JPS63151954A - Positive electrification type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance electrification capability, sensitivity, and stability against repeated uses by laminating a first photosensitive layer containing a first electric charge generating material higher in photosensitivity in negative electrification than in positive electrification and a second photosensitive layer containing a second charge generating material higher in photosensitivity in positive electrification than in negative electrification to form a composite photosensitive layer. CONSTITUTION:The first photosensitive layer located on the surface of the photosensitive body and containing the first charge generating material higher in photosensitivity in negative electrification than in positive electrification and the second photosensitive layer located on the side of a substrate and containing the second charge generating material higher in photosensitivity in positive electrification than in negative electrification are laminated to form the composite photosensitive layer, thus permitting the obtained photosensitive body to be extremely enhanced in photosensitivity, stabilized in chargeability characteristics against repeated uses, and adapted to practical uses. As the usable binder material, polyethylene, polypropylene, addition polymerization type resins, such as melamine resins, polymerization addition type resins polycondensation type resins, and polymer organic semiconductors, such as poly-N-vinylcarbazole, are embodied.

Description

[Detailed Description of the Invention] (Object of the Invention) (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor, and more particularly, it relates to an electrophotographic photoreceptor that is positively charged by an anode corona discharge and then exposed to light. This invention relates to a charged electrophotographic photoreceptor.

(Prior art) Electrophotographic photoreceptors are positively charged type due to chronic corona charging.
There are two types of negatively charged types.

Many negatively charged photoreceptors have been developed in which a charge generation layer and a charge transport layer are successively laminated on a conductive support, and some are known to have excellent initial characteristics. However, cathode corona discharge tends to generate ozone, and the deterioration of the photoreceptor due to the oxidizing effect of this ozone and the contamination of the copying environment due to ozone have become problems, and it is desirable to develop a positively charged electrophotographic photoreceptor with excellent characteristics. It is rare.

(Problems to be Solved by the Invention) Generally, the photoconductive process of an electrophotographic photoreceptor consists of a photocharge generation process and a charge transport process.

Conventionally known electrophotographic positively charged photoreceptors are the two mentioned above.
These processes can be roughly divided into those in which each process is performed using one type of substance, and those in which each process is performed using different types of substances.

As such electrophotographic photoreceptors, there are the following three types, limited to entertainment-separated photoreceptors in which charge generation and charge transport are performed using different materials.

■Those with a dispersed structure in which a charge generation material and charge transport material are dispersed in one layer■Those with a structure in which a charge transport layer and a charge generation layer are laminated in order on a conductive support■On a conductive support A structure in which a charge generation layer and a charge transport layer are laminated in order.
Both have the problem of low sensitivity.

The type (■) has not been studied much because there is no material with excellent charge transport.

In addition, in order to improve the sensitivity of photoreceptors of types ① and ②, studies are being conducted to increase the concentration of charge-generating materials or add charge-transporting materials; There is a problem that the charging ability is low because the speed is low.

The present invention has been made with attention to this point, and provides a positively charged electrophotographic photoreceptor of a type that is positively charged by an anode corona discharge and then exposed to light without deterioration of the photoreceptor due to ozone generation or ozone oxidation. The purpose is to

(Structure of the Invention) (Means for Solving the Problems) In the positively charged electrophotographic photoreceptor of the present invention, the photosensitive layer includes a first charge-generating substance that has higher photosensitivity when negatively charged than when positively charged. It is characterized by laminating a first photosensitive layer containing a second photosensitive layer containing a second charge-generating substance that has higher photosensitivity when positively charged than when negatively charged.

The comparison of photosensitivity when positively charged and negatively charged in the present invention is based on the results of preparing a single-layer photoreceptor made of a charge generating substance and a binder resin and evaluating the photosensitivity.

Specifically, perylene pigments, □ perinone pigments, and polycyclic quinone pigments are examples of the first charge-generating substance that has higher photosensitivity when negatively charged than when positively charged. On the other hand, phthalocyanine pigments, azo compounds, and indigo pigments are examples of second charge-generating substances that have higher photosensitivity when positively charged than when charged squarely.

The layer structure of the photoreceptor of the present invention basically has two layers containing the above-mentioned charge-generating substance on a conductive support, and contains a charge-generating substance that has higher photosensitivity when positively charged than when negatively charged. When the second photoreceptor layer is located on the side of the conductive support that is the lower layer, a photoreceptor exhibiting excellent photosensitive properties can be obtained.

If necessary, a charge transport layer and an undercoat layer may be formed between the photosensitive layer containing these two types of charge generating substances and the conductive support. It is also possible to form a retainer 1111 on the surface of the photoreceptor.

The thickness of the photosensitive layer containing the charge generating substance on the surface side is preferably at least 0.5 katai (preferably 1 -) or more. In other words, if the thickness of the charge generation layer on the surface side is too thin,
If the surface of the charge generation layer is subjected to mechanical damage during repeated use and during cleaning, part of the layer may be scraped off or black lines may appear on the image. Therefore, it is preferable to set the film thickness to 0.5 凱 or more.

If the thickness of the layer containing the charge-generating substance is too large, the number of thermally excited carriers generated will increase, resulting in insufficient charging ability at high temperatures. Therefore, it is desirable that the thickness of the two layers containing the charge generating substance be 30 mm or less (preferably 20 mm or less).

In other words, the photoreceptor of the present invention is a first photoreceptor with excellent electron transport ability.
A second photosensitive layer with excellent hole transport ability is placed on the surface side of the photoreceptor.
By providing the photosensitive layer on the conductive support side, it becomes possible to efficiently transport the generated carriers, thereby making it possible to obtain a highly sensitive photoreceptor. Therefore, it is desirable to add a carrier transport material having a high hole transport ability to at least the second photosensitive layer on the conductive support side.

The carrier transport substances used in the present invention include oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imitazole derivatives, imidasilone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Pyrazoline derivatives, oxacilone derivatives,
benzothiazole derivatives, penzimitazole derivatives,
They may be quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, and the like.

Binder materials, particularly binder resins, that can be used in the present invention include, for example, polyethylene, polypropylene, acrylic resins, methacrylic resins, vinyl chloride resins,
Addition polymerization type resins, polyaddition type resins, polycondensation type resins such as vinyl acetate resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and repetitions of these resins. Poly-N- Examples include polymeric organic semiconductors such as vinyl carbazole.

By the way, the support 1 on which the above-mentioned photosensitive layer is to be provided is a metal plate,
A conductive material 1111 made of a metal drum or a conductive polymer, a conductive compound such as indium oxide, or a metal such as aluminum, palladium, or gold is provided on a substrate such as paper or a plastic film by means such as coating, vapor deposition, or lamination. The one that consists is used.

The photosensitive layer can be provided by the following method.

That is, the above-mentioned carrier-generating substance is made into fine particles in a dispersion medium using a ball mill, a homomixer, etc., and a binder resin and, if necessary, a carrier transporting substance are added, mixed and dispersed, and the obtained dispersion is applied. .

The carrier transport layer can also be formed by applying a solution of a carrier transport material.

(Function) As described above, the electrophotographic photoreceptor according to the present invention has a first photosensitive layer containing a first charge-generating substance that has higher photosensitivity when negatively charged than when positively charged, which is located on the surface side of the photoreceptor, and a conductive support side. The second photosensitive layer, which contains a second charge-generating substance that has higher photosensitivity when positively charged than when negatively charged, is laminated to provide extremely high photosensitivity and is stable even with repeated use. It had very good charging characteristics and was of practical use. In addition,
There is no problem even if the first and second photosensitive layers each have a plurality of layers as long as the effects of the present invention are obtained.

(Example) Hereinafter, the present invention will be described with reference to specific examples.

The charge-generating substance 10y shown in Table 1 was converted into a boary arylate 10w.
The mixture was added to t% trichloroethane solution 5009 and dispersed in a ball mill for 30 hours to obtain a dispersion. Table 1 shows this dispersion.
Each electrophotographic photoreceptor was prepared by sequentially applying and drying a coating solution prepared by adding a predetermined amount of the charge transport material shown in FIG.

The thus obtained electrophotographic photoreceptor was tested using an electrostatic tester rsP-
428 type" (manufactured by Kawaguchi Electric) and conducted the following characteristic tests. That is, a voltage of +6 to ■ is applied to the charger to charge the photosensitive layer by corona discharge for 5 seconds, and then the potential at this time is automatically set to V for 5 seconds. ), then the illuminance at the surface of the photosensitive layer 35. The exposure aperture required to attenuate the surface potential of the photosensitive layer to 1/2 by irradiating light from a tungsten lamp in the state of guX, that is, the half-reduction exposure ff1E1/2 was determined.

In addition, the initial acceptance potential VA during charging by the corona discharge and the acceptance potential VA after -galocopy were measured.

For a rough comparison, the layer containing the charge-generating substance is 1.4°. A layered photoreceptor was prepared and patent evaluation was conducted in the same manner.

As a result, the electrophotographic photoreceptor according to the present invention has good sensitivity and charging ability, whereas Comparative Example 1 has low sensitivity and Comparative Example 2 has a photoreceptor with extremely low charging ability after retraction. Met.

Examples 7 to 11 A hydrazone compound 5 shown in the following structural formula (D) was placed on an aluminum plate.
A solution prepared by dissolving G and butyral resin 109 in cyclohexanone 909 was applied and dried to form a charge transport layer with a thickness of 5 mm.

On this charge transport layer, a coating material having the composition shown in Table 2 was laminated in the same manner as in Examples 1 to 6 to prepare a photoreceptor.

Further, as Comparative Examples 3 and 4, photoreceptors having a single charge generation layer were prepared and their characteristics were evaluated.

As a result, the electrophotographic photoreceptor according to the present invention had good sensitivity and charging ability, whereas the comparative example had low sensitivity and charging ability.

Margins below (Effects of the Invention) As is clear from the results of the examples above, the electrophotographic photoreceptor of the present invention is excellent in both charging ability and sensitivity, and exhibits stable characteristics even when used repeatedly.

Agent: Patent Attorney Noriyuki Chika Same Bamboo Flower Kikuo

Claims (3)

[Claims] (1) An electrophotographic photoreceptor having a photosensitive layer provided on a conductive support, wherein the photosensitive layer includes: i) a first charge-generating substance that has higher photosensitivity when negatively charged than when positively charged; A first photosensitive layer, and ii) a second photosensitive layer containing a second charge-generating substance that has higher photosensitivity when positively charged than when negatively charged, and the second photosensitive layer is a conductive support. A positively charged electrophotographic photoreceptor characterized by being located on the body side. (2) The positively charged electrophotographic photoreceptor according to claim 1, wherein the first charge generating substance is at least one of a perylene pigment, a perinone pigment, and a polycyclic quinone pigment. (3) The positively charged electrophotographic photoreceptor according to claim 1, wherein the second charge generating substance is at least one of phthalocyanine, azo, and indigo pigments.