JP2002062684A - Electrostatic charge image developing toner and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner and a method for forming images by using the toner showing good dispersibility between binder resin and source material and excellent blocking resistance and offset characteristics. SOLUTION: The electrostatic charge image developing toner has the following features. (1) The binder resin during melting and kneading is styrene resin containing 200 to 1000 ppm residual monomers. (2) The coloring agent is carbon black containing at least an organic volatile component. (3) The organic volatile component in the carbon black during melting and kneading is decreased by thermal polymerization reaction with the residual monomers in the binder resin. (4) The weight average particle size of the toner is 7.5 to 10.5 μm and its absolute specific gravity (g/cc) ranges from 1.1 to 1.3. In the method for image formation, the above toner is mixed with a magnetic carrier to prepare a two- component developer, which is then electrified and deposited on the surface of a developer carrying body equipped with magnets, and then the toner is deposited on an electrostatic image on an electrostatic charge image holding body to develop the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for forming a toner image by developing an electrostatic image in an image forming method such as electrophotography.

[0002]

2. Description of the Related Art The functions of an image forming apparatus using an electrophotographic technique, such as a copying machine and a laser beam printer, have become more versatile, and there has been a demand for higher definition and higher image quality. Accordingly, toner particles having a finer particle diameter than before have been used. However, when the particle diameter of the toner particles is reduced, the material dispersibility of each toner is further required. When the toner diameter is reduced with the conventional dispersibility, high definition of the image is achieved,
A decrease in image density and fogging due to poor charging are likely to occur, and contamination inside the apparatus due to scattered toner has often been a problem.

As means for solving the above problem, Japanese Patent Laid-Open Publication
No. 1-344829 discloses that in a toner containing a binder resin, a colorant and a wax component, the amount of residual monomers in the toner is reduced as much as possible to improve the dispersibility between raw materials in the toner. There have been proposed new toners and improved image forming methods with improved chargeability and blocking resistance of the toners. However, a binder resin in which only the residual monomer amount is reduced requires strict demonomer treatment, which is not only disadvantageous in terms of cost, but also reduces the effect of the residual monomer in the toner when used. However, rather, it is greatly affected by organic volatile components contained in other materials such as carbon black, and often suffers from a decrease in offset resistance during heat fixing and a decrease in blocking resistance due to toner aggregation. Had become.

Many organic volatile components contained in carbon black have a vinyl group in a benzene skeleton, and these compounds have a property of undergoing a thermal polymerization reaction with a vinyl monomer remaining in a binder resin during toner production. ing. However, if the amount of residual monomers in the binder resin is small during the melt-kneading, these residual monomers are volatilized and a sufficient thermal polymerization reaction does not occur. Therefore, only organic volatile components remain as monomers even after the toner is formed. It is considered that such a problem occurred due to the presence of a low molecular weight polymer (oligomer) having a very low softening point in part.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic charge developing toner capable of solving the above-mentioned problems, and more particularly, to an electrostatic charge developing toner having excellent blocking resistance and offset resistance. To provide an image forming method using the same.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems. As a result, the present inventors have found that a toner containing at least a binder resin and carbon black remains in the binder resin at the time of melt-kneading. By optimizing the monomer and reducing the amount of organic volatile components in the entire toner as much as possible, it is possible to improve the dispersibility between raw materials in the toner, and to obtain a toner with excellent blocking resistance and offset resistance. The present invention has been completed.

That is, the present invention relates to a toner for developing an electrostatic image obtained by melt-kneading at least a binder resin, a colorant, a charge controlling agent and a magnetic fine powder, and cooling and finely pulverizing the toner.
The binder resin at the time of melt kneading reduces the residual monomer to 200 to 10
A styrene-based resin containing 00 ppm, and the colorant is carbon black containing at least an organic volatile component;
The organic volatile components in the carbon black during the melt-kneading are reduced by a thermal polymerization reaction with the residual monomer in the binder resin, and the weight average particle diameter is 7.5 to 10.5.
The present invention relates to a toner for developing an electrostatic image, characterized in that the toner has a true specific gravity (g / cc) of 1.1 to 1.3 μm.

The binder resin used in the present invention has a softening point of 145 ° C. to 165 ° C. and a residual monomer content of 200 p.
a resin selected from the group consisting of a styrene-based polymer, a styrene-based copolymer, a styrene-acrylate-based copolymer, a styrene-methacrylate-based copolymer, and a mixture thereof in a range of from pm to 1000 ppm. preferable.

When the content of the magnetic fine powder in the toner of the present invention is 1 to 10% by weight, 79.58 kA / m (1
A toner for developing an electrostatic image in which the saturation magnetization [σs (Am2 / kg)] of the toner under a magnetic field of K Oersted satisfies the following condition is preferable. 0.1 <σs <3.0 Further, the toner of the present invention has a dielectric loss (ta).
nδ (× 10 ⁻³ )) and electric resistance (R (× 10 ⁺⁹ ))
It is preferable that the following conditions are satisfied. 1.5 <tanδ <4.0, 200 <R <350

Further, according to the present invention, a magnet is provided as a two-component developer in which at least the toner developer is mixed with a magnetic carrier, as an independent developing cartridge detachable from the main body of the image forming apparatus (magnetic sleeve). The present invention relates to an image forming method characterized in that a charge is attached to a surface of a developer carrier, and a toner is attached to an electrostatic charge image on an electrostatic charge image holding member for development. Further, the present invention provides an image forming apparatus which is used in an image forming apparatus incorporated as a process cartridge detachable from an image forming apparatus main body, wherein a clearance between an electrostatic image holding body and a developer carrying body holding the toner is 1 mm or more. It relates to a forming method.

[0011]

Embodiments of the present invention will be described below in detail. First, the toner for developing an electrostatic image of the present invention has a weight average particle diameter of 7.5 to 10.5 μm.
It is characterized in that the true specific gravity (g / cc) is 1.1 to 1.3, and that the organic volatile components in the carbon black are reduced by the thermal polymerization reaction with the residual monomer in the binder resin during melt kneading. There is. Here, the true specific gravity of the toner particles or the toner is measured using a pycnometer cell. The weight average particle size is measured by a Coulter counter method. As an apparatus for measuring the toner particles and the average particle diameter of the toner by the Coulter counter method, for example, Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Co., Ltd.) is used. As the electrolyte, about 1% NaCl aqueous solution is prepared using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter Corporation) can be used. The measuring method is as follows.
A surfactant (preferably an alkylbenzene sulfonate) is used as a dispersing agent in 0.1 to 5 ml.
ml, and 2 to 20 mg of the measurement sample.

The electrolytic solution in which the sample is suspended is subjected to dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and
The volume distribution and the number distribution are calculated by measuring the volume and the number of the toner particles or the toner by using a 1300 μm aperture as the aperture. Then, a weight average particle diameter (D4) based on the weight of the toner particles or the toner is determined.
In the above measurement method, even when an external additive is externally added to the toner particles, the weight average particle diameter of the toner generally shows substantially the same value as the weight average particle diameter of the toner particles. As channels, 2.00 to less than 2.52 μm;
Less than 17 μm; 3.17 to less than 4.00 μm; 4.00
~ 5.04 μm; 5.04-6.35 μm;
6.35 to less than 8.00 μm; 8.00 to 10.08 μm
less than m; 10.08 to less than 12.70 μm; 12.70
16.0 to less than 20 μm; 16.00 to less than 20.20 μm; 20.20 to less than 25.40 μm;
Less than 2.00 μm; using 13 channels of 32.00 to less than 40.30 μm, and a particle size of 2.00 μm to 4
For particles less than 0.30 μm.

Here, in order to faithfully reproduce an electrostatic latent image of one dot unit on the photosensitive drum, the weight average particle diameter of the toner is preferably 10.5 μm or less. However, when the average particle diameter is 7.5 μm or less, the toner scattering increases in the developing system of the present invention. This is because as the particle diameter of the toner decreases, the number of particles that are not influenced by the electrostatic force increases. Normally, when the clearance between the sleeve of the developer carrier and the photosensitive drum is as narrow as 1 mm or less, the scattering of the toner is small. However, in the process cartridge that can be attached to and detached from the image forming apparatus main body of the present invention, the clearance is small. This is because the effect is more remarkable because the thickness is 1 mm or more.

The true specific gravity (g / c) of the toner of the present invention is
c) is preferably from 1.1 to 1.3. However, the true specific gravity is 1.1
In the following, the difference in specific gravity with the magnetic carrier becomes too large, which lowers the mixing efficiency and is one of the causes of causing toner scattering and fogging due to poor charging of the replenishment toner, which is not preferable. When the true specific gravity is 1.3 or more, a strong centrifugal force is applied as the developing sleeve rotates. If the centrifugal force is larger than the combined force of the magnetic force and the electrostatic force, the toner is scattered, which is not preferable. Such adjustment of the true specific gravity can be adjusted by the amount of the magnetic fine powder, pigment, and the like to be contained in the toner particles.

An image developing method in which the toner of the present invention is preferably used is a two-component developer in which a toner and a magnetic carrier are mixed, and a magnet is installed in a developer carrier. There is a method in which the developer is held, triboelectric charging is performed on a developer carrier (carrier), and the charged toner adheres to the electrostatic image of the electrostatic image holder to develop. In the toner of the present invention, 79.58 kA / m (1 k
Oersted) magnetic saturation [σ
s (Am ² / kg)] preferably satisfies the condition of 0.1 <σs <3.0. When the saturation magnetization s is 0.1
Am ² / kg or less is not preferable because the magnetic binding force is weak and the fogging phenomenon cannot be suppressed. Saturation magnetization σs is 3.0 A
Above m ² / kg, the magnetic binding force is dominant and the image density becomes undesirably low. In this case, the relationship between the residual magnetization [σr (Am ² / kg)] and the saturation magnetization [σs (Am ² / kg)] of the magnetic fine powder is σr / σs <0.2.
It is preferably 5.

In such a developing method, the toner of the present invention has a weight average particle diameter of 7.5 to 10.5 μm.
When toner particles are used, fog in a high-temperature and high-humidity environment, a phenomenon of low solid black density during durability, and a drum fusing phenomenon of a magnetic fine powder in a low-temperature and low-humidity environment are likely to occur. These problems can be effectively solved by controlling the magnetic force (σr / σs) of the magnetic fine powder in the toner. In a high-temperature, high-humidity environment, magnetic force is applied to the toner so that fog development of the toner with low triboelectric charge can be suppressed, thereby maintaining the image density and better preventing fog. can do.

Further, by controlling the amount of magnetic fine powder on the surface of the toner carrier by optimizing the conditions of melt kneading and the amount of magnetic fine powder, it is possible to prevent the fusion of magnetic powder to the photosensitive drum during durability in a low temperature and low humidity environment. Becomes possible. Further, even in a high-temperature and high-humidity environment, toner particles having a high triboelectric charge are easily developed selectively, so that fogging and scattering can be suppressed. Magnetic force σr / σs of magnetic fine powder in toner
When a magnetic fine powder having a particle size of 0.25 or more is used, the magnetic binding force does not act effectively, so that fogging easily occurs in a high-temperature and high-humidity environment, and a solid black density thin phenomenon at the time of durability tends to occur. -In a low humidity environment, the drum fusion phenomenon is likely to occur. When σr / σs is less than 0.05,
Conversely, the magnetic binding force becomes dominant, and image density tends to decrease in all environments, which is not preferable. A more preferable range is a case where 0.1 <σr / σs <0.2. Here, the magnetic characteristics were measured using VSMP-1-10 (manufactured by Toei Kogyo Co., Ltd.) with an external magnetic field of 79.58 kA / m.

The toner of the present invention contains a magnetic fine powder. As the magnetic fine powder used here, there is a metal oxide having magnetism including elements such as iron, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon. The weight average particle size of these magnetic fine powders is preferably 0.05 to 0.30 μm. If the weight average particle size is smaller than 0.05 μm, the dispersion tends to be poor depending on the physical shearing force. In the case of toner, the magnetic force is not uniform, and the magnetic binding force varies depending on the direction of the magnetic field. On the other hand, when the weight average particle size is larger than 0.30 μm, the number required for uniformly dispersing a small amount of magnetic fine powder as in the present invention is small, and this also undesirably increases the variation in magnetic binding force. The shape of the magnetic fine particles constituting the magnetic fine powder used in the present invention includes an octahedron, a hexahedron, and a sphere. An octahedral shape, which is more susceptible to shearing force, is preferred in order to prevent rotation in the dispersion process and achieve high dispersion, since image density and fog latitude can be widened.

In order to further satisfy the object of the present invention at a higher level, the magnetic fine particles constituting the magnetic fine powder have at least an aminosilane group and an electric resistance of 1 × 1.
It is preferably from 0 ^{3 to} 9 × 10 ³ . Electric resistance is 1 ×
In the case of 10 ³ or less, the presence of aminosilane groups on the surface of the magnetic fine powder particles is extremely sparse, so that the wettability between the resin to be fed during kneading and the magnetic fine powder is reduced, and the magnetic fine powder is removed from the toner particles during toner production. The body is easily detached, and drum fusion is likely to occur due to the released magnetic fine powder. If the electric resistance is larger than 9 × 10 ³ , the resistance of the whole toner is increased, which causes a decrease in density due to charge-up. A more preferred resistance range is 3 × 10 ³
５5 × 10 ³ .

The content of the magnetic fine powder in the toner particles is 10% by weight from the viewpoint of suppressing the occurrence of fogging and adjusting the true specific gravity.
Hereinafter, preferably 1 to 10% by weight, more preferably 1 to 10% by weight.
5% by weight is good. When the amount is less than 1% by weight, it is difficult to suppress the fogging phenomenon in the toner particles having a weight average particle diameter of 7.5 to 9.5 μm. When the amount is more than 10% by weight, the magnetic binding force is dominant. The image density is low,
The amount of magnetic powder that has fallen off increases, and drum fusion tends to occur. This is because, when the content of the magnetic powder is large, the true specific gravity of the toner is increased to 1.3 or more, and the toner is scattered by receiving a stronger centrifugal force as the developing sleeve rotates as described above. When the content of the magnetic powder is small, the true specific gravity of the toner is reduced to 1.1 or less, and as described above, the difference in specific gravity with the magnetic carrier as a two-component developer becomes too large, and the mixing efficiency is reduced, and the toner is Is one of the causes of toner scattering and fogging due to poor charging.

The toner particles of the present invention may contain a wax. Examples of the wax include paraffin wax and its derivatives, microcrystalline wax and its derivatives, fish tropsch wax and its derivatives, polyolefin wax and its derivatives, carnauba wax and its derivatives, long-chain carboxylic acid and its derivatives, long-chain alcohol and its Derivatives. Derivatives include oxides, block copolymers of vinyl monomers and waxes, and graft modified products of vinyl monomers and waxes.

In particular, the wax preferably used in the present invention is preferably a low molecular weight polypropylene wax, and preferably has a number average molecular weight (Mn) of 6,000 to 8,000 by gel permeation chromatography (GPC). Generally, under conventional kneading conditions, the kneading temperature immediately after the kneaded material is discharged from the kneader is an important parameter for knowing the kneading state. At a kneading temperature 15 to 30 ° C. higher than the softening point of the PP wax, the dispersibility of the wax in the binder resin is good, and in such a case, the wettability between the binder resin and the magnetic fine powder is also high. Thus, the object of the present invention can be achieved better.

The colorant used in the present invention contains at least carbon black, and if necessary, dyes and other pigments can be used. Colorants particularly preferably used as carbon black include carbon black such as furnace black, acetylene black, thermal, and black. Among these carbon blacks, those having a primary particle diameter of 15 to 30 nm, which are excellent in dispersibility in a resin, are desirable, and those which are acidic (pH 7 or less) without impairing other raw material properties during toner production are desirable. . Other dyes and other pigments include, for example, nigrosine dyes, carmine dyes, various basic dyes acid dyes, oil dyes, dyes such as anthraquinone dyes; benzidine yellow organic pigments,
There are quinanthrin organic pigments, rhodamine organic pigments, phthalocyanine organic pigments, zinc oxide, titanium oxide, and the like. Since the toner of the present invention contains magnetic fine particles as a coloring component, the addition amount of a coloring agent such as carbon black may be small, and usually 3 to 7 parts by weight per 100 parts by weight of resin. It is possible to fully satisfy the function.

In these carbon blacks, naphthalene, acenaphthene, phenanthrene, anthracene, fluorancene, benzo (a) anthracene, chrysene, and benzene are used as organic volatile components derived from an aromatic raw material oil during the production of carbon black. Many compounds having a highly reactive vinyl group in the benzene skeleton, such as benzo (e) pyrene and benzo (b) fluorancene, remain and are contained. When an organic volatile component is present alone, these compounds cause a reduction in resin strength, causing problems such as a decrease in offset resistance and blocking resistance and an unpleasant odor during fixing. The present invention is characterized in that this problem is made harmless by a combination of the following resin at the time of kneading the toner.

Here, the binder resin used in the toner of the present invention will be described below. Examples of the binder resin of the toner used in the present invention include polystyrene; poly-P-
Homopolymers of substituted styrenes such as chlorostyrene and polyvinyltoluene; styrene-P-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer Styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl Styrene-based copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, and styrene-acrylonitrile-indene copolymers are exemplified.
In particular, a crosslinked styrene resin is also a preferable binder resin. Further, other resins may be appropriately blended. For example, other resins include polyvinyl chloride, phenolic resin, naturally modified phenolic resin, naturally modified maleic acid resin, acrylic resin, mehacryl resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy Resins, xylene resins, polyvinyl acetals, terpene resins, coumarone indene resins, petroleum resins and the like.

When a styrene copolymer is produced, comonomer for styrene monomer is acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate,
2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate,
Monocarboxylic acid having a double bond such as acrylonitrile, methacrylonitrile, acrylamide or a substituted product thereof; dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, or dimethyl maleate and substitution thereof Body: vinyl ester such as vinyl chloride, vinyl acetate, vinyl benzoate; ethylene olefin such as ethylene, propylene, butylene; vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone; vinyl methyl ether, vinyl ethyl ether, vinyl Examples include vinyl ethers such as isobutyl ether.

These vinyl monomers are used alone or in combination with a styrene monomer. As a crosslinking agent for obtaining a crosslinked styrene-based resin, a compound having two or more polymerizable double bonds is mainly used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters having two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinylaniline; Divinyl compounds such as divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups. These crosslinking agents are used alone or in combination. Styrenic resins can be obtained by gel permeation chromatography (GP
In C), the weight average molecular weight (Mw) is 15 × 10 ⁴
２５25 × 10 ⁴ , number average molecular weight (Mn) is 2 × 10 ³ 〜
It is 4 × 10 ³ and the softening point is preferably 145 ° C. to 165 ° C.

The styrenic resin used in the present invention preferably has a residual monomer content of 200 ppm to 1000 ppm. Here, the residual monomer amount is 200
ppm or less, the polymerization reaction with the organic volatile components remaining in the carbon black is not sufficient.
This is not preferable because a large number of unreacted monomers remain in the formed toner. Such a styrene-based resin having a large amount of residual monomer does not require strict demonomerization treatment, and thus is inexpensive in cost and advantageous in raw material cost. When these residual monomers exist alone,
This results in a decrease in the strength of the resin, resulting in problems such as a decrease in offset resistance and blocking resistance and an unpleasant odor during fixing. However, during the toner manufacturing process,
By heating to a melt-kneading temperature 15 ° C. to 30 ° C. higher than the softening point of the styrene-based resin, a polymerization reaction occurs with the organic volatile components (compound having a vinyl group in the benzene skeleton) remaining in the carbon black to produce a low molecular weight compound. Detoxification can be achieved by polymerization. As described above, the feature of the present invention is that by optimizing the amount of the monomer remaining in the styrene resin, the organic volatile component in the carbon black is thermally polymerized with the residual monomer in the binder resin during the melt-kneading of the toner. And it is rendered harmless.

In the present invention, the residual monomer in the styrenic resin can be quantitatively determined by a method using thermogravimetry (TG), which is determined as the amount of weight loss during heating using a thermobalance or the like, or by gas chromatography (GC). ) Can be applied. Among these, the method using GC is a particularly effective method. In the present invention, when the residual monomer in the styrene-based resin is quantified by TG, the residual monomer can be determined from the loss on heating observed when the sample is heated to 200 ° C. Specific examples are described below. <TG measurement conditions> Apparatus: TGA-7, PE7700 (manufactured by PerkinElmer) Temperature rising rate: 10 ° C / min Measurement environment: under N ₂ atmosphere

A specific example in the case of quantifying the residual monomer in the styrene-based resin using GC will be described below. <GC measurement conditions> Apparatus: GC-14A (manufactured by Shimadzu Corporation) Column: fused silica capillary column (J & W SCI)
ENTIFC; size: 30m x 0.249mm,
Liquid phase; DBWAX, film thickness: 0.25 μm) Sample: 100 m using 2.55 mg of DMF as an internal standard
Add 1 liter of acetone to make a solvent with internal standard. Next, 400 mg of the toner is made into a 10 ml solution with the above solvent. After 30 minutes on an ultrasonic shaker, leave for 1 hour. Next, the mixture is filtered with a 0.5 μm filter. The volume of the implanted sample is 4 μl. Detector: FID (split comparison: 1:20) Carrier gas: N ₂ gas Oven temperature: 70 ° C. → 220 ° C. (After waiting at 70 ° C. for 2 minutes, the temperature is increased at a rate of 5 ° C./min.) Inlet temperature: 200 ° C Detector temperature: 200 ° C Calibration curve preparation: DMF similar to the sample solution, gas chromatographic measurement of the standard sample in which the target monomer was added to the acetone solution, and the weight ratio of the monomer to the internal standard DMF / Area ratio is determined.

It is preferable to use an organometallic compound as a charge control agent in the toner of the present invention. Among the organometallic compounds, those containing an organic organic compound which is particularly rich in vaporizability or sublimability as a ligand or a counter ion are useful.
Such an organometallic compound includes an azo-based metal complex represented by the following general formula. Among such azo-based metal complexes, it is preferable to use a charge control agent containing Cr as a central metal and represented by the following structural formula (1) or (2). The charge control agent is preferably added in the range of 0.5 to 3 parts by weight based on 100 parts by weight of the toner.

[0032]

Embedded image

[0033]

Embedded image

In the toner of the present invention, charging stability,
In order to improve developability, fluidity and durability, it is preferable to externally add an inorganic fine powder to toner particles. This is closely related to the configuration of the drum cartridge in the present invention. In a normal cartridge, the toner collected by the cleaning member is collected by its own weight in the direction of gravity opposite to that on the photosensitive drum, and is collected in a box by a spiral member or the like. The cleaning space of the drum cartridge of the present invention has also been reduced due to the recent tendency toward miniaturization. Therefore, the toner collected by the cleaning member is collected in a box while being pressed against the photosensitive drum. Therefore, the fusion of the magnetic fine powder to the drum becomes remarkable.

In order to eliminate such problems, it is necessary to improve the fluidity of the toner itself and reduce the coefficient of friction with the drum. For this reason, in a structure like the present drum cartridge, an inorganic fine powder larger than usual is externally added to prevent the above-mentioned problem. However, such fine powder usually has a strong negative charging property, and excessive external addition causes charge-up of the entire toner, which is one of the factors that cause problems such as a decrease in image density. Therefore, it is preferable to use the inorganic fine powder in an amount of 0.3 to 1 part by weight based on 100 parts by weight of the toner.

Examples of the inorganic fine powder include silica fine powder, titanium oxide fine powder, and alumina fine powder. In particular, inorganic fine powder having a specific surface area in the range of 90 to 150 m ² / g by nitrogen adsorption measured by the BET method gives good results. In addition, inorganic fine powder, if necessary, for the purpose of hydrophobicity, charge control, silicone varnish, various modified silicone varnish, silicone oil, various modified silicone oil, silane coupling agent, silane coupling agent having a functional group, It is also preferable to be treated with a treating agent such as another organosilicon compound. Two or more treatment agents may be used. Particularly, silica fine powder surface-treated with silicone oil is preferable.

As other additives, lubricants such as Teflon (registered trademark), zinc stearate, polyvinylidene fluoride, and silicone oil particles (containing about 40% of silica) are preferably used. Further, abrasives such as cerium oxide, silicon carbide, calcium titanate and strontium titanate are preferably used, and among them, strontium titanate is preferred. Further, a small amount of a caking preventing agent; a conductivity-imparting agent such as carbon black, zinc oxide, antimony oxide, and tin oxide; and white fine particles and black fine particles having a polarity opposite to that of the toner particles may be used in a small amount.

In the image forming method using the toner of the present invention, it is preferable to use 1 to 10 parts by weight of the toner of the present invention mixed with 100 parts by weight of the magnetic carrier described below as a two-component developer. The magnetic carrier used in this case is preferably an iron powder carrier.
This is because the clearance between the developing sleeve (developer carrier) and the doctor blade or the clearance between the developer carrier and the electrostatic image carrier (photosensitive drum) in the process cartridge suitable for the image forming method of the present invention is 1. 0m
m or more. Such a wide clearance has an advantage that the production cost is not required because the accuracy of the cartridge itself is rough and good. On the other hand, the ears of the developer on the developer carrying member become longer, and carrier adhesion is likely to occur. In this cartridge, the rotation direction of the sleeve and the rotation direction of the drum are opposite to each other in order to simplify the gear arrangement of the rotating member and reduce the cost. For this reason, the developing system has a greater stress on the ears of the developer and is more likely to cause carrier adhesion. In such a developing system, for example, a ferrite carrier described in JP-B-56-52305 has a low saturation magnetization,
Carrier adhesion occurs as the carrier particles are reduced in size,
There is a drawback that the photoreceptor and the cleaning blade are scratched and the durability of the member is significantly shortened. Therefore, an iron powder carrier having a stronger magnetic force is suitable for the present invention.

At present, iron powder-based carriers generally put into practical use are classified into the following two types according to their external shapes. One of them has an irregular shape with no fixed shape. As described in JP-B-55-40863, the raw iron powder is sintered, pulverized and classified, so that it becomes an amorphous iron powder carrier. Higher ears become harder, Soli
It is easy for nicks (toner peeling portions) to occur in the d portion (solid black portion). Further, "cracks" and "chips" are apt to occur in the process of transporting the developer, and these damage the photoreceptor surface and consequently deteriorate the image. Further, there is a disadvantage that the fluidity of the developer is poor, the deterioration of the developer is accelerated, and the torque applied to the developing roller during the transportation process is increased.

The other one is a so-called atomized iron powder having a spherical or nearly spherical granular shape, which is preferably used in the present invention. In this case, since the shape is close to a spherical shape, the irregular shaped iron powder does not have a defect and has excellent characteristics. However, since the specific surface area is smaller than that of the irregular carrier, in the development using the small particle size toner as in the present invention, the charging ability is reduced. For this reason, a carrier specific surface area corresponding to the specific surface area of the toner is required, and it is necessary to reduce the particle diameter. The carrier particle diameter suitable for the toner of the present invention is preferably 80 μm or less. However, when the carrier particle diameter is 40 μm or less, the fluidity deteriorates, which is one of the causes of problems such as poor charging and increased spent. Therefore, the carrier particle diameter is preferably 40 to 80 μm. Further, the true specific gravity of the carrier is preferably 6.0 or more in order to optimize the mixing and stirring properties in consideration of the specific gravity difference from the toner of the present invention. However, when the true specific gravity exceeds 8.0, the rubbing force of the drum increases, which is one of the causes of deterioration of image quality. Therefore, the carrier specific gravity is preferably 6.0 to 8.0.

It is desirable that the magnetic carrier be coated with a resin as an insulating film. As the resin that can be used for the coat, any resin that has been conventionally used can be used, but a silicone resin is more preferable. Examples of the silicone resin include silicone varnishes (TSR 115, TSR 114, TSR 110 manufactured by Toshiba).
2, TSR 110, YR 3061, TSR 110,
TSR 116, TSR 117, TSR 108, TSR
IO9, TSR 180, TSR 181, TSR 18
7, TSR 144, TSR 165, KR 271, KR 272, KR 275, KR 28 manufactured by Shin-Etsu Silicone Co., Ltd.
0, KR 282, KR 267, KR 269, KR 2
11, KR 212, etc.), alkyd-modified silicone varnish (TSR 184, 185, etc., manufactured by Toshiba), epoxy-modified silicone varnish (TSR 194, YS, manufactured by Toshiba)
54), polyester-modified silicone varnish (such as TSR 187 manufactured by Toshiba), acrylic-modified silicone varnish (such as TSR 170 and 171 manufactured by Toshiba), urethane-modified silicone varnish (such as TSR 175 manufactured by Toshiba), and reactive silicone resin (such as Shin-Etsu Silicone Co., Ltd.) Made by KAl00
8, KBE1003, KBCl003, KBM 30
3, KBM 403, KBM 503, KBM 602,
KBM 603).

Next, a method for producing toner particles by melt-kneading will be described. As the kneading machine used in the present invention, it is preferable to knead using an extruder in response to the recent mass production of toner. In particular, a twin-screw extruder is a preferable kneader from the viewpoint of quality stability and mass productivity. Specific examples include TEM-100B (manufactured by Toshiba Machine) and PCM-87 (manufactured by Ikegai Iron Works). In the present invention, in a melt-kneading step for producing toner particles, a mixture containing at least a binder resin, a colorant, a magnetic fine powder and a wax is produced by a kneader under the following conditions. Kneading temperature: softening point temperature of resin and wax + 15 ° C. to 3
0 ° C. Rotational speed: 150 to 210 rpm Supply amount: 80 to 140 kg / hr The obtained kneaded material is rolled and cooled by a conventionally known method.
Pulverization, fine pulverization by a jet stream, and classification are performed to obtain desired toner particles.

In the toner of the present invention, the organic volatile components in the carbon black during the above-mentioned melt-kneading are reduced by the thermal polymerization reaction with the residual monomers in the binder resin. Good dispersibility between raw materials such as body and wax and the binder resin can be obtained. Here, regarding the dispersibility of the magnetic fine powder and the wax in the toner particles, the dielectric loss tan δ of the toner
And by measuring the resistance value R. Generally, when the dispersibility of the material components in the toner is poor t
The value of anδ is large, and the resistance value is small. When the dispersibility is good, the value of tan δ is small and the resistance value R is large. However, when the dispersion is too high, the toner resistance value increases and the developing property is reduced. In the toner of the present invention, tan δ (× 10 ⁻³ ) and resistance value R (× 10
⁺⁹ ) is preferably the following conditions. 1.5 <tan δ <4.
0, and preferably 200 <R <350.

The method of measuring tan δ will be described below. First, the measurement was performed using a dielectric replacement measuring device (TSR-10T, manufactured by Ando Electric Co., Ltd.). As a measurement method, first,
From the obtained toner, a sample for measurement of about 1.6 mm is prepared using a tablet molding machine. Next, the sample is mounted inside the solid electrode, and the electrode is plugged into a thermostat. The measurement mode of the measurement device is set to the zero balance mode, the PATIO value is determined according to the measurement frequency, and a balance operation is performed. The value of the conductance at this time is R ₀ . Further, the measurement mode is changed and the balance operation is performed in the same manner as the zero balance. At this time, the capacitance is Cx and the conductance is R '. tan δ can be determined as follows using the above measured values.

First, permittivity (ε ′) = Cx / C ₀ (1) where C ₀ is a geometric capacitance which is a capacitance when the dielectric is replaced with air. On the other hand, the dielectric loss factor (ε ″) is obtained by the following equation: Dielectric loss factor (ε ″) = Gx / ωC ₀ (2) where ω is an angular frequency, and ω = 2πf (f is a frequency Hz ), Gx is the conductance, and is represented by Gx = PATIO value × (R′−R _o ). tan δ is represented by tan = ε ″ / ε ′ (3), and by substituting equations (1) and (2) into equation (3), tan δ becomes Gx / ωGx = PATIO value ×
It was expressed as (R′−R _o ) / 2πfCx, and tan δ was measured by substituting the measured values. The measurement method in the present application was performed at a measurement frequency of 1 kHz, and the corresponding PATIO value was 1 × 10 ⁹ .

An example of an image forming method using the toner of the present invention will be described with reference to FIG. First, a voltage is applied by the charging charger 2, the surface of the electrostatic image carrier (hereinafter, referred to as a photosensitive drum) 1 is charged to a negative polarity, and a digital latent image of image scanning is exposed by exposure by the laser beam generating means 3. The toner carrier (developing sleeve) 4 formed on the drum 1 and containing a magnet is
Developing device 7 including doctor blade 5 as developer layer thickness regulating means, developer supply roller 6 and stirring means 15
The developer (two components of toner and magnetic carrier) 8 in the inside adheres electrostatically, and the photosensitive drum 1 and the developing sleeve 4 come close to each other,
The latent image on the photosensitive drum 1 is reversely developed with toner. At this time, the conductive base of the photosensitive drum 1 is grounded in the developing section, and a DC bias is applied to the developing sleeve 4 by bias applying means 9. When the transfer paper P is conveyed and arrives at the transfer portion, the transfer paper P is charged by the voltage applying means 11 from the back surface (the surface opposite to the photosensitive drum 1 side) of the transfer paper P by the roller transfer means 10, so that the surface of the photosensitive drum 1 is charged. The developed image (toner image) is transferred onto transfer paper P by roller transfer means 10.

The transfer paper P separated from the photosensitive drum 1 is
A fixing process is performed by the heating and pressing roller fixing device 12 to fix the toner image on the transfer paper P. The toner remaining on the photosensitive drum 1 after the transfer process is cleaned by the elastic blade 13 and collected in the collection box 14. The photosensitive drum 1 after being cleaned by the cleaning means
Is repeated from the charging step using the charging charger 2. The photosensitive drum 1 has a photosensitive layer and a conductive substrate. A non-magnetic cylindrical developing sleeve 4 serving as a toner carrier rotates so as to advance in a direction opposite to the surface of the photosensitive drum 1 in the developing section. Inside the developing sleeve 4, a multi-pole permanent magnet (magnet roll) as a magnetic field generating means is arranged so as not to rotate. The developer (toner and magnetic carrier) 8 in the developing device 7 is supplied from the developer supply roller 6 onto the surface of the non-magnetic cylinder 4, and the developing sleeve 4
Is applied to the toner developer 8 by, for example, a negative triboelectric charge due to the friction between the surface of the doctor blade 5 and the doctor blade 5.

In the developing section, a DC bias may be applied to the developing sleeve 4 by a bias means. The DC bias may be -400V to -500V. When the toner is transferred in the developing section, the toner is transferred to the electrostatic image side by the action of electrostatic and bias on the surface of the photosensitive drum. The photosensitive drum 1 has a conductive base layer formed of a conductive metal such as aluminum and a photoconductive layer formed on its outer surface as basic constituent layers, and is rotated at a predetermined peripheral speed (process speed). You. The surface of the photosensitive drum 1 is charged to a predetermined polarity and potential by the charging charger 2. Next, an electrostatic image is formed by the image exposure 3, and the electrostatic image is sequentially visualized as a toner image by the developing means from the developing sleeve 4.

Next, the process cartridge in the image forming apparatus of the present invention will be described. The process cartridge of the present invention has at least a developing unit and a latent image holding member individually formed as cartridges, and is configured to be detachable from an image forming apparatus main body (for example, a copying machine, a laser beam printer, a facsimile machine). ing. here,
An example of an embodiment is a process cartridge in which a developing unit from a developing sleeve, a drum-shaped electrostatic image holder (photosensitive drum), a cleaning unit having a cleaning blade, a charging charger as a primary charging unit, and the like are integrated. You.

In this embodiment, the developing means has a doctor blade as a developer layer thickness regulating means and a developer comprising a toner and a magnetic carrier in a toner container, and uses the developer. A predetermined electric field is formed between the photosensitive drum and the developing sleeve as a toner carrier by the developing bias voltage from the above, and the developing process is performed. In order to carry out this development step suitably,
The distance between the photosensitive drum and the developing sleeve is adjusted to 1 mm or more. In the above description, the embodiment in which the four components of the developing unit, the latent image holding unit, the cleaning unit, and the primary charging unit are integrally formed into a cartridge has been described. However, in the present invention, the developing unit, the electrostatic image holding unit, Are not particularly limited as long as they are separately made into cartridges.

[0051]

EXAMPLES The present invention will be described more specifically based on the following examples.

Example 1 (i) 100 parts by weight of binder resin (a) Styrene-n-butyl acrylate copolymer (St
-Ac copolymer weight ratio = 80:20) (b) Weight average molecular weight (Mw) 200,000, Number average molecular weight (Mn) 3000 (c) Softening point: 155 ° C (d) Oxidation 0.2 KOHmg / mg (e) Residual monomer amount 500 ppm (f) Loss modulus at 140 ° C. G ″: 1.5 × 10 ⁴ dy
n / cm ²

(Ii) 3 parts by weight of magnetic fine powder (a) Weight average particle diameter R: 0.20 μm (b) Shape of magnetic fine particles: octahedron (c) σr / σs: 0.15 [-] (d) r = 4 × 10 ³ [Ω · cm] (iii) 1.5 parts by weight of negative charge control agent (a) Monoazo complex represented by the above structural formula (1) (b) Primary particle diameter: 7 μm

(Iv) 2 parts by weight of wax (a) Low molecular weight polypropylene (b) Softening point: 155 ° C. (c) Measurement method of softening point: DSC endothermic peak temperature (v) 6 parts by weight of carbon black (a) pH: 3 (b) Primary particle diameter: 30 μm

The above materials (Toner Formulation 1 in Table 1) were mixed with a Henschel mixer to obtain a mixture, and the obtained mixture was introduced into a twin-screw extruder (model name "PCM-65" (manufactured by Ikegai Iron Works)). , The screw rotation speed 180 (r
pm), set temperature 100 ° C, supply amount of mixture 110kg
/ Hr was subjected to melt-kneading of the mixture. The temperature of the kneaded material immediately after kneading was 180 ° C. (production condition 1 in Table 2).

The kneaded material is coarsely ground to 1 mm or less with a hammer mill.
Crushed, and the obtained coarsely pulverized material is collided with a jet stream
The product was finely pulverized with an air current pulverizer to obtain a finely pulverized product. Weight of toner particles
The amount average particle diameter (D50) of 8.2 μm
Table 3 shows the physical properties of the particles. Obtained toner particles 100
Parts by weight, silane coupling agent and dimethyl silicone
Hydrophobic silica fine powder surface-treated with oil (BE
T specific surface area 120m ^Two/ G) 0.55 parts by weight
Thus, a negatively triboelectric toner was prepared.

In order to evaluate the toner by the image forming method, a laser beam printer (trade name AR-) that develops an electrostatic image by a reversal developing method having a resolution of 600 dpi.
160, a fixing temperature of 160 ° C., manufactured by Sharp Corporation) A toner and a magnetic carrier are introduced into a developing device of a process cartridge as a two-component developer in a ratio of 1 to 10 parts by weight of the former and 100 parts by weight of the latter. The cartridge was mounted on a laser beam printer, and an image output test was performed under each environment. Furthermore, the image quality of the dot latent image was evaluated by the following evaluation method using a laser beam printer modified so as to have a resolution of 1200 dpi. Table 3 shows the evaluation results.

Evaluation Method (a) Image Density Measuring Method Using a Macbeth densitometer, a black portion of a copy sample obtained by copying three sheets using an original including a black circle having a diameter of 55 mm was measured and averaged. 2nd sheet (initial), 200,00
The image density of the solid black image on the 0th day (20k) was measured by a Macbeth densitometer. Evaluation criteria of image density (ID) 5; 1.4 or more 4; 1.3 to 1.4 3; 1.2 to 1.3 2; 1.0 to 1.2 1; 1.0 or less

(B) Fog density measurement method Whiteness of A4 size white paper is measured in advance by a whiteness meter (Hunter whiteness meter, manufactured by Nippon Denshoku Industries Co., Ltd.), and the value is defined as a first measured value. Next, using a manuscript including a white circle having a diameter of 55 mm,
The white portions of the copy samples obtained by copying three sheets (initial) and 200,000 sheets (20k) are measured by the whiteness meter described above, and this value is used as a second measured value. The value obtained by subtracting the value of the second measurement value from the first measurement value is defined as the initial and 20k fog values.
The difference from the whiteness was determined, and the value at which the difference was the maximum was shown. Evaluation criteria for fog density (BG) 5; 0.4 or less 4: 0.6 to 0.43; 0.8 to 0.62; 1.0 to 0.81; 1.0 or more

(C) 600 dpi dot image A one-dot toner image is formed under an image forming condition capable of forming 600 dot latent images per inch, and the toner image is enlarged and the image quality is visually determined as follows. It was rated on a scale. 5; excellent 4; good 3; normal 2; slightly poor 1; bad (toner scattering is observed, and the shape of the dot image is irregular.)

(D) Offset resistance Evaluation was made based on the degree of occurrence of the second sheet (initial) and the 200,000th sheet (20k). 5; did not occur at all. 3: There are several occurrences, but there is no practical problem. 1: There are many occurrences (several tens), and there is a problem in practical use. Rank 4 is an intermediate level between ranks 5 and 3, and rank 2
Is an intermediate level between ranks 3 and 1. The comprehensive evaluation was the average of the above evaluations.

(E) Blocking resistance Evaluation was made based on the degree of occurrence of the second sheet (initial) and the 200,000th sheet (20k). 5; did not occur at all. 3: There are several occurrences, but there is no practical problem. 1: There are many occurrences (several tens), and there is a problem in practical use. Rank 4 is an intermediate level between ranks 5 and 3, and rank 2
Is an intermediate level between ranks 3 and 1. The comprehensive evaluation was the average of the above evaluations.

Examples 2 to 12 Various kinds of resins (residual monomers and softening points) used in Example 1 were changed, and the amount of the magnetic fine powder added, the average particle diameter of the toner and the like were changed. Table 3 summarizes the physical properties and evaluation results of each toner obtained according to the toner formulation (Table 1) and the manufacturing conditions (Table 2).

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

The toner of the present invention has good dispersibility between raw materials and excellent anti-offset properties and anti-blocking properties by regulating the amount of residual monomers in the binder resin. It has become possible to provide a toner that does not cause such a problem. In addition, since a styrene-based resin as a binder resin can be used because a relatively large amount of residual monomer is contained, a styrene-based resin which does not require a special demonomerization treatment cost can be used, so that a less expensive one can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an image forming method of an electrophotographic apparatus using a toner of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charger 3 Laser light generating means 4 Developing sleeve 5 Doctor blade 6 Developer supply roller 7 Developing device 8 Toner developer 9 Bias applying means 10 Roller transferring means 11 Voltage applying means 12 Heating / pressurizing roller fixing device 13 Elasticity Blade 14 Collection Box

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme Court ゛ (Reference) G03G 9/08 361 381 (72) Inventor Yoshiaki Akazawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka In-company (72) Inventor Yasuharu Morinishi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takahiro Bito 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72 ) Inventor Yuichiro Takei 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (in reference) 2H005 AA01 AA02 AB02 CA04 CB18 DA08 EA01 EA02 EA03 EA05 EA07 EA10 FA02 2H077 AD06 AD13 AD35 AE03 AE03 AE03 BA07

Claims (6)

[Claims] 1. An electrostatic image developing toner obtained by melting and kneading at least a binder resin, a colorant, a charge controlling agent and a magnetic fine powder, and cooling and finely pulverizing the toner. From 200 to 10
A styrene-based resin containing 00 ppm, and the colorant is carbon black containing at least an organic volatile component;
The organic volatile components in the carbon black during the melt-kneading are reduced by a thermal polymerization reaction with the residual monomer in the binder resin, and the weight average particle diameter is 7.5 to 10.5.
A toner for developing an electrostatic image, wherein the toner has a true specific gravity (g / cc) of 1.1 to 1.3 μm. 2. The binder resin has a softening point of 145 ° C. to 165 ° C.
2. A styrene-based resin selected from the group consisting of styrene-based polymers, styrene-based copolymers, styrene-acrylate-based copolymers, styrene-methacrylate-based copolymers, and mixtures thereof. 3. The toner for developing an electrostatic image according to item 1. 3. The content of the magnetic fine powder is 1 to 10% by weight.
The toner for developing an electrostatic image according to claim 1, wherein the saturation magnetization [σs (Am ² / kg)] of the toner under a magnetic field of 79.58 kA / m (1 K Oersted) satisfies the following condition. 0.1 <σs <3.0 4. The toner has a dielectric loss [tan δ].
The electrostatic image developing toner according to claim 1, wherein (× 10 ⁻³ )] and electrical resistance [R (× 10 ⁺⁹ )] satisfy the following condition. 5. 1.5 <tanδ <4.0, 200 <R <350 5. A two-component developer obtained by mixing a magnetic carrier with the toner for developing an electrostatic image according to claim 1 and charging the toner to a surface of a developer carrier on which a magnet is installed. An image forming method, wherein the toner is adhered to an electrostatic image on the electrostatic image carrier and developed. 6. The image forming apparatus according to claim 5, wherein the clearance between the electrostatic image holding member and the developer holding member holding the toner is 1 mm or more, and is used in an image forming apparatus incorporated as a detachable cartridge in the image forming apparatus main body. Image forming method.