JPH0545932A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To make the electrostatic charge distribution of a toner sharp and to improve the electrostatic charge characteristics of the toner by incorporating a metal complex compd. having specified charge controlling characteristics into the toner. CONSTITUTION:A compd. expressed by formula I is incorporated into the toner. In the formula I, A1 is a hydrogen atom, halogen atom, or alkyl group, R1-R4 are hydrogen atoms or alkyl groups, M is a bivalent metal such as beryllium, calcium, zinc, barium, copper, etc. The compd. of formula I is a Schiff base metal complex to which a substd. or unsubstd. amiono group is introduced and it acts as a positive charge controlling agent. This compd. has good solubility with a binder resin, and the obtd. toner has high specific charge amt. and good stability for a long time. Thus, the toner can give clear image for electrostatic recording even when it is stored 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. Examples of 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-45-26478, JP-B-41-20).
1531) Phthalocyanine pigments (eg, JP-A-52-45)
931) Also, as an example of a colorless negative charge control agent, Japanese Patent Publication No.
9-7384 or the charge control agents described in JP-A-61-3149, and (2) as positive charge control agents, nigrosine dyes, organic tin compounds such as dibutyltin oxide (eg, JP-B-57-
29704) and the like are known, but a toner containing them 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. Further, 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 a difficulty in dispersibility. Is JP-A-61-3149
However, since these compounds have a low melting point, they have poor thermal stability during toner production and it is difficult to produce a stable toner. Furthermore, JP-A-61-149967 and JP-A-63-206767 introduce a metal complex of a Schiff base, but a toner containing this compound as a charge control agent is not good in chargeability and stability over time. There are drawbacks. 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, positively charged charge which has good dispersibility in a binder resin, is not affected by changes in temperature and humidity, and has high charge controllability. Another object of the present invention is to provide a control agent, and further to provide a positively chargeable toner which is excellent in rising of charge and stability over time and gives an image with high gradation.

[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), A ₁ represents a hydrogen atom, an alkyl group or a halogen atom, R _{1 to} R ₄ each independently represent a hydrogen atom or an alkyl group, and M represents a divalent metal.) The present invention provides an electrophotographic toner containing at least one compound represented by:

The metal complex of the Schiff base introduced with the substituted or unsubstituted amino group represented by the formula (1) acts as a positive charge control agent, but this one has good compatibility with the binder resin, The toner containing this has a high specific charge amount and has good stability over time, so that it can provide a stable and clear image in the image formation of electrostatic recording even if the toner is stored for a long time. is there. The present invention will be described in detail. The compound of formula (1) is a complex of a divalent metal such as beryllium, calcium, zinc, barium or copper, and a zinc complex is particularly preferable. Specific examples of the formula (1) contained in the toner as the charge control agent in the present invention include, but are not limited to, the compounds represented by the following structural formulas.

In the compound whose basic structure is represented by the formula (2), A ₁ , R _{1 to} R ₄ and M are shown in Table 1. Also, A ₁
When is other than hydrogen, the substitution position is indicated.

[0012]

[Chemical 3]

Table 1 Specific example number A ₁ R ₁ R ₂ R ₃ R ₄ M 1. H CH ₃ CH ₃ CH ₃ CH ₃ Zn 2. 5 CH ₃ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Zn 3. 6 Cl CH ₃ CH ₃ CH ₃ CH ₃ Zn 4. HC ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Zn 5. HHHHH Zn 6. 6 C ₂ H ₅ HHHH Ca 7. H CH ₃ CH ₃ CH ₃ CH ₃ Be 8. 5 C ₂ H ₅ CH ₃ CH ₃ CH ₃ CH ₃ Cu 9. HC ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Ca 10. HC ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Be 11. 6 C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Cu 12. H CH ₃ CH ₃ C ₂ H ₅ C ₂ H ₅ Zn 13. H CH ₃ CH ₃ C ₂ H ₅ C ₂ H ₅ Ba 14. 3 Cl H CH ₃ H CH ₃ Cu 15. HH CH ₃ H CH ₃ Cu 16. 5 CH ₃ H CH ₃ H CH ₃ Zn 17. 5 C ₃ H ₇ H CH ₃ H CH ₃ Be 18. 3 Br HC ₂ H ₅ HC ₂ H ₅ Zn 19. 6 C ₂ H ₅ HC ₂ H ₅ HC ₂ H ₅ Zn 20. H CH ₃ C ₂ H ₅ CH ₃ C ₂ H ₅ Zn 21. HHHC ₂ H ₅ C ₂ H ₅ Zn 22. HHHC ₂ H ₅ C ₂ H ₅ Ba 23. H nC ₄ H ₉ nC ₄ H ₉ nC ₄ H ₉ nC ₄ H ₉ Zn 24. 6 nC ₄ H ₉ nC ₄ H ₉ nC ₄ H ₉ nC ₄ H ₉ nC ₄ H ₉ Be 25. H tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ Ba 26. Cl tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ Zn 27. 5 tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ Cu 28. H tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ Be 29. H tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ tC ₄ H ₉ Ba 30. 6 Cl nC ₆ H ₁₃ nC ₆ H ₁₃ nC ₆ H ₁₃ nC ₆ H ₁₃ Zn 31. H nC ₆ H ₁₃ nC ₆ H ₁₃ nC ₆ H ₁₃ nC ₆ H ₁₃ Be 32. H nC ₉ H ₁₉ nC ₉ H ₁₉ nC ₉ H ₁₉ nC ₉ H ₁₉ Zn 33. 5 F nC ₄ H ₉ nC ₈ H ₁₇ nC ₄ H ₉ nC ₈ H ₁₇ Zn

Table ₁ shows A ₁ , R _{1 to} R ₄ and M in the compound whose basic structure is represented by the formula (3). Also, A
_{When 1} was other than hydrogen, the substitution position was indicated.

[0015]

[Chemical 4]

Table 2 Specific example number A ₁ R ₁ R ₂ R ₃ R ₄ M 34. H CH ₃ CH ₃ CH ₃ CH ₃ Zn 35. HC ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Zn 36. 4 CH ₃ CH ₃ CH ₃ CH ₃ CH ₃ Ba 37. 6 Cl CH ₃ CH ₃ CH ₃ CH ₃ Zn 38. 4 C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Ba 39. 3 Br C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ C ₂ H ₅ Zn 40. HHHHH Be 41. 4 tC ₄ H ₉ HHHH Cu

These compounds are, for example, benzene,
In a solvent such as toluene, the Schiff base obtained by reacting an aminosalicylaldehyde derivative with ethylenediamine is dissolved in a solvent such as acetone, and an aqueous solution of an inorganic metal salt is added thereto to cause a reaction, which is obtained by adjusting the pH. Be done.

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 method of kneading the binder resin under melting with an apparatus, then cooling and solidifying the solidified material into a particle size of 3 to 20 μm by a crusher such as a jet mill or a ball mill, a colorant, a binder resin and a compound of the formula (1) 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. In this case, the binder resin is usually 99 to 65%, preferably 98 to 85%, the colorant is 1.0 to 15%, more preferably 1.5 to 10%, and the charge control agent is 0.1 to 30%. It is used in a proportion of 0.5 to 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 nearly colorless, there is an advantage that it can be used together with various colorants without being influenced by the hue of the colorant used in the toner.

[0021]

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.

Synthetic Example (Specific Example (1)) 11.6 parts of 4-diethylaminosalicylaldehyde was added to 1
Dissolve in 50 parts of benzene, add 1.2 parts of ethylenediamine little by little thereto, and heat under reflux for 8 hours.
Remove the water produced in the ean-Stark trap.
Benzene was distilled off with an evaporator to produce a Schiff base 11.
Get 7 copies. Next, 11.7 parts of the obtained Schiff base was dissolved in 300 parts of acetone, and a solution of 6.2 parts of zinc acetate in 100 parts of water was added dropwise to the solution and reacted for 2 hours under reflux, Ammonia water (10 parts) was added, and the mixture was filtered, washed with water and then with acetone to obtain 8.5 parts of the compound of the specific example (1) (light yellow crystals).

Example 1 Styrene-butyl acrylate copolymer (binder) 100 parts Low molecular weight polyethylene 3 parts CI. Disperse Yellow 164 (colorant) 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.
The initial specific charge of was measured to be +32.7 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 time-dependent stability test (charge amount time-dependent change test, charge amount moisture resistance stability test) was carried out using the developer A, and the results are shown in Table 3 below.
And the results of Table 4 were obtained.

Table 3 Charge Aging Change Test (Unit: + μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging Agent A 32.7 32.9 33.0 32.6 32.4 32.3

Table 4 Moisture resistance stability test of charge amount (unit: + μC / g) Initial charging After humidity resistance test Attenuation rate (%) 32.7 29.5 9.8

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 aging test 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 measured by a blow-off method. taking measurement. Charge amount moisture resistance stability test Similar to the above charge amount aging 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. 1
After contact charging for 5 minutes, 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 specific example (4) 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 +28.3 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 conducted in the same manner as in Example 1 using Developer B, 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 B 28.3 29.0 29.4 29.5 29.4 29.1

Table 6 Charge amount humidity resistance stability test (unit: + μC / g) Initial charge After humidity resistance test Decay rate (%) 28.3 25.4 10.2

As can be seen from the above results, the temporal stability and humidity resistance stability of the developer B were extremely excellent.

Example 3 Styrene-acrylic acid methyl ester copolymer 100 parts Low molecular weight polypropylene 3 parts CI. Solvent Blue 111 1.5 parts Compound of Specific Example (10) 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 the developer C was measured by a blow-off charge amount measuring device to be +34.4 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, a time-dependent stability test was conducted in the same manner as in Example 1 using the developer C, 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 C 34.4 35.6 34.8 32.8 32.5 32.0

Table 8 Charge amount humidity resistance stability test (unit, + μC / g) Initial charge After humidity resistance test Decay rate (%) 34.4 31.6 8.1

As shown in the above results, the stability of developer C with time and the stability against humidity 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 (24) 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 the developer D was measured by a blow-off charge amount measuring device to be +27.9 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, when a temporal stability test was performed using Developer D in the same manner as in Example 1, 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 D 27.9 28.6 28.7 28.7 28.8 29.1

Table 10 Moisture resistance stability test for charge amount (unit: + μC / g) Initial charging After humidity resistance test Attenuation rate (%) 27.9 24.5 12.2

As can be seen from the above results, the temporal stability and humidity resistance stability of the developer D were extremely excellent.

Example 5 Epoxy resin 100 parts CI. Disperse Red 60 1.2 parts Compound of Specific Example (32) 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, which was +3.
It was 1.3 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 Developer E, and 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 E 31.3 32.3 32.5 32.9 33.1 33.1

Table 12 Charge amount humidity stability test (unit: + μC / g) Initial charge After humidity resistance test Decay rate (%) 33.1 30.7 7.3

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

Example 6 Styrene-butyl acrylate copolymer 100 parts Molecular weight polyethylene 3 parts Kayaset Yellow 963 1.2 parts Compound of the specific example (36) 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 this developer F was measured by a blow-off charge amount measuring device to be +29.5 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 performed using the developer F in the same manner as in Example 1, the results shown in Tables 13 and 14 below were obtained.

Table 13 Charge amount aging test (unit, + μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Imaging agent F 29.5 30.0 30.7 30.6 30.3 30.2

Table 14 Moisture resistance stability test of charge amount (unit: + μC / g) Initial charging After humidity resistance test Attenuation rate (%) 29.5 26.8 9.2 As the above results, the temporal stability and humidity resistance stability of the developer F are extremely high. Was excellent.

Examples 7-16 Developers were prepared in the same manner as in Example 1 using the compounds shown in the "Compound" column and the colorants shown in the "Colorant" column in Tables 15 and 17. 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) Time (h) Example compound Colorant 0.25 0.5 1.0 2.0 4.0 6.0 7. Specific example (3) CI.Dis.Y.164 22.1 22.4 22.4 22.3 22.1 22.1 8. Specific example (6) CI.Pig.R.9 18.2 19.5 19.9 18.7 18.5 17.9 9. Specific example (10) CI.Dis.B.81 31.1 31.7 30.3 29.4 29.3 29. 01 10. Specific example (16) CI.Pig.Y.1 17.2 19.1 19.2 20.2 20.8 21. 2 11. Specific example (20) CI.Pig.R.146 27.3 28.2 29.3 29.5 29.9 29.6

Table 16 Moisture resistance stability test of charge amount (unit: + μC / g) Example Initial charging After humidity resistance test Attenuation rate (%) 7. 22.1 19.8 10.4 8. 18.2 15.8 13.2 9. 31.1 28.5 8.4 10. 17.2 15.9 7.6 11. 27.3 23.9 12.4

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 12. Specific example (25) CI.Sol.R.146 28.7 29.4 29.8 30.2 30.5 30.7 13. Specific example (27) Kayaset.Y.963 24.9 27.8 28.2 28.5 28.9 29.2 14. Specific example (31) CI.Sol.B.111 21.8 24.2 24.6 24.5 24.3 24.3 15. Specific example (35) CI.Dis.R.60 29.3 29.6 29.5 29.3 29.1 28.9 16. Specific example (40) CARBON BLACK 16.2 17.5 17.2 17.0 16.6 15.4

Table 18 Charge amount humidity resistance stability test (unit, + μC / g) Example Initial charge After humidity resistance test Decay rate (%) 12. 28.7 26.0 9.4 13. 24.9 22.2 10.8 14. 21.8 20.3 6.9 15. 29.3 26.8 8.5 16. 16.2 14.4 11.1

Comparative Example 1-2 A developer was prepared in the same manner as in Example 1 except that the compounds of the following formulas (4) and (5) were used, and the initial specific charge of each of the obtained toners was measured. Tables 19 and 20 show the results of carrying out the stability test with time in the same manner as in Example 1.

[0055]

[Chemical 5]

[0056]

[Chemical 6]

Table 19 Charge amount aging test (unit: −μC / g) Time (h) Comparative example Compound 0.25 0.5 1.0 2.0 4.0 6.0 1. Formula (4) 0.7 1.2 3.9 6.2 8.6 9.2 2. Formula (5) 1.7 2.7 3.8 6.2 6.8 7.5

Table 20 Charge amount humidity resistance stability test (unit, -μC / g) Comparative example Initial charge After humidity resistance test Attenuation rate (%) 1. 0.7 0.6 14 2. 1.7 1.4 24

As shown in the above results, the toners using any of the compounds were negatively charged, and the charge amount was low. Further, the developer was lacking in stability over time.

(Note) Colorant CI. : Color Index, Sol: Solve
nt, Dis: Disperse, Pig: Pigment,
B: Blue, R: Red, Y: Yellow, and Kayaset are trade names of Nippon Kayaku Co., Ltd., organic pigments.

[0061]

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 nearly colorless, it is possible to select an arbitrary colorant according to the hue required for the color toner, and to prevent the original hue of the dye or pigment from occurring. There is also no feature.

Claims (1)

[Claims] 1. An electrophotographic toner comprising at least one compound represented by the following formula (1): (In the formula (1), A ₁ represents a hydrogen atom, an alkyl group or a halogen atom, R _{1 to} R ₄ each independently represent a hydrogen atom or an alkyl group, and M represents a divalent metal.)