JPS61122653A - Electrophotographic sensitive body and formation of image - Google Patents

Abstract

PURPOSE:To enable a good image to be obtained by successively laminating a prescribed undercoat layer, an electrostatic charge transfer layer, and a charge generating layer on a conductive substrate. CONSTITUTION:The electrophotographic sensitive body is prepared by successively laminating on the substrate 1 the undercoat 2 prepared by dispersing a conductive powder having charge receptivity to an electron donor into a resin, the charge transfer layer 3 made of an electron donor and a film forming resin, when needed, and the charge generating layer 4 capable of generating carriers on receiving light. As the charge receptive conductive powder, e.g., carbon black, iron oxide, tin oxide, antimony oxide, indium oxide, conductive zinc oxide, copper iodide, lead oxide, etc., are usable.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor in which an undercoat layer, a charge transport layer, and a charge generation layer are sequentially laminated on a substrate, and an image forming method using the photoreceptor. Regarding the method.

[Prior art]

Conventionally, it has been known that a charge transport layer containing an electron donating compound as a charge transport material and a charge generation layer having a function of generating charge carriers are sequentially laminated on a substrate as a laminated electrophotographic photoreceptor for positively charging. It is being In this case, it is effective to provide an undercoat layer on the substrate in order to improve the adhesion of the charge transport layer to the substrate and protect the defects on the substrate.

Conventionally, the undercoat layer is made of syposivinyl alcohol, I-richinyl methyl ether, +f? 1J-N-vinylimidazole, ethylcellulose, methylcellulose, ethylene-acrylic acid copolymer, casein, gelatin, ? Liamide etc. are known.

The first characteristic required of the undercoat layer is electrical characteristics. Since it is used in an electrophotographic photoreceptor, it is important not to affect the electrophotographic properties, and for this purpose it is necessary to have low electrical resistance. If the electrical resistance is high, a charged potential will be applied to the undercoat layer, and a so-called residual potential will cause fogging on the image.

Furthermore, it is necessary that the electrical resistance is unaffected by changes in the external environment, in particular by changes in atmospheric humidity. For example, when the electrical resistance increases due to low humidity, fogging will occur.

Additionally, the substrate is usually cleaned to remove surface scratches and defects.
It is used after being processed into a mirror surface, but the drawback is that mirror processing results in extremely high costs.

Even if a thin undercoat layer is formed on a substrate that is not mirror-finished and a photosensitive layer is formed thereon, the resulting image will have many defects and is impractical. The trap of using a non-mirrored substrate to reduce the cost of photoreceptors requires the use of a sufficiently thick undercoat layer to completely cover defects, but with conventional materials, due to the residual potential, It was not possible to increase the film thickness. [Problems to be Solved by the Invention] The present invention reduces the electrical resistance of the undercoat layer and makes it possible to form the layer sufficiently thick, so that a good image can be obtained using a substrate that is not subjected to any mirror finishing. A laminated type electrophotographic photoreceptor for positively charging that can be freely charged and an image forming method using the photoreceptor?
It is about providing.

[Means to solve the problem]

According to the present invention, there is provided a subbing layer in which conductive powder having charge injection properties with respect to an electron donating compound is dispersed in a resin, a charge transporting layer comprising an electron donating compound and optionally a film-forming resin; An electrophotographic photoreceptor is provided in which a charge generation layer having the function of generating charge carriers by light is laminated on a substrate in this order.

According to the present invention, by using a powder having a charge injection property with respect to an electron-donating compound as a conductive powder dispersed in an undercoat layer, image exposure is performed after positively charging a photoreceptor. Residual charge can be prevented and sensitivity can be improved in the image forming method.
' Examples of such conductive powders having charge injection properties include carzen black, iron oxide, tin oxide, antimony oxide,
Indium oxide, conductive zinc oxide.

Copper iodine, lead oxide, etc. are used. Also used is one in which insulating powder is coated with the above-mentioned conductive powder. For example, insulating powders such as titanium oxide, zinc oxide, Δlium sulfate, alumina, silica, calcium carbonate, packum carbonate, and magnesium oxide may be coated with one or more of tin oxide, antimony oxide, indium oxide, and the like.

Further, a mixture of the above-mentioned conductive powder and insulating powder may be used within a permissible range of electrical resistance.

Further, the photoreceptor of the present invention can also be applied to an image forming method in which the photoreceptor is positively charged and subjected to image exposure, and then the photoreceptor is negatively charged and image formation is performed again, thereby repeatedly using the photoreceptor.

In this method, the photoreceptor is negatively charged when forming a black and white reversal image on the photoreceptor and developing it with positive toner to transfer the toner image, or when erasing a latent image formed on the photoreceptor, or This is for cases where it is applied to a specific electrophotographic process.

If the photoreceptor is negatively charged, normal image formation will not occur, so it is preferable that the photoreceptor is not charged with a negative potential. For this purpose, when the photoreceptor is negatively charged, holes should be injected into the charge transport layer from the undercoat layer side to neutralize the negative potential (note that the charge generation layer is Target,
Since the resistance is low and the film thickness is thin, it can be assumed that the negative potential is mostly applied to the charge transport layer).

For this purpose, the conductive substance used in the undercoat layer needs to have charge injection properties with respect to the electron donating compound.

On the other hand, the light used to expose the photoreceptor is absorbed by the charge generation layer on the surface, but since the charge generation layer is thin, not all of the light is absorbed and some light is transmitted.

It is advantageous to reflect the transmitted light on the undercoat layer and absorb it again on the charge generation layer, as this improves the sensitivity by that amount (
The charge transport layer is transparent or light-colored, so light can easily pass through it).

6. Therefore, it is preferable for the conductive powder used in the undercoat layer to be white or light-colored rather than colored.

Among these, powders of tin oxide and antimony oxide are preferred in consideration of the particle size dispersibility, electrical conductivity, whiteness, etc. of the powder. Further, powder obtained by coating insulating white powder with tin oxide and antimony oxide can also be suitably used. Such insulating white powders include the above-mentioned titanium oxide, silica, and calcium carbonate.

Examples include zinc oxide. Among them, titanium oxide is most suitable. There are rutile type and anatase type powders in the crystal system of titanium oxide, and the present invention may use either of them.
It is not particularly limited.

The total amount of the coating layer relative to the titanium oxide powder is 5 to 5.
67 inches is suitable. If it is less than this, the specific resistance will not be low and the conductivity will not be sufficient. If it exceeds this range, there will be disadvantages such as a decrease in mechanical strength, coarsening of particles, and high cost.

The components of the coating layer are 1 to 20% antimony oxide and the remainder tin oxide. When the amount of antimony oxide is less than 1 µl, good conductivity cannot be obtained, and when it exceeds 2(l), the powder becomes blue-black in color. A method in which titanium oxide powder is dispersed in water, an acetate solution of tin chloride and antimony chloride is added thereto, and tin oxide and antimony oxide are precipitated on the titanium oxide surface by hydrolysis. A method of spraying an aqueous solution of tin chloride and antimony chloride onto titanium oxide powder heated to high temperature to form tin oxide and antimony oxide through thermal decomposition, 50-100
A solution of tin chloride and antimony chloride dissolved in sufficient hydrochloric acid water to prevent hydrolysis and an ammonia aqueous solution are simultaneously added to a titanium oxide aqueous suspension at ℃, and by hydrolysis through neutralization, tin oxide and tin oxide are formed on the titanium oxide surface. There are methods such as precipitating antimony oxide. The average particle size of the powder is 0.1-0.5
μ and specific resistance are preferably 2 to 500 −.

A paint for the undercoat layer is obtained by dispersing such powder in a binder resin. An organic solvent is used as necessary to disperse it in the resin. The resin must meet the following conditions: (1) strong adhesion to the substrate, (2) good powder dispersibility, and (3) sufficient solvent resistance. Particularly suitable are thermosetting resins such as hardening resins, polyurethane resins, epoxy resins, alkyd resins, phenol resins, polyester resins, silicone resins, and acrylic-melamine resins.

The volume resistivity of the resin in which surface-treated titanium oxide is dispersed is 10"Qers or less, preferably 106 to 1012Qa.
ft is suitable. Therefore, in the coating film, the proportion of surface-treated titanium oxide is preferably 30% or more by volume and 60% or more by weight.

Furthermore, if the resistivity is sufficiently low, it is also effective to use other pigments in combination to reduce the cost of the paint or increase the whiteness of the paint, and K does not have a coating layer. Ordinary titanium oxide powder is suitable. Furthermore, in order to improve the smoothness of the paint surface, it is preferable to use titanium monoxide powder whose surface has been treated with alumina. A method of alumina treatment on the surface of titanium oxide is, for example, by dispersing titanium oxide powder in an aqueous solution of aluminum salt, adding an alkali to the solution, precipitating aluminum hydroxide onto the titanium oxide powder, and dispersing it. There is a way to heat it up.

The above-mentioned powder is dispersed in a resin by a conventional method to form a paint, which is applied as an undercoat layer onto the substrate of an electrophotographic photoreceptor. After coating, an undercoat layer is formed by drying and, if necessary, heat treatment. Although the film thickness depends on the degree of defects in the rough substrate, it is preferably about the square of the maximum surface roughness of the substrate.

The charge transport layer to be formed on the undercoat layer has, for example, a polycyclic aromatic structure in the main chain or side chain, or indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, oxadiazole,
It is formed by using a compound with a nitrogen-containing cyclic structure such as pyrazoline, thiadiazole, or triapool, or an electron-donating compound such as a hydrazone compound, alone or, if necessary, in combination with a resin that improves film-forming properties. . This is because when the electron-donating compound has a low molecular weight, it has poor film-forming properties by itself, and even when the electron-donating compound has a high molecular weight, it is used to improve mechanical strength. In addition, the resins include polycargenate, polyarylate, polystyrene,
Examples include polymethacrylic acid esters, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer, /IJ sulfone, and the like. The thickness of the charge transport layer is approximately 8 to 25 microns.

The charge generation layer includes azo pigments such as Sudan red and Diane blue, disazo pigments, algol yellow, anthinthrone, pyrene quinone pigments, f) quinone pigments, quinocyanine pigments, perylene pigments, indigo 9 pigments such as indigo and thioindigo, and copper lid o' Charge-generating substances such as phthalocyanine pigments such as 7-anine and aluminophthalocyanine, quinacridone pigments, pyrylium salts, and azulenium salts are combined with polyester, polyvinyl acetate, acrylic resin,
Polyvinyl butyral, poly-nylpyrrolidone, methylcellulose, hydroxyglobil methylcellulose, cellulose esters%/! jsfL/n,
It is formed by dispersing it in a resin such as polycarbonate, polyarylate, or polysulfone. In addition, in order to increase the strength of the charge generation layer, S 102 , A
It is also effective to co-disperse inorganic pigments such as t205, SICJ4C, CaO2, TiO2, and powders such as Teflon, polyethylene, delif, vinylisoy, etc. in order to increase slipperiness. A surfactant may also be used during dispersion.

To form a charge generation layer on the charge transport layer, use a dispersion liquid for the charge generation layer (using an organic solvent for dispersion if necessary).
dissolves the charge transport layer and cannot be coated. Spraying is the best method to apply the coating without dissolving the charge transport layer.

According to the spray method, the dispersion is sprayed with air, and the solvent evaporates briefly before it is deposited on the charge transport layer, and the solvent evaporates in a short time after it has been deposited, making it difficult to cover the charge transport layer. The effect of dissolution is small. The thickness of the charge generation layer is preferably about 0.2 to 5 microns.

〔·Effect of the invention〕

Since the electrophotographic photoreceptor according to the present invention may have a rough substrate surface, processing of the substrate can be significantly reduced. Next, since the photoreceptor is positively charged, it has advantages for electronic copying machines, such as stable corona discharge, lower amount of ozone generation, less deterioration of the photoreceptor, and easy developer matching. There are advantages.

On the other hand, even if it is applied to a special electrophotographic process in which the photoreceptor is positively charged to form an image and then negatively charged, it is preferable because the stain position is changed to O by negative charging.

Further, in the electrophotographic photoreceptor according to the present invention, which has a powder-dispersed undercoat layer below the photosensitive layer, the powder-dispersed undercoat layer has a property of scattering light on its surface. Even when used in so-called radar beam printers, etc., which use radar light for printing, it has the property of preventing phenomena such as interference caused by reflection of laser light on the substrate surface, so it is also effective for such applications. used for.

Example 1 As a base, 60φ×260 aluminum cylinders were prepared. The maximum roughness of the surface was measured to be 5μ.

On the other hand, titanium oxide powder (trade name: ECT62, manufactured by Titan Kogyo Co., Ltd.) is coated with tin oxide containing 10% antimony oxide so as to account for 75% by weight of titanium oxide.
Titanium oxide powder coated with 50 parts (by weight, same below) and 2% by weight of alumina based on titanium oxide (product name: 5)
R-1, manufactured by Sakai Chemical Industry Co., Ltd.) 50 parts of two types of powder,
Resol type phenolic resin (trade name Nibryophen 5010. Manufactured by Dainippon Ink Chemical Co., Ltd., solid content 58%)
and 60 parts of methyl ethyl ketone.

After mixing thoroughly, the mixture was dispersed in a sol mill for 6 hours. Add silicone leveling agent (product name: 5H2) to this.
8PA, )-000025 parts (manufactured by Resilicone) were added.

This paint was adjusted to have a viscosity of 90 ap.
Thereafter, it was applied to the above substrate by a dipping method, air-dried for 10 minutes, and then heated and cured at 150° C. for 20 minutes. In this way, a paint layer with a thickness of 18 μm was formed. The maximum roughness of this surface is 0
It was 875μ.

10 parts of a hydrazone compound represented by the structural formula, styrene-acrylonitrile copolymer (trade name: 5AN-C,
A coating solution consisting of 10 parts (manufactured by Mitsubishi Monnant Co., Ltd.) and 80 parts of toluene was applied onto the above substrate by a dipping method, and heated at 100°C for 3
Heating was performed for 0 minutes to form a charge transport layer with a thickness of 18 μm.

Next, 5 parts of bisazo pigment with the structural formula was mixed with 20% dioxane of polycarbonate resin (trade name: A2200, manufactured by Idemitsu).
The mixture was mixed with 25 parts of the solution and dispersed in a sand mill for 2 hours. This dispersion was used with a Binks spray gun at an air pressure of 1°5 kg/6n.

Spray coating was carried out by moving the gun in the longitudinal direction of the substrate while rotating the substrate at 12 Orpm, with a coating amount of 8 m and 11 minutes at a distance of 3 between the nozzle of the gun and the substrate. Thereafter, it was dried at 80° C. to form a charge generation layer with a thickness of 1.2 μm. FIG. 1 shows a cross-sectional view of an electrophotographic photoreceptor. Reference numeral 1 indicates a substrate, 2 a conductive layer, 3 a charge transport layer, and 4 a charge generation layer.

The electrophotographic photoreceptor produced in this way! + 5.6 kV corona charging, image exposure, dry toner development, toner transfer to plain paper, cleaning process with urethane rubber blade (hardness 70', pressure 5 gw/crn, angle to photoconductor 200), 20 l, x - The electrophotographic characteristics were evaluated by attaching it to an electrophotographic copying machine that has processes such as full-second exposure (post-exposure).

When measuring the potential, the dark area potential (VD) is +650V, the light area potential (vL) is +100V, and the contrast is 55.
It was 0■. And I was able to take a good copy image.

On the other hand, photoreceptors in which a charge transport layer and a charge generation layer are provided on a substrate without forming a conductive layer have uneven images depending on the roughness of the substrate. Moreover, the photosensitive layer was easily peeled off. Next, as an undercoat layer, methoxymethylated nylon described in JP-A No. 58-95351 was coated on the substrate.
．． When 5 μm was applied, the peeling became more frequent, but the image unevenness due to roughness remained the same.

Example 2 10 parts of titanium oxide powder (manufactured by Titan Kogyo Co., Ltd.), 1 part of tin oxide powder (manufactured by Mitsubishi Metals Co., Ltd.), acrylic resin (trade name Niacridi, RiA405, manufactured by Dainippon Ink Co., Ltd.) )
16 parts of melamine resin (trade name: Varnish No-Bekkamin L121, manufactured by Dainippon Ink Co., Ltd.) and 20 parts of toluene were dispersed in a sol mill over 6 hours. This was applied onto the same substrate as in Example 1 and cured at 150° C. for 30 minutes to form a conductive layer with a thickness of 20 μm. The surface roughness of this surface is 1.1μ.

there were.

A charge transport layer similar to that in Example 1 was formed thereon.

Next, a charge generation layer was formed in the same manner as in Example 1 except that the pigment was 5 parts of G-type copper 7 talocyanine (trade name: Rio Photon, manufactured by Toyo Ink@).

The electrophotographic photoreceptor 5 manufactured in this way was subjected to inversion image exposure by applying +5.5 kV corona charging 6 and deflecting semiconductor radar light with a wavelength of 820 nm using a polygon prism, as shown in the schematic cross section of FIG. 7. Toner development 8. -5.
Toner image on plain paper 1 by 8 kV colossal charger 10
It was attached to a laser printer having processes such as transfer to 1 and cleaning device 12 for evaluation. The potential after charging was sgov, the potential after laser light irradiation was 90 V, and the potential after transfer was OV. Since the transfer is negatively charged, charge is injected from the conductive layer to the charge transport layer, and no potential is applied to it, causing it to burn. Therefore, post-exposure as in the electronic copying machine of Example 1 was unnecessary.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electrophotographic photoreceptor according to the present invention, and FIG. 2 shows an image forming method. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Undercoat layer, 3... Charge transport layer, 4... Charge generation layer, 5... Electrophotographic photoreceptor, 6...
...10 Charger, 7...Exposure, 8...Developer, 9...
・Toner, 10...-Charger, 11...Paper, 12.
・Cleaning device.

Claims (7)

[Claims] (1) An undercoat layer in which conductive powder having charge injection properties with respect to an electron-donating compound is dispersed in a resin, a charge transport layer consisting of an electron-donating compound and a film-forming resin as necessary, and a light An electrophotographic photoreceptor in which a charge generation layer having the function of generating charge carriers is laminated in this order on a substrate. (2) The above-mentioned charge injection powder is selected from conductive powders such as carbon black, iron oxide, tin oxide, antimony oxide, indium oxide, zinc oxide, copper iodide, and lead oxide. Electrophotographic photoreceptor according to item 1 (3) The electrophotographic photoreceptor according to claim 2, wherein the powder having charge injection properties is an insulating powder coated with the conductive powder. (4) The electrophotographic photoreceptor according to claim 2, wherein the powder having charge injection properties is a mixture of an insulating powder and a conductive powder. (5) The above insulating powder is titanium oxide, insulating zinc oxide,
The electrophotographic photoreceptor according to claim 3 or 4, which is selected from barium sulfate, barium carbonate, alumina, silica, calcium carbonate, barium carbonate, and magnesium oxide. (6) A conductive layer formed by dispersing in a resin powder that has charge injection properties with respect to an electron-donating compound, a charge transport layer formed of an electron-donating compound and, if necessary, a film-forming resin, and a charge-transferring layer formed by light-induced charging. An image forming method characterized in that an electrophotographic photoreceptor in which a charge generation layer having a function of generating a carrier is laminated in this order on a substrate is positively charged and then imagewise exposed. (7) After forming an image by the method described in claim 6, developing the toner, and transferring the toner image onto plain paper, the electrophotographic photoreceptor is negatively charged, and then the image is formed again. An image forming method according to claim 6, wherein the image forming method is carried out.