JPH035765A - Developer - Google Patents

Abstract

PURPOSE:To improve image quality such as high image density and gradation reproducibility by using carbon black for a toner coloring agent and preparing carrier particles formed by coating a core material with a styrene/acrylic copolymer and a developer. CONSTITUTION:The carbon black used as the coloring agent has 50 to 70 mmu average grain size, 10 to 40 m2/g surface area, 50 to 100 cc/100 g-DBP oil absorption and 6.0 to 9.0 pH value. The carrier is formed by using ferrite particles for the core material and coating the core material with the copolymer formed from styrene and acrylic acid or methacrylic or the lower ester thereof and the compd. expressed by formula I. The copied images which have high image densities and sharp gradation characteristics and are free from fogging in non- image parts are obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry two-component developer for electrophotography, and in particular uses carbon black, which has excellent coloring power, as a toner colorant to produce a clear color tone and This invention relates to a dry two-component developer capable of maintaining high image density.

[Prior Art] In electrophotography, an electrostatic latent image is usually formed by imparting a uniform surface charge to a photoconductive photoreceptor and then performing image exposure, and this electrostatic latent image is developed. A visible image is formed by developing with an agent.

Methods for developing such electrostatic latent images can be broadly classified into liquid development methods and dry development methods. The liquid development method is a method in which development is performed using a liquid developer consisting of various pigments, materials, and dyes dispersed as fine particles in an insulating organic liquid.
The dry development method is a method using a fine powder called a toner, which is made by dispersing a colorant in a resin. In the latter method, a toner is charged to a polarity opposite to that of the electrostatic latent image, and the charged toner is electrostatically attached to the electrostatic latent image to form a visible image.

This dry development method includes a method using a so-called one-component developer whose main component is only the toner, and a method using a two-component developer in which a carrier such as iron powder or glass beads is mixed with the toner. The former includes the cloud method described in U.S. Pat. No. 2,784,109, and the latter includes the cascade method described in U.S. Pat. No. 2.6111.552, U.S. Pat. Examples include the magnetic brush method described in No. 063, and the touchdown method. The visible image formed by toner adhering to the electrostatic latent image by these developing methods is directly placed on the photoreceptor,
or after being transferred onto paper or other image support, heat, pressure,
It is fixed by solvent vapor or the like.

As the developing method according to the present invention, from the above-mentioned developing method,
Examples include magnetic brush method and cascade method.

The image quality of a visible image obtained by a two-component developer used in this developing method is determined by gradation, resolution, sharpness, etc., but is mostly evaluated by image density.

Regarding image density, there are other factors such as the triboelectricity of toner and carrier, sustainability of appropriate toner density during toner replenishment, and agitation of developer in the developing machine.
The disadvantages of two-component developers are that they suffer from charging deterioration in durability tests, lack stability such as decline in image density, and the resulting image density is naturally low.

[Problems to be Solved by the Invention] Conventionally, carbon black has been often used as a black coloring agent in these two-component developers made of toner and carrier. As an example of use, JP-A-59-2184
As disclosed in Japanese Patent Application No. 63, etc., in this case, the toner contains carbon pretta as a coloring agent at a ratio of 15 IIi amount % or more based on the total toner amount, and development and development.
When obtaining a visible image through the transfer and fixing process, there may be fog caused by toner adhesion to non-image areas, a decrease in dispersibility,
There is a difference in the amount of triboelectric charge between low temperature, low humidity, high temperature and high temperature environments. Moreover, in JP-A No. 60-129756, etc., the content of carbon black is 0.1 to 2.01 parts per 100 g of binder resin, and with these contents, the image In addition to using carbon black as the colorant, which causes problems such as a decrease in concentration and the formation of streaks, the binder resin contains a colorant of 21m or more and a charge control agent, and fluidity improvers are added. Although prior art technology has been disclosed, such as black toner that is made of black toner, the current situation is that it causes problems such as the difficulty of delicate color tone control and the requirement for high precision in the copying process, resulting in a decline in copy quality. .

SUMMARY OF THE INVENTION Therefore, in order to solve the above-mentioned problems, an object of the present invention is to develop a two-component system that can provide a high image density, have clear gradation, and obtain a copy image with no fog in non-image areas. The goal is to provide medicine.

[Means and effects for solving the problems] The present invention provides a developer comprising at least a toner having carbon black as a colorant and a carrier, wherein the carbon black has an average particle size of 50 to 70 g and a surface area of 10 to 40 m2/ g, oil absorption 50-100cc/10Og-DBP, pH value 6
．． 0 to 9.0, and the carrier uses ferrite particles as a core material, and is a copolymer produced from styrene, acrylic acid, methacrylic acid, or a lower ester thereof, and the compound represented below. This developer is characterized in that the core material is coated with.

The present invention will be explained in detail below.

The carbon black used in the present invention has an average particle size of 50 to
70Pa+, surface area 10-40 is 7g, oil absorption is 50
~100cc/100g-DBP. More preferable ranges are 60-70H, 30-40m2/g, respectively.
60-70cc/100g-DBP. If the average particle size is smaller than 50 mp, the amount of triboelectrification between the toner particles and the carrier particles will decrease, causing toner scattering and fogging, and if the surface area exceeds 40a + 7g,
A toner scattering phenomenon occurs at the edges of the resulting visible image, and the oil absorption amount is 100cc/100g-
If the DBP is exceeded, carbon black particles will aggregate during image fixing, and if the DBP is less than 50cc/100g-DBP, sufficient image density cannot be obtained.If the pH value is less than 6.0, carbon black particles in the binder resin will aggregate. The black dispersion becomes non-uniform, resulting in unstable charging ability.

In measuring the physical properties of carbon black, the particle diameter is determined by directly and selectively counting the particle diameter in a scanning electron micrograph. The measurement is AS
It is carried out in accordance with the BH3 formula in TM method D3 method 37-78.

According to the flow shown in Figure 1, add N2 and l to carbon black.
A mixed gas of LE is flowed to adsorb N2, the amount of which is detected by a thermal conductivity cell, and the specific surface area of the sample is calculated from the amount of N2 adsorbed.

l) After drying the sample at 105°C for 1 hour, accurately weigh 0.1 to 1 g, place it in a 0-shaped tube, and attach it to the channel.

2) Change the N,/Ife mixture ratio using a flowmeter and set it to a predetermined P/Pa.

3) After opening cock C and introducing adsorbed gas into the sample layer,
Immerse the tube in liquid N2 to adsorb N.

4) After reaching adsorption equilibrium, remove the liquid N2 and expose it to the air for about 30 seconds, then immerse the 0-shaped tube in water at room temperature.
Attach and detach.

5) Draw a desorption curve on a recorder and measure the area.

6) Using a calibration curve created by introducing a known amount of N prior to these operations, determine the adsorption amount of N at a predetermined P/P from the area obtained for the sample.

Below, the surface area is determined by applying the following formula.

PO: Saturated vapor pressure of adsorbate at measurement temperature P: Pressure at adsorption equilibrium C: Adsorption amount at adsorption equilibrium C: The relationship between constant p/po and P/ν (Pa-P) is a straight line,
Find ν1 from the slope and intercept. Once ν is determined, the specific surface area S is calculated using the following formula.

5=AXv, , Operate the cock of the abutment meter to completely DBP so that no air bubbles remain in the automatic billet system.
(Dibutyl phthalate) and set the equipment specifications as follows.

(1) Spring tension 2.68 kg/cm (2) Rotor rotation speed 125 rpm (3) Torque limit switch scale 5 (4) Damper valve 0.1
50 (!1.) DBP dropping speed 4 mj/5inD
After adjusting the dropping rate of BP by actual measurement, put a certain amount of dry sample into the mixing chamber of the abutment meter, set the billet counter to 0 point, and set the switch to automatic to start dropping. When the torque reaches the set point (5 in this case), the limit switch is activated to automatically stop dripping, read the scale (V) on the billet counter at that time, and calculate the oil absorption amount using the following formula.

OA"-X100 0^: Oil absorption amount (ml/loo g) V: DR used up to the end point (limit switch activation point)
Amount of IP used (mj) W: Meloniness of dry sample (g) pH value Weigh out 1 to 10 g of carbon black into a beaker, add water at a ratio of 10 ml per 1 g of sample, cover with a timer, and boil for 15 minutes. do. A few drops of ethyl alcohol may be added to help wet the sample.

After boiling, cool to room temperature, remove the supernatant liquid by decanting or centrifugation, and leave a slurry.Glass is in this slurry! Insert the electrode of the ipH meter 1. JISZ8802 (
pl+ measurement method). in this case,
The measured value may change depending on the insertion position of the electrode, so move the beaker to change the position of the electrode, and be careful to make sufficient contact between the electrode surface and the muddy surface, so that the pH value remains constant. Read the value at 7.

In the present invention, carbon black is contained in an amount of 2.0 to 101fI, preferably 3.0 to 7%, based on the total weight of the toner.
l! The amount of carbon black added is preferably 2. If the amount of OIli is less than %, the resulting visible image will become rough and the image density will decrease, and conversely,
If the content is more than 0fii%, it becomes a factor that causes blurring and fogging on the image.

Carbon black that satisfies the characteristics specified in the present invention is made into a toner using a suitable binder resin by a known toner manufacturing method.

Examples of the binder resin include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, and styrene. - Vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer) , styrene-octyl acrylate copolymer [combination, styrene-phenyl acrylate copolymer, etc.], styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, etc.) styrene-based resins (styrene or styrene-substituted polyester resins, phenolic resins, epoxy resins, polyester resins, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resins, Polyurethane resin, silicone resin, ketone resin, ethylene-dityl acrylate copolymer, xylene resin,
Particularly preferred resins for carrying out the present invention include polyvinyl butyral resins and styrene-acrylic acid ester resins and polyester resins.

In particular, the following formula (wherein R is ethylene or propylene group, x, y
are each an integer of 1 or more, and the average value of X+y is 2 to 10. ) as a diol component, and a carboxylic acid component consisting of a bivalent or higher carboxylic acid, its acid anhydride, or its lower alkyl ester (e.g., fumaric acid, maleic acid, maleic anhydride, phthalate). It is more preferable to use a polyester resin obtained by cocondensation-polymerizing at least a polyester resin with an acid such as terephthalic acid, trimellitic acid, pyromellitic acid, etc., since it has sharp melting characteristics.

It is also preferable to add a charge control agent to the toner according to the present invention in order to stabilize the negative charge characteristics. In this case, a colorless or light-colored negative charge control agent that does not affect the color tone of the toner is preferred. Examples of negative charge control agents include metal complexes of alkyl-substituted salicylic acids (e.g., di-tert-
Examples include organic gold J7111) bodies such as chromium complexes or zinc complexes of butylsalicylic acid. When the negative charge control agent is added to the toner, it is added in an amount of 0.1 to 101 parts, preferably 0.5 to Bff, based on the xooii part of the binder resin.
It is preferable to add i parts.

Further, any fluid improver can be used in the present invention as long as it can increase fluidity when added to the colorant-containing resin particles when comparing before and after addition.

For example, fluororesin powder, such as vinylidene fluoride fine powder, polytetrafluoroethylene fine powder, etc.; or fatty acid metal salts, such as zinc stearate, calcium stearate, lead stearate, etc.; or metal oxides, such as zinc oxide powder; Alternatively, there are finely powdered silica, that is, wet-processed silica, dry-processed silica, and treated silica obtained by subjecting these silicas to surface treatment with a silane coupling agent, a titanium coupling agent, silicone oil, etc.

A preferred fluidity improver is a fine powder produced by vapor phase oxidation of a silicon halide compound, so-called dry process silica or fumed silica.
It is produced by a conventionally known technique, for example, by utilizing a thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is as follows.

5IC1a + 2112 + 02→SIO* +
In addition, in this manufacturing process, it is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds, such as aluminum chloride or titanium chloride, together with the silicon halide compound, and these are also included. do.

The average primary particle size of the particles is preferably within the range of 0.001 to 2μ, particularly preferably 0.00μ.
It is preferable to use silica fine powder within the range of 2 to 0.2 microns.

Commercially available silica fine powders produced by vapor phase oxidation of silicon halogen compounds used in the present invention include those commercially available under the following trade names, for example.

Aerosil (AERO5IL) 1
30 Nippon Aerosil 20000 80 T600 OX170 MOX 110 OK 84 Ca-0-5IL M-5
Cabot Co., Ltd. (C^DOT Co.) MS-
75-75 15-5 H-5 V7'/Car Wacker tldk N 20
V15 Guacca Chemi N20N20
E (WACKER-CIIE GMBII)
T3040 D-C7 Fin Silica (Flne 5111ca) Dow Corning Go, Inc. Fransol Fransil In addition, treated silica fine powder is obtained by hydrophobizing silica fine powder produced by gas phase oxidation of the silicon halogen compound. It is more preferable to use the body.

Among the treated silica fine powders, it is particularly preferred that the silica fine powders be treated so that the degree of hydrophobicity as measured by a methanol titration test is in the range of 30 to 80.

Hydrophobicity can be imparted by chemical treatment with an organosilicon compound that reacts with fine silica powder or physically adsorbs it.

In a preferred method, fine silica powder produced by vapor phase oxidation of a silicon halide is treated with an organosilicon compound.

Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate , vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane and 2 to 12 siloxane units per molecule, with one unit per molecule at each end. Examples include dimethylpolysiloxane containing a hydroxyl group bonded to St. These may be used alone or in a mixture of two or more.

The particle size of the treated silica fine powder is 0.003-0.
It is preferable to use one in the range of 1μ.

Commercially available products include Taranox-500 (Talco),
^ERO5IL R-1172 (Japan Aerosil Co., Ltd.) etc.

The amount added to the colorant-containing resin particles is 1
0.01 to 1 ollifi parts per 00 parts by weight, preferably 0.1 to 5 parts! It is i quantity part. If the amount is less than 0.0111 part, there is no effect on improving fluidity, and if it is more than the homffk part, fogging, blurring of characters, and scattering inside the machine will be promoted.

The particle size distribution of the carbon black toner used in the present invention has a volume average diameter of 7.0 μ to 14.0 μ, preferably 7.5 μ to 13.5 μ, more preferably 7.9 μ to
13.0μ, and the number average distribution of 6.35μ or less is 5
0% or less, preferably 40% or less, more preferably 30% or less
% or less, and the volume average distribution of 20.2μ or more is 9% or less, preferably 7% or less, more preferably 5% or less.

The carrier used in the present invention uses ferrite particles with light load and long life as a core material, but there are no special restrictions on the manufacturing method.

The carrier of the present invention uses the above ferrite particles as a core material,
The core material is coated with a copolymer consisting of styrene, acrylic acid or methacrylic acid, or a lower ester thereof, and the compound shown below.

Examples of monomers for the copolymer include styrene, 2-ethylhexyl acrylate, methacrylic acid, methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, propylene oxide, and the like.

In the present invention, the carrier core material can be coated with conventionally known methods such as dissolving or suspending the coating resin in a solvent and applying it and adhering it to the carrier, or simply mixing it with powder. Both are applicable.

In addition, in the particle size distribution of the particles, the carrier between 250 and 350 meshes is 70% by weight of the total weight, preferably 80% by weight of the total weight.
It is desirable to have at least % by weight.By creating such a sharp particle size distribution, it is possible to reduce the amount of fine powder carrier, which has a weak magnetic force relative to the strength of the mirroring force, and prevent the carrier from adhering to the latent image carrier. reactor.

The weight average particle size of such a carrier is generally 30 to 65 mm, preferably 35 to 60 I&m. If the particle size is smaller than 30 Pn+, the carrier will be easily developed on the latent image carrier, The image holder and cleaning blade are likely to be damaged. On the other hand, if the particle size is larger than 65 pm, the toner retention ability of the carrier will be reduced, resulting in uneven solid images, toner scattering, fogging, etc.

Further, the range of the desired triboelectric charge characteristic of the carbon black toner of the present invention for the styrene-acrylic copolymer resin-coated ferrite carrier containing 70% by weight or more of the carrier of 250 Mesh Bath and 350 Meshion is -10
It is from -30 pc/g, preferably from -15 to -30, more preferably from -15 to -25 pc/g.

The above-mentioned coated ferrite carrier has the effect of distinctively bringing out the charging characteristics of carbon black toner in a two-component developer.

If it is less than -10 μc/g, the scattering from the developing sleeve during development will be extremely high, and the temperature will be high in a high temperature environment (30°C).

Below 80% [1], it causes scattering inside the copying machine, making it practically impractical.

In addition, if it is -30pc/g or more, the toner will electrostatically adhere strongly to the carrier surface under a substantially normal temperature and low humidity environment (20°C, 10% R11), and the toner will be transferred onto the photosensitive drum having an electrostatic latent image. toner transfer becomes impossible.

When preparing a two-component developer by mixing the carbon black toner and carrier according to the present invention, the mixing ratio is 3.0 to 15% by weight, preferably 4.0 to 13% by weight, as a toner concentration in the developer. % by weight usually gives good results. If the toner concentration is less than 5.0% by weight, the image density will be too low to be practical, and if it is more than 15!11% by weight, fogging and scattering within the machine will increase and the useful life of the developer will be shortened.

Examples of the developing method of the developer according to the present invention include the above-mentioned magnetic brush method, cascade method, etc., but as a more preferable method, in the developing section, a developer supporting member and an electrostatic latent image carrier are used. There is also a method of obtaining a toner-developed image on the surface of the tU image carrier by setting the gap between the toner layer and the toner layer to be wider than the toner layer thickness and applying an alternating electric field.

Each measurement method of the present invention will be described below.

(1) Particle size distribution measurement: The measuring device is a Coulter counter T^-II type (
CX-1 and an interface (manufactured by Nikkaki) that outputs the number average distribution and volume average distribution using
Connect a personal computer (Canon!RI) and prepare a 1% NaCj aqueous solution using primary sodium chloride as the electrolyte.

As a measuring method, 0.1 to 5 taR of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 mj of the electrolytic aqueous solution, and 0.5 to 50 g of the measurement sample is added.

The electrolyte in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μ was measured using the Coulter Counter T^-II type using a 100 μ aperture. Measure the volume average distribution,
Find the number average distribution.

From the volume average distribution and number average distribution thus determined, the volume average particle diameter and number average distribution of 6.35 μ or less and the volume average distribution of 20.2 μ or more are obtained.

(2)! i Amount Average Particle Size Measurement (according to JIS-82601): 1. Weigh about 100 g of carrier to the order of 0.1 g.

2. For ii, use a standard sieve of 100 to 500 mesh (hereinafter referred to as sieve) and 100.200.25 from the top.
Stack them in order of size: 0°350, 400.500,
A tray is placed at the bottom, and the carrier particles are placed in a sieve on top and covered with a lid.

3. Sieve this using a vibrator for 15 minutes at a horizontal rotation rate of 285±6 times per minute and an impulse rate of 150±10 times per minute.

4. After sieving, weigh out the iron powder in each part and tray to the nearest 0.1 g.

5,! Calculate to the second decimal place from the i amount amount fraction, JIS
- Round to one decimal place using Z8401.

However, (the dimensions of the frame 1 and ii are such that the inner diameter from the sieve surface is 200 mm)
The depth from the top surface to the sieve surface should be 45 m. 2. The total weight of the iron powder in each part should not be less than 99% of the mass of the carrier particles started. ) (3) Measurement of triboelectric charge: The measurement method will be explained in detail using drawings.

FIG. 2 is an explanatory diagram of an apparatus for measuring the amount of triboelectric charge of toner. First, gold Y with 500 mesh screen 3 at the bottom! A mixture of toner and carrier whose weight ratio is 1:9 for which the amount of triboelectric charge is to be measured is placed in a measuring container 2 made of
100m! Place in a polyethylene bottle with a capacity of about 10
Shake by hand for ~40 seconds, the mixture (developer) will be approximately 0.5 ~
Add 1.5 g and cover with J7fE lid. The weight of the entire crucian carp measurement container 2 is L (g), and the zeroth order is:
In the suction device 1 (at least the part in contact with the measurement container 2 is an insulator), suction is drawn from the suction lower, and the air volume control valve 6 is adjusted to set the pressure of the vacuum gauge 5 to 250 mm^q. In this state, suction is performed for a sufficient period, preferably 2 minutes, to remove the toner by suction. Let the potential of the electrometer 9 at this time be V (volt),
Here, 8 is a capacitor whose capacity is C (μF), and the weight of the entire measurement container after suction is weighed as Wi (g).
The amount of triboelectric charge (μc/g) of this toner is calculated as shown below.

(However, the measurement conditions are 23° C. and 60% old I.) The carrier used in the measurement is a styrene acrylic resin coated free light carrier having 7011 iffi% or more of carrier particles of 250 mesh bath and 35 G mesh.

The sample toner and carrier used for measurement are at least 1 in each environment.
After leaving it for 2 hours, use it for IF coulometric measurement.

Further, the measurement of the amount of triboelectric charge is carried out at 23° C. under a 60% old 1 environment.

[Example] The present invention will be described in detail below with reference to Examples.

Example! The black powder with the mu average particle size of 12 μI having the above configuration is used as a toner classified product.

The manufacturing method is to sufficiently premix the above prescription amounts using a Henschel mixer, melt-knead them at least twice using a three-roll mill, cool them, and coarsely crush them using a hammer mill to about 1 to 21 ml. It was pulverized to a particle size of 40 μm or less using an air jet type pulverizer. Further, the obtained finely pulverized product was classified and a particle size of 2 to 23μ was selected so as to have the particle size distribution of the present invention.

The carbon black in the above has an average particle size of 60μ
m, surface area 3om2/g, oil absorption ff165cc/100
A material having a physical property value of 8.0 for g- and 1'l monovalence was used. In addition, fine silica powder treated with hexamethyldisilazane is used as a fluidity improver in the toner according to the present invention. A toner was prepared by adding 0.5 parts by weight to one part by weight of Ii.

On the other hand, as a carrier, styrene-2-ethylhexyl acrylate-methyl methacrylate-2hydroxyethyl methacrylate-methacrylic acid-ethyl acrylate-propylene oxide (copolymerization ratio 10:8:35;
C coated with 5:20:12:10)
U-Zn-Fe type ferrite particles are used.

Toner 10 obtained by the above 4M composition! A developer having a total weight of 100 parts is prepared by mixing 90 parts of carrier and 90 parts of carrier. When repeated development was carried out using this developer using a commercially available electrophotographic copying machine (trade name: NP C0LOR-T manufactured by Canon), the image density was high, and
A clear copy image without image density unevenness or fogging was obtained. Furthermore, in order to check the durability of the above developer,
After conducting a durability test of 10,000 sheets (normal temperature 23℃, 6
0% R10, a clear image without fog (reflection density 1.51) similar to the initial image was obtained, and on the other hand, under a high temperature atmosphere (30°C).

80% old 1) and under low temperature and low concentration atmosphere (20℃, 10
%RH), a good visible image without image density unevenness or fog was obtained. Table 3 shows the amount of triboelectric charge at this time.

Hereinafter, it is preferable to use an RD-918 anti-elbow densitometer (manufactured by Macbeth) for image density measurement.

Example 2 The toner composition of Example 1 is the same except that the amount of carbon black contained in the toner is 12% by weight based on the toner weight, and the carrier composition and developer adjustment are also described in Examples below. 1. With this developer, Ichiha's electrophotographic copying machine (product name C0LOR)
Development was performed repeatedly using LASE II C0PIER (manufactured by Canon). At this time, a bias electric field consisting of an alternating current component and a direct current component is applied between the developer carrying member and the latent image holding member.
If z, the peak voltage is 1800 Vpp, the latent image charging potential is -650 V, the image exposure voltage is -150 V, and the DC bias potential is -470 V. As a result, a clear copy image with high image density and no scratches, density unevenness, or fog was obtained. Furthermore, in order to investigate the durability of the above developer,
When a durability test was repeated for 10,000 sheets, the image density was as high as 1.80, but the fog in the non-image area remained the same as at the initial stage. Table 3 shows the amount of triboelectric charge at this time.

Example 3 Carbon black used as a colorant has an average particle size of 81
3mg, surface area 20a+'/g, oil absorption fi76cc/1
00g and a pH value of 6.0, and the carrier particles to be stirred and mixed with the toner having the carbon black include:
Styrene-methyl methacrylate-ethyl acrylate-propylene oxide (copolymerization ratio 25:30:30:Is
) was used.

A developer was prepared in accordance with Example 1 using the toner and carrier obtained with the above configuration, and the same evaluation was carried out one after another. As a result, a high density and clear visible image without fogging or toner scattering was obtained.

Table 3 shows the amount of triboelectric charge at this time.

Comparative Example 1 A toner was obtained in the same manner as in Example 1 except for carbon black. This toner is referred to as "Comparative Toner 1." The carbon black in Comparative Toner 1 has an average particle size of 23 mg and a surface area of 125 m2.
7g, oil absorption 57cc7100g-DBP, and pH
The value is 2.5.

Using this comparative toner 1 and the carrier in Example 1, a developer was prepared in the same manner as in Example 1, and an actual photographic test was conducted. Although it was stable, overall image density unevenness occurred, good gradation could not be obtained, and image quality deteriorated. Table 3 shows the amount of triboelectric charge at this time.

Comparative Example 2 In the toner composition of Example 1, the amount of carbon black contained in the toner was 12I per toner weight! The same procedure was used except that the content was %, and the carrier composition, developer adjustment, and evaluation method were also the same as in Example 1.The image density was as high as 1.96, but On the other hand, fogging occurred in non-image areas from the beginning. In addition, when a durability test was performed, the image density was as high as 1.80 even when 500 sheets were printed, but the fog in the non-image area remained the same as in the initial stage. Friction 11F at this time
The amount of electricity is shown in Table-3.

Example 4 In Example 1, 7 parts by weight of carbon black was added to 100 parts by weight of the binder resin, and styrene was used as a carrier.
2-ethylhexyl acrylate-methyl methacrylate-
Propylene oxide (copolymerization ratio 40: 25: 25
: When a developer was prepared in the same manner except that Cu-Zn-Fe ferrite particles coated with 10) were used and the same evaluation was carried out sequentially, a clear image was obtained, and it was found that the developer could not be deposited on the latent image carrier. No problems such as adhesion of carrier particles, fogging, or toner scattering were observed. Furthermore, durability evaluations were performed, and images with clear gradation without fogging were obtained, similar to the initial images, even under various environmental conditions. Table 3 shows the amount of triboelectric charge at this time.

Comparative Example 3 In the toner composition of Example 1, the amount of carbon black contained in the toner was 1.5 @% by amount based on the toner weight, and the carbon black had various characteristics such as an average particle diameter of 28 mμ and a surface area. 90m27g, oil absorption 99cc
/long-DBP and the pH value was 2.8, the developer was prepared according to Example 1, and a real-photograph test was conducted. Although no fogging occurred in the non-image area, the image Concentration is 0.95 (23℃, 60% R11
) and only a low value was obtained.

Friction 1F1 at this time! The amounts are shown in Table-3.

Table 3 [Effects of the Invention] As explained above, according to the present invention, in two-component development in electrophotography, carbon black is used as the toner colorant and styrene-acrylic copolymer resin is used as the core material. By preparing coated carrier particles and developer,
It is possible to improve image quality such as high image density and gradation reproducibility, and it has the effect of reducing the number of toners during storage and preventing fogging in non-image areas.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a carbon black surface area measuring device according to the present invention. FIG. 2 is a diagram schematically showing an apparatus for measuring the amount of triboelectric charge of toner according to the present invention.

Claims (3)

[Claims] (1) A developer comprising at least a toner having carbon black as a colorant and a carrier, wherein the carbon black has an average primary particle size of 50 to 70 mμ and a surface area of 10 to 70 mμ.
40m^2/g, oil absorption 50-100cc/100g-
DBP, the pH value is 6.0 to 9.0, and the carrier uses ferrite particles as a core material, and is produced from styrene, acrylic acid or methacrylic acid, or a lower ester thereof, and the compound represented below. A developer characterized in that the core material is coated with a copolymer. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (2) The developer according to claim 1, wherein the amount of carbon black contained in the toner is 2.0 to 10% by weight of the toner. (3) The developer according to claim 1, wherein in the particle size distribution of the carrier, the carrier between 250 and 350 mesh accounts for 70% by weight or more of the total weight.