JPH06208230A - Laminate type electrophotographic receptor and coating material for electric charge generating layer - Google Patents

Abstract

PURPOSE:To enhance the dispersibility of a coating material for an electric charge generating layer, to form a satisfactory coating film free from unevenness and to stably obtain an excellent article free from unevenness in sensitivity as an electrophotographic receptor. CONSTITUTION:The objecitive coating material for an electric charge generating layer consists of an electric charge generating material, a resin binder, polydimethylsiloxane and a solvent for converting them into the coating material. An electric charge generating layer is laminated on an electric conductive substrate by dip coating with the coating material and an electric charge transferring layer is further laminated on the electric charge generating layer to obtain the objective electrophotographic receptor.

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 laminate type electrophotographic photoreceptor having a photosensitive layer composed of an organic charge generating layer and an organic charge transporting layer. The present invention relates to a coating material for forming and forming a generating layer.

[0002]

2. Description of the Related Art Conventionally, as electrophotographic photoconductors, photoconductors made of inorganic photoconductive substances such as selenium, selenium-tellurium alloy, cadmium sulfide and zinc oxide have been widely used, but in recent years, they are easy to synthesize. Research on organic photoconductive substances having characteristics such as selection of a compound exhibiting photoconductivity in an appropriate wavelength range is under way.

An electrophotographic photosensitive member using an organic photoconductive substance as a photosensitive layer has advantages such as easy film formation, high flexibility and a great degree of freedom in designing, inexpensive and non-polluting. However, the sensitivity and the photoreceptor life were inferior as compared with the inorganic photoconductive substance. Therefore, in order to improve them, a multi-layer type electrophotographic photoreceptor in which a charge generating layer and a charge transport layer have different functions to form a photosensitive layer has been proposed and put to practical use. Since the charge transporting agent generally used in this laminated electrophotographic photoreceptor is an electron-donating substance such as pyrazoline, hydrazone, or oxazole, the charge transporting layer is a hole transporting type, and therefore the charge transporting layer is formed on the charge generating layer. When laminated, they are used with negative charging.

On the other hand, as the charge generating substance used in the charge generating layer, organic pigments and dyes such as phthalocyanine type, azo type, squarylium type, perylene type, cyanine type, etc. are used. Wavelength range (80
Phthalocyanine compounds having absorption around 0 nm) have been widely used in recent years as charge generating substances for electrophotographic photoreceptors for laser beam printers. As the phthalocyanine-based charge generating substance, various crystal 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, α-type Although β-type copper phthalocyanine, titanyl phthalocyanine, and the like 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 with which extremely high sensitivity can be obtained (for example, electron (The Journal of the Photographic Society, 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, a laminate comprising a charge-generating layer and a charge-transporting layer in which a titanyl phthalocyanine pigment having various crystal forms is used as a charge-generating substance in an electrophotographic photoreceptor having high sensitivity. Although many type organic photoconductors have been extensively studied, most of these pigments are granular crystals having a size of about 0.1 μm or less, and they are mixed with a binder resin which has been used for a general charge generation layer. Is difficult to disperse, and it has been difficult to obtain a coating material that can stably obtain a good coating film even if various dispersion or kneading methods are used.

That is, using an ordinary binder resin such as polyvinyl butyral resin and an ordinary alcohol-based paint-forming solvent, shake continuously with glass beads in a container, or prepare a dispersion paint using an ultrasonic homogenizer. In the method, the thickness of the charge generation layer becomes uneven,
There is a problem in that the pigment in the charge generation layer aggregates and becomes non-uniform, resulting in non-uniform sensitivity as an electrophotographic photoreceptor.

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

[0008]

In view of the above-mentioned problems, the laminated electrophotographic photoreceptor of the present invention is a laminated organic photoreceptor having a photosensitive layer comprising at least a charge generation layer and a charge transport layer. The generating layer contains at least a charge generating substance, a binder resin and polydimethylsiloxane.

Further, in view of the above-mentioned problems, the charge generation layer coating composition of the present invention has the following properties:
At least a charge-generating substance, a binder resin, and polydimethylsiloxane are contained in a paint-forming solvent.

[0010]

The electrophotographic photosensitive member of the present invention is a laminated organic photosensitive member having a photosensitive layer comprising at least a charge generating layer and a charge transporting layer. By containing siloxane as a dispersion aid or an anti-settling agent,
Improves the dispersibility and dispersion uniformity of the organic pigment that is the charge generation material, and provides good electrophotography without uneven density due to uneven charge generation layer film thickness or pigment aggregation. It is a photoreceptor.

The charge generation layer coating material of the present invention is a coating material used for coating formation of the charge generation layer, wherein at least the charge generation material and the binder resin are used as a dispersion aid or an anti-settling agent in polydimethylsiloxane. By improving the dispersibility, the dispersion uniformity and the dispersion stability of the organic pigment as the charge generating substance, there is no non-uniformity of the charge generation layer film thickness or the density of the pigment due to aggregation of the pigment, that is, The present invention makes it possible to stably produce a good electrophotographic photosensitive member having no uneven sensitivity with high yield.

[0012]

EXAMPLES The laminated electrophotographic photoreceptor and the coating material for the charge generating layer of the present invention will be described in detail below.

First, the charge generation layer coating material of the present invention, that is, the coating material used for coating and forming the charge generation layer in a normal laminated organic photoreceptor will be described. This paint comprises a charge generating substance, a binder resin, polydimethylsiloxane and a paint forming solvent.

The charge-generating substance used in the coating material for the charge-generating layer of the present invention may be any organic pigment that has appropriate light absorption and charge-generating ability and can be used as an ordinary laminated electrophotographic photoreceptor. A phthalocyanine-based pigment, particularly a titanyl phthalocyanine pigment, is preferable as a highly sensitive material.

As the binder resin used in the coating material for the charge generating layer of the present invention, a well-known resin such as 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, but having a butyralization degree of 50 to 70 mol% in consideration of dispersibility of the charge generating substance. Is preferred. If the degree of butyralization is too small, it becomes water-soluble, and if the degree of butyralization is too large, the affinity with the charge generating substance decreases, which is not preferable. With respect to the molecular weight, any polymer having a degree of polymerization of about 200 to 2,000 may be used, but a higher molecular weight provides better dispersibility 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 will deteriorate, and if it is too large, it will be difficult to form the layer, which is not preferable.

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

The polydimethylsiloxane used as a dispersion aid or an anti-settling agent in the charge generation layer coating composition of the present invention is polydimethylsiloxane which is commercially available as ordinary silicone oil and has a viscosity of several tens to several hundreds cSt, Those having a number average molecular weight of thousands to tens of thousands are used. By this addition, the surface tension of the paint is lowered and the pigment dispersibility as a paint is remarkably improved. It is considered that this is because the pigments weakly interact with each other via the polydimethylsiloxane chain, thereby weakening the cohesive force between the strong pigments.

If the amount of polydimethylsiloxane added to the coating is too small, it will not be effective as a dispersion aid or anti-settling agent, and if it is too large, the foaming of the coating will be too large, and the film-forming property will be problematic. There is. From the viewpoint of dispersibility, it is desirable to add 0.01 parts by weight or more of polydimethylsiloxane when the total weight of the coating is 100 parts. Generally, the solid content concentration in the coating material is adjusted to a viscosity at which an appropriate film thickness as the charge generation layer can be obtained, although it depends on the binder resin used and the coating method of the coating film. %, And the above conditions were satisfied, for example, with respect to 100 parts by weight of the total paint, 4 parts by weight of total solid content and 0.04 parts by weight of polydimethylsiloxane.

Various organic solvents can be used as the paint-forming solvent used for the charge generation layer paint of the present invention.
An alcohol solvent, particularly a butanol solvent, is preferable from the viewpoint of layer formation or the relationship with the substrate.

Further, as a method for forming a dispersion having a coating composition having the above composition, a method of repeatedly shaking with glass beads in a glass bottle can be used.

The charge generation layer coating material of the present invention has been described above in detail. Next, a detailed description will be given of an electrophotographic photoreceptor in which a charge generation layer formed by coating the charge generation layer coating material is laminated on a charge transport layer. The laminated electrophotographic photoreceptor of the present invention is a laminated organic photoreceptor in which the photosensitive layer on the conductive support comprises at least a charge transport layer and a charge generation layer.

The conductive support of the laminated electrophotographic photosensitive member of the present invention may be any one having a conventionally known conductivity, and a metal plate such as aluminum or aluminum alloy and a drum are generally used. To be

The charge generating layer of the laminated electrophotographic photoreceptor of the present invention comprises at least a charge generating substance, a binder resin and polydimethylsiloxane. The charge generation layer is formed on the conductive support using the above-mentioned coating material for the charge generation layer by a coating method such as a dip coating method, a spin coating method, a spray coating method, or an electrostatic coating method. The thickness of the charge generation layer is preferably about 0.1 to 1 μm in view of characteristics. If the film thickness is too thin, the charge generation amount is small and sufficient sensitivity cannot be obtained, and if the film thickness is too thick, the charging property is lowered, and the charging property and the repeated stability of sensitivity are impaired. When a charge generation layer is formed on a conductive support, butyral resin, vinyl acetate resin or polyamide resin is used to improve the adhesion between the conductive support and the charge generation layer or to prevent charge injection from the conductive support side. It is also possible to provide a layer having a thickness of 0.1 to 1 μm.

The charge transport layer of the laminated electrophotographic photoreceptor of the present invention comprises at least a charge transport substance and a binder resin. The charge transport material is an alkyl group, an alkoxyl group, an amino group, an imino group, a compound having an electron-donating property such as an imide group, anthracene, phenanthrene, 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 is polycarbonate resin, polyarylate resin, polyester resin, acrylic resin,
Conventionally known thermoplastic resins and thermosetting resins such as styrene resins can be used. Among them, solvent resistance is required when the photosensitive layer is laminated on the charge transport layer and the charge generation layer is laminated thereon, 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. From the characteristics, the content of the binder resin is preferably 60% by weight or less based on the total amount of the charge transport layer. For the charge transport layer, a coating material obtained by dissolving a predetermined amount of a charge transport substance and a binder resin in an organic solvent is used, and a dip coating method, a spin coating method, a spray coating method, or a static coating method is applied to the charge generation layer. It is formed by a coating method such as an electric coating method. The thickness of the charge transport layer is characteristically 5 to 30 μm.
A degree is preferable. If the film thickness is too thin, the chargeability will decrease, and if it is too thick, the sensitivity will decrease.

The charge generation layer coating material and the laminated electrophotographic photoreceptor of the present invention have been described above in detail. Specifically, the dispersibility of the charge generation layer coating composition was improved, and the nonuniformity of the charge generation layer film thickness and sensitivity of the multilayer electrophotographic photoreceptor obtained thereby was eliminated. It is shown below.

The first embodiment of the present invention will be described below. Α-type titanyl phthalocyanine obtained by converting crude titanyl phthalocyanine obtained from phthalonitrile and titanium tetrachloride into α-type crystals by solvent treatment
m) 27 parts by weight of vinyl butyral resin (Sekisui Chemical Co., Ltd., trade name S-REC BL-1) 6.5 parts by weight and solvent-soluble fluororesin (SCM13 manufactured by Asahi Glass Co., Ltd.)
3) 6.5 parts by weight, 0.4 parts by weight of polydimethylsiloxane (TSF451-100 manufactured by Toshiba Silicone Co., Ltd.), 1
1000 parts by weight of propanol, glass beads (diameter 1 m
m) 1500 parts by weight was shaken in a glass bottle for 15 hours to obtain a charge generation layer coating material.

Using the paint thus obtained, immediately after preparation of the paint, a pulling rate of 100 mm / min was set on an aluminum drum which had been subjected to an alumite treatment by a dip coating method.
To form a charge generation layer. The coating film was dried at 100 ° C. for 1 hour.

The appearance of the coating film of the charge generation layer thus obtained was evaluated for the presence or absence of pigment density unevenness or color unevenness. The evaluation results are shown in (Table 1). In this table, the appearance evaluation ○ indicates a good state where no unevenness is seen,
Δ indicates that there is some unevenness, and × indicates that there is unevenness.

[0029]

[Table 1]

Further, 1,1-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene (1 part by weight) and a polycarbonate resin (trade name: Macrohole N manufactured by Bayer Co.)
A coating material prepared by dissolving 1 part by weight of methylene chloride in 9 parts by weight was applied onto the charge generation layer by dip coating and dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm.

The electrostatic characteristics of the photoconductor drum thus manufactured were evaluated. FIG. 1 shows an electrostatic characteristic evaluator of an electrophotographic photosensitive member according to an embodiment of the present invention. Figure 1
In 101, 101 is a photoconductor 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 colored glass filter (UV cut). As the surface electrometer, MODEL344 manufactured by Trek Japan Co., Ltd. was used. The electrostatic characteristics are measured at room temperature and normal humidity (20 ° C, 50% RH) in a surface electrometer when the potential after negative corona charging measured by the surface electrometer measurement probe (1) is kept constant at 700V. The post-exposure potential measured with the measurement probe (2) was measured as the sensitivity. The exposure was performed with an optical filter as 800 nm monochromatic light, 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, since the charge generation layer coating material is composed of the charge generation substance, the binder resin, the polydimethylsiloxane and the paint-forming solvent, there is no unevenness of the pigment or uneven color. A charge generating layer having a film-forming property is obtained, and a multilayer electrophotographic photosensitive member is formed by stacking a charge generating layer and a charge transport layer in this order on a conductive support by a dip coating method using this coating solution. The body has 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 the coating material for the charge generation layer was prepared, but in the second embodiment, the charge generation layer was formed after standing for 5 hours after preparation of the coating material. 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 evaluation results 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, the charge generation layer and the charge transport layer are formed in the same manner as in the first embodiment except that the charge generation layer coating material is prepared as follows. Evaluation was carried out in the same manner as in the examples. First, 27 parts by weight of α-type titanyl phthalocyanine and vinyl butyral resin (Sekisui Chemical Co., Ltd., trade name S-REC BL-1) 6.5
Parts by weight and solvent-soluble fluororesin (SC manufactured by Asahi Glass Co., Ltd.
M133) 6.5 parts by weight, 1 part propanol 1000 parts by weight and glass beads (diameter 1 mm) 1500 parts by weight were shaken in a glass bottle for 15 hours to obtain a charge generation layer coating material.

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 vinyl butyral resin (Sekisui Chemical Co., Ltd., trade name S-REC BL-1) and solvent-soluble fluororesin (SCM133, Asahi Glass Co., Ltd.) 6.5. A charge generation layer was prepared in the same manner as in Example 1 except that 13 parts by weight of a vinyl butyral resin (trade name: S-REC BL-1 manufactured by Sekisui Chemical Co., Ltd.) was used instead of the weight part. A charge transport layer was formed, and evaluation was performed 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 (Sekisui Chemical Co., Ltd., trade name S-REC BL-1) and solvent-soluble fluororesin (SCM133, Asahi Glass Co., Ltd.) 6.5. A charge generation layer coating material was prepared by using 13 parts by weight of vinyl butyral resin (Sekisui Chemical Co., Ltd., trade name S-REC BL-1) and 13 parts by weight of solvent-soluble fluororesin (SCM133, Asahi Glass Co., Ltd.) instead of parts by weight. Then, the charge generation layer and the charge transport layer were formed in the same manner as in the first embodiment except that the pulling rate when forming the charge generation layer by the dip coating method was 50 mm / min. Evaluation was carried out in the same manner as.

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 generation layer was formed immediately after preparing the charge generation layer coating material.
In the comparative example of 1, the charge generating layer was formed in the same manner as in the first comparative example except that the charge generating layer was formed after standing for 3 hours after preparation of the coating material.
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).

[0043]

The laminated electrophotographic photosensitive member and the coating material for the charge generating layer of the present invention have been described in detail above, and the present invention has the following effects.

Since the coating material for the charge generating layer is composed of the charge generating substance, the binder resin, the polydimethylsiloxane and the paint-forming solvent, the charge generating layer having good coatability without unevenness of pigment or unevenness of color is stabilized. A multilayer electrophotographic photosensitive member obtained by laminating a charge generation layer and a charge transport layer in this order on a conductive support by a dip coating method using this coating solution is excellent in sensitivity. It has electrophotographic sensitivity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrostatic characteristic evaluation device for an electrophotographic photosensitive member according to a first embodiment of the present invention.

[Explanation of symbols]

 101 Photosensitive Drum 102 Corona Charger 103 Electrometer Probe A 104, 107 Tungsten Lamp 105 Interference Filter (800 nm) 106 Electrometer Probe B 108 Colored Glass Filter (UV Cut)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsumugi Kobayashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masatoshi Maeda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A laminate type organic photoconductor in which a photosensitive layer on a conductive support comprises at least a charge generation layer and a charge transport layer, wherein at least the charge generation substance, a binder resin and polydimethylsiloxane are contained in the charge generation layer. An electrophotographic photosensitive member comprising: 2. The electrophotographic photosensitive member according to claim 1, wherein the charge generating substance in the charge generating layer is a phthalocyanine pigment. 3. The electrophotographic photosensitive member according to claim 1, wherein the charge generating substance in the charge generating layer is an α-type oxotitanium phthalocyanine pigment. 4. A paint used for coating and forming the charge generating layer of a laminated organic photoreceptor, wherein a photosensitive layer on a conductive support comprises at least a charge generating layer and a charge transporting layer, and at least a charge generating substance. A coating material for a charge generating layer, characterized by containing a binder resin and polydimethylsiloxane in a coating solvent.