JP2837468B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor.

[Prior Art] Inserting an undercoat layer between a photosensitive layer and a support is a known technique for obtaining good chargeability and good adhesiveness.

However, even if the undercoat layer is provided, when the material is formed of a material that reduces electric resistance under high humidity conditions, charge injection from the support occurs, and as a result, minute black spots are generated in the reversal development process. Inconvenience such as appearing on the image is seen. Conversely, when the material of the undercoat layer is formed of a material that does not reduce the electric resistance under high humidity conditions, the electric resistance increases in a low humidity environment and the residual potential increases. In order to solve these problems, it is known that a polyamide resin, which is an alcohol-soluble resin, is used as a blocking layer, and an additive is added to the blocking layer to control the conductivity and create an optimal blocking layer (undercoat layer). However, as one of the methods, there is a method in which an inorganic pigment (for example, TiO ₂ ) and an electrolyte-based additive (—Na ₂ SO ₃ , Li ₂ SO ₄ etc) are added.

This is an excellent formulation that can solve the above-mentioned problems, but also when the moisture content of the undercoat layer is large, corrosion on the surface of the A1 support occurs when stored under high temperature and high humidity for a long time. There is a problem that it deteriorates, and it is desired to improve one step.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoconductor in which corrosion of an A1 support is suppressed under such circumstances.

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that an alcohol-soluble polyamide resin is used as a blocking layer to contain a conductive polymer and an electrolyte-based additive. It was found that a good photoreceptor free from the above problems could be obtained under a wide range of environmental conditions from high humidity to low humidity.

However, the photoreceptor having an undercoat layer of the above formulation is corroded on the surface of the A1 support when stored at high temperature and high humidity for a long period of time. As a cause of this, it was found that the moisture content of the undercoat layer had an influence, and it was found that a photoconductor having good characteristics without corrosion of the A1 support could be obtained by setting the specific moisture content. That is, the gist of the present invention is to provide a photosensitive layer in which an undercoat layer, a charge generation layer and a charge transfer layer are sequentially laminated on an A1 support or a photosensitive member having a photosensitive layer containing a charge generation material and a charge transfer material on an undercoat layer. An electrophotographic photoreceptor characterized in that the undercoat layer has a saturated moisture content at 20 ° C. and 90% RH of not more than 0.02 g per 1 g of the undercoat layer.

In order to control the moisture content of the undercoat layer, for example, the type of resin used in the undercoat layer may be selected from those having appropriate moisture content characteristics, or a resin having a low moisture content and a resin having a high moisture content may be appropriately used. It can be performed by mixing them at an appropriate ratio, or by mixing an inorganic pigment or the like in a resin and adjusting the mixing ratio to an appropriate value.

As the resin of the undercoat layer between the A1 support and the photosensitive layer, a water-soluble or alcohol-soluble resin is used. The thickness of the undercoat layer is preferably 0.1 to 10 μm, and more preferably 1 to 5 μm in terms of characteristics.

Corrosion of the A1 support has the same effect as the adhesion of moisture to the A1 surface because the undercoat layer contains moisture.
If chloride ions are present even at m, the A1 oxide film undergoes local destruction, causing pits (pitting corrosion)-corrosion.

In addition, the A1 alloy contains Ti, Fe, etc. as impurities, and since the ionization tendency is A1>Ti> Fe, a local battery is formed between A1 and the impurities, and the impurities become the poles of the cathode reaction and corrosion proceeds. I do. At this time, if an electrolyte-based substance is present, it is considered that the reaction of the local battery is accelerated and corrosion is more likely to occur.

The present invention will be described in more detail below. As described above, the photoreceptor used in the present invention has a configuration in which an undercoat layer and a photosensitive layer are sequentially laminated on a conductive substrate. The conductive substrate is aluminum.

Examples of the conductive polymer used in the undercoat layer include a polymer containing a sodium sulfonate group, an anionic conductive polymer represented by a polymer containing an ammonium sulfonate group, and a polymer containing a quaternary ammonium base. And a cationic conductive polymer represented by

The undercoat layer contains an inorganic pigment. Examples of such inorganic pigments include titanium dioxide, zinc oxide, zinc white, lead white, lithopone, calcium carbonate, alumina, barium sulfate, and white carbon, and preferably have a refractive index of 1.9 or more in visible light or near infrared light. It is an inorganic white pigment having a relatively high value. In particular, the addition of an inorganic white pigment is effective in preventing the occurrence of moire.

Further, sodium sulfonate (-Na ₂ SO ₃₎ inclusions, lithium sulfate (Li ₂ SO ₄₎ and the like as a material of the electrolyte system is added.

The undercoat layer contains a conventionally used binder (low-resistance resin). Although it may be used here, the binder is soluble in water or alcohol in consideration of the condition that it is also dissolved in the solvent for dissolving the conductive polymer and is not immersed in the photosensitive layer forming solution applied on the undercoat layer. Is preferred. Specific examples include polyvinyl alcohol, sodium polyacrylate, CMC, casein, sodium alginate, nylon, copolymerized nylon, and alkoxymethylated nylon.

To form an undercoat layer with these materials, a conductive polymer, a solvent, an electrolyte-based additive, and an inorganic pigment are added,
If necessary, the binder may be placed in a ball mill or the like to disperse the pigment well, and the resulting dispersion may be applied on a conductive substrate and dried. Undercoat layer thickness is 0.3-20μm
It is about.

The ratio of the conductive polymer, the inorganic pigment, and the binder varies depending on the material used, and thus cannot be determined uniformly. However, when the total of the conductive polymer and the binder is 1 part, the inorganic pigment is in a weight ratio. 10 parts or less, preferably 0.05
About 10 parts is appropriate. Also, the ratio between the conductive polymer and the binder cannot be determined uniformly, but when the conductive polymer is 1 part, the binder is 0 to 0 by weight.
A suitable amount is 200 parts, preferably about 10 to 200 parts.

The photosensitive layer is (1) a charge transport complex formed by a combination of an electron donating compound and an electron accepting compound (USP348
4237), (2) Organic photoconductor sensitized by adding a dye (described in JP-B-48-25658), (3)
Pigment dispersed in a hole or electron active matrix (described in JP-A-47-30328 and JP-A-47-18545); (4) Functional separation into a charge generation layer and a charge transport layer (Described in JP-A-49-105537), (5) a eutectic complex comprising a dye and a resin as a main component (described in JP-A-47-10785), and (6) a charge transport complex. It may be formed of any of conventionally known organic photoconductors such as those containing an organic pigment or an inorganic charge generating material (described in JP-A-49-91648).

However, among these, in particular, the laminated type photoreceptor of the type (4) has high sensitivity, and various materials can be selected in accordance with the function, and furthermore, the effect is further enhanced by applying a high electric field. It is even more advantageous.

The charge generation layer is composed of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a square pigment,
A charge-generating substance such as selenium powder, selenium alloy powder, amorphous silicon powder, zinc oxide powder, cadmium sulfide powder is dispersed in a binder resin solution such as polyester, polycarbonate, polyvinyl butyral, and acrylic resin, and this is dispersed on an undercoat layer. It is formed by coating on. The thickness of the charge generation layer is suitably about 0.01 to 2 μm.

The charge transport layer is composed of an α-phenylstilbene compound (JP-A
58-198043), hydrazone compounds (Japanese Unexamined Patent Publication No.
55-46760) is dissolved in a film-forming resin such as polyester, polysulfone, polycarbonate, polymethacrylates, polystyrene, and the like. 10 ~
What is necessary is just to apply about 30 micrometers. Here, the film-forming resin is used because the charge transporting substance generally has a low molecular weight and poor film-forming properties by itself.

The sightseeing body thus produced is suitable for repeated use, and if necessary, a protective layer similar to the conventional one can be provided on the surface of the photosensitive layer.

If such a photoreceptor is stored under high temperature and high humidity as described above, corrosion of the surface of A1 and deterioration of characteristics occur.

The present invention aims at preventing the corrosion of the A1 support or reducing the corrosion speed, and preventing the deterioration of the property or reducing the speed of the property deterioration by specifying the moisture content of the undercoat layer.

Example 1 Alcohol-soluble copolymerized nylon (CM-800 manufactured by Toray Industries, Inc.)
0) 200 g of this conductive polymer dissolved in methanol 2000 g (manufactured by Sanyo Chemical Industries, Ltd. Chemistat 6120) 20 g titanium oxide powder (Ishihara Sangyo Kaisha, Ltd. A-100) and 800g added, further Li ₂
1.6 g of SO ₄ was added and dispersed in a ball mill for 12 hours. The resulting coating solution was applied by dip coating to the surface of an aluminum drum (conductive substrate) of 80 mmφ x (length) 340 mm,
After drying at 10 ° C. for 10 minutes, an undercoat layer having a thickness of about 2 μm was formed.

On the other hand, butyral resin (S-LEC BL- manufactured by Sekisui Chemical Co., Ltd.)
S) 10 g was dissolved in 300 g of cyclohexanone, and this was added to the following structural formula Add 20 g of trisazo pigment represented by
Dispersion was performed for 8 hours. Subsequently, 420 g of cyclohexanone was added to the mixture, and the mixture was dispersed for 3 hours, taken out of the container, and diluted with cyclohexanone while stirring to obtain a solid content of 1.5% by weight to prepare a charge generation layer forming liquid.
This solution was dip-coated on the undercoat layer and dried at 120 ° C. for 10 minutes to form a charge generation layer having a thickness of about 0.3 μm.

Further, 240 g of polycarbonate resin (Panlite K-1300 manufactured by Teijin Chemicals Ltd.) is dissolved in 1800 g of tetrahydrofuran, A solution obtained by dissolving 140 g of the charge transporting material represented by is dip-coated on the charge generating layer, dried at 120 ° C. for 13 minutes, and dried for about 22 minutes.
A charge transport layer having a thickness of μm was formed to produce a laminated electrophotographic photosensitive member.

At the same time, an undercoat layer is coated on a Teflon sheet with a wire bar using a coating liquid for the undercoat layer, dried under the same conditions, and then peeled off. This is a trace moisture measuring device [Mitsubishi Kasei Corporation] CA-05
After leaving for 20 hours at 20 ° C. and 90% RH using a mold, the water content was measured and found to be 0.02 g / g.

The photosensitive member coated with the above photosensitive layer is heated at 45 ° C. and 90% RH for 1 hour.
Although stored for a year, the A1 surface was good without corrosion.

Comparative Example 1 A photosensitive layer was prepared in the same manner as in Example 1, except that the amount of TiO ₂ in the undercoat layer was changed to 100 g. The content of water was 0.06 g / g by the same measurement. This photoreceptor is 45 ℃, 90% RH
Under the following environment, the A1 support corroded in one day.

Comparative Examples 2 and 3 A photosensitive layer was coated in the same manner as in Example 1 except that the amount of TiO ₂ was changed to 540 g and 275 g. The measurement results of the water content were 0.045 g and 0.03 g per 1 g of the undercoat layer.

When the above-mentioned photoreceptor was stored in an environment of 95 ° C. and 90% RH, corrosion of the A1 surface occurred in the former in one month and in the latter in three months.

[Effects of the Invention] According to the present invention, by reducing the moisture content of the undercoat layer, it is possible to prevent the corrosion of the surface of the A1 support under high temperature and high humidity or to significantly reduce the corrosion speed.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Takaaki Ikegami 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-63-169657 (JP, A) JP-A-62-258471 (JP, A) JP-A-62-280852 (JP, A) JP-A-61-254951 (JP JP, A) JP-A-63-234261 (JP, A) JP-A-62-280768 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/14 101

Claims (1)

(57) [Claims] An electrophotographic photosensitive member having a photosensitive layer on an A1 support, wherein an undercoat layer is provided between the support and the photosensitive layer.
The undercoat layer is composed of a water-soluble or alcohol-soluble resin, a conductive polymer, an additive for an electrolyte thread, and an inorganic pigment. The undercoat layer has a water content when placed in an atmosphere of 20 ° C. and 90% RH for 20 hours. An electrophotographic photoreceptor characterized in that the amount is 0.02 g or less per 1 g of the undercoat layer.