vinyltoluene, and substituted products thereof, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, acrylic Monocarboxylic acid having a double bond such as lauryl acid, stearyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylamide, or the like; Dicarboxylic acids having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; and substituted products thereof; for example, vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc .; For example, Ethylene-based olefins such as ethylene, propylene, butylene, etc .; for example, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc .; for example, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc .; In the present invention, these are used alone or in combination.
[0014]
Furthermore, in the present invention, compounds having two or more polymerizable double bonds, for example, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, Carboxylic acid esters having two double bonds such as 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and compounds having three or more vinyl groups; It is also preferable to use a cross-linking agent such as a single or a mixture so that the binder resin is in the form of a cross-linked resin.
[0015]
In the molecular weight distribution in gel permeation chromatograph (GPC), the binder resin formed by the above-described materials used in the present invention has a weight average molecular weight in the range of 3,000 to 50,000, and 100,000 to 10,000,000. Each of the ranges has one or more peaks, the number average molecular weight (Mn) is in the range of 1,000 to 50,000, the weight average molecular weight (Mw) is in the range of 10,000 to 1,000,000, and the weight average The Mw / Mn ratio of the number average molecular weight to the molecular weight is preferably Mw / Mn = 1000 or less. When a binder resin having such a molecular weight distribution is used, the cohesive force between the resin molecules can be kept strong and the elasticity can be maintained even when the toner is melted at the time of fixing. It is possible to make it difficult for the magnetic iron oxide exposed on the particle surface to enter the melted toner. As a result, a larger amount of magnetic iron oxide can be present on the surface of the fixed image. Therefore, by using such an electrostatic charge image developing toner of the present invention, a paper such as a paper discharge roller can be more reliably used. Toner adhesion to the conveying member is suppressed.
[0016]
In the present invention, the molecular weight distribution of the binder resin was measured by GPC under the following conditions.
<GPC measurement conditions for resin>
・ Apparatus: GPC-150C (manufactured by Waters)
Column: 7 columns of KF801-7 (manufactured by SHODEX)
・ Temperature: 40 ℃
・ Solvent: THF (tetrahydrofuran)
-Flow rate: 1.0 ml / min.
Sample: 0.1 ml of a sample having a concentration of 0.05 to 0.6% by weight is injected
The molecular weight calibration curve prepared using the monodisperse polystyrene standard sample was used for the measurement of the molecular weight of the sample under the above conditions.
[0017]
As a method for synthesizing the resin composition constituting the toner for developing an electrostatic charge image of the present invention, a conventionally known method can be used. Examples thereof include an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and a solution polymerization method. Among them, the emulsion polymerization method is a method in which a monomer (monomer) almost insoluble in water is dispersed as small particles in an aqueous phase with an emulsifier, and polymerization is performed using a water-soluble polymerization initiator. In this method, the reaction heat can be easily controlled, and the phase in which the polymerization is carried out (the oil phase composed of the polymer and the monomer) and the aqueous phase are separate, so the termination reaction rate is low, and as a result, The polymerization rate is high, and a high polymerization degree can be obtained. Further, the reason is that the polymerization process is relatively simple and that the polymerization product is fine particles, so that it is easy to mix with the colorant, the charge control agent and other additives in the production of the toner. Thus, there is an advantage as a method for producing a binder resin for toner. However, in the emulsion polymerization method, since the emulsifier is added, the produced polymer easily contains impurities, and an operation such as salting out is required to take out the polymer. In order to avoid this complexity, it is preferable to use the suspension polymerization method described below.
[0018]
In order to prepare a binder resin suitable for the present invention, the suspension polymerization method is preferably carried out with 100 parts by weight or less (preferably 10 to 90 parts by weight) of the monomer with respect to 100 parts by weight of the aqueous solvent. Examples of the dispersant that can be used include polyvinyl alcohol, partially saponified polyvinyl alcohol, calcium phosphate, and the like, and a suitable amount varies depending on the amount of monomer with respect to the aqueous solvent, but generally, with respect to 100 parts by weight of the aqueous solvent, It is used in the range of 0.05 to 1 part by weight. The polymerization temperature is suitably about 50 to 95 ° C., but should be appropriately selected depending on the initiator used and the target polymer.
[0019]
Further, when the bulk polymerization method is used, it is possible to obtain a low molecular weight polymer by polymerizing at a high temperature to increase the termination reaction rate, but there is a problem that the reaction is difficult to control.
On the other hand, when the solution polymerization method is used, a low molecular weight polymer can be easily obtained under mild conditions by utilizing the difference in radical chain transfer caused by the solvent or by adjusting the initiator amount and the reaction temperature. be able to. Therefore, it is a preferable method when it is going to obtain a low molecular weight body. Among them, by adjusting the acid component and molecular weight to a high degree, for example, a method of obtaining a low molecular weight polymer by mixing polymers having different molecular weights and compositions, or a method of post-adding monomers having different compositions, etc. Is preferred.
Suitable solvents used in the solution polymerization method include, for example, xylene, toluene, cumene, cellosolve acetate, isopropyl alcohol, benzene and the like. In the case of a styrene monomer mixture, xylene, toluene or cumene is preferred. The solvent to be used may be appropriately selected depending on the polymer to be polymerized.
[0020]
Next, the magnetic iron oxide that constitutes the electrostatic image developing toner of the present invention together with the binder resin described above will be described.
First, in the electrostatic image developing toner of the present invention, magnetic iron oxide having a sphericity (Ψ) of 0.8 or more is used. That is, when the sphericity (Ψ) is smaller than 0.8, the contact area is increased, not only the function as a spacer is lowered, but also the adhesion with the binder resin is increased, so that the magnetic iron oxide is reduced. It becomes difficult to be present on the toner surface, and the effect of suppressing the adhesion of toner to a paper conveying member such as a paper discharge roller cannot be sufficiently obtained.
[0021]
In the present invention, the sphericity (Ψ) of the magnetic iron oxide was measured as follows. First, using an electron micrograph of magnetic iron oxide, 100 or more magnetic iron oxide particle images are randomly selected from the photograph, and the minimum length and maximum length of each particle are measured to determine the ratio. Next, the case where 100 particles were performed was shown below, but the average value of these ratios was obtained and used as the sphericity (Ψ).
[Expression 1]

[0022]
  The toner for developing an electrostatic charge image of the present invention has a melt index (MI) value of 15 at 125 ° C. and a load of 5 kg.g / 10 min.In the case of the following, a more preferable effect is obtained. That is, a toner having magnetic iron oxide and a binder resin satisfying this condition shows a behavior that the magnetic iron oxide is most easily exposed on the toner surface in the pulverization step at the time of toner production. On the other hand, MI is 15g / 10 min.If it is larger, the magnetic iron oxide is less likely to be exposed on the toner surface, so that it is difficult to sufficiently obtain the effect of preventing the toner from adhering to a paper conveying member such as a discharge roller intended by the present invention.
  In the present invention, the melt index (MI) was measured by a manual cutting method under the following measurement conditions using an apparatus described in JIS K7210. At this time, the measured value is converted into a 10-minute value.
  ・ Measurement temperature: 125 ℃
  ・ Load: 5kg
  -Sample filling amount: 5-10g
[0023]
Further, in the electrostatic image developing toner of the present invention, an effect of moderately weakening the adhesion between the nitrile group in the binder resin used in the present invention and the magnetic iron oxide can be obtained. It is preferable to use magnetic iron oxide containing silicon element. Further, it is preferable to use a magnetic iron oxide having a silicon element content of 0.1 to 10% by weight, more preferably 0.2 to 4% by weight based on the iron element. That is, as a result of studies by the present inventors, by using magnetic iron oxide containing silicon element at such a ratio, the adhesion between the nitrile group in the binder resin and the magnetic iron oxide is moderately increased. The weakening effect is further improved, and the magnetic iron oxide can be more easily exposed on the surface of the toner particles.
[0024]
On the other hand, when the content of silicon element in the magnetic iron oxide is less than 0.1% by weight based on the iron element, the silicon added to make the magnetic iron oxide easy to be exposed on the toner particle surface. It is difficult to obtain sufficient elemental effects. In the present invention, as described above, the silicon element content is more preferably 0.2% by weight or more. On the other hand, when the content of silicon element in the magnetic iron oxide is more than 10% by weight based on the iron element, the adhesion between the binder resin and the magnetic iron oxide becomes too weak and exposed to the toner particle surface. In some cases, the magnetic iron oxide is easily detached from the toner particles, and as a result, the amount of the magnetic iron oxide exposed on the surface of the toner particles is reduced. In the present invention, as described above, the silicon element content is more preferably 4% by weight or less.
[0025]
In the present invention, further, the silicon element is contained in the magnetic iron oxide at the above-described content, and the magnetic iron oxide is dissolved from the surface, and the dissolution liquid is dissolved until the iron element has a dissolution rate of 20% by weight. The value B / A of the ratio of B to A and the surface of the magnetic iron oxide, where B is the content of silicon element present therein and A is the total content of silicon element in the magnetic iron oxide When the content of silicon existing in C is C, it is preferable to use a material in which the value C / A of the ratio of C to the content A satisfies the following relationship. That is, the value of B / A is (B / A) × 100 = 44 to 100%, and the value of C / A is (C / A) × 100 = 10 to 95%, more preferably Use (B / A) × 100 = 44 to 84% and (C / A) × 100 = 10 to 55%.
[0026]
That is, in the present invention, magnetic iron oxide in which silicon element is distributed so as to satisfy the above conditions is used as a constituent material of the toner. Further, it can be more difficult to enter the melted toner, and the function as a spacer of the magnetic iron oxide existing on the surface of the fixed image described above can be made more effective. As a result, the contact area of the fixed image with respect to the paper discharge roller is reduced, and the effect of suppressing toner adhesion to the paper discharge roller can be improved.
[0027]
On the other hand, the above-described magnetic iron oxide is dissolved from the surface, the content B of silicon element existing until the dissolution rate of iron element reaches 20% by weight, and the total amount of silicon element in the magnetic iron oxide. When a material having a ratio (B / A) smaller than 44% with respect to the content A is used, magnetic iron oxide tends to easily enter the melted toner during fixing, which is not preferable. On the other hand, in the present invention, all silicon elements may be used up to a dissolution rate of iron element of 20% by weight (B / A) = 100%, but (B / A) may be used. If the ratio is too large, irregularities increase on the surface of the magnetic iron oxide and it becomes brittle, so that chipping is likely to occur in the kneading process at the time of toner production. Therefore, the shape of the magnetic iron oxide is reduced to a sphericity (Ψ) 0.8. It may become difficult to maintain above. Therefore, in the present invention, as described above, it is more preferable to use a material having a ratio of (B / A) within 84%.
[0028]
Further, in addition to the above, the ratio (C / A) of the content C of silicon present on the surface of the magnetic iron oxide and the total content A of silicon elements in the magnetic iron oxide is less than 10%. If it is used, the effect as a spacer is hardly obtained. On the other hand, when the ratio of (C / A) is too large, it is difficult to keep the silicon element uniformly on the surface of the magnetic iron oxide, and it is difficult to obtain a stable spacer effect, which is not preferable. Therefore, in the present invention, as described above, the (C / A) ratio is within 95%, more preferably within 55%.
[0029]
As described above, when forming the electrostatic image developing toner of the present invention, the silicon element is distributed so that the ratio of (B / A) and the ratio of (C / A) satisfy a specific value. It was found that good magnetic toner characteristics can be obtained by using magnetic iron oxide. In other words, in order to obtain a more remarkable effect of the present invention, the distribution of silicon elements present in the magnetic iron oxide particles increases continuously or stepwise from the inside to the surface of the magnetic iron oxide particles. It is shown that it is preferable to form the toner for developing an electrostatic charge image of the present invention using a toner that tends to be used.
[0030]
Such magnetic iron oxide particles having a silicon element distribution suitable for the toner for developing an electrostatic charge image of the present invention can be produced, for example, by the following method.
After adding a predetermined amount of the silicic acid compound to the ferrous salt aqueous solution, an aqueous solution containing ferrous hydroxide is prepared by adding an equivalent or equivalent alkali such as sodium hydroxide to the iron component. First, magnetic iron oxide particles were obtained by blowing air while maintaining the pH of the prepared aqueous solution at 7 or more, preferably 8 to 10, and oxidizing the ferrous hydroxide while heating the aqueous solution to 70 ° C. or more. A seed crystal that forms the core of
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing the seed crystals based on the amount of alkali added previously. While maintaining the pH of the solution at 6 to 10, the reaction of ferrous hydroxide proceeds while blowing air, and magnetic iron oxide particles are grown with the seed crystal as the core. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but it is preferable not to make the pH of the liquid less than 6. Then, by adjusting the pH of the solution at the end of the oxidation reaction, a predetermined amount of the silicate compound can be ubiquitous on the surface layer and the surface of the magnetic iron oxide particles.
[0031]
In the above, examples of the silicate compound to be added to the ferrous salt aqueous solution include silicates such as commercially available sodium silicate, and silicate such as sol-like silicate produced by hydrolysis. It should be noted that other additives such as aluminum sulfate and alumina may be added as long as the present invention is not adversely affected.
[0032]
In addition, as ferrous salts, it is generally possible to use iron sulfate produced as a by-product during the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet, and iron chloride, etc. Can also be used. In the above-described method for producing magnetic iron oxide by the aqueous solution method, in general, iron sulfate having an iron concentration of 0.5 to 2 mol / l is used in order to prevent an increase in viscosity during the reaction and to balance with the solubility of iron sulfate. Used. The concentration of iron sulfate employed at this time generally tends to be finer as the product becomes thinner. In the reaction, the product tends to be atomized more easily as the amount of air is larger and the reaction temperature is lower.
[0033]
In the toner for developing an electrostatic charge image of the present invention, magnetic iron oxide particles having a silicic acid component and having a silicon element specifically distributed are produced by the above-described production method, and the obtained magnetic iron oxide particles are used. It is preferable to prepare a toner.
In the present invention, the content C of the silicon element present on the surface of the magnetic iron oxide particles was determined by the following method. First, about 3 liters of deionized water is put into a 5 liter beaker and heated in a water bath so that the temperature becomes 50-60 ° C. To this, about 25 g of magnetic iron oxide particles slurried with about 400 ml of deionized water is added while being washed with about 300 ml of deionized water, and added to the 5 liter beaker together with the deionized water.
[0034]
Then, while maintaining the temperature at about 60 ° C. and the stirring speed at about 200 rpm, special grade sodium hydroxide is added to make a 1N sodium hydroxide solution. As a result, dissolution of a silicon compound such as silicic acid on the surface of the magnetic iron oxide particles starts. Thirty minutes after the start of dissolution, 20 ml of a sodium hydroxide aqueous solution is sampled from the beaker and filtered through a 0.1 μ membrane filter, and the filtrate is collected. Then, the silicon element is quantified using plasma emission spectroscopy (ICP) using the filtrate as a measurement sample.
At this time, the content C of silicon element present on the surface of the magnetic iron oxide particles was determined by measuring the concentration of silicon element per unit (mg / l) in the sodium hydroxide aqueous solution, and measuring the silicon per unit weight of the magnetic iron oxide sample. It calculated | required as element content (mg / g).
[0035]
Furthermore, in the present invention, the content of silicon element in the magnetic iron oxide particles (% by weight based on iron element), the dissolution rate of iron element, and until the dissolution rate of this iron element reaches 20% by weight. The content B of silicon element present in the solution and the total content A of silicon element in the magnetic iron oxide particles were determined by the following method.
First, about 3 liters of deionized water is placed in a 5 liter beaker and heated in a water bath to 45 to 50 ° C. To this, about 25 g of magnetic iron oxide particles slurried with about 400 ml of deionized water is added while being washed with about 300 ml of deionized water, and added to the 5 liter beaker together with the deionized water.
[0036]
Next, while maintaining the temperature at about 50 ° C. and the stirring speed at about 200 rpm, special grade hydrochloric acid is added to start dissolution of magnetic iron oxide. At this time, the magnetic iron oxide concentration is about 5 g / l, and the aqueous hydrochloric acid solution has a concentration of about 3 N. Sample several times about 20 ml of hydrochloric acid aqueous solution from the beaker several times during the period from the start of dissolution until it becomes transparent, and filter with a 0.1 μ membrane filter to collect the filtrate. Then, using the filtrate as a measurement sample (each sample), the concentration of iron element and silicon element (mg / l) per unit in hydrochloric acid aqueous solution was determined using plasma emission spectroscopy (ICP).
[0037]
From the above measurement results, the dissolution rate of the iron element for each sample was calculated by the following equation.
[Expression 2]

The content of silicon element based on iron element was determined by measuring the iron element concentration and silicon element concentration per unit for the hydrochloric acid aqueous solution sample obtained by dissolving all of the magnetic iron oxide as described above. Calculated by the following equation.
[Equation 3]

[0038]
The total content A of silicon element in the magnetic iron oxide particles is determined by measuring the concentration of silicon element per unit in the hydrochloric acid aqueous solution of the sample sampled after all the magnetic iron oxide particles are dissolved. The silicon element content per weight (mg / g) was obtained. Further, the silicon element content B of the magnetic iron oxide particles was measured for a sample in which the iron element dissolution rate calculated above was 20% among the samples sampled stepwise according to the degree of dissolution. Using the concentration of silicon element per unit (mg / l) in the hydrochloric acid aqueous solution, the silicon element content (mg / g) per unit weight of the magnetic iron oxide sample was obtained.
[0039]
As specific methods for measuring the silicon element contents A, B and C, the following two methods may be mentioned. First, as a first method, the magnetic iron oxide to be used is divided into two, and on the other hand, the silicon element concentration is measured by the above-described operation, and the silicon element content A and There is a method of obtaining B and separately measuring the silicon element content C on the surface of the magnetic iron oxide particles by the above-described operation using another magnetic iron oxide divided into two. As a second method, the silicon element content C on the surface of the magnetic iron oxide is measured by the above-described operation, and after the measurement, the magnetic iron oxide remaining on the filter paper is used as a sample. According to the measurement operation of the element contents A and B, the silicon element content B ′ (= corresponding to the amount obtained by subtracting the content C from the content B) and the total content A ′ up to 20% of the dissolution rate of the iron element There is a method of measuring (= corresponding to the amount obtained by removing the content C from the content A) and finally calculating the content A and B.
[0040]
The electrostatic charge image developing toner of the present invention comprising the above-described constituent materials may contain a charge control agent as necessary. Examples of the charge control agent that can be used in this case include a negative charge control agent such as a metal complex salt of a monoazo dye, a salicylic acid, an alkyl salicylic acid, a dialkyl salicylic acid, or a metal complex of naphthoic acid. . In the case of a positively chargeable toner, for example, a positive charge control agent such as a nigrosine compound or an organic quaternary ammonium salt can be used.
In the present invention, it is preferable that the toner contains a wax if necessary. Examples of the wax used here include paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, carnauba wax and derivatives thereof, and the like. The derivatives include block copolymers with oxides and vinyl monomers, and graft modified products.
[0041]
In addition, the electrostatic charge image developing toner of the present invention is mixed with inorganic fine powder or hydrophobic inorganic fine powder in order to improve environmental stability, charging stability, developability, fluidity and storage stability. It is preferable. Specifically, for example, silica fine powder, titanium oxide fine powder, or a hydrophobized product thereof can be used. These are preferably used alone or in combination. As the silica fine powder, both a so-called dry process produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass or the like can be used. In particular, there are few silanol groups on the surface and inside, and Na₂O, SO_Three ^2-Dry silica is more preferable because there are few production residues such as. In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides in the production process by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds. However, these can also be used in the present invention.
[0042]
Furthermore, the silica fine powder used in the present invention is preferably hydrophobized. As a method of hydrophobizing treatment, hydrophobicity is imparted by chemically treating the silica fine powder with an organosilicon compound that reacts or physically adsorbs with the silica fine powder. As a particularly preferred hydrophobic treatment method, for example, after dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound is treated with a silane coupling agent or simultaneously with a silane coupling agent, The method of processing with such an organosilicon compound is mentioned.
[0043]
Examples of the silane coupling agent used in the hydrophobization treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyl. Dichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethyl Acetoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3 -Divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and hydroxyl groups having 2 to 12 siloxane units per molecule, each bonded to a silicon atom in the terminal unit And dimethylpolysiloxane having
[0044]
Moreover, silicone oil is mentioned as an organosilicon compound used by said hydrophobic treatment. Preferred silicone oils include those having a viscosity at 25 ° C. of 30 to 1000 centistokes. Specifically, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, Fluorine-modified silicone oil and the like are particularly preferable.
There are various methods for treating silicone oil. For example, a method may be used in which silicone oil is added to silica fine powder treated with a silane coupling agent, and these are directly mixed using a mixer such as a Henschel mixer, or silicone oil is added to the silica fine powder as a base. You may use the method of spraying. Alternatively, a method may be used in which silicone oil is dissolved or dispersed in a suitable solvent, silica fine powder is added and mixed, and then the solvent is removed.
[0045]
If necessary, an external additive other than the above-described silica fine powder or composite fine powder of silica fine powder and titanium oxide fine powder may be added to the toner for developing an electrostatic charge image of the present invention. External additives include, for example, charging aids, conductivity-imparting agents, fluidity-imparting agents, anti-caking agents, release agents during heat roll fixing, lubricants, abrasives, resin fine particles and inorganic fine particles, etc. Is mentioned.
Specific examples include lubricants such as Teflon, zinc stearate, and polyvinylidene fluoride. Among these, polyvinylidene fluoride is preferable. Alternatively, for example, a polishing agent such as cerium oxide, silicon carbide, strontium titanate and the like can be mentioned, and among these, strontium titanate is preferable. Alternatively, for example, fluidity imparting agents such as titanium oxide and aluminum oxide can be mentioned, and among these, hydrophobic ones are particularly preferable. A small amount of an anti-caking agent, a conductivity imparting agent such as carbon black, zinc oxide, antimony oxide or tin oxide, or white and black fine particles having opposite polarity can be used as a developing property improver.
[0046]
The toner for developing an electrostatic charge image of the present invention is prepared by sufficiently mixing the above-described toner constituent materials with a mixer such as a ball mill, and then melting and kneading them using a heat kneader such as a heating roll, a kneader, and an extruder. And after the meat is minced and cooled and solidified, it can be produced by grinding and strict classification.
[0047]
【Example】
  Examples belowReference examplesThe present invention will be described more specifically with reference to comparative examples, but the present invention is not limited thereto.
(Binder Resin Production Example 1)
  A 4-necked flask was charged with 180 parts by weight of degassed water and 20 parts by weight of a 2% by weight aqueous solution of polyvinyl alcohol, then 15 parts by weight of acrylonitrile, 65 parts by weight of styrene, 15 parts by weight of lauryl methacrylate, monobutyl maleate. A mixed solution composed of a solution of 5 parts by weight and 2.0 parts by weight of di-t-butylperoxyhexahydroterephthalate was added and stirred to obtain a suspension.
  Next, after fully replacing the inside of the flask with nitrogen, the temperature was raised to 80 ° C. to initiate polymerization. After maintaining the temperature of 80 ° C. for 12 hours, the polymerization was further completed by maintaining the temperature at 95 ° C. for 5 hours. This was separated, washed with water and dried to obtain a polymer 1-1.
[0048]
Next, 300 parts by weight of xylene is put into a four-necked flask, and the inside of the container is sufficiently replaced with nitrogen while stirring, and then heated to reflux. Under this reflux, a mixture of 15 parts by weight of acrylonitrile, 75 parts by weight of styrene, 9.5 parts by weight of lauryl methacrylate, 0.5 parts by weight of monobutyl maleate, and 3 parts by weight of di-tert-butyl peroxide was added. After dripping over time, it hold | maintained for 2 hours, superposition | polymerization was completed, the organic solvent was distilled off, and the polymer 1-2 was obtained.
[0049]
Next, 100 parts by weight of xylene, 30 parts by weight of the polymer 1-1 obtained above and 70 parts by weight of the polymer 1-2, were added in a total of 100 parts by weight. After stirring and holding for 12 hours, the organic solvent was distilled off to obtain a resin. Next, the obtained resin was cooled, solidified, and pulverized to obtain a binder resin 1 for toner. Table 1 shows the physical properties of the resultant binder resin 1 for toner.
[0050]
(Binder Resin Production Example 2)
As a mixed solution, a mixed solution composed of 20 parts by weight of acrylonitrile, 65 parts by weight of styrene, 10 parts by weight of acrylate-2-ethylhexyl, 2 parts by weight of monobutyl maleate, and 1.1 parts by weight of di-tert-butyl peroxide is used. Except for the above, a polymer 2-2 was obtained in the same manner as in the production method of the polymer 1-2 in Production Example 1 of the binder resin. A resin obtained in the same manner as in the binder resin production example 1 except that the obtained polymer 2-2 was used was cooled, solidified, and pulverized to obtain a toner binder resin 2. The properties of the obtained binder resin 2 for toner are shown in Table 1.
[0051]
(Binder Resin Production Example 3)
A 4-necked flask was charged with 180 parts by weight of degassed water and 20 parts by weight of a 2% by weight aqueous solution of polyvinyl alcohol, and then 2 parts by weight of acrylonitrile, 70 parts by weight of styrene, 21 parts by weight of acrylic acid-n-butyl, A mixed solution consisting of a solution of 7 parts by weight of monobutyl maleate and 2.4 parts by weight of di-t-butylperoxyhexahydroterephthalate was added and stirred to obtain a suspension.
After sufficiently replacing the inside of the flask with nitrogen, the temperature was raised to 85 ° C. to initiate polymerization. After maintaining the temperature at 85 ° C. for 12 hours, the polymerization reaction was completed by further maintaining at 95 ° C. for 5 hours. This was separated, washed with water and dried to obtain a polymer 3-1.
[0052]
Next, as a mixed solution, the monomer composition is composed of 85 parts by weight of styrene, 14 parts by weight of acrylate-n-butyl, 1 part by weight of monobutyl maleate, and 2.5 parts by weight of di-tert-butyl peroxide. Polymerization was carried out in the same manner as in the production method of the polymer 1-2 in Production Example 1 of the binder resin, except that the polymer 3-2 was obtained.
To 100 parts by weight of xylene, 15 parts by weight of the polymer 3-1 obtained above and 85 parts by weight of the polymer 3-2 were put in a total of 100 parts by weight, heated and stirred under reflux, After holding for 12 hours, the organic solvent was distilled off to obtain a resin. The obtained resin was cooled, solidified, and pulverized to obtain a binder resin 3 for toner. The properties of the obtained binder resin 3 for toner are shown in Table 1.
[0053]
(Binder Resin Production Example 4)
A 4-necked flask was charged with 180 parts by weight of degassed water and 20 parts by weight of a 2% by weight aqueous solution of polyvinyl alcohol, followed by 35 parts by weight of acrylonitrile, 50 parts by weight of styrene, 12 parts by weight of lauryl methacrylate, monobutyl maleate 3 A mixed solution composed of a solution of parts by weight and 3.0 parts by weight of di-t-butylperoxyhexahydroterephthalate was added and stirred to obtain a suspension.
Furthermore, after the inside of the flask was sufficiently substituted with nitrogen, the temperature was raised to 90 ° C. to initiate polymerization. After maintaining at a temperature of 90 ° C. for 12 hours, the polymerization was completed by further maintaining at 95 ° C. for 5 hours. This was filtered off, washed with water and dried to obtain a polymer 4-1.
[0054]
Next, the monomer composition is heavy except that 35 parts by weight of acrylonitrile, 55 parts by weight of styrene, 8 parts by weight of lauryl methacrylate, 2 parts by weight of monobutyl maleate, and 3.5 parts by weight of di-tert-butyl peroxide. Polymerization was carried out in the same manner as in the case of producing the polymer 1-1, and a polymer 4-2 was obtained.
To 100 parts by weight of xylene, a total of 100 parts by weight of 35 parts by weight of the polymer 4-1 obtained above and 65 parts by weight of the polymer 4-2 was added, and the mixture was heated and stirred under reflux. After holding for 12 hours, the organic solvent was distilled off to obtain a resin. The obtained resin was cooled, solidified, and pulverized to obtain a binder resin 4 for toner. The properties of the obtained binder resin 4 for toner are shown in Table 1.
[0055]
(Comparative production example of binder resin)
A 4-necked flask was charged with 180 parts by weight of degassed water and 20 parts by weight of a 2% by weight aqueous solution of polyvinyl alcohol, then 72 parts by weight of styrene, 28 parts by weight of acrylic acid-n-butyl, and di-t- A mixed solution consisting of a solution of 1 part by weight of butyl peroxyhexahydroterephthalate was added and stirred to obtain a suspension.
Furthermore, after the inside of the flask was sufficiently substituted with nitrogen, the temperature was raised to 75 ° C. to initiate polymerization. After maintaining at a temperature of 75 ° C. for 12 hours, the polymerization was completed by further maintaining at 95 ° C. for 5 hours. This was separated, washed with water and dried to obtain a polymer 5-1.
[0056]
Next, a manufacturing example of a binder resin except that the monomer composition is a mixed liquid composed of 87 parts by weight of styrene, 13 parts by weight of acrylic acid-n-butyl, and 2 parts by weight of di-tert-butyl peroxide. Polymerization was carried out in the same manner as in the case of the polymer 1-1 in No. 1 to obtain a polymer 5-2.
To 100 parts by weight of xylene, 25 parts by weight of the polymer 5-1 obtained above and 75 parts by weight of the polymer 5-2 were put in a total of 100 parts by weight, heated and stirred under reflux, After holding for 12 hours, the organic solvent was distilled off to obtain a resin. The obtained resin was cooled, solidified, and pulverized to obtain a binder resin for comparative toner. The properties of the obtained binder resin for comparative toner are shown in Table 1.
[0057]
[Table 1]
Table 1: Properties of binder resin for toner used in Examples and Comparative Examples

[0058]
(Production example 1 of magnetic iron oxide)
After adding sodium silicate so that the content of silicon element with respect to iron element is 1.6% by weight in ferrous sulfate aqueous solution, 1.0 to 1.1 equivalents with respect to iron ions An aqueous solution containing ferrous hydroxide was prepared by mixing a caustic soda solution.
Air was blown in while maintaining the pH of this aqueous solution at 9, and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals. Next, an aqueous ferrous sulfate solution was added to the slurry so as to be 0.9 to 1.2 equivalents relative to the initial alkali amount (sodium component of sodium silicate and sodium component of caustic soda). The pH of the solution was maintained at 8, and the oxidation reaction was advanced while blowing air, and the pH was adjusted at the end of the oxidation reaction to make the silicic acid component ubiquitous on the surface of the magnetic iron oxide particles. The produced magnetic iron oxide particles were washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain magnetic iron oxide particles 1. Table 2 shows characteristics of the obtained magnetic iron oxide particles 1 such as a distribution state of silicon element.
[0059]
(Production example 2 of magnetic iron oxide)
Magnetic iron oxide particles 2 containing no silicon element were obtained in the same manner as in Magnetic Iron Oxide Production Example 1 except that sodium silicate was not added. Table 2 shows characteristics of the obtained magnetic iron oxide particles 2 such as a distribution state of silicon element.
[0060]
(Production Example 3 of Magnetic Iron Oxide)
Further, silicate fine powder is added to the magnetic iron oxide particles 1 so that the content of silicon element is 3.3% by weight with respect to the iron element, and the magnetic iron oxide particles 3 are mixed by a Henschel mixer. Obtained. Table 2 shows the characteristics of the obtained magnetic iron oxide particles 3 such as the distribution state of silicon element.
[0061]
(Production Example 4 of Magnetic Iron Oxide)
Silicic acid fine powder was added to the magnetic iron oxide particles 2 so that the silicon element content was 0.7% by weight with respect to the iron elements, and mixed with a Henschel mixer to obtain magnetic iron oxide particles 4. . Table 2 shows characteristics such as distribution state of the silicon element of the obtained magnetic iron oxide particles 4.
[0062]
(Production Example 5 of Magnetic Iron Oxide)
Production Example 1 of Magnetic Iron Oxide except that after adding sodium silicate so that the content of silicon element is 1.0% by weight with respect to iron element, the silicon element is not present on the surface. In the same manner, magnetic iron oxide particles 5 were obtained. Table 2 shows the characteristics of the obtained magnetic iron oxide particles 5, such as the distribution of silicon elements.
[0063]
(Comparative production example of magnetic iron oxide)
Magnetic iron oxide particles for comparison in octahedron (sphericity Ψ = 0.69) were obtained by adding no sodium silicate and changing the temperature and pH. Table 2 shows characteristics of the obtained magnetic iron oxide particles for comparison, such as silicon element distribution.
[0064]
[Table 2]
Table 2: Characteristics of magnetic iron oxide particles

[0065]
Example 1
・ 100 parts by weight of binder resin 1 for toner
-Magnetic iron oxide particles 1 100 parts by weight
-Negative charge control agent (azo iron complex) 1.5 parts by weight
・ Polyethylene wax (molecular weight 700) 3 parts by weight
After mixing the above materials, the mixture was kneaded with a twin screw extruder, and then subjected to coarse pulverization, fine pulverization, and classification steps to obtain toner particles. Further, 1.0 part by weight of hydrophobic silica was mixed with 100 parts by weight of the toner particles with a Henschel mixer to obtain a toner for developing an electrostatic image of this example having an average particle diameter of 6.8 μm. The MI of the toner was 3.1 (g / 10 min.).
[0066]
Example 2
An electrostatic charge image developing toner of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of binder resin 2 for toner was used. The MI of the toner was 1.4 (g / 10 min.).
[0067]
Example 3
An electrostatic charge image developing toner of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of the binder resin 3 for toner was used. The MI of the toner was 12.0 (g / 10 min.).
[0068]
Example 4
A toner for developing an electrostatic charge image of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of magnetic iron oxide particles 3 were used. The MI of the toner was 3.3 (g / 10 min.).
[0069]
Example 5
An electrostatic charge image developing toner of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of magnetic iron oxide particles 4 were used. The MI of the toner was 3.0 (g / 10 min.).
[0070]
Example 6
An electrostatic charge image developing toner of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of magnetic iron oxide particles 5 were used. The MI of the toner was 2.9 (g / 10 min.).
[0071]
referenceExample1
  In the same manner as in Example 1 except that 100 parts by weight of magnetic iron oxide particles 2 are used,referenceAn example electrostatic toner image developing toner was obtained. The MI of the toner was 2.8 (g / 10 min.).
[0072]
Example 8
An electrostatic charge image developing toner of this example was obtained in the same manner as in Example 1 except that 100 parts by weight of the toner binder resin 4 was used. The MI of the toner was 21.7 (g / 10 min.).
[0073]
Comparative Example 1
A toner for developing an electrostatic charge image of a comparative example was obtained in the same manner as in Example 1 except that 100 parts by weight of the binder resin for comparative toner was used. The MI of the toner was 6.8 (g / 10 min.).
[0074]
Comparative Example 2
A toner for developing an electrostatic image of a comparative example was obtained in the same manner as in Example 1 except that 100 parts by weight of the binder resin for comparative toner and 100 parts by weight of comparative magnetic iron oxide particles were used. The MI of the toner was 7.2 (g / 10 min.).
[0075]
(Evaluation)
  Example 1 to above6,8,Reference Example 1,Each of the electrostatic image developing toners obtained in Comparative Examples 1 and 2 was evaluated as follows. Canon's laser printer LBP-430 (8-sheet machine) is speeded up to 12-sheet machine, the temperature setting of the fixing unit is changed to a higher level, and the contact pressure between the discharge roller and transfer paper is increased to discharge paper. What was remodeled so that the toner easily adheres to the roller was used as an evaluation machine.
  Then, an image output test of 5,000 sheets was performed in a normal temperature and humidity environment, and for every 1,000 sheets, the toner adhesion to the discharge roller was determined as “effect on image” and “toner on the surface of the discharge roller. Evaluation was made from two viewpoints of “observation of adhesion”. Evaluation was performed according to the following criteria. Note that x indicates that a jam (paper jam) has occurred, and the evaluation was terminated at that time. The evaluation results are shown in Table 3.
[0076]
1. Evaluation of toner adhesion to paper discharge rollers
A: No toner adheres to the surface of the paper discharge roller.
○: A little toner adheres to the surface of the paper discharge roller, but there is no influence on the image.
○ △: There is a slight influence on the image, but it is a good level.
Δ: Image defect occurs but no jam occurs.
X: Jam occurs due to toner adhering to the paper discharge roller.
[0077]
[Table 3]

[0078]
【The invention's effect】
As described above, according to the present invention, the problem of toner adhesion to a paper conveying member such as a paper discharge roller, which has become more conspicuous as the machine becomes smaller, faster, and more durable, is solved. A toner for developing an electrostatic image is provided.

Claims (7)

In an electrostatic charge image developing toner containing at least a binder resin and magnetic iron oxide, the binder resin has a vinyl resin containing a nitrile group, and the sphericity (Ψ) of the magnetic iron oxide is 0. 8 or more, and the content of silicon element in the magnetic iron oxide is 0.00 on the basis of the iron element. 2 to 4% by weight, the toner for developing electrostatic images, 125 ° C., a melt index in 5kg load (MI) is 15 g / 10min. An electrostatic charge image developing toner characterized by:   The ratio of the content B of silicon element present until the magnetic iron oxide is dissolved from the surface and the dissolution rate of iron element reaches 20% by weight, and the total content A of silicon element in the magnetic iron oxide is (B / A) × 100 = 44 to 100%, and the ratio of the content C of silicon present on the surface of the magnetic iron oxide to the content A is (C / A) × 100. The toner for developing an electrostatic charge image according to claim 1, wherein = 10 to 95%. And the content B of silicon element dissolution rate of dissolving pre Symbol magnetic iron oxide from the surface iron element is present until it is 20% by weight, the ratio of the total content A of silicon element of the magnetic iron oxide (B / A) × 100 = 44 to 84%, and the ratio of the content C of silicon present on the surface of the magnetic iron oxide to the content A is (C / A) × 100. The toner for developing an electrostatic charge image according to claim 1, wherein = 10 to 55%.   The toner for developing an electrostatic charge image according to any one of claims 1 to 3, wherein a nitrile group contained in the binder resin is 9.4 to 943 mmol / 100 g.   The electrostatic image developing toner according to claim 1, wherein the binder resin is a copolymer of at least acrylonitrile and another vinyl monomer.   The electrostatic image developing toner according to claim 5, wherein the total content of acrylonitrile contained in the binder resin is 0.5 to 50% by weight.   In the molecular weight distribution in the gel permeation chromatograph (GPC) of the THF soluble content of the binder resin, the molecular weight ranges from 3,000 to 50,000 and 100,000 to 10,000,000, respectively, and has one or more peaks, and 7. The electrostatic charge image development according to claim 1, wherein the number average molecular weight (Mn) is 1,000 to 50,000, the weight average molecular weight (Mw) is 10,000 to 1,000,000, and Mw / Mn is 1000 or less. Toner.