JP3641732B2 - Toner for developing electrostatic image and image forming method - Google Patents

Description

【００３２】
ここで、Ｒ₁は水素原子、ヒドロキシ基、アルキル基、アリール基、アルコキシ基、又は
【００３３】
【化２】

【００３４】
を表し、Ｒ₂は結合基（例えば、アルキレン基、アリーレン基、アラルキレン基、−ＮＨ−，−ＮＨＣＯ−或いはこれらの基を任意に組み合わせた基等が挙げられる）、又は単なる結合手を表し、Ｒ₃〜Ｒ₅はそれぞれ水素原子、アルキル基、アリール基を表し、Ｘはハロゲン原子を表す。Ｒ₁〜Ｒ₅で表される各基は置換基を有するものも含まれる。
【００３５】
【化３】

【００３６】
Ｒ₆及びＲ₇はそれぞれ水素原子、ヒドロキシ基、アルキル基、アリール基又はアルコキシ基を表し、これらの基は置換基を有するものも含まれる。Ｒ₁〜Ｒ₅、Ｘは一般式（１）のＲ₁〜Ｒ₅、Ｘと同義である。ｍ，ｎはそれぞれ１以上の整数を表す。又、上記化２で表される基
は、具体的には下記構造式で表されるものが挙げられるが、これらに限定されるものではない。
【００３７】
【化４】

【００３８】
【化５】

【００３９】
【化６】

【００４０】
アンモニウム塩を官能基として有するポリシロキサンを得る方法としては、アンモニウム塩を官能基として有するオルガノハロゲン化シランと、特にアンモニウム塩基を有していないオルガノハロゲン化シランを用いて重合段階で共重合せしめることにより導入する方法、オルガノハロゲン化シランを用いた重合により得たポリシロキサンにアンモニウム塩を官能基として有する有機基により一部を変性する方法等によって得ることができる。オルガノハロゲン化シランの代わりにオルガノアルコキシシランを用いてもよい。又、一部の化合物については市販品として入手することもできる。
【００４１】
これらのうち、正帯電性疎水性シリカはアンモニウム変性ポリシロキサンで処理されることが好ましい。
【００４２】
本発明のトナーを構成する着色粒子について説明する。
【００４３】
着色粒子は、結着樹脂と着色剤と必要に応じて使用されるその他の添加剤とを含有してなり、その平均粒径は体積平均粒径で通常、１〜３０μｍ、好ましくは５〜２０μｍである。着色粒子を構成する結着樹脂としては特に限定されず、従来公知の種々の樹脂が用いられる。例えば、スチレン系樹脂、アクリル系樹脂、スチレン／アクリル系樹脂、ポリエステル樹脂等が挙げられる。着色粒子を構成する着色剤も特に限定されず、従来公知の種々の材料が使用される。例えばカーボンブラック、ニグロシン染料、アニリンブルー、カルコイルブルー、クロムイエロー、ウルトラマリンブルー、デュポンオイルレッド、キノリンイエロー、メチレンブルークロライド、フタロシアニンブルー、マラカイトグリーンオクサレート、ローズベンガル等が挙げられる。その他の添加剤としては以下に記載する荷電制御剤、低分子量ポリオレフィン、カルナウバワックス等の定着性改良剤等が挙げられる。
【００４４】
又、本発明のトナーは、磁性体を含有させて一成分磁性トナーとして使用する場合、キャリアと混合して二成分現像剤として使用する場合、非磁性トナーを単独で使用する場合が考えられ何れも好適に使用することができるが、本発明ではキャリアと混合して使用する二成分現像剤が好ましい。磁性トナーを得る場合には着色粒子に添加剤として磁性体粒子が含有される。磁性体粒子としては平均一次粒子径が０．１〜２．０μｍのフェライト、マグネタイト等の粒子が用いられる。磁性体粒子の添加量は着色粒子中の２０〜７０重量％である。
【００４５】
二成分現像剤を構成するキャリアとしては、鉄、フェライト等の磁性材料粒子のみで構成される非被覆キャリア、或いは磁性材料粒子表面を樹脂等によって被覆した樹脂被覆キャリアの何れを使用してもよい。樹脂被覆キャリアとしては、フッ素系樹脂被覆キャリア、スチレンアクリル樹脂被覆キャリア、シリコーン樹脂被覆キャリア等が挙げられ、好ましくはシリコーン樹脂被覆キャリアである。
【００４６】
本発明のトナー自体を正帯電性化するために必要な荷電制御剤の例を以下に挙げるが、これらに限定されるものではない。
【００４７】
ニグロシン染料、４級アンモニウム塩化合物、トリフェニルメタン系化合物等が挙げられ、４級アンモニウム塩化合物としては、具体的には下記一般式（３）で表される化合物
【００４８】
【化７】

【００４９】
（Ｒ₁〜Ｒ₄はそれぞれ炭素数が１〜３０個のアルキル基、アルケニル基、アリール基、アラルキル基及びアリール基を有するアルキル基を示し、Ａはアニオンを示す。好ましいものとしては、Ｒ₁〜Ｒ₃はそれぞれ炭素数が８〜２２個の長鎖アルキル基或いは長鎖アルケニル基であり、Ｒ₄は炭素数が１〜７個のアルキル基或いはベンジル基であり、更に好ましくはＲ₁〜Ｒ₂はそれぞれ炭素数が８〜２２個の長鎖アルキル基或いは長鎖アルケニル基であり、Ｒ₃〜Ｒ₄は炭素数が１〜７個のアルキル基或いはベンジル基である。前記アニオンとしてはスルフォン基、モリブデン酸基、タングステン酸基が好ましい。）等が挙げられる。具体的な例示化合物を下記に示す。
【００５０】
１） （Ｃ₁₆Ｈ₃₃）₂Ｎ⁺（ＣＨ₃）₂１／４｛Ｍｏ₈Ｏ₃₆｝^4-
２） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（ＣＨ₃）₂１／４｛Ｍｏ₈Ｏ₃₆｝^4-
３） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（ＣＨ₂Ｃ₆Ｈ₅）₂１／４｛Ｍｏ₈Ｏ₃₆｝^4-
４） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（Ｃ₄Ｈ₉）₂１／４｛Ｍｏ₈Ｏ₃₆｝^4-
５） （Ｃ₁₄Ｈ₂₉）₂Ｎ⁺（ＣＨ₃）₂１／４｛Ｍｏ₈Ｏ₃₆｝^4-
６） （Ｃ₁₆Ｈ₃₃）₂Ｎ⁺（ＣＨ₃）₂１／１０｛Ｈ₂Ｗ₁₂Ｏ₄₂｝₁₀ ^-
７） （Ｃ₁₄Ｈ₂₉）₂Ｎ⁺（ＣＨ₃）₂１／１０｛Ｈ₂Ｗ₁₂Ｏ₄₂｝₁₀ ^-
８） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（ＣＨ₃）₂１／１０｛Ｈ₂Ｗ₁₂Ｏ₄₂｝₁₀ ^-
９） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（ＣＨ₂Ｃ₆Ｈ₅）₂１／１０｛Ｈ₂Ｗ₁₂Ｏ₄₂｝₁₀ ^-
１０） （Ｃ₁₆Ｈ₃₃）（Ｃ₁₄Ｈ₂₉）Ｎ⁺（Ｃ₄Ｈ₉）₂１／１０｛Ｈ₂Ｗ₁₂Ｏ₄₂｝₁₀ ^-
又、トリフェニルメタン系化合物としては、以下の式で表される化合物が挙げられる。
【００５１】
【化８】

【００５２】
Ｒ₁〜Ｒ₆は、水素原子又は炭素数１〜６のアルキル基を示す。これらは異なっていても、又同じでも良い。具体的には以下のものを挙げることができる。
【００５３】
【化９】

【００５４】
次に、本発明の第１及び第２の態様のトナーを用いる画像形成方法について説明する。図１は本発明の画像形成方法の実施に用いることができる画像形成装置を示す。
【００５５】
正帯電有機光導電性感光層を備えた感光体（潜像担持体）１０の周囲に、帯電極１１、現像機構１２、転写分離極１３、クリーニング機構１４、除電ランプ１５が配置されている。給紙機構１６からの記録材は、搬送機構である搬送ローラ１７ａ，１７ｂ，１７ｃにより搬送され、転写分離極１３によりトナー像の転写を受けた後、定着機構１８により定着されて画像が形成される。転写後に感光体１０上に残留したトナーはクリーニング機構１４により掻き取り除去される。回収したトナーは、リサイクル機構１９により再度現像機構１２に戻されて再使用される。
【００５６】
以下、各工程ごとに説明する。
【００５７】
（現像工程）
樹脂微粒子を必須成分として固着しているトナーを用いて構成した１成分現像剤又は２成分現像剤を現像剤搬送担体により現像領域に搬送し、この現像剤により感光体上の静電潜像を現像して、未定着トナー画像を形成する。現像方法としては、特に限定されず、従来公知の方法を適用することができる。具体的には以下の方法を挙げることができる。
【００５８】
（１）接触磁気ブラシ現像法
この方法では、図２に示すように、現像剤搬送担体２１上に、現像領域の間隙より穂立ちの高い現像剤の磁気ブラシを形成し、この磁気ブラシを現像領域に搬送して感光体１０上の静電潜像を摺擦しながら磁気ブラシ中のトナーを静電潜像に付着させて現像を行う。尚、２２は主撹拌ローラ、２３は補助撹拌ローラ、２４はトナー搬送スクリュー、２５は穂立ち規制板、２６はドクターブレードである。感光体１０は特に限定されないが、ＯＰＣが好ましい。
【００５９】
（２）ジャンピング磁気ブラシ現像法
この方法では、現像剤搬送担体上に、現像領域の間隙より穂立ちの低い現像剤の磁気ブラシを形成し、この磁気ブラシを現像領域に搬送するとともに、現像領域に振動電界を作用させることにより磁気ブラシ中のトナーを飛翔させて静電潜像に付着させて現像を行う。
【００６０】
（転写工程）
現像により得られた感光体上の未定着トナー画像を記録材に転写する。この転写工程においては、静電転写方式或いはバイアス転写方式の何れも適用できるが、特に静電転写方式が好ましい。具体的には、例えば直流コロナ放電を生じさせる転写器を、記録材を介して感光体に対向するよう配置し、記録材にその裏面側から直流コロナ放電を作用させることにより感光体の表面に担持されていた未定着トナー画像を記録材の表面に転写する。
【００６１】
（クリーニング工程）
転写工程を経た後に感光体上に残留したトナーをクリーニングする。クリーニング手段は、特に限定されないが、感光体の表面に接触配置したクリーニングブレードを有するクリーニング装置が好ましい。このクリーニング装置によれば、感光体の表面がクリーニングブレードにより摺擦されることにより、残留トナーが掻き取られ除去される。
【００６２】
（リサイクル工程）
クリーニングにより回収したトナーを、適宜のリサイクルシステムにより再び現像機構に戻してこれを再使用する。
【００６３】
図３はリサイクルシステムの一例を示す説明図である。
【００６４】
１０は感光体、１２は現像機構、１４はクリーニング機構、１９はリサイクル機構、３１は磁気ブラシ機構、３２はトナー受入れ分配機構、３３はスクリューコンベア、３４は第１スクリュー、３５は第２スクリューである。この例の装置は、第１スクリュー３４と第２スクリュー３５とによりスクリューコンベア３３よりのトナーをトナー受入れ分配機構３２に供給するようにしたものである。即ち、第１スクリュー３４及び第２スクリュー３５は、それぞれ内部に回転軸とこの回転軸に沿ってスパイラル状に設けた羽根を有し、第１スクリュー３４においては、スクリューコンベア３３により送られたトナーが回転軸の回転に伴って羽根により順次押し上げられて第２スクリュー３５に送られ、この第２スクリュー３５においては、第１スクリュー３４と同様の原理で水平方向にトナーが順次送られてトナー受入れ分配機構３２に供給され、回収されたトナーが再び感光体１０上の静電潜像の現像に供される。
【００６５】
（定着工程）
転写工程によって、未定着トナー画像が転写された記録材を、加熱定着機構により定着処理し、記録材上に定着トナー画像を形成する。
【００６６】
（クリーニングブレードの構成）
クリーニングブレードの構成は、図４又は図５に記載される構成の何れも使用することができる。図４又は図５に於いてホールダー１４ｂにクリーニングブレード１４ａを保持する構成である。又、感光体は１０である。ホールダー１４ｂと感光体１０が形成する角度は、何れも図に示したθ₁が２０〜９０°、好ましくは３０〜７５°である。クリーニングブレード自体を構成する材料としては、シリコンゴム、ウレタンゴムなどの弾性体を使用することができる。この場合、ゴム硬度が３０〜９０°のものがよい。厚みは２〜１０ｍｍ、ホールダー部外の長さは５〜４０ｍｍがよい。感光体１０に対する圧接力は５〜３０ｇｆ／ｍｍが好適である。
【００６７】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されない。
【００６８】
《酸化チタンの製造》
下記表１に示す酸化チタンを調製した。尚、酸化チタンの数平均一次粒子径は走査型電子顕微鏡で４００００倍に拡大した写真を用いて測定した結果、２０ｎｍである。
【００６９】
【表１】

【００７０】
１＊：オクチルトリメトキシシラン、２＊：ドデシルトリメトキシシラン、３＊：ヘキシルトリメトキシシシラン
注）表面処理剤の量は酸化チタンに対して５重量％で処理を行った。
【００７１】
《着色粒子製造例》
スチレンアクリル樹脂１００部に対してカーボンブラック８部、低分子量ポリプロピレン６部及び荷電制御剤として例示化合物１）を１部添加し、予備混合した後に溶融混練、粉砕、分級を行い、体積平均粒径が８．２μｍの着色粒子を得た。これを着色粒子１とする。又、着色粒子製造例に於いて、荷電制御剤を例示化合物３）に変更した他は同様にして体積平均粒径が８．１μｍの着色粒子を得た。これを着色粒子２とする。又、着色粒子製造例に於いて、荷電制御剤を例示化合物６）に変更した他は同様にして体積平均粒径が８．０μｍの着色粒子を得た。これを着色粒子３とする。
【００７２】
《トナー製造例》
上記着色粒子１に対して酸化チタン１を０．６重量％、アンモニウム変性ポリシロキサンで処理した正帯電性シリカ（数平均一次粒子径＝１２ｎｍ／鉄粉との帯電量＝９０μＣ／ｇ）を０．８重量％添加し、ヘンシェルミキサー（内容量＝１０リットル）にて４０ｍ／分の周速条件で１０分間混合し、トナーを得た。これをトナー１とする。トナー製造例に於いて、酸化チタン１を酸化チタン２へ変更した他は同様にしてトナーを得た。これをトナー２とする。トナー製造例に於いて、着色粒子１を着色粒子２へ変更し、酸化チタン１を酸化チタン３へ変更した他は同様にしてトナーを得た。これをトナー３とする。トナー製造例に於いて、着色粒子１を着色粒子３へ変更し、酸化チタン１を酸化チタン４へ変更し添加量を０．４重量％とした他は同様にして本発明のトナーを得た。これをトナー４とする。トナー製造例に於いて、酸化チタン１を酸化チタン５へ変更した他は同様にしてトナーを得た。これをトナー５とする。トナー製造例に於いて、酸化チタン１を酸化チタン６へ変更した他は同様にしてトナーを得た。これをトナー６とする。
【００７３】
《現像剤調製》
上記で調製したトナーを用いて現像剤を調製した。キャリアとして、体積平均粒径が６１μｍのリチウムフェライトキャリアにシリコーン樹脂を被覆したキャリアを用いた。トナー濃度が５％になるようにトナーとキャリアを混合し、現像剤を調製した。トナー１〜６に対応する現像剤を現像剤１〜６とする。
【００７４】
得られた現像剤１〜６を複写機３１３５（コニカ（株）社製）に採用し、以下の実験を行った。尚、前記複写機は、図３に示した型のリサイクル方式に改造し、又感光体として積層型有機感光体を用い、クリーニング条件としては、図４に記載した構成とし、ホールダーと感光体が形成する角度θ_１が２２°であり、クリーニングブレード自体を構成する材料としては、ウレタンゴムを使用した。ウレタンゴムのゴム硬度は６５°であり、厚みは２ｍｍ、ホールダー部外の長さは８ｍｍとした。又、感光体に対する圧接力は１５ｇｆ／ｍｍである。
【００７５】
（評価）
評価項目は、高温高湿（３３℃／８０％ＲＨ）での環境条件にて、画素率が５％の原稿を連続で１０万枚印字し、画像濃度及びカブリの発生状況、更に感光体に対する傷の発生による画像欠陥の有無を評価した。画像欠陥は、０．２ｍｍφ以上の黒点が画像上に発生した場合を欠陥有りとして判定した。尚、画像濃度はマクベス社製ＲＤ−９１８を用いた絶対反射濃度で示し、カブリ濃度は支持体（紙）の濃度を「０」とした相対反射濃度で示した。
【００７６】
結果を以下の表２に示す。
【００７７】
【表２】

【００７８】
表２の結果から明らかなように、ｐＨが６〜８の酸化チタンを用いた現像剤１〜４は、画像濃度及びカブリ濃度の、初期段階及び１０万枚後の推移に大差がなく、しかも１０万枚処理した後での感光体に対するトナーの付着及び欠陥がないなど耐久性も良好であり、総合的に優れた性能を有することが分かる。又、水分量＝０．３〜２．０重量％、かつ比抵抗＝１５００〜１００００Ωｃｍの酸化チタンを用いた現像剤１〜４も同様に優れた性能を有することがわかる。しかしながら、これらの範囲外の現像剤５及び６は、１０万枚処理するという負荷条件の後では、画像濃度及びカブリ濃度が十分ではなく、しかもその際の画像欠陥は相当なものであることが分かる。
【００７９】
【発明の効果】
本発明により、帯電を均一化してカブリ、画像の環境依存性を向上し、又現像剤の耐久性を改善した静電荷像現像用トナーを提供することができるという顕著に優れた効果を奏する。又、感光体に対する付着等の問題、画像欠陥を発生しにくい静電荷像現像用トナーの提供も同様にして可能である。
【図面の簡単な説明】
【図１】画像形成装置の横断面図である。
【図２】接触磁気ブラシ現像法を示す図である。
【図３】リサイクルシステムの一例を示す図である。
【図４】クリーニングブレードの構成を示す図である。
【図５】クリーニングブレードの構成を示す図である。
【符号の説明】
１０ 感光体
１１ 帯電極
１２ 現像機構
１３ 転写分離極
１４ クリーニング機構
１４ａ クリーニングブレード
１４ｂ ホールダー
１５ 除電ランプ
１６ 給紙機構
１７ａ，ｂ，ｃ 搬送ローラ
１８ 定着機構
１９ リサイクル機構
２１ 現像剤搬送担体
２２ 主撹拌ローラ
２３ 補助撹拌ローラ
２４ トナー搬送スクリュー
２５ 穂立ち規制板
２６ ドクターブレード
３１ 磁気ブラシ機構
３２ トナー受入れ分配機構
３３ スクリューコンベア
３４ 第１スクリュー
３５ 第２スクリュー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic charge image developing toner and an image forming method used for image formation in copying machines, printers and the like.
[0002]
[Prior art]
Conventionally, as an electrophotographic developer used for developing an electrostatic latent image formed on an electrophotographic photosensitive layer, various pigments or dyes such as carbon black and phthalocyanine blue are colored on various resins. One-component developer composed of a toner obtained by melting and kneading and then pulverizing after use as an agent, or glass beads, iron having an average particle diameter of approximately the same as the particle diameter of the toner as a carrier, or up to 500 μm, Two-component developers in which toner is mixed with particles such as nickel and ferrite, or those coated with various resins are generally known. In particular, the toner development mechanism using a two-component developer generates a charge having a polarity opposite to that of the latent image on the toner due to frictional charging between the toner and the carrier, and develops and transfers the toner to the latent image portion on the photoreceptor. It is a mechanism to make it.
[0003]
However, with these developers alone, it is not possible to obtain a desired charge amount, charging speed, charge exchangeability, uniformity of charging, environmental dependency of image quality, durability of the developer, and the like. Therefore, a charge controller is often added as an additive.
[0004]
For example, in the case of negative chargeability, silica is used, but there are problems that developability and toner charge exchange property are poor, reverse polarity toner is easily generated, and fog is likely to occur. In addition, it is known that silica is used for the positively chargeable toner, but in this case as well, fogging due to the reverse polarity toner is likely to occur, which is more remarkable than in the case of the negatively chargeable toner. Moreover, in recent years, models using organic photoreceptors (OPC) are becoming mainstream in copying machines, and therefore, positively charged toner is increasingly desired.
[0005]
In order to solve these problems, Japanese Patent Application Laid-Open No. 62-129866 discloses that titania particles having a particle size of 0.05 μm or less are used as an external additive simultaneously with silica fine particles. Was not enough. Japanese Patent Application Laid-Open No. 2-43564 describes a technique for preventing fogging caused by reverse polarity toner by attaching silica fine particles having a particle size of 0.05 μm or less and titania particles having an average particle size of 0.1 μm or more to the surface of the toner particles. Has been. However, in these patent techniques, sufficient fog prevention, uniformity of charging, environmental dependency of image quality and durability of the developer have not been achieved, and further improvement is desired.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to develop electrostatic charge image development in which fog and image quality (image) are more environmentally dependent due to uniform charging and developer durability is improved. It is to provide a toner. Another object of the present invention is to provide a toner for developing an electrostatic charge image that hardly causes problems such as adhesion to a photoreceptor and image defects.
[0007]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitution.
[0008]
(1) at least colored particles;According to the following measurement methodAn electrostatic charge image developing toner comprising: titanium oxide having a pH of 6 to 8; and fine particles having positively chargeable hydrophobic silica.
  Measuring method: 100 ml of water from which carbon dioxide has been removed (water not containing carbon dioxide as defined in 3.6 (3) of JIS-K 8001) is added to 5.0 g of titanium oxide, and then boiled for 5 minutes. Then, after cooling, supplementing the water reduced by boiling by adding water containing no carbon dioxide, the supernatant is separated and the pH is measured.
[0009]
(2) It is characterized by containing fine particles having at least colored particles, titanium oxide having a water content of 0.3 to 2.0% by weight, and a specific resistance of 1500 to 10000 Ωcm and positively charged hydrophobic silica. Toner for developing electrostatic images.
[0010]
(3) a step of developing the electrostatic latent image formed on the photosensitive member with toner, a step of transferring the toner developed on the photosensitive member to the transfer member, a step of cleaning untransferred toner, and a cleaning unit. 3. An image forming method comprising a step of returning the collected toner to a developing unit, wherein the toner is the electrostatic image developing toner according to 1 or 2 above.
[0011]
As a result of intensive studies, the present inventors have found that the positively chargeable toner is caused by the strong positive chargeability possessed by the positively chargeable silica itself as a factor that causes the change in chargeability due to environmental changes. When the positive chargeability itself is strong, there is an influence of moisture in the environment, and as a result, it is estimated that the change in chargeability occurs.
[0012]
That is, it is presumed that a portion having positive chargeability is easily affected by moisture or the like, and as a result, leakage of charge from the portion is likely to occur.
[0013]
When positively charged silica is used, it has been found that the problem of charging leakage and the like is improved by uniformly adhering it to the toner surface by localizing the charging property. In the present invention, the titanium oxide is held on the toner surface, so that the adhesion to the positively charged portion of the toner surface occurs. It is estimated that the effect could be prevented. In addition, when used in combination with positively chargeable silica, the combination of positively chargeable silica and the above-mentioned titanium oxide allows silica and titanium oxide to be uniformly mixed on the toner surface, reducing the influence of moisture and the like due to environmental fluctuations. It is estimated that Although the effect of titanium oxide itself is not clear, it can be attached to the positively charged portion of the toner surface by shifting the pH from neutral to weakly alkaline, and further dispersion of positively charged silica itself. Is estimated to be uniform.
[0014]
In addition, fluctuations due to moisture adsorption can be prevented by setting the moisture content within a specific range, and excessive chargeability of the positively chargeable silica and positively chargeable charge control agent can be prevented by lowering the resistance. As a result, it is presumed that stable chargeability could be maintained over a long period of time.
[0015]
As described above, since the positively chargeable silica can be uniformly dispersed in the toner of the present invention, the adhesion to the photoreceptor can be reduced, and the occurrence of abnormalities on the photoreceptor can be prevented. It is estimated that
[0016]
Hereinafter, the present invention will be described in detail.
[0017]
A first aspect of the present invention is an electrostatic charge image developing toner (hereinafter referred to as toner) comprising at least colored particles and fine particles having titanium oxide having a pH of 6 to 8 and positively charged hydrophobic silica. In addition, the second aspect includes at least colored particles and fine particles having a water content = 0.3 to 2.0% by weight and a specific resistance = 1500 to 10,000 Ωcm of titanium oxide and positively charged hydrophobic silica. An electrostatic charge image developing toner. In addition, the embodiment using the toner includes a step of developing the electrostatic latent image formed on the photosensitive member with the toner, a step of transferring the toner developed on the photosensitive member to the transfer member, The image forming method includes a step of cleaning the transfer toner and a step of returning the toner collected by the cleaning unit to the developing unit.
[0018]
The titanium oxide used as the fine particles constituting the toner of the first aspect of the present invention is characterized by having a pH of 6-8.
[0019]
A method for adjusting the pH of titanium oxide will be described below. The pH of titanium oxide can be adjusted by the presence of sodium sulfate on the surface. As a method of leaving sodium sulfate, a step of preparing titanium oxide, that is, titanium hydroxide extracted from iron ore is treated with an alkali solution to prepare titanium oxide, followed by firing and further grinding. Adjust the particle size with. Thereafter, it is dispersed in water, sodium hydroxide is added, and sulfuric acid is further added to adjust the pH so that sodium sulfate can be present on the surface.
[0020]
Moreover, as a pH measuring method of titanium oxide, it measures by the following method. That is, it is a method of measuring the pH of water after adding water to a sample (titanium oxide) and boiling. Specifically, using water from which carbon dioxide has been removed (using water that does not contain carbon dioxide as defined in 3.6 (3) of JIS-K 8001), the above-described measurement was performed on 5.0 g of the sample used for measurement. 100 ml of water and then boil for 5 minutes. After cooling, after adding water not containing carbon dioxide and supplementing with water reduced by boiling, the supernatant is separated and the pH is measured to obtain the pH value of titanium oxide.
[0021]
When the pH of titanium oxide is high, that is, higher than 8, the alkalinity becomes excessive and the positive chargeability becomes high. As a result, uniform dispersion on the toner surface becomes difficult and the effect of the present invention cannot be exhibited. In addition, when the pH is low, that is, lower than 6, adhesion to the positively charged portion existing on the toner surface becomes strong, and as a result, the uniform dispersibility on the toner surface is lowered, and the effect of the present invention is reduced. Cannot be achieved.
[0022]
The titanium oxide is preferably surface-treated with the following alkyltrialkoxysilane coupling agent. Specifically, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane and the like can be mentioned as specific compounds. As a method of surface-treating titanium oxide using these, the above alkyltrialkoxysilane coupling agent is added to a solvent such as toluene, and then titanium oxide is added, and then the temperature condition is 25 to 100 ° C. for 10 minutes to 10 minutes. It can process by stirring for time. The amount of treatment is 1 to 10% by weight of the above-mentioned coupling agent with respect to titanium oxide. When this amount is small, the effect of the surface treatment cannot be exhibited, and when it is excessive, there arises a problem that the alkyltrialkoxysilane coupling agent exists in a free state.
[0023]
The titanium oxide used as the fine particles constituting the toner of the second aspect of the present invention is characterized by a moisture content of 0.3 to 2.0% by weight and a specific resistance of 1500 to 10000 Ωcm. Moreover, it is preferable that the titanium oxide of this aspect also has a pH in the range of 6-8.
[0024]
A method for measuring the moisture content of titanium oxide will be described. The moisture content is measured by the following method. That is, it is performed by the Karl Fischer coulometric titration method. Specifically, using an automatic heat vaporization moisture measurement system (AQS-724, Hiranuma Sangyo Co., Ltd.), titanium oxide left for 24 hours in a 20 ° C./50% RH environment is precisely weighed into a 20 ml glass sample tube. And then sealed with a Teflon-coated silicone rubber packing. In order to correct the moisture present in the sealed environment, two empty samples are measured simultaneously. The measurement is performed for 1 minute under the conditions of heating temperature = 110 ° C./carrier gas (nitrogen) flow rate = 150 ml / min. Hydranal Aqualite RS (manufactured by Riedel de Haen) and Aqualite C (manufactured by Kanto Chemical Co., Inc.) were used as reagents.
[0025]
When the water content of titanium oxide is excessive, that is, when it is more than 2.0% by weight, a problem of charging leakage due to the influence of moisture occurs, and stable charging property cannot be ensured. When the amount of water is small, that is, less than 0.3% by weight, the effect of stably maintaining the positive chargeability is reduced, and as a result, uniform chargeability cannot be stabilized.
[0026]
A method for measuring the specific resistance of titanium oxide will be described. The specific resistance is measured by a measuring method using a parallel electrode to which a voltage of 1 kV is applied after being allowed to stand for 24 hours or more under ambient conditions at normal temperature and normal humidity (23 ° C./50% RH). The specific resistance itself can be adjusted by treating the surface of the titanium oxide itself with a hydrophobizing agent. When the specific resistance is low, that is, when it is lower than 1500 Ωcm, the charge is discharged and the charge cannot be kept stable. On the other hand, when the specific resistance is high, that is, when it is higher than 10000 Ωcm, there is no discharge of charge, but the accumulation of charge increases, and as a result, the charge amount cannot be stabilized over a long period of time.
[0027]
The positively charged hydrophobic silica used as the fine particles constituting the toner of the first or second aspect of the present invention will be described.
[0028]
The positively charged hydrophobic silica that can be used in the present invention is a silica that can have a charge amount of +10 μC / g or more with respect to the iron powder. This silica is treated with the following nitrogen-containing coupling agent, amino-modified silicone oil, amino-modified silicone varnish, ammonium-modified polysiloxane, etc., on hydrophilic silica having a number average primary particle size of 5 to 500 nm. The chargeability can be positively charged. In addition, the evaluation of the charge amount with the iron powder was performed by adding 1% by weight of the above silica to a spherical iron powder of 100 μm under an environmental condition of normal temperature and humidity (20 ° C./50% RH), Shake for 20 minutes using a shaker YS-LD (manufactured by Yayoi Co., Ltd.). Furthermore, the result calculated from the charge amount when blown for 20 seconds using a blow-off charge amount measuring device (manufactured by Toshiba) is used.
[0029]
Among the above, examples of the nitrogen-containing coupling agent include, for example, 1) γ- (2-aminoethyl) aminopropyltrimethoxysilane, 2) γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, 3) γ-methacryloxypropyltrimethoxysilane, 4) N-β- (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride and the like.
[0030]
Further, as the ammonium-modified polysiloxane, specifically, the polysiloxane having an ammonium base includes, for example, dimethylpolysiloxane containing a structural unit represented by the general formula (1). It is represented by a structural formula.
[0031]
[Chemical 1]

[0032]
Where R₁Is a hydrogen atom, a hydroxy group, an alkyl group, an aryl group, an alkoxy group, or
[0033]
[Chemical 2]

[0034]
Represents R₂Represents a bonding group (for example, an alkylene group, an arylene group, an aralkylene group, —NH—, —NHCO— or a group in which these groups are arbitrarily combined), or a simple bond,_Three~ R_FiveEach represents a hydrogen atom, an alkyl group, or an aryl group, and X represents a halogen atom. R₁~ R_FiveEach group represented by includes a group having a substituent.
[0035]
[Chemical 3]

[0036]
R₆And R₇Each represents a hydrogen atom, a hydroxy group, an alkyl group, an aryl group or an alkoxy group, and these groups include those having a substituent. R₁~ R_Five, X is R in the general formula (1)₁~ R_Five, X is synonymous. m and n each represents an integer of 1 or more. In addition, the group represented by the above chemical formula 2
Specific examples include those represented by the following structural formulas, but are not limited thereto.
[0037]
[Formula 4]

[0038]
[Chemical formula 5]

[0039]
[Chemical 6]

[0040]
As a method for obtaining a polysiloxane having an ammonium salt as a functional group, an organohalogenated silane having an ammonium salt as a functional group and, in particular, an organohalogenated silane having no ammonium base may be copolymerized in the polymerization stage. Or a method in which a part of the polysiloxane obtained by polymerization using an organohalogenated silane is modified with an organic group having an ammonium salt as a functional group. An organoalkoxysilane may be used in place of the organohalogenated silane. Some compounds can also be obtained as commercial products.
[0041]
Of these, the positively charged hydrophobic silica is preferably treated with ammonium-modified polysiloxane.
[0042]
The colored particles constituting the toner of the present invention will be described.
[0043]
The colored particles contain a binder resin, a colorant, and other additives used as necessary, and the average particle size is usually a volume average particle size of 1 to 30 μm, preferably 5 to 20 μm. It is. The binder resin constituting the colored particles is not particularly limited, and various conventionally known resins are used. For example, a styrene resin, an acrylic resin, a styrene / acrylic resin, a polyester resin, and the like can be given. The colorant constituting the colored particles is not particularly limited, and various conventionally known materials are used. Examples thereof include carbon black, nigrosine dye, aniline blue, calcoyl blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and rose bengal. Other additives include charge control agents, fixing agents such as low molecular weight polyolefins and carnauba wax described below.
[0044]
Further, the toner of the present invention may be used as a one-component magnetic toner containing a magnetic material, mixed with a carrier to be used as a two-component developer, or a non-magnetic toner may be used alone. In the present invention, a two-component developer used by mixing with a carrier is preferable. When obtaining a magnetic toner, the colored particles contain magnetic particles as an additive. As the magnetic particles, particles such as ferrite and magnetite having an average primary particle diameter of 0.1 to 2.0 μm are used. The amount of magnetic particles added is 20 to 70% by weight in the colored particles.
[0045]
As the carrier constituting the two-component developer, either an uncoated carrier composed only of magnetic material particles such as iron or ferrite, or a resin-coated carrier whose magnetic material particle surface is coated with a resin or the like may be used. . Examples of the resin-coated carrier include a fluorine-based resin-coated carrier, a styrene acrylic resin-coated carrier, a silicone resin-coated carrier, and the like, and preferably a silicone resin-coated carrier.
[0046]
Examples of the charge control agent necessary for positively charging the toner of the present invention are given below, but the invention is not limited thereto.
[0047]
Nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds and the like can be mentioned. As the quaternary ammonium salt compounds, specifically, compounds represented by the following general formula (3)
[0048]
[Chemical 7]

[0049]
(R₁~ R_FourRepresents an alkyl group having 1 to 30 carbon atoms, an alkenyl group, an aryl group, an aralkyl group and an aryl group, and A represents an anion. Preferred is R₁~ R_ThreeAre each a long-chain alkyl group or a long-chain alkenyl group having 8 to 22 carbon atoms, and R_FourIs an alkyl group having 1 to 7 carbon atoms or a benzyl group, more preferably R₁~ R₂Are each a long-chain alkyl group or a long-chain alkenyl group having 8 to 22 carbon atoms, and R_Three~ R_FourIs an alkyl group having 1 to 7 carbon atoms or a benzyl group. The anion is preferably a sulfone group, a molybdate group, or a tungstate group. ) And the like. Specific exemplary compounds are shown below.
[0050]
1) (C₁₆H₃₃)₂N⁺(CH_Three)₂1/4 {Mo₈O₃₆}^Four-
2) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_Three)₂1/4 {Mo₈O₃₆}^Four-
3) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH₂C₆H_Five)₂1/4 {Mo₈O₃₆}^Four-
4) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(C_FourH₉)₂1/4 {Mo₈O₃₆}^Four-
5) (C₁₄H₂₉)₂N⁺(CH_Three)₂1/4 {Mo₈O₃₆}^Four-
6) (C₁₆H₃₃)₂N⁺(CH_Three)₂1/10 {H₂W₁₂O₄₂}_Ten ^-
7) (C₁₄H₂₉)₂N⁺(CH_Three)₂1/10 {H₂W₁₂O₄₂}_Ten ^-
8) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_Three)₂1/10 {H₂W₁₂O₄₂}_Ten ^-
9) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH₂C₆H_Five)₂1/10 {H₂W₁₂O₄₂}_Ten ^-
10) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(C_FourH₉)₂1/10 {H₂W₁₂O₄₂}_Ten ^-
Moreover, as a triphenylmethane type compound, the compound represented by the following formula | equation is mentioned.
[0051]
[Chemical 8]

[0052]
R₁~ R₆Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. These may be different or the same. Specifically, the following can be mentioned.
[0053]
[Chemical 9]

[0054]
Next, an image forming method using the toner according to the first and second aspects of the present invention will be described. FIG. 1 shows an image forming apparatus that can be used for carrying out the image forming method of the present invention.
[0055]
A belt electrode 11, a developing mechanism 12, a transfer separation electrode 13, a cleaning mechanism 14, and a charge eliminating lamp 15 are disposed around a photosensitive member (latent image carrier) 10 having a positively charged organic photoconductive photosensitive layer. The recording material from the paper feed mechanism 16 is conveyed by conveyance rollers 17a, 17b, and 17c, which are conveyance mechanisms, and after the toner image is transferred by the transfer separation pole 13, it is fixed by the fixing mechanism 18 to form an image. The The toner remaining on the photoreceptor 10 after the transfer is scraped off by the cleaning mechanism 14. The collected toner is returned again to the developing mechanism 12 by the recycling mechanism 19 and reused.
[0056]
Hereinafter, each step will be described.
[0057]
(Development process)
A one-component developer or a two-component developer constituted by using a toner in which resin fine particles are fixed as essential components is conveyed to a development area by a developer conveyance carrier, and an electrostatic latent image on a photoreceptor is formed by the developer. Development is performed to form an unfixed toner image. The developing method is not particularly limited, and conventionally known methods can be applied. Specifically, the following methods can be mentioned.
[0058]
(1) Contact magnetic brush development method
In this method, as shown in FIG. 2, a developer magnetic brush having a higher spike than the gap in the development area is formed on the developer transport carrier 21, and the magnetic brush is transported to the development area to be photoreceptor 10. Development is performed by adhering the toner in the magnetic brush to the electrostatic latent image while rubbing the electrostatic latent image on the upper surface. Reference numeral 22 is a main stirring roller, 23 is an auxiliary stirring roller, 24 is a toner conveying screw, 25 is a spike control plate, and 26 is a doctor blade. The photoconductor 10 is not particularly limited, but OPC is preferable.
[0059]
(2) Jumping magnetic brush development method
In this method, a developer magnetic brush having a lower spike than the gap in the development area is formed on the developer transport carrier, and the magnetic brush is transported to the development area and an oscillating electric field is applied to the development area. Development is performed by causing the toner in the magnetic brush to fly and adhere to the electrostatic latent image.
[0060]
(Transfer process)
The unfixed toner image on the photoreceptor obtained by development is transferred to a recording material. In this transfer step, either an electrostatic transfer method or a bias transfer method can be applied, but an electrostatic transfer method is particularly preferable. Specifically, for example, a transfer device that generates a DC corona discharge is disposed so as to face the photoconductor through a recording material, and a DC corona discharge is applied to the surface of the photoconductor from the back side of the recording material. The carried unfixed toner image is transferred to the surface of the recording material.
[0061]
(Cleaning process)
The toner remaining on the photoreceptor after the transfer process is cleaned. The cleaning means is not particularly limited, but a cleaning device having a cleaning blade disposed in contact with the surface of the photoreceptor is preferable. According to this cleaning device, the surface of the photoreceptor is rubbed with the cleaning blade, so that residual toner is scraped off and removed.
[0062]
(Recycling process)
The toner collected by cleaning is returned to the developing mechanism again by an appropriate recycling system and reused.
[0063]
FIG. 3 is an explanatory diagram showing an example of a recycling system.
[0064]
10 is a photosensitive member, 12 is a developing mechanism, 14 is a cleaning mechanism, 19 is a recycling mechanism, 31 is a magnetic brush mechanism, 32 is a toner receiving and distributing mechanism, 33 is a screw conveyor, 34 is a first screw, and 35 is a second screw. is there. In the apparatus of this example, the toner from the screw conveyor 33 is supplied to the toner receiving and distributing mechanism 32 by the first screw 34 and the second screw 35. That is, each of the first screw 34 and the second screw 35 has a rotating shaft and blades provided in a spiral shape along the rotating shaft. In the first screw 34, the toner sent by the screw conveyor 33 is provided. As the rotary shaft rotates, the blades are sequentially pushed up by the blades and sent to the second screw 35. In the second screw 35, toner is sequentially sent in the horizontal direction on the same principle as the first screw 34, and the toner is received. The toner supplied to the distribution mechanism 32 and collected is again used for developing the electrostatic latent image on the photoreceptor 10.
[0065]
(Fixing process)
The recording material onto which the unfixed toner image has been transferred in the transfer process is fixed by a heat fixing mechanism to form a fixed toner image on the recording material.
[0066]
(Configuration of cleaning blade)
As the configuration of the cleaning blade, any of the configurations described in FIG. 4 or FIG. 5 can be used. 4 or 5, the cleaning blade 14a is held in the holder 14b. The number of photoconductors is 10. The angle formed between the holder 14b and the photosensitive member 10 is θ shown in the figure.₁Is 20 to 90 °, preferably 30 to 75 °. As a material constituting the cleaning blade itself, an elastic body such as silicon rubber or urethane rubber can be used. In this case, the rubber hardness is preferably 30 to 90 °. The thickness is preferably 2 to 10 mm, and the length outside the holder is preferably 5 to 40 mm. The pressure contact force with respect to the photoreceptor 10 is preferably 5 to 30 gf / mm.
[0067]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.
[0068]
<< Production of titanium oxide >>
Titanium oxide shown in Table 1 below was prepared. In addition, the number average primary particle diameter of titanium oxide is 20 nm as a result of measuring using a scanning electron microscope using a photograph enlarged 40000 times.
[0069]
[Table 1]

[0070]
1 *: Octyltrimethoxysilane, 2 *: Dodecyltrimethoxysilane, 3 *: Hexyltrimethoxysilane
Note) The amount of the surface treatment agent was 5% by weight with respect to titanium oxide.
[0071]
<Examples of colored particle production>
8 parts of carbon black, 6 parts of low molecular weight polypropylene and 1 part of Exemplified Compound 1) as a charge control agent are added to 100 parts of styrene acrylic resin, premixed, melt kneaded, pulverized, classified, and volume average particle size Yielded colored particles of 8.2 μm. This is designated as colored particles 1. In addition, colored particles having a volume average particle size of 8.1 μm were obtained in the same manner except that the charge control agent was changed to Exemplified Compound 3) in the colored particle production example. This is designated as colored particles 2. Further, colored particles having a volume average particle diameter of 8.0 μm were obtained in the same manner except that the charge control agent was changed to Exemplified Compound 6) in the colored particle production example. This is designated as colored particles 3.
[0072]
<Example of toner production>
Positively charged silica (number average primary particle diameter = 12 nm / charge amount with iron powder = 90 μC / g) treated with 0.6% by weight of titanium oxide 1 and ammonium-modified polysiloxane with respect to the colored particles 1 is 0. 8 wt% was added and mixed for 10 minutes at a peripheral speed of 40 m / min with a Henschel mixer (internal volume = 10 liters) to obtain a toner. This is toner 1. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 2. This is toner 2. A toner was obtained in the same manner as in the toner production example except that the colored particles 1 were changed to colored particles 2 and the titanium oxide 1 was changed to titanium oxide 3. This is toner 3. The toner of the present invention was obtained in the same manner as in the toner production example except that the colored particles 1 were changed to colored particles 3, the titanium oxide 1 was changed to titanium oxide 4 and the addition amount was 0.4% by weight. . This is referred to as Toner 4. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 5. This is designated as Toner 5. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 6. This is designated as Toner 6.
[0073]
<< Developer preparation >>
A developer was prepared using the toner prepared above. As the carrier, a carrier obtained by coating a lithium ferrite carrier having a volume average particle diameter of 61 μm with a silicone resin was used. Toner and carrier were mixed so that the toner concentration was 5% to prepare a developer. Developers corresponding to the toners 1 to 6 are referred to as developers 1 to 6.
[0074]
The obtained developers 1 to 6 were employed in a copying machine 3135 (manufactured by Konica Corporation), and the following experiment was performed. The copying machine is modified to the recycling system of the type shown in FIG. 3, a laminated organic photoconductor is used as the photoconductor, and the cleaning conditions are as shown in FIG. Forming angle θ₁Was 22 °, and urethane rubber was used as a material constituting the cleaning blade itself. The rubber hardness of the urethane rubber was 65 °, the thickness was 2 mm, and the length outside the holder was 8 mm. The pressing force against the photosensitive member is 15 gf / mm.
[0075]
(Evaluation)
The evaluation items were printing 100,000 originals with a pixel rate of 5% continuously under environmental conditions of high temperature and high humidity (33 ° C./80% RH). The presence or absence of image defects due to scratches was evaluated. The image defect was determined to be defective when a black spot of 0.2 mmφ or more occurred on the image. The image density is indicated by the absolute reflection density using RD-918 manufactured by Macbeth Co., and the fog density is indicated by the relative reflection density where the density of the support (paper) is “0”.
[0076]
The results are shown in Table 2 below.
[0077]
[Table 2]

[0078]
As is apparent from the results in Table 2, developers 1 to 4 using titanium oxide having a pH of 6 to 8 have no significant difference in the transition of the image density and fog density in the initial stage and after 100,000 sheets. It can be seen that the toner has good durability such as no adhesion of toner and defects on the photoreceptor after processing 100,000 sheets, and has excellent overall performance. It can also be seen that developers 1 to 4 using titanium oxide having a water content of 0.3 to 2.0% by weight and a specific resistance of 1500 to 10000 Ωcm have excellent performance as well. However, the developers 5 and 6 outside these ranges may not have sufficient image density and fog density under the load condition of processing 100,000 sheets, and the image defects at that time may be considerable. I understand.
[0079]
【The invention's effect】
According to the present invention, it is possible to provide a toner for developing an electrostatic charge image in which charging is made uniform to improve fog and image environmental dependency and to improve the durability of the developer. It is also possible to provide toner for developing an electrostatic image that is less likely to cause problems such as adhesion to the photoreceptor and image defects.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an image forming apparatus.
FIG. 2 is a diagram showing a contact magnetic brush developing method.
FIG. 3 is a diagram illustrating an example of a recycling system.
FIG. 4 is a diagram illustrating a configuration of a cleaning blade.
FIG. 5 is a diagram illustrating a configuration of a cleaning blade.
[Explanation of symbols]
10 photoconductor
11 Band electrode
12 Development mechanism
13 Transfer separation electrode
14 Cleaning mechanism
14a Cleaning blade
14b holder
15 Static elimination lamp
16 Paper feed mechanism
17a, b, c Transport roller
18 Fixing mechanism
19 Recycling mechanism
21 Developer carrier
22 Main stirring roller
23 Auxiliary stirring roller
24 Toner conveying screw
25 Earing restriction board
26 Doctor blade
31 Magnetic brush mechanism
32 Toner receiving and distributing mechanism
33 Screw conveyor
34 First screw
35 Second screw

Claims (8)

A toner for developing an electrostatic charge image, comprising at least colored particles and fine particles having titanium oxide having a pH of 6 to 8 and positively charged hydrophobic silica by the following measurement method .
Measuring method: 100 ml of water from which carbon dioxide has been removed (water not containing carbon dioxide as defined in 3.6 (3) of JIS-K 8001) is added to 5.0 g of titanium oxide, and then boiled for 5 minutes. Then, after cooling, supplementing the water reduced by boiling by adding water containing no carbon dioxide, the supernatant is separated and the pH is measured.   2. The electrostatic image developing toner according to claim 1, wherein the titanium oxide is surface-treated with an alkyltrialkoxysilane.   3. The electrostatic image developing toner according to claim 1, further comprising a charge control agent for positive charging.   An electrostatic charge comprising at least colored particles, fine particles having titanium oxide having a water content of 0.3 to 2.0% by weight and a specific resistance of 1500 to 10,000 Ωcm and a positively chargeable hydrophobic silica. Toner for image development. 5. The electrostatic image developing toner according to claim 4, wherein the titanium oxide has a pH of 6 to 8 according to the following measuring method .
Measuring method: 100 ml of water from which carbon dioxide has been removed (water not containing carbon dioxide as defined in 3.6 (3) of JIS-K 8001) is added to 5.0 g of titanium oxide, and then boiled for 5 minutes. Then, after cooling, supplementing the water reduced by boiling by adding water containing no carbon dioxide, the supernatant is separated and the pH is measured.   6. The electrostatic image developing toner according to claim 4, further comprising a charge control agent for positive charging.   7. The electrostatic image developing toner according to claim 1, wherein the positively chargeable hydrophobic silica is treated with an ammonium-modified polysiloxane.   The electrostatic latent image formed on the photoreceptor is developed with toner, the toner developed on the photoreceptor is transferred to the transfer body, the untransferred toner is cleaned, and the cleaning unit collects the electrostatic latent image. 8. An image forming method comprising a step of returning toner to a developing section, wherein the toner is the electrostatic image developing toner according to claim 1.

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