JP2004191618A - Electrostatic charge image developing toner, method for manufacturing electrostatic charge image developing toner and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner having excellent offset resistance and showing preferable storage property, and to provide a method for manufacturing the toner and a method for forming an image by using the toner. <P>SOLUTION: In the electrostatic charge image developing toner comprising toner particles containing at least a resin and a coloring agent, the toner particle has a core containing a resin (A) and at least one layer of a shell containing a resin (B) and covering the core. The film thickness of the outermost layer of the shell is 50 nm to 600 nm. Thereby, the obtained toner for electrostatic charge image development has excellent offset resistance and shows high storage property. The invention also presents a method for manufacturing the toner and a method for forming an image by using the toner. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０１０６】
【化２】

【０１０７】
上記記載の離型剤、一般式で表される定着改良剤の添加量としては、静電荷像現像用トナー全体に１質量％〜３０質量％、好ましくは２質量５〜２０質量％、さらに好ましくは３質量％〜１５質量％である。
【０１０８】
（現像剤）
本発明のトナーは、一成分現像剤でも二成分現像剤として用いてもよいが、非磁性一成分現像剤として特に好ましく用いられる。
【０１０９】
また、本発明のトナーは、高い定着性を発揮し、特開平８−３２８２９５号公報に記載されているようなオフセット現象を回避するため、結晶性化合物を含有し、且つ該結晶性化合物に起因する示差熱分析における吸熱ピークが、６０℃〜１２０℃に１つ以上存在し、その吸熱量が４Ｊ／ｇ〜３０Ｊ／ｇであることが好ましい。
【０１１０】
本発明の画像形成方法について説明する。
本発明のトナーは、トナー像が形成された画像形成支持体を、定着装置を構成する加熱ローラと加圧ローラとの間に通過させて熱定着する工程を含む画像形成方法（本発明の画像形成方法）に好適に使用される。
【０１１１】
図１は、本発明の画像形成方法において使用する定着装置の一例を示す断面図であり、図１に示す定着装置は、加熱ローラ１００と、これに当接する加圧ローラ２００とを備えている。なお、図１において、Ｔは転写紙（画像形成支持体）上に形成されたトナー像である。
【０１１２】
加熱ローラ１００は、フッ素樹脂または弾性体からなる被覆層１２０が芯金１１０の表面に形成されてなり、線状ヒーターよりなる加熱部材１３を内包している。
【０１１３】
芯金１１０は、金属から構成され、その内径は１０ｍｍ〜７０ｍｍとされる。芯金１１０を構成する金属としては特に限定されるものではないが、例えば鉄、アルミニウム、銅等の金属あるいはこれらの合金を挙げることができる。
【０１１４】
芯金１１０の肉厚は０．１ｍｍ〜１５ｍｍとされ、省エネルギーの要請（薄肉化）と、強度（構成材料に依存）とのバランスを考慮して決定される。例えば、０．５７ｍｍの鉄よりなる芯金と同等の強度を、アルミニウムよりなる芯金で保持するためには、その肉厚を０．８ｍｍとする必要がある。
【０１１５】
被覆層１２０を構成するフッ素樹脂としては、ＰＴＦＥ（ポリテトラフルオロエチレン）およびＰＦＡ（テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体）などを例示することができる。
【０１１６】
フッ素樹脂からなる被覆層１２０の厚みは１０μｍ〜５００μｍとされ、好ましくは２０μｍ〜４００μｍとされる。
【０１１７】
フッ素樹脂からなる被覆層１２０の厚みが１０μｍ未満であると、被覆層としての機能を十分に発揮することができず、定着装置としての耐久性を確保することができない。一方、５００μｍを超える被覆層の表面には紙粉によるキズがつきやすく、当該キズ部にトナーなどが付着し、これに起因する画像汚れを発生する問題がある。
【０１１８】
また、被覆層１２０を構成する弾性体としては、ＬＴＶ、ＲＴＶ、ＨＴＶなどの耐熱性の良好なシリコーンゴムおよびシリコーンスポンジゴムなどを用いることが好ましい。
【０１１９】
被覆層１２０を構成する弾性体のアスカーＣ硬度は、８０°未満とされ、好ましくは６０°未満とされる。
【０１２０】
また、弾性体からなる被覆層１２０の厚みは０．１ｍｍ〜３０ｍｍとされ、好ましくは０．１ｍｍ〜２０ｍｍとされる。
【０１２１】
被覆層１２０を構成する弾性体のアスカーＣ硬度が８０°を超える場合、および当該被覆層１２０の厚みが０．１ｍｍ未満である場合には、定着のニップを大きくすることができず、ソフト定着の効果（例えば、平滑化された界面のトナー層による色再現性の向上効果）を発揮することができない。
【０１２２】
加熱部材１３０としては、ハロゲンヒーターを好適に使用することができる。
加圧ローラ２００は、弾性体からなる被覆層２２が芯金２１の表面に形成されてなる。被覆層２２０を構成する弾性体としては特に限定されるものではなく、ウレタンゴム、シリコーンゴムなどの各種軟質ゴムおよびスポンジゴムを挙げることができ、被覆層１２０を構成するものとして例示したシリコーンゴムおよびシリコーンスポンジゴムを用いることが好ましい。
【０１２３】
被覆層２２０を構成する弾性体のアスカーＣ硬度は、８０°未満とされ、好ましくは７０°未満、更に好ましくは６０°未満とされる。
【０１２４】
また、被覆層２２０の厚みは０．１ｍｍ〜３０ｍｍとされ、好ましくは０．１〜２０ｍｍとされる。
【０１２５】
被覆層２２０を構成する弾性体のアスカーＣ硬度が８０°を超える場合、および被覆層２２０の厚みが０．１ｍｍ未満である場合には、定着のニップを大きくすることができず、ソフト定着の効果を発揮することができない。
【０１２６】
芯金２１０を構成する材料としては特に限定されるものではないが、アルミニウム、鉄、銅などの金属またはそれらの合金を挙げることができる。
【０１２７】
加熱ローラ１００と加圧ローラ２００との当接荷重（総荷重）としては、通常４０Ｎ〜３５０Ｎとされ、好ましくは５０Ｎ〜３００Ｎ、さらに好ましくは５０Ｎ〜２５０Ｎとされる。この当接荷重は、加熱ローラ１００の強度（芯金１１０の肉厚）を考慮して規定され、例えば０．３ｍｍの鉄よりなる芯金を有する加熱ローラにあっては、２５０Ｎ以下とすることが好ましい。
【０１２８】
また、耐オフセット性および定着性の観点から、ニップ幅としては４ｍｍ〜１０ｍｍであることが好ましく、当該ニップの面圧は０．６×１０^５Ｐａ〜１．５×１０^５Ｐａであることが好ましい。
【０１２９】
図１に示した定着装置による定着条件の一例を示せば、定着温度（加熱ローラ１００の表面温度）が１５０℃〜２１０℃の範囲が好ましく、定着線速が８０ｍｍ／秒〜６４０ｍｍ／秒の範囲が好ましい。
【０１３０】
本発明において使用する定着装置には、必要に応じてクリーニング機構を付与してもよい。この場合には、シリコーンオイルを定着部の上ローラ（加熱ローラ）に供給する方式として、シリコーンオイルを含浸したパッド、ローラ、ウェッブ等で供給し、クリーニングする方法が使用できる。
【０１３１】
シリコーンオイルとしては耐熱性の高いものが使用され、ポリジメチルシリコーン、ポリフェニルメチルシリコーン、ポリジフェニルシリコーン等が使用される。粘度の低いものは使用時に流出量が大きくなることから、２０℃における粘度が１Ｐａ・ｓ〜１００Ｐａ・ｓのものが好適に使用される。
【０１３２】
但し、本発明による効果は、シリコーンオイルを供給しない、または、シリコーンオイルの供給量がきわめて低い定着装置により、画像を形成する工程を含む場合に特に顕著に発揮される。従って、シリコーンオイルを供給する場合であっても、その供給量は２ｍｇ／Ａ４以下とすることが好ましい。
【０１３３】
シリコーンオイルの供給量を２ｍｇ／Ａ４以下とすることにより、定着後の転写紙（画像支持体）に対するシリコーンオイルの付着量が少なくなり、転写紙へ付着したシリコーンオイルによるボールペン等の油性ペンの記入しずらさがなく、加筆性が損なわれることはない。
【０１３４】
また、シリコーンオイルの変質による耐オフセット性の経時的な低下、シリコーンオイルによる光学系や帯電極の汚染などの問題を回避することができる。
【０１３５】
ここに、シリコーンオイルの供給量は、所定温度に加熱した定着装置（ローラ間）に転写紙（Ａ４サイズの白紙）を連続して１００枚通過させ、通紙前後における定着装置の質量変化（Δｗ）を測定して算出される（Δｗ／１００）。
【０１３６】
図２は、中間転写体（転写ベルト）を用いた、本発明の画像形成装置の一例を示す断面図である。
【０１３７】
図２において、カラー画像を得るため画像形成装置は、複数個の画像形成ユニットを備え、各画像形成ユニットにてそれぞれ色の異なる可視画像（トナー画像）を形成し、該トナー画像を同一中間転写体に順次重ねて転写するような画像形成方法である。
【０１３８】
ここでは、第１、第２、第３及び第４の画像形成ユニットＰａ、Ｐｂ、Ｐｃ及びＰｄが並設されており、該画像形成部はそれぞれ静電潜像形成体である感光体１ａ、１ｂ、１ｃ及び１ｄを具備している。感光体１ａ、１ｂ、１ｃ及び１ｄはその外周側に潜像形成部２ａ、２ｂ、２ｃ及び２ｄ、現像部３ａ、３ｂ、３ｃ及び３ｄ、転写放電部４ａ、４ｂ、４ｃ及び４ｄ、クリーニング部材及びゴムブレードを有するクリーニング器５ａ、５ｂ、５ｃ及び５ｄ、帯電器６ａ、６ｂ、６ｃ及び６ｄが配置するものである。
【０１３９】
この様な構成にて、先ず、第１画像形成ユニットＰａの感光体１ａ上に潜像形成部２ａによって原稿画像における、例えばイエロー成分色の潜像が形成される。該潜像は現像部３ａのイエロートナーを含有する現像剤で可視画像とされ、転写放電部４ａにて、転写ベルト２１に転写される。
【０１４０】
一方、上記の様にイエロートナー画像が転写ベルト２１に転写されている間に、第２画像形成ユニットＰｂではマゼンタ成分色の潜像が感光体１ｂ上に形成され、続いて現像部３ｂでマゼンタトナーを含有する現像剤で可視画像とされる。この可視画像（マゼンタトナー画像）は、上記の第１画像形成ユニットＰａでの転写が終了した転写ベルトが転写放電部４ｂに搬入されたときに、該転写ベルト２１の所定位置に重ねて転写される。
【０１４１】
以下、上記と同様な方法により第３、第４の画像形成ユニットＰｃ、Ｐｄによりシアン成分色、ブラック成分色の画像形成が行われ、上記同一の転写ベルト上に、シアントナー画像、ブラックトナー画像が重ねて転写される。この様な画像形成プロセスが終了した時点で、転写ベルト２１上に多色重ね合せ画像が得られる。一方、転写が終了した各感光体１ａ、１ｂ、１ｃ及び１ｄはクリーニング器５ａ、５ｂ、５ｃ及び５ｄにより残留トナーが除去され、引き続き行われる次の潜像形成のために供せられる。
【０１４２】
なお、前記画像形成装置では、転写ベルト２１が用いられており、図７において、転写ベルト２１は右側から左側へと搬送され、その搬送過程で、各画像形成ユニットＰａ、Ｐｂ、Ｐｃ及びＰｄにおける各転写放電部４ａ、４ｂ、４ｃ及び４ｄを通過し各色転写画像が転写される。
【０１４３】
転写ベルト２１が第４画像形成ユニットＰｄを通過すると、ＡＣ電圧が分離除電放電器２２ｄに加えられ、転写ベルト２１は除電され、転写材Ｐにトナー像が一括転写される。その後転写材Ｐは定着装置２３に入り、定着され、排出口２５から排出され、カラー画像が得られる。
【０１４４】
なお、図中の２２ａ、２２ｂ、２２ｃ及び２２ｄは分離除電放電器であり、トナー像の転写を終えた転写ベルト２１は、ブラシ状クリーニング部材とゴムブレードを併用したクリーニング器２４により、転写残トナーがクリーニングされて、次の画像形成に備えられる。
【０１４５】
なお、前記の様に、搬送ベルトの如き長尺の転写ベルト２１を用いて、その上に多色重ね合せ像を作り、それを転写材に一括転写する構成にしても、その画像形成ユニットにそれぞれ独立した転写ベルトを具備させ、それから転写材へ、順次各転写ベルトから転写する構成にしてもよい。
【０１４６】
尚、前記転写ベルトとしては、例えばポリイミド、ポリエーテル、ポリアミドあるいはテトラフルオロエチレン・パーフルオロビニルエーテル共重合体等の表面抵抗が１０^１４Ω以上で、厚さ２０μｍ程度の高抵抗フィルムの上に、フッ素系またはシリコン系樹脂に導電剤を添加して表面抵抗を１０^５〜１０^８Ωとした５〜１５μｍ厚の離型層を設けてなるエンドレスフィルムが用いられる。
【０１４７】
【実施例】
以下、実施例により本発明を説明するが、本発明はこれらに限定されない。
【０１４８】
実施例１
《コア用ラテックス１の調製》
下記のように、第１段重合、第２段重合、次いで、第３段重合を行い、多層構造を有するコア用ラテックス１を調製した。
【０１４９】
（１）第１段重合
攪拌装置、温度センサー、冷却管、窒素導入装置を取り付けた５０００ｍｌのセパラブルフラスコに、下記式（１０１）で表されるアニオン系界面活性剤
式（１０１）：Ｃ_１０Ｈ_２１（ＯＣＨ_２ＣＨ_２）_２ＯＳＯ_３Ｎａ
４ｇをイオン交換水３０４０ｇに溶解させた界面活性剤溶液（水系媒体）を仕込み、窒素気流下２３０ｒｐｍの攪拌速度で攪拌しながら、内温を８０℃に昇温させた。
【０１５０】
この界面活性剤溶液に、重合開始剤（過硫酸カリウム：ＫＰＳ）１０ｇをイオン交換水４００ｇに溶解させた開始剤溶液を添加し、温度を７５℃とした後、スチレン５２８ｇ、ｎ−ブチルアクリレート２０４ｇ、メタクリル酸６８ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステル２４．４ｇからなる単量体混合液を１時間かけて滴下し、この系を７５℃にて２時間にわたり加熱、攪拌することにより重合（第一段重合）を行い、ラテックスを調製した。これを「ラテックス（１Ｈ）」とする。
【０１５１】
第１段重合で精製したラテックス１ＨのＭｗは１４０００であった。ここで、Ｍｗは重量平均分子量である。
【０１５２】
（２）中間層の形成（第二段重合）
攪拌装置を取り付けたフラスコ内において、スチレン９５ｇ、ｎ−ブチルアクリレート３６ｇ、メタクリル酸９ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステル０．５９ｇからなる単量体混合液に、離型剤として、上記１９）で表される化合物（以下、「例示化合物（１９）」という。）７７ｇを添加し、９０℃に加温し溶解させて単量体溶液を調製した。
【０１５３】
一方、アニオン系界面活性剤（上記式（１０１））１ｇをイオン交換水１５６０ｍｌに溶解させた界面活性剤溶液を９８℃に加熱し、この界面活性剤溶液に、核粒子の分散液であるラテックス（１Ｈ）を固形分換算で２８ｇ添加した後、循環経路を有する機械式分散機「クレアミックス（ＣＬＥＡＲＭＩＸ）」（エム・テクニック（株）製）により、前記例示化合物（１９）の単量体溶液を８時間混合分散させ、分散粒子径（２８４ｎｍ）を有する乳化粒子（油滴）を含む分散液（乳化液）を調製した。
【０１５４】
次いで、この分散液（乳化液）に、重合開始剤（ＫＰＳ）５ｇをイオン交換水２００ｍｌに溶解させた開始剤溶液を添加し、この系を９８℃にて１２時間にわたり加熱攪拌することにより重合（第二段重合）を行い、ラテックスを得た。これを「ラテックス（１ＨＭ）」とする。
【０１５５】
前記ラテックス（１ＨＭ）を乾燥し、走査型電子顕微鏡で観察したところ、ラテックスに取り囲まれなかった例示化合物（１９）を主成分とする粒子（４００〜１０００ｎｍ）が観察された。
【０１５６】
第２段重合で精製したラテックス１ＨＭのＭｗは８００００であった。
（３）外層の形成（第三段重合）
上記の様にして得られたラテックス（１ＨＭ）に、重合開始剤（ＫＰＳ）６．８ｇをイオン交換水２６５ｍｌに溶解させた開始剤溶液を添加し、８０℃の温度条件下に、スチレン２４９ｇ、ｎ−ブチルアクリレート８８．２ｇ、メタクリル酸２ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステル７．４５ｇからなる単量体混合液を１時間かけて滴下した。滴下終了後、２時間にわたり加熱攪拌することにより重合（第三段重合）を行った後、２８℃まで冷却し、コア用ラテックス１を得た。
【０１５７】
第三段重合で外層形成に用いられた重合体のＭｗは１００００であった。
コア用ラテックス１を構成する複合樹脂粒子の重量平均粒径は１２２ｎｍであった。
【０１５８】
《コア用ラテックス２の調製》
コア用ラテックス１の調製において、外層形成（第三段重合）に用いた、スチレンを２４２．５ｇ、ｎ−ブチルアクリレートを９６．５ｇ、メタクリル酸を１８ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステルを８．０ｇに変更した以外は同様にして、コア用ラテックス２を調製した。
【０１５９】
得られたコア用ラテックス１、コア用ラテックス２の物性を下記に示す。
ラテックス番号 Ｍｗ Ｔｇ１ Ｔｓｐ１
（コア用） （重量平均分子量） （ガラス転移点） （軟化点）
１ ３５０００ ５０℃ １２０℃
２ ３００００ ４７℃ １１７℃
ここで、各々のラテックスのＭｗ（重量平均分子量）は、第１段〜第３段重合によって得られたコアの分子量である。
【０１６０】
《シェル用ラテックス１の調製》
上記のコア用ラテックス１の第１段重合において、スチレンを５４４ｇ、ｎ−ブチルアクリレートを１８８ｇ、メタクリル酸を６８ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステルを２４．４ｇに変更した単量体混合液を用いた以外は同様にして、重合反応及び反応後の処理を行い、シェル用ラテックス１を調製した。
【０１６１】
《シェル用ラテックス２の調製》
シェル用ラテックス１の調製において、スチレンを５４０ｇ、ｎ−ブチルアクリレートを１９２ｇ、メタクリル酸を６８ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステルを３０．０ｇに変更した以外は同様にして、重合反応及び反応後の処理を行い、シェル用ラテックス２を調製した。
【０１６２】
《シェル用ラテックス３の調製》
シェル用ラテックス１の調製において、スチレンを５２８ｇ、ｎ−ブチルアクリレートを２０４ｇ、メタクリル酸を６８ｇ、ｎ−オクチル−３−メルカプトプロピオン酸エステルを１５．０ｇに変更した以外は同様にして、重合反応及び反応後の処理を行い、シェル用ラテックス３を調製した。
【０１６３】
得られたシェル用ラテックス１、２及び３の物性を下記に示す。
ラテックス番号 Ｍｗ Ｔｇ２ Ｔｓｐ２
（シェル用） （重量平均分子量） （ガラス転移点） （軟化点）
１ １５０００ ５３℃ １１５℃
２ １００００ ５２℃ １１０℃
３ ３８０００ ４９℃ １２１℃
《着色粒子の作製例》
下記のようにして、着色粒子Ｂｋ１〜Ｂｋ５（ブラック）、Ｂｋ６及びＢｋ７（各々、比較用）の着色粒子を作製した。
【０１６４】
《着色粒子Ｂｋ１の作製》
（１）着色剤の分散液１の調製
前記式（１０１）で表される、アニオン性界面活性剤９０ｇをイオン交換水１６００ｍｌに攪拌溶解した。この溶液を攪拌しながら、カーボンブラック（リーガル３３０Ｒ：キャボット社製）４００．０ｇを徐々に添加し、次いで、攪拌装置「クレアミックス」（エム・テクニック（株）製）を用いて分散処理して、着色剤粒子の分散液（以下、「着色剤分散液１」という。）を調製した。
【０１６５】
この着色剤分散液１における着色剤粒子の粒子径を、電気泳動光散乱光度計「ＥＬＳ−８００」（大塚電子社製）を用いて測定したところ、１１０ｎｍであった。
【０１６６】
（２）（凝集・融着）会合粒子の調製：コア形成
４２０．７ｇ（固形分換算）のコア用ラテックス１と、イオン交換水９００ｇと「着色剤分散液１」２００ｇとを、温度センサー、冷却管、窒素導入装置、攪拌装置を取り付けた反応容器（四つ口フラスコ）に入れ攪拌した。容器内の温度を３０℃に調整した後、この溶液に５モル／リットルの水酸化ナトリウム水溶液を加えてｐＨを８〜１１．０に調整した。
【０１６７】
次いで、塩化マグネシウム・６水和物２ｇをイオン交換水１０００ｍｌに溶解した水溶液を、攪拌下、３０℃にて１０分間かけて添加した。３分間放置した後に昇温を開始し、この系を６０分間かけて９０℃まで昇温した。その状態で、「コールターカウンターＴＡ−ＩＩ」にて会合粒子の粒径を測定し、個数平均粒径が４μｍ〜７μｍになった時点で、塩化ナトリウム４０．２ｇをイオン交換水１０００ｍｌに溶解した水溶液を添加して粒子成長を停止させ、更に、熟成処理として液温度９８℃にて６時間にわたり加熱攪拌することにより融着を継続させ、コア粒子を形成させた。
【０１６８】
（３）シェリング操作（シェルの形成）
次いで、９６ｇのシェル用ラテックス１を添加し、３時間にわたり加熱攪拌を継続し、コア粒子表面に、シェル用ラテックス１のラテックス粒子を融着させ、シェル層を形成させた。
【０１６９】
ここで、塩化ナトリウム４０．２ｇを加え、８℃／分の条件で３０℃まで冷却し、塩酸を添加してｐＨを２．０に調整し、攪拌を停止した。生成した塩析、凝集、融着粒子を濾過し、４５℃のイオン交換水で繰り返し洗浄し、その後、４０℃の温風で乾燥することにより、コアと前記コア上にシェル層を有する着色粒子Ｂｋ１を得た。
【０１７０】
尚、着色粒子作製において、前記、凝集工程のｐＨ、シェル用ラテックス１（別途調製した、シェル用ラテックス２を用いてもよい）の添加タイミング、撹拌強度を制御することにより、着色剤分散状態を制御し、更に、液中分級により、粒径および粒度分布の変動係数等を任意に調整出来る。
【０１７１】
《着色粒子Ｂｋ２〜Ｂｋ７の作製》
着色粒子Ｂｋ１の作製において、コア用ラテックス１、シェル用ラテックス１の代わりに、表１に記載のコア用ラテックス、シェル用ラテックスを用いた以外は同様にして、着色粒子Ｂｋ２〜Ｂｋ７を各々作製した。
【０１７２】
《トナー、現像剤の調製》
上記で調製した着色粒子Ｂｋ１〜Ｂｋ７に、それぞれ疎水性シリカ（数平均一次粒径＝１２ｎｍ、疎水化度＝６８）を１．０質量％及び疎水性酸化チタン（数平均一次粒径＝２０ｎｍ、疎水化度＝６３）を１．２質量％添加し、ヘンシェルミキサーにより混合して、本発明のトナー１〜５、比較のトナー６及び７を各々調製した。
【０１７３】
次いで、上記調製した各トナーに対して、シリコーン樹脂を被覆した体積平均粒径６０μｍのフェライトキャリアを混合し、それぞれトナー濃度が６％の現像剤１〜５、比較の現像剤１、２を各々調製した。
【０１７４】
上記のようにして調製した各トナー、各現像剤の詳細を、表１に示す。
【０１７５】
【表１】

【０１７６】
上記で得られた黒色用の現像剤Ｂｋ１〜Ｂｋ７を各々、市販のコニカＳｉｔｉｏｓ７０７５（線速３７０ｍｍ／秒）を用いて下記の評価を行った。
【０１７７】
《トナー保存性の評価》
上記調製した各トナー２ｇをサンプル管に取り、タッピングデンサーで５００回振とうした後、５５℃、３５％ＲＨの環境下で２時間放置した。次いで、４８メッシュの篩いに入れ、一定の振動条件で篩い、メッシュ上の残留したトナー量の比率（質量％）を測定し、これをトナー凝集率とし、下記のようにトナー保存性をランク評価した。
【０１７８】
◎：トナー凝集率が１５質量％未満である（保存性が極めて良好）
○：トナー凝集率が１５〜４５質量％である（保存性が良好）
△：トナー凝集率が４６〜６０質量％である（実用可）
×：トナー凝集率が６０質量％を越える（実用不可）
《耐オフセット性の評価》
コニカ株式会社製デジタル複写機「７０６５」の定着装置を改造し、下記条件にて画像オフセットとヒートローラのトナー汚れ評価を行った。
【０１７９】
定着装置はヒートローラに接触しているクリーニング機構等を全て取り外し、ヒートローラへは何も接触しないように改造した。複写環境は常温常湿（２５℃、５５％ＲＨ）に設定し、装備されている定着用のヒートローラの表面温度（ローラの中心部で測定）を１５０℃〜１８０℃の範囲で、５℃刻みで変化させ、各表面温度において、搬送方向に直交する位置に５ｍｍ幅のベタ黒帯状画像を有するＡ４サイズの普通紙を縦送りで搬送定着した後、搬送方向に直交する位置に５ｍｍ幅のベタ黒帯状画像と２０ｍｍ幅のハーフトーン画像を有するＡ４サイズの普通紙を横送りで搬送し、得られた各サンプルについて、定着オフセットに起因する画像汚れ（画像オフセット）及びヒートローラ表面のトナー汚れを目視観察し、下記の基準に則り耐オフセット性の評価を行った。
【０１８０】
◎ ：画像汚れ、トナー汚れともに、全く発生は認められない
○ ：画像汚れ、トナー汚れともに、ほぼ発生は認められない
△ ：画像汚れはないが、トナー汚れが認められる
× ：画像汚れ、トナー汚れともに発生が認められる
××：著しい画像汚れ、トナー汚れが認められる
上記評価ランクにおいて、◎及び○が実用上許容の範囲にあると判定した。
【０１８１】
得られた結果を表２に示す。
【０１８２】
【表２】

【０１８３】
表２より、比較に比べて、本発明の試料は、トナーの保存安定性、耐オフセット性が向上していることが明らかである。
【０１８４】
【発明の効果】
本発明により、耐オフセット性に優れ、且つ、良好な保存性を示す静電荷像現像用トナー、該トナーの製造方法及び前記トナーを用いる画像形成方法を提供することが出来た。
【図面の簡単な説明】
【図１】本発明において使用する定着装置の一例を示す断面図を表す。
【図２】中間転写体（転写ベルト）を用いた、本発明の画像形成装置の一例を示す断面図である。
【符号の説明】
８ 記録材
１００ 加熱ローラ
１１０ 芯金
１２０ 被覆層
１３０ 加熱部材
２００ 加圧ロール
２１０ 芯金
２２０ 被覆層
Ｔ 記録材上に形成されたトナー像
Ｐ 転写材
Ｐａ、Ｐｂ、Ｐｃ、Ｐｄ 画像形成ユニット
１ａ、１ｂ、１ｃ、１ｄ 感光体
２ａ、２ｂ、２ｃ、２ｄ 潜像形成部
３ａ、３ｂ、３ｃ、３ｄ 現像部
４ａ、４ｂ、４ｃ、４ｄ 転写放電部
５ａ、５ｂ、５ｃ、５ｄ クリーニング器
６ａ、６ｂ、６ｃ、６ｄ 帯電器
２２ａ、２２ｂ、２２ｃ、２２ｄ 分離除電放電器
２１ 転写ベルト
２３ 定着装置
２４ クリーニング器
２５ 排出口[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic image, a method for manufacturing the toner for developing an electrostatic image, and an image forming method.
[0002]
[Prior art]
Conventionally, the toner for developing an electrostatic image used in the development of electrophotography is generally prepared by melting and kneading a colorant (carbon black, magnetic powder, pigment, etc.), a charge control agent, and other additives in a thermoplastic resin, Grinded, classified and prepared ones have been used.
[0003]
In order to improve various problems seen in conventional electrostatic image developing toners produced by these pulverization methods, it is desired that the electrostatic latent image developing toner has a small particle size from the viewpoint of high image quality. .
[0004]
As a technique for reducing the particle size of the toner, a method for producing the toner by an emulsion polymerization method, a suspension polymerization method, or the like (for example, see Patent Documents 1, 2, and 3) has been developed.
[0005]
In recent years, polymerized toners (also referred to as polymerized toners) have been actively developed as a method for producing small particle size toners. The polymerization method toner includes a method of preparing an irregularly-shaped toner (emulsion-association (aggregation) type toner) by aggregating and fusing the resin particles and the colorant particles that are emulsion-associated (aggregated), and radical polymerizable toner. There is a method of dispersing a monomer and a colorant, then dispersing droplets in an aqueous medium or the like so as to have a desired toner particle diameter, and preparing toner particles through a process of suspension polymerization (suspension polymerization toner). .
[0006]
However, toner particles produced by applying the suspension polymerization method (for example, see Patent Document 4) can form a spherical toner having a uniform surface property, so that the uniformity among the toners is improved. However, since the shape is spherical, the adhesion to the latent image carrier becomes high, so that there is a problem in offset resistance (image offset and toner stain on a heat roller), and an emulsion polymerization association type toner is preferable. In such a case, it is difficult to avoid the exposure of the colorant and the wax on the surface of the toner particles. As a result, the offset resistance and the storage stability of the toner are also disadvantageous.
[0007]
Therefore, a technique for forming a shell of the colored resin particles with a resin (for example, see Patent Document 5) has been studied. The shelling of the colorant particles prevented the colorant and wax from being exposed to the toner surface.
[0008]
However, in recent years, when applied to low-temperature fixing and oil-less fixing, which are highly demanded in the industry, when the shell resin is easily melted, the wax easily exudes, but there is a problem that the storage stability of the toner is easily deteriorated. On the other hand, if the shell resin is designed to be hard (it becomes difficult to melt), there is a problem that offset tends to occur on the low temperature side. That is, there is a trade-off relationship between the prevention of offset at low temperature and the toner storability in the design of the shell resin, and a toner showing sufficient performance in both the offset resistance and the toner storability has not yet been obtained. There is no current situation.
[0009]
[Patent Document 1]
JP-B-36-10231
[0010]
[Patent Document 2]
Japanese Patent Publication No. 47-518305
[0011]
[Patent Document 3]
Japanese Patent Publication No. 51-14895
[0012]
[Patent Document 4]
Japanese Patent Publication No. 3-36060
[0013]
[Patent Document 5]
JP-A-2002-116574
[0014]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a toner for developing an electrostatic image, which is excellent in offset resistance and exhibits good storage stability, a method for producing the toner, and an image forming method using the toner.
[0015]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitutions 1 to 6.
[0016]
1. In a toner for developing an electrostatic image containing toner particles containing at least a resin and a colorant, the toner particles have a core containing a resin A and at least one layer of a shell containing a resin B covering the core. And an outermost layer of the shell having a thickness of 50 nm to 500 nm.
[0017]
2. 2. The electrostatic image developing toner according to item 1, wherein the resin A is manufactured through a step of manufacturing by polymerizing a polymerizable monomer in an aqueous medium.
[0018]
3. The glass transition point (Tg1) of the resin A constituting the core is smaller than the glass transition point (Tg2) of the resin B constituting the outermost surface layer of the shell, and the softening point (Tsp1) of the resin A is 3. The electrostatic image developing toner according to item 1 or 2, wherein the toner is larger than a softening point (Tsp2) of the resin B.
[0019]
4. The electrostatic image developing toner according to any one of claims 1 to 3, wherein the outermost surface layer of the shell substantially contains only the resin B as a component.
[0020]
5. 5. The method for producing the toner for developing an electrostatic image according to any one of items 1 to 4, further comprising a step of producing a resin by polymerizing a polymerizable monomer in an aqueous medium. A method for producing an image developing toner.
[0021]
6. Forming an electrostatic image on the electrostatic image carrier, forming a toner image by developing the electrostatic image with a developer containing the electrostatic image developing toner according to any one of the above 1 to 4; An image forming method, comprising the steps of: transferring the toner image onto a recording material; and thermally fixing the toner image transferred onto the recording material.
[0022]
Hereinafter, the present invention will be described in detail.
The present inventors have conducted various studies on the above problems, and as a result, as described in claim 1, in an electrostatic image developing toner including toner particles containing at least a resin and a colorant, the toner particles are: By having a core containing the resin A and at least one layer of the shell containing the resin B covering the core, the outermost surface layer of the shell is adjusted to have a thickness of 50 nm to 500 nm, so that the shell has a high durability. A toner for developing an electrostatic image with excellent offset properties and good storability was obtained.
[0023]
《Toner particles》
The toner particles (also referred to as toner particles for developing an electrostatic image) according to the present invention will be described.
[0024]
The toner particles according to the present invention have a core (also referred to as a core portion or a core region) and at least one shell on the core (also referred to as having a core-shell structure).
[0025]
The toner particles according to the present invention have a core-shell structure, and the core-shell structure may be a composite resin particle having a multilayer structure prepared using a suspension polymerization method, or an emulsion polymerization described below, particularly a multistage polymerization method. Using a coagulant or the like, a composite resin particle having a multilayer structure and a colorant dispersion prepared by using a flocculant are obtained by aggregating and fusing, on a core particle prepared in the form of a colored resin particle. It is preferable that at least one shell (also referred to as a shell layer) is provided by a shelling operation described later.
[0026]
The aggregates of the colored resin particles and the aggregates of the composite resin particles used as the core of the toner particles according to the present invention are further prepared using a separately prepared resin dispersion (also referred to as latex) or the like. A shelling operation is performed on the particle surface to form at least one shell layer on the core. Further, an external additive is added on the outermost surface layer of the shell layer to form toner particles having a core-shell structure.
[0027]
"shell"
Here, forming a shell means that a shell is formed on the core when the layer covering the outer surface of the core (also referred to as coating) is 30% by surface area or more of the outer surface of the core. Further, in the present invention, it is preferable that 70% by surface area or more of the outer surface of the core is covered, and more preferably 80% by surface area or more.
[0028]
《Thickness of shell outermost layer》
It is essential that the thickness of the outermost layer of the toner particles according to the present invention be in the range of 50 nm to 500 nm from the viewpoint of improving anti-offset properties and storage stability, but preferably in the range of 100 nm to 300 nm. is there.
[0029]
《Core and shell thickness ratio》
The thickness ratio of the outermost layer of the core and the shell (which may be a single layer or a plurality of layers) of the toner particles according to the present invention is preferably in the range of core / shell = 100/1 to 100/10, and more preferably 100/100. / 3 to 100/8.
[0030]
Further, as the core of the toner particles according to the present invention, a core obtained by simply aggregating and fusing the above composite resin particles may be used.
[0031]
<< Measurement method of film thickness of outermost layer of shell >>
In the present invention, the thickness of the outermost surface layer of the shell is determined based on the TEM (transmission electron microscope) photograph of the toner particles in the region where the colorant (carbon black, yellow pigment, magenta pigment, cyan pigment, etc.), wax or the like exists ( The core) is confirmed by visual observation, the distance from the outermost surface of the toner particles to the core is randomly measured at ten points, and the film thickness of the outermost surface layer is calculated from the average value. Note that the number of toner particles to be subjected to TEM imaging is at least 50 or more.
[0032]
An imaging method using a transmission electron microscope uses a generally known method performed when measuring toner particles, that is, as a specific method for measuring a tomographic plane of a toner, a normal temperature curing epoxy resin is used. After sufficiently dispersing the toner, the toner may be embedded and cured, and after dispersing in styrene fine powder having a particle diameter of about 100 nm, followed by pressure molding, the obtained block may be ruthenium tetroxide, or After osmium tetroxide is used in combination and dyed, a flaky sample is cut out using a microtome provided with diamond teeth, and a tomographic morphology of the toner is photographed using a transmission electron microscope (TEM).
[0033]
Here, as the transmission electron microscope, a model well known to those skilled in the art is usually sufficiently observed. For example, LEM-2000 type (manufactured by Topcon Corporation), JEM-2000FX (manufactured by JEOL Ltd.) and the like are used. .
[0034]
(Glass transition point (Tg1) of resin A constituting core)
The glass transition point of the resin A constituting the core of the toner particles will be described.
[0035]
The glass transition point (Tg1) of the resin A is preferably in the range of 40 ° C. to 55 ° C., and more preferably in the range of 45 ° C. to 52 ° C. Here, the resin A may be a homopolymer (homopolymer) or a copolymer (copolymer), and may be a single resin or a mixture.
[0036]
(Glass transition point (Tg2) of resin B constituting the outermost surface layer of the shell)
The glass transition point of the resin B constituting the outermost surface layer of the shell provided on the core of the toner particles will be described.
[0037]
The glass transition point (Tg2) of the resin B constituting the outermost layer of the shell of the toner particles according to the present invention is preferably in the range of 50 ° C to 60 ° C, more preferably 52 ° C to 55 ° C. Range. Here, the resin B may be a homopolymer (homopolymer) or a copolymer (copolymer), or may be a single resin or a mixture.
[0038]
The glass transition point (Tg1) of the resin A constituting the core of the toner particles according to the present invention is preferably smaller than the glass transition point (Tg2) of the resin B constituting the outermost surface layer. That is, the following relational expression (1) is satisfied.
[0039]
Relational expression (1)
Tg1 + 2 ° C ≦ Tg2 ≦ Tg1 + 10 ° C
(Softening point of resin A constituting core (Tsp1))
It is essential that the glass transition point (Tsp1) of the resin A constituting the core of the toner particles according to the present invention be higher than the softening point (Tsp2) of the resin B constituting the outermost surface layer. The softening point (Tsp1) is preferably in the range of 110 ° C. to 125 ° C., and more preferably in the range of 115 ° C. to 120 ° C.
(Softening point (Tsp2) of resin B constituting the outermost surface layer of the shell)
The softening point (Tsp2) of the resin B constituting the outermost surface layer of the shell of the toner particles according to the present invention is preferably in the range of 100 ° C to 115 ° C, more preferably in the range of 110 ° C to 115 ° C. It is.
[0040]
The softening point (Tsp1) of the resin A constituting the core of the toner particles according to the present invention is preferably larger than the softening point (Tsp2) of the resin B constituting the outermost surface layer, and more preferably the following. This is to satisfy the relational expression (2).
[0041]
Relational expression (2)
Tsp1-10 ° C ≦ Tsp2 ≦ Tsp1-2 ° C
Further, it is preferable that the outermost surface layer of the shell contains substantially only the resin B as a component. Here, the phrase “substantially only the resin B is used as a component” means that when the resin B occupies 99% by mass or more of all components of the outermost surface layer of the shell, it is defined as substantially only the resin B, and other components are used. (Constituent components other than the resin B), for example, it does not contain a coloring agent, a wax (a release agent, and the like).
[0042]
The method for measuring the glass transition point and the softening point according to the present invention will be described below.
(Measurement of glass transition point)
The glass transition points of the resin A constituting the nucleation region of the toner particles and the resin B constituting the outermost surface layer are values measured by DSC, and the intersection between the baseline and the slope of the endothermic peak is the glass transition point. Point. Specifically, using a differential scanning calorimeter, the temperature is raised to 100 ° C., left at that temperature for 3 minutes, and then cooled to room temperature at a decreasing temperature of 10 ° C./minute. Then, when this sample was measured at a heating rate of 10 ° C./min, an extension of the baseline below the glass transition point and a tangent showing the maximum slope from the rising portion of the peak to the peak of the peak. The intersection is indicated as the glass transition point.
[0043]
As a measuring device, DSC-7 manufactured by PerkinElmer was used.
(Measurement of softening point)
The softening points of the resin A forming the nucleation region of the toner particles and the resin B forming the outermost surface layer are values measured using a flow tester. Specifically, using a flow tester “CFT-500” (manufactured by Shimadzu Corporation), the diameter of the pores of the die was 1 mm, the length was 1 mm, and the load was 20 kg / cm.²1 cm under the condition of a heating rate of 6 ° C./min.³The temperature corresponding to 1/2 of the height from the outflow start point to the outflow end point when the sample is melted out is shown as the softening point.
[0044]
As a means for adjusting the glass transition point, softening point, and the like of the resin constituting the outermost surface layer of the core and shell of the toner particles according to the present invention to the above-mentioned preferable ranges, the glass transition point (Tg) may be determined by forming the resin. With respect to the adjustment of the composition ratio of the polymerizable monomer and the softening point (Tsp), predetermined values can be obtained by adjusting the molecular weight of the resin.
[0045]
(Molecular weights of resin A constituting the core and resin B constituting the outermost surface layer of the shell)
The preferred ranges of the molecular weights of the resin A constituting the core of the toner particles and the resin B constituting the outermost surface layer of the shell are as follows.
[0046]
(A) Resin A constituting core
The molecular weight of the resin A constituting the core is 2.5 × 10 in weight average molecular weight (Mw).⁴~ 4 × 10⁴Are preferred.
[0047]
(B) Resin B constituting the outermost surface layer of the shell
The molecular weight of the resin B forming the outermost surface layer of the shell is preferably 8,000 to 20,000 in terms of weight average molecular weight (Mw).
[0048]
(Measurement of molecular weight of resin)
The method for measuring the molecular weight of the resin according to the present invention is measured by using GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a solvent.
[0049]
For measurement, 1.0 mg of THF is added to 0.5 mg to 5 mg of the sample, more specifically, 1 mg, and the mixture is stirred at room temperature using a magnetic stirrer or the like to be sufficiently dissolved. Next, after treating with a membrane filter having a pore size of 0.45 μm to 0.50 μm, the mixture is injected into GPC. GPC measurement conditions are as follows: stabilize the column at 40 ° C., flow THF at a flow rate of 1.0 ml / min, and inject about 100 μl of a 1 mg / ml concentration sample for measurement. The column is preferably used in combination with a commercially available polystyrene gel column. For example, a combination of Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 manufactured by Showa Denko Co., Ltd., and TSK gel G1000H, G2000H, G3000H, G4000H, G5000H, G6000H, G7000H, TSK guard manufactured by Tosoh Corporation. column and the like. As the detector, a refractive index detector (IR detector) or a UV detector may be used. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. It is preferable to use about 10 polystyrenes for preparing a calibration curve.
[0050]
(Resin constituting toner particles)
The resin constituting the toner particles according to the present invention will be described.
[0051]
As the resin used for each of the nucleation region, the intermediate layer, and the outermost surface layer of the toner particles according to the present invention, a polymer obtained by polymerizing a polymerizable monomer as described below is used. Can be done.
[0052]
The resin according to the present invention contains, as a component, a polymer obtained by polymerizing at least one polymerizable monomer. Examples of the polymerizable monomer include styrene, o-methylstyrene, and m-methylstyrene. Methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p Styrene or styrene derivatives such as -n-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, methyl methacrylate, ethyl methacrylate, methacryl N-butyl acrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, Methacrylate derivatives such as n-octyl acrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, acrylic Acrylate derivatives such as isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, and the like; Olefins such as ethylene, propylene and isobutylene; halogenated vinyls such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride and vinylidene fluoride; vinyl propionate; vinyl acetate , Vinyl esters such as vinyl benzoate, vinyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone, N-vinyl carbazole, N-vinyl indole, N -N-vinyl compounds such as vinylpyrrolidone, vinyl compounds such as vinylnaphthalene and vinylpyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide. These vinyl monomers can be used alone or in combination.
[0053]
Further, it is more preferable to use a combination of those having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, those having a substituent such as a carboxyl group, a sulfonic acid group, or a phosphoric acid group as a constituent group of a monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, and fumaric acid. Acid, monoalkyl maleate, monoalkyl itaconic acid, styrenesulfonic acid, allylsulfosuccinic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy Propyl methacrylate and the like.
[0054]
Furthermore, polyfunctional such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. A resin having a crosslinked structure can be obtained by using a hydrophilic vinyl.
[0055]
(Polymerization initiator)
These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. Examples of the oil-soluble polymerization initiator include 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, and 1,1'-azobis (cyclohexane-1-carbo). Azo or diazo polymerization initiators such as nitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4- t-butylperoxycyclohexyl) propane, tris The (t-butylperoxy) triazine peroxide polymerization initiator or a peroxide, such as and the like polymeric initiator having a side chain.
[0056]
When the emulsion polymerization method is used, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and salts thereof, and hydrogen peroxide.
[0057]
Dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate , Bentonite, silica, alumina and the like. Further, a surfactant generally used as a surfactant such as polyvinyl alcohol, gelatin, methyl cellulose, sodium dodecylbenzenesulfonate, an ethylene oxide adduct, and higher alcohol sodium sulfate can be used as a dispersion stabilizer.
[0058]
<< Production method of toner for developing electrostatic images >>
The method for producing the electrostatic image developing toner of the present invention will be described.
[0059]
The toner particles according to the present invention produce fine resin particles (also referred to as polymerized particles) by suspension polymerization or emulsion polymerization of a monomer in a liquid to which an emulsion of necessary additives is added. After that, it is preferable to manufacture by an emulsion association method in which an organic solvent, an aggregating agent and the like are added and association (aggregation, fusion) is performed.
[0060]
In addition, at the time of polymerization, a resin containing a polymer exhibiting a glass transition point or a softening point in a specific range can be synthesized by properly using the above-mentioned polymerization initiator according to the purpose.
[0061]
At the time of association, a method of mixing and dispersing with a dispersion liquid such as a release agent and a colorant necessary for forming the toner particles, and preparing a toner composition such as a release agent and a colorant in a monomer. A method in which the components are dispersed and emulsion polymerization is carried out is exemplified. Here, the association means that a plurality of resin particles and colorant particles are fused.
[0062]
In the suspension polymerization and the emulsion polymerization, it is preferable to use an aqueous medium, and the aqueous medium is one containing at least 50% by mass of water.
[0063]
That is, for example, in the suspension polymerization method, a coloring agent and, if necessary, a mold release agent, a charge control agent, various constituent materials such as a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, Various constituent materials are dissolved or dispersed in the polymerizable monomer using a sand grinder, an ultrasonic disperser or the like. The polymerizable monomer in which the various constituent materials are dissolved or dispersed is dispersed in an aqueous medium containing a dispersion stabilizer into oil droplets of a desired size as a toner by using a homomixer or a homogenizer. Thereafter, the polymerization reaction is advanced by heating. After completion of the reaction, the toner of the present invention is prepared by removing the dispersion stabilizer, filtering, washing and drying.
[0064]
In addition, as a method for producing the toner particles according to the present invention, a method of preparing resin particles by associating or fusing them in an aqueous medium to form a core (when forming a core, a colorant is coexistent). Or may not coexist). Although this method is not particularly limited, for example, the methods described in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904 can be used. That is, for example, a method of associating a plurality of fine particles composed of a resin and a colorant and the like, or dispersed particles of a constituent material such as a colorant and resin particles emulsion-polymerized with an emulsifier as described above, Is dispersed using an emulsifier, and at the same time a coagulant having a critical coagulation concentration or more is added and salted out.At the same time, the formed polymer is heat-fused at a temperature equal to or higher than the glass transition temperature of the polymer itself to gradually form fused particles. When the target particle size is reached, a large amount of water is added to stop the particle size growth, and the shape is controlled by smoothing the particle surface while heating and stirring, and the particles are hydrated. There is a method of forming a toner by heating and drying in a fluidized state as it is. In the formation of the fused particles, an organic solvent infinitely soluble in water may be added together with the coagulant.
[0065]
In the present invention, it is preferable to use composite resin particles having a multilayer structure and obtained by a multistage polymerization method as the resin particles prepared by the emulsion polymerization. In the present invention, a toner is obtained through a step of aggregating / fusing the composite resin particles and the colorant particles with an aggregating agent (where an external additive known to those skilled in the art may or may not be used). In some cases, when not used, the colored particles are used as they are as toner particles).
[0066]
Particularly, in the case of toner particles obtained through a step of aggregating / fusing composite resin particles obtained by a two-stage polymerization method and colorant particles, the composite resin particles have a peak or shoulder molecular weight of 100,000. Having a central portion (nucleus) formed from a high molecular weight resin of about 1,000,000 and an outer layer (shell) formed from a low molecular weight resin having a peak or shoulder molecular weight of 1,000 to 50,000. Preferably, a release agent is contained in the central portion (core).
[0067]
In the case of a toner obtained by aggregating / fusing composite resin particles obtained by a three-stage polymerization method and colorant particles, the composite resin particles have a peak or shoulder molecular weight of 100,000 to 1,1. A central portion (nucleus) formed from a high molecular weight resin of 1,000,000, an intermediate layer formed of a resin having a peak or shoulder molecular weight of 25,000 to 150,000, and a middle portion formed of a resin having a peak or shoulder molecular weight of 1,000 to 50. And an outer layer (shell) formed of a low molecular weight resin of 2,000, and the intermediate layer preferably contains a release agent.
[0068]
As the core of the toner particles according to the present invention, “composite resin particles” having a multilayer structure are preferably used. Here, the composite resin particles refer to the core so as to cover the surface of the core particles made of resin. The resin that forms the particles refers to resin particles having a so-called multilayer structure in which one or more coating layers made of resins having different molecular weights and / or compositions are formed.
[0069]
Further, the "center (core)" of the composite resin particles refers to "core particles" constituting the composite resin particles.
[0070]
The “outer layer (shell)” of the composite resin particles refers to the outermost layer of “one or more coating layers” constituting the composite resin particles.
[0071]
Further, the “intermediate layer” of the composite resin particles refers to a coating layer formed between a central portion (core) and an outer layer (shell).
[0072]
Here, the outer layer (shell) is merely the outer layer of the composite resin particles, not the outermost layer of the toner particles according to the present invention. The outermost surface layer of the toner particles of the present invention has a shell formed on the outer layer surface of the composite resin particles by a shelling operation. The shell may be a single or multi-layer construction.
[0073]
The molecular weight distribution of the composite resin particles is not monodisperse, and the composite resin particles generally have a molecular weight gradient from the center (core) to the outer layer (shell).
[0074]
In the present invention, the “multi-stage polymerization method” for obtaining composite resin particles refers to a method in which a monomer (n) is subjected to a polymerization treatment (n-th stage) in the presence of resin particles (n). The monomer (n + 1) is subjected to a polymerization treatment (the (n + 1) th step), and a polymer of the monomer (n + 1) is dispersed and / or dispersed on the surface of the resin particle (n). Or a method of forming a coating layer (n + 1) made of a resin having a different composition).
[0075]
Here, when the resin particles (n) are core particles (n = 1), a “two-stage polymerization method” is performed. When the resin particles (n) are composite resin particles (n ≧ 2), It becomes a multi-stage polymerization method of three or more stages.
[0076]
In the present invention, “aggregation / fusion” may mean that aggregation and fusion of particles (loss of interface between particles) occur simultaneously, or aggregation and fusion may occur simultaneously.
[0077]
Here, agglomeration indicates that the dispersion stability of the latex particles is reduced and the particles gather together, and fusion by heat is not included in the aggregation. In other words, even if the particles are agglomerated, the outer shape of each particle remains.
[0078]
In addition, fusion refers to a state in which the resin constituting the latex particles is softened by the application of heat, the particles adhere to each other, and the interface between the particles disappears.
[0079]
In order to simultaneously perform the aggregation and the fusion, it is necessary to aggregate the particles (the composite resin particles and the colorant particles) under a temperature condition equal to or higher than the glass transition temperature (Tg) of the resin constituting the composite resin particles.
[0080]
A plurality of resins having different compositions and / or molecular weights exist in the composite resin particles obtained by the multi-stage polymerization method. Therefore, the toner obtained by aggregating / fusing the composite resin particles and the colorant particles has extremely small variations in composition, molecular weight, and surface characteristics among the toner particles.
[0081]
According to such a toner having a uniform composition, molecular weight, and surface characteristics among toner particles, good adhesion (high fixing strength) to an image support is maintained in an image forming method including a fixing step by a contact heating method. Meanwhile, the offset resistance and the anti-winding property can be improved, and an image having an appropriate gloss can be obtained.
[0082]
The toner of the present invention forms composite resin particles in the absence of a colorant, adds a colorant particle dispersion to the composite resin particle dispersion, and aggregates / melts the composite resin particles and the colorant particles. It is preferably prepared by allowing to adhere.
[0083]
As described above, by preparing the composite resin particles in a system in which no colorant is present, the polymerization reaction for obtaining the composite resin particles is not hindered. For this reason, according to the toner of the present invention, excellent offset resistance is not impaired, and contamination of the fixing device and image contamination due to accumulation of toner do not occur.
[0084]
In addition, as a result of reliably performing the polymerization reaction for obtaining the composite resin particles, no monomer or oligomer remains in the obtained toner particles, and the heat fixing step of the image forming method using the toner. Does not cause off-flavors.
[0085]
Further, the surface characteristics of the obtained toner particles are uniform and the charge amount distribution is sharp, so that an image having excellent sharpness can be formed for a long period of time.
[0086]
《Chain transfer agent》
For the purpose of adjusting the molecular weight of the resin constituting the composite resin particles, a generally used chain transfer agent can be used.
[0087]
The chain transfer agent is not particularly limited. For example, mercaptans such as octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide and α-methyl Styrene dimer and the like are used.
[0088]
《Polymerization initiator》
The polymerization initiator used in the present invention will be described.
[0089]
The radical polymerization initiator for obtaining the composite resin particles can be appropriately used as long as it is a water-soluble radical polymerization initiator.
[0090]
Specific examples of the radical polymerization initiator include, for example, persulfates (potassium persulfate, ammonium persulfate, etc.), azo compounds (4,4′-azobis-4-cyanovaleric acid and its salts, 2,2′-azobis ( 2-amidinopropane) salts), peroxide compounds and the like.
[0091]
Further, the above radical polymerization initiator can be combined with a reducing agent, if necessary, to form a redox initiator. By using the redox initiator, the polymerization activity is increased, the polymerization temperature is lowered, and the polymerization time can be further reduced.
[0092]
The polymerization temperature is not particularly limited as long as it is equal to or higher than the minimum radical generation temperature of the polymerization initiator, and is, for example, in the range of 50 to 90 ° C. However, by using a polymerization initiator that starts at room temperature such as a combination of hydrogen peroxide and a reducing agent (such as ascorbic acid), it is possible to perform polymerization at room temperature or higher.
[0093]
《Surfactant》
The surfactant used in the present invention will be described.
[0094]
In order to perform polymerization using the above-mentioned radical polymerizable monomer, it is necessary to disperse oil droplets in an aqueous medium using a surfactant. The surfactant that can be used at this time is not particularly limited, but the following ionic surfactants can be mentioned as preferred examples.
[0095]
Examples of the ionic surfactant include sulfonates (sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfondiphenylurea-4,4-diazo-bis-amino-8-naphthol-6). Sodium sulfonate, ortho-carboxybenzene-azo-dimethylaniline, sodium 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sulfonate), sulfuric acid Ester salts (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, sodium stearate) Beam, calcium oleate and the like).
[0096]
Further, a nonionic surfactant can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, esters of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide, esters of higher fatty acids and polyethylene glycol, esters of higher fatty acids and polypropylene oxide, sorbitan esters And the like.
[0097]
The weight average particle size (dispersion particle size) of the composite resin particles is preferably in the range of 10 to 1000 nm, more preferably in the range of 30 to 300 nm.
[0098]
The weight average particle size is a value measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).
[0099]
The glass transition temperature (Tg) of the resin component (the resin introduced by the composite resin particles) constituting the toner of the present invention is preferably in the range of 48 ° C to 74 ° C, more preferably 52 ° C to 65 ° C. . Further, the softening point of the resin component is preferably in the range of 95C to 140C.
[0100]
"Release agent"
The release agent used in the toner of the present invention will be described.
[0101]
The content ratio of the release agent constituting the toner for developing an electrostatic image of the present invention is usually 1% by mass to 30% by mass, preferably 2% by mass to 20% by mass, more preferably 3 to 15% by mass. It is said.
[0102]
As the release agent, low molecular weight polypropylene (number average molecular weight = 1500 to 9000), low molecular weight polyethylene, or the like may be added, and a preferable release agent is an ester compound represented by the following general formula.
[0103]
General formula
R₁-(OCO-R₂)_n
In the formula, n represents an integer of 1 to 4, preferably 2 to 4, more preferably 3 to 4, and particularly preferably 4.
[0104]
R₁, R₂Represents a hydrocarbon group which may have a substituent.
R₁: Carbon number = 1 to 40, preferably 1 to 20, more preferably 2 to 5
R₂: Carbon number = 1 to 40, preferably 16 to 30, more preferably 18 to 26
Hereinafter, specific examples of the ester compound represented by the above general formula will be shown, but the present invention is not limited thereto.
[0105]
Embedded image

[0106]
Embedded image

[0107]
The amount of the release agent described above and the amount of the fixing improver represented by the general formula are 1% by mass to 30% by mass, preferably 2% by mass to 20% by mass, more preferably 2% by mass, based on the whole toner for developing an electrostatic image. Is from 3% by mass to 15% by mass.
[0108]
(Developer)
The toner of the present invention may be used as a one-component developer or a two-component developer, but is particularly preferably used as a non-magnetic one-component developer.
[0109]
Further, the toner of the present invention exhibits a high fixing property and contains a crystalline compound in order to avoid the offset phenomenon described in JP-A-8-328295. Preferably, one or more endothermic peaks in the differential thermal analysis are present at 60 ° C. to 120 ° C., and the endothermic amount is 4 J / g to 30 J / g.
[0110]
The image forming method of the present invention will be described.
The toner of the present invention includes an image forming method including a step of heat-fixing an image forming support having a toner image formed thereon between a heating roller and a pressure roller constituting a fixing device (image forming method of the present invention). Forming method).
[0111]
FIG. 1 is a cross-sectional view illustrating an example of a fixing device used in the image forming method of the present invention. The fixing device illustrated in FIG. 1 includes a heating roller 100 and a pressure roller 200 that contacts the heating roller 100. . In FIG. 1, T is a toner image formed on a transfer paper (image forming support).
[0112]
The heating roller 100 has a coating layer 120 made of a fluororesin or an elastic body formed on the surface of a metal core 110, and includes a heating member 13 composed of a linear heater.
[0113]
The core metal 110 is made of metal and has an inner diameter of 10 mm to 70 mm. The metal constituting the metal core 110 is not particularly limited, and examples thereof include metals such as iron, aluminum, and copper, and alloys thereof.
[0114]
The thickness of the core bar 110 is 0.1 mm to 15 mm, and is determined in consideration of a balance between a demand for energy saving (thinning) and a strength (depending on a constituent material). For example, in order to maintain the same strength as a 0.57 mm iron core with an aluminum core, the thickness of the aluminum core must be 0.8 mm.
[0115]
Examples of the fluororesin that forms the coating layer 120 include PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer).
[0116]
The thickness of the coating layer 120 made of fluororesin is 10 μm to 500 μm, and preferably 20 μm to 400 μm.
[0117]
If the thickness of the coating layer 120 made of fluororesin is less than 10 μm, the function as the coating layer cannot be sufficiently exhibited, and the durability as a fixing device cannot be secured. On the other hand, there is a problem that the surface of the coating layer having a thickness of more than 500 μm is easily scratched by paper dust, and toner or the like adheres to the scratched portion, thereby causing image stains.
[0118]
It is preferable to use silicone rubber and silicone sponge rubber having good heat resistance such as LTV, RTV, and HTV as the elastic body constituting the coating layer 120.
[0119]
The Asker C hardness of the elastic body constituting the coating layer 120 is less than 80 °, preferably less than 60 °.
[0120]
The thickness of the coating layer 120 made of an elastic material is set to 0.1 mm to 30 mm, preferably 0.1 mm to 20 mm.
[0121]
When the Asker C hardness of the elastic body constituting the coating layer 120 exceeds 80 °, and when the thickness of the coating layer 120 is less than 0.1 mm, the fixing nip cannot be increased, and soft fixing is performed. (For example, the effect of improving the color reproducibility by the toner layer at the smoothed interface) cannot be exhibited.
[0122]
As the heating member 130, a halogen heater can be suitably used.
The pressure roller 200 has a coating layer 22 made of an elastic material formed on the surface of the metal core 21. The elastic body constituting the coating layer 220 is not particularly limited, and examples thereof include urethane rubber, various soft rubbers such as silicone rubber, and sponge rubber. It is preferable to use silicone sponge rubber.
[0123]
The Asker C hardness of the elastic body constituting the coating layer 220 is less than 80 °, preferably less than 70 °, and more preferably less than 60 °.
[0124]
The thickness of the coating layer 220 is 0.1 mm to 30 mm, and preferably 0.1 to 20 mm.
[0125]
If the Asker C hardness of the elastic body constituting the coating layer 220 exceeds 80 °, and if the thickness of the coating layer 220 is less than 0.1 mm, the fixing nip cannot be increased, and the soft fixing It cannot be effective.
[0126]
The material constituting the cored bar 210 is not particularly limited, but may be a metal such as aluminum, iron, or copper, or an alloy thereof.
[0127]
The contact load (total load) between the heating roller 100 and the pressure roller 200 is usually 40N to 350N, preferably 50N to 300N, and more preferably 50N to 250N. The contact load is defined in consideration of the strength of the heating roller 100 (thickness of the core 110). For example, in the case of a heating roller having a core of 0.3 mm made of iron, the contact load is set to 250 N or less. Is preferred.
[0128]
In addition, from the viewpoint of offset resistance and fixability, the nip width is preferably 4 mm to 10 mm, and the nip surface pressure is 0.6 × 10⁵Pa ~ 1.5 × 10⁵Pa is preferred.
[0129]
As an example of the fixing conditions by the fixing device shown in FIG. 1, the fixing temperature (surface temperature of the heating roller 100) is preferably in a range of 150 ° C. to 210 ° C., and the fixing linear velocity is in a range of 80 mm / sec to 640 mm / sec. Is preferred.
[0130]
The fixing device used in the present invention may be provided with a cleaning mechanism as needed. In this case, as a method of supplying the silicone oil to the upper roller (heating roller) of the fixing unit, a method of supplying and cleaning with a pad, a roller, a web, or the like impregnated with the silicone oil can be used.
[0131]
As the silicone oil, those having high heat resistance are used, such as polydimethyl silicone, polyphenylmethyl silicone, and polydiphenyl silicone. Since those having a low viscosity have a large outflow amount during use, those having a viscosity at 20 ° C. of 1 Pa · s to 100 Pa · s are preferably used.
[0132]
However, the effect of the present invention is particularly remarkably exhibited when an image is formed by a fixing device that does not supply silicone oil or that uses a very small amount of silicone oil. Therefore, even when silicone oil is supplied, the supply amount is preferably 2 mg / A4 or less.
[0133]
By setting the supply amount of the silicone oil to 2 mg / A4 or less, the amount of the silicone oil adhering to the transfer paper (image support) after fixing is reduced, and an oil-based pen such as a ballpoint pen is filled with the silicone oil adhered to the transfer paper. There is no difficulty, and the rewriting is not impaired.
[0134]
In addition, it is possible to avoid problems such as deterioration of the anti-offset property with time due to deterioration of the silicone oil and contamination of the optical system and the electrode strip with the silicone oil.
[0135]
Here, the supply amount of the silicone oil is determined by changing the mass of the fixing device (Δw) before and after passing 100 sheets of transfer paper (white paper of A4 size) continuously through the fixing device (between the rollers) heated to a predetermined temperature. ) Is calculated (Δw / 100).
[0136]
FIG. 2 is a cross-sectional view illustrating an example of the image forming apparatus of the present invention using an intermediate transfer member (transfer belt).
[0137]
In FIG. 2, an image forming apparatus for obtaining a color image includes a plurality of image forming units, each of which forms a visible image (toner image) having a different color, and transfers the toner images to the same intermediate transfer. This is an image forming method in which images are sequentially transferred onto a body.
[0138]
Here, first, second, third, and fourth image forming units Pa, Pb, Pc, and Pd are provided side by side, and the image forming units are each a photosensitive member 1a that is an electrostatic latent image forming member. 1b, 1c and 1d. The photoconductors 1a, 1b, 1c and 1d have latent image forming sections 2a, 2b, 2c and 2d, developing sections 3a, 3b, 3c and 3d, transfer discharge sections 4a, 4b, 4c and 4d, a cleaning member, Cleaning devices 5a, 5b, 5c and 5d having rubber blades and charging devices 6a, 6b, 6c and 6d are arranged.
[0139]
With such a configuration, first, for example, a latent image of a yellow component color in a document image is formed on the photoconductor 1a of the first image forming unit Pa by the latent image forming unit 2a. The latent image is converted into a visible image by the developer containing the yellow toner in the developing unit 3a, and is transferred to the transfer belt 21 by the transfer discharging unit 4a.
[0140]
On the other hand, while the yellow toner image is being transferred to the transfer belt 21 as described above, a magenta component color latent image is formed on the photoreceptor 1b in the second image forming unit Pb, and subsequently the magenta A visible image is formed by a developer containing a toner. This visible image (magenta toner image) is transferred onto the transfer belt 21 at a predetermined position when the transfer belt, which has been transferred by the first image forming unit Pa, is carried into the transfer discharge unit 4b. You.
[0141]
Hereinafter, images of cyan component color and black component color are formed by the third and fourth image forming units Pc and Pd in the same manner as described above, and a cyan toner image and a black toner image are formed on the same transfer belt. Are transferred in a superimposed manner. When such an image forming process is completed, a multicolor superimposed image is obtained on the transfer belt 21. On the other hand, the residual toner is removed from the photoconductors 1a, 1b, 1c, and 1d after the transfer by the cleaning devices 5a, 5b, 5c, and 5d, and the photoconductors 1a, 1b, 5c, and 5d are provided for the subsequent latent image formation.
[0142]
In the image forming apparatus, the transfer belt 21 is used. In FIG. 7, the transfer belt 21 is conveyed from right to left, and in the conveyance process, the transfer belt 21 in each of the image forming units Pa, Pb, Pc, and Pd. Each color transfer image is transferred by passing through each of the transfer discharge sections 4a, 4b, 4c and 4d.
[0143]
When the transfer belt 21 passes through the fourth image forming unit Pd, an AC voltage is applied to the separation / discharge discharger 22d, the transfer belt 21 is discharged, and the toner image is collectively transferred to the transfer material P. Thereafter, the transfer material P enters the fixing device 23, is fixed, is discharged from the discharge port 25, and a color image is obtained.
[0144]
In the drawing, reference numerals 22a, 22b, 22c and 22d denote separation / discharge dischargers, and the transfer belt 21 which has finished transferring the toner image is transferred by a cleaning device 24 using both a brush-like cleaning member and a rubber blade. Is cleaned and prepared for the next image formation.
[0145]
In addition, as described above, even when a multi-color superimposed image is formed on a long transfer belt 21 such as a conveyor belt and the image is collectively transferred to a transfer material, the image forming unit may be used. Independent transfer belts may be provided, and the transfer material may be sequentially transferred from each transfer belt to a transfer material.
[0146]
The transfer belt has a surface resistance of 10 such as polyimide, polyether, polyamide or tetrafluoroethylene / perfluorovinyl ether copolymer.¹⁴A conductive agent is added to a fluorine-based or silicon-based resin on a high-resistance film having a thickness of about⁵-10⁸An endless film provided with a release layer having a thickness of 5 to 15 μm of Ω is used.
[0147]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0148]
Example 1
<< Preparation of latex 1 for core >>
As described below, the first-stage polymerization, the second-stage polymerization, and then the third-stage polymerization were performed to prepare a core latex 1 having a multilayer structure.
[0149]
(1) First stage polymerization
An anionic surfactant represented by the following formula (101) is placed in a 5000 ml separable flask equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device.
Formula (101): C₁₀H₂₁(OCH₂CH₂)₂OSO₃Na
A surfactant solution (aqueous medium) in which 4 g was dissolved in 3040 g of ion-exchanged water was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm in a nitrogen stream.
[0150]
An initiator solution obtained by dissolving 10 g of a polymerization initiator (potassium persulfate: KPS) in 400 g of ion-exchanged water was added to this surfactant solution, and the temperature was adjusted to 75 ° C., followed by 528 g of styrene and 204 g of n-butyl acrylate. A monomer mixture comprising 68 g of methacrylic acid and 24.4 g of n-octyl-3-mercaptopropionate was added dropwise over 1 hour, and the system was heated and stirred at 75 ° C. for 2 hours to carry out polymerization. (First-stage polymerization) was performed to prepare a latex. This is designated as “latex (1H)”.
[0151]
The Mw of latex 1H purified by the first-stage polymerization was 14,000. Here, Mw is a weight average molecular weight.
[0152]
(2) Formation of intermediate layer (second stage polymerization)
In a flask equipped with a stirrer, a monomer mixture comprising 95 g of styrene, 36 g of n-butyl acrylate, 9 g of methacrylic acid, and 0.59 g of n-octyl-3-mercaptopropionate was used as a releasing agent as described above. 77 g of a compound represented by the formula (19) (hereinafter referred to as "exemplary compound (19)") was added, and the mixture was heated to 90 ° C and dissolved to prepare a monomer solution.
[0153]
On the other hand, a surfactant solution obtained by dissolving 1 g of an anionic surfactant (formula (101)) in 1560 ml of ion-exchanged water is heated to 98 ° C., and latex, which is a dispersion of core particles, is added to the surfactant solution. After adding 28 g of (1H) in terms of solid content, a monomer solution of the exemplified compound (19) was prepared using a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. Was mixed and dispersed for 8 hours to prepare a dispersion liquid (emulsion liquid) containing emulsified particles (oil droplets) having a dispersed particle diameter (284 nm).
[0154]
Next, an initiator solution obtained by dissolving 5 g of a polymerization initiator (KPS) in 200 ml of ion-exchanged water was added to this dispersion liquid (emulsion liquid), and the system was heated and stirred at 98 ° C. for 12 hours to carry out polymerization. (Second stage polymerization) was performed to obtain a latex. This is referred to as “latex (1HM)”.
[0155]
The latex (1HM) was dried and observed with a scanning electron microscope. As a result, particles (400 to 1000 nm) mainly composed of the exemplified compound (19) not surrounded by the latex were observed.
[0156]
The Mw of the latex 1HM purified by the second-stage polymerization was 80,000.
(3) Formation of outer layer (third stage polymerization)
An initiator solution obtained by dissolving 6.8 g of a polymerization initiator (KPS) in 265 ml of ion-exchanged water was added to the latex (1HM) obtained as described above, and 249 g of styrene was added under a temperature condition of 80 ° C. A monomer mixture composed of 88.2 g of n-butyl acrylate, 2 g of methacrylic acid, and 7.45 g of n-octyl-3-mercaptopropionate was added dropwise over 1 hour. After completion of the dropping, polymerization (third stage polymerization) was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain latex 1 for a core.
[0157]
The Mw of the polymer used for forming the outer layer in the third polymerization was 10,000.
The weight average particle size of the composite resin particles constituting the core latex 1 was 122 nm.
[0158]
<< Preparation of latex 2 for core >>
In the preparation of the latex 1 for the core, 242.5 g of styrene, 96.5 g of n-butyl acrylate, 18 g of methacrylic acid, n-octyl-3-mercaptopropionate used for forming the outer layer (third stage polymerization) were used. Was changed to 8.0 g to prepare latex 2 for a core.
[0159]
The physical properties of the obtained core latex 1 and core latex 2 are shown below.
Latex number Mw Tg1 Tsp1
(For core) (weight average molecular weight) (glass transition point) (softening point)
135000 50 ° C 120 ° C
2 30000 47 ° C 117 ° C
Here, Mw (weight average molecular weight) of each latex is the molecular weight of the core obtained by the first to third stage polymerizations.
[0160]
<< Preparation of latex 1 for shell >>
In the first stage polymerization of the core latex 1 described above, a monomer mixture was obtained in which 544 g of styrene, 188 g of n-butyl acrylate, 68 g of methacrylic acid, and 24.4 g of n-octyl-3-mercaptopropionate were used. A polymerization reaction and a post-reaction treatment were carried out in the same manner except that the liquid was used to prepare a shell latex 1.
[0161]
<< Preparation of latex 2 for shell >>
In the preparation of latex 1 for shell, the polymerization reaction and the polymerization were carried out in the same manner except that 540 g of styrene, 192 g of n-butyl acrylate, 68 g of methacrylic acid, and 30.0 g of n-octyl-3-mercaptopropionate were used. After the reaction, a latex 2 for shell was prepared.
[0162]
<< Preparation of latex 3 for shell >>
In the preparation of latex 1 for shell, the polymerization reaction and the polymerization were carried out in the same manner except that 528 g of styrene, 204 g of n-butyl acrylate, 68 g of methacrylic acid, and 15.0 g of n-octyl-3-mercaptopropionate were used. After the reaction, a latex for shell 3 was prepared.
[0163]
The physical properties of the obtained shell latexes 1, 2 and 3 are shown below.
Latex number Mw Tg2 Tsp2
(For shell) (Weight average molecular weight) (Glass transition point) (Softening point)
1 15000 53 ° C 115 ° C
2 10000 52 ° C 110 ° C
338000 49 ° C 121 ° C
<< Production example of colored particles >>
Colored particles of colored particles Bk1 to Bk5 (black), Bk6 and Bk7 (each for comparison) were produced as described below.
[0164]
<< Preparation of colored particles Bk1 >>
(1) Preparation of Colorant Dispersion 1
90 g of the anionic surfactant represented by the formula (101) was dissolved by stirring in 1600 ml of ion-exchanged water. While stirring the solution, 400.0 g of carbon black (Regal 330R: manufactured by Cabot Corporation) was gradually added, and then dispersed using a stirrer “CLEARMIX” (manufactured by M Technique Co., Ltd.). And a dispersion of colorant particles (hereinafter referred to as “colorant dispersion 1”).
[0165]
The particle size of the colorant particles in this colorant dispersion 1 was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.
[0166]
(2) Preparation of (aggregation / fusion) associated particles: core formation
420.7 g (in terms of solid content) of core latex 1, 900 g of ion-exchanged water and 200 g of “colorant dispersion 1” were placed in a reaction vessel (4) equipped with a temperature sensor, a cooling pipe, a nitrogen introduction device, and a stirring device. And stirred. After adjusting the temperature in the container to 30 ° C., a 5 mol / liter aqueous sodium hydroxide solution was added to the solution to adjust the pH to 8 to 11.0.
[0167]
Next, an aqueous solution in which 2 g of magnesium chloride hexahydrate was dissolved in 1,000 ml of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, heating was started, and the system was heated to 90 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with a “Coulter counter TA-II”, and when the number average particle size became 4 μm to 7 μm, an aqueous solution in which 40.2 g of sodium chloride was dissolved in 1,000 ml of ion-exchanged water Was added thereto to stop the particle growth, and as a ripening treatment, the mixture was heated and stirred at a liquid temperature of 98 ° C. for 6 hours to continue the fusion to form core particles.
[0168]
(3) Shelling operation (shell formation)
Next, 96 g of the shell latex 1 was added, and the heating and stirring were continued for 3 hours to fuse the latex particles of the shell latex 1 on the core particle surface to form a shell layer.
[0169]
Here, 40.2 g of sodium chloride was added, the mixture was cooled to 30 ° C. at a rate of 8 ° C./min, the pH was adjusted to 2.0 by adding hydrochloric acid, and the stirring was stopped. The resulting salted-out, agglomerated, fused particles are filtered, washed repeatedly with ion exchanged water at 45 ° C., and then dried with warm air at 40 ° C. to give a colored particle having a core and a shell layer on the core. Bk1 was obtained.
[0170]
In the preparation of the colored particles, the colorant dispersion state is controlled by controlling the pH in the aggregating step, the timing of adding the latex for shell 1 (a separately prepared, latex for shell 2 may be used), and the stirring intensity. The particle diameter and the variation coefficient of the particle size distribution can be arbitrarily adjusted by controlling and further classifying in the liquid.
[0171]
<< Preparation of Colored Particles Bk2-Bk7 >>
In the production of the colored particles Bk1, colored particles Bk2 to Bk7 were produced in the same manner except that the core latex and the shell latex shown in Table 1 were used instead of the core latex 1 and the shell latex 1. .
[0172]
<< Preparation of toner and developer >>
To the colored particles Bk1 to Bk7 prepared above, 1.0% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, respectively) Hydrophobicity = 63) was added by 1.2% by mass and mixed with a Henschel mixer to prepare Toners 1 to 5 of the present invention and Comparative Toners 6 and 7, respectively.
[0173]
Next, a ferrite carrier coated with a silicone resin and having a volume average particle diameter of 60 μm was mixed with each of the toners prepared above, and developers 1 to 5 having a toner concentration of 6% and comparative developers 1 and 2, respectively, were used. Prepared.
[0174]
Table 1 shows details of each toner and each developer prepared as described above.
[0175]
[Table 1]

[0176]
The following evaluations were performed on each of the black developers Bk1 to Bk7 obtained above using a commercially available Konica Sitios 7075 (linear speed: 370 mm / sec).
[0177]
<< Evaluation of Toner Storage >>
2 g of each prepared toner was placed in a sample tube, shaken 500 times with a tapping denser, and then left at 55 ° C. and 35% RH for 2 hours. Next, the mixture is sieved under a 48-mesh sieve and sieved under a constant vibration condition. The ratio (mass%) of the amount of toner remaining on the mesh is measured, and this is defined as a toner aggregation rate. did.
[0178]
A: The toner aggregation rate is less than 15% by mass (very good storage stability)
：: The toner aggregation rate is 15 to 45% by mass (good storage stability)
Δ: The toner aggregation rate is 46 to 60% by mass (practicable)
×: toner aggregation rate exceeds 60% by mass (not practical)
《Evaluation of offset resistance》
The fixing device of the digital copier “7065” manufactured by Konica Corporation was modified, and the image offset and the toner stain on the heat roller were evaluated under the following conditions.
[0179]
The fixing device was modified so that all cleaning mechanisms and the like that were in contact with the heat roller were removed and nothing was contacted with the heat roller. The copying environment was set to normal temperature and normal humidity (25 ° C., 55% RH), and the surface temperature of the equipped heat roller for fixing (measured at the center of the roller) was 5 ° C. in the range of 150 ° C. to 180 ° C. At each surface temperature, A4 size plain paper having a 5 mm wide solid black band image is transported and fixed at a position perpendicular to the transport direction at each surface temperature, and then a 5 mm width paper is placed at a position perpendicular to the transport direction. A4 size plain paper having a solid black band image and a halftone image with a width of 20 mm is conveyed laterally, and for each of the obtained samples, image stains caused by fixing offset (image offset) and toner stains on the heat roller surface. Was visually observed, and the anti-offset property was evaluated according to the following criteria.
[0180]
◎: No occurrence of image stain and toner stain was observed at all
: Almost no occurrence is observed in both image stains and toner stains
Δ: No image stain, but toner stain is observed
×: Both image stains and toner stains are observed.
XX: Marked image stain and toner stain are observed.
In the above-mentioned evaluation ranks, ◎ and ◎ were judged to be within a practically acceptable range.
[0181]
Table 2 shows the obtained results.
[0182]
[Table 2]

[0183]
From Table 2, it is clear that the sample of the present invention has improved storage stability and offset resistance of the toner as compared with the comparison.
[0184]
【The invention's effect】
According to the present invention, it is possible to provide a toner for developing an electrostatic image, which is excellent in offset resistance and exhibits good preservability, a method for producing the toner, and an image forming method using the toner.
[Brief description of the drawings]
FIG. 1 is a sectional view illustrating an example of a fixing device used in the present invention.
FIG. 2 is a cross-sectional view illustrating an example of the image forming apparatus of the present invention using an intermediate transfer member (transfer belt).
[Explanation of symbols]
8 Recording materials
100 heating roller
110 core metal
120 coating layer
130 Heating member
200 pressure roll
210 core metal
220 coating layer
T Toner image formed on recording material
P transfer material
Pa, Pb, Pc, Pd Image forming unit
1a, 1b, 1c, 1d photoreceptor
2a, 2b, 2c, 2d Latent image forming section
3a, 3b, 3c, 3d developing section
4a, 4b, 4c, 4d Transfer discharge unit
5a, 5b, 5c, 5d Cleaning device
6a, 6b, 6c, 6d Charger
22a, 22b, 22c, 22d Separated neutralization discharger
21 Transfer belt
23 Fixing device
24 Cleaning device
25 outlet

Claims (6)

In a toner for electrostatic image development including toner particles containing at least a resin and a colorant,
The toner particles have a core containing the resin A and at least one layer covering the core and a shell containing the resin B, and the outermost surface layer of the shell has a thickness of 50 nm to 500 nm. For developing electrostatic images. 2. The electrostatic image developing toner according to claim 1, wherein the resin A is manufactured through a process of manufacturing by polymerizing a polymerizable monomer in an aqueous medium. The glass transition point (Tg1) of the resin A constituting the core is smaller than the glass transition point (Tg2) of the resin B constituting the outermost layer of the shell, and the softening point (Tsp1) of the resin A is 3. The electrostatic image developing toner according to claim 1, wherein the toner has a softening point (Tsp2) higher than that of the resin B. The electrostatic image developing toner according to any one of claims 1 to 3, wherein the outermost surface layer of the shell substantially contains only the resin B as a constituent component. 5. The method for producing the toner for developing an electrostatic image according to claim 1, further comprising a step of producing a resin by polymerizing a polymerizable monomer in an aqueous medium. A method for producing a toner for developing a charge image. Forming an electrostatic image on the electrostatic image carrier, developing the electrostatic image with a developer containing the electrostatic image developing toner according to any one of claims 1 to 4, to form a toner image. An image forming method, comprising: a forming step; a step of transferring the toner image onto a recording material; and a step of thermally fixing the toner image transferred onto the recording material.

Images