JP6143703B2 - Conductive roller, developing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a conductive roller, a developing device, and an image forming apparatus. More specifically, the present invention contributes to forming a high-quality image with high density and no white spots, and has a low environmental load and a developing device. The present invention also relates to an image forming apparatus that contributes to environmental protection and can form a high-quality image with high density and no white spots.

  Various image forming apparatuses using an electrophotographic system are employed in printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof. An image forming apparatus using an electrophotographic system includes various types of rollers. As such a roller, for example, a conductive roller having conductivity or semi-conductivity such as a developing roller that carries and conveys the developer and supplies the developer to the image carrier, and a developer supply roller that supplies the developer while charging the developer. Sex rollers. This conductive roller is usually provided with a coating layer as the outermost layer, for example, in order to improve the charging property to the developer, the carrying property, and the like.

  For example, Patent Document 1 discloses that an oil-free alkyd resin and a melamine resin are provided on a surface portion of a conductive layer provided on a developing roller in order to reliably obtain a high-quality image by suppressing the occurrence of other image defects such as ground cover. It is described to contain. Patent Document 2 discloses an oil-free alkyd resin, a melamine resin, and an epoxy resin in a semiconductive resin layer provided on a developing roller in order to obtain a good image that does not cause image defects such as image fogging, image unevenness, and ghost. It is described to contain.

  Patent Document 3 discloses that the conductive resin layer is a coating film of a mixture of a specific polyurethane-based binder resin and a specific conductive filler, so that the developing roller having a urethane coat layer has light resistance, In addition to satisfying both environmental properties and polymer solution stability, it is also excellent in physical properties such as high elongation, surface physical properties such as surface friction fastness, flex resistance, etc. It is described that a volume specific resistance value that is stable against changes in temperature and humidity is maintained.

Japanese Patent Application Laid-Open No. 10-115979 JP 2002-014534 A Japanese Patent No. 2801724

  The developing roller of Patent Document 1 obtains a high-quality image by preventing leakage due to charge accumulation on the roller surface, and the charge amount tends to be suppressed. In addition, the developing roller of Patent Document 2 obtains a good image by improving the charging performance, but the charging performance is not sufficient, and there is room for improving the environmental uniformity in addition to the charging performance. . In particular, when these developing rollers are used together with a negatively charged developer, the charge amount and its environmental uniformity tend to be insufficient. As a result, the image density is lowered, or a developer unfixed portion (also referred to as a white portion) is generated. The environmental uniformity is an index indicating that the variation in charge amount is small in each environment of normal temperature, high temperature and high humidity, and low temperature and low humidity.

  In order to synthesize a specific polyurethane-based binder resin used in the developing roller described in Patent Document 3, stannous chloride, stannic chloride, tetra-n-butyltin, tri-n-butyltin acetate, n- Tin catalysts such as butyltin trichloride, trimethyltin hydroxide, dimethyltin dichloride, dibutyltin acetate, dibutyltin dilaurate and tin octenoate are preferably used, and these tin catalysts remain. Although the amount of tin catalyst used is not large, from the viewpoint of environmental protection in recent years, a conductive roller that avoids the use of tin catalyst and does not contain tin is desired.

  However, urethane resins and polyester polyols synthesized without using a tin catalyst have a new problem that the curing rate is slow, the reaction is insufficient, and the polymer solution stability is insufficient. Accordingly, there is a need for a urethane-based coating material for a roller that can be rapidly cured without using a tin catalyst.

It is an object of the present invention to provide a conductive roller and a developing device with a low environmental load that contribute to forming a high-quality image with a high density and no unfixed portion of the developer.
It is another object of the present invention to provide an image forming apparatus that contributes to environmental protection and can form a high-quality image with a high density and no unfixed portion of the developer.

  The present inventor has examined various materials for forming a coating layer from the viewpoint of density of an image formed by an image forming apparatus and occurrence of white spots, and uses a reaction product of alkyd polyol, polyisocyanate, and melamine resin. Even though the environmental load can be reduced without using a tin catalyst that causes the above-mentioned new problems, the coat layer has a uniform and large charge amount on the entire surface, and is excellent as a coating layer forming material. It was found that it can be replaced with a urethane resin that exhibits its characteristics. Based on these findings, the present inventor has further researched and made the present invention.

The object of the present invention has been achieved by the following means.
(1) A conductive roller comprising a reaction layer of alkyd polyol, polyisocyanate and melamine resin, and having a tin-free coating layer as an outermost layer.
(2) The conductive roller according to (1), wherein the melamine resin is contained in an amount of 3 to 60 parts by mass with respect to a total of 100 parts by mass of the alkyd polyol and the polyisocyanate.
(3) The conductive roller according to (1) or (2), wherein the alkyd polyol has a weight average molecular weight of 3000 to 4000.
(4) The conductive roller according to any one of (1) to (3), wherein the coat layer has a dynamic hardness of 0.2 to 15 N / mm ² .
(5) A developing device comprising the conductive roller according to any one of (1) to (4) and a developer as a developing roller.
(6) An image forming apparatus comprising: an image carrier; and the conductive roller according to any one of (1) to (4) as a developing roller arranged in non-contact with the image carrier.

  In the present invention, “tin-free” means that tin (including a tin compound) is not substantially contained, and does not exclude even unavoidable inclusion. Preferably, the tin content in the coat layer is 1000 ppm or less.

The conductive roller of the present invention and the development device of the present invention including the conductive roller can contribute to forming a high-quality image having a low environmental load and high density and no white spots.
In addition, the image forming apparatus of the present invention includes the conductive roller of the present invention, which contributes to environmental protection and can form a high-quality image with a high density and no developer unfixed portion.

FIG. 1 is a front view showing an example of the conductive roller of the present invention. In FIG. 1, the thickness of the coat layer is exaggerated. FIG. 2 is a schematic view showing an example of the developing device of the present invention and the image forming apparatus of the present invention.

An example of the conductive roller of the present invention will be described.
The conductive roller 1 which is an example of the conductive roller of the present invention includes a shaft body 2 and a coating layer 3 as shown in FIG. If this electroconductive roller 1 is provided with the coat layer 3, another structure will not be specifically limited. For example, the conductive roller of the present invention may have an intermediate layer such as an adhesive layer, a primer layer, and an elastic layer disposed between the shaft body and the coat layer.

  The conductive roller 1 is positively charged with respect to the developer. The larger the charge amount of the conductive roller 1, the higher the density and the image without white spots can be formed, preferably 10 nC or more, more preferably 10 to 180 nC.

The charge amount of the conductive roller 1 can be measured as follows. That is, using a test piece made of stainless steel (SUS) subjected to the same surface treatment as that of the conductive roller, a cascade type charge measuring device “TS-100A” (at a temperature of 23 ° C. and a relative humidity of 50%) ( Measure the amount of charge using the product name, manufactured by Toshiba Chemical Corporation.
This measuring device is a contact charge amount measuring device that uses a spherical reference contact powder, is poured from a hopper onto a 60-degree inclined plate (sample plate), and is received in a metal container on an insulating plate. This instrument can measure with high accuracy and detect extremely slight changes in the chemical composition of the solid surface with the same sensitivity as ESCA (Electron Spectroscopy for Chemical Analysis, a type of electron spectroscopy that analyzes solid surface and chemical bonding state). can do. For the measurement of the charge amount, spherical ferrite powder (particle size 100 μm) whose surface was treated with a silicone resin as a reference contact powder, and a SUS plate (100 × 75 × 0. 5 mm) coated with alkyd urethane resin with a film thickness of 20 μm. The pouring time is 5 seconds, and each measurement is performed three times on the same sample plate, taking care that the powder flows to a new part of the sample surface, and this average value is measured on the surface of the coated resin (conductive roller 1). Contact charge amount.

  The shaft body 2 is basically the same as the shaft body in a conventionally known conductive roller. The shaft body 2 is a so-called “core metal” composed of iron, aluminum, stainless steel, brass, or the like, and has good conductive characteristics. The shaft body 2 may be made conductive by plating an insulating core body such as a thermoplastic resin or a thermosetting resin. Further, the shaft body 2 may be solid or hollow, and a hollow structure is adopted in order to reduce the weight.

The coat layer 3 is disposed on the outer peripheral surface of the shaft body 2 via an adhesive layer or a primer layer. This coat layer 3 is formed by curing a urethane composition to be described later on the outer peripheral surface of the shaft body 2 and contains a reaction product of alkyd polyol, polyisocyanate and melamine resin, and does not contain tin.
When the coating layer 3 does not contain tin, the disposal of the conductive roller 1 after use is easy, and tin is not eluted from the conductive roller 1 and can sufficiently meet the demand for environmental protection. .

  The coat layer 3 contains a reaction product of alkyd polyol, polyisocyanate, and melamine resin. By containing this reaction product, the above-mentioned new problem due to tin does not occur, and the charge amount is uniform over the entire surface, and the environmental uniformity is also good. As a result, a substantially uniform predetermined amount of developer, particularly a negatively charged developer, can be carried and transported over the entire surface of the coat layer 3. Therefore, the density of the formed image can be set to a predetermined density or a preset density, and a high-quality image with almost no white spots can be formed.

The reaction product may be any product obtained by reacting the above-described components, and various low molecular compounds, oligomers, or high molecular compounds may be mentioned. Examples of such a reaction product include a copolymer of an alkyd polyurethane composed of an alkyd polyol and a polyisocyanate and a melamine resin.
The coating layer 3 only needs to contain the above-described reactant, and in addition to the reactant obtained by reacting all three of alkyd polyol, polyisocyanate, and melamine resin, at least two of alkyd polyol, polyisocyanate, and melamine resin. May contain what reacted, and may contain unreacted alkyd polyol, polyisocyanate, and melamine resin individually, respectively. The alkyd polyol, polyisocyanate and melamine resin will be described later.

The content of the reactant in the solid content of the coat layer 3 is not particularly limited as long as it is an amount capable of forming the coat layer 3 having a predetermined layer thickness. The content is preferably at least mass%, more preferably at least 75 mass%.
The melamine resin contained in the coat layer 3 is preferably 3 to 60 parts by mass, more preferably 5 to 50 parts by mass, and still more preferably 10 to 50 parts by mass with respect to 100 parts by mass in total of the alkyd polyol and the polyisocyanate. When the content of the melamine resin is within the above range, the coat layer 3 exhibits a large charge amount and appropriate flexibility, and can greatly contribute to the formation of a higher quality image.

  The coat layer 3 preferably contains a conductivity imparting agent. Examples of the conductivity imparting agent include “conductivity imparting agent” described in JP-A-2008-070420, such as carbon black. The conductivity imparting agent is preferably 1 to 15 parts by mass, particularly preferably 2 to 12 parts by mass with respect to 100 parts by mass in total of the alkyd polyol, polyisocyanate and melamine resin.

  The coat layer 3 preferably further contains an ionic liquid. Examples of the ionic liquid include pyridinium ionic liquid, phosphonium ionic liquid, quaternary amine ionic liquid, and the like. The ionic liquid is preferably 0.1 to 12 parts by mass, particularly preferably 1 to 6 parts by mass with respect to 100 parts by mass in total of the alkyd polyol, polyisocyanate and melamine resin.

  The coat layer 3 may contain various additives in addition to the above-described reactants, preferably a conductivity imparting agent and an ionic liquid. Examples of the additives include chain extenders, catalysts, surfactants, flame retardants, colorants, fillers, plasticizers, stabilizers and mold release agents, and additives described in JP-A-2008-070420. It is done. An additive is contained in the range of content which does not impair the objective of this invention.

The coating layer 3 is resistant to cracks and has excellent durability and can be conveyed without damaging the developer to contribute to high-quality image formation. The dynamic hardness is 0.2 to 15 N / mm. ² is preferable, and 0.5 to 5 N / mm ² is particularly preferable. Dynamic hardness is the value which measured the test piece produced using the urethane composition mentioned later which forms the coat layer 3 by "DUH-211S" (brand name, Shimadzu Corporation make).

  The coat layer 3 preferably has a layer thickness of 1 to 30 μm. As will be described later, when the coat layer 3 itself exhibits elasticity, the coat layer may be a thin layer, and may be set to a layer thickness of 2 to 20 μm, for example.

The coat layer 3 develops elasticity and is flexible, and even if no elastic layer or the like having a buffer function is provided between the shaft body 2 and the coat layer 3, the developer can be prevented from being destroyed. Therefore, the conductive roller of the present invention may or may not be provided with an elastic layer. The conductive roller 1 does not include an elastic layer. The conductive roller without the elastic layer is preferably used as various rollers for the non-contact type image forming apparatus, and the conductive roller with the elastic layer is used as various rollers for the contact type image forming apparatus. It is preferable. The elasticity expressed by the coat layer 3 is preferably 1 × 10 ⁷ to 1 × 10 ⁹ , for example, in terms of the elastic modulus characteristic by a load addition method of indentation hardness. This elastic modulus characteristic can be measured by “DUH-211S” (trade name, manufactured by Shimadzu Corp.), as well as dynamic hardness and indentation elastic modulus.

  The conductive roller 1 is manufactured by forming a coat layer 3 on the outer peripheral surface of the shaft body 2. In order to manufacture the conductive roller 1, first, the shaft body 2 is prepared. For example, the shaft body 2 is prepared in a desired shape by a known method. The shaft body 2 may be coated with a primer or an adhesive before the coat layer 3 is formed. The primer or the adhesive is dissolved in a solvent or the like as desired, and is applied to the outer peripheral surface of the shaft body 2 according to a conventional method such as a dip method or a spray method.

The coat layer 3 is prepared by applying a urethane composition to the prepared shaft body 2 or the outer peripheral surface of the primer layer or adhesive layer formed as desired, and then heat-curing the applied urethane composition. Formed. Examples of the coating of the urethane composition include a coating method in which a coating liquid of the urethane composition is applied, a dipping method in which the shaft body 2 is immersed in the coating liquid, and a spray coating method in which the coating liquid is sprayed on the shaft body 2. The known coating method is used. The urethane composition may be applied as it is. In addition, for example, volatile solvents such as alcohols such as methanol and ethanol, aromatic solvents such as xylene and toluene, ester solvents such as ethyl acetate and butyl acetate, or urethane compositions to which water is added (coating liquid) ) May be applied.
The method of curing the urethane composition thus coated may be any method that can apply heat necessary for curing the urethane composition, for example, the shaft body 2 coated with the urethane composition. The method of heating with a heater is mentioned. The heating temperature when the urethane composition is heat-cured is, for example, 100 to 200 ° C, particularly 120 to 160 ° C, and the heating time is preferably 10 to 120 minutes, particularly preferably 30 to 60 minutes.

  The urethane composition forming the coat layer 3 contains an alkyd polyol, a polyisocyanate, and a melamine resin, and optionally contains a conductivity imparting agent, an ionic liquid, a solvent, a catalyst, and various additives. This urethane composition is substantially free of tin catalyst.

The alkyd polyol is a polyol obtained by a condensation reaction using an oil or fat, a fatty acid, a carboxylic acid, and a polyol compound as essential components. The alkyd polyol preferably has a weight average molecular weight of 3000 to 4000 in that the coating layer 3 can easily develop the hardness in the above range. The weight average molecular weight can be determined by gel permeation chromatography (GPC) under the following conditions and converted to standard polystyrene.
<Conditions>
Apparatus: Shodex GPC-101
Column: 2 GPC KF-800RL (reference side)
2 GPC KF-806L (sample side separation column)
Mobile phase: THF
Flow rate: 1 ml / min
Column chamber temperature: 40 ° C
Detector: RI detector Sample pretreatment method: Dissolve 5 mg of sample in 10 ml of THF.
Standard polystyrene molecular weights: 3,800,000, 600,000, 200,000, 110,000, 50,000, 17,500, 4,000, 800

The alkyd polyol preferably has a hydroxyl value of 5 to 500 KOHmg / g, and more preferably 10 to 400 KOHmg / g. When the hydroxyl value of the alkyd polyol is within the above-described range, a desired crosslinking density can be obtained, whereby solvent resistance and extensibility can be obtained. The hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of alkyd polyol is acetylated. Specifically, the hydroxyl value of the alkyd polyol is a value measured by a neutralization titration method described in JIS K0070, which is a hydroxyl value measurement method using an acetic anhydride-pyridine acetylating agent.
The hydroxyl value of the alkyd polyol can be adjusted by, for example, the hydroxyl value of the polyol compound, or the molar ratio of the polyol compound to fat or fatty acid or carboxylic acid. Specifically, when the hydroxyl value of the polyol compound is increased and the molar ratio is increased, the hydroxyl value of the alkyd polyol is increased.

The method and conditions for the condensation reaction of fats and oils, fatty acids and polyol compounds are not particularly limited, and known ones can be appropriately employed.
In this condensation reaction, no tin compound is used as a catalyst.

Oils and fats refer to triglycerides of fatty acids. For example, linseed oil, linseed oil, persimmon oil, tall oil, palm oil, soybean oil, castor oil, safflower oil, morning glory oil, pear oil, rapeseed oil, bran oil, cottonseed oil, palm oil, palm kernel oil, sardine oil Squid liver oil and the like.
Fatty acid refers to an aliphatic monocarboxylic acid of alkyl, alkenyl, alkynyl. For example, the fatty acid obtained from the said fats and oils, tall oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, glycidyl ester of Versatic acid (for example, “Cardura E” (trade name), manufactured by Shell), octylic acid and the like can be mentioned.

  Although it does not specifically limit as carboxylic acid, For example, a succinic acid, adipic acid, azelaic acid, sebacic acid, a hetic acid anhydride, a hymic anhydride, a maleic acid (including maleic anhydride), a fumaric acid, itaconic acid, citracone Acid, glutaconic acid, aliphatic carboxylic acid such as 1,2,5-hexanetricarboxylic acid, 1,1-cyclohexanedicarboxylic acid, hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, Methyl hexahydrophthalic acid, 4-tertiary butylcyclohexane monocarboxylic acid, hexahydrobenzoic acid, phthalic acid (including phthalic anhydride), isophthalic acid, or terephthalic acid, tetrachlorophthalic anhydride, tetrahydrophthalic anhydride, hexa Hydrophthalic acid, benzoic acid, p-tarsha -Butylbenzoic acid, p-methylbenzoic acid, trimellitic acid (including trimellitic anhydride), pyromellitic acid (including pyromellitic anhydride), 1,4-cyclohexanedicarboxylic acid, 1,2,4- Alicyclic carboxylic acids such as benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexatricarboxylic acid or 2,5,7-naphthalenetricarboxylic acid, aromatic carboxylic acids or methyl thereof Examples thereof include esters and the like, and methylcyclohexenic carboxylic acid anhydride.

  The polyol compound means one having two or more hydroxyl groups in one molecule. Although not particularly limited, for example, ethylene glycol, propylene glycol, propanediol, butylene glycol, pentanediol, hexanediol, methylpentanediol, neopentyl glycol, triethylene glycol, cyclohexanedimethanol, hydrogenated bisphenol A, 1,4- Bis (hydroxymethyl) cyclohexane, 2,2,4-trimethyl-1,3-pentanediol, hydroxypivalylhydroxypivalate, glycerin, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol or their dimers And the like.

  Examples of the polyisocyanate include isophorone diisocyanate (IPDI), 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6 -TDI), 3,3'-vitrylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate uretidinedione (of 2,4-TDI) Dimer), 1,5-naphthylene diisocyanate, metaphenylene diisocyanate, hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), carbodiimide-modified MDI, orthotoluidine diisocyanate, xylene Isocyanate, p-phenylene diisocyanate, and diisocyanates such as lysine diisocyanate methyl ester, triphenylmethane-4,4 ', 4' '- triisocyanate such triisocyanates, polymeric MDI, etc., and these derivatives. Examples of derivatives include polyisocyanates of polyisocyanates, urethane-modified products modified with polyols (including urethane prepolymers), dimers formed by uretidione, isocyanurate-modified products, carbodiimide-modified products, uretonimine-modified products, allophanate-modified products, Examples include urea-modified products and burette-modified products. Polyisocyanate can be used alone or in combination of two or more.

  The conductivity-imparting agent, ionic liquid, and various additives are as described above.

  As the catalyst, a catalyst used at the time of alkyd polyol and / or urethane synthesis can be used without particular limitation, but tin and a tin compound are not used. In other words, the alkyd polyol and / or the above-described reactants are synthesized substantially without using a tin catalyst. Examples of the catalyst used in the present invention include acid catalysts such as zinc compounds, cobalt compounds, titanium compounds, enzyme catalysts, and p-toluenesulfonic acid.

  The solvent is preferably used for the purpose of reducing the viscosity of the urethane composition and improving the coating property. Solvents that can be used are not particularly limited, and examples thereof include alcohol solvents such as methanol and ethanol, aromatic solvents such as xylene and toluene, and ester solvents such as ethyl acetate and butyl acetate.

The content rates of the alkyd polyol, polyisocyanate and melamine resin in the solid content of the urethane composition are basically the same as the above content rates in the solid content of the coat layer 3.
The reaction ratio of alkyd polyol, polyisocyanate and melamine resin is expressed as follows in terms of molar ratio. That is, the molar ratio ([NCO] / [OH]) between the hydroxyl group [OH] of the alkyd polyol and the isocyanate group [NCO] of the polyisocyanate is obtained by a general equivalent calculation, and is 1: 1 to 1: 1. Is preferably in the range of .1. Moreover, it is preferable that the molar ratio ([NH] / [OH]) of the amino group [NH] of the melamine resin to the polyol is in the range of 0.04: 1 to 0.93: 1.

  In the alkyd polyol, polyisocyanate and melamine resin, a reaction product is produced by the reaction of the hydroxyl group of the alkyd polyol and the amino group of the melamine resin with the isocyanate group of the polyisocyanate due to the presence of the catalyst, heating and the like. This reaction product is a resin having a urethane bond formed by a reaction between a hydroxyl group of an alkyd polyol and an isocyanate group of a polyisocyanate, and a urea bond formed by a reaction between an amino group of a melamine resin and an isocyanate group of a polyisocyanate. . The reactant may be any product obtained by reacting these three components. For example, the compound which has the urethane block which alkyd polyol and polyisocyanate react, and the melamine resin couple | bonded or reacted with this urethane block is mentioned. Moreover, the compound which has a urethane bond and a urea bond formed by reaction of an alkyd polyol, polyisocyanate, and a melamine resin is mentioned. Furthermore, an allophanate bond formed by further reacting (crosslinking) the isocyanate group of the polyisocyanate with the above-mentioned urethane bond, and a burette bond formed by further reacting (crosslinking) the isocyanate group of the polyisocyanate with the above-described urea bond. The compound which has is mentioned.

  In this way, the conductive roller 1 having the coat layer 3 on the outer peripheral surface of the shaft body 2 can be manufactured.

When the conductive roller has an elastic layer, after the rubber composition for forming the elastic layer is cured on the outer peripheral surface of the shaft body, the urethane composition is applied on the elastic layer and cured.
The elastic layer is formed, for example, by heat-curing a rubber composition on the outer peripheral surface of the shaft body. For example, the elastic layer is formed on the outer peripheral surface of the shaft body by performing heat curing and molding simultaneously or continuously by a known molding method.
As the rubber composition for forming the elastic layer, known ones can be used without particular limitation, and examples thereof include a urethane rubber composition and a silicone rubber composition.
When the coat layer is formed on the outer peripheral surface of the elastic layer thus formed as described above, a conductive roller provided with the elastic layer and the coat layer is manufactured.

Next, an example of the developing device and the image forming apparatus (non-contact type) of the present invention will be described with reference to FIG.
As shown in FIG. 2, the image forming apparatus 10 as an example described above transfers and conveys the plurality of image carriers 11B, 11C, 11M, and 11Y provided in the developing units B, C, M, and Y of the respective colors. A tandem color image forming apparatus arranged in series on the top. Therefore, the developing units B, C, M, and Y are arranged in series on the transfer conveyance belt 6. The developing unit B includes an image carrier 11B such as a photosensitive member (also referred to as a photosensitive drum), a charging unit 12B such as a charging roller, an exposure unit 13B, a developing unit 20B, and an image carrier via the transfer conveyance belt 6. A transfer unit 14B that contacts the body 11B, such as a transfer roller, and a cleaning unit 15B are provided.

  The developing device 20B is an example of the developing device of the present invention, and includes the conductive roller of the present invention and a developer 22B as shown in FIG. Therefore, in this image forming apparatus 10, the conductive roller of the present invention, for example, the conductive roller 1B, is mounted as the developer carrier 23B, 23C, 23M, and 23Y. Specifically, the developing device 20B includes a casing 21B that houses a one-component non-magnetic developer 22B, a developing roller that is a developer carrier 23B that supplies the developer 22B to the image carrier 11B, and a developer. A developer amount adjusting means 24B for adjusting the thickness of 22B, for example, a blade is provided. In the developing device 20B, as shown in FIG. 2, the developer amount adjusting means 24B is in contact with or in pressure contact with the outer peripheral surface of the developer carrier 23B. The developing units C, M, and Y are basically configured in the same manner as the developing unit B. The same elements are denoted by the same reference numerals and symbols C, M, or Y indicating the respective colors, and the description thereof is omitted. To do.

  In the image forming apparatus 10, the developer carrier 23B is arranged at an interval so that the surface thereof is not in contact with the surface of the image carrier 11B. That is, the image forming apparatus 10 is a so-called “non-contact image forming apparatus”. In FIG. 2, the developer carrier 23B and the image carrier 11B appear to be in contact with each other, but there is actually a slight interval.

  The fixing unit 30 is disposed on the downstream side of the developing unit Y. The fixing unit 30 includes a fixing roller 31, an endless belt support roller 33 disposed in the vicinity of the fixing roller 31, a fixing roller 31, and an endless belt support roller in a housing having an opening 35 through which the recording medium 16 passes. 33, an endless belt 36 wound around 33, and a pressure roller 32 disposed opposite to the fixing roller 31. The fixing roller 31 and the pressure roller 32 are in contact with or pressed against each other via the endless belt 36. It is a pressure heat fixing device which is supported in a freely rotatable manner. At the bottom of the image forming apparatus 10, a cassette 41 that houses the recording body 16 is installed. The transfer conveyance belt 17 is wound around a plurality of support rollers 42.

  Each of the developers 22B, 22C, 22M and 22Y used in the image forming apparatus 10 may be a dry developer or a wet developer as long as it can be charged by friction, and a non-magnetic developer or a magnetic developer. An agent may be used. One component non-magnetic black developer 22B, cyan developer 22C, magenta developer 22M and yellow developer 22Y are accommodated in the housings 21B, 21C, 21M and 21Y of the developing units.

  The image forming apparatus 10 forms a color image on the recording body 16 as follows. First, in the developing unit B, an electrostatic latent image is formed by the exposure unit 13B on the surface of the image carrier 11B charged by the charging unit 12B, and the black electrostatic latent image is developed by the developer 22B supplied by the developer carrier 23B. The image is developed. The black electrostatic latent image is transferred to the surface of the recording medium 16B when the recording medium 16 passes between the transfer means 14B and the image carrier 11B. Next, in the same manner as in the developing unit B, a cyan image, a magenta image, and a yellow image are superimposed on the recording medium 16 in which the electrostatic latent image is visualized as a black image by the developing units C, M, and Y, respectively. A color image is visualized. Next, the recording body 16 in which the color image is visualized is fixed to the recording body 16 by the fixing unit 30 as a permanent image. In this way, a color image can be formed on the recording medium 16.

  In the tandem type image forming apparatus 10, the conductive roller of the present invention having a coating layer containing a reaction product of alkyd polyol, polyisocyanate and melamine resin and containing no tin as an outermost layer is mounted as a developer carrier 23B. Thus, the developing device 20 and the tandem type image forming apparatus 10 can form a high-quality image having a high density and no unfixed portion of the developer.

  The image forming apparatus 10 is an image forming apparatus such as a copying machine, a facsimile machine, or a printer. Although the image forming apparatus 10 has been described with reference to the example in which the conductive roller of the present invention is used as a developing roller as an example of the developer carrier 23, the conductive roller of the present invention is used as a developer supply roller. Even if it is used, a high-quality image can be formed similarly.

  The conductive roller, the developing device, and the image forming apparatus of the present invention are not limited to the above-described examples, and various modifications can be made as long as the object of the present invention can be achieved.

  For example, the conductive roller has a so-called straight shape in which the outer diameter is substantially the same from one end to the other end in the axial direction. In the present invention, the conductive roller may have a cylindrical shape. For example, the shape is not particularly limited. For example, the outer diameter at the central portion in the axial direction may be a so-called reverse crown shape whose outer diameter is smaller than the outer diameter at both ends, and the outer diameter at the central portion in the axial direction. However, it may be a so-called crown shape that is larger than the outer diameter at both ends.

  The image forming apparatus 10 is an electrophotographic image forming apparatus. However, in the present invention, the image forming apparatus is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Good. Further, the image forming apparatus in which the conductive roller of the present invention is disposed is not limited to a tandem color image forming apparatus in which a plurality of image carriers including developing units of respective colors are disposed in series on a transfer conveyance belt, For example, a monochrome image forming apparatus provided with a single developing unit, a four-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier onto an endless belt may be used. The developer 22 used in the image forming apparatus 10 is a one-component nonmagnetic developer. However, in the present invention, the developer 22 may be a one-component magnetic developer or a two-component nonmagnetic developer. Or a two-component magnetic developer.

  The image forming apparatus 10 is a so-called “non-contact image forming apparatus” in which the image carrier 11 and the developer carrier 23 of the developing device 20 are arranged with a gap. The apparatus may be a so-called “contact image forming apparatus” in which the surface of the developer carrying member is disposed so as to come into contact or pressure contact with the surface of the image carrying member.

  The developer used in the developing device and the image forming apparatus is preferably a negatively charged developer. As the negatively charged developer, known ones can be used.

  The conductive roller, the developing device, and the image forming apparatus of the present invention are not limited to the above-described examples, and various modifications can be made as long as the object of the present invention can be achieved.

Example 1
An electroless nickel-plated shaft (made by SUM22, diameter 10 mm, length 275 mm) 2 was washed with ethanol, and a silicone primer (trade name “Primer No. 16”, Shin-Etsu Chemical Co., Ltd.) on its surface. Applied). The primer-treated shaft body 2 was fired at a temperature of 150 ° C. for 10 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer on the surface of the shaft body 2.

A urethane composition having the following composition was prepared, applied to the outer peripheral surface of the shaft body 2 by a spray coating method, and heated at 150 ° C. for 15 minutes to form a coat layer 3 having a layer thickness of 20 μm. In this way, the conductive roller 1 shown in FIG. 1 was manufactured.
<Composition of urethane composition>
(1) Alkyd polyol (trade name: ST-190, manufactured by Toshin Yushi Co., Ltd., weight average molecular weight 3400) 65 parts by mass (2) Polyisocyanate (trade name: Vernock D-800, manufactured by DIC) 35 parts by mass (3 ) Melamine resin (trade name: Super Becamine L117-60, manufactured by DIC) 10 parts by mass (4) Carbon black (trade name “Toka Black # 5500”, manufactured by Tokai Carbon Co., Ltd.) 5 parts by mass (alkyd polyol, polyisocyanate) And 4.5 parts by mass for a total of 100 parts by mass of melamine resin)
(5) Catalyst (chemical name: p-toluenesulfonic acid salt, trade name: p-toluenesulfonic acid salt (PTSA), manufactured by Nacalai Techs) 3,000 ppm
(6) 20 parts by mass of butyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent (7) 4 parts by mass of small-diameter silica (average particle diameter 1.5 μm, trade name “ACEMATT OK-607”, manufactured by Degussa)

(Examples 2 to 5)
In the urethane composition of Example 1, a conductive roller 1 was produced in the same manner as in Example 1 except that the melamine resin was changed to the content shown in Table 1.

(Comparative Example 1)
A conductive roller was produced in the same manner as in Example 1 except that the melamine resin was not used in the urethane composition of Example 1.

(Comparative Example 2)
In the urethane composition of Example 1, the alkyd polyol was changed to the content shown in Table 1, and a conductive roller was produced in the same manner as in Example 1 except that the polyisocyanate was not used.

(Comparative Example 3)
A conductive roller was produced in the same manner as in Example 1 except that the following melamine resin composition was used instead of the urethane composition of Example 1.
<Composition of melamine resin composition>
(1) Melamine resin (trade name: Super Becamine L117-60, manufactured by DIC) 100 parts by mass (2) Carbon black (trade name “Toka Black # 5500”, manufactured by Tokai Carbon Co.) 5 parts by mass (3) Catalyst (Chemical name: p-toluenesulfonic acid salt, trade name: p-toluenesulfonic acid salt (PTSA), manufactured by Nacalai Techs) 3,000 ppm
(4) 20 parts by mass of butyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent

(Measurement of charge amount)
The charge amount (nC) of the manufactured conductive roller was measured as described above in an environment of 23 ° C. and 50% relative humidity using a cascade type charge amount measuring device “TS-100A” (manufactured by Toshiba Chemical). It was measured. The results are shown in Table 1.

(Measurement of dynamic hardness)
The dynamic hardness of the manufactured conductive roller was measured as described above. The results are shown in Table 1.

As shown in Table 1, each of the conductive rollers of Examples 1 to 5 exhibited a high charge amount of 10 nC or more. Accordingly, any of the conductive rollers of Examples 1 to 5 can contribute to the image forming apparatus forming a high-quality image having a high density and no unfixed portion of the developer. In any of the conductive rollers of Examples 1 to 5, the coating layer 3 is formed without using a tin catalyst, the environmental load is small, and it can sufficiently meet recent environmental protection requirements.
In contrast, the conductive roller of Comparative Example 1 had a charge amount of zero. Further, although the conductive rollers of Comparative Examples 2 and 3 had a large charge amount, cracks were generated in the coat layer, and they could not be used as rollers.

DESCRIPTION OF SYMBOLS 1 Conductive roller 2 Shaft body 3 Coat layer 6 Transfer conveyance belt 10 Image forming apparatus 11B, 11C, 11M, 11Y Image carrier 12B, 12C, 12M, 12Y Charging means 13B, 13C, 13M, 13Y Exposure means 14B, 14C, 14M, 14Y Transfer means 15B, 15C, 15M, 15Y Cleaning means 20 Developing means 21B, 21C, 21M, 21Y, 34 Housings 22B, 22C, 22M, 22Y Developers 23B, 23C, 23M, 23Y Developer carrier (conductive) Sex roller)
24B, 24C, 24M, 24Y Developer regulating member 30 Fixing means 31 Fixing roller 32 Pressure roller 33 Endless belt support roller 36 Endless belt B, C, M, Y Developing unit

Claims (6)

  A conductive roller comprising a coating layer containing a reaction product of alkyd polyol, polyisocyanate and melamine resin and containing no tin as an outermost layer.   2. The conductive roller according to claim 1, wherein the melamine resin is contained in an amount of 3 to 60 parts by mass with respect to 100 parts by mass in total of the alkyd polyol and the polyisocyanate.   The conductive roller according to claim 1, wherein the alkyd polyol has a weight average molecular weight of 3000 to 4000. It said coating layer is a conductive roller according to claim 1 having a dynamic hardness of 0.2~15N / mm ^2.   The developing device which has the electroconductive roller and developer as described in any one of Claims 1-4 as a developing roller. An image forming apparatus comprising: an image carrier; and the conductive roller according to any one of claims 1 to 4 as a developing roller disposed in non-contact with the image carrier.

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