JP2001281982A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where an image that is always without any fault in developing by a conductive roll method. SOLUTION: In the developing device provided with a toner cartridge storing toner as developer, a toner feeding roll and a developing roll and forming a toner image by feeding toner to an electrostatic latent image on a surface of a photoreceptor, the toner feeding roll and the developing roll are provided to be conductive and when applied voltage is 100 V to 500 V, an electrical resistance value of the toner feeding roll is always made smaller than an electrical resistance value of the developing roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for a printer for electrophotography, electrostatic recording, and the like.
A toner cartridge containing toner as a developer,
The present invention relates to a developing device that has a toner supply roller and a developing roller and supplies toner to an electrostatic latent image on the surface of a photoreceptor to form a toner image.

[0002]

2. Description of the Related Art In recent years, a conductive roller system has been widely adopted as a developing roller and a toner supply roller used in a developing device arranged in a developing process in an electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer, and a facsimile. I have. This method has features that the product cost can be reduced because an expensive magnet roller is not used, a one-component non-magnetic developer (toner) can be used, and a space can be reduced. . Such a conductive developing roller and a conductive toner supply roller are required to have low electric resistance. Conventionally, a conductive polymer material such as rubber or urethane mixed with carbon black or an ionic conductive agent is generally used for this type of conductive roller.

[0003]

However, a developing roller which is always used in contact with a photosensitive drum and a toner supply roller which is always used in contact with toner which is a developer, have characteristics which should be considered for their counterparts. The materials used are selected and used because of the differences in their electrical resistance. It has been found that this can happen. The present invention has been made in view of such a conventional situation, and an object of the present invention is to provide a developing device that always forms an image without any problem in the development using a conductive roller method.

[0004]

The present inventors have examined the developing roller and the toner supply roller used in the developing device in which the above-mentioned image defect has occurred. It has been found that an image defect occurs when the electric resistance value of the toner supply roller is large. As a result of further research, it is possible to select a material suitable for each function for these two types of conductive rollers, but the electrical resistance value of the two types increases with environmental changes such as temperature and humidity. Even if they change each other, it is found that a defect-free image can be formed when a material is selected such that the electric resistance value of the toner supply roller is always smaller than the electric resistance value of the developing roller. The present invention has been made based on such findings.

That is, the present invention relates to a developing apparatus having a toner cartridge containing toner as a developer, a toner supply roller and a developing roller, and supplying toner to an electrostatic latent image on the surface of a photoreceptor to form a toner image. Wherein the toner supply roller and the developing roller are conductive, and the electric resistance value of the toner supply roller at an applied voltage of 100 V to 500 V is always smaller than the electric resistance value of the developing roller. is there.

[0006]

FIG. 1 is a schematic view of a developing section of a laser printer which is an example of a developing apparatus according to the present invention. Reference numeral 1 in the figure denotes a photoconductor, whose surface is uniformly charged by a primary charger 2, and then an image signal transmitted from a control unit (not shown) is converted into an optical signal using an LED array print head 3. After conversion, this is exposed on the surface of the photoreceptor 1 to form an electrostatic latent image. This electrostatic latent image is stored in a toner cartridge 4 and is developed by toner supplied to the photoconductor 1 via a toner supply roller 5 and a developing roller 6 to form a toner image. The toner image formed on the surface of the photoreceptor 1 is transferred to a paper surface supplied from a paper magazine 7 by a transfer charger 8 and fixed by a heat fixing device 9, and the paper is transported in the direction of the arrow.
Is discharged. The photoreceptor 1 after the transfer is returned to the initial state by the cleaning unit 10.

The developing roller used in the developing device of the present invention is conductive, and a conductive elastic layer is formed on the outside of a good conductive shaft in the same manner as that conventionally used as a conventional conductive developing roller. Things. For the conductive elastic layer, an elastic material obtained by adding a conductive agent to an appropriate rubber-like elastic body to impart conductivity is used. Here, the rubber-like elastic body is not particularly limited, and can be arbitrarily selected from those conventionally used in conductive developing rollers. Examples of the rubbery elastic body include nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, silicone rubber, urethane rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber. And the like. These may be used alone or in combination of two or more. Among them, nitrile rubber, urethane rubber, epichlorohydrin rubber, ethylene propylene rubber, ethylene propylene diene rubber, and silicone rubber are particularly preferable.

Further, the toner supply roller used in the developing device of the present invention is conductive, and a conductive roller is provided on the outside of a good conductive shaft in the same manner as conventionally used as a conductive toner supply roller. A foamed elastic layer is formed. For the conductive foamed elastic layer, a foamed elastic material obtained by adding a conductive agent to an appropriate foamed elastic body and imparting conductivity is used. Here, the foamed elastic body is not particularly limited, and may be arbitrarily selected from those conventionally used in conductive toner supply rollers.
The Asker F hardness of the foamed elastic body is preferably 30 to 100 °, more preferably 40 to 100 °, and most preferably 5 to 100 °.
0 to 100 °. The number of cells of the foamed elastic body is 25.
50 to 1200 pieces per mm are preferred.

Examples of the foamed elastic body include ester polyurethane foam, ether polyurethane foam, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, silicone rubber, and urethane. Rubber material foams such as rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber can be used. These rubber materials may be used alone or as a foam in combination of two or more. Of these, ester polyurethane foam, ether polyurethane foam, nitrile rubber foam, urethane rubber foam, ethylene propylene rubber foam, ethylene propylene diene rubber foam, and silicone rubber foam are particularly preferred.

As the conductive agent, an ionic conductive agent or an electronic conductive agent is used. Examples of the ion conductive agent include tetraethylammonium, tetrabutylammonium,
Perchlorates, chlorates, hydrochlorides, bromine such as dodecyltrimethylammonium (eg, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (eg, stearyltrimethylammonium), benzyltrimethylammonium, modified fatty acid dimethylethylammonium Acid salt,
Ammonium salts such as iodate, borofluoride, sulfate, ethyl sulfate, carboxylate and sulfonate; and perchlorine of alkali metals and alkaline earth metals such as lithium, sodium, potassium, calcium and magnesium Acid, chlorate, hydrochloride, bromate, iodate,
Borofluoride, trifluoromethyl sulfate, sulfonate and the like can be mentioned.

Examples of the electronic conductive agent include conductive carbon such as Ketjen black and acetylene black;
SAF, ISAF, HAF, FEF, GPF, SRF,
Rubber carbon such as FT and MT; carbon for oxidation-treated ink, pyrolytic carbon, natural graphite, artificial graphite; conductive metal oxides such as tin oxide, titanium oxide and zinc oxide; nickel, copper, silver, Examples thereof include metals such as germanium.

These conductive agents may be used alone or in combination of two or more. The amount of addition is not particularly limited. In the case of the ionic conductive agent, it is usually 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the rubber-based elastic body. Selected by range. On the other hand, in the case of the electronic conductive agent, it is selected in the range of 1 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the rubber-based elastic body. Note that, in addition to the conductive agent, other rubber additives such as a known filler and a crosslinking agent can be appropriately added to the conductive elastic layer as needed.

Further, in the present invention, when the conductive foamed elastic body of the toner supply roller is formed of polyurethane foam, the acetone foam of the polyurethane foam is used so that the deposit on the surface of the roller does not fuse the toner. Since the extraction rate is preferably 5% by weight or less, it is necessary to sufficiently examine the amount of the conductive agent to be added.
That is, if a large amount of carbon black (for example, channel black) having a large amount of volatilization is blended, the acetone extraction ratio is increased. Can be reduced.

In the developing device of the present invention, the toner supply roller and the developing roller are electrically conductive, and the electric resistance of the toner supply roller is always higher than the electric resistance of the developing roller at an applied voltage of 100 V to 500 V. It is a requirement to be small. The electric resistance value of the conductive roller is
Normally, it is 10 ⁴ to 10 ¹¹ Ω, and the object of the present invention is achieved if the electric resistance of the toner supply roller is always smaller than the electric resistance of the developing roller while having such electric resistance. Although it is possible, the difference is particularly preferably 0.5 or more as a difference between a common logarithmic value of an electric resistance value (Ω).

The developing device of the present invention includes a mode in which the developing roller and the photosensitive member are set in a non-contact state, such as a jumping developing method. However, there are cases where the developing roller is a contact conductive roller in contact with the photosensitive member. , A particularly high effect can be obtained.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Examples 1 to 3 and Comparative Examples 1 to 3 The printers shown in FIG.
The three types of toner supply rollers Y and Z and the two types of developing rollers A and B are arranged in various combinations, and the temperature and the humidity (15 ° C.
・ 10% RH and high temperature and high humidity (33 ℃ ・ 85% R)
An image was formed in two environments H), and the image quality of the image was evaluated.

The developing roller A used here was produced by the following method. Polyether polyol having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin (OH value: 33 mgKOH / g)
100 parts (parts by weight, hereinafter the same), 1.0 part of 1,4-butanediol, 0.5 part of nickel acetylacetonate
, 0.01 part of dibutyltin dilaurate and 0.005 part of sodium perchlorate were added and mixed using a mixer to prepare a polyol composition. After stirring this polyol composition under reduced pressure to remove bubbles, urethane-modified MDI
(Diphenylmethane diisocyanate) (17.5 parts) was added and stirred for 2 minutes. Next, this was poured into a mold in which a metal shaft was previously heated to 110 ° C. and cured at 110 ° C. for 2 hours to form a conductive elastic layer on the outer periphery of the metal shaft to obtain a roller. The surface of the obtained roller was polished, and the surface was adjusted to JIS 10-point average roughness of 4.0 μmRz.

Next, as a resin for forming the resin coating layer,
Oil-free alkyd resin (manufactured by Dainippon Ink, M6
402) and a melamine resin (manufactured by Dai Nippon Ink Co., Ltd., Super Beckamine L-145-60, solid content ratio 60% by weight) so that the oil-free alkyd resin and the melamine resin have a solid content weight ratio of 80/20. Mixed with methyl ethyl ketone as a solvent, and the solid concentration is 20% by weight.
It was adjusted to be. 20 parts by weight (20 phr) of carbon (De) per 100 parts by weight of the solid content of this mixture
manufactured by gussa, Priotex L6: average particle size 18
nm) and dispersed using a paint shaker to prepare a coating solution. The roller was immersed in the coating liquid, pulled up, and heated at 130 ° C. for 3 hours to produce a developing roller A having a cured resin coating layer. The developing roller B was manufactured by the same method except that the mixing amount of carbon in the manufacturing method of the developing roller A was changed to 10 parts by weight (10 phr).

The toner supply roller X used here
Was manufactured by the following method. 90 g of a polyether polyol having a weight average molecular weight of 5,000 obtained by addition polymerization of ethylene oxide and propylene oxide with glycerin as a starting material was used in a weight ratio of 2,4-tolylene diisocyanate to 2,6-tolylene diisocyanate of 8: 2.
After sufficiently stirring, the mixture was kept at 60 ° C., and the stirring was repeated every 12 hours to obtain a polyether polyol prepolymer after 48 hours. The isocyanate content of the obtained prepolymer is 6.7% by weight.
Met. 110 g of this prepolymer, 20 g of water, 0.1 g of tetramethylethylenediamine (amine catalyst), 2.5 g of a silicone foam stabilizer having a hydroxyl group introduced into a terminal, and 2.5 g of acetylene black were mixed. This mixture is coated on the inner surface of the cylinder with Teflon (registered trademark),
Pour into a cylindrical mold closed at the end with a removable cap and place in a hot air oven adjusted to 70 ° C.
The mixture was left for a period of time to obtain a foam-cured polyurethane foam.

The cured polyurethane foam was removed from the mold by removing the cap at the end of the mold, and passed through a roll to undergo a crushing treatment. Next, a hole having an inner diameter of 5 mm was formed at the center of the circle on the end face of the cylinder, and a shaft coated with an adhesive and having a galvanized sulfur free-cutting steel having an outer diameter of 6.0 mm and a length of 240 mm was press-fitted. After heating and bonding in an oven at 60 ° C. for 15 minutes, the outer diameter of the cylinder was 13.0.
The toner supply roller X was manufactured by polishing with a grinding stone so as to have a thickness of 0.2 mm. The number of cells of the prepared toner supply roller X is 25.
150 to 160 pieces per mm, and foam hardness was 70 to 80 ° in Asker F hardness.

The toner supply rollers Y and Z were manufactured in the same manner except that the amount of acetylene black mixed in the method of manufacturing the toner supply roller X was changed to 2.0 g and 1.0 g, respectively. The number of cells of the prepared toner supply roller Y is 150 to 170 per 25 mm, the foam hardness is 80 to 90 ° in Asker F hardness, and the number of cells of the toner supply roller Z is 140 to 16 per 25 mm.
0 foam hardness was 70-80 ° in Asker F hardness.

Examples 1 to 3 are combinations in which the electric resistance value of the toner supply roller is always smaller than the electric resistance value of the developing roller, and Comparative Examples 1 to 3 are the opposite combinations. Table 1 shows the results of the image quality evaluation together with the electrical resistance values of the combined developing roller and toner supply roller.

[0024]

[Table 1]

[0025]

According to the present invention, the relationship between the electric resistance value of the conductive developing roller and the electric resistance value of the conductive toner supply roller is always set at the practical application voltage of 100 V to 500 V. Since the resistance value is made smaller, the toner is appropriately charged by the toner supply roller, and the charged toner is appropriately attracted to the developing roller, so that a good image can always be formed. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a developing unit of a laser printer which is an example of a developing device according to the present invention.

FIG. 2 is a schematic view showing a method for measuring an electric resistance value of the conductive roller shown in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Primary charger 3 LED array print head 4 Toner cartridge 5 Toner supply roller 6 Developing roller 7 Paper magazine 8 Transfer charger 9 Thermal fixing device 10 Cleaning unit 11 Applied voltage 12 Aluminum plate

Claims (6)

[Claims] 1. A developing device, comprising: a toner cartridge containing a toner as a developer; a toner supply roller; and a developing roller, for supplying the toner to an electrostatic latent image on the surface of a photoreceptor to form a toner image. The supply roller and the developing roller are conductive, and the applied voltage is 100 V to 5
A developing device wherein the electric resistance value of the toner supply roller at 00V is always smaller than the electric resistance value of the developing roller. 2. The developing device according to claim 1, wherein said toner is a one-component non-magnetic toner. 3. The developing device according to claim 1, wherein said developing roller is a contact conductive roller. 4. A difference between an electric resistance value of the toner supply roller and an electric resistance value of the developing roller is 0.5 or more as a difference between common logarithmic values of respective electric resistance values (Ω). The developing device as described in the above. 5. The developing roller forms a conductive elastic layer on the outside of a good conductive shaft, and further has on its surface a resin layer different from the material constituting the conductive elastic layer or conductive fine particles on the resin. The developing device according to claim 1, wherein a resin layer containing semiconductive fine particles is formed. 6. The toner supply roller has a conductive foamed elastic layer having a cell number of 50 to 1200 cells per 25 mm and an Asker F hardness of 30 to 100 ° outside a good conductive shaft. The developing device according to claim 1, wherein