JP4139032B2 - Charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charger applied to a copying machine, a facsimile, a printer, and the like, and an image forming method using the charger.
[0002]
[Prior art]
Conventional charging systems are mainly based on the use of corona discharge. However, since corona discharge applies an electric field in the air, there are problems in that a large amount of harmful substances such as ozone and NOx are generated, the charging efficiency is low, and the amount of electricity is wasted. In addition, the need for a voltage source close to 4 kV causes an increase in the cost of the apparatus, and also presents a danger. It is urgent to improve such a system because of recent environmental considerations. Against this background, roller charging with little corona discharge, charge injection type brush charging, internal polarization type charging, and the like have been studied. Each feature is described below.
[0003]
a. Contact charging system such as roller (blade) charger
Roller charging can greatly reduce the amount of ozone generated compared to corotron or the like. However, since a voltage is applied to the narrow gap between the photoconductor and the roller in principle to cause corona discharge, ozone generation cannot be reduced to zero. Further, since ozone is generated in the vicinity of the photoconductor, photoconductor deterioration due to ozone remains as a problem. Although a method of reducing the resistance of the roller surface and preventing discharge has been considered, electric charges concentrate on pinholes existing on the photoconductor, and voltage cannot be applied to the photoconductor. As a result, problems such as white spots occur.
[0004]
In the case of a blade shape, as seen in Japanese Patent Laid-Open No. 8-6282, a method of avoiding discharge, such as increasing the resistance in a region not in contact with the photoreceptor, is considered. As a result, discharge can be avoided, but since countermeasures against pinholes are not taken, it is difficult to implement. Further, in the case of a blade, since the friction coefficient is much larger than the rolling friction of the roller, there is a concern about problems such as wear of the photoreceptor due to this.
[0005]
b. Charge injection method using brush charger
The charge injection method is a method in which charges are directly injected into the photoreceptor without causing discharge. For this reason, in principle, it is a system that can be charged efficiently without generating ozone. However, since there is a pinhole in the photoconductor, charge concentration occurs when the metal is brought into direct contact with the photoconductor, and it cannot be uniformly charged. Moreover, if injection is performed by bringing a medium resistance member into contact to prevent this, discharge occurs or the injection speed becomes very slow. Although attempts have been made to modify the surface of the photoconductor to increase the injection efficiency (see, for example, JP-A-6-3921), there are many problems at present.
[0006]
c. Internal polarization type charging system
The persistent internal polarization method is a method of forming a latent image on a photoconductor by polarizing the electric charge generated by the photoconductor with an external electric field and sustaining it. This persistent internal polarization image (light electret) method has been actively studied for a long time, like the electrostatic image (xerography). In addition, a method of applying charging using this principle has been considered for a long time. This charging method is ozone-free in principle, and it seems that problems such as pinhole problems, non-uniformity, and discharge caused by charge injection can be solved. In recent years, environmental problems such as ozone have been taken up, and this type of charging method has been reported. However, at present, problems such as charging efficiency remain.
[0007]
[Problems to be solved by the invention]
In the conventional internal polarization type charging method, an electrode is brought into contact when a voltage is applied. In the case of negative charging, it is desired that negative charges (electrons) are held near the surface, and only positive charges (holes) drift to the substrate side. In the currently used organic photoreceptors, electrons are considered to have very little mobility compared to holes and hardly move when a voltage is applied. However, if the electrodes are brought into contact with each other and the electrons move to the charger side, the charging efficiency is lowered. For this reason, it is necessary to devise a technique for preventing electrons from flowing into the charger.
[0008]
Accordingly, the present invention provides a charger capable of achieving high efficiency without causing electrons to flow inside the charger when an internal polarization charging method is used, and an image forming method using the charger. The purpose is to provide.
[0009]
[Means for Solving the Problems]
  According to the first aspect of the present invention, a charge pair of holes and electrons is generated by irradiating light to an object to be imaged, and positive and negative charges are generated by drifting charges of one polarity by an external voltage. The charging device that polarizes and charges the object to be charged is composed of a magnetic brush including magnetic conductive fine particles that are in contact with the charged object, and the magnetic conductive fine particles cause the charge of the same polarity as the charging polarity to flow away to the charger side. The anti-flow-off layer is provided, and the anti-flow-off layer is made of an insulating film formed on a portion that contacts the charged body..
  The invention according to claim 2 irradiates a charged object for image formation with light to generate a charge pair of holes and electrons, and drifts the charge of one polarity by an external voltage, thereby generating positive and negative charges. The charger that polarizes and charges the object to be charged includes a flow prevention layer that prevents the charge having the same polarity as the charge polarity from flowing to the charger side, and the flow prevention layer contacts the object to be charged. A charge-polarity charge is an electron..
  According to a third aspect of the present invention, in the charger according to the second aspect, the N-type semiconductor satisfies a range of 1 nm <Ld <1 μm, where Ld is a thickness of a depletion layer formed on the surface thereof. Characterized by.
  The invention described in claim 4 irradiates a charged object for image formation with light to generate a charge pair of holes and electrons, and drifts the charge of one polarity by an external voltage, thereby generating positive and negative charges. The charger that polarizes and charges the object to be charged includes a flow prevention layer that prevents the charge having the same polarity as the charge polarity from flowing to the charger side, and the flow prevention layer contacts the object to be charged. A charge-polarity charge is a hole.Charger.
  According to a fifth aspect of the present invention, in the charger according to the fourth aspect, the P-type semiconductor satisfies a range of 1 nm <La <1 μm, where La is a thickness of a depletion layer formed on the surface thereof. Characterized by.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
  A first embodiment of the present invention will be described with reference to FIGS.The
[0034]
The present embodiment is applied to a part of an image forming process in an image forming apparatus such as a digital copying machine. A charger 2 for charging a photosensitive member 1 as a member to be charged is connected to a charging light source 3 and a voltage application. The apparatus 4 is integrated with the apparatus 4.
[0035]
a. Voltage application device 4
On the surface of the transparent substrate 5, a conductive transparent film 6 and an insulating transparent thin film 7 functioning as an insulating film serving as a flow-off preventing layer are laminated. Further, an electrode can be removed from the conductive transparent film 6 in order to allow voltage application by an external power source 8. The material of the transparent substrate 5 may be glass, plastic, or the like, but is formed in a cylindrical shape using an acrylic resin because of its versatility and mechanical strength. Thereby, the charger 2 of the present embodiment has a charging roller structure as shown in FIG. The diameter of the cylindrical transparent substrate 5 is 20 mm, and the thickness is 5 mm at which sufficient strength can be obtained. Friction between the cylindrical transparent substrate 5 and its support 9 is made small so that it can rotate freely. Further, the support 9 is provided with mobility so that the drum-shaped photoreceptor 1 and the charger 2 are always in contact with each other with sufficient pressure.
[0036]
The conductive transparent film 6 is formed on the surface of the transparent substrate 5 by forming a transparent, conductive and appropriate elastic material. In the present embodiment, it is formed by a method in which transparent conductive fine particles are dispersed in a transparent base material having elasticity. This means that the fine particles retain conductivity and the base material retains elasticity. In this embodiment, transparent conductive material such as ITO, zinc oxide, titanium oxide, antimony oxide, iridium oxide, tin oxide zirconium oxide doped with antimony or tantalum is pulverized into fine particles of the order of μm, and this is a transparent polycarbonate. And sufficiently dispersed in a base material such as polyurethane, acrylic, epoxy, silicon, alkyd, vinyl chloride-vinyl acetate copolymer. Conductivity is 1 × 10^FourΩ・It should be about cm.
[0037]
In order to provide the charger 2 with a function that prevents holes (or electrons) from flowing away, it is necessary to interpose an insulator in a portion that contacts the photoreceptor 1. This insulator also needs to be transparent and have some elasticity. Therefore, in the present embodiment, from the simplicity of the manufacturing method, the insulating transparent thin film 7 is made of a conductive transparent film by using an insulating polycarbonate as a base material when forming the conductive transparent film 6 described above. 6 is formed on the surface. The film thickness of the polycarbonate may be about several μm, and is formed by spraying. The material may be a transparent elastic body as described above.
[0038]
b. Light source 3
As the light source, a lamp light source, a laser light source, and the like are conceivable. In this embodiment, as shown in FIGS. 3 to 5, an LED array 11 in which a plurality of LEDs 10 are arranged is used. In recent years, LED arrays have been applied as high-density writing systems such as copying machines, and have a lot of technical accumulation. As the light source 3 in the present embodiment, it is only necessary to uniformly apply sufficient light to the photosensitive member 1, and it is not necessary to reduce the spot diameter of each LED 10. Therefore, it is not necessary to arrange fine LEDs in a horizontal row as conventionally used. Therefore, in this embodiment, as shown in FIGS. 4 and 5, the array structure has about 6 rows and 30 columns. At this time, it is also necessary to devise measures to prevent interference fringes and the like. Therefore, optical systems 12 and 13 having a lens function are incorporated between the LED 10 and the photoconductor 1 so that the light of the LED 10 efficiently illuminates the photoconductor 1. Reference numeral 14 denotes an LED array substrate, and 15 denotes a base of the light source 3. As shown in FIGS. 2 and 3, this is fixed to the support 9 inside the transparent substrate 5 via the substrate 15 so that the surface of the photoreceptor 1 is always illuminated. The wavelength of the LED 10 was 650 nm.
[0039]
c. Photoconductor 1
In this embodiment, the charging polarity is positive charging. Positive charging is attracting attention because of the small amount of ozone generated by the charger. However, organic photoreceptors (OPC) are difficult to obtain satisfactory characteristics, and development is delayed. Organic photoreceptors include single-layer photoreceptors such as phthalocyanine and pyrylium salts. Further, in the case of a laminated type photoreceptor, it can be classified into a charge generation layer and a charge (hole or electron) transfer layer. For the charge generation layer, a photoconductive material such as Se, perylene, azo, or phthalocyanine can be considered. The hole transfer layer includes polyvinylcarbazole-based polymer transfer agents, molecular hole transfer agents such as hydrazone compounds, pyrazoline compounds, and phenylamine compounds, and polysilane-based transfer agents. In the case of a molecular hole transfer agent, ester resin, carbonate polymer or the like is used as a binder. Candidates for the electron transfer agent include polyvinylcarbazole, 4-butoxylcarbonyl-9-fluoridenemalonitryl and the like.
[0040]
Further, the positively charged photoreceptor includes an inorganic photoreceptor found in a-Si: H. In this embodiment, an a-Si: H-based photoreceptor 1 is used.. ThisSince a-Si: H is an inorganic substance, it has high mechanical strength and high wear resistance. Further, an inorganic semiconductor, particularly Si, can be easily doped, and a high-quality photoconductor with little dark attenuation can be made by adding one P-type layer for positive charging.
[0041]
d. How it works
In the present embodiment, along with light irradiation by the light source 3, the charger 2 having a charging roller structure is brought into contact with the surface of the photoreceptor 1 to perform charging. Light irradiation causes a current to flow through the LED 10 to emit light. The irradiation time is uniquely determined from the rotation speed of the photoreceptor 1 and the width of the LED array 11. The amount of light was adjusted to about 100 lx. An electrode is provided on the conductive transparent film 6 of the charger 2, and a voltage defined at 600 V is applied by an external power source 8. At this time, the base 16 of the photoreceptor 1 is dropped to the ground. The voltage application time is about 0.02 s because the nip width is about 2 mm. As a result, a charge of 500 V could be obtained.
[0042]
In such an operation, in the present embodiment, an insulating film made of the insulating transparent thin film 7 is formed on the surface of the charger 2 to form a band structure as schematically shown in FIG. Even when a voltage is applied, since the insulating film made of the insulating transparent thin film 7 is larger than the band gap of the photosensitive member 1 as schematically shown in FIG. 6B, it has a function capable of preventing the loss of electrons. Thereby, electrons generated by light irradiation during charging can be efficiently held on the surface of the photoreceptor 1.
[0043]
  A second embodiment of the present invention will be described with reference to FIGS. Portions that are the same as or correspond to those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments in order).)
[0044]
The present embodiment is characterized by the laminated structure of the photoconductor as the member to be charged, and other than that, it conforms to the first embodiment. Therefore, the structure and image forming method of the laminated photoconductor 21 as the present embodiment. Only the principle will be described, and other description will be omitted. However, since the charging polarity of the multilayer photoreceptor 21 is negative, it is necessary to reverse the polarity of the applied voltage in the operation method.
[0045]
The multilayer photoreceptor 21 of the present embodiment is formed by sequentially laminating an undercoat layer 23, a second charge generation layer 24, a charge transport layer 25, and a first charge generation layer 26 on a metal substrate 22. . That is, a region where a charge contributing to charging is generated and a region where a charge contributing to exposure is generated are separately provided as the first charge generation layer 26 and the second charge generation layer 24, which is conventionally known. In contrast to the laminated type photoconductor, the charge generation layer existing inside is a second charge generation layer, and the first charge generation layer is added to the surface layer side. Details of each layer configuration will be described later.
[0046]
In such a charging process using the multilayer photoreceptor 21, as shown in FIG. 8A, a voltage is applied by the external power source 8 between the base 22 and the charger 2 opposed to the surface side. In the state where an electric field is applied in the laminating direction of the laminated photoconductor 21, the light source 3 for charging simultaneously irradiates the light 30 having the wavelength λ1 = 660 nm, so that the first charge generation layer 26 on the surface side is positive. A charge (hole) 31a and a negative charge (electron) 31b are generated in pairs and polarized by the action of an electric field, and the positive charge 31a is moved to the inner layer side. At the time of exposure, as shown in FIG. 8B, the exposure light 32 having a wavelength of λ2 = 780 nm is selectively irradiated with an exposure light source, whereby the positive charge 31a generated in the second charge generation layer 24 is polarized. Neutralize. As described above, in both processes of charging and exposure, it is the positive charge 31a that moves in the charge transport layer 25, and the surface of the multilayer photoreceptor 21 is charged to a negative polarity. As a result, an image forming apparatus using an electrophotographic process similar to that in a general digital copying machine or the like can be configured.
[0047]
Next, details of the multilayer photoreceptor 21 will be described.
a. First charge generation layer 26
In this layer, a photosensitive material having an absorption peak in the visible light region (500 to 700 nm) that has been used for analog is conventionally used. As the charge generating agent, thiapyrylium salt, polycyclic quinone type, perylene type, indigo derivative or bisazo pigment type are used. These are put into a binder material such as polyvinyl butyral resin. The film thickness is about 1 μm to 10 μm and is formed by a spray coating method.
[0048]
b. Charge transport layer 25
Conventionally, a general hole transport material is used for the charge transport layer 25. Examples of the charge transfer agent include oxadiazole derivatives, pyrazoline derivatives, hydrazone derivatives, triphenylmethane derivatives, oxazole derivatives, triarylamine derivatives, diphenylmethane derivatives, stilbene derivatives, butadiene derivatives, polyvinylcarbazole, polysilane derivatives, and the like. Polycarbonate resin and polyester resin were used as the binder. The concentration of the transfer agent was about 50%. The film thickness is about 20 μm and is formed by dipping coating.
[0049]
c. Second charge generation layer 24
The second charge generation layer 24 has a long wavelength (780 nm) that has been used for conventional digital. Examples of the charge generating agent include squarylium dyes, metal-free phthalocyanine-based, metal phthalocyanine-based, azurenium salt dyes, squalinic acid derivatives, and trisazo pigments. These were put into a binder material such as polyvinyl butyral resin. The film thickness is about 0.5 μm and is formed by dipping coating.
[0050]
d. Undercoat layer 23 and substrate 22
As the undercoat layer 23, an alumite substrate 22 made of Al is used. The normal undercoat layer only needs to prevent the injection of the holes 31a from the base body 22, but in the present embodiment, adjustment must be made so that the holes 31a generated during charging pass through the base body 22. Therefore, the undercoat layer 23 is formed to be slightly thinner 15 μm.
[0051]
Incidentally, in the current internal polarization type charging method, an existing one is used as a photoconductor as in the photogenerating charging method disclosed in, for example, JP-A-8-76559 and JP-A-9-26681. . In such a state, as shown in FIG. 17, there is a problem that the battery is positively charged and the currently mainstream negatively charged electrophotographic process cannot be used. In FIG. 17, the multilayer photoconductor 101 is formed by laminating a charge generation layer 103 and a charge transport layer 104 on a substrate 102. Reference numeral 105 denotes light emitted during charging, and reference numeral 106 denotes a counter electrode for generating an electric field by applying a voltage based on the power source 107 between the base 102 and the charging. Further, at the time of charging, the operation of irradiating the light 105 and the operation of applying an electric field by the counter electrode 106 are performed at the same time. However, in FIG. 17, for the sake of convenience, they are divided into (a) and (b). FIG. 17A shows a state where positive charges (holes) 108a and negative charges (electrons) 108b are generated in pairs in the charge generation layer 103 by irradiation with light 105, and FIG. This shows that the positive charge 108a moves to the surface layer side through the charge transport layer 104.
[0052]
On the other hand, in order to negatively charge, a method using a single layer type photoreceptor as shown in FIG. 20 is also considered. In FIG. 18, a single-layer type photoreceptor 111 is formed by providing a photosensitive layer 113 on a substrate 112. Reference numeral 114 denotes light emitted during charging, and reference numeral 115 denotes a counter electrode for generating an electric field by applying a voltage based on the power source 116 between the base 112 and the charging. Further, at the time of charging, the operation of irradiating the light 114 and the operation of applying the electric field by the counter electrode 115 are performed at the same time, but in FIG. 18, for the sake of convenience, they are divided into (a) and (b). 18A shows a state in which positive charges 117a and negative charges 117b are generated in pairs on the photoconductor 113 due to the irradiation of light 114, and FIG. 18B shows the positive charges 117a due to the action of an electric field. It shows a state of moving to the side. However, since the single-layer type photoreceptor 111 is inferior in charging ability or the like, it is desirable to use a laminated photoreceptor as in the case of this embodiment.
[0053]
The problems in the cases shown in FIGS. 17 and 18 are improved by the present embodiment.
[0054]
  A third embodiment of the present invention will be described with reference to FIGS.The
[0055]
In the present embodiment, the charging roller-shaped voltage applying device 42 constituting the charger 41 and the charging light source 43 are separated in time series (that is, in the direction of rotation of the multi-layer photosensitive member 21). Arranged. Here, the charging light source 43 is located upstream of the voltage applying device 42 in the rotation direction. Thereby, the light irradiation process and the voltage application process in the charging process are separated in time series. In FIG. 9, in addition to the charger 41, an exposure device 44, a developing device 45, a transfer device 47 for the transfer paper 46, a fixing device 48, and the like are sequentially provided around the multilayer photoconductor 21 in accordance with an electrophotographic process. It is arranged.
[0056]
Next, the configuration and operation method of the charger 41 will be described.
a. Voltage application device 42
The voltage application device 42 of the present embodiment has a charging roller structure and has a function of applying a voltage. However, since the light source is made independent, it does not have to be transparent. As shown in FIG. 10, it has a laminated structure of a conductive cylindrical substrate 49, a conductive elastic body 50, and an insulating film 51 on the surface. The cylindrical base 49 is preferably formed by forming a conductor film on the surface of a metal conductor such as Al, SUS, or Fe, or an insulator such as acrylic resin or plastic. Volume resistance is 1 × 10²If it is Ωcm or less, resins and rubbers containing various conductive agents can also be used. In the present embodiment, it is made of Al in terms of manufacturing cost and the like. That is, after processing Al into a cylindrical shape with a diameter of 20 mm and a thickness of 2 mm, a roughness of 0.1 mm order is applied with a grinder so that the surface has good adhesion.
[0057]
A conductive elastic body 50 having a thickness of 5 mm as shown in FIG. 10 is formed on the surface layer. The conductive elastic body 50 is obtained by dispersing conductive fine particles in an elastic base material. Various thermoplastic elastomers such as polyester elastomers, polyamide elastomers, polyurethane elastomers, soft vinyl chloride resins, styrene-butadiene-styrene block copolymer elastomers, and acrylic elastomers are suitable for the base material. 6, nylon 6,6, nylon 6-nylon 6,6 copolymer, nylon 6,6-nylon 6,10 copolymer, polyamide such as alkoxymethylated nylon such as methoxymethylated nylon, copolyamide or the like Modified products of the above, silicone resins, acetal resins such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymers, ionomers, and the like can also be used. As rubber, natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, chloroprene rubber, butyl rubber, silicon rubber Urethane rubber and acrylic rubber are preferred. In the present embodiment, silicon resin is used.
[0058]
As the dispersed conductive fine particles, conductive carbon black, metal powder such as silver, gold, copper, brass, nickel, aluminum, stainless steel, and powder conductive agent such as tin oxide based conductive agent can be used. In addition, nonionic, anionic, cationic, and amphoteric organic conductive agents and organotin conductive agents can also be used. In addition, in order to effectively perform uniform dispersion of the conductive agent, a part of acid-modified resin or rubber copolymerized with ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic anhydride may be used. It is valid. In the present embodiment, conductive carbon black is used. The conductive particle carbon black is dispersed in a base silicon resin melted by heat, and is fitted into a mold and cooled to obtain a solid having a desired shape. The conductivity thus obtained can be appropriately adjusted depending on the material ratio. In this embodiment, the resistance value is adjusted to about 10 Ωcm.
[0059]
One layer of the insulating film 51 is formed on the surface of the conductive elastic body 50 thus formed as an anti-flow-off layer to prevent the electron flow from the multilayer photoconductor 21. As the insulating film 51, a resin or rubber adjusted to have an appropriate resistance value depending on the composition of the conductive agent and the layer thickness is used. The types of the resin and rubber may be the same as those described above, but besides these, fluorine-based resins or rubbers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetra Fluoroethylene-hexafluoropropylene copolymer (PTFE / HFP), perfluoroalkoxy fluororesin and the like are preferably used. In particular, the use of these fluorine-based resins and rubbers has a great merit in terms of the life of the multilayer photosensitive member 21 and the charging roller (voltage applying device 42) because it is inactive and has a small friction coefficient.
[0060]
The resistance value of the insulating film 51 is generally 1 × 10.⁹~ 1x10¹⁵Ωcm, especially 1 × 10^Ten~ 1x10¹¹Ωcm. A film thickness of about 1 μm is sufficient, and if it is thicker than that, a voltage drop becomes a problem. In addition, the thickness of this film must be uniform so as not to cause charged spots. A dipping method is used as the film forming method. Thereby, a film having good adhesion can be obtained.
[0061]
b. Light source 43 for charging
As the charging light source 43, the same LED array 11 as that described in the first embodiment is used. The LED array 11 is fixed with a space of about several mm without contacting the photoreceptor 1. For this reason, the toner on the photoreceptor 1 is not stained.
[0062]
c. How it works
In the present embodiment, after the light irradiation by the charging light source 43, the voltage application device 42 having a charging roller structure is brought into contact with the laminated photoreceptor 21 and a voltage is applied through the external power source 8 to perform charging. Light irradiation causes a current to flow through the LED to emit light. The irradiation time is uniquely determined from the rotational speed of the laminated photoconductor 21 and the width of the LED array 11. The amount of light was adjusted to about 100 lx. Since the lifetime of the photogenerated charge is about 1 s, light irradiation and voltage application are not performed simultaneously, but the voltage is applied as soon as possible. An electrode is provided on the conductive cylindrical base 49 in the voltage application device 42, and a voltage defined at 600 V is applied by the external power supply 8. At this time, the base 22 of the multilayer photoreceptor 21 is dropped to ground. The voltage application time is about 0.02 s because the nip width is about 2 mm. As a result, a charge of about 500 V could be obtained.
[0063]
A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized by the surface member of the charging roller structure voltage application device 52 in the charger 41, and other than that, according to the third embodiment described above, only the charging roller structure voltage application device 52 is provided. The other explanation is omitted.
[0064]
The charging roller structure voltage application device 52 of the present embodiment is substantially the same in form as the charging roller structure voltage application device 42 shown in the third embodiment, but as shown in FIG. The configuration is different. The configuration will be described below. First, in accordance with the configuration of the voltage application device 42, the conductive base 53 and the conductive elastic body 54 are made of a silicon base material containing Al and carbon black particles. However, the materials mentioned in the third embodiment can be substituted. The carbon black particles are dispersed in the molten base material silicon rubber, and the wettability at that time is also good. As a result, a silicon rubber film is formed on the surface of the carbon black particles. A solid of a desired shape can be obtained by fitting this into a mold and cooling. The conductivity thus obtained can be appropriately adjusted depending on the material ratio. The conductive carbon black particles do not come into direct contact with the laminated photoreceptor 21, and silicon rubber is always sandwiched between them. Silicone rubber is insulative and does not flow electrons. Thereby, it is possible to prevent the electron flow from the multilayer photosensitive member 21 to the charger 41. That is, it is not necessary to form the insulating film 51 in the third embodiment.
[0065]
  A fifth embodiment of the present invention will be described with reference to FIG.The
[0066]
As shown in FIG. 12, the present embodiment is characterized by a voltage application device 61 in the charger 41, and includes a charging blade 62. Other points are the same as in the case of the fourth embodiment, and other explanations are omitted.
[0067]
The charging blade 62 uses a conductive metal as a base, a conductive elastic body is installed on the base, and an edge portion is finished at a highly accurate angle. Further, the nip width between the front end portion of the charging blade 62 and the laminated photoreceptor 21 is designed to be about 2 mm, and an equalizing function and a pressure releasing mechanism are provided. As a result, even with a high-speed machine, the laminated photoconductor 21 and the charging blade 62 can be stably bonded and applied with a voltage for about 0.02 s.
[0068]
The conductive elastic body in the charging blade 62 is obtained by dispersing conductive fine particles in an elastic base material. The materials described in the third embodiment can be used for the base material. In the present embodiment, a polyurethane rubber having sufficient elasticity and excellent wear resistance is used. As the dispersed conductive fine particles, the materials described in the third embodiment can be used. In this embodiment, conductive carbon black particles are used in consideration of the environment and the like. The size of the fine particles may be on the order of μm. The conductive carbon black particles are dispersed in the base material polyurethane rubber melted by heat, and the wettability is good at that time. As a result, a polyurethane rubber film is formed as an insulating film 63 on the surface of the conductive carbon black particles. A solid of a desired shape can be obtained by fitting this into a mold and cooling. The conductivity thus obtained can be appropriately adjusted depending on the material ratio. Further, the conductive carbon black particles are not directly in contact with the laminated photoreceptor 21, and the polyurethane rubber in the insulating film 63 is always sandwiched therebetween. Polyurethane rubber is insulative and does not carry electrons. Thereby, it is possible to prevent the electron flow from the multilayer photosensitive member 21 to the charger 41.
[0069]
In the electrophotographic process, there are a static elimination step and a cleaning step, and each uses a static elimination lamp and a cleaning blade. In the present embodiment, each device can be replaced by a charger 41 (charging light source 43... Neutralizing action, charging blade 62... Cleaning action).
[0070]
  A sixth embodiment of the present invention will be described with reference to FIG. This embodiment isClaim 1This corresponds to the described invention.
[0071]
As shown in FIG. 13, the present embodiment is characterized by a voltage application device 65 in the charger 41, and includes a magnetic brush 66. Other points are the same as those in the fourth and fifth embodiments, and other descriptions are omitted.
[0072]
In the present embodiment, as shown in FIG. 13, the voltage application device 65 is constituted by a magnetic brush 66. A magnet 68 is installed inside the shaft 67 of the magnetic brush 66, and carriers (fine particles with a particle size of several μm) are attracted by the magnetic force. The carrier may be metal particles such as Fe, Cu, Co, Ni, Sn, Ag, Mn, Ti, or an alloy thereof. In this embodiment, Fe is used because of its versatility and good environment. After processing Fe to a particle size of several μm, the surface is thermally oxidized. Thereby, a desired insulating film 69 can be easily obtained. The insulating film 69 preferably has a range of 1 μm to 1 nm. In this embodiment, the conditions are set so as to be about 20 nm. The thermal oxidation condition is that a desired insulating film 69 is obtained by heating at 300 ° C. for 20 minutes in an oxygen atmosphere. The magnetic brush 66 connects several carrier particles to connect the support and the laminated photoconductor 21. That is, the carrier passes through the insulating film 69 formed on the carrier surface. For this reason, it is necessary to prevent the voltage drop from increasing in the total of the insulating films 69 that pass therethrough. Therefore, in the present embodiment, the insulating film 69 is designed to be as thin as 20 nm. In this way, the charging of the magnetic brush 66 by the carrier having the insulating film 69 prevents the electrons from flowing from the laminated photoreceptor 21 and can be charged efficiently.
[0073]
  A seventh embodiment of the present invention will be described with reference to FIG. This embodiment isClaim 2This corresponds to the described invention.
[0074]
In the present embodiment, when the charge of charge polarity is an electron (negative charge), the voltage application device 4, 61, 65 or the like is in contact with a member to be charged (for negative charge, the laminated photosensitive member 21). It is characterized in that the provided anti-flow-off layer is formed of an N-type semiconductor 71. The N-type semiconductor 71 only needs to be provided on the surface, and as a form of the voltage application device, any of a charging roller, a charging blade, and a magnetic brush can be formed in substantially the same manner. The N-type semiconductor 71 may be a commonly used material such as Si. In this embodiment, a method is used in which these materials are pulverized and solidified with a binder in the form of fine particles. However, when applied to the magnetic brush 66, the semiconductor fine particles are used as they are as carriers.
[0075]
As the semiconductor fine particles, Si, αSn, Sn, C, SiC, GaAs, ZnO, CdTe, InP, Ge, InSb, InAs, InP, GaP, GaSb, AlSb, Te, ZnSb, or the like are used. In the present embodiment, Si with a lot of technology accumulated so far is used. Doping is P in the ingot state, 1 × 10¹⁷/ Cm^ThreeThe concentration should be about. Concentration is 1x10¹⁶/ Cm^Three~ 1x10¹⁸/ Cm^ThreeAs a result, the depletion layer formed on the surface of the N-type semiconductor 71 is several nm to several hundred nm. With such a material, it is possible to use, for example, a piece of a wafer that is currently discarded at a semiconductor factory. Such Si is sufficiently pulverized to have a particle size on the order of μm, preferably about 1 μm. The fine particles are solidified with a binder such as polycarbonate resin or polyester resin. By such a solidification method, a charging roller, a charging blade and the like are made. By bonding them to a conductive support, voltage application devices 4, 61, 65 are obtained.
[0076]
In the case of the present embodiment, a Schottky barrier 72 is formed on the surface layer by making the surface of the charger an N-type semiconductor 71 as shown in the band structure diagram schematically shown in FIG. It is considered that the Schottky barrier 72 is formed even when the Schottky barrier 72 is in contact with the multilayer photoreceptor 21. Thereby, when a voltage is applied here, as shown in FIG. 14, it is possible to selectively prevent electrons flowing from the multilayer photosensitive member 21 to the charger. This improves the efficiency during charging. Further, by using a semiconductor, the depletion layer 73 having an appropriate thickness can be formed only on the surface. Even if the thickness of the semiconductor fluctuates on the order of millimeters, the depletion layer 73 formed on the surface layer is defined by the doping amount. It is relatively easy to adjust the doping amount in the manufacturing process. Thereby, it is not necessary to form with high precision like the insulating film mentioned above, and manufacturing cost can be reduced.
[0077]
  An eighth embodiment of the present invention will be described with reference to FIG. This embodiment isClaims 4 and 5This corresponds to the described invention.
[0078]
In the present embodiment, when the charge of charge polarity is a hole (positive charge), it is provided in a portion that comes into contact with a member to be charged (photosensitive member 1 for positive charge) such as the voltage application devices 4, 61, 65. It is characterized in that the anti-flow-off layer is formed of a P-type semiconductor 76.
[0079]
As the P-type semiconductor 76, a material doped with the above-described inorganic semiconductor material such as Si can be used. However, in this embodiment, an organic semiconductor is used because of its elasticity and ease of manufacture. Organic semiconductors may be those used for photoconductors and the like, which are generally P-type. For example, oxadiazole derivatives, pyralizone derivatives, triphenylmethane derivatives, oxazole derivatives, triarylamine derivatives, butadiene derivatives, and the like. These materials are dispersed in a binder. As the binder, polycarbonate resin, polyester resin, or the like can be used. The film thickness was about 20 μm and was formed by dipping coating. Thereby, a P-type semiconductor having a free shape can be molded on the support, and a charging roller, a charging blade, and the like can be designed.
[0080]
Therefore, the N-type semiconductor 71 is replaced with the P-type semiconductor 76 when the charge of charge polarity is a hole, which is basically the same as in the seventh embodiment.
[0081]
  A ninth embodiment of the present invention will be described with reference to FIG.The
[0082]
The image forming process of the present embodiment is basically the same as in the case of the third embodiment shown in FIG. 10, but the light source 81 in the charger 41 serves as both a charging light source and an exposure light source. It is configured. That is, in the process of irradiating and charging the multilayer photosensitive member 21 with the light source 81, the light source 81 is selectively irradiated with light according to the image signal to form a latent image as exposure light. For this reason, the exposure device 44 becomes unnecessary.
[0083]
The light source 81 according to the present embodiment has substantially the same shape and function as the charging light source 43 according to the third embodiment. While being transmitted to the light source 81, the dot diameter of the LED corresponds to the dot diameter of the image formation, so the dot diameter is miniaturized to 30 μm.
[0084]
【The invention's effect】
  Claim 1ClearlyAccording to the present invention, since the anti-flow-off layer for preventing the charge having the same polarity as the charge polarity from flowing to the charger side is provided, for example, the electrons are not lost inside the charger, and the internal polarization type charging method is used. In this case, since the anti-flow-off layer is formed of an insulating film, it is possible to reliably prevent the electric charge having the same polarity as the charge polarity from flowing to the charger side. In addition, since the insulating film is made of a conductive member made of conductive fine particles and an insulating base material that holds these fine particles, and the charger surface is coated with the insulating film, the loss of charge is prevented. Even if the coating of the conductive fine particles on the surface is peeled off, no more charge will flow than the charge is accumulated in the conductive fine particles. Therefore, by making the coating layer sufficiently thin, The voltage drop can be prevented from becoming large.
  According to the second aspect of the present invention, since the anti-flow-off layer is made of an N-type semiconductor, a barrier can be formed against electrons and the outflow of electrons can be prevented.
According to the fourth aspect of the present invention, since the anti-flow-off layer is made of a P-type semiconductor, a barrier can be formed against holes and the outflow of holes can be prevented.
[Brief description of the drawings]
FIG. 1 is a principle sectional structural view showing the vicinity of a charger according to a first embodiment of the present invention.
FIG. 2 is a schematic perspective view of the charger.
FIG. 3 is a schematic front view thereof.
FIG. 4 is a schematic longitudinal sectional side view showing the light source structure.
FIG. 5 is a bottom view showing the light source structure.
FIG. 6 is a schematic energy band structure diagram before and after voltage application.
FIG. 7 is a cross-sectional structural view showing the principle of a multilayer photoreceptor according to a second embodiment of the present invention.
FIG. 8 is a cross-sectional structure diagram for explaining the principle of charging and exposure processes.
FIG. 9 is a principle configuration diagram of an image forming apparatus according to a third embodiment of the present invention.
FIG. 10 is a sectional view showing the structure of the charging roller.
FIG. 11 is a cross-sectional structural view showing a charging roller structure according to a fourth embodiment of the present invention.
FIG. 12 is a principle configuration diagram of an image forming apparatus according to a fifth embodiment of the present invention.
FIG. 13 is a principle configuration diagram of an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 14 is a schematic energy band structure diagram showing a seventh embodiment of the present invention.
FIG. 15 is a schematic energy band structure diagram showing an eighth embodiment of the present invention.
FIG. 16 is a diagram illustrating the basic configuration of an image forming apparatus according to a ninth embodiment of the present invention.
FIG. 17 is a cross-sectional structure diagram for explaining the principle of a conventional charging and exposure process using a multilayer photoreceptor.
FIG. 18 is a cross-sectional structure diagram for explaining the principle of a conventional charging and exposure process using a single layer type photoreceptor.
[Explanation of symbols]
1 Photoconductor = Charged body
2 Charger
3 Light source for charging
4 Voltage application device
7 Insulating film = Flow-off prevention layer
21 Laminated Photoconductor = Charged Body
24. Charge generation area for exposure
25 Charge transport layer
26 Charge generation area for charging
41 Charger
42 Voltage application device
43 Light source for charging
51 Insulating film = flow-off prevention layer
52 Voltage application device
61 Voltage application device
62 Charging blade
63 Insulating film = Anti-flow-off layer
65 Voltage application device
66 Magnetic Brush
71 N-type semiconductor = loss prevention layer
76 P-type semiconductor = loss prevention layer

Claims (5)

The charged object for image formation is irradiated with light to generate a charge pair of a hole and an electron, and the charge of one polarity is drifted by an external voltage to polarize the positive and negative charges to change the charged object. In the charger to be charged,
The magnetic conductive particle comprises a magnetic brush containing magnetic conductive fine particles in contact with the object to be charged, and the magnetic conductive fine particle is provided with a flow prevention layer for preventing the charge having the same polarity as the charge polarity from flowing to the charger side, and the flow prevention layer Is made of an insulating film formed on a portion in contact with the member to be charged . The charged object for image formation is irradiated with light to generate a charge pair of a hole and an electron, and the charge of one polarity is drifted by an external voltage to polarize the positive and negative charges to change the charged object. In the charger to be charged,
A flow-out prevention layer that prevents the charge having the same polarity as the charge polarity from flowing to the charger side is formed, and the flow-out prevention layer is made of an N-type semiconductor formed in a portion in contact with the object to be charged. Charger characterized in that the electric charge is an electron . 3. The charger according to claim 2, wherein the N-type semiconductor satisfies a range of 1 nm <Ld <1 μm, where Ld is a thickness of a depletion layer formed on a surface thereof . The charged object for image formation is irradiated with light to generate a charge pair of a hole and an electron, and the charge of one polarity is drifted by an external voltage to polarize the positive and negative charges to change the charged object. The charger to be charged includes a flow-out prevention layer that prevents the charge having the same polarity as the charge polarity from flowing to the charger side, and the flow-out prevention layer is a P-type formed in a portion in contact with the object to be charged. A charger made of a semiconductor, wherein the charge of charge polarity is a hole . 5. The charger according to claim 4, wherein the P-type semiconductor satisfies a range of 1 nm <La <1 μm, where La is a thickness of a depletion layer formed on the surface thereof .

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