JPH04182652A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve optical fatigue characteristics without increasing residual potential by forming an electric charge generating layer contg. a phthalocyanine pigment, satd. linear polyester resin, benzoguanamine resin and a specified hindered amine compd. CONSTITUTION:An electric charge generating layer contg. 100 pts. wt., in total, of 100 pts. wt. linear polyester resin and 10-30 pts. wt. benzoguanamine resin as resin binders, 40-200 pts. wt. phthalocyanine pigment and a hindered amine compd. is formed. The amine compd. is represented by the formula (where R is H or alkyl) and is used by 5-50 pts. wt. per 100 pts. wt. of the pigment. Excess electric charges generated in the electric charge generating layer and electric charges trapped in the layer are efficiently captured and vanished by the hindered amine compd. to prevent fatigue. Since the resin binders are cured, superior solvent resistance is ensured, the amine compd. is prevented from leaching out and entering an electric charge transferring layer at the time of forming the layer and electric charges are not trapped in the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and particularly to a functionally separated electrophotographic photoreceptor suitable for a laser beam printer.

[Prior Art] Many electrophotographic photoreceptors, both organic and inorganic, have been proposed, and among them, a functionally separated photoreceptor consisting of a charge generation layer and a charge transport layer is used as a high-sensitivity photoreceptor for copying. It has been put into practical use as a photoconductor for machines and laser beam printers.

As the charge generation material of the charge generation layer, for example, Japanese Patent Application Laid-open No. 59
Phthalocyanine pigments shown in Japanese Patent Laid-Open No. 15253, disazo pigments shown in Japanese Patent Application Laid-Open No. 116040/1983, and the like have been put into practical use. On the other hand, as the charge transporting substance of the charge transporting layer, poly-N-vinylcarbazole series shown in JP-A-52-77730, pyrazoline derivatives shown in JP-A-49-105537, JP-A-55-35319 The oxazole compounds and thiazole compounds shown in , as well as the hydrazone compounds shown in JP-A No. 59143, etc., have been proposed.

The charge-generating substance and the charge-transporting substance do not have film-forming properties by themselves, and are formed into a film by being dispersed or dissolved in a solvent together with a binder resin, coated on a conductive support, and dried. Conventionally, these binder resins include polyester resin, phenol resin, butyral resin, melamine resin, formal resin, epoxy resin, silicone resin,
Urethane resin, polycarbonate resin, methacrylic resin.

Acrylic resin, styrene resin, etc. are used.

These binder resins are used alone or as a mixture of two or more.

Usually, electrophotographic photoreceptors undergo a charging process using corona charging.
Exposure process to form a latent image of the original image, development process to make the latent image into a visible image with toner, transfer process to transfer the toner to paper etc., removal of residual toner adhering to the surface of the photoreceptor and static electricity removal. It is used after repeated cleaning steps. Therefore, electrophotographic photoreceptors are required to have stable electrophotographic properties such as charging properties and sensitivity over a long period of time even after repeated use.

Photofatigue development is one of the factors that causes changes in the charging characteristics, sensitivity, etc. of electrophotographic photoreceptors used in copying machines, laser beam printers, and the like. The cause of this is that the photoreceptor is irradiated with external light during the exposure process, cleaning process, and handling of the photoreceptor, and the charges generated in the charge generation layer are gradually trapped in the main charge generation layer. It is thought that during corona charging, this charge neutralizes the surface charge, resulting in a decrease in charging potential. As a way to solve this optical fatigue,
For example, a method using a specific hydrazone compound and a specific pyrazoline compound shown in Japanese Patent Publication No. 60-58468,
Alternatively, a method using a mixed system of charge transporting substances, such as a method using two specific hydrazone compounds shown in JP-A No. 61-134767;
A method of adding a benzophenone derivative to a charge transport layer as shown in No. 65, or Japanese Patent Application Laid-Open No. 63-206757
A method of adding a hindered amine compound to a charge transport layer as shown in JP-A-63-274958, and a method of adding a dye to a charge transport layer as shown in JP-A-63-274958 are known.

[Problems to be Solved by the Invention] In recent years, copying machines, laser beam printers, etc. are required to have high-speed printing (copying) and high definition. stability is required. Therefore, as a measure against optical fatigue in electrophotographic photoreceptors, it has become difficult to achieve both high sensitivity and potential stability, depending on the method of improving the charge transport layer as described above. That is, when optical fatigue characteristics are improved for the purpose of stabilizing the potential in order to obtain high definition, there is a problem in that the residual potential increases.

An object of the present invention is to provide an electrophotographic photoreceptor that has high sensitivity, exhibits less deterioration in chargeability due to optical fatigue, and exhibits almost no increase in residual potential even after repeated use.

[Means for Solving Problem 81] The present invention provides a functionally separated electrophotographic photoreceptor having a charge generation layer provided on a conductive support and a charge transport layer provided on the layer. An electrophotographic photoreceptor characterized in that the charge generation layer contains a phthalocyanine pigment, a saturated linear polyester resin, a benzoguanamine resin, and a hindered amine compound having one or more of the following formula (I) in one molecule.

(However, in the formula, R represents H or an alkyl group.) The hindered amine compound represented by the general formula (I) of the present invention is
It is known as an antioxidant for plastics and is easily available.

Further, the present invention uses a charge transporting substance together with a charge generating substance, and the charge transporting substance includes, for example, oxadiazole,
Examples include triazole, imidazole, oxazole, pyrazoline, benzothiazole, triphenylamine, hydrazone, and derivatives of these substances, which can be used alone or in combination of two or more.

The blending ratio of the linear polyester resin and benzoguanamine resin as the binder resin is 5 to 100 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the former. The blending ratio of the binder resin and phthalocyanine pigment is 10 to 900 parts by weight of the latter to 100 parts by weight of the former.
Parts by weight, preferably 40 to 200 parts by weight. Further, the amount of the phthalocyanine pigment and the hindered amine compound represented by the general formula (I) of the present invention is 1 to 100 parts by weight, preferably 5 to 50 parts by weight, per 100 parts by weight of the former.

The conductive support forming the photosensitive layer has a volume resistivity of 1
Those having a conductivity of 0.010 Ωcm or less are preferable, such as aluminum, alloys of aluminum and other metals, iron,
Use metal plates of lead or copper, metal compound plates such as tin oxide, indium oxide, copper iodide, chromium oxide, etc., conductive plastic plates, or plastics, paper, glass, etc. that have been made conductive by vapor deposition, sputtering, etc. be able to.

These supports are generally cylindrical or sheet-like, but are not particularly limited in shape.

[Function] The reason why the use of the charge generation layer of the present invention improves the photofatigue properties and suppresses the increase in residual potential due to repeated use is that the hindered amine compound absorbs excess charge generated within the charge generation layer. It efficiently captures and erases trapped charges to prevent optical fatigue, and because the binder resin is hardened, it has excellent solvent resistance, and hindered amine compounds are eluted when forming the charge transport layer. This is considered to be because the charge transport layer is prevented from being mixed into the charge transport layer, and as a result, charges are not trapped within the charge transport layer. This is largely different from the method disclosed in JP-A No. 63-206757, in which a hindered amine compound is added to the charge transport layer to improve optical fatigue properties.

Further, JP-A-63-18355 describes a method of adding a hindered amine compound to a photosensitive layer for the purpose of obtaining an electrophotographic photoreceptor having excellent ozone resistance and durability. The mixture of saturated polyester resin and benzoguanamine resin as the binder resin shown in the present invention exhibits an excellent effect on the dispersion stability of phthalocyanine pigments, and enables the production of a thin and uniform charge generation layer, resulting in high sensitivity. It is believed that the binder resin is the above-mentioned resin and the pigment is limited to a phthalocyanine pigment, as disclosed in the above-mentioned JP-A-6
This is a major difference from No. 3-18355.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

[Examples 1 to 5 and Comparative Example 1] A charge generation layer was formed on a 100 μm aluminum plate by a dipping method using a coating liquid having the composition shown in Table 1.
Dry at °C. The thickness of the charge generation layer was 1 μm or less. The coating liquid is prepared by dissolving the saturated linear polyester resin and benzoguanamine resin in a mixed solvent, and then adding and dissolving the hindered amine compound. Thereafter, a phthalocyanine compound was added, and the mixture was stirred for 5 hours using a shaking type stirrer.A charge transport layer was coated on this charge generation layer using a dipping method with a coating liquid having the composition shown in Table 2. It was dried at 110°C to obtain an electrophotographic photoreceptor. The thickness of the charge transport layer is 15μ
It was m.

Table 2 The produced electrophotographic photoreceptors were evaluated for optical fatigue characteristics and residual potential.

It was irradiated with a fluorescent lamp with an illuminance of 1000 lux for 60 minutes, and the surface potential was evaluated as a ratio to the surface potential before irradiation with the fluorescent lamp. Further, the surface potential was measured using an electrostatic recording paper evaluation device (manufactured by Yoro Denki, Model 5P-428) in static mode 3 under the conditions of a corona applied voltage of -5.5 kV.

In addition, the residual potential was measured using the electrostatic recording paper evaluation device described above.
The surface potential was expressed as the surface potential after 0.2 seconds of irradiation with an illumination intensity of 50 lux (tungsten lamp) for 0.2 seconds when charged at 700V.

Table 3 shows the characteristics of the electrophotographic photoreceptor produced in this example according to the above evaluation method.

Table 3: Hindered amine compounds (mark LA63)
As the amount of addition increased, the optical fatigue properties improved, but on the contrary, the residual potential tended to increase.

Next, changes in residual potential due to repeated use were investigated.

In the repeated test, the sample was attached to a rotating drum with a circumferential speed of about 190 cm/min, and then -5.2 KV was applied to a corona charger installed near the drum while the drum was rotating.
After charging by applying a voltage of
Tungsten lamp light installed in the direction of 50 degrees (illuminance 50
The exposure process was repeated for 5 hours. Thereafter, the residual potential was measured in the same manner as described above. The results are shown in Table 4.

As shown in Table 4, it was found that by adding the hindered amine compound, the residual potential was stabilized even after repeated use.

[Comparative Example 2] Electrophotographic photosensitive material was prepared in the same manner as in the above Example except that the benzoguanamine resin (Melan 366) was excluded and the amount of the hindered amine compound (Mark LA63) was changed to 5 parts by weight in the composition shown in Table 1 above. The body was created.

The resulting photoreceptor was measured for optical fatigue properties and residual potential before and after repeated testing. As a result, the optical fatigue property was 75%
, initial residual potential -150V, residual potential after repeated tests -
It was 250■.

As described above, when the benzoguanamine resin (Melan 366) was not included, the photofatigue properties were the same as those of Y, but the residual potential was significantly increased. This is considered to be because the saturated polyester resin (Vylon 200) was eluted during the coating of the charge transport layer, and the hindered amine compound (mark LA63) was eluted and mixed into the charge transport layer.

[Effects of the Invention] In the electrophotographic photoreceptor of the present invention, the charge generation layer is made of a phthalocyanine pigment and a saturated linear polyester resin.

By containing a benzoguanamine-based resin and a hindered amine compound having one or more of formula (I) in one molecule, it is possible to improve the optical fatigue properties without increasing the residual potential, resulting in a long-life functionally separated type. An electrophotographic photoreceptor can be obtained.

Claims (1)

[Scope of Claims] 1. A functionally separated electrophotographic photoreceptor having a charge generation layer provided on a conductive support and a charge transport layer provided on the layer, wherein the charge generation layer comprises phthalocyanine. 1. A photoreceptor for electrophotography, which comprises a pigment based on a saturated linear polyester resin, a benzoguanamine resin, and a hindered amine compound having one or more of the following general formula (I) in one molecule. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R in the formula represents H or an alkyl group)