JPH11249385A - Electrifying member and electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member having excellent durability that stable performance is achieved over a long term without deteriorating the performance due to the adhesion of toner. SOLUTION: This electrifying member is provided with an elastic layer 3 and a coating film layer 4 formed on the outside of the layer 3; and the layer 4 is constituted of a coating film incorporating water-based resin and having >=70% water resistant insolubility expressed by an expression; water resistant insolubility(%)=(B/A)×100 (provided that A means the weight of the coating film before it is immersed in water, and B means the weight of the coating film after it is immersed in the water whose temperature is 25 deg.C for 2 hours).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and a charging device 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 the contact charging method, for example, a resin solution in which a resin such as acrylic, urethane, nylon or the like is dissolved in an organic solvent is coated on the surface of an elastic layer such as rubber or urethane foam. It is known that a coating layer of such a resin is formed by applying a dipping method, a spraying method or the like to secure the smoothness of the surface and prevent the toner from adhering.

[0006]

However, in this contact charging method, since the charging member and the non-charged body are always in contact with each other, a conventional corona discharge method in which the charged body is charged in a non-contact manner from a wire or the like is used. In comparison, the durability of the charging member often becomes a problem. The durability of the charging member seems to be due to deterioration of the charging member itself due to abrasion or the like and to the effect of residual toner.

In this case, regarding the deterioration of the charging member itself due to wear, in order to increase the wear resistance of the charging member,
It is conceivable to simply arrange a film made of a material having excellent wear resistance on the surface of the member. However, since such a material is generally a hard material, cracks occur during operation or the charged object is shaved. And other problems.

[0008] Regarding the effect of residual toner, a small amount of toner remaining on the member to be charged adheres to the charging member due to transfer failure or cleaning failure. In severe cases, the toner is embedded and fixed on the surface of the charging member. This seems to cause poor charging. Originally, it is a fundamental measure against such a problem to improve the transfer efficiency and the cleaning efficiency so that the residual toner does not reach the charging section by the charging member. It is difficult to eliminate 100%. Therefore, in order to prevent the residual toner from adhering to the surface of the charging member, it has been proposed to coat the surface of the charging member with a fluororesin or a silicone resin. It cannot be prevented.

The present invention has been made in view of the above circumstances. Even when the present invention is used in an electrostatic latent image process in a copying machine, a printer, or the like, it is stable for a long period of time without deteriorating performance due to toner adhesion or the like. An object of the present invention is to provide a charging member having excellent durability capable of exhibiting performance, and a charging device using the charging member.

[0010]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that a charging member having a coating layer formed outside the elastic layer is a charged member. When the object to be charged is charged by applying a voltage between the member and the object to be charged, the coating layer is formed using an aqueous resin, and the following relational expression (1) is used. Water insolubility (%) = (B / A) × 100 (1) (where A represents the weight of the coating before immersion in water, and B represents the coating after immersion in water at 25 ° C. for 24 hours) (Indicated by weight), so that the water-insoluble ratio of the coating layer is adjusted to be 70% or more, so that the charging member can be stably charged for a long period of time without deteriorating the performance of the charging member due to toner adhesion or the like. It has been found that the operation can be performed, and the present invention has been completed.

That is, by using a water-based resin for the coating layer, when forming the coating layer on the elastic layer by dipping or spraying, a smooth member surface can be obtained without swelling of the elastic layer. Thereby, the adhesion of the residual toner is effectively prevented, and the durability of the coating film itself is improved by adjusting the water-insoluble ratio as described above. It is maintained and exhibits excellent durability.

Therefore, according to the present invention, by applying a voltage between the member to be charged and the member to be charged,
In a charging member for charging a member to be charged, an elastic layer and a coating layer formed directly or via another layer outside the elastic layer, wherein the coating layer contains an aqueous resin And a charging member comprising a coating film having a water insolubility rate of 70% or more, a charging member in contact with a member to be charged and charging the member to be charged, and a member to be charged and a charging member And a voltage applying means for applying a voltage between the charging device and the charging device, wherein the charging member of the present invention is used as the charging member.

Hereinafter, the present invention will be described in more detail.
As described above, the charging member of the present invention has an elastic layer and a coating layer formed on the elastic layer, and its form can be stably contacted with the member to be charged. Any form can be used as long as it can uniformly apply electric charge to the layer to be charged by applying a voltage. For example, various forms such as a roll, a plate, a block, a sphere, and a brush can be used. However, it is usually preferable to form a roll. For example, as shown in FIG. 1, the charging member 1 in which the elastic layer 3 is formed on the outer periphery of the shaft 2 and the coating layer 4 is formed on the outside of the elastic layer 3 is illustrated in the case of forming a roll. can do. In this case, the shaft 2
A metal or plastic shaft can be used, and the shaft 2 can be omitted depending on the form of the charging member, the mechanism of the charging device using the charging member, and the like.

The elastic layer 3 is not particularly limited, and may be rubber, resin, or a foam thereof (hereinafter, referred to as a rubber or resin).
"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 preferred. More preferably, a polyurethane foam having an expansion ratio of 1.5 to 50 times is used. The foam density in this case is 0.0
About 5 to 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 lauryl trimethyl alcohol
Ammonium, stearyltrimethylammonium, octane
Tadodecyl trimethyl ammonium, dodecyl trimethyl
Luammonium, hexadecyltrimethylammonium
Dimethyl ethyl ammonium perchlorate
Acid salt, chlorate, borofluoride, sulfate, etosa
C, such as sulfate, benzyl bromide and benzyl chloride
Cations such as quaternary ammonium salts
Surfactant, aliphatic sulfonate, higher alcohol
Sulphate ester, higher alcohol ethylene oxide
Addition sulfates, higher alcohol phosphates,
Higher alcohol ethylene oxide addition phosphate ester salt
And other zwitterions such as betaines
Surfactant, higher alcohol ethylene oxide, poly
Ethylene glycol fatty acid ester, polyhydric alcohol fat
Antistatic of nonionic antistatic agents such as fatty acid esters
Agent, LiCF_ThreeSO_Three, NaClO_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)_TwoEtc. C
a²⁺ , Ba²⁺ Metal salts of the second group of the periodic table, such as
Has at least one or more hydroxyl groups, carbohydrates,
Isocyanates such as xyl groups and primary or secondary amine groups
Having a group having active hydrogen that reacts with 1,4-
Butanediol, ethylene glycol, polyethylene glycol
Recall, propylene glycol, polyethylene glyco
Or complexes of polyhydric alcohols such as
Ethylene glycol monomethyl ether, ethylene glycol
Complexes with monools such as coal monoethyl ether
Ion conductive agent, Ketjen Black EC, acetylene
Conductive carbon such as black, SAF, ISAF, H
For rubber such as AF, FEF, GPF, SRF, FT, MT
Carbon (color) ink and oxidized carb
Carbon, pyrolytic carbon, natural graphite, artificial graphite
Site, antimony-doped tin oxide, titanium oxide, suboxide
Metals and metals such as lead, nickel, copper, silver, germanium
Oxide, polyaniline, polypyrrole, polyacetylene
And the like. In this case, these
The amount of the conductive agent is appropriately selected according to the type of the composition.
In general, the volume resistivity of the elastic layer 3 is 10⁰-10⁸Ω ・ c
m, preferably 10^Two-10⁶Adjust to Ω · cm
Is done.

Next, the coating layer 4 contains an aqueous resin,
And the following relational expression (1): Water-insoluble ratio (%) = (B / A) × 100 (1) (where A represents the weight of the coating film before immersion in water, and B represents the weight of water at 25 ° C.) Water insolubility expressed by 70% or more, preferably 80% or more;
More preferably, it is formed with a coating film of 90% or more.

The aqueous resin used for the coating layer 4 is not particularly limited as long as it is capable of forming a coating film satisfying the above-mentioned water-insoluble ratio, but is not particularly limited. From the viewpoints of smoothness of the obtained coating film, toner adhesion, etc., fluorine resin, polyvinyl acetal resin, vinylidene chloride resin, urethane resin, polyester resin, acrylic resin and the like are preferably used, and one or two of these are used. The above water-based resins can be used as a mixture. Here, the water-based resin may be any solvent such as a water-soluble type, an emulsion type, and a suspension type as long as the solvent is water.

As the water-based resin used for the coating layer 4, various ones can be used as described above, but it is particularly preferable that the water-based resin contains a water-based fluororesin. Specific examples of the aqueous fluororesin include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer , Polychlorotrifluoroethylene, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride and the like,
Particularly, a dispersion type aqueous fluororesin in which these fine particles are dispersed in water is preferably used, and more preferably, a dispersion type aqueous fluororesin in which polytetrafluoroethylene fine particles 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.

If necessary, a crosslinking agent can be added to the coating layer 4 to crosslink the water-based resin, whereby the water-insoluble ratio and the contact angle described below are adjusted to desired values. be able to. In this case, the cross-linking agent is appropriately selected according to the type of the resin used and the like, and may be any one as long as a desired cross-linking effect can be obtained. And phenolic cross-linking agents are used, and in particular, epoxy- and melamine-based cross-linking agents are preferably used. The amount of the crosslinking agent to be added is usually 0.1 to 100 parts by weight of the resin.
Although it is in the range of 1 to 50 parts by weight, it can be appropriately adjusted so as to obtain a desired water insolubility and a contact angle, and there is no problem even if the amount exceeds the above range.

The coating layer 4 can be added or adjusted with conductivity by adding a conductive agent, and usually has a volume resistivity of 10 ³ to 10 ¹² Ωcm, particularly 10 ⁵ to 10 ¹⁰ Ωcm.
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. -40% by weight, especially 5-20%
% By weight.

In this case, although there is no particular limitation, the carbon used as a conductive agent in the coating layer 4 is not particularly limited, but has an oxygen content of 5%.
As described above, it is preferably at least 7%, more preferably at least 9%, and the pH is preferably at least 5, particularly at least 6, and more preferably at least 7. That is, the oxygen content of ordinary carbon is about 0.1 to 3%, and there is carbon partially oxidized, but the carbon oxidized slightly increases the oxygen content. PH tends to shift toward the acidic side as the carbon becomes acidic, and when carbon is added to an aqueous resin (specifically, an aqueous fluororesin), the stability may decrease. On the contrary,
The carbon suitably used in the present invention maintains neutrality or alkalinity despite its 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 carboxyl group, a hydroxyl group, a functional group such as a ketone group is attached to the carbon surface,
In addition, those obtained by substituting a part of hydrogen contained in these functional groups with an alkali metal such as sodium are preferably used.

Although not particularly limited, the coating layer 4 has a contact angle with water of 50 degrees or more, especially 7
0 degree or more, more preferably adjusted to be 80 degrees or more, in this case, the contact angle adjustment by selecting the type of aqueous resin, or by adjusting the amount of the crosslinking agent added,
Can be done.

Here, the coating layer 4 only needs to contain the above-mentioned aqueous resin and have the above-mentioned resistance to water insolubility.
If necessary, a resin other than the aqueous resin may be contained as long as it satisfies the above-mentioned resistance to water insolubility and does not deviate from the object of the present invention. In addition, the coating layer 4 may be a plurality of layers as necessary.

Further, a thickener, a thixotropic agent,
An appropriate additive such as a structural viscosity imparting agent can be added in an appropriate amount as needed.

The coating layer 4 is the outermost layer of the charging member of the present invention, that is, the layer forming the surface of the member.
The surface roughness of the coating layer is the surface roughness of the member. In this case, the surface roughness of the coating layer, that is, the surface roughness of the member,
Although not particularly limited, the JIS 10-point average roughness Rz is preferably 4 μm or less, particularly 3 μm or less, and more preferably 2 μm or less, and the coating layer is formed using the aqueous resin so as to satisfy the water-insoluble resistance. By forming 4,
Such a surface roughness can be easily achieved.

Although not particularly limited, the thickness of the coating layer 4 is 30 μm or less, particularly 1 to 15 μm.
The thickness is preferably 30 μm or less.
If it exceeds, the hardness of the coating film layer 4 may be impaired due to too high hardness.

The method for forming the coating film layer 4 is not particularly limited, but a coating material containing the above-mentioned components constituting the coating film layer 4 is prepared, and the coating material is applied by dipping or spraying. The method is preferably used.

As described above, the charging member of the present invention is formed by forming the coating layer 4 on the outer periphery of the elastic layer 3 as the outermost layer. Another coating layer may be formed as an intermediate layer between them. For example, when the elastic layer 3 is formed using a polyurethane foam, an acrylic resin, a polyester resin, a polyurethane resin, a nylon resin, or the like is used for the purpose of reducing noise when a voltage is applied and improving the surface smoothness of the elastic layer 3. A coating film obtained by adding a conductive agent to a base resin such as a resin, an epoxy resin, a urethane-modified acrylic resin, a butyral resin, a phenol resin, a vinylidene chloride copolymer, and a polyvinyl acetal resin may be provided as an intermediate layer. Although not particularly limited, it is preferable to use an aqueous resin as a resin for forming a coating film provided as the intermediate layer.

The charging member of the present invention uses an aqueous resin for the coating layer 4 so that when the coating layer is formed on the elastic layer 3 or the intermediate layer by dipping or spraying, the elastic layer 3 And a smooth surface of the member is obtained without swelling of the intermediate layer, whereby the adhesion of the residual toner is effectively prevented, and the water-insoluble ratio of the coating layer 4 is adjusted as described above. The durability of the coating film itself is improved, the effect of preventing the adhesion of the toner is favorably maintained for a long time, and excellent durability is exhibited. When only the organic solvent-based resin is used as the coating film layer 4, good surface smoothness cannot be obtained first, and the residual toner adheres from the beginning of use. By simply using an aqueous resin without control, the surface smoothness can be obtained, so that adhesion of the residual toner is unlikely to occur in the initial stage of use, but the durability of the coating film itself is poor and the coating film deteriorates due to long-term use It is difficult to maintain good performance over a long period of time.

The charging member of the present invention is disposed in contact with a member to be charged, such as a photosensitive drum, and by applying a voltage between the member to be charged and the charging member of the present invention, the member to be charged is applied. In this case, the voltage applied between the charging member and the member to be charged may be a DC voltage or an AC voltage, and is not particularly limited.
It is preferable to perform charging by applying a voltage in which an AC voltage is superimposed on a DC voltage, so that the member to be charged can be charged more uniformly. Although not particularly limited, the contact pressure between the charging member of the present invention and the member to be charged is 50 to 2000 g, particularly 100 to 1000 g.
It is preferable to obtain favorable charging.

As for the charging device using the charging member of the present invention, for example, as shown in FIG.
To a member to be charged 5 such as a photosensitive drum at a predetermined pressure,
A charging device configured to apply a voltage between the voltage applying means 6 and the charged object 5 can be exemplified, but is not limited thereto.
The form and the voltage application method by the voltage application means 6 may be appropriately changed.

[0032]

According to the charging member of the present invention, even when the charging member is used in an electrostatic latent image process in a copying machine, a printer, or the like, the charging performance is stable over a long period of time without causing a decrease in performance due to toner adhesion or the like. Can be demonstrated. Therefore, according to the charging device using the charging member of the present invention, without causing a decrease in charging performance due to long-term use,
Good charging operation can be stably performed over a long period of time.

[0033]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

EXAMPLE An elastic layer A having a thickness of 3000 μm was formed on the outer periphery of a metallic shaft, a coating layer A having a thickness of 300 μm was formed on the elastic layer A, and a coating layer A having a thickness of 300 μm was formed. The coating layer B was formed thereon to prepare a charging roller. The elastic layer A, the coating layer A and the coating layer B are as follows. The surface roughness of the obtained charging roller is JIS 10 point average roughness R
The z was 0.7 μm, and the contact angle with water was 80.5 degrees.

Elastic Layer A A polyurethane foam having a density of 0.5 g / cm ³ prepared by adding carbon to a polyester polyol or isocyanate. Coating layer A was formed by applying a paint obtained by adding carbon to an aqueous acrylic resin, and the volume resistivity was adjusted to 5 × 10 ⁷ Ωcm. Coating layer B Water-dispersed fluororesin, vinylidene chloride-based copolymer latex, and resin blended with polyvinyl acetal resin are molded by applying a paint containing carbon and an epoxy-based crosslinking agent, and the volume resistivity is 5.1 × 10
^It was adjusted to ⁷ Ωcm. As the carbon, one having an oxygen content of 10% and a pH of 7.33 was used, and 5 phr of an epoxy-based crosslinking agent was added to the resin. The water insolubility of the coating layer B itself was measured and found to be 81.5%.

When the obtained charging roller was mounted on a printer and an image was formed, a good image was obtained. Further, even when 6000 images were continuously formed, no deterioration of the image was observed.

Comparative Example 1 A charging roller similar to that of the example was prepared except that the coating layer B was changed to the following coating layer C. The surface roughness of the obtained charging roller was 0.9 μm in terms of JIS 10-point average roughness Rz, and the contact angle with water was 4 μm.
0.9 degrees.

[0038] except that no addition of the coating layer C epoxy crosslinking agent is a coating film obtained in the same manner as in the coating layer B. The water-insoluble ratio of the coating film layer C itself was measured and found to be 44.3%.

The obtained charging roller was subjected to a continuous image output test for 6000 sheets in the same manner as in the example. As a result, a good image was obtained in the initial stage, but a point-like defect was generated in the image from around 2500 sheets. When the roller was observed, it was found that the toner had bitten and accumulated on the surface.

Comparative Example 2 A charging roller was prepared in the same manner as in the Example, except that the coating layer A was replaced with the following coating layer D and the coating layer B was replaced with the following coating layer E. The surface roughness of the obtained charging roller was 9.5 μm in terms of JIS 10-point average roughness Rz.
m, the contact angle with water was 75.6 degrees.

Coating layer D The coating layer was formed by applying a coating material in which ketjen black carbon was added to urethane dissolved in toluene, and the volume resistivity was adjusted to 7 × 10 ⁷ Ωcm. Coating layer E is formed by applying a coating obtained by adding Ketjen black carbon to nylon dissolved in methanol,
The volume resistivity was adjusted to 2 × 10 ⁷ Ωcm. The water insolubility of the coating layer E itself was measured and found to be 96.7%.

When an image forming test was performed on the obtained charging roller in the same manner as in the example, dot-like defects occurred in the image from the beginning. When the roller was observed, toner adhered to the concaves and convexes on the surface. Was.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the charging member of the present invention.

FIG. 2 is a schematic view showing an example of the charging device of the present invention.

[Explanation of symbols]

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

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/00 C09D 133/00 167/00 167/00 175/04 175/04 201/00 201/00

Claims (8)

[Claims] 1. A charging member for charging a member to be charged by applying a voltage between the member and the member to be charged by bringing the member into contact with the member to be charged. Or a coating layer formed through another layer, wherein the coating layer contains an aqueous resin, and the following relational expression (1): Water-insoluble ratio (%) = (B / A) × 100 (1) (where A represents the weight of the coating film before immersion in water, and B represents the weight of the coating film after immersion in water at 25 ° C. for 24 hours). % Of the coating film. 2. The charging member according to claim 1, wherein a contact angle of the member surface with water is 50 degrees or more. 3. The charging member according to claim 1, wherein the JIS 10-point average roughness Rz of the member surface is 4 μm or less. 4. The method according to claim 1, wherein the coating layer is a fluororesin, a polyvinyl acetal resin, a vinylidene chloride resin, a urethane resin,
The charging member according to any one of claims 1 to 3, wherein the charging member contains one or more aqueous resins selected from a polyester resin and an acrylic resin. 5. The charging member according to claim 1, wherein the coating film layer is a coating film containing carbon having an oxygen content of 5% or more and a pH of 5 or more. 6. The coating film according to claim 1, wherein the coating layer contains one or more crosslinking agents selected from isocyanate-based, melamine-based, epoxy-based, and phenol-based. Charging member. 7. The elastic layer has a density of 0.05 to 0.9 g.
The charging member according to any one of claims 1 to 6, wherein the charging member is formed using a polyurethane foam having a density of / cm ³ . 8. A charging device, comprising: a charging member that contacts a member to be charged and charges the member to be charged; and a voltage applying unit that applies a voltage between the member to be charged and the charging member. A charging device using the charging member according to claim 1 as the charging member.