JP2008280445A - Electroconductive roller and manufacturing method of electroconductive roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive roller such as a developing roller, a toner-conveying roller, a charging roller or the like that is inexpensive and exhibits good performances by forming a resin coating film layer by application directly onto an elastic layer composed of a polyurethane foam with good control of the surface properties while omitting formation of a sealing layer. <P>SOLUTION: The electroconductive roller comprises an elastic layer composed of a polyurethane foam prepared by the mechanical blowing of a polyurethane raw material comprising a polyol component and an isocyanate component, characterized in that the polyurethane foam constituting the elastic layer has a density of 0.75-0.99 g/cm<SP>3</SP>from the surface to a depth of 0.05 mm and a density of 0.2-0.7 g/cm<SP>3</SP>within the range of 0.05 mm thickness from the central part in the thickness direction with the difference of the density between the surface part and the central part of at least 0.25 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive roller such as a developing roller, a toner conveying roller, and a charging roller used in an electrophotographic apparatus, and a method for manufacturing the conductive roller.

  Conventionally, a polyurethane foam is used as an elastic layer for conductive rollers such as a developing roller, a toner conveying roller, and a charging roller used in an electrophotographic apparatus, and the elastic layer is formed of a polyurethane foam. Thus, it is possible to reduce the weight and cost of the roller.

  As described above, the conductive roller having an elastic layer formed of a foam is usually formed by coating and forming a resin coating layer constituting the roller surface on the elastic layer, and the surface property of the roller is adjusted by this coating layer. To be done.

  However, even if the surface of the polyurethane foam has relatively fine bubbles obtained by mechanical stirring foaming (mechanical froth method), there are holes due to the opening of the foamed cells. Even if formed, a recess due to the hole appears on the resin layer, and the surface roughness of the roller cannot be sufficiently controlled, and it is difficult to obtain a good image.

  Therefore, conventionally, a sealing layer for filling holes existing on the surface of the elastic layer made of polyurethane foam is applied and a resin coating layer is formed thereon to form a multi-layered conductive roller. (Patent Document 1, etc.).

  However, the method of forming the sealing layer in addition to the resin coating layer complicates the manufacturing process and increases the cost. Therefore, the resin coating that directly forms the roller surface on the surface of the elastic layer made of polyurethane foam is used. It is desired to obtain a conductive roller having good performance by coating and forming a film layer.

JP-A-9-262912

  The present invention has been made in view of the above circumstances, and even if a resin coating layer is directly formed on an elastic layer made of polyurethane foam, the surface properties can be controlled well, and the formation of a sealing layer is omitted. An object of the present invention is to obtain a conductive roller such as a developing roller, a toner conveying roller, and a charging roller having low cost and good performance.

  As a result of intensive studies to achieve the above object, the present inventor forms an elastic layer around a core metal with a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component. When the conductive roller is obtained, the bubbles appearing on the surface of the elastic layer by increasing the density in the vicinity of the surface of the polyurethane foam forming the elastic layer by variously devising the raw material components and setting the conditions for foam molding The resin coating film is directly applied on the elastic layer by reducing the number of holes and reducing the density of the central portion in the thickness direction and maintaining good flexibility by omitting the sealing layer. It has been found that a conductive roller having good performance can be obtained even if a layer is formed.

Therefore, as a result of further investigation on the specific density setting of the polyurethane foam forming the elastic layer, the present inventor has found that the density from the surface of the elastic layer to the depth of 0.05 mm is from 0.75 to 0. .99 g / cm ³ , density in the thickness direction 0.05 mm thickness range is 0.2 to 0.7 g / cm ³ , and the difference between the surface density and the central density is 0.25 g / cm If it is ³ or more, the surface properties of the roller can be reliably adjusted by forming a resin coating layer directly on the elastic layer made of polyurethane foam, and sufficient flexibility as a conductive roller can be maintained. The inventors have found that a conductive roller having good performance can be produced at low cost by omitting the formation of the sealing layer, and the present invention has been completed.

Accordingly, the present invention provides a conductive roller having an elastic layer made of a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component, and the polyurethane foam forming the elastic layer is formed from the surface. The density up to a depth of 0.05 mm is 0.75 to 0.99 g / cm ³ , the density in the thickness 0.05 mm range at the center in the thickness direction is 0.2 to 0.7 g / cm ³ , and these surfaces Provided is a conductive roller characterized in that the difference in part density and central part density is a foam of 0.25 g / cm ³ or more.

  Furthermore, the present inventor has the density distribution of an elastic layer made of such polyurethane foam when mechanically foaming from a polyurethane raw material containing a polyol component and an isocyanate component to form an elastic layer around the core metal. As a result of intensive studies on the method of forming a foam, when a polyurethane material that has been mechanically agitated and foamed is poured into a mold, the polyurethane material is poured into a mold at room temperature or in a cooled state without preheating the mold. After the casting, the mold is heated to the thermosetting temperature and the polyurethane foam is thermally cured, so that the cell diameter of the foam surface portion is small and the cell diameter of the central portion is relatively large. It has been found that a polyurethane foam having a density distribution with a large density, a small density at the center, and a relatively large density distribution is obtained.

That is, when a polyurethane raw material that has been mechanically agitated and foamed is cast into a mold and an elastic layer of polyurethane foam is formed around the core metal, conventionally, the mold is preheated to a heat curing temperature of 50 to 80 ° C. The polyurethane raw material is cast and thermosetting is performed. The present inventors cast the polyurethane raw material into a mold at a normal temperature of 25 to -10 ° C or in a cooled state without preheating the mold. Thereafter, the mold is heated to a thermosetting temperature to carry out thermosetting, whereby the density from the surface to a depth of 0.05 mm is 0.75 to 0.99 g / cm ³ , and the thickness in the center in the thickness direction is 0.00. at a density of 05mm range 0.2 to 0.7 g / cm ^3, and a polyurethane foam having a difference 0.25 g / cm ³ or more special density distribution of these surface part density and the central portion density (density gradient) It is possible to get the body and this special polyurethane foam The present inventors have found that a conductive roller having an elastic layer formed by a body can be obtained.

  Accordingly, the present invention provides a method for producing the above-described conductive roller according to the present invention, in which a polyurethane raw material containing a polyol component and an isocyanate component is mechanically agitated and foamed, poured into a mold in which a core metal is disposed, and thermally cured to obtain a core. In the method for producing a conductive roller in which an elastic layer made of a polyurethane foam is formed around gold, the polyurethane raw material is poured into a mold at room temperature or in a cooled state at 25 to -10 ° C. without preheating the mold. The present invention provides a method for producing a conductive roller, characterized in that, after molding, the temperature is raised to a thermosetting temperature and thermosetting is performed.

  The conductive roller of the present invention has a high density in the vicinity of the surface of the polyurethane foam forming the elastic layer, a small number of bubble holes appearing on the surface of the elastic layer, and a relatively low density at the center in the thickness direction. It has flexibility and can be manufactured at a low cost by forming the resin coating layer directly on the elastic layer by omitting the above-mentioned sealing layer, and can reliably exhibit good performance. Is.

Hereinafter, the present invention will be described in more detail.
As described above, the conductive roller of the present invention is a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component, and an elastic layer is formed around the core metal.

  In this case, the polyol component is not particularly limited, and any known polyol as a raw material polyol for producing urethane foam can be used. For example, a polyether polyol, a polyester polyol, or a polyester polyether polyol can be used for a roller. Although it can select suitably according to this invention, in this invention, especially polyester polyol and polyether polyol are used preferably, and any one or both of these can be mixed and used.

  More specifically, as polyether polyol, polyether polyol obtained by addition polymerization of alkylene oxide such as polyethylene oxide or propylene oxide to glycerin, etc., polyether polyol obtained by ring-opening polymerization of tetrahydrofuran, Examples thereof include polyether polyols such as polytetramethylene glycol, ethylene glycol, propanediol, and butanediol.

  Polyester polyols include condensation polyester polyols obtained by condensation of dicarboxylic acids with diols, triols, etc., lactone polyester polyols obtained by ring-opening polymerization of lactones based on diols and triols, and ends of polyether polyols. A polyol such as an ester-modified polyol obtained by ester-modifying lactone with lactone is exemplified.

  These polyols are not particularly limited, but preferably have a number average molecular weight of 360 to 5600, particularly preferably 400 to 1,000, a hydroxyl value of 30 to 390 mgKOH, particularly preferably 180 to 390 mgKOH, and the number of functional groups. It is preferable that it is 2.5-3, and also about polyether polyol, it is preferable that ethylene oxide content is 1-10%.

  Next, the isocyanate is not particularly limited, and can be appropriately selected from conventionally known various isocyanate compounds. Specific examples include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), modified TDI, modified MDI, modified HDI and the like, and in particular, modified TDI, modified MDI, and modified HDI are preferably used. It is done. In this case, the type of the modified product is not particularly limited, but a polyol-modified product is preferable. Among them, a polyol-modified TDI is particularly preferably used in combination with the polyether polyol or polyester polyol. These isocyanates are not particularly limited, but the NCO content is preferably 1 to 25%, particularly 4 to 10%.

  Usually, this polyurethane foam is blended with a conductive agent to impart or adjust conductivity. As the conductive agent, a known ionic conductive agent or electronic conductive agent can be used, and further, an ionic conductive agent and an electronic conductive agent can be used in combination.

  Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (for example, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (for example, stearyltrimethylammonium), benzyltrimethylammonium, and a modified fatty acid dimethylethylammonium. Perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate, sulfonate, etc. ammonium salt, lithium, sodium Perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, trifluoromethyls of alkali metals and alkaline earth metals such as potassium, calcium and magnesium Sulfates, such as sulfonate are exemplified.

  In addition, as the electronic conductive agent, conductive carbon such as ketjen black and acetylene black; rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; carbon for ink subjected to oxidation treatment, Examples include pyrolytic carbon, natural graphite, and artificial graphite; conductive metal oxides such as tin oxide, titanium oxide, and zinc oxide; metals such as nickel, copper, silver, and germanium.

  Furthermore, in the polyurethane foam constituting the elastic layer of the conductive roller of the present invention, in addition to the polyol component, isocyanate component and conductive agent, a foam stabilizer, a cross-linking agent, a surfactant, a catalyst are optionally used. An appropriate amount of known additives such as these can be added.

  Examples of the foam stabilizer include polydimethylsiloxane-polyethylene oxide copolymer, polydimethylsiloxane-polypropylene oxide copolymer, polydimethylsiloxane-polyethylene adipate copolymer, and the like.

  Examples of the catalyst include dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dibutyltin marker tide, dibutyltin thiocarboxylate, dibutyltin dimalenate, dioctyltin marker peptide, dioctyltin thiocarboxylate as organometallic catalysts. , Phenylmercury, silver propionate, tin octenoate, amine catalyst triethylamine, N, N, N ′, N′-tetramethylethylenediamine, triethylenediamine, N-methylmorpholine, dimethylaminoethanol, bis (2-dimethylaminoethyl) ) Ether, 1,8-diazabicyclo (5,4,0) -undecene-7 and the like are preferably used. These catalysts may be used alone or in combination of two or more.

  The conductive roller of the present invention is prepared by mixing the isocyanate component, the polyol component, the conductive agent, and the additive that is added as necessary, and casting the mixture into a mold in which the core metal is set by foaming with mechanical stirring. And heat curing to form an elastic layer made of polyurethane foam around the core metal.

In this case, in the present invention, the density distribution of the polyurethane foam forming the elastic layer is adjusted, and the density from the elastic layer surface to a depth of 0.05 mm is 0.75 to 0.99 g / cm ³ , the thickness. direction central portion of the thickness of 0.05mm range density 0.2 to 0.7 g / cm ^3, and in which the difference between these surface portions density and the central portion density was 0.25 g / cm ³ or more.

Here, when the density of the surface portion is less than 0.75 g / cm ³ , the polyurethane foam tends to swell with the coating solvent, and the control of the surface roughness becomes difficult, and the object of the present invention cannot be achieved. On the other hand, if the density of the central portion is less than 0.2 g / cm ³ , the hardness of the polyurethane foam becomes too soft, and the pressure contact force to the mating member becomes weak when used as a roller. When it exceeds 7 g / cm ³ , the polyurethane foam becomes hard and the softness as the foam material cannot be obtained, and in any case, the object of the present invention cannot be achieved. Further, when the difference between the surface density and the central density is less than 0.25 g / cm ^3, it is difficult to reduce the hardness and control the surface roughness. In this case, the object of the present invention can be sufficiently achieved. Absent. In addition, the preferable range of surface part density is 0.85-0.99 g / cm < ³ >, the preferable range of center part density is 0.3-0.5 g / cm < ³ >, and the preferable range of density difference is 0.5 g / cm. cm ³ or more.

Moreover, although it does not restrict | limit in particular, it is preferable that the average density of the whole elastic layer is 0.5-0.8 g / cm < ³ >, especially 0.6-0.7 g / cm < ³ >. In this case, even if the above-mentioned density distribution is satisfied, if the average density of the entire elastic layer is less than 0.5 g / cm ³ , the density difference between the surface portion and the central portion cannot be sufficiently obtained. On the other hand, if it exceeds 0.8 g / cm ³ , it may be impossible to obtain the properties as a foam.

  Furthermore, the thickness of the elastic layer made of this polyurethane foam is appropriately set depending on the use of the conductive roller and the design of the electrophotographic apparatus on which the roller is set, and is not particularly limited. The thickness is preferably 10 mm, particularly 3 to 6 mm. In the elastic layer having such a thickness, the object of the present invention can be achieved more reliably by setting the above density distribution.

  Here, the density distribution can be achieved by changing the cell diameter of the polyurethane foam cells between the surface portion and the central portion. Of course, the number of cells in the surface portion and the central portion can be achieved. Although other factors such as the difference also affect the density of the foam, adjusting the cell diameter of the bubbles is very effective in achieving the above density distribution, and the surface state where the sealing layer can be omitted. It is also effective from the point of obtaining.

  The cell diameter of the bubbles is not particularly limited, but the range from the surface to a depth of 0.05 mm (hereinafter, the average cell diameter in the “surface portion” is 0.005 to 0.15 mm and the thickness direction The thickness of the central portion is in the range of 0.05 mm (hereinafter, the average cell diameter in the “central portion” is preferably 0.01 to 0.5 mm, more preferably the cell diameter of the surface portion is 0.005 to 0.05 mm. The cell diameter of the central part is 0.01 to 0.1 mm If the cell diameter of the surface part deviates from the above range, even if the density distribution is achieved, pinholes are generated on the surface, and the surface roughness is controlled. In addition, if the cell diameter in the central portion deviates from the above range, the cells may be crushed or the printed image may be affected even if the density distribution is achieved. Although not particularly limited, Bubbles of the polyurethane foam for forming the elastic layer of, preferably a closed cell.

  Various conditions for molding the polyurethane material that has been mechanically agitated and foamed into a mold and forming an elastic layer on the outer periphery of the core metal should be appropriately selected according to the type of each component used. It is only necessary that the elastic layer made of the polyurethane foam having the above density distribution can be molded.

  As described above, the present invention, as an example of molding conditions capable of achieving the above density distribution, casts a polyurethane raw material that has been mechanically agitated and foamed into a mold at room temperature to cooling temperature, and is thermoset after casting. We propose a method of raising the mold temperature.

  In this case, the mold temperature at the time of casting the polyurethane raw material is 25 ° C. to −10 ° C., preferably 25 ° C. to 15 ° C. from normal temperature to cooling temperature. As a result, the air bubbles in the vicinity of the surface in contact with the molding surface of the mold can be made relatively small so that the density can be made relatively high. The density distribution of the polyurethane foam forming the elastic layer can be adjusted within the range of the present invention.

  Here, when the mold temperature at the time of casting exceeds 25 ° C., the bubbles near the surface of the polyurethane foam increase and the density increases, and the density distribution defined in the present invention can be achieved. On the other hand, when the temperature is lower than −10 ° C., the liquid flow of the urethane foam at the time of molding deteriorates, causing problems such as generation of voids.

  In addition, after casting, the mold is heated to a normal thermosetting temperature and the temperature is raised. The thermosetting temperature at that time depends on the components of the polyurethane raw material and the required hardness and thickness of the elastic layer. Although it sets suitably and is not restrict | limited in particular, Usually, it is preferable to set it as 90-120 degreeC, especially 100-110 degreeC. In this case, the rate of temperature increase when the temperature is raised from 25 to -10 ° C during the casting to the thermosetting temperature is not particularly limited, but is 2 to 1200 ° C / min, particularly 600 to 1200 ° C. When the temperature is less than 2 ° C./min, the curing time is unnecessarily long and the production efficiency is greatly reduced, and the foam cell may be crushed. If it exceeds / min, bubbles on the surface portion become large, the density of the surface portion decreases, and the above density distribution may not be achieved.

  In the production method of the present invention, the temperature of the mold is controlled as described above, and the elastic layer is molded from polyurethane foam. At this time, although not particularly limited, after the polyurethane material mechanically agitated and foamed is poured into a mold, the opening of the mold such as a gate hole or a gas vent hole is hermetically sealed and held in pressure. It is preferable that the mold is heated to a thermosetting temperature to perform thermosetting. Thus, by carrying out the pressure holding, it is possible to prevent the bubbles from expanding more than necessary, and in particular, it is possible to effectively prevent the density of the surface portion of the polyurethane foam from increasing.

  The preparation of the polyurethane raw material to be cast into the mold is not particularly limited as long as the above components are mixed, mechanically agitated and foamed according to a conventional method, and cast into the mold. Regarding the mixing of each component, the catalyst, foam stabilizer and ionic conductive agent are preferably premixed with the polyol component and then mixed with the isocyanate component. When carbon black is used, the carbon black is preliminarily mixed with the isocyanate component. It is preferable to mix with the polyol component after mixing.

  As described above, the conductive roller of the present invention has an elastic layer made of a polyurethane foam having a specific density distribution. For example, in the case of a developing roller, a toner conveying roller, a charging roller, and the like, Usually, a resin coating layer is formed on this elastic layer. In this case, in the present invention, the resin coating layer can be formed directly on the elastic layer without forming the sealing layer, and thus the sealing layer can be omitted. Good surface properties can be obtained, and the manufacturing cost can be reduced by omitting the sealing layer.

  The resin coating layer can be formed using a known resin selected according to the use of the roller, and examples thereof include urethane resin, acrylic resin, acrylic urethane resin, fluorine resin, and silicone resin. The

  In this resin coating layer, an appropriate additive can be blended depending on the use of the roller, for example, the same conductive agent or resin curing agent as exemplified in the elastic layer, if necessary. An appropriate amount can be added.

In addition, resin particles and the like can be mixed and dispersed in the resin coating layer in order to adjust the surface roughness of the roller. In this case, the resin particles can be appropriately selected according to the type of resin forming the surface resin layer, the thickness of the surface resin layer, and the like. Specific examples include urethane resin particles, acrylic resin particles, silicone resin particles, silica particles, polyamide resin particles, nylon resin particles, and the like, and one or more of these can be used. Further, the shape, size, particle size distribution, etc. of the particles are appropriately selected and are not particularly limited. Usually, spherical, square and needle-shaped particles are preferably used, and the particle size is D ⁵⁰ = 1. ˜50 μm, in particular D ⁵⁰ = 5-20 is preferred.

  The thickness of the resin coating layer is appropriately set according to the type of resin constituting the resin layer, the use of the roller, the characteristics of the elastic layer, etc., and is not particularly limited, but is usually 1 to It is preferably 20 μm, particularly 5 to 10 μm. The resin coating layer may be formed by laminating a plurality of layers, and can usually be 1 to 5 layers.

  The resin coating layer is formed by dissolving and dispersing the above resin components and additives in a solvent such as methyl ethyl ketone, methyl isobutyl ketone, toluene, ethyl acetate, methyl cyclohexane, and dipping the resin paint. It may be applied on the elastic layer by a known method such as spraying or roll coating.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example.

[Examples 1-3 and Comparative Examples 1-4]
Polyurethane foams having the blending compositions shown in Tables 1 and 2 below were foamed to form an elastic layer (thickness 3 mm) made of polyurethane foam on the outer periphery of the core metal (6 mmφ). At this time, liquid A mixed with isocyanate and carbon black and liquid B mixed with polyol, foam stabilizer, ionic conductive agent and catalyst are prepared in advance, and these liquid A and liquid B are mixed with mechanical stirring. The polyurethane foam elastic layer was formed on the outer periphery of the core metal by foaming together and casting into a metal mold in which the core metal was set. In this case, in Examples 1 to 3 and Comparative Examples 2 to 4, the mold was cast at room temperature of 25 ° C. without preheating, and the temperature was raised to 70 ° C. at a rate of 700 ° C./min after casting, Molding was performed. On the other hand, in Comparative Example 1, the above A and B mixed liquids were poured into a mold preheated to 70 ° C. and molded at the same temperature. In Examples 1 to 3 and Comparative Examples 1, 3, and 4, the gate hole and the vent hole were sealed and held immediately after casting, and thermosetting was performed as it was. On the other hand, in Comparative Example 2, the gate hole and the gas vent hole were not sealed, and thermosetting was performed with the gate hole and the gas vent hole left open. In addition, all the compounding parts in Table 1, 2 are a mass part. The details of the isocyanate component and the polyol component in Tables 1 and 2 are as follows.

Polyol-modified tolylene diisocyanate (1)
Asahi Glass Urethane Co., Ltd., prototype “BS008”

Polyether polyol (2)
“EXCENOL 430” manufactured by Asahi Glass Urethane Co., Ltd.

Polyether polyol (3)
“SANNICS FA-951” manufactured by Sanyo Chemical Industries, Ltd.

Polyester polyol (4)
"Kuraray polyol F-510" manufactured by Kuraray Co., Ltd.

Polyether polyol (5)
“Exenol 420” manufactured by Asahi Glass Urethane Co., Ltd.

  The obtained foam density of the elastic layer, the foam density of the surface part, the foam density of the central part, and the density difference between the surface part and the central part were measured. The results are shown in Tables 1 and 2, and a graph showing the dense portion distribution of the elastic layer cross section is shown in FIG. Moreover, the cell diameter of the surface part and the center part was measured. The results are shown in Tables 1 and 2.

Next, a coating material having the following composition was applied onto the elastic layer to form a surface resin layer having a thickness of 10 μm, thereby obtaining a conductive roller.
Coating compositions <br/> urethane resin (manufactured by Nippon Polyurethane Co., Ltd. "N5196") 100 parts by weight Carbon black 35 parts by weight urethane particles (manufactured by Dainippon Ink and Chemicals, "Burnock", spherical, D ⁵⁰ = 10 [mu] m) 10 parts by weight Methyl ethyl ketone 350 parts by mass Part isocyanate curing agent ("Coronate HX" manufactured by Nippon Polyurethane Co., Ltd.) 20 parts by mass

  About each obtained roller, according to JISB0601 (2001), the arithmetic mean height (Ra) of the contour curve and the average length (Ra) of the contour curve element were measured, and surface roughness was investigated. Moreover, the static resistance at the time of 100V application was measured with the resistance measuring machine made from an Advantest company. Furthermore, Asker C hardness was measured. These results are shown in Tables 1 and 2.

  Then, each of the above rollers is mounted on a printer cartridge as a developing roller, and this cartridge is set in a laser beam printer “Laser Jet 4050” manufactured by Hewlett-Packard Co. to print a solid black image. , ○ △, △, × evaluated in four stages. The results are shown in Tables 1 and 2.

As shown in Table 1, the density from the surface to a depth of 0.05 mm is 0.75 to 0.99 g / cm ³ , and the density in the thickness direction 0.05 mm is 0.2 mm. in ~0.7g / cm ^3, and the conductive roller of examples 1 to 3 the difference between these surface portions density and the central portion density to form an elastic layer at 0.25 g / cm ³ or more polyurethane foam, Even if the resin coating layer is formed directly by omitting the sealing layer, it is possible to obtain a good surface property, to exhibit good performance as a developing roller, and to form a good image. It was done.

  On the other hand, as shown in Tables 1 and 2, the conductive rollers of Comparative Examples 1 to 4 have a low density of the surface portion. In Comparative Examples 1 and 2, the density of the surface portion and the central portion is also low. Since it is small, the surface properties of the roller, particularly the surface roughness (Ra), cannot be sufficiently controlled, and therefore it has been confirmed that the image quality is greatly inferior and it is difficult to omit the sealing layer.

  In Comparative Example 1, the mold was preheated to a thermosetting temperature of 70 ° C. and the elastic layer was molded. For this reason, the density of the surface portion was low and the density difference was also small. Further, Comparative Example 2 was formed without holding pressure with the gate hole and the gas vent hole opened, and this also has an insufficient surface portion density and insufficient density difference. It has become.

It is a graph which shows the density distribution of the elastic layer of each electroconductive roller obtained by the Example and the comparative example.

Claims (11)

In a conductive roller having an elastic layer made of a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component,
The polyurethane foam forming the elastic layer has a density of 0.75 to 0.99 g / cm ³ from the surface to a depth of 0.05 mm, and a density in the range of 0.05 mm at the center in the thickness direction is 0.00. 2～0.7G / in cm ^3, and the conductive roller, wherein a difference between these surface portions density and the central portion density of 0.25 g / cm ³ or more foam. The conductive roller according to claim 1, wherein the polyurethane foam forming the elastic layer has an average density of 0.5 to 0.8 g / cm ³ .   The polyurethane foam forming the elastic layer has an average cell diameter of 0.005 to 0.15 mm in the range from the surface to a depth of 0.05 mm, and an average cell in the thickness range of 0.05 mm in the center in the thickness direction. The conductive roller according to claim 1, wherein the conductive roller is a foam having a diameter of 0.01 to 0.5 mm.   The conductive roller according to claim 1, wherein the elastic layer has a thickness of 1 to 10 mm.   The conductive roller according to any one of claims 1 to 4, wherein the polyurethane foam forming the elastic layer is a foam having closed cells.   The polyurethane foam forming the elastic layer is obtained by using a polyester polyol or a polyether polyol or both of them as a polyol component and using a polyol-modified tolylene diisocyanate as an isocyanate component. The conductive roller according to any one of claims.   The conductive roller according to claim 1, wherein one or more resin coating layers are formed on the elastic layer. A conductive roller that forms a resilient layer of polyurethane foam around a core metal by mechanically foaming a polyurethane raw material containing a polyol component and an isocyanate component, casting it into a mold having a core metal, and thermosetting it. In the manufacturing method of
Without preheating the mold, the polyurethane raw material is poured into a mold at a room temperature of 25 to -10 ° C. or in a cooled state, and then heated to a thermosetting temperature to be thermally cured. Roller manufacturing method.   The method for producing a conductive roller according to claim 8, wherein a temperature rising rate of the mold is 2 to 1200 ° C./min.   10. The mold according to claim 8 or 9, wherein the polyurethane raw material is poured into the mold, the mold opening is sealed and pressure-maintained, and the mold is heated while maintaining the pressure-maintained state to perform thermosetting. Manufacturing method of conductive roller.   The solvent-based paint is directly applied onto the elastic layer of the roller removed from the mold to form one or more resin coating layers according to any one of claims 8 to 10. Manufacturing method of conductive roller.

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