JP3194692B2 - 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 which has excellent stain resistance and can reliably obtain a good image even when used in a high-speed machine for a long time, 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, a pressure developing method is known (US Pat. No. 3,152,352).
No. 012, No. 3731146, etc.), according to this method, the magnetic material is unnecessary, so that the apparatus can be easily simplified and downsized, 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 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 provided, and the developing roller 1, the photosensitive drum 5, and the toner applying roller 4 rotate in the directions of arrows in the figure, respectively, so that the toner 6 is applied to the surface of the developing roller 1 by the toner applying roller 4. Supplied,
The toner is arranged in a uniform thin layer by the layering blade 7, and in this state, the developing roller 1 rotates while being in contact with the photosensitive drum 5, so that the toner formed in the thin layer is transferred from the developing roller 1 to the photosensitive drum 5. The latent image adheres to the latent image so that the latent image can be 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 the surface of the photosensitive drum 5 after transfer by a cleaning blade 10. The remaining toner is removed.

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 3a made of an elastic body provided with conductivity. The hardness of these elastic bodies is an important characteristic for obtaining a uniform nip between the photosensitive drum and the developing roller. Is preferable because the nip width with the above becomes large. Also, the reduction in hardness works advantageously to reduce the driving torque.

[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, NBR or EPDM, if the hardness is reduced to obtain good adhesion, contamination of the photosensitive drum 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 toner becomes clogged and the roller becomes hard, or the toner is charged poorly. May decrease. In addition, the above tendency is not only sponge body,
The same applies to a roller having a surface to which toner easily adheres. 3. In general, when the developing roller is composed of a single layer of elastomer, the surface friction coefficient is very large, so that a large load is applied between the developing blade and the photoconductor, and the image defect is caused by uneven toner conveyance or jitter in driving. Easy to bring. 4. Since the developing roller rotates in contact with the developing blade and the photosensitive drum, the higher the hardness of the roller, the more easily the roller is worn and easily damaged. For this reason, the image deteriorates during long-term use.

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 and the like, and has uneven density and background fog. It is an object of the present invention to provide a developing roller and a developing device using the developing roller, which can obtain a high-quality image without a problem and which does not cause deterioration of the image even when used for a long time when used in a high-speed machine. .

[0008]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have found that a shaft and a roller provided with at least two or more conductive elastic layers around the shaft according to claim 1 are: The base material of the elastic layer is urethane,
In addition, the outermost layer of the elastic layer is mainly made of hydrophobic polycarbonate.
And liquid diphenylmethane diisocyanate
A urethane elastomer, and have reached the found present invention to be effective in achieving Yotsute, the above object that has a roller, characterized in that at least one layer foam other than the outermost layer .

[0009]

In other words, the roller of the present invention has the outermost layer made of a urethane elastomer composed of a hydrophobic polyol and liquid diphenylmethane diisocyanate, thereby improving the contamination and durability of the photoreceptor drum and the like. By having at least one urethane foam as a layer, the hardness of the entire roller can be easily reduced to 40 degrees or less in JIS-A hardness .

Hereinafter, the present invention will be described in more detail. There is no particular limitation on the shaft used in the present invention,
Metal or plastic may be used as long as it can hold and rotate the roller body. The roller body is composed of two or more layers of polyurethane composition, and the outermost layer is mainly composed of hydrophobic polyol and liquid diphenylmethane.
It is necessary that at least one of the polyurethane elastomer comprising diisocyanate and the elastic layer other than the outermost layer is a polyurethane foam layer. When the polyurethane composition of the roller body is one layer, it becomes either a polyurethane elastomer or a polyurethane foam,
As described above, it becomes impossible to satisfy all of the non-contamination, low hardness, and abrasion resistance of the photosensitive drum and the recording paper.

In the present invention, the polyurethane elastomer of the outermost layer has a function of abrasion resistance, and the polyurethane foam of the layer other than the outermost layer has a function of low hardness. The low hardness in the present invention is defined as JIS-A hardness of 40 degrees or less. The most common structure of the roller provided by the present invention is a two-layer structure, in which the outer layer is a polyurethane elastomer and the inner layer is a polyurethane foam. The thickness of the layer is not particularly limited because it differs depending on the use of the roller, but the thickness of the outer layer is required to be 0.1 mm or more in consideration of durability. The outer layer is 0.
If it is thinner than 1 mm, the durability when contact with other members and abrasion progresses is insufficient.

The structure of the roller provided by the present invention may have two or more layers. In this case, the outermost layer is mainly hydrophobic
Polyol and liquid diphenylmethane diisocyanate
And any combination except that at least one of the elastic layers other than the outermost layer is a polyurethane foam. Examples of combinations include elastomer / foam / foam, elastomer / foam / elastomer,
Innumerable examples include elastomer / elastomer / foam, elastomer / foam / foam / foam, and elastomer / foam / elastomer / foam / foam.

[0013] The interface between the layers in the roller provided by the present invention, ie, elastomer / foam, elastomer /
One of the features of the present invention is that an adhesive is not required in the elastomer and the foam / foam. The bonding between the layers can be achieved by the chemical bonding, compatibility, and immersion effect of the urethane compositions, so that the step of applying the adhesive can be omitted. When another layer (elastomer or foam) is formed on the foam layer, the outer skin of the foam layer, that is, the skin layer may be removed by polishing,
Another layer may be formed as it is without polishing, because in any case, the interlayer can be bonded without an adhesive. In addition, regarding the roller according to the present invention, a surface resin coat or a conductive coat used in a normal developing roller may be applied. In that case, the resin used is not particularly limited, but generally, urethane-based resin, polyamide-based resin, fluorine-based resin, silicone-based resin, acrylic-based resin, melamine-based resin, urethane-modified acrylic There are a resin, a soluble nylon resin, a water-based resin, a polycarbonate resin and the like, and these can be used after imparting conductivity.

In the present invention, the roller composed of two or more layers of urethane is basically based on the use of two or more polyurethane compositions. However, in a special case, a single polyurethane composition may form a multilayer. . That is, it is called the integral skin molding method,
This is because if the outermost leather-like skin layer is regarded as a polyurethane elastomer, it can be a multi-layer roller continuously formed up to the inner polyurethane foam.

In the present invention, at least the outermost layer is mainly hydrophobic.
Polyol and Liquid Diphenylmethane Diisocyanate
And a urethane elastomer comprising: As the hydrophobic polyol, a polyolefin polyol or a silicone polyol, a fluorine polyol, a castor oil-based polyol, a dimer acid polyol, or a mixture thereof is used. The number of functional groups of the polyol is preferably 2 to 4. The molecular weight is preferably from 500 to 5,000, and more preferably from 1,000 to 3,000. If it is smaller than this range, the obtained polyurethane elastomer is too hard, and if it is larger than this range, the viscosity of the polyol is too high, which is not preferable.

Examples of the polyolefin polyol include polyisoprene polyol, polybutadiene polyol, and styrene and acrylonitrile copolymers thereof, and hydrogenated products thereof. Furthermore, polytetramethylene ether glycol may be mixed with these hydrophobic polyols for the purpose of lowering the viscosity without increasing the physical properties and improving the castability.

Polytetramethylene ether glycol
The usual polytetramethylene ether glycol
In addition to the alkyl group such as a methyl group in the methylene group
Grafted with a substituent or propylene on its main chain
Alkylene oxides such as oxides are copolymerized
Can also be used.

Liquid diphenylmethane diisocyanate
In particular, liquid diphenylmethane 4,4 ′ diisocyanate is preferably used. Examples of the liquid diphenylmethane 4,4 'diisocyanate include carbodiimide-modified diphenylmethane 4,4' diisocyanate or uretonimine-modified diphenylmethane 4,4 'diisocyanate or crude diphenylmethane 4,4' diisocyanate (also called crude MDI or polymeric MDI). Is preferably used as a mixture thereof.
Suitable isocyanates having a number of functional groups of from more than 2 to 5 and preferably from 2.5 to 4. If it is less than this range, the resulting polyurethane elastomer may contaminate the contacted material, and it becomes undesirably brittle above this range.

The mixing ratio of the polyol and the isocyanate is suitably adjusted so that the ratio of the isocyanate group to the hydroxyl group in the polyol is 0.7 to 2.0, preferably 0.9 to 1.3. If it is less than this range, the resulting polyurethane elastomer may contaminate the contacted material, and it becomes undesirably brittle above this range.

As a conductive material for imparting conductivity, Ketjen Black E is first exemplified as a powder.
C, conductive carbon such as acetylene black, SAF,
ISAF, HAF, FEF, GPF, SRF, FT, M
Carbon for rubber such as T, carbon for color (ink) subjected to oxidation treatment, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium, etc. And conductive polymers such as polyaniline, polypyrrole, and polyacetylene. Among them, carbon black is inexpensive and easily controls conductivity in a small amount. Usually, urethane 1
0.5 to 50 parts by weight, especially 1 to 30 parts by weight, per 100 parts by weight
It is suitably used in the range of parts by weight.

Examples of ionic conductive materials include sodium perchlorate, lithium perchlorate, calcium perchlorate,
Inorganic ionic conductive materials such as lithium chloride, and organic ionic conductive materials such as modified aliphatic dimethylammonium ethosulfate, stearyl ammonium acetate, lauryl ammonium acetate, octadecyltrimethylammonium perchlorate, and tetrabutylammonium borate. Is a charge transfer complex. In the present invention, the elastic layer is not particularly limited,
By the above carbon black blending, the resistance value becomes 10
It is preferably from ³ to 10 ¹⁰ Ωcm, particularly preferably from 10 ⁴ to 10 ⁸ Ωcm. If the resistance value is less than 10 ³ 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, fogging tends to occur.

In the outermost elastomer layer, for example, various charge control agents such as nigrosine, triaminophenylmethane, and cationic dye, and silicone resin for the purpose of controlling the amount of toner charge on the surface when used as a developing member. And fine powders such as silicone rubber and nylon. In this case, the addition amount of these additives is preferably 1 to 5 parts by weight, and the fine powder is preferably 1 to 10 parts by weight, based on 100 parts by weight of the polyurethane.

In order to produce an integral skin foam from the above polyol and isocyanate, a usual integral skin foam molding method is applied. That is, a polyol and an isocyanate are vigorously stirred and mixed together with a silicone-based surfactant having an appropriate foam-regulating power, bubbles are taken into the reaction mixture, and the inside is hardened while the bubbles are involved, while bubbles near the surface are erased. It is obtained by pouring a reaction mixture conditioned so as to foam and have a suitable skin layer into a temperature-controlled mold.

As described above, in the roller obtained by the present invention, the layer which is not the outermost layer is made of a foam, and the foam density is determined by the inside of the roller obtained by the integral skin foam molding method. The foamed part is also 0.02-
0.9 g / cm ³ , preferably 0.2 to 0.7 g / cm
³ The roller obtained by the above-described method has characteristics such as low hardness, good abrasion resistance, and low contamination, and can solve the conventional problems.

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. [Example 1] Prepolymer 1 obtained by reacting tolylene diisocyanate with a polyether polyol having 3 functional groups and a molecular weight of 5,000 so that the NCO% becomes 6.7.
To 00 parts, 6.55 parts of 1,4-butanediol, 2 parts of a silicone surfactant, 0.0 parts of dibutyltin dilaurate
1 part and 2.0 parts of acetylene black were added, and the mixture was stirred for 2 minutes using a mixer. A shaft having an outer diameter of 8 mm was set in advance, and the reaction mixture was poured into a mold preheated to 60 ° C. Cure at 12 ° C. for 12 hours. Polish after removal from mold
An outer layer having an outer diameter of 15 mm was a urethane foam roller. According to the method described below, a roller having a hydrophobic urethane elastomer as the outermost layer and having a two-layer structure with an inner diameter of 16 mm was obtained from the urethane foam roller obtained as described above.

First, the number of functional groups is 2.36 and the molecular weight is 2800.
After defoaming 100 parts of the polyisoprene polyol under reduced pressure for 30 minutes under vacuum, 12.7 parts of crude diphenylmethane-4.4 'diisocyanate having an NCO% of 31.7, 0.01 part of dibutyltin dilaurate and 3.5 parts of acetylene black are used. After stirring for 3 minutes while also defoaming under reduced pressure, the urethane foam roller obtained above was set in advance, poured into a mold having an inner diameter of 17 mm preheated to 90 ° C., and cured at 90 ° C. for 16 hours. Then, after the mold was released, it was polished to an outer diameter of 16 mm and a surface roughness Rz of 7 μm. The JIS-A hardness of the completed roller was 32 degrees. In order to test the contamination of the roller to the photosensitive drum, the roller was pressed against the photosensitive drum of NEC Printer PC-PR1000E / 4 with a load of 500 g at both ends.
It was left for 5 days under the conditions of 55 ° C. and 85% humidity. No trace was left on the surface of the photosensitive drum after the removal, and there was no effect even if the image was mounted on the printer and displayed.

FIG. 2 shows the characteristics of the developing roller.
Using a non-magnetic one-component toner having an average particle diameter of 7 μm and a linear velocity of 60 mm / sec and 120 mm
/ Sec (the peripheral speed ratio between the developing roller and the photosensitive drum is 2:
In 1), an image was formed by a reversal phenomenon, and the image quality (sharpness of characters, uniformity of density, fog) was evaluated. Also, images are output up to 4000 sheets at a linear speed of 60 mm / sec.
The image quality of the initial stage was compared.

Example 2 Functional group number 2.36, molecular weight 2
800 parts of polyisoprene polyol, NCO
% Of crude diphenylmethane-4.4 'diisocyanate with 31.7 parts, 2 parts of silicone surfactant,
After adding 0.01 part of dibutyltin dilaurate and 3.5 parts of acetylene black and stirring with a double stirring type mixer for 2 minutes, a shaft having an outer diameter of 8 mm was set in advance, and an inner diameter of 16 mm was preheated to 40 ° C. It was poured into a mold, cured at 90 ° C. for 16 hours, demolded, and provided with a skin layer having an outermost layer thickness of 200 μm and an inner density of 0.1 μm.
An integral skin type urethane roller as a foam of 5 g / cm ³ was obtained. JIS-A of the obtained roller
The hardness was 29 degrees, and there was no problem in contamination of the photosensitive drum. The same evaluation as in Example 1 was performed for the developing roller.

Comparative Example 3 Functional group number 2.36, molecular weight 2
100 parts of 800 polyisoprene polyol in vacuum
After degassing under reduced pressure for 0 minutes, 12.7 parts of crude diphenylmethane-4,4 ′ diisocyanate having an NCO% of 31.7, 0.01 part of dibutyltin dilaurate and 3.5 parts of acetylene black were added, and degassing was performed under reduced pressure. After stirring for 3 minutes, the mixture was poured into a mold having an inner diameter of 17 mm preheated to 90 ° C., cured at 90 ° C. for 16 hours, removed from the mold, and polished.
A 6 mm urethane elastomer roller was used. The JIS-A hardness of the obtained roller was 47 degrees, and there was no problem in contamination of the photosensitive drum. Regarding the developing roller,
The same evaluation as in Example 1 was performed.

Comparative Example 1 In Example 1, an outermost layer was formed on a urethane foam using a urethane elastomer according to the following method. Functional group number 3, molecular weight 50
After defoaming 92 parts of a polyether polyol having a molecular weight of 400 and 8 parts of a polyether polyol having a molecular weight of 400 with a vacuum for 30 minutes, a crude diphenylmethane having an NCO% of 31.7% was obtained.
16.19 parts of 4,4 ′ diisocyanate, 0.01 part of dibutyltin dilaurate and 3.5 parts of acetylene black
After stirring for 3 minutes while also degassing under reduced pressure, a shaft with an outer diameter of 8 mm was set in advance, poured into a mold with an inner diameter of 17 mm preheated to 90 ° C, and cured at 90 ° C for 16 hours. After the molding, the resultant was polished to an outer diameter of 16 mm to obtain a urethane roller having a two-layer structure. At this time, polishing was performed under the same conditions, but the surface roughness was 5 μm. The JIS-A hardness of the obtained developing roller was 33 degrees. However, when a contamination test with the photosensitive drum was performed, a mark was left on the surface of the photosensitive member. After that there was no problem.

Comparative Example 4 Functional group number 2.36, molecular weight 2
NCO% to 100 parts of 800 polyisoprene polyol
12.7 parts of crude diphenylmethane-4,4 'diisocyanate with 31.7%, 2% silicone surfactant
Parts, 0.01 parts of dibutyltin dilaurate and 3.5 parts of acetylene black were added, and the mixture was stirred for 2 minutes with a double stirrer, and a shaft having an outer diameter of 8 mm was set in advance, and the inner diameter was preheated to 60 ° C. The mixture was poured into a 17 mm mold, cured at 60 ° C. for 16 hours, and removed from the mold. After polishing, a roller having an outer diameter of 16 mm was used. JIS-A hardness is 2
Since it was 8 degrees and there was no problem with the contamination of the photosensitive drum, the same evaluation as in Example 1 was performed.

Comparative Example 2 A two-layer structure was formed in the same manner as in Comparative Example 1 , except that the polyol was changed to 100 parts of a polyether polyol having a molecular weight of 5,000 and the isocyanate was changed to 5.68 parts of tolylene diisocyanate. A urethane roller was obtained. About this roller,
As a result of a test of the contamination with the photosensitive drum, a clear mark was formed on the photosensitive member, and a defect of a level that caused a problem also appeared in the image.

The examples and comparative examples described in detail above are summarized in Table 1.

[Table 1]

[0034]

That is, in the roller of the present invention, the outermost layer
Mainly hydrophobic polyol and liquid diphenylmethane diisocyanate
By improving the contamination and durability of the photoreceptor drum by being a urethane elastomer comprising an anate, and by having at least one or more urethane foams as other elastic layers other than the outermost layer, the entire roller can be easily formed. The hardness can be reduced to 40 degrees or less in JIS-A hardness.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view illustrating an example of a developing device used by the developing roller of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Development roller 2 Shaft 3a Elastic layer 3b Outermost layer 4 Roller for toner application 5 Photosensitive drum 6 Toner (non-magnetic one-component developer) 7 Layering blade 8 Transfer part 9 Cleaning part 10 Cleaning blade

Continuation of the front page (56) References JP-A-5-46020 (JP, A) JP-A-3-223878 (JP, A) JP-A-63-100482 (JP, A) JP-A-63-231469 (JP, A) JP-A-3-249675 (JP, A) JP-A-5-351110 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/03-15/095 G03G 15/02 101 G03G 15/16 103

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. In a developing roller that contacts the latent image holding member holding the electrostatic latent image on the surface in a state and visualizes the electrostatic latent image, the elastic layer is urethane composed of two or more layers, and the outermost layer is main
With hydrophobic polyol and liquid diphenylmethane diisocyanate
A developing roller, which is a urethane elastomer composed of a foam and at least one layer other than the outermost layer is a foam. 2. A latent image holding member for holding an electrostatic latent image on a surface thereof, and a non-magnetic one-component developer is carried on an outer peripheral surface of the latent image holding member. in the developing device the magnetic one-component developer is adhered to the electrostatic latent image on the latent image bearing member surface the electrostatic latent image formed by and a developing roller to visualize claim 1, wherein as said developing roller
A developing roller using the developing roller.