JP3063439B2 - Laminated electrophotographic photoreceptor and paint for charge generation layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor containing an organic photoconductive substance, and more particularly to a laminated electrophotographic photoreceptor having a photosensitive layer comprising an organic charge generation layer and an organic charge transport layer, and an electric charge. The present invention relates to a paint for a generating layer.

[0002]

2. Description of the Related Art Conventionally, photoreceptors made of inorganic photoconductive materials such as selenium, selenium-tellurium alloy, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors, but in recent years they have been easily synthesized. Researches on organic photoconductive materials having characteristics such as selection of a compound exhibiting photoconductivity in an appropriate wavelength range are being advanced.

An electrophotographic photoreceptor using an organic photoconductive material for a photosensitive layer has advantages such as easy film formation, high flexibility and great design freedom, low cost and no pollution. However, the sensitivity and the life of the photoconductor were inferior to those of the inorganic photoconductive substance. Therefore, in order to improve them, a laminated type electrophotographic photoreceptor in which a photosensitive layer is formed by separating functions into a charge generation layer and a charge transport layer has been proposed and put to practical use. The charge transporting agent generally used in this layered type electrophotographic photoreceptor is an electron donating substance such as pyrazoline, hydrazone, oxazole, etc., so that the charge transporting layer is a hole transporting type, so that the charge transporting layer is formed on the charge generating layer. When they are stacked, they are used with negative charge.

On the other hand, as the charge generating material used for the charge generating layer, organic pigments and dyes such as phthalocyanine, azo, squarylium, perylene, and cyanine are used. Wavelength region (80
In recent years, phthalocyanine compounds having absorption at around 0 nm) have been widely used as charge generating substances for electrophotographic photoreceptors for laser beam printers. Examples of the phthalocyanine-based charge generating substance include various crystalline forms of copper phthalocyanine and other metal phthalocyanines or metal-free phthalocyanines, specifically, ε-type copper phthalocyanine, τ-type metal-free phthalocyanine, X-type metal-free phthalocyanine, and α-type. And β-type copper phthalocyanine and titanyl phthalocyanine can be used. In recent years, titanyl phthalocyanine having a crystal form such as α-type has been actively studied as a charge-generating substance having extremely high sensitivity (for example, Journal of the Photographic Society of Japan, Vol. 29, page 250, Vol. 29, page 373, Journal of Imaging Technology, Vol. 17, page 46, Vol. 17, page 202, etc.).

[0005]

As described above, as an electrophotographic photoreceptor having high sensitivity, a laminate comprising a charge generation layer using a titanyl phthalocyanine pigment having various crystal forms as a charge generation material and a charge transport layer. Type organic photoreceptors have been actively studied, but most of these pigments are granular crystals with a size of about 0.1 μm or less, and are mixed with binder resins that have been used for ordinary charge generation layers. However, it is difficult to obtain a coating material which can stably obtain a good coating film by using various dispersion or kneading methods.

That is, a conventional binder resin such as a polyvinyl butyral resin and a normal alcohol-based coating solvent are used for continuous shaking together with glass beads in a container, or dispersion coating using an ultrasonic homogenizer. In the method, the thickness of the charge generation layer becomes uneven,
There has been a problem that the pigment in the charge generation layer becomes non-uniform due to aggregation or the like, and the sensitivity as an electrophotographic photoreceptor becomes non-uniform.

Further, even when a good coating film is temporarily obtained by using a strong dispersing method, the above-mentioned nonuniformity gradually occurs with time, and the yield in mass production is low. there were.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the laminated electrophotographic photoreceptor of the present invention is a laminated organic photoreceptor having at least a photosensitive layer comprising a charge generation layer and a charge transport layer. The generation layer contains at least a charge generation substance, a binder resin, and gas-phase synthetic silica hydrophobized with polydimethylsiloxane.

In view of the above problems, the paint for a charge generation layer of the present invention comprises, in a paint used for forming a charge generation layer,
At least a charge generating substance, a binder resin, and a gas phase synthetic silica hydrophobized with polydimethylsiloxane are contained in a solvent for coating.

[0010]

The electrophotographic photoreceptor of the present invention is a laminated organic photoreceptor having at least a photosensitive layer comprising a charge generation layer and a charge transport layer, wherein the charge generation layer contains at least a charge generation material and a binder resin together with polydimethylsiloxane. By containing gas-phase synthetic silica hydrophobized with siloxane as a dispersing aid or an anti-settling agent, the dispersibility and dispersion uniformity of the organic pigment serving as the charge generating substance are improved, and the charge generating layer thickness becomes uneven. A good electrophotographic photoreceptor having no non-uniformity in density due to agglomeration of pigments or pigments, that is, non-uniformity in sensitivity.

Further, the coating material for forming a charge generating layer according to the present invention contains a gas phase synthetic silica hydrophobized with polydimethylsiloxane together with at least a charge generating material and a binder resin in a coating material used for forming the charge generating layer. Alternatively, by containing the organic pigment as a charge generating substance in a paint-forming solvent as an anti-settling agent, the dispersibility, uniformity and dispersion stability of the organic pigment serving as a charge generating substance are improved, and the charge generating layer thickness becomes non-uniform and the pigment is aggregated. Therefore, it is possible to stably produce a good electrophotographic photoreceptor having no nonuniform density due to the above, that is, no nonuniform sensitivity.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The laminated electrophotographic photoreceptor of the present invention and the paint for a charge generating layer will be described in detail below.

First, the paint for the charge generating layer of the present invention, that is, the paint used for forming and applying the charge generating layer in the ordinary laminated organic photoreceptor will be described. This paint comprises a charge generating substance, a binder resin, gas-phase synthetic silica hydrophobized with polydimethylsiloxane, and a paint-forming solvent.

The charge generating substance used in the coating for the charge generating layer of the present invention may be any organic pigment which has a suitable light absorption and charge generating ability and can be used as a normal laminated electrophotographic photosensitive member. A phthalocyanine-based pigment, particularly a titanyl phthalocyanine pigment, is preferred as a highly sensitive product.

Further, as the binder resin used for the coating material for the charge generation layer of the present invention, a well-known resin such as a vinyl butyral resin can be used. For example, the vinyl butyral resin used in the following examples is obtained by saponifying and acetalizing a vinyl acetate resin, and has a butyralization degree of 50 to 70 mol% in consideration of the dispersibility of the charge generating substance. Is preferred. If the butyralization degree is too small, it becomes water-soluble, and if it is too large, the affinity with the charge generating substance decreases, which is not preferable. The molecular weight may be about 200 to 2000, but the larger the molecular weight is, the better the dispersibility is, even if the ratio of the binder resin to the charge generating substance is small. However, if the molecular weight is too small, the mechanical properties of the layer decrease, and if it is too large, it becomes difficult to form the layer, which is not preferable.

When the ratio of the charge generating substance to the binder resin is too large, the sensitivity when the charge generating layer is used as a charge generating layer in a laminated electrophotographic photoreceptor is lowered, and when the amount of the charge generating substance is too large, the dispersibility is poor. Become. An appropriate ratio is one part by weight of the charge generating substance, and 0.3 to 1.5 of the binder resin.
Parts by weight, preferably 0.5 to 1 part by weight.

The gas-phase synthetic silica hydrophobized with polydimethylsiloxane used as a dispersing aid or an anti-settling agent in the paint for a charge generating layer of the present invention has a silanol group on the surface of ordinary fine particles of a gas-phase synthetic silica. It is important that the coating liquid is hydrophobized with dimethylsiloxane, and this addition slightly increases the viscosity of the coating liquid. However, the increase in the viscosity significantly improves the dispersibility of the pigment as a paint that cannot be explained at all.

It is considered that this is because the pigment and the silica weakly interact with each other via the polydimethylsiloxane chain on the silica surface, thereby weakening the cohesive force between the strong pigments.

If the amount of the gas-phase synthetic silica hydrophobized with polydimethylsiloxane is too small, there is no effect as a dispersing aid or an anti-settling agent. The chargeability and sensitivity of the electrophotographic photoreceptor are reduced, and the repetition stability is poor. Assuming that the total weight of the coating composition is 100 parts, addition of 0.05 part by weight or more of silica is required from the viewpoint of dispersibility. Further, if the total solid content in the coating material for forming the charge generation layer after drying is 100 parts, it is required that the amount of silica be 5 parts by weight or less from the viewpoint of electrostatic characteristics. In general, the solid content concentration in a paint depends on the binder resin to be used and the method of applying a coating film, but is adjusted to a viscosity at which an appropriate film thickness can be obtained as a charge generation layer. %, For example, 4 parts by weight of the total solids and about 0.08 parts by weight of silica with respect to 100 parts by weight of the total coating material, satisfying the above conditions.

Various organic solvents can be used as a paint forming solvent used in the paint for a charge generation layer of the present invention.
Alcohol-based solvents, particularly butanol-based solvents, are preferred in view of the formation of the layer or the relationship with the substrate.

As a method of dispersing a paint having the above composition, a method of repeatedly shaking together with glass beads in a glass bottle can be used.

In the foregoing, the paint for a charge generation layer of the present invention has been described in detail. Next, an electrophotographic photoreceptor in which a charge generation layer formed by applying the charge generation layer paint and a charge transport layer is laminated will be described in detail. The laminated electrophotographic photoreceptor of the present invention is a laminated organic photoreceptor in which a photosensitive layer on a conductive support comprises at least a charge transport layer and a charge generation layer.

The conductive support of the laminated electrophotographic photoreceptor of the present invention may be any one having a conventionally known conductivity. Generally, a metal plate such as aluminum or an aluminum alloy, a drum, or the like is used. Can be

The charge generation layer of the layered electrophotographic photoreceptor of the present invention comprises at least a charge generation substance, a binder resin, and gas phase synthetic silica hydrophobized with polydimethylsiloxane.

The charge generation layer is formed on the conductive support by using the above-mentioned paint for the charge generation layer, by dip coating, spin coating,
It is formed by a coating method such as a spray coating method or an electrostatic coating method. The thickness of the charge generation layer is 0.1 to 1 in terms of characteristics.
It is preferably about μm. If the film thickness is too small, the amount of charge generation is small and sufficient sensitivity cannot be obtained. If the film thickness is too large, the chargeability decreases, and the chargeability and the repetition stability of the sensitivity are impaired. When a charge generation layer is formed on a conductive support, a butyral resin, a vinyl acetate resin, or a polyamide resin is used to improve the adhesion between the conductive support and the charge generation layer or prevent charge injection from the conductive support side. 0.1 ~ 1μ
m layers can also be provided.

The charge transporting layer of the electrophotographic photosensitive member of the present invention comprises at least a charge transporting substance and a binder resin. Charge-transporting substances include compounds having an electron donating property such as an alkyl group, an alkoxyl group, an amino group, an imino group, and an imide group, anthracene, phenanthrene, and a polycyclic aromatic compound such as pyrene or a derivative containing the same, indole, oxazole, Heterocyclic compounds such as carbazole, pyrazoline, imidazole, oxadiazole, thiazole, and triazole or derivatives containing the same are used. Binder resin, polycarbonate resin, polyarylate resin, polyester resin, acrylic resin,
A conventionally known thermoplastic resin or thermosetting resin such as a styrene resin can be used. Among them, solvent resistance is required when the charge generation layer is laminated on the charge transport layer as the photosensitive layer, and mechanical properties such as abrasion resistance are required when the charge transport layer is formed on the upper layer. Therefore, a polycarbonate resin is often used. The content of the binder resin is preferably 60% by weight or less based on the total amount of the charge transport layer. Further, the charge transport layer is formed by dissolving a predetermined amount of a charge transport material and a binder resin in an organic solvent, and is coated on the charge generation layer by a dip coating method, a spin coating method, a spray coating method, or a static coating method. It is formed by a coating method such as an electric coating method. The thickness of the charge transport layer is 5 to 30 μm
The degree is preferred. If the film thickness is too small, the chargeability is reduced, and if it is too large, the sensitivity is reduced.

The paint for a charge generation layer and the laminated electrophotographic photoreceptor of the present invention have been described above in detail. Example 1 shows that the dispersibility of the coating material for the charge generation layer was improved, and the resulting nonuniformity in the thickness and sensitivity of the charge generation layer of the laminated electrophotographic photoreceptor was obtained in Example 1. It is shown below.

Hereinafter, a first embodiment of the present invention will be described. Α-type titanyl phthalocyanine obtained by treating crude titanyl phthalocyanine obtained from phthalonitrile and titanium tetrachloride with α-type crystals by solvent treatment (granular, approximately 0.1 μm in particle size)
27 parts by weight and 6.5 parts by weight of a vinyl butyral resin (Slec BL-1 manufactured by Sekisui Chemical Co., Ltd.) and a solvent-soluble fluororesin (SCM133 manufactured by Asahi Glass Co., Ltd.)
6.5 parts by weight of a gas-phase synthetic silica hydrophobized with polydimethylsiloxane (trade name: Cabosil TS, manufactured by Cabot Corporation)
-720) 0.8 parts by weight, 1000 parts by weight of propanol, and 1000 parts by weight of glass beads (diameter 1 mm) were shaken in a glass bottle for 15 hours to obtain a paint for a charge generation layer.

Using the paint thus obtained, immediately after the preparation of the paint, a lifting speed of 100 mm / min was lifted onto an alumite-treated aluminum drum by a dip coating method.
Thus, a charge generation layer was formed. The coating was dried at 100 ° C. for 1 hour.

As the appearance evaluation of the coating film of the charge generation layer thus obtained, the presence or absence of unevenness in pigment concentration or color was evaluated. The evaluation results are shown in (Table 1). In this table, a circle in the appearance evaluation indicates a good state in which no unevenness is observed,
Δ indicates that a little unevenness is observed, and X indicates a state full of unevenness.

[0031]

[Table 1]

Further, 1 part by weight of 1,1-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene and a polycarbonate resin (macrohole N, trade name, manufactured by Bayer AG)
Using a coating material in which 1 part by weight was dissolved in 9 parts by weight of methylene chloride, dip coating was performed on the charge generation layer, and dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm.

The photosensitive drum thus manufactured was evaluated for electrostatic characteristics. FIG. 1 shows an apparatus for evaluating electrostatic characteristics of an electrophotographic photosensitive member according to an embodiment of the present invention. FIG.
In the figure, 101 is a photosensitive drum, 102 is a corona charger, 103 and 106 are electrometer probes, 104 and 107 are tungsten lamps, 105 is an interference filter (800 nm), and 108 is a color glass filter (UV cut). As the surface electrometer, Model 344 manufactured by Trek Japan KK was used. The electrostatic property is measured in a normal temperature / humidity (20 ° C./50% RH) environment, when the potential after negative corona charging measured by the surface potential meter measurement probe (1) is constant at 700 V, the surface potentiometer. The post-exposure potential measured by the measurement probe (2) was measured as sensitivity. Exposure was performed with an optical filter as monochromatic light of 800 nm, and the exposure amount was 0 to 4.238 μJ / cm ² . The evaluation results are shown in (Table 1).

As described above, according to the present embodiment, the paint for the charge generation layer is composed of the charge generation substance, the binder resin, the gas phase synthetic silica hydrophobized with polydimethylsiloxane, and the solvent for forming the paint. A charge-generating layer having good coating properties without unevenness or color unevenness is obtained.Using this coating solution, a charge-generating layer and a charge-transporting layer are laminated on a conductive support in the order of dip coating. The laminated electrophotographic photosensitive member formed by the above method has a good electrophotographic sensitivity.

Next, a second embodiment of the present invention will be described. In the first embodiment of the present invention, the charge generation layer was formed immediately after preparing the coating for the charge generation layer. In the second embodiment, except that the charge generation layer was formed after being left for 5 hours after the preparation of the coating, A charge generation layer and a charge transport layer were formed in the same manner as in the first embodiment, and evaluation was performed in the same manner as in the first embodiment.

The results of the evaluation are shown in Table 1. Next, a first comparative example of the present invention will be described.

In the first embodiment of the present invention, a charge generation layer and a charge transport layer were formed in the same manner as in the first embodiment except that the coating for the charge generation layer was prepared as follows. Evaluation was performed in the same manner as in the examples. First, 27 parts by weight of α-type titanyl phthalocyanine and 6.5 parts of vinyl butyral resin (trade name: SREC BL-1 manufactured by Sekisui Chemical Co., Ltd.)
Parts by weight and solvent-soluble fluororesin (SC manufactured by Asahi Glass Co., Ltd.)
M133) 6.5 parts by weight, 1 part by weight of propanol, and 1000 parts by weight of glass beads (diameter: 1 mm) were shaken in a glass bottle for 15 hours to obtain a paint for a charge generation layer.

The evaluation results are shown in (Table 1). Next, a second comparative example of the present invention will be described.

In the first comparative example of the present invention, 6.5 parts by weight of a vinyl butyral resin (trade name: SREC BL-1 manufactured by Sekisui Chemical Co., Ltd.) and 6.5 parts of a solvent-soluble fluororesin (SCM133 manufactured by Asahi Glass Co., Ltd.) were used. The charge generation layer was prepared in the same manner as in the first example except that 13 parts by weight of a vinyl butyral resin (trade name: SREC BL-1 manufactured by Sekisui Chemical Co., Ltd.) was used instead of part by weight to prepare the charge generation layer paint. Then, a charge transport layer was formed and evaluated in the same manner as in the first example.

The evaluation results are shown in (Table 1). Next, a third comparative example of the present invention will be described.

In the first comparative example of the present invention, 6.5 parts by weight of vinyl butyral resin (trade name: SREC BL-1 manufactured by Sekisui Chemical Co., Ltd.) and 6.5 parts of a solvent-soluble fluororesin (SCM133 manufactured by Asahi Glass Co., Ltd.) were used. Instead of parts by weight, 13 parts by weight of vinyl butyral resin (trade name: SREC BL-1 manufactured by Sekisui Chemical Co., Ltd.) and 13 parts by weight of a solvent-soluble fluororesin (SCM133 manufactured by Asahi Glass Co., Ltd.) are used to prepare a paint for a charge generation layer. Then, a charge generation layer and a charge transport layer were formed in the same manner as in the first example except that the lifting speed when forming the charge generation layer by the dip coating method was set to 50 mm / min. Evaluation was performed in the same manner as described above.

The evaluation results are shown in (Table 1). Next, a fourth comparative example of the present invention will be described.

In the first comparative example of the present invention, the charge generating layer was formed immediately after the preparation of the coating for the charge generating layer.
In Comparative Example 2, the charge generation layer was formed in the same manner as in the first comparative example, except that the charge generation layer was formed after being left for 3 hours after preparing the paint.
A charge transport layer was formed and evaluated in the same manner as in the first comparative example.

The evaluation results are shown in (Table 1).

[0045]

As described above, the laminated electrophotographic photoreceptor and the paint for the charge generating layer of the present invention have been described in detail. According to this, the present invention has the following effects.

Since the coating for the charge generating layer is composed of a charge generating substance, a binder resin, gas-phase synthetic silica hydrophobized with polydimethylsiloxane, and a solvent for forming a coating, a good coating film without unevenness of pigment or color is obtained. -Type electrophotographic photoconductor, in which a stable charge-generating layer can be obtained stably, and a charge-generating layer and a charge-transporting layer are laminated in this order on a conductive support by dip coating using this coating solution. The photoreceptor has good electrophotographic sensitivity without sensitivity unevenness.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for evaluating electrostatic characteristics of an electrophotographic photosensitive member according to a first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Photoreceptor drum 102 Corona charger 103 Electrometer probe A 104, 107 Tungsten lamp 105 Interference filter (800 nm) 106 Electrometer probe B 108 Color glass filter (UV cut)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsumugi Kobayashi 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Masatoshi Maeda 1006 Okadoma Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. JP-A-60-158458 (JP, A) JP-A-4-308853 (JP, A) JP-A-4-345166 (JP, A) JP-A-61-239248 (JP, A) JP-A-3-116153 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/05 103 G03G 5/06 371

Claims (5)

(57) [Claims] 1. A laminated organic photoreceptor wherein the photosensitive layer on the conductive support comprises at least a charge generation layer and a charge transport layer, wherein the charge generation layer contains at least a charge generation substance, a binder resin, An electrophotographic photoreceptor, comprising gas-phase synthetic silica hydrophobized with dimethylsiloxane. 2. The charge generation layer according to claim 1, wherein the content of the vapor-phase synthetic silica hydrophobized with the polydimethylsiloxane is 3% or less by weight.
The electrophotographic photosensitive member according to the above. 3. A charge-generating substance of the charge generating layer is an electrophotographic photosensitive member according to claim 1 or 2, characterized in that the α-type oxotitanium phthalocyanine pigments. 4. A coating material for use in coating and forming the charge generation layer of a laminated organic photoreceptor wherein the photosensitive layer on the conductive support comprises at least a charge generation layer and a charge transport layer, wherein at least a charge generation material and A paint for a charge generation layer, comprising a binder resin and a gas-phase synthetic silicide hydrophobized with polydimethylsiloxane in a paint-forming solvent. 5. The content of the gas-phase synthetic silica hydrophobized with the polydimethylsiloxane with respect to the total solid content of the charge generation layer coating material is not more than 5% by weight. 4. The paint for a charge generation layer according to 4.