JP5332195B2 - Developing roller and image forming apparatus - Google Patents

Description

  The present invention provides an image forming apparatus having a developing mechanism for supplying a developer to a latent image holding member carrying an electrostatic latent image to visualize the electrostatic latent image, and supplying the developer to the latent image holding member. The present invention relates to a developing roller used for image forming, and an image forming apparatus using the developing roller.

  For example, in an image forming apparatus such as an electrophotographic apparatus such as a printer or a copying machine, a developing operation for supplying a developer (toner) to a latent image holding member carrying an electrostatic latent image to visualize the electrostatic latent image is performed. Is called. In this case, a semiconductive elastic roller is generally used as a developing roller for supplying the developer.

  As this developing roller, a roller using a polyurethane foam as an elastic layer is known. In this case, since a foam having relatively fine bubbles is obtained, a polyurethane foam obtained by mechanical stirring foaming (mechanical floss method) is preferably used. Conventionally, a polyurethane resin paint is applied on the polyurethane foam elastic layer. Is applied to secure toner filming resistance, but this developing roller cannot always obtain sufficient toner chargeability. In order to obtain sufficient toner chargeability, it has been proposed to form a surface layer with a silicone resin (Patent Document 1).

  However, the silicone resin is inferior in dispersibility of the conductive agent carbon black, easily causes coating unevenness, and it is difficult to form a uniform coating film without unevenness, and the coating film unevenness may affect the image quality. It was.

Japanese Patent Laid-Open No. 11-65268

  The present invention has been made in view of the above circumstances, and has a developing roller that is excellent in durability, toner chargeability, and toner filming resistance, and that can reliably obtain a good image, and image formation using the developing roller. An object is to provide an apparatus.

As a result of intensive studies to achieve the above object, the present inventor formed a surface resin layer on the outer periphery of the semiconductive elastic layer formed around the core metal directly or through an intermediate layer, and developed it. When obtaining a roller, a fluororesin having a hydroxyl group and a silicone graft resin are used in combination at a predetermined ratio as a base resin for the surface resin layer, and the surface resin layer is cured by using an isocyanate curing agent. It has been found that a developing roller that is excellent in durability, toner chargeability, and toner filming resistance and can reliably obtain a good image can be obtained by forming it, and the present invention has been completed.

Accordingly, the present invention provides a developing roller in which a semiconductive elastic layer is formed around a metal core, and a surface resin layer is further formed on the elastic layer directly or via an intermediate layer. Is a cured product obtained by curing a graft resin obtained by mixing and reacting a fluororesin having a hydroxyl group and a silicone graft resin and grafting polysiloxane onto the fluororesin with an isocyanate curing agent, and the fluororesin that mixing ratio of the silicone-grafted resin is formed with a cured product of the mass was 70 / 30-2 / 98 ratio, and the resin composition the molecular weight of the silicone graft resin is the number average molecular weight 1000 to 10000 A developing roller is provided.

  The present invention also provides an image forming apparatus provided with a developing mechanism that supplies a developer to a latent image holding member carrying an electrostatic latent image to visualize the electrostatic latent image, and uses the developer as a latent image holding member. The present invention provides an image forming apparatus using the developing roller of the present invention as the developing roller to be supplied.

  The developing roller of the present invention is excellent in durability, toner charging property, and toner filming resistance. According to the image forming apparatus using this developing roller, a good image can be stably obtained over a long period of time. Is.

Hereinafter, the present invention will be described in more detail.
For example, as shown in FIG. 1, the developing roller of the present invention includes a cored bar 1, an elastic layer 2 formed around the cored bar 1, and a surface resin layer 3 formed on the outer periphery of the elastic layer 2. In the present invention, the surface resin layer 3 is formed of a resin composition containing a fluororesin having a hydroxyl group, a silicone graft resin, and an isocyanate curing agent.

  The elastic layer 2 is not particularly limited and can be formed of an elastic body that is usually used as an elastic layer of a developing roller. In the present invention, a polyurethane foam is preferably used, and a polyol component and an isocyanate component are preferably used. A polyurethane foam formed by foaming the polyurethane raw material contained by mechanical stirring is particularly preferably used.

  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 500 to 5,000, particularly preferably 1,000 to 3,000, a hydroxyl value of 21 to 244 mgKOH, particularly preferably 37 to 112 mgKOH, and the number of functional groups. It is preferable that it is 2-3.

  Next, the isocyanate is not particularly limited, and can be appropriately selected from conventionally known various isocyanate compounds. Specifically, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), modified TDI, modified MDI, modified HDI, etc. are exemplified, 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 20%.

  Usually, a conductive agent is blended in the polyurethane foam of the elastic layer 2 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 peptide, dibutyltin thiocarboxylate, dibutyltin dimalenite, 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 elastic layer 2 is prepared by mixing the isocyanate component, the polyol component, and a conductive agent added as necessary, and the additive, mechanically agitating and foaming, and casting into a mold in which a core metal is set, and thermosetting. By doing so, it can be formed around the cored bar 1.

  Next, the surface resin layer 3 is formed of a resin obtained by blending and curing an isocyanate curing agent with a fluororesin having a hydroxyl group and a silicone graft resin.

  Here, the fluororesin having a hydroxyl group can be prepared by a known method, but a commercially available product can also be used. Specifically, Lumiflon LF-100, LF-200, manufactured by Asahi Glass Co., Ltd. LF-400, LF-600; Cefal coat A606X, A202B, CF-803 manufactured by Central Glass Co., Ltd .; Zaffle GK-510 manufactured by Daikin Industries, Ltd. are exemplified, and one or more of these are used. be able to.

  Examples of the silicone graft resin include silicone-modified acrylic resins grafted with silicone, which can be prepared by a known method. Commercially available silicone graft resins can also be used. Specific examples of commercially available products include Silaplane FM-0711 (number average molecular weight 1000), FM-0721 (number average molecular weight 5000), FM-0725 (number average molecular weight 10,000) manufactured by Chisso Corporation; X-22-174DX etc. made by Corporation | KK etc. are illustrated, These 1 type (s) or 2 or more types can be used.

  The molecular weight of the silicone graft resin is not particularly limited, but is preferably 1000 to 30000, particularly 1000 to 10000, and more preferably 1000 to 3000 in terms of number average molecular weight, and is less than 1000. And unreacted silicone graft resin may bleed out and contaminate the photoconductor. On the other hand, if it exceeds 10000, the hardness of the coating will increase excessively, and the toner will be easily damaged and durable. An image defect that sometimes causes development streaks may occur.

  The mixing ratio of the fluororesin having a hydroxyl group and the silicone graft resin is not particularly limited, but is usually a fluororesin having a hydroxyl group by mass ratio / silicone graft resin = 70/30 to 2/98, particularly 65. / 35 to 10/90. In this case, if the fluororesin is excessive and the silicone acrylic resin is excessive, slipping performance and wear performance may be reduced, causing problems such as filming where the toner adheres to the developing roller. If the acrylic resin is excessive, charging performance to the toner may be deteriorated and image defects such as “fogging” may occur.

As the above-mentioned fluororesin having a hydroxyl group and silicone graft resin, commercially available products obtained by mixing these at a predetermined ratio and chemically bonding them can be used. It can be illustrated.

  Next, as the isocyanate curing agent, a known polyisocyanate can be used. Specifically, commercially available products such as Coronate HX and Coronate L manufactured by Nippon Polyurethane; Takenate D140N manufactured by Mitsui Chemicals Polyurethane are suitable. Can be used for

  The amount of the isocyanate curing agent is appropriately set according to the type of the fluororesin and silicone graft resin having the hydroxyl group and the type of the isocyanate curing agent, and is not particularly limited. It is preferable to set it as 20-80 mass parts with respect to 100 mass parts of total amounts of a fluororesin and silicone graft resin, especially 30-70 mass parts.

  In the surface resin layer 3, in addition to the fluorine resin having a hydroxyl group, the silicone graft resin, and the isocyanate curing agent, a known additive blended in the coating layer of the developing roller may be blended as necessary. For example, the same conductive agent and resin particles as exemplified in the elastic layer can be blended as necessary.

The resin particles can be appropriately selected according to the kind of the fluororesin having the hydroxyl group or the silicone graft resin, the thickness of the surface resin layer, etc., for example, urethane resin particles, acrylic resin particles, silicone resin particles, silica particles. Polyamide resin particles, nylon resin particles, etc. are exemplified, 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 surface roughness of the roller can be adjusted by dispersing and blending these resin particles in the surface resin layer 3.

  The surface resin layer 3 is not particularly limited, but the surface static friction coefficient (JIS K7125) is preferably 0.1 to 0.6 μs, particularly preferably 0.2 to 0.5 μs. If it is too large, there may be a problem of so-called filming in which toner adheres. On the other hand, if it is too small, charging of the toner becomes difficult to control, and inconvenience such as fogging may occur. The static friction coefficient can be easily measured using a known measuring instrument such as “Tribogear μs Type 94i” manufactured by HEIDON.

  The thickness of the surface resin layer 3 is not particularly limited, but is usually 3 to 50 μm, particularly preferably 5 to 30 μm. In this case, the surface resin layer 3 is usually formed directly on the elastic layer 2, but if necessary, one or more intermediate layers are formed on the elastic layer 3, and this intermediate layer is formed. It can also be formed on the roller surface. In this case, the intermediate layer can be formed using a known resin such as a urethane resin, a urethane acrylic resin, a fluororesin, a silicone resin, or an acrylic resin.

  The surface resin layer 3 and the intermediate layer are formed by dissolving and dispersing the resin components and additives in a solvent such as methyl ethyl ketone, methyl isobutyl ketone, toluene, ethyl acetate, and methylcyclohexane to prepare a resin paint. What is necessary is just to apply on an elastic layer by well-known methods, such as a dipping, a spray, and a roll coater. Further, the intermediate layer can also be formed using a water-based resin, and thus can be configured in consideration of the environment. In this case, as the water-based resin, any of a fluororesin, an acrylic resin, a urethane resin, and the like may be used, but a urethane resin is also preferably used from the viewpoint of the resilience performance.

  The developing roller of the present invention is an image forming apparatus provided with a developing mechanism that supplies a developer to a latent image holding member carrying an electrostatic latent image and visualizes the electrostatic latent image, and carries the developer. It is used as a developing roller that supplies the latent image holding member. An example of such an image forming apparatus is an apparatus having the configuration shown in FIG.

  In other words, this apparatus is disposed in a state where the developing roller 5 is in contact with or close to the photosensitive drum (latent image holding member) 6 and is further disposed in a state in which the toner conveying roller 4 is in contact with the developing roller 5. Then, by rotating the photosensitive drum 6, the developing roller 5, and the toner transport roller 4 in the direction of the arrows in the figure, the toner t is transported from the toner reservoir in the toner cassette by the toner transport roller 4, and the developing roller 5 The toner t is adjusted to a uniform thin layer by the stratified blade 7 and the developing roller 5 rotates in this state in contact with or close to the photosensitive drum 6, thereby forming the toner formed in a thin layer. t adheres to the latent image on the photosensitive drum 6 from the developing roller 5, and the latent image is visualized to develop and form an image. In the figure, reference numeral 8 denotes a transfer unit, which transfers a toner image onto a recording medium 9 such as paper. Reference numeral 10 denotes a cleaning unit. After the transfer by the cleaning blade 11, the photosensitive drum 6 is transferred. The toner remaining on the surface is removed. In FIG. 2, charging means such as a charging roller are omitted.

  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.

[Example 1]
A polyurethane foam having the following composition was subjected to foam molding to form an elastic layer (thickness 4 mm) made of polyurethane foam on the outer periphery of the core metal (4 mmφ). At this time, A liquid in which polyol, foam stabilizer, ionic conductive agent, and catalyst are mixed and B liquid in which isocyanate and carbon black are mixed are prepared in advance, and these A liquid and B liquid are mechanically stirred and mixed. The polyurethane foam elastic layer having a density of 0.7 g / cm ³ was formed on the outer periphery of the core metal by foaming together and casting into a mold in which the core metal was set.
[Composition composition]
Polyol-modified tolylene diisocyanate 100 parts by mass (Asahi Glass Urethane Co., Ltd. prototype “BS 008” NCO content 6.7%)
Polyester polyol 24 parts by mass (Kuraray Co., Ltd. “Kuraray polyol F-510” hydroxyl value 336, functional group number 3)
Conductive carbon black 2 parts by mass Foam stabilizer (polydimethylsiloxane / polyethylene oxide copolymer) 5 parts by mass Ion conductive agent (sodium perchlorate) 0.3 parts by mass Catalyst (dibutyltin dilaurate) 0.2 parts by mass

  Next, 35 parts by mass of carbon black, urethane particles with respect to 100 parts by mass of “ZX007C” manufactured by Fuji Kasei Kogyo Co., Ltd., which is a mixed resin of a fluororesin having a hydroxyl group (FEVE) and a silicone graft resin (number average molecular weight 1000) (Negami Kogyo “Art Pearl C800”, average particle size 8.8 μm) 10 parts by weight are dispersed in methyl ethyl ketone 350 parts by weight, and then an isocyanate curing agent (Nippon Polyurethane “Coronate HX” 30 parts by weight is added. The coating for the surface resin layer was prepared by stirring with a stirring motor for 30 minutes, and this coating was applied on the elastic layer to form a surface resin layer having a thickness of 10 μm, thereby obtaining a developing roller.

[Example 2]
Surface resin in the same manner as in Example 1 except that the mixed resin was replaced with “ZX017” manufactured by Fuji Kasei Kogyo Co., Ltd., which is a mixed resin of a fluororesin having a hydroxyl group (FEVE) and a silicone graft resin (number average molecular weight 10,000). A coating material for the layer was prepared, and this coating material was applied on the same elastic layer as in Example 1 to form a surface resin layer having a thickness of 10 μm to obtain a developing roller.

[ Reference example ]
Surface resin as in Example 1 except that the mixed resin was replaced with “ZX022” manufactured by Fuji Kasei Kogyo Co., Ltd., which is a mixed resin of a fluororesin having a hydroxyl group (FEVE) and a silicone graft resin (number average molecular weight 20000). A coating material for the layer was prepared, and this coating material was applied on the same elastic layer as in Example 1 to form a surface resin layer having a thickness of 10 μm to obtain a developing roller.

[Example 4]
A urethane emulsion paint (“E-400” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied on the elastic layer formed in the same manner as in Example 1 to form an intermediate layer having a thickness of 70 μm. A surface resin layer similar to 1 was formed to obtain a developing roller.

[Comparative Example 1]
A coating for the surface resin layer was prepared in the same manner as in Example 1 except that a silicone resin (“SR2410” manufactured by Toray Dow Corning Co., Ltd.) was used instead of the above mixed resin. A surface resin layer having a thickness of 10 μm was formed on the same elastic layer to obtain a developing roller.

[Comparative Example 2]
A paint for the surface resin layer was prepared in the same manner as in Example 1 except that a urethane resin (“N5196” manufactured by Nippon Polyurethane Co., Ltd.) was used instead of the above mixed resin. A surface resin layer having a thickness of 10 μm was formed on the elastic layer to obtain a developing roller.

  For each of the developing rollers, the surface hardness was measured using a micro rubber hardness meter (“MD-1” manufactured by Kobunshi Keiki Co., Ltd.), and the surface roughness (JIS B0601) and static friction coefficient (JIS K7125) were measured. The results are shown in Table 1. The roller resistance value was measured by the following method, and the photoreceptor contamination, image density, fog resistance, and toner filming resistance were evaluated by the following methods. The results are also shown in Table 1.

[Roller resistance value]
With the developing roller pressed in parallel with the flat plate electrode and a weight of 500 g applied to both ends of the core bar in the direction of the flat plate electrode, a voltage of DC 100 V was applied between the core bar and the flat plate electrode, and the current flowing at that time Was measured, and the resistance was calculated from the current value.

[Photoconductor contamination]
The developing roller is 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, and after one week, the developing roller and the photosensitive drum are incorporated into an actual machine (“LBP4600” manufactured by Hured Packard). Then, the image was printed out, and the contamination on the surface of the photosensitive drum at the portion that had been in contact with the developing roller for one week was evaluated according to the following criteria.
○: No contamination of the photosensitive drum was observed.
Δ: Slight contamination of the photosensitive drum was observed.
X: Bleed and obvious contamination was observed on the photosensitive drum.

[Image density]
The developing roller is incorporated in the toner cartridge, and is in a low temperature and low humidity (15 ° C., 10% RH) environment (LL environment), in a normal temperature and normal humidity (25 ° C., 50% RH) environment (NN environment), and in a high temperature and high humidity (30 ° C., Under a 80% RH environment (HH environment), continuous image formation with a printing rate of 2% was performed using “Color LBP4600” manufactured by Hewlett-Packard Company, and solid images and halftone images were formed initially and after printing 5000 sheets. The density unevenness of the obtained image was visually evaluated according to the following criteria.
○: No density unevenness.
Δ: Some uneven density.
X: There is clear density unevenness.

[Cover resistance]
Each developing roller was incorporated into a laser beam printer ("LBP4600" manufactured by Hured Packard), and the printer was forcibly stopped during the printing of a solid white image, and the amount of toner flying to the photosensitive drum in the white background portion was evaluated. The evaluation was carried out by comparing the density by tape transfer (measured with a Macbeth densitometer) and performing a three-level evaluation according to the following criteria.
○: Less than 0.15 Δ: 0.15 or more, less than 0.20 ×: 0.20 or more

[Toner filming resistance]
A toner was applied to the surface of the developing roller, incorporated into a toner cartridge, and left to stand at 40 ° C. and 95% RH for 1 week, and then an image was formed. The toner filming resistance was evaluated according to the following criteria.
○: No toner adhered to the developing roller surface from the first sheet.
Δ: No toner adhered to the surface of the developing roller by the 10th sheet.
X: Toner adhered to the surface of the developing roller even when the number of sheets exceeded 10.

  As shown in Table 1, it was confirmed that the developing roller of the present invention was excellent in durability, toner chargeability, and toner filming resistance, and a good image could be obtained reliably.

It is a schematic sectional drawing which shows an example of this invention developing roller. It is the schematic which shows an example of the developing mechanism using a developing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core metal 2 Elastic layer 3 Surface resin layer 4 Toner conveyance roller 5 Developing roller 6 Photosensitive drum (latent image holding body)
7 Lamination blade 8 Transfer section 9 Paper (recording medium)
10 Cleaning unit 11 Cleaning blade t Toner

Claims (4)

In the developing roller formed by forming a semiconductive elastic layer around the core metal and further forming a surface resin layer directly or via an intermediate layer on the elastic layer,
The surface resin layer is a cured product obtained by curing a graft resin obtained by mixing and reacting a fluororesin having a hydroxyl group and a silicone graft resin and grafting polysiloxane onto the fluororesin with an isocyanate curing agent, the mixing ratio between the fluorine resin and silicone graft resin is 70 / 30-2 / 98 in mass ratio, and the molecular weight of the silicone-grafted resin is formed by the cured product of the resin composition is the number average molecular weight 1000 to 10000 A developing roller.   The developing roller according to claim 1, wherein the surface resin layer has a static friction coefficient μs of 0.1 to 0.6.   The developing roller according to claim 1, wherein a urethane resin layer formed by applying a urethane emulsion paint between the elastic layer and the surface resin layer is provided as an intermediate layer.   In an image forming apparatus provided with a developing mechanism for supplying a developer to a latent image holding member carrying an electrostatic latent image to visualize the electrostatic latent image, a developing roller for supplying the developer to the latent image holding member. An image forming apparatus using the developing roller according to claim 1.

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