JP2007114630A - 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 in which the performance of the toner after a copying test can be rapidly and readily evaluated without carrying out the copying test and a heating test. <P>SOLUTION: The method has a step of charging the electrophotographic toner into a plurality of aqueous methanol solutions varying in toner concentrations, a step of measuring the ratio of the floating electrophotographic toner or the ratio of the settled electrophotographic toner to the charged electrophotographic toner, a step of deriving the hydrohobing degree or hydrophobic uniformity of the electrophotographic toner from the transition of the ratio of the floating electrophotographic toner or the ratio of the settled electrophotographic toner, and a step of evaluating the electrophotographic toner based on the evaluation standard of whether the hydrohobing degree and hydrophobic uniformity of the electrophotographic toner are respectively within the prescribed range or not. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner evaluation method and an electrophotographic toner.

It is well known that in an electrophotographic image forming apparatus, as the number of copies increases, the toner in the developing device deteriorates, and this causes various problems.
For example, the toner charge amount decreases, resulting in a decrease in image density, an increase in fog, missing characters, and the like.
In order to prevent such problems, various research and development have been conducted on toner.

  In order to evaluate the performance, mainly the durability, of these various toners produced in the research and development process, the produced toner is actually used in a copying machine, a printer, etc. A method in which image density, fog density, toner charge amount, and the like are measured and compared with initial values has been generally used.

However, in such an evaluation method, for example, in the case of the one-component development method, the evaluation result is obtained so that the performance of the toner cannot be evaluated unless a copy test for consuming the toner of one toner cartridge is performed. It took a long time and hindered rapid research and development.
In addition, it requires a lot of labor and cost.
Furthermore, since a huge amount of paper is used for the copy test, establishment of a new evaluation method has been desired from the viewpoint of effective utilization of limited resources.
On the other hand, a proposal such as a blocking test by a heating test has been made (for example, Patent Document 1).

JP 2003-255583 A

  The present invention has been made in view of such problems, and an object of the present invention is to provide an electrophotographic image that can quickly and easily evaluate the performance of a toner after a copy test without performing a copy test or a heat test. Another object of the present invention is to provide a toner evaluation method.

The present invention has solved the above problems by the following technical configuration.
(1) A step of introducing an electrophotographic toner into a plurality of aqueous methanol solutions having different concentrations, and a ratio of a floating electrophotographic toner or a settling electrophotographic toner to the charged electrophotographic toner And the degree of hydrophobicity and hydrophobic uniformity of the electrophotographic toner from the transition of the ratio of the floating electrophotographic toner or the ratio of the electrophotographic toner that has settled as the methanol concentration changes A method for evaluating electrophotographic toner, comprising: a step of deriving the property, and a step of evaluating the toner for electrophotography based on whether the degree of hydrophobicity and the hydrophobic uniformity fall within a predetermined range, respectively. .
(2) The step of introducing the electrophotographic toner into water or an aqueous methanol solution, and adding methanol to the water or aqueous methanol solution, the ratio or sedimentation of the floating electrophotographic toner accompanying the change in methanol concentration. The degree of hydrophobicity of the electrophotographic toner from the step of measuring the transition of the ratio of the electrophotographic toner that is floating and the transition of the ratio of the floating electrophotographic toner or the ratio of the sedimented electrophotographic toner And a step of deriving hydrophobic uniformity, and a step of evaluating the toner for electrophotography based on whether the degree of hydrophobicity and the hydrophobic uniformity fall within a predetermined range, respectively. Evaluation method.
(3) The degree of hydrophobicity is 50% hydrophobicity, the hydrophobic uniformity is 50% to 10% hydrophobic uniformity, and the step of evaluating the electrophotographic toner has a degree of hydrophobicity of 50%. The evaluation of the electrophotographic toner according to (1) or (2) above, wherein the evaluation standard is 30 vol% or more and 50% to 10% hydrophobic uniformity is less than 20 vol% difference. Method.
(4) The toner for electrophotography, wherein the 50% hydrophobicity is 30 vol% or more, and the 50% to 10% hydrophobic uniformity is less than 20 vol% difference.
(5) The toner for electrophotography according to (4), wherein a cyclic siloxane compound or linear silicone oil and hydrophobic silica are adhered to the surface of the toner base particles.

According to the present invention, it is possible to provide an electrophotographic toner evaluation method capable of quickly and easily evaluating the performance of a toner after a copy test without performing a copy test or a heat test.
In addition, there is little fluctuation in charging even at high temperature and high humidity and low temperature and low humidity, no photoconductor filming, fogging and missing characters occur, and excellent cleaning properties, high resolution and high quality images can be obtained. An electrophotographic toner can be provided.

The method for evaluating the electrophotographic toner of the present invention will be specifically described.
First, a plurality of methanol aqueous solutions having different concentrations are prepared, and a certain amount of electrophotographic toner is charged therein. Then, the ratio of the electrophotographic toner that floats or settles to the total amount of the electrophotographic toner that is input is measured by wt% or the like, and the electrophotographic toner that floats or settles due to the change in the concentration of methanol. From the ratio transition, the degree of hydrophobicity and hydrophobic uniformity of the electrophotographic toner are derived using graphs and mathematical formulas.

Hydrophobicity: The degree of hydrophobicity refers to the degree of hydrophobicity with respect to an aqueous methanol solution. Specifically, it refers to the methanol concentration at which a predetermined ratio a (for example, 50 wt%) remains floating with respect to the total amount of toner charged in the methanol aqueous solution.
The degree of hydrophobicity when the predetermined ratio a is 50 wt% is referred to as 50% degree of hydrophobicity x (see FIGS. 1A and 1C), and so on.
A degree of hydrophobicity x of 50% is considered effective for showing the average hydrophobicity of the toner.

Hydrophobic uniformity: Hydrophobic uniformity refers to the degree of wettability with respect to an aqueous methanol solution between individual toner particles. Specifically, with respect to the total amount of toner charged in the methanol aqueous solution, the methanol concentration when it remains floating by a predetermined ratio b1 (for example, 50 wt%) and the predetermined ratio b2 (for example, 10 wt%) different from b1 are floated. The concentration difference (vol% difference) from the methanol concentration when remaining.
The concentration difference when the predetermined ratio b1 is 50 wt% and the predetermined ratio b2 is 10 wt% is called 50% to 10% hydrophobic uniformity d (see FIGS. 1A and 1C), and so on. To do.
It is considered that the smaller the 50% to 10% hydrophobic uniformity d, the more rapidly the amount of sedimentation increases, and the wettability between individual toner particles is uniform.
The 50% to 10% hydrophobic uniformity d empirically has a small error in measurement, and its quality is in good agreement with the quality of actual toner characteristics.

Then, the toner is evaluated depending on whether or not these 50% hydrophobicity x and 50% to 10% hydrophobic uniformity d are within predetermined ranges.
For example, the evaluation criterion can be that 50% hydrophobicity x is 30 vol% or more and 50% to 10% hydrophobic uniformity d is less than 20 vol% difference.
The 50% hydrophobization degree x may be 35 vol% or more, or 50 vol% or more.
When the 50% hydrophobicity degree x is less than 30 vol%, the physical adhesion between the photoconductor and the toner and the cohesive force between the toner particles become strong, resulting in missing characters.
The 50% to 10% hydrophobic uniformity d can be less than 8 vol% difference or less than 5 vol% difference.
If the 50% to 10% hydrophobic uniformity d is 20 vol% or more, the charge amount between the toner particles becomes non-uniform, so that so-called selective development occurs in which toner particles with a higher charge amount are consumed earlier in the developing device. , Fogging occurs.
The method for evaluating an electrophotographic toner of the present invention can be evaluated even with a slight difference in the toner surface, and is particularly suitable for evaluation of a toner that has been surface-treated with an external additive or the like.

The electrophotographic toner evaluation method of the present invention is performed as described above, but is not necessarily limited thereto. For example, it can be as follows.
○ Floating with the change in methanol concentration by adding the methanol for electrophotography to one water or methanol aqueous solution instead of multiple methanol aqueous solutions and adding pure methanol to it gradually. Alternatively, the transition of the ratio of the electrophotographic toner that has settled can be measured. While the measurement is simple, there is a possibility that pure methanol directly touches the toner and affects the measurement result.
O Instead of 50% hydrophobicity, it is also possible to derive 0% hydrophobicity (concentration of methanol at which all toner settles) and evaluate the toner based on this. While the measurement is simple, the result may be affected by some toner having a high degree of hydrophobicity.
○ Instead of 50% to 10% hydrophobic uniformity, 100% to 0% hydrophobic uniformity (concentration difference between the methanol concentration at which toner precipitation starts and the methanol concentration at which toner precipitation ends) is derived, based on this It is also possible to evaluate the toner. Although the measurement is simple, the result may be affected by some toners having a high degree of hydrophobicity and some toners having a low degree of hydrophobicity.
○ An aqueous ethanol solution or the like can be used instead of the aqueous methanol solution.

Next, the electrophotographic toner of the present invention will be described.
According to the electrophotographic toner evaluation method of the present invention, the electrophotographic toner of the present invention has a 50% hydrophobicity x of 30 vol% or more and a 50% to 10% hydrophobic uniformity d of less than 20 vol% difference. It is characterized by being evaluated.
The 50% hydrophobization degree x is more preferably 35 vol% or more, and most preferably 50 vol% or more.
A toner having a 50% hydrophobicity degree x of less than 30 vol% is not preferable because missing characters occur.
The 50% to 10% hydrophobic uniformity d is more preferably less than 8 vol% difference, and most preferably less than 5 vol% difference.
A toner having a 50% to 10% hydrophobic uniformity d of 20 vol% or more is not preferable because fogging occurs.

The electrophotographic toner of the present invention is produced as follows.
That is, the method for producing an electrophotographic toner of the present invention includes a step of hot-melting and kneading a formulation mainly composed of a binder resin and a charge control agent to obtain a kneaded product, and crushing and classifying the kneaded product to obtain a toner base And obtaining a mixture by mixing and stirring the toner base particles with a predetermined external additive such as a cyclic siloxane compound or a linear silicone oil. If necessary, a flow modifier is added to the mixture. And stirring.
More specifically, the toner base particles used in the electrophotographic toner are a binder resin, a charge control agent, and other additives, if necessary, blended into a predetermined composition, and this mixture is mixed with a biaxial kneader, It is manufactured by melt-kneading using an extruder, roll mill, or the like, pulverizing the obtained lump by an air flow type pulverizing means such as a jet mill, and classifying the particles into particles having a predetermined particle size by a classifier.
In addition, it may be based on other granulation methods such as a suspension polymerization method and a spray drying method.

  The binder resin is not particularly limited as long as it is conventionally used in toners, but styrene-acrylic resin, polystyrene, polyethylene, vinyl resin, polyacrylate, polymethacrylate, polyvinylidene chloride, polyacrylonitrile, Thermosetting resins such as modified acrylic resins, phenolic resins, melamine resins, and urea resins can be used in addition to thermoplastic resins such as polyethers, polycarbonates, polyesters, cellulosic resins, and copolymer resins of these monomers. 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.

The toner for electrophotography of the present invention can be obtained by attaching an external additive such as a cyclic siloxane compound or a linear silicone oil to the obtained toner base particles.
As the external additive, a cyclic siloxane compound is preferable, and a cyclic siloxane compound represented by the following formula (1) is more preferable.

（ただしｎは３ないし１０のいずれかが好ましく、さらに好ましくは３〜７、さらに好ましくは３〜５、もっとも好ましくは５である。Ｒは水素、炭素数１〜３のアルキル基、炭素数１〜３のアルキル変性基のいずれかが好ましく、さらに好ましくは水素、炭素数１〜３のアルキル基のいずれか、もっとも好ましくはメチル基である。Ｒ′はアルキル基、不飽和脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、縮合環炭化水素基およびこれらの変性基のいずれかが好ましく、さらに好ましくはアルキル基、フェニル基、ビニル基およびこれらの変性基のいずれか、もっとも好ましくはメチル基である。）

(However, n is preferably any of 3 to 10, more preferably 3 to 7, more preferably 3 to 5, and most preferably 5. R is hydrogen, an alkyl group having 1 to 3 carbon atoms, or 1 carbon atom. Is preferably any one of ˜3, more preferably hydrogen, any one of 1 to 3 carbon atoms, and most preferably a methyl group, R ′ being an alkyl group or an unsaturated aliphatic hydrocarbon group. , An alicyclic hydrocarbon group, an aromatic hydrocarbon group, a condensed ring hydrocarbon group and any of these modified groups are preferred, more preferably any of an alkyl group, a phenyl group, a vinyl group and any of these modified groups, Most preferably, it is a methyl group.)

The kinematic viscosity of an external additive such as a cyclic siloxane compound or a linear silicone oil used in the present invention is preferably 50 mm ² / s or less at 25 ° C., more preferably 20 mm ² / s or less.
When the kinematic viscosity of an external additive such as a cyclic siloxane compound or a linear silicone oil exceeds 50 mm ² / s, the surface of the toner base particles cannot be uniformly coated, and the hydrophobic uniformity is poor. Therefore, it is not preferable.
Cyclic siloxane compounds or linear silicone oils with a kinematic viscosity of 50 mm ² / s or less have a lower boiling point than silicone oils conventionally used in toners, but low-temperature fixing is the mainstream in recent fixing devices. There is no problem in practical use.

One type of external additive such as a cyclic siloxane compound or a linear silicone oil can be used, but a plurality of types can be mixed and used as necessary.
The selection and mixing ratio of an external additive such as a cyclic siloxane compound or a linear silicone oil is ultimately determined by the charging characteristics, fluidity, etc. of the desired toner.

  The amount of the external additive such as cyclic siloxane compound or linear silicone oil used in the present invention is preferably 0.01 to 2.0 parts by weight, more preferably 0 to 100 parts by weight of the toner. 0.01 to 1.0 part by weight, most preferably 0.01 to 0.1 part by weight.

  In this case, if the amount is less than 0.01 part by weight, the object of the present invention cannot be achieved, and if it exceeds 2.0 parts by weight, the fluidity between toner particles is unfavorably deteriorated.

  There is a method in which a powdery external additive such as silica is treated with a hydrophobic material with a cyclic siloxane compound or a linear silicone oil, and the silica is attached to the toner. The surface cannot be covered completely, and the effect of the present invention cannot be obtained.

  In the present invention, an external additive such as a cyclic siloxane compound or a linear silicone oil is directly adhered to the surface of the toner base particles by stirring with a mixer such as a Henschel mixer or a super mixer. A sufficient effect can be brought about. Further, spraying or the like can be performed while the toner base particles are being stirred.

  Furthermore, it is preferable to externally add a flow modifier described below as required.

  As the flow modifier, hydrophobic silica, colloidal silica, fatty acid metal salt, alumina, titanium compound, resin fine particles and the like can be used as appropriate, and hydrophobic silica is preferred from the viewpoint of chargeability.

  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.

<Method for producing 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.

  Comparative Examples 1 to 6 and Comparative Example 1 in which the cyclic siloxane compound or linear silicone oil as an external additive shown in Table 1 is attached or not attached to the surface of the toner base particles and hydrophobic silica is added externally. The electrophotographic toners of Examples 1 to 3 were prepared.

This will be specifically described below.
Example 1
To 100 parts by weight of the toner base particles, 0.06 part by weight of dimethyl cyclic siloxane (D5) represented by the formula (2), which is a cyclic siloxane compound, was added and stirred with a super mixer.

  After stirring, 0.4 wt% of hydrophobic silica for fluid modification coated with silica with a linear dimethyl silicone oil (trade name: KF96-50CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was further added and mixed. The toner for electrophotography of Example 1 was obtained.

(Example 2)
An electrophotographic toner of Example 2 was obtained in the same manner as in Example 1 except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with the dimethyl cyclic siloxane (D4) represented by the formula (3). It was.

(Example 3)
The electrophotographic toner of Example 3 was obtained in the same manner as in Example 1 except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with the vinylmethyl cyclic siloxane (V4) represented by the formula (4). Obtained.

Example 4
The electrophotographic toner of Example 4 in the same manner as in Example 1 except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with a fluorinated alkyl cyclic siloxane (F3) represented by the formula (5). Got.

(Example 5)
Example 5 was carried out in the same manner as in Example 1, except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with a linear dimethyl silicone oil (20CS) shown in Table 1 and Formula (6). An electrophotographic toner was obtained.

（ただしｋは１以上の整数）

(Where k is an integer greater than 1)

(Example 6)
Example 6 was carried out in the same manner as in Example 1 except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with a linear dimethyl silicone oil (50CS) shown in Table 1 and Formula (6). An electrophotographic toner was obtained.

（ただしｋは１以上の整数）

(Where k is an integer greater than 1)

(Comparative Example 1)
In Example 1, instead of a hydrophobic silica coated with a linear dimethyl silicone oil (trade name: KF96-50CS, manufactured by Shin-Etsu Chemical Co., Ltd.) without attaching a cyclic siloxane compound or a linear silicone oil. An electrophotographic toner of Comparative Example 1 was obtained in the same manner as in Example 1 except that hydrophobic silica coated with octamethylcyclotetrasiloxane (D4) was used.

(Comparative Example 2)
In Example 1, an electrophotographic toner of Comparative Example 2 was obtained in the same manner as in Example 1 except that no cyclic siloxane compound or linear silicone oil was attached.

(Comparative Example 3)
Comparative Example 3 in the same manner as in Example 1 except that the dimethyl cyclic siloxane (D5) used in Example 1 was replaced with a linear dimethyl silicone oil (200CS) shown in Table 1 and Formula (6). An electrophotographic toner was obtained.

（ただしｋは１以上の整数）

(Where k is an integer greater than 1)

  The electrophotographic toners of Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated by the electrophotographic toner evaluation method of the present invention.

<Derivation of 50% Hydrophobicity x and 50% to 10% Hydrophobic Uniformity d by the Evaluation Method of Electrophotographic Toner of the Present Invention>
a) Methanol (made by Wako Pure Chemical Industries, purity 99.9%) and ion-exchanged water are mixed to prepare methanol aqueous solutions each having a methanol concentration of 10 vol% to 70 vol% in increments of 5 vol%, and 100 ml of glass samples Place 80 ml in a jar.
b) Add 2.0 g of toner into the aqueous methanol solution in the glass sample bottle, cover the bottle, and stir for 30 minutes on a vertical motion shaker.
c) Remove the glass sample bottle from the shaker and place it on a horizontal table to stand overnight.
d) The toner particles floating on the upper part of the glass sample bottle are collected on an evaporating dish using a 10 ml Komagome pipette, dried in an oven at 50 ° C. overnight, and the weight is measured.

As a measurement result, FIG. 1 shows the relationship between the methanol concentration (vol%) on the horizontal axis and the floating toner (wt%) with respect to the total amount of toner on the vertical axis.
That is, FIG. 1 is a diagram showing the relationship between the floating toner and the methanol concentration by the electrophotographic toner evaluation method of the present invention, wherein (a) shows the evaluation results regarding the toners of Examples 1 to 4, Is the evaluation result regarding the toners of Examples 5 to 6, and (c) is the evaluation result regarding the toners of Comparative Examples 1 to 3.
From FIG. 1, for the toners of Examples 1 to 6 and Comparative Examples 1 to 3, the methanol concentration when 50 wt% of toner remains floating is calculated to be 50% hydrophobicity x, and 50 wt% of toner. The concentration difference (vol% difference) between the methanol concentration when the toner remains floating and the methanol concentration when the 10 wt% toner remains floating is calculated to be 50% to 10% hydrophobic uniformity d.

  As an example, for Example 1 and Comparative Example 3, 50% hydrophobization degree x and 50% to 10% hydrophobic uniformity d are illustrated.

  As evaluation criteria, the evaluation when the 50% hydrophobization degree x is 30 vol% or more and the 50% to 10% hydrophobic uniformity d is less than 20 vol% is evaluated as ◯, and the evaluation when it is not x As shown in Table 2.

表２に示したように、実施例１〜６は５０％疎水化度ｘが３８．５〜５０．６ｖｏｌ％であり、又、５０％〜１０％疎水均一性ｄが３．７〜１６．０ｖｏｌ％差であり、５０％疎水化度ｘも５０％〜１０％疎水均一性ｄも本発明の作用効果を奏するために十分な値であった（評価○）。
しかし、比較例１および２は５０％疎水化度ｘが２９．０ｖｏｌ％および２８．５ｖｏｌ％と不十分であり、比較例３は５０％〜１０％疎水均一性ｄが２１．７ｖｏｌ％差と不十分であり、いずれも５０％疎水化度ｘと５０％〜１０％疎水均一性ｄとを同時に満足しないので問題がある（評価×）。

As shown in Table 2, in Examples 1 to 6, the 50% hydrophobicity x is 38.5 to 50.6 vol%, and the 50% to 10% hydrophobic uniformity d is 3.7 to 16. The difference was 0 vol%, and the 50% hydrophobicity x and the 50% to 10% hydrophobic uniformity d were sufficient values to achieve the effects of the present invention (evaluation ○).
However, Comparative Examples 1 and 2 have insufficient 50% hydrophobicity x of 29.0 vol% and 28.5 vol%, and Comparative Example 3 has a difference of 50% to 10% hydrophobic uniformity d of 21.7 vol%. There is a problem because both are insufficient and both do not satisfy the degree of hydrophobicity x of 50% and the uniformity of hydrophobicity d of 50% to 10% (evaluation x).

  Next, a copy test was performed on the electrophotographic toners obtained in Examples 1 to 6 and Comparative Examples 1 to 3.

<Copy test>
Under normal temperature and humidity (25 ° C./55% RH, hereinafter referred to as N / N), under high temperature and high humidity (30 ° C./80% RH, hereinafter referred to as H / H), and under low temperature and low humidity (10 ° C./20 % RH, hereinafter referred to as L / L), a continuous laser copy test using a commercially available laser printer (printing speed A4 paper 25 sheets / min) using a non-magnetic one-component minus toner was performed. Evaluation was performed.

  Furthermore, in the N / N copy test, image density, fogging, and missing characters were evaluated.

  A specific evaluation method is shown below.

(I) Development sleeve charge amount (μc / g)
In order to obtain the developing sleeve charge amount A, the developing device containing the electrophotographic toner is allowed to stand for 24 hours, and then the stirrer of the developing device is stirred for 10 minutes, and then obtained by the following measuring device.

  FIG. 2 is a schematic view of a measuring apparatus for obtaining the developing sleeve charge amount A. FIG.

  In FIG. 2, 31 is a developing sleeve, 32 is an electrophotographic toner, 33 is a suction machine, 34 is a Q meter, and 35 is a filter.

  Here, the suction device 33 sucks the suction port close to the surface of the electrophotographic toner 32 on the surface of the developing sleeve 31 and sucks it using a vacuum cleaner or the like.

  The Q meter is a charge measuring device attached to a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical Corporation.

  Specifically, the developing sleeve charge amount A can be obtained as follows.

  (1) Put two paper filters 35 on the suction nozzle of the suction machine 33 so as to overlap each other.

  (2) The weight ma (g) before suction of the suction nozzle is measured.

  (3) The electrophotographic toner 32 adhering to the surface of the developing sleeve 31 is sucked by a suction nozzle for one minute while being moved 20 cm in the longitudinal direction of the developing sleeve 31, and the charge amount q (μc) is obtained by a Q meter 34. .

  (4) The weight mb (g) of the suction nozzle to which the toner for electrophotography after suction is attached is measured.

(5) Then, the weight m (g) of the attracted electrophotographic toner is obtained from mb-ma, and the developing sleeve charge amount A can be obtained by the following equation.
A = q / m (μc / g)

(Ii) Image density Image density: The reflection density of the solid image portion was measured with a Macbeth reflection densitometer (RD-914).

(Iii) Fog Fog: The reflection density of the non-image area was measured with a Macbeth reflection densitometer (RD-914).

(Iv) Missing characters Missing characters: Thirty symbols “i” were printed on the A4 plate and visually checked for missing characters.

  Table 3 shows the result of the copy test.

  As is apparent from Table 3, the charge amount of the developing sleeve after copying 3000 sheets from the initial stage (hereinafter referred to as the end stage; the same applies to the table) is the same as or higher than that of the comparative example. Indicates.

  In particular, Example 1 showed an excellent developing sleeve charge amount stably in all environments.

  The image density was not significantly different between the example and the comparative example.

The fog appeared at the end of Comparative Example 3.
Missing characters appeared at the end of Comparative Examples 1 and 2.

That is, in Examples 1 to 6, in which the evaluation by this evaluation method was sufficient for both 50% hydrophobicity x and 50% to 10% hydrophobic uniformity d, the developing sleeve charge amount was kept high, and the image density There is no problem in terms of fogging and missing characters.
However, in Comparative Example 3 in which 50% to 10% hydrophobic uniformity d was 20 vol% or more, fogging occurred, and Comparative Examples 1 to 2 in which 50% hydrophobicity x was less than 30 vol% were characters. Omission has occurred and none of them are practical.
Therefore, the evaluation by this evaluation method is in good agreement with the actual toner characteristics.

FIG. 3 shows the relationship between the number of copies and the developing sleeve charge amount in the N / N copy test.
As is clear from FIG. 3, the developing sleeve charging amounts of Examples 1 to 6 were the same or higher for any number of copies compared to Comparative Examples 1 to 3.
It is known that the decrease in the charge amount of the developing sleeve is closely related to the occurrence of fog and missing characters.
Therefore, the evaluation by this evaluation method is considered to be in good agreement with the actual toner characteristics at any copy number.

It is a figure which shows the relationship between the floating toner and the methanol density | concentration by the evaluation method of the electrophotographic toner of this invention, Comprising: (a) is the evaluation result regarding the toner of Examples 1-4, (b) is Examples 5-6. (C) is the evaluation result regarding the toners of Comparative Examples 1 to 3. Schematic diagram of a measuring device for determining the charge amount of the developing sleeve The figure which shows the relationship between the number of copies in a N / N copy test, and developing sleeve charge amount

Explanation of symbols

31 Developing sleeve 32 Electrophotographic toner 33 Suction machine 34 Q meter 35 Filter

Claims (5)

Introducing the electrophotographic toner into a plurality of methanol aqueous solutions having different concentrations;
Measuring the ratio of the floating electrophotographic toner or the settling electrophotographic toner to the charged electrophotographic toner; and
Deriving the degree of hydrophobicity and hydrophobic uniformity of the electrophotographic toner from the transition of the ratio of the floating electrophotographic toner or the ratio of the sedimented electrophotographic toner accompanying the change in methanol concentration; ,
And evaluating the electrophotographic toner based on whether the degree of hydrophobicity and the hydrophobic uniformity are within a predetermined range, respectively. Charging the electrophotographic toner into water or an aqueous methanol solution;
Adding methanol to the water or aqueous methanol solution, and measuring the transition of the ratio of the electrophotographic toner floating or the ratio of the electrophotographic toner settling with the concentration change of methanol;
Deriving the degree of hydrophobicity and hydrophobic uniformity of the electrophotographic toner from the transition of the ratio of the floating electrophotographic toner or the ratio of the sedimented electrophotographic toner;
And evaluating the electrophotographic toner based on whether the degree of hydrophobicity and the hydrophobic uniformity are within a predetermined range, respectively. The hydrophobicity is 50% hydrophobicity, and the hydrophobic uniformity is 50% to 10% hydrophobic uniformity,
The step of evaluating the electrophotographic toner is characterized in that 50% hydrophobicity is 30 vol% or more and 50% to 10% hydrophobic uniformity is less than 20 vol% difference. The method for evaluating an electrophotographic toner according to claim 1. An electrophotographic toner, wherein the 50% hydrophobicity is 30 vol% or more, and the 50% to 10% hydrophobic uniformity is less than 20 vol%. 5. The toner for electrophotography according to claim 4, wherein a cyclic siloxane compound or linear silicone oil and hydrophobic silica are adhered to the surface of the toner base particles.

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