JP2005164776A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increase of frictional force between a photoreceptor and a cleaning blade, which is conductive to curl of the cleaning blade, in an image forming method using the photoreceptor having high durability. <P>SOLUTION: In the image forming method in which the electrophotographic photoreceptor having a universal hardness HU of 150-220 N/mm<SP>2</SP>when indented under a maximum load of 6 mN and having an elastic deformation ratio of 44-65% is charged by contact charge, when the length of one side of a charging means outside a developable longitudinal width is represented by L (mm) and discharge current per unit length of a surface of the photoreceptor by charge at the outside of the developable longitudinal width by I (μA/mm), expression: 0.5≤LI×L≤0.75 is satisfied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus. More specifically, an electrophotographic photosensitive member is used to charge the photosensitive member, a charging step for charging the photosensitive member, an information writing step for forming an electrostatic latent image on the charging surface of the photosensitive member, and a developer carried on the developer carrier. A development process for developing the electrostatic latent image as a toner image, a transfer process for transferring the toner image on the photosensitive member to the transfer member side by applying an electric field between the photosensitive member and the transfer member, and after the toner image transfer The present invention relates to an image forming method including a cleaning step of collecting residual toner particles on the surface of a photoreceptor.

  In an image forming method used for an electrophotographic apparatus, an electrostatic recording apparatus, and the like, various methods are known as a method for forming a latent image on a photosensitive member such as an electrophotographic photosensitive member or an electrostatic recording dielectric.

  For example, in electrophotography, an electrical latent image is formed by uniformly charging a photoconductor using a photoconductive material as a latent photoconductor to the required polarity and potential, and then performing image pattern exposure. In general, the toner is developed and visualized, and this is transferred and fixed to a transfer medium such as paper.

  Conventionally, in this type of image forming method, by providing a protective layer on the outermost surface layer, an electrophotographic photosensitive member that has excellent durability against wear and scratches and can maintain high quality image quality. A device using a body has been proposed (see, for example, Patent Document 1 and Patent Document 2).

  In particular, a photoreceptor having a protective layer made of a curable resin can increase elasticity while maintaining a large HU (Universal Hardness Value). This type of photoreceptor having both rigidity and elasticity is strong against abrasion and has high durability. In such an image forming method using a photoconductor, since it is resistant to rubbing with a cleaning blade or the like, the durable life and potential change of the photoconductor can be suppressed, and stable image output performance can be obtained over a long period of time.

  On the other hand, in an electrophotographic image forming method, it is known that discharge products due to various charges such as NOx, SOx, ozone, and the like are generated depending on the charging energy when the photosensitive member is charged. In the case of corona charging and roller contact charging, which are the main methods of electrification in electrophotography, if the charging energy is insufficient, charging failure tends to occur, resulting in halftone unevenness and sandy fog in a low humidity environment, which affects the image quality. Therefore, it is difficult to avoid the generation of a certain amount of discharge products.

  These discharge products adhere to the photoreceptor and cause the slippage of the photoreceptor surface to deteriorate. For this reason, a frictional force is increased between the cleaning blade in contact with the photosensitive member and the photosensitive member, causing the photosensitive member driving torque to be increased, drooping, and blade chatter (vibration), leading to poor cleaning.

  In particular, when using a highly durable photoreceptor that is difficult to scrape as described above, the surface of the photoreceptor is difficult to be refreshed, and surface chargeable organisms are likely to adhere and accumulate, so that the initial slipperiness is good. However, cleaning may fail due to repeated image formation. In particular, even when the plastic deformation is small, the total deformation amount is large, that is, in the case of a highly durable photoreceptor having a rubber behavior, the friction with the cleaning blade is particularly large. As a result, blades and drums are easily broken, and the durability life is shortened in that respect.

  Furthermore, in a high temperature environment, the blade hardness is soft due to the temperature characteristics of the cleaning blade, and serious problems such as turning over the cleaning blade are likely to occur.

  Further, when the charging method is contact charging, since the discharge occurs in the vicinity of the surface of the photosensitive member, the surface deterioration is remarkable, and it is more severe against turning.

On the other hand, in the image forming apparatus according to the present invention, an external additive having a function of a lubricant is included in the developer, and a part of the developer can function as a lubricant. For this reason, a part of the developer developed on the photosensitive member from the developing means and remaining on the photosensitive member as a transfer residual toner, particularly when an external additive acts as a lubricant, is applied from the developing device to the photosensitive member. Lubricant is sent to the cleaning device to improve the sliding property between the cleaning blade and the photosensitive member, and to help clean the transfer residual toner. For this reason, since a new lubricant is always present on the surface of the photoreceptor, it is possible to suppress the destruction of the cleaning blade or the drum due to the deterioration of the slipperiness at the cleaning portion.
Japanese Patent Laid-Open No. 05-181299 JP 2002-082469 A

  However, there is a portion where it is difficult to supply the lubricant by development while being charged by the charging roller.

  When the cleaning blade reaches the shortest part of the blade, the toner remains on the photoconductor. Therefore, it is necessary to prevent the toner from reaching the shortest part, and developer is supplied from the developing unit to the photoconductor. It must be set long enough with a margin than the part to be. That is, the end portion of the cleaning blade intentionally requires a portion where the toner hardly exists on the photoreceptor.

  Furthermore, if the length of the charging roller is shorter than or equal to that of the developing roller, the toner is developed in an uncharged portion, resulting in an increase in toner consumption and increased toner scattering. Therefore, in general, the length of the charging roller is set longer than the length of the developing roller.

  As a result, there is a need for a portion that is charged by the charging means and has a cleaning blade, even though the developer is unlikely to be sufficiently supplied to the photoreceptor.

  The portion where it is difficult to supply the lubricant by development while being charged by the charging roller made in this way cannot increase the frictional force between the blade and the surface of the photosensitive member due to charging, and as a result the cleaning blade turns over. Vibration of the blade and the photosensitive member may occur.

  Accordingly, an object of the present invention is to eliminate the problem of turning over the cleaning blade of the contact charging type image forming method using the conventional highly durable photoconductor having high hardness and high elasticity as described above, and the structure is simple. Another object of the present invention is to provide an image forming method with high image quality, high durability and long life in addition to easy maintenance.

  The present invention provides the following image forming method for achieving the above object.

(1) A charging process in which an image carrier is charged in contact with the surface of the image carrier, a latent image forming process in which an electrostatic latent image is formed on a charging surface of the image carrier, and a toner carried on a developing roller An image forming method comprising: a developing step of developing the electrostatic latent image as a toner image by reversal development; a transfer step of transferring the toner image to a recording medium; and a cleaning step of cleaning the transfer residual toner with an elastic blade. The surface of the photosensitive layer was subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of 25 ° C. and 50% humidity, and the HU (universal hardness value) when pressed at a maximum load of 6 mN was 150 N / mm ^2. above 220 N / mm ² or less, and a electrophotographic photosensitive member elastic deformation rate is less than or equal to 65% or more 44%, is the charging means have been applied AC voltage, and from the developable longitudinal width The length of one side outside the developable longitudinal width of the charging means is L (mm), and the discharge current per unit length by charging outside the developable longitudinal width of the photoreceptor surface is When I (μA / mm), the following formula 0.5 ≦ L
I x L ≤ 0.75
An image forming method characterized by satisfying

  (2) The image formation according to (1), wherein the absolute value of the surface potential of the photoconductor charged by the charging means outside the developable longitudinal width of the surface of the photoconductor is larger than the absolute value of the potential of the developing bias. Method.

(3) The discharge current I (μA / mm) per unit length due to charging outside the developable longitudinal width of the surface of the photoreceptor is expressed by the following formula: 0.01 ≦ I
(2) The image forming method characterized by satisfying the above.

  (4) The discharge current due to charging within the developable longitudinal width of the surface of the photoreceptor is 0.1 (μA / mm) or more and 2.0 (μA / mm) or less (1) to ( 3) The image forming method.

  (5) The image forming method according to (4), wherein the resistance of the charging means outside the developable longitudinal width is higher than the resistance of the portion within the developable longitudinal width.

  (6) The image forming method according to (5), wherein a portion outside the developable longitudinal width of the charging unit is coated with a material having a higher volume resistance than the surface of the charging roller body and the photoreceptor.

  (7) The photoreceptor has a protective layer, and the protective layer is a group selected from the group consisting of a curable phenol resin and a hydroxyphenyl group, a hydroxyalkoxy group, or a hydroxyphenyl group which may have a substituent. The image forming method according to claim 1, further comprising a charge transport material having at least one of the following.

As described above, according to the present invention, the HU (universal hardness value) when pushed in with a maximum load of 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and the elastic deformation rate is 44% or more and 65 %, The absolute value of the potential on the surface of the photoreceptor is higher than the absolute value of the potential of the developing roller outside the developable longitudinal width. The length of one side outside the developable longitudinal width of the charging means is L (mm), and the discharge current per unit length by charging outside the developable longitudinal width of the surface of the photoreceptor is I (μA / mm). When the following formula 0.5 ≦ L
I x L ≤ 0.75
By setting the charging conditions so as to satisfy the above conditions, the toner cleaning blade is stabilized and good cleaning is performed while preventing toner scattering at the edge of the developing device, and a long-life, high-quality image is formed. Can be done.

<Image forming process>
FIG. 1 shows an example of an image forming apparatus according to the present invention. This figure is a longitudinal sectional view showing a schematic configuration of the laser beam printer. The printer shown in the figure includes a drum-type electrophotographic photosensitive member 101 as a photosensitive member. The photosensitive member 101 is rotationally driven in the direction of an arrow by a driving unit (not shown). Around the photosensitive member 101, a charging roller 102, which is a primary charging unit, an exposure unit 103, a developing unit (developing unit) 104, and a transfer charging unit (transfer unit) 105 are arranged almost sequentially along the rotation direction. ing. Further, a fixing device 106 is disposed on the downstream side (left side in the figure) of the transfer charger 105 in the conveyance direction (arrow direction) of the transfer material 111. The surface of the photoreceptor 101 is uniformly charged by the primary charger 102. Next, image exposure is performed by the laser beam emitted from the exposure means 103, the electric charge of the laser beam irradiated portion is removed, and an electrostatic latent image is formed. The electrostatic latent image on the photoconductor 101 is developed with the charged toner of the developing device 104. The developed toner image on the photoreceptor 101 is transferred by the transfer charger 105 to the transfer material 111 conveyed in the direction of the arrow. After the toner image is transferred, the transfer material 111 is conveyed to a fixing device 106 where the toner image is fixed on the surface by being heated and pressurized. The untransferred toner remaining on the photosensitive member after the transfer is collected and removed by an elastic cleaning blade in contact with the counter of the drum of the cleaning device 107.

[Cleaning process]
The cleaning device 107 is means for collecting and cleaning the transfer residual toner remaining on the photoconductor after the toner transfer. In the present invention, the toner on the photosensitive member is cleaned by bringing an elastic blade made of polyurethane rubber into contact with the rotation of the photosensitive member with a counter as shown in FIG. The toner and the lubricant scraped off by the cleaning blade are received by the scooping sheet, and sent to the waste toner box by a toner feed blade or a screw.

[Charging process]
The contact charging member of the present invention is not particularly selected as long as it is a member that makes contact with a photosensitive member such as a roller, a brush, or a plate type, and among them, the roller type charging member has an area used for charging. Since it can ensure widely, it is more preferable from the viewpoint of contamination of the charging member surface.

  A member 102 in FIG. 1 is a conductive elastic roller (charging roller) as a flexible contact charging member disposed in contact with the photosensitive member 101 with a predetermined pressing force. Further, FIG. 2 is a schematic diagram showing the length relationship between the charging roller and each module. Here, the length a is “within the developable longitudinal width” where toner can be supplied from the developing roller to the photoreceptor, b is “charge width” (charge roller length), and c is “outside developable longitudinal width” in the charge width. is there. The length L (mm) on one side outside the developable longitudinal width of the charging means of the present invention refers to the length of one side of the c portion.

  It is desirable that the length of the charging roller outside the developable longitudinal width is longer than the developable longitudinal width, and the photoreceptor is charged even outside the developable longitudinal width. In particular, in the reverse development, since the absolute value of the potential of the uncharged portion of the photoreceptor is smaller than that of the developing roller, the toner tends to adhere to the potential. Even if it is outside the developable longitudinal width, if there is an uncharged place on the photoconductor near the developable longitudinal width, the toner easily moves from the developing means to the photoconductor, and therefore the developing means. Toner scattering occurs at the edges. Further, even if the length of the charging roller outside the developable longitudinal width is sufficiently secured, if the charging is insufficient, the toner is likely to adhere and the scattering tends to occur.

It is important that the charging roller 102 as a contact charging member functions as an electrode. That is, it is necessary to provide sufficient elasticity to obtain a sufficient contact state with the member to be charged and at the same time to have a sufficiently low resistance to charge the moving member to be charged. On the other hand, it is necessary to prevent voltage leakage when a low-voltage defect site such as a pinhole is present in the member to be charged. When an electrophotographic photoreceptor is used as the member to be charged, a resistance of 10 ⁴ to 10 ⁷ Ω is desirable in order to obtain sufficient chargeability and leakage resistance. If the hardness of the charging roller is too low, the shape is not stable and the contact property with the member to be charged is deteriorated. If the hardness is too high, the charging nip A cannot be secured between the member and the member to be charged. Since the micro-contact property to the surface of the charged body is deteriorated, the preferred range of Asker C hardness is 25 to 50 degrees. The material of the charging roller 102 is not limited to the elastic foam, but the material of the elastic body may be EPDM, urethane, NBR, silicone rubber, carbon black, metal oxide, etc. Examples thereof include a rubber material in which a conductive material is dispersed and a foamed material of these materials. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance.

  In the present invention, the charging is performed by setting a DC voltage value so that the photosensitive member has a desired potential and applying it, and superimposing an alternating voltage on the surface of the photosensitive member as an energy for charging. For example, when a potential of −600 V is applied to the surface of the photoreceptor, a −600 V DC voltage is applied, and an AC voltage of about 0.1 to 3.0 kV is superimposed depending on the charging means and the resistance of the photoreceptor. To do.

  In the contact charging in the present invention, it is necessary to cause some discharge between the charging member and the photosensitive member in order to ensure sufficient chargeability by applying the charge. In particular, when charging is performed by applying an AC voltage having excellent charging uniformity, stabilization of the potential by discharging is indispensable. If this discharge is insufficient, charging unevenness will occur and unevenness will occur in halftone, or a charging failure that will cause black spots on the white background of the image, such as sandy fog, will occur. The image quality is greatly changed and the influence on the image is likely to occur. When the image forming layer is formed by charging the photoconductor by applying an AC voltage superimposed on the DC voltage, the discharge current due to charging within the developable longitudinal width is preferably 0.1 μA / mm or more.

  However, even if the discharge amount is too large, an increase in abrasion due to deterioration of the surface of the photoreceptor, a cleaning failure due to a decrease in slipperiness, and the like may occur. When the image forming layer is formed by charging the photoconductor by applying an AC voltage superimposed on a DC voltage, the discharge current due to charging within the developable longitudinal width is desirably 2.0 μA / mm or less.

<Measurement method of charge / discharge current amount>
Subsequently, a method for measuring a discharge current in primary charging in the present invention will be described.

  The measured value in the practical form is obtained as follows. A measurement schematic circuit diagram is shown in FIG. First, a current is applied to the charging roller by applying a voltage from an external power source. Since the current flowing from the charging roller flows to the ground of the photosensitive member, an ammeter is installed at this ground portion to measure the amount of current actually flowing. This current amount is measured by changing the AC voltage, and the result is plotted with the current amount on the vertical axis and the applied voltage on the horizontal axis as shown in FIG.

  The discharge current is obtained by measuring the amount of current that changes when the voltage applied to the charging roller is changed as shown in FIG. In a state where normal discharge does not occur, the current increases linearly with respect to the applied voltage. On the other hand, when the voltage exceeds a certain applied voltage, the current starts to increase off the straight line. The amount of current that has increased off this straight line is the discharge current value in the present invention, and the portion A in FIG. 4 is the discharge current value. Since the discharge current of the portion A is the discharge current of the entire charging roller, the discharge current per unit length in the longitudinal direction of the charging roller is obtained by dividing the measured discharge current amount by the length of the charging roller. It is done.

Therefore, when the resistance value between the charging roller and the photosensitive member is the same inside and outside the developable longitudinal width, the measured charging roller for the discharge current I (μA / mm) per unit outside the developable longitudinal width. If the overall discharge current is I _a (μA) and the length of the charging roller is L _b (mm), the following equation (1) is established.

I = I _a / L _b (1)
When the resistance value between the charging roller and the photoconductor is different inside and outside the developable longitudinal width, it is desirable to actually measure the discharge current per unit length. For example, as shown in FIG. 5, the charging roller may be prepared by leaving only the portion outside the developable longitudinal width of the charging roller and removing the developable longitudinal width portion. At this time, when the charging roller is pressurized with a spring or the like, the spring pressure is adjusted in order to match the pressure state with the original charging roller. For example, a weak spring obtained by dividing the spring constant by the length ratio is produced and used. If the discharge current value actually measured at this time is I _a ′ (μA) and the length outside the developable longitudinal width of the charging roller is L ₂ (mm), the discharge current per unit outside the developable longitudinal width The following equation (2) holds for I (μA / mm).
I = I _a '/ L ₂ (2)
<Photoreceptor manufacturing method>
The surface used in the present invention is subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of 25 ° C. and 50% humidity, and the HU (Universal Hardness Value) when pressed at a maximum load of 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and is described in detail, including a manufacturing method for an electrophotographic photosensitive member having high durability of the elastic deformation ratio is less than 65% 44%.

  The electrophotographic photoreceptor of the present invention preferably has mainly a laminated structure. In the electrophotographic photoreceptor of the present invention, a charge generation layer and a charge transport layer are provided in this order on a support, and a protective layer is provided on the outermost surface. Further, an undercoat layer for the purpose of preventing interference fringes or the like may be provided between the support and the charge generation layer.

  The support itself can be conductive, for example, aluminum, aluminum alloy, or stainless steel. In addition, aluminum, aluminum alloy, or indium oxide-tin oxide alloy is formed by vacuum deposition. The support having the layer formed, the plastic, the conductive fine particles (for example, carbon black, tin oxide, titanium oxide, silver particles, etc.) and the appropriate support resin impregnated into the plastic or paper, the conductive binder A plastic having a resin can be used.

  Further, a binder layer (adhesive layer) having a barrier function and an adhesive function can be provided between the support and the photosensitive layer. The binder layer is used to improve the adhesion of the photosensitive layer, improve the coatability, protect the support, cover defects on the support, improve the charge injection from the support, and protect against electrical breakdown of the photosensitive layer. It is formed. The binder layer can be formed of casein, polyvinyl alcohol, ethyl cellulose, ethylene-acrylic acid copolymer, polyamide, modified polyamide, polyurethane, gelatin, aluminum oxide, or the like. The film thickness of the binder layer is preferably 5 μm or less, and particularly preferably 0.1 to 3 μm.

  Examples of the charge generating substance used in the present invention include (1) azo pigments such as monoazo, disazo and trisazo, (2) phthalocyanine pigments such as metal phthalocyanine and nonmetal phthalocyanine, and (3) indigo compounds such as indigo and thioindigo. Pigments, (4) perylene pigments such as perylene anhydride and perylene imide, (5) polycyclic quinone pigments such as anthraquinone and pyrenequinone, (6) squarylium dyes, (7) pyrylium salts and thiapyrylium salts ( 8) Triphenylmethane dyes, (9) inorganic substances such as selenium, selenium-tellurium and amorphous silicon, (10) quinacridone pigments, (11) azulenium salt pigments, (12) cyanine dyes, (13) xanthene dyes, 14) Quinone imine dye, (15) Su Lil dyes, and (16) cadmium sulfide and (17) zinc oxide.

  Examples of the binder resin used for the charge generation layer include polycarbonate resin, polyester resin, polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, vinyl acetate resin, phenol resin, Examples thereof include, but are not limited to, silicone resins, polysulfone resins, styrene-butadiene copolymer resins, alkyd resins, epoxy resins, urea resins, and vinyl chloride-vinyl acetate copolymer resins. These can be used alone or as a mixture or as a copolymer polymer.

  The solvent used for the charge generation layer coating is selected from the solubility and dispersion stability of the resin used and the charge generation material, but examples of the organic solvent include alcohols, sulfoxides, ketones, ethers, esters, Aliphatic halogenated hydrocarbons or aromatic compounds can be used.

  The charge generation layer is well dispersed by a method such as a homogenizer, ultrasonic wave, ball mill, sand mill, attritor or roll mill, together with a binder resin and a solvent in an amount of 0.3 to 4 times the mass of the charge generation material, It is formed by coating and drying. The thickness is preferably 5 μm or less, and particularly preferably in the range of 0.01 to 1 μm.

  In addition, various sensitizers, antioxidants, ultraviolet absorbers, plasticizers, and known charge generating substances can be added to the charge generation layer as necessary.

  The charge transport materials used include various triarylamine compounds, various hydrazone compounds, various styryl compounds, various stilbene compounds, various pyrazoline compounds, various oxazole compounds, various thiazole compounds, and various triarylmethane compounds. Compound etc. are mentioned.

  Examples of the binder resin used for forming the charge transport layer include acrylic resin, styrene resin, polyester, polycarbonate resin, polyarylate, polysulfone, polyphenylene oxide, epoxy resin, polyurethane resin, alkyd resin, and unsaturated resin. The resin chosen is preferred. Particularly preferred resins include polymethyl methacrylate, polystyrene, styrene-acrylonitrile copolymer, polycarbonate resin and diallyl phthalate resin.

  The charge transport layer is generally formed by dissolving the charge transport material and the binder resin in a solvent and applying them. The mixing ratio (mass ratio) of the charge transport material and the binder resin is about 2: 1 to 1: 2. Solvents include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, chlorinated hydrocarbons such as chlorobenzene, chloroform and carbon tetrachloride, tetrahydrofuran, Ethers such as dioxane are used. When this solution is applied, for example, a coating method such as a dip coating method, a spray coating method and a spinner coating method can be used, and drying is preferably 10 ° C to 200 ° C, more preferably 20 ° C to 150 ° C. The temperature is in the range of 5 minutes to 5 hours, and more preferably 10 minutes to 2 hours.

  The charge transport layer is electrically connected to the above-described charge generation layer, receives charge carriers injected from the charge generation layer in the presence of an electric field, and transports these charge carriers to the interface with the protective layer. It has a function. Since this charge transport layer has a limit to transport charge carriers, the film thickness cannot be increased more than necessary, but it is preferably 5 to 40 μm, and particularly preferably 7 to 30 μm.

  Furthermore, an antioxidant, an ultraviolet absorber, a plasticizer, and a known charge transport material can be added to the charge transport layer as necessary.

Further, in the present invention, the protective layer is applied and cured on the charge transport layer to form a film, and a hardness test is performed using a Vickers square pyramid diamond indenter in an environment having a surface of 25 ° C. and a humidity of 50%. A photoreceptor having a HU (Universal Hardness Value) of 150 N / mm ² or more and 220 N / mm ² or less when pushed in with a maximum load of 6 mN and an elastic deformation rate of 44% or more and 65% or less is completed.

<Protective formation method 1>
As a protective layer for an electrophotographic photoreceptor satisfying the above conditions, a compound obtained by polymerizing a hole transporting compound having two or more chain polymerizable functional groups in the same molecule as shown in the following (Chemical Formula 1) is contained. There is a protective layer.

式中、Ａは正孔輸送性基を示す。Ｐ¹及びＰ²は連鎖重合性官能基を示す。Ｐ¹とＰ²は同一でも異なってもよい。Ｚは置換基を有してもよい有機残基を示す。ａ、ｂ及びｄは０又は１以上の整数を示し、ａ＋ｂ×ｄは2以上の整数を示す。また、ａが２以上の場合Ｐ¹は同一でも異なってもよく、ｄが２以上の場合Ｐ²は同一でも異なってもよく、またｂが２以上の場合、Ｚ及びＰ2は同一でも異なってもよい。

In the formula, A represents a hole transporting group. P ¹ and P ^{2 each} represent a chain polymerizable functional group. P ¹ and P ² may be the same or different. Z represents an organic residue which may have a substituent. a, b and d represent 0 or an integer of 1 or more, and a + b × d represents an integer of 2 or more. When a is 2 or more, P ¹ may be the same or different. When d is 2 or more, P ² may be the same or different. When b is 2 or more, Z and P 2 are the same or different. Also good.

  By polymerizing a hole transporting compound having two or more chain-polymerizable functional groups in the same molecule, the compound having a hole transporting ability in the protective layer has at least two or more crosslinking points. It is incorporated into the dimensional cross-linked structure via a covalent bond. The hole transporting compound can be either polymerized alone or mixed with a compound having another chain polymerizable group, and the kind / ratio is arbitrary. As used herein, the compound having another chain polymerizable group includes any monomer or oligomer / polymer having a chain polymerizable group. When the functional group of the hole transporting compound and the functional group of the other chain polymerizable compound are the same group or a group that can be polymerized with each other, they both take a copolymerized three-dimensional crosslinked structure via a covalent bond. Is possible. When both functional groups are functional groups that do not polymerize with each other, the photosensitive layer is a mixture of at least two or more three-dimensional cured products or other chain-polymerizable compound monomers in the three-dimensional cured product as a main component. Although it is comprised as the thing containing the hardened | cured material, it is also possible to form an IPN (Inter Penetrating Network), ie, an interpenetrating network structure, by controlling the compounding ratio / film forming method well.

  In the present invention, the protective layer contains at least one selected from the group consisting of fluorine atom-containing resin, carbon fluoride, and polyolefin resin as a lubricant, and preferred compounds include the following. However, it is not limited to these compounds.

  Preferred as the fluorine atom-containing resin is a polymer or copolymer resin of a compound selected from vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoropropylene, perfluoroalkyl vinyl ether, and Examples include resin fine particles.

Examples of the carbon fluoride include compounds represented by (CF) _n and (C ₂ F) _n .

  Preferred examples of the polyolefin resin include homopolymer resins such as polyethylene resin, polypropylene resin and polybutene resin, copolymer resins such as ethylene-propylene copolymer and ethylene-butene copolymer, and resin powder.

  These lubricants can be used alone or in combination of two or more at any ratio.

  The protective layer may contain a dispersant for the lubricant, a dispersion aid, other various additives, a surfactant, and the like.

  By containing at least one of fluorine atom-containing resin, carbon fluoride, and polyolefin resin as a lubricant in the protective layer, the surface slipperiness and water repellency of the photoreceptor can be improved, and charging during repeated use, Deterioration of transfer efficiency and slipperiness due to chemical deterioration of the surface layer due to development, transfer, etc., and further deterioration of electrical properties such as sensitivity reduction and potential reduction are prevented. Filming, fusing, and cleaning failure even during repeated use It is possible to suppress the occurrence of image defects such as image blur / flow. Particularly preferable results are obtained when the fluorine-containing resin is used.

  In the present invention, the proportion of the lubricant contained in the protective layer is preferably 1 to 70%, more preferably 5 to 50%, based on the total weight of the layer to be the surface layer. When the amount of the lubricant is more than 70%, the mechanical strength of the layer serving as the surface layer tends to be lowered, and when it is less than 1%, the water repellency and slipperiness of the layer serving as the surface layer may not be sufficient.

  In the present invention, a charge transport material can be contained in the protective layer containing the cured product of the hole transporting compound having the chain polymerizable group.

  The protective layer is generally formed by applying a solution containing the hole transporting compound and then carrying out a polymerization reaction, but a cured product obtained by reacting a solution containing the hole transporting compound in advance. After obtaining the above, it is possible to form a protective layer by dispersing or dissolving in the solvent again. As a method for applying these solutions, for example, a dip coating method, a spray coating method, a curtain coating method, a spin coating method, and the like are known, but the dip coating method is preferable from the viewpoint of efficiency / productivity.

  In the present invention, the hole transporting compound having a chain polymerizable group is preferably polymerized by radiation. The greatest advantage of polymerization by radiation is that a polymerization initiator is not required, which makes it possible to produce a very high-purity three-dimensional photosensitive layer and to ensure good electrophotographic characteristics. In addition, because it is a short and efficient polymerization reaction, it is highly productive, and because of its high radiation permeability, it inhibits curing when thick films and additives such as additives are present in the film. The influence of the is very small. However, depending on the type of the chain polymerizable group and the type of the central skeleton, the polymerization reaction may not easily proceed, and in this case, it is possible to add a polymerization initiator within a range that does not affect the reaction. The radiation used at this time is an electron beam and a gamma ray. In the case of electron beam irradiation, any type of accelerator such as a scanning type, an electro curtain type, a broad beam type, a pulse type, and a laminar type can be used. When irradiating with an electron beam, the irradiation conditions are very important in the photoreceptor of the present invention in order to develop electric characteristics and durability. In the present invention, the acceleration voltage is preferably 250 kV or less, and optimally 150 kV or less. The dose is preferably in the range of 10 kGy to 1000 kGy. When the accelerating voltage exceeds the above, the electron beam irradiation damage tends to increase on the characteristics of the photoreceptor. Further, when the dose is less than the above range, the curing tends to be insufficient, and when the dose is large, the photoreceptor characteristics are likely to be deteriorated.

<Protective layer formation method 2>
Furthermore, the electrophotographic photoreceptor protective layer that satisfies the conditions of the present invention is selected from the group consisting of a curable phenol resin and a hydroxyphenyl group that may have a hydroxyalkyl group, a hydroxyalkoxy group, or a substituent. There is a protective layer containing a charge transport material having at least one of the groups.

  The curable phenol resin, which is a binder resin used for the protective layer, is generally a resin obtained by a reaction between phenols and formaldehyde. There are two types of phenolic resins: a resole type obtained by reacting with phenol with an excess of formaldehyde and an alkali catalyst, and a novolak obtained by reacting with phenol and an excess of phenol with formaldehyde. Divided into molds.

  The resol type is also soluble in alcohol and ketone solvents, and is three-dimensionally crosslinked and polymerized by heating to form a cured product. On the other hand, the novolak type generally does not cure even when heated as it is, but forms a cured product by adding a formaldehyde source such as paraformaldehyde or hexamethylenetetramine and heating.

  In general, the resol type is used as a varnish for paints, adhesives, cast products and laminates, and the novolak type is mainly used as a molding material or a binder.

  The phenolic resin used as the binder resin in the present invention can be used in either the above-mentioned resol type or novolak type, but it is a resol type from the viewpoint of curing without adding a curing agent and operability as a paint. Is preferably used.

  In the present invention, these phenol resins can be used singly or in combination of two or more, and a resol type and a novolac type can also be mixed and used.

  For example, the protective layer can be formed using a polyhydroxymethylated bisphenol compound having two or more hydroxymethyl groups.

  The skeleton of the above-described bisphenol compound has a structure represented by the following formula (Chemical Formula 2).

式中、Ｘは単結合若しくは２価の結合基を、Ｒ_１及びＲ_２はそれぞれ置換基としてハロゲン原子、アリール基、ビニル基、置換基を有してもよいアルキル基、置換基を有してもよい環状アルキル基、置換基を有してもよいアルコキシ基、置換基を有してもよいアリール基又は置換基を有してもよい複素環基を表す。

In the formula, X represents a single bond or a divalent linking group, and R ₁ and R ₂ each have a halogen atom, an aryl group, a vinyl group, an alkyl group which may have a substituent, or a substituent as a substituent. A cyclic alkyl group which may be substituted, an alkoxy group which may have a substituent, an aryl group which may have a substituent or a heterocyclic group which may have a substituent;

  This polyhydroxymethyl bisphenol compound is subjected to heat treatment to form an ether bond or a further methylene bond by a condensation reaction between hydroxymethyl groups, or to form an ortho position between the hydroxymethyl group and the phenolic hydroxyl group. A methylene bond is formed by a condensation reaction with a hydrogen atom in the para position, and a three-dimensional cured film having a high crosslinking density can be obtained by the occurrence of these condensation reactions between various molecules. These condensation reactions are essentially reactions that are not hindered by moisture and oxygen in the air, and proceed sufficiently even in a system to which a charge transport material is added. The crosslinking reaction by heat treatment of the polyhydroxymethyl bisphenol compound has a feature that it is not necessary to add a curing catalyst generally used for thermosetting. Therefore, when the compound of the present invention is used as a surface layer of an electrophotographic photoreceptor, problems such as an increase in residual potential and a decrease in resistance of the outermost surface layer due to the residual curing catalyst do not occur.

  In addition, the polyhydroxymethyl bisphenol compound of the present invention does not require the addition of a curing catalyst, and the hydroxymethyl group itself is sufficiently stable against moisture unlike isocyanates and silicone resins. It is also excellent in sex.

  The protective layer of the present invention is formed by applying a coating obtained by dissolving or diluting a curable phenolic resin with a solvent or the like onto a photosensitive layer, and a polymerization reaction occurs after coating to form a cured layer. As a form of polymerization, it proceeds by addition and condensation reaction with heat, and after coating the protective layer, it is heated to cause a polymerization reaction to produce a polymer hardened layer.

  The charge transport material having a hydroxyalkyl group, a hydroxyalkoxy group or a hydroxyphenyl group which may have a substituent of the present invention is preferably a triphenylamine derivative.

  Examples of the substituent that the hydroxyphenyl group may have include halogen atoms such as fluorine, chlorine, bromine and iodine, and optionally substituted methyl, ethyl, propyl and butyl groups. Alkyl groups, alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group which may have a substituent, aryl groups such as phenyl group, naphthyl group, anthryl group and pyrenyl group which may have a substituent Or heterocyclic groups such as pyridyl group, thienyl group, furyl group and quinolyl group which may have a substituent.

  Among the charge transport materials used in the present invention, the charge transport material having a hydroxyalkyl group or a hydroxyalkoxy group is preferably a compound having a specific structure represented by the following (Chemical Formula 3).

式中、Ｒ₁₁、Ｒ₁₂およびＲ₁₃はそれぞれ炭素数１〜８の枝分かれしてもよい２価の炭化水素基を表し、α、βおよびγはそれぞれ置換基としてハロゲン原子、置換基を有してもよいアルキル基、置換基を有してもよいアルコキシ基、置換基を有してもよいアリール基、置換基を有してもよい複素環基を１つ以上有してもよいベンゼン環を表し、ａ１、ｂ１およびｃ１は１または０であり、ｍ１およびｎ１は０または１である。

In the formula, R ₁₁ , R ₁₂ and R ₁₃ each represent a divalent hydrocarbon group having 1 to 8 carbon atoms which may be branched, and α, β and γ each have a halogen atom or a substituent as a substituent. An optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group, and an optionally substituted heterocyclic group Represents a ring, a1, b1 and c1 are 1 or 0, and m1 and n1 are 0 or 1.

  In addition, the charge transport material used in the present invention is formed by uniformly dissolving or dispersing in a coating material for producing the protective layer and applying it. The mixing ratio of the charge transporting material and the curable phenolic resin of the present invention is preferably a mass ratio of charge transporting material / curable phenolic resin = 0.1 / 10-20 / 10, particularly 0.5 / 10-10. / 10 is preferred. If the amount of the charge transport material is too small relative to the curable phenol resin, the effect of lowering the residual potential is reduced, and if it is too much, the strength of the protective layer may be reduced.

The protective layer used in the present invention does not essentially transfer charges as a resistor, but an electrophotographic photosensitive member provided with a protective layer by transferring charges using a charge transport material contained in the protective layer. The sensitivity is maintained and the residual potential is lowered. Therefore, it is not necessary to set the volume resistivity as a resistor low. By setting the volume resistivity to 1 × 10 ¹² (Ω · cm) or more, the flow of the formed electrostatic latent image is high. Can be suppressed in dimension.

  In the electrophotographic photosensitive member having the protective layer described above, by further containing fluorine atom-containing resin fine particles, the releasability on the surface of the electrophotographic photosensitive member can be improved at a higher level.

  Examples of the fluorine atom-containing resin fine particles include ethylene tetrafluoride, ethylene trifluoride chloride resin, hexafluoroethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and copolymers thereof. Of these, it is preferable to select one or more types as appropriate, and particularly preferred are tetrafluoroethylene resin and vinylidene fluoride resin. The molecular weight distribution and particle size of the resin particles can be appropriately selected and are not particularly limited.

  As the solvent for preparing the outermost surface layer coating solution, the polyhydroxymethylbisphenol compound of the present invention and the charge transporting material are sufficiently dissolved, and further, the lower layer charge transporting layer in contact with the outermost surface layer coating solution or A solvent that does not adversely affect the charge generation layer or the like is preferable.

  Therefore, as solvents, alcohols such as methanol, ethanol and 2-propanol, ketones such as acetone, cyclohexanone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, ethers such as tetrahydrofuran and dioxane, toluene and xylene, etc. Aromatic hydrocarbons, halogenated hydrocarbons such as chlorobenzene and dichloromethane, and the like may be used in combination. Among these, the most suitable solvents for the form of the present invention are alcohols such as methanol, ethanol and 2-propanol.

  Conventionally, known charge transport materials are generally insoluble or hardly soluble in alcohol solvents, and uniform dissolution in the polyhydroxymethylbisphenol compound of the present invention is difficult. When contained, it is soluble in a solvent containing alcohol as a main component, and has little influence on the lower layer such as a charge transport layer.

  As a method for applying the outermost surface layer of the present invention, general coating methods such as a dip coating method, a spray coating method, a spinner coating method, a roller coating method, a Meyer bar coating method and a blade coating method can be used.

  In the present invention, an additive for an antioxidant may be added to the outermost surface layer for the purpose of preventing deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated during charging.

<Method for evaluating physical properties of photoreceptor surface>
After the photoconductor for hardness test prepared as described above is left in an environment of 25 ° C. and 50% humidity for 24 hours, Hu and elastic deformation are performed using the above-described microhardness measuring device Fischerscope H100V (Fischer). The rate was determined.

  The HU (universal hardness value) and elastic deformation rate in the present invention are the microhardness measuring device Fischerscope that continuously applies a load to the indenter and directly reads the indentation depth under the load to obtain the continuous hardness. Measurement was performed using H100V (Fischer). The indenter used was a Vickers square pyramid diamond indenter with a face angle of 136 °. The load conditions were measured stepwise up to a final load of 6 mN (273 points with a holding time of 0.1 s for each point).

  An outline of the output chart is shown in FIG. 6, and an example in which the electrophotographic photosensitive member of the present invention is measured is shown in FIG. The vertical axis represents the load (mN) and the horizontal axis represents the indentation depth h (μm), which is the result of increasing the load stepwise and applying the load to 6 mN, and then decreasing the load stepwise in the same manner.

  HU (universal hardness value: hereinafter referred to as HU) is defined by the following equation (3) from the indentation depth under the same load when indented at 6 mN.

弾性変形率は圧子が膜に対して行った仕事量（エネルギー）、すなわち圧子の膜に対する荷重の増減によるエネルギーの変化より求めたものであり、下記式（４）からその値は求まる。全仕事量Ｗｔ(nW)は図６中のA-B-D-Aで囲まれる面積で表され、弾性変形の仕事量Ｗｅ（ｎＷ）はC-B-D-Cで囲まれる面積で表される。

The elastic deformation rate is obtained from the work (energy) performed by the indenter on the membrane, that is, the change in energy due to the increase or decrease of the load on the membrane of the indenter, and the value can be obtained from the following equation (4). The total work amount Wt (nW) is represented by the area surrounded by ABDA in FIG. 6, and the elastic deformation work amount We (nW) is represented by the area surrounded by CBDC.

Elastic deformation rate = We / Wt × 100 (%) (4)
As described above, the performance required for the organic electrophotographic photosensitive member includes improved durability against mechanical deterioration. In general, the hardness of the film is higher as the amount of deformation with respect to external stress is smaller, and it is considered that the electrophotographic photosensitive member having higher pencil hardness or Vickers hardness naturally improves durability against mechanical deterioration. However, the high hardness obtained by these measurements has not always been expected to improve durability.

As a result of intensive studies, we have found that mechanical deterioration of the surface layer of the photoreceptor is less likely to occur particularly in a high temperature, high humidity environment when the values of HU and elastic deformation ratio are within a certain range, and the present invention has been achieved. That is, a hardness test is performed using a Vickers square pyramid diamond indenter, the HU when pressed at a maximum load of 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and the elastic deformation rate is 44% or more and 65% or less. By using the electrophotographic photosensitive member, which is Also, the further improvement of properties and is more preferably HU value is 160 N / mm ² or more 200 N / mm ² or less.

Although it is impossible to separate HU and elastic deformation rate, for example, when HU exceeds 220 N / mm ² , the elastic deformation rate is 44% when the friction with the cleaning blade increases at high temperatures. If the elastic deformation rate is less than 65%, the elastic force of the photosensitive member is insufficient. If the elastic deformation rate is higher than 65%, the elastic deformation amount is small even if the elastic deformation rate is high. Pressure is applied and deep scratches occur. Therefore, it is considered that a material having a high HU is not necessarily optimal as a photoconductor.

Also, when the HU is less than 150 N / mm ² and the elastic deformation rate exceeds 65%, even if the elastic deformation rate is high, the amount of plastic deformation increases, and the paper dust or toner sandwiched between the cleaning blade and the charging roller Scraping may cause scraping or fine scratches.

  In this example, two types of protective layers were formed to obtain two types of photoreceptors.

<Photoreceptor Production Example 1>
Using an aluminum cylinder (JIS A3003 aluminum alloy) having a length of 260.5 mm and a diameter of 30 mm as a support, a 5% by mass methanol solution of polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) was applied thereon by a dipping method. An undercoat layer having a thickness of 0.5 μm was formed.

  Next, 3 parts of hydroxygallium phthalocyanine crystal and 2 parts of polyvinyl butyral having the strongest peak at a diffraction angle 2θ ± 0.2 of 28.1 ° in X-ray diffraction of CuKα as a charge generating material are added to 100 parts of cyclohexanone. Disperse in a sand mill using 1 mmφ glass beads for 1 hour, add 100 parts of methyl ethyl ketone and dilute it to prepare a charge generation layer coating, and immerse this charge generation layer coating on the undercoat layer This was applied and dried at 90 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.17 μm.

  Next, 7 parts of a charge transport material compound of the formula

及びポリカーボネート樹脂（ユーピロンZ４00、三菱エンジニアリングプラスチックス（株）社製）１０部を、モノクロロベンゼン105部よびジクロロメタン35部に溶解した。この溶液を、前記電荷発生層上に浸漬塗布し、１１０℃で１時間熱風乾燥し、膜厚が１３μｍの電荷輸送層を形成した。電荷輸送層の上にこのさらに保護層を形成させた。

And 10 parts of polycarbonate resin (Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) were dissolved in 105 parts of monochlorobenzene and 35 parts of dichloromethane. This solution was dip-coated on the charge generation layer and dried with hot air at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 13 μm. This further protective layer was formed on the charge transport layer.

  In this embodiment, reversal development is used, and the photoreceptor is formed by stacking three layers on an aluminum cylinder having a diameter of 30 mm as described above, and then using a hole transporting compound represented by the following (Chemical Formula 5) as an electron beam. It is an organic photoreceptor in which a surface layer containing a compound polymerized by irradiation is applied and cured.

この正孔輸送性化合物45部をn-プロピルアルコール55部に溶解し、さらにテトラフルオロエチレン微粒子を５重量部添加して、高圧分散機（マイクロフルイタイザー、Microfluidics社製）にて分散させた表面保護層用塗料を調整した。この塗料を前記４層感光体上に塗布したのち、加速電圧150KV、線量４0ｋＧｙの条件で電子線を照射し、膜厚３μmの保護層を形成し、電子写真感光体Ａを得た。

A surface obtained by dissolving 45 parts of this hole transporting compound in 55 parts of n-propyl alcohol, adding 5 parts by weight of tetrafluoroethylene fine particles, and dispersing with a high-pressure disperser (Microfluidizer, manufactured by Microfluidics). The protective layer paint was prepared. After applying this paint on the four-layer photoconductor, an electron beam was irradiated under the conditions of an acceleration voltage of 150 KV and a dose of 40 kGy to form a protective layer having a thickness of 3 μm, and an electrophotographic photoconductor A was obtained.

<Protective layer production example 2>
Next, the second type of protective layer will be described in detail below including the manufacturing method.

  All of the ortho-position hydrogen atoms of the phenolic hydroxyl group of bisphenol represented by the following (Chemical Formula 6) as a curable phenol resin as a binder resin for the protective layer on the same three-layered photoreceptor as in photoreceptor production example 1. 100 parts of a tetrakishydroxymethyl-bisphenol compound substituted with a hydroxymethyl group and 70 parts of a charge transport material represented by the following (Chemical Formula 7), 42 parts of tetrafluoroethylene fine particles, and 150 parts of ethanol are mixed, A coating solution is prepared by dissolving in a solvent dispersed with a high-pressure disperser (Microfluidizer, manufactured by Microfluidics), dip-coated on the charge transport layer, and dried with hot air at 145 ° C. for 1 hour to form a membrane. An outermost surface layer having a thickness of 3 μm was provided. Here, the film thickness of the outermost surface layer was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd.).

以上のように作製した保護層を有する感光体を感光体Ｂとする。

The photoreceptor having the protective layer produced as described above is referred to as a photoreceptor B.

  Table 1 shows the values of Hu and We on the surfaces of the obtained photoreceptor A and photoreceptor B.

（実施例１〜６）
キヤノン製レーザービームプリンターＬＢＰ−１７６０に本発明を適用した帯電条件ないしは感光体を適用させて実施例ないしは比較例とした。帯電に印加する電圧には外部高圧電源を使用した。本実施例では高圧電源により帯電ローラに印加される交流電圧を制御して放電電流を適正値に設定するものである。

(Examples 1-6)
Examples or comparative examples were made by applying charging conditions or photoconductors to which the present invention was applied to a Canon laser beam printer LBP-1760. An external high-voltage power supply was used as the voltage applied for charging. In this embodiment, the AC voltage applied to the charging roller by the high voltage power source is controlled to set the discharge current to an appropriate value.

Implementation environment Temperature 32.5 ° C Humidity 85.0%
Image forming apparatus main body Canon laser beam printer LBP-1760 modified development toner Developer for LBP-1760 (magnetic one component toner)
Development bias -460V DC voltage applied (1.6kVpp AC voltage superimposed)
Developing roller developer coat width 210mm (developable longitudinal width)
Continuous paper 2% original 1000 sheets Photoconductor Photoconductor A or Photoconductor B
Charging LBP-1760 charging roller (224mm length) DC applied voltage -600V
As a result of comparing the cleaning property and the charging property by changing the AC applied voltage, the length L (mm) of one side outside the developable longitudinal width of the charging unit, and the unit length per unit length due to the charging outside the developable longitudinal width. The results are shown in Table 2 together with the discharge current I (μA / mm). The cleaning property was evaluated as a cleaning friction level, and the charging property was evaluated as a halftone unevenness level. Further, the scattering due to the toner flying from the developing device to the photoconductor which occurs when the potential outside the developable width of the photoconductor does not become normal was also evaluated.

  The cleaning friction level was evaluated based on the following criteria evaluated with an actual machine.

◎ Good without squeezing ○ Slight squeal only when stopped × Cleaning blade turned over and unable to clean The halftone unevenness level was evaluated based on the following criteria using an actual machine.

◎ No unevenness ○ Slightly uneven but almost invisible △ Uneven but inconspicuous × Overall unevenness and conspicuous scattering levels were evaluated by evaluating with the actual machine according to the following criteria.

◎ Almost no scattering ○ Slightly scattered but slightly adhered to the edge of the photoconductor △ Although scattered, the image edge is slightly stained and not noticeable × Scattering is severe and drops on the image Dirty images

比較例1ないし比較例３はクリーニングブレードがめくれてしまい、画像形成が行えなかった。比較例２ないし比較例４はハーフトーンでムラがひどく、まともな画像が得られなかった。

In Comparative Examples 1 to 3, the cleaning blade turned up, and image formation could not be performed. In Comparative Examples 2 to 4, halftone was very uneven and a decent image could not be obtained.

  On the other hand, as in Examples 1 to 3, 4 to 6, the potential of the surface of the photoreceptor is higher than the potential of the developing roller outside the developable longitudinal width, and the discharge current (I × L) due to charging is Image formation with no problem was possible at 0.75 μA or less. Preferably, as in Examples 1, 2, 4 and 5, the discharge current I (μA / mm) per unit length due to charging outside the developable longitudinal width is 0.01 μA / mm or more, so that better image formation is achieved. I did it.

(Examples 7 to 12)
Examples or comparative examples were made by applying charging conditions or photoconductors to which the present invention was applied to a Canon laser beam printer LBP-1760. An external power source was used for charging. In this embodiment, the length of one side outside the developable longitudinal width of the charging means is changed to an appropriate value by changing the length of the charging roller, thereby setting the discharge current outside the developable width of the charging roller to an appropriate value. is there.

Implementation environment Temperature 32.5 ° C Humidity 85.0%
Image forming apparatus main body Canon laser beam printer LBP-1760 modified development toner Developer for LBP-1760 (magnetic one component toner)
Development bias -460V DC voltage applied (1.6kVpp AC voltage superimposed)
Developing roller developer coat width 210mm (developable longitudinal width)
Continuous paper 2% original 1000 sheets Photoconductor Photoconductor A or Photoconductor B
Change the length of the charging roller for LBP-1760 (224mm-210.8mm)
DC applied voltage -600V
AC applied voltage 1170Vpp Frequency 900Hz
The result of comparing the length outside the developable width of this charging roller with the cleaning property, chargeability, and the degree of toner scattering, the length L (mm) on one side outside the developable longitudinal width of the charging means, the developable longitudinal width Table 3 shows the discharge current I per unit length (μA / mm) due to external charging. The same evaluation as in Examples 1 to 6 was performed, and the cleaning property was evaluated as a cleaning friction level, the charging property was evaluated as a halftone unevenness level, and the toner scattering was evaluated as a toner scattering level.

比較例５ないし比較例７はクリーニングブレードがめくれてしまい、画像形成が行えなかった。比較例６ないし比較例８は現像可能長手幅外での感光体の帯電不足によりトナー飛散がひどく、画像が汚れてしまった。これに対し、実施例実施例７〜９、１０〜１２のとおり、帯電手段の現像可能長手幅外の片側の長さ（Ｌ）が０．５ｍｍ以上であってかつ感光体表面の現像可能長手幅外での帯電による放電電流（Ｉ×Ｌ）が０．７５μA以下で問題の無い画像形成が行えた。

In Comparative Examples 5 to 7, the cleaning blade turned up, and image formation could not be performed. In Comparative Examples 6 to 8, toner scattering was severe due to insufficient charging of the photoreceptor outside the developable longitudinal width, and the image was soiled. On the other hand, as in Examples 7-9 and 10-12, the length (L) on one side outside the developable longitudinal width of the charging means is 0.5 mm or more, and the developable longitudinal of the surface of the photosensitive member. When the discharge current (I × L) due to charging outside the width was 0.75 μA or less, image formation with no problem could be performed.

(Examples 13 to 18)
Examples or comparative examples were made by applying charging conditions or photoconductors to which the present invention was applied to a Canon laser beam printer LBP-1760. In this embodiment, the surface of the charging roller outside the developable longitudinal width is cured by applying a coating having a volume resistance higher than that of the charging roller body and the photoreceptor surface after curing, and the resistance of the charging roller within the developable longitudinal width is cured. Further, by increasing the resistance of the charging roller outside the developable longitudinal width, the charging / discharging current amount outside the imageable longitudinal width is optimized without affecting the image portion.

Implementation environment Temperature 32.5 ° C Humidity 85.0%
Image forming apparatus main body Canon laser beam printer LBP-1760 modified development toner Developer for LBP-1760 (magnetic one component toner)
Development bias -460V DC voltage applied (1.6kVpp AC voltage superimposed)
Developing roller developer coat width 210mm (developable longitudinal width)
Continuous paper 2% original 1000 sheets Photoconductor Photoconductor A or Photoconductor B
Charging roller Applying urethane-based insulating paint to the surface outside the developable longitudinal width of the LBP-1760 charging roller (224 mm in length) and curing.
DC applied voltage -600V
AC applied voltage 1170Vpp Frequency 900Hz
The urethane insulating coating was applied by dip coating in which a masked roller was dipped in the coating solution and pulled up, and then allowed to stand for 1 hour in a constant temperature bath at 160 ° C. to be cured. In this example, this process was repeated to change the number of coatings, and several types of charging rollers were produced. An AC bias of 1170 Vpp was applied to this charging roller. At this time, the discharge current within the developable longitudinal width was 0.116 μA / mm.

  The result of comparison of the number of times of applying the insulating paint, the cleaning property, the charging property, and the degree of the toner scattering is shown as the length L (mm) on one side outside the developable longitudinal width of the charging means and the charging outside the developable longitudinal width. Table 4 shows the discharge current I per unit length (μA / mm). The same evaluation as in Examples 1 to 6 was performed, and the cleaning property was evaluated as a cleaning friction level, the charging property was evaluated as a halftone unevenness level, and the toner scattering was evaluated as a toner scattering level.

比較例９ないし比較例１１はクリーニングブレードがめくれてしまい、画像形成が行えなかった。比較例１０ないし比較例１２は現像可能長手幅外での感光体の帯電不足によりトナー飛散がひどく、画像が汚れてしまった。

In Comparative Examples 9 to 11, the cleaning blade turned up, and image formation could not be performed. In Comparative Examples 10 to 12, toner scattering was severe due to insufficient charging of the photoreceptor outside the developable longitudinal width, and the image was soiled.

  On the other hand, as in Examples 13 to 15 and 16 to 18, the potential on the surface of the photoreceptor is higher than the potential of the developing roller outside the developable longitudinal width, and the discharge current (I × L) due to charging. Was 0.75 μA or less, and no problem image formation was possible. Preferably, as in Examples 13, 14, 16, and 17, the discharge current I (μA / mm) per unit length due to charging outside the developable longitudinal width is 0.010 μA / mm or more, and better image formation is achieved. I did it.

  The method for reducing the discharge current for charging outside the developable longitudinal width is not limited to this embodiment, and the charging roller outside the developable longitudinal width is covered with tape or powder, or the developable longitudinal width. The same effect can be obtained even if the resistance of the external photoconductor is increased.

(Industrial applicability)
As a result of intensive studies by the present inventors, a hardness test was performed using a Vickers square pyramid diamond indenter, particularly in an environment where the surface was 25 ° C. and 50% humidity, and HU (universal hardness value) when pushed in with a maximum load of 6 mN. The electrophotographic photosensitive member having a durability of 150 N / mm ² or more and 220 N / mm ² or less and having an elastic deformation ratio of 44% or more and 65% or less is charged by contact charging to form a developer. In the image forming method in which the latent image is developed, the developed toner is transferred to a medium such as paper, and the untransferred toner on the photosensitive member is cleaned with a cleaning blade, the charging unit has a longer longitudinal width than the developable longitudinal width. The length of one side outside the developable longitudinal width of the charging means is L (mm), and the discharge current per unit length by charging outside the developable longitudinal width of the surface of the photosensitive member is I (μA). / Mm) Formula 0.5 ≦ L
I x L ≤ 0.75
It has been found that stable image formation without turning over the cleaning blade can be performed when satisfying the above.

  In a system in which contact roller charging / blade cleaning is performed on the photosensitive member, cleaning becomes difficult due to a decrease in drum slipperiness due to discharge by the charging roller. In particular, the charging of the photosensitive member outside the developer roller width where the developer is difficult to reach causes a local friction increase between the drum and the cleaning blade, making it difficult to clean the entire photosensitive member. Therefore, the present invention reduces discharge outside the developable longitudinal width. Since there is little electric discharge outside the developable longitudinal width, the photoconductor slippage outside the developable longitudinal width does not deteriorate. As a result, it is possible to prevent cleaning problems such as turning over or vibration of the entire cleaning blade due to an increase in the frictional force between the cleaning blade and the photosensitive member outside the developable longitudinal width where it is difficult to supply toner and lubricant.

1 is a schematic sectional view showing an image forming apparatus of the present invention. It is the schematic showing the relationship of the length of the charging roller of this invention, a developing roller, and a cleaning blade. It is the schematic which shows the structure which calculates | requires discharge current. It is a graph for calculating | requiring a discharge current. It is the schematic which shows the example of a measurement of the discharge by the charging roller outside developable longitudinal width. It is the schematic of the output chart which measures the elasticity modulus of the electrophotographic photosensitive member of this invention. It is the example which measured the elasticity modulus of the electrophotographic photosensitive member of this invention.

Explanation of symbols

101 photoconductor
102 Charging roller
103 Exposure equipment
104 Developer
105 Transfer material
106 Fixing device
107 Cleaning device
111 Transfer media
201 photoconductor
202 Charging roller
203 Developing roller
204 Cleaning blade
301 photoconductor
302 Charging roller
303 AC voltage power supply
304 ammeter

Claims (7)

The image carrier and the charging step for contacting and charging the surface of the image carrier, the latent image forming step for forming an electrostatic latent image on the charging surface of the image carrier, and the toner carried on the developing roller An image forming method comprising: a developing step of developing an electrostatic latent image as a toner image by reversal development; a transfer step of transferring the toner image onto a recording medium; and a cleaning step of cleaning residual toner with an elastic blade. The surface of the layer is subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of 25 ° C. and 50% humidity, and the HU (universal hardness value) when pressed at a maximum load of 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and a electrophotographic photosensitive member elastic deformation rate is less than or equal to 65% or more 44%, is the charging means have been applied AC voltage, and longer length than the developable longitudinal width The width of one side outside the developable longitudinal width of the charging means is L (mm), and the discharge current per unit length by charging outside the developable longitudinal width of the surface of the photoreceptor is I ( μA / mm), the following formula 0.5 ≦ L
I x L ≤ 0.75
An image forming method characterized by satisfying   2. The image forming method according to claim 1, wherein the absolute value of the surface potential of the photoconductor charged by the charging means outside the developable longitudinal width of the surface of the photoconductor is larger than the absolute value of the potential of the developing bias. The discharge current I (μA / mm) per unit length due to charging outside the developable longitudinal width of the surface of the photoreceptor is expressed by the following formula: 0.01 ≦ I
The image forming method according to claim 2, wherein:   4. The image formation according to claim 1, wherein a discharge current by charging within the developable longitudinal width of the surface of the photoreceptor is 0.1 (μA / mm) to 2.0 (μA / mm). Method.   5. The image forming method according to claim 4, wherein the resistance of the charging means outside the developable longitudinal width is higher than the resistance of the portion within the developable longitudinal width.   6. The image forming method according to claim 5, wherein a portion outside the developable longitudinal width of the charging means is coated with a material having a volume resistance higher than that of the charging roller main body and the photosensitive member surface. The photoreceptor has a protective layer, and the protective layer is at least one selected from the group consisting of a curable phenolic resin and a hydroxyalkyl group, a hydroxyalkoxy group, or an optionally substituted hydroxyphenyl group. The image forming method according to claim 1, further comprising a charge transport material having one of them.

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