JPH0990660A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) Abstract: An intermediate layer having low resistance and good environmental resistance is provided to obtain a photoconductor having excellent electrical characteristics, image quality, repeatability, and environmental resistance. An intermediate layer composed of a polysulfide polymer, an amino resin, and iodine fixed to these is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate layer of an electrophotographic photosensitive member, and more particularly to an intermediate layer of an electrophotographic photosensitive member which has good electric characteristics and image quality and is stable.

[0002]

2. Description of the Related Art Electrophotographic photoconductors (hereinafter also simply referred to as photoconductors) used in electrophotographic apparatuses starting from the invention of Carlson have hitherto been inorganic photoconductive materials such as selenium, selenium alloys, zinc oxide, and cadmium sulfide. The mainstream was the use of materials. However, recently, in view of nontoxicity, film-forming property, light weight, low price and the like, development of a photoconductor using an organic photoconductive material has been actively promoted. Among them, the photosensitive layer is divided into a charge generation layer that receives light to generate charge carriers and a charge transfer layer that moves the generated charge carriers. It is common. This photoconductor has the advantages that the sensitivity is significantly improved by forming and combining each layer with a material optimal for the function of each layer, and that the spectral sensitivity can be increased depending on the light wavelength for exposure. Therefore, it has become the mainstream of development and has been used in electrophotographic devices such as copiers, printers and fax machines.

The mainstream of the function-separated layered type organic photoconductors currently in practical use is a structure in which a charge generation layer and a charge transfer layer are laminated in this order on a conductive substrate. . Such a photosensitive member is obtained by sublimating or vapor-depositing an organic charge generating agent on a conductive substrate, or coating and drying a coating liquid in which the organic charge generating agent is dispersed and dissolved in an organic solvent together with a binder. Then, a charge generation layer is formed, and subsequently, a coating liquid in which a charge transfer agent is dissolved in an organic solvent together with a binder is applied and dried to form a charge transfer layer. Basically, the basic performance as a photoreceptor for image formation can be exhibited with such a layer structure. However, practically, it is important to obtain a good image free from defects, and it is required to maintain a good image quality even after repeated use for a long period of time. For that purpose, it is necessary to form a photosensitive layer having a uniform and defect-free film quality and the electric characteristics of the photoconductor are excellent, and the film thickness and the electric characteristics are stable even after long-term use. It is necessary.

By the way, the charge generation layer absorbs light to generate charge carriers, but the generated charge carriers move quickly without recombination and disappearance or trapping, and the conductive substrate or the charge is discharged. It needs to be injected into the moving bed. For this reason, it is desirable to make the charge generation layer as thin as possible, and in the currently practiced photoreceptors, the charge generation layer having a film thickness of the submicron order is usually formed. Since the charge generation layer is formed as such a thin film, stains on the surface of the conductive substrate, unevenness in shape and properties, and roughness appear as film formation unevenness of the charge generation layer, resulting in an image. There is a problem that image defects such as white spots, black spots, and uneven density occur. As the conductive substrate, generally, an aluminum alloy drawn cylinder or a cylinder whose surface is smoothed by cutting and polishing is used, but it is included as a variation in the surface roughness of the substrate, surface stains, and alloy components. Due to variations in the amount of metal deposits and variations in surface properties due to variations in the degree of surface oxidation, film formation unevenness occurs in the charge generation layer formed on the surface, and It will have a big impact on quality.

In order to avoid such unevenness of film formation and to obtain a blocking effect for preventing deterioration of the charge retention characteristic of the photoconductor due to injection of holes from a conductive substrate, which is required separately, conductivity An intermediate layer made of an n-type resin having a low electric resistance has been provided on the surface of a substrate.

[0006]

As the resin used for the intermediate layer for such purpose, solvent-soluble polyamide, polyvinyl alcohol, polyvinyl butyral,
Resins such as casein are known. These resins are
An ultrathin film, for example, a thin film having a thickness of 0.1 μm or less, can sufficiently perform its function only for the purpose of the blocking layer. But for other purposes,
That is, a thin film of 0.5 μm or more is used to cover the surface shape of the conductive substrate, variations in surface properties and surface stains, and to improve the non-uniformity of wetting of the charge generation layer coating liquid and eliminate film formation unevenness. Although depending on the processing conditions of the substrate and the state of surface contamination, a film thickness of 1 μm or more is required in some cases. However, when such a thick resin layer is formed from the above-mentioned polyvinyl alcohol, solvent-soluble polyamide, casein, etc., the residual potential rises, and the electrical characteristics of the photoconductor fluctuate in environments of low temperature and low humidity and high temperature and high humidity. There was a problem that it would occur. This is because these resins have high water absorption and their electric conduction is largely due to ionic conduction due to dissociated hydrogen ions or hydroxy ions in the absorbed water, and the electric resistance of the resin layer is greatly increased due to the water contained in the resin layer. Because it fluctuates.

Various conventional materials have been proposed as a material suitable for the intermediate layer because the electric resistance of such a thick film layer is low and the electric resistance changes little even with changes in the surrounding environment. . For example, regarding solvent-soluble polyamide resins, those which specify the chemical structure of the polyamide resin are disclosed in JP-A-2-193152 and JP-A-3-28.
Japanese Patent Publication No. 2-59458, which is disclosed in JP-A-8157, JP-A-4-31870 and the like, and which is expected to have an effect of suppressing an electric resistance change due to an environmental change by adding an additive to a polyamide resin. Japanese Patent Laid-Open Publication No. 3-
No. 150572, JP-A No. 2-53070, and the like are disclosed. Also, a mixture of a polyamide resin and another resin is used to adjust the electric resistance and is expected to have the effect of weakening the influence of environmental changes.
No. 652, Japanese Patent Application Laid-Open No. 3-81778, Japanese Patent Application Laid-Open No. 2
It is disclosed in, for example, Japanese Patent No. 281262. But,
The main material used in these methods is a polyamide resin, and the influence of temperature and humidity cannot be avoided.

An example of using a cellulose derivative as a material other than the polyamide resin (Japanese Patent Laid-Open No. 2384/1990).
59), examples using polyether urethane (JP-A-2-115858, JP-A-2-280170), examples using polyvinylpyrrolidone (JP-A-2-
No. 105349), examples using polyglycol ether (Japanese Patent Application Laid-Open No. 2-79859), etc., and crosslinking from the idea that the amount of water in the resin layer does not depend on environmental changes. It is also proposed to use a volatile resin, for example, an example in which a melamine resin is used (Japanese Patent Laid-Open No. Hei 4)
No. 22966, Japanese Patent Publication No. 4-31576, Japanese Patent Publication No. 4-31577), an example using a phenol resin (Japanese Patent Laid-Open No. 3-48256), and a large amount of filler (for example, anatase type titanium oxide) is added. A proposal (Japanese Patent Application Laid-Open No. 4-328567) is known. However, these methods are also effective when the resin layer is extremely thin, but when the film is relatively thick such as several μm, the resistance of the photoconductor becomes high, which causes an increase in residual potential.

In order to eliminate the above-mentioned drawbacks, a method of providing a resin layer in which a conductive powder such as tin oxide or indium oxide is dispersed has been proposed (Japanese Patent Publication No. 1-511).
Japanese Patent No. 85, Japanese Patent Publication No. 2-48175, Japanese Patent Publication No. 2-
No. 60177, Japanese Patent Publication No. 2-62861). However, such a method also has many difficulties in preparing a resin coating solution in which the conductive powder is uniformly dispersed, and it is difficult to store the coating solution stably so that the conductive powder does not separate and settle. However, it is unavoidable that minute projections are often formed on the surface of the resin layer formed by coating the conductive powder due to separation and aggregation of the conductive powder, which causes image defects on the photoreceptor. Therefore, there is also proposed a method of forming an intermediate layer by using an organometallic compound instead of the conductive powder as described above, and applying a coating solution in which an organometallic compound is dissolved in an organic solvent together with a resin (Patent Publication 3- 4904, JP-A-2-59767). However, in this method as well, the coating solution is unstable, and there are many problems to be solved for industrial mass production. In particular, as in recent years, there has been a strong demand for cost reduction of photoconductors, and the adoption of aluminum pipes with a relatively low degree of processing has attracted attention, while the resolution of copiers, printers, and fax machines has become more sophisticated and highly durable. In the case where is required, the importance of an intermediate layer having excellent coating film smoothness, stable to environmental changes, and low resistance increases.

The present invention has been made in view of the above-mentioned points, and an object thereof is to provide an intermediate layer having a low resistance, a smoothness of a coating film and a good environmental stability, so that the electric characteristics and the image quality are excellent and the repeating characteristics are excellent. , It is to provide an electrophotographic photoreceptor having excellent environment resistance.

[0011]

According to the present invention, the above object is to provide an electrophotographic photosensitive member comprising a conductive substrate on which an intermediate layer is provided and which is provided with a photosensitive layer, wherein the intermediate layer is a polysulfide polymer. And a cured film containing an amino resin and iodine fixed thereto as main components.

In the above invention, the polysulfide polymer has a disulfide bond in the repeating unit of the main chain, the amino resin is a melamine resin or a benzoguanamine resin, and the intermediate layer contains a polyisocyanate. Alternatively, it is effective that the iodine content is 0.1 to 5% by weight, preferably 0.2 to 2% by weight, based on the total solid content of the resin.

By using a cured film composed of a polysulfide polymer and an amino resin and iodine fixed thereto as an intermediate layer, the thickness is extremely large, for example, 10 μm to 20 μm.
Even with a film thickness of μm, the residual potential is low, and problems such as deterioration of charging characteristics and increase of residual potential do not occur even after repeated use, and under wide operating environment conditions from high temperature / high humidity to low temperature / low humidity. It is possible to obtain a photoconductor having excellent electric characteristics and image quality.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polysulfide polymer according to the present invention is obtained by polycondensing bis (2-chloroethyl) formal with sodium disulfide or adding bis (2-chloroethyl) formal to ethylene dichloride and / or trichloropropylene. It is a liquid to solid rubbery substance obtained by polycondensing chloroalkylene with sodium disulfide, and is characterized by having a disulfide bond in the repeating unit of the polymer main chain. These are manufactured and marketed by Thiocol under the names Thiocor-FA, Thiocor-ST, Thiocor-LP and the like.

The amino resin is dicyandiamide,
Urea compounds such as urea and thiourea, and triazine compounds such as melamine, isomeramine, and benzoguanamine are subjected to methylolation and methylene condensation under an alkaline catalyst in a large amount of butanol or isobutanol together with excess formaldehyde, and then butyl ether under an acid catalyst. It is synthesized by performing conversion. The degree of condensation varies depending on the amount of excess formaldehyde and the strength of the alkali catalyst used at that time, but generally the number average molecular weight is 2000 to 4000.
A condensate of is produced. When the reaction is carried out with only the acid catalyst from the beginning, a condensate having a number average molecular weight of about 1000 is obtained. The amino resin thus obtained is butylated urea resin,
It has long been known as butylated melamine resin, butylated benzoguanamine resin, butylated melamine benzoguanamine co-condensation resin, and includes, for example, Uban (manufactured by Mitsui Toatsu Chemical Co., Inc.), Beckamine, Super Beckamine (Dainippon Ink and Chemicals ( Co., Ltd.) and the like.

Polyisocyanate refers to an isocyanate compound having two or more isocyanate groups in the structure, for example, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, o-trizine isocyanate, 2,4. -Tolylene diisocyanate, 2,6-tolylene diisocyanate,
It refers to a diisocyanate compound such as 1,5-naphthalene diisocyanate, a polyisocyanate compound obtained by converting these into biuret, a polyisocyanate compound obtained through isocyanurate, or a polyisocyanate compound obtained through uretdione, or a blocked product thereof. When used in the present invention, it is preferable to use a blocked polyisocyanate in consideration of the stability of the coating liquid. Examples of the blocked polyisocyanate include a caprolactam block type,
Methyl ethyl ketoxime block type, etc., such as Desmodur BL3175, Desmodur BL4165 from Bayer, Orestar NP1060PB from Mitsui Toatsu Chemicals, Inc., Vernock D-500, Vernock D- from Dainippon Ink and Chemicals, Inc. It is marketed under the name 550.

In the present invention, iodine is added to a cured product of a polysulfide polymer and an amino resin. As a method therefor, a coating liquid is prepared by further dissolving iodine in a solution of the polysulfide polymer and the amino resin (and polyisocyanate). Then, it is applied to the conductive substrate, dried, and heated to be added simultaneously with the curing reaction. Apply a solution of polysulfide polymer and amino resin (and polyisocyanate) dissolved on a conductive substrate,
The dried and heated cured film is immersed in a solution containing iodine for a predetermined time to cause an addition reaction. The cured film prepared in step 1 is left in iodine vapor for a predetermined time to cause an addition reaction.

Although any of the above methods can be used, it is preferable to use the method because of the ease of controlling the steps. The amount of iodine added was 0.
1-5% by weight, preferably 0.2-2% by weight is sufficient. To create a cured film, the heating temperature is 100 ° C to 200 ° C.
It is necessary to heat at 5 ° C for 5 to 60 minutes. Curing catalyst, to lower the curing temperature or shorten the time
For example, dibutyltin laurate or the like can be added, and a curing catalyst for polysulfide polymer, for example, lead dioxide, manganese dioxide, zinc peroxide, cobalt octylate or the like can be used in combination.

These systems also include zinc oxide, alumina,
Fillers such as titanium oxide and silicon oxide can be added, and additives such as antioxidants and leveling agents can also be added. In addition to the above system, polyester resin, polycarbonate resin, polyamide resin, polystyrene resin, styrene acrylate resin, etc. can be added. The intermediate layer of the present invention can be formed by coating the above-mentioned composition on a conductive substrate.

The conductive substrate is made of aluminum, copper, zinc,
A drum, sheet or paper made of metal or alloy such as nickel or iron, non-metal such as paper, plastics, glass and the like, laminated, coated or blended with a conductive substance can be used. These are subjected to surface treatments such as surface roughening treatment, oxidation treatment, chemical treatment, ozone treatment, ultraviolet ray treatment and plasma treatment to improve the adhesion with the undercoat layer.
The intermediate layer thus formed has a sufficiently low electric resistance and is stable, and hardly changes even when the environment changes greatly from high temperature and high humidity to low temperature and low humidity. Therefore, even if the thickness of the intermediate layer is increased to about 10 μm to 20 μm, the photoconductor has excellent electrical characteristics, and even if it is repeatedly used, fluctuations in the electrical characteristics such as a decrease in charge level and an increase in residual potential occur. Absent. Further, by forming such a thick film intermediate layer, variations in the properties of the conductive substrate surface, shape defects, variations in roughness, dirt, etc. are covered, and a uniform photosensitive layer with few film defects is formed thereon. In particular, even in the case of a function-separated laminated type photoreceptor in which the photosensitive layer is laminated in the order of the charge generation layer and the charge transfer layer, a thin charge generation layer can be easily formed without causing unevenness in film formation. be able to. As a result, it is possible to obtain a photoconductor that can stably obtain a high-quality image with few image defects.

As described above, the present invention is particularly effective for a function-separated laminated type photoreceptor in which a photosensitive layer is laminated in the order of a charge generation layer and a charge transfer layer. In such a photoreceptor, the charge generation layer is a coating liquid in which a pigment such as a phthalocyanine-based pigment, an anthrone pigment, a perylene pigment, a perinone pigment, an azo pigment, or a disazo pigment is dispersed in a solution in which an appropriate binder resin is dissolved. Can be applied on the above-mentioned intermediate layer and dried to form a coating film having a film thickness of 0.1 μm to 1 μm. On top of that, a coating solution prepared by dissolving an enamine compound, a hydrazone compound, a styryl compound, an amine compound together with a binder resin compatible with these compounds, for example, polycarbonate, polyester, polystyrene, styrene acrylate, etc., is applied. By drying, a charge transfer layer having a film thickness of 5 μm to 40 μm can be formed.

[0022]

【Example】

Examples 1 to 10 and Comparative Examples 1 to 5 As the conductive substrate used in this example, the outer diameter is 30 mm, the inner diameter is 28 mm, the length is 260.5 mm, and the surface roughness is 2.0 μm at the maximum height (Rmax). Create an intermediate layer on an aluminum cylinder.

Preparation of intermediate layer A coating solution of dichloromethane (30% by weight) having the composition shown in Table 1 was prepared, applied on an aluminum cylinder prepared previously, and heated at 150 ° C. for 1 hour to obtain a cured thickness of 10 μm. An intermediate layer was created.

[0024]

[Table 1]

In the above table, Uban 20HS, Uban 2020, Uban 20SB, Cymel 1141 etc. are melamine resins, Super Beckamine TD126, Cymel 1128 are benzoguanamine resins, Beckamine P138.
Is a butylated urea resin. Manufacturers of polysulfide polymers, amino resins, polyisocyanates, etc. in the above table are as follows.

(1) Thiokol LP-2: Toray Thiokol Co., Ltd. (2) Thiokol LP-3: Toray Thiokol Co., Ltd. (3) Uban 20HS: Mitsui Toatsu Chemicals, Inc. (4) Uban 2020 : Mitsui Toatsu Chemical Co., Ltd. (5) Uban 20SB: Mitsui Toatsu Chemical Co., Ltd. (6) Super Beckamine TD-126: Dainippon Ink and Chemicals Co., Ltd. (7) Beckamine P-138: Large Made by Nippon Ink Chemical Co., Ltd. (8) Cymel 1128: Made by Mitsui Cytec Co., Ltd. (9) Cymel 1141: Made by Mitsui Cytec Co., Ltd. (10) Dicyandiamide: Made by Nippon Carbide Industries Co., Ltd. (11) Olester 1060PB : Mitsui Toatsu Chemical Co., Ltd. (12) Burnock D550: Dainippon Ink and Chemicals Co., Ltd. (13) Titanium oxide TTO-55 (S): Ishihara Sangyo Co., Ltd. (14) Sparse Silica Aerosil 200: manufactured by Nippon Aerosil Co., Ltd. Production of photoconductor X type metal-free phthalocyanine (manufactured by Dainippon Ink and Chemicals, Inc .: trade name "on each aluminum cylinder provided with the intermediate layer as described above. First Gen Blue 8120B "
1 part by weight of a vinyl chloride-based copolymer resin (manufactured by Nippon Zeon Co., Ltd .: trade name "MR-110") and 1 part by weight of methylene chloride were dispersed by a paint shaker to prepare a coating solution, which was applied by dip coating to obtain a dry thickness of 0. A charge generation layer of 0.2 μm was formed. Then, on top of this, polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Inc .: trade name "Iupilon PCZ-300")
A coating solution prepared by dissolving 10 parts by weight and 10 parts by weight of N, N-diethylaluminumbenzaldehyde diphenylhydrazone in 80 parts by weight of tetrahydrofuran was applied by dip coating to obtain a dry thickness of 20.
A charge transfer layer having a thickness of μm was formed to prepare each of the photoconductors of Examples 1 to 10 and Comparative Examples 1 to 5.

Evaluation of Photoreceptor The electric characteristics of the thus prepared photoreceptor were evaluated by a photoreceptor process tester. The photoconductor is attached to a tester, charged at −600 V with a corotron while rotating at a peripheral speed of 78.5 mm / sec, and the potential when no light is irradiated is defined as the dark part potential V _O. After that, the potential when left in the dark for 5 seconds is measured and the potential holding ratio V _K5 (%) during that period is obtained. Then, the wavelength is 780 nm and the irradiance is ² μW / cm ^2.
Of the light, and the potential after 0.2 seconds, the bright part potential V
i. The potential after irradiation for 1.5 seconds is defined as the residual potential V _r . The process of charging and exposing as one cycle as described above was repeated 10,000 times, and the characteristics of the photoconductor were measured at the initial (first) and after repeating 10,000 times. The results are shown in Table 2.
Is shown in

[0028]

[Table 2]

As shown in Table 2, a photoreceptor containing no iodine or a small iodine content in the intermediate layer has a high residual potential and poor repetitive characteristics. Further, even if the iodine content is too high, there is a tendency for charge reduction. Further, when the amino resin is other than melamine resin and benzoguanamine resin, the residual potential rises after repeated use.

Next, the characteristics of these photoconductors are measured in a low temperature and low humidity environment (L, L: temperature 10 ° C., relative humidity 50%) and a high temperature and high humidity environment (H, H: temperature 35 ° C., relative humidity 85%). And examined its environmental dependence. The results are shown in Table 3.

[0031]

[Table 3]

Next, these photoconductors were attached to a laser beam printer (manufactured by Hewlett-Packard Co .: trade name "Laser Jet III"), and a low temperature and low humidity environment (L, L
L), normal temperature and high humidity environment (N, N: temperature 25 ° C, relative humidity 5)
0%), printing was performed in a high temperature and high humidity environment (H, H), and the image quality at the initial stage and after printing 10,000 sheets was evaluated. The results are shown in Table 4. The image quality is evaluated by 90 mm x 90 m on the surface of the photoconductor.
The number of black spots having a diameter of 0.2 mm or more existing in the area of a square of m is performed, less than 5 is ◎, 5 or more and less than 20 is ○, 20 or more and less than 50 is △, and 50 or more is. The ordering was performed as x.

[0033]

[Table 4]

As can be seen from Table 4, the image quality of the photoconductor of the example is good, and the image quality of the photoconductor of the comparative example is not deteriorated even when the environment is changed or the printing is repeated. It hardly happens and is stable.

[0035]

According to the electrophotographic photoreceptor of the present invention, a photosensitive layer is laminated on a conductive substrate via an intermediate layer,
The intermediate layer is a cured film containing a polysulfide polymer and an amino resin and a certain amount of iodine in them, or a cured film containing polyisocyanate in them, whereby the electrical resistance is sufficiently low and environmental stability is ensured. An intermediate layer having good properties is obtained. For this reason, the electrical characteristics and image quality are good even if the film thickness is increased by one digit or more compared to the conventional one.
A photoreceptor that can be used repeatedly is obtained. Furthermore, it is possible to obtain a photoconductor whose electric characteristics and image quality are not easily affected by the external environment and which can be used repeatedly. Further, by forming such a thick film intermediate layer, various defects on the surface of the conductive substrate are covered, and a uniform photosensitive layer having few film defects can be formed on the conductive substrate. Even in the case of a function-separated type photoconductor in which the generation layer and the charge transfer layer are laminated in this order, the photoconductor can be easily formed without causing unevenness in the film formation of the thin charge generation layer to enhance the productivity of the photoconductor be able to.

Claims (5)

[Claims] 1. An electrophotographic photoreceptor comprising an electroconductive substrate having an intermediate layer provided thereon and a photosensitive layer provided thereon, wherein the intermediate layer comprises a polysulfide polymer, an amino resin and iodine fixed thereto as main components. An electrophotographic photoreceptor characterized by being a cured film. 2. The electrophotographic photosensitive member according to claim 1, wherein the polysulfide polymer has a disulfide bond in the repeating unit of the main chain. 3. The electrophotographic photosensitive member according to claim 1, wherein the amino resin is a melamine resin or a benzoguanamine resin. 4. The electrophotographic photosensitive member according to claim 1, wherein the intermediate layer is a cured film containing polyisocyanate. 5. The iodine content is 0.
The electrophotographic photosensitive member according to claim 1, wherein the content is 1 to 5% by weight, preferably 0.2 to 2% by weight.