JP2001324866A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device on which a toner supply roller consisting of an elastic foam is mounted and which can obtain an image having no failure such as irregular pitch or irregular density. SOLUTION: In this 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, the compression spring constant of the toner supply roller consisting of the elastic foam is 0.25 to 5.0 N/mm and is smaller than that of the developing roller. The deformation of the developing roller when the toner supply roller is made to abut on the developing roller, is cased by the deformation of the toner supply roller substantially, and the toner supply roller is disposed so that biting amount by the developing roller may be 0.5 to 2 mm and its pressing force to the developing roller may be <=6.0 N.

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, etc. The present invention relates to a developing device that forms a toner image by supplying toner to an electrostatic latent image on the surface of a photoconductor.

[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. SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional situation, and a developing apparatus capable of obtaining an image free from defects such as pitch unevenness and density unevenness in a developing apparatus equipped with a toner supply roller made of a foamed elastic body. The purpose is to provide.

[0004]

The inventors of the present invention have investigated the toner supply roller which has caused the above-mentioned image defects. As a result, if the pressing force of the toner supply roller against the developing roller is too large, the developing roller If the rotational torque of the toner fluctuates and pitch unevenness occurs in the image, and if the pressing force of the toner supply roller against the developing roller is too small, the toner cannot be sufficiently supplied to the developing roller. Found to occur. As a result of further research, despite the hardness of the toner supply roller being appropriate, the amount of biting of the developing roller into the toner supply roller was not appropriate, so that an appropriate pressing force was not obtained and a stable frictional force was obtained. As a result, it has been found that unevenness in pitch is generated in the image, and image defects such as unevenness in the density of the image due to fluctuations in the toner supply property have occurred. Then, when the hardness of the toner supply roller and the amount of biting of the developing roller into the toner supply roller are made appropriate and the pressing force of the toner supply roller against the developing roller is made appropriate, an image without trouble is formed. I found that I can do it. 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. In the apparatus, the compression spring constant of the toner supply roller made of foamed elastic material is 0.2.
5 to 5.0 N / mm and smaller than the compression spring constant of the developing roller, and the deformation of the roller when the toner supply roller contacts the developing roller is substantially due to the deformation of the toner supply roller; A developing device, wherein the toner supply roller is disposed such that the amount of bite by the developing roller is 0.5 to 2 mm and the pressing force against the developing roller is 6.0 N or less; and the developer device. The present invention provides an image forming apparatus equipped with a.

[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 toner supply roller according to the present invention has a compression spring constant of 0.25 to 5.0 N / mm, and preferably has a compression spring constant of 0.4 to 4.0 N / mm. And particularly preferably 0.7 to 3.0 N / mm. If the compression spring constant is less than 0.25 N / mm, there is a disadvantage that the toner is not sufficiently frictionally charged, and if it exceeds 5.0 N / mm, there is a disadvantage that the toner is not sufficiently conveyed. Further, the compression spring constant of the toner supply roller according to the present invention needs to be smaller than the compression spring constant of the developing roller. However, if the compression spring constant of the toner supply roller is equal to or greater than the compression spring constant of the development roller, the toner supply When the roller comes into contact with the developing roller, the developing roller is deformed, so that a certain amount of toner is not reacted. The difference between the compression spring constant of the developing roller and the compression spring constant of the toner supply roller is preferably 30 N / mm or more. In the developing device of the present invention, the deformation of the developing roller when the toner supplying roller is brought into contact with the developing roller is substantially due to the deformation of the toner supplying roller. 0.5 to 2m
m, preferably 0.5 to 1.5 mm, and the pressing force against the developing roller is 6.0 N or less, preferably 5.0 N or less. If the amount of bite by the developing roller of the toner supply roller is less than 0.5 mm, there is a problem that the toner remaining on the developing roller cannot be sufficiently scraped off. If the amount exceeds 2 mm, the toner is not sufficiently conveyed to the developing roller. Inconvenience occurs. When the pressing force of the toner supply roller against the developing roller exceeds 6.0 N,
There is a disadvantage that the rotational torque of the developing roller fluctuates.

The foamed elastic body forming such a toner supply roller may be any foamed elastic body having the above characteristics, such as ester-based polyurethane foam, ether-based polyurethane foam, nitrile rubber, ethylene propylene rubber, and 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 according to the present invention comprises:
It may be conductive, and can be produced by forming a conductive foamed elastic layer on the outside of a good conductive shaft in the same manner as conventionally used as a conductive toner supply roller. 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. Also in the case of the conductive foamed elastic body, the number of cells is preferably 50 to 1200 per 25 mm.

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.

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 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, as described above, the compression spring constant of the developing roller needs to be equal to or greater than the compression spring constant of the toner supply roller. The developing roller used in the developing device of the present invention is conductive, and has a conductive elastic layer formed on the outside of a good conductive shaft, similarly to those conventionally used as a conventional conductive developing roller. . 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 particularly preferable.

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. The resin coating layer is usually formed by dipping a coating liquid (using an alcoholic solvent such as methanol and a ketone-based solvent such as methyl ethyl ketone as a solvent) in which a crosslinkable resin, a crosslinking agent and various additives are dissolved or dispersed. , Roll coater method, doctor blade method, spray method, etc.
It can be formed by drying at a temperature of about 0 ° 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 In the printer shown in FIG. 1, a developing roller X and toner supply rollers A, B, C, D or E having different roller diameters are combined, or An image was formed in a low-temperature, low-humidity (15 ° C., 10% RH) environment, and the image quality of the image was evaluated.

The developing roller X 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)
To 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, The polyol composition was prepared by mixing using a mixer. 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 is polished, and the surface is JIS 10
The point average roughness was adjusted to 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 liquid, pulled up, and heated at 130 ° C. for 3 hours to produce a developing roller X having a cured resin coating layer. The outer diameter of the obtained developing roller X was 16.0 mm, and the compression spring constant was 45 N / mm. The method of measuring the compression spring constant will be described later.

Further, the toner supply rollers A,
B, C, D, E, F and G were prepared by preparing a polyol prepolymer as a main raw material by the following method. 20% by weight of a polymer polyol having a solid content of about 28% and a polyether polyol having a molecular weight of 5000 to which 15% by weight of ethylene oxide and 85% by weight of propylene oxide are added to glycerin; 40% by weight of a hydrophilic polyether polyol having a molecular weight of 3400 to which 25% by weight of an oxide is added, and 15% by weight of ethylene oxide and 85% of propylene oxide in glycerin.
9% by weight in combination with 40 parts by weight of a polyether polyol having a molecular weight of 4800 to which
0 g and 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 8: 2.
After stirring sufficiently, the mixture was kept at 60 ° C., and the stirring was repeated every 12 hours to obtain a polyether polyol prepolymer after 48 hours. To 110 g of this prepolymer were added 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.
g were mixed.

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 outer diameter of the cylinder is 11.4 mm, 12.0 mm, 13.0 m
m, 15.0 mm, 16.0 mm, 13.0 mm and 15.0
mm and the toner supply rollers A,
B, C, D, E, F and G were prepared. The number of cells of the toner supply rollers A, B, C, D and E was 120 to 160 per 25 mm, and the compression spring constant was 1.5 N / mm. Further, the number of cells of each of the toner supply rollers F and G is 100 to 25 mm.
150 compression spring constants were 4.5 N / mm. Table 1 shows the injection amount of the mixture into the mold and the outer diameter of the rollers for producing the toner supply rollers A, B, C, D and E.

[0021]

[Table 1]

As shown in FIG. 2, the toner supply rollers A to G are foamed elastic rollers in which a foamed elastic roller 12 is arranged around a metal rotating shaft 11, and in this embodiment, This 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 printer, the axial distance between the developing roller 6 and the toner supply roller 5 is fixed at 13.5 mm, and the outer diameter of the developing roller X is 16.0 mm, so that the outer diameter is 11.4 mm (roller A), 12 0.0mm (roller B),
13.0mm (roller C), 15.0mm (roller D), 1
When a 6.0 mm (roller E), 13.0 mm (roller F) or 15.0 mm (roller G) toner supply roller is provided, the amount of penetration of the developing roller X into the toner supply roller is 0.2 mm ( Roller A), 0.5 mm (roller B), 1.
0mm (roller C), 2.0mm (roller D), 2.5mm
(Roller E), 1.0 mm (Roller F) and 2.0 mm
(Roller G). In this embodiment, the compression spring constants of the developing roller and the toner supply roller were 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 rotating shaft 11 of the toner supply roller 5 or the developing roller 6 is horizontally identified by a V-block 13, and the force gauge 14 installed above the roller 12 is moved downward at a constant speed (0.1 mm / se
c) and compressed to a depth of about 1.0 mm by a disc-shaped compression jig (disc indenter) 15 having a diameter of 13 mm provided at the tip of the force gauge 14. From the measured stress-strain curve, And a method of calculating a spring constant. This measurement was performed at intervals of 30 mm in the longitudinal direction of the roller, and at intervals of 30 degrees in the circumferential direction of the roller, and was calculated as an average value. The toner supply roller used in this embodiment measures the compression spring constant by the method shown in FIG.
An image forming test was performed by arranging the toner supply roller 5 of the printer shown in FIG. 1. The developing roller 6
, The developing roller X was disposed. 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 supply and scraping of the toner by the toner supply roller are performed properly, and the fluctuation of the rotation torque of the developing roller is not caused. As a result, 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 according to the present invention.

FIG. 3 is a schematic diagram illustrating a method of measuring a compression spring constant of the developing roller and the toner supply roller described in the embodiment.

[Description of Signs] 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: Rotary shaft 12: Foam elastic roller 13: V block 14: Force gauge 15: Compression jig (disc indenter)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 13/00 G03G 15/08 507E

Claims (5)

[Claims] 1. A developing device comprising: a toner cartridge containing a toner as a developer; 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. The compression spring constant of the toner supply roller made of an elastic material is 0.25 to 5.0 N / mm.
And when the toner supply roller is in contact with the development roller, the deformation of the roller is substantially due to the deformation of the toner supply roller. The amount of biting by the roller is 0.5 to 2 mm, and the pressing force against the developing roller is 6.0.
A developing device, wherein the developing device is arranged to be N or less. 2. The developing device according to claim 1, wherein a difference between a compression spring constant of the toner supply roller and a compression spring constant of the developing roller is 30 N / mm or more. 3. The developing device according to claim 1, wherein the toner supply roller has a foamed elastic layer having a cell number of 50 to 1200 per 25 mm outside the shaft. 4. The developing device according to claim 3, wherein the shaft is a good conductive shaft, and the foamed elastic layer is a conductive foamed elastic layer. 5. An image forming apparatus equipped with the developing device according to claim 1.