JP2011221130A - Conductive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material with which excellent anti-bleeding effect and excellent reduction of the hardness can be achieved at a high level.SOLUTION: A conductive material includes a conductive substrate, a first elastic layer which includes rubber and has conductivity and a second elastic layer formed on the surface of the first elastic layer. The second elastic layer includes at least one compound selected from compounds with the predetermined structures expressed by the general formulas (1)-(3) described in the specification.

Description

The present invention relates to a conductive member used for an electrophotographic apparatus or the like.

  In order to secure a contact nip with the photosensitive member, the charging member for charging the photosensitive member by contacting the photosensitive member in the electrophotographic apparatus generally has a configuration having a conductive elastic layer containing rubber. It has been adopted. The charging member having such a configuration has conventionally been known as a so-called bleed, in which a low molecular component contained in an elastic layer oozes out on the surface of the charging member. In response to such a problem, Patent Document 1 discloses that a conductive composition for OA equipment includes a rubber composition containing a gelling agent that gels a plasticizer of rubber as a constituent material of the conductive roll for OA equipment. It has been proposed that both low hardness and bleed resistance can be achieved. And as a specific example of the said gelling agent, patent document 1 has mentioned the amino acid type gelling agent, the hydroxy stearic acid type gelling agent, and the rosin type gelling agent.

JP 2008-249860 A

  When the present inventors examined the conductive roll for OA equipment which concerns on patent document 1, it acquired recognition that the further reduction in hardness was calculated | required. Therefore, an object of the present invention is to provide a conductive member that can achieve excellent bleed resistance and low hardness at a high level.

The conductive member according to the present invention has a conductive base, a conductive first elastic layer containing rubber, and a second elastic layer formed on the surface of the first elastic layer, and the second elastic layer. The layer is characterized by containing at least one compound selected from the group consisting of compounds represented by the following formulas (1) to (3).

In formula (1), n represents an integer of 1 or more and 2 or less, and R ₁ , R ₂ and R ₃ each independently represents an alkyl group having 1 to 11 carbon atoms or a phenyl group. In formula (2), m represents an integer of 0 or more and 1 or less, and R ₄ and R ₅ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In formula (3), x and y each independently represent an integer of 0 or more, and the total of x and y is 12 or more and 20 or less.

  According to the present invention, it is possible to obtain a conductive member that achieves excellent bleeding resistance and low hardness at a high level.

(A) And (b) is typical sectional drawing which shows the example of the electroconductive member of this invention. It is a typical sectional view showing an example of an electrophotographic apparatus. (A) And (b) is a schematic diagram for demonstrating the resistance measuring method of an electroconductive member.

  The conductive roller as one aspect of the conductive member of the present invention is formed on the surface of the conductive base 1, the first elastic layer 2 containing rubber, and the first elastic layer 2, as shown in FIG. And a second elastic layer 3. And the 2nd elastic layer 3 contains the 1 or 2 or more compound chosen from the group which consists of a compound shown by following formula (1)-(3).

In the structural formula (1), n represents an integer of ₁ to _2, and R ₁ , R _2, and R ₃ each independently represents an alkyl group having 1 to 11 carbon atoms or a phenyl group. In Structural Formula (2), m represents an integer of 0 or more and 1 or less, and R ₄ and R ₅ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In Structural Formula (3), x and y each independently represent an integer of 0 or more, and the total of x and y is 12 or more and 20 or less.
According to this configuration, the low molecular component that has oozed out of the first elastic layer is gelled by the compound represented by the above formula (1), (2), or (3) in the second elastic layer, and the conductive member Bleed to the surface of the is suppressed. As described above, the conductive member of the present invention supports the first elastic layer with the function for achieving the low hardness of the conductive member, and the second elastic layer with the function for improving the bleed resistance. By doing so, low hardness and bleed resistance can be achieved at a high level.

<Conductive substrate>
As a material constituting the conductive substrate, a known material that is rigid and exhibits conductivity can be used. Specific examples include metals such as iron, aluminum, titanium, copper and nickel.

<< first elastic layer >>
The first elastic layer includes a rubber component.

<< Rubber component >>
Specific examples of the rubber component include the following. ECO (epichlorohydrin rubber); EPM (ethylene propylene rubber); EPDM (ethylene propylene diene rubber); norbornene rubber; NBR (acrylonitrile butadiene rubber); chloroprene rubber; natural rubber; isoprene rubber;
Butadiene rubber; styrene-butadiene rubber; urethane rubber; silicone rubber; hydrogenated acrylonitrile rubber; epichlorohydrin rubber; butylcomb; ethylene oxide / propylene oxide / allyl glycidyl ether copolymer rubber.

<< Conductive agent >>
In order to impart conductivity to the elastic layer, the elastic body can contain a conductive agent. Examples of the conductive agent include an ionic conductive agent and an electronic conductive conductive agent. Further, they can be used alone or in combination with several kinds of ionic conductive agents and several kinds of electronic conductive agents.

(1) Ionic conductive agent Examples of the ionic conductive agent include perchlorates such as LiClO ₄ and NaClO ₄ and quaternary ammonium salts. These can be used alone or in combination of two or more.

(2) Electroconductive agent Specific examples of the electroconductive conductive material include the following (A) to (C).
(A) Metallic powders and fibers such as aluminum, palladium, iron, copper, and silver.
(I) Graphite.
(C) Metal powder.
(D) Metal oxides such as titanium oxide, tin oxide, and zinc oxide.
(E) Metal compound powders such as copper sulfide and zinc sulfide.
(F) The surface of the insulating particles is tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, titanium, chromium, tungsten, iron, cobalt, nickel, palladium, rhodium, osmium, iridium, platinum, Etc. are adhered by electrolytic treatment, spray coating, and mixed shaking.
(G) Carbon powders such as acetylene black, ketjen black, PAN (polyacrylonitrile) -based carbon, and pitch-based carbon.
(K) A combination of two or more selected from the groups (A) to (K).

<< Amount of conductive agent >>
In the present invention, the blending amount of the conductive agent in the first elastic layer is such that the volume resistivity of the first elastic layer is the middle resistance region (volume resistivity is 1 × 10 ⁴ Ω · cm in the following three environments). The amount is preferably 1 × 10 ⁸ Ω · cm or less.
Low temperature and low humidity (L / L) environment (temperature 15 ° C., relative humidity 10%).
Normal temperature and humidity (N / N) environment (temperature 23 ° C., relative humidity 55%).
High temperature and high humidity (H / H) environment (temperature 30 ° C., relative humidity 80%).

<< Method for measuring volume resistivity of elastic layer >>
The volume resistivity of the first and second elastic layers can be determined by the following methods, respectively. After the elastic layer is molded into a sheet having a thickness of 1 mm, platinum is vapor-deposited on both sides to produce an electrode and a guard electrode. Then, using a microammeter (trade name: ADVANTEST R8340A ULTRA HIGH RESISTANCE METER, manufactured by Advantest Co., Ltd.), a voltage of 200 V is applied between both electrodes, and the current after 30 seconds is measured. The volume resistivity of the elastic layer is calculated from this measured value, the layer thickness, and the electrode area.

<< Plasticizer >>
In order to reduce the hardness of the first elastic layer, the first elastic layer can contain a plasticizer. Specific examples of the plasticizer are listed below. These can be used alone or in combination of two or more.
-Paraffinic, naphthenic and aromatic process oils as petroleum softeners.
-As a plant softener, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, wax, rosin, pine oil, tall oil, etc.
Adipate plasticizers such as dioctyl adipate (DOA), diisodecyl adipate (DIDA), dibutyl glycol adipate, dibutylbitol adipate and the like.
Sebacate plasticizers such as dioctyl sebacate (DOS) and dibutyl sebacate (DBP).
Phosphate plasticizers such as tricresyl phosphate (TCP) cresyl phenyl phosphate (CDP), tributyl phosphate (TBP), trioctyl phosphate (TOP), and tributoxyethyl phosphate (TBXP).
・ Polyether and polyester plasticizers.

  The addition amount of these plasticizers may be set to 5 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the polymer elastic body (rubber component) from the viewpoint of flexibility of the conductive elastic body. It is preferably 10 parts by mass or more and 300 parts by mass or less.

<< Other additives >>
In addition, necessary additives such as a filler, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a scorch preventing agent, a dispersing agent and a release agent may be added to the first elastic layer.

<< Method for Forming First Elastic Layer >>
As a molding method of the first elastic layer, a rubber component as a raw material of the first elastic layer, a conductive agent and, if necessary, a plasticizer and an additive are mixed, and then, extrusion molding, injection molding, compression molding and the like are performed. The method of shape | molding by a well-known method is mentioned.

<Second elastic layer>
The second elastic layer formed on the surface of the first elastic layer can contain the above-described rubber component in the same manner as the first elastic layer, and the rubber components of the first and second elastic layers are the same. May be used, or different ones may be used. The second elastic layer can contain at least one compound selected from the group consisting of the compounds represented by the formulas (1) to (3) in addition to the rubber component similar to the first elastic layer. These compounds adsorb the low molecular components of the rubber in the first elastic layer and the plasticizer added as necessary, and further the low molecular components of the rubber in the second elastic layer, to the surface of the conductive member. The bleeding of the low molecular component and the plasticizer can be effectively suppressed.

<< Total Addition Amount of Compounds Represented by Formula (1), Formula (2), and Formula (3) >>
The total content of each compound represented by the above formulas (1) to (3) in the second elastic layer is the content of low molecular components and plasticizers in the first elastic layer and the second elastic layer, What is necessary is just to set suitably in consideration of a necessary bleeding suppression effect.

<< Method for Forming Second Elastic Layer >>
As a method for forming the second elastic layer, a rubber component that is a raw material of the second elastic layer, at least one of the compounds represented by formulas (1) to (3), and a conductive agent, if necessary The method of mixing with an agent etc. and shape | molding by well-known methods, such as extrusion molding, is mentioned. Further, the second elastic layer may be formed by molding on the first elastic layer, or a second elastic layer previously formed may be coated on the first elastic layer. Furthermore, the first elastic layer and the second elastic layer may be molded simultaneously. As described above, as the rubber component that is the raw material of the second elastic layer, the same material as the rubber component that is the raw material of the first elastic layer can be used. Moreover, as a standard of the layer thickness of the second elastic layer, 0.01 mm to 2 mm, particularly 0.02 mm to 1.5 mm is preferable.

<Asker C hardness of conductive member>
The Asker C hardness of the conductive member is preferably 85 ° or less, and more preferably 80 ° or less. If it is 85 ° or less, the nip width between the conductive elastic member and the mating member can be ensured, so that the electrophotographic characteristics are particularly stable. The Asker C hardness is a hardness measured using an Asker C spring rubber hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with the Japan Rubber Association standard SRIS0101. The Asker C hardness value of the conductive member according to the present invention is measured 30 seconds after the hardness meter is brought into contact with the conductive member left in the N / N environment for 12 hours or more with a force of 10 N. Value.

<Electric resistance of conductive elastic member>
The electrical resistance of the conductive member can be measured as follows. That is, when the conductive member is in the shape of a roller, as shown in FIG. 3, the photosensitive member is exposed to the same stress as in the use state when the conductive member is used in an image forming apparatus such as an electrophotographic apparatus shown in FIG. The electrical resistance is measured when the cylindrical metal 25 having the same curvature as the body is in contact with the energized current. In FIG. 3A, 24 a and 24 b are bearings fixed to weights, and apply a stress that pushes vertically downward to both ends of the conductive base (shaft) 1 of the conductive elastic roller 27. A cylindrical metal 25 is positioned in a vertically downward direction of the conductive elastic roller 27 in parallel with the conductive elastic roller 27. Then, the conductive elastic roller 27 is pressed against the bearings 24a and 24b as shown in FIG. 3B while rotating the columnar metal 25 by a driving device (not shown). The cylindrical metal 25 is rotated at the same rotational speed as that of the photosensitive drum in use, and a DC voltage of −200 V is applied from the resistance measurement power source 26 while the conductive elastic roller 27 is driven to rotate. The current flowing out of the current is measured with an ammeter 28. The electrical resistance of the conductive elastic roller 27 is calculated from the applied voltage and the measured current at this time. In the embodiment, a force of 5N is applied by bearings fixed to weights at both ends of the shaft of the conductive elastic roller so as to contact a cylindrical metal having a diameter of 30 mm, and the cylindrical metal is caused to have a peripheral speed of 150 mm / s. It was rotated with. When the conductive member is not in the form of a roller, metal is deposited on the surface of the conductive member, and the volume resistivity between the conductive base and the surface of the conductive member is measured.

The electrical resistance of the conductive member is preferably 1 × 10 ⁴ Ω or more in the H / H environment described above and 1 × 10 ⁸ Ω or less in the L / L environment. In an N / N environment, it is preferably 2 × 10 ⁴ Ω or more and 6 × 10 ⁷ Ω or less. By setting the electric resistance of the conductive member in the L / L environment to 1 × 10 ⁸ Ω or less, unevenness of the electrophotographic output due to variation in the position of the resistance of the conductive member is particularly unlikely to occur, which is preferable. In addition, when the electrical resistance of the conductive member in the high temperature and high humidity environment is 1 × 10 ⁴ Ω or more, the applied charge does not particularly leak, and the density unevenness of the electrophotographic output appears on the halftone image. It is preferable because it prevents easily. Further, it is preferable to set the resistance in the N / N environment within the above range because charging is easily stabilized and occurrence of horizontal stripe-shaped charging unevenness is easily prevented.

  Hereinafter, the present invention will be described in more detail by way of examples. In the following, commercially available high-purity products were used unless otherwise specified. In the following examples, a roller-shaped member was used as the conductive elastic member of the present invention. For the first elastic layer and the surface layer (second elastic layer) used in the following examples, the layer thickness and volume resistivity were measured by the evaluation methods described above or described later, respectively. For each of the conductive elastic rollers having the first and second elastic layers in each example, the electrical resistance, Asker C hardness, oozing out of plasticizer (bleed), and halftone are evaluated by the evaluation methods described above or later. The presence or absence of contact marks on the image was evaluated.

<Example 1>
<< Preparation of unvulcanized rubber composition for forming first elastic layer >>
The following materials were mixed with a 6 liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) for 16 minutes at a filling rate of 70 vol% and a blade rotation speed of 30 rpm to obtain an unvulcanized rubber composition A1. .

  (Material of unvulcanized rubber composition A1)

  Next, the following materials were mixed in an open roll having a roll diameter of 12 inches (30.5 cm) at a front roll rotation speed of 8 rpm, a rear roll rotation speed of 10 rpm, and a roll gap of 2 mm for 20 minutes, and then the roll gap was set to 0.5 mm. Thinning was performed 10 times. This obtained unvulcanized rubber composition A2 for 1st elastic layer formation. The unvulcanized rubber composition contains 10 parts by mass of a plasticizer with respect to 100 parts by mass of a polymer elastic body (base rubber: NBR).

<< Preparation of unvulcanized rubber composition for forming second elastic layer >>
The following materials were kneaded with a 6 liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) at a filling rate of 70 vol% and a blade rotation speed of 30 rpm for 16 minutes to obtain an unvulcanized rubber composition B1. It was.

  (Material of unvulcanized rubber composition B1)

  Next, the following materials were kneaded with an open roll having a roll diameter of 12 inches (30.5 cm) at a front roll rotation speed of 8 rpm, a rear roll rotation speed of 10 rpm, and a roll gap of 2 mm for 20 minutes, and then the roll gap of 0.5 mm. As thin as 10 times. Thereby, an unvulcanized rubber composition B2 for forming the second elastic layer was obtained. The unvulcanized rubber composition contains 10 parts by mass of the compound represented by the above formula 4 with respect to 100 parts by mass of a polymer elastic body (base rubber: NBR).

  Each of the unvulcanized rubber compositions A2 and B2 was extruded into a sheet having a thickness of 1 mm, and vulcanized at a temperature of 140 ° C. for 20 minutes to obtain two rubber sheets. These were allowed to stand in an N / N environment for 12 hours, electrodes were deposited, and volume resistivity was measured.

<< Manufacture of conductive roller >>
Next, the unvulcanized rubber composition A2 and the unvulcanized rubber composition B2 are simultaneously extruded from a crosshead die, and the outer peripheral surface of the tube of the unvulcanized rubber composition A2 is unvulcanized rubber composition B2. To obtain a non-vulcanized rubber tube coated with a tube (length in the axial direction = 270 mm, diameter of the center hole = 5.5 mm, diameter of the tube made of the unvulcanized rubber composition A2 = 10 mm, unvulcanized The outer diameter of the tube made of the vulcanized rubber composition B2 = 13 mm).
Next, the unvulcanized rubber tube was put into a vulcanizing can and heated at a temperature of 140 ° C. for 30 minutes. After that, a conductive metal bar having a polyester adhesive applied to a thickness of 10 μm around a solid stainless steel rod having a diameter of 6 mm and a length of 252 mm was inserted into the center hole of the heat-treated rubber tube, and was heated in a hot air oven. A conductive roller was obtained by heating at a temperature of 160 ° C. for 30 minutes. This method was repeated to produce a total of four conductive rollers.
<< Evaluation 1 >>
With respect to one of the four conductive rollers manufactured as described above, a laminated body of the first elastic layer and the second elastic layer was cut out in the central portion in the axial direction of the conductive roller. Further, the surface of the laminate was cut with a razor in a direction perpendicular to the roller axial direction, and the thickness of each elastic layer was measured using a scanning electron microscope (SEM).
<< Evaluation 2 >>
After the second conductive roller was left in an N / N environment for 24 hours, the electrical resistance and Asker C hardness were measured.
<< Evaluation 3 >>
A third conductive roller was placed on a glass plate, allowed to stand in an H / H environment for 2 weeks, and then allowed to stand in an N / N environment for 1 day. And the infrared absorption spectrum of each surface of the contact part and non-contact part with the glass plate of a conductive elastic roller was obtained. As a result of comparing the infrared absorption spectra at the contact portion and the non-contact portion, no bleed such as plasticizer was observed on the surface of the contact portion between the conductive elastic roller and the glass plate.
<< Evaluation 4 >>
A fourth conductive roller was incorporated in the electrophotographic apparatus shown in FIG. 2 as a charging roller 6 that contacts the photosensitive drum 5 and charges the photosensitive drum 5. The electrophotographic apparatus in which the photosensitive drum 5 and the charging roller 6 were in contact with each other was left in a harsh environment (temperature 40 ° C., relative humidity 95%) for 2 weeks, and then a halftone image was output. When the obtained halftone image was visually observed, image unevenness (contact mark) due to contact of the charging roller 6 could not be observed.
The operation of the electrophotographic apparatus shown in FIG. 2 is as follows. The photosensitive drum 5 as an image carrier is primarily charged by the charging roller 6 while rotating in the direction of the arrow, and then an electrostatic latent image is formed by the exposure light 11 from an exposure unit (not shown). The developer 13 in the developer container 16 is carried on the surface of the developing roller 7 while being rubbed and charged between the developing roller 7 and the developing blade 15 and conveyed to the surface of the photosensitive drum 5. As a result, the electrostatic latent image is developed and a toner image is formed. The toner image is transferred to the recording medium 9 between the transfer roller 8 and the photosensitive drum 5, and then conveyed while being sandwiched between the fixing member 18 and the pressure roller 10, and fixed by applying heat and pressure. The toner remaining on the surface of the photosensitive drum 5 without being transferred is cleaned by the cleaning blade 12. Voltages are applied to the charging roller 6, the developing roller 7, the transfer roller 8, and the like from the charging power source 21, the developing power source 23, and the transfer power source 22 of the image forming apparatus, respectively.

<Example 2>
The compound of the formula (4) in the unvulcanized rubber composition B2 used in Example 1 was changed to a compound of the following formula (5) (trade name: Gelall MD-CM30G, manufactured by Shin Nippon Rika Co., Ltd.). Except for the above, four conductive rolls were produced in the same manner as in Example 1. Using these, the same evaluation as in Example 1 was performed.

<Example 3>
Example except that the compound of formula (4) in the unvulcanized rubber composition B2 of Example 1 was changed to a compound of the following formula (6) (trade name: Solid X, manufactured by Yokoseki Oil & Fat Co., Ltd.) 4 conductive rollers were produced in the same manner as in Example 1. Using these, the same evaluation as in Example 1 was performed.

<Comparative Example 1>
Except that the second elastic layer was formed using an unvulcanized rubber composition obtained by removing the compound of the formula (4) from the unvulcanized rubber composition B2 of Example 1, four conductive materials were formed in the same manner as in Example 1. Sex rollers were manufactured. These were evaluated in the same manner as in Example 1.

The evaluation results of Examples 1 to 3 and Comparative Example 1 are shown in Tables 5 to 6 below. In addition, regarding the numerical values described in the volume resistivity and electrical resistance in Tables 5 to 6, for example, 1.0E + 04 means 1.0 × 10 ⁴ .

  The conductive member of the present invention can be incorporated into an electrophotographic apparatus and used as various types of conductive elastic members such as a charging roller, a developing roller, a transfer roller, and a cleaning roller.

DESCRIPTION OF SYMBOLS 1 ... Conductive base | substrate 2 ... 1st elastic layer 3 ... 2nd elastic layer 5 ... Photoconductor drum 6 ... Charge roller 7 ... Development roller 8 ... Transfer roller 9 ... Recording medium 10 ... Addition Pressure roller

Claims (1)

It has a conductive base, a conductive first elastic layer containing rubber, and a second elastic layer formed on the surface of the first elastic layer, and the second elastic layer has the following formula (1) to A conductive member comprising at least one compound selected from the group consisting of compounds represented by (3):

(In the formula (1), n represents an integer of ₁ to _2, and R ₁ , R ₂ and R ₃ each independently represents an alkyl group having 1 to 11 carbon atoms or a phenyl group. In the formula (2) , M represents an integer of 0 to 1, and R ₄ and R ₅ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein x and y are each independently 0 The above integers are shown, and the sum of x and y is 12 or more and 20 or less).

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