JPH07248642A - Two-constituent developer for developing electrostatic charge image and image forming method - Google Patents

Abstract

PURPOSE:To provide a two-constituent developer preventing image quality defects such as the reduction of the image density and density irregularity at the time of development in the noncontact state with a latent image carrier, obtaining a high-quality image, capable of forming an excellent color image having no image irregularity and color mixture when applied to multi-color superposed development, and excellent in image quality maintenance property and to provide an image forming method using it. CONSTITUTION:This two-constituent developer is made of a toner and a carrier, and it is held in no contact with an electrostatic latent image carrier and flys the toner via the alternating electric field. The external additive of the toner contains inorganic fine grains having the average grain size of 25-80nm as the essential constituent, and the total coverage F of the inorganic fine grains is 0.3 or above. In forming the image, the two-constituent developer containing the carrier for developing an electrostatic charge image is held in no contact with the electrostatic latent image carrier, and the toner is flown by the alternating electric field for development.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component electrostatic image developing device for use in a system in which an electrostatic latent image formed by electrophotography, electrostatic recording or the like is developed by flying toner. The present invention relates to a developer and an image forming method using the developer.

[0002]

2. Description of the Related Art A method for visualizing image information through an electrostatic latent image such as an electrophotographic method is currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on a photosensitive member by a charging and exposing process, the electrostatic latent image is developed with a developer containing toner, and then transferred and fixed to be visualized. The developer used here is composed of a toner and a carrier.
There are two-component developers and one-component developers such as magnetic toners, which are used alone as toners, but in two-component developers, the carrier shares functions such as stirring, carrying, and charging of the developer. Since the functions are separated as described above, they have characteristics such as good controllability and are widely used at present. In addition, as a developing method, the cascade method or the like was used in old days,
Currently, the magnetic brush method, which uses a magnetic roll as the developer transporting unit, is the mainstream.

In recent years, a color image forming apparatus using an electrophotographic system has been widely used. In such an apparatus, a method of repeating the steps of charging, exposing, developing and transferring is general. That is, the charging, exposing, developing and transferring steps are repeated four times in total for the number of colors of yellow, magenta, cyan and black toners. However, in such a method, since the toner image is transferred onto the transfer material each time the development of each color is completed, a means for transporting the transfer material is required, and there is a problem that the apparatus itself becomes large. Further, in the system in which the latent image carrier is present alone on the drum or belt in the apparatus, the latent image carrier has the number of colors forming the color image until the final color image formed product is obtained. Therefore, there is a problem that the copying speed is slower than that of the single-color image forming apparatus because the rotation is repeated by the amount.

In order to solve such a problem, a plurality of toner images are superposed and developed on the same latent image carrier.
A small-sized high-speed device has been proposed in which transfer is performed in a single process. In this method, since development is repeatedly performed on the toner image formed on the latent image carrier, the developer at the subsequent stage mechanically contacts the toner image formed on the latent image carrier. There is a problem in that the toner image is disturbed (image disturbance), or a part of the toner image is scraped and mixed in the developing device in the subsequent stage, and the color of the developer changes (color mixing). Therefore, using a magnetic roll as a developer carrying carrier, a method of developing by applying an AC electric field while keeping the latent image carrier and the developer in a non-contact state, and a method of developing by applying only a DC electric field Has been proposed, and from the viewpoint of the image quality of a line image, particularly the reproducibility of a fine line, the former method of developing by applying an AC electric field is considered to be advantageous. In this developing method, in order to keep the magnetic brush layer formed by the two-component developer in a non-contact state with the latent image carrier, the magnetic brush layer is made thinner than the conventional contact developing method. Need to In this case, since the amount of toner that can be supplied to the developing space is relatively small, a sufficient image density cannot be obtained unless the toner in the developing space is transferred to the latent image with higher efficiency than in the contact developing method.

In the non-contact developing method, it is generally said that the carrier-toner adhesion force typified by the carrier-toner image force contributes largely to the force that hinders development. This is because the force for canceling the carrier-toner adhesion force, which is represented by the image force between the photoconductor and the toner, generated by contact with the photoconductor on the magnetic brush layer in the contact development method is weak in the non-contact development method. Is believed to be. Therefore, in order to obtain high development efficiency with the non-contact development method, this carrier
It is important to control the toner adhesion force, and for example, JP-A-62-182775 and JP-A-63 may be used.
No. 231369, a specific particle size (7 to 20
nm) or specific specific surface area (30-60 m ² / g)
A method has been proposed in which the metal-oxide particles containing a metal oxide are added to the surface of the toner and are interposed between the toner and the carrier to reduce the adhesive force between the carrier and the toner. However, in these methods, the external additive is likely to be buried in the toner due to the stress received by the developer member during the formation of the magnetic brush layer, and it becomes difficult to suppress and stabilize the adhesive force between the carrier and the toner. There was a problem.

Further, in order to prevent problems due to burial of external additives in the above-mentioned non-contact developing method, JP-A-5-2283 discloses a BET specific surface area of 100 to 400 m ² / g. Bulk density is 100 to 3
It has been proposed to use external additives, both having a relatively high value of 00 g / l.

By the way, in order to obtain high image quality by electrophotography, it is effective to make the toner particle size smaller, but the adhesive force between the carrier and the toner tends to increase as the toner particle size decreases. is there. Also, the smaller the particle size of the toner, the larger the total area in contact with the carrier,
Inevitably, the external additive is more likely to be stressed by the carrier when the developer is conveyed in the developing machine or when the magnetic brush layer is formed, and the external additive is easily buried in the toner. Therefore, it is difficult to achieve a high image quality with a small particle size toner by the non-contact development method from the viewpoint of initial developability and development stability, and the external additive described in JP-A No. 5-2283 is used as a small particle. No satisfactory result was obtained even when used for the diameter toner. Further, in order to improve the developing efficiency, there is also a method of strengthening the developing electric field applied to the magnetic brush layer by a means such as making the gap between the magnetic roll and the latent image carrier small or increasing the applied voltage of the developing bias. It is valid. However, in these methods, the toner image on the latent image carrier is electrostatically disturbed by the bias applied at the time of developing another color toner in the subsequent stage during multicolor superposition development, which causes image disturbance and color mixture. In many cases, it is difficult to set conditions especially when using a small particle size toner.

[0008]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems in the prior art. That is, an object of the present invention is to provide a two-component developer for developing an electrostatic charge image that satisfies the following requirements. (1) When developing in a non-contact state with respect to the latent image carrier, it is possible to prevent image quality defects such as reduction in image density and uneven density, and to obtain a high quality image. (2) Even when applied to multicolor superposition development, an excellent color image without image distortion or color mixture can be formed. (3) Excellent image quality maintenance.

[0009]

Means for Solving the Problems As a result of intensive studies made by the present inventors for reducing and stabilizing the adhesive force between a carrier and a toner in a non-contact developing method, the fine particles to be externally added to the toner have a specific particle diameter. Using inorganic fine particles, and
The inventors have found that the above object can be achieved by optimizing the ratio of the fine particles covering the toner surface (hereinafter referred to as coverage), and completed the present invention. The present invention relates to a two-component developer for electrostatic charge image development comprising a toner and a carrier, which is held in non-contact with an electrostatic latent image carrier and is used for developing by flying the toner by an alternating electric field. External additive has an average particle size of 25
Inorganic fine particles of nm to 80 nm are essential components, and the total coverage F of the inorganic fine particles represented by the following formula (1) is 0.3 or more. F = f1 + f2 + f3 + ... fn (1) [where f is the coverage of various inorganic fine particles having an average particle size of 25 nm to 80 nm, and is represented by the following formula (2):

[Equation 2] (In the formula, dt is the average particle diameter of the toner, da is the average particle diameter of the fine particles, ρt is the true specific gravity of the toner, ρa is the true specific gravity of the fine particles, Ct is the weight part of the toner, and Ca is the weight part of the fine particles.) Where n is the average particle size of 25n added to the toner.
It is the total number of types of inorganic fine particles of m to 80 nm. The image forming method of the present invention is characterized in that the above-mentioned two-component developer for electrostatic image development is held in non-contact with the electrostatic latent image carrier, and toner is caused to fly by an AC electric field for development. And

The present invention will be described in detail below. In the present invention, inorganic fine particles are used as an external additive. Specifically, TiO ₂ , SiO ₂ , Al ₂ O ₃ , MgO and C are used.
uO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , Ba
O, CaO · SiO ₂ , K ₂ O (TiO ₂ ) _n , Al ₂
O ₃ · 2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO
₄ , MgSO ₄ , MoS ₂ , silicon carbide, boron nitride,
Inorganic fine powders such as carbon black, graphite and fluorinated graphite, and polymer fine powders such as polystyrene, polycarbonate, polymethylmethacrylate and polyvinylidene fluoride can be used, and they can be used alone or in admixture of two or more. Among these fine powders, inorganic fine powders such as titanium oxide (TiO ₂ ) and silica (SiO ₂ ) can improve the fluidity in order to suppress the adhesive force between the carrier and the toner and enhance the non-contact developing property. It is preferably used without damaging it.

In the present invention, in order for these inorganic fine particles to sufficiently exert the effect as a spacer, the particle size thereof needs to be 25 nm to 80 nm,
More preferably, it is 30 nm to 60 nm.
When the average particle size of the inorganic fine particles is smaller than 25 nm, the inorganic particles are likely to be embedded in the toner, and the adhering force between the carrier and the toner increases with stirring in the developing machine, resulting in deterioration of the developability. Further, when the average particle size of the inorganic fine particles is larger than 80 nm, the adhesive force of the inorganic fine particles to the toner becomes poor, and the inorganic fine particles may move to the concave portion of the toner due to the stress received in the developing machine, or be detached from the toner. As a result, the effect of suppressing the adhesive force between the carrier and the toner cannot be obtained, so that the developability is insufficient.

Further, the coverage of the inorganic fine particles with respect to the toner is represented by the sum of the coverage f of various inorganic fine particles corresponding to the average particle diameter of 25 nm to 80 nm calculated based on the above formula (2), that is, the above formula (1). It is necessary that the total coverage F to be provided is 0.3 or more. In the present invention, for the purpose of improving the fluidity of the toner and the cleaning property, inorganic fine particles or organic fine particles having a particle size outside the above range can be used in combination. And is not included in the relational expressions (2).

When the sum F of the coverage f of various inorganic fine particles having an average particle diameter of 25 nm to 80 nm is smaller than 0.3, the probability of contact between the toner resin component and the carrier surface is high, and the adhesive force between the carrier and the toner is sufficient. It cannot be suppressed, and the adhesion state of the inorganic fine particles to the toner sensitively affects the developing property, which is not preferable. In the present invention,
The coverage F is set to 0.3 or more, which is based on the formulas (1) and (2), and is based on the toner particle size, the true specific gravity and the inorganic fine particle size, and the true specific gravity. It may be done by adjusting. As the true specific gravity, a value measured using a constant volume gas compression type particle density measuring device is used.

In the present invention, by using the above-mentioned inorganic fine particles as an external additive, the adhesive force between the carrier and the toner can be reduced and a sufficient image density can be obtained.
The reason why the inorganic fine particles reduce the adhesive force between the carrier and the toner is not necessarily clear, but (1): the interposition of the inorganic fine particles between the carrier and the toner reduces the area where the resin component of the toner directly contacts the carrier. The smaller size reduces the physical adhesion. (2): The conductivity of the toner surface is increased by the presence of the inorganic fine particles, and the electric charge density is made uniform on the toner surface by the diffusion of the electric charge into the toner concave portion, which is difficult to contact with the carrier, and works on the contact surface between the carrier and the toner. It seems that phenomena such as reduction of the image power are occurring.

Next, the toner in the present invention will be described. The toner is a binder resin in which a colorant or the like is dispersed, and examples of the binder resin used in the toner include styrenes such as styrene, p-chlorostyrene, and α-methylstyrene; methyl acrylate, acrylic acid. Ethyl, n-propyl acrylate, lauryl acrylate, acrylic acid 2
-Α-methylene aliphatic monocarboxylic acid esters such as ethylhexyl, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; 2 −
Vinyl pyridines such as vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; ethylene, propylene, isoprene, butadiene and the like. Of unsaturated hydrocarbons and halides thereof, halogenated unsaturated hydrocarbons such as chloroprene, and the like, or copolymers obtained by combining two or more of these monomers, and , A mixture of these, and further a rosin-modified phenol formalin resin,
Epoxy resin, polyester resin, polyurethane resin,
Examples include non-vinyl condensation resins such as polyamide resins, cellulose resins and polyether resins, or mixtures of these with the above vinyl resins.

Among these binder resins, polyester resin can be preferably used. The polyester resin can be produced by reacting a polyhydric alcohol with a polybasic carboxylic acid or a reactive acid derivative thereof. Examples of the polyhydric alcohol constituting the polyester resin include, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol,
1,3-Propylene glycol, 1,4-butanediol, neopentylene glycol, cyclohexanedimethanol and other diols, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropyleneated bisphenol A and other bisphenol A alkylenes Examples thereof include oxide addition compounds and other dihydric alcohols. Examples of polybasic carboxylic acids include malonic acid, succinic acid, adipic acid, sebacic acid,
Alkyl succinic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, cyclohexanedicarboxylic acid, isophthalic acid, terephthalic acid,
Other dibasic carboxylic acids, or acid anhydrides thereof, alkyl esters, reactive acid derivatives such as acid halides and the like can be mentioned.

In addition to these carboxylic acids, in order to make the polymer non-linear to the extent that tetrahydrofuran-insoluble matter is not generated, a polyhydric alcohol having a valence of 3 or more and / or 3
A polybasic carboxylic acid having a valency or higher may be added. Examples of the trihydric or higher polyhydric alcohol include sorbitol,
1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl −
1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trimethylolbenzene and the like can be mentioned. Examples of the tribasic or higher polybasic carboxylic acid include 1,2,4-butanetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,
2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid and the like can be mentioned.

Among these polyester resins, obtained from a polycondensate containing an aromatic polycarboxylic acid and bisphenol A as main monomer components, for example, terephthalic acid-ethylene oxide adduct of bisphenol A-cyclohexanedimethanol. Which is a linear polyester having a softening point of 90 to 150 ° C., a glass transition point of 50 to 70 ° C., a number average molecular weight of 2,000 to 6,000, and a weight average molecular weight of 8.0.
00 to 150,000, acid value 5 to 30, hydroxyl value 25 to
Those having 45 are particularly preferably used.

Similarly, as the colorant used for the toner,
Carbon black, nigrosine dye, aniline blue,
Calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, rose bengal, phthalocyanine blue, malachite green oxalate, lamp black, C.I. I. Pigment Red 48: 1, C.I.
I. Pigment Red 122, C.I. I. Pigment
Red 57: 1, C.I. I. Pigment Yellow 97,
C. I. Pigment Yellow 12, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3, or a mixture thereof.

The content of the colorant is preferably in the range of 1 to 8 parts by weight with respect to 100 parts by weight of the binder resin. When the content of the colorant is less than 1 part by weight, the coloring power is weakened, and when it is more than 8 parts by weight, the transparency of the toner is deteriorated. The average particle diameter of the toner particles is preferably 10 μm or less. If the average particle diameter is larger than 10 μm, the faithful reproducibility of the latent image is deteriorated and it becomes impossible to obtain a high quality image. The toner particles in the present invention include, as necessary, a salicylic acid metal salt, a metal-containing azo compound, a charge control agent such as nigrosine or a quaternary ammonium salt, a low molecular weight polypropylene, a low molecular weight polyethylene, an offset preventive agent such as a wax, and a cleaning agent. Other known components such as auxiliaries can also be blended.

If the charge amount of the toner is too high, the adhesion of the toner to the carrier becomes too large, and the toner cannot be developed. Further, if the charge amount becomes too low, the adhesion of the toner to the carrier becomes too small, and a toner cloud due to free toner is generated, which causes a problem of fog in printing. Therefore, from the viewpoint of developing the toner, the charge amount of the toner in the developer is 5 to 50 μC / g, preferably 10 to 40 μC / g in absolute value.
It is desirable to be in the range of.

The developer of the present invention is used as a two-component developer. As the carrier used in the present invention, a known carrier such as a carrier obtained by coating the surface of the magnetic core particles with a resin or a carrier obtained by melting and kneading a magnetic powder in a resin or dispersing by a polymerization method may be used. it can.

Examples of the binder resin used in the carrier of the present invention include polyolefin compounds such as ethylene, propylene and butylene, as well as styrenes such as styrene, chlorostyrene and vinylstyrene; vinyl acetate, vinyl propionate and benzoate. Vinyl esters such as vinyl acrylate and vinyl butyrate; methyl acrylate, ethyl acrylate,
Α-methylene aliphatic monocarboxylic acid esters such as butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, vinyl ethyl ether,
Examples thereof include vinyl ethers such as vinyl butyl ether; and homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. In particular, typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-
Examples thereof include butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene and polypropylene. Further, for the purpose of controlling charging, it is also possible to use fluororesin, silicone resin, polyamide, polyester, polyurethane and the like in combination.

As the core particles or magnetic powder used in the present invention, all ferromagnetic fine powders can be usually used, and specifically, ferric tetroxide, δ-iron sesquioxide, various ferrite powders, Examples thereof include chromium oxide and various metal powders such as iron, nickel and stainless. When a resin-coated carrier is used, the coating resin amount is 0.2% by weight to 10%.
%, Especially 0.4 to 5% by weight is preferred.
When the magnetic powder-dispersed carrier is used, the resin content is preferably 10 to 80% by weight, and particularly preferably 15 to 65% by weight.

The carrier in the present invention preferably has a relatively small particle size. In non-contact development, it is necessary to increase the electric field strength of the latent image, and it is important to narrow the gap between the developing roll and the latent image carrier. The interval is 0.2 ~
Since 0.8 mm is common, the developer layer formed on the developing roll needs to be a thin layer of 0.1 to 0.6 mm. When such a thin developer layer is formed by using a large carrier having an average particle diameter of 100 μm which is usually used, the developer layer becomes a coarse developer layer with gaps, and image quality unevenness occurs in a copied image. Also, if the carrier is too small, the magnetic binding force acting on the carrier weakens,
The carrier will be developed. Therefore, the average particle size of the carrier is 20 to 70 μm, particularly 30 to 50 μm.
m is preferred.

The saturation magnetization of the carrier used in the present invention is preferably in the range of 15 to 75 emu / g. When the saturation magnetization is less than 15 emu / g, carrier is likely to adhere to the latent image carrier. Further, when the saturation magnetization exceeds 75 emu / g, it becomes difficult to form a thin layer of the developer layer, the spike height and packing density of the magnetic brush are likely to be non-uniform, and image quality defects such as low image density and density unevenness are likely to occur. .

The carrier used in the present invention may further contain, as other constituent materials, a filler such as carbon black and titanium oxide powder, a coupling agent and a charge control agent.

An example of a procedure for forming a color image by applying the two-component developer for developing an electrostatic image of the present invention to the superposed development of a plurality of colors by non-contact development will be described below. Figure 1
FIG. 3 is a conceptual diagram of an apparatus for forming a four-color image. In the image forming apparatus of FIG. 1, the photoconductor belt 1 uniformly charged by the first scorotron 2 is exposed by the first exposure unit 3 to form a first-color electrostatic latent image. At this time, the exposure is performed on the image portion to remove the charge on the image portion. The formed electrostatic latent image is subjected to so-called reversal development by the first-color yellow developing machine 4, and a first-color yellow toner image is formed on the photosensitive belt 1. Then, the photoconductor belt 1 is uniformly recharged by the second scorotron 5, and then exposed by the second exposure means 6.
A second color electrostatic latent image is formed, and the reversal development is performed by the magenta developing machine 7. Further, the photosensitive belt 1 is uniformly recharged by the third scorotron 8 and then exposed by the third exposing means 9 to form a latent image of the third color, which is reversed by the third cyan developing machine 10. Development is performed. After that, the photosensitive belt 1 is further uniformly recharged by the fourth scorotron 11, and then exposed by the fourth exposing means 12 to form a latent image of the fourth color, and the fourth black developing machine 1 is formed.
The reversal development is carried out by 3. In this way, four color toner images of yellow, magenta, cyan and black are formed on the photosensitive belt 1, and the transfer corotron 14 transfers the four color toner images onto the transfer material 15. After the transfer, the toner remaining on the photosensitive belt 1 is removed by the cleaner brush 16. In addition, reference numerals 17, 18, and 19 are drive rolls for making full use of the photosensitive belt 1.

In the present invention, each of the developing machines 4, 7,
As for 10 and 13, a method is adopted in which development is performed in a state where the developer does not come into contact with the photosensitive belt 1. This prevents the toner image developed on the photosensitive belt 1 prior to the overdevelopment from being disturbed in the subsequent developing process. Further, even if the photosensitive belt 1 is drum-shaped, no trouble occurs.

FIG. 2 is a diagram for explaining the image forming process of FIG. First, the photosensitive belt 1 is uniformly charged to V ₁ . Next, the latent image V ₁₁ of the first color is formed by exposure, and the developing device 4 develops the yellow toner.
A developing bias including a DC component and an AC component is applied to the developing device 4. Next, the second charging is performed, the potential of the photosensitive belt 1 is set to V _1, and then the latent image V _{12 is} exposed by the second color exposure.
And a magenta toner is developed by the developing device 7. A developing bias including a DC component and an AC component is also applied to the developing machine 7. After that, the charging is performed for the third time, the potential of the photosensitive belt 1 is set to V _1, and then the latent image V ₁₃ is formed by the exposure of the third color, and the developing device 10 develops the cyan toner. A developing bias including a direct current component and an alternating current component is also applied to the developing machine 10. After that, the fourth charging is performed to set the potential of the photosensitive belt 1 to V ₁
Then, the latent image V ₁₄ is formed by the exposure of the fourth color, and the developing machine 1
3 develops black toner. A developing bias including a DC component and an AC component is also applied to the developing machine 13. In this way, a four-color print is formed.

[0031]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. A. Preparation of colored particles (Production of yellow particles) Linear polyester resin 100 parts by weight (terephthalic acid-ethylene oxide adduct of bisphenol A-linear polyester obtained from cyclohexanedimethanol; glass transition point 62 ° C, number average molecular weight 4000, weight average molecular weight 5000, acid value 25) Yellow pigment (CI Pigment Yellow 12) 3 parts by weight The above mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and then classified with an air classifier. And the average particle size is 7 μm
Negatively chargeable yellow particles.

(Production of Magenta Particles) 100 parts by weight of linear polyester resin (equivalent to that used for yellow particles) 3 parts by weight of magenta pigment (CI Pigment Red 122) Melt the above mixture with a twin-screw extruder After kneading and pulverizing with a jet mill, classify with an air classifier to obtain an average particle size of 7 μm
Negatively charged magenta particles.

(Production of Magenta Particles) 100 parts by weight of linear polyester resin (equivalent to that used for yellow toner) 3 parts by weight of magenta pigment (CI Pigment Red 57) The above mixture is melted by a twin-screw extruder. After kneading and pulverizing with a jet mill, classify with an air classifier to obtain an average particle size of 7 μm
Negatively charged magenta particles.

(Production of Cyan Particles) Linear polyester resin 100 parts by weight (equivalent to that used for yellow particles) Cyan pigment (CI Pigment Blue 15: 3) 3 parts by weight The above mixture is twin-screw extruder. Melt and knead with, pulverize with a jet mill, classify with an air classifier, average particle size is 7μm
Negatively charged cyan particles.

(Production of Black Particles) Linear polyester resin 100 parts by weight (equivalent to that used for yellow particles) Carbon black 3 parts by weight The above mixture was melt-kneaded by a twin-screw extruder and pulverized by a jet mill. , Classify with wind classifier, average particle size is 9μm
Negatively charged black particles of

B. Preparation of Toner With the composition shown in Table 1, external additives were added to the colored particles using a Henschel mixer.

[Table 1]

C. Preparation of carrier (Production of resin-coated carrier) Cu-Zn ferrite (saturation magnetization 22 emu / g, 100 parts by weight average particle size 40 μm) 15% toluene solution of polymethylmethacrylate 10 parts by weight The above components were placed in a vacuum kneader. Toluene is removed by vacuum drying while mixing with stirring, and resin coated carrier A
Got

(Magnetic powder dispersion type carrier) Magnetite (EPT1000, manufactured by Toda Kogyo Co., Ltd.) 70 parts by weight Styrene-methyl methacrylate-butyl methacrylate 27 parts by weight Copolymer (copolymerization ratio 30/60/10) 6-nylon 3 parts by weight Parts The above components are melt-kneaded with a pressure kneader, further pulverized and classified using a turbo mill and a classifier to give an average particle size of 47
A magnetic powder-dispersed carrier B having a μm and a saturation magnetization of 56 emu / g was obtained.

D. Single Color Image Forming Test Toners a to f were combined with the carriers shown in Table 2 and mixed at a toner concentration of 8% by weight with a V-type mixer to obtain a two-component developer. The charge amount at this time is 25 to 35 μC / g
Was in the range. These two-component developers were applied to the magenta developing machine of the apparatus shown in FIG. 1 to conduct a monochromatic image forming test.
The photoreceptor belt is a belt-shaped organic photoreceptor having a circumference of 900 mm, the peripheral speed is 150 mm / s, and the charging potential is -800 V.
And A 400 dpi LED was used as each exposure means. The diameter of the developing sleeve of the developing machine is 18 mm, the distance between the developing sleeve and the photosensitive drum is 0.6 mm, the thickness of the developer layer on the sleeve is 0.35 mm, and the peripheral speed is 400 m.
It was set to m / s, and the development was performed in a state where the developer did not come into contact with the photosensitive drum. The process conditions are as follows. First, the potential of the photosensitive belt is charged to -800V, the latent image potential is lowered to -200V by exposure, and the magenta developing machine has a DC component of -750V and an AC component of frequency 5.0.
A developing bias including kHZ and VP-P = 1.5 kV was applied.

Table 2 shows the results of evaluating the samples as described above. The criteria for evaluation are as follows. Monochromatic image density reproducibility: Image density is X-Rite "R" 4
04 (manufactured by X-Rite). ◯ indicates that the measured value was 1.2 or more in the initial image quality, and the measured value fluctuation range was less than 0.3 in the 10,000-sheet maintenance test,
X indicates a measured value of less than 1.2 in the initial image quality, 1000
In the 0-sheet maintenance test, the fluctuation range of measured values is 0.3 or more. Single-color image deterioration: ◯ indicates that fog and toner cloud did not occur, Δ indicates that fog did not occur but toner cloud occurred, and x indicates that both fog and toner cloud occurred. Single-color granularity: a single-color halftone image was visually evaluated, ◯ indicates good uniformity, Δ indicates slightly poor uniformity, and x indicates poor uniformity.

[0041]

[Table 2]

E. Multicolor Overlaid Image Formation Test Toners b, g, h, and i in Table 1 were combined with carrier B and mixed with a V-type mixer at a toner concentration of 8% by weight to obtain a two-component developer. The amount of charge at this time was in the range of 25 to 35 μC / g for each color. These two-component developers were applied to the apparatus shown in FIG. 1 to perform a multicolor overlapping image forming test. As the photosensitive belt, a belt-shaped organic photosensitive material having a peripheral length of 900 mm was used, the peripheral speed was 150 mm / s, and the charging potential was -800V. As each exposure means, 400
An LED of dpi was used. The diameter of the developing sleeve of each developing machine is 18 mm, the distance between the developing sleeve and the photosensitive drum is 0.6 mm, and the thickness of the developer layer on the sleeve is 0.35 m.
m, the peripheral speed was set to 400 mm / s, and the development was performed in a state where the developer did not contact the photosensitive drum. Referring to the process conditions according to FIG. 2, first, the potential V ₁ of the photosensitive belt is charged to −800 V, the latent image potential V ₁₁ of the first color is reduced to −200 V by exposure, and the yellow toner of the yellow developing machine is discharged. It was developed. At this time, a developing bias containing -750 V as a DC component, a frequency of 5.0 kHz as an AC component, and VP-P = 1.5 kV was applied to the yellow developing machine.

Next, the second charging is performed to set the potential V ₁ of the photosensitive belt to −800 V, and then the second color image portion potential V _{12 is set} to −200 V by the exposure of the second color, and the magenta developing device magenta. The toner was developed. A developing bias containing -750 V as a DC component, a frequency of 5.0 kHz as an AC component, and VP-P = 1.5 kV was applied to the magenta developing machine. After that, the third charging is performed to set the potential V ₁ of the photosensitive belt to −800 V, and then the image portion potential V ₁₃ of the third color is set to −200 V by the exposure of the third color, and the cyan toner is developed by the cyan developing machine. went. The cyan developing machine has a DC component of -750V and an AC component of frequency 5.0.
A developing bias including kHZ and VP-P = 1.5 kV was applied. Thereafter, perform fourth charge, after the potential V ₁ of the photosensitive belt to -800 V, 4 an image portion potential V ₁₄ of the fourth color with exposure at color and -200 V, the developing of the black toner by the black developing machine I went. The black developing machine has a DC component of -850V, an AC component of a frequency of 7.0kHz and VP-
A developing bias including P = 1.5 kV was applied. In this way, four colors were copied and the sample was evaluated.
It was possible to obtain a full-color, high-quality copy image having no image disturbance and no color mixture, which is equivalent to that obtained by the contact development method.

[0044]

As described above, the developer for developing an electrostatic charge image of the present invention has an average particle diameter of 25 nm as an external additive for toner.
To 80 nm inorganic fine particles and the total coverage F of the inorganic fine particles is 0.3 or more. Therefore, when used in a non-contact development type image forming method, (1) latent image bearing (2) When applied to multicolor superimposition development, which can prevent image quality defects such as reduction in image density and unevenness in density when developing in a non-contact state with the body, Also has excellent effects that an excellent color image without image distortion and color mixture can be formed, and that (3) image quality maintenance is excellent.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus for carrying out an image forming method of the present invention.

FIG. 2 is a diagram illustrating an image forming process when the image forming apparatus of FIG. 1 is used.

[Explanation of symbols]

1 ... Photosensitive belt, 2 ... 1st scorotron, 3 ... 1st
Exposing means, 4 ... yellow developing machine, 5 ... second scorotron, 6 ... second exposing means, 7 ... magenta developing machine, 8 ...
Third scorotron, 9 ... Third exposure means, 10 ... Cyan developing machine, 11 ... Fourth scorotron, 12 ... Fourth exposing means, 13 ... Black developing machine, 14 ... Transfer corotron, 15
... transfer material, 16 ... cleaner brush, 17, 18 and 19 ... drive roll.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Budoo 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Masanori Ichimura 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. A two-component developer for developing an electrostatic charge image comprising a toner and a carrier, which is used in a system of holding an electrostatic latent image carrier in a non-contact manner and flying the toner by an alternating electric field to develop the toner. External additive has an average particle size of 25n
Inorganic fine particles of m to 80 nm become an essential component,
A two-component developer for developing an electrostatic image, wherein the total coverage F of the inorganic fine particles represented by the following formula (1) is 0.3 or more. F = f1 + f2 + f3 + ... fn (1) [where f is the coverage of various inorganic fine particles having an average particle size of 25 nm to 80 nm, and is represented by the following formula (2): (In the formula, dt is the average particle diameter of the toner, da is the average particle diameter of the fine particles, ρt is the true specific gravity of the toner, ρa is the true specific gravity of the fine particles, Ct is the weight part of the toner, and Ca is the weight part of the fine particles.) Where n is the average particle size of 25n added to the toner.
It is the total number of types of inorganic fine particles of m to 80 nm. ] 2. The electrostatic latent image developing two-component developer according to claim 1 is held in non-contact with an electrostatic latent image carrier, and toner is caused to fly by an AC electric field for development. Image forming method.