JPH0688035A - Production of bisazo pigment and electrophotographic photoreceptor containing the same - Google Patents

Abstract

PURPOSE:To obtain an asymmetrical bisayo pigment excellent in electrophotographic characteristics in high yields by using a number of specified couplers under specified conditions in the coupling reaction in which the diazo component is a bis (diazonium) salt. CONSTITUTION:The pigment is prepared by using 1.8-2.2mol, per mol of the bis (diazonium) salt, mixture of couplers of formulas II and III in a molar ratio of the coupler of formula I to the couplers of formulas I and II of 0.5-0.9 in a coupling reaction in which the diazo component is a bis (diazonium) salt of formula I (wherein X is an anionic functional group).

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 bisazo pigment used in an electrophotographic photoreceptor or a photoelectric conversion element.

[0002]

2. Description of the Related Art In recent years, many electrophotographic photoreceptors using organic substances have been proposed, and various organic substances have been put to practical use. Among them, many bisazo pigments have excellent properties as charge generation materials.

Bisazo pigments are generally obtained by a coupling reaction of 1 mol of a bis (diazonium) salt and 2 mol of the same coupler. On the other hand, asymmetric bisazo dyes having different couplers among benzidine dyes are known (Yutaka Hosoda: Dye Chemistry, Gihodo (P183)). This utilizes the fact that the coupling speed of one of the bis (diazonium) salts is higher than that of the second one, and Japanese Patent Application No. 03-188716 was also based on this idea. According to Japanese Patent Application No. 03-188716 (see the publication), an asymmetric bisazo pigment has higher sensitivity than a symmetrical bisazo pigment or a mixture of symmetrical bisazo pigments.

In the bisazo pigment described in the above-mentioned Japanese Patent Application No. 03-188716, isolation of the monoazo compound at the time of completion of the first-stage coupling in the production of the bisazo pigment improves the stability of the diazonium salt. Since it is extremely difficult to consider, it results in a mixture of symmetrical and asymmetrical bisazo pigments. However, it cannot be said that the method for producing an asymmetric bisazo pigment is sufficiently studied in the publication.

[0005]

The object of the present invention is to obtain a process for the production of asymmetric bisazo pigments having a high degree of electrophotographic properties.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to a method for producing an asymmetric bisazo pigment, and as a result, when the coupling order of different coupler species and the coupler ratio at this time were changed, and when different coupler species were used. In the present invention, it was discovered that the bisazo pigment obtained under certain specific reaction conditions has excellent electrophotographic characteristics, such as when the coupler ratio is changed when the coupling is carried out in the homogeneous mixture system of I arrived.

That is, according to the present invention, in the coupling reaction using the bis (diazonium) salt represented by the general formula (I) as the diazo component, 1 mol of the bis (diazonium) salt is used for 1 mole of the formula (Ar ¹ -H). ) And (Ar ² —H) are used in the amount of 1.8 to 2.2 mol, and the molar ratio of the coupler is (Ar ¹ -H) / ((Ar ¹ -H) + (Ar ^2- ).
H)) is greater than 0.5 and less than 0.9 is provided.

[0008]

[Chemical 1]

[0009]

[Chemical 2]

[0010]

[Chemical 3]

The bisazo pigment synthesized in the present invention refers to a mixture of bisazo pigments represented by the following formulas (II-1), (II-2) and (II-3).

[0012]

[Chemical 4]

[0013]

[Chemical 5]

[0014]

[Chemical 6]

That is, when the coupler of formula (Ar ¹ -H) is coupled first, a monoazo pigment is first produced,
A partially symmetrical bisazo pigment (II-2) is also produced as a by-product. Furthermore, by adding a coupler of the formula (Ar ² —H) together with the asymmetric bisazo pigment (II-1), a partially symmetric bisazo pigment (II-
It seems that 3) is a byproduct. Also, when coupling is performed in a coupler homogeneous mixing system, the same formulas II-1, II-2, II-3 are used.
A mixture of each bisazo pigment of is obtained. The production ratio of these bisazo pigments (formula II-1, II-2, II-3) slightly changes depending on the reaction conditions, which results in a large difference in electrophotographic properties.

Although it is easily assumed that the electrophotographic characteristics are changed by changing the composition ratio of different coupler species, in the pigment mixture of the present invention, the coupler molar ratio (Ar ¹ -H) / ((Ar ^{1 -H) + (Ar 2 -H} ))
If the reaction is carried out at a ratio of more than 0.5 and less than 0.9, satisfactory photoreceptor characteristics can be obtained.

More particularly, the molar ratio of the coupler (Ar ^1-
H) / ((Ar ¹ -H) + (Ar ² -H)) is in the vicinity of 0.5 to 0.6, first the coupler of the formula (Ar ¹ -H) is added, and then the formula (Ar ² -H) The method in which a coupler is added exhibits higher sensitivity than the case where coupling is performed in the reverse order of addition or in a homogeneous mixture system. On the other hand, the synthesis yield increases as the proportion of the coupler of the formula (Ar ¹ -H) increases and the reaction in the homogeneous mixture system becomes higher.

In other words, in the present invention, by arranging the molar ratio of the coupler and the order of addition of the coupler to be specific, a synthesis with a high yield and high sensitivity can be obtained as compared with the method of Japanese Patent Application No. 03-188716. A method is provided.

The method for producing the bisazo pigment according to the present invention will be described more specifically. One of the different couplers, together with a bis (diazonium) salt represented by the general formula (I),
Dissolve in an organic solvent such as N-dimethylformamide (hereinafter referred to as DMF) and dimethylsulfoxide, and then dissolve at room temperature for 10
After stirring for -60 minutes, preferably 10-30 minutes, a solution of another coupler as a powder or dissolved in the above organic solvent is added thereto all at once. Then about -10 to 4
The pigment may be formed by dropping an aqueous alkali solution such as an aqueous solution of sodium acetate or an organic base at a temperature of 0 ° C. The reaction is completed in 5 minutes to 3 hours. After the completion of the reaction, the formed precipitate is collected by filtration and purified by an appropriate method, for example, washing with water or an organic solvent, recrystallization and the like to obtain a bisazo pigment. Further, in a homogeneous mixture system, two kinds of couplers may be dissolved in the above organic solvent together with a bis (diazonium) salt, and then a coupling reaction may be carried out in the same manner as above.

Next, a case of producing an electrophotographic photosensitive member using the bisazo pigment obtained by the production method of the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view of a typical example of the photosensitive member according to the present invention, in which 1 is a conductive support, 2 is a photosensitive layer, 3 is a charge carrying layer, and 4 is a charge generating layer. FIG. 4 shows a photosensitive layer (2) in which a charge generating material is mainly dispersed on a conductive support.
Is provided. In addition to this, various intermediate layers may be provided to stabilize the charging property or improve wear resistance.

The thickness of the charge carrier layer 3 in FIG.
Suitably the amount of charge transport material in the charge transport layer 3 at 0 micron, preferably 10 to 20 microns is 10 to 95% by weight, preferably 30 to 90% by weight. The thickness of the charge generating layer 4 is 5 μm or less, preferably 2 μm or less, and the amount of the charge generating material is 10 to 100%, preferably 50 to 90% by weight. The film thickness of the photosensitive layer in FIG. 4 is 5 to 50 μm, preferably 15 to 30 μm.

In the production of any of these photoconductors, a metal plate or metal foil such as aluminum, a plastic film on which a metal such as aluminum is vapor-deposited, or a paper which has been subjected to a conductive treatment is used as the conductive support 1. Used.

The charge carrier material in the present invention is not limited to a particular one. For example, benzidine compounds such as Japanese Patent Publication No. 58-32372, biphenylylamine compounds such as JP-A No. 1-178669, triarylamine compounds such as Japanese Patent Application No. 1-77839, and Japanese Patent Application No. 64-566. Ethylene compounds, distyrylbenzene compounds such as Japanese Patent Application Nos. 62-98394 and 56-29245, styrylpyrene compounds such as Japanese Patent Application No. 2-94812, JP-A-55-139066 and JP-A 52-139065 and other oxadiazole compounds, hydrazone compounds such as JP-A-55-154955, JP-A-55-156954, JP-A-55-52063 and JP-A-56-81850, No. 52-128373, arylidene fluorene compounds, JP-A-58-198425, JP-A-57-73075
No. stilbene system, JP-A-55-88064, JP-A-49-105
Pyrazoline compounds such as 537, JP-B-45-555, JP-B
51-10983, JP-A-55-108667 and other polyarylalkane compounds, JP-A-51-94829 and JP-A-51-98260, styrylanthracene compounds, and JP-A-58-58552. Examples include carbazole compounds.

As the charge generating material, not only the bisazo pigment produced according to the present invention but also the following charge generating materials may be used in combination. CI Pigment Blue 25 (Color Index Cl 21180), CI Pigment Red 41 (Cl 21200), CI Eye Acid Red 52 (Cl 45100), CI Eye Basic Red 3 (Cl 45210), an azo pigment having a carbazole skeleton (Japanese Patent Laid-Open No. 52- 95033), an azo pigment having a distyrylbenzene skeleton (see JP-A-53-133444), an azo pigment having a triphenylamine skeleton (see JP-A-53-132347), and a dibenzothiophene skeleton. Azo pigments (see JP-A-54-21728), azo pigments having an oxadiazole skeleton (see JP-A-54-12742), and azo pigments having a fluorenone skeleton (JP-A-54-12728).
54-22834), azo pigments having a bisstilbene skeleton (see JP-A-54-17733), azo pigments having a distyryl oxadiazole skeleton (see JP-A-54-2129), and CI Pigment Blue 16 (Cl
74100) and other phthalocyanine-based pigments, CI Bad Brown 5 (Cl 73410), CI Bad Dye (C
73030) and other indigo pigments, Argos Scarlet B (manufactured by Bayer), Indanth Scarlet R
(Made by Bayer Co.) and the like perylene pigments.

[0026]

The present invention will be described in more detail with reference to the following examples.

Example 1 3.725 g (12.5 mmol) of 2-hydroxy-3-naphthoic acid-0-chloroanilide (hereinafter referred to as (Ar ¹ -H)) and 2-hydroxy-3
- naphthoic acid -m- methylanilide (hereinafter (Ar ² -
H)) 2.078 g (7.5 mmol) of DMF 800 m
It was dissolved in 1, and 9-fluorenone-2,7-bis (diazonium tetrafluoroborate) 4.08 g (10
Mmol), to which sodium acetate trihydrate was added.
A solution prepared by dissolving 5.44 g (40 mmol) in 30 ml of water was added to 2
The mixture was added dropwise at 8 ° C or lower over 20 minutes. Then at room temperature 2
After stirring for a time, the generated crystals were filtered. DM this crude product
The mixture was stirred with 800 ml of F at 80 ° C. for 2 hours and filtered. After performing this washing operation three times, stirring and washing with 800 ml of water twice, and heating and drying under reduced pressure, 6.53 g of bluish black powder (yield 8
0.4%) was obtained. Elemental analysis value (%) Actual measurement value (C ₄₇ H ₂₈ N ₆
O ₅ Cl ₂ : C ₄₉ H ₃₄ N ₆ O ₅ = 5: 3):
It shows in Table 1.

[Examples 2 to 3] Molar ratio (Ar ¹ -H) /
A bluish black powder was obtained by the same treatment as in Example 1 except that ((Ar ¹ -H) + (Ar ² -H)) was changed to 0.75 and 0.875.

Example 4 Coupler (Ar ¹ -H) 1.5
67 g (5.263 mmol) was dissolved in 200 ml DMF and 2.04 g (5 mmol) of the bis (diazonium) salt of Example 1 was dissolved.
Was added and stirred at room temperature for 10 minutes. Thereafter, 1.313 g (4.737 mmol) of the coupler (Ar ² —H) was added to DMF20.
A solution dissolved in 0 ml was added at once. 2.72 g (20 mmol) of sodium acetate trihydrate was added to 15 m of water.
The liquid dissolved in 1 was added dropwise at 28 ° C. or lower over 20 minutes. Then, it stirred at room temperature for 2 hours, and formed crystals were filtered. The crude product was stirred with 400 ml of DMF at 80 ° C. for 2 hours and filtered. After performing this washing operation 3 times, water 4
The mixture was stirred and washed twice with 00 ml and dried by heating under reduced pressure to obtain 2.99 g (yield 74.0%) of bluish black powder. Elemental analysis value (%) Actual value (C ₄₇ H ₂₈ N ₆ O ₅ Cl ₂ : C ₄₉ H ₃₄ N ₆ O ₅
= Calculated value as 10: 9): shown in Table 1.

[Examples 5 to 6] Molar ratio (Ar ¹ -H) /
A bluish black powder was obtained by the same treatment as in Example 4 except that ((Ar ¹ -H) + (Ar ² -H)) was changed to 0.625 and 0.75.

[Example 7] Molar ratio (Ar ¹ -H) /
Example 4 except that ((Ar ¹ -H) + (Ar ² -H)) was changed to 0.625 and the coupler addition order was first (Ar ² -H) and then (Ar ¹ -H). The same treatment as described above was performed to obtain a bluish black powder.

[Comparative Examples 1 and 2] Molar ratio (Ar ¹ -H) /
A bluish black powder was obtained in the same manner as in Example 1 except that ((Ar ¹ -H) + (Ar ² -H)) was 0.5 or less.

[Comparative Examples 3 to 4] Molar ratio (Ar ¹ -H) /
A bluish black powder was obtained in the same manner as in Example 4 except that ((Ar ¹ -H) + (Ar ² -H)) was 0.5 or less.

[Comparative Example 5] The order of addition of the couplers was first the coupler (Ar ² -H) and then the coupler (Ar ¹ -H).
A bluish black powder was obtained in the same manner as in Example 4 except that the above procedure was used.

Table 1 shows the elemental analysis values (actually measured values and calculated values) of the powders obtained in the above Examples and Comparative Examples.

[0036]

[Table 1]

The composition used for the elemental analysis calculation of Table 1 is shown in Table 2
Shown in.

[Table 2]

0.25 g of the bisazo pigment (charge generating material) thus obtained, 0.1 g of butyral resin (XYHL manufactured by Union Carbide Plastics Co., Ltd.) and 5.9 g of cyclohexanone were placed in a 50 ml sample bottle and a YTZ ball having a diameter of 5 mm was used. Milling was carried out for 4 days by adding 105 g. Further, 6.25 g of cyclohexanone was added and milling was performed for 3 days. One gram of this mill base was taken out and diluted with 0.85 g of methyl ethyl ketone and 1 g of cyclohexanone. The resulting dispersion was applied onto a conductive support made of aluminum vapor-deposited polyester base using a doctor blade and naturally dried to form a charge generation layer. Furthermore, 0.68 parts of the following charge carrier material, 0.75 parts of polycarbonate resin (Panlite K1300, Teijin Ltd.), 0.15 parts of a dichloromethane solution containing 0.1% by weight of silicone oil and dichloromethane.
After mixing and dissolving 5.7 parts, this was applied onto the charge generation layer using a doctor blade and dried at 80 ° C. for 2 minutes and 120 ° C. for 5 minutes to form a charge generation layer having a thickness of about 20 μm. A body (photoreceptor Nos. 1 to 7) was obtained.

[Chemical formula 7]

Comparative Examples 7 to 11 Symmetric Bisazo Pigment (II
-2) and the symmetrical bisazo pigment (II-3) were mixed in the composition shown in Table 3 at the time of preparing the milling liquid to prepare photoconductors (comparative photoconductor Nos. 6 to 10) in the same manner as above.

[0041]

[Table 3]

Next, in order to examine the sensitivity of the thus obtained laminated type electrophotographic photosensitive member in the visible region, an electrostatic copying paper tester (SP428 type manufactured by Kawaguchi Denki Seisakusho) was used for this photosensitive member in the dark. After charging for 6 seconds by corona discharge of 6 kv for 20 seconds and then leaving it in the dark for 20 seconds, surface potential VO
(V) was measured. Then, irradiate a tungsten lamp light so that the illuminance on the surface of the photoconductor becomes 4.51 ux.
Exposure amount E1 / 2 until the potential from the bolt becomes 1/2
(Lux seconds) was calculated. The results are shown in Table 4 and FIG.

As is apparent from FIG. 1, it is understood that the photoreceptor using the bisazo pigment obtained in the present invention has extremely high sensitivity to the simple mixed system of the comparative example.

FIG. 2 shows the respective synthetic yields. Clearly, the yield is higher in the case of simultaneous addition. That is, Japanese Patent Application
Examples 1-3 as compared with 03-188716 (Comparative Examples 2, 4-5)
Gives a bisazo pigment in high yield. Further, Example 4 to
According to 6, a highly sensitive product can be obtained in a high yield.

[0045]

[Table 4]

[0046]

As described above, according to the present invention, an asymmetric bisazo pigment can be obtained in a high yield, and with the asymmetric bisazo pigment, an electrophotographic photoreceptor having high sensitivity can be obtained.

[Brief description of drawings]

FIG. 1 is a molar ratio of a coupler (Ar ¹ -H) / ((Ar ¹
-H) + (diagram illustrating a relationship between the sensitivity of the electrophotographic photosensitive member is made from Ar ² -H)) and the resulting bisazo pigment.

2 is a coupler molar ratio (Ar ¹ -H) / ((Ar ¹
-H) + (graph showing the relationship between the synthesis yield of Ar ² -H)) and the resulting bisazo pigment.

[Figure 3]

FIG. 4 is a schematic view of a cross section of the electrophotographic photosensitive member according to the present invention.

[Explanation of symbols]

 1 Conductive Support 2 Photosensitive Layer 3 Charge Transport Layer 4 Charge Generation Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G03G 5/06 348 9221-2H 350 C 9221-2H (72) Inventor Hiroshi Adachi Naka, Ota-ku, Tokyo Magome 1-3-6 In Ricoh Co., Ltd. (72) Inventor Tomohiro Inoue 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Co., Ltd. (72) Mitsuru Hashimoto 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 in Ricoh Co., Ltd.

Claims (4)

[Claims] 1. In a coupling reaction using a bis (diazonium) salt represented by the general formula (I) as a diazo component, 1 mol of the bis (diazonium) salt is added to 1 mole of the formula (Ar ¹
-H) and coupler of the formula (Ar ² -H) - 1.8
To 2.2 mol, and the molar ratio of the coupler (Ar ¹ -H)
A method for producing a bisazo pigment, wherein / ((Ar ¹ -H) + (Ar ² -H)) is larger than 0.5 and smaller than 0.9. 2. A method of reacting with a coupler represented by formula (Ar ¹ —H) ^first and then with a coupler represented by formula (Ar ² —H).
A method for producing the bisazo pigment described. 3. The method for producing a bisazo pigment according to claim 1, wherein the coupling reaction is carried out in a homogeneous mixed system of couplers represented by formula (Ar ¹ -H) and formula (Ar ² -H). 4. A photoconductor for electrophotography, comprising the bisazo pigment obtained from claim 1, 2 or 3 as a charge generating material.