JP3673775B2 - Developing roller and electrophotographic developing apparatus - Google Patents

Description

表１に示した結果から明らかなように、実施例においてはローラ表面のいずれの場所においても５μｍ四方に流れる電流総和値を適正化した現像ローラは電荷のリークによる画像不良を効果的に制御することができ、かつセット跡による画像不良も生じず高品位の画像を得ることができることが判明した。比較例３では、実施例２とローラ電気抵抗が同じであってもカーボンブラックの分散が局所的に悪いので、流れる電流総和値が大きく、結果リークによる画像不良を生じている。
【発明の効果】
以上説明したように、本発明の現像ローラ及びこれを用いた現像装置によれば、リークによる画像不良を効果的に防止することができ、かつ同時にセット跡による画像不良の発生も防止でき、高品位の画像を得ることが可能である。
【図面の簡単な説明】
【図１】本発明の現像ローラの構造を示す断面図である。
【図２】本発明の現像ローラを利用したレーザープリンタの構成を示す概念図である。
【図３】本発明の電気抵抗測定機を示す概念図である。
【符号の説明】
１ 芯金
２ 半導電性弾性層
３ 半導電性樹脂層
４ 現像ローラ
５ 感光ドラム
６ トナー塗布用ローラ
７ 現像ブレード
８ 帯電ローラ
９ クリーニングブレード
１０ 転写ローラ
１１ 定着ローラ
１８ 現像ローラ
１９ ＳＵＳドラム
２０ 直流電源
２１ 内部抵抗[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing roller and a developing device used in an electrophotographic apparatus such as a copying machine or a laser printer.
[0002]
[Prior art]
Conventionally, in an electrophotographic apparatus such as a copying machine or a laser printer or an electrostatic recording apparatus, a non-magnetic one-component developer is supplied to a photosensitive drum or the like holding a latent image, and the developer is attached to the latent image on the photosensitive drum. As a development method for visualizing the latent image, a pressure development method is known. According to this method, since no magnetic material is required, the image forming apparatus can be easily simplified and downsized, and the toner can be easily colored.
[0003]
In this developing method, a developing roller carrying toner (non-magnetic one-component developer) is brought into contact with a latent image holding body holding an electrostatic latent image such as a photosensitive drum, so that the toner becomes a latent image on the latent image holding body. Development is carried out by adhering, and it is necessary to form the developing roller with a conductive elastic body. In the above apparatus, the developing roller rotates while being in contact with the photosensitive member, so that the toner adheres from the developing roller to the photosensitive member. At the time of contact between the developing roller and the photosensitive member, the developing roller is made of an elastic material and a voltage is applied to the toner image on the photosensitive member in order to ensure a uniform pressure contact width to the photosensitive member. Therefore, the roller electrical resistance is required to be in the middle resistance range. At the same time, there is a demand for preventing uniform leakage of electric conductivity and locally generated current (having leakage resistance). Therefore, an elastic layer adjusted to a desired electrical resistance value is formed, and on the outer periphery thereof, a resin such as nylon or urethane is roughened to obtain wear resistance, toner chargeability, toner transportability and to ensure appropriate surface roughness. In many cases, a surface layer to which an insulating material or a conductive material for ensuring conductivity is added is provided.
[0004]
[Problems to be solved by the invention]
In developing leak resistance, the volume resistivity of the semiconductive coating layer is measured. However, in this measurement method, the measurement area is macroscopic.
[0005]
In addition, even if the amount of the electronic conductive material is increased to realize a region with low electrical resistance, if the dispersion state of the electronic conductive material is poor, current leakage occurs due to local uneven electrical resistance, resulting in poor image quality. Will occur. In addition, the use of an ion conductive material alone or in combination with an electronic conductive material has some effect on improving leakage resistance by reducing the amount of the electronic conductive material. If unevenness of the active substance is not taken into account, current leakage will still occur. In addition, a problem such as a large change in electrical resistance of the roller due to environmental fluctuations occurs, and at the same time, an image defect due to a set mark due to the pressure contact between the developing blade and the developing roller becomes remarkable. Accordingly, a problem to be solved by the present invention is to provide a developing roller that has good leak resistance and gives a high-quality image without image defects due to set marks.
[0006]
[Means for Solving the Problems]
The present invention provides a developing roller having at least one semiconductive layer around a cored bar, wherein the outermost surface layer of the developing roller is 15 to 45 parts by mass with respect to 100 parts by mass of the resin component and the resin component. When a voltage of 10 V is applied to an arbitrarily selected 5 μm square area on the outer periphery of the developing roller, the total current flowing is 1.0 × 10 to 1.0 × 10 ⁴ nA. The present invention relates to a developing roller.
[0007]
Of the layers constituting the semiconductive layer, the outermost surface layer preferably contains a resin component and an electronic conductive material.
[0008]
The electronic conductive material is preferably carbon black.
[0009]
In the developing roller, among the layers constituting the semiconductive layer, assuming that the content of carbon black with respect to 100 parts by mass of the resin component forming the outermost surface layer is n parts by mass, a value of n × total current value / 10000 is obtained. It is preferable that it is 0.01-50 nA.
[0010]
Furthermore, the present invention relates to a developing roller characterized in that a coating material is applied to the outer peripheral portion of the developing roller and the conductive material is dispersed in advance using ultrasonic vibration.
[0011]
Furthermore, the present invention relates to an electrophotographic process cartridge having a developing roller.
[0012]
Furthermore, the present invention has a developing roller for visualizing the toner image by forming a toner thin film on the surface by contacting the latent image carrier in this state and supplying the toner to the latent image carrier. The present invention relates to a characteristic electrophotographic image forming apparatus.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a developing roller having at least one semiconductive layer around a cored bar, wherein the outermost surface layer of the developing roller is 15 to 45 parts by mass with respect to 100 parts by mass of the resin component and the resin component. When a voltage of 10 V is applied to an arbitrarily selected 5 μm square area on the outer periphery of the developing roller, the total current flowing is 1.0 × 10 to 1.0 × 10 ⁴ nA. The present invention relates to a developing roller.
[0014]
As already known in terms of leakage resistance, if there are too many electron conductive substances, image defects will occur due to current leakage.
[0015]
By using the roller according to the present invention, it is possible to obtain a developing roller that is resistant to environmental fluctuations without causing image defects due to pressure contact marks.
[0016]
In a developing roller using an electronic conductive material, even if the electrical resistance value of the roller is the same, an image defect due to leakage may occur depending on the dispersion state of the electronic conductive material. However, image defects due to current leakage can be prevented by using a roller having a current sum of local portions of the roller of 1.0 × 10 to 1.0 × 10 ⁴ nA.
[0017]
The semiconductive layer can be used as two or more layers. The semiconductive layer formed on the outer periphery of the roller uses an elastomer such as EPDM or urethane, a foam material, or other resin molding as a base material. By using such a molded body, a developing roller having low hardness and low compression set can be obtained. In addition, it is preferable to use an electronic conductive material such as carbon black, metal, or metal oxide as the conductive material for the semiconductive layer forming the outer peripheral portion, but an ionic conductive material such as sodium perchlorate. Those blended with can also be used. Examples of the electronic conductive material include conductive carbon such as ketjen black EC and acetylene black, rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, and a color-treated carbon ( Ink), metals such as carbon, copper, silver, germanium, and metal oxides may be mentioned. Among these electronically conductive materials, carbon black that is easy to control the conductivity with a small amount is preferably used. These conductive powders are preferably used in an amount of preferably 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass with respect to 100 parts by mass of the base material. Examples of ionic conductive materials used as conductive materials include inorganic ionic conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate and lithium chloride, and modified aliphatic dimethylammonium ethosulphate. An organic ionic conductive material such as stearyl ammonium acetate is used.
[0018]
Regarding the dispersion of the raw materials, a ball mill, a sand mill, a liquid collision type dispersion, an ultrasonic dispersion or the like can be used alone or in combination. For example, it is preferable that 30 parts by mass of alumina balls 10φ and 30 parts by mass of 15φ are mixed with 100 parts by mass of the coating material constituting the surface layer, and mixed at a rotation speed of 20 rpm for 12 hours or more. The mixing time of the ball mill may be changed according to the content of carbon black in the paint.
[0019]
A developing roller using two semiconductive layers according to the present invention will be described. As shown in FIG. 1, the developing roller of the present invention has a semiconductive elastic layer 2 on the outer periphery of a highly conductive shaft 1, and this semiconductive elastic layer 2 is a semiconductive outermost surface layer. It is formed by covering with a conductive resin layer 3. In the present invention, the total value of the current that flows when a voltage of 10 V is applied to an arbitrarily selected 5 μm square area on the surface of the outer periphery of the roller when a voltage of 10 V is applied to the developing roller at any location on the roller surface is 1. 0.0 × 10 to 1.0 × 10 ⁴ nA can be adjusted as described later. Here, the thickness of the entire semiconductive layer is preferably 1 to 6 mm. More preferably, the thickness of the entire semiconductive layer is 2 to 5 mm. Moreover, it is preferable that the thickness of the semiconductive layer which forms an outer peripheral part is 3-100 micrometers. More preferably, the thickness of the semiconductive layer forming the outer peripheral portion is 10 to 30 μm.
[0020]
Specifically, the base material of the semiconductive elastic layer 2 in the developing roller illustrated in FIG. 1 is polyurethane, natural rubber, butyl rubber, nitrile rubber, polyisoprene rubber, polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene. Examples thereof include propylene rubber, ethylene-propylene-diene rubber, chloroprene rubber, acrylic rubber, and mixtures thereof. Silicone rubber is preferably used because it is soft and has little compression set.
[0021]
Examples of the silicone rubber used here include dimethyl silicone rubber, diphenyl silicone rubber, and fluorosilicone rubber. As the silicone rubber, for example, a curable organopolysiloxane and a crosslinked one using a curing agent having a siloxane skeleton can be used. As the curable organopolysiloxane, for example, dimethylpolysiloxane or an organopolysiloxane having a functional group that reacts with a curing agent such as a vinyl group at the terminal can be used. Moreover, organohydrogenpolysiloxane can be used as a hardening | curing agent. The alkenyl group of the curable organopolysiloxane is a site that reacts with the active hydrogen of the organohydrogenpolysiloxane that is a curing agent to form a crosslinking point, and the type is not particularly limited, but the reactivity with the active hydrogen For reasons such as being high, at least one of a vinyl group and an allyl group is preferable, and a vinyl group is particularly preferable.
[0022]
As an appropriate electric resistance region of the semiconductive layer, a volume resistivity adjusted to 1 × 10 ³ to 1 × 10 ¹⁰ Ω · cm, preferably 1 × 10 ⁴ to 1 × 10 ⁸ Ω · cm is used. When the volume resistivity is in the range of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · cm, the problem of charge leakage does not occur, an appropriate image density is obtained, and problems such as fog do not occur.
[0023]
Here, any material can be used as the highly conductive shaft 1 as long as it has good conductivity. Usually, it is a metal cylindrical body having an outer diameter of 4 to 10 mm made of aluminum, iron, SUS, or the like. It is preferable to use one. The thickness of one layer of the elastic layer is preferably 1 to 6 mm. The developing roller preferably has an Asker C hardness of 25 to 65 °.
[0024]
Of the layers constituting the semiconductive layer, the outermost surface layer preferably contains a resin component and an electronically conductive substance.
[0025]
Next, the outermost surface layer covering the semiconductive elastic layer 2 is specifically polyamide resin, fluorine resin, hydrogenated styrene-butylene resin, polyurethane resin, silicone resin, polyester resin, phenol resin, imide resin, olefin resin. Etc. When the semiconductive resin layer 3 which is the outermost surface layer is formed of a polyurethane resin, the polyurethane resin is preferably used because it has a large ability to charge toner by friction and has wear resistance. The thickness of the outermost surface layer is preferably 3 to 100 μm so as not to impair the flexibility of the elastic layer and to have good wear resistance. More preferably, the outermost surface layer is 10 to 30 μm.
[0026]
Next, examples of the electronic conductive material used to impart conductivity to the semiconductive elastic layer 2 include conductive carbon such as ketjen black EC and acetylene black, SAF, ISAF, HAF, FEF, GPF, Examples thereof include carbon for rubber such as SRF, FT, and MT, carbon for color (ink) subjected to oxidation treatment, metals such as copper, silver, and germanium, and metal oxides. Among these electronically conductive materials, carbon black that is easy to control the conductivity with a small amount is preferably used. These conductive powders are preferably used in an amount of preferably 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass with respect to 100 parts by mass of the base material. In this way, by using an electronic conductive material as the conductive material for the outermost surface layer, it is possible to obtain a developing roller having good electrical resistance characteristics even at a local portion. In addition, there is little change in electrical resistance due to environmental changes, and image deterioration caused by this change does not occur. When the developing blade comes into pressure contact with the developing roller, the ion conductive material is unevenly distributed, and pressure contact traces such as the developing blade are generated, and defects such as horizontal stripes do not occur in the image. In the present invention, it is possible to provide a developing roller excellent in leak resistance even when only an electronic conductive material is used.
[0027]
In order to obtain the electric resistance required for the developing roller, it is preferable to blend the conductive material in a ratio of 1 to 70 parts by mass with respect to 100 parts by mass of the resin component constituting the outermost surface layer. More preferably, it can be used at a ratio of 1 to 50 parts by mass.
[0028]
Further, in the present invention, among the layers constituting the semiconductive layer, when the content of carbon black with respect to 100 parts by mass of the resin component forming the outermost surface layer is n parts by mass, the value of n × total current value / 10000 is obtained. It is preferable that it is 0.01-50 nA. As described above, by setting the value of n × current sum value / 10000 to 0.01 to 50 nA, it is possible to more effectively prevent image defects due to leakage.
[0029]
Further, it is preferable that the developing roller is one in which a coating material is applied to the outer peripheral portion, and the coating material is obtained by dispersing a conductive substance in advance using ultrasonic vibration. As an ultrasonic disperser, for example, Branson 8510 can be used.
[0030]
In order to obtain particularly good dispersion, it is preferable to use dispersion by an ultrasonic irradiator. Furthermore, after the surface roughening material is dispersed as necessary, a curing agent or a curing catalyst is added and a paint obtained by stirring is applied by a method such as spraying or dipping. As a result, a developing roller having a total current value of 1.0 × 10 to 1.0 × 10 ⁴ nA flowing in 5 μm square when 10 V is applied can be obtained at any location on the roller surface.
[0031]
The present invention relates to an electrophotographic process cartridge having the developing roller.
[0032]
Also, an electrophotographic image forming apparatus having a developing roller for carrying a toner on the surface to form a toner thin film, and in this state, contacting the latent image carrier and supplying the toner to the latent image carrier The present invention relates to an electrophotographic image forming apparatus having a developing roller. The developing roller according to the present invention can be used in an electrophotographic image forming apparatus. As shown in FIG. 2, the electrophotographic image forming apparatus has a toner application roller 6 for supplying toner, a charging roller 8 for charging the photosensitive drum 5, and a toner image corresponding to the photosensitive drum 5 holding an electrostatic latent image. The toner is supplied to the surface of the developing roller 4 by the developing roller 4 and the toner application roller 6 for forming the toner, and the developing roller 7 for adjusting the toner into a more uniform thin layer. In this state, the developing roller 4 is photosensitive. By rotating while in contact with the drum 5, the toner formed in a thin layer adheres to the latent image on the photosensitive drum 5 from the developing roller 4, and the latent image is visualized. In FIG. 2, reference numeral 10 denotes a transfer portion, which transfers a toner image onto a recording medium such as paper. Reference numeral 9 denotes a cleaning blade, which remains on the surface of the photosensitive drum 5 after transfer. Toner is removed. Further, reference numeral 11 in FIG. 2 denotes a fixing roller, which fixes toner on a recording medium such as paper with heat and pressure.
[0033]
【Example】
(Example 1)
A core metal having an outer diameter of 8 mm is placed concentrically in a cylindrical mold having an inner diameter of 16 mm, and liquid conductive silicone rubber (two-part silicone rubber: Asker C hardness 35 degrees: volume resistivity 1.0 as an elastic layer) × 10 + E7 Ω · cm) was cast, placed in an oven at 130 ° C. and heat-molded for 20 minutes. After demolding, secondary vulcanization was performed in an oven at 200 ° C. for 4 hours to obtain a roller having an elastic layer thickness of 4 mm. Next, a polyol (trade name: Nipponporan N5033, manufactured by Nippon Polyurethane Co., Ltd.) is diluted with methyl ethyl ketone so as to have a concentration of 10%, and carbon black (MA100 (trade name): manufactured by Mitsubishi Chemical Corporation) is used as a conductive substance. 15 parts by mass with respect to 100 parts by mass of the total solid content of the polyol and the isocyanate compound to be added later, nylon beads (trade name: SP500, manufactured by Toray Industries, Inc.) as a surface roughening material, and the total solid content of the isocyanate compound to be added later Addition of 20 parts by mass with respect to 100 parts by mass, stirring and dispersing with a ball mill for 12 hours, and further coating with an ultrasonic compound (8510: Branson sales company) for 1 hour, an isocyanate compound (trade name: Coronate L, (Made by Nippon Polyurethane Co., Ltd.) , A urethane paint is prepared by stirring, applied to a previously molded roller by dipping to a film thickness of 15 μm, dried in an oven at 80 ° C. for 15 minutes, and then cured in an oven at 140 ° C. for 4 hours, A developing roller was obtained.
(Example 2)
A developing roller was obtained in the same manner as in Example 1 except that carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation) was used as the conductive material and the amount was 30 parts by mass with respect to 100 parts by mass of the total solid content of the polyol and isocyanate compound. It was.
(Example 3)
Example 1 except that carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation) as a conductive substance is 45 parts by mass with respect to 100 parts by mass of the total solid content of polyol and isocyanate compound, and ultrasonic dispersion is set to 4 hours. Similarly, a developing roller was obtained.
( Comparative Example 1 )
A developing roller was obtained in the same manner as in Example 1 except that commercially available sodium perchlorate was used as the conductive material in an amount of 2 parts by mass with respect to 100 parts by mass of the total solid content of polyol and isocyanate compound.
(Comparative Example 2 )
A developing roller was obtained in the same manner as in Example 1 except that carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation) was used as the conductive material at 50 parts by mass with respect to 100 parts by mass of the total solid content of polyol and isocyanate compound. It was.
(Comparative Example 3 )
Carbon black (MA100 (trade name): manufactured by Mitsubishi Chemical Corporation) as the conductive material is 30 parts by mass with respect to 100 parts by mass of the total solid content of the polyol and isocyanate compound, and is the same as in Example 1 without using a ball mill. A developing roller was obtained.
<Measurement of roller electrical resistance>
The roller electrical resistance of the roller was measured using an electrical resistance measuring machine shown in FIG. 3 at a voltage of 100 V and a roller rotation speed of 1 rps, and the average value for 30 seconds was defined as the roller electrical resistance value. . The results of measuring the electrical resistance of each roller are shown in Table 1.
<Measurement of total current value>
The current total value of the roller was measured by cutting the roller surface into 3 mm squares, fixing the roller surface to a sample table with a conductive adhesive, and performing simultaneous AFM current measurement with a scanning probe microscope SPA400 (manufactured by Seiko Instruments). SI-AF01-R was used as a cantilever. The measurement conditions were a scanning range of 5 μm, an applied voltage of 10 V, and a measurement data number of 256 × 256. The obtained current image was converted into ASCII data, and the sum of the current values was obtained. Table 1 shows the current value of each roller.
<Leak image evaluation>
The roller leak is evaluated by using a photoconductor with a pinhole having a diameter of 0.2 mm in the non-image area, and outputting a halftone image in a low temperature and low humidity environment (15 ° C / 10% RH) with a color laser printer. The horizontal streaks of the pinhole part and the unevenness of the image were visually determined. Table 1 shows the determination results for each roller.
<Set image evaluation>
The roller is pressed against a flat plate with a 1 kg load (500 g load on both ends of the core) and left in a high temperature and high humidity environment (40 ° C., 95% RH) for 30 days, and then a low temperature and low humidity environment (using a color laser printer) The solid image was output at 15 ° C./10% RH), and the presence or absence of image streaks was visually evaluated. Table 1 shows the determination results for each roller.
[0034]
[Table 1]

As is apparent from the results shown in Table 1, in the embodiment, the developing roller that optimizes the total current value flowing in a 5 μm square at any location on the roller surface effectively controls image defects due to charge leakage. It was found that a high-quality image can be obtained without causing image defects due to set marks. In Comparative Example 3 , even though the roller electrical resistance is the same as in Example 2, the dispersion of carbon black is locally bad, so that the total value of the flowing current is large, resulting in image defects due to leakage.
【The invention's effect】
As described above, according to the developing roller of the present invention and the developing device using the same, it is possible to effectively prevent image defects due to leakage, and at the same time, prevent occurrence of image defects due to set marks. It is possible to obtain a quality image.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a developing roller of the present invention.
FIG. 2 is a conceptual diagram showing a configuration of a laser printer using the developing roller of the present invention.
FIG. 3 is a conceptual diagram showing an electrical resistance measuring machine according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Core metal 2 Semiconductive elastic layer 3 Semiconductive resin layer 4 Developing roller 5 Photosensitive drum 6 Toner application roller 7 Developing blade 8 Charging roller 9 Cleaning blade 10 Transfer roller 11 Fixing roller 18 Developing roller 19 SUS drum 20 DC power supply 21 Internal resistance

Claims (5)

In the developing roller having at least one or more semiconductive layers around the cored bar, the outermost surface layer of the developing roller has a resin component and an electronic conductivity of 15 to 45 parts by mass with respect to 100 parts by mass of the resin component. Containing chemical substances,
A developing roller having a total current value of 1.0 × 10 to 1.0 × 10 ⁴ nA when a voltage of 10 V is applied to an arbitrarily selected 5 μm square area on the outer peripheral portion of the developing roller . The developing roller according to claim 1, wherein said electron conductive material and wherein the carbon black der Rukoto. Coating is applied to the outer periphery of the developing roller, paint is using ultrasonic vibration, the developing roller according to claim 1 or 2, characterized in that by dispersing pre-conductive material. Electrophotographic process cartridge according to claim Rukoto that having a developing roller according to any one of claims 1 to 3. In an electrophotographic image forming apparatus having a developing roller for forming a toner thin film by carrying a toner on the surface, and contacting the latent image carrier in this state and supplying the toner to the latent image carrier for visualization an electrophotographic image forming apparatus, wherein the developing roller is the developing roller according to any one of claims 1 to 4.

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