JP2008026380A - Non-contact type electrifying roller, electrifying device equipped with non-contact type electrifying roller and image forming apparatus equipped with electrifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-contact type electrifying roller which has very little swell expansion compared to the conventional one in the range of the environmental conditions of an image forming apparatus, is free from the occurrence of cracks that may result in image formation failure, also free from bleeding-out of an ion conductive agent, ensures suppression of variation of electrification potential relative to a body to be electrified, and further is hardly subject to sputtering action during discharge, and to provide an electrifying device equipped with the non-contact type electrifying roller and an image forming apparatus equipped with the electrifying device. <P>SOLUTION: (1) The non-contact type electrifying roller is obtained by forming an oxide film of aluminum on the surface of a support composed of aluminum alloy, and forming a silica film obtained by using alkoxy silane on the surface of the oxide film. (2) The non-contact type electrifying roller described in (1) is such that the oxide film and the silica film obtained by using the alkoxy silane are resistance adjusting layers and a protective layer composed of resin composition including conductive particulates dispersed therein is formed on the surface of the resistance adjusting layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-contact charging roller that charges a surface of an image carrier in a non-contact manner, a charging device including the non-contact charging roller, and an image forming apparatus including the charging device.

Charging devices used in electrophotographic image forming apparatuses such as copiers and laser printers are charged at a low voltage to suppress the formation of ozone and nitrogen oxides, downsized image forming apparatuses, In order to reduce the cost and the like, a contact-type charging roller is used in which the charging potential applying surface of the charging roller is in contact with the photosensitive member.
The material used as the charging potential application surface of the contact-type charging roller is made by dispersing conductive fine particles such as carbon black in an elastic member such as acrylonitrile butadiene rubber or epichlorohydrin rubber, and having a volume resistivity of 10 ⁶ to 10 ^9. Apply a thin (0.1-0.2 μm) composition containing water-repellent fluororesin, etc. on the surface, with a thickness of 2 to 3 mm, preventing contamination and setting environment (high temperature and high humidity) However, at high temperatures and high humidity in the installation environment, the elastic member easily expands and swells and changes the charging performance.
Similarly, a surface coating film made of polysilazane is formed on the surface of an elastic member such as polyurethane having an electrical resistance of 10 ³ to 10 ¹⁰ Ωcm in which a conductivity imparting agent such as carbon black is dispersed to reduce the friction coefficient, A conductive roller is known that has a low adhesiveness and a small change in outer diameter and electrical resistance due to sliding and press-rotating (see Patent Document 1). The elastic member easily expands and swells, and changes the charging performance. In addition, since the surface is contact type, paper dust of recording paper, toner remaining on the surface of the photoreceptor and the like are likely to become dirty, and problems are likely to occur in terms of durability in long-term use.
For this reason, non-contact type charging rollers that improve the expansion / swellability of the member that forms the charging potential applying surface, are less likely to adhere dirt, and have a relatively low maintenance frequency have come to be used.

In a non-contact type charging roller, a polyether ester amide component, which is a polymer surfactant, is contained in an ABS resin on a conductive support, and is coated with a thickness of 0.5 to 1 mm by injection molding, and a resistance adjusting layer. And 50 to 60% by weight of conductive agent fine particles such as tin oxide, ITO (indium tin oxide), carbon black, and the like on the surface, and adjusted so that the volume resistivity is 10 ¹⁰ to 10 ¹² Ωcm. What formed the protective layer with a film thickness of 5-10 micrometers which consists of a composition is used. In this non-contact type charging roller, the resistance adjustment layer on the conductive support is a resin, and the protective layer is also made of an acrylic, silicon, urethane or fluorine-based resin and conductive fine particles. In contrast, the swelling expansion amount is relatively small with respect to changes in temperature and humidity conditions, and the charging gap in the non-contact type is rarely narrowed.
However, when the polyether ester amide component is contained in the ABS resin to form a resistance adjusting layer, the volume resistivity value of the ABS resin is high (10 ¹² to 10 ¹⁶ Ωcm), so that it decreases to 10 ⁸ to 10 ⁹ Ωcm. Therefore, it is necessary to mix and disperse a large amount of 10 ⁷ to 10 ⁸ Ωcm polyether ester amide component (about 100 to 120 parts by weight with respect to 100 parts by weight of ABS resin), and depending on temperature and humidity conditions, saturated water absorption 50 to 70 % Of the polyetheresteramide component is easily affected. For this reason, some surfactants such as quaternary ammonium salts are added to suppress the addition amount of the polyetheresteramide component by adding 3 to 5% by weight.
In addition, when injection molding is performed with the polyether ester amide component contained in the ABS resin, if the moisture absorption amount of the pellet material for injection molding is large, foam will be generated and defective molding will occur. Is used after dehumidifying to 0.5 to 1% by mass.

The protective layer formed on the resistance adjustment layer is formed by spray coating or the like using an isocyanate curing agent so as to have a film thickness of 5 to 15 μm, and then heated at 100 to 130 ° C. for about 30 minutes. In order to form by performing, it will harden | cure on the surface in the state which the lower resistance adjustment layer thermally expanded.
In the image forming apparatus, an operating environment ranging from high temperature and high humidity (30 ° C. and 90% RH) to low temperature and low humidity (10 ° C. and 15% RH) is assumed, but the non-contact type charging roller formed by the above method is Since the saturated water absorption rate of the polyether ester amide component of the resistance adjusting layer is as high as 50 to 70%, the moisture swells through the protective layer under high temperature and high humidity conditions.
In addition, when the resistance adjustment layer material is cured in the molding die during the injection molding process, the polyether ester amide component increases in the weld line, the electrical resistance of the portion decreases, and the electric path for applying the charging potential It tends to generate heat, becomes denatured and becomes brittle, and when the operating environment of the image forming apparatus becomes low temperature and low humidity (10 ° C., 15% RH), it causes a difference in shrinkage and easily causes cracks.

As a related known technique, Patent Document 2 discloses a thermoplastic composition in which an ion conductive material composed of a polyether ester amide-containing compound or a quaternary ammonium base-containing compound of a polymer type ion conductive material is dispersed on a conductive support. A charging member is disclosed in which a resistance adjusting layer is formed by injection molding or extrusion molding, and the surface thereof is coated with a protective layer made of a ceramic hybrid material containing a polysiloxane component in an acrylic skeleton.
However, when the resistance adjusting layer is formed by injection molding or extrusion molding using the thermoplastic composition, the protective layer is formed on the surface by increasing the thickness of the layer to about 1 to 2 mm in order to ensure the fluidity of the molten material. The resistance adjustment layer is likely to be cracked by swelling in the vicinity of the surface due to the solvent at the time of forming the protective layer, or the resistance adjustment layer is thermally expanded or dried by heat drying when forming the protection layer. Invite moisture. In addition, the polyether ester amide component increases in the weld line part in the molding die, and it becomes easy to generate heat by forming an electric circuit, and the resin component is easily modified and deteriorated to cause cracks. An ionic conductive material such as a quaternary ammonium salt in the resistance adjustment layer bleeds out to the surface of the protective layer, thereby changing the charged potential of the charged body.

In Patent Document 3, the environmental stability is improved by covering with a protective layer from the outer peripheral surface of the resistance adjusting layer to the side surfaces of both ends. However, the protective layer is a thin film of about 10 μm, and the conductive fine particles are 50 Since it is added to 60% by weight, moisture easily permeates. Further, since the polyether ester amide component of the resistance adjusting layer easily absorbs moisture and swells, the protective layer is easily cracked. In addition, when the resistance adjustment layer is formed by injection molding with the thermoplastic composition, it is necessary to form a protective layer on the surface by increasing the thickness of the layer to about 1 to 2 mm in order to ensure the fluidity of the molten material. Further, the resistance adjusting layer swells due to the solvent at the time of forming the protective layer, and cracks are easily generated.
Further, when the resistance adjusting layer material is cured in the molding die during the injection molding process, the polyether ester amide component increases in the weld line, the electric resistance of the portion decreases, and the electric path when the charging potential is applied Heat is generated, the resin is denatured and deteriorated and becomes brittle. When the operating environment of the image forming apparatus is low temperature and low humidity (10 ° C. and 15% RH), a difference in shrinkage is easily generated and cracks are easily generated.

In Patent Document 4, a protective layer is composed of a hybrid resin containing a fluorine component and a polysiloxane oligomer in an acrylic skeleton in order to prevent toner fixation and charging failure associated therewith and improve durability during long-term use. A method is disclosed.
However, when injection molding is performed using a thermoplastic composition containing a polyether ester amide component in the resistance adjustment layer, in order to ensure the fluidity of the molten material, the thickness of the layer is increased to about 1 to 2 mm. There is a disadvantage that a protective layer needs to be formed on the surface, and the vicinity of the surface of the resistance adjusting layer is easily swollen by a solvent at the time of forming the protective layer, and cracks are easily generated.
In addition, when the resistance adjustment layer material is cured in the molding die during the injection molding process, the polyether ester amide component increases in the weld line, and the electric resistance of the portion decreases to provide an electric circuit for applying a charging potential. When heat is generated, the resin is denatured and deteriorated and becomes brittle, and when the operating environment of the image forming apparatus is low temperature and low humidity (10 ° C., 15% RH), a difference in shrinkage is easily generated and cracks are easily generated.
In addition, the small-diameter non-contact type charging roller has a drawback that rigidity is lowered because the metal shaft member, which is a conductive support in the central portion, is formed relatively thin, and the charging potential between the surface of the photosensitive member and the charging roller is low. The variation in the charging gap formed by the imparting surface is increased, and charging unevenness to the photosensitive member is likely to occur.
For this reason, there is a tendency to increase the superimposed AC (alternating current) voltage to prevent charging unevenness of the DC (direct current) voltage applied to the charging roller, and the weld line polyether formed in the resistance adjusting layer of the charging roller. The current in the portion where the ester amide component is increased is increased, and the degradation is deteriorated and becomes brittle, and cracks are easily generated.
In addition, the charged potential application surface has a strong corona discharge and is easily damaged by the generated ozone and sputtering action.

JP-A-9-90739 JP 2003-76116 A JP 2004-70172 A JP 2004-109528 A

  The present invention has been made in view of the above circumstances, and in the range of environmental conditions (10 ° C. 15% to 30 ° C. 90%) of the image forming apparatus, the swelling and expansion is very small as compared with the conventional non-contact type charging roller. In addition, there is no occurrence of cracks that cause image formation defects, there is no bleed-out of the ionic conductive agent, charging potential fluctuation to the charged body can be suppressed, and furthermore, it can be subjected to sputtering action during discharge. An object of the present invention is to provide a small number of non-contact type charging rollers, a charging device including the non-contact type charging roller, and an image forming apparatus including the charging device.

The above problems are solved by the following inventions 1) to 4) (hereinafter referred to as the present invention 1 to 4).
1) A non-contact type charging roller characterized in that an aluminum oxide film is formed on the surface of a support made of an aluminum alloy, and a silica film obtained by using alkoxysilane is formed on the surface of the oxide film.
2) A silica film obtained using an oxide film and alkoxysilane is used as a resistance adjustment layer, and a protective layer made of a resin composition in which conductive fine particles are dispersed is formed on the surface of the resistance adjustment layer. 1) The non-contact type charging roller described.
3) As a non-contact type charging roller that is in contact with both ends of the photoconductor of the image forming apparatus and forms a charging gap in a range that becomes a charging surface of the photoconductor to apply a charging potential to the photoconductor 1) or 2 A charging device comprising the non-contact type charging roller according to claim 1.
4) An image forming apparatus comprising the charging device according to 3) as a charging device for charging the surface of the photoreceptor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 8A is a configuration diagram of a black and white and color image forming apparatus using a function-separated organic photoconductor and using the Carlson process. Toner image forming units 81 for each color of cyan, magenta, yellow, and black are sequentially arranged. Has been placed.
FIG. 8B shows the configuration of the toner image forming unit 81, centering on a cylindrical function-separated organic photoconductor 82 having an outer diameter φ of 30 to 100 mm, and a charging unit 83, an optical writing unit 84, A developing unit 85 and a cleaning unit 86 are arranged, configured for each color toner, and arranged on the transfer belt 88 of the transfer unit 87.
The surface of the function-separated organic photoconductor 82 is charged with a positive or negative voltage of 600 to 800 V by a charging roller 89, forms a latent image with a laser beam 810, and electrostatically attaches toner with a developing member 811. Then, the toner image is electrostatically transferred onto the recording paper 812 by the transfer member 813, and the recording paper 812 on which the image is formed is conveyed to the fixing unit 814 in FIG. The image is fixed by heating and pressing.

In recent years, a method for charging a photoconductor of an image forming apparatus such as a copying machine or a laser printer has been proposed in order to reduce the size of the charging device and save space, and to reduce the amount of ozone generated when a charged potential is applied to the photoconductor. In addition, a proximity roller charging method that enables low voltage charging is employed.
In this proximity roller charging, a conductive rubber having a thickness of 1 to 2 mm in which a conductive agent such as carbon black is dispersed and mixed is used, and its resistance value is set to 10 ⁸ in order to prevent uneven charging during image formation. Use a contact-type charging roller that is controlled to 10 ⁹ Ωcm and makes contact with the photoreceptor without making a charging gap using its elasticity, or a polymer compound such as polyetheresteramide and a quaternary ammonium salt, etc. A resistance adjustment layer is formed by coating the surface of a conductive support with a thickness of 0.5 to 1 mm by injection molding with an ABS resin whose resistance value is controlled to 10 ⁸ to 10 ⁹ Ωcm by containing an ionic conductive material. A protective layer made of a thermoplastic resin composition in which conductive fine particles such as tin oxide, ITO (indium tin oxide), and carbon black are dispersed is formed on the surface of the resistance adjustment layer; Charging at a low voltage by using a non-contact type charging roller that is in non-contact with the photosensitive member by bringing the both ends into contact with each other using a charging gap holding member and having a gap of 50 to 100 μm close to each other. I am letting.

<Causes of damage to resistance adjustment layer and protective layer of non-contact type charging roller>
As shown in FIG. 3A, in the non-contact type charging roller, a metal shaft member 30 is used as a support for applying a charging voltage, and a bearing portion 31, a voltage application bearing portion 32, an outer diameter of 8 to 8 are used. A 12 mm covering portion 33 is integrally formed.
As shown in FIG. 3B, an ABS resin (thermoplastic resin) containing a polymer compound such as polyetheresteramide and an ion conductive substance such as a quaternary ammonium salt is formed on the peripheral surface of the covering portion 33. Is used to form a resistance adjusting layer 34 by coating with a thickness of 0.5 to 1 mm by injection molding, and tin oxide, ITO (indium tin oxide), carbon is formed on the surface of the resistance adjusting layer 34 A protective layer 35 having a thickness of 5 to 10 μm is formed of a thermoplastic resin composition having an electric resistance of 10 ¹² to 10 ¹³ Ωcm in which conductive fine particles such as black are dispersed.
In the non-contact type charging roller, the gap forming members 36 and 37 are covered to form a gap by making contact with both ends of the photoreceptor to form a desired charging gap.
The thickness of the gap forming members 36 and 37 is usually about 50 to 60 μm in order to make the applied voltage low, and adhesive tapes such as Teflon (registered trademark) and polyimide, heat-shrinkable Teflon (registered trademark) tubes, and Resin or the like is used.

As shown in FIG. 3C, the non-contact type charging roller shown in FIG. 3B is used to come into contact with both ends of the photosensitive member of the image forming apparatus, and the charging gap 39, When 310 and 311 are formed, in the charging gap 310 in the central portion of the photoconductor, the gap tends to be narrowed, and the charging potential is changed at 5 to 10 V per 1 μm of the narrowing amount. Problems that cause unevenness and roughness are likely to occur.
This is because the metal shaft member 30 of the non-contact type charging roller is reduced in diameter to reduce the size of the image forming apparatus, and the mechanical strength in the axial direction is lowered. 36 and 37, the charging gap 310 is 50-60 μm. However, depending on the accuracy of forming the non-contact type charging roller 312 and the photosensitive member 313, the charging gap 310 in the central portion is larger than the charging gap 50-60 μm in the central portion in the axial direction. There is a tendency to be narrowed by about 5 to 10 μm.
Further, in the central portion of the non-contact type charging roller, if the metal shaft member 30 is used without any treatment, the shaft portion of the covering portion 33 is likely to be shaken by 10 to 20 μm. As a result, the toner comes in contact with the remaining toner, and the toner adheres to the central portion of the non-contact type charging roller and becomes contaminated.

Further, when the metal shaft member 30 of the non-contact type charging roller is used while the mechanical strength in the axial direction is low, the accuracy of the width of the charging gap 310 in the central portion and the outer diameter shape affect the formation of the charging gap, The superimposed AC voltage (Vp-p) is raised to prevent charging unevenness, and the discharge current is a thin line formed at the place where the flow front portions of the resin meet when the resistance adjustment layer 34 is molded with the resin. There is a tendency to flow in a weld line.
In the weld line, the polyether ester amide component, which is a polymer surfactant for adjusting resistance, is likely to aggregate, the discharge current increases in the aggregated part, heat generation is increased, and deterioration is likely to occur. Highly hygroscopic polyether ester amide component absorbs moisture, lowers electrical resistance, discharge current tends to increase, promotes deterioration of deterioration, easily causes cracks in the resistance adjustment layer, and changes to low temperature and low humidity conditions. Cracks occur at the parts that are cut.

In the case of the non-contact type charging roller, when correcting the charging unevenness without correcting the shape and accuracy of the metal shaft member 30 with respect to the linearity of the shaft, etc., it is superimposed to correct the charging unevenness. The AC applied voltage (Vp-p) is about -2000 to -2400V with respect to the charging of the photoconductor of -800V. As a result, the surface of the charging roller is discharged at a high voltage, and due to the generated ions and sputtering action, the degree of decomposition and wear of the resin component, which is the binder of the protective layer on the outermost surface, increases, and the formed image becomes rough. Will occur and the life of parts will be shortened and will be replaced.
Also, the surface of the organic photoreceptor is damaged by the collision of the generated ions and electrons, and the life of the photoreceptor is reduced due to decomposition and wear of the resin forming the photosensitive layer. In addition, when discharging at a high voltage, the amount of ozone and nitrogen oxide generated increases, and the indoor environment in which the image forming apparatus is installed is contaminated with odors.
In FIG. 3C, reference numerals 314 and 315 denote gears, and reference numeral 316 denotes an inter-axis distance.

<Configuration of Non-Contact Charging Roller of the Present Invention>
Therefore, in the present invention, as shown in FIG. 1 (a), a support 11 made of an aluminum alloy is formed on a metal shaft member 10, and the surface thereof has a nose R1 to 5 mm at a cutting edge, a 5 Turned with a diamond tool of 10 °, a squeeze angle of 15 to 20 °, a roughness of the blade surface of 0 to 0.2 μm, and a round radius of the cutting edge ridge formed by the blade surface of 0 to 0.5 μm. An aluminum oxide film 12 is formed, and a silica film 13 obtained by using alkoxysilane is further coated to form a non-contact type charging roller.
As shown in FIG.1 (b), the detailed structure of the layer formed sequentially uses the support body 14 (JIS H 4080 1999 description, alloy number 1000s, 5000s, 6000s description) which consists of aluminum alloys. ) Is anodized using an inorganic or organic acid having a concentration of 0.5 to 2.5 mol / L as an electrolytic solution to form an oxide film 16 having a thickness of 10 to 30 μm in which fine holes 15 are formed. .
Next, alkoxysilane (tetraethoxysilane, polytetraethoxysilane, etc.), which is a colorless transparent liquid containing 28.8% by weight of SiO _2, is applied to the surface of the oxide film 16 and baked at 100 to 150 ° C. for 1 hour. A silica film 17 is formed.
The barrier layer 18 at the bottom of the micropores 15 should be anodized for about 10 minutes using boric acid as an electrolyte until the current becomes almost zero at a voltage of 250 V, and the withstand voltage is improved by increasing the film thickness. preferable.

Further, as shown in FIG. 1C, the surface of the silica film 13 obtained by using alkoxysilane is coated with a protective layer 113 to obtain a non-contact type charging roller. The protective layer 113 is formed of a resin composition made of a fluororesin-based ceramic hybrid paint and carbon black having an electrical resistance of 10 ¹² to 10 ¹³ Ωcm and a film thickness of 5 to 15 μm in which conductive fine particles are dispersed.
Further, as shown in FIG. 1 (d), any one of SUS440A, SUS440B, SUS440C, and SUS440F stainless steel rods is used as the metal shaft member 114, and the outer peripheral surface has a hardness of HRC54 to 65. Used after being cured. If the non-contact type charging roller is formed by using the metal shaft member 114 having an increased mechanical strength by quenching and hardening the outer peripheral surface in this way, the shaft runout accuracy deteriorates as the strength increases. Therefore, it is easy to secure the charging gap to be set.

FIG. 2A shows the structure of a conventional non-contact type charging roller using a thermoplastic resin composition for the resistance adjusting layer. On the metal shaft member 20, a polymer compound such as polyether ester amide and four The resistance adjustment layer 21 of the ABS resin composition, which is adjusted to have an electric resistance value of 10 ⁸ to 10 ⁹ Ωcm by containing an ion conductive material such as a quaternary ammonium salt, is injection-molded with a film thickness of 0.5 to 1 mm. And a protective layer 22 made of a thermoplastic resin composition adjusted to have an electric resistance value of 10 ¹⁰ to 10 ¹² Ωcm by dispersing conductive fine particles on the outermost surface is formed with a film thickness of 5 to 15 μm. Has been.
FIG. 2B is a diagram showing a flow state of the molten ABS resin composition in the mold when the conventional resistance adjusting layer 21 is coated with an injection molding machine. The state of the parting line 25 formed at the joint of the movable mold 24 and the weld line 27 at the flow tip meeting portion of the ABS resin composition flowing into the mold from the injection port 26 is shown, and the metal shaft member 28 is shown. It is formed as a streak in the axial direction.

The parting line 25 almost disappears in the outer diameter turning process in the next step, but the weld line 27 is particularly in the film thickness direction depending on molding conditions such as mold temperature and resin melting temperature, and the blending ratio of the ABS resin composition. As shown in FIG. 2 (c), the outer diameter appears so as to be visually confirmed as a streak 210 on the resistance adjusting layer surface 29 that has been turned.
In the line 210 of the weld line 27, an ion conductive polymer compound component such as polyether ester amide is condensed in a width of 5 μm to form a portion having a reduced electric resistance value, and the environment at high temperature and high humidity. Under certain conditions, it becomes a highly hygroscopic state peculiar to polyether ester amide components, and the electric resistance value is lowered. As a result, when the discharge current increases at that portion, heat is generated and the resin material is denatured and deteriorated and becomes brittle. When the environmental conditions are changed to low temperature and low humidity conditions, cracks are generated due to a difference in expansion and contraction.
In particular, when the shaft deflection of the non-contact type charging roller is large, the AC voltage 1800 to 2000V superimposed on the DC voltage is increased to 2000 to 2400 V in order to alleviate the uneven charging of the charged body, so that the discharge current also increases. As a result, the denaturation and deterioration of the resin material is further accelerated, and cracks are more likely to occur.
Also, in the weld line 27 and the parting line 25, unlike other parts, when thermal stress is applied during molding, the solvent during the formation of the protective layer is easily impregnated and promotes cracking. It becomes easy.

<Method for surface turning of outer diameter of support made of aluminum alloy>
FIG. 4 is a view showing a method of turning an outer diameter surface by coating a support member 41 made of an aluminum alloy on a metal shaft member 40 whose shaft runout has become highly accurate by quenching and centerless grinding. As shown in FIG. 4 (b), the cutting tool for turning uses a diamond cutting tool 42 capable of forming a sharp cutting edge in order to keep cutting resistance low. The diamond cutting tool 42 has a cutting edge nose R1 to 5 mm, a dent angle of 5 to 10 °, a squeeze angle of 15 to 20 °, and has a blade surface roughness of 0 to 0.2 μm and is formed by the blade surface. The round radius of the ridge is set to 0 to 0.5 μm. By making the squeeze angle as sharp as 15 to 20 °, it becomes possible to keep the processing resistance low, suppress the increase in the outer diameter of the central portion in the axial direction of the non-contact charging roller, and suppress the generation of burrs. Therefore, the abnormal discharge portion is not formed.
Turning is performed by blowing compressed air containing cutting oil from the air nozzle 46 onto the tip of the diamond tool 42 in order to suppress heat generation and guide the chips to the suction device. The diamond cutting tool 42 is attached with the squeeze surface 47 facing downward and sucking chips with the lower hood 48. And in order to prevent chips from adhering to or being caught on the surface of the work piece, the chips are sucked by the chip collection device 49 by securing the chip suction speed according to the cutting speed, Chips are stored in a box 410, compressed and collected.

  Using the diamond cutting tool 42, for example, as shown in FIG. 4A, a spindle chuck 43 (air balloon chuck manufactured by Fujii Seimitsu Kogyo Co., Ltd.) of a synchronous rotary turning device (RL600 model manufactured by Egro Co., Ltd.) of the spindle and tail shaft. To clamp the outer diameter of the bearing portion for voltage application of the non-contact type charging roller, and to clamp the outer diameter of the bearing portion of the non-contact type charging roller by the tail shaft chuck 44 (air balloon chuck manufactured by Fujii Seimitsu Kogyo). Synchronous rotation drive of 5000 to 6000 rpm is given to the tail shaft, roughing is performed by moving the tool post 45 with the diamond cutting tool 42 attached at a turning feed of 0.1 mm / rev and a cutting depth of 5 to 10 μm. Finishing is performed at 5 μm to obtain a surface with a surface roughness of 0.5 to 3 μm Rz (JIS B 0601 1994).

<Method for forming oxide film and silica film>
The support 41 made of an aluminum alloy having a finished outer diameter surface has an inorganic acid or organic acid (for example, sulfuric acid, phosphoric acid, oxalic acid, malonic acid) as an electrolytic solution, a concentration of 0.5 to 2.5 mol / L, and a liquid temperature. An anodizing treatment of 20 to 30 ° C. and an electrolytic current of 0.8 to ² A / d ² is performed for 0.5 to 2 hours to form an oxide film having a film thickness of 10 to 30 μm and washed with ion-exchanged water. After that, it is heated and dried at 130 ° C. for 30 minutes to remove moisture in the micropores formed in the oxide film.
On the oxide film, alkoxysilane is applied using the coating apparatus shown in FIG.
The rotational speed of the metal shaft member mounting main shaft 411 and the presser shaft 412 is set to 600 rpm, the moving speed of the spray nozzle 413 is set to 10 to 20 mm / second, and 1 to 2 cc of the tetraethoxysilane is applied to the outer diameter surface 414 of the oxide film. Apply. After finger-drying (to the extent that it feels dry when touched with a finger), it is dried by heating at 100 to 150 ° C. for 1 hour to form a silica film obtained using an alkoxysilane having a thickness of 0.05 to 0.2 μm.

<Method of forming a protective layer on a resistance adjustment layer by a silica film obtained using an oxide film and alkoxysilane>
Fluororesin in which 20 to 50% by weight of conductive fine particles such as tin oxide, ITO (indium tin oxide) and carbon black are mixed and dispersed using the oxide film of the charging roller and a silica film obtained by using alkoxysilane as a resistance adjusting layer. A ceramic composite resin paint containing at least one of acrylic resin, silicone resin, and polyurethane resin is applied with the same application apparatus as in FIG. 4C, and the protective layer has an electrical resistance value of 10 ¹⁰ to 10 ¹² Ωcm. Is formed with a film thickness of 5 to 15 μm.
FIG. 5 is a diagram showing a method of polishing the surface of the formed protective layer. As shown in FIG. 5A, fine protrusions 51 of the ceramic composite resin paint are formed on the surface of the protective layer 50. FIG. If it is used as it is as the surface of the charging roller as it is, the protrusion 51 becomes a discharge point and a strong discharge is performed, which causes roughness in image formation. Therefore, the surface is polished and smoothed by wrapping paper.
FIG. 5B is a schematic diagram of the polishing apparatus, and the tape reel 53 storing the wrapping paper 52 of No. 2000 to 3500 is moved from the tape reel 53 to the take-up tape reel 56 via the tension roller upper 54 and the tension roller lower 55. The surface to be a protective layer of the non-contact type charging roller 57 is polished while being wound at a thickness of 20 to 50 mm, and a polished surface having a surface roughness with a protrusion removed of 0.1 to 3 μm Rz (JIS B 0601 1994) is obtained. A protective layer surface 57 as shown in FIG. 5C is formed. Next, if both ends are covered with the charging gap forming members 36 and 37, the non-contact charging roller of the second aspect of the present invention can be obtained.

<Charging Characteristics of Non-Contact Charging Rollers of Inventions 1 and 2 and Non-Contact Charging Roller with Only Oxide Film Formed on Support Surface>
FIG. 6A is a configuration diagram of a charging potential measuring device for a non-contact type charging roller, in which both ends of the non-contact type charging roller 60 are coated with a width of 10 mm with an adhesive tape having a film thickness of 50 μm serving as a charging gap forming member. The photosensitive member was brought into contact with the photosensitive member with a load of 2 to 4 N and disposed with a charging gap of 50 μm. The layer structure of the functionally separated organic photoreceptor 61 is an aluminum substrate (φ30 mm), an undercoat layer 5 μm (melamine alkyd resin, oxidized Ti dispersion), a charge generation layer 0.5 μm (charge generation agent titanyl phthalocyanine, butyral resin), charge The transport layer is 30 μm (charge transport agent stilbene-based, polycarbonate resin).
The equipment used for the measurement is a high-voltage power supply 62 (FLUKE 415B 0 to ± 3 KV), a surface potential meter 63 (TREK 344), a potential measurement probe 64 (for TREK 344), a measurement interval of about 1 mm, and a charging potential recorder 65 (GRAPHTEC SERVO 150). , An ozone measuring device 66 (a gas detector tube of Komyo Chemical Co., Ltd.).
The function-separated organic photoconductor 61 was rotated at a linear speed of 250 mm / sec in the dark box 67, and the potential charged on the surface of the photoconductor 61 was removed using a conductive static eliminating brush 68.

FIG. 6B is a recording chart in which the charge potential to the function-separated organic photoconductor 61 is measured with a conventional non-contact type charging roller in which only the oxide film 610 is formed on the support surface. The charging potential measurement time (15 seconds / 5 mm), and the vertical axis represents the photosensitive member charging potential (200 V / 10 mm). The measurement environment is a room temperature of 22 to 23 ° C. and a humidity of 52 to 55%.
As can be seen from the voltage applied to the non-contact type charging roller from -900V, the rising charging potential 611 to the photosensitive member starts to rise by about -90V, and in the range 612 of the applied voltage from -1000V to -1600V, from 30 to The charging potential has 150 V and the amplitude unstable region 613, and in the range 614 of the charging potential of -400 to -800 V to the photosensitive member used in the image forming apparatus, it tends to be difficult to obtain stable charging.

FIG. 6C shows the present invention 1 in which a silica film 615 obtained by using alkoxysilane is formed on an oxide film 610 of a conventional non-contact type charging roller having a charging potential having the unstable region 613. 6 is a recording chart in which the charging potential of the non-contact charging roller is measured in the same manner.
As can be seen from the figure, the applied voltage to the non-contact type charging roller starts from −900V, the rising charging potential 616 to the photosensitive member starts to increase by about −40V, and the charging potential to the photosensitive member used in the image forming apparatus is −400. In a range 617 of -800V, stable charging can be obtained. Further, in the range from the position 618 where the applied voltage −900V is applied to the non-contact type charging roller to the position 619 where the applied voltage −2500V, the charging potential of the photosensitive member rises at almost equal intervals, and the charging potential having linearity with respect to the applied voltage. It has become. In the range of the oxide film thickness of 10 to 30 μm and the silica film thickness of 0.1 to 0.2 μm, substantially the same results are obtained.
Further, assuming that image formation is performed at a photosensitive member charging potential of -800 V, the photosensitive member charging potential 620 is stable when a DC-1660 V applied voltage is continuously applied to the non-contact charging roller for 2 minutes.

FIG. 7 shows a non-contact type charging roller of the present invention 2 in which a silica film obtained by using alkoxysilane is formed on an oxide film to form a resistance adjusting layer and a protective layer 70 is further formed on the surface. 6 is a recording chart in which the charging potential is measured in the same manner as in FIG.
On the resistance adjustment layer made of silica film obtained by using an oxide film and alkoxysilane, paint (ceramic F, Si, tile top made by SK Kaken, or a mixture of tile tops) or carbon black (Mitsubishi Chemical) is used as a ceramic hybrid resin. Ketjen Black EC) 0.2-0.5% by weight was mixed, applied with a spray device of FIG. 3 (c) to a film thickness of 5-15 μm, preheated at 80 ° C. for 30 minutes, and then 160 ° C. The protective layer 70 was formed by performing main drying for 30 minutes.
As can be seen from the figure, stable charging was obtained in the range 71 of the charging potential of −400 to −800 V used in the image forming apparatus. Further, in the range from the position 72 where the applied voltage −900V is applied to the non-contact type charging roller to the position 73 where the applied voltage −1600V is applied, the potential to the photosensitive member rises at almost equal intervals, and the charging is linear with respect to the applied voltage. It became a potential.
Further, assuming that image formation is performed at a photosensitive member charging potential of -800 V, the photosensitive member charging potential 74 at the protective layer when a DC-1600 V applied voltage is continuously applied to the non-contact charging roller for 5 minutes is It was stable at -800V.

In this way, an aluminum oxide film of 10 to 30 μm is formed using an aluminum alloy as a support, and a silica film of 0.1 to 0.2 μm obtained by using alkoxysilane is formed on the surface to form a non-contact type charging roller. Therefore, the photosensitive member can be charged with linearity corresponding to the voltage applied to the non-contact type charging roller, and a silica film obtained by using an oxide film and an alkoxysilane is used as a resistance adjusting layer. By forming the protective layer, the resistance adjustment layer surface wear and tear are eliminated by sputtering, and in addition to durability, in the same manner as when there is no protective layer, it corresponds to the voltage applied to the non-contact type charging roller. The photosensitive member can be charged with linearity.
In addition, since the resistance adjustment layer is formed of an inorganic film of silica (SiO ₂ ) obtained using aluminum oxide (Al ₂ O ₃ ) and alkoxysilane, resistance using ABS resin or the like even under high temperature and high humidity conditions Compared with the adjustment layer, the swelling and expansion is very small, and the resistance adjustment layer does not cause cracks that affect image formation.

  The charging device according to the third aspect of the present invention incorporating the non-contact type charging roller according to the first and second aspects of the present invention applies a desired charging potential to the photosensitive member and superimposes an AC bias voltage (Vp-p) to prevent uneven charging. Layer structure that can easily apply a charging potential without increasing the resistance, and does not use a polymer surfactant such as polyether ester amide in the resistance adjustment layer, so that the swelling expansion is very small and cracks such as weld lines are likely to occur. Therefore, it becomes a stable charging device with good durability.

According to the non-contact type charging roller of the first aspect of the present invention, a non-contact type charging roller using a thermoplastic resin composition in which a polymer surfactant and an ionic conductive agent are mixed as an environmental condition of an image forming apparatus at high humidity. Compared with very little swelling expansion, there is no cracking that causes image formation defects, and no ionic conductive agent such as quaternary ammonium salt is used, so there is no bleed out of the ionic conductive agent, and the charged object is charged. Potential fluctuation can be suppressed.
According to the non-contact charging roller of the second aspect of the present invention, a non-contact charging roller using a thermoplastic resin composition in which a polymer surfactant and an ionic conductive agent are mixed as an environmental condition of an image forming apparatus at high humidity. Compared with the resistance adjustment layer, the swelling and expansion of the resistance adjustment layer is very small, there is no occurrence of cracks in the resistance adjustment layer and cracks in the protective layer that cause image formation defects, and ionic conductive agents such as quaternary ammonium salts are used in the resistance adjustment layer. Because it is not used, there is no bleed-out of the ionic conductive agent on the surface of the protective layer, and the resistance adjustment layer surface is not directly exposed by covering the protective layer. And the fluctuation of the charged potential on the member to be charged can be suppressed.

According to the charging device of the present invention 3, excessive discharge (electron avalanche) is suppressed by providing the non-contact type charging roller of the first or second invention, and accordingly, generation of ozone is suppressed, and each of the DC applied voltages is suppressed. The charged potential of the charged object corresponding to the voltage becomes stable, and the superimposed AC applied voltage can be reduced.
According to the image forming apparatus of the fourth aspect of the invention, since the image forming apparatus includes the charging device of the third aspect of the present invention, contamination of the indoor environment in which the image forming apparatus is installed is not increased.

Examples and Comparative Examples are shown below, but the present invention is not limited to these Examples.
In addition, Keyence LS type laser measuring machine for outer diameter measurement, Mitutoyo 0-25mm micrometer for gap tape thickness measurement, Keyence LS type laser measuring machine and φ30 steel cylindrical jig (accuracy: 1 μm / 350 mm), Ricoh Imagio Color Copier was used for image formation, and Gasetech GV-100S (ozone gas detector tube 0.05 to 0.6 ppm, 5 times standard) was used for ozone measurement.

Example 1
A stainless steel rod (manufactured by SUS440C, diameter 11.3 mm) was used as the metal shaft member, vacuum-hardened and hardened so that the outer peripheral surface had a hardness HRC58, and then grinding was performed to a diameter of 11 mm.
Next, after coating a support made of an aluminum alloy (aluminum alloy seamless pipe JIS H 4080 1999 alloy number 5056, inner diameter 11 mm, wall thickness 1 mm) on a stainless steel rod, the surface was turned to an outer diameter of φ11.9 mm. . A diamond bite was used for turning, and in order to suppress heat generation and guide the chips to the suction device, compressed air containing cutting oil was blown from the air nozzle to the tip of the diamond bite. A surface with a surface roughness of 0.5 to 3 μm Rz (JIS B 0601 1994) was obtained through roughing and finishing.
Subsequently, malonic acid is used as an electrolytic solution for the support made of the above aluminum alloy with the outer diameter surface finished, and the concentration is 2.5 mol / L, the liquid temperature is 25 ° C., and the electrolytic current is 0.8 A / d ² for 40 minutes. An anodizing treatment was performed to form an oxide film with a thickness of 30 μm, washed with ion-exchanged water, and then dried by heating at 130 ° C. for 30 minutes to remove moisture in the micropores formed in the oxide film. .
Next, a tetraethoxysilane solution (manufactured by Wako Pure Chemical Industries, Ltd.) containing 28.8% of SiO ₂ , which is a material containing alkoxysilane, was applied onto the oxide film using the coating apparatus of FIG. . The rotational speed of the metal shaft member mounting main shaft and the presser shaft is 600 rpm, the moving speed of the spray nozzle is 10 mm / second, and 1-2 cc of the tetraethoxysilane solution is applied several times to the outer diameter surface of the oxide film, After finger-drying (to the extent that it feels dry when touched with a finger), it was dried by heating at 150 ° C. for 1 hour to form a silica film obtained using an alkoxysilane having a thickness of 0.15 μm.
Next, an adhesive tape (50 μm adhesive tape made by Nichiban: width 10 mm) was coated on both ends as a charging gap forming member to obtain a sample of a non-contact type charging roller.
Measurement was performed using this sample. The results are shown in Table 1.

Example 2
On the silica film obtained by using alkoxysilane, carbon black (Mitsubishi Chemical Ketjen Black EC) is mixed in an amount of 0.2 to 0.5% by weight to a ceramic hybrid resin paint (manufactured by SK Kaken: Ceratite F). Then, the film is applied so as to have a film thickness of 10 to 15 μm using the coating apparatus of FIG. Except for these points, a non-contact charging roller sample was obtained in the same manner as in Example 1.
When this sample was used in the same manner as in Example 1, the results shown in Table 1 were obtained.

Comparative Example 1
A stainless steel rod (made of SUS303, diameter 9.98 mm, no quenching treatment) was used as the metal shaft member, and ABS resin containing polyether ester amide and an ionic conductive agent as the resistance adjustment layer was formed by injection molding to a thickness of 0. An outer diameter φ11 having a protective layer formed to a thickness of about 10 μm by applying a ceramic hybrid resin composition made of acrylic silicon resin, isocyanate curing agent and ITO (indium tin oxide) to the surface. A sample of a non-contact type charging roller of 9 mm (corresponding to a service part of a conventional Ricoh digital color copying machine Imagioneo C600) was obtained.
When this sample was used in the same manner as in Example 1, the results shown in Table 1 were obtained.

Comparative Example 2
A stainless steel rod (made of SUS303, diameter 8 mm, no quenching treatment) is used as a metal shaft member, and a carbon black is mixed and dispersed in epichlorohydrin rubber and a conductive agent as a resistance adjustment layer to a thickness of 1.5 mm. Sample of non-contact charging roller with outer diameter of φ11mm formed by applying 0.1 to 0.2μm in thickness of fluororesin paint (corresponding to the service parts of the conventional Ricoh digital color copier Imagioneo C285) Got.
When this sample was used in the same manner as in Example 1, the results shown in Table 1 were obtained.

表１から分るように、実施例１、２では、金属製軸部材に焼入れ硬化処理をして研削加工を施すことにより、非接触帯電ローラ中央部の外径の増径量が、比較例１、２の半分以下になり、ギャップ変動量も向上し、画像ムラを防止するためのＡＣ重畳電圧を上昇させることもなかった。
実施例のオゾン発生量は、比較例１とは大差無いが、比較例２のゴム製非接触帯電ローラに比べて半減し、暗箱内でのオゾン臭を感じない程度となった。

As can be seen from Table 1, in Examples 1 and 2, by increasing the outer diameter of the central portion of the non-contact charging roller by subjecting the metal shaft member to quench hardening and grinding, a comparative example The gap fluctuation amount was improved and the AC superimposed voltage for preventing image unevenness was not increased.
The amount of ozone generated in the example was not much different from that in Comparative Example 1, but was reduced to half that of the rubber non-contact charging roller in Comparative Example 2 so that the ozone odor was not felt in the dark box.

(A) A cross-sectional view of a non-contact type charging roller in which a silica film obtained by applying an oxide film to an aluminum alloy support on a metal shaft member and using an alkoxysilane, (b) an oxide film and an alkoxysilane Explanatory drawing (partially enlarged view) showing the detailed structure of the silica film obtained by using, (c) a cross-sectional view showing a non-contact type charging roller with a protective layer coated on the surface of the silica film, (d) quench hardening treatment Sectional drawing which shows the non-contact-type charging roller using the metal shaft members which gave. (A) The figure which shows the structure of the conventional non-contact-type charging roller which used the thermoplastic resin composition for the resistance adjustment layer, (b) The resistance adjustment layer of the conventional non-contact-type charging roller formed by injection molding Explanatory drawing of the parting line and weld line which are formed in this figure, (c) State explanatory drawing of the weld line state of the resistance adjustment layer surface formed by injection molding. (A) Front view of metal shaft member of non-contact type charging roller, (b) Front view of non-contact type charging roller, (c) Front view of non-contact type charging roller, photoconductor and its gap. The figure which shows the method of carrying out the turning process of the outer diameter surface by coat | covering the support body which consists of aluminum alloys on the metal shaft member to which axial runout became high precision by hardening and centerless grinding. (A) Top view of turning method, (b) Diamond bite attachment drawing of turning and schematic diagram of chip collection method, (c) Top view of spray coating apparatus. The figure which shows the method of grind | polishing the formed protective layer surface. (A) Surface state diagram of protective layer in spray coating device, (b) Schematic diagram of lapping paper polishing device, (c) Surface state diagram of protective layer after polishing. (A) An explanatory diagram of a charging potential measuring device for a non-contact type charging roller, (b) a recording chart for measuring a charging potential to a photoconductor with a non-contact type charging roller in which only an oxide film is formed on the surface of a support, c) A recording chart in which the charging potential on the photosensitive member of the non-contact type charging roller of the present invention was measured by coating the oxide film formed on the support surface with a silica film obtained by using alkoxysilane to form a resistance adjusting layer. . 3 is a recording chart in which a charging potential to a photoconductor is measured when an oxide film is coated with a silica film to form a resistance adjusting layer and further a protective layer is coated to form a non-contact charging roller. FIG. 2A is a schematic configuration diagram of a black and white and color image forming apparatus using a function-separated organic photoconductor and using a Carlson process, and FIG. 3B is a diagram illustrating a configuration of a toner image forming unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal shaft member 11 Support body 12 Oxide film 13 Silica film obtained using alkoxysilane 14 Support body 15 Micropore 16 Oxide film 17 Silica film obtained using alkoxysilane 18 Barrier layer 113 Protective layer 114 Quenching hardening Treated metal shaft member 20 Metal shaft member 21 Resistance adjustment layer 22 Protective layer 23 Fixed die 24 Movable die 25 Parting line 26 Inlet 27 Weld line 28 Metal shaft member 29 Turned resistance adjustment layer Surface 210 Line 30 Metal shaft member 31 Bearing portion 32 Voltage application bearing portion 33 Cover portion 34 Resistance adjustment layer 35 Protective layer 36 Charging gap forming member 37 Charging gap forming member 38 Charging surface 39 Charging gap 310 Charging gap 311 Charging gap 312 Non-contact charging roller 313 Body 314 Gear 315 Gear 316 Distance between shafts 40 Hardened and hardened metal shaft member 41 Aluminum alloy support 42 Diamond bit 43 Turning device spindle chuck 44 Turning device tail shaft chuck 45 Tool post 46 Air nozzle 47 Squee surface 48 Hood 49 Chip recovery device 410 Box 411 Metal shaft member mounting main shaft 412 Presser shaft 413 Spray nozzle 414 Oxidized film outer surface 50 Protective layer 51 Protrusion 52 Wrapping paper 53 Tape reel 54 Tension roller upper 55 Tension roller lower 56 Winding tape reel 57 Surface of the protective layer having a polished surface 60 Non-contact type charging roller 61 Functional separation type organic photoconductor 62 High voltage power supply 63 Surface potential meter 64 Surface potential meter probe 65 Charge potential recorder 66 Ozone measuring device 67 Dark box 6 8 Static elimination brush 610 Oxide film 611 Rising charging potential 612 Applied voltage -1000 to -1600 V range 613 Amplitude unstable region 614 Charging potential at oxide film -400 to -800 V range 615 Silica film 616 Rising charging potential 617 Charged potential of silica film obtained by using the range of −400 to −800 V 618 Applied voltage −900 V position 619 Applied voltage −2500 position 620 Charged potential of silica film obtained using oxide film and alkoxysilane 70 Protection Layer 71 Range of charged potential at resistance adjusting layer and protective layer -400 to -800V 72 Position of applied voltage -900V 73 Position of applied voltage-1600V 74 Photoconductor charging potential at protective layer 81 Toner image forming unit 82 Function separation Type organic photoreceptor 83 Charging unit 84 Light Inclusive unit 85 developing unit 86 cleaning unit 87 the transfer unit 88 transfer belt 89 charging roller 810 laser beam 811 developing member 812 recording paper 813 transferring member 814 fixing unit

Claims (4)

  A non-contact type charging roller, wherein an aluminum oxide film is formed on the surface of a support made of an aluminum alloy, and a silica film obtained by using alkoxysilane is formed on the surface of the oxide film.   A silica film obtained using an oxide film and an alkoxysilane is used as a resistance adjustment layer, and a protective layer made of a resin composition in which conductive fine particles are dispersed is formed on the surface of the resistance adjustment layer. The non-contact charging roller according to 1.   3. A non-contact type charging roller that is in contact with both ends of the photosensitive member of the image forming apparatus and forms a charging gap in a range that becomes a charging surface of the photosensitive member to apply a charging potential to the photosensitive member. A non-contact type charging roller. An image forming apparatus comprising the charging device according to claim 3 as a charging device for charging the surface of the photoreceptor.

Images