JP2911520B2 - Particle generating apparatus and particle generating method - Google Patents

Description

The present invention relates to an apparatus and a method for producing ultrafine particles of an organic photoconductor used in the production of an electrophotographic photoreceptor. The present invention relates to an apparatus and method for producing ultrafine particles by a medium evaporation method and recovering the same. The gas evaporation method is to heat, evaporate, and heat various substances in an inert gas atmosphere introduced into a vacuum vessel.
This is a method in which sublimation is performed, and the obtained vapor molecules are gradually cooled while colliding with inert gas molecules, whereby the molecules are aggregated to form ultrafine particles, and the ultrafine particles are collected.

[Conventional technology]

An electrophotographic photosensitive member has a basic structure in which a photosensitive layer is formed on a conductive substrate. As a photoconductive material for forming the photosensitive layer, one using selenium has conventionally been generally used, and cadmium sulfide, zinc oxide and the like are also known as other inorganic photoconductive materials.

However, in recent years, attempts have been made to improve the film forming property by using an organic photoconductive substance, and to increase the productivity by producing by coating. When an organic conductive material is used, there is an advantage that the color sensitivity can be freely controlled by selecting a sensitizer such as a dye or a pigment to be used. Organic photoconductive materials include poly-N-vinylcarbazole and 2,5-bis (P-diethylaminophenyl)
1,3,4-oxadiazole and the like are known.

On the other hand, in recent years, various studies have been made on ultrafine particles of the order of μm or Å. Such ultrafine particles are produced by paying attention to exhibiting high activity by increasing the specific surface area.

In this case, among others, the gas evaporation method is receiving attention.
Heretofore, this method has been directed toward research on obtaining ultrafine particles of an inorganic or metallic material exclusively. For example, as described in "Functional Materials", June 1987, pp. 44-49,
Research has also been made on obtaining organic ultrafine particles.

In any case, conventionally, the recovery of the ultrafine particles evaporated in the gas and adhered to the adherend is performed as shown in FIG. 6 or FIG.

That is, the first method is, as shown in FIG. 6 (a), a container 50 for accommodating the evaporable material M, a flat or curved plate 51 as an adherend, and a container for collecting falling powder if necessary.
52 is disposed in a vacuum chamber (not shown), and while the inert gas is fed into the vacuum chamber and the inside thereof is evacuated to a vacuum state, the container 50 and / or the evaporable material M Is heated and evaporated, and the evaporated material is adhered to the curved plate 51. Thereafter, as shown in FIG.
The adhesion material layer on the surface 51 is scraped off by a brush 53 or the like and collected in a collection box 54.

In the second method, as shown in FIG. 7 (a), a plastic web 60 as an adherend is wound on a reel 62 while being fed from the reel 61. The evaporating material M is adhered in a suitable evaporating manner, and when the evaporating material M is collected, the web 60 is unwound from the reel 62 on which the web 60 has been wound up as shown in FIG. The conductive material M is scraped by a brush or the like and collected in the collection box 54.

[Problems to be solved by the invention]

However, since the first method is a batch method,
The powder is sequentially laminated on the collecting plate over time, and adheres to a predetermined thickness. Therefore, no matter how the collection plate is cooled, the laminated powder layer receives radiant heat from the evaporation source,
In the case of powder having poor heat resistance, thermal degradation is particularly severe.
In the case of a material that grows in the form of needles, particles grow in a web shape (thread shape), and the desired ultrafine particles cannot be obtained.
In addition, during the lamination, extra particles fall and it is difficult to collect them properly. Furthermore, as in the second method described below, two steps of adhesion and recovery are performed, so that the operation is inefficient.

On the other hand, in the second method, in addition to the two steps, the material is scraped off between the reels, so that the scraping is not stable, the web is made of plastic, and the web is Since it is fixed, it cannot be brushed strongly and is hard to scrape off. Therefore, the recovery workability is poor and the recovery rate is poor.

On the other hand, the present applicant has previously proposed in Japanese Patent Application No. 1-143479 that the attached ultrafine particles are scraped off while the blade is in contact with the drum-shaped adherend. In this case, a metal roll was used as an adherend in order to strongly press the blade.

The previously proposed method is capable of continuously removing and recovering ultrafine particles in one step, but is excellent, but when the particle diameter becomes smaller, when a metal roll is used as the adherend, the adhesive force of the ultrafine particles is reduced by the gravity. And inertia force,
It was recognized that it was difficult to remove well.

Therefore, a main object of the present invention is to provide a fine particle generating apparatus and a fine particle generating method which are extremely excellent in removing ultrafine particles, have high recovery efficiency, and have excellent properties of the recovered ultrafine particles.

[Means for solving the problem]

An object of the present invention is to provide a fine particle generation device used in a gas evaporation method, comprising: a storage container that stores an evaporable material and heats and evaporates the evaporable material; Comprises an outer cylindrical rotary drum made of a fluororesin, and contacts the surface of the rotary drum downstream of the storage container in the rotation direction of the rotary drum to scrape and collect ultrafine particles attached to the surface. This can be solved by having a configuration in which

Further, in the fine particle generation method using the in-gas evaporation method, the evaporable material is heated and evaporated from the storage container, and is adhered to the surface of the outer cylindrical rotating drum at least the surface of which is made of fluororesin, and then continuously. The problem can also be solved by scraping and collecting the ultrafine particles attached to the surface.

As described below, these devices and methods of the present invention
At least the surface of the adherend can be made of a fluororesin.

(Operation)

In the present invention, using the adherend of the outer cylindrical surface, in the process of rotating it, so as to scrape the ultrafine particles adhered to the surface, the ultrafine particles adhered is quickly scraped off, from the evaporation source It is possible to obtain ultrafine particles having excellent properties and physical properties without thermal degradation of the ultrafine particles, and to generate, remove and recover the ultrafine particles in one step.

Further, since at least the surface of the rotating drum as the adhered body of the ultrafine particles is made of fluororesin, it can be easily removed from the rotating drum by the removing means.

[Specific configuration of the invention]

 Hereinafter, the present invention will be described in more detail.

FIG. 1 shows a first embodiment of the present invention. In a vacuum chamber 1, a container 2 for an evaporable material M, an outer cylindrical rotating drum 3, and a recovery box 4 partially open facing the same. Are arranged. The vacuum chamber 1 has a supply pipe 5 for an inert gas G such as argon or helium, and a vacuum pump 6.
Are connected to each other, and a pressure gauge 8 for detecting the degree of vacuum is attached to the exhaust pipe 7.
The rotating drum 3 is located above the container 2. Further, the collection box 4 is formed of a heat shielding material, and is thermally shielded from a portion where the evaporable material M adheres to the storage container 2 and the rotating drum 3.

On the other hand, in the collection box 4, the outer cylindrical brush 9 having a large number of brush bristles 9 </ b> B around the brush roll 9 </ b> A is brought into contact with the surface of the rotation drum 3 via the opening of the collection box 4. It is provided with a rotation axis parallel to the rotation axis. Further, in the embodiment, the rotary drum 3 is rotated clockwise by a drive motor (not shown), and the brush 9 is configured such that the brush roll 9A is rotated clockwise by a drive motor (not shown). .

In the rotation range of the brush bristles 9B of the brush 9, the swing-off blade 10 is provided in a state fixed to the collection box 4.

Further, the container 2 of the evaporable material M is preferably formed of a heat-resistant material such as a ceramic, and the container 2 and / or the directly evaporable material M are heated by heating, induction heating, laser heating, resistance heating, or the like. The material M is heated to a temperature at which the material M is sufficiently evaporated by heating the electron gun or the like.
At that time, the rotating drum 3 is kept at a temperature in the vacuum chamber 1 and preferably cooled, for example, to 10 ° C. or less. This cooling can be performed by passing a cooling heat medium, such as cooling water, through the rotating drum 3.

In the present invention, at least the surface of the rotating drum 3 is assumed to exhibit adherence of ultrafine particles. As a specific example of the means for this, the rotary drum 3 is formed of a fluororesin.

In the apparatus configured as described above, the inside of the vacuum chamber 1 is depressurized by the vacuum pump 6 to a high vacuum, and then an inert gas is fed in, preferably maintained at 0.01 to 50 Torr. When the evaporating material M is heated in this state, the gas evaporates, and the evaporated material M continuously adheres to the surface of the rotating drum 3 as ultrafine particles. The attached ultrafine particles M are scraped off by the brush 9 contacting countercurrently at the contact portion and collected in the collection box 4. Also, the ultrafine particles M attached to the brush bristles 9B are scraped off in the same manner because the tips of the bristles come into contact with the blade 10. Rotary drum 3 stripped of ultrafine particles M and stripped
The next new ultrafine particles are adhered to the surface of. In this way, the attachment and scraping of the ultrafine particles M are continuously performed on the surface of the rotating drum 3. Therefore, the ultrafine particles adhered to the surface of the rotating drum 3 are quickly scraped off again without receiving the radiant heat from the heat source for heating the material, so that deterioration (thermal damage) due to heat as in the first conventional method is caused. And high quality ultrafine particles can be obtained.
The time from the evaporation adhesion to the scraping can be set, for example, by adjusting the rotation speed of the rotary drum 3.

When the amount of the ultrafine particles collected in the collection box 4 reaches a certain amount, the vaporization operation in the gas is terminated, and the vacuum chamber 1 is opened to be taken out.

On the other hand, in the present invention, as described above, the rotating drum 3 is formed of a fluorine resin or the like so as to be non-adhesive to the ultrafine particles so that the ultrafine particles adhered to the surface thereof can be removed satisfactorily. . On the other hand, in the present invention,
Regarding the means for removing the ultrafine particles M from the rotating drum 3,
Not limited.

FIG. 2 shows a second embodiment, in which a scraping blade 10 is brought into contact with the rotating drum 3 to scrape off the ultrafine particles M adhered to the surface of the rotating drum 3. The rotating drum 3 is obtained by coating the surface of a metal roll 3A with a non-adhesive material 3B of ultrafine particles made of fluororesin. As described above, in the present invention, the entire rotary drum 3 may be made non-adhesive to ultrafine particles, or only the surface may be made non-adhesive. Further, when static electricity is generated on the surface of the rotating drum 3 to hinder removal of the ultrafine particles M, the ground brush 11 is brought into contact with the metal roll 3A or the surface of a non-adhesive material (not shown) as shown in FIG. It is good to ground in the ground.

In the first embodiment, the material of the brush bristles 9B, the planting density,
The height, thickness and the like can be appropriately selected. As a material, a metal fiber is usually used. However, if the material M generates static electricity and tends to adhere to the brush, carbon fiber can be used as a material of the brush bristles 9B. It is desirable that the tip of the brush bristles 9B be angular rather than spherical.

FIG. 3 shows a third embodiment, in which ultrafine particles M adhered to the surface of the rotary drum 3 are removed by wiping. Web 12A as wiping means
While feeding the web 12A from the feeding roll 12B
The web 12A is pressed against the surface of the rotating drum 3 by the pressing roll 12C, and the ultrafine particles M attached to the surface of the rotating drum 3 are transferred to the web 12A and wiped off.
It is configured to be wound in 2D.

FIG. 4 shows a fourth embodiment in which the ultrafine particles M are removed by a wiping method as in the third embodiment. As a wiping means, for example, a rubber roll 13 having an adhesive material surface is used. The super-fine particles M attached thereto are transferred to the rotating drum 3 while being in contact therewith.

FIG. 5 shows a fifth embodiment, in which a suction nozzle 15 connected to a vacuum pump 14 is disposed on the surface of the rotary drum 3 so as to face the same, and the ultrafine particles adhered to the surface of the rotary drum 3 by the suction force of the vacuum pump 14. M is collected by suction.

In the present invention, the surface of the rotating drum as an object to which ultrafine particles are adhered is, as described above, non-adhesive to ultrafine particles, and the material is preferably plastic, especially fluororesin. Can be. Examples of the fluorine resin include tetrafluoroethylene resin (PTFE), ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer (PFA), ethylene tetrafluoride / propylene hexafluoride copolymer (FEP), Ethylene resin (PCTF
E), vinyl fluoride resin (PVF), vinylidene fluoride resin (PVDF) and the like.

It should be noted that the constituent materials of the apparatus other than the rotary drum 3, for example, the collection box 4 of the first embodiment, can also be formed of a non-adhesive material.

In each of the above examples, the evaporable material is supplied to the storage container in a batch manner, but a large amount of evaporation can be performed by continuously supplying the evaporable material to the heating container in the vacuum chamber by a screw feeder or the like.

In the present invention, the target ultrafine particles can be suitably applied in the case of obtaining 100 to tens of thousands, particularly, ten to several thousand of particles. The type of the ultrafine particles may be an inorganic material, a metal material, or an organic material. In particular, the present inventors have confirmed that they are most suitable for obtaining an organic pigment for obtaining an organic photoreceptor, especially for obtaining an anthranthrone pigment.

The organic photoreceptor can generally be obtained by applying a dispersion of organic photoconductor particles in a dispersant and a binder resin on a conductive substrate using a disperser.

In this case, the photoconductor finally obtained includes a single-layer photoconductor in which organic photoconductor particles (pigment) are dispersed in a charge transport material as a charge generation material on a conductive substrate; There is a function-separated type photoreceptor in which a charge generating material layer is formed on a conductive substrate and a charge transporting material layer is formed thereon.
The present invention is suitable for obtaining ultrafine particles in the production of both types of photoconductors.

Example Next, an example will be described to clarify the effects of the present invention.

(Example 1) Evaporation in gas was performed by the apparatus shown in FIG.

Ultrafine organic pigment particles used for producing an organic photoreceptor for electrophotography were produced and collected. As this organic pigment,
Using 4,10-dibromoanthranthrone, the vacuum chamber was placed under a helium gas atmosphere, the pressure was reduced to 10 ^-1 Torr, the material was heated to 300 to 350 ° C, and the material was vacuum evaporated to obtain ultrafine particles according to the method shown in FIG. . As a rotating drum, PT
The FE resin was used.

As a result, ultra-fine particles without thermal degradation were recovered with a recovery rate of about 45%. Further, it has been clarified from other experiments that the recovery rate can be almost 100% by controlling the diameter and the evaporation rate of the rotating drum.

Comparative Example 1 The same organic pigment was obtained by the conventional method 1 shown in FIG.
As a result, the recovered powder was in a thread form, the inside thereof was orange, and the surface was crimson. The effect of thermal deterioration was clearly recognized, and the recovery was 35 to 40%.

Comparative Example 2 The same organic pigment was recovered by the conventional method 2 shown in FIG. As a result, ultrafine particles could be obtained, but the operation time was required to be 200 times as long as that of Example 1 (total 50 hours), and the recovery rate was extremely low at 6 to 7%.

(Comparative Example 3) The same as Example 1 except that a stainless steel drum was used as the rotating drum.

As a result, various conditions were changed, but the recovery rate was 92%
Was the limit. In addition, it was confirmed that the residual ultrafine particles adhered to the surface of the rotating drum in the form of a film after continuous operation for about 3 hours.

〔The invention's effect〕

As described above, according to the present invention, it is possible to generate and recover ultrafine particles that are extremely excellent in removing ultrafine particles, have high recovery efficiency, and have excellent properties of the recovered ultrafine particles.

[Brief description of the drawings]

FIG. 1 is a schematic view of a first embodiment of the present invention, FIG. 2 is a schematic view of a second embodiment, (a) is a side view, (b) is a front view, and FIG. FIG. 4 is a schematic diagram of the fourth embodiment, FIG. 5 is a schematic diagram of the fifth embodiment, and FIGS. 6 and 7 are schematic explanatory diagrams of the prior art. DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Container, 3 ... Rotary drum, 4 ... Recovery box, 6 ... Vacuum pump, 9 ... Brush, 10 ... Blade, 12A ... Wiping web, 13 ...
Wiping roll, 15: suction nozzle, M: evaporable material (ultra fine particles), G: inert gas

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B01J 19/00 B22F 9/12 C23C 14/24

Claims (2)

(57) [Claims] An apparatus for generating fine particles for use in an in-gas evaporation method, comprising: a storage container for storing an evaporable material and heating and evaporating the evaporable material; and a rotatably provided above the storage container. An outer cylindrical rotating drum having a surface made of a fluororesin, and contacting the surface of the rotating drum on the downstream side of the storage container in the rotating direction of the rotating drum to scrape ultrafine particles adhered to the surface. A fine particle generation device characterized by being configured to collect. 2. A method for producing fine particles using an in-gas evaporation method, comprising: evaporating an evaporable material from a storage container by evaporating the material and attaching the material to at least the surface of a rotary drum having an outer cylindrical surface made of a fluororesin; A method for producing fine particles, comprising continuously scraping and collecting ultrafine particles adhered to the surface.