JP2004226615A - Development device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device that prevents a density decrease and an image defect such as a soiled base and steadily develops a satisfactory image by preventing caking on a development sleeve in such a manner that the surface characteristics of the development sleeve (10-point average roughness indicated by Rz and an average interspace between local peaks indicated by S) are regulated with respect to the toner particle diameter of developer to be used, and to provide an image forming apparatus using the development device. <P>SOLUTION: The development device 4 includes: a rotary developer carrier 16; and a developer restricting member 21 that restricts the thickness of the layer of the two-component developer 18 composed of magnetic carrier and toner, the layer being formed on the surface of the developer carrier 16. In the development device 4, the surface 16a of the developer carrier 16, when the average particle diameter of the toner is Dμm, satisfies the conditions expressed by the formula 1, D/4≤Rz≤D and 4D≤S≤10D (wherein Rz is 10-point average roughness and S is an average spacing between local peaks). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

《Ｒｚ：十点平均粗さ Ｓ：局部山頂の平均間隔》
を満足する現像装置を最も主要な特徴とする。
請求項２記載の発明では、現像剤担持体と現像剤規制部材との隙間Ｇを０．３ｍｍ＜Ｇ＜０．７ｍｍとする請求項１に記載の現像装置を主要な特徴とする。
請求項３記載の発明では、現像剤担持体の表面は、長軸方向にＶ字溝を等間隔有している請求項１に記載の現像装置を主要な特徴とする。
請求項４記載の発明では、前記トナーのＤｖが４〜８μｍであり、Ｄｖ／Ｄｎが１．０５〜１．３０（Ｄｖは体積平均粒径、Ｄｎは個数平均粒径）である請求項１に記載の現像装置を主要な特徴とする。
請求項５記載の発明では、請求項１〜４のいずれか１項に記載の現像装置を備えた画像形成装置を主要な特徴とする。
【０００５】
【発明の実施の形態】
以下、図面により本発明の実施の形態を詳細に説明する。図１は現像装置および感光体ユニットを示す画像形成装置の概略図である。像担持体（感光体ドラム）１は矢印方向Ａに回転される。像担持体の周囲には帯電装置２、露光装置３、現像装置４、転写装置５、クリーニング装置６、除電装置７が配置されている。
感光体ドラム１は帯電装置２の具体例である帯電ローラ８により一様に帯電され、露光装置３のレーザにより静電潜像が形成され、現像装置４によりトナー像が形成される。その後、転写ベルト９上で図示しない転写紙に転写され、転写紙は分離爪１０により感光体ドラム１より引き剥がされ、図示しない定着器により転写紙上の現像剤（トナー）１８は転写紙に定着される。
また、感光体ドラム１上に残留しているトナーはクリーニング装置６内のクリーニングブレード１１により除去され、トナー回収羽根１２によりトナー回収路１３へ移動し、トナー回収路１３内のトナー回収コイル１４により回収される。その後、感光体ドラム１は除電装置７内の具体例である除電ランプ１５により表面の電位が除電される。このような帯電工程、露光工程、現像工程、転写工程、クリーニング工程および除電工程が繰り返して実行される。
現像装置４は、現像剤担持体（現像スリーブ）１６、現像剤容器１７、この現像剤容器１７内の２成分現像剤（トナー）１８、現像剤容器１７内下部に取り付けられたトナー濃度センサ１９、２成分現像剤１８を撹拌し現像スリーブ１６へ供給する搬送スクリュ２０、現像スリーブ１６の感光体ドラム１への供給量を規制する現像剤規制部材（ドクタブレード）２１により構成されている。現像剤１８は磁性キャリアと非磁性のトナーとを混合してなる２成分現像剤である。
本発明では現像装置４の現像スリーブ１６の表面１６ａの状態が、現像剤として使用するトナー１８の平均粒径をＤとしたとき、以下に示す条件、すなわち、

（Ｒｚ：十点平均粗さ Ｓ：局部山頂の平均間隔）、を満足するように設けられる。
ここで、十点平均粗さＲｚおよび局部山頂の平均間隔ＳはＪＩＳＢ０６０１に規定されているパラメータであり、Ｒｚは以下の式で与えられる。

【０００６】
図２は局部山頂の平均間隔Ｓを示す粗さ曲線図である。局部山頂の平均間隔Ｓは図２に示す局部山頂の間隔値Ｓｉの値の平均値であり、以下の式で与えられる。

まず、前記現像スリーブ１６の表面１６ａをサンドブラスト−Ｆ１２０のアルミナ材を使用して粗面化し、３種類の導電性テフロン（登録商標）樹脂−ＭＰ６１４を静電塗装して焼成した。なお、本発明の測定における現像スリーブ１６の表面１６ａの測定は接触式表面粗さ計ＳＵＲＦＣＯＭ５９０Ａ（株式会社東京精密製）を使用した。
トナーの平均粒径をＤμｍとしたとき現像剤担持体（現像スリーブ）１６の表面１６ａが下記条件

（Ｒｚ：十点平均粗さ Ｓ：局部山頂の平均間隔）を満足する。
現像剤担持体（現像スリーブ）１６の表面１６ａのＲｚがＤ／４より小さい場合には現像剤１８と現像スリーブ１６の表面１６ａでの摩擦係数が低くなり、現像剤１８を安定して供給することができず画像濃度が低くなってしまう。また、十点平均粗さＲｚが平均粒径Ｄよりも大きくなる場合、現像剤規制部材（ドクタブレード）２１によるストレスが部分的に大きくなってしまい、経時で現像剤１８の劣化が起こり異常画像の原因となる。
ここで、ＲｚがＤよりも小さい場合においては、現像剤（トナー）１８が現像スリーブ１６の表面１６ａの凹部にトラップされ固着を引き起こす恐れがある。そこで、局部山頂の平均間隔Ｓを規定する必要がある。
現像スリーブ１６の表面１６ａのＳが４Ｄより小さい場合はＲｚが上記条件を満たした場合においても、局部的な凹部にトナー１８がトラップされ、トナー１８が表面１６ａ上に留まりスリーブ固着が発生しやすい。
また、局部山頂の平均間隔Ｓが１０Ｄよりも大きくなる場合には現像剤の供給量にバラツキが生じ、画像濃度ムラの原因となる。つまり、４Ｄ≦Ｓ≦１０Ｄとすることで表面１６ａの凹凸にトナー１８がトラップされるのを防ぎかつ安定して現像剤１８を供給できる。
【０００７】
このように現像スリーブ１６の表面特性を平均トナー粒径で規定することにより、スリーブ固着の発生を防ぐことができる。
現像剤担持体１６と現像剤規制部材２１との隙間Ｇを０．３ｍｍ＜Ｇ＜０．７ｍｍとする。現像剤担持体（現像スリーブ）１６と現像剤規制部材（ドクタブレード）２１の隙間Ｇを０．３ｍｍ以下にすると、現像剤汲み上げ不良が起こり画像濃度を上昇できない。
また、上記隙間Ｇを０．７ｍｍ以上にすると現像剤汲み上げ過多による現像スリーブ１６表面１６ａに現像剤溜まりが発生し、濃度ムラが起こる。さらに、ドクタブレード２１でのストレスが大きくなり、現像剤１８の滞留が起こりスリーブ固着を起こしやすい。現像スリーブ１６の表面特性を平均トナー粒径で規定する現像スリーブ１６を用いた場合においても、隙間Ｇを０．３＜Ｇ＜０．７ｍｍ、好ましくは、０．４＜Ｇ＜０．６ｍｍにすることでより高画質な画像を得ることができる。
【０００８】
図３は現像スリーブ表面に設けた溝を示す概略図である。現像装置４の現像スリーブ１６とドクタブレード２１との隙間Ｇを、０．３ｍｍ＜Ｇ＜０．７ｍｍに設定する。また、現像装置４の現像スリーブ１６の表面１６ａに図３に示すような角度９０°深さ０．２ｍｍのＶ字溝１６ｂを設けた。本発明の評価ではφ２０のスリーブを用い、このＶ字溝を５０本等間隔に設けた。
現像剤担持体１６の表面１６ａは、長軸方向にＶ字溝１６ｂを等間隔で有している。現像剤担持体（現像スリーブ）１６の表面１６ａが平面であると現像スリーブ１６と現像剤１８（主にキャリア）との摩擦係数が低くなり、現像剤汲み上げ不良が起こる懸念がある。
本発明に用いた現像スリーブ１６にＶ字溝１６ｂを設けることで、現像スリーブ１６の表面１６ａと現像剤１８（主にキャリア）との滑りを防止し搬送性を向上させることでより安定して現像剤１８の供給を行うことができる。
現像剤のトナー１８としてはＤｖが４〜８μｍであり、Ｄｖ／Ｄｎが１．０５〜１．３０であるトナー１８を用いる（Ｄｖは体積平均粒径、Ｄｎは個数平均粒径）。一般に２成分現像剤１８においては、長期にわたる現像装置４内での循環で選択現像（画像パターンに応じたトナー粒径を有するトナー粒子が選択的に現像される）が起こり、現像剤１８中のトナー粒子が変動してしまう。つまり、粒径の小さなトナー、大きなトナーの割合が高くなる傾向にある。
スリーブ固着の原因としては、現像スリーブ１６にトナーが滞留することが挙げられる。また、粒径の小さなトナーは表面の小さな溝に入りやすくスリーブ固着を加速させる要因となる。よって、使用するトナー粒径がＤｖ／Ｄｎが１．０５〜１．３０、好ましくは１．１０〜１．２５を満足すると、選択現像が起こりにくく、長期にわたって粒径の変動がなく安定した画像を得ることができる。
【０００９】
一般的には、トナー１８の粒子径は小さければ小さいほど、高解像で高画質の画像を得るために有利であるといわれているが、逆に転写性やクリーニング性に対しては不利である。本発明においても指定範囲よりも体積平均粒径が小さい場合、現像装置４における長期の撹拌において現像剤１８のキャリアの表面にトナーが融着しキャリアの帯電能力を低下させるといった不具合が発生した。
逆に、トナーの粒子径が本発明の範囲よりも大きい場合には、高解像で高画質の画像を得ることが難しくなるとともに、トナー粒子径の変動が大きくなる場合が多い。また、Ｄｖ／Ｄｎが１．３０よりも大きい場合も同様である。
さらに、Ｄｖ／Ｄｎが１．０５より小さい場合には、トナー挙動の安定化、帯電量の均一化の面から好ましい面もあるが、細線部分を小サイズ粒子で現像、一方、ベタ画像を大きなサイズの粒子を中心に現像するといった、トナー粒径による機能分離ができにくくなるため、かえって好ましくない。
Ｖ字溝１６ｂを設ける現像スリーブ１６と前記の粒径を有したトナーにより、高解像で高画質でありかつスリーブ固着を防止できるので長期にわたり安定した画像を提供できる現像装置となる。
【００１０】
ここでＤｖ／Ｄｎの測定法について述べる。コールカウンター法によるトナー粒子の粒度分布の測定装置としては、コールターカウンターＴＡ−ＩＩ（コールター社製）を用いた。
電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤（好ましくはアルキルベンゼンスルフォン酸塩）を０．１〜５ｍｌ加える。ここで、電解液とは１級塩化ナトリウムを用いて約１％ＮａＣｌ水溶液を調整したもので、例えばＩＳＯＴＯＮ−ＩＩ（コールター社製）が使用できる。ここで、さらに測定試料を２〜２０ｍｇ加える。
試料を懸濁した電解液は、超音波分散器で約１〜３分間分散処理をおこない、前記測定装置により、アパーチャとして１００μｍアパーチャを用いて、トナー粒子またはトナーの体積、個数を測定して、体積分布と個数分布を算出する。得られた分布から、トナーの体積平均粒径（Ｄｖ）、個数平均粒径（Ｄｎ）を求めることができる。
チャンネルとしては、２．００〜２．５２μｍ未満；２．５２〜３．１７μｍ未満；３．１７〜４．００μｍ未満；４．００〜５．０４μｍ未満；５．０４〜６．３５μｍ未満；６．３５〜８．００μｍ未満；８．００〜１０．０８μｍ未満；１０．０８〜１２．７０μｍ未満；１２．７０〜１６．００μｍ未満；１６．００〜２０．２０μｍ未満；２０．２０〜２５．４０μｍ未満；２５．４０〜３２．００μｍ未満；３２．００〜４０．３０μｍ未満の１３チャンネルを使用し、粒径２．００μｍ以上４０．３０μｍ未満の粒子を対象とする。
本発明の効果を確認するために４本の現像スリーブを比較評価した。現像スリーブ表面の各特性値は表１に示す通りである。
【表１】

【００１１】
図４は４本の現像スリーブに５００００枚の画像通紙を行った結果を示す特性図である。使用トナーは平均粒径６μｍのトナーを使用した。図において、横軸は現像スリーブ１６とドクタブレード２１の隙間Ｇであり、縦軸にスリーブ固着ＩＤを示した。
ここで、スリーブ固着ＩＤとは画像評価後の現像スリーブ１６の表面１６ａをプリンタックでテープ転写し測定したＩＤである。このスリーブ固着ＩＤが０．１を越えると濃度ムラや地汚れなどの異常画像を引き起こす。
この結果より図中のＮＯ．１およびＮＯ．２の現像スリーブではスリーブ固着が発生せず、さらに現像スリーブ１６とドクタブレード２１の隙間Ｇを０．３〜０．７にすることで画像濃度不良や濃度ムラなどの副作用も発生しない。
図５はＤｖ／Ｄｎを初期状態で１．０５〜１．３０にしたトナーＡと粒径制御をしていないトナーＢによる１５００００枚の画像通紙評価の結果を示す特性図である。図５において、Ｄｖ／Ｄｎを初期状態で１．０５〜１．３０にしたトナーＡと粒径制御をしていないトナーＢによる１５００００枚の画像通紙評価をおこなった。また、現像スリーブ１６は表１に記載したＮＯ．１とＮＯ．４を用い、現像スリーブ１６とドクタブレード２１の隙間Ｇは０．５に設定した。
この結果粒径を制御していないトナーＢは小粒径トナー比率が増えることで、経時でスリーブ固着が加速している。ところが形状制御をおこなっているトナーＡは経時での粒径分布変動が少ないために、経時でもスリーブ固着に対して余裕度が高い。
【００１２】
【発明の効果】
以上説明したように、請求項１によれば、記載された表面の条件を満たす現像剤担持体（現像スリーブ）を用いることで、スリーブ固着による濃度低下、地汚れといった異常画像を防ぐことができる。
請求項２によれば、現像剤担持体と現像剤規制部材との隙間Ｇを規定することによって、現像剤の供給量を安定させることでさらなる高画質で安定した画像を供給できる。
請求項３によれば、現像剤担持体の表面に長軸方向にＶ字溝を等間隔に設けることによって現像剤の供給量を安定させることでさらなる高画質で安定した画像を供給できる。
請求項４によれば、 Ｄｖが４〜８μｍであり、Ｄｖ／Ｄｎが１．０５〜１．３０であることによって、通常の画像の高精細化だけでなく、経時でも安定して高画質の画像を提供できる。
請求項５によれば、上述した現像スリーブを使用することによって、高解像で高画質であり且つスリーブ固着を防止できるので長期にわたり安定した画像を提供できる画像形成装置を提供できる。
【図面の簡単な説明】
【図１】現像装置および感光体ユニットを示す画像形成装置の概略図である。
【図２】局部山頂の平均間隔Ｓを示す粗さ曲線図である。
【図３】現像スリーブ表面に設けた溝を示す概略図である。
【図４】４本の現像スリーブに５００００枚の画像通紙を行った結果を示す特性図である。
【図５】Ｄｖ／Ｄｎを初期状態で１．０５〜１．３０にしたトナーＡと粒径制御をしていないトナーＢによる１５００００枚の画像通紙評価の結果を示す特性図である。
【符号の説明】
４ 現像装置
１６ 現像剤担持体（現像スリーブ）
１６ａ 現像スリーブの表面
１６ｂ 現像スリーブの表面のＶ字溝
１８ 現像剤（トナー）
２１ 現像剤規制部材（ドクターブレード）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device using a two-component developer and an image forming apparatus using the same.
[0002]
[Prior art]
2. Description of the Related Art In a developing device of an electrophotographic image forming apparatus, it is known that a force for separating a toner from a developing sleeve is applied by grounding a developer regulating member that regulates a toner thickness on a developing sleeve surface or by applying a voltage. It is also known to prevent the sticking of the sleeve by changing the magnetic force in the developing sleeve or forming an irregular concavo-convex pattern on the surface of the developing sleeve (for example, see Patent Document 1). It is also known that the ten-point average roughness Rz and the average interval Sm of irregularities are defined as surface characteristics of the developing sleeve (see Patent Document 3, for example).
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-228706 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-242711 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-258992
[Problems to be solved by the invention]
However, conventionally, in an image forming apparatus using this type of developing device, for example, a copying machine or a laser printer, for example, sand blasting is performed on the developer carrying member (developing sleeve) in order to secure a pumping amount of the developer on the developer carrying member. A developer regulating member (doctor blade) is provided in order to perform such a surface treatment or to make the layer thickness of the developer uniform.
However, when the image forming operation is repeated, stress is applied to the developer between the image carrier (photoreceptor) and the developing sleeve and between the developing sleeve and the doctor blade, and the toner is melted and fixed on the developing sleeve by frictional heat or the like. The phenomenon occurs. When the toner is fixed on the developing sleeve, an abnormal image such as a decrease in density and background stain is generated.
Further, it has been clarified that the characteristics of the surface of the developing sleeve, the toner particle size, and the toner particle size distribution are largely involved as factors of the sticking of the sleeve. Furthermore, once sleeve sticking occurs, the surface of the developing sleeve is covered with toner, and the sticking tends to accelerate over time.
For example, in Japanese Patent Application Laid-Open Publication No. H11-163, the developer regulating member is grounded or a voltage is applied to apply a force to separate the toner from the developing sleeve. However, with this method, it is not possible to control all the movements of the toner, and the margin is small.
For example, in Patent Literature 2, a change in magnetic force in the developing sleeve and an irregular concavo-convex pattern formed on the surface of the developing sleeve prevent sticking of the sleeve. However, since this method has an irregular concavo-convex pattern, there is a concern that fixation may be accelerated in combination with the physical properties of the toner.
For example, Patent Document 3 specifies a ten-point average roughness Rz and an average interval Sm of irregularities as surface characteristics of a developing sleeve. However, in this method, the existence of fine irregularities in the roughness curve is neglected, and the effect of the toner particle size is not taken into account.
In addition, for example, in Japanese Patent Application Laid-Open No. H11-163, a ten-point average roughness Rz and an average interval Sm of irregularities are defined by a carrier particle size as surface characteristics of a developing sleeve. However, this method may not be sufficient for the same reason as in Patent Document 3 described above.
Therefore, an object of the present invention is to solve the above problems by defining the characteristics of the developing sleeve surface (ten-point average roughness: Rz, average interval of local peaks: S) by the toner particle diameter of the developer used. Accordingly, an object of the present invention is to provide a developing device capable of preventing abnormal images such as density reduction and background contamination by preventing sticking of a sleeve, and obtaining a stable and good image, and an image forming apparatus using the same.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the invention according to claim 1, a developer regulating member that regulates a layer thickness of a rotating developer carrier and a two-component developer composed of a magnetic carrier and a toner laminated on the surface of the developer carrier. When the average particle size of the toner is D μm, the surface of the developer carrier

<< Rz: 10-point average roughness S: Average interval between local peaks >>
The most important feature is a developing device satisfying the above.
According to a second aspect of the present invention, a main feature of the developing device according to the first aspect is that a gap G between the developer carrying member and the developer regulating member is set to 0.3 mm <G <0.7 mm.
According to a third aspect of the present invention, the developing device according to the first aspect is characterized in that the surface of the developer carrier has V-shaped grooves at regular intervals in the long axis direction.
In the invention according to claim 4, Dv of the toner is 4 to 8 μm, and Dv / Dn is 1.05 to 1.30 (Dv is a volume average particle diameter, Dn is a number average particle diameter). Is a main feature.
According to a fifth aspect of the invention, an image forming apparatus provided with the developing device according to any one of the first to fourth aspects is a main feature.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an image forming apparatus showing a developing device and a photoconductor unit. The image carrier (photosensitive drum) 1 is rotated in the arrow direction A. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a cleaning device 6, and a charge removing device 7 are arranged around the image carrier.
The photosensitive drum 1 is uniformly charged by a charging roller 8 as a specific example of the charging device 2, an electrostatic latent image is formed by the laser of the exposure device 3, and a toner image is formed by the developing device 4. Thereafter, the transfer paper is transferred onto a transfer paper (not shown) on the transfer belt 9, the transfer paper is peeled off from the photosensitive drum 1 by a separation claw 10, and a developer (toner) 18 on the transfer paper is fixed on the transfer paper by a fixing device (not shown). Is done.
The toner remaining on the photosensitive drum 1 is removed by a cleaning blade 11 in the cleaning device 6, moves to a toner collection path 13 by a toner collection blade 12, and is moved by a toner collection coil 14 in the toner collection path 13. Collected. Thereafter, the surface of the photosensitive drum 1 is neutralized by a neutralization lamp 15 which is a specific example in the neutralization device 7. Such a charging step, an exposure step, a development step, a transfer step, a cleaning step and a charge removal step are repeatedly executed.
The developing device 4 includes a developer carrier (developing sleeve) 16, a developer container 17, a two-component developer (toner) 18 in the developer container 17, and a toner concentration sensor 19 attached to a lower portion inside the developer container 17. It comprises a transport screw 20 for stirring the two-component developer 18 and supplying it to the developing sleeve 16, and a developer regulating member (doctor blade) 21 for regulating the supply amount of the developing sleeve 16 to the photosensitive drum 1. The developer 18 is a two-component developer obtained by mixing a magnetic carrier and a non-magnetic toner.
In the present invention, when the state of the surface 16a of the developing sleeve 16 of the developing device 4 is D, the average particle diameter of the toner 18 used as a developer is as follows:

(Rz: ten-point average roughness S: average distance between local peaks).
Here, the ten-point average roughness Rz and the average interval S between local peaks are parameters defined in JIS B0601, and Rz is given by the following equation.

[0006]
FIG. 2 is a roughness curve diagram showing an average interval S between local peaks. The average interval S between the local peaks is an average value of the interval values Si of the local peaks shown in FIG. 2 and is given by the following equation.

First, the surface 16a of the developing sleeve 16 was roughened using an alumina material of Sandblast-F120, and three types of conductive Teflon (registered trademark) -MP614 were electrostatically coated and fired. The surface 16a of the developing sleeve 16 in the measurement of the present invention was measured using a contact type surface roughness meter SURFCOM590A (manufactured by Tokyo Seimitsu Co., Ltd.).
When the average particle diameter of the toner is D μm, the surface 16 a of the developer carrier (developing sleeve) 16 has the following conditions.

(Rz: ten-point average roughness S: average interval between local peaks).
When Rz of the surface 16a of the developer carrier (developing sleeve) 16 is smaller than D / 4, the friction coefficient between the developer 18 and the surface 16a of the developing sleeve 16 becomes low, and the developer 18 is supplied stably. And the image density is lowered. Further, when the ten-point average roughness Rz is larger than the average particle diameter D, the stress by the developer regulating member (doctor blade) 21 partially increases, and the developer 18 deteriorates with time, resulting in an abnormal image. Cause.
Here, when Rz is smaller than D, there is a possibility that the developer (toner) 18 is trapped in the concave portion of the surface 16a of the developing sleeve 16 and causes sticking. Therefore, it is necessary to define the average interval S between the local peaks.
When S on the surface 16a of the developing sleeve 16 is smaller than 4D, even when Rz satisfies the above condition, the toner 18 is trapped in the local concave portion, the toner 18 stays on the surface 16a, and the sleeve is easily fixed. .
When the average interval S between the local peaks is larger than 10D, the supply amount of the developer varies, which causes image density unevenness. That is, by setting 4D ≦ S ≦ 10D, it is possible to prevent the toner 18 from being trapped in the unevenness of the surface 16a and to supply the developer 18 stably.
[0007]
By thus defining the surface characteristics of the developing sleeve 16 by the average toner particle diameter, it is possible to prevent the sleeve from sticking.
The gap G between the developer carrier 16 and the developer regulating member 21 is set to 0.3 mm <G <0.7 mm. If the gap G between the developer carrier (developing sleeve) 16 and the developer regulating member (doctor blade) 21 is set to 0.3 mm or less, poor developer pumping occurs and the image density cannot be increased.
Further, when the gap G is set to 0.7 mm or more, the developer is accumulated on the surface 16a of the developing sleeve 16 due to excessive pumping of the developer, and density unevenness occurs. Further, the stress at the doctor blade 21 increases, so that the developer 18 stays and the sleeve is easily fixed. Even when the developing sleeve 16 that defines the surface characteristics of the developing sleeve 16 by the average toner particle size is used, the gap G is set to 0.3 <G <0.7 mm, preferably 0.4 <G <0.6 mm. By doing so, a higher quality image can be obtained.
[0008]
FIG. 3 is a schematic view showing grooves provided on the surface of the developing sleeve. The gap G between the developing sleeve 16 of the developing device 4 and the doctor blade 21 is set to 0.3 mm <G <0.7 mm. Further, a V-shaped groove 16b having an angle of 90 ° and a depth of 0.2 mm as shown in FIG. 3 was provided on the surface 16a of the developing sleeve 16 of the developing device 4. In the evaluation of the present invention, a sleeve having a diameter of 20 was used, and 50 V-shaped grooves were provided at regular intervals.
The surface 16a of the developer carrier 16 has V-shaped grooves 16b at regular intervals in the long axis direction. If the surface 16a of the developer carrier (developing sleeve) 16 is flat, the coefficient of friction between the developing sleeve 16 and the developer 18 (mainly the carrier) becomes low, and there is a concern that poor developer pumping may occur.
By providing the V-shaped groove 16b in the developing sleeve 16 used in the present invention, slippage between the surface 16a of the developing sleeve 16 and the developer 18 (mainly a carrier) is prevented, and the transportability is improved, thereby more stably. The developer 18 can be supplied.
As the toner 18 of the developer, a toner 18 having Dv of 4 to 8 μm and Dv / Dn of 1.05 to 1.30 is used (Dv is a volume average particle diameter, Dn is a number average particle diameter). In general, in the two-component developer 18, selective development (toner particles having a toner particle diameter according to an image pattern are selectively developed) occurs by circulation in the developing device 4 for a long period of time. The toner particles fluctuate. That is, the ratio of toner having a small particle size and toner having a large particle size tends to increase.
The cause of the sticking of the sleeve is that the toner stays in the developing sleeve 16. Further, the toner having a small particle diameter easily enters a small groove on the surface, which is a factor of accelerating the fixing of the sleeve. Therefore, if the toner particle diameter used satisfies Dv / Dn of 1.05 to 1.30, preferably 1.10 to 1.25, selective development is difficult to occur, and stable image without fluctuation in particle diameter over a long period of time. Can be obtained.
[0009]
Generally, it is said that the smaller the particle size of the toner 18 is, the more advantageous it is to obtain a high-resolution and high-quality image. However, it is disadvantageous to the transferability and the cleaning property. is there. Also in the present invention, when the volume average particle size is smaller than the specified range, there is a problem that the toner is fused to the surface of the carrier of the developer 18 during long-term stirring in the developing device 4 and the charging ability of the carrier is reduced.
Conversely, when the particle size of the toner is larger than the range of the present invention, it is difficult to obtain a high-resolution image with high resolution, and the toner particle size often fluctuates. The same applies when Dv / Dn is greater than 1.30.
Further, when Dv / Dn is smaller than 1.05, there is a preferable surface in terms of stabilizing the behavior of the toner and making the charge amount uniform. However, the thin line portion is developed with the small-sized particles, and the solid image is enlarged. Since it is difficult to separate functions based on the toner particle diameter, such as developing mainly particles of a size, it is not preferable.
The developing sleeve 16 provided with the V-shaped groove 16b and the toner having the above-mentioned particle diameter can provide a high-resolution and high-quality image and can prevent the sticking of the sleeve.
[0010]
Here, a method of measuring Dv / Dn will be described. A Coulter Counter TA-II (manufactured by Coulter Co., Ltd.) was used as an apparatus for measuring the particle size distribution of toner particles by the Coal Counter method.
0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution. Here, the electrolytic solution is prepared by adjusting about 1% NaCl aqueous solution using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter Inc.) can be used. Here, 2 to 20 mg of the measurement sample is further added.
The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the measurement device was used to measure the volume and the number of toner particles or toner using a 100 μm aperture as an aperture. Calculate volume distribution and number distribution. From the obtained distribution, the volume average particle diameter (Dv) and the number average particle diameter (Dn) of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 8.35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to less than 12.70 μm; 12.70 to less than 16.00 μm; 16.00 to less than 20.20 μm; 25 channels of less than 40 μm; 25.40 to less than 32.00 μm; using 13 channels of 32.00 to less than 40.30 μm, and targeting particles having a particle size of 2.00 μm or more and less than 40.30 μm.
In order to confirm the effect of the present invention, four developing sleeves were comparatively evaluated. Each characteristic value of the developing sleeve surface is as shown in Table 1.
[Table 1]

[0011]
FIG. 4 is a characteristic diagram showing the result of passing 50,000 images through four developing sleeves. The toner used had an average particle diameter of 6 μm. In the figure, the horizontal axis represents the gap G between the developing sleeve 16 and the doctor blade 21, and the vertical axis represents the sleeve fixing ID.
Here, the sleeve fixing ID is an ID measured by transferring the surface 16a of the developing sleeve 16 after image evaluation by tape transfer using a printer. If the sleeve fixing ID exceeds 0.1, an abnormal image such as density unevenness or background contamination is caused.
From this result, NO. 1 and NO. In the developing sleeve No. 2, no sleeve sticking occurs, and by setting the gap G between the developing sleeve 16 and the doctor blade 21 to 0.3 to 0.7, side effects such as poor image density and uneven density do not occur.
FIG. 5 is a characteristic diagram showing the results of image passing evaluation of 150,000 sheets of toner A in which Dv / Dn is initially set to 1.05 to 1.30 and toner B in which the particle diameter is not controlled. In FIG. 5, image passing evaluation of 150,000 sheets was performed using toner A with Dv / Dn of 1.05 to 1.30 in the initial state and toner B without particle size control. Further, the developing sleeve 16 has the NO. 1 and NO. 4, the gap G between the developing sleeve 16 and the doctor blade 21 was set to 0.5.
As a result, the toner B whose particle diameter is not controlled increases the ratio of the small particle diameter toner, so that the fixing of the sleeve with time is accelerated. However, the toner A whose shape is controlled has a small variation in particle size distribution over time, and therefore has a high margin for sticking to the sleeve even over time.
[0012]
【The invention's effect】
As described above, according to the first aspect, by using the developer carrier (developing sleeve) that satisfies the described surface conditions, it is possible to prevent an abnormal image such as a decrease in density due to sticking of the sleeve and a background stain. .
According to the second aspect, by defining the gap G between the developer carrying member and the developer regulating member, the supply amount of the developer is stabilized, so that a higher-quality and stable image can be supplied.
According to the third aspect, by providing V-shaped grooves on the surface of the developer carrier at equal intervals in the long axis direction, the supply amount of the developer is stabilized, so that a higher-quality and stable image can be supplied.
According to claim 4, since Dv is 4 to 8 μm and Dv / Dn is 1.05 to 1.30, not only high definition of a normal image but also stable image quality over time can be obtained. Images can be provided.
According to the fifth aspect, by using the above-described developing sleeve, it is possible to provide an image forming apparatus capable of providing a high-resolution and high-quality image and preventing the sleeve from sticking, thereby providing a stable image for a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image forming apparatus showing a developing device and a photoconductor unit.
FIG. 2 is a roughness curve diagram showing an average interval S between local peaks.
FIG. 3 is a schematic view showing grooves provided on the surface of a developing sleeve.
FIG. 4 is a characteristic diagram showing a result of passing 50,000 images through four developing sleeves.
FIG. 5 is a characteristic diagram showing results of image passing evaluation of 150,000 sheets of toner A in which Dv / Dn is initially set to 1.05 to 1.30 and toner B in which particle diameter is not controlled.
[Explanation of symbols]
4 Developing device 16 Developer carrier (developing sleeve)
16a Surface of the developing sleeve 16b V-shaped groove 18 on the surface of the developing sleeve 18 Developer (toner)
21 Developer regulating member (doctor blade)

Claims (5)

In a developing device including a rotating developer carrier and a developer regulating member that regulates a layer thickness of a two-component developer including a magnetic carrier and a toner laminated on the surface thereof, an average particle diameter of the toner is reduced. When the surface of the developer carrying member is D μm, the following conditions are satisfied.

(Rz: 10-point average roughness S: Average interval between local peaks)
A developing device characterized by satisfying the following. 2. The developing device according to claim 1, wherein a gap G between the developer carrier and the developer regulating member is set to 0.3 mm <G <0.7 mm. 3. 2. The developing device according to claim 1, wherein the surface of the developer carrier has V-shaped grooves at regular intervals in a longitudinal direction. 2. The toner according to claim 1, wherein Dv of the toner is 4 to 8 [mu] m, and Dv / Dn is 1.05 to 1.30 (Dv is a volume average particle diameter, and Dn is a number average particle diameter). Developing device. An image forming apparatus comprising the developing device according to claim 1.

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