JP2004302031A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus comprising a plurality of image forming units and capable of producing a good color electrophotographic image by directly transferring a toner image formed on a photoreceptor of each image forming unit onto a recording material and superposing toner images on the recording material, and to provide an image forming method. <P>SOLUTION: In the image forming apparatus in which color toner images in a plurality of image forming units are sequentially transferred in a superposed state from electrophotographic photoreceptors onto a recording material to form a color toner image and this color toner image is fixed to form a color image, turbidity of each color toner used in developing means of the plurality of image forming units is <60, the turbidity difference between such color toners is a maximum of 5-45, and one of the plurality of developing means contains a black toner whose turbidity is <25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１６１】
【表２】

【０１６２】
〔現像剤の作製〕
トナー１Ｂｋ〜１Ｃ、トナー２Ｂｋ〜２Ｃ、トナー３Ｂｋ〜３Ｃ、トナー４Ｂｋ〜４Ｃ、トナー５Ｂｋ〜５Ｃ、トナー６Ｂｋ〜６Ｃｃの各トナー１０質量部と、スチレン−メタクリレート共重合体で被覆した４５μｍフェライトキャリア１００質量部とを混合することにより、評価用の現像剤１Ｂｋ〜１Ｃ、現像剤２Ｂｋ〜２Ｃ、現像剤３Ｂｋ〜３Ｃ、現像剤４Ｂｋ〜４Ｃ、現像剤５Ｂｋ〜５Ｃ、現像剤６Ｂｋ〜６Ｃｃを作製した。
〔感光体の作製〕
下記のごとくして、実施例に用いる感光体を作製した（各実施例の感光体は各画像ユニット共、同じ種類の感光体を用いる為、計４本以上を作製した）。
【０１６３】
感光体１の作製
下記中間層塗布液を調製し、洗浄済み円筒状アルミニウム基体上に浸漬塗布法で塗布し、乾燥膜厚０．３μｍの中間層を形成した。
【０１６４】
〈中間層（ＵＣＬ）塗布液〉
ポリアミド樹脂（アミランＣＭ−８０００：東レ社製） ６０ｇ
メタノール １６００ｍｌ
下記塗布液成分を混合し、サンドミルを用いて１０時間分散し、電荷発生層塗布液を調製した。この塗布液を浸漬塗布法で塗布し、前記中間層の上に乾燥膜厚０．２μｍの電荷発生層を形成した。
【０１６５】

下記塗布液成分を混合し、溶解して電荷輸送層塗布液を調製した。この塗布液を前記電荷発生層の上に浸漬塗布法で塗布し、膜厚２０μｍの電荷輸送層を形成した。
【０１６６】

感光体２の作製
感光体１の作製において、電荷輸送層までは同様に塗布した。
【０１６７】

を混合し、溶解して表面保護層塗布液を調製した。この塗布液を前記電荷輸送層の上に浸漬塗布法で塗布し、１００℃、４０分の加熱硬化を行い乾燥膜厚４μｍの表面保護層を形成し、感光体２を作製した。
【０１６８】
実施例１（表面層にフッソ系樹脂粒子を含有する感光体２を用いた例）
〈評価〉
図１記載のタンデム型デジタル複写機の各画像形成ユニットの感光体で作製した前記感光体２を搭載し、各現像手段の現像剤に表２記載の現像剤群（Ｎｏ．１〜２１）を順次搭載し、評価を行なった。
【０１６９】
評価は、オリジナル画像に白地部、Ｂｋ及びＹ、Ｍ、Ｃのソリッド（べた）画像部、文字画像部、ハーフトーン画像を有するＡ４画像を常温常湿（２０℃５０％ＲＨ）下、モノクロ画像とカラー画像を１０：１の比率で、合計１万枚印刷し評価した。評価項目、評価方法、評価基準を下記に記載する。尚、鮮鋭性の評価では、下記に示すように環境条件を変化して評価した。
【０１７０】
文字チリ
文字画像を形成し、目視及び２０倍ルーペにて文字周辺のトナーチリを観察し、以下の基準で評価した。
【０１７１】
◎：ルーペ観察でも、文字周辺のトナーチリが観察されない（良好）
○：目視では判別できないが、ルーペでは文字周辺のトナーチリが観察される（実用上問題ない）
×：目視で文字周辺のトナーチリが観察され、文字の鮮鋭性が劣る（実用上問題あり）
転写抜け
濃度０．４のハーフトーン画像を記録紙（坪量２００ｇ／ｍ^２）に形成し、転写抜けによるホワイトスポットの発生を目視にて評価した。
【０１７２】
◎◎：まったく転写抜けない（非常に良好）
◎：画像１００枚あたり裏面のみ１〜２個の転写抜けが存在するものの凝視しなければで判別きない（良好）
○：画像５０枚あたり１〜４個の転写抜けが存在するものの凝視しなければ判別できない（実用上問題ない）
×：画像５０枚あたり、表裏関係なく、５個以上の明瞭な転写抜けが存在する（実用上問題あり）
ブラックスポット
ハーフトーン画像上のブラックスポット（苺状のスポット画像）の発生状況を下記の基準で判定した。
【０１７３】
◎；感光体上にブラックスポットの発生核がみられず、ハーフトーン画像にもブラックスポットの発生なし（良好）
○；感光体上にブラックスポットの発生核がみられるが、ハーフトーン画像にはブラックスポットの発生なし（実用上問題なし）
×；感光体上にブラックスポットの発生核がみられ、ハーフトーン画像にもブラックスポットが発生している（実用上問題有り）
画像濃度
画像濃度の測定は、各色のべた部を濃度計「ＲＤ−９１８」（マクベス社製）を使用し、記録紙をゼロとした相対反射濃度で測定した。
【０１７４】
◎：Ｂｋ及びＹ、Ｍ、Ｃのソリッド（べた）画像部の各濃度が１．２以上（良好）
○：Ｂｋ及びＹ、Ｍ、Ｃのソリッド（べた）画像部の各濃度が０．８以上（実用上問題なし）
×：Ｂｋ及びＹ、Ｍ、Ｃのソリッド（べた）画像部の各濃度が０．８未満（実用上問題あり）
鮮鋭性
画像の鮮鋭性は、低温低湿（１０℃２０％ＲＨ）、高温高湿（３０℃８０％ＲＨ）の両環境において画像を出し、文字潰れで評価した。３ポイント、５ポイントの文字画像を形成し、下記の判断基準で評価した。
【０１７５】
◎：３ポイント、５ポイントとも明瞭であり、容易に判読可能
○：３ポイントは一部判読不能、５ポイントは明瞭であり、容易に判読可能
×：３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能色再現
カラー画像の色再現は、Ｙ、Ｍ、Ｃの各トナーの２種の混色で得られるＢ（青）、Ｇ（緑）、Ｒ（赤）の彩度を測定し、評価した。
【０１７６】
彩度評価は分光測色計「ＣＭ−１００」（ＳＣＥ方式、ミノルタ（株）製）を用い、視野２°、光源色Ｄ６５の条件で行なった。評価基準を下記に示す。
【０１７７】
◎：彩度（Ｃ^＊）の数値が、Ｂ＞３５、Ｇ＞５０、Ｒ＞６３で、各色が鮮やかに出ており、良好な色再現がなされている（良好）
○：彩度（Ｃ^＊）の数値が、Ｂ≧３０、Ｇ≧４０、Ｒ≧６０で、実用上良好な色再現がなされている（実用上、問題なし）
△：彩度（Ｃ^＊）の少なくとも１つの数値が、Ｂ≧３０、Ｇ≧４０、Ｒ≧６０を満足していない（実用性に関し、再評価が必要）
×：彩度（Ｃ^＊）の少なくとも２つの数値が、Ｂ≧３０、Ｇ≧４０、Ｒ≧６０を満足していない（実用上、問題あり）
その他、評価条件
画像形成のライン速度Ｌ／Ｓ：１８０ｍｍ／ｓｅｃ
感光体（４０ｍｍφ）の帯電条件：非画像部の電位は、電位センサで検知し、フィードバック制御できるようにし、その制御可能範囲は−５００Ｖ〜−９００Ｖであり、全露光した場合の感光体の表面電位は−５０〜０Ｖの範囲にした。
【０１７８】
像露光光：半導体レーザ（波長：７８０ｎｍ）
転写条件
転写ベルト：カーボンを分散したウレタンゴム製を使用時の伸長率３％で用いた。
【０１７９】
転写極：コロナ放電器、放電ワイヤと感光体ドラム２１Ｙ、２１Ｍ、２１Ｃ、２１Ｂｋとの間隔７．０ｍｍ、放電ワイヤの線径０．０８ｍｍ、放電ワイヤの材質ＷＯ_３、電極プレートの材質ＳＵＳ３０４
転写電流電源電圧：＋３．５ＫＶ〜＋７．５ＫＶ
感光体のクリーニング条件
クリーニングブレード：ウレタンゴムブレードを感光体回転方向にカウンター方式で当接した。
【０１８０】
結果を表３に示す。
【０１８１】
【表３】

【０１８２】
上記表３より、本発明の要件を満足する現像剤群、即ち、複数の画像形成ユニットの現像手段に用いられる各色トナーの濁度が６０未満で、各色トナー間の濁度の差が最大５〜４５であり、且つ該複数の現像手段の１つが濁度が２５未満の黒色系トナーの構成を満たす現像剤群（Ｎｏ．２、３、４、５、６、７、９、１０、１１、１３、１４、１９、２０）は文字チリ、転写抜け、ブラックスポット、画像濃度、鮮鋭性、色再現とも実用範囲以上の良好な評価を達成しているのに対し、本発明外の現像剤群（Ｎｏ．１、８、１２、１５、１６、１７、１８、２１）では、各色トナー間の濁度の差が４．１のＮｏ．１ではトナーの流動性が十分でなく、転写抜けが発生し、画像濃度、鮮鋭性が低下しており、濁度の差が４７のＮｏ．８、Ｎｏ．２１では帯電量のバランスの不安定さから、文字チリ（カラーの文字チリ）が多く、鮮鋭性、色再現が低下している。Ｎｏ．２１では、転写抜けも発生している。又、各色トナーのいずれかの濁度が６０以上の現像剤群（Ｎｏ．１２、Ｎｏ．１５、Ｎｏ．１８）は遊離外添剤が過多となり、ブラックスポットが多発して鮮鋭性、色再現が低下している。又、濁度が２５以上の黒色系トナーＢｋを現像剤として用いた現像剤群（Ｎｏ．１６、Ｎｏ．１７、Ｎｏ．１８）は、文字チリが発生し、鮮鋭性、色再現も劣化している。本発明の要件を満たす前記現像剤群の中でも、各色トナー間の濁度の差が最大１０〜３５で且つ黒トナーの濁度が２０未満の現像剤群（Ｎｏ．４、５、６、９、１０、２０）は改善効果が顕著である。
【０１８３】
実施例２（感光体１を用い、表面エネルギー低下剤を供給した例）
上記実施例１のタンデム型デジタル複写機の各画像形成ユニットの感光体を感光体２から感光体１に変更し、各クリーニング装置を図２に示した剤付与手段を兼ねたブラシロールを持つクリーニング手段に変更し、表面エネルギー低下剤のステアリン酸亜鉛を図２の２５ｋに設置して、感光体表面にブラシロールを介してステアリン酸亜鉛を供給しながら、実施例１と同様の各画像形成ユニットの現像手段の現像剤群（トナー群）を組み合わせて評価した。評価項目、評価方法、評価基準も実施例１と同様にした。
【０１８４】
図２の剤付与手段を有するクリーニング手段のクリーニング条件
クリーニングブレード：ウレタンゴムブレードを感光体回転方向にカウンター方式で当接した。
【０１８５】
クリーニングブラシ：導電性アクリル樹脂、ブラシ毛密度（３×１０^３／ｃｍ^２）、食い込み量を１．０ｍｍに設定した。
【０１８６】
上記の条件での評価をした。その結果、実施例１とほぼ同一の評価結果が得られた。即ち、感光体の表面層がフッ素系樹脂粒子を含有していなくても、感光体表面に表面エネルギー低下剤を供給することにより、実施例１と同様の効果が得られる。
【０１８７】
実施例３（トナーの粒度分布を変更した例）
（トナー７Ｂｋ、７Ｙ、７Ｍ、７Ｃの作製）
前記トナー２Ｂｋ、２Ｙｂ、２Ｍ、２Ｃのトナー製造において、遠心沈降法による液中の分級のレベルを変えて、Ｍ（ｍ_１＋ｍ_２）等を変えた以外は、同様にしてトナー７Ｂｋ、７Ｙ、７Ｍ、７Ｃを作製した。トナー７Ｂｋ、７Ｙ、７Ｍ、７Ｃのトナーの個数平均粒径、Ｍ（ｍ_１＋ｍ_２）及びトナー濁度を表４に示す。
【０１８８】
これらのトナーの各トナー１０質量部と、スチレン−メタクリレート共重合体で被覆した４５μｍフェライトキャリア１００質量部とを混合することにより、評価用の現像剤７Ｂｋ、７Ｙ、７Ｍ、７Ｃとした現像剤２２群を作製した。
（トナー８Ｂｋ、８Ｙ、８Ｍ、８Ｃの作製）
前記トナー２Ｂｋ、２Ｙｂ、２Ｍ、２Ｃのトナー製造において、遠心沈降法による液中の分級のレベルを変えて、Ｍ（ｍ_１＋ｍ_２）等を変えた以外は、同様にしてトナー８Ｂｋ、８Ｙ、８Ｍ、８Ｃを作製した。トナー８Ｂｋ、８Ｙ、８Ｍ、８Ｃのトナーの個数平均粒径、Ｍ（ｍ_１＋ｍ_２）及びトナー濁度を表４に示す。
【０１８９】
これらのトナーの各トナー１０質量部と、スチレン−メタクリレート共重合体で被覆した４５μｍフェライトキャリア１００質量部とを混合することにより、評価用の現像剤８Ｂｋ、８Ｙ、８Ｍ、８Ｃとした現像剤２３群を作製した。
【０１９０】
【表４】

【０１９１】
実施例１の組み合わせＮｏ．４の現像剤４群（トナー２Ｂｋ、２Ｙｂ、２Ｍ、２Ｃ）の代わりに現像剤２２群、２３群を用いた他は、実施例１と同様にして評価を行った。その結果を表５に示す。
【０１９２】
【表５】

【０１９３】
表５より、前記トナー粒子の相対度数の和（Ｍ）が７０％以上の現像剤２２群は、（Ｍ）が７０％未満の現像剤２３群に比し、評価項目の改善度が優れていることが見られる。
【０１９４】
【発明の効果】
本発明を用いることにより、感光体から直接記録材に転写するタンデム型電子写真方式の文字画像及びカラー画像の改善を達成でき、転写抜けや文字チリ等の画像欠陥を防止でき、且つ画像濃度や鮮鋭性が良好なカラー画像を形成できる画像形成装置、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】本発明の一実施の形態を示すカラー画像を作製できる画像形成装置の断面構成図である。
【図２】本発明の画像形成ユニットに設置されるクリーニング手段の構成図である。
【符号の説明】
２０Ｙ、２０Ｍ、２０Ｃ、２０Ｂｋ 画像形成ユニット
２１Ｙ、２１Ｍ、２１Ｃ、２１Ｂｋ 感光体ドラム（像形成体）
２２Ｙ、２２Ｍ、２２Ｃ、２２Ｂｋ 帯電手段
２３Ｙ、２３Ｍ、２３Ｃ、２３Ｂｋ 露光手段
２４Ｙ、２４Ｍ、２４Ｃ、２４Ｂｋ 現像手段
２５Ｙ、２５Ｍ、２５Ｃ、２５Ｂｋ クリーニング手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus used as a color copying machine or a color printer, and an image forming method using the image forming apparatus.
[0002]
[Prior art]
In recent years, color copiers and color printers also tend to seek color images. Color image forming methods of high practical value are roughly classified into commonly used names, such as a transfer drum method, an intermediate transfer method, a KNC method (a method of forming a multi-color superimposed image on a photoconductor and collectively transferring), a tandem method. There are four types of methods.
[0003]
Of course, since these are names given from different viewpoints, for example, the intermediate transfer system and the tandem system naturally exist.
[0004]
As one mode of an image forming apparatus for forming a tandem type color image, a toner image is formed on each electrophotographic photosensitive member (hereinafter, also simply referred to as a photosensitive member) corresponding to each color of yellow, magenta, cyan, and black. There is known an image forming apparatus that forms a color image by superimposing toner images on a recording material (Japanese Patent Application Laid-Open No. H11-157,086). The tandem type color image forming apparatus forms a color image by superimposing toner images having different hues formed by a plurality of image forming units on a recording material, so that an electrophotographic type image forming apparatus capable of forming a high-speed color image is provided. An image forming apparatus can be developed.
[0005]
In the tandem type color image formation, the toner image is often transferred from the electrophotographic photosensitive member of each image forming unit directly to a recording material (hereinafter, also referred to as recording paper) so that the toner images are superimposed. Image defects due to the defects are likely to occur.
[0006]
For example, in the transfer of toner from a photoreceptor to a recording material, poor transfer is likely to occur depending on the type of recording material such as paper, and image defects such as a decrease in image density, transfer omission, and character dust due to transfer bleeding occur. As a result, a color image with reduced sharpness tends to be formed. In particular, when a black-based image is present in a color image and a character dust or the like is generated in the black-based image due to transfer and repelling, the image quality tends to be significantly deteriorated.
[0007]
Further, in a color image forming apparatus, the ratio of producing a character image is larger than that of a color image, and the wear of a photoconductor that forms a black image and the deterioration of a developer are apt to progress. As a result, the chargeability of the black image, Maintaining good developability and transferability is also important in producing a color image. Therefore, in order to improve the quality of color images, it is important to prevent charge omission, developability, loss of transfer due to transfer failure, sharpness deterioration due to character dust, and deterioration of color reproduction, mainly for black images. is necessary.
[0008]
In order to improve the chargeability, developability and transferability, which cause image defects, fine particles are contained in the surface layer of the electrophotographic photoreceptor to make the surface uneven, and to apply toner on the surface of the photoreceptor. Techniques such as reducing adhesion and improving transferability have been studied. For example, it has been reported that an alkylsilsesquioxane resin fine particle is contained in a photosensitive layer (Patent Document 2). However, the alkyl silsesquioxane resin fine particles have a hygroscopic property, and in a high-humidity environment, the wettability of the surface of the photoreceptor, that is, the surface energy is increased, and a problem such that transferability is likely to be lowered occurs. On the other hand, an electrophotographic photoreceptor containing a fluororesin powder to reduce the surface energy of the photoreceptor surface has been reported. However, fluororesin powder does not provide sufficient surface strength, causing streak failures due to scratches on the photoreceptor surface, and image blurring easily (Patent Document 3).
[0009]
That is, in a tandem color image forming method in which a toner image is directly transferred from an electrophotographic photosensitive member to a recording material, a color image is formed to prevent image defects such as a reduction in image density that is conspicuous in a color image, transfer omission, and character dust. It is not enough to simply improve the photoreceptor described above, and it improves the developability and transferability of each color toner, especially the developability and transferability of black toner, and the visualization of an electrostatic latent image on the photoreceptor. It has been found that it is necessary to improve transferability and at the same time to improve the transferability of the toner image from the photoreceptor to the recording material and to sufficiently transfer the toner image onto the recording material.
[0010]
[Patent Document 1]
JP 2001-222129 A
[0011]
[Patent Document 2]
JP-A-5-181291
[0012]
[Patent Document 3]
JP-A-63-56658
[0013]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems. An object of the present invention is to have a plurality of image forming units, transfer a toner image formed on a photoreceptor of each image forming unit directly to a recording material, and superimpose the toner image on the recording material to obtain a good image. It is an object of the present invention to provide an image forming apparatus and an image forming method for producing a color electrophotographic image, and in particular, in a color image, to prevent a black image including a character image from deteriorating in reproduction, and to prevent character dust and transfer omission. An object of the present invention is to provide an image forming apparatus and an image forming method for producing a color image capable of preventing image defects and reproducing sharpness and color reproduction satisfactorily.
[0014]
[Means for Solving the Problems]
According to the present invention, a toner image of each color is formed on an electrophotographic photoreceptor using a toner whose color is changed for each of a plurality of image forming units, and the respective color toner images are sequentially superimposed on a recording material from the electrophotographic photoreceptor and transferred. In the image forming apparatus for forming a color toner image and fixing the color toner image to form a color image, the amount of the free external additive of each color toner formed on the photoreceptor and the balance thereof are determined by the developing property. The present invention has been found to be greatly involved in the transfer of toner images of various colors on a photoconductor to a recording material and superimposing toners on the recording material, and has completed the present invention. That is, by reducing the amount of free external additives of the black toner among the toners of each color and using a toner having a large amount of free external additives for at least one toner, the reproduction of the black toner image is kept good. Also, the transferability of the toner of each color toner image from the photoreceptor to the recording material is remarkably improved, and there are few image defects such as transfer omission and character dust which are likely to occur in a color image, and the sharpness is good. Can be formed.
[0015]
That is, the object of the present invention is achieved by adopting any one of the following constitutions.
1. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, the turbidity of each color toner used in the developing means of the plurality of image forming units is less than 60, the difference in turbidity between the respective color toners is 5 to 45 at the maximum, and one of the plurality of developing means An image forming apparatus comprising a black toner having a turbidity of less than 25.
[0016]
2. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, at least one surface layer of the electrophotographic photosensitive member of the plurality of image forming units contains fluorine-based resin particles, and the turbidity of each color toner used in the developing unit of the plurality of image forming units is An image form characterized by having a turbidity difference between toners of each color of less than 60 and a maximum of 5 to 45, and wherein one of the plurality of developing means contains a black toner having a turbidity of less than 25. Apparatus.
[0017]
3. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, at least one of the plurality of image forming units has an agent applying unit for supplying a surface energy reducing agent to the surface of the electrophotographic photoreceptor, and each color used for a developing unit of the plurality of image forming units is provided. The turbidity of the toner is less than 60, the difference in turbidity between each color toner is 5 to 45 at the maximum, and one of the plurality of developing means contains a black toner having a turbidity of less than 25. An image forming apparatus symptoms.
[0018]
4. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, the turbidity of each color toner used in the developing means of the plurality of image forming units is less than 60, the turbidity difference between each color toner is 5 to 45 at the maximum, and the particle size distribution of each color toner is When the particle diameter of the toner particles is D (μm), the natural logarithm InD is plotted on the horizontal axis, and the horizontal axis is plotted in a histogram showing the number-based particle size distribution divided into a plurality of classes at intervals of 0.23. Te, the relative frequency of the toner particles contained in the modal class (m ₁ ) And the relative frequency (m) of the toner particles contained in the class with the highest frequency next to the mode. ₂ ) Is 70% or more.
[0019]
5. 5. The image forming apparatus according to claim 1, wherein the difference in turbidity between the toners of each color is 10 to 35 at the maximum.
[0020]
6. The plurality of image forming units are four image forming units, an image forming unit having a black toner, an image forming unit having a yellow toner, an image forming unit having a magenta toner, and an image forming having a cyan toner. The image forming apparatus according to any one of the above items 1 to 5, comprising a unit.
[0021]
7. 7. The image forming apparatus according to claim 1, wherein the black toner has a toner turbidity of less than 20.
[0022]
8. An image forming method, comprising: forming an electrophotographic image by using the image forming apparatus according to any one of (1) to (7).
[0023]
Hereinafter, the present invention will be described in more detail.
In the present invention, the turbidity of the toner is defined as follows and can be measured.
[0024]
Turbidity; HAZE value = defined as the percentage of diffused component / total transmitted component.
Toner turbidity measurement method: 5.0 g of toner is dispersed in 50 ml of an aqueous solution containing 1 ml of a surfactant (detergent family, manufactured by Kao Corporation), and separated using a centrifuge (2000 rpm: 10 minutes). . Since the toner component precipitates, a supernatant liquid which is a free component is collected. Using a COH-300A manufactured by Nippon Denshoku Co., Ltd., the HAZE value (percentage:% is omitted) of the ratio of the diffusion component of the total transmission component to the incident light is defined as the turbidity of the toner. .
[0025]
When the value of the turbidity of the toner is large, it means that there are many free components of fine particles such as external additives.
[0026]
In the present invention, the turbidity of each color toner used in the developing means of the plurality of image forming units is less than 60, the difference in turbidity between each color toner is 5 to 45 at the maximum, and one of the plurality of developing means is By using a toner group that is a black toner having a turbidity of less than 25, a good toner image compatible with both a character image and a color image is separately formed for each color on a plurality of photoconductors. The sharpness and color reproduction are excellent without causing image defects such as transfer of the toner image onto the recording material, superimposition, transfer omission, and character dust. A character image and a color image can be formed.
[0027]
That is, when the turbidity of each color toner is 60 or more, the free components of the fine particles are large, so that the free components are scattered on the photoreceptor, and the character dust and the sharpness are easily reduced. Further, a large amount of released components adhere to the surface of the photoreceptor, and image defects such as black spots (strawberry-like spot images) are likely to occur. Further, when the turbidity of each color toner is less than 60 and the difference in turbidity of each color toner is less than 5 at the maximum, the transferability of the toner from the photoreceptor to the recording material is liable to be deteriorated, and the transfer loss and the image density of the color image are reduced. , Sharpness, color reproduction, etc. are likely to occur. On the other hand, if the difference in turbidity between the toners of each color is larger than 45 at the maximum, it is difficult to control the balance of the charge amount between the toners, and it is easy to cause character dust and to deteriorate sharpness.
[0028]
The turbidity of each color toner is less than 60, preferably less than 50, and most preferably less than 40. On the other hand, the difference in turbidity between the toners of each color is 5 to 45 at the maximum, and more preferably 10 to 35.
[0029]
As each color toner of the present invention, it is preferable to use a toner group of four colors of a black toner, a yellow toner, a magenta toner, and a cyan toner. By using the four color toners, both the character image and the color image can be produced clearly and vividly.
[0030]
The turbidity of the black toner among the toners of each color is less than 25. When the turbidity of the black toner is less than 25, sharpness and color reproduction of both the character image and the color image are hardly deteriorated, and a good image can always be produced.
[0031]
Further, among the color images, the toner having the maximum turbidity is preferably a yellow toner. Even if the turbidity of the yellow toner increases, the sharpness and color reproducibility of the toner are relatively low.
[0032]
In order to control the turbidity of the toner within the range of less than 60 according to the above definition and the measuring method, and to make the difference of the turbidity between the respective toners a maximum of 5 to 45, the external additive particles adhering to the surface of the toner are required. It is important to select the type and control the degree of fixation of the external additive particles (hereinafter simply referred to as external additive) to the toner surface.
[0033]
The number average particle diameter of the external additive preferably used in the present invention is 0.05 to 0.5 μm.
[0034]
When the particle size of the external additive is smaller than 0.05 μm, the physical adhesion between the toner photoreceptors is not reduced, so that the transferability is reduced, and as a result, the image density is reduced.
[0035]
When the particle size is larger than 0.5 μm, the external additive once adhered is easily separated and released due to stress such as stirring in the developing device, and the liberated amount is accumulated in the developing device. , Re-aggregate, become nuclei during transfer, and cause transfer omission. Further, since a large amount of released components adhere to the surface of the photoconductor, filming on the surface of the photoconductor is likely to occur.
[0036]
The amount of the external additive to be added to the toner is 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the colored particles (toner before addition of the external additive) (hereinafter, unless otherwise specified, “parts” "Parts by mass") are preferred, and 1.0 to 4.0 parts are particularly preferred.
[0037]
If the amount is less than 0.05 part, the effect of reducing the physical adhesive force cannot be obtained, so that the transferability tends to decrease. If the amount is more than 5.0 parts, an excessive amount of the external additive is present on the toner surface, so that the toner tends to be easily separated and released due to stress such as stirring in the developing device. Therefore, the released matter is accumulated in the developing device, re-agglomerated in the developing device, and becomes a nucleus. When the nucleus is mixed into the developed toner image, transfer omission is likely to occur at the time of transfer. Further, since a large amount of the released components adhere to the surface of the photoconductor, toner filming on the surface of the photoconductor easily occurs.
[0038]
The method for controlling the state of adhesion of the external additive to the colored particles is not limited, and any generally used external additive device for fine particles and a device for fixing or fixing to the toner surface can be used.
[0039]
As a specific device for immobilization, a Henschel mixer, a Lödige mixer, a TURBO SPHERE mixer, or the like can be used. Among them, the Henschel mixer can be suitably used in view of the fact that the mixing and fixing of the external additives can be performed by the same apparatus, and that the stirring and mixing and the external heating are easy.
[0040]
As a mixing method at the time of the fixing process, it is preferable that the peripheral speed at the tip of the stirring blade is 5 to 50 m / s. Preferably, the treatment is performed at 10 to 40 m / s. In addition, it is preferable that the external additive is uniformly adhered to the surface of the resin particles by performing pre-mixing. As a method of controlling the temperature, it is preferable to adjust the temperature to a necessary temperature by using warm water or the like from the outside.
[0041]
The method of measuring the temperature is to measure the temperature of the portion where the toner flows while the toner is being stirred and mixed. In addition, it is preferable to carry out cooling and crushing steps by flowing cold water after the fixing treatment.
[0042]
As a method of controlling the degree of immobilization of the external additive on the surface of the colored particles, the colored particles and the external additive are stirred and mixed under the condition of Tg−20 ≦ (stirring / mixing temperature) ≦ Tg + 20, and the mechanical impact force is adjusted. The external additive particles can be uniformly adhered to the surface of the colored particles by adjusting an arbitrary time while imparting the particles.
[0043]
Here, Tg refers to the glass transition temperature of the toner or the binder resin constituting the toner. The glass transition temperature was measured using a DSC7 differential scanning calorimeter (manufactured by PerkinElmer). The measurement method was as follows: the temperature was raised from 0 ° C. to 200 ° C. at 10 ° C./min, and then cooled from 200 ° C. to 0 ° C. at 10 ° C./min to erase the previous history. The temperature was raised to 200 ° C., and the endothermic peak temperature of the second heat was determined and defined as Tg. When there were a plurality of endothermic peaks, the temperature of the main endothermic peak was defined as Tg.
[0044]
The Tg of the toner or the binder resin constituting the toner is preferably from 40 to 70C. If the temperature is lower than 40 ° C., the storage stability of the toner is poor and the toner is aggregated. If it is higher than 70 ° C., it is not preferable from the viewpoints of fixability and productivity.
[0045]
From the viewpoint of imparting fluidity, an external additive may be further externally added after controlling the attachment of the external additive, but it is necessary that the turbidity of the toner falls within the range of the present invention.
[0046]
The method for measuring the number average particle diameter of the external additive was observed using a transmission electron microscope and displayed using the value measured by image analysis.
[0047]
The composition of the external additive is not particularly limited, and any external additive can be used.
[0048]
For example, various inorganic oxides, nitrides, borides and the like are suitably used as the inorganic external additives. For example, silica, alumina, titania, zirconia, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, zinc oxide, chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, tellurium oxide, manganese oxide, Examples include boron oxide, silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, and boron nitride.
[0049]
Further, the inorganic external additive may be subjected to a hydrophobic treatment. When performing the hydrophobic treatment, it is preferable to perform the hydrophobic treatment with a so-called coupling agent such as various titanium coupling agents and silane coupling agents, and higher fatty acid metal salts such as aluminum stearate, zinc stearate, and calcium stearate. Those subjected to a hydrophobic treatment are also preferably used.
[0050]
Also, when a resin external additive is used, its composition is not particularly limited. Generally, vinyl organic external additive particles and external additive particles such as melamine / formaldehyde condensate, polyester, polycarbonate, polyamide, and polyurethane are preferable. The reason for this is that it can be easily produced by a production method such as an emulsion polymerization method or a suspension polymerization method.
[0051]
Next, the toner preferably used in the present invention will be described.
The toner of the present invention preferably has a number average particle diameter of 3 to 8 μm. In the case where toner particles are formed by a polymerization method, the particle diameter is determined by the concentration of the coagulant, the amount of the organic solvent added, or the fusing time, and the composition of the polymer itself, in the toner manufacturing method described in detail below. Can be controlled by
[0052]
When the number average particle diameter is 3 to 8 μm, the amount of toner particles having a large adhesive force that adheres to the photoreceptor and causes filming is reduced, and the transfer efficiency is increased to improve the halftone image quality. The image quality of fine lines and dots is improved.
[0053]
In the particle size distribution of the toner used in the present invention, when the particle size of the toner particles is D (μm), the natural logarithm InD is plotted on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. In the histogram showing the particle size distribution of, the relative frequency (m ₁ ) And the relative frequency (m) of the toner particles contained in the class with the highest frequency next to the mode. ₂ )) Is preferably 70% or more.
[0054]
Relative frequency (m ₁ ) And relative frequency (m ₂ When the sum (M) of the toner image is 70% or more, the dispersion of the particle size distribution of the toner particles becomes narrow. Therefore, by using the toner in the image forming step, the primary transfer property and the secondary transfer of the toner image are performed. And the occurrence of selective development can be reliably suppressed.
[0055]
In the present invention, the histogram showing the number-based particle size distribution includes a natural logarithm lnD (D: particle size of individual toner particles) at intervals of 0.23 and a plurality of classes (0 to 0.23: 0.23 to 0.23). 0.46: 0.46 to 0.69: 0.69 to 0.92: 0.92 to 1.15: 1.15 to 1.38: 1.38 to 1.61: 1.61-1. 84: 1.84 to 2.07: 2.07 to 2.30: 2.30 to 2.53: 2.53 to 2.76...). The histogram is prepared by transferring particle size data of a sample measured by a Coulter Multisizer to a computer via an I / O unit under the following conditions, and creating the data by a particle size distribution analysis program in the computer. is there.
[0056]
〔Measurement condition〕
(1) Aperture: 100 μm
(2) Sample preparation method: An appropriate amount of a surfactant (neutral detergent) is added to 50 to 100 ml of an electrolytic solution [ISOTON R-11 (manufactured by Coulter Scientific Japan)], and the mixture is stirred. Add. This system is prepared by subjecting the system to a dispersion treatment with an ultrasonic disperser for one minute.
[0057]
The particle size of the toner used in the present invention is preferably 3 to 8 μm in terms of volume average particle size. The volume average particle size and the particle size distribution of the toner can be measured using a Coulter Counter TA-II, a Coulter Multisizer, a SLAD1100 (a laser diffraction particle size measuring device manufactured by Shimadzu Corporation), or the like. In the Coulter Counter TA-II and the Coulter Multisizer, the particle size distribution in the range of 2.0 to 40 μm was measured using an aperture having an aperture diameter of 100 μm.
[0058]
The method for producing the toner is not particularly limited. However, a polymerized toner (also referred to as a polymerized toner) is preferable in that it is simple as a production method and has excellent uniformity as compared with a pulverized toner.
[0059]
The term “polymerized toner” refers to a toner obtained by forming a toner binder resin and forming the toner shape by polymerization of a raw material monomer of the binder resin and a subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization and emulsion polymerization and, if necessary, a subsequent step of fusing particles together. Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then polymerizing the same, a toner having a uniform particle size distribution and shape can be obtained.
[0060]
In any case, the object of the present invention can be achieved as long as it satisfies the requirements of the present invention, whether it is a pulverized toner or a polymerized toner.
<< Configuration of Toner Used in the Present Invention and Production Method >>
The production method of the toner used in the present invention is the most commonly used pulverization method, i.e., a method in which a binder resin and a colorant, and other various additives that are added as necessary are kneaded and pulverized and then classified and produced. Alternatively, resin particles containing a release agent and a colorant may be synthesized and produced in a medium.
[0061]
As a method of fusing in an aqueous medium, for example, a method described in JP-A-63-186253, JP-A-63-282749, JP-A-7-146585, or the like, And the like.
[0062]
The resin particles used here preferably have a weight average particle size of 50 to 2,000 nm. These resin particles may be formed by any granulation polymerization method such as emulsion polymerization, suspension polymerization, or seed polymerization. It is a polymerization method.
[0063]
Hereinafter, conventionally known polymerizable monomers can be used as the monomers used in the production of the resin in any of the production methods. Further, one kind or a combination of two or more kinds can be used so as to satisfy required characteristics.
[0064]
The binder resin is not particularly limited, and a generally known binder resin such as a styrene resin, an acrylic resin, a styrene-acryl resin, a polyester resin, a styrene-butadiene resin, and an epoxy resin is used. Can be.
[0065]
Examples of the resin constituting the styrene resin, the acrylic resin, and the styrene-acryl resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, and 3,4-. Dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, p- Styrene such as n-decylstyrene, pn-dodecylstyrene or a styrene derivative, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-methacrylate Octyl, 2-ethylhexyl methacrylate, Methacrylate derivatives such as stearyl acrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-acrylate Acrylate derivatives such as -butyl, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, and the like; As monomers constituting the resin, and these can be used alone or in combination.
[0066]
Other specific examples of the vinyl polymer include olefins such as ethylene, propylene, and isobutylene; vinyl chloride, vinylidene chloride; halogen-based vinyls such as vinyl bromide, vinyl fluoride, and vinylidene fluoride; and propionic acid. Vinyl esters such as vinyl, vinyl acetate and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl carbazole; N-vinyl N-vinyl compounds such as indole and N-vinylpyrrolidone; vinyl compounds such as vinylnaphthalene and vinylpyridine; acrylonitrile, methacrylonitrile, acrylamide, N-butylacrylamide, N, N-dibutylacrylamide, methacrylic Amide, N- methacrylamide, there are acrylic acid or methacrylic acid derivatives such as N- octadecyl acrylamide. These vinyl monomers can be used alone or in combination.
[0067]
Further, examples of monomers for obtaining a carboxylic acid-containing polymer with a styrene-acrylic resin (vinyl resin) include acrylic acid, methacrylic acid, α-ethylacrylic acid, fumaric acid, maleic acid, itaconic acid, and silicic acid. Examples thereof include cinnamic acid, monobutyl maleate, monooctyl maleate, cinnamic anhydride, and methyl alkenyl succinate half ester.
[0068]
Further, a crosslinking agent such as divinylbenzene, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and triethylene glycol dimethacrylate may be added.
[0069]
The polyester resin is a resin obtained by condensation-polymerizing a divalent or higher carboxylic acid and a divalent or higher alcohol component. Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutacoic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n- Dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, and the like, and these acid anhydrides can also be used.
[0070]
Examples of the dihydric alcohol component constituting the polyester resin include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) Etherified bisphenols such as -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane, ethylene glycol, diethylene glycol, triethylene glycol, 2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol 1,4, butenediol, neopentyl glycol, 1,5-pentane glycol, 1,6-hexane glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A , Bisphenol Z, hydrogenated bisphenol A and the like.
[0071]
Examples of the polyester resin having a crosslinked structure include the following trivalent carboxylic acids such as 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, and 1,2,4-naphthalenetricarboxylic acid. , 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra ( Methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empoletrimeric acid and the like. These acid anhydrides or polyhydric alcohol components, specifically sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol Litol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentatriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethyl A crosslinked polyester resin can be obtained by adding methylolpropane, 1,3,5-trihydroxymethylbenzene, or the like.
[0072]
In the present invention, black toner (hereinafter also referred to as toner Bk), yellow toner (hereinafter also referred to as toner Y), magenta toner (hereinafter also referred to as toner M), cyan toner (hereinafter referred to as toner C) ), Inorganic pigments and organic pigments can be used.
[0073]
Conventionally known inorganic pigments can be used. Specific examples of the inorganic pigment are shown below.
[0074]
As the black pigment, for example, carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite are also used.
[0075]
These inorganic pigments can be used alone or in combination of two or more as desired. The amount of the pigment to be added is 2 to 20% by mass, preferably 3 to 15% by mass, based on the polymer.
[0076]
When used as a magnetic toner, the above-mentioned magnetite can be added. In this case, from the viewpoint of imparting predetermined magnetic properties, it is preferable to add 20 to 60% by mass to the toner.
[0077]
Conventionally known organic pigments can also be used. Specific organic pigments are exemplified below.
[0078]
Examples of pigments for magenta or red (magenta color) include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 222 and the like.
[0079]
Pigments for orange or yellow (yellow) include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138 and the like.
[0080]
Examples of green or cyan pigments (cyan color) include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
[0081]
These organic pigments can be used alone or in combination of two or more as desired. The amount of the pigment to be added is 2 to 20% by mass, preferably 3 to 15% by mass, based on the polymer.
[0082]
The colorant can be used after surface modification. As the surface modifier, a conventionally known one can be used, and specifically, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent and the like can be preferably used.
[0083]
To the toner obtained in the present invention, a so-called external additive can be added and used for the purpose of improving fluidity and cleaning property. As described above, these external additives are not particularly limited, and various inorganic particles, organic particles, and lubricants can be used.
[0084]
Further, a lubricant may be added to the toner as an external additive separately from the external additive particles. Examples of the lubricant include salts of zinc, aluminum, copper, magnesium, calcium, etc. of stearic acid, salts of zinc, manganese, iron, copper, magnesium, etc. of oleic acid, and salts of zinc, copper, magnesium, calcium, etc. of palmitic acid. Metal salts of higher fatty acids such as salts of linoleic acid such as zinc and calcium, and salts of ricinoleic acid such as zinc and calcium.
[0085]
The addition amount of these lubricants is preferably about 0.1 to 5% by mass based on the toner.
In the toner-forming step, the above-mentioned external additive may be added to the toner particles obtained above for the purpose of improving, for example, fluidity, chargeability, and cleaning properties. As a method for adding the external additive, various known mixing devices such as a Turbula mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer can be used.
[0086]
The toner may include a material capable of imparting various functions as a toner additive in addition to the binder resin and the colorant. Specific examples include a release agent and a charge control agent.
[0087]
As the release agent, various known ones, specifically, olefinic waxes such as polypropylene and polyethylene, modified products thereof, natural waxes such as carnauba wax and rice wax, fatty acid bisamide and the like Examples include amide waxes. It has already been mentioned that these are preferably added as release agent particles and are preferably salted out / fused together with the resin or colorant.
[0088]
Similarly, various known charge control agents, which can be dispersed in water, can be used. Specific examples include a nigrosine dye, a metal salt of naphthenic acid or a higher fatty acid, an alkoxylated amine, a quaternary ammonium salt compound, an azo metal complex, a metal salt of salicylic acid or a metal complex thereof.
[0089]
《Developer》
The toner used in the present invention may be used as a one-component developer or a two-component developer, but is preferably a two-component developer.
[0090]
When used as a one-component developer, there is a method in which the toner is used as it is as a non-magnetic one-component developer, but usually, magnetic particles of about 0.1 to 5 μm are contained in toner particles to form a one-component magnetic developer. Used. As a method of containing the same, it is common to make the non-spherical particles contain the same as the coloring agent.
[0091]
Further, it can be used as a two-component developer by mixing with a carrier. In this case, as the magnetic particles of the carrier, conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead are used. Particularly, ferrite particles are preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 60 μm.
[0092]
The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution analyzer “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.
[0093]
The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. Although there is no particular limitation on the resin composition for coating, for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for forming the resin dispersion type carrier is not particularly limited, and a known resin can be used.For example, a styrene acrylic resin, a polyester resin, a fluorine-based resin, a phenol resin, or the like can be used. it can.
[0094]
Next, the photoreceptor used in the present invention will be described in detail.
The electrophotographic photoreceptor used in the image forming apparatus of the present invention may be any of an inorganic photoreceptor and an organic photoreceptor, but when forming a latent image, the color sensitivity to a laser beam used for image exposure, Organic photoreceptors are preferred from the viewpoint of good productivity and the like.
[0095]
Here, the organic photoreceptor means an electrophotographic photoreceptor configured by giving an organic compound at least one of a charge generation function and a charge transport function, which are indispensable for the configuration of the electrophotographic photoreceptor. All known organic electrophotographic photoreceptors such as a photoreceptor composed of an organic charge generating substance or an organic charge transporting substance, and a photoreceptor having a charge generating function and a charge transporting function composed of a polymer complex are included.
[0096]
It is preferable that the electrophotographic photoreceptor used in the image forming apparatus of the present invention has a photoreceptor surface with low surface energy properties to improve transferability of toner from the photoreceptor to a recording material. As a measure for this, one is to make the surface layer of the photoreceptor a surface layer containing fluorine resin particles in the present invention, and the other is to supply a surface energy reducing agent to the surface of the photoreceptor Accordingly, the surface energy of the photoconductor can be reduced, and the transferability of the toner from the photoconductor to the recording material can be improved. By lowering the surface energy of the photoreceptor and using the toner group whose toner turbidity has been adjusted as described above, the synergistic effect provides good sharpness for both character images and color images, and color A color electrophotographic image with good reproduction can be provided.
[0097]
Further, the surface layer of the electrophotographic photoreceptor of the present invention preferably has a contact angle with water of 90 ° or more by reducing the surface energy. When the contact angle with water is 90 ° or more, the cleaning property of the toner and the like can be improved, and the transfer property of the toner from the photoconductor to the recording material can be improved.
[0098]
Examples of the fluorine-based resin particles include polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene chloride, polyvinyl fluoride, polytetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and polytetrafluoroethylene- Resin particles such as propylene hexafluoride copolymer, polyethylene-trifluoroethylene copolymer, polytetrafluoroethylene-propylene hexafluoride-perfluoroalkylvinyl ether copolymer, and the like, and a volume average particle size Is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. The amount of the fluorine resin particles contained in the photoreceptor of the present invention is preferably 0.1 to 90% by mass, more preferably 1 to 50% by mass, based on the binder resin in the surface layer of the photoreceptor. If the content is less than 0.1%, sufficient printing durability and lubricity cannot be imparted to the photosensitive layer, and the primary transferability of the toner is little improved, resulting in a decrease in image density, transfer omission, and sharpness. Deterioration and the like are likely to occur. If it exceeds 90% by mass, the formation of the surface layer tends to be difficult.
[0099]
The volume average particle diameter of the fluororesin particles is measured by a laser diffraction / scattering particle size distribution analyzer “LA-700” (manufactured by Horiba, Ltd.).
[0100]
The surface contact angle of the photoreceptor is determined by measuring the contact angle of pure water with a contact angle meter (CA-DT.A type: manufactured by Kyowa Interface Science Co., Ltd.) in an environment of 20 ° C. and 50% RH.
[0101]
Next, the surface energy reducing agent will be described. Here, the surface energy lowering agent refers to a substance that is attached to the surface of the electrophotographic photosensitive member and reduces the surface energy of the electrophotographic photosensitive member. A material that increases the contact angle (contact angle with pure water) by 1 ° or more.
[0102]
Incidentally, examples of the surface energy reducing agent include fatty acid metal salts.
The surface energy reducing agent is not limited to fatty acid metal salts and the like, as long as it increases the contact angle (contact angle with pure water) of the surface of the electrophotographic photosensitive member by 1 ° or more.
[0103]
As the surface energy reducing agent used in the present invention, a fatty acid metal salt is most preferable as a material having spreadability on the surface of the photoreceptor and uniform film forming performance. The metal salt of a fatty acid is preferably a metal salt of a saturated or unsaturated fatty acid having 10 or more carbon atoms. Examples include aluminum stearate, indium stearate, gallium stearate, zinc stearate, lithium stearate, magnesium stearate, sodium stearate, aluminum palmitate, aluminum oleate, and the like, and more preferably metal stearate. .
[0104]
Among the above-mentioned fatty acid metal salts, a fatty acid metal salt having a high outflow rate of a flow tester has a high cleavage property, and can form a layer of a fatty acid metal salt more effectively on the surface of the photoreceptor of the present invention. The range of outflow velocity is 1 × 10 ^-7 More than 1 × 10 ^-1 The following is preferable, and 5 × 10 ^-4 More than 1 × 10 ^-2 It is most preferred that: The outflow velocity of the flow tester was measured using a Shimadzu flow tester “CFT-500” (manufactured by Shimadzu Corporation).
[0105]
FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus that can produce a color image according to an embodiment of the present invention.
[0106]
In the image forming apparatus of FIG. 1, four image forming units 20Y, 20M, 20C, and 20Bk are provided along a transfer belt (recording material transport belt) 115.
[0107]
Each image forming unit includes a photosensitive drum 21Y (21M, 21C, 21Bk), a scorotron charger (charging means) 22Y (22M, 22C, 22Bk), an exposure optical system (exposure means) 23Y (23M, 23C, 23Bk), It is composed of a developing device (developing means) 24Y (24M, 24C, 24Bk) and a cleaning device (cleaning means) 25Y (25M, 25C, 25Bk), and the photosensitive drum (21Y, 21M, 21C, 21Bk) of each image forming unit. Each of the toner images formed thereon is transferred onto a recording material (recording paper such as plain paper or transparent ground) P conveyed at a proper timing by a transfer unit 34Y (34M, 34C, 34Bk) as a transfer unit. The images are sequentially transferred to form a superimposed color toner image.
[0108]
The recording material P is conveyed on the transfer belt 115, and is discharged by a paper separation AC static eliminator 161 as a recording material separating unit, and a separation claw 210, which is a separation member provided on the conveyance unit 160 at a predetermined interval. By this, it is separated from the conveyor belt.
[0109]
Next, the recording material P is conveyed to a fixing device (fixing unit) 40 including a heating roller 41 and a pressure roller 42 after passing through the conveyance unit 160, and the heating material 41 and the pressure roller 42 The recording material P is nipped by the formed nip portion T, and the superimposed toner image on the recording material P is fixed by applying heat and pressure, and then discharged outside the apparatus.
[0110]
As the exposure means, a scanning optical system using a semiconductor laser, a solid-state scanner such as an LED or a liquid crystal shutter, or the like can be used as an image exposure light source.
[0111]
The transfer belt 115 that conveys the recording material includes a polymer film such as polyimide, polycarbonate, or PVdF, or a conductive rubber obtained by adding a conductive filler such as carbon black to synthetic rubber such as silicone rubber or fluorine rubber. It may be used in a drum shape or a belt shape, but a belt shape is preferred from the viewpoint of the degree of freedom in device design.
[0112]
It is preferable that the surface of the transfer belt is appropriately roughened. By setting the ten-point surface roughness Rz of the transfer belt to 0.5 to 2 μm, the adhesion between the recording material and the transfer belt is increased, the swing of the recording material on the transfer belt is prevented, and the recording material is removed from the photosensitive member. The transferability of the toner image to the toner can be improved.
[0113]
The present invention is characterized in that a latent image on an electrophotographic photosensitive member is developed while a surface energy reducing agent is applied to the surface of the electrophotographic photosensitive member, and the latent image is visualized as a toner image. As a method of applying to the photoreceptor, there is a method of adding a surface energy reducing agent to a developer and applying the agent to the photoreceptor from the developer, but in the present invention, it is preferable to use a method different from such a method. That is, when the surface energy reducing agent is mixed with the developer, the mixing affects the charging characteristics of the toner, the developing characteristics such as fluidity, and it is difficult to achieve a sufficient mixing amount. Speaking of the relationship with the toner of the present invention, by mixing a developer with a surface energy reducing agent, transfer omission and the effect of preventing the occurrence of character dust are likely to be significantly reduced. It is preferable to use different means and methods.
[0114]
That is, the present invention preferably has an agent applying means for supplying a surface energy reducing agent to the surface of the electrophotographic photosensitive member. The agent applying means can be installed at an appropriate position around the electrophotographic photoreceptor, but in order to effectively use the installation space, a part of the charging means, developing means, and cleaning means shown in FIG. May be installed. Hereinafter, an example in which an agent applying unit is used in combination with a cleaning unit will be described.
[0115]
FIG. 2 is a configuration diagram of a cleaning unit installed in the image forming unit of the present invention.
[0116]
The cleaning means is used as a cleaning means for 25Y, 25M, 25C, 25Bk and the like in FIG. The cleaning blade 25a of FIG. 2 is attached to the support member 25b. As the material of the cleaning blade, a rubber elastic body is used, and as the material, urethane rubber, silicone rubber, fluorine rubber, chloropyrene rubber, butadiene rubber, and the like are known. Of these, urethane rubber is another material. It is particularly preferable because it has excellent wear characteristics as compared with rubber.
[0117]
On the other hand, the support member 25b is formed of a plate-shaped metal member or a plastic member. As the metal member, a stainless steel plate, an aluminum plate, a vibration control steel plate, or the like is preferable.
[0118]
In the present invention, it is preferable that the tip of the cleaning blade that is in pressure contact with the surface of the photoconductor is pressed in a state in which a load is applied in a direction opposite to the rotation direction of the photoconductor (counter direction). As shown in FIG. 2, it is preferable that the tip of the cleaning blade forms a pressing surface when pressing against the photosensitive member.
[0119]
Preferred values of the contact load P and the contact angle θ of the cleaning blade on the photoconductor are P = 5 to 40 N / m and θ = 5 to 35 °.
[0120]
The contact load P is a normal direction vector value of the pressing force P ′ when the cleaning blade 25a is brought into contact with the photosensitive drum 1.
[0121]
Is the angle between the tangent line X at the contact point A of the photoconductor and the blade before deformation (indicated by a dotted line in the drawing). Reference numeral 25e denotes a rotation shaft that allows the support member to rotate, and 25g denotes a load spring.
[0122]
The free length L of the cleaning blade represents the length of the tip of the blade before deformation from the position of the end B of the support member 25b as shown in FIG. A preferred value of the free length is L = 6 to 15 mm. The thickness t of the cleaning blade is preferably 0.5 to 10 mm. Here, the thickness of the cleaning blade indicates a direction perpendicular to the bonding surface of the support member 25b as shown in FIG.
[0123]
A brush roll 25c also serving as an agent applying means is used as the cleaning means in FIG. The brush roll has a function of removing the toner attached to the photoconductor 1 and a function of collecting the toner removed by the cleaning blade 25a, and also has a function as an agent applying unit for supplying a surface energy reducing agent to the photoconductor. That is, the brush roll comes into contact with the photoreceptor 1, and at the contact portion, the traveling direction rotates in the same direction as the photoreceptor 1 to remove the toner and paper dust on the photoreceptor and remove the toner removed by the cleaning blade 25 a. Is transported and collected by the transport screw 25j. In this path, it is preferable to remove a removed substance such as toner transferred from the photoconductor 1 to the brush roll 25c by bringing a flicker 25i as a removing unit into contact with the brush roll 25c. Further, the toner attached to the flicker is removed by the scraper 25d, and the toner is collected by the transport screw 25j. The collected toner is taken out as waste, or is conveyed to a developing device via a toner recycling pipe (not shown) to be reused. As a material for the flicker 25i, a metal tube such as stainless steel or aluminum is preferably used. On the other hand, as the scraper 25d, an elastic plate such as a phosphor bronze plate, a polyethylene terephthalate plate, or a polycarbonate plate is used.
[0124]
A surface energy lowering agent (solid material such as zinc stearate) 25k is attached to the brush roll by pressing with a spring load of 25s. A surface energy reducing agent is supplied to the surface.
[0125]
A conductive or semiconductive brush roll is used as the brush roll 25c.
[0126]
Although any material can be used as the material of the brush of the brush roll used in the present invention, it is preferable to use a fiber-forming polymer having hydrophobicity and a high dielectric constant. Examples of such a polymer include rayon, nylon, polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, and vinylidene chloride. -Acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol formaldehyde resin, styrene-alkyd resin, polyvinyl acetal (for example, polyvinyl acetal) Butyral) and the like. These binder resins can be used alone or as a mixture of two or more. Particularly preferred are rayon, nylon, polyester, acrylic resin and polypropylene.
[0127]
The brush may be a conductive or anti-conductive brush, and may be a material in which a low-resistance substance such as carbon is contained in a constituent material and adjusted to an arbitrary specific resistance.
[0128]
The specific resistance of the brush bristles of the brush roll was measured at room temperature and normal humidity (temperature 26 ° C., relative humidity 50%) with a voltage of 500 V applied to both ends of a single 10 cm long bristles. ¹ Ωcm-10 ⁶ Those within the range of Ωcm are preferred.
[0129]
That is, the brush roll is made of 10 core material such as stainless steel. ¹ Ωcm-10 ⁶ It is preferable to use conductive or semiconductive brush bristles having a specific resistance of Ωcm. 10 ¹ If the specific resistance is lower than Ωcm, banding or the like due to discharge is likely to occur. Also, 10 ⁶ If it is higher than Ωcm, the potential difference from the photoreceptor becomes low, and cleaning failure easily occurs.
[0130]
The thickness of one brush bristles used for the brush roll is preferably 5 to 20 denier. If it is less than 5 denier, there is no sufficient rubbing force, so that the surface deposits cannot be removed. On the other hand, if it is larger than 20 denier, the brush becomes rigid, so that the surface of the photoreceptor is damaged and abrasion proceeds, thereby shortening the life of the photoreceptor.
[0131]
The term “denier” as used herein is a numerical value obtained by measuring the mass of the brush bristles (fibers) constituting the brush in a length of 9000 m in g (gram) units.
[0132]
The brush bristle density of the brush is 4.5 × 10 ² / Cm ² ~ 2.0 × 10 ⁴ / Cm ² (The number of brush hairs per square centimeter). 4.5 × 10 ² / Cm ² If it is less than 1, the stiffness is low, the rubbing force is weak, and the rubbing is uneven, so that the attached matter cannot be removed uniformly. 2.0 × 10 ⁴ / Cm ² If it is larger, the photoreceptor will be worn because it becomes rigid and the rubbing force will be strong, and a defective image such as a black stripe due to fog or a scratch due to a decrease in sensitivity will occur.
[0133]
The bite amount of the brush roll used in the present invention with respect to the photoconductor is preferably set to 0.4 to 1.5 mm, more preferably 0.5 to 1.2 mm. This biting amount means a load on the brush generated by the relative movement between the photosensitive drum and the brush roll. This load corresponds to the rubbing force received from the brush when viewed from the photoconductor drum, and defining the range means that the photoconductor needs to be rubbed with an appropriate force.
[0134]
This biting amount refers to the length of biting into the interior when it is assumed that when the brush abuts on the photoreceptor, the brush bristles do not bend on the surface of the photoreceptor but enter the interior linearly.
[0135]
In the photoreceptor to which the surface energy reducing agent is supplied, since the abrasion force of the photoreceptor surface by the brush is small, if the bite amount is smaller than 0.4 mm, filming of the toner or paper powder on the photoreceptor surface is suppressed. And a defect such as unevenness occurs on the image. On the other hand, if it is larger than 1.5 mm, the abrasion force of the photoreceptor surface by the brush is too large, so that the abrasion amount of the photoreceptor increases, fog due to a decrease in sensitivity or scratches on the photoreceptor surface occur, This is a problem because a streak failure occurs on an image.
[0136]
As a core material of the roll portion used for the brush roll, metal such as stainless steel and aluminum, paper, and plastic are mainly used, but are not limited thereto.
[0137]
The brush roll used in the present invention preferably has a configuration in which a brush is provided on the surface of a columnar core material via an adhesive layer.
[0138]
It is preferable that the brush roll rotates so that the contact portion moves in the same direction as the surface of the photoconductor. If the contact portion moves in the opposite direction, if excessive toner is present on the surface of the photoconductor, the toner removed by the brush roll may spill out and stain the recording material or the apparatus.
[0139]
When the photoreceptor and the brush roll move in the same direction as described above, the surface speed ratio of the two is preferably a value within the range of 1: 1.1 to 1: 2. If the rotation speed of the brush roll is lower than that of the photoconductor, the toner removal ability of the brush roll is reduced, and cleaning failure is likely to occur. If the rotation speed of the brush roll is higher than the photoconductor, the toner removal capability becomes excessive and blade bounding or turning over occurs. Easier to do.
[0140]
【Example】
Next, embodiments of the present invention will be specifically described, but the configuration of the present invention is not limited to this.
(Preparation of toner)
(Production of Toner 1Bk, 1Ya, 1Yb, 1M, 1C)
0.90 kg of sodium n-dodecyl sulfate and 10.0 liters of pure water were added and dissolved by stirring. 1.20 kg of Regal 330R (carbon black manufactured by Cabot Corporation) was gradually added to this solution, and the mixture was stirred well for 1 hour, and then continuously dispersed for 20 hours using a sand grinder (medium type disperser). This is referred to as “colorant dispersion liquid 1”.
[0141]
Further, a solution composed of 0.055 kg of sodium dodecylbenzenesulfonate and 4.0 liters of ion-exchanged water is referred to as “anionic surfactant solution A”.
[0142]
A solution consisting of 0.014 kg of a 10 mol adduct of nonylphenol polyethylene oxide and 4.0 liters of ion-exchanged water is referred to as “nonionic surfactant solution B”.
[0143]
A solution prepared by dissolving 223.8 g of potassium persulfate in 12.0 liters of ion-exchanged water is referred to as “initiator solution C”.
[0144]
A WAX emulsion (polypropylene emulsion having a number average molecular weight of 3000: a number average primary particle diameter: 120 nm / solid content concentration = 29.) Was placed in a 100-liter GL (glass lining) reactor equipped with a temperature sensor, a cooling pipe, and a nitrogen introducing device. (9%) 3.41 kg, the whole amount of “anionic surfactant solution A” and the whole amount of “nonionic surfactant solution B” were added, and stirring was started. Next, 44.0 liters of ion-exchanged water was added.
[0145]
Heating was started, and when the liquid temperature reached 75 ° C., the entire amount of “initiator solution C” was added dropwise. Thereafter, while controlling the liquid temperature at 75 ° C. ± 1 ° C., 12.1 kg of styrene, 2.88 kg of n-butyl acrylate, 1.04 kg of methacrylic acid, and 548 g of t-dodecyl mercaptan were added dropwise. After completion of the dropwise addition, the liquid temperature was raised to 80 ° C. ± 1 ° C., and the mixture was heated and stirred for 6 hours. Next, the liquid temperature was cooled to 40 ° C. or lower, stirring was stopped, and the mixture was filtered with a pole filter to obtain a latex. This is designated as "latex-A".
[0146]
The glass transition temperature of the resin particles in Latex-A was 57 ° C., the softening point was 121 ° C., the molecular weight distribution was weight average molecular weight = 12.7 million, and the weight average particle size was 120 nm.
[0147]
A solution obtained by dissolving 0.055 kg of sodium dodecylbenzenesulfonate in 4.0 liters of ion-exchanged pure water is referred to as “anionic surfactant solution D”.
[0148]
Further, a solution obtained by dissolving 0.014 kg of nonylphenol polyethylene oxide 10 mol adduct in 4.0 liters of ion-exchanged water is referred to as “nonionic surfactant solution E”.
[0149]
A solution prepared by dissolving 200.7 g of potassium persulfate (manufactured by Kanto Chemical Co., Ltd.) in 12.0 liters of ion-exchanged water is referred to as “initiator solution F”.
[0150]
A WAX emulsion (polypropylene emulsion with a number average molecular weight of 3000: number average primary particle diameter: 120 nm / solids concentration: 29.9%) was placed in a 100-liter GL reactor equipped with a temperature sensor, a cooling tube, a nitrogen introducing device, and a comb baffle. 3.41 kg, the entire amount of “anionic surfactant solution D” and the entire amount of “nonionic surfactant solution E” were added, and stirring was started.
[0151]
Next, 44.0 liters of ion-exchanged water was charged. Heating was started, and when the liquid temperature reached 70 ° C., “Initiator solution F” was added. Next, a solution in which 11.0 kg of styrene, 4.00 kg of n-butyl acrylate, 1.04 kg of methacrylic acid and 9.02 g of t-dodecylmercaptan were previously mixed was added dropwise. After completion of the dropwise addition, the mixture was heated and stirred for 6 hours while controlling the liquid temperature to 72 ° C. ± 2 ° C. Further, the liquid temperature was raised to 80 ° C. ± 2 ° C., and the mixture was heated and stirred for 12 hours. The liquid temperature was cooled to 40 ° C. or lower, and the stirring was stopped. The solution is filtered through a Pall filter, and this filtrate is referred to as “latex-B”.
[0152]
In addition, the glass transition temperature of the resin particles in Latex-B was 58 ° C, the softening point was 132 ° C, the molecular weight distribution was weight average molecular weight = 245,000, and the weight average particle size was 110 nm.
[0153]
A solution obtained by dissolving 5.36 kg of sodium chloride as a salting-out agent in 20.0 liters of ion-exchanged water is referred to as “sodium chloride solution G”.
[0154]
A solution obtained by dissolving 1.00 g of a fluorine-based nonionic surfactant in 1.00 liter of ion-exchanged water is referred to as “nonionic surfactant solution H”.
[0155]
In a 100-liter SUS reaction vessel equipped with a temperature sensor, a cooling pipe, a nitrogen introduction device, and a particle size and shape monitoring device, the above-prepared latex-A = 20.0 kg, latex-B = 5.2 kg, and colorant Dispersion 1 = 0.4 kg and ion-exchanged water 20.0 kg were added and stirred. Then, the mixture was heated to 40 ° C., and sodium chloride solution G, 6.00 kg of isopropanol (manufactured by Kanto Chemical Co., Ltd.) and nonionic surfactant solution H were added in this order. Then, after standing for 10 minutes, the temperature was raised, the temperature was raised to 85 ° C. in 60 minutes, and the mixture was heated and stirred at 85 ± 2 ° C. for 0.5 to 3 hours, and subjected to salting-out / fusion. Diameter growth (salting out / fusion step). Next, 2.1 liters of pure water was added to stop the particle size growth, and a fused particle dispersion was prepared.
[0156]
In a 5 liter reaction vessel equipped with a temperature sensor, a cooling pipe, and a monitoring device for particle size and shape, 5.0 kg of the above-prepared fused particle dispersion liquid was placed. The shape was controlled by heating and stirring for 5 to 15 hours (shape control step). Thereafter, the mixture was cooled to 40 ° C. or lower and the stirring was stopped. Next, classification is performed in the liquid by a centrifugal sedimentation method using a centrifugal separator, and the liquid is filtered through a sieve having openings of 45 μm, and the filtrate is used as an associated liquid. Next, non-spherical particles in the form of a wet cake were filtered from the association liquid using a Nutsche. Thereafter, the substrate was washed with ion-exchanged water. The non-spherical particles were dried at a suction air temperature of 60 ° C. using a flash jet drier, and then dried at a temperature of 60 ° C. using a fluidized bed drier. To 100 parts by mass of the obtained colored particles, 0.5 parts by mass of hydrophobic silica (hydrophobicity = 75 / number average primary particle size = 12 nm) and 0.25 parts by mass of 0.05 μm titanium oxide were added. And a Henschel mixer with a peripheral speed of 40 m / s at 52 ° C. for 10 minutes to obtain “toner 1Bk”.
[0157]
In the production of toner 1Bk, C.I. I. "Toner 1Ya" was obtained in the same manner except that Pigment Yellow 185 was used. Further, the peripheral speed of the Henschel mixer was slightly reduced to obtain “Toner 1Yb”.
[0158]
In the production of toner 1Bk, C.I. I. "Toner 1M" was obtained in the same manner except that Pigment Red 122 was used.
[0159]
In the production of toner 1Bk, C.I. I. “Toner 1C” was obtained in the same manner except that Pigment Blue 15: 3 was used. The number average particle diameter of the toners 1Bk, 1Ya, 1M, and 1C, M (m ₁ + M ₂ ) Are shown in Table 1, and the measurement results of the toner turbidity are shown in Table 2. Further, the number average particle diameter of toner 1Yb, M (m ₁ + M ₂ ) Was almost the same as the toner 1Ya.
(Production of Toner 2Bk, 2Ya to 2Yf, 2M, 2C)
In the preparation of the toners 1Bk, 1Y, 1M and 1C, hydrophobic silica (hydrophobicity = 75 / number average primary particle diameter = 12 nm) was replaced with hydrophobic silica (hydrophobicity = 77 / number average primary particle diameter = 20 nm). And toners 2Bk, 2Ya to 2Yf, 2M, and 2C were produced in the same manner except that the peripheral speed and time of the Henschel mixer were changed. Table 2 shows the measurement results of the turbidity of the toners 2Bk, 2Ya to 2Yf, 2M, and 2C. Incidentally, the number average particle diameter of these toners, M (m ₁ + M ₂ ) Basically correspond to each color of the toners 1Bk, 1Ya, 1M, and 1C (the number average particle diameter of the toner, M (m ₁ + M ₂ )) Was almost the same as the measurement result.
(Production of Toners 3Bk, 3Ya to 3Yd, 3M, 3C)
In the preparation of the toners 1Bk, 1Y, 1M and 1C, the hydrophobic silica (hydrophobicity = 75 / number average primary particle diameter = 12 nm) was changed from 0.5 parts by mass to 1.8 parts by mass, and the Henschel mixer was used. Except that the peripheral speed and the mixing time were changed, toners 3Bk, 3Ya to 3Yd, 3M, and 3C were produced in the same manner. Table 2 shows the measurement results of the turbidity of the toners 3Bk, 3Ya to 3Yd, 3M, and 3C. The number average particle diameter of these toners, M (m ₁ + M ₂ Are basically the same as the measurement results corresponding to the colors of the toners 1Bk, 1Ya, 1M, and 1C.
(Production of Toners 4Bk, 4Ya to 4Yc, 4M, 4C)
In the production of the toners 1Bk, 1Y, 1M and 1C, the hydrophobic silica (hydrophobicity = 75 / number average primary particle diameter = 12 nm) was changed from 0.5 parts by mass to the hydrophobic silica (hydrophobicity = 77 / number average). The toners 4Bk, 4Ya to 4Yc, 4M, and 4C were produced in the same manner except that the primary particle diameter was changed to 1.9 parts by mass and the peripheral speed and mixing time of the Henschel mixer were changed. Table 2 shows the measurement results of the turbidity of the toners 4Bk, 4Ya to 4Yc, 4M, and 4C. The number average particle diameter of these toners, M (m ₁ + M ₂ Are basically the same as the measurement results corresponding to the colors of the toners 1Bk, 1Ya, 1M, and 1C.
(Production of Toners 5Bk, 5Y, 5Ma to 5Mc, 5C)
In the production of the toners 1Bk, 1Y, 1M and 1C, the hydrophobic silica (hydrophobicity = 75 / number average primary particle diameter = 12 nm) was changed from 0.5 parts by mass to the hydrophobic silica (hydrophobicity = 77 / number average). The toners 5Bk, 5Y, 5Ma to 5Mc, and 5C were prepared in the same manner except that the primary particle diameter was changed to 3.1 parts by mass and the peripheral speed and mixing time of the Henschel mixer were changed. Table 2 shows the measurement results of the turbidity of the toners 5Bk, 5Y, 5Ma to 5Mc, and 5C. The number average particle diameter of these toners, M (m ₁ + M ₂ Are basically the same as the measurement results corresponding to the colors of the toners 1Bk, 1Ya, 1M, and 1C.
(Production of Toners 6Bk, 6Y, 6M, 6Ca to 6Cc)
Toners 6Bk, 6Y, 6M, and 6Ca to 6Cc were prepared in the same manner as in the preparation of toners 1Bk, 1Y, 1M, and 1C, except that the peripheral speed and mixing time of the Henschel mixer were changed. Table 2 shows the measurement results of the turbidity of the toners 6Bk, 6Y, 6M, and 6Ca to 6Cc. The number average particle diameter of the toner, M (m ₁ + M ₂ Are basically the same as the measurement results corresponding to the colors of the toners 1Bk, 1Ya, 1M, and 1C.
[0160]
[Table 1]

[0161]
[Table 2]

[0162]
(Preparation of developer)
45 μm ferrite carrier 100 coated with 10 parts by weight of each of toner 1Bk-1C, toner 2Bk-2C, toner 3Bk-3C, toner 4Bk-4C, toner 5Bk-5C, toner 6Bk-6Cc, and a styrene-methacrylate copolymer The developer 1Bk-1C, the developer 2Bk-2C, the developer 3Bk-3C, the developer 4Bk-4C, the developer 5Bk-5C, and the developer 6Bk-6Cc for evaluation were prepared by mixing with the mass part. .
(Preparation of photoreceptor)
The photoconductors used in the examples were manufactured as described below (four or more photoconductors in each example were manufactured because the same type of photoconductor was used in each image unit).
[0163]
Production of photoconductor 1
The following intermediate layer coating solution was prepared and applied by dip coating on a cleaned cylindrical aluminum substrate to form an intermediate layer having a dry film thickness of 0.3 μm.
[0164]
<Intermediate layer (UCL) coating liquid>
Polyamide resin (Amilan CM-8000: manufactured by Toray Industries) 60 g
1600 ml of methanol
The following coating liquid components were mixed and dispersed for 10 hours using a sand mill to prepare a charge generating layer coating liquid. This coating solution was applied by dip coating to form a charge generation layer having a dry film thickness of 0.2 μm on the intermediate layer.
[0165]

The following coating solution components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied on the charge generation layer by a dip coating method to form a charge transport layer having a thickness of 20 μm.
[0166]

Production of photoconductor 2
In the preparation of the photoreceptor 1, coating was performed in the same manner up to the charge transport layer.
[0167]

Was mixed and dissolved to prepare a coating solution for the surface protective layer. This coating solution was applied on the charge transport layer by a dip coating method, and was heated and cured at 100 ° C. for 40 minutes to form a surface protective layer having a dry film thickness of 4 μm.
[0168]
Example 1 (Example using photoconductor 2 containing fluorine resin particles in surface layer)
<Evaluation>
The photosensitive member 2 made of the photosensitive member of each image forming unit of the tandem type digital copying machine shown in FIG. 1 is mounted, and a developer group (No. 1 to 21) shown in Table 2 is used as a developer of each developing means. It was mounted sequentially and evaluated.
[0169]
The evaluation was performed using an A4 image having a white background portion, a solid image portion of Bk and Y, M, and C, a character image portion, and a halftone image in an original image under normal temperature and normal humidity (20 ° C., 50% RH) in monochrome image. And a color image were printed at a ratio of 10: 1 for a total of 10,000 sheets and evaluated. The evaluation items, evaluation methods, and evaluation criteria are described below. In the evaluation of sharpness, evaluation was performed while changing environmental conditions as shown below.
[0170]
Character chile
A character image was formed, and toner dust around the character was observed visually and with a 20-power loupe, and evaluated according to the following criteria.
[0171]
：: No toner dust around the characters is observed even with a loupe (good)
：: Indistinguishable by visual observation, but toner dust around characters is observed with a loupe (no problem in practical use)
×: Toner dust around the character is visually observed, and the sharpness of the character is poor (a problem in practical use)
Missing transfer
A halftone image having a density of 0.4 was recorded on a recording paper (basis weight 200 g / m2). ² ), And the occurrence of white spots due to transfer omission was visually evaluated.
[0172]
◎◎: No transfer loss (very good)
：: One or two transfer omissions exist only on the back surface per 100 images, but cannot be determined without staring (good)
：: Although there are 1 to 4 transfer omissions per 50 images, they cannot be identified without staring (there is no practical problem).
×: Five or more clear transfer omissions exist on 50 sheets of images regardless of the front / back side (there is a problem in practical use)
Black spot
The occurrence of black spots (strawberry spot images) on the halftone image was determined based on the following criteria.
[0173]
A: No nuclei of black spots were found on the photoreceptor, and no black spots were found on halftone images (good)
；: Black spot generation nuclei are observed on the photoreceptor, but no black spot is generated in the halftone image (no problem in practical use)
X: Black spot generation nuclei were observed on the photoreceptor, and black spots were also generated on the halftone image (a problem in practical use)
Image density
The image density was measured by using a densitometer “RD-918” (manufactured by Macbeth) to measure the solid portion of each color at a relative reflection density where the recording paper was zero.
[0174]
A: Each density of Bk, Y, M and C solid (solid) image portions is 1.2 or more (good)
：: Each density of Bk, Y, M and C solid (solid) image portions is 0.8 or more (no problem in practical use)
X: Each density of Bk and Y (solid) image part of M, C is less than 0.8 (practical problem)
Sharpness
The sharpness of the image was evaluated under both low-temperature and low-humidity (10 ° C., 20% RH) and high-temperature, high-humidity (30 ° C., 80% RH) environments, and evaluated by character collapse. Three-point and five-point character images were formed and evaluated according to the following criteria.
[0175]
：: 3 points and 5 points are clear and easily legible
：: 3 points are partially unreadable, 5 points are clear and easily readable
×: 3 points are almost unreadable, and 5 points are partially or completely unreadable color reproduction.
The color reproduction of a color image was evaluated by measuring the saturation of B (blue), G (green), and R (red) obtained by two types of mixed colors of Y, M, and C toners.
[0176]
The chroma evaluation was performed using a spectrophotometer “CM-100” (SCE method, manufactured by Minolta Co., Ltd.) under the conditions of a visual field of 2 ° and a light source color of D65. The evaluation criteria are shown below.
[0177]
◎: Saturation (C ^* ) Are B> 35, G> 50, R> 63, each color is vivid, and good color reproduction is achieved (good).
○: Saturation (C ^* ) Are B ≧ 30, G ≧ 40, R ≧ 60, and good color reproduction is achieved in practical use (no problem in practical use)
Δ: Saturation (C ^* ) Does not satisfy B ≧ 30, G ≧ 40, R ≧ 60 (re-evaluation is required for practicality)
×: Saturation (C ^* ) Do not satisfy B ≧ 30, G ≧ 40, and R ≧ 60 (practically problematic)
Other evaluation conditions
Line speed L / S for image formation: 180 mm / sec
Charging condition of photoconductor (40 mmφ): The potential of the non-image area is detected by a potential sensor, and feedback control is performed. The controllable range is from −500 V to −900 V, and the surface of the photoconductor when fully exposed The potential was in the range of -50 to 0V.
[0178]
Image exposure light: semiconductor laser (wavelength: 780 nm)
Transfer conditions
Transfer belt: A transfer belt made of urethane rubber in which carbon was dispersed was used at an elongation ratio of 3%.
[0179]
Transfer pole: Corona discharger, spacing 7.0 mm between discharge wires and photoconductor drums 21Y, 21M, 21C, 21Bk, wire diameter of discharge wires 0.08mm, material WO of discharge wires ₃ , Material of electrode plate SUS304
Transfer current power supply voltage: +3.5 KV to +7.5 KV
Photoconductor cleaning conditions
Cleaning blade: A urethane rubber blade was brought into contact with the photosensitive member in the rotating direction by a counter method.
[0180]
Table 3 shows the results.
[0181]
[Table 3]

[0182]
From Table 3, it can be seen that the developer group that satisfies the requirements of the present invention, that is, the turbidity of each color toner used in the developing means of a plurality of image forming units is less than 60, and the difference in turbidity between each color toner is at most 5 To 45, and one of the plurality of developing means satisfies the configuration of the black toner having a turbidity of less than 25 (Nos. 2, 3, 4, 5, 6, 7, 9, 10, 11). , 13, 14, 19, and 20) achieve good evaluations over practical ranges in character dust, transfer omission, black spot, image density, sharpness, and color reproduction. In the groups (Nos. 1, 8, 12, 15, 16, 17, 18, 21), the turbidity difference between the toners of each color was 4.1. In No. 1, the fluidity of the toner was not sufficient, transfer omission occurred, and the image density and sharpness were reduced. 8, No. In No. 21, character dust (color character dust) is large due to instability of the balance of the charge amount, and sharpness and color reproduction are deteriorated. No. In No. 21, transfer omission has also occurred. Further, in the developer group (No. 12, No. 15, No. 18) in which the turbidity of one of the toners of each color is 60 or more, the amount of free external additives becomes excessive, and black spots are frequently generated, resulting in sharpness and color reproduction. Is declining. Further, in the developer group (No. 16, No. 17, No. 18) using the black toner Bk having a turbidity of 25 or more as a developer, character dust occurs, sharpness and color reproduction are deteriorated. ing. Among the developer groups satisfying the requirements of the present invention, a developer group in which the difference in turbidity between toners of each color is 10 to 35 at the maximum and the turbidity of black toner is less than 20 (No. 4, 5, 6, 9) , 10 and 20) have a remarkable improvement effect.
[0183]
Example 2 (Example of using photoreceptor 1 and supplying a surface energy reducing agent)
The photoreceptor of each image forming unit of the tandem type digital copying machine according to the first embodiment is changed from the photoreceptor 2 to the photoreceptor 1, and each cleaning device has a brush roll which also serves as an agent applying unit shown in FIG. Each of the image forming units is the same as in Example 1 while zinc stearate, a surface energy reducing agent, is installed at 25k in FIG. 2 and zinc stearate is supplied to the photoreceptor surface via a brush roll. Were evaluated in combination with the developer group (toner group) of the developing means. Evaluation items, evaluation methods, and evaluation criteria were the same as in Example 1.
[0184]
Cleaning conditions of the cleaning means having the agent applying means of FIG.
Cleaning blade: A urethane rubber blade was brought into contact with the photosensitive member in the rotating direction by a counter method.
[0185]
Cleaning brush: conductive acrylic resin, brush bristle density (3 × 10 ³ / Cm ² ), The bite amount was set to 1.0 mm.
[0186]
The evaluation was performed under the above conditions. As a result, almost the same evaluation results as in Example 1 were obtained. That is, even if the surface layer of the photoreceptor does not contain fluorine-based resin particles, the same effect as in Example 1 can be obtained by supplying the surface energy reducing agent to the surface of the photoreceptor.
[0187]
Embodiment 3 (example in which the particle size distribution of toner is changed)
(Production of Toners 7Bk, 7Y, 7M, 7C)
In the production of the toners 2Bk, 2Yb, 2M and 2C, the classification level in the liquid by the centrifugal sedimentation method was changed to obtain M (m ₁ + M ₂ ), And the like, except that toners 7Bk, 7Y, 7M, and 7C were prepared. The number average particle diameter of the toners of the toners 7Bk, 7Y, 7M, and 7C, M (m ₁ + M ₂ ) And the toner turbidity are shown in Table 4.
[0188]
By mixing 10 parts by mass of each of these toners and 100 parts by mass of a 45 μm ferrite carrier coated with a styrene-methacrylate copolymer, developers 22Bk, 7Y, 7M and 7C for evaluation were used. Groups were made.
(Production of Toners 8Bk, 8Y, 8M, 8C)
In the production of the toners 2Bk, 2Yb, 2M and 2C, the classification level in the liquid by the centrifugal sedimentation method was changed to obtain M (m ₁ + M ₂ ), Etc., except that toners 8Bk, 8Y, 8M, and 8C were produced in the same manner. The number average particle diameter of the toners of the toners 8Bk, 8Y, 8M, and 8C, M (m ₁ + M ₂ ) And the toner turbidity are shown in Table 4.
[0189]
By mixing 10 parts by mass of each of these toners and 100 parts by mass of a 45 μm ferrite carrier coated with a styrene-methacrylate copolymer, developers 23Bk, 8Y, 8M and 8C for evaluation were prepared. Groups were made.
[0190]
[Table 4]

[0191]
The combination No. of the first embodiment. The evaluation was performed in the same manner as in Example 1 except that the developers 22 and 23 were used instead of the developers 4 (toners 2Bk, 2Yb, 2M and 2C). Table 5 shows the results.
[0192]
[Table 5]

[0193]
According to Table 5, the developer 22 group in which the sum (M) of the relative frequencies of the toner particles is 70% or more has a higher degree of improvement in the evaluation items than the developer 23 group in which the (M) is less than 70%. Can be seen.
[0194]
【The invention's effect】
By using the present invention, it is possible to achieve improvement of a tandem type electrophotographic character image and a color image directly transferred from a photoreceptor to a recording material, to prevent image defects such as transfer omission and character dust, and to improve image density and image density. An image forming apparatus and an image forming method capable of forming a color image with good sharpness can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus that can produce a color image according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a cleaning unit installed in the image forming unit of the present invention.
[Explanation of symbols]
20Y, 20M, 20C, 20Bk image forming unit
21Y, 21M, 21C, 21Bk Photoconductor drum (image forming body)
22Y, 22M, 22C, 22Bk Charging means
23Y, 23M, 23C, 23Bk Exposure means
24Y, 24M, 24C, 24Bk developing means
25Y, 25M, 25C, 25Bk Cleaning means

Claims (8)

A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, the turbidity of each color toner used in the developing means of the plurality of image forming units is less than 60, the difference in turbidity between the respective color toners is 5 to 45 at the maximum, and one of the plurality of developing means One containing a black toner having a turbidity of less than 25. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, at least one surface layer of the electrophotographic photosensitive member of the plurality of image forming units contains fluorine-based resin particles, and the turbidity of each color toner used in the developing unit of the plurality of image forming units is An image form characterized by having a turbidity difference between toners of each color of less than 60 and a maximum of 5 to 45, and wherein one of the plurality of developing means contains a black toner having a turbidity of less than 25. Apparatus. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, at least one of the plurality of image forming units has an agent applying unit for supplying a surface energy reducing agent to the surface of the electrophotographic photoreceptor, and each color used for a developing unit of the plurality of image forming units is provided. The turbidity of the toner is less than 60, the difference in turbidity between each color toner is 5 to 45 at the maximum, and one of the plurality of developing means contains a black toner having a turbidity of less than 25. An image forming apparatus symptoms. A plurality of image forming units having at least an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, and a transfer unit are arranged and provided, and on the electrophotographic photoreceptor using a toner of which coloring is changed for each of the plurality of image forming units. An image for forming a color toner image by forming a color toner image by sequentially superimposing and transferring each color toner image from an electrophotographic photosensitive member onto a recording material to form a color toner image; and fixing the color toner image to form a color image In the forming apparatus, the turbidity of each color toner used in the developing means of the plurality of image forming units is less than 60, the turbidity difference between each color toner is 5 to 45 at the maximum, and the particle size distribution of each color toner is When the particle diameter of the toner particles is D (μm), the natural logarithm InD is plotted on the horizontal axis, and the horizontal axis is plotted in a histogram showing the number-based particle size distribution divided into a plurality of classes at intervals of 0.23. Te, a relative frequency of toner particles included in the modal class (m _1), the sum of the relative frequency of toner particles included in the next higher frequency of class modal class (m _{2) (M)} 70 % Or more. The image forming apparatus according to any one of claims 1 to 4, wherein a difference in turbidity of each color toner is 10 to 35 at the maximum. The plurality of image forming units are four image forming units, an image forming unit having a black toner, an image forming unit having a yellow toner, an image forming unit having a magenta toner, and an image forming having a cyan toner. The image forming apparatus according to claim 1, comprising a unit. The image forming apparatus according to any one of claims 1 to 6, wherein the toner turbidity of the black toner is less than 20. An image forming method, comprising: forming an electrophotographic image by using the image forming apparatus according to claim 1.

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