JP2003029525A - Toner supply roller and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner supply roller by which an image without any failure such as a pitch irregularity and density unevenness is obtained and which consists of a foamed elastic body, and to provide a developing device on which the toner supply roller is mounted. SOLUTION: This toner supply roller supplies toner to a developing roller to form a visible image by feeding toner carried on a surface to an image forming body by abutting on the developing roller. The roller consists of a shaft and a foamed elastic body layer formed on the outer circumference of the shaft, and annular projected lines having height of >0 and <=1 mm and width of 1-5 mm are formed at positions separated by 10-30 mm from both ends of the surface of the foamed elastic body layer in a roller longitudinal direction. The coefficient of frictional resistance of a roller surface is 0.4-3.0 and also the compression spring constant of the foamed elastic body layer is 0.25-5.0 N/mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device mounted on a printer for electrophotography, electrostatic recording or the like, in which toner is conveyed to an image forming body such as a photoconductor or paper to form a visible image on the surface thereof. The present invention relates to a toner supply roller for supplying toner to a developing roller, and a developing device equipped with the toner supply roller.

[0002]

2. Description of the Related Art In recent years, a conductive roller system has been widely adopted for a developing roller and a toner supplying roller used in a developing device arranged in a developing process of an electrophotographic apparatus such as an electronic copying machine, a laser beam printer, and a facsimile. There is. In such a system, the toner is triboelectrically charged by rubbing the toner supply roller against the developing roller, so that the toner supply roller has stable friction (pressing force) with the developing roller and high toner supply to the friction portion. Sex is required. Thus, conventionally, a foamed elastic material made of foamed rubber or urethane has been generally used for this kind of toner supply roller.

[0003]

However, the inventors of the present invention have examined the performance of the conventional toner supply roller made of a foamed elastic material, and found that the developed image has defects such as pitch unevenness and density unevenness. I found out that The present invention has been made in view of the above conventional circumstances, and in a developing device equipped with a toner supply roller made of a foamed elastic body, it is possible to obtain an image without defects such as uneven pitch and uneven density. It is an object of the present invention to provide a toner supply roller made of an elastic body and a developing device equipped with the toner supply roller.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have investigated the toner supply roller having the above-mentioned image defect and found that the surface of the foamed elastic layer of the toner supply roller has the same height in the roller longitudinal direction. Therefore, the amount of toner supplied to the developing roller is different between the both ends and the center of the toner supplying roller in the longitudinal direction. I found that unevenness occurs. This is because the toner on the toner supply roller spreads toward both ends of the toner supply roller when it rubs against the developing roller, so that the amount of toner near both ends of the toner supply roller increases. I understood. Then, by providing annular projections at positions 10 to 30 mm from both ends in the longitudinal direction of the toner supply roller, the amount of toner supplied to the developing roller is stabilized, and an image without defects such as density unevenness is formed. I found that I can. As a result of further research, if the height and width of the ring-shaped ridges are made appropriate and the hardness and surface friction resistance of the foamed elastic body are made appropriate, it is possible to form a defect-free image. I found that I can do it. The present invention has been made based on such findings.

That is, the present invention relates to a toner supply roller that supplies toner to a developing roller that forms a visible image by conveying the toner carried on the surface to an image forming body and supplies the toner to the developing roller. A shaft and an elastic foam layer formed on the outer circumference of the shaft, and the height is more than 0 and 1 mm or less and the width is 1 to 10 mm from the both ends in the roller longitudinal direction on the surface of the elastic foam layer. An annular ridge of 5 mm is formed, and the friction coefficient of the roller surface is
0.4 to 3.0 and the compression spring constant of the foam elastic layer is
The present invention provides a toner supply roller characterized by 0.25 to 5.0 N / mm, a developing device equipped with the toner supply roller, and an image forming apparatus equipped with the developer device.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The toner supply roller of the present invention is 10 to 30 m from both ends in the roller longitudinal direction on the surface of the foamed elastic layer.
An annular ridge is formed at the position m. The position of this annular ridge is 20 to 30 mm from both ends of the roller.
Is preferred. This ring-shaped ridge is 30
If the position is more than 10 mm, the disadvantage that toner is not conveyed locally occurs, and it is 10 mm from both ends of the roller.
If the position is below the range, there is a disadvantage that the toner amount cannot be adjusted by blocking. This annular ridge has a height of more than 0 and 1 mm or less and a width of 1 to 5 mm, but the height is preferably 0.5 to 1 mm and the width is 1
-3 mm is preferable. The height of this annular ridge is 1 mm
If it exceeds, the disadvantage that the toner is not sufficiently tribocharged occurs. If the width of the ring-shaped ridge exceeds 5 mm, the toner is locally strongly frictionally charged, and if it is less than 1 mm, the ring-shaped ridge falls down, so that the toner is blocked. The inconvenience of not being made occurs.

The coefficient of frictional resistance of the surface of the toner supply roller of the present invention is 0.4 to 3.0, preferably 0.4 to 2.5.
If the frictional resistance coefficient is less than 0.4, the toner cannot be transported because the slippage is too large, and if it exceeds 3.0, the toner is damaged much, and the toner is easily deteriorated. It causes the inconvenience. The toner supply roller of the present invention has a compression spring constant of 0.2.
5 to 5.0 N / mm, the compression spring constant is
It is preferably 0.3 to 3.0 N / mm, and particularly preferably 0.4 to 1.5 N / mm. The compression spring constant is 0.25
If it is less than N / mm, the toner is not sufficiently triboelectrically charged, and if it exceeds 5.0 N / mm, there is a disadvantage that the toner is greatly damaged.

The foamed elastic body forming such a toner supply roller may be one having the above-mentioned characteristics, for example, ester polyurethane foam, ether polyurethane foam, nitrile rubber, ethylene propylene rubber, ethylene propylene diene. Examples thereof 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 preferable.

Further, the toner supply roller of the present invention may be electrically conductive, and like the one usually used as a conductive toner supply roller in the past, electrically conductive foam is formed on the outside of the good conductive shaft. It can be manufactured by forming an elastic layer. For the conductive foam elastic layer, a foam elastic material in which a conductive agent is added to a suitable foam elastic body to impart conductivity is used.

An ion conductive agent or an electronic conductive agent is used as a conductive agent added when imparting conductivity to the foamed elastic body. Examples of the ion conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (eg, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (eg, stearyltrimethylammonium), benzyltrimethylammonium, and modified fatty acid dimethylethylammonium. Perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate, ammonium salt such as sulfonate, lithium, sodium , Alkali metal or alkaline earth metal perchlorate such as potassium, calcium, magnesium,
Examples thereof include chlorate, hydrochloride, bromate, iodate, borofluoride, trifluoromethyl sulfate and sulfonate.

Examples of the electronic conductive agent include conductive carbon such as Ketjen black and acetylene black;
SAF, ISAF, HAF, FEF, GPF, SRF,
Carbon for rubber such as FT and MT; carbon for ink subjected to oxidation treatment, pyrolytic carbon, natural graphite, artificial graphite; conductive metal oxide such as tin oxide, titanium oxide, 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 kinds. Further, the addition amount thereof is not particularly limited, but in the case of the ionic conductive agent, it is usually in the range of 0.01 to 5 parts by mass, preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the foamed elastic body. Is selected in. On the other hand, in the case of the electronic conductive agent, it is selected in the range of 1 to 50 parts by mass, preferably 5 to 40 parts by mass with respect to 100 parts by mass of the rubber elastic body. In addition to the conductive agent, other rubber additives such as known fillers and cross-linking agents may be appropriately added to the conductive elastic layer, if necessary.

Further, in the present invention, when the conductive foam elastic body of the toner supply roller is formed of polyurethane foam, acetone of polyurethane foam is used so that the deposit on the surface of the roller does not fuse the toner. Since it is preferable that the extraction rate is 5% by mass or less, it is necessary to thoroughly examine the blending amount of the conductive agent to be added.
In other words, if a large amount of carbon black with a large amount of volatilization (eg, channel black) is added, the acetone extraction rate will increase, while if a carbon black with a large oil absorption amount (eg, acetylene black or oil furnace black with a high structure) is added, the acetone extraction rate will increase. Can be reduced.

The toner supply roller of the present invention can be used, for example, by being mounted in the developing section of the laser printer shown in FIG. 1 which is an example of the developing device. Reference numeral 1 in the figure is a photoconductor, and the surface of the photoconductor 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 by using an LED array print head 3. After conversion, the surface of the photoconductor 1 is exposed to form an electrostatic latent image. This electrostatic latent image is housed in the toner cartridge 4, and is developed by the toner supplied to the photoconductor 1 via the toner supply roller 5 and the developing roller 6 to form a toner image. The toner image formed on the surface of the photoconductor 1 is transferred to the paper surface supplied from the paper magazine 7 by the transfer charger 8 and fixed by the thermal fixing device 9, and the paper is conveyed and discharged in the arrow direction. The photoconductor 1 after 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 electrically conductive, and a conductive elastic layer is formed on the outer side of the good conductive shaft in the same manner as that conventionally used as a conductive developing roller. It is a thing. For the conductive elastic layer, an elastic material obtained by adding conductivity to the appropriate rubber-like elastic body to give conductivity is used. here,
The rubber-like elastic body is not particularly limited and can be arbitrarily selected from those conventionally used in the conductive developing roller. Examples of the rubber-like 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, epichlorohydrin rubber. And so on. 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 suitable.

In the developing roller according to the present invention, a resin coating having a thickness of 1 to 100 μm, which is made of a crosslinkable resin such as an alkyd resin, a phenol resin, a melamine resin and a mixture thereof, is used to prevent contamination of the photoconductor. It is preferred that the 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. For the resin coating layer, usually, a coating liquid obtained by dissolving or dispersing a crosslinkable resin, a crosslinking agent and various additives (using an alcohol solvent such as methanol or a ketone solvent such as methyl ethyl ketone as a solvent) is dipped. Law,
After coating on the elastic layer by roll coater method, doctor blade method, spray method, etc., room temperature or 50
It can be formed by drying at a temperature of about 170 ° C. and crosslinking and curing.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. Examples 1 to 3 and Comparative Examples 1 to 12 In the printer shown in FIG. 1, a developing roller A and toner supplying rollers B, C, D, E, F, G, H, I, J, K,
L, M, N, O or P was combined and incorporated, an image was formed in an environment of constant temperature and constant humidity (25 ° C., 50% RH), and the image quality of the image was evaluated.

The developing roller A used here was manufactured by the following method. Polyether polyol having a molecular weight of 5000 by adding propylene oxide and ethylene oxide to glycerin (OH value: 33 mgKOH / g)
To 100 parts (parts by mass, the same applies hereinafter), 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 are added, A polyol composition was prepared by mixing using a mixer. This polyol composition was stirred under reduced pressure for defoaming, then 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 ground to a surface of JIS 10
The point average roughness was adjusted to 4.0 μmRz.

Next, as the resin for forming the resin coating layer,
Oil-free alkyd resin (manufactured by Dainippon Ink and Co., M6
402) and melamine resin (manufactured by Dainippon Ink and Chemicals, Super Beckamine L-145-60, solid content 60% by mass) so that the oil-free alkyd resin and melamine resin have a solid content weight ratio of 80/20. Is mixed with methyl ethyl ketone as a solvent, and the solid content concentration is 20% by mass.
Was adjusted so that 20 parts by mass (20 phr) of carbon (De) per 100 parts by mass of solid content of this mixture
Printex L6 manufactured by Gussa: average particle size 18
nm) was mixed and dispersed using a paint shaker to prepare a coating liquid. The above roller was immersed in this coating liquid, pulled up, and heated at 130 ° C. for 3 hours to prepare a developing roller A having a cured resin coating layer. The developing roller A thus obtained had an outer diameter of 16.0 mm.

Further, the toner supply roller B used here,
C, D, E, F, G, H, I, J, K, L, M, N, O
And P were prepared by preparing a polyol prepolymer as the main raw material by the method shown below. 15% by mass of ethylene oxide and 85% of propylene oxide in glycerin
With 20 parts by mass of a polymer polyol having a solid content of about 28%, in which a polyether polyol having a molecular weight of 5000 with addition of mass% is a base polyol, and with a molecular weight of 3400 in which 75% by mass of ethylene oxide and 25% by mass of propylene oxide are added to glycerin. 40 parts by weight of a certain hydrophilic polyether polyol and 1 part of glycerin with ethylene oxide
A total weight of 90 g was obtained by combining 5 parts by mass and 40 parts by mass of a polyether polyol having a molecular weight of 4800 with addition of 85% by mass of propylene oxide.
20 g of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 8: 2 was mixed and sufficiently stirred, then, the mixture was kept at 60 ° C., and the stirring was repeated every 12 hours. After a period of time, a prepolymer of polyether polyol was obtained. 110 g of this prepolymer
20 g of water, 0.1 g of tetramethylethylenediamine (amine catalyst), and 2.5 g of a silicone foam stabilizer having a hydroxyl group introduced at the end were mixed.

This mixture has an annular groove at predetermined positions near both ends of the inner surface of the cylinder, the inner surface of which is coated with Teflon (registered trademark), the end of which is closed by a removable lid, and the center of which is formed. 0.9 for a specified amount (a standard specified amount is 1 at a value corresponding to the volume of the mold, which is a value corresponding to the volume of the mold) in a cylindrical mold in which a shaft plated with zinc free-cutting steel is placed.
The toner supply roller is made of polyurethane foam of various hardnesses by adjusting the injection amount in the range of up to 1.5 times, injecting it, closing the lid, and leaving it in a hot air oven adjusted to 70 ° C. for 8 to 10 hours. Got In addition, as a cylindrical mold, prepare one in which the depth, width, and distance from both ends of the annular groove formed on the inner surface of the cylinder are changed, and the height of the annular convex line provided on the roller surface is prepared. , Toner supply rollers B, C, D, E, F, G having different widths and distances from both ends of the roller.
H, I, J, K, L, M, N, O and P were obtained. The toner supply roller P is a roller similar to the toner supply roller B, in which a silicone-based paint is applied and processed to reduce the surface friction resistance. The outer diameter of the portions of the toner supply rollers B to P other than the ring-shaped protrusions was set to 16.0 mm. As shown in FIG. 2, the toner supply rollers B to P are foam elastic rollers in which a roller 12 made of a foam elastic material is arranged around a rotating shaft 11 made of metal. In FIG. 2, reference numeral 12a is an annular ridge. 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 conducted.

Further, in this embodiment, the compression spring constant of the toner supply roller was measured in the circumferential direction of the roller and the longitudinal direction of the roller by the measuring method shown in FIG. As shown in FIG. 3, the rotary shaft 11 of the toner supply roller 5 is set to V
The force gauge 14 installed on the upper part of the roller 12 is horizontally identified by the block 13 and is moved downward at a constant speed (0.1 mm).
/ Sec), and a disc-shaped compression jig (disc indenter) 1 having a diameter of 13 mm provided at the tip of the force gauge 14
5 was compressed to a depth of about 1.0 mm and the spring constant was calculated from the measured stress-strain curve.
This measurement is at 30 mm intervals in the longitudinal direction of the roller.
The measurement was performed at 30 degree intervals in the roller circumferential direction and calculated as an average value. In addition, the friction tester “H” manufactured by Shinto Kagaku Co., Ltd.
The surface friction resistance of the toner supply roller was measured using "EIDON Tribogear" according to the method shown in FIG. As shown in FIG. 4, the toner supply roller 5 is moved to the movable stage 16
And was moved in the direction of the arrow at a friction speed of 100 mm / min. The material to be rubbed was an acrylic round bar 17 having a diameter of 12 mm, which was placed in a direction perpendicular to the toner supply roller 5 and rubbed with a load 19 of 0.1N. The frictional resistance at this time was measured by the load cell 18. The acrylic material was selected as the friction material,
This is because the main component of the toner is similar to the acrylic material, and the friction due to this combination simulates the friction between the toner supply roller and the toner.

For the toner supply roller used in this embodiment, the compression spring constant was measured by the method shown in FIG.
Further, after the surface frictional resistance was measured by the method shown in FIG. 4, the printer was arranged as the toner supply roller 5 of the printer shown in FIG. 1 and an image forming test was conducted. Further, the developing roller A is arranged as the developing roller 6. The image forming test was carried out by feeding A4 size paper in the longitudinal direction and printing 10 dark gray solid images under a constant temperature and constant humidity (25 ° C., 50% RH) environment. The results are shown in Table 1.

[0024]

[Table 1]

[0025]

According to the present invention, when the toner is rubbed between the toner supply roller and the developing roller, it is formed near both ends of the roller surface with respect to the toner which is spread from the center of the roller toward both ends of the roller. The ring-shaped ridge becomes a barrier against toner movement, and as a result, the toner movement amount is adjusted,
A certain amount of toner can be supplied to the developing roller over the entire area in the longitudinal direction of the roller, and the coefficient of frictional resistance of the roller surface and the hardness of the elastic foam layer become appropriate. Is preferable, and the toner conveyance, the toner charging and the toner scraping performed between the toner supply roller and the developing roller are preferably performed, so that a good image without defects such as pitch unevenness and density unevenness can be formed. it can. Therefore, according to the developing device equipped with the toner supply roller of the present invention, it is possible to surely obtain a good image.

[Brief description of 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 showing a method for measuring the compression spring constant of the toner supply roller shown in the embodiment.

FIG. 4 is a schematic diagram showing a method for measuring the surface frictional resistance of the toner supply roller shown in the embodiment.

[Explanation of symbols]

1: photoconductor 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: Heat fixing device 10: Cleaning unit 11: rotation axis 12: Foam elastic roller 12a: annular ridge 13: V block 14: Force gauge 15: Compression jig (disk indenter) 16: Movable stage 17: Acrylic round bar 19: Applied load

Claims (5)

[Claims] 1. A toner supply roller that supplies toner to a developing roller that forms a visible image by conveying toner carried on the surface to an image forming body and supplies the toner to the developing roller, the shaft and the shaft. An annular ring having a height of more than 0 and 1 mm or less and a width of 1 to 5 mm at a position of 10 to 30 mm from both ends in the roller longitudinal direction on the surface of the foamed elastic body layer. The ridges are formed, and the frictional resistance coefficient of the roller surface is 0.4 to 3.0,
Moreover, the compression spring constant of the foam elastic layer is 0.25 to 5.0 N / m.
The toner supply roller is characterized by being m. 2. The ring-shaped ridges are located 20 to 30 mm from both ends in the roller longitudinal direction on the surface of the foamed elastic body layer, and have a height of 0.5 to 1 mm and a width of 1 to 3 mm. The toner supply roller according to claim 1. 3. The shaft is a good conductive shaft, and the foam elastic body layer is a conductive foam elastic layer.
The toner supply roller described in 1. 4. A developing device equipped with the toner supply roller according to claim 1. 5. An image forming apparatus equipped with the developing device according to claim 4.