JP3102018B2 - Electrostatic latent image developing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to a magnetic brush developing method, and more particularly, to a magnetic brush developing method in which a magnet is fixed and a developer carrier is rotated to convey and develop a developer.

[0002]

[Prior art]

The magnetic brush developing method is a basic method in the electrostatic latent image developing method, and among them, there are various methods, but a magnet is fixedly arranged inside a developer carrier, and 2. Description of the Related Art In general, a method is employed in which a developer held on a developer carrier is conveyed to a development area and developed by rotating a developer carrier present on the outer periphery.

However, in this method, the image is easily affected by the mixture ratio of the toner. That is, when the mixing ratio of the toner is increased, the rising probability of the toner charge is reduced due to a decrease in the relative contact probability with the carrier, and the amount of charge of the toner is insufficient, that is, due to the presence of the poorly charged toner, the toner is scattered as a result. And the like. Further, when the relative toner amount increases, the toner aggregates cannot be sufficiently disintegrated by mechanical mixing and stirring or by mixing and stirring on the developer carrier, and the toner aggregates are developed. This causes poor transfer at the time, causing white spots. Further, toner fog is deteriorated due to the presence of the toner aggregates and the poorly charged toner. In particular, when a toner having a small particle diameter is used and the toner mixing ratio increases, the above tendency is remarkably exhibited.

[0004]

[Problems to be solved by the invention]

The present invention has been made in view of the above circumstances, and has a magnet body fixedly disposed therein, and develops by rotating a developer carrier that is arranged to face the electrostatic latent image carrier. While holding the developer on the surface of the developer carrier, the developer is conveyed to the developing area, and the electrostatic latent image formed on the surface of the electrostatic latent image carrier is developed, and the toner is scattered without being affected by the toner mixing ratio. It is an object of the present invention to provide an electrostatic latent image developing method which does not cause toner fogging, white spots on an image and the like.

[0005]

[Means for Solving the Problems]

In the present invention, a magnet body is fixedly arranged inside,
By rotating the developer carrier opposed to the electrostatic latent image carrier, the developer is transported to the developing area while being held on the surface of the developer carrier, and is formed on the surface of the electrostatic latent image carrier. In the developing method for developing the formed electrostatic latent image, the developer comprises a toner and a resin-coated carrier having a polyolefin resin coating layer, and the resin coating layer is formed by polymerizing an olefin monomer on the surface of the core material. It has a large number of pores formed by the polymerization on the surface of the coating layer, the average pore diameter of these pores is 0.1 to 0.5 μm
And a method for developing an electrostatic latent image.

The electrostatic latent image developing method according to the present invention belongs to a magnetic brush developing method, and includes a non-magnetic developer carrier having a built-in magnet body opposed to the surface of a photoconductor that is driven to rotate. While the developer supplied to the developer carrier is held on the outer peripheral surface of the developer carrier by a magnet body and a magnetic force, the developer carrier is rotated, and the developer carrier and the photoconductor are brought into a developing area where the developer and the photoconductor are close to each other. The developer is transported and developed.

[0007] Such a method is a known developing method, and in the present invention, it can be applied to all types of developing apparatuses capable of performing the developing method. FIG. 3 shows an example of a developing device for use in the electrostatic latent image developing method according to the present invention for simplicity.

In FIG. 3, (12) is a developing device, (11) is a photoconductor, and in the developing device (12), (13) is a developer carrier, (14) is a magnet, and (16) Is a bucket roller, (17)
Is a spiral screw, (18) is a toner hopper,
(19) indicates a layer thickness regulating blade, (D) indicates a developer, and (T) indicates a toner. In the developing device having the above configuration, a DC component (15) having the same polarity as the electrostatic latent image is applied to the developer carrier (13) as a developing bias.

The developer (D) in the developing device (12) is mixed and stirred by a bucket roller (16) rotating in the direction of the arrow in the drawing, and is triboelectrically charged. By using a carrier having pores on its surface as described later as a developer, the toner is excellent in charge rising property and is uniformly and triboelectrically charged. The triboelectrically charged developer is a developer carrier (13)
The developer carrier (13) is supplied onto the developer carrier (13) in the direction of the arrow, and is conveyed over the developer carrier (13), and is regulated to a constant layer pressure by a layer thickness regulating blade (19). B), and the electrostatic latent image on the surface of the photoconductor (11) is developed.

The developer held on the developer carrier conveyed to the development area is contact-developed in a state where the developer is brought into contact with the electrostatic latent image carrier and a magnetic brush, or an electrostatic latent image carrier The electrostatic latent image is developed using a flying development method or the like that is performed while keeping the magnetic brush and the magnetic brush in a non-contact state.

[0011] A change in the amount of toner consumed by development per sheet and a change in the amount of toner newly replenished in the developer accompanying the change causes a change in the toner mixing ratio, thereby causing the above-described problem. . In the holder, by using a carrier having pores on its surface, which will be described later, adverse effects due to a change in the toner mixing ratio can be prevented. The developer used in the above-described developing method includes at least a resin-coated carrier and a toner.

First, the resin-coated carrier will be described. A sectional view of the resin-coated carrier of the present invention is schematically shown in FIG. 1 for easy understanding, and a schematic sectional view of a conventional resin-coated carrier is shown in FIG. That is, the resin-coated carrier of the present invention comprises a carrier core material (1), a resin coating layer (2) covering the carrier core material (1), and pores (3) formed on the surface of the resin coating layer. A major feature is that pores (3) are present, as compared with the conventional resin-coated carrier shown in FIG.

As described above, when the pores are present on the surface of the resin-coated carrier, the toner (for example, a small particle size toner)
When used together, sufficient contact between the toner particles (4) and the carrier particles can be ensured, the toner can be quickly charged, and each toner particle can be charged sufficiently uniformly. In addition, it is possible to prevent toner scattering due to poor charging.

Further, the pores on the carrier surface are excellent in capturing toner particles, and this is also effective in preventing toner scattering. Further, due to the presence of the pores, frequent contact between the toner and the carrier occurs, which is effective in preventing aggregation of the toner and further in breaking up the aggregated toner. As a result, the problem of aggregation of the toner is solved.

The pores on the surface of the resin-coated carrier of the present invention are specifically defined by the pore size distribution, the average pore size, and the total pore volume. The diameter of each pore present on the surface of the resin coating layer is 0.001 to 3μ
m, preferably 0.001 to 2 μm, more preferably 0.005 to
Desirably, it is distributed in the range of 2 μm. Pore size
If the particle size is less than 0.001 μm, a sufficient effect cannot be expected from the viewpoint of the crushing property of the toner. If the particle size is larger than 3 μm, the toner trapping property becomes too strong, and the fluidity and developability may be impaired.

The average pore diameter is desirably in the range of 0.1 to 0.5 μm, corresponding to the distribution range of the pore diameter described above. By setting the average pore diameter within the above range, the disintegration property of the toner and the charging characteristics for the toner can be improved.

In the present invention, the total pore volume is expressed in two ways: a total pore volume per 1 g of a carrier (1 ml / g) and a total pore volume per 1 ml of a coating resin layer (ml / ml). The total pore volume (ml / g) per 1 g of the carrier can be determined by mercury holosimetry. In the carrier of the present invention, the value is 0.001 to 0.1 ml / g, preferably 0.01 to 0.1 ml / g.
It is desirable to have a value of 〜0.05 ml / g. Its value is 0.00
If it is smaller than 1 (ml / g), the pores present on the carrier surface are insufficient, and the effect of the pores may not be obtained. If it is more than 0.1 ml / g, the pores are too large and the coating layer becomes brittle.

The total pore volume (ml / ml) per 1 ml of the coating resin is obtained by converting the above-mentioned total pore volume (ml / g) per 1 g of the carrier from the true specific gravity of the coating layer and the filling rate of the carrier core material. Can be obtained by In the carrier of the present invention, it is desirable that the value has a value of 0.1 to 2 ml / ml, preferably 0.5 to 1.5 ml / ml. If the value is less than 0.1 ml / ml, the pores existing on the carrier surface are insufficient, and the effect of the pores may not be obtained. If it is larger than 2 ml / ml, the number of pores is too large and the coating layer becomes brittle.

Next, the constituent materials of the carrier of the present invention will be described. As a carrier core material which is a component of the carrier of the present invention, a carrier core material having a size of at least 20 μm (average particle diameter) is used from the viewpoint of preventing carrier adhesion (scattering) to the electrostatic latent image carrier. In order to prevent the occurrence of streaks and the like and to prevent the image quality from lowering, a material having a size of at most 100 μm is used. As specific materials, those known as two-component carriers for electrophotography, for example, ferrite, magnetite, iron, nickel,
Metals such as cobalt, these metals and zinc, antimony,
Alloys or mixtures with metals such as aluminum, lead, tin, hissmas, beryllium, manganese, selenium, tungsten, zirconium, and vanadium; metal oxides such as iron oxide, titanium oxide, and magnesium oxide; and nitrides such as chromium nitride and vanadium nitride , A mixture with a carbide such as silicon carbide, tungsten carbide and the like, a ferromagnetic ferrite, a mixture thereof and the like.

As the carrier coating resin, particularly when the toner used in combination with the carrier is liable to be spent,
From the viewpoint of prevention of spent, a coating resin having good releasability, for example, a polyolefin resin is preferable.

The carrier surface of the present invention is preferably coated with a carrier coating resin at 70% or more, preferably 90% or more, and more preferably 95% or more. If the coverage is lower than 70%, the characteristics of the carrier core itself (instability of environmental resistance, decrease of electric resistance, instability of charging) appear strongly through the background, and the advantage of resin coating cannot be used.

[0022] The filling rate of the carrier core material is about 90 wt% or more, preferably 95 wt% or more.
Set to wt% or more. The filling rate may be interpreted as indirectly defining the thickness of the resin coating layer of the carrier. If the filling rate of the carrier core material is smaller than 90 wt%, the coating layer becomes too thick, and is actually applied to the developer. Also, peeling of the coating layer, increase in the amount of charge, etc., do not satisfy the durability and charge stability required for the developer, and are also inferior in fine line reproducibility in image quality, image density is reduced, etc. Problems arise.

It is also possible to indirectly express the resin coating layer thickness by specific gravity. The specific gravity of the carrier of the present invention is greatly affected by the type of the carrier core material, but as long as the carrier core material is applied, 3.5 to 7.5, preferably 4.0 to 6.0, more preferably 4.
Indicates a value in the range of about 0 to 5.5. If the value is out of the range, the same adverse effects as those of the carrier which is not coated with the appropriate filling rate occur as described above.

The electric resistance of the resin-coated carrier of the present invention is 1 × 10 ⁶ to
It is set to about 1 × 10 ¹⁴ Ω · cm, preferably about 10 ⁸ to 10 ¹³ Ω · cm, and more preferably about 10 ⁹ to 10 ¹² Ω · cm. When the electric resistance is lower than 1 × 10 ⁶ Ω · cm, the carrier develops, and the image quality deteriorates. If it is larger than 1 × 10 ¹⁴ Ω · cm, the toner is excessively charged, so that an appropriate image density cannot be obtained. It can be considered that the electric resistance indirectly expresses the above-mentioned resin covering ratio and carrier filling ratio.

It is preferable that the carrier used in the present invention further imparts irregularities to the resin coating layer. FIG. 1 shows a mode in which the resin coating layer (2) has irregularities, and the pores (3)
Exists on the surface of the resin coating layer (2) having the unevenness. By providing such irregularities on the surface of the carrier, a carrier having improved toner charging characteristics, toner scattering, toner aggregation and crushing properties, and the like can be obtained.

The surface irregularities will be described in more detail. The uneven structure of the coating layer of the surface coating layer is represented by the following formula [I];

(Equation 1) [Where the outer circumference represents the outer circumference of the projected image of the carrier particles, and the area represents the average value of the projected area of the carrier particles. ], The value is preferably in the range of 130 to 200. The S value indicates the degree of unevenness of the particle surface.
From the value. The shape coefficient S can be measured by, for example, an image analyzer (Luzex 5000; manufactured by Nippon Regulator Co., Ltd.). It does not mean that it must not.

The carrier coating resin layer of the present invention may contain additives such as fine particles having a charge imparting function or conductive fine particles. Fine particles having a charge imparting function include CrO ₂ , Fe ₂ O ₃ , F
e ₃ O ₄ , IrO ₂ , MnO ₂ , MoO ₂ , NbO ₂ , PtO ₂ , TiO ₂ , Ti ₂ O ₃ , T
_{i 3 O 5, WO 2,} V 2 O 3, Al 2 O 3, MgO, SiO 2, ZrO 2, metal oxides such as BeO, nigrosine base, Spiron Black TRH
And the like, as specific examples.

Examples of the conductive fine particles include carbon black such as carbon black and acetylene black, carbides such as SiC, TiC, MoC and ZrC, nitrides such as BN, NbN, TiN and ZrN, and magnetic powders such as ferrite and magnetite. Can be mentioned.

Addition of a metal oxide, a metal fluoride and a metal nitride is effective in further increasing the chargeability. It is considered that such an effect is exhibited by synergistic effects of charging the components and the toner due to the contact between the toner and the complex interface composed of these compounds, the coating resin and the core material.

The addition of carbon black is effective in enhancing the developability and obtaining an image having a high image density and a clear contrast. It is considered that the addition of conductive fine particles such as carbon black moderately lowers the electric resistance of the carrier, and the charge leakage and accumulation are performed in a well-balanced manner.

One of the features of the conventional binder type carrier is that it has excellent halftone reproducibility and gradation reproducibility. In the case of the resin-coated carrier of the present invention, magnetic powder is added to the resin-coated layer. By adding the carrier, a carrier having excellent gradation reproducibility can be obtained. This is considered to be because the addition of the magnetic powder to the resin coating layer resulted in a surface composition similar to that of the binder type carrier, and the chargeability and specific gravity approached those of the binder type carrier.

The addition of a boride or a metal carbide is effective in raising the charge. The size and amount of the additive are not particularly limited as long as various properties of the carrier of the present invention, which are described in the present specification, such as morphology of pores, coverage, and various properties such as electric resistance, are satisfied. In terms of the size of the fine particles, in relation to a preferred method of manufacturing the carrier of the present invention described below, for example, the particle size is such that the particles are uniformly dispersed on a slurry without aggregating in a resin solution or dehydrated hexane. The volume average particle diameter may be 2 to 0.01 μm, preferably about 1 to 0.01 μm.

As described above, the addition amount of the two fine particles cannot be unequivocally defined as described above. However, the addition amount is 0.1 wt% to 60 wt%, preferably 1.0 wt% to 40 wt% based on the coating resin.
Is appropriate.

In particular, according to the present invention, when the filling rate is set in the range of 90 to 97 wt%, additives such as fine particles having a charge imparting function or conductive fine particles are added to the resin coating layer. Is preferred. When the filling rate of the carrier is as small as about 90 wt% and the thickness of the coating layer is relatively thick, when the continuous copying of fine lines is performed using such a carrier, the problem that the reproducibility is reduced occurs. The problem is solved by the addition of the above-mentioned additives.

Next, a method for producing the resin-coated carrier having pores of the present invention will be described. A preferred method for producing the carrier of the present invention is a coating polymerization coating method. The surface polymerization coating method comprises: (1) a product obtained by previously contacting a highly active catalyst component containing titanium and / or zirconium and soluble in a hydrocarbon solvent with (2) a carrier core material; 3) using an organoaluminum compound, an olefin monomer on the surface of the carrier core material,
For example, it can be formed by polymerizing ethylene. When fine particles having a charge imparting function or conductive fine particles are further added, these additives may be added and present during the formation of the coating layer. More specifically,
The method described in -106808 is suitable. The publication is hereby incorporated by reference as part of the present specification.

When a carrier coating layer is formed by this surface polymerization coating method, the coating layer having pores described above on the surface can be formed on the carrier surface. A highly durable carrier having excellent adhesion to the coating layer can be obtained.

The toner used in combination with the carrier is not particularly limited, and after mixing and kneading a thermoplastic resin, a colorant and / or a charge imparting agent, and the like,
A pulverization method toner obtained by pulverization and classification, or a colorant and / or a charge imparting agent dispersed in a monomer, and a suspension polymerized toner obtained by polymerizing the same, or a low softening point substance such as a colorant and a wax or fixing. Wall material (capsule shell) with a softening point higher than those around the liquid containing resin for application
Wrapped capsule toner, or a photoconductive toner having a surface coated with a photoconductive substance.
Use one of about 20 μm.

Further, a fluidizing agent may be added to the toner of the present invention. As the fluidizing agent, silica, aluminum oxide, titanium oxide, a mixture of silica and aluminum oxide, silica
A titanium oxide mixture or the like is used. In particular, a mixture of silica and titanium oxide is more preferable, and the ratio of silica to titanium oxide is 0.1 to 0.3% by weight of silica / titanium oxide / 0.1 to 1% by weight, and it is preferable to add 0.1 to 2% by weight to the toner.
The fluidizing agent may be subjected to a hydrophobic treatment with a coupling agent or a surfactant.

The developer obtained in this way is excellent in toner charging rise, toner scattering prevention, and toner crushing property.

The mixing ratio of the toner and the carrier is 2 to 20% by weight, preferably 3 to 15% by weight, and more preferably 4 to 12% by weight. If the mixing ratio of the toner is less than 2% by weight, the charge amount of the toner becomes high, and a sufficient image density cannot be obtained. If the mixing ratio is more than 20% by weight, the inside of the copying machine is contaminated due to toner scattering, and Toner fog occurs. Hereinafter, the present invention will be described with reference to examples.

(1) Production Example of Toner Component parts by weight Polyester resin 100 (softening point: 130 ° C., glass transition point: 60 ° C., AV25, OHV38) Carbon black (manufactured by Mitsubishi Kasei Corporation, MA # 8) 5・ Dye (Hodogaya Chemical Industries, Spiron Black TRH) 3

After the above materials were sufficiently mixed by a ball mill, they were kneaded on three rolls heated to 140 ° C. After cooling the kneaded material,
Coarse pulverization was performed using a feather mill, and fine pulverization was performed using a jet mill.

After that, air classification was performed to obtain a volume average particle size of 8.1 μm.
0.3 wt% of hydrophobic silica (R974, manufactured by Nippon Aerosil Co., Ltd.) was added to the toner, and mixed using a Henschel mixer to obtain a toner.

Production Example 1 of Carrier (1) Preparation of Titanium-Containing Catalyst Component In a 500 ml-volume flask purged with argon, 200 ml of dehydrated n-heptane was added at room temperature, and the pressure was previously reduced at 120 ° C. (2 mmH 2).
g) A slurry is prepared by adding 15 g (25 mmol) of dehydrated magnesium stearate. Titanium tetrachloride 0.
After dropping 44 g (2.3 mmol), the temperature was raised, and the mixture was reacted under reflux for 1 hour to obtain a viscous transparent titanium-containing catalyst component solution.

(2) Evaluation of Activity of Titanium-Containing Catalyst Component 400 ml of dehydrated hexane, 0.8 mmol of triethylaluminum, 0.8 mmol of diethylaluminum chloride and the titanium-containing catalyst component obtained in the above (1) were placed in an autoclave having an inner volume of 1 L and purged with argon. 0.004 mmol as a titanium atom was sampled and charged, and the temperature was raised to 90 ° C.
At this time, the internal pressure of the system was 1.5 kg / cm ² G. Next, after supplying hydrogen and increasing the pressure to 55 kg / cm ² G, the total pressure was 9.5 kg / cm ²
Ethylene was continuously supplied so as to maintain G, and polymerization was carried out for 1 hour to obtain 70 g of a polymer. Polymerization activity is 365mg
/ g · Ti · Hr, and the MFR (melt flowability at 190 ° C. under a load of 2.16 kg; JIS K7210) of the obtained polymer was 40.

(3) Reaction of Titanium-Containing Catalyst Component with Filler and Polymerization of Ethylene An autoclave having an inner volume of 1 L and purged with argon was placed at room temperature in 500 ml of dehydrated hexane and reduced pressure at 200 ° C. for 3 hours (2 mmH 2).
g) 450 g of the dried sintered ferrite powder F-200 (manufactured by Powder Tech, average particle size 70 μm) was added, and stirring was started.
Next, the temperature was raised to 40 ° C., and the titanium-containing polymerization catalyst component (1) was added in an amount of 0.02 mmol as a titanium atom, and the reaction was carried out for about 1 hour. Then, triethyl aluminum 2.0
Mmol and 2.0 mmol of diethylaluminum chloride were added, and the temperature was raised to 90 ° C. The internal pressure of the system at this time is 1.5k
g / cm ² G. Then, hydrogen was supplied, after boosting the 2 kg / cm ² G, the total pressure ferrite-containing polyethylene composition of the total amount 473g subjected to 40 minutes polymerization while continuously feeding ethylene to maintain the 6 kg / cm ² G I got The dried powder was uniformly grayish white, and when observed with an electron microscope, the ferrite surface was thinly covered with polyethylene, and no aggregation of ferrite particles was observed in polyethylene.

When this composition was measured by TGA (thermal balance), the core material filling rate was 95.2 wt%. Thereafter, it was put into a hot air flow set at 120 ° C., and subjected to a heat treatment for 2.0 hours. The obtained carrier was classified with a 106 μm sieve to remove aggregates.

Production Example 2 of Carrier In a 1-liter autoclave having an inner volume replaced with argon, the titanium-containing catalyst component prepared in (1) of Production Example 1 was added to 450 g of ferrite in the same manner as in (3) of Production Example 1. 0.02 mmol was added as an atom, and the reaction was carried out for 1 hour.
Then, carbon black (Ketchen black DJ-600, manufactured by Lion Akzo) 0.4 from the autoclave upper nozzle
7g was charged. The carbon black used was dried under reduced pressure at 200 ° C. for 1 hour and then slurried with dehydrated hexane. Thereafter, 2.0 mmol of triethylaluminum and 2.0 mmol of diethylaluminum chloride were added, and the temperature was raised to 90 ° C. The internal pressure at this time was 1.5 kg / cm ² G. Then supply hydrogen,
After boosting to 2kg / cm ² G, the total pressure subjected to 45 minutes polymerization while continuously feeding ethylene to keep the 6kg / cm ² G,
A total of 469.3 g of a polyethylene composition containing ferrite and carbon black was obtained. The dried powder exhibited a uniform black color. According to an electron microscope, it was observed that the ferrite surface was thinly covered with polyethylene, and that carbon black was uniformly dispersed in the polyethylene. When this composition was measured by TGA (thermal balance), the core filling rate was 95.9 wt%, and the weight ratio of ferrite, polyethylene, and carbon black was 24: 1: 0.025 when calculated from the charged amount. . Thereafter, it was put into a hot air flow set at 120 ° C., and subjected to a heat treatment for 2.0 hours. 1 earned carrier
Classification was performed with a 06 μm sieve to remove aggregates.

Carrier Production Example 3 An argon-purged 1 L internal volume autoclave was prepared in the same manner as in Carrier Production Example 1 for 450 g of ferrite.
The titanium-containing catalyst component prepared in (1) of Production Example 1 was added in an amount of 0.01 mmol as a titanium atom, and reacted for 1 hour. Thereafter, 0.50 g of carbon black (Ketchen black EC, manufactured by Lion Akzo) was charged from the upper nozzle of the autoclave. The carbon black used was dried under reduced pressure at 200 ° C. for 1 hour and then slurried with dehydrated hexane. Thereafter, 1.0 mmol of triethylaluminum and 1.0 mmol of diethylaluminum chloride were added, and 90 ° C.
The temperature rose. The internal pressure at this time was 1.5 kg / cm ² G.
Then 1-butene 37.5 introduce mmol (2.1 g), followed by supplying hydrogen, it was boosted to 2 kg / cm ² G, while continuously feeding ethylene to keep the total pressure 6kg / cm ² G 28 Polymerization was carried out for one minute to obtain a total of 467 g of a ferrite and carbon black-containing polyethylene composition. The dried powder exhibited a uniform black color. According to an electron microscope, it was observed that the ferrite surface was thinly covered with the polymer, and the carbon black was uniformly dispersed in the polymer. When this composition was measured by TGA (thermal balance), the weight ratio of ferrite, polymer, and carbon black was 27: 1: 0.03. Further, the polymer excluding ferrite and carbon black by Soxhlet extraction (solvent, xylene) was analyzed by IR. As a result, it was confirmed that the polymer was a polyethylene copolymer containing 8 wt% of butene.

Thereafter, the mixture was put into a hot air stream set at 120 ° C., and subjected to a heat treatment for 2.5 hours. The obtained carrier was classified with a 106 μm sieve to remove aggregates.

Production Example 4 of Carrier Acrylic resin solution having a solid ratio of 2% (Acrydec A405: manufactured by Dainippon Ink Co., Ltd.) was used as a coating solution, and sintered ferrite powder (F-200: manufactured by Powder Tech, average particle size) was used as a core material. Diameter 70μ
m) was applied by a Spira coater (manufactured by Okada Seiko Co., Ltd.) so that the core material could be coated at 1.0 wt%. Thereafter, the temperature in the system was raised to 150 ° C. to cure the resin, and a thermosetting acrylic resin-coated carrier was obtained. The core filling rate of the obtained carrier was 99.0% by weight.

The total pore volume (g / g) per 1 g of the carrier obtained in Production Examples 1 to 4, and the total pore volume (m
l / ml), average pore diameter (μm), core material filling rate (wt%), true specific gravity (g / cm ³ ), bulk specific gravity (g / cm ³ ), electrical resistance and specific surface area (m ² / g) Are shown in Table 1.

[0053]

The total pore volume and average pore diameter of the carrier are values calculated from the measurement result of the carrier pore distribution. The pore distribution of the carrier was determined by mercury porosimetry. The measurement was performed using a pore sizer 9310 (manufactured by Shimadzu Corporation) and the contact angle of mercury was 130.
゜ The surface tension was 484 dyn / cm. The results are shown in FIG. 4 to FIG.

FIG. 4 is a diagram showing the relationship between the pore diameter and the penetration volume.
The intrusion volume represents the pore volume into which mercury was injected up to the maximum pressure at the time of measurement. FIG. 5 to FIG. 7 are diagrams showing the relationship between the pore diameter and the volume fraction. The volume fraction is the percentage of the pore volume occupying a certain pore diameter range to the total pore volume, expressed as a percentage.

The specific gravity measurement is as follows: • Electronic balance: one with a sensitivity of 0.1 mg. -Pycnometer: A specific gravity bottle with a gerysack thermometer specified in JIS R3501 (Glassware for analytical chemistry), internal volume
50 ml.・ Constant temperature water tank: The one that can keep water temperature at 23 ± 0.5 ℃. The measurement was carried out using a measuring device equipped with the following procedures.

(1) Weigh accurately the mass of a previously dried pycnometer to 0.1 mg. (2) Fill the pycnometer with sufficiently degassed n-heptene and hold it in a constant temperature water bath at 23 ± 0.5 ° C. for 1 hour, then adjust the liquid surface exactly to the marked line. Remove from the water bath, wipe off any external water, and weigh accurately to the nearest 0.1 mg. (3) Next, after emptying the pycnometer,
15 g is sampled, weighed again accurately to the order of 0.1 mg, and the mass of the sample is obtained by subtracting the result of (1).

(4) 20 to 30 ml of degassed n-heptene is gently added to the pycnometer containing the sample, and after completely covering the sample, air in the liquid is gently removed in a vacuum desiccator. (5) Next, the pycnometer is filled with n-heptene which has been degassed to near the marked line, and kept in a constant temperature water bath at 23 ± 0.5 ° C. for 1 hour. Remove the liquid after aligning it exactly to the marked line, wipe off the external water completely, and weigh accurately to the nearest 0.1 mg.

(6) The specific gravity is calculated by the following equation. S = ab * / (bc + a) where, S: specific gravity a: mass of sample (g) b: mass when immersion liquid is filled up to the marked line of pycnometer (g) c: pycnometer contained in the sample The mass (g) when the immersion liquid was filled up to the marked line of d: Specific gravity of the immersion liquid at 23 ° C. The bulk specific gravity was based on JIS Z2504.

The electric resistance is 1 mm thick and 50 m diameter on a metallic circular electrode.
Place the sample so that it is m, place an electrode with a mass of 895.4 g, a diameter of 20 mm, a guard electrode with an inner diameter of 38 mm, and an outer diameter of 42 mm, read the current value one minute after applying a DC voltage of 500 V, and measure the volume resistivity of the sample. It was converted to ρ. The measurement environment was a temperature of 25 ± 1 ° C. and a relative humidity of 55 ± 5%. The measurement was repeated five times, and the average was taken.

The specific surface area was measured by a BET method using nitrogen gas adsorption. The apparatus used was Flowsorb 2300 (manufactured by Shimadzu Corporation).

Evaluation of Charging Rise Property The toner mixing ratio was 2 wt% based on the carriers obtained in Production Examples 2 and 4 (= Comparative Example) and the toner obtained in the Production Example.
The amount of charge (q) in the developer mixing time is determined by the method described in “Determining the Charge Rate of Developer” using the developer adjusted as described in “Journal of Electrophotographic Society, Vol. 27, No. 3, (1988)”.
Was measured. FIG. 8 shows the relationship between log (qm-q) and t based on the measured data. Here, qm indicates a saturated (or maximum) charge amount.

The log (qm−q) shows linearity with respect to the time t, and the slope of the log (qm−q) can indicate the magnitude of the charging rising speed. The steeper the slope of the straight line, the faster the rise of charging.

It can be seen that the carrier of Production Example 2 has superior charging start-up characteristics to the carrier of Production Example 4 (= Comparative Example). The carriers of Production Examples 1 and 3 also exhibited excellent charge rising properties as in Production Example 2.

Evaluation by Developing Apparatus (Evaluator) A developing apparatus having the configuration shown in FIG. 3 was used.
Using a laser printer (reversal development) with a recording density of 400 dpi equipped with a negatively chargeable organic photoreceptor, printing was performed under the following conditions, and toner scattering, toner fog, and white spots on halftone images were evaluated. .・ Photoreceptor peripheral speed: 110mm / sec ・ Photoreceptor surface potential: non-image part potential -600V, image part potential -70V ・ Development bias: -500V ・ Developer carrier peripheral speed / photoreceptor peripheral speed = 1.4 ・ Development Gap: 0.6mm

(Gap Between Photoconductor and Developer Carrier) Regulation Gap: 0.5 mm

(Gap between the developer carrier and the layer thickness regulating blade) Carrier: Production Example 2 and Production Example 4 (Comparative Example) Toner: toner obtained in the above Production Example

(Evaluation Method) The toner mixture ratio was changed (4 to 12% by weight) with the combination of the carrier and the toner to prepare a developer, and printing was performed with the above-described evaluation machine, and the image quality was evaluated.

(Perspective of Evaluation) A 2 × 2 dot halftone image was formed on the entire surface of A4 paper, and the occurrence of white spots (voids) was evaluated by visual observation. Images of various patterns were printed, and the occurrence of toner fogging on the background (= white background) was visually observed, and the density uniformity of the image was evaluated using a reflection densitometer.

(Evaluation Results) When the carrier of Production Example 4 was used, as the mixing ratio of the toner increased from 4 wt% → 6 wt% → 8 wt% → 10 wt% → 12 wt%, many white spots in the halftone dot image were generated. Then, toner fog worsened. When the carrier of Production Example 2 was used, even if the toner mixing ratio was changed as described above, the state of white spots and toner fog in the halftone dot image did not change, and a good image without any problem was obtained.

Further, the carrier of Production Example 2 was excellent in the density unevenness of the image portion as well as the carrier of Comparative Example. Further, even when printing was performed with the carrier of Production Example 2, toner scattering and toner fogging did not occur, and high quality image quality could be maintained.

[0072]

【The invention's effect】

In a magnetic brush developing method in which the inner magnet is fixed and the developer carrier is rotated, the use of a resin-coated carrier having a large number of pores on the surface makes it possible to improve the charge rising property of the toner and prevent toner scattering. Is prevented, and a good image free of toner fog and white spots of a halftone dot image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a resin-coated carrier of the present invention.

FIG. 2 is a schematic sectional view of a conventional resin-coated carrier.

FIG. 3 is a sectional view showing an example of a developing device for carrying out the present invention.

FIG. 4 is a diagram showing a relationship between a pore diameter of a carrier surface pore and a penetration volume.

FIG. 5 is a view showing the relationship between the pore diameter and the volume fraction of the carrier surface pores obtained in each carrier production example.

FIG. 6 is a diagram showing the relationship between the pore diameter and the volume fraction of carrier surface pores obtained in each carrier production example.

FIG. 7 is a diagram showing the relationship between the pore diameter and the volume fraction of the pores on the carrier surface obtained in each carrier production example.

FIG. 8 is a diagram illustrating a relationship between a mixing time of a developer and a rise of a toner charge amount.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Junji Machida 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-57-94754 (JP, A) JP-A-58-192056 (JP, A) JP-A-2-69771 (JP, A) JP-A-61-270769 (JP, A) JP-A-64-20561 (JP, A) JP-A Sho 60 −106808 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/10

Claims (3)

(57) [Claims] 1. A magnet body is fixedly disposed inside,
By rotating the developer carrier opposed to the electrostatic latent image carrier, the developer is transported to the developing area while being held on the surface of the developer carrier, and is formed on the surface of the electrostatic latent image carrier. In the developing method for developing the formed electrostatic latent image, the developer comprises a toner and a resin-coated carrier having a polyolefin resin coating layer, and the resin coating layer is formed by polymerizing an olefin monomer on the surface of the core material. Has a large number of pores formed by the polymerization on the surface of the coating layer, the average pore diameter of the pores is 0.1 to 0.5 μm
A method for developing an electrostatic latent image, comprising: 2. The method according to claim 2, wherein the pores of the carrier have a prepore volume (ml / g).
2. The electrostatic latent image developing method according to claim 1, wherein the amount is 0.001 to 0.1 (ml / g) per 1 g of the carrier. 3. The electrostatic latent image developing method according to claim 1, wherein the specific gravity of the carrier is 3.5 to 7.5.