JP4966581B2 - Developing roller and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a developing roller and an image forming apparatus provided with the developing roller, and in particular, is excellent in compression set performance and toner fusing resistance when used for a long time in a high-temperature and high-humidity environment, and a good image can be obtained. The present invention relates to a developing roller and an image forming apparatus including the developing roller and capable of forming a good image.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, as a developing method for visualizing a latent image by supplying toner to a photosensitive drum holding a latent image and attaching the toner to the latent image on the photosensitive drum. A pressure development method is known. In the pressure development method, for example, after the photosensitive drum is charged to a constant potential, an electrostatic latent image is formed on the photosensitive drum by an exposure machine, and further, a developing roller carrying toner is placed on the electrostatic latent image. Development is performed by bringing the toner into contact with the latent image on the photosensitive drum in contact with the held photosensitive drum.

  In the above pressure development method, the developing roller must rotate while securely holding the photosensitive drum, so that polyurethane, silicone rubber, acrylonitrile is placed on the outer periphery of the shaft made of a highly conductive material such as metal. -Semiconductive elastic body in which carbon black or metal powder is dispersed in an elastomer such as butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), or a foam obtained by foaming these. It has a structure in which a semiconductive elastic layer made of is formed. In some cases, a surface coating layer is further formed on the surface of the elastic layer for the purpose of controlling the chargeability and adhesion to the toner and preventing the photosensitive drum from being contaminated by the elastic layer.

  On the other hand, in recent years, with the increase in color, high speed, high image quality, and energy saving of image forming apparatuses, the number of image forming apparatuses using low-melting toner is increasing. Here, when using a low-melting toner, the low-melting toner is damaged by repeated compression or friction between the components, and the toner is aggregated and fused, and thus, such as fogging. Image defects are likely to occur. That is, since the toner deteriorates at the end of the life of the toner cartridge and the chargeability becomes non-uniform, there is a problem that an image defect occurs or the life is shortened. Therefore, there is a demand for a developing roller having a low hardness that hardly damages the toner. For example, a developing roller (Patent Document 1) in which a base material (elastic layer) is softened or adipic acid ester compound is blended as a plasticizer. A developing roller having a soft coating film (surface coating layer) is known (Patent Document 2).

JP 2003-15404 A JP 2005-128067 A

  However, since materials with low hardness tend to have large compression set, conventionally it has been very difficult to balance both hardness and compression set sufficiently low. In addition, when a coating film containing an adipate ester compound as a plasticizer is used, the coating film becomes soft, but the compression set performance is poor, and after leaving it in a high temperature and high humidity environment while being in contact with the photosensitive drum. When the image is printed, the contact mark is generated, and in addition, there are problems such as causing toner fusion when used for a long time in a high temperature and high humidity environment, and causing vertical streaks on the image. It was.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and particularly excellent in compression set performance and toner fusing resistance when used for a long time in a high-temperature and high-humidity environment, and a good image can be obtained. It is to provide a developing roller. Another object of the present invention is to provide an image forming apparatus provided with such a developing roller and capable of forming a good image.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have developed an elastic layer and a surface coating layer formed on the elastic layer. By using a urethane resin in which a lactone-modified polyol is crosslinked with two or more polyisocyanates containing at least isophorone diisocyanate for the surface coating layer, the hardness and compression set of the developing roller are sufficiently reduced, and the toner is deteriorated. In addition to making it difficult, the toner fusing resistance can be improved when used for a long time in a high-temperature and high-humidity environment, and a good image can be stably formed by incorporating the developing roller. As a result, the present invention has been completed.

That is, the developing roller of the present invention is a developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, and a surface coating layer formed on the outer peripheral surface of the elastic layer.
The elastic layer is made of foam;
The surface coating layer includes a urethane resin obtained by crosslinking a lactone-modified polyol with two or more kinds of polyisocyanates including at least isophorone diisocyanate.

  In a preferred embodiment of the developing roller of the present invention, the foam is made of polyurethane.

  In another preferred embodiment of the developing roller of the present invention, the bubbles of the foam are closed cells.

  In another preferred embodiment of the developing roller of the present invention, the two or more kinds of polyisocyanates are isophorone diisocyanate and hexamethylene diisocyanate.

  In another preferred embodiment of the developing roller of the present invention, the molar ratio of the isophorone diisocyanate to the hexamethylene diisocyanate is 3: 1 to 1: 3.

  In another preferred embodiment of the developing roller of the present invention, an intermediate layer is formed between the elastic layer and the surface coating layer.

  The image forming apparatus of the present invention includes the developing roller.

  According to the present invention, there is provided a developing roller that does not contaminate the photosensitive drum, does not deteriorate the toner, has a small compression set, and is excellent in toner fusing resistance when used for a long time in a high temperature and high humidity environment. There is an advantageous effect of being able to. Further, there is an advantageous effect that it is possible to provide an image forming apparatus that includes the developing roller and can form a good image.

<Developing roller>
Hereinafter, the developing roller of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the developing roller of the present invention. The developing roller 1 in the illustrated example includes a shaft 2, an elastic layer 3 formed on the outer periphery of the shaft 2, and a surface coating layer 4 formed on the outer peripheral surface of the elastic layer 3. In the figure, the surface coating layer 4 is composed of one layer, but the surface coating layer 4 of the developing roller of the present invention may be composed of two or more layers. In the developing roller of the present invention, since the surface coating layer 4 is disposed on the outer peripheral surface of the elastic layer 3, it is possible to sufficiently prevent the contaminants oozing out from the elastic layer 3 from contaminating the photosensitive drum. it can.

  In the developing roller of the present invention, the elastic layer 3 is made of a foam, and the surface coating layer 4 includes a urethane resin in which a lactone-modified polyol is crosslinked with two or more kinds of polyisocyanates including at least isophorone diisocyanate. And Since the elastic layer 3 is made of a foam, the compression set performance can be improved, and delamination with the surface coating layer 4 hardly occurs during use. As a result, the durability of the developing roller itself can be reduced. It can be improved. In addition, since the surface coating layer 4 contains the urethane resin, the hardness of the developing roller is reduced and the toner is not damaged, and further, the compression set of the developing roller is reduced, and the high temperature and high humidity environment is achieved. The toner fusing resistance at the time of long-time use is improved, and a good image can be formed.

  The shaft 2 of the developing roller of the present invention is not particularly limited as long as it has good electrical conductivity. For example, a metal core made of a metal such as iron, stainless steel, or aluminum, or a hollow interior is hollowed out. A metal shaft such as a metal cylinder or a highly conductive plastic shaft can be used.

The elastic layer 3 of the developing roller of the present invention is made of a foam and can contain other components such as a conductive agent as necessary. An elastomer can be used to form the foam. Examples of the elastomer include polyurethane, silicone rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber, and styrene-butadiene rubber (SBR). Butadiene rubber, isoprene rubber, polynorbornene rubber, butyl rubber, chloroprene rubber, acrylic rubber, epichlorohydrin rubber (ECO), ethylene-vinyl acetate copolymer (EVA), and mixtures thereof. Among these, Polyurethane is preferred because it is made of the same urethane as the surface coating layer 4 containing the urethane resin, and therefore has better adhesion to the surface coating layer. The foam constituting the elastic layer 3 can be formed by chemically foaming the elastomer using a foaming agent, or mechanically entraining and foaming air like a polyurethane foam. Here, in the foam constituting the elastic layer 3, the expansion ratio is preferably 1.5 to 50 times, and the density is preferably 0.05 to 0.9 g / cm ³ .

  Moreover, it is suitable that the bubble in this foam is a closed cell from the point which the compression set performance improves by making the bubble of the foam which comprises the said elastic layer 3 into a closed cell. Here, in order to make the bubbles of the foam into closed cells, a technique in which the above-mentioned elastomer raw material is foamed by mechanical stirring is suitably employed.

  Examples of the conductive agent that can be used for the elastic layer 3 include an electronic conductive agent and an ionic conductive agent. Electronic conductive agents include conductive carbon such as ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, and carbon black for color subjected to oxidation treatment. , Pyrolytic carbon black, natural graphite, artificial graphite, antimony-doped tin oxide, ITO, tin oxide, titanium oxide, zinc oxide and other metal oxides, nickel, copper, silver, germanium and other metals, polyaniline, polypyrrole, polyacetylene, etc. Conductive whiskers such as conductive polymer, carbon whisker, graphite whisker, titanium carbide whisker, conductive potassium titanate whisker, conductive barium titanate whisker, conductive titanium oxide whisker, and conductive zinc oxide whisker. The blending amount of the electronic conductive agent is preferably in the range of 1 to 50 parts by mass, more preferably in the range of 5 to 40 parts by mass with respect to 100 parts by mass of the elastomer.

  Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium, perchlorate, chlorate, hydrochloride, bromate, and the like. Ammonium salts such as salts, iodates, borofluorides, sulfates, ethyl sulfates, carboxylates, sulfonates; alkaline metals such as lithium, sodium, potassium, calcium, magnesium, alkaline earth metals Examples include perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, trifluoromethyl sulfate, and sulfonate. The compounding amount of the ionic conductive agent is preferably in the range of 0.01 to 10 parts by mass, more preferably in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the elastomer. The said electrically conductive agent may be used individually by 1 type, may be used in combination of 2 or more type, and may combine an electronic conductive agent and an ionic conductive agent.

The elastic layer 3 preferably has a resistance value of 10 ³ to 10 ¹⁰ Ωcm, more preferably 10 ⁴ to 10 ⁸ Ωcm, depending on the blending of the conductive agent. If the resistance value of the elastic layer 3 is less than 10 ³ Ωcm, electric charges may leak to the photosensitive drum or the developing roller itself may be damaged by voltage, and if it exceeds 10 ¹⁰ Ωcm, ground fog is likely to occur.

  The elastic layer 3 may contain a crosslinking agent such as an organic peroxide and a vulcanizing agent such as sulfur in order to make the elastomer into a rubbery material as necessary. Sulfur accelerators, vulcanization accelerators, vulcanization retarders, and the like may be included. The elastic layer 3 is further used for rubber such as a filler, a peptizer, a foaming agent, a plasticizer, a softener, a tackifier, an anti-tacking agent, a separating agent, a release agent, an extender, and a coloring agent. You may contain a compounding agent.

  The surface coating layer 4 of the developing roller of the present invention mainly contains a urethane resin obtained by crosslinking a lactone-modified polyol with two or more kinds of polyisocyanates containing at least isophorone diisocyanate, and optionally contains other components such as a conductive agent. . The lactone-modified polyol can be produced by modifying the end of the polyol with a lactone such as ε-caprolactone, and a commercially available product can also be used. From the viewpoint of achieving both compression set performance and toner fusing resistance, the lactone-modified polyol may have a polystyrene-equivalent number average molecular weight (Mn) of 1000 to 5000 as measured by gel permeation chromatography. The molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) in terms of polystyrene and the number average molecular weight (Mn) measured by gel permeation chromatography is more preferable. Is preferably 2.5 or less, and more preferably 2.0 or less.

  Examples of the polyol modified with the lactone include polyether polyols obtained by addition polymerization of alkylene oxide such as ethylene oxide and propylene oxide to glycerin, polytetramethylene glycol, glycerin, ethylene glycol, propylene glycol, butanediol, pentanediol, and hexane. Examples include diol, octanediol, polybutadiene polyol, polyisoprene polyol, and polyester polyol.

  The polyisocyanate that crosslinks the lactone-modified polyol is two or more types of polyisocyanates containing at least isophorone diisocyanate. By using isophorone diisocyanate, the toner fusing resistance during long-term use of the developing roller is improved. it can. Among the above two or more types of polyisocyanates, polyisocyanates other than isophorone diisocyanate (IPDI) include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), hydrogenated diphenylmethane diisocyanate, hydrogenated triphenyl isocyanate. Examples include diisocyanate, hexamethylene diisocyanate (HDI), and nurate-modified hexamethylene diisocyanate. From the viewpoint of achieving both low hardness of the surface coating layer and compression set performance, the two or more types of polyisocyanates used for crosslinking the lactone-modified polyol are preferably isophorone diisocyanate and hexamethylene diisocyanate, The molar ratio of diisocyanate to hexamethylene diisocyanate is preferably 3: 1 to 1: 3.

  The surface coating layer 4 can further contain a catalyst for promoting a crosslinking reaction between the lactone-modified polyol and the two or more types of polyisocyanates. Examples of the catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate; organic lead compounds such as lead octenoate; triethylamine, Monoamines such as dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine, tetramethylhexanediamine; triamines such as pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetramethylguanidine; triethylenediamine, dimethylpiperazine, Cyclic amines such as methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine, dimethylimidazole Alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine, and hydroxyethylmorpholine; ether amines such as bis (dimethylaminoethyl) ether and ethylene glycol bis (dimethyl) aminopropyl ether And the like. Of these catalysts, organotin compounds are preferred. These catalysts may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the lactone-modified polyol.

The surface coating layer 4 can be blended with a conductive agent for the purpose of controlling its conductivity, and examples of the conductive agent are the same as those exemplified as the conductive agent used for the elastic layer 3. can do. Here, in the case of an ionic conductive agent, the blending amount of the conductive agent in the surface coating layer 4 is preferably 20 parts by mass or less, and 0.01 to 20 parts by mass with respect to 100 parts by mass of the urethane resin constituting the surface coating layer 4. In the case of an electronic conductive agent, the range of 1 to 70 parts by mass with respect to 100 parts by mass of the urethane resin constituting the surface coating layer 4 is more preferable. Is preferable, and the range of 5 to 50 parts by mass is more preferable. The surface coating layer 4 is preferably adjusted to have a volume resistance in the range of 10 ³ to 10 ¹⁰ Ω · cm by adding the conductive agent, and in the range of 10 ⁴ to 10 ⁸ Ω · cm. It is more preferable to adjust so that it becomes.

  The surface coating layer 4 is preferably blended with fine particles from the viewpoint of controlling toner transportability. Examples of the fine particles include crosslinked particles such as urethane particles, acrylic particles, silicone particles, polyamide particles, and fluorine particles. Here, the compounding amount of the fine particles in the surface coating layer 4 is preferably in the range of 5 to 40 parts by mass, more preferably in the range of 7 to 30 parts by mass with respect to 100 parts by mass of the lactone-modified polyol constituting the surface coating layer 4.

  The thickness of the surface coating layer 4 is not particularly limited, but is preferably 30 μm or less, and more preferably in the range of 1 to 15 μm. If the thickness of the surface coating layer 4 exceeds 30 μm, the surface coating layer 4 may become hard and the flexibility may be impaired, and durability may be reduced, cracking may occur due to use, or toner may be damaged. There is a possibility that the toner adheres to the photosensitive drum or the stratified blade, resulting in an image defect.

  The method for forming the surface coating layer 4 is not particularly limited. A coating material containing each component constituting the surface coating layer 4 is prepared, and the coating material is applied by a dipping method, a spray method, or a roll coating method. A drying method is preferably used.

  In the illustrated developing roller 1, the surface coating layer 4 is disposed on the elastic layer 3, but an intermediate layer may be formed between the elastic layer 3 and the surface coating layer 4. By forming such an intermediate layer, for example, the intermediate coating layer can be made softer than the surface coating layer, and damage to the toner can be greatly improved.

  As for the surface roughness of the developing roller of the present invention, the JIS 10-point average roughness (Rz) is preferably 10 μm or less. When the JIS 10-point average roughness (Rz) of the developing roller exceeds 10 μm, the toner conveyance amount tends to increase, but the toner charge amount is insufficient, causing background fogging and poor gradation in the image. .

The resistance value of the developing roller of the present invention is not particularly limited, but in order to obtain a good image, the electric resistance is preferably 10 ³ to 10 ¹⁰ Ω, and 10 ⁴ to 10 ⁸ Ω. Is more preferable. If the resistance value of the developing roller is less than 10 ³ Ω, gradation control is extremely difficult, and bias leakage may occur if the photosensitive drum is defective. On the other hand, if the resistance value exceeds 10 ¹⁰ Ω, for example, when developing toner on a photosensitive drum, the developing bias causes a voltage drop due to the high resistance of the developing roller itself, and a sufficient developing bias for development cannot be secured. Thus, a sufficient image density cannot be obtained. The resistance value is measured, for example, by pressing the outer peripheral surface of the developing roller against a flat plate or cylindrical counter electrode with a predetermined pressure, applying a voltage of 100 V between the shaft and the counter electrode, and obtaining from the current value at that time. be able to. In this way, by appropriately and uniformly controlling the resistance value of the developing roller, the electric field strength for moving the toner can be kept appropriate and uniform.

  The developing roller of the present invention preferably has an Asker C hardness of 60 ° or less. If it is a low-hardness developing roller with Asker C hardness of 60 ° or less, the toner will be damaged between the developing roller and the photosensitive drum, blade, toner supply roller and the like when incorporated in the image forming apparatus. And a sufficiently good image can be formed.

<Image forming apparatus>
The image forming apparatus of the present invention includes the above-described developing roller that does not contaminate the photosensitive drum, does not deteriorate the toner, and has a small compression set, and does not cause image defects such as fogging. A good image can be formed stably. The image forming apparatus of the present invention is not particularly limited except that the developing roller is used, and can be manufactured by a known method.

  The image forming apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a partial cross-sectional view of an example of the image forming apparatus of the present invention. The image forming apparatus of the illustrated example includes a toner supply roller 6 for supplying toner 5, a photosensitive drum 7 that holds an electrostatic latent image, and the above-described toner disposed between the toner supply roller 6 and the photosensitive drum 7. The developing roller 1, the stratified blade 8 provided in the vicinity of the developing roller 1 (upper part in the figure), the charging roller 9 located in the vicinity of the photosensitive drum 7 (upper in the figure), and the vicinity of the photosensitive drum 7 (in the figure) A transfer roller 10 positioned on the lower side and a cleaning unit 11 provided adjacent to the photosensitive drum 7. The image forming apparatus of the present invention can further include a known component (not shown) that is usually used in the image layer forming apparatus.

  In the image forming apparatus of the illustrated example, after the photosensitive drum 7 is charged to a constant potential by the charging roller 9, an electrostatic latent image is formed on the photosensitive drum 7 by an exposure machine (not shown). Next, the toner supply roller 6, the developing roller 1, and the photosensitive drum 7 rotate in the direction of the arrow in the drawing, so that the toner 5 on the toner supply roller 6 is sent to the photosensitive drum 7 through the developing roller 1. It is done. The toner 5 on the developing roller 1 is adjusted to a uniform thin layer by the stratifying blade 8, and the toner 5 is transferred from the developing roller 1 to the photosensitive drum 7 by rotating while the developing roller 1 and the photosensitive drum 7 are in contact with each other. It adheres to the electrostatic latent image and the latent image becomes visible. The toner 5 attached to the latent image is transferred onto a recording medium such as paper by the transfer roller 10, and the toner 5 remaining on the photosensitive drum 7 after the transfer is removed by the cleaning blade 12 of the cleaning unit 11. Here, in the image forming apparatus of the present invention, the developing roller 1 does not contaminate the above-described photosensitive drum, does not deteriorate the toner, has a small compression set, and is used for a long time in a high temperature and high humidity environment. By using the developing roller of the present invention having excellent toner fusing resistance at the time, it is possible to stably form a good image.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Production of roller body)
100 parts by mass of urethane prepolymer synthesized from tolylene diisocyanate (TDI) and polyether polyol and 2 parts by mass of acetylene black are mixed to prepare a urethane prepolymer in which acetylene black is dispersed. did. On the other hand, 30 parts by mass of polyether polyol and 0.1 part by mass of sodium perchlorate (NaClO ₄ ) were mixed while heating to 70 ° C., and 4.5 parts by mass of polyether-modified silicone oil (foam stabilizer), dibutyltin dilaurate (Catalyst) 0.2 parts by mass was mixed to prepare a mixture, which was used as component B. Next, the A component and the B component are foamed by a mechanical floss method, and further injected into a cylindrical mold set with a core metal, and a roller body having an elastic layer made of foamed polyurethane is formed by RIM molding. Produced.

Example 1
Lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 30 parts by mass, urethane particles (manufactured by Negami Kogyo, trade name: Art Pearl C800, average particle size 8.8 μm) ) 10 parts by mass are dispersed in 480 parts by mass of methyl ethyl ketone (MEK), and then 33 parts by mass of isophorone diisocyanate nurate trimer (Degussa Huls, product name: Bestanat T1890E, NCO% = 12%) and hexamethylene 15 parts by mass of a diisocyanate trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) was added, and the mixture was stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. The obtained coating material was applied to the outer periphery of a roller main body having an elastic layer made of urethane foam to form a surface coating layer, thereby producing a developing roller.

(Example 2)
Lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 30 parts by mass, acrylic particles (manufactured by Soken Chemicals, trade name: MX1000, average particle size 10.0 μm) 10 Parts by weight of methyl ethyl ketone (MEK) 473 parts by mass, and then isophorone diisocyanate nurate trimer (Degussa Huls, trade name: Bestanat T1890E, NCO% = 12%) and hexamethylene diisocyanate A trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) 8 parts by mass was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 3)
Lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 30 parts by mass, urethane particles (manufactured by Negami Kogyo, trade name: Art Pearl C800, average particle size 8.8 μm) ) 10 parts by mass in 485 parts by mass of methyl ethyl ketone (MEK), and then 19 parts by mass of isophorone diisocyanate nurate trimer (manufactured by Degussa Huls, trade name: Vestanate T1890E, NCO% = 12%) and hexamethylene 17 parts by weight of a diisocyanate trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) was added and stirred for 30 minutes with a stirring motor to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

Example 4
A lactone-modified polyol (Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass and carbon black 30 parts by mass are dispersed in 490 parts by mass of methyl ethyl ketone (MEK), and then a nurate trimer of isophorone diisocyanate. (Degussa Huls, product name: Vestanate T1890E, NCO% = 12%) 33 parts by mass and hexamethylene diisocyanate trimer (product name: Coronate Hx, NCO% = 21%) 15 parts by mass The mixture was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 5)
100 parts by mass of a lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH number 56) and 30 parts by mass of carbon black are dispersed in 483 parts by mass of methyl ethyl ketone (MEK), and then a nurate trimer of isophorone diisocyanate. (Degussa Huls, trade name: Vestanate T1890E, NCO% = 12%) 52 parts by weight and hexamethylene diisocyanate trimer (Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) 8 parts by weight The mixture was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 6)
A lactone-modified polyol (Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass and carbon black 30 parts by mass are dispersed in methyl ethyl ketone (MEK) 495 parts by mass, and then isophorone diisocyanate nurate trimer. (Degussa Huls, trade name: Bestanat T1890E, NCO% = 12%) 19 parts by weight and hexamethylene diisocyanate trimer (Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) 17 parts by weight The mixture was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material obtained in this way instead of the coating material of Example 1.

(Example 7)
Lactone modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 15 parts by mass, urethane particles (manufactured by Negami Kogyo, trade name: Art Pearl C800, average particle size 8.8 μm) ) 10 parts by mass are dispersed in 495 parts by mass of methyl ethyl ketone (MEK), and then 33 parts by mass of isophorone diisocyanate nurate trimer (Degussa Huls, trade name: Bestanat T1890E, NCO% = 12%) and hexamethylene 15 parts by mass of a diisocyanate trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) was added, and the mixture was stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 8)
Lactone modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH number 56) 100 parts by mass, carbon black 45 parts by mass, urethane particles (manufactured by Dainippon Ink & Chemicals, trade name: Vernock CFB101-40, average grain) 10 parts by mass of 14 μm in diameter) are dispersed in 465 parts by mass of methyl ethyl ketone (MEK), and then 33 parts by mass of isophorone diisocyanate nurate trimer (manufactured by Degussa Huls, trade name: Bestanat T1890E, NCO% = 12%) 15 parts by mass of hexamethylene diisocyanate trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%) was added, and the mixture was stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

Example 9
100 parts by mass of a lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH number 56) and 15 parts by mass of carbon black are dispersed in 505 parts by mass of methyl ethyl ketone (MEK), and then a nurate trimer of isophorone diisocyanate. (Degussa Huls, product name: Vestanate T1890E, NCO% = 12%) 33 parts by mass and hexamethylene diisocyanate trimer (product name: Coronate Hx, NCO% = 21%) 15 parts by mass The mixture was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 10)
A lactone-modified polyol (Daicel Chemical Industries, trade name: PCL220AL, OH number 56) 100 parts by mass and carbon black 45 parts by mass are dispersed in 475 parts by mass of methyl ethyl ketone (MEK), and then an isophorone diisocyanate nurate trimer. (Degussa Huls, product name: Vestanate T1890E, NCO% = 12%) 33 parts by mass and hexamethylene diisocyanate trimer (product name: Coronate Hx, NCO% = 21%) 15 parts by mass The mixture was added and stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Example 11)
A urethane emulsion paint (produced by Daiichi Kogyo Seiyaku Co., Ltd., prototype E4000) is applied as an intermediate layer to the outer periphery of the roller body having the elastic layer made of the urethane foam, and then the paint of Example 1 is applied. Thus, a developing roller was produced.

(Comparative Example 1)
Lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 30 parts by mass, urethane particles (manufactured by Negami Kogyo, trade name: Art Pearl C800, average particle size 8.8 μm) ) 10 parts by mass are dispersed in 460 parts by mass of methyl ethyl ketone (MEK), and then 65 parts by mass of isophorone diisocyanate nurate trimer (manufactured by Degussa Huls, trade name: Bestanat T1890E, NCO% = 12%) is added. The mixture was stirred with a stirring motor for 30 minutes to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

(Comparative Example 2)
Lactone-modified polyol (manufactured by Daicel Chemical Industries, trade name: PCL220AL, OH value 56) 100 parts by mass, carbon black 30 parts by mass, urethane particles (manufactured by Negami Kogyo, trade name: Art Pearl C800, average particle size 8.8 μm) ) 10 parts by mass is dispersed in 500 parts by mass of methyl ethyl ketone (MEK), and then 30 parts by mass of hexamethylene diisocyanate trimer (manufactured by Nippon Polyurethane, trade name: Coronate Hx, NCO% = 21%), The mixture was stirred for 30 minutes with a stirring motor to prepare a coating material for surface coating. A developing roller was produced using the coating material thus obtained in place of the coating material of Example 1.

  Various physical properties and image characteristics of the developing rollers of Examples and Comparative Examples were measured by the following methods. The results of evaluation of each example and comparative example are shown in Table 1.

(1) Surface hardness The surface hardness of the developing roller of each Example and Comparative Example was measured using a micro rubber hardness meter MD-1 (manufactured by Kobunshi Keiki Co., Ltd.).

(2) Roller resistance The roller resistance of each Example and the comparative example was calculated | required as follows. That is, the outer peripheral surface of the developing roller was pressed against a cylindrical counter electrode with a pressure of 1 kg, a voltage of 100 V was applied between the shaft and the counter electrode, and the current value was obtained.

(3) Surface roughness JIS 10-point average roughness (Rz) of each Example and Comparative Example was evaluated based on JIS B0601.

(4) Contamination of photosensitive drum The developing roller of each Example and Comparative Example was pressed against the photosensitive drum with a load of 1 kg and left under high temperature and high humidity of 40 ° C. and 95% RH. The image was taken out after a predetermined period (one week), the developing roller was assembled into an actual machine, an image was taken out, and the image of the developing roller and the contact portion was judged according to the following criteria. Circle: No photosensitive drum contamination was observed, Triangle: Photosensitive drum contamination was slightly observed, x: Bleed and photosensitive drum contamination was observed.

(5) Appearance (painting team)
The appearance of the developing roller of each Example and Comparative Example was visually determined based on the following criteria. Circle: No unevenness (no image unevenness), Triangle: Some unevenness (no image unevenness), x: Unevenness (with image unevenness)

(6) Image Density The developing roller of each Example and Comparative Example is incorporated in a cartridge, and is in a low temperature and low humidity (LL) environment (15 ° C., 10% RH), in a high temperature and high humidity (HH) environment (30 ° C., 80% RH) ), Continuous image formation with a printing rate of 2% was performed using a color LBP4600 manufactured by Hewlett-Packard Co., and solid images and halftone images were formed initially and after printing 5000 sheets. The solid image and the halftone image were visually judged according to the following criteria. Circle: no density unevenness, triangle: some density unevenness, x: density unevenness

(7) Compression set A test similar to the photosensitive drum contamination was performed. After the test, the developing roller was taken out, and the developing roller was assembled into an actual machine to form an image. The image of the developing roller and the contact portion was judged according to the following criteria. Circle: No contact mark with the photosensitive drum, Triangle: Some contact mark with the photosensitive drum, ×: Clear contact mark with the photosensitive drum.

(8) Fog resistance During the printing of a solid white image, the printer was forcibly stopped, and the amount of toner flying to the photosensitive drum in the white background portion was measured by density comparison by tape transfer (measured with a Macbeth densitometer). Circle: less than 0.15, triangle: 0.15 to 0.20, x: 0.20 or more.

(9) Toner fusing resistance The surface of the developing roller of each example and comparative example was covered with toner, and the toner was assembled in a cartridge and allowed to stand at 40 ° C. and 95% RH for 1 week, and then imaged. Double circle: No adhesion of toner on the surface of the developing roller even when 10,000 sheets were used. Circle: An adhesion of toner on the surface of the developing roller from 6000 to 9000 sheets. Triangle: 2000. From 1 to 5000 sheets, toner adheres to the surface of the developing roller, and x: Toner adheres to the surface of the developing roller up to 1000 sheets.

  As is clear from Table 1, the developing roller of the embodiment according to the present invention does not contaminate the photosensitive drum, and since the compression set is small, there is no pressure contact mark of the blade, and the damage to the toner is small. Since the toner fusing resistance was excellent, a good image could be stably formed.

It is sectional drawing of an example of the developing roller of this invention. 1 is a partial cross-sectional view of an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing roller 2 Shaft 3 Elastic layer 4 Surface coating layer 5 Toner 6 Toner supply roller 7 Photosensitive drum 8 Layering blade 9 Charging roller 10 Transfer roller 11 Cleaning part 12 Cleaning blade

Claims (9)

In a developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, and a surface coating layer formed on the outer peripheral surface of the elastic layer,
The elastic layer is made of foam;
The developing roller, wherein the surface coating layer includes a urethane resin obtained by crosslinking a lactone-modified polyol with two or more kinds of polyisocyanates including at least isophorone diisocyanate.   The developing roller according to claim 1, wherein the foam is made of polyurethane.   The developing roller according to claim 1, wherein the bubbles of the foam are closed cells.   2. The developing roller according to claim 1, wherein the two or more types of polyisocyanates are isophorone diisocyanate and hexamethylene diisocyanate.   The developing roller according to claim 4, wherein a molar ratio of the isophorone diisocyanate to the hexamethylene diisocyanate is 3: 1 to 1: 3.   The developing roller according to claim 1, wherein the surface coating layer further contains a conductive agent.   7. The developing roller according to claim 1, wherein the surface coating layer further contains fine particles.   The developing roller according to claim 1, wherein an intermediate layer is formed between the elastic layer and the surface coating layer.   An image forming apparatus comprising the developing roller according to claim 1.

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