JP3984835B2 - Contact charging member and contact charging device - Google Patents

Description

【００５６】
【実施例２】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
導電性酸化スズの量を５５質量部、へキサメチレンジイソシアネートの量を１７．８質量部とした以外は実施例１と同様にして表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．８７）
得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ２１μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、１１．７ＫＯＨｍｇ／ｇであった。
【００５７】
同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、６×１０¹²Ωｃｍであった。
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００５８】
【実施例３】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
導電性酸化スズの量を４５質量部、ヘキサメチレンジイソシアネートの量を８．９質量部とした以外は実施例１と同様にして表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．４４）得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ１９μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、５０．８ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、４×１０¹²Ωｃｍであった。
【００５９】
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６０】
【実施例４】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
導電性酸化スズの量を６０質量部、ヘキサメチレンジイソシアネートの量を１９．３質量部とした以外は実施例１と同様にして表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．９４）
得られた表面層用塗料を用いて実施例１と同様にして、厚さ２２μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、５．４２ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、５．５×１０¹²Ωｃｍであった。
（３）帯電部材の評価上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６１】
【実施例５】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
ポリエステルポリオール（水酸基価１５０ＫＯＨｍｇ／ｇ）７１質量部、メチルエチルケトン１２９質量部、導電性酸化スズ４０質量部を小型のビーズミルを用いて分散させた後、へキサメチレンジイソシアネート１１．４質量部を添加、溶解し表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．３３）
得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ２０μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、９９．９ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、４．５×１０¹²Ωｃｍであった。
【００６２】
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６３】
【比較例１】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
導電性酸化スズの量を７０質量部、へキサメチレンジイソシアネートの量を２０質量部とした以外は実施例１と同様にして表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．９７）
得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ１８μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、２．３０ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、６．０×１０¹²Ωｃｍであった。
【００６４】
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６５】
【比較例２】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
導電性酸化スズの量を５０質量部とした以外は比較例１と同様にして表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．９７）得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ１８μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、２．３０ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフイルムを作製し、体積固有抵抗値を測定したところ、２．０×１０¹⁴Ωｃｍであった。
【００６６】
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６７】
【比較例３】
（１）導電性弾性層の作成
実施例１と同様に行った。
（２）表面層の作成
ポリエステルポリオール（水酸基価２２５ＫＯＨｍｇ／ｇ）７１質量部、メチルエチルケトン１２９質量部、導電性酸化スズ３０質量部を小型のビーズミルを用いて分散させた後、ヘキサメチレンジイソシアネート２１．４質量部を添加、溶解し表面層形成用樹脂塗料を調製した。（ＮＣＯ／ＯＨ＝０．４２）得られた表面層形成用樹脂塗料を用いて実施例１と同様にして、厚さ２２μｍの表面層を有する帯電部材を得た。ポリウレタン樹脂中の水酸基価は、１３１ＫＯＨｍｇ／ｇであった。同時に、４０μｍ厚のフィルムを作製し、体積固有抵抗値を測定したところ、０．９×１０¹²Ωｃｍであった。
【００６８】
（３）帯電部材の評価
上記帯電部材を、実施例１と同じ条件で初期画像評価、耐久試験、リーク試験を行った。結果を表１に示す。
【００６９】
【発明の効果】
本発明により、帯電均一性に優れ、かつ感光体の放電絶縁破壊による画像欠陥等の発生のない接触式帯電部材、及びそれを用いた接触式帯電装置を提供することが出来る。
【図面の簡単な説明】
【図１】 本発明の接触式帯電装置を用いた画像形成装置の一例を示す概略構成図である。
【図２】 本発明の接触式帯電部材の一例を示す断面図である。
【符号の説明】
１ 感光体（被帯電体）
１ａ 導電性基体
１ｂ 感光層
２ 接触式帯電部材
２ａ 導電性基体
２ｂ 導電性弾性層
２ｃ 抵抗制御層
２ｄ 表面層
３ 電源
４ 露光手段
５ 現像手段
６ 転写手段
７ 被印刷物
８ クリーニング手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a contact charging member and a contact charging device mainly used in an electrophotographic image forming apparatus.
[0002]
[Prior art]
An electrophotographic image forming apparatus such as an electrophotographic copying machine, an electrophotographic printer, or an electrostatic recording apparatus has a primary charging unit for charging an image carrier, a transfer unit for attracting a developer on the image carrier onto a printing material, and the like. And a means for uniformly charging the member to be charged. As a charging method used at that time, a contact charging method in which the amount of ozone generated is much smaller than that of the conventional corona charging method has been studied, and recently, a part of the charging method has been put into practical use.
[0003]
In the contact charging method, a charged member to which a voltage is applied is brought into contact with the member to be charged to charge the member to be charged. It is common to charge the body. Many techniques related to the contact charging method have been proposed (Japanese Patent Laid-Open Nos. 57-178267, 56-104351, 58-40566, 58-139156, (Kaisho 58-150975).
[0004]
Further, the original purpose of the charging member is to hold the member to be charged at a predetermined potential, and for this purpose, an appropriate design of the surface layer is particularly important. For example, in Japanese Patent Application Laid-Open No. 06-248174, a polymer composition comprising a polyol containing polyether polyol or polyester polyol and polyisocyanate, and containing a conductive material, the conductive material comprises an alkali metal salt, and A roll is disclosed in which a layer made of a polymer composition is formed on the surface of a metal core, wherein the molecular composition has an OH / NCO ratio of 0.7 or more and less than 1. With this configuration, there is a feature that the polyurethane polymer composition has no variation in electric resistance and no precipitation of alkali metal salt as a conductive material.
[0005]
However, although many proposals have been made regarding the contact charging method and charging member, when a charged member is charged by applying a voltage, particularly a DC voltage, by contacting a conventional charging member to the charged member, It is easy to generate streak images due to non-uniformity of the image, and pinholes are generated due to discharge breakdown of the photoconductor due to direct application of voltage. For example, in the case of a cylindrical photoconductor, the current in the entire axial direction is The drawbacks such as the fact that the entire axial direction may not be charged due to the flow through the pinhole have not yet been solved.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, to have excellent charging uniformity and to prevent occurrence of image defects due to discharge dielectric breakdown of a photoreceptor, and a contact charging device using the same. Is to provide.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the above problems of the charging member (charging uniformity, leakage property), the present inventors, etc., (1) The resistance was adjusted by dispersing the minimum necessary conductive material in the binder resin having a low volume resistivity. By constituting the surface layer with the material, the above two problems can be solved simultaneously. (2) The volume resistivity of the material having a hydroxyl group in the binder resin has a good correlation with the absolute amount of the hydroxyl group. In particular, the present inventors have found that a polyurethane resin is a suitable material because the amount of hydroxyl group can be controlled relatively freely by appropriately adjusting the ratio of a polyol compound and an isocyanate compound as raw materials.
[0008]
That is, the present invention is as follows.
(1) A conductive substrate, a conductive elastic layer provided on the conductive substrate, a polyurethane resin and 30 to (20000/301) parts by mass of a conductive material with respect to 100 parts by mass of the polyurethane resin. Volume resistivity value is4x10 ¹² ~ 6 × 10 ¹² And a polyurethane resin in which the molar ratio of hydroxyl group (OH) to isocyanate group (NCO) is 0.3 ≦ NCO / OH <1.0. A contact-type charging member, which is a polyurethane resin obtained from a raw material and has a hydroxyl value of 5 KOHmg / g or more and 100 KOHmg / g or less.
(2) The contact-type charging member according to (1), wherein the conductive material is a metal oxide, carbon black, or a spherical carbon material.
(3) The contact charging member according to (1), wherein the conductive material is tin oxide.
(4) The contact-type charging member according to any one of (1) to (3), wherein the volume resistivity value of the surface layer is larger than the volume resistivity value of the conductive elastic layer.
(5) In a contact charging device having a charging member and charging the charged member by applying a voltage to the charging member brought into contact with the charged member, the charging member comprises (1) to (4) A contact-type charging device according to any one of the above, characterized in that it is a contact-type charging member.
(6) The contact charging device according to (5), wherein the voltage is only a DC voltage.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0010]
The charging member of the present invention has a conductive substrate, a conductive elastic layer provided on the conductive substrate, and a surface layer containing a polyurethane resin. The polyurethane resin of the surface layer is made of a polyurethane raw material. The contact type charging member has a molar ratio of hydroxyl group (OH) to isocyanate group (NCO) of 0.3 ≦ NCO / OH <1.0, and a hydroxyl value of 5 KOHmg / g or more and 100 KOHmg / g or less.
[0011]
One embodiment of the contact-type charging member of the present invention is shown in FIG.
[0012]
The contact-type charging member of the present invention comprises a cored bar 2a that is a conductive substrate to which a voltage is applied, a conductive elastic layer 2b that imparts elasticity, and a surface layer 2d that is a coating layer that comes into contact with the object to be charged. If necessary, a resistance control layer 2c for controlling the resistance of the charging member may be provided outside the conductive elastic layer 2b.
[0013]
A cored bar 2a, which is a conductive substrate used in the present invention shown in FIG. 2, is a stainless steel cylinder. Other materials that constitute the conductive substrate include, for example, metals such as iron, aluminum, titanium, copper and nickel, alloys such as stainless steel, duralumin, brass and bronze containing these metals, and carbon black and carbon fibers. It is also possible to use a known material that is rigid and exhibits electrical conductivity, such as a composite material hardened in (1). Moreover, as a shape, it can also be set as the cylindrical shape which made the center part the cavity other than a column shape.
In the present invention, first, the conductive elastic layer 2b is formed on the outer periphery of the conductive substrate 2a.
[0014]
Conductive elastic layer is made of metal powder or fiber such as aluminum, palladium, iron or copper; conductive polymer powder such as polyacetylene, polypyrrole or polythiophene; carbon black; titanium oxide, tin oxide or zinc oxide. Metal oxide powder such as metal oxide, copper sulfide and zinc sulfide, or the surface of appropriate particles tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, A layer made of conductive resin such as powder, acetylene black, ketjen black and other conductive materials dispersed by electrolytic treatment, spray coating, mixed shaking of lead, platinum, rhodium, etc. Can be mentioned. Alternatively, a material obtained by laminating or coating the surface of rubber or insulating resin with a metal or another conductive material can be used.
[0015]
Rubbers used for the conductive elastic layer include EPM (ethylene / propylene rubber), EPDM (ethylene / propylene rubber), norbornene rubber, NBR (nitrile rubber), chloroprene rubber, natural rubber, isoprene rubber, butadiene rubber, styrene. -Butadiene rubber, chlorosulfonated polyethylene, hydrin rubber, urethane rubber, silicone rubber and the like can be mentioned, and examples of the insulating resin include polycarbonate and polyester.
[0016]
The conductive elastic layer has a volume resistivity of 10¹-10¹¹Ωcm is preferred, especially 10²-10^TenA range of Ωcm is preferred. The volume specific resistance value may be adjusted by adjusting the amount of conductive material such as carbon black, conductive metal oxide, metal powder, or conductive polymer powder added to the rubber or insulating resin. The compounding quantity is 0.5-300 mass parts with respect to 100 mass parts of rubber | gum or insulating resin, Preferably it is 3-100 mass parts.
[0017]
The film thickness of the conductive elastic layer is preferably in the range of 0.5 to 10 mm, particularly 1 to 6 mm.
[0018]
In order to set the film thickness of the conductive elastic layer within the above range, when the conductive elastic layer is formed, for example, when the film thickness is controlled by injection molding, the elastic layer material after vulcanization is used at the time of vulcanization. There are methods such as designing a mold in consideration of thermal deformation (dimensions and shape), and controlling the film thickness by polishing after extrusion, and optimizing the polishing conditions of the polishing machine.
[0019]
Examples of the method for forming the conductive elastic layer include known methods such as extrusion molding, injection molding, and compression molding by mixing the raw materials for the conductive elastic layer. The conductive elastic layer may be produced by directly forming a conductive elastic layer on a conductive substrate, or may be formed by forming a tube shape on a conductive substrate. Note that the surface may be polished and the shape may be adjusted after the production of the conductive elastic layer.
[0020]
After the conductive elastic layer is completed, a surface layer containing a polyurethane resin is provided as the covering layer.
[0021]
Examples of the polymer raw material for the polyurethane resin of the surface layer include the following polyol compounds and isocyanate compounds.
[0022]
Examples of polyol compounds include oil-free polyester polyols using dibasic acids such as phthalic acid and adipic acid, and alcohols such as TMP, ethylene glycol, hexanediol, and neopentyl glycol as raw materials; soybean oil, castor oil Polyester polyols such as coconut oil; polyether polyols using alkylene oxides such as propylene oxide and ethylene oxide as raw materials; copolymers of acrylic acid ester, methacrylic acid ester, hydroxyethyl methacrylate (HEMA), styrene, acrylic acid, etc. Acrylic polyol, which is a fluorine polyol, which is an organic fluorine compound in which an OH group is introduced into a polymer chain, an epoxy polyol having an epoxy group, polytetramethylene glycol by polymerization of THF ; Polycarbonate polyol; and compounds and mixtures thereof having a terminal hydroxyl group such as polybutadiene polyols butadiene as a raw material can be cited.
[0023]
As isocyanate compounds, aromatic isocyanate compounds such as tolylene diisocyanate, metaxylylene diisocyanate, diphenylmethane isocyanate, polymethylene polyphenyl isocyanate, water addition of the above isocyanates, aliphatic isocyanate compounds such as hexamethylene diisocyanate, and these isocyanate compounds And blocked isocyanate compounds in which the isocyanate group is blocked with phenol, ketoxime, aromatic secondary amine, tertiary alcohol, amide, lactam, heterocyclic compound, sulfite or the like.
[0024]
The above-mentioned polyol compound and isocyanate compound can be dissolved in a solvent such as benzene, toluene, nitrobenzene, dibutyl ether, methyl ethyl ketone, dioxane, acetonitrile, etc., so that a coating method that does not disturb the conductive elastic layer that is the lower layer during molding It is possible to take
[0025]
In addition, polyurethane and elastomer can be dissolved in N-methylpyrrolidone, dimethylacetamide, DMF, pyridine, benzyl alcohol, etc. and molded again.
[0026]
As a catalyst for promoting the formation of a polymer, naphthenic acid salts such as magnesium naphthenate and cobalt naphthenate, organotin compounds such as dibutyltin dilaurate and dimethyltin dilaurate, N-methylmorpholine, N, N, N ′, N′— An amine compound such as tetramethylpolymethylenediamine may be added. The addition amount of the catalyst is preferably in the range of 0.001 to 5% by mass with respect to the polymer.
[0027]
The polyurethane resin used for the surface layer of the present invention has a molar ratio of hydroxyl group (OH) to isocyanate group (NCO) of the polyurethane polymerization raw material of 0.3 ≦ NCO / OH <1.0. NCO / OH is preferably 0.4 to 0.99. When NCO / OH is less than 0.3, the strength of the material is insufficient due to the low degree of cross-linking. Therefore, if a surface layer is formed with such a material, the surface layer will crack during use, resulting in poor charging. Tend to cause image defects. When NCO / OH is 1.0 or more, there are few hydroxyl groups in a polyurethane resin, and it is difficult to adjust the volume specific resistance value of polyurethane resin itself to a desired value.
[0028]
The hydroxyl value of the polyurethane resin of the present invention is 5 KOHmg / g or more and 100 KOHmg / g or less, preferably 10 KOHmg / g or more and 50 KOHmg / g or less.
[0029]
When the hydroxyl value is lower than 5 KOHmg / g, the volume resistivity value of the polyurethane resin itself becomes high, and it is necessary to add and disperse a large amount of conductive material in order to control the resistance range of the desired surface layer. According to the study by the present inventors, such a material has a large voltage dependency even when the resistance is combined under a certain voltage, and the resistance tends to extremely decrease under the application of a high voltage. . In order to improve the charging uniformity, it is necessary to reduce the resistance of the surface layer under the application of a low voltage, but the leakage property deteriorates for the above reason. On the contrary, if the resistance at the time of applying a high voltage is increased, the leakage property is good, but the charging uniformity is deteriorated, so that the charging uniformity and the leakage property cannot be made compatible. In addition, when a large amount of conductive material is added and dispersed, micro resistance unevenness of the surface layer increases, and the charging uniformity tends to deteriorate.
[0030]
When the hydroxyl value is higher than 100 KOHmg / g, the volume resistivity of the polyurethane resin itself decreases, and the resistance can be adjusted by adding and dispersing a small amount of conductive material. Although a good surface layer can be obtained, the tackiness of the material (especially under high temperature and high humidity) is increased. Therefore, when a surface layer is formed with such a material, a developer, paper powder, etc. are attached during use. There is a tendency to generate image defects due to charging defects.
[0031]
In order to set the hydroxyl value of the polyurethane to 50 KOHmg / g or more and 100 KOHmg / g or less, the ratio of the polyol compound and the isocyanate compound as raw materials may be adjusted as appropriate.
[0032]
Conductive materials contained in the surface layer include conductive materials made of metal oxides such as titanium oxide, tin oxide and zinc oxide, conductive materials made of carbon black, spherical carbon materials, etc., alone or in combination of two or more. May be used.
[0033]
  Surface layerThe amount of these conductive materials added to the resin is such that the volume resistivity of the surface layer resin is 10⁶-10¹⁴It is preferable to determine to be Ωcm. Further, as shown in Japanese Patent Application No. 62-230334, the volume resistivity of the surface layer is preferably larger than the volume resistivity of the lower layer in contact with the surface layer. In the present invention, the “lower layer in contact with the surface layer” is mainly a conductive elastic layer. Specifically, the volume resistivity of the surface layer is 10⁶-10¹⁴The volume resistivity of the conductive elastic layer is 10 Ωcm.¹-10¹¹It is preferably Ωcm.
[0034]
  As specific content of the electrically conductive material used for a surface layer, 30-200 mass parts is preferable with respect to 100 mass parts of polyurethane resins.Surface layerIf the volume specific resistance value is smaller than the volume specific resistance value of the conductive elastic layer, the resistance of the charging member is likely to decrease under application of a high voltage, resulting in poor leakage.
[0035]
The volume specific resistance value is measured using a resistance value measuring machine (trade name: Hiresta UP, J-Box, manufactured by Mitsubishi Chemical Corporation) with a sheet sample of a conductive elastic layer and a surface layer material. The measurement is performed under the condition of applying a DC voltage of 100 V for 30 seconds.
The film thickness of the surface layer is preferably 1 to 500 μm, particularly preferably 2 to 200 μm.
[0036]
  Surface layerTo make the film thickness within the above range,Surface layerIn molding, the solid content, viscosity and the like of the resin coating for forming the surface layer are controlled by adjusting to an appropriate range according to the molding method. The film thickness is measured by the following method.
1) A sample is cut out with a knife from nine places on the charging member (in the case of a roller shape, 10 mm from both ends and three positions in the center and three places in the circumferential direction (starting at 120 ° starting from an arbitrary place)). .
2) The cross section of each sample is observed with an optical microscope (about 400 times), and the film thickness of the surface layer is obtained. The arithmetic average of 9 points is used as the surface layer thickness.
[0037]
As a method for forming the surface layer, the material constituting the surface layer was dispersed by a known method using a conventionally known dispersion apparatus using beads such as a sand mill, paint shaker, dyno mill, pearl mill, and the like. The resin coating for forming the surface layer is applied on the surface of the charging member, in the present invention, on the conductive elastic layer by dipping or spray coating.
[0038]
The resistance control layer 2c may be provided as necessary between the elastic layer and the surface layer in order to eliminate partial resistance unevenness of the charging member and improve resistance uniformity.
[0039]
The shape of the charging member may be any shape such as a roller, a brush, a blade, or a belt, and can be selected according to the specifications and form of the electrophotographic apparatus. Among these, a roller shape is preferable.
[0040]
<2> Contact type charging device of the present invention
FIG. 1 shows a schematic configuration diagram of an image forming apparatus (copier) incorporating a contact charging device using the contact charging member of the present invention.
[0041]
In the contact charging member 2 of the present invention, a vibration voltage such as a DC voltage or a superimposed voltage of a DC voltage and an AC voltage is applied from a power source 3 to a conductive substrate.
[0042]
  In the contact charging device of the present invention, by using the contact charging member of the present invention as the charging member, (1) the resistance of the charging member is stable from low voltage to high voltage as described above. The voltage dependency of the resistance is small. (2) With a small amount of conductive material addedSurface layerBecause the resistance can be controlled stably,Surface layerThe effect of the charging member itself, such as microscopic resistance unevenness, is small. Therefore, the charging device using the charging member is “excellent in charging uniformity and does not cause image defects due to discharge dielectric breakdown of the photoreceptor”. Things can be configured. The voltage applied to the conductive substrate may be either a DC voltage or an oscillating voltage such as a superimposed voltage of an AC voltage and a DC voltage. In any case, the excellent effects of the present invention can be exhibited. In particular, the effect is remarkable when only the DC voltage is used without the AC power supply.
[0043]
In the conventional charging member, when only the DC voltage is applied and the photosensitive member is charged, the charging unevenness is likely to occur due to micro resistance unevenness of the surface layer, compared with the case where the AC voltage is superimposed. Although there is a problem that leakage easily occurs, the use of the charging member of the present invention significantly improves the uniform charging property and leakage resistance of the surface of the photosensitive member, so that the charging process can be performed only with a DC voltage. In addition, as DC voltage, 800-2000V is preferable.
[0044]
In the contact charging member 2 of the present invention, a oscillating voltage such as a DC voltage or a superimposed voltage of a DC voltage and an AC voltage is applied from a power source 3 to a cored bar 2a which is a conductive substrate.
[0045]
The contact-type charging member 2 is in contact with the photoreceptor 1 as a member to be charged with a predetermined contact force by a pressing means (not shown). The contact force is preferably a contact force of 100 to 800 g load on one side and 200 to 1600 g load on both sides.
[0046]
In the image forming apparatus of FIG. 1, the contact charging member 2 and the photosensitive member 1 rotate in the directions of the arrows, respectively, and the photosensitive layer 1 b of the photosensitive member with which the contact charging member 2 contacts is charged by the voltage applied by the power source 3 Then, an electrostatic latent image is formed by the exposure unit 4, the electrostatic latent image is developed by the developing unit 5, a toner image is formed on the photosensitive layer 1 b, and is transferred onto the substrate 7 by the transfer unit 6. A permanent image is formed. The transfer residual toner that has not been transferred is collected by the cleaning means 8.
[0047]
【Example】
Hereinafter, the contact charging member and the contact charging device of the present invention will be described in detail with reference to examples.
[0048]
[Example 1]
(1) Preparation of conductive elastic layer
100 parts by mass of silicone rubber, 5 parts by mass of zinc oxide, 7 parts by mass of conductive carbon black, and 20 parts by mass of industrial paraffin were sufficiently mixed and kneaded using a closed mixer, and then 2 parts of dicumyl peroxide by an open roll. Part was added to prepare a compound for a conductive elastic layer. This compound for conductive elastic layer was heated and vulcanized at 150 ° C. for 15 minutes on a stainless steel core having a diameter of 6 mm to produce a silicone rubber roller having a conductive elastic layer having a thickness of 3 mm.
[0049]
At the same time, a vulcanized sheet (2 mm thick) was prepared, and the volume resistivity value was measured using a Hiresta UP manufactured by Mitsubishi Chemical (23 ° C./60%, 100 V applied, 30 seconds).⁷It was Ωcm.
[0050]
  (2) Preparation of surface layer Lactone modified acrylic polyol (Hydroxyl group90 KOHmg / g) 71 parts by mass, methyl ethyl ketone 129 parts by mass, conductive oxidationTinAfter dispersing 50 parts by mass using a small bead mill, 14.3 parts by mass of hexamethylene diisocyanate was added and dissolved to prepare a resin coating for forming a surface layer. (NCO / OH = 0.70)
The surface layer-forming resin paint was dip-coated on the silicone rubber roller and dried at 150 ° C. for 1 hour to obtain a charging member having a surface layer with a thickness of 20 μm. In polyurethane resinHydroxyl groupThe value was 27.3 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared, and the volume resistivity value was measured using a Hiresta UP manufactured by Mitsubishi Chemical (100 V applied, 30 seconds).¹²It was Ωcm.
[0051]
(3) Evaluation of charging member
The charging member is attached to a primary charger position of a cartridge used in a laser beam printer (Laser Jet 4si Hewlett Packard), a bias of DC voltage −1160V is applied, and initial image evaluation and leakage are performed in an environment of 23 ° C./60%. A test and an endurance test of 8,000 sheets were performed. The results are shown in Table 1.
[0052]
<1> Image uniformity
The horizontal streaks appearing in the horizontal halftone image with 1 dot and 2 spaces were evaluated. The evaluation criteria are as follows.
Y: No horizontal stripe
△: Horizontal stripes
×: Many transverse muscles
[0053]
<2> Durability
(1) Surface layer dirt
After endurance, density unevenness appearing in a horizontal halftone image of 1 dot and 2 spaces was evaluated. The evaluation criteria are as follows.
○: Good density unevenness
Δ: Slight density unevenness
×: Remarkable density unevenness
(2) Surface layer crack
The surface of the charging roller after durability was observed with an optical microscope, and the degree of cracking was evaluated based on the following criteria.
◯: Only minor cracks are observed
Δ: Cracks are partially observed
X: Remarkable cracks are observed
[0054]
<3> Pinhole leak test
Using a photosensitive drum having a pinhole, a horizontal hole (horizontal black streak) caused by a pinhole appearing in a horizontal halftone image of one dot and two spaces was evaluated (DC voltage −1160 V). The evaluation criteria are as follows.
○: No through hole
Δ: Slightly through
×: Significant side-through
[0055]
[Table 1]

[0056]
[Example 2]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Conductive oxidationTinThe surface layer-forming resin coating was prepared in the same manner as in Example 1 except that the amount of hexamethylene diisocyanate was 17.8 parts by weight. (NCO / OH = 0.87)
A charging member having a surface layer with a thickness of 21 μm was obtained in the same manner as in Example 1 by using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 11.7 KOH mg / g.
[0057]
At the same time, a film having a thickness of 40 μm was prepared and the volume resistivity was measured.¹²It was Ωcm.
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0058]
[Example 3]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Conductive oxidationTinA surface layer-forming resin coating was prepared in the same manner as in Example 1 except that the amount of was changed to 45 parts by mass and the amount of hexamethylene diisocyanate was changed to 8.9 parts by mass. (NCO / OH = 0.44) A charging member having a surface layer having a thickness of 19 μm was obtained in the same manner as in Example 1 using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 50.8 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared, and the volume resistivity was measured.¹²It was Ωcm.
[0059]
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0060]
[Example 4]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Conductive oxidationTinThe surface layer-forming resin paint was prepared in the same manner as in Example 1 except that the amount of the styrene was 60 parts by mass and the amount of hexamethylene diisocyanate was 19.3 parts by mass. (NCO / OH = 0.94)
Using the obtained surface layer coating material, a charging member having a surface layer with a thickness of 22 μm was obtained in the same manner as in Example 1. In polyurethane resinHydroxyl groupThe value was 5.42 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared and its volume resistivity was measured to be 5.5 × 10.¹²It was Ωcm.
(3) Evaluation of Charging Member The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0061]
[Example 5]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Polyester polyol (Hydroxyl group150 KOHmg / g) 71 parts by mass, methyl ethyl ketone 129 parts by mass, conductive oxidationTinAfter 40 parts by mass was dispersed using a small bead mill, 11.4 parts by mass of hexamethylene diisocyanate was added and dissolved to prepare a resin coating for forming a surface layer. (NCO / OH = 0.33)
A charging member having a surface layer with a thickness of 20 μm was obtained in the same manner as in Example 1 using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 99.9 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared and the volume resistivity value was measured.¹²It was Ωcm.
[0062]
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0063]
[Comparative Example 1]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Conductive oxidationTinA surface layer-forming resin coating was prepared in the same manner as in Example 1 except that the amount of hexamethylene diisocyanate was 20 parts by mass. (NCO / OH = 0.97)
A charging member having a surface layer with a thickness of 18 μm was obtained in the same manner as in Example 1 by using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 2.30 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared, and the volume resistivity value was measured.¹²It was Ωcm.
[0064]
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0065]
[Comparative Example 2]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Conductive oxidationTinA surface layer-forming resin paint was prepared in the same manner as in Comparative Example 1 except that the amount of was changed to 50 parts by mass. (NCO / OH = 0.97) A charging member having a surface layer with a thickness of 18 μm was obtained in the same manner as in Example 1 using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 2.30 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared and the volume resistivity was measured.¹⁴It was Ωcm.
[0066]
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0067]
[Comparative Example 3]
(1) Preparation of conductive elastic layer
  The same operation as in Example 1 was performed.
(2) Creation of surface layer
  Polyester polyol (Hydroxyl groupValency: 225 KOHmg / g) 71 parts by mass, methyl ethyl ketone 129 parts by mass, conductive oxidationTinAfter 30 parts by mass was dispersed using a small bead mill, 21.4 parts by mass of hexamethylene diisocyanate was added and dissolved to prepare a resin coating for forming a surface layer. (NCO / OH = 0.42) A charging member having a surface layer having a thickness of 22 μm was obtained in the same manner as in Example 1 using the obtained resin coating for forming a surface layer. In polyurethane resinHydroxyl groupThe value was 131 KOH mg / g. At the same time, a film having a thickness of 40 μm was prepared and the volume resistivity value was measured.¹²It was Ωcm.
[0068]
(3) Evaluation of charging member
The charging member was subjected to initial image evaluation, durability test, and leak test under the same conditions as in Example 1. The results are shown in Table 1.
[0069]
【The invention's effect】
According to the present invention, it is possible to provide a contact-type charging member that is excellent in charging uniformity and does not cause image defects due to discharge dielectric breakdown of the photoreceptor, and a contact-type charging device using the contact-type charging member.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus using a contact charging device of the present invention.
FIG. 2 is a cross-sectional view showing an example of a contact charging member of the present invention.
[Explanation of symbols]
1 Photoconductor (Subject to be charged)
1a Conductive substrate
1b Photosensitive layer
2 Contact-type charging member
2a Conductive substrate
2b Conductive elastic layer
2c Resistance control layer
2d surface layer
3 Power supply
4 Exposure means
5 Development means
6 Transfer means
7 Substrate
8 Cleaning means

Claims (6)

Volume specific resistance containing a conductive substrate, a conductive elastic layer provided on the conductive substrate, a polyurethane resin and 30 to (20,000 / 301) parts by mass of a conductive material with respect to 100 parts by mass of the polyurethane resin A contact-type charging member having a surface layer having a value of 4 × 10 ^{12 to} 6 × 10 ¹² Ωcm,
The polyurethane resin is a polyurethane resin obtained from a polyurethane raw material in which the molar ratio of hydroxyl group (OH) to isocyanate group (NCO) is 0.3 ≦ NCO / OH <1.0. The hydroxyl value of the polyurethane resin is A contact-type charging member that is 5 KOHmg / g or more and 100 KOHmg / g or less. Before Kishirube material is a metal oxide, the contact type charging member according to claim 1 Ru carbon black or spherical carbon material der. Contact charging member according to claim 1 wherein the conductive material is Ru tin der oxide. The contact-type charging member according to claim 1, wherein a volume resistivity value of the surface layer is larger than a volume resistivity value of the conductive elastic layer. In a contact charging device that has a charging member and charges the charged member by applying a voltage to the charging member that is in contact with the charged member.
A contact-type charging device, wherein the charging member is the contact-type charging member according to claim 1. The contact charging device according to claim 5, wherein the voltage is only a DC voltage .

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