JPH0895292A - Electrophotographic toner - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic toner having satisfactory electrostatic chargeability of each particle, maintaining high image density and a fog-free image and withstanding use over a long period of time by using a specified large particle diameter toner and a specified small particle diameter toner. CONSTITUTION: This electrophotographic toner consists of a large particle diameter toner contg. at least a resin binder having acid value of <5mgKOH/g and a colorant of pH 6-8 and a small particle diameter toner contg. at least a resin binder having acid value of 5-30mgKOH/g and a colorant of pH 2-6. Since the electrostatic charge of the small particle diameter toner is suppressed and the large particle diameter toner is electrostatically charged as usual, the small particle diameter toner is prevented from remaining and accumulating in a developer, sticking to the surface of a carrier, practically reducing the surface area of the carrier and blocking triboelectric charge with the carrier. Toner particles are produced by blending a bonding resin with additives such as a colorant, an electric charge controlling agent and a releasing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner used for image formation by applying a so-called Carlson process in an electrostatic copying machine, a laser beam printer or the like.

[0002]

2. Description of the Related Art A two-component developer consisting of toner and carrier is generally used in the development of an electrostatic copying machine or a laser beam printer. Most of the electric charge of the toner is given by frictional charging, and the charging is mainly performed by friction with the magnetic carrier. BACKGROUND ART Conventionally, research has been conducted on a developer exhibiting preferable charging characteristics by selecting various materials of a charge imparting member such as a toner and a carrier so that a good image can be formed.

[0003]

However, in the case of a two-component developer, the smaller particle size toner in the whole toner is highly charged, and therefore the smaller the particle size toner having the toner particle size distribution is, the less developed it is. Remains in. When this small particle size toner is accumulated, it adheres to the surface of the carrier and substantially reduces the surface area of the carrier, which hinders triboelectric charging between the toner and the carrier. Therefore, problems such as fogging, toner scattering, and deterioration of toner transfer efficiency due to poor charging occur.

The present invention has been made in view of the above circumstances, and provides an electrophotographic toner which has good chargeability of each toner, maintains a high image density and a fog-free image, and can be used for a long period of time. The purpose is to provide.

[0005]

According to the present invention, a binder resin having an acid value of less than 5 KOHmg / g and a pH of 6 to 8 are used.
A large particle diameter toner containing at least the above colorant, a binder resin having an acid value of 5 to 30 KOHmg / g, and a pH of 2
An electrophotographic toner comprising a small particle diameter toner containing at least the colorants Nos. 6 to 6 is provided.

The above electrophotographic toner having a large particle diameter having a central particle diameter of 9 μm to 13 μm and having a particle diameter of 5 μm or less is substantially not contained, and is 20 μm.
The content of the above is 3 vol% or less, the center particle size of the small particle size toner is 6 μm to 10 μm, and the size of the particle is 5 μm or less is contained by 7 vol% or less and substantially 20 μm or more is contained. And the center particle size of the electrophotographic toner comprising a large particle size toner and a small particle size toner is 7 μm to 12 μm.
The toner for electrophotography according to claim 1, wherein 3% by volume or less of 5 μm or less and 2% by volume or less of 20 μm or more is provided.

[0007]

The toner for electrophotography according to the present invention has an acid value of 5K.
A large particle size toner containing at least a binder resin of less than OH mg / g and a colorant having a pH of 6 to 8, and an acid value of 5
-30 KOHmg / g binder resin and pH 2-6
The first feature is that the toner comprises a small particle size toner containing at least the colorant of As a result of various studies conducted by the present inventor focusing on the particle size distribution of the toner and the characteristics of the binder resin and the colorant, the acid value of the binder resin is 5 to 3
If the pH of the coloring agent is 2 to 6 at 0 KOHmg / g,
In the kneading step at the time of toner production, the binder resin and the colorant repel each other, resulting in poor dispersion of the colorant in the binder resin, resulting in lumps of poorly dispersed colorant in the toner particles. It is based on the new finding that it will be higher. That is, according to the present invention, the charging of the small particle size toner is suppressed to a low level by the above means, and the charging of the large particle size toner is made normal so that the small particle size toner having a toner particle size distribution remains in the developer, The problems such as the accumulation and adhesion to the surface of the carrier to reduce the substantial surface area of the carrier and the inhibition of triboelectric charging between the toner and the carrier have been solved.

The center particle size of the large particle size toner is 9 μm to 13 μm
m, the center particle size of the small particle size toner is 6 μm to 10 μm, and the center size of the whole toner obtained by mixing the large particle size toner and the small particle size toner is preferably 7 μm to 12 μm. If the difference between the center particle size of the small particle size toner and that of the large particle size toner deviates from the above range and the difference becomes large, the fluidity of the toner decreases due to the effect of the small particle size toner or the copy image due to the effect of the large particle size toner. This is because the resolution of may decrease. Further, if the center particle size of the entire toner is smaller than 7 μm, the hiding property may be lowered and the image density may be lowered, while if the center particle size is larger than 12 μm, the image resolution may not be improved.

Further, it is preferable that the large particle size toner does not include particles having a particle size of 5 μm or less, but contains particles having a particle size of 20 μm or more in an amount of 3 vol% or less. If there is a particle diameter of 5 μm or less, it is not developed and remains in the developer. When this small particle size toner is accumulated, it adheres to the surface of the carrier and substantially reduces the surface area of the carrier, which hinders triboelectric charging between the toner and the carrier. Therefore, problems such as fogging, toner scattering, and deterioration of toner transfer efficiency due to poor charging occur. Particle size is 2
When the content of particles having a particle size of 0 μm or more is more than 3 vol%, the image density becomes good but the image quality deteriorates.

The small particle size toner preferably has a particle size of 5 μm or less, 7 vol% or less, and does not include 20 μm or more. If the particle size of the particles having a particle size of 5 μm or less is more than 7 vol%, the image quality is improved, but the image density cannot be maintained, and the image density is lowered when a plurality of sheets are copied. On the other hand, the particle size is 20
If the particle size is more than μm, it is likely to adhere to the non-image area of the photoconductor to cause background fog.

In the electrophotographic toner, the particle size is 5 μm
In order to control the content of the following or those having a particle size of 20 μm or more, the setting conditions of the existing classifier can be changed. For example, styrene as a binder resin
When an acrylic resin is used, toner particles having a wide particle size distribution can be obtained in the pulverizing step, so the content of particles having a particle size of 5 μm or less and those having a particle size of 20 μm or more can be easily adjusted by controlling the classification conditions. .

The toner particles in the present invention are manufactured by adding additives such as a colorant, a charge control agent and a release agent to the binder resin. A styrene resin, an acrylic resin, a styrene-acrylic resin, a polyester resin, a polyurethane resin, a silicone resin, a polyamide, a modified rosin, or the like is used as the binder resin as the toner component.

Examples of the monomer serving as a base of styrene-acrylic resin include the following. Styrene, α-methylstyrene, p-methylstyrene, pt
-Styrene derivatives such as butyl styrene, p-chlorostyrene, hydroxystyrene, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate. , Nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate,
Glycidyl methacrylate, methoxyethyl methacrylate, propoxyethyl methacrylate, poxyethyl methacrylate, methoxydiethylene glycol methacrylate, ethoxydiethylene glycol methacrylate, methoxyethylene glycol methacrylate, poxytriethylene glycol methacrylate, methoxydipropylene glycol methacrylate, methacrylic acid Phenoxyethyl, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol methacrylate, benzyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, N-vinyl-2 methacrylate -Pyrrolidone, methacrylonitrile, Tacrylamido, N-methylol methacrylamide, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate 2-hydroxy-3-phenyloxypropyl acrylate, glycidyl acrylate, acrylonitrile, acrylamide, N-methylol acrylamide, Diacetone acrylamide, vinyl pyridine, phthalimidoethyl acrylate, phthalimidopropyl acrylate, morpholinopropyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, divinylbenzene, reaction products of glycol with methacrylic acid or acrylic acid, for example Ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanedio Dimethacrylate, 1,5-pentanediol dimethacrylate,
1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
Tripropylene glycol dimethacrylate, hydroxypiparic acid neopentyl glycol ester dimethacrylate, trimethylolethane trimethacrylate,
Pentaerythritol tetramethacrylate, trismethacryloxyethyl sulphate, bis (methacryloyloxyethyl) hydroxyethyl isocyanurate,
Tris (methacryloyloxyethyl) isocyanurate, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, Neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, tripropyl diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, trimethylethane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate Acrylate, pentaerythritol tetraacrylate, trisacryloxyethylphosphophe , Bis (methacryloyloxyethyl) hydroxyethyl isocyanurate, tris (methacryloyloxyethyl) isocyanate, glycidyl methacrylate and methacrylic acid or acrylic acid half ester compound, bisphenol epoxy resin and methacrylic acid or acrylic acid half ester compound , A half-esterified product of glycidyl acrylate and methacrylic acid or acrylic acid. Among these monomers, preferable ones having one vinyl group in one molecule include styrene, styrene derivatives, methacrylic acid esters, acrylic acid esters, etc., and particularly 1 to 5 carbon atoms in the alkyl group. Methacrylic acid or an alkyl ester of acrylic acid having is preferred.

As the monomer having two or more vinyl groups in one molecule, divirbenzene, dimethacrylate and diacrylate of alkylene glycol having 2 to 6 carbon atoms are preferable, and these are usually contained in all monomers. 0
~ 20 wt% is used. The mixture of the various monomers can be subjected to any polymerization such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., to obtain the binder resin of the toner of the present invention.

The glass transition temperature of the binder resin for toner used in the present invention is particularly preferably adjusted to 50 to 90 ° C. If the glass transition temperature is less than 50 ° C., the toner tends to block during storage or in the developing machine. Further, when the glass transition temperature exceeds 90 ° C., the toner manufacturing efficiency decreases, and it is necessary to raise the fixing temperature, resulting in poor energy efficiency.

As the binder resin of the present invention, other resins may be used in addition to the above resins, or two or more kinds may be used in combination. As the carbon black, conventionally known carbon black can be used. For example, the following can be preferably used. Furnace black, channel black, gas black, oil black, carbon black such as acetylene black, lamp black, aniline black and the like can be mentioned. The above carbon black is
"Printex 95, 90, 85, 80, 75, P,
L, A, G, U, V "," Special Black "
100, 250, 350, 550 "(all manufactured by Degussa)," Monarch 700, 800, 880, 900, 1 "
000 "," Mohgal L "," Regal 400R, 50 "
0R, 660R, 330, 400, 500, 300I,
99I "," Black Pearls 700, 800, 88
0, 900, 1000, 1100, 1300L ",
"Vulcan XC-72R", "Vulcan X-72",
"Elftex 8, 12", "Stelling R" (above, manufactured by Cabot), "Raven 11, 15, 30,
35, 40, 50, 150, 410, 420, 430,
450, 500, 825, 850, 890, 1000,
1020, 1030, 1035, 1040, 1085,
1170, 1200, 1500, 1800, 2000,
2100, 3500, 5250, 5750, 7000,
8000, 8800 "," Neo Spectra AG, T
"A", "Statex F-12", "Moraco H, L"
S "," Conductex SC, 950, 975 "(above, made by Columbia Carbon Co., Ltd.)," MCF-88, MA "
-100, 600, 11, 8 "(above, manufactured by Mitsubishi Kasei)
Commercially available products such as the above can be preferably used. Oil absorption of these carbon blacks is 150cc / 100
g or more, volatile matter 30 wt% or less, specific surface area 240 m
2 / g or more, especially oil absorption of 160cc / 100g
Above, volatile matter 20wt% or less, specific surface area 250m2
The above is preferable. Here, the "oil absorption" is measured by taking 100 g of carbon black, dropping dibutyl phthalate, repeating kneading, and terminating when the whole becomes putty-like putty, and the amount of dibutyl phthalate required for this is measured. It is something. “Volatile content” is measured by the ratio of the weight loss after heating the carbon black to about 950 ° C. In addition, "specific surface area" is Braunauer-Emmeett-Te
It is measured by the nitrogen adsorption method (BET method) by the ller method.

As the charge control agent, two types of charge control agents for positive charge control and negative charge control are used depending on the polarity of the toner. Examples of the charge control agent for controlling the positive charge include organic compounds having a basic nitrogen atom, such as basic dyes, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds and aminosilanes.

Examples of the charge control agent for negative charges include oil-soluble dyes such as nigrosine base, oil black and spirone black, metal-containing azo dyes, naphthenic acid metal salts, alkylsalicylic acid metal salts, fatty acid soaps, resin acid soaps. Etc. are used. As the release agent, polypropylene, butene, pentene, hexene, heptene, octene, nonene, decene, 3-methyl-1-butene, 3-methyl-2-pentene, 3-propyl-5-methyl-2-hexene, etc. Polymers of olefin monomers or copolymers of the above olefin monomers with acrylic acid, methacrylic acid, vinyl acetate, etc., lower alcohol esters of fatty acids such as butyl stearate, propyl stearate, higher aliphatic alcohol esters, "palm aceti" Alcohol bis such as (Hokkaido Yushi Co., Ltd.), "Hoechst Wax E, OP" (Hextor Actien Gel Shaft), higher alcohol esters of fatty acids such as carnauba wax, "Hoechst Wax C" (Hextor Actien Gel Shaft), etc. Fatty acid amide compounds, other, di Emissions-based resin, hydroxyl group-containing vinyl resin, there is a carboxyl group-containing vinyl resin. These release agents are 0.1 to 2 with respect to the binder resin.
It is preferable to add 0 wt%, particularly 1 to 10 wt%.

The magnetic powder includes metal powders of iron, manganese, nickel, cobalt, etc., magnetite, copper-zinc ferrite, barium-zinc ferrite, manganese-zinc ferrite, lithium-zinc ferrite, magnesium-manganese ferrite, magnesium-manganese. Ferrite, magnesium-copper-zinc ferrite, barium-
Various ferrites such as nickel zinc ferrite and barium-copper-zinc ferrite are preferable. Magnetite is particularly preferable. The particle size of these magnetic powders is preferably 0.8 μm or less, more preferably 0.1 μm or less.

Further, in order to improve the fluidity of the toner of the present invention, inorganic fine powder is contained in the toner. In addition, the inorganic fine powder controls the charging of the toner as an incidental action. As the inorganic fine powder, hydrophobic silica fine powder is particularly preferable. This is because it has excellent environmental resistance and contributes not only to improving the fluidity of the toner but also to charging stability. Other examples of the inorganic fine powder include titanium oxide and aluminum oxide. These inorganic fine powders may be used alone or in combination of two or more kinds.

Inorganic fine powders that can be preferably used in the present invention include hydrophobic silica "R97".
4 ”,“ R972 ”,“ R202 ”,“ R805 ”,
"R812" (all manufactured by Nippon Aerosil Co., Ltd.), "Taranox 500" (manufactured by Tarco), "Cab-O-Si"
l ”,“ M-5 ”,“ MS-7 ”,“ MS-75 ”,
"HS-5", "EH-5", "S-17", "TS-"
720 "(above, manufactured by Cabot).

For titanium oxide, "Titanium Dioxide P2
5 "," T-805 "(all manufactured by Nippon Aerosil Co., Ltd.),
Examples include "Titanium Black 12S" (manufactured by Mitsubishi Metals).
For aluminum oxide, there is "Aluminium Oxide C" (all manufactured by Nippon Aerosil Co., Ltd.). The content ratio of the inorganic fine powder is 0.05 to 2.0 wt% with respect to the toner particles.
Is preferred. Content of inorganic fine powder is 2.0
If the content exceeds 50% by weight, problems such as adhesion to the carrier and photoconductor and destabilization of toner chargeability may occur. On the other hand, if the content of the inorganic fine powder is less than 0.05% by weight, toner fluidity is improved. This is because there is a possibility that the

The hydrophobized silica fine powder is, for example, a fine powder of silicon dioxide whose surface silicon atoms are silanol groups,
For example, octyltrichlorosilane, decyltrichlorosilane, noninonyltrichlorosilane, 4-isopropylphenyltrichlorosilane, 4-tert-butylphenyltrichlorosilane, dimethyldichlorosilane, cibentyldichlorosilane, dimethyldichlorosilane, dipentyldichlorosilane. , Dihexyldichlorosilane, dioctyldichlorosilane, dinonyldichlorosilane, didecyldichlorosilane, didodecyldichlorosilane, 4
-Tert-butylphenyloctyldichlorosilane,
Dioctyldichlorosilane, didecenyldichlorosilane, dinonenyldichlorosilane, di-2-ethylhexyldichlorosilane, di-3,3-dimethylpentyldichlorosilane, trimethylchlorosilane, trihexylchlorosilane, trioctyl By reacting with a compound such as chlorosilane, tridecylchlorosilane, dioctylchlorosilane, octyldimethylchlorosilane, and 4-isopropylphenyldiethylchlorosilane, a hydrophobic group is formed on the surface silicon atom of the silicon dioxide particle through an oxygen atom. It is a combination. Manufacture of Toner A binder resin, a colorant, a charge control agent, a release agent and the like are mixed and stirred. The mixing and stirring should be performed under the condition that a low load and a low shearing force are applied, and in general, various mixing and stirring devices such as a conical blender, a ribbon blender, a V-type blender, a Nauta mixer, a Henschel mixer, and a ball mill can be used. The mixing and stirring temperature is preferably lower than the glass transition point (Tg) of the binder resin. The required mixing / stirring time varies depending on the type of equipment and the input amount, but is generally in the range of 10 to 300 minutes.

The premix thus obtained is melt-kneaded by a roll, uniaxial or biaxial extrusion kneader, etc., and the kneaded product is cooled and then pulverized by a pulverizer such as a feather mill or jet mill. The toner particles are classified by various wind classifiers. The obtained toner particles are sprinkled with an inorganic fine powder in the mixing stirrer to obtain an electrophotographic toner. The electrophotographic toner of the present invention obtained by mixing and dispersing toner particles and inorganic fine powder in this manner is useful as both a one-component developer and a two-component developer. When used as one component, the toner particles containing the above-mentioned magnetic material and the hydrophobic silica fine particles are mixed and dispersed to obtain a developer. When used as a two-component developer, an electrophotographic toner composed of toner particles and inorganic fine powder is combined with a carrier to form a developer. As the carrier, glass beads, oxidized or unoxidized iron powder, uncoated carrier such as ferrite, or magnetic substance such as iron, nickel, cobalt, ferrite is used as acrylic polymer, fluororesin polymer, polyester, modified silicon. There are coated carriers coated with a polymer such as a resin. Among these, in the present invention, copper-zinc ferrite, barium-zinc ferrite,
Various metal ferrites such as barium-nickel ferrite, nickel-zinc ferrite, manganese-zinc ferrite, lithium-zinc ferrite, magnesium-copper-zinc ferrite, magnesium-manganese ferrite, barium-nickel-zinc ferrite, barium-copper-zinc ferrite Is preferred. Further, a carrier in which each ferrite is coated with an acrylic resin is more preferable in terms of life and environmental resistance. The carrier is generally 30 to 500.
It has a particle size of μm. The toner concentration is preferably 2 to 15%.

[0025]

EXAMPLES Hereinafter, the electrophotographic toner of the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 (Component of Toner 1) Styrene-acrylic polymer 100 parts by weight (Binder resin acid value 3 KOHmg / g) Carbon black (pH 7) 9 parts by weight Chromium complex salt dye (charge control agent) 1 part by weight Low molecular weight Polypropylene (releasing agent) 2 parts by weight The above components are melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and air-classified with a classifier to give an average particle diameter of 11 μm.
Thus, particles of Toner 1 having a volume fraction of 5 μm or less and 0% and a volume fraction of 20 μm or more and 2% were obtained.

(Component of Toner 2) Styrene-acrylic polymer 100 parts by weight (Binder resin acid value 20 KOHmg / g) Carbon black (pH 3) 9 parts by weight Chromium complex salt dye (charge control agent) 1 part by weight Low molecular weight Polypropylene (release agent) 2 parts by weight The above components are treated in the same manner as in Toner 1, and the average particle size is 8 μm.
Thus, particles of Toner 2 having a volume fraction of 5 μm or less of 4% and a volume fraction of 20 μm or more of 0% were obtained.

The particles of the toners 1 and 2 and the hydrophobic silica fine particles are mixed and dispersed in a proportion of 0.3% by weight based on the total amount of the toner, and a volume fraction of 5 μm or less with an average particle diameter of 10 μm is 2%. A final electrophotographic toner having a volume fraction of 20 μm or more and 1% was obtained. Table 1 shows the evaluation results of each item. Example 2 Same as Example 1 except that the acid value of the binder resin of Toner 2 was changed to 10 KOHmg / g and the colorant pH was changed to 5. Example 3 Same as Example 1 except that the acid value of the binder resin of Toner 2 was changed to 30 KOHmg / g and the pH of the colorant was changed to 2. Comparative Example 1 Same as Example 1 except that the acid value of the binder resin of Toner 1 was changed to 20 KOHmg / g and the pH of the colorant was changed to 3. Comparative Example 2 The procedure of Example 1 was repeated, except that the acid value of the binder resin of Toner 2 was changed to 0 KOHmg / g and the pH of the colorant was changed to 7. Comparative Example 3 In the same manner as in Example 1, except that the finally obtained toner has a center particle size of 13 μm, a volume fraction of 5 μm or less is 0%, and a volume fraction of 20 μm or more is 4%. did. (Evaluation Test) With respect to the toners obtained in each of the examples and the comparative examples, a ferrite carrier having an average particle size of 80 μm was blended and uniformly stirred and mixed to prepare a two-component developer having a toner concentration of 3.5%. Next, using a copying machine manufactured by Mita Kogyo Co., Ltd. (trade name "DC-4585"), as shown in Table 2, environmental conditions were changed for each predetermined number of sheets, and a total of 20,000 sheets were copied. However, the original used for copying was an original having an area ratio of 15% of black portions including characters and black solid portions. And it evaluated according to the following test methods. (1) Image Density (ID) Measurement Using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.), the density of the black solid portion of the copied image after copying 20,000 sheets was measured. (2) Measurement of Fog Density (FD) The fog density was measured by measuring the density of the blank area of the copied image after copying 20,000 sheets using the reflection densitometer. (3) Resolution The resolution (lines / mm) was defined as the maximum number of straight lines that can be distinguished by using a document that is evenly divided into a width of 1 mm so that the black lines have the same width and spacing. (4) Toner particle size distribution in the developer After the copying of 20,000 sheets, the toner in the developer is separated from the carrier in an aqueous solution of a surfactant, and a Coulter counter (TA- (2) manufactured by Coulter, Inc.) is used. The volume fraction W1 of 5 μm or less was measured. (5) Toner scattering The state inside the copying machine at the end of copying 20,000 sheets was visually judged and evaluated according to the following criteria.

◯: No toner scattering Δ: Slight toner scattering X: Toner scattering (6) Transfer efficiency The total amount of toner consumed by copying 20,000 sheets and the total amount collected in the cleaning unit were measured, and the following formula was used. The transfer efficiency was determined by.

[0029]

[Equation 1] Transfer efficiency (%) = (consumption amount (g) -recovery amount (g)) / consumption amount (g) × 100

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

According to the present invention, when the acid value of the binder resin of the large particle size toner is less than 5 KOHmg / g, the pH of the colorant is low.
Is 6 or more and less than 8 and the acid value of the binder resin of the small particle size toner is 5 KOHmg / g or more and 30 KOHmg / g and the pH of the colorant is 2 or more and less than 6 It is possible to obtain a high-concentration, high-image-quality and long-life developer that does not accumulate the toner having a small particle size in the developer by averaging the charge amount in.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiteru Hatase 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (2)

[Claims] 1. A large particle diameter toner containing at least a binder resin having an acid value of less than 5 KOHmg / g and a colorant having a pH of 6 to 8, a binder resin having an acid value of 5 to 30 KOHmg / g and a pH of 2. An electrophotographic toner comprising a small particle diameter toner containing at least the coloring agent of Nos. 6 to 6. 2. The center particle size of the large particle size toner is 9 μm to 13
The particle size of the small particle size toner is 6 μm to 10 μm and the particle size of the small particle size toner is 6 μm to 10 μm. Contains 7 vol% or less of 5 μm or less, 2
Substantially free of particles having a size of 0 μm or more, the electrophotographic toner having a large particle size toner and a small particle size toner has a central particle size of 7 μm to 12 μm, and particles having a particle size of 5 μm or less are 3 vol% or less and 20 μm or more. The toner for electrophotography according to claim 1, wherein the content of the toner is 2 vol% or less.