JP4377569B2 - Image forming method using toner for developing electrostatic image - Google Patents

Description

【００１４】
本発明では、順次重ね合わされ、最上位に重ねられる現像用トナーの１５０℃における動的粘弾性測定より求めた緩和時間ｔ=０.１ｓｅｃにおける緩和弾性率が最も低くなるように重ね合わせて現像することでトナー層の定着性がよくなる。また、上記記載の緩和弾性率が重ね合わせの上位に行くほど低くなるように重ね合わせ順序を設定することでトナー層の定着性が最もよくなる。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態を詳述する。本発明に用いられるトナーは少なくとも結着樹脂及び着色顔料から構成され、必要に応じて帯電制御剤やＷＡＸ類等を添加して製造される。
【００１６】
トナーに用いる結着樹脂としては公知の樹脂を含む広い範囲から選択できる。例えば、ポリスチレンやスチレン−アクリル酸エステル共重合体などのスチレン系樹脂、塩化ビニル樹脂、フェノール樹脂、エポキシ樹脂、ポリエステル樹脂、ポリウレタン樹脂、及びポリビニルブチラール樹脂等が挙げられ、これらの樹脂のうちのいずれかが単独であるいは２種以上の樹脂が併用して用いられる。またこれらの樹脂は、合成段階から結晶性ＷＡＸ類や非相溶性物質を予め微分散されたものでもよい。これらの中で、特に樹脂弾性等の熱的性質に優れたポリエステル樹脂あるいはポリエーテルポリオール樹脂を主成分として構成されることが望ましい。
【００１７】
電子写真用トナーに使用される着色剤としては、トナーに一般に用いられている公知の顔料を採用することができる。具体的には、例えばマジェンタ顔料としては、着色用マジェンタ顔料が、Ｃ.Ｉ.ピグメントレッド１２２あるいは２０２のキナクリドン顔料、Ｃ.Ｉ.ピグメントレッド５７のレーキアゾ顔料、Ｃ.Ｉ.ピグメントレッド１４９、１９０あるいは２２４のペリレン顔料、Ｃ.Ｉ.ピグメントレッド１８４あるいは１８５のナフトールーベンズイミダゾロン顔料等を用いることができるが、これらに限られるものではない。これらの着色剤は、一種類のみを用いてもよく、適宜組み合わせても良い。着色剤の使用量は、特に限定されるものではない。
【００１８】
本発明に用いられるトナーには結着樹脂と着色剤以外の添加剤、例えば帯電制御剤やＷＡＸ類等を含んでもよい。カラートナー用の帯電制御剤としては、正帯電性であれば４級アンモニウム塩、負帯電性であればアルキルサリチル酸の金属塩等の無色の帯電制御剤を使用することが望ましい。
【００１９】
該トナーの製造方法としては、結着樹脂、着色剤もしくは予め結着樹脂中に着色剤を予備分散させたいわゆるマスターバッチ組成物などの主成分に必要に応じて帯電制御剤やＷＡＸ類、分散剤といった添加材料を混合機で乾式混合した後、熱溶融混練して均一分散させ、粉砕し分級するといった工程で行なわれる。混合機はヘンシェルミキサー（三井鉱山社製）、スーパーミキサー（川田社製）、メカノミル（岡田精工社製）などのヘンシェルタイプの混合装置、オングミル（ホソカワミクロン社製）、ハイブリダイゼーションシステム（奈良機械製作所製）、コスモシステム（川崎重工業社製）等の装置などを、混練機はＴＥＭ−１００Ｂ（東芝機械製），ＰＣＭ−６５／８７（池貝製）等の１軸もしくは２軸のエクストルーダー、あるいはニーディックス（三井鉱山社製）などのオープンロール方式のものを用いればよい。特に溶融混練操作においては、添加剤を効率よく分散させるために溶融時の樹脂粘度が下がりすぎないよう低温度での高シェア混練が望ましく、特にオープンロール方式のものなどが望ましい。トナー粒子の粉砕にはジェット気流を用いた衝突式気流粉砕機、機械式粉砕機等を用いることができ、風力等による分級を施して所定粒度に調整する。また水溶液中あるいは溶剤中で粒子を生成する懸濁法、乳化凝集法、液中乾燥法等のいわゆる重合法によって得ることもできる。
【００２０】
このようにして製造されたトナー粒子は、体積平均粒径が３〜１０μｍで粒度分布はよりシャープな分布を有するものがよいが、通常の粉砕法で得られうる粒度のものが使用できる。具体的には体積平均粒径Ｄ５０に対し、０．５×Ｄ５０以下の粒子が２０ｐｏｐ％以下、２×Ｄ５０以上の粒子が２ｖｏｌ％以下であるように調整することが望ましい。
【００２１】
該トナー粒子には用途に応じて、流動化剤、帯電調整・表面抵抗調製剤等の外添を施して使用すればよい。これらに使用する無機微粉体としては、例えばシリカ微粉体、酸化チタン微粉体、アルミナ微粉体等が挙げられる。また無機微粉体は、必要に応じ、疎水化、帯電性コントロールの目的でシリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シランカップリング剤、官能基を有するシランカップリング剤、その他の有機ケイ素化合物の如き処理剤で処理されていることも好ましい。処理剤は２種類以上使用しても良い。
他の添加剤としては、例えばフッ素樹脂、ステアリン酸亜鉛、ポリフッ化ビニリデン、シリコーンオイル粒子（約４０％のシリカ含有）の如き滑剤が好適に用いられる。またトナー粒子と逆極性の白色微粒子を現像性向上剤として少量用いても良い。
【００２２】
以下、動的粘弾性測定方法について具体的に説明する。得られたトナーを０．８ｇ準備し、錠剤成形器を用いて室温２５℃、１ｋｇｆ／ｃｍ²にて３０秒間プレスし、厚み１．５ｍｍ程度、直径２５ｍｍφの測定用サンプルを作成する。使用した装置はＣＳＭストレスレオメータ（Ｂｏｈｌｉｎ社製）を用いた。測定条件は、以下のとおりとした。測定温度１５０℃、パラレルプレートを使用し、ギャップ１．０ｍｍ、ひずみ３％で、角周波数１００〜０．１ｒａｄ/ｓの範囲内でＡｕｔｏｓｔｒｅｓｓで測定した。測定温度は、画像形成装置に備わる定着システムにおける定着温度に近い温度であることが望ましい。
【００２３】
本発明の画像形成方法において、例えば定着手段におけるトナーの定着プロセススピードは１１７ｍｍ/ｓｅｃであり、その定着プロセスの進行方向に対する定着領域（ニップ幅）が５ｍｍである。このような加熱定着ローラーと圧力ローラーの組み合わせからなる定着装置では、加熱・加圧時間は約０．０４秒と概算され、この時間内で加熱と変形が同時に行われる。このため、定着時間付近での瞬間的なせん断変形に対応した粘弾性測定の結果から判断することができれば望ましい。したがって、オシレーションである動的粘弾性測定から推測される緩和弾性率の結果は、上記の定着プロセスに最も近い指標を与えると考えられるため、本発明に至った。好ましくは、過剰なひずみが瞬間的に与えられる歪制御型レオメーターを用いて緩和弾性率を実測するのがよい。
【００２４】
本発明の画像形成方法において、少なくとも２個以上のトナーを重ね合わせて画像出力を行うような場合、このようなトナーの粘弾性特性とトナー転写順位の優位性を考慮した画像形成プロセスを取り入れることにより、定着性にも優れ、さらに、高精彩のフルカラー画像形成が行える画像形成方法を提供することができる。ただし、定着性の試験をできるかぎり定量的に行うために、できるかぎりベタパッチの画出し評価を行うことが望ましい。
【００２５】
【実施例】
以下実施例および比較例に基づいて、本発明を具体的に説明する。
［トナーの製造方法］
ガラス転移温度Ｔｇ=６４℃、４ｍｍフロー軟化温度Ｔ４ｍ=１０９℃のポリエステル樹脂、予め結着樹脂中に４０重量％の濃度で予備混練分散させた顔料混練物及び帯電制御剤をヘンシェルミキサーに投入し１０分間混合した原材料混合物を得た。マジェンタは、Ｃ.Ｉ.ピグメントレッド１２２、製造するトナーの所望の顔料濃度に応じ各組成材料は下記に示す条件を満たす量をそれぞれ投入した。
【００２６】
トナー中顔料濃度Ｃ重量％のトナーを製造する場合の原材料投入量は、
結着樹脂 ポリエステル樹脂 （９８−Ｙ）重量部
顔料混練物 Ｙ 重量部
帯電制御剤 アルキルサリチル酸金属塩 ２ 重量部
とした。但し、Ｃ／１００＝０．４×Ｙ／１００を満たす。
【００２７】
マジェンタ顔料としてはＣ.Ｉ.ピグメントレッド１２２を、シアン顔料としてはＣ.Ｉ.ピグメントブルー１５：３ (大日本インキ化学株式会社製)を、また、イエロー顔料としてはＣ.Ｉ．ピグメントイエロー７４（山陽色素社製）を各々用いた。着色剤の顔料濃度Ｙは、マジェンタ顔料、シアン顔料では、Ｙ＝５、１０、１５とし、イエロー顔料では、Ｙ＝４，８，１２とした。
【００２８】
得られた原材料は三井鉱山（株）製ニーディックスＭＯＳ１４０−８００で溶融混練分散させた。本実施例における混練条件は、フロントロールの供給側温度６０℃、排出側温度３０℃、バックロールの供給、排出側温度ともに２０℃、フロントロール回転数７５ｒｐｍ、バックロール回転数６０ｒｐｍ、原材料供給速度１０ｋｇ/ｈで行った。なお全てのサンプルで混練分散工程における赤外線非接触温度計による混練材料の温度はいずれの混練ポイントにおいても１２０℃以下であった。
【００２９】
このように得られた混練物は冷却、粗砕の工程を経て、ジェット式粉砕機によって微粉砕した後、風力分級を行い、コールターマルチサイザーＩＩで粒度を確認しながら、所定の体積平均粒径Ｄ５０で、各々０.５×Ｄ５０以下の粒子が２０ｐｏｐ％以下、２×Ｄ５０以上の粒子が２ｖｏｌ％以下の粒度分布を有するトナー粉末に調整した。得られたトナー粒子１００重量部と、シランカップリング剤とジメチルシリコーンオイルとで表面処理している疎水性シリカ微粉体（ＢＥＴ比表面積１２０ｍ²／ｇ）０．５０重量部とを混合して、負摩擦帯電性のトナーを調製し、各々体積平均粒子径が６．５μｍである表１に記載の９種のカラートナーＣ１〜Ｙ３を得た。
【００３０】
【表１】

【００３１】
［画出し試験］
画像形成装置として、６００ｄｐｉの解像度を有するデジタル複写機（商品名ＡＲ−Ｃ２５０、定着温度１６０℃、シャープ株式会社製）用の現像器にトナーとキャリアを前者５重量部、後者９５重量部の割合で配合した二成分現像剤を導入し、画出し試験を行った。定着条件は、ニップ幅を５ｍｍ、プロセススピードを１１７ｍｍ/ｓ、圧力２．３ｋｇ/ｃｍ²に設定した。この装置における従来の基準となる色定着の順番は、３色のカラーを定着させる場合、シアンを最下位部、その上にマジェンタで、最上位部がイエローである。
【００３２】
［動的粘弾性測定］
得られたトナーを０．８ｇ準備し、錠剤成形器を用いて室温２５℃、１ｋｇｆ／ｃｍ²にて３０秒間加圧下にてプレスし、厚み１．５ｍｍ程度、直径２５ｍｍφの測定用サンプルを作成する。各トナーサンプルの動的粘弾性測定は、ＣＳＭストレスレオメータ（Ｂｏｈｌｉｎ社製）を用い、測定温度１５０℃、一定ひずみ３％で高角周波数側から低角周波数側まで１００〜０．１ｒａｄ/ｓの範囲にて行った。１５０℃におけるトナーサンプルＣ１の角周波数ωの対数値に対する貯蔵弾性率Ｇ'(ω )及び損失弾性率Ｇ"(ω)の対数値をプロットした結果を図1に示す。
【００３３】
測定結果から、ある緩和時間ｔ=1/ω にて定義される緩和弾性率Ｇ(ｔ)を下記式を用いて計算し、１５０℃、緩和時間ｔ=０．１ [ｓ]( ω=１０[ｓ^-1])の場合で比較した。各トナーの緩和弾性率の対数値を上記表１に示す。
【００３４】
【数２】

【００３５】
［定着性試験］
印字面を中にして折り曲げた後、８５０ｇのローラーを一定加圧になるように一往復転がすことにより荷重を与え、境界部分の折り曲げ部分を所定のハケで印字紙上トナー層を５回こすり払うことにより定着性試験を行った。ここで、折り曲げ部分にできたライン幅をＬとし実施内容とともに図２に示している。トナー層の定着性は、紙への接着性とトナー層の溶融性に依存する。このトナー層の剥離性を、一定荷重下にて折り曲げ、できた幅Ｌを目視することにより次の４段階に分けて読み取った。
◎：幅Ｌがかなり細くまた薄くトナー層がよく溶融し定着されている。
○：幅Ｌが約０．３ｍｍ未満程度で微細線であり切れ目がある。
△：幅Ｌが約０．５ｍｍ程度で細線がはっきりしていてつながりがよい。
×：幅Ｌがかなり乱れておりトナー層が定着されていない。
【００３６】
各色トナーをマジェンタ、イエロー、シアンの順に、Ｍ,Ｙ,Ｃとしたときの各色トナーの緩和弾性率をＧＭ(ｔ),ＧＹ(ｔ),ＧＣ(ｔ)と表記することにする。
（比較例１）印刷紙に近い方から各トナー色を、Ｃ２、Ｙ２、Ｍ２の順番で重ね合わせて画出し評価を行い、定着性試験を試みた。
（実施例１）印刷紙に近い方から各トナー色を、Ｃ２、Ｙ２、Ｍ１の順番で重ね合わせて画出し評価を行い、定着性試験を試みた。
（比較例２）印刷紙に近い方から各トナー色を、Ｃ１、Ｍ１、Ｙ３の順番で重ね合わせて画出し評価を行い、定着性試験を試みた。
ただし、画出し評価は、ベタパッチ画像出力とした。上記の結果を表２に示す。
【００３７】
【表２】

上記比較例１の結果から、従来の定着順位であるシアン、マジェンタ、イエローに対し、１５０℃、緩和時間ｔ=０.１ｓｅｃでの緩和弾性率の値がＹ２、Ｃ２よりも高いサンプルトナーＭ２を最上位層として定着させたために、定着性試験の結果が悪くなった。また、実施例１の結果から、緩和弾性率の値が最も低いトナーサンプルＭ１を最上位層として定着させたところ、定着性試験の結果は良くなった。これに対して、比較例２の結果から、従来の定着順位で、緩和弾性率の値が最も大きいトナーサンプルＹ３を最上位層として定着させたところ定着性結果は悪くなることが確認された。
【００３８】
【発明の効果】
以上、説明したように、本発明における少なくとも着色剤及び結着樹脂からなる複数の静電荷現像用現像用トナーを用いる画像形成方法において、重ねられる各現像用トナーの１５０℃における動的粘弾性測定より求めた緩和時間ｔ=０.１ｓｅｃにおける緩和弾性率が、付着性、定着性に優れた高画質な定着画像を得るための有効な指標となることが分かる。
【００３９】
即ち、順次重ね合わされ、最上位に重ねられる現像剤の１５０℃における動的粘弾性測定より求めた緩和時間ｔ=０.１ｓｅｃにおける緩和弾性率が最も低いことを特徴とする電子写真用現像用トナーを用いた画像形成方法により、定着性に優れ画像が得られることができる。また、それぞれの緩和弾性率の値は重ね合わせの上位に行くほど低くなることを満たすことが望ましい。
以上の結果、定着性に優れた高精彩のフルカラー画像の形成が行える画像形成方法を提供することができる。
【図面の簡単な説明】
【図１】トナーサンプルＣ１の動的粘弾性測定結果を示す図。
【図２】定着性試験方法を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method by superposition used in electrophotography, electrostatic development, and the like. In particular, the present invention relates to a method for forming a high-definition full-color image having excellent adhesion and fixing properties.
[Prior art]
In general, in electrophotography, in order to visualize a latent image formed on a photosensitive member, a toner having a predetermined charging property is developed in a developing device, and is heated and pressurized in a fixing system and fixed on a sheet. The copy image is obtained by fixing. A normal fixing system or fixing means is a fixing device composed of a combination of a heat fixing roller and a pressure roller, and the toner is offset by toner offset to the fixing / pressure roller due to repeated copying, or is contaminated by carrier or dust. appear. In order to remove dirt on the fixing unit such as the roller, the fixing unit is often equipped with various cleaning brushes.
[0003]
On the other hand, as a developer for forming an image, a two-component developer including a toner and a carrier and a one-component developer including only a toner are used. In order to prevent the offset phenomenon in the fixing portion, the toner is adjusted to have a molecular weight of a binder resin in the toner or contain various waxes.
[0004]
A general fixing system includes a heat roller, a pressure roller, and a cleaning roller. These arrangements, contact area or fixing area (nip width) between the heat roller and the pressure roller, pressure conditions, fixing temperature, heat roller, Fixing conditions are determined by settings such as the surface properties, material, and process speed of the pressure roller. In such a fixing device, a fixing temperature range and a pressure condition that do not cause an offset within a limited fixing time are optimized.
[0005]
In recent years, the speed-up technology from monochrome electrophotography to full-color electrophotography has progressed, and further higher definition and higher image quality have been demanded. In general, in full-color electrophotography, it is known that a multicolor image is obtained by superposing at least three colors of toner on a printing paper surface. In this principle, the toner layer inevitably increases in thickness and becomes bulky, and there is a problem that the image quality deteriorates because the gloss distribution of the image occurs in the printing paper surface.
[0006]
Further, the glossiness of the image is greatly affected by the surface state of the toner layer and also changes depending on the thickness of the toner layer. It is known that the melting state of the toner at the time of fixing depends on the viscoelastic characteristics of the toner, and many proposals have been made simply as an index of glossiness of the toner or toner constituent components. As described in Japanese Patent No. 2841332, in a full-color electrophotographic method for forming a color image using three primary color toners of yellow, magenta and cyan and a black toner, storage elastic modulus G ′ (ω) = 10 ⁵ (dyn / cm ² ), the relationship between the viscoelasticity (tan δ) of the three primary color toner and the viscoelasticity (tan δ) of the black toner is 2.8 <tan δ of the three primary color toner <tan δ <3.8 of the black toner. There has been invented a full-color electrophotographic method characterized by satisfying. According to the present invention, the gloss of the entire color image is improved by making the toner constituting the black portion in which the thickness of the toner layer is thinned by UCR processing (under color removal), that is, the black toner is more glossy than the other three primary colors. Homogenize and improve image quality.
[0007]
However, in the above-described invention, the black toner and the three primary colors are made glossy easily by optimizing the viscoelasticity of the black toner in the comparison of the viscoelasticity of the three primary color toner and the black toner. It does not describe the effect of overlapping toners. On the other hand, the fixability of the toner layer is closely related not only to the melted state and surface state of the toner layer but also to the adhesiveness to paper. Is not pursued.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide an image forming method capable of forming a high-definition full-color image in which a toner layer on a printing paper surface has excellent adhesion and fixability.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have controlled a plurality of constituent toners by comparing the viscoelastic characteristics of the toner, that is, the relaxation elastic modulus, as a quantitative index of fixing properties. As a result, it was found that the fixing property of the image forming layer by superimposing can be improved. Further, in full-color electrophotography, color expression is performed by superimposing colors. Therefore, it is indispensable to improve the fixability of paper by increasing the meltability of the developer superimposed on the uppermost layer. In the present invention, it has been found that an image forming method capable of improving the fixability by optimizing the viscoelastic characteristics of the developer stacked on the uppermost layer and forming a high-definition full-color image can be provided.
[0010]
First, the present invention relates to an image forming method using a plurality of electrostatic charge developing toners composed of at least a colorant and a binder resin. This is an image forming method using an electrostatic charge image developing toner characterized by having the lowest relaxation elastic modulus at a relaxation time t = 0.1 sec determined from elasticity measurement.
[0011]
Secondly, in the image forming method using a plurality of electrostatic charge developing toners composed of at least a colorant and a binder resin, the present invention is obtained by measuring dynamic viscoelasticity at 150 ° C. of developing toners that are sequentially stacked. An image forming method using a toner for developing an electrostatic charge image, wherein a relaxation elastic modulus at a relaxation time t = 0.1 sec decreases as it goes higher in the superposition.
[0012]
The specific steps of the dynamic viscoelasticity measurement of the present invention are as follows. {Circle around (1)} At least two primary colors are prepared for each of the three primary colors in which only a part by weight of the same colorant with respect to the same binder resin is changed in a plurality of electrostatic charge developing toners composed of at least a colorant and a binder resin. (2) The dynamic viscoelasticity of all the sample toners is measured at a melting temperature sufficiently away from the glass transition temperature of the binder resin. (3) From the obtained result, the relaxation elastic modulus is obtained by the following calculation formula. Here, if the measurement temperature and the fixing temperature are as close as possible, the result of the viscoelasticity measurement of the toner and the result of the fixing test can be made to correspond well.
[0013]
[Expression 1]

[0014]
In the present invention, the development toners that are sequentially overlapped and developed on top are overlapped and developed so that the relaxation elastic modulus at the relaxation time t = 0.1 sec obtained from the dynamic viscoelasticity measurement at 150 ° C. is the lowest. This improves the fixability of the toner layer. In addition, the fixing property of the toner layer is best by setting the overlapping order so that the relaxation elastic modulus described above becomes lower as it goes higher in the overlapping.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. The toner used in the present invention is composed of at least a binder resin and a color pigment, and is manufactured by adding a charge control agent, WAXs, and the like as necessary.
[0016]
The binder resin used for the toner can be selected from a wide range including known resins. Examples thereof include styrene resins such as polystyrene and styrene-acrylic acid ester copolymers, vinyl chloride resins, phenol resins, epoxy resins, polyester resins, polyurethane resins, and polyvinyl butyral resins, and any of these resins. Are used alone or in combination of two or more resins. These resins may be those in which crystalline WAXs and incompatible materials are finely dispersed in advance from the synthesis stage. Among these, a polyester resin or a polyether polyol resin excellent in thermal properties such as resin elasticity is particularly preferable.
[0017]
As the colorant used in the electrophotographic toner, a known pigment generally used for the toner can be employed. Specifically, for example, as the magenta pigment, a coloring magenta pigment may be CI pigment red 122 or 202 quinacridone pigment, CI pigment red 57 lake azo pigment, CI pigment red 149, 190. Alternatively, 224 perylene pigment, CI Pigment Red 184 or 185 naphthol-benzimidazolone pigment, and the like can be used, but are not limited thereto. These colorants may be used alone or in appropriate combination. The amount of the colorant used is not particularly limited.
[0018]
The toner used in the present invention may contain additives other than the binder resin and the colorant, such as a charge control agent and WAXs. As the charge control agent for the color toner, it is desirable to use a colorless charge control agent such as a quaternary ammonium salt for positive chargeability and a metal salt of alkylsalicylic acid for negative chargeability.
[0019]
As a method for producing the toner, a charge control agent, WAXs, dispersion, etc. may be added to a main component such as a binder resin, a colorant, or a so-called master batch composition in which a colorant is preliminarily dispersed in a binder resin in advance. After the additive material such as the agent is dry-mixed with a mixer, it is heated and kneaded, uniformly dispersed, pulverized and classified. Henschel mixers (made by Mitsui Mining Co., Ltd.), super mixers (made by Kawada Co., Ltd.), mechanom mills (made by Okada Seiko Co., Ltd.), etc. ), Equipment such as Cosmo System (manufactured by Kawasaki Heavy Industries, Ltd.), etc., kneading machines are TEM-100B (manufactured by Toshiba Machine), PCM-65 / 87 (manufactured by Ikegai), etc. An open roll type such as Dix (Mitsui Mining Co., Ltd.) may be used. Particularly in the melt-kneading operation, in order to disperse the additive efficiently, high shear kneading at a low temperature is desirable so that the resin viscosity at the time of melting does not decrease too much, and an open roll system is particularly desirable. For the pulverization of the toner particles, a collision-type air pulverizer using a jet air current, a mechanical pulverizer, or the like can be used. It can also be obtained by a so-called polymerization method such as a suspension method in which particles are produced in an aqueous solution or a solvent, an emulsion aggregation method, a drying method in a liquid, or the like.
[0020]
The toner particles thus produced preferably have a volume average particle size of 3 to 10 μm and a sharper particle size distribution, but those having a particle size that can be obtained by a normal pulverization method can be used. Specifically, it is desirable to adjust so that particles of 0.5 × D50 or less are 20 pop% or less and particles of 2 × D50 or more are 2 vol% or less with respect to the volume average particle diameter D50.
[0021]
The toner particles may be used after externally adding a fluidizing agent, a charge adjusting / surface resistance adjusting agent, etc., depending on the application. Examples of the inorganic fine powder used in these include silica fine powder, titanium oxide fine powder, and alumina fine powder. In addition, inorganic fine powders can be made into silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, etc. It is also preferable to treat with a treating agent such as an organosilicon compound. Two or more kinds of treatment agents may be used.
As other additives, for example, a lubricant such as a fluororesin, zinc stearate, polyvinylidene fluoride, and silicone oil particles (containing about 40% silica) is preferably used. A small amount of white fine particles having a polarity opposite to that of the toner particles may be used as a developability improver.
[0022]
Hereinafter, the dynamic viscoelasticity measuring method will be specifically described. 0.8 g of the obtained toner is prepared and pressed using a tablet molding machine at room temperature of 25 ° C. and 1 kgf / cm ^{2 for} 30 seconds to prepare a measurement sample having a thickness of about 1.5 mm and a diameter of 25 mmφ. The apparatus used was a CSM stress rheometer (Bohlin). The measurement conditions were as follows. Using a parallel plate, the measurement temperature was 150 ° C., and the gap was 1.0 mm, the strain was 3%, and the measurement was performed with an autostress within the range of an angular frequency of 100 to 0.1 rad / s. The measurement temperature is preferably close to the fixing temperature in the fixing system provided in the image forming apparatus.
[0023]
In the image forming method of the present invention, for example, the fixing process speed of the toner in the fixing unit is 117 mm / sec, and the fixing area (nip width) with respect to the direction of progress of the fixing process is 5 mm. In such a fixing device comprising a combination of a heat fixing roller and a pressure roller, the heating / pressurizing time is estimated to be about 0.04 seconds, and heating and deformation are simultaneously performed within this time. For this reason, it is desirable to be able to judge from the result of the viscoelasticity measurement corresponding to the instantaneous shear deformation near the fixing time. Therefore, the result of the relaxation modulus estimated from the dynamic viscoelasticity measurement which is oscillation is considered to give the closest index to the above fixing process, and thus the present invention has been achieved. Preferably, the relaxation elastic modulus is actually measured using a strain control type rheometer to which an excessive strain is instantaneously applied.
[0024]
In the image forming method of the present invention, when an image is output by superposing at least two or more toners, an image forming process taking into account the viscoelastic characteristics of the toner and the superiority of the toner transfer order is incorporated. Accordingly, it is possible to provide an image forming method that is excellent in fixing property and that can form a high-definition full-color image. However, in order to perform the fixability test as quantitatively as possible, it is desirable to evaluate the solid patch image as much as possible.
[0025]
【Example】
Hereinafter, based on an Example and a comparative example, this invention is demonstrated concretely.
[Toner Production Method]
A polyester resin having a glass transition temperature Tg = 64 ° C., 4 mm flow softening temperature T4m = 109 ° C., a pigment kneaded material preliminarily kneaded and dispersed in a binder resin at a concentration of 40% by weight, and a charge control agent are charged into a Henschel mixer. A raw material mixture was obtained that was mixed for 10 minutes. Magenta put CI Pigment Red 122 and the respective composition materials in amounts satisfying the following conditions according to the desired pigment concentration of the toner to be produced.
[0026]
The amount of raw material input when producing a toner with a pigment concentration of C weight% in the toner is
Binder resin Polyester resin (98-Y) parts by weight Pigment kneaded product Y parts by weight Charge control agent Alkyl salicylic acid metal salt 2 parts by weight. However, C / 100 = 0.4 × Y / 100 is satisfied.
[0027]
CI pigment red 122 as a magenta pigment, CI pigment blue 15: 3 (manufactured by Dainippon Ink & Chemicals, Inc.) as a cyan pigment, and CI pigment as a yellow pigment. Pigment Yellow 74 (manufactured by Sanyo Dye) was used. The pigment concentration Y of the colorant is Y = 5, 10, 15 for magenta pigments and cyan pigments, and Y = 4, 8, 12 for yellow pigments.
[0028]
The obtained raw material was melt-kneaded and dispersed with a Niedix MOS140-800 manufactured by Mitsui Mining Co., Ltd. The kneading conditions in this example are: front roll supply side temperature 60 ° C., discharge side temperature 30 ° C., back roll supply and discharge side temperatures 20 ° C., front roll rotation speed 75 rpm, back roll rotation speed 60 rpm, raw material supply speed The test was carried out at 10 kg / h. In all samples, the temperature of the kneaded material by the infrared non-contact thermometer in the kneading and dispersing step was 120 ° C. or less at any kneading point.
[0029]
The kneaded product thus obtained is subjected to cooling and coarse crushing steps, finely pulverized by a jet type pulverizer, air classification, and confirming the particle size with Coulter Multisizer II, while maintaining a predetermined volume average particle size. D50 was adjusted to a toner powder having a particle size distribution in which particles of 0.5 × D50 or less were 20 pop% or less, and particles of 2 × D50 or more were 2 vol% or less. 100 parts by weight of the obtained toner particles and 0.50 parts by weight of hydrophobic silica fine powder (BET specific surface area 120 m ² / g) surface-treated with a silane coupling agent and dimethyl silicone oil are mixed, A negative triboelectric chargeable toner was prepared, and nine color toners C1 to Y3 shown in Table 1 each having a volume average particle diameter of 6.5 μm were obtained.
[0030]
[Table 1]

[0031]
[Image output test]
The ratio of 5 parts by weight of the former and 95 parts by weight of the latter in the developing unit for a digital copying machine (trade name AR-C250, fixing temperature 160 ° C., manufactured by Sharp Corporation) having a resolution of 600 dpi as an image forming apparatus. The two-component developer blended in (1) was introduced and an image output test was conducted. Fixing conditions were set such that the nip width was 5 mm, the process speed was 117 mm / s, and the pressure was 2.3 kg / cm ² . The conventional standard color fixing order in this apparatus is that when fixing three colors, cyan is the lowest part, magenta above it, and the highest part is yellow.
[0032]
[Dynamic viscoelasticity measurement]
0.8 g of the obtained toner was prepared and pressed under pressure at room temperature 25 ° C. and 1 kgf / cm ^{2 for} 30 seconds using a tablet molding machine to prepare a measurement sample having a thickness of about 1.5 mm and a diameter of 25 mmφ. To do. For the dynamic viscoelasticity measurement of each toner sample, a CSM stress rheometer (manufactured by Bohlin) was used, and a measurement temperature of 150 ° C., a constant strain of 3%, and a range from 100 to 0.1 rad / s from the high angle frequency side to the low angle frequency side. I went there. FIG. 1 shows a result of plotting logarithmic values of the storage elastic modulus G ′ (ω) and the loss elastic modulus G ″ (ω) against the logarithmic value of the angular frequency ω of the toner sample C1 at 150 ° C.
[0033]
From the measurement results, the relaxation elastic modulus G (t) defined at a certain relaxation time t = 1 / ω is calculated using the following formula, and the relaxation time t = 0.1 [s] (ω = 10 Comparison was made in the case of [s ⁻¹ ]). The logarithmic value of the relaxation modulus of each toner is shown in Table 1 above.
[0034]
[Expression 2]

[0035]
[Fixability test]
Fold the printing surface inward, then apply a load by rolling the 850g roller back and forth to a constant pressure, and scrape the toner layer on the printing paper 5 times with the specified brush at the border. The fixability test was conducted. Here, the line width formed at the bent portion is L and shown in FIG. The fixability of the toner layer depends on the adhesion to paper and the meltability of the toner layer. The peelability of the toner layer was read by dividing it into the following four stages by bending it under a constant load and visually observing the resulting width L.
A: The width L is very thin and thin, and the toner layer is well melted and fixed.
A: The width L is less than about 0.3 mm and is a fine line and has a cut.
(Triangle | delta): The width L is about 0.5 mm, a thin line is clear, and a connection is good.
X: The width L is considerably disturbed and the toner layer is not fixed.
[0036]
The relaxation elastic moduli of the color toners are denoted as GM (t), GY (t), and GC (t) when each color toner is M, Y, and C in the order of magenta, yellow, and cyan.
(Comparative Example 1) Each toner color was superposed in the order of C2, Y2, and M2 from the side closer to the printing paper to evaluate the image formation, and a fixability test was attempted.
(Example 1) Each toner color was superposed in the order of C2, Y2, and M1 from the side closer to the printing paper to evaluate the image output, and a fixability test was attempted.
(Comparative Example 2) Each toner color was superposed in the order of C1, M1, and Y3 from the side closer to the printing paper to evaluate the image output, and a fixability test was attempted.
However, the image output evaluation was a solid patch image output. The results are shown in Table 2.
[0037]
[Table 2]

From the results of Comparative Example 1, sample toner M2 having a relaxation elastic modulus value higher than Y2 and C2 at 150 ° C. and relaxation time t = 0.1 sec is compared with cyan, magenta, and yellow, which are conventional fixing orders. Since it was fixed as the uppermost layer, the result of the fixing test was deteriorated. Further, from the result of Example 1, when the toner sample M1 having the lowest value of the relaxation elastic modulus was fixed as the uppermost layer, the result of the fixability test was improved. On the other hand, from the result of Comparative Example 2, it was confirmed that when the toner sample Y3 having the largest relaxation elastic modulus value was fixed as the uppermost layer in the conventional fixing order, the fixability result deteriorated.
[0038]
【The invention's effect】
As described above, in the image forming method using a plurality of developing toners for electrostatic charge development consisting of at least a colorant and a binder resin in the present invention, the dynamic viscoelasticity measurement at 150 ° C. of each developing toner to be overlaid is performed. It can be seen that the relaxation modulus at the relaxation time t = 0.1 sec obtained is an effective index for obtaining a high-quality fixed image having excellent adhesion and fixability.
[0039]
That is, the developing toner for electrophotography characterized by having the lowest relaxation elastic modulus at the relaxation time t = 0.1 sec determined by dynamic viscoelasticity measurement at 150 ° C. An image can be obtained with an excellent fixability by an image forming method using the above. Moreover, it is desirable to satisfy that the value of each relaxation elastic modulus becomes lower as it goes higher in the superposition.
As a result, it is possible to provide an image forming method capable of forming a high-definition full-color image having excellent fixability.
[Brief description of the drawings]
FIG. 1 is a diagram showing the results of dynamic viscoelasticity measurement of a toner sample C1.
FIG. 2 is a view showing a fixability test method.

Claims (2)

In an image forming method using a plurality of electrostatic charge developing toners composed of at least a colorant and a binder resin, and an image forming apparatus having a process speed of 117 mm / sec and a fixing nip width of 5 mm, development that is sequentially superimposed on a printing paper surface At 150 ° C., a measurement toner having a thickness of 1.5 mm and a diameter of 25 mmφ obtained by pressing 0.8 g of the developing toner using a tablet molding machine at room temperature of 25 ° C. and 1 kgf / cm ^{2 for} 30 seconds. An image forming method using a toner for developing an electrostatic charge image, wherein a relaxation elastic modulus at a relaxation time t = 0.1 sec obtained by dynamic viscoelasticity measurement is lower as it goes higher in the superposition. 2. The image forming method according to claim 1 , wherein the image forming is a full-color image.

Images