JPH0560975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a dry toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Prior art] Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Many methods are known, as described in Japanese Patent No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the The latent image is developed using toner, the toner image is transferred to a transfer material such as paper as required, and then fixed by heat, pressure, solvent vapor, etc. to obtain a transferred product.

The toner used for these is triboelectrically charged to a positive or negative charge depending on the polarity of the electrostatic latent image to be developed.

Toners used in these development methods include those obtained by kneading and pulverizing a mixture consisting of at least a binder resin and a colorant, and classifying if necessary, or toners or capsules obtained by polymerization methods. Examples include toner.

Here, methods for charging the developer include a charge injection method that makes the toner conductive and injects charge, a dielectric polarization method that uses dielectric polarization under an electric field, and a corona charger that applies a shower of charged ions to particles. There is a flow charging method, a friction charging method in which the toner is charged by rubbing the toner against an object at a position where the frictional charging series is different from that of the toner. Among these, in the charge injection method, since the toner becomes conductive, it is difficult to transfer a particle image from a latent image surface to a fixing object such as paper. Furthermore, dielectric polarization cannot produce a sufficiently large charge.

On the other hand, in the charging method using an ion charger, there are technical difficulties in uniformly exposing the toner to the ion flow, and the amount of charge cannot be adjusted with good reproducibility.

The triboelectric charging method is currently widely used because it can be adjusted to a sufficient amount of charge using insulating toner particles and is reproducible. However, since the frictional charge is proportional to the amount of frictional work, it is difficult to keep the amount of frictional work of toner particles constant in practical development. It has the disadvantage of being susceptible to

In addition, due to the gradual increase in toner agent that permanently adheres to the surface of each part of the carrier and developing device where toner is triboelectrically charged, resin components, wax components, etc. in the toner cause fluctuations in triboelectric characteristic values. There was a problem in that when a large number of copies were made, the quality of the copied images deteriorated.

As a solution to this problem, it has been proposed to add fine powdered silica to toner alone or together with other functional materials.
54-16219, JP-A-55-120041, JP-A-53-81127
etc. Also, the silica itself was published in Japanese Unexamined Patent Application Publication No. 1983-
Improvements have been made for the purpose of controlling hydrophobicity and chargeability, such as in JP-A No. 60754, JP-A No. 58-186751, and JP-A No. 59-200252.

However, the method of adding these
It is common to simply add or to mix at a circumferential speed of about several m/sec to 40 m/sec using a stirring blade in a mixer such as a Henschel mixer or Papenmeyer. As an example of these devices, the structure of a Henschel mixer is shown in FIG. In this device, colored particles and various additives such as silica are dispersed by rotating the blades attached to the rotating shaft in the center. Some of the additives are electrostatically attached to the surface of the colored particles, and some of the additives are It exists in a free state and contributes to the fluidity of the toner. However, in this method, there is a large difference in circumferential speed between the vicinity of the rotating shaft in the center and the tip of the stirring blade, and since there is no blade-shaped part in the rotating shaft, the stirring force and dispersion force are It is partially different, resulting in a non-uniform dispersion state. As a result, the state of adhesion of silica to the surface of the colored particles becomes uneven, and a toner with poorly dispersed silica adhering to it is produced, and such silica is easily liberated. Free silica is easily consumed by copying, and the amount of silica in the developing device decreases, causing a decrease in toner fluidity and image density, and aggregated free silica also causes an increase in fog.

Further, since a mixer having such a structure performs batch-type mixing, the dust concentration during mixing is high, and it usually takes a long time of several minutes to disperse the dust uniformly. Therefore, once dispersed particles tend to aggregate again, and friction between particles,
Also, heat is generated due to friction between the particles and the blade, which tends to cause fused substances. If such aggregates or fused materials are mixed into a toner as a final product, the quality of the toner will be degraded.

On the other hand, the idea of fixing powdered silica to the surface of colored particles has been around for a long time.One method is to add powdered silica together with a binder for colored particles, a coloring agent, a charge control agent, etc., melt and knead it, and then cool it. This method involves pulverizing, classifying if necessary, and converting into toner. However, when producing toner using this method, a large amount of silica must be added at the time of melting and kneading in order to ensure that silica exists on and near the surface of the toner to obtain a sufficient effect. ,
This not only involves considerable manufacturing difficulties, but also causes a decrease in fixing performance, which is particularly noticeable in heat-fixed toners. Further, in such a method, since there is little silica present on the toner surface, the above-mentioned problems in image quality can be improved, but it cannot be said to be sufficient. Regarding the addition of silica to toner, please refer to Japanese Patent Publication No. 44-18995, Japanese Patent Publication No. 55-81623, Japanese Patent Publication No.
56-1946 etc. are exemplified.

On the other hand, another method for dispersing silica onto the surface of colored particles is to add colored particles and silica powder.
There is a method of mixing, heating above the softening point, and fixing it to the surface.
125943 etc. However, since this method is carried out at high temperatures, there is a risk of fusion of particles and is not practical.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a method for manufacturing a toner that overcomes the above-mentioned toner defects. In particular, it is an object of the present invention to provide a method for efficiently producing dry toner of good quality.

That is, the present invention provides a method for producing a toner by mixing colored resin particles having at least a binder resin and a colorant, and an additive, in which the colored resin particles and the additive are mixed at an ambient temperature of 10 to 90°C. Below, there is an impact part having a minimum gap of 0.5 to 30 mm formed by a rotating piece and a fixed piece rotating at a tip circumferential speed of 30 to 130 m/sec, or at least two types of tip rotating pieces with a tip circumferential speed of 30 to 130 m/sec.
Formed from a rotating piece rotating at 130m/sec
Pass through the impact part with the shortest gap of 0.5-30mm,
The colored resin particles and additives are mixed, and the mixed powder of the mixed colored resin particles and additives is circulated to the impact part and mixed again, and the total mixing time in the impact part is within 60 seconds. The present invention relates to a method for manufacturing a dry toner characterized by mixing the toner as follows.

Further, in the insulating toner, it is important to adjust the amount of triboelectric charge to a constant value. In other words, one of the important characteristics of being able to obtain good images even under different environments, and also being able to obtain good images that are as good as the initial image even during continuous image production, is how to control the amount of triboelectric charge. be. In general, improving the rise of triboelectric charging tends to increase its absolute amount, and especially in low humidity environments, it becomes necessary to create a large electric field to transfer the excessively charged toner to the latent image surface. There is a risk of burden on the system and discharge due to insulation breakdown.

On the other hand, if the absolute charge is suppressed, it takes time to build up a sufficient charge, especially in a high-humidity environment, and it eliminates toner that adheres to areas other than the latent image area due to forces other than electrical forces. This may cause problems such as smearing the image.

In order to solve this problem, it is known to uniformly adhere an additive such as silica powder to the surface of colored resin particles (hereinafter referred to as "colored particles") to control triboelectric charging properties. At this time, the additive powder must be sufficiently loosened and adhered to the surface of the colored particles in a uniformly dispersed state, and it is desirable that the additive powder be adhered to all the colored particles in the same manner.

For this purpose, it is difficult to ensure reliable dispersion using a conventional batch-type device as shown in FIG. 4, because the dust concentration is high, and dispersion using only stirring blades has a weak impact, which led to the present invention.

[Means and effects for solving the problem] That is, the present invention aims to strongly and reliably disperse the impact caused by the rotating blade. Next, preferred manufacturing methods are described below, but are not limited thereto.

FIG. 1-1 is a first example of an apparatus specifically explaining the present invention, and FIG. 1-2 is a detailed view of the impact part. In Fig. 1-1, toner and various additives are inputted from a material input valve 1, and as the rotating shaft 3 is rotated by a motor, the dispersing blade 4 and the rotating piece 5 are rotated. The material is carried by the generated airflow to the center of the device from the inlet chamber 2, passes through the impact section 10, passes through the return path 12 from the outlet chamber 11, and is carried to the center of the device again, where it circulates within the device. . When the mixing is completed, the product passes from the outlet chamber 11 through the return path 12 and is recovered from the product take-out valve 13.

At this time, the colored particles and various additives that have aggregated due to their fine particle sizes are mixed while being uniformly dispersed by the high speed rotation of the dispersion blade 4 and the rotating piece 5.

By passing through the impact part 10 with a narrow clearance many times, the dispersion force at the impact part is strong, so that it is reliably dispersed. The mixing time is preferably within 60 seconds, more preferably within 30 seconds. If the time is longer than 60 seconds, the additive will stick to the surface of the colored particles due to the impact, reducing its effectiveness as an additive and causing deterioration in charging properties. In addition, the gap a between the liners of the rotating pieces 5 and 9 in FIGS. 1-2 is 0.5
mm to 30 mm is preferred. This is because if a is smaller than 0.5 mm, heat will be generated due to the impact with the powder, causing the generation of fused materials, and if it exceeds 30 mm, the shearing force will weaken and it will be difficult to sufficiently disperse the additive.

Here, the circumferential speed of the tip of the rotating piece is preferably 30 to 130 m/sec. When mixing at a circumferential speed lower than 30 m/sec, the dispersion force becomes weaker and the dispersion becomes insufficient. Furthermore, if the mixing speed exceeds 130 m/sec, the colored particles will be crushed.

The ambient temperature when mixing is performed in this device is 10
The temperature is preferably adjusted to 90°C, more preferably 10 to 70°C; if it exceeds 90°C, fused materials are likely to occur. Therefore, the temperature may be adjusted by flowing cooling water or the like into the jacket portion 15.

Next, Fig. 2-1 shows a second example of the device of the present invention to be specifically explained, Fig. 2-2 is a perspective view of the mixing section, and Fig. 2-3 shows details of the mixing section. It is a diagram.

In FIG. 2-1, colored particles and various additives are introduced through the material input port 16, and the rotating shaft 20 is rotated at high speed by a motor.
When the rotor 21 rotates, the airflow generated by the rotation passes through the return path 17, is carried to the center of the device through the inlet 19, passes through the mixing section, and is assisted by the airflow generated by the blower blades 23 through the return path 24. 17, the material is transported back to the mixing section through the inlet 19 and circulates within the device. When the mixing is completed, the mixed product passes through the return path 17 from the outlet 24 and is recovered from the product outlet 18.

At this time, the colored particles and the various additives that have aggregated due to their fine particle sizes are mixed while being uniformly dispersed by the high speed rotation of the rotor 21.

Good dispersion is achieved by reliably passing through the impact area with narrow clearance many times. The mixing time is preferably within 60 seconds, more preferably within 30 seconds. If the time is longer than 60 seconds, the additive will stick to the toner surface due to the impact, reducing its effectiveness as an additive and causing deterioration in charging properties. Moreover, the gap 29 between the outer tangent line 28 of the rotor 21 and the inner tangent line 27 of the liner 22 in FIGS. 2-3 is preferably 0.5 mm to 30 mm. This is the same as the device shown in Figure 1, with the gap 2
If 9 is narrower than 0.5mm, it may generate heat due to impact with powder and cause fused materials, and if it exceeds 30mm,
The shear force weakens and sufficient dispersion of the additive becomes impossible. The circumferential speed of the rotating piece is preferably 30 to 130 m/sec.
When mixing at a circumferential speed lower than 30 m/sec, the dispersion force becomes weaker and the dispersion becomes insufficient. Also, 130
If mixing exceeds m/sec, the colored particles will be crushed. The ambient temperature during mixing with this device is preferably 10 to 90°C, more preferably 10°C to 90°C.
It is better to adjust the temperature so that it is ~70℃, 90℃
If the temperature exceeds ℃, fused substances are likely to occur. Therefore, the temperature may be adjusted by flowing cooling water or the like into the jacket portion 26.

On the other hand, in order to mix more effectively with the device used in the present invention, the colored particles and various additives are lightly stirred in advance before being mixed in the device, and the macroscopically dispersed additives are mixed into the colored particles. It is effective to attach it to the surface. This helps the mixing in this device and allows higher quality toner to be obtained. As such a pre-mixer, for example, a device of the type shown in FIG. 3 (Nauta mixer: manufactured by Hosokawa Micron Co., Ltd.) is used.
can be exemplified.

[Example] Examples using the present invention will be specifically described below.

Example 1 Styrene-acrylic acid ester system 100 parts by weight Resin (weight average molecular weight approximately 300,000) Magnetite (BET value 8 m ² /g) 60 parts by weight Low molecular weight polyethylene 2 parts by weight Negative charge control agent 2 parts by weight Above formulation Toner raw material consisting of a mixture of approximately
After melting and kneading at 180°C for about 1.0 hour, it was cooled and solidified, coarsely pulverized with a hammer mill, and then processed with a supersonic jet mill manufactured by Nippon Neumatics Industries Co., Ltd. to a weight average particle size of 10.5 μm (containing 9.3% by weight of particles with a particle size of 5.04 μm or less). A crushed product was obtained. The obtained pulverized product was classified using a DS classifier manufactured by Nihon Neumatic Kogyo, and the weight average particle size was determined as a powder from which fine powder was removed.
11.5μm (0.3% by weight of particles with an average particle size of 5.04μm or less)
Colored particles containing (containing) were obtained. Obtained colored particles
100 parts by weight and 0.3 parts by weight of fine silica powder were charged into the Nauta mixer shown in FIG. 3 and premixed. When the obtained premix was observed under an electron microscope, it was found that the fine silica powder was macroscopically dispersed in an aggregated state.

Next, the obtained premixed product was introduced into a mixing and dispersing apparatus shown in FIG. 1-1 to perform mixing and dispersion.

The mixing conditions are: peripheral speed of the tip of the rotating piece 50 m/sec,
The mixing time was 10 seconds and the ambient temperature was 30°C.

When the product thus obtained was observed under an electron microscope, it was confirmed that most of the silica was dispersed down to the primary particles and was uniformly adhered to the surface of the colored particles. Furthermore, no aggregates of free silica were found.

Next, the obtained product is transferred to a Canon copier.
When I put it in the developing device of NP270RE and developed it,
A good image with an image density of 1.28 was obtained. In addition, there was little fog, and no increase in fog was observed even when the film was left at an ambient temperature of 35°C and high humidity of 90% for a long period of time.

Example 2 The colored particles and silica fine powder obtained by the method shown in Example 1 were premixed in the same manner as in Example 1, and
Mixing was carried out using the apparatus shown in Figure 2-1.

The mixing conditions are: gap 29 is 2 mm, rotor peripheral speed is 40
m/sec, mixing time 20 seconds, and ambient temperature 30°C.
When the thus obtained product was evaluated in the same manner as in Example 1, similar effects were obtained.

Comparative Example 1 A classified product obtained in the same manner as in Example 1 was introduced into a Henschel mixer shown in FIG. 4, and mixed with silica. Circumferential speed 30m/sec, processing time 3 minutes, processing temperature 25
Mixing was performed at °C to obtain a product.

When the obtained toner was observed under an electron microscope, it was found that the silica was attached to the toner surface in an unraveled state, and aggregates of free silica were also observed.

The obtained toner is transferred to a Canon copier NP270RE.
When the toner was put into a developing device and developed, reverse fog was noticeable compared to the toner obtained in Example 1.
When the film was left at an ambient temperature of 35°C and high humidity of 90%, fogging increased further.

[Effects of the Invention] As described above, according to the method of the present invention, the colored particles and additives are reliably mixed by the impact of the rotating piece and by passing through a small gap and repeating this process many times. Because the additives adhere to the surface of the colored particles in a uniform and well-dispersed state, the triboelectric properties of the toner are stable, and toner quality does not deteriorate under fluctuating environmental conditions or when copying a large number of sheets. .

In addition, in the method of the present invention, since additives such as silica are dispersed close to the primary particles and attached to the surface of the colored particles, once attached, it is difficult to release them, and the resulting toner can be left for a long time. It also has the advantage of being less prone to deterioration over time.

[Brief explanation of the drawing]

Figure 1-1 is an example of an apparatus for mixing additives with colored particles, and Figure 1-2 is a detailed view of the impact section of the apparatus. FIG. 2-1 is a diagram schematically showing another example for mixing additives into colored particles, and FIG. 2-2 is a perspective view of an impact part,
Figures 2-3 are detailed views of the impact section. Figure 3 shows
FIG. 2 is a diagram schematically showing an example of a stirring device for pre-dispersing colored particles and additives. FIG. 4 is a schematic diagram showing an example of a device conventionally used for mixing additives with colored particles. DESCRIPTION OF SYMBOLS 1... Material input valve, 2... Inlet chamber, 3... Rotating shaft, 4... Dispersion blade, 5... Rotating piece (blade),
6... Partition disk, 7... Casing, 8... Rotor, 9... Liner, 10... Impact part, 11...
Outlet chamber, 12... Return path, 13... Product take-out valve, 14... Blower, 15... Jacket, 1
6...Material input port, 17...Return path, 18...
...Product outlet, 19...Inlet, 20...Rotary shaft,
21...Rotor (with plate), 22...Liner, 23...Blower blade, 24...Outlet, 25...
Casing, 26... Jacket, 27... Inscribed line of liner, 28... External tangent line of rotor, 29...
... Gap, 30... Stirring bar, 31... Stirring rod revolution drive motor, 32... Powder stirring tank, 33... Discharge port, 34... Stirring bar rotation drive motor, 35...
Jacket, 36... Stirring bar, 37... Motor, 38... Lid, 39... Base, 40... Control board, 41... Cylinder, 42... Lid lock, 43... Cylinder, 44... Direction Control unit, 45... Discharge port, a... Gap between rotating piece and liner.

Claims (1)

[Claims] 1. In a method for producing a toner by mixing colored resin particles having at least a binder resin and a colorant, and additives, the colored resin particles and additives are mixed at an ambient temperature of 10 to 90°C. Under conditions, tip peripheral speed 30~130
An impact part with a minimum gap of 0.5 to 30 mm formed by a rotating piece and a fixed piece rotating at m/sec, or at least two types of tip peripheral speeds of 30 to 130 m/sec
0.5~30mm formed from a rotating piece rotating in
The colored resin particles and the additive are mixed together, the mixed powder of the mixed colored resin particles and the additive is circulated through the impact area and mixed again, and the impact area is passed through an impact area having a minimum gap of The total mixing time in
A method for producing dry toner, characterized by mixing within 60 seconds. 2. The method for producing a dry toner according to claim 1, wherein the colored resin particles and additives are premixed in advance.