JP2001183873A - Carrier for development of electrostatic latent image and electrostatic latent image developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone resin coated carrier which is free from spending adhesion to its surface and the peeling of its coat even in repetitive use over a long period of time, stabilizes the quantity of triboelectric charges and developing characteristics, can retain good quality of a formed image over a long period of time without causing troubles such as carrier trailing, toner scattering in a machine, surface fog and defective image density and has a long service life and a developer. SOLUTION: The developer is a two-component developer comprising the silicone resin coated carrier and a positive charge type toner. The average particle diameter of the silicone resin coated carrier is 60-110 μm, the average thickness of the silicone resin coating layer is 0.1-0.3 μm and the resistance of the carrier is 1.5×108-1.5∼1011 Ωcm. The concentration of the toner is 3.0-5.0 wt.% and the quantity of triboelectric charges by a suction method is +10 to +20 μc/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry two-component developer and a carrier for developing an electrostatic latent image formed by electrophotography.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method such as an electrostatic copying machine or a laser printer, a toner for developing an electrostatic latent image on the surface of a photoreceptor and the toner are frictionally charged and adsorbed. In this state, a two-component developer containing a magnetic carrier that rotates inside the developing device and supplies toner to the photoconductor is used. For the purpose of preventing spent toner from adhering to the carrier and adjusting the charging characteristics, coating the surface of the carrier with styrene acrylic resin, acrylic resin, styrene resin, silicone resin, acrylic modified silicone resin, fluororesin, etc. is generally performed. Is being done. Examples of the coating resin having good anti-spent properties include silicone resin and fluororesin having a low surface tension. Fluororesins themselves tend to be negatively charged and should be suitable for positively charged toners. However, fluororesins are difficult to use because of their drawbacks such as easy detachment due to their binding to the carrier core. Silicone resin has excellent anti-spent properties and binding force with the carrier core, but if the coating amount is large, the carrier resistance increases and the image density decreases.On the other hand, if the coating amount is small, the film peels due to repeated use and the developer It is difficult to coat properly, such as shortening the service life.

In order to improve the quality of a formed image, reduce toner scattering and extend the life of a developer, it is important that the amount of triboelectric charge of the toner is within an appropriate range and does not fluctuate over a long period of use. Generally, the triboelectric charge is +10 μc
/ G or less, a sufficient image density can be obtained, but the toner is easily detached from the carrier, and toner scattering and fog are deteriorated. When the triboelectric charge is +20 μc / g or more, the toner does not scatter, but a sufficient image density cannot be obtained. In response to such a demand, a two-component developer in which a positively charged toner and a silicon-coated carrier are combined has been proposed in which the average particle size of the carrier is 40 to 60 μm (Japanese Patent Application Laid-Open No. 9-90).
43910). However, there is a close relationship between the carrier particle size and the so-called carrier pulling and carrier jumping phenomena.
It is well known that it easily adheres to the photoreceptor due to the attractive force of the electrostatic force with the photoreceptor against the magnetic binding force with the developing sleeve and the repulsive force by the bias voltage from the developing sleeve. is there.

Usually, the particle size of the carrier is adjusted by sieving with a mesh. However, it is difficult to cut the small particle size of 44 μm or less by sieving while maintaining the average particle size at 40 to 60 μm. In addition, the carrier of 40 to 60 μm generally has low fluidity, and when a developer is used with a high toner concentration in order to obtain a sufficient image density, the fluidity of the developer itself is reduced, and the toner charge amount due to poor mixing of the replenishment toner is reduced. Due to the decrease, toner scattering, fogging and the like are likely to occur. The fact is that the higher the copying speed, the lower the mixing characteristics of the replenishment toner, and the widespread use in high-speed machines has not progressed.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned prior art, and in a developer in which a positively chargeable toner and a resin-coated carrier are combined, the amount of triboelectric charge can be increased over a long period of time from the initial use. It is an object of the present invention to provide a two-component developer which can be stably maintained at an appropriate level.

[0006]

According to the present invention, there is provided a two-component developer comprising a silicone resin-coated carrier and a positively-chargeable toner. Having an average particle size of 60 to 110 μm, an average thickness of the resin coating layer of 0.1 to 0.3 μm, and a volume resistivity of 1.5 × 10 ^8.
1.5 × 10 ¹¹ Ωcm, and the triboelectric charge amount is -10
It is characterized by being a carrier for developing an electrostatic latent image of −20 μC / g. According to a second aspect of the present invention, there is provided the electrostatic latent image developing carrier according to the first aspect, wherein the content ratio of the small particle size portion of 44 μm or less is 2 wt% or less.

According to a third aspect of the present invention, there is provided a two-component developer comprising a silicone resin-coated carrier and a positively chargeable toner, wherein the silicon-coated carrier has an average particle size of 60 to 11%.
0 μm, the average thickness of the resin coating layer is 0.1 to 0.3 μm
m, the volume resistivity of the carrier is 1.5 × 10 ⁸ to 1.5
× 10 ¹¹ Ωcm, and the triboelectric charge amount is +10 to +20 μ
C / g is an electrostatic latent image developer.
According to a fourth aspect of the present invention, the toner content is 3.0 to 5.0 wt.
%, And is the electrostatic latent image developer according to claim 3. Conventionally, as a device for measuring the triboelectric charge amount of a two-component developer, a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical has been used. This apparatus is a method in which only the toner is blown out of the Faraday gauge through a mesh with nitrogen gas. As a result, the so-called overcharged toner, which is relatively firmly electrostatically adsorbed on the carrier surface, is also blown off and added, so that the measured value becomes higher than the toner charge amount actually used for development. is there. Although there is a method of lowering the blow pressure in order to prevent the above-mentioned overcharged toner from being blown, the measured value is not stable because uniform blow cannot be performed.

Therefore, the present inventors can measure the charge amount of only the effective toner to be used for development by using a suction type triboelectric charge amount measuring apparatus STC-50 (manufactured by Sankyo Piotech). Was found. This is because air suction through the mesh can softly separate and suction only the toner in the developer. FIG. 3 is a view schematically showing the suction-type triboelectric charge amount measuring apparatus STC-50, and FIG. 4 is a view schematically showing the measuring section shown in FIG. This device includes a balance 9, a measuring unit 10, a control unit 11, a charge meter 12, and a suction pump 13. The measuring unit 10 has a shield case 14, and a Faraday gauge 16 is installed inside the shield case 14 via an insulating material 15. A ventilation hole 18 to which a dust screen 17 is attached is provided at an upper portion of the shield case 14, and a mesh 19 is provided at a bottom portion of the Faraday gauge 16, so that the suction pump 13 sucks the air from a lower side surface of the shield case 14. It has become. The suction pressure is detected by a pressure sensor (not shown) from the side surface of the shield case 14 and is controlled by the control unit 11. The Faraday gauge 16 is electrically connected to the charge meter 12,
The charge amount of the measurement sample in the Faraday gauge 16 is measured by the charge amount meter 12.

In this measuring device, first, the weighed developer sample is put into the Faraday gauge 16 of the measuring section 10 shown in FIG. The charge amount after suction is read, and the mass of the sample remaining in the Faraday gauge 16 is measured. The measured value of the mass is regarded as the carrier mass, and the toner triboelectric charge is calculated according to the following equation. Toner triboelectric charge (μC / g) = read charge (μC)
/ {Sample mass before suction (g) -Sample mass after suction (g)} The measurement environment is 20 ± 2 ° C., 65 ± 5% RH,
Stainless steel (400 mesh) is used for the mesh of FIG. 2, the suction pressure is 0.3 KPa, and the suction time is 60 seconds.
c.

The frictional charge amount of the carrier is calculated by the following equation, and has a value of the opposite polarity which is substantially equal to the absolute value of the toner charge amount. Carrier triboelectric charge (μC / g) = read charge (μC / g)
C) / Sample mass after suction (g) In the two-component developer of the present invention, the toner triboelectric charge needs to be in the range of +10 to 20 μC / g. If the toner triboelectric charge is less than +10 μC / g, image fogging and toner scattering will occur. On the other hand, if the toner triboelectric charge is larger than +20 μC / g, the image density becomes low.

The triboelectric charge of the carrier of the present invention is a value of the opposite polarity which is substantially equal to the absolute value of the triboelectric charge of the toner used in the developer of the present invention.
It should be in the range of μC / g. The triboelectric charge of the carrier can be adjusted by changing the heat treatment conditions of the coat layer described later, and the charge is increased by setting the heat treatment temperature to be higher or making the heat treatment time longer.
In the present invention, among the coating resins, a silicone resin having excellent stability in maintaining the charge amount in repeated use and a long developer life is used. The present inventors have found that the average particle size of the silicon-coated carrier is preferably in the range of 60 to 110 μm. Compared to a small particle size carrier having an average particle size of less than 60 μm, the carrier particle size of the present invention has the following advantages.

First, since the specific surface area is small and the flowability is excellent, the dispersion state of the carrier is good in the resin coating step, and the coating resin is easily applied uniformly to the carrier particles. The generation is small and the heat conduction efficiency to the carrier particles is excellent, and a strong binding property can be obtained with a smaller coating film thickness. Second, the mechanical stress to the mixing and stirring in the developing device during copying is small, and the coat layer is not easily peeled off. Third, due to the synergistic effects of the high fluidity of the carrier itself and the small specific surface area of the developer used at a low toner concentration, the toner is excellent in the toner mixing characteristics to the developer and the toner is hardly scattered. Fourth, the phenomenon of carrier adhesion to the photoconductor can be effectively prevented.

When the average particle diameter of the carrier is less than 60 μm,
The portion having a small particle diameter of 44 μm or less which is difficult to remove easily adheres to the photoreceptor, causing the following problems. If the adhered carrier remains on the photoreceptor without being transferred, the cleaning unit rubs the photoreceptor with a streak and damages the photoreceptor in a streak shape, and black stripe-like copy stains are continuously generated. In addition, since the attached carrier exists between the photoreceptor and the transfer paper with a certain thickness, the toner in the image area within a certain range cannot be transferred around the carrier, resulting in a white drop. If it exceeds 110 μm, the effective specific surface area of the carrier is limited, and fog and toner scattering may occur due to poor charging of the replenishment toner.

The thickness of the coating resin is 0.10 to 0.30 μm
The range of m is preferred. Increasing the film thickness causes a decrease in charging characteristics and an increase in electric resistance, and decreasing the film thickness causes an increase in the charge amount and a decrease in electric resistance. Coating thickness is 0.1
If it is less than 0 μm, the image density (ID) can be satisfied, but a pre-drawing phenomenon, toner scattering and fog occur in a high humidity environment. Although the initial charge amount is high, since the volume specific electric resistance value of the carrier is less than 1.5 × 10 ⁷ Ωcm, the developing electrode effect of the developer becomes excessive, and the toner developing amount rises more than necessary and the development is performed. This is because a part of the developing toner on the image is spilled in the rubbing direction of the magnetic brush of the agent to cause blurring of the image. In addition, in repeated use for a long period of time, the surface of the core material is exposed due to peeling of the coat, so that the effect of preventing spent is impaired and the charge amount is reduced, so that the durability is reduced.
In addition, when the carrier is charged from the toner and is developed together with the toner in the image area and the adhered carrier remains on the photoreceptor without being transferred, the photoreceptor is damaged in a streak shape when rubbed with a cleaning blade. Copy smearing occurs continuously. In addition, since the attached carrier exists between the photoreceptor and the transfer paper with a certain thickness, the toner in the image area within a certain range cannot be transferred around the carrier, resulting in a white drop.

If the coating thickness exceeds 0.30 μm,
Rear volume specific resistance 1.5 × 10 ¹¹Ωcm or less
And the image density decreases. Also charged
Rising performance (the ratio of the initial charge of mixing to the saturation charge)
Rate), the charge amount in repeated use
Is liable to gradually decrease and fog and toner scattering are likely to occur. Carry
A volume resistivity is 6 × 10¹¹Within the range of Ωcm,
Obtain a particularly preferred carrier in the above carrier characteristics
be able to. The toner concentration is in the range of 3.0 to 5.0 wt%.
Enclosures are preferred. If it is less than 3.0% by weight, the image density is low.
Over 5.0 wt%, toner scattering, fog, high humidity
It is prone to environmental pulling phenomena.

The magnetic particles constituting the carrier include, for example, particles of iron, oxidized iron, reduced iron, ferrite, magnetite, copper, silicon steel, nickel, cobalt, etc .; Examples include alloy particles, particles obtained by dispersing fine particles of each of the above materials in a binder resin, and the like. Among them, ferrite-based particles which have a small rate of change in electrical resistance due to environmental and temporal changes and can form soft spikes which come into contact with the surface of the photoreceptor when a magnetic field is applied in the developing device are preferably used.
Ferrite-based particles include zinc-based ferrite, nickel-based ferrite, copper-based ferrite, nickel-zinc-based ferrite, manganese-magnesium-based ferrite, and copper-based ferrite.
Examples of the particles include magnesium ferrite, manganese-zinc ferrite, and manganese-copper-zinc ferrite.

As the silicone resin for carrier coating,
Toray Dow Corning Silicone SR2400, S
R2406, KR9706, KR27 manufactured by Shin-Etsu Chemical Co., Ltd.
1, KR255, KR251 and the like. As the resin coating method, a fluidized-bed spray drying method, an immersion method, and the like are used. The carrier used in the present invention is about 150-250 after the core agent is coated with silicone resin.
By performing high-temperature treatment at a temperature of 1 to 3 hours at a temperature of 1 to 3 hours and performing a sufficient curing reaction of the silicone resin coat layer, a long life performance excellent in abrasion resistance and anti-spent properties can be obtained even in long-term repeated use. The triboelectric charge amount of the carrier can be adjusted by the heat treatment conditions, and the charge amount can be increased and adjusted by increasing the heat treatment time or extending the heat treatment time.

The toner in the developer of the present invention is obtained by forming a core particle by mixing, melt-kneading, pulverizing and classifying a binder resin, a wax, a colorant, a charge controlling agent and the like at a desired mixing ratio. It is made by externally adding various additives in order to give fluidity, chargeability, photoreceptor cleaning effects, and the like. Examples of the binder resin for toner used in the present invention include polystyrene, poly-α-methylstyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid. Copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, etc.), styrene-methacrylate copolymer (Styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer), styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylate copolymer Styrene-based resin such as styrene or styrene-based resin Homopolymer or copolymer), ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, rosin-modified maleic resin, epoxy resin,
Polyester resins and the like, which may be used alone or
A mixture of two or more types is used.

The releasing agent for toner (offset preventing agent) used in the present invention includes, for example, aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, Various waxes can be mentioned. Among them, the weight average molecular weight is 1000-1
Aliphatic hydrocarbons of about 0000 are preferred. Specifically, low molecular weight polyethylene, low molecular weight polypropylene,
One or a combination of two or more of paraffin wax, a low-molecular-weight olefin polymer composed of olefin units having 4 or more carbon atoms is suitable. As the colorant for the toner used in the present invention, besides carbon black, a color pigment and a color dye which can be used for ordinary color toners can be used. As the carbon black, channel black, gas furnace black, oil furnace black, thermal black, acetylene black and the like are used. As the colorant for the color, an azo or benzidine pigment (for yellow toner), a quinacridone pigment (for magenta toner), a copper phthalocyanine pigment (for cyan toner), or the like is used in the present invention. Examples of the charge control agent for controlling positive charges include nigrosine dyes, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and the like, and quaternary ammonium salts. Fine particles such as hydrophobic silica, titanium oxide, alumina, magnetite, and acrylic resin powder are used as other externally-added treating agents.

The average particle size of the carrier of the present invention can be determined by a sieving method (Nikkan Kogyo Shimbun;
P54). For sieving, five types of meshes having nominal dimensions of 44, 63, 74, 105 and 149 μm and a Ro-Tap shaker were used.
The carrier specific surface area of the present invention was measured by a cantasorb (BET method measuring device manufactured by Yuasa Ionics Co., Ltd., outlined in Nikkan Kogyo Shimbun: Powder Fluid Measurement Handbook P101-102). The film thickness of the carrier-coated resin of the present invention can be obtained from the following equation using the specific surface area of the carrier (cm ² / g), the amount of the resin coated per gram of the carrier (g), and the specific gravity of the resin (≒ 1 g / cm ³ ). Resin coat film thickness (cm) = [resin coat amount (g / carrier g) / resin specific gravity (g / cm ³ )] / specific surface area (cm ² /
g) The carrier resistance of the present invention can be measured using the bridge-type electric resistance measuring device shown in FIGS. 1 and 2 and a super insulation meter Model SM-5E (manufactured by Toa Denpa Kogyo Co., Ltd.). Since the static resistance is measured in a state where the carrier particles are connected in a chain in a magnetic field, the electric resistance of the carrier can be measured as a value that is approximated by a magnetic brush and is not affected by development conditions. For the sake of understanding in the drawings, the dimensions do not always correspond to the sizes in the drawings. As shown, copper electrode plates 1 and 2 are fixed on the upper surface of the acrylic resin substrate 8 in parallel with a gap of 2.0 mm therebetween. 1000 on the back side of copper electrodes 1 and 2
A Gaussian magnet is provided to create a magnetic field between the electrodes. When 0.2 g of the carrier sample is set between the electrodes, the carrier sample is filled as shown in 7 with a chain structure according to the lines of magnetic force. 10 seconds after applying a DC voltage of 1000 V to terminals 5 and 6, the carrier electrical resistance value is measured using a super-insulation meter.
Read with Model SM-5E (Toa Denpa Kogyo).

The read value is determined from the magnet area (3 cm ² ) and the inter-electrode distance (2 mm) using the following formula to determine the volume specific resistance. Volume specific resistance (Ωcm) = resistance value (Ω) × (3 cm ² /
0.2cm) The measurement environment was 20 ± 2 ° C and 65 ± 5% RH, and the temperature of the carrier sample and the measuring instrument was controlled for at least 8 hours.
Perform humidity control.

[0022]

Next, the present invention will be described specifically with reference to examples. Example of toner production ・ Styrene / n-butyl methacrylate copolymer 100 parts by weight (weight average molecular weight 300,000, number average molecular weight 8,000) ・ NP055 (low molecular weight polypropylene manufactured by Mitsui Chemicals, Inc.) 2 parts by weight ・ Printex 90 (Degussa) 6 parts by weight ・ Nigrosine dye 3 parts by weight Mixing (Henschel mixer) → Kneading (Twin screw extruder) → Coarse pulverization (Hammer mill) → Fine pulverization (Jet mill) → Classification (Wind classification) ), Toner particles having an average diameter of 9.5 μm were obtained.

-100 parts by weight of toner particles-0.3 parts by weight of silica (aminohexyltriethoxysilane treated product, average diameter: 10 nm)-0.2 parts by weight of titanium oxide (average diameter: 50 nm) 0.2 parts by weight of the above material, Henschel mixer At high speed to obtain a product toner. [Example 1] The average particle diameter was 90 µm and the saturation magnetization was 60 emu.
/ G of ferrite core material is spray-coated with a coating agent comprising the following components using a fluidized bed coating apparatus, and then heated to 210 ° C.
For 90 minutes to produce a carrier. * Coating agent KR271 (Straight silicon resin manufactured by Shin-Etsu Chemical Co., Ltd., solid content: 50 wt%) 9.0 parts by weight Printex L (carbon black manufactured by Degussa) 0.045 parts by weight Solvent (toluene) 500 parts by weight Carrier specific surface area The average thickness of the carrier coat layer calculated from the amount of the coat resin is 0.2 μm, and the volume resistivity of the carrier measured by the bridge method is 7.5 ×.
It was 10 ⁹ Ωcm. 95 parts by weight of this carrier and 5 parts by weight of positively charged toner are mixed with a laboratory mixer (manufactured by Hosokawa Micron)
And a developer was manufactured, and the charge amount of the toner was measured to be +15.3 μC / g. Table 1 shows the results of Example 1 described above. [Example 2] A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the heat treatment temperature was changed to 200 ° C.

The average thickness of the carrier coat layer calculated from the specific surface area of the carrier and the amount of the coating resin is 0.2 μm.
The volume specific resistance of the carrier measured by the bridge method was 3 × 10 ⁹ Ωcm. 95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was +12.9 μC / g. Example 2 above
Table 1 shows the results. [Example 3] The heat treatment temperature was set to 220 ° C and the heat treatment time was set to 1
A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the time was changed to 20 minutes.

The average thickness of the carrier obtained by calculation from the specific surface area of the carrier and the amount of the coating resin was 0.2 μm, and the volume resistivity of the carrier measured by the bridge method was 1.05 × 10 ¹⁰ Ωcm. Was. 95 parts by weight of this carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was +19.7 μC / g. Table 1 shows the results of Example 3 described above. [Example 4] The heat treatment temperature was 225 ° C and the heat treatment time was 1
The same material composition and production as in Example 1 except that the particle size of the ferrite core material was changed to 65 μm, the added amount of the silicon resin KR251 was changed to 20 parts by weight, and the added amount of carbon was changed to 0.1 parts by weight in 20 minutes. The carrier was manufactured by the method. The average film thickness of the carrier calculated from the specific surface area of the carrier and the amount of the coating resin was 0.22 μm, and the volume resistivity of the carrier measured by the bridge method was 1.05 × 10 ¹⁰ Ωcm.

95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured to be +17.2.
μC / g. Table 1 shows the results of Example 4 described above. [Example 5] The heat treatment temperature was 225 ° C and the heat treatment time was 1
The same material composition as in Example 1 except that the particle size of the ferrite core material was changed to 105 μm, the addition amount of the silicon resin KR251 to 6.5 parts by weight, and the addition amount of carbon to 0.032 parts by weight in 20 minutes. The carrier was manufactured by the manufacturing method. The average film thickness of the carrier calculated from the specific surface area of the carrier and the amount of the coating resin is 0.2 μm, and the volume specific resistance of the carrier measured by the bridge method is 6 × 10 ⁹ Ω.
cm. 95 parts by weight of the present carrier and positively charged toner 5
The parts by weight were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured.
It was 1 μC / g. Table 1 shows the results of Example 5 described above. Example 6 The amount of the silicone resin KR251 was adjusted to 5.
A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the addition amount of carbon black was changed to 0 part by weight, the amount of carbon black added was changed to 0.025 part by weight, and the heat treatment time was changed to 105 minutes. The average film thickness of the carrier calculated from the specific surface area of the carrier and the amount of the coating resin is 0.11 μm, and the volume specific resistance of the carrier measured by the bridge method is 4.5 × 10 ⁸ Ω.
cm. 95 parts by weight of the present carrier and positively charged toner 5
The parts by weight were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured.
It was 9 μC / g. Table 1 shows the results of Example 6 described above. [Example 7] The addition amount of the silicone resin KR251 was 13
A carrier was produced by the same material composition and production method as in Production Example 1 except that the weight parts and the carbon addition amount were changed to 0.065 parts by weight. The average film thickness of the carrier calculated from the specific surface area of the carrier and the amount of the coating resin is 0.3 μm, and the volume specific resistance of the carrier measured by the bridge method is 7.5 ×.
It was 10 ¹⁰ Ωcm. 95 parts by weight of this carrier and 5 parts by weight of positively charged toner are mixed with a laboratory mixer (manufactured by Hosokawa Micron)
And a developer was manufactured, and the charge amount of the toner was measured to be +13.3 μc / g. Table 1 shows the results of Example 7 described above. Example 8 The particle size of the ferrite core material was 65 μm, 44
A carrier was manufactured by the same material composition and manufacturing method as in Example 4 except that the content ratio of μm or less was 2.5 wt%. The average film pressure of the carrier calculated from the specific surface area of the carrier and the amount of the coating resin is 0.2 μm, and the volume resistivity of the carrier measured by the bridge method is 1.1 × 10 ¹⁰ Ωc.
m.

95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured to be +17.5.
μC / g. Table 1 shows the results of Example 8 described above. Comparative Example 1 The particle size of the ferrite core material was 45 μm, the addition amount of silicone resin KR251 was 24 parts by weight, the addition amount of carbon black was 0.12 parts by weight, and the heat treatment temperature was 22.
A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the heat treatment time was changed to 0 ° C. and the heat treatment time was changed to 120 minutes.

The average thickness of the carrier obtained by calculation from the carrier particle size and the amount of the coating resin is 0.18 μm, and the volume specific resistance of the carrier measured by the bridge method is 1.35.
× 10 ¹⁰ Ω. 95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured.
It was 18.5 μC / g. Table 2 shows the results of Comparative Example 1 described above. [Comparative Example 2] The particle size of the ferrite core material was 130 µm, the addition amount of silicone resin KR251 was 4.5 parts by weight, the addition amount of carbon black was 0.022 parts by weight, the heat treatment temperature was 220 ° C, and the heat treatment time was 120. A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the carrier was changed.

By calculation from the carrier particle size and the coating resin amount,
The obtained average thickness of the carrier is 0.2 μm,
The volume specific resistance of the carrier measured by the ridge method is 4.5 ×
10 ⁹Ωcm. 95 parts by weight of this carrier and positive charge
Lab mixer (made by Hosokawa Micron) with 5 parts by weight of toner
Was mixed to produce a developer and the toner charge was measured.
+10.6 μC / g. The results of Comparative Example 2 above
It is described in Table 2. [Comparative Example 3] The heat treatment temperature was set to 180 ° C and the heat treatment time was set to 6
Except for changing to 0 minutes, the same material composition and
The carrier was manufactured by a manufacturing method. Carrier specific surface area and coat
The average film thickness of the carrier calculated from the amount of the resin is 0.
2 μm, the volume of the carrier measured by the bridge method
Individual resistance is 1.2 × 10⁹Ωcm.

95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the charge amount of the toner was measured.
C / g. Table 2 shows the results of Comparative Example 3 described above. [Comparative Example 4] The heat treatment temperature was 230 ° C and the heat treatment time was 1
Except for changing to 50 minutes, the same material composition as in Example 1,
The carrier was manufactured by the manufacturing method. The average thickness of the carrier obtained by calculation from the carrier specific surface area and the amount of the coating resin,
The carrier had a volume resistivity of 1.5 × 10 ¹⁰ Ωcm as measured by the bridge method.

95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured to be +21.8.
μC / g. Table 2 shows the results of Comparative Example 4 described above. [Comparative Example 5] The addition amount of the silicone resin KR251 was 3.
A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the amount of carbon added was changed to 0 parts by weight, the amount of carbon added was changed to 0.015 parts by weight, and the heat treatment time was changed to 105 minutes. The average film thickness of the carrier calculated from the carrier particle size and the coating resin amount was 0.07 μm, and the volume resistivity of the carrier measured by the bridge method was 1.2 × 10 ⁸ Ωcm.

95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was measured to be +18.1.
μC / g. Table 2 shows the results of Comparative Example 5 described above. [Comparative Example 6] The addition amount of the silicone resin KR251 was 18
A carrier was manufactured by the same material composition and manufacturing method as in Example 1 except that the amount of carbon added was changed to 0.09 parts by weight, and the heat treatment temperature was changed to 220 minutes. The average film thickness of the carrier calculated from the carrier particle size and the coating resin amount is
The carrier had a volume specific resistance of 4.5 × 10 ¹¹ Ωcm as measured by the bridge method. 95 parts by weight of the carrier and 5 parts by weight of the positively charged toner were mixed with a laboratory mixer (manufactured by Hosokawa Micron) to produce a developer, and the toner charge amount was +11.9 μC / g. Table 2 shows the results of Comparative Example 6 described above.

Using nine types of developers comprising the positively-chargeable toner and the carrier obtained as described above, a copy test of 100,000 sheets was performed using a Cleage 7325 copying machine manufactured by Mita Kogyo. (Note: In Comparative Examples 1, 2, 3, and 4, the satisfactory initial image quality was not obtained as described below, and therefore, only the initial copy was stopped.) The results are shown in Tables 1 and 2. In Tables 1 and 2, the charge amount at the initial stage and after 100,000 sheets and the toner concentration after 100,000 sheets are measured by a suction-type frictional charge amount measuring apparatus:
It measured using STC-50 type (made by Sankyo Piotech). The measurement conditions were a suction pressure of 0.3 kPa and a suction time of 60
Seconds. Similarly, the image densities (I
D) and fog density (FD) were measured using a reflection density measuring device manufactured by Nippon Denshoku Co., Ltd. The image density is a measured value of the density of a solid black portion. The fog density is obtained by subtracting the reflection density of blank white paper before copying from the reflection density of the non-image portion after copying.
Regarding the image density, 1.3 or more was evaluated as acceptable and less than 1.3 was evaluated as unacceptable. Regarding the fog density, 0.005 or less was acceptable and 0.006 or more was not acceptable.

The forward pulling was evaluated by bleeding due to toner scattering in front of the solid image when the copying machine was left in an environment of 28 ° C. and 90% RH and copying was resumed 12 hours later.
The image blank was evaluated based on the presence or absence of a blank image in the solid image obtained from the entire black paper chart. The stain on the copy after 200,000 copies was evaluated based on whether toner scattered from the developer on the developing sleeve fell to the transfer section of the transfer paper and caused stain on the back of the copy. The black streak is an image defect that occurs when the carrier that has caught between the cleaning blade and the photosensitive drum in the cleaning section damages the photosensitive member circumferentially. Copy test results: Table 1 shows the copy results of the examples, and Table 2 shows the copy results of the comparative examples.

Examples 1 to 7: Good image quality was maintained throughout the initial to 200,000 copies. Example 8 Although image white spots due to carrier pulling were slightly confirmed, good image quality was obtained. Comparative Example 1 The initial image density was 1.21 and did not satisfy the standard (1.3 or more), and image white spots due to carrier pulling were confirmed. Comparative Example 2 Initial fog density is 0.011 and is standard (0.005 or less)
Was not satisfied, and a forward drawing occurred in a high humidity environment (28 ° C., 90% RH). Comparative Example 3 The initial charge amount was low at +8.5 μC / g, the fog density was 0.010, which did not satisfy the standard (0.005 or less), and the forward charge was low in a high humidity environment (28 ° C., 90% RH). occured. Comparative Example 4 The initial charge amount was high at +21.8 μC / g, and the image density was 1.23, which did not satisfy the standard (1.3 or more). Comparative Example 5 Although the initial charge amount was +18.1 μC / g, there was no problem in the image density and the fog density in the initial stage.
90% RH).

After 200,000 sheets, the charge amount is +9.1 μC / g.
Fog density above the standard (0.005
0.009) for: Further, after copying 100,000 sheets, the toner was scattered from the developer and the back of the copy due to the scattered toner accumulated on the lower side of the developing machine was observed. Further, black streaks were observed in the circumferential direction of the photoconductor drum, and scratches were confirmed at the photoconductor corresponding to the black streaks. Comparative Example 6 The initial image density was 1.21 and did not satisfy the standard (1.3 or more). After 200,000 sheets, the charge amount decreased to +8.3 μC / g, and a fog density higher than the standard (0.012 for 0.005 or less) was generated. In addition, a lot of toner scattered from the developer, and the back of the copy due to the scattered toner deposited on the lower side of the developing machine was observed.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

As described above, in a two-component developer composed of a positively chargeable toner and a magnetic carrier, the amount of triboelectric charge stably changes even after repeated use for a long time, and good image quality including image density and fog density is maintained. In addition, image white spots due to carrier development adhesion on the photoreceptor, image black streaks due to photoreceptor scratches are effectively prevented, and copy contamination due to toner scattering inside the machine,
Image bleeding and bleeding in a high humidity environment are effectively prevented.

[Brief description of the drawings]

FIG. 1 A jig for measuring the electrical resistance of a carrier and a super insulation meter as viewed from the front.

FIG. 2 A jig for measuring the electrical resistance of a carrier and a super insulation meter viewed from directly above.

FIG. 3 is a schematic diagram of a suction-type frictional charge measuring device.

FIG. 4 is a schematic diagram of a measuring unit of the measuring device of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Copper plate electrode (left) 2 Copper plate electrode (right) 3 Magnet (left) 4 Magnet (right) 5 Terminal (left) 6 Terminal (right) 7 Carrier particles filled between electrodes with magnets attached on the back side 8 Acrylic Resin base 9 Balance 10 Measuring unit 11 Control unit 12 Charge meter 13 Suction pump 14 Shield case 15 Insulation material 16 Faraday gauge 17 Dust wire mesh 18 Vent hole 19 mesh

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 7, 2000 (200.7.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

2. A two-component developer comprising a silicon resin-coated carrier and a positively chargeable toner, wherein the silicon-coated carrier has an average particle size of 60 to 110 μm and an average film thickness of the resin coating layer of 0.1 to 0.1 μm. 0.3 μm, 100 of carrier
A volume resistivity value of 1.5 × 10 ⁸ to 1.5 × 10 ¹¹ Ωcm after 10 seconds from application of a DC voltage of 0 V, and 4
An electrostatic latent image developer characterized in that the content ratio of a small particle size portion of 4 μm or less is 2 wt% or less , and the toner triboelectric charge is +10 to +20 μC / g.

3. The electrostatic latent image developer according to claim 2 , wherein the toner content is 3.0 to 5.0 wt%.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

According to the present invention, there is provided a two-component developer comprising a silicone resin-coated carrier and a positively-chargeable toner. A resin coating layer consisting of: having an average particle diameter of 60 to 110 μm, an average thickness of the resin coating layer of 0.1 to 0.3 μm, and applying a DC voltage of 1000 V
The volume resistivity after 10 seconds is 1.5 × 10 ⁸ to 1.5 ×
10 ¹¹ Ωcm, content ratio of small particle size of 44 μm or less
Is 2 wt% or less , and the triboelectric charge amount is −10 to −20 μm.
It is a carrier for developing an electrostatic latent image having a C / g.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

According to a second aspect of the present invention, there is provided a two-component developer comprising a silicone resin-coated carrier and a positively-chargeable toner, wherein the silicon-coated carrier has an average particle diameter of 60 to 11.
0 μm, the average thickness of the resin coating layer is 0.1 to 0.3 μm
m, 10 seconds after applying a DC voltage of 1000 V of the carrier
The subsequent volume resistivity value is 1.5 × 10 ⁸ to 1.5 × 10 ¹¹
Ωcm , content ratio of the small particle size portion of the carrier of 44 μm or less
Rate is 2 wt% or less , and the toner triboelectric charge amount is +10 to
The electrostatic latent image developer is +20 μC / g. According to the third aspect of the present invention, the toner content is 3.0 to 3.0.
3. The electrostatic latent image developer according to claim 2 , wherein the amount is 5.0 wt%. Conventionally, as a device for measuring the triboelectric charge amount of a two-component developer, a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical has been used. This apparatus is a method in which only the toner is blown out of the Faraday gauge through a mesh with nitrogen gas. As a result, the so-called overcharged toner, which is relatively firmly electrostatically adsorbed on the carrier surface, is also blown off and added, so that the measured value becomes higher than the toner charge amount actually used for development. is there. Although there is a method of lowering the blow pressure in order to prevent the above-mentioned overcharged toner from being blown, the measured value is not stable because uniform blow cannot be performed.

Claims (4)

[Claims] 1. A carrier core material having a resin coat layer made of a cured silicone resin on the surface thereof, and having an average particle size of 60 to 1
10 μm, the average thickness of the resin coat layer is 0.1 to 0.3 μm
m, volume specific resistance is 1.5 × 10 ⁸ to 1.5 × 10 ¹¹
A carrier for developing an electrostatic latent image, wherein the carrier is Ωcm and the triboelectric charge amount is -10 to -20 μC / g. 2. The method according to claim 1, wherein the content ratio of the small particle size portion of 44 μm or less is 2
The carrier for developing an electrostatic latent image according to claim 1, wherein the carrier is not more than wt%. 3. A two-component developer comprising a silicone resin-coated carrier and a positively chargeable toner, wherein the silicon-coated carrier has an average particle size of 60 to 110 μm and an average thickness of the resin coating layer of 0.1 to 0.1 μm. An electrostatic latent image developing device characterized in that the carrier has a volume resistivity of 1.5 × 10 ⁸ to 1.5 × 10 ¹¹ Ωcm and a toner triboelectric charge of +10 to +20 μC / g. Agent. 4. The electrostatic latent image developer according to claim 3, wherein the toner content is 3.0 to 5.0 wt%.