JP2008129495A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner using a masterbatch of a binder resin and a charge control agent and capable of satisfying both of cleaning property and charging property. <P>SOLUTION: The electrophotographic toner is obtained by a method including a masterbatch step of melt-kneading and pulverizing raw materials including such a binder resin (A) and a charge control agent, and a dilution step of mixing pulverized powder obtained at the masterbatch step with at least another binder resin (B) and melt-kneading the mixture, wherein the charge control agent is a chromium complex of a salicylic acid compound, and the toner has a volume median particle diameter of 7.0-10.0 μm and a variation coefficient to a volume particle size distribution of 25-35%. The toner includes small particle diameter toner having a volume median particle diameter of 5.0-6.0 μm and a variation coefficient to a volume particle size distribution of 20-25%, and a ratio (Is/It) of X-ray intensity (Is) of chromium in the fluorescent X-ray analysis of the small particle diameter toner to X-ray intensity (It) of chromium in the fluorescent X-ray analysis of the total toner including the small particle diameter toner is 0.5-1.0. <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, and the like, a two-component developer containing the toner, the toner, and the two The present invention relates to an image forming method using a component developer.

  The toner for electrophotography is produced by adding a binder resin as a main component and, if necessary, adding a colorant, a charge control agent, a release agent and the like. As a method for producing these toners, all the raw materials are mixed at once and heated, melted and dispersed by a kneader or the like to obtain a uniform composition, which is then cooled, pulverized and classified. Is generally adopted.

On the other hand, from the viewpoint of improving the dispersibility of additives such as colorants and charge control agents, after producing a master batch composed of an additive and a binder resin, the obtained master batch is mixed with a further binder resin, There are methods for producing toner. Patent Document 1 discloses a toner using a masterbatch containing a resin having a specific acid value in order to improve pigment dispersion and improve color reproducibility. Patent Document 2 discloses a toner production method using a master batch containing a resin having a specific softening point in order to improve the dispersibility of the charge control agent and improve the charge rising property.
JP 2004-45617 A JP 2004-170710 A

  When the master batch is used, the dispersibility of additives such as a colorant and a charge control agent is improved, and similarly to a large particle size toner, a toner in which the additive is uniformly present can be obtained even for a small particle size toner. Color development and chargeability can be improved. However, since the small particle size toner has a stronger adhesion to the device than the large particle size toner, it easily causes contamination in the device, and the toner obtained using the master batch of the binder resin and the charge control agent is In addition, since the additive is uniformly present in the small particle size toner, the adhesion force of the small particle size toner becomes stronger and the cleaning defect is likely to occur.

  An object of the present invention is to provide a toner that can achieve both cleaning properties and chargeability even when a master batch of a binder resin and a charge control agent is used, a two-component developer containing the toner, the toner, and the toner. An object of the present invention is to provide an image forming method using a two-component developer.

The present invention
[1] A master batch process in which a raw material containing the binder resin (A) and the charge control agent is melt-kneaded and pulverized, and the pulverized product obtained in the master batch process is mixed with at least a further binder resin (B). An electrophotographic toner obtained by a method including a dilution step of melt kneading, wherein the charge control agent is a chromium complex of a salicylic acid compound, and the softening point of the pulverized product obtained in the master batch step The ratio of the softening point of the resin (B) (the softening point of the pulverized product / the softening point of the binder resin (B)) is 1.30 to 1.50, the volume median particle size of the toner is 7.0 to 10.0 μm, and the volume particle size X-ray fluorescence analysis of a small particle size toner having a coefficient of variation of 25 to 35% with respect to the distribution, a volume median particle size of 5.0 to 6.0 μm and a coefficient of variation with respect to the volume particle size distribution of 20 to 25%. X-ray intensity (Is) of chromium and the small particle size toner. The total specific toner of the fluorescent X-ray of chromium X-ray intensity in the analysis (It) (Is / It) is 0.5 to 1.0, an electrophotographic toner,
[2] An image forming method using the electrophotographic toner according to [1] in a non-contact developing type image forming apparatus,
[3] A two-component developer comprising the electrophotographic toner described in [1] and a carrier, and [4] a two-component developer described in [3] in a non-contact developing type image forming apparatus. The present invention relates to an image forming method to be used.

  The toner of the present invention has an excellent effect that both cleaning properties and charging properties can be achieved even when a binder resin and a charge control agent master batch are used.

  The toner of the present invention includes a masterbatch process in which a raw material containing a binder resin (A) and a charge control agent is melt-kneaded and pulverized, and a pulverized product obtained in the masterbatch process is further bound with a binder resin (B). An electrophotographic toner obtained by a toner production method including a dilution step of mixing and melt-kneading with a softening point of a pulverized product obtained in the master batch step and a softening point of the binder resin (B) One characteristic is that the ratio is within a specific range. Usually, the masterbatch process is introduced to improve the dispersibility of the additive. If the softening points of the pulverized product and the binder resin (B) obtained in the masterbatch process are comparable, both The dispersibility at the time of kneading | mixing improves by adapting. However, in the present invention, regardless of the softening point of the binder resin (A) or the binder resin (B), by using a chromium complex of a salicylic acid compound as a charge control agent, the binder is kneaded in the masterbatch process. It is presumed that a crosslink is formed between the resin (A) and the chromium complex of the salicylic acid compound. By adjusting the degree of cross-linking formation, the softening point of the pulverized product obtained in the master batch process can be made slightly higher than the softening point of the binder resin (B). It is considered that the content of the charge control agent in the toner having a small particle diameter can be controlled by suppressing the dispersion.

  The toner of the present invention includes a masterbatch process in which a raw material containing a binder resin (A) and a charge control agent is melt-kneaded and pulverized, and a pulverized product obtained in the masterbatch process is further bound with a binder resin (B). And a diluting step of mixing and melting and kneading the toner.

  The method for producing the toner is not particularly limited as long as it includes the master batch step and the dilution step. For example, the pulverized product obtained in the masterbatch step is subjected to a dilution step in which it is mixed with a further binder resin or a known toner raw material and melt kneaded, and the obtained kneaded product is appropriately cooled to a pulverizable state, pulverized, By classification, a toner can be produced.

  In the master batch process, the raw material containing the binder resin (A) and the charge control agent is melt-kneaded and pulverized.

  In the present invention, it is preferable to use at least a linear polyester as the binder resin (A).

  In the alcohol component of the linear polyester, the divalent diol includes polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4- Hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) Alkylene oxide adducts of bisphenol A such as propane and polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3 -Propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butynediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cycl Hexane dimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A, and the like.

  In the carboxylic acid component, the divalent dicarboxylic acid compounds include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, and sebacic acid. , Azelaic acid, malonic acid; alkenyl succinic acid or alkyl succinic acid such as n-dodecenyl succinic acid and n-dodecyl succinic acid; and acid anhydrides thereof, lower alkyl (carbon number 1-4) esters and the like.

  If the polyester is substantially linear, each component further contains a trivalent or higher monomer, that is, a trivalent or higher polyhydric alcohol and / or a trivalent or higher polyvalent carboxylic acid compound. Also good. In that case, the content of the trivalent or higher monomer is preferably 2 mol% or less in both the alcohol component and the carboxylic acid component.

  Examples of trihydric or higher polyhydric alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, etc. Can be mentioned.

  Trivalent or higher polyvalent carboxylic acid compounds include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2 , 4-Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid and acid anhydrides thereof, lower alkyl (C1-4) ester, and the like.

  Linear polyester is a polycondensation of an alcohol component and a carboxylic acid component at a temperature of 180 to 250 ° C., for example, in an inert gas atmosphere, if necessary, using an esterification catalyst in the same manner as ordinary polyester. Can be manufactured.

  The content of the linear polyester is preferably 20 to 100% by weight, more preferably 40 to 100% by weight, still more preferably 60 to 100% by weight in the binder resin (A) used in the masterbatch process, and 80 to 100%. More preferred is weight percent.

  The softening point of the binder resin (A) is preferably 90 to 130 ° C, more preferably 95 to 125 ° C, from the viewpoint of poor dispersion due to heat generation during kneading. The glass transition point is preferably 50 to 70 ° C., more preferably 55 to 65 ° C., and the acid value is preferably 5 to 30 mg KOH / g, and 15 to 25 mg KOH / g, from the viewpoint of storage stability when dispersed into a toner. g is more preferred. In addition, in this specification, a softening point, a glass transition point, and an acid value are measured by the method as described in the below-mentioned Example.

  The present invention has one feature in that a chromium complex of a salicylic acid compound is used as a charge control agent from the viewpoint of charge stability. As a chromium complex of a salicylic acid compound, for example, the formula (I):

(Wherein R ¹ , R ² and R ³ are each independently a hydrogen atom, a linear or branched alkyl group or alkenyl group having 1 to 10 carbon atoms, M is chromium, and m is an integer of 2 or more. , N represents an integer of 1 or more)
The compound represented by these is preferable.

Examples of commercially available chromium complexes of salicylic acid compounds include “Bontron E-81” (manufactured by Orient Chemical Co., Ltd.), in which R ¹ is a hydrogen atom, and R ² and R ³ are tert-butyl groups.

  Although the chromium complex of a salicylic acid compound may be used in the dilution step after the master batch step, it is preferably used only in the master batch step from the viewpoint of adjusting dispersibility. The toner of the present invention may contain a charge control agent other than the chromium complex of the salicylic acid compound as long as the effects of the present invention are not impaired. Other charge control agents include triphenylmethane dyes containing tertiary amines as side chains, quaternary ammonium salt compounds, polyamine resins, positive charge control agents such as imidazole derivatives and metal-containing azo complexes, benzylic acid In order to obtain high image quality, which is the object of the present invention, the content of the chromium complex of the salicylic acid compound in the charge control agent is 70% by weight. The above is preferable, 80% by weight or more is more preferable, 90% by weight is further preferable, and substantially 100% by weight is further preferable.

  In the masterbatch process, from the viewpoint of ensuring good dispersibility, the charge control agent is preferably melt kneaded with the binder resin (A) at a high concentration, and the binder resin (A) and the charge control agent in the masterbatch process are preferred. The weight ratio (binder resin (A) / charge control agent) is preferably 80/20 to 25/75, and more preferably 60/40 to 40/60.

  The content of the charge control agent in the toner is the total amount of the binder resin, that is, the binder resin (A) used in the master batch process and the binder resin (B) used in the dilution process, from the viewpoint of the charge rising speed. 3 parts by weight or more is preferable, 100 to 6.0 parts by weight is more preferable, and 3.5 to 5.0 parts by weight is more preferable with respect to the total amount of 100 parts by weight.

  The raw material containing the binder resin (A) and the charge control agent is preferably mixed with a Henschel mixer or the like and then subjected to melt kneading.

  As the kneader used in the master batch process, a known melt kneader used for melt kneading in a dry method can be used without any particular limitation. Specifically, a single-screw kneader, a twin-screw kneader , Continuous kneaders, batch kneaders, roll mills, continuous open roll type kneaders, etc., among these, open roll type kneaders are the kneaders that can most effectively suppress the decrease in viscosity due to heat generation during kneading. preferable.

  In the master batch process, when the binder resin (A) and the charge control agent are melt-kneaded, a small amount of an organic solvent may be added. The organic solvent plays a role of increasing the wettability of the charge control agent to the resin and improving the dispersibility. In addition, when using an organic solvent, it is preferable to evaporate at the time of kneading | mixing so that the residual amount of the organic solvent in the kneaded material after a masterbatch process may be 1 weight% or less.

  The kneaded material obtained in the masterbatch process is appropriately cooled to such an extent that it can be pulverized, and pulverized using a turbo mill, a jet mill or the like. The particle size of the obtained pulverized product is not particularly limited, but is preferably about the same as the particle size of the binder resin (B) used in the dilution step from the viewpoint of uniform mixing.

  The softening point of the pulverized product thus obtained is preferably 140 to 170 ° C, more preferably 145 to 160 ° C, from the viewpoint of dispersibility. The softening point can be adjusted by the kneading time in the master batch process. Specifically, the softening point of the pulverized product can be increased by increasing the kneading time.

  The ratio between the softening point of the pulverized product obtained in the masterbatch process and the softening point of the binder resin (B) (softening point of the pulverized product / softening point of the binder resin (B)) is 1.30 to 1.50, preferably 1.31 to 1.48. More preferably, it is 1.32 to 1.45. When the ratio is higher than 1.50, the softening point of the masterbatch is too high and does not match the binder resin, causing a poor dispersion of the charge control agent at the time of toner formation, thereby reducing the image quality. On the other hand, when the ratio is lower than 1.30, the dispersion of the charge control agent becomes too good and excessively exists in the small particle size toner, and the adhesion force of the small particle size toner having strong adhesion force is inherently high. Further increased, poor cleaning occurs and image quality is degraded.

  In the dilution step, the pulverized product obtained in the master batch step is mixed with a further binder resin (B) and melt-kneaded.

  The binder resin (B) used in the dilution process is preferably a polyester from the viewpoint of ensuring dispersibility, and may be the same as or different from the linear polyester used in the masterbatch process. It may be a cross-linked polyester that is not shaped. Further, the difference in softening point between the binder resin (A) and the binder resin (B) used in the masterbatch process is preferably 20 ° C. or less. From the viewpoint of dispersibility, the softening point of the binder resin (A) is It is preferably the same as the softening point of the binder resin (B) or lower than the softening point of the binder resin (B).

  The blending amount of the pulverized product obtained in the masterbatch step is preferably 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin (B).

  The dilution process is not limited to one time but may be performed a plurality of times.

  Examples of the binder resin other than polyester used in the masterbatch process and dilution process in the present invention include styrene-acrylic resin, epoxy resin, polycarbonate, polyurethane and the like. Moreover, you may use a charge control agent not only in a masterbatch process but in a dilution process.

  Furthermore, in the present invention, as a raw material of the toner, in addition to the binder resin and the charge control agent, a colorant, a release agent, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, Additives such as an antioxidant, an anti-aging agent, and a cleaning property improver can be appropriately blended in each step, preferably in a dilution step.

  In the dilution step, the same kneader as in the master batch step can be used, but in the present invention, a biaxial kneader is preferable from the viewpoint of adjusting the dispersibility of the charge control agent.

  The kneaded product obtained in the dilution step is appropriately cooled to such an extent that it can be pulverized, and pulverized and classified to produce a toner. A fluidity improver such as hydrophobic silica may be added as an external additive to the toner surface.

The volume-median particle size (D ₅₀ ) of the toner obtained by the present invention is 7.0 to 10.0 μm, preferably 7.5 to 9.5 μm, more preferably 8.0 to 9.0 μm. The coefficient of variation with respect to the volume particle size distribution is 25 to 35%, preferably 27 to 33%. 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% calculated from the smaller particle size, and the coefficient of variation. (CV value) is the following formula:
CV value (%) = [standard deviation in volume particle size distribution] / [volume median particle size] × 100
The value calculated by The volume median particle size (D ₅₀ ) and the coefficient of variation are measured by the methods described in the examples below.

  In the present invention, from the viewpoint of controlling the content of the charge control agent in the small particle size toner, the X-ray intensity (Is) of chromium in the fluorescent X-ray analysis of the small particle size toner contained in the toner, and the small particle size It is desirable that the ratio (Is / It) of chromium X-ray intensity (It) in the fluorescent X-ray analysis of all toners including the diameter toner is 0.5 to 1.0, preferably 0.55 to 0.97, more preferably 0.60 to 0.96. In the present specification, the ratio of the X-ray intensity (Is) of chromium of the small particle size toner to the X-ray intensity (It) of chromium of all the toners is measured by the method described in Examples described later.

  The small particle size toner in the present invention has a volume median particle size of 5.0 to 6.0 μm, preferably 5.3 to 5.8 μm, and a coefficient of variation with respect to the volume particle size distribution of 20 to 25%, preferably 21 to 23%. Refers to toner. The small particle size toner can be obtained by classifying all toners using an air classifier or the like.

  The toner of the present invention can be used as a one-component developing toner as it is or as a two-component developer by mixing with a carrier. Accordingly, the present invention also provides a two-component developer containing the toner and carrier.

In the present invention, from the viewpoint of image characteristics, it is preferable to use a carrier with low saturation magnetization that weakens the area around the magnetic brush. Saturation magnetization of the carrier is preferably ^{40~100Am 2 / kg, 50~90Am 2 /} kg is more preferable. The saturation magnetization is preferably 100 Am ² / kg or less from the viewpoint of adjusting the hardness of the magnetic brush and maintaining gradation reproducibility, and preferably 40 Am ² / kg or more from the viewpoint of preventing carrier adhesion and toner scattering.

  As the core material of the carrier, those made of known materials can be used without particular limitation, for example, ferromagnetic metals such as iron, cobalt, nickel, magnetite, hematite, ferrite, copper-zinc-magnesium ferrite, Examples thereof include alloys and compounds such as manganese ferrite and magnesium ferrite, and glass beads. Among these, magnetite, ferrite, copper-zinc-magnesium ferrite and manganese ferrite are preferable from the viewpoint of durability and chargeability.

  The surface of the carrier may be coated with a resin from the viewpoint of preventing spent. The resin that coats the carrier surface varies depending on the toner material. For example, fluororesin such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin such as polydimethylsiloxane, polyester, styrenic resin, Examples include acrylic resins, polyamides, polyvinyl butyral, aminoacrylate resins, and the like, and silicone resins are preferred from the viewpoint of durability. These can be used singly or in combination of two or more. The coating method of the core material with a resin is, for example, applied by dissolving or suspending a coating material such as resin in a solvent and adhering to the core material. There is no particular limitation such as a method of mixing and a method of simply mixing with powder.

  In the two-component developer of the present invention obtained by mixing the toner and the carrier, the toner content is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the carrier from the viewpoint of charging efficiency, and 2 to 8 Part by weight is more preferred.

  The toner and the two-component developer of the present invention can be used for both the contact development method and the non-contact development method, but the image forming apparatus of the non-contact development method is particularly high in development stress. By using it, the effect of the present invention is more remarkably exhibited. Therefore, the present invention further provides an image forming method in which the toner and the two-component developer of the present invention are used in a non-contact developing type image forming apparatus.

  The image forming method of the present invention can form an image through a known process except that it has a feature in a developing process for developing an electrostatic latent image. As a process in the image forming method, in addition to the developing process, for example, a fixing process for fixing the transferred toner image, a process for forming an electrostatic latent image on the surface of the photoreceptor (charging / exposure process), and a developed toner image on paper And the like (transfer process), a process of removing toner remaining on a developing member such as a photosensitive drum (cleaning process), and the like.

  Further, since the toner and the two-component developer of the present invention can maintain good cleaning properties and maintain excellent image quality even during long-term printing, the linear speed is 750 mm / sec or more, preferably 850 It can also be suitably used in an image forming method using a high-speed developing device of ˜2000 mm / sec.

[Softening point of pulverized material (master batch) obtained in resin and master batch process]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min, a 1.96 MPa load is applied by a plunger, and the sample is 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 cooled to 0 ° C at a cooling rate of 10 ° C / min was measured at a heating 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 showing 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 size (D ₅₀ ) and coefficient of variation of all toners and small toners]
Measuring instrument: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter)
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 above dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 mL of electrolyte is added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare a dispersion.
Measurement conditions: By adding the sample dispersion to 100 mL of the electrolytic solution, the particle size of 30,000 particles is adjusted to a concentration that can be measured in 20 seconds, and then 30,000 particles are measured, Determine the volume-median particle size (D ₅₀ ) and coefficient of variation.

[Ratio of the X-ray intensity (Is) of chromium in small toner and the X-ray intensity (It) of chromium in all toners]
Using a fluorescent X-ray analyzer “ZSX100e” (manufactured by Rigaku Corporation), the X-ray intensity is measured under the following conditions, and the ratio (Is / It) is calculated.
1) Put about 1.5g of toner into a sample vinyl ring (diameter: 32mm, length: 5mm) and press form with a 10-ton press.
2) Excitation conditions Target: Rh
Tube current: 50mA
Tube voltage: 50mV
Primary filter: OUT
3) Optical system conditions Attenuator: 1/1
Slit: COARSE
Spectroscopic crystal: LiF
Detector: SC
Sample mask diameter: 30mmφ
4) Scanning conditions Spectrum: Cr-Kα
Peak (deg): 69.3
Start (deg): 67
End (deg): 72
Step (deg): 0.02
Scan speed (deg / min): 30

Resin production example 1
Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 1050 g, fumaric acid 355 g, hydroquinone (polymerization inhibitor) 1 g and dibutyltin oxide (esterification catalyst) 1.4 g under nitrogen atmosphere at normal pressure, After reacting at 210 ° C. for 5 hours, resin A was obtained by reacting at 210 ° C. under reduced pressure (70 kPa). The obtained resin had a softening point of 102.0 ° C., an acid value of 19.8 mgKOH / g, and a glass transition point of 58.0 ° C.

Resin production example 2
1040 g of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 10 g of polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, 199 g of terephthalic acid, and dibutyltin oxide ( 4 g of the esterification catalyst) was reacted at 230 ° C. for 5 hours under a nitrogen atmosphere under normal pressure, and further reacted under reduced pressure (70 kPa). The temperature was cooled to 210 ° C., 209 g of fumaric acid and 1 g of hydroquinone were added, reacted for 5 hours, and further reacted under reduced pressure (70 kPa) to obtain Resin B. The obtained resin had a softening point of 107.5 ° C., an acid value of 21.3 mgKOH / g, and a glass transition point of 64.4 ° C.

Masterbatch production examples 1-4
50 parts by weight of resin A as a binder resin and 50 parts by weight of “Bontron E-81” (manufactured by Orient Chemical Co., Ltd.) as a charge control agent are melt-kneaded for the times shown in Table 1 in a continuous two-open roll kneader. After cooling, it was coarsely pulverized to a size of 2 mm or less with a coarse crusher.

Master batch production example 5
50 parts by weight of resin A as binder resin, “Bontron E-84” (zinc complex of salicylic acid compound (in formula (I), R ¹ is a hydrogen atom, R ² and R ³ are tert-butyl groups, M Is a compound represented by zinc), manufactured by Orient Chemical Co., Ltd.) 50 parts by weight in a continuous two-open roll kneader for the time shown in Table 1, cooled, and then cooled to 2 mm or less with a crusher. Coarsely pulverized to size.

Toner production examples 1 to 5
100 parts by weight of resin B as binder resin, 4 parts by weight of yellow pigment “Toner Yellow HG” (manufactured by Clariant) as a colorant, 1 part by weight of polyolefin wax “High Wax NP-055” (manufactured by Mitsui Chemicals) as a release agent, And after mixing 10 parts by weight of the master batch shown in Table 2 with a Henschel mixer, using a twin-screw kneader “PCM-45” (manufactured by Ikegai Co., Ltd.), melt-kneading, cooling with a drum flaker, Coarsely pulverized. Thereafter, the mixture was finely pulverized with a jet mill and classified with an airflow classifier to obtain toner base particles having a volume-median particle diameter (D ₅₀ ) and a coefficient of variation shown in Table 2.

  Example 1 Example: To 100 parts by weight of the obtained toner base particles, 0.6 part by weight of hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd.) was added, stirred for 90 seconds, and sieved with a wire mesh having an opening of 100 μm. Toners 1 and 2 and Comparative Examples 1 to 3 were obtained.

The obtained toner was classified by a wind classifier “MINI DISPERSION SEPARATOR TYPE MDS 130” (manufactured by Nippon Pneumatic Industry Co., Ltd.), and the volume-median particle size (D ₅₀ ) and small coefficient of variation shown in Table 2 were obtained. A diameter toner was obtained.

Test Example 1 [Cleanability]
The toner shown in Table 2 was mounted on “Vario Stream 9000” (linear speed: 1000 mm / sec) manufactured by Ossprinting Systems Co., Ltd., and up to 200,000 images with a printing rate of 1% were printed. At that time, each time 10,000 sheets were printed, a blank sheet was printed, and the occurrence of blank lines was visually observed, and the cleaning property was evaluated according to the following evaluation criteria. The results are shown in Table 2. In addition, the printing durability when streaks are confirmed is also shown.

[Evaluation criteria for cleaning properties]
◎: No streaks due to poor cleaning on paper up to 200,000 prints ○: Streaks due to poor cleaning after printing 110,000 to 190,000 sheets ×: Streaks due to poor cleaning after printing within 100,000 sheets

Test Example 2 [Chargeability]
Toner 3.0g and carrier (manufactured by Kanto Denka Co., Ltd., average particle size 60μm) 47.0g are placed in a 50mL plastic bottle, mixed at 250r / min using a ball mill, and using a Q / M meter (manufactured by Epping) The charge amount was measured. After a predetermined mixing time, a specified amount of developer was put into a cell attached to the Q / M meter, and only the toner was sucked through a sieve having a mesh size of 32 μm (stainless steel, twill, wire diameter: 0.0035 mm) for 90 seconds. The voltage change on the carrier generated at that time was monitored, and the value of [total amount of electricity after 90 seconds (μC) / amount of attracted toner (g)] was calculated as the charge amount (μC / g). The results are shown in Table 2.

  From the above results, it can be seen that the toners of the examples are excellent in cleaning property and charging property. The toner of Comparative Example 1 is excellent in chargeability because the ratio of the softening point of the pulverized product obtained in the masterbatch process and the softening point of the binder resin B is low and the dispersibility of the charge control agent is high. It is thought that the result was inferior in cleaning property. Further, in the toner of Comparative Example 2, since the ratio of the softening point of the pulverized product obtained in the masterbatch process and the softening point of the binder resin B is too high, the kneading in the dilution process becomes uneven and the dispersibility of the charge control agent is reduced. It is considered that the result was inferior in charging property and cleaning property. Further, the toner of Comparative Example 3 using a zinc complex of a salicylic acid compound as a charge control agent has a binder resin and a charge control agent that have the same masterbatch kneading time as the masterbatch used in Comparative Example 2. Since it is difficult to form a cross-link between the two, the softening point of the pulverized product obtained in the masterbatch process cannot be increased, and the dispersibility of the charge control agent cannot be adjusted, resulting in poor cleaning properties. became.

  The toner for electrophotography of the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (6)

  A masterbatch process in which a raw material containing the binder resin (A) and the charge control agent is melt-kneaded and pulverized, and the pulverized product obtained in the masterbatch process is mixed with at least a further binder resin (B) and melted. An electrophotographic toner obtained by a method including a dilution step of kneading, wherein the charge control agent is a chromium complex of a salicylic acid compound, and the softening point of the pulverized product obtained in the masterbatch step and the binder resin ( B) softening point ratio (softening point of pulverized product / softening point of binder resin (B)) is 1.30 to 1.50, volume median particle size of the toner is 7.0 to 10.0 μm, and fluctuation with respect to volume particle size distribution The coefficient of chromium is 25 to 35%, the volume-median particle size contained in the toner is 5.0 to 6.0 μm, and the coefficient of variation with respect to the volume particle size distribution is 20 to 25%. X-ray intensity (Is) and total toner containing the small particle size toner A toner for electrophotography having a ratio (Is / It) of X-ray intensity (It) of chromium of 0.5 to 1.0 in X-ray fluorescence X-ray analysis.   2. The electrophotographic toner according to claim 1, wherein the content of the charge control agent is 3 parts by weight or more with respect to 100 parts by weight of the total amount of the binder resin.   An image forming method using the electrophotographic toner according to claim 1 in a non-contact developing type image forming apparatus.   A two-component developer comprising the electrophotographic toner according to claim 1 or 2 and a carrier.   An image forming method using the two-component developer according to claim 4 in an image forming apparatus of a non-contact developing type. 6. The image forming method according to claim 3, wherein the linear velocity of the image forming apparatus is 750 mm / sec or more.