JP3829877B2 - Charging member - Google Patents

Description

  The present invention relates to a charging member used for a charging roll, a charging blade, or the like in an electrophotographic apparatus such as a copying machine, a printer, or a facsimile.

  An electrophotographic copying machine forms a document image as an electrostatic latent image on the surface of a photosensitive drum, forms a toner image by attaching toner to the image, and transfers the toner image onto a copy sheet for copying. is there. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and an original image is projected onto the charged portion through the optical system, and the portion where the light passes through is projected. An electrostatic latent image is formed by eliminating the charge. An example of copying by such a mechanism will be described with reference to FIG. That is, the outer peripheral surface of the photosensitive drum 1 is charged by applying a voltage to the charging roller 2 by rotating the charging roller 2 around the outer peripheral surface of the photosensitive drum 1 rotating in the direction of the arrow about the shaft 1a. Is done. Reference numeral 3 denotes an exposure mechanism, through which slit exposure 8 of the original optical image reaches the surface of the photosensitive drum 1, and an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 1. Reference numeral 4 denotes a developing device which forms a toner image by attaching toner to the electrostatic latent image. A paper feed mechanism roll 6 supplies the copy paper 11 to the surface of the photosensitive drum 1 and transfers the toner image onto the copy paper 11 via the transfer roll 5. Reference numeral 7 denotes a fixing roll for passing and fixing the copy paper 11 on which the toner image is formed. In this way, a copy (copy) is obtained. The surface of the photosensitive drum 1 is subjected to transfer residual image and residual toner removed by a cleaner 9 and further irradiated with an entire surface by an eraser lamp 10 to be zero potential to prepare for the next charging. In FIG. 4, reference numeral 12 denotes a power source that applies a voltage of about 1 to 3 kV to the charging roll 2.

Conventionally, as a material for forming the charging member such as the charging roll 2, polymer components such as epichlorohydrin-ethylene oxide copolymer rubber, acrylonitrile butadiene rubber, and urethane rubber are represented by the following general formula (A). A conductive material to which an ionic conductive agent that is a quaternary ammonium salt is generally added in an amount of about 0.001 to 10 parts by weight (hereinafter abbreviated as “part”) is used. In such a conductive material, by adding the quaternary ammonium salt, the volume resistivity in the range of 10 ⁵ to 10 ⁹ Ω · cm can be stably and uniformly exhibited. Thus, a material having a small change in volume resistivity and surface resistivity due to environmental temperature change can be obtained.

  However, with the conventional ion conductive agent, there is a limit to lowering the resistance even if the amount added is increased. For example, in the case of adding a large amount of ion conductive agent with reduced resistance, There is a problem that the ionic conductive agent bleeds out. In addition, there is a large increase in electrical resistance when energized, and charging problems occur over time, resulting in a problem of image defects.

  Furthermore, the ionic conductive agent has poor conductivity imparting characteristics, and the ionic conductive material has poor electrical durability characteristics, affecting the product performance as it is.

  The present invention has been made in view of such circumstances, and it is possible to reduce resistance with a low addition amount, to suppress an increase in electrical resistance during energization, and to prevent image defects. The purpose is to provide a charging member.

  In order to achieve the above object, the charging member of the present invention contains a quaternary ammonium salt represented by the following general formula (1) as an ionic conductive agent in epichlorohydrin-ethylene oxide copolymer rubber. It takes the composition of using the material to do.

  That is, the present inventors have conducted intensive research focusing on quaternary ammonium salts, which are ionic conductive agents, in order to obtain a charging member forming material that can adjust the electric resistance to a lower range than before with a low addition amount. Repeated. And, focusing on the four substituents bonded to N on the positive ion side of the quaternary ammonium salt, we recalled that good results could be obtained when all of the four substituents are alkyl groups. It was found that good results were not always obtained for all alkyl groups. Therefore, as a result of further research and development on the preferred alkyl group, when any one of the four alkyl groups bonded to N is an octyl group and the remaining three are methyl groups, The present inventors have found that the charge amount of a certain N is increased and have reached the present invention.

  As described above, the charging member of the present invention includes a material containing epichlorohydrin-ethylene oxide copolymer rubber containing the specific quaternary ammonium salt represented by the general formula (1) as an ionic conductive agent. It is formed by using. And since any one of the alkyl groups bonded to N on the positive ion side of the specific quaternary ammonium salt is an octyl group and the remaining three are methyl groups, N is the center of the positive ion. The amount of charge increases, and the electric resistance can be adjusted to a lower range than in the prior art. In addition, since the resistance is reduced with a low addition amount, problems such as bleed out do not occur.

  And if the compounding quantity of the quaternary ammonium salt represented by the said General formula (1) is set to a specific range, it will become easy to reduce to a desired electrical resistance, and generation | occurrence | production of bloom out will be suppressed much more effectively. It becomes possible.

  The charging member of the present invention can be obtained by using a specific polar polymer and a material containing a quaternary ammonium salt represented by the following general formula (1) as an ionic conductive agent.

In the present invention, in the general formula (1), any one of R ^{1 to} R ⁴ is an octyl group.

Moreover, in the said General formula (1), the remaining alkyl groups (alkyl groups other than an octyl group) represented by R < ¹ > -R < ⁴ > become a methyl group.

In the general formula (1), the n-valent anion represented by X ⁿ⁻ is not particularly limited, and examples thereof include halogen ions such as F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ , ClO ₄ ⁻ , and the like. BF ₄ ⁻ , SO ₄ ²⁻ , HSO ₄ ⁻ , CH ₃ SO ₄ ⁻ , C ₂ H ₅ SO ₄ ⁻ , CH ₃ SO ₃ ⁻ , C ₂ H ₅ SO ₃ ⁻ , COOH ^{− and the} like. Among these, Br ⁻ , I ⁻ , ClO ₄ ⁻ , HSO ₄ ⁻ , and C ₂ H ₅ SO ₄ ⁻ are preferable because the resistance can be lowered.

  In the said General formula (1), the integer of 1-4 is preferable among the integers of 1-6 represented by n, Most preferably, it is an integer of 1-2.

  And, like the quaternary ammonium salt represented by the general formula (1), when one of the four alkyl groups bonded to N is an octyl group and the remaining three are methyl groups, Charge amount increases.

  As the specific polar polymer used for the material for forming the charging member of the present invention, epichlorohydrin-ethylene oxide copolymer rubber (ECO) is used because the electric resistance of the polar polymer itself is low.

  The blending amount of the specific quaternary ammonium salt with respect to the specific polar polymer is preferably set in the range of 0.05 to 5 parts of the specific quaternary ammonium salt with respect to 100 parts of the polar polymer, Particularly preferred is 0.5 to 3 parts. That is, if the blending amount of the specific quaternary ammonium salt is less than 0.05 parts, it is difficult to lower the electric resistance to a desired value. Conversely, if it exceeds 5 parts, the compatibility with the polar polymer is poor. This is because it tends to worsen the bloom.

  In addition to the specific polar polymer and the specific quaternary ammonium salt, the charging member forming material of the present invention includes a crosslinking agent, a crosslinking accelerator, a processing aid, an antiaging agent, a softening agent, and a reinforcing agent. Etc. may be added as necessary.

In the charging member forming material of the present invention, an electronic conductive material may be used in combination with the specific quaternary ammonium salt. Examples of the electronic conductive material include metal powder such as aluminum powder and stainless steel powder; conductive metal oxide such as c-ZnO, c-TiO ₂ , c-Fe ₃ O ₄ , and c-SnO ₂ ; graphite, carbon Examples thereof include conductive powders such as black. These may be used alone or in combination of two or more. In addition, the above “c−” means having conductivity.

  A charging roll will be described as an example of a charging member using the above forming material.

  As an example of the charging roll, there may be mentioned one constituted by a shaft body, a conductive elastic layer formed on the outer periphery thereof, and a resistance adjusting layer formed on the outer periphery thereof.

  The shaft body is not particularly limited, and for example, a metal core made of a metal cylinder or a metal cylinder body hollowed out inside is used.

The conductive elastic body layer formed on the outer periphery of the shaft body along the circumference is formed of an elastic body or a foamed body. Examples of the material for forming the conductive elastic layer include synthetic rubbers such as polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), and styrene-butadiene rubber, which are used alone or in combination. Such a conductive elastic layer usually has a conductivity of about 10 ¹ to 10 ⁵ Ω · cm. The thickness is usually set to about 1 to 10 mm, preferably about 2 to 4 mm.

  In particular, when the hardness (JIS A) of the conductive elastic layer is set to 25 (Hs) or less, in the case of using it as a charging roll in an apparatus as shown in FIG. Occurrence of image quality defects (horizontal unevenness) and fogging due to slight vibration between rolls is prevented. Thus, in order to set the hardness of the conductive elastic layer itself to a desired value, a softening agent such as oil is added. As the softening agent, naphthenic oil or the like is preferably used. Furthermore, carbon black such as ketjen black is used as a conductive agent as necessary.

  The resistance adjusting layer formed on the outer periphery of the conductive elastic layer is formed by adding the specific quaternary material to the above-described forming material of the charging member of the present invention, that is, epichlorohydrin-ethylene oxide copolymer rubber. It is formed using a material containing an ammonium salt. And the thickness is normally set to 10-1000 micrometers, and the suitable range is 80-700 micrometers.

  And in such a charging roll, it is especially preferable to take the structure by which the protective layer was formed in the outer periphery of the said resistance adjustment layer. Further, a softener migration preventing layer is formed between the conductive elastic layer and the resistance adjusting layer as necessary.

As the protective layer formed as the outermost layer on the outer periphery of the resistance adjusting layer, conventionally known ones such as N-methoxymethylated nylon, fluorine resin, urethane resin and acrylic resin can be used as they are. When a conductive agent such as carbon black is mixed and dispersed in this protective layer, the conductivity at low temperature and low humidity becomes good, and good performance is exhibited even in a low temperature and low humidity environment. Such a protective layer is usually preferably set to a thickness of 1 to 25 μm, and a particularly suitable range is 3 to 20 μm. Moreover, the electrical resistance value of this protective layer is set to 10 ⁷ to 10 ¹¹ Ω · cm. The conductive agent is not limited to carbon black, and a conventionally known conductive agent can be used in place of the carbon black.

The softening agent migration prevention layer formed as necessary between the conductive elastic layer and the resistance adjusting layer is used to prevent exudation of a softening agent such as oil contained in the conductive elastic layer. Formed for prevention. A conventionally known material such as N-methoxymethylated nylon can be used for this softener migration preventing layer. The thickness of the softener migration preventing layer is generally set to 1 to 20 μm, preferably 3 to 10 μm. The electric resistance of the softener migration preventing layer is set to 10 ⁵ Ω · cm or less. Conventionally known conductive agents such as carbon black are used as the conductive agent.

  Such a charging roll can be manufactured as follows, for example. An adhesive is applied to the outer peripheral surface of the core metal, and after forming the conductive elastic body layer using the rubber composition described above using mold vulcanization, the surface of the conductive elastic body layer is necessary. Depending on the method, the softener transition prevention layer-resistance adjustment layer-protective layer is applied and dried by spraying, dipping, etc., and heated as necessary to form in order, and the adhesive on the outer peripheral surface of the core metal Prepare a non-vulcanized / unfoamed conductive elastic layer tube-shaped molded product and a resistance-adjusted layer tube-shaped molded product, and place the above three types in the mold from the center in the mold. Gold, conductive elastic layer, resistance adjustment layer are arranged in this order, vulcanized and foamed to form a roll having the structure of core metal-conductive elastic layer-resistance adjustment layer, and the protective layer is formed by the above method. Manufactured by a forming method or the like.

  The resistance adjustment layer is formed by adding the specific quaternary ammonium salt as an ionic conductive agent to the epichlorohydrin-ethylene oxide copolymer rubber (ECO), which is a polar polymer, and the others as necessary. Add the additives. Next, by kneading them using a kneader such as a kneader or Banbury mixer, there is a method of forming an unvulcanized rubber composition, dissolving and coating in a solvent, and a method of using a molding machine such as an extruder as it is, For example, in the coating method, the unvulcanized rubber composition is dissolved in an appropriate solvent (for example, methyl ethyl ketone, methyl isobutyl ketone, etc.), coated on the outer peripheral surface of the conductive elastic layer, dried, and then heated and vulcanized. Can be formed. In the coating, it is preferable to use a dip method. More specifically, the solution containing the unvulcanized rubber composition is stored as a dip solution in a tank 24 as shown in FIG. Next, a rubber film made of the unvulcanized rubber composition is formed on the outer peripheral surface of the conductive elastic layer by vertically standing the roll 25 on which the conductive elastic layer is formed and repeatedly immersing it in the solution. To form. At this time, it is preferable to set the conditions such as the dip solution viscosity, the raising / lowering speed, the number of times of raising / lowering, and the drying time so that the liquid film of the solution is in the range of 10 to 200 μm. For such a liquid film formed, drying is performed at a temperature of 25 to 80 ° C. for 0.5 to 4 hours to remove the solvent, followed by heating at a temperature of 150 to 200 ° C. for 10 minutes to 2 hours. The rubber film is vulcanized to form a resistance adjusting layer. Next, after the resistance adjustment layer is formed as described above, a resin liquid composed of N-methoxymethylated nylon, and in some cases a resin liquid mixed with a conductive agent or the like is coated by spraying, dipping, or the like. It is dried and, if necessary, is heat-treated to crosslink and form a protective layer. In this way, a charging roll having a layer structure as shown in FIGS. 2 and 3 is obtained. In FIGS. 2 and 3, 26 is a metal core, 27 is a conductive elastic layer, 28 is a softener migration preventing layer, 29 is a resistance adjusting layer, and 30 is a protective layer. 2 and 3, the conductive elastic layer 27 can be formed of a foam. In this case, the softener migration preventing layer 28 may not be provided.

  Specific examples of the charging member of the present invention include a charging blade in addition to the charging roll.

  Next, examples will be described together with comparative examples.

[Examples 1 to 3, Comparative Examples 1 to 5]

[Preparation of conductive elastic layer forming material]
As a conductive elastic layer forming material, a rubber composition was prepared using the following components.

Polynorbornene rubber 100 parts Ketjen black 50 parts Naphthenic oil 400 parts

(Preparation of softener migration prevention layer forming material)
A carbon black-dispersed resin liquid was prepared using the following components as the softener migration preventing layer forming material.

N-methoxymethylated nylon 100 parts Carbon black 15 parts

(Preparation of resistance adjustment layer forming material)
As the resistance adjustment layer forming material, each component shown in Table 1 below, that is, ECO (equimolar copolymer of epichlorohydrin and ethylene oxide) as a polar polymer, lead red as an acid acceptor, and thiourea-based cross-linking Accelerating agent (manufactured by Sanshin Chemical Co., Ltd., Sunseller 22C) and quaternary ammonium salts represented by the following formulas (2) to (4) as ionic conductive agents are blended in proportions shown in the same table. Then, an unvulcanized rubber composition was prepared by kneading using a Banbury mixer.

(Preparation of protective layer forming material)
As the protective layer forming material, a resin liquid was prepared using each component shown below.

N-methoxymethylated nylon 100 parts Carbon black 8 parts

  Next, after an adhesive is applied to the outer periphery of a metal core made of a metal shaft having a diameter of 8 mm, the rubber composition of the conductive elastic layer forming material is used on the outer periphery, and mold vulcanization is used as a whole. The conductive elastic body layer was formed so that the outer diameter of each was 15 mm. Next, the carbon black-dispersed resin liquid for the softener migration preventing layer forming material was spray coated on the outer periphery of the conductive elastic layer, and then dried to form a softener migration preventing layer having a thickness of 6 to 10 μm. On the other hand, after roll-kneading the rubber composition for forming the resistance adjusting layer, it was dissolved in a solvent of methyl ethyl ketone / methyl isobutyl ketone = 3/1 (weight ratio), and the viscosity was adjusted to 500 centipoise to prepare a dip solution. . In this liquid, the cored bar on which the softening agent migration preventing layer was formed as described above was immersed and coated, and then pulled up and dried, followed by heat treatment for crosslinking. Subsequently, a resin solution for forming a protective layer was spray-coated on the surface and then dried to form a protective layer. As a result, a target charging roll was produced.

  The electric resistance of each charging roll thus obtained was measured by a metal roll electrode method as shown in FIG. That is, while the both ends of the charging roll 31 are pressed against the metal roll 32 having a diameter of 30 mm with a load of 4.9 N, the metal roll 32 is rotated in the direction of the arrow at a rotation speed of 60 rpm, and the charging roll 31 is moved to the metal roll 32. It was rotated in the direction of the arrow by the accompanying rotation. And the voltage of 100V was applied to the end of the said charging roll 31, the electric current value was measured, and the electrical resistance value (initial resistance) was calculated | required. Next, an electric resistance value (endurance resistance) was obtained by measuring a current value after 10 hours while energizing in the state of FIG. And the raise degree of the electrical resistance was computed from these measurements. These results are shown in Tables 2 to 3 below.

  On the other hand, the obtained charging roll was allowed to stand for 1 week under high-temperature and high-humidity conditions (40 ° C. × 95% RH) and then left at room temperature (25 ° C. × 50% RH) for one day, and the surface of the charging roll was visually observed. Observed. In the evaluation, a case where no bloom / bleed was confirmed was evaluated as “◯”, and a case where bloom / bleed was confirmed and the image was affected was evaluated as “×”. The results are shown in Tables 2 to 3 below.

  From the results of Tables 2 to 3, the example products were excellent in that not only the initial resistance value but also the durability resistance value was low and the resistance increase was small. In addition, no bloom or bleed is confirmed, and it can be seen that it is excellent as a charging roll.

It is explanatory drawing which shows an example of the manufacturing method of a charging roll. 1 is a cross-sectional perspective view illustrating a configuration of a charging roll that is an example of a charging member of the present invention. It is sectional drawing which shows the structure of the charging roll which is an example of the charging member of this invention. It is explanatory drawing which shows the structure of an electrophotographic copying machine typically. It is explanatory drawing which shows the measuring method of the electrical resistance of a charging roll.

Explanation of symbols

26 Core Bar 27 Conductive Elastic Layer 28 Softener Migration Prevention Layer 29 Resistance Adjustment Layer 30 Protective Layer

Claims (3)

A charging member formed by using a material containing an epichlorohydrin-ethylene oxide copolymer rubber containing a quaternary ammonium salt represented by the following general formula (1) as an ionic conductive agent.

  The charging member according to claim 1, comprising an electronic conductive material together with the ionic conductive agent. The charging member according to claim 1 or 2, wherein a blending amount of the quaternary ammonium salt is set in a range of 0.05 to 5 parts by weight with respect to 100 parts by weight of the polar polymer.

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