JPS62295082A - Electrophotographic development method - Google Patents

Abstract

PURPOSE:To eliminate the deterioration of image quality, fogging, void, shortened life of a developer by the decreased electric charge quantity, etc., by depositing a specific two-component type dry developer on a developing roll, rotating the cylindrical sleeve thereof, bringing the same into contact with the surface of an electrostatic latent image carrying body and developing the electrostatic latent image to a sensible image. CONSTITUTION:This method consists in bringing the two-component type developer, which is prepd. by dispersing pulverized magnetic material particles into a binder resin essentially consisting of an acrylic polymer to prepare a carrier having >=50mum average grain size and mixing such carrier with a toner, into contact with the surface of the electrostatic latent image carrying body by rotating the cylindrical sleeve while depositing said developer on the developing roll consisting of the cylindrical sleeve and the magnet member fixed and disposed to the inside thereof thereby developing the electrostatic latent image to the sensible image. This developer is superior in the reproducibility of fine lines as well as in all respects including the shortened life of the developer and the fogging under high humidity, etc. which are considered to arise from the decreased charge quantity as compared to the case in which a dispersion type carrier consisting of a binder resin and magnetic powder and having <=50mum grain size is used.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic development method using a two-component dry developer.

[Traditional technology]

In electrophotography or electrostatic recording, an electrostatic latent image formed on a photoreceptor or electrostatic recording medium is developed using a magnetic brush development method, the developed image is transferred to a transfer body, and then fixed. Methods of obtaining copies are well known.

A two-component developer consisting of a carrier and a toner is generally used as a developer for development, but this is achieved by agitating the carrier and toner in a developing device to triboelectrically charge the toner, forming an electrostatic latent image on the toner. By applying a charge of opposite polarity, it is fixed. It is attached to the m image and developed. As a carrier for such a two-component developer, a particle size of 100 to 500 μm, which is larger than that of the toner, is usually used, but when used on a carrier with a large particle size,
The drawback is that the low potential portions in the electrostatic latent image have poor developability and gradation reproducibility is poor. In addition, when the ratio of toner to carrier increases, toner adhesion to non-image areas tends to occur, the so-called capri phenomenon, and when used for a long time, the amount of charge decreases, image density reproducibility decreases, and background areas There was a drawback that fogging development occurred.

In order to overcome these drawbacks, attempts have been made to reduce the weight of the carrier or reduce the particle size of the carrier. For example, Japanese Patent Application Laid-Open No. 48-68235 describes a magnetic brush developer using a carrier having a large particle size carrier mixed with a small particle size carrier approximately equal to the particle size of the toner. This developer has good gradation reproducibility and is less prone to toner adhesion to the carrier.
It has the advantage of little change in chargeability. Also, Japanese Patent Application Publication No. 5
4-66134 and Japanese Patent Application Laid-Open No. 55-32073 disclose a magnetic brush using particles having a particle size of, for example, 5 to 40 μm, in which magnetic powder is dispersed in a binder resin, as carrier particles. A method for carrying out development is described.

This developing method has the advantage of excellent reproducibility (D') and that carrier particles are less likely to adhere to the latent image surface.

[Problems to be Solved by the Invention] However, when magnetic brush development is performed for a long time using the developer described in JP-A-48-68235, small particle carriers adhere to the m image. The content of small particle size carriers in the developer gradually decreases, and the effect of mixing small particle size carriers disappears, resulting in the same drawbacks as when using large particle size carriers.

On the other hand, JP-A-54-66134 and JP-A-55-
The developing method described in Japanese Patent No. 32073 has various drawbacks when performing high-speed development.

In other words, if you use a type of developing roll that has a sleeve and an internally fixed magnet and transports the developer by rotating the sleeve, even if the carrier is around the entire circumference, the carrier particles will not reach the latent image surface. If magnetic brush development is performed for a long time due to adhesion, a change in chargeability, or a decrease in the absolute amount of toner in the development area, development results such as a decrease in image density or the occurrence of fog. It was something. This phenomenon was particularly noticeable when a repelling magnetic pole or a wide magnetic pole was used as the developing magnetic pole.

When a durability test was conducted using a developer containing a binder resin and a small particle carrier made of a magnetic material, as the number of copies increased, image density unevenness, fogging, etc. were observed to occur. However, this is considered to be due to a decrease in the amount of toner'R electricity. In other words, this is thought to be due to the fact that the toner and carrier are no longer sufficiently triboelectrically charged because the absolute amount of carrier in the developer is reduced due to adhesion.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic developing method in which disadvantages such as image quality deterioration due to carrier adhesion on a photoreceptor, fogging, white spots, and shortened developer life due to a substantial decrease in charge amount are improved. There is a particular thing.

[Means for resolving the gap]

The purpose of the present invention is to provide magnetic fine particles in a binder resin mainly composed of an acrylic polymer. Average particle size of dispersed particles: 50 μm
By rotating the cylindrical sleeve while carrying the above carrier on a developing roll consisting of a two-component dry developer mixed with toner and a magnetic member fixedly disposed inside the cylindrical sleeve. This can be achieved by an electrophotographic development method in which an electrostatic latent image is visualized by bringing it into contact with the surface of an electrostatic latent image carrier. That is, when the present inventors used a 2#:part developer consisting of toner and a relatively large carrier in which magnetic powder was dispersed in an acrylic binder resin, the same binder resin and magnetic powder were used. Compared to the case where a dispersed carrier with a particle size of 50 μm or less is used, there is a decrease in developer life, which is thought to occur due to a decrease in fine line reproducibility and charge amount, and a fogging phenomenon under high stain 1. The present invention was completed based on this finding.

In addition, when the above developer is used, the above effects can be seen when any known magnetic brush development method is adopted, but the development method is particularly developed using a cylindrical sleeve and a magnet fixedly disposed inside the sleeve. A remarkable effect can be obtained when using a developing method in which toner is carried on a developing roll consisting of a member, and a cylindrical sleeve is rotated to bring the toner into contact with the surface of the electrostatic latent image carrier to make it visible. It was seen.

Furthermore, even better results were obtained when the magnet member was arranged to form a repulsive magnetic field at the development nip position. The binder resin of the developer carrier used in the present invention is composed mainly of an acrylic polymer.

The acrylic polymer used as the binder resin of the carrier according to the present invention is a single polymer or a copolymer of acrylic ester or methacrylic ester. Specific examples of monomers constituting these acrylic polymers are as follows. Each compound can be mentioned.

Specifically, examples include esters of acrylic acid and methacrylic acid with alkyl alcohols, halogenated alkyl alcohols, alkoxyalkyl alcohols, aralkyl alcohols, and alkenyl alcohols. Specific examples of the alcohol constituting the ester include methyl alcohol, ethyl alcohol, flobyl alcohol, methyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dotecyl alcohol, tetratecyl alcohol, and hexyl alcohol. Alkyl alcohols such as tacyl alcohol; partially halogenated alkyl alcohols; methoxyethyl alcohol, ethoxyethyl alcohol,
Ethoxyethoxyethyl alcohol, methoxypropyl A
/ Flucol, ethoxypropyl alcohol (MO!a
Flucoxyalkyl alcohol; benzyl alcohol,
Examples include aralkyl alcohols such as phenylethyl alcohol and phenylpropyl alcohol; and alkenyl alcohols such as allyl alcohol and crotonyl alcohol.

One or more of the above acrylic monomers may be used, but if necessary, one of the other copolymerizable monomers may be used.
One species or two or more species may be used.

In this case, the acrylic monomer 2) E'? Monomer 5
It is desirable that it accounts for 0% by weight or more, preferably 60M or more.

Specific examples of other copolymerizable monomers include the following compounds.

That is, styrene and its derivatives, such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, flobylstyrene, methylstyrene, hexylstyrene,
Examples include hexylstyrene, octylstyrene-substituted alkylstyrene, fluorostyrene, chlorostyrene, bromostyrene, dipromostyrene, dihalogenated styrene such as iodostyrene, and furthermore nitrostyrene, acetylstyrene, methoxystyrene, and the like.

Also, polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethyl acrylic acid, crotonic acid, α-
Addition-polymerizable unsaturated aliphatic monocarboxylic acids such as methyl crotonic acid, α-ethyl crotonic acid, isocrotonic acid, tiglic acid, ungellic acid, or maleic acid, fumaric acid,
Examples include addition-type legal unsaturated aliphatic silcarboxylic acids such as itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, and dihydromuconic acid.

Furthermore, metal salts of these carboxylic acids can also be used, and this metal salt formation can be carried out after the completion of polymerization.

Further, examples thereof include esterified products of the above-mentioned addition polymerizable unsaturated carboxylic acid and alcohols such as alkyl alcohols, halogenated alkyl alcohols, alkoxyalkyl alcohols, aralkyl alcohols, and alkenyl alcohols.

9L, amides and nitriles derived from the addition-polymerizable unsaturated carboxylic acids; aliphatic monoolefins such as ethylene, propylene, butene, and imbutylene; vinyl chloride, vinyl bromide, vinyl iodide, L2-) chloroethylene, Halogenated aliphatic olefins such as L2-diglomoethylene, L2-short ethylene, isoprodinyl chloride, impropenyl bromide, allyl chloride, allyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; L3-butadiene, L3-pentadiene, 2-methyl-L3-butadiene, Z3-dimethyl-L3-butadiene, Z4-
Examples include conjugated diene aliphatic diolefins such as hexadiene and 3-methyl-2,4-hexadiene.

Further examples include vinyl acetates, vinyl ethers, and nitrogen-containing vinyl compounds such as vinyl carbazole, vinyl pyridine, and vinyl pyrrolidone.

The particle size of the carrier needs to be 50 μm or more as an average particle size, but from the viewpoint of adhesion of the carrier to the photoreceptor and image quality, it is preferably 50 μm to 200 μm1 and preferably 6 μm.
It is 0 to 150 μm. When the average particle size is 50 μm or less, the phenomenon of adhesion to the photoreceptor occurs and the life of the developer is shortened.

Possible materials include, for example, magnetite, gamma hematite, red iron, chromium oxide, nickel, manganese, iron, cobalt, and nickel alloys. These magnetic powders have an average particle size of 0.05μ to 5μ, preferably 0.1μ to
1μ is good. In addition, the proportion of magnetic powder in the total carrier components is 30 to 95) IIE amount, preferably 45 to 9
0 weight chi is good.

These carriers made of magnetic powder and binder resin depend on the seeding method! ll can be manufactured. For example, a method in which resin and magnetic powder are melt-kneaded using a Banbury mixer, Nigu, roll mill, extruder, etc., cooled, pulverized, and classified, or a spray method in which magnetic powder is mixed and fractionated in a resin solution and then spray-dried. By a dry method, or by dispersing predetermined materials such as monomers and resin components to constitute the binder resin in a suitable solvent and polymerizing this suspension,
Suspension polymerization methods and the like can be applied to obtain the desired carrier. In addition, the particle size of the carrier can be adjusted by controlling the pulverization conditions after melt-kneading, by obtaining the desired particle size by classification, or by preparing multiple types of carrier particles with different particle size distributions in advance. There is a method of preparing a carrier in advance and mixing it to obtain a carrier having the entire desired particle size distribution.

In the present invention, the carrier described above can be used as it is as carrier particles, but the surface of the carrier can also be subjected to surface treatment or coating treatment with a resin, a coupling agent, an interfacial agent, a charge control agent, a fine powder, etc.

Further, the carrier particles are preferably spherical particles that have been subjected to a spherical treatment.

The toner used in the present invention is fine particles in which a colorant is completely dispersed in a binder resin, and the average particle size is, for example, 3 to 2.
0 μm, preferably 5 to 18 μm.

Any known binder resin can be used for the toner. For example, homopolymers or copolymers of styrene and its derivatives such as styrene, vinyltoluene, α-methylstyrene, chlorostyrene, and aminostyrene, methacrylic acid and methacrylic acid esters such as methyl methacrylate, ethyl meth 2-lylate, and methyl methacrylate. , acrylic acid and methyl acrylate, ethyl acrylate, butyl acrylate, acrylic esters such as 2-ethylhexyl acrylate, dienes such as butadiene and isoprene, acrylonitrile, vinyl ethers, maleic acid and maleic esters, maleic anhydride , homopolymers or copolymers of vinyl monomers such as vinyl chloride and vinyl acetate, polyesters, polyamides, polyurethanes, epoxy resins, polycarbonates, silicone resins, fluororesins, phenolic resins, petroleum resins, rosins and their derivatives , pedestals, natural waxy substances, etc. can be used alone or in a mixed form.

Coloring agents include carbon blank, oil black, black dyes and pigments such as graphite, nigrosine dye, aniline blue, alcoil blue, chrome yellow, ultramarine blue, Typhon oil retsch, cow Norin yellow, methylene blue, and phthalocyanine blue. , malachite, lamp black, rose bengal, etc., as well as C,
Acetoacetate arylamide-based disazo yellow pigments such as Co., Ltd., Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 74, Tsukasa 97, and 98; Acetoacetate arylamide disazo yellow pigments such as C0 Co., Ltd., Pigment Yellow 12, Pigment Yellow 13, and 14. ,C,
■, Nrubento Yellow 19, PI77, PI79, C1
Yellow dye such as Ko-・Desnogus Yellow 164, C0
Engineering, Pigmentlets) '48. 49:1. 53:1
, 57:1. 81. 122, 5th grade red or purple pigment, C, ■.

Solvent Red 52% Solvent Red 58% 8th grade red dye,
C0■, Pigment Blue 1s: 3. Examples include blue pigments such as the same phthalocyanine and its derivatives or modified products, and other colored or colorless sublimable dyes.

Additionally, various additives can be added to the toner. Examples of additives include charge control agents, fluidity improvers (silica, alumina, etc.), fixing aids (waxes), plasticizers, and the like.

The toner can be produced by a method similar to that of the carrier described above, and is composed of a core material and a wall material. It may also be a so-called microcapsule toner.

The toner and carrier are preferably mixed in an amount of 2 to 30 parts by weight, preferably 3 to 20 parts by weight, per 100 parts by weight of the carrier.

Furthermore, an external additive may be added to the developer according to the present invention. Examples of the external additives include commonly used external additives such as abrasives, fluidity improvers, and anti-filming agents.

External additives that can be suitably used in the present invention include fine powders of acrylic polymers or copolymers such as alumina, silica, polyacrylate, and polymethacrylate.

An electrophotographic process to which the developing method of the present invention is applied will be explained based on the drawings.

FIG. 1 is a schematic diagram of an example of an apparatus for implementing the electrophotographic developing method of the present invention. The photoreceptor 1 has a photoconductive layer on its surface and first passes through a charging device M2 along the process direction. The charging device 2 has a mechanism for generating corona discharge,
The photoconductive layer of the photoreceptor 1 that has passed is uniformly charged.

After that, the uniformly charged photoconductive layer passes through the exposure slit 3 and uses its photoconductivity to form an electrostatic latent image corresponding to image information, which is then transported to the next developing section. be done. The developing section is composed of a housing 5 having a developer supply source 4 therein, a developer and a developing roll 6 carrying the developer, and converts the electrostatic latent image conveyed to the developing section. By rubbing with the developer carried on the surface of the developing roll, toner is attached to the latent image by electrostatic force, and the latent image is visualized. The visualized image area then comes into contact with the transfer material conveyed from the paper feed section 7 via the paper feed roll 8 at the transfer device portion. The transfer device 9 also has a mechanism for generating corona discharge. The toner image corresponding to the latent image passing through the transfer device is attracted onto the transfer material, and a toner image is completely formed on the transfer material.

Next, the transfer material is peeled off from the photoreceptor by a peeling member 10 and conveyed to a fixing device 11, where a permanent toner image is formed on the transfer material by heating or pressure.

In the electrophotographic process, the developing section used in the developing method of the present invention includes a housing 5 having a developer supply source 4 therein, a developer and a developing roll 6 carrying the developer.
As shown in an enlarged view in FIG. 2, the developing roll consists of a non-magnetic conductive cylindrical developing sleeve 12 that carries developer and a magnet member 13 disposed inside the developing sleeve 12.
The developer is carried on the developing sleeve 12 by the magnetic attraction force of the magnetic member, forming a magnetic brush. In the developing method of the present invention, in particular, the magnet member inside the sleeve is fixedly disposed, and the rotation of the outer sleeve transports the developer, supplying the developer to the developing area facing the photoreceptor. This method can completely effectively prevent the carrier in the developer of the present invention from adhering to the surface of the photoreceptor, and can also provide very good images over a long period of time without reducing the charge i of the developer. Obtainable.

The magnet member fixedly disposed inside the sleeve is preferably disposed so as to form a repulsive magnetic field as shown in FIG. The corner stone member disposed to form a repulsive magnetic field in such a development area can be of any shape as long as it forms a repulsive magnetic field.
The shapes shown in Figures (al, Cbl and (cl) are available.

〔Effect of the invention〕

In the case of a development method in which the omega stone is fixed and the sleeve is rotated, the problem that occurs when using a developer containing a carrier of relatively small particle size consisting of a binder resin and magnetic powder is caused by the carrier being attached to the photoreceptor. By using the method of the present invention, phenomena such as image deterioration (decreased density, early generation of capri) due to the deterioration of the Teiden lid can be prevented by using magnetic powder as a carrier particle in a binder resin mainly composed of an acrylic electrolyte. This improvement was achieved by using a carrier with a relatively large particle size (50 μm or more) in which the particles were dispersed. In other words, it is possible to prevent the carrier from adhering to the photoreceptor without reducing the fine line reproducibility and solid area reproducibility, which are the advantages of using a small particle carrier.
Chargeability can be maintained and good images can be obtained over a long period of time.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to these Examples in any way.

Aoxt part of a copolymer (N total average molecular weight of about 20,000) of methyl methacrylate/styrene (80/20 CM weight ratio) and 70 parts by weight of magnetic iron oxide powder are heated and kneaded. This kneaded material was melted at 180°C and pulverized using a completely cold air treatment spray dryer, and the resulting powder was sieved to obtain a carrier according to the present invention (sample 1) having an average particle size of 100 μm and a particle size range of 53 to 200 μm. ) was obtained.

This carrier message was previously known as a carrier, that is, an insulating carrier (CuZn ferrite core coated with the same copolymer as in the example, average particle size 90 μm).
carrier: sample 2), conductive carrier (iron oxide powder with an average particle size of 100 μm: sample 3), and magnetic fine particle dispersed small particle size carrier (carrier with the same composition as in the example, after melting and kneading the electrolyte and magnetic powder. Average particle size after crushing and classification 2
5 μm: Evaluated as a developer together with sample 4).

The toner used was a toner with an average particle size of 11 μm consisting only of styrene-acrylic resin and carbon black, and the toner concentration was 10! For all other carriers, the toner density is ft.
A developer was prepared by mixing 3 parts by weight.

For these developers, using an apparatus configured as shown in FIG. 1 with a photoreceptor speed of 350 w/sec and a magnet-fixed magnetic sleeve speed of 550 wrr/sec, initial band density, solid image density, background contamination, and density were measured. Reproducibility, adhesion of carrier to photoreceptor, and band 1 when running 50,000 sheets! In addition, the test was conducted under high humidity (30℃, 80%L(,H,)) and low humidity (10℃, 30%R,f(・)) environmental conditions. The results shown in the following table were obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an example of an apparatus for implementing the electrophotographic developing method of the present invention, Fig. 2 is an enlarged view of the developing roll portion, Fig. 3 is an enlarged view of the developing nip portion, Fig. 4 (a), T 'b) and +c
> indicates an example of the structure of a developing magnet that forms a repulsive magnetic field. Symbols in the figure: 1... Photoreceptor; 2... Charging device; 3...
・Exposure slit; 4...Developer supply source: 5...Housing; 6...Developing roll; 7...Paper feeding section;
8... Paper feed roll; 9... Transfer device; 1
0... Peeling member; 11... Fixing device; 12... Developing sleeve; 13... Magnet member. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1) A two-component dry developer in which a toner is mixed with a carrier having an average particle diameter of 50 μm or more, which is made by dispersing fine magnetic particles in a binder resin mainly composed of an acrylic polymer, The cylindrical sleeve is rotated while being supported on a developing roll consisting of the cylindrical sleeve and a magnet member fixedly disposed inside the cylindrical sleeve, and the electrostatic latent image is brought into contact with the surface of the electrostatic latent image carrier. An electrophotographic development method characterized by imaging. 2) Claim 1, wherein the internal fixed magnet member is arranged to form a repulsive magnetic field at the development nip position.
The electrophotographic development method described in section.