JP3740310B2 - Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member, a process cartridge having an electrophotographic photosensitive member, and an electrophotographic apparatus, and more particularly, an electrophotographic photosensitive member having a photosensitive layer containing a polyarylate resin of a specific bisphenol, and the electrophotographic photosensitive member. The present invention relates to a process cartridge and an electrophotographic apparatus.
[0002]
[Prior art]
One representative image holding member is an electrophotographic photosensitive member. In recent years, electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers because of its immediacy and high-quality images. There are inorganic materials such as selenium, cadmium sulfide, and zinc oxide as the core photoconductor. However, in recent years, from the viewpoint of pollution-free, high productivity, ease of material design, and future prospects. Organic materials are being actively developed.
[0003]
These electrophotographic photoreceptors are naturally required to have various characteristics such as electrical, mechanical, and optical characteristics according to the applied electrophotographic process. In particular, in a photoreceptor that is used repeatedly, electrical and mechanical forces such as charging-exposure-development-transfer-cleaning are repeatedly applied directly or indirectly, and thus durability against them is required. .
[0004]
In an organic photoconductor, an organic photoconductive material is usually dissolved or dispersed in a binder resin to form a coating film and used. The coating film is formed by dissolving or dispersing the organic photoconductive material and the binder resin in a solvent and then coating and drying. As the binder resin, materials such as vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride and copolymers thereof, polycarbonate, polyester, polyarylate, polysulfone, phenoxy resin, epoxy resin, silicone resin, and the like are used. Yes.
[0005]
These organic photoreceptors have excellent mass productivity and are relatively inexpensive to produce. However, when conventional resins are used for the photoreceptors, the problem of image defects due to the occurrence of solvent cracks occurs. Therefore, improvement of the solvent crack resistance is desired. In addition, the inclusion of a low-molecular charge transport material reduces the mechanical strength inherent to the binder resin, which may impair the durability of the photoreceptor due to deterioration of the photoreceptor, scratches, cracks, etc. There was room for improvement.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide an electrophotographic photosensitive member having stable characteristics in repeated use, achieving high mechanical strength, and having high wear resistance, and a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member. There is.
[0007]
[Means for Solving the Problems]
In accordance with the present invention, in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer contains a polyarylate resin having at least a structural unit represented by the following general formula (1), A process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member are provided.
[0008]
[ Chemical 4 ]
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0010]
Polyarylate resin having a fluorene having a substituent represented by the general formula (1) is excellent in compatibility with the charge transporting material, the effect of preventing cracks are more exerted.
[0011]
Further, by copolymerizing a bisphenol of other structures as shown in one general formula (2), it is possible to improve the solubility of the strength of the resin or resin in the solvent. In particular, in the polyarylate resin represented by the general formula ( 2 ), R ¹⁵ and R ¹⁶ are both methyl groups, R ¹⁷ and R ¹⁸ are both hydrogen, and R ¹⁹ and R ²⁰ are both methyl groups. A system obtained by copolymerizing a polyarylate resin having a fluorene structure represented by the general formula ( 1 ) can exhibit more wear strength.
[0012]
Furthermore, there is production by a high productivity dip coating method, which is one of the characteristics of organic photoreceptors. Depending on the compatibility of the system used, such as the solubility of the binder resin and the storage stability of the solution , Copolymerization with polyarylate as shown in the general formula ( 2 ), blending with polyarylate resin or polycarbonate resin of other structure can be performed, and characteristics such as improvement in productivity can be imparted.
[0013]
By using a polyarylate resin having fluorene for the photoreceptor, the effect of preventing cracks could be improved. Although the mechanism of the effect in the present invention has not been fully elucidated, the materials used for the charge transport material are mainly low-molecular substances having a large number of aromatic rings, which are dispersed in the resin and retained in the resin. Therefore, it is presumed that it is effective to introduce more aromatic rings into the resin.
[0014]
The polyarylate having a fluorene structure used in the present invention has many aromatic rings in the fluorene moiety as well as the aromatic ring in the phthalic acid moiety, so that the compatibility improvement of the charge transfer material and the crack prevention effect are obtained. Furthermore, it is considered that the stress relaxation when the charge transfer material is added to the resin works effectively by the fluorene moiety appropriately restricting the arrangement of the polymer chain or the polymer chain. In addition, by copolymerizing with polyarylate of other structure with excellent mechanical strength, the resin itself is given wear resistance, and as a photoconductor due to the synergistic effect of improving compatibility with the charge transport material described above. It is thought that the durability of is improved.
[0015]
The polyarylate resin of the general formula (1) preferably has a molecular weight of Mw = 10000 to 200000, and particularly preferably 50000 to 150,000 in terms of strength, productivity and the like.
[0016]
Shows the specific examples of the structural unit represented by the general formula (1) below.
[0017]
[ Table 1 ]
[0018]
Further, the structural unit represented by the general formula (2), the general formula (1) and the general formula is represented as a copolymer of (5), and specific examples thereof include structural units example described above (1-1) And a copolymer of specific structural unit examples (5-1) to (5-6) of the following general formula (5), and the combination is not limited.
[0019]
The ratio of copolymerization can produce the effect of each characteristic in the general formula (1) / general formula ( 2 ) = 95/5 to 5/95, but the effect of the wear resistance of the present invention is more manifested. Therefore, it is preferable to set it as 80 / 20-20 / 80. The molecular weight is preferably Mw = 10000 to 200000, particularly 50000 to 150,000.
[0020]
Next, specific examples of the structural unit shown by the general formula (5), limited to this structure is not.
[0021]
[Table 2 ]
[0022]
Next, the polyarylate represented by the general formula (1) of the present invention can be used by mixing with the polycarbonate represented by the general formula (6). And the stability of the solution is improved. The mixing ratio can be expressed by the general formula (1) / general formula (6) = 5/95 to 95/5, and is preferably 20/80 to 80/20 in order to efficiently express the effect.
[0023]
Although the molecular weight of General formula (6) is not specifically limited, Preferably it is Mv = 20000-80000. Specific examples of the structural unit represented by the general formula (6) are shown below. There is no limitation to the combination in structure and mixing.
[0024]
[Table 3 ]
[0025]
The polyarylate compound used in the present invention is synthesized by a conventional method. As an example, a synthesis example of a copolymer of the general formula ( 1 ) / constituent unit example (5-2) is shown below.
[0026]
A bisphenol monomer constituting the general formula ( 1 ) / example of structural unit (5-2) (= 3/7) was added to and dissolved in a 10% aqueous sodium hydroxide solution. Further, trimethylbenzylammonium chloride was added as a polymerization catalyst and stirred. Separately, an equivalent mixture of terephthalic acid chloride / isophthalic acid chloride was dissolved in dichloromethane. The dichloromethane solution was added to the previously prepared aqueous sodium hydroxide solution with stirring to initiate polymerization.
[0027]
The polymerization was stirred for 3 hours while keeping the reaction temperature at 25 ° C. or lower. Thereafter, the reaction was terminated by adding acetic acid, and washing with water was repeated until the aqueous phase became neutral. After washing, the polymer was precipitated by dropwise addition to methanol with stirring. Furthermore, the polymer was vacuum-dried to obtain the compound of the present invention.
[0028]
Hereinafter, the configuration of the electrophotographic photoreceptor of the present invention will be described.
[0029]
The electrophotographic photoreceptor of the present invention is a single layer type in which the photosensitive layer contains the charge transport material and the charge generation material in the same layer, the charge transport layer containing the charge transport material, and the charge generation layer containing the charge generation material The present invention is applied to any of the laminated types having the following.
[0030]
The binder resin and the solvent for forming the photosensitive layer of the present invention are not limited in the photosensitive layer to be used, and dissolve and disperse a material (for example, a charge generation material or a charge transport material) for forming a photosensitive member on the binder resin. In a layer to be used, for example, a multilayer type photoreceptor, it can be a charge generation layer, a charge transport layer and a protective layer, and can also be a single layer type.
[0031]
As the charge generating material in the present invention, those generally known can be used, such as selenium-tellurium, pyrylium, metal phthalocyanine, metal-free phthalocyanine, anthrone, dibenzpyrenequinone, trisazo, cyanine, disazo, Examples of the pigment include monoazo, indigo, and quinacdrine. These pigments were well dispersed by using a homogenizer, ultrasonic dispersion, ball mill, vibration mill, sand mill attritor, roll mill, liquid collision type high speed disperser, etc. together with binder resin and solvent having a weight of 0.3 to 4 times. A dispersion is obtained. In the case of a multilayer type photoreceptor, a charge generation layer is obtained by applying this solution and drying. The film thickness is preferably 5 μm or less, and particularly preferably 0.1 to 2 μm.
[0032]
As the charge transport material, those usually used can be used, and examples thereof include triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, triallylmethane compounds, thiazole compounds, and the like. . These compounds are dissolved in a solvent together with a binder resin to form a solution. In the case of a multilayer photoreceptor, a charge transport layer is obtained by applying this solution and drying. The film thickness is preferably 5 to 40 μm, and particularly preferably 15 to 30 μm.
[0033]
When the photosensitive layer is a single layer type, it can be formed by applying a dissolved solution in which the charge generating material or charge transporting material as described above is dispersed and dissolved in the binder resin as described above and drying. . The film thickness is preferably 5 to 40 μm, and particularly preferably 15 to 30 μm.
[0034]
Moreover, as a protective layer, it can obtain by apply | coating and drying the solution which melt | dissolved the binder resin mentioned above in the solvent. If necessary, a material for an electrophotographic photosensitive member, a conductive material for controlling a resistance value, a lubricant for imparting lubricity, and the like can be added. In a photoreceptor without a protective layer, an antioxidant or a lubricant can be used for the surface layer as necessary.
[0035]
In the present invention, an intermediate layer having an adhesion function and a charge barrier function can be provided between the support and the photosensitive layer, or between the conductive layer and the photosensitive layer, if necessary. 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 a solvent, applied and dried. The thickness of the intermediate layer is preferably 0.05 to 5 μm, and particularly preferably 0.2 to 1 μm. The ratio (weight ratio) between the solvent and the material of the intermediate layer is preferably 1 / 0.5 to 1/2.
[0036]
There is no limitation on the method for applying these photoconductors, and any of the commonly known means such as dip coating, spray coating, and bar coating can be used.
[0037]
FIG. 1 shows a schematic configuration of an electrophotographic apparatus using a process cartridge having the electrophotographic photosensitive member of the present invention.
[0038]
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 at a predetermined positive or negative potential on its peripheral surface by the primary charging unit 3 and then output from an exposure unit (not shown) such as slit exposure or laser beam scanning exposure. The exposure light 4 that is emphasized and modulated corresponding to the time-series electrical digital image signal of the target image information is received. In this way, electrostatic latent images corresponding to target image information are sequentially formed on the peripheral surface of the photoreceptor 1.
[0039]
The formed electrostatic latent image is then developed with toner by the developing unit 5, and the developed toner image is synchronized with the rotation of the photoconductor 1 between the photoconductor 1 and the transfer unit 6 from a paper supply unit (not shown). The toner image formed and supported on the surface of the photosensitive member 1 is sequentially transferred by the transfer means 6 onto the transfer material 7 taken out and fed.
[0040]
The transfer material 7 that has received the transfer of the toner image 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 an image formed product (print, copy).
[0041]
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.
[0042]
In the present invention, a plurality of components such as the electrophotographic photosensitive member 1, the primary charging unit 3, the developing unit 5 and the cleaning unit 9 described above 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.
[0043]
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. Light emitted by driving the LED array, driving the liquid crystal shutter array, or the like.
[0044]
The electrophotographic photosensitive member of the present invention can be used not only for electrophotographic copying machines but also widely for electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.
[0045]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “parts” represents parts by weight.
[0046]
Example 1
A coating composed of the following materials was applied on a 30 mmφ × 357 mm aluminum cylinder by a dip coating method and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm.
[0047]
Conductive pigment: SnO ₂ coated 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 2/8 20 parts ]
Next, a solution obtained by dissolving 3 parts of N-methoxymethylated nylon and 3 parts of copolymer nylon in a mixed solvent of 65 parts of methanol / 30 parts of n-butanol is applied onto this conductive layer by a dip coating method and dried. As a result, an intermediate layer having a thickness of 0.5 μm was formed.
[0049]
Next, 9.0 ° of black grayed angle in CuKα characteristic X-ray diffraction (2 [Theta] ± 0.2 °), 14.2 °, 23.9 °, oxytitanium phthalocyanine 4 parts having strong peaks at 27.1 ° , 2 parts of polyvinyl butyral (trade name: ESREC BM2, manufactured by Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone were dispersed in a sand mill apparatus using 1 mmφ glass beads for 4 hours, and then 100 parts of ethyl acetate was added to prepare a dispersion for charge generation layer. Prepared. This dispersion was applied onto the intermediate layer by a dip coating method and dried to form a charge generation layer having a thickness of 0.1 μm.
[0050]
Next, 7 parts of an amine compound having the following structural formula:
[Chemical formula 5 ]
[0052]
1 part of an amine compound of the following structural formula
[Chemical 6 ]
[0054]
As a binder resin, 10 parts of the compound (Mw = 75000) represented by the structural unit example (1-1) was dissolved in a mixed solvent of 50 parts monochlorobenzene / 30 parts dichloromethane to obtain a coating solution for a charge transport layer. The coating solution was applied by dip coating and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 27 μm.
[0055]
Next, evaluation will be described. As the apparatus, a Canon Co., Ltd. copier GP210 (contact charging method) was used. First, the initial potential was measured. The dark part potential Vd = −700V and the bright part potential Vl = −200V. The A4 size plain paper is performed 10,000 sheets copying in intermittent mode once you stop every single copy, was then measured amount of wear of the photoconductor thickness.
[0056]
Further, sebum was attached to the surface of a new photoreceptor and left for 72 hours, and the presence or absence of solvent cracks was observed by microscopic observation (100 times). Observe 10 observation points. “○” indicates that there are no cracks at all observation points. “△” indicates that there is only one observation point. “△” indicates that there are 2 or more observation points. The occurrences were marked “x”.
[0057]
(Example 2 )
A photoconductor was prepared in the same manner as in Example 1 except that a copolymer (Mw = 80000) of structural unit examples (1-1) / (5-1) = 50/50 was used as the binder resin for the charge transport layer. did.
[0058]
(Example 3 )
A photoconductor was prepared in the same manner as in Example 1 except that a copolymer (Mw = 80000) of structural unit examples (1-1) / (5-2) = 50/50 was used as the binder resin for the charge transport layer. did.
[0059]
(Example 4 )
5 parts of copolymer (Mw = 80000) of constituent unit example (1-1) / (5-2) = 70/30 as binder resin for charge transport layer, polyarylate of constituent unit example (5-2) A photoconductor was prepared in the same manner as in Example 1 except that the resin was changed to 5 parts.
[0060]
(Example 5 )
As a binder resin for the charge transport layer, 5 parts of a copolymer (Mw = 80000) of structural unit examples (1-1) / (5-2) = 30/70 are represented by structural unit examples (6-5). A photoconductor was prepared in the same manner as in Example 1 except that 5 parts of polycarbonate Z (Iupilon Z200 manufactured by Mitsubishi Gas Chemical) was used.
[0061]
(Comparative Example 1)
A photoconductor was prepared in the same manner as in Example 1 except that the polyarylate (Mw = 70000) shown in the structural unit example (5-1) was used as the binder resin for the charge transport layer.
[0062]
(Comparative Example 2)
A photoconductor was prepared in the same manner as in Example 1 except that polyarylate (Mw = 70000) represented by the following structural formula (7) was used as the binder resin for the charge transport layer.
[0063]
[Chemical 7 ]
[0064]
The results are shown in Table 4 .
[0065]
[Table 4 ]
[0066]
As shown in Table 4 , the photoreceptor of the present invention exhibited mechanical durability (wear resistance) and excellent solvent crack resistance. Further, even when the unsubstituted fluorene type polymer shown in Comparative Example 2 was compared with the substituted type of the present invention, it was superior in wear resistance and solvent crack resistance. That is, by introducing a substituent, it is presumed that the steric arrangement between the polymer chain and the polymer is moderately limited to an appropriate arrangement. Furthermore, the arrangement increases the affinity with the organic photoconductive material in the polymer, improves the wear resistance as a photosensitive layer, and reduces the occurrence of stress in the entanglement between the polymer chain and the polymer that induces solvent cracks. It is estimated that The superiority of the polyarylate resin shown in the present invention was demonstrated.
[0067]
【The invention's effect】
According to the present invention, by using a polyarylate resin having a specific fluorene structure, an electrophotographic photoreceptor having improved wear resistance and solvent crack resistance in repeated use, and a process having this electrophotographic photoreceptor It has become possible to provide a cartridge and an electrophotographic apparatus.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus using a process cartridge having the electrophotographic photosensitive member of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoconductor 2 axis | shaft 3 Charging means 4 Exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Rail

Claims (5)

An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a polyarylate resin having at least a structural unit represented by the following general formula (1) :
. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer contains at least a polyarylate copolymer of a structural unit represented by the following general formula ( 2 ):
(In the formula, R ^{15 to} R ¹⁸ represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group, an alkoxy group having 1 to 5 carbon atoms, or a halogen atom. X ² represents a single bond, —CR ^19. R ^20- represents R ¹⁹ and R ²⁰ represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkylidene group formed by combining R ¹⁹ and R ²⁰ , and s and t represent positive integers. ). The photosensitive layer contains a polyarylate copolymer having a copolymer of a structural unit represented by the general formula (1) and a structural unit represented by the following general formula (5) as a structural unit. The electrophotographic photosensitive member according to claim 1:
(Wherein R ^{21 to} R ²⁴ represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group, an alkoxy group having 1 to 5 carbon atoms, or a halogen atom. X ³ represents a single bond, —CR ^25. R ^26- represents R ²⁵ and R ²⁶ represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkylidene group formed by the combination of R ²⁵ and R ²⁶ ). An electrophotographic photosensitive member according to any one of claims 1 to 3 charging means for charging the electrophotographic photosensitive member, a developing means for developing an electrophotographic photosensitive member which is formed of an electrostatic latent image with toner, and transfer A process cartridge which integrally supports at least one means selected from the group consisting of cleaning means for collecting toner remaining on the photoreceptor after the process and is detachable from the main body of the electrophotographic apparatus . The electrophotographic photosensitive member according to any one of claims 1 to 3 charging means for charging the electrophotographic photoreceptor, exposing means for forming an electrostatic latent image was exposed to the charged electrophotographic photosensitive member, electrostatic An electrophotographic apparatus comprising: a developing unit that develops an electrophotographic photosensitive member having a latent image formed thereon with toner; and a transfer unit that transfers a toner image on a transfer material.