JP2007333857A - Developing roller, developing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller with low hardness and low resistance, with no occurrence of soiling in a photoreceptor, without any image density unevenness or density deterioration and adapting to speeding up and high definition in image quality in an electrophotographic apparatus for the developing roller provided with an elastic layer with NBR as a base and given conductivity by adding carbon black. <P>SOLUTION: When making the developing roller with the elastic layer and a coated layer sequentially formed on an outer periphery surface of a shaft core body, NBR with acrylonitrile amount at 31 to 60 mass% is used as rubber which is main component for the elastic layer and the carbon black with DBP oil absorption amount at 80 to 140 ml/100 g and polyester plasticizer with average molecular weight within a range of 2,000 to 12,000 are contained and selected for specified ranges. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller that is used in contact with a photoreceptor incorporated in an electrophotographic system such as a copying machine, a printer, or a facsimile receiver, a developing device using the same, and an image forming apparatus It is.

In electrophotographic apparatuses such as copiers, facsimiles, and printers, an elastic roller having electrical conductivity (electric resistance) suitable for the purpose is generally used to charge a photoreceptor or to visualize an electrostatic latent image. It has been.
In an electrophotographic apparatus of a one-component development system, a developer (toner) is moved from a developing roller that is in pressure contact with or close to each other to a photoreceptor (drum) to develop an electrostatic latent image, and development is performed. . The developing roller used in such an electrophotographic apparatus is easy to deform and recovers deformation because the developer roller is pressed against or close to the photoreceptor with a predetermined contact width, or carries the developer thinned by a blade or the like. It is necessary to be excellent. Further, these developing rollers are required to have appropriate and uniform conductivity so as not to cause image unevenness.

  In order to satisfy these requirements, conventionally, a developing roller according to the present invention has an elastic layer made of a rubber material imparted with conductivity formed on the outer periphery of the shaft core. In the contact development, the elastic layer of the developing roller needs to be pressed against the photosensitive member with a predetermined contact width, is easily deformed, and at the same time has excellent deformation recovery (set recovery), and a semiconductive region. Therefore, electrical resistance characteristics are required. If the hardness is lowered in order to obtain good followability to the surface of the photoconductor, the photoconductor may be contaminated.

  As a means for imparting conductivity, a conductive filler, specifically, carbon black may be used. In that case, it is difficult to control the dispersibility of the carbon black, and it is difficult to obtain sufficient stability (environment dependency, voltage dependency) of the resistance characteristics. In the electrophotographic process, as the image quality is improved and full color is developed, the developer for forming the image is required to have a finer particle diameter and the resistance characteristic of the developing roller is very small. For example, a developing roller using an elastic layer made of silicone rubber that is flexible and has excellent setting properties can be used. However, silicone rubber itself is a relatively expensive material.

  Furthermore, in order to provide adhesiveness with the coating layer provided on the outer periphery, it is necessary to provide an adhesive layer in the middle or to treat the surface of the silicone rubber, so that it is relatively expensive as a developing roller. Is. Therefore, it has been desired to provide a developing roller that is cheaper than before. A wide variety of rubber materials used for the developing roller have been studied, and they are properly used depending on the purpose. Among them, there is a method of using acrylonitrile butadiene rubber (hereinafter abbreviated as NBR), which is relatively inexpensive.

  Conventionally, a developing roller having an elastic layer formed of NBR and a developing roller having a coating layer formed on the outer peripheral surface of the NBR elastic layer have been studied. Among them, NBR has a relatively high hardness, and in order to achieve advanced functions as a developing roller, NBR has various problems such as lowering hardness, reducing (suppressing) photoreceptor contamination, and controlling carbon black dispersion. Attempts have been made.

  In the case where the resistance is adjusted by adding carbon black, there is a problem that uniform dispersion is difficult and the hardness increases depending on the amount added.

  On the other hand, for example, a developer carrier (developing roller) in which the material of the dielectric layer (corresponding to the elastic layer) is mainly NBR is disclosed.

Without adding a compounding agent such as carbon black, the dielectric constant can be greatly adjusted by the content of acrylonitrile, and the developer carrier can be easily elasticized according to the form of the photoreceptor while maintaining high elasticity. By deforming, an appropriate developing nip width can be reliably obtained. (Patent Document 1)
In addition, by adding a conductive polymer substance to NBR, etc., and using peroxide as a cross-linking agent, the conductive polymer substance has a three-dimensional network structure, thereby achieving uniform resistance and low resistance characteristics. A developing roller that maintains and retains elastic properties is disclosed. (Patent Document 2)
In addition, as a countermeasure against the increase in hardness when carbon black is added, it has been studied to reduce the hardness of an elastic layer based on NBR to which carbon black is added by blending or foaming rubber.
For example, by blending an ethylenically unsaturated nitrile-conjugated diene-based solid rubber such as NBR and an ethylenically unsaturated nitrile-conjugated diene-based liquid rubber such as liquid NBR, the hardness can be reduced and the photosensitive member can be obtained. A contamination-preventing semiconductive rubber roll is disclosed. (Patent Document 3)
Further, a developing roller is disclosed in which the elastic layer is a foam having a JIS-A hardness of 5 to 25 degrees so that an appropriate nip width with respect to the photoreceptor (drum) can be easily obtained and the photoreceptor is not contaminated. . (Patent Document 4)
However, in these developing rollers, the carbon black added is not particularly studied.
JP 62-143074 A Japanese Patent Laid-Open No. 2003-263021 Special registration 3646754 JP 2000-242074 A

  In recent years, the required performance of the developing roller used in the electrophotographic apparatus has become more advanced as the speed of the electrophotographic apparatus increases and the image quality becomes higher, and further improvement is required. . At the same time, a low cost and stable performance is required.

  In particular, it is necessary for the contact development to have a low hardness and rubber elasticity for obtaining a predetermined contact width (nip width) with respect to the photoreceptor, and to have an electrical resistance characteristic called a semiconductive region. In particular, when NBR is used for the elastic layer, it is required that components contained in the elastic layer hardly bleed on the surface of the developing roller and do not cause contamination of the photoreceptor.

An object of the present invention is to solve the problems in such a developing roller. In particular, an object of the present invention is to develop a developing roller having an elastic layer based on NBR and imparted with conductivity by adding carbon black, having low hardness, low resistance, no contamination of the photoreceptor, and uneven image density. Another object of the present invention is to obtain a developing roller that can cope with higher speed and higher image quality of an electrophotographic apparatus with no decrease in density.
The developing roller refers to a latent image carrier for forming an electrostatic latent image by an electrophotographic method and a contact or pressure contact with the surface of the latent image carrier while carrying a developer in a thin film shape. In this state, the developer is supplied to the electrostatic latent image formed on the latent image carrier to develop the electrostatic latent image.

  In order to solve the above-mentioned problems, the present inventors have intensively studied and studied.

  According to the present invention, while being a developing roller using an elastic layer based on NBR, which is relatively inexpensive and imparted with carbon black, it has both low hardness and low resistance performance, and Bleed (oil transfer) can be suppressed and contamination of the photoreceptor can be prevented.

  The developing roller of the present invention uses NBR having an acrylonitrile amount of 31 mass% or more and 60 mass% or less as a rubber as a main component of the elastic layer, and has a DBP oil absorption of 80 ml / 100 g or more and 140 ml / 100 g or less. Carbon black and a polyester plasticizer having a mass average molecular weight of 2000 or more and 12000 or less are contained. Here, DBP means dibutyl phthalate.

  In the case of the combination of NBR having an acrylonitrile content of 31% by mass or more and 60% by mass or less and a polyester plasticizer as described above, it is easy to achieve both desired low hardness and low resistance. However, when the acrylonitrile content is relatively increased, the electrical resistance tends to become more environmentally dependent. Therefore, it is necessary to impart conductivity with carbon black and further increase the resistance stability. By using carbon black to impart conductivity as described above, it is possible to increase the amount added without increasing the rubber hardness more than necessary, and to keep the electrical resistance environmental dependency low. Is possible. Further, the polyester plasticizer added for reducing the hardness is less likely to bleed when the molecular weight is large, but at the same time, the softening action is also reduced. If the addition amount is simply increased, bleeding tends to occur and there is a concern that the resistance will increase. By adding carbon black, bleeding of the plasticizer can be suppressed and the resistance can be lowered. In particular, carbon black as described above is highly effective because it can be added in a larger amount.

  The effect of preventing the bleeding of the polyester plasticizer has a correlation with the product of the DBP oil absorption (D) of the carbon black to be used and the number of added parts (Fc) of the carbon black. When carbon black is used as described above, The effect of reducing bleeding is increased with respect to the increase in hardness (reinforcing property). That is, by satisfying the relationship of the mathematical formula (1), both low hardness and low resistance can be achieved and bleed can be reduced.

0.010 ≦ Fp / (Fc × D) ≦ 0.025 (1)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
Fc: Number of added carbon black parts (parts by mass) relative to the rubber component in the elastic layer
Fp: Number of added polyester plasticizer to the rubber component in the elastic layer (parts by mass)
Furthermore, the value of Fp / (Fc × D) is preferably 0.010 or more and 0.020 or less.
In the developing roller of the present invention, the amount of acrylonitrile of the NBR in the elastic layer is more preferably 36% by mass or more and 55% by mass or less.

The polyester plasticizer used for the elastic layer of the developing roller of the present invention has a mass average molecular weight in the range of 2000 or more and 12000 or less, but the mass average molecular weight is 3500 or more and 10,000. The following is more preferable. Adipic acid esters, azelaic acid esters, and sebacic acid esters that are relatively easy to increase in molecular weight are more preferable. That is, it refers to using adipic acid, azelaic acid, sebacic acid as a raw material of the polybasic acid component that condenses the polyester plasticizer,
Specifically, it is preferable to contain one or more structural units represented by chemical formulas (1) to (3).
—CO— (CH ₂ ) ₄ —CO— Chemical Formula (1)
—CO— (CH ₂ ) ₇ —CO— Chemical Formula (2)
—CO— (CH ₂ ) ₈ —CO— Chemical Formula (3)
The rubber of the elastic layer of the developing roller of the present invention is preferably crosslinked with sulfur. In the case of sulfur crosslinking, the production method is less restricted, and a cheaper and more stable production method can be selected.
Moreover, it is preferable that the carbon black contained in the rubber of the elastic layer of the developing roller of the present invention satisfies the formula (2).

0.005 ≦ D / N ≦ 0.014 (2)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
N: Nitrogen specific surface area of carbon black in the elastic layer (m ² / g)
By using the above carbon black, it is easy to obtain a good dispersion state, and it is easy to impart conductivity to the rubber without increasing the hardness of the elastic layer more than necessary.
Furthermore, the value of D / N is more preferably 0.010 or more and 0.014 or less.

  Further, the coating layer of the developing roller of the present invention is preferably a crosslinked rubber, particularly a crosslinked urethane rubber, and the degree of swelling of the crosslinked urethane rubber with toluene at 25 ° C. is 150% or more and 300%. The following range is more preferable. In the present invention, bleeding of plasticizers and the like contained in the elastic layer is suppressed, but this is not sufficient depending on the use environment, and migration can be further prevented by the coating layer of the crosslinked rubber. In particular, when urethane rubber is used, it is preferable from the aspects of thin film formation, deformation followability, charge imparting property, and the like. In the case of the crosslinked urethane rubber, by setting the degree of swelling with toluene within the above range, crystallization of the urethane rubber is promoted, and more stable bleed suppression can be obtained.

  In the developing device of the present invention, by providing the developing roller described above, the developing device can cope with higher speed of the electrophotographic apparatus and higher quality of the image without unevenness of image density and lowering of density.

  As described above, the present inventors have developed a low-hardness and low-resistance developing roller that does not cause contamination of the photosensitive member, and an electrophotographic apparatus that is free from unevenness in image density and density reduction when used as a developing roller. The present inventors have found a developing device that can cope with higher speed and higher image quality, and have completed the present invention.

  That is, the developing roller of the present invention is a developing roller in which an elastic layer and a coating layer are sequentially formed on the outer periphery of the shaft core and the shaft core, and the elastic layer has an acrylonitrile amount of 31% by mass or more, It is composed of rubber containing NBR of 80% by mass or less and 80% by mass or less and 100% by mass or less. Carbon black is contained in the elastic layer and contained in an amount of 10 parts by mass to 80 parts by mass with respect to 100 parts by mass of the rubber component The DBP oil absorption of the carbon black is 80 ml / 100 g or more and 140 ml / 100 g or less, and the elastic layer contains a polyester plasticizer in an amount of 20 to 90 parts by mass with respect to 100 parts by mass of the rubber component. The developing roller is characterized in that the weight average molecular weight of the polyester plasticizer is in the range of 2000 or more and 12000 or less and satisfies the formula (1).

0.010 ≦ Fp / (Fc × D) ≦ 0.025 (1)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
Fc: Number of added carbon black parts (parts by mass) relative to the rubber component in the elastic layer
Fp: The number of parts of the polyester plasticizer added to the rubber component in the elastic layer (parts by mass)

According to the present invention, in a developing roller having an NBR-based elastic layer to which conductivity is imparted by adding carbon black, low hardness and low resistance, and without causing photoconductor contamination, image density unevenness and density It is possible to obtain a developing roller that can cope with higher speed of the electrophotographic apparatus and higher quality of the image without deterioration.
Further, in the developing device using the developing roller of the present invention, the photosensitive member is not contaminated, and there is no unevenness of image density or density reduction, and a high-quality image can be obtained even in a high-speed electrophotographic apparatus. .

Hereinafter, the present invention will be described in more detail.

  1 and 2 schematically show an example of the structure relating to the developing roller of the present invention. The developing roller 1 illustrated in FIGS. 1 and 2 has a shaft core 11 that is usually formed of a conductive material such as metal as a shaft core at the center, and an outer peripheral surface of the shaft core 11 as a roller layer. An elastic body layer (base layer) 12 is fixed on the surface, and a coating layer (surface layer) 13 is laminated on the outer peripheral surface of the elastic body layer 12. Here, a description will be given of a developing roller having two layers on the outer peripheral surface of the shaft core as described above.

  As the shaft core body 11, a shaft core body having a columnar shape or a hollow cylindrical shape and formed of a conductive material such as metal can be used. Even if such a developing roller is used with an electrical bias applied or grounded, the main body is made of a non-conductive material instead of being composed of a conductive material. It is also possible to use a material which is formed of a material and has a structure in which the surface is subjected to a conductive treatment satisfying desired conductivity, for example, a coating with a highly conductive coating layer.

  Since a developing roller used in an electrophotographic apparatus is generally used with an electric bias applied or grounded, the shaft core body is a conductive base, so-called shaft core metal. 11 forms. For example, in the developing roller, the shaft core 11 is not only a support member, but also functions as an electrode of the developing member. For example, a metal or alloy such as aluminum, copper alloy, stainless steel, or the like, Iron, synthetic resin, etc., plated with chromium, nickel, etc. At least the outer peripheral surface is composed of a conductive material sufficient to apply a predetermined voltage to an elastic layer such as rubber formed thereon To do. In the developing roller used in the electrophotographic apparatus, the outer diameter of the conductive substrate that is the shaft core is usually in the range of 4 to 10 mm.

The elastic body layer 12 serving as a base layer has flexibility, and can be formed as a molded body using rubber as a raw material main component. As the raw material rubber of the elastic layer 12, NBR having an acrylonitrile amount of 31% by mass to 60% by mass is used. If the amount of acrylonitrile is less than 31% by mass, sufficient conductivity cannot be obtained when the carbon black of the present invention is used, resulting in high resistance or stable resistance uniformity. In addition, when the amount of acrylonitrile exceeds 60% by mass, the performance of NBR itself as a rubber is not sufficient, and it is difficult to obtain and is not very practical including productivity. More preferably, the amount of acrylonitrile is in the range of 36 to 55% by mass. In this range, desired conductivity can be stably obtained without increasing the hardness of the elastic layer more than necessary.
NBR having an acrylonitrile amount of 31 to 60% by mass is a main component and an essential component in the present invention, and is contained in an amount of 80% by mass to 100% by mass with respect to the rubber component. The rubber component refers to a raw rubber and does not include various additives such as a crosslinking agent, a catalyst, and a dispersion accelerator that are used when forming a rubber molding. That is, other than NBR having an acrylonitrile amount of 31 to 60% by mass, other rubbers can be blended in the range of 0% by mass to 20% by mass. The rubber to be blended is not particularly limited, but it is necessary to consider compatibility during blending. Moreover, the rubber | gum which can be blended may be used in combination of 2 or more type as needed. Examples of the rubber to be blended include ethylene-propylene-diene copolymer rubber (EPDM), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluorine rubber, and silicone. It can be selected from rubber materials such as rubber, epichlorohydrin rubber, hydride of NBR, polysulfide rubber and urethane rubber.
An elastic layer is formed by blending various additives and the like into the above rubber material, that is, rubber containing 80 to 100% by mass of NBR having an acrylonitrile amount of 31 to 60% by mass as necessary. be able to. Additives are components that are necessary for the functions required for the elastic layer itself, such as conductive agents, non-conductive fillers, etc., depending on the application of the developing roller, and are also used when forming rubber moldings. Various additive components are used. For example, various additives such as a cross-linking agent, a catalyst, and a dispersion accelerator can be appropriately blended with the main rubber material. These addition amounts can also be selected according to the characteristics required for the intended application.

Carbon black is an essential component as a conductive agent added for the purpose of imparting conductivity to the elastic layer. Carbon black having a DBP oil absorption of 80 ml / 100 g or more and 140 ml / 100 g or less of the carbon black isolated from the elastic layer is contained in an amount of 10 to 80 parts by mass with respect to 100 parts by mass of the rubber component. Further, the DBP oil absorption amount and the number of added parts of the carbon black satisfy the relationship of the mathematical formula (1) described above.
The DBP oil absorption amount of carbon black indicates the DBP absorption amount per 100 g of carbon black, and is one of the indexes for determining the size of the structure of carbon black. The structure of carbon black is formed by uniting carbon black unit particles in a chain shape, and the size of the carbon black determines the electrical conductivity of the carbon black. In the present invention, the DBP oil absorption is measured according to JISK6217-4.
If the DBP oil absorption of the carbon black is less than 80 ml / 100 g, the amount added to obtain the desired conductivity increases, the hardness of the elastic layer becomes higher than necessary, and the rubber component (acrylonitrile amount 31 to 60% by mass) It is difficult to disperse uniformly in a rubber containing 80 to 100% by mass of NBR. On the other hand, when it exceeds 140 ml / 100 g, the desired conductivity can be easily obtained with a small addition amount, but it becomes difficult to obtain resistance stability due to the small addition amount of carbon black itself, and at the same time, the polyester plasticizer described later. The bleed cannot be sufficiently suppressed.

The carbon black used in the present invention is not particularly limited as long as it has the above characteristics, whether it is a commercially available product, a product obtained by treating a commercially available product, or a newly produced product. . Examples thereof include oil furnace black, gas furnace black, channel type carbon black, and those obtained by oxidizing these carbon blacks.
Further, the addition amount of the carbon black needs to be 10 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the rubber component forming the elastic layer. If the amount is less than 10 parts by mass, sufficient and stable conductivity cannot be imparted. If the amount exceeds 80 parts by mass, desired rubber elasticity cannot be obtained. A preferred range for the amount of carbon black added is 20 to 60 parts by mass. Within this range, it is easy to suppress bleed of the polyester plasticizer described later, while at the same time obtaining desired conductivity without increasing the hardness of the elastic layer more than necessary.
Moreover, it is preferable that carbon black contained in the rubber of the elastic layer of the present invention satisfies Formula (2).

0.005 ≦ D / N ≦ 0.014 (2)
D: DBP oil absorption of carbon black in the elastic layer (mg / 100 g)
N: Nitrogen specific surface area of carbon black in the elastic layer (m ² / g)
The nitrogen specific surface area indicates the amount of nitrogen adsorbed per gram, and is a numerical value related to the specific surface area of carbon black, in other words, the particle size. The ratio of the DBP oil absorption amount / nitrogen specific surface area indicates the oil absorption amount per carbon black surface area, and is an index indicating the degree of structure development. The larger this ratio is, the greater the effect of reinforcing the rubber, and the conductivity of the rubber. To increase. In the present invention, the DBP oil absorption is measured in accordance with JISK6217-2.

Here, when the ratio of DBP oil absorption amount / nitrogen specific surface area (D / N) of the carbon black used in the present invention is in the above range, the rubber layer is electrically conductive without increasing the hardness of the elastic layer more than necessary. It is possible to impart sex. When the term D / N in the formula (2) is 0.005 ml / m ² or more, it can be uniformly and sufficiently dispersed in the elastic layer. When the term D / N in Equation (2) is 0.014 ml / m ² or less, the reinforcing property is appropriate and the hardness of the elastic layer can be kept low.
The value of D / N is more preferably 0.010 or more and 0.014 or less from the viewpoint of easily imparting electrical conductivity. Within this range, a low resistance developing roller can be easily obtained.

  The average particle size of the carbon black used in the present invention is not particularly limited, but is limited by the DBP oil absorption amount / nitrogen specific surface area ratio from the viewpoint of dispersibility in NBR and conductivity imparting property.

  As the conductive agent, in addition to the above carbon black, various conductive metals such as graphite, aluminum, copper, tin, stainless steel, or alloys, tin oxide, zinc oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution Further, various conductive metal oxides such as tin oxide-indium oxide solid solution, and fine powders such as insulating substances coated with these conductive materials can be used, but there is no particular problem even if carbon black alone is used.

  As means for dispersing a fine powdery conductive agent such as carbon black in the main rubber material, conventionally used means such as a roll kneader, Banbury mixer, ball mill, sand grinder, paint shaker, etc. What is necessary is just to use suitably according to the rubber material of a main component.

In addition, as a means for imparting conductivity to the elastic layer, a method of adding a conductive polymer compound together with a conductive agent can be used. For example, as a conductive polymer compound, as a host polymer, polyacetylene, poly (p-phenylene), polypyrrole, polythiophenine, poly (p-phenylene oxide), poly (p-phenylene sulfide), poly (p-ferene vinylene) ), Poly (2,6-dimethylphenylene oxide), poly (bisphenol A carbonate), polyvinylcarbazole, polydiacetylene, poly (N-methyl-4-vinylpyridine), polyaniline, polyquinoline, poly (phenylene ether sulfone) and the like. These are used as dopants, such as AsF ₅ , I ₂ , Br ₂ , SO ₃ , Na, K, ClO ₄ , FeCl ₃ , F, Cl, Br, I, Kr, and other ions, Li, TCNQ (7 , 7,8,8-tetracyanoquinodimethane) What is available. However, these compounds are relatively expensive and are not used more than necessary.

  The plasticizer added to the elastic body layer for the purpose of adjusting the hardness is limited to the polyester type in terms of compatibility with NBR.

The polyester plasticizer in the present invention is produced by condensing a polybasic acid component and a polyhydric alcohol component, if necessary, using a monohydric alcohol and / or a monobasic acid as a terminal terminating component. What will be done.
A general main chain structure of a polyester plasticizer is, for example, chemical formula (4).

-(CO-A-CO-O-B-O) n- Chemical formula (4)
Here, a dibasic acid (HOOC-A-COOH) is shown as an example of the polybasic acid component, and a dihydric alcohol (HO-B-OH) is shown as an example of the polyhydric alcohol component.

Further, when alcohol is used as a terminal terminating component, a general structural formula is, for example, chemical formula (5). RO- (CO-A-CO-OBO) n-CO-A-CO-OR chemical formula (5)
Here, it is shown as a monohydric alcohol (R—OH).
Examples of the polybasic acid component include those having an aliphatic dibasic acid as a main component such as malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, and the like. A small percentage of aromatic polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, or aliphatic polybasic acids such as butanetricarboxylic acid, tricarbaryl acid, citric acid, etc. Can also be used.

  Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2,2-dimethyl-1,3- Propanediol, 2,2-diethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,5-hexanediol Aliphatic glycols such as 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, and 2,2,4-trimethyl-1,3-pentanediol. Other main ingredients include small percentages of glycerin, trimethylolpropane, trimethylolethane, pentae It can also be used polyhydric alcohols such as Suritoru.

  Examples of the terminal termination component include methanol, ethanol, propanol, isopropanol, butanol, sec-butanol, isobutanol, hexanol, isohexanol, heptanol, isoheptanol, octanol, isooctanol, 2-ethylhexanol, iso Fatty monohydric alcohols such as nonyl alcohol, isodecanol, isoundecanol, isotridecyl alcohol, benzyl alcohol and the like, acetic acid, propionic acid, butyric acid, isobutyric acid, octylic acid, 2-ethylhexylic acid, lauric acid, myristic acid, palmitic acid Examples thereof include aliphatic monobasic acids such as acid, stearic acid and 12-hydroxystearic acid.

  The ratio of each component used in the production of the polyester plasticizer varies depending on the type of component used, the characteristics of the target polyester plasticizer, the molecular weight, and the like. -80 mass%, polyhydric alcohol component 10-80 mass%, end-stopping component 0-50 mass%.

Among the polyester plasticizers listed above, those containing one or more structural units represented by chemical formulas (1) to (3) are preferred from the viewpoint of relatively easily increasing the molecular weight.
The “structural unit” in the present invention is a structural unit derived from a polybasic acid component (for example, an aliphatic dibasic acid such as malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid). It is.
For example, the -CO-A-CO- moiety in the above chemical formula (4) and chemical formula (5) corresponds.
Examples of plasticizers having chemical formula (1), chemical formula (2), and chemical formula (3) include those obtained by condensing adipic acid and 1,4-butanediol and terminating with octanols, adipic acid and 1,4 -Butanediol condensed and end-capped with isononyl alcohol, azelaic acid and 1,5-pentanediol condensed and octanol-terminated, sebacic acid and 1,4-butanediol condensed with butyl It is possible to select a product suitable for the present invention from commercially available products.
The mass average molecular weight of the extracted polyester plasticizer in the present invention is in the range of 2000 or more and 12000 or less. If the mass average molecular weight is less than 2,000, bleeding tends to occur and the concern about contamination of the photoreceptor increases. When the mass average molecular weight exceeds 12000, it is necessary to increase the amount added to obtain the effect as a plasticizer, and it is difficult to soften the hardness of the elastic layer. Furthermore, the mass average molecular weight is preferably in the range of 3500 or more and 10,000 or less. Within this range, the hardness of the elastic layer can be softened to obtain desired conductivity, and at the same time, the combination with the above-mentioned NBR and carbon black can easily suppress the bleeding of the polyester plasticizer.
The polyester plasticizer in the present invention contains 20 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the rubber component. When the amount is less than 20 parts by mass with respect to 100 parts by mass of the rubber component, it is difficult to stably obtain the effect of addition. On the other hand, when it exceeds 90 parts by mass with respect to 100 parts by mass of the rubber component, it is difficult to solve the problem caused by bleeding of the polyester plasticizer even when the inventive idea of the present invention is used.
In the present invention, the DBP oil absorption amount of carbon black, the number of added parts, and the number of added parts of the polyester plasticizer satisfy the relationship of the mathematical formula (1).

0.010 ≦ Fp / (Fc × D) ≦ 0.025 (1)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
Fc: Number of added carbon black parts (parts by mass) relative to the rubber component in the elastic layer
Fp: Number of added polyester plasticizer to the rubber component in the elastic layer (parts by mass)
When the mathematical formula (1) is not satisfied, there are the following problems. When the value of the term Fp / (Fc × D) in the formula (1) is less than 0.010, the amount of carbon black added is relatively larger than the amount of polyester plasticizer added, and the elastic layer becomes hard. It will not show sufficient elasticity. When the value of the term Fp / (Fc × D) in the formula (1) exceeds 0.025, the amount of the polyester plasticizer added is relatively large with respect to the amount of carbon black added, and it is easy to bleed. It is difficult to completely prevent contamination of the photoreceptor.
According to the desired hardness, the number of added parts of the polyester plasticizer may be adjusted. From the viewpoint of reducing bleeding, the value of Fp / (Fc × D) is 0.010 or more and 0.020 or less. Preferably there is.
If it is this range, it will become easier to obtain the effect of bleed reduction.

  Examples of the non-conductive filler that can be added to the rubber molded body include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, and the like.

The vulcanized product obtained from the NBR of the present invention or the rubber composition thereof is usually prepared by once preparing an unvulcanized compounded rubber in the same manner as when vulcanizing general rubber, It is manufactured by forming into the intended shape and then vulcanizing. Here, as the vulcanizing agent, organic peroxides, sulfur, sulfur compounds, sulfur-containing organic vulcanizing agents, triazine compounds, and the like are used, and the use of sulfur and sulfur compounds is particularly preferable.
Examples of the organic peroxide include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2 , 5-Di-methyl-2,5-di (t-butylperoxy) hexane, 2,5-di-methyl-2,5-di (t-butylperoxy) hexyne, 1,3-bis (t -Butylperoxy-isopropyl) benzene, t-butylperoxy-isopropyl carbonate, acetylcyclohexylsulfonyl peroxide, isobutyl peroxide, di-isopropyl peroxydicarbonate, di-allyl peroxydicarbonate, di-n-propylper Oxydicarbonate, di- (2-ethoxyethyl) peroxydicarbonate, (Methoxyisopropyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-hexylperoxyneohexanate, di (3-methyl-3-methyloxybutyl) peroxydicarbonate, t-butylperoxyneo Decanate, t-hexyl peroxyneodecanate, t-butyl peroxyneohexanate, 2,4-dichlorobenzoyl peroxide, t-hexyl peroxypivalate, t-butyl peroxypivalate, 3, 3, 5-trimethylhexanoyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, cumylperoxyoctate, acetyl peroxide, t-butylperoxy (2-ethylhexanate), benzoyl Oxide, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexane, t-butylperoxymaleic acid, t-butylperoxylaurate, t-butylperoxy3,3 , 5-trimethylhexanate, cyclohexanone peroxide, t-butylperoxyallyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,2-bis (t-butylperoxy) octane , T-butyl peroxyacetate, 2,2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t -Butyl diperoxyisophthalate, methyl ethyl ketone peroxide, α, α'- (T-butylperoxy-m-isopropyl) hexane, di-isopropylbenzene-hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, 2,5-dimethyl Examples include hexane-2,5-dihydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.
Also, sulfur-based vulcanizing agents (sulfur / sulfur compounds) include powdered sulfur, sulfur flower, highly dispersible sulfur, insoluble sulfur, surface-treated sulfur, colloidal sulfur, sulfur chloride, sulfur monochloride, sulfur dichloride. Etc. Examples of the sulfur-containing organic vulcanizing agent include morpholine disulfide, alkylphenol disulfides, thiuram disulfide, N, N′-dithio-bis (hexahydro-2H-azepinone-2), 2- (4′-morpholinodithio) benzothiazole. Etc. Furthermore, examples of the triazine compound include 2,4,6-trimercapto-S-triazine, 2-di-n-butylamino-4,6-dimercapto-S-triazine, and the like. The above vulcanizing agents can be used alone or in combination of two or more.

  The compounding quantity of these vulcanizing agents is 0.1-15 mass parts normally with respect to 100 mass parts of rubber components, Preferably it is 0.5-10 mass parts.

  When an organic peroxide is used as a vulcanizing agent, sulfur, p-quinonedioxime, p-benzoquinonedioxime, p, p'-dibenzoylquinonedi is used in combination with the organic peroxide. Oxime, N-methyl-N'-4-dinitroaniline, N, N'-m-phenylene dimaleimide, dipentamethylene thiuram pentasulfide, dinitrosobenzene, divinylbenzene, triallyl cyanurate, triallyl isocyanurate, triazine Thiol, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triac Rate, erythritol tetramethacrylate, trimethylolpropane trimethacrylate, diallyl melamine, trimethacrylate, dimethacrylate, divinyl adipate, vinyl butyrate, vinyl stearate, liquid polybutadiene rubber, liquid polyisoprene rubber, liquid styrene-butadiene rubber, liquid acrylonitrile Co-crosslinking agents such as butadiene rubber, magnesium diacrylate, calcium diacrylate, aluminum acrylate, zinc acrylate, stannous acrylate, zinc methacrylate, magnesium methacrylate, and zinc dimethacrylate can be blended. These co-crosslinking agents can be used alone or in combination of two or more. The compounding quantity of a co-crosslinking agent is 0.5-20 mass parts normally with respect to 100 mass parts of rubber components.

  Moreover, a vulcanization accelerator can be used when using a sulfur type vulcanizing agent as a vulcanizing agent. Examples of such a vulcanization accelerator include aldehyde ammonia such as hexamethylenetetramine and acetaldehyde / ammonia; n-butyraldehyde-aniline condensate, butyraldehyde-monobutylamine condensate, heptaldehyde-aniline condensation. , Aldehyde amines such as tricrotonylidene and tetramine condensates; guanidine salts such as diphenylguanidine, di-o-tolylguanidine, ortho-tolyl, biguanide, dicatechol, diort, tolyl, and guanidine salts of boric acid; 2-mercaptoimidazoline Imidazolines such as 2-mercaptobenzothiazole, 2-mercaptothiazoline, dibenzothiazyl disulfide, zinc salt of 2-mercaptobenzothiazole, and 2-mercaptobenzothiazole Lithium salt, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthio-carbamoylthio) benzothiazole, 2- (4'-morpholino Dithio) benzothiazole, thiazoles such as 4-morpholino-2-benzotheazyl disulfide; N-cyclohexyl-2-benzothiazole sulfenamide, N, N-dicyclohexyl-2-benzothiazyl sulfenamide, N-oxydiethylene Sulfenamides such as 2-benzothiazyl sulfenamide, N, N-diisopropyl-2-benzothiazyl sulfenamide, Nt-butyl-2-benzothiazyl sulfenamide; thiocarbanide, ethylene thiourea ( 2 Mercaptoimidazoline), diethyl thiourea, dibutyl thiourea, mixed alkyl thiourea, tolyl methyl thiourea, dilauryl thiourea and other thioureas; dimethyl dithiocarbamate sodium, diethyl dithiocarbamate sodium, di-n-butyl carbamine Acid sodium, lead dimethyl dithiocarbamate, lead diamyl dithiocarbamate, zinc diamyl dithiocarbamate, zinc diethyl dithiocarbamate, zinc di-n-butyl dithiocarbamate, zinc dibenzyl dithiocarbamate, N-pentamethylene dithiocarbamate Zinc, zinc ethylphenyl dithiocarbamate, selenium dimethyl dithiocarbamate, selenium diethyl dithiocarbamate, tellurium diethyl dithiocarbamate , Dithiocarbamates such as cadmium diethyl dithiocarbamate, copper dimethyl dithiocarbamate, iron dimethyl dithiocarbamate, bismuth dimethyl dithiocarbamate, piperidine dimethyl dithiocarbamate, pipecoline methylpentamethylene dithiocarbamate, activated dithiocarbamate; Methylthiuram monosulfide, tetramethylthiuram disulfide, active tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N'-dimethyl-N, N'-diphenylthiuram disulfide, dipentamethylene Thiuram disulfide, dipentamethylene thiuram tetrasulfide, mixed alkyl thiuram disulfide, etc. Urams; Zanthates such as sodium isopropyl xanthate, zinc isopropyl xanthate, zinc butyl xanthate; 4,4'-dithiodimorpholine, aminodialkyldithiophosphate, zinc-o, on-butyl-phospho Examples include rosiothioate, 3-mercaptoimidazoline-thione-2, and thioglycolate. These vulcanization accelerators can be used alone or in combination of two or more. The compounding quantity of a vulcanization accelerator is 0.1-20 mass parts normally with respect to 100 mass parts of rubber components, Preferably it is 0.2-10 mass parts.

  Moreover, in addition to the said vulcanizing agent and vulcanization accelerator, a vulcanization | cure acceleration | stimulation adjuvant can also be added as needed. Examples of such vulcanization acceleration aids include magnesium oxide, zinc white, activated zinc white, surface-treated zinc white, zinc carbonate, composite zinc white, composite active zinc white, surface-treated magnesium oxide, calcium hydroxide, and poles. Metal oxides such as fine calcium hydroxide, lead monoxide, risurge, red lead, white lead; organic acids such as stearic acid, oleic acid, lauric acid, zinc stearate, calcium stearate, potassium stearate, sodium stearate ( Salt) and the like, particularly zinc white and stearic acid are preferred. These vulcanization acceleration aids can be used alone or in admixture of two or more. The compounding quantity of a vulcanization | cure acceleration | stimulation adjuvant is 0.5-20 mass parts normally with respect to 100 mass parts of rubber components.

  In addition to the rubber composition of the present invention, an ultraviolet absorber, a light stabilizer, a flame retardant, an antistatic agent, a conductive plasticizer, a liquid rubber, a functional group-containing oligomer, a colorant, an oil resistance improver, a foaming agent, A scorch inhibitor, tackifier, water-removing agent, activator, wax, coupling agent, peptizer, antibacterial agent, foaming aid, processing aid and the like can be blended.

  In preparing a rubber composition using the NBR of the present invention, conventionally known kneaders, extruders, vulcanizers, and the like can be used. Other polymers to be mixed with the NBR of the present invention, a blending method such as a filler, a plasticizer, and a vulcanizing agent, and a blending order are not particularly limited. For example, a modified ethylene copolymer using a Banbury mixer or the like is used. Examples include a method of adding a vulcanizing agent or the like using a roll or the like after mixing rubber, a filler, a softening agent and the like.

In the case where the developing roller and the photosensitive member are used in pressure contact, in order to ensure a uniform nip width at the time of contact and satisfy a suitable set recoverability, the thickness of the elastic layer is Preferably, it is 0.5 mm or more, and more preferably 1.0 mm or more.
The thickness of the elastic body layer is not particularly limited as long as the outer diameter accuracy of the produced elastic roller is not impaired, but generally, if the thickness of the elastic body layer is excessively increased, the production cost of the rubber molded body is reduced. It becomes difficult to keep within the proper range. Considering these practical restrictions, the thickness of the elastic layer is preferably 6.0 mm or less, more preferably 5.0 mm or less. Therefore, the thickness of the elastic layer is desirably selected in the range of 0.5 to 6.0 mm, and more desirably selected in the range of 1.0 to 5.0 mm. The thickness of the elastic body layer is appropriately selected according to the hardness.

  The hardness (Asker-C) of the elastic body layer 12 is selected in the range of 10 to 70 °. When the hardness (Asker-C) is 10 ° or more, appropriate rubber elasticity is obtained, and when it is 70 ° or less, an appropriate nip width can be obtained. More preferably, the hardness (Asker-C) of the rubber molded body forming the elastic layer is desirably selected in the range of 15 to 55 °.

As described above, the coating layer (surface layer) 13 is laminated on the outer peripheral surface of the elastic body layer 12.
In the present invention, the component for forming the coating layer 13 as the surface layer is not particularly limited, but polyamide resin, urethane resin, urea resin, and the like are particularly preferable from the viewpoint of self-film reinforcing property, toner charging property, and the like. Preferably used. From the viewpoint of providing the coating layer 13 with an action of suppressing bleeding such as a polyester plasticizer added to the elastic layer 12, a crosslinked rubber is preferable.

  In particular, in the case of a crosslinked urethane resin, the degree of swelling with toluene at 25 ° C. is preferably in the range of 150% to 300%. If the degree of swelling with toluene at 25 ° C. is 150% by mass or more, the coating layer 13 will not be too hard, and the deformation followability to the elastic layer 12 will be sufficient, and even when subjected to repeated temperature history of cold and heat Since stress does not increase, it is difficult to deteriorate. Moreover, if the swelling degree by 25 degreeC toluene is 300 mass% or less, the effect | action of the bleeding suppression by the coating layer 13 will be acquired. Furthermore, when the degree of swelling of the crosslinked urethane resin with toluene at 25 ° C. is in the range of 190 to 260% by mass, it is excellent in terms of moderate flexibility and bleed suppression, and is more preferable.

  As the urethane resin, for example, carbon black is blended in a polyurethane prepolymer, and the prepolymer is obtained by a crosslinking reaction, or a conductive material is blended in a polyol, and this polyol is polyisocyanate by a one-shot method. What was obtained by the method of making it react with a rice cake is mention | raise | lifted.

  In this case, the polyhydroxyl compound used for obtaining the polyurethane includes polyols used in the production of general flexible polyurethane foams and urethane elastomers, such as polyether polyols having a polyhydroxyl group at the terminal, polyester polyols, and both. In addition to polyether polyester polyols that are polymers, polyolefin polyols such as polybutadiene polyols and polyisoprene polyols, and general polyols such as so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in polyols Can be used.

  In addition, as the isocyanate compound, polyisocyanate similarly used for producing general flexible polyurethane foam and urethane elastomer, that is, tolylene diisocyanate (TDI), crude TDI, 4,4'-diphenylmethane diisocyanate (MDI), crude MDI, aliphatic polyisocyanates having 2 to 18 carbon atoms, alicyclic polyisocyanates having 4 to 15 carbon atoms, and mixtures and modified products of these polyisocyanates such as prepolymers obtained by partially reacting with polyols Used.

  Examples of the urethane resin include one-pack type and two-pack type containing polyisocyanate, and an epoxy resin or a melamine resin may be used as a crosslinking agent as necessary.

  Examples of the polyamide resin include polyamides 6,6,6,6,10,6,12,11,12,12,12, and polyamides obtained by polycondensation between different types of polyamide monomers. From the viewpoint of workability, alcohol-soluble ones are preferably used. For example, those obtained by adjusting the molecular weight of a polyamide terpolymer or quaternary copolymer, or those obtained by methoxymethylating polyamide 6 or polyamide 12 to make them soluble in alcohol or water.

  One or two or more of urethane resin, polyamide resin, and other modified resins can be used in combination, and a toner suitable for the developing system can be selected appropriately according to the developing system. Charge amount can be obtained.

  Furthermore, in order to form the coating layer 13 as a surface layer with good film formability, components necessary for the functions required for the coating layer itself, such as a conductive agent, non-conductive material, are used in accordance with the specific application of the elastic roller. Fillers can be added. Further, various additive components used when forming and laminating the outer periphery of the elastic layer 12, for example, various additives such as a crosslinking agent, a catalyst, and a dispersion accelerator may be appropriately blended in the main resin material. it can. Note that additives such as a conductive agent and a non-conductive filler can be appropriately selected from those exemplified above as additives that can be contained in the elastic layer according to the main resin material. Moreover, the addition amount can be suitably selected according to the addition purpose, as long as the characteristics of the coating layer to be formed are maintained within the range where the effects of the present invention are exhibited.

  The addition amount of the carbon black component is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber forming the coating layer. Unlike the case where the elastic layer 12 is used, the coating layer 13 which is often a thin film can be added in a relatively large amount depending on the type of carbon black and the type of resin (rubber) serving as a base. For example, when a urethane resin is used as a base, it is preferably 15 to 50 parts by mass. Furthermore, it is more preferable that it is 20-40 mass parts. Here, when determining the mass percentage of carbon black, the “resin component” means a urethane resin polyol, diisocyanate, blend with other resins, the resin, its monomer component, curing agent component, crosslinking agent component, etc. The additive itself such as a conductive agent and a non-conductive filler is not included on the basis of the resin itself or a component constituting the resin and a component that is a main component as a film forming component of the coating layer.

  The elastic modulus of the coating layer 13 is not particularly limited as long as the film property and durability are practically obtained. The covering layer 13 is desired to exhibit high followability to deformation of the elastic body layer 12, and therefore, the film body forming the covering layer preferably has a low hardness and elastic modulus.

  The thickness of the covering layer 13 is preferably selected to be 2 μm or more in order to ensure sufficient wear resistance. On the other hand, the developing roller is an elastic roller having conductivity, and in this case, in order to achieve uniform conductivity, the thickness of the coating layer is preferably limited to 100 μm or less. Moreover, if the thickness of the coating layer is 2 μm or more, it is easy to apply and form uniformly on the elastic layer surface with a desired thin film thickness, while the hardness of the coating layer is the hardness of the elastic layer. Even when the thickness is relatively higher than the hardness, it is preferable that the film thickness is 100 μm or less because the influence on the deformability of the entire developing roller is not increased. Further, the thickness of the coating layer may be appropriately selected according to the hardness and the like in the above range. For example, when a urethane resin is used as a base, a film thickness in the range of 5 to 25 μm is more preferable. Within this range, there are many advantages such as high wear resistance, small influence on hardness, and easy provision of the resin layer itself. The thickness of the coating layer of the present invention is determined by measuring the cross section with an optical microscope or the like using a sample cut out from a roller.

  For forming the coating layer 13, it is possible to use a method in which a polymer raw material, which is a raw material of the film body, is applied in the form of liquid or solution to the surface of the elastic body layer, and then the film body is formed. The coating method of the film body material is not particularly limited, but the resin material is uniformly coated on the surface of the elastic layer with a desired thickness by a method such as air spray, roll coating, curtain coating, dipping or the like. Thereafter, in order to obtain a film body, heat treatment may be performed as necessary.

The two-layer developing roller in which the elastic layer 12 and the coating layer 13 are laminated in this order on the shaft core 11 has been described above. The layer structure on the outer periphery of the shaft core in the developing roller according to the present invention is three layers. You may have the above multilayered structure. For example, a developing roller in which another layer is provided between the elastic body layer 12 and the covering layer 13 or a developing roller in which the elastic body layer 12 itself is composed of a plurality of layers can be used. In any configuration, there is no problem as long as the effect of the present invention can be obtained.
The numerical values used in the present invention were measured according to the following method.

<DBP oil absorption>
It was measured in accordance with JISK6217-4.

<Nitrogen specific surface area>
It is measured in accordance with JISK6217-2.

<Mass average molecular weight>
GPC column “TSKgel Super HM-M” (trade name, manufactured by Tosoh Corporation) was used as a solvent, using a high-performance liquid chromatograph analyzer “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) connected in series. Under the measurement conditions of (THF), temperature 40 ° C., flow rate 0.6 ml / min, RI (refractive index) detector, the measurement sample was measured as a 0.1 mass% THF solution. A calibration curve was created using several types of monodisperse standard polystyrene (manufactured by Tosoh Corporation) as a standard sample for creating a calibration curve, and the mass average molecular weight was determined from the retention time of the measurement sample obtained based on this. .

<Swelling degree with toluene>
A film or sheet having a thickness of 50 to 500 μm is cut out as a sample of 5 mm length × 20 mm width and immersed in 50 ml of 25 ° C. toluene. The mass of the sample containing toluene is measured every 24 hours. The sample mass W (g) when the difference between the two measured values measured at intervals of 24 hours becomes 1% or less of the sample mass. The sample is then air-dried, dried at 120 ° C. for 3 hours to remove toluene, and the mass Wo (g)) is measured. At this time, W / Wo (%) was calculated as the degree of swelling. That is, 100% which does not swell at all.

  As described above, the developing roller of the present invention is a developing roller that has low hardness and low resistance and hardly causes contamination of the photoreceptor. Because of this advantage, when used as a developing roller in an electrophotographic apparatus or the like, the photosensitive member is not contaminated, and there is no unevenness of image density and no decrease in density. An image can be obtained.

  FIG. 3 is a cross-sectional view showing a schematic configuration of the developing device and the image forming apparatus used as the developing roller of the present invention.

  In this image forming apparatus, the photosensitive drum 21 as a latent image carrier rotates in the direction of arrow A, and the region of the photosensitive drum 21 that has passed therethrough is uniformly charged by the charging device 22 for charging the photosensitive drum 21. Is done. Further, in this charged region, an electrostatic latent image is formed on the surface by laser light 23 which is an exposure means for writing the electrostatic latent image. The electrostatic latent image is provided close to the photosensitive drum 21 and is given toner as a developer by the developing device 2 held in a process cartridge 24 (not shown) that is detachable from the image forming apparatus main body. The toner image is developed and visualized as a toner image.

  For development, a method such as so-called reversal development in which a toner image is formed on the exposed portion can be used. The visualized toner image (image) on the photosensitive drum 21 is transferred onto a transfer paper 33 such as paper by a transfer roller 29. The paper 33 to which the toner image has been transferred is subjected to a fixing process by the fixing device 32, discharged outside the device, and the printing operation is completed. The transfer roller 33 is configured to press the transfer paper 33 from the back surface to the area holding the toner image on the photosensitive drum 21 to transfer the toner image onto the surface of the transfer paper. The transfer roller 33 is an area holding the toner image on the photosensitive drum. On the contrary, the toner image transfer is promoted by being charged. The transfer sheet 33 is pressed against the surface of the photosensitive drum 21 by automatically inserting the transfer sheet 33 into a portion where the photosensitive drum 21 and the transfer roller 29 are in contact with each other. Achieved.

  On the other hand, the untransferred toner remaining on the photosensitive drum 21 without being transferred is scraped off by the cleaning blade 30 and stored in the waste toner container 31, and the above process is repeated on the cleaned photosensitive drum 21. The same image can be copied or a new image can be transferred.

  In the example shown in the figure, the developing device 2 is located opposite to the developing device 34 containing a non-magnetic toner 28 as a one-component developer and the photosensitive drum 21 located in an opening extending in the longitudinal direction in the developing container 34. And a developing roller 25 as a developer carrier, and the electrostatic latent image on the photosensitive drum 21 is developed and visualized.

  The developing roller 25 is in contact with the photosensitive drum 21 with a contact width. In the developing device 2, the auxiliary roller 26 having elasticity is brought into contact with the abutting portion of the elastic blade 27 with the surface of the developing roller 25 in the developing container 34, and rotates upstream of the developing roller 25 in the rotation direction. Supported as possible. As the structure of the auxiliary roller 26, a foamed skeleton-like sponge structure or a fur brush structure in which fibers such as rayon or nylon are planted on a cored bar is used for supplying the toner 28 to the developing roller 25 and stripping off the undeveloped toner. It is preferable from the point. In the present embodiment, an auxiliary roller 26 having a diameter of 16 mm, in which polyurethane foam is provided on the shaft core, is used.

  An effective contact width of the auxiliary roller 26 with respect to the developing roller 25 is 1 to 8 mm, and it is preferable that the developing roller 25 has a relative speed at the contact portion. In this embodiment, the contact width is set to 3 mm, and the driving means (not shown) is set so that the peripheral speed of the auxiliary roller 26 is 50 mm / s during development operation (the relative speed with respect to the developing roller 25 is 130 mm / s). To rotate at a predetermined timing.

  Hereinafter, the present invention will be described more specifically with reference to examples. Here, a description will be given of a developing roller having two layers on the outer peripheral surface of the shaft core as described above. These examples are examples of the best mode of the present invention, but the present invention is not limited to the examples. The developing roller produced by the method shown in the embodiment can be suitably used as a developing roller used in an electrophotographic apparatus or the like in its application.

[Example 1] Developing roller 1
An adhesive (primer) applied and baked on the outer peripheral surface of a SUS metal core (φ8 mm) subjected to nickel plating as a shaft core was used.
NBR "JSR N230H" (trade name, manufactured by JSR Corporation) [hereinafter referred to as rubber A] 100 parts by mass, zinc oxide 5 parts by mass, stearic acid 2 parts by mass, calcium carbonate 30 parts by mass, 2-mercaptobenzimidazole (MB ) 0.5 parts by mass, carbon black “Toka Black # 7360SB” (trade name, manufactured by Tokai Carbon Co., Ltd.) [hereinafter referred to as carbon black I] 60 parts by mass, polyester plasticizer “Polysizer W-4000” (trade name) 80 parts by mass (hereinafter referred to as “plasticizer P”) were kneaded for 10 minutes in a closed mixer adjusted to 50 ° C. to prepare a raw material compound.

  In this raw material compound, 1.2 parts by mass of dispersible sulfur “Sulfax 200S” (trade name, manufactured by Tsurumi Chemical Co., Ltd., purity: 99.5%) with respect to the rubber component (100 parts by mass of rubber A in Example 1). 1 part by weight of di-2-benzothiazolyl disulfide “Noxeller DM” (trade name, manufactured by Ouchi Shinsei Chemical), dipentamethylene thiuram tetrasulfide “Noxeller TRA” (trade name, manufactured by Ouchi Shinsei Chemical) 1 part by mass, 0.5 parts by mass of tetramethylthiuram monosulfide “Noxeller TS” (trade name, manufactured by Ouchi Shinsei Chemical Co., Ltd.) are added and kneaded for 10 minutes in a two-roll mill cooled to 20 ° C. A compound for an elastic layer was obtained.

  This elastic compound is formed into a tube shape by extrusion molding, primary vulcanization is performed by steam vulcanization at 130 ° C. for 30 minutes, further secondary vulcanization is performed by electric furnace at 140 ° C. for 30 minutes, and a rubber tube is formed. Obtained. After this tube was cut, a SUS metal core (φ8 mm) with nickel plating as a shaft core body was press-fitted, and the surface was polished to obtain an elastic roller of φ16 mm.

  Next, the solid content of the isocyanate “Coronate L” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curing agent is 10 mass relative to the solid content of 100 parts by weight of the polyol “Nipporan 5033” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.). 22 parts by mass of carbon black “MA11” (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) as a conductive agent, using methyl ethyl ketone as a main solvent, sufficiently stirred, and an organic solvent mixed solution having a uniform solid content of 11% It adjusted so that it might become. The elastic roller is immersed in this coating solution for coating, and then pulled up, dried, and heat-treated at 145 ° C. for 30 minutes, whereby a surface layer having a thickness of about 20 μm (hereinafter referred to as coating layer V). A developing roller 1 was prepared on the outer periphery of the elastic layer.

[Example 2] Developing roller 2
The developing roller 2 is the same as in Example 1 except that the rubber component used in the elastic layer is changed to NBR “JSR N224SH” (trade name, manufactured by JSR) (hereinafter referred to as “rubber B”) to 100 parts by mass. Was made.

[Example 3] Developing roller 3
The developing roller 3 is the same as in Example 1 except that the rubber component used for the elastic layer is changed to NBR “JSR N222L” (trade name, manufactured by JSR) (hereinafter referred to as “Rubber C”) to 100 parts by mass. Was made.

[Embodiment 4] Developing roller 4
The developing roller was the same as in Example 1 except that the rubber component used for the elastic layer was changed to NBR “Nipol DN002” (trade name, manufactured by Nippon Zeon Co., Ltd.) (hereinafter referred to as “Rubber D”) to 100 parts by mass. 4 was produced.

[Embodiment 5] Developing roller 5
The rubber component used for the elastic layer was NBR “Nipol DN003” (trade name, manufactured by Nippon Zeon Co., Ltd.) [hereinafter referred to as rubber E] 85 parts by mass, epichlorohydrin rubber “Epichromer H” (trade name, manufactured by Daiso Corporation) [ Hereinafter, referred to as rubber H] A developing roller 5 was produced in the same manner as in Example 1 except that the mixture was 15 parts by mass.

[Embodiment 6] Developing roller 6
As a rubber component used for the elastic layer, rubber C is 100 parts by mass, carbon black is “Toka Black # 7350” (trade name, manufactured by Tokai Carbon Co., Ltd.) (hereinafter referred to as “carbon black J”), and an addition amount is 40. A developing roller 6 was produced in the same manner as in Example 1 except that the mass part was changed.

[Embodiment 7] Developing roller 7
As a rubber component used for the elastic layer, rubber B is 100 parts by mass, carbon black is “Raven 820” (trade name, manufactured by Columbian Chemicals Company) (hereinafter referred to as carbon black K), and an addition amount is 40 parts by mass. A developing roller 7 was produced in the same manner as in Example 1 except that the change was made.

[Eighth Embodiment] Developing Roller 8
The developing roller 8 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber C, carbon black, and 35 parts by mass of carbon black K.

[Embodiment 9] Developing roller 9
The developing roller 9 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber D, carbon black, and 30 parts by mass of carbon black K.

[Embodiment 10] Developing roller 10
The rubber component used for the elastic layer is the same as in Example 1 except that the rubber C is 100 parts by mass, the amount of carbon black I added is changed to 15 parts by mass, and the amount of plasticizer P added is changed to 30 parts by mass. Thus, the developing roller 10 was produced.

[Embodiment 11] Developing roller 11
The developing roller 11 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber C and the addition amount of carbon black I was changed to 75 parts by mass.

[Embodiment 12] Developing roller 12
The rubber component used for the elastic layer is changed to 100 parts by mass of rubber C, and the plasticizer is changed to a polyester plasticizer "Polysizer W-2300" (trade name, manufactured by Dainippon Ink Co., Ltd.) [hereinafter referred to as plasticizer Q]. The developing roller 12 was produced in the same manner as in Example 1 except that the addition amount was 50 parts by mass.

[Embodiment 13] Developing roller 13
The rubber component used in the elastic layer is 100 parts by mass of rubber C, the addition amount of carbon black I is changed to 35 parts by mass, and the plasticizer is a polyester plasticizer "Polysizer P-202" (trade name, Dainippon Ink The developing roller 13 was produced in the same manner as in Example 1 except that the addition amount was changed to 70 parts by mass.

[Embodiment 14] Developing roller 14
The rubber component used for the elastic layer was the same as in Example 1 except that the rubber C was 100 parts by mass, the amount of carbon black I added was changed to 15 parts by mass, and the amount of plasticizer P added was 20 parts by mass. Thus, the developing roller 14 was produced.

[Embodiment 15] Developing roller 15
The rubber component used for the elastic layer was the same as in Example 1 except that the rubber C was 100 parts by mass, the amount of carbon black I was changed to 75 parts by mass, and the amount of plasticizer P was 90 parts by mass. Thus, the developing roller 15 was produced.

[Embodiment 16] Developing roller 16
The rubber component used for the elastic layer was developed in the same manner as in Example 1 except that the rubber C was 100 parts by mass, the plasticizer was changed to the polyester plasticizer “plasticizer S”, and the addition amount was 80 parts by mass. A roller 16 was produced.
The plasticizer S is condensed using azelaic acid as a polybasic acid component, 1,5-pentanediol as a polyhydric alcohol component, and terminated using octanol as a terminal termination component, and has a mass average molecular weight. What produced 6000 thing was used.

[Embodiment 17] Developing roller 17
The same raw material compound as in Example 1 was prepared, and “Perhexine 25B-40” (trade name, product name manufactured by NOF Corporation; 40% product) 7.5 with respect to the rubber content (100 parts by mass of rubber A) 7.5 3 parts by mass, triallyl isocyanurate “TAIC” (trade name, manufactured by Nippon Kasei Co., Ltd.) is added and kneaded for 10 minutes in a two-roll machine cooled to 20 ° C. to obtain a compound for an elastic layer. It was. A developing roller 17 was produced in the same manner as in Example 1 except that this elastic compound was used.

[Embodiment 18] Developing roller 18
As a surface layer, 22 parts by mass of carbon black “MA11” (trade name, manufactured by Mitsubishi Chemical Corporation) as a conductive agent is added to 100 parts by mass of alcohol-soluble polyamide resin “Amilan CM8000” (trade name, manufactured by Toray Industries, Inc.) Methanol was used as the main solvent, and the mixture was sufficiently stirred to prepare a uniform organic solvent mixed solution having a solid content of 18%. The elastic roller is immersed in this coating solution for coating, and then pulled up, dried, and heat treated at 85 ° C. for 30 minutes, so that a surface layer of about 15 μm (hereinafter referred to as coating layer W) is elastic. A developing roller 18 was produced in the same manner as in Example 1 except that it was provided on the outer periphery of the body layer.

[Embodiment 19] Developing roller 19
As a surface layer, 22 parts by mass of carbon black “MA11” (trade name, manufactured by Mitsubishi Chemical Corporation) as a conductive agent is added to 100 parts by mass of a solid content of polyol “Nipporan 5230” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.). Then, methyl ethyl ketone was used as a main solvent, and the mixture was sufficiently stirred to prepare a mixed organic solvent solution having a uniform solid content of 10%. The elastic roller is immersed and coated in this coating solution, and then pulled up, dried, and heat-treated at 130 ° C. for 30 minutes, whereby a surface layer having a thickness of about 20 μm (hereinafter referred to as coating layer X). A developing roller 19 was produced in the same manner as in Example 1 except that was provided on the outer periphery of the elastic layer.

[Embodiment 20] Developing roller 20
As a surface layer, solid content 4 of isocyanate “Coronate L” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curing agent with respect to 100 parts by mass of solid content of polyol “Nipporan 5196” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.). 22 parts by mass of carbon black “MA11” (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) as a conductive agent is added, and the mixture is stirred thoroughly and mixed with an organic solvent having a uniform solid content of 10%. It adjusted so that it might become a solution. The elastic roller is immersed in this coating solution for coating, and then pulled up, dried, and heat-treated at 145 ° C. for 30 minutes, so that an approximately 18 μm surface layer (hereinafter referred to as coating layer Y) is elastic. A developing roller 20 was produced in the same manner as in Example 1 except that it was provided on the outer periphery of the body layer.

[Example 21] Developing roller 21
As a surface layer, solid content 6 of isocyanate “Coronate L” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curing agent with respect to 100 parts by mass of solid content of polyol “Nipporan 5025” (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.). 22 parts by mass of carbon black “MA11” (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) as a conductive agent is added, and the mixture is stirred thoroughly and mixed with an organic solvent having a uniform solid content of 12%. It adjusted so that it might become a solution. The elastic roller is dipped and coated in this coating solution, and then pulled up, dried, and heat-treated at 145 ° C. for 30 minutes, whereby a surface layer having a thickness of about 20 μm (hereinafter referred to as coating layer Z). The developing roller 21 was produced in the same manner as in Example 1 except that was provided on the outer periphery of the elastic layer.

[Comparative Example 1] Developing roller 22
The developing roller was the same as in Example 1 except that the rubber component used in the elastic layer was changed to NBR “Nipol DN401” (trade name, manufactured by Nippon Zeon Co., Ltd.) (hereinafter referred to as “Rubber F”) to 100 parts by mass. 22 was produced.

[Comparative Example 2] Developing roller 23
The developing roller was the same as in Example 1 except that the rubber component used for the elastic layer was changed to NBR “Nipol 1043” (trade name, manufactured by Nippon Zeon Co., Ltd.) [hereinafter referred to as “Rubber F”] to 100 parts by mass. 23 was produced.

[Comparative Example 3] Developing roller 24
A developing roller 24 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was a mixture of 50 parts by mass of rubber E and 50 parts by mass of rubber H.

[Comparative Example 4] Developing roller 25
As a rubber component used in the elastic layer, rubber C is changed to 100 parts by mass, and carbon black is changed to “# 45L” (trade name, manufactured by Mitsubishi Chemical Corporation) [hereinafter referred to as carbon black L], and the addition amount is 75. A developing roller 25 was produced in the same manner as in Example 1 except that the mass part was changed.
[Comparative Example 5] Developing roller 26
As a rubber component used for the elastic layer, rubber C is changed to 100 parts by mass, and carbon black is changed to “# 44” (trade name, manufactured by Mitsubishi Chemical Corporation) (hereinafter referred to as carbon black M). A developing roller 26 was produced in the same manner as in Example 1 except that the mass part was changed.

[Comparative Example 6] Developing roller 27
As the rubber component used for the elastic layer, the rubber C is changed to 100 parts by mass, and the carbon black is changed to “Vulcan XC72” (trade name, manufactured by Cabot Specialty Chemicals, Inc.) (hereinafter referred to as carbon black N). A developing roller 27 was produced in the same manner as in Example 1 except that the addition amount was changed to 20 parts by mass.

[Comparative Example 7] Developing roller 28
The rubber component used in the elastic layer is changed to 100 parts by mass of rubber C and the carbon black is changed to “Ketjen Black EC” (trade name, manufactured by Ketjen Black International) (hereinafter referred to as “Carbon Black O”). The developing roller 28 was produced in the same manner as in Example 1 except that the addition amount was changed to 20 parts by mass.

[Comparative Example 8] Developing roller 29
A developing roller 29 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber C and the addition amount of carbon black I was changed to 8 parts by mass.

[Comparative Example 9] Developing roller 30
The developing roller 30 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber C and the addition amount of carbon black I was changed to 90 parts by mass.

[Comparative Example 10] Developing roller 31
The rubber component used in the elastic layer is changed to 100 parts by mass of rubber C, and the plasticizer is changed to an epoxy plasticizer “Eposizer W-109EL” (trade name, manufactured by Dainippon Ink Co., Ltd.) [hereinafter referred to as plasticizer T]. Then, the developing roller 31 was produced in the same manner as in Example 1 except that the addition amount was 80 parts by mass.

[Comparative Example 11] Developing roller 32
The rubber component used for the elastic layer is changed to 100 parts by mass of rubber C, and the plasticizer is changed to a polyester plasticizer “Polysizer W-1600” (trade name, manufactured by Dainippon Ink Co., Ltd.) [hereinafter referred to as plasticizer U]. The developing roller 32 was produced in the same manner as in Example 1 except that the addition amount was 50 parts by mass.

[Comparative Example 12] Developing roller 33
The developing roller 33 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was 100 parts by mass of rubber C and no plasticizer P was added.

[Comparative Example 13] Developing roller 34
The developing roller 34 was produced in the same manner as in Example 1 except that the rubber component used in the elastic layer was changed to 100 parts by mass of rubber C and the addition amount of the plasticizer P was changed to 120 parts by mass.

[Comparative Example 14] Developing roller 35
The developing roller 35 is produced in the same manner as in Example 1 except that the rubber component used in the elastic layer is 100 parts by mass of rubber C, the plasticizer is changed to plasticizer Q, and the addition amount is changed to 20 parts by mass. did.

[Comparative Example 15] Developing roller 36
As a rubber component used for the elastic layer, the rubber C is 100 parts by mass, the addition amount of the carbon black I is changed to 30 parts by mass, the plasticizer is changed to the plasticizer Q, and the addition amount is 80 parts by mass. A developing roller 36 was prepared in the same manner as in Example 1.
The amounts of acrylonitrile of rubbers A to G are shown in Table 1. The rubber H is epichlorohydrin rubber and does not contain acrylonitrile.

  Table 2 shows the DBP oil absorption (referred to as D), nitrogen specific surface area (referred to as N), and D / N values of carbon blacks I to O.

Table 3 shows the weight average molecular weights of the plasticizers P to S and U and the main components of the repeating units.
The plasticizer T is not a polyester plasticizer.

Table 4 shows the values of the degree of swelling of the coating layers V, Y, and Z with toluene. The covering layers W and X are not cross-linked and dissolve when immersed in toluene.
Table 5 shows combinations of elastic layers and coating layers of the developing rollers 1 to 36 corresponding to Examples 1 to 21 and Comparative Examples 1 to 15.

  The following evaluations were performed on the created developing rollers 1 to 36.

[Characteristic evaluation]
<Hardness (nip width)>
Using a 300 mm long semi-cylindrical glass with a curved surface equivalent to Φ30 mm, a nip width when the developing roller shaft core is pressed against a curved surface equivalent to Φ30 mm with a load of 500 g (1 kg total) on one side The nip state was observed with a microscope from the opposite side and evaluated.
◎: Nip width of 0.8 mm or more even at the developing roller central portion ◯: Nip width of 0.7 mm or more and less than 0.8 mm at the developing roller central portion Δ: Nip width of 0.5 mm or more and less than 0.7 mm at the developing roller central portion Width x: Nip width of less than 0.5 mm at the center of the developing roller.

<Electrical resistance>
A load of 500 g on each side is applied to the shaft core of the developing roller and brought into contact with a 30 mm diameter SUS cylinder, and the cylinder is rotated at a rotation speed such that the roller makes one rotation per second. 100 V DC was applied to the entire apparatus, and the roller resistance was calculated and evaluated from the voltage applied to the reference resistance 10 kΩ at that time.
◎: 1 × 10 ⁶ or less of roller resistance 〇: 1 × 10 ⁶ ultra to 1 × 10 ⁸ or less of roller resistance △: 1 × 10 ⁸ super to 1 × 10 ¹⁰ or less of the roller resistance ×: 1 × ¹⁰ 10 more than Roller resistance.

<Bleed>
A developing roller is incorporated in the cartridge and left in an environmental tester at room temperature of 35 ° C. and relative humidity of 85% RH for 14 days. Then, the cartridge is disassembled in an environment of room temperature of 25 ° C. and relative humidity of 50% RH, and the surface of the photoconductor is removed. The presence or absence of adhesion to the surface and the presence or absence of bleeding on the surface of the developing roller were visually observed.
A: There is no adhesion on the surface of the photoreceptor, and there is no bleed on the surface of the developing roller.
○: There is no adhesion on the surface of the photoreceptor, but slight bleeding is observed on the surface of the developing roller.
Δ: There is no adhesion on the surface of the photoreceptor, but bleeding is observed on the surface of the developing roller.
X: Adhesion on the surface of the photoreceptor is observed.

  As an image forming apparatus, an organic photoreceptor digital printer “LBP5500” (trade name, manufactured by Canon Inc.) using a laser beam was prepared. This “LBP5500” (trade name) is a tandem type color printer that includes four toner color cartridges, each of which is provided with image writing means (laser beam), and a transfer belt. The standard image creation capability is 17 sheets / minute for A4 size.

  The cartridge has a photosensitive drum, a charging roller as a charging unit (a Kapton (trademark) sheet is provided in contact with the photosensitive drum for cleaning the charging roller), and a developing roller as a developing unit. Further, a supply roller for supplying toner to the developing roller and scraping the return toner that has not been used for forming the toner image remaining on the developing roller to frictionally charge the toner is provided. A developer regulating blade is provided in contact with the developing roller to make the amount of the toner constant and apply frictional charging (corresponding to the one-component contact developing system). The developing roller is in contact with the photosensitive drum.

  Further, the cartridge is provided with a cleaning blade that comes into contact with the photosensitive drum and wipes off toner remaining on the photosensitive drum, transfer material waste, etc. on the photosensitive drum to remove the charge remaining on the photosensitive drum before charging by the charging roller. Pre-exposure means is provided.

  The apparatus was processed so that the output speed of LBP5500 (trade name) was increased to 22 sheets / minute of A4 paper, and the developing rollers 1 to 36 produced in this example and the comparative example were incorporated as developing rollers of the cyan color cartridge, respectively. . Further, each of the magenta, yellow, and black cartridges was placed in each station with the toner extracted and the toner remaining amount detection mechanism disabled.

(Image evaluation)
Using the image forming apparatus modified as described above, the standard chart (FIG. 4) was continuously output (500 sheets per day) and output to a predetermined number of sheets according to the following evaluation items. For the transfer material, the LETTER-sized plain paper “XEROX 4024 paper” (trade name) was output as a solid image on the 10th and 6010th sheets, and as a halftone image on the 11th sheet.
The 6010th image is output on the 10th image on the 13th day.

<Initial concentration>
Using a reflection densitometer RD918 (manufactured by Macbeth) for a solid image (tenth image) whose entire image area is uniform, measure the density of the solid black portion when solid printing is performed, and average the image density. It was.
A: The average value is 1.20 or more. O: The average value is 1.15 or more and less than 1.20. Δ: The average value is 1.10 or more and less than 1.20 ×: The average value is less than 1.10.

<Durability concentration>
Using a reflection densitometer RD918 (manufactured by Macbeth) for a solid image (6010th sheet) with a uniform image area as a whole, measure the density of the solid black portion at the time of solid printing, and average the image density. It was.
A: The average value is 1.20 or more. O: The average value is 1.15 or more and less than 1.20. Δ: The average value is 1.10 or more and less than 1.20 ×: The average value is less than 1.10.

<Initial density unevenness>
The shade unevenness appearing in the image obtained by the solid image (10th image) and the halftone image (11th image) where the entire image area is uniform is visually observed by five inspectors, and the following criteria are evaluated. I got it. Then, the evaluation results of five inspectors were ranked, and the median value (third evaluation) was set as the evaluation for the sample.
A: The shading unevenness is inconspicuous and good for both solid images and halftone images.
◯: Light and shade unevenness is slightly noticeable in a solid image but at a level that does not cause a problem. In a halftone image, it is not noticeable and good.
(Triangle | delta): Although a shading unevenness is seen a little with a solid image and a halftone image, it is a level which is satisfactory.
X: Density unevenness is observed in both solid images and halftone images. In solid images, white spots are conspicuous due to insufficient nip width in the center, and the impression is poor.

<Comprehensive evaluation>
The results of the above evaluations (hardness, electrical resistance, bleed, initial concentration, durability concentration, initial concentration unevenness) were integrated and evaluated comprehensively according to the following criteria.
◎: Items with ◎: ○: Electrical resistance, initial concentration is ◯ or more, hardness, bleed is △ or more, endurance concentration, initial density unevenness is △ or more, and one is over △: Other than endurance concentration Table 5 shows the results of evaluation based on the above criteria.
As shown in Table 6, Examples 1-21 gave good results, and Examples 3 and 4 showed particularly good results.

It is a figure which shows typically an example of the whole structure of the developing roller of this invention. It is sectional drawing which shows typically the two-layer structure of a roller layer in the developing roller of this invention. It is sectional drawing of FIG. It is explanatory drawing of the image forming apparatus using the developing device of this invention. It is a standard chart used for evaluation of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Developing roller 2 ... Developing apparatus 3 ... Image forming apparatus 11 ... Shaft core body 12 ... Elastic body layer (base layer)
13 ... Coating layer (surface layer)
21 ... Photosensitive drum 22 ... Charging roller 23 ... Laser beam 24 ... Process cartridge (not shown)
25 ... developing roller 26 ... auxiliary roller 27 ... elastic blade 28 ... toner 29 ... transfer roller 30 ... cleaning blade 31 ... waste toner container 32 ... fixing device 33 ... paper 34 ... developing container

Claims (9)

In a developing roller having an axial core body and an elastic layer and a coating layer sequentially formed on the outer peripheral surface of the axial core body, the elastic layer contains at least raw rubber, carbon black, and a polyester plasticizer, and the raw rubber Among them, acrylonitrile butadiene rubber having an acrylonitrile amount of 31% by mass or more and 60% by mass or less is contained in an amount of 80% by mass or more and 100% by mass or less with respect to the raw rubber, and the carbon black is 10 parts by mass or more with respect to 100 parts by mass of the raw rubber. 80 parts by mass or less, and the carbon black has a DBP oil absorption of 80 ml / 100 g or more and 140 ml / 100 g or less, and the elastic layer contains a polyester plasticizer in an amount of 20 parts by mass or more and 90 parts by mass with respect to 100 parts by mass of the raw rubber. Part or less, the weight average molecular weight of the polyester plasticizer is in the range of 2000 or more and 12000 or less, and Developing roller and satisfies the equation (1).
0.010 ≦ Fp / (Fc × D) ≦ 0.025 (1)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
Fc: The number of parts (parts by mass) of carbon black added to the raw rubber in the elastic layer
Fp: The number of added parts of the polyester plasticizer to the raw rubber in the elastic layer (parts by mass)
However, DBP is dibutyl phthalate (the same applies hereinafter). 2. The developing roller according to claim 1, wherein the amount of acrylonitrile of the acrylonitrile butadiene rubber in the elastic layer is from 36% by mass to 55% by mass with respect to the raw rubber. The polyester plasticizer of the elastic layer contains at least one structural unit represented by the following chemical formula (1), chemical formula (2), and chemical formula (3). Development roller.
—CO— (CH ₂ ) ₄ —CO— Chemical Formula (1)
—CO— (CH ₂ ) ₇ —CO— Chemical Formula (2)
—CO— (CH ₂ ) ₈ —CO— Chemical Formula (3) The developing roller according to claim 1, wherein a mass average molecular weight of the polyester plasticizer of the elastic layer is in a range of 3500 or more and 10,000 or less. The developing roller according to claim 1, wherein the rubber of the elastic layer is crosslinked with sulfur. 6. The developing roller according to claim 1, wherein the carbon black contained in the rubber of the elastic layer satisfies the following formula (2).
0.005 ≦ D / N ≦ 0.014 (2)
D: DBP oil absorption of carbon black in the elastic layer (ml / 100 g)
N: Nitrogen specific surface area of carbon black in the elastic layer (m ² / g)
However, the unit of D / N is ml / m ² The developing roller according to any one of claims 1 to 6, wherein the coating layer is a crosslinked urethane rubber, and the 25 ° C toluene swelling degree of the crosslinked urethane rubber is 150% by mass or more and 300% by mass or less. . A developing roller that carries a developer in a state of being opposed to the latent image carrier on which an electrostatic latent image is formed, and the developer roller applies the developer to the latent image carrier, thereby developing the latent image into the developer; 8. A developing device for visualizing an image, wherein the developing device is any one of the developing rollers according to claim 1. A latent image carrier on which an electrostatic latent image is formed by electrophotography, a charging device for charging the latent image carrier with a charge amount necessary for forming the electrostatic latent image, An image having an electrostatic latent image forming device for forming a latent image, a developing device for attaching a developer to the electrostatic latent image for visualization, and a transfer device for transferring an image made of the developer onto transfer paper A forming device,
The developing device holds the developer carried on the surface of the latent image carrier on which the electrostatic latent image is formed in a state where the developer is carried in a state of being opposed to or pressed against the surface of the latent image carrier. A developing roller for supplying an electrostatic latent image to visualize the electrostatic latent image, wherein the developing roller is the developing roller according to claim 1. Image forming apparatus.

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