JPH0693137B2 - Developer for electrostatic image development - Google Patents

Description

The present invention relates to a magnetic toner for visualizing an electrostatic latent image in an image forming method such as electrophotography and electrostatic recording.

[Prior Art] In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their applications have been widespread and demands on their image quality have become strict. For example, in copying an image such as a general document or book, it is required to reproduce extremely fine and faithful reproduction of fine characters without being crushed or broken.

However, the latent image on the photoreceptor of the image forming device is 100μ
In the case of a line image of m or less, the reproducibility of fine lines is generally poor, and the sharpness of the line image is still insufficient.

Further, recently, in an image forming apparatus such as an electrophotographic printer that uses a digital image signal, a latent image is formed by gathering dots having a constant potential, and a solid portion, a halftone portion, and a light portion have a dot density. It is expressed by changing.

However, when the toner particles do not faithfully adhere to the dots and the toner particles protrude from the dots, it is impossible to obtain the gradation of the toner image corresponding to the ratio of the black and white dot densities of the digital latent image. There is a problem. Furthermore, in order to improve the image quality, when the dot size is reduced to improve the resolution, the reproducibility of the latent image formed from minute dots becomes more difficult, resulting in poor resolution and gradation, and sharpness. The image tends to be lacking in size.

Further, although the image quality is good at the initial stage, the image quality may deteriorate during continuous copying or printing. It is considered that this development is caused by the fact that only the toner particles that are easily developed are first consumed and the toner particles with poor developability accumulate and remain in the developing machine while copying or printing out.

So far, some developers have been proposed for the purpose of improving image quality.

JP-A-51-3244 proposes a non-magnetic toner intended to improve the image quality by regulating the particle size distribution. Among the toners, the toner having a particle diameter of 8 to 12 μm is mainly used, and it is relatively coarse. According to the study by the present inventors, it is difficult to obtain a uniform “paste” on the latent image. Also, 5 μm or less is 30% by number or less, and 20 μm or more is 5
From the characteristic of being less than the number%, the uniformity of the particle size distribution also tends to be low in that it is broad. In order to form a clear image using a toner having such a coarse toner particle and a broad particle size distribution, the toner particles are superposed in a thick manner to fill the gaps between the toner particles to form an apparent image. There is also a problem that it is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density increases.

Further, Japanese Laid-Open Patent Publication No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former, but the size of particles having an intermediate weight is as coarse as 8.5 to 11.0 μm, and high resolution is obtained. As a toner of No. 5, there is still room for improvement. JP-A-58-129437 proposes a non-magnetic toner having an average particle size of 6 to 10 μm and a maximum number of particles of 5 to 8 μm. However, the number of particles of 5 μm or less is as small as 15% by number or less, and an image lacking sharpness tends to be formed.

Further, US Pat. No. 4,299,900 proposes a jumping developing method using a developer having 10 to 50% by weight of a magnetic toner of 20 to 35 μm. That is, the magnetic toner is triboelectrically charged, the toner layer is evenly and thinly coated on the sleeve, and the toner particle size is devised so as to improve the environment resistance of the developer. However,
Considering more stringent requirements such as fine line reproducibility and resolution,
It is not sufficient and further improvement is required.

[Problems to be Solved by the Invention] Under such circumstances, the present inventors have a problem that long ears (toner particle chains) of magnetic toner and disturbed ears are present on the sleeve surface in the developing region. The present invention has been discovered, and the present invention has been clarified and the present invention has been achieved.

According to the studies made by the present inventors, it was found that toner particles having a particle size of 5 μm or less clearly reproduce the contour of the latent image and have a main function of fine toner paste to the entire latent image. In particular, in the electrostatic latent image on the photoconductor, electric field lines are concentrated, so that the electric field strength is higher at the edge portion which is the contour than inside, and the sharpness of the image quality is determined by the quality of the toner particles gathered at this portion. According to the study by the present inventors, it was found that the amount of particles of 5 μm or less is effective for solving the problem of sharpness of image quality.

However, when the particle size of the toner is reduced, the unit surface area per unit weight of the toner particle is increased, so that the charge amount per toner particle is increased. Therefore, as the particle size is reduced, the magnetic toner has a large amount of charge due to frictional charging, and gradually becomes overcharged.

Therefore, simply reducing the toner particle size, which is conventionally used, tends to cause excessive charging, and the charge amount further increases when used in low humidity, high speed machines, etc. In many cases, it causes rustling, scattering, and a decrease in image density.

Even with a small particle size magnetic toner, which has a thin and uniform toner coat and is advantageous against uneven sleeve coat, uneven sleeve coat may occur under severe usage conditions.

From the above, there is a need for a developer capable of maintaining the high image quality achieved by the small particle size magnetic toner for a long period of time under any conditions of use, that is, under any environment and model.

An object of the present invention is to provide a developer which solves the above problems.

A further object of the present invention is to provide a developer having a high image density, reproducibility of fine lines without fog and excellent gradation.

A further object of the present invention is to provide a developer which does not change its performance even after continuous use for a long time.

A further object of the present invention is to provide a developer which has no change in performance with respect to environmental changes and has excellent durability.

A further object of the present invention is to provide a developer having excellent transferability.

Further, an object of the present invention is to provide a developer capable of obtaining a high image density with a small consumption amount.

Further, an object of the present invention is to provide a developer capable of forming an image excellent in resolution, gradation and fine line reproducibility even in an image forming apparatus using a digital image signal.

[Means and Actions for Solving the Problems] More specifically, the present invention is a developer for developing an electrostatic charge image containing a positively chargeable magnetic toner containing at least a binder resin and magnetic powder. In 17 to 60% by number of magnetic toner particles having a particle size of 5 μm or less are contained.
The magnetic toner particles having a particle diameter of 8 to 12.7 μm are contained in an amount of 1 to 33% by number, the magnetic toner particles having a particle diameter of 16 μm or more are included in an amount of 0.5% by volume or less, and the volume average particle diameter of the magnetic toner is 4 to 10 μm, the triboelectrification characteristic with iron powder is 50 μc / g (absolute value) or less, and the number average particle diameter is 0.5.
Carbon allotrope or metal oxide as a charge relaxation agent fine powder having a particle size of μm or less is internally or externally added to the magnetic toner particles, and positively chargeable hydrophobic silica fine powder is externally added to the magnetic toner particles. The present invention relates to a developer for developing an electrostatic charge image.

The magnetic toner of the present invention having the above particle size distribution can faithfully reproduce even the fine lines of the latent image formed on the photoconductor, and reproduces dot latent images such as halftone dots and digital images. It also provides an image excellent in gradation and resolution. In addition, high image quality can be maintained even when copying or printing is continued, and even in the case of high-density images, good development can be performed with less toner consumption than conventional magnetic toner, which is economical. Also, it has an advantage in downsizing of the copying machine or the printer body.

The reason why such effects are obtained in the magnetic toner of the present invention is not necessarily clear, but it is presumed as follows.

That is, one feature of the magnetic toner of the present invention is that the magnetic toner particles having a particle diameter of 5 μm or less account for 17 to 60% by number. In the conventional magnetic toner, magnetic toner particles having a particle size of 5 μm or less are difficult to control the charge amount, impair the fluidity of the magnetic toner, and are a component that scatters the toner and stains the machine, and further causes image fogging. As an ingredient, it was considered necessary to actively reduce it.

However, according to the study by the present inventors, it was found that magnetic toner particles having a particle size of 5 μm or less are an essential component for forming a high quality image.

For example, by using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm, the surface potential on the photoconductor is changed, and a large development potential contrast, in which a large number of toner particles are easily developed, to a halftone, and a very small amount The latent image with the surface potential changed on the photoconductor is developed up to a small development potential contrast where only the toner particles are developed, and the developed toner particles on the photoconductor are collected and the toner particle size distribution is measured to be 8 μm or less. It was found that there are many magnetic toner particles, especially many magnetic toner particles of 5 μm or less. That is, when the magnetic toner particles having a particle diameter of 5 μm or less, which is most suitable for development, are smoothly supplied to the development of the latent image on the photoconductor, they are faithful to the latent image and do not protrude from the latent image and are truly reproducible. You will get an excellent image of.

In addition, one feature of the magnetic toner of the present invention is that the number of particles in the range of 8 to 12.7 μm is 1 to 33% by number. This is related to the necessity of the presence of magnetic toner particles having a particle size of 5 μm or less, as described above, and the magnetic toner particles having a particle size of 5 μm or less have the ability to exactly cover the latent image and faithfully reproduce it. However, in the latent image itself, the electric field strength of the peripheral edge portion is higher than that of the central portion, so that the inside of the latent image has thinner toner particles than the edge portion,
The image density may appear light. In particular, the magnetic toner particles of 5 μm or less have a strong tendency. However, the present inventors have found that the problem can be solved and further improved by containing 1 to 33% by number of toner particles in the range of 8 to 12.7 μm. That is, 8
It is considered that the toner particles in the range of particle size of ˜12.7 μm have an appropriately controlled charge amount with respect to the magnetic toner particles of particle size of 5 μm or less, but the electric field strength is smaller than the edge portion of the latent image. It is supplied to the inside to compensate for the small amount of toner particles inside the edge portion to form a uniform developed image, resulting in a sharp image with excellent resolution and gradation at high density. Is provided.

Further, the number% of particles having a particle size of 5 μm or less
The magnetic toner of the present invention satisfies the relationship of N / V = -0.04N + k (where 4.5≤k≤6.5 and 17≤N≤60) between (N) and volume% (V). Preferred, along with other features
The magnetic toner of the present invention having a particle size distribution satisfying this range can achieve more excellent developability.

The present inventors, while studying the state of the particle size distribution of 5 μm or less, found that there is a fine powder existence state that is most suitable for achieving the purpose as shown by the above formula. That is, for a certain N value, a large N / V indicates that particles with a size of 5 μm or less are widely included, and a small N / V indicates a high abundance near 5 μm. , It is understood that there are few particles with a particle size smaller than that, N /
Good fine line reproducibility and high resolution are achieved when the value of V is in the range of 2.1 to 5.82, N is in the range of 17 to 60, and the above relational expression is further satisfied. However, the developer of the present invention has a margin in the range of the magnetic toner, and even if it deviates from this range, it is not bad.

For magnetic toner particles having a particle size of 16 μm or more,
It is preferably 0.5% by volume or less, and as small as possible.

By a completely different concept from the conventional viewpoint, the magnetic toner of the present invention solves the conventional problems and is capable of withstanding the recent demands for high image quality.

The configuration of the present invention will be described in more detail.

Magnetic toner particles with a particle size of 5 μm or less are 17-60 of the total number of particles.
%, Preferably 25 to 50% by number, more preferably 30 to 50% by number. When less than 17% by number of magnetic toner particles having a particle diameter of 5 μm or less, there are few magnetic toner particles effective for high image quality. Particularly, as the toner is used by continuing copying or printing out, the effective magnetic toner particles are effective. The components are decreased, the balance of the particle size distribution of the magnetic toner as shown in the present invention is deteriorated, and the image quality is gradually deteriorated. On the other hand, if it exceeds 60% by number, magnetic toner particles tend to aggregate with each other, resulting in toner lumps having a particle size larger than the original particle size, resulting in rough image quality, lower resolution, or edge of latent image. The density difference between the inner part and the inner part becomes large, and the image tends to be hollow.

Particles in the range of 8 to 12.7 μm are preferably 1-33% by number, and more preferably 8-20% by number. If it is more than 33% by number, the image quality is deteriorated, and more than necessary development, that is, excessive toner overload occurs, resulting in an increase in toner consumption. On the other hand, if it is less than 1% by number, it becomes difficult to obtain a high image density.

In addition, as described above, it is preferable that the number% (N%) and the volume% (V%) of the magnetic toner particle group having a particle size of 5 μm or less are satisfied. There is a relationship of N / V = -0.04N + k. In this relationship, k is 4.5 ≦ k as described above.
Positive number in the range of ≦ 6.5, but preferably 4.5 ≦ k ≦ 6.0
And N is 17 ≦ N ≦ 60 as shown above, but preferably 25 ≦ N ≦ 50.

When k <4.5, the number of magnetic toner particles having a particle size smaller than 5.0 μm is small, resulting in poor image density, resolution and sharpness. The proper presence of fine magnetic toner particles, which has been conventionally considered unnecessary, contributes to close packing of toner in development and formation of a uniform image without roughness. In particular, by evenly filling the fine lines and the contour portion of the image, the sharpness is visually enhanced. That is, when k <4.5, these properties are inferior due to the lack of the particle size distribution component.

From another point of view, in terms of production, it is necessary to cut a large amount of fine powder by classification or the like in order to satisfy the condition of k <4.5, which is disadvantageous in terms of yield and toner cost.
When k> 6.5, the presence of more fine powder than necessary causes
The image density tends to decrease as the copying is repeated. Such a phenomenon is caused by an excess amount of finely powdered magnetic toner particles having an unnecessarily large amount of electric charge, which is charged and adhered on the developing sleeve to prevent the normal magnetic toner from being carried and charged on the developing sleeve. It is thought that this will occur.

If the magnetic toner particles having a particle diameter of 16 μm or more is 0.5 volume% or less, fine line reproducibility is excellent, and coarse toner particles of 16 μm or more are projected on the thin layer surface of the toner particles developed on the photoconductor during transfer. In addition, a good contact state is formed between the photoconductor and the transfer paper via the toner layer, and the transfer condition does not fluctuate, so that a good transfer image can be formed.

The volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 to
The value is 9 μm, and this value cannot be considered without distinction from the above-mentioned constituent elements. When the volume average particle diameter is 4 μm or less, the amount of toner adhered on the transfer paper is small in an application having a high image area ratio such as a graphic image,
The problem of low image density is likely to occur. It is considered that this is due to the same reason as the reason why the internal density is lowered with respect to the edge portion in the latent image described above. If the volume average particle is 10 μm or more, the resolution is not good, and at the beginning of copying, if the use is continued at all, the image deterioration is likely to occur.

True density of the magnetic toner of the present invention is preferably from 1.30~1.90g / cm ^3, more preferably from 1.40~1.80g / cm ^3. In this range, the magnetic toner having a specific particle size distribution of the present invention can exert the most effect in terms of high image quality and durability stability. When the true density of the magnetic toner is less than 1.30, the weight of the magnetic toner particles themselves is too light, and the reversal fog and the excessive sticking of the toner particles tend to cause the thin lines to be crushed, popped, and the resolution to deteriorate. Also, if the true density of the magnetic toner is larger than 1.90, the image density will be thin and the image will lack sharpness such as broken fine lines.Because the magnetic force will also become relatively large, the ears of the toner will become long or branched. In this case, when the latent image is developed, the image quality is disturbed and a rough image is likely to occur.

In order to obtain even better developing characteristics, the magnetic toner of the present invention has a residual magnetization σr of 0.5 to 6 emu / g and a saturation magnetization σ
It is preferable that s is 15 to 40 emu / g and the coercive force Hc is 20 to 100 ested (Oe) (the measured magnetic field is 1 KOe in each case).

As the binder resin used in the toner of the present invention, the following binder resin for toner can be used when a heating and pressure roller fixing device having a device for applying oil is used.

For example, homopolymers of styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene and their substitution products; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers. , Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl Styrene-based copolymers such as ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, ethylene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol Resin, natural modified fiber Nole resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin , Petroleum resin can be used.

In the heating and pressure roller fixing method in which oil is hardly applied, the so-called offset phenomenon in which a part of the toner image on the toner image supporting member is transferred to the roller and the adhesion of the toner to the toner image supporting member are important problems. is there. Toners that fix with less heat energy usually tend to be blocked or caked during storage or in a developing device, so these problems must be taken into consideration at the same time. Although the physical properties of the binder resin in the toner are most involved in these phenomena, studies by the present inventors have revealed that when the content of the magnetic material in the toner is reduced, the toner image supporting member is fixed during fixing. Adhesion of the toner to the toner is improved, but offset is likely to occur, and blocking or caking is likely to occur. Therefore, the selection of the binder resin is more important when the heating and pressure roller fixing method in which the oil is hardly applied is used in the present invention. Preferred binder materials include crosslinked styrenic copolymers or crosslinked polyesters.

Examples of the comonomer for the styrene monomer of the styrene-based copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid. Acids, monocarboxylic acids having a double bond such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide and the like; or maleic acid, butyl maleate, etc. Dicarboxylic acids having double bonds such as methyl maleate, dimethyl maleate and the like, and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc .; for example ethylene, propylene Ethylenic olefins such as butylene; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl monomers such as Are used alone or in combination of two or more.

As the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, and examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate.
Carboxylic acid ester having two double bonds such as ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and 3 or more vinyls A compound having a group; is used alone or as a mixture.

When the pressure fixing method is used, it is possible to use a binder resin for pressure fixing toner such as polyethylene,
Polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

In the magnetic toner of the present invention, it is preferable to use a charge control agent in the toner particles (internal addition) or to mix with the toner particles (external addition). The charge control agent makes it possible to control the optimum charge amount according to the developing system, and particularly in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge. It is possible to further clarify the function separation and the mutual complementarity for improving the image quality depending on the particle size range as described above. Examples of positive charge control agents include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate; dibutyltin oxide, dioctyltin. Diorganotin oxides such as oxides and dicyclohexyltin oxide; dibutyltin borate,
Diorgano tin borates such as dioctyl tin borate and dicyclohexyl tin borate may be used alone or in combination of two or more. Of these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

Also, the general formula R ₁ : H, CH ₃ R ₂ , R ₃ : substituted or unsubstituted alkyl group (preferably C ₁ ~
A homopolymer of a monomer represented by C ₄ ): or a copolymer with a polymerizable monomer such as styrene, acrylic acid ester, and methacrylic acid ester as described above can be used as a positive charge control agent. These charge control agents also have an action as (all or part of) a binder resin.

It is preferable to use the above-mentioned charge control agent (which does not function as a binder resin) in the form of fine particles. In this case, the number average particle diameter of the charge control agent is, specifically,
It is preferably 4 μm or less (further, 3 μm or less).

When internally added to toner, such a charge control agent is a binder resin.
It is preferable to use 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) per 100 parts by weight.

The magnetic toner of the present invention may be mixed with an additive as required. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used with respect to 100 parts by weight of the binder resin. Other additives include lubricants such as zinc stearate, abrasives such as silicon carbide, flowability-imparting agents such as colloidal silica, and anti-caking agents.

In addition, wax-like substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, sazol wax, and paraffin wax are added in an amount of 0.5 to 5 for the purpose of improving releasability at the time of heat roll fixing.
Addition of about wt% to the magnetic toner is also one of the preferable modes of the present invention.

Further, the magnetic toner in the present invention may also serve as a colorant, but contains a magnetic material. Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-excessive ferrite.
Metals such as iron, cobalt, nickel or these metals and aluminum, cobalt, copper, lead, magnesium,
Examples thereof include alloys with metals such as tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium, and mixtures thereof.

These ferromagnetic materials have an average particle size of 0.1-1 μm, preferably
It is preferably about 0.1 to 0.5 μm, and the amount contained in the magnetic toner is 40 to 150 parts by weight, preferably 60 to 120 parts by weight, based on 100 parts by weight of the resin component.

Further, as a result of earnest studies on the magnetic toner as described above, the present inventor has stabilized the chargeability of the toner by using a developer containing a specific substance, and has an environmental stability (especially under low humidity), It has been found that the durability can be improved.

The developer of the present invention is based on the above knowledge, and the magnetic toner having the above-mentioned particle size distribution and material constitution has a triboelectric charging property with iron powder of 50 μc / g (absolute value) or less, preferably 20
Fine particles of a charge easing agent having a number average particle diameter of 0.5 μm or less and μc / g (absolute value) or less are mixed with magnetic toner particles (internal addition) or mixed with magnetic toner particles (external addition). It is characterized by being used.

The content of the charge relaxation agent fine powder used in the present invention is, in the case of internal addition, 0.1 to 50 parts by weight, preferably 0.2 to 30 parts by weight, relative to 100 parts by weight of the binder resin, and in the case of external addition, Magnetic toner 1
0.01-5 parts by weight, preferably 0.02-3, relative to 00 parts by weight
Parts by weight.

Specific examples of the above charge easing agent include the following substances.

For example, substances consisting mainly of carbon atoms such as carbon black and graphite, magnesium oxide, alumina, titanium oxide, iron oxide, nickel oxide, copper oxide, chromium oxide, zinc oxide, tin oxide, cerium oxide, cobalt oxide, zirconium oxide, etc. Examples thereof include metal oxides mainly composed of metal atoms (one kind or many kinds) and oxygen atoms.
It is considered that these substances are less likely to be charged, or are exposed to moisture in the air, and easily release charges. In fact, the charge of these substances on iron powder is less than 20 μc / g (absolute value).

By including an appropriate amount of fine powders of these substances in the magnetic toner, it is possible to suppress excessive triboelectric charging and release excessively charged electric charges. That is, it is considered that these fine powders act as a charge easing agent that reduces the triboelectric charge amount of the magnetic toner to an appropriate size.

On the other hand, the magnetic toner of the present invention has a small particle size, and the charge amount is likely to be large, and the smaller the average particle size is, the larger the charge amount becomes, and the charge control becomes more difficult.

When these magnetic toners are overcharged, image defects such as rubbing, scattering, and density decrease occur. In addition, particles with a small particle size in the magnetic toner become overcharged, the mirroring power with the sleeve becomes strong, and they adhere to the sleeve surface, which interferes with the triboelectrification of the developer and causes particles with poor charging, causing fog. May increase, the image density may decrease, and uneven sleeve coat may occur.

Therefore, the smaller the particle size of the developer of the present invention, the more remarkable the effect.

The magnetic toner of the present invention has many particles of 5 μm or less, and the developer of the present invention is preferable in order to prevent excessive charging of these particles and control the charge amount of the magnetic toner. As a method of incorporating the charge relaxation agent fine powder into the developer of the present invention, there are an internal addition method and an external addition method. However, since the external addition method is more present on the surface of the magnetic toner, a small addition amount is required. Great effect can be expected. Further, when the effect is exerted in a very small amount or when it is easily detached from the surface of the magnetic toner, it is well dispersed in the developer, so that the addition amount can be increased or a method by internal addition for fixing to the surface of the magnetic toner is also possible. It is valid. Further, when the fine particles in the developer of the present invention have magnetism, the internal addition method can be used as long as it is within the range of desired magnetic characteristics required for the magnetic toner. However, when the magnetic characteristics of the magnetic toner are greatly affected, the addition amount can be reduced by external addition to achieve the purpose.

When the absolute value of triboelectricity exceeds 50 μc / g, the relaxation of charging may not be sufficient, and when the polarity is opposite to the polarity of the magnetic toner, fogging may increase or the density may decrease. May adversely affect sex.

If the number average particle size exceeds 0.5 μm, the dispersibility in the developer becomes poor, the particles may vary, the developability may be adversely affected, and a good image such as fogging may be provided. It may not be possible, and the smaller the average particle diameter of the magnetic toner of the present invention, the greater the influence.

When the content is more than the predetermined content, the amount of decrease in the charge amount becomes large under high humidity and the like, and image defects such as low image density occur. On the other hand, when the content is less than the predetermined content, the effect of alleviating the electrostatic charge cannot be exerted well, and the electrostatic charge is apt to be overcharged, which may cause a decrease in density and unevenness of the sleeve coat.

It is necessary to add fine silica powder to the magnetic toner of the present invention. A magnetic toner having a particle size distribution as a feature of the present invention has a larger specific surface area than conventional toners. When the magnetic toner particles are brought into contact with the surface of a cylindrical electric sleeve having a magnetic field generating means therein for frictional electrification, the number of contact between the toner particle surface and the sleeve is increased as compared with the conventional magnetic toner, It is easy for abrasion of toner particles and contamination of the sleeve surface to occur. When the magnetic toner according to the present invention is combined with the silica fine powder, the silica fine powder is present between the toner particles and the surface of the sleeve, so that the wear is remarkably reduced. As a result, the life of the magnetic toner and the sleeve can be extended, stable chargeability can be maintained, and a developer having a magnetic toner superior in long-term use can be obtained. further,
The magnetic toner particles having a particle diameter of 5 μm or less, which play a major role in the present invention, exhibit more effects in the presence of fine silica powder and can stably provide a high-quality image.

Furthermore, the present inventor has found that among the above-mentioned developers, some of the positively chargeable developers cause a decrease in the charge amount under high humidity and cause a decrease in the density, or the charge uniformity is impaired. It has been found that some developers have a lot of fog.

However, when the developer of the present invention is used as a positively chargeable developer, the silica fine powder added for preventing abrasion of the toner and stain on the sleeve surface is positively charged rather than negatively charged. It was found that the fine silica powder is preferable because it does not impair the charging stability, the concentration does not decrease even under high humidity, the charging is excellent, and the fogging is extremely small.

The developer of the present invention is based on the above findings, and is characterized in that it is used by incorporating the positively charged hydrophobic silica fine powder into the developer as described above.

As a method for obtaining the positively chargeable silica fine powder, the above-mentioned untreated silica fine powder is used and at least one nitrogen atom is contained in the side chain.
There is a method of treating with a silicone oil having three or more organo groups, a method of treating with a nitrogen-containing silane coupling agent, or a method of treating with both of them.

As the untreated silica fine powder referred to here, both silica fine powder produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, use the silica fine powder by the dry method. Is preferred.

The dry method referred to here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halogen compound. For example, in a method utilizing a thermal decomposition and diffusion reaction of silicon tetrachloride gas in oxygen hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl In the above manufacturing process, for example, by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound, a composite fine powder of silica and another metal oxide can be obtained. Are also possible and include them.

Examples of commercially available silica fine powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention include those commercially available under the following trade names.

AEROSIL 130 Aerosil Japan 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL (Ca-O-zil) M-5 (CABOTO Co.) MS-7 MS-75 HS-5 EH -5 Wacker HDK N 20 (Wacker HDK.N20) V15 (WACKER-CHEMIE GMBH) N20E T30 T40 DC Fine Silica (Dow Corning Co.) Fransol (Fransol) (Frandil) On the other hand, as a method for producing the silica fine powder used in the present invention by a wet method, various conventionally known methods can be applied.
For example, the decomposition of sodium silicate by an acid and the general reaction formula are shown below.

Na ₂ O ・ XSiO ₂ ＋ HCl ＋ H ₂ O → SiO ₂・ nH ₂ O ＋ NaCl Others, decomposition of sodium silicate with ammonia salts or alkali salts, decomposition of sodium silicate by acid after generating alkaline earth metal silicate There are a method of making silicic acid, a method of making a sodium silicate solution into silicic acid by an ion exchange resin, a method of using natural silicic acid or a silicate, and the like.

Any of silica silicates such as anhydrous silicon dioxide (silica) and aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate, etc. can be applied to the silica fine powder.

Examples of commercially available silicic acid fine powders synthesized by the wet method include those commercially available under the following trade names.

Carplex Shionogi Nepseal Nippon Silica Tokseal, Fineseal Tokuyama Soda Vitaseal Takihi Shilton, Shirnex Mizusawa Kagaku Starsil Kamijima Kagaku Himejiru Ehime Yakuhin Syroid Fuji-Dilson Hi-Sil Pittsburgh Plate Glass.Co. (Pittsburgh Plate Glass) Durosil Ultorasil Ultra-Ultra Fiillstoff-Gesells chaft Marquart Manosil Hardman and Holden Hoesch Chemische Fabrik Hoesch KG Chemische Fabrik Hoesch KG Sil-Stone Stoner Rubber Co. Nalco Nalco Chem. Co. Quso Philadelphia Quartz Co. Imil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch. KG Calsil Fiillstoff-Gesellschaft Marquart Imperial Chemical Industries. Ltd. (Chemical) Joseph Crosfiels & Sons. Ltd. (Joseph Crossfield & Sons) Manosil (Manosir) Hardman and Holden (Vulkasil) Farbenfabriken Bryer.A .-G. (Farben Fabry-Kenbayer) Tufknit Durham Chemicals. Ltd. (Doulham Chemicals) Sylmos Shiraishi Kogyo Starlex Kamishima Chemical Fricosyl Polywood Manure Of the above silica fine powders, those having a specific surface area of 30 m ² / g or more (particularly 50 to 400 m ² / g) by nitrogen adsorption measured by the BET method give good results.

In the present invention, the positively chargeable silica refers to one having a positive triboelectric charge with respect to the iron powder carrier when measured by the blow-off method.

As the silicon oil having a nitrogen atom in the side chain used for the treatment of the silica fine powder, a silicon oil having at least a partial structure represented by the following formula is used.

(In the formula, R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represent hydrogen, an alkyl group or an aryl group, and R ₅ Represents a nitrogen-containing heteroenvironment) The alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, and a substituent such as halogen within a range not impairing the charging property. May have.

The nitrogen-containing silane coupling agent used in the present invention generally has a structure represented by the following formula.

Rm-Si-Yn (R represents an alkoxy group or halogen, Y represents an amino group or an organo group having at least one nitrogen atom, m and n are integers of 1 to 3 and m + n
= 4. Examples of the organo group having at least one nitrogen atom include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group.
As the nitrogen-containing heterocyclic group, there are an unsaturated heterocyclic group and a saturated heterocyclic group, and known ones can be applied.
Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the followings.

The heterocyclic group used in the present invention is preferably a 5-membered ring or a 6-membered ring in view of stability.

Examples of such treating agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, and monobutylsilane. Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ
-Propylphenylamine, trimethoxysilyl-γ-
There are propylbenzylamine and the like, and as the nitrogen-containing heterocycle, those having the above structure can be used. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, Examples include trimethoxysilyl-γ-propylimidazole and the like.

The applied amount of these treated positively charged positive silica fine powders is
The effect is exhibited when the amount is 0.01 to 8 parts by weight with respect to 100 parts by weight of the positively chargeable magnetic toner, and particularly preferably, the positive chargeability having excellent stability is exhibited when 0.1 to 5 parts by weight is added. With respect to the addition form, to describe a preferred embodiment, it is preferable that 0.1 to 3 parts by weight of the treated silica fine powder is attached to the surface of the toner particles with respect to 100 parts by weight of the positively chargeable magnetic toner.

The silica fine powder used in the present invention may be treated in combination with a treatment agent such as a charge amount adjusting silane coupling agent, silicone oil, or an organic silicon compound for the purpose of making it hydrophobic, if necessary. It is treated with the above-mentioned treatment agent that reacts with the body or physically adsorbs. Examples of such a treating agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimesyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyldimethylchlorosilane. , Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyl Dimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-dif Sulfonyl tetramethyldisiloxane, and has from one molecule per 2 12 siloxane units, there is a dimethylpolysiloxane having a hydroxyl group bonded to Si addressed one each unit located at the ends.

As the silicone oil, one represented by the following formula is generally used.

A preferred silicone oil having a viscosity at 25 ° C. of about 5 to 5000 centistokes is used.
For example, methyl silicone oil, dimethyl silicone oil, phenyl methyl silicone oil, chlorophenyl methyl silicone oil, alkyl modified silicone oil, fatty acid modified silicone oil, polyoxyalxin modified silicone oil, etc. are preferable. These are 1
Used as a seed or a mixture of two or more kinds.

Incorporation of the above positively-charged hydrophobic silica fine powder in the developer further improves the charging stability, so that the latitude of the charge-releasing fine powder can be widened.

Further, according to the study by the present inventors, it was found that when the developer of the present invention is applied for electrostatic image development, scratches on the surface of the photoconductor and abrasion of the surface are increased. However, in order to reduce or prevent these developments, the magnetic toner is
It has been found that it is preferable to contain the fluorine-containing resin fine particles.

Examples of the fluorine-containing resin fine particles in the present invention include the following fine particles of a homopolymer of a fluorine-containing monomer, a copolymer of two or more kinds, or a copolymer with another monomer. Examples of the fluorine-containing monomer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, 1-chloro-1,2-difluoroethylene, 1,2-dichloro-1,2-difluoroethylene, Bromtrifluoroethylene, 3,3,3-trifluoropropene, 3-chloro-3,3-difluoro-1-propene, 3
-Fluoro-3,3-dichloro-1-propene, 1-chloro-
1-fluoroethylene, 1,1-difluoro-2-chloroethylene, 1,1-dichloro-2-fluoroethylene, 1-chloro-2,2-difluoroethylene, 1,1-dichloro-2,2 -Difluoroethylene, chlorotrifluoroethylene, 1-bromo-1-fluoroethylene, 1-chloro-2-fluoroethylene, fluorine-substituted compounds of acrylic acid and methacrylic acid, and derivatives thereof. Particularly preferred are tetrafluoroethylene, vinylidene fluoride, and tetrafluoroethylene-vinylidene fluoride copolymer fine particles, and more preferably the formula when measured in acetone by F ¹⁹ nuclear magnetic resonance method. [In the formula, Sa represents the area of the absorption peak at approximately −23.5 ± 1 ppm, Sb represents the area of the absorption peak at approximately −27.5 ± 1 ppm, Sc represents the area of the absorption peak at approximately −45.8 ± 1 ppm, and Sd represents Shows the area of the absorption peak at approximately -48.1 ± 1 ppm (However, 1,1,2-trichloro-1,2,2
-Using trifluoroethane)].

These F ¹⁹ NMR absorption spectra, for example J. Polymer SeiA
l As shown on page 1305 (1963), the vinylidene fluoride polymer Absorption based on the chemical shift of.

That is, the absorption of −23.5 ppm is due to the repeated absorption of regular head-to-tail bonds of CF ₂ —CH ₂ units. The measurement method by F ¹⁹ -nuclear magnetic resonance is as follows. The sample is extracted at a temperature from room temperature to 50 ° C, and its acetone solution or heavy acetone solution is used for the measurement. The measurement was performed using an FX-90Q type high resolution NMR device manufactured by JEOL Ltd. at an observation frequency of 84.25 MHz, an observation width of 9000 Hz, and an offset frequency of 55.33 KHz.

Chemical shifts are shown based on 1,1,2-trichloro-1,2,2-trifluoroethane. At this time, CF ₂ 4
Two chemical shifts are −23.5 ± 1ppm, −27.5 ± 1ppm, −
The values were 45.8 ± 1ppm and -48.1 ± 1ppm. At this time, when the toner extract and the vinylidene fluoride polymer were measured, respectively, the chemical shifts of both were substantially the same and there was no difference. From the integrated values of these peaks, Sa, S
b, Sc, Sd were calculated.

The particle diameter of the fluorine-containing resin fine particles in the present invention is 0.05 to 1 μm.
m, particularly preferably 0.1 to 0.5 μm. If the particle size exceeds 1.0 μm, the dispersion between the toner particles is not sufficient, the fluidity and lubricity cannot be imparted to the toner, and the effect is not exhibited. Also,
If it is less than 0.05 μm, the surface of the toner is covered with ultrafine particles, so that the chargeability of the toner is impaired and the effect cannot be obtained.
Further, the shape is preferably powdery and close to a sphere.

The fluorine-containing resin fine particles in the invention are mixed in the developer in the invention by internal addition or external addition.
When the fine particles are externally added and mixed, the addition amount to the magnetic toner is preferably 0.01 to 2.0% by weight, particularly 0.02 to 1.0% by weight, and when internally added and mixed, 0.5 to 5% by weight, particularly 2 to
4% by weight is preferred.

Conventionally, these fluorine-containing fine particles have been known to be a friction-reducing substance that prevents fusion or filming of the developer to the surface of the photoreceptor by being contained in the developer. As a result of diligent research, a unique effect was found to reduce or prevent the increase in abrasion of the surface of the photoreceptor and the occurrence of scratches on the surface when applied to the above-mentioned developer. Although the reason for the effect is not clear, when the developer of the present invention is used, since the unit surface area per unit weight of the developer particles becomes large, it is considered that residual developer during cleaning after transfer on the photosensitive member. The contact area with the photoconductor increases, and the photoconductor surface is easily abraded. However, since the fluorine-containing fine particles are present on or near the surface of the developer,
It is considered that since the contact area between the developer and the photoreceptor is reduced, the occurrence of abrasion and scratches on the surface of the photoreceptor can be reduced or prevented.

In particular, in the magnetic toner in which the above-mentioned fine powder and the above fine particles are combined, although the reason is not clear, it stabilizes the existence state of the fine powder adhering to the toner, for example, the adhered fine powder is released from the toner. In addition, the effects on toner abrasion and sleeve stain are not reduced, and the charging stability can be further increased.

As described above, the latitude of the developer of the present invention is widened, which is preferable.

In producing the magnetic toner according to the present invention, the magnetic toner constituent materials as described above are thoroughly mixed by a ball mill or other mixing machine, and then well kneaded by using a heat kneader such as a heat roll kneader or an extruder, followed by cooling. After solidification, a method of obtaining a magnetic toner by mechanical pulverization and classification is preferable. Alternatively, a method of obtaining a magnetic toner by spray drying after dispersing the constituent materials in a binder resin solution,
Alternatively, a polymerization toner manufacturing method in which a predetermined material is mixed with a monomer to form a binder resin to form an emulsion suspension and then polymerized to obtain a magnetic oner; or a so-called micro toner composed of a core material and a shell material is used. In the encapsulated toner, a method such as a method of incorporating a predetermined material into the core material or the shell material or both of them can be applied. Further, if necessary, desired additives can be sufficiently mixed with a mixer such as a Henshur mixer to produce the developer for developing an electrostatic charge image according to the present invention.

The developer of the present invention can be used by any conventionally known means for one-component development for developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing and the like.

Further, the developer of the present invention is preferably applied to an image forming method for developing a latent image while causing toner to fly from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoconductor. That is, the developer is tribo-charged mainly by contact with the sleeve surface and is applied in a thin layer on the sleeve surface. The thin layer of the developer is formed thinner than the gap between the photoreceptor and the sleeve in the developing area. In developing the latent image on the photoconductor, it is preferable that the developer having triboelectric charge is flown from the sleeve to the photoconductor while applying an alternating electric field between the photoconductor and the sleeve.

Examples of the alternating electric field include a pulse electric field, an AC bias, or a synergistic AC and DC bias.

[Example] In the following examples and comparative examples, the fine line reproducibility was measured by the following method. That is, an image obtained by copying an original document of a fine line with a width of 100 μm accurately under appropriate copying conditions is used as a measurement sample, and using a Luzex 450 particle analyzer as a measuring device, a line width is displayed by an indicator from an enlarged monitor image. Measure. At this time, since the measurement position of the line width has unevenness in the width direction of the thin line image of the toner, the average line width of the unevenness is used as the measurement point. From this, the fine line reproducibility value (%) is calculated by the following formula.

The resolution was measured by the following method. That is, a pattern consisting of five thin lines with the same line width and spacing,
2.8, 3.2, 3.6, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1 or 8 within 1 mm.
Create an original image that is drawn as if there were 0.
An image obtained by copying an original document containing these 10 types of line images under appropriate copying conditions is observed with a magnifying glass, and the number of images (lines / mm) in which fine lines are clearly separated gives the resolution value. To do.

The larger this number is, the higher the resolution is.

The toner particle size distribution can be measured by various methods,
The particle size distribution of the present invention is a value measured using a Coulter counter, and was measured as follows. That is, a Coulter Counter-TA-II type (manufactured by Coulter) is used as a measuring device, an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) for outputting number distribution and volume distribution are connected, and an electric field is connected. As a liquid, a 1% NaCl aqueous solution is prepared using first grade sodium chloride. As a measuring method, a surfactant as a dispersant in the electrolytic aqueous solution of 100 to 150 ml, preferably an alkylbenzene sulfonate of 0.1 to 5 is used.
ml, and 2 to 20 mg of the measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the coater counter TAII type uses 100 μ aperture as an aperture, which is 2 to 4 based on the number.
The particle size distribution of the 0 μ particles was measured and then the value according to the invention was determined.

The true density of the magnetic toner can be measured by several methods. In this example, the following method was adopted as an accurate and simple method for measuring fine powder. That is, a cylinder made of stainless steel having an inner diameter of 10 mm and a length of about 5 cm, a disc having an outer diameter of about 10 mm and a height of 5 mm which can be closely fitted therein, and a piston having an outer diameter of about 10 mm and a length of about 8 cm are prepared. Put a disk at the bottom of the cylinder, then put about 1g of the sample to be measured and gently push in the piston. A force of 400 kg / cm ² is applied to this with a hydraulic press, and what is compressed for 5 minutes is taken out. The weight of this compressed sample is weighed (wg), the diameter (Dcm) and height (Lcm) of the compressed sample are measured with a micrometer, and the true density is calculated by the following formula.

The charge amount of the fine powder was measured by using a device for measuring the charge amount as shown in FIG. First, a fine measuring powder and an iron carrier (200 to 300
About 1 g of a 2:98 (fine powder) mixture in a weight ratio of (mesh) is put and a lid 41 made of metal is put. At this time, the total weight of the measurement container 39 is weighed and set as W ₁ (g). Next, in the suction device 38 (at least the portion in contact with the measurement container 39 is an insulator), suction is performed from the suction port 44 to adjust the air volume control valve 43 to adjust the pressure of the vacuum gauge 42 to 250 m.
mH ₂ O In this state, suction is sufficiently performed to remove fine powder by suction. The potential of the electrometer 46 at this time is V (volt). Here, 45 is a capacitor, and the capacity is O (μF). In addition, weigh the entire measuring container after suction and W ₂ (g)
And The triboelectric charge amount (μc / g) of this fine powder is calculated by the following formula.

However, the measurement conditions are 23 ° C and 60% RH.

The carrier (iron powder) used for the measurement is 200 to 300 mesh, but in order to eliminate errors, the carrier is sufficiently sucked by the above suction device, and the carrier passing through the 400 mesh screen is removed and then fine powder. Mixed with.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. All parts in the following formulations are parts by weight.

Example 1 After thoroughly mixing the above materials with a blender, they were kneaded with a twin-screw kneading extruder set at 150 ° C. The obtained kneaded product was cooled, coarsely pulverized with a cutter mill, medium pulverized with a pin mill which was a mechanical pulverizer, and further finely pulverized with a fine pulverizer using a jet stream to obtain a fine pulverized product. The crushed powder was classified by a fixed wall type air classifier to produce classified powder. Furthermore, the finely divided powder and the coarse powder are simultaneously strictly removed by a multi-division classifier (Elbowjet classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect to classify the obtained classified powder into black with a volume average particle size of 7.4 μm. Fine powder (magnetic toner) was obtained.

The particle size distribution of the obtained magnetic toner, which is a black powder having a positive chargeability, measured by using a Coulter Counter TAII type equipped with an aperture of 100 μ as described above is shown in Table 1 below.

For reference, the classification process using a multi-division classifier is first
The cross-sectional perspective view (three-dimensional view) of the multi-division classifier is shown schematically in FIG.

The following materials were added to 100 parts by weight of the obtained black fine powder magnetic toner and mixed with a Henschel mixer to obtain a positively chargeable one-component magnetic developer having a magnetic toner.

The particle size distribution and various characteristics of this magnetic toner are shown in Table 2.

The prepared one-component developer was put into a developing device shown in FIG. 3 of the accompanying drawings to carry out a developing test. The developing conditions will be described with reference to FIG. The one-component developer 31 has an arrow 36
It was applied in a thin layer on the surface of the stainless steel cylindrical sleeve 33 rotating in the direction of through the magnetic blade 32, and the gap between the sleeve 33 and the blade 32 was set to about 250 μm. Sleeve 33
Has a fixed magnet 35 as a magnetic field generating means, and the fixed magnet 35 forms a magnetic field of 1000 gauss in the vicinity of the sleeve surface in the developing area in the vicinity of the photosensitive drum 34 having the organic photoconductive layer having a negatively charged latent image. ing. The closest distance between the photosensitive drum 34 rotating in the direction of arrow 37 and the sleeve 33 is about 300μ.
set to m. It is to be noted that, between the photosensitive drum 34 and the sleeve 33, 2000 Hz / 135 which is a synergistic AC bias and DC bias.
A bias of 0 Vpp was applied. The one-component developer layer on the sleeve 33 had a layer thickness of about 75 to 150 μm, and in the developing area, the developer formed ears having a height of about 95 μm.

The negatively charged latent image formed on the photosensitive drum 34 was developed by flying a one-component developer 31 having a positive triboelectric charge. The image output test was continuously performed 10,000 times to generate 10,000 toner images. The results are shown in Table 2.

As is clear from Table 2, the developer of the present invention is excellent in the high image density in both the line portion and large area portion of characters, no fog, halftone reproducibility, fine line reproducibility and resolution. And, even after outputting 10,000 images, the first high image quality was maintained. Also, the copy cost was small and the economy was excellent. Also, 15 ℃, 10% RH, 32.5 ℃, 85% RH
Similarly good results were obtained under the environment.

The multi-division classifier used in this example and the classifying process by the classifier will be described with reference to FIGS. 1 and 2. The multi-division classifier 1 is shown in FIG. 1 and FIG.
It has a shape shown by the side walls 22 and 24, the lower wall has a shape shown by 25, and the side wall 23 and the lower wall 25 are provided with knife-edge type classification edges 17 and 18, respectively. , 18, the classification zone is divided into three. A raw material supply nozzle 16 that opens into the classification chamber is provided in the lower portion of the side wall 22, and a Coanda block 26 that is bent downward with respect to the extension direction of the bottom tangent of the nozzle to form an elliptical arc is provided. Upper wall of classification room
27 is a knife edge type air intake edge 19 toward the bottom of the classification chamber
In addition, the upper part of the classification chamber is provided with an inlet pipe opening to the classification chamber.
There are 14 and 15. Further, the inlet pipes 14 and 15 are provided with first and second gas introduction adjusting means 20 and 21 such as dampers and static pressure gauges 28 and 29. At the bottom of the classification chamber, discharge pipes 11, 12, and 13 having discharge ports opening to the inside of the chamber are provided corresponding to the respective fractionation areas. The classified powder is introduced under reduced pressure from the supply nozzle 16 into the classification area, moves by drawing the curved line 30 by the action of the Coanda effect of the Coanda block 26 by the Coanda effect, and the action of the high-speed air flowing at that time, and the coarse powder 11, The black fine powder 12 and the ultrafine powder 13 having a predetermined volume average particle size and particle size distribution were classified.

The positively-charged hydrophobic silica used here was manufactured as follows.

Silica fine powder synthesized by the dry method (trade name, Aerosil # 130, specific surface area of about 130 m ² / g, manufactured by Aerosil Co., Ltd.) 100 parts by weight is stirred to keep the temperature at about 250 ° C. and amine is added to the side chain. Silicone oil with (viscosity at 25 ℃
20 parts by weight of 70 cps and an amine equivalent of 830) were sprayed and treated for 10 minutes to prepare finely charged silica fine powder.

Example 2 A magnetic toner was obtained in the same manner as in Example 1 except that 3 parts by weight of carbon black was added to the raw material used in Example 1. The particle size distribution and various physical properties are shown in Table 1.

To 100 parts by weight of this magnetic toner, 0.6 parts by weight of positively charged hydrophobic dry silica (used in Example 1) was added and mixed with a Henschel mixer to prepare a one-component magnetic developer.

Table 2 shows the results of a copying test of this developer as in Example 1. As is clear from this table, good image quality was obtained, and the image was clear without fog in the background portion and inverted portion. The same effect was obtained under the environment of 15 ℃, 10% RH, 32.5 ℃, 85% RH.

Example 3 The following materials were added to 100 parts by weight of the magnetic toner obtained in Example 1 and mixed with a Henschel mixer to prepare a one-component magnetic developer.

Table 2 shows the results of a copying test of this developer in the same manner as in Example 1. As a result, an image having a high density, a fine halftone texture, and no fog was obtained. Also, 15 ℃, 10% RH,
The same effect was obtained under the environment of 32.5 ℃ and 85% RH.

Comparative Example 1 0.4 part by weight of negatively charged hydrophobic dry silica (BET 300 m ² / g) was added to 100 parts by weight of the magnetic toner obtained in Example 2 and mixed by a Henschel mixer to obtain a one-component magnetic developer. .

The result of the copying test similar to that of the example 1 is applied to the second developing agent.
Shown in the table. There was no problem with the image, but the fog was noticeable in the early days, and the halftone part was slightly shaky.
Also, although it was slightly fogged under the environment of 15 ° C and 10% RH, there were no large image defects. However, the initial concentration was low in the environment of 32.5 ° C and 85% RH (1.15),
It became 1.30.

Comparative Example 2 In the developer of Example 4, negatively charged hydrophobic wet silica (BET 150 m ^{2 /} g) 0.6 was used in place of the positively charged hydrophobic dry silica.
A one-component magnetic developer was obtained in the same manner as in Example 3 except that parts by weight were used.

Table 2 shows the results of a copying test performed on this developer in the same manner as in Example 1. There was no problem with the image quality, but the fog on the reversal part was inferior to that of Example 3, and the temperature was 15% and 10% R
It was further increased in the copy test under the H environment. Also, 32.5
The density was a little low (1.25-1.30) under the environment of ℃ and 85% RH, and the halftone reproduction was a little inferior.

[Effects of the Invention] The present invention is as described above, and exhibits the following excellent effects in various developing methods.

(1) It is a developer that gives an image excellent in fine line reproducibility and resolution.

(2) A developer that has a high image density and excellent gradation, and that gives an image with no fog on white areas and inverted areas.

(3) A developer that gives a high image density with a small consumption amount.

(4) A developer that does not change its performance with respect to environmental changes and has excellent durability under low humidity and high humidity.

(5) The developer has no change in performance even when used continuously for a long time.

(6) It is a developer that provides good halftone reproduction and gives a moist halftone image.

[Brief description of drawings]

FIG. 1 is an explanatory view of a classification process using a multi-division classification means, FIG. 2 is a schematic sectional perspective view of the multi-division classification means, and FIG. 3 is a development used for image formation in Examples and Comparative Examples. FIG. 4 is a schematic sectional view of the device, and FIG. 4 is an explanatory view of the device for measuring the triboelectric charge amount. 1 …… Multi-division classifier, 11 …… Coarse powder 12 …… Powder with a predetermined particle size 13 …… Fine powder, 26 …… Coanda block 31 …… One-component magnetic developer, 32 …… Blade 33 …… Sleeve , 34 …… Photosensitive drum 35 …… Fixed magnet, 36 …… Bias applying means 39 …… Measuring container 40 …… Screen (400 mesh) 44 …… Suction port, 45 …… Condenser 46 …… Electrometer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G03G 9/097 G03G 9/08 351 368 374 375 (72) Inventor Satoshi Yoshida 3 Shimomaruko Ota-ku, Tokyo Canon No. 30-2 Canon Inc. (56) Reference JP-A-51-3244 (JP, A) JP-A-54-72054 (JP, A) JP-A-55-120046 (JP, A) JP-A 58-129437 (JP, A) JP-A-62-61058 (JP, A)

Claims (1)

[Claims] 1. A developer for electrostatic charge image development containing a positively chargeable magnetic toner containing at least a binder resin and magnetic powder, wherein the magnetic toner particles having a particle size of 5 μm or less are 17 to 30 μm. Contains 60% by number, 8 to 12.7 μm
Magnetic toner particles having a particle diameter of 1 to 33% by number, magnetic toner particles having a particle diameter of 16 μm or more at 0.5 volume% or less, and the volume average particle diameter of the magnetic toner is 4 to
10 μm, and the frictional charging property with iron powder is 50 μc /
A carbon allotrope or a metal oxide as a charge relaxation agent fine powder having a number average particle size of not more than g (absolute value) of not more than 0.5 μm is internally or externally added to the magnetic toner particles and has a positive charging property. A developer for electrostatic charge image development, characterized in that fine particles of hydrophobic silica are externally added to magnetic toner particles.