JPH08219143A - Electric conductive roll - Google Patents

Abstract

PURPOSE: To provide an electric conductive roll which there is not problem of bread and which has low hardness by adding reactive plasticizer which is reacted to premolymer of kneaded type urethane or which is taken in a prepolymer as homopolymer so as to form a roll main body. CONSTITUTION: An electric conductive roll 10 is provided with a core 12, and a cylindrical roll main body 14 for winding up the core 12. The roll main body 14 is formed of a kneaded type urethane with which electric conductive fine powder and ion electric conductor are covered. The resistance value of the electric conductive roll 10 is set properly and correctly according to the additive amount of the ion electric conductor without forcibly controlling an electric resistance value by electric conductive carbon in the case where the additive amount of the electric conductive carbon is 30weight% and less. The additive amount of electric conductive fine powder such as electric conductive carbon is preferably set to 30weight% and less. A shore A hardness is reduced to 25 deg. to 48 deg. without being generated bread of plasticizef by adding reactive plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll,
In particular, the present invention relates to a conductive roll suitable for use as a charging roll, a developing roll and a transfer roll incorporated in an electrophotographic device such as a copying machine, a printer and a facsimile.

[0002]

2. Description of the Related Art Appropriate elasticity, Shore A hardness, and proper and uniform conductivity are required for charging, developing and transferring rolls used in electrophotographic equipment. A rubber material such as urethane is generally used for such a roll, and a plasticizer such as process oil or dioctyl phthalate is used for adjusting the hardness of the roll. Thus, a desired low hardness conductive roll can be obtained.

[0003]

However, such a conventional plasticizer does not react with the urethane polymer and is not incorporated therein, but it is merely dispersed in the polymer itself. Therefore, the plasticizer dispersed in the polymer sometimes exudes from the roll.

In particular, a roll to which carbon black, which is conductive fine particles, is added in order to increase the conductivity, has a hardness increased by the addition of the carbon black. Therefore, a plasticizer is an indispensable element for reducing the hardness. Becomes For this reason, the problem of bleeding of the plasticizer, that is, bleeding, from the roll to which such carbon black has been added cannot be avoided.

The bleeding of such a plasticizer adheres to a photoreceptor such as OPC of a photographic electronic device to deteriorate the quality of an image, and causes the deterioration of durability due to the generation of roll cracks.

Accordingly, it is an object of the present invention to provide a low hardness conductive roll which does not cause the problem of bleeding.

[0007]

In order to solve the above-mentioned problems, the present invention basically involves reacting with a prepolymer as a base material of kneaded urethane as a base material, reacting with the prepolymer, Alternatively, it is characterized by adding a reactive plasticizer which itself is incorporated into the prepolymer as a homopolymer.

[0008]

Since the reactive plasticizer is incorporated in the prepolymer or forms a homopolymer by itself, it is generated when the commonly used process oil or dioctyl phthalate (DOP) is used. The hardness of the roll body can be reduced without causing such bleeding.

The reactive plasticizer added to reduce the hardness is a plasticizer containing at least one of an allyl group, a glycidyl group or an isocyanate group having one reaction active point in its molecule. As shown in the reaction formula of FIG. 1 (A), the allyl group in the molecule has a double bond of π bond and σ bond before the reaction, but the carbon is more bonded than the σ bond by the reaction. It is considered that the weak π bond is cleaved, and this is σ-bonded with another molecule to be incorporated into the prepolymer, or itself forms a homopolymer. In addition, the glycidyl group, as shown in the reaction formula of FIG.
The bond between carbon and oxygen is ring-closed, but it is thought that the reaction opens this part and binds it with other molecules to be incorporated into the prepolymer or to itself form a homopolymer. To be Regarding the isocyanate group, NCO- is considered to be incorporated into the prepolymer molecule.

Each of the reactive plasticizers is incorporated into the molecule of the prepolymer when the prepolymer is heat-cured, or is incorporated as a homopolymer by itself so as to enhance the plasticity of the polymer. . In this way, the reactive plasticizer forms a part of the polymer by its own reaction, and thus does not cause bleeding unlike plasticizers such as process oil and dioctyl phthalate, which cause cracks, and cracks. With this, a low hardness conductive roll is formed.

Examples of reactive plasticizers containing an allyl group are:
There is Unisafe PKA-5016 (made by NOF Corporation). Examples of reactive plasticizers containing a glycidyl group include Denacol EX-121, 145 or 171 (all manufactured by Nagase Kasei Kogyo Co., Ltd.). An example of a reactive plasticizer containing isocyanate groups is octadecyl isocyanate.

By adding the reactive plasticizer, it is possible to reduce the hardness of the conductive roll without causing bleeding and cracking unlike the plasticizer. In addition to this, conductive fine powder and ionic conductivity are added. By using both the agents together, it is possible to further prevent a large change in electric resistance value due to the temperature and humidity of the environment and its variation.

In the case of a roll in which conductive fine powder such as carbon black is mixed in order to adjust the electric resistance value of the roll, there is no proportional relationship between the added amount of conductive fine particles and the resistance value. However, the resistance value of the roll cannot be accurately controlled by the addition amount of the conductive fine particles, and the resistance value varies. On the other hand, in the roll using the ionic conductive agent instead of the conductive fine powder, the resistance value greatly varies depending on the temperature and humidity of the environment, and the resistance value changes with time due to continuous voltage application, Eventually,
The rubber lacks durability because it shows an extremely high resistance value inherent to rubber to which an ionic conductive agent is not added.

However, by using both the conductive fine powder and the ionic conductive agent in combination, it is possible to prevent a large change in electric resistance value due to environmental temperature and humidity and its variation, as described above.

The ionic conductive agent is added to adjust the conductivity of urethane. In addition, the conductive fine powder does not provide an amount of conductivity to urethane by itself, but appropriately disperses the ionic conductive agent in a matrix form and acts as an intermediate medium for the transfer of charges by ions.

By adding an ion conductive agent to the kneaded urethane prepolymer and dispersing it appropriately, and by adding and dispersing an appropriate amount of conductive fine powder, the conductive fine powder can be dispersed without agglomeration. It is possible to disperse between the conductive agents and also to properly disperse the ionic conductive agent in a matrix form.

Since the conductive fine powder is dispersed between the ions, it can act as an intermediate medium for the charge transfer by the ions, thereby reducing the migration distance of the ions and reducing the ion mobility due to environmental changes. It is considered that the influence of the change is reduced and the change of the ion concentration difference with time is suppressed, and as a result, the change of the resistance value with time and the change due to the environment are suppressed.

The appropriate amount of the conductive fine powder is an amount such that the mixed conductive fine powder does not show conductivity in the roll body, that is, the conductive fine powder has a chain structure for increasing the conductivity of the roll body. Is an amount that does not form. Therefore, the conductive fine powder may be in such an amount that the roll body alone forms a partial chain structure that does not show conductivity. As described above, by using the ionic conductive agent and the conductive fine powder in combination, the conductive roll is formed without largely changing the resistance value depending on the environmental temperature and the humidity and having less variation in the resistance value.

Further, by adding a reactive plasticizer, it is possible to reduce the hardness of the roll main body without causing bleeding. A low-hardness conductive roll that does not cause deterioration of the image quality is formed.

To form a kneaded urethane, a prepolymer is formed by reacting an isocyanate with a polyol having one or more ether, ester and carbonate linkages. Then, using a roll mill or a kneader, a predetermined amount of ionic conductive agent, conductive fine powder, reactive plasticizer and, if necessary, a cross-linking agent are sequentially kneaded into the prepolymer, and this prepolymer is formed into a predetermined shape. And subjected to a crosslinking treatment such as heating. Further, after the cross-linking treatment, the molded product is processed into predetermined dimensions and completed. The ionic conductive agent can be incorporated into the prepolymer during the formation thereof.

As the cross-linking agent, a suitable amount of peroxide such as dialkyl peroxide typified by conventionally well-known dicumyl peroxide can be used. An alkali metal salt or a quaternary ammonium salt can be used as an ionic conductive agent that is a regulator of the electric resistance value of the conductive roll. Since a proportional relationship is found between the added amount of the ionic conductive agent and the resistance value, the desired resistance value can be achieved relatively easily and accurately by adjusting the added amount.

When the electric resistance value of the conductive roll is 10 ³ Ω or less, when the conductive roll is used as a charging roll, a transfer roll or a developing roll provided in association with a photosensitive drum of an electronic copying machine, for example. In addition, the photosensitive drum that holds the electrostatic latent image is destroyed by electric discharge, or the potential is lowered due to the bias leak, so that the image quality is lowered.

Further, the electric resistance value of the conductive roll is 10 ¹⁰
If it exceeds Ω, when the conductive roll is used as, for example, a charging roll, the photosensitive drum cannot be sufficiently charged, and when it is used as a charge eliminating roll of the photosensitive drum, the photosensitive drum should be sufficiently discharged. I can't. Further, even if it is used as a transfer or cleaning roll, a roll having such a high resistance value cannot obtain a sufficient potential, resulting in a decrease in efficiency.

From this point of view, it is desired that the electric resistance value of the conductive roll is 10 ⁴ to 10 ¹⁰ Ω. In order to satisfy this demand, that is, in order to obtain the electric resistance value of 10 ⁴ to 10 ¹⁰ Ω required for the conductive roll, the addition amount of the ion conductive agent is 1 * 10 with respect to 100 g of the polyol.
^{-5 to} 2 * 10 ^-2 mol is desirable.

As the conductive fine powder, conductive carbon or the like can be used. When the weight of the conductive fine powder is 30% by weight or more of the whole, in a normal use state,
This alone may form a chain structure that imparts conductivity to the roll, which greatly affects the control of electric resistance due to the addition of the ion conductive agent, and also greatly increases the hardness of the roll.

Therefore, the ionic conductive agent is appropriately dispersed in a matrix and the conductive fine powder is formed without forming a chain structure that controls conductivity in the conductive fine powder and without significantly increasing the hardness of the roll. In order to act as an intermediate medium for transfer of electric charge by ions, the conductive fine powder is preferably less than 30% by weight based on the whole. Further, by setting the conductive fine powder to less than 30% by weight, the addition of the conductive fine powder does not cause a large increase in hardness.

Further, the reactive plasticizer for reducing the hardness is
Since it forms a part of the polymer by its own reaction, it does not cause bleeding like process oil or plasticizer such as dioctyl phthalate which causes cracks, and does not cause cracks, which results in low hardness. A conductive roll is formed.

The kneading type urethane thus formed exhibits a relatively low hardness of Shore A hardness of 60 ° or less, but the compression set is adjusted by adjusting the Mooney viscosity and the addition amount of the crosslinking agent. Could be prevented from increasing.

[0029]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 2 is a schematic diagram showing a conductive roll according to the present invention together with a device for measuring its electrical resistance. The conductive roll 10 according to the present invention can be used as, for example, a charging roll, a developing roll or a transfer roll incorporated in an electrophotographic device such as a printer and a facsimile. The conductive roll 10 includes a cored bar 12 and a cylindrical roll body 14 surrounding the cored bar. The roll body is made of a kneading type urethane containing conductive fine powder and an ion conductive agent. A specific method of forming the conductive roll 10 and the like will be described in detail next in Examples 1 and 2.

<Example 1> 100 parts by weight of Sannix PP2000 (manufactured by Sanyo Chemical Industry Co., Ltd.) as a polymer which is a base material of a kneading type urethane, and perchlorine which is one of alkali metal salts as an ion conductive agent. 1 part by weight of lithium acid, 0.05 part by weight of trimethyltin hydroxide as a catalyst and 4 as an isocyanate,
4′-Diphenylmethane diisocyanate (MDI) is reacted at 100 ° C. for 12 hours to prepare a prepolymer dough including an ion conductive agent. The addition amount of 4,4′-diphenylmethane diisocyanate (MDI) is 1
The Mooney viscosity of the dough at 00 ° C. is adjusted to be within the range of 10 to 60.

This dough is kneaded using a roll mill, and the ion conductive agent is dispersed appropriately by this kneading, and then Ketjen Black EC-DJ600 (Ketjen) which is one of conductive carbons as conductive fine powder. -Add a specified amount of Black International Co., Ltd.). The amount of conductive carbon added was increased stepwise from 0 to 30% by weight in order to measure the change in electrical resistance using this as a parameter.

After the added conductive carbon is uniformly dispersed in the dough, 20 parts by weight of Unisafe PKA-5016 (manufactured by NOF Corporation) having an allyl group is added as a reactive plasticizer. Unisafe PKA-5016 is
It has an average molecular weight of 1600 and its structural formula is C
H ₃ CH ₂ CH ₂ CH ₂ O (E0) _m (PO) _n CH ₂
It is shown by CH = CH ₂ . In this formula, EO represents ethylene oxide, PO represents propylene oxide, and m and n each represent a positive integer. This EO
The molar ratio of / PO is 50/50.

After thoroughly mixing this reactive plasticizer into the dough, 0.5 part by weight of dicumyl peroxide was added as a crosslinking agent. Using the prepolymer thus obtained as a molding material, the core metal 12 (outer diameter 6 mm, length 250 m
m), using a dedicated mold set at 160 ℃, 20
Press molding was carried out under the molding conditions of minutes. This molded product is
The outer diameter of the roll body 14 is 12 mm and the total length thereof is 225 mm, and the roll 10 is completed.

In order to measure the resistance value of the conductive carbon contained in the roll body 14 for each weight%, the conductive roll 10 is placed on the electrode member 16 made of SUS304 plate as shown in FIG. The resistance value between the core metal 12 of the roll 10 and the electrode member 16 was measured by using ULTRA HIGH RESISTANCE METER R8340A (manufactured by Advantest Corporation) with a load of 500 g applied to the end. The applied voltage at that time was 300V. In addition, as the environment at the time of measurement, the temperature is 5 ° C., the humidity is 20%, and the temperature is low and low humidity (L / L), the temperature is 22 ° C., the humidity is 50%, the medium temperature and humidity (N / N), the temperature is 35 ° C., and the humidity is 85%. Each electric resistance value under high temperature and high humidity (H / H) was measured.

The measurement results are shown in the explanatory view shown in FIG. Further, FIG. 3 shows the measurement result of the volume resistivity which does not change due to the shape or the like. This volume resistivity was measured according to JIS-K6723 for 2 mm sheet molded products of each urethane having different contents of conductive carbon. Further, in order to examine the durability of each urethane, the electric resistance value after continuously applying a voltage of 1000 V for 100 hours was measured, and the measurement result is shown in the bottom row of FIG.

In the EC-DJ600 addition amount column shown in FIG. 3, the content of the conductive carbon is 0, that is, the conventional conductivity using the latter without using the conductive fine powder and the ionic conductive agent together. Corresponds to the role example. In this example, the electrical resistance value changes from 1 * 10 ⁷ Ω to 4 * 1 depending on the environmental change from low temperature / low humidity (L / L) to high temperature / high humidity (H / H).
There is a large change in the order of 0 ⁴ Ω and 10 ³ and it can be seen that it is easily affected by environmental changes. Also, the result of the durability test shows 2 * 10 ⁹ Ω, which is almost the high resistance value of the urethane base material itself, and the durability is poor.

On the other hand, in each of the conductive rolls of the present invention in which the amount of EC-DJ600 added was increased stepwise from 5 to 30% by weight, the electric resistance value was 10 ⁶ regardless of environmental changes. Alternatively, it only changes within the same order of 10 ³ and has very low dependency on environmental changes. Also,
Even in the durability test, the electric resistance value does not change beyond the order, and the urethane base material itself does not exhibit a high resistance value, and thus has excellent durability.

Further, in this addition amount range, 30% by weight
Except for the fact that the electric resistance values did not change significantly with respect to the increase in the added amount, the conductive carbon added should not form a chain structure that contributes to the increase in conductivity. Conceivable. Therefore, in the conductive roll, the electrical resistance value is not strongly controlled by the conductive carbon when the addition amount is less than 30% by weight, and the resistance value of the roll is properly and accurately determined according to the addition amount of the ionic conductive agent. Can be set to. For these reasons, it is desirable that the amount of conductive fine powder such as conductive carbon added be less than 30% by weight.

Further, in such a roll, by adding the reactive plasticizer, the Shore A hardness can be greatly reduced to 25 ° to 48 ° without causing bleeding of the plasticizer. When such a low-hardness roll was applied to the charging roll of the image forming apparatus and halftone, black solid, and still images were output, good images were obtained.

<Example 2> 100 parts by weight of Hiprox DP-2000 (manufactured by Dainippon Ink and Chemicals, Inc.) as a base polymer of a kneading type urethane was used as conductive fine powder and conductive carbon was used as Ketjen Black. EC-
P (manufactured by Ketjen Black International Co., Ltd.) was added in a predetermined amount and sufficiently stirred to disperse it.

Thereafter, 0.01 parts by weight of dibutyltin dilaurylate (DBTL) as a catalyst, 5 parts by weight of octadecyl isocyanate, which is an isocyanate having one reaction active point, as a reactive plasticizer, and 4 parts as an isocyanate. 4′-Diphenylmethane diisocyanate (MDI) is added and reacted at 100 ° C. for 20 hours to prepare a prepolymer fabric containing conductive carbon. The addition amount of 4,4′-diphenylmethane diisocyanate (MDI) is adjusted so that the Mooney viscosity of the dough at 100 ° C. is within the range of 10 to 60.

This dough is kneaded back using a roll mill,
This tetrabutylammonium Monumentale um fluoride trihydrate as an ion conductive agent _{([CH 3 (CH 2)} 3] 4 NF · 3
0.5 parts by weight of H ₂ O) is added. Then, 0.5 part by weight of dicumyl peroxide is added as a crosslinking agent to form a prepolymer. Example 1 using this prepolymer
Conductive rolls and sheet moldings similar to those in 1 were prepared, and the same resistance measurement as in Example 1 was performed for each. In addition, also in Example 2, as in the case of Example 1, the amount of the conductive carbon added is 0 to 30.
Gradually increased up to wt%.

The measurement results are shown in the explanatory view shown in FIG. The EC-P addition amount 0 column shown in FIG. 4 corresponds to an example of a conventional conductive roll having a conductive carbon inclusion amount of 0. In an example in which the amount of conductive carbon added is 0,
As described in Example 1, it can be seen that the electric resistance value is easily affected by the environmental change due to the environmental change from low temperature and low humidity (L / L) to high temperature and high humidity (H / H). Also in the measurement result of the durability test, the electric resistance value varies and the durability is poor.

When the amount of EC-P added is 5 to 30% by weight,
In both cases, the electric resistance value is 1 regardless of environmental changes.
It only changes within the same order of 0 ⁷ or 10 ⁴ ,
As in Example 1, the dependence on environmental changes is very low. Also in the durability test, the electric resistance value does not change beyond the order, and the durability is excellent. In addition, in the range of the added amount, except for 30% by weight, the respective electric resistance values did not largely change compared with the increase of the added amount, and thus the added conductive carbon contributes to the increase of the conductivity. It is considered that the chain structure is not formed to the extent that Therefore, in the conductive roll, the electrical resistance value is not strongly controlled by the conductive carbon when the addition amount is less than 30% by weight, and the resistance value of the roll is properly and accurately determined according to the addition amount of the ionic conductive agent. Can be set to.

Further, in such a roll, by adding the reactive plasticizer, the Shore A hardness can be greatly reduced to 31 ° to 59 ° without causing bleeding of the plasticizer. Was applied to the same charging roll as in Example 1, and a good image was obtained.

When the amount of EC-P added reached 30% by weight, the electric resistance value drastically decreased to the order of 10 ⁴ , showing that the conductive carbon strongly affects the electric resistance. . Therefore, when the amount of EC-P added is 30% by weight or more, it becomes difficult to set the resistance value of the roll properly and accurately.

Therefore, also in Example 2, it is desirable that the amount of conductive fine powder such as conductive carbon added be less than 30% by weight. As a result, it is possible to achieve appropriate elasticity and low hardness without using a plasticizer, show an appropriate value without variation in quality, and do not significantly change the resistance value due to environmental changes, and it has excellent durability. A conductive roll can be obtained.

[0048]

As described above, according to the present invention, by incorporating the reactive plasticizer in the kneading type urethane, the hardness of the conductive roll can be reduced without causing the bleeding phenomenon of the plasticizer. Can be planned. Therefore, even when the low-hardness conductive roll according to the present invention is applied to a high-speed rotating portion of an electrophotographic apparatus, a clear image can be obtained without generating abnormal noise. Furthermore, by including both a proper amount of conductive fine powder and an ionic conductive agent in the kneading type urethane, the resistance value does not greatly change due to environmental changes such as temperature and humidity, and the durability is excellent. It is possible to obtain a uniform conductive roll having a desired electric resistance value.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a reaction of a reactive plasticizer according to the present invention.

FIG. 2 is a schematic view showing a conductive roll according to the present invention together with an electric resistance measuring device.

FIG. 3 is an explanatory diagram showing electric resistance characteristics of a conductive roll according to the present invention.

FIG. 4 is an explanatory diagram showing electric resistance characteristics of another conductive roll according to the present invention.

[Explanation of symbols]

 10 Conductive Roll 12 Core Bar 14 Roll Body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G03G 15/16 103 G03G 15/16 103 (72) Inventor Koichi Shizuru Shiritate, Tsurumi-ku, Yokohama-shi, Kanagawa 2-3-6 Hokushin Industry Co., Ltd.

Claims (5)

[Claims] 1. A roll main body is formed by adding a reactive plasticizer, which reacts with the prepolymer or is itself incorporated into the prepolymer as a homopolymer, to a kneaded urethane prepolymer. Conductive roll. 2. The reactive plasticizer is a plasticizer containing at least one of an allyl group, a glycidyl group, or an isocyanate group having one reaction active site in its molecule. The conductive roll described. 3. The conductive roll according to claim 1, wherein the prepolymer further contains conductive fine powder and an ionic conductive agent. 4. The conductive roll according to claim 3, wherein the conductive fine powder is added in an amount that does not form a chain structure for increasing the conductivity of the roll body. 5. The conductive roll according to claim 3, wherein the conductive fine powder is less than 30% by weight.