JPS63273869A - Electrophotographic sensitive body and electrophotographic method using it - Google Patents

Abstract

PURPOSE:To enable analog copying, digital copying, and the maintenance of both by forming the uppermost layer of a second electric charge generating layer made of Se alloy and a first charge generating layer having photocharge generating ability in response to light in wavelengths spectrally longer than the light to which the second charge generating layer responds. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive supporting body 1 an interlayer 2, the first charge generating layer 3, a charge transfer layer 4, and the second charge generating layer 5 made of the SE alloy, or alternatively, on the conductive supporting body 1, the first charge generating layer 3, the charge transfer layer 4, and the second charge generating layer 5 made of the Se alloy, then the first charge generating layer 3 has photocharge generating ability in each case in response to light in wavelengths spectrally longer than the light to which the second charge generating layer 5 responds, thus permitting analog copying and digital copying to be selectively carried out and durability to be enhanced.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electrophotographic photoreceptor and an electrophotographic method using the photoreceptor, and more specifically, the present invention relates to an electrophotographic photoreceptor and an electrophotographic method using the photoreceptor. The present invention relates to a laminated electrophotographic photoreceptor suitable for a bipolar image forming method and an image forming method thereof.

[Prior Art] In recent years, the performance of electrophotographic copying machines has improved markedly, and it has become possible to stably obtain high-quality images.

By the way, as a means for forming an electrostatic latent image on a photoreceptor,
In general, after uniformly charging the photoreceptor, (i) image exposure is performed using reflected light or transmitted light of the copy document using a light source such as a tungsten lamp, halogen lamp, or fluorescent pair, and the electrostatic latent image is (11) Semiconductor laser, HE! A ``digital image forming method'' is known in which an electrostatic latent image is formed by exposing an image composed of dots using a light source such as a -Ne laser.

The former (i) is particularly advantageous for obtaining a continuous-tone or intermediate-tone emphasized image, while the latter (ii) is useful for obtaining a negative image or a positive image (both dot-shaped images) through reversal development. This is a particularly advantageous method.

When considering the configuration for providing both of the above functions in one electrophotographic copying machine, it is necessary to install a light source such as a tungsten lamp for analog exposure and a light source such as a semiconductor laser for digital exposure inside the copying machine. Although it is easy to do so, having two sets of photoreceptors and developing systems, one for analog and one for digital, increases the size of the machine and is also highly undesirable in terms of cost.

If there is a photoreceptor for electrophotography that has good sensitivity to both of the above light sources with a single photoreceptor and can simultaneously produce high-quality images by image forming methods using either light source, it is possible to combine the photoreceptor and the developing system. It is possible to design a very compact and low-cost multifunctional copying machine that only requires one set.

However, the reality is that there is currently no electrophotographic photoreceptor that completely satisfies these requirements and the characteristics (cost durability, etc.) required for an electrophotographic photoreceptor.

For example, as one photoreceptor based on the above idea, a CGL sensitive to light of 700 nm or more, a charge transfer layer (CTL), and a CGL sensitive to light of 4.00 to 700 nm may be laminated on a support in this order. Accordingly, there is a photoreceptor that has the sensitivity with an analog light source when positively charged and the sensitivity with a digital light source when negatively charged. (Tokugan Sho 6
(No. 1-145948) This photoreceptor shows good sensitivity in both positive and negative charging, but the top layer CGL is composed of a thin layer of organic matter, and it lacks the mechanical strength required for electrophotographic photoreceptors. Therefore, the object of the present invention is to exhibit better sensitivity in both positive and negative charging, and to improve analog copying using a tungsten lamp or the like as a light source, or a semiconductor laser, etc. as a light source. The present invention provides a male photographic photoreceptor that can selectively perform digital copying using a light source and has improved durability, and a bipolar electrophotographic method using this photoreceptor.

[Structure] The photoreceptor of the present invention has an intermediate layer, a first charge generation layer, a charge transfer layer, and a second charge generation layer on a conductive support, or a first charge generation layer, a charge transfer layer on a conductive support. , in a structure in which second charge generation layers are laminated in this order, the second charge generation layer in the uppermost layer is an SE-based alloy layer, and the first charge generation layer is irradiated with light having a wavelength longer than that of the second charge generation layer. The charge generation layer has a photocharge generation ability.

In addition, the electrophotographic method of the present invention uses this photoreceptor to obtain visible images. = BWJ, apply a positive charge when imagewise exposed to light with a wavelength of <mainly 450 to 700 nm), and apply a negative charge when imagewise exposed with light of a wavelength in the infrared region (mainly 700 nm or more). configured.

The invention will now be explained in more detail with reference to the accompanying drawings. FIG. 1 (al(b)) shows a cross-sectional view of the photoreceptor according to the present invention, and the numbers assigned therein are 1 for the conductive support, 2 for the intermediate layer, 3 for the first charge generation layer, and 4 for the conductive support. is the charge transfer layer,
5 represents the second charge generation layer.

That is, the electrophotographic photoreceptor of the present invention has a first charge generation layer on a conductive support, or an intermediate layer between the first charge generation layer and the conductive support, a charge transfer layer thereon, and a top layer. A photosensitive layer consisting of a laminated second charge generation layer made of a Se-based alloy is provided.

When this photoreceptor is positively charged, positive charges exist on the surface of the photoreceptor, and negative charges exist at the interface between the support and the first charge generation layer or intermediate layer. When this is irradiated with visible wavelength light (mainly 400 to 700 nm) from a tungsten lamp, charge carriers (a pair of positive polarity and negative polarity) are generated in that region by the second charge generation layer, and the negative polarity carriers neutralizes the positive charge on the surface of the photoreceptor, and the positive carrier is injected into the charge transfer layer and moves by being attracted to the negative charge on the support interface side (generally used charge transfer layers are carriers with positive polarity ) and neutralize the negative charges on the interface. On the other hand, positive charges remain on the surface of the photoreceptor in the non-exposed areas, forming an electrostatic latent image.

Next, negative charges exist on the surface of the photoreceptor, and positive charges exist on the interface between the support and the first charge generation layer or intermediate layer.

In addition to this, light in the infrared region such as semiconductor lasers (mainly 70
0 nm or longer), this light passes through the second charge generation layer and the charge transfer layer and reaches the first charge generation layer, where the first charge generation layer generates charge carriers (positive and negative polarity pairs). ) occurs and the negative polarity carrier is neutralized with the positive charge on the interface on the support side, and the positive polarity carrier is injected into the charge transfer layer and moves by being attracted to the negative charge on the surface of the photoreceptor. Neutralize the charge. On the other hand, negative charges remain on the surface of the photoreceptor in the non-exposed areas, forming an electrostatic latent image.

A feature of the present invention is that a Se-based alloy is used for the second charge generation layer, which is the uppermost layer. Due to its mechanical strength (compared to organic charge generation layers), high charge generation ability for visible light, and high infrared light transmittance, when constructed like the photoreceptor of the present invention, it has bipolar properties. This results in good charging sensitivity and durability.

To actually produce the photoreceptor of the present invention, an intermediate layer is formed as necessary on a conductive support, a first charge generation layer is formed thereon by coating before vacuum, and then charge transfer The layer may be formed by applying and drying a resin solution containing a charge-transferable substance, and a second charge-generating layer made of an Se-based alloy may be formed as the uppermost layer by a method such as vacuum deposition.

Here, as the conductive support, a conductor or an insulator treated for conductivity is used.

For example, a metal such as A1, Ag, Au, or a conductive material such as n2o3.5n02 is placed on an insulating support such as a metal or alloy such as Fe, Cu, or Au, or polyester, polycarbonate, polyimide, or glass. Examples include paper on which a thin film is formed, paper treated with conductivity, and the like.

Note that the shape of the conductive support is not particularly limited, and a plate, cylinder, or belt shape may be used as required.

The intermediate layer is effective in improving charging properties and fatigue characteristics, and its volume resistivity is 105 to io+4 Ωcm, preferably 10'' to 10 uΩcm. The thickness of the intermediate layer is 0.1 to 10 μΩcm.
10 μm is appropriate.

Examples of materials for the intermediate layer having such functions include resin layers such as polyamide resin, polyvinyl alcohol, -9= polyvinyl acetal, and polyacrylic acid;
Alternatively, TiO2, 5no2, Si0
2, MCl0. Silane coupling agents such as trimethylmonomethoxysilane and γ-glycidoxypropyltrimethoxysilane for dispersing white pigments such as Metal alkoxides such as rhabtoxide and zirconium tetrabutoxide can be used.

The first charge generation layer is a layer that has a charge generation ability in a longer wavelength light region (mainly 700 nm or more) than the second charge generation layer, and such materials include:
Metal-free phthalocyanine, metal phthalocyanine, square dye, azulenium dye, trisazo pigment, Se-based alloy, etc. can be used.

These materials can be used alone by vacuum deposition or by casting dissolved in a solvent, or they can be crushed into fine particles to produce polyester, polystyrene, polycarbonate, polyacrylate, polyvinyl butyral, polyvinyl acetate, and ethyl cellulose. It is used by dispersing it in resins such as

The thickness of this first charge generation layer is preferably about 0.05 to 3 μm. Further, when the charge generating substance is used dispersed in a resin, the amount of the charge generating substance in the first charge generating layer is preferably about 1 to 95% by weight.

The charge transport layer formed on the first charge generation layer is made of a charge transporting material such as polyvinylcarbazole, α-phenylstilhene compound (Japanese Patent Application Laid-Open No. 58-198043M), hydrazone compound (Japanese Patent Application Laid-Open No. 55-46760). It is formed by dissolving it in a resin that has film-forming properties.

This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. As such film-forming resins, condensation resins such as polyamide, polyurethane, polyester, Epoquine resin, polyketone, and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, and polyacrylamide are used, but they do not have insulating properties. Any resin that is adhesive and transparent to infrared light can be used. Plasticizers are added to these resins if necessary, and examples of such plasticizers include halogenated paraffins, polychlorinated biphenyls, dimethylnaphthalene, and dibutyl phthalate.

The thickness of the charge transfer layer is 3 to 100 μm, preferably 5 to 5 μm.
0 μm is appropriate. The amount of the charge transport material in the charge transport layer is 10 to 95% by weight, preferably 30 to 90% by weight.

The second charge generation layer formed on the top layer is made of a 3e-based alloy (Se,
5e-AS-based Se alloys are preferred in terms of mechanical and thermal stability. In this case, the AS content of the Se-ΔS alloy is 0.5 to 5
0% by weight, preferably 20-40% by weight. In addition, halogen (forCl, etc.) may be included if necessary.The appropriate amount of halogen is 10 to 10,000 ppm.In this way, since the second charge generation layer is a very thin layer, it is better than SE alloy. Electrophotographic photoreceptor consisting of (film thickness 50~
60 um), the material cost is lower and flexibility can be achieved.

The laminated electrophotographic photoreceptor according to the present invention has the above-mentioned structure, but InO2 is used as a support for glass or resin.
When using a transparent conductive support on which a thin film of a conductive material such as 3,5nQ2 is formed and light irradiation is performed from the support side, the support (intermediate layer), the second charge generation layer, the charge transfer layer, It goes without saying that even with a structure in which the first charge generation layer is laminated in this order, the same function as the bipolar photoreceptor as in the present invention is achieved.

Further, if the charge transfer layer has a structure similar to that of the present invention in which the mobility of negative charge carriers is high, a photoreceptor having functions of negatively charged analog copying and positively charged digital copying can be obtained.

However, there is a problem in that it is difficult to form a charge transfer layer with high negative charge carrier mobility.

Next, an image forming method using this photoreceptor will be explained.

As described above, when this photoreceptor is positively charged and imagewise exposed to visible light, an electrostatic latent image is formed on the surface of the photoreceptor due to the positive charge.

If this is developed with negative polarity toner (electroscopic fine particles), a positive image can be obtained (analog copying with positive charging).

On the other hand, when a photoreceptor is negatively charged and image exposure is performed using infrared light from a semiconductor laser or the like, an electrostatic latent image due to the negative charges is formed on the surface of the photoreceptor in areas that are not exposed to light. A negative image can be obtained by developing this with positive polarity toner. Alternatively, a positive image can be obtained by performing reversal development using negatively charged toner. (Digital copying with negative charge)
.

As is clear from the above, when designing a copying machine that has both the functions of positively charged analog copying and negatively charged digital copying using reversal development, if this photoreceptor is used, the development system will also be able to use negatively charged toner. It is possible to design a very compact and low-cost copying machine by using only one set of copying machines.

The present invention will be explained in detail below by way of examples.

Example 1 Aluminum cylindrical support (outer diameter 80 mmφ, length 3
40 mm) and 1 part by weight of TiO2 (Tie Bake manufactured by Ishihara Sangyo Co., Ltd.) and 1 part by weight of polyamide resin (C manufactured by Toshisha Co., Ltd.).
t4-8000) 1 u methanol
25 An intermediate layer forming solution prepared by dispersing in a ball mill for 12 hours was coated by a dipping method so that the film thickness after drying was approximately 2 μm to form an intermediate layer.

On this intermediate layer, 12 parts by weight of a mixed polyester resin containing the following trisazo pigment (Vylon 200 manufactured by Toyobo Co., Ltd.) 360 parts by weight of cyclohexanone: Cyclohexanone: Methyl ethyl ketone (MEK) = 1
: A dispersion prepared by diluting with 500 parts by weight of a mixed solvent of 1 (weight ratio) was coated by a dipping method to form a first charge generation layer having a thickness of about 0.15 μm.

Next, on this first charge generation layer, a polycarbonate resin having the following composition (Panlite C-1400 manufactured by Kinjinsha Co., Ltd.) was applied in an amount of 150 parts by weight, tetrahydrofuran 910, silicone oil (KF50 manufactured by Shin-Etsu Chemical Co., Ltd.) was coated in an amount of 0.03 parts by weight. A charge transfer layer was provided by coating using a dipping method.

Furthermore, the support on which each of the above layers was formed was set in the mandrel part 6 of the vacuum evaporation apparatus shown in FIG. Heating the evaporation source 15 while keeping it heated at A
A second charge generation layer was formed by depositing 5e-A3 alloy 16 containing 35.5% by weight of S to a thickness of 1 μm. FIG. 4 shows the spectral sensitivity of the photoreceptor thus obtained when charged to both positive and negative polarities. It can be seen that good sensitivity is shown in visible light and infrared light.

Comparative Example 1 On the same support as in Example 1, the intermediate N, the first charge generation diagram, and the charge transfer layer exactly the same as in Example 1 were formed.

After pulverizing and dispersing 300 parts by weight of cyclohexanone in a ball mill for 48 hours, 30 parts by weight of polystyrene (HR I) was added and diluted with 400 parts by weight of a mixed solvent of cyclohexanone:MEK=1:1 (weight ratio). Apply the dispersion by spraying to a thickness of approximately 1 μm.
A thick second charge generation layer was formed.

These photoreceptors were set in the copying machine shown in Figure 3 and tested.

In order to obtain an analog image by positive charging using the photoreceptor of Example 1, first, a voltage of 6 kV is applied to the positive charger 22 to charge the surface of the photoreceptor 21 to 800 V, and the analog light (visible range light) optical system is After image exposure with No. 23 (halogen lamp light), development (negative polarity toner), transfer, and fixing, a very clear image was obtained.

On the other hand, in order to obtain a digital image by negative charging, a voltage of 16 KV is applied to the negative charger 24, and a voltage of 180 KV is applied to the surface of the photoreceptor.
Charged with 0V, image exposure is performed using digital light (infrared light) optical system 25 (semiconductor laser light (780 mm)), and due to reversal phenomenon (negative polarity toner), the exposed area becomes a ring image,
As a result of the transfer and fixing, a clear digital image was obtained, similar to when positively charged.

As a result of collecting chestnut-covered images in this manner, clear images were obtained in both polarities even after more than 20,000 images were taken.

In comparison, when the photoreceptor of Comparative Example 1 was used, a clear image was obtained up to 2,000 sheets as in Example 1, but after that, the second charge generation layer was scratched and the image was Black streak-like abnormalities began to occur, making it unbearable for practical use.

As is clear from this, it can be seen that good durability is exhibited by using the 3e alloy as the second charge generation layer.

[Effects] As is clear from the above explanation, the photoreceptor configured according to the present invention has both the functions of analog copying and digital copying, and in this way, one photoreceptor can perform both functions. By realizing this retention, it becomes possible to design a compact and low-cost multifunctional copying machine. Further, the photoreceptor of the present invention has improved mechanical strength and excellent durability, and has the remarkable effect of being able to consistently obtain clear images.

[Brief explanation of the drawing]

1(a) and 1(b) are diagrams illustrating a cross section of the photoreceptor of the present invention, FIG. 2 is a vacuum evaporation apparatus, FIG. 3 is a diagram illustrating the electrophotographic method of the present invention, The figure shows the spectral sensitivity (800V→
400V). 1... Conductive support, 2... Intermediate layer, 3...
First charge generation layer, 4... Charge transfer layer, 5... Second charge generation layer, 21... Photoreceptor, 22... Positive charger, 24... Negative charger, 23...・Analog (visible light) tip thread, 25・
...Digital light (infrared light) optical system.

Claims (2)

[Claims] (1) An intermediate layer, a first charge generation layer, a charge transfer layer, a second charge generation layer on a conductive support, or a first charge transfer layer on a conductive support.
In an electrophotographic photoreceptor having a structure in which a charge generation layer, a charge transfer layer, and a second charge generation layer are laminated in this order, the second charge generation layer as the uppermost layer is an Se alloy layer, and the first charge generation layer is a second charge generation layer. A laminated type bipolar electrophotographic photoreceptor, characterized in that the charge generation layer has a photocharge generation ability in light having a wavelength longer than that of the layer. (2) An intermediate layer, a first charge generation layer, a charge transport layer, a second charge generation layer, or a first charge transfer layer on the conductive support.
In an electrophotographic photoreceptor having a structure in which a charge generation layer, a charge transfer layer, and a second charge generation layer are laminated in this order, the second charge generation layer as the uppermost layer is an Se alloy layer, and the first charge generation layer is a second charge generation layer. In a method of forming images using an amphipolar electrophotographic photoreceptor with a charge generation layer having a photocharge generating ability for light with a wavelength longer than that of the visible region (mainly 400 to 7
An electrophotographic method characterized by applying a positive charge when performing imagewise exposure with light having a wavelength of 00 nm or more, and applying a negative charge when performing imagewise exposure with light having a wavelength in the infrared region (mainly 700 nm or more). .