JPH0644160B2 - Method for manufacturing electrophotographic photosensitive material - Google Patents

Description

The present invention relates to a method for producing a photosensitive material for electrophotography used in an electrophotographic process. More specifically, the present invention relates to a method for producing a squarylium compound used as a photoconductive material.

[Conventional technology]

Conventionally, as an electrophotographic light-sensitive material, an inorganic light-sensitive material such as amorphous selenium, selenium alloy, cadmium sulfide, and zinc oxide, and an organic light-sensitive material represented by polyvinylcarbazole and a polyvinylcarbazole derivative have been widely known.

It is well known that amorphous selenium or selenium alloy has extremely excellent properties as a photosensitive material for electrophotography and is put to practical use. However, there is a drawback in that its production requires a complicated process of vapor deposition, and the vapor deposition film produced is not flexible. Although it is used as a dispersion type photosensitive material in which zinc oxide is dispersed in a resin, such a photosensitive material has a problem in mechanical strength and cannot be used repeatedly as it is.

Polyvinylcarbazole, which is widely known as an organic photoconductive material, has advantages such as transparency, film-forming property, and flexibility, but since polyvinylcarbazole itself has no sensitivity in the visible light region, it remains as it is. However, various sensitization methods have been devised accordingly. However, when polyvinylcarbazole is spectrally sensitized with a dye sensitizer, the spectral sensitivity range is expanded to the visible light range, but the sensitivity is not sufficient as a photoreceptor for electrophotography, and light fatigue is severe. It has the disadvantage of being new. Further, when chemically sensitized with an electron-accepting compound, a photoreceptor having sufficient sensitivity can be obtained as a photoreceptor for electrophotography, and some of them have been put into practical use However, there are some problems such as life.

In recent years, various types of organic photoreceptors have been studied, and it has been reported that, in particular, a laminated photoreceptor having a charge generation layer and a charge transport layer has superior electrical characteristics to conventional ones. Bisazos, trisazos, phthalocyanines, pyryliums, squaryliums and the like are known as charge generating materials used for these photoconductors, and phthalocyanines as those having sensitivity from the visible region to the near infrared region. , Trisazos, and square liliums have been reported.

However, phthalocyanines have a drawback that the spectral sensitivity is biased to a long wavelength and inferior in red reproducibility, and trisazos have not been able to have excellent electric characteristics and sufficient sensitivity. Further, JP-A-49-105536 Although the squarylium compounds shown in the above have relatively high sensitivity, they have drawbacks in charging property, dark decay, etc., and have not achieved both high sensitivity and low dark decay.

[Problems to be solved by the invention]

An object of the present invention is to solve the above-mentioned drawbacks, to provide a method for producing an electrophotographic photosensitive material having spectral sensitivity from the visible region to the near infrared region and having high sensitivity and excellent electrical characteristics. is there.

[Means and Actions for Solving Problems]

The object of the present invention can be achieved by an electrophotographic photosensitive material comprising an asymmetric squarylium compound represented by the following general formula (I) and a method for producing the same.

In the formula, Ar ₁ and Ar ₂ are not the same as each other and are represented by the general formula (II) {In the formula, R ₁ and R ₂ are independent of each other and are an alkyl group having 1 to 20 carbon atoms, an unsubstituted or substituted phenyl group, or a general formula (III) (In the formula, R ₄ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms,
Hydroxyl group, alkoxy group having 1 to 4 carbon atoms, halogen atom,
It represents a nitro group, a cyano group, a carboxyl group, an alkoxycarbonyl group having 1 to 4 carbon atoms, and a trifluoromethyl group. ), R ₃ represents a hydrogen atom, a hydroxyl group, a methyl group, a trifluoromethyl group, a halogen atom or a carboxyl group. } Represents the substituent.

The asymmetric squarylium compound represented by the general formula (I) can be synthesized in three steps as shown in the following formula.

In the above formula, each symbol has the same meaning as described above.

In the first step [A], 3,4-dichloro-3-cyclobutene-1,2-dione of the formula (IV) is added to the aniline derivative of the formula (V) in a solvent in a molar ratio of 0.5 to 5 with respect to the aniline derivative. The compound of formula (VI) is obtained by reacting at a temperature below room temperature in the presence of a catalyst in a molar ratio of 1 or more.

As the solvent, nitrobenzene, carbon disulfide, dichloromethane, carbon tetrachloride, 1,2-dichloroethane and the like which are commonly used in Friedel-Crafts reaction can be used. As the catalyst, Lewis acids such as aluminum chloride, antimony chloride, iron chloride, titanium chloride, boron trifluoride, tin chloride, bismuth chloride, zinc chloride and mercury chloride can be used.

In the second step [B], the compound of formula (VI) obtained in the reaction of the first step is hydrolyzed to give a compound of formula [VII]. Hydrolysis can be carried out, for example, by refluxing in acetic acid containing a small amount of water.

In the third step [C], the compound of the formula (VI
The compound of formula (V) is reacted with the compound of formula (I) in a solvent by a reflux method or a reduced pressure method to obtain the target asymmetric squarylium compound (I). As the solvent, a primary or secondary alcohol having 2 to 10 carbon atoms, or an azeotropic mixture of those alcohols and an aromatic hydrocarbon such as benzene, toluene or xylene can be used.

The asymmetric squarylium compound according to the present invention can also be obtained by a general method for synthesizing a squarylium compound. That is, a total of 2 mol of two different amine derivatives can be simultaneously reacted with 1 mol of squaric acid. However, the squarium compound obtained at this time is a mixture of an asymmetric squarylium compound and a symmetric squarylium compound, and it is difficult to control the ratio of the products and separate and purify a single product, and there is a large variation in electrical characteristics and sensitivity. The former is more preferable because it has problems such as a decrease.

The asymmetric squarylium compound (I) obtained by the production method of the present invention is a single substance, is easy to purify, and has a small variation in electric characteristics.

Specific examples of the asymmetric squarylium compound represented by the general formula (I) are shown by structural formulas. In the formula, Me is a methyl group,
Et represents an ethyl group and Pr represents a propyl group.

1. 2. 3. 4. 5. 6. 7. 8. 9. Ten. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. twenty one. twenty two. twenty three. twenty four. twenty five. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. The asymmetric squarylium compound (I) obtained by the production method of the present invention can be used in an electrophotographic photoreceptor having a multilayer structure. That is, in an electrophotographic photoreceptor including a photosensitive layer having a two-layer structure composed of a charge generating layer and a charge transporting layer, a charge generating layer containing a squarylium compound and a well-known charge transporting layer 3 are provided, thereby providing high sensitivity and chargeability. Thus, it is possible to obtain a photoreceptor having improved electric characteristics such as dark decay.

As the charge transport layer, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, p-
Diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N
Hydrazones such as -α-naphthyl-N-phenylhydrazone; 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [quinolyl (2)]-3- Pyrazolines such as (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, oxazole compounds such as 2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, bis (4-diethylamino-2)
-Methylphenyl) -phenylmethane and other triarylmethane compounds, N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine and the like A binder resin containing a diamine compound or a photoconductive polymer such as poly-N-vinylcarbazole or polyvinylanthracene is used.

The structure of the electrophotographic photoreceptor having a two-layer structure using the squarylium compound obtained by the production method of the present invention will be described. As shown in FIGS. 1 and 2, the square lilium pigment is provided on the conductive support 1. A photosensitive layer 4 is provided, which is a laminate of a charge generation layer containing a charge transport layer and a charge transport layer 3 containing a charge transport material. The stacking order of the charge generation layer 2 and the charge transport layer 3 is arbitrary.

The charge generation layer may be formed of square lilium pigment alone, or may be formed in combination with a binder resin.
The ratio of the pigment to the binder resin is 10% by weight to 90% by weight, preferably 10% by weight to 50% by weight.

As a method of forming a charge generation layer by using a squarerium pigment alone without using a binder resin together, there are a solvent coating method and a vacuum deposition method.

The thickness of the charge generation layer is 0.1 to 3 µ, preferably 0.2 to 1 µ.

When the pigment is dispersed in the binder, the pigment is crushed and used, and the crushing method can be a known method such as SPEX MILL, ball mill, RED DEVIL (trade name) and the like.

The binder for the charge generation layer may or may not have photoconductivity by itself. Examples of the binder having photoconductivity include polyvinylcarbazole, polyvinylcarbazole derivatives, polyvinylnaphthalene, polyvinylanthracene, polyvinylpyrene, and other photoconductive polymers, and other organic matrix materials having a charge transporting ability.

Also, a known insulating resin having no photoconductivity can be used as the binder. Known insulating resins include polystyrene, polyester, polyvinyltoluene, polyvinylanisole, polychlorostyrene, polyvinylbutyral, polyvinylacetate, polyvinylbutylmethacrylate, copolystyrene-butadiene,
Polysulfone, copolystyrene-methylmethacrylate, polycarbonate, etc. can be used.

At this time, a plasticizer may be used in the same manner as a general polymer material for the purpose of further improving the mechanical strength of the obtained photoreceptor. As the plasticizer, for example, chlorinated paraffin, chlorinated biphenyl, phosphate-based plasticizer, phthalate-based plasticizer, etc. can be used, and 0 to the binder can be used.
The mechanical strength of the photoconductor can be further improved by adding 10% by weight without deteriorating the sensitivity and electric characteristics of the photoconductor.

Protective layer or photosensitive layer 4 and conductive support 1 on photosensitive layer 4
You may insert an intermediate | middle layer between them. Examples of the protective layer include those in which a metal oxide is dispersed in a resin and those in which an electron-accepting compound is added to the resin. Examples of the intermediate layer include a metal oxide such as aluminum oxide, an acrylic resin, a phenol resin, a polyester resin, and polyurethane.

The binder in which the square lilium pigment is dispersed is coated on the conductive support. As the coating method, there are methods such as a dipping method, a spray method, a bar coater method, an applicator method and the like, and any method can form a good photosensitive layer.

As the conductive support, a metal, paper subjected to a conductive treatment, a polymer film having a conductive layer, glass, or the like can be used.

The electrophotographic photoreceptor obtained by the production method of the present invention,
It can be widely used not only in copying machines but also in semiconductor laser printers.

Next, the present invention will be described with reference to examples.

〔Example〕

Synthesis example 3,4-dichloro-3-cyclobutene-1,2-dione
4.12g and aluminum chloride 4.40g methylene chloride 30m
The temperature was kept below 5 ° C. and stirred until aluminum chloride was dissolved. N- (p-chlorophenyl) -N'-
A solution prepared by dissolving 6.32 g of methylaniline in 10 m of methylene chloride was added dropwise over 45 minutes, and then stirred for 4 hours while maintaining the liquid temperature at 5 ° C or lower. After completion of the reaction, it is washed with HC and water, then separated by column chromatography, and the following formula (V
4.00 g (yield 42%) of the product represented by III) was obtained.

Next, 3.58 g of the compound (VIII) was added to 35 m of glacial acetic acid and 3.5 m of water.
The resulting solution was cooled to room temperature and the precipitated crystals were separated to obtain 2.76 g of a product represented by the following formula (IX) (yield: 82%).

Next, 1.33 g of the product (IX) and 0.56 g of ethylmethylaniline were dissolved in a mixed solvent of 10 m of butanol and 10 m of toluene, heated to reflux for 2.5 hours while removing water produced during the reaction, and then cooled to room temperature to precipitate. The separated crystals were separated and washed with butanol, toluene, methanol and ether to obtain 0.92 g of the product (X: Concrete Example No. 21) (yield 51
%) Was obtained.

Decomposition point: 213 ° C Elemental analysis: Calculated value C72.88%, H5.66%, N6.30% Measured value C73.00%, H5.71%, N6.04% Example 1 of the specific example No. 17 1 part by weight of the compound represented by the structural formula and polyester resin (manufactured by Deupon, Adhesive 49000)
1 part by weight and 10 parts by weight of tetrahydrofuran were added, and the mixture was pulverized and mixed with a ball mill for 4 hours, and the resulting dispersion was applied onto a polyester film [made by Toray, Metalmy (registered trademark)] on which aluminum was vapor-deposited using a bar coater. ℃
And dried for 5 hours to form a charge generation layer having a film thickness of 1 μm.

N, N'-diphenyl-N, N 'is formed on the charge generation layer.
-Bis- (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine 1 part by weight, polycarbonate resin [manufactured by Teijin, Panlite (registered trademark)] 1 part by weight,
A uniform solution consisting of 10 parts by weight of tetrahydrofuran was applied using an applicator and dried at 70 ° C. for 16 hours to form a 22 μ-thick charge transport layer, to prepare a photoreceptor.

Then, using an electrostatic copying paper tester (Kawaguchi Denki, Electrostatic Paper Analyzer SP-428), negative corona discharge of -6KV was applied to the corona discharge, and then left in the dark for 2 seconds. Using a tungsten lamp, irradiate the photosensitive layer with light so that the surface illuminance is 10 lux, and obtain the exposure amount E1 / 2 at which the surface potential becomes 1/2 of the surface potential V _D after standing in the dark. It was The result is that the initial charging potential V _O
= -970V, potential after being left in the dark for 2 seconds V _DDP = -890V, E
1/2 = 3.0 lux · sec and residual potential R _p = −0V.

In addition, the following measurement was performed to clarify that it has an extremely excellent sensitivity to long-wavelength light. After charging the above photoreceptor by corona discharge in a dark place, the photoreceptor was irradiated with 1 μW / cm ² of monochromatic light dispersed at 800 nm using a monochromator. Then, the amount of exposure was determined by measuring the time until the surface potential became 1/2. As a result, 14.6er
It was g / cm ² .

Examples 2 to 7 As shown in Table 1, instead of the square lilium pigment of Concrete Example No. 17 in Example 1, Nos. 18, 21, 24,
Table 2 shows the results of evaluation and preparation of the photoconductors performed in the same manner as in Example 1 except that 28, 34, and 37 [each of Examples 2 to 7] were used.

EFFECTS OF THE INVENTION The present invention provides a method for producing a photosensitive material for electrophotography, which has spectral sensitivity from the visible region to the near-infrared region, and is composed of an asymmetric squarylium compound having high sensitivity and excellent electrical characteristics. In a photoreceptor for electrophotography including a photosensitive layer having a two-layer structure consisting of a charge generation layer and a charge transport layer,
By providing a charge generation layer containing a squarylium compound and a known charge transport layer 3 obtained by the production method of the present invention, a photoreceptor having high sensitivity and improved chargeability and electric characteristics during dark decay. Can be manufactured.

Electrophotographic photoreceptors using these asymmetric square lilium pigments can be widely used not only in copying machines but also in semiconductor laser printers.

[Brief description of drawings]

1 and 2 are sectional views of examples of the electrophotographic photosensitive member of the present invention. Reference numerals in the figure: 1 ... Conductive support; 2 ... Charge generation layer; 3 ... Charge transport layer; 4 ... Photosensitive layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoshi Saeki, Satoshi Saeki 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Zero Tsux Co., Ltd., Takematsu Plant (72) Inventor, Kaoru, 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture, Fuji Zero Tux Co., Ltd. Takematsu Business In-house (56) References JP 61-87647 (JP, A) JP 60-142946 (JP, A)

Claims (1)

[Claims] 1. A formula (IV) 3,4-dichloro-3-cyclobutene-1, represented by
2-dione and general formula (V) [Wherein, R ₁ and R ₂ are independent of each other, and are an alkyl group having 1 to 20 carbon atoms, an unsubstituted or substituted phenyl group, or the general formula (III) (In the formula, R ₄ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms,
Hydroxyl group, alkoxy group having 1 to 4 carbon atoms, halogen atom,
It represents a nitro group, a cyano group, a carboxyl group, an alkoxycarbonyl group having 1 to 4 carbon atoms, and a trifluoromethyl group. ) Represents a benzyl group, and R ₃ represents a hydrogen atom, a hydroxyl group, a methyl group, a trifluoromethyl group, a halogen atom or a carboxyl group. ) Represents a substituent represented by. ] By reacting with a compound represented by the general formula (VI) (Wherein R ₁ , R ₂ and R ₃ have the same meanings as described above), and the compound is then hydrolyzed to give a compound of the general formula (VII) (Wherein R ₁ , R ₂ and R ₃ have the same meanings as described above), and the compound of the general formula (VII) is reacted with the compound of the general formula (V) to give a compound Formula (I) [In the formula, Ar ₁ and Ar ₂ are not the same as each other, and are represented by the general formula (II) (Wherein R ₁ , R ₂ and R ₃ have the same meanings as described above). ] The manufacturing method of the electrophotographic photosensitive material which consists of an asymmetric squarylium compound characterized by being a compound shown by these.