JP5302590B2 - Charging roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging roll which can effectively suppress the generation of charging noise. <P>SOLUTION: The charging roll is constituted by expansion-molding an urethane foaming material around a metal core. The urethane foaming material is a compound of a polyol component and a (&beta;) polyisocyanate component, and the polyol component is composed of polyether polyol A in which number average molecular weight: MnA is 2,000 to 4,000, polyether polyol B in which the number average molecular weight: MnB is 4,000 to 10,000 and polyether-based polymer polyol, MnA and MnB fulfill a prescribed relationship and at the same time, the amount of polyether polyol A in the compound: X<SB>A</SB>(parts by weight), the amount of polyether polyol B in the compound: X<SB>B</SB>(parts by weight), and the amount of polyether-based polymer polyol in the compound: X<SB>C</SB>(parts by weight) satisfy a specified relationship. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roll used for charging an image carrier made of an electrophotographic photosensitive member, an electrostatic recording dielectric, or the like in an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system. It is.

  2. Description of the Related Art Conventionally, in an image forming apparatus (hereinafter referred to as an electrophotographic apparatus) such as a copying machine, a printer, and a facsimile using an electrophotographic system, an image carrier such as an electrophotographic photosensitive member (drum) is used as an outer peripheral surface of a charging roll. A so-called roll charging method is adopted in which the surface of the image carrier is charged by bringing the image carrier and the charging roll into contact with each other and rotating them.

  In addition, as a charging roll used in such a roll charging system, those having various structures have been conventionally used. For example, a conductive elastic layer made of a non-foaming conductive rubber material is provided around a core metal serving as a roll shaft at a predetermined thickness, and the conductive elastic layer is necessary on the outer peripheral surface of the conductive elastic layer. Accordingly, a resistance adjusting layer made of a semiconductive rubber material is provided, and a roll provided with a protective layer made of a semiconductive resin material as the outermost layer is used as a charging roll.

  By the way, since the roll charging method is such that the image carrier and the charging roll are brought into contact as described above, a so-called charging sound is generated in the vicinity of the contact portion between the image carrier and the charging roll. It has been known.

  Examples of a method capable of suppressing the generation of the charging sound include reducing the hardness of the conductive elastic layer made of a non-foaming conductive rubber material in the charging roll having the structure as described above. If the hardness of the conductive elastic layer made of such a non-foaming conductive rubber material is lowered, the compression set of the conductive elastic layer may be deteriorated, and thus the roll may be deteriorated. there were.

  Further, in order to effectively suppress the generation of charging noise, a charging roll that employs a layer made of a predetermined conductive foam instead of a conductive elastic layer made of a non-foaming conductive rubber material has been conventionally used. Several more have been proposed.

For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 7-92775), a charging member (charging roll) for charging an object to be charged having a specific gravity of 0.1 g / cm ³ or more and 0.6 g / cm ³ or less. A charging member (charging roll) having a foam layer, a support member that supports the foam layer and to which a voltage is applied, and a resistance layer provided closer to the charged body than the foam layer is proposed. Has been. Patent Document 2 (Japanese Patent Laid-Open No. 2000-29273) has a structure in which a cylindrical cored bar and a conductive rubber layer concentrically stacked around the cored bar are provided. In the conductive roller, the rubber layer is composed of at least two layers, and among the rubber layers, the inner rubber layer has a foaming ratio of 2.0 to 4.0 and a degree of openness. Those having a foam layer of 1.3 or more have been proposed. Further, in Patent Document 3 (Japanese Patent Laid-Open No. 2003-162105), a conductive material having a three-dimensional network structure obtained by heating and foaming a predetermined binder material in which a foaming agent is kneaded on the outer periphery of a metal shaft. An electrophotographic roller is shown in which an elastic layer is formed and a semiconductive elastic layer is formed on the outer periphery of the conductive elastic layer.

  However, when the present inventors examined the above-described conventional charging rolls, those charging rolls can suppress the generation of charging noise to some extent, but cannot be said to be sufficiently suppressed. Met. That is, in recent years, there has been a demand for an improvement in image quality and an increase in printing speed for electrophotographic equipment. The AC voltage tends to be applied, and charging noise is more likely to occur than in the past. In addition, due to the downsizing of the main body of the equipment, the charged sound is more likely to leak out of the equipment than before, and various electrophotographic equipment has been installed and used near the user with the recent personal use. There has been a lot to be done. Under such circumstances, the development of a novel charging roll that can more effectively suppress the generation of charging noise is eagerly desired.

JP-A-7-92775 JP 2000-29273 A JP 2003-162105 A

  The present invention has been made in the background of such circumstances, and a problem to be solved is to provide a charging roll that can effectively suppress the generation of charging noise. .

And in order to solve such a subject, this invention has a longitudinal bar-shaped metal core used as a roll axis, and a urethane sponge layer around the metal core, the urethane sponge layer comprising a polyol component and In a charging roll formed by foam molding of a urethane foam raw material which is a blend with a polyisocyanate component, the polyol component is a polyether polyol A having a number average molecular weight: MnA of 2000 to 4000, and a number average molecular weight: It is composed of polyether polyol B having MnB of 4000 to 10,000, and polyether polymer polyol, MnA and MnB satisfy the following formula (1), and blending amount of polyether polyol A: X _A (parts by weight) ), the amount of polyether polyol B: X _B (parts by weight), and polyether polymer polyol over The amount of blending: X _C (parts by weight) is, the charging roll and satisfies the following formula (2) and (3), is to its gist.
MnA: MnB = 1: 2 to 1: 3 (1)
X _A : X _B = 2: 1 to 8: 1 (2)
(X _A + X _B ): X _C = 85: 15 to 95: 5 (3)

  In addition, in such a charging roll according to the present invention, in one of its preferred embodiments, a protective layer is provided on the outer peripheral surface of the urethane sponge layer.

  In another preferred embodiment of the charging roll of the present invention, a resistance adjusting layer is provided between the urethane sponge layer and the protective layer.

  As described above, the charging roll according to the present invention has a core metal and a urethane sponge layer around the core, and the urethane sponge layer is made of three kinds of polyols that satisfy a predetermined condition. It is formed by foam molding of a urethane foam raw material which is a blend of a polyol component and a polyisocyanate component. The urethane sponge layer obtained by using such a specific urethane foam raw material has excellent cell connectivity, and its hardness is effectively low, so when the charging roll of the present invention is used in various electrophotographic devices. The generation of charging noise can be advantageously suppressed.

  Moreover, since the charging roll of this invention has the urethane sponge layer excellent in cell connectivity, the shape recoverability after deform | transforming a roll shape is favorable. In addition, at the time of molding such a urethane sponge layer, gas escape is favorable, shrinkage deformation is advantageously suppressed, and the followability to the inner surface shape of the mold is improved. This charging roll is a roll excellent in shape stability and adapted to the shape or size of the molding cavity.

  Furthermore, in the charging roll according to the present invention, since the urethane sponge layer has a low hardness, the stress applied to the image carrier such as the photosensitive drum and the toner is effectively reduced, and the grounding property to the photosensitive drum is improved. improves. For this reason, when the charging roll of the present invention is used in an electrophotographic apparatus, image defects are less likely to occur even when a large amount of printing is performed, and image unevenness due to non-uniform charging of a photosensitive drum or the like may occur. It can be effectively suppressed.

  By the way, the charging roll according to the present invention has a long bar-shaped cored bar serving as a roll axis, and a urethane sponge layer around the cored bar. The urethane sponge layer includes a specific polyol component, It is formed by foaming a urethane foam raw material that is a blend with an isocyanate component.

  Among the urethane foam raw materials used in manufacturing such a charging roll, as a polyol component which is a characteristic part of the present invention, two types of polyether polyols having different number average molecular weights and a polyether polymer polyol are used. .

-Polyether polyol-
Specifically, as two types of polyether polyols having different number average molecular weights, those having a number average molecular weight: MnA of 2000 to 4000 (polyether polyol A) and number average molecular weights: MnB of 4000 to 10,000 (Polyether polyol B) is used. If a polyether polyol having a number average molecular weight of less than 2,000 is used, the hardness of the resulting urethane sponge layer becomes too low, and the intended roll shape may not be obtained by foam molding. On the other hand, when a polyether polyol having a number average molecular weight exceeding 10,000 is used, the cell connectivity in the resulting urethane sponge layer is deteriorated and the hardness is increased, and the charging roll having such a urethane sponge layer is used in an electrophotographic apparatus. This is because there is a possibility that the generation of charging noise cannot be effectively suppressed. In the present invention, any polyether polyol having such a number average molecular weight, which has been conventionally used in the production of urethane foams, can be used. Specifically, Actcall EP550N, MF-12, EP-828 (all trade names, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.), SANNIX GL-3000 (trade names, manufactured by Sanyo Chemical Industries, Ltd.), Preminol Examples include 7012 (trade name, manufactured by Asahi Glass Co., Ltd.) and the like. In addition, the number average molecular weight in this specification and a claim is measured by GPC (Gel permeation Chromatography) method (gel permeation chromatography method).

In the present invention, among the two types of polyether polyols having the number average molecular weight described above, each of the number average molecular weights (MnA, MnB) satisfies the following formula (1) and polyether polyol A and polyether polyol B: Are used together. That is, when two types of polyether polyols each having a number average molecular weight satisfying the following formula (1) are used in combination, the compatibility of the two types of polyether polyols in the urethane foam raw material is effectively reduced, When foaming a urethane foam material with a moderately low compatibility, the resulting cell membrane is not uniform and partially broken during the foaming process, resulting in excellent cell connectivity of the resulting urethane sponge layer. It will be a thing.
MnA: MnB = 1: 2 to 1: 3 (1)

  Here, the number average molecular weight of the polyether polyol A: MnA, the polyether polyol B having a number average molecular weight MnB which is too small (MnB <2MnA) and two types of polyether polyols having different number average molecular weights There is a possibility that the effect of using the combination, that is, the improvement of the connectivity in the urethane sponge layer cannot be advantageously achieved. Conversely, when the polyether polyol B having a number average molecular weight: MnB that is too large relative to the number average molecular weight: MnA of the polyether polyol A is used (MnB> 3MnA), cell connectivity in the resulting urethane sponge layer is improved. However, the compatibility of these two types of polyether polyols deteriorates, and the target roll shape may not be obtained by foam molding.

Further, each of the number average molecular weight of polyether polyol A and polyether polyols B satisfies the above formula (1), each amount thereof: X _A, X _B (parts by weight) satisfies the following formula (2) Used in quantitative proportions. When the blending amount of the polyether polyol B: X _B , the blending amount of the polyether polyol A: X _A is too small (X _A <2X _B ). On the other hand, if the blending amount of polyether polyol A: X _A is too large (X _A > 8X _B ), cell connectivity in the resulting urethane sponge layer is improved, but by foam molding This is because the target roll shape may not be obtained.
X _A : X _B = 2: 1 to 8: 1 (2)

-Polyether polymer polyol-
In producing the charging roll of the present invention, a polyether polymer polyol is further used as the polyol component in the urethane foam raw material in addition to the polyether polyol A and the polyether polyol B as described above. By using such a polyether polymer polyol, the cell connectivity of the resulting urethane sponge layer is effectively improved.

  In the present specification and claims, the polyether polymer polyol is a polymer obtained by dispersing a vinyl polymer in a polyether polyol, or a copolymer obtained by copolymerizing a polyether polyol and a vinyl polymer. In the present invention, any polyether-based polymer polyol generally used in the production of urethane foam can be used as long as the object of the present invention is not impaired. Specifically, POP-31-28 (trade name, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) can be exemplified.

In addition, in the present invention, such a polyether polymer polyol has a blending amount: X _C (part by weight) between the above two blending amounts of polyether polyol: X _A and X _B (part by weight). Is used in a quantitative ratio satisfying the following formula (3). The total amount of polyether polyol: (X _A + X _B ) The amount of polyether polymer polyol: X _C is too small. In other words, two types of polyether polyol and polyether polymer polyol total amount: per 100 parts by weight, the amount of the polyether polymer polyol: If X _C is less than 5 parts by weight, is a fear that the improvement of the cell communicating with the urethane sponge layer can not been achieved effectively There, while the amount of the polyether polymer polyol: X _C is too large: the (amount of polyether polymer polyol X _C is more than 15 parts by weight), is roll-shaped to the desired obtained by foam molding Because there is no fear.
(X _A + X _B ): X _C = 85: 15 to 95: 5 (3)

  On the other hand, in the urethane foam raw material for producing the charging roll of the present invention, a polyisocyanate component is an essential component together with the three types of polyols described above. As the polyisocyanate component, all known polyisocyanates having at least two or more functional groups can be used, for example, 2,4- and 2,6-tolylene diisocyanate (TDI), orthotoluidine diisocyanate (TODI), naphthylene diene. Isocyanate (NDI), xylylene diisocyanate (XDI), 4,4′-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, polymethylene polyphenyl isocyanate, polymeric polyisocyanate, etc. can be used alone or in combination. .

  In the present invention, the polyol component and the polyisocyanate component in the urethane foam raw material generally have a weight ratio (polyol component: polyisocyanate component) of about 9: 1 to 5: 5, as in the past. It is blended as follows.

In addition, such urethane foam raw materials include carbon black, metal powder, conductive metal oxide, quaternary ammonium salt, etc. so that the desired charging roll can finally exhibit the desired conductivity. The conductive agent is blended. The blending amount is appropriately adjusted so that the urethane sponge layer formed of the urethane foam raw material blended with the conductive agent usually has a volume resistance value of about 1 × 10 ³ to 1 × 10 ⁶ Ω · cm. It is determined.

  Further, water is used as a foaming agent in the urethane foam raw material in order to foam polyurethane formed by reacting a polyol component and a polyisocyanate component. The amount of water added as the blowing agent is generally about 0.1 to 3.0 parts by weight, preferably about 0.5 to 2.0 parts by weight, based on 100 parts by weight of the polyol component. Is adopted. If the amount of water added is small, there is a problem that it is difficult to perform sufficient foaming and the formed cells are too large. On the other hand, if the amount of water added is too large, the foaming speed is high, and the foaming reaction proceeds too much in the casting machine before the urethane foam material is injected into the mold. As a result, the raw material in the middle of the reaction leaks from the casting port, making it difficult to perform a stable injection operation into the mold, resulting in problems such as poor yield.

  In addition, the urethane foam raw material as described above may be added to various additives such as a catalyst, a foam stabilizer, a flame retardant, a viscosity reducer, a stabilizer, a filler, a cross-linking agent, and a colorant as necessary. However, it can be added appropriately within a range not impairing the object of the present invention.

  And the charging roll which concerns on this invention which has a urethane sponge layer of predetermined thickness is obtained by foam-molding such a urethane foam raw material around a longitudinal bar-shaped metal core. Hereinafter, a method for producing a charging roll in which a urethane sponge layer is provided on the outer peripheral surface of the cored bar, and a resistance adjusting layer and a protective layer are sequentially laminated on the outer side in the radial direction of the cored bar. An example is shown.

  First, a so-called pipe mold having a pipe-shaped mold structure is prepared as a mold (molding mold) having a molding cavity that gives a roll shape of a target charging roll. The pipe type is composed of a pipe having a length substantially equal to the axial length of the urethane sponge layer in the charging roll, and two caps attached to both ends of the pipe and closing each end. In a state where a long bar-shaped core bar serving as a roll shaft is set in the pipe, both ends of the pipe are closed with two caps and the core bar is supported by these two caps. Thus, a molding cavity that gives the roll shape of the target charging roll is formed in the pipe. In addition, as a longitudinal bar-shaped cored bar used as a roll shaft, a metal conductive shaft body made of stainless steel or the like having a predetermined length is used.

A tube made of a predetermined rubber material is set in the pipe mold to provide a resistance adjusting layer. As in the conventional tube, a conductive agent, preferably an ionic conductive agent or an antistatic agent, is blended in a rubber material such as epichlorohydrin rubber, epichlorohydrin-ethylene oxide copolymer rubber, acrylonitrile-butadiene rubber (NBR), and the like. The volume resistivity is obtained by extrusion molding using a rubber composition generally prepared to be about 1 × 10 ⁷ to 1 × 10 ¹⁰ Ω · cm. In addition, although the thickness of this tube is suitably determined according to the thickness of the target resistance adjusting layer, it is generally about 10 to 1000 μm, preferably about 100 to 500 μm.

  After setting such a tube in a pipe mold, a urethane foam raw material prepared in advance is injected between the tube and the metal core. The mold is closed, and foam molding is performed in accordance with the same operation as before.

Then, the molded product obtained by such foam molding is removed from the pipe mold, and then a protective layer is formed on the outer peripheral surface thereof, whereby the intended charging roll is obtained. The protective layer is provided to prevent toner and the like from being deposited on the roll surface. For example, a nylon material such as N-methoxymethylated nylon or a fluorine-modified acrylate resin is used. A conductive agent such as carbon black or conductive metal oxide is blended in the resin composition or the like, and the volume resistivity is about 1 × 10 ⁸ to 1 × 10 ¹³ Ω · cm. The Rukoto. Moreover, such a protective layer is formed in accordance with a known coating technique such as dipping or roll coating, as in the prior art, and its thickness is usually about 3 to 20 μm.

  In the charging roll thus obtained, the urethane sponge layer is excellent in cell connectivity, and the hardness of the roll as a whole is advantageously low. When used in, the generation of charging noise due to contact with an image carrier such as a photosensitive drum is effectively suppressed.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, in addition to the specific description described above, the present invention includes various changes, modifications, and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that improvements and the like can be added.

First, in order to prepare a urethane foam raw material, polyether polyols shown in Table 1 below and polyether polymer polyols (trade name: POP-31-28, manufactured by Mitsui Chemical Polyurethane Co., Ltd.) are used as polyols. Fifteen types of polyol compounding agents containing these were prepared according to the compounding compositions shown in Tables 2 and 3 below. The composition other than the polyol component is as follows.
Blending amount ・ Ketjen EC 2 parts by weight (conductive agent, manufactured by Ketjen Black International Co., Ltd.)
・ Kaorizer NO.31 0.5 part by weight (Tertiary amine catalyst, manufactured by Kao Corporation)
・ Toyocat HX-35 0.1 parts by weight (tertiary amine catalyst, manufactured by Tosoh Corporation)
・ Dibutyltin dilaurate (tin-based catalyst) 0.1 parts by weight ・ L-5309 3 parts by weight (silicone foam stabilizer, manufactured by Nihon Unicar Co., Ltd.)
・ Water (foaming agent) 2 parts by weight

  Also, 26.9 parts by weight of Sumijour VT-80 (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.) containing a prepolymer as a polyisocyanate component was prepared as a polyisocyanate compounding agent.

  The thus obtained polyol compounding agent and polyisocyanate compounding agent were mixed so as to have a weight ratio of polyol compounding agent: polyisocyanate compounding agent = 100: 25 to prepare a urethane foam raw material.

On the other hand, the resistance adjusting layer forming material having the following composition was kneaded in a kneader, extruded into a tube by an extruder, vulcanized at 180 ° C. for 60 minutes, cut, and thickness: 0 A rubber elastic tube of 5 mm × outer diameter: 12 mm × length: 224 mm was produced.
Compounding amount ・ Hydrin T3102 100 parts by weight (Epichlorohydrin rubber, manufactured by Nippon Zeon Co., Ltd.)
・ Zinc oxide 5 parts by weight ・ DHT4A (Acid acceptor, manufactured by Kyowa Chemical Industry Co., Ltd.) 8 parts by weight ・ Lunac S30 (Stearic acid, manufactured by Kao Corporation) 0.5 part by weight ・ Ionic conductive agent (tetrabutylammonium chloride) 1 part by weight-Silica 50 parts by weight-Vulcanizing agent (sulfur) 1.05 parts by weight-Vulcanization accelerator (dibenzothiazole disulfide) 1.5 parts by weight-Vulcanization accelerator (tetramethylthiuram monosulfide) 0. 5 parts by weight

  Next, using a pipe mold as a mold, a core metal made of stainless steel (SUS304) having an outer diameter: 6 mm × length: 260 mm is arranged in the molding cavity (inner diameter: 12 mm), while the inner surface of the molding cavity is arranged. The rubber elastic tube obtained above was inserted and set.

Then, in a state where the core metal is disposed in the pipe mold and the rubber elastic body tube is set, the urethane foam raw material prepared above is injected into the molding cavity, and is foam-cured at 120 ° C. for 60 minutes. Thus, a foam molded product was produced. After cooling the mold, the obtained molded product is taken out from the pipe mold, and on the outer peripheral surface of the outer layer formed by the rubber elastic tube, a protective layer as the outermost layer is formed using a resin composition according to the following composition. Were prepared according to a roll coating method, and 15 kinds of intended charging rolls were obtained (Examples 1 to 8, Comparative Examples 1 to 7). Each of the obtained charging rolls had a roll outer diameter: 12 mm, a resistance adjustment layer thickness: 500 μm, and a protective layer thickness: 10 μm. Moreover, when preparing the resin composition, the dispersion process was performed using the sand mill.
Compounding amount ・ Kayner SL 100 parts by weight (acrylic fluororesin, manufactured by Elfatochem Japan)
-Graft carbon 30 parts by weight-MEK (methyl ethyl ketone) 200 parts by weight

  The obtained 15 types of charging rolls were evaluated for roll hardness, air flow rate, and charging sound, and the results are shown in Tables 2 and 3 below. Moreover, about each charging roll, the surface (any surface of axial both end surfaces) where the urethane sponge layer was exposed was observed with a scanning electron microscope (SEM). An SEM photograph of the charging roll according to Example 2 is shown in FIG.

-Roll hardness-
The charging roll is supported by the cored bar portions at both ends thereof, and a plate shape having a width: 50 mm × 50 mm (thickness: 7 mm) near the central portion in the axial direction of the roll portion (urethane sponge layer + resistance adjusting layer + protective layer). A jig having a pressing surface was pressed at a speed of 10 mm / min, and the load (gf) when the jig was displaced by 0.5 mm was used as the hardness of the roll.

-Airflow-
As shown in (a) and (b) of FIG. 2, a sample 10 in a state in which the other roll portions are removed from each charging roll while leaving the roll portions having an axial length of 5 mm, This is fitted and fixed in a holding hole 14 provided in an aluminum holding ring 12 and having an inner diameter (φ) smaller by 0.1 mm than the outer diameter (D) of the charging roll, as shown in FIG. The holding cylinder 16 was airtightly fixed to the opening end so that one end side of the sample 10 in the axial direction was exposed to the atmosphere, while the other end side was exposed to the inside of the holding cylinder 16. The vacuum pump 20 is provided via the flow meter 18 so as to communicate with the inside of the holding cylinder 16, while the manometer 22 as a pressure gauge for detecting the pressure in the holding cylinder 16 is provided. The pump 20 is operated so that the difference between the pressure inside the holding cylinder 16 detected by the manometer 22 and the external air pressure becomes 1.5 kPa, and the air flow rate at that time is measured by the flow meter 18, and the measurement is performed. The air flow rate (cc / min · cm ² ) was calculated by dividing the value by the cross-sectional area of the urethane sponge layer portion of Sample 10.

−Charging sound−
As shown in FIG. 3, the developing unit in the cartridge container 26 of the laser beam printer (LASER JET 4350, manufactured by Hewlett-Packard Co.) 24 is removed while a charging roll is attached in the cartridge container 26, and a signal generator (NF1731, manufactured by NF Circuit Design Block Co., Ltd.) 30 is connected to a high-voltage amplifier (609C, manufactured by Lec Co., Ltd.) 32, and the high-voltage amplifier 32 is grounded, and the electrode terminal of the cartridge container 26 is connected with a high-voltage cable. Connected to. Then, while rotating the photosensitive member 28 at 30 rpm, a voltage of 2 kV _PP and −600 V is applied to the charging roll while changing the frequency between 2400 and 3400 Hz to charge the photosensitive member 28. The charging sound generated at the position at a distance of 10 mm from the abutting position in a direction that is horizontal to the abutting position between the photosensitive member 28 and the charging roll and perpendicular to the axial direction of the photosensitive member 28 at various frequencies. Thus, the measurement was performed by a sound level meter (NL01A, manufactured by Lion Co., Ltd.) 36 to which a linear coder (LR04, manufactured by Lion Co., Ltd.) 34 was connected. The noise level was evaluated by the A characteristic.

  As is clear from the results in Tables 2 and 3, the charging roll (Examples 1 to 8) according to the present invention effectively suppresses the generation of charging noise when used in an actual machine. It was recognized that it was possible.

It is a SEM photograph of the urethane sponge layer about the charging roll concerning one example of the present invention. It is explanatory drawing which shows the measurement method of the air flow rate of the urethane sponge layer in a charging roll, Comprising: (a) is explanatory drawing which shows the apparatus arrangement | positioning form of the whole system, (b) is the sample taken out from each charging roll It is explanatory drawing which shows the set form. It is explanatory drawing which shows roughly the apparatus for measuring the charging sound which attaches a charging roll to a real machine and operates this real machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sample 12 Holding ring 14 Holding hole 16 Holding cylinder 18 Flowmeter 20 Vacuum pump 22 Manometer 24 Laser beam printer 26 Cartridge container 28 Photoconductor 30 Signal generator 32 High-voltage amplifier 34 Linear coder 36 Noise meter 36

Claims (3)

It has a long bar-shaped cored bar that becomes a roll shaft and a urethane sponge layer around the cored bar, and the urethane sponge layer is formed by foam molding of a urethane foam raw material that is a blend of a polyol component and a polyisocyanate component. A charging roll made of
The polyol component is composed of a polyether polyol A having a number average molecular weight: MnA of 2000 to 4000, a polyether polyol B having a number average molecular weight: MnB of 4000 to 10,000, and a polyether polymer polyol, MnA And MnB satisfy the following formula (1), and the blending amount of the polyether polyol A: X _A (parts by weight), the blending amount of the polyether polyol B: X _B (parts by weight), and the polyether polymer polyol Blending amount: X _C (parts by weight) satisfies the following formulas (2) and (3).
MnA: MnB = 1: 2 to 1: 3 (1)
X _A : X _B = 2: 1 to 8: 1 (2)
(X _A + X _B ): X _C = 85: 15 to 95: 5 (3)   The charging roll according to claim 1, wherein a protective layer is provided on an outer peripheral surface of the urethane sponge layer. The charging roll according to claim 2, wherein a resistance adjusting layer is provided between the urethane sponge layer and the protective layer.

Images