JPH10198076A - Carrier for developing electrostatic latent image, electrostatic latent image developer using same and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sticking of a carrier under high bias voltage at ordinary temp. and humidity or high temp. and humidity and to form an image having stable image quality by specifying resistivity in different electric fields. SOLUTION: This carrier for developing an electrostatic latent image satisfies ρ2 >=ρ1 and ρ1 >=10<14> [ρ1 is resistivity (Ω.m) in an electric field of 10<5> V/m and ρ2 is resistivity (Ω.m) in an electric field of 10<6.5> V/m]. A carrier generally has potential dependency in a high electric field of about 10<6> V/m and the resistivity lowers somewhat in the high electric field. This carrier, however, has no potential dependency (ρ2 =ρ1 ) even in such a high electric field or the resistivity ρ2 is higher than the resistivity ρ1 (ρ2 >ρ1 ).

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 carrier used for developing an electrostatic latent image in electrophotography and electrostatic recording, and an electrostatic latent image developing apparatus using the same. And an image forming method.

[0002]

2. Description of the Related Art In an electrophotographic method, a latent image carrier (hereinafter, may be referred to as a "photoconductor") is charged with a charge.
An exposure step of forming an electrostatic latent image on a photoreceptor, a development step of developing the electrostatic latent image with a developer, a transfer step of transferring the developed image to a transfer target such as paper, It comprises a fixing step for fixing the toner on the transfer member and a cleaning step for removing the developer remaining on the photosensitive member.

[0003] As the developer used in the electrophotographic method, there are two kinds of a one-component developer composed of only a toner and a two-component developer composed of a toner and a magnetic carrier. A two-component developer is suitable for the following small particle size toner. As a developing method using a two-component developer, there are a contact type developing method in which a carrier holding a toner forms a magnetic brush on a surface of a developer carrying member, and the magnetic brush is brought into contact with a surface of a photoreceptor to perform development. There are two types of non-contact developing methods in which a developing bias voltage is applied to a developer carrying member to perform development without bringing a carrier into contact with the surface. In particular, the latter is advantageous over the former in that the magnetic brush does not damage the photoreceptor and has a superior solid image, and is particularly suitable for application to a color printer.

In the non-contact type two-component developing method, an AC voltage obtained by superimposing a DC voltage on a developer carrier is normally biased in order to improve image quality and prevent toner adhesion (fogging) in a non-image area. A high electric field of 10 ⁶ (V / m) or more acts between the developer carrier and the photoconductor. Under such a high electric field, if the resistivity of the carrier particles is low, a charge having a polarity opposite to that of the charge on the surface of the photoreceptor is injected into the carrier particles, and a Coulomb force acts between the charge on the surface of the photoreceptor and the carrier particles. Also, the carrier adheres to the surface of the photosensitive member, that is, the carrier adheres. When a carrier is attached to an image surface on a photoreceptor, the carrier is not transferred to a transfer target in a transfer process, and a white spot is formed, thereby causing a fatal image defect. Therefore, it is necessary for the carrier to maintain insulation even under the high electric field.

As a carrier having an insulating property, a carrier having a resistivity of 10 ¹³ (Ω · cm) or more has been proposed as described in Japanese Patent Publication No. 5-8424 and Japanese Patent Application Laid-Open No. 4-321078. . The carriers described in the above publications can prevent carrier adhesion at normal temperature and normal humidity, but generally, the resistivity of the carrier tends to decrease as a high electric field is applied, and particularly, development is performed at high temperature and high humidity. Moisture adhering to the developer forms a conductive path in the developer layer, and carrier adhesion due to the charge injection tends to occur. It is generally known that the dependence of the developer on the charging environment also depends on the core material of the carrier. The carrier surface is oxidized and is not properly charged with the toner, so that good image quality cannot be obtained.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a stable image having no carrier adhesion under a high bias voltage, at normal temperature and normal humidity, and at high temperature and high humidity. An electrostatic latent image developing carrier suitable for contact development,
An object of the present invention is to provide an electrostatic latent image developer and an image forming method using the same.

[0007]

The above object is achieved by the present invention which is described below.
Achieved by light. That is, in the present invention, an electric field of 10^Five(V
/ M) is ρ₁(Ω · m), 10^6.5(V /
m) is given by ρ _Two(Ωm), ρ_Two
≧ ρ₁And ρ₁≧ 10¹⁴Is characterized by
Latent image developing carrier, and electrostatic latent image development using the same
An image agent and an image forming method. In addition, the present invention
Ku (Li_TwoO)_x(Fe_TwoO_Three)_1-x(here,
“X” and “1-x” represent a molar ratio, and “x” is 0.1
7 or less) is provided with a resin coating on the core material represented by
Having the above-mentioned resistance characteristics.
Image carrier, electrostatic latent image developer and image carrier using the same
It is a forming method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described by way of embodiments.
This will be described in detail. In the present invention, for electrostatic latent image development
Carrier (hereinafter simply referred to as “carrier”) resistivity
Is characterized by an electric field of 10^Five(V / m)
ρ₁(Ω · m), 10^6.5The resistivity at (V / m) is ρ
_Two(Ω · m)_Two≧ ρ ₁And ρ₁
≧ 10¹⁴It is necessary to be. Career is common
To 10⁶(V / m) in a high electric field around
And the resistivity decreases as the electric field increases. Only
However, the carrier of the present invention can be charged even under such a high electric field.
No position dependence (ρ_Two= Ρ₁) Or 10^Five(V /
m) resistivity ρ₁1 that has a higher electric field than (Ω · m)
0^6.5Resistivity ρ at (V / m)_Two(Ω · m)
White (ρ_Two> Ρ₁)
It is. Also, ρ₁The value of¹⁴(Ω · m)
The above is necessary, but preferably 10^Fifteen(Ω · m) or less
Above, more preferably 10¹⁶(Ω · m) or more. Up
Ρ_Two≧ ρ₁, And ρ₁≧ 10¹⁴Any of the conditions
If not, the carrier will easily adhere to the photoreceptor surface.
In particular, under high temperature and high humidity, carrier adhesion becomes remarkable. Ma
Also, the breakdown of the bias voltage is likely to occur.
You.

In the present invention, the resistivity of the carrier is determined by tapping after placing the carrier particles in a container having a cross-sectional area of 8 × 10 ⁻³ (m ² ) at a temperature of about 1 mm under normal temperature and normal humidity and tapping. A load of 5 × 10 ⁻¹ (kg / m ² ) is applied to the particles, and a voltage that generates an electric field of 10 ⁵ (V / m) and 10 ^6.5 (V / m) is applied between the load and the bottom electrode. It is a value obtained by reading the current value at the time of performing.

The carrier of the present invention comprises (1) magnetic particles,
(2) A magnetic material particle is used as a core material (hereinafter sometimes referred to as a “carrier core”) and its surface is coated with a known resin such as a vinyl resin or a wax such as stearic acid to form a coating layer. Resin-coated carrier particles, or (3) magnetic-particle-dispersed carrier particles obtained by dispersing magnetic fine particles in a binder resin, and satisfying the above-mentioned resistance conditions.

When the resin is coated on the resin-coated carrier particles (2), the coating resin may be a polyolefin resin, for example, polyethylene or polypropylene; a polyvinyl or polyvinylidene resin, for example, polystyrene, acrylic resin, polyacrylonitrile. , Polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin comprising an organosiloxane bond or the same. Modified product; fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; Emissions; polycarbonate; amino resins such as urea - formaldehyde resins; can be mentioned epoxy resins are not particularly limited thereto. Further, the resin coating amount is set at 0.1 to the core material.
It is preferably from 1 to 10.0 parts by weight. If it is less than 0.1 part by weight, the core material is easily exposed on the carrier surface,
The surface composition of the carrier is likely to be non-uniform. Meanwhile, 1
If the amount exceeds 0.0 parts by weight, the particles are likely to agglomerate during resin coating, and it is difficult to obtain uniformly coated particles. As the resin coating method, for example, a dipping method in which the magnetic particles are dipped in a solvent for forming the coating layer, a spray method in which a solution for forming the coating layer is sprayed on the surface of the magnetic particles,
The fluidized bed method of spraying the coating layer forming solution while the magnetic particles are suspended by flowing air, the kneader coater method of mixing the magnetic particles and the coating layer forming solution in a kneader coater and removing the solvent are already known. Although the following technique can be used, it is preferable to use a fluidized bed method capable of uniformly coating the resin.

In the magnetic particle-dispersed carrier particles (3), the binder resin may be a polyolefin resin, for example, polyethylene or polypropylene; a polyvinyl or polyvinylidene resin, for example, polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, or polyvinyl acetate. Alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin comprising organosiloxane bond or modified product thereof; fluororesin For example, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate Amino resins such as urea - formaldehyde resins; can be mentioned epoxy resins are not particularly limited thereto. The magnetic material-dispersed carrier particles can be obtained by kneading a charge controlling agent or magnetic material particles into the above-mentioned binder resin, and performing pulverization and classification. The carrier of the present invention may be any of the carriers (1) to (3) as long as the above-described resistance characteristics can be obtained, but such resistance characteristics can be easily obtained (2). It is preferable to use a resin-coated carrier.

As a material of the magnetic particles, any material which can satisfy the above-mentioned resistance characteristics when formed into a carrier is used.
Any conventionally known one can be used, but in the present invention, ferrite,
Particularly, Li-ferrite is preferably used. Further L
Among the i-ferrites, (Li ₂ O) _x (Fe ₂ O ₃ )
_1-X (where “x” and “1-x” represent a molar ratio,
"X" represents 0.17 or less) is particularly preferably used. By using a material having such a composition, a carrier core having the above-described desired resistance range can be easily obtained. If x exceeds 0.17, characteristics of Li that are easily affected by temperature and humidity appear, and the dependence of the developer on the charging environment is undesirably deteriorated.

The particle size distribution of the carrier of the present invention can be adjusted to a desired particle size distribution by a centrifugal classifier, an inertial classifier, or a sieve. The particle size of the carrier of the present invention is preferably 10
To 100 μm, more preferably 20 to 50 μm. If the particle size of the carrier is smaller than 10 μm, carrier scattering is likely to occur, while if it is larger than 100 μm, the magnetic brush becomes coarse and the image quality deteriorates. Further, in order to obtain a desired magnetic force distribution, the magnetic force may be selected by a known method.

The carrier for developing an electrostatic latent image according to the present invention includes:
Used as a two-component developer by mixing with a toner. The toner is obtained by melt-kneading a binder resin with a colorant and other additives, cooling, pulverizing, and, if necessary, classifying the binder resin according to a conventional method. Styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate; acrylic acid Α-methylene aliphatic monocarboxylic acid esters such as methyl, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Examples thereof include vinyl ethers such as methyl ether, vinyl ethyl ether and vinyl butyl ether; homopolymers and copolymers such as vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. Particularly typical binder resins include polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and styrene-maleic anhydride. Copolymers, polyethylene and polypropylene can be mentioned. In addition, polyester resin,
Examples include polyurethane resin, epoxy resin, silicone resin, polyamide resin, modified rosin, paraffin, and waxes.

[0016] Colorants for the toner include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and lamp black. , Rose Bengal, C.I.
I. Pigment Red 48: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 57:
1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 12, C.I. I. Pigment Blue 1
5: 1, C.I. I. Pigment Blue 15: 3 and the like can be exemplified as typical examples, but the present invention is not limited to these. The toner may optionally contain known additives such as a charge control agent and a fixing aid. 30 μm as the weight average particle size of the toner
Hereinafter, it is preferably 4 to 20 μm.

It is preferable to externally add silica surface-treated with silicone oil to the toner in order to improve fluidity, cohesion and environmental stability. Representative examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, and alkyl-modified silicone oil substituted with an ethyl group or a propyl group. The amount of silica added to the toner is preferably 0.05% by weight to 2% by weight, more preferably 0.1% by weight to 1.0% by weight, and still more preferably 0.2% by weight to 0.8% by weight. is there. If the content is less than 0.05% by weight, the effect of increasing the charge amount and the fluidity effect is small,
If the content exceeds% by weight, problems such as a low concentration may occur due to an increase in the charge amount. Further, any silica may be used as long as at least one or more of the added silicas are treated with silicone oil.

It is preferable that titanium oxide is externally added to the toner. Under high temperature and high humidity, while maintaining the amount of charge of the toner necessary for development, the uniformity of charge on the toner particle surface, the charge exchange between toner particles is accelerated, the charge speed is improved, and the charge distribution is improved. Can be sharpened. As a result, it is possible to significantly improve the environmental dependence of the charge amount of the toner composition. The surface-treated titanium oxide is produced by a wet method and has a water-soluble component content of less than 0.2% by weight. As the surface treatment, various coupling agents such as a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent, and silicone oil can be used. Among these, the use of a silane coupling agent is particularly preferred because it prevents the reduction in charge of titanium dioxide, improves its maintainability and hydrophobicity, and provides high charge exchangeability and high image quality with less fog. preferable. The amount of the surface-treated titanium oxide added to the toner is preferably 0.05% by weight.
To 2% by weight, more preferably 0.5% to 1.5% by weight, even more preferably 0.7% to 1.1% by weight. If it is less than 0.05% by weight, the effect of improving the charge exchange property is small, and if it is more than 2% by weight, the image quality is deteriorated due to the impact of the carrier.

When the developer is prepared by mixing the toner and the carrier, the ratio of the toner is 0.3 to 0.3% of the entire developer.
A range of 30% by weight is preferred. Further, alumina, tin oxide, strontium oxide, various resin powders, and other conventionally known external additives can be blended to improve the fluidity of the developer.

The thus-obtained electrostatic latent image developer is
Forming a latent image on the latent image carrier, developing the latent image using a developer, transferring the developed toner image onto a transfer member, and heating and fixing the toner image on the transfer member It is used as a developer in an image forming method having a fixing step. In particular, the developing step includes forming a thin layer of developer on a developer carrier, applying a developing bias voltage to the developer carrier, and performing non-contact development, that is, an image forming method by a so-called non-contact developing method. Is preferable because high resistance is maintained even when a high bias voltage is applied, environmental stability is high, and a stable high-quality image is obtained.

[0021]

The present invention will now be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples. (Developing Apparatus) FIG. 1 shows an image recording apparatus used in this embodiment. In FIG. 1, reference numeral 1 denotes a photosensitive drum as a latent image carrier, and the photosensitive drum 1 is formed by forming a thin photosensitive layer 1b on the surface of a cylindrical member 1a made of a conductive material. As the photoconductor layer 1b, for example, a negatively charged organic photoconductor (hereinafter, referred to as “OPC”)
Is used. Further, for example, the outer diameter of the photosensitive drum 1 is set to 100 mm, and the linear velocity of the surface movement of the photosensitive drum 1, that is, the process speed is set to 160 mm / s.

In this image recording apparatus, the photosensitive drum 1 is driven to rotate in a direction indicated by an arrow by driving means (not shown). Around the photoconductor drum 1, along a rotation direction thereof, a charger 2, an exposure unit 3, and a developing device 4 having a developer carrier 11 formed of a cylindrical member facing the photoconductor drum 1. Pre-transfer corotron 5 and transfer corotron 6
, Peeling corotron 7, cleaner 8, light neutralizer 9
Are sequentially arranged.

First, the surface of the photosensitive drum 1 is uniformly charged to -450 V by the charger 2. Subsequently, the image portion is exposed to the laser beam by the exposure means 3 to form a latent image having an exposed portion potential of -200 V.
And the toner is developed and visualized. At this time, a developing bias is applied to the developer carrier 11 by a developing bias power source (not shown). In this embodiment, the developing bias is an AC voltage on which a DC voltage is superimposed. The DC component of the developing bias voltage is set to -400 V, the AC component is a rectangular wave having a frequency of 6 kHz, and the peak-to-peak voltage is 1.5 kV.
Set to. The surface moving linear velocity of the developer carrier 11 was set at 320 mm / s. Next, on the photosensitive drum 1 on which the toner image was formed, uniform negative charging was performed by the pre-transfer corotron 5 in this embodiment. this is,
Regarding the adhesion of the carrier to the photosensitive drum 1 that occurs unintentionally during the development, the adhesion of the carrier is evaluated on the recording paper 10 so that the carrier is transferred onto the recording paper 10 together with the toner. That's why.

Subsequently, the toner image formed on the photosensitive drum 1 is transferred onto the recording paper 10 by charging the transfer corotron 6. Thereafter, the recording paper 10 is peeled off from the surface of the photosensitive drum 1 by the charging of the peeling corotron 7, and is conveyed to a fixing device (not shown), where the toner image is fixed on the recording paper 10, and a series of image recording steps is performed. finish. The surface of the photosensitive drum 1 after the transfer of the toner image and the step of peeling off the recording paper 10 are finished with the cleaner 8.
After the residual toner has been cleaned, the residual charge is removed by exposure by the light neutralizer 9 to prepare for the next image recording step.

Hereinafter, the developing device 4 used in this embodiment will be described with reference to FIG. The developing device 4 is provided with a developing opening 16 at a portion of a developing housing 15 in which a developer is accommodated and opposed to the photosensitive drum 1.
6, a developing roll 12 is provided. The developing roll 12 includes a cylindrical developer carrier 11 that rotates in the direction of the arrow, and shafts at both ends (not shown). In this embodiment, the outer diameter of the developing roll 12 is 18 m.
m, the gap between the photosensitive drum 1 and the developer carrier 11 is 30
The thickness is set to 0 μm, and the developer 14 is kept in a non-contact state with the photosensitive drum 1 as a layer on the developer carrier 11. The developer 14 held by the developer carrier 11 is transported to a development area facing the photoconductor drum 1 as the developer carrier 11 rotates, and
Develop the upper latent image. Further, the developer 14 that has passed through the developing area is separated from the developer carrier 11 by the scraper 13 and falls into the developer pool, mixed with the additional toner supplied from a toner supply device (not shown), and To be used.

(Manufacture of Carrier) Polymethyl methacrylate (Mw = 100,000) as a coating resin is dissolved in a 15% solution of toluene in a carrier core fine particle having a weight average particle diameter of 40 μm having a composition shown in Table 1, and a fluidized bed method or a kneader is used. Carrier particles were prepared by changing the coating amount by a coater method. The amount and method of application of the coating resin are as shown in Table 1. Here, the coating amount is represented by parts by weight of the coating resin solution with respect to 1,000 parts by weight of the carrier core. (Measurement of Resistance Value) The resistivity of each carrier was measured by the method described above. The resistivity ρ _{1 of} each carrier under a 10 ⁵ (V / m) electric field and the resistivity ρ under a 10 ^6.5 (V / m) electric field
₂ is shown in Table 1.

[0027]

[Table 1]

(Production of Toner ) Toner A / Polyester resin (synthesized from bisphenol A-ethylene oxide diadduct, bisphenol A-propylene oxide diadduct, terephthalic acid, trimellitic acid, Mw = 14,000, Tg = 62) 87 ° C., THF insoluble content 25%) 87 parts by weight ・ Coloring material (cyanine blue 4933M: manufactured by Dainichi Seika) 3 parts by weight ・ Polypropylene wax (Viscol 660P manufactured by Sanyo Chemical Co., Ltd.) 6 parts by weight Reserve the above raw materials with the above composition. After mixing, water was added by 3% with a twin screw extruder and melt-kneaded while keeping the temperature of the kneaded product at 110 ° C., followed by rolling, cooling, and preliminary grinding with a hammer mill or the like. Thereafter, the mixture was finely pulverized by a jet mill, and fine and coarse powders were cut by an air classifier to produce negatively chargeable polyester-based magenta toner particles having a weight average particle diameter of 7 μm. The particle size was measured using a Coulter Counter TA-II (aperture diameter: 100 μm). This toner particle 1
To 00 parts, 0.2 parts of silica treated with silicone oil as an external additive and 1.2 parts of surface-treated titanium oxide are added and mixed with a Henschel mixer, and silica fine particles and titanium oxide fine particles are adhered to the surface. Thus, a negatively charged magenta toner was obtained. (Preparation of Developer) Examples 1-4 and Comparative Examples 1-3
Were mixed with 6 parts by weight of toner A to prepare seven types of developers.

(Evaluation) Normal temperature and normal humidity (25 ° C., 50% R)
H) and a high-temperature, high-humidity (30 ° C., 75% RH) environment, using the developers of the examples and comparative examples, a durability test of 100,000 copies was performed. Later, the carrier adhesion and the image density were evaluated. Table 2 shows the results.

[0030]

[Table 2]

The evaluation method and evaluation criteria for the above durability test are as follows. Evaluation of Carrier Adhesion Carrier adhesion was evaluated by printing an image of a so-called alternating line in which a line image and a background portion were arranged at regular intervals, as shown in FIG. The cycle of the alternating lines is 2 cycles / mm, and the ratio of the image portion to the background portion is 1: 1. In such an alternating line, an electrostatic latent image in which the image portion and the background portion are adjacent to each other at a very small interval exists on the surface of the photoconductor, and the electrostatic latent image causes a so-called fringe near the photoconductor surface. An electric field is generated, and in the peripheral portion of the image, an electrostatic attractive force acts on the carrier charged to the opposite polarity to the toner. Therefore, such an alternating line is an image in which carrier adhesion easily occurs, and is suitable for evaluation of carrier adhesion.
The evaluation index of carrier adhesion was the area ratio of carrier particles on the background of the alternating line. To measure the area ratio,
An image analyzer (trade name: LUZEX-5000) was used. The evaluation criteria are as follows. ：: When the area ratio of the carrier particles is less than 0.5% Δ: When the area ratio of the carrier particles is 0.5% or more and 1.0% or less X: The area ratio of the carrier particles exceeds 1.0% If

Image Density Image density is a reflection densitometer (trade name: X-RITE310)
Was measured for solid images. The evaluation criteria are:
If it is 2 or more, both the solid image and the line image have a sufficient image density, and if it is 1.8 or more, it is more preferable. ◎: 1.8 or more ：: 1.2 or more and less than 1.8 ×: Less than 1.2 Overall evaluation In all of the above evaluations, those without x were evaluated as ○, and those with at least one x were evaluated as x. did.

[0033]

According to the present invention, there is provided a carrier for developing an electrostatic latent image, wherein the carrier is prevented from adhering under a high bias voltage and at a normal temperature and a normal humidity, and a high temperature and a high humidity. An electrostatic latent image developer and an image forming method using the same can be provided. In particular, according to the present invention, even when used in non-contact development suitable for forming a color image, carrier adhesion is prevented under normal temperature and normal humidity and high temperature and high humidity, and an image of good image quality can be obtained. An electrostatic latent image developing carrier, an electrostatic latent image developer using the same, and an image forming method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an image recording apparatus used in an embodiment.

FIG. 2 is a schematic sectional view illustrating a part of a developing device of the image recording apparatus of FIG. 1;

FIG. 3 is a diagram showing alternating lines used in the evaluation of carrier adhesion in Examples.

[Explanation of symbols]

 1: Photoconductor drum 1a: Cylindrical member 1b: Photoconductor layer 2: Charger 3: Exposure means 4: Developing device 5: Corotron before transfer 6: Transfer corotron 7: Peeling corotron 8: Cleaner 9: Optical neutralizer 10: Recording Paper 11: developer carrier 12: developing roll 13: scraper 14: developer 15: developing housing 16: opening for development

Claims (10)

[Claims] The resistivity when the electric field is 10 ⁵ (V / m) is ρ ₁ (Ω · m), and the resistivity when the electric field is 10 ^6.5 (V / m) is ρ
₂ (Ω · m), ρ ₂ ≧ ρ ₁ , and
A carrier for developing an electrostatic latent image, wherein ρ ₁ ≧ 10 ¹⁴ . 2. The electrostatic latent image developing carrier according to claim 1, wherein a resin coating is provided on the core material. 3. The electrostatic latent image developing carrier according to claim 2, wherein the core material is ferrite. 4. The electrostatic latent image developing carrier according to claim 2, wherein the core material is Li-ferrite. 5. The core material is (Li ₂ O) _x (Fe ₂ O ₃ )
_1-x (where “x” and “1-x” represent a molar ratio,
3. The electrostatic latent image developing carrier according to claim 2, wherein "x" represents 0.17 or less. 6. The electrostatic latent image developing carrier according to claim 1, wherein the average particle diameter is 10 to 100 μm. 7. The resin coating amount is 0.1 to 1 with respect to the core material.
The carrier for developing an electrostatic latent image according to claim 2, wherein the carrier is 0.0% by weight. 8. An electrostatic latent image developer comprising at least toner particles comprising a binder resin and a colorant, and a carrier for developing an electrostatic latent image, wherein the carrier for developing an electrostatic latent image is provided. 8. An electrostatic latent image developer, which is the electrostatic latent image developing carrier according to 7. 9. A step of forming a latent image on a latent image carrier, a developing step of developing the latent image using a developer, a step of transferring the developed toner image onto a transfer body, An image forming method having a fixing step of heating and fixing a toner image, wherein the electrostatic latent image developer according to claim 8 is used as the developer. 10. The method according to claim 9, wherein in the developing step, a thin layer of the developer is formed on the developer carrier, and a non-contact development is performed by applying a developing bias voltage to the developer carrier. The image forming method as described in the above.