JPH0455299B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing a specific azine compound in its photosensitive layer. Prior Art Conventionally, inorganic materials such as selenium, cadmium sulfide, and zinc oxide have been used as photoconductive materials for photoreceptors used in electrophotography. The "electrophotographic method" referred to here generally refers to
A photoconductive photoreceptor is first charged in a dark place, for example by corona discharge, and then imagewise exposed to selectively dissipate the charge only in the exposed areas to obtain an electrostatic latent image. This is an image forming method in which images are developed and visualized using electrostatic fine particles (toner) made of colorants such as dyes and pigments and binders such as polymeric substances to form images. The basic characteristics required of the photoreceptor in such electrophotography are (1) ability to be charged to an appropriate potential in the dark, (2) low charge dissipation in the dark, (3) For example, the charge can be quickly dissipated by light irradiation. Incidentally, it is a fact that each of the above-mentioned inorganic substances has many advantages, but also has various disadvantages. For example, selenium, which is currently widely used, fully satisfies conditions (1) to (3) above, but the manufacturing conditions are difficult, the manufacturing cost is high, it is not flexible, and it cannot be processed into a belt shape. It also has disadvantages, such as being difficult to handle and being sensitive to heat and mechanical shock, requiring careful handling.
Cadmium sulfide and zinc oxide are used as photoreceptors by being dispersed in resin as a binder.
It cannot be used repeatedly as it is because of mechanical defects such as smoothness, hardness, tensile strength, and abrasion resistance. In recent years, electrophotographic photoreceptors using various organic materials have been proposed in order to eliminate the drawbacks of these inorganic materials, and some of them have been put into practical use. For example, poly-N-vinylcarbazole and 2,4,7
- trinitrofluoren-9-one (described in U.S. Pat. No. 3,484,237); a photoreceptor made by sensitizing poly-N-vinylcarbazole with a pyrylium salt dye (Japanese Patent Publication No. 48-25658); (described in JP-A-47-37543), a photoreceptor whose main component is an organic pigment (described in JP-A-47-37543), a photoreceptor whose main component is a eutectic complex consisting of a dye and a resin (described in JP-A-47-37543)
(described in Publication No. 10785). Although these photoreceptors have excellent properties and are considered to be of high practical value, considering the various requirements for photoreceptors in electrophotography, it is still difficult to fully meet these requirements. The reality is that we are not getting anything that satisfies us. However, all of the photoreceptors mentioned so far differ depending on the purpose or manufacturing method, but in general, good characteristics can be obtained by using excellent photoconductive materials. be. Purpose An object of the present invention is to provide a photoreceptor that can eliminate the various drawbacks of the conventional photoreceptor described above and fully satisfy the conditions required in electrophotography. Another object of the present invention is to provide an electrophotographic photoreceptor that is easy to manufacture, relatively inexpensive, and has excellent durability. Structure As a result of research and consideration on many photoconductive substances, the inventor found the following general formula () {In the formula, R ₁ and R ₂ are an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group, and at least one of R ₁ and R ₂ represents a substituted or unsubstituted aral group. Ar
is a substituted or unsubstituted naphthyl group, or [However, R ₃ is hydrogen, an alkyl group, an alkoxy group, a halogen atom, or

A substituted amino group represented by the formula (where R ₄ and R ₅ are an alkyl group,
a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group), m is 1,
It is an integer of 2 or 3. ]n represents an integer of 0 or 1. } It has been found that an azine compound represented by the following formula works effectively as a photoconductive substance for an electrophotographic photoreceptor. Here, examples of substituents on the naphthyl group of Ar include alkyl groups, alkoxy groups, halogen atoms, substituted amino groups, and R ₁ or R ₂ ,
Examples of the substituent on the aralkyl group or aryl group of R ₄ or R ₅ include an alkyl group, an alkoxy group, a halogen atom, a dialkylamino group, an acyl group, and a cyano group. Furthermore,
As will be clear from the description below, this azine compound is
It has also been found that the photoreceptors can be combined with a variety of materials to create photoreceptors with unexpected effects. The present invention was completed based on these findings. That is, the present invention provides an electrophotographic photoreceptor comprising a photosensitive layer provided on a conductive support, characterized in that the photosensitive layer contains an azine compound represented by the above general formula (). It is. The invention will now be explained in more detail with reference to the accompanying drawings. 1 to 3 are cross-sectional views of three typical examples of the photoreceptor according to the present invention, and the numbers assigned thereto are 1 for the conductive support, 2, 2',
2'' represents a photosensitive layer, 3 represents a charge generation substance, 4 represents a charge transport medium or charge transport layer, and 5 represents a charge generation layer. The azine compound represented by the general formula () used in the present invention is as follows: General formula () [In the formula, _{R 1} and R ₂ are the same as the above general formula ()] and the following general formula () The same as formula (), l is 0 or 1.] can be produced by a conventional method.That is, if necessary, a small amount of acid (glacial acetic acid or inorganic acid) and a condensation reaction between a hydrazone compound [general formula ()] and an aldehyde compound [general formula ()] of equal molecular weight in a solvent such as alcohol or N,N-dimethylformamide. Specific examples of the azine compound represented by the general formula () thus obtained are illustrated in Table-1. A specific example of production is as follows. Production example Benzophenone hydrazone 39.3g (0.2mol)
and 4-N,N-diethylaminobenzaldehyde
Dissolve 35.4g (0.2mol) in ethanol 1,
One drop of 95% sulfuric acid was added thereto, and after stirring at room temperature for 2 hours, the reaction mixture was diluted with 2 portions of water.
The precipitated powder was separated by filtration, washed with water, and dried to obtain a yellow powder. The yield was 75.4g. Then, it was recrystallized from ethanol to obtain pure benzophenone-4-N,N-diethylaminobenzaldehyde azine in the form of yellow needles. The yield was 57.9 g (yield 81.4%), and the melting point was 92.0-93.2°C. (Exemplary Compound No. 46) The photoreceptor of the present invention contains one or more of the above-mentioned azine compounds in the photosensitive layer. It can be used as shown in FIG. 2 or 3. The photoreceptor in FIG.
A photosensitive layer 2 made of the following is provided. The azine compound here acts as a photoconductive substance, and the generation and transfer of charge carriers necessary for light attenuation take place via the azine compound. However, since azine compounds have almost no absorption in the visible region of light, in order to form images with visible light, it is necessary to sensitize them by adding a sensitizing dye that has absorption in the visible region. . The photoreceptor shown in FIG. 2 has a photosensitive layer 2' on a conductive support 1, in which a charge generating substance 3 is dispersed in a charge transport medium 4 made of an azine compound and a binder.
is provided. The azine compound here together with the binder (or binder and plasticizer) forms the charge transport medium 4, while the charge generating substance 3 (charge generating substance such as an inorganic or organic pigment) generates the charge carriers. In this case, the charge transport medium 4 is mainly responsible for receiving charge carriers generated by the charge generating substance 3 and transporting them. The basic condition for this photoreceptor is that the absorption wavelength regions of the charge generating substance and the azine compound do not overlap with each other, mainly in the visible region. This is because in order to efficiently generate charge carriers in the charge generation material 3, it is necessary to transmit light to the surface of the charge generation material. The azine compound represented by the general formula () has almost no absorption in the visible region, generally absorbs light in the visible region, and works particularly effectively as a charge transport material when combined with a charge generating substance 3 that generates charge carriers. This is its characteristic. The photoreceptor shown in FIG. 3 has a photosensitive layer 2'' formed of a laminated layer of a charge generation layer 5 mainly composed of a charge generation substance 3 and a charge transport layer 4 containing an azine compound on a conductive support 1. In this photoreceptor, light transmitted through the charge transport layer 4 reaches the charge generation layer 5, and charge carriers are generated in that region, while the charge transport layer 4 receives injection of charge carriers. ,
The generation of charge carriers necessary for optical attenuation is performed by a charge generation substance 3, and the charge carrier transport is performed by a charge transport layer 4 (mainly an azine compound). This mechanism is similar to the explanation given for the photoreceptor shown in FIG. In order to actually produce the photoreceptor of the present invention, in the case of the photoreceptor shown in FIG. 1, one or more azine compounds are dissolved in a solution containing a binder, and then a sensitizing agent The photosensitive layer 2 may be formed by preparing a liquid containing the above ingredients, applying it onto the conductive support 1, and drying it. The thickness of the photosensitive layer 2 is 3 to 50 μm, preferably 5 to 50 μm.
20 μm is appropriate. The amount of the azine compound in the photosensitive layer 2 is 30 to 70% by weight, preferably about 50% by weight, and the amount of the sensitizing dye in the photosensitive layer 2 is
It is 0.1 to 5% by weight, preferably 0.5 to 3% by weight. As a sensitizing agent, Brilliant Green,
Victoria Blue B, Methyl Violet, Crystal Violet, Ashit Violet 6B
Triarylmethane dyes such as Rhodamine B, Rhodamine 6G, Rhodamine G Extra,
Xanthene dyes such as eosin S, erythrosin, rose bengal, fluorescein, thiazine dyes such as methylene blue, cyanine dyes such as cyanine, 2,6-diphenyl-4-(N,
N-dimethylaminophenyl) thiapyrylium perchlorate, benzopyrylium salt (Special Publication 1972-
Examples include pyrylium dyes such as those described in Japanese Patent No. 25658). Note that these sensitizing agents may be used alone or in combination of two or more. In addition, in order to produce the photoreceptor shown in FIG.
Fine particles of the charge generating substance 3 are dispersed in a solution containing one or more azine compounds and a binder, and this is coated on the conductive support 1 and dried to form the photosensitive layer 2'. good. The thickness of the photosensitive layer 2' is 3 to 50 μm, preferably 5 μm.
~20 μm is appropriate. The amount of the azine compound in the photosensitive layer 2' is 10 to 95% by weight, preferably 30 to 90% by weight.
The amount of the charge generating substance 3 in the photosensitive layer 2' is 0.1 to 50% by weight, preferably 1 to 20% by weight.
Weight%. Examples of the charge generating substance 3 include inorganic pigments such as selenium, selenium-tellurium, cadmium sulfide, cadmium-selenium sulfide, and α-silicon; examples of organic pigments include CI Pigment Blue 25 (Color Index CI 21180) and CI Pigment Lets. 4 (CI 21200), CI Basic Red 52 (CI 45100), CI Basic Red 3 (CI 45210), azo pigment having a carbazole skeleton (described in JP-A-53-95033),
Azo pigments having a distyrylbenzene skeleton (described in JP-A-53-133445), azo pigments having a triphenylamine skeleton (described in JP-A-53-132347), azo pigments having a dibenzothiophene skeleton (described in JP-A-54-21728), an azo pigment having an oxadiazole skeleton (described in JP-A-54-21728),
12742), azo pigments having a fluorenone skeleton (described in JP-A-54-22834), azo pigments having a bisstilbene skeleton (described in JP-A-54-22834),
-17733), azo pigments with a distyryloxadiazole skeleton (described in JP-A-54-2129), azo pigments with a distyrylcarbazole skeleton (described in JP-A-54-14967) ), such as C.I. Pigment Blue.
16 (CI 74100), indigo pigments such as CI Butt Brown 5 (CI 73410), CI Butt Dai (CI 73030), Argo Scarlet B (manufactured by Bayer),
Examples include perylene pigments such as Indus Thread Scarlet R (manufactured by Bayer AG). Note that these charge generating substances may be used alone or in combination of two or more types. Furthermore, in order to produce the photoreceptor shown in FIG. 3, the charge generating substance 3 is vacuum-deposited on the conductive support 1, or fine particles of the charge generating substance 3 are deposited in a suitable form with a binder dissolved therein if necessary. The charge generation layer 5 is formed by applying a dispersion in a suitable solvent, drying it, and if necessary, performing surface finishing and film thickness adjustment by methods such as buffing. The charge transport layer 4 may be formed by applying a solution containing one or more azine compounds and a binder thereon and drying it. The charge generating material 3 used to form the charge generating layer 5 here is the same as that used in the description of the photosensitive layer 2'. The thickness of the charge generation layer 5 is 5 μm or less, preferably 2 μm.
m or less, and the thickness of the charge transport layer 4 is 3 to 50 μm.
A suitable thickness is preferably 5 to 20 μm. When the charge generating layer 5 is of a type in which fine particles of the charge generating substance 3 are dispersed in a binder, the proportion of the fine particles of the charge generating substance 3 in the charge generating layer 5 is 10 to 95% by weight, preferably It is about 50 to 90% by weight. Also,
The amount of azine compound in the charge transport layer 4 is 10 to 95
The weight percent is preferably 30 to 90 weight percent. In the production of these photoreceptors, a metal plate or foil made of aluminum or the like, a plastic film deposited with a metal such as aluminum, or paper subjected to conductive treatment is used as the conductive support 1. In addition, as a binder, condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polyketone, polycarbonate, polyvinyl ketone, polystyrene, polycarbonate, etc.
Vinyl polymers such as N-vinylcarbazole and polyacrylamide are used, but any insulating and adhesive resin can be used. A plasticizer may be added to the binder if necessary, and examples of such plasticizers include halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, and dibutyl phthalate. Furthermore, the photoreceptor obtained in the above manner has
An adhesive layer or barrier layer can be provided between the conductive support and the photosensitive layer, if necessary. Materials used for these layers include polyamide, nitrocellulose, aluminum oxide, etc., and the film thickness is preferably 1 μm or less. To make a copy using the photoreceptor of the present invention, the photoreceptor surface is charged and exposed, then developed and, if necessary, transferred to paper or the like. The photoreceptor of the present invention has excellent advantages such as high sensitivity and flexibility. Examples are shown below. In the following examples, all parts are by weight. Example 1 76 parts of Diane Blue (CI Pigment Blue 25, CI 21180) and 2 parts of polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) were used as charge generating substances.
% tetrahydrofuran solution and 3,700 parts of tetrahydrofuran were ground and mixed in a ball mill.
The resulting dispersion was applied using a doctor blade onto the aluminum surface of a conductive support made of a polyester base coated with aluminum vapor, and air-dried to form a charge generation layer with a thickness of about 1 μm. On the other hand, 2 parts of No. 46 azine compound and polycarbonate resin (Panlite) were used as charge transport substances.
After mixing and dissolving 2 parts of K1300 (manufactured by Teijin Ltd.) and 16 parts of tetrahydrofuran to form a solution, this was applied onto the charge generation layer using a doctor blade, heated to 80°C for 2 minutes, and then heated to 105°C. This was dried for 5 minutes to form a charge transport layer with a thickness of about 20 μm, thereby producing photoreceptor No. 1. Examples 2 to 22 Photoreceptors Nos. 2 to 22 were prepared in exactly the same manner as in Example 1, except that the charge generating substance and the charge transporting substance (azine compound) were replaced with those shown in Table 2.

【table】

【table】

【table】

[Table] Example 23 On an aluminum plate having a thickness of approximately 300 μm, selenium was vacuum-deposited to a thickness of approximately 1 μm to form a charge generation layer. Next, 2 parts of No. 47 azine compound, 3 parts of polyester resin (Polyester Adhesive 49000 manufactured by Dupont) and 45 parts of tetrahydrofuran were mixed and dissolved to prepare a charge transport layer forming liquid, and this was added to the above charge generation layer (selenium). After coating with a doctor blade on the vapor deposited layer and drying naturally,
A charge transport layer having a thickness of about 10 μm was formed by drying under reduced pressure to obtain photoreceptor No. 23 of the present invention. Example 24 Perylene pigment instead of selenium was used to form a charge generation layer (however, the thickness was about 0.3 μm), and exposure was carried out in the same manner as in Example 23, except that the azine compound No. 67 was used instead of No. 47. Body No. 24 was created. Regarding photoreceptors No. 1 to 24 thus made,
Using a commercially available electrostatic copying paper testing device (KK Kawaguchi Electric Seisakusho SP428 model), corona discharge of -6KV or +6KV was performed for 20 seconds to charge the paper, and the surface potential was then left in a dark place for 20 seconds. Vpo (volt)
, then irradiate the photoreceptor surface with tungsten lamp light so that the illumination intensity is 4.5 lux, and measure the time (seconds) until the surface potential becomes 1/2 of Vpo.
was determined, and the exposure amount E1/2 (lux seconds) was calculated. The results are shown in Table-3. In addition, each of the above-mentioned photoreceptors is charged using a commercially available electrophotographic copying machine, and then light is irradiated through the original image to form an electrostatic latent image, which is developed using a dry developer. When the resulting image (toner image) was electrostatically transferred onto plain paper and fixed, a clear transferred image was obtained. A similarly clear transferred image was obtained when a wet developer was used as the developer.

【table】

[Table] Effects As stated above, the photoreceptor of the present invention fully satisfies the conditions required for a photoreceptor and forms clear images by using the azine compound represented by the above general formula (). It is something.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views enlarged in the thickness direction of an electrophotographic photoreceptor according to the present invention. DESCRIPTION OF SYMBOLS 1... Conductive support, 2, 2', 2''... Photosensitive layer, 3... Charge generating substance, 4... Charge transporting medium or charge transporting layer, 5... Charge generating layer.

Claims (1)

[Scope of Claims] 1. A photoreceptor for electrophotography, comprising a photosensitive layer containing as an active ingredient at least one azine compound represented by the following general formula () on a conductive support. {In the formula, R ₁ and R ₂ are an alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group, and at least one of R ₁ and R ₂ represents a substituted or unsubstituted aral group. Ar
is a substituted or unsubstituted naphthyl group, or [However, R ₃ is hydrogen, an alkyl group, an alkoxy group, a halogen atom, or a substituted amino group represented by the formula (wherein R ₄ and R ₅ are an alkyl group,
a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group), m is 1,
It is an integer of 2 or 3. ]n represents an integer of 0 or 1.