JP2002072628A - Electrostatic charging roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic charging roller which obviates the occurrence of an image defect by deformation even when this roller is built into a cartridge, is stored for a long period and is put into a state that the roller is held in pressurized contact with a photoreceptor drum and which makes the reference by permanent compression set of a coating film to define and makes it possible to obtain always good images. SOLUTION: The electrostatic charging roller 1 which is brought into contact with abutment on a body to be electrostatically charged and electrostatically charges the body to be electrostatically charged by impressing voltage between itself and the body to be electrostatically charged has an elastic layer 3 and a coating film layer 4 formed directly or through another layer on the outer side of this elastic layer 3. The electrostatic charging roller described above satisfies the conditions that the residual strain P value measured under specific conditions of a coating film material forming the coating film layer 4 is <=55%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller suitably used for charging an object to be charged such as a photosensitive member in an electrostatic latent image process in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine or a printer, first, the surface of a photoreceptor is uniformly charged, and an image is projected on the photoreceptor from an optical system so that a portion of the photoreceptor exposed to light is exposed. An electrostatic latent image is obtained by an electrostatic latent image process of forming a latent image by erasing the charge, 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. The method has been taken.

In this case, a corona discharge method has been generally adopted as an operation for initially charging the photosensitive member. However, since this corona discharge method requires application of a high voltage of 6 to 10 kV, it is not preferable from the viewpoint of safe maintenance of the machine. Also, ozone,
Since harmful substances such as NO _x is generated, there are also environmental issues.

[0004] For this reason, charging schemes that can perform charging with a lower applied voltage than corona discharge and that can suppress the generation of harmful substances such as ozone have been undertaken. As a method, a contact method has been proposed in which a charging member to which a voltage is applied is brought into contact with a member to be charged such as a photoreceptor at a predetermined pressure to charge the member to be charged.

In this case, as a charging member used in this contact charging method, for example, a resin solution in which a resin such as urethane or nylon is dissolved in an organic solvent is dipped on the surface of an elastic layer such as rubber or urethane foam. It is known that a coating layer such as urethane or nylon is formed by applying the toner by a spraying method or the like to secure the smoothness of the surface and prevent the adhesion of the toner.

[0006]

However, in this contact charging system, when a charging roller as a charging member is incorporated in a cartridge and stored for a long period of time, the charging roller is brought into pressure contact with the photosensitive drum as a member to be charged for a long time. Then, the charging roller is deformed, and if the deformation is not restored, an image defect occurs. For this reason, it is required that the elastic body and the coating film constituting the charging roller have a small compression set, but the standard has not been clarified so far, and in particular, the degree of the compression set causes an image defect. It was unknown if it would occur. Such a compression set is not uniquely determined only by the resin material of the coating film, but can also vary depending on a crosslinking agent, a drying temperature, and the like.

Accordingly, an object of the present invention is to provide a coating film having a permanent compression set which does not cause an image defect due to deformation even when it is stored in a cartridge for a long time and kept in pressure contact with a photosensitive drum for a long time. It is an object of the present invention to provide a charging roller that clarifies the standard and can always obtain excellent images.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the coating material forming the coating layer was measured under specific conditions found by the present inventors. When the value of the obtained compression set is not more than a certain value, it has been found that an excellent image can always be obtained without causing image defects due to deformation, and the present invention has been completed. That is,
The present invention is as described below.

(1) A charging roller for charging a member to be charged by applying a voltage between the member and the member to be charged by contacting the member with the member. In a charging roller having a coating layer formed directly or via another layer on the outside, the coating material for forming the coating layer is represented by the following formula: P = (X-100) / (140-100) ) × 100 (where X is a value determined through the following steps 1 to 6. 1. The above coating material is cast on a flat plate and
Dry at ~ 120 ° C and adjust to a 300 µm thick coating.
2. The dried coating film is cut into a strip of 100 mm x 5 mm. 3. The cut coating film is stretched 40% to 140 mm and left for 24 hours in a humid environment at a temperature of 40 ° C. and a humidity of 90%. 4. After standing for 24 hours, temperature 25 ° C, humidity 50%
Release the elongation under normal temperature and normal humidity. 5. Fifteen minutes after release, the length of the coating film was measured, and the length was designated as X. The charging roller satisfies that the P value represented by ()) is 55% or less. As a result, the state of occurrence of image defects can be directly grasped only from the coating film material, and a charging roller that does not cause image defects due to deformation can be provided.

(2) In the charging roller of (1),
The charging roller has a P value of 50% or less. This is a more reliable P value range for obtaining an excellent image.

(3) The charging roller according to (1) or (2), wherein the thickness of the coating layer is 20 to 600 μm. When the thickness of the coating film layer is within this range, the above-mentioned conditions regarding the P value can be suitably applied.

(4) In the charging roller according to any one of (1) to (3), the coating layer is a charging roller containing an acrylic resin. Thereby, the condition relating to the P value can be satisfactorily satisfied.

(5) The charging roller according to any one of (1) to (4), wherein one or more outer layers are formed on the coating layer. Also in this case, it is possible to provide a charging roller that does not cause an image defect due to deformation by applying the above-described condition regarding the P value.

(6) In the charging roller of (5),
A charging roller in which the thickness of the outer layer is 30 μm or less. It is a preferable range as the thickness of the outer layer from the viewpoint of flexibility.

(7) In the charging roller according to any one of the above (1) to (6), the member surface has a JIS 10-point average roughness R
This is a charging roller in which z is 4 μm or less. This allows
Image defects due to toner clogging in the concave portions can be prevented.

(8) In the charging roller according to any one of (1) to (7), the elastic layer has a density of 0.05 to 0.5.
This is a charging roller formed using a 9 g / cm ³ polyurethane foam. Thereby, good physical properties can be obtained as the elastic layer.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. As described above, the charging roller of the present invention has an elastic layer and a coating layer formed on the elastic layer. For example, FIG. 1 illustrates the charging roller 1 in which the elastic layer 3 is formed on the outer periphery of the shaft 2 and the coating layer 4 is formed outside the elastic layer 3. In this case, a metal or plastic shaft can be used as the shaft 2, and depending on the form of the charging roller and the mechanism of the charging device in which the charging roller is used, etc.
This shaft 2 can be omitted.

The elastic layer 3 is not particularly limited, and can be formed of rubber or resin, or a foam thereof (hereinafter referred to as “foam”). Specifically, polyurethane, silicone rubber, Butadiene rubber,
Isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, styrene-butadiene-styrene rubber, a rubber composition having a base rubber such as epichlorohydrin rubber is exemplified, but polyurethane is particularly preferable. More preferably, a polyurethane foam having an expansion ratio of 1.5 to 50 times is used. The foam density in this case is 0.05 to
About 0.9 g / cm ³ is appropriate.

A conductive agent is added to the elastic layer 3.
Thereby, a predetermined resistance value can be provided. Its guidance
The electric agent is not particularly limited, and may be lauryl trimethyl alcohol.
Ammonium, stearyltrimethylammonium, octane
Tadodecyl trimethyl ammonium, dodecyl trimethyl
Luammonium, hexadecyltrimethylammonium
Of modified fatty acid and dimethylethylammonium salt
Borates, chlorates, borofluorides, sulfates, ethates
Sulfate, benzyl bromide, benzyl chloride, etc.
Cations such as quaternary ammonium salts such as benzyl halide salts
Ionic surfactant, aliphatic sulfonate, higher alcohol
Sulfuric acid ester, higher alcohol ethylene oxide
Sulfuric acid ester addition salt, higher alcohol phosphate ester
Salt, higher alcohol ethylene oxide added phosphate ester
Anionic surfactants such as sodium salts and amphoteric surfactants such as various betaines
On-surfactant, higher alcohol ethylene oxide,
Polyethylene glycol fatty acid ester, polyhydric alcohol
Antistatic agents such as nonionic antistatic agents such as fatty acid esters
Stopper, LiCF_ThreeSO_Three, NaCl_Four, LiAsF₆, Li
BF_Four, NaSCN, KSCN, NaCl, etc.⁺, N
a⁺, K⁺Metal salt of Group 1 of the Periodic Table, or NH_Four ⁺
Electrolytes such as salts, and Ca (ClO_Four)_TwoCa such as ²⁺, B
a²⁺Metal salts of the second group of the periodic table, and their charging
The inhibitor has at least one hydroxyl group,
With isocyanates such as primary or secondary amine groups
And those having a group having active hydrogen. Change
Include 1,4-butanediol, ethylene glycol
Recall, polyethylene glycol, propylene glyco
And polyhydric alcohols such as polyethylene glycol
Complexes such as derivatives of ethylene glycol ethylene glycol
Ether, ethylene glycol monoethyl ether, etc.
Conductive agents such as complexes with monools, or ketch
Conductive cars such as enblack EC and acetylene black
Bon, SAF, ISAF, HAF, FEF, GPF, S
RF, FT, MT, etc. rubber carbon, oxidized
Color (ink) carbon, pyrolytic carbon, natural
Graphite, artificial graphite, antimony doped
Tin oxide, titanium oxide, zinc oxide, nickel, copper, silver,
Metals and metal oxides such as rumanium, polyaniline
Conductive polymers such as lipirole and polyacetylene
I can do it. In this case, the compounding amount of these conductive agents depends on the composition
The volume resistance of the elastic layer 3 is appropriately selected according to the type of
Rate is 10⁰-10⁸Ω · cm, preferably 10^Two-10⁶Ω
・ Adjusted to be cm.

Next, the coating layer 4 has the following formula: P = (X−100) / (140−100) × 100 (where X is a value obtained through the following steps 1 to 6). 1. The above-mentioned coating material was cast on a flat plate and 100
Dry at ~ 120 ° C and adjust to a 300 µm thick coating.
2. The dried coating film is cut into a strip of 100 mm x 5 mm. 3. The cut coating film is stretched 40% to 140 mm and left for 24 hours in a humid environment at a temperature of 40 ° C. and a humidity of 90%. 4. After standing for 24 hours, temperature 25 ° C, humidity 50%
Release the elongation under normal temperature and normal humidity. 5. Fifteen minutes after release, the length of the coating film was measured, and the length was designated as X. ) Is 55% or less, preferably 50% or less.

The above equation indicates that even if the charging roller is incorporated in the cartridge and stored for a long period of time, and is kept in pressure contact with the photosensitive drum for a long period of time, deformation of the coating film without causing image defects due to deformation. 1 shows a criterion based on permanent set and has been found by the present invention. The P value obtained based on this equation is 55% or less, preferably 50%.
%, It is possible to provide a charging roller capable of always obtaining excellent images irrespective of the type of the coating material, the drying conditions, and the type of the crosslinking agent. The P value can vary depending on the type of the resin, the amount and type of the cross-linking agent, the drying temperature, the amount and type of the additive such as carbon, and the like. What is necessary is just to determine the conditions for forming the coating film layer that satisfy the condition of the P value.

The coating layer 4 is usually formed of a resin to which a conductive agent is added. In this case, any resin can be used as a resin for forming the coating film as long as it can add a conductive agent, and is not particularly limited. When forming
A water-based resin is preferably used to ensure smoothness. As the water-based resin, if the solvent is water, any of a water-soluble type, an emulsion type, a suspension type and the like may be used. In particular, a resin having an active hydrogen such as a carboxyl group, a hydroxyl group or an amino group is preferably used. Specific examples of such an aqueous resin include polyester-based, acrylic-based, urethane-based, and hot-water-soluble resins such as polydioxolan, and the like.In particular, acrylic resins are conventionally used generally as resins for charging rollers. Since the dielectric constant is considerably smaller than urethane or nylon used in the field, the electrostatic capacity is also reduced, and the electric attraction and repulsion between the charging roller and the object to be charged by applying an AC voltage is reduced, and the charging is performed. It is particularly preferably used because it can reduce sound.

In this case, the acrylic resin is not particularly limited, but has a glass transition temperature of -60 to 20 ° C.
Preferably, a temperature of -50 to 10C is suitably used.
That is, when the glass transition temperature exceeds 20 ° C., it is possible to form a coating film on the elastic layer 3, but cracks or the like are easily generated at the time of charging operation, which may not be practical. On the other hand, those having a glass transition temperature lower than −60 ° C. have good flexibility but strong adhesion, and are practically used due to problems in workability in forming a coating film and compatibility with a general photoreceptor as a member to be charged. Not very good.

The acrylic resin includes a thermoplastic type and a cross-linked type such as self-crosslinking, melamine cross-linking, isocyanate cross-linking, and any type of acrylic resin within the above glass transition temperature range. Can also be suitably used, and is not particularly limited, but on a coating film forming step,
The thermoplastic type is particularly preferably used in terms of hardness and hardness.

The coating layer 4 can be provided or adjusted with conductivity by adding a conductive agent, and usually has a volume resistivity of 10 ³ to 10 ¹² Ω · cm, particularly 10 ⁵ to 10 ¹⁰ Ω.・ Cm
It is preferable to adjust so that In this case, as the conductive agent, the same conductive agent as that exemplified in the elastic layer 3 can be exemplified, but carbon is particularly preferably used. The amount of the conductive agent to be added is appropriately selected depending on the type of the conductive agent and the like so as to have the above volume resistivity, and is not particularly limited. ~ 60% by weight, especially 10-4
It is about 0% by weight.

Further, appropriate additives such as a thickener, a thixotropy-imparting agent, and a structural viscosity-imparting agent can be added to the coating layer 4 as needed. The additive may be either inorganic or organic.

The thickness of the coating layer 4 is not particularly limited, but is preferably a thin layer so as not to impair the flexibility of the elastic layer 3, specifically 1 mm or less, more preferably 800 μm. Hereinafter, it is particularly preferable to set the thickness to 20 to 600 μm.

Although not particularly shown in FIG. 1, the charging roller of the present invention may further include one additional layer on the coating layer 4 according to the purpose of preventing toner adhesion and ensuring surface smoothness. Alternatively, two or more outer layers can be provided.

The outer layer can be formed of any suitable resin such as nylon, polyester, urethane-modified acrylic resin, phenol resin, acrylic resin, epoxy resin, urethane resin, urea resin, fluororesin, etc. In particular, a fluororesin is preferably used from the viewpoint of the surface smoothness of the charging roller and low adhesion to a photoreceptor or the like.

Examples of the fluororesin include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, Polychlorotrifluoroethylene, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, and the like, and a dispersion-type aqueous fluororesin obtained by dispersing these fine particles in water is particularly preferably used. ,
More preferably, a dispersion type aqueous fluororesin in which fine particles of polytetrafluoroethylene are dispersed in water is used. The particle size of the fluororesin fine particles used is not particularly limited, but is preferably 5 μm or less, particularly preferably 0.05 to 1 μm.

The outer layer can be formed by mixing other resins with these fluororesins as long as the effect of the fluororesins is not impaired. In this case, as the other resin mixed with the fluororesin, polyvinyl acetal resin, urethane resin, polyester resin, acrylic resin, nylon resin, epoxy resin, vinylidene chloride-based copolymer, and the like. The outer layer can be formed by mixing two or more kinds with the fluororesin. Among these resins, polyvinyl acetal resin from the viewpoint of film formation and resistance uniformity of the fluororesin,
Urethane resins, polyester resins, and vinylidene chloride copolymers are preferred, and polyvinyl acetal resins are particularly preferred.

In this outer layer, a conductive agent can be added to impart or adjust conductivity. In this case, the conductive agent is not particularly limited, but carbon is preferably used, and particularly, a charging roller is used. It is preferable to use carbon as a conductive agent for the outermost layer that forms the surface of the substrate. In this case, the carbon used for the outer layer is not particularly limited, but the oxygen content is preferably 5% or more, particularly preferably 7% or more, and more preferably 9% or more, and the pH is 5 or more. In particular, it is preferably 6 or more, more preferably 7 or more. That is, the oxygen content of ordinary carbon is 0.1
３3%, some of which have been oxidized, but the oxidized carbon tends to shift its pH toward the acidic side as the oxygen content increases slightly. In some cases, when carbon becomes acidic, the stability may decrease when added to an aqueous fluororesin. On the other hand, the carbon suitably used in the present invention maintains neutrality or alkalinity despite having a high oxygen content, and can be stably added to the aqueous fluororesin. . Although the detailed structure of carbon having such an oxygen content and pH is not clear, a functional group such as a carboxyl group, a hydroxyl group, or a ketone group is attached to the carbon surface, and a part of hydrogen contained in these functional groups is removed. Those substituted with an alkali metal such as sodium are preferably used.

The amount of the conductive agent to be added can be appropriately adjusted so as to obtain a desired resistance. In this case, the resistance of the outer layer is 10 ³ to 10 ¹² Ω · cm, particularly 1
It is preferable to be 0 ⁵ to 10 ¹⁰ Ω · cm, and the addition amount of the conductive agent can be adjusted so as to achieve such a volume resistivity. Usually 0.01 to 40% by weight of the outer layer, especially
It is about 20% by weight.

To the outer layer, as in the case of the coating layer 4, an appropriate additive such as a thickener, a thixotropy-imparting agent, or a structural viscosity-imparting agent is added if necessary. In this case, the additive may be either inorganic or organic.

The thickness of the outer layer is not particularly limited, but is preferably 30 μm or less, particularly preferably 5 to 15 μm. When the thickness of the outer layer exceeds 30 μm, the outer layer becomes hard and flexibility increases. It may be damaged, the durability may be reduced, and cracks may occur due to use.

The method of forming the coating layer 4 and, if necessary, the outer layer formed on the coating layer 4 is not particularly limited. A method of preparing and applying this paint by dipping or spraying is preferably used.

The charging roller of the present invention has the elastic layer 3, the coating layer 4, and the outer layer provided as necessary, and can be formed into a roller shape as shown in FIG. 1, for example. However, if necessary, another layer may be provided between the elastic layer 3 and the coating layer 4. For example, when the elastic layer 3 is formed using a polyurethane foam, an acrylic resin, a polyester resin, or the like is used in order to more effectively prevent noise generation when a voltage is applied and to improve the surface smoothness of the elastic layer 3. An intermediate layer in which a conductive agent is added to a base resin such as a polyurethane resin, a nylon resin, an epoxy resin, a urethane-modified acrylic resin, a butyral resin, a phenol resin, a vinylidene chloride-based copolymer, and a polyvinyl acetal resin may be provided.

The resistance value of the charging roller of the present invention is appropriately selected depending on the charging device to be mounted and the member to be charged, and is not particularly limited. It is preferably from 10 ² to 10 ¹² Ω · cm, and particularly preferably from 10 ⁵ to 10 ¹⁰ Ω · cm.

Although the charging roller of the present invention is not particularly limited, its electrostatic capacity is 1 × 10 ⁻⁹ F or less, particularly 8 × 10 ⁻¹⁰ F or less, and further 6 × 10 ⁻¹⁰ F or less. F or less, whereby the generation of noise during the charging operation can be more effectively suppressed. In this case, the capacitance can be determined by, for example, a measuring method using an impedance analyzer or an electrical measurement using a metal drum.

The method of measuring the capacitance will be described in detail.
First, measurement with an impedance analyzer, for example, in the case of a roll-shaped charging roller, press the roll-shaped charging roller against a metal or other highly conductive plate or drum, and place an impedance analyzer measuring device between the roll and the highly conductive plate or drum. Is connected, and the capacitance is calculated by an impedance analyzer.

The electrical measurement for a metal drum 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 while being pressed against each other, and a voltage is applied between the two rotating under the pressed state under predetermined conditions. In this case, the predetermined condition is substantially the same condition as the voltage applied to the charging roller in a printer or a copier. For example, in the case of an organic photosensitive drum, the charging potential is often about -700 V. To replenish the charge,
A DC current of about 7 μA flows through the roll, and a DC resistance can be obtained by passing this current to the metal drum. In addition, there are printers and copiers that allow AC current to flow in order to maintain a uniform charging potential.The AC current is controlled at a constant current, and the AC resistance must be obtained by passing this AC current to a metal drum. Can be. Therefore, the capacitance can be calculated by substituting the DC resistance value and the AC resistance value for the roll circuit model as a parallel model of the DC resistance component and the capacitance component.

Further, if there are irregularities on the surface of the charging roller,
Since the toner may be clogged in the recesses and cause image defects, it is preferable that the surface of the member is as smooth as possible. Specifically, JIS 10 point average roughness Rz is 4 μm.
m, particularly preferably 3 μm or less, more preferably 2 μm or less.

The charging roller of the present invention is disposed in contact with a member to be charged such as a photosensitive drum, and is charged by applying a voltage between the member to be charged 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, but is a voltage obtained by superimposing the AC voltage on the DC voltage. Is preferably applied to perform charging, so that the member to be charged can be charged more uniformly. Although not particularly limited, the contact pressure between the charging roller of the present invention and the member to be charged is 50 to 2000 g, particularly 100 to 1 g.
000 g is preferable, whereby good charging can be reliably obtained.

For the charging device using the charging roller of the present invention, for example, as shown in FIG. 2, the charging roller 1 of the present invention is brought into contact with a member 5 to be charged such as a photosensitive drum, A charging device configured to apply a voltage between the charging member 5 and the charging member 5 can be exemplified, but is not limited thereto. The voltage application method and the like according to 6 may be appropriately changed.

[0045]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1-4, Comparative Examples 1, 2 Conductive urethane foam (density 0.48 g / cm ³ )
On the surface of the elastic layer composed of
F, each having a thickness of 10 μm on the surface of the coating layer.
After forming an outer layer of m, various charging rollers were experimentally manufactured. Here, the coating layers A to F were formed by changing the crosslinking agent for the water-based acrylic resin and the drying temperature and applying a coating material to which carbon was added, and the following P values were obtained. The P value measurement conditions were determined according to the above-described conditions according to the present invention. A: 92.3%, B: 76.2%, C: 65.6%,
D: 50.1%, E: 42.7%, F: 25.2%

The outer layer is formed by applying a paint in which carbon is added to a resin obtained by blending a water-dispersible fluororesin, a vinylidene chloride copolymer latex, and a polyvinyl acetal resin, and has a volume resistivity of 5%. It was adjusted to × 10 ⁷ Ωcm. The carbon used had an oxygen content of 10% and a pH of 7.33.

The surface roughness of each of the obtained charging rollers was 0.3 μm in terms of JIS 10-point average roughness Rz, and the hardness (JIS)
-A) was 57 ° and the capacitance was 4 × 10 ⁻¹⁰ F. The capacitance was measured by rotating the obtained roller and the metal drum while pressing them against each other, and applying a direct current of 7 μm between the two.
A DC resistance value was obtained from a DC voltage when A was supplied, and an AC voltage was measured when an AC current of 560 μA was supplied, and the roller was calculated as a parallel model of a DC resistance component and a capacitance component.

500 g each at both ends of each test charging roller
, The charging roller is brought into contact with the photoreceptor at a pressure of 1000 g, left at 50 ° C. and 95 RH for 3 days, then the roller is taken out, and the dent amount of the contacting portion is measured with a laser outer diameter measuring device (Mitsutoyo). (Manufactured by the company). The results obtained are shown in Table 1 below. In addition, the charging roller having the dent was mounted on a printer, and an image was displayed at a temperature of 15 ° C. and a humidity of 10% RH. A good image was obtained. A sample for which a good image was not obtained was evaluated as x. The results obtained are shown in Table 1 below.

[0050]

[Table 1]

[0051]

According to the charging roller of the present invention, when the charging operation is performed by the contact charging method, the deformation hardly occurs, and the occurrence of an image defect due to the deformation can be prevented as much as possible.

[Brief description of the drawings]

FIG. 1 is a 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging roller 2 Shaft 3 Elastic layer 4 Coating layer 5 Charged body 6 Voltage applying means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 133/00 C09D 133/00 201/00 201/00 F term (Reference) 2H003 BB11 CC05 3J103 AA02 AA14 AA15 AA36 BA41 FA03 FA30 GA02 GA57 GA58 HA03 HA04 HA05 HA11 HA12 HA20 HA31 HA41 HA43 HA48 HA53 4J038 CG141 DD001 DF021 DG031 GA03 GA06 GA09 HA026 KA12 MA13 MA14 NA11 NA20 PB11 PC07 PC08

Claims (8)

[Claims] 1. A charging roller for charging a member to be charged by applying a voltage between the member and a member to be charged by contacting the member with the member. And a coating layer formed directly or via another layer, the coating material forming the coating layer is represented by the following formula: P = (X-100) / (140-100) × 100 (where X is a value obtained through the following steps 1 to 6. 1. The above coating material is cast on a flat plate and
Dry at ~ 120 ° C and adjust to a 300 µm thick coating.
2. The dried coating film is cut into a strip of 100 mm x 5 mm. 3. The cut coating film is stretched 40% to 140 mm and left for 24 hours in a humid environment at a temperature of 40 ° C. and a humidity of 90%. 4. After standing for 24 hours, temperature 25 ° C, humidity 50%
Release the elongation under normal temperature and normal humidity. 5. Fifteen minutes after release, the length of the coating film was measured, and the length was designated as X. A) a charging roller satisfying a P value of 55% or less. 2. The charging roller according to claim 1, wherein said P value is 50% or less. 3. The charging roller according to claim 1, wherein said coating layer has a thickness of 20 to 600 μm. 4. The charging roller according to claim 1, wherein the coating layer contains an acrylic resin. 5. The charging roller according to claim 1, wherein one or more outer layers are formed on the coating layer. 6. The charging roller according to claim 5, wherein said outer layer has a thickness of 30 μm or less. 7. The charging roller according to claim 1, wherein the member surface has a JIS 10-point average roughness Rz of 4 μm or less. 8. The elastic layer has a density of 0.05 to 0.9 g.
The charging roller according to any one of claims 1 to 7, wherein the charging roller is formed by using a polyurethane foam having a density of / cm ³ .