JPH0259987B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a dry developer for visualizing electrical latent images in electrophotography, electrostatic recording, etc., and particularly to a one-component developer that uses only toner particles without using carrier particles. . (Prior Art) The method of forming an electrical latent image is conventionally well known. For example, in electrophotography, a photoconductor layer is usually charged and then a light image based on an original image is irradiated to form a light-irradiated area. Reduce or eliminate electrostatic charge to form an electrostatic latent image. This latent image is then developed with a developer called toner. As is well known, development methods are broadly divided into methods using wet developers and methods using dry developers, and the latter include two-component development methods that use two types of particles, carrier and toner, and those that use only toner. It is classified as a one-component development method. A two-component developer imparts an electric charge to toner particles through frictional charging of carrier particles and toner particles. Therefore, it is possible to control the charge of the toner relatively easily by selecting carrier and toner materials, and two-component developers are the mainstream of current developing methods. However, since frictional charging is used as the charging principle, the charging property may change over time with repeated use, causing the developer to deteriorate, or the charging property may differ between high temperature and high humidity and low temperature and low humidity. It has the disadvantage that it cannot necessarily be used stably in all environments. Furthermore, since not only toner particles but also carrier particles are used, the developing device becomes large and heavy, and the cost also increases. In order to solve these problems, in recent years, research and development have been actively conducted to review and develop single-component developers that do not use carrier particles. In the case of a one-component developer, since only toner particles are used, the problem is how to impart charge to the toner. When a relatively conductive toner is used to charge the toner by electrostatic induction, changes in charging over time such as triboelectric charging and environmental dependence can be ignored, and good developability can always be obtained. However, since conductive or semiconductive toner is used, it is difficult to transfer the image onto paper or the like. Methods of imparting electric charge to toner through contact between the toner and developing device members such as blades and developer sleeves, frictional charging, or frictional charging between toner particles have also been proposed and put to practical use.
The drawbacks of conventional two-component developers, such as changes in charging properties over time and environmental dependence, cannot essentially be overcome because they utilize triboelectric charging. The method of charging toner by ion irradiation using a corotron or the like also has many practical problems such as uneven charging, corotron contamination, and ozone generation. A method using dielectric polarization has also been proposed, but in this case, development can only be done in principle in areas where the electric field intensity changes significantly, and this is not common. As described above, conventional one-component development methods and developers do not fully satisfy toner charging, developability, and transferability, and it is difficult to overcome the drawbacks of two-component development methods and developers. Not yet. From the viewpoint of developer materials, conventional two-component developers use a combination of two types, carrier particles and toner particles, and separate and share the developer function between them. On the other hand, single-component developers add to the toner the functions that were previously shared by carrier particles.
It is necessary to separate and share functions within the toner. However, at present, material design guidelines for multifunctional one-component developers that fully satisfy these requirements have not yet been established. (Object of the Invention) Therefore, an object of the present invention is to provide a developer composition that is excellent in charging and developing methods even when carrier particles are not used. Another object of the present invention is to provide a developer composition with excellent developability and transferability. Still another object of the present invention is to provide a developer composition whose charging, development, and transfer properties are stable against environmental changes such as temperature and humidity. Still another object of the present invention is that upon repeated use,
It is an object of the present invention to provide a developer composition that does not change its charging, developing, or transfer properties, and that does not substantially change over time or deteriorate. Still another object of the present invention is to provide a developer composition capable of forming good and stable images in any image forming process. Still another object of the present invention is to develop, develop and
An object of the present invention is to provide a developer composition having excellent transferability. (Structure of the Invention) The above-mentioned object is to prepare 15 to 70% by weight of magnetic powder having an average particle size of 0.01 μm to 2 μm, a styrene monomer component, and the following general formula (A): (In the above formula, R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, and may be the same or different, and R At least one of ₂ and _R3 is a lower alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4. Insulating particles having an average particle size of 1 to 50 μm and having a binder resin containing 20% by weight or more in the binder resin component are added and mixed in a range of 0.1 to 2.0% by weight to the insulating particles. conductive particles that are loosely adhered or fixed to the surface of the insulating particles, and the electrical resistivity as a whole is 10 ¹⁵ Ω.
This can be achieved with a developer composition characterized in that it is larger than cm. Generally, regardless of magnetic toner or non-magnetic toner,
The charging and developing mechanisms of high-resistance single-component developers are complex, and, with some exceptions, have not yet been fully elucidated in terms of physical properties. This is because high-resistance one-component developers are difficult to handle from a material science standpoint, such as composite material particles in an electrically dielectric region, and image-forming processes such as development and transfer require high electric fields and short development times. However, this is based on the complexity of development, in which the developer is not stationary but is in motion. In other words, stably imparting a charge to a high-resistance single-component developer and controlling its developability and transferability requires a high electric field (usually around 10 ³ to 10 ⁵ V/cm) and a short period of time (10 ^-1 to 10 5 V/cm).
It would be good to understand the problem of how to precisely control and design the electrical response of the developer at a time of about 10 ^-3 sec). As a result of extensive studies, the inventor of the present invention discovered that by making a nitrogen-containing polar functional group and a conductive component coexist on the surface of developer particles, and further adjusting the electrical resistivity of the developer particles to be greater than 10 ¹⁵ Ωcm, It has been found that extremely good and stable charging, development and transfer properties can be obtained.
The developer of the present invention can be used, for example, in the development area (electric field
10 ⁴ V/cm), time 10 ^-2 sec),
Instantly obtains a charge, provides excellent solid black, fine line, and gradation reproduction, and produces good developed images without contamination in non-image areas.
No change over time is observed even after repeated use. In addition, charging, development, and transfer properties are extremely stable, from a low-temperature, low-humidity environment of 10°C and 15% humidity to a high-temperature, high-humidity environment of 30°C and 85% humidity. Incidentally, even in a high temperature and high humidity environment, the electrostatic transfer rate is approximately 80% or more, and there is no deterioration in image quality due to developer scattering during transfer. High image quality and stability over time that surpass the two-component developers that are reaching maturity.
It was confirmed that it has environmental stability. Furthermore, the developer of the present invention has a wide selection tolerance for image forming processes and photosensitive materials, and basically has a wide selection range for photosensitive materials.
It was also confirmed that development with negative polarity is possible. Although the detailed mechanism of why the developer of the present invention has such excellent image forming properties is not necessarily clear, it is due to the interaction between the nitrogen-containing polar functional group on the surface of the developer particle and the conductive component. This is presumably because the generation, exchange, movement, and retention of charges are performed stably, especially in the presence of an electric field. In addition, the reason why the transferability is good even under high temperature and high humidity despite containing a conductive component is not only because the macroscopic electrical resistivity of the developer is high, but also because the charge on the surface of the developer particles is uniform. This seems to be because it is difficult to generate a local high electric field during transfer, and charge injection from the side of the transfer target such as paper is blocked. Hereinafter, the configuration of the present invention will be explained in more detail.
First, as monomer components for introducing a nitrogen-containing polar functional group into the binder resin, N-methylaminoethyl acrylate, N-ethylaminoethyl acrylate, N,N-dimethylaminoethyl acrylate, N,N -Substituted amino group-containing acrylates such as diethylaminoethyl acrylate, N,N-dibutylaminoethyl acrylate, N,N-diethylaminopropyl acrylate, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate , N-methylaminoethyl methacrylate, N-ethylaminoethyl methacrylate, 2-N,N-dicyclohexylaminoethyl methacrylate, N,N-dibutylaminoethyl methacrylate, 2-phenylaminoethyl methacrylate, 2-dibenzylaminoethyl methacrylate substituted amino group-containing methacrylates such as aminostyrene, dimethylaminoethylstyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, allylamines such as allylamine, allylmethylamine, N-vinylpyridine, 2 Vinylpyridines such as -vinyl-5-methylpyridine, vinylamines, vinylquinolines and allylquinolines, acrylamides, N-vinylamides, etc. can be used. These monomers can be polymerized and used as a homopolymer, or vinyl monomers such as styrenes, methacrylates, acrylates, and dienes, which are usually used as monomer components of binder resins for developers, can be used. It is possible to copolymerize with a polymer and introduce a nitrogen-containing polar functional group into the binder resin. Also, polyamide,
Resins having nitrogen-containing polar functional groups such as polyamines, polyurethanes, and polyureas may be used as they are as part of the binder resin. Furthermore, nitrogen-containing polar functional groups such as substituted amino groups can be introduced into polymer side chains, terminals, etc. using chemical reactions such as polymer reactions, or furthermore, polymer side chains, terminals, etc. can be substituted. Treatments such as converting the amino group into a quaternary ammonium salt may also be performed. In this way, the nitrogen-containing polar functional groups introduced into the binder resin, especially the functional groups rich in electron toner properties or cationic properties such as substituted amino groups, generally have a good charge in coexistence with the conductive component. Although it exhibits exchangeability, in order to satisfy all the various physical and chemical requirements from all steps of image formation as a developer, substituted amino group-containing methacrylate or acrylate represented by the general formula (A) is required. It is necessary to use a binder resin containing as a monomer component. The monomer represented by the general formula (A) is combined with monomers commonly used as binder resin components such as styrene, vinyltoluene, n-butyl methacrylate, and methyl methacrylate so that the glass transition temperature is approximately 40 to 70°C. , it is desirable to copolymerize and use. Although it cannot be specified simply because it depends on the form of use, the electrical properties of the developer tend to be stabilized by adjusting the composition so that the amine value is about 5 to 80, preferably about 10 to 50. Here, ``Amine value indicates the number of mg of potassium hydroxide equivalent to 1 g of amine.The nitrogen-containing polar functional group must be present on the developer particle surface together with the conductive component.Substituted amino group In order to make it easier for the nitrogen-containing polar functional groups such as, etc. to be selectively exposed on the developer surface, it is desirable to control the positioning of these functional groups at the ends of the molecular chain or adjust the molecular weight distribution. The number average molecular weight of the binder resin containing the monomer component represented by formula (A) is preferably 30,000 or less, which is less likely to cause entanglement of molecular chains, and more preferably,
It is very effective to control it within the range of 2000 to 10000. In addition to the binder resin component containing the nitrogen-containing polar functional group, examples of the binder resin include styrene resin, acrylic resin, polyethylene, polypropylene, polyethylene oxide, polypropylene oxide, ethylene-vinyl acetate copolymer, chlorinated polyethylene, etc. Olefin resins, epoxy resins, polyesters, polycarbonates, polyamides, polyurethanes, silicone resins, fluorine-containing resins, diene resins such as butadiene and isoprene, petroleum resins, phenolic resins, rosin-modified resins, etc. Used as adhesive resin. One or more synthetic and natural resins may be mixed. The mixed form may be a polyar blend or a chemically bonded finely mixed state such as graft copolymerization. Also, development,
In accordance with the requirements of image forming processes such as fixing, these binder resin components can be made of crystalline/amorphous, linear/nonlinear (branched, crosslinked, interpenetrating, etc.) homopolymers/copolymers (random, alternating, etc.). A physical structure such as a block, a graft, etc.) may be selected and used together with a chemical structure. In addition, when using various binder resin components together,
It is preferable to use the binder resin component containing a nitrogen-containing polar functional group in an amount of 20% by weight or more, preferably 40% by weight or more of the total binder resin component. As a conductive component, the electrical resistivity is approximately 10 ⁸ Ωcm.
The following semiconductive and conductive materials can be used. These materials include metal powders such as gold, silver, copper, iron, aluminum, and nickel, metal oxides such as tin oxide, iron oxide, and ferrite, inorganic materials such as carbon black and graphite, polyacetylene,
Examples include organic semiconductors such as organic charge transfer complexes and conductors. However, in order to achieve rapid charge exchange and transfer under an electric field, the electrical resistivity of the conductive component must be approximately
It is desirable that the material is highly conductive with a conductivity of 10 ³ Ωcm or less.
Inorganic powders such as silica with a conductive thin film layer such as carbon black powder or tin oxide on the surface are easy to use. Among them, carbon black powder with a particle size of about 10 mμ to 70 mμ is extremely convenient for practical use. The conductive component must exist as a discontinuous layer on at least the surface layer portion of the insulating particles together with the nitrogen-containing polar functional group in the insulating particles. For this reason, the conductive component may be added inside the insulating particles, but beyond that, the conductive component is added and mixed after the insulating particles are prepared, and the conductive component is added to the surface of the insulating particles. A method of adhering or fixing is very effective. Therefore, when adding, mixing, and adhering a conductive component to the surface of an insulating particle, it is difficult to unconditionally specify the particle size, shape, specific gravity, etc. of the insulating particle and the conductive component, but the insulating particle By adding approximately 0.1 to 2.0% by weight of a conductive component to the insulating particles and mixing with a high-speed stirring mixer, V-type blender, etc., a discontinuous layer of the conductive component can be formed on the surface of the insulating particles. is good. For example, if the insulating particles are carbon black powder with a particle size of 15 μm and a specific gravity of 2.0, and the conductive component is carbon black powder with a particle size of 20 μm and a specific gravity of 1.8, the optimal amount of the conductive component to be added to the insulating particles is approximately 0.3% to 0.6% by weight. % by weight. Note that, if necessary, the conductive component may be fixed to the surface of the insulating particles by means such as hot air. Here, adhesion refers to a state in which conductive particles are loosely arranged on the surface of an insulating particle due to electrostatic force and can move relatively freely on the particle surface, and adhesion refers to a state in which conductive particles are loosely arranged on the surface of an insulating particle and can move relatively freely on the particle surface. A state where free movement on the particle surface is restricted by being embedded in the surface of the particle by mechanical/thermal force. When the developer of the present invention is used as a magnetic one-component developer, magnetic powders such as metals such as iron, cobalt, and nickel, alloys thereof, and metal oxides are added to the binder resin of the insulating particles. There is a need. In the case of magnetic toner, Fe ₃ O ₄ , γ-Fe ₂ O ₃ ,
Cobalt-added iron oxide and MnZn ferrite,
Ferrite powders such as NiZn ferrite and Zn ferrite are used. These magnetic powders can be selected as either granular or acicular powder depending on the application, and the particle size can be varied.
About 0.01μm to 2μm, particularly preferably from 0.1μm
Granular magnetic powder of about 1 μm is easy to use. These magnetic powders may contain surfactants, long-chain fatty acids and their derivatives, silane coupling agents, titanate coupling agents, -COOH groups, -
Surface treatment is performed with oligomers, polymers, etc. having polar functional groups such as OH groups and _-NH2 groups, or a polymerization reaction is performed on the surface of the magnetic powder to coat the surface of the magnetic material with a polymer component. Afterwards, it may be added and mixed into the binder resin for use. The content of magnetic powder in the insulating particles varies depending on the development method etc. or the specific gravity of the magnetic powder, but it is preferably used in the range of 15 to 70% by weight based on the binder resin. . In particular, when it is used in a range of 40 to 60% by weight, the objects and advantages of the present invention can be fully exhibited. In addition, if the magnetic powder is conductive or semiconductive, if the structure is controlled so that the magnetic powder is exposed on the surface layer of the insulating particles, it is possible to share the function of the conductive component. be. In addition to this, various additives such as colorants can be contained inside the insulating particles. As the colorant, conventionally known carbon black, magenta, yellow, various cyan pigments, nigrosine, fast blue, and other various dyes can be used. Furthermore, it may contain a surfactant, a quaternary ammonium salt, a charge control agent such as a metal-containing dye having an organic complex structure, a plasticizer, a granular or fibrous organic and inorganic filler, a blowing agent, an antioxidant, and the like. In addition to the conductive component, the surface of the insulating particles is also used to further improve the fluidity and storage stability of the developer, or to prevent toner from filming on photosensitive materials. Other external additives may be added for the purpose of improving the cleaning properties of the material. These external additives include long-term fatty acids such as stearic acid, their esters, amides, metal salts, and fine powders such as molybdenum disulfide, graphite fluoride, silicon carbide, boron nitride, silica, aluminum oxide, titanium dioxide, and zinc oxide. , fine powders such as fluorine-based resins, polycyclic aromatic compounds, wax-like substances, crosslinked or non-crosslinked resin fine powders, and although not necessarily limited, they usually have a low surface energy with a critical surface tension of 30 dyn/cm or less. , solid fine particles having a smooth surface with a coefficient of friction of 0.1 or less, or fine particles having non-adhesive properties and some abrasive properties. Furthermore, if necessary, a treatment for fixing these external additives to the surface of the toner particles using hot air or the like may be performed. The developer composition of the present invention can be produced by melt-kneading the binder resin and other additives, followed by pulverization, by spray drying, or by direct polymerization using suspension polymerization or emulsion polymerization. Basically, any manufacturing method can be used. However, no matter what manufacturing method is adopted, manufacturing conditions must be selected so that the nitrogen-containing polar functional groups and conductive components of the binder resin are dispersed discontinuously and uniformly on the surface of the developer particles. is important. Incidentally, it is desired that the particle size of the developer particles be adjusted to about 1 to 50 .mu.m, preferably to an average particle size of about 5 to 20 .mu.m. Therefore, if necessary, the particle size is adjusted by a classification operation. As mentioned above, an average particle size of 1 to 100 ml containing a predetermined amount of magnetic powder of a specific particle size and a specific binder resin.
By sparsely adhering or fixing a predetermined amount of conductive components to the surface of 50 μm insulating particles, it is possible to obtain a developer composition with an overall electrical resistivity greater than 10 ¹⁵ Ω·cm. can. In the present invention, the electrical resistivity of the developer was defined based on the following measurement method. Developer particles with a diameter of 50mm
Sandwiched between electrodes with a guard electrode, load 200
g/cm ² , the distance between the electrodes, that is, the thickness of the developer particle layer, is adjusted to about 1 mm, and a DC voltage from 100 V to 1000 V is sequentially applied. After each voltage application, the current value was read 1 minute later, static electricity was removed for 1 minute, and then another voltage was applied, and the operation was repeated in the same manner. The current values thus obtained for each applied voltage were converted into volume resistivity and plotted, and the electrical resistivity at an electric field of about 10 ⁴ V/cm was adopted as the electrical resistivity of the developer. The developer of the present invention, when used as a one-component developer without carrier particles, fully exhibits its characteristics and provides advantages over conventional one-component and two-component developers. However, even when the developer of the present invention is used as a toner or carrier for a two-component developer, a two-component developer with good charging characteristics can be provided. In addition, when used as a one-component developer, it is easier to use magnetic toner by mixing magnetic powder into the developer particles as described above, but of course, even when image formation is performed as a non-magnetic toner. , the effects of the present invention are fully exhibited and achieved. Furthermore, in the case of magnetic toner, it is also possible to develop a magnetic latent image in addition to an electrical latent image. The developer composition of the present invention is not only capable of developing electrostatic latent images of both positive and negative polarity, but also transferable under high temperature and high humidity despite containing conductive particles on the surface. The properties are good. The reason for this is that conductive particles are loosely adhered or fixed to the surface of insulating toner particles, so that even when a transfer electric field is applied, the charge distribution on the surface of the toner particles is uniform, and the development This seems to be due to the fact that the electrical resistivity of the agent is greater than 10 ¹⁵ Ω·cm.
If the electrical resistivity of the developer is smaller than 10 ¹⁵ Ω・cm, the transfer performance under both high temperature and high humidity conditions and low temperature and low humidity conditions will decrease, and the environmental dependence of transfer performance is particularly problematic under high temperature and high humidity conditions. sex increases. (Examples) Hereinafter, the present invention will be explained by examples, but of course the present invention is not limited only to these examples. In addition, in the following examples, parts represent parts by weight. (Comparative Example 1) - Styrene resin (number average molecular weight 4000) 40 parts - Styrene/n-butyl methacrylate copolymer 50 parts (styrene = 60%, number average molecular weight 40000) - Triiron tetraoxide (particle size = 0.3 μm) , granular powder) was melt-kneaded in a rotor-rotating kneader, cooled, pulverized, and further classified to have an average particle size of 13.8 μm, which is referred to as toner a. Next, this toner is coated with carbon black (particle size
Toner B was prepared by adding 0.6% by weight of 24 mμ, ) and mixing with a high-speed stirring mixer. (Example 1) The styrene resin of Comparative Example-1 was replaced with diethylaminoethyl methacrylate-styrene copolymer (diethylaminoethyl methacrylate component 7 mol%, number average molecular weight 4000, amine value 30), and the average particle size was changed using the same formulation as above. A 13.5 μm toner c was prepared. To this toner, 0.6% by weight of the same carbon black as in Comparative Example-1 was added and mixed, and toner d
was prepared. Toners a, b, of Comparative Example-1 and Example-1
Typical characteristics of c and d and FX manufactured by Fuji Xerox Co., Ltd.
The table below shows the image characteristics evaluated using a modified -2300 copying machine incorporating a one-component developer.

[Table] ×...Poor As seen from the table, the toner d of the present invention exhibits very good image characteristics, ranging from a low temperature and low humidity environment of 10°C and 15% humidity to 30°C and 85% humidity. The image quality was extremely stable even with environmental changes up to high temperature and high humidity environments. Furthermore, even during continuous copying of 50,000 sheets, the image quality was always clear and no changes over time or deterioration of the developer were observed. Toner c, which does not contain conductive carbon black, is also better than toners a and b, but toner d
It doesn't come close to that. When toners a, b, c, and d were observed using transmission and scanning electron microscopes, and the outermost surface composition of the toners was analyzed using ESCA, it was found that toners a,
In all cases b, c, and d, it was confirmed that the magnetic powder layer was partially exposed on the toner surface. Although toner c is not as good as toner d, it shows better developability compared to toners a and b because of the diethylamino groups in the binder resin present on the surface of toner c and the partially exposed semiconductive This seems to be because charge exchange and transfer with triiron tetroxide are promoted to some extent. In addition,
From the ESCA data, it seems that the degree of magnetic powder exposure of toners c and d is slightly lower than that of toners a and b. Furthermore, the presence of N atoms on the surfaces of toners c and d was confirmed by ESCA, and it was confirmed that diethylamino groups were effectively present on the toner surfaces. Further, in both toners b and d, it was confirmed by electron microscopy that carbon black powder was adhered very uniformly and discontinuously to the toner particle surfaces. (Comparative Example 2) Two parts of nigrosine dye was further added to the composition of Comparative Example-1, and the same formulation was used to knead, grind, and classify to obtain a toner with an average particle size of 13.4 μm and an electrical resistivity of 3.9×10 ¹⁵ Ωcm. Ta. The image quality of this toner was evaluated in the same manner as Comparative Example-1, but the image quality was inferior as in Comparative Example-1. Similarly, the image quality of the toner prepared by adding 0.6% by weight of carbon black to the present toner was also not excellent. (Example 2) - 90 parts of styrene/n-butyl methacrylate/diethylaminoethyl methacrylate copolymer (composition ratio is 65/35/5 in order, number average molecular weight
28000, amine value 20) - Knead 100 parts of triiron tetroxide (particle size = 0.3 μm, granular powder), then crush and classify to determine the average particle size.
A toner of 14.1 μm was obtained. More carbon black
Mixed with 0.55% by weight, electrical resistivity 5.0×10 ¹⁵ Ω
Adjusted to m. When the image quality of this toner was evaluated in the same manner as in Example-1, very clear image quality was obtained. It was also extremely stable against repeated copying of 50,000 sheets and environmental changes from high temperature and high humidity to low temperature and low humidity. (Example 3) The image quality of the toner d of Example 1 was evaluated in the same manner as in Example 1 using a modified FX-2300 copying machine incorporating an organic photoconductor that forms a negative charge latent image. An image as good as or better than 1 was obtained. Of course, the environmental stability and stability over time were also good. (Example 4) - 28 parts of styrene/dimethylaminoethyl methacrylate copolymer (97% styrene, amine value 17, number average molecular weight
2900) - 20 parts of styrene/butadiene crosslinked polymer (gel fraction 90%) - 2 parts of polypropylene wax - 50 parts of triiron tetroxide (particle size 0.5 μm) were kneaded, crushed, and classified in the same manner as in Example-1. As a result, a toner having an average particle size of 12.7 μm was obtained. Furthermore, 0.65% by weight of carbon black is added and mixed, resulting in an electrical resistivity of 6.1.
A toner of ×10 ¹⁵ Ωcm was prepared. The image quality of this toner was evaluated in the same manner as in Example-3, and extremely excellent image characteristics were confirmed. There were no problems with both environmental stability and stability over time.

Claims (1)

[Claims] 1. Magnetic powder with an average particle size of 0.01 μm to 2 μm
~70% by weight, styrene monomer component and the following general formula
(A)： (In the above formula, R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, and may be the same or different, and R At least one of ₂ and _R3 is a lower alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4. Insulating particles having an average particle size of 1 to 50 μm and having a binder resin containing 20% by weight or more in the binder resin component, and 0.1 to 2.0% by weight of the insulating particles are added and mixed. and conductive particles loosely attached or fixed to the surface of the insulating particles,
A developer composition characterized in that its overall electrical resistivity is greater than 10 ¹⁵ Ω·cm.