JPH0534986A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To ensure sharp distribution of the amt. of electric charges, moisture resistance and aging stability for a color toner and to enable the selection of an arbitrary colorant according to the hue required by the color toner by incorporating a specified compd. as a colorless electric charge controlling agent. CONSTITUTION:At least one kind of compd. represented by formula I is contained. In the formula I, each of R1-R4 is H, halogen, 1-4C alkyl, etc., R1 and R2 may bond to each other to form a ring, R3 and R4 may bond to each other to form a ring and A<+> is a cation. The compd. acts as a negative charge controlling agent and has satisfactory compatibility with a resin binder. A toner contg. the compd. has a large amt. of electric charges and satisfactory aging stability and can stably give a clear image by electrostatic recording even after storage for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a toner used for developing an electrostatic latent image in electrophotography, electrostatic recording and the like.

[0002]

2. Description of the Related Art Image forming processes such as electrostatic recording and electrostatic photography using static electricity are performed by using phthalocyanine pigment, selenium,
A process of forming an electrostatic latent image by an optical signal on a photoreceptor obtained by applying a photoconductive substance such as cadmium sulfide or amorphous silicon onto a substrate such as aluminum or paper,
In the two-component developing method, the colored fine particles adjusted to 5 to 50 μm called a toner are contact-charged with a carrier (iron powder, ferrite powder, etc.), and in the one-component developing method, the toner is directly charged. After that, the electrostatic latent image is made to act and visualized. The toner needs to be provided with a charge corresponding to the polarity of the electrostatic latent image formed on the photoconductor, that is, either positive or negative charge.

Colored fine particles generally called toner are composed of a binder resin and a colorant as essential components, and magnetic powder as an optional component. As a method for imparting an electric charge to the toner, the charge characteristics of the binder resin itself can be utilized without using a charge control agent, but they are inferior in stability over time and moisture resistance and cannot obtain good image quality. Therefore, a charge control agent is usually added for the purpose of holding the charge of the toner and controlling the charge.

The quality characteristics required of the toner include excellent chargeability, fluidity, fixability, etc., but these quality characteristics are greatly influenced by the charge control agent used in the toner. The charge control agents conventionally added to toners include (1) 2: 1 type metal-containing complex salt dyes as colored negative charge control agents (eg, JP-B-45-2647).
8, JP-B-41-201531) Phthalocyanine pigment (eg, JP-A-52-45931), and JP-B-59-7384 or JP-A-61738 as an example of a colorless negative charge control agent.
-3149 and the like, and (2) as a positive charge control agent, a nigrosine dye, an organotin compound such as dibutyltin oxide (eg, JP-B-57-2970).
4) and the like are known, but a toner containing these as a charge control agent does not sufficiently satisfy the quality characteristics required for the toner such as chargeability and stability over time.

That is, since the 2: 1 metal-containing complex salt dye known as a negative charge control agent and the nigrosine dye known as a positive charge control agent are themselves colored, a toner having a limited hue centered on black is used. It has a drawback that it can only be used for a long time and that the stability of the toner against continuous copying is not good. An example of a negatively charged negative charge control agent is a metal complex of an aromatic dicarboxylic acid (Japanese Patent Publication No. 59-7384). However, this compound has the drawback that it cannot be completely colorless and its dispersibility is difficult. There is. Further, as a colorless negative charge control agent, there is a compound introduced in JP-A-61-3149. However, since this compound has a low melting point, it has poor thermal stability during toner production, and it is difficult to produce a stable toner. There is a drawback that As described above, the known charge control agent does not sufficiently satisfy the quality characteristics required for the toner.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a colorless negatively-charged charge which has good dispersibility in a binder resin, is not affected by changes in temperature and humidity, and has high charge controllability. Provides a control agent, and also provides a negatively chargeable toner that has excellent charge buildup, stability over time, and environmental resistance (does not include chromium metal, which poses a risk of environmental pollution), and that gives high gradation images. To do.

[0007]

The present inventors have made diligent efforts to solve the above-mentioned problems, and as a result of including a specific compound in the toner, the charge distribution of the toner is sharpened and the charging characteristics are significantly improved. The present invention has been completed by finding out that it is improved. That is, the present invention uses the formula (1)

[0008]

[Chemical 2]

(In the formula (1), R _{1 to} R ₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, a nitro group, a cyano group or an aryl group, and R ₁ And R ₂ and R ₃ and R ₄ may combine with each other to form a ring, and A ⁺ represents a cation.)
The present invention provides an electrophotographic toner containing at least one compound represented by:

The compound of the formula (1) acts as a negative charge control agent, but it has a good compatibility with the binder resin, and the toner containing it has a high specific charge amount and its stability over time. Since the toner is good, it provides a stable and clear image in the image formation of electrostatic recording even if the toner is stored for a long time. It also does not include metals that may cause environmental pollution. The present invention will be described in detail. Specific examples of A ⁺ (cation) in the formula (1) include hydrogen ion, sodium ion, potassium ion, ammonium ion, aliphatic ammonium ion, alicyclic ammonium ion, heterocyclic ammonium ion, phosphonium ion, and the like. These may have a substituent. In addition, specific examples of the compound represented by the formula (1) include compounds represented by the following structural formulas, but the compound is not limited to these. In the specific examples, Me represents a methyl group, Et represents an ethyl group, Ph represents a phenyl group, and tBu represents a tert-butyl group.

Specific examples of compounds

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[Chemical 49]

These compounds can be obtained, for example, by dissolving thiosalicylic acid or a thiosalicylic acid derivative in a solvent such as methanol, and adding an aqueous solution of zinc acetate to the mixture in a molar ratio of 2: 1 to carry out a reaction. The cation of the complex salt thus formed can be exchanged for another cation by a known method. Next, synthetic examples of the compound of the formula (1) of the present invention are shown. Unless otherwise specified, the middle part of the synthesis examples represents parts by weight.

Synthesis Example 1. (Specific Example (1)) 12.3 parts of thiosalicylic acid was dissolved in 300 parts of methanol, and 8.8 parts of zinc acetate dissolved in 100 parts of water was added dropwise to the solution and heated under reflux for 1 hour. .. After allowing to cool, it was filtered and washed with methanol to obtain 9.2 parts of colorless crystals.

Synthesis Example 2. (Specific Example (10)) A sodium hydroxide aqueous solution was added to the reaction solution obtained in Synthesis Example 1 to adjust the pH to 9 to 10, and then the crystals were separated by filtration and washed with methanol and water until the pH reached 7. 11.6 parts of colorless crystals are obtained.

Synthesis Example 3. (Specific Example (13)) Ammonia water was added to the reaction solution obtained in Synthesis Example 1 to adjust the pH to 9 to 10, and then the crystals were separated by filtration, washed with methanol and then with water until the pH became 7, and colorless. Crystal 1
0.5 part was obtained.

Synthesis Example 4. (Specific Example (18)) 6.2 parts of thiosalicylic acid was dissolved in 150 parts of methanol, and a solution prepared by dissolving 8.8 parts of zinc acetate in 100 parts of water was added dropwise to the solution and heated under reflux for 1 hour. Then, what melt | dissolved 7.6 parts of 5-chlorothiosalicylic acid in 150 parts of methanol is added, and it heats under reflux for 1 hour. After allowing to cool, it was filtered and washed with methanol to give colorless crystals.
I got 3 parts.

As a method for producing a toner containing the compound of the formula (1), a mixture of the compound of the formula (1), a colorant and a binder resin can be heated and mixed with a heating kneader, a two-roll roll or the like. A binder resin melted and kneaded in an apparatus, and then cooled and solidified to obtain a particle size of 3 to 20 μ by a crusher such as a jet mill or a ball mill. The compound is dissolved in a solvent (eg, acetone, ethyl acetate), stirred, thrown into water for reprecipitation, filtered, dried, and then pulverized with a pulverizer such as a ball mill to 3-2.
There is a method of obtaining by pulverizing to a particle size of 0 μ. The compound of formula (1), the colorant and the monomer of the binder resin are uniformly suspended in water, the monomer is polymerized in the form of fine particles under stirring to form a precipitate, and the precipitate is filtered, Washing with water,
Dry to a fine powder and classify it to 3-20μ
There is a method for obtaining the target product of the particle size of the above, and a soft particle upper core material (core particle) containing a low melting point resin for pressure fixing, a coloring component, a magnetic substance, etc. It can also be used as an outer shell material of a microcapsule toner having a shell-covered form. Furthermore, the colored fine particles not containing a charge control agent are prepared by the above method, and then the compound of the formula (1) is fixedly added to the particle surface by a mechanochemical method or the like alone or together with an external additive such as colloidal silica. You can also In this case, the binder resin is usually 99 to 65%, more preferably 98 to 85%,
The colorant is 1.0 to 15%, more preferably 1.5 to 10%
%, The charge control agent is preferably 0.1 to 30%, more preferably 0.5
Used at a rate of ˜5% (both by weight).

Examples of colorants that can be used in the electrophotographic toner of the present invention include inorganic pigments such as carbon black and ultramarine blue, CI. Pigment Yellow 1, CI. Pigment Red 9,
CI. Pigment Blue 15, organic pigments such as CI. Solven
t Yellow 93, CI. SolventRed 146, CI. Solvent
Blue 35, CI. Disperse Yellow 42, CI. Dispe
rse Red 59, CI. Conventionally known coloring agents such as oil-soluble dyes such as Disperse Blue 81 (CI is an abbreviation for color index, the same applies hereinafter) can be mentioned. Further, as the binder resin, polystyrene, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, acrylic resin, styrene-maleic acid copolymer, polyvinyl chloride, polyvinyl acetate, olefin resin, polyester resin, polyurethane Resin, epoxy resin, etc. alone or
It can be mixed and used. Further, a flow agent such as silicon oxide, an antifoggant such as mineral oil, various magnetic materials for one-component system, a conductivity-imparting agent such as zinc oxide, etc. may be added to the electrophotographic toner of the present invention as required. Good.

The toner obtained in the present invention is, for example, 200
Mesh-like iron powder (carrier) and, for example, 3-8: 9
7-92 (toner: iron powder) is mixed in a weight ratio to form a developer, which is used in the developing step in electrophotography. The electrophotographic toner of the present invention has a sharp charge amount distribution and good stability over time as compared with a toner using a conventional charge control agent. As a result, an image with extremely high gradation is obtained and the repetitive image forming ability is extremely good. Further, since the compound of the formula (1) is colorless, there is an advantage that it can be used together with various colorants regardless of the hue of the colorant used in the toner.

[0066]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts represent parts by weight unless otherwise specified.

Example 1 Styrene-butyl acrylate copolymer (binder) 100 parts Low molecular weight polyethylene 3 parts CI. Disperse Yellow 164 (coloring agent) 1.2 parts Compound of specific example (1) 1.5 parts Melt-mixing treatment (10 minutes) with a kneader adjusted to 120 to 140 ° C., followed by cooling and solidification I'm sorry. Then, after coarsely pulverizing with a coarse pulverizer, fine pulverization was performed with a jet mill pulverizer, and further classified with an air stream type classifier to obtain a toner having a particle size of 5 to 20 μm. The toner thus obtained was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer A. Next, the developer A is measured by a blow-off charge amount measuring device.
When the initial specific charge of was measured, it was -33.9 μC / g
Met. Further, copying was carried out by a copying machine using the developer A, and a clear yellow image excellent in gradation and not impeding the hue of the colorant was obtained. Also,
A stability test with time (charge amount change test, charge amount humidity resistance stability test) was carried out using the developer A.
And the results of Table 2 were obtained.

Table 1 Charge amount aging test (unit: −μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent A 33.9 35.8 36.4 36.5 36.6 36.6

Table 2 Moisture resistance stability test of charge amount (unit: -μC / g) Initial charging After humidity resistance test Decay rate (%) 33.9 30.7 9.4

As shown in the above results, the temporal stability of the developer A was extremely excellent. The stability test with time was performed by the following method. Charge amount stability test with time A developer (mixture of toner and iron powder carrier) is weighed in a poly container and contact charged by a ball mill at 120 rpm for 6 hours, and the charge amount of the toner at each time is blow-off method. To measure. Charge amount moisture resistance stability test Similar to the above charge amount aging stability test, the developer was weighed in a poly container, the container was opened and left at 35 ° C. and 90% RH for 2 days, and a ball mill at 120 rpm was used. After 15 minutes of contact charging, the charge amount of the toner is measured by the blow-off method.

Example 2 Polyester resin 100 parts Carbon black 6.0 parts Compound of the specific example (10) 1.5 parts Melt mixing treatment (10 minutes) with a kneader adjusted to 120-140 ° C. After that, it was cooled and solidified. Then, after coarse pulverization with a coarse pulverizer, fine pulverization with a jet mill pulverizer, and further classification with an air stream classifier to obtain a toner having a particle size of 5 to 20 μm. The obtained toner was mixed with an iron powder carrier of about 200 mesh and 3:97 (toner:
Iron powder carrier) was mixed in a weight ratio to obtain a developer B. Next, when the initial specific charge amount of the developer B was measured by a blow-off charge amount measuring device, it was −29.1 μC / g. Further, copying was carried out with a copying machine using this developer B, and a black image excellent in gradation was obtained. Further, when a temporal stability test was performed in the same manner as in Example 1 using Developer B, the results shown in Tables 3 and 4 below were obtained.

Table 3 Charge amount aging test (unit, −μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent B 29.1 31.0 33.3 33.3 33.4 33.5

Table 4 Charge amount humidity resistance stability test (unit, -μC / g) Initial charge After humidity resistance test Decay rate (%) 29.1 26.5 8.9

As can be seen from the above results, developer B was extremely excellent in stability over time and humidity resistance.

Example 3 Styrene-acrylic acid methyl ester copolymer 100 parts Low molecular weight polypropylene 3 parts CI. Solvent Blue 111 1.5 parts The compound of the specific example (14) 1.5 parts

The above mixture was dissolved in a mixed solvent of 1000 parts of acetone and ethyl acetate (volume ratio 8: 2), and stirred at room temperature for 1 hour. This mixture is then added to 10,000
Part of the mixture was added dropwise to water with stirring to cause precipitation. The formed precipitate was filtered and dried to obtain a coarse particle toner.
Then, fine pulverization was carried out with a jet mill pulverizer, and further classification was carried out with a gas stream type classifier to obtain a toner of 5-20 μm. The obtained toner was mixed with an iron powder carrier of about 200 mesh and 3: 9.
7 (toner: iron powder carrier) mixed in a weight ratio of developer C
Got Then, the initial specific charge amount of this developer C was measured by a blow-off charge amount measuring device to find that it was −32.1 μC.
/ G. Further, copying was carried out by a copying machine using this developer C, and a clear blue image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, when a temporal stability test was performed in the same manner as in Example 1 using Developer C, the results shown in Tables 5 and 6 below were obtained.

Table 5 Charge amount aging test (unit, -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent C 32.1 32.4 32.3 32.3 32.9 33.0

Table 6 Charge amount humidity resistance stability test (unit, -μC / g) Initial charge After humidity resistance test Decay rate (%) 32.1 30.4 5.3

As shown in the above results, the temporal stability and humidity resistance stability of the developer C were extremely excellent.

Example 4 Epoxy resin 100 parts CI. Disperse Red 60 1.2 parts CI. Disperse Violet 17 0.3 parts Compound of the specific example (16) 2.0 parts The mixture having the above composition was melt-mixed with a kneader adjusted to 110 to 130 ° C., then naturally cooled and solidified.
Next, fine pulverization was performed with a coarse pulverizer and a jet mill pulverizer, and further classification was performed with an airflow classifier to obtain a toner having a particle size of 5 to 20 μm. 0.3 part of colloidal silica was mixed with 100 parts of the obtained toner by a Henschel mixer. This was mixed with about 200 mesh iron powder carrier and 3:97.
(Toner: iron powder carrier) mixed in a weight ratio of developer D
Got Then, the initial specific charge amount of this developer D was measured by a blow-off charge amount measuring device to be -21.8 μC.
/ G. Further, copying was carried out by a copying machine using this developer D, and a clear red image excellent in gradation and not hindering the original hue of the colorant was obtained.
Further, a time-dependent stability test was conducted in the same manner as in Example 1 using Developer D, and the results shown in Tables 7 and 8 below were obtained.

Table 7 Charge amount aging test (unit: −μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent D 21.8 23.7 24.1 24.3 24.5 24.5

Table 8 Charge amount humidity resistance stability test (unit, -μC / g) Initial charge After humidity resistance test Decay rate (%) 21.8 18.7 14.2

As shown in the above results, the temporal stability of the developer D was extremely excellent.

Example 5 Epoxy resin 100 parts CI. Disperse Red 60 1.2 parts Compound of Specific Example (21) 2.0 parts The mixture having the above composition was melt-mixed with a kneader adjusted to 120 to 130 ° C., then naturally cooled and solidified.
Next, fine pulverization was performed with a coarse pulverizer and a jet mill pulverizer, and further classification was performed with an airflow classifier to obtain a toner having a particle size of 5 to 20 μm. To 100 parts of the obtained toner, 0.3 part of colloidal silica was added and mixed with a Henschel mixer. This was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer E. Then, the initial specific charge amount of the developer E was measured by a blow-off charge amount measuring device.
It was 7.8 μC / g. Further, copying was carried out by a copying machine using the developer E, and a clear red image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, a time-dependent stability test was conducted in the same manner as in Example 1 using the developer E, and the results shown in Tables 9 and 10 below were obtained.

Table 9 Charge amount aging test (unit: −μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent E 27.8 29.2 31.8 31.9 32.5 32.8

Table 10 Charge amount humidity stability test (unit: -μC / g) Initial charge After humidity resistance test Decay rate (%) 27.8 26.3 5.4

As shown in the above results, the temporal stability of the developer E was extremely excellent.

Example 6 Styrene-butyl acrylate copolymer 100 parts Molecular weight polyethylene 3 parts Kayaset Yellow 963 1.2 parts Compound of the specific example (22) 1.5 parts The mixture of the above composition was adjusted to 125-140 ° C. After melt-mixing treatment (10 minutes) with a kneader, it was cooled and solidified. Then, after coarsely pulverizing with a coarse pulverizer, fine pulverization was performed with a jet mill pulverizer, and further classified with an air stream type classifier to obtain a toner having a particle size of 5 to 20 μm. The toner thus obtained was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer F. Then, the initial specific charge amount of the developer F was measured by a blow-off charge amount measuring device to be −27.3 μC / g
Met. Further, when copying was performed by a copying machine using this developer F, a clear yellow image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, when a temporal stability test (charge amount temporal change test, charge amount moisture resistance stability test) was conducted using the developer F in the same manner as in Example 1, the results shown in Tables 11 and 12 below were obtained.

Table 11 Charge amount aging test (unit: −μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent F 27.3 30.0 30.7 31.1 31.5 31.4

Table 12 Moisture resistance stability test of charge amount (unit: -μC / g) Initial charging After humidity resistance test Attenuation rate (%) 27.3 25.0 8.4 As shown by the above results, the stability of the developer F with time was extremely excellent.

Example 7 Methyl styrene monomer 75 parts Ethyl acrylate monomer 20 parts Kayase Blue 814 1.8 parts Benzoyl peroxide 6 parts Compound of the above-mentioned specific example (47) 2 parts The mixture having the above composition is used for 5 minutes using a homomixer. The mixture is stirred and mixed to obtain a homogeneous liquid substance, which is added to a dispersion liquid of water: 120 parts / magnesium carbonate: 2.3 parts, and stirred by a homomixer at 6500 rpm for 5 minutes to obtain a uniform suspension.
Add this suspension to a 300 ml three-necked flask and
Polymerize at 70 ° C for 5 hours with stirring at rpm,
After allowing to cool to 40 ° C., 90 parts of a 5% dilute hydrochloric acid aqueous solution was added, filtered, washed with water and dried at 40 ° C. to obtain a toner having a particle size of 5 to 20 μm. 0.3 part of colloidal silica was mixed with 100 parts of the obtained toner by a Henschel mixer. This was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer G. Then, the initial specific charge amount of the developer G was measured by a blow-off charge amount measuring device to be -20.3 μC / g.
Met. Further, when copying was performed by a copying machine using this developer G, a clear blue image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, when a temporal stability test was performed using Developer G in the same manner as in Example 1, the results shown in Tables 13 and 14 below were obtained.

[0092]

Table 14 Charge amount humidity resistance stability test (unit: μC / g) Initial charge After humidity resistance test Decay rate (%) 20.3 19.1 6.0

As shown in the above results, the temporal stability of the developer G was extremely excellent.

Example 8-19 A developer was prepared in the same manner as in Example 1 using the compounds shown in the column of "Compound" and the colorants shown in the column of "Colorant" in Tables 15-18, The initial specific charge amount of each of the obtained toners was measured, and a stability test with time was performed in the same manner as in Example 1. The toners using any of the compounds showed little change in the charge amount, and the temporal stability of the developer was extremely excellent. Further, when copied by a copying machine, all the developers were excellent in gradation and a clear image having the original hue of the colorant was obtained.

Table 15 Charge amount aging test (unit: −μC / g) Example time (h) 0.25 0.5 1.0 2.0 4.0 6.0 8. Specific example (2) CI.Dis.Y.164 23.5 24.5 24.6 24.8 25.1 25.3 9. Specific example (4) CI.Dis.B.81 21.2 21.4 21.7 23.0 23.2 23.5 10. Specific example (5) CI.Dis.R.60 20.1 21.5 21.5 21.3 21.1 21.9 11. Specific example (6) CI.Pig.R.9 25.1 27.9 28.3 28.4 28.5 28.5 12. Specific example (7) CI.Pig.R.146 26.8 27.5 28.8 29.0 29.2 29.2

Table 16 Charge amount humidity resistance stability test (unit, -μC / g) Example Initial charge After humidity resistance test Attenuation rate (%) 8. 23.5 19.9 15.3 9. 21.2 18.0 15.1 10. 20.1 18.1 10.0 11. 25.1 21.6 13.9 12. 26.8 23.6 12.0

Table 17 Charge amount aging test (unit, -μC / g) Time (h) Example compound Colorant 0.25 0.5 1.0 2.0 4.0 6.0 13. Specific example (8) CARBON BLACK 26.8 28.3 29.3 29.5 29.9 29.6 14. Specific example (9) CI.Pig.Y.1 17.2 19.1 19.2 20.2 20.8 21.2 15. Specific example (11) CI.Sol.R.146 28.7 29.4 29.8 30.2 30.5 30.7 16. Specific example (13) Kayaset.Y.963 24.9 27.8 28.2 28.5 28.9 29.2 17. Specific example (15) CI.Sol.B.111 21.8 24.2 24.6 24.5 24.3 24.3 18. Specific example (19) CI.Dis.B.35 20.2 21.9 22.2 22.0 22.1 22.3 19. Specific example (24) CI.Pig.R.146 18.7 19.5 19.9 19.8 19.6 19.5

Table 18 Charge amount humidity resistance stability test (unit, -μC / g) Example Initial charge After humidity resistance test Attenuation rate (%) 13. 26.8 23.9 10.8 14. 17.2 16.2 5.8 15. 28.7 26.2 8.7 16. 24.9 23.2 6.8 17. 21.8 21.0 3.7 18. 20.2 19.5 3.5 19. 18.7 17.6 5.9

(Note) Colorant CI. : Color Index, Sol: Solve
nt, Dis: Disperse, Pig: Pigme
nt, B: Blue, R: Red, Y: Yellow,
Kayaset is a trade name of Nippon Kayaku Co., Ltd., an organic pigment

[00101]

The electrophotographic toner obtained in the present invention has a sharp charge amount distribution, humidity resistance and stability over time as compared with the toner using the conventional charge control agent. As a result, an image with extremely high gradation is obtained, and the repetitive image forming ability is extremely good. In addition, since the charge control agent itself is essentially colorless, it is possible to select an arbitrary colorant in accordance with the hue required for the color toner, and what is the original hue of the dye or pigment. Another feature is that it does not interfere.

Claims (1)

What is claimed is: 1. An electrophotographic toner comprising at least one compound represented by the following formula (1): (In the formula (1), R _{1 to} R ₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, a nitro group, a cyano group or an aryl group,
R ₁ and R ₂ and R ₃ and R ₄ may combine with each other to form a ring, and A ⁺ represents a cation. )