JP2004233596A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roll whose durability is high, whose toner electrification property is excellent and by which an excellent image is obtained. <P>SOLUTION: The developing roll is provided with a shaft body 11, a base rubber layer 12 formed on the outer periphery of the shaft body and a surface layer 13 formed directly or through another layer on the outer periphery of the base rubber layer 12. The surface layer 13 is formed of at least either (A): silicone resin partially modified with acrylic resin or (B): silicone resin partially modified with polyester resin. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５８】
【表２】

【００５９】
【表３】

【００６０】
上記表１〜表３の結果から、実施例品はいずれも、低硬度で、所望するレベルの電気抵抗を有し、帯電性および耐摩耗性等に優れており、良好な画像が得られるようになることがわかる。
【００６１】
これに対し、その表層が通常のシリコーン樹脂により形成された比較例１のロールは、表面硬度が高く、さらに、表層中にカーボンが分散せず、所望するレベルの電気抵抗とならないため、現像ロールとしての製品性に劣ることわかる。なお、比較例１におけるトナー帯電性等の評価は、表層中にカーボンが分散しないため、評価できなかった。また、アクリル樹脂やポリエステル樹脂によって表層が形成された比較例２および比較例３のロールは、トナー帯電性が充分に得られず、現像ロールとしての製品性に劣ることわかる。さらに、表層を形成せず、シリコーンゴム層のみの単層構造である比較例４のロールは、耐摩耗性に劣ることから、耐久後の画質悪化を引き起こすおそれがあり、実使用に耐え得るものとはならないことがわかる。
【００６２】
【発明の効果】
以上のように、本発明の現像ロールは、シリコーンゴム等の弾性体からなるベースゴム層の外周に形成されている表層が、アクリル樹脂またはポリエステル樹脂で部分的に変性されたシリコーン樹脂よって形成されて構成されている。そのため、低硬度でかつ低抵抗であり、耐久性およびトナー帯電性に優れている。そして、これにより、良好な画像を得ることができる。また、ベースゴム層からの低分子量分のブリードアウトも、抑えることができる。
【００６３】
特に、上記変性シリコーン樹脂における、アクリル樹脂またはポリエステル樹脂による変性比率が、特定の範囲に設定されていると、カーボン分散性、トナー帯電性、耐久性が良好となり、先に述べたような本発明の現像ロールの各特性のバランスが、より向上するようになる。
【図面の簡単な説明】
【図１】本発明の現像ロールの一例を示す断面図である。
【図２】ロール電気抵抗の測定方法を示す説明図である。
【符号の説明】
１１ 軸体
１２ ベースゴム層
１３ 表層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing roll used in an electrophotographic apparatus such as an electrophotographic copying machine and a printer.
[0002]
[Prior art]
Among the developing rolls used in electrophotographic copying machines, printers, and the like, as a soft developing roll configured using an elastic body, for example, an elastic body such as silicone rubber is provided on the outer periphery of a core metal serving as a shaft, The surface layer is formed by polishing a single layer structure of the elastic layer by polishing it, or applying a solution of a resin or rubber material such as urethane resin, acrylic resin, polyamide resin or the like to the surface of the elastic layer. One having a formed laminated structure can be mentioned.
[0003]
A single-layer structure having only an elastic layer made of silicone rubber is characterized by the fact that, due to the characteristics of the silicone rubber, it is necessary to ensure toner charging properties and to prevent fogging (meaning that toner is flying where there is no image). In this case, and exhibits good performance in this regard. However, its performance is specified because of its difficulty in terms of durability (wear resistance) and its single-layer silicone rubber elastic layer. Therefore, it is difficult to optimize factors such as resistance, surface roughness, and hardness for ensuring good image quality in each system such as a copying machine, and it is difficult to meet demands for high image quality and high durability.
[0004]
On the other hand, a laminated structure having a surface layer made of a urethane resin or the like has improved durability (abrasion resistance) as well as the surface layer according to the toner used for image formation in each system. By appropriately selecting the material, it is possible to secure various characteristics required for the developing roll, such as toner charging properties, toner transport properties, and toner filming resistance. In addition, the surface layer can prevent bleed-out of low molecular weight components from silicone rubber or the like, which is a material for forming the elastic layer. However, there is a disadvantage that the toner chargeability, which is an important characteristic, is poor. Under such circumstances, a technology has been proposed in which a silicone resin, which is a resin material having better charging characteristics than a conventional surface material such as a urethane resin, is used as a surface material of a developing roll (for example, see Patent Document 1). .
[0005]
[Patent Document 1]
JP-A-11-65268
[Problems to be solved by the invention]
However, even when a silicone resin is used as the surface layer material, it is necessary to impart conductivity to the surface layer in order to set the resistance value to the level required for the developing roll. Since the dispersibility of carbon black, which is a conductive material, is poor, it is difficult to impart conductivity to the surface layer by this dispersion. Therefore, in the technique of the above-mentioned document, the surface layer is formed to have a thickness of 0.5 μm or less, so that a resistance value of a level required for the developing roll can be obtained. However, if control is performed so that the surface layer thickness is reduced in this way, the productivity is inferior, and the hardness of the silicone resin is high. When such a silicone resin solution is applied, there is a problem that wrinkles easily occur during production or use and it becomes difficult to obtain a good image due to a difference in hardness.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a developing roll which is excellent in durability and toner chargeability and can obtain a good image.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the developing roll of the present invention has a shaft, a base rubber layer formed on the outer periphery thereof, and a surface layer formed directly or via another layer on the outer periphery of the base rubber layer. Wherein the surface layer is formed by at least one of the following (A) and (B).
(A) A silicone resin partially modified with an acrylic resin.
(B) A silicone resin partially modified with a polyester resin.
[0009]
That is, the present inventors have conducted a series of studies in order to achieve both excellent chargeability as seen in a single-layer product having only a silicone rubber layer and durability of a resin-based surface layer. In the process, if the surface layer of the roll is formed of a normal silicone resin, there is a possibility that the above-described adverse effects due to poor dispersibility of carbon black may occur. Instead of the silicone resin, the use of a silicone resin partially modified with an acrylic resin or a polyester resin, which is presumed to be excellent in dispersibility of carbon black, was recalled. Then, when carbon black was actually dispersed in this modified silicone resin, it was confirmed that carbon black was excellent in dispersibility compared to a normal silicone resin. When the surface layer was formed on the outer periphery, it was found that the intended purpose could be achieved, and the present invention was reached.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail.
[0011]
For example, as shown in FIG. 1, the developing roll of the present invention has a structure in which a base rubber layer 12 is formed along the outer peripheral surface of a shaft 11 and a surface layer 13 is formed on the outer peripheral surface. be able to. In the present invention, the base rubber layer 12 is formed by using an elastic body such as silicone rubber, and the surface layer 13 is formed by at least one of the following (A) and (B).
(A) A silicone resin partially modified with an acrylic resin.
(B) A silicone resin partially modified with a polyester resin.
[0012]
The shaft 11 is not particularly limited. For example, a metal core or a hollow metal cylinder is used. And, as the metal material, aluminum, stainless steel and the like can be mentioned. Note that an adhesive, a primer, or the like may be applied on the shaft 11 as needed. The adhesive, the primer and the like may be made conductive as necessary.
[0013]
As a material for forming the base rubber layer 12 formed on the outer peripheral surface of the shaft 11, silicone rubber is often used because of its excellent compression set. The silicone rubber is not particularly limited, but it is preferable to use a dimethyl silicone polymer obtained by adding a vinyl group as a crosslinking site to a dimethyl silicone oil and adding dimethyl silicone oil.
[0014]
The base rubber layer 12 is usually formed with a suitable amount of a conductive agent such as carbon black.
[0015]
As described above, at least one of the following (A) and (B) is used as a material for forming the surface layer 13 formed on the outer peripheral surface of the base rubber layer 12.
(A) A silicone resin partially modified with an acrylic resin.
(B) A silicone resin partially modified with a polyester resin.
[0016]
Regarding the silicone resin as a material for forming the surface layer 13, the modification with the acrylic resin is performed by modifying an alkynol group (—ROH) (mainly —CH ₂ OH), which is a functional group of the thermosetting acrylic resin, and an organo-based material related to the silicone resin. Done by condensation with siloxanol or organosiloxane. The condensation may be either graft polymerization or block copolymerization. By appropriately changing the ratio of the thermosetting acrylic resin, a silicone resin having a desired modification ratio can be synthesized.
[0017]
Further, with respect to the silicone resin as a material for forming the surface layer 13, the modification with the polyester resin is performed by condensation of an alcoholic hydroxyl group of the polyester resin with a hydroxyl group or an alkoxy group of the silicone resin. The condensation may be either graft polymerization or block copolymerization. As described above, a silicone resin having a desired modification ratio can be synthesized by appropriately changing the ratio of the polyester resin. That is, by adjusting the denaturation ratio, it is possible to optimize hardness, durability, and the like for ensuring a good image in each system such as a copying machine.
[0018]
The modification ratio of the silicone resin, which is a material for forming the surface layer 13, with an acrylic resin or a polyester resin is preferably set in the range of 10 to 50%, and more preferably in the range of 20 to 40%. That is, when the modification ratio is less than 10%, the carbon dispersibility in the surface layer 13 tends to be inferior, so that the resistance reduction of the roll may be hindered, and the hardness of the roll may be reduced. This is because there is a possibility that it will not be performed. Conversely, if the modification ratio exceeds 50%, the toner chargeability may be impaired or the toner may be fogged on the photosensitive drum.
[0019]
A conductive agent is appropriately added to the material for forming the surface layer 13 in order to secure conductivity. Examples of the conductive agent include carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c-SnO ₂ , and ionic conductive agents (quaternary ammonium salts, boric acid) which are conventionally used. Salts, surfactants and the like). The mixing ratio of the conductive agent to 100 parts by weight (hereinafter, abbreviated as "parts") of the modified silicone resin is preferably 5 to 100 parts, more preferably 10 to 60 parts.
[0020]
In addition to the above components, other additives can be appropriately compounded as needed in the material for forming the surface layer 13. Other additives include fillers such as calcium carbonate, talc, clay, and silica, stabilizers, ultraviolet absorbers, charge control agents, reinforcing agents, lubricants, release agents, dyes, pigments, flame retardants, and oils. And the like.
[0021]
The material for forming the surface layer 13 is used as a coating liquid by dissolving in an organic solvent or the like. Examples of the organic solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, and dimethylformamide. These may be used alone or in combination of two or more. In particular, it is preferable to use toluene as the organic solvent from the viewpoint of solubility in the material for forming the surface layer 13. The viscosity of the coating liquid thus obtained is preferably 0.005 to 6 Pa · s from the viewpoint of coatability and the like.
[0022]
The developing roll of the present invention can be produced, for example, as follows.
[0023]
That is, first, each component for the base rubber layer 12 is kneaded with a kneading machine such as a kneader to prepare a base rubber layer 12 forming material. Further, the components for the surface layer 13 are dissolved in an organic solvent and dispersed by a sand mill or the like to prepare a material for forming the surface layer 13 (coating liquid).
[0024]
Then, the metal shaft 11 is set in the hollow portion of the cylindrical mold, and the base rubber layer 12 forming material is poured into the gap between the cylindrical mold and the shaft 11. The mold is covered and heated to crosslink the base rubber layer 12 forming material. Thereafter, the base roll having the base rubber layer 12 formed on the outer peripheral surface of the shaft body 11 is taken out by removing the mold from the cylindrical mold. The surface of the base roll is subjected to corona discharge treatment or plasma treatment as necessary. If necessary, a conventionally known adhesive such as a coupling agent is applied to the surface of the base roll. Then, the solution for forming the surface layer 13 is applied to the outer periphery of the base rubber layer 12 of the base roll. This coating method is not particularly limited, and a conventional method such as a dipping method, a spray method, and a roll coating method can be applied. After coating, drying and heating (vulcanization, conditions: 120 to 200 ° C. × 20 to 90 minutes) are performed to remove and crosslink the solvent in the surface layer 13 forming solution. I do. In this way, a target developing roll can be produced (see FIG. 1).
[0025]
In this developing roll, the thickness of the base rubber layer 12 is preferably set usually in the range of 0.5 to 10 mm, particularly preferably 1 to 6 mm. Further, the thickness of the surface layer 13 is preferably set in a range of 3 to 100 μm, and particularly preferably 5 to 50 μm.
[0026]
Although an example of the developing roll of the present invention has a two-layer structure as shown in FIG. 1, the present invention is not limited to this, and the developing roll is provided between the base rubber layer 12 and the surface layer 13. An appropriate number of layers are formed with an intermediate layer interposed. However, the surface layer 13 needs to be formed of the special silicone resin as described above.
[0027]
Next, examples will be described together with comparative examples.
[0028]
Embodiment 1
[Base rubber layer forming material]
Silicone rubber (X34-264, manufactured by Shin-Etsu Chemical Co., Ltd.).
[0029]
(Surface layer forming material)
A solution for surface layer formation was prepared by dispersing 100 parts of an acrylic-modified silicone resin (prototype number: AS-5) having an acrylic modification ratio of 5% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. Was prepared.
[0030]
[Production of developing roll]
Next, a core made of SUS303 (diameter: 10 mm) was prepared as a shaft, and an adhesive applied to the outer peripheral surface thereof was set inside the roll mold, and the gap between the shaft and the inner peripheral surface of the roll mold was set. The compound which is the base rubber layer forming material is cast into the part, and after being heated and vulcanized (180 ° C. × 20 minutes), demolded and further subjected to secondary vulcanization (200 ° C. × 4 hours) Thus, a base rubber layer (4 mm thick) was formed on the outer periphery of the shaft. The corona treatment was performed on the outer peripheral surface of the base rubber layer in the shaft body (base roll) with the base rubber layer obtained in this manner using a high-frequency power supply device. Then, after applying the coating liquid comprising the above surface layer forming material to the outer peripheral surface of the base rubber layer subjected to the above processing, drying and heating are performed to form a surface layer (thickness: 10 μm). Was obtained (see FIG. 1).
[0031]
Embodiment 2
A solution for surface layer formation was prepared by dispersing 100 parts of an acrylic-modified silicone resin (prototype number: AS-10) having an acrylic modification ratio of 10% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0032]
Embodiment 3
100 parts of an acrylic modified silicone resin (prototype number: AS-20) having an acrylic modification ratio of 20% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0033]
Embodiment 4
A solution for surface layer formation was prepared by dispersing 100 parts of an acrylic-modified silicone resin (prototype number: AS-30) having an acrylic modification ratio of 30% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0034]
Embodiment 5
A solution for surface layer formation was prepared by dispersing 100 parts of an acrylic modified silicone resin (prototype number: AS-40) having an acrylic modification ratio of 40% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0035]
Embodiment 6
100 parts of an acrylic modified silicone resin (prototype number: AS-50) having an acrylic modification ratio of 50% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a surface layer forming solution is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0036]
Embodiment 7
A solution for surface layer formation was prepared by dispersing 100 parts of an acrylic modified silicone resin (prototype number: AS-60) having an acrylic modified ratio of 60% and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0037]
Embodiment 8
100 parts of a polyester-modified silicone resin (prototype number: ES-5) having a polyester modification ratio of 5% and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0038]
Embodiment 9
100 parts of a polyester-modified silicone resin (prototype number: ES-10) having a polyester modification ratio of 10% and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0039]
Embodiment 10
100 parts of a polyester-modified silicone resin (prototype number: ES-20) having a polyester modification ratio of 20% and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0040]
Embodiment 11
100 parts of a polyester-modified silicone resin having a polyester modification ratio of 30% (prototype number: ES-30) and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0041]
Embodiment 12
100 parts of a polyester-modified silicone resin having a polyester modification ratio of 40% (prototype number: ES-40) and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0042]
Embodiment 13
100 parts of a polyester-modified silicone resin (prototype number: ES-50) having a polyester modification ratio of 50% and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0043]
Embodiment 14
100 parts of a polyester-modified silicone resin (prototype number: ES-60) having a polyester modification ratio of 60% and 40 parts of carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) are dispersed in 400 parts of toluene, and a solution for forming a surface layer is dispersed. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0044]
[Comparative Example 1]
By dispersing 100 parts of a silicone resin (manufactured by Toray Dow Corning Silicone, SR2410) and 40 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, MA-100) in 400 parts of toluene, a silicone resin solution having a modification ratio of 0% is prepared. Was prepared. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0045]
[Comparative Example 2]
An acrylic resin solution was prepared by dispersing 100 parts of an acrylic resin (Hyper D-100E, manufactured by Negami Kogyo Co., Ltd.) and 40 parts of carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation) in 400 parts of toluene. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0046]
[Comparative Example 3]
A polyester resin solution was prepared by dispersing 100 parts of a polyester resin (manufactured by Toyobo Co., Byron 20SS) and 40 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, MA-100) in 400 parts of toluene. The surface layer forming solution thus obtained was used in place of the surface layer forming material of Example 1. Otherwise, in the same manner as in Example 1, a developing roll was produced.
[0047]
[Comparative Example 4]
A roll similar to the base roll of Example 1 was prepared, and only the surface was polished without forming a surface layer, and this was used as a developing roll.
[0048]
Each of the thus obtained developing rolls was subjected to comparative evaluation and measurement of each characteristic according to the following criteria. These results are shown in Tables 1 to 3 below.
[0049]
〔surface hardness〕
The surface hardness of the developing roll was measured using a micro rubber hardness meter MD-1 (manufactured by Kobunshi Keiki Co., Ltd.).
[0050]
[Roll electric resistance]
The roll electrical resistance was measured by a metal roll electrode method using an apparatus as shown in FIG. That is, the developing roll 62 is brought into contact with the metal roll 61 made of stainless steel, and both ends of the developing roll 62 are pressed with a load of 1000 g (9.8 N). In this state, a voltage of 100 V is applied to one end of the developing roll 62. The electrical resistance was measured.
[0051]
(Carbon dispersibility)
Using a particle size distribution analyzer, Microtrac UPA (manufactured by Nikkiso Co., Ltd.), carbon dispersibility is indicated by ○ when the median diameter is smaller than 0.3 μm, Δ when the median diameter is in the range of 0.3 to 1 μm, and X when the median diameter is larger than 1 μm. Was evaluated.
[0052]
(Residual charge)
The residual charge of the developing roll was measured with a surface electrometer manufactured by Trek. Then, those in which the measured value of the residual charge was less than 20 V were evaluated as ○, those in the range of 20 to 50 V were evaluated as Δ, and those exceeding 50 V were evaluated as ×.
[0053]
(Toner chargeability)
The charge amount per unit weight of the toner layer-formed on the developing roll was measured with a Q / M measuring device (Model 210HS, manufactured by Trek). When the measured value of the toner charge amount at that time exceeds 15 (-μC / g), the result is ○. When the measured value of the toner charge amount is in the range of 10 to 15 (-μC / g), the result is Δ. Was evaluated as x.
[0054]
[Fog resistance]
The evaluation machine was forcibly stopped during image formation, and the amount of toner flying on the photosensitive drum in a white background portion was measured by density comparison by tape transfer (measured with a Macbeth densitometer). Then, those with measured values of less than 0.03 were evaluated as ○, those with 0.03 to 0.05 as Δ, and those with more than 0.05 were evaluated as x.
[0055]
(Abrasion resistance)
Using a simple idle jig, the cartridge on which the developing roll for evaluation was set was idled for 3 hours under the condition that the linear velocity of the developing roll was 180 mm / sec, and the outer diameter change of the roll before and after the endurance was measured. When the change in outer diameter was less than 5 μm, it was evaluated as ○, when it was 5 to 10 μm, and when it exceeded 10 μm.
[0056]
[Usability evaluation]
The obtained developing roll was incorporated into an electrophotographic printer, and printing was actually performed. Then, the image quality of the print image was visually evaluated. That is, a character was printed, and a printed image having no problem and clearly printed up to a thin line was evaluated as ○, and thereafter, evaluated in 順 に and × in order of good image.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
[Table 3]

[0060]
From the results shown in Tables 1 to 3, all of the examples were low in hardness, had a desired level of electrical resistance, were excellent in chargeability and abrasion resistance, etc., so that good images could be obtained. It turns out that it becomes.
[0061]
On the other hand, the roll of Comparative Example 1 in which the surface layer is formed of a normal silicone resin has a high surface hardness, does not disperse carbon in the surface layer, and does not have a desired level of electrical resistance. It is inferior to the productability as a product. In addition, the evaluation of the toner chargeability and the like in Comparative Example 1 could not be performed because carbon was not dispersed in the surface layer. Further, it can be seen that the rolls of Comparative Examples 2 and 3 in which the surface layer was formed of an acrylic resin or a polyester resin did not have sufficient toner chargeability and were inferior in productability as a developing roll. Further, the roll of Comparative Example 4 having a single-layer structure of only a silicone rubber layer without forming a surface layer is inferior in abrasion resistance, and may cause deterioration in image quality after durability, and can withstand actual use. It turns out that it does not become.
[0062]
【The invention's effect】
As described above, in the developing roll of the present invention, the surface layer formed on the outer periphery of the base rubber layer made of an elastic material such as silicone rubber is formed of a silicone resin partially modified with an acrylic resin or a polyester resin. It is configured. Therefore, it has low hardness and low resistance, and is excellent in durability and toner chargeability. As a result, a good image can be obtained. Also, bleed-out of low molecular weight from the base rubber layer can be suppressed.
[0063]
In particular, when the modification ratio of the modified silicone resin with an acrylic resin or a polyester resin is set in a specific range, carbon dispersibility, toner chargeability, and durability are improved, and the present invention as described above is used. The balance of each characteristic of the developing roll is further improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a developing roll of the present invention.
FIG. 2 is an explanatory diagram showing a method for measuring a roll electric resistance.
[Explanation of symbols]
11 Shaft 12 Base rubber layer 13 Surface layer

Claims (2)

A shaft, a base rubber layer formed on the outer periphery thereof, and a developing roll including a surface layer formed directly or via another layer on the outer periphery of the base rubber layer, wherein the surface layer is as follows: A developing roll formed of at least one of (A) and (B).
(A) A silicone resin partially modified with an acrylic resin.
(B) A silicone resin partially modified with a polyester resin. The developing roll according to claim 1, wherein the modification ratio of the surface layer forming material (A) and (B) with an acrylic resin or a polyester resin is set in a range of 10 to 50%.

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