JPH03206466A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain the toner for developing electrostatic charge images having good performance by introducing secondary air and executing pulverization by using an impingement type pneumatic pulverizer which is provided with a supplying port for materials to be pulverized in an acceleration pipe and has a secondary introducing port between the supplying port for the materials to be pulverized and the outlet of the acceleration pipe. CONSTITUTION:The impingement type pneumatic pulverizer has the accelerating pipe 32 for transporting and accelerating powder by a high-pressure gas and a pulverizing chamber 35 and an impingement member 36 for pulverizing the powder ejected from the accelerating pipe 32 by impingement force. The impingement member 36 is provided in the pulverizing chamber 35 so as to face the outlet 34 of the accelerating pipe. The supplying port 31 for the materials to be pulverized is provided in the accelerating pipe 32 and the secondary air is introduced between the supplying port 31 for the materials to be pulverized and the outlet 34 of the accelerating pipe from the secondary air introducing port 41 to execute the pulverization. The excellent toner for developing electrostatic charge images which is stable and high in image density, has good durability, and is free from image defects, such as fogging and cleaning defects, is obtd. at the low cost in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a manufacturing method for obtaining a toner for developing electrostatic images by pulverizing solid particles having a binder resin.

[Prior Art] In image forming methods such as electrophotography, electrostatic photography, and electrostatic printing, toner is used to develop electrostatic images.

The general manufacturing method for electrostatic image developing toner, which requires the final product to be fine particles, includes a binder resin to fix it on the transfer material, and various colorants to give the toner its color. , a charge control agent for imparting charge to particles, and JP-A-54-42141, JP-A-55
In the so-called one-component development method as shown in Japanese Patent No. 18656, various magnetic materials are used to impart transportability to the toner itself, and a release agent and a fluidity imparting agent are added as needed in a dry process. After mixing, the mixture is melted and kneaded using general-purpose mixing equipment such as a roll mill or extruder, cooled and solidified, and then pulverized using various types of pulverizing equipment such as jet air flow type pulverizers and mechanical impact type pulverizers. By classifying the toner, the particle size can be adjusted to the size required for the toner. If necessary, a fluidizing agent, a lubricant, etc. are dry-mixed into the toner. When used in a so-called two-component development method, the toner is mixed with various magnetic carriers and then used for image formation.

Furthermore, with the recent widespread use and mass consumption of copies, printed matter, etc., there is a demand for low-cost, high-performance developers.

As mentioned above, various types of pulverizers are used to obtain toner particles, which are fine particles. However, for pulverizing toner mainly containing binder resin, jet airflow type pulverizers that use jet airflow, especially collision A pneumatic crusher is preferably used.

Furthermore, these pulverizers are connected to a classifier, as shown in the flow shown in Figure 6, and the pulverized particles are classified into fine particles and coarse particles by the classifier, and the coarse particles are sent back to the pulverizer. It is used as a pulverization means to perform back-pulverization to obtain fine particles as a pulverized product.

Conventionally, the classifier used as this crushing means is:
There are rotor type classifiers that classify by forcibly creating a swirling airflow by rotating classification blades, and spiral airflow classifiers that classify by creating a swirling airflow using airflow introduced from the outside. For classification, a spiral air classifier with no moving parts in the powder contacting part is preferably used.

As a typical example, a dispersion separator (DS-UR type manufactured by Nippon Pneumatic Kogyo Co., Ltd.) as shown in FIG. 7 is generally used.

However, the powder material supply section to the classification chamber of this type of air classifier as shown in FIG. A supply cylinder 80 is connected to the upper outer peripheral surface of the guide cylinder 50. The supply cylinder 80 is connected to the outer periphery of the guide cylinder 50 so that the powder material supplied via the supply cylinder 80 is introduced into the guide cylinder in a circumferential tangential direction. When the powder material is supplied into the guide cylinder 50 from the supply cylinder 80,
The powder material descends while rotating along the circumferential surface of the guide tube 50. In this case, the powder material descends in a band shape from the supply tube 80 along the inner peripheral surface of the guide tube 50, so the distribution and concentration of the powder material flowing into the classification chamber 40 becomes uneven (the powder material flows into the classification chamber along the inner circumference of the guide tube 50). Powder material flows only from part of the surface),
Poor dispersion. Further, if the throughput is large, the powder material is more likely to aggregate, and furthermore, the dispersion is not sufficiently performed, resulting in a problem that highly accurate classification cannot be performed.

Therefore, the finely pulverized product becomes a powder with a wide particle size distribution, and as a result, there is a problem in that it causes a phenomenon such as a decrease in yield in the classification step to remove the fine powder in the next step. In addition, a part of the powder that has been crushed to a particle size smaller than the desired size is recycled to the crusher as coarse powder, so that ultrafine powder (powder that is too fine to be suitable as a toner) is likely to be generated.

This ultra-fine powder has a strong attraction to the particles, so it is difficult to remove even with a classification process that removes the fine powder. When such powder is used as a toner, it may cause a decrease in image density, fogging, and even development. This causes unevenness on the sleeve, etc., which deteriorates image quality.

On the other hand, a collision-type air-flow pulverizer using a jet stream conveys the object to be crushed by a jet stream, collides the object with a collision member, and crushes it by the impact force, which is different from the conventional collision-type air-flow crusher. The machine has a configuration as shown in Fig. 8.

Outlet 4 of acceleration tube 42 connected to high pressure gas supply nozzle 33
A collision member 46 is provided opposite to the acceleration tube 42, and by the flow of the high-pressure gas supplied to the acceleration tube 42, the object to be crushed is transported into the inside of the acceleration tube 42 from the object supply port 3l communicated with the middle of the acceleration tube 42. This is sucked and injected together with high-pressure gas to collide with the collision surface 47 of the collision member, and the impact causes it to be pulverized.

However, in the above-mentioned conventional example, it is difficult to sufficiently disperse the material to be pulverized that is suctioned into the acceleration tube in the high-pressure airflow, and the particle mixture air stream in which the material to be pulverized is placed on the high-pressure airflow ejected from the outlet of the acceleration tube. The material to be crushed is separated into a stream with a high concentration of the material to be crushed and a stream with a low concentration, so that the material to be crushed is
The collision will be partially concentrated on the opposing collision member, and reagglomeration is likely to occur on the collision member, leading to a deterioration in the classification accuracy of the classifier, as well as a decrease in crushing efficiency and processing capacity. It's causing it.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a toner for developing an electrostatic image, which solves the above-mentioned drawbacks.

Specifically, an object of the present invention is to provide a method for producing a toner for developing electrostatic images having good performance by obtaining a finely pulverized product with a precise particle size distribution.

A further object of the present invention is to provide a manufacturing method for efficiently manufacturing toner for developing electrostatic images having a smaller particle size.

[Means and effects for solving the problems] The method for producing toner for developing electrostatic images of the present invention includes a classification plate having an inclined shape with a high central part at the bottom of a classification chamber, and conveying air in the classification chamber. A fine powder discharge chute connects the fine powder to a discharge port provided in the center of the classification plate. In addition to discharging
This is an airflow classifier that discharges coarse powder from a discharge port formed on the outer periphery of a classification plate, and an annular guide chamber that communicates with the powder supply tube is provided at the top of the classification chamber, and the guide chamber and the classification chamber are connected to each other. An air classifier having a plurality of louvers whose tips are oriented tangentially to the inner circumferential direction of the guide chamber between them, an acceleration tube for accelerating the conveyance of powder using high-pressure gas, a crushing chamber, and the acceleration A collision type air flow crusher is equipped with a collision member for crushing powder ejected from a tube by a collision force, and the collision member is provided in a crushing chamber facing an outlet of the acceleration tube. Grinding is carried out by introducing secondary air using a crushing means consisting of a collision type airflow crusher, which has a material supply port and a secondary air inlet between the material supply port and the acceleration tube outlet. Features.

FIG. 6 is an example of a flowchart showing the configuration of the crushing means used in the method for producing toner for developing electrostatic images of the present invention, and FIG. 1 and FIG. FIG. 3 is a diagram schematically showing an embodiment of the machine, and FIGS. 3 to 5 are diagrams schematically showing an embodiment of the impingement type air flow crusher.

In Fig. 1, 1 indicates a cylindrical main body casing, 2
indicates a lower casing, to which a hopper 3 for discharging coarse powder is connected. The inside of the main body casing 1 is
A classification chamber 4 is formed, and the upper part of the classification chamber 4 is closed by an annular guide chamber 5 attached to the upper part of the main casing 1 and a conical (umbrella-shaped) upper cover 6 whose central part is raised. .

A plurality of loopers 7 arranged in the circumferential direction are provided on the partition wall between the classification chamber 4 and the guide chamber 5, and the powder material and air sent into the guide chamber 5 are swirled into the classification chamber 4 from between each looper 7. Let it flow.

Classifying loopers 9 arranged in the circumferential direction are provided in the lower part of the main body casing 1, and classified air that causes a swirling flow is introduced into the classifying chamber 4 from the outside through the classifying loopers 9.

At the bottom of the classification chamber 4, a conical (umbrella-shaped) classification plate 1O with a high central portion is provided, and a coarse powder discharge port 11 is formed around the outer periphery of the classification plate 1O. Further, a fine powder discharge chute 12 is connected to the center of the classification plate 1O, and the lower end of the chute 12 is bent into an L-shape, and this bent end is located outside the side wall of the lower casing 2.

Further, the chute is connected to a suction fan via a fine powder collection means such as a cyclone or a dust collector, and the suction fan applies suction force to the classification chamber 4, and the suction flows into the classification chamber 4 from between the loopers 9. The air creates the swirling flow required for classification.

The air classifier has the above-mentioned structure. When the air containing the powder material is supplied, the air containing the powder material passes from the guide chamber 5 between the loopers 7 and flows into the classification chamber 4 while being dispersed at a uniform concentration while swirling.

The powder material flowing into the classification chamber 4 is swirled by the suction fan connected to the fine powder discharge chute 12, and the swirling of the powder material is increased by the suction air flow flowing from between the classification loopers 9 at the bottom of the classification chamber. The coarse powder is centrifuged into coarse powder and fine powder by the centrifugal force acting on the classification chamber 4, and the coarse powder swirling around the outer periphery of the classification chamber 4 is discharged from the coarse powder discharge port 11 and transferred to the lower hopper 3.
The waste is discharged from the airflow crusher and fed again to the impingement type air flow crusher.

Further, the fine powder moving toward the center along the upper inclined surface of the classification plate IO is discharged as a finely pulverized product to the fine powder collecting means by the fine powder discharge chute 12.

All the air that flows into the classification chamber 4 together with the powder material flows in the form of a swirling flow, so the velocity toward the center of the particles swirling within the classification chamber 4 is relatively small compared to the centrifugal force.
In the classification chamber 4, classification into small separated particles is performed, and fine powder with a very small particle size can be discharged to the fine powder discharge chute 12. Furthermore, since the powder material flows into the classification chamber at a substantially uniform concentration, it is possible to obtain powder with a fine distribution.

Therefore, since it can be obtained as a finely pulverized product as a powder with a fine distribution, as described above, ultrafine powder is not generated, and as a result, a toner having good performance when made into a final product can be obtained.

Further, in FIG. 3, the powder material 45 to be crushed is supplied to the acceleration tube 32 from the object supply port 3l provided in the acceleration tube 32. A compressed gas such as compressed air is introduced into the acceleration tube 32 from a compressed gas supply nozzle 33, and the material to be crushed 45 supplied to the acceleration tube 32 is instantly accelerated to have a high velocity. . Further, by introducing secondary air from the secondary air introduction port 4l provided between the material to be crushed supply port 3l of the acceleration tube 32 and the acceleration tube outlet 34, the material to be crushed in the acceleration tube is dispersed. Accelerator tube outlet 34
By ejecting the material to be crushed more uniformly and causing it to collide efficiently with the collision surface 37 of the opposing collision member 36, the crushability can be improved compared to the conventional method. The secondary air introduced here contributes to loosening and dispersing the agglomeration of the material to be crushed, which is moving at high speed within the acceleration tube. Further, it has the effect of accelerating the flow along the inner wall of the acceleration tube, which is a portion where the acceleration gas flow velocity distribution is slow within the acceleration tube.

As shown in FIG. 3, the collision member 36 has a conical shape at the tip of the collision surface, which is caused by heat generation at the extreme part of the collision member, like a material containing thermoplastic resin. It is preferable for materials that are easily fused to prevent fusion. Furthermore, in order to promote secondary collision from the collision member to the crushing chamber wall and improve the crushing efficiency, the tip part has an apex angle of 110° or more.
Collision members having a conical shape of less than 80° are more preferred.

As explained above, because the material to be crushed inside the accelerator tube is well dispersed, there is no possibility of powder particles agglomerating and over-grinding, which is the case with conventional methods, and a crushed product with a fine particle size distribution can be obtained. It will be done.

Therefore, in combination with the effect of the air classifier described above, it is possible to efficiently obtain toner having good performance as a final product. Furthermore, the effect of the method of the present invention becomes more pronounced as the particle size becomes smaller.

[Example] Hereinafter, the present invention will be explained in detail based on examples.

Example 1 A toner raw material consisting of a mixture of the above formulation was melt mixed using a twin-screw extruder PCM-30 (manufactured by Ikegai Tekko Co., Ltd.). After cooling, a coarsely ground product of 0.1 to 1 mm was obtained using a hammer mill.

The obtained coarsely pulverized material is divided into the air classifier shown in Fig. 1 and the collision type air pulverizer shown in Fig. 3 (the collision surface of the collision member has an apex angle of 1
4. The compressed gas is supplied to the impingement type airflow crusher from the compressed gas supply nozzle. 0Nm”/min (
5kgf/cm”), the secondary air is F in Fig. 5,
0.0 each from 6 locations: G, H, J, L, M. 05Nm”/
Compressed air of min (5.5 kgf/cm") was introduced to perform fine pulverization so that the volume average particle size of the finely pulverized product was 11 pm (measured using a Coulter counter, the same applies hereinafter).

The particle size distribution of the finely pulverized product at this time is a volume average particle size of 11
．． ogm, 6.35pm or less volume frequency 12.1%,
The volume frequency of 20.2#La+ or more was 0.6%.

Fine powder is removed from this finely pulverized product using an elbow jet classifier (manufactured by Nippon Steel Mining Co., Ltd.), resulting in a volume average particle size of 11.6)
m, 6.35H or less volume frequency 2.3%, 20.2μ
A classified product with a volume frequency of 0.9% or more was obtained in a yield of 83%. Adding 0.4% by weight of silica to this classified product,
This was used as a toner sample.

Comparative Example 1 The coarsely pulverized material used in Example 1 was separated using a conventional air classifier DS-UR model (manufactured by Nippon Pneumatic Kogyo Co., Ltd.) as shown in FIG. 7 and a conventional air classifier as shown in FIG. A crushing means consisting of a jet mill PJM-I type (the collision surface of the collision member is a plane perpendicular to the axial direction of the accelerator tube) pressurizes at 4Nm"/win (5kgf/cm"). Fine pulverization was performed using air to give a volume average particle size of 11 pm.

At this time, the amount of finely pulverized product (=the amount of coarsely pulverized material supplied) was about 0.6 times that of Example 1, and the particle size distribution of the finely pulverized product was 11. 1 dom, 6.35 #Lm or less volume frequency 15.3%, 20.2μm or more volume frequency 1.3%
Met.

Fine powder was removed from this finely pulverized product using an elbow jet classifier, and the volume average diameter was 11.6 Pm, the volume frequency of 6.35 pm or less was 2.7%, and the volume frequency of 20.2 μm or more was 1.
A 6% fractionated product was obtained with a yield of 74%. To this classified product, 0.4% by weight of silica was externally added and mixed to prepare a toner sample.

Both toner samples of Example 1 and Comparative Example 1 were transferred to a copying machine NP.
A copying test was conducted using -5040 (manufactured by Canon). As a result of an endurance test of 10,000 sheets of each in a normal environment of 23° C. and 65% RH, the initial image density of the toner of Example 1 was 1.32, and the image density during durability was 1.37±0.03.
The image density was almost uniform, and the decrease in density due to toner replenishment was within 0.05, which had almost no effect on the image. Furthermore, no cleaning defects or filming occurred during the durability test.

On the other hand, the toner of Comparative Example 1 had an initial image density of 1. 10
However, as the durability progressed, the image density rose to a level of 1.35 ± 0.07, but when replenishing toner, the image density dropped to 1.05 again, and it took quite a while before the image density returned to a sufficient level. required the number of sheets. Furthermore, about 30
A cleaning failure occurred around ,000 sheets. When a similar durability test was conducted in a low humidity environment of 15° C. and 10% RH, the toner of Comparative Example 1 caused wavy unevenness on the developing sleeve, and white spots occurred in the all-black image.

A toner raw material consisting of a mixture of the above formulation was coarsely pulverized in the same manner as in Example 1.

Furthermore, fine pulverization was performed using the same pulverization means as in Example 1. 4. From the compressed gas supply nozzle to the collision type air flow crusher.
6m”/win (6kgf/cm”), secondary air is
0.0% each from the 6 locations F, G, H, J, L, and M in Figure 5. 05Nm”/win (5.5kgf/cm”
) was introduced to perform pulverization to obtain a pulverized product with a volume average particle size of 7 μm. The particle size distribution of this finely pulverized product has a volume average particle size of 7. Jo+, 5.04
The volume frequency was 20.0% for pm or less, and 0.4% for 12.7 μm or more. This finely pulverized product was classified using an elbow jet classifier, with a yield of 79%, a volume average particle size of 7.6 #Lm, a volume frequency of 7.5% below 5.04 μm,
A classified product with a volume frequency of 1.0% was obtained.

To this classified product, 0.6% by weight of silica was externally added and mixed to prepare a toner sample.

Comparative Example 2 The coarsely pulverized material used in Example 2 was pulverized using the same conventional pulverizing means as in Comparative Example 1. Collision type air flow crusher 4. 6
Pressurized air of m''/win (6 kgf/cm2) was supplied to perform fine pulverization so that the volume average particle size of the finely pulverized product was 7#II1.

At this time, the amount of finely pulverized material (=the amount of coarsely pulverized material supplied) was approximately 0.55 times that of Example 2, and the particle size distribution of the obtained pulverized product was as follows: volume average particle diameter of 6.9 μm, 5. 04μm or less volume frequency 30.3%, 12.7pm or more volume frequency 4
．． It was 7%.

This finely pulverized product is classified using an elbow jet classifier to obtain classified products with a volume average particle diameter of 7.6 pm, a volume frequency of 7.7% for particles of 5.04 m or less, and a volume frequency of 1.2% for particles of 12.7 H or more. Obtained with a yield of 61%. To this classified product, 0.6% by weight of silica was externally added and mixed to prepare a toner sample.

Each toner sample of Example 2 and Comparative Example 2 was transferred to a copying machine NP-
A copying test was conducted using 4835 (manufactured by Canon). When the durability was up to 50,000 sheets under normal environment,
The toner of Example 2 maintained an image density within a range of ±0.05 from the initial density of 1.38 without any decrease in density during replenishment, and no phenomenon of poor cleaning or image staining occurred. The toner of Comparative Example 2 had an initial density of 1.20, and the image density increased with durability to 1.35±0.
07, but when replenishing toner, it dropped again to 1.15. In addition, a cleaning failure occurred after 30,000 sheets were printed.

Example 3 The coarsely crushed material used in Example 2 was pulverized using the same pulverizing means as in Example 1.

4.6 m from the compressed gas supply nozzle to the collision type air flow crusher
/win (6kgf/cm”), secondary air is 0.0% each from 6 locations F, G, H, J, L, and M in Figure 5.
Introducing compressed air at a rate of 5 Nm"/min (5.5 kgf/cm") to produce a finely pulverized product with a volume average particle size of 6 pm.
It was finely pulverized so that The particle size distribution of this finely pulverized product is as follows: volume average particle size: 5.9H; Volume frequency below OOpm was 15.2%, and volume frequency above 10.08 1Lm was 1.5%. This finely pulverized product was classified using an elbow jet classifier, with a yield of 75% and a volume average particle size of 6.
5pm, 4.00pm or less volume frequency 5.3%, 1
A classified product with a volume frequency of 1.6% over 0.08 1Lrn was obtained. To this classified product, 1.2% by weight of silica was externally added and mixed to prepare a toner sample.

Comparative Example 3 The coarsely pulverized material used in Example 2 was pulverized using the same conventional pulverizing means as in Comparative Example 1. Collision type air flow crusher 4. 6m
Pressurized air of "/win (6 kgf/cm") was supplied to perform pulverization so that the volume average particle size of the pulverized product was 6 pm.

The amount of finely pulverized material (=the amount of coarsely pulverized material supplied) at this time was about 0.5 times that of Example 3, and the particle size distribution of the obtained pulverized product was as follows: volume average particle diameter of 6.2 pm, 4. The volume frequency below OOpm was 15.8%, and the volume frequency above 10.08 gm was 3.3%.

This finely pulverized product was classified using an elbow jet classifier to obtain a volume average particle size of 6.7 pm.4. OOpm or less volume frequency 5.6%, 10.081zm or more volume frequency 2.
A 4% classified product was obtained with a yield of 65%. To this classified product, 1.2% by weight of silica was externally added and mixed to prepare a toner sample.

Each toner sample of Example 3 and Comparative Example 3 was transferred to a copying machine N.
A copying test was conducted using P-4835 (manufactured by Canon). When the toner of Example 3 was subjected to durability up to 50,000 sheets in a normal environment, there was no decrease in density during replenishment, and the image density was maintained within the range of ±0.05 from the initial density of 1.25. While the phenomenon of image staining did not occur, the initial density of the toner of Comparative Example 3 was 1.05, and the image density increased with durability to 1.20±.
0.07, but when replenishing toner the l. It has dropped to 05. Further, cleaning failure occurred after 20,000 sheets were printed.

Furthermore, in a low humidity environment, the toner of Comparative Example 3 was
The fogging was poor compared to that of the previous model. [Effects of the Invention] As explained above, by using the toner manufacturing method of the present invention, the image density is stably high compared to the conventional method.
An excellent toner for developing electrostatic images that has good durability and is free from image defects such as fog and poor cleaning can be obtained at a low cost. Further, there is an advantage that an electrostatic image developing toner having a smaller particle size can be effectively obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of one embodiment of the air classifier used in the manufacturing method of the present invention, and FIG. 2 is a schematic sectional view taken along the line AA' in FIG.
FIG. FIG. 3 is a schematic cross-sectional view of one embodiment of the collision type air flow crusher used in the manufacturing method of the present invention, and FIGS. 4 and 5 are B-B'c-c' in FIG. 3, respectively. FIG. FIG. 6 is a flowchart showing the configuration of the crushing means used in the manufacturing method of the present invention. FIG. 7 and FIG. 8 are schematic diagrams of a conventional air classifier and an impingement type air current crusher, respectively. 4... Classification room 5... Information room 8...
Supply cylinder 7... Looper 9... Classifying looper lO... Classifying plate 3l... Material to be crushed supply port 32... Accelerator tube 33... Compressed gas supply nozzle 34... Accelerator tube outlet 35 ...Crushing chamber
36... Collision member 37... Collision surface of collision member 39... Discharge port 4l... Secondary air supply port

Claims (2)

[Claims] (1) A composition containing at least a binder resin and a colorant is melt-kneaded, the kneaded material is cooled and solidified, and the solidified material is pulverized by a pulverizing means having an air classifier and an impact type air pulverizer to obtain a toner. In the manufacturing method, the air classifier has an inclined classification plate with a high central part at the bottom of the classification chamber, and the powder material supplied together with conveying air flows into the classification chamber through a classification louver. It is centrifuged into fine powder and coarse powder by swirling with air current, and the fine powder is discharged to the fine powder discharge chute connected to the discharge port provided in the center of the classification plate, and the coarse powder is formed on the outer periphery of the classification plate. This is an airflow classifier that discharges the air from a discharge port, and an annular guide chamber is provided at the top of the classification chamber that communicates with the powder supply tube, and between the guide chamber and the classification chamber there is a This is an airflow classifier equipped with a plurality of louvers whose tips are oriented in the tangential direction of and a collision member for pulverizing powder ejected by collision force,
In a collision-type air flow crusher in which the collision member is provided in a crushing chamber facing an accelerating tube outlet, a to-be-pulverized material supply port is provided in the accelerating tube, and secondary air is provided between the to-be-pulverized material supply port and the accelerating tube outlet. A method for producing toner for developing an electrostatic image, comprising using an impact-type airflow pulverizer having an inlet, and performing pulverization by introducing secondary air. (2) Claim (1) characterized in that the crushing means is a collision type air flow crusher in which the tip of the collision surface of the collision member has a conical shape with an apex angle of 110° or more and less than 180°. ) The method for producing a toner for developing electrostatic images.