JP3379280B2 - Semiconductive roll - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive roll used as a charging member, a transfer member or a developing member in an electrophotographic image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile. More specifically, the present invention relates to a semiconductive roll of an image forming apparatus, which is suitable for weight reduction and speedup by forming a polyurethane elastic layer containing an ion conductive agent on the outer circumference of a rotating shaft.

[0002]

2. Description of the Related Art In a charging member of an image forming apparatus, a general elastomer such as ethylene-propylene-diene rubber (EPDM), urethane rubber, silicone rubber, or polyolefin rubber is used, and conductive powder such as carbon black or conductive metal oxide or Conventionally, a roll in which an ionic conductive agent is dispersed to have conductivity has been used. As the semiconductive resistance layer of the roll, in addition to the coating film and the tube of the resin mixture containing the conductive powder in the polymer composition, various resins containing an antistatic agent containing a surfactant as a main component. Alternatively, a rubber composition is used. However, when carbon black, a metal oxide, or the like is used as the conductive powder, if the electric resistance value of the roll is set within the range of 10 ⁴ to 10 ⁹ Ω, the resistance value greatly varies,
Occurrence of image defects such as black spots, white spots, and partial charging failure can be seen. On the other hand, it has been attempted to use various antistatic agents or highly dielectric liquids as the conductive agent, but the electric resistance of the semiconductive elastic layer formed is unstable, and the photoconductor is not exposed in a low temperature and low humidity environment. May result in poor charging.
Further, contamination of the photoconductor due to seepage of the conductive agent becomes a problem. In order to solve these problems, perchlorate is used as an ion-conducting agent, and a semiconducting polymer compound having a polyether bond in a repeating unit is used as a matrix component of a semiconducting foamed polymer layer. A sex roll is proposed in, for example, Japanese Patent Laid-Open No. 5-100449.
Further, a semi-conductive roll using, for example, lithium perchlorate as an ion conductive agent and polyurethane having excellent abrasion resistance, stain resistance, and permanent strain characteristics as a rubber material of the roll is disclosed in JP-A-6-35298. Japanese Patent Laid-Open No. 6-20
It is proposed in Japanese Patent No. 0921. These semi-conductive rolls have the advantages that the variation in the electric resistance value is small, stable conductivity is exhibited, and contamination of the photoreceptor due to seepage of the conductive agent can be avoided.

However, these semiconductive rolls have a large electrostatic interaction between the ionic conductive agent and the polyurethane matrix, and thus have poor electrical characteristics in a relatively low resistance region corresponding to speeding up of the image forming apparatus. It is stable, and its performance deteriorates quickly after long-term continuous use. Therefore, since the roll has a relatively short life, the replacement frequency of the charging member increases, which is economically disadvantageous. Further, a semiconductive elastic body layer containing lithium perchlorate dispersed in a polyurethane matrix containing a polyoxyalkylene such as polyethylene oxide or polypropylene oxide as a polyol component,
Since it has only conductivity of about 10 ⁵ to 10 ⁹ Ω, and ion migration occurs along the polyether chain of polyoxyalkylene, the ion conductivity is easily affected by the segmental motion of polyurethane, and the degree of crosslinking and glass transition It is bound by temperature (Tg). In such a semiconductive roll, the matrix component is mainly an amorphous polymer having a polyether or polyester structure as the main chain, and lithium perchlorate in the matrix of 0.05 to 0.05%.
In the case of containing 0.1%, the polyoxyalkylene component is crystallized at about 10 to 20 ° C. or lower, and the conductivity is rapidly lowered to 10 ⁹ Ω. Therefore, in the conventional polyurethane semiconductive roll containing the ion conductive agent, it is impossible to charge the photoconductor or supply a sufficient current for transferring the toner image from the photoconductor.

In an image forming apparatus adopting an electrophotographic system, for example, a charging roll is usually used by applying a load to both ends thereof. Therefore, as described in JP-A-5-100549, in the semi-conductive solid roll, the contact width (nip width) between the roll and the photosensitive member surface is different at the roll end portion and the central portion, resulting in a drum shape. A non-uniform nip state may occur. Therefore, in the case of printing on A3 type paper by an electrophotographic printer, the central portion of the roll may not come into contact with the photoconductor, resulting in uneven charging of the photoconductor surface. Therefore, in order to obtain a uniform nip, a method of increasing the load by using a core metal having a large diameter can be considered. However, if the load is increased, the nip pressure between the roll and the photoconductor rises even if the hardness of the roll itself is lowered, so the amount of wear of the photoconductor increases and the toner adheres to the surface. In this case, there is a possibility that charging failure or image defect may occur. On the other hand, a single-layer sponge roll formed by blending a surfactant (silicone foam stabilizer) as an antistatic agent is described in JP-A-6-74231. According to this sponge roll,
In addition to avoiding contamination of the photoconductor, there is no occurrence of filming. However, in the charging roll, when the sponge layer has a large cell (bubble) diameter, uneven charging is likely to occur on the surface of the photosensitive member in contact with the sponge layer, so that the foamed cell pattern may appear on the image. Further, on the transfer roll, black and white dots appear due to uneven transfer at the pinhole portion, and it is difficult to obtain stable image quality.

[0005]

As described above, none of the conventional semiconductive rolls is fully satisfactory in practical use. That is, in a semiconductive roll containing an ion conductive agent dispersed in polyurethane, the electrical characteristics on the low resistance side in the medium resistance region are unstable, and it is not possible to cope with the speedup of the image forming apparatus. There is a problem that the conductivity of lithium is easily restricted by the degree of crosslinking of the matrix and Tg, and a sufficient current cannot be supplied during charging or transfer in a low temperature environment. On the other hand, when a semiconductive solid roll is used as the charging member, the nip state between the roll and the photoconductor may become non-uniform, and the surface of the photoconductor cannot be uniformly charged. Furthermore, in a single-layer sponge roll containing a surfactant, uneven charging and uneven transfer may occur. Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a semiconductive roll of an image forming apparatus capable of coping with an increase in process speed. Another object of the present invention is to prevent crystallization of the polyether component constituting the matrix in a low temperature environment,
It is intended to provide a semi-conductive roll having high ionic conductivity and stable electric resistance characteristics against environmental changes by reducing the binding of anions at cross-linking points. Furthermore, another object of the present invention is to provide a semi-conductive roll that is free from the possibility of uneven charging and uneven transfer.

[0006]

The present inventor has conducted extensive studies to improve the instability of electrical characteristics of a semiconductive roll in the medium resistance region used in an image forming apparatus. In a polyurethane matrix containing an ionic conductive agent having a relatively small variation in electric resistance, the ionic conductivity is constrained by the cross-linking degree of the matrix and Tg, and the polyether component of polyurethane is crystallized in a low temperature environment and the conductivity becomes We have obtained the knowledge that it drops sharply. Then, based on this finding, by using a polyether polyol having a specific substituent introduced as a polyol component of polyurethane, 10 ⁴ to 1
The present invention was accomplished by finding that a semiconductive roll having a stable electric resistance can be obtained within the range of ⁰⁹ Ω. That is, the semiconductive roll of the present invention comprises a rotating shaft and a cylindrical polyurethane elastic layer containing an ion conductive agent formed on the outer periphery thereof, and as a polyol component of polyurethane, carbon is present in at least a polyether chain. It is characterized in that a polyether polyol in which a hydrocarbon group of several 4 or more, a halogenated alkyl group, a polyether group or a polyester group is branched is used.

A preferred embodiment of the present invention is a semiconductive roll having a polyurethane elastic body layer having a skin layer made of a polyurethane elastic body formed on the surface thereof. Further, the perchlorate used as an ion conductive agent is added to the polyurethane constituting the polyurethane elastic body layer in an amount of 0.05 to
Add 20% by weight. Examples of the above polyether polyols include chloromethylated modified polyethylene glycol represented by the following general formula (I), alkoxymethylated modified polyethylene glycol represented by the general formula (II), and polypolyethylene represented by the general formula (III). One or more selected from oxyethylene-modified glycerol, methoxyethoxyethyl glycidyl ether-modified polyester polyol represented by the chemical formula (IV), and glycidyl ether-modified polyether polyol are preferably used.

[0008]

[Chemical 3] (In the formula, m ₁ , n ₁ , m ₂ , and n ₂ are such that m ₁ and n ₁ and m ₂ and n ₂ are in a molar ratio of 50 to 70:50 to 30. Also, n ₃ and n ₄ And n ₅ are each an integer of 1 to 3.)

The present invention will be described in detail below. The semiconductive roll of the present invention is composed of at least a rotating shaft and a polyurethane elastic layer containing an ion conductive agent formed on the outer periphery thereof. As the rotating shaft, for example, a conductive core metal such as aluminum, copper alloy, stainless steel, chromium or iron plated with nickel or nickel or a hollow cylindrical body is used. The polyurethane elastic body layer can be formed by polymerizing a polyisocyanate component and a polyol component containing an ion conductive agent.

As the polyisocyanate component, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate,
p-xylylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-diphenyl diisocyanate, 4,4'-diphenyl diisocyanate, o-tolidine diisocyanate, m-tolidine diisocyanate, 3,3'-diphenylmethane diisocyanate,
Examples include 4,4'-diphenylmethane diisocyanate, prepolymers of a polyisocyanate compound having an isocyanate group at the terminal and a polyol. These polyisocyanate components may be used alone or in combination of two or more.

As the polyol component, polyalkylene glycol such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol, polyether polyol such as polyalkylene glycol copolymer such as poly (oxyethylene-oxypropylene) glycol, and hydroxyl group at the terminal Saturated polyester with,
Ε-caprolactone ring-opening polymer having a hydroxyl group at the terminal,
Examples thereof include polyester polyols such as polycarbonate polyols obtained from ethylene carbonate and hexamethylene glycol. Further, a chain extender can be used as a polyol component. As the chain extender, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, glycerin, hexanetriol, trimethylolpropane, pentaerythritol, sorbitol, hydroquinone, bisphenol. A, bisphenol F, etc. are mentioned.

In the present invention, at least a polyether polyol in which a hydrocarbon chain having 4 or more carbon atoms, a halogenated alkyl group, a polyether group or a polyester group is branched is used as the polyol component. Here, the “polyether chain” refers to the chain structure of the polyether polyol as described above. As the hydrocarbon group having 4 or more carbon atoms, a linear or branched alkyl group such as butyl group, hexyl group, octyl group, dodecyl group, octadecyl group, aryl group such as phenyl group, naphthyl group, benzyl group, etc. Is mentioned. Examples of the halogenated alkyl group include the above-mentioned alkyl groups in which one or more halogen atoms such as fluorine, chlorine and bromine are substituted, methyl group, ethyl group and propyl group. The polyether group may be substituted with a monovalent residue of the above-mentioned polyether polyol which may substitute an alkyl group at the end (bonds with an oxygen atom to form an alkoxy group) directly in the polyether chain, or with a methyl group. A group in which the above monovalent residue is substituted with an alkyl group such as a group, an ethyl group, a propyl group and a butyl group, that is, an alkyl group having a plurality of oxygen atoms (ether groups) may be substituted in the polyether chain. . The polyester group, like the polyether group, may be substituted with an alkyl group at the end (bonding with an oxygen atom to form an ester group), which is one of the above polyester polyols.
The valent residue may be directly substituted on the polyether chain, or the alkyl group substituted with the monovalent residue may be substituted on the polyether chain. Further, the polyether group and the polyester group are polyether-polyester groups or polyester-groups containing both groups in one branched side chain at the same time.
It may be a polyether group.

Among such polyether polyols, typically, chloromethylated modified polyethylene glycol represented by the general formula (I), that is, poly [oxyethylene-CO-oxy (chloromethyl) ethylene] glycol ( I),

[Chemical 4] Alkoxymethylated modified polyethylene glycol represented by the general formula (II), that is, poly [oxyethylene-CO-
Oxy (methoxydiethoxymethyl) ethylene] glycol (II),

[Chemical 5] Polyoxyethylene-modified glycerol represented by the general formula (III), that is, glycerol-1,2,3-tri [polyoxy (methoxydiethoxymethyl) ethylene]
Ether triol (III),

[Chemical 6] Methoxyethoxyethyl glycidyl ether (IV) represented by chemical formula (IV)

[Chemical 7] Examples of the polyether polyol and the polyester polyol modified by

The molecular weight of the polyether polyols represented by the general formulas (I) to (III) is 3000 to 5000.
It is preferably in the range of. When the molecular weight is less than 3000, the relative proportion of the hard segment (polyisocyanate component and, in some cases, chain extender) in the polyurethane increases, and the hardness of the polyurethane elastic layer becomes too high. On the other hand, when the molecular weight exceeds 5,000, the viscosity of the composition for forming a polyurethane elastic body layer described later becomes high, and it becomes difficult to uniformly disperse the ionic conductive agent in the composition, and thus the semiconductivity produced. The electric resistance value of the elastic roll becomes uneven. General formula (I)
The symbols m ₁ , m ₂ and n _{1 to} n _{5 in} (III) are, as defined above, m ₁ and n ₁ and m ₂ and n ₂ in a molar ratio of 50 to 70:50 to 30, respectively. And n ₃ , n ₄ and n ₅ are each an integer of 1 to 3. When n ₁ and n ₂ are less than 30 mol%, there is ion uptake due to electrostatic interaction between the ion conductive agent and the ether chain in the main chain, and T
g is also close to the conventional value of about -50 ° C, and sufficient ionic conductivity cannot be exhibited. On the other hand, when n ₁ and n ₂ are more than 50 mol%, the degree of polymerization of the produced polymer is lowered, the hardness of the polyurethane elastic layer is increased, and the crosslinking density is too high. When n _{3 to} n ₅ are integers of 4 or more, the steric hindrance of the polyoxyethylene side chain in the polyoxyethylene-modified glycerol (III) is large, and the modified glycerol (III) is copolymerized as a comonomer component. Difficult,
As the oxyethylene main chain, a 1-3 mer is suitable.
The above various polyol components may be used alone or in combination of two or more, and the above polyether polyol alone may be used as the polyol component.

As the ion conductive agent, lithium fluoride, lithium chloride, lithium chlorate, lithium perchlorate, lithium carbonate, sodium hydrogensulfate, sodium phosphate, sodium perchlorate, sodium thiocyanate,
Potassium phosphate, potassium perchlorate, potassium thiocyanate, KMgCl ₃ , PbClF, NaAl (S
O ₄ ) ₂ , metal salts of phosphomolybdate, phosphotungstate, etc., tetramethylammonium hydroxide, octyltrimethylammonium, lauryltrimethylammonium, octadecyltrimethylammonium, benzyltrimethylammonium, dioctyldimethylammonium, dilauryldimethylammonium, etc. Examples thereof include quaternary ammonium chlorides, bromides, nitrites, sulfates, perchlorates and the like. Among these, perchlorate having a high compatibility with the polyol component is preferably used, and lithium perchlorate is particularly preferable. These ion conductive agents may be used alone or in combination of two or more. The ion conductive agent is preferably contained in an amount of 0.05 to 20% by weight based on the total amount of polyurethane constituting the polyurethane elastic body layer, that is, the total polymerization components of polyurethane. When the content of the ion conductive agent is less than 0.05% by weight, the electric resistance of the elastic layer cannot be sufficiently reduced, and the electric resistance of the semiconductive roll is within a predetermined range (10 ⁴
It is difficult to adjust to 10 ⁹ Ω). On the other hand, if the content exceeds 20% by weight, the compatibility with polyurethane deteriorates and the ionic conductive agent cannot be uniformly dispersed in the elastic body layer, and the reactivity of the polymerization component decreases to form the product. The ratio of the low molecular weight polymer in the polyurethane to be used increases, and the durability of the semiconductive roll becomes poor. In particular,
When the content of the ion-conducting agent is in the range of 0.1 to 2% by weight, the rate of polymerization reaction (urethane reaction) does not decrease, which is preferable.

The semiconductive roll of the present invention can be manufactured by either the one-shot method or the prepolymer method. For example, the one-shot method is manufactured as follows. First, a polyisocyanate component, a polyol component containing at least the above polyether polyol, an ion-conducting agent, and if necessary, an appropriate additive are sufficiently mixed to prepare a composition for forming a polyurethane elastic layer.
Then, the composition for elastic layer formation is injected into a mold supporting a rotating shaft by an extrusion molding method, a reaction injection molding method, or the like, and heated at 100 to 160 ° C. for 30 minutes to 2 hours. During this period, the polyisocyanate component and the polyol component are polymerized to produce rubber-like polyurethane. After that, when the polyurethane is cooled and taken out from the mold, as shown in FIG. 1, a semiconductive layer having a cylindrical polyurethane elastic body layer 2 containing an ion conductive agent on the outer periphery of the rotating shaft 1 is formed. A sex roll A is obtained. The polyurethane elastic layer is preferably a foam having closed cells. In order to form a foam, a foaming agent is previously mixed in the elastic layer forming composition or an inert gas is mixed by a gas mixing method, and the foaming gas of the foaming agent is added to the polyurethane in the mold. Alternatively, an inert gas may be mixed.

As the foaming agent, conventionally known ones can be used. For example, azo compounds such as azodicarbonamide and diazoaminobenzene, benzenesulfonyl hydrazide, p.
-Sulfohydrazide compounds such as toluenesulfonylhydrazide and nitroso compounds such as dinitrosopentamethylenetetramine. The blending amount of the foaming agent with respect to the polyurethane is preferably in the range of 2 to 8% by weight. Nitrogen gas, carbon dioxide gas or the like is used as the inert gas. Examples of the additive include a polymerization catalyst such as tin octoate and dibutyltin dilaurate, a silicone-based foam stabilizer, a cross-linking agent, a foaming aid, and an antioxidant. The expansion ratio of the foam is preferably in the range of 110 to 200%,
The range of 130 to 140% is particularly preferable. Expansion ratio is 1
When it is less than 10%, a relatively rigid semiconductive roll is obtained, and when the semiconductive roll is used as a charging member,
If the surface of the photoconductor is charged for a long period of time, the surface may be damaged. On the other hand, when the expansion ratio exceeds 200%, the foamed region of the elastic layer partially becomes open cells,
The elastic restoring force becomes small, which is not preferable.

As shown in FIG. 2A, the semi-conductive roll A as described above is formed with a skin layer 3 of about 0.1 to 1 mm on the surface of the polyurethane elastic layer 2 in contact with the mold surface by the sandwich injection molding method. The rolled roll (A1) is preferred. When the skin layer 3 is formed, even if the semiconductive layer (2, 3) has a single-layer structure, the adhesion with the photoconductor is improved, so that the photoconductor surface can be charged more uniformly. Further, the cleaning property is improved and the surface of the photoconductor is not contaminated. Further, as shown in FIG. 2B, the semiconductive roll A may be a roll (A2) in which the surface of the elastic layer 2 is covered with a protective layer 4 instead of the skin layer 3. Further, as shown in FIG. 2C, it may be a semiconductive roll (A3) in which the resistance adjusting layer 5 is provided between the elastic layer 2 and the protective layer 4 '. The protective layer 4 is formed by coating the semiconductive layer 2 with, for example, a thin layer of a rubber-like polymer such as polyurethane. The resistance adjusting layer 5 is made of a rubber-like polymer such as polyurethane, epichlorohydrin-ethylene oxide, or polyolefin, and is made of a conductive material such as the ion conductive agent, carbon black, a solid solution of tin oxide and antimony oxide, or a solid solution of tin oxide and indium oxide. It is preferable that the layer is composed of a layer containing a conductive powder, and the ion conductive agent and the conductive powder are separately contained in two layers. The protective layer 4'is composed of a thin layer of N-methoxymethylated nylon or the like.

The semiconductive roll A of the present invention (hereinafter referred to as A1
(A3 including A3) can be used not only as a charging roll but also as a developing roll and a transfer roll. When used as a charging roll, it is necessary to adjust its electric resistance within the range of 10 ⁴ to 10 ⁷ Ω. When it is used as a developing roll, it is applied to a one-component or two-component magnetic developing device, and its electric resistance is 10
It is in the range of ⁵ to 10 ⁶ Ω. When used as a transfer roll, it is not necessary to form the skin layer 3 and the protective layer 4 shown in FIG. 2 because they are pressed against the surface of the photoconductor through a transfer material such as paper. Its electrical resistance is in the range of 10 ⁶ to 10 ⁹ Ω. However, when the foamed cell diameter of the polyurethane elastic layer 2 is large, the transfer current for transferring the toner image does not sufficiently flow to the roll A, and resistance unevenness easily occurs, so that transfer failure easily occurs. Is preferably formed.

[0020]

The semiconductive roll (A) of the present invention comprises, as a polyol component of polyurethane constituting the polyurethane elastic layer (2), at least a polyether chain having a hydrocarbon group having 4 or more carbon atoms, a halogenated alkyl group, A polyether polyol having a branched polyether group or polyester group is used. Then, the oxygen atom in the polar polyurethane matrix having a polyether chain and the cation of the ion conductive agent form a complex, the polyether chain is crosslinked, and the ion moves due to the molecular motion of the polyurethane segment. By introducing a copolymer such as polyoxyethylene or a prepolymer or a bulky short side chain such as a chloromethyl group into such a crosslinked polyether chain, the Tg of the polyurethane is lowered, and there is less ionic constraint at the crosslink point. Become. As a result, the segmental motion of the polyurethane is further promoted, which facilitates the movement of ions even in a low temperature environment, which not only makes it possible to impart high electrical conductivity, but also increases the electrical resistance of the semiconductive roll (A). Environmental dependence is reduced. Also, the skin layer (3)
In the case of using the semiconductive roll (A1) having the above, a uniform nip width can be obtained with a low nip pressure, and a stable image without black spots and white spots can be obtained.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. (Image Forming Apparatus) FIG. 3 is an overall explanatory view of an image forming apparatus in which the semiconductive roll of the present invention is incorporated as a charging member, and is a vertical cross-sectional view in the left-right direction of the central portion. In FIG. 3, a cylindrical photoconductor 11 that rotates in the direction of the arrow is arranged inside the main body of the image forming apparatus U and functions as an electrostatic latent image carrier. A laser writing device 12 that writes an electrostatic latent image on the surface of the photoconductor 11 is arranged on one side inside the main body of the image forming apparatus U. Around the photoconductor 11, along the rotation direction thereof, a charger 13 that uniformly charges the surface of the photoconductor 11 in sequence, a developing device 14 that visualizes the electrostatic latent image,
A transfer device 15 for transferring the visualized toner image onto a sheet (transfer material) and a cleaning device 16 for removing the residual toner on the photoconductor 11 are arranged. The developing device 14 includes a developing container 14a. In the developing container 14a, a stirring member 14b for stirring the toner,
14b, a developing roller 14c, and a toner supply roller 14d that supplies toner to the developing roller 14c. The developing roller 14c faces the opening of the developing container 14a,
It is supported by the developing container 14a with a slight gap from the surface of the photoreceptor 11. Further, the cleaning device 16 includes a casing 16a. A blade holder 16b made of metal is fixed to the casing 16a, and a sheet-like cleaning blade 16c is fixed to the tip of the blade holder 16b. The edge portion of the cleaning blade 16c is in contact with the surface of the photoconductor 11 at its tip.

At the lower part of the main body of the image forming apparatus U, a paper feed tray 17 for accommodating paper is arranged. Paper tray 1
A paper take-out roller 18 for taking out the paper one by one from the paper feed tray 17 is arranged at the upper end portion of the paper 7. A pair of paper conveying rollers 19 is provided above the side of the paper take-out roller 18.
A pair of paper guides 20 for guiding the paper conveyed by is arranged. The heating roller 21a and the pressure roller 21b are provided on the other side of the inside of the main body of the image forming apparatus U.
A fixing device 21 having a
A transport path 22 for transporting the sheet on which the toner image is transferred is provided between the transfer device 15 and the transfer device 15. Further, above the fixing device 21, a pair of discharge rollers 23 and a conveyance path 24 for guiding the sheet on which the toner image is fixed from the fixing device 21 to the discharge roller 23 are provided. A discharge tray 25 is formed on the upper surface of the main body of the image forming apparatus U to accommodate the paper discharged from the discharge rollers 23.

(Semi-Conductive Charging Roll) FIG. 4 is an enlarged view of a main part of FIG. 3 showing the structure of the charger. In FIG.
The charger 13 includes the semiconductive roll A as a charging member. The semi-conductive roll A is supported on both ends of the rotary shaft 1 by support members 31 fixed to the casing 16 a of the cleaning device 16. Further, by the urging force of the two pressure springs 32, one end of which is fixed to the support member 31 and the other end of which is fixed to the end of the rotary shaft 1,
The semiconductive roll A is in contact with the surface of the photoconductor 11. A metal pad holder 33 is fixed to the support member 31, and even if the toner adheres to the surface of the semiconductive roll A very slightly by the sheet-like cleaning pad 34 fixed to the tip end thereof. It is designed to remove this. Further, a superposed oscillating voltage, which is a bias voltage, is applied to the rotary shaft 1 of the semi-conductive roll A by the DC component from the DC power source 35 and the AC component of the sine wave from the AC power source 36 connected in series. It is like this. Therefore, the polyurethane elastic body layer 2 is interposed via the conductive rotating shaft 1.
Thus, the surface of the photoconductor 11 rotating in a predetermined direction while being in contact with the elastic layer 2 can be uniformly charged.

The operation of the image forming apparatus U in the present invention is as follows.
It is the same as the conventional one, and will be briefly described as follows. As described above, by the semiconductive roll A to which the superposed oscillating voltage is applied, the photoconductor 11 that rotates in the arrow direction
Is uniformly charged on its surface. A laser writing device 12 writes an electrostatic latent image on the uniformly charged photoconductor 11. The electrostatic latent image on the photoconductor 11 is developed into a toner image by the developing device 14. The toner image is transferred by the transfer device 15 onto the paper conveyed from the paper feed tray 17. After the transferred toner image is fixed by the fixing device 21, the paper is discharged onto the discharge tray 25 by the discharge roller 23. Further, the toner remaining on the surface of the photoconductor 11 after the toner image is transferred onto the paper is cleaned by the cleaning device 1.
Removed by 6.

Example 1 The following composition was thoroughly stirred and then cooled to 4 ° C., and then 35 parts by weight of tolylene diisocyanate (PAPI-135: manufactured by Mitsubishi Kasei Dow Co., Ltd.) was added thereto while blowing nitrogen gas. By stirring, a mixture containing bubbles of nitrogen gas was obtained. Polyester polyol (molecular weight 1000) 70 parts by weight (Sanester No22: Sanyo Chemical Co., Ltd.) Polyether polyol 20 parts by weight (P-L2100: Sanyo Chemical Co., Ltd.) Chloromethylated modified polyethylene glycol (I) 10 parts by weight (molecular weight 3400) _{; m 1: n 1 = 54} : 46) of lithium perchlorate 0.5 parts by weight of the silicone foam stabilizer (molecular weight 2000) 2 parts by weight of water 0.3 wt outer diameter 6mm of SUS (stainless steel) steel rotary shaft ( 1) is supported, and the above mixture is poured into a mold having an inner diameter of 12 mm preheated to 120 ° C. and maintained at the same temperature for 1 hour, and a polyurethane elastic layer (2) is provided on the outer circumference of the rotating shaft (1) excluding both ends. ) Was formed. Semi-conductive roll (A) manufactured in this way
Is DC 100 at low temperature and low humidity (15 ℃, 30% RH).
The resistance when V was applied was 4.0 × 10 ⁵ Ω, and the hardness (Asker A) was 36 °.

(Print Test) The semiconductive roll (A) manufactured as described above was mounted on the image forming apparatus (U) shown in FIG. 3 as a charging member of the charger (13). In this embodiment, this image forming apparatus (U) is used as a laser beam printer. From the DC power supply (35) and the AC power supply (36) connected in series, a DC component of -350 V and a frequency of 35
A superposed vibration voltage of 0 Hz and peak-to-peak voltage (V _PP ) of 2000 V with a sinusoidal AC component is applied to a semi-conductive roll (A) having an outer diameter of 12 mm, and brought into contact with the semi-conductive roll (A). Uniformly the surface of the photoconductor (11) with an outer diameter of 30 mm-
It was charged to 350V. The process speed of the printer is variable in two steps of 28 mm / sec and 56 mm / sec. Image forming apparatus described above
An image test was performed under low temperature and low humidity (15 ° C., 30% RH) by operating the laser beam printer having the same action as (U), and good image quality was obtained at any process speed.

Example 2 A semiconductive roll was manufactured in the same manner as in Example 1 except that the composition was changed as follows. The low temperature and low humidity (15
The resistance was 2.5 × 10 ⁴ Ω and the hardness (Asker A) was 53 ° when a direct current of 100 V was applied at 30 ° C. and 30% RH. The following adduct 108.6 parts by weight Polyester polyol of Example 1 100 wt Methoxyethoxyethyl glycidyl ether (IV) 8.6 wt Polyoxyethylene modified glycerol (III) 10.5 parts by weight (n _{3 to} n ₅ = 1) Perchlorine Lithium acid 0.2 parts by weight Silicone foam stabilizer of Example 1 2 parts by weight Water 0.3 parts by weight (print test) The manufactured semiconductive roll was applied to the image forming apparatus shown in FIG. Wear, Example 1
An image test was conducted in the same manner as
Good image quality was obtained at any process speed of mm / sec.

Comparative Example 1.5 parts by weight of 1,4-butanediol as a polyol component and trimethylolpropane (manufactured by Tokuyama Soda Co., Ltd.)
8.6 parts by weight, 4,4 'as polyisocyanate component
-Diphenylmethane diisocyanate (Millionate M
A semiconductive roll was produced in the same manner as in Example 1 except that 30 parts by weight of TL (manufactured by Nippon Polyurethane Co., Ltd.) was used. Direct current under low temperature and low humidity (15 ℃, 30% RH) 1
The resistance at the time of applying 00V was 5.0 × 10 ⁷ Ω, and the hardness (Asker A) was 50 °. (Print Test) The manufactured semiconductive roll was mounted on the image forming apparatus shown in FIG.
An image test was conducted in the same manner as in 1., but good image quality was obtained at a process speed of 28 mm / sec, but defective charging occurred at a high process speed of 56 mm / sec.

[0029]

EFFECTS OF THE INVENTION According to the semiconductive roll of the present invention, the coordination bond between the ether group in the polyurethane matrix and the cation of the ionic conductive agent can be suppressed, so that it can be used in any temperature range from low temperature low humidity to high temperature high humidity. The electrical resistance characteristics are stable even in an environment for a long period of time. Therefore, when the semiconductive roll of the present invention is used as a charging member, compared with a conventional charging roll in which a nonionic conductive powder such as an ion conductive agent such as lithium perchlorate or carbon black is dispersed, It is possible to obtain a semiconductive roll excellent in uniformity of electric resistance in a relatively low medium resistance region of 10 ⁴ to 10 ⁶ Ω, and it is possible to prevent pinhole leakage due to concentration of charging current. Further, even when the temperature is low and the humidity is low, the variation in electric resistance is small, and since the roll has a low hardness, it contacts the surface of the photoconductor with a uniform nip width, so that the process speed of the image forming apparatus can be increased. It can be suitably used not only as a charging member but also as a developing member and a transfer member in the medium resistance region. Further, according to the embodiment of the present invention in which a skin layer is formed on the surface of the polyurethane elastic body layer, the adhesion with the photoconductor is improved even with a single layer structure, so that it is particularly suitable as a charging roll for uniformly charging the photoconductor surface. Can be used for Also,
It is also suitable as a transfer roll having no resistance unevenness, in which case a good image is formed without the risk of image quality defects.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a semiconductive roll shown as an example of the present invention.

FIG. 2 is a vertical cross-sectional view of a semiconductive roll shown as another example of the present invention, FIG. 2A is a semiconductive roll formed by a sandwich injection molding method, and FIG. 2B is FIG. 2A.
Is a semiconductive roll having a different surface layer, and FIG. 2C is a semiconductive roll provided with a resistance adjusting layer.

FIG. 3 is an overall explanatory view of an image forming apparatus in which the semi-conductive roll of the present invention is incorporated as a charging member, and is a vertical cross-sectional view in the horizontal direction of the central portion.

FIG. 4 is an enlarged view of a main part of FIG. 3, showing a structure of a charger.

[Explanation of symbols]

A, A1, A2, A3 ... Semi-conductive roll, 1 ... Rotating shaft,
2 ... Polyurethane elastic layer, 3 ... Skin layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-74231 (JP, A) JP-A-6-250493 (JP, A) JP-A-6-35298 (JP, A) JP-A-6- 200921 (JP, A) JP-A-7-13402 (JP, A) JP-A-6-124034 (JP, A) JP-A-5-197257 (JP, A) JP-A-7-72721 (JP, A) JP 8-72172 (JP, A) JP 8-72173 (JP, A) JP 63-179959 (JP, A) JP 5-241364 (JP, A) JP 7-238219 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 B32B 27/40 F16C 13/00 G03G 15/08 501 G03G 15/16 103

Claims (3)

(57) [Claims] 1. A hydrocarbon comprising a rotating shaft and a cylindrical polyurethane elastic layer containing an ion-conducting agent formed on the outer periphery of the rotating shaft, the hydrocarbon component having at least a polyether chain of 4 or more carbon atoms as a polyol component of polyurethane. A semiconductive roll characterized by using a polyether polyol having a branched group, a halogenated alkyl group, a polyether group or a polyester group. 2. The ionic conductive agent is a perchlorate, and the perchlorate is contained in an amount of 0.05 to 20% by weight based on the polyurethane constituting the polyurethane elastic layer. Semi-conductive roll. 3. The polyether polyol is a chloromethylated modified polyethylene glycol represented by the following general formula (I), an alkoxymethylated modified polyethylene glycol represented by the general formula (II), or a general formula (III) Represented polyoxyethylene-modified glycerol, chemical formula (I
The semiconductive roll according to claim 1 or 2, which is one or more selected from polyester polyols and polyether polyols modified with methoxyethoxyethyl glycidyl ether represented by V). [Chemical 1] [Chemical 2] (In the formula, m ₁ , n ₁ , m ₂ , and n ₂ are such that m ₁ and n ₁ and m ₂ and n ₂ are in a molar ratio of 50 to 70:50 to 30. Also, n ₃ and n ₄ And n ₅ are each an integer of 1 to 3.)