JP2007316126A - Method for evaluating electrophotographic toner, and electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating an electrophotographic toner capable of evaluating quantitatively in what kind of status inorganic particulates exist in the surface of the whole of a toner particle group, and further, to provide an electrophotographic toner in which inorganic particulates are uniformly present on the surfaces of the toner particles, and printing quality is stable. <P>SOLUTION: The method for evaluating an electrophotographic toner is composed of: a fractionation step where an electrophotographic toner composed of toner host particles and an external additive is fractionated into a plurality of fractionated toners and the remaining toner using an oscillation transfer type fluidity measurement device; a measurement step where each amount of the external additive comprised in a plurality of the fractionated toners and the remaining toner is measured; and a derivation/evaluation step where the dispersion ununiformity index and the external additive peeling index of the external additive are derived from the relation between a plurality of the fractionated toners, the remaining toner, and each amount of the external additive, so as to be evaluated. The fractionation step is characterized in that the fractionation is performed in such a manner that the weight of the remaining toner is controlled to 30 wt.% of the total toner weight. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for evaluating an electrophotographic toner used for image formation by electrophotography and an electrophotographic toner.

  As an image forming method using an electrostatic latent image developing method typified by electrophotography, there are those described in US Pat. Nos. 2,297,691 and 2,357,809. They form an electrostatic latent image on the surface of the photoreceptor, and develop the electrostatic latent image into a toner image with a dry developer composed of at least a colored fine powder (toner). In this method, a final image is formed by a transfer process for transferring a toner image and a fixing process for fixing the toner image on a recording material by heating or pressurization.

  In order for the final image to be formed with a good image quality over a long period of time, it is necessary that the toner for developing an electrostatic image (sometimes referred to simply as toner) has high fluidity and maintains stable chargeability. . As a technique for improving the fluidity of toner, it is known to add and mix inorganic fine particles such as silica as external additives to toner base particles containing a colorant in a binder resin (for example, Patent Documents). 1).

  In this method, inorganic fine particles are adhered to the toner surface to form irregularities, thereby increasing the average distance between the toner and reducing van der Waals force between the toner particles to increase fluidity. However, the more inorganic fine particles are adhered, the more effective.

  However, since the inorganic fine particles exist as secondary agglomerated particles, if they are present in large quantities, they are not sufficiently crushed when mixed with the toner particles, and are unevenly present on the toner particle surface or peeled off from the toner particles. There's a problem. In such a case, the print quality of the toner is not constant, which may cause a void phenomenon that causes the image to be lost or a density unevenness phenomenon that the density of the solid portion is not constant.

  Conventionally, there is only a method for evaluating the state of the inorganic fine particles on the surface of the toner particles using an electron micrograph. However, in this method, the adhesion state can be evaluated only locally, and appropriate inorganic fine particles in the entire toner particle group cannot be confirmed.

JP-A-4-152353

  The present invention has been made in view of the above-described problems, and its objective is to quantitatively determine in what state inorganic fine particles are present on the entire surface of the toner particle group. An object of the present invention is to provide an electrophotographic toner evaluation method that can be evaluated, and to provide an electrophotographic toner in which inorganic fine particles are uniformly present on the surface of the toner particles and the printing quality is stable.

  The present invention has solved the above problems by the following technical configuration.

(1) Using a vibration transfer type fluidity measuring device, a plurality of fractionated toners and a fractionation step of fractionating the electrophotographic toner composed of toner base particles and an external additive into residual toners; A measurement step of measuring the amount of the external additive contained in the fractional toner and the residual toner, and a dispersion non-uniformity index of the external additive from the relationship between the plurality of fractional toners, the residual toner and the amount of the external additive An electrophotographic toner evaluation method comprising a derivation and evaluation step for deriving and evaluating an external peeling index, wherein the fractionation step fractionates the residual toner to be 30% by weight of the total toner weight. And a method for evaluating an electrophotographic toner.
(2) The electrophotographic image according to (1), wherein a dispersion disproportionation index in the derivation evaluation step is 0.03 or less, and the external additive peeling index is 0 or more and less than 0.3. Toner evaluation method.
(3) An electrophotographic toner obtained by externally adding at least silica to a toner base particle, wherein the silica has a dispersion disproportionation index of 0.03 or less and an external addition peeling index of 0 or more and 0. An electrophotographic toner, wherein the toner is less than .3.
(4) The toner for electrophotography as described in (3) above, wherein titanium oxide is further externally added and the titanium oxide has an exfoliation index of 0 or more and less than 0.3.

According to the present invention, it is possible to provide an evaluation method for an electrophotographic toner capable of quantitatively evaluating the state in which inorganic fine particles are present on the entire surface of a toner particle group, It is possible to provide an electrophotographic toner in which fine particles are uniformly present on the surface of the toner particles and the printing quality is stable.
Therefore, according to the electrophotographic toner evaluation method and the electrophotographic toner of the present invention, it is possible to prevent the occurrence of uneven density phenomenon and void phenomenon in the copy image due to the adhesion of inorganic fine particles on the surface of the toner particles. .

The method for evaluating the electrophotographic toner of the present invention will be specifically described.
First, an electrophotographic toner comprising toner base particles to be measured and an external additive is put into a vibration transfer type fluidity measurement device (Etowas Corporation: vibration transfer type fluidity measurement device). According to the vibration transfer type fluidity measuring apparatus, the fluidity of the whole toner group can be measured from the shape of the toner, the state of the external additive, and the like by applying vibration to the toner put in the bowl.
(Fractionation step)
According to the vibration transfer type fluidity measuring device, toner can be collected sequentially from the difference in fluidity against vibration. Then, the toner sequentially collected according to the difference in fluidity is fractionated into a plurality of fractionated toners and a residual toner for each predetermined amount. At this time, large toner with low fluidity or angular toner was collected at the first stage along the time series, and gradually a spherical toner with high fluidity or an external additive adhered appropriately over time. Toner is collected.
In collection, when fractionation is performed up to 70% by weight with low fluidity, the fractionation is stopped, and the remaining toner is scraped out to collect all the residual toner. Therefore, the residual toner corresponds to 30% by weight with high fluidity in the total toner weight.
The residual toner contains a large amount of toner having a very high fluidity and a small amount of peeled external additive.

The fractionation step will be described with reference to FIG.
FIG. 1 is a graph showing the relationship between the amount collected by a vibration transfer type fluidity measuring device and time.
The vertical axis is the collection amount (% by weight) with respect to the whole toner group, and “stage” 1st, 2nd, 3rd,. The horizontal axis is the time required for fractionation.
1.0 g of electrophotographic toner externally added with 0.4 parts by weight of silica and 0.5 parts by weight of titanium oxide with respect to 100 parts by weight of toner base particles is put into the vibration transfer type fluidity measuring device toner. Fractionated.
Here, as shown in FIG. 1, 0% to 10% (0 g to 0.1 g) collected first is 1st fraction toner, 10% to 20% (0.1 g to 0.2 g) is 2nd. Fraction toner, 20% to 30% (0.2 g to 0.3 g) 3rd fraction toner, 30% to 40% (0.3 g to 0.4 g) 4th fraction toner, 40% to 50 % (0.4 g to 0.5 g) of 5th fraction toner, 50% to 60% (0.5 g to 0.6 g) of 6th fraction toner, 60% to 70% (0.6 g to 0.00 g). 7g) was the 7th fraction toner, and the last 70% to 100% (0.7g to 1.0g) was the 8th residual toner.

(Measurement step)
Next, the amount (% by weight) of the external additive contained in each of the plurality of fractionated toners and the residual toner is measured.
Specifically, for each toner, the amount of silica contained in the toner (% by weight) and the amount of titanium oxide (% by weight) were measured using a fluorescent X-ray measurement apparatus (manufactured by JEOL Datum, trade name: JSX-). 3201) and measured by fluorescent X-ray analysis.
As the measurement sample, each toner powder was put in a molding resin ring and pellets having a diameter of 30 mm and a thickness of about 2 mm were formed using a hydraulic press.

(Derivation evaluation step)
Next, from the transition of the amount of silica (% by weight) and the amount of titanium oxide (% by weight) associated with the change in fluidity, that is, from the relationship between multiple fractional toners, residual toner and the amount of external additives, the following analysis Using the procedure, the dispersion disparity index and external peeling index of the external additive are derived.
First, the dispersion non-uniformity index will be described with reference to FIG.
FIG. 2 is a diagram showing the relationship between the amount of the external additive contained in the fractionated toner and the fractionated toner.
The vertical axis represents the amount (% by weight) of the external additive contained in the fractionated toner obtained by fluorescent X-ray analysis, and the horizontal axis represents the “stage” of the fractionated toner.
For each fractionated toner, the amount of silica (wt%) and the amount of titanium oxide (wt%) contained in the toner were plotted. At this time, with respect to the horizontal axis, if the amount of each fractional toner is uniform, the interval is set at equal intervals, and if not, the position is corrected according to the amount of fractional toner. Here, since the amount of each fractionated toner is 0.1 g and uniform, the horizontal axis is taken at equal intervals.
In FIG. 2, the silica contained in the fractionated toner is indicated by a square mark, and the titanium oxide contained in the fractionated toner is indicated by a triangle mark.
Then, according to the plot, linear graphs F and G were obtained by the method of least squares.
F is a graph for silica, G is a graph for titanium oxide, a is an X-axis displacement from 1st to 7th, b1 is a Y-axis displacement (% by weight) of graph F when the X-axis displacement is a, and b2 is This is the Y-axis displacement (% by weight) of the graph G when the X-axis displacement is a.

Dispersion non-uniformity index: The dispersion non-uniformity index refers to a change in the amount of the external additive of the toner accompanying a change in fluidity. Specifically, the dispersion disproportionation index referred to in the present invention is the amount of external additive (% by weight) contained in the fractionated toner on the vertical axis, the fractionated toner on the horizontal axis, and the X-axis displacement is This is the absolute value of the Y-axis displacement b1, b2 when a.
In FIG. 2, the dispersion disparity index of silica is the absolute value of b1, and the dispersion disproportionation index of titanium oxide is the absolute value of b2.
If the dispersion disproportionation index is 0, the amount of the external additive is invariant to the difference in fluidity. That is, the amount of external additive does not affect the difference in fluidity. If the value of the dispersion non-uniformity index is large, the amount of the external additive varies depending on the difference in fluidity. That is, it is considered that the nonuniformity of the amount of the external additive affects the difference in fluidity.

Next, the external additive peeling index will be described with reference to FIG.
FIG. 3 is a diagram showing the relationship between the amount of the external additive contained in the fraction toner and the residual toner and the fraction toner and the residual toner. That is, FIG. 2 is a plot in which the amounts of silica and titanium oxide contained in the residual toner are added.
The vertical axis represents the amount (% by weight) of the external additive contained in the fractionated toner and the residual toner, and the horizontal axis represents the “stage” of the fractionated toner and the residual toner.
For each fractionated toner or residual toner on the horizontal axis, the amount of silica (wt%) and the amount of titanium oxide (wt%) contained in the toner were plotted. In FIG. 3, the silica contained in the fractionated toner is indicated by a square mark, and the titanium oxide contained in the fractionated toner is indicated by a triangle mark. Further, the silica contained in the residual toner is indicated by black square marks, and the titanium oxide contained in the residual toner is indicated by black triangle marks.
H 2 _{SiO 2} is the amount of silica in the residual toner (% by weight), M _{SiO 2} is the average amount of silica in the fractionated toner (% by weight), and _{HM SiO 2} is the amount of silica in the residual toner H _{SiO 2 in the} fractionated toner. The value obtained by subtracting the average value M _SiO2 of silica (wt%), _HTiO2 is the amount of titanium oxide (wt%) in the residual toner, and _MTiO2 is the average value (wt%) of titanium oxide in the fractionated toner. , _{H-M TiO2} is a value obtained by subtracting the average value _{M TiO2} of the titanium oxide content in the fraction toner from the amount of titanium oxide _{H TiO2} in the residual toner (wt%).

External additive peel index: The external additive peel index refers to the degree of exfoliation of the external additive accompanying the change in fluidity. Specifically, a value obtained by subtracting “average value of external additive amount (weight%) contained in fractionated toner” from “external additive amount (weight%) contained in residual toner” HM _{SiO 2} , H-M _TiO2 .
In FIG. 3, silica is _{HM SiO2} and titanium oxide is _HMTiO2 .
When the external additive peel index is 0, the external additive is hardly peeled off, and when the external additive peel index is large, it is considered that the external additive peel is markedly caused.

Then, the toner for electrophotography can be evaluated based on whether or not the dispersion disproportionation index and the external additive peeling index fall within predetermined ranges.
For example, as specified in claim 2, it is preferable that the evaluation standard is that the dispersion disproportionation index is 0.03 or less and the external additive peeling index is 0 or more and less than 0.3. It is.
The dispersion disproportionation index is preferably 0.02 or less, more preferably 0.01 or less.
If the dispersion non-uniformity index exceeds 0.03, the external additive is remarkably biased, and the density unevenness phenomenon is likely to occur. The influence of silica is particularly great on the relationship between the dispersion non-uniformity index and the density unevenness phenomenon.
The external additive peeling index may be 0 or more and 0.2 or less, and may be 0 or more and 0.1 or less.
If the external additive peeling index is less than 0, the amount of the external additive is considered to be insufficient, and if it exceeds 0.3, the toner is deteriorated due to a lot of peeling, so that a void phenomenon is likely to occur. The relationship between the exfoliation index and the void phenomenon is particularly affected by silica and titanium oxide.

Next, the electrophotographic toner of the present invention will be described.
The electrophotographic toner of the present invention is an electrophotographic toner obtained by externally adding at least silica to toner base particles, and the dispersion disproportionation index of silica is 0.03 or less, and the external additive The peeling index is 0 or more and less than 0.3.
The dispersion disproportionation index is more preferably 0.02 or less, and most preferably 0.01 or less.
When the dispersion non-uniformity index exceeds 0.03, the external additive is remarkably biased, and uneven density development is likely to occur.
The external additive peeling index is more preferably 0 or more and 0.2 or less, and most preferably 0 or more and 0.1 or less.
If the external additive peeling index is less than 0, the amount of the external additive is considered to be insufficient, and if it exceeds 0.3, the toner is deteriorated due to a lot of peeling, so that a void phenomenon is likely to occur.
Further, it is more preferable that the electrophotographic toner of the present invention further comprises external addition of titanium oxide, and the external addition peeling index of titanium oxide is 0 or more and less than 0.3. As for titanium oxide, if it is less than 0, the amount of the external additive is considered to be insufficient.
Furthermore, it is preferable that the dispersion disproportionation index of titanium oxide is 0.03 or less.

The electrophotographic toner of the present invention is produced as follows.
That is, the electrophotographic toner of the present invention comprises a melt-kneading step for obtaining a kneaded product by heat-melting and kneading a composition mainly composed of a binder resin and a charge control agent, and pulverizing and classifying the kneaded product to form toner base particles. Is obtained by mixing and stirring the toner base particles with a predetermined external additive, and a removing step of removing fine powder and exfoliated material.
More specifically, a binder resin, a charge control agent, and other additives as necessary are blended into a predetermined composition, and this mixture is melt-kneaded using a twin-screw kneader, an extruder, a roll mill, etc. A melt-kneading step for obtaining a kneaded product of the above, a pulverizing and classifying step for obtaining toner base particles by pulverizing the obtained kneaded material with an air flow type pulverizing means such as a jet mill and classifying the particles into particles of a predetermined particle size with a classifier The toner base particles are mixed and stirred with a predetermined external additive such as inorganic fine particles and various mixers to obtain a mixture, and fine powder and exfoliated material are utilized using a vibration transfer type fluidity measuring device and a bag filter. It comprises a removal step for removing.
The steps until obtaining toner base particles can also be performed by other granulation methods such as suspension polymerization and spray drying.

  The binder resin used in the present invention is not particularly limited as long as it is conventionally used for toner, but styrene-acrylic resin, polystyrene, polyethylene, vinyl resin, polyacrylate, polymethacrylate, polychlorinated resin. In addition to thermoplastic resins such as vinylidene, polyacrylonitrile, polyether, polycarbonate, polyester, cellulosic resin, and copolymer resins of these monomers, thermosetting resins such as modified acrylic resin, phenol resin, melamine resin, urea resin, etc. Can be used. A mixture of these may also be used.

  As the charge control agent, any charge control agent used for toners can be used, but iron-based metal-containing dyes, chromium-based dyes, nigrosine compounds, quaternary ammonium salts, and the like that particularly improve frictional chargeability can be preferably used. .

  Other additives that may be added as needed include colorants such as carbon black and colorants, fixing aids such as low molecular weight polypropylene, mold release agents, and magnetic powder.

  As external additives, various silicas such as hydrophobic silica and colloidal silica, titanium compounds such as fatty acid metal salts, alumina and titanium oxide, resin fine particles and the like can be used as appropriate, and at least silica from the viewpoint of chargeability and fluidity. Is necessary.

  The obtained electrophotographic toner can be used as a one-component developer, or can be mixed with a carrier and used as a two-component developer.

  Any carrier can be used as long as it is a known carrier. From the viewpoint of magnetic force, charging characteristics, shape, etc., for example, a ferrite carrier or a granulated magnetite carrier produced by a spray dry-granulation-firing process is preferable. Can be used.

<Manufacture of toner base particles>
Styrene-acrylic acid ester copolymer resin (trade name: TTR-591, manufactured by Fujikura Kasei Co., Ltd.)
90.0 parts by weight of charge control agent (Nigrosine dye trade name: CCA3, manufactured by Chuo Gosei Co., Ltd.) 3.6 parts by weight of carbon black (trade name: Mitsubishi Carbon # 40, manufactured by Mitsubishi Chemical Corporation) 4.6 parts by weight of low molecular weight polypropylene (Product name: Viscol 660P, manufactured by Sanyo Chemical Industries)
1.8 parts by weight

  The raw materials having the above blending ratio are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air classifier, resulting in a volume average particle size (D50) of 9 Toner base particles for a non-magnetic one-component developer of 0.0 μm were obtained. The volume average particle diameter (D50) is a volume-based integrated 50% value by Coulter counter TA-II type.

  The toner base particles were processed as shown below to prepare electrophotographic toners of Examples and Comparative Examples.

Example 1
0.4 parts by weight of hydrophobic silica coated with linear dimethyl silicone oil (trade name: KF96-50CS, manufactured by Shin-Etsu Chemical Co., Ltd.) and titanium oxide (manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by weight of the toner base particles. , Primary particle diameter 10 nm, BET specific surface area 65 ± 10, treatment agent octylsilane) 0.5 parts by weight were mixed and stirred with a super mixer to obtain a mixture. The mixing and stirring time was 12 minutes.
Thereafter, the toner was fractionated by the aforementioned vibration transfer type fluidity measuring device, and the residual toner corresponding to 30% by weight of the toner weight was removed.
The obtained toner was collected and fractionated again by a vibration transfer type fluidity measuring device to remove residual toner corresponding to 30% by weight of the toner weight.
Further, the same operation was repeated once again to remove residual toner corresponding to 30% by weight of the toner weight, and the electrophotographic toner of Example 1 was obtained.

(Example 2)
In place of the vibration transfer type fluidity measurement device, the electrophotographic sample of Example 2 was used in the same manner as in Example 1 except that the fine powder and the exfoliated material were removed using a bag filter (Bleet type) repeatedly 10 times. A toner was obtained.

(Example 3)
The mixing and stirring time was set to 15 minutes, and instead of the vibration transfer type fluidity measurement device, the fine powder and the exfoliated material were removed by using a bag filter (Bleet type) once, in the same manner as in Example 1. The toner for electrophotography of Example 3 was obtained.

Example 4
Hydrophobic silica 0.3 parts by weight and titanium oxide 0.4 parts by weight. Instead of the vibration transfer type fluidity measuring device, fine powder and exfoliated material are removed using a bag filter (Bleet type) once. Except that, an electrophotographic toner of Example 4 was obtained in the same manner as Example 1.

(Comparative Example 1)
An electrophotographic toner of Comparative Example 1 was obtained in the same manner as Example 3 except that the mixing and stirring time was 12 minutes. The electrophotographic toner of Comparative Example 1 is a conventional general electrophotographic toner.

(Comparative Example 2)
An electrophotographic toner of Comparative Example 2 was obtained in the same manner as in Example 3 except that the mixing and stirring time was 6 minutes.

(Comparative Example 3)
The electrophotographic toner of Comparative Example 3 was prepared in the same manner as in Example 3 except that 1.2 parts by weight of hydrophobic silica, 1.5 parts by weight of titanium oxide and 12 minutes of mixing and stirring were used. Obtained.

(Comparative Example 4)
The electrophotographic toner of Comparative Example 4 was prepared in the same manner as in Example 3 except that 0.1 part by weight of hydrophobic silica and 0.1 part by weight of titanium oxide were used, and the mixing and stirring time was 12 minutes. Obtained.
Table 1 shows the main production conditions for the electrophotographic toners of Examples and Comparative Examples.

In addition, the silica in Table 1 is a hydrophobic silica coated with a linear dimethyl silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.).
The titanium oxide in Table 1 is titanium oxide (manufactured by Nippon Aerosil Co., Ltd., primary particle diameter 10 nm, BET specific surface area 65 ± 10, treating agent octylsilane).

The electrophotographic toners of the above examples and comparative examples were evaluated by the electrophotographic toner evaluation method of the present invention.
The evaluation results are shown in Table 2.

  Next, for the electrophotographic toners of Examples and Comparative Examples, a copy test was actually performed, and a void phenomenon and a density unevenness phenomenon were measured as print quality.

<Copy test>
Continuous 3000 page copy test at room temperature and normal humidity (25 ° C / 55% RH, hereinafter referred to as N / N) using a commercially available laser printer (printing speed A4 paper 25 sheets / min) using non-magnetic one-component minus toner. The void phenomenon and density unevenness phenomenon were measured.

Density non-uniformity phenomenon: A 1.0 cm × 1.0 cm square solid pattern is printed on A4 paper at regular intervals of 15 lines in the main scanning direction and 11 lines in the sub scanning direction, and the reflection density of the square solid in one page is Macbeth. All were measured with a reflection densitometer (RD-914), and the difference between the maximum value and the minimum value was regarded as density unevenness. Therefore, a smaller value indicates better image quality without density unevenness, and if it is 0.25 or less, there is no practical problem.
Void phenomenon: A lattice pattern was printed on A4 paper, and the image was looked with a magnifying glass 50 times, and the presence or absence of voids, i.e., point-like white spots, was visually determined.
Table 3 shows the result of the copy test.

As shown in Table 3, in Examples 1 to 4, the density unevenness phenomenon had no practical problem and no void phenomenon.
In particular, Examples 1 and 2 showed stable printing quality with suppressed density unevenness.
On the other hand, in Comparative Example 1, the density unevenness phenomenon has no practical problem, but a small number of void phenomena were found.
In Comparative Examples 2, 3, and 4, the density unevenness phenomenon has a practical problem, and many void phenomena were found.
As described above, the evaluation method of the present invention and the actual print quality are in good agreement, and it has been found that the evaluation method of the present invention is effective in determining the print quality.
It was also found that the electrophotographic toner of the present invention has excellent print quality.

A graph showing the relationship between the amount collected and time taken by the vibration transfer type fluidity measurement device The figure which shows the relationship between the amount of the external additive contained in fractionated toner, and fractionated toner The figure which shows the relationship between the amount of external additives contained in fraction toner and residual toner and fraction toner and residual toner

Explanation of symbols

a 1st to 7th X-axis displacement b1, b2 Dispersion non-uniformity index F Graph for silica G Graph for titanium oxide H Silica amount in _SiO2 residual toner M Average value of silica amount in _SiO2 fractionated toner H- M _SiO2 outer添剥away exponential mean value _{H-M TiO2} titanium oxide titanium oxide of the titanium oxide amount _{M TiO2} fraction in the toner in an outer添剥away exponent _{H TiO2} residual toner silica

Claims (4)

A fractionation step of fractionating electrophotographic toner comprising toner base particles and external additives into a plurality of fractionated toners and residual toners using a vibration transfer type fluidity measuring device; and the plurality of fractionated toners And a measuring step for measuring the amount of the external additive contained in the residual toner,
An electrophotographic toner comprising a plurality of fractionated toners, a residual toner, and a derivation evaluation step for deriving and evaluating a dispersion non-uniformity index and an external addition peeling index of the external additive from the relationship between the amount of the external additive and the amount of the external additive Evaluation method,
The method for evaluating an electrophotographic toner, wherein the fractionation step fractionates the residual toner to be 30% by weight of the total toner weight. 2. The electrophotographic toner evaluation according to claim 1, wherein the dispersion disproportionation index in the derivation evaluation step is 0.03 or less, and the external additive peeling index is 0 or more and less than 0.3. Method. An electrophotographic toner obtained by externally adding at least silica to toner base particles,
The toner for electrophotography, wherein the silica has a dispersion disproportionation index of 0.03 or less, and an external additive peeling index of 0 or more and less than 0.3. 4. The toner for electrophotography according to claim 3, further comprising titanium oxide externally added, wherein the titanium oxide has an exfoliation index of 0 or more and less than 0.3.

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