JP2795168B2 - Developing roller and developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller for visualizing an electrostatic latent image with a non-magnetic one-component developer in an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus. More specifically, the present invention relates to a developing roller having excellent stain resistance and capable of reliably obtaining a good image even in long-term use, and a developing device using the roller.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, a non-magnetic one-component developer is supplied to a photosensitive member holding a latent image and the latent image on the photosensitive member is supplied to the photosensitive member. As a developing method for visualizing a latent image by attaching a developer, a pressure developing method is known (US Pat. No. 3,515,2012).
According to this method, since a magnetic material is not required, the apparatus can be simplified and downsized easily, and the toner can be easily colored.

In this pressure development method, a developing roller carrying a toner (a non-magnetic one-component developer) is brought into contact with a latent image holding member such as a photosensitive drum holding an electrostatic latent image, and the toner is transferred to the latent image holding member. The development is carried out by adhering to the latent image on the holding member. For this reason, it is necessary to form the developing roller with a conductive elastic body.

That is, in this pressure developing method, as shown in FIG. 2, for example, a toner applying roller 4 for supplying toner and a photoconductor 5 holding an electrostatic latent image
The developing roller 1 is disposed in contact with the photoconductor 5 and slightly separated from the toner coating roller 4. The developing roller 1, the photoconductor 5 and the toner coating roller 4 are respectively arranged in the directions indicated by arrows in FIG. By the rotation, the toner 6 is supplied to the surface of the developing roller 1 by the toner applying roller 4, and the toner is arranged in a uniform thin layer by the layering blade 7, and the developing roller 1 contacts the photoconductor 5 in this state. By rotating while rotating, the toner formed in a thin layer adheres to the latent image on the photoconductor 5 from the developing roller 1 and the latent image is visualized. In the drawing, reference numeral 8 denotes a transfer unit, which transfers a toner image to a recording medium such as paper. Reference numeral 9 denotes a cleaning unit, which is provided on a surface of the photoreceptor 5 after transfer by a cleaning blade 10. The remaining toner is removed.

In this case, the developing roller 1 must rotate while reliably maintaining a state in which the developing roller 1 is in close contact with the photosensitive member 5.
For this reason, as shown in FIG. 1, silicone rubber, NB
It has a structure in which a conductive agent is blended into an elastic rubber such as R or EPDM or urethane foam to form an elastic layer 3 made of an elastic body having conductivity.

[0006]

However, the conventional developing roller has the following disadvantages due to the characteristics of the elastic layer. 1. When the elastic layer is formed of an elastic rubber such as silicone rubber or NBR, if the hardness is lowered to obtain good adhesion, contamination of the photoconductor may occur. 2. When the elastic layer is formed from a sponge body such as urethane foam, if the toner enters the elastic layer and is used for a long period of time, the roller may become hard due to toner clogging, or toner charging failure may occur, resulting in poor image quality. May decrease.

Further, a developing roller composed of a single elastic layer generally has insufficient charging rise characteristics of toner on the roller, and causes problems such as poor cleaning due to fogging selective development due to poor charging of toner and a decrease in print density. Easy,
The print quality is significantly reduced by long-term continuous printing. This phenomenon is particularly remarkable under a high temperature and high humidity environment.

The present invention has been made in view of the above circumstances, has low hardness and good adhesion, does not cause inconvenience such as contaminating a photoreceptor, etc., and has no unevenness in density or background fog. An object of the present invention is to provide a developing roller capable of obtaining a high-quality image and not causing deterioration in image quality even when used for a long period of time, and a developing device using the developing roller.

[0009]

The present inventors have made intensive studies to achieve the above object, and as a result, have found that a developing roller in which a conductive elastic layer is formed on the outer periphery of a good conductive shaft is provided. Forming the elastic layer by adding carbon black having a pH of 5 or more to a urethane elastomer obtained by using a polyolefin polyol as a polyol, and in particular, setting the resistivity of the urethane elastomer to 10 ⁴
〜１０10 ¹⁰ Ωcm, hardness is 55 ° on JIS-A scale
Hereinafter, the surface roughness is measured at 10 μm Rz in terms of JIS 10-point average roughness.
By performing the following adjustment, a non-magnetic one-component developer is carried on the surface of the developing roller to form a thin layer of the developer, and this is brought into contact with a latent image holding member such as a photoreceptor to hold the latent image. When developing the electrostatic latent image of the body, the developing roller is in good contact with the latent image holding member, and there is no inconvenience such as contamination of the latent image holding member. A high-quality image is obtained, and the image quality is not deteriorated even when used for a long period of time. The elastic layer of the roller is formed by blending silicone powder with such a urethane elastomer to provide a high-temperature, high-humidity environment. It has been found that the excellent performance described above can be surely exhibited even below, and the present invention has been completed.

Accordingly, the present invention provides an electroconductive elastic layer formed on the outer periphery of a highly conductive shaft, and a nonmagnetic one-component developer carried on the surface of the elastic layer to form a thin layer of the developer. In this state, the developer is brought into contact with the latent image holding member holding the electrostatic latent image on the surface to adhere the developer from the thin layer to the electrostatic latent image on the surface of the latent image holding member. A developing roller for visualizing an image, wherein the elastic layer is formed of a urethane elastomer containing carbon black having a pH of 5 or more, and the urethane elastomer is obtained by using a polyolefin polyol as a polyol. Provide rollers.

In a preferred embodiment of the present invention, the urethane elastomer forming the elastic layer has a resistivity of 10 ⁴ to 10 ¹⁰ Ωcm, a hardness of 55 ° or less on a JIS-A scale, and a surface roughness of JIS 10 points average roughness 10
Provided are a developing roller having a μmRz or less and a developing roller in which a urethane elastomer for forming an elastic layer contains silicone powder.

Further, the present invention provides a roller- or drum-shaped latent image holding member for holding an electrostatic latent image on a surface thereof, and a latent image holding member provided with a non-magnetic one-component developer on an outer peripheral surface thereof. The non-magnetic one-component developer is adhered to the electrostatic latent image on the surface of the latent image holding member by rotating the surface of the latent image holding member in contact with the surface of the latent image holding member. A developing device comprising a developing roller for visualization, wherein the developing roller according to the present invention is used as the developing roller.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1, the developing roller of the present invention is formed by forming a conductive elastic layer 3 on the outer periphery of a good conductive shaft 2.

As the shaft 2, any shaft having good conductivity can be used, but usually a metal core made of a solid metal body or the inside is hollowed out. A metal shaft such as a metal cylinder is used.

Next, the elastic layer 3 formed on the outer periphery of the shaft 2 is made of a urethane elastomer containing carbon black having a pH of 5 or more. In this case, the urethane elastomer is made of a polyolefin polyol as a polyol. Any method may be used, and any method may be used. For example, a method of blending carbon black into a polyurethane prepolymer, crosslinking and curing the prepolymer, blending a conductive material with a polyol,
The polyol can be obtained by a method such as a method of reacting with a polyisocyanate by a one-shot method. Further, thermoplastic urethane may be used.

In the present invention, the urethane elastomer forming the elastic layer 3 uses a polyolefin polyol as the polyol. In this case, specific examples of such polyolefin polyols include polybutadiene polyols and polyisoprene polyols. By combining a urethane elastomer using these polyolefin polyols with the above-mentioned carbon black having a pH of 5 or more, unevenness in concentration and ground density can be obtained. It is possible to reliably obtain a high-quality image without fogging or the like.

The polyisocyanate used for obtaining the urethane elastomer is not particularly limited, but a polycisocyanate having a bent molecular structure is preferably used. The indicated polyisocyanates are preferably used. Such a polyisocyanate prevents crystallization of the polyurethane chain, so that the hardness can be easily reduced, and furthermore, the entanglement of the molecular chain can be easily formed, so that a so-called pseudo-crosslinked structure can be obtained.

[0018]

Embedded image (In the formula, R represents a carbon-carbon bond or an alkylene group, and R ′ represents hydrogen or an alkyl group.)

Specific examples of such a polyisocyanate include 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.
Toluene diisocyanate, a mixture thereof, m-tetramethylxylylene diisocyanate, m-xylene diisocyanate, m-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, and the like. Of these, diphenylmethane-4,4'-diisocyanate is particularly preferred. Particularly, a modified diphenylmethane-4,4'-diisocyanate containing uretonimine-modified diphenylmethane-4,4'-diisocyanate is preferable from the viewpoint of reducing photoreceptor contamination. In addition,
This content ratio is preferably 5 to 50% by weight. Further, crude diphenylmethane-4,4′-diisocyanate is also preferably used.

In the developing roller of the present invention, the urethane elastomer is blended with carbon black to impart conductivity, and the conductive urethane elastomer is used to provide the elastic layer 3.
, And in this case, carbon black having a pH of 5 or more was used. That is, it is known that the triboelectrification characteristics of carbon black become positive as the pH value increases and conversely become negative as the pH decreases. In this case, the developing roller of the present invention has a non-magnetic property. The carbon black has a pH of 5 or more to negatively charge the toner of the one-component developer.
In fact, when using a non-magnetic one-component negatively chargeable toner,
On the roller containing carbon black having a value of less than 5, the amount of the toner of the opposite polarity increased and toner dust was observed.

As long as the carbon black used in the developing roller of the present invention has a pH of 5 or more, any of acetylene black, Ketjen black, furnace black and the like can be used, but furnace black having a pH of 6 or more is particularly preferable. used.

Here, the pH of carbon black varies depending on the number of functional groups, particularly carboxyl groups, etc. on the surface of carbon black, and serves as an index for knowing acidity and basicity. That is, generally, the surface of carbon black contains oxygen-containing functional groups such as phenolic hydroxyl groups, carboxyl groups, and quinone-type oxygen, and the number of these surface functional groups differs depending on the type of carbon black. In this case, the surface properties of the carbon black mainly differ depending on the production method, and there are many functional groups on the surface of the channel black, but few on the surfaces of the furnace black and the acetylene black. For the pH of the carbon black, for example, about 5 g of a sample is boiled in 150 cc of distilled water for 5 minutes, left to cool to room temperature, and centrifuged (2,000 RPM) for 3 minutes in a centrifuge. The sludge can be separated by removing the supernatant, put into a beaker as a measurement sample, and measure the pH with a pH meter to determine the sludge.

The elastic layer 3 thus obtained is
Although it is not particularly limited, the resistance value is 10 ⁴ to 10 ¹⁰ Ωcm,
In particular, it is preferably set to 10 ⁶ to 10 ⁹ Ωcm. If the resistance value is less than 10 ⁴ Ωcm, electric charge may leak to the photosensitive drum or the like, or the developing roller itself may be broken by the voltage. On the other hand, if the resistance value exceeds 10 ¹⁰ Ωcm, fog tends to occur. In this case, the resistance value may be adjusted by using other conductive additives such as metal powder and metal oxide together with the carbon black. The mixing ratio of the carbon black to the urethane elastomer is not particularly limited, and is generally in a range where the resistance value of the elastic layer can be adjusted to the above range. Specifically, 100 parts of the urethane elastomer (parts by weight, hereinafter 0.5 for the same)
-50 parts, especially 1-30 parts. Also,
The adjustment of the resistance value may be performed by blending an ion conductive substance such as sodium perchlorate and tetraethylammonium chloride.

The hardness of the elastic layer 3 is not particularly limited, but is not more than 55 ° on a JIS-A scale, especially 25 °.
It is preferable to set it to 45 °. In this case, the hardness is 55
Exceeding ° may result in a small contact area with the photosensitive drum or the like, making it impossible to perform good development.However, when the hardness is too low, the compression set becomes large, and the developing roller is deformed or eccentric for some reason. In this case, uneven image density occurs. For this reason, even when the hardness of the elastic layer is set to a low hardness, it is preferable to reduce the compression set as much as possible, specifically, it is preferable to set it to 20% or less.

The surface roughness of the elastic layer 3, that is, the surface roughness of the developing roller of the present invention is not particularly limited, but is not more than 10 μm Rz in terms of JIS 10-point average roughness, particularly 1
８8 μmRz is preferred. Surface roughness 10μ
If it exceeds mRz, the thickness of the toner layer of the non-magnetic one-component developer (toner) and the uniformity of charging may be impaired.
By adjusting the thickness to 10 μmRz or less, the adhesion of the toner can be improved, and the deterioration of the image due to the wear of the roller during long-term use can be more reliably prevented.

The developing roller of the present invention uses a polyolefin polyol as a polyol and forms the elastic layer 3 with the urethane elastomer containing carbon black having a pH of 5 or more. Preferably, the resistance of the elastic layer 3 made of the urethane elastomer is as follows: Although the hardness and the surface roughness are adjusted as described above, the elastic layer 3 can be formed by further adding a silicone powder to the urethane elastomer, whereby the performance degradation under a high temperature and high humidity environment is prevented. It is possible to effectively prevent the occurrence of fog, particularly in a high-temperature and high-humidity environment.

That is, since urethane elastomers generally have high hygroscopicity, the toner charging ability on the roller surface decreases under high temperature and high humidity. This leads to an increase in the amount of weakly charged toner in the toner layer on the roller surface, causing fogging. On the other hand, silicone powder is excellent in water repellency and by dispersing it in urethane elastomer,
In particular, it is possible to suppress moisture absorption on the roller surface. Therefore, by adding the silicone powder to the urethane elastomer to form the elastic layer of the roller, it is possible to prevent the toner charging property from being lowered under high temperature and high humidity without contaminating the image carrier, and to obtain a clear image without fog. Can be reliably obtained even under high temperature and high humidity.

The silicone powder may be any of fine particles of a silicone resin, fine particles of a silicone rubber, and particles of a silicone oil supported on an inorganic carrier. Particles having a particle size of 0.1 to 20 μm, more preferably 0.5 to 5 μm, are preferably used. In this case, if the particle size of the silicone powder exceeds 20 μm, the smoothness of the roller surface becomes non-uniform, and the chargeability of the toner becomes non-uniform, which may cause deterioration in image quality. The amount of the silicone powder is not particularly limited, but is usually about 0.1 to 30 parts, and especially about 1 to 1 part, per 100 parts of the urethane elastomer.
It is desirable to use about 0 parts. Further, various charge control agents can be added for the purpose of controlling the toner charge amount on the roller surface using the urethane elastomer. The added charge control agent is a dye or pigment used for toner charge control, and examples thereof include nigroshi, triaminotriphenylmethane dye, cationic dye, dioxazine, azo pigment, azochrome complex, and quinacridone. . The charge control agent is preferably added in an amount of about 0.1 to 20 parts, particularly about 1 to 5 parts, based on 100 parts of the urethane elastomer.

The developing roller of the present invention can be incorporated in a normal developing device using a non-magnetic mono-component developer. Specifically, as shown in FIG. 2, a toner applying roller for supplying toner The developing roller 1 of the present invention is disposed between the photosensitive drum 5 and the photosensitive drum 5 holding the electrostatic latent image in a state where the developing roller 1 is in contact with the photosensitive drum 5, and the toner applying roller 4 supplies the toner 6 to the developing roller 1. The toner is supplied to the photosensitive drum 5 from the thin layer, and the toner is adhered to the electrostatic latent image on the photosensitive drum 5 to visualize the latent image. Can be. Note that FIG.
Is described in the prior art, and the description is omitted.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Example 1 Polyisoprene polyol having a molecular weight of 2500 (OH group =
47.1) 3.32 parts of acetylene black (manufactured by Denka, pH 6.9) was mixed with 100 parts (parts by weight, the same applies hereinafter) and stirred for 30 minutes to prepare a polyol composition. Thereafter, crude MDI (NCO% = 31.7) was added to 13.
33 parts, 0.001 part of dibutyltin dilaurate,
Stir for 3 minutes. Next, the shaft is placed, and 90 ° C.
The reaction mixture is poured into a mold heated to
A curing reaction was performed at 12 ° C. for 12 hours, and an elastic layer was formed on the outer periphery of the shaft to obtain a roller having the structure shown in FIG. The surface of the obtained roller was polished, and the surface was adjusted to JIS 10-point average roughness of 7 μmRz to obtain a developing roller A. In addition, 1 part of silicone powder (Toray Silicone Co., Ltd., Trefil E-500, particle size: 3 μm) was added to the above polyol composition, and a developing roller B was manufactured in the same manner.

Example 2 Uretonimine-modified MDI 30 in place of crude MDI
1% modified MDI containing 1% by weight (NCO% = 29.0)
Developing rollers A (without silicone powder) and B (with silicone powder) were prepared in the same manner as in Example 1 except that 3.47 parts were used.

Comparative Example 1 Polyether polyol (Exenol 828 of Asahi Glass Co., Ltd.) having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin (OH)
33) 100 parts of 1,4-butanediol 1.0
Part, silicon surfactant L-520, manufactured by Nihon Yunika Co., Ltd.)
1.5 parts, nickel acetylacetonate 0.5 parts, dibutyltin dilaurate 0.01 parts and carbon black PRINTEX-U (manufactured by Degussa, pH 4.0) 30
Part, and after pre-mixing using a mixer, kneading with a paint roll to uniformly disperse the carbon black,
After preparing a polyol composition, stirring the polyol composition under reduced pressure to remove bubbles, and then urethane-modified MDI
(Sumitomo Bayer Urethane Co., Ltd., Sumidur PF)
Developing rollers A (without silicone powder) and B were added in the same manner as in Example 1 except that 7.5 parts were added, the mixture was stirred for 2 minutes, and then cast into a mold heated to 110 ° C. and cured for 2 hours.
(Compound of silicone powder) was produced.

Comparative Example 2 A developing roller A (silicone powder) was prepared in the same manner as in Comparative Example 1 except that the addition amount of 1,4-butanediol was 3 parts and the addition amount of Sumidur PF was 27.5 parts. Body unmixed) and B
(Compound of silicone powder) was produced.

Comparative Example 3 Instead of carbon black, natural graphite AOP
Developing rollers A (without silicone powder) and B (with silicone powder) were manufactured in the same manner as in Comparative Example 1 except that 15 parts (manufactured by Nippon Graphite Co., pH 6.3) were added.

Comparative Example 4 In the surface polishing step, the developing rollers A (without silicone powder) and B (no silicone powder) were prepared in the same manner as in Comparative Example 1 except that the surface roughness was adjusted to 13 μm Rz by JIS 10-point average roughness. Silicone powder formulation) was produced.

Comparative Example 5 A developing roller A (without silicone powder) was produced in the same manner as in Comparative Example 1 except that 8.3 parts of tolylene diisocyanate was added instead of the urethane-modified MDI.

Comparative Example 6 A developing roller A (without silicone powder) was prepared in the same manner as in Comparative Example 1 except that 1.0 part of acetylene black (manufactured by Denka, pH 6.9) was added instead of carbon black. Manufactured.

The following characteristic tests were performed on the developing rollers obtained in Examples 1 and 2 and Comparative Examples 1 to 6. Table 1 shows the results. (1) Electric Resistance A sheet-like sample prepared under the same conditions as each roller was measured using a resistivity meter Hiresta (manufactured by Mitsubishi Yuka Corporation) by applying a voltage of 100 V. (2) Hardness and Compression Permanent A sheet-like sample prepared under the same conditions as each roller was measured according to JIS-K6301 (hardness is A type). (3) Surface roughness For each roller, a surface roughness meter Handy Surf E-30
It was measured using a type A (manufactured by Tokyo Seimitsu Co., Ltd.). (4) Contamination of photosensitive drum Each roller was pressed against a photosensitive drum for printer SP-3 manufactured by Ricoh Co., Ltd. with a load of 500 g, and left at 30 ° C. and 85% RH for 72 hours to visually check the surface of the photosensitive drum for contamination. Confirmed. (5) Toner charge amount Each roller is mounted on the developing unit shown in FIG. 2 as a developing roller and rotated at a peripheral speed of 50 mm / sec to form a uniform thin toner layer on the surface of the developing roller. The layer was sucked with air and introduced into a Faraday gauge, and the charge amount was measured. (6) Image output Each roller is attached to the developing unit shown in FIG. 2 as a developing roller, and images are output while reversing development and rotating at a linear speed of 60 mm / sec. Was evaluated for fog and toner dust.
At the same time, the state of toner filming on the roller surface after 2,000 prints was also observed.

[0039]

[Table 1]

As is clear from the results shown in Table 1, according to the development of the present invention, a high-quality image free from uneven density and background fog can be obtained without inconvenience such as contamination of the photoreceptor. In addition, it was confirmed that the image quality did not deteriorate even after long-term use, and that the addition of the silicone powder could prevent the performance deterioration even under high temperature and high humidity. It was also found that the charge amount of the toner was improved by the addition of the charge control agent.

[0041]

As described above, according to the developing roller of the present invention, it has low hardness and good adhesion, does not cause inconvenience such as contaminating a photoreceptor, etc., and has uneven density and ground. A high-quality image without fogging or the like can be obtained, and the image quality does not deteriorate even after long-term use.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a developing roller of the present invention.

FIG. 2 is a schematic sectional view showing an example of the developing device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Development roller 2 Shaft 3 Elastic body 4 Toner application roller 5 Photosensitive drum (latent image holding body) 6 Toner (non-magnetic one-component developer) 7 Layering blade 8 Transfer part 9 Cleaning part 10 Cleaning blade

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/08 F16C 13/00

Claims (8)

(57) [Claims] An elastic layer having conductivity is formed on the outer periphery of a good conductive shaft. A non-magnetic one-component developer is carried on the surface of the elastic layer to form a thin layer of the developer. In this state, the developer contacts the latent image holding member holding the electrostatic latent image on the surface, and causes the developer to adhere to the electrostatic latent image on the surface of the latent image holding member from the thin layer, thereby visualizing the electrostatic latent image. In the developing roller, the elastic layer is made of a urethane elastomer containing carbon black having a pH of 5 or more, and the urethane elastomer is obtained using a polyolefin polyol as a polyol. 2. The urethane elastomer forming the elastic layer has a resistivity of 10 ⁴ to 10 ¹⁰ Ωcm and a hardness of JIS-
The developing roller according to claim 1, wherein the A scale has a surface roughness of 55 ° or less, and the surface roughness has a JIS 10-point average roughness of 10 µmRz or less. 3. The developing roller according to claim 1, wherein the carbon black is furnace black. 4. A urethane elastomer comprising uretonimine-modified diphenylmethane-4,
Modified diphenylmethane containing 4'-diisocyanate
4. The developing roller according to claim 1, wherein the developing roller is obtained by using 4,4'-diisocyanate. 5. The developing roller according to claim 1, wherein the urethane elastomer is obtained by using crude diphenylmethane-4,4′-diisocyanate as the isocyanate. 6. The developing roller according to claim 1, wherein the urethane elastomer forming the elastic layer contains a silicone powder. 7. The developing roller according to claim 1, wherein the urethane elastomer forming the elastic layer contains a charge control agent. 8. A roller-like or drum-like latent image holding member for holding an electrostatic latent image on the surface thereof, and a non-magnetic one-component developer carried on the outer peripheral surface of the latent image holding member. A developing roller that visualizes the electrostatic latent image by causing the non-magnetic one-component developer to adhere to the electrostatic latent image on the surface of the latent image holding member by rotating in conjunction with the rotational movement of the latent image holding member; A developing device comprising: the developing roller according to claim 1 as the developing roller.