JP2901162B2 - Electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 utilizing static electricity include phthalocyanine pigments, 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, amorphous silicon or the like on a substrate such as aluminum or paper;
In the two-component developing method, the colored fine particles adjusted to 5 to 50 μ called the toner are charged by contacting the toner with a carrier (iron powder, ferrite powder, etc.). In the one-component developing method, the toner is directly charged. After that, it is made to act on the electrostatic latent image to make it visible. Note that the toner needs to be provided with a charge corresponding to the polarity of the electrostatic latent image formed on the photoreceptor, that is, any of positive and negative charges.

[0003] Colored fine particles generally called a toner are composed of a binder resin and a coloring material as essential components, and magnetic powder and the like as other optional components. As a method for imparting charge to the toner, the charge characteristics of the binder resin itself can be used without using a charge control agent, but they are inferior in stability over time and moisture resistance and cannot obtain good image quality. Accordingly, 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, and the like. These quality characteristics are greatly affected by the charge control agent used in the toner. Conventional charge control agents added to toner include (1) a 2: 1 type metal-containing complex dye as a colored negative charge control agent (eg, Japanese Patent Publication No. 45-2647).
8, JP-B-41-201531) phthalocyanine pigments (for example, JP-A-52-5931). Examples of colorless negative charge control agents are JP-B-59-7384 or JP-A-61-73184.
And (2) as a positive charge control agent, an organotin compound such as a nigrosine dye or dibutyltin oxide (eg, Japanese Patent Publication No. 57-2970).
4) are known, but toners containing these as a charge control agent do not sufficiently satisfy quality characteristics required for the toner such as chargeability and stability over time.

That is, since a 2: 1 metal-containing complex dye known as a negative charge control agent and a nigrosine dye known as a positive charge control agent are themselves colored, a toner having a limited hue centering on black is used. And the toner has poor stability over time for continuous copying of toner. Further, as an example of the negatively charge-controlling agent which is almost colorless, a metal complex of an aromatic dicarboxylic acid can be mentioned (Japanese Patent Publication No. 59-7384). However, this is a disadvantage that it cannot be completely colorless and has a disadvantage in its dispersibility. 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 is difficult to produce a stable toner due to poor thermal stability during toner production. There is a disadvantage that it is. As described above, the known charge control agents do 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 charged material which has good dispersibility in a binder resin, has high charge controllability without being affected by changes in temperature and humidity. Provides a control agent, and provides a negatively chargeable toner that excels in charge rise, stability over time and environmental friendliness (does not include chromium metal or the like, which may cause environmental pollution), and that provides images with high gradation. Is to do.

[0007]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above-mentioned problems, and as a result, by including a specific compound in the toner, the charge distribution of the toner is sharpened and the charge characteristics are greatly improved. The present invention has been completed. That is, the present invention relates to the formula (1)

[0008]

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[0009] In (Equation (1) represents R _1, R ₂ 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 may combine to form a ring.) The present invention provides an electrophotographic toner comprising at least one compound represented by the formula:

The compound of the formula (1) functions as a negative charge control agent, but has good compatibility with the binder resin, and the toner containing the compound has a high specific charge amount and has a long-term stability. Because of its good quality, even if the toner is stored for a long period of time, a stable and clear image can be obtained in electrostatic recording image formation. It does not include metals that may cause environmental pollution. The present invention will be described in detail. Specific examples of the compound represented by the formula (1) include compounds represented by the following structural formulas, but are not limited thereto. 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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[0013]

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[0014]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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These compounds are obtained, for example, by dissolving thiosalicylic acid or a thiosalicylic acid derivative in a solvent such as methanol, adding a zinc acetate solution to the mixture in a molar ratio of 1: 1 and reacting the resultant. Next, a synthesis example of the compound of the formula (1) of the present invention will be described. In the synthesis examples, parts represent parts by weight unless otherwise specified.

Synthesis Example (Specific Example (1)) A solution prepared by dissolving 6.2 parts of thiosalicylic acid in 100 parts of methanol and dissolving 8.8 parts of zinc acetate in 100 parts of methanol was added dropwise at room temperature. After stirring for one hour,
Filter and wash with water and methanol to obtain colorless crystals 8.3
Got a part. The structure of the obtained compound was confirmed by elemental analysis, infrared absorption spectrum, and DSC.

The results of elemental analysis of this compound are shown below. Analytical value H: 1.68%, C: 38.67%, S: 14.96%, Z
n: 29.3% Theoretical value H: 1.85%, C: 38.65%, S: 14.74%, Z
n: 30.0%

FIG. 1 shows a chart of the infrared absorption spectrum of this compound.

The decomposition temperature of this compound by DSC (differential scanning calorimetry) was 478.1 ° C.

The compounds of the specific examples (2) to (21) were synthesized in the same manner, and the elemental analysis, infrared absorption spectrum, DS
C confirmed its structure.

As a method for producing a toner containing the compound of the formula (1), a mixture comprising the compound of the formula (1), a colorant and a binder resin can be mixed by heating using a heating kneader, a two-roller or the like. A method in which the mixture obtained by kneading the binder resin in a molten state with an apparatus and then cooling and solidifying the mixture is pulverized to a particle size of 3 to 20 μm with a pulverizer such as a jet mill or a ball mill. The compound is dissolved in a solvent (eg, acetone, ethyl acetate), stirred, thrown into water to reprecipitate, filtered, dried, and then crushed with a pulverizer such as a ball mill.
There is a method obtained by pulverizing to a particle size of 0μ. 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 more preferably 0.1 to 30%. It is used at a ratio of 0.5 to 5% (all by weight).

Examples of the colorant that can be used in the electrophotographic toner of the present invention include inorganic pigments such as carbon black and ultramarine blue; 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 or dispersible dyes such as Disperse Blue 81 (CI stands for Color Index, the same applies hereinafter). Also,
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 resins and the like can be used alone or as a mixture. Further, the electrophotographic toner of the present invention contains a fluidizing agent such as silicon oxide,
An anti-fogging agent such as mineral oil, various magnetic substances for one-component system, and a conductivity-imparting agent such as zinc oxide may be added as necessary.

The toner obtained in the present invention is, for example, 200
Mesh iron powder (carrier) and, for example, 3-8: 9
7-92 (toner: iron powder) is mixed at a weight ratio such as a developer to be used in a developing process in electrophotography. The toner for electrophotography of the present invention has a sharper charge amount distribution and better stability over time than toners using a conventional charge control agent. As a result, it is characterized in that 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 with various colorants without depending on the hue of the colorant used in the toner.

[0041]

EXAMPLES 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 are by weight unless otherwise specified.

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 A mixture of the above composition is melt-mixed (10 minutes) in a kneader adjusted to 120 to 140 ° C, then cooled and solidified. I was sorry. Next, after coarse pulverization by a coarse pulverizer, fine pulverization was performed by a jet mill pulverizer, and further classification was performed by an airflow 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 in a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer A. Next, the developer A
Was measured, the initial specific charge was -32.3 μC / g.
Met. Further, when copying was performed by a copying machine using this developer A, a clear yellow image was obtained with excellent gradation and without hindering the original hue of the colorant. Also,
When a stability test with time (charge amount change over time test, charge amount humidity resistance test) was performed using developer A, the following Table 1 was obtained.
And the result of Table 2 was obtained.

Table 1 Charge amount aging test (unit: -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer A 32.3 34.2 34.9 35.0 35.1 35.1

Table 2 Charge Amount Moisture Resistance Stability Test (Unit, -μC / g) Initial Charge After Moisture Resistance Test Decay Rate (%) 32.3 29.3 9.3

As described above, the stability of the developer A over time was extremely excellent. The aging stability test was performed according to the following method. Aging time change test A developer (a mixture of a toner and an iron powder carrier) is weighed in a plastic container and contact-charged with 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. Measure. Charge Amount Moisture Resistance Stability Test In the same manner as the charge amount aging change test, the developer was weighed in a poly container, the container was opened, left at 35 ° C. and 90% RH for 2 days, and then subjected to a ball mill at 120 rpm. 1
After contact charging for 5 minutes, the charge amount of the toner is measured by a blow-off method.

Example 2 100 parts of a polyester resin 6.0 parts of carbon black 1.5 parts of the compound of the specific example (2) 1.5 parts of the mixture having the above composition was melt-mixed in a kneader adjusted to 120 to 140 ° C. (10 minutes) After that, it was cooled and solidified. Next, after coarse pulverization with a coarse pulverizer, fine pulverization was performed with 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. The obtained toner was mixed with an iron powder carrier of about 200 mesh and 3:97 (toner:
(Iron powder carrier) 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 -27.6 μC / g. Further, when a copying machine was used to make a copy using this developer B, a black image having excellent gradation was obtained. When a stability test with time was carried out 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 Aging Test (Unit, -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer B 27.6 30.5 30.5 30.4 30.2 29.5

Table 4

As described above, the stability of the developer B with time was extremely excellent.

Example 3 Styrene-methyl acrylate copolymer 100 parts Low molecular weight polypropylene 3 parts CI. Solvent Blue 111 1.5 parts Specific compound (3) 1.5 parts

The above mixture was dissolved in 1000 parts of a mixed solvent of acetone and ethyl acetate (volume ratio: 8: 2) and stirred at room temperature for 1 hour. Next, this mixture was dropped into 10,000 parts of water with stirring to precipitate. The resulting precipitate was filtered and dried to obtain a coarse particle toner. Next, fine pulverization was performed with a jet mill pulverizer, and further classification was performed with an airflow type classifier to obtain a 5-20 μm toner. The obtained toner was mixed with about 200 mesh iron powder carrier and 3:97
(Toner: iron powder carrier) was mixed at a weight ratio to obtain a developer C. Next, when the initial specific charge amount of the developer C was measured by a blow-off charge amount measuring device, it was -29.1 μC /
g. Further, when copying was performed by a copying machine using this developer C, a clear blue image with excellent gradation and without hindering the original hue of the colorant was obtained. Also,
When a stability test with time was carried out in the same manner as in Example 1 using Developer C, the results shown in Tables 5 and 6 below were obtained.

Table 5 Time-dependent change test of charge amount (unit: -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer C 29.1 30.4 30.3 30.3 30.9 31.1

Table 6 Charge Amount Moisture Resistance Stability Test (Unit, -μC / g) Initial Charge After Moisture Resistance Test Decay Rate (%) 29.1 27.5 5.5

As described above, the stability of the developer C over time was extremely excellent.

Example 4 100 parts of epoxy resin CI. Disperse Red 60 1.2 parts CI. Disperse Violet 17 0.3 parts Compound of specific example (5) 2.0 parts The mixture having the above composition was melt-mixed in a kneader adjusted to 110 to 130 ° C, and then spontaneously cooled and solidified.
Subsequently, coarse pulverization and fine pulverization are performed by a coarse pulverizer and a jet mill pulverizer, and further classified by an airflow classifier to obtain a particle size of 5-2.
0 μ toner was obtained. 0.3 part of colloidal silica was mixed with 100 parts of the obtained toner using 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 D. Next, the initial specific charge amount of the developer D was measured by a blow-off charge amount measuring device.
0.3 μC / g. Further, when copying was performed by a copying machine using this developer D, a clear red image was obtained which had excellent gradation and did not hinder the original hue of the colorant. When a stability test with time was carried out in the same manner as in Example 1 using Developer D, the results shown in Tables 7 and 8 below were obtained.

Table 7 Charge change aging test (unit: -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer D 20.3 22.4 23.1 23.1 23.3 23.5

Table 8 Charge Amount Moisture Resistance Stability Test (Unit, -μC / g) Initial Charge After Moisture Resistance Test Decay Rate (%) 20.3 17.4 14.3

As described above, the stability of the developer D over time was extremely excellent.

Example 5 100 parts of epoxy resin CI. Disperse Red 60 1.2 parts Compound of specific example (6) 2.0 parts The mixture having the above composition was melt-mixed in a kneader adjusted to 120 to 130 ° C, and then spontaneously cooled and solidified.
Subsequently, coarse pulverization and fine pulverization are performed by a coarse pulverizer and a jet mill pulverizer, and further classified by an airflow classifier to obtain a particle size of 5-2.
0 μ toner was obtained. 0.3 parts of colloidal silica was added to 100 parts of the obtained toner 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. Next, the initial specific charge amount of the developer E was measured by a blow-off charge amount measuring device.
It was 27.5 μC / g. Further, when copying was performed by a copying machine using this developer E, a clear yellow image was obtained with excellent gradation and without hindering the original hue of the colorant. When a stability test with time was carried out in the same manner as in Example 1 using the developer E, the results shown in Tables 9 and 10 were obtained.

Table 9 Change over time in charge amount (unit: -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer E 27.5 28.7 31.3 31.4 32.1 32.5

Table 10 Charge Amount Moisture Resistance Stability Test (Unit, -μC / g) Initial Charge After Moisture Resistance Test Decay Rate (%) 27.5 26.0 5.5

As shown in the above results, the stability over time 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 (11) 1.5 parts The mixture having the above composition was adjusted to 125-140 ° C. After melt-mixing (10 minutes) in a kneader, the mixture was cooled and solidified. Next, after coarse pulverization by a coarse pulverizer, fine pulverization was performed by a jet mill pulverizer, and further classification was performed by an air current 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 in a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer F. Next, the initial specific charge amount of the developer F was measured by a blow-off charge amount measuring device, and was -26.2 μC / g.
Met. Further, when copying was performed by a copying machine using this developer F, a clear red image was obtained with excellent gradation and without hindering the original hue of the colorant. Further, a aging stability test (charge amount aging change test, charging amount moisture resistance stability test) was carried out in the same manner as in Example 1 using developer F, and the results in Tables 11 and 12 below were obtained.

Table 11 Change in charge amount over time (unit: -μC / g) Time (h) 0.25 0.5 1.0 2.0 4.0 6.0 Developer F 26.2 28.8 29.6 30.0 30.1 30.3

Table 12 Moisture Resistance Stability Test of Charge Amount (Unit: -μC / g) Initial Charge After Moisture Resistance Test Decay Rate (%) 26.2 24.0 8.4 As shown in the above results, the stability of developer F with time was extremely excellent.

Example 7-11 A developer was prepared in the same manner as in Example 1 using the compounds shown in the column of "Compound" in Tables 13 and 14 and the coloring agent shown in the column of "Colorant". The initial specific charge amount of each of the obtained toners was measured, and a temporal stability test was performed in the same manner as in Example 1. The toner using any of the compounds showed little change in the amount of charge, and the stability over time of the developer was extremely excellent. When the images were copied with a copying machine, all of the developing agents were excellent in gradation, and a clear image having the original hue of the colorant was obtained.

Table 13 Change in charge amount over time (unit: -μC / g) Time (h) Example Compound Colorant 0.25 0.5 1.0 2.0 4.0 6.0 7. Specific example (4) CI.Dis.R.60 25.6 28.4 28.8 28.9 29.0 29.0 Specific example (12) CI.Pig.R.146 26.3 27.2 28.5 28.6 28.9 29.0 9. Specific example (15) CI.Dis.B.35 21.3 23.0 23.4 23.2 23.1 23.3 10. Specific example (17) Kayaset.Y.963 18.9 19.7 20.1 20.3 20.0 19.5 11. Example (20) Carbon Black 22.3 23.5 23.5 23.3 23.1 22.8

Table 14 Charge Amount Moisture Resistance Stability Test (Unit, -μC / g) Example Initial Charge After Moisture Resistance Test Decay Rate (%) 25.6 22.0 14.0 8. 26.3 23.1 12.2 9. 21.3 20.5 3.8 10. 18.9 17.7 6.3 11. 22.3 20.1 9.9

(Note) Colorant CI .: Color Index, Sol .: Solvent, Dis .: Disper
se, Pig .: PigmentB .: Blue, R .: Red, Y .: Yell
ow and Kayaset are trade names of Nippon Kayaku Co., Ltd., organic pigments

[0070]

The toner for electrophotography obtained according to the present invention has a sharp charge distribution, excellent moisture resistance and excellent stability over time as compared with a toner using a conventional charge control agent. As a result, it is characterized in that an image having extremely high gradation is obtained and the repetitive image forming ability is extremely good. Further, since the charge control agent itself is essentially colorless, any colorant can be selected according to the hue required for the color toner, and the original hue of the dye or pigment is not hindered at all. Another feature is that there is no need to do it.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of a compound of “Specific Example (1)” used in the present invention. In FIG. 1, the horizontal axis represents the wavelength (cm ^-1 ), and the vertical axis represents the transmittance (%).

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 9/08 CA (STN)

Claims (1)

(57) [Claims] 1. An electrophotographic toner comprising at least one compound represented by the following formula (1): ## STR1 ## (In the formula (1), R ₁ and R ₂ 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 may combine to form a ring. )