JPH0693136B2 - 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.

In addition, although the image quality is good in 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 during the continuous copying or printing, and the toner particles having poor developability accumulate and remain in the developing machine.

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. There is still room for improvement as the toner of the above.

Japanese Unexamined Patent Publication (Kokai) No. 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 μ, but particles of 5 μm or less are as few as 15% by number or less, An image lacking in sharpness tends to be formed.

Also, in U.S. Pat. No. 4,299,900, a shampling developing method using a developer having 10 to 50% by weight of a magnetic toner of 20 to 35 μm is proposed. 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 photosensitive member, electric lines of force are concentrated, so that the edge portion, which is a contour, has higher electrolytic strength than the inside, and the sharpness of the image quality is determined by the quality of the toner particles gathered in 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.

Further, an object of the present invention is to provide a developer having high image density, excellent fine line reproducibility and excellent gradation.

A further object of the present invention is to provide a developer which does not change its performance after long-term use.

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, especially in low humidity.

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 magnetic toner containing at least a binder resin and magnetic powder, and the magnetic toner has a thickness of 5 μm. Magnetic toner particles having the following particle sizes are contained in an amount of 17 to 60% by number, and 8 to 12.7
1 to 33% by number of magnetic toner particles having a particle size of μm are contained, and 0.5% of magnetic toner particles having a particle size of 16 μm or more are contained.
The content of the magnetic toner is 4% by volume or less and the volume average particle diameter of the magnetic toner is 4
~ 10μm, and further 50μ frictional charging characteristics with iron powder
c / g (absolute value) or less, preferably 20 μc / g (absolute value) or less, and carbon allotrope or metal oxide as a magnetic powder of a charge easing agent having a number average particle diameter of 0.5 μm or less is a magnetic toner. The present invention relates to a developer for developing an electrostatic charge image, which is internally or externally added to particles.

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. Furthermore, 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 toners, 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 toner particles inside the latent image are thinner than the edge portion, and the image density may appear thin. . In particular, the magnetic toner particles of 5 μm or less have a strong tendency. However, the present inventors have found that 1% by number of toner particles in the range of 8 to 12.7 μm is used.
By containing 33% by number, this problem is solved,
We have found that it can be made even clearer. That is, 8 to 1
It is considered that the toner particles having a particle size range of 2.7 μm have an appropriately controlled charge amount with respect to the magnetic toner particles having a particle size of 5 μm or less, but the inside of the electric field strength is smaller than the edge portion of the latent image. Is supplied to the edge portion to compensate for the small amount of toner particles on the inner side of the edge portion to form a uniform developed image, resulting in a sharp image with excellent resolution and gradation at high density. It is what is done.

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 and, along with other features, the magnetic toner of the present invention having a particle size distribution satisfying this range can achieve better 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, a large N / V for a certain N value indicates that particles with a size of 5 μm or less are widely included, and a small N / V means that the abundance of particles near 5 μm is high. It is understood that the value of N / V is in the range of 2.1 to 5.82, and N is high.
Good fine line reproducibility and high resolution are achieved in the range of 17 to 60 and when 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, the magnetic toner particles are likely to aggregate with each other, resulting in a toner lump having a particle size larger than the original particle size, resulting in a rough image quality, a decrease in resolution, or an edge portion of the latent image. The difference in density between the inside and the inside becomes large, and the image tends to be slightly hollow.

The particles in the range of 8 to 12.7 μm are preferably 1-33% by number, and more preferably 8-20% by number. 33 pieces%
When the amount is larger, the image quality is deteriorated, and more development than necessary is required.
That is, the toner is excessively overloaded, 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.

Further, as described above, it is preferable to satisfy the relation between the number% (N%) and the volume% (V%) of the magnetic toner particle group having a particle size of 5 μm or less, N / V = −0.04N + k. I have a relationship. 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. If the volume average particle diameter is less than 4 μm, the amount of toner adhered on the transfer paper is small in applications where the image area ratio such as a graphic image is high.
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. When the volume average particle size exceeds 10 μm, the resolution is not good, and the quality of the image is likely to be deteriorated at the beginning of copying even if the use is continued even if it is good.

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 10 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 magnetic toner of the present invention, the binder resin for toner described below can be used when a heating / pressurizing 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 copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; 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.

Here, a compound having two or more polymerizable double bonds is mainly used as the cross-linking agent, and examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol diethylene. Carboxylic acid ester having two double bonds such as methacrylate and 1,3-butanediol dimethacrylate; divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and having 3 or more vinyl groups Compounds; are 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 in the mixture 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 the positive charge control agent 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 oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin 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
~ C ₄ ) a homopolymer of a monomer represented by: 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. In some cases, these charge control agents also have an action as (all or part of) a binder resin.

As the negative charge control agent that can be used in the present invention,
For example, organic metal complexes and chelate compounds are effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tertiary-butyl chromium salicylate, and particularly acetylacetone metal complex,
Salicylic acid-based metal complexes or salts are preferable, and salicylic acid-based metal complexes or salicylic acid-based metal salts are particularly preferable.

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.

It is preferable to add silica fine 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, Abrasion of toner particles and contamination of the sleeve surface are likely 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.

As the silica fine powder, silica fine powder produced by a dry method or a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use the silica fine powder by the dry method.

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 oxidation 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, aluminum chloride or
By using another metal halogen compound such as titanium chloride together with a silicon halogen compound, it is possible to obtain a composite fine powder of silica and another metal oxide, which is also included.

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 V15 (WACKER-CHEMIE GMBH) N20E T30 T-40 DC Fine Silica (Dow Corning Co.) Fransol (Fransol) (Fransil) On the other hand, various conventionally known methods can be applied to the method for producing the silica fine powder used in the present invention by a wet method.
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 Vita Seal Takiki Shilton, Shirnex Mizusawa Kagaku Starsil Kamijima Kagaku Himezir Ehime Yakuhin Syroid Fuji-Dilson Hi-Sil Pittsburgh Plate Glass.Co. (Pittsburgh Plate Glass) Durosil Ultorasil (Ultraseal) Fiillstoff-Gesells chaft Marquart Manosil (Manosir) Hardman and Holden Hoesch Hoesch Chemische Fabrik Hoesch KG ) Sil-Stone Stoner Rubber Co. Nalco Nalco Chem. Co. Quso Philadelphia Quartz Co. Luffia Quarts Imsil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch. KG Calsil Fiillstoff-Gesellschaft Marquart Imperial Chemical Industries. Ltd. Microcal Joseph Crosfiels & Sons. Ltd. Joseph Crossfield and Sons Manosil Hardman and Holden Vulkail Farbenfabriken Bryer.A.- G. (Farben Fabry-Kenbayer) Tufknit Durham Chemicals. Ltd. (Doulham Chemicals) Sylmos Shiraishi Kogyo Starlex Kamishima Chemical Fricosil 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. 0.01 to 8 parts by weight of silica fine powder, preferably 0.1 to 100 parts by weight of magnetic toner.
It is recommended to use 1-5 parts by weight.

The silica fine powder used in the present invention may be treated with a treating agent such as a silane coupling agent, an organic silicon compound, or silicone oil for the purpose of charge stability and hydrophobicity, if necessary. Is treated with the above-mentioned treating agent that reacts with or physically adsorbs. Examples of such treating agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, vinyltriethoxysilarane, vinyltrimethoxysilane, methyltrichlorosilane, allyldimethylchlorosilane, Allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorotran, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldi Siloxane, 1,3-divinyltetramethyldisiloxane, 1,3-
Examples include diphenyltetramethyldisiloxane and dimethylpolysiloxane having 2 to 12 siloxane units per molecule and each terminally located unit containing a Si-bonded hydroxyl group.

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, polyoxyalkylene modified silicone oil and the like are preferable. These are 1
Used as a seed or a mixture of two or more kinds.

The magnetic toner of the present invention may be mixed with various additives 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, for example, lubricants such as zinc stearate, abrasives such as silicon carbide, fluidity imparting agents, 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 of 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 oxide such as magnetite, γ-iron oxide, ferrite, iron-excess type ferrite; iron,
Metals such as cobalt and nickel or these metals and metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium Alloys 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.

Furthermore, 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, environmental stability (especially under low humidity), and durability. It has been found that it can improve the sex.

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 size 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). ) Is used as a feature.

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 to 10 parts by weight with respect to 00 parts by weight, preferably 0.02 to 5
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, from oxide, zinc oxide, tin oxide, cerium oxide, cobalt oxide, zirconium oxide, etc. Examples thereof include metal oxides mainly composed of metal atoms (one or several) 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 powder of these substances in the magnetic toner, it is possible to suppress appropriate triboelectrification and release an excessively charged electric charge. 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.

If the magnetic toner becomes overcharged, it will become loose, scatter,
Image defects such as 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 effect of the developer of the present invention becomes more remarkable as the particle size becomes smaller.

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. Also,
When the effect is exhibited even in a very small amount or when the magnetic toner is easily detached from the surface of the magnetic toner, the amount of addition can be increased or the method of internal addition for fixing to the surface of the magnetic toner is also effective in order to disperse well in the developer. . When the fine powder in the developer of the present invention has 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.

If the absolute value of the triboelectrification property exceeds 50 μc / g, the charge may not be sufficiently relaxed.If the polarity is opposite to the polarity of the magnetic toner, the fog may increase or the density may decrease. May be adversely affected.

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 fog may be provided. In some cases, 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.

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 method in which a predetermined material is mixed with a monomer that constitutes the binder resin to form an emulsion suspension, and then a magnetic toner is polymerized to obtain a toner, or a so-called micro-method including 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 Henschel mixer to produce the developer for developing an electrostatic 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 a 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) for outputting number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) are connected, and an electrolytic solution is used. Prepares a 1% NaCl aqueous solution using primary 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 with an ultrasonic disperser, and the coater counter TAII type is used to make the aperture 2 to 4 based on the number of 100 μ as the aperture.
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 1 g of the sample to be measured, and gently push in the piston. ・ Apply a force of 400 kg / cm ^{2 to} this with a hydraulic press and take out the one compressed for 5 minutes. 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 developer and the fine powder was measured by using a device for measuring the charge amount as shown in FIG. First, a metal measuring container 3 with a 400-mesh screen 40 at the bottom 3
Into a metal lid, the charge amount of the developer and the fine powder and the iron carrier (200-200 mesh) in the weight ratio of 1: 9 (developer), 2:98 (fine powder) were mixed with about 1 g. 41
do. At this time, weigh the entire measuring container 39 and
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 mmH ₂ O. In this state, sufficient suction is performed to remove the developer and fine powder by suction. The potential of the electrometer 46 at this time is V (volt). Here, 45 is a condenser, and the capacity is 0.
(ΜF). In addition, the total weight of the measuring container after suction is weighed and is W ₂ (g). The triboelectric charge amount (μc / g) of this developer and 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 before the developer. , Mixed with fine powder.

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 is cooled, coarsely pulverized by a cutter mill, then medium pulverized by a pin mill which is a mechanical pulverizer, and further finely pulverized by a fine pulverizer using a jet stream, and fine pulverization obtained. The powder was classified by a fixed wall type air classifier to produce classified powder. Furthermore, the finely divided powder and coarse powder are strictly removed at the same time using a multi-division classifier (Nippon Mining Co., Ltd. elbow jet classifier) that uses the Coanda effect to obtain a black powder with a volume average particle size of 7.5 μm. Fine powder (magnetic toner) was obtained. The black fine powder obtained had a value of +10 μc / g when the triboelectric charge was measured after mixing with the iron powder carrier.

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.

0.5 parts by weight of hydrophobic dry silica (BET specific surface area 200 m ² / g) was added to 100 parts by weight of the obtained black fine powder magnetic toner, and mixed by a Henschel mixer to have positively chargeable one-component magnetic development. I used it as an agent.

The properties of this developer are as shown in Table 1.

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
A thin layer was applied via a magnetic blade 32 onto the surface of a stainless steel cylindrical rib 33 rotating in the direction of, and the gap between the sleeve 33 and the blade 32 was set to about 250 μm. The sleeve 33 has a fixed magnet 35 as a magnetic field generating means, and a magnetic field of 1000 gauss is fixed near the surface of the sleeve in the developing area in the vicinity of the photosensitive drum 34 having an organic photoconductive layer having a negatively charged latent image. Is forming. The closest distance between the photosensitive drum 34 rotating in the direction of arrow 37 and the sleeve 33 is about 300 μm.
Set to. In addition, between the photosensitive drum 34 and the sleeve 33,
200Hz / 1350Vpp with AC bias and DC bias synergistic
Was applied. The one-component developer layer on the sleeve 33 has a layer thickness of about 75 to 150 μm, and in the developing area,
The developer formed spikes with 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 has excellent image reproducibility and fine line reproducibility in both the line portion such as characters and the large area portion, and even after printing 10,000 sheets. , The initial good image quality was maintained. Further, the amount of developer consumed was small and the economy was excellent. Also, 15 ℃, 10% R
Even under the H environment, similarly good copying test results were obtained.

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, and has a shape shown by the lower wall 25, and the side wall 23 and the lower wall 25 are provided with knife-edge type classification edges 17 and 18, respectively. According to 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 equipped with a knife-edge type air inlet edge 19 toward the lower part of the classification chamber, and an air inlet pipe 1 that opens to the classification chamber is provided at the upper part of the classification chamber.
There are 4,15. 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.

Example 2 A magnetic toner having a volume average particle diameter of 7.7 μm was obtained by the same production method as in Example 1 except that carbon black was used as the raw material used in Example 1. The particle size distribution is shown in Table 1. The amount of triboelectricity with the iron powder carrier was +14 μc / g.

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

The properties of this developer are as shown in Table 1.

Table 2 shows the results of a copying test of 10,000 times the same as in Example 1 using this developer.

As is clear from Table 2, excellent images were obtained. Similarly, good copying test results were obtained under the environment of 150 ° C and 10% RH.

Example 3 100 parts by weight of the magnetic toner obtained in Example 2 were mixed with the following materials with a Henschel mixer to prepare a one-component developer.

This developer was subjected to a copy test on 10,000 sheets in the same manner as in Example 1. The results are shown in Table 2, and a good image was obtained. Similarly, good copying test results were obtained even under the environment of 15 ° C and 10% RH.

Example 4 Using the above materials, the volume average particle size is the same as in Example 1.
7.8μ magnetic toner was obtained. The charge amount was −13 μc / g. The following materials were added to 100 parts by weight of this magnetic toner and mixed with a Henschel mixer to prepare a negatively chargeable one-component magnetic developer.

The particle size distribution of this magnetic toner is as shown in Table 1.

This one-component magnetic developer was applied to NP7550 (manufactured by Canon Inc.) equipped with an amorphous silicon photosensitive drum that forms a positively charged electrostatic charge image, and a copying test was performed on 10,000 sheets.

As shown in Table 2, a stable and clear high-quality image was obtained, and the toner consumption was excellent. Also, 15 ℃, 1
Even under the environment of 0% RH, similarly good copy test results were obtained.

Comparative Example 1 0.4 part by weight of hydrophobic silica (BET 200 m ² / g) was mixed with 100 parts by weight of the magnetic toner obtained in Example 2 with a Henschel mixer to prepare a one-component developer.

Table 2 shows the results of a copying test performed on this developer in the same manner as in Example 1. Good image was obtained, but 15 ℃, 10% R
In the copy test under H, as the number of durable sheets progressed, the roughness was observed, and the image density decreased (at the beginning of 1.35 → 10000 sheets 1.1
5) was seen. Further, unevenness of the sleeve coat was observed in the non-image area during the copy test.

Comparative Example 2 A magnetic toner having a volume average particle size of 11.5 μm was obtained by the same material composition and manufacturing method except that the magnetic iron oxide used in Example 4 was changed to 60 parts by weight. The particle size distribution is shown in Table 1. The frictional charge with the iron powder carrier was −9 μc / g. This magnetic toner was externally added in the same manner as in Example 4 to obtain a one-component developer.

Table 2 shows the results of a copying test performed on this developer in the same manner as in Example 4. The image density was good, but the fine line reproducibility and resolution were slightly inferior, and the toner consumption was rather high. The image density (1.32 → 1.35) was high under the environment of 15 ℃ and 10% RH, but fine line reproducibility (120% → 130%) and resolution (4.5%
This was inferior to the consumption (0.059 g / sheet) per book / mm → 4.0 pieces / mm.

[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 is excellent in gradation and gives an image without fog.

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

(4) A developer that does not change in performance due to environmental changes and has excellent durability, especially in low humidity.

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

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a classification process using a multi-division classifying means, FIG. 2 is a schematic sectional perspective view of the multi-division classifying means, and FIG. 3 is an example and a comparative example. FIG. 4 is a schematic sectional view of a developing device used for image formation, and FIG. 4 is an explanatory view of a device for measuring a 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

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Claims (1)

[Claims] 1. A developer for electrostatic charge image development comprising a magnetic toner containing at least a binder resin and magnetic powder, wherein the magnetic toner particles having a particle diameter of 5 μm or less are 17 to 60% by number. Magnetic toner particles having a particle diameter of 8 to 12.7 μm are contained in an amount of 1 to 33% by number, and a diameter of 16 μm is contained.
0.5% by volume or less of the magnetic toner particles having the above particle diameter are contained, the volume average particle diameter of the magnetic toner is 4 to 10 μm, and the triboelectric property with iron powder is 50 μc / g (absolute value) or less. And a carbon allotrope or a metal oxide as a charge relaxation agent fine powder having a number average particle diameter of 0.5 μm or less is internally or externally added to magnetic toner particles. Agent.