JP4662644B2 - Charging roller and charging device using the same - Google Patents

Description

【００４３】
【発明の効果】
以上説明してきたように、本発明によれば、良好な帯電性能を有する帯電ローラを得ることができ、この帯電ローラを搭載した帯電装置においては、黒ポチ等の画像不良の発生のない高い画像性を実現することができる。
【図面の簡単な説明】
【図１】本発明の帯電ローラの一例を示す断面図である。
【図２】本発明に係る帯電装置の一例を示す概略図である。
【図３】実施例で用いた抵抗測定方法を示す説明図である。
【符号の説明】
１ 帯電ローラ
２ シャフト
３ 基層
４ 接着層
５ 塗膜層
５ａ 下層
５ｂ 上層
６ 電圧印加手段
７ 被帯電体
８ リング電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging roller (hereinafter, also simply referred to as “roller”) that is suitably used for charging a charged object such as a photosensitive member in an electrostatic latent image process in a copying machine, a printer, or the like.
[0002]
[Prior art]
Conventionally, in an electrophotographic apparatus such as a copying machine or a printer, first, the surface of the photoconductor is uniformly charged, and an image is projected from the optical system onto the photoconductor to erase the charged portion of the light. An electrostatic latent image is obtained by an electrostatic latent image process for forming a latent image, and then printing is performed by forming a toner image by attaching toner and transferring the toner image to a recording medium such as paper. Yes.
[0003]
In this case, a corona discharge method has been generally employed as an operation for charging the first photoreceptor. However, this corona discharge method requires application of a high voltage of 6 to 10 kV, which is not preferable from the viewpoint of safety maintenance of the machine, and harmful substances such as ozone and NO _x are generated during corona discharge. There were also environmental problems.
[0004]
For this reason, efforts have been made to charge systems that can be charged at a lower applied voltage than corona discharge and that can suppress the generation of harmful substances such as ozone. There has been proposed a charging method using a contact method in which a charging member to which a voltage is applied is brought into contact with a charged body such as a photosensitive body at a predetermined pressure to charge the charged body.
[0005]
As a charging member used in this contact charging method, for example, a conductive elastic layer (base layer) made of rubber, urethane foam or the like is formed on the outer periphery of a core metal (shaft), and further, surface smoothness is ensured or toner is used. In order to prevent adhesion, charging with a coating layer formed by applying a resin solution in which a resin such as urethane or nylon is dissolved in an organic solvent or a resin solution dissolved or dispersed in water by dipping or spraying. Laura is known.
[0006]
In such a charging roller, if the resistance value is too high, an image failure occurs due to a charging failure of the charged object such as the photosensitive member. Conversely, if the resistance value is too low, the value of the current flowing through the photosensitive member becomes large, so There is an inconvenience such as shortening, and therefore there is an appropriate area for the roller resistance. Therefore, in order to obtain such appropriate roller resistance, a plurality of resistance layers are further provided on the base layer. For example, in a roller having a layer structure in which a two-layer resistance layer composed of an upper layer and a lower layer is provided on a base layer, a desired resistance as a charging roller is obtained by appropriately setting the resistance of these three layers.
[0007]
On the other hand, in the charging roller having a multilayer film structure, particularly when a foamed body such as urethane foam is used as the base layer, if a foam cell exists on the surface of the base layer, the base layer and a resistance layer (lower layer) provided thereon are provided. There is a problem in that the adhesiveness between the two is insufficient. If the adhesion between layers is insufficient, the mechanical strength of the resistive layer coating film is low, so deterioration tends to occur, charging performance deteriorates and charging failure occurs, and the coating film peels off when used in actual equipment. In order to solve this problem, it is known to provide an adhesive layer for improving adhesion between the base layer and the lower layer.
[0008]
[Problems to be solved by the invention]
However, in the conventional charging roller provided with such an adhesive layer, although the adhesion between the base layer and the lower layer is improved, there is a problem in the charging ability, and black spots (spots) are generated on the image. Image defects.
[0009]
Accordingly, an object of the present invention is to provide a multilayer roller structure charging roller having a configuration in which an adhesive layer is provided between the base layer and the resistance layer. An object of the present invention is to provide a high-performance charging roller that has charging performance and does not cause image defects.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the charging roller of the present invention is as follows.
(1) A charging roller that contacts a member to be charged and charges the member to be charged by applying a voltage to the member to be charged, and is bonded to the base layer on the outer peripheral surface of the shaft. In a charging roller in which a layer and a coating layer including at least a lower layer and an upper layer are sequentially provided,
The base layer is made of urethane foam, the lower layer of the coating layer includes an acrylic resin, the upper layer of the coating layer includes a fluororesin, and the volume resistance value of the base layer is 0.01 to 0.03 MΩ · The volume resistance value of the adhesive layer is 0.01 to 2 MΩ · cm, and the volume resistance value of each layer of the coating layer is 10 ³ to 10 ¹² Ω · cm. It is a charging roller.
[0014]
(2) The charging roller according to (1), wherein the adhesive layer has a thickness of 1 to 100 μm.
[0015]
(3) The charging roller of (1) or (2) above, wherein the JIS 10-point average roughness Rz of the member surface is 6 μm or less.
[0016]
(4) A charging device using the charging roller of any one of (1) to (3) above.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
As described above, the charging roller of the present invention has a multilayer structure in which a plurality of coating layers are formed on a base layer, which is a conductive elastic layer, via an adhesive layer, and the resistance values of the base layer and the adhesive layer are set to a predetermined value. By making it within the range, good charging performance is realized. FIG. 1 illustrates a charging roller 1 in which a base layer 3 is formed on the outer periphery of a shaft 2 and a coating layer 5 composed of a lower layer 5a and an upper layer 5b is formed outside the elastic layer 3 with an adhesive layer 4 interposed therebetween. In this case, a metal or plastic shaft can be used as the shaft 2, and the shaft 2 can be omitted depending on the form of the charging roller or the mechanism of the charging device using the charging roller.
[0018]
In the present invention, the base layer 3 has a volume resistance value (hereinafter also referred to as “resistance value”) of 0.03 MΩ · cm or less, preferably 0.01 MΩ · cm to 0.03 MΩ · cm, and the adhesive layer 4. The volume resistance value (hereinafter also referred to as “resistance value”) is 2 MΩ · cm or less, preferably 0.01 MΩ · cm to 2 MΩ · cm. Conventionally, it is known that the volume resistance values of the base layer and the adhesive layer are 0.05 MΩ · cm and 6 MΩ · cm, respectively, but in the present invention, the volume resistance values of these layers are within the above ranges. Thus, an excellent charging roller having an appropriate charging performance as a charging roller and having no image defects such as black spots on an image when used in an actual machine is realized.
[0019]
The base layer 3 is not particularly limited as long as the resistance value satisfies the above range, and can be formed of rubber or resin, or a foam thereof (hereinafter referred to as “foam”). Is a rubber composition using, for example, polyurethane, silicone rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, styrene-butadiene-styrene rubber, epichlorohydrin rubber or the like as a base rubber. Things. Among these, polyurethane is particularly preferable, and a polyurethane foam having an expansion ratio of 1.5 to 50 times is more preferable. In this case, the foam density is suitably about 0.05 to 0.9 g / cm ³ .
[0020]
In the present invention, a conductive agent is added to the base layer 3 in order to obtain a resistance value satisfying the above range. The conductive agent to be used is not particularly limited, but lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, perchlorate, chlorate of modified fatty acid / dimethylethylammonium salt , Cationic surfactants such as quaternary ammonium salts such as borohydride, sulfate, ethosulphate, benzyl bromide, benzyl chloride and the like quaternary ammonium salts, aliphatic sulfonates, Anionic surfactants such as higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher alcohol phosphates, higher alcohol ethylene oxide addition phosphates, and zwitterionic surfactants such as various betaines Agents, higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, nonionic antistatic agents such antistatic agents such as polyhydric alcohol fatty acid _{esters, LiCF 3 SO 3, NaCl 4} , LiAsF 6, LiBF 4, NaSCN, KSCN, NaCl Such as Li ⁺ , Na ⁺ , K ^+, etc., Group 1 metal salts, NH ₄ ⁺ salts, etc., electrolytes such as Ca (ClO ₄ ) ₂ , Ca ²⁺ , Ba ^2+, etc. A metal salt of Group 2 of the Periodic Table, and those antistatic agents having at least one group having an active hydrogen that reacts with an isocyanate such as a hydroxyl group, a carboxyl group, or a primary or secondary amine group. Can be mentioned. Furthermore, these and the like, complexes of polyhydric alcohols such as 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol and polyethylene glycol and derivatives thereof, or monools such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether Ionic conductive agents such as complexes with carbon, conductive carbon such as ketjen black EC and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, etc., color subjected to oxidation treatment (Ink) carbon, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium and other metals and metal oxides, polyaniline polypyrrole, poly Conductive polymers such as acetylene and the like. In order to obtain a desired resistance value, the blending amount of these conductive agents is preferably 0.5 wt% to 50 wt%, particularly 1 wt% to 40 wt%.
[0021]
Further, the adhesive layer 4 has a resistance value that satisfies the above range, and has a function of improving the adhesion between the base layer 3 and the coating layer 5. Examples of the forming material include nylon, polyester, urethane-modified acrylic resin, phenol resin, acrylic resin, urethane resin, epoxy resin, urea resin, and the like. Resistance value. The addition amount of the conductive agent is preferably 1% by weight to 100% by weight, and particularly preferably 10% by weight to 30% by weight, whereby a desired resistance value can be realized. In addition, the thickness of the adhesive layer 4 is preferably 1 to 100 μm, more preferably 10 to 30 μm, in order to ensure the adhesion between the base layer 3 and the coating layer 5.
[0022]
In the illustrated example, the coating layer 5 has a two-layer configuration including a lower layer 5a and an upper layer 5b. However, the coating layer 5 is not particularly limited to this, and may be three or more layers. Each layer of the coating film layer 5 can be formed of an appropriate resin according to the purpose. For example, nylon, polyester, urethane-modified acrylic resin, phenol resin, acrylic resin, epoxy resin, urethane resin, urea resin, fluorine resin However, it is not limited to these. In particular, it is preferable that at least one layer of the coating layer 5 contains an acrylic resin. Acrylic resin has a much lower dielectric constant than urethane or nylon, which has been generally used as a charging roller resin, and has a smaller electrostatic capacity. This is because the electric attractive force / repulsive force is reduced, so that the charging noise can be reduced.
[0023]
In this case, the acrylic resin is not particularly limited, but those having a glass transition temperature of −60 to 20 ° C., preferably −50 to 10 ° C. are suitably used. That is, when the glass transition temperature exceeds 20 ° C., it is possible to form a coating film, but cracking or the like is likely to occur immediately during the charging operation, and it may not be practically used, while the glass transition temperature is − Those having a temperature lower than 60 ° C. have good flexibility, but are strongly adhered, and are not so practically preferred due to workability during coating film formation and compatibility with general photoreceptors as charged bodies. In addition, acrylic resins include thermoplastic types and crosslinking types such as self-crosslinking, melamine crosslinking, and isocyanate crosslinking, and any type is suitable as long as it is within the above glass transition temperature range. Can be used. In particular, a thermoplastic type is preferably used in the coating film forming process and from the viewpoint of hardness.
[0024]
Further, it is preferable that the outermost surface layer of the coating film layer 5, in the illustrated example, the upper layer 5 b has a material structure suitable for the purpose of preventing toner adhesion, ensuring surface smoothness, etc. From the viewpoint of low adhesion to a photoreceptor or the like, a fluororesin is preferably used. Examples of fluororesins include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, polychlorotriethylene. Fluoroethylene, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, etc., and those obtained by polymerizing these in solution and solvent-based fluorine in which the polymerized resin is dissolved in an organic solvent Resin or the like is used.
[0025]
The coating layer 5 can be imparted or adjusted with conductivity by adding a conductive agent. The conductive agent used may be the same as described above, and is not particularly limited, but is preferably carbon, and in particular, the outermost surface layer of the coating layer that forms the surface of the charging roller is electrically conductive. It is preferable to use carbon as the agent.
[0026]
The addition amount of the conductive agent can be appropriately adjusted so as to obtain a desired resistance, whereby the resistance of each layer of the coating film layer 5 is 10 ³ to 10 ¹² Ω · cm, respectively. In particular, 10 ⁵ to 10 ¹⁰ Ω · cm is preferable. When carbon is used as the conductive agent, the amount added is usually 10 to 100% by weight of the outer layer, particularly about 20 to 40% by weight.
[0027]
In addition, an appropriate amount of an appropriate additive such as a thickener, thixotropy imparting agent, or structural viscosity imparting agent can be added to the coating layer 5 as desired. In this case, the additive is an inorganic or organic additive. Either may be sufficient.
[0028]
The thickness of the coating layer 5 is not particularly limited, but is preferably a thin layer so as not to impair the flexibility of the base layer 3, and specifically 1 to 30 μm, particularly 1 to 10 μm. It is preferable that
[0029]
The method for forming the adhesive layer 4 and the coating layer 5 is not particularly limited, but a method of preparing a paint containing each component for forming each layer and applying the paint by a dipping method or a spray method is preferable. Can be used.
[0030]
The resistance value as the charging roller of the present invention may be appropriately selected according to the charging device and the member to be charged, and is not particularly limited. However, in order to obtain a good image, the volume resistance value is 10 ^2. 10 ¹² Ω · cm, particularly 10 ⁵ to 10 ¹⁰ Ω · cm.
[0031]
The charging roller of the present invention preferably has a capacitance of 1 × 10 ⁻⁹ F or less, particularly 8 × 10 ⁻¹⁰ F or less, more preferably 6 × 10 ⁻¹⁰ F or less. Noise generation during operation can be more effectively suppressed. In this case, the capacitance can be obtained by, for example, a measurement method using an impedance analyzer measuring machine or an electrical measurement using a metal drum as a counterpart.
[0032]
The capacitance measurement method will be described in detail. First, in the case of a roll-shaped charging roller, for example, in the case of a roll-shaped charging roller, the roll-shaped charging roller is pressed against a highly conductive plate or drum such as a metal, In this method, an impedance analyzer measuring machine is connected between a plate and a drum, and the capacitance is calculated by the impedance analyzer.
[0033]
In addition, electrical measurement with a metal drum as a counterpart is a method of calculating the capacitance assuming that the charging roller is operating in a printer, a copying machine, or the like. For example, in the case of a roll-shaped charging roller, a metal drum and a roll are rotated in a pressed state, and a voltage is applied under a predetermined condition between the two rotating in the pressed state. In this case, the predetermined condition is substantially the same as the voltage applied to the charging roller in the printer or copying machine. For example, in the case of an organic photosensitive drum, the charged potential is often about −700 V. In order to replenish the charged charge, a DC current of about 7 μA flows through the roll, and the DC resistance can be obtained by flowing this current against the metal drum. In addition, there are printers and copiers that allow an alternating current to flow in order to maintain a uniform charging potential. The alternating current is controlled at a constant current, and the alternating current is flowed against a metal drum to determine the alternating current resistance. Can do. Therefore, the capacitance can be calculated by substituting the DC resistance value and the AC resistance value with the circuit model of the roll as a parallel model of the DC resistance component and the capacitance component.
[0034]
If the surface of the charging roller is uneven, toner may clog in the recess and cause image defects. Therefore, the surface of the member is preferably as smooth as possible, preferably JIS 10-point average roughness. The thickness Rz is 6 μm or less, particularly 3 μm or less, and further 2 μm or less.
[0035]
As described above, the charging roller of the present invention is disposed in contact with a charged body such as a photosensitive drum, and is charged by applying a voltage between the charged body and the charging roller of the present invention. It charges the body. In this case, the voltage applied between the charging roller and the member to be charged may be a DC voltage or an AC voltage, and is not particularly limited. However, a voltage obtained by superimposing the AC voltage on the DC voltage is applied. It is preferable to perform charging, whereby the object to be charged can be more uniformly charged. In addition, the contact pressure between the charging roller of the present invention and the member to be charged is preferably 50 to 2000 g, particularly 100 to 1000 g, whereby good charging can be reliably obtained.
[0036]
With respect to the charging device using the charging roller of the present invention, for example, as shown in FIG. A charging device configured to apply a voltage between the body 7 and the body 7 can be exemplified, but the invention is not limited thereto, and the form of the body 7 to be charged and the charging roller 1 and the voltage applied by the voltage applying means 6 The application method and the like can be changed as appropriate.
[0037]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.
[0038]
Examples 1-3 and Comparative Examples 1-3
First, on the outer periphery of the shaft 2 as the conductive substrate, in addition to the materials shown below, the base layer 3 whose resistance value was adjusted by changing the addition amount of carbon black as the conductive agent as shown in Table 1 below. And a thickness of 3 mm. At this time, as shown in FIG. 3, the resistance value was measured by applying a voltage of 250 V between the cored bar and the 0.5 cm wide electrode and measuring the resistance at that time.
<Material of base layer>
Polyol: 100 parts by weight Isocyanate: 30 parts by weight
Next, an adhesive layer 4 having a resistance value adjusted by changing the amount of the conductive agent in the same manner as described above was formed on the base layer 3 with a thickness of 30 μm.
<Material of adhesive layer>
Urethane resin: 100 parts by weight
Next, the lower layer 5 a and the upper layer 5 b shown in FIG. 1 were sequentially formed on the adhesive layer 4 to produce the charging roller 1. The roller surface had a JIS 10-point average roughness Rz of 1.0 μm and a capacitance of 6 × 10 ⁻¹⁰ F. The electrostatic capacity is obtained by rotating the obtained roller and the metal drum in pressure contact with each other, obtaining a DC resistance value from a DC voltage when a DC current of 7 μA is applied between them, and supplying an AC current of 560 μA. The AC voltage was measured, and the roller was calculated as a parallel model of a DC resistance component and a capacitance component.
<Lower layer material>
Acrylic resin: 100 parts by weight Resistance: 10 ⁶ Ω · cm
<Upper layer material>
Fluororesin: 100 parts by weight Resistance: 10 ⁶ Ω · cm
[0041]
Each obtained charging roller was attached to a printer, and an image was taken out at a temperature of 25 ° C. and a humidity of 55% RH, and the occurrence of black spots on the image was evaluated. The evaluation criteria are as follows. The obtained results are also shown in Table 1 below.
○: No black spots △: 1cm ² in the black spots number 1 to 5 ×: black spot number 6 or more [0042] of 1cm within the ²
[Table 1]

[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a charging roller having good charging performance, and in a charging device equipped with this charging roller, a high image without occurrence of image defects such as black spots. Can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a charging roller of the present invention.
FIG. 2 is a schematic view showing an example of a charging device according to the present invention.
FIG. 3 is an explanatory diagram showing a resistance measurement method used in Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Charging roller 2 Shaft 3 Base layer 4 Adhesive layer 5 Coating layer 5a Lower layer 5b Upper layer 6 Voltage applying means 7 Charged body 8 Ring electrode

Claims (4)

A charging roller that abuts on a member to be charged and charges the member to be charged by applying a voltage between the member to be charged, on the outer peripheral surface of the shaft, a base layer, an adhesive layer, In a charging roller in which a coating layer including at least a lower layer and an upper layer is sequentially provided,
The base layer is made of urethane foam, the lower layer of the coating layer includes an acrylic resin, the upper layer of the coating layer includes a fluororesin, and the volume resistance value of the base layer is 0.01 to 0.03 MΩ · The volume resistance value of the adhesive layer is 0.01 to 2 MΩ · cm, and the volume resistance value of each layer of the coating layer is 10 ³ to 10 ¹² Ω · cm. Charging roller. The charging roller according to claim 1, wherein the thickness of the adhesive layer is 1 to 100 [mu] m. The charging roller according to claim 1 or 2 , wherein the member surface has a JIS 10-point average roughness Rz of 6 µm or less. Charging apparatus characterized by using a charging roller as claimed in any one of claims 1-3.

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