JPH0996925A - Developer for developing electrostatic latent image and developing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a change in the surface shape of a carrier caused in a developer using a polyolefin coated carrier and the problem of fog in use over a long period of time, to obtain a developer having stable developing property over a long period of time and to provide a developing method. SOLUTION: In this developer consisting of a polyolefin coated carrier and a toner, the wt. average mol.wt. of the polyolefin coating the carrier is 5.0×10<4> -5.0×10<6> and the polyolefin contains a low mol.wt. component whose mol.wt. is <=8.5×10<3> by <=10wt.% of the total amt.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a developer used in an electrophotographic system is composed of so-called toner and carrier which can be designed so that the functions of developing and fixing, charging and charging of developer can be separated. Two-component developers are widely used. As the carrier used here, a carrier in which magnetic particles composed of ferrite, iron powder, or the like is used as it is, or a resin-coated carrier in which the surface of these magnetic particles is coated with a resin is known. Of these, resin-coated carriers are preferably used from the viewpoints of ease of charge control and carrier durability.

Conventionally, styrene / acrylic resins, polyester resins, silicone resins and the like have been widely used as carrier coating resins. Recently, it has been proposed to coat the carrier with polyolefin.

Since the resin itself does not have a polar group, polyolefin has good water repellent property and releasability, and therefore, it is said that it has excellent durability when applied to an electrophotographic carrier.

However, when polyolefin is used as a carrier coating resin, the resin itself tends to be plastically deformed, which causes a new problem that has not been found in conventional carriers.

First, the change in the uneven surface shape of the carrier changes the charge imparting ability of the carrier. As a result, the developing performance of the developer becomes unstable when it is used for a long period of time.

Further, fine particles are generally externally added to the toner surface for the purpose of imparting fluidity and chargeability.
There also occurs a phenomenon that the fine particles externally added to the toner are taken into the carrier coating resin. This is also
The charge imparting ability of the carrier is lowered, and the developing performance becomes unstable in the case of long-term use.

Furthermore, in order to control the volume resistivity, which is the electrical resistance value of the carrier, and to control the charge imparting performance, fine particles according to the purpose are added to polyolefin and used as a carrier coating resin. There is a case.
However, in this case, with the plastic deformation of the carrier coating resin, the dispersion state of the fine particles added to the carrier coating resin changes, and the volume resistivity and charge imparting performance of the carrier, which are the functions imparted by the fine particles, change. The phenomenon occurs. As a result, the developing performance of the developer becomes unstable.

As described above, when polyolefin is used as the carrier coating resin, there are many problems not found in the conventional resin coated carrier, and it is not possible to obtain a developer having sufficiently stable characteristics. The current situation is not.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems occurring in a developer using a polyolefin-coated carrier and provides a developer for developing an electrostatic latent image which has stable developing characteristics for a long period of time. Especially.

[0011]

Means for Solving the Problems As a result of earnest research on a polyolefin-coated carrier, the inventors of the present invention positively inhibit plastic deformation of polyolefin by limiting the content of a molecular weight component in a specific range in a carrier-coated resin. It was found that the development characteristics of the developer can be stabilized for a long period of time.

Specifically, the structure of the present invention is achieved by adopting the following structure.

[1] In a developer for developing an electrostatic latent image, which comprises a carrier coated with a polyolefin and a toner, the polyolefin coating the carrier has a weight average molecular weight of 5.0 × 10 ⁴ to 5.0 × 10 ⁶ . A developer for developing an electrostatic latent image, characterized in that the content of a low molecular weight component having a molecular weight of 8.5 × 10 ³ or less in the range is 10% by weight or less of the whole.

[2] An extraction means is used as an operation for controlling the content of the low molecular weight component having a molecular weight of 8.5 × 10 ³ or less in the molecular weight distribution of the carrier coating resin polyolefin [1] The developer for developing an electrostatic latent image according to item 1.

[3] The polyolefin-coated carrier is
The developer for developing an electrostatic latent image according to [1] or [2], which is coated by a surface polymerization coating method.

[4] In a method of developing an electrostatic latent image formed on a photoreceptor using a developer for developing an electrostatic latent image containing a resin-coated carrier, the resin-coated carrier has a polyolefin weight average molecular weight of 5.0 x 10 ^{4 to} 5.0
A method of developing an electrostatic latent image, characterized in that the content of a low molecular weight component having a molecular weight of 8.5 × 10 ³ or less in the range of × 10 ⁶ is 10% by weight or less of the whole.

[5] In a developer for developing an electrostatic latent image comprising a carrier coated with a polyolefin and a toner, the polyolefin coating the carrier has a weight average molecular weight of 5.0 × 10 ⁴ to 5.0 × 10 ⁶ . A developer for developing an electrostatic latent image, characterized in that the content of a low molecular weight component having a molecular weight of 8.5 × 10 ³ or less in the range is 5% by weight or less of the whole.

The structure of the present invention will be described in detail below.

The carrier used in the developer of the present invention is a magnetic particle whose surface is coated with polyolefin.

As the magnetic particles that are the core material of the carrier used in the present invention, a substance that is strongly magnetized in that direction by a magnetic field can be used. Specifically, ferromagnetic metals such as nickel, cobalt, and the like, such as iron, ferrite, and magnetite, or alloys or compounds containing these metals can be used. Further, the surface of the magnetic particles may be further oxidized or reduced. In addition,
Ferrite here is a generic term for iron-containing magnetic compounds, and is not limited to the spinel type.

The weight average particle diameter of the magnetic particles is
It is preferably in the range of 40 to 90 μm.

The polyolefin coating the surface of the magnetic particles is specifically a resin composed of a known aliphatic hydrocarbon monomer such as ethylene, propylene, butene and cyclopentene, and other vinyl. A resin obtained from a system monomer or a resin composed of a copolymer. Further, a resin formed by combining one or more of these monomers can also be used. Among these, particularly preferable performance can be obtained by using polyethylene having ethylene as a monomer as the coating resin.

The method for producing the carrier used in the present invention is not particularly limited, and a known coating method can be applied.

Specifically, for example, a method in which a polyolefin resin is dissolved in an appropriate solvent and spray-coated on the surface of the magnetic particles, a polyolefin resin powder is electrostatically adhered to the surface of the magnetic particles, and the melting point of the resin material is further added. A method of mechanically fixing while heating in the vicinity or higher, a method of polymerizing and growing an olefin monomer on the surface of magnetic particles, and a method described in JP-A-60-106808 (surface polymerization coating method), etc. Can be applied. Also, among these coating methods,
By using the method of coating by polymerizing and growing an olefin monomer on the magnetic particle surface, it is possible to uniformly form a resin coating layer having a sufficient thickness, so that a developer with more stable characteristics can be obtained. Is preferred.

Here, the resin coating amount of the carrier is preferably in the range of 1.0 to 10.0% by weight based on the whole carrier.

If necessary, functional fine particle materials such as conductive fine particles and charge control fine particles may be added to the coating resin of the carrier used in the present invention. In this case, a known material can be used as the functional fine particle material that can be introduced into the coating resin.

As the conductive fine particles, it is possible to use fine particles whose volume resistivity of the carrier can be adjusted by adding them. Specifically, metal fine particles of iron, aluminum, nickel, etc., carbon black, conductive titania, silicon carbide, tin oxide, magnetite, etc., or a mixture thereof can be used.

As the charge control fine particles, known inorganic or organic charge control fine particles can be used. Examples of the inorganic charge control fine particles include fluorine compounds such as carbon fluoride and magnesium fluoride, metal oxides such as silicon oxide, titanium oxide, aluminum oxide and zinc oxide, calcium carbonate, barium titanate, and aluminum silicate.
Magnesium silicate or the like, or mixtures thereof can be used. The surface of these charge control particles may be surface-treated with a coupling agent containing a polar group. As the coupling treatment agent, a fluorine-based coupling agent, an amine-based coupling agent or the like can be used. Examples of organic charge control fine particles include metal complex type azo compounds such as chromium and iron, salicylic acid type compounds, copper phthalocyanine type compounds, calixarene type compounds, quaternary ammonium salt compounds, polyamine type compounds, triphenylmethane type compounds. Fine particles of a compound, a guanidine compound, an imidazole compound, a molybdic acid chelate compound and the like can be used.

When fine particles are added to the coating resin, the average primary particle diameter of the fine particles is preferably within the range of 1/5000 to 1/50 of the weight average particle diameter of the carrier. The average primary particle size of the fine particles can be easily obtained by observing with an electron microscope.

In the present invention, the method for keeping the molecular weight distribution of the coating resin within an appropriate range is not particularly limited as long as the object can be achieved. Specifically, a method of selecting or controlling the activity of the polymerization catalyst so that a low molecular weight component does not occur during the olefin monomer polymerization for producing a polyolefin, and the low molecular weight component is removed in advance before coating the carrier with the polyolefin. A method of removing the low molecular weight component from the coating resin layer after carrier coating, a method of simultaneously performing carrier coating while removing the low molecular weight component, etc. depending on the resin coating method. Selection or a plurality of methods can be used in combination.

However, it is particularly preferable to use a known extraction means such as a Soxhlet extractor and, after coating the carrier resin, a solid-liquid extraction method under reflux with a hydrocarbon solvent such as n-hexane or toluene. A good result can be obtained by selecting the method of removing by.

The molecular weight distribution and weight average molecular weight of the polyolefin can be measured by gel permeation chromatography (GPC).

Specifically, the GPC model 150C (WA
TERS) was used. O-Dichlorobenzene (Butyl Hydroxy Toluene) as a solvent
Was added), and the measurement temperature was set to 135 ° C. and the measurement flow rate was set to 1.0 ml / min. As a measurement sample,
Prepare a 0.1% by weight sample solution as the sample resin concentration,
0.4 ml was injected into the measuring part. The column of the measurement unit may be selected as necessary and is not particularly limited, but for example, S
hodex A-80M, HT-800P, HT-80
6M (Showa Denko) etc. can be used. Impurities (components other than the coating resin such as magnetic particles and functional fine particles added to the coating resin) generated during the preparation of the sample solution are removed by a metal sintering filter before the measurement.

For the measurement of the sample, a calibration curve prepared in advance with plural kinds of monodisperse polystyrene and diphenylmethane was used.

The molecular weight of the present invention is 8.5 × 10.
The content of the low molecular weight component of ³ or less is obtained as an area ratio from the obtained GPC chart.

In the present invention, the polyolefin used to coat the carrier used has a weight average molecular weight of 5.0 × 1.
Good results can be obtained in the range of 0 ^{4 to} 5.0 × 10 ⁶ ,
The range of 1.0 × 10 ^{5 to} 1.0 × 10 ⁶ is more preferable. When the weight average molecular weight is less than 5.0 × 10 ⁴ ,
In addition to the deterioration of carrier fluidity, it becomes difficult to suppress the content of low molecular weight components. The weight average molecular weight is 5.0.
If it exceeds x10 ⁶ , it is difficult to coat the surface of the magnetic particles with a resin, which may cause film peeling.

According to the studies by the present inventors, the low molecular weight component in the polyolefin as the coating resin has a correlation with the easiness of plastic deformation of the carrier surface, and the molecular weight is 8.5 × 10 5.
It was found that the smaller the content of the low molecular weight component of ³ or less, the more the plastic deformation can be suppressed and, as a result, the carrier performance can be stabilized for a long time.

Specifically, the molecular weight of 8.5 in the polyolefin coating the carrier used in the present invention.
The content of low molecular weight components of 10 ³ or less correlates with the easiness of plastic deformation of the carrier surface, and is 10% by weight of the whole.
It was found that good results can be obtained when the content is below, but it is more preferable that the content is 5% by weight or less. Of course, this value may be 0%.

Further, in the present invention, after removing the low molecular weight component of the carrier coating resin, mechanical stress is applied to the carrier surface in order to block the fine voids generated on the surface and inside and smooth the surface. The performance of the developer can be further improved. Here, as the mechanical stress, a known mixer, granulator, crusher or the like can be used. Specifically, for example, Mechanomill (made by Okada Seiko Co., Ltd.), Henschel mixer (Mitsui Mining Co., Ltd.)
Vertical granulator (Pawrec Co., Ltd.)
), Hybridizer (Nara Machinery Co., Ltd.), Mechanofusion System (Hosokawa Micron Co., Ltd.)
Manufactured) can be used. Further, since the carrier surface from which the low molecular weight components have been removed is less likely to undergo plastic deformation, it is preferable to simultaneously perform heating within the range of 50 to 150 ° C. when performing this treatment.

The volume resistivity of the carrier used in the present invention is 1.0 × 10 ^{8 to} 5.0 × 10 ¹⁴ Ω.
A range of cm is preferred. Furthermore, 1.0 × 10 ⁹ to 1
The range of × 10 ¹⁴ Ωcm is preferable.

Here, the method for measuring the volume resistivity of the carrier is as follows.
After filling the m ² insulating cylindrical container and determining the sample height under a load of 500 g, an electric field of DC 100 V is applied to measure the current value. The volume resistivity can be calculated from the obtained sample height and current value by the following formula.

Volume resistivity value (Ωcm) = 100 (V) -Cross sectional area (cm ² ) / Current value (A) -Sample height (cm) (Formula 1) Polyolefin coating of the present invention The toner mixed with the carrier is not particularly limited as long as it is a toner that meets the purpose of developing the electrostatic latent image, and a known toner can be used.

The toner is composed of at least a binder resin and a colorant, and may further contain other additives if necessary. The weight average particle size is preferably 1 to 2
It is 0 μm, more preferably 4 to 15 μm. In addition,
The toner used in the present invention, the weight average particle diameter of the magnetic particles,
It can be determined by using a laser diffraction particle size distribution analyzer HELOS (manufactured by Sympatech Co., Ltd.).

The binder resin constituting the toner is not particularly limited, and various conventionally known resins can be used. For example, a styrene resin, an acrylic resin, a styrene / acrylic copolymer resin, a polyester resin, etc. may be mentioned.

The colorant constituting the toner is not particularly limited, and various conventionally known materials can be used. Examples thereof include carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and rose bengal.

Other additives that can be used as required include charge control agents, release agents such as polyolefin wax and natural wax, magnetic powders, dispersion aids for these additives, and other known materials. Can be used.

The method for producing the toner is not particularly limited, and a known method can be used. Specifically, the constituent materials are mixed, melted and kneaded, and then subjected to a cooling step, pulverization and classification to obtain a toner, and a pulverization method for obtaining a toner, or emulsion polymerization, suspension polymerization, etc. to obtain a toner. A polymerization method or the like can be used.

Further, as the fluidity imparting agent, inorganic fine particles or organic fine particles may be added to the toner surface. As the inorganic fine particles, inorganic oxide particles such as silica, titania and alumina are preferable. Furthermore, these inorganic fine particles may be hydrophobized with a silane coupling agent, a titanium coupling agent, or the like.

As the developer, the above toner and the resin-coated carrier are mixed and used. In this case, the toner is preferably mixed and used in a proportion of 2 to 10% by weight based on the whole developer. A known mixer can be used as a mixer for mixing the toner and the resin-coated carrier.

[0050]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

<Production Example of Toner><Toner1> Styrene / n-butyl methacrylate copolymer resin (softening point 132 ° C., glass transition point 60 ° C.): 100 parts by weight carbon black (MA # 8, Mitsubishi Kasei Co., Ltd.) ): 8 parts by weight Low molecular weight polypropylene (Viscor 550P, Sanyo Kasei Co., Ltd.): 5 parts by weight Charge control agent (TP-302, Hodogaya Chemical Co., Ltd.): 3 parts by weight The above materials are ball milled. After thoroughly mixing, the mixture was melt-kneaded with a three-roll roller heated to 140 ° C. The kneaded product was left standing and cooled, coarsely pulverized using a feather mill, and further finely pulverized by a jet mill. After that, the air is classified, and the average particle size is 7.0μ.
m colored particles were obtained.

Thereafter, 0.5% by weight of hydrophobic silica fine particles (H-2050EP, Hoechst Co., Ltd.) was added to the colored particles.
And titania fine particles (TAF-510, Fuji Titanium Co., Ltd.)
0.4 wt% was added and mixed to obtain a positively charged toner 1.

<Toner 2> Polyester resin (Tufton NE-382, manufactured by Kao Corporation): 100 parts by weight Brilliant Carmine 6B (CI. 15850): 3 parts by weight Natural wax (refined carnauba wax No. 1, Noda) Wax Co., Ltd .: 3 parts by weight Charge control agent (E-84, manufactured by Orient Chemical Industry Co., Ltd.): 5 parts by weight An average particle diameter of 7.5 μm was obtained by the same method as in the preparation example of Toner 1. To obtain colored particles of.

Thereafter, 0.5% by weight of hydrophobized silica fine particles (R-974, manufactured by Nippon Aerosil Co., Ltd.) was added to the colored particles.
And 0.3% by weight of hydrophobized titania fine particles (T-805, manufactured by Nippon Aerosil Co., Ltd.) were added and mixed to obtain a negatively charged toner 2.

<Production Example of Carrier><CarrierA> In an autoclave, 500 ml of dehydrated n-hexane and magnetic particles (Cu-Zn ferrite, weight average particle diameter 60 μm) 45 previously dried under reduced pressure were used.
Add 0 g and stir. Next, 2.0 mmol of Ziegler-Natta catalyst was added and stirred to carry the catalyst on the surface of the magnetic particles.

Next, 0.22 g of carbon black (Ketchen Black EC, manufactured by Lion Akzo Co., Ltd.) was charged from the nozzle in the upper part of the autoclave. In addition,
Carbon black was dried under reduced pressure and mixed with dehydrated n-hexane to form a slurry.

After that, pressure is applied and the mixture is heated at 90 ° C. for 5 minutes.
By continuously supplying ethylene gas for 0 minutes, ethylene was polymerized on the surface of the magnetic particles to obtain a polyethylene-coated carrier A.

As a result of measuring the molecular weight distribution of the coating resin of the carrier A, the weight average molecular weight Mw was 380,000 and 8.5.
The amount of low molecular weight components of 10 ³ or less was 12.6% by weight.

<Carrier B> Production example of carrier A except that 0.5 g of conductive fine particles (T-1, manufactured by Mitsubishi Materials Corp., average primary particle size: 0.1 μm) was added instead of carbon black. Similarly, a polyethylene-coated carrier B was obtained.

As a result of measuring the molecular weight distribution of the coating resin of the carrier B, the weight average molecular weight Mw was 350,000 and 8.5.
The low molecular weight component having a molecular weight of × 10 ³ or less was 13.8% by weight.

<Carrier C> A polyethylene-coated carrier C was obtained in the same manner as in the production example of carrier A except that carbon black was not added.

As a result of measuring the molecular weight distribution of the coating resin of the carrier C, the weight average molecular weight Mw was 420,000 and 8.5.
The low molecular weight component of 10 ³ or less was 12.0% by weight.

<Carrier D> A polyethylene-coated carrier D was prepared in the same manner as in the production example of carrier A except that the type of Ziegler-Natta catalyst was changed and that magnetite (weight average particle diameter 55 μm) was used as the magnetic particles. Obtained.

As a result of measuring the molecular weight distribution of the coating resin of the carrier D, the weight average molecular weight Mw was 170,000 and 8.5.
The low molecular weight component of 10 ³ or less was 16.2% by weight.

<Carrier 1> Carrier A was subjected to a solid-liquid extraction treatment of low molecular weight components for 10 minutes under reflux of n-hexane using a Soxhlet extractor to obtain Carrier 1.

<Carriers 2 to 5> Carriers 2 to 5 were obtained by subjecting carriers A to D to solid-liquid extraction of low molecular weight components for 60 minutes under reflux of n-hexane using a Soxhlet extractor. .

<Carriers 2+ to 5+> Mechanomill (manufactured by Okada Seiko Co., Ltd.) was used as carriers 2 to 5 subjected to solid-liquid extraction treatment.
, And the stirring blade rotation speed 2000r under heating at 80 ℃
Stirring was performed at pm, and a treatment for applying mechanical stress to the carrier surface was performed. This treatment is performed for 60 minutes, and carrier 2+
Got ~ 5 +.

The following table shows the measurement results of the molecular weight distribution of each carrier.

[0069]

[Table 1]

<< Performance Evaluation 1 >> For each of the above carriers,
The positively charged toner 1 was mixed so that the toner concentration would be 6% by weight to prepare developers A to D and 1 to 5. Each developer is put into a U-Bix4155 copying machine (manufactured by Konica Corporation), and in a single sheet intermittent mode under high temperature and high humidity (30 ° C., 80% R).
50,000 sheets under H), 5 under low temperature and low humidity (10 ° C, 20% RH)
A total of 100,000 sheets were copied, and the following evaluations were performed.

[Image Density] A total of 5 at the four corners and the center of the image
An original having a solid image with an original reflection density of 1.30 was copied at various locations, the relative reflection density of the output image with respect to a white paper was measured at five locations, and the average value was calculated. A reflection densitometer RD-917 (manufactured by Macbeth Co., Ltd.) was used for density measurement, and an average image density of 1.28 or more was judged to be good. The evaluation was conducted at the initial stage and at the end of copying.

[Background Fog Density] Relative reflection densities of a total of five non-image areas near the four corners and the central portion of the image with respect to white paper were measured, and an average value thereof was obtained. A reflection densitometer RD-917 (manufactured by Macbeth Co., Ltd.) was used for density measurement, and it was judged that a background fog density average value of 0.005 or less was good. The evaluation was conducted at the initial stage and at the end of copying.

[Change in Surface Shape of Carrier] Before and after the completion of copying, the developer was sampled from the inside of the developing device and the state change of the resin coating layer surface of the carrier was compared by a scanning electron microscope (SEM). The smaller the change, the more stable and the better.

[0074]

[Table 2]

<< Performance Evaluation 2 >> For each of the above carriers,
Negatively charged toner 2 was mixed so that the toner concentration would be 6% by weight to prepare developers A to D and 1 to 5. Each developer,
It was put into a Konica 6192 copier (manufactured by Konica Corp.) and operated in a single sheet intermittent mode under high temperature and high humidity (30 ° C., 80% R).
50,000 sheets under H), 5 under low temperature and low humidity (10 ° C, 20% RH)
A total of 100,000 sheets were copied, and the same evaluation as in Performance Evaluation 1 was performed.

[0076]

[Table 3]

As described above, in the present invention, the deformation of the carrier coating resin surface is suppressed by removing the low molecular weight component in the carrier coating resin, polyolefin, up to 10% by weight in the developer consisting of toner and carrier. However, it is possible to provide a developer for developing an electrostatic latent image which exhibits stable developing characteristics for a long period of time.

[0078]

According to the present invention, the problems of carrier surface shape change and fogging caused by long-term use, which occur in a developer using a polyolefin-coated carrier, are solved, and an electrostatic latent image is developed which has stable development characteristics for a long time. A developer can be provided.

By using the developer of the present invention, it is possible to obtain an electrostatic latent image developing method capable of obtaining stable developing characteristics for a long period even when used in a high speed copying machine or in any environment.

Claims (5)

[Claims] 1. A developer for developing an electrostatic latent image comprising a carrier coated with a polyolefin and a toner, wherein the polyolefin coating the carrier has a weight average molecular weight of 5.0.
It is in the range of × 10 ^{4 to} 5.0 × 10 ⁶ and has a molecular weight of 8.
The content of low molecular weight components of 5 × 10 ³ or less is 1 of the whole.
A developer for developing an electrostatic latent image, which is 0% by weight or less. 2. The extraction means is used as an operation for controlling the content of low molecular weight components having a molecular weight of 8.5 × 10 ³ or less in the molecular weight distribution of polyolefin as a carrier coating resin. The developer for developing an electrostatic latent image as described above. 3. The developer for developing an electrostatic latent image according to claim 1, wherein the polyolefin-coated carrier is coated by a surface polymerization coating method. 4. A method of developing an electrostatic latent image formed on a photoreceptor with a developer for developing an electrostatic latent image containing a resin-coated carrier, wherein the resin-coated carrier has a polyolefin weight average molecular weight of 5 0.0 x 10 ^{4 to} 5.0 x 10 ⁶
And the content of the low-molecular weight component having a molecular weight of 8.5 × 10 ³ or less is 10% by weight or less based on the whole, and the latent electrostatic image developing method is characterized. 5. In a developer for developing an electrostatic latent image comprising a carrier coated with a polyolefin and a toner, the weight average molecular weight of the polyolefin coating the carrier is 5.0.
It is in the range of × 10 ^{4 to} 5.0 × 10 ⁶ and has a molecular weight of 8.
The content of low molecular weight components of 5 × 10 ³ or less is 5 of the whole.
A developer for developing an electrostatic latent image, which is less than or equal to wt%.