JP2959685B2 - Method for producing fine-particle powder, fine-particle powder, and method for forming functional film containing fine-particle powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fine particle powder such as an organic photoconductor used in the production of an electrophotographic photosensitive member, a fine particle powder and the formation of a functional film using the fine particle powder. About the method. In particular, the present invention relates to a technique for obtaining ultrafine particles using a gas evaporation method.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member has a basic structure in which a photosensitive layer is formed on a conductive substrate.

Conventionally, selenium is generally used as a photoconductive material for forming the photosensitive layer, and cadmium sulfide and zinc oxide 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 photoconductive substance is used, there is an advantage that 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-
Vinyl carbazole, 2,5-bis (P-diethylaminophenyl) -1,3,4-oxadiazole and the like are known.

[0005] On the other hand, in recent years, various studies have been made on fine particle powder of the order of μm or Å. Such a fine particle powder is produced by paying attention to exhibiting high activity by increasing its specific surface area.

[0006] Generally, as a method for obtaining fine particles or attaching the fine particles to the surface of a substrate, a gas phase generation method (electric furnace method, chemical flame method, plasma method, gas evaporation method), a liquid phase generation method (precipitation method). Method, solvent evaporation method), or physical pulverization method (using a sand mill, a ball mill, an attritor, or the like).

In general, when a material is evaporated in a high vacuum and adhered to a substrate, it becomes a vapor-deposited film and cannot be recovered as a powder. However, the above-mentioned gas evaporation method has an advantage that it can be recovered as fine particles. Attracting attention for reasons.
In the gas evaporation method, an inert gas is introduced into a vacuum vessel, and various substances are heated in an inert gas atmosphere to evaporate or sublimate, and the resulting vapor molecules collide with the inert gas molecules. In this method, the molecules are gradually cooled while the molecules are aggregated to form fine particle powder, and the fine particle powder is collected.

Heretofore, this method has been directed toward research on obtaining fine particles of inorganic or metallic materials exclusively. For example, "Functional Materials", June 1987, 44-4.
As described on page 9, research has also been conducted on obtaining organic fine particle powder. Specifically, an evaporative material is charged into a vacuum vessel, an inert gas is introduced, and the evaporative material is heated to evaporate or sublimate to generate fine particle powder. A mode is adopted in which a web is successively attached at a certain speed from a reel to a take-up reel, and then the fine particles attached to the web are collected by scraping.

[0009]

Generally, it is desired that the particles be made finer in view of electrophotographic characteristics and the like. The obtained particle size is affected by the pressure, the evaporation rate, the distance between the evaporation source containing the evaporable material and the adhered substrate, and the like. As the formation progressed, the particles were fused, the BET specific surface area became small, it became difficult to obtain isolated fine particles, and substantially no fine particles could be achieved.

Accordingly, an object of the present invention is to obtain finer powder particles by a gas evaporation method.

[0011]

The object of the present invention is to introduce an evaporable material into a vacuum vessel, introduce a non-reactive gas, and heat or evaporate the evaporable material to evaporate or sublimate the fine particle powder. In the gas evaporation method to get the body,
The problem can be solved by introducing a gas containing oxygen into the vacuum vessel together with the non-reactive gas.

In the case where the final product is manufactured by applying fine particles, a volatile material is charged into a vacuum vessel, a non-reactive gas is introduced, and the volatile material is heated. In the in-gas evaporation method of evaporating or sublimating to obtain fine particle powder, a gas containing oxygen is introduced into the vacuum vessel together with the non-reactive gas, and the obtained fine particle powder is dispersed in the liquid. And
The dispersion can be easily obtained by applying the dispersion to a target surface.

In this case, it is desirable to mix the non-reactive gas and the gas containing oxygen while adjusting the respective flow rates thereof and introduce the mixed gas into the vacuum vessel. Further, by controlling the oxygen concentration, the characteristics of the fine particles or the functional film to be obtained can be controlled. The effect of the present invention appears more remarkably when the evaporable material is a raw material for an organic photoconductor material, and particularly when it is 4,10 -dibromoanthranthrone . The oxygen concentration in the vacuum vessel was 0.01 to 50%, the degree of vacuum in the vacuum vessel can be 10 ^-2 ~10 ² Torr.

[0014] A gas in which an evaporative material is charged into a vacuum vessel, a gas containing oxygen is introduced simultaneously with a non-reactive gas, and the evaporative material is heated to evaporate or sublimate to obtain fine particle powder. BE by medium evaporation method
Fine particle powder having a T value of 20 m ² / g or more can be obtained.

When the evaporable material is a raw material for an organic photoconductor material, a photosensitive drum for electrophotography can be obtained by applying the above-mentioned dispersion to a drum substrate.

[0016]

According to the conventional method, the vacuum chamber contains only Ar gas.
Only an inert gas such as He or He was introduced. Why conventional, but not clear why or not introduced but the inert gas, and that there was no need to introduce the oxygen in the case where the metal is evaporated in the gas, in the case of organic materials, thermal evaporation or sublimation It is presumed that this was due to concerns about burning or carbonization at high temperatures.
Further, since an organic substance, it is determined that there is no oxidation of the resulting formed article by a gas evaporation process, and the change in quality due to oxidation is also considered to have been determined not.

However, surprisingly, the present inventors dare to introduce oxygen gas into the vacuum vessel together with the inert gas, and the physical properties of the resulting product will be as described below.
It has been found that it is possible to obtain isolated fine particles having an extremely high BET specific surface area value, which is extremely excellent, especially as compared with the case where oxygen gas is not introduced. It has also been found that at normal processing temperatures, no combustion or carbonization occurs.
Furthermore, according to the present invention, when oxygen gas is introduced together with the inert gas during the in-gas processing, it is clear that even after being taken out of the vacuum vessel, there is no change in the physical properties and good electrophotographic characteristics are exhibited. became.

[0018]

The present invention will be described in more detail below. FIG. 1 shows a specific example of a method for producing and recovering fine particles by an in-gas evaporation method of the present invention. In a vacuum vessel 1, a container 2 for an evaporable material M, a feeding reel 3, a take-up reel 4, and A collection web 5 that is fed from the pay-out reel 3 and wound on the take-up reel 4 is provided. The vacuum vessel 1 contains an inert gas such as argon or helium, and a N ₂ gas or the like.
A supply pipe 6 for the non-reactive gas G with the evaporation material M, an oxygen gas supply pipe 6, and an exhaust pipe 8 connected to a vacuum pump 7 are in communication with each other. Attached. Further, it is preferable that the container 2 of the evaporable material M is formed of a heat-resistant material such as ceramic, and the container 2 and / or the direct evaporable material M
Is heated to a temperature at which the material M is sufficiently evaporated by heater heating, induction heating, laser heating, resistance heating, electron gun heating, or the like.

In the apparatus thus constructed, the pressure inside the vacuum vessel 1 is reduced by the vacuum pump 7,
After evacuating to 0 ^-4 Torr or less, oxygen gas is fed from the supply pipe 6 together with the non-reactive gas, and the
0 under the conditions of ^-2 to 10 about ² Torr, and heated against vaporizable material M, cause the gas evaporation, the evaporated material M
Continuously adhere to the surface of the moving web 5.
Thus, when the process of adhering to the surface of the rotating drum 3 is finally completed, the web 5 is taken together with the take-up reel 4 into the vacuum container 1.
The evaporable material M can be scraped off from the web 5 after being taken out or by a scraping means (not shown) arranged opposite to the web 5 near the take-up reel 4 in the vacuum vessel 1. As scraping means,
Means such as brushing, scraping with a blade, and wiping with a wiping cloth can be used.

In the present invention, the oxygen gas includes not only a pure oxygen gas but also a gas containing oxygen such as air. Since air mainly consists of nitrogen which is not reactive with oxygen, in the present invention, blowing of only air may be used. The oxygen gas concentration is preferably 0.01 to 50%, particularly preferably 5 to 25%.
When the oxygen concentration is low, the effect of the present invention does not appear remarkably, while when it is excessively high, the effect is saturated.

Usually, it is preferable that the non-reactive gas and the oxygen gas are blown from a common supply pipe 6, but they can be fed from separate supply pipes. In the case of blowing from a single supply pipe, in order to set the oxygen concentration, as shown in FIG. 8, it is divided into a non-reactive gas path and an oxygen gas path, and the filters 10 and the gate valves 11, 12 are provided in those paths. , A flow control valve 13 and a flow controller 14 are provided, and a mixing cylinder 15 for each of the supplied gases is provided.
It can be blown into the vacuum vessel 1. In this case, the flow controllers 14 and 14 are adjusted while having a correlation by a controller (not shown). The mixing cylinder 15 can be filled with a Raschig ring, or a static mixer or the like can be provided for mixing. Further, the flow rate of one gas can be made constant while the flow rate of the other gas can be adjusted.

In the present invention, the target fine particle powder can be suitably applied when obtaining ultrafine particles of 100 to tens of thousands, especially 10 to several thousand of particles. According to the present invention, in particular, BET as fine particle powder used when obtaining an electrophotographic photoreceptor
Those having a value of 20 m ² / g or more can be easily obtained. The type of the fine particle powder may be an inorganic material, a metal material, or an organic material. The present inventors have found that an organic photoconductor material for obtaining an organic photoreceptor, particularly an organic pigment, particularly an anthranthrone - based pigment, such as 4,10 -dibromoanthranthrone whose structural formula is shown in FIG. It has been confirmed that there is.

The organic photoreceptor is a conductive substrate (drum substrate)
The organic photoconductive particles can be generally obtained by applying a dispersion of the organic photoconductor particles in a binder resin or another layer on the binder resin.

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

As described above, in the present invention, fine particles having a high BET value can be obtained. Therefore, when an electrophotographic photoreceptor is obtained, the time required for dispersion in a liquid is greatly reduced. . Incidentally, according to the present invention, conventionally, the dispersion time on the order of several hours to one hundred hours can be reduced to the dispersion time on the order of several minutes to several hours. Also, the dispersing method is not a conventional dispersing machine in which the operation is difficult, such as a sand mill, an attritor, a ball mill, or a media-type dispersing machine or a kneading machine, or a roll mill, and a high shear force is applied.
Operations such as stirring and ultrasonic dispersion can be easily performed, and a method of dispersing with low shear force can be adopted. Thus, the performance of the material does not deteriorate and a good functional film can be formed. In the conventional dispersing method or dispersing machine, deterioration due to impact or contamination of the medium and deterioration due to a high shear rate (shear stress) are severe. Further, the stirring and ultrasonic dispersion methods are excellent in workability.

According to the present invention, it is possible to obtain an electrophotographic photoreceptor by applying the conductive substrate by immersing it in the above-mentioned dispersion liquid or by applying the conductive substrate to the conductive substrate using an annular coating device such as a slide bead. it can.

Example Next, the effect of the present invention will be clarified by an example. Organic pigment fine-particle powder used for producing an organic photoreceptor for electrophotography was produced and collected by the equipment shown in FIG. As the organic pigment, 4,10-dibromoanthranthrone was used, the vacuum vessel was placed under a helium gas atmosphere, and
Under the same conditions in which the pressure was reduced to 0.5 Torr and the material was heated to 300 to 350 ° C. and evaporated in vacuum, the fine particles and the fine particles obtained mainly depended on the presence or absence of oxygen gas and the amount of oxygen gas introduced (oxygen concentration). Changes in electrophotographic characteristics when an electrophotographic photoreceptor was manufactured using fine particles were examined.

2 and 3 show the characteristics of the electrophotographic photosensitive member. FIG. 2 shows the case where oxygen gas is not introduced, and FIG. 3 shows the case where oxygen gas is introduced so that the oxygen concentration becomes 15%. The potential Va and the dark decay potential Vd were examined. In the case where oxygen gas is not introduced, since the potential is excessively high, a large amount of exposure is required before the potential drops to the minimum potential (white potential) of the copying machine standard. , It is found that the exposure amount is small and the sensitivity is high.

FIG. 4 shows charging (saturation) depending on the doping amount of oxygen.
A change in the potential was examined, and it was found that the charging potential decreased when the oxygen concentration was high. FIG. 5 shows the change in sensitivity depending on the oxygen doping amount. When the oxygen concentration is high, the sensitivity (exposure amount (Lux · se) required to decrease the potential from 600 V to 100 V
c)) has been shown to improve. FIG. 6 shows the doping amount of oxygen in the gloss when the dispersion of the fine particle powder was left for one day, applied to a smooth glass surface, and then measured for gloss (using a variable-angle gloss meter manufactured by Nippon Denshoku Co., Ltd.). It was found that the greater the oxygen doping amount, the better the gloss of the coating film, the better the coated surface of the photosensitive drum, and the better the image quality when copying.

FIG. 7 shows the change in the BET value of the fine particles depending on the oxygen doping amount, measured using a specific surface area measuring device manufactured by Shimadzu Corporation. It is found that the BET value increases as the oxygen doping amount increases.

[0031]

As described above, according to the present invention, finer fine particle powder can be obtained, and when applied to electrophotography, its electrophotographic characteristics can be improved. And can contribute to quality improvement.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a method for producing fine particle powder of the present invention.

FIG. 2 is a potential diagram of an electrophotographic photosensitive member according to a conventional method.

FIG. 3 is a potential diagram of the electrophotographic photosensitive member according to the method of the present invention.

FIG. 4 is a graph showing a change in charging (saturation) potential depending on an oxygen doping amount.

FIG. 5 is a graph showing a change in sensitivity depending on an oxygen doping amount.

FIG. 6 is a graph showing a change in gloss of oxygen after doping with a dispersion liquid of fine particle powders.

FIG. 7 is a graph showing a change in BET value of fine particles depending on the doping amount of oxygen.

FIG. 8 is a schematic explanatory view of a method of mixing and adjusting a flow rate of gas.

FIG. 9 is a diagram of a 4,10 -dibromoanthranthrone formula.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Container, 5 ... Web, 7 ... Vacuum pump, M ... Evaporable material, G ... Non-reactive gas

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-240860 (JP, A) JP-A-63-95101 (JP, A) JP-A-3-60732 (JP, A) JP-A 63-95 31533 (JP, A) JP-A-63-38625 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/00-5/16 B01J 19/00

Claims (12)

(57) [Claims] An evaporating material is charged into a vacuum container having a reduced pressure, and a gas is introduced into the vacuum container.
In the gas evaporation method of heating or evaporating or sublimating the evaporable material to obtain fine particle powder, the gas is a gas containing a non-reactive gas and oxygen,
A method for producing fine particle powder, wherein the oxygen concentration in the vacuum vessel is 0.01 to 50%. 2. The method for producing fine particle powder according to claim 1, wherein the non-reactive gas and the gas containing oxygen are mixed while adjusting the respective flow rates thereof and introduced into a vacuum vessel. 3. The method for producing fine particle powder according to claim 1, wherein characteristics of the fine particle powder are controlled by controlling an oxygen concentration. 4. The method for producing fine particle powder according to claim 1, wherein said evaporative material is a raw material for an organic photoconductor material. 5. The method according to claim 1, wherein the evaporative material is 4,10-dibromoanthranthrone. 6. A vacuum degree in the vacuum vessel is 10 ⁻² to 10 ^2.
The method for producing fine particle powder according to any one of claims 1 to 5, which is Torr. 7. A gas in which an evaporable material is charged into a vacuum vessel having a reduced pressure, at least a non-reactive gas is introduced, and the evaporable material is heated to evaporate or sublimate to obtain fine particle powder. Fine particle powder obtained by a medium evaporation method, wherein the fine particle powder has a BET value of 20 m ² / g or more. 8. An evaporative material is charged into a vacuum container having a reduced pressure, a gas containing non-reactive gas and oxygen is introduced into the vacuum container, and the oxygen concentration in the vacuum container is reduced to 0.1%. After heating the evaporable material to evaporate or sublimate to obtain fine particle powder, the dispersion liquid obtained by dispersing the fine particle powder in a liquid is applied to a target surface. A method for forming a functional film, comprising: 9. The method according to claim 8, wherein the evaporable material is a raw material for an organic photoconductor material. 10. The method according to claim 8, wherein the evaporable material is 4,10-dibromoanthranthrone. 11. The degree of vacuum in the vacuum container is 10 ⁻² to 10
^The method for forming a functional film according to any one of claims 8 to 10, wherein the method is ² Torr. 12. The method according to claim 8, wherein the target surface is a surface of a photosensitive drum substrate for electrophotography.