JP2887215B2 - Method for dispersing phthalocyanine pigment and method for producing electrophotographic photoreceptor - 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 dispersing a phthalocyanine pigment and a method for producing an electrophotographic photosensitive member using a dispersion obtained by the dispersion method.

[0002]

2. Description of the Related Art Conventionally, various types of dispersing apparatuses for dispersing solids such as pigments have been considered, such as a roll mill, a ball mill, a vibrating ball mill, an attritor or a colloid mill.

Among them, a method using a so-called sand mill dispersing device, which is effective and representative means, is to disperse a medium such as glass beads inside a vessel and finely disperse it by rotating a disk or a drum which is a rotating dispersing means. There is.

When a pigment or the like is dispersed using a sand mill dispersion apparatus, there are a continuous dispersion method having a mechanism for circulating a liquid to be dispersed, and a batch dispersion method having no mechanism. In the case of the continuous dispersion method, the dispersion liquid is filled in the whole vessel, which has an advantage that the dispersion efficiency is improved. However, there is a disadvantage that a large amount of the liquid to be dispersed is required and that the time for actual dispersion, that is, the time for staying in the vessel is short. In addition, in the case of a liquid to be dispersed having a high viscosity, a bypass phenomenon occurs in the vessel (when the liquid to be dispersed is circulating from the bottom to the top in the vessel, pressure concentrates on a portion where the viscosity of the liquid to be dispersed is low). The phenomenon that the liquid to be dispersed comes off with insufficient dispersion) occurs,
There is a possibility that a place where the dispersion is sufficiently performed and a place where the dispersion is difficult, and uniform dispersion may not be performed.

On the other hand, in the batch-type dispersion method, the bypass phenomenon does not occur, and the residence time in the vessel is not shortened. However, in the case of the batch type, there is a dead space between the upper pig and the dispersion, and the dispersion or medium is often repelled by the uppermost disk or drum, and the dispersion efficiency is significantly lower than that of the continuous type. There was a disadvantage of becoming.

[0006] Among the pigments, phthalocyanine pigments,
Particularly, the crystal forms of the oxytitanium phthalocyanine pigment are various, and depending on the dispersion method, the crystal forms may be changed before and after the dispersion.

[0007] With the recent improvement in image quality in the field of electrophotography, a dispersion method has been studied which can stably and uniformly disperse fine particles in a short time without converting the crystal form with high dispersion efficiency.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dispersion method which does not have the above-mentioned drawbacks, that is, has a high dispersion efficiency and can be uniformly dispersed in a short period of time into fine particles. It is in.

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

Another object of the present invention is to provide a dispersion method capable of obtaining a dispersion liquid having a small particle size without causing a coating film defect when a film is formed.

Another object of the present invention is to provide a dispersion method which can be used for forming a photosensitive layer of an electrophotographic photoreceptor to obtain a dispersion capable of producing an electrophotographic photoreceptor without causing image defects. To provide.

Another object of the present invention is to provide a method for dispersing a dispersion which can be used for an electrophotographic photoreceptor for a long period of time because the property of the dispersion to increase the particle size and is maintained even during circulation.

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

[0014]

That is, according to the present invention, a mixture containing a phthalocyanine pigment and a dispersion medium is mixed with each other by 43 to 43%.
A method for dispersing a phthalocyanine pigment, comprising a step of causing collision at a flow rate of 75 m / sec.

Further, the present invention is a method for producing an electrophotographic photoreceptor, which comprises a step of forming a charge generation layer from the dispersion obtained by the above dispersion method.

In the present invention, the mixture is guided to the interaction chamber by the pressure of an air pump or a mechanical pump, and the introduced mixture is placed inside the chamber at 2 hours.
After being branched into two flow paths, these branched mixtures are collided in a collision zone. It is considered that the interaction between the impact force at that time and the cavitation due to the vacuum effect generated when the mixture fluid passes at a high speed causes the atomization effect and the uniform dispersion effect.

FIG. 1 shows an example in which the dispersing device used in the present invention is disassembled for each member.

In FIG. 1, a mixture containing a phthalocyanine pigment and a dispersion medium is introduced into a member 1 by a pump (not shown) in the direction of the arrow. The arrows indicate the flow of the mixture. The introduced mixture is branched into two streams by two holes provided in the member 2, and the branched mixture collides downstream of the member 2. At this time, the flow rate of the mixture is greatly accelerated because the flow path is narrowed by the holes provided in the member 2. The impinging mixture is split off again by the element 3 into two streams and then discharged through the element 4.

By dispersing the phthalocyanine pigment using such a dispersing device, the pigment can be made into a uniform dispersion in a short time. In particular, this is an extremely effective means for dispersing a phthalocyanine pigment as a charge generating substance contained in an electrophotographic photoreceptor coating liquid which requires a fine dispersion particle diameter and uniformity of dispersion.

The flow rate at the time of impinging the mixture is 43 m /
If it is less than sec or exceeds 75 m / sec, the particle size will increase during circulation, and the manufactured photoreceptor will cause image defects.

According to the present invention, even when oxytitanium phthalocyanine crystals, of which many types of crystal forms have been confirmed among phthalocyanine pigments, are dispersed, the crystal forms do not change before and after the dispersion. In particular, the Bragg angle 2θ ± 0.2 ° in X-ray diffraction of CuKα is 9.0 °, 14.2
The present invention is effective for the dispersion of phthalocyanine crystals having relatively unstable crystal forms such as so-called type I oxytitanium phthalocyanine having strong peaks at °, 23.9 ° and 27.1 °.

Hereinafter, an electrophotographic photosensitive member having a photosensitive layer containing type I oxytitanium phthalocyanine crystal using the dispersion method of the present invention will be described in detail.

As typical examples of the constitution of the photosensitive layer of the electrophotographic photosensitive member, a so-called single layer type containing an I-type oxytitanium phthalocyanine as a charge generating substance and a charge transporting substance in the same layer, A so-called laminated type in which the function is separated into a charge generation layer containing titanium phthalocyanine and a charge transport layer containing a charge transport material is exemplified.

Regarding a coating liquid for forming a layer containing a phthalocyanine pigment, irrespective of a single layer type or a laminated type, the dispersion method of the present invention is used.

The coating solution for the charge generating layer may be, for example, oxytitanium phthalocyanine of the type I in an appropriate organic solvent such as tetrahydrofuran, cyclohexanone, methyl ethyl ketone, ethyl acetate, methanol, methyl cellosolve, or the like.
It is prepared as a dispersion by the dispersion method of the present invention using acetone, dioxane, N, N-dimethylformamide or the like as a dispersion medium. At this time, a polymer substance may be added together as a binder, or the binder may be added after the pigment and the dispersion medium are dispersed in advance.

The binder can be selected from a wide range of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinyl carbazole, polyvinyl anthracene and polyvinyl pollene. Preferably, polyvinyl butyral, polyarylate (such as a condensation polymer of bisphenol A and phthalic acid), polycarbonate, polyester,
Phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulosic resin, urethane resin, epoxy resin,
Insulating resins such as casein, polyvinyl alcohol, and polyvinylpyrrolidone can be used.

The ratio of the binder in the charge generation layer is 80% by weight.
Or less, particularly preferably 40% by weight or less.

The ratio of the solid component including the pigment and the binder to the dispersion medium may be about 0.5 to 80% by weight. Particularly, when the charge generating material of the electrophotographic photosensitive member is dispersed, the content is preferably 3 to 15%.

The charge generation layer is formed by applying a dispersion containing the above-mentioned substances on a conductive support, and the thickness thereof is preferably 5 μm or less, particularly preferably 0.1 μm or less.
It is preferably from 0.5 to 1 μm.

The charge transport layer is formed by coating and drying a coating material in which a charge transport material and a binder are dissolved in a solvent.

Examples of the charge transport material used include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, triallylmethane compounds, and the like. ** After the pigment and the dispersion medium are dispersed in advance, the binder may be added.

As the binder, those described above can be used.

The film thickness is preferably 5 to 40 μm, particularly preferably 1 to 40 μm.
0 to 30 μm is preferred.

When the photosensitive layer is a single layer, the photosensitive layer can be formed in the same manner by using the above-mentioned materials.
40 μm is preferable, and particularly preferably 10 to 30 μm.

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

In the present invention, a thin protective layer may be provided on the photosensitive layer 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 and the like can be used. The electrophotographic photosensitive member obtained by the production method of the present invention is a laser beam printer, an LED printer,
The present invention can be widely applied to not only printers such as RT printers but also ordinary electrophotographic copying machines, facsimile machines and other electrophotographic application fields.

[0038]

The present invention will be described below with reference to examples. In the examples, “parts” indicates “parts by weight”.

Example 1 I-type oxytitanium phthalocyanine (10 g), butyral resin (Eslec BM-
2, 5 g of cyclohexanone and 135 g of cyclohexanone
Was dispersed using a dispersing apparatus as shown in FIG. The flow velocity at the time of collision of the mixture is 66 m / sec,
The dispersion time was about 10 seconds. Repeat the dispersion three times,
A dispersion was obtained.

The particle size of the dispersion thus obtained was measured immediately after the dispersion and the particle size after the dispersion was allowed to stand for 5 days after the dispersion. Furthermore, after dispersion, 1 liter /
The particle size after circulation at a flow rate of min for 30 days was measured. The particle size was measured using a centrifugal particle size analyzer (CAPA500) manufactured by HORIBA, Ltd. based on the liquid phase sedimentation method, and the obtained average particle size was used as the particle size of the dispersion.
Table 1 shows the results. From Table 1, it can be seen that the pigment is finely dispersed in the liquid and hardly increases the particle size even when left untreated.

The dispersion liquid after standing for the previous 5 days was diluted to 2% by weight with a mixed solvent of cyclohexanone / ethyl acetate = 1/1 (weight ratio) and adjusted to 50 μm with a wire bar.
It was applied to an aluminum sheet. When the obtained coating film was visually observed, a uniform coating film with no bumps or spots was obtained. This shows that a stable dispersion having a small particle size can be obtained even if the dispersion time is short.

Further, the oxytitanium phthalocyanine before and after the dispersion was analyzed using an X-ray diffractometer RAD-R
CuKα characteristic X-ray diffraction measurement was performed using the A system. Before the dispersion, the pigment powder was measured, and after the dispersion, the dispersion was applied to a slide glass and dried. The results are shown in FIGS. 2 and 3, it can be seen that the crystal form does not change before and after dispersion.

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

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

[0045]

Embedded image 10 parts of bisphenol Z-type polycarbonate resin (viscosity average molecular weight 22,000) was
And 10 parts of dichloromethane. This paint is applied on the charge generation layer by dipping,
For 1 hour to form a 20 μm charge transport layer.

The electrophotographic photoreceptor thus manufactured was subjected to -5.6 KV corona charging, image exposure, toner phenomenon,
Copying was performed by attaching to an electrophotographic copying machine having a toner transfer process to plain paper and a cleaning process using a urethane rubber blade. Table 3 shows the results.

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

Further, the obtained coating film was uniform as in Example 1.

(Example 5) The flow rate of the mixture at the time of collision was 46
A dispersion was obtained and evaluated in the same manner as in Example 1 except that m / sec was used. Table 1 shows the dispersion particle size of each dispersion, 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 rate at the time of collision of the mixture was 72 m / sec. Was evaluated.
Table 1 shows the dispersion particle size of the dispersion, and Table 2 shows the characteristics of the photoreceptor.

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

In the coating film obtained by the dispersion circulated for 30 days, spots and spots were observed.

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

In the coating film obtained from the dispersion circulated for 30 days, spots and spots were observed.

[0055]

[Table 1]

[0056]

[Table 2] Table 2 shows that the electrophotographic photoreceptor prepared using the dispersion 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, the phthalocyanine pigment can be dispersed in uniform and stable fine particles efficiently without crystal conversion in a very short time,
It has excellent stability during circulation, so that no film defects occur when a film is formed. Further, the electrophotographic photoreceptor manufactured using the dispersion liquid dispersed by the dispersion method of the present invention can obtain a good image without image defects.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which a dispersion device used in the present invention is disassembled for each member.

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

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

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

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

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

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

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

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

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobuyuki Hami 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Junichi Kishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Hiroshi Aoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-4-337362 (JP, A) JP-A-1-177039 ( JP, A) JP-A-1-176434 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/00-5/16 C09B 67/20 C09B 67/50 C09B 67 / 46 B01F 5/00 B01F 13/00 B01F 15/00

Claims (4)

(57) [Claims] 1. A method for dispersing a phthalocyanine pigment, comprising a step of causing a mixture containing a phthalocyanine pigment and a dispersion medium to collide with each other 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 method according to claim 1, wherein the oxytitanium phthalocyanine crystal has a Bragg angle 2θ ± in X-ray diffraction of CuKα.
0.2 ° is 9.0 °, 14.2 °, 23.9 ° and 2
3. The phthalocyanine pigment dispersion method according to claim 2, wherein the phthalocyanine pigment is an oxytitanium phthalocyanine crystal having a strong peak at 7.1 °. 4. A method for producing an electrophotographic photoreceptor, comprising a step of forming a charge generation layer from a dispersion obtained by the dispersion method according to claim 1, 2, or 3.