JPH04372955A - Dispersion of phthalocyanine pigment and manufacture of electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To provide the dispersion capable of efficiently dispersing a phthalocyanine pigment into uniform and stable fine grains with no crystal conversion in a very short time and maintaining the stability during circulation and the manufacture of an electrophotographic photoreceptor capable of obtaining a good image with no image defect. CONSTITUTION:The process in which a mixture containing a phthalocyanine pigment and a dispersion medium collides together at the flow speed 43-75m/sec via a dispersion device constituted of members 1-4 is provided in the dispersion method of the phthalocyanine pigment, the phthalocyanine pigment can be efficiently dispersed into uniform and stable fine grains with no crystal conversion, the stability is maintained during circulation, no paint film defect is generated when a film is formed, and an electrophotographic photoreceptor made of a dispersion solution obtained in this dispersion method can obtain a good image with no image defect.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dispersing phthalocyanine pigments and a method for producing an electrophotographic photoreceptor using the dispersion obtained by the dispersion method.

0002

2. Description of the Related Art Conventionally, various types of dispersion devices for dispersing solids such as pigments have been considered, such as roll mills, ball mills, vibrating ball mills, attritors, and colloid mills.

[0003] Among these methods, an effective and representative method is a method using a so-called sand mill dispersion device in which a medium such as glass beads is placed inside a Betu cell and finely dispersed by rotating a disk or drum serving as a rotational dispersion means. There is.

When dispersing pigments and the like using a sand mill dispersion device, there are two types: a continuous dispersion method that has a mechanism for circulating the liquid to be dispersed, and a batch dispersion method that does not have this mechanism. Continuous dispersion methods have the advantage of improving dispersion efficiency because the entire vessel is filled with the dispersion liquid. This method requires a large amount of the liquid to be dispersed, and has the disadvantage that the time for actual dispersion, that is, the time for residence in the vessel, is short. In addition, in the case of a liquid to be dispersed that has a high viscosity, a bypass phenomenon occurs within the vessel (when the liquid to be dispersed is circulated from the bottom to the top of the vessel, pressure is concentrated in the lower viscosity part of the liquid to be dispersed). This may cause the liquid to be dispersed to escape upwards while remaining insufficiently dispersed, resulting in areas where it is sufficiently dispersed and areas where it is difficult to disperse, and uniform dispersion may not be possible.

On the other hand, in the batch type dispersion method, the bypass phenomenon does not occur, and the residence time in the vessel does not become short. However, in the case of the batch type, there is a dead space between the top lid and the dispersion liquid, and the liquid to be dispersed and the medium are often splashed away by the uppermost disk or drum, resulting in significantly lower dispersion efficiency than in the continuous type. There was a drawback.

[0006] Among the pigments, phthalocyanine pigments,
In particular, there are many different crystal forms of oxytitanium phthalocyanine pigments, and depending on the dispersion method, the crystal forms may change before and after dispersion.

[0007] With the recent improvement in image quality in the field of electrophotography, studies are being conducted on dispersion methods that can stably and uniformly disperse fine particles in a shorter time and with higher dispersion efficiency without converting the crystal form.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly efficient dispersion method that does not have the above-mentioned drawbacks and can disperse particles evenly and stably into fine particles in a short period of time. There is a particular thing.

Another object of the present invention is to provide a dispersion method capable of dispersing a phthalocyanine pigment without changing its crystal form.

Another object of the present invention is to provide a dispersion method that can produce a dispersion with small particle sizes without causing coating defects during film formation.

Another object of the present invention is to provide a dispersion method that can be used to form a photosensitive layer of an electrophotographic photoreceptor to obtain a dispersion liquid that can produce an electrophotographic photoreceptor without image defects. It is about providing.

Another object of the present invention is to provide a method for dispersing a dispersion, which has a small particle-enhancing property and is maintained even during circulation, so that it can be used in an electrophotographic photoreceptor for a long period of time.

Another object of the present invention is to provide a method for manufacturing an electrophotographic photoreceptor using a dispersion obtained by the above-mentioned dispersion method.

[0014]

[Means for Solving the Problems] That is, the present invention provides a method for mixing a mixture containing a phthalocyanine pigment and a dispersion medium with
This is a method for dispersing phthalocyanine pigments, which comprises a step of colliding at a flow rate of 75 m/sec.

The present invention also provides a method for producing an electrophotographic photoreceptor, which includes the step of forming a charge generation layer using a dispersion obtained by the above-mentioned dispersion method.

[0016] In the present invention, the mixture is guided into the interaction chamber by pressure from an air pump or a mechanical pump, and the introduced mixture is heated inside the chamber by two
After being branched into two channels, these branched mixtures are collided in a collision zone. It is believed that the interaction between the impact force at that time and the cavitation caused by the vacuum effect that occurs when the fluid of the mixture passes at high speed causes atomization and uniform dispersion.

FIG. 1 shows an example of disassembling the dispersion device used in the present invention into parts.

In FIG. 1, a mixture containing a phthalocyanine pigment and a dispersion medium is introduced into a member 1 in the direction of the arrow by a pump (not shown). Note that the arrows indicate the flow of the mixture. The introduced mixture is split into two streams by two holes provided in the member 2, and these branched mixtures collide on the downstream side of the member 2. At this time, since the flow path becomes narrow due to the holes provided in the member 2, the flow rate of the mixture is greatly accelerated. The impinged mixture is again split into two streams by element 3 and then discharged through element 4.

By dispersing the phthalocyanine pigment using such a dispersing device, it is possible to form a uniform dispersion of the pigment in a short time. In particular, it is an extremely effective means for dispersing phthalocyanine pigments as charge-generating substances contained in electrophotographic photoreceptor coating solutions that require fine dispersed particle size and uniformity of dispersion.

[0020] The flow velocity when the mixture collides is 43 m/
If it is less than sec or exceeds 75 m/sec, particles will increase during circulation, and the manufactured photoreceptor will develop image defects.

According to the present invention, even when oxytitanium phthalocyanine crystals, which are known to have many types of crystal forms among phthalocyanine pigments, are dispersed, no change in crystal form occurs before and after dispersion. In particular, the Bragg angle 2θ±0.2° in X-ray diffraction of CuKα is 9.0° and 14.2°.
The present invention is effective for dispersing phthalocyanine crystals having relatively unstable crystal forms, such as so-called type I oxytitanium phthalocyanine, which has strong peaks at 23.9° and 27.1°.

Hereinafter, the dispersion method of the present invention will be explained in detail, taking as an example an electrophotographic photoreceptor having a photosensitive layer containing type I oxytitanium phthalocyanine crystals.

Typical examples of the structure of the photosensitive layer of an electrophotographic photoreceptor include a so-called single layer type in which type I oxytitanium phthalocyanine, which is a charge generating substance, and a charge transport substance are contained in the same layer, and A so-called laminated type layer includes a charge generation layer containing titanium phthalocyanine and a charge transport layer containing a charge transport material, which are functionally separated.

[0024] The dispersion method of the present invention is used for coating liquids for forming a layer containing a phthalocyanine pigment, regardless of whether it is a single layer type or a multilayer type.

The coating solution for the charge generation layer is, for example, a type I oxytitanium phthalocyanine mixed with a suitable organic solvent such as tetrahydrofuran, cyclohexanone, methyl ethyl ketone, ethyl acetate, methanol, methyl cellosolve,
A dispersion liquid is prepared by the dispersion method of the present invention using acetone, dioxane, N,N-dimethylformamide, etc. as a dispersion medium. At this time, a polymeric substance may be added together as a binder, or the binder may be added after the pigment and dispersion medium have been predispersed.

The binder can be selected from a wide variety of insulating resins and also from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpolene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester,
Examples include insulating resins such as phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

The proportion of binder in the charge generation layer is 80% by weight.
It is preferably at most 40% by weight or less, particularly preferably at most 40% by weight.

The proportion of the solid content including the pigment and binder to the dispersion medium may be about 0.5 to 80% by weight. In particular, when dispersing a charge generating substance for an electrophotographic photoreceptor, the amount is preferably 3 to 15%.

Further, the charge generation layer is formed by coating a dispersion containing the above-mentioned substances on a conductive support, and the thickness thereof is preferably 5 μm or less, particularly 0.5 μm or less.
05 to 1 μm is preferable.

The charge transport layer is mainly formed by applying and drying a paint in which a charge transport substance and a binder are dissolved in a solvent.

[0031] Examples of the charge transport substance used include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, and triallylmethane compounds. **The binder may be added after the pigment and dispersion medium are predispersed.

[0032] Furthermore, as the binder, those mentioned above can be used.

[0033] The film thickness is preferably 5 to 40 μm, particularly 1
0 to 30 μm is preferable.

Even when the photosensitive layer is a single layer, it can be formed in the same manner using the above-mentioned materials, and the film thickness is 5 to 5.
The thickness is preferably 40 μm, particularly preferably 10 to 30 μm.

In the present invention, a subbing layer having an adhesive function and a barrier function can be provided between the photosensitive layer and the conductive support.

Further, in the present invention, a thin protective layer may be provided on the photosensitive layer in order to protect the photosensitive layer from external impact.

As a method for applying these various layers, a dipping method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, etc. can be used. The electrophotographic photoreceptor obtained by the manufacturing method of the present invention can be used in laser beam printers, LED printers, C
It can be widely applied not only to printers such as RT printers, but also to ordinary electrophotographic copying machines, facsimile machines, and other electrophotographic application fields.

[0038]

[Examples] The present invention will be explained below with reference to Examples. In the examples, parts indicate parts by weight.

(Example 1) 10 g of type I oxytitanium phthalocyanine, butyral resin (S-LEC BM-2
(manufactured by Sekisui Chemical) and 135 g of cyclohexanone were dispersed using a dispersion apparatus as shown in FIG. The flow velocity of the mixture at the time of collision was 66 m/sec, and the dispersion time was about 10 seconds. Dispersion was repeated three times to obtain a dispersion liquid.

The particle diameter of the thus obtained dispersion was measured immediately after dispersion and after the dispersion was allowed to stand for 5 days. Furthermore, after dispersion, 1 liter/m with a diaphragm pump.
The particle size was measured after circulation for 30 days at a flow rate of in. The particle size was measured using a centrifugal particle size analyzer (CAPA500) manufactured by Horiba, Ltd. whose basic principle is liquid phase sedimentation, and the obtained average particle size was taken as the particle size of the dispersion. The results are shown in Table 1. From Table 1, it can be seen that the pigment is finely dispersed in the liquid and hardly increases in size even if left standing.

The dispersion after being left for 5 days was diluted to a 2% by weight solution using a mixed solvent of cyclohexanone/ethyl acetate = 1/1 (weight ratio), and then diluted to 50 μm with a wire bar.
Coated on an aluminum sheet. When the obtained coating film was visually observed, it was found that a uniform coating film was obtained without any bumps or spots. This shows that even if the dispersion time is short, a stable dispersion with a small particle size can be obtained.

[0042] Oxytitanium phthalocyanine before and after dispersion was analyzed using an X-ray diffractometer RAD-
CuKα characteristic X-ray diffraction measurements were performed using the A system. Before dispersion, the pigment powder was measured, and after dispersion, the dispersion liquid was applied onto a glass slide and dried. The results are shown in Figures 2 and 3. It can be seen from FIGS. 2 and 3 that the crystal form did not change before and after dispersion.

Further, the dispersion obtained above was applied as a coating liquid for the charge generation layer by dipping onto a cleaned aluminum cylinder of 30φ×250mm, and dried at 110° C. for 10 minutes to give a coating of 0.05 mm. A charge generation layer having a thickness of 3 μm was formed.

Next, 10 parts of a triphenylamine compound having the structure shown by the following formula,

[0045]

embedded image 10 parts of bisphenol Z type polycarbonate resin (viscosity average molecular weight: 22,000) was dissolved in 50 parts of monochlorobenzene and 10 parts of dichloromethane. This paint was applied onto the charge generation layer described above by dipping, and dried at 110° C. for 1 hour to form a charge transport layer of 20 μm.

The electrophotographic photoreceptor produced in this way was installed in an electrophotographic copying machine that has -5.6 KV corona charging, image exposure, toner phenomenon, toner transfer to plain paper, and cleaning steps using a urethane rubber blade. I made a copy. The results are shown in Table 3.

(Examples 2 to 4) Dispersions were obtained and evaluated in the same manner as in Example 1, except that type A, B and Y oxytitanium phthalocyanines were used instead of type I oxytitanium phthalocyanine. Table 1 shows the dispersed particle size of each dispersion, Table 2 shows the characteristics of the photoreceptor, and X-ray diffraction patterns of the pigment before and after dispersion are shown in FIGS. 4 to 9.

[0048] Also, the obtained coating film was also uniform as in Example 1.

(Example 5) The flow velocity at the time of collision of the mixture was set to 46
A dispersion was obtained and evaluated in the same manner as in Example 1 except that the dispersion was changed to m/sec. Table 1 shows the dispersed particle size of each dispersion liquid, and Table 2 shows the characteristics of the photoreceptor.

The obtained coating film was uniform as in Example 1 (Example 6) The dispersion was prepared in the same manner as in Example 1 except that the flow velocity at the time of collision of the mixture was 72 m/sec. was evaluated. Table 1 shows the dispersed particle size of the dispersion liquid, and Table 2 shows the characteristics of the photoreceptor.

Furthermore, the obtained coating film was uniform as in Example 1 (Comparative Example 1) Dispersion was carried out in the same manner as in Example 1, except that the flow velocity at the time of collision of the mixture was 36 m/sec. A liquid was obtained and evaluated. Table 1 shows the dispersed particle size of each dispersion liquid, and Table 2 shows the characteristics of the photoreceptor.

[0052] In addition, spots and pock-like spots were observed in the coating film obtained from the dispersion that was circulated for 30 days.

(Comparative Example 2) The flow velocity at the time of collision of the mixture was set to 96
A dispersion was obtained and evaluated in the same manner as in Example 1 except that the dispersion was changed to m/sec. Table 1 shows the dispersed particle size of each dispersion liquid, and Table 2 shows the characteristics of the photoreceptor.

[0054] In addition, spots and pock-like spots were observed in the coating film obtained from the dispersion that was circulated for 30 days.

[0055]

[Table 1]

[0056]

[Table 2] Table 2 shows that the electrophotographic photoreceptor produced using the dispersion liquid obtained by the dispersion method of the present invention can provide a good image without image defects.

[0057]

As described above, according to the present invention, phthalocyanine pigments can be efficiently dispersed into uniform and stable fine particles without crystal conversion in a very short time.
It has excellent stability during circulation, so no coating defects occur when it is formed. Further, an electrophotographic photoreceptor manufactured using a dispersion liquid dispersed by the dispersion method of the present invention can obtain good images without image defects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example in which a dispersion device used in the present invention is disassembled into parts.

FIG. 2 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment before dispersion in Example 1.

FIG. 3 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment after dispersion in Example 1.

FIG. 4 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment before dispersion in Example 2.

FIG. 5 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment after dispersion in Example 2.

FIG. 6 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment before dispersion in Example 3.

7 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment after dispersion in Example 3. FIG.

8 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment before dispersion in Example 4. FIG.

9 is a CuKα characteristic X-ray diffraction diagram of the oxytitanium phthalocyanine pigment after dispersion in Example 4. FIG.

Claims (4)

[Claims] 1. A method for dispersing a phthalocyanine pigment, which comprises the step of colliding mixtures containing a phthalocyanine pigment and a dispersion medium at a flow rate of 43 to 75 m/sec. 2. The method for dispersing a phthalocyanine pigment according to claim 1, wherein the phthalocyanine pigment is a crystal of oxytitanium phthalocyanine. 3. The oxytitanium phthalocyanine crystal has a Bragg angle of 2θ± in X-ray diffraction of CuKα.
0.2° is 9.0°, 14.2°, 23.9° and 2
The method for dispersing a phthalocyanine pigment according to claim 2, which is an oxytitanium phthalocyanine crystal having a strong peak at 7.1°. 4. A method for producing an electrophotographic photoreceptor, comprising the step of forming a charge generation layer using a dispersion obtained by the dispersion method according to claim 1, 2 or 3.