JP4530660B2 - Coating composition for conductive roller and conductive roller - Google Patents

Description

The present invention relates to a conductive roller coating composition and a conductive roller coated with the coating composition. Such a conductive roller is used in charging, developing, transferring, cleaning and the like in an electrophotographic apparatus such as a copying machine or a printer, an electrostatic recording apparatus or the like.

  Conventionally, in an electrophotographic process in a copying machine or a printer, the surface of a photosensitive member (latent image holding member) is first uniformly charged, and an image is projected onto the photosensitive member from an optical system so that it is exposed to light. An electrostatic latent image is formed by erasing the charged part, and copying or the like is performed by attaching toner, transferring the toner image onto paper or the like, and cleaning after transfer.

  As a method for charging the photoreceptor, a corona discharge method has been generally adopted. However, this corona discharge method is not preferable from the viewpoint of safety maintenance of the apparatus because it is necessary to apply a high voltage of 6 to 10 kV, and environmental substances such as ozone are generated during corona discharge. Also had the above problem. Therefore, various charging methods that can be charged at a voltage lower than that of corona discharge and that can suppress the generation of harmful substances such as ozone have been studied. As one of such charging methods, A so-called contact charging method has been proposed in which a charging roller to which a voltage is applied is brought into contact with a photosensitive drum as a member to be charged with a predetermined pressing force, thereby charging the member to be charged.

  As a charging roller used in this contact charging method, for example, on the surface of an elastic layer such as rubber or polyurethane foam, for example, acrylic, urethane, It is known that a resin layer is formed by applying a resin solution such as nylon, polyethylene, epoxy, polyester, polyether, polystyrene, phenol, polyamide, and urethane-modified acrylic by dipping or spraying.

  As for development, a non-magnetic one-component developer (toner) is supplied to a latent image holder such as a photosensitive drum holding a latent image, and the developer is attached to the latent image of the photosensitive drum and the like. As a development method for visualizing the pressure, a pressure development method is known. Since this developing method does not require a magnetic material, there are advantages that the apparatus can be easily simplified and miniaturized and toner can be easily colored.

  In this pressure development system, development is carried out by bringing a developing roller carrying toner into contact with a latent image holding body holding an electrostatic latent image such as a photosensitive drum and attaching the toner to the latent image. The developing roller used in the developing system needs to be formed of an elastic body having conductivity.

  In this case, since the developing roller must rotate while securely holding the state in close contact with the photosensitive drum, silicone rubber, acrylonitrile butadiene rubber (NBR), ethylene is provided on the outer periphery of the shaft made of a highly conductive material such as metal. It has a structure in which an elastic layer made of an elastic body obtained by adding a conductive agent to an elastic rubber such as propylene diene terpolymer (EPDM), polyurethane foam or the like and imparting conductivity is formed. In addition, for the purpose of improving the surface friction properties, image quality, and the like, it has also been proposed to provide a skin layer imparted with conductivity by blending conductive powder on the elastic layer.

  Durability as one of the paints applied to form the coating film on the surface of the conductive roller, which has been used for charging, developing, transferring, cleaning, etc. And a fluororesin containing a fluoroolefin as a monomer unit, a curing agent having a crosslinking reactivity with the fluororesin, a conductive agent, and optionally an organic or inorganic filler. A fluororesin-based coating composition has been proposed (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 10-90972 (claims, etc.) Japanese Patent Laid-Open No. 10-268613 (claims, etc.) JP 2001-154456 A (Claims etc.)

  In recent years, with the increase in color and speed of electrophotographic machines, the toner used has shifted from pulverized toner to polymerized toner, and there is a tendency to lower the glass transition point (Tg) of the polymerized toner due to the demand for higher speed. It has become stronger, and even with a conductive roller coated with a fluororesin coating composition, it has become impossible to exhibit sufficient performance with respect to toner adhesion. As a result, toner adheres to the roller, resulting in a decrease in durability and further causing a serious defect in the image.

  Accordingly, an object of the present invention is to apply a coating composition for a conductive roller having excellent toner adhesion without impairing the durability derived from a fluororesin containing a fluoroolefin as a monomer unit, and the coating composition. A conductive roller.

（式中、Ｘは炭素数１〜２０のアルキレン基、パーフロロアルキレン基、または部分フッ素化アルキレン基であり、直鎖状、分岐状、または主鎖または側鎖中に酸素原子が介入したものでもよく、Ｒ^１はＨ、ＣＨ_３、Ｃｌ、ＦまたはＣＮである）で表される化合物、および、次式、

で表される化合物を含むフッ素樹脂（Ｂ）５〜５０重量部と、前記フッ素樹脂（Ｂ）と反応性を有するポリイソシアネート化合物からなる硬化剤（Ｃ）１〜４０重量部と、導電剤（Ｄ）１〜６０重量部と、を含んでなることを特徴とするものである。 In order to solve the above-described problems, the conductive roller coating composition of the present invention comprises poly (tetrafluoroethylene), poly (vinylidene fluoride), poly (ethylene / tetrafluoroethylene) copolymer, poly (fluorinated fluoride). Vinylidene / tetrafluoroethylene) copolymer, poly (tetrafluoroethylene / hexafluoropropylene) copolymer, poly (vinyl fluoride ether), poly (vinyl fluoride / tetrafluoroethylene) copolymer, poly 75 to 90 parts by weight of a fluororesin (A) selected from (vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene) copolymer and poly (vinylidene fluoride / hexafluoropropylene) copolymer, and the fluorine Having compatibility with the resin (A) and having at least the following formula as a monomer component:

(In the formula, X is an alkylene group having 1 to 20 carbon atoms, a perfluoroalkylene group, or a partially fluorinated alkylene group, linear, branched, or an oxygen atom intervening in the main chain or side chain. And R ¹ is H, CH ₃ , Cl, F or CN), and

5 to 50 parts by weight of a fluororesin (B) containing a compound represented by formula (1), 1 to 40 parts by weight of a curing agent (C) comprising a polyisocyanate compound reactive with the fluororesin (B), and a conductive agent ( D) 1 to 60 parts by weight.

Further, the conductive roller of the present invention is a conductive roller comprising a shaft, an elastic layer carried on the outer periphery of the shaft, and a coating film formed on the surface of the elastic layer.
The coating film is formed of the conductive roller coating composition of the present invention.

  According to the present invention, a conductive roller excellent in toner adhesion and durability can be provided.

Hereinafter, embodiments of the present invention will be specifically described.
The conductive roller coating composition of the present invention comprises a fluororesin (A) containing a fluoroolefin as a monomer unit, a side having compatibility with the fluororesin (A) and having a CF ₃ group at the end. A fluororesin (B) having a chain and a functional group capable of undergoing a crosslinking reaction of the same type as the fluororesin (A), and a curing having a crosslinking reactivity with the fluororesin (A) and the fluororesin (B) An agent (C) and a conductive agent (D) are included.

  The fluororesin (A) containing a fluoroolefin as a monomer unit may be any resin that can be dispersed or dissolved in an organic solvent. Specific examples thereof include poly (tetrafluoroethylene), poly (vinylidene fluoride), poly (Ethylene / tetrafluoroethylene) copolymer, poly (vinylidene fluoride / tetrafluoroethylene) copolymer, poly (tetrafluoroethylene / hexafluoropropylene) copolymer, poly (vinyl fluoride ether), poly ( (Vinyl fluoride ether tetrafluoroethylene) copolymer and the like. Of these, vinylidene fluoride polymers are particularly preferable from the viewpoints of compatibility with other components and solubility in solvents. Examples of the vinylidene fluoride polymer include poly (vinylidene fluoride), poly (vinylidene fluoride / tetrafluoroethylene) copolymer, poly (vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene) copolymer, poly ( Tetrafluoroethylene / hexafluoropropylene) copolymer, poly (vinylidene fluoride / hexafluoropropylene) copolymer, and the like.

  The fluorine content of the fluororesin (A) is preferably 5 to 40% by weight. When the content is less than 5% by weight, durability based on the fluororesin cannot be sufficiently obtained. On the other hand, when the content exceeds 40% by weight, solvent solubility or compatibility with other components is lowered.

  Next, examples of the monomer of the fluororesin (B) include fluorinated (meth) acrylates represented by the following general formula (b).

（式中、Ｘは炭素数１〜２０のアルキレン基、パーフロロアルキレン基、または部分フッ素化アルキレン基であり、直鎖状、分岐状、または主鎖または側鎖中に酸素原子が介入したものでもよく、Ｒ¹はＨ、ＣＨ₃、Ｃｌ、ＦまたはＣＮである）にて表わされる化合物であるが、耐久性などの向上の観点から、式中Ｘのアルキル基、パーフロロアルキレン基または部分フッ素化アルキレン基の炭素数は４以上が好ましく、６以上が更に好ましい。特に好ましくは、−（ＣＨ₂）₂−（ＣＦ₂）₇−である。

(In the formula, X is an alkylene group having 1 to 20 carbon atoms, a perfluoroalkylene group, or a partially fluorinated alkylene group, linear, branched, or an oxygen atom intervening in the main chain or side chain. Or R ¹ is H, CH ₃ , Cl, F, or CN). From the viewpoint of improving durability and the like, an alkyl group, a perfluoroalkylene group or a moiety of X in the formula The fluorinated alkylene group preferably has 4 or more carbon atoms, more preferably 6 or more. Particularly preferred is — (CH ₂ ) ₂ — (CF ₂ ) ₇ —.

  The fluorine content of the fluororesin (B) is preferably 3 to 60% by weight. When the content is less than 3% by weight, durability based on the fluororesin cannot be obtained. On the other hand, when the content exceeds 60% by weight, solvent solubility or compatibility with other components is lowered. The glass transition point (Tg) of the fluororesin (B) is preferably in the range of 0 ° C. to 80 ° C. in order to obtain good toner adhesion.

  Next, the type of the curing agent (C) is not particularly limited, and two or more reactions in the molecule react with the functional groups introduced into the above-described fluororesins (A) and (B). Any reactive polyfunctional compound having a functional functional group may be used.

  The reactive functional group may be the same as that introduced into each polymer, for example, a hydroxyl group, a thiol group, a carboxyl group, an amino group, an isocyanate group, an aziridinyl group, a glycidyl group, an alkoxysilyl group, Silanol group, cyclocarbonate group, acid anhydride group, vinyl group, enol ether group, thioether group, active ester group, acetoacetate group, metal salt, metal oxide and those functional groups blocked with various blocking agents Is mentioned. There may be one kind of functional group to be contained, or two or more kinds.

  As this hardening | curing agent (C), an organic epoxy compound and an organic polyisocyanate compound are preferable from industrial usefulness. Examples of the organic epoxy compound include compounds containing two or more glycidyl groups in the molecule. For example, various epoxy resins and low molecular compounds having two or more glycidyl groups include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, sorbitol polyglycidyl ether, polyethylene Glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6 hexanediol diglycidyl ether, glycerin polyglycidyl ether, diglycerin polyglycidyl ether, trimethylolpropane polyglycidyl Ether, spiroglycol diglycidyl ether, etc. It is not particularly limited thereto.

  Examples of the organic polyisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4′-. Diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′biphenylene diisocyanate, 3,3′-dimethoxy-4,4′biphenylene diisocyanate 3,3′-dichloro-4,4′- Biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene dii Cyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'- Dicyclohexylmethane diisocyanate, 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate and the like, dimers, trimers or phenols, oximes, alcohols, active methylenes, mercaptans, acid amides of these compounds , Imides, amines, imidazoles, ureas, carbamates, imines or sulfites partially blocked with polyisocyanates Etc. The.

Next, the conductive agent (D) is not particularly limited, and perchlorate of lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, modified fatty acid / dimethylethylammonium salt. Cationic surfactants such as quaternary ammonium salts such as chlorinates, borofluoride salts, sulfate salts, ethosulphate salts, benzyl bromide salts, benzyl chloride salts, and the like, aliphatic Anionic surfactants such as sulfonates, higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher alcohol phosphates, higher alcohol ethylene oxide addition phosphates, and zwitterionic fields such as various betaines Active agents, higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, nonionic antistatic agents such antistatic agents such as polyhydric alcohol fatty acid _{esters, LiCF 3 SO 3, NaCl 4} , LiAsF 6, LiBF 4, NaSCN, KSCN, Li ⁺ , such as NaCl, Li ⁺ , Na ⁺ , K ^+, etc. Group 1 metal salts, electrolytes such as NH ₄ ⁺ salts, Ca ²⁺ , such as Ca (ClO ₄ ) ₂ , Ba ^2+, etc. A metal salt belonging to Group 2 of the periodic table and an antistatic agent having at least one group having an active hydrogen that reacts with an isocyanate such as a hydroxyl group, a carboxyl group, or a primary or secondary amine group Is mentioned. Furthermore, these and complexes with polyhydric alcohols such as 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, polyethylene glycol and their derivatives, or monools such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether Ionic conductive agents such as complexes with carbon, conductive carbon such as ketjen black EC and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, etc., color subjected to oxidation treatment (Ink) carbon, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium and other metals and metal oxides, polyaniline polypyrrole, poly Conductive polymers such as acetylene and the like.

  Moreover, it is possible to introduce | transduce various fillers (E) into the coating composition for conductive rollers of this invention according to the objective. For example, an appropriate amount of a filler such as a thickener, thixotropy imparting agent, structural viscosity imparting agent and the like can be appropriately added as desired. In this case, the filler may be either inorganic or organic. .

  The blending ratio of the coating composition for the conductive roller of the present invention is preferably 20 to 90 parts by weight of the fluororesin (A), 5 to 50 parts by weight of the fluororesin (B), and cured in order to obtain a desired effect. The agent (C) is 1 to 40 parts by weight and the conductive agent (D) is 1 to 60 parts by weight. Moreover, when mix | blending an organic or inorganic filler, it is 50 weight part or less with respect to 100 weight part of all resins.

  Next, in the conductive roller of the present invention, as shown in FIG. 1, it is important to use the above-described coating composition of the present invention as the coating layer 4. Other configurations of the shaft 2 and the elastic layer 3 About etc., it can determine suitably according to common usage and it does not restrict | limit in particular.

  For example, the shaft 2 can be formed of metal or plastic. The material of the elastic layer 3 is not particularly limited as long as it has an elastic function. For example, foamed polyurethane, silicone rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene butadiene rubber, butadiene rubber, Examples include isoprene rubber, natural rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber. These may be used singly or in combination of two or more, but foamed polyurethane, silicone rubber, and ethylene propylene rubber are particularly suitable.

In the elastic layer 3, a filler such as silica and calcium carbonate, a plasticizer, a crosslinking accelerator, a crosslinking retarder, an antiaging agent, a colorant and the like may be appropriately blended as necessary. The elastic layer 3 may be a foam. In this case, a density of about 0.05 to 0.9 g / cm ³ is appropriate.

  The method for forming the coating layer 4 with the coating composition of the present invention is not particularly limited, but after adjusting to a suitable concentration or viscosity with a solvent suitable for the purpose as required, the coating composition is dipped. A method of applying by spraying or spraying can be preferably used.

The volume resistance of the obtained coating film is preferably 10 ⁶ to 10 ¹² Ω · m.

  The thickness of the coating layer 4 is not particularly limited, but is preferably a thin layer so as not to impair the flexibility of the elastic layer 3, and specifically 1 to 30 μm, particularly 1 to The thickness is preferably 20 μm.

Hereinafter, the present invention will be described in detail based on examples.
Synthesis Example 1 (Synthesis of Polymer B-1)
A glass flask equipped with a stirrer, a condenser and a thermometer is charged with fluorine-based monomers (b1) to (b5) at the blending ratios shown in Table 1 below, and azobis as a polymerization initiator under reflux in a nitrogen gas stream. After adding 0.5 part by weight of isobutyronitrile and 0.6 part by weight of lauryl mercaptan as a molecular weight regulator, the mixture was heated to reflux for 11 hours to complete the polymerization.

Synthesis Examples 2 to 5 (Synthesis of Polymer B-2 to Polymer B-5)
Polymers B-2 to B-5 were obtained in the same manner as in Synthesis Example 1 except that the blending ratios of the fluorine-based monomers (b1) to (b6) were changed as shown in Table 1 below.

  Various physical properties of the obtained polymers B-1 to B-5 are shown in Table 1 below. The structural formulas of the fluorinated monomers (b1) to (b6) used in this example are as follows.

＊１：１５０℃−３ｈｒ加熱後の重量変化
＊２：ＪＩＳ Ｋ−００７０
＊３：ポリスチレン換算ＧＰＣ法

* 1: Weight change after heating at 150 ° C. for 3 hours * 2: JIS K-0070
* 3: Polystyrene equivalent GPC method

Examples 1 to 4, Reference Example, Comparative Example 1
Each obtained fluororesin (B-1)-(B-5), fluororesin (A), hardening | curing agent (C), electrically conductive agent (D), and a filler (E) as needed Were blended according to the formulation shown in Table 2 below to prepare various coating compositions for conductive rollers. In addition, the coating composition which does not mix | blend a fluororesin (B) was also prepared as a comparative example.

Next, a stainless steel cylindrical shaft with a diameter of 6 mm is passed through the center of the cylindrical mold, and the conductive agent, foaming agent, and curing agent are dispersed / dissolved between the shaft and the cylindrical mold in the usual manner. The liquid polyol thus injected was injected and cured / foamed by heating to produce a polyurethane roller. The coating composition was applied to the outer peripheral surface of the polyurethane roller, and the thickness of the coating layer after curing and drying was 10 μm. The volume resistance value of the coating layer was 1 × 10 ⁹ Ω · m.

  The conductive roller thus prepared was mounted on a printer cartridge as a charging roller, and an image printing test was performed with a commercially available color printer to evaluate toner adhesion and durability. The obtained results are shown in Table 2 below.

＊１：ポリイソシアネート
＊２：カーボンブラック
＊３：有機系（シリカ）、無機系（ポリエチレンビーズ）
＊４：ＭＥＫ（メチルエチルケトン）、ＭＩＢＫ（メチルイソブチルケトン）
＊５：重合トナーを用い画像出力１０００枚後のローラ表面を目視観察した。
○ 良好
△ 普通
× 不良
＊６：重合トナーを用い画像出力１００００枚後の出力画像を目視観察した。
○ 良好
△ 普通
× 不良

* 1: Polyisocyanate * 2: Carbon black * 3: Organic (silica), inorganic (polyethylene beads)
* 4: MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone)
* 5: The surface of the roller after 1000 image outputs was visually observed using polymerized toner.
○ Good Δ Normal × Poor * 6: The output image after 10,000 image outputs was visually observed using polymerized toner.
○ Good △ Normal × Bad

  Since the conductive roller according to the present invention is excellent in toner adhesion and durability, it is very useful in recent colorization and further speed-up electrophotographic machines and the like.

It is sectional drawing of the electroconductive roller which concerns on one embodiment of this invention.

Explanation of symbols

1 Conductive roller 2 Shaft 3 Elastic layer 4 Coating layer

Claims (8)

Poly (tetrafluoroethylene), poly (vinylidene fluoride), poly (ethylene / tetrafluoroethylene) copolymer, poly (vinylidene fluoride / tetrafluoroethylene) copolymer, poly (tetrafluoroethylene / hexafluoropropylene) Copolymers, poly (vinyl fluoride ether), poly (vinyl fluoride ether / tetrafluoroethylene) copolymers, poly (vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene) copolymers and poly (fluorocarbons). 75 to 90 parts by weight of a fluororesin (A) selected from vinylidene chloride / hexafluoropropylene) copolymer,
It has compatibility with the fluororesin (A), and as a monomer component , at least the following formula:

(In the formula, X is an alkylene group having 1 to 20 carbon atoms, a perfluoroalkylene group, or a partially fluorinated alkylene group, linear, branched, or an oxygen atom intervening in the main chain or side chain. And R ¹ is H, CH ₃ , Cl, F or CN) , and

5 to 50 parts by weight of a fluororesin (B) containing a compound represented by :
1 to 40 parts by weight of a curing agent (C) made of a polyisocyanate compound having reactivity with the fluororesin (B) ,
1 to 60 parts by weight of a conductive agent (D),
A coating composition for a conductive roller, comprising:   The coating composition for conductive rollers according to claim 1, wherein the fluorine content of the fluororesin (A) is 5 to 40% by weight and the fluorine content of the fluororesin (B) is 3 to 60% by weight.   The coating composition for conductive rollers according to claim 1 or 2, wherein the glass transition point (Tg) of the fluororesin (B) is in the range of 0 ° C to 80 ° C. Formula (b) X in the _{- (CH 2) 2 - (} CF 2) 7 - a a conductive roller coating composition as claimed in any one of claims 1-3.   The conductive roller coating composition according to any one of claims 1 to 4, comprising an organic or inorganic filler (E).   The coating composition for conductive rollers according to claim 5, wherein the organic or inorganic filler (E) is 50 parts by weight or less with respect to 100 parts by weight of the total resin. In a conductive roller comprising a shaft, an elastic layer carried on the outer periphery of the shaft, and a coating film formed on the surface of the elastic layer,
The said coating film is formed with the coating composition for conductive rollers as described in any one of Claims 1-6, The conductive roller characterized by the above-mentioned. The conductive roller according to claim 7, wherein the volume resistance of the coating film is 10 ⁶ to 10 ¹² Ω · m.

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