JP2008145706A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner capable of giving high-quality images in long-term printing durability even when the toner contains, as a binder resin, a polyester obtained by using a phthalic acid-based carboxylic acid compound. <P>SOLUTION: The electrophotographic toner comprises, as a binder resin, a polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid-based carboxylic acid compound with an alcohol component, wherein the content of toluic acid in the toner ranges from 15 to 35 ppm. The electrophotographic toner comprises, as a binder resin, a polyester obtained by condensation polymerization of a carboxylic acid component containing terephthalic acid including p-toluic acid as an impurity by 60 to 140 ppm, with an alcohol component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

  The binder resin, which is the main component of the toner raw material, has a great influence on the performance required for the toner, and therefore various characteristics are required. For example, along with the recent trend toward higher speed, there is a demand for high heat-resistant storage stability of resins, and binder resins having a high glass transition point are desired. Along with the recent demand for higher image quality, a long-life toner capable of stably obtaining a high-quality image over a long period of time is desired.

  On the other hand, for the purpose of reducing odor, a toner in which the content of an aldehyde compound in a polystyrene polymer or a polyester resin is defined (see Patent Documents 1 and 2, etc.). No consideration has been made.

In addition, techniques for forcibly adding monocarboxylic acid to improve various properties have been studied (see Patent Documents 3 to 5 and the like), but studies on image quality stability in long-term printing have not been made.
Japanese Patent Laid-Open No. 3-101746 JP 2002-72547 A Japanese Patent Laid-Open No. 2-989 JP-A 62-45622 JP-A 64-24827

  Polyesters obtained using phthalic acid-based carboxylic acid compounds such as terephthalic acid have a relatively high glass transition point and excellent heat-resistant storage stability, while improving image quality stability over long-term printing durability is desired. .

  An object of the present invention is to provide an electrophotographic toner capable of obtaining a high-quality image in long-term printing durability even when a polyester obtained by using a phthalic acid-based carboxylic acid compound is contained as a binder resin. It is in.

The present invention
[1] An electrophotographic toner comprising, as a binder resin, a polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid-based carboxylic acid compound and an alcohol component, wherein the toluic acid in the toner A toner for electrophotography having a content of 15 to 35 ppm, and [2] a polyester obtained by condensation polymerization of a carboxylic acid component containing terephthalic acid containing 60 to 140 ppm of p-toluic acid as an impurity and an alcohol component. The present invention relates to an electrophotographic toner containing as a resin.

  The toner for electrophotography of the present invention has an excellent effect that a high-quality image can be obtained even in long-term printing durability.

  The toner of the present invention contains a polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid-based carboxylic acid compound and an alcohol component, and the content of toluic acid in the toner is within a predetermined range. The toluic acid is derived from impurities of a phthalic acid-based carboxylic acid compound used as a carboxylic acid component of the polyester.

  In the present invention, phthalic acid carboxylic acid is a general term for phthalic acid and its isomers, isophthalic acid and terephthalic acid, phthalic acid compounds and anhydrides of these acids, alkyl (C1-3). A derivative such as an ester is referred to as a phthalic acid carboxylic acid compound. As an industrial process for producing phthalic carboxylic acids, the Amoco process (see K. Weisserme, HJ Arpe, Industrial Organic Chemistry, Main Raw Materials and Intermediates, 4th edition, Tokyo Kagaku Dojin Publishing, p.441-443 ”) is common. However, it is known that the phthalic acid-based carboxylic acid and its derivatives obtained by this method contain toluic acid and carboxybenzaldehyde as impurities. It is considered that the amount of impurities contained in the toner is preferably as low as possible. However, in the toner of the present invention, toluic acid contained as an impurity in the phthalic acid carboxylic acid compound used as a raw material monomer for polyester is adjusted within a predetermined range. Therefore, high-quality images can be obtained even during long-term printing, although the details of the reason are unclear, but a small amount of toluic acid present in the toner is It is presumed that the increase in the charge amount of the toner (charging up of the charge) is suppressed, and the effect of the present invention is more conspicuous when the toner contains a colorant and / or a charge control agent. This is presumed to be due to some interaction between toluic acid and the colorant and / or charge control agent.

  Toluic acid includes the isomers of o-toluic acid, m-toluic acid and p-toluic acid. The phthalic acid compound may contain o-toluic acid, the isophthalic acid compound may contain m-toluic acid, and the terephthalic acid compound may contain p-toluic acid. Among these toluic acids, p-toluic acid is preferable from the viewpoint of further enhancing the effects of the present invention.

  From the above viewpoint, the content of toluic acid, preferably p-toluic acid, in the toner is 15 to 35 ppm, preferably 20 to 35 ppm, more preferably 20 to 30 ppm. The content of toluic acid in the toner is measured by the method described in Examples below.

  Further, in the toner of the present invention, it is preferable that the content of carboxybenzaldehyde derived from the impurities of the phthalic acid carboxylic acid compound is in a predetermined range, like toluic acid, from the viewpoint of further enhancing the effects of the present invention. Carboxybenzaldehyde, like toluic acid, suppresses the increase in toner charge amount (charging charge-up) associated with long-term printing, and interacts between carboxybenzaldehyde and colorants and / or charge control agents. It is estimated to be. There are isomers of 2-carboxybenzaldehyde, 3-carboxybenzaldehyde, and 4-carboxybenzaldehyde in carboxybenzaldehyde, 2-carboxybenzaldehyde in phthalic acid, 3-carboxybenzaldehyde in isophthalic acid, and terephthalic acid. 4-carboxybenzaldehyde may be contained as impurities, respectively.

  From the above viewpoint, the content of carboxybenzaldehyde in the toner is 3 to 7 ppm, preferably 4 to 7 ppm, and more preferably 4 to 6 ppm. The content of carboxybenzaldehyde in the toner is measured by the method described in Examples below.

  As described above, the toner of the present invention contains polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid carboxylic acid compound and an alcohol component as described above. Polyesters obtained using phthalic acid-based carboxylic acid compounds have a relatively high glass transition point and excellent heat-resistant storage stability. Therefore, toners containing such polyesters are often exposed to high-temperature environments. Also, it can be suitably used.

  As one of means for adjusting the amount of toluic acid and / or carboxybenzaldehyde in the toner, a polyester in which the content of impurities in the phthalic acid-based carboxylic acid compound used as the carboxylic acid component is within a predetermined range is used. It is characterized by. As the phthalic acid-based carboxylic acid, isophthalic acid and terephthalic acid having a higher effect on heat-resistant storage stability are preferable, and terephthalic acid is more preferable. From such a viewpoint, it is desirable to use terephthalic acid having a content of p-toluic acid contained as an impurity of 60 to 140 ppm, preferably 80 to 129 ppm. Further, the content of 4-carboxybenzaldehyde in terephthalic acid is 15 to 25 ppm, preferably 17 to 22 ppm. The contents of p-toluic acid and 4-carboxybenzaldehyde in terephthalic acid are measured by the method described in Examples below.

  Further, as one of means for adjusting the amount of toluic acid and / or carboxybenzaldehyde in the toner, the content of toluic acid and / or carboxybenzaldehyde in the polyester is measured in advance so that it becomes a predetermined amount. It may be a method of adding toluic acid and / or carboxybenzaldehyde.

  60 mol% or more is preferable in a carboxylic acid component, and, as for content of a phthalic acid type carboxylic acid compound, 70-90 mol% is more preferable.

  Carboxylic acid components other than phthalic acid-based carboxylic acid compounds include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, n-dodecyl Examples thereof include aliphatic dicarboxylic acids such as succinic acid and n-dodecenyl succinic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and anhydrides and alkyl (C1 to C3) esters of these acids. Such acids, anhydrides of these acids, and alkyl esters of these acids are collectively referred to herein as carboxylic acid compounds.

  The carboxylic acid component is a trivalent or higher polyvalent carboxylic acid compound, preferably a trimellitic acid compound, more preferably trimellitic anhydride, from the viewpoint of improving offset resistance, expanding molecular weight distribution, and low-temperature fixability. It is desirable to contain. The content of the trivalent or higher polyvalent carboxylic acid compound is preferably 5 mol% or more, more preferably 9 to 30 mol%, and even more preferably 15 to 25 mol% in the carboxylic acid component.

  As the alcohol component, the formula (I):

(In the formula, RO is an alkylene oxide, R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of added moles of alkylene oxide, and the sum of x and y is 1 to 16 is preferable, 1 to 8 is more preferable, and 1.5 to 4 is more preferable)
It is preferable that the alkylene oxide addition product of bisphenol A represented by these is contained. By using this compound as an alcohol component, a higher quality image can be maintained even during long-term printing, but this is because the alkylene oxide of bisphenol A having an aromatic ring and toluic acid or carboxybenzaldehyde contained in the toner is used. Presumably due to interaction with the adduct.

  Examples of alkylene oxide adducts of bisphenol A represented by the formula (I) include polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis Examples include alkylene (carbon number 2-3) oxide (average added mole number 1-16) adducts of bisphenol A such as (4-hydroxyphenyl) propane.

  The content of the alkylene oxide adduct of bisphenol A represented by the formula (I) is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more in the alcohol component, substantially 100 mol% is more preferable.

  Other alcohol components include ethylene glycol, propylene glycol, glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, and their alkylene (2 to 4 carbon atoms) oxide (average added mole number 1 to 16). ) Additives and the like.

  The alcohol component may contain a monovalent alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound other than toluic acid as appropriate from the viewpoints of molecular weight adjustment and offset resistance improvement.

  The polyester is obtained, for example, by subjecting an alcohol component and a carboxylic acid component to condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst.

  The softening point of the polyester is preferably 85 to 170 ° C, more preferably 90 to 165 ° C, and still more preferably 95 to 160 ° C.

  The glass transition point of the polyester is preferably 50 to 80 ° C, more preferably 55 to 75 ° C, and still more preferably 60 to 70 ° C, from the viewpoint of heat resistant storage stability.

  The acid value of the polyester is preferably 4 to 35 mgKOH / g, more preferably 8 to 30 mgKOH / g, from the viewpoint of environmental resistance and chargeability.

  In the present invention, the polyester may be a polyester modified to such an extent that the characteristics are not substantially impaired. Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Polyester.

  The toner of the present invention is a polyester other than the polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid carboxylic acid compound and an alcohol component, a vinyl resin such as a styrene-acrylic resin, an epoxy resin, a polycarbonate, Polyurethane, a hybrid resin having two or more kinds of resin components, and the like may be contained as a binder resin, but the content of the polyester is preferably 50 to 100% by weight in the binder resin, and 70 to 100% by weight. % Is more preferred, and substantially 100% by weight is even more preferred.

  Further, the toner of the present invention includes a colorant, a charge control agent, a release agent, a conductivity adjusting agent, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, and a magnetic substance. An agent may be added as appropriate.

  As the colorant, it is possible to use dyes, pigments, and the like that are used as colorants for black toners or color toners. Carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, Rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, disazo yellow and the like can be mentioned, and these can be used alone or in admixture of two or more. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner of the present invention may be either a black toner or a color toner, but as a colorant, the formula (II):

Pigment Red (PR) 122 (red pigment) and / or Formula (III):

Higher quality images can be maintained by the color toner containing Pigment Yellow (PY) 185 (yellow pigment) represented by: Conventionally, these pigments are excellent in color developability, but have an aromatic ring, so the amount of charge tends to increase with printing (charging charge up), and a stable image is maintained over long-term printing. It was difficult. However, in the present invention, although the reason is unknown, even if these pigments having an aromatic ring are contained, the toluic acid or carboxybenzaldehyde contained in the toner interacts with these pigments and the toluyl in the toner. It is presumed that good charge stability can be maintained because charge-up of the charge is suppressed by the acid.

  As charge control agents, metal-containing azo dyes, copper phthalocyanine dyes, metal compounds of salicylic acid derivatives, negatively chargeable charge control agents such as nitroimidazole derivatives; nigrosine dyes, triphenylmethane dyes, quaternary ammonium salt compounds, polyamine resins And positively chargeable charge control agents such as imidazole derivatives. In addition, as the charge control agent, a polymer type such as a resin can be used. In consideration of the chargeability of the toner, either a negative charge property or a positive charge property may be used as the charge control agent, or both may be used in combination.

  In the present invention, among the charge control agents, a compound having an aromatic ring is preferable from the viewpoint of obtaining a high charge amount, and the compound represented by formula (IV):

(In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms or an allyl group, M is zinc, zirconium, chromium, aluminum, More preferred is a metal compound of a salicylic acid derivative represented by copper, nickel or cobalt, m is an integer of 2 or more, and n is an integer of 1 or more. A compound having an aromatic ring, especially a metal compound of a salicylic acid derivative, is excellent in charge amount level, but has an aromatic ring, so the charge amount is likely to increase with printing durability (charge charge up) and long-term. It was difficult to maintain a stable image with printing durability. However, the toner of the present invention can maintain high quality image quality even when these charge control agents are contained. Although the reason is unknown, good charge stability is maintained because charge-up is suppressed by toluic acid in the toner due to the interaction between toluic acid and carboxybenzaldehyde contained in the toner and these charge control agents. It is estimated that it can be done. Such a metal compound may be either a metal salt or a metal complex.

In the formula (IV), R ² is preferably a hydrogen atom, and R ¹ and R ³ are preferably a branched alkyl group, more preferably a tert-butyl group.

  Among zinc, zirconium, chromium, aluminum, copper, nickel, and cobalt shown as M, zinc and chromium are preferable because of good charging effect.

As a commercially available product suitably used in the present invention, wherein R ² is a hydrogen atom and R ¹ and R ³ are tert-butyl groups, “Bontron E-84” (M: zinc, manufactured by Orient Chemical Industries, Ltd.) "TN-105" (M: zirconium, manufactured by Hodogaya Chemical Co., Ltd.), "Bontron E-81" (M: chromium, manufactured by Orient Chemical Industries, Ltd.), and the like.

  A metal compound of a salicylic acid derivative can be easily synthesized by the method described in CLARK, J. L. KAO, H (1948) J. Amer. Chem. Soc. 70, 2151. For example, 2 mol of sodium salt of salicylic acid (including sodium salt of salicylic acid derivative) and 1 mol of zinc chloride are mixed in a solvent, mixed, heated and stirred to obtain a zinc compound. it can. This metal compound is a white crystal and does not show color even when dispersed in a binder resin. Metal compounds other than zinc compounds can also be produced according to the method described above.

  The content of the charge control agent is preferably 0.1 to 8 parts by weight and more preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  Mold release agents include ester waxes such as carnauba wax, rice wax, and candelilla wax, synthetic waxes such as polypropylene wax, polyethylene wax, and Fischer Tropu, coal-based waxes such as montan wax, petroleum waxes such as paraffin wax, alcohol These waxes may be used, and these waxes may be used alone or in admixture of two or more. Of these, ester waxes are preferred and carnauba waxes are more preferred because of their good compatibility with polyester. The content of the release agent is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

The toner of the present invention may be any conventionally known method such as a kneading pulverization method or a phase inversion emulsification method, but a pulverized toner by a melt kneading method is preferable from the viewpoint of productivity and dispersibility of the colorant. . The pulverized toner by the melt-kneading method is, for example, a binder resin, a colorant, a charge control agent, a release agent, etc. are uniformly mixed with a mixer such as a Henschel mixer, and then a sealed kneader or a single or biaxial extrusion. It can be produced by melt-kneading with a machine, open roll type kneader or the like, cooling, pulverizing and classifying. Further, inorganic fine particles such as hydrophobic silica or resin fine particles may be externally added to the obtained toner surface. The volume median particle size (D ₅₀ ) of the toner is preferably 3 to 15 μm. In the present specification, the volume median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The electrophotographic toner of the present invention can be used as a one-component developing toner or as a two-component developer mixed with a carrier.

  In addition, since the electrophotographic toner of the present invention contains polyester having excellent charging stability as a binder resin, it can be suitably used for a non-magnetic one-component development system.

[Softening point of resin]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C / min, and a load of 1.96 MPa was applied by a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . Plot the plunger drop amount of the flow tester against the temperature, and let the softening point be the temperature at which half the sample flowed out.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The temperature at the intersection of the extended line of the baseline below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Acid value of the resin]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume-median particle diameter of toner (D ₅₀ )]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 100μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in the electrolytic solution to a concentration of 5% by weight to obtain a dispersion.
Dispersion conditions: 10 mg of a measurement sample is added to 5 ml of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 ml of an electrolyte is added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare a dispersion.
Measurement conditions: After adjusting the particle size of 30,000 particles to a concentration that can be measured in 20 seconds by adding the sample dispersion to 100 ml of the electrolyte solution, 30,000 particles are measured, Determine the volume median particle size (D ₅₀ ).

[Contents of terephthalic acid and toluic acid in toner]
1. Instruments and equipment
(1) Complete liquid chromatograph: degasser, pump, oven, injector, UV detector column (ODS)
(2) Balance, Erlenmeyer flask, shaker, micro syringe 2. reagent
(1) Benzoic acid, o-, p- or m-toluic acid (standard)
(2) Ammonia water
(3) Eluent (acetonitrile aqueous solution (25% by volume) + 0.1% by volume trifluoroacetic acid (TFA) aqueous solution (75% by volume))
3. Method
(1) Weigh accurately 0.5 g of sample and put into a 100 ml volumetric flask.
(2) Add 10 ml of 2N ammonia water to dissolve the sample.
(3) Make a total of 100 ml with pure water.
(4) Inject 5 μl of the sample into the liquid chromatography and record the chromatogram.
<Measurement conditions>
A) Eluent flow rate: 0.5ml / min
B) UV wavelength: 230nm
C) Column: ODS
4). Calculation
(1) Obtain the toluic acid concentration by the peak area method by chromatographic analysis (absolute calibration curve method).
(2) Round the first decimal place to an integer value (unit: ppm).

[Content of terephthalic acid and carboxybenzaldehyde (CBA) in toner]
1. Instruments and equipment
(1) Complete liquid chromatograph: degasser, pump, oven, injector, UV detector column (ODS)
(2) Balance, Erlenmeyer flask, shaker, micro syringe 2. reagent
(1) 2-, 3- or 4-CBA standard solution
(2) Ammonia water
(3) Eluent (acetonitrile aqueous solution (16 vol%) + 1 vol% acetic acid aqueous solution (84 vol%))
3. Method
(1) Weigh accurately 0.5 g of sample and put into a 100 ml volumetric flask.
(2) Add 10 ml of 2N ammonia water to dissolve the sample.
(3) Make a total of 100 ml with pure water.
(4) Inject 5 μl of the sample into the liquid chromatography and record the chromatogram.
<Measurement conditions>
A) Eluent flow rate: 0.4ml / min
B) UV wavelength: 256nm
C) Column: ODS
4). Calculation
(1) Obtain the CBA concentration by the peak area method by chromatographic analysis (absolute calibration curve method).
(2) Round the first decimal place to an integer value (unit: ppm).

Production example of terephthalic acid
In 95 wt% acetic acid, Co / Mn acetate was used as a catalyst, and air oxidation of p-xylene was performed in a Hastelloy autoclave reaction vessel under the temperature and pressure conditions shown in Table 1. Then, it cooled and the crude crystal | crystallization of terephthalic acid was obtained.

  Next, the obtained crude crystalline terephthalic acid was dissolved in water at 225 to 275 ° C. under pressure, and hydrogenated with a Pd / C catalyst. During the hydrogenation reaction, the amount of p-toluic acid and 4-carboxybenzaldehyde (4-CBA) was measured over time, and when the remaining amount shown in Table 1 was reached, the catalyst was removed by filtration to complete the reaction. As a result, terephthalic acids a to d were obtained.

Resin production example 1
A 5 liter batch reactor equipped with a gas introduction tube, a condenser and a stirrer was charged with 2450 g (7 mol) of polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0 mol). ) -2,2-bis (4-hydroxyphenyl) propane 975 g (3 mol), terephthalic acid a1328 g (8 mol) and dibutyltin oxide 10.3 g were heated to 235 ° C. and normal pressure (101.3 kPa ) For 5 hours. Thereafter, the pressure was reduced to 3 kPa, and the reaction was further continued for 2 hours, followed by cooling to 220 ° C. and adding 384 g (2 mol) of trimellitic anhydride. Further, the reaction was carried out at 215 ° C. and normal pressure (101.3 kPa) for 30 minutes, and then under reduced pressure at 13.3 kPa. The softening point is measured over time as an index of the degree of polymerization, and when the softening point reaches 120 ° C, the inside of the reactor is returned to normal pressure (101.3 kPa), and the polycondensation reaction is completed by stopping heating and stirring. To obtain polyester A. The entire amount of the obtained polyester A was extracted from the reaction vessel, cooled to 40 ° C., and then pulverized.

Resin production example 2
Polyesters B to D were obtained in the same manner as in Resin Production Example 1 except that terephthalic acids b to d were used instead of terephthalic acid a.

  Table 2 shows the softening point, glass transition point, and acid value of the obtained polyesters A to D.

Examples 1 and 2 and Comparative Examples 1 and 2
100 parts by weight of binder resin shown in Table 3, 2 parts by weight of carnauba wax (manufactured by Kato Yoko Co., Ltd.), 3 parts by weight of colorant (PR 122, manufactured by Dainippon Ink & Chemicals) and charge control agent “Bontron E-84” 1 part by weight (manufactured by Orient Chemical Co., Ltd.) was mixed with a Henschel mixer for 2 minutes, and then melt-kneaded at 100 ° C. with a twin screw extruder. Thereafter, the mixture was coarsely pulverized and finely pulverized by a jet mill to obtain a magenta toner having a volume median particle size (D ₅₀ ) of 8.0 μm. To 100 parts by weight of the obtained magenta toner, 0.5 part by weight of hydrophobic silica “TS530” (manufactured by Cabot) was added and mixed, and surface treatment was performed. Table 3 shows the contents of p-toluic acid and 4-carboxybenzaldehyde in the obtained toner.

Example 3
A toner was obtained in the same manner as in Example 1 except that 3 parts by weight of PY 185 (manufactured by BASF) was used instead of PR 122 as a colorant. Table 3 shows the contents of p-toluic acid and 4-carboxybenzaldehyde in the obtained toner.

Test Example 1 [dot reproducibility]
Mount magenta toner on IPSIO COLOR 2000 non-magnetic development unit (Ricoh), output 50μm x 70μm checkered image on plain paper XEROX4200, and reproduce dots according to the following evaluation criteria Sex was evaluated. The results are shown in Table 4.

〔Evaluation criteria〕
A: The ratio of defective dots is 2 or less per 100, which is very good.
◯: The ratio of defective dots is 3-5, which is good.
Δ: The ratio of defective dots is 6 to 7, which is practical.
X: The ratio of defective dots is 8 to 10, which is slightly problematic in practical use.
XX: The ratio of defective dots is 11 or more, which is not practical.

Test example 2 [fine line reproducibility]
A fine line image was printed out and the resolution was observed using a magnifying glass (25 times magnification). Fine line reproducibility was evaluated from the average of 10 locations according to the following evaluation criteria. The results are shown in Table 4.

〔Evaluation criteria〕
A: The resolution is 8 (line / mm) or more, which is very good.
○: The resolution is 7 or more and less than 8, which is good.
Δ: The resolution is 6 or more and less than 7, which is practical.
X: The resolution is 5 or more and less than 6, which is slightly problematic for practical use.
XX: The resolution is less than 5 and is not practical.

Test Example 3 [Hue Change]
In the same way as in Test Example 1, the toner is mounted, and 10000 sheets of images with a printing rate of 5% per sheet are printed continuously using plain paper “XEROX4200”, and the hue changes between the first sheet and the 10000th sheet. Difference (ΔE) was measured using “Spectrodensitometer 938” (manufactured by X-LITE) and evaluated according to the following evaluation criteria. The results are shown in Table 4.

〔Evaluation criteria〕
(Double-circle): (DELTA) E is less than 2.0 and is especially favorable on actual use.
○: ΔE is 2.0 or more and less than 5.0, which is good in practical use.
(Triangle | delta): (DELTA) E is 5.0 or more and less than 7.0, and it can be actually used.
X: ΔE is 7.0 or more and less than 10.0, and there is a problem in actual use.
XX: ΔE is 10.0 or more, impractical.

  From the above results, it can be seen that, compared with Comparative Examples 1 and 2, the toners of Examples 1 to 3 are excellent in both dot reproducibility and fine line reproducibility and have good image quality stability. Further, it can be seen that the toners of Examples 1 to 3 have a small hue change even when using a colorant and a charge control agent that tend to cause a hue change due to an increase in charge amount associated with long-term printing durability.

  The electrophotographic toner of the present invention is used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

Claims (5)

  An electrophotographic toner comprising, as a binder resin, a polyester obtained by condensation polymerization of a carboxylic acid containing a phthalic acid-based carboxylic acid compound and an alcohol component, wherein the toner has a toluic acid content. An electrophotographic toner of 15 to 35 ppm.   The electrophotographic toner according to claim 1, wherein the content of p-toluic acid in the toner is 15 to 35 ppm.   The electrophotographic toner according to claim 1 or 2, wherein the content of carboxybenzaldehyde in the toner is 3 to 7 ppm.   An electrophotographic toner comprising, as a binder resin, a polyester obtained by condensation polymerization of a carboxylic acid component containing terephthalic acid containing 60 to 140 ppm of p-toluic acid as an impurity and an alcohol component.   The toner for electrophotography according to claim 4, wherein the content of 4-carboxybenzaldehyde in terephthalic acid is 15 to 25 ppm.