JP2694551B2 - Negatively chargeable two-component developer for electrostatic image development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is a negatively chargeable two-component development for electrostatic image development used for development of an electrostatic latent image in electrophotography and electrostatic recording. Regarding agents. More specifically, a negative electrode for electrostatic charge image development comprising a core material and a coating resin layer, which has a carrier and a toner excellent in charging property, surface contamination resistance, mechanical strength, adhesion between the core and the coating layer, and the like. The present invention relates to a chargeable two-component developer.

2. Description of the Related Art Conventionally, as a method of developing an electrostatic latent image using a toner in electrophotography, a method using a so-called two-component developer in which a small amount of toner is dispersed in a medium called a carrier is widely used. There is a method using a so-called one-component developer in which the toner is used alone without using the toner. The present invention relates to a two-component developer comprising a toner and a carrier among the above-mentioned developers.

In general, a two-component developer is a toner that charges a toner to a required amount of electrification and a charging polarity by friction with a carrier and develops an electrostatic image by using electrostatic attraction. Therefore, in order to obtain a good visible image, it is necessary that the triboelectrification property which is mainly determined by the relationship with the carrier is good.

Generally, the carrier constituting the two-component developer is roughly classified into a conductive carrier and an insulating carrier, but in the conductive carrier, the triboelectric chargeability against the toner is unstable,
Further, there is a defect that a visible image formed by the developer is fogged. That is, as the developer is used, the toner particles adhere to and accumulate on the surface of the iron powder carrier particles (spent toner), so that the electric resistance of the carrier particles increases, the bias current decreases, and the triboelectrification property increases. Becomes unstable, the image density of the visible image formed as a result decreases, and fog increases. Therefore, if the copying operation is continuously performed by an electronic copying apparatus using a developer containing an iron powder carrier, the developer deteriorates in a small number of times, so that it is necessary to replace the developer at an early stage, resulting in a high cost. It will be.

On the other hand, when a so-called insulative carrier in which the surface of a carrier core material made of a ferromagnetic material such as iron, nickel or ferrite is coated with an insulative resin is used, toner particles may be fused to the carrier surface. Compared with the case of a conductive carrier, it is extremely small, and at the same time, it is easy to control the triboelectrification property between the toner and the carrier, excellent in durability and long in service life, which is particularly suitable for high-speed electronic copying machines There is an advantage.

However, in this insulating carrier, the coating layer that covers the surface of the carrier core material has sufficient abrasion resistance (durability), and the coating layer has good adhesion prevention to prevent filming by toner on the carrier surface. It is required to have characteristics and to obtain a charged state having a desired size and polarity by the friction with a specific toner used together with the carrier (chargeability).

That is, the insulating carrier is rubbed with other carrier particles, toner particles, container walls, etc. in the developing unit, but when the coating layer is worn by this friction, the stability of the charging characteristics caused by friction with the toner is lost. As a result, it becomes impossible to give a desired charge state to the toner particles.

Even if the coating layer of the insulative carrier has sufficient friction resistance, if the adhesiveness to the core material is poor, the coating layer may be peeled or crushed by the above-mentioned friction, and the charging characteristics may be lost. You will be told. Further, when toner adheres to the surface of the coating layer to form a film, the charging characteristics also become unstable. In such a case, in any case, it becomes necessary to replace the entire developing device with a new one at an early stage.

To solve the above problems, for example, if the coating resin amount is increased to increase the coating strength, the carrier itself is strongly charged to the opposite polarity to the toner particles due to the insulating property of the coating resin, and the background portion The problem of carrier adhesion to the carrier will occur, and if the surface of the carrier core material itself is smoothed and then coated with resin for the purpose of making the carrier surface uniform after resin coating, the carrier surface will surely Although it is made uniform, the adhesiveness between the carrier core material and the coating resin becomes unstable, and the coating resin that can be used is limited to the resin having good adhesiveness.

As described above, there is a close relationship between the surface layer of the carrier core material and the characteristics of the coating resin and the resin-coated carrier, and even today, a satisfactory coated carrier has not been developed.

Further, in recent years, demands for high definition and high image quality of copying machines have been increasing in the market, and in the technical field, an attempt has been made to achieve high image quality color by reducing the particle size of toner. However, as the particle size becomes smaller, the surface area per unit weight increases, and the amount of electrification of the toner tends to increase, and there is a concern that the image density will be low and the durability will deteriorate. In addition, since the charged amount of the toner is large, the adhesion between the toners is strong, the fluidity is reduced, and problems occur in the stability of toner supply and in the application of tribo to the supplied toner.

In addition, since the color toner does not contain a conductive substance such as a magnetic material or carbon black, there is no portion that leaks the charge, and the amount of charge generally tends to increase.

Furthermore, in this technical field, polyester resins are often used as color binder resins today, but toners made of polyester resins are generally susceptible to temperature and humidity, and have an excessive charge amount under low humidity. There is an urgent need to develop a color toner having a stable amount of electricity in a wide range of environments due to the problem of insufficient charge amount under high humidity.

For the reasons described above as well, there are great expectations for the carrier that mainly controls the triboelectric chargeability of the toner, and a carrier that simultaneously satisfies charging stability, impact resistance, abrasion resistance, good adhesion to the core, etc. There is a strong demand for the development of a negatively chargeable two-component developer for developing an electrostatic image comprising

[Problems to be Solved by the Invention] An object of the present invention is to provide a negatively chargeable two-component developer for developing an electrostatic charge image, which solves the above problems.

That is, an object of the present invention is to provide a negatively chargeable two-component developer for developing an electrostatic charge image, which is not easily influenced by environment such as temperature and humidity and has stable triboelectric chargeability.

A further object of the present invention is to provide a negatively chargeable two-component developer for developing an electrostatic charge image, which has clear image characteristics without fog and has excellent durability and stability.

A further object of the present invention is to provide a negatively chargeable two-component developer for electrostatic image development, which has a high image density, excellent color mixing properties, and particularly excellent OHP transparency.

[Means and Actions for Solving the Problem] The present invention has a volume average diameter of 4 to 10 μm in which a colorant and a charge control agent are dispersed in a negatively chargeable insulating polyester resin.
0 for the weight of non-magnetic color toner and carrier core material.
Weight average diameter 30 coated with 1 to 5.0% by weight of electrically insulating resin
A negatively chargeable two-component developer for electrostatic image development having a carrier having a carrier of ˜65 μm, wherein the electrically insulating resin is (a) a styrene-acrylic resin crosslinked with a derivative containing a triazine ring;
(B) Vinylidene fluoride that has a polarity opposite to that of the styrene-acrylic copolymer with respect to the surface of the carrier core material /
A polymer blend with a tetrafluoroethylene copolymer, wherein the styrene-acrylic resin and the vinylidene fluoride /
It is blended with the tetrafluoroethylene copolymer in a weight ratio of 30:70 to 70:30, and the copolymerization molar ratio of the vinylidene fluoride / tetrafluoroethylene copolymer is 70:30 to 95 :. And a negatively chargeable two-component developer for developing an electrostatic charge image.

Here, the styrene-acrylic resin is at least one monomer selected from styrene monomers, at least acrylic acid (or ester thereof) monomer and methacrylic acid (or ester thereof) monomer. A copolymer obtained by polymerizing one kind of monomer is crosslinked with a derivative containing a triazine ring.

In the past styrene-acrylic copolymer coated resin, the adhesive force to the carrier surface is certainly large, but the film strength is not sufficient for long-term use, and the film peels off after long-term use. However, the styrene-acryl copolymer crosslinked with the derivative containing a triazine ring as in the present invention increases the strength (durability) of the film itself and has stable properties for a long period of time.

JP-A-60-57352 discloses a technique in which a styrene-acrylic resin is crosslinked with a derivative containing a triazine ring, thereby increasing the strength of a coating layer. In addition to the effect, in triboelectrification with the polyester-based toner, the function separation is designed in consideration of the dispersibility of the negative resin in order to suppress the electrification amount of the toner.

That is, in the present invention, the vinylidene fluoride / tetrafluoroethylene copolymer charges the carrier core material in a polarity opposite to that of the above-mentioned styrene-acrylic copolymer, and the styrene-acrylic copolymer is used. Control the positive chargeability of the carrier itself by blending with the polymer,
As a result, the triboelectric charging with the negatively chargeable toner is effective in controlling the amount of electrostatic charge of the toner.

At this time, the dispersibility and compatibility of the negative resin always poses a problem, but in the styrene-acrylic copolymer of the type crosslinked with the derivative containing a triazine ring as in the present invention, the negatively charged fluorine-containing resin is used. Are more easily dispersed on the surface of the carrier, giving a stable and uniform amount of electrification to the toner.

At this time, the weight ratio of the styrene-acrylic copolymer and the negative resin is preferably within the range of 30:70 to 70:30. If the polymer blend ratio of the negative resin exceeds 70%, the compatibility of the resin is poor, and if it is less than 30%, the film formability and abrasion resistance are excellent, but the effect of suppressing the excessive amount of electrification is not exhibited.

The copolymerization molar ratio of vinylidene fluoride / tetrafluoroethylene copolymer contained in the coating layer of the carrier of the present invention is 70: 3.
A range of 0 to 95: 5 is preferred, more preferably 75:25 to 90: 1.
It is in the range of 0. When the molar composition ratio of the copolymer is in the above range, the solvent solubility becomes good and the film forming property and the film strength are improved, so that the durability is ultimately improved.

As the carrier core material used in the present invention, for example, surface-oxidized or non-oxidized metals such as iron, nickel, copper, zinc, cobalt, manganese, chromium, rare earths and their alloys or oxides and ferrites can be used. . A particularly preferred form is a ternary ferrite of Cu-Zn-Fe,
The manufacturing method is not particularly limited.

The average particle size of these carriers is preferably 30 to 65 µ.

The carrier particles of the present invention are obtained by subjecting the above-mentioned core material to a surface treatment with the above-mentioned polymer (including a copolymer) according to the present invention, and forming the copolymer on the surface of the core material by chemical bonding or adsorption. It can be obtained by forming a combined coating layer.

For surface treatment of the core material, for example, the carrier core material is immersed in a solution obtained by dissolving a mixture of the above-mentioned polymer, copolymer or other resin material in an appropriate solvent,
Thereafter, a method of removing the solvent, drying and baking at a high temperature, or a method of suspending the core material in a fluidized bed, spray-coating the polymer solution, drying and baking at a high temperature can be used. The method is not specially limited.

The amount of the compound to be treated may be appropriately determined so that the carrier satisfies the above-mentioned conditions, but is generally preferably 0.1 to 5% by weight (preferably 0.3 to 3% by weight) based on the carrier of the present invention.

Examples of the styrene resin as the coating resin for the carrier core material usable in the present invention include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-
There are chlorostyrene copolymers, styrene-butadiene copolymers, styrene-vinyl chloride copolymers, styrene-vinyl acetate copolymers, and the like. Examples of acrylic resins include acrylic ester copolymers (methyl acrylate copolymer). (Coalescence, methyl acrylate copolymer, butyl acrylate copolymer, octyl acrylate copolymer, phenyl acrylate copolymer, 2-ethylhexyl acrylate copolymer)
And the like, and methacrylate ester copolymers (methyl methacrylate copolymer, ethyl methacrylate copolymer, butyl methacrylate copolymer, phenyl methacrylate copolymer) and the like.

Derivatives containing a triazine ring include hexamethoxymelamine and butylated melamine, but there is no limitation to these.

The polyester resin is most suitable as the binder resin for toner used in the present invention.

Polyester resins have excellent fixing properties and are suitable for color toners, but have a strong negative charging ability and tend to be excessively charged. Therefore, when the polyester resin is used in the present invention, adverse effects are improved, and an excellent toner is obtained.

In particular, (Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2
~ 10. ) A bisphenol derivative or a substituted product represented by the formula (1) and a carboxylic acid component comprising a carboxylic acid having a valence of 2 or more or an acid anhydride thereof or a lower alkyl ester thereof (eg fumaric acid, maleic acid,
Polyester resins obtained by at least copolycondensation of maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are preferred.

In particular, the toner has an apparent viscosity of 5 × 10 ^{4 to} 5 × 10 ⁶ poise at 90 ° C., preferably 7.5 because of its transparency with a trapene.
× 10 ^{4 to} 2 × 10 ⁶ poise, more preferably 10 ⁵ to 10 ⁶ poise, and the apparent viscosity at 100 ° C. is 10 ^{4 to} 5 × 10 ⁵ poise, preferably 10 ^{4 to} 3.0 × 10 ⁵ poise. Preferably 1
A color OHP having good transparency can be obtained by having a porosity of 0 ^{4 to} 2 × 10 ⁵ , and fixability as a full-color toner,
Good results are obtained in color mixing and high temperature offset resistance.

In particular, for toner, the absolute value of the difference between the apparent viscosity P _{1 at} 90 ° C and the apparent viscosity P _{2 at} 100 ° C is 2 × 10 ⁵ poise <| P ₁
It is preferably in the range of −P ₂ | <4 × 10 ⁶ poises.

When the above resin is used to form fine particles, most of them show a negative charge property without using a charge control agent, and can be used as they are in the present invention, preferably a charge control agent imparting a negative charge property is used. It is better to use.

As the charge control agent used in the present invention, a conventionally known load control agent can be used.

For example, organic salts or complexes containing a divalent or higher valent metal can be used. Effective metal species are Al, Ba, Ca, Cd,
Examples include polyvalent materials such as Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sn, Sr, and Zn. As the organometallic compound, a carboxylate, an alkoxylate, an organometallic complex, and a chelate compound of the above metals are effective, and examples thereof include zinc acetate, magnesium acetate, calcium acetate, aluminum acetate, magnesium stearate, calcium stearate, and stearin. There are aluminum acid, aluminum isopropoxide, aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3,5-di-tert-butylsalicylate, and the like, with acetylacetone metal complex and salicylic acid metal salt being particularly preferable.

In the present invention, a light-colored salicylic acid-based chromium salt, zinc salt or aluminum salt is particularly preferred. When the charge control agent is blended in the toner, it is added in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.

As the colorant used in the toner of the present invention, all known colorants can be used, and examples thereof include carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue.

If necessary, the toner of the present invention may be mixed with an additive within a range that does not impair the properties of the toner. Examples of such an additive include a lubricant such as zinc stearate and polyvinylidene fluoride, or a fixing agent. There are auxiliary agents (for example, low molecular weight polyethylene, low molecular weight polypropylene, etc.) and the like.

In the production of the toner of the present invention, a hot roll, kneader, kneading the constituent materials well by a hot kneader such as an extruder, then mechanical pulverization, a method of obtaining by classification, or a colorant or the like in the binder resin solution A method in which a material is dispersed and then spray-dried, or a method in which a predetermined material is mixed with a monomer to constitute a binder resin and then the emulsion is polymerized to obtain a toner. Each method such as the method can be applied.

The colorant-containing fine particles used in the present invention have a volume average diameter of 4 to 10 μm, and coarse particles of 16.0 μm or more have a volume distribution.
It is preferably 2.5% or less.

Since the toner used in the present invention has a small particle diameter, the toner adheres faithfully to a minute electrostatic latent image, and the toner adherence at the end of the electrostatic latent image is less disturbed. As a result, an image with high resolution and good color reproducibility can be obtained. In particular, in photographic images, there are many halftone areas, which are collections of minute latent images,
Further, the effect of the particle size appears, and a good image is obtained.

As the flow improver used in the present invention, any one can be used as long as it can be added to the colorant-containing resin particles to increase the flowability before and after the addition.

For example, a fluorine resin powder, that is, fine powder of vinylidene fluoride, fine powder of polytetrafluoroethylene, or the like; or a fatty acid metal salt, such as zinc stearate, calcium stearate, or lead stearate; or a metal oxide,
That is, there are zinc oxide powder and the like; or fine powder silica, that is, wet-process silica, dry-process silica, and silica obtained by subjecting the silica to a surface treatment with a silane coupling agent, a titanium coupling agent, silicon oil, or the like.

The amount of the fluidity improver added to the colorant-containing resin particles is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the resin particles. If the amount is less than 0.01 part by weight, there is no effect on improving the fluidity.

Further, the toner in the present invention may be fixed and embedded in the surface of the toner by the mechanical impact of the fluidity imparting agent as described above.

[Example] Hereinafter, an example of the present invention will be described in detail. Note that “%” and “parts” indicate “% by weight” and “parts by weight”.

Toner Production Example 1 Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts acid 5 parts phthalocyanine pigment 5 parts ditertiary butyl salicylic acid 4 parts Chromium complex salt was sufficiently premixed by a Henschel mixer and at least three roll mill The mixture was melt-kneaded twice or more, cooled, coarsely pulverized to about 1 to 2 mm by using a hammer mill, and then finely pulverized by a fine pulverizer by an air jet system. Further, the obtained finely pulverized product was classified and 2 to 10 μm was selected so as to obtain the particle size distribution of the present invention to obtain colorant-containing resin particles (volume average particle size 7.8 μm).

The apparent viscosity of the colorant-containing resin particles is 6.0 × 10 ⁵ at 90 ° C.
Poise was 1.1 × 10 ⁴ poise at 100 ° C.

To 100 parts of the colorant-containing resin particles, 0.6 part of colloidal silica (primary particle diameter of 0.1 to 0.2 μm observed by an electron microscope) was externally added to give a cyan toner.

Toner Production Example 2 CI Pigment Yellow Instead of Phthalocyanine Pigment
3.5 parts of 17 was used to obtain a 7.6 μm yellow toner.

Toner Production Example 3 CI Solvent Red 49 instead of phthalocyanine pigment
0.9 parts, CI Solvent Red 52 1.0 parts, 7.5 μm
Magenta toner.

Toner Production Example 4 CI Pigment Yellow instead of Phthalocyanine Pigment
Using 17 parts of 1.2, CI Pigment Red 5 of 2.8 parts, and CI Pigment Blue 15 of 1.5 parts, a black toner of 7.5 μm was obtained.

Carrier Production Example 1 Vinylidene fluoride and ethylene tetrafluoride were mixed in a molar ratio of 8
A vinylidene fluoride / tetrafluoroethylene copolymer obtained by reacting at 0:20 and a styrene-acrylic copolymer (30:60:10) consisting of styrene, methyl methacrylate and 2-hydroxyethyl acrylate Weight average diameter 52μ, 35μ or less of polymer blended with a resin cross-linked with hexamethoxymethylmelamine at a weight ratio of 50:50
3.5%, 35-40μ8%, 14μ or more 0.5% particle size distribution
A Cu-Zn-Fe-based ferrite carrier was coated with 1% by weight to obtain a carrier 1.

Carrier Production Example 2 Carrier 2 was prepared in the same manner as in Production Example 1 except that butylated melamine was used as a crosslinking agent instead of hexamethoxymethylmelamine in Carrier Production Example 1.
And

Production Example 3 of Carrier Production Example from a resin obtained by crosslinking a copolymer of 50% styrene, 20% methyl methacrylate and 30% 2-ethylhexyl acrylate with hexamethoxymethylmelamine, vinylidene fluoride / ethylene tetrafluoride and a polymer blend. Carrier 3 was obtained in the same manner as in 1.

Carrier Production Example 4 The ferrite resin used in Carrier 1 was coated with 3% of the coated resin used in Carrier 1 to obtain Carrier 4.

Production Example 5 of Carrier Same as Production Example 1 from a polymer blend of styrene-methylmethacrylate-2-hydroxyethylmethacrylate resin and vinylidene fluoride / tetrafluoroethylene which were not crosslinked with hexamethoxymethylmelamine in Production Example 1 of carrier. Was used as Comparative Carrier 1.

Production Example 6 of Carrier Vinylidene fluoride and ethylene tetrafluoride in a molar ratio of 8
Comparison was made in the same manner as in Production Example 1 except that the styrene-acrylic copolymer was not blended using only the vinylidene fluoride / tetrafluoroethylene copolymer obtained by reacting at 0:20. Carrier 2

Carrier Production Example 7 Using only a styrene-acrylic copolymer consisting of styrene-methylmethacrylate-2-hydroxyethyl acrylate crosslinked with hexamethoxymelamine, except that vinylidene fluoride / tetrafluoroethylene was not blended. Comparative carrier 3 was prepared in the same manner as in Production Example 1.

Carrier Production Example 8 Comparative Carrier 4 was prepared in the same manner as in Production Example 1 except that the styrene-acrylic resin used in Production Example 2 and the negative resin were used in a blend ratio of 90:10.

Carrier Production Example 9 Comparative Carrier 5 was prepared in the same manner as in Production Example 1 except that the molar ratio of vinylidene fluoride / tetrafluoroethylene was changed to 50:50 in Production Example 1.

Production Example 10 of Carrier A styrene-acrylic copolymer (30:60:10) consisting of styrene-methyl methacrylate-2-hydroxyethyl acrylate was coated on the core used in Production Example 1 to obtain Comparative Carrier 6. .

Table 1 shows the results of image formation using a commercially available full-color copying machine CLC-1 (manufactured by Canon Inc.), in which each carrier shown in Carrier Production Examples 1 to 10 was used and image formation was performed while toner was supplied as needed. The toner is 4 as shown in Toner Production Examples 1 to 4.
A full color image was obtained using color toners.

EFFECT OF THE INVENTION Since the present invention uses a polymer blend of a specific styrene-acrylic resin and a vinylidene fluoride / fluorinated ethylene copolymer as a coating resin for a carrier, the film has sufficient strength and is stable for a long period of time. It has the above-mentioned characteristics and exhibits an effect of controlling the amount of electrostatic charge of the toner in the frictional charging with the negatively chargeable toner.

Claims (6)

(57) [Claims] 1. A volume average diameter of 4 to 10 μm in which a colorant and a charge control agent are dispersed in a negatively chargeable insulating polyester resin.
0 for the weight of non-magnetic color toner and carrier core material.
Weight average diameter 30 coated with 1 to 5.0% by weight of electrically insulating resin
A negatively chargeable two-component developer for electrostatic image development having a carrier having a carrier of ˜65 μm, wherein the electrically insulating resin is (a) a styrene-acrylic resin crosslinked with a derivative containing a triazine ring;
(B) Vinylidene fluoride that has a polarity opposite to that of the styrene-acrylic copolymer with respect to the surface of the carrier core material /
It is a polymer blend with a tetrafluoroethylene copolymer, and the styrene-acrylic resin and the vinylidene fluoride / tetrafluoroethylene copolymer are blended at a weight ratio of 30:70 to 70:30. A negatively charging two-component developer for developing an electrostatic image, wherein the copolymerization molar ratio of the vinylidene fluoride / tetrafluoroethylene copolymer is 70:30 to 95: 5. 2. A styrene-acrylic resin is selected from the group consisting of one or more styrene monomers, acrylic acid monomers, acrylic acid ester monomers, methacrylic acid monomers and methacrylic acid ester monomers. The negative charging for electrostatic image development according to claim 1, wherein a copolymer obtained by polymerizing at least one selected monomer is crosslinked with a derivative containing a triazine ring. Two-component developer. 3. The negatively charging two-component developer for developing an electrostatic charge image according to claim 1, wherein the carrier core material is a ferrite core material having a composition of Cu--Zn--Fe. 4. The non-magnetic color toner has an apparent viscosity of 5 × 10 ^{4 to} 5 × 10 ⁶ poise at a temperature of 90 ° C. and a temperature of 100.
The negatively chargeable two-component development for electrostatic charge image development according to any one of claims (1) to (3), characterized in that the apparent viscosity at ° C is 1 x 10 ^{4 to} 5 x 10 ⁵ poise. Agent. 5. The absolute value of the difference between the apparent viscosity at a temperature of 90 ° C. and the apparent viscosity at a temperature of 100 ° C. of the non-magnetic color toner is within a range of 2 × 10 ^{5 to} 4 × 10 ⁶ poises. The negatively charging two-component developer for developing an electrostatic charge image according to claim (4). 6. The non-magnetic color toner has a fluidity improvement of 0.01 to 10 parts by weight with respect to 100 parts by weight of colorant-containing resin particles containing the insulating polyester resin, the colorant and the charge control agent. The negatively chargeable two-component developer for developing an electrostatic charge image according to any one of claims (1) to (5), wherein the agent is externally added.