JPH07181748A - Two-component developer for electrostatic latent image development - Google Patents

Abstract

PURPOSE:To prevent a coated carrier from being a spent, to prevent wear of the coating layer of the carrier, and to obtain safe triboelectrification and sharp and uniform distribution of triboelectric charges even for repeated use, and to obtain good images for a long time by controlling the hardness of the coating film of the coated carrier and the specific surface area and the add amt. of an external additive compounded in the toner. CONSTITUTION:This developer consists of at least a toner and a coated carrier the core particles of which are coated with a film. The toner particles contain at least a binder resin, coloring agent and polarity controlling agent and have 5 to 10mum volume averaged grain size with external addition of inorg. fine particles. When the surface hardness of the coated carrier (pencil hardness measured by a pencil scratching test specified by JIS K5400) and the product of the square root of the specific surface area by BET method of the additive for the toner and the add amt. (wt.%) of the additive to the toner are taken as ordinate and abscissa, respectively, as shown in the figure, the surface roughness, specific surface area and add amt. are controlled to be in the region defined by points A, B, C, D in the figure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer used in electrophotography, electrostatic printing and the like.

[0002]

2. Description of the Related Art As a method of developing an electrostatic latent image using toner, a cascade developing method (US Pat. No. 2,618,855) is used.
No. 2) and a magnetic brush development method (US Pat. No. 2874).
No. 063) is known. In both of these methods, a two-component dry developer is used.

In this two-component dry developer, fine toner particles are held on the surface of a relatively large particle by an electric force generated by friction between the two particles, and when the developer approaches an electrostatic latent image. , The attraction force in the electrostatic latent image direction with respect to the toner particles overcomes the binding force between the toner particles and the carrier particles by the electric field formed by the electrostatic latent image, and the toner particles are attracted and adhered onto the electrostatic latent image to be statically attached. The latent image is visualized. Then, the developer is repeatedly used while replenishing the toner consumed by the development.

Generally used as a carrier material for a two-component developer is a metal oxide such as magnetite or ferrite, which has a smaller apparent density than an iron powder carrier and is lighter as a developer. Since it is possible, when the developer is stirred in the developing device, there is an advantage that the stirring resistance becomes small. In addition, the residual magnetic flux density is lower than that of the iron powder carrier, the coercive force is small, and the area of the hysteresis loop is small as a result, and the initial characteristics are always maintained for magnetization reversal and magnetization history. It has characteristics. Also magnetite,
Since ferrite and the like are oxides, they are chemically stable and are less likely to undergo chemical changes due to ozone, NOx, etc. generated in the copying machine.

However, such metal oxide carriers such as ferrite and magnetite also collide between developer particles due to high-speed development or copying of a large number of sheets, or mechanical collision such as collision between developer particles and inner wall of development, or Due to the heat generated by these actions, a toner film is formed on the carrier surface,
There is a drawback that so-called “spent” occurs, the charging characteristics of the carrier decrease with the use time, and toner scattering, background fog, etc. occur.

In order to prevent such spent formation,
Conventionally, a method of coating various resins on the surface of core particles of a carrier has been proposed. For example, it is a carrier coated with a styrene-methacrylate copolymer, a styrene polymer, a tetrafluoroethylene polymer or the like. However, this type of carrier is unlikely to cause spent toner, but with repeated use, the coating resin on the surface wears and the initial performance can be maintained due to changes in resistance due to exposure of core particles and changes in surface properties. There is a problem of disappearing. In particular, when a toner is mixed with a hard additive such as an inorganic fine powder for the purpose of improving the fluidity of the toner, the friction of the carrier coating layer is remarkable and the life of the developer is shortened.

[0007]

Thus, in order to eliminate the inconvenience, carrier particles having a coating layer on the surface of which a silicone resin is cured and fine particles of hydrophobic silica having a hydrophobicity index of 50 or more are provided on the surface. A two-component type developer in combination with the toner particles contained therein has been proposed (JP-A-62-1).
80375). However, in the case where an image is formed using the developer disclosed herein, it is a fact that a good quality copy may not always be obtained for a long period of time. An object of the present invention is to solve the above problems,
To provide a dry two-component type developer which has a small amount of friction of a carrier coating layer, has stable triboelectric charge even after repeated use, has a sharp and uniform triboelectric charge amount distribution, and can obtain a good image for a long period of time. .

[0008]

The two-component developer for developing an electrostatic latent image of the present invention comprises at least a coated carrier coated with a coating film of core particles, and at least a binder resin, a colorant and a polarity control agent. The toner has a volume average particle diameter of 5 to 10 μm and an inorganic fine powder added externally, and as shown in the accompanying drawings, the horizontal axis indicates the surface hardness of the coated carrier (pencil scratch defined by JIS K5400). Pencil hardness in the test), and the vertical axis represents BE of the toner external additive
When the product of the square root of the specific surface area in the T method and the addition amount (wt%) with respect to the toner is taken as the product of these, points A, B,
It is characterized in that it is within the range surrounded by C and D. As a result of earnest studies on the two-component developer, the present inventors have solved the above problems by adjusting the hardness of the coat carrier coating layer and the specific surface area and addition amount of the external additive compounded in the toner. The present invention has been made based on this finding.

Therefore, the developer of the present invention is blended in the toner and the hardness of the coating layer of the coat carrier because the abrasion of the coating layer of the coat carrier is generated by the fluidity modifier externally added to the toner. If the relationship between the specific surface area and the addition amount of the external additive is within the range shown in FIG. 1, it is possible to prevent the spent on the coated carrier while maintaining the fluidity of the toner, and also to prevent the abrasion of the coating layer, which enables repeated use. Also, the triboelectrification is safe, the triboelectrification amount distribution is sharp and uniform, and a good image can be obtained for a long period of time.

The present invention will be described in more detail below. In the present invention, the hardness of the coating layer of the coated carrier is JIS
It is measured by the pencil scratch test method defined by K5400. In the present invention, the pencil hardness of the carrier coating layer needs to be between 3H and 7H. A developer in which the pencil hardness of the coating layer of the carrier is less than 3H and the external additive of inorganic fine powder is added to the toner is inferior in abrasion resistance of the coating layer. If the hardness is greater than 7H, the spent will proceed even if the inorganic fine powder external additive is added to the toner. Further, in the present invention, it is necessary that the product of the square root of the specific surface area of the external additive (inorganic fine powder) of the toner in the BET method and the addition amount (wt%) with respect to the toner is between 1.5 and 8.5. is there.

The inorganic fine powder externally added to the toner affects the abrasion of the coat carrier coating layer due to the difference in BET specific surface area even with the same addition amount. There is a correlation with the amount of scraping.

Now, (BET) ^{0 5} × (added amount to toner: wt%). ． ． Taking (I) as a parameter, if this value is 1.5 or less, the fluidity of the toner cannot be sufficiently obtained. Moreover, this value is 8.5.
In the above case, the fluidity of the toner is too large, so that triboelectrification by stirring with the coat carrier cannot be sufficiently obtained, the charge amount distribution becomes broad, and fogging by the oppositely charged toner occurs.

In the present invention, it is desirable to use a silicone resin as the main component of the carrier coating layer. As the silicone resin, any conventionally known silicone resin may be used, and examples thereof include straight silicones consisting only of organosiloxane bonds represented by the following formula and silicone resins modified with alkyd, polyester, epoxy, urethane and the like. . The straight silicone may have the following structure.

[0014]

[Chemical 1] (R in the formula¹Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
Or phenyl group, R²And R³Is the number of hydrogen atoms and carbon atoms
1-4 alkoxy group, phenyl group, phenoxy group, charcoal
An alkenyl group having 2 to 4 elementary atoms, an alkenyl group having 2 to 4 carbon atoms
Lucenyloxy group, hydroxy group, carboxyl group,
Tylene oxide group, glycidyl group or represented by the following formula
Base.

[Chemical 2] However, R^Four, R^FiveIs a hydroxy group, carboxyl group, carbon
Alkyl groups having 1 to 4 atoms, and alcohols having 1 to 4 carbon atoms
Xy group, alkenyl group having 2 to 4 carbon atoms, number of carbon atoms
2-4 alkenyloxy groups, phenyl groups, phenoxy
It is a base. , K, l, m, n, o, p are integers of 1 or more.
Show. In addition to the unsubstituted substituents,
Amino group, hydroxy group, carboxyl group, mercap
Group, alkyl group, phenyl group, ethylene oxide
Have substituents such as groups, glycidyl groups, halogen atoms
May be. )

Commercial products of straight silicone resin are KR271, KR255, KR15 manufactured by Shin-Etsu Chemical Co., Ltd.
2. SR24 made by Toray Dow Corning Silicone
11, SR2405, etc. As the modified silicone resin, Shin-Etsu Chemical Co., Ltd. KR206 (alkyd modified),
Examples include KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified), Toray Dow Corning Silicone SR2115 (epoxy modified) and SR2110 (alkyd modified).

In the present invention, as a method for synthesizing a thermoplastic silicone resin, for example, a polyorganosiloxane containing a silanol group is obtained by subjecting an organosilanol produced by hydrolyzing an organochlorosilane or an organoalkoxysilane with excess water to a condensation reaction. After obtaining the silanol group, the silanol group is obtained by silylation with a silane compound having a hydrolyzable group such as alkoxysilane such as trimethylmethoxysilane and trimethylethoxysilane. Crush these silicone resins to 1
Used as particles of 0-100 μm.

The inorganic fine powder externally added to the toner is the BE
It is desirable that the T specific surface area is in the range of 70 to 250 m ² / g. If the BET specific surface area is less than 70 m ² / g, the fluidity-imparting effect is not sufficient even if the amount added to the toner is 1 wt% or more. If the BET specific surface area is more than 250 m ² / g, the additive is repeatedly used as a toner. It will be embedded in the surface and the effect of giving sufficient fluidity will not be obtained.

In the present invention, if silica is used as the externally added inorganic fine powder, the triboelectric charge distribution of the toner can be sharpened due to the high chargeability of silica itself.

The hydrophobicity of the externally added inorganic fine powder is 70%.
The above is desirable. If the degree of hydrophobicity is less than 70, the hydrophobicity is not sufficient, and in a high humidity environment, fluidity is insufficient and the triboelectric charge amount becomes low, and problems such as fogging occur and stable images can be obtained. It's gone. The degree of hydrophobicity here is defined as follows. Mix 0.2 g of sample with 50 cc of water, put the tip of the pipette in this mixture, and drop methanol with the pipette in this state. Methanol necessary for all the sample to be below the liquid level (wet) When the amount (cc) is measured and the value is defined as Acc, it means a value obtained by the following formula [A / (50 + A)] × 100.

In the present invention, the carrier powder particles coated with a resin having a pencil hardness of 3H or more may be conventionally known ones, for example, ferromagnetic metals such as iron, cobalt and nickel; synthesis of magnetite, hematite, ferrite and the like. Compounds; glass beads and the like can be mentioned. The average particle size of these powder particles is usually 10 to 1000 μm, preferably 3
It is 0 to 500 μm. The amount of the coating resin used is usually 1 to 10% by weight based on the carrier core particles.

A conductive fine powder and a coupling agent may be added to the coating layer composition. As a method for forming the coating layer, the resin may be applied to the surface of the carrier core particles by a method such as a spraying method or a dipping method as in the conventional method.

As the toner constituting the developer together with the electrostatic latent image developing carrier of the present invention, those manufactured by a conventionally known method can be used. Specifically, it is obtained by melt-kneading a mixture of a binder resin, a colorant, and a polarity control agent (containing optional additives as necessary) with a hot roll mill, cooling and solidifying, and pulverizing and classifying the mixture. .

As the binder resin, all known binder resins can be used. For example, polystyrene, poly p-
Styrene and homopolymers of styrene such as polyvinyltoluene and its substitution products, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-methyl acrylate copolymers, Styrene-ethyl acrylate copolymer, styrene-
Butyl acrylate copolymer, styrene-methylmethacrylate copolymer, styrene-ethylmethacrylate copolymer, styrene-butylmethacrylate copolymer, styrene-α-chloromethylmethacrylate copolymer, Styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-maleic acid copolymer,
Styrene-based copolymers such as styrene-maleic acid ester copolymers, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic Acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination. In particular, by using a polyester resin as the binder resin, it is possible to obtain an electrophotographic developer which does not impair the vinyl chloride matt fusion resistance and the original color of the color material of the color toner.

The polarity controlling agent may be a conventionally known one, for example, a metal complex salt of a monoazo dye, nitrohumic acid and its salt, salicylic acid, naphthoic acid, a metal complex amino compound of Co, Cr, Fe or the like of a dicarboxylic acid, a secondary compound. There are quaternary ammonium compounds and organic dyes. The amount of the polarity control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, the toner production method including the dispersion method, and the like, and is not uniquely limited. Preferably 0.1 to 20 parts by weight relative to 100 parts by weight of binder resin
Used in the range of parts by weight. If the amount is less than 0.1 parts by weight, the amount of charge of the toner is insufficient, which is not practical. On the other hand, when the amount exceeds 20 parts by weight, the amount of charge of the toner is too large and the electrostatic attraction with the carrier increases, so that the fluidity of the developer decreases and
This causes a decrease in image density.

As the colorant, for example, carbon black, aniline black, furnace black, lamp black and the like can be used as black colorants. Examples of cyan colorants that can be used include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue.
Examples of magenta colorants that can be used include rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, and alizarin lake. As the yellow colorant, for example, chrome yellow, benzidine yellow, Hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used.

The toner may contain a magnetic material and be used as a magnetic toner. The magnetic material contained in the magnetic toner includes magnetite, hematite, iron oxides such as ferrite, metals such as iron, cobalt and nickel, or metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc and antimony, Examples thereof include alloys of metals such as beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium, and mixtures thereof. It is desirable that these ferromagnetic materials have an average particle size of about 0.1 to 2 μm, and the amount contained in the toner is about 20 to 200 parts by weight, and particularly preferably 100 parts by weight of the binder resin with respect to 100 parts by weight of the binder resin. It is 40 to 150 parts by weight per part.

Other additives that can be added to the toner include inorganic fine powders such as cerium oxide, silicon oxide, titanium oxide and silicon carbide. Among these, colloidal silica is particularly preferable.

The amount of the carrier and toner used in the present invention is preferably such that the toner particles adhere to the carrier surface of the carrier particles and occupy 30 to 90% of the surface area of the carrier particles.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. All parts are by weight.

Here, manufacturing examples of some carriers are shown. Carrier Production Example 1 (Composition of coating layer forming liquid) Acrylic resin (BR-83: Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts After mixing a coating layer forming liquid with a homomixer, a fluidized bed type coating device was used. Ferrite core particles 100
It was coated on 0 part and dried at room temperature for 5 hours to obtain carrier particles A. In addition, a coating forming solution of the above formulation was added to a SUS having a thickness of 1 mm.
Spray applied to the plate and dried at room temperature for 5 hours, then JIS K5
The pencil hardness was H when the pencil scratch test defined by 400 was conducted.

Carrier Production Example 2 (Composition of coating layer forming liquid) Acrylic resin (BR-83: manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts After mixing a coating layer forming liquid with a homomixer, a fluidized bed type coating apparatus Using ferrite core particles 100
Apply to 0 parts and dry at 70 ° C for 24 hours to obtain carrier particles B.
And Further, a coating forming liquid having the above-mentioned formulation was added with S having a thickness of 1 mm.
Spray coated on US plate and dried at room temperature for 5 hours, then JIS
When the pencil scratch test specified in K5400 was conducted, the pencil hardness was 4H.

Carrier Production Example 3 (Composition of coating layer forming liquid) Silicone resin 100 parts (SR-2410: manufactured by Toray Dow Corning Silicone Co., Ltd.) A coating layer forming liquid consisting of 100 parts of toluene was mixed with a homomixer and then fluidized bed type. Ferrite core particles 100 using a coating device
0 part was coated and dried at room temperature for 5 hours to obtain carrier particles C. In addition, a coating forming solution of the above formulation was added to a SUS having a thickness of 1 mm.
Spray applied to the plate and dried at room temperature for 5 hours, then JIS K5
When the pencil scratch test defined by 400 was conducted, the pencil hardness was 2H.

Carrier Production Example 4 (Composition of coating layer forming liquid) Silicone resin 100 parts (SR-2410: manufactured by Toray Dow Corning Silicone Co., Ltd.) A coating layer forming liquid consisting of 100 parts of toluene was mixed with a homomixer and then fluidized bed type. Ferrite core particles 100 using a coating device
Apply to 0 parts and dry at 230 ° C for 2 hours to obtain carrier particles D
And Further, a coating forming liquid having the above-mentioned formulation was added with S having a thickness of 1 mm.
Spray coated on US plate and dried at room temperature for 5 hours, then JIS
When the pencil scratching test specified in K5400 was conducted, the pencil hardness was 5H.

Carrier Production Example 5 (Composition of coating layer forming liquid) Acrylic resin (BR-83: manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts After mixing a coating layer forming liquid with a homomixer, a fluidized bed type coating apparatus Using ferrite core particles 100
Apply to 0 parts and dry at 300 ° C for 2 hours to obtain carrier particles E.
And Further, a coating forming liquid having the above-mentioned formulation was added with S having a thickness of 1 mm.
Spray coated on US plate, dried at 300 ℃ for 2 hours, then JI
When the pencil scratch test defined by SK5400 was conducted, the pencil hardness was 6H.

Carrier Production Example 6 (Composition of coating layer forming liquid) Silicone resin 100 parts (SR-2410: manufactured by Toray Dow Corning Silicone Co., Ltd.) A coating layer forming liquid consisting of 100 parts of toluene was mixed with a homomixer and then fluidized bed type. Ferrite core particles 100 using a coating device
Apply to 0 parts and dry at 450 ° C for 4 hours to obtain carrier particles F
And Further, a coating forming liquid having the above-mentioned formulation was added with S having a thickness of 1 mm.
Spray coated on US plate and dried at 450 ℃ for 4 hours, then JI
When the pencil scratch test specified in SK5400 was conducted, the pencil hardness was 8H.

Next, some toner production examples will be shown. Toner Production Example 1 Styrene-acrylic copolymer resin (Haimer 75: Sanyo Chemical Co., Ltd.) 93 parts Carbon black (# 44: Mitsubishi Kasei Co., Ltd.) 5 parts Metal-containing azo dye (Spiron Black RH: Hodogaya Chemical Co., Ltd.) 2 The mixture of parts was melt-kneaded with a hot roll at 120 ° C., cooled and solidified, crushed with a Gemmill, and classified to obtain base particles having an average particle size of about 8 μm. 99.8 parts of these particles contained fine particles of titania (P-2 with a specific surface area of 50 m ² / g).
5: manufactured by Nippon Aerosil Co., Ltd.) was mixed with a mixer to obtain toner particles a.

Toner Production Example 2 In Production Example 1, 99.0 parts of base particles and 1.0 of external additive.
Toner b was obtained in the same manner as in Production Example 1 except that the parts were used.

Toner Production Example 3 Toner c was obtained in the same manner as in Production Example 1 except that the external additive was alumina fine particles having a specific surface area of 82 m ² / g (RFY-C: manufactured by Nippon Aerosil Co., Ltd.). It was

Toner Production Example 4 In Production Example 1, the external additive was alumina fine particles (RFY-).
C: manufactured by Nippon Aerosil Co., Ltd.), and 99.5 parts of base particles,
Toner d was obtained in the same manner as in Production Example 1 except that 0.5 part of the external additive was used.

Toner Production Example 5 In Production Example 1, the external additive was used, and the hydrophobicity was 60 and the specific surface area was 1.
Toner e was obtained in the same manner as in Production Example 1 except that 10 m ² / g was changed to silica fine particles (R972D: manufactured by Nippon Aerosil Co., Ltd.).

Toner Production Example 6 In Production Example 1, the external additive was silica fine particles (R972D: manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 110 m ² / g, and 99.5 parts of base particles and 0.5 part of external additive. A toner f was obtained in the same manner as in Production Example 1 except for the above.

Toner Production Example 7 In Production Example 1, the external additive was used, and the hydrophobicity was 50 and the specific surface area was 2.
Toner g in the same manner as in Production Example 1 except that 50 m ² / g was changed to silica fine particles (R976: manufactured by Nippon Aerosil Co., Ltd.).
Got

Toner Production Example 8 In Production Example 1, the external additive was silica fine particles (R976: manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 250 m ² / g.
Toner h was obtained in the same manner as in Production Example 1 except that 99.5 parts of base particles and 0.5 part of the external additive were used.

Toner Production Example 9 In Production Example 1, the external additive was silica fine particles (R976: manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 250 m ² / g.
A toner i was obtained in the same manner as in Production Example 1 except that 99.4 parts of the base particles and 0.6 part of the external additive were used.

Toner Production Example 10 In Production Example 1, the external additive was used and the degree of hydrophobicity was 5, and the specific surface area was 38.
Toner j was obtained in the same manner as in Production Example 1 except that 0 m ² / g of silica fine particles (380: manufactured by Nippon Aerosil Co., Ltd.) were used, and 99.6 parts of base particles and 0.4 parts of an external additive were used.

Toner Production Example 11 In Production Example 1, the external additive was used, and the hydrophobicity was 70 and the specific surface area was 1.
70 m ² / g of silica fine particles (H-2000: manufactured by Wacker Chemical Co., Ltd.), mother particles of 99.5 parts, and an external additive of 0.1.
Toner k was obtained in the same manner as in Production Example 1 except that the amount was 5 parts.

97 parts of these carrier particles and 3 parts of toner particles were mixed by a ball mill for 30 minutes to prepare a developer. This developer was used for 30 times with Ricoh Copier FT-6960L.
A copying test was performed on 10,000 sheets, and the charge amount of the developer, background stain, and transferability were evaluated at the initial stage and after 300,000 sheets.

(Evaluation of background stain) A white image was copied to observe the background stain on the copy paper and evaluated as follows. ⊚: Nothing is observed even when observed with a 10 times magnifying glass. ◯: Toner particles are slightly observed when observed with a 10 times magnifying glass. B: Toner particles are slightly observed visually. X: Very many toner particles are visually observed. (Evaluation of transferability) 100 μ × 100 μ dot is 10 m
Copy the image with 10 dots x 10 dots arranged at m intervals,
The number of transferred images with no image loss was evaluated as follows. A: 90% or more B: 90 to 70% X: 70% or less

The evaluation results are shown in Tables 1 and 2.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

EFFECTS OF THE INVENTION By using the two-component type developer for developing an electrostatic latent image within the range defined by the present invention, the coat carrier coating layer is less likely to be scraped off even after repeated use over a long period of time, and the coating with toner particles is performed. By preventing the spent on the carrier surface, it is possible to obtain a stable image in which problems such as image fog do not easily occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between the surface hardness of a carrier coating layer and (specific surface area of toner external additive) × (toner addition amount).

Claims (5)

[Claims] 1. A coated carrier coated with at least a coating film of core particles, and a toner in which an inorganic fine powder is externally added to particles having a volume average particle diameter of 5 to 10 μm containing at least a binder resin, a colorant and a polarity control agent. As shown in the accompanying drawings, the horizontal axis represents the surface hardness (JI
The pencil hardness in a pencil scratching test defined by SK5400) is taken, and the vertical axis represents the square root of the specific surface area of the external additive of the toner by the BET method and the amount added to the toner (wt).
%), These relationships are within the range enclosed by points A, B, C, and D. A two-component developer for electrostatic latent image development. 2. The two-component developer for electrostatic latent image development according to claim 1, wherein the main component of the coat film of the coat carrier is a silicone resin. 3. The BET specific surface area of the external additive is 70 to 2
The two-component developer for developing an electrostatic latent image according to claim 1 or 2, which has a range of 50 m ² / g. 4. The two-component developer for electrostatic latent image development according to claim 1, 2 or 3, wherein the external additive is silica. 5. The two-component developer for developing an electrostatic latent image according to claim 1, wherein the hydrophobicity of the external additive is 70 or more.