JP6531611B2 - Solid lubricant and image forming method - Google Patents

Description

  The present invention relates to solid lubricants and imaging methods.

  In part of the electrophotographic printing process, a developing step of supplying toner onto the image bearing member on which the electrostatic latent image is formed to form a toner image according to the electrostatic latent image, and recording the toner image A transfer step of transferring to a medium and a cleaning step of removing toner not transferred to the recording medium from the image carrier are included. In the cleaning step, a lubricant is used to improve the transfer efficiency by enhancing the releasability between the toner and the image carrier, and to suppress the abrasion of the surface of the image carrier (photosensitive member) and the cleaning blade that cleans the surface. There is known a technique of applying to the surface of an image carrier (see, for example, Patent Document 1).

  However, it is known that image memory tends to occur in a mechanism for applying a lubricant. The image memory is a phenomenon in which unevenness in the coating thickness of the lubricant occurs and unevenness in the surface potential according to the difference in coating thickness occurs on the image carrier, whereby density unevenness appears on the image. The image memory is particularly noticeable when an image having a high printing rate area and a low printing area is continuously printed. This is because when the lubricant is abraded with the magnetic brush in the development step, the area with a high coverage rate is scraped more than the area with a low coverage rate.

  Patent Document 1 describes a lubricant having a positively chargeable fatty acid metal salt and a negatively chargeable charge control agent. In the lubricant described in Patent Document 1, the fatty acid metal salt and the charge control agent cancel each other's charge, thereby suppressing the decrease in the surface potential of the image carrier, even if the coating thickness unevenness occurs, the image It is difficult to express as uneven density on the top.

Unexamined-Japanese-Patent No. 2010-133997

  Further, in recent years, in the field of electrophotographic printing technology, further speeding up and further improvement in image quality are required. In order to increase the speed of such printing technology, it is assumed that the scraping power of the developing brush becomes strong, and uneven coating thickness of the lubricant and triboelectric charging become noticeable. In addition, it is assumed that, in the case of high image quality printing technology, it is necessary to take measures in accordance with a rapid change in printing rate such as the outline of characters.

  However, since the lubricant described in Patent Document 1 does not have the effect of suppressing unevenness in the application thickness of the lubricant, the effect of suppressing the image memory is not sufficient due to the speeding up of printing.

  Therefore, an object of the present invention is to provide a solid lubricant and an image forming method capable of suppressing the generation of an image memory even when an image having a large difference in printing rate in an image plane is continuously output. It is.

  In order to solve the above problems, the present invention is a solid lubricant which is applied to the surface of an image carrier of an image forming apparatus in electrophotography and forms a solid lubricant layer on the surface of the image carrier. A solid lubricant comprising a fatty acid metal salt, a charge control agent, and polyethylene, wherein the polyethylene has an acid value of 1 mg KOH / g or more.

  Further, in order to solve the above problems, according to the present invention, there are provided a step of charging an image carrier, a step of forming an electrostatic latent image on the charged image carrier, and the image carrier on which an electrostatic latent image is formed. Forming a solid lubricant layer on the surface of the image carrier, the step of carrying toner corresponding to the electrostatic latent image on the body, the step of transferring the toner carried on the image carrier to the transfer material, and A solid lubricant according to an embodiment of the present invention, the image forming method including a process and a process of removing the residue on the image carrier after transferring the toner to a transfer material An image forming method to be used is provided.

  The present invention can provide a solid lubricant and an image forming method capable of suppressing generation of an image memory even when an image having a large difference in printing rate in an image plane is continuously output.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2A is a view schematically showing the configuration around the cleaning device in one embodiment of the present invention, and FIG. 2B is a view schematically showing the configuration around the cleaning device in another embodiment of the present invention It is.

  Hereinafter, an embodiment of the present invention will be described.

(Composition of solid lubricant)
The solid lubricant according to the embodiment of the present invention is a solid lubricant for forming a layer of a solid lubricant on the surface of a photoreceptor by being applied to the surface of a photoreceptor (image carrier) of an image forming apparatus in electrophotography. It is a lubricant.

  The solid lubricant contains a fatty acid metal salt, a charge control agent, and polyethylene having an acid value.

  As fatty acid metal salts, known fatty acid metal salts (metal soaps) that can be used as a lubricant in an electrophotographic image forming apparatus can be used. The fatty acid metal salt may be of one type or of two or more types. The fatty acid metal salt is a metal salt of fatty acid and is obtained, for example, by neutralization of a fatty acid and an alkaline compound containing the metal.

  The carbon number of the fatty acid is preferably in the range of 10 to 30, and more preferably in the range of 12 to 28, from the viewpoint of compatibility with polyethylene and the spreadability of the solid lubricant. Examples of fatty acids include stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid and behenic acid. Also, examples of metals include zinc, magnesium, calcium, barium and lithium. As a fatty metal salt obtained from these fatty acids and metals, zinc stearate which is easy to spread and has less unevenness in its application thickness is preferable.

  Polyethylene has a predetermined acid value. The acid value of polyethylene is 1 mg KOH / g or more, and more preferably 5 mg KOH / g or more. When the acid value of polyethylene is less than 1 mg KOH / g, there is a possibility that the coating thickness unevenness of the solid lubricant on the photosensitive member can not be suppressed. Moreover, it is preferable that the acid value of polyethylene is 80 mgKOH / g or less. When the acid value of polyethylene is more than 80 mg KOH / g, the interaction between the photosensitive member and the polyethylene becomes strong, and as a result, the spread of the fatty acid metal salt may be inhibited, which may cause uneven coating thickness.

  The acid value is the number of mg of KOH required to neutralize the acid component in 1 g of polyethylene. The acid value can be determined by the test method defined in JIS K0070. The acid value can be adjusted, for example, by the amount of acid groups introduced into the acid value polyethylene or by mixing polyethylenes having different acid values.

  The number average molecular weight of polyethylene is preferably in the range of 1000 to 10000. When the number average molecular weight of the polyethylene is less than 1000, the polyethylene may be fused to the photosensitive member during operation of the image forming apparatus, and the coating thickness of the solid lubricant may not be constant. On the other hand, when the number average molecular weight of polyethylene is more than 10000, the movement of the polar group in the polyethylene molecule is limited, the interaction with the polar group on the surface of the photoreceptor is reduced, and the adhesion of polyethylene to the photoreceptor is not good. It may be enough.

  The melting point of polyethylene is preferably 100 ° C to 160 ° C. When the melting point of polyethylene is less than 100 ° C., the polyethylene may be fused to the photosensitive member during operation of the image forming apparatus, and the coating thickness of the solid lubricant may not be constant. On the other hand, when the melting point of polyethylene is more than 160 ° C., the movement of the polar group in the polyethylene molecule is limited, so the interaction with the polar group of the photoreceptor is reduced, and the adhesion of polyethylene to the photoreceptor is insufficient. May be

  The addition amount of polyethylene is preferably in the range of 3 to 10 parts by mass with respect to 100 parts by mass of the total mass of fatty acid metal salt, charge control agent and polyethylene. If the amount of polyethylene added is less than 3%, the adhesion of polyethylene to the photoreceptor may not be sufficient. On the other hand, when the addition amount of polyethylene is more than 10 parts by mass, the interaction between the photosensitive member and the polyethylene becomes strong, and the adhesion of the polyethylene to the photosensitive member may become strong. Thereby, the spread of the fatty acid metal salt may be inhibited, and the coating thickness unevenness of the solid lubricant may be aggravated.

  Examples of polyethylene include oxidized polyethylene and polyethylene having an acid group (acid-modified polyethylene). Oxidized polyethylene is obtained by directly oxidizing polyethylene. The oxidized polyethylene can be produced by a known method, and for example, JP-A 2004-75749, JP-A 11-80252, JP-A 10-279624, JP-A 04-328108, JP-A-H04-328108. It is possible to manufacture by the method as described in 01-022905 gazette and Japanese Patent Publication No. 2010-515819 gazette.

  Examples of the acidic group in the polyethylene having the acidic group include a carboxyl group and a carboxylic acid anhydride group. The acidic group may be one or more kinds. The polyethylene having an acidic group can be prepared, for example, by a copolymer of an acidic monomer having an acidic group and ethylene. Examples of polyethylene having an acidic group include copolymerized polyethylene obtained by copolymerizing unsaturated carboxylic acid and ethylene, and copolymerized polyethylene obtained by copolymerizing unsaturated carboxylic anhydride and ethylene . The acidic monomer is, for example, a compound having a (meth) acryloyl group. It is a compound having a carbon-carbon double bond and an acidic group. Examples of acid number monomers include maleic acid, acrylic acid, maleic anhydride and methacrylic acid.

  The polyethylene having an acidic group can be produced by a known method (acid modification). For example, JP-A-2014-198847, JP-A-2011-162797, JP-A-2003-252927, and JP-A-2000 And JP-A-9-506658.

  The polyethylene is preferably oxidized polyethylene. Since oxidized polyethylene generally has an affinity for inorganic compounds, metals and the like, the dispersibility of the charge control agent in the fatty acid metal salt becomes high, and the charging unevenness can be suppressed.

  Examples of charge control agents include metal complexes, inorganic fine particles and organic fine particles. Examples of metal complexes include zinc salicylate complexes and salicylchromium complexes. Examples of the inorganic fine particles include silica and titania. Examples of organic fine particles include polymethyl methacrylate resin (PMMA). When zinc stearate is used as the fatty acid metal salt described above, it is preferable to use a negatively chargeable charge control agent as the charge control agent. Since zinc stearate is positively chargeable, charge bias can be canceled by using a negatively chargeable charge control agent. In particular, the charge control agent is preferably an azo compound chromium complex, a zinc salicylate complex, or a chromium salicylate complex. These complexes have a high effect of imparting chargeability, so the amount of addition may be small.

  The addition amount of the charge control agent is preferably in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the total weight of the fatty acid metal salt, the charge control agent and the polyethylene. When the addition amount of the charge control agent is less than 1 part by mass, the effect of imparting the chargeability may not be obtained. On the other hand, when the addition amount of the charge control agent is more than 10 parts by mass, the charge polarity of the charge control agent is excessively expressed, which may deteriorate the image memory.

  The solid lubricant is obtained by melting and mixing the fatty acid metal salt, the charge control agent and the polyethylene and then cooling to solidify it into the desired shape. For example, the solid lubricant can be produced in a rod-like shape by a melt-molding method in which a melt mixture of a fatty acid metal salt, a charge control agent and polyethylene is injected into a mold. A particulate solid lubricant can be produced by granulation of droplets of the melt mixture, spraying of the melt mixture, or the like. Furthermore, a powdery solid lubricant can also be produced by subjecting the above-mentioned compact to a grinding treatment.

(Action)
The solid lubricant according to the present embodiment can suppress the generation of an image memory by using it as a lubricant to a photosensitive member after transfer in an electrophotographic image forming method. In particular, even when an image having a large difference in printing rate is continuously output, generation of an image memory can be suppressed thereafter. The reason will be described below.

  First, the solid lubricant contains a fatty acid metal salt. Fatty acid metal salts are known as lubricants for photoreceptors. However, when a fatty acid metal salt is used alone as a solid lubricant, the affinity to the surface of the photoreceptor may be insufficient. More specifically, the fatty acid metal salt is usually a compound mainly composed of an aliphatic alkyl group having 10 or more carbon atoms. However, in general, the composition of the surface of the photoreceptor does not include a compound having an aliphatic alkyl group having 10 or more carbon atoms. Therefore, a solid lubricant using a fatty acid metal salt alone tends to have insufficient adhesion and affinity to the surface of the photoreceptor.

  For this reason, the solid lubricant on the surface of the photosensitive member is easily scraped off by the magnetic brush in the developing step and easily peeled off. At that time, a large amount of solid lubricant is scraped off by the magnetic brush in the developing process, compared to the portion corresponding to the low printing ratio area of the photosensitive member in the high printing ratio area of the photosensitive member. Thereby, when printing continuously based on the image pattern which has an area | region where the printing rate is high, and an area | region where printing rate is low, the application | coating nonuniformity in application | coating thickness of the solid lubricant depending on printing rate will arise.

  In addition, a solid lubricant using a fatty acid metal salt alone is charged by friction with a magnetic brush (carrier). As a result, the potential of the surface of the photoreceptor coated with the solid lubricant is displaced. As a result, in the photosensitive member, the portion corresponding to the low printing rate region has a large potential change compared to the portion corresponding to the high printing rate region.

  As described above, when a fatty acid metal salt is used alone as a solid lubricant, an image having a large printing ratio is continuously formed due to a defect in coating thickness unevenness and a charging property of the solid lubricant depending on the printing ratio. When output is performed, there is a possibility that an image memory may occur thereafter.

  On the other hand, in the solid lubricant according to the present embodiment, the generation of the image memory can be suppressed even when an image having a large printing rate is continuously output. The reason is considered to be as follows.

  As described above, the solid lubricant according to the present embodiment has a fatty acid metal salt, a charge control agent, and polyethylene having a predetermined acid value. Polyethylene having a predetermined acid value has higher adhesion and affinity to the surface of the photoreceptor than fatty acid metal salts. The reason why polyethylene having an acid value has high adhesion and affinity to the surface of the photoreceptor is that polyethylene having an acid value is less hydrophobic than fatty acid metal salts, and the polarity of the surface composition of the photoreceptor is polar. It is considered to be closer to In addition, functional groups (for example, amino groups in the charge transport layer material, and hydroxyl groups in external additives attached from the toner to the surface of the photoreceptor, etc.) are usually present on the surface of the photoreceptor, and the acid value It is considered to be due to the strong affinity to the polar group of polyethylene. For this reason, the solid lubricant according to the present embodiment adheres strongly to the photosensitive member and becomes difficult to be scraped off by the magnetic brush in the developing step, so that the coating thickness unevenness is suppressed.

  In addition, since the solid lubricant according to the present embodiment has a charge control agent, the charge due to the fatty acid metal salt can be canceled. Furthermore, polyethylene having an acid value contained in the solid lubricant according to the present embodiment has weak negative chargeability. Therefore, the solid lubricant according to the present embodiment can further cancel the positive charge generated by the fatty acid metal salt when used in combination with the positively chargeable fatty acid metal salt.

  Therefore, by using the solid lubricant according to the present embodiment, the coating property on the surface of the photosensitive member is excellent regardless of the amount of the transfer residual component on the surface of the photosensitive member, and the coating thickness unevenness is prevented. At the same time, the chargeability is improved and the image memory is suppressed.

(Image forming method and image forming apparatus)
The solid lubricant described above can be used in an electrophotographic image forming method. By using the solid lubricant in an image forming method, generation of an image memory can be suppressed.

  The image forming method according to the present embodiment includes the steps of: charging the photosensitive member; forming an electrostatic latent image on the charged photosensitive member; and forming an electrostatic latent image on the photosensitive member on which the electrostatic latent image is formed. A step of supporting the corresponding toner, a step of transferring the toner carried on the photosensitive member to the transfer material, a step of forming a solid lubricant layer on the surface of the photosensitive member, and a step of transferring the toner to the transfer material Removing the residue on the photoreceptor.

  As mentioned above, the solid lubricant may be in the form of a rod and a powder. When the solid lubricant has a rod-like shape, it is applied to the surface of the photosensitive member to form a solid lubricant film. When the solid lubricant is in the form of powder, it is added as an external additive to the toner, and the toner containing the powder solid lubricant is applied to the surface of the photosensitive member to form a solid lubricant film. Form. When a powdery solid lubricant is added as an external additive for toner, the content of the powdery solid lubricant is in the range of 0.1 to 1.0% by mass with respect to the toner base. If the content of the powdery solid lubricant is less than 0.1% by mass with respect to the toner base, the function of the solid lubricant may not be exhibited. On the other hand, when the content of the powdery solid lubricant is more than 1.0% by mass with respect to the toner base, the function of the solid lubricant is saturated and the stability of the charge amount of the toner against the change of temperature and humidity Also, the fluidity of the toner may be deteriorated. The particle diameter of the solid lubricant is preferably in the range of 1 to 15 μm. When the particle diameter of the solid lubricant is less than 1 μm, the solid lubricant is difficult to be detached from the toner, and there is a possibility that the supply of the solid lubricant to the photoreceptor is insufficient. On the other hand, when the particle diameter of the solid lubricant is more than 15 μm, the solid lubricant may be easily detached from the toner, and the application unevenness of the solid lubricant may easily occur.

  When a mixture of powder of fatty acid metal salt, charge control agent and polyethylene powder is added to toner instead of powdery solid lubricant, fatty acid metal salt adheres to the area corresponding to low printing ratio Since polyethylene and a charge control agent may adhere to a portion corresponding to a high printing rate area, they do not function as solid lubricants.

  The image forming method can be carried out in the same manner as the known image forming method in the electrophotographic system except using the solid lubricant.

  Further, an image forming apparatus for carrying out the image forming method can be configured in the same manner as a known image forming apparatus except that the solid lubricant described above is used.

  Hereinafter, an image forming method according to the present embodiment and an image forming apparatus that can be used for the image forming method will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of the image forming apparatus 10. As shown in FIG. FIG. 2A is a view schematically showing the configuration around the cleaning device 36 according to an embodiment of the present invention, and FIG. 2B is a view schematically showing the configuration around the cleaning device 36 according to another embodiment of the present invention. FIG. The image forming apparatus 10 includes an image reading unit 20, an image forming unit 30, an intermediate transfer unit 40, a fixing device 60, and a recording medium conveyance unit 80.

  The image reading unit 20 reads an image from the document D and obtains image data for forming an electrostatic latent image. The image reading unit 20 includes a sheet feeding device 21, a scanner 22, a CCD sensor 23, and an image processing unit 24.

  The image forming unit 30 includes, for example, four image forming units 31 corresponding to the respective colors of yellow, magenta, cyan and black. The image forming unit 31 includes a photosensitive member 32, a charging device 33, an exposure device 34, a developing device 35, and a cleaning device 36.

  The photosensitive member 32 is a negatively charged organic photosensitive member having photoconductivity. The charging device 33 charges the photosensitive body 32. The charging device 33 is, for example, a corona charging device (non-contact charging device). In addition, the charging device 33 may be a contact charging device that brings a contact charging member such as a charging roller, a charging brush, or a charging blade into contact with the photosensitive member 32 for charging.

  The exposure device 34 irradiates light to the charged photoreceptor 32 to form an electrostatic latent image on the surface of the photoreceptor 32. The exposure device 34 includes, for example, a semiconductor laser as a light source, and a light deflection device (polygon motor) that irradiates the photosensitive member 32 with laser light according to an image to be formed. The developing device 35 supplies toner to the surface of the photosensitive member 32 on which the electrostatic latent image is formed, and forms a toner image corresponding to the electrostatic latent image on the surface of the photosensitive member 32. The developing device 35 is, for example, a known developing device in an electrophotographic image forming apparatus.

  The cleaning device 36 removes residual toner and the like adhering to the surface of the photosensitive member 32. Here, the term "toner image" refers to a state in which toner is gathered in the form of an image. The cleaning device 36 includes a cleaning container 36A opening toward the photosensitive member 32, a cleaning blade 36B disposed in contact with the surface of the photosensitive member 32 at the opening of the cleaning container 36A, and a surface of the photosensitive member 32. , A solid lubricant 36D in contact with the surface of the rotation brush 36C, and an urging member 36E for urging the solid lubricant 36D toward the rotation brush 36C. The cleaning blade 36B is, for example, an elastic blade made of rubber.

  The solid lubricant 36D has a fatty acid metal salt, polyethylene having an acid value, and a charge control agent, and the image is printed continuously even on the basis of an image pattern having regions with greatly different printing rates in the image. It is configured not to generate memory. The shape of the solid lubricant 36D can be appropriately determined within a range that can be applied to the surface of the photosensitive member 32 by the rotating brush 36C. For example, a rod-like shape (a rectangular solid having a length equal to the axial length of the rotating brush 36C) ).

  The rotating brush 36C is configured to be rotatable in the forward or reverse direction with respect to the photosensitive member 32. The rotating brush 36C is made of, for example, a metal rotatable shaft, and a plurality of flexible resin hairs which stand up from the circumferential surface of the shaft.

  A known toner can be used as the toner. The toner may be a one-component developer or a two-component developer. The one-component developer is composed of toner particles. The two-component developer is also composed of toner particles and carrier particles. The toner particles are composed of toner base particles and an external additive such as silica attached to the surface thereof. The toner base particles are composed of, for example, a binder resin, a colorant and a wax.

  The intermediate transfer unit 40 includes a primary transfer unit 41 and a secondary transfer unit 42.

  The primary transfer unit 41 includes an intermediate transfer belt 43, a primary transfer roller 44, a backup roller 45, a plurality of first support rollers 46, and a cleaning device 47. The intermediate transfer belt 43 is an endless belt. The intermediate transfer belt 43 is stretched by a backup roller 45 and a first support roller 46. The intermediate transfer belt 43 travels at a constant speed in one direction on the endless track by rotationally driving at least one of the backup roller 45 and the first support roller 46.

  The secondary transfer unit 42 includes a secondary transfer belt 48, a secondary transfer roller 49, and a plurality of second support rollers 50. The secondary transfer belt 48 is an endless belt. The secondary transfer belt 48 is stretched by a secondary transfer roller 49 and a second support roller 50.

  The fixing device 60 includes a fixing belt 61, a heating roller 62, a first pressure roller 63, a second pressure roller 64, a heater, a temperature sensor, an air flow separating device, a guide plate, and a guide roller. And.

  In the fixing belt 61, a base layer, an elastic layer, and a releasing layer are laminated in this order. The fixing belt 61 is axially supported by the heating roller 62 and the first pressure roller 63 in a state in which the base layer is on the inside and the release layer is on the outside.

  The heating roller 62 has a rotatable aluminum sleeve and a heater 65 disposed therein. The first pressure roller 63 has, for example, a rotatable core metal and an elastic layer disposed on the outer peripheral surface thereof.

  The second pressure roller 64 is disposed to face the first pressure roller 63 with the fixing belt 61 interposed therebetween. The second pressure roller 64 is disposed close to and away from the first pressure roller 63. When the second pressure roller 64 approaches the first pressure roller 63, the first pressure roller 64 receives the first pressure roller 64 via the fixing belt 61. The elastic layer of the pressure roller 63 is pressed to form a fixing nip portion which is a contact portion with the fixing belt 61.

  The air flow separation device is a device for generating an air flow from the downstream side in the moving direction of the fixing belt 61 to the fixing nip portion to promote separation of the recording medium S from the fixing belt 61.

  The guide plate is a member for guiding the recording medium S having the unfixed toner image to the fixing nip portion. The guide roller is a member for guiding the recording medium on which the toner image is fixed from the fixing nip portion to the outside of the image forming apparatus 10.

  The recording medium conveyance unit 80 includes three sheet feeding tray units 81 and a plurality of registration roller pairs 82. In the paper feed tray unit 81, recording media (standard paper, special paper, and the like in the present embodiment) identified based on basis weight, size, and the like are accommodated for each preset type. The resist roller pair 82 is arranged to form a desired transport path.

(Image formation method)
Next, the operation (image forming method) of the image forming apparatus 10 described above will be described.

  The image forming method using the image forming apparatus 10 includes the steps of: charging the photosensitive body 32, forming an electrostatic latent image on the charged photosensitive body 32, and charging the photosensitive body 32 on which the electrostatic latent image is formed. The process of supporting the toner corresponding to the electrostatic latent image, the process of transferring the toner carried by the photosensitive body 32 to the transfer material, the process of forming a solid lubricant layer on the surface of the photosensitive body 32, the toner Removing the residue on the photoreceptor 32 after transfer to the transfer material.

  First, the scanner 22 optically scans and reads the document D on the contact glass. Reflected light from the document D is read by the CCD sensor 23 and becomes input image data. The input image data is subjected to image processing in the image processing unit 24 and sent to the exposure device 34.

  The photosensitive member 32 rotates at a constant circumferential speed. The charging device 33 uniformly charges the surface of the photosensitive member 32 to a negative polarity. In the exposure device 34, the polygon mirror of the polygon motor is rotated at high speed, and the laser light corresponding to the input image data of each color component is developed along the axial direction of the photosensitive member 32, and the photosensitive member 32 along the axial direction. The outer peripheral surface of the Thus, an electrostatic latent image is formed on the surface of the photosensitive member 32.

  In the developing device 35, the toner particles are charged by stirring and transporting the two-component developer in the developing container 35A, and the two-component developer is transported to the developing roller and forms a magnetic brush on the surface of the developing roller. The charged toner particles electrostatically adhere to the portion of the electrostatic latent image on the photoreceptor 32 from the magnetic brush. Thus, the electrostatic latent image on the surface of the photosensitive member 32 is visualized, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive member 32. That is, toner corresponding to the electrostatic latent image is carried on the photosensitive member on which the electrostatic latent image is formed.

  The toner image on the surface of the photosensitive member 32 is transferred to the intermediate transfer belt 43 by the intermediate transfer unit 40. When the intermediate transfer belt 43 is in pressure contact with the photosensitive member 32 by the primary transfer roller 44, a primary transfer nip is formed for each photosensitive member 32 by the photosensitive member 32 and the intermediate transfer belt 43. At the primary transfer nip, toner images of the respective colors are sequentially overlapped and transferred onto the intermediate transfer belt 43.

  On the surface of the photosensitive member 32 after transfer, a powdery lubricant in which the rotating brush 36C scrapes the solid lubricant 36D is supplied from the rotating brush 36C to which the rod-shaped solid lubricant 36D is pressed. Applied to

  The pulverized lubricant includes fatty acid metal salt, polyethylene having an acid value, and a charge control agent, and the polyethylene having an acid value has an appropriate polarity, and the composition of the surface of the photosensitive member 32, It has appropriate adhesion and affinity to each of the composition constituting the toner and the fatty acid metal salt. In addition, since polyethylene having an acid value has negative chargeability, it is possible to cancel the positive charge generated by the fatty acid metal salt. Therefore, the lubricant adheres uniformly to the surface of the photosensitive member 32.

  The portion of the surface of the photosensitive member 32 to which the solid lubricant 36D is applied reaches the cleaning blade 36B. The transfer residual toner on the surface of the photosensitive member 32 and the excess solid lubricant 36D are scraped off by the cleaning blade 36B and stored in the cleaning container 36A. Thus, the residual toner after transfer is removed from the surface. On the other hand, the solid lubricant 36D is leveled and spread on the surface of the photosensitive member 32 to form a uniform layer of solid lubricant 36D.

  Further, by applying the solid lubricant 36D to the surface of the photosensitive member 32, the friction between the cleaning blade 36B in contact with the surface of the photosensitive member 32 and the surface of the photosensitive member 32 is in the contact length direction of the cleaning blade 36B. It is alleviated in the whole. Thus, wear of the cleaning blade 36B is suppressed, and wear of the surface of the photosensitive member 32 is also suppressed. As described above, the solid lubricant 36D is applied to the surface of the photoconductor 32 after the toner is transferred to the transfer material and before the residue on the photoconductor 32 is removed, and the film of the solid lubricant 36D is formed. Form

  The surface of the photosensitive member 32 on which the transfer residual toner has been removed by the cleaning device 36 and the layer of the solid lubricant 36 D having a uniform thickness is charged by the charging device 33 again. Since the layer of solid lubricant 36D is uniformly formed on the surface of the photosensitive member 32, the surface of the photosensitive member 32 is uniformly charged. Therefore, the image density unevenness caused by the charging unevenness is prevented.

  On the other hand, the secondary transfer roller 49 is in pressure contact with the backup roller 45 via the intermediate transfer belt 43 and the secondary transfer belt 48. Thus, the intermediate transfer belt 43 and the secondary transfer belt 48 form a secondary transfer nip. The recording medium S passes through the secondary transfer nip. The recording medium S is conveyed by the recording medium conveyance unit 80 to the secondary transfer nip.

  When the recording medium S is conveyed to the secondary transfer nip by the recording medium conveyance unit 80, a transfer bias is applied to the secondary transfer roller 49. By application of the transfer bias, the toner image carried on the intermediate transfer belt 43 is transferred to the recording medium S at the secondary transfer nip. The recording medium S onto which the toner image has been transferred is conveyed by the secondary transfer belt 48 toward the fixing device 60.

  The fixing device 60 forms a fixing nip by the fixing belt 61 and the first pressure roller 63, and heats and presses the conveyed recording medium S at the fixing nip portion. The toner particles constituting the toner image on the recording medium S are heated, the entire toner particles are rapidly melted, the toner component adheres to the recording medium S, and it is rapidly solidified. Thus, the toner image is fixed to the recording medium S. The recording medium S on which the toner image is fixed is discharged to the outside of the apparatus by a discharge unit provided with a discharge roller. Thus, a high quality image is formed.

  The image forming apparatus 10 is not limited to the above configuration. For example, as shown in FIG. 2B, the rotating brush 36C, the solid lubricant 36D and the biasing member 36E may be disposed at a position between the cleaning blade 36B and the charging device 33. In this case, the solid lubricant 36 D is applied to the surface of the photosensitive member 32 before the photosensitive member 32 is charged, after removing the residue on the photosensitive member 32, and the solid lubricant 36 D Form a film of lubricant. The rotating brush 36C, the solid lubricant 36D and the biasing member 36E are located between the transfer device as shown in FIG. 2A and the cleaning blade 36B, and the cleaning blade 36B and the charging device as shown in FIG. 2B. It may be in both of the positions between 33 and 33. In this case, after transferring the toner to the transfer material, before removing the residue on the photosensitive member 32, and after removing the residue on the photosensitive member 32, before charging the photosensitive member 32. The solid lubricant 36D is applied to the surface of the photosensitive member 32 to form a film of the solid lubricant 36D.

  Furthermore, when disposed in the position shown in FIG. 2B, the lubricant application device is a member for leveling the applied lubricant, such as an elastic blade disposed in contact with the surface of the photosensitive member 32 or the like. It may further have an elastic brush, an elastic belt, an elastic roller, and the like.

  The rotating brush 36C is a member to which a lubricant can be supplied from the solid lubricant 36D, such as an elastic belt or an elastic roller, which abuts the surface of the photoconductor 32, and the lubricant is applied to the surface of the photoconductor 32. It may be other application members that can be applied. Furthermore, the rotating brush 36C and the other application members may be arranged to abut the surface of the photosensitive member 32 only at the time of application.

  The solid lubricant 36 D is a block of a rectangular solid integrally formed, but may be any form that can be applied to the surface of the photosensitive member 32, for example, a particulate solid lubricant contained in a container It may be

  Furthermore, the image forming apparatus in the case of using a powdery solid lubricant does not have the rotating brush 36C and the biasing member 36E in the image forming apparatus 10. In this case, the solid lubricant is added to the toner as an external additive, and is applied to the surface of the photosensitive member 32 together with the toner.

  EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

1. Preparation of solid lubricant (solid lubricant 1)
The following components were mixed in the following amounts to prepare a first mixture. At this time, using a Helsinki mixer (Nippon Coke Co., Ltd.) as a mixer, mixing was performed for 3 minutes with a peripheral speed of 35 m / sec and a processing temperature of 32 ° C.
Fatty acid metal salt 920 parts by mass Charge control agent 50 parts by mass Polyethylene 30 parts by mass

  As a fatty acid metal salt, zinc stearate (zinkstearate G; NOF Corporation) was used. As a charge control agent, zinc salicylate complex (BONTRON E-84; Orient Chemical Industry Co., Ltd.) was used. As polyethylene, oxidized polyethylene (High Wax 4051E; Mitsui Chemicals, Inc.) was used.

  The first mixture was used to prepare a rod-like solid lubricant 8 mm long × 10 mm wide × 330 mm long using a general-purpose injection molding machine.

(Solid lubricant 2)
No. The charge control agents of No. 1 and No. 1 shown in Table 1 were used. A solid lubricant 2 was produced in the same manner as the solid lubricant 1 except that the charge control agent was changed to No. 2. No. As a charge control agent of 2, the salicylic acid chromium complex (BONTRON E-81; Orient Chemical Industries, Ltd., "BONTRON" is a registered trademark of the company) was used.

(Solid lubricant 3)
No. The charge control agents of No. 1 and No. 1 shown in Table 1 were used. A solid lubricant 3 was produced in the same manner as the solid lubricant 1 except that the charge control agent was changed to No. 3. No. As a charge control agent of 3, an azo compound chromium complex (BONTRON S-34; Orient Chemical Industry Co., Ltd.) was used.

(Solid lubricant 4)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 4 was produced in the same manner as the solid lubricant 1 except that the polyethylene of 2 was used. No. As polyethylene of 2, the polyethylene oxide (AC 395; Honeywell Japan Ltd.) was used.

(Solid lubricant 5)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 5 was produced in the same manner as the solid lubricant 1 except that it was changed to polyethylene of 3. No. As polyethylene of 3, the polyethylene oxide (high wax 210MP; Mitsui Chemical Co., Ltd.) was used.

(Solid lubricant 6)
No. The fatty acid metal salt of No. 1 is shown in Table 1. A solid lubricant 5 was produced in the same manner as the solid lubricant 1 except that it was changed to a fatty acid metal salt of 2. No. As fatty acid metal salt of 2, zinc oleate (Daiwax OZ; Dainichi Chemical Industry Co., Ltd.) was used.

(Solid lubricant 7)
No. The charge control agents of No. 1 and No. 1 shown in Table 1 were used. A solid lubricant 7 was produced in the same manner as the solid lubricant 6 except that the charge control agent was changed to No. 4. No. As a charge control agent of 4, the diketone zinc silicate complex (BONTRON P-16; Orient Chemical Industry Co., Ltd.) was used.

(Solid lubricant 8)
No. The charge control agents of No. 1 and No. 1 shown in Table 1 were used. A solid lubricant 8 was produced in the same manner as the solid lubricant 8 except that the charge control agent was changed to No. 5. No. As the charge control agent of No. 5, hydrophobic silica (AEROSIL R-805; Nippon Aerosil Co., Ltd., “AEROSIL” is a registered trademark of Evonik Degussa Co., Ltd.) was used.

(Solid lubricant 9)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 9 was produced in the same manner as the solid lubricant 1 except that polyethylene of 4 was used. No. As polyethylene No. 4, acid-modified polyethylene (High Wax 1105A; Mitsui Chemical Co., Ltd.) was used.

(Solid lubricant 10)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 10 was produced in the same manner as the solid lubricant 1 except that the polyethylene of No. 5 was used. No. As polyethylene of 5, the acid-modified polyethylene (AC 405; Honeywell Japan Ltd.) was used.

(Solid lubricant 11)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 10 was produced in the same manner as the solid lubricant 1 except that the polyethylene of No. 6 was used. No. As polyethylene of 6, the acid-modified polyethylene (AC 5120; Honeywell Japan Ltd.) was used.

(Solid lubricant 13)
No. A solid lubricant 13 was produced in the same manner as the solid lubricant 1 except that the polyethylene of 1 was not contained.

(Solid lubricant 14)
No. No. 1 shown in Table 1 was obtained. A solid lubricant 14 was produced in the same manner as the solid lubricant 1 except that the polyethylene of 7 was used. No. As polyethylene No. 7, polyethylene without oxidation (High Wax NP055; Mitsui Chemical Co., Ltd.) was used.

  About solid lubricants 1-14, classification, solid lubricant No. 1. The fatty acid metal salt, polyethylene and charge control agent are shown in Table 1.

2. Evaluation of solid lubricant The image memory, the charging unevenness and the coating thickness unevenness were evaluated for each lubricant.

(1) Evaluation of image memory Evaluation of the image memory can be made by using a commercially available image forming apparatus (Bizhub Pro C1100; Konica, equipped with solid lubricants 1-11, 13 and 14 under conditions of temperature 20 ° C. and humidity 50% RH). Minolta Co., Ltd., “bizhub” is a registered trademark of the company, printed as shown below, and evaluated based on the printed image output.

Image chart with 100% printing rate (cyan) in the left half and 0% printing rate in the right half toward the transport direction of recording medium A (A3 size J paper; Konica Minolta Business Solutions Inc.) The sheet was printed on 100 sheets of recording medium A using solid lubricants 1 to 11, 13 and 14 (also referred to as “image chart A”). Next, an image chart (hereinafter also referred to as “image chart B”), which is a halftone image with a printing rate of 40% (cyan), on the entire surface of the recording medium B (POD gloss coated paper; 128 g / m ² ), Printing was made on recording medium B. Finally, in the recording medium B on which the image chart B is printed, the density difference of the printed image is between the area corresponding to the printing rate of 100% of the image chart A and the area corresponding to the printing rate of 0% of the image chart A. It was confirmed whether there was any. Then, solid lubricants 1 to 11, 13 and 14 were evaluated according to the following criteria.

Rank 5: Fit: Magnified observation with a 20 × magnification microscope can not confirm the density difference of the printed image.
Rank 4: Conformance: Although the density difference of the printed image can not be confirmed visually, the density difference of the printed image can be confirmed if magnified and observed using a microscope with a magnification of 20 times.
Rank 3: Conformance: Although the difference in density of the printed image can not be confirmed by ordinary visual observation, the printed image can be obtained by staring at a close distance from about 10 ° diagonally above the recording medium B disposed immediately below the fluorescent lamp. The difference in concentration can be confirmed.
Rank 2: Incompatible: Regardless of the angle at which the recording medium B is observed, the density difference of the printed image can be visually confirmed.
Rank 1: Nonconformity: The density difference of the printed image can be clearly confirmed visually.

  The solid lubricant 1 was pulverized for 10 minutes using a Helsinki mixer (Nippon Coke Co., Ltd.) at a rotor peripheral speed of 35 m / sec and a treatment temperature of 32 ° to obtain a powdery solid lubricant 12. Obtained. Using 4 parts by mass of solid lubricant 12 powder and 100 parts by mass of cyan toner for Bizhub Rro C1100, using a Helsinki mixer (Nippon Coke Co., Ltd.), the peripheral blade speed is 35 m / sec, and the processing temperature is 32 ° C 30 A mixing process was performed for a minute to obtain a cyan toner to which the powdery solid lubricant 12 was externally added. The cyan toner to which the powdery solid lubricant 12 was externally added and the cyan toner mounted as standard on Bizhub Rro C1100 were substituted. Furthermore, the lubricant rod mounted as standard on the drum unit for cyan toner printing was removed. And it printed similarly to the case where solid lubricants 1-11, 13 and 14 were used, and evaluated similarly.

(2) Charging unevenness evaluation The charging unevenness is evaluated by printing the image chart A on 100 sheets of the recording medium A using solid lubricants 1 to 14 and then printing the image chart A on the surface of the photosensitive member after printing. The surface potential difference ΔV between the area of 100% printing rate and the area of 0% printing rate was measured. The measurement of the surface potential of the photosensitive member surface was carried out using a modified machine provided with a surface voltmeter instead of the developing means of the above-mentioned commercially available image forming apparatus (Bizhub Pro C1100; Konica Minolta Co., Ltd.). It was prepared to be Then, it was determined that the surface potential difference ΔV was 40 V or less.

(3) Evaluation of coating thickness nonuniformity Evaluation of coating thickness nonuniformity is printing of the image chart A on the surface of the photosensitive member after printing after printing on 100 sheets of the recording medium A using solid lubricants 1 to 14 It carried out by measuring the light absorbency of the area | region of 100% of area | region, and the area | region of 0% of printing ratio, respectively. The measurement of the absorbance was performed using a reflection spectrophotometer (FE-3000; Otsuka Electronics Co., Ltd.) on the surface of the photosensitive member removed from the image forming apparatus after printing 100 sheets. It is considered that the smaller the decrease in absorbance of the portion corresponding to the area of 0% coverage to the area corresponding to the area of 100% coverage, the smaller the influence of film thickness reduction due to scraping, and the smaller the coating thickness unevenness. . And when it satisfied the following formula, it was considered as adaptation.
Part corresponding to area of 100% printing ratio / part corresponding to area of 100% printing ratio × 100> 50 (%)

  About solid lubricants 1-14, classification, solid lubricant No. 1. The evaluation results of the image memory, the evaluation results of the charging unevenness and the evaluation results of the coating thickness unevenness are shown in Table 2.

  As shown in Table 2, in the solid lubricant 13 according to the comparative example, since polyethylene having an acid value was not contained, the image memory, the charging unevenness and the coating thickness unevenness were poor. This is because the solid lubricant 13 does not contain polyethylene having an acid value, there is no polar group that reacts with the functional group on the surface of the photoreceptor, and the adhesion of the solid lubricant 13 to the photoreceptor is increased. It is thought that it was not there. Further, in the solid lubricant 14 according to the comparative example, since polyethylene does not have an acid value, the image memory, the charging unevenness and the coating thickness unevenness were poor. This is considered to be because the adhesion of the solid lubricant to the photosensitive member did not increase because polyethylene contained in the solid lubricant 14 does not have an acid value.

  On the other hand, in the solid lubricants 1 to 12 containing a fatty acid metal salt, a charge control agent, and polyethylene having an acid value of 1 mg KOH / g or more, image memory, charging unevenness and coating thickness unevenness were good. Since the solid lubricant contains polyethylene having a predetermined acid value, the affinity between the solid lubricant and the surface of the photoreceptor is improved, and the positive charge of the fatty acid metal salt can be further canceled. It was thought that it was something. Further, from the results of the solid lubricants 1 and 12, the solid lubricant according to the present embodiment has good image memory, charging unevenness and coating thickness unevenness regardless of the form.

  When solid lubricants 1 to 5 and 7 to 12 are used, the surface potential of the portion corresponding to the area of 0% printing ratio is the surface potential of the surface of the portion corresponding to the area of 100% printing ratio. When the image memory is observed, the image density in the area where the printing rate is 0% in the image chart B is relatively higher than the image density in the area where the printing rate is 100%. It was observed as a positive memory. In addition, when the solid lubricant 6 was used, the surface potential of the region where the printing ratio was 0% was higher than the surface potential of the region where the printing ratio was 100%, and was observed as a negative memory.

  According to the present invention, in the electrophotographic photosensitive member of the electrophotographic image forming apparatus, the image memory, the charging unevenness, and the coating thickness unevenness can be enhanced, and such characteristics can be exhibited over a long period of time. be able to. Therefore, according to the present invention, further high durability and further spread of the electrophotographic image forming apparatus are expected.

DESCRIPTION OF SYMBOLS 10 image forming apparatus 20 image reading unit 21 sheet feeding device 22 scanner 23 CCD sensor 24 image processing unit 30 image forming unit 31 image forming unit 32 photoreceptor 33 charging device 34 exposure device 35 developing device 35A developing container 36 cleaning device 36A cleaning container 36B cleaning blade 36C rotating brush 36D solid lubricant 36E biasing member 40 intermediate transfer portion 41 primary transfer unit 42 secondary transfer unit 43 intermediate transfer belt 44 primary transfer roller 45 backup roller 46 first support roller 47 cleaning device 48 secondary transfer Belt 49 Secondary transfer roller 50 Second support roller 60 Fixing device 61 Fixing belt 64 Second pressure roller 80 Recording medium conveyance unit 81 Paper feed tray unit 82 Registration roller Pair D document S recording medium

Claims (8)

A solid lubricant which is applied to the surface of an image carrier of an image forming apparatus in the electrophotographic system to form a layer of a solid lubricant on the surface of the image carrier,
Fatty acid metal salt,
Charge control agent,
Contains polyethylene and
The acid value of the polyethylene is 1 mg KOH / g or more.
Solid lubricant. The fatty acid metal salt is zinc stearate,
The charge control agent is a negatively chargeable charge control agent.
The solid lubricant according to claim 1.   The solid lubricant according to claim 1, wherein the charge control agent is a metal complex.   The solid lubricant according to any one of claims 1 to 3, wherein the polyethylene is oxidized polyethylene.   The solid lubricant according to any one of claims 1 to 4, wherein the acid value of the polyethylene is 80 mg KOH / g or less.   The solid lubricant according to any one of claims 1 to 5, which is formed in a rod shape. A step of charging the image carrier, a step of forming an electrostatic latent image on the charged image carrier, and allowing the toner corresponding to the electrostatic latent image to be carried on the image carrier on which the electrostatic latent image is formed The steps of: transferring the toner carried on the image carrier to a transfer material; forming a solid lubricant layer on the surface of the image carrier; and transferring the toner onto the transfer material. And removing the residue on the support.
The image formation method which uses the solid lubricant as described in any one of Claims 1-6 for the said solid lubricant.   After transferring the toner to the transfer material, before removing the residue on the image carrier, and after removing the residue on the image carrier, before charging the image carrier 8. The image forming method according to claim 7, wherein the solid lubricant is applied to the surface of the image bearing member to form a film of the solid lubricant.

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