JPH11133655A - Toner used in non-magnetic contact one-component type developing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner from being accumulated on the bottom of a developing housing and to remarkably reduce necessary developing torque by specifying the roundness and the drop amount in a drop amount tester concerning toner used in a non-magnetic contact one-component type developing system where the rotating directions of a developing roller and a sub roller are to trail downward. SOLUTION: As for the toner used in the non-magnetic contact one-component type developing system where the rotating directions of the developing roller 2 and the sub roller 3 are to trail downward; the roundness is larger than 0.94 and the drop amount in the drop amount tester is >=10 g/5 min. A system where the rotating directions of the developing roller 2 and a photoreceptor drum 1 are to trail upward or a system where the ratio of the circumferential speed of the sub roller 3 to the developing roller 2 is 1.05 to 3.1 is desirable as the non-magnetic contact one-component type developing system. The fluidity of the toner is very excellent, so that the toner accumulated on the bottom part 5 is smoothly pressed out to the acting position of a stirring paddle 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used in a non-magnetic contact one-component developing system, and more particularly to an image forming apparatus such as a laser printer, a facsimile, a digital copy and the like. And a toner capable of remarkably reducing a developing torque.

[0002]

2. Description of the Related Art In image formation using electrophotography, an electrostatic latent image is formed on a photosensitive drum, the electrostatic latent image is developed with toner to make a visible image, and the toner image is transferred to a transfer paper. Then, a fixing method is adopted.

[0003] The developing system used for electrophotography includes a two-component magnetic developing system using a mixture of a toner and a magnetic carrier, a one-component magnetic developing system using a one-component toner containing magnetic powder, and a non-magnetic one-system. A non-magnetic one-component developing method using a component toner is known.
The non-magnetic one-component contact developing method is the most excellent in terms of miniaturization, cost, and simplicity of operation of the developing device.

There is a great demand for miniaturization of a non-magnetic contact one-component developing system, and in order to meet this demand, a method of reducing the diameter of a photosensitive drum together with a developing roller and a toner supply sub-roller and making them contact each other has been proposed. Has been adopted. In order to do so, the driving motor and the driving power supply need to be reduced as well. Further, a trail that reduces the driving torque in the rotation directions of the developing roller and the sub-roller, and furthermore, the developing roller and the photosensitive drum is employed.

Japanese Patent Application Laid-Open No. Hei 9-197710 discloses a latent image forming member for forming a latent image, and a toner layer formed on the surface of the latent image forming member by rotating while being pressed against the latent image forming member. A latent image is developed by a developing device having a toner layer carrier for developing the latent image to be developed, a toner supply member for supplying toner to the toner layer carrier, and a supply auxiliary member in contact with or close to the supply member. In developing, when the area of a toner projected image is A and the area of a circle whose peripheral length is L is AL,
A developing method using a pulverized non-magnetic one-component toner in which the average circularity (A / AL) of the toner is 0.94 or less is described.

[0006]

However, when the amorphous non-magnetic one-component toner obtained by the pulverizing method is applied to the microminiature non-magnetic contact one-component developing system, the toner is supplied from the sub-roller to the developing roller. Some of the toner not supplied to the developing roller tends to accumulate sequentially on the bottom of the developing housing. In such an ultra-small developing unit, the gap between the bottom of the developing housing and the sub-roller is very narrow, and the accumulated toner reaches the nip position between the developing roller and the sub-roller. Therefore, the torque of both rolls becomes very large, and there is a disadvantage that the drive gear is eventually locked.

As a measure to prevent this, an electrode (aluminum sheet) with a positive voltage applied to the bottom of the developing housing
It has been proposed to prevent the toner from accumulating by sticking the toner and repelling the toner (a patent is also pending). However, even with this countermeasure, it is difficult to completely prevent the toner from accumulating, and the work of attaching an aluminum sheet in assembling the apparatus is inferior in workability and requires a special process.

Accordingly, an object of the present invention is to provide a toner capable of preventing the accumulation of toner on the bottom of the developing housing and significantly reducing the necessary developing torque in the non-magnetic contact one-component developing system. To be.

[0009]

According to the present invention, there is provided a toner for use in a non-magnetic contact one-component developing system in which the rotation direction of a developing roller and a sub-roller is a trail downward, and has a circularity of 0.1. A toner having a drop amount of more than 94 and a drop amount of 10 g / 5 min or more in a drop amount tester is provided. The non-magnetic contact one-component developing system targeted by the toner of the present invention is a system in which the rotation direction of the developing roller and the photosensitive drum is a trail upward, and the peripheral speed ratio between the developing roller and the sub-roller. Is preferably 1.05 to 3.1 times.

[0010]

DETAILED DESCRIPTION OF THE INVENTION

[Operation] In the present invention, the circularity (C) is defined as follows, assuming that the area of a toner projected image is A and the area of a circle whose peripheral length is L is AL, as is generally used. It means a value represented by the formula C = A / AL.

On the other hand, the drop amount in the drop amount tester is
The value measured in the following test method. Drop Amount Measurement 30 g of the electrophotographic toner is placed in a 300 mL cylindrical container (with a lid), stirred upside down about 30 times, and the fluidity is measured using the apparatus shown in FIG. The apparatus includes a hopper 101 on which a sample toner is loaded, a toner replenishing roller 102 disposed at a bottom opening 111 of the hopper 101, and a tray 1 provided below the hopper 101.
03. Further, the toner supply roller 102
Has a diameter of 16 mm and a length of 94 mm with irregularities on the surface
And is configured to drop the sample toner from the hopper 101 to the tray 103 by rotating. Then, a predetermined amount of the toner for electrophotography is placed on the hopper 101, the toner supply roller 102 is rotated at a constant speed, and the amount of toner that falls on the tray 103 during a fixed time is obtained to evaluate the fluidity of the toner. Things. The toner supply roller 102 is JIS B095
The knurls specified in 1 are 0.2 in the twill module (m) (pitch: 0.628 mm, r: 0.06 mm,
h 0.132 mm). Toner supply roller 1
The rotation speed of 02 is set to 5 revolutions per minute, and the amount of drop on the tray 103 is measured in 5 minutes.

In FIG. 2, which shows a main part of a non-magnetic contact one-component developing system to which the toner of the present invention is applied, this developing system forms a small-diameter photosensitive drum for forming and carrying an electrostatic latent image. 1, a small-diameter developing roller 2 that carries a charged toner layer and contacts the photosensitive drum 1,
And a sub-roller 3 which comes into contact with the developing roller 2 and supplies toner thereto. Below the developing roller 2, a blade 4 that regulates the thickness of the toner layer on the developing roller so as to be in contact with the developing roller 2 and also serves to charge the toner.
Is provided. Below the sub-roller 3, at a small interval, is the bottom portion 5 of the developing housing. In addition, a stirring paddle 6 for stirring the one-component toner is provided inside the developing housing in the vicinity of the sub-roller 3.

The transfer paper 7 is supplied to the upper portion of the photosensitive drum 1 in a one-pass face-down state, and the transfer of the toner image to the transfer paper is performed. As already pointed out, the sub roller 3 and the developing roller 2 are in contact with each other, and the developing roller 2 and the photosensitive drum 1 are in contact with each other by a trail (a forward direction at a contact portion).
Further, since the transfer paper is supplied as described above, in FIG. 2, the photosensitive drum 1 rotates clockwise, the developing roller 2 rotates counterclockwise, and the sub-roller 3 rotates clockwise. For this reason, the rotation direction of the developing roller 2 and the sub-roller 3 becomes a trail in the downward direction, and the toner is accumulated between the sub-roller 3 and the bottom 5 of the developing housing, which causes an increase in torque and a lock of the driving gear.

In the present invention, in the non-magnetic contact one-component developing system, as the toner, the above-mentioned toner having a circularity of greater than 0.94 and a drop amount of 10 g / 5 min or more in a drop amount tester is used. . Of course, also in this case, the toner 8 falls between the sub-roller 3 and the bottom 5 of the developing housing and gradually accumulates. However, in the present invention, since the fluidity of the toner is very good, the toner accumulated at the bottom portion is smoothly pushed out to the operating position of the stirring paddle 6 by the toner that sequentially falls. For this reason, below the developing roller 2 and the sub-roller 3, the toner that has fallen without being supplied to the developing roller 2 without collecting the toner exceeding a certain fixed amount passes through the stirring paddle 6 again. And the toner is again useful for toner supply.

Table 1 of the embodiment described below shows the relationship between the circularity and the amount of fall of the toner used and the occurrence of lock of the drive gear. When both the circularity and the amount of fall satisfy the conditions of the present invention. In addition, it is clear that the occurrence of drive gear lock is avoided.

In the non-magnetic contact one-component developing system to which the toner of the present invention is applied, the peripheral speed ratio of the sub-roller 3 to the developing roller 2 is in the range of 1.05 to 3.1. It is preferable to form a high-density image without generation. That is, if the peripheral speed ratio falls below the above range, the image density tends to decrease due to insufficient toner supply, while if it exceeds the upper range, the image fog tends to increase due to excessive toner supply. Table 2 in Examples described later shows that
This relationship is clearly shown.

Thus, according to the present invention, in a small non-magnetic contact one-component developing system, the developing torque (the developing roller and the sub-roller and the developing roller and the photosensitive drum) can be made very small. Thus, the drive motor and the drive power supply can be reduced in size. Further, since the toner in the developing device is uniformly stirred and the toner is uniformly consumed, the toner can be effectively used.
Further, there is an advantage that the fluidity of the toner can be ensured throughout the life of the toner.

[Toner] The toner used in the present invention has a circularity of more than 0.94, particularly 0.95 or more, and a drop amount of 10 g / 5 min or more, particularly 10.0 to 14.0 g, in a drop amount tester. This toner is in the range of / 5 min, and is different from an irregular toner by a pulverization method, and a spherical toner produced by a polymerization method or spheroidization of the irregular toner is suitable for this toner.

The spherical toner is composed of a fixing resin component, a colorant, a high molecular weight or low molecular weight charge control agent,
It contains a release agent or the like, and preferably has a median diameter of 1 to 30 μm, particularly 5 to 25 μm, and D25 / D
Monodisperse particles having a degree of dispersion of a particle size represented by 75 of 2.0 or less, particularly 1.8 or less, or particles close thereto. In the present specification, D25 and D75 represent particle diameters corresponding to 25% and 75% of the total volume of the toner particles.

The polymerization spherical toner is obtained by subjecting a toner-forming composition containing at least a radical polymerization initiator, a vinyl monomer which can be a fixing resin and a colorant to suspension polymerization in an aqueous medium. .

As long as the degree of circularity is within the above range, spherical toners obtained by other methods can of course be used. For example, an irregular toner obtained by kneading, pulverizing and classifying a resin composition for forming a toner is heated in a stream of hot air. Molten, spheroidized toner, or a melt of the toner forming resin composition is sprayed into a hot atmosphere,
Spherically granulated toners are also used for the purpose of the present invention. Hereinafter, a suitable polymerization method toner will be described.

The vinyl monomer capable of forming the fixing resin is water-insoluble and can form a thermoplastic resin having a fixing property and an electric detecting property. Examples thereof include, but are not limited to, vinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, and monoolefin monomers.

As the vinyl aromatic monomer, the following formula (1)

Embedded image In the formula, R ₁ is a hydrogen atom, a lower alkyl group or a halogen atom, R ₂ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, a nitro group, or a vinyl group, and φ is a phenylene group. Of vinyl aromatic hydrocarbons such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-, m-, p-chlorostyrene, p-ethylstyrene and divinylbenzene alone or in combination of two or more. Can be mentioned.

As the acrylic monomer, the following formula (2)

Embedded image In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and R ₄ is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, or a vinyl ester group. Acrylic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, methacrylic acid-2
-Ethylhexyl, β-hydroxyacrylate,
γ-hydroxypropyl acrylate, δ-hydroxybutyl acrylate, β-hydroxyethyl methacrylate,
Examples include ethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate.

Other monomers include vinyl esters such as vinyl formate, vinyl acetate and vinyl propionate; vinyl ethers such as vinyl-n-butyl ether, vinyl phenyl ether and vinyl cyclohexyl ether; diolefins, especially butadiene. , Isoprene, chloroprene and the like: monoolefins, particularly ethylene, propylene, isobutylene, butene-1, pentene-1, 4-methylpentene-1 and the like. Suitable monomers are styrene monomers, acrylic monomers, styrene-acryl monomers, and the like.

As the colorant for the toner, an inorganic or organic pigment or dye is used, and suitable examples thereof are as follows. The colorant is preferably used in an amount of 3 to 20% by weight per resin in the toner. Black pigments Carbon black, acetylene black, lamp black, aniline black. Yellow pigment Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hanser yellow G,
Hanser Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigment Red lead graphite, molybdenum orange, permanent orange GTR, pyrazolo orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK. Red pigment Bengala, cadmium red, lead red, cadmium mercury sulfide, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B. Purple pigment Manganese purple, fast violet B, methyl violet lake. Blue pigment Navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, indanthrene blue B
C. Green pigment chrome green, chromium oxide, pigment green B,
Malachite Green Lake, Fanal Yellow Green G. White pigment Zinc white, titanium oxide, antimony white, zinc sulfide. Extender barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white.

As the radical polymerization initiator, a radical polymerization initiator known per se, for example, an azo compound type, a hydroperoxide type, a peroxide type, a peracid type initiator and a redox type initiator are used. Suitable examples of the initiator include, but are not limited to, the following. 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-cyclopropylpropionitrile), 2,2'-azobis (4-
Methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis (1-cyclohexanecarbonitrile), benzoyl peroxide, (1-phenylethyl) azodiphenylmethane.

The toner forming composition for forming the spherical toner may contain a toner auxiliary known per se.
Examples of the toner auxiliary include a charge control agent and a release agent.

As the release agent, various waxes, polypropylene wax, polyethylene wax, acid-modified products thereof and the like are used, and these can be contained in the toner forming composition in the size of emulsion particles.

Examples of the charge controlling agent include those known per se, for example, oil-soluble dyes such as nigrosine base (CI 5045), oil black (CI 26150), and spiron black;
In addition to a metal salt of naphthenic acid, a fatty acid metal soap, a metal-containing complex dye, and the like, a water-soluble monomer having a charge controllable functional group copolymerizable with the vinyl monomer may be used. Examples of such a monomer include a sulfonic acid, a phosphoric acid, a carboxylic acid type anionic group, and a cationic group such as a primary-, secondary- or tertiary-amino group and a quaternary animonium group. Radical polymerizable monomers having an electrolytic group of
A suitable example is as follows.

Styrenesulfonic acid, sodium styrenesulfonate, 2-acrylamide 2-methylpropanesulfonic acid, 2-acid phosphooxypropyl methacrylate, 2-acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, acrylic Acid, methacrylic acid, fumaric acid, crotonic acid, tetrahydroterephthalic acid, itaconic acid, aminostyrene, aminoethyl methacrylate, aminopropyl acrylate, diethylaminopropyl acrylate, γ-N- (N ′, N′-diethylaminoethyl) aminopropyl methacrylate , Trimethyl ammonium propyl methacrylate.

Further, electrolysis of the above-mentioned sulfonic acid, phosphoric acid, carboxylic acid type anionic groups, or cationic groups such as primary-, secondary- or tertiary-amino groups and quaternary animonium groups. It is also possible to introduce a charge control group at the polymer terminal by using a radical initiator having a functional group.

In producing the polymerization toner, a toner-forming composition containing a vinyl monomer and the like is suspended in water. In this case, the concentration of the composition is generally between 1 and 50.
%, Especially 5 to 30% by weight, the size of the suspended particles is generally 1 to 30 μm, in particular 5 to 25 μm.
It is appropriate to adjust to m.

If necessary, a dispersion stabilizer can be used to stabilize the suspension state of the toner forming composition. Examples of such a dispersion stabilizer include polymers soluble in a medium such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyacrylic acid, polyacrylamide, polyethylene oxide, poly (hydroxystearic acid-g-methyl methacrylate-CO). A (methacrylic acid) copolymer, a nonionic or ionic surfactant or an inorganic powder such as calcium phosphate is appropriately used. The dispersion stabilizer is present in the system in an amount of 0.1 to 10% by weight, especially
It is preferably added in an amount of 0.5 to 5% by weight.

The amount of the initiator in the toner-forming composition is from 0.3 to 30% by weight, based on the monomer, preferably from 0.3 to 30% by weight.
The content is preferably 5 to 10% by weight.

In the polymerization, the reaction system is replaced with an inert gas such as nitrogen, and the polymerization is carried out at a temperature of 40 to 100 ° C., particularly 50 to 90 ° C. while maintaining the above-mentioned suspension state. Of course, mild stirring can be performed to homogenize the reaction system. Since the polymerization product after the reaction is obtained in the form of granules having the above-mentioned particle size range, the resulting particles are filtered, washed with water or a suitable solvent if necessary, and dried to obtain toner particles.

It is effective to externally add a fluidity improving agent (surface treatment agent) to the toner particles in order to improve the fluidity of the particles. That is, by spraying a fluidity improver (surface treatment agent) such as carbon black, hydrophobic amorphous silica, hydrophobic fine alumina powder, fine titanium oxide, and fine spherical resin,
The final toner is used. The flow improver (surface treatment agent) is preferably used in an amount of 0.1 to 3.0% by weight per toner.

In order to improve the flowability, heat resistance and offset resistance of the polymerized toner, the polymerization average molecular weight is generally 10,000 to 150,000, preferably 1,000.
0 to 100000 is preferred.

In the toner of the present invention, the above-described control of the drop amount is also affected by the circularity and the particle size of the toner particles, but is controlled by a treatment with a fluidity improver (surface treatment agent) or a charge control agent. It also depends on the charge amount. In short, the amounts and types of these components may be changed so that the falling amount falls within the range specified in the present invention.

[Non-Magnetic Contact One-Component Developing System] FIG. 3 shows an example in which the non-magnetic contact one-component developing system according to the present invention is applied to a printer 12. The printer 12 includes an airframe housing 20. A box-shaped main body 21 having at least an open front upper part;
A cover 2 pivotally mounted on an upper part of the shaft 1 by a shaft 22
3 is included. The process unit 14 is disposed inside the body housing 20.

The process unit 14 includes a photosensitive unit 40 and a developing unit 50. The developing unit 50 is swingably provided on the photosensitive unit 40 via the support shaft 15.

The photoreceptor unit 40 rotatably supports a photoreceptor drum 42, and a charging mechanism 43 is provided around the photoreceptor drum 42.
And a foreign matter collecting brush 44.

The developing device unit 50 has a developing housing 51, and includes a developing roller 53 housed in the housing and a sub-roller 54 which comes into contact with the developing roller 53 and supplies toner thereto. Below the developing roller 53, there is provided a blade 56 which regulates the thickness of the toner layer on the developing roller and also serves to charge the toner so as to be in contact therewith. Below the sub-roller 54, at a small interval, is the bottom 57 of the developing housing. In addition, a stirring paddle 55 for stirring the one-component toner is provided inside the developing housing 51 in the vicinity of the sub-roller 54.

The photosensitive unit 40 and the developing unit 5
A tension spring 52 is provided between the developing roller 53 and the developing roller 53 so as to press the developing roller 53 against the photosensitive drum 42. In this press-contact state, a passage 41 for image exposure is formed diagonally below the photosensitive drum 42.

A laser unit 24 is housed in the housing body 21 of the machine housing. Laser light output from the unit 24 is guided to the photosensitive drum 42 through the exposure passage 41. .

Further, a paper feed tray 28 and a paper discharge tray 27 are provided in the machine housing 20, and between them,
The pre-transfer guide plate 45, the transfer roller 31, which is opposed to and close to the photosensitive drum, the post-transfer guide plate 46, the fixing roller 25, and the discharge roller 26 are provided in this order. At the end of the paper feed tray 28, a paper feed roller 2 driven during printing is provided.
9 and a friction pad 30 are provided so that paper can be fed one by one.

The upper portion 452 of the pre-transfer guide plate 45, the transfer roller 31, the upper portion of the post-transfer guide plate 46, the upper portion of the fixing roller 25, and the upper portion of the discharge roller 26 are provided on the cover 23. On the other hand, the lower portion 451 of the pre-transfer guide plate 45, the lower portion of the post-transfer guide plate 46, the fixing roller 2
The lower portion of the transfer roller 5 and the lower portion of the discharge roller 26 are provided in the housing body 21 so that when the cover 23 is opened, all of these transfer paper passages are opened, so that a paper jam can be easily removed. .

As the photosensitive drum 42, any photosensitive drum provided with an electrophotographic photosensitive layer on a conductive metal drum can be used. From the viewpoint of preventing the generation of ozone, it is desirable to use a positively charged photoconductor. As the organic photoreceptor, a charge transporting agent, particularly a combination of a hole transporting agent and an electron transporting agent and a monodispersed layer type photoreceptor containing a charge generating agent in a resin medium or a charge transporting agent containing a charge transporting agent are used. The photoreceptor may be a laminate type photoreceptor having a layer and a charge generating layer containing a charge generating agent. In this case, the charge generating layer (CGL) and the charge transporting layer (CTL) are laminated in this order or the reverse order. Photoconductor may be used.

Examples of the charge generating agent include selenium, selenium-tellurium, amorphous silicon, pyrylium salt,
Azo pigments, disazo pigments, ancesthrone pigments,
Phthalocyanine-based pigments, indico-based pigments, selen-based pigments, toluidine-based pigments, pyrazoline-based pigments, perylene-based pigments, quinacridone-based pigments, and the like are exemplified, and one or more of them are mixed so as to have an absorption wavelength range in a desired region. Used.

Various resins can be used as the resin medium in which the charge generating agent is dispersed, such as a styrene polymer, an acrylic polymer, a styrene-acrylic polymer, an ethylene-vinyl acetate copolymer, polypropylene,
Olefin polymers such as ionomers, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester,
Alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin,
Various polymers such as a phenol resin and a photocurable resin such as an epoxy acrylate can be exemplified. These binder resins may be used alone or in combination of two or more.
Suitable resins are styrenic polymers, acrylic polymers,
Styrene-acrylic polymer, polyester, alkyd resin, polycarbonate, polyarylate and the like.

As the charge transporting agent, any electron transporting or hole transporting agent known per se can be used alone or in combination of two or more, and is not limited thereto. -N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5-
Diphenyl-1,3,4-oxadiazole, 2,5-bis-
(4-diethylaminophenyl) -1,3,4-oxadiazole, bis-diethylaminophenyl-1,3,6-oxadiazole, 4,4′-bis (diethylamino) -2,2′-
Dimethyltriphenylmethane, 2,4,5-triaminophenylimidazole, 2,5-bis (4-diethylaminophenyl) -1,3,4-triazole, 1-phenyl-3-
(4-diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazoline, p-diethylaminobenzaldehyde- (diphenylhydrazone), tetra (m-methylphenyl) metaphenylenediamine, N,
Hole transporting agents such as N, N ', N'-tetraphenylbenzidine derivatives, N, N'-diphenyl-N, N'-dixylylbenzidines, 2-nitro-9-fluorenone, 2,7-dinitro -9-fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene , Dinitroacridine, dinitroanthraquinone, 3,5-dimethyl-
Electron transporting agents such as 3 ′, 5′-di-t-butyldiphenoquinone and naphthoquinone derivatives are used.

In the monodispersed photoreceptor, the charge generating agent (CGM) is preferably contained in the photosensitive layer in an amount of 1 to 7% by weight, particularly 2 to 5% by weight, based on the solid content. The agent (CTM) is preferably contained in the photosensitive layer in an amount of 20 to 70% by weight, particularly 25 to 60% by weight, based on the solid content. Further, from the point of sensitivity and the wide range of applications that enable reversal development, it is preferable to use a combination of an electron transporting agent (ET) and a hole transporting agent (HT),
In this case, the weight ratio of ET: HT is 10: 1 to 1: 1.
It is most preferably in the range of 0, especially 1: 5 to 1: 1.

As the charging mechanism 43, a corona charger such as a corotron or a scorotron is used. For the purpose of stably and uniformly charging the photosensitive layer, a scotron charger, that is, a corona wire and a shield And a charger provided with a grid provided at the opening of the shield on the photoconductor side is particularly suitable. In the apparatus shown in FIG. 3, the charging mechanism 43 is provided below the photoconductor drum 42, and is arranged so that the influence of the discharge product on the photoconductor is reduced as much as possible. The saturation charging potential of the photoconductor is generally 5
It is preferable to perform charging so as to be in the range of 00 to 2000 volts.

The developing roller 53 and the sub-roller 54 used in this image forming system are formed of a conductive elastic (rubber) roller. The elastic roller is obtained by molding a composition obtained by mixing a conductive powder such as conductive carbon black or metal powder with an elastomer polymer such as urethane rubber or silicone rubber.

The volume resistance of the elastic developing roller 53 is:
Generally, it is preferably in the range of 10 ^{4 to} 10 ⁹ Ω · cm. If it is higher than the above range, it is difficult to apply a bias voltage. Tends to occur.

The hardness (Asker C hardness) of the elastic developing roller is preferably in the range of 60 to 85. If the hardness is higher than the above range, the toner layer should be brought into uniform contact with the surface of the photoreceptor. When the temperature is lower than the above range, it is difficult to transmit a sufficient pressure contact force, and the developing roller is liable to be worn. Further, regarding the surface roughness of the developing roller, the ten-point average roughness RZ defined in JIS B 0601 is preferably in the range of 5.0 to 12.0 in terms of toner holding properties and developability.

As the sub roller 54, a roller made of a conductive elastic material is used as in the case of the elastic developing roller 53. However, it is suitable for the sub-roller to have a considerably smaller hardness than the developing roller. Generally, 75 to 95 degrees of Asker F hardness is appropriate.

The stirring paddle 55 is used to stir the one-component toner contained in the developing housing and to supply the one-component toner to the sub-roller. A stirring frame member provided on the rotating shaft is provided. And a flexible sheet member provided at the end of the frame member. The frame member and the sheet member are provided with a large number of holes so that the degree of stirring is not excessive. I am adjusting. The elastic sheet is formed of, for example, a PET film or the like, and is provided with elasticity so as to be in a curved state. Thus, the elastic sheet also acts to press the one-component toner against the sub-roller, and the one-component The supply of the system toner is performed smoothly.

A bias voltage for enabling reversal development is applied to the developing roller 53. This bias potential has the same polarity as the charged potential of the unexposed portion of the photoreceptor and, in absolute value, is higher than the potential of the exposed portion and lower than the potential of the unexposed portion. It is preferable to make . On the other hand, it is preferable to apply a bias potential having the same polarity as the developing bias potential and a high absolute value to the sub-roller 54 in order to smoothly supply the one-component toner to the developing roller. Generally, it is preferable to apply a voltage that is higher by 0 to 600 volts in absolute value than the developing bias voltage.

As shown in FIG. 3, the sub-roller 54 and the developing roller 53 contact downward by trailing, while the developing roller 53 and the photosensitive drum 42 contact upward by trailing. Is preferably in the range of 1.05 to 3.1, while the peripheral speed ratio of developing roller 53 / photosensitive drum 42 is suitably in the range of 1.2 to 3. When the peripheral speed ratio is smaller than the above range, the supply of the one-component toner becomes insufficient. On the other hand, when the peripheral speed ratio is larger than the above range, the abrasion tendency of the roller or the drum increases.

The transfer roller 31 applies a transfer voltage from the back side of the transfer paper in a non-contact state with the photosensitive drum, and is also a conductive rubber roller. This conductive rubber roller is similar to that of the developing roller, but its Asker C hardness is preferably 50 to 80.

Image formation in this non-magnetic one-component contact developing system is performed as follows.

1) Charging Step: The photosensitive layer of the photosensitive drum 42 rotates in the direction of the arrow (clockwise) in FIG. 3, and is uniformly charged by a corona (eg, a positive corona) from the charging mechanism 43. . Generally, the surface potential of the photosensitive layer is set in the range of 500 to 2000 V in absolute value.

2) Image exposure step: In response to print data from a personal computer or word processor connected to the printer 12, a laser beam from the laser unit 24 is passed through the exposure passage 41 to the photosensitive drum 4.
The photosensitive layer 2 is exposed to light to form an electrostatic latent image. As a result of performing the image exposure using the laser light, the potential of the portion corresponding to the light beam image of the photosensitive layer (that is, the portion irradiated with the laser light) becomes
The absolute value is 0 V to 300 V, and the potential of the portion not irradiated with the laser beam (background) is maintained at the dark decay potential from the main charging potential, and an electrostatic latent image is formed.

3) Developing Step: The one-component toner is stirred by the stirring paddle 55 and charged by friction with the stirring paddle 55 or the wall of the developing housing 51. The charged one-component toner is moved in the direction of the arrow (clockwise) in FIG.
Is supplied to the surface of the sub-roller 54 which is rotating at a speed, is supported and transported to the developing roller 53 which is rotating counterclockwise, and is supplied to the developing roller 53. The thickness of the one-component toner layer on the surface of the developing roller 53 is regulated by the blade 56, and development is performed in contact with the photosensitive layer of the photosensitive drum 42. The one-component toner used in this development is charged to have the same polarity as the potential of the unexposed portion of the photosensitive layer, whereby the toner adheres to the laser beam irradiated portion by reversal development. Will be

4) Transfer process: The transfer paper stored in the paper feed tray 28 is supplied one by one between the transfer roller 31 and the photosensitive drum 42 by the paper feed roller 29 and the friction pad 30. The transfer of the toner image is performed in contact with the photosensitive drum 42 having the one-component toner image.

5) Fixing Step: The transfer paper on which the toner image has been transferred is supplied to a pair of fixing rollers 25, and the toner image is heated and fixed. The transfer paper on which the toner image has been fixed is discharged onto a tray 27 by a discharge roller 26.

6) Post-process: Foreign matter such as paper dust adhering on the photosensitive drum 42 is removed from the surface of the photosensitive drum by the foreign matter collecting brush 44, while toner remaining on the photosensitive drum surface is Cleaning by the contact of

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

Preparation of Toner Toner A: pulverized toner (no spheronization treatment) This toner uses styrene-acryl as a binder resin, is premixed using a Henschel mixer, and the mixture is extruded by a twin screw kneader. And melt kneading. Then, the kneaded material is pulverized and classified, and further subjected to an external addition treatment of 1 wt% of silica as a surface treating agent, whereby toner A is obtained.
The volume average particle diameter of the toner is a median value (D ₅₀ ) of 9.0.
μm. The circularity defined above of this toner is 0.3
2, and the value obtained by the drop amount tester was 5.56.
(G / 5 min). Toner B: Polymerized toner This toner comprises a radical polymerization initiator, a styrene monomer,
It is obtained by subjecting a toner-forming composition containing an acrylic monomer, a colorant, and a synthetic wax to suspension polymerization in an aqueous medium and externally adding 0.5 wt% of silica as a surface treatment agent. The volume average particle diameter of the toner is 9.0 μm (D ₅₀ ). The circularity of the toner defined above was 0.95, and the value measured by the drop tester was 8.29 (g / 5 min). Toner C: Polymerized toner The toner B was prepared by adding the surface treating agent to the toner B in an amount of 1.0 wt%. The circularity defined above of this toner is 0.9.
5, and the value obtained by the drop tester was 10.2.
(G / 5 min).

The relationship between the circularity and the amount of fall of the toner and the drive gear
An experiment showing the relationship The laser fax "TC-720" manufactured by Mita Kogyo Co., Ltd. was modified so as to adopt the configuration shown in FIGS. 2 and 3, and a confirmation experiment was conducted with the above toner. The results are as shown in Table 1. In the case of the toner A, several hundreds of prints (A4 length conversion) accumulate toner at the bottom of the housing corresponding to the sub-roller.
Eventually, the drive gear was locked. At the beginning, the toner B was driven without any problem. However, since about 1000 prints, the movement of the sub-roller and the developing roller became sober for the same reason as described above, and the drive gear was locked immediately. . On the other hand, the flow of the toner in the toner C developing device was very good, and the toner C was driven without any problem even if it exceeded 3,000 sheets. This is considered to be due to the fact that toner having an appropriate value for the degree of circularity and the amount of drop is used.

The peripheral speed ratio of the sub roller to the developing roller and
Experiment showing the relationship between print images The "TC-720 modified" used in the above-mentioned experiment was further modified to have an external motor so that the peripheral speed of the sub-roller with respect to the developing roller could be changed. In a state where the peripheral speed ratios shown in Table 2 are shown, continuous printing (A4 length conversion) of 3,000 sheets was performed, and the first print and 500
A total of seven samples are extracted, one for each sheet. Then, the sample is measured with a reflection densitometer (Model No. TC-
6D), the image density (ID) of the output image and the fog density (FD) of the margin are measured, and the average value is shown in Table 2. As a result, if the peripheral speed ratio is too small as 1.0, the amount of toner supplied to the developing roller is insufficient, and only a toner having a low image density lower than ID 1.330, which is generally defined as a normal image density, can be provided. . Conversely, if the peripheral speed ratio is as high as 3.5, the amount of toner supplied to the developing roller will be excessive, and an image will be formed which greatly exceeds the fog density FD 0.005 which is generally considered to be no problem. Therefore, it is understood that the peripheral speed ratio should be specified in the range of 1.05 to 3.1.

[0073]

[Table 1]

[0074]

[Table 2] Note) 3000 continuous prints are performed, and a total of seven samples are extracted, one for the first print and one for every 500 prints, and a reflection densitometer (Model TC-6D manufactured by Tokyo Denshoku Co., Ltd.) is used. The image density (ID) of the solid black part and the fog density (FD) of the margin part of the output image were measured using this method.

[0075]

According to the present invention, the toner used in the non-magnetic contact one-component developing system in which the rotation direction of the developing roller and the sub-roller is a trail is downward.
The drop amount is larger than 94 and the drop amount in the drop amount tester is 10
By using a toner having a g / 5 min or more, accumulation of the toner on the bottom of the developing housing is prevented, and the toner can be effectively used, and the required developing torque can be significantly reduced. For this reason, according to the present invention, the developing housing is reduced in size and the driving mechanism thereof is also of a small output, so that the image forming apparatus is reduced in weight,
In addition, the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of an apparatus used for measuring a fall amount.

FIG. 2 is an explanatory diagram for explaining the principle of the present invention.

FIG. 3 is a side view showing a simplified arrangement of an image forming apparatus to which the developing system of the present invention is applied. (A) is a side view of the entire apparatus, and (B) is an enlarged view near the exposure passage.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 developing roller 3 sub-roller 4 blade 5 bottom of phenomenon housing 6 stirring paddle 7 transfer paper 12 printer 14 process unit 15 support shaft 20 body housing 21 box-shaped main body 22 shaft 23 cover 24 laser unit 25 fixing roller 27 discharge Paper tray 28 Paper feed tray 29 Paper feed roller 30 Friction pad 31 Transfer roller 40 Photoconductor unit 41 Exposure passage 42 Photoconductor drum 43 Charging mechanism 44 Foreign matter collection brush 45 Pre-transfer guide plate 46 Post-transfer guide plate 50 Developing device unit 51 Developing housing 52 Tension spring 53 Developing roller 54 Sub-roller 56 Blade 57 Bottom 101 Hopper 102 Toner supply roller 103 Receiving tray 111 Bottom opening

Claims (3)

[Claims] 1. A toner used in a non-magnetic contact one-component developing system in which a rotation direction of a developing roller and a sub-roller is a trail, and has a circularity of 0.94.
Is larger than 10g in the drop tester
/ 5 min or more. 2. The toner according to claim 1, wherein the non-magnetic contact one-component developing system is a system in which a rotation direction of a developing roller and a photosensitive drum is an upward trail. 3. The non-magnetic contact one-component developing system according to claim 1, wherein a peripheral speed ratio of a developing roller to a sub-roller is 1.0.
2. The toner according to claim 1, wherein the system has a ratio of 5 to 3.1 times.