JP2004138897A - Single component magnetic positively charged toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-component magnetic positively charged toner that has excellent low-temperature fixability and offset resistance superior to conventional corresponding toner, that has excellent initial electrification buildup as a positively charged toner, and is capable of maintaining stable and proper electrostatic chargeability for a long period of time. <P>SOLUTION: The toner is manufactured by: employing, as mutually independent resins for fixing, two styrene based polymers, (a) a high molecular weight body whose molecular weight main peak is located at 100,000 or above in gel permeation chromatography and (b) a low molecular weight body whose molecular weight main peak is located at 12,000 or below in gel permeation chromatography; mixing at least with wax, a charge control agent and a magnetic powder at a weight ratio of (a)/(b)=10/90 to 40/60 at the time of toner manufacturing; and then melting/kneading, pulverizing and classifying the resultant mixture. Desirably, the resin for fixing this toner has an acid value of 0.5 mgKOH/g or below. <P>COPYRIGHT: (C)2004,JPO

Description

次にこの混合物を、ヘンシェルミキサーを用いてさらに混合した後、ロールミルを用いて溶融混練し、冷却後、ターボミルを用いて微粉砕した。
【００６６】
そしてこの微粉砕物を分級して、体積平均粒径が７．０〜８．０μｍである非磁性１成分正帯電トナーを製造した。
結着樹脂の酸価は、０ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は０重量％であった。
実施例２
結着樹脂のうち高分子量体（ａ）として、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が９００，０００であるスチレン−アクリル酸共重合体を用いるとともに、低分子量体（ｂ）として、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が５，５００であるスチレン−アクリル酸共重合体を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００６７】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０．１ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は８重量％であった。
【００６８】
実施例３
結着樹脂のうち高分子量体（ａ）として、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が８００，０００であるスチレン−アクリル酸共重合体を用いるとともに、低分子量体（ｂ）として、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が８，０００であるスチレン−アクリル酸共重合体を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００６９】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０．４ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は１０重量％であった。
【００７０】
実施例４
結着樹脂のうち高分子量体（ａ）として、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が１，０００，０００であるスチレン−アクリル酸共重合体を用いるとともに、低分子量体（ｂ）として、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が４，０００であるスチレン−アクリル酸共重合体を用い、さらに中間分子量体（ｃ）として、乳化重合法にて合成した、ＧＰＣにおけるメインピークの分子量が５５，０００であるスチレン−アクリル酸共重合体を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００７１】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０．４ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は０重量％であった。
【００７２】
実施例５
結着樹脂のうち高分子量体（ａ）として、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が１，０００，０００であるスチレン−アクリル酸共重合体を用いるとともに、低分子量体（ｂ）として、ワックス（低分子量ポリエチレン）の存在下で、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が４，０００であるスチレン−アクリル酸共重合体を用い、なおかつ低分子量ポリエチレンを省略したこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００７３】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は０重量％であった。
【００７４】
比較例１
結着樹脂のうち高分子量体としては、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が８００，０００であるスチレン−アクリル酸共重合体を用いた。
また低分子量体としては、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が６，８００であるスチレン−アクリル酸共重合体を用いた。
【００７５】
そしてこの高分子量体と低分子量体とを、重量比で３０／７０の割合で混合して溶融、混練したのち粉砕して製造した配合樹脂を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
各成分の配合割合は下記の通り。

結着樹脂の酸価は、４ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は１０重量％であった。
【００７６】
比較例２
結着樹脂のうち高分子量体としては、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が１，９８０，０００であるスチレン−アクリル酸共重合体を用いた。
また低分子量体としては、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が５，０００であるスチレン−アクリル酸共重合体を用いた。
【００７７】
そしてこの高分子量体と低分子量体とを、重量比で２０／８０の割合で混合して溶融、混練したのち粉砕して製造した配合樹脂を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０．５ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は１０重量％であった。
【００７８】
比較例３
結着樹脂として、低分子量体（ｂ）としての、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が５，５００であるスチレン−アクリル酸共重合体と、中間分子量体（ｃ）としての、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が６８，０００であるスチレン−アクリル酸共重合体とを用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００７９】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、０．８ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は０重量％であった。
【００８０】
比較例４
結着樹脂として、高分子量体（ａ）としての、溶液重合法にて合成した、ＧＰＣにおけるメインピークの分子量が９００，０００であるスチレン−メタクリル酸共重合体と、低分子量体（ｂ）としての、懸濁重合法にて合成した、ＧＰＣにおけるメインピークの分子量が１０，０００であるスチレン−メタクリル酸共重合体とを用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
【００８１】
各成分の配合割合は下記の通り。

結着樹脂の酸価は、１．７ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は１０重量％であった。
【００８２】
比較例５
結着樹脂としてポリエステル樹脂を用いたこと以外は実施例１と同様にして、非磁性１成分正帯電トナーを製造した。
各成分の配合割合は下記の通り。

結着樹脂の酸価は、６．８ｍｇＫＯＨ／ｇであった。またトナーの、テトラヒドロフラン不溶分の含有割合は１０重量％であった。
【００８３】
実機試験Ｉ
上記各実施例、比較例で製造したトナー１００重量部に対して、疎水性乾式シリカ粒子（比表面積１３０ｍ^２／ｇ）０．５重量部と、チタニア粒子（嵩密度０．４ｇ／ｍｌ）１．０重量部とを加えてヘンシェルミキサーで混合した後、京セラミタ（株）製のレーザープリンタ〔エコシス（京セラ（株）の登録商標）ＬＳ−３８００、ａ−Ｓｉ感光体ドラム、印刷速度２４枚／分、定着温度１９５℃〕のトナーカートリッジに充てんした状態で、以下の各試験を行った。
【００８４】
（ソリッド画像濃度の測定）
温度２３℃、相対湿度４５〜５０％の常温常湿条件下で、実施例、比較例のトナーをレーザープリンタのトナーカートリッジに充てんした直後の１枚目として、ソリッド（黒ベタ）の画像を印刷した。そして黒ベタ部の９箇所の画像濃度をマクベス濃度計〔グレタマクベス社製のＲＤ？１９Ｉ〕を用いて測定し、その平均値を求めて初期の画像濃度とした。
【００８５】
次に、１枚目の画像形成をした後のレーザープリンタを用いて、常温常湿条件下で、ＩＳＯ４％の標準画像を１日あたり１万枚、合計３０万枚にわたって連続印刷した後、上記と同じソリッド（黒ベタ）の画像を印刷した。そして黒ベタ部の９箇所の画像濃度をマクベス濃度計〔グレタマクベス社製のＲＤ？１９Ｉ〕を用いて測定し、その平均値を求めて３０万枚後の画像濃度とした。
また１枚目の画像形成をした後のレーザープリンタを、温度３３℃、相対湿度８５％の高温高湿条件下で８時間、放置した後、同条件下で、上記と同じソリッド（黒ベタ）の画像を印刷した。そして黒ベタ部の９箇所の画像濃度をマクベス濃度計〔グレタグマクベス社製のＲＤ？１９Ｉ〕を用いて測定し、その平均値を求めて高温高湿での画像濃度とした。
【００８６】
（画像濃度の均一性評価）
上記ソリッド画像濃度の測定で得た、初期、３０万枚後、および高温高湿の各画像の黒ベタ部を目視にて観察して、その均一性を下記の基準で評価した。
○：均一性良好。
△：若干ムラがあった。均一性不良。
×：ひどいムラがあった。均一性極めて不良。
【００８７】
（地肌カブリの評価）
上記ソリッド画像濃度の測定で得た、初期、３０万枚後、および高温高湿の各画像の、黒ベタ部の周囲の余白部を目視にて観察して、余白部分にトナーが付着するカブリの状態を、下記の基準で評価した。
○：地肌カブリなし。良好。
△：やや地肌カブリが見られた。不良。
【００８８】
×：ひどい地肌カブリが見られた。極めて不良。
結果を表１に示す。
【００８９】
【表１】

【００９０】
表より、比較例１のトナーは、初期の画像濃度の均一性こそ良好であったものの、既に初期の段階で画像濃度が低い上、地肌カブリが極めて不良という結果を生じた。また連続印刷の途中の２万枚目で、感光体へのトナーの付着を生じたので、３０万枚後の測定および観察は断念した。さらに高温高湿条件では画像濃度が著しく低下するとともに、画像濃度の均一性が不良になり、さらに地肌カブリも極めて不良であった。
【００９１】
これらの原因としては、比較例１において、結着樹脂としての高分子量体と低分子量体とを、あらかじめ溶融混練した後、さらにワックスその他と溶融混練してトナーを製造しており、かかる長時間にわたる溶融混練により、特に高分子量体の分子鎖が切断されて、低分子量体よりもさらに分子量の小さい成分が多量に発生して、トナーの強度が大きく低下したことが考えられた。
また比較例２のトナーは、初期の画像濃度こそ良好であったものの、既に初期の段階で、画像濃度の均一性、および地肌カブリがともに不良という結果を生じた。また３０万枚後の画像濃度が大きく低下した。さらに高温高湿条件では画像濃度が僅かに低下したが、画像濃度の均一性と地肌カブリがともに良好という結果が得られた。
【００９２】
比較例２において、比較例１よりも僅かながら結果を改善できた原因としては、ＧＰＣにおけるメインピークの分子量が１，９８０，０００という極めて分子量の大きい成分を高分子量体として用いたため、比較例１と比べて、溶融混練による高分子鎖の切断は生じたものの、それによるトナーの強度の低下をある程度、抑制できたことが考えられた。
比較例３のトナーは、既に初期の段階で画像濃度が低く、かつ画像濃度の均一性、および地肌カブリがともに不良という結果を生じた。また連続印刷の途中の５万枚目で、感光体へのトナーの付着を生じたので、３０万枚後の測定および観察は断念した。さらに高温高湿条件では画像濃度が著しく低下するとともに、画像濃度の均一性と、地肌カブリとがともに極めて不良であった。
【００９３】
この原因としては、比較例３のトナーが高分子量体を含有しないため、トナーの強度が低いことが考えられた。
比較例４のトナーは、初期の段階での画像濃度が僅かに低い上、画像濃度の均一性、および地肌カブリがともに不良という結果を生じた。また定着性能が悪かったため、３０万枚後の測定および観察は初めから実施しなかった。
この原因としては、比較例４のトナーが高分子量体を多量に含有しているため、トナーの強度は良好であるものの、低温定着性が悪いことが考えられた。
【００９４】
また比較例４のトナーは、高温高湿条件では、画像濃度はあまり低下しなかったが、画像濃度の均一性と、地肌カブリとがともに極めて不良であった。
この原因としては、比較例４のトナーの、分子量分布のバランスが悪いことが考えられた。
さらに比較例５のトナーは、初期の段階での画像濃度が僅かに低いものの、画像濃度の均一性、および地肌カブリはともに良好であった。しかし３０万枚後の画像濃度が大きく低下した上、画像濃度の均一性、および地肌カブリはともに極めて不良であった。さらに高温高湿条件でも、画像濃度が大きく低下した上、画像濃度の均一性、および地肌カブリはともに極めて不良であった。
【００９５】
この原因としては、比較例５のトナーがポリエステル樹脂を使用したものであって、酸価が高いために、正帯電プロセスに十分に適応し切れなかったことが考えられた。
これに対し実施例１〜５のトナーはいずれも、初期の画像濃度が高い上、画像濃度の均一性、および地肌カブリがともに良好であった。また３０万枚後の画像濃度も十分に高い上、画像濃度の均一性、および地肌カブリはともに良好であった。さらに高温高湿条件でも、画像濃度が十分に高い上、画像濃度の均一性、および地肌カブリはともに良好であった。
【００９６】
また実施例１〜５のトナーはいずれも、トナーブロッキングを生じたり、画像形成の各プロセスでの不具合などを生じたりすることも無かった。例えばレーザープリンタの現像手段における、現像剤担持体上でのトナーの薄層形成も良好に行われた。
さらに表には示していないものの、実施例１〜５のトナーは何れも、温度１０℃、相対湿度１５％の低温低湿条件でも画像濃度が十分に高い上、画像濃度の均一性、および地肌カブリはともに良好であった。
【００９７】
実機試験ＩＩ
前記各実施例、比較例で製造したトナー１００重量部に対して、疎水性乾式シリカ粒子（比表面積１３０ｍ^２／ｇ）０．５重量部と、チタニア粒子（嵩密度０．４ｇ／ｍｌ）１．０重量部とを加えてヘンシェルミキサーで混合した後、京セラミタ（株）製のレーザープリンタ〔エコシス（京セラ（株）の登録商標）ＬＳ−３８００、ａ−Ｓｉ感光体ドラム、印刷速度２４枚／分〕を、定着温度を自由に調整できるように改造した改造機のトナーカートリッジに充てんした状態で、以下の各試験を行った。
【００９８】
（最低定着温度の測定）
実施例、比較例のトナーをトナーカートリッジに充てんしたレーザープリンタの電源をオンにした後、印刷可能の状態になってすぐにソリッドの画像を５枚、連続して印刷した。
そしてこの５枚の画像について、それぞれ黒ベタ部の画像濃度をマクベス濃度計〔グレタマクベス社製のＲＤ？１９Ｉ〕を用いて測定し、その平均値を求めてこすり前画像濃度とした。
【００９９】
次に、各画像の黒ベタ部の表面を、綿布を用いてこすった後、再びその画像濃度をマクベス濃度計〔グレタマクベス社製のＲＤ？１９Ｉ〕を用いて測定し、その平均値を求めてこすり後画像濃度とした。こすり試験の条件は、荷重１，０００ｇで１０回とした。
そして式：
維持率（％）＝（こすり後画像濃度）／（こすり前画像濃度）×１００
で求められる画像濃度の維持率が９０％以上のものを定着性良好として評価した。
【０１００】
この試験を、レーザープリンタの定着温度を５℃ずつ変化させながら繰り返し行い、上記維持率が９０％以上で、定着性良好という結果が得られた最低の温度を最低定着温度として記録した。
（高温オフセット発生温度の測定）
実施例、比較例のトナーをトナーカートリッジに充てんしたレーザープリンタの電源をオンにした後、印刷可能の状態になってすぐにオフセット検出用の画像を３０枚、定着温度の変動をモニターしながら連続して印刷した。
【０１０１】
画像は、印刷した紙の、紙送り方向の先頭部分に相当する領域に、当該紙送り方向と直交し、かつ定着部の熱ローラの軸方向と平行する、一定幅の帯状の黒ベタ部と文字部とを有し、それ以後の領域は空白としたものである。オフセットが発生すると、絵出しした紙の余白部分のうち、黒ベタ部および文字部と熱ローラのピッチが一致する領域（「ローラピッチ部」とする）に、オフセット画像を確認することができる。
【０１０２】
そして定着温度が安定した２０枚の画像の余白部分を目視にて観察して、オフセット画像を確認できたか否かによってオフセット発生の有無を決める。
この試験を、レーザープリンタの定着温度を５℃ずつ変化させながら繰り返し行い、オフセットが発生した最低の温度を、高温オフセット発生温度として記録した。
（非オフセット領域の評価）
上記高温オフセット発生温度から、先の最低定着温度を差し引いた温度差を、非オフセット領域として求めた。最低定着温度が低く、高温オフセット発生温度が高く、そして非オフセット領域が広いほど、トナーは、低温定着性に優れるとともに耐オフセット性にも優れたものであると評価することができる。
【０１０３】
結果を表２に示す。
【０１０４】
【表２】

【０１０５】
表より、比較例１のトナーは最低定着温度が高い上、高温オフセット発生温度が低く、非オフセット領域が極めて狭いことから、低温定着性、耐オフセット性ともに悪いことが判った。これは、前記のように比較例１のトナーが、高分子鎖の切断によって発生した分子量の小さい成分を多量に含んでおり、高分子量体の樹脂強度が低下したためと考えられた。
また比較例２のトナーは、比較例１に比べて高温オフセット発生温度が高いものの、最低定着温度も高いことから、非オフセット領域は依然として狭く、バランスの悪い結果となった。これは、比較例２のトナーが、前記のように極めて分子量の大きい成分を高分子量体として用いたためと考えられた。
【０１０６】
比較例３のトナーは、比較例１に比べて最低定着温度が低いものの、高温オフセット発生温度も低く、非オフセット領域が極めて狭いことから、特に耐オフセット性が悪いことが判った。これは、前記のように比較例３のトナーが高分子量体を含有しないためと考えられた。
比較例４のトナーは、比較例２よりもさらに高温オフセット発生温度が高いことから、耐オフセット性が良好であることが判った。しかし最低定着温度も高いことから、非オフセット領域はそれなりに広いものの、低温定着性が不十分で、画像形成装置の省エネルギー化の要求には十分に対応できないことがわかった。
【０１０７】
この原因は、比較例４のトナーが、前記のように高分子量体を多量に含むためと考えられた。
さらにポリエステル樹脂を用いた比較例５のトナーは、最低定着温度が低く、かつ非オフセット領域がそれなりに広いことから、低温定着性は良好であることがわかった。しかし高温オフセット発生温度は依然として僅かに低いことから、耐オフセット性は未だ十分でないことが判った。
【０１０８】
またこの比較例５のトナーは、前記のように正帯電特性が悪いことから、トナーとしてバランスが取れていないことが判った。
これに対し実施例１〜５のトナーはいずれも、最低定着温度が低く、高温オフセット発生温度が高い上、非オフセット領域が十分に広いことから、低温定着性および耐オフセット性に優れた、バランスの取れた良好なトナーであることが確認された。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic one-component positively charged toner used in an image forming apparatus using an electrophotographic technique.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a laser printer, an electrostatic copying machine, or a plain paper facsimile machine, first, the surface of a photoconductive photoreceptor is uniformly charged by a charging unit, and is then exposed to light by an exposing unit and statically exposed. After forming the electrostatic latent image, the electrostatic latent image is developed into a toner image by a developing unit.
Next, this toner image is transferred to the surface of a printing material such as paper by a transfer device, and then heated and pressed to a fixed temperature through a fixing device to fix the surface of the printing material, thereby performing a series of image forming steps. Complete.
[0003]
The photoreceptor after the transfer of the toner image is prepared for the next image formation by removing the toner remaining on the surface of the photoreceptor by a cleaning unit and, if necessary, exposing the surface to light by using a discharge lamp to remove the charge.
Among the above, in the step of developing an electrostatic latent image into a toner image, a dry development method is generally used, and among them, a two-component developer using a two-component developer in which a toner and a carrier such as iron powder are mixed is particularly preferable. A developing method, a magnetic one-component developing method using a magnetic one-component toner containing a magnetic powder in a toner without using a carrier, and the like are widely used.
[0004]
The magnetic one-component toner used in the latter magnetic one-component developing method is obtained by mixing and kneading, for example, a binder resin composed of a styrene-based polymer, a wax as a release agent, a charge controlling agent such as a dye, and a magnetic powder. , Pulverized and then classified. The average particle size of the toner is about 5 to 15 μm. Further, an external additive such as silica or titania may be externally added to the toner in order to further impart fluidity or improve cleaning properties.
[0005]
In recent years, digitalization of copiers has been progressing, and compounding with various functions has been progressing, and power consumption is equal to or higher than before despite having various functions. There is a need to make it smaller.
Regardless of copiers, laser printers, etc., energy saving is widely discussed.
For this reason, during operation of the apparatus, the amount of energy that can be transferred to the fixing unit that needs to be continuously heated to the predetermined fixing temperature is becoming smaller, and in order to cope with this, it is necessary to lower the toner at a lower fixing temperature. Demands for improving low-temperature fixability for fixing are becoming more stringent.
[0006]
In the market for copiers, laser printers, and the like, high-speed printing and miniaturization of machines have been remarkably progressing.
For this reason, the toner has a so-called sharp melt property in which the entire amount is melted neatly at a time by heating for a shorter time as the printing speed increases, and the toner also has better low-temperature fixability. It has been demanded.
It is also required that the toner has image characteristics in accordance with the increase in the printing speed, that is, the charging characteristics are stable even when the printing speed is increased.
[0007]
In the case of medium- and low-speed copiers and laser printers used in offices and homes, where the size of machines is decreasing, the amount of power used as a heat source in the fixing unit is further limited, and the power converter is compact due to its compact size. Since such a device cannot be built in, the toner is also required to have sharp melt and excellent low-temperature fixability.
In these applications, since the warm-up time after turning on the power is short, the initial charge rise of the toner is performed so that the toner can be immediately charged to a predetermined charge amount by a shorter charging operation (such as stirring). Is also required to be good.
[0008]
In addition, the toner image is not limited to the use of an image forming apparatus such as a copying machine or a laser printer.Basically, a toner image transferred onto a printing material such as paper is printed on paper when passing through a fixing unit of the apparatus. Instead of being fixed, a part of the toner adheres to the heat roller of the fixing means, and so-called offset occurs, in which the adhered toner is re-adhered to another position on the same paper or to the next paper and fixed. Therefore, it is required to have excellent offset resistance.
[0009]
In other words, toner is required not only to be used in image forming apparatuses such as copiers and laser printers, but also to have excellent low-temperature fixing properties, to be sharp melt, to have stable charging, and to have excellent offset resistance. is there.
Patent Document 1 discloses a toner in which a vinyl polymer appropriately crosslinked by adding a crosslinking agent and a molecular weight modifier during polymerization of a resin as a binder resin is disclosed. It has been shown that the above-mentioned toners having excellent anti-offset properties.
[0010]
Patent Document 2 discloses a toner using, as a binder resin, a vinyl copolymer obtained by copolymerizing a polymerizable monomer in the presence of a natural gas or coal-based Fischer-Tropschwax, It is shown that there is an effect of suppressing high-temperature offset.
Patent Document 3 discloses that a high-molecular weight polymer synthesized by a suspension polymerization method and a low-molecular weight polymer synthesized by a solution polymerization method, both of which are styrene-acrylic copolymers, are added to a solvent and heated. Disclosed is a toner using a binder resin prepared by completely dissolving with stirring and continuing stirring for about 2 hours and then removing the solvent.
[0011]
Further, Patent Documents 4 and 5 disclose a styrene-acrylic copolymer, a binder resin prepared by uniformly melt-blending a high molecular weight substance and a low molecular weight substance, or a combination of plural kinds of polymerization methods. A toner using a binder resin containing a high molecular weight substance and a low molecular weight substance synthesized by multi-stage polymerization is disclosed.
These Patent Documents 3 to 5 each show that a high molecular weight substance in the binder resin has an effect of increasing the offset resistance and a low molecular weight substance has an effect of improving the low-temperature fixability.
[0012]
Further, recently, there has been proposed a toner in which a polyester resin is used as a binder resin to stably charge with a sharp melt and has excellent offset resistance.
[0013]
[Patent Document 1]
JP-B-51-23354 (column 6, line 14 to column 7, line 9)
[Patent Document 2]
Japanese Patent No. 3058829 (column 0005, column 0006, column 0039)
[Patent Document 3]
Patent No. 03168351 (Column 0080, Column 0081)
[Patent Document 4]
JP-A-5-53372 (column 0010, column 0019 to column 0021)
[0014]
[Patent Document 5]
JP-A-5-53373 (column 0010, column 0020 to column 0022)
[0015]
[Problems to be solved by the invention]
In particular, in recent years, in a copier, a laser printer, and the like, as a result of the fact that the apparatus is made up of small, lightweight, and simpler elements, a magnetic one-component developing method having a simple developing configuration is often used. Has been reached.
As the magnetic one-component developing method, a reversal developing method in which a positively charged photoreceptor that generates a small amount of ozone, which may affect the environment, and a positively charged toner, is becoming widespread.
[0016]
However, since the magnetic one-component toner usually contains solid magnetic powder that does not contribute to fixing in about 30 to 60% of the total amount, it is difficult at present to further improve the fixing performance.
In view of such a current situation, each of the above-described prior arts has the following problems.
For example, since the toner of Patent Document 1 has a gel component, it certainly exhibits an excellent effect in improving the offset resistance. However, since a crosslinked vinyl polymer is used as the binder resin, which is a raw material for the gel, even if a molecular weight modifier is added during the synthesis to suppress the increase in the molecular weight, the binder resin has a high molecular weight. become. For this reason, in particular, when a magnetic one-component toner containing magnetic powder is used, the low-temperature fixability of the toner may be significantly reduced.
[0017]
Further, in the toner of Patent Document 2, since wax is added at the time of manufacturing the resin, the effect of improving the dispersibility thereof and improving the offset resistance of the toner can be obtained. However, improvement in low-temperature fixability cannot be expected so much. Moreover, since a relatively large amount of wax is added, the cohesiveness of the toner increases, which may cause instability of charging. Further, since the amount of the wax is large, the amount of the resin is reduced. Therefore, particularly when the magnetic one-component toner containing the magnetic powder is configured, the fixing strength of the toner is reduced, and the charging characteristics and the image characteristics are deteriorated. There is a possibility that fine powder (magnetic powder separated from toner, fine particles of wax, or the like) that causes the toner may be generated. In addition, the fine powder may cause contamination of peripheral units such as the photosensitive drum, or hinder the fixing of the toner, thereby causing image deterioration or deteriorating low-temperature fixability and offset resistance.
[0018]
In Patent Document 3, as described above, a high molecular weight substance and a low molecular weight substance are once dissolved in a solvent and sufficiently mixed, and then dried to produce a binder resin. Further, the binder resin thus produced is further melt-kneaded with a wax, a charge control agent, and the like, and then pulverized and classified to produce a toner.
As a result, the time during which a large shear stress is applied to the resin at the time of mixing or melt-kneading becomes longer, and in particular, the molecular chains of the high molecular weight material are cut, and a large amount of components having a smaller molecular weight than the low molecular weight material are generated. .
[0019]
Also, in Patent Documents 4 and 5, a toner is prepared by uniformly blending a low-molecular-weight compound and a high-molecular-weight compound with each other to prepare a binder resin, then melt-kneading with a wax, a charge control agent, and the like, and further pulverizing and classifying the toner. Has been manufactured. As a result, the time during which a large shear stress is applied to the resin at the time of kneading is also prolonged. As a result, the molecular chain of the high molecular weight substance is particularly broken, and a large amount of components having a lower molecular weight than the low molecular weight substance are generated.
A large amount of a component having a small molecular weight causes a decrease in the strength of the binder resin and, consequently, the strength of the toner itself.
[0020]
For this reason, particularly when a magnetic one-component toner is used, the fixing strength of the toner is reduced, or the strength of the toner itself is reduced and stress is applied in a developing unit or the like to cause deformation and deterioration. There is a risk of generating fine powder which causes deterioration of the characteristics.
Also, there is a possibility that the low-temperature fixability and the anti-offset property may be reduced due to the decrease in the fixing strength of the toner and the fact that the fine powder separated from the toner by the stress in the developing unit prevents the fixation of the toner. is there.
[0021]
In addition, the synthesis methods by multi-stage polymerization described in Patent Documents 4 and 5 have problems that the steps are too complicated, the molecular weight is not easily controlled, and it is difficult to produce a binder resin having a target molecular weight distribution. is there. In addition, there is also a problem that the production cost of the binder resin is too high, so that it is not possible to sufficiently cope with the current trend in which a configuration as simple as possible is required.
Further, all of the toners described in each of the above patent documents introduce a considerable amount of acid value into the binder resin. Is shown. For this reason, even if the positive chargeability is imparted by adding a positive charge control agent, the initial rise of charging may be poor, or stable and appropriate charging performance may not be maintained over a long period of time.
[0022]
Further, a toner using a polyester resin as a binder resin can be satisfactorily pulverized during toner production because the polyester resin is tougher than a styrene-based polymer such as a styrene-acrylic copolymer. Therefore, there is a problem that the productivity of the toner is low. Further, since the polyester resin has a high acid value, poor positive charging characteristics are a major drawback, and there is a problem in using it as a positively charged toner.
SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic one-component positively charged toner which is more excellent in low-temperature fixing property and offset resistance than ever before.
[0023]
Another object of the present invention is to provide a magnetic one-component positively-charged toner which has a good initial charge rise as a positively-charged toner and can maintain stable and appropriate charging performance for a long period of time.
[0024]
Means for Solving the Problems and Effects of the Invention
The invention according to claim 1 is a styrene-based polymer,
(A) a high molecular weight substance having a main peak molecular weight of 300,000 or more in gel permeation chromatography;
(B) a low molecular weight substance having a main peak molecular weight of 15,000 or less in gel permeation chromatography,
As binder resins independent of each other, at the time of toner production, at least (a) / (b) = 10/90 to 40/60 by weight and at least a charge controlling agent and a magnetic powder are mixed, and then melt-kneaded. A magnetic one-component positively charged toner characterized by being manufactured by pulverization and classification.
[0025]
In the structure of the first aspect, the high molecular weight substance (a) and the low molecular weight substance (b) are used as binder resins independent of each other as described above, and are used for the first time during the production of the toner together with other components constituting the toner. After mixing, melt kneading, pulverization, and classification are performed to produce a toner.
For this reason, the time during which shear stress is applied to the fixing resin during toner production is reduced, and the generation of a large amount of components having a smaller molecular weight than that of the low molecular weight product, particularly when the molecular chains of the high molecular weight material are cut, is suppressed. can do.
[0026]
This prevents the fixing strength of the toner or the strength of the toner itself from decreasing, and causes a deterioration in the charging characteristics and image characteristics even if the toner is deformed or deteriorated by applying stress in the developing unit. Can be suppressed from being generated.
As a result, the fixing strength of the toner is reduced, and the fine powder separated from the toner due to the stress in the developing unit is prevented from hindering the fixing of the toner. This makes it possible to provide a magnetic one-component positively charged toner having excellent properties.
[0027]
In addition, the molecular weight of the main peak in the gel permeation chromatograph of the high molecular weight is limited to 300,000 or more, when the molecular weight of the high molecular weight is smaller than this, mainly due to the high molecular weight, This is because the effect of improving the offset resistance of the toner cannot be obtained.
The reason why the molecular weight of the main peak in the gel permeation chromatograph of the low molecular weight compound is limited to 15,000 or less is that when the molecular weight of the low molecular weight compound is larger than this, it is mainly due to the low molecular weight compound. This is because the effect of improving the low-temperature fixability of the toner cannot be obtained.
[0028]
Further, when the high molecular weight compound (a) and the low molecular weight compound (b) are used at a weight ratio of (a) / (b) = 10/90 to 40/60, If the amount is small, the effect of improving the offset resistance of the toner due to the high molecular weight body cannot be obtained. Conversely, if the low molecular weight body is less than this range, the low-temperature fixing property of the toner due to the low molecular weight body will not be obtained. Is not obtained.
The invention according to claim 2 is a styrene-based polymer, wherein the molecular weight of the main peak in the gel permeation chromatograph is an intermediate molecular weight between the high molecular weight substance and the low molecular weight substance, which is an intermediate value of the molecular weight of the main peak. 2. The magnetic one-component positive electrode according to claim 1, wherein the binder is contained in the binder resin in a proportion of 20% by weight or less based on the total amount of the high molecular weight substance, the low molecular weight substance, and the intermediate molecular weight substance. It is a charged toner.
[0029]
In the structure of the second aspect, the intermediate molecular weight has intermediate properties between the high molecular weight and the low molecular weight, so that the homogeneity of the binder resin is improved, and particularly the strength of the toner is improved.
The reason why the intermediate molecular weight is contained at a ratio of 20% by weight or less based on the total amount of the high molecular weight, low molecular weight and intermediate molecular weight as the binder resin is that the intermediate molecular weight is larger than this range. This is because the proportion of the high molecular weight substance is relatively small, and the effect of improving the offset resistance of the toner by the high molecular weight substance may be reduced. Further, the proportion of the low molecular weight body is relatively small, and the effect of improving the low-temperature fixability of the toner by the low molecular weight body may be reduced.
[0030]
The invention according to claim 3 uses a styrene-based polymer synthesized by a suspension polymerization method and having a main peak molecular weight of 300,000 to 1.1 million as synthesized by a suspension polymerization method. The magnetic one-component positively charged toner according to claim 1, wherein:
In the configuration of claim 3, since the high molecular weight compound is synthesized by a suspension polymerization method suitable for the synthesis of the high molecular weight compound, the synthesized high molecular weight compound has a sharp molecular weight distribution and a sharp melt property. Have.
[0031]
In addition, the suspension polymerization method is a polymerization method in which chain transfer is smaller than other polymerization methods. Therefore, the synthesized high molecular weight polymer is likely to be a flexible resin with less branching and less entanglement between molecular chains. Because of this, even when melt-kneaded during toner production, such high molecular weight materials are not easily subjected to shear stress, so it is even more reliable that molecular chains are cut and a large amount of components having a lower molecular weight than low molecular weight materials are generated. Can be suppressed. And since a high molecular weight body maintains high molecular performance, generation | occurrence | production of a high temperature offset can be suppressed.
[0032]
The reason why the molecular weight of the main peak of the high molecular weight substance in gel permeation chromatography is limited to 300,000 or more is the same as the above. The reason why the molecular weight is limited to 1.1 million or less is that when the molecular weight of the high molecular weight substance is larger than this, even if the high molecular weight substance and the low molecular weight substance are not melt-kneaded in advance, they are independent from each other during the toner production. Even if a toner is manufactured by blending it as a component, or a polymer is synthesized by a suspension polymerization method to impart flexibility, the molecular chain is cut by the shear stress during melt-kneading and the component having a small molecular weight This is because it may not be possible to prevent the generation of a large amount of toner and the deterioration of the toner characteristics.
[0033]
The invention according to claim 4 is a styrene-based polymer having a main peak molecular weight of 1,000 to 15,000 in a gel permeation chromatograph synthesized by an emulsion polymerization method or a solution polymerization method as a low molecular weight substance. 2. The magnetic one-component positively charged toner according to claim 1, wherein the toner is combined.
According to the configuration of claim 4, the low molecular weight compound is synthesized by an emulsion polymerization method or a solution polymerization method suitable for the synthesis of the low molecular weight compound, and thus the synthesized low molecular weight compound has a sharp molecular weight distribution and a sharp melt. It has the following characteristics. It also has excellent low-temperature fixability.
[0034]
The reason why the molecular weight of the main peak of the low molecular weight compound in gel permeation chromatography is limited to 15,000 or less is based on the same reason as described above. The reason why the molecular weight is limited to 1,000 or more is that when the molecular weight of the low molecular weight substance is smaller than this, the molecular chain of the high molecular weight substance is cleaved and a large amount of low molecular weight components are generated. This is because there is a possibility that deterioration of the properties of the toner cannot be completely prevented.
[0035]
The invention according to claim 5 is characterized in that a main peak molecular weight in gel permeation chromatography exceeds 15,000, synthesized by a suspension polymerization method, an emulsion polymerization method or a solution polymerization method, as an intermediate molecular weight substance, and The magnetic one-component positively charged toner according to claim 2, wherein a styrene-based polymer having a molecular weight of less than 300,000 is used.
As described above, as the intermediate molecular weight, those produced by any polymerization method such as a suspension polymerization method, an emulsion polymerization method and a solution polymerization method can be used.
[0036]
Further, since the intermediate molecular weight is required to have an intermediate molecular weight between the high molecular weight and the low molecular weight, the molecular weight of the main peak in gel permeation chromatography exceeds 15,000 as described above, And less than 300,000.
The invention according to claim 6 is the magnetic one-component positively charged toner according to claim 1 or 2, wherein the acid value of the binder resin is 0.5 mgKOH / g or less.
[0037]
In the configuration of claim 6, the charge control is performed by limiting the acid value of the binder resin composed of the high molecular weight compound and the low molecular weight compound, or the high molecular weight compound, the low molecular weight compound and the medium molecular weight compound to the above range. The toner in a state in which the agent is not added can be made to exhibit a tendency of being uncharged or positively charged. For this reason, by adding a charge control agent for positive charging to impart positive charging properties, the initial charging rise as a positively charged toner is good, and stable and appropriate charging performance can be maintained over a long period of time. A magnetic one-component positively charged toner can be obtained.
[0038]
According to a seventh aspect of the present invention, there is provided the magnetic one-component positively charged toner according to the first or second aspect, wherein the content of the tetrahydrofuran-insoluble component is in the range of 3 to 15% by weight.
If the content of tetrahydrofuran insolubles, that is, the component having an extremely high molecular weight in the high-molecular-weight product is less than 3% by weight, the offset resistance of the toner may be insufficient. If it exceeds 15% by weight, the low-temperature fixability of the toner may be insufficient.
[0039]
The invention according to claim 8 is characterized in that after pre-mixing the binder resin and the wax, at least the charge control agent and the magnetic powder are added and mixed, and further kneaded, pulverized and classified to produce. The magnetic one-component positively charged toner according to claim 1 or 2.
The invention according to claim 9 is characterized in that at least a charge control agent and a magnetic powder are added to a binder resin polymerized in the presence of a wax, mixed, and further kneaded, pulverized, and classified to produce. The magnetic one-component positively charged toner according to claim 1 or 2.
[0040]
In each case, the wax can be more uniformly dispersed in the toner, so that the offset resistance of the toner can be improved.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described.
<Binder resin>
As the binder resin, as described above, both are styrene-based polymers,
(A) a polymer having a main peak molecular weight of 300,000 or more in a gel permeation chromatograph (hereinafter abbreviated as “GPC”);
(B) a low molecular weight compound having a main peak molecular weight of 15,000 or less in GPC;
Is used.
[0042]
Further, as the binder resin, the high molecular weight polymer (a) and the low molecular weight polymer (b) are further used as styrene polymers.
(C) an intermediate molecular weight product in which the molecular weight of the main peak in GPC is an intermediate value of the molecular weight of the main peak of the high molecular weight product and the low molecular weight product;
Can also be used in combination.
Among the above, the high molecular weight compound (a) is preferably synthesized by a suspension polymerization method, and the main peak molecular weight in GPC is preferably 300,000 to 1.1 million.
[0043]
The low molecular weight compound (b) is preferably synthesized by an emulsion polymerization method or a solution polymerization method, and the molecular weight of the main peak in GPC is preferably from 1,000 to 15,000.
Further, the medium molecular weight compound (c) may be synthesized by any polymerization method such as a suspension polymerization method, an emulsion polymerization method or a solution polymerization method, and its main peak molecular weight in GPC exceeds 15,000, and Preferably it is less than 10,000.
[0044]
These reasons are as described above.
In order to make the effect of improving the offset resistance of the toner due to the high molecular weight substance (a) more effective, the molecular weight of the main peak of the high molecular weight substance (a) in GPC should be within the above range. Of these, it is particularly preferable that the number be from 700,000 to 1.1 million.
In order to make the effect of improving the low-temperature fixability of the toner by the low molecular weight compound (b) more effective, the molecular weight of the main peak in GPC of the low molecular weight compound (b) should be within the above range. Among them, it is more preferably 3,000 to 9,000.
[0045]
In order to further improve the effect of improving the homogeneity of the toner due to the intermediate molecular weight (c), the molecular weight of the main peak of the intermediate molecular weight (c) in GPC should be within the above range. However, it is more preferably 50,000 to 60,000.
The mixing ratio of the high molecular weight compound (a) and the low molecular weight compound (b) as the binder resin needs to be in the range of (a) / (b) = 10/90 to 40/60 by weight ratio. .
When the intermediate molecular weight compound (c) is used in combination as the binder resin, the content of the high molecular weight compound (a), the low molecular weight compound (b), and the total amount of the intermediate molecular weight compound (c) is 20% by weight or less. It is preferable to include them.
[0046]
Further, the acid value of the binder resin composed of the high molecular weight compound (a) and the low molecular weight compound (b) or the high molecular weight compound (a), the low molecular weight compound (b) and the medium molecular weight compound (c) is 0.5 mg KOH. / G or less.
These reasons are also as described above.
In order to make the effect of using the high molecular weight compound (a) and the low molecular weight compound (b) together more effective, the mixing ratio (a) / (b) of the two is as described above. Even within the range, it is more preferably 20/80 to 30/70.
[0047]
Further, in the system using the intermediate molecular weight compound (c) in combination, in order to make the effect of adding the intermediate molecular weight substance (c) even more effective, the high molecular weight substance (c) It is even more preferable that the ratio of a), the low molecular weight compound (b) and the intermediate molecular weight compound (c) to the total amount is particularly 3 to 8% by weight within the above range.
Examples of the styrene-based polymer as the high-molecular-weight (a), low-molecular-weight (b), and intermediate-molecular-weight (c) include homopolymers composed of one of various styrene-based monomers. And copolymers of two or more styrene-based monomers and copolymers of styrene-based monomers with other monomers.
[0048]
Among them, examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene. , P-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, p One or more of -n-decylstyrene, pn-dodecylstyrene and the like can be mentioned.
[0049]
Further, as the other monomer that can be copolymerized with the styrene-based monomer, a monomer having a carboxyl group or an acid anhydride group, which has a function of adjusting the acid value of the resin, is preferable. Examples of the monomer include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, cinnamic acid, vinyl acetic acid, isocrotonic acid, tiglic acid, angelic acid, and α- or β-alkyl derivatives thereof. One or more kinds of unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, alkenyl succinic acid, itaconic acid, mesaconic acid, dimethylmaleic acid, dimethylfumaric acid and monoester derivatives or anhydrides thereof; Can be mentioned.
[0050]
Among them, acrylic acid, methacrylic acid or maleic acid monoester is particularly preferred from the viewpoint of improving development stability and offset resistance.
Among them, the maleic acid monoester is preferably one obtained by esterifying maleic acid with an aliphatic alcohol having 1 to 8 carbon atoms. More specifically, for example, monomethyl maleate, monoethyl maleate, monopropyl maleate, monobutyl maleate, monopentyl maleate, monohexyl maleate, monoheptyl maleate, monooctyl fumarate, etc. Can be.
[0051]
The above-mentioned carboxyl group- or acid anhydride-containing monomer is used in consideration of adjusting the acid value of the binder resin to 0.5 mgKOH / g or less as described above, and the total amount of the monomers constituting the binder resin is considered. It is preferable to mix at a ratio of 0.1 to 20% by weight, preferably 0.2 to 15% by weight.
As the monomer for adjusting the acid value, a monomer containing a carboxyl group or an acid anhydride is preferable because it has a low solubility in an aqueous suspension at the time of synthesis and a solubility in an organic solvent or another monomer. This is because it can be used in the form of an ester having a high molecular weight.
[0052]
Other monomers that can be copolymerized with the styrene monomer include, in addition to the above, for example, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; and unsaturated monomers such as butadiene and isoprene. Saturated polyenes; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, ethyl methacrylate, and methacrylic Propyl acrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate Etc. α Methylene aliphatic monocarboxylic esters; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, 1-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate Acrylates such as stearyl acrylate, stearyl acrylate, 2-chloroethyl acrylate and phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone; vinyl naphthalenes; acrylonitrile, methacrylonitrile, acrylic One or more of acrylic acid derivatives such as amides or methacrylic acid derivatives can be mentioned.
[0053]
Among them, acrylates are particularly preferred from the viewpoint of toner fixability.
<wax>
As the wax as a release agent, amide wax, ester wax, Fischer-Tropsch wax, polyolefin and the like are preferable. Examples of the polyolefin include polyethylene, polypropylene, polyisobutylene, polybutene, polypentene, and polyhexene.
[0054]
The melting point of the polyolefin as the wax is preferably 120 ° C. or less, more preferably 60 to 120 ° C. If the melting point exceeds this range, the low-temperature fixability of the toner may be reduced. Conversely, if the ratio is below this range, the toner may fuse to the surface of the photoreceptor during image formation, or toner blocking may occur during storage of the toner.
The molecular weight of the polyolefin is not limited to this, but considering the melting point and the effect of increasing the offset resistance, the viscosity of the release agent itself, and the like, the weight average molecular weight Mw is preferably 1,000 to 100,000, More preferably, it is 6,000 to 40,000. Further, the number average molecular weight Mn is preferably from 1,000 to 30,000, and more preferably from 3,000 to 15,000. Further, the ratio Mw / Mn indicating the molecular weight distribution is preferably from 1 to 5, and more preferably from 1.05 to 3.
[0055]
The amount of the wax is preferably 1 to 10 parts by weight, more preferably 2 to 6 parts by weight, based on 100 parts by weight of the binder resin. The amount of the release agent is preferably as large as possible from the viewpoint of improving the offset resistance. However, when the amount exceeds the above range, the release agent may not be uniformly dispersed in the binder resin, or the strength and the chargeability of the toner may be adversely affected. There is. Conversely, when the value is below the above range, the effect of improving the offset resistance may be insufficient.
[0056]
<Charge control agent>
As the charge control agent, a charge control agent for controlling positive charge for positively charging the toner is used.
Examples of the charge control agent for positive charge control include basic dyes, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, organic compounds having a basic nitrogen atom such as aminosilanes, and fillers surface-treated with the above compounds. Can be mentioned. In addition, examples of the charge control agent for controlling positive charges include charge control resins such as a styrene resin containing a basic nitrogen atom.
[0057]
The compounding amount of the charge control agent (or charge control resin) is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin.
<Magnetic powder>
Examples of the magnetic powder include metals such as cobalt, iron, nickel, aluminum, copper, magnesium, tin, zinc, antimony, beryllium, bismuth, calcium, selenium, titanium, tungsten, and vanadium, and compounds of these metals (such as oxides). ), Alloys or mixtures of various known magnetic powders.
[0058]
The amount of the magnetic powder is preferably 20 to 200 parts by weight, more preferably 50 to 150 parts by weight, based on 100 parts by weight of the binder resin.
<Production of magnetic one-component positively charged toner>
As described above, the magnetic one-component positively charged toner of the present invention uses the high molecular weight substance (a) and the low molecular weight substance (b) as independent binder resins in a weight ratio of (a) / (B) After mixing at least a wax, a charge control agent, and a magnetic powder at a ratio of 10/90 to 40/60, the mixture is melt-kneaded, pulverized, and classified to produce a product.
[0059]
Also, as described above, the binder resin, that is, the high molecular weight compound (a) and the low molecular weight compound (b) are pre-mixed with the wax in advance, and the remaining components are added and mixed, and further kneaded and crushed. If it is manufactured by classification, the dispersibility of the wax can be improved.
At this time, the intermediate molecular weight compound (c) may be mixed at the same time as the high molecular weight compound (a) and the low molecular weight compound (b), or may be used in a state of being mixed with any of the components in advance. In some cases, the intermediate molecular weight compound (c) is simultaneously synthesized as a secondary component when synthesizing the high molecular weight compound (a) or the low molecular weight compound (b). The mixture of the high molecular weight compound (a) and the intermediate molecular weight compound (c) or the mixture of the low molecular weight compound (b) and the intermediate molecular weight compound (c) may be used as a binder resin for mixing.
[0060]
For mixing, a dry blender, a Henschel mixer, a ball mill or the like is used.
For the melt kneading, a kneading device such as a Banbury mixer, a roll, a single screw or a twin screw kneading extruder is used.
<Magnetic one-component positively charged toner>
The particle size of the magnetic one-component positively charged toner of the present invention thus produced is not particularly limited, and may be in a range usually used. However, when the toner is used as a small particle size toner, it is preferable to adjust the volume-based average diameter (median diameter measured by a Coulter counter) to be 5 to 11 μm, particularly 6 to 9 μm.
[0061]
The toner preferably contains a tetrahydrofuran-insoluble component in a range of 3 to 15% by weight based on the total amount of the toner excluding an external additive described below. The reason is as described above.
Various external additives may be externally added to the toner in order to improve its fluidity and charging characteristics.
As such external additives, conventionally known ones such as fine powders of metal oxides such as alumina, silica, titania and zinc oxide, and fine particles of fluororesin can be used.
[0062]
Although the external additive amount of the external additive is not limited to this, for example, the total amount of one or more external additives is preferably 0.1 to 3.0 parts by weight based on 100 parts by weight of the toner. .
[0063]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples.
Example 1
As the polymer (a) of the binder resin, a styrene-acrylic acid copolymer having a main peak molecular weight of 1,000,000 in GPC synthesized by a suspension polymerization method was used.
[0064]
Further, as the low molecular weight compound (b), a styrene-acrylic acid copolymer having a main peak molecular weight of 4,000 synthesized by a solution polymerization method was used.
These styrene acrylic acid copolymers were first premixed with low molecular weight polyethylene as a wax, and then a nigrosine dye as a charge control agent and magnetite powder as a magnetic powder were added and mixed.
The mixing ratio of each component is as follows.
[0065]

Next, the mixture was further mixed using a Henschel mixer, melt-kneaded using a roll mill, cooled, and finely ground using a turbo mill.
[0066]
This finely pulverized product was classified to produce a non-magnetic one-component positively charged toner having a volume average particle size of 7.0 to 8.0 μm.
The acid value of the binder resin was 0 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 0% by weight.
Example 2
Among the binder resins, a styrene-acrylic acid copolymer having a main peak molecular weight of 900,000 in GPC synthesized by a suspension polymerization method and a low molecular weight compound (b) were used as the high molecular weight compound (a). Non-magnetic one-component positively charged in the same manner as in Example 1 except that a styrene-acrylic acid copolymer having a main peak molecular weight in GPC of 5,500 synthesized by a solution polymerization method was used. A toner was manufactured.
[0067]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0.1 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 8% by weight.
[0068]
Example 3
A styrene-acrylic acid copolymer having a main peak molecular weight of 800,000 in GPC synthesized by a suspension polymerization method is used as the high molecular weight compound (b) as the high molecular weight compound (b) in the binder resin. ), A non-magnetic one-component positive charge was obtained in the same manner as in Example 1 except that a styrene-acrylic acid copolymer having a main peak molecular weight in GPC of 8,000 synthesized by a solution polymerization method was used. A toner was manufactured.
[0069]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0.4 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 10% by weight.
[0070]
Example 4
As the high molecular weight polymer (a) of the binder resin, a styrene-acrylic acid copolymer having a main peak molecular weight of 1,000,000 in GPC synthesized by a suspension polymerization method is used, and a low molecular weight polymer is used. As (b), a styrene-acrylic acid copolymer having a main peak molecular weight in GPC of 4,000, which was synthesized by a solution polymerization method, was further synthesized as an intermediate molecular weight (c) by an emulsion polymerization method. A non-magnetic one-component positively charged toner was manufactured in the same manner as in Example 1 except that the styrene-acrylic acid copolymer having a main peak molecular weight of 55,000 in GPC was used.
[0071]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0.4 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 0% by weight.
[0072]
Example 5
As the high molecular weight polymer (a) of the binder resin, a styrene-acrylic acid copolymer having a main peak molecular weight of 1,000,000 in GPC synthesized by a suspension polymerization method is used, and a low molecular weight polymer is used. As (b), a styrene-acrylic acid copolymer having a main peak molecular weight of 4,000 in GPC synthesized by a solution polymerization method in the presence of a wax (low molecular weight polyethylene), and a low molecular weight polyethylene A non-magnetic one-component positively-charged toner was produced in the same manner as in Example 1 except that was omitted.
[0073]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 0% by weight.
[0074]
Comparative Example 1
A styrene-acrylic acid copolymer having a main peak molecular weight of 800,000 in GPC, which was synthesized by a solution polymerization method, was used as the high molecular weight polymer in the binder resin.
Further, as the low molecular weight substance, a styrene-acrylic acid copolymer having a main peak molecular weight of 6,800 in GPC synthesized by a solution polymerization method was used.
[0075]
Then, in the same manner as in Example 1 except that the high molecular weight substance and the low molecular weight substance were mixed at a weight ratio of 30/70, melted, kneaded, and then pulverized to produce a compounded resin, A non-magnetic one-component positively charged toner was produced.
The mixing ratio of each component is as follows.

The acid value of the binder resin was 4 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 10% by weight.
[0076]
Comparative Example 2
A styrene-acrylic acid copolymer having a main peak molecular weight of 1,980,000 synthesized by a suspension polymerization method and having a molecular weight of 1,980,000 was used as a high molecular weight polymer in the binder resin.
In addition, as the low molecular weight compound, a styrene-acrylic acid copolymer having a main peak molecular weight in GPC of 5,000 synthesized by a suspension polymerization method was used.
[0077]
Then, in the same manner as in Example 1 except that the high-molecular weight body and the low-molecular weight body were mixed at a weight ratio of 20/80, melted, kneaded, and then pulverized to produce a compounded resin, A non-magnetic one-component positively charged toner was produced.
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0.5 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 10% by weight.
[0078]
Comparative Example 3
As a binder resin, a styrene-acrylic acid copolymer having a main peak molecular weight of 5,500 in GPC synthesized by a solution polymerization method as a low molecular weight compound (b) and an intermediate molecular weight compound (c) In the same manner as in Example 1 except that a styrene-acrylic acid copolymer having a main peak molecular weight in GPC of 68,000, synthesized by a suspension polymerization method, was used. A charged toner was manufactured.
[0079]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 0.8 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 0% by weight.
[0080]
Comparative Example 4
As a binder resin, a styrene-methacrylic acid copolymer having a main peak molecular weight of 900,000 in GPC synthesized by a solution polymerization method as a high molecular weight substance (a) and a low molecular weight substance (b) A non-magnetic one-component positive component was prepared in the same manner as in Example 1 except that a styrene-methacrylic acid copolymer having a main peak molecular weight in GPC of 10,000 synthesized by a suspension polymerization method was used. A charged toner was manufactured.
[0081]
The mixing ratio of each component is as follows.

The acid value of the binder resin was 1.7 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 10% by weight.
[0082]
Comparative Example 5
A non-magnetic one-component positively charged toner was produced in the same manner as in Example 1 except that a polyester resin was used as the binder resin.
The mixing ratio of each component is as follows.

The acid value of the binder resin was 6.8 mgKOH / g. The content of the tetrahydrofuran-insoluble component in the toner was 10% by weight.
[0083]
Actual machine test I
With respect to 100 parts by weight of the toners manufactured in the above Examples and Comparative Examples, hydrophobic dry silica particles (specific surface area: 130 m ² / G) 0.5 part by weight and 1.0 part by weight of titania particles (bulk density 0.4 g / ml) were added and mixed with a Henschel mixer, and then a laser printer manufactured by Kyocera Mita Co., Ltd. [Ecosys (Kyocera) The following tests were carried out in a state in which the toner cartridge was filled with a toner cartridge of LS-3800 (registered trademark), an a-Si photosensitive drum, a printing speed of 24 sheets / min, and a fixing temperature of 195 ° C.].
[0084]
(Measurement of solid image density)
Printing a solid (black solid) image as the first sheet immediately after filling the toners of Examples and Comparative Examples into a toner cartridge of a laser printer under normal temperature and normal humidity conditions of a temperature of 23 ° C. and a relative humidity of 45 to 50%. did. Then, the image density of the nine black solid portions was measured using a Macbeth densitometer [RD? 19I], and the average value was obtained as the initial image density.
[0085]
Next, using a laser printer after forming the first image, a standard image of ISO 4% was continuously printed on a total of 300,000 sheets per day under normal temperature and normal humidity conditions for 10,000 sheets per day. The same solid (black solid) image was printed. Then, the image density of the nine black solid portions was measured using a Macbeth densitometer [RD? 19I], and the average value was determined as the image density after 300,000 sheets.
The laser printer after forming the first image was left for 8 hours under a high-temperature and high-humidity condition of a temperature of 33 ° C. and a relative humidity of 85%, and then under the same conditions, the same solid (black solid) as above. Image was printed. Then, the image density of the nine black solid portions was measured using a Macbeth densitometer [RD? 19I], and the average value was determined as the image density at high temperature and high humidity.
[0086]
(Evaluation of uniformity of image density)
The solid black portions of the initial, after 300,000 sheets, and high-temperature and high-humidity images obtained by the measurement of the solid image density were visually observed, and the uniformity was evaluated according to the following criteria.
：: Good uniformity.
Δ: Some unevenness was observed. Poor uniformity.
X: There was severe unevenness. Extremely poor uniformity.
[0087]
(Evaluation of background fog)
In the initial, after 300,000 sheets, and in the high-temperature and high-humidity images obtained by the measurement of the density of the solid image, the margins around the solid black area are visually observed, and fog in which toner adheres to the margins is observed. Was evaluated according to the following criteria.
：: No background fog. Good.
Δ: Slight fog was observed. Bad.
[0088]
×: Severe background fog was observed. Extremely bad.
Table 1 shows the results.
[0089]
[Table 1]

[0090]
As can be seen from the table, although the toner of Comparative Example 1 had good initial image density uniformity, the image density was already low at the initial stage and the background fog was extremely poor. Further, since toner adhered to the photoreceptor on the 20,000th sheet during continuous printing, measurement and observation after 300,000 sheets were abandoned. Further, under high-temperature and high-humidity conditions, the image density was significantly reduced, the uniformity of the image density was poor, and the background fog was extremely poor.
[0091]
The reason for this is that, in Comparative Example 1, a high molecular weight substance and a low molecular weight substance as binder resins were melt-kneaded in advance, and then melt-kneaded with wax or the like to produce a toner. It is considered that the melt-kneading over a long period of time particularly breaks the molecular chain of the high molecular weight substance, generates a large amount of components having a lower molecular weight than the low molecular weight substance, and greatly reduces the strength of the toner.
Further, the toner of Comparative Example 2 had a good initial image density, but at the initial stage, both the uniformity of the image density and the background fog were poor. Further, the image density after 300,000 sheets was greatly reduced. Further, under the condition of high temperature and high humidity, the image density slightly decreased, but the result that both the uniformity of the image density and the background fog were good was obtained.
[0092]
In Comparative Example 2, the reason why the result was slightly improved compared to Comparative Example 1 was that a component having a very high molecular weight of 1,980,000 having a main peak in GPC was used as a high molecular weight substance. It was considered that although the polymer chains were cut by the melt-kneading as compared with the above, the decrease in the strength of the toner due to the breaking could be suppressed to some extent.
The toner of Comparative Example 3 had a result that the image density was low at the initial stage, and the uniformity of the image density and the background fog were both poor. In addition, since toner adhered to the photoreceptor on the 50,000th sheet during the continuous printing, measurement and observation after 300,000 sheets were abandoned. Further, under high-temperature and high-humidity conditions, the image density was significantly reduced, and the uniformity of the image density and the background fog were both extremely poor.
[0093]
It is considered that the reason for this is that the toner of Comparative Example 3 does not contain a high molecular weight substance, so that the strength of the toner is low.
In the toner of Comparative Example 4, the image density in the initial stage was slightly low, and the uniformity of the image density and the background fog were both poor. Further, the measurement and observation after 300,000 sheets were not carried out from the beginning because of poor fixing performance.
It is considered that the reason for this is that the toner of Comparative Example 4 contains a large amount of a high molecular weight substance, so that the toner has good strength but poor low-temperature fixability.
[0094]
In the toner of Comparative Example 4, the image density did not decrease significantly under the conditions of high temperature and high humidity, but both the uniformity of the image density and the background fog were extremely poor.
It is considered that the cause is that the molecular weight distribution of the toner of Comparative Example 4 is poor.
Further, the toner of Comparative Example 5 had a slightly low image density at the initial stage, but had good image density uniformity and background fog. However, the image density after 300,000 sheets was greatly reduced, and the uniformity of the image density and the background fog were both extremely poor. Further, even under high temperature and high humidity conditions, the image density was greatly reduced, and the uniformity of the image density and the background fog were both extremely poor.
[0095]
It is conceivable that the reason for this was that the toner of Comparative Example 5 used a polyester resin and had a high acid value, so that it could not be sufficiently adapted to the positive charging process.
On the other hand, all of the toners of Examples 1 to 5 had high initial image density, good uniformity of image density, and good background fog. The image density after 300,000 sheets was sufficiently high, and the uniformity of the image density and the background fog were both good. Further, under high temperature and high humidity conditions, the image density was sufficiently high, and the uniformity of the image density and the background fog were both good.
[0096]
In addition, none of the toners of Examples 1 to 5 caused toner blocking or a problem in each process of image formation. For example, in a developing means of a laser printer, formation of a thin layer of toner on a developer carrying member was also successfully performed.
Further, although not shown in the table, all of the toners of Examples 1 to 5 have sufficiently high image density even under low-temperature and low-humidity conditions of a temperature of 10 ° C. and a relative humidity of 15%, uniformity of image density, and background fog. Were both good.
[0097]
Actual machine test II
With respect to 100 parts by weight of the toners manufactured in the above Examples and Comparative Examples, hydrophobic dry silica particles (specific surface area of 130 m) were used. ² / G) 0.5 part by weight and 1.0 part by weight of titania particles (bulk density 0.4 g / ml) were added and mixed with a Henschel mixer, and then a laser printer manufactured by Kyocera Mita Co., Ltd. [Ecosys (Kyocera) (Registered trademark of LS-3800, a-Si photosensitive drum, printing speed: 24 sheets / min.) Into a toner cartridge of a remodeled machine modified so that the fixing temperature can be freely adjusted. Each test was performed.
[0098]
(Measurement of minimum fixing temperature)
After turning on the power of the laser printer in which the toners of the examples and the comparative examples were filled in the toner cartridges, five solid images were successively printed immediately after the printer was ready for printing.
Then, for each of these five images, the image density of the solid black portion was measured using a Macbeth densitometer [RD? 19I], and the average value was determined as the image density before rubbing.
[0099]
Next, the surface of the black solid portion of each image was rubbed with a cotton cloth, and the image density was measured again using a Macbeth densitometer [RD? 19I], and the average value was determined as the image density after rubbing. The conditions of the rubbing test were 10 times with a load of 1,000 g.
And the formula:
Retention rate (%) = (image density after rubbing) / (image density before rubbing) × 100
Those having an image density maintenance ratio of 90% or more as determined in the above were evaluated as having good fixing properties.
[0100]
This test was repeated while changing the fixing temperature of the laser printer in steps of 5 ° C., and the lowest temperature at which the above-mentioned maintenance rate was 90% or more and good fixability was obtained was recorded as the minimum fixing temperature.
(Measurement of hot offset occurrence temperature)
After turning on the power of the laser printer filled with the toner of the example and the comparative example in the toner cartridge, immediately after the printer is ready for printing, 30 images for offset detection are continuously performed while monitoring the fluctuation of the fixing temperature. And printed.
[0101]
The image is printed in a region corresponding to the leading portion in the paper feeding direction of the printed paper, and a black solid portion having a certain width, which is orthogonal to the paper feeding direction and parallel to the axial direction of the heat roller of the fixing unit. And a character area, and the area after that is blank. When the offset occurs, the offset image can be confirmed in a region (referred to as a “roller pitch portion”) where the pitch of the black solid portion and the character portion matches the pitch of the heat roller in the blank portion of the imaged paper.
[0102]
Then, the margins of the twenty images with stable fixing temperatures are visually observed, and the presence or absence of the offset is determined depending on whether or not the offset image has been confirmed.
This test was repeated while changing the fixing temperature of the laser printer in steps of 5 ° C., and the lowest temperature at which offset occurred was recorded as the hot offset occurrence temperature.
(Evaluation of non-offset area)
A temperature difference obtained by subtracting the minimum fixing temperature from the high-temperature offset occurrence temperature was determined as a non-offset region. The lower the minimum fixing temperature, the higher the high-temperature offset occurrence temperature, and the wider the non-offset region, the more the toner can be evaluated as having excellent low-temperature fixability and excellent offset resistance.
[0103]
Table 2 shows the results.
[0104]
[Table 2]

[0105]
From the table, it was found that the toner of Comparative Example 1 had a low minimum fixing temperature, a low high-temperature offset occurrence temperature, and a very small non-offset region, and thus had poor low-temperature fixing properties and offset resistance. This is considered to be because the toner of Comparative Example 1 contained a large amount of a component having a small molecular weight generated by the cleavage of the polymer chain as described above, and the resin strength of the high molecular weight material was reduced.
Further, although the toner of Comparative Example 2 had a higher hot offset occurrence temperature than Comparative Example 1, the non-offset region was still narrow because the minimum fixing temperature was high, resulting in poor balance. This is considered to be because the toner of Comparative Example 2 used a component having an extremely high molecular weight as a high molecular weight substance as described above.
[0106]
Although the toner of Comparative Example 3 had a lower minimum fixing temperature than that of Comparative Example 1, the toner had a low hot offset occurrence temperature and a very small non-offset region, and thus was found to have particularly poor offset resistance. This was considered because the toner of Comparative Example 3 did not contain a high molecular weight substance as described above.
Since the toner of Comparative Example 4 had a higher hot offset generation temperature than Comparative Example 2, it was found that the toner had good offset resistance. However, since the minimum fixing temperature was high, it was found that although the non-offset area was reasonably wide, the low-temperature fixing property was insufficient and the image forming apparatus could not sufficiently cope with the demand for energy saving.
[0107]
The cause was considered to be that the toner of Comparative Example 4 contained a large amount of a high molecular weight substance as described above.
Furthermore, since the toner of Comparative Example 5 using a polyester resin had a low minimum fixing temperature and a relatively wide non-offset region, it was found that the low-temperature fixing property was good. However, since the hot offset occurrence temperature was still slightly low, it was found that the offset resistance was not yet sufficient.
[0108]
Further, since the toner of Comparative Example 5 had poor positive charging characteristics as described above, it was found that the toner was not balanced.
In contrast, all of the toners of Examples 1 to 5 have a low minimum fixing temperature, a high high-temperature offset occurrence temperature, and a sufficiently wide non-offset region, and thus have excellent low-temperature fixability and offset resistance. It was confirmed that the obtained toner was good.

Claims (9)

Both are styrenic polymers,
(A) a high molecular weight substance having a main peak molecular weight of 300,000 or more in gel permeation chromatography;
(B) a low molecular weight substance having a main peak molecular weight of 15,000 or less in gel permeation chromatography,
As binder resins independent of each other, at the time of toner production, at least (a) / (b) = 10/90 to 40/60 by weight and at least a charge control agent and a magnetic powder are mixed, and then melt-kneaded. A magnetic one-component positively-charged toner produced by pulverization and classification. In the case of a styrene polymer, the molecular weight of the main peak in the gel permeation chromatograph is an intermediate molecular weight of the high molecular weight and the low molecular weight, which is an intermediate value of the molecular weight of the main peak, as a binder resin. 2. The magnetic one-component positively charged toner according to claim 1, wherein the toner is contained in a proportion of 20% by weight or less based on the total amount of the high molecular weight substance, the low molecular weight substance and the intermediate molecular weight substance. 2. A styrene polymer having a main peak molecular weight of 300,000 to 1.1 million in a gel permeation chromatograph, which is synthesized by a suspension polymerization method, is used as the high molecular weight polymer. Magnetic one-component positively charged toner. A styrene-based polymer having a main peak molecular weight of 1,000 to 15,000 in a gel permeation chromatograph, which is synthesized by an emulsion polymerization method or a solution polymerization method, is used as the low molecular weight substance. The magnetic one-component positively charged toner according to claim 1. A styrene-based polymer having a main peak molecular weight of more than 15,000 and less than 300,000 in a gel permeation chromatograph synthesized by a suspension polymerization method, an emulsion polymerization method or a solution polymerization method as an intermediate molecular weight product. 3. The magnetic one-component positively charged toner according to claim 2, wherein the toner is combined. 3. The magnetic one-component positively charged toner according to claim 1, wherein an acid value of the binder resin is 0.5 mg KOH / g or less. 3. The magnetic one-component positively charged toner according to claim 1, wherein the toner contains a tetrahydrofuran-insoluble content in a range of 3 to 15% by weight. 3. The magnetic material according to claim 1, wherein the binder resin and the wax are premixed in advance, and then at least a charge control agent and a magnetic powder are added and mixed, and further kneaded, pulverized, and classified. One-component positively charged toner. 3. The magnetic material according to claim 1, wherein at least a charge control agent and a magnetic powder are added to the binder resin polymerized in the presence of the wax, mixed, and further kneaded, pulverized, and classified. Component positively charged toner.