JPH04204545A - Electrostatic latent image developer - Google Patents

Abstract

PURPOSE:To exhibit high positive electrification stably for a long period and to obtain an image of high resolution by mixing inorganic fine particles obtained through surface treatment of polysiloxane having ammonium salt as a functional group, toner having a specific mean particle diameter, and a resin-covered carrier with each other. CONSTITUTION:Toner having a mean particle diameter of 2-6mum, obtained by combining inorganic fine particles prepared by surface treatment of polysiloxane having ammonium salt as a functional group with primary particles of a mean particle diameter 0.1-3mum prepared by a polymerization method in an aquatic medium in the same aquatic medium, is mixed with a resin- covered carrier. As the inorganic fine particle, a fine particle of, for example, silica, alumina, titanium oxide and the like are adopted, wherein a silica fine particle is particularly desirable in view of fluidity improvement. A containing ratio of the inorganic fine particle in the toner is desirably 0.5-3 weight %, and 0.5-2 weight % is particularly desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrostatic latent image developer comprising a mixture of inorganic fine particles, toner, and carrier.

[Conventional technology]

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

In recent years, organic photoconductive photoreceptors (hereinafter abbreviated as "organic photoreceptors") have been increasingly used as photoreceptors from the viewpoint of durability and environmental friendliness. The polarity of the electrostatic latent image formed on the surface of the organic photoreceptor is generally negative because there are relatively many types of photoconductive substances that can constitute 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 a toner, a technique is conventionally known in which an aminosilane coupling agent or silica fine particles treated with a combination of an aminosilane coupling agent and a silane coupling agent are externally added to the toner. Kaisho 5
3-22447 and 53-66235). However, with this technique, there are many hydrophilic groups on the surface of the silica particles, so they are easily affected by humidity and have a problem of being highly dependent on the environment.

On the other hand, as a technique for reducing the environmental dependence of silica fine particles, a technique has been proposed in which fine silicic acid powder treated with silicone oil having an amine in its side chain is externally mixed into toner (Japanese Unexamined Patent Application Publication No. 59/1983). -Refer to Publication No. 201063)
. However, in this technology, the surface of the silicic acid fine powder is treated with a sticky oil substance, so the silicic acid fine powder easily adheres to the surface of the photoreceptor, gear particles, etc. and contaminates it.
There is a problem in that cleaning performance and toner triboelectricity deteriorate.

Furthermore, in order to solve the above problem, a technique has been proposed in which inorganic fine particles surface-treated with polysiloxane having an ammonium salt as a functional group are externally mixed into the toner (JP-A-1-114857, J. (Refer to each publication No.-114858).

According to this technology, since it has an ammonium salt structure,
It can impart high positive chargeability to the toner compared to amino groups, and has low tackiness and adhesion, so there is less risk of contaminating the carrier and photoreceptor, and good cleaning and triboelectric charging properties can be obtained. In addition, the surface of inorganic fine particles
Second, since no hydrophilic zyte remains, environmental dependence is also improved.

[Invention or problem to be solved]

However, when such inorganic fine particles with weak adhesion are used, there is a problem that the inorganic fine particles are easily separated from the toner in the developer. In particular, when a resin-coated carrier is used in combination, the free inorganic fine particles act as an "abrasive" and the resin coating layer of the carrier is scratched by the agitation mechanism in the developing device, resulting in poor charging performance and durability. There are problems that have a negative impact on

This problem becomes particularly noticeable when toner with small particle size is used to improve resolution. In other words, as the particle size of the toner decreases, the specific surface area increases, the amount of inorganic fine particles externally added and mixed increases, the absolute amount of liberated inorganic fine particles also increases, and the polishing effect on the resin coating layer of the carrier increases. It is from.

As described above, the conventional techniques are still unable to sufficiently respond to the reduction in toner particle size, which is an essential condition for the development of developers suitable for high image quality in recent years.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrostatic latent image developer that has low environmental dependence, causes little carrier contamination, stably exhibits high positive chargeability over a long period of time, and can produce images with high resolution. There is a particular thing.

[Means to solve the problem]

The electrostatic latent image developer of the present invention comprises inorganic fine particles surface-treated with polysiloxane having an ammonium salt as a functional group, and an average particle size of 0 obtained by a polymerization method in an aqueous medium.
, a toner having an average particle diameter of 2 to 6 μm, which is formed by bonding primary particles of 1 to 3 μm in the aqueous medium, and a resin-coated carrier are mixed.

Moreover, it is preferable that the inorganic fine particles are silica fine particles.

[Effect]

Average particle size obtained by polymerization method in aqueous medium: 0.1~
Toner with an average particle diameter of 2 to 6 μm, which is made by combining primary particles of 3 μm in the aqueous medium, is different from toner obtained by a normal pulverization method, and has very smooth dimple-like irregularities or irregular shapes with many presences. It will be of the form.

Therefore, when inorganic fine particles whose surface is treated with polysiloxane having an ammonium salt as a functional group are added to this toner and mixed with stirring, most of the inorganic fine particles try to enter the recesses of the toner during stirring, so that the inorganic fine particles are It becomes difficult for the toner to be released from the surface. Furthermore, since the toner recesses are very smooth, there is no risk of interfering with frictional charging between the carrier and the toner.

Furthermore, in order to obtain high resolution, a small toner with an average particle diameter of 2 to 6 μm is used, so in order to fully demonstrate the effect of adding inorganic fine particles, it is necessary to add a large amount of the inorganic fine particles. However, as mentioned above, there are many recesses on the surface of the toner, and the area on which inorganic fine particles can adhere is sufficiently large, so even when a large amount of inorganic fine particles are added, the inorganic fine particles are removed from the toner. There is little risk of release.

As a result, the effect of adding the inorganic fine particles whose surface is treated with polysiloxane having ammonium salt as a functional group is reliably exhibited, the environmental dependence is reduced (the triboelectric chargeability is improved), and the inorganic fine particles are Since there is less risk of the carrier being liberated, there is less contamination of the carrier, and charging stability and durability are improved.Furthermore, high-resolution images can be stably obtained over a long period of time with the small diameter toner.

[Specific structure of the invention]

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

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

Inorganic fine particles surface-treated with ammonium salt-modified polysiloxane have high positive chargeability, exhibit stable chargeability against environmental changes, and improve the cleaning performance of photoreceptors.

The ammonium salt-modified polysiloxane is preferably dimethylpolysiloxane having an ammonium base,
This is usually a dimethylpolysiloxane containing a structural unit represented by the following general formula (1), and specifically, it is represented by the following general formula (2).

5i-0- ■ RI2 N-RI6.X- ■ R'' (R11 represents a hydrogen atom, hydroxy group, alkyl group, aryl group, alkoxy group, or R'' ■ RI2 N-R14.

R15.

R"I R" and R" each represent a hydrogen atom, an alkyl group,
Represents an aryl group. X represents a halogen atom. In addition, R
"+R", R13, R"+R15 may have a substituent.) General formula (2) (R21, R22 are each a hydrogen atom, a hydroxy group,
It represents an alkyl group, an aryl group, or an alkoxy group, and may have a substituent. R"l R"l R1"lR1
1, R15, and x are the same as in the above general formula (1). m.

Each n represents an integer of 1 or more. ) R12N+ R16.

-(CH2)2-N+-CH,・CI-■ CH3 ■ (CH2)3 N” CH3・CI-CH3 −(CH2)3-N” −(CH2),=CH3・C1
-CH3 (CH2)3 N” (CH2)IT CH3
・CI-CH3 Structural formula■ Nawate-(CH2)3 -N"-CH3・CI-CH3 Structural formula■-(CH2)3-N"-H-Cl-■-I Structural formula■ Sho-(CH2)2 - N" -H-CI-ShouCHl □ -(CH,) 2-N" -H-CI -RUCH3 -(CH2), -NH-(CH2)2-N"-CH3・
C do ■ CH3 Structural formula 〇-(CH2)3-NH-CO-N”-H-Cl-■ Structural formula O ■ (CH2)a N” H-CI- ■ CH2CH7-C00C2H5 (CH2)3 N” H =CI -■ Cl-13 Structural formula 0 Structural formula [phase] (CH2)3 N'' H-CI -1 11- Structural formula 0 %Formula% Structural formula [phase] Obtain polysiloxane having ammonium salt as a functional group Methods include a method in which an organohalogenated silane having an ammonium salt as a functional group and an organohalogenated silane that does not have an ammonium base are copolymerized in the polymerization step; It can be obtained by a method of partially modifying a polysiloxane obtained by polymerization with an organic group having an ammonium salt as a functional group.

Furthermore, organoalkoxysilane may be used instead of organohalogenated silane. Moreover, the compound of - part can also be obtained as a commercially available product.

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

Known techniques can be used to treat the surface of inorganic fine particles with ammonium salt-modified polysiloxane. Specifically, for example, inorganic fine particles are dispersed in a solution of ammonium salt-modified polysiloxane dissolved in a solvent. After that, the solvent is removed by filtration or spray drying, and then a solution of ammonium salt-modified polysiloxane dissolved in a solvent is spray applied to the inorganic fine particles using a method of curing by heating or using a fluidized bed device. Then, a method of curing the film by removing the solvent by heating and drying may be used.

The particle size of the inorganic fine particles whose surface has been treated with the ammonium salt-modified polysiloxane thus obtained is the average particle size of the primary particles, or 3 mμ to 2 μm, particularly 5 mμ to 2 μm.
It is preferable that the diameter is within the range of 500 mμ. In addition, the specific surface area according to the BET method is 20 to 500 m2/
It is preferable that it is g.

If the average particle size and specific surface area are within the above ranges, the cleaning performance will be good even when using a blade-type cleaning device, and the fluidity of the developer will be good, and a sufficient image will be obtained. A good image with no density or unevenness can be obtained.

The inorganic fine particles treated with ammonium salt-modified polysiloxane are added to and mixed with toner powder from the outside, and are attached to the surface of the toner particles for use.

The content of such inorganic fine particles is preferably from 0.5 to 3% by weight, particularly preferably from 0.5 to 2% by weight.

If the content ratio is within this range, appropriate positive chargeability and fluidity can be obtained, stable chargeability can be obtained even under changes in the environment, and carrier particles, developing sleeves, etc. made of free inorganic fine particles can be obtained. Appropriate positive chargeability can be provided for a long period of time without causing contamination.

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

The above-mentioned secondary site can be obtained, for example, by emulsion polymerization.

Further, the secondary particles are particles in which primary particles are bonded to each other by ionic bonds, hydrogen bonds, metal coordination bonds, weak acid-weak base bonds, bonds due to van der Waals forces, etc.

Examples of monomers for obtaining primary particles include styrene monomers, acrylic monomers, and other monomers having polar groups.

Styrene monomers include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-
Methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert
-butylstyrene, p-n-hequinrustyrene, p-n
-octylstyrene, p-n-nonylstyrene, p-n
-decylstyrene, p-n-F decylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, and the like.

Examples of acrylic monomers include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate,
Dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl acid n-
Examples include butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methanolylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.

Other monomers having polar groups include acrylic acid, methacrylic acid, fumaric acid, maleic acid,
Carboxyl groups (-COO
α,β-ethylenically unsaturated compound having H), sulfonated styrene or its Na salt, allylsulfosuccinic acid, octyl allylsulfosuccinate or its Na salt
α, β-ethylenically unsaturated compounds having a sulfonic group (-3O3H) such as salts, and those having a basic polar group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate-1, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, quaternary ammonium salts of these compounds, 3-dimethylaminophenyl acrylate, 2-hydroxy-3-methacrylogicypropyltrimethylammonium salts, etc. having an amine group or a quaternary ammonium base having 1 to 12 carbon atoms;
(meth)acrylic esters of aliphatic alcohols, acrylamide, N-butylacrylamide, N,N-dibutylacrylamide, piperidylacrylamide, methacrylamide, N-butylmethacrylamide, N,N
- (meth)acrylic acid amides such as dimethylacrylamide, N-octadenyl acrylamide or (meth)acrylic acid amides with optional monomer or di-alkyl substitution on N, vinylpyridine, vinylpyrrolidone, vinyl N-
Vinyl compounds substituted with a heterocyclic group having N as a ring member such as methylpyridinium chloride and vinyl N-ethylpyridinium chloride; -diallylalkylamine, and the like.

Among the monomers for obtaining primary particles, the blending ratio (weight ratio) of styrene monomer and acrylic monomer is 90 to 90.
20+10-80 is preferable, especially 70-3030
~70 is preferred.

The proportion of other monomers having polar groups is preferably 0.05 to 30 parts by weight, particularly 1 to 20 parts by weight, based on 100 parts by weight of the styrene monomer and acrylic monomer. is preferred.

The polymerization composition for obtaining primary particles may contain various additives as necessary.

Such additives include colorants, charge control agents, and the like.

Colorants include carbon black, nigrosine dye,
Examples include aniline blue, calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rho 19 = one's bengal, mixtures thereof, and others.

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

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

According to a resin-coated carrier made of silicone resin or fluorine resin, its surface energy is considerably reduced, and transfer and adhesion of toner substances and inorganic fine particles to the carrier particle surface is difficult to occur, and contamination of the carrier is considerably suppressed.
A developer with extremely high durability can be obtained.

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

The silicone resin preferably has an organic group such as an alkyl group or an aromatic group as a constituent unit, and particularly preferably one having an organic group such as a methyl group or a phenyl group. Compounds for obtaining silicone resins having such organic groups include dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane,
Examples include modified products of these. In particular, polysiloxanes having methyl groups or phenyl groups have excellent negative charging properties. In addition, by appropriately selecting the content ratio of methyl groups and phenyl groups among the above organic groups, properties such as hardness, toughness, and triboelectricity of the coating layer of the carrier can be adjusted. The conditions required for the l-toner used in combination with the toner are considerably relaxed, and the range of toner selection is widened.

Commercially available silicone varnishes include 5R2101 and S.
H997, S H994, S R2202, 5E91
40.5H643, S H2O47, JCR6100,
JCR6101 (manufactured by Tomu Silicone Co., Ltd.),
KR271, KR272, KR274, KR216, K
R280, KR282, KR26], KR2
60, KR255, KR266, KR251, KR]5
5, KR152, KR2+4, KR2
20, X-40-171, KR201, SA-4,
Examples include KR5202, KR3093, and EC100I (manufactured by Shin-Etsu Chemical Co., Ltd.).

Commercially available silicone rubber products include SH4]0.5H4
32, 5H433, 5H740, 5H35U, 5H7
5U, 5H84] U, 5H1125U, 5H1603
U, 5H665U, 5E955U, 5H502U
, 5RX-440U (manufactured by 1.-Le Silicone Co., Ltd.), and the like.

The fluorine-based resin is not particularly limited as long as it contains a fluorine atom;
Examples thereof include a polymer obtained by polymerizing the monomer shown in 3) or (4), a vinylidene fluoride-tetrafluoroethylene copolymer, and the like.

General formula (3) % formula % General formula (4) R” CH,=C ■ Coo (CH2), (CF2), H (in the formula, R” and R”1 each represent a hydrogen atom or a methyl group , n, p each represent an integer from 1 to 8, m,
Each q represents an integer from 1 to 19. ) The above general formula (3
) or (4), the monomers represented by the following general formula (5) or (6) are particularly preferred from the viewpoint of triboelectric charging properties.

General formula (5) %Formula% General formula (6) R” CH2=C COOCH2(CF2)sH (Formula r11, R51, Rat each represent a hydrogen atom or a methyl group, r represents an integer of 1 to 2, S is 2-4
represents an integer. ) Also, among the monomers represented by the general formula (3) or (4), in particular, 1,1-dihydroperfluoroethyl methacrylate, 1,1,3-trihydroperfluoro-methacrylate N-propyl and the like are preferred.

In addition, when using vinylidene fluoride-ethylene tetrafluoride copolymer, the copolymerization molar ratio of these is 75.
The range of 25 to 95.5 is preferable, especially 75:25
-87.5: The range of 12.5 is preferable. Within this range, the coating liquid used for forming the coating layer can be easily prepared, and the resulting coating layer can have a high mechanical strength and a resin-coated carrier with excellent durability.

Specific examples of the fluororesin include, but are not limited to, those listed below. Note that in the following specific examples, n represents an integer of 1 or more.

~24- Fluorine resin■ CI-I.

one (CH2-C), - ■ C00CH2CF3 Fluorine resin■ CH.

■ -(CH, -C), - COOCH2CF2 CF3 Fluororesin ■ I C0OCH2(CF2)2HC00CT-T3 Fluororesin ■ CH2 ■ -(CH2-C). - ■ COOCH2 (CF 2) 4 H Fluorine resin ■ HH (I - (CII2-C). - C00CR2 (CF2) 3CF3 Fluorine resin ■ CH3 - (CH2-C). - C00CH2 (CF 2) 5H Fluorine System resin■ CH3CH3 -(CH2-C)□ □ (CH2-C') ,,-)
I C0OCH2(CF2)2 CF3 COOCH3 A resin-coated carrier is prepared by dissolving a coating resin in an organic solvent to prepare a coating liquid, and applying this coating liquid to the carrier by a method such as a dipping method, a dry spray method, or a fluidized bed method. After coating the surface of the core material particles to form a coating layer, the coating layer can be further formed by heating or standing.

The core particles of the resin-coated carrier include silica sand, glass,
It is possible to use particles conventionally used as core material particles of carriers, such as metals. Among these, materials that are strongly magnetized in the direction of a magnetic field, such as ferrite and magnetite, as well as iron, nickel,
Metals that exhibit ferromagnetism such as cobalt, or alloys or compounds containing these metals; alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment, such as manganese-copper-aluminum or manganese - Particles made of a type of alloy called Heusler alloy such as copper-tin or chromium dioxide can be preferably used.

The weight average particle size of the resin-coated carrier is usually 10 to 300
The thickness is preferably .mu.m, particularly preferably 20 to 100 .mu.m.

The electrostatic latent image developer of the present invention can be suitably used in an electrophotographic copying machine equipped with an organic photoreceptor. The specific structure of the organic photoreceptor is not particularly limited, and various structures can be adopted.

〔Example〕

The present invention will be described in detail below, but the present invention is not limited to these embodiments.

<Inorganic Fine Particles A> A treatment liquid was prepared by dissolving polysiloxane having an ammonium salt represented by the following structural formula as a functional group in xylene as its constituent unit.

(X is an integer) Next, silica fine particles [Aerotsuru 200J (Nippon Ichi 29-, ,,-).

(manufactured by Aerosil) was placed in a mixer, and the polysiloxane was sprayed at a ratio of 5% by weight to the silica particles.Then, these were placed in a flask and heated at 200°C for 5 hours while stirring. The solvent xylene was removed over a period of time to obtain inorganic fine particles whose surface was treated with polysiloxane having an ammonium salt as a functional group.

The inorganic fine particles A have an average particle diameter of 12 mμ,
The BET specific surface area was 115 m2/g.

<Inorganic fine particles B> Silica fine particles "Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.)" were placed in a closed Henschel mixer heated to 100°C, and the silica fine particles were mixed with a solution of amino group-containing silicone oil in isopropyl alcohol ( A viscosity of 1,200 cps and an amino equivalent of 3,500) were sprayed at a ratio such that the amino group-containing silicone oil was 2.0% by weight, stirred at high speed, and then dried at a temperature of 150°C. Comparative inorganic fine particles B whose surface was treated with silicone oil were obtained.

<Carrier A> 5 parts of silicone rubber rS H2O47J (manufactured by Tomu Silicone Co., Ltd.) and 0.05 part of benzoyl peroxide were mixed into spherical Cu-Zn ferrite particles (manufactured by Nippon Tetsuko Co., Ltd.) using a fluidizing bed device. ) 100 parts by spray coating, further heat-treated at 200°C for 5 hours to sinter, and then the aggregates were sieved to obtain carrier A having a coating layer made of sintered silicone rubber. Manufactured. The average particle size of this carrier was 81 μm.

<Carrier B> Vinylidene fluoride-tetrafluoroethylene copolymer "VT-
100'' (copolymerization molar ratio 80/20. Intrinsic viscosity 0, 9
5 (///g, manufactured by Daikin Industries) 6g,
Methyl methacrylate copolymer [Acrivet MFJ
(manufactured by Mitsubishi Rayon Co., Ltd.) in 500 ml of a mixed solvent of acetone and methyl ethyl ketone (mixed volume ratio 1:1) to prepare a coating liquid. I of Cu-Zn ferrite particles of
kg, further heat treated at 200°C for 5 hours, and then the agglomerates were sieved to a thickness of approximately 2 μm.
A carrier B was produced having a coating layer of . The average particle size of this carrier B was 82 μm.

<L-ner A> 100 parts of water and 1 part of polyoxyethylene alkyl ether
1.5 parts of sodium alkylbenzenesulfonate, and 0.5 parts of potassium persulfate were added a mixture of 60 parts of styrene, 40 parts of butyl acrylate, and 8 parts of acrylic acid. , at 70°C with stirring 8
Polymerization was carried out for a period of time to obtain an emulsion of primary particles with a solid content of 50%.

A mixture of 120 parts of the emulsion of the secondary particles, 5 parts of nigrosine dye, 5 parts of carbon black, and 380 parts of water was dispersed and stirred using a slasher, and then heated to about 30°C for 2 hours.
Holds time. Thereafter, the mixture was heated to 70°C with further stirring and maintained for 3 hours. During this time, I observed it with a microscope, and -
It was confirmed that secondary particles were obtained by association of secondary particles.

Thereafter, after cooling, the obtained liquid dispersion was filtered through Buchner, washed with water, and vacuum dried at 50-31 = °C for 10 hours to reduce the average particle size to 5.
．． Toner A of 5 μm was obtained.

Toner B> 100 parts of polystyrene/n-butyl acrylate-1 copolymer (copolymerization weight ratio 82:18), 5 parts of carbon black, and 2 parts of nigrosine were mixed in a V-type blender, and then The mixture was melt-kneaded using this roll, then cooled, coarsely pulverized using a hammer mill, finely pulverized using a jet mill, and then classified using an air classifier to obtain toner B having an average particle size of 5.9 μm.

[Examples and comparative examples]

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

0.5 parts of inorganic fine particles are added to 50 parts of toner and mixed using a Henschel mixer to retain the inorganic fine particles on the surface of the toner particles, and further mixed with 950 parts of carrier to develop an electrostatic latent image. obtained the drug.

Table 1 <Actual photo test> An electrophotographic image comprising 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 copying machine "rU-Bix1017" (manufactured by Konica ■) under high temperature and high humidity environmental conditions of 30°C and 80% relative humidity, each developer obtained in the Examples and Comparative Examples was used to produce 5,000 copies. Since there was no downtime of 5 hours for each copy, a live copying test was conducted in which copied images were formed 300,000 times, and the following items were evaluated.

The above-mentioned photoreceptor is a negatively chargeable 2, which is formed using an anthrone pigment as a carrier generating substance and a triphenylamine derivative as a carrier transporting substance.
It is constructed by laminating a layered photosensitive layer on a rotating drum-shaped aluminum conductive support.

<Fog> Fog was determined by measuring the relative density of the copied image of the white background area, which is 0.0 from the original density, using a "Sakura Densitometer" (manufactured by Konica Corporation). Note that the white background reflection density was set to 0.0. For evaluation, relative concentration is less than 0.01 as ○, 0. O1
A score of less than 0.03 was marked as △, and a score of 0.03 or more was marked as ×.

<Charging Rise> Fog was determined by measuring copy images obtained immediately after a 5-hour pause every 5,000 copies.

<Toner scattering> Visually observe the inside of the electrophotographic copying machine and the copied images,
○ if there is no toner scattering and the condition is good.
A case where some amount of toner scattering was observed but at a practical level was rated △, and a case where a large amount of toner scattering was observed and there was a practical problem was rated x.

<Resolution> Based on JA324916, the blade has 6.3, 8.0, 10.0, and 1 horizontal lines at equal intervals per mm.
Using 2.5 Char 1, the blades with discernable horizontal lines were displayed as resolution.

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

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

The above results are shown in Table 2.

As can be understood from the results in Table 2, according to the developer of the present invention, high-resolution copy images can be obtained many times without fogging or toner scattering. Further, the toner has good charge rise and charge stability. Further, there is little change in the resin coverage of the carrier, and the durability of the carrier is good.

〔Effect of the invention〕

As explained in detail above, according to the electrostatic latent image developer of the present invention, inorganic fine particles surface-treated with polysiloxane having an ammonium salt as a functional group are obtained by a polymerization method in an aqueous medium. Primary particles with a particle size of 0.1 to 3 μm are bonded together in the aqueous medium, and the average particle size is 2 to 3 μm.
Since it is well incorporated into the surface of the 6 μm toner particles and is difficult to separate, the inorganic fine particles can stably exhibit suitable positive chargeability over a long period of time, and the durability of the resin-coated carrier is also improved.

Claims (2)

[Claims] (1) Inorganic fine particles surface-treated with polysiloxane having ammonium salt as a functional group and primary particles with an average particle size of 0.1 to 3 μm obtained by polymerization in an aqueous medium are bonded in the aqueous medium. The average particle size is 2 to 6.
An electrostatic latent image developer characterized by being made of a mixture of μm toner and a resin-coated carrier. (2) An electrostatic latent image developer, wherein the inorganic fine particles according to claim 1 are silica fine particles.