JP2001324865A - Toner supply roller and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner supply roller consisting of an elastic foam and a developing device, on which the toner supply roller is mounted, capable of obtaining an image having no failure such as irregular pitch or irregular density. SOLUTION: This toner supply roller is mounted on the developing device having a toner cartridge storing toner as developer, the toner supply roller and a developing roller and forming a toner image by supplying the toner to an electrostatic latent image on the surface of a photoreceptor, and consists of the elastic foam, whose compression spring constant is 0.25 to 5.0 N/mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner supply roller and a development device in a development device of a printer for electrophotography and electrostatic recording, and more particularly, to a toner cartridge containing toner as a developer and a toner supply roller. And a developing roller having a developing roller and supplying toner to an electrostatic latent image on a photoreceptor surface to form a toner image, and a developing device.

[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. In such a method, the toner is frictionally charged by rubbing the toner supply roller against the developing roller. Therefore, the toner supply roller has a stable friction property (pressing force) with the developing roller and a high toner supply to the frictional portion. Is required. Conventionally, a foamed elastic material obtained by foaming rubber, urethane, or the like is generally used for this type of toner supply roller.

[0003]

However, the present inventors have examined the performance of a conventional toner supply roller made of a foamed elastic body, and found that a problem occurs in a developed image due to pitch unevenness or density unevenness. It turned out that there was. The present invention has been made in view of such a conventional situation, and is provided with a toner supply roller made of a foamed elastic material and a toner supply roller capable of obtaining an image free from defects such as pitch unevenness and density unevenness. An object is to provide a developing device.

[0004]

The inventors of the present invention have examined the toner supply roller which has caused the above-mentioned image defects. As a result, when the hardness of the toner supply roller is too high, the rotational torque of the developing roller fluctuates. It has been discovered that pitch unevenness occurs in the image and that if the hardness of the toner supply roller is too low, the toner cannot be sufficiently supplied to the developing roller, resulting in image density unevenness. As a result of further studies, if the hardness of the toner supply roller varies, the pressing force against the developing roller will be partially different, so that the toner supplying roller is strongly pressed or weakly pressed against the developing roller. Or
As a result of not being able to obtain stable frictional properties (pressing force), the rotational torque of the developing roller fluctuates, causing pitch unevenness in the image, and the toner supply property fluctuates, causing image defects such as uneven image density. I found that. And, when the hardness of the toner supply roller represented by a compression spring constant that can accurately know the partial hardness of the foamed elastic body is made uniform and appropriate, it is possible to form an image without any trouble. . The present invention has been made based on such findings.

That is, the present invention comprises a toner cartridge containing a toner as a developer, a toner supply roller and a development roller, and supplies toner to an electrostatic latent image on the surface of a photoreceptor to form a toner image. A toner supply roller comprising a foamed elastic body mounted on an apparatus, wherein a compression spring constant is 0.25 to 5.0 N / mm, and a developing device equipped with the toner supply roller And an image forming apparatus equipped with the developing device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The toner supply roller of the present invention has a compression spring constant of 0.25 to 5.0 N / mm, and this compression spring constant is 0.4 to 4.0 N / mm. Preferably, it is particularly preferably from 0.7 to 3.0 N / mm. When the compression spring constant is less than 0.25 N / mm, there is a disadvantage that the toner is not sufficiently triboelectrically charged.
If the ratio exceeds, there is a disadvantage that the toner is not sufficiently conveyed. In the toner supply roller of the present invention, the fluctuation range of the compression spring constant in the roller circumferential direction is preferably within a range of ± 20% of the specified value of the compression spring constant. If this fluctuation range exceeds the range of ± 20%, a good image may not be obtained. Further, in the toner supply roller of the present invention, the fluctuation width of the compression spring constant in the roller longitudinal direction is:
In a region excluding a range within 20 mm from both ends of the roller, the compression spring constant is preferably within a range of ± 20% of a specified value. If this fluctuation range exceeds the range of ± 20%, a good image may not be obtained. Here, the prescribed value of the compression spring constant refers to the value of the compression spring constant set in the range of 0.25 to 5.0 N / mm.

The foamed elastic body forming such a toner supply roller may be any foamed elastic body having the above-mentioned properties. For example, ester-based polyurethane foam, ether-based polyurethane foam, nitrile rubber, ethylene propylene rubber, ethylene propylene diene Examples include foams of rubber materials such as rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, silicone rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber. These may be used alone or in combination of two or more to form a foam. Of these, ester polyurethane foam, ether polyurethane foam, nitrile rubber foam, ethylene propylene rubber foam, ethylene propylene diene rubber foam, and silicone rubber foam are particularly preferred. The number of cells of the foamed elastic body is 5 per 25 mm.
0 to 1200 pieces are preferred.

Further, the toner supply roller of the present invention may be conductive, and conductive foam is formed on the outside of a good conductive shaft in the same manner as conventionally used as a conductive toner supply roller. It can be manufactured by forming an elastic layer. 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. Even in the case of a conductive foamed elastic body, the number of cells is 25.
50 to 1200 pieces per mm are preferred.

As the conductive agent to be added when imparting conductivity to the foamed elastic body, an ionic conductive agent or an electronic conductive agent is used. Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (eg, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (eg, stearyltrimethylammonium), benzyltrimethylammonium, and a modified fatty acid dimethylethylammonium. Ammonium salts such as perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate and sulfonate, lithium and sodium Perchlorates of alkali metals and alkaline earth metals such as, potassium, calcium, magnesium,
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.

[0011] These conductive agents may be used alone or in combination of two or more. The amount of addition is not particularly limited, but in the case of the ionic conductive agent, usually 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the foamed 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 may be used to prevent the deposits on the roller surface from fusing 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.

The toner supply roller of the present invention can be used, for example, by mounting it on a developing section of a laser printer shown in FIG. 1 which is an example of a developing device. 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 thermal fixing device 9, and the paper is transported and discharged in the direction of the arrow. 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. The conductive elastic layer is made of an elastic material obtained by adding a conductive agent as described above to an appropriate rubber-like elastic body to impart conductivity. 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 preferred.

In the developing roller according to the present invention, a resin coating having a thickness of 1 to 100 μm made of a cross-linkable resin such as an alkyd resin, a phenol resin, a melamine resin and a mixture thereof for preventing contamination of the photoreceptor. Preferably, a layer is provided on the roller surface. These crosslinkable resins may contain various additives such as a charge control agent, a lubricant, a conductive agent, and other resins, if desired. Usually, the resin coating layer is dipped with a coating liquid obtained by dissolving or dispersing a cross-linkable resin, a cross-linking agent and various additives (using an alcohol-based solvent such as methanol and a ketone-based solvent such as methyl ethyl ketone as a solvent). Method, roll coater method, doctor blade method, spray method, etc., and then apply at room temperature or 50-1
It can be formed by drying at a temperature of about 70 ° C. and crosslinking and curing.

[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 5 The developing roller A and the toner supply rollers B, C, D, E, F, G, H or I are combined in the printer shown in FIG. Low humidity (15 ℃ ・ 10% RH)
An image was formed in the environment described above, and the image quality of the image was evaluated. The developing roller A used here was produced by the following method. 1,4-butanediol 1.0 was added to 100 parts (parts by weight, the same applies hereinafter) of polyether polyol (OH value: 33 mgKOH / g) having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin.
Parts, 0.5 parts of nickel acetylacetonate, 0.01 parts of dibutyltin dilaurate and 0.00 parts of sodium perchlorate
Five parts were added and mixed using a mixer to prepare a polyol composition. After stirring and defoaming the polyol composition under reduced pressure, 17.5 parts of urethane-modified MDI (diphenylmethane diisocyanate) was added and stirred for 2 minutes. Next, this was cast into a mold in which the metal shaft was heated to 110 ° C. in advance, 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 a 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
Gussa, Printex L6: average particle size 18
nm) and dispersed using a paint shaker to prepare a coating solution. The roller was immersed in the coating solution, pulled up, and heated at 130 ° C. for 3 hours to produce a developing roller A having a cured resin coating layer.

Further, the toner supply rollers B,
C, D, E, F, G, H, and I were prepared by preparing a polyol prepolymer as a main raw material by the method described below. Molecular weight of glycerin of 15% by weight of ethylene oxide and 85% by weight of propylene oxide added
A polymer polyol having a solid content of about 28% (hereinafter, referred to as a polyether polyol having a base weight of
A polyol X), a hydrophilic polyether polyol having a molecular weight of 3400 obtained by adding 75% by weight of ethylene oxide and 25% by weight of propylene oxide to glycerin (hereinafter referred to as polyol Y), 15% by weight of ethylene oxide and 15% by weight of propylene oxide to glycerin. 85% by weight
To a total weight of 90 g by combining a polyether polyol having a molecular weight of 4800 (hereinafter, referred to as polyol Z) to which 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are added in a weight ratio. After mixing 20 g of the 8: 2 mixture and stirring thoroughly, the mixture was kept at 60 ° C and the stirring was repeated every 12 hours.
After 48 hours, a prepolymer of polyether polyol was obtained. To 110 g of this prepolymer were mixed 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. This mixture is applied to a cylindrical mold whose inner surface is coated with Teflon (registered trademark) and whose end is closed by a removable lid (a value corresponding to the volume of the mold; And adjust the injection amount in the range of 0.9 to 1.5 times
Close the mold lid and place in a hot air oven adjusted to 70 ° C for 8 ~.
The mixture was allowed to stand for 10 hours to obtain foamed and cured polyurethane foams of various hardnesses. Toner supply rollers B, C, D,
Table 1 shows the amounts of the above-mentioned polyol components for preparing E, F, G, H, and I and the amounts of the mixture injected into the mold.

[0019]

[Table 1]

The cured polyurethane foam is released from the mold,
A glassing treatment was performed by passing through a roll. Next, a hole having an inner diameter of 5 mm was made at the center of the circle at the end face of the cylinder, and an outer diameter of 6.0 mm with an adhesive applied and a length of 240 mm
A zinc-coated shaft was press-fitted into a sulfur free-cutting steel. After heating and bonding for 15 minutes in an open at 60 ° C., the toner is polished with a grindstone so that the outer diameter of the cylinder becomes 13.0 mm, and eight kinds of toner supply rollers B, C, and C with different hardness (compression spring constant) are obtained. D, E, F, G, H, and I were made.
The produced toner supply rollers B, C, D, E, F, G,
The number of cells for both H and I was 170 per 25 mm
~ 200.

As shown in FIG. 2, the toner supply roller of the present invention is a foamed elastic roller in which a foamed elastic roller 12 is disposed around a metal rotating shaft 11. In the embodiment of the present invention, the toner supply roller was arranged as the toner supply roller 5 of the printer shown in FIG. 1, and an image forming test was performed. In this example, the compression spring constant of the foamed elastic roller was measured in the circumferential direction of the roller and in the longitudinal direction of the roller by the measuring method shown in FIG. As shown in FIG. 3, the rotation shaft 11 of the toner supply roller 5 is
In the block 13, the force gauge 14 is horizontally identified, and the force gauge 14 installed above the foamed elastic roller 12 is moved downward at a constant speed (0.1 mm / sec).
4 is compressed to a depth of about 1.5 mm by a disc-shaped compression jig (disc indenter) 15 having a diameter of 13 mm provided at the tip end, and a spring constant is calculated from a measured stress-strain curve. went. This measurement is 30 m in the longitudinal direction of the roller.
m at intervals of 30 degrees in the circumferential direction of the roller,
Calculated as the range of change from the median (specified value). According to the measurement shown in FIG. 3, it is possible to measure the partial surface hardness of the roller, which cannot be measured by the conventionally used F-type hardness meter.

The toner supply roller used in this embodiment measures the compression spring constant by the method shown in FIG. 3, and then is arranged as the toner supply roller 5 of the printer shown in FIG. Tested. The developing roller 6 was provided with a developing roller A. From the viewpoint of toner supply from the toner supply roller to the developing roller,
The nip width between the developing roller and the toner supply roller is generally
Although 0.5 to 5.0 mm is considered to be preferable, in the present embodiment, it was 4.5 mm. The image forming test in this example was performed in a low-temperature and low-humidity (15 ° C., 10% RH) environment as a condition in which an image defect easily occurs. Table 2 shows the results.

[0023]

[Table 2]

[0024]

According to the present invention, the toner supply roller is suitably pressed against the developing roller, the fluctuation of the rotation torque of the developing roller is not caused, and the toner is preferably transported to the photoconductor developing section. Therefore, a good image free from defects such as uneven pitch and uneven density can be formed.

[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 perspective view of a toner supply roller of the present invention.

FIG. 3 is a schematic diagram showing a method of measuring a compression spring constant of the toner supply roller shown in the embodiment.

[Explanation 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: Rotation Shaft 12: Foam elastic roller 13: V-block 14: Force gauge 15: Compression jig (disk indenter)

Claims (7)

[Claims] An image forming apparatus includes a toner cartridge containing toner as a developer, a toner supply roller, and a developing roller, and is mounted on a developing device that supplies toner to an electrostatic latent image on a photoreceptor surface to form a toner image. And a compression spring constant of 0.25 to 5.0.
N / mm. 2. The toner supply roller according to claim 1, wherein a fluctuation range of the compression spring constant in the roller circumferential direction is within a range of ± 20% of a specified value of the compression spring constant. 3. The variation range of the compression spring constant in the longitudinal direction of the roller is ± 20% of a specified value of the compression spring constant in a region excluding a range within 20 mm from both ends of the roller. The toner supply roller as described in the above. 4. The toner supply according to claim 1, wherein the toner supply roller is formed by forming a foamed elastic layer having 50 to 1200 cells per 25 mm outside the shaft. roller. 5. The toner supply roller according to claim 4, wherein the shaft is a good conductive shaft, and the foamed elastic layer is a conductive foamed elastic layer. 6. A developing device equipped with the toner supply roller according to claim 1. 7. An image forming apparatus equipped with the developing device according to claim 6.