JP4366153B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus of a type that develops an electrostatic latent image on an organic photoreceptor with a two-component developer. More specifically, an electrophotographic photosensitive member, a charging unit that charges the photosensitive member, a latent image forming unit that forms an electrostatic latent image on the charging surface of the photosensitive member, and a two-component developer carried on the developer carrier. Developing means for developing the electrostatic latent image on the photosensitive member as a toner image, transferring means for transferring the toner image on the photosensitive member to the transferred member side by applying an electric field between the photosensitive member and the transferred member, and the toner image The present invention relates to an image forming apparatus including a cleaning unit that collects residual toner particles on the surface of a photoreceptor after transfer.

  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 and an electrostatic recording dielectric. For example, in electrophotography, an electric latent image is formed by performing image pattern exposure after uniformly charging a photoconductor using a photoconductive material as a photoconductor to a required polarity and potential. In general, the toner is developed with a toner to be visualized, and this is transferred and fixed on a transfer medium such as paper. Conventionally, as this type of image forming apparatus, there is one that uses an electrophotographic photosensitive member that is highly resistant to shaving and highly durable (see, for example, Patent Document 1).

In an electrophotographic image forming apparatus, it is known that various discharge products such as NO _x , SO _x, and ozone are generated by charging energy when charging a photosensitive member. These discharge products adhere to the photoreceptor and deteriorate the slipperiness of the photoreceptor surface. At this time, if the photosensitive member (hereinafter sometimes referred to as “photosensitive drum” or “drum”) is highly durable, the surface thereof is difficult to be refreshed, and when the drum is scraped, the lubricating action by the generated powder is also expected. Hard to do. When the toner remaining on the drum after toner transfer is cleaned with a blade, the friction between the photosensitive member and the cleaning blade used for the cleaning increases, and a phenomenon called vibration occurs that causes the blade to vibrate. Thus, the external additive and the toner are easily removed. In addition, foreign particles such as toner particles and paper dust are easily caught between the cleaning blade and the drum, and the toner tends to stay in one place.

For these problems, it is necessary to form a dampening layer having sufficient lubricity and toner blocking capability on the cleaning blade. For this purpose, a means for providing a lubricant supply member or a means for making the charging part and transfer part also serve as a lubricant supply means has been proposed, but from the viewpoint of maintenance such as space saving and replacement of lubricant supply parts. Preferably not. Means for causing the lubricant supply means to also serve as a charging portion and a transfer portion have been proposed, but in that case, the lubricant must be supplied. On the other hand, if the means also serves to supply the lubricant to the developer, the lubricant is automatically supplied when the developer is supplied. In that case, it is preferable to stabilize the damming layer by increasing the amount of the external additive as much as possible so that the lubricant is sufficiently supplied to the cleaning blade.
JP 2000-66425 A

However, in a two-component developer that can achieve higher image quality as a developer than a one-component developer, the external additive other than the toner base and carrier increases the friction between the toner and the carrier when the amount of the external additive is increased. Charging is hindered and external additives are likely to accumulate, and the amount of external additives that can be added is small compared to a one-component developer. For this reason, the amount of the external additive supplied to the cleaning blade and the drum contact portion such as toner remaining after transfer is small, and foreign matters such as carrier, toner and paper dust are easily caught between the blade portions, and the drum is easily damaged. Therefore, in the case of a two-component developer, it is necessary to provide an effective auxiliary cleaning effect for the external additive without increasing the amount of external addition.
Accordingly, an object of the present invention is to provide an image forming apparatus that achieves both high image quality with a two-component developer and long life with a highly durable drum, and has a simple structure and easy maintenance.

In order to achieve the above object, the present invention provides:
(1) It has a photosensitive layer on a conductive support, and the surface of the photosensitive layer has a surface protective layer containing a polymer of a hole transporting compound represented by the following formula (2), at a temperature of 25 ° C. and humidity. A hardness test is performed using a Vickers square pyramid diamond indenter in a 50% environment, and the HU (universal hardness value) when pressed with a load of maximum 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and An electrophotographic photosensitive member having an elastic deformation rate of 44% or more and 65% or less of the photosensitive layer, charging means for charging the surface of the photosensitive member, and latent image formation for forming an electrostatic latent image on the charging surface of the photosensitive member Developing means for developing the electrostatic latent image as a toner image by a two-component developer comprising toner and carrier containing external additives, transfer means for transferring the toner image to a recording medium, and transfer residual toner. Cleaning means to remove from the photoreceptor. In the image forming apparatus , the liberation rate of the external additive from the toner is 1% by number or more and 50% by number or less, and the average primary particle diameter of the external additive is 0.07 μm or more and 2.0 μm. An image forming apparatus characterized by the following is provided.

  Further, according to the present invention, the liberation rate of the external additive is 1.5% by number or more and 30% by number or less, and the cleaning unit pushes the elastic blade against the photosensitive drum. In the image forming apparatus (3) of (1) or (2), which is a means for cleaning the toner by contact, the ratio of the amount of external additive to the toner is 0.2% or more and 3.1% or less. The image forming apparatus (4) according to any one of the above (1) to (3) and the above (1) to (3) wherein the external additive amount of the external additive to the toner is 0.3% or more and 2.6% or less. An image forming apparatus (5) is provided.

As a result of intensive studies by the present inventors, a hardness test was performed using a Vickers square pyramid diamond indenter in an environment with a surface temperature of 25 ° C. and a humidity of 50%, and the HU (universal hardness value) when indented with a maximum load of 6 mN. ) Is 150 N / mm ² or more and 220 N / mm ² or less, and an electrophotographic photosensitive member having an elastic deformation rate of 44% or more and 65% or less is developed with a two-component developer containing a carrier. In the image forming apparatus in which the developed toner is transferred to a medium such as paper and the transfer residual toner on the photosensitive member is cleaned with a cleaning blade, the average particle diameter of primary particles is used as an external additive in the two-component developer. Of 0.07 μm or more and 2.0 μm or less, and the liberation rate of the external additive from the toner base is 1% by number or more and 50% by number or less, depending on the appropriate elasticity and hardness of the photoreceptor. Very good high To demonstrate the durability and the photoconductor - toner between the cleaning blade and it found that easily act as a lubricant.

  This is because when a highly durable photoconductor whose surface is hard to scrape is rubbed against the cleaning blade, a phenomenon called a chatter occurs that causes the external additive and toner to come off easily. If this happens, foreign particles such as toner particles and paper dust may be caught between the cleaning blade and the photoconductor, and it will easily stay in one place, which will easily cause scratches on the photoconductor. The presence of external additive particles having an average particle size of 0.07 μm or more and 2.0 μm or less improves the catching between the toner base and the antiskid layer, makes it easy to dampen the toner base and is free from the toner. In order to separate the toner from the toner and form a stable and sufficient amount of blocking layer, foreign particles such as toner particles and paper dust are sandwiched between the cleaning blade and the drum. This is because it is suppressed and scratches are less likely to occur on the photoconductor. Even if particles having an average primary particle size of 0.07 μm or more and 2.0 μm or less are present, if the release rate is low, it is difficult to form a blocking layer. Conversely, even if the release rate from the toner is high, the primary particle If there is no particle having an average particle diameter of 0.07 μm or more and 2.0 μm or less, it becomes difficult to dam the toner and the damaging layer is easily broken. However, if the liberation rate exceeds 50% by number, it is not preferable because an external additive is easily accumulated in the developing device and the developing performance is remarkably deteriorated. From the above, there are externally added particles having an average primary particle size of 0.07 μm or more and 2.0 μm or less, and it is necessary to suppress the liberation rate of the external additive within a certain range.

According to the present invention, the HU (universal hardness value) when pushed in with the maximum load of 6 mN under the above measurement conditions 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%. In an image forming apparatus for developing with the two-component developer for the following electrophotographic photosensitive member, the primary particle has an external additive having an average particle size of 0.07 μm or more and 2.0 μm or less, and the external additive By making the total liberation rate of 1% to 50% by weight, it is possible to apply and supply the lubricant to the photoconductor with a simple configuration, prevent deterioration of the drum due to the photoconductor cleaning blade, and high An image forming apparatus having high image quality and high durability can be provided.

  FIG. 1 shows an example of an image forming apparatus according to the present invention. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a digital copying machine. The copying machine shown in FIG. 1 (hereinafter also referred to as “image forming apparatus”) includes a drum-type electrophotographic photosensitive member 101 as a photosensitive member. The photosensitive drum 101 is rotationally driven in a direction indicated by an arrow by a driving unit (not shown). Around the photosensitive drum 101, a charging roller 102, which is a primary charging unit, an exposure device 103, a developing device (developing unit) 104, a transfer charging unit (transfer unit) 105, and a separation charging unit are arranged almost sequentially along the rotation direction. 106 is arranged. Further, a fixing device 107 is disposed on the downstream side (left side in the figure) of the separation charger 106 in the conveyance direction (arrow direction) of the transfer material 111. The surface of the photosensitive drum 101 is uniformly charged by the charging roller 102. Next, image exposure is performed by the laser beam emitted from the exposure device 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 photosensitive drum 101 is developed with the charged toner of the developing device 104. The developed toner image on the photosensitive drum 101 is transferred by the transfer charger 105 to the transfer material 111 conveyed in the direction of the arrow. The transfer material 111 after the toner image is transferred is separated from the surface of the photosensitive drum 101 by the separation charger 106 and conveyed to the fixing device 107. The transfer material 111 is heated and pressed here to fix the toner image on the surface. The untransferred toner remaining on the photoconductor after the transfer is collected and removed by an elastic cleaning blade in contact with the counter of the drum of the cleaning device 108. Each of the above members and processes will be described in detail below.

[Photoconductor]
A photosensitive drum 101 in FIG. 1 is a rotating drum type electrophotographic photosensitive member as a photosensitive member (charged member). The electrophotographic photosensitive member of the image forming apparatus of this example (the present invention) is an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and the photosensitive layer has the same intramolecular structure as represented by the following general formula (1). And an electrophotographic photoreceptor containing a compound obtained by polymerizing a hole transporting compound having two or more chain polymerizable functional groups.

（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。又、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、又、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 represent a chain polymerizable functional group. P ¹ and P ² may be the same or different. Z may have a substituent. A, b and d are 0 or an integer of 1 or more, a + b × d is an integer of 2 or more, and when a is 2 or more, P ¹ may be the same or different , D is 2 or more, P ² may be the same or different, and when b is 2 or more, Z and P ² may be the same or different.)

  In this example, by polymerizing a hole transporting compound having two or more chain-polymerizable functional groups in the same molecule, in the photosensitive layer, the compound having a hole transporting ability is at least two crosslinked. It is incorporated into the three-dimensional crosslinked structure with a point through a covalent bond. The hole transporting compound can be polymerized only by itself, or can be mixed and polymerized with a compound having another chain polymerizable group, and the kind and ratio thereof are all arbitrary. The compound having another chain polymerizable group referred to here includes any of a monomer, an oligomer and a 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 three-dimensional cross-linked structure by copolymerization via a covalent bond. It 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 kinds of three-dimensional cured products or other chain-polymerizable compound monomers or the like in a main component three-dimensional cured product. Although it is comprised as what contains hardened | cured material, it is also possible to form IPN (Inter Penetrating Network), ie, an interpenetrating network structure, by controlling the compounding ratio and the film forming method well.

In this example, the photosensitive layer contains at least one selected from the group consisting of a fluorine atom-containing resin, a carbon fluoride, and a polyolefin-based resin as a lubricant. Preferred examples of the compound include the following. However, this example is not limited to these compounds. Preferred as the fluorine atom-containing resin is a polymer or copolymer of a compound selected from the group consisting of vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoropropylene, and perfluoroalkyl vinyl ether. Examples thereof include polymer resins and resin fine particles. Examples of the carbon fluoride include a compound represented by (CF) _n or (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 resin and ethylene-butene copolymer resin, and resin powder. These lubricants can be used alone or in combination of two or more at any ratio. Further, the photosensitive layer of this example may further contain a surfactant, etc., in addition to the lubricant dispersant, dispersion aid, and other various additives.

  The structure of the photoreceptor used in this example includes a structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are stacked in this order as a photosensitive layer on a conductive support. It is possible to take any configuration of a single layer in which a substance and a charge transporting substance are dispersed in the same layer. In the former laminated type, a structure having two or more charge transport layers is also possible. In any of these cases, the photosensitive layer only needs to contain the polymer of the hole transporting compound having the chain polymerizable group. However, in view of characteristics as an electrophotographic photosensitive member, in particular, electrical characteristics such as residual potential and durability, it is a functionally separated layer structure in which a charge generation layer / charge transport layer are laminated in this order, and at least charge transport. The layer preferably contains a polymer of a hole transporting compound having the chain polymerizable group, and the surface layer can be highly durable without deteriorating the charge transporting ability.

  In this example, the slipping property and water repellency of the surface of the photoreceptor can be improved by containing at least one of fluorine atom-containing resin, carbon fluoride and polyolefin resin as a lubricant in the photosensitive layer. Prevents deterioration in transfer efficiency and slipperiness due to chemical deterioration of the surface layer due to charging, development, transfer, etc. during use, as well as deterioration in electrical properties such as sensitivity reduction and potential reduction. It is possible to suppress the occurrence of image defects such as image forming, fusing, cleaning failure, and image blur / flow. Particularly preferable results are obtained when the fluorine atom-containing resin is used. In this example, it is most effective to add the lubricant to the surface layer of the photoreceptor in any case.

  Next, a method for producing the electrophotographic photoreceptor in this example will be specifically described. The support for the electrophotographic photosensitive member may have any conductivity, for example, aluminum, copper, chromium, nickel, zinc, stainless steel or other metal or alloy formed into a drum or sheet, aluminum and copper Metal foils such as those laminated on plastic films, aluminum, indium oxide, tin oxide, etc. deposited on plastic films, metals with conductive layers applied alone or with binder resin, plastic films And paper. In this example, an undercoat layer having a barrier function and an adhesive function can be provided on the conductive support. The undercoat layer can be used to improve the adhesion of the photosensitive layer, improve coating properties, protect the support, cover defects on the support, improve charge injection from the support, or protect against electrical breakdown of the photosensitive layer. Formed for. Materials for the undercoat layer include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, ethylene-acrylic acid copolymer, casein, polyamide, N-methoxymethylated 6 nylon, copolymer nylon, glue and gelatin Etc. are known. These are dissolved in a solvent suitable for each and coated on a support. The film thickness at that time is preferably 0.1 to 2 μm.

  When the photoreceptor used in this example is a function separation type photoreceptor, a charge generation layer and a charge transport layer are laminated. Examples of the charge generation material used in the charge generation layer include selenium-tellurium, pyrylium, thiapyrylium dyes, organic dyes having various central metals and crystal systems, specifically, for example, α, β, γ, ε, and X type Phthalocyanine compounds, anthanthrone pigments, dibenzpyrenequinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, monoazo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanine pigments, quinocyanines, and quinocyanine Examples thereof include amorphous silicones described in the publication. In the case of a function-separated type photoconductor, the charge generation layer includes the charge generation material, such as a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, etc. It is well dispersed by a method, and the dispersion is applied and dried, or formed as a single composition film such as a vapor-deposited film of the charge generation material. The film thickness is preferably 5 μm or less, and particularly preferably in the range of 0.1 to 2 μm. Examples of using binder resins are polymer resins of vinyl compounds such as polystyrene resins, polyvinyl acetate resins, polyvinyl chloride resins, acrylic ester resins, methacrylic ester resins, vinylidene fluoride resins, trifluoroethylene resins, etc. And copolymer resins, polyvinyl alcohol resins, polyvinyl acetal resins, polycarbonate resins, polyester resins, polysulfone resins, polyphenylene oxide resins, polyurethane resins, cellulose resins, phenol resins, melamine resins, silicon resins, and epoxy resins.

  In the present example, the hole transporting compound having a chain polymerizable functional group has a charge transport layer on the charge generation layer described above or a charge transport layer composed of a charge transport material and a binder resin on the charge generation layer. After forming, it can be used as a surface protective layer having a hole transport capability. In any case, the surface layer is generally formed by applying a polymerization reaction after applying the solution containing the hole transporting compound, but the solution containing the hole transporting compound is reacted in advance. Then, after obtaining a cured product, it is possible to form a surface layer by dispersing or dissolving in a 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. From the viewpoint of efficiency and productivity, the dip coating method is preferable. Also, vapor deposition, plasma, and other known film forming methods can be selected as appropriate.

  In this example, the hole transporting compound having a chain polymerizable group is preferably polymerized by radiation. The greatest advantage of radiation polymerization is that it does not require a polymerization initiator, which makes it possible to produce a photosensitive layer made of a very high-purity three-dimensional cross-linked polymer and ensure good electrophotographic properties. Is a point. In addition, since the polymerization reaction is a short time and efficient polymerization reaction, the productivity is high, and further, due to good radiation transmission, a shielding material such as a thick film or an additive is present in the film. The influence of the inhibition of curing at the time 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, the polymerization initiator can be added within a range that does not affect the polymerization reaction. The radiation used at this time is an electron beam and a γ-ray. In the case of electron beam irradiation, any of a scanning type, an electro curtain type, a broad beam type, a pulse type, and a laminar type can be used as an accelerator. In the case of irradiating an electron beam, the irradiation conditions are very important in the photoreceptor of this example in order to develop electric characteristics and durability. In this example, 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 1,000 kGy, more preferably in the range of 30 kGy to 500 kGy. When the acceleration voltage exceeds the above range, 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 deteriorate.

  The amount of the hole transporting compound when the hole transporting compound having a chain polymerizable group is used as a material for the charge transporting layer is the above general formula with respect to the total mass of the charge transporting layer film after polymerization. It is desirable that the hydrogenated product of a hole transporting compound having a chain polymerizable functional group represented by (1) is contained in an amount of 20% or more, preferably 40% or more in terms of molecular weight. If it is less than that, the charge transporting ability of the formed charge transport layer is lowered, and problems such as a decrease in sensitivity as a photoreceptor and an increase in residual potential occur. In this case, the thickness of the charge transport layer is preferably 1 to 50 μm, and particularly preferably 3 to 30 μm.

  When the hole transporting compound is used as a surface protective layer on the charge generation layer and the charge transport layer, the charge transport layer corresponding to the lower layer is an appropriate charge transport material such as poly-N-vinylcarbazole, polystyrylanthracene, etc. High molecular weight compounds having a heterocyclic ring or condensed polycyclic aromatic ring, heterocyclic compounds such as pyrazoline, imidazole, oxazole, triazole and carbazole, triarylalkane derivatives such as triphenylmethane, and triarylamine derivatives such as triphenylamine A low molecular weight compound such as a phenylenediamine derivative, an N-phenylcarbazole derivative, a stilbene derivative, or a hydrazone derivative is dispersed and dissolved in a solvent together with an appropriate binder resin (which can be selected from the aforementioned resin for charge generation layer). The solution is applied and dried by the known method described above. It can be formed. In this case, the ratio of the charge transport material to the binder resin is preferably selected in the range of 30 to 100, preferably 50 to 100, when the total mass of both is 100. If the amount of the charge transporting material is less than that, the charge transporting ability of the charge transporting layer is lowered, and problems such as a decrease in sensitivity and an increase in residual potential occur as a photoreceptor. The film thickness of the charge transport layer is determined so that the total film thickness combined with the upper surface protective layer is 1 to 50 μm, and is preferably adjusted in the range of 5 to 30 μm. In this example, in any of the cases described above, the charge transport material can be contained in a photosensitive layer containing a cured product of the hole transport compound having the chain polymerizable group.

  In the case of a single-layer type photosensitive layer, a charge generating substance is simultaneously contained in the solution containing the hole transporting compound, and this solution may be provided with an appropriate undercoat layer or intermediate layer. The hole transporting compound is contained on a single layer type photosensitive layer composed of a charge generation material and a charge transport material provided on a conductive support, and a case where it is formed by a polymerization reaction after coating on the body. Any of the cases where the polymerization reaction is performed after the application of the solution is possible.

  In this example, the ratio of the lubricant contained in the photosensitive layer is preferably 1 to 70%, more preferably 5 to 50%, based on the total mass 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. A photoconductor having a surface layer containing a hole transporting compound obtained by polymerizing a compound having an unsaturated functional group in the molecule, produced as described above, is disclosed in Japanese Patent Application Laid-Open No. 2001-166509. The problems of the electrophotographic photoreceptor using the above resin as a surface layer are solved, the film strength is increased to improve the wear resistance and scratch resistance, and the precipitation resistance is good, There is very little change or deterioration in the characteristics of the electrophotographic photosensitive member such as an increase in the residual potential during repeated use, and stable performance can be exhibited even during repeated use, and the abrasion resistance of the surface layer of the electrophotographic photosensitive member and The electrophotographic photosensitive member has improved scratch resistance, long life and high image quality.

この感光ドラムは矢印の方向に２１０ｍｍ／ｓｅｃ.の周速度をもって回転駆動される。保護層の膜厚は表面層の磨耗量と電子写真装置の寿命との関係から最適な膜厚が決定できるが、図１に示す例では５μｍとなるように塗工条件を調整した。
In the copying machine shown in FIG. 1 employs a reversal development, the photosensitive drum 101, after overlaid with 4-layer on an aluminum cylinder having a diameter of 30 mm, as a surface protective layer, the electron beam irradiation of the formula (2) polymerization hole-transporting compound coating was cured those having containing an organic photosensitive drum to form a surface layer.

This photosensitive drum is driven to rotate in the direction of the arrow at a peripheral speed of 210 mm / sec. The film thickness of the protective layer can be determined from the relationship between the amount of wear of the surface layer and the life of the electrophotographic apparatus, but the coating conditions were adjusted to 5 μm in the example shown in FIG.

This electrophotographic photosensitive member is subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of a temperature of 25 ° C. and a humidity of 50%, and a HU (Universal Hardness Value) when pressed with a load of 6 mN at the maximum is 150 N / mm ^2. The electrophotographic photosensitive member has an elastic deformation rate of 44% or more and 65% or less and not less than 220 N / mm ² . The HU (universal hardness value) and elastic deformation rate in this example are the microhardness measuring device Fischer that continuously applies the load to the indenter, directly reads the indentation depth under the load, and obtains the continuous hardness. Measurement was performed using a scope 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. 3, and an example in which the electrophotographic photosensitive member of this example 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 similarly.

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

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 of the indenter on the membrane, and the value can be obtained from the following equation (ii). The total work Wt (nW) is represented by an area surrounded by A-B-D-A in FIG. 3, and the elastic deformation work We (nW) is represented by an area surrounded by C-B-D-C. Is done.

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 found that mechanical deterioration of the surface layer of the photoconductor hardly occurs 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. The use of a certain electrophotographic photosensitive member has improved dramatically. Moreover, 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 the HU and the elastic deformation rate cannot be separated, for example, when the HU exceeds 220 N / mm ² , the elastic force of the photosensitive member is insufficient when the elastic deformation rate is less than 44%. Therefore, if the elastic deformation rate is larger than 65%, even if the elastic deformation rate is high, the elastic deformation amount becomes small. As a result, a large pressure is applied locally, resulting in deep scratches on the photoreceptor. Therefore, it is considered that the one with a high HU is not necessarily optimal as the photosensitive member. Also, if 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 is By rubbing, the photoconductor may be scraped or fine scratches may occur.

[Charging]
In FIG. 1, reference numeral 102 denotes a conductive elastic roller (charging roller) as a flexible contact charging member disposed in contact with the photosensitive drum 101 with a predetermined pressing force. The charging roller 102 as a contact charging member in this example is formed by forming an intermediate resistance layer made of rubber or foam on a cored bar. The middle resistance layer was formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfurizing agent, a foaming agent, and the like, and was formed in a roller shape on the core metal. Thereafter, the surface was polished as necessary. The roller resistance of the charging roller 102 of this example was measured and found to be 100 kΩ. The roller resistance was measured by applying 100 V between the metal core and the aluminum substrate in a state where the charging roller 102 was pressure-bonded to the aluminum substrate having a diameter of 30 mm so that a total pressure of 1 kg was applied to the metal core of the charging roller 102. .

Here, it is important that the charging roller 102 as a contact charging member functions as an electrode. In other words, it is necessary to provide a sufficient contact state with the object to be charged by providing elasticity, and at the same time to have a sufficiently low resistance to charge the moving object to be charged. On the other hand, it is necessary to prevent voltage leakage when a to-be-charged body has a low breakdown voltage defect portion such as a pinhole. 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. Furthermore, it is desirable that the surface of the charging roller 102 has micro unevenness so that the lubricant can be held. If the hardness of the charging roller 102 is too low, the shape is not stable, so that 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 member to be charged is deteriorated, the preferred 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 substance is dispersed, and those obtained by foaming these materials. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive material. The charging roller 102 is arranged to be pressed against the photosensitive drum 101 as a member to be charged with a predetermined pressing force against elasticity, and in this example, a charging nip portion having a width of several mm is formed.

[exposure]
In FIG. 1, reference numeral 103 denotes a laser beam scanner (exposure apparatus) including a laser diode and a polygon mirror. The laser beam scanner 103 outputs laser light whose intensity is modulated in accordance with the time-series electric digital pixel signal of the target image information, and scans and exposes the uniformly charged surface of the rotating photosensitive drum 101 with the laser light ( L). By this scanning exposure L, an electrostatic latent image corresponding to target image information is formed on the surface of the rotary photosensitive drum 101. The light source used for the electrostatic latent image forming means may be an LED array. In this case, an LED at a position corresponding to the target image information is turned on to form an electrostatic latent image on the surface of the photosensitive drum 101. . Further, in the copying machine of this example, the exposure means is only the light source used for the electrostatic latent image forming means, and no static elimination light is provided. The surface of the photosensitive drum 101 is uniformly charged to −400 V by the primary charging roller 102. Next, image exposure is performed at 600 dpi (dot / inch) with a laser beam having a wavelength of 680 nm emitted from the semiconductor laser of the exposure apparatus 103, and the electrostatic latent image is formed by removing the charge at the laser beam irradiated portion.

[developing]
In FIG. 1, reference numeral 104 denotes a developing device, and the developing method is a two-component contact developing method. The electrostatic latent image formed on the rotating photosensitive drum 101 is developed as a toner image by the developing device 104. A schematic sectional view of the developing device is shown in FIG. A conveying screw 202 is accommodated in the developing chamber. The developer in the developing chamber is transported in the longitudinal direction of the developing sleeve 201 by the rotational driving of the transport screw 202. A conveying screw 203 is accommodated in the storage chamber. The conveying screw 203 conveys the toner along the longitudinal direction of the developing sleeve by its rotation. The developer conveying direction by the conveying screw 203 is opposite to that by the conveying screw 202. The partition wall 204 has openings on the front side and the back side (not shown), and the developer conveyed by the conveying screw 203 is delivered to the conveying screw 202 from one of the openings and conveyed by the conveying screw 202. The developed developer is delivered to the conveying screw 203 from the other one of the openings. The toner is charged to a polarity for developing the latent image by friction with the magnetic particles. An opening is provided in a portion of the developer container close to the photosensitive drum 101, and a nonmagnetic developing sleeve 201 such as aluminum or nonmagnetic stainless steel is provided in the opening.

  The developing sleeve 201 rotates in the direction of the arrow to carry and carry the developer obtained by mixing the toner and the carrier to the developing unit. The developer magnetic brush carried on the developing sleeve 201 contacts the photosensitive drum 101 rotating in the direction of the arrow at the developing portion, and the electrostatic latent image is developed at the developing portion. Note that a vibration bias voltage obtained by superimposing a DC voltage on an AC voltage is applied to the developing sleeve 201. The dark part potential (non-exposed part potential) and the bright part potential (exposed part potential) of the latent image are located between the maximum value and the minimum value of the vibration bias potential. As a result, an alternating electric field whose direction changes alternately is formed in the developing portion. In this alternating electric field, the toner and the carrier vibrate violently, and the toner adheres to the photosensitive drum 101 corresponding to the latent image by shaking the electrostatic restraint on the sleeve and the carrier.

  The difference (peak-to-peak voltage) between the maximum value and the minimum value of the vibration bias voltage is preferably 1 to 5 kV, and the frequency is preferably 1 to 10 kHz. As the waveform of the vibration bias voltage, a rectangular wave, a sine wave, a triangular wave, or the like can be used. The DC voltage component is between the dark part potential and the bright part potential of the latent image, but the absolute value is closer to the dark part potential than the minimum bright part potential. This is preferable for preventing adhesion of fog toner. The minimum gap between the developing sleeve 201 and the photosensitive drum 101 (the minimum gap position is in the developing portion) is preferably 0.2 to 1 mm. Reference numeral 205 denotes a developer layer thickness regulating blade that regulates the layer thickness of the two-component developer carried and conveyed by the developing sleeve 201 to the developing unit. The developer regulated by the blade 205 and conveyed to the developing unit has a height on the sleeve surface of the magnetic brush of the developer formed by a magnetic field in the developing unit by the developing magnetic pole S1 described later. It is preferable that the amount is 1.2 to 3 times the minimum gap value between the sleeve and the photosensitive drum in the removed state.

  A roller-shaped magnet 206 is fixedly disposed in the developing sleeve 201. The magnet 206 has a developing magnetic pole S1 facing the developing portion. A magnetic brush of developer is formed by the developing magnetic field formed by the developing magnetic pole S1 in the developing portion, and the magnetic brush contacts the photosensitive drum 101 to develop the dot distribution electrostatic latent image. At that time, both the toner adhering to the ears (brushes) of the magnetic carrier and the toner adhering to the sleeve surface instead of the ears are transferred to the exposed portion of the latent image and developed. The peak value of the strength (magnetic flux density in the direction perpendicular to the sleeve surface) of the developing magnetic field by the developing magnetic pole S1 on the surface of the developing sleeve 201 is preferably 500 to 2,000 Gauss. In this example, the magnet has N1, N2, N3, and S2 poles in addition to the developing magnetic pole S1. With the above configuration, as in the conventional case, the developer pumped up at the N2 pole by the rotation of the developing sleeve 201 is conveyed from the S2 pole to the N1 pole, and is regulated by the regulating blade 205 in the middle to form a developer thin layer. Then, the developer spiked in the magnetic field of the developing magnetic pole S1 develops the electrostatic latent image on the photosensitive drum 101. Thereafter, the developer on the developing sleeve 201 falls into the stirring chamber by the repulsive magnetic field between the N3 pole and the N2 pole. The developer that has fallen into the stirring chamber is stirred by the conveying screws 202 and 203.

Here, a polymerized toner preferably applied to the image forming apparatus of this example and a manufacturing method thereof will be described. Examples of the polymerizable monomer constituting the polymerizable monomer system used in this example and toner property imparting agents such as a colorant include the following.
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate and phenyl acrylate , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate Methacrylic acid esters such as dimethylaminoethyl methacrylate and ethyl amino ethyl methacrylate, and other acrylonitrile, methacrylonitrile and monomers acrylamide.
These monomers can be used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of toner development characteristics and durability.

In this example, the monomer system may be polymerized by adding a resin having a polar group. Examples of polar resins that can be used in this example are given below.
(1) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, and copolymers with styrene and unsaturated carboxylic acid esters.
(2) Anionic polymers include nitrile monomers such as acrylonitrile, halogen-containing monomers such as vinyl chloride, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, other unsaturated dibasic acids, Examples thereof include polymers such as saturated dibasic acid anhydrides, nitro monomers, and copolymers with styrene monomers.
These polar resins are localized near the surface of the toner, thereby improving toner blocking resistance. As addition amount, 0.1-10 mass% is preferable.

  As the colorant used in this example, known ones can be used. For example, carbon black, iron black, C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Dyes such as basic green 6, yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, hansa yellow G, permanent yellow NCG, tartrazine lake, molybdenum orange, permanent orange GTR, benzidine orange G, cadmium red, Permanent Red 4R, Watching Red Calcium Salt, Brilliant Carmine 3B, Fast Violet B, Methyl Violet Lake, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Quinacridone, Rhodamine Lake, Phthalocyanine Blue, Fast Sky Blue, Pigment Green B, There are pigments such as Malachite Green Lake and Final Yellow Green G. In this example, since the toner is preferably obtained by using the suspension polymerization method, it is necessary to pay attention to the polymerization inhibitory property and water phase transfer property of the colorant. Preferably, surface modification, for example, polymerization inhibition is required. It is better to have a hydrophobic treatment with no substances. In particular, since dye-based colorants and carbon black have many polymerization inhibiting properties, care must be taken when using them. A preferable method for surface-treating the dye-based colorant includes a method in which a polymerizable monomer is polymerized in the presence of these dyes in advance, and the obtained colored polymer is added to the monomer system. In addition to carbon black, the carbon black may be grafted with a substance that reacts with the surface functional groups of the carbon black, such as polyorganosiloxane.

  In this example, for the purpose of improving the releasability at the time of fixing with a hot roll, waxes generally used as a releasing agent such as a hydrocarbon compound may be blended in the toner. Examples of the waxes used in this example include paraffinic and polyolefinic waxes, and modified products thereof, for example, oxides and grafted products, higher fatty acids, metal salts thereof, amide waxes, and the like. These waxes preferably have a softening point of 40 to 130 ° C., preferably 50 to 120 ° C. according to the ring and ball method (JIS K2531). If the softening point is lower than 40 ° C., the toner has insufficient blocking resistance and shape retention. When the temperature exceeds 130 ° C., the effect of releasability becomes insufficient. The addition amount of these release agents is preferably 0.1 to 50% by mass.

  In this example, it is desirable to add a charge control agent to the toner material for the purpose of controlling the chargeability of the toner. As these charge control agents, among the known ones, those having almost no polymerization inhibition and aqueous phase transfer properties are used. For example, as a positive charge control agent, a nigrosine dye, a triphenylmethane dye, a quaternary ammonium salt, Examples of negative charge control agents include metal-containing salicylic acid compounds, metal-containing monoazo dye compounds, styrene-acrylic acid copolymers, and styrene-methacrylic acid copolymers. . The addition amount of these charge control agents is preferably 0.1 to 10% by mass.

  As the polymerization initiator, any suitable polymerization initiator such as 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′- Azo or diazo polymerization initiators such as azobis (cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone Examples thereof include peroxide-based polymerization initiators such as peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide. These polymerization initiators are preferably added in an amount of 0.5 to 20% by mass of the polymerizable monomer. In this example, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass. The external additive for the purpose of imparting various properties used in this example preferably has a particle size of 1/10 or less of the weight average particle size of the toner particles from the viewpoint of durability when added to the toner. The particle diameter of the external additive means the average particle diameter of the primary particles obtained by observing the surface of the toner particles with an electron microscope. As external additives for the purpose of imparting these characteristics, for example, the following are used.

1) Fluidity imparting agent: metal oxide (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Each of them is more preferably hydrophobized.
2) Abrasive or cleaning aid: metal oxide (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (sulfuric acid) Calcium, barium sulfate, calcium carbonate, etc.).
3) Lubricant: Fluorine resin powder (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salt (zinc stearate, calcium stearate, etc.), etc.
4) Charge controllable particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.), carbon black, etc.

  These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, per 100 parts by weight of toner particles. These external additives may be used alone or in combination, but in this example, silicon oxide and titanium oxide are used as fluidity imparting agents, and strontium titanate is used as an abrasive or cleaning aid. ing.

  Any appropriate dispersion stabilizer is added to the aqueous medium used in this example. For example, as an inorganic compound, calcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, Examples thereof include silica and alumina. As the organic compound, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and its salt, starch and the like can be dispersed in an aqueous phase. This dispersion stabilizer is preferably used in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

  Further, 0.001 to 0.1 parts by mass of a surfactant may be used for fine dispersion of these dispersion stabilizers. This is to promote the intended action of the dispersion stabilizer, and specific examples thereof include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, and lauric acid. Sodium, potassium stearate, calcium oleate, etc. are mentioned. Among these dispersion stabilizers, when an inorganic compound is used, a commercially available one may be used as it is, but in order to obtain finer particles, the inorganic compound may be produced in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution may be mixed under high stirring.

  The polymerized toner preferably used in this example can be obtained by the following method. That is, a monomer system in which a release agent, a colorant, a charge control agent, a polymerization initiator, and other external additives are added to a polymerizable monomer, and the monomer system is uniformly dissolved or dispersed by a homogenizer or an ultrasonic disperser. Is dispersed in an aqueous medium containing a dispersion stabilizer by a normal stirrer, homomixer or homogenizer. Preferably, granulation is carried out by adjusting the stirring speed and time so that the monomer droplets have the desired toner particle size, generally 30 μm or less. Thereafter, stirring may be performed to such an extent that the particle state is maintained by the action of the dispersion stabilizer, and the sedimentation and floating of the particles are prevented. Polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. In addition, the temperature may be raised in the latter half of the polymerization reaction, and further, in order to remove unreacted polymerizable monomers and by-products that cause odor during toner fixing, the latter half of the reaction or after the completion of the reaction. A part of the aqueous medium may be distilled off.

  Further, the toner used in this example is used as a mixture with carrier powder when used as a two-component developer. In this case, the mixing ratio of the toner and the carrier powder is 0.1 to 50% by mass, preferably 0.5 to 10% by mass, and more preferably 3 to 5% by mass as the toner concentration. As the carrier that can be used in this example, all known ones can be used. For example, iron powder, ferrite powder, magnetic powder such as nickel powder, glass beads, etc., and their surface fluororesin, vinyl The thing processed with resin or silicone resin etc. are mentioned.

[Transfer]
In FIG. 1, reference numeral 105 denotes a medium resistance transfer roller as a contact transfer unit, which is brought into pressure contact with the photosensitive drum 101 at a predetermined pressure to form a transfer nip portion. A transfer material 111 as a recording medium is fed to the transfer nip portion from a paper feed unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 105, so that the photosensitive drum 101 side The developer images are sequentially transferred onto the surface of the transfer material 111 fed to the transfer nip portion by electrostatic force and pressing force.

[Fixing]
Reference numeral 107 in FIG. 1 denotes a fixing device such as a thermal fixing method. The transfer material 111 that has received the transfer of the developer image on the photosensitive drum 101 side is separated from the surface of the rotating photosensitive drum 101 and introduced into the fixing device 107, and the developer image is fixed by the heat and pressure of the fixing roller. It is discharged out of the apparatus as an image formed product (print, copy). This fixing device has a fixing roller and a pressure roller. In this example, the fixing roller is released by coating a PFA resin tube having a thickness of 50 μm on an aluminum core having a diameter of 40 mm and a thickness of 1 mm. A layer was formed. A heater for heating the fixing roller from the inside is installed inside the core of the fixing roller. For the fixing roller, an elastic layer of 8 mm thick silicone sponge rubber is formed on an iron core bar having a diameter of 14 mm, and a release layer is formed by coating a 50 μm thick PFA resin tube thereon. The configuration was as follows. The fixing roller has a hardness of about 56 ° (measured with an Asker C hardness meter at a load of 1 kg). In this example, this fixing roller was pressed against the fixing roller by a pressing means with a pressing force of 20 Newton (N) to form a fixing nip having a width of about 5 mm between the fixing roller and the fixing roller.

[cleaning]
Reference numeral 108 in FIG. 1 denotes a cleaning device that collects and cleans transfer residual toner remaining on the photoreceptor after toner transfer. The cleaning of the toner on the photoconductor in this example is performed by bringing an elastic blade formed by molding polyurethane rubber having a hardness of 77 ° into a plate shape having a thickness of 2.0 mm to abut against the rotation of the photoconductor with a counter. The contact angle of the cleaning blade to the drum is 30 °, the amount of entry is 0.75 mm, and the distance (free length) from the adhesive fixing position of the blade to the tip is 5 mm. The toner and lubricant scraped off by the cleaning blade are received by the scooping sheet and sent to the waste toner box by the toner feeding blade and the screw.

  In the above-described main body configuration, using the photoconductor produced as described above, the release rate is determined by varying the particle size of the external additive of the toner to be developed and the stirring time of the external additive. The drum scratches at that time were compared and evaluated. The liberation rate of the external additive is included in the toner particles with respect to the sum of the number of carbon atoms contained in the toner particles and atoms contained in the lubricating compound (for example, fluorine atoms for fluororesin and zinc atoms for zinc stearate). It is represented by the ratio of the number of atoms contained in the non-lubricating compound. The liberation rate can be measured according to the principle described on pages 65-68 of the “Japan Hardcopy 97” paper collection. Specifically, the toner particles are introduced into the plasma one by one, and from the obtained emission spectrum, Element, the number of toner particles and the particle size of the toner particles can be known, and the liberation rate can be measured from the emission spectrum.

According to the above measurement method, the liberation rate of the lubricating compound is determined by the following formula (iii) from the emission of carbon atoms, which are constituent elements of the binder resin contained in the toner particles, and the emission of atoms of the lubricating compound. It is done.
(Iii) Free rate of external additive (number%) = (Number of light emission of only atoms contained in external additive) × 100 / (Number of light emission of atoms contained in external additive that emitted light simultaneously with carbon atom) + (Number of light emission of atoms in external additive)
In the above formula, “simultaneously emitted” means emission of atoms contained in a compound having lubricity and emission within 2.6 msec from emission of a carbon atom, and is included in a compound having lubricity after that. The emission of atoms is the emission of only atoms contained in the compound having lubricity. Further, simultaneous emission of carbon atoms and atoms contained in the external additive means synchronization with the toner particles, and light emission of only the atoms contained in the external additive means that the external additive is removed from the toner particles. It means that it is free. The liberation rate was measured using a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation) using an emission spectrum.

  The specific measurement method is as follows. First, using helium gas containing 0.1% oxygen, measurement is performed in an environment at a temperature of 23 ° C. and a humidity of 60%, and the toner sample is left in the same environment overnight to adjust the humidity. In the measurement, carbon atoms are measured in channel 1 (measurement wavelength 247.860 nm, K factor is the recommended value), and atoms contained in the external additive are measured in channel 2, and the number of emission of carbon atoms in one scan is measured. Sampling is performed so as to be 1,000 to 1,400 times, and scanning is repeated until the total number of light emission of carbon atoms reaches 10,000 or more, and the number of light emission is integrated. At this time, in the distribution in which the number of light emission of the carbon atom is on the vertical axis and the cube root voltage of the carbon atom is on the horizontal axis, the distribution has one maximum and further has a valley-free distribution. Sampling and measuring. Based on this data, the noise cut level of all atoms is set to 1.50 V, and the liberation rate of the external additive is calculated using the above formula (iii).

  The liberation rate of the external additive in this example is defined as an integrated value of the liberation rates of all the external additives contained other than the toner base. In this example, 0.4 parts by mass of silicon oxide (average particle size of primary particles 0.01 μm), 0.2 part by mass of titanium oxide (average particle size of primary particles 0.03 μm) and strontium titanate (primary as external additives) The average particle diameter of the particles is 0.05 to 3 μm) and 0.1 to 4.0 parts by mass. At this time, the liberation rate is calculated for the Si element and the Ti element, and the value obtained by integrating these is the external additive. This is the total liberation rate. After the external addition, the size of the diameter is confirmed with a scanning electron microscope FE-SEM (Hitachi, Ltd. S-800). The average particle size of primary particles of the external additive in this example is obtained by measuring the average particle size of primary particles of 100 particles confirmed by this SEM and calculating the average value.

Next, the present invention will be described more specifically with reference to examples and comparative examples.
In the following examples and comparative examples, a photosensitive drum in which a layer containing a polymer of a hole transporting compound having a chain polymerizable group described above is used as a protective layer is used, and the HU in the above measurement conditions is used. The elastic deformation rate is 190 N / mm ² and 52%, respectively.

In the following Examples and Comparative Examples, external addition stirring is performed by rotating a stirring blade at 4,000 rpm with a Henschel mixer. The liberation rate of the external additive from the toner varies depending on the stirring time. Drum scratches were evaluated for the developers prepared based on these particle sizes, external addition stirring time, and external addition amount. For comparison, the digital type copier described in the embodiment was compared with the state of drum scratches when 200,000 sheets were printed. The drum scratch level was evaluated based on the following criteria using 200,000 sheets of actual machine paper.
• ○: Minor, even if there are no scratches.
Δ: Although there is a scratch of about 3 μm at most, it does not reach the charge transport layer and has no effect on the output image.
X: Scratches reach the charge transport layer and affect the output image.

Regarding the development density, after the endurance of image output was 10,000 sheets, the density of the output solid image was measured with a Macbeth reflection densitometer and evaluated according to the following criteria.
・ ○: Reflection density 1.4 or more.
-: Reflection density 1.0 or more and less than 1.4.
*: Reflection density is less than 1.0.

<Examples 1-6, Comparative Examples 1-2>
First, the average particle size of primary particles of strontium titanate was evaluated, and the toner with external addition and stirring was evaluated until the liberation rate of strontium titanate was about 6% by number. The results are shown in Table 1 below. The external addition amount of strontium titanate at this time is constant at 0.9% by mass. In the table, strontium titanate is abbreviated as STC.

  As is apparent from Table 1, if the average particle size of the primary particles of strontium titanate is 0.07 μm or more and 2.0 μm or less, the effect of drum scratches does not appear in the output image, and high durability can be realized. Even if the liberation rate is high as in Comparative Example 1, if the average particle size of the primary particles of strontium titanate is less than 0.07 μm, charging failure due to scratches occurs and there is no effect. Further, when the average particle diameter of primary particles of strontium titanate is 3 μm as in Comparative Example 2, the development durability is lowered. This is a mechanical force in the developing device due to the size of the external additive, and the external additive is easily peeled off from the toner, and is difficult to move to the drum together with the toner, and the external additive is easily accumulated in the developing device. It depends. Also, with the same mass, the number of externally added particles is reduced, the size is the same as that of the toner, and the effect of preventing the toner and foreign matters from slipping through is reduced, so that the drum scratches are slightly worsened. It is done. Note that the evaluation of drum scratches is performed by replacing the developer with 50,000 sheets, but in Comparative Example 2, the developer is replaced with 10,000 sheets.

<Examples 7 to 12 and Comparative Examples 3 to 4>
Next, the evaluation was made on a toner in which the release rate was changed with strontium titanate having an average primary particle size of 1.5 μm and agitation time for external addition. The results are shown in Table 2 below. The external addition amount of strontium titanate is constant at 0.9% by mass. In the table, strontium titanate is abbreviated as STC.

  As is clear from Table 2, if the total external additive release rate is 1.0% to 50%, the effect of drum scratches does not appear in the output image and does not significantly affect the developability. Durability was realized. When the liberation rate was 1.5% by number or more, the drum scratch was more effective, and when it was 30% by number or less, development was hardly affected. On the other hand, as in Comparative Example 3, even if the average particle diameter of the primary particles of strontium titanate is sufficient, if the liberation rate is less than 1.0% by number, charging failure due to scratches occurs and the effect is obtained. There wasn't. When the liberation ratio is 60% by number as in Comparative Example 4, the development is affected and the image density is lowered. This is presumably because if the release rate is too high, the external additive is supplied to the drum together with the toner and is not easily consumed, and the external additive accumulates in the developing device.

<Examples 13 to 19 and Comparative Examples 5 to 6>
Drum scratches and developability were evaluated by changing the external addition amount of strontium titanate and the liberation rate of the external additive. The results are shown in Table 3 below. The average particle diameter of primary particles of externally added strontium titanate is constant at 1.5 μm. In the table, strontium titanate is abbreviated as STC.

  As apparent from Table 3, if the external additive amount is varied while keeping the external stirring time constant, the release rate of the external additive at that time is 1.0% to 50% by number. High durability could be realized without the influence appearing in the output image and without greatly affecting the developability. When the liberation ratio is 1.5% by number or more, there is an effect due to drum scratches, and when it is 30% by number or less, the development is hardly affected. When the amount of external addition of strontium titanate was small and the liberation rate was small as in Comparative Example 5, charging failure due to drum scratches occurred and there was no effect. Further, when the amount of the external additive was increased as in Comparative Example 6 and the liberation rate was 50% by number, the developability deteriorated, and the density was lowered by 10,000 sheets of image output durability. This is presumably because the consumption of strontium titanate did not catch up with the amount of external addition, and the external additive accumulated in the developing device.

  In the above examples, compared with the comparative example, there was an effect in suppressing drum scratches, high durability was achieved, and sufficient developability was achieved. When externally adding to a two-component developer, the external additive particles and their conditions have been optimized so that a stable and sufficient external additive cleaning blade blocking layer can be formed without increasing the external addition amount. There is no need for the supply application member and its supply labor, and drum scratches can be suppressed. The present invention is not limited to the application to the spherical polymerized toner, but is effective when an irregularly pulverized toner or a spheroidized pulverized toner is used as a toner base. The charging method is not limited to roller charging, and the same effect can be obtained by corona charging. The externally added primary particles having an average particle size of 0.07 μm or more and 2.0 μm or less are not limited to strontium titanate, and cleaning can be performed using other types of particles such as titanium oxide and PTFE particles. By forming a stable blocking layer on the blade, drum scratches can be suppressed.

  According to the present invention, an electrophotographic image forming apparatus of a type that develops an electrostatic latent image on an organic photoreceptor with a two-component developer can be provided. More specifically, an electrophotographic photosensitive member, a charging unit that charges the photosensitive member, a latent image forming unit that forms an electrostatic latent image on the charging surface of the photosensitive member, and a two-component developer carried on a developer carrier. Developing means for developing the electrostatic latent image on the photosensitive member as a toner image by means of, a transfer means for transferring the toner image on the photosensitive member to the transferred member side by applying an electric field between the photosensitive member and the transferred member, and toner An image forming apparatus including a cleaning unit that collects residual toner particles on the surface of the photoreceptor after the image transfer can be provided.

1 is a schematic sectional view showing an image forming apparatus of the present invention. 1 is a schematic cross-sectional view of a developing device of the present invention. The figure which shows the result of the hardness test of the electrophotographic photoreceptor using a Vickers square pyramid diamond indenter. The figure which shows the result of the hardness test of the electrophotographic photoreceptor using a Vickers square pyramid diamond indenter.

Explanation of symbols

101: Photosensitive drum 102: Primary charger (charging roller)
103: Exposure apparatus (laser beam scanner)
104: Development device 105: Transfer charger (transfer roller)
106: separation charger 107: fixing device 108: cleaning device 111: transfer material 201: developing sleeve 202, 203: conveying screw 204: partition 205: developer layer thickness regulating blade 206: magnet A: charging nip L: scanning exposure

Claims (1)

A photosensitive layer is provided on a conductive support, and the surface of the photosensitive layer has a surface protective layer containing a polymer of a hole transporting compound represented by the following formula (2), at a temperature of 25 ° C. and a humidity of 50%. A hardness test is performed using a Vickers square pyramid diamond indenter in an environment, 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 the photosensitive layer An electrophotographic photosensitive member having an elastic deformation ratio of 44% or more and 65% or less, charging means for charging the surface of the photosensitive member, and latent image forming means for forming an electrostatic latent image on the charging surface of the photosensitive member; Developing means for developing an electrostatic latent image as a toner image by a two-component developer comprising a toner containing an external additive and a carrier, transfer means for transferring the toner image to a recording medium, and transfer residual toner from a photoreceptor. Images having cleaning means to be removed In the image forming apparatus , the liberation rate of the external additive from the toner is 1% by number or more and 50% by number or less, and the average primary particle diameter of the external additive is 0.07 μm or more and 2.0 μm or less. An image forming apparatus.

Images