JPH10301326A - Negative charge type magnetic developer and image forming method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an image free from voids and to ensure satisfactory image quality by using a negative charge type magnetic developer consisting of specified toner particles, a flowability improver and specified particles of a metallic salt of a fatty acid. SOLUTION: This magnetic developer consists of toner particles having 5-12 μm volume 50% diameter Dt50 and contg. a resin binder having 3-30 mgKOH/g acid value and magnetic powder having <=0.5 μm number average particle diameter, a flowability improver and particles of a metallic salt of a fatty acid satisfying the formulae Ds50/Dt50<=0.6 and Ds84/Ds16<=6 (where Ds16, Ds50 and Ds84 are the volume 16% diameter, 50% diameter and 84% diameter of the particles, respectively). A monomer forming the resin binder may be added and polymerized at the time of preparing the toner particles but a polymer such as a vinyl copolymer or polyester resin is preferably used as the resin binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a negatively charged magnetic developer and an image forming method using the same. For more information,
The present invention relates to a negatively charged magnetic developer comprising specific toner particles, a fluidity improver, and specific fatty acid metal salt particles, and an image forming method using the same. The negatively charged magnetic developer of the present invention,
Used for electrophotographic copying machines, laser beam printers, etc.

[0002]

2. Description of the Related Art The use of a one-component magnetic developer makes it possible to reduce the size of the developing device and the image forming apparatus main body, and these devices have the advantage of being excellent in reliability such as maintainability. In recent years, its use has been active mainly in forming apparatuses. In the above-described apparatus, in order to quickly charge these magnetic developers and efficiently form a thin layer of the developer on the developing sleeve, a layer forming member is often provided in contact with the developing sleeve. Have been done. Further, as a photoreceptor holding an electrostatic latent image, various electric characteristics can be obtained by selecting a material, etc., the safety as a material is high, and processing into a drum, a sheet, a belt, and the like is easy. Organic photoconductor (OP
C) is frequently used, and a rubber blade of polyurethane or the like is generally used as a method of cleaning residual particles after transfer of a developed image.

[0003] A magnetic developer is obtained by incorporating a magnetic material into the developer. As a method for producing these developers, the respective constituent materials are mixed, melt-kneaded, pulverized, and the like.
A so-called pulverization method for obtaining toner particles by classification is mainly used. Additives such as silica fine particles are externally added to the toner particles in order to improve the fluidity thereof and facilitate the formation of a toner layer on the developing sleeve, thereby preparing a magnetic developer.

[0004]

When developing with a one-component magnetic developer, it is a major problem how to sufficiently charge the developer particles. The surface of the OPC photoreceptor is made of an organic polymer material, and its hardness is smaller than that of the inorganic photoreceptor. Therefore, the surface of the OPC photoreceptor is continuously rubbed with a cleaning blade interposed with a developer. Wear and polishing streaks are likely to occur. In some cases, the developer is rubbed into the polishing streaks, causing dot-like or film-like defects on the photoreceptor. Such deterioration of the surface causes a remarkable decrease in the electrical characteristics of the photoreceptor, and it is a problem to be solved that fatal contamination occurs in the obtained image. Further, depending on the dispersion state of the magnetic powder particles contained in the toner, the magnetic particles themselves may be exposed on the toner surface, for example, causing damage to the photoreceptor, and eventually causing a fatal defect in the image. Therefore, selection of magnetic powder is an important issue.

[0005] First, the problem of charging property relating to the development of developer particles will be described. Originally, in a one-component magnetic developer,
Since the charging mechanism of the developer particles is based on the contact with the developing sleeve, there is less contact opportunity and contact time for charging as compared with a two-component developer having carrier particles, and as a result, the amount of charge per particle And the distribution of the charge amount as the developer must include a large amount of the opposite polarity portion. Furthermore, if the developer is used for a long time, the charge amount of the developer is low, and if the polarity of the charge amount distribution is large, the image density of the obtained image is low, and the fog becomes remarkable. However, the biggest problem is that the transferability of the developer particles in the transfer step is deteriorated, and more specifically, the missing of the transferred image tends to occur. The hollow part of the image is a fatal problem in the image forming apparatus because it makes the characters and lines in the image part unclear. Furthermore, when the charge amount is reduced and the stability is poor after long-term use, the above problem is further promoted. These problems are more likely to become more apparent as developer particles are reduced in size in response to recent market demands for higher image quality.

In order to solve these problems, by providing a layer forming member which is in contact with and pressed against the developing sleeve on the apparatus side, the charging ability to the developer particles is enhanced as compared with the case where only the developing sleeve is used. Therefore, the charge amount of the developer particles relatively increases, and the opposite polarity portion of the charge amount distribution decreases. Accordingly, although image density and image dropout tend to be improved, the stability of the developer charge amount during long-term use is not essentially improved, and the image quality deteriorates over long-term use. Still remains.

[0007] Furthermore, since the image dropout is a problem of transfer, there has been an attempt to improve the dropout by increasing the output of a transfer device (corona charger, roller charger, etc.) in the transfer step. However, in this method, a new problem arises that even if the hollowing is improved, the generation of ozone, NOx (nitrogen oxide), etc. becomes remarkable due to an increase in output. Such a substance promotes oxidation of the surface of the OPC and adsorption of foreign substances, particularly when the OPC is used as the photoconductor, thereby deteriorating its performance. Furthermore, since it is discharged outside the apparatus system, there is a problem that it has a bad influence on the human body and the environment.

On the other hand, as an improvement on the developer side, in particular, in the case of a developer having a load electrode property, a polymerizable monomer having an acid group such as a carboxylic acid is used as a component during the production of a binder resin, so that the developer is improved. It has been known that the negative chargeability of the toner can be improved. This method is an effective method for maintaining the stability of the developer charge amount. However, on the other hand, since these acid groups are hydrophilic groups, in a high-humidity environment, moisture is adsorbed to the developer and charge leakage easily occurs. As a result, there is still a problem that the chargeability is not stable, and the density of an image is increased and the image density is reduced. This improvement is required.

In the case of a magnetic developer, fine magnetic powder may be exposed on the surface of the toner particles. Therefore, the degree of dispersion of the magnetic powder in the resin greatly affects the triboelectric charging property.
It affects the deterioration of toner development characteristics and durability. For example, damage to the photoreceptor due to magnetic powder agglomerates in the toner due to uneven dispersion of the magnetic powder particles during kneading, and fog deterioration due to an increase in opposite polarity fine particles due to uneven charging. Further, when these developers are exposed to a high-temperature and high-humidity environment, the aggregation of the toner due to the magnetic force cannot be sufficiently resolved, and the effect on the image quality and the image density is inevitable.

Next, the problem of contamination on the OPC by the developer particles will be described. In many cases, a large amount of a flow improver such as inorganic fine particles such as silica fine particles is externally added to the toner particles as a flow improver for forming a uniform layer on the developing sleeve. Coarse aggregates are mixed in such inorganic fine particles, which damage the OPC photoreceptor, from which the developer is fixed or fused, thereby causing image contamination. Therefore, if external additives are added after removing coarse aggregates or a fluidity improver that does not originally contain them is selected, the phenomenon of photoreceptor contamination certainly tends to decrease, but is completely eliminated. Cannot be avoided.

In addition, such fine particles change from time to time due to their dropping off from the toner particles or being embedded in the surface of the toner particles. This causes a problem in that the resulting image quality is unstable and the stability of the obtained image quality is lacking. Further, the magnetic powder contained in the magnetic developer may be exposed on the surface of the toner particles.
It damages C and induces contamination on the OPC. In particular, when exposed to a high-temperature, high-humidity environment, the effect becomes more remarkable. Therefore, selection as a magnetic powder requires careful examination.

As described above, there are still problems to be improved in the one-component developer, and individual problems have been individually proposed. However, there is a proposal for solving the above problems comprehensively. It has not been done yet. In addition, there is a limit to the measures on the device side, and measures as a developer have been desired. The present invention has been made in view of the above situation, and has been made in order to solve the problem, and an object of the present invention is to provide a one-component developer and an image forming method capable of obtaining good image quality without image dropout. It is in.

It is another object of the present invention to provide a one-component developer and an image forming method capable of obtaining good image quality with high image density, low fog and excellent sharpness. Another object of the present invention is to provide a one-component developer free of toner scattering and an image forming method. Another object of the present invention is to provide a one-component developer and an image forming method which are free from contamination due to fixation and fusing of a developer to an OPC photoreceptor. It is another object of the present invention to provide a one-component developer and an image forming method which have little change in image quality even under various environmental conditions of a combination of temperature and humidity.

Another object of the present invention is to provide a one-component developer and a method for forming an image, which have high durability and reliability with little deterioration in image density and image quality even during long-term or continuous use. Another object of the present invention is to provide a one-component developer and an image forming method capable of obtaining a sufficient image quality with a small amount of toner consumption.

[0015]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a negatively charged magnetic developer comprising specific toner particles, a fluidity improver and specific fatty acid metal salt particles. The present inventors have found that the above object is satisfied by the above and an image forming method using the same, and have completed the present invention. That is, the gist of the present invention, Toner particles containing a binder resin having an acid value of 3 to 30 mg KOH / g and a magnetic powder having a number average particle size of 0.5 μm or less and having a volume 50% diameter Dt50 of 5 to 12 μm, a fluidity improver and the following formula Negatively-charged magnetic developer comprising fatty acid metal salt particles satisfying (1) and (2);

[0016]

Ds50 / Dt50 ≦ 0.6 (1) Ds84 / Ds16 ≦ 6 (2)

[In the formulas (1) and (2), Ds16, Ds50 and Ds84 each represent 16% by volume of the fatty acid metal salt particles.
Diameter, 50% diameter and 84% diameter]. A developing sleeve for holding a developer and a layer forming member pressed against the developing sleeve are provided, and the layered developer is developed on a photoconductor made of an organic photoconductor, and a transfer material is transferred from the photoconductor. 2. An image forming method including a step of cleaning the photoreceptor with a cleaning blade after transferring to a photosensitive drum, wherein the developer is the negatively charged magnetic developer according to item 1. ,It is in. Hereinafter, the present invention will be described in detail.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Toner particles used in the present invention are usually mixed with magnetic powder and a binder resin and, if necessary, with auxiliaries such as a coloring agent, a charge controlling agent and a releasing agent.
It is a fine powder obtained by melt-kneading, pulverizing and classifying.
At that time, the binder resin is added as a monomer,
Polymerization may be performed during preparation of the toner particles, but it is more convenient and preferable to use a polymer that has been polymerized in advance.

Among the toner components, the binder resin has an acid value of 3 to 30 mgKOH / g, and the resin having an acid value of 3 to 30 mgKOH / g includes:
Vinyl copolymers or polyester resins are preferred. A toner using a binder resin having an acid value of less than 3 (including 0) tends to lower the image density particularly, which is not preferable in terms of image. Conversely, if it exceeds 30, the hygroscopicity particularly under high humidity increases, and problems such as a reduction in image density and a noticeable density unevenness arise.
Therefore, in order to obtain stable image quality that is not affected by environmental changes, the acid value is preferably 3 to 30 mgKOH / g as described above. Here, the acid value refers to the number of mg of potassium hydroxide required to neutralize the acid content contained in 1 g of the resin, and is measured by the method described in JIS K0070. In the case of producing toner particles by a pulverization method, a resin having the above-mentioned acid value may be used as a raw material resin at the time of melt-kneading, and in the case of a polymerization method, the monomer composition may have the above-mentioned acid value. Should be selected. Hereinafter, description will be given in accordance with the pulverization method.

An example of the vinyl copolymer will be described. The vinyl copolymer having an acid value within the above range can be obtained by copolymerizing one or more vinyl monomers and an acid capable of polymerizing these vinyl monomers. First, the polymerizable acid may be any known acid monomer having a polymerizable bond such as a double bond in the structural formula, and examples thereof include non-polymerizable acids such as acrylic acid and methacrylic acid. Saturated monocarboxylic acids, α-chloroacrylic acid, substituted monocarboxylic acids such as α-bromoacrylic acid, fumaric acid, maleic acid, maleic anhydride, unsaturated dicarboxylic acids such as monobutyl maleate, anhydrides thereof, and the like. Half esters and the like.

The vinyl monomer used in the present invention has a polymerizable vinyl bond represented by the formula CH ₂ ＣＨCH— in the structural formula. Such vinyl monomers include, for example, styrene, chlorostyrene,
Styrenes such as α-methylstyrene; methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, methyl methacrylate, ethyl methacrylate, n-methacrylic acid
Monocarboxylic acid esters such as butyl and 2-ethylhexyl methacrylate; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride and vinyl acetate; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl naphthalenes; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N
N-vinyl compounds such as -vinylindole and N-vinylpyrrolidene; and one or more of these are used as vinyl monomers. Among these,
Styrene copolymer, styrene-acrylic copolymer,
A combination of monomers that results in a styrene-methacrylic copolymer is preferred. Further, a copolymer crosslinked with a known crosslinking monomer such as divinylbenzene may be used.

One or more vinyl monomers are copolymerized with a polymerizable acid by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like. At this time, the blending ratio is determined so that the copolymer has an acid value of 3 to 30 mgKOH / g. The compounding ratio is determined by the type and number of the monomers to be used and cannot be determined uniformly, but may be determined so that the synthesized copolymer has an acid value of 3 to 30 mgKOH / g.

The polyester resin comprises a polyhydric alcohol and a polybasic acid, and if necessary, at least one of the polyhydric alcohol and the polybasic acid contains a trifunctional or higher polyfunctional component (crosslinking component). Obtained by polymerizing the monomer composition. In this case, as the dihydric alcohol used for the synthesis of the polyester resin, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,1,
3-propylene glycol, 1,4-butanediol,
Neopentyl glycol, 1,4-butenediol,
Diols such as 1,5-pentanediol and 1,6-hexanediol, bisphenol A such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A and polyoxypropylene bisphenol A, and alkylene oxide adducts thereof; Others can be mentioned. Among these monomers, it is particularly preferable to use a bisphenol A alkylene oxide adduct as a main component monomer, and more preferably an adduct having an average alkylene oxide addition number of 2 to 7 per molecule.

Examples of the trihydric or higher polyhydric alcohol involved in the crosslinking of the polyester include sorbitol and 1,1
2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol,
Tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-
Examples thereof include 1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and others.

On the other hand, polybasic acids include, for example, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid Acids, malonic acid, anhydrides of these acids,
Lower alkyl esters, or n-dodecenyl succinic acid,
Examples thereof include alkenyl succinic acids or alkyl succinic acids of n-dodecyl succinic acid, and other divalent organic acids.

Examples of the tribasic or higher polybasic acid involved in the crosslinking of the polyester include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid,
1,2,4-cyclohexanetricarboxylic acid, 2,5
7-naphthalenetricarboxylic acid, 1,2-4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxy)
Methane, 1,2,7,8-octanetetracarboxylic acid,
And their anhydrides and others. These polyester resins can be synthesized by a usual method. Specifically, the reaction temperature (170 to 250
C.) and reaction pressure (5 mmHg to normal pressure) are determined according to the reactivity of the monomer, and the reaction may be terminated when predetermined physical properties are obtained.

The magnetic powder for obtaining the magnetic developer includes:
Operating environment temperature of printers, copiers, etc. (with 0-60 ° C
Near), ferromagnetic or ferromagnetic
Substances such as magnetite (Fe_ThreeO_Four),
Maghematite (γ-Fe_TwoO _Three), Magnetite and ma
Guhematite intermediate, ferrite (M_xFe
_3-XO_FourWhere M is Mn, Fe, Co, Ni, Cu,
X represents 0, such as Mg, Zn, Cd, or a mixed crystal system thereof.
Spinel ferrite and BaO.
6Fe_TwoO_Three, SrO.6Fe_TwoO_ThreeEtc. Hexagonal Blow
It, Y_ThreeFe_FiveO₁₂, Sm_ThreeFe_FiveO₁₂Garnet
Oxide, CrO_TwoRutile oxides such as Fe, M
Metals such as n, Ni, Co, Cr and other ferromagnetic alloys
Ferromagnetic or ferrimagnetic at around 0-60 ° C
And the like, and these are not limited to single use
Alternatively, two or more kinds can be used in combination. Among them, magnetite
G, maghematite, magnetite and maghematite
Intermediates are preferred, and magnetite is particularly preferred.
You.

The amount of the magnetic powder to be added varies significantly depending on the developing method and the toner particle size.
0 to 80% by weight, more usually 25 to 60% by weight, is contained. The number average particle diameter of the magnetic powder is preferably 0.5 μm or less, more preferably 0.3 μm or less, and particularly preferably 0.2 μm or less fine particles in terms of performance. In addition, as a method of specifying the number average particle diameter of the magnetic powder,
Using a transmission electron microscope, magnetic particles in a photograph of a thin section of the toner taken at a magnification of 20,000 times were randomly extracted by about 300 times.
The number is selected and the horizontal Feret diameter is calculated.

The reason why the magnetic powder according to the present invention has good performance can be estimated as follows. That is, since the magnetic fine particles according to the present invention have a very small average particle diameter, they are easily dispersed in the binder resin as fine particles. In addition, the acidic component-containing resin according to the present invention has particularly good dispersibility. Due to these synergistic effects, the resin is essentially covered with the resin, so that it is hardly exposed on the toner surface. Even if these magnetic fine particles are exposed on the toner surface, O
This is probably because the PC surface is hardly damaged. If the magnetic powder according to the present invention satisfies the particle size requirement, a good state can be obtained irrespective of its shape, such as spherical, acicular or polyhedral.

The magnetic powder can be used also as a coloring agent. As the coloring agent that can be added as required, any suitable pigment or dye can be used as long as it is conventionally used. For example, carbon black, titanium oxide, zinc white, alumina white, calcium carbonate, navy blue or the like inorganic pigments, monoazo pigments, disazo pigments, copper phthalocyanine pigments, organic pigments such as quinacridone pigments, anthraquinone dyes, rhodamine dyes and the like. They may be used alone or as appropriate.

As the charge control agent usable in the present toner,
It is a negative charge control agent for obtaining a load electrode property. For example, JP-A-58-208750, JP-A-59-783.
No. 61, etc .;
No. 27726, a salicylic acid metal complex described in JP-A-63-163374, a calixarene compound containing no metal element described in JP-A-5-119535, and the like. No. As a method of incorporating the charge control agent into the toner, there are a method of adding the charge control agent inside the toner and a method of externally adding the same. When added internally, the amount of these compounds used is usually 0.05 to 2 parts by weight based on 100 parts by weight of the binder resin.
The amount is preferably 0 parts by weight, more preferably 0.1 to 10 parts by weight. When externally added, resin 100
It is preferably 0.01 to 10 parts by weight based on parts by weight.

In addition, as the auxiliary agent which can be added to the toner for the purpose of improving the thermal characteristics and physical characteristics, known ones can be used. For example, polyalkylene wax, paraffin wax as a releasing agent can be used. , Higher fatty acids, fatty acid amides and the like. The amount of the binder resin 1
0.1 to 10 parts by weight is preferable with respect to 00 parts by weight.
An outline of a method for producing toner particles by a pulverization method is described below. First, a binder resin, a colorant, a charge control agent, and the like, which are constituent materials of the toner, are blended and mixed at a predetermined ratio. As a device at this time, a gravity drop mixer such as a V blender or a ball mill, or a high-speed fluid mixer such as a Henschel mixer (manufactured by Mitsui Miike Kakoki) or a super mixer (manufactured by Kawata) is used. .

After mixing, the mixture is melt-kneaded. Examples of the apparatus used in the melt kneading step include a two- or three-roll mill, a Banbury mixer, a single-screw or twin-screw extruder, and the like. In this step, a component having compatibility with the binder resin is melted with the resin, and a component such as a charge control agent having no compatibility with the binder resin is dispersed in the molten resin.

Next, after cooling and solidifying the melt-kneaded product,
The toner particles are manufactured through the steps of coarse pulverization, fine pulverization and classification. Hammer mills and cutter mills are used for coarse pulverization, and mechanical pulverizers such as high-speed rotary pulverizers and jet pulverizers such as impact-type jet mills and fluidized-bed jet mills are used for fine pulverization. For example, a forced vortex centrifugal classifier or an inertial classifier is used.

The toner particles relating to the magnetic developer of the present invention have a volumetric 50% diameter Dt50 of 5 to 12 after pulverization and classification.
A micrometer is preferable because a high quality image can be obtained. When the thickness is less than 5 μm, toner scattering is severe and fogging of an obtained image is deteriorated.
If it exceeds m, the sharpness of the obtained image tends to decrease, which is not preferable.

The particle size is measured by a laser diffraction type particle size distribution measuring system Heros & Rodos (SYMPAT, Germany).
It is preferable to carry out the process under the following conditions by using a coulter counter (manufactured by Coulter, USA). Dispersion method: Flow-type dispersion unit Dispersion air pressure: 2 bar Lens focal length: 100 mm Measurement time: 3 seconds The magnetic developer of the present invention comprises these toner particles, a flowability improver, and fatty acid metal salt particles.

A fluidity improver is externally added to the toner particles according to the present invention. Examples of the fluidity improver include fine particles of inorganic oxides such as silica, alumina, and titania, and resin beads such as polymethyl methacrylate, Teflon, and silicone resin. In the present invention, it is more preferably at least one selected from silica, alumina and titania, and most preferably all are silica fine particles. Further, it is preferable that the fluidity improver such as silica fine particles has an average primary particle diameter of 5 to 50 nm. The method for producing the silica fine particles according to the present invention may be either a dry method or a wet method. Further, it is desirable that the surface is subjected to a hydrophobic treatment. Specific examples of the hydrophobizing agent include hexamethyldisilazane and silicone oil, and it is preferable that the hydrophobizing agent is subjected to the hydrophobizing treatment with any of them. On the other hand, for example, when treated with dimethyldichlorosilane as a hydrophobizing agent, the resulting fluidity improver tends to leave coarse aggregates, which may cause photoreceptor scratches. Not preferred. In the present invention, the particle diameter of the fatty acid metal salt particles satisfies the following formulas (1) and (2).

[0038]

Ds50 / Dt50 ≦ 0.6 (1) Ds84 / Ds16 ≦ 6 (2)

[In the formulas (1) and (2), Ds16, Ds50 and Ds84 each represent 16% by volume of the fatty acid metal salt particles.
Diameter, 50% diameter, and 84% diameter]. Conventionally, fatty acid metal salts have been used in the contact rubbing step (photoreceptor and cleaning blade, etc.) in the electrophotographic process to smooth out the rubbing by the frictional action of the particles. It has been known to be effective in preventing adhesion due to frictional heat and the like. The present inventors adopt the fatty acid metal salt particles having a special particle size distribution satisfying the above formulas (1) and (2),
Especially in the case of a one-component magnetic developer, in addition to the above-mentioned effects, the chargeability of the toner particles is increased, the reverse polarity portion of the charge amount distribution is reduced, and the long-term stability of the chargeability is also improved, thereby resulting in an image dropout. And the like, there is an effect of improving image quality required items. These also improve problems such as poor charging of the acid component-containing resin under high humidity.

The measurement of the particle size and the particle size distribution described above is desirably performed using the above-described apparatus and conditions. The fatty acid metal salt particles according to the present invention are characterized by having a small particle size and a narrow range of the particle size distribution as shown by the above formulas (1) and (2). In equation (1), Ds50 / Dt
When the value of 50 is larger than 0.6, it means that the particle size of the fatty acid metal salt particles is close to or larger than the particle size of the toner particles. It is not preferable because it drops off from the agent and scatters outside the system, not only contaminating the apparatus, but also being detected as large-grained fog on the image. Further, in the formula (2), when Ds84 / Ds16 representing the width of the particle size distribution of the particles exceeds 6 and is large, the particle sizes of the particles are not uniform, so that the chargeability of the developer can be stably maintained for a long period of time. This makes it difficult to suppress variations in image quality. The particle size distribution of the fatty acid metal salt particles is desirably a single-peak distribution.

The fatty acids of the fatty acid metal salt particles used in the present invention include monovalent saturated fatty acids such as butyric acid, valeric acid, lauric acid, myristic acid, palmitic acid, stearic acid and montanic acid, adipic acid, pimelic acid, and the like. Suberic acid, polyvalent saturated fatty acids such as azelaic acid and sebacic acid, monounsaturated fatty acids such as crotonic acid and oleic acid, and polyunsaturated fatty acids such as maleic acid and citraconic acid, In the present invention, a metal salt of a saturated or unsaturated fatty acid having 8 to 35 carbon atoms can be preferably used, and stearic acid is particularly desirable. Metal salts include lithium, sodium, potassium, copper,
Including, but not limited to, rubidium, silver, zinc, magnesium, calcium, strontium, aluminum, iron, cobalt, nickel salts and mixtures thereof.
Among the above, stearic acid is more preferable as the fatty acid, and a metal selected from zinc, magnesium, calcium, and aluminum is more preferable as the metal. Among them, it is particularly preferable to use zinc stearate.

As a method for adding the fluidity improver and the fatty acid metal salt particles to the toner particles, it is preferable to externally add the particles using a high-speed fluid mixer or the like. If necessary, these additives may be individually or mixed in advance and pulverized to remove coarse aggregates and externally add the toner particles. The addition amount of these particles is preferably 0.01 to 3 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the toner particles.
03 to 1 part by weight, and 0.05 to 3 parts of the fluidity improver.
It is preferable to add 0.1 parts by weight, more preferably 0.1 to 2 parts by weight.

[0043]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples and comparative examples, “parts” simply means “parts by weight”. Example 1 A magnetic one-component developer was prepared according to the following compounding ratio. Styrene resin 100 parts (Monomer weight ratio: styrene / n-butyl acrylate / methacrylic acid = 37/12/1, acid value about 12 mg KO
H / g) Charge control agent Chromium-containing gold azo dye 2 parts (Bontron S-34, manufactured by Orient Chemical Co.) 70 parts of magnetite magnetic powder (number average particle diameter about 0.15 μm) Low molecular weight polypropylene 3 parts (Viscol 550P, Sanyo) Kaseisha)

The raw materials are mixed by a high-speed fluid mixer, melt-kneaded by a twin-screw extruder, coarsely ground by a hammer mill, and finely ground by a mechanical grinder Cryptron (manufactured by Kawasaki Heavy Industries, Ltd.). After pulverization, it was classified with a zigzag classifier (manufactured by Alpine). The average particle size Dt50 of the toner particles is 10.
It was 0 μm. With respect to 100 parts of the toner particles, 0.3 part of zinc stearate particles having an average particle diameter Ds50 of 2.9 μmDs84 / Ds16 of 2.8 and an average primary particle diameter of which hydrophobic treatment was performed with hexamethyldisilazane were about 0.6 parts of 10 nm silica fine particles were externally added with a high-speed mixer to obtain a negatively charged magnetic developer. Each particle size distribution of the toner particles and the zinc stearate particles was measured by a Heros & Rodos system.

As a real image evaluation apparatus, a commercially available printer employing a magnetic one-component developing system was modified and used. The photoreceptor of this printer is a drum-shaped laminated OPC having a diameter of 30 mm with a surface layer containing a polycarbonate resin, and a urethane rubber cleaning blade as a cleaning member is pressed against the photoreceptor. In the developing device, a urethane rubber blade (developer layer forming member) is pressed against a stainless steel developing sleeve containing a magnet. On the other hand, the fixing device is of a heat roller type, the upper roller (toner contact surface) is formed of a fluorine resin surface, the lower roller is formed of silicone resin, and the upper roller has a built-in fixing lamp. To control the roller surface to about 180 ° C. Next, a fixed amount of the magnetic developer is supplied to the developing device so that about 7,000 sheets can be printed.

The evaluation method is as follows.
The sample was placed in a normal temperature and normal humidity atmosphere at 55 ° C. and a relative humidity of 55%, and was continuously photographed.
The image quality such as image dropout, image density, fog, etc. was excellent through actual photographing of 000 sheets, and toner scattering was good without any problem. In addition, no poor cleaning on the OPC and no fusing phenomenon such as developer particles were observed, and the durability was sufficient. There was no peeling of the image after fixing, the fixing property was good, and no offset phenomenon occurred. On the other hand, the developer and the printer were brought into a high-temperature and high-humidity condition of a temperature of 35 ° C. and a relative humidity of 85%, and the same continuous actual photographing was performed. The result was almost the same as the result in a normal temperature and normal humidity environment. Further, the developer and the printer were brought into a high-temperature, high-humidity condition of a temperature of 10 ° C. and a relative humidity of 20%, and the same continuous actual photographing was performed. The result was almost the same as the result in a normal temperature and normal humidity environment.

Example 2 Toner particles were obtained in exactly the same manner as in Example 1, except that the Dt50 of the toner particles was 7.1 μm.
Hereinafter, the same zinc stearate particles and silica fine particles as used in Example 1 were similarly added to prepare a magnetic developer. The actual photographing apparatus and method were performed in the same manner as in Example 1.
As a result, good results were obtained in the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment as in Example 1.

Example 3 Using the toner particles prepared in Example 1, 100 parts of the toner particles had a Ds50 of 4.7 μm and a Ds84 / Ds16.
With the exception that 0.3 parts of zinc stearate particles having a particle size of 3.7 and 1.0 parts of silica fine particles having an average primary particle diameter of about 30 nm hydrophobized with hexamethyldisilazane are added.
A magnetic developer was prepared in the same manner as in Example 1. Hereinafter, the actual photographing evaluation was performed in the same manner as in Example 1 for the actual photographing apparatus and method. As a result, good results were obtained in the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment as in Example 1.

Example 4 To 100 parts of the toner particles used in Example 1, 0.3 part of the zinc stearate particles used in Example 1 and an average primary particle diameter of about 10 nm which had been hydrophobized with silicone oil were used. A magnetic developer was prepared in the same manner as in Example 1 except that 0.6 part of silica fine particles was added. Hereinafter, the actual photographing evaluation was performed for both the actual photographing apparatus and method in the same manner as in Example 1. As a result, good results were obtained in the normal temperature and normal humidity environment, the high temperature and high humidity environment, and the low temperature and low humidity environment as in Example 1.

Example 5 Among the raw materials used in Example 1, magnetite magnetic powder having a number average particle diameter of about 0.1 μm was used.
In the same manner as in the above, toner particles were produced. The parts by weight of magnetite and the other raw materials and the parts thereof were the same as those in Example 1. Dt50 of the obtained toner particles is 10.
It was 0 μm. As in Example 1, zinc stearate particles and silica fine particles were added to 100 parts of the toner particles to obtain a magnetic developer. Hereinafter, the evaluation of the actual photographing was performed in the same manner as in Example 1 except for the supply amount of the magnetic developer in both the actual photographing apparatus and the actual photographing method. As a result, the evaluation result in a normal temperature and normal humidity environment is excellent even when the actual photograph reaches 9000 sheets.
No poor cleaning on the PC and no fusing phenomenon such as developer particles were observed, and good image quality was obtained as in Example 1. In addition, in a high-temperature and high-humidity environment and in a low-temperature and low-humidity environment, the results were as good as in Example 1.

Comparative Example 1 Using the toner particles prepared in Example 1, 100 parts of the toner particles had a Ds50 of 7.0 μm and a Ds84 / Ds16.
Example 1 except that 0.3 parts of zinc stearate particles having a particle size of 3.8 and 0.6 parts of silica fine particles having an average primary particle diameter of about 10 nm which had been hydrophobized with hexamethyldisilazane were added. Similarly, a magnetic developer was prepared. Hereinafter, the actual photographing evaluation was performed in the same manner as in Example 1 for the actual photographing apparatus and method. As a result, large fog was generated from the beginning of the actual shooting, which was not preferable in terms of image quality.

Comparative Example 2 Using the toner particles prepared in Example 1, 100 parts of the toner particles had a Ds50 of 3.3 μm and a Ds84 / Ds16.
Example 1 except that 0.3 parts of zinc stearate particles having a particle size of 6.4 and 0.6 parts of silica fine particles having an average primary particle diameter of about 10 nm hydrophobized with hexamethyldisilazane were added. Similarly, a magnetic developer was prepared. Hereinafter, the actual photographing evaluation was performed in the same manner as in Example 1 for the actual photographing apparatus and method. As a result, good image quality was obtained in the initial stage of actual photographing, but the image density began to decrease after about 3000 sheets, and there was a problem in image quality.

Comparative Example 3 The toner particles prepared in Example 5 were used, and Ds50 was 7.0 μm and Ds84 / Ds16 based on 100 parts of the toner particles.
Of zinc stearate having a particle size of 3.8 and 0.6 parts of silica fine particles having an average primary particle diameter of about 10 nm, which has been hydrophobized with hexamethyldisilazane, are externally added by a high-speed fluid mixer. Thus, a magnetic developer was prepared. Hereinafter, the actual photographing evaluation was performed in the same manner as in Example 1 for the actual photographing apparatus and method.
As a result, fog worsened from the beginning of the actual shooting, and there was a problem in image quality.

Comparative Example 4 Of the raw materials used in Example 1, a magnetite magnetic powder having a number average particle diameter of about 0.6 μm was used.
Toner particles were produced using exactly the same material, number of copies, and the same manufacturing method as in Example 1. Dt50 of the obtained toner particles is 1
0.2 μm. As in Example 1, zinc stearate particles and silica fine particles were added to 100 parts of the toner particles to obtain a magnetic developer. As a result, good image quality was obtained in the initial stage of actual shooting, but after about 5,000 sheets, many spot-like white spot defects were observed in the solid portion of the image, causing a problem in image quality.

[0055]

According to the one-component developer of the present invention and the image forming method using the same, the following effects can be obtained, and the industrial use value thereof is high. (1) Good image quality without image dropout is obtained. (2) Good image quality with high image density, less fog, and excellent sharpness. (3) There is no toner scattering. (4) There is no contamination due to fixation or fusion of the developer to the OPC photoconductor. (5) There is little change in image quality even under various environmental conditions of a combination of temperature and humidity. (6) Even in long-term or continuous use, there is little deterioration in image density and image quality, and durability and reliability are high. (7) Sufficient image quality can be obtained with a small amount of toner consumption. (8) Fixing can be performed with low energy, and there is no fixing machine contamination or image contamination due to the offset phenomenon.

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI G03G 9/08 368 381

Claims (12)

[Claims] 1. A toner comprising a binder resin having an acid value of 3 to 30 mg KOH / g and a magnetic powder having a number average particle diameter of 0.5 μm or less and having a volume 50% diameter Dt50 of 5 to 12 μm and fluidity. A negatively charged magnetic developer comprising an enhancer and fatty acid metal salt particles satisfying the following formulas (1) and (2). Ds50 / Dt50 ≦ 0.6 (1) Ds84 / Ds16 ≦ 6 (2) [In the formulas (1) and (2), Ds16, Ds50 and Ds84 are
These represent the 16%, 50% and 84% diameters of the fatty acid metal salt particles, respectively. 2. The method according to claim 1, wherein the binder resin is a vinyl copolymer or a polyester resin.
4. The negatively charged magnetic developer according to item 1. 3. The number average particle diameter of the magnetic powder is 0.3 μm.
The negatively charged magnetic developer according to claim 1 or 2, wherein: 4. The negatively charged magnetic developer according to claim 1, wherein the fluidity improver is silica. 5. The fluidity improver having an average primary particle size of 5
The negatively charged magnetic developer according to any one of claims 1 to 4, wherein the thickness is from 50 to 50 nm. 6. The negatively charged magnetic developer according to claim 1, wherein the fluidity improver has been subjected to a hydrophobic treatment. 7. The negatively charged magnetic developer according to claim 6, wherein the fluidity improver is subjected to a hydrophobic treatment with hexamethyldisilazane or silicone oil. 8. The negatively charged magnetic developer according to claim 1, wherein the fatty acid metal salt particles are metal stearate particles. 9. The negatively charged magnetic developer according to claim 8, wherein the metal stearate is zinc stearate. 10. The toner according to claim 1, wherein the fluidity improver is contained in an amount of 0.05 to 3 parts by weight and the fatty acid metal salt particles in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the toner particles. 10. The negatively charged magnetic developer according to any one of 1 to 9. 11. A developing sleeve for holding a developer and a layer forming member pressed against the developing sleeve, wherein the layered developer is developed on a photoconductor made of an organic photoconductor, and 2. The image forming method according to claim 1, further comprising the step of cleaning the photosensitive member with a cleaning blade after transferring the image from the body to the transfer material.
An image forming method, comprising the negatively chargeable magnetic developer according to any one of items 1 to 10. 12. The image forming method according to claim 11, wherein the photoconductor is an organic photoconductor.