JP3899960B2 - Developing roll - Google Patents

Description

【００５３】
【表２】

【００５４】
上記表の結果から、実施例品はいずれも、トナー帯電性、トナー搬送性に優れているとともに、トナーフィルミング等も生じず、耐久後であってもプリント画像の劣化がほとんどみられないことがわかる。これに対し、最外層形成材料中のＰＶＢとポリウレタンとの配合割合が、本願発明に規定の範囲から若干外れる比較例１品および比較例２品では、１万枚プリント後（耐久後）のプリント画像の画質が劣っていたり、トナー固着の評価が劣っていることがわかる。そして、最外層のポリマーがＰＶＢのみからなる比較例３品では、表面硬度が高すぎ、鮮明なプリント画像が得られないことがわかる。また、ＰＶＢの配合割合の低すぎる比較例４品では、摩擦によるロール表面温度の上昇により、トナー劣化が生じ、耐久後の画質に悪影響が出ていることがわかる。そして、最外層のポリマーがポリウレタンのみからなる比較例５品や、アクリルのみからなる比較例６品の場合も、耐久後の画質が悪いことがわかる。
【００５５】
【発明の効果】
以上のように、本発明の現像ロールは、その最外層が、ＰＶＢおよび特定のポリウレタンを主成分とし、かつこれらが特定の割合で含有されてなる樹脂組成物によって形成されている。そのため、現像ロールの性能であるトナー帯電性やトナー搬送性を損なうことなく、低摩擦化がなされるようになる。その結果、層形成部材との摩擦による熱の発生が抑えられるようになるため、使用を継続しても、熱によって層形成部材にトナーが融着したり、熱劣化したりすることがなくなり、優れたプリント画像を得ることができるようになる。また、融点の低いトナーを使用した場合であっても、上記の融着等が生じないことから、画像の不具合を生じずに低電力化を達成することもできる。
【００５６】
特に、最外層表面の静動摩擦係数が特定の範囲に設定されていると、摩擦熱がより抑えられるようになるため、トナー劣化がさらに生じにくくなり、より優れたプリント画像を得ることができる。
【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。
【図３】 静動摩擦係数計による摩擦係数の測定状態を示す説明図である。
【図４】 （ａ）は上記摩擦係数の測定に用いる圧接子の断面図であり、（ｂ）は上記圧接子の正面図である。
【図５】 上記現像ロールの使用状態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 中間層
１４ 最外層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing roll used in an electrophotographic apparatus such as an electrophotographic copying machine or a printer.
[0002]
[Prior art]
In general, copying by an electrophotographic copying machine is performed as follows. That is, a document image is formed as an electrostatic latent image on a rotating photosensitive drum, and a toner image is formed by attaching toner to the image, and copying is performed by transferring the toner image onto a copy sheet. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected onto the charged portion via the optical system, and is exposed to light. An electrostatic latent image is formed by canceling the charging of the portion. As developing methods for developing an electrostatic latent image on a photosensitive drum and forming a visible image, various methods have been proposed conventionally depending on the type of developer used. As an example, a one-component development system using only toner as a developer is known.
[0003]
As a developing device used for the one-component developing method, for example, a developing device 1 as shown in FIG. 5 has been proposed. In this developing device 1, a developing roll 3 that carries a one-component developer (toner) 2 is accommodated in a toner box 5 that is in contact with the photosensitive drum 4 and opened to the photosensitive drum 4 side. Further, the developing roll 3 is in contact with an elastic roll 6 using a foam made of polyurethane foam, sponge or the like, and the rotation of the elastic roll 6 in the direction of the arrow causes the toner 2 to be placed on the outer periphery of the developing roll 3. A layer is formed. On the other hand, the toner box 5 is provided with a layer forming member 7. The layer forming member 7 is in pressure contact with the outer peripheral surface of the developing roll 3.
[0004]
In such a developing device 1, a toner image is formed on the outer peripheral surface of the photosensitive drum 4 as follows. That is, first, the developing roll 3 and the photosensitive drum 4 rotate as shown by the arrows in the drawing. Accordingly, the toner 2 is frictionally charged by friction between the layer forming member 7 and the outer peripheral surface of the developing roll 3, and a uniform thickness toner layer is formed on the outer peripheral surface of the developing roll 3. Then, the toner 2 in the toner layer is subjected to an electrostatic latent image by an electric attractive force of an electrostatic latent image (charged with a polarity opposite to that of the toner 2) formed on the outer peripheral surface of the photosensitive drum 4. Appears as a toner image. In this way, a toner image is formed on the outer peripheral surface of the photosensitive drum 4. The toner that has not participated in the toner image formation is collected in the toner box 5 and repeatedly used.
[0005]
Here, the developing roll 3 has a configuration in which, for example, a base rubber layer made of an elastic material such as silicone rubber is formed on the outer peripheral surface of the shaft body, and an outermost layer made of a resin material or rubber material is formed on the outer peripheral surface. Is done. With such a configuration, the outermost layer prevents the low molecular weight from bleeding out from silicone rubber or the like which is a material for forming the base rubber layer. Further, by appropriately selecting the outermost layer forming material of the developing roll 3 so as to be the outermost layer most suitable for the toner to be used, toner chargeability, toner transportability, toner filming resistance, etc. are ensured. become. As such an outermost layer forming material, conventionally, urethane resin, acrylic resin, polyamide resin and the like are used.
[0006]
[Problems to be solved by the invention]
However, when the conventional outermost layer forming material as described above is used, the toner component adheres to the layer forming member 7 due to the continued use of the developing roll 3, and a uniform toner layer cannot be formed, resulting in image defects. There is a difficulty that the toner is generated and a toner that is collected is deteriorated by heat. This is because, when the above-mentioned conventional outermost layer forming material is used, the frictional resistance of the roll surface is large, and the pressure contact portion of the layer forming member 7 with the developing roll 3 is locally heated by the continued use, and the heat It is considered that the toner is fused or deteriorated due to the above. In particular, in recent years, the melting point of toner tends to be lowered in order to achieve low power consumption, so it can be said that toner deterioration due to heat generation is likely to proceed.
[0007]
The present invention has been made in view of such circumstances, and its object is to provide a developing roll that is excellent in toner chargeability, toner transportability, and the like, and that does not cause toner deterioration and can provide good image quality. To do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the developing roll of the present invention is a developing roll in which at least one layer is formed on the outer peripheral surface of the shaft body, and the outermost layer is formed by the following resin composition (X). It is configured to be.
(X) below (A) and (B) as a main component, and (A) the content of component and component (B), in a weight ratio, (A) / (B) = 90/10 ~ 6 0 / Resin composition set in the range of 40 .
(A) Polyvinyl butyral.
(B) At least one of polytetramethylene ether glycol (PTMG) polyurethane and adipate polyurethane .
[0009]
That is, the present inventors have repeated a series of studies to solve the above problems. In the process, the present inventors obtained knowledge that, when polyvinyl butyral (hereinafter abbreviated as “PVB”) is used as the outermost layer forming material of the developing roll, the frictional resistance of the roll surface can be kept low. In order to improve the frictional resistance of the roll surface, which is a disadvantage of the conventional developing roll, by using PVB, research was repeated. As a result, it was found that PVB shows high compatibility with polyurethane. Then, PVB was blended in a specific ratio with respect to a specific polyurethane, and when this was used as the outermost layer forming material, it was found that low friction could be achieved without impairing toner chargeability and toner transportability. The present invention has been reached.
[0010]
In particular, if the static friction coefficient on the outermost layer surface is set within a specific range, the frictional heat can be further suppressed, so that the toner deterioration is less likely to occur and the image quality is further improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail.
[0012]
In the developing roll of the present invention, for example, as shown in FIG. 1, a base rubber layer 12 is formed along the outer peripheral surface of a shaft body 11, an intermediate layer 13 is formed on the outer peripheral surface, and the outermost surface is further covered with an outermost surface. A structure in which the outer layer 14 is formed can be used. In the present invention, the outermost layer 14 is characterized in that it is formed of a resin composition containing PVB and a specific polyurethane as main components and containing them in a specific ratio. Here, the “main component” means a component that greatly affects the properties of the composition, and usually means 50% by weight or more of the whole, and includes the case where the whole consists of only the main component.
[0013]
The shaft body 11 is not particularly limited as long as it has conductivity, and a metal core made of a metal solid body or a metal cylinder body hollowed out inside is used. Examples of the material of the shaft body 11 include aluminum and stainless steel. Moreover, an adhesive agent, a primer, etc. can be apply | coated on the shaft 11 as needed. The adhesive, primer, etc. may be made conductive as necessary.
[0014]
The base rubber layer 12 forming material formed on the outer peripheral surface of the shaft body 11 is not particularly limited, and examples thereof include silicone rubber, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), Examples thereof include polyurethane-based elastomers, which are used alone or in combination of two or more. Of these, silicone rubber is preferred from the viewpoint of low hardness and less sag. Moreover, carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c-SnO ₂ , ionic conductive agent (quaternary ammonium salt, borate, surfactant) Etc.) may be appropriately added to the base rubber layer 12 forming material.
[0015]
The material for forming the intermediate layer 13 formed on the outer peripheral surface of the base rubber layer 12 is not particularly limited. For example, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), Examples thereof include polyurethane-based elastomers, chloroprene rubber (CR), natural rubber, butadiene rubber (BR), butyl rubber (IIR), hydrin rubber, nylon, and the like, which are used alone or in combination of two or more. Among these, H-NBR is particularly preferable from the viewpoint of adhesiveness and coating solution stability.
[0016]
As described above, the outermost layer 14 forming material formed on the outer peripheral surface of the intermediate layer 13 is mainly composed of PVB and a specific polyurethane, and contains a resin composition in a specific ratio. Is used.
[0017]
The PVB is a resin having a cyclic acetal structure obtained by reacting polyvinyl alcohol with butyraldehyde in the presence of an acid catalyst, and apparently a terpolymer structure comprising a vinyl butyral unit, a vinyl acetate unit, and a vinyl alcohol unit. It is what has.
[0018]
The above specific polyurethane includes at least one of polytetramethylene ether glycol (PTMG) polyurethane and adipate polyurethane in terms of excellent characteristics (in terms of performance of the developing roll), low friction coefficient, solvent solubility, and the like. On the other hand (PTMG-based polyurethane and / or adipate-based polyurethane) is used. In addition, the polyurethane is preferably a linear one, but if necessary, a functional group such as —OH, —NCO, —NH ₂ or the like is added to the terminal or side chain, and an isocyanate compound, an amine compound, an epoxy compound, etc. May be cross-linked.
[0019]
The content of the PVB in the resin composition is the outermost layer 14 formed material (A component) and polyurethane (B component), the weight ratio of (A) / (B) = 90/10 ~ 6 0/4 0 Set to range. That is, in the above ratio, if the amount of the component (A) is too large, the toner chargeability and toner transportability are impaired. Conversely, if the amount of the component (A) is too small, the friction on the roll surface is reduced. It is because it will not be made. Then, arbitrary favored with the proportion (weight ratio) is in the range of (A) / (B) = 8 0/2 0~ 7 0/3 0. That is, by setting in such a range, the compatibility between the low friction of the roll surface and the toner charging property and the like, because so preferable results are obtained.
[0020]
In addition to the component (A) and the component (B), other additives can be appropriately blended in the special outermost layer 14 forming material as necessary. Other additives include conductive agents such as carbon black, graphite and potassium titanate, fillers such as titanium oxide, calcium carbonate, talc, clay and silica, stabilizers, UV absorbers, charge control agents, and reinforcement. Agents, lubricants, mold release agents, dyes, pigments, flame retardants, oils and the like.
[0021]
The developing roll of the present invention can be produced, for example, as follows.
[0022]
That is, first, the components for forming the base rubber layer 12 are kneaded with a kneader such as a kneader to produce the base rubber layer 12 forming material. Further, each component for forming the intermediate layer 13 is kneaded using a kneader such as a roll, and an organic solvent is added to the mixture, mixed, and stirred to prepare the intermediate layer 13 forming material (coating liquid). To do. Further, each component for the outermost layer 14 forming material is dissolved in an organic solvent and dispersed by a sand mill or the like, thereby producing the outermost layer 14 forming material (coating liquid).
[0023]
Next, a metal shaft 11 is set in the hollow portion of the cylindrical mold, and the base rubber layer 12 forming material is cast 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 formed by forming the base rubber layer 12 on the outer peripheral surface of the shaft body 11 is taken out from the cylindrical mold. If necessary, the surface of the base roll is subjected to corona discharge treatment or plasma treatment. Further, a coupling agent is applied to the surface of the base roll as necessary. And the coating liquid used as the intermediate | middle layer 13 formation material is apply | coated to the outer periphery of the base rubber layer 12 of the said base roll, or after the said base roll is immersed and pulled up in the said coating liquid, drying and heat processing are performed. Thus, the intermediate layer 13 is formed on the outer periphery of the base rubber layer 12. Further, the outermost layer 14 forming solution is applied to the outer periphery of the intermediate layer 13. This coating method is not particularly limited, and conventional methods such as a dipping method, a spray method, and a roll coating method can be applied. And about what removes and bridge | crosslinks the solvent in the said outermost layer 14 formation solution by performing drying and heat processing (vulcanization process, conditions: 120-200 degreeC x 20-90 minutes) after coating. Perform cross-linking. In this way, a roll having a three-layer structure as shown in FIG. 1 can be produced.
[0024]
In this developing roll, the thickness of the base rubber layer 12 is preferably set in the range of usually 0.5 to 10 mm, particularly preferably 1 to 6 mm. Moreover, it is preferable to set the thickness of the intermediate | middle layer 13 in the range of 3-90 micrometers, Especially preferably, it is 5-40 micrometers in thickness. And it is preferable to set the thickness of the outermost layer 14 to the range of 3-100 micrometers, Most preferably, it is 5-50 micrometers in thickness.
[0025]
In the developing roll of the present invention thus obtained, it is preferable that the dynamic friction coefficient μk of the outermost layer surface is set to μk <0.35 and the static friction coefficient μs is set to μs <0.40. More preferably, μk <0.30 and μs <0.35. In other words, if the static friction coefficient is set in such a range, the frictional heat on the roll surface can be further suppressed, so that toner deterioration is less likely to occur, and as a result, the image quality is further improved. is there. The static friction coefficient can be measured by, for example, a static friction coefficient meter manufactured by Kyowa Interface Science Co., Ltd.
[0026]
As an example of the developing roll of the present invention, the one having a three-layer structure is shown in FIG. 1, but the layer formed on the outer periphery of the shaft body 11 does not necessarily have to be three layers. An appropriate number of layers is formed. However, the outermost layer (that layer in the case of a single layer) must be formed of the outermost layer 14 forming solution.
[0027]
Next, examples will be described together with comparative examples.
[0028]
[Example 1]
[Base rubber layer forming material]
Silicone rubber (X34-264, manufactured by Shin-Etsu Chemical Co., Ltd.).
[0029]
[Interlayer formation material]
H-NBR (Zetpol 0020, manufactured by Nippon Zeon Co., Ltd.) 100 parts by weight (hereinafter abbreviated as “parts”), stearic acid 0.5 parts, zinc white (ZnO) 5 parts, carbon black (Denka Black HS- 100, manufactured by Denki Kagaku Kogyo Co., Ltd.) 40 parts, 1 part of crosslinking accelerator BZ, 2 parts of crosslinking accelerator CZ and 1 part of sulfur are kneaded and then dispersed in an organic solvent to form an intermediate layer. A working solution was prepared.
[0030]
[Outermost layer forming material]
PVB and (Denka Butyral # 2000, manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) 9 0 parts (manufactured by Mirasen E-34, TSE, Inc.) polyurethane and 10 parts of carbon black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.), 10 parts Were mixed and then dispersed in methyl ethyl ketone to prepare an outermost layer forming solution.
[0031]
[Preparation of developing roll]
Next, a core made of SUS303 (diameter 10 mm) is prepared as a shaft, and an outer peripheral surface coated with an adhesive is set inside the roll mold, and a gap between the shaft and the roll mold inner peripheral surface. A base rubber layer (thickness 4 mm) was formed on the outer periphery of the shaft body by casting the compound as the base rubber layer forming material on the part, heat vulcanizing (150 ° C. × 30 minutes), and then removing the mold. . The shaft body with the base rubber layer thus obtained is removed from the mold, and the reaction is completed as necessary (200 ° C. × 4 hours). Next, after applying the coating solution made of the intermediate layer forming material on the outer peripheral surface of the base rubber layer, drying and heat treatment are performed to form an intermediate layer (thickness 20 μm) on the outer peripheral surface of the base rubber layer. After applying the coating solution made of the outermost layer forming material on the outer peripheral surface of the intermediate layer, drying and heat treatment are performed to form the outermost layer (thickness 10 μm) on the outer peripheral surface of the intermediate layer, and development with a three-layer structure A roll was obtained (see FIG. 1).
[0032]
[Example 2]
An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 80 parts and the blending ratio of polyurethane was 20 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0033]
[Example 3]
An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 70 parts and the blending ratio of polyurethane was 30 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0034]
[Example 4]
An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 60 parts and the blending ratio of polyurethane was 40 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0035]
[ Comparative Example 1 ]
The outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 95 parts and the blending ratio of polyurethane was 5 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0036]
[ Comparative Example 2 ]
An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 50 parts and the blending ratio of polyurethane was 50 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0037]
[Comparative Example 3 ]
The outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 100 parts (without polyurethane). Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0038]
[Comparative Example 4 ]
The outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 40 parts and the blending ratio of polyurethane was 60 parts. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0039]
[Comparative Example 5 ]
Polyurethane (Elastolan ET1040, manufactured by Mitsui Takeda Chemical Co., Ltd.) was used as the polymer for the outermost layer forming material. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0040]
[Comparative Example 6 ]
As a polymer of the outermost layer forming material, an acrylic resin (Hyperl D-100E, manufactured by Negami Industrial Co., Ltd.) was used. Other than that, a developing roll was produced in the same manner as in Example 1 (the manufacturing method and the thickness of each layer were the same as in Example 1).
[0041]
Each developing roll thus obtained was subjected to comparative evaluation and measurement of each characteristic according to the following criteria. These results are shown together in Tables 1 and 2 below.
[0042]
〔surface hardness〕
The surface hardness of the developing roll was measured using a micro rubber hardness meter MD-1 type (manufactured by Kobunshi Keiki Co., Ltd.).
[0043]
[Roll electrical 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, both ends of the developing roll 62 are pressed with a load of 1000 g (9.8 N), and a voltage of 100 V is applied to one end of the developing roll 62 in this state. The electrical resistance was measured.
[0044]
[Surface roughness (Rz)]
The surface roughness (circumferential direction) of the developing roll surface was measured according to JIS B 0601 with Surfcom (manufactured by Tokyo Seimitsu Co., Ltd.). Rz is a 10-point average obtained from a roughness curve obtained by cutting off a surface waviness component longer than a predetermined wavelength from an outline (this is referred to as a cross-sectional curve) that appears at the cut edge when cut along a plane perpendicular to the unevenness. Indicates roughness.
[0045]
[Dynamic friction coefficient (μk), Static friction coefficient (μs)]
It measured using the static friction coefficient meter (made by Kyowa Interface Science Co., Ltd.) as shown in FIG. That is, using the resin composition that is the outermost layer forming material of the developing roll, a coating film 11 having a thickness of 50 to 100 μm is prepared, and this is set on the fixing table 12, and the moving speed is 0.3 cm / second, the load The measurement was performed under the condition of 100 g. In FIG. 3, 13 is a press contact, 14 is a balance for zero point adjustment, 15 is a load cell, and 16 is a load (100 g). 4A is a cross-sectional view of the press contact 13, and FIG. 4B is a front view of the press contact 13. As shown in FIG.
[0046]
[Toner charge amount]
The charge amount per unit weight of the toner layered on the developing roll was measured with a Q / M measuring device (MODEL 210HS, manufactured by Trek).
[0047]
[Toner transport amount]
The toner layer-formed on the developing roll was transferred by tape, and the weight per unit area was measured.
[0048]
[Surface temperature after endurance]
The obtained developing roll was idled for 3 hours in an actual machine, and the temperature change of the roll surface due to frictional heat with the layer forming member incorporated in the actual machine was measured with a radiation thermometer (IT-330, manufactured by Horiba Ltd.). And measured.
[0049]
(Image evaluation)
The obtained developing roll was incorporated into an electrophotographic printer and actually printed. The image quality of the printed image was visually evaluated at the initial stage and after printing 10,000 sheets (after durability). That is, characters were printed, and there was no problem in the printed image, and those printed clearly up to the fine line were evaluated as “◯”.
[0050]
[Toner filming properties]
After 10,000 sheets were printed (after endurance), the presence or absence of toner filming on the developing roll was visually determined. Then, the case where toner filming did not occur was evaluated as ◯, and the case where toner filming occurred was evaluated as x.
[0051]
[Toner fixing]
After 10,000 sheets were printed (after endurance), the presence or absence of toner sticking to the layer forming member in the electrophotographic printer was visually determined. And, ○ what toner adhesion did not occur, that the even toner adhesion was slightly occurred △, it was evaluated as × what toner adhesion occurs.
[0052]
[Table 1]

[0053]
[Table 2]

[0054]
From the results in the above table, all the products of the examples are excellent in toner chargeability and toner transportability, do not cause toner filming, etc., and there is almost no deterioration of the printed image even after durability. I understand. On the other hand, in the comparative example 1 product and the comparative example 2 product in which the blending ratio of PVB and polyurethane in the outermost layer forming material slightly deviates from the range specified in the present invention, printing after 10,000 sheets printing (after durability) It can be seen that the image quality is inferior and the toner adhesion evaluation is inferior. And it turns out that the surface hardness is too high in the comparative example 3 goods whose polymer of the outermost layer consists only of PVB, and a clear printed image cannot be obtained. In addition, it can be seen that in the comparative example 4 product having a blending ratio of PVB that is too low, toner deterioration occurs due to an increase in the roll surface temperature due to friction, and the image quality after durability is adversely affected. Then, the outermost layer of the polymer and Comparative Example 5 product consisting only of poly urethane, in the case of Comparative Example 6 dishes comprising only acrylic, it can be seen that the image quality after the durability test is bad.
[0055]
【The invention's effect】
As described above, the outermost layer of the developing roll of the present invention is formed of a resin composition containing PVB and a specific polyurethane as main components and containing them in a specific ratio. For this reason, low friction can be achieved without impairing the toner chargeability and toner transportability, which are the performance of the developing roll. As a result, generation of heat due to friction with the layer forming member can be suppressed, so that even if the use is continued, the toner does not fuse with the layer forming member due to heat or heat deterioration occurs. An excellent print image can be obtained. Further, even when a toner having a low melting point is used, the above-mentioned fusing or the like does not occur, so that low power can be achieved without causing image defects.
[0056]
In particular, when the static friction coefficient of the outermost layer surface is set within a specific range, the frictional heat is further suppressed, so that toner deterioration is less likely to occur and a more excellent printed image can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a developing roll of the present invention.
FIG. 2 is an explanatory diagram showing a method for measuring roll electrical resistance.
FIG. 3 is an explanatory diagram showing a measurement state of a friction coefficient by a static friction coefficient meter.
4A is a cross-sectional view of a press contact used for measuring the friction coefficient, and FIG. 4B is a front view of the press contact.
FIG. 5 is an explanatory diagram showing a usage state of the developing roll.
[Explanation of symbols]
11 Shaft body 12 Base rubber layer 13 Intermediate layer 14 Outermost layer

Claims (1)

A developing roll having at least one layer formed on an outer peripheral surface of a shaft, wherein the outermost layer is formed of the following resin composition (X).
(X) below (A) and (B) as a main component, and (A) the content of component and component (B), in a weight ratio, (A) / (B) = 90/10 ~ 6 0 / Resin composition set in the range of 40 .
(A) Polyvinyl butyral.
(B) At least one of polytetramethylene ether glycol (PTMG) polyurethane and adipate polyurethane .

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