JPH0995623A - Titanyl phthalocyanine particle and its production and photoreceptor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a titanyl phthalocyanine particle, having a specific crystal structure and a specified specific surface area, capable of reducing the temperature dependence of sensitivity with a high sensitivity when used for electrophotography and useful as electrophotographic photoreceptors. SOLUTION: This titanyl phthalocyanine particle has the maximum peak at 27.2 deg. Bragg angle (2θ±0.2 deg.) in X-diffractometry with Cu-Kα radiations and, as necessary, further peaks at 9.6 deg. and 24.1 deg. and the BET specific surface area regulated to <=22m<2> /g. The particle obtained by preparing diiminoindoline from phthalonitrile and ammonia, reacting the resultant diiminoindoline with an alkoxy titanate, etc., at a low temperature, etc., dissolving the prepared crude pigment in sulfuric acid, pouring the solution into water, then carrying out the freezing treatment of the prepared hydrous paste, affording an α type crystalline powder and treating the resultant powder with an organic solvent in the presence of water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phthalocyanine known as a blue pigment, and more particularly to an electrophotographic photoreceptor using titanyl phthalocyanine pigment particles.

[0002]

2. Description of the Related Art Phthalocyanine pigments were introduced in 1907 by Bra.
It was discovered by un. Then, the structure determination (R.
P. Linstead; J. C. S. , 1016, 19
After a number of studies such as 34), copper phthalocyanine was put on the market by ICI in 1935. Since then, it has been used as a pigment having weather resistance and robustness for kneading into inks and polymers.

On the other hand, the principle of electrophotography was invented by Carlson in 1938, and a copying machine using a selenium photoconductor was announced in 1950, and is now an essential item for offices.

Since then, inorganic materials such as selenium have been widely used as photoconductors in electrophotographic copying machines. However, in recent years, with the development of electronic technology, electrophotography has often been used as an image forming unit of a laser printer.

As a photosensitive material for a laser printer, a material sensitive to the near infrared region, which is the oscillation wavelength of a semiconductor laser as a light source, is required. Therefore, blue photosensitive pigments have been demanded, and phthalocyanines have been attracting attention as well as squarylium pigments and trisazo pigments.

Phthalocyanines have been attracting attention for their photocurrent characteristics (Eley, DD, Natu).
Re, 162, 819 1948), the encounter with electrophotography is old, and it was announced in 1964 that it exhibits excellent properties as a photoreceptor for electrophotography in the state of dispersed pigments, which is now the mainstream. It is (USP 3816
No. 118).

Among the phthalocyanines, the X type (Japanese Patent Publication No.
9-4338) and τ type metal-free phthalocyanine, ε
Type copper phthalocyanine and the like are known, but in recent years, titanyl phthalocyanine has attracted attention because of its high sensitivity, and among them, Y type crystals show excellent properties (Kinoshita, Japan.
Hard Copy 89 'Proceedings 103 198
7).

The Y-type crystal has a maximum peak at 27.2 ° in a Bragg 2θ range of ± 0.2 ° in Cu-Kα X-ray diffraction and a strong peak at 9.6 ° and 24.1 °. And has water reversibly inside the crystal. This crystal is a Sanyo dye (JP-A-63-203).
65) and its existence was clarified, and its application to electrophotography was announced by Konica (Japanese Patent Laid-Open No. 64-17066). In particular, highly purified chlorine-free Y-type titanyl phthalocyanine has a photon efficiency of 0.94, which is an astonishing value. Several studies have been conducted on the cause of this high sensitivity, and it is reported that the J-type aggregate structure and water inside the crystal help dissociate the photocharge (Fujimaki, IS &T's 7th Internationala.
L Congress Proceedings 269, 1991).
The Y-type crystal can be obtained by treating an α-type crystal (also known as low-crystalline α-type or amorphous) obtained by acid paste treatment with an organic solvent in the presence of water. A wide range of organic solvents can be selected as long as water coexists, and aromatic compounds (JP-A-63-20365), tetrahydrofuran (JP-A-2-28265), halogenated hydrocarbons (JP-A-3-35064), A wide variety of ketones and esters (JP-A-4-224872). This indicates the importance of the presence of water in Y-type crystal formation.

However, the presence of water, which is one of the causes of high sensitivity, leads to the fact that the photosensitivity is highly dependent on humidity. The decrease in sensitivity under low humidity was a major problem with Y-type crystals. Inclusion of alkylene diols in the photoconductor as a moisturizer (Japanese Patent Laid-Open No. 5-313389) makes a considerable improvement, but is not sufficient.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Y-type titanyl phthalocyanine (hereinafter sometimes abbreviated as TiOPc) crystal which has high sensitivity for use in electrophotography and has little humidity dependency of sensitivity. Especially.

[0011]

The object of the present invention is attained by adopting one of the following constitutions.

[1] Titanyl phthalocyanine particles having a maximum peak at a Bragg angle 2θ ± 0.2 ° of 27.2 ° in Cu-Kα X-ray diffraction and a BET specific surface area of 22 m ² / g or less.

[2] The Bragg angle 2θ ± 0.2 ° in X-ray diffraction of Cu-Kα has a maximum peak at 27.2 °, and also has peaks at 9.6 ° and 24.1 °. And titanyl phthalocyanine particles having a BET specific surface area of 22 m ² / g or less.

[3] The pigment is dissolved in sulfuric acid and poured into water,
Next, the method for producing titanyl phthalocyanine particles according to claim 1, wherein the α-type crystal powder obtained by freezing the water-containing paste is treated with an organic solvent in the presence of water.

[4] An electrophotographic photoreceptor containing the titanyl phthalocyanine particles according to claim 1, 2 or 3.

The measurement by the BET method determines the surface area from the amount of gas (nitrogen) physically adsorbed on the surface of a solid.
It is possible to obtain the size of the primary particles without dispersing them to the stage of the primary particles. Specifically, for example, a flow type automatic specific surface area measuring device (Micromeritics Flow Soap)
BET specific surface area can be measured by Shimadzu Corporation.

As a result of investigations, the present inventors have found that a Y-type titanyl phthalocyanine having a specific surface area of 22 m ² / g or less by the BET method can achieve the object, and arrived at the present invention.

That is, as a Y-type crystal, 35 m ² /
g or more is known (Japanese Patent Laid-Open No. 4-198367),
It was said to have good dispersibility. The present invention is very different from the above and found that those having a viscosity of 22 m ² / g or less have little humidity dependency of photosensitivity.

It is not clear why the Y-type titanyl phthalocyanine particles having this property have improved humidity dependency as compared with conventional particles, but the author has a large particle size (small surface area) and It is considered to be related to the fact that water molecules inside the crystal are effectively kept. However, too large a particle size has a problem that the resolution is deteriorated and image defects are likely to occur, so that the BET specific surface area is 2 m ²
/ G or more.

The inventors of the present invention have aimed to obtain an α-form (hydrated paste), which is an acid paste before the Y-form crystal, by subjecting it to a freezing treatment, rather than treating it with an organic solvent as a paste as in the conventional formulation. BET specific surface area 2
It has been found to obtain particles of 2 m ² / g or less. It is considered that the titanyl phthalocyanine particles were aggregated by the pressure of the ice crystals that grew by the freezing treatment, and as a result, the particle size of the Y-shaped particles that had undergone this step was increased. From the conventional common general knowledge, it is feared that if the particle size is large, poor dispersion may occur, resulting in an image defect when the electrophotographic photoreceptor is formed.

However, at least in the range of the present invention, the particle size does not become hard even if the particle size becomes large, and even when it is easily dispersed into an electrophotographic photosensitive member, it does not appear as an image defect. The frozen low-crystallinity α-type particles of the present invention may be redispersed in water and subsequently treated with an organic solvent, or may be added as a dry powder directly to a mixed liquid of water and an organic solvent. . Both give Y-type crystals.

The method for producing the Y-type titanyl phthalocyanine of the present invention will be described in detail.

As described above, the Y-type titanyl phthalocyanine of the present invention comprises three steps of the crude product synthesis, the acid paste step, and the crystal conversion step.

Crude Synthesis The crude titanyl phthalocyanine used in the present invention can be obtained by heating phthalonitrile and titanium halide as is usually done. It can also be obtained by producing diiminoisoindoline from phthalonitrile and ammonia and reacting it with another titanium compound such as alkoxy titanate at a low temperature. The former method is inexpensive but requires equipment to withstand high temperatures (180-250 ° C.) and acid gases. In addition, some halogenated impurities are contained in a chlorine content of about 0.5%. On the other hand, the latter increases the number of processes by one step, so that the raw material cost increases, but the reaction temperature can be lower than that of the former (120 to 200 ° C.), no acid gas is generated, and no special device is required. Above all, halogenated impurities do not form as by-products, and the electrophotographic photosensitive member made of Y-type titanyl phthalocyanine using this as a raw material exhibits extremely high sensitivity.

Acid Paste Step This is a step of dissolving the obtained crude product in sulfuric acid and pouring it into water to make it amorphous. To be precise, even if it is called amorphous, it should be called a low crystalline α type, and the lower the water temperature, the more the amorphous property increases, the higher the water temperature, and the more the stagnation time before washing, the more the α type develops. It is better to have an α-type property to make a Y-type, and the water temperature is usually 15 to 35 ° C. The volume ratio of sulfuric acid / water is 1/10 to 1 /
About 30 is normal. Washing and filtration are repeated to obtain a wet paste of titanyl phthalocyanine. In the conventional production of Y-type titanyl phthalocyanine, the obtained wet paste is directly or heat-dried, and the resulting powder is subjected to the next step of crystal transformation. In the present invention, the paste is used after freezing. For the freezing treatment, a dedicated freeze-drying device may be used. Alternatively, the powder may be simply frozen using a normal freezer, thawed, filtered, and then dried to obtain a powder. The paste immediately after the acid paste treatment contains 7 to 10 times its own weight of water, but after freezing it has a weight of 3 to 4 times its own weight.
It contains only twice the amount of water, and when thawed, the water separates.

Crystal Conversion Step For the final crystal conversion step, a conventionally known Y-type synthesis method can be used. That is, the α-type crystal (low-crystalline α-type) obtained through the acid paste treatment and the freeze-drying step is treated with an organic solvent in the presence of water. The organic solvent can be selected from a wide range, and is aromatic (JP-A-63-20365), tetrahydrofuran (JP-A-2-28265), halogenated hydrocarbon (JP-A-3-35064), ketone or ester (particularly). No. Hei 4-224872).

The mechanical conditions of the treatment can be any method from ordinary gentle stirring to a method of adding mechanical shear with a sand grinder or the like. The temperature may be any temperature at which water is a liquid, and can be selected from 0 to 100 ° C.

When the Y-type titanyl phthalocyanine of the present invention is used as an electrophotographic photosensitive member, it can be used in all the conventionally known techniques. That is, a photosensitive layer containing the Y-type titanyl phthalocyanine of the present invention and having a thickness of 10 to 40 μm after drying is provided on a conductive substrate obtained by vapor-depositing a metal on an aluminum drum or a plastic sheet. The photosensitive layer may be a single layer or a laminated photoreceptor in which the carrier generation layer (CGL) and the carrier transport layer (CTL) are functionally separated. The Y-type titanyl phthalocyanine of the present invention is added to the carrier generation layer alone or together with a binder. The film thickness is usually 0.2 to 2.0 μm, and the binder / pigment weight ratio is 0 to 3.

In a usual negatively charged photoreceptor, an amine compound having a hole-transporting ability, such as hydrazone, pyrazoline, benzidine, and styryl compound, can be used as a carrier-transporting material in the carrier-transporting layer. Of these, particularly excellent are those having a triphenylamine structure in the molecule. The Y-type titanyl phthalocyanine of the present invention is used as a carrier-generating substance (CGM), but other known CGMs such as a metal-free phthalocyanine pigment, an azo pigment, and a condensed polycyclic pigment may be used in combination.

Further, a hindered amine compound, a hindered phenol compound or the like generally known as an antioxidant may be added to the electrophotographic photosensitive member for the purpose of improving the repeating characteristics.

An intermediate layer may be provided between the conductive substrate and the carrier generation layer for the purpose of improving the adhesiveness and preventing image defects. As the material for the intermediate layer, a resin such as polyamide or polybutyral, as well as a zirconium alkoxide, or a metal alkoxide known as a metal coupling agent, such as alkoxy titanate, which gives a polymer by hydrolysis can be used.

[0032]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1 1,3-Diiminoisoindoline (29.3 g) was dispersed in ortho-dichlorobenzene (200 ml), titanium tetrabutoxide (20.4 g) was added, and the mixture was mixed in a nitrogen atmosphere at 1 g.
Heated at 45-155 ° C for 5 hours. After cooling, the precipitated crystals were filtered, washed with chloroform, washed with 2% aqueous hydrochloric acid solution, washed with water, washed with methanol and dried to obtain 26.2 g of crude titanyl phthalocyanine. Figure 1 shows the crystal form of this product.
Shown in This is an A-type (JP-A-62-67094) crystal.

Then, this crude titanyl phthalocyanine 2
0.5 g is dissolved by stirring in 200 ml of concentrated sulfuric acid at 5 ° C. or lower for 1 hour, and this is poured into 4 l of water at 20 ° C. (acid paste treatment). The precipitated crystals were filtered and thoroughly washed with water to obtain 180 g of wet paste. This paste was put in a freezer at -15 ° C to be frozen. Then, after returning this to room temperature and thawing, a little water is separated. This was filtered and the solid content was dried by heating to obtain the freeze-dried low crystalline TiOPc powder of the present invention. The crystal form of this product is shown in FIG. We call this amorphous for convenience, but it is an α-type crystal although its crystallinity is low (JP-A-61-239).
248 technology).

Ortho-dichlorobenzene 250 in a flask
ml and water 250 ml were mixed, and 18.0 g of the above freeze-dried α-type TiOPc powder was added to the mixture under stirring. After the addition, the mixture was further stirred at room temperature for 30 minutes, then heated to 60 ° C. and stirred for 6 hours. After allowing to cool, it was poured into a large amount of methanol and the precipitated crystals were filtered and washed with methanol to obtain Y-type titanyl phthalocyanine. Figure 3 shows the crystal form of this product.
Shown in When the BET specific surface area was measured by a flow type automatic specific surface area measuring device (Micromeritics Flow Soap Model Shimadzu Corporation), it was 16.5 m ² / g.

Example 2 Acid paste treatment was carried out in the same manner as in Example 1,
180 g of the freeze-treated wet paste was obtained (solid content: 20 g, balance: water). This was thawed and diluted with 90 ml of water without drying to obtain an aqueous suspension. 250 ml of orthodichlorobenzene was added to this with stirring. The mixture was further stirred at room temperature for 30 minutes, then heated to 60 ° C. and stirred for 6 hours. After allowing to cool, it was poured into a large amount of methanol and the precipitated crystals were filtered and washed with methanol to obtain Y-type titanyl phthalocyanine. The crystal form of this product is shown in FIG. BE
The T specific surface area was 17.1 m ² / g.

Comparative Example 1 180 g (solid content 20) of the wet paste of the above example
g, 160 g of water) were directly added to a mixed solution of 250 ml of orthodichlorobenzene and 90 ml of water without freezing. After charging, stir at room temperature for another 30 minutes, then at 60 ° C
And stirred for 6 hours. After allowing to cool, the mixture was poured into a large amount of methanol, and the precipitated crystals were filtered and washed with methanol to obtain a conventional Y-type titanyl phthalocyanine. The crystal form of this product is shown in FIG. 4 (spectral difference with the crystal of Example 2 is not observed). The BET specific surface area was measured. It was 24.6 m ² / g.

Y-type TiO that has undergone the intermediate freezing process of the present invention
In order to show the industrial effectiveness of Pc, an application example used for an electrophotographic photoreceptor is shown.

Application Example 1 1 part of Y-type TiOPc obtained by freezing the intermediate obtained in Example 1, 10 parts by weight of methoxymethylpentanone, 80 parts by weight of t-butyl acetate, silicone resin (“KR5240” manufactured by Shin-Etsu Chemical Co., Ltd.) 0 0.7 parts by weight, 1.4-butanediol 0.5
Parts by weight were added and dispersed using a sand mill. On the other hand, a polyamide base “CM8000” (manufactured by Toray Industries, Inc.) was applied to a polyester base on which aluminum was vapor-deposited by applying a wire bar to form an undercoat layer having a thickness of 0.3 μm, and then the obtained dispersion was applied to the wire bar. The carrier generation layer was 0.2 μm thick. Then, the carrier transport material (A-
1) 1 part and polycarbonate resin "Iupilon Z20"
0 "(Mitsubishi Gas Chemical Co., Ltd.) and a trace amount of silicone oil" KF54 "(Shin-Etsu Chemical Co., Ltd.) dissolved in 10 parts by weight of 1.2-dichloroethane are blade-coated to form a carrier transport layer having a thickness of 20 μm. I made a photoconductor sheet.

[0040]

Embedded image

Application Example 2 Y-type Ti obtained by freeze-drying the intermediate in Application Example 1 above
A photoconductor sheet was prepared in the same manner as in Application Example 1 except that Y-type TiOPc, which was the intermediate frozen product prepared in Example 2, was replaced with OPc.

COMPARATIVE APPLICATION EXAMPLE 2 In the above-mentioned application example, the intermediate type frozen Y-type TiOPc
Instead of the conventional formulation of Y-type TiOPc obtained in Comparative Example, a photoconductor sheet was prepared in the same manner as in Application Example 1.

Evaluation After mounting the obtained photoreceptor on an aluminum drum, 20
"Konica 9028" under the environment of 50 ℃ and 50% RH
(Using a semiconductor laser light source with a light emission wavelength of 780 nm manufactured by Konica Corporation) Installed in a modified machine, the grid voltage Vc is -600
After adjusting to V, the unexposed potential Vh and the potential Vl of the exposed portion at the time of light irradiation of 0.7 mW were measured. Also 10 ℃, 20
After being transferred to an environment of% RH and sufficiently adapted to the environment (left standing for 24 hours), Vh and Vl were measured under the above-mentioned conditions.

20 ° C., 50% RH 10 ° C., 20% RH Vh Vl Vh Vl Application Example 1 -598V -40V -601V -49V Application Example 2 -598V -40V -601V -48V Comparative Application Example 1 -596V -41V- 602V-57V The photoconductors of Application Examples 1 and 2 using the Y-type TiOPc that has been subjected to the intermediate freezing treatment of the present invention have good sensitivity, and the sensitivity decrease under low temperature and low humidity is lower than that of the conventional product (Comparative Application Example 1). It is at half the level that is practically no problem. Since the application examples 1 and 2 have the same BET specific surface area value and electrophotographic performance within the error range, the property of TiOPc is determined by the freezing treatment.
Obviously it is not dry.

[0045]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a Y-type titanyl phthalocyanine crystal having high sensitivity when used in electrophotography and having little humidity dependency of sensitivity.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction spectrum diagram of titanyl phthalocyanine (A type).

FIG. 2 is an X-ray diffraction spectrum diagram of titanyl phthalocyanine (α type).

FIG. 3 is an X-ray diffraction spectrum diagram of titanyl phthalocyanine (Y type).

FIG. 4 is an X-ray diffraction spectrum diagram of titanyl phthalocyanine (Y type).

Claims (4)

[Claims] 1. Titanyl phthalocyanine particles having a maximum peak at a Bragg angle 2θ ± 0.2 ° of 27.2 ° in Cu-Kα X-ray diffraction and a BET specific surface area of 22 m ² / g or less. 2. A Bragg angle 2θ ± 0.2 ° in X-ray diffraction of Cu-Kα has a maximum peak at 27.2 °, and also has peaks at 9.6 ° and 24.1 °. And BE
Titanyl phthalocyanine particles having a T specific surface area of 22 m ² / g or less. 3. The method according to claim 1, wherein the pigment is dissolved in sulfuric acid and poured into water, and the α-type crystal powder obtained by freezing the hydrous paste is treated with an organic solvent in the presence of water. For producing titanyl phthalocyanine particles. 4. An electrophotographic photosensitive member comprising the titanyl phthalocyanine particles according to claim 1, 2 or 3.