JPS583541B2 - Denshishashinyoukankoutai - Google Patents

Description

[Detailed description of the invention] The present invention relates to a novel electrophotographic photoreceptor.

In recent years, as a method of electrophotography, for example,
The steps of primary charging exposure, secondary charging (opposite polarity to the primary charging), image exposure, development, and then fixing, as described in Japanese Patent Publication No. 13437, Japanese Patent Publication No. 47-17871, etc. (referred to as the polarity reversal method) or a method that employs primary charging, image exposure plus secondary charging (referred to as the polarity reversal method) or, for example, as shown in Japanese Patent Publication No. 13190/1983.
There is a method called a modification of the so-called Xerox method, which consists of the steps of (opposite polarity to the primary charging), whole surface exposure, development, and fixing.

In these methods, the potential of the conductive layer on the insulating layer is made to have opposite polarity in the areas that receive the optical image and the areas that do not, so they have the advantage that high-quality images with sufficient contrast can be obtained. have.

Conventionally, the electrophotographic photoreceptor used in this new method is composed of three layers: a conductive support, a photoconductor layer, and a transparent insulator layer.

This type of photoreceptor is applicable not only to polarity reversal methods but also to ordinary electrophotographic methods (consisting of steps of charging, image exposure, development, and then fixing).

However, with this type of electrophotographic photoreceptor, the advantages of the polarity reversal method cannot be fully exploited, and the sensitivity and sharpness are lacking.

On the other hand, Japanese Patent Publication No. 43-16198, Japanese Patent Publication No. 45-5
A photoconductive layer as shown in Japanese Patent No. 349, etc.
The electrophotographic photoreceptor (hereinafter referred to as photoreceptor A) is composed of three layers: a conductive support, an inorganic photoconductor layer, and an organic photoconductor layer. It is thought that the organic photoconductor layer functions as a charge generation layer and as a charge transfer layer, and is said to have excellent sensitivity and be effective in the Carlson method.

FIG. 1 is an enlarged cross-sectional view of photoreceptor A, in which 1 is a conductive layer;
Reference numeral 2 indicates a selenium vapor deposited layer (an inorganic photoconductor layer that serves as a charge generation layer), and 3 indicates a polyvinyl Rubazole PVK layer (an organic photoconductor layer that serves as a charge transfer layer).

Now, when this photoreceptor A is irradiated with light, only positive charges are injected from the selenium layer to the PVK layer.

Therefore, when used in the Carlson method, it can only be used with a negative charge, and has almost no photosensitivity when charged with a positive charge.

In other words, when photoreceptor A is irradiated with light, positive charges tend to move from the bottom to the top (from the charge generation layer 2 to the charge transfer layer 3), but negative charges tend to move from the bottom to the top. It's hard to go.

Furthermore, when carrying out a polarity reversal method using a photoreceptor (hereinafter referred to as photoreceptor B) consisting of a conductive support, an inorganic photoconductor layer, an organic photoconductor layer, and a transparent insulating layer, the photopic primary charging is If it is positive, it is difficult for negative charges to collect on the lower surface of the insulating layer, and in order to obtain the necessary potential difference, the amount of light during primary charging must be increased.

Furthermore, when the photopic primary charging is negative, although the primary charging seems to be effective, the charge movement during image irradiation does not occur, and the image quality tends to deteriorate.

As described above, the reality is that an electrophotographic photoreceptor that is effective for the above-mentioned novel electrophotographic copying method using a photoreceptor having a charge generation layer and a charge transfer layer has not yet been developed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that eliminates these conventional drawbacks and allows clear copies to be obtained at all times.

Another object of the present invention is to provide an electrophotographic photoreceptor that is effective not only for ordinary electrophotographic operations, but especially for the above-mentioned novel electrophotographic copying method.

The present inventors conducted research on the above-mentioned photoreceptors A and B,
Further investigation led to photoreceptor A as shown in Figure 2.
A photoreceptor was created in which the layer positions of the charge generation layer 2 and charge transfer layer 3 were reversed, and the transfer of charges was investigated. When used in the Carlson method, it was confirmed that it could only be used with a positive charge. .

As a result of further investigation based on these findings, it was discovered that a photoreceptor structure in which a charge generation layer is provided on both sides of a charge transfer layer provides excellent effects.

The present invention was completed based on this knowledge.

That is, the present invention provides an electrophotographic photoreceptor comprising a conductor layer, a photoreceptor layer, and a transparent insulating layer, wherein the photoreceptor layer comprises:
Consisting of a stack (multilayer) of a charge transfer layer and two charge generation layers sandwiching the charge transfer layer, or a stack of a charge transfer layer and a charge generation layer in which fine particles of a charge generation substance are present dispersed. (multilayer).

Embodiments of the photoreceptor of the present invention are illustrated in FIGS. 3 and 4.

In FIG. 3, a charge generation layer 21, a charge transfer layer 3, a second charge generation layer 22, and a transparent insulator layer 4 are sequentially laminated on the conductor layer 1.

Here, the first charge generation layer 21, the second charge generation layer 22, and the charge transfer layer 3 constitute a photoreceptor layer.

In FIG. 4, a charge generation layer 2, a charge transfer layer 3' containing a charge generation substance 23, and a transparent insulator layer 4 are formed on a conductor layer 1.
are stacked in sequence.

In this case, the photoreceptor layer is composed of the charge generation layer 2 and the charge transfer layer 3'.

Now, the case where a polarity reversal development operation is performed using the photoreceptor of the present invention shown in FIG. 3 will be described.
When exposure (E1) is performed at the same time as the positive primary charging, the positive charges generated in the second charge generation layer 22 move downward, and at the same time, the negative charges are accumulated in the charge generation layer 22 (Fig. 5a). reference).

hv indicates light, and 5 indicates a corona discharger. Next, the positive charge on the transparent insulating layer is removed by secondary reverse charging in the dark (preferably leaving a small amount of charge), and a positive charge is generated corresponding to the negative charge accumulated in the charge generation layer 22. Charges are induced in the conductor layer (electrode) 1 (see FIG. 5b).

If image irradiation is performed in this state, the negative charge will essentially move downward due to the light irradiation (
(see Figure 5c) is neutralized by a positive charge.

Actually, from the first charge generation layer 21 in the portion irradiated with light, +
moves upward and neutralizes the negative charge above.

As a result, negative charges remain on the surface of only the portions that were not irradiated with light, resulting in a latent image (Figure 5d).

If this is developed, a visible image will be obtained.

Although the photoreceptor of the present invention has been described above using the so-called polarity reversal method, the photoreceptor of the present invention can also be used by a copying method consisting of the steps of primary charging, image exposure plus secondary charging, and full-surface exposure as described above. The body shows sufficient effects.

What must be noted here is that the thickness of the second charge generation layer 22 must be set to an appropriate value.

If the second charge generation layer 22 is too thick, satisfactory photosensitivity cannot be obtained.

Furthermore, although the above description is based on the example of the photoreceptor shown in FIG. 3, the same applies to the photoreceptor shown in FIG.

Therefore, the amount of the charge generating substance 23 dispersed in the charge transfer layer 3' must be such that light can reach the charge generating layer 2.

In the present invention, the material for the conductor layer 1 may be, for example, a metal substrate such as brass or aluminum, or a metal-deposited film or paper.

Further, as the material of the first charge generation layer 21 and the second charge generation layer 22, for example, Se, Se-Te, Se-Te-A
Alloys such as s, CdS, ZnS, CaSe, Zn
Examples include those mainly composed of inorganic compounds such as O, to which organic pigments such as methylene blue and crystal violet, and sensitizing dyes such as phthalocyanine, cyanine dyes, ketonaphthylene cyanine dyes, and xanthene dyes are added.

Appropriately, the thickness of the first charge generation layer 21 is about 0.001 to 10μ, and the thickness of the second charge generation layer 22 is about 0.001 to 10μ, and can be formed by a vapor deposition method, a coating method, or the like. can.

Examples of materials used for the charge transfer layer 3 include transparent organic semiconductor polymers or organic semiconductor monomers, such as poly-N-vinylcarbazole or its derivatives, anthracene, pyrene, naphthacene, oxydiazole or its derivatives, 1, Examples include 3,4-triazole or its derivatives, and pyrazoline or its derivatives.

The thickness of the charge transport layer is suitably about 1 to 100 microns.

In addition, as shown in FIG. 4, a charge generation substance 23 (same material as the charge generation layer 2) is provided in the charge transfer layer 3'.
is contained, the particle size of the charge generating substance is approximately 0.
．． The amount thereof is approximately 0.05-50% by weight of the charge transfer layer 3'.

In addition, the transparent insulating layer 4 is made of polyethylene terephthalate,
A transparent resin film such as polyester or cellulose acetate is used, and the appropriate thickness is about 1 to 50 μm.

To actually produce the electrophotographic photoreceptor of the present invention, for example, selenium is vapor-deposited (first charge generation layer 21) on an aluminum plate (conductor layer 1), and then poly-N-vinylcarbazole and acrylic A charge transfer layer 3 is formed by coating a mixture with a binder resin such as resin, epoxy resin, vinyl resin, silicone resin, alkyd resin, or polyester resin, and selenium is further deposited on this layer (second charge generation). layer 22), and finally, polyethylene terephthalate (transparent insulator layer 4) is bonded thereon via an adhesive.

As described above, the electrophotographic photoreceptor of the present invention exhibits remarkable effects compared to conventional photoreceptors, especially in new electrophotographic copying methods such as polarity reversal method, and always maintains contrast. Copies with high gradation and excellent gradation can be obtained.

These effects are proven from the following examples.

Example 1 (Creation of photoreceptor for comparison) A 0.7 μ thick Se-Te alloy (Te content: 6% by weight) was deposited on an aluminum base, and 10% of polyester adhesive 49000 was applied as a binder thereon. 1% by weight of poly-N-vinyl Rubazol by coating
A polyethylene terephthalate film having a thickness of 16 μm was adhered thereto via an insulating adhesive layer (approximately 5 μm thick) to prepare an electrophotographic photoreceptor B (comparative product).

(Creation of the photoreceptor of the present invention) The same process as that of the above-mentioned "photoreceptor for comparison" was carried out except that a selenium vapor deposited layer with a thickness of approximately 0.2 μm was provided between the poly-N-carbazole layer and the adhesive layer. A photographic photoreceptor (product of the present invention) was manufactured.

The measurement method is to charge the photosensitive plate by moving two charge wires (60 μφ gold-plated tungsten wire) at a speed of 10 cm/sec at a distance of 9 cm from the photosensitive plate.

Note that a 500W tungsten lamp was used for exposure.

A comparison between the product of the present invention and the comparative product, where the irradiation amount was 500 lux・sec in V3, that is, image exposure, is as shown in Figure 6. In the comparative product, E1 (simultaneous exposure amount during primary charging) was 100 lux.・For sec, V2-V3=△
It can be seen that while V can only be about 400V, the product of the present invention can also get △V≒1000V.

This means that the comparative product requires a significantly larger amount of E1 or that E1 is ineffective.

In addition, V2 is the voltage of secondary reverse charging, and V3 is a potential attenuation curve due to exposure. In the figure, the solid line shows the product of the present invention, and the dashed-dotted line shows the comparative product.

Example 2 A poly-N-vinyl material with a 0.7μ thick Se-Te alloy (Te content 6% by weight) deposited on an aluminum base and 10% by weight of polyester adhesive 49000 added thereon as a binder. 1 by coating Rubazol
CdS powder (unsensitized, manufactured by General Electric Company, 118-8-2) was added to the binder (styrene-butadiene copolymer) in a ratio of 1=1.
(volume ratio) is applied to a thickness of approximately 1μ, and then an insulating adhesive layer (approximately 5μ thick) is applied on top of this to a thickness of 16μ.
A photoreceptor for electrophotography was made by bonding thick polyethylene terephthalate film.

This photoreceptor exhibited almost the same properties as the product of the present invention in Example 1.

[Brief explanation of the drawing]

Fig. 1 is an enlarged sectional view of a Pana photoreceptor, Fig. 2 is an enlarged sectional view of a photoreceptor obtained by reversing the charge generation layer and charge transfer layer of the Pana photoreceptor, and Figs. 3 and 4 are in accordance with the present invention. FIGS. 5a to 5d are diagrams for explaining the movement of charges when the polarity of the photoreceptor of the present invention is reversed, and FIG. 6 is an enlarged cross-sectional view of the photoreceptor of the present invention and a comparative photoreceptor. It is a graph showing the results of comparative tests and measurements on the body. DESCRIPTION OF SYMBOLS 1... Conductor layer, 2... Charge generation layer, (21... First charge generation layer, 22... Second charge generation layer), 3, 3'... Charge transfer layer, 4... Transparent insulating layer , 5...corona discharger.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor comprising a conductor layer, a photoreceptor layer, and a transparent insulator layer, the photoreceptor layer comprises a charge transfer layer and two charge generation layers sandwiching the charge transfer layer. An electrophotographic photoreceptor comprising a laminated layer of. 2. An electrophotographic photoreceptor comprising a conductor layer, a photoreceptor layer, and a transparent insulator layer, wherein the photoreceptor layer is composed of a laminate of a charge transfer layer and a charge generation layer in which fine particles of a charge generation substance are dispersed. An electrophotographic photoreceptor characterized by: