JP4042755B2 - Developing roll - Google Patents

Description

  The present invention relates to a developing roll used in an electrophotographic apparatus such as an electrophotographic copying machine or a printer.

Conventionally, as a developing roll used in an electrophotographic copying machine, a base rubber layer is formed on the outer peripheral surface of a shaft body, and an intermediate layer (for example, a softener migration preventing layer or a resistance adjusting layer) is formed on the outer peripheral surface. Furthermore, a structure having a surface layer formed on the outer peripheral surface thereof is used. As the material for the surface layer, for example, a binder for paint such as polycarbonate-based or ether-based urethane resin or acrylic resin is used as a main component. In this solvent solution, conductive carbon black ( A material in which an electronic conductive agent) is dispersed is used (see Patent Documents 1 and 2).
JP 2003-3032 A JP 2002-363426 A

  By the way, in recent years, for the purpose of suppressing power consumption and high-speed printing in an electrophotographic copying machine or the like, a toner having a low melting point has been promoted. However, such a low-melting-point toner is easily melted by frictional heat generated by pressing of the developing roll and other regulating members. In particular, the melted toner and its external additive adhere to the outer peripheral surface of the developing roll. Cheap. As the cause, the following reasons (1) to (3) can be considered. That is, (1) the outermost layer of the conventional developing roll is inferior in elongation characteristics, so stress on the toner and contact member (regulating member) cannot be relieved, and as a result, toner melting is likely to occur. (2) In the surface layer The dispersion state of the conductive carbon black tends to be in a locally aggregated state, resulting in large variations in the electrical resistance of the roll surface, and toner adhesion is likely to occur starting from the aggregation point. (3) End of voltage application This is because the toner scraping property deteriorates due to the residual charge remaining on the later developing roll, resulting in toner accumulation.

  As described above, when melted toner or the like adheres to the outer peripheral surface of the developing roll (filming), the surface roughness of the roll increases, and as a result, the toner conveyance amount increases and the toner chargeability due to surface alteration is increased. This causes a problem that image degradation (fogging, roughness, etc.) is caused.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a developing roll that is excellent in toner adhesion resistance to a low melting point toner and can obtain a good image.

In order to achieve the above object, the developing roll of the present invention comprises a shaft, a base rubber layer formed on the outer periphery thereof, and a surface layer formed on the outer periphery of the base rubber layer directly or via another layer. The surface layer is formed of a resin composition that contains the following components (A) to (C) and does not contain an electronic conductive agent.
(A) A polyether polyol having an average molecular weight (Mn) in the range of 650 to 3000 having two or more functional groups.
(B) Diisocyanate.
(C) Aromatic bifunctional chain extender.

  That is, the present inventors have intensively studied to solve the above problems. In the course of the research, as a result of further research focusing on the surface layer of the developing roll, it contains a polyether polyol of a specific molecular weight, a diisocyanate, and an aromatic bifunctional chain extender, and has electronic conductivity. It was recalled that the surface layer was formed with a resin composition free from the agent. As a result, the elongation property of the surface layer becomes large, the stress caused by the toner and the contact member can be relieved, and the electrical responsiveness is also improved, so that the toner scraping property on the developing roll after the voltage application is completed. The experimental results were also good. Furthermore, since the surface layer does not contain an electronic conductive agent and its molecular level resistance is uniform, toner accumulation due to variations in electrical resistance is small, and further, since compression set is small, It has been found that image defects due to pressing can be suppressed, and as a result, the intended purpose can be achieved, and the present invention has been achieved.

  As described above, the surface layer of the developing roll of the present invention contains a polyether-based polyol having a specific molecular weight, a diisocyanate, and an aromatic bifunctional chain extender and does not contain an electronic conductive agent. It is formed by the resin composition. Therefore, the developing roll of the present invention has excellent toner adhesion resistance to low melting point toner. Further, since the durability of the roll surface is also improved, no settling occurs. By incorporating the developing roll of the present invention into an electrophotographic apparatus such as a full-color LBP (laser beam printer) or a full-color MFP (multifunction printer), good copying without image defects (fogging, roughness, etc.) over a long period of time An image can be obtained.

  In particular, when the surface layer material contains an ionic conductive agent, toner accumulation due to variations in electrical resistance does not occur, and the electrical resistance of the roll surface can be set to a desired value.

  Further, when surface roughness forming particles having an average particle diameter within a specific range are dispersed in the resin composition as the surface layer forming material, the toner chargeability and toner transportability are further improved. .

  Next, an embodiment of the present invention will be described.

  For example, as shown in FIG. 1, the developing roll of the present invention has a base rubber layer 12 formed along the outer peripheral surface of a shaft body 11 and a surface layer 13 formed on the outer peripheral surface. And, in the developing roll of the present invention, the greatest feature is that the surface layer 13 is formed of a specific resin composition.

  The shaft body 11 is not particularly limited, and may be, for example, a cored bar made of a hollow cylindrical body other than the solid body as shown in the figure. The forming material is not particularly limited, and examples thereof include metal materials such as aluminum and stainless steel. In addition, you may apply | coat an adhesive agent, a primer, etc. on the shaft 11 as needed. In addition, the adhesive, primer, etc. may be made conductive as necessary.

The base rubber layer 12 formed on the outer peripheral surface of the shaft body 11 is formed of, for example, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, polyurethane elastomer, or the like. Among these, it is preferable to use conductive silicone rubber from the viewpoint of low hardness and less sag. It should be noted that various additives such as a conductive agent and silicone oil are appropriately blended with this material. Various conductive agents such as carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c-SnO ₂ (where “c-” means conductivity) Can be given. Examples of the silicone oil include various types such as dimethyl silicone oil.

The material for forming the surface layer 13 formed on the outer peripheral surface of the base rubber layer 12 contains a specific resin composition, that is, the following components (A) to (C), and an electronic conductive agent (conductive) A resin composition containing no carbon black or the like is used.
(A) A polyether polyol having an average molecular weight (Mn) in the range of 650 to 3000 having two or more functional groups.
(B) Diisocyanate.
(C) Aromatic bifunctional chain extender.

  As described above, the polyol of the component (A) must have an average molecular weight (Mn) in the range of 650 to 3000. Preferably, the average molecular weight (Mn) is in the range of 1000 to 2000. That is, if the average molecular weight (Mn) of the polyol is less than 650, the soft segment ratio in the polymer becomes low, the resistance becomes high, and a desired electric resistance value cannot be achieved. This is because if the molecular weight (Mn) exceeds 3000, the soft segment ratio in the polymer is excessively increased and the mechanical properties are impaired. Further, the polyol of the component (A) needs to be a polyether-based polyol having two or more functional groups and having an ether structure in the main chain. Specific examples of such polyols include polyether polyols such as polyoxytetramethylene glycol (PTMG), polyethylene glycol (PEG), and polyoxypropylene glycol (PPG).

  The diisocyanate [(B) component] used together with the polyol of the component (A) is not particularly limited, and examples thereof include 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2 , 4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 3,3′-vitrylene-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 2,4-tolylene diisocyanate uretidine dione (a dimer of 2,4-TDI), 1,5-naphthylene diisocyanate, metaphenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate ( Hydrogenated MDI), Carbo Imide-modified MDI, ortho-toluidine diisocyanate, xylene diisocyanate, paraphenylene diisocyanate, lysine diisocyanate methyl ester, and the like. And these are used individually or in combination of 2 or more types.

  The blending amount of the diisocyanate [component (B)] is preferably set in the range of 5 to 200 parts with respect to 100 parts by weight (hereinafter abbreviated as “part”) of the polyol component (A). Especially preferably, it is 15-100 parts.

  The aromatic bifunctional chain extender [component (C)] used together with the components (A) and (B) includes methylenebis (2-methyl-6ethylaniline), 2,2 ', 3,3'- Tetrachloro-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, trimethylene-bis (4-aminobenzoate), 4,4'-diamino-3,3'-diethyl- 5,5'-dimethyldiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4'-diaminodiphenylsulfone, 2 , 2-bis (4-hydroxyphenyl) hexafluoropropane and the like. These may be used alone or in combination of two or more.

  The blending amount of the aromatic bifunctional chain extender [component (C)] is preferably set in the range of 1 to 50 parts with respect to 100 parts of the polyol component (A). Particularly preferred is 3 to 30 parts.

  In addition to the chain extender of the component (C), other chain extenders may be used in combination as the material for forming the surface layer 13. In this case, the ratio of the other chain extender is used in the range of 0 to 80% by weight of the whole chain extender. And as said other chain extender, it is not specifically limited, For example, 1, 4- butanediol (1, 4-BD), ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylene glycol, triethylene glycol, trimethylolpropane (TMP), glycerin, pentaerythritol, sorbitol, 1,2,6-hexanetriol, etc., molecular weight of 300 or less Polyols and the like. These may be used alone or in combination of two or more.

  By the way, in this invention, it is prohibited to contain electronic conductive agents, such as electroconductive carbon black, in the formation material of the said surface layer 13. As shown in FIG. As described above, this is because the use of an electronic conductive agent may cause a large variation in electrical resistance on the roll surface. Therefore, in the present invention, imparting conductivity to the surface layer 13 is appropriately performed by an ionic conductive agent such as a quaternary ammonium salt, a borate, a surfactant, a metal ion, or polyethylene oxide (PEO). As a result, it is possible to suppress variations in electrical resistance, and as a result, toner accumulation does not occur, and the electrical resistance on the roll surface can be set to a desired value.

  In addition, it is preferable that roughness forming particles having an average particle diameter of 1 to 50 μm are dispersed in the material for forming the surface layer 13 because toner chargeability and toner transportability are improved. The average particle diameter of the roughness forming particles is more preferably in the range of 5 to 15 μm. The average particle size of the particles is a value derived using a sample arbitrarily extracted from the population. In addition, if the particle size is not uniform, as in the case of a particle shape that is not a true sphere but an elliptical sphere (a sphere with an elliptical cross section), the simple average value of the longest diameter and the shortest diameter is the particle diameter of the particle. To do.

  The material for forming the roughness forming particles is not particularly limited, and examples thereof include silica, urethane resin, polyamide resin, fluorine resin, acrylic resin, urea resin, and silicone resin. These may be used alone or in combination of two or more. Among these, silica that can highly charge the toner is preferably used.

  Further, the dispersion ratio of the roughness forming particles is preferably set in the range of 5 to 50 parts, more preferably 10 to 30 parts with respect to 100 parts of the surface layer 13 material (material excluding the particles). It is a range. By setting it within this range, a desired effect (an effect of improving toner chargeability and toner transportability) can be advantageously obtained.

  In addition to the above-described components, the surface layer 13 may be formed of a catalyst, a stabilizer, an ultraviolet absorber, a reinforcing agent, a lubricant, a release agent, a dye, a pigment, a flame retardant, an oil, and the like as necessary. These other additives can be appropriately blended.

  And the formation material of the said surface layer 13 is used as a coating liquid by melt | dissolving in an organic solvent. Examples of the organic solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These may be used alone or in combination of two or more. In particular, MEK is preferably used as the organic solvent in terms of solubility in the material for forming the surface layer 13. And it is preferable at points, such as coating property, that the coating liquid obtained in this way shall make the density | concentration about 5 to 30 weight%.

  Here, the developing roll of the present invention can be produced, for example, as follows.

  That is, first, the respective components for the base rubber layer 12 are kneaded by a kneader such as a kneader to produce a base rubber layer 12 forming material. Further, each component for the surface layer 13 is dissolved in an organic solvent and dispersed by a sand mill or the like, thereby preparing a surface layer 13 forming material (coating liquid).

  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. And the coating liquid for the said surface layer 13 formation is applied to the outer peripheral surface of the base rubber layer 12 in the said base roll. 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. Then, after the coating, drying and heat treatment (vulcanization treatment at 120 to 200 ° C. for 20 to 90 minutes) are performed to remove the solvent in the coating liquid for forming the surface layer 13 and form the surface layer 13. . In this way, a developing roll having a two-layer structure as shown in FIG. 1 can be produced.

  In this developing roll, the thickness of the base rubber layer 12 is preferably set in the range of 0.5 to 10 mm, particularly preferably in the range of 1 to 6 mm. Moreover, it is preferable to set the thickness of the surface layer 13 in the range of 1-100 micrometers, Especially preferably, it exists in the range of 5-50 micrometers in thickness.

  As an example of the developing roll of the present invention, a two-layer structure as shown in FIG. 1 is given, but the present invention is not limited to this, and the base rubber layer 12 and the surface layer 13 are not limited to this. Further, two or more layers may be formed by appropriately interposing a softener migration preventing layer, a resistance adjusting layer, and the like.

  Examples of the material for forming the softener migration preventing layer include a material in which a conductive agent such as carbon black is blended with a polyamide resin such as N-methoxymethylated nylon or polyester. These may be used alone or in combination of two or more.

  Examples of the material for forming the resistance adjusting layer include hydrin rubber, EPDM, SBR, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), polyurethane elastomer, carbon black, metal Examples thereof include those containing a conductive agent such as oxide, quaternary ammonium salt, borate and lithium perchlorate. These may be used alone or in combination of two or more.

  And the formation material of each of these layers is also used as a coating liquid by dissolving in an organic solvent, and the respective layers are formed by applying the coating liquid by a conventionally known method.

  The developing roll of the present invention thus obtained can be applied to a general electrophotographic apparatus. In particular, the developing roll for an electrophotographic apparatus using a low melting point toner such as a full color LBP or a full color MFP is used. It can be suitably used as a developing roll. By incorporating the developing roll of the present invention into an electrophotographic apparatus such as a full color LBP or a full color MFP, a good copy image can be obtained over a long period of time.

  Next, examples will be described together with comparative examples.

  First, prior to the examples and comparative examples, the following materials were prepared as surface layer materials for the developing roll.

[Polyol a]
Polyether polyol having an average molecular weight (Mn) of 250 (manufactured by BASF, PolyTHF250)

[Polyol b]
Polyether polyol having an average molecular weight (Mn) of 650 (manufactured by BASF, PolyTHF 650)

[Polyol c]
Polyether polyol having an average molecular weight (Mn) of 1000 (manufactured by Mitsubishi Chemical Corporation, PTMG1000)

[Polyol d]
Polyether polyol having an average molecular weight (Mn) of 3000 (manufactured by Mitsubishi Chemical Corporation, PTMG3000)

[Polyol e]
Polyether polyol with an average molecular weight (Mn) of 4000 (Mitsui Takeda Chemical Co., PC-284)

[Diisocyanate a]
TDI (Nippon Polyurethane, Coronate T-100)

[Diisocyanate b]
MDI (Nippon Polyurethane, Millionate MT)

[Aromatic chain extender]
Methylenebis (2-methyl-6ethylaniline) (Ihara Chemical Industries, Cure Lead MED)

[Aliphatic chain extender]
1,2-ethylenediamine (Wako Pure Chemical Industries, ethylenediamine)

(Roughness forming particles)
Urethane resin particles with an average particle size of 15 μm (Daimic Seika Co., Ltd., Dimic beads UCN5150D)

[Examples 1-3, Comparative Examples 1-3]
After filling a mold in which a core metal (diameter 10 mm, made of SUS304) serving as a shaft body is set with conductive silicone rubber (X-34-264 A / B, manufactured by Shin-Etsu Chemical Co., Ltd.) as a base rubber layer material Then, heat crosslinking was performed under predetermined conditions. Thereafter, the mold was removed, and a base roll having a base rubber layer formed along the outer peripheral surface of the shaft body was produced. Next, the components shown in Table 1 below are blended in the proportions shown in the table, and a surface layer forming material is prepared as a coating solution having a concentration of 20% by weight, which is blended and dissolved in an organic solvent (MEK). did. Next, the surface layer material was applied to the outer peripheral surface of the base roll, and then heat crosslinking was performed under the conditions of 185 ° C. × 60 minutes to form a surface layer. In this manner, a two-layer developing roll having a base rubber layer formed on the outer peripheral surface of the shaft and a surface layer formed on the outer peripheral surface was produced. The base rubber layer had a thickness of 3 mm and the surface layer had a thickness of 10 μm.

  Each developing roll thus obtained was subjected to comparative evaluation and measurement of each characteristic according to the following criteria. These results are shown in Table 2 below.

[Electric resistance]
Measurement was performed 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.

[Elastic modulus]
The elastic modulus (MPa) of the roll surface layer was measured according to JIS K-6301-1975.

[Electric response]
At a temperature of 15 ° C. and a humidity of 10% RH, as shown in FIG. 3, while rotating the developing roll 51 in the direction of the arrow at a roll rotation speed of 70 rpm, a corona discharge wire (corotron) 52 is used on the outer peripheral surface. Was applied to charge the outer peripheral surface of the developing roll. Then, a residual charge q _s on the outer peripheral surface of the developing roll was measured with a surface potential meter 53. Furthermore, the residual charge q _f after 1 second from the application stop was also measured. Then, from these values, (q _s −q _f ) / q _s × 100 (%) was obtained and used as an index of electrical response.

[Sag resistance]
The developing roll was assembled in a toner cartridge (Canon, EP-85 cyan) and left for 2 weeks under conditions of 40 ° C. and humidity 95% RH, and then a solid image was printed. Then, the case where the image was left unacceptable was evaluated as ◯, and the image where the image was left untreated was evaluated as x.

[Anti-fogging resistance]
The developing roll was incorporated into an electrophotographic copying machine and an image was actually output. Then, the evaluation machine was forcibly stopped during image output, and the amount of toner flying to the photosensitive drum in the white background portion was measured by density comparison by tape transfer (measured with a Macbeth densitometer). And the measured value was evaluated as ○ when the value was less than 0.15, and x when the value was 0.15 or more.

  From the results of the above table, all of the examples have desired elasticity and electric resistance, are excellent in electric response, and do not cause sag and fog. From this, it can be seen that a good image can be obtained by using the example product.

  On the other hand, it can be seen that the roll of Comparative Example 1 using an aliphatic chain extender in the surface layer material has a too low elastic modulus and sag. Moreover, since the molecular weight of the polyol component in the surface layer material is too smaller than the predetermined range, the roll of Comparative Example 2 has low electrical responsiveness and causes problems such as fogging. On the contrary, the roll of Comparative Example 3 has an excessively low elastic modulus and deteriorates sag because the molecular weight of the polyol component in the surface layer material is too larger than the predetermined range.

It is sectional drawing which shows an example of the image development roll of this invention. It is explanatory drawing which shows the measuring method of roll electrical resistance. It is explanatory drawing which shows the measuring method of a residual charge.

Explanation of symbols

11 Shaft body 12 Base rubber layer 13 Surface layer

Claims (3)

A developing roll comprising a shaft, a base rubber layer formed on the outer periphery thereof, and a surface layer formed on the outer periphery of the base rubber layer directly or via another layer, wherein the surface layer comprises the following A developing roll characterized by being formed of a resin composition containing components (A) to (C) and free of an electronic conductive agent.
(A) A polyether polyol having two or more functional groups and an average molecular weight (Mn) in the range of 650 to 3000.
(B) Diisocyanate.
(C) Aromatic bifunctional chain extender.   The developing roll according to claim 1, wherein the surface layer is formed of a resin composition containing an ionic conductive agent together with the components (A) to (C).   The developing roll according to claim 1 or 2, wherein particles for forming a surface roughness having an average particle diameter of 1 to 50 µm are dispersed in a resin composition which is a material for forming the surface layer.

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