JP2888966B2 - Electrostatic latent image developer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic latent image developer obtained by mixing inorganic fine particles, a toner, and a carrier.

[Conventional technology]

In an example of electrophotography, generally, an electrostatic latent image is formed on the surface of a photoreceptor by charging and image exposure, and then the electrostatic latent image is developed with toner. After the image is transferred to a recording material such as the above, the image is fixed to form a copy image.

As a photoreceptor, in recent years, from the viewpoint of durability and environmental friendliness,
Organic photoconductive photoconductor (hereinafter abbreviated as "organic photoconductor")
Are often used. The polarity of the electrostatic latent image formed on the surface of the organic photoreceptor is generally set to a negative polarity because there are relatively many types of photoconductive substances that can form the photosensitive layer.

In order to develop an electrostatic latent image of negative polarity, a developer containing toner charged to the opposite positive polarity is required.

As a technique for positively charging the toner, there has been conventionally known a technique in which an aminosilane coupling agent or silica fine particles treated by using an aminosilane coupling agent and a silane coupling agent in combination is externally added to the toner. Kaisho
53-22447 and 53-66235). But,
In this technique, there are many hydrophilic groups on the surface of the silica fine particles, so that they are susceptible to humidity and have a large environmental dependency.

On the other hand, as a technique for reducing the environmental dependency of silica fine particles, a technique has been proposed in which silica fine powder treated with a silicone oil having an amine in a side chain is externally added to a toner and mixed (Japanese Patent Application Laid-Open No. 59-1984). No. 201063). However, in this technique, since the surface of the silicic acid microfluid is treated with an adhesive oil substance, the silicic acid fine powder easily adheres to and contaminates the photoreceptor surface, carrier particles, and the like. There is a problem that the triboelectrification property of the toner decreases.

Further, in order to solve the above problem, there has been proposed a technique of externally adding and mixing inorganic fine particles obtained by surface-treating polysiloxane having an ammonium salt as a functional group to a toner (JP-A-1-114857, JP-A-1-114857). −114858).

According to this technique, since the toner has an ammonium salt structure, a higher positive chargeability can be imparted to the toner than an amino group, and the adhesiveness and adhesion are reduced. Good cleaning properties and triboelectric charging properties are obtained. In addition, since no hydrophilic sites remain on the surface of the inorganic fine particles, environmental dependency is also improved.

[Problems to be solved by the invention]

However, when such inorganic fine particles having weak adhesion are used, there is a problem that the inorganic fine particles are easily released from the toner in the developer. In particular, when a resin-coated carrier is used in combination, the released inorganic fine particles act as an "abrasive", so that the resin coating layer of the carrier is broken by the stirring mechanism in the developing device, and the chargeability and durability are improved. There is a problem that adversely affects

This problem is particularly remarkable when a toner having a small particle size is used to increase the resolution. That is, as the particle size of the toner decreases, the specific surface area increases, the required amount of the inorganic fine particles to be externally added increases, the absolute amount of the inorganic fine particles increases, and the polishing effect of the carrier on the resin coating layer increases. Because.

As described above, the conventional technology cannot sufficiently cope with the recent reduction in toner particle size, which is an essential condition for the development of a developer suitable for high image quality.

Therefore, an object of the present invention is to provide an electrostatic latent image developer that has low environmental dependency, has low carrier contamination, exhibits high positive chargeability stably over a long period of time, and obtains a high-resolution image. It is in.

[Means for solving the problem]

The electrostatic latent image developer of the present invention has inorganic fine particles obtained by surface-treating a polysiloxane having an ammonium salt as a functional group, and an average particle diameter obtained by a polymerization method in an aqueous medium.
The toner is characterized in that a toner having an average particle diameter of 2 to 6 μm, in which primary particles of 0.1 to 3 μm are bonded in the aqueous medium, and a resin-coated carrier are mixed.

Further, the inorganic fine particles are preferably silica fine particles.

[Action]

Average particle size obtained by polymerization method in aqueous medium 0.1 ~
A toner having an average particle diameter of 2 to 6 μm formed by bonding primary particles of 3 μm in the aqueous medium is different from a toner obtained by an ordinary pulverization method, and has an irregular shape having many very smooth dimple-like irregularities. In the form of

Therefore, when inorganic fine particles obtained by surface-treating a polysiloxane having an ammonium salt as a functional group are added to the toner and mixed by stirring, most of the inorganic fine particles try to enter the concave portions of the toner during stirring, so that the inorganic fine particles are It is less likely to be released from the toner surface. Further, since the concave portion of the toner is very smooth, there is no possibility that the frictional charging between the carrier and the toner is prevented.

Further, since a small-diameter toner having an average particle diameter of 2 to 6 μm is used to obtain high resolution, it is necessary to add a large amount of the inorganic fine particles in order to sufficiently exert the effect of adding the inorganic fine particles. However, as described above, the surface of the toner has a large number of concave portions and the area to which the inorganic fine particles can adhere is sufficiently large. Even when a large amount of the inorganic fine particles is added, the inorganic fine particles are liberated from the toner. Less likely to occur.

As a result, the effect of adding the inorganic fine particles obtained by surface-treating the polysiloxane having an ammonium salt as a functional group is reliably exerted, the environment dependence is reduced, and the triboelectric charging property is improved. Further, since the inorganic fine particles are less likely to be released, the carrier is less contaminated, and the charge stability,
The durability is improved. Further, a high-resolution image can be stably obtained over a long period of time by the small-diameter toner.

[Specific configuration of the invention]

 Hereinafter, the configuration of the present invention will be specifically described.

The inorganic fine particles constituting the electrostatic latent image developer of the present invention are obtained by subjecting a polysiloxane having an ammonium salt as a functional group (hereinafter appropriately referred to as “ammonium salt-modified polysiloxane”) to a surface treatment.

According to the inorganic fine particles surface-treated with the ammonium salt-modified polysiloxane, the positive chargeability is high, the chargeability is stable against environmental changes, and the cleaning property of the photoreceptor is improved.

As the ammonium salt-modified polysiloxane, dimethylpolysiloxane having an ammonium base is preferable, which is usually a dimethylpolysiloxane containing a structural unit represented by the following general formula (1). ).

General formula (1) (R ¹¹ is a hydrogen atom, a hydroxy group, an alkyl group, an aryl group, an alkoxy group, or Represents

R ¹² is a bonding group, an alkylene group, an arylene group,
It represents an aralkylene group, -NH-, -NHCO-, a group obtained by combining these groups, or a mere bond. R ¹³ ,
R ¹⁴ and R ¹⁵ each represent a hydrogen atom, an alkyl group, or an aryl group. X represents a halogen atom. Note that R ¹¹ , R ₁₂ , R
₁₃ , R ₁₄ and R ¹⁵ may have a substituent. ) General formula (2) (R ²¹ and R ²² each represent a hydrogen atom, a hydroxy group, an alkyl group, an aryl group, or an alkoxy group, and may have a substituent. R ₁₁ , R ₁₂ , R ₁₃ , R ¹⁴ , R ₁₅ , X is the same as in the general formula (1), and m and n each represent an integer of 1 or more.

Also, Specific examples thereof include, but are not limited to, those represented by the following structural formulas.

As a method for obtaining a polysiloxane having an ammonium salt as a functional group, an organohalogenated silane having an ammonium salt as a functional group and particularly an organohalogenated silane not having an ammonium base are copolymerized in a polymerization step. It can be obtained by a method of introducing, a method of partially modifying a polysiloxane obtained by polymerization using an organohalogenated silane with an organic group having an ammonium salt as a functional group, or the like. Also,
An organoalkoxysilane may be used instead of the organohalogenated silane. In addition, some compounds can be obtained as commercial products.

Examples of the inorganic fine particles treated with the ammonium salt-modified polysiloxane include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide,
Fine particles such as chromium oxide, cerium oxide, antimony trioxide, zirconium oxide, and silicon carbide can be used. Among them, silica fine particles are particularly preferable from the viewpoint of improving fluidity.

As a method of treating the surface of the inorganic fine particles with the ammonium salt-modified polysiloxane, a known technique can be used. Specifically, for example, the inorganic fine particles are dispersed in a solution in which the ammonium salt-modified polysiloxane is dissolved in a solvent. After that, the solvent is removed by filtration or spray drying, and then cured by heating, or using a fluidized bed apparatus, a solution obtained by dissolving the ammonium salt-modified polysiloxane in the solvent is spray-coated on the inorganic fine particles, Then, a method of removing the solvent by heating and drying to cure the film, or the like can be used.

The particle size of the inorganic fine particles whose surface is treated with the ammonium salt-modified polysiloxane thus obtained is such that the average particle size of the primary particles is 3 μm to 2 μm, particularly 5 μm to 50 μm.
It is preferably within the range of 0 mμ. Also, BET
The specific surface area by the method is preferably from 20 to 500 m ² / g. If the average particle size and the specific surface area are in the above ranges,
For example, when a blade-type cleaning device is used, good cleaning performance is exhibited, the fluidity of the developer is good, and a satisfactory image with sufficient image density and unevenness can be obtained.

The inorganic fine particles treated with the ammonium salt-modified polysiloxane are externally added to and mixed with the toner powder to be attached to the surface of the toner particles and used.

The content ratio of such inorganic fine particles is preferably 0.5 to 3% by weight of the toner, particularly preferably 0.5 to 2% by weight. When the content is within this range, appropriate positive chargeability and fluidity can be obtained, and stable chargeability is exhibited even with environmental changes, and carrier particles, developing sleeves, and the like due to free inorganic fine particles. , And proper positive charging property can be provided for a long period of time.

The toner constituting the electrostatic latent image developer of the present invention has an average particle diameter obtained by a polymerization method in an aqueous medium of 0.1 to 3 μm.
Is a toner having an average particle diameter of 2 to 6 μm formed by bonding the primary particles of the present invention in the aqueous medium.

The primary particles are obtained, for example, by an emulsion polymerization method. The secondary particles are particles in which primary particles are bonded to each other by an ionic bond, a hydrogen bond, a metal coordination bond, a weak acid-weak base bond, a bond by van der Waals force, or the like.

Examples of monomers for obtaining primary particles include styrene-based monomers, acrylic monomers, and other monomers having a polar group.

Styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α
-Methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene , Pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene and the like.

Examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, and 2-ethylhexyl acrylate. , Stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α
-Methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylic acid
-Octyl, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like.

Other monomers having a polar group include those having an acidic polar group, such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, monobutyl maleate, and monooctyl maleate. Or a carboxyl group (—COOH) such as salts of these metals (Na, Zn, etc.)
An α, β-ethylenically unsaturated compound having a sulfone group (—SO ₃ H) such as an α, β-ethylenically unsaturated compound having the following formula: sulfonated styrene or its Na salt, allyl sulfosuccinic acid, octyl allyl sulfosuccinate or its N salt. Saturated compounds, those having a basic polar group, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, quaternary ammonium salts of these compounds, 3-cymethylaminophenyl acrylate, 2-hydroxy -3- (meth) acrylic acid esters of aliphatic alcohols having an amine group such as methacryloxypropyltrimethylammonium salt or a quaternary ammonium salt group having 1 to 12 carbon atoms, acrylamide, N-butylacrylamide, N (Meth) acrylamides such as N, N-dibutylacrylamide, piperidylacrylamide, methacrylamide, N-butylmethacrylamide, N, N-dimethylacrylamide, N-octadecylacrylamide, or any monomer or di-alkyl substituted on N (Meth) acrylamide, vinyl pyridine, vinyl pyrrolidone, vinyl N
-Methylpyridinium chloride, vinyl compounds substituted with a heterocyclic group having N as a ring member such as vinyl N-ethylpyridinium chloride, N, N-diallylmethylammonium chloride, N, N-diallylethylammonium chloride and the like N-diallylalkylamine, and the like.

In the monomers for obtaining the primary particles, the mixing ratio (weight ratio) of the styrene monomer and the acrylic monomer is 90 to 90%.
20: 10-80 is preferable, and 70-30: 30-70 is particularly preferable.

The mixing ratio of the other monomer having a polar group is preferably from 0.05 to 30 parts by weight, and particularly preferably from 1 to 20 parts by weight, based on a total of 100 parts by weight of the styrene-based monomer and the acrylic-based monomer. .

Various additives may be contained in the structure for polymerization for obtaining the primary particles as necessary. Such additives include colorants, charge control agents and the like.

Colorants include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red,
Quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxaleto, lamp black, rose bengal, mixtures thereof, and the like.

Examples of the charge control agent include metal complex dyes, nigrosine dyes, and ammonium compounds.

The carrier constituting the electrostatic latent image developer of the present invention is a resin-coated carrier in which the surface of core material particles is coated with a resin. As the resin for coating the carrier, a silicone resin or a fluorine resin is particularly preferable from the viewpoint of making the toner positively chargeable.

According to a resin-coated carrier made of a silicone-based resin or a fluorine-based resin, the surface energy of the carrier is considerably reduced, transfer adhesion of toner substances and inorganic fine particles to the carrier particle surface is hardly generated, and contamination of the carrier is considerably suppressed.
A developer with remarkably excellent durability can be obtained.

As the silicone resin, silicone varnish,
Examples include silicone rubber and silicone resin.

As the silicone resin, those having an organic group such as an alkyl group or an aromatic group as a structural unit are preferable,
Particularly, those having an organic group such as a methyl group and a phenyl group are preferable. Examples of the compound for obtaining such a silicone resin having an organic group include dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, and modified products thereof. In particular, a polysiloxane having a methyl group or a phenyl group has excellent negative chargeability. Further, in the organic group, a methyl group,
By appropriately selecting the content ratio of the phenyl group, characteristics such as hardness, toughness, and triboelectricity of the coating layer of the carrier can be adjusted, and thus are required for the toner used in combination with the resin-coated carrier. The conditions are considerably relaxed, and the selection range of the toner is widened.

Commercially available silicone varnishes include SR2101 and SH99
7, SH994, SR2202, SE9140, SH643, SH2047, JCR6100,
JCR6101 (all made by Toray Silicone), KR271, KR
272, KR274, KR216, KR280, KR282, KR261, KR260, KR2
55, KR266, KR251, KR155, KR152, KR214, KR220, X-
40-171, KR201, SA-4, KR5202, KR3093, EC1001 (all manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

Commercially available silicone rubber includes SH410, SH432, SH
433, SH740, SH35U, SH75U, SH841U, SH1125U, SH1603
U, SH665U, SH955U, SH502U, and SRX-440U (all manufactured by Toray Silicone Co., Ltd.).

The fluorine-based resin is not particularly limited as long as it is a resin containing a fluorine atom. For example, a polymer obtained by polymerizing a monomer represented by the following general formula (3) or (4), a fluorocarbon resin, And vinylidene fluoride-tetrafluoroethylene copolymer.

General formula (3) General formula (4) (In the formula, R ³¹ and R ⁴¹ each represent a hydrogen atom or a methyl group, n and p each represent an integer of 1 to 8, and m and q each represent an integer of 1 to 19.) Among the monomers represented by (3) or (4), a monomer represented by the following general formula (5) or (6) is particularly preferable in terms of triboelectricity.

General formula (5) General formula (6) (In the formula, R ⁵¹ and R ⁶¹ each represent a hydrogen atom or a methyl group, r represents an integer of 1 to 2, and s represents an integer of 2 to 4.) Further, the general formula (3) or ( Among the monomers represented by 4), particularly preferred are 1,1-dihydroperfluoroethyl methacrylate and 1,1,3-trihydroperfluoro-n-propyl methacrylate.

When a vinylidene fluoride-ethylene tetrafluoride copolymer is used, the copolymerization molar ratio is 75: 2.
A range of 5 to 95: 5 is preferred, and a range of 75:25 to 87.5: 12.5 is particularly preferred. Within such a range, the preparation of the coating liquid used for forming the coating layer becomes easy, and a resin-coated carrier having high mechanical strength and excellent durability of the obtained coating layer can be obtained.

Specific examples of the fluorine-based resin include the following, but are not limited thereto. In addition,
In the following specific examples, n represents an integer of 1 or more.

The resin-coated carrier is prepared by dissolving a coating resin in an organic solvent to prepare a coating solution, and applying the coating solution to the surface of the core material particles of the carrier by, for example, a dipping method, a dry spray method, or a fluidized bed method. After forming the coating layer by heating, it can be further formed by heating or standing.

As the core particles of the resin-coated carrier, those conventionally used as core particles of the carrier, such as silica sand, glass, and metal, can be used. Among them, substances which are strongly magnetized in the direction by a magnetic field in particular, such as ferrite, magnetite, iron, nickel, cobalt and other ferromagnetic metals, or alloys or compounds containing these metals, and ferromagnetic elements However, it is preferable to use an alloy which exhibits ferromagnetism by appropriate heat treatment, for example, an alloy of a kind called a Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin, or particles made of chromium dioxide or the like. Can be.

The weight average particle size of the resin-coated carrier is usually 10 to 300μ.
m is preferable, and 20 to 100 μm is particularly preferable.

The electrostatic latent image developer of the present invention can be suitably used for an electrophotographic copying machine having an organic photoreceptor. The specific configuration of the organic photoreceptor is not particularly limited, and various configurations can be adopted.

〔Example〕

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these embodiments.

<Inorganic Fine Particle A> As a constituent unit, a polysiloxane having an ammonium salt represented by the following structural formula as a functional group was dissolved in xylene to prepare a treatment liquid.

Next, silica fine particles “Aerosil 200” (manufactured by Nippon Aerosil Co., Ltd.) are put into a mixer, and the above-mentioned polysiloxane is sprayed on the silica fine particles at a ratio of 5% by weight. While stirring, xylene as a solvent was removed at a temperature of 200 ° C. for 5 hours to obtain inorganic fine particles A surface-treated with polysiloxane having an ammonium salt as a functional group.

The inorganic fine particles A had an average primary particle size of 12 mμ and B
The ET specific surface area was 115 m ² / g.

<Inorganic Fine Particles B> Silica fine particles “Aerosil 200” (manufactured by Nippon Aerosil Co., Ltd.) are placed in a sealed Henschel mixer heated to 100 ° C., and a solution in which an amino group-containing silicone oil is dissolved in isopropyl alcohol with respect to the silica fine particles ( A viscosity of 1200 cps, amino equivalent of 3500) is sprayed at a rate such that the amino group-containing silicone oil becomes 2.0% by weight, followed by high-speed stirring, and then dried at a temperature of 150 ° C., and then the surface is treated with the amino group-containing silicone oil. The treated inorganic fine particles B for comparison were obtained.

<Carrier A> 5 parts of silicone rubber "SH2047" (manufactured by Toray Silicone Co., Ltd.) and 0.05 parts of benzoyl peroxide were used in a fluidized bed apparatus, and 100 parts of spherical Cu-Zn ferrite particles (manufactured by Nippon Iron Powder Co., Ltd.) And then heat treated at 200 ° C. for 5 hours for sintering, then sieving the aggregates,
A carrier A having a coating layer made of a sintered product of silicone rubber was manufactured. The average particle size of this carrier A is 81 μm
Met.

<Carrier B> Vinylidene fluoride-tetrafluoroethylene copolymer “VT-
100 "(copolymer molar ratio 80:20, intrinsic viscosity 0.95dl / g, manufactured by Daikin Industries, Ltd.) 6g and methyl methacrylate copolymer" Acrypet MF "(manufactured by Mitsubishi Rayon Co., Ltd.) 6g were mixed with acetone and methyl ethyl ketone. Is dissolved in 500 ml of a mixed solvent (mixing volume ratio 1: 1) to prepare a coating solution, and the coating solution is applied to 1 kg of spherical Cu-Zn ferrite particles using a fluidized bed apparatus, Further heat treatment at 200 ° C for 5 hours,
Next, the aggregate was sieved to produce a carrier B having a coating layer having a thickness of about 2 μm. The average particle size of the carrier B was 82 μm.

<Toner A> 100 parts of water and polyoxyethylene alkyl ether 1
, 60 parts of styrene, 40 parts of butyl acrylate, and 8 parts of acrylic acid were added to an aqueous solution mixture of 1.5 parts of sodium alkylbenzene sulfonate and 0.5 part of potassium persulfate. For 8 hours to obtain an emulsion of primary particles having a solid content of 50%.

A mixture of 120 parts of the emulsion of the primary particles, 5 parts of nigrosine dye, 5 parts of carbon black, and 380 parts of water was maintained at about 30 ° C. for 2 hours while stirring and dispersing with a slasher. Then, warm to 70 ° C with further stirring and
Hold for hours. Observation with a microscope during this time confirmed that primary particles were associated and secondary particles were obtained. After cooling, the obtained liquid dispersion was subjected to Buchner filtration, washed with water,
Vacuum drying at 50 ° C for 10 hours, the average particle size is 5.5
μm of toner A was obtained.

<Toner B> 100 parts of a polystyrene / n-butyl acrylate copolymer (copolymer weight ratio 82:18), 5 parts of carbon black,
After mixing with 2 parts of nigrosine by a V-type blender, the mixture was melt-kneaded by two rolls, then cooled, coarsely ground by a hammer mill, further finely ground by a jet mill, and then classified by an air classifier. Average particle size
5.9 μm of toner B was obtained.

[Examples and Comparative Examples]

Each developer was prepared by the following method using the combinations shown in Table 1 below.

To 50 parts of the toner, 0.5 part of inorganic fine particles were added, and the mixture was mixed with a Henschel mixer to hold the inorganic fine particles on the surface of the toner particles.
950 parts were mixed to obtain an electrostatic latent image developer.

<Actual photo test> An electrophotographic copying machine including an organic photoreceptor for forming a negative electrostatic latent image, a contact-type magnetic brush developing device, and a cleaning device having a cleaning blade made of urethane rubber. Using a modified machine of “U-Bix1017” (manufactured by Konica Corporation), using the developers obtained in Examples and Comparative Examples under a high-temperature and high-humidity environment condition of a temperature of 30 ° C. and a relative humidity of 80%, A real-photographing test for forming a copy image was performed 300,000 times while providing a 5-hour pause for every 5000 copies, and the following items were evaluated.

The above-mentioned organic photoreceptor has a negative chargeability 2 formed by using an anthrone-based pigment as a carrier generating substance and a triphenylamine derivative as a carrier transporting substance.
The photosensitive layer has a layer structure and is formed by laminating on a rotating drum-shaped aluminum conductive support.

<Fog> Using a “Sakura Densitometer” (manufactured by Konica Corporation), the relative density of the copied image in the white background portion where the document density was 0.0 was measured and judged. The white background reflection density was set to 0.0. For evaluation, if the relative concentration is less than 0.01 Δ was 0.01 or more and less than 0.03, and × was 0.03 or more.

<Electrification Startup> A copy image obtained immediately after pausing for 5 hours for every 5000 copies was measured for stiffness and judged.

<Toner scattering> Visually observe the inside of the electrophotographic copying machine and the copied image. A case where toner scattering was slightly observed but at a practical level was rated as “A”, and a case where toner scattering was recognized a lot and had a problem in practice was rated as “D”.

<Resolution> In accordance with JIS Z4916, a chart was used in which 6.3, 8.0, 10.0, and 12.5 horizontal lines were provided at equal intervals per mm as a grade, and the grade in which the horizontal lines could be distinguished was displayed as the resolution.

<Charge stability> The toner charge amount at the start and at the end of 300,000 copies
It was measured by the blow-off method and the difference was indicated. Generally, if the difference is 5 μC / g or less, the charging stability is considered to be good.

<Resin Coverage of Carrier> The resin coverage of the carrier at the time of manufacturing the carrier and at the end of 300,000 copies was measured from the weight change of the carrier before and after dissolving and removing the resin on the carrier surface with methyl ethyl ketone.

 Table 2 shows the above results.

As understood from the results in Table 2, according to the developer of the present invention, a high-resolution copy image can be obtained many times without fogging or toner scattering. In addition, the charge rising and charge stability of the toner are good. Also,
The change in the resin coverage of the carrier is small and the durability of the carrier is good.

〔The invention's effect〕

As described in detail above, according to the electrostatic latent image developer of the present invention, inorganic fine particles obtained by surface treating polysiloxane having an ammonium salt as a functional group can be obtained by a polymerization method in an aqueous medium. The primary particles having an average particle size of 0.1 to 3 μm are bonded in the aqueous medium to have an average particle size of 2 to 2.
Since the particles of 6 μm are well incorporated into the surface of the toner particles and are not easily released, the inorganic fine particles can stably exhibit a suitable positive charging property over a long period of time, and also improve the durability of the resin-coated carrier.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-243963 (JP, A) JP-A-63-282275 (JP, A) JP-A-2-51164 (JP, A) JP-A-4- 198944 (JP, A) JP-A-63-225247 (JP, A) JP-A-1-114858 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08

Claims (1)

(57) [Claims] An inorganic fine particle obtained by surface-treating a polysiloxane having an ammonium salt as a functional group, and primary particles having an average particle size of 0.1 to 3 μm obtained by a polymerization method in an aqueous medium are joined in the aqueous medium. Average particle size is 2
An electrostatic latent image developer comprising a mixture of a toner of about 6 μm and a resin-coated carrier.