JP3805113B2 - Charging method, charging device, and image recording apparatus using the charging device - Google Patents

Description

画像欠陥評価は中間調画像を出力して、画像の欠陥数から評価を行った。本画像形成装置（プリンタ）は６００ｄｐｉレーザスキャナを使用し画像形成を行った。本評価において中間調画像とは、主走査方向の１ラインを記録し、その後２ラインを非記録とする縞模様を意味し全体として中間調の濃度を再現している。本実施例では反転現像系で画像形成を行っているので、画像露光が阻害された場合、現像時にリークが生じた場合何れも、白点として画像に現れる。これらの欠陥部位の数を以下の基準で評価した。
【０１９６】
×：中間調画像中に直径０．３ｍｍ以上の白点が５０以上存在する
○：中間調画像中に直径０．３ｍｍ以上の白点が６〜４９存在する
◎：中間調画像中に直径０．３ｍｍ以上の白点が５以下である
また、評価はＡ４紙を用い１００枚（Ａ４縦方向）の印字を行った後に行った。
【０１９７】
比較例１においては、帯電促進粒子の脱落が多く、その後の露光あるいは現像時に画像欠陥を生じている。比較例において粒子の脱落が多いことは次のように予想するものである。
【０１９８】
帯電促進粒子ｍは、帯電ローラ２の相互に働く力は多くはファンワールス力による付着力や、帯電促進粒子が導電性若干の摩擦帯電特性をもつために生じる静電引力によるものと思われる。しかしながら、これらの力の大きさは決して多くなく帯電促進粒子は容易に感光ドラム１へと脱落してしまう。更に、これらの力は帯電促進粒子ｍが何層にも帯電ローラ２に塗布された場合、最表面の粒子の拘束力は更に小さなものとなり粒子の脱落が生じると予想される。帯電ローラ２上で帯電促進粒子ｍの層厚規制するため場所により粒子層が多くなる箇所が生じることは避け難い状況である。
【０１９９】
感光ドラム１へと脱落した帯電促進粒子ｍは、レーザスキャナなどによる画像情報記録時に未露光部を作り記録画像に欠陥を生じる。また、現像時には、感光ドラム１に上に存在する帯電促進粒子がトナーが感光ドラムに転写現像されるのを妨害する。あるいは、現像ローラに印加された現像バイアスのリークなどの弊害を生じ画像不良を起こす。
【０２００】
一方、実施例１においては、粒子の塗布を非画像記録時に行い、帯電ローラ２上に帯電促進粒子を馴染ませることで、何層にも粒子が塗布されている部分をなくし、均一に帯電ローラ２上に分布させる。この状態で画像記録を行うことで、帯電促進粒子ｍの脱落量を著しく減少させ画像欠陥を改善した。
【０２０１】
同様にして、実施例２においても、塗布形態はちがうものの、帯電促進粒子ｍを搬送塗布するファーブラシ３７の駆動を制御することで同問題を解決した。
【０２０２】
さらに、実施例３においては、塗布ローラ３９ｃを介して帯電ローラ２に塗布を行うよう構成し、塗布ローラ３９ｃを帯電ローラ２に離間可能に取り付けたことにより、同問題を解決した。
【０２０３】
実施例４においては、ドラムクリーナを配さずトナーリサイクルを実現する構成においても、帯電促進粒子の供給を非画像記録時におこなう事で同様の効果を得ている。
【０２０４】
〈その他〉
１）本発明において、像担持体としての感光体１の表面に電荷注入層を設けて感光体表面の抵抗を調節して用いた方が好ましい。
【０２０５】
図６は表面に電荷注入層１６を設けた感光体１の層構成模型図である。即ち該感光体１は、アルミドラム基体（Ａｌドラム基体）１１上に下引き層１２、正電荷注入防止層１３、電荷発生層１４、電荷輸送層１５の順に重ねて塗工された一般的な有機感光体に電荷注入層１６を塗布することにより、帯電性能を向上したものである。
【０２０６】
電荷注入層１６は、バインダーとしての光硬化型のアクリル樹脂に、導電性粒子（導電フィラー）としてのＳｎＯ₂ 超微粒子１６ａ（径が約０．０３μｍ）、重合開始剤等を混合分散し、塗工後、光硬化法により膜形成したものである。
【０２０７】
また、加えて４フッ化エチレン樹脂（商品名テフロン）などの滑剤も内包させることにより、感光体表面の表面エネルギーを抑えて、帯電促進粒子ｍの付着を全般的に抑える効果がある。
【０２０８】
電荷注入層１６として重要な点は、表層の抵抗にある。電荷の直接注入による帯電方式においては、被帯電体側の抵抗を下げることでより効率良く電荷の授受が行えるようになる。一方、感光体として用いる場合には静電潜像を一定時間保持する必要があるため、電荷注入層１６の体積抵抗値としては１×１０⁹ 〜１×１０¹⁴（Ω・ｃｍ）の範囲が適当である。
【０２０９】
また本構成のように電荷注入層１６を用いていない場合でも、例えば電荷輸送層１５が上記抵抗範囲に或る場合は同等の効果が得られる。
【０２１０】
さらに、表層の体積抵抗が約１０¹³Ωｃｍであるアモルファスシリコン感光体等を用いても同様な効果が得られる。
【０２１１】
２）可撓性の接触帯電部材としての帯電ローラ２は実施形態例の帯電ローラに限られるものではない。
【０２１２】
また可撓性の接触帯電部材は帯電ローラの他に、ファーブラシ、フェルト、布などの材質・形状のものも使用可能である。また、これらを積層し、より適切な弾性と導電性を得ることも可能である。
【０２１３】
３）接触帯電部材２や現像スリーブ４ａに対する印加バイアスにＡＣ電圧（交番電圧）を含ませる場合におけるそのＡＣ電圧の波形としては、正弦波、矩形波、三角波等適宜使用可能である。また、直流電源を周期的にオン／オフすることによって形成された矩形波であっても良い。このように交番電圧の波形としては周期的にその電圧値が変化するようなバイアスが使用できる。
【０２１４】
４）静電潜像形成のための画像露光手段としては、実施形態例の様にデジタル的な潜像を形成するレーザ走査露光手段に限定されるものではなく、通常のアナログ的な画像露光やＬＥＤなどの他の発光素子でも構わないし、蛍光燈等の発光素子と液晶シャッター等の組み合わせによるものなど、画像情報に対応した静電潜像を形成できるものであるなら構わない。
【０２１５】
５）像担持体は静電記録誘電体等であっても良い。この場合は、該誘電体面を所定の極性・電位に一様に一次帯電した後、除電針ヘッド、電子銃等の除電手段で選択的に除電して目的の静電潜像を書き込み形成する。
【０２１６】
６）現像手段４は実施形態例では一成分磁性トナーによる反転現像器を例に説明したが、現像器構成について特に限定するものではない。正規現像器であってもよい。
【０２１７】
７）像担持体からトナー画像の転写を受ける被記録体は転写ドラム等の中間転写体であってもよい。
【０２１８】
８）トナー粒度の測定方法の１例を述べる。測定装置としては、コールターカウンターＴＡ−２型（コールター社製）を用い、個数平均分布、体積平均分布を出力するインターフェイス（日科機製）及びＣＸ−１パーソナルコンピュータ（キヤノン製）を接続し、電解液は一級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調製する。
【０２１９】
測定法としては、前記電解水溶液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ホン酸塩０．１〜５ｍｌ加え、更に測定試料を０．５〜５０ｍｇ加える。
【０２２０】
試料を懸濁した電解液は、超音波分散器で約１〜３分間分散処理を行い、前記コールターカウンターＴＡ−２型により、アパーチャーとして１００μアパーチャーを用いて２〜４０μｍの粒子の粒度分布を測定して、体積平均分布を求める。これらの求めた体積平均分布より体積平均粒径を得る。
【０２２１】
【発明の効果】
以上述べたように本発明によれば、接触帯電部材として帯電ローラやファーブラシなど簡易な部材を用いた場合でも、また接触帯電部材の汚染にかかわらず、該接触帯電部材に対する帯電に必要な印加バイアスは被帯電体に必要な帯電電位相当の電圧で十分であり、放電現象を用いない安定かつ安全な接触帯電装置、即ち低印加電圧・オゾンレスで、帯電均一性に優れ且つ長期に渡り安定した性能の直接帯電装置を簡易な構成で実現することができる。
【０２２２】
そしてこの帯電装置を像担持体の帯電手段として用いることで、接触帯電方式の画像記録装置、接触帯電方式・転写方式の画像記録装置、さらには接触帯電方式・転写方式・トナーリサイクルシステムの画像記録装置について、接触帯電部材として帯電ローラやファーブラシ等の簡易な部材を用いて、また該接触帯電部材のトナー汚染にかかわらず、低印加電圧でオゾンレスの直接帯電とトナーリサイクルシステムを問題なく実行可能にし、高品位な画像形成を長期に渡り維持させること、画像比率の高い画像を出力した後でも高品位な画像形成を長期に渡り維持させること等ができる。
【０２２３】
非画像記録中に接触帯電部材に対する帯電促進粒子塗布を行い、接触帯電部材上に帯電促進粒子を十分に馴染ませてから画像記録動作にはいることで、帯電促進粒子の像担持体への脱落を十分に減少させて、画像欠陥を改善した。
【０２２４】
本構成は、接触帯電部材に対し拘束力の小さい帯電促進粒子の被帯電体もしくは像担持体への実質的な付着防止のためには非常に有効であり、付着量の低減は帯電促進粒子の節約からも大きなメリットである。
【０２２５】
また、帯電促進粒子を接触帯電部材上に均一に塗布することが困難であるため、塗布動作を止めてから回転することで接触帯電部材上の帯電促進粒子を均一化する効果もある。
【０２２６】
さらに、実施例１、同３特に同４においては、帯電促進粒子塗布手段がトナーによる汚染も防止でき、より長寿命の画像記録装置を構成可能である。
【図面の簡単な説明】
【図１】実施例１の画像記録装置の概略構成図
【図２】帯電促進粒子塗布手段の拡大模型図
【図３】実施例２の帯電促進粒子塗布手段の拡大模型図
【図４】実施例３の帯電促進粒子塗布手段の拡大模型図
【図５】実施例４の画像記録装置（クリーナレス）の概略構成図
【図６】表面に電荷注入層を設けた感光体の一例の層構成模型図
【図７】帯電特性グラフ
【符号の説明】
１ 感光ドラム（像担持体、被帯電体）
２ 帯電ローラ（接触帯電部材）
３Ａ・３Ｂ・３Ｃ 帯電促進粒子塗布手段
３０ 転写材（被記録体）
３１ 帯電促進粒子供給部材（帯電促進粒子チップ部材）
ｍ 帯電促進粒子
３２ チップ支持体
３３ ハウジング
３６ ソレノイド
３７ ファーブラシローラ
３９ｆ ファーブラシ
４ レーザビームスキャナ（露光器）
５ 現像器
５ａ 現像スリーブ
ｔ 現像剤（トナー）
６ 転写ローラ
７ 定着装置
８ クリーナ（感光ドラムクリーニング装置）
Ｓ１〜Ｓ３ バイアス印加電源[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging method and a charging device for charging an object to be charged. More specifically, the present invention relates to a charging method and a charging device for charging a surface of a member to be charged with a flexible charging member that forms a nip portion with the member to be charged.
[0002]
The present invention also relates to an image recording apparatus (image forming apparatus) such as a copying machine or a printer using the charging apparatus as a charging processing unit for an image carrier.
[0003]
[Prior art]
Conventionally, for example, in an image recording apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an image carrier (an object to be charged) such as an electrophotographic photosensitive member or an electrostatic recording dielectric is uniformly charged to a required polarity and potential. A corona charger (corona discharger) is often used as a charging device for processing (including charge removal processing).
[0004]
A corona charger is a non-contact type charging device. For example, a corona charger is provided with a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and a discharge opening is opposed to an image carrier as a charged body. The image carrier surface is charged to a predetermined level by exposing the image carrier surface to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode.
[0005]
Recently, medium- and low-speed image recording devices have advantages such as low ozone and low power compared to corona chargers as charging devices for charged objects such as image carriers. Many devices have been proposed and put into practical use.
[0006]
The contact charging device contacts a charged object such as an image carrier with a conductive charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type, and the charging member (contact charging member). A predetermined charging bias is applied to a contact charger (hereinafter referred to as a contact charging member) to charge the charged object surface to a predetermined polarity and potential.
[0007]
For charging mechanism of contact charging (charging mechanism, charging principle), (1). Discharge charging system and (2). Two types of charging mechanisms of the direct charging system coexist, and each characteristic appears depending on which is dominant.
[0008]
(1). Discharge charging system (discharge charging mechanism)
In this system, the surface of the member to be charged is charged by a discharge phenomenon generated in a minute gap between the contact charging member and the member to be charged.
[0009]
Since the discharge charging system has a constant discharge threshold value for the contact charging member and the member to be charged, it is necessary to apply a voltage larger than the charging potential to the contact charging member. Further, although the generation amount is remarkably smaller than that of the corona charger, it is unavoidable that a discharge product is generated in principle, and thus harmful effects due to active ions such as ozone are unavoidable.
[0010]
(2). Direct charging system (direct injection charging mechanism)
In this system, the surface of the charged body is charged by directly injecting the charge from the contact charging member to the charged body. It is also called direct charging, injection charging, or charge injection charging.
[0011]
More specifically, a medium-resistance contact charging member comes into contact with the surface of the member to be charged, and charge is directly injected into the surface of the member to be charged without going through a discharge phenomenon, that is, basically using no discharge. Therefore, even if the applied voltage to the contact charging member is an applied voltage that is equal to or lower than the discharge threshold, the object to be charged can be charged to a potential corresponding to the applied voltage. Since this direct charging system does not involve the generation of ions, no adverse effects caused by the discharge products occur.
[0012]
However, since it is directly charged, the contact property of the contact charging member to the member to be charged greatly affects the charging property. Therefore, the contact charging member needs to be configured more densely, have a large speed difference from the object to be charged, and must be configured to contact the object to be charged more frequently.
[0013]
A) Roller charging
In the contact charging device, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable in terms of charging stability and is widely used.
[0014]
The charging mechanism of the roller charging is dominated by the discharge charging system (1).
[0015]
The charging roller is made of a conductive or medium resistance rubber material or foam. In addition, there are those obtained by laminating these to obtain desired characteristics.
[0016]
The charging roller has elasticity in order to obtain a certain contact state with a member to be charged (hereinafter referred to as a photosensitive member), but has a large frictional resistance, and is often driven by the photosensitive member or at a slight speed. Driven with a difference. Therefore, even if direct charging is attempted, a decrease in absolute charging ability, lack of contactability, unevenness on the roller, and uneven charging due to the adherence of the photosensitive member cannot be avoided. The system is dominant.
[0017]
FIG. 7 is a graph showing an example of charging efficiency in contact charging. The horizontal axis represents the bias (applied DC voltage) applied to the contact charging member, and the vertical axis represents the photosensitive member charging potential (drum potential) obtained at that time.
[0018]
The charging characteristic in the case of conventional roller charging is represented by A. That is, charging starts after the discharge threshold of about −500V. Therefore, when charging to -500 V, apply a DC voltage of -1000 V, or in addition to a charging voltage of -500 V DC, apply an AC voltage with a peak-to-peak voltage of 1200 V so as to always have a potential difference greater than the discharge threshold. Thus, a method of converging the photoreceptor potential to the charging potential is common.
[0019]
More specifically, when the charging roller is brought into pressure contact with an OPC photoconductor having a thickness of 25 μm, the surface potential of the photoconductor starts to rise when a voltage of about 640 V or more is applied. Thereafter, the photosensitive member surface potential increases linearly with a slope of 1 with respect to the applied voltage. This threshold voltage is defined as the charging start voltage Vth.
[0020]
That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, the charging roller requires a DC voltage higher than that required, that is, Vd + Vth. A method of charging by applying only the DC voltage to the contact charging member in this way is referred to as a “DC charging method”.
[0021]
However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations, and Vth fluctuates when the film thickness changes due to the photoconductor being scraped. Therefore, the potential of the photoconductor is set to a desired value. It was difficult.
[0022]
Therefore, an AC component having a peak-to-peak voltage of 2 × Vth or more is added to a DC voltage corresponding to a desired Vd, as disclosed in Japanese Patent Laid-Open No. 63-149669, in order to further uniform charge. An “AC charging method” is used in which the superimposed voltage is applied to the contact charging member. This is for the purpose of smoothing the potential due to AC, and the potential of the charged body converges to Vd, which is the center of the peak of the AC voltage, and is not affected by disturbances such as the environment.
[0023]
However, even in such a contact charging device, the essential charging mechanism uses a discharge phenomenon from the contact charging member to the photosensitive member, so that the voltage applied to the contact charging member is photosensitive as described above. A value higher than the body surface potential is required, and a trace amount of ozone is generated.
[0024]
Further, when AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging sound) between the contact charging member and the photosensitive member due to an AC voltage electric field, and surface of the photosensitive member due to discharge As a result, the deterioration and the like became remarkable, which was a new problem.
[0025]
B) Fur brush charging
Fur brush charging uses a member (fur brush charger) having a conductive fiber brush portion as a contact charging member, and the conductive fiber brush portion is brought into contact with a photosensitive member as a member to be charged, and a predetermined charging bias is applied. This is applied to charge the photoreceptor surface to a predetermined polarity and potential.
[0026]
The charging mechanism of the fur brush charging is dominated by the discharge charging system (1).
Fur brush chargers are available in fixed and roll types. A fixed type is a medium-resistance fiber folded into a base fabric and bonded to an electrode. The roll type is formed by winding a pile around a metal core. The fiber density is 100 / mm ² However, the contact is still insufficient for sufficiently uniform charging by direct charging, and the mechanical structure for the photoreceptor is sufficient for sufficiently uniform charging by direct charging. It is necessary to have a speed difference that is difficult, which is not realistic.
[0027]
The charging characteristics of the fur brush charged when a DC voltage is applied are the characteristics shown in FIG. Accordingly, in the case of fur brush charging, both the fixed type and the roll type are charged using a discharge phenomenon by applying a high charging bias.
[0028]
C) Magnetic brush charging
Magnetic brush charging uses a member (magnetic brush charger) having a magnetic brush portion formed in a brush shape by magnetically constraining conductive magnetic particles with a magnet roll or the like as a contact charging member, and the magnetic brush portion is to be charged. And a predetermined charging bias is applied to charge the surface of the photosensitive member to a predetermined polarity and potential.
[0029]
In the case of this magnetic brush charging, the direct charging system (2) is dominant in the charging mechanism.
[0030]
By using conductive magnetic particles having a particle diameter of 5 to 50 μm constituting the magnetic brush portion and providing a sufficient speed difference from the photoreceptor, uniform direct charging is possible.
[0031]
As indicated by C in the charging characteristic graph of FIG. 7, it is possible to obtain a charging potential substantially proportional to the applied bias.
[0032]
However, there are other disadvantages such as a complicated apparatus configuration and conductive magnetic particles constituting the magnetic brush portion falling off and adhering to the photoreceptor.
[0033]
Japanese Patent Laid-Open No. 6-3921 proposes a method of injecting charges into a charge holding member such as a trap level on the surface of a photoreceptor or a conductive particle of a charge injection layer to perform contact injection charging. Since the discharge phenomenon is not used, the voltage required for charging is only the desired photoreceptor surface potential, and ozone is not generated. Furthermore, since no AC voltage is applied, no charging noise is generated, and this is an excellent charging system that is ozone-free and has low power compared to the roller charging system.
[0034]
D) Toner recycling system (cleanerless)
In the transfer type image recording apparatus, the developer (toner) remaining on the photoconductor (image carrier) after transfer is removed from the photoconductor surface by a cleaner (cleaning device) to become waste toner. It is desirable that waste toner does not come out from the viewpoint of environmental protection. Therefore, the toner recycling system (or toner recycling system) is configured to eliminate the cleaner and remove the transfer residual toner on the photosensitive member after transfer from the photosensitive member by “development simultaneous cleaning” by the developing device and collect and reuse it in the developing device. Process) image recording devices have also appeared.
[0035]
Simultaneous development cleaning refers to the toner remaining on the photoconductor after the transfer, during the subsequent development, that is, the photoconductor is subsequently charged and exposed to form a latent image, and a fog removal bias ( This is a method of recovery by a fog removal potential difference Vback, which is a potential difference between the DC voltage applied to the developing device and the surface potential of the photoreceptor. According to this method, since the transfer residual toner is collected by the developing device and reused after the next step, waste toner can be eliminated, and troublesome maintenance can be reduced. In addition, the cleanerless has a great space advantage, and the image recording apparatus can be greatly downsized.
[0036]
Since the toner recycling system does not remove the transfer residual toner from the surface of the photosensitive member by a dedicated cleaner as described above, it reaches the developing device via the charging unit and is used again in the development process. When contact charging is used as the charging means for the photosensitive member, how to charge the photosensitive member with an insulating toner interposed in the contact portion between the photosensitive member and the contact charging member is a problem. . In the above-described roller charging or fur brush charging, the transfer residual toner on the photosensitive member is diffused and non-patterned, and charging by discharging by applying a large ba ice is often used. In magnetic brush charging, powder is used as the contact charging member, so there is an advantage that the magnetic brush portion of the conductive magnetic particles, which is the powder, can flexibly contact the photoconductor to charge the photoconductor, but the device configuration is complicated. That is, the harmful effect caused by dropping off of the conductive magnetic particles constituting the magnetic brush portion is great.
[0037]
E) Powder application to contact charging member
Japanese Patent Publication No. 7-99442 discloses a contact charging device in which powder is applied to a contact surface between a contact charging member and a surface to be charged in order to prevent uneven charging and perform stable uniform charging. The contact charging member (charging roller) is driven to rotate (no speed difference drive), and the generation of ozone products is significantly less than that of corona chargers such as scorotron. As in the case of the roller charging described above, the charging principle is still mainly based on charging by discharge. In particular, in order to obtain more stable charging uniformity, a voltage obtained by superimposing an AC voltage on a DC voltage is applied, and therefore, more ozone products are generated due to discharge. Therefore, when the apparatus is used for a long period of time or when a cleanerless image recording apparatus is used for a long period of time, adverse effects such as image flow due to ozone products tend to appear.
[0038]
Japanese Patent Application Laid-Open No. 5-150539 discloses that in an image forming method using contact charging, charging inhibition due to toner particles and silica fine particles adhering to the surface of the charging means during repeated image formation for a long time is prevented. For this reason, it is disclosed that the developer contains at least visible particles and conductive particles having an average particle size smaller than the visible particles. However, this contact charging is based on the discharge charging mechanism, not the direct injection charging mechanism, and has the above-described problems due to discharge charging.
[0039]
[Problems to be solved by the invention]
1) As described in the section of the prior art, in the conventional contact charging, the surface of the contact charging member can be directly charged with a simple structure using a charging roller or a fur brush as the contact charging member. However, the contact with the member to be charged was not ensured, and direct charging was impossible.
[0040]
Further, the contact charging member is likely to be contaminated by picking up foreign matter from the surface of the charged body, and if the adhered dirt is insulative, charging failure is likely to occur.
[0041]
Therefore, in contact charging, even when a simple member such as a charging roller or a fur brush is used as the contact charging member, direct charging that is superior in charging uniformity and stable over a long period of time regardless of contamination of the contact charging member. That is, it is expected to realize ozone-less injection charging with a simple configuration at a low applied voltage.
[0042]
An object of the present invention is to meet the above-described demand for a contact charging method and a contact charging device.
[0043]
2) In the image recording apparatus, when a contact charging device is adopted as the charging means of the image carrier, ozone-less injection charging is realized at a low applied voltage with a simple configuration using a charging roller or a fur brush as a contact charging member. If possible, it is extremely effective in terms of apparatus configuration and performance.
[0044]
In addition, in the case of a transfer type image recording apparatus adopting a contact charging device as a charging means for the image carrier, a developer image (toner image) formed and supported on the image carrier is transferred to the recording material with respect to contamination of the contact charging member. Even in the case of an image recording apparatus equipped with a dedicated cleaner for removing the transfer residual toner on the image carrier after the transfer, it is difficult to completely remove the transfer residual toner on the image carrier with the cleaner. The toner that slightly passes through the cleaner is carried to the charging part, which is the contact part between the contact charging member and the image carrier, by the movement of the surface of the image carrier, and adheres to and mixes with the contact charging member. Gradually contaminated with toner.
[0045]
Since conventional toner is an insulator, the presence of toner in the charging portion, which is the contact portion between the contact charging member and the image carrier, or contamination of the contact charging member with the toner is a charge inhibiting factor, and charging It will cause defects.
[0046]
In particular, the image recording apparatus of the toner recycling system (cleanerless) does not use a dedicated cleaner for removing the transfer residual toner on the surface of the image carrier after the transfer, and therefore the transfer residual toner on the surface of the image carrier after the transfer. Is carried as it is by the movement of the surface of the image carrier to the charging portion which is the contact portion between the image carrier and the contact charging member, so that the contact charging member is significantly contaminated with toner.
[0047]
Accordingly, the present invention relates to a contact charging type image recording apparatus, a contact charging type / transfer type image recording apparatus, and a contact charging type / transfer type / toner recycling system image recording apparatus. Using a simple member such as a brush, and regardless of toner contamination of the contact charging member, ozone-less direct charging and toner recycling system can be executed without problems at a low applied voltage, and high-quality image formation can be performed over a long period of time. The purpose is to maintain high-quality image formation over a long period of time even after outputting an image with a high image ratio.
[0048]
[Means for Solving the Problems]
The present invention is a charging method, a charging device, and an image recording apparatus using the charging device, characterized by the following configuration.
[0049]
(1) A charging method for charging the surface of a member to be charged with a flexible charging member that forms a nip portion with the member to be charged;
The charging member moves with a speed difference with respect to the member to be charged, and has charging promoting particle supplying means for supplying charging promoting particles to the charging member,
A mode for supplying the charge promoting particles from the charge promoting particle supplying means to the charging member; After A mode, A charging method comprising: a B mode in which an object to be charged is charged without supplying charging promoting particles from a charging promoting particle supplying unit to a charging member.
[0050]
(2) The A mode is an A1 mode in which the charge promoting particles are supplied from the charge promoting particle supplying means to the charging member; After A1 mode The charging method according to (1), which comprises an A2 mode in which the charged body and the charging member are driven and the charge accelerating particles are adapted to the charging member.
[0051]
(3) The volume resistance of the charge promoting particles is 10 ¹² The charging method according to (1) or (2), wherein the charging method is Ω · cm or less.
[0052]
(4) The volume resistance of the charge promoting particles is 10 ^Ten The charging method according to (1) or (2), wherein the charging method is Ω · cm or less.
[0053]
(5) The charging method according to any one of (1) to (4), wherein a voltage is applied to the charging member.
[0054]
(6) The charging method according to any one of (1) to (5), wherein the member to be charged and the charging member move in opposite directions at the nip portion.
[0055]
(7) A charging device that charges the surface of a member to be charged with a flexible charging member that forms a nip portion with the member to be charged;
The charging member moves with a speed difference with respect to the member to be charged, and has charging promoting particle supplying means for supplying charging promoting particles to the charging member,
As an operation mode of the apparatus, A mode in which the charge promoting particles are supplied from the charge promoting particle supplying means to the charging member, and B to charge the object to be charged without supplying the charge promoting particles from the charging promoting particle supplying means to the charging member. A charging device having a mode.
[0056]
(8) The A mode includes an A1 mode in which the charge accelerating particles are supplied from the charge accelerating particle supply means to the charging member, and an A2 mode in which the charged object and the charging member are driven to adjust the charging accelerating member to the charging member. (6) The charging device according to (7).
[0057]
(9) The volume resistance of the charge promoting particles is 10 ¹² The charging device according to (7) or (8), wherein the charging device is Ω · cm or less.
[0058]
(10) The volume resistance of the charge promoting particles is 10 ^Ten The charging device according to (7) or (8), wherein the charging device is Ω · cm or less.
[0059]
(11) The charging device according to any one of (7) to (10), wherein a voltage is applied to the charging member.
[0060]
(12) The charging device according to any one of (7) to (11), wherein the member to be charged and the charging member move in opposite directions at the nip portion.
[0061]
(13) An image recording apparatus that performs image recording by applying an image forming process including a step of charging the image carrier to the image carrier,
The process means for charging the image bearing member is the charging device according to any one of (7) to (12),
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode.
[0062]
(14) Image carrier, charging means for charging the image carrier, information writing means for forming an electrostatic latent image on the charging surface of the image carrier, and development for visualizing the electrostatic latent image with a developer And an image recording apparatus that is repeatedly used for image formation, and a transfer unit that transfers the developer image to the recording medium, and a cleaning unit that cleans the transferred image carrier. ,
The process means for charging the image bearing member is the charging device according to any one of (7) to (12),
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode.
[0063]
(15) Image carrier, charging means for charging the image carrier, information writing means for forming an electrostatic latent image on the charging surface of the image carrier, and development for visualizing the electrostatic latent image with a developer And a transfer means for transferring the developer image to the recording medium. The developer remaining on the image carrier after the developing means transfers the developer image to the recording medium is temporarily transferred to at least the charging means. An image recording apparatus having an image carrier cleaner-less configuration that is carried and collected again by the developing means through the image carrier,
The process means for charging the image bearing member is the charging device according to any one of (7) to (12),
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode.
[0064]
(16) The image recording apparatus according to (14) or (15), wherein the information writing means for forming an electrostatic latent image on the charging surface of the image carrier is an image exposure means.
[0065]
<Operation>
a) The charge accelerating particles are conductive particles for the purpose of assisting charging, and uniform and stable direct charging is realized by using these particles. The volume resistance of the charge promoting particles is 1 × 10 ¹² Ω · cm or less, more preferably 1 × 10 ^Ten It is desirable that it is below Ω · cm.
[0066]
That is, the above-described charging promoting particles are charged from a charging promoting particle supplying member that contacts the charging member or via a charging promoting particle applying member with respect to a flexible charging member that forms a nip portion with a charged body. By being supplied from the accelerating particle supply member, contact charging of the object to be charged is performed in a state where the charge accelerating particles are present in the charging part which is a nip part between the object to be charged and the contact charging member.
[0067]
b) Since the charge promoting particles are present in the charging portion, which is the nip portion between the charged body and the contact charging member, the frictional effect of the particles increases the frictional resistance, so that the speed difference with respect to the charged body remains as it is. Even a charging roller that was difficult to hold and contact can be brought into contact with the surface of the object to be charged easily and effectively with a speed difference. At the same time, the charge accelerating particles fill the unevenness of the contact charging member to improve the contact property with respect to the object to be charged, and the contact charging member comes into close contact with the surface of the object to be charged through the particles and more frequently contacts the surface of the object to be charged. It becomes the structure which contacts.
[0068]
By providing a speed difference between the contact charging member and the member to be charged, the chance of the charge accelerating particles coming into contact with the member to be charged at the nip portion between the contact charging member and the member to be charged is greatly increased and high contact is achieved. The charge accelerating particles present in the nip portion between the contact charging member and the object to be charged can rub the surface of the object to be charged without any gap so that the charge can be directly injected into the object to be charged. Direct charging (injection charging) is dominant in the contact charging of the member to be charged by the charging member due to the presence of the charge accelerating particles.
[0069]
c) As a configuration for providing a speed difference, the contact charging member is rotationally driven to provide a speed difference with the charged body. Although it is possible to move the contact charging member in the same direction as the movement direction of the surface of the member to be charged, a difference in speed is possible, but the charging property of injection charging is the ratio of the peripheral speed of the member to be charged and the peripheral speed of the contact charging member. Therefore, in order to obtain the same peripheral speed ratio as in the reverse direction, the rotational speed of the contact charging member is larger in the forward direction than in the reverse direction. This is advantageous.
[0070]
The peripheral speed ratio described here is
Peripheral speed ratio (%) = (charging member peripheral speed−charged object peripheral speed) / charged object peripheral speed × 100
(The charging member peripheral speed is a positive value when the surface of the charging member moves in the same direction as the surface of the member to be charged in the nip portion).
[0071]
d) When an insulating material that is a charge-inhibiting factor is present in the charging portion, which is the nip portion between the object to be charged and the contact charging member, or the contact charging member is contaminated with such an insulating material. However, since the charge promoting particles are present in the charging portion, which is the nip portion between the charged body and the contact charging member, the contact charging member can be kept in close contact with the charged body and the contact resistance can be maintained. Ozone-less direct charging can be stably maintained over a long period of time by voltage, and uniform chargeability can be provided.
[0072]
e) By providing a supply means for supplying the charge accelerating particles to the contact charging member, even if the charge accelerating particles fall off from the charging portion, which is the nip portion between the charged object and the contact charging member, as the apparatus is used. The charging portion is replenished with the charging portion, and the charging characteristics are prevented from being lowered due to dropping / decreasing of the charging promoting particle from the charging portion, so that the direct charging property can be stably maintained over a long period of time.
[0073]
f) Charge accelerating particles intervening in the charging portion, which is the nip portion between the member to be charged and the contact charging member, adhere to the member to be charged together with the charging operation, and decrease if the charge accelerating particles existing around the contact charging member are not replenished. However, in the present invention, the charge promoting particles are applied and supplied to the contact charging member by the charge promoting particle supplying means.
[0074]
However, the charge accelerating particles applied and supplied to the contact charging member may adhere excessively to the member to be charged due to repeated charging, which may adversely affect the subsequent process. In the image recording apparatus, the excessive charge promoting particles existing on the member to be charged, that is, the image carrier, may cause problems such as blocking exposure light when forming a latent image by image exposure in the subsequent process. Further, adverse effects may occur in the subsequent development process using toner.
[0075]
Accordingly, in the application and supply of the charge accelerating particles to the contact charging member, the charge accelerating particles are stably supplied to obtain uniform chargeability, and the adhesion of the charge accelerating particles to the charged body is reduced as much as possible. It is important to form a recorded image without image defects.
[0076]
In the present invention, A mode for supplying the charge promoting particles from the charge promoting particle supplying means to the contact charging member, After A mode, By providing a B mode that charges the object to be charged without supplying the charge accelerating particles from the charge accelerating particle supplying means to the contact charging member, the charge accelerating particles are moved by the operation in the B mode when the operation requires uniform charging. The charge-promoting particles are supplied to the contact charging member in the A mode during an operation in which the charging target is prevented from falling off and uniform charging is not required.
[0077]
Accordingly, it is possible to perform an excellent charging process that does not excessively contaminate the charged object with the charge accelerating particles while performing charging by direct charge injection without discharge.
[0078]
The A mode is an A1 mode in which the charge promoting particles are supplied from the charge promoting particle supplying means to the contact charging member, After A1 mode By adopting the A2 mode in which the charged body and the contact charging member are driven and the charge promoting particles are made to conform to the charging member, dropping of the charge promoting particles can be more reliably reduced.
[0079]
In addition, the object to be charged and the contact charging member are driven so as to move in opposite directions at the nip portion, so that charging efficiency can be further improved and dropping of the charge accelerating particles can be sufficiently reduced.
[0080]
Therefore, in the image recording apparatus, it is possible to prevent adverse effects caused by excessive charge accelerating particles that fall off on the image carrier, that is, image defects such as image defects occur during exposure and development after the charging process. Can be prevented.
[0081]
In an image recording apparatus having a cleaner-less structure, toner recycling and direct injection charging are realized, and dropping of charged particles from the contact charging member is sufficiently reduced. , No image defects , An excellent image recording apparatus can be configured.
[0082]
g) Thus, a high charging efficiency that could not be obtained by conventional roller charging or the like can be obtained, and a charging potential almost equal to the voltage applied to the contact charging member can be given to the member to be charged. Even when a simple member such as a brush or a fur brush is used, a voltage equivalent to the charging potential necessary for the object to be charged is sufficient as the bias applied to the contact charging member regardless of contamination of the contact charging member. In addition, a stable and safe contact charging device that does not use a discharge phenomenon, that is, a direct charging device that has low applied voltage and ozoneless, excellent charging uniformity, and stable performance over a long period of time can be realized with a simple configuration.
[0083]
h) By using the above charging device as the charging means of the image carrier, contact charging type image recording device, contact charging type / transfer type image recording device, and further contact charging type / transfer type / toner recycling system For image recording devices, a simple member such as a charging roller or fur brush is used as a contact charging member, and ozone-less direct charging and toner recycling system can be performed at low voltage regardless of toner contamination. This makes it possible to maintain high-quality image formation over a long period of time, and maintain high-quality image formation over a long period of time even after outputting an image with a high image ratio.
[0084]
In the image recording apparatus of the toner recycling system (cleanerless), since the contact charging member is in contact with the image carrier with a speed difference, the contact charging member and the image carrier are separated from the transfer unit. The pattern of the residual toner that has reached the charging portion, which is the nip portion, is disturbed and broken, and the previous image pattern portion does not appear as a ghost in the halftone image.
[0085]
Since the charge-promoting particles are present in the charging portion that is the nip portion between the contact charging member and the image carrier, the contact charging member can be maintained in close contact with the image carrier and the contact resistance can be maintained. Regardless of contamination by residual toner, ozone-less direct charging can be stably maintained over a long period of time with a low applied voltage, and uniform charging properties can be provided.
[0086]
i) The transfer residual toner adhering to and mixed in the contact charging member is gradually discharged from the contact charging member onto the image carrier, reaches the development site along with the movement of the image carrier surface, and is simultaneously cleaned (collected) by the developing means. (Toner recycling).
[0087]
DETAILED DESCRIPTION OF THE INVENTION
<Example 1> (FIG. 1)
FIG. 1 is a schematic structural model diagram of an example of an image recording apparatus according to the present invention.
[0088]
The image recording apparatus of the present embodiment is a contact charging type laser printer using a transfer type electrophotographic process.
[0089]
(1) Overall schematic configuration of printer
Reference numeral 1 denotes an image carrier, and in this embodiment, a φ30 mm rotating drum type negative-polarity OPC photoreceptor (negative photoreceptor, hereinafter referred to as a photosensitive drum). The photosensitive drum 1 is rotationally driven at a constant speed of 50 mm / sec (= process speed PS, printing speed) in the clockwise direction of the arrow.
[0090]
Reference numeral 2 denotes a conductive elastic roller (hereinafter referred to as a charging roller) as a contact charging member disposed in contact with the photosensitive drum 1 with a predetermined pressing force.
[0091]
n is a charging nip portion which is a nip portion between the photosensitive drum 1 and the charging roller 2.
Reference numeral 3A denotes a charge accelerating particle supply means for the charging roller 2. The charge accelerating particle supply means 3A applies and supplies the charge accelerating particles m to the outer peripheral surface of the charging roller 2, and the nip portion between the photosensitive drum 1 and the charging roller 2 is supplied. The charge promoting particles m are interposed in the charging nip n.
[0092]
The charging roller 2 is rotationally driven in the reverse direction (counter) with respect to the rotation direction of the photosensitive drum 1 at the charging nip n, and contacts the surface of the photosensitive drum 1 with a speed difference. M is a drive source of the charging roller 2.
[0093]
A predetermined charging bias, in this example, a DC voltage of −700 V, is applied to the charging roller 2 from the charging bias application power source S1.
[0094]
As a result, the peripheral surface of the rotating photosensitive drum 1 is uniformly contact-charged to substantially the same potential as the applied charging bias applied to the charging roller 2 by a direct charging (injection charging) method.
[0095]
The charging roller 2, the charge accelerating particle supply means 3A, direct charging and the like will be described in detail in another section.
[0096]
Reference numeral 4 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like. This laser beam scanner 4 performs time-series electrical processing of target image information. Digital A laser beam whose intensity is modulated corresponding to the pixel signal is output, and the uniformly charged surface of the rotating photosensitive drum 1 is scanned and exposed L with the laser beam.
[0097]
By this scanning exposure L, an electrostatic latent image corresponding to target image information is formed on the surface of the rotary photosensitive drum 1.
[0098]
Reference numeral 5 denotes a developing device. The electrostatic latent image on the surface of the rotary photosensitive drum 1 is developed as a toner image by the developing unit 5 at the development site a.
[0099]
The developing device 5 of this embodiment is a reversal developing device using a one-component magnetic toner (negative toner) as the developer t. Reference numeral 5a denotes a non-magnetic rotating developing sleeve as a developer carrying member enclosing a magnet roll 5b. The toner t as a developer in the developing device 5 is regulated in the process of being conveyed on the rotating developing sleeve 5a. The blade 5c is subjected to layer thickness regulation and charge application.
[0100]
The toner t coated on the rotating developing sleeve 5a is conveyed to a developing portion (developing region) a which is a portion facing the photosensitive drum 1 and the sleeve 5a by the rotation of the sleeve 5a. A developing bias voltage is applied to the sleeve 5a from a developing bias applying power source S2.
[0101]
In this embodiment, the developing bias voltage is
DC voltage: -500V
AC voltage: Peak-to-peak voltage 1600V, frequency 1.8kHz, rectangular wave
The superimposed voltage was
[0102]
As a result, the electrostatic latent image on the photosensitive drum 1 side is reversely developed with the toner t.
[0103]
The one-component magnetic toner t, which is a developer, is prepared by mixing binder resin, magnetic particles, and charge control agent, and kneading, pulverizing, and classifying, and then adding a fluidizing agent as an external additive. It was created. The weight average particle diameter (D4) of the toner was 7 μm.
[0104]
Reference numeral 6 denotes a medium resistance transfer roller as a contact transfer means, which is brought into pressure contact with the photosensitive drum 1 to form a transfer nip portion b. A transfer material 30 as a recording medium is fed to the transfer nip b from a paper feed unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 6 from a transfer bias application power source S3. As a result, the toner image on the photosensitive drum 1 side is sequentially transferred onto the surface of the transfer material 30 fed to the transfer nip b.
[0105]
The transfer roller 6 used in this embodiment has a roller resistance value of 5 × 10, in which a medium resistance foam layer 6b is formed on a cored bar 6a. ⁸ The transfer was performed by applying a voltage of +2.0 kV to the cored bar 6a. The transfer material 30 introduced into the transfer nip portion b is nipped and conveyed by the transfer nip portion b, and the toner images formed and supported on the surface of the rotary photosensitive drum 1 on the surface side thereof are successively subjected to electrostatic force and pressing force. Will be transcribed.
[0106]
Reference numeral 7 denotes a fixing device such as a heat fixing method. The transfer material 30 that has been fed to the transfer nip b and has received the transfer of the toner image on the photosensitive drum 1 side is separated from the surface of the rotating photosensitive drum 1 and introduced into the fixing device 7 to receive the toner image fixing. It is discharged out of the apparatus as an image formed product (print, copy).
[0107]
Reference numeral 8 denotes a photosensitive drum cleaner (cleaning device). The rotary photosensitive drum 1 after the transfer of the toner image to the transfer material P has a cleaning blade (elastic blade) in which the residual toner remaining on the drum surface is in contact with the cleaning member 8a of the cleaner 8, in this example, the photosensitive drum 1 surface. Is scraped off, cleaned, and repeatedly used for image formation. Transfer residual toner scraped from the surface of the photosensitive drum 1 by the cleaning blade 8a is accumulated as waste toner in the cleaner container.
[0108]
(2) Charging roller 2
The charging roller 2 as a flexible contact charging member in this embodiment is formed by forming a middle resistance layer 2b of rubber or foam on a core metal 2a.
[0109]
The middle resistance layer 2b is formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfurizing agent, a foaming agent, and the like, and is formed in a roller shape on the core metal 2a. Thereafter, the surface was polished as necessary to prepare a charging roller 2 which is a conductive elastic roller having a diameter of 12 mm and a longitudinal length of 200 mm.
[0110]
The roller resistance of the charging roller 2 of this example was measured and found to be 100 kΩ. The roller resistance is measured by applying 100 V between the core metal 2a and the aluminum drum in a state where the charging roller 2 is pressure-bonded to a 30 mm diameter aluminum drum so that the total pressure of 1 kg is applied to the core metal 2a of the charging roller 2. did.
[0111]
Here, it is important that the charging roller 2 as a contact charging member functions as an electrode. In other words, it is necessary to provide a sufficient contact state with the member to be charged by providing elasticity, and at the same time to have a sufficiently low resistance to charge the moving member to be charged. On the other hand, it is necessary to prevent voltage leakage when a low-voltage defect site such as a pinhole is present in the member to be charged. When an electrophotographic photosensitive member is used as the member to be charged, 10 is necessary to obtain sufficient chargeability and leakage resistance. ^Four -10 ⁷ A resistance of Ω is desirable.
[0112]
It is desirable that the surface of the charging roller 2 has micro unevenness so that the charge accelerating particles m can be held.
[0113]
If the hardness of the charging roller 2 is too low, the shape is not stable, so that the contact with the member to be charged is deteriorated. If the hardness is too high, the charging nip n cannot be secured between the member and the member to be charged. Since the micro contact property to the surface of the member to be charged is deteriorated, the preferred Asker C hardness is 25 to 50 degrees.
[0114]
The material of the charging roller 2 is not limited to the elastic foam, and the material of the elastic body may be EPDM, urethane, NBR, silicone rubber, or the like such as carbon black or metal oxide for resistance adjustment to IR or the like. Examples thereof include a rubber material in which a conductive material is dispersed and a foamed material of these materials. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance.
[0115]
The charging roller 2 is disposed in contact with the photosensitive drum 1 as a member to be charged against elasticity with a predetermined pressing force, and in this embodiment, a charging nip portion n having a width of several millimeters is formed.
[0116]
In this embodiment, the charging roller 2 is driven to rotate in the clockwise direction of the arrow at about 80 rpm so that the surface of the charging roller and the surface of the photosensitive member move at the same speed in the opposite directions in the charging nip portion n. That is, the surface of the charging roller 2 as the contact charging member has a speed difference with respect to the surface of the photosensitive drum 1 as the member to be charged.
[0117]
Then, a DC voltage of −700 V was applied as a charging bias from the power source S1 to the metal core 2a of the charging roller 2.
[0118]
(3) Charge accelerating particle supply means 3A
FIG. 2 is an enlarged model view of the charge accelerating particle supply means 3A. In this embodiment, the charge accelerating particle supply means 3A includes a charge accelerating particle supply member 31, a support 32 of the charge accelerating particle supply member, and a pressure applied to the charge roller 2 by the charge accelerating particle supply member 31 connected to the support. The pressure control means 36 for controlling the operation, the transmission means 34 for transmitting the power from the control means, the housing 33 in which the charge accelerating particle supply member 31 is accommodated, and the like are disposed on the upper side of the charging roller 2. The lower surface of the charge accelerating particle supply member 31 in the housing 33 is always in contact with the upper surface of the charging roller 2 by the weight of the charge accelerating particle supply member 31 and the support 32 of the member.
[0119]
The pressing control means 36 is constituted by, for example, a solenoid coil, and performs a pressing operation and a releasing operation. The solenoid 36 that is the pressing control means is configured to push out the yoke (plunger) 36a when the coil in the solenoid is energized.
[0120]
When the coil of the solenoid 36 is energized (solenoid-on), as shown in FIG. 2A, the solenoid yoke 36a pushes down the transmission means 34 against the spring 35, and the charge accelerating particle supply member 31 It will be in the state contact | abutted with the dead weight containing the support body 32. FIG.
[0121]
On the other hand, when the coil of the solenoid 36 is not energized (solenoid-off), the transmission means 34 is pushed up by the spring 35 as shown in FIG. The body 32 is pulled up, and the charge accelerating particle supply member 31 is not in contact with the charging roller 2.
[0122]
The solenoid 36 is controlled to be turned on / off in this manner, whereby the contact and release of the charge accelerating particle supply member 31 with respect to the charging roller 2 are controlled.
[0123]
The charge accelerating particle supply member 31 is a member obtained by binding and solidifying the charge accelerating particles m in a chip shape (charge accelerating particle chip member), and can be cut by itself like white ink or wax stone by contact with the rotating charging roller 2. This is a member for applying and supplying the charge accelerating particles m to the surface of the charging roller 2.
[0124]
For example, it is a chip-like one in which charging promoting particles m such as zinc oxide particles and alumina powder are bound in a solvent with a binder resin. As a specific formulation, a styrene acrylic resin as a binder resin is dissolved in ethanol at a concentration of 5 wt%, and the charge promoting particles m such as zinc oxide particles 7 times by weight with respect to the binder resin 1 are mixed. Then, this solution is put into a mold, shaped and dried to obtain the charge accelerating particle supply member 31 in a form in which the charge accelerating particles m are bound and solidified in a chip shape.
[0125]
In this embodiment, the charge promoting particles m have a specific resistance of 10 ⁶ An alumina powder having an Ω · cm and an average particle diameter of 3 μm was used.
[0126]
As the material of the charge accelerating particles m, various conductive particles such as conductive inorganic particles such as other metal oxides, mixtures with organic substances, or those obtained by subjecting them to surface treatment can be used.
[0127]
The particle resistance is 10 to 10 because the specific resistance is exchanged through particles. ¹² Ω · cm or less is required, more preferably 10 ^Ten Ω · cm or less is desirable.
[0128]
The resistance was measured by the tablet method and normalized. That is, the bottom area 2.26cm ² Approximately 0.5 g of a powder sample was placed in the cylinder, and 15 kg of pressure was applied to the upper and lower electrodes. At the same time, a voltage of 100 V was applied to measure the resistance value, and then normalized to calculate the specific resistance.
[0129]
The particle size is desirably 50 μm or less in order to obtain good charging uniformity. In the present invention, the particle diameter when the particles constitute an aggregate is defined as the average particle diameter as the aggregate. For the measurement of the particle size, 100 or more samples were extracted from observation with an optical or electron microscope, the volume particle size distribution was calculated with the maximum horizontal chord length, and the 50% average particle size was determined.
[0130]
There is no problem that the charge promoting particles exist not only in the state of primary particles but also in the state of aggregation of secondary particles. In any aggregate state, the form is not important as long as the function as the charge promoting particles can be realized as the aggregate.
[0131]
As the charge accelerating particles, colorless or white particles are suitable so as not to interfere with the latent image exposure particularly when used for charging the photoreceptor.
[0132]
Further, it is desirable that the charge accelerating particles are white or transparent so as not to hinder exposure, and are preferably non-magnetic.
[0133]
Further, considering that the charge accelerating particles are partially transferred from the photoreceptor to the recording medium P, it is desirable that the color recording is colorless or white. In order to prevent light scattering by particles during image exposure, the particle size is desirably equal to or smaller than the constituent pixel size. As the lower limit of the particle size, 10 nm is considered to be the limit as a particle that can be stably obtained.
[0134]
(4) Direct charging
The charge accelerating particle m is applied and supplied by the charge accelerating particle chip member 31 of the charge accelerating particle supply means 3A that comes into contact with the charging roller 2 so that the charging nip portion between the photosensitive drum 1 and the charging roller 2 is supplied. Contact charging of the photosensitive drum 1 is performed in a state where the charge promoting particles m exist in n.
[0135]
That is, the presence of the charge accelerating particles m in the charging nip n between the photosensitive drum 1 and the charging roller 2 results in a large frictional resistance due to the lubricant effect of the particles m, and the speed difference with respect to the photosensitive drum 1 is left as it is. Even a charging roller that is difficult to hold and contact can be brought into contact with the surface of the photosensitive drum 1 without difficulty and with an effective speed difference. At the same time, the charging roller 2 comes into close contact with the surface of the photosensitive drum 1 through the particles m, that is, the charge accelerating particles fill the unevenness of the charging roller which is a contact charging member, with respect to the photosensitive drum 1 which is an object to be charged. The contact property is improved and the photosensitive drum 1 surface is contacted more frequently.
[0136]
Since a speed difference can be provided between the charging roller 2 and the photosensitive drum 1, the chance of the charge accelerating particles m contacting the photosensitive drum 1 at the nip portion between the charging roller 2 and the photosensitive drum 1 is remarkably increased. The contact property can be obtained, and the charge accelerating particles m existing in the nip portion between the charging roller 2 and the photosensitive drum 1 can rub the surface of the photosensitive drum 1 without gap so that the charge can be directly injected into the photosensitive drum 1. The contact charging of the photosensitive drum 1 by the charging roller 2 is dominated by direct charging (injection charging) due to the presence of the charge accelerating particles.
[0137]
The image recording apparatus (printer) of this embodiment is provided with a cleaner 8 for removing the transfer residual toner from the surface of the photosensitive drum 1 after transfer, but actually the transfer residual toner is completely removed from the surface of the photosensitive drum 1. In particular, in the cleaning with the elastic blade 8a used in the present embodiment, the fine powder having a small particle diameter can pass through the blade 8a so that the blade does not turn over. Therefore, even in the image recording apparatus provided with the cleaner 8, the toner (insulating substance), which is a charging inhibiting factor that can be slightly removed from the cleaner, is carried to the charging nip portion n and is in an intervening state. The roller 2 becomes contaminated with toner.
[0138]
Even in such a case, the charge accelerating particles m are present in the charging nip portion n between the photosensitive drum 1 and the charging roller 2, so that the charging roller 2 is prevented from being contaminated and the contact property of the charging roller 2 is reduced. Since the close contact property and contact resistance to the photosensitive drum 1 can be maintained, ozone-less direct charging can be stably maintained over a long period of time with a low applied voltage, and uniform chargeability can be provided.
[0139]
By providing a supply member (charging accelerating particle chip member) 31 for supplying the charging accelerating particles m to the charging roller 2, the charging accelerating particles are discharged from the charging nip n between the photosensitive drum 1 and the charging roller 2 as the apparatus is used. Even if m falls off, the charging accelerating particle m is replenished to the charging nip portion n, and the charging characteristics are prevented from being deteriorated due to dropping / decreasing of the charging accelerating particle m from the charging nip portion n. Can be maintained stably over a long period of time.
[0140]
In this embodiment, the charge accelerating particles m are supplied to the charging roller 2 by supplying the charge accelerating particles m supplied to the charging roller 2 by scraping the charge accelerating particle chip 31 itself as a charging accelerating particle supplying member. Since the charge promoting particles m are supplied to the charging roller 2 as a solidified chip-like member, the charging promoting particles m are stably handled without being scattered and easily handled. Can be supplied to.
[0141]
Thus, a high charging efficiency that cannot be obtained by conventional roller charging as a contact charging device can be obtained, and a charging potential almost equal to the voltage applied to the charging roller 2 can be applied to the photosensitive drum 1. Even when a simple charging roller 2 is used, regardless of contamination of the charging roller 2, a voltage corresponding to the charging potential required for the photosensitive drum 1 is sufficient as the bias applied to the charging roller 2, and the discharge is sufficient. A stable and safe contact charging device that does not use a phenomenon, that is, a direct charging device that has low applied voltage and ozoneless, excellent charging uniformity, and stable performance over a long period of time can be realized with a simple configuration.
[0142]
In a contact charging type image recording apparatus and a contact charging type / transfer type image recording apparatus, a simple charging roller 2 is used as a contact charging member, and the application of low voltage regardless of toner contamination of the charging roller 2. Ozone-free direct charging with voltage can be performed without problems, maintaining high-quality image formation for a long time, maintaining high-quality image formation for a long time even after outputting an image with a high image ratio, etc. it can.
[0143]
If the amount of charge-promoting particles intervened in the charging nip n between the photosensitive drum 1 as the image carrier and the charging roller 2 as the contact charging member is too small, the lubricating effect by the particles cannot be sufficiently obtained, and the charging roller 2 and the photosensitive drum 1 is so large that it is difficult to drive the charging roller 2 to the photosensitive drum 1 with a speed difference. That is, the driving torque becomes excessive, and if the surface is rotated forcibly, the surfaces of the charging roller 2 and the photosensitive drum 1 are scraped. Furthermore, the effect of increasing the contact opportunity by the particles may not be obtained, and sufficient charging performance cannot be obtained. On the other hand, when the amount of the inclusion is too large, dropping of the charge accelerating particles from the charging roller 2 is remarkably increased, which adversely affects image formation.
[0144]
According to experiments, the amount of intervention is 10 ² Piece / mm ² The above is desirable. 10 ² Piece / mm ² If it is lower, a sufficient lubrication effect and an effect of increasing the contact opportunity cannot be obtained, resulting in a decrease in charging performance.
[0145]
More desirably 10 ^Three ~ 5x10 ^Five Piece / mm ² This amount of inclusion is preferred. 5 × 10 ^Five Piece / mm ² If the value exceeds 1, the dropout of the particles to the photoreceptor 1 is remarkably increased, and the exposure amount to the photosensitive drum 1 is insufficient regardless of the light transmittance of the particles themselves. 5 × 10 ^Five Piece / mm ² In the following, the amount of dropped particles can be kept low, and the adverse effect can be improved. When the abundance of particles dropped on the photosensitive drum 1 in the intervening amount range is measured, 10 is obtained. ² -10 ^Five Piece / mm ² Therefore, the abundance that is not harmful to image formation is 10 ^Five Piece / mm ² The following is desired: In other words, the condition for applying and supplying the charge accelerating particles to the charging roller 2 by the charge accelerating particle chip member 31 is set so that the amount of the charge accelerating particles in the charging nip n is such an intervening amount.
[0146]
In this embodiment, an average of 500 pieces / mm ² Abundance. The coating amount is 10 ^Five Piece / mm ² The following is preferable, but in order to record a halftone image and fine lines more accurately, a smaller abundance 10 ^Four Piece / mm ² Below, further 10 ^Three Piece / mm ² The following abundance is desirable. In the charge accelerating particle supply means 3A of this configuration, when the charge accelerating particles are continuously supplied, about 3000 particles / mm ² In this embodiment, as will be described later, the charge accelerating particles are applied on the charging roller 2 by the charge accelerating particle supply means 3A, so that the charge accelerating particles are present on the photosensitive drum 1. It became possible to reduce the amount to an appropriate value.
[0147]
A method for measuring the intervening amount and the existing amount on the photosensitive drum 1 will be described. It is desirable that the amount of intervening is directly measured at the charging nip n between the charging roller 2 and the photosensitive drum 1, but most of the particles present on the photosensitive drum 1 before contacting the charging roller 2 move in the opposite direction while contacting. Therefore, in the present invention, the amount of particles on the surface of the charging roller 2 immediately before reaching the charging nip portion n is used as the intervening amount. Specifically, the rotation of the photosensitive drum 1 and the charging roller 2 is stopped in a state where no charging bias is applied, and the surfaces of the photosensitive drum 1 and the charging roller 2 are video microscope (OLYMPUS OVM1000N) and digital still recorder (DELTIS manufactured). SR-3100). The charging roller 2 is in contact with the slide glass under the same conditions as the case where the charging roller 2 is in contact with the photosensitive drum 1, and the contact surface of the charging roller 2 is 10 or more with a 1000 × objective lens from the back surface of the slide glass. I took a picture. In order to separate individual particles from the obtained digital image, binarization processing was performed with a certain threshold value, and the number of regions where particles were present was measured using desired image processing software. Further, the abundance on the photosensitive drum 1 was also measured by photographing the same on the photosensitive drum 1 with a similar video microscope.
[0148]
(5) Operation mode of charging promotion particle application
The charge accelerating particles m intervening in the charging nip n adhere to the photosensitive drum 1 as the member to be charged along with the charging operation, and the charge accelerating particles existing around the charging roller 2 as the contact charging member are reduced unless replenished. However, in this embodiment, as described above, the charge accelerating particles m are applied and supplied to the charging roller 2 by the charge accelerating particle supply means 3A.
[0149]
However, the charge accelerating particles applied and supplied to the charging roller 2 may adhere excessively to the photosensitive drum 1 due to repeated charging, which may adversely affect the subsequent process. In other words, the charge accelerating particles that are excessively present on the photosensitive drum 1 may cause adverse effects such as blocking exposure light in the image exposure process after charging. Further, adverse effects may occur in the subsequent development process using toner.
[0150]
Therefore, in the application and supply of the charge accelerating particles to the charging roller 2 as the contact charging member, the charge accelerating particles are stably supplied to obtain uniform charging properties, and the charge accelerating particles are supplied to the photosensitive drum 1 as the image carrier. Therefore, it is important to form a recorded image free from image defects.
[0151]
Therefore, in this embodiment, the charge accelerating particle application was performed in the following operation mode. That is, the basic operation modes of the charge accelerating particle supply means 3A are the following A mode and B mode.
[0152]
A mode: The charge accelerating particles are applied to the charging roller 2.
B mode: image recording is performed without applying charging promoting particles to the charging roller 2
a) When starting the printer for the first time, the A mode is performed, and the charge accelerating particles are uniformly applied to the charging roller 2.
[0153]
b) Thereafter, the mode is changed to the B mode, and in the case of the present embodiment, the B mode operation is performed at the time of printing for 30 minutes or 100 sheets, and then the mode is shifted to the A mode.
[0154]
c) Return to B mode again after A mode ends.
[0155]
d) By repeating these steps, it is possible to hold the charge promoting particles on the charging roller 2 uniformly and uniformly.
[0156]
Furthermore, it is more preferable to divide the A mode into two modes as shown below.
[0157]
A1 mode: The charge accelerating particle supply member 31 is brought into contact with the charging roller 2 to perform the application operation of the charge accelerating particles.
A2 mode: The charge promoting particle supply member 31 is separated from the charging roller 2 and the photosensitive drum 1 and the charging roller 2 are driven.
That is, when the mode is shifted to the A mode, the A1 mode is first performed to apply the charge accelerating particles to the charging roller 2. However, when the mode is shifted to the B mode, the charge accelerating particles on the charging roller 2 may not be sufficiently familiar with the surface of the charging roller. Accordingly, the charge-promoting particles may fall off for a while after entering the B mode. Therefore, it is effective to provide the A2 mode in the latter half of the A mode so that the charge accelerating particles are sufficiently adapted to the surface of the charging roller.
[0158]
In this manner, the charge promoting particles are applied during non-image recording, and the charge promoting particles are sufficiently acclimated onto the charging roller before entering the image recording operation. Was sufficiently reduced and image defects were improved.
[0159]
This configuration is very effective for preventing substantial adhesion of the charge promoting particles having a small binding force to the contact charging member to the object to be charged or the image bearing member. It is a big merit from saving.
[0160]
Further, since it is difficult to uniformly apply the charge accelerating particles onto the contact charging member, there is an effect of making the charge accelerating particles on the contact charging member uniform by rotating after stopping the application operation.
[0161]
Further, the charge accelerating particle applying means 3A prevents the toner on the charging roller 2 as the contact charging member from being contaminated, so that a longer life image recording apparatus can be configured.
[0162]
<Example 2> (FIG. 3)
The present embodiment is another configuration example of the charge accelerating particle supply unit, and FIG. 3 is a schematic diagram of the configuration of the charge accelerating particle supply unit 3B.
[0163]
In the present embodiment, a configuration in which the fur brush roller 37 is brought into contact with the charging roller 2 to supply the charge accelerating particles m is employed.
[0164]
The fur brush roller 37 refreshes the surface of the charging roller 2 and can hold a large number of charge promoting particles m between the fibers, and can easily transfer the particles to the outer surface of the charging roller 2. Can be performed stably.
[0165]
The charge accelerating particle supply means 3B of this embodiment includes a housing container 38, a fur brush roller 37, a regulating member 39a, a sealing sheet 39b, and charge accelerating particles m.
[0166]
The housing container 38 is a horizontally long container that is substantially the same length as the charging roller 2 and has an opening on the lower surface side, and accommodates the fur brush roller 37 and the charge promoting particles m therein.
[0167]
The fur brush roller 37 contacts the charging roller 2 over almost the entire length of the roller at the lower surface side opening of the housing container 38 and rubs the outer surface of the charging roller to apply refreshing and charging promoting particles on the charging roller 2. In the housing container 38, both end shaft portions are rotatably supported between both end plates of the housing container 38, and are horizontally long members having substantially the same length as the charging roller 2. .
[0168]
The fur brush roller 37 is formed by winding and fixing a fur brush 37a formed by weaving fibers into a base fabric to form a pile. The fiber density is 500 / mm as the folding density on the base fabric. ² The length of the bristle (free length) was 3 mm. The distance between the core metal 37b of the charging roller 2 and the core metal 37b of the fur brush roller 37 is set such that the surface layer of the charging roller 2 is located at a position of 2 to 3 mm from the surface layer of the core metal 37b with respect to the 3 mm bristle. The fur brush roller 37 was adjusted and brought into contact with the charging roller 2.
[0169]
The regulating member 39a serves to regulate the charge accelerating particles excessively supplied to the charging roller 2, and is a horizontally long blade member having the same length as that of the charging roller 2. The side wall plate is fixedly disposed along the length of the side wall plate on the downstream side in the rotation direction, and the lower side is in close contact with or lightly in contact with the outer surface of the charging roller 2.
[0170]
The sealing sheet 39b is a horizontally long plastic sheet piece having a relatively low waist. Leakage of charge promoting particles from the gap between the lower side portion of the side wall plate on the upstream side in the rotation direction of the charging roller 2 of the housing container 38 and the charging roller 2. It serves to prevent An inwardly bent edge is formed along the length of the lower side of the side wall plate on the upstream side of the rotation direction of the charging roller 2 of the housing container 38, and the lower surface of the inwardly bent edge extends along the length of the edge. Thus, the base side of the sealing sheet 39b is bonded and fixed, and the leading end is brought into close contact with or lightly in contact with the outer surface of the charging roller 2. The sealing sheet 39b substantially closes the gap between the lower side of the side wall plate on the upstream side of the rotation direction of the charging roller 2 of the housing container 38 and the charging roller 2, thereby preventing leakage of the charge promoting particles.
[0171]
The charge accelerating particles m stored in the housing container 38 are stored in a state of being accommodated in a substantially sealed space surrounded by the housing container 38, the regulating member 39a, the sealing sheet 39b, and the upper surface portion of the charging roller 2. Thus, leakage and scattering outside the housing container 38 is prevented. A large number of charge promoting particles m are held on the fur brush 37 a of the fur brush roller 37 disposed in the housing container 38.
[0172]
In the charge accelerating particle supply means 3B of this embodiment, the application of the charge accelerating particles m to the charging roller 2 is turned on / off by controlling the driving of the fur brush roller 37. Since the fur brush roller 37 holds the charge accelerating particles m and supplies them to the charging roller 2, the supply of particles to the charging roller 2 can be remarkably reduced by stopping the fur brush 37. As the operation timing, the driving of the fur brush 37 is controlled at the same timing (A / B mode, A1 / A2 mode) as in the first embodiment.
[0173]
<Example 3> (FIG. 4)
The present embodiment is another configuration example of the charge accelerating particle supply means, and FIG. 4 is a structural model diagram of the charge accelerating particle supply means 3C.
[0174]
In this embodiment, in the process of applying the charge accelerating particles m to the charging roller 2, the application is performed once on the application roller 39 c in the middle, and then transferred from the application roller 39 c to the charging roller 2. The application roller 39c includes a cored bar 39d and an elastic layer 39e.
[0175]
In the present embodiment, the application and supply of the charge accelerating particles to the application roller 39c is the same as in the second embodiment by using the charge accelerating particle supply means in which the fur brush 37 is included in the housing container 38 containing the charge accelerating particles m. The application of the charge accelerating particles to the application roller 39c was stably performed.
[0176]
The coating roller 39c is brought into contact with the charging roller 2, and the charging roller m is charged on the surface of the charging roller while rotating the coating roller 39c at a speed of 100 to 150% with respect to the charging roller 2 while rotating. The composition to apply is taken.
[0177]
Then, the entire charging accelerating particle supply means 3C including the application roller 39c and the housing container 38 is controlled to come into contact with and separate from the charging roller 2 by means of a contact / separation moving means (not shown). The coating operation is turned on / off by separating the coating.
[0178]
In this embodiment, the charge accelerating particle supply means 3C is controlled to move toward and away at the same timing (A / B mode, A1 / A2 mode) as in Embodiment 1, and the application roller 39c is brought into contact with or separated from the charging roller 2. To turn on / off the coating operation.
[0179]
<Example 4> (FIG. 5)
This embodiment is a printer of a toner recycling system (cleaner-less) in which the cleaner 8 is eliminated from the printer of the first embodiment.
[0180]
In the present embodiment, conductive zinc oxide particles are used as the charge promoting particles m constituting the charge promoting particle tip member 31 of the charge promoting particle supply means 3A.
[0181]
Since the other apparatus configuration is the same as that of the printer of the first embodiment, the description thereof will be omitted.
[0182]
In the cleanerless image recording apparatus, a dedicated cleaner for removing the transfer residual toner on the surface of the photosensitive drum after transfer is not used, so that the transfer residual toner on the surface of the photosensitive drum after transfer is transferred to the photosensitive drum 1 and the charging roller. 2 is carried as it is by the movement of the photosensitive drum surface, the amount of toner present in the charging nip n is larger than that of the printer provided with the cleaner 8 of Example 1, and the charging roller 2 The amount of toner adhering to and mixed in increases.
[0183]
However, even in such a case, the charge accelerating particles m are present in the charging nip n between the photosensitive drum 1 and the charging roller 2, so that the charging roller 2 is prevented from being contaminated and the contact with the toner is reduced. Therefore, ozone-less direct charging can be stably maintained over a long period of time with a low applied voltage, and uniform chargeability can be provided.
[0184]
Since the charging roller 2 is in contact with the photosensitive drum 1 with a speed difference, the pattern of untransferred toner from the transfer portion b to the charging nip portion n of the charging roller 2 and the photosensitive drum 1 is disturbed. In the halftone image, the previous image pattern portion does not appear as a ghost.
[0185]
It is desirable that the charging roller 2 is rotationally driven to temporarily collect and level the transfer residual toner, and the rotational direction of the charging roller 2 is opposite to the moving direction of the photosensitive drum surface.
[0186]
As in the case of the printer of the first embodiment, supply of the charge accelerating particles m to the charging roller 2 is performed by supplying the charge accelerating particles m to the charging roller 2 by shaving itself. Since the charge accelerating particles m are supplied to the charging roller 2 as the member 31, the charging accelerating particles m can be supplied to the charging roller 2 stably and easily without scattering. In addition, particularly in the configuration of the toner recycling system (cleanerless) as in this example, there is a great effect that the transfer residual toner can be circulated in the charging roller 2 without stagnation and the charge accelerating particles can be supplied. That is, the supply of the charge promoting particles m to the charging roller 2 and the toner leveling on the charging roller are performed simultaneously.
[0187]
The transfer residual toner adhering to and mixed in the charging roller 2 is gradually discharged from the charging roller 2 onto the photosensitive drum, reaches the development site a as the photosensitive drum surface moves, and is simultaneously cleaned (collected) by the developing device 5 (development). Toner recycling).
[0188]
As described above, the simultaneous development cleaning is performed in the image forming process in which the toner remaining on the photoreceptor 1 after the transfer is continued, that is, the photoreceptor is continuously charged and exposed to form a latent image, and the latent image is developed. At this time, the image is recovered by the fog removal bias of the developing device, that is, the fog removal potential difference Vback which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photosensitive member. In the case of reversal development as in the printer in this embodiment, this simultaneous development cleaning is performed by attaching toner from the dark portion potential of the photosensitive member to the developing sleeve and from the developing sleeve to the bright portion potential of the photosensitive member. Made by the action of an electric field.
[0189]
In this embodiment, zinc oxide particles are used as the charge accelerating particles m to be supplied to the charging roller 2, and the zinc oxide particles as the charge accelerating particles m tend to charge the toner negatively in the frictional charging characteristics with the toner. It has characteristics. That is, there is an effect of making the toner negative on the charging roller 2 and an effect of improving the toner discharge performance.
[0190]
By supplying the charge accelerating particle chip member 31 to the charging roller 2 and supplying the charge accelerating particle m, it is possible to circulate the transfer residual toner without stagnation and simultaneously supply the charge accelerating particle to the charging roller. Become. At this time, the toner charge on the charging roller is normally frictionally charged.
[0191]
In addition, in the present embodiment, the chip member 31 in which the charge accelerating particles are solidified as in the first embodiment is attached to the charging roller 2 so as to be able to contact and separate, and the charging accelerating particles are supplied to the charging roller 2 at a desired timing. Controlled to do.
[0192]
Further, since the function of disturbing the transfer residual toner is reduced when the chip member is separated, the transfer residual pattern is made non-patterned by contact with the fur brush 39f or the like.
[0193]
<Comparative Examples 1-4>
Comparative Examples 1 to 4 basically correspond to Examples 1 to 4, respectively, but differ only in the application operation of the charge accelerating particles. In the comparative example, the coating operation is always performed, and the charge accelerating particle supply means 3A, 3B, and 3C are operated in synchronization with the driving of the photosensitive drum 1 and the charging roller 2. However, in the comparative example 4, the fur brush 39f which is a disturbance member provided in the fourth embodiment is not equipped.
[0194]
Evaluation results: Table 1 shows the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4, and describes the effectiveness of this example.
[0195]
[Table 1]

In the image defect evaluation, a halftone image was output, and evaluation was performed from the number of image defects. This image forming apparatus (printer) performed image formation using a 600 dpi laser scanner. In this evaluation, the halftone image means a striped pattern in which one line in the main scanning direction is recorded and then two lines are not recorded, and the halftone density is reproduced as a whole. In this embodiment, since image formation is performed in a reversal development system, both when image exposure is hindered and when leakage occurs during development, it appears in the image as a white spot. The number of these defect sites was evaluated according to the following criteria.
[0196]
×: 50 or more white spots having a diameter of 0.3 mm or more exist in the halftone image
○: There are 6 to 49 white spots with a diameter of 0.3 mm or more in the halftone image.
A: The white spot having a diameter of 0.3 mm or more is 5 or less in the halftone image.
The evaluation was performed after printing 100 sheets (A4 lengthwise direction) using A4 paper.
[0197]
In Comparative Example 1, the charge accelerating particles often fall off, and image defects occur during subsequent exposure or development. In the comparative example, it is expected that the particles fall off as follows.
[0198]
It is considered that the charge-promoting particles m are mostly caused by the mutual force of the charging roller 2 due to the adhesion force due to the Van Waals force and the electrostatic attractive force generated because the charge-promoting particles have a slight conductive triboelectric property. However, the magnitude of these forces is never large, and the charge accelerating particles easily fall off to the photosensitive drum 1. Further, it is expected that when these charge accelerating particles m are applied to the charging roller 2 in several layers, the binding force of the outermost particles becomes smaller and the particles fall off. In order to regulate the layer thickness of the charge accelerating particles m on the charging roller 2, it is difficult to avoid the occurrence of a location where the particle layer increases depending on the location.
[0199]
The charge accelerating particles m that have fallen onto the photosensitive drum 1 form an unexposed portion when image information is recorded by a laser scanner or the like, causing defects in the recorded image. Further, at the time of development, the charge accelerating particles present on the photosensitive drum 1 prevent the toner from being transferred and developed on the photosensitive drum. Alternatively, image defects occur due to problems such as leakage of the developing bias applied to the developing roller.
[0200]
On the other hand, in Example 1, the particles are applied during non-image recording, and the charge-accelerating particles are acclimated onto the charging roller 2, thereby eliminating the number of layers where the particles are applied and uniformly charging the roller. 2 is distributed. By performing image recording in this state, the amount of charge-promoting particles m falling off was significantly reduced and image defects were improved.
[0201]
Similarly, in Example 2, although the application form was different, the problem was solved by controlling the driving of the fur brush 37 for conveying and applying the charge accelerating particles m.
[0202]
Further, in the third embodiment, the application roller 39c is applied to the charging roller 2, and the application roller 39c is attached to the charging roller 2 so as to be separable.
[0203]
In the fourth embodiment, the same effect can be obtained by supplying the charge accelerating particles during non-image recording even in a configuration in which toner recycling is realized without providing a drum cleaner.
[0204]
<Others>
1) In the present invention, it is preferable that a charge injection layer is provided on the surface of the photoreceptor 1 as an image carrier to adjust the resistance of the photoreceptor surface.
[0205]
FIG. 6 is a model diagram of the layer structure of the photoreceptor 1 having the charge injection layer 16 on the surface. That is, the photosensitive member 1 is generally coated on an aluminum drum substrate (Al drum substrate) 11 in the order of an undercoat layer 12, a positive charge injection preventing layer 13, a charge generation layer 14, and a charge transport layer 15. The charge performance is improved by applying the charge injection layer 16 to the organic photoreceptor.
[0206]
The charge injection layer 16 is made of SnO as conductive particles (conductive filler) on a photo-curable acrylic resin as a binder. ₂ Ultrafine particles 16a (diameter of about 0.03 μm), a polymerization initiator and the like are mixed and dispersed, and after coating, a film is formed by a photocuring method.
[0207]
In addition, by incorporating a lubricant such as tetrafluoroethylene resin (trade name Teflon), the surface energy on the surface of the photoreceptor is suppressed, and the adhesion of the charge accelerating particles m is generally suppressed.
[0208]
An important point as the charge injection layer 16 is the resistance of the surface layer. In the charging method using direct injection of charges, charges can be exchanged more efficiently by reducing the resistance on the charged object side. On the other hand, since the electrostatic latent image needs to be held for a certain time when used as a photoconductor, the volume resistance value of the charge injection layer 16 is 1 × 10 6. ⁹ ~ 1x10 ¹⁴ A range of (Ω · cm) is appropriate.
[0209]
Even when the charge injection layer 16 is not used as in this configuration, for example, when the charge transport layer 15 is within the resistance range, the same effect can be obtained.
[0210]
Furthermore, the volume resistance of the surface layer is about 10 ¹³ A similar effect can be obtained by using an amorphous silicon photoconductor having an Ωcm.
[0211]
2) The charging roller 2 as a flexible contact charging member is not limited to the charging roller of the embodiment.
[0212]
In addition to the charging roller, the flexible contact charging member can be made of a material or shape such as a fur brush, felt, or cloth. Moreover, these can be laminated | stacked and it can also obtain more suitable elasticity and electroconductivity.
[0213]
3) When an AC voltage (alternating voltage) is included in the bias applied to the contact charging member 2 and the developing sleeve 4a, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Further, it may be a rectangular wave formed by periodically turning on / off a DC power source. In this way, a bias that changes the voltage value periodically can be used as the waveform of the alternating voltage.
[0214]
4) The image exposure means for forming the electrostatic latent image is not limited to the laser scanning exposure means for forming a digital latent image as in the embodiment, but a normal analog image exposure or Other light emitting elements such as LEDs may be used, and any combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter may be used as long as it can form an electrostatic latent image corresponding to image information.
[0215]
5) The image carrier may be an electrostatic recording dielectric or the like. In this case, the dielectric surface is uniformly primary-charged to a predetermined polarity and potential, and then selectively neutralized by a neutralizing means such as a static elimination needle head or an electron gun to write and form a target electrostatic latent image.
[0216]
6) In the embodiment, the developing unit 4 has been described by taking a reversal developing unit using a one-component magnetic toner as an example, but the configuration of the developing unit is not particularly limited. A regular developing device may be used.
[0217]
7) The recording medium that receives the transfer of the toner image from the image carrier may be an intermediate transfer body such as a transfer drum.
[0218]
8) An example of a toner particle size measuring method will be described. As a measuring device, a Coulter counter TA-2 type (manufactured by Coulter Inc.) was used, and an interface (manufactured by Nikka) and a CX-1 personal computer (manufactured by Canon) that output number average distribution and volume average distribution were connected, and electrolysis was performed. Prepare 1% NaCl aqueous solution using primary sodium chloride.
[0219]
As a measuring method, a surfactant, preferably 0.1 to 5 ml of alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 0.5 to 50 mg of a measurement sample is further added.
[0220]
The electrolyte in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the particle size distribution of 2 to 40 μm particles is measured using the 100 μ aperture as the aperture by the Coulter Counter TA-2 type. Then, the volume average distribution is obtained. The volume average particle diameter is obtained from the obtained volume average distribution.
[0221]
【The invention's effect】
As described above, according to the present invention, even when a simple member such as a charging roller or a fur brush is used as the contact charging member, the application necessary for charging the contact charging member is possible regardless of contamination of the contact charging member. The voltage equivalent to the charging potential required for the object to be charged is sufficient, and it is a stable and safe contact charging device that does not use the discharge phenomenon, that is, low applied voltage and ozoneless, excellent charging uniformity and stable for a long time. A direct charging device with high performance can be realized with a simple configuration.
[0222]
By using this charging device as a charging means for the image carrier, contact charging type image recording device, contact charging type / transfer type image recording device, and further contact charging type / transfer type / toner recycling system image recording. With regard to equipment, simple members such as charging rollers and fur brushes can be used as contact charging members, and ozone-less direct charging and toner recycling systems can be executed without problems regardless of toner contamination on the contact charging members. In addition, high-quality image formation can be maintained over a long period of time, and high-quality image formation can be maintained over a long period of time even after an image with a high image ratio is output.
[0223]
By applying charge-accelerating particles to the contact charging member during non-image recording and fully charging the charge-accelerating particles on the contact charging member before entering the image recording operation, the charge-accelerating particles drop off from the image carrier. Was sufficiently reduced to improve the image defects.
[0224]
This configuration is very effective for preventing substantial adhesion of the charge promoting particles having a small binding force to the contact charging member to the object to be charged or the image bearing member. It is a big merit from saving.
[0225]
Further, since it is difficult to uniformly apply the charge accelerating particles onto the contact charging member, there is an effect of making the charge accelerating particles on the contact charging member uniform by rotating after stopping the application operation.
[0226]
Further, in Embodiments 1 and 3 and 4 in particular, the charge accelerating particle applying means can prevent contamination with toner, and a longer-life image recording apparatus can be configured.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image recording apparatus according to a first embodiment.
FIG. 2 is an enlarged model view of the charging accelerating particle applying means.
FIG. 3 is an enlarged model view of the charge accelerating particle applying unit of Example 2.
FIG. 4 is an enlarged model view of the charge accelerating particle applying unit of Example 3.
FIG. 5 is a schematic configuration diagram of an image recording apparatus (cleanerless) according to a fourth embodiment.
FIG. 6 is a model diagram of a layer structure of an example of a photoreceptor having a charge injection layer on the surface.
[Fig. 7] Charging characteristic graph
[Explanation of symbols]
1 Photosensitive drum (image carrier, charged body)
2 Charging roller (contact charging member)
3A / 3B / 3C Charge Accelerating Particle Coating Means
30 Transfer material (recording medium)
31 Charge Accelerated Particle Supply Member (Charge Accelerated Particle Chip Member)
m Charge accelerating particles
32 Chip support
33 Housing
36 Solenoid
37 Fur Brush Roller
39f Fur brush
4 Laser beam scanner (exposure device)
5 Developer
5a Development sleeve
t Developer (toner)
6 Transfer roller
7 Fixing device
8 Cleaner (Photosensitive drum cleaning device)
S1 to S3 Bias applied power supply

Claims (16)

A charging method of charging the surface of a charged body with a flexible charging member that forms a nip portion with the charged body,
The charging member moves with a speed difference with respect to the member to be charged, and has charging promoting particle supplying means for supplying charging promoting particles to the charging member,
A mode in which the charge promoting particles are supplied from the charge promoting particle supply means to the charging member, and a B mode in which the charge promoting particles are not supplied from the charge promoting particle supply means to the charging member after the A mode. A charging method characterized by comprising: The A mode includes an A1 mode in which the charge accelerating particles are supplied from the charge accelerating particle supply unit to the charging member, and an A2 mode in which the charged body and the charging member are driven after the A1 mode so that the charging accelerating particles become familiar with the charging member. The charging method according to claim 1, wherein: The charging method according to claim 1, wherein the volume resistance of the charge accelerating particles is 10 ¹² Ω · cm or less. 3. The charging method according to claim 1, wherein the volume resistance of the charge accelerating particles is 10 ¹⁰ Ω · cm or less. The charging method according to claim 1, wherein a voltage is applied to the charging member. 6. The charging method according to claim 1, wherein the member to be charged and the charging member move in opposite directions at the nip portion. A charging device that charges the surface of a charged body with a flexible charging member that forms a nip portion with the charged body,
The charging member moves with a speed difference with respect to the member to be charged, and has charging promoting particle supplying means for supplying charging promoting particles to the charging member,
As an operation mode of the apparatus, A mode in which the charge promoting particles are supplied from the charge promoting particle supplying means to the charging member, and B to charge the object to be charged without supplying the charge promoting particles from the charging promoting particle supplying means to the charging member. A charging device having a mode. The A mode includes an A1 mode in which the charge accelerating particles are supplied from the charge accelerating particle supply means to the charging member, and an A2 mode in which the charged object and the charging member are driven to make the charging accelerating member conform to the charging member. The charging device according to claim 7. The charging device according to claim 7 or 8, wherein the volume resistance of the charge accelerating particles is 10 ¹² Ω · cm or less. The charging device according to claim 7 or 8, wherein the volume resistance of the charge accelerating particles is 10 ¹⁰ Ω · cm or less. The charging device according to claim 7, wherein a voltage is applied to the charging member. The charging device according to claim 7, wherein the member to be charged and the charging member move in opposite directions at the nip portion. An image recording apparatus that performs image recording by applying an image forming process including a step of charging the image carrier to the image carrier,
The process means for charging the image carrier is the charging device according to any one of claims 7 to 12,
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode. An image carrier, a charging means for charging the image carrier, an information writing means for forming an electrostatic latent image on a charging surface of the image carrier, and a developing means for visualizing the electrostatic latent image with a developer, A transfer unit that transfers the developer image to a recording medium; and a cleaning unit that cleans the image carrier after the transfer.
The process means for charging the image carrier is the charging device according to any one of claims 7 to 12,
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode. An image carrier, a charging means for charging the image carrier, an information writing means for forming an electrostatic latent image on the charging surface of the image carrier, and a developing means for visualizing the electrostatic latent image with a developer, A transfer unit that transfers the developer image to a recording medium, and the developer that has transferred the developer image to the recording medium after the developer unit has transferred the developer image to the recording medium, at least temporarily charged on the charging unit; An image recording apparatus having an image carrier cleaner-less configuration that is again collected by the developing means through the image carrier,
The process means for charging the image carrier is the charging device according to any one of claims 7 to 12,
An image recording apparatus, wherein image recording is not performed in the A mode, but image recording is performed within the B mode. 16. The image recording apparatus according to claim 14, wherein the information writing means for forming an electrostatic latent image on the charging surface of the image carrier is an image exposure means.

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