JP3340978B2 - 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 drum holding a latent image and the latent image on the photosensitive drum is supplied to the photosensitive drum. As a developing method for visualizing a latent image by attaching a developer, pressure development is known (US Pat. No. 31,520).
According to this method, since no magnetic material is required, the apparatus can be simplified and downsized, and the tray can be easily colored.

In this pressure development method, a developing roller carrying a tray (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 tray is moved 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 development method, for example, as shown in FIG. 2, a toner-applying roller 4 for supplying toner and a photosensitive drum 5 holding an electrostatic latent image are provided. The developing roller 1 is disposed in contact with the photosensitive drum 5, and the developing roller 1, the photosensitive drum 5, and the toner applying roller 4 rotate in the direction of the arrow in FIG. The toner 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. In this state, the developing roller 1 rotates while being in contact with the photosensitive drum 5.
The toner formed in the thin layer adheres to the latent image on the photosensitive drum 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.
Is a cleaning unit, and its cleaning blade 1
0 removes toner remaining on the surface of the photosensitive drum 5 after transfer.

In this case, the developing roller 1 includes a photosensitive drum 5
It is necessary to rotate while securely maintaining a state of being in close contact with the shaft. Therefore, as shown in FIG.
It has a structure in which a conductive agent is blended into an elastic rubber such as NBR or EPDM, urethane foam, or the like to form an elastic layer 3 made of an elastic body provided with conductivity.

[0006]

However, the conventional developing roller comprising a single-layer elastic body has the following disadvantages due to the characteristics of the elastic layer. 1 . Silicone rubber, NBR, When the elastic layer with an elastic rubber such as EPDM, low hardness in order to obtain good adhesion
With degrees of, in some cases contamination of the photosensitive drum is generated. 2 . When forming a common elastic layer of urethane-based elastomer, but less developing roller of contamination to photosensitive drum obtained, not particularly charge rising property of the toner on the roller at high temperature and high humidity environment is sufficiently, the toner charge Problems such as fogging due to failure, poor cleaning due to selection phenomena, and reduced print density are likely to occur, and the print quality is significantly reduced by long-term continuous printing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a low hardness and good adhesion, does not cause inconvenience such as contaminating a photoreceptor and the like, and has a low temperature and a low humidity to a high temperature and a high humidity. wide without such density unevenness and fogging in an environment high-quality image can be obtained. Moreover aims to provide a developing device using no developing roller and the developing roller be caused degradation of the image even in long-term use And

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, in a developing roller in which a conductive elastic layer is formed on the outer periphery of a good conductive shaft, The elastic layer is made of a polyurethane resin having a water absorption of 3% or less and has a resistivity of 10 ⁴ to 10 ⁴ .
By adjusting the hardness to 10 ¹⁰ Ωcm and the hardness to 55 ° or less on a JIS-A scale, a non-magnetic one-component developer is carried on the surface of the developing roller to form a thin layer of the developer. Developing the electrostatic latent image on the latent image holding member by bringing the developing roller into close contact with the latent image holding member and contaminating the latent image holding member. It has been found that a high-quality image free from uneven density and fogging can be obtained under a wide range of environmental conditions without any occurrence, and that the image quality does not deteriorate even after long-term use.

Further, the conventional single-layer roller has a water absorption of 3
% Of a polyurethane resin having a skin layer (skin layer) of not more than 10% by weight, it has been found that a developing roller having excellent performance equivalent to the above can be obtained.

Therefore, the present invention provides (1) an elastic layer having conductivity 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, and in this state, the electrostatic latent image is brought into contact with a latent image holding member holding the surface, and In the developing roller for adhering the developer to the electrostatic latent image on the surface of the latent image holding member and visualizing the electrostatic latent image, the elastic layer is made of a polyurethane resin containing a conductive additive, and has a resistivity of But
10 ⁴ to 10 ¹⁰ Ωcm, the water absorption of which is at least 3.
A developing roller, wherein a skin layer made of a polyurethane resin is formed on the outer periphery of the base roller which is 2%, and a polyurethane resin forming the skin layer has a water absorption of 3% or less; and

(2) A roller-like or drum-like latent image holding member that holds an electrostatic latent image on the surface, and a non-magnetic one-component developer is carried on the outer peripheral surface of the latent image holding member. By rotating in conjunction with the rotational movement of the latent image holding member,
In the developing apparatus comprising; and a developing roller to visualize the non-magnetic one-component developer attached so the toner to the electrostatic latent image of the latent image bearing member surface with the electrostatic latent image, as the developing roller (1 And a developing device using the developing roller described in (1 ) .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION 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.

Here, as the shaft 2, any shaft having good conductivity can be used. However, usually, a core bar made of a metallic solid body or a metallic cylinder having a hollow inside is used. A metallic shaft such as a body is used. next,
Elastic layer formed on the outer periphery of the shaft 2 is for water absorption and containing not conductive additive of 3% or less of the polyurethane resin, the polyurethane resin in this case is any of those produced by various methods But, for example, blending carbon black in the polyurethane prepolymer,
It can be obtained by a method of crosslinking and curing, a method of mixing a conductive material with a polyol, and reacting the polyol with a polyisocyanate by a one-shot method.

The polyol used in the present invention is selected from polyether polyols, polyester polyols, preferably polyolefin polyols, such as polybutadiene polyol and polyisoprene polyol, so that the reaction product with polyisocyanate has a water absorption of 3%. Any one or a combination of two or more polyols can be selected.

The water absorption referred to herein is JIS-K7209.
(1984) This is the water absorption defined by the "Testing Methods for Water Absorption and Boiling Water Absorption of Plastics", and the measuring method followed the method A described in JIS-K7209. That is, the conditioned test piece was weighed and designated as M1, this test piece was placed in a container placed in water maintained at a temperature of 23 ± 2 ° C., immersed for 24 ± 1 hour, and then the test piece was taken out. The water absorption was calculated according to the following equation by weighing and setting this as M2. Water absorption = (M2−M1) / M1 × 100 (%)

When the elastic layer is formed of a polyurethane elastomer using a general polyol, especially when the temperature and the humidity are high (33 ° C., 85% RH), the rising properties of the toner on the roller are not sufficient, and the toner is charged. Image fogging due to defects occurs. The water absorption of these elastic layers was determined to be 3% or more. On the other hand, as a result of intensive studies, the electrification characteristics of the toner on the roller under high temperature and high humidity were improved by controlling the water absorption of the elastic layer to 3% or less by selecting the polyol, and the poor charging of the toner. The fogging due to was able to be reduced. More preferably, the polyol is selected so that the water absorption of the elastic layer is suppressed to 2% or less.
By doing so, it was also found that fogging due to poor charging of the toner can be eliminated even under high temperature and high humidity.

The polyisocyanate is not particularly limited, but a polyisocyanate having a bent molecular structure is preferably used, and particularly a polyisocyanate represented by the following general formula (Chemical Formula 1) is preferably used. . Since such a polyisocyanate can prevent crystallization of the polyurethane chain, it is easy to reduce the hardness, easily form entanglement of molecular chains, and have a pseudo-crosslinked structure, so that it is easy to remove the mold.

[0018]

Embedded image (Wherein, R represents a carbon-carbon bond or an alkylene group;
Represents hydrogen or an alkyl group. )

[0019] Specific examples of such polyisocyanates, 2, 4-toluene diisocyanate, 2, 6-
Toluene diisocyanate, mixtures thereof, m- tetramethyl xylylene diisocyanate over preparative, m- xylylene diisocyanate, m- phenylene diisocyanate, and the like.

The conductivity-imparting substance is not particularly limited, but may be an electron-conductivity-imparting substance such as carbon black, graphite, metal filler, metal oxide, metal perchlorate, surfactant, and the like. Or a combination thereof. The addition amount of these conductivity-imparting substances can be adjusted so that the resistance value of the elastic layer becomes a desired value.

The resistance value of the elastic layer 3 thus obtained is 10 ⁴ to 10 ¹⁰ Ωcm, especially 10 ⁶ to 10 ⁹ Ωc.
When it is less than 10 ⁴ , the 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, when it exceeds 10 ¹⁰ Ωcm, fogging is likely to occur.

The hardness of the developing roller formed by the elastic layer thus obtained is 55 ° or less, preferably 50 ° or less on a JIS-A scale. In this case there is a risk that the contact area between the photosensitive drum and the like exceeds 55 ° can not be performed would have good development small, deformation or eccentricity to the developing roller for some reason such as viewing problems and compression set dimensional accuracy during molding When this occurs, uneven image density occurs.

Furthermore, as a result of repeated studies, even when a polyurethane resin having a water absorption of 3% or more is used as the elastic layer,
And forming a skin layer made of polyurethane resin on the outer circumference of the roller that the water absorption of poly urethane resin 3% or less,
It has been found that by setting the content to preferably 2% or less, the same effect as when the water absorption of the elastic body itself is controlled can be obtained. The thickness of the skin layer is not particularly limited, but is preferably 10 μm or more. It is technically difficult to uniformly form a skin layer having a thickness of 10 μm or less on the outer periphery of the roller. If a hole is formed in the skin layer, the portion causes image defects such as fogging.

The developing roller of the present invention can be incorporated in an ordinary developing device using a non-magnetic one-component developer, and more specifically, as shown in FIG. The developing roller 1 of the present invention is disposed in contact with the photosensitive drum 5 between the developing roller 1 and the photosensitive drum 5 holding the electrostatic latent image, and toner 6 is supplied to the developing roller 1 by the toner coating roller 4. The toner is supplied from the thin layer to the photosensitive drum 5 and the toner is attached to the electrostatic latent image on the photosensitive drum 5 to visualize the latent image. I can do it. Since the details of FIG. 2 have been described in the related art, the description thereof is omitted.

[0025]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Production Examples , Examples, and Comparative Examples, but the present invention is not limited to the following Examples.

Production Example Polybutadiene-based polyol (R15HT, manufactured by Idemitsu Petrochemical Co., Ltd.) having a molecular weight of 1200 and having an allyl-type primary hydroxyl group at the terminal of polybutadiene, and TDI-8
0 (Sumijur T, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
-80) Prepolymer 15 with 7% NCO%
Polyethylene polyol with a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to parts and glycerin (Exenol 828, manufactured by Asahi Glass Co., Ltd.)
An isocyanate composition obtained by stirring and mixing 85 parts of a prepolymer having an NCO% of 7% prepared with TDI-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80) was mixed with 7.15 parts of 1,4 butanediol, 1 part of silicon surfactant (L520, manufactured by Nippon Yunika), dibutyltin dilaurate (Nitto Kasei, Neostan U-1)
00) 0.2 part and 3.5 parts of acetylene black (Denka black, Denka black) were added, and the mixture was stirred and mixed.
And heated for 2 hours to form an elastic layer on the outer periphery of the metal shaft to obtain a roller having the structure shown in FIG. Polish the surface of the obtained roller to JIS
A 10-point average roughness was adjusted to 7 μmRz by the -B-0601 method to obtain a developing roller.

Example 1 A polybutadiene-based polyol having a molecular weight of 1200 and having an allyl-type primary hydroxyl group at the terminal of polybutadiene (R15HT, manufactured by Idemitsu Petrochemical Co., Ltd.) was formed on the same roller surface as that prepared in Production Example. And 100 parts of a prepolymer having an NCO% of 7% prepared with TDI-80 (Sumijur T-80, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
7.15 parts of 1,4 butanediol, 1 part of a silicon surfactant (L520, manufactured by Nippon Yunika), dibutyltin dilaurate (manufactured by Nitto Kasei Corporation, Neostan U-10)
0) 0.1 parts with stirring and coating after coating to a coating thickness of 80
A μm developing roller was obtained.

Example 2 Polybutadiene-based polyol having a molecular weight of 1200 and having an allyl-type primary hydroxyl group at the terminal of polybutadiene (R15HT, manufactured by Idemitsu Petrochemical Co., Ltd.) on the same roller surface as that prepared in the production example. And TDI-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80), 50 parts of a prepolymer having an NCO% of 7%, and propylene and ethylene oxide added to glycerin to obtain a polymer having a molecular weight of 5000. Ether polyol (Exenol 828, manufactured by Asahi Glass Co., Ltd.) and TDI
-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80) was mixed with an isocyanate composition obtained by stirring and mixing 50 parts of a prepolymer having an NCO% of 7%.
7.15 parts of butanediol, 1 part of a silicone surfactant (L520, manufactured by Nippon Unica), dibutyltin dilaurate (Neostan U-100, manufactured by Nitto Kasei Co., Ltd.)
One part was stirred and mixed, followed by coating to obtain a developing roller having a coating thickness of 20 μm.

Example 3 A polybutadiene-based polyol having a molecular weight of 1200 and having an allyl-type primary hydroxyl group at the terminal of polybutadiene (R15HT, manufactured by Idemitsu Petrochemical Co., Ltd.) was formed on the same roller surface as that prepared in the Production Example. And TDI-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80), 50 parts of a prepolymer having an NCO% of 7%, and propylene and ethylene oxide added to glycerin to obtain a polymer having a molecular weight of 5000. Ether polyol (Exenol 828, manufactured by Asahi Glass Co., Ltd.) and TDI
-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80) was mixed with an isocyanate composition obtained by stirring and mixing 50 parts of a prepolymer having an NCO% of 7%.
7.15 parts of butanediol, 1 part of a silicone surfactant (L520, manufactured by Nippon Unica), dibutyltin dilaurate (Neostan U-100, manufactured by Nitto Kasei Co., Ltd.)
One part was stirred and mixed, followed by coating to obtain a developing roller having a coating thickness of 85 μm.

Example 4 A polybutadiene-based polyol having a molecular weight of 1200 and having an allyl-type primary hydroxyl group at the terminal of polybutadiene (R15HT, manufactured by Idemitsu Petrochemical Co., Ltd.) was formed on the same roller surface as that prepared in Production Example. And TDI-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80), 50 parts of a prepolymer having an NCO% of 7%, and propylene and ethylene oxide added to glycerin to obtain a polymer having a molecular weight of 5000. Ether polyol (Exenol 828, manufactured by Asahi Glass Co., Ltd.) and TDI
-80 (Sumitomo Bayer Urethane Co., Ltd., Sumidur T-80), an isocyanate composition obtained by stirring and mixing 50 parts of a prepolymer having an NCO% of 7%, 3.5 parts of acetylene black, 1,4 butanediol 7.15
Part, silicon surfactant (L520, manufactured by Nippon Yunika)
One part and 0.1 part of dibutyltin dilaurate (Neostan U-100, manufactured by Nitto Kasei Co., Ltd.) were stirred and mixed, followed by coating to obtain a developing roller having a coating thickness of 200 μm.

[0031] Similarly the roller surface to that prepared in Comparative Example 1 Production Example, by adding propylene oxide and ethylene oxide to glycerol, molecular weight 5000 and the polyether polyol (manufactured by Asahi Glass Co., Ltd., EXCENOL 828) and TDI-
Prepolymer 1 having an NCO% of 7% made by Sumitomo Bayer Urethane Co., Ltd., manufactured by Sumitomo Bayer Urethane Co., Ltd.
To 00 parts, 7.15 parts of 1,4 butanediol, 1 part of a silicon surfactant (manufactured by Nippon Yunika, L520), and 0.1 part of dibutyltin dilaurate (manufactured by Nitto Kasei Corporation, Neostan U-100) are added. After stirring and mixing, coating was performed to obtain a developing roller having a coating thickness of 60 μm.

COMPARATIVE EXAMPLE 2 Polyether polyol (boranol 3022J, manufactured by Dow Chemical Japan Co., Ltd.) having a molecular weight of 3,000 by adding propylene oxide to glycerin, and TDI-
Prepolymer 1 having an NCO% of 7% made by Sumitomo Bayer Urethane Co., Ltd., manufactured by Sumitomo Bayer Urethane Co., Ltd.
To 00 parts, 7.15 parts of 1,4 butanediol, 1 part of a silicon surfactant (manufactured by Nippon Yunika, L520), and 0.1 part of dibutyltin dilaurate (manufactured by Nitto Kasei Corporation, Neostan U-100) are added. After stirring and mixing, coating was performed to obtain a developing roller having a coating thickness of 50 μm.

The above production examples, Examples 1 to 4 and Comparative Example 1
The following characteristic tests were performed on the developing rollers obtained in Nos. 1 to 2 . The results are shown in Tables 1 to 3.

[0034]

[Table 1]

[Table 2]

[Table 3]

(1) Volume resistance A sheet-like sample prepared under the same conditions as each roller was measured using a resistivity meter Hiresta (manufactured by Mitsubishi Yuka).
The measurement was performed by applying a voltage of 100V. (2) 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.). (3) Image test Each roller is attached to the developing unit shown in FIG. 2 as a developing roller, and under normal temperature and normal humidity (23 ° C., 55% RH) and high temperature and high humidity conditions (33 ° C., 85% RH). And reversal development,
An image was formed while rotating at a linear speed of 60 mm / sec, and the occurrence of fog and toner dust was evaluated at the initial stage. At the same time, the state of toner filming on the roller surface after 5000 prints was also observed.

As is evident from the results of Tables 1 to 3, the present invention provides a clear, non-fogging environment even in a high-temperature and high-humidity environment where the charge amount of the non-magnetic one-component developer is reduced and image quality is likely to deteriorate. It is possible to obtain a developing roller that can obtain a high-quality image and that does not cause deterioration in image quality even when used for a long time.

[0037]

As described above, according to the developing roller of the present invention, the amount of charge of the non-magnetic one-component developer is reduced, and even under high temperature and high humidity where image quality is liable to be deteriorated, there is no fog. It is possible to obtain a developing roller and a developing device that can obtain a high-quality image and do not cause deterioration in image quality even when used for a long time.

[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]

REFERENCE SIGNS LIST 1 developing roller 2 shaft 3 elastic layer 4 toner coating roller 5 photosensitive drum (latent image carrier) 6 toner (non-magnetic one-component developer) 7 layering blade 8 transfer unit 9 cleaning unit 10 cleaning blade

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 1-252979 (JP, A) JP-A 1-124881 (JP, A) JP-A 5-72882 (JP, A) JP-A 4- 356081 (JP, A) JP-A-3-249675 (JP, A) Material Database Editing Committee, Material Database-Organic Materials, Nikkan Kogyo Shimbun, March 31, 1989, p. 510 Chemical Society of Japan, Chemical Handbook, Advanced Edition, 2nd Edition, Maruzen Co., Ltd., June 10, 1975, p. 1057 (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/08-13/095 G03G 15/08-15/095

Claims (2)

(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. Developing the developer from the thin layer onto the electrostatic latent image on the surface of the latent image holding member and visualizing the electrostatic latent image in contact with the latent image holding member holding the electrostatic latent image on the surface in the state At the roller,
The elastic layer is made of a polyurethane resin containing a conductive additive, has a resistivity of 10 ⁴ to 10 ¹⁰ Ωcm, and has a water absorption of at least 3.2%. A developing roller, wherein a skin layer is formed, and a polyurethane resin forming the skin layer has a water absorption of 3% or less. 2. A roller-like or drum-like latent image holder for holding an electrostatic latent image on a surface thereof, and a non-magnetic one-component developer carried on an outer peripheral surface of the latent image holder. By developing the non-magnetic one-component developer by attaching toner to the electrostatic latent image on the surface of the latent image holding member by rotating in synchronization with the rotational movement of the latent image holding member, developing the electrostatic latent image A developing device comprising a roller, wherein the developing roller according to claim 1 is used as the developing roller.