JP3594053B2 - Conductive member and electrophotographic apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive member such as a developing member and a transfer member used in a mechanism such as a packaging member having an antistatic function, a shock absorbing member, or electrophotography, and an electrophotographic apparatus using the same.
[0002]
Problems to be solved by the prior art and the invention
In recent years, with the development of electrophotographic technology, demands for conductive members used in image forming apparatuses such as laser printers and dry copying have been increasing. In particular, elastic rollers used in processes such as development and transfer have attracted attention. .
Conventionally, conductive members used in such applications are made of a high-molecular elastomer material such as rubber or urethane adjusted to a predetermined resistance value by mixing a filler such as metal or metal oxide powder or whiskers and / or carbon black. And polymer foam materials. The performance required of these conductive members is a predetermined electric resistance value in a medium resistance region of 1 × 10 ⁴ Ωcm to 1 × 10 ¹² Ωcm, more preferably 1 × 10 ⁷ Ωcm to 1 × 10 ¹⁰ Ωcm. In addition, the fluctuation range of the electric resistance at low temperature and low humidity and the high temperature and high humidity range are small, and the fluctuation range of the electric resistance when energized continuously is small.
[0003]
However, by mixing a metal or metal oxide powder or a filler such as whisker and / or conductive carbon black such as acetylene black or Ketjen black, a polymer elastomer or polymer foam adjusted to a predetermined resistance value is used. The conductive member has a large variation in electric resistance at the time of manufacture, so that a component having substantially a predetermined resistance value cannot be stably manufactured. Accordingly, the present inventor has found that the use of medium-structure carbon black instead of high-structure carbon black, which was conventionally considered suitable for imparting conductivity to polymer elastomers and polymer foams, makes it relatively easy to control the electrical resistance. (Japanese Patent Laid-Open No. 7-53860). However, even such a conductive member using carbon black has a drawback that the electric resistance usually gradually increases by continuous energization.
[0004]
Other means for obtaining the conductive member include inorganic ionic substances such as lithium perchlorate, sodium perchlorate, calcium perchlorate and / or lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride. , Dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, modified aliphatic dimethyl ethyl ammonium ethosulfate and other cationic surfactants, lauryl betaine, stearyl betaine, dimethyl alkyl lauryl betaine, etc. Quaternary ammonium salts such as amphoteric surfactants, tetraethylammonium perchlorate, tetrabutylammonium perchlorate, and tetrabutylammonium borofluoride; There is also a method using a polymer elastomer material such as rubber or urethane or a polymer foam material adjusted to a predetermined resistance value by mixing a conductive agent made of an organic ionic substance and / or an antistatic agent such as hydrophilic polyether or polyester. . However, a conductive member such as a polymer elastomer or a polymer foam, which is adjusted to a predetermined resistance value by mixing such a substance, has a drawback in that the fluctuation range of the electric resistance at low temperature and low humidity and at high temperature and high humidity is large. There is.
[0005]
The present invention has been made in view of the above circumstances, and in a conductive member used in a mechanism such as electrophotography, an increase in electric resistance due to normal continuous energization is small. An object of the present invention is to provide a conductive member having a small fluctuation range of electric resistance and an electrophotographic apparatus using the same.
[0006]
[Means for Solving the Problems]
The conductive member according to claim 1 of the present invention is a conductive member used in a mechanism such as electrophotography, wherein the conductive member comprises a urethane containing a polyether polyol to which ethylene oxide and propylene oxide are randomly added as a polyol component. And when the conductive member has a specific surface area determined by a nitrogen adsorption method of X [m ² / g] and a DBP oil absorption of Y [ml / 100 g], 25 ≦ X ≦ 130 and −0.43X + 88 ≦ It is characterized by containing carbon black satisfying Y ≦ −0.43X + 134.
[0007]
The conductive member according to claim 2 of the present invention is characterized in that, in the polyether polyol, the proportion of ethylene oxide contained in all the polyether polyol components is 3 to 50% by weight.
[0008]
Conductive member according to claim 3 of the present invention is characterized in that the conductive member is Asker C hardness of 70 ⁰ or less of the foam.
[0009]
According to a fourth aspect of the present invention, there is provided an electrophotographic apparatus, wherein a developer is carried on a surface of the conductive member according to any one of the first to third aspects to form a thin film of the developer. A developing device for contacting or approaching the latent image holding member holding the image on the surface to adhere the developer to the electrostatic latent image on the surface of the latent image holding member and to visualize the electrostatic latent image; And
[0010]
According to a fifth aspect of the present invention, there is provided an electrophotographic apparatus, wherein the recording medium is charged by the conductive member according to any one of the first to third aspects, and the developer is recorded on the electrostatic latent image visualized by the developer. It has a transfer device for transferring to a surface.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
That is, conventional gas blacks such as Ketjen black and acetylene black, which have been considered suitable for imparting conductivity to a polymer member made of a polymer elastomer or a polymer foam, ISAF grade or SAF grade oil furnace black, Mitsubishi Chemical # In high structure carbon blacks such as 3050 and # 3250 conductive black, the electrical resistance sharply decreases with an increase in the blending amount. It is difficult to stably produce members. On the other hand, low-structure carbon blacks such as FT-grade, MT-grade thermal black, and SRF-grade oil furnace black require a large amount of compounding to obtain a predetermined resistance value, so that the flexibility of the polymer member is significantly reduced. It does not function as a conductive member that is damaged, and it is difficult to foam, especially when producing a polymer foam member.
[0012]
On the other hand, ink blacks such as GPF grade and FEF grade oil furnace black, Mitsubishi Chemical # 10, # 25, # 33, CF9, # 52, # 44, # 45, Degussa Printex 55, Colombian Raven 780, etc. The electrical resistance is relatively easy to control with a compounding amount of carbon black having a medium structure such as that described above, in a range that does not lose the flexibility of the conductive member. Even a medium structure carbon black needs to have an appropriate specific surface area in order to control electric resistance. For example, carbon black having an extremely large specific surface area, such as Mitsubishi Chemical # 2300 or # 2500, or carbon black having an extremely small specific surface area, such as lamp black, has a required compounding amount to obtain a predetermined resistance value even in a medium structure. Tends to be large.
[0013]
Also, it was found that the electrical resistance of HAF-grade oil furnace black sharply decreased with an increase in the blending amount, despite the fact that HAF-grade oil-furnace black was low-structure compared to FEF-grade oil-furnace black based on DBP oil absorption. Although the reason for this is not clear, carbon black having a remarkably large specific surface area requires a large amount of compounding to obtain a predetermined resistance value due to difficulty in dispersing carbon in the conductive member. It is considered that the carbon black having a small primary particle size has a large primary particle size of the carbon black, and the structure determined from the DBP oil absorption and the morphological structure related to conductivity do not always correspond well.
[0014]
In the range where the specific surface area is not extremely large or small, the conductivity of the conductive member containing carbon black having the same structure but different specific surface area is larger than that of the structure determined from the DBP oil absorption as the specific surface area is larger. Since the structure determined from the typical aspect ratio is high, the change in conductivity is considered to be rapid. These points were comprehensively determined, and the present inventors tested various carbon blacks. As a result, when the specific surface area was X [m ² / g] and the DBP oil absorption was Y [ml / 100 g], 25 carbon black ≦ X <130 and -0.43 X +88 ≦ Y ≦ -0.43 X + 134 has been found that can stably control the electric resistance without impairing the flexibility of the conductive members. This range is illustrated in FIG.
[0015]
However, when the ordinary polyether polyurethane using the above carbon black is continuously energized at a voltage of about 1000 [V], the electric resistance increases. Such a phenomenon is a phenomenon that is less affected when conductivity is imparted with a high-structure carbon black such as electrified black. In particular, the lower the structure of a carbon black, the greater the rate of increase in electrical resistance. This is because when a conductive member is filled with a conductive filler to create a conductive member in the medium resistance region, the resistance is determined by the amount of the conductive path and the width of the insulating gap, and the amount of the path is dominant in high structure carbon. On the other hand, in low-structure carbon, the width of the gap is dominant, and due to continuous energization of the member, the member generates heat, so the conductive member deteriorates and the electrical resistance of the gap increases. . FIG. 2 schematically shows this state. The amount of carbon black defined in the present invention is preferably from 2 to 8 parts by weight, based on 100 parts by weight of urethane. If it is less than 2, it is difficult to control the resistance.
[0016]
Therefore, by increasing the heat resistance of the polymer member, it is possible to suppress an increase in resistance during continuous energization. Specifically, using a polyurethane containing a polyether polyol to which ethylene oxide and propylene oxide are randomly added as a component. This object can be effectively achieved by preparing a conductive member. In particular, the polyether polyol described in the patent of the present inventors (Japanese Patent Application No. 7-247830) is preferable.
The proportion of ethylene oxide contained in all the polyether polyol components is 3 to 50% by weight, more preferably 5 to 20% by weight, and if less than 5% by weight, the reactivity is inferior and molding is difficult, The ions are difficult to move due to low hydrophilicity, and it is difficult to secure the conductivity of the roller. On the other hand, when the content is more than 20% by weight, heat resistance is deteriorated, which is not preferable. In addition, other known polyols such as polyether polyol, polyester polyol, acrylic polyol, acrylonitrile polyol, polytetramethylene ether polyol, polybutadiene polyol, polyisoprene polyol, and polycarbonate polyol are mixed as long as the effects of the present invention are not impaired. You may.
[0017]
In addition, an ionic conductive agent comprising an inorganic ionic substance such as lithium perchlorate or an organic ionic substance such as a quaternary ammonium salt, a cationic surfactant, and the like, as long as the effects of the present invention are not impaired. Anionic surfactants, amphoteric surfactants such as various betaines, and nonionic antistatic agents such as hydrophilic polyethers and polyesters may be used in combination.
[0018]
Also, there is no limitation on the urethane forming method, and one-shot method and prepolymer method can be used, and the hardness of the conductive member can be reduced by forming a foam by a mechanical floss method, a water foaming method, a CFC foaming method, or the like. It is preferable for applications that need to be reduced. Incidentally, the hardness of the conductive member of the present invention is preferably 70 ⁰ or less in Asker C scale, unfavorably decreases the transfer efficiency more than 70 ^0.
[0019]
There is no limitation on the shape of the above-mentioned member used in the transfer device and / or the developing device, but it is usually used in the form of a roller having a metal core disposed at the center. A transfer device and / or a developing device of an electrophotographic apparatus manufactured by using such a member have a long life without a rise in resistance during energization. In addition, compared to a transfer device and / or a developing device that is prepared using a member imparted with conductivity by a conventionally used ionic conductive agent, the change in electrical resistance at high temperature and high humidity and at low temperature and low humidity is smaller. This is preferable because the capacity of the power supply can be reduced.
[0020]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Note that the humidity is a relative humidity.
[0021]
[Example 1]
Propylene oxide and ethylene oxide are randomly added to glycerin, the content of the ethylene oxide unit is 12%, the molecular weight is 3500, 100 parts by weight of polyether polyol, 1,4-butanediol is 6.05 parts by weight, 22 parts by weight of isocyanate, 4 parts by weight of a reactive silicone surfactant, 0.01 part by weight of dibutyltin dilaurate, DBP oil absorption 63 [ml / g] with a specific surface area of 60 [m ² / g] measured by nitrogen adsorption Was mixed with a mixer to prepare a urethane foam transfer roller having a diameter of 16.5 mm and a length of 215 mm, which was disposed around a metal shaft having a diameter of 6 mm.
[0022]
Next, the transfer roller was placed on a copper plate having a thickness of 2 mm, and the electrical resistance between the cored bar and the copper plate was measured while pressing both ends of the roller with a force of 500 g each. The temperature and humidity at the time of measurement were 20 ° C. and 55%, respectively. The electric resistance was 7.8 × 10 ⁷ Ω when the applied voltage was 1,000 V. Further, when the temperature and the humidity at the time of measurement are 32.5 ° C. and 85%, respectively, the applied resistance is 8.0 × 10 ⁷ Ω at 15 ° C. and the electric resistance is 5.0 × 10 ⁷ Ω at the applied voltage of 1,000 V. It was 7 × 10 ⁷ Ω.
[0023]
Further, the transfer roller was incorporated in an image forming apparatus shown in FIG. The power supply was set to be 5 A constant current. When a grayscale, solid black, and solid white image was printed at an environment of 15 ° C. and 10%, respectively, a good image was obtained. In an environment of 32.5 ° C., 85%, respectively, the temperature and humidity were respectively. When a grayscale, black solid, or white solid image was printed, a good image was obtained.
[0024]
Next, the photosensitive member of the image forming apparatus was changed to an aluminum tube, and rotated continuously for 150 hours while applying a voltage of 1,000 V in an environment where the temperature and humidity were 25 ° C. and 55%, respectively. Leave for 48 hours in an environment with a humidity of 15 ° C. and 10% for 48 hours, place the transfer roller on a 2 mm-thick copper plate in the same environment, and press the both ends of the roller with 500 g of force between the core metal and the copper plate. Was measured for electrical resistance. The electric resistance was 6.0 × 10 8 Ω when the applied voltage was 1,000 V. This transfer roller was assembled in an image forming apparatus in the same manner as described above, and when a gray scale, black solid, or white solid image was printed in an environment of 15 ° C. and 10%, a good image was obtained.
[0025]
[Comparative Example 1]
The polyol to be blended was a polyether polyol having a molecular weight of 5,000 containing 16.0% of ethylene oxide units only at the terminals, and the blending amount of 1,4-butanediol was 6.47 parts, and the blending amount of carbon black was 3 parts. An experiment was performed in the same manner as in Example 1 except that the experiment was performed. The initial electrical resistance was the same as in Example 1, but the electrical resistance after continuous energization was 2.0 × 10 ⁹ Ω at 15 ° C. and 10%. Compared with the example, the urethane foam of this comparative example has a large increase in resistance during continuous energization. The transfer roller was assembled in the image forming apparatus in the same manner as described above, and when a gray scale, black solid, or white solid image was printed in an environment of 15 ° C. and 10%, a transfer failure phenomenon in which the blackness of the black solid image was insufficient was observed. Appeared.
[0026]
[Example 2]
Same as Example 1 except that the carbon black to be blended had a specific surface area of 27 [m ² / g] measured by nitrogen adsorption and a DBP oil absorption of 87 [ml / g], and the blending amount of carbon black was 5 parts by weight. Then, a transfer roller was prepared. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 2.5 × 10 ⁹ Ω. When an image was printed in the same manner as in Example 1, a good image was obtained.
[0027]
[Comparative Example 2]
Example 1 was the same as Example 1 except that the carbon black to be blended was a DBP oil absorption of 115 [ml / g] with a specific surface area of 117 [m ² / g] measured by the nitrogen adsorption amount, and the carbon black blending amount was 5 parts by weight. Similarly, a transfer roller was manufactured. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 6 × 10 ⁵ Ω. When an image was printed in the same manner as in Example 1, a good image was not obtained.
[0028]
[Example 3]
Example 1 was the same as Example 1 except that the carbon black to be blended had a DBP oil absorption of 53 [ml / g] at a specific surface area of 127 [m ² / g] measured by the nitrogen adsorption amount and a carbon black blending amount of 5 parts by weight. Similarly, a transfer roller was manufactured. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and the humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 2 × 10 ⁷ Ω. When an image was printed in the same manner as in Example 1, a good image was obtained.
[0029]
[Comparative Example 3]
Same as Example 1 except that the carbon black to be blended had a specific surface area of 27 [m ² / g] measured by nitrogen adsorption and a DBP oil absorption of 68 [ml / g], and the blending amount of carbon black was 5 parts by weight. Then, a transfer roller was prepared. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 1 × 10 ¹⁰ Ω. When an image was printed in the same manner as in Example 1, a good image was not obtained.
[0030]
[Example 4]
The same as Example 1 except that the carbon black to be blended had a specific surface area of 42 [m ² / g] measured by nitrogen adsorption and a DBP oil absorption of 115 [ml / g], and the blending amount of carbon black was 3 parts by weight. Then, a transfer roller was prepared. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 3 × 10 ⁸ Ω. When an image was printed in the same manner as in Example 1, a good image was obtained.
[0031]
[Comparative Example 4]
Same as Example 1 except that the carbon black to be blended had a specific surface area of 90 [m ² / g] measured by the nitrogen adsorption amount, a DBP oil absorption of 110 [ml / g], and the blending amount of carbon black was 5 parts by weight. Then, a transfer roller was prepared. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 4 × 10 ⁵ Ω. When an image was printed in the same manner as in Example 1, a good image was not obtained.
[0032]
[Example 5]
The same as Example 1 except that the carbon black to be blended had a specific surface area of 55 [m ² / g] measured by nitrogen adsorption and a DBP oil absorption of 70 [ml / g], and the blending amount of carbon black was 5 parts by weight. Then, a transfer roller was prepared. The electrical resistance of this transfer roller was measured in the same manner as in Example 1. When the temperature and humidity at the time of measurement were 20 ° C., 55%, and the applied voltage was 1,000 V, the electric resistance of the roller was 3 × 10 ⁸ Ω. When an image was printed in the same manner as in Example 1, a good image was obtained.
[0033]
【The invention's effect】
As described above, the conductive member of the present invention is a conductive member used in a mechanism such as electrophotography, wherein the conductive member is a polyether polyol to which ethylene oxide and propylene oxide are randomly added as a polyol component. When the conductive member is made of urethane and the specific surface area by the nitrogen adsorption method is X [m ² / g] and the DBP oil absorption is Y [ml / 100 g], 25 ≦ X ≦ 130 and −0. 43X + 88 ≦ Y ≦ −0.43X + 134 By using a conductive member characterized by containing carbon black, an increase in electrical resistance due to continuous energization is usually small, and a low temperature low humidity and high temperature high humidity The fluctuation range of the electric resistance can be reduced, and the conductive member can be transferred to an electrophotographic apparatus used in a mechanism such as an electrophotographic apparatus. Wood, can be suitably used in the developing member or the like.
[Brief description of the drawings]
FIG. 1 is a graph showing characteristics of carbon black according to the present invention.
FIG. 2 is a schematic view showing the structure of carbon black according to the present invention.
FIG. 3 is a schematic diagram illustrating an example of an image forming apparatus to which the conductive member of the present invention is mounted.

Claims (5)

In a conductive member used in a mechanism such as electrophotography, the conductive member is made of urethane containing a polyether polyol to which ethylene oxide and propylene oxide are randomly added as a polyol component, and the conductive member is nitrogen-adsorbed. Assuming that the specific surface area by the method is X [m ² / g] and the DBP oil absorption is Y [ml / 100 g], carbon black satisfying 25 ≦ X ≦ 130 and −0.43X + 88 ≦ Y ≦ −0.43X + 134 is contained. A conductive member comprising: 2. The conductive member according to claim 1, wherein in the polyether polyol, a ratio of ethylene oxide contained in all the polyether polyol components is 3 to 50% by weight. 3. According to claim 1 or 2, wherein the conductive member, characterized in that the conductive member is Asker C hardness of 70 ⁰ or less of the foam. A developer is carried on the surface of the conductive member according to any one of claims 1 to 3 to form a thin film of the developer, and in this state, the electrostatic latent image is brought into contact with the latent image holding member holding the surface. Or an electrophotographic apparatus comprising a developing device for adhering the developer to the electrostatic latent image on the surface of the latent image holding member in close proximity to the electrostatic latent image to visualize the electrostatic latent image. A transfer device for charging a recording medium with the conductive member according to any one of claims 1 to 3, and transferring the developer to the recording medium from an electrostatic latent image visualized by the developer. Electrophotographic equipment.

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