JPS5939740B2 - electrophotographic method - Google Patents

Description

【発明の詳細な説明】 本発明は、改良された電子写真方法に係り、特に階調性
の高い原画像の忠実な再現を可能とした電子写真方法に
関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved electrophotographic method, and particularly to an electrophotographic method that enables faithful reproduction of an original image with high gradation.

従来、エレクトロ・ファックス方法或はカールソン方法
等に続いて提案された特公昭４２−２３９１０号を基本
とする電子写真方法が、高コントラストの静電潜像を得
られる方法として知られ、実用に供されている。Conventionally, the electrophotographic method based on Japanese Patent Publication No. 42-23910, which was proposed following the electro-fax method and Carlson method, is known as a method for obtaining high-contrast electrostatic latent images, and has not been put into practical use. has been done.

即ち、その方法は、第１図ａに示すように、導電性層１
、光導電性層２、及び絶縁性層３を基本構成とする感光
体Ａ上に、コロナ放電器４で所定極性の（図示例では迫
−１））一様帯電を施し、次いで第１図をに示すように
、明部５、暗部６を有するオリジナル像１の光像を感光
体表面に露光し、同時にコロナ放電器８で一次帯電と逆
極性若しくはＡＣコロナ除電を施し、次いで第１図Ｃに
示すように、全面均一露光を施すことによつて感光体表
面に高コントラストの静電潜像を形成するものである。That is, the method is as shown in FIG.
, a photoconductive layer 2, and an insulating layer 3 are uniformly charged with a predetermined polarity (-1 in the illustrated example) by a corona discharger 4, and then, as shown in FIG. As shown in FIG. 1, a light image of an original image 1 having a bright part 5 and a dark part 6 is exposed on the surface of a photoreceptor, and at the same time, a corona discharger 8 performs primary charging and reverse polarity or AC corona charge removal. As shown in C, a high-contrast electrostatic latent image is formed on the surface of the photoreceptor by uniformly exposing the entire surface.

第１図ｄに示すのは、上記のＡＣコロナ除電の場合の方
法に於ける感光体表面電位の変化を示すもので、実線が
前記オリジナル像の暗部に相当する部分の電位を、破線
が、その明部の電位を示すものである。この方法では、
その明部電位によりカブリを生ずる場合もあつたので、
例えは、特公昭４７−２６９１１号に提案された様に、
前述ＡＣコロナ除電に前帯電と逆極性の直流成分を印加
して、第２図示のように表面電位を制御して画質を改良
することを可能とした。FIG. 1d shows the change in the surface potential of the photoreceptor in the above-mentioned AC corona static elimination method, where the solid line represents the potential of the portion corresponding to the dark part of the original image, and the broken line represents the potential of the portion corresponding to the dark part of the original image. It shows the potential of the bright part. in this way,
In some cases, the bright area potential caused fogging, so
For example, as proposed in Special Publication No. 47-26911,
By applying a DC component of opposite polarity to the pre-charging to the AC corona charge removal described above, it was possible to control the surface potential and improve the image quality as shown in the second figure.

同様の効果を得る為に第３図コロナ放電器８の前面にグ
リッド９を設け、そのグリッド９を接地電位或は一次帯
電と逆極性の電圧を印加する所謂グリッド制御すること
も提案されていた。In order to obtain a similar effect, it has also been proposed to provide a grid 9 in front of the corona discharger 8 shown in Figure 3, and apply so-called grid control to the grid 9 by applying a ground potential or a voltage of opposite polarity to the primary charge. .

特にこの場合、感光体表面電位がグリッド９の電位に収
束するように働くので、プロセス実施の際のＡＣコロナ
が雰囲気変化によつて変動すること等による画質の不安
定を除去でき、又潜像コントラストを上昇できる等の画
質の改良は可能となつた。Particularly in this case, since the surface potential of the photoreceptor converges to the potential of the grid 9, it is possible to eliminate instability in image quality caused by fluctuations in the AC corona due to changes in the atmosphere during the process, and also to remove latent images. It has become possible to improve image quality, such as increasing contrast.

即ち、第３図をに実線で示すのがグリッド制御を行つた
場合の暗部電位ＶＤ、破線で示すのがグリッド制御を行
わなかつた場合の暗部電位ＶＤ忙あるが、除電終了時点
に於いてＶＤの方がＶ。That is, in FIG. 3, the solid line indicates the dark potential VD when grid control is performed, and the broken line indicates the dark potential VD when grid control is not performed. is more V.

′よりも△りたけ高く、従つてグリッド制御を行つた場
合の全面露光後の暗部電位ＶＤＬＰ方がグリッド制御を
行わなかつた場合の全面露光後の暗部電位ＶＤ’Ｌより
も△り高くなる。従つて全面露光後の明部電位ＶＬＬと
上記明部電位ＶＬＬと上記暗部電位ＶＤ’Ｌとの電位差
よりも△Ｖだけ大きくなり、これによつてグリツド制御
した場合の方が潜像コントラストが向上することになる
。この様な改良によつて、高コントラストでカブリのな
い良好な画像が得られるものの、微妙な階調性を有する
印刷物等のオリジナル原稿のコピーに際して忠実な再現
が極めて困難であつた。Therefore, the dark potential VDLP after full exposure when grid control is performed is Δ higher than the dark potential VD'L after full exposure when grid control is not performed. Therefore, the potential difference between the bright area potential VLL after full exposure and the above-mentioned bright area potential VLL and the above-mentioned dark area potential VD'L is larger by △V, and as a result, the latent image contrast is improved when grid control is performed. I will do it. Although these improvements make it possible to obtain good images with high contrast and no fog, it has been extremely difficult to faithfully reproduce original documents such as printed matter having delicate gradations when copying original documents.

これは、原稿濃度Ｄと感光体表面電位Ｖの関係（或は露
光量（ト）０ｇＥ）一表面電位Ｖ）が、第４図ａ或はｂ
のような形をしているので、トーン再現町能な範囲、即
ち、Ｄ−Ｖ（或は１０ｇＥ−Ｖ）が略直線的に変化する
領域（ダイナミツクレンジ）が０．６前後しか得られな
いことによるもので、印刷再現範囲が１．６〜１．８あ
る印刷原稿濃度に対して、そのダイナミツクレンジが狭
いので、再現画像では、原稿の暗い部分７７）一層暗く
、明るい部分は一層明るい硬調なものとなつて、極めて
トーン再現性の忠実度が低下することが避け得なかつた
ものである。本発明は、上述の点に鑑み、高コントラス
トでダィナミツクレンジの広い良好な画像再現を可能と
する電子写真方法を提供するものである。This means that the relationship between the original density D and the photoreceptor surface potential V (or exposure amount (g) 0gE) - surface potential V) is as shown in Figure 4 a or b.
Since it has a shape like This is due to the fact that the printing reproduction range is 1.6 to 1.8, which is the density of the printed original, and the dynamic range is narrow. This results in bright, high-contrast tones, and it is unavoidable that the fidelity of tone reproducibility is extremely degraded. In view of the above points, the present invention provides an electrophotographic method that enables good image reproduction with high contrast and a wide dynamic range.

本発明の電子写真方法は、導電性基体、光導電層、及び
絶縁層を基本構成とする感光体を用い、その感光体表面
を一様帯電し、次いで感光体に画像露光を施すと同時に
上記一様帯電と逆極性成分を有するコロナ放電により除
電し、更に上記画像露光光量よりも低レベルの露光量で
画像露光を施ずと同時Ｚこ上記一様帯電と逆極件成分を
有するコロナ放電により上記除電による電位よりも低い
電位となるように除電し、その後感光体全面に一様露光
を行つて静電潜像を形成することを特徴とするものであ
る。以下本発明の詳細を、第５図乃至第７図に従つて説
明する。The electrophotographic method of the present invention uses a photoreceptor whose basic composition is a conductive substrate, a photoconductive layer, and an insulating layer, uniformly charges the surface of the photoreceptor, and then imagesically exposes the photoreceptor while simultaneously performing the above-described steps. Static charge is removed by a corona discharge having a uniform charge and a component of opposite polarity, and furthermore, without performing image exposure at a lower level of exposure light than the above image exposure light amount, a corona discharge having a uniform charge and a component of a reverse polarity is generated. The method is characterized in that the static electricity is removed to a potential lower than the potential due to the electricity removal described above, and then the entire surface of the photoreceptor is uniformly exposed to form an electrostatic latent image. The details of the present invention will be explained below with reference to FIGS. 5 to 7.

導電性基板１、光導電層２、透明絶縁層３を層合して基
本構成とした感光体Ａを用い、先ず滞電工程としてその
感光体の表面にコロナ放電器で例えば正（４）の一様一
次帯電を施す。A photoreceptor A having a basic structure of a conductive substrate 1, a photoconductive layer 2, and a transparent insulating layer 3 is used. First, as a charging step, the surface of the photoreceptor is charged with, for example, positive (4) with a corona discharger. Apply uniform primary charging.

この一様帯電により光導電層２と透明絶縁層３との界面
及びその近傍に絶縁層３表面の電荷と逆極性電荷（図示
例負（へ））の電荷層が形成される（第５図ａ）。この
とき、感光体表面は、一様に電位ＶＯとなる（第５図ｂ
）。そして，感光体表面の電荷密度も一様に００となる
（第５図ｃ）。次いで、第Ｌ露光工程を以下の如く行う
。オリジナルとして連続的に濃度変化する濃度ウエツジ
を用い、比較的高強度で感光体表面へ露光を成す（第６
図１ａ）。この露光と同時に、コロナ放電器８により、
交流コロナ放電若しくは一次帯電と逆極性コロナ放電を
成す。このコロナ放電器は、放電コロナ量を制御するグ
リツド９が設けらへ制９１１電圧が印加される。この制
岬電圧は、一次帯電位より低い適当な電位Ｖ１に設定さ
れている。これにより感光体表面は略制脚亀位Ｖ１に成
される（第６図１ｂ）。一方感光体表面の電荷密度は、
濃度ウエツジを用いての感光体露光により変化する（第
６図１ｃ）。特に暗部例に対し明部側で電荷の減少が著
しく暗部側は略直線的に変化している。次いで、第２露
光工程として、前記第１露光工程と略同一の操作を、オ
リジナルの露光量を減し、又グリツドの制御電位を前回
の電位Ｖ１より低いＶ２として実施する。（第６図２ａ
）。このようにして、感光体の表面電位は略Ｖ２となり
（第６図２ｂ）表面電荷密度は、明部で相当量残留して
いるものの著しく減少する（第６図２ｃ）。又比較的暗
部側で露光像に応じた濃度変化を示している。更らに、
必要に応じて第３露光工程として、前記第２露光工程と
略同一の操作を、オリジナルの露光量を減して露光する
一方、グリツド９への印加電圧極性を前記電位Ｖ２より
更に低くし、要すれば図示の如く逆極性とした電位Ｖ３
を印加して、同時除電を成す（第６図３ａ）。これによ
り、感光体の表面電位は略Ｖ３となり（第６図３ｂ）、
その表面電荷は第６図３ｃに示す如く、明部に於ても、
光像濃度に従つた直線状の変化を示し、結果的に、オリ
ジナル光像と略同様のγ値を示す電荷密度変化を示ず。
次いで、光像露光後の感光体面を全面露光することによ
り、（第７図ａ）、感光体の表面電位が、その表面電荷
密度に応じて現われる（第７図ｂ）。この様にして形成
された静電潜鐵は、オリジナル像の階調性を十分再現す
るものであつた。Due to this uniform charging, a charge layer having a polarity opposite to the charge on the surface of the insulating layer 3 (negative in the illustrated example) is formed at the interface between the photoconductive layer 2 and the transparent insulating layer 3 and in the vicinity thereof (Fig. 5). a). At this time, the surface of the photoreceptor uniformly becomes the potential VO (Fig. 5b)
). The charge density on the surface of the photoreceptor also uniformly becomes 00 (FIG. 5c). Next, the L-th exposure step is performed as follows. As the original, a density wedge that continuously changes density is used to expose the surface of the photoreceptor with relatively high intensity (6th
Figure 1a). Simultaneously with this exposure, the corona discharger 8
It forms an alternating current corona discharge or a corona discharge with a polarity opposite to that of the primary charge. This corona discharger is provided with a grid 9 for controlling the amount of discharged corona, to which a control voltage 911 is applied. This cape voltage is set to an appropriate potential V1 lower than the primary band potential. As a result, the surface of the photoreceptor is brought into a substantially restrained leg position V1 (FIG. 6, 1b). On the other hand, the charge density on the surface of the photoreceptor is
It changes by exposing the photoreceptor using a density wedge (FIG. 6, 1c). In particular, compared to the example of the dark area, the charge decreases significantly on the bright side and changes almost linearly on the dark side. Next, as a second exposure step, substantially the same operation as the first exposure step is performed with the original exposure amount reduced and the control potential of the grid set to V2, which is lower than the previous potential V1. (Figure 6 2a
). In this way, the surface potential of the photoreceptor becomes approximately V2 (FIG. 6, 2b), and the surface charge density decreases significantly, although a considerable amount remains in the bright area (FIG. 6, 2c). Also, the density changes in accordance with the exposed image on the relatively dark side. Furthermore,
If necessary, as a third exposure step, substantially the same operation as the second exposure step is performed with the original exposure amount reduced, while the polarity of the voltage applied to the grid 9 is further lowered than the potential V2, If necessary, the potential V3 is reversed in polarity as shown in the figure.
is applied to achieve simultaneous static elimination (FIG. 6, 3a). As a result, the surface potential of the photoreceptor becomes approximately V3 (Fig. 6, 3b),
The surface charge is as shown in Figure 6, 3c, even in the bright area.
It shows a linear change according to the optical image density and, as a result, does not show a charge density change showing a γ value that is approximately the same as the original optical image.
Next, by exposing the entire surface of the photoreceptor after the photoimage exposure (FIG. 7a), the surface potential of the photoreceptor appears in accordance with its surface charge density (FIG. 7b). The electrostatic latent iron thus formed was able to sufficiently reproduce the gradation of the original image.

上記露光工程の繰返し回数は、そのオリジナル光像の濃
度変化量に応じて適宜選択することは勿論である。又、
露光量、設定電位等も適宜最適に設定することは勿論で
ある。It goes without saying that the number of repetitions of the above exposure step is appropriately selected depending on the amount of change in density of the original optical image. or,
It goes without saying that the exposure amount, set potential, etc. are appropriately set optimally.

第８図に示すのが、本発明方法を適用した装置構成例を
説明するもので、ドラム状とした感光体Ｄの周辺に配置
したプロセス手段を示すものである。FIG. 8 illustrates an example of the configuration of an apparatus to which the method of the present invention is applied, and shows process means arranged around a drum-shaped photoreceptor D.

矢印方向に回転する感光体ドラムに最初に作用する位置
にコロナ放電器４が配置され、次いで光学的に背面を開
放した露光同時用コロナ放電器８が位置する。A corona discharger 4 is placed at a position where it first acts on the photoreceptor drum rotating in the direction of the arrow, followed by a simultaneous exposure corona discharger 8 whose back surface is optically open.

コロナ放電器と感光体の間には、除電電位を制御するグ
リツド９が設けられ、グリツド９には、３種の異なる電
圧を印加できる様に、９−α，９−β，９−γの３群に
分けて相互の絶縁性を保つたもので感光体に光像露光と
共に最初に作用するコロナを制御する９−α域のグリツ
ドには、一次帯電と同極性で若干低めの電位Ｖ１を印加
し、続く９−β域のグリツドに於ては更に電圧降下させ
た電位Ｖ２を印加し、更に続く９−γ域のグリツドに於
ては逆極性の電位３を印加する様に構成している。一方
、除電器９の光学的に開放された後方の光路上に、濃度
の異なるフイルタ一１０を配置して、９−αの域へは直
接光像が、９−β域では若干濃度を有する該フイルタ一
１０の１０１部を通して、又９−γ域では更らに濃度を
有する１０２部を通して各々光像露光を可能としたもの
である。続く感光体面に全面露光を施す様に光源１１が
配置されている。A grid 9 for controlling the static elimination potential is provided between the corona discharger and the photoreceptor, and the grid 9 has voltages 9-α, 9-β, and 9-γ so that three different voltages can be applied. The grid is divided into three groups to maintain mutual insulation, and the grid in the 9-α range, which controls the corona that first acts on the photoreceptor when the photoimage is exposed, is charged with a potential V1, which has the same polarity as the primary charge and is slightly lower. In the subsequent grid in the 9-β region, a potential V2 with a further voltage drop is applied, and in the subsequent grid in the 9-γ region, a potential 3 of the opposite polarity is applied. There is. On the other hand, a filter 10 with different densities is arranged on the optically open rear optical path of the static eliminator 9, so that a direct light image is produced in the 9-α region and has a slight density in the 9-β region. It is possible to perform optical image exposure through 101 parts of the filter 10 and through 102 parts having a higher density in the 9-.gamma. region. A light source 11 is arranged so as to expose the entire surface of the subsequent photoreceptor.

上記構成装置の動作を第８図ｂに示す表面電位変化曲線
を参照して以下説明する。The operation of the above-mentioned component device will be explained below with reference to the surface potential change curve shown in FIG. 8b.

ドラム状感光体は矢印方向に回転し、先ずコロナ放電器
４により表面電位ＶＯに帯電される。次いで感光体は光
像露光同時除電器９位置に至つて、先ずα域で、比較的
強い原画像露光を受け、同時にグリツドの９−α域での
ＶＯ（５０Ｖの間の適当なバイアス電位Ｖ１を印加して
の除電々圧制御により感光体表面は略Ｖ１迄除電される
。次いでβ域で、その感光体面はフイルタ一１０で露光
量を減少された光像露光を受け、同時にグリツドの９−
β域でＶ１より低いバイアス電圧Ｖ２で除電々圧制御し
て、感光体表面は略Ｖ２迄除電される。The drum-shaped photoreceptor rotates in the direction of the arrow and is first charged to a surface potential VO by the corona discharger 4. Next, the photoreceptor reaches the photoimage exposure and simultaneous static eliminator 9 position, where it is first exposed to a relatively strong original image in the α region, and at the same time is applied with an appropriate bias potential V1 between VO (50 V) in the 9-α region of the grid. The surface of the photoreceptor is neutralized to approximately V1 by voltage control for removing static electricity by applying a voltage of −
In the β range, static electricity removal is controlled using a bias voltage V2 lower than V1, and the surface of the photoreceptor is neutralized to approximately V2.

続いて、感光体がγ域を通過するに際して、フイルタ一
１０の１０２部分で更に露光量を減少さわた光像露光を
受け同時にグリッドの９−γ域でＶ２よりも低いバイア
スＶ３をグリツドに印加して感光体表面は略Ｖ３迄除電
される。次に、感光体表面は、ランプ１１で全面露光さ
れ高コントラスト静電潜像が形成される。次いで図示し
ない現像装置で現像顕画され、該現像々は転写材に転写
して、利用する。一方、転写後の感光体面はクリーニン
グして再用に備えることは勿論である、該装置によつて
形成された画像は、第８図ｃに実線で示す様に階調性の
高い原稿濃度を十分再現しうる広いダイナミツクレンジ
を有するものである。Subsequently, as the photoreceptor passes through the γ region, it is exposed to a light image whose exposure amount is further reduced at the 102 portion of the filter 10, and at the same time, a bias V3 lower than V2 is applied to the grid in the 9-γ region of the grid. The surface of the photoreceptor is then neutralized to approximately V3. Next, the entire surface of the photoreceptor is exposed by the lamp 11 to form a high contrast electrostatic latent image. Next, the image is developed and developed using a developing device (not shown), and the developed images are transferred to a transfer material for use. On the other hand, it goes without saying that the surface of the photoreceptor after transfer must be cleaned and prepared for reuse.The image formed by this device has an original density with high gradation, as shown by the solid line in Figure 8c. It has a wide dynamic range that can be reproduced satisfactorily.

破線で示すのが従来の方法の場合である。以一ヒ具体例
に詳述した様に、本発明は、オリジナル像の階調性を忠
実に再現することを可能とするものである。しかも、本
発明は、階調性再現の為のプロセス制御も極めて簡易で
有効に成しうるものである。The case of the conventional method is shown by a broken line. As described in detail in the concrete examples below, the present invention makes it possible to faithfully reproduce the gradation of an original image. Moreover, according to the present invention, process control for gradation reproduction can be performed extremely simply and effectively.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図ａ−ｄは本発明の係る電子写真方法を説明する工
程図及ひ表面電位図。 第２図は、本発明の係る電子写真方法に於ける異なる表
面電位図。第３図Ａ，ｂは、本発明の係る電子写真法に
於ける改良例及びその表面電位図。第４図Ａ，ｂは、画
像濃度一表面電位特性図。第５図、乃至第７図は本発明
に基く電子写真方法に於けるプロセス工程、表面電位図
及び表面電荷図。第８図ａは本発明に基く具体例装置の
説明図。図ｂは表面電位図及び図ｃは潜像電位一原稿濃
度特性図。図中１・・・・・・導電性層、２・・・・・
・光導電性層、３・・・・・・絶縁性層、４・・・・・
・一次帯電器、７・・・・・・オリジナル原稿、８・・
・・・・露光同時放電器、９・・・・・・グリツド、１
０・・・・・・フィルタ一、１１・・・・・・全面露光
ランプ。1A to 1D are process diagrams and surface potential diagrams illustrating the electrophotographic method according to the present invention. FIG. 2 shows different surface potential diagrams in the electrophotographic method according to the present invention. FIGS. 3A and 3B show an improved example of the electrophotographic method according to the present invention and its surface potential diagram. FIGS. 4A and 4B are image density-surface potential characteristic diagrams. 5 to 7 are process steps, surface potential diagrams, and surface charge diagrams in the electrophotographic method based on the present invention. FIG. 8a is an explanatory diagram of a specific example device based on the present invention. Figure b is a surface potential diagram, and Figure c is a latent image potential vs. document density characteristic diagram. In the figure, 1... conductive layer, 2...
・Photoconductive layer, 3... Insulating layer, 4...
・Primary charger, 7...Original manuscript, 8...
...simultaneous exposure discharger, 9...grid, 1
0...Filter 1, 11...Full exposure lamp.

Claims (1)

【特許請求の範囲】[Claims] １ 導電性基体、光導電層、及び絶縁層を基本構成とす
る感光体を用い、その感光体表面を一様帯電し、次いで
感光体に画像露光を施すと同時に上記一様帯電と逆極性
成分を有するコロナ放電により除電し、更に上記画像露
光光量よりも低レベルの露光量で画像露光を施すと同時
に上記一様帯電と逆極性成分を有するコロナ放電により
上記除電により電位よりも低い電位となるように除電し
、その後感光体全面に一様露光を行つて静電潜像を形成
することを特徴とする電子写真方法。1 Using a photoreceptor whose basic composition is a conductive substrate, a photoconductive layer, and an insulating layer, the surface of the photoreceptor is uniformly charged, and then the photoreceptor is subjected to imagewise exposure, and at the same time a component with a polarity opposite to the uniform charging is applied. The charge is removed by a corona discharge having a polarity of 100%, and imagewise exposure is performed at a lower level of exposure than the imagewise exposure light amount.At the same time, the potential becomes lower than the potential due to the charge removal by a corona discharge having a polarity component opposite to the uniform charging. An electrophotographic method characterized by removing static electricity as described above, and then uniformly exposing the entire surface of a photoreceptor to form an electrostatic latent image.