JP3953072B2 - Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge having the electrophotographic photosensitive member, and an electrophotographic apparatus, and more specifically, an electrophotographic photosensitive member having a surface layer containing a specific resin, and a process having the electrophotographic photosensitive member. The present invention relates to a cartridge and an electrophotographic apparatus.

  The electrophotographic method uses a photoconductive material comprising a support that is coated with an insulating substance in a dark place and whose electric resistance changes according to the dose received during image exposure (see Patent Document 1). Basic characteristics required for an electrophotographic photosensitive member using this photoconductive material are (1) that it can be charged to an appropriate potential in a dark place, (2) that there is little potential dissipation in the dark place, and ( 3) The charge can be quickly dissipated by light irradiation.

  Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductive compound such as selenium, zinc oxide and cadmium sulfide has been widely used. However, these satisfy the conditions (1) to (3), but are not always satisfactory in terms of thermal stability, moisture resistance, durability and productivity.

  In order to overcome the disadvantages of inorganic photoreceptors, electrophotographic photoreceptors based on various organic photoconductive compounds as main components have been actively developed in recent years.

  Furthermore, the organic photoconductive compound can freely select the photosensitive wavelength region of the electrophotographic photosensitive member depending on the compound. For example, an azo pigment has been disclosed as a substance exhibiting high sensitivity in the visible region (Patent Literature). 2 and 3), and compounds having sensitivity to the infrared region are shown (see Patent Documents 4 and 5).

  Among these materials, those showing sensitivity in the infrared region are used in laser beam printers (hereinafter abbreviated as LBP) and LED printers that have made remarkable progress in recent years, and the frequency of demand thereof has increased.

  When an electrophotographic photoreceptor using these organic photoconductive compounds is used as a function-separated photoreceptor in which a charge transport layer and a charge generation layer are laminated in order to satisfy both electrical and mechanical properties. There are many. On the other hand, as a matter of course, the electrophotographic photosensitive member is required to have sensitivity, electrical characteristics, and optical characteristics according to the applied electrophotographic process.

  In particular, in electrophotographic photoreceptors that are used repeatedly, electrical and mechanical external forces such as corona or direct charging, image exposure, toner development, transfer process and surface cleaning are directly applied to the surface of the electrophotographic photoreceptor. , Durability against them is also required.

  Specifically, it is suitable for electrical deterioration due to ozone and nitrogen oxides during charging, mechanical deterioration in which the surface is worn or scratched due to discharge during charging and rubbing of the cleaning member, and electrical deterioration. Durability is required.

  The electrical deterioration is particularly a phenomenon in which a carrier is accumulated in a portion irradiated with light and a potential difference is generated from a portion not irradiated with light, which occurs as a photo memory.

  Unlike inorganic photoreceptors, organic photoreceptors that are often soft in material are poor in durability against mechanical deterioration, and improvement in durability is particularly desired.

  Various attempts have been made to satisfy the durability characteristics required for the photoreceptor as described above.

  A polycarbonate resin having a bisphenol A skeleton as a resin that is often used for the surface layer and has good wear characteristics and electrical properties has attracted attention. Has a problem.

  (1) It has poor solubility and exhibits good solubility only in a part of halogenated aliphatic hydrocarbons such as dichloromethane and 1,2-dichloroethane, and these solvents have low boiling points. When a photoreceptor is manufactured using the prepared coating solution, the coated surface is likely to be whitened. It also takes time to manage the solid content of the coating liquid.

  (2) Solvents other than halogenated aliphatic hydrocarbons are partially soluble in tetrahydrafuran, dioxane, cyclohexane, or mixed solvents thereof, but the solution gels in several days. It is not suitable for photoconductor production due to poor properties.

  (3) Even if the above (1) and (2) are further improved, a solvent crack is likely to occur in the polycarbonate resin having bisphenol A as a skeleton.

  (4) In addition, with the conventional polycarbonate resin, the coating formed with the resin is not lubricious, so the photoconductor is easily scratched, and the cleaning setting that reduces the wear amount of the electrophotographic photoconductor causes image defects. Or cleaning failure due to early deterioration of the cleaning blade or toner fusion may occur.

  The solution stability mentioned in the above (1) and (2) can be solved by using a polycarbonate Z resin having a bulky cyclohexylene group as a polymer structural unit or by copolymerizing with bisphenol Z or bisphenol C. I came.

  Solvent cracks can also be solved by using silicon-modified polycarbonate or ether-modified polycarbonate (see Patent Documents 6 and 7). However, these modified polycarbonates have a structure that has flexibility against internal stress in the polymer to prevent solvent cracks compared to conventional polycarbonate resins, resulting in a decrease in the mechanical strength of the polymer body. There was a drawback of doing.

  Furthermore, in recent years, a direct charging method in which a voltage is directly applied to a charging member and a charge is applied to an electrophotographic photosensitive member is becoming mainstream (see Patent Documents 8 and 9).

  This is a method in which a roller-shaped charging member made of conductive rubber or the like is directly brought into contact with the electrophotographic photosensitive member to apply a charge. Ozone generation is significantly less than that of scorotron, etc. Around 80% of the current that flows is wasted because it flows to the shield, whereas direct charging has the merit of being very economical because there is no wasted amount.

  However, direct charging has the disadvantage that the charging stability is very poor due to charging by discharge according to Paschen's law. As a countermeasure, a so-called AC / DC charging method in which an AC voltage is superimposed on a DC voltage has been devised (see Patent Document 10).

Although this charging system improves the stability during charging, the amount of discharge on the surface of the electrophotographic photosensitive member is greatly increased due to the superposition of AC, so that the amount of abrasion of the electrophotographic photosensitive member increases. It has arisen newly, and not only mechanical strength but also electrical strength has been demanded.
US Patent No. 2,297,691 JP-A-61-272754 JP 56-167759 A JP 57-19576 A Japanese Patent Laid-Open No. 61-228453 JP-A-6-51544 JP-A-6-75415 JP 57-17826 A JP 58-40566 A JP-A 63-149668

  An object of the present invention is to provide an electrophotographic photoreceptor excellent in solvent crack resistance and mechanical strength, having good electrical resistance, high sensitivity and low photomemory, and a process cartridge and an electronic device having the electrophotographic photoreceptor It is to provide a photographic apparatus.

  The present invention provides an electrophotographic photosensitive member having a support and a photosensitive layer, wherein the surface layer of the electrophotographic photosensitive member contains a polyester resin having a repeating unit represented by the following formula (3). It is a photographic photoreceptor.

（式（３）中、Ａｒ_２は置換基を有しても良いアルキレン基を示し、Ｒ_９からＲ_１２は水素原子、ハロゲン原子または置換基を有しても良いアルキル基を示す。）

(In formula (3), Ar ₂ represents an alkylene group which may have a substituent, and R ₉ to R ₁₂ represent a hydrogen atom, a halogen atom or an alkyl group which may have a substituent.)

  The electrophotographic photoreceptor according to claim 1, wherein the polyester resin is a copolymer having a repeating unit represented by the formula (3) and a repeating unit represented by the following formula (4). It is. The polymer of the repeating unit represented by the formula (3) or the copolymer of the repeating unit represented by the formulas (3) and (4) is hereinafter referred to as a polymer of the present invention.

（式（４）中、Ａｒ_３は置換されても良いアルキレン基を示す。）

(In formula (4), Ar ₃ represents an optionally substituted alkylene group.)

  The present invention also provides a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member.

  According to the present invention, it has excellent solvent crack resistance without impairing mechanical strength, and further has high mechanical strength, good electrical characteristics against discharge due to direct charging, and reduced electron memory. It has become possible to provide a photographic photoreceptor, and a process cartridge and an electrophotographic apparatus having the electrophotographic photoreceptor.

  Examples of the alkyl group in the above formulas (3) and (4) include groups such as methyl, ethyl, propyl, and butyl. Examples of the alkylene group include groups such as methylene, ethylene, propylene, and butylene. Include atoms such as fluorine and chlorine.

  In addition, examples of the substituent that the alkylene group and the alkyl group may have include an alkyl group such as methyl, ethyl, and propyl, and a halogen atom such as fluorine and chlorine.

  Specific examples of the repeating unit represented by the above formulas (3) and (4) are shown below, but are not limited thereto.

  The electrophotographic photosensitive member of the present invention has excellent electrophotographic characteristics, particularly excellent mechanical strength and solvent crack resistance, and also excellent electrical resistance characteristics.

  Since the polymer of the present invention has a rigid terephthalic acid structure having a rigid property and an aliphatic hydrocarbon structure having a flexible property (so-called toughness) at the same time, it has flexibility (so-called toughness) in the properties of a hard but brittle rigid unit. It is considered that the addition has excellent mechanical strength and improved solvent crack resistance.

  The polymer of the present invention may be a polymer composed of a single main chain repeating unit or a copolymer composed of two or more different types of repeating units.

  Further, it may be used as a copolymer or alloy (including a blend) with an existing resin such as polycarbonate or polyarylate.

  However, in that case, it is desirable that the ratio of the polymer of the present invention is 10 mol% or more.

  The polymer of the present invention can be obtained by polymerizing a carboxylic acid component of terephthalic acid or isophthalic acid and an arbitrary aliphatic diol. At this time, the carboxylic acid component is preferably used as an acid chloride.

  Hereinafter, the configuration of the electrophotographic photoreceptor of the present invention will be described.

  In the electrophotographic photoreceptor of the present invention, the photosensitive layer may be a single layer type in which the charge transport material and the charge generation material are contained in the same layer, or may be a stacked type in which the charge transport layer and the charge generation layer are separated, From the viewpoint of electrophotographic characteristics, a laminated type is preferable.

  The support to be used is not particularly limited as long as it has conductivity, and examples thereof include metals such as aluminum and stainless steel, metals provided with a conductive layer, paper, and plastics, and examples of the shape include a sheet shape and a cylindrical shape.

  When the image input is laser light such as LBP, a conductive layer may be provided for the purpose of preventing interference fringes due to scattering and covering scratches on the support. This can be formed by dispersing conductive powder such as carbon black and metal particles in a binder resin. The thickness of the conductive layer is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  An intermediate layer having an adhesive function is provided thereon. Examples of the material for the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are dissolved in an appropriate solvent and applied. The thickness of the intermediate layer is preferably 0.05 to 5 μm, and more preferably 0.3 to 1 μm.

  A charge generation layer is formed on the intermediate layer. Examples of the charge generating material used in the present invention include selenium tellurium, pyrylium, thiapyrylium dyes, phthalocyanine, anthanthrone, dibenzpyrenequinone, trisazo, cyanine, disazo, monoazo, indigo, quinacridone, and asymmetric quinocyanine pigments. In the case of the function separation type, the charge generation layer is composed of the above charge generation material with a binder resin and a solvent in an amount of 0.3 to 4 times, a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, and a liquid collision type high speed. It is formed by dispersing well by a method such as a disperser, applying a dispersion, and drying. The film thickness of the charge generation layer is preferably 5 μm or less, more preferably 0.1 to 2 μm.

  The charge transport layer is formed by applying and drying a paint in which a charge transport material and the polymer of the present invention as a binder resin are dissolved in a solvent. Examples of the charge transport material used include triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, triallylmethane compounds, and thiazole compounds.

  These are combined with 0.5 to 2 times the amount of binder resin, applied, and dried to form a charge transport layer. The film thickness of the charge transport layer is preferably 5 to 40 μm, and more preferably 15 to 30 μm.

  FIG. 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.

  In the figure, reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is rotated about a shaft 2 in the direction of an arrow at a predetermined peripheral speed. In the rotation process, the photosensitive member 1 is uniformly charged with a positive or negative predetermined potential on its peripheral surface by the primary charging unit 3, and then exposed from an exposure unit (not shown) such as slit exposure or laser beam scanning exposure. Receive light 4. In this way, electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor 1.

  The formed electrostatic latent image is then developed with toner by the developing unit 5, and the developed toner developed image is rotated between the photosensitive member 1 and the transfer unit 6 from a sheet feeding unit (not shown). The image is sequentially transferred by the transfer means 6 to the transfer material 7 that is synchronously taken out and fed.

  The transfer material 7 that has received the image transfer is separated from the surface of the photosensitive member, introduced into the image fixing means 8, and subjected to image fixing, thereby being printed out as a copy (copy).

  After the image transfer, the surface of the photoreceptor 1 is cleaned by removing the transfer residual toner by the cleaning unit 9 and further subjected to charge removal processing by the pre-exposure light 10 from the pre-exposure unit (not shown), and then repeatedly. Used for image formation. When the primary charging unit 3 is a contact charging unit using a charging roller or the like, pre-exposure is not always necessary.

  In the present invention, a plurality of components such as the above-described electrophotographic photosensitive member 1, primary charging unit 3, developing unit 5, and cleaning unit 9 are integrally coupled as a process cartridge. May be configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. For example, at least one of the primary charging unit 3, the developing unit 5, and the cleaning unit 9 is integrally supported together with the photosensitive member 1 to form a cartridge, and is detachable from the apparatus main body using guide means such as a rail 12 of the apparatus main body. The process cartridge 11 can be obtained.

  Further, when the electrophotographic apparatus is a copying machine or a printer, the exposure light 4 is reflected or transmitted light from the original, or the original is read by a sensor and converted into a signal, and a laser beam scanning performed according to this signal is performed. The light is emitted by driving the LED array and the liquid crystal shutter array.

  The electrophotographic photosensitive member of the present invention can be used not only in electrophotographic copying machines but also widely in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

(Synthesis Example 1)
Benzene dimethanol (1.0 mol), ethylene glycol (1.0 mol), terephthalic acid (1.0 mol), and isophthalic acid (1.0 mol) were placed in a SUS container and heated and stirred at 250 ° C. After 1 hour, the reaction temperature was raised to 280 ° C., and the mixture was further heated and stirred for 2 hours.

  After cooling, it was dissolved in 1.5 liters of dichloromethane and reprecipitated from methanol. The precipitate was collected by filtration and dried to obtain a colorless polymer (resin having the following repeating unit 1-1).

  The final yield was 80%.

  A description will be given below in accordance with examples. In the examples, “parts” represents parts by weight. Moreover, resin No. in an Example. 1 to 3 were polymerized in the same manner as in the above synthesis examples to synthesize resins having structures corresponding to the exemplified compounds.

Example 1
Using a 30 mm diameter, 254 mm long aluminum cylinder as a support, a coating composed of the following materials is applied onto the support by a dip coating method and thermally cured at 140 ° C. for 30 minutes to form a 17 μm thick conductive layer. Formed.

Conductive pigment: SnO ₂ coated treated barium sulfate 10 parts Resistance adjusting pigment: Titanium oxide 2 parts Binder resin: Phenol resin 6 parts Leveling material: Silicone oil 0.001 part Solvent: Methanol, methoxypropanol 0.2 / 0.8 20 copies

  Next, a solution obtained by dissolving 3 parts of N methoxymethylated nylon and 3 parts of copolymer nylon in a mixed solvent of 70 parts of methanol and 30 parts of n-butanol is applied by dip coating method and dried. A 0.7 μm intermediate layer was formed.

  Next, oxytitanium phthalocyanine (TiOPc) 4 having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° of the Bragg angle 2θ ± 0.2 ° of CuKα characteristic X-ray diffraction. Parts, polyvinyl butyral resin (trade name: ESREC BM2, manufactured by Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone were dispersed for 4 hours in a sand mill using φ1 mm glass beads, and then 100 parts of ethyl acetate was added to disperse the charge generation layer. A liquid was prepared. This was applied by a dip coating method and dried to form a charge generation layer having a thickness of 0.3 μm.

  Next, the resin No. of Table 1 synthesized by the same method as in the above synthesis example. 10 parts of the polymer described in 1 and 8 parts of the following compound (CT-1 / CT-2 = 9/1) were dissolved in a mixed solvent of 50 parts of monochlorobenzene and 50 parts of dichloromethane.

  This paint was applied by a dip coating method and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 24 μm.

  Next, evaluation will be described.

  The created photoreceptor was mounted on a modified Hewlett-Packard LBP “Laser Jet 4 plus” (process speed 71 mm / sec). In the modification, the setting was changed so that the peak-to-peak voltage during charging increased by 30%.

  The electrophotographic photosensitive member thus prepared was subjected to a paper passing durability test (HH durability) at 28 ° C. and 90% RH with this apparatus.

  The durability test was an intermittent mode in which each sheet was stopped once, and an eddy current film thickness measuring machine (Permascope type 111) manufactured by Fischer was used for the measurement of the amount of wear.

  If the toner runs out, it is replenished and it lasts until there is a problem with the image. Moreover, it was abraded for 30 minutes using a Taber abrasion tester using an abrasive tape, and the weight loss at that time was measured.

  Furthermore, a part of the electrophotographic photosensitive member is irradiated with light from a white fluorescent lamp at 2000 Lux for 30 minutes, and after being left for 5 minutes, the light portion potential is measured and how much the light portion potential has dropped before the light is irradiated. Measured and used as a photo memory value.

  Further, for the solvent cracking property, sebum was attached to the surface of the photoreceptor and allowed to stand for 72 hours, and the presence or absence of the solvent crack was observed by microscopic observation.

  The results are shown in Table 3.

分子量はゲルパーミエーションクロマトグラフィーで測定した。

The molecular weight was measured by gel permeation chromatography.

(Examples 2-3)
Resin No. 1 in Table 1 was used as the binder for the charge transport layer. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that 2 to 3 were used. The results are shown in Table 3.

(Comparative Examples 1-4)
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the resins of Conditions 1 to 4 shown in Table 2 were used. The results are shown in Table 3.

条件１及び５のカルボン酸成分は、テレフタル酸／イソフタル酸をモル比で１／１とした。

The carboxylic acid component under conditions 1 and 5 was terephthalic acid / isophthalic acid in a molar ratio of 1/1.

  From the above results, it was clarified that the electrophotographic photosensitive member of the present invention has excellent solvent crack resistance and good durability characteristics.

1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.

Claims (4)

An electrophotographic photosensitive member having a support and a photosensitive layer, wherein the surface layer of the electrophotographic photosensitive member contains a polyester resin having a repeating unit represented by the following formula (3).

(In formula (3), Ar ₂ represents an alkylene group which may have a substituent, and R ₉ to R ₁₂ represent a hydrogen atom, a halogen atom or an alkyl group which may have a substituent.) The electrophotographic photoreceptor according to claim 1, wherein the polyester resin is a copolymer having a repeating unit represented by the formula (3) and a repeating unit represented by the following formula (4).

(In formula (4), Ar ₃ represents an optionally substituted alkylene group.)   The electrophotographic photosensitive member according to claim 1 and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means are integrally supported and detachable from the main body of the electrophotographic apparatus. Process cartridge characterized by.   An electrophotographic apparatus comprising the electrophotographic photosensitive member according to claim 1, a charging unit, an exposure unit, a developing unit, and a transfer unit.

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