JPH06345992A - Production of type x metal-free phthalocyanine - Google Patents

Abstract

PURPOSE:To produce a type X metal-free phthalocyanine which gives a coated member consisting of a support and a coating layer of, e.g. an electrophotographic photoreceptor having excellent characteristics and which gives a coating fluid used for producing the coated member and excellent in storage stability. CONSTITUTION:In this process for producing a type X metal-free phthalocyanine by dry milling an alpha-form metal-free phthalocyanine in a ball mill to transform to the type X crystal form, the dry milling is performed for more than twice the length of time from the initiation of dry milling to the saturation of the crystalline transition to the type X metal-free phthalocyanine to effect the production thereof. The extent of progress of the crystalline transition can be judged by sampling the powder with the elapse of time for observation of, e.g. the X-ray diffraction pattern and the infrared spectrum.

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 an X-type metal-free phthalocyanine, more specifically, it has excellent properties when used as a coated member such as an electrophotographic photoreceptor and is used for producing various coated members. The present invention relates to a method for producing an X-type metal-free phthalocyanine having excellent long-term storage stability of a coating liquid.

X-type metal-free phthalocyanine, which exhibits high photosensitivity from the visible light region to the near infrared region, is a photoelectric conversion element utilizing the photoelectric conversion action of a substance, such as a solar cell, a photosensor, an optical switching element, or an electrophotographic device. It can be effectively used as a photoactive substance in a photoconductor or the like, and in particular, it is being actively studied in recent years as a photosensitive pigment for an electrophotographic photoconductor.

[0003]

2. Description of the Related Art Various photoelectric conversion elements using a photoelectric conversion substance, particularly electrophotographic photoreceptors, have been conventionally used in Se, Se /
Inorganic materials such as Te, Se / As, CdS, Si and ZnO have been used, but none of them are sufficiently satisfactory in terms of the width of photosensitive wavelength range, safety, processability, and economical efficiency. It has been found that organic compounds of various chemical structures called organic photo-semiconductors (abbreviated as OPC) are excellent materials that supplement the drawbacks of inorganic substances, and many useful OPCs have been found. There are some that have been put to practical use.

Among them, phthalocyanines are one of the most excellent OPCs, and have a wide photosensitive wavelength range from the visible light region to the near infrared region, high photosensitivity, stability (durability),
It is famous for its outstanding features such as safety, coating / workability, and economic efficiency. For phthalocyanines, copper, vanadium, iron, cobalt, nickel, titanium, zirconium, indium, germanium, tin, lead, molybdenum,
Various metal phthalocyanines that form a complex salt with metal ions such as silicon, or metal-free phthalocyanines are known, and all are known as useful OPCs.

The present invention relates to a method for producing a metal-free phthalocyanine among phthalocyanines, and in particular, OP disclosed in, for example, Japanese Patent Publication No. 44-14106.
As C, an X-type metal-free phthalocyanine (X-form metal-containing phthalocyanine obtained by subjecting an α-type metal-free phthalocyanine having an extremely low activity to a crystalline form which is highly active and useful as a photoconductive material in electrophotography by mechanical treatment is used. High in the visible to near infrared region, such as those called metal-free phthalocyanine) or those of the same type as the X-type metal-free phthalocyanine described in JP-A-2-233769 (ie, X-type metal-free phthalocyanine). Although it is related to the method for producing metal-free phthalocyanine that exhibits photosensitivity, it exhibits excellent properties (for example, high photosensitivity, wide photosensitivity range, and small dark decay) when used for coated members such as electrophotographic photoconductors. It is not enough to do this, and it is not industrially applicable unless it causes trouble during the production of the coated member.

That is, a coated member such as an electrophotographic photosensitive member is usually a conductive support such as various metals, metal laminated films and papers, films and papers processed with a conductive agent, metal fiber mixed papers and nonwoven fabrics. It is manufactured by forming a coating layer in the form of a thin film on a flat plate as well as a curved plate. At this time, a pigment such as phthalocyanine may be formed into a thin film by a vapor deposition method, but the productivity is remarkably inferior, so at present, it is dispersed in an organic solvent together with a binder and other materials to form a coating liquid. , Coating on the support
It is usually dried.

The present invention relates to an electrophotographic photosensitive member in particular, and will be described in detail below. However, there are various structures, and when broadly classified, the phthalocyanine of the phthalocyanine is formed on a conductive support which may be provided with an anchor coat. Such a single layer structure in which a color material having a remarkable photoelectric conversion function (this is called a charge generation material CGM) and, if necessary, a charge transport material (called CTM) are dispersed in an insulating binder and coated Things and CGM
The present invention includes an X-type metal-free phthalocyanine suitable for use in electrophotographic photoreceptors of all structures, including those having a laminated structure in which layers and CTM layers are overcoated.

In electrophotography, electrostatic charge is charged in the dark on the electrophotographic photoreceptor layer, and then imagewise exposure is performed to increase the electric conductivity of the exposed portion to eliminate the charge. As a result, a latent image consisting of electrostatic charge is formed, and then a dry colored powder or suspension of colored powder called toner is brought into contact with it to obtain a visible image corresponding to the electrostatic latent image (development). The basics of

In order to obtain a good quality image, the surface of the coating layer is required to have high smoothness. Therefore, the pigment such as phthalocyanine in the coating liquid for producing the electrophotographic photosensitive layer is a fine powder having a size of a few μm or less, which is as close to a spherical shape as possible, and undergoes deterioration such as crystal growth or aggregation during storage of the coating liquid. Don't wake it up However, according to the experience of the present inventor, the coating liquid prepared by using the X-type metal-free phthalocyanine has a good liquidity as the coating liquid immediately after the preparation, and the electrophotographic photosensitive material coated / produced. Even if the body is not abnormal, when the coating liquid is stored for a long period of time, abnormal liquidity, especially abnormal increase in viscosity, pigment aggregation, poor dispersion, etc. may be observed and the product may become unusable (in that case , Crystal growth into needle-like crystals having a length of several μm or more is often observed by an electron microscope), and it is necessary to examine the countermeasure, and as a result of various experiments, the present invention was born. is there.

The metal-free phthalocyanine is an organic pigment exhibiting so-called polymorphism or polymorphism having various crystal structures, and the X-type metal-free phthalocyanine having a crystal structure exhibiting extremely high photosensitivity in electrophotography is For example, as described in JP-B-44-14106, the β type (most stable crystal structure) is first synthesized, and then the concentrated type sulfuric acid / water system reprecipitation treatment is performed to form the α type (most unstable crystal structure). It can be produced by transforming the crystal and finally converting the α-form metal-free phthalocyanine into the X-form (metastable crystal structure) by means such as mechanical milling treatment such as ball milling. And which crystal type is X
It can be determined by utilizing a line diffraction pattern or an infrared spectrum.

The present inventor, referring to the literature, first synthesizes β-type metal-free phthalocyanine, then transforms it into α-type by sulfuric acid / water reprecipitation treatment, and then as a mechanical grinding treatment method, dry milling with a ball mill. The crushing method was adopted. The degree of crystal transition from α-type to X-type was determined by sampling the required minimum amount of powder every predetermined time from the start of milling and utilizing the X-ray diffraction pattern and infrared spectrum. At the same time, a coating liquid was prepared for each sample, the viscosity was first measured, an electrophotographic photosensitive member was prepared on the same day, and the electrophotographic characteristic values were measured at a later date. Then, each coating liquid was tightly stoppered and stored in a constant dark place.

[0012] As a result, when the coating liquid is sufficiently converted to the X-type and the electrophotographic characteristics are good, the coating liquid after storage is remarkably thickened and deteriorated, and can no longer be used as a coating liquid. I experienced that.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coated member such as an electrophotographic photoreceptor having excellent characteristics, and to provide an X-type coating material having excellent storage stability of a coating liquid for producing the coated member. A method for producing a metal phthalocyanine is provided.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an X-type metal-free phthalocyanine which comprises crystallizing the α-form metal-free phthalocyanine by a ball mill dry milling process. It was solved by performing the ball mill dry milling treatment for a total time of more than twice the time from the start of the ball mill dry milling treatment to the time when the crystal transition to the X-type metal-free phthalocyanine reached saturation. It was Whether or not the transition reached saturation could be determined by X-ray diffraction or infrared spectrum.

In the α-type metal-free phthalocyanine, CuKα
In the X-ray diffraction pattern (CuKX-ray) for the X-ray of, the Bragg angle is around 2θ = 6.8 °, while for the X-type,
Since maximum intensity peaks are observed near θ = 7.6 °, the ratio of these peak intensities is an index of the α-type / X-type abundance ratio. In the infrared spectrum, 700
Several absorption peaks of 800 cm ^-1 from the (in α-type near 733cm ^-1, absorption peaks each specific around 754cm ^-1 in X type) significantly different at α type and X-type since the arrow tension α It gives an index of the degree of transition from type to type X. Therefore,
In the present invention, the degree of crystal transition to the X type was mainly determined by utilizing these spectra (whether the conversion from α type to X type is no longer saturated, even if the numerical values of these peak intensity ratios are exhausted). It is an index to know, not a quantitative analysis value).

As a conversion method from the α type to the X type, as described in the above-mentioned publicly known publications, a dry milling method by a ball mill (particularly, neat milling without a mixture) is considered in terms of cost and labor. But it is practical. In addition, JP-A-4-
No. 4264 describes the use of a planetary ball mill (hereinafter abbreviated as a planetary mill), but this is in principle the same crusher as a conventional ball mill, and the processing time for both rotation and revolution of the pot is combined. In the present invention, it is included in the ball mill since In addition, the temperature around the ball mill during the milling process did not need to be considered so much in the common living temperature range. Because during the grinding operation,
In a ball mill, especially in a planetary mill, the temperature in itself rises considerably, and the powder in the pot also rises in temperature accordingly.

Thus, the required minimum amount of the metal-free phthalocyanine powder is sampled with the lapse of time from the start of milling (eg, every 8 hours or 24 hours), and the degree of crystal transition from the α-type to the X-type is determined as X. It was judged by a line diffraction pattern, an infrared spectrum and the like. At the same time, a coating liquid was prepared for each sample, the viscosity at 20 ° C. was immediately measured using an E-type viscometer, an electrophotographic photosensitive member was prepared on the same day, and the electrophotographic characteristic values were measured at a later date. Then, each coating solution was sealed and stored in a constant dark place (≦ 25 ° C.), the viscosity and the like were measured at 1-week intervals, and it was visually observed whether the liquid was good or bad.

As a result, the conversion from α-type to X-type reached saturation, and the electrophotographic characteristic values were also good, not only the samples of the grinding time, but also the samples subjected to the grinding treatment for a longer time than the coating time. The liquid increased in viscosity after 1 week, and the viscosity increased further thereafter, and it was found that the blue pigment had agglomerated and separated from the vehicle (poor dispersion), and it could no longer be applied. It was However, in samples that were milled for more than twice the time required for reaching the crystal-type transition saturation, the coating liquid showed alterations such as thickening not only after 1 week but also after storage for several weeks. In addition, the electrophotographic photoreceptor prepared using the coating liquid after storage did not show any deterioration in the electrophotographic characteristics as well as the coated surface state.

As seen in the above Japanese Patent Publication No. 44-14106, etc., it is considered industrially customary to finish the milling treatment in the minimum time when it is judged that the conversion to the X-type is sufficient. To continue the milling process for a long time, which is more than twice as long, is, so to speak, insane,
For the first time in the present invention, it has been found that such a method is suitable for providing an X-type metal-free phthalocyanine pigment powder having excellent storage stability in coating liquid. The reason for this is considered to be that a mechanochemical decomposition reaction occurs slightly to generate a trace amount of impurities, which acts on the powder to prevent crystal growth.

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight unless otherwise specified.

Example 1 P. J. Brachy et al. (Journal of Heterocyclic Chemistry, Vol. 7, p. 1403, 19
The following operation was carried out using β-type metal-free phthalocyanine synthesized as a starting pigment with reference to 70 years edition).
100 parts of the pigment (β-type purple crystal) was gradually added to 2,000 parts of reagent grade sulfuric acid (concentration 97%) under cooling with an ice-water bath to dissolve, and filtered using a glass filter. This solution was added to 10,000 parts of distilled water while maintaining the temperature below 20 ° C.
The mixture was added dropwise over 0 minutes, and after stirring for a while, the mixture was allowed to stand overnight, the supernatant was removed by decantation, the precipitate was filtered off with suction, and the filter cake was washed with water until it became neutral, and further washed with water many times. Finally, after washing with methanol, dry at 70 ° C overnight or more to
92 parts of type metal-free phthalocyanine was obtained.

120 g of the α-type metal-free phthalocyanine obtained by the above method was added to an alumina pot (capacity: 2,000 m).
l) Alumina balls (diameter 20 mm) 2,000
Put 0g in a constant temperature room controlled at room temperature 40 ℃, 10
The ball milling process was started at a rotation speed of 0 revolutions / minute. Thereafter, in principle, the required minimum amount of pigment powder was sampled every day (24 hours), and the X-ray diffraction pattern and infrared absorption spectrum were measured. The milling process was performed for up to 35 days.

In the metal-free phthalocyanine before milling for 0 hour, that is, before milling, in the X-ray diffraction pattern using the X-ray corresponding to the wavelength of CuKα as the radiation source, the Bragg angle 2
θ = 6.80, 7.45, 13.67, 13.85, 1
4.98, 15.71, 16.18, 20.55, 2
2.13, 24.27, 26.68, 26.87, 2
7.05, 27.21, 27.38, 27.50, 2
A specific strong diffraction peak was observed at an error range of ± 0.2 ° at 7.62 °, and it was confirmed to be α type. In the infrared absorption spectrum, 765 (weak) per 700 cm ⁻¹ ,
Three absorption peaks peculiar to α-type were observed at 733 (strongest) and 713 cm ^-1 (strong). Milling process 8 days (8 x
24 hours), the Bragg angles 2θ = 7.60, 9.18, 11.24, X-ray diffraction pattern,
14.38, 15.24, 16.84, 17.37, 2
0.40, 20.89, 21.66, 22.30, 2
3.88, 26.25, 27.36, 28.63, 3
At 0.56 °, a strong diffraction peak specific to the X-type was observed within an error range of ± 0.2 degrees. However, 2θ = 6.82
Since a weak peak (shoulder) that may be due to untransferred α-type was observed at °, the ratio of the intensity to the peak intensity at 2θ = 7.60 ° was determined. The other sampling samples were similarly processed.

As a general rule, the pigment powder samples taken every day were prepared by coating a coating solution having the following composition to prepare an electrophotographic photoreceptor, and the electrophotographic characteristic values were measured. Metal-free phthalocyanine powder sample 1 part Acrylic copolymer (binder) 5 parts Dioxane (organic solvent) 80 parts Shaking these three with glass beads in a closed container for 2 hours using a paint conditioner. And the glass beads were removed by sieving to obtain a dark blue coating liquid. Immediately, the viscosity at 20 ° C. was measured using an E-type viscometer. In addition, each coating solution was applied onto an aluminum plate subjected to surface anodization treatment using a wire bar so that the solid coating amount after drying was 5 g / m ² , dried at 80 ° C., and then placed in a black bag. I put it in and left it for a day. The rest of the coating liquid was stored in a closed container in the dark at 25 ° C or lower.

Table 1 shows the data on the ball milling treatment time and the storage stability of the coating solution. From Table 1, the viscosity and the appearance of the coating solution are normal on the day of preparation regardless of the milling time, but the coating solution using the pigment powder having a milling time of 0 to 21 days is stored 3 to 4 weeks after storage. It can be seen that the storage stability of the coating solution is good only when the viscosity and the appearance become abnormal (thickening, aggregation, poor dispersion, etc.) and only when the grinding treatment is performed for 28 days or more.

The electrophotographic characteristics of the single-layer type electrophotosensitive material prepared by using the preparation coating liquid were measured by an electrostatic recording test apparatus (SP-428 manufactured by Kawaguchi Electric Co., Ltd.). Measurement conditions: Applied voltage + 6kV, light source tungsten
Lamp, sample surface illuminance 2 lux

Table 2 shows the intensity ratio of each peculiar peak in the X-ray diffraction pattern and the electrophotographic characteristic value at each grinding treatment time. In Table 2, I is the peak intensity, V ₀ (volt) is the initial potential, DD (%) is the surface potential residual percentage in the dark for 10 seconds, and E _1/2 (lux · second) is the potential half exposure amount.

[0028]

[Table 1] In Table 1, ◯ means good, Δ means slightly bad, and ● means bad.

[0029]

[Table 2]

From Table 2, 2θ = 6.
Intensity ratio of peaks near 8 ° and around 7.6 ° (I _6.8 ° /
It can be seen that I _7.6 °) becomes smaller with the lapse of time from the start of milling, but becomes almost constant after 8 to 9 days of milling, and the electrophotographic characteristics also become constant. So in this case,
It can be seen that the milling time at which the transition to Form X reaches saturation is 8 to 9 days. However, as can be seen from Table 1, the coating solution prepared by using the pigment powder having the milling time of 8 to 9 days has poor storage stability, and it is only after the milling treatment for 28 hours or more, A coating liquid with good storage stability can be obtained.

Example 2 15 g of α-type metal-free phthalocyanine obtained by the method described in Example 1 was placed in an agate pot (capacity 250 ml), 7 agate balls (diameter 20 mm) were added, and a planetary mill was used. Using P-5 (manufactured by Fritsch Japan), the disc was set at 360 rpm and the pot was set at 780 rpm, and the mixture was milled at room temperature (≤25 ° C). In principle, the minimum required amount of pigment powder was sampled at 8-hour intervals, and various measurements were performed in the same manner as in Example 1. Up to 1 grinding process
Up to 20 hours.

Table 3 shows the planetary mill grinding time and the viscosity of the coating solution prepared using each pigment powder sample and the results of visual evaluation after 4 weeks of storage on the day of preparation and in the dark at 25 ° C. or less. As shown, the viscosity on the day of preparation is low and the visual evaluation result is good, regardless of the length of time of grinding, but in many cases, the viscosity increases after 4 weeks of storage, and the visual evaluation result also becomes poor. Will continue. However, only the coating liquid prepared by using the powder sample milled for 72 hours or more maintains a good condition after 4 weeks of storage.

On the other hand, FT-of the powder sample at each grinding time
The absorbance ratio of two absorption peaks specific to α type and X type in the infrared spectrum (KBr tablet method) was determined. Then, a single-layer type electrophotographic photosensitive member was prepared in the same manner as in Example 1 using each preparation coating liquid, and electrophotographic characteristic values were measured by the same method. The results are summarized in Table 4.

[0034]

[Table 3] In Table 3, ◯ means good, Δ means slightly bad, and ● means bad.

[0035]

[Table 4]

In Table 4, the infrared spectrum 733
cm ^-1 and around 754cm absorbance ratio of a peak in the vicinity of ^-1 (A
bs. ₇₃₃ / Abs. ₇₅₄ ) decreases with the lapse of milling time, but after the milling time of 32 hours, it becomes almost constant, and the electrophotographic characteristics also become constant. Therefore, in this case, it can be seen that the transition saturation reaching milling time is 32 hours. However, as shown in Table 3, not only the grinding time of 32 hours,
The coating solution prepared using these pigment powders has a poor storage stability even after a longer period of time, and a coating solution having a good storage stability can be obtained only after milling for a long time of 72 hours or more. Was obtained.

Example 3 An electrophotographic photosensitive member was prepared by the method described above using the coating solution prepared in Examples 1 and 2 and stored for 4 weeks.
From the coating solution having a significantly increased viscosity, the leveling of the solution at the time of application was poor and only a badly coated surface with streaky coating unevenness was obtained, and therefore the measurement of electrophotographic characteristics was omitted. However,
Since a coating liquid having a normal coating surface was obtained from the coating liquid having good storage stability, the electrophotographic characteristic values were measured. The results are shown in Table 5.
Shown in.

[0038]

[Table 5]

From Table 5, a coating liquid having good storage stability (storage 4
The electrophotographic characteristic values of the coated members prepared after (a week later) showed no deterioration, even when compared with the values of the coated members prepared immediately after the preparation, and the storage stability of the electrophotographic characteristics was good. I know there is.

[0040]

INDUSTRIAL APPLICABILITY In the method for producing X-type metal-free phthalocyanine by ball mill dry milling of α-form metal-free phthalocyanine, it is sufficient to start dry milling and to reach the saturation of crystal transition to X-type metal-free phthalocyanine. Until time of
When the milling is performed for a total time of more than 2 times, X which is excellent in characteristics when used for a coated member such as an electrophotographic photoreceptor and is excellent in storage stability of the coating liquid for producing the coated member. A type metal-free phthalocyanine can be produced. Then, the degree of progress of crystal transition can be determined by utilizing a measuring means such as an X-ray diffraction pattern or an infrared spectrum.

Claims (1)

[Claims] 1. A crystal form transition of α-type metal-free phthalocyanine by a ball mill dry milling process.
In the method for producing type-metal-free phthalocyanine, the total time that exceeds twice the time from the time when the ball mill dry milling process of α-type metal-free phthalocyanine is started to the point when the crystal transition to X-type metal-free phthalocyanine reaches saturation. X is characterized by performing ball mill dry grinding treatment over time, X
Method for producing type metal-free phthalocyanine.