Developing roller

Abstract

To provide a developing roller with improved environmental dependence. [Solution] The present invention relates to a developing roller 1 comprising a shaft 2, an elastic layer 3 provided on the outer circumference of the shaft 2, and a coating layer 4 provided on the outer circumference of the elastic layer 3, wherein the elastic layer 3 contains silicone rubber, and the coating layer 4 contains a urethane resin formed from a coating layer composition containing at least one of a sebaciate-modified polyol and a castor oil-modified polyol, and an isocyanate compound.

Description

[Technical Field]

[0001] This invention relates to a developing roller. [Background technology]

[0002] Developing rollers used in image forming devices such as photocopiers, printers, and facsimile machines employing electrophotography have the function of transporting toner to an image carrier on which an electrostatic latent image has been formed. Various studies are being conducted to improve the toner transport capacity and durability of developing rollers. For example, Patent Document 1 proposes a roller that is low hardness and highly durable without contaminating the recording paper, comprising an elastic layer whose base material is urethane and an outermost layer made of urethane formed from a hydrophobic polyol and isocyanate. Furthermore, Patent Document 2 proposes a conductive roller in which, in order to obtain a conductive roller with low hardness and reduced compression set, a castor oil-modified polyol is used as the polyol component in the polyurethane foam, and a modified TDI with an NCO content of 1-15% is used as the isocyanate component. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-208087 [Patent Document 2] Japanese Patent Publication No. 2008-280447 [Overview of the project] [Problems that the invention aims to solve]

[0004] The developing roller has a problem in that its electrostatic charge changes depending on the humidity of the operating environment, which affects printing performance. This invention has been made in view of the above circumstances, and aims to provide a developing roller with improved environmental dependence. [Means for solving the problem]

[0005] The inventors of the present invention discovered that the above problems could be solved by forming a urethane resin coating layer using a highly hydrophobic polyol, leading to the present invention. [1] The present invention relates to a developing roller comprising a shaft, an elastic layer provided on the outer circumference of the shaft, and a coating layer provided on the outer circumference of the elastic layer, wherein the elastic layer contains silicone rubber, and the coating layer is formed from a coating layer composition containing at least one of sebaciac acid-modified polyol and castor oil-modified polyol and an isocyanate compound, and contains a urethane resin. [2] The developing roller described in [1] above, wherein the polyol is a castor oil modified polyol. [3] The developing roller described in [2] above, wherein the acid value of the castor oil-modified polyol is 5.0 mg KOH / g or less. [4] The developing roller described in [2] above, wherein the viscosity of the castor oil-modified polyol at 25°C is 300 mPa·s or more and 2000 mPa·s or less. [5] The developing roller described in [2] above, wherein the moisture content of the castor oil-modified polyol is 0.05% or less. [6] The developing roller described in [2] above, wherein the hydroxyl group of the castor oil-modified polyol is 40 mg KOH / g or more and 170 mg KOH / g or less. [7] The developing roller according to [2] above, wherein the number of functional groups of the castor oil-modified polyol is 1 or more and 4 or less. [Effects of the Invention]

[0006] According to the present invention, a developing roller with improved environmental dependence can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view showing one embodiment of the developing roller of the present invention. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. [developing roller] As shown in Figure 1, the developing roller 1 of the present invention comprises a shaft 2, an elastic layer 3 provided on the outer circumference of the shaft 2, and a coating layer 4 provided on the outer circumference of the elastic layer 3, wherein the elastic layer 3 contains silicone rubber, and the coating layer 4 contains a urethane resin formed from a coating layer composition containing at least one of a sebaciate-modified polyol and a castor oil-modified polyol, and an isocyanate compound. The details of each component are described below.

[0009] (Axis) The shaft 2 can preferably be a conventionally known shaft used in developing rollers, which has conductive properties. The shaft 2 is preferably made of at least one metal selected from the group consisting of, for example, iron, aluminum, stainless steel, and brass. Such a shaft 2 is also generally known as a "core metal".

[0010] The shaft 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft 2 may comprise, for example, a core made of an insulating resin and a plating layer provided on this core. Such a shaft 2 can be obtained, for example, by plating a core made of an insulating resin to make it conductive. The shaft 2 is preferably a core metal in order to obtain good conductivity characteristics.

[0011] The shape of the shaft 2 is preferably, for example, rod-shaped, tubular, etc. The cross-sectional shape of the shaft 2 may be, for example, circular, elliptical, or non-circular, such as a polygon. The outer surface of the shaft 2 may be treated with cleaning, degreasing, priming, etc.

[0012] The axial length of the shaft body 2 is not particularly limited and may be appropriately adjusted according to the form of the image forming apparatus to be installed. Further, the diameter (diameter of the circumscribed circle) of the shaft body 2 is also not particularly limited and may be appropriately adjusted according to the form of the image forming apparatus to be installed.

[0013] (Elastic layer) The elastic layer 3 is provided to impart to the developing roller 1 a hardness and elasticity that can press the photosensitive member with an appropriate nip width and nip pressure so that toner can be supplied to the electrostatic latent image formed on the surface of the photosensitive member without excess or deficiency. The elastic layer 3 contains silicone rubber. For example, the elastic layer 3 is formed by extruding the following composition for the elastic layer onto the outer peripheral surface of the shaft body 2 and subjecting it to vulcanization and polishing. The composition for the elastic layer contains at least (a) organopolysiloxane, (b) conductivity-imparting agent, (c) filler, and (d) vulcanizing agent.

[0014] (a) Organopolysiloxane As the organopolysiloxane, an organopolysiloxane having a polymerization degree of 100 or more represented by the following average composition formula (I) is preferable. R 1 a SiO (4-a) / 2 (I) (In the formula, R 1 represents the same or different unsubstituted or substituted monovalent hydrocarbon groups, and a is a positive number of 1.95 or more and 2.05 or less.)

[0015] R 1 Examples of R 1These hydrocarbon groups may be groups in which some or all of the hydrogen atoms are substituted with substituents. The substituents may be, for example, halogen atoms, cyano groups, etc. Examples of hydrocarbon groups with substituents include chloromethyl groups, trifluoropropyl groups, and cyanoethyl groups.

[0016] It is preferable that the molecular chain ends of the organopolysiloxane are sealed with trialkylsilyl groups such as trimethylsilyl groups, dialkylaralkylsilyl groups such as dimethylvinylsilyl groups, dialkylhydroxysilyl groups such as dimethylhydroxysilyl groups, or trialkylaralkylsilyl groups such as trivinylsilyl groups.

[0017] Organopolysiloxanes preferably have two or more alkenyl groups in the molecule. Organopolysiloxanes are R 1 It is preferable that the organopolysiloxane contains 0.001 mol% to 5 mol% (more preferably 0.01 mol% to 0.5 mol%) of alkenyl groups. Vinyl groups are particularly preferred as the alkenyl groups in the organopolysiloxane.

[0018] Organopolysiloxanes can be obtained, for example, by co-hydrolysis condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as trimers or tetramers of siloxanes. Organopolysiloxanes may basically be linear diorganopolysiloxanes, but may be partially branched. Furthermore, organopolysiloxanes may be a mixture of two or more organisms with different molecular structures.

[0019] The organopolysiloxane preferably has a kinematic viscosity of 100 cSt or more at 25°C, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. Furthermore, the degree of polymerization of the organopolysiloxane is preferably, for example, 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0020] (b) Conductivity imparting agent Examples of the conductivity-imparting agent include conductive powders such as conductive carbon, carbon for rubber, metals, and conductive polymers. As the conductive powder, it is preferable to use carbon black. Examples of the carbon black include furnace black such as Ketjenblack (registered trademark), acetylene black, channel black, thermal black, and the like. The resistance value of the elastic layer 3 is preferably adjusted to be in the range of 4 to 9 (logΩ).

[0021] (c) Filler Examples of the filler include silica-based fillers. Examples of the silica-based fillers include fumed silica, precipitated silica, and the like.

[0022] As the silica-based filler, R 2 Si(OR 3 )3 surface-treated with a silane coupling agent can be preferably used. Here, R 2 may be a group having a vinyl group or an amino group, and for example, may be a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, a mercapto group, or the like. R 3 may be an alkyl group, and for example, may be a methyl group, an ethyl group, or the like. The silane coupling agent can be easily obtained, for example, under the trade names "KBM1003", "KBE402", etc. manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of the silica-based filler with a silane coupling agent according to a conventional method. As the surface-treated silica-based filler, commercially available products may be used, and for example, products under the trade name "Zeothix 95" manufactured by J.M. HUBER Corporation can be mentioned.

[0023] The blending amount of the silica-based filler is preferably 11 parts by mass or more and 39 parts by mass or less, more preferably 15 parts by mass or more and 35 parts by mass or less, based on 100 parts by mass of the (a) organopolysiloxane. Furthermore, the average particle size of the silica-based filler is preferably between 1 μm and 80 μm, and more preferably between 2 μm and 40 μm. The average particle size of the silica-based filler can be measured as the median diameter using a particle size distribution analyzer based on laser diffraction.

[0024] (d) vulcanizing agent Examples of vulcanizing agents include addition vulcanizing agents and organic peroxide vulcanizing agents. Suitable addition-curing agents include, for example, organohydrogenpolysiloxanes known as addition-reaction type vulcanizing agents having two or more SiH groups (SiH bonds) in one molecule. Addition-curing agents can be used individually or in combination of two or more. The amount of addition vulcanizing agent is usually preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the elastic layer composition.

[0025] When using addition vulcanizing agents, organic peroxide vulcanizing agents can crosslink millable-type silicone rubber on their own, but when used in combination with addition vulcanizing agents as auxiliary vulcanizing agents, the physical properties of the resulting rollers, such as strength and distortion, can be further improved.

[0026] Examples of organic peroxide vulcanizing agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The amount of organic peroxide vulcanizing agent added is usually preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 8 parts by mass or less, per 100 parts by mass of the elastic layer composition.

[0027] It is preferable to use an addition reaction catalyst in combination with the addition vulcanizing agent. Examples of addition reaction catalysts include platinum black, dic platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetate, palladium-based catalysts, rhodium-based catalysts, etc. The amount of this addition reaction catalyst added can be in catalytic amounts.

[0028] (Other ingredients) Furthermore, the composition for the elastic layer may contain various additives. Examples of such additives include auxiliary agents such as chain extenders, catalysts, dispersants, anti-aging agents, antioxidants, foaming agents, and fillers other than silica, such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, and solvents. These additives may be commonly used additives or additives specially used depending on the application.

[0029] The elastic layer 3 may be polished to a desired outer diameter. The outer diameter of the elastic layer 3 is not particularly limited, but is preferably 6 mm or more and 25 mm or less, and more preferably 7 mm or more and 21 mm or less.

[0030] The thickness of the elastic layer 3 is not particularly limited, but is preferably 0.1 mm or more and 6 mm or less, and more preferably 1 mm or more and 4 mm or less. In this specification, the thickness refers to the thickness in the direction perpendicular to the axial direction of the developing roller 1.

[0031] The outer surface of the elastic layer 3 may be subjected to surface treatments such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, itro treatment, or flame treatment for purposes such as improving adhesion with the coating layer 4.

[0032] (covering layer) The coating layer 4 contains a urethane resin formed from a coating layer composition comprising (A) a polyol, which is at least one of sebaciac acid-modified polyols and castor oil-modified polyols, and (B) an isocyanate compound.

[0033] (A) Polyol The polyol is at least one of sebaciate-modified polyols and castor oil-modified polyols. Preferably, it is a castor oil-modified polyol. "Castor oil-modified polyols" refer to linear or branched polyesters obtained by the reaction of castor oil fatty acids with polyols (low molecular weight polyols and / or polyether polyols). Examples include diglycerides and monoglycerides of fatty acids constituting castor oil, mono, di, or triesters of castor oil fatty acids and trimethylol alkanes, and mono, di, or triesters of castor oil fatty acids and polypropylene glycol. The castor oil-modified polyol used in the present invention is preferably one that has the following properties.

[0034] The acid value of the castor oil-modified polyol is preferably 5.0 mg KOH / g or less. The hydroxyl value of the castor oil-modified polyol is preferably 40 mg KOH / g or more and 170 mg KOH / g or less. The number of functional groups in the castor oil-modified polyol is preferably 1 to 4, and more preferably 2 to 3. The moisture content of the castor oil-modified polyol is preferably 0.05% or less.

[0035] The viscosity of the castor oil-modified polyol at 25°C is preferably between 300 mPa·s and 2000 mPa·s. Viscosity measurement shall be in accordance with JIS K7117-1.

[0036] As for commercially available sebacate polyester polyols, URIC manufactured by Ito Oil Co., Ltd. is a good example. Examples include the SE series (SE-2003, SE-2606), HS2H-201AP, HS2H-351A, HS2H-451A, HS2H179A, HS2H-359T-CR, HS2H-458T, HS2F-231AS, HS2F-136P, HS2F-306P, HS2E-581A, HS2D-121A, HS2F-237P, HS Polyol 1000, HS Polyol 2000, HS2N-221A, HS2N-521A, HS2N-220S, HS2N-226P, HS2B-222A, HOKOKUOLHT-110, HOKOKUOLHT-210, HOKOKUOLHT-250, etc. Castor oil modified polyols can be commercially available.

[0037] Commercially available castor oil-modified polyols include the URIC H series (H-30, H-31, H-52, H-57, H-62, H-73X, H-81, H-102, H-420, H-854, H-870, H-1823, H-1824, HF-1300, HF-2050), URIC POLYCASTOR series (POLYCASTOR #10, POLYCASTOR #30), URIC Y series (Y-403, Y-406), URIC AC series (AC-005, AC-006, AC-009, H-368), URIC PH series (PH-319, PH-5001, HF-2009), and URIC, all manufactured by Ito Oil Co., Ltd. Examples include the F-series (F-15, F-25, F-40, F-60, F-97, F-135).

[0038] (B) Isocyanate compounds As isocyanate compounds for curing polyols, various isocyanate compounds commonly used in the preparation of polyurethanes, such as aromatic isocyanate compounds, aliphatic isocyanate compounds, and alicyclic isocyanate compounds, can be used. Examples of aromatic isocyanate compounds include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and 3,3'-dimethylbiphenyl-4,4'-diisocyanate. Examples of aliphatic isocyanate compounds include hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornene diisocyanate methyl (NBDI), xylylene diisocyanate (XDI), and tetramethyl xylylene diisocyanate (TMXDI). Furthermore, examples of alicyclic isocyanate compounds include transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and 4,4'-dicyclohexylmethane diisocyanate.

[0039] The mixing ratio of polyol and polyisocyanate is not particularly limited, but it is generally preferable that the molar ratio (NCO / OH) of hydroxyl groups (OH) in the polyol to isocyanate groups (NCO) in the polyisocyanate is between 0.7 and 1.15. A molar ratio (NCO / OH) of 0.85 to 1.10 is more preferable in that it can prevent hydrolysis of the polyurethane. In practice, however, considering the working environment and errors during the process, an amount equivalent to 3 to 4 times the appropriate molar ratio may be added.

[0040] The coating layer composition may also contain auxiliary agents commonly used in the reaction between (A) a polyol and (B) an isocyanate compound, such as chain extenders and crosslinking agents. Examples of chain extenders and crosslinking agents include glycols, hexanetriol, trimethylolpropane, and amines.

[0041] The thickness of the coating layer 4 is preferably 0.1 μm or more and 3 μm or less, and more preferably 0.2 μm or more and 1.5 μm or less.

[0042] The developing roller 1 contains a urethane resin in its coating layer 4, which is formed from a coating layer composition comprising at least one of a sebaciate-modified polyol and a castor oil-modified polyol, and an isocyanate compound. As a result, the coating layer 4 does not absorb moisture, making it less susceptible to humidity and reducing changes in the charged state. Furthermore, because the elastic layer 3 contains silicone rubber, the adhesion of the coating layer 4 is good, making it possible to provide a highly durable developing roller. [Examples]

[0043] The present invention will be described in detail below with reference to examples. However, the present invention is not limited in any way to the examples shown below.

[0044] [Example 1] Cast films (film size: 3cm x 3cm, film thickness: 750μm~800μm) were prepared from the following coating layer compositions and dried at 105°C for 1 hour. -Coating layer composition- (A) Polyol Sebacate acid-modified polyol (product name "URIC SE2013C", manufactured by Ito Oil Co., Ltd.) 100 parts by mass (B) Isocyanate compound (product name "Duranate TPA-100", manufactured by Asahi Kasei Corporation) 20 parts by mass

[0045] [Examples 2 to 5] Cast films were prepared in the same manner as in the examples, except that the following polyols were used. The castor oil-modified polyols used in Examples 2 to 5 are listed below. Their details are shown in Table 1. • Castor oil-modified polyol 1 (product name "URIC H1830", manufactured by Ito Oil Co., Ltd.) • Castor oil-modified polyol 2 (product name "URIC H30", manufactured by Ito Oil Co., Ltd.) • Castor oil-modified polyol 3 (product name "URIC H57", manufactured by Ito Oil Co., Ltd.) • Castor oil-modified polyol 4 (product name "URIC HF2009", manufactured by Ito Oil Co., Ltd.)

[0046] [Table 1]

[0047] [Comparative Example 1] A cast film was prepared in the same manner as in the examples, except that the polyol was changed to 28 parts by mass of linear polyester polyol and 14 parts by mass of an isocyanate compound (product name "Duranate TPA-100", manufactured by Asahi Kasei Corporation).

[0048] [evaluation] Water absorption tests were conducted on the cast films of the above examples and comparative examples.

[0049] (Water absorption test) The mass of the cast film after drying was measured. Next, the cast film was immersed in purified water, and its mass was measured after 1 day and 4 days of immersion. The difference was calculated. The measurement results are shown in Table 2.

[0050] [Table 2]

[0051] As shown in Table 2, the cast films of Examples 1 to 5, which used sebaciate-modified polyol or castor oil-modified polyol as raw materials for the urethane resin, exhibited low water absorption. This low water absorption indicates that the change in the charged state due to humidity is small, and an improvement in the environmental dependence of the developing roller can be expected. Therefore, an electrophotographic image forming apparatus equipped with such a developing roller maintains good image quality even under environmental changes such as high temperature and high humidity, and low temperature and low humidity. [Explanation of Symbols]

[0052] 1. Developing roller 2-axis body 3. Elastic layer 4 Covering layer

Claims

1. It comprises a shaft, an elastic layer provided on the outer circumference of the shaft, and a coating layer provided on the outer circumference of the elastic layer, The elastic layer includes silicone rubber, A developing roller containing a urethane resin, the coating layer of which is formed from a coating layer composition comprising at least one polyol, selected from sebaciac acid-modified polyol and castor oil-modified polyol, and an isocyanate compound.

2. The developing roller according to claim 1, wherein the polyol is a castor oil-modified polyol.

3. The developing roller according to claim 2, wherein the acid value of the castor oil-modified polyol is 5.0 mg KOH / g or less.

4. The developing roller according to claim 2, wherein the viscosity of the castor oil-modified polyol at 25°C is 300 mPa·s or more and 2000 mPa·s or less.

5. The developing roller according to claim 2, wherein the moisture content of the castor oil-modified polyol is 0.05% or less.

6. The developing roller according to claim 2, wherein the hydroxyl group of the castor oil-modified polyol is 40 mg KOH / g or more and 170 mg KOH / g or less.

7. The developing roller according to claim 2, wherein the number of functional groups in the castor oil-modified polyol is 1 or more and 4 or less.

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