JP2007034268A - Image forming apparatus and image forming method - Google Patents

Abstract

Provided are an image forming apparatus and an image forming method which have high transfer efficiency and can stably obtain a good image even when used for a long period of time without causing image defects such as “missing”.
An electrostatic latent image carrier, electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and developing the electrostatic latent image with toner to form a toner At least a developing unit that forms an image and a transfer unit that transfers the toner image to a recording medium. And the average value F of the non-electrostatic adhesion force between the toner and the electrostatic latent image carrier is expressed by a volume average particle diameter Dt of the toner and an average particle diameter Da of the external additive. In the image forming apparatus and the image forming method, the value [F / (Dt × Da)] divided by the product is 7.5 × 10 ⁴ N / m ² or less.
[Selection figure] None

Description

  The present invention relates to an image forming apparatus and an image forming method used for a copying machine, electrostatic printing, a printer, electrostatic recording, and the like.

  Conventionally, various methods are known for electrophotography. Generally, the surface of an electrostatic latent image carrier is charged, and the surface of the charged electrostatic latent image carrier is exposed to static electricity. An electrostatic latent image is formed. Next, the electrostatic latent image is developed with toner, and a toner image is formed on the electrostatic latent image carrier. In addition, the toner image on the electrostatic latent image carrier is directly transferred onto the recording medium via an intermediate transfer member, and the transferred toner image is fixed by heating, pressing, or a combination thereof. As a result, a recorded matter in which an image is formed on the recording medium is obtained. The toner remaining on the electrostatic latent image carrier after the toner image transfer is cleaned by a known method such as a blade, a brush, or a roller.

  In recent years, as a trend of electrophotographic technology, high image quality, digitalization, colorization, and high speed have been demanded. For example, a high-resolution image having a resolution of 1200 dpi or higher has been studied, and in order to realize this point, a higher-definition image forming method than ever is desired. In order to form a high-definition image with respect to the toner and developer for visualizing the electrostatic latent image, further reduction in the particle size is being studied and realized.

  Further, in order to cope with the digitization of images, the uniformity of dots forming images is required, and the uniformity of the toner forming dots is also required. For this reason, the pulverized toner is spherically processed by the hot air granulation method and the fluidized granulation method, rather than the pulverized toner having a non-uniform shape produced by a mechanical pulverization method that has been mainly used conventionally. A spherical toner such as a toner or a polymerized toner by a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method or the like is more advantageous.

Further, in order to speed up the output of a color image, each toner image formed on each electrostatic latent image carrier using a plurality of electrostatic latent image carriers and developing means is passed through an intermediate transfer member. Alternatively, a tandem type electrophotographic system that directly transfers onto a recording medium is used. However, in order to cope with further increase in image output speed, it is necessary to rotate a roller used for development at high speed in order to greatly increase the development amount per unit time.
In this case, the toner on the developing roller is subject to the regulation of the toner layer thickness by a regulating member in the one-component development method, and mechanical stress due to the stirring with the carrier and the regulation of the magnetic head height in the two-component development method. However, the stress received by the toner increases due to the high speed rotation of the developing roller. Therefore, in order to ensure fluidity, the toner surface is coated with fine particles (external additive), but mechanical stress has an influence on the toner such as burying and separation of the external additive. By such embedding and separation of the external additive, the adhesion between the toner and other members and between the toners increases, the transfer rate decreases, and part of the image, particularly the center of the fine line, does not transfer, and “collapse” occurs. There is a problem that it becomes easy to do. As a result, in order to suppress the burying and separation of the external additive, measures such as reducing mechanical stress are taken, but sufficient effects are not obtained.

In addition, Patent Document 1 and Patent Document 2 propose that an increase in toner adhesion to mechanical stress is suppressed by using an external additive having a large particle diameter that is difficult to be embedded in the toner.
In addition, the “collapse” phenomenon of the transfer is caused by the adhesion force of the toner compressed by the pressure between the image carrier and the transfer member, particularly the non-electrostatic adhesion force that does not depend on the charging of the toner. This is considered to be because the transfer of toner cannot be controlled by the Coulomb force. For example, Patent Document 3 defines a range of the magnitude of the non-electrostatic adhesion force. In Patent Document 4 and Patent Document 5, the range of non-electrostatic adhesive force dependency on the toner particle diameter is defined to suppress “missing”.

  However, the non-electrostatic adhesion force depends on the particle size of the external additive. However, Patent Documents 1 to 5 specify nothing about the relationship between the non-electrostatic adhesion force and the particle size of the external additive. In addition, the relationship between the non-electrostatic adhesion force when using an external additive having a large particle size and “collapse” has not been sufficiently studied.

  Accordingly, there is a demand for prompt provision of an image forming apparatus and an image forming method that have high transfer efficiency and can stably obtain a good image even when used for a long period of time without causing image defects such as “missing”. is the current situation.

JP 2001-83735 A JP 2002-31638 A JP 2000-66441 A JP 2001-318485 A JP 2001-255679 A

  An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, the present invention provides an image forming apparatus and an image forming method with high transfer efficiency and capable of stably obtaining a good image even when used for a long period of time without causing image defects such as “blank”. With the goal.

Means for solving the problems are as follows. That is,
<1> An electrostatic latent image carrier, electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and developing the electrostatic latent image with toner to form a toner image An image forming apparatus having at least developing means for forming the toner image and transfer means for transferring the toner image to a recording medium.
The surface of the toner is coated with an external additive containing fine particles having an average particle diameter Da of 100 to 300 nm, and an average value F of non-electrostatic adhesion force between the toner and the electrostatic latent image carrier. Is divided by the product of the volume average particle diameter Dt of the toner and the average particle diameter Da of the external additive [F / (Dt × Da)] is 7.5 × 10 ⁴ N / m ² or less. The image forming apparatus is characterized by the above. In the image forming apparatus according to <1>, the toner is coated with a large particle size external additive, and the value F / regarding the non-electrostatic adhesion force F, the toner particle size Dt, and the external additive particle size Da of the toner. By setting (Dt × Da) within an appropriate range, the transfer efficiency is high, image defects such as voids do not occur, and stable and good images can be obtained even after long-term use.
<2> The image forming apparatus according to <1>, wherein the image forming apparatus is a tandem type in which a plurality of image forming elements including at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit are arranged. It is. In the image forming apparatus described in <2>, by setting F / (Dt × Da) to an appropriate range for each color toner, the transfer efficiency is high, image defects such as voids do not occur, and the length is long. A stable and good color image can be obtained even when used for a period of time.
<3> The transfer unit performs secondary transfer of the intermediate transfer member onto which the toner image formed on the electrostatic latent image carrier is primarily transferred and the toner image carried on the intermediate transfer member to the recording medium. The image forming apparatus according to any one of <1> to <2>, further including a next transfer unit.
<4> The image forming apparatus according to any one of <1> to <3>, wherein the volume average particle diameter Dt of the toner is 2 to 7 μm. In the image forming apparatus according to <4>, deterioration in image quality can be suppressed by setting the toner particle diameter within a certain range.
<5> The image forming apparatus according to any one of <1> to <4>, wherein an average value of a toner shape factor SF1 is 100 to 130. In the image forming apparatus according to <5>, by using a spherical toner having an average value of the toner shape factor SF1 of 100 to 130, an image with good dot uniformity and high quality can be obtained.
<6> The image forming apparatus according to any one of <1> to <5>, wherein the toner is a polymerized toner produced by a polymerization method. In the image forming apparatus described in <6>, since the spherical toner is produced by the polymerization method, the toner shape and particle size can be easily controlled, and the toner productivity can be improved.
<7> The average ratio of the area ratio (external additive coverage) of the portion where the external additive having an average particle diameter Da of 100 to 300 nm attached to the surface area of one toner particle is 5 to 90% <1 > To <6>. In the image forming apparatus according to <7>, burying and separation of the external additive can be suppressed by adjusting the external additive coverage to be within a certain range.
<8> Any one of <1> to <7>, wherein the external additive is at least one selected from hydrophobized silica, hydrophobized titanium, and hydrophobized alumina. The image forming apparatus described. In the image forming apparatus according to <8>, by containing at least one selected from hydrophobized silica, hydrophobized titanium, and hydrophobized alumina as an external additive. Excellent environmental stability and good transfer characteristics can be obtained.
<9> Any one of <1> to <8> above, wherein the average value Sm of the surface irregularities of the electrostatic latent image carrier and the volume average particle diameter Dt of the toner satisfy the following formula: Sm ≧ 10 Dt The image forming apparatus described.

<10> An electrostatic latent image forming step of forming an electrostatic latent image on the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with toner to form a toner image, and the toner In an image forming method including at least a transfer step of transferring an image to a recording medium,
The surface of the toner is coated with an external additive containing fine particles having an average particle diameter Da of 100 to 300 nm, and an average value F of non-electrostatic adhesion force between the toner and the electrostatic latent image carrier. Is divided by the product of the volume average particle diameter Dt of the toner and the average particle diameter Da of the external additive [F / (Dt × Da)] is 7.5 × 10 ⁴ N / m ² or less. The image forming method is characterized by the above. In the image forming method according to <10>, the toner is coated with a large particle size external additive, and the value F / relating to the non-electrostatic adhesion force F, the toner particle size Dt, and the external additive particle size Da of the toner. By setting (Dt × Da) within an appropriate range, transfer efficiency is high, image defects such as voids do not occur, and stable and good images can be obtained even after long-term use.
<11> Using the tandem type image forming apparatus in which a plurality of image forming elements each having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit are arranged. The image forming method described. In the image forming method described in <11>, by setting F / (Dt × Da) to an appropriate range for each color toner, the transfer efficiency is high, image defects such as voids do not occur, and the length is long. A stable and good color image can be obtained even when used for a period of time.
<12> In the transfer step, an intermediate transfer member on which the toner image formed on the electrostatic latent image carrier is primarily transferred, and a toner image carried on the intermediate transfer member is secondarily transferred to a recording medium. The image forming method according to any one of <10> to <11>, wherein a next transfer unit is used.
<13> The image forming method according to any one of <10> to <12>, wherein the volume average particle diameter Dt of the toner is 2 to 7 μm. In the image forming method described in <13>, the deterioration of the image quality can be suppressed by setting the particle diameter of the toner within a certain range.
<14> The image forming method according to any one of <10> to <13>, wherein an average value of a toner shape factor SF1 is 100 to 130. In the image forming method described in <14>, by using the toner that has been spheroidized in the manufacturing process or in the post-manufacturing process, the dot uniformity is good and a high-quality image can be obtained.
<15> The image forming method according to any one of <10> to <14>, wherein the toner is a polymerized toner produced by a polymerization method. In the image forming method described in <15>, since a spherical toner is produced by a polymerization method, the toner shape and particle size can be easily controlled, and the toner productivity can be improved.
<16> From <10> to <15, wherein an average value of a covering area ratio, which is a ratio of an area to which an external additive having an average particle diameter Da of 100 to 300 nm adhered to a surface area of one toner particle, is 5 to 90%. > The image forming method according to any one of the above. In the image forming method described in <16>, the burying and separation of the external additive can be suppressed by adjusting the external additive coverage to be within a certain range.
<17> The external additive is any one of <10> to <16>, wherein the external additive is at least one selected from hydrophobized silica, hydrophobized titanium, and hydrophobized alumina. The image forming method described. In the image forming method according to <17>, by containing at least one selected from hydrophobized silica, hydrophobized titanium, and hydrophobized alumina as an external additive. Excellent environmental stability and good transfer characteristics can be obtained.
<18> The average value Sm of the surface irregularities of the electrostatic latent image carrier and the volume average particle diameter Dt of the toner satisfy any of the following formulas <10> to <17> satisfying the following formula: Sm ≧ 10 Dt The image forming method described. In the image forming method according to <18>, the use of the electrostatic latent image carrier having an average surface irregularity period of 10 times or more of the volume average particle diameter of the toner results in good graininess. An image is obtained.

  According to the present invention, it is possible to solve the conventional problems, transfer efficiency is high, and image formation such as “hollow-out” does not occur, and a stable and good image can be obtained even when used for a long period of time. An apparatus and an image forming method can be provided.

(Image forming method and image forming apparatus)
The image forming apparatus of the present invention comprises at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit, and other units appropriately selected as necessary. For example, the image forming apparatus includes a fixing unit, a discharging unit, a cleaning unit, a recycling unit, a control unit, and the like.
The image forming method of the present invention includes at least an electrostatic latent image forming step, a developing step, and a transfer step, and other steps appropriately selected as necessary, for example, a fixing step, a charge eliminating step, a cleaning step, It includes a recycling process, a control process, and the like.
In this case, the image forming apparatus is preferably a tandem type in which a plurality of image forming elements each having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit are arranged. In this tandem system, the image forming elements for yellow, magenta, cyan, and black are mounted, and each toner image is formed in parallel by four image forming elements, and is recorded on a recording medium (transfer paper) or an intermediate transfer member. Since they are overlapped with each other, a color image can be formed at high speed.

  The image forming method of the present invention can be preferably carried out by the image forming apparatus of the present invention, the electrostatic latent image forming step can be performed by the electrostatic latent image forming means, and the developing step is the developing The transfer step can be performed by the transfer unit, and the other steps can be performed by the other units.

-Electrostatic latent image forming step and electrostatic latent image forming means-
The electrostatic latent image forming step is a step of forming an electrostatic latent image on the electrostatic latent image carrier.

<Electrostatic latent image carrier>
The electrostatic latent image carrier (hereinafter sometimes referred to as “photoreceptor” or “electrophotographic photoreceptor”) has a support and at least a photosensitive layer on the support, and is further necessary. Depending on the case, it has other layers.

  Here, the surface of the photoreceptor is uneven due to the influence of the surface properties of the support, the formation conditions of the photoreceptor, and the like. In the developing step, the toner adheres to the photoconductor, and an adhesion force is generated between the toner and the photoconductor. If the period of the unevenness of the photoconductor is about the same as the toner particle size, the toner is removed. When the toner comes into contact with the convex portion, the adhesive force is small because the contact area is small. However, when the toner is in contact with the concave portion, the adhesive area is large, so that the adhesive force is large and the variation in the adhesive force is large. Further, when the variation in the adhesion force between the toner and the photoconductor is increased, the variation in the transferability of the toner is increased in the transfer process, and the graininess is lowered. Further, when the unevenness period of the photoconductor is sufficiently larger than the toner particle size or smaller than the toner particle size, there is a variation in the adhesion force between the toner and the photoconductor as compared to the case where the toner particle size is the same. small. However, it is difficult to form an unevenness in which the unevenness period of the photoconductor is smaller than the toner particle size. Therefore, it is preferable that the average value Sm of the surface unevenness of the photoconductor is sufficiently larger than the volume average particle diameter Dt of the toner, more preferably Sm ≧ 10 Dt, and further preferably Sm ≧ 20 Dt. .

As the electrostatic latent image carrier, in the first embodiment, a support and a single-layer type photosensitive layer are provided on the support, and a protective layer, an intermediate layer, and other layers as necessary. It has.
Further, as the electrostatic latent image carrier, in the second embodiment, a support, and a laminated photosensitive layer having at least a charge generation layer and a charge transport layer in this order are provided on the support, As needed, it has a protective layer, an intermediate | middle layer, and another layer. In the second embodiment, the charge generation layer and the charge transport layer may be laminated in reverse.

-Support-
The support is not particularly limited as long as it has a volume resistance of 10 ¹⁰ Ω · cm or less, and can be appropriately selected according to the purpose. For example, aluminum, nickel, chromium, nichrome, copper Metals such as gold, silver and platinum; metal oxides such as tin oxide and indium oxide, film or cylindrical plastic, paper coated, or aluminum, aluminum alloy, nickel, stainless steel, etc. Or a tube subjected to surface treatment such as cutting, super-finishing, polishing or the like after being made into a raw tube by a method such as extruding and drawing them. Further, an endless nickel belt and an endless stainless steel belt disclosed in JP-A-52-36016 can also be used as a support. Further, a nickel foil having a thickness of 50 to 150 μm may be used, or a surface of a polyethylene terephthalate film having a thickness of 50 to 150 μm may be subjected to conductive processing such as aluminum deposition.

In addition, those in which conductive powder is dispersed in an appropriate binder resin and coated on the support can also be used as the support of the present invention.
Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver, or metal oxide powder such as conductive tin oxide and ITO. Etc. The binder resin used at the same time includes polystyrene resin, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester resin, polyvinyl chloride resin, vinyl chloride-vinyl acetate. Copolymer, polyvinyl acetate resin, polyvinylidene chloride resin, polyarylate resin, phenoxy resin, polycarbonate resin, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral resin, polyvinyl formal resin, polyvinyl toluene resin, poly-N-vinyl carbazole, An acrylic resin, a silicone resin, an epoxy resin, a melamine resin, a urethane resin, a phenol resin, an alkyd resin, etc. are mentioned.
The conductive layer can be provided by dispersing and applying these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene and the like.

  Furthermore, it is electrically conductive by a heat shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be used favorably as a conductive support.

-Multilayer type photosensitive layer-
The multilayer photosensitive layer has at least a charge generation layer and a charge transport layer in this order, and further includes a protective layer, an intermediate layer, and other layers as necessary.

  The charge generation layer includes at least a charge generation material, and includes a binder resin and, if necessary, other components.

  There is no restriction | limiting in particular as said charge generation substance, Although it can select suitably according to the objective, Either an inorganic material and an organic material can be used.

  The inorganic material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, and selenium-arsenic compounds. It is done.

  There is no restriction | limiting in particular as said organic type material, According to the objective, it can select suitably according to the objective, For example, C.I. Pigment Blue 25 (Color Index CI.21180), C.I. Pigment Red 41 ( CI 21200), CI Acid Red 52 (CI 45100), CI Basic Red 3 (CI 45210), azo pigments having a carbazole skeleton, azo pigments having a distyrylbenzene skeleton, triphenylamine Azo pigments having a skeleton, azo pigments having a dibenzothiophene skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a fluorenone skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, di Has a styrylcarbazole skeleton Azo pigments such as Zo pigment; phthalocyanine pigments such as C.I. Pigment Blue 16 (C.I. 74100); indigo such as C. I.But Brown (C.I. 73410), C.I. Pigments; perylene pigments such as Argol Scarlet 5 (manufactured by Bayer), Indusence Scarlet R (manufactured by Bayer); and squalic dyes. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, For example, a polyamide resin, a polyurethane resin, an epoxy resin, a polyketone resin, a polycarbonate resin, a silicone resin, an acrylic resin, a polyvinyl butyral resin, polyvinyl Formal resin, polyvinyl ketone resin, polystyrene resin, poly-N-vinyl carbazole resin, polyacrylamide resin, and the like can be given. These may be used individually by 1 type and may use 2 or more types together.

  Furthermore, you may add a charge transport material as needed. In addition to the binder resin, a polymer charge transport material can be added as the binder resin for the charge generation layer.

The method for forming the charge generation layer is roughly classified into a vacuum thin film preparation method and a casting method from a solution dispersion system.
Examples of the former method include a glow discharge polymerization method, a vacuum deposition method, a CVD method, a sputtering method, a reactive sputtering method, an ion plating method, and an accelerated ion injection method. This vacuum thin film manufacturing method can satisfactorily form the inorganic material or organic material described above.
In order to provide the charge generation layer by the latter casting method, a charge generation layer coating solution is used and a conventional method such as a dip coating method, a spray coating method, or a bead coating method is used. it can.

The organic solvent used for the charge generation layer coating liquid is not particularly limited and may be appropriately selected depending on the intended purpose. For example, acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, Chloroform, dichloromethane, dichloroethane, dichloropropane, trichloroethane, trichloroethylene, tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, isopropyl alcohol, butanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, propyl cellosolve, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, tetrahydrofuran, methyl ethyl ketone, dichloromethane, methanol, and ethanol having a boiling point of 40 to 80 ° C. are particularly preferable because they can be easily dried after coating.
The charge generation layer coating solution is produced by dispersing and dissolving the charge generation material and a binder resin in the organic solvent. Examples of the method for dispersing the organic pigment in the organic solvent include a dispersion method using a dispersion medium such as a ball mill, a bead mill, a sand mill, and a vibration mill, and a high-speed liquid collision dispersion method.

  The thickness of the charge generation layer is usually preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

  The charge transport layer is a layer intended to hold a charged charge and to couple the charge generated and separated in the charge generating layer by exposure to the charged charge that has been held. In order to achieve the purpose of holding the charged charge, it is required that the electric resistance is high. Further, in order to achieve the purpose of obtaining a high surface potential with the charged charge that has been held, it is required that the dielectric constant is small and the charge mobility is good.

  The charge transport layer includes at least a charge transport material, and includes a binder resin and, if necessary, other components.

Examples of the charge transport material include a hole transport material, an electron transport material, and a polymer charge transport material.
Examples of the electron transporting material (electron accepting material) include chloranil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro. -9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, and the like. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the hole transporting material (electron donating material) include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4- Dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, etc. . These may be used individually by 1 type and may use 2 or more types together.

Examples of the polymer charge transport material include those having the following structure.
(A) Polymer having carbazole ring For example, poly-N-vinylcarbazole, JP-A-50-82056, JP-A-54-9632, JP-A-54-11737, JP-A-4-175337 And the compounds described in JP-A-4-183719 and JP-A-6-234841.
(B) Polymer having a hydrazone structure For example, JP-A-57-78402, JP-A-61-20953, JP-A-61-296358, JP-A-1-134456, JP-A-1-134456 179164, JP-A-3-180851, JP-A-3-180852, JP-A-3-50555, JP-A-5-310904, JP-A-6-234840, and the like. It is done.
(C) Polysilylene polymer For example, JP-A-63-285552, JP-A-1-88461, JP-A-4-264130, JP-A-4-264131, JP-A-4-264132, Examples thereof include compounds described in Kaihei 4-264133 and JP-A-4-289867.
(D) Polymer having a triarylamine structure For example, N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-134457, JP-A-2-282264, JP-A-2- Examples thereof include compounds described in JP-A-304456, JP-A-4-133305, JP-A-4-133066, JP-A-5-40350, and JP-A-5-202135.
(E) Other polymers For example, formaldehyde condensation polymer of nitropyrene, JP-A-51-73888, JP-A-56-150749, JP-A-6-234836, JP-A-6-234837 And the compounds described.

  In addition to the above, the polymer charge transporting material includes, for example, a polycarbonate resin having a triarylamine structure, a polyurethane resin having a triarylamine structure, a polyester resin having a triarylamine structure, and a triarylamine structure. And a polyether resin. Examples of the polymer charge transporting material include JP-A 64-1728, JP-A 64-13061, JP-A 64-19049, JP-A-4-11627, JP-A 4-116627. JP 2225014, JP 4-230767, JP 4-320420, JP 5-232727, JP 7-56374, JP 9-127713, JP 9-222740. And compounds described in JP-A-9-265197, JP-A-9-211877, JP-A-9-30495, and the like.

  Examples of the polymer having an electron donating group include not only the above-mentioned polymer but also a copolymer with a known monomer, a block polymer, a graft polymer, a star polymer, It is also possible to use a crosslinked polymer having an electron donating group as disclosed in JP-A-109406.

Examples of the binder resin include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyethylene resin, polyvinyl chloride resin, polyvinyl acetate resin, polystyrene resin, phenol resin, epoxy resin, polyurethane resin, polyvinylidene chloride resin, Examples thereof include alkyd resins, silicone resins, polyvinyl carbazole resins, polyvinyl butyral resins, polyvinyl formal resins, polyacrylate resins, polyacrylamide resins, and phenoxy resins. These may be used individually by 1 type and may use 2 or more types together.
The charge transport layer may also contain a copolymer of a crosslinkable binder resin and a crosslinkable charge transport material.

  The charge transport layer can be formed by dissolving or dispersing these charge transport materials and a binder resin in an appropriate solvent, applying the solution, and drying. In addition to the charge transport material and the binder resin, an appropriate amount of additives such as a plasticizer, an antioxidant, and a leveling agent may be added to the charge transport layer as necessary.

  The thickness of the charge transport layer is not particularly limited and can be appropriately selected according to the purpose. The thickness is preferably 5 to 100 μm, and the charge transport layer can be thinned in recent demands for higher image quality. In order to achieve a high image quality of 1200 dpi or more, 5 to 30 μm is more preferable.

-Single layer photosensitive layer-
The single-layer type photosensitive layer includes a charge generation material, a charge transport material, a binder resin, and other components as necessary.
As the charge generating substance, charge transporting substance, and binder resin, the above-described materials can be used.
Examples of the other components include plasticizers, fine particles, and various additives.

  The thickness of the single-layer type photosensitive layer is preferably 5 to 100 μm, and more preferably 5 to 50 μm. When the thickness is less than 5 μm, the chargeability may be lowered, and when it exceeds 100 μm, the sensitivity may be lowered.

A protective layer may be provided on the photosensitive layer as necessary. The protective layer contains at least a binder resin, a charge transport material, and, if necessary, other components.
The above-mentioned materials can be used as the binder resin and the charge transport material.
Various additives may be added to the protective layer as necessary for the purpose of improving adhesiveness, smoothness, and chemical stability.
There is no restriction | limiting in particular in the thickness of the said protective layer, According to the objective, it can select suitably, For example, 1-15 micrometers is preferable and 1-10 micrometers is more preferable.

  An undercoat layer may be provided between the support and the photosensitive layer as necessary. The undercoat layer is provided for the purpose of improving adhesiveness, preventing moire, improving the coatability of the upper layer, and reducing residual potential.

The undercoat layer contains at least a resin and fine powder, and further contains other components as necessary.
Examples of the resin include water-soluble resins such as polyvinyl alcohol resin, casein, and sodium polyacrylate; alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon; polyurethane resins, melamine resins, alkyd-melamine resins, and epoxy resins. And a curable resin that forms a three-dimensional network structure.
Examples of the fine powder include metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide, metal sulfides, and metal nitrides.
There is no restriction | limiting in particular about the thickness of the said undercoat layer, According to the objective, it can select suitably, 0.1-10 micrometers is preferable and 1-5 micrometers is more preferable.

In the photoreceptor, an intermediate layer may be provided on the support, if necessary, in order to improve adhesion and charge blocking properties. The intermediate layer contains a resin as a main component, and it is desirable that these resins are resins having a high solvent resistance with respect to an organic solvent in view of applying a photosensitive layer thereon with a solvent.
The resin can be appropriately selected from those similar to the above undercoat layer.

The formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then performing imagewise exposure, and is performed by the electrostatic latent image forming unit. Can do.
The electrostatic latent image forming means includes, for example, at least a charger that uniformly charges the surface of the electrostatic latent image carrier and an exposure device that exposes the surface of the electrostatic latent image carrier imagewise. Prepare.

The charging can be performed, for example, by applying a voltage to the surface of the electrostatic latent image carrier using the charger.
The charger is not particularly limited and may be appropriately selected depending on the purpose. For example, a known contact charging device including a conductive or semiconductive roller, brush, film, rubber blade, etc. And non-contact chargers using corona discharge such as corotrons and corotrons.

The shape of the charging member may take any form such as a magnetic brush or a fur brush in addition to the roller, and can be selected according to the specifications and form of the electrophotographic apparatus. The magnetic brush includes, for example, various ferrite particles such as Zn—Cu ferrite as a charging member, and includes a nonmagnetic conductive sleeve for supporting the charging member, and a magnet roll included therein. As the material of the fur brush, for example, a fur treated with carbon, copper sulfide, metal or metal oxide is used, and this is wound around or pasted on a metal or other conductive metal core. Use a charger.
The charger is not limited to the contact charger as described above. However, since an image forming apparatus in which ozone generated from the charger is reduced is obtained, a contact charger is used. preferable.
It is preferable that the charger is disposed in contact or non-contact with the electrostatic latent image carrier and charges the surface of the electrostatic latent image carrier by applying a direct current and an alternating voltage.
Further, the charging device is a charging roller disposed in close proximity to the electrostatic latent image carrier via a gap tape, and the electrostatic latent image carrier is applied by applying a direct current and an alternating voltage to the charging roller. Those that charge the surface are preferred.
The exposure can be performed, for example, by exposing the surface of the latent electrostatic image bearing member imagewise using the exposure device.
The exposure device is not particularly limited as long as it can expose the surface of the electrostatic latent image carrier charged by the charger so as to form an image to be formed, and is appropriately selected according to the purpose. For example, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system can be used.
In the present invention, a back light system in which imagewise exposure is performed from the back side of the electrostatic latent image carrier may be employed.

-Development process and development means-
The developing step is a step of developing the electrostatic latent image with toner or the developer to form a toner image (visible image).

<Toner>
As the toner, a substantially spherical toner that is spheroidized in the manufacturing process or in the post-manufacturing process is preferably used from the viewpoint of uniformity of dots forming an image, high transfer efficiency, and the like.
Here, the toner spheroidized in the post-manufacturing process is, for example, a toner obtained by spheroidizing pulverized toner with heat or mechanical force. On the other hand, the spheroidized toner in the production process is a toner produced by a polymerization method such as a dispersion polymerization method, a suspension polymerization method, or an emulsion polymerization method. In particular, the polymerization method is excellent in terms of toner shape, ease of particle size control, productivity, and the like, and is suitable as a method for producing the spherical toner.

The average value of the shape factor SF1 of the toner is preferably 100 to 130, and more preferably 100 to 120.
The toner shape factor SF1 is expressed by the following mathematical formula 1. The area indicates the projected area of the toner, the maximum length indicates the maximum length in the projected image of the toner, and the closer SF1 is to 100, the more spherical the shape.
<Formula 1>
SF1 = 100 × (maximum length) ² × π / (area × 4)
Specifically, the SF1 can be obtained by observing the toner with a high-magnification microscope such as an electron microscope and measuring the image of the toner image.

  The production method and material of the toner are not particularly limited and can be appropriately selected from known ones according to the purpose, but is preferably a substantially spherical toner. As a method for producing such a toner, a pulverization and classification method described in Journal of the Imaging Society of Japan, Vol. 43, No. 1 (2004), or the like, an oil phase is emulsified, suspended or aggregated in an aqueous medium. Examples thereof include suspension polymerization, emulsion polymerization, and polymer suspension, which form toner mother particles.

  The pulverization method is a method for obtaining mother particles of the toner by, for example, melting and kneading a toner material, pulverizing, classifying and the like. In the case of the pulverization method, the shape may be controlled by applying a mechanical impact force to the obtained toner base particles for the purpose of making the toner spherical. In this case, the mechanical impact force can be applied to the toner base particles using an apparatus such as a hybridizer or mechanofusion.

The suspension polymerization method is an oil-soluble polymerization initiator, emulsification described later in an aqueous medium in which a colorant, a release agent, and the like are dispersed in a polymerizable monomer and a surfactant and other solid dispersant are contained. Emulsified and dispersed by the method. Thereafter, a polymerization reaction is performed to form particles, and then wet processing for attaching inorganic fine particles to the toner particle surfaces in the present invention may be performed. At that time, it is preferable to treat the toner particles from which excess surfactant and the like are removed by washing.
Examples of the polymerizable monomer include acrylic acids, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, and other acids, acrylamide, By using a part of acrylate or methacrylate having amino group such as methacrylamide, diacetone acrylamide or their methylol compounds, vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethyleneimine, dimethylaminoethyl methacrylate, etc. Functional groups can be introduced.
In addition, by selecting a dispersant having an acidic group or a basic group as the dispersant to be used, the functional group can be introduced by adsorbing and dispersing the dispersant on the particle surface.

  As the emulsion polymerization method, a water-soluble polymerization initiator and a polymerizable monomer are emulsified in water using a surfactant, and a latex is synthesized by a usual emulsion polymerization method. Separately, a dispersion in which a colorant, a release agent and the like are dispersed in an aqueous medium is prepared, and after mixing, the toner is aggregated to a toner size and heat-fused to obtain a toner. Thereafter, wet processing of inorganic fine particles described later may be performed. A functional group can be introduced on the surface of the toner particles by using a latex similar to the monomer that can be used in the suspension polymerization method.

  Among these, since the selectivity of the resin is high, the low-temperature fixability is high, the granulation property is excellent, and the particle size, the particle size distribution, and the shape can be easily controlled. It is preferable that the toner is granulated by emulsifying or dispersing the dispersion in an aqueous medium.

The toner material solution is obtained by dissolving the toner material in a solvent, and the toner material dispersion liquid is obtained by dispersing the toner material in a solvent.
Examples of the toner material include an adhesive base obtained by reacting an active hydrogen group-containing compound, a polymer capable of reacting with the active hydrogen group-containing compound, a binder resin, a release agent, and a colorant. And other components such as resin fine particles and a charge control agent as necessary.
The adhesive base material exhibits adhesiveness to a recording medium such as paper, and is formed by reacting the active hydrogen group-containing compound and a polymer capable of reacting with the active hydrogen group-containing compound in the aqueous medium. It may contain at least a polymer and may further contain a binder resin appropriately selected from known binder resins.

  The volume average particle diameter Dt of the toner is preferably 2 to 7 μm, and more preferably 3 to 6 μm. If the volume average particle diameter Dt is less than 2 μm, the proportion of fine toner particles having a particle diameter of 1 μm or less that tends to cause image defects may increase. If the volume average particle diameter Dt exceeds 7 μm, the image quality of the electrophotographic image is improved. It may be difficult to meet the requirements.

  In the toner, a large particle size external additive having an average particle size Da of 100 to 300 nm is used. When the average particle diameter Da is less than 100 nm, the effect of suppressing the burying of the external additive may be insufficient. When the average particle diameter Da exceeds 300 nm, the adhesion to the toner base particles is reduced and the toner is separated from the toner. The component members of the image forming apparatus such as the photoreceptor are easily damaged by the separated external additive. An external additive having a small particle size is effective for improving the fluidity of the toner, and it is preferable to use an external additive having an average particle size of 100 nm or less in the toner used in the present invention.

  The coverage of the large particle size external additive having an average particle diameter Da of 100 to 300 nm is preferably 5 to 90%, more preferably 15 to 75%, and still more preferably 30 to 60%. When the external additive coverage is less than 5%, the effect of suppressing the burying of the external additive is insufficient, and the effect of suppressing the burying may be maintained as the coating rate is higher, exceeding 90%. In some cases, the amount of external additives not directly on the toner base particles increases, so that the toner particles may be easily separated.

Here, the external additive coverage increases with the amount of the external additive added, but there are various particle sizes and shapes of the toner base particles, particle sizes and shapes of the external additives, mixing conditions with the toner base particles, and the like. Influenced by factors. Further, the coverage of the external additive varies among the toners, and there is also nonuniformity on the surface of the toner base particles and on the coating state. Conventionally, no consideration has been given to coating the external additive with a large particle diameter uniformly between the toner and the surface of the mother particles.
There is no restriction | limiting in particular as said mixing method, According to the objective, it can select suitably, For example, the well-known method using various mixing apparatuses, such as a V-type blender, a Henschel mixer, a mechano-fusion, can be used. Immediately before mixing the external additive, the process of loosening the external additive, or stepwise mixing from a loose condition to a strong condition, makes it possible to adhere the large particle size external additive uniformly at a certain coverage. Can be made.

There is no restriction | limiting in particular as said external additive, According to the objective, it can select suitably from well-known organic fine particles or inorganic fine particles. As the inorganic fine particles, it is preferable to use at least one of silica, titanium, and alumina, for example. In the case of these inorganic fine particles having hygroscopicity, those subjected to a hydrophobization treatment are preferably used in consideration of environmental stability. The hydrophobic treatment can be performed by reacting the hydrophobic treatment agent with the fine powder at a high temperature.
There is no restriction | limiting in particular as said hydrophobization processing agent, According to the objective, it can select suitably, For example, a silane coupling agent, silicone oil, etc. are mentioned.

<Developer>
The developer contains at least the toner and contains other appropriately selected components such as a carrier. The developer may be a one-component developer or a two-component developer. However, when it is used for a high-speed printer or the like corresponding to the recent improvement in information processing speed, the life is improved. In view of the above, the two-component developer is preferable.
In the case of the one-component developer using the toner, even if the balance of the toner is performed, the fluctuation of the toner particle diameter is small, the filming of the toner on the developing roller, and a blade for thinning the toner The toner is not fused to such a member, and good and stable developability and an image can be obtained even when the developing device is used for a long time (stirring). Further, in the case of the two-component developer using the toner, even if the toner balance for a long period of time is performed, the fluctuation of the toner particle diameter in the developer is small, and it is good and stable even for a long period of stirring in the developing device. Developability is obtained.

  There is no restriction | limiting in particular as said carrier, Although it can select suitably according to the objective, What has a core material and the resin layer which coat | covers this core material is preferable.

  There is no restriction | limiting in particular as a material of the said core material, It can select suitably from well-known things, For example, 50-90 emu / g manganese-strontium (Mn-Sr) type material, manganese-magnesium (Mn-) Mg) -based materials and the like are preferable, and highly magnetized materials such as iron powder (100 emu / g or more) and magnetite (75 to 120 emu / g) are preferable in terms of securing image density. In addition, a weakly magnetized material such as a copper-zinc (Cu—Zn) -based (30 to 80 emu / g) is advantageous in that it can weaken the contact with the photoconductor in which the toner is in a spiked state and is advantageous in improving the image quality. Is preferred. These may be used alone or in combination of two or more.

The particle diameter of the core material is an average particle diameter (volume average particle diameter (D ₅₀ )), preferably 10 to 200 μm, and more preferably 20 to 100 μm.

  The material of the resin layer is not particularly limited and can be appropriately selected from known resins according to the purpose. For example, amino resins, polyvinyl resins, polystyrene resins, halogenated olefin resins, Polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, fluorine And a copolymer of vinylidene fluoride and vinyl fluoride, a fluoroterpolymer such as a terpolymer of tetrafluoroethylene, vinylidene fluoride and a non-fluorinated monomer, and a silicone resin. These may be used individually by 1 type and may use 2 or more types together.

  The resin layer may contain conductive powder or the like as necessary. Examples of the conductive powder include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. The average particle diameter of these conductive powders is preferably 1 μm or less. When the average particle diameter exceeds 1 μm, it may be difficult to control electric resistance.

For example, the resin layer is prepared by dissolving the silicone resin or the like in a solvent to prepare a coating solution, and then uniformly coating the coating solution on the surface of the core material by a known coating method, drying, and baking. It can be formed by doing. Examples of the application method include an immersion method, a spray method, and a brush coating method.
There is no restriction | limiting in particular as said solvent, Although it can select suitably according to the objective, For example, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cellosolve, butyl acetate, etc. are mentioned.
The baking is not particularly limited, and may be an external heating method or an internal heating method. For example, a stationary electric furnace, a fluid electric furnace, a rotary electric furnace, a burner furnace, etc. The method of using, the method of using a microwave, etc. are mentioned.

The amount of the resin layer in the carrier is preferably 0.01 to 5.0% by mass.
When the amount is less than 0.01% by mass, the uniform resin layer may not be formed on the surface of the core material. When the amount exceeds 5.0% by mass, the resin layer becomes thick. In some cases, granulation of carriers occurs, and uniform carrier particles may not be obtained.

When the developer is the two-component developer, the content of the carrier in the two-component developer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, 90 to 98% by mass Is preferable, and 93-97 mass% is more preferable.
The mixing ratio of the toner and the carrier of the two-component developer is generally 1 to 10.0 parts by mass of the toner with respect to 100 parts by mass of the carrier.

The toner image (visible image) can be formed, for example, by developing the electrostatic latent image using the toner or the developer, and can be performed by the developing unit.
The developing unit is not particularly limited as long as it can be developed using, for example, the toner or the developer, and can be appropriately selected from known ones. For example, the toner or developer is accommodated. Preferred examples include those having at least a developing unit capable of bringing the toner or developer into contact or non-contact with the electrostatic latent image.

  The developing unit may be a dry developing type, a wet developing type, a single color developing unit, or a multi-color developing unit. For example, a toner having a stirrer for charging the toner or the developer by frictional stirring and a rotatable magnet roller is preferable.

  In the developing device, for example, the toner and the carrier are mixed and agitated, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a raised state to form a magnetic brush. . Since the magnet roller is disposed in the vicinity of the electrostatic latent image carrier (photoconductor), a part of the toner constituting the magnetic brush formed on the surface of the magnet roller is electrically attracted. It moves to the surface of the electrostatic latent image carrier (photoconductor) by force. As a result, the electrostatic latent image is developed with the toner, and a visible image is formed with the toner on the surface of the electrostatic latent image carrier (photoconductor).

-Transfer process and transfer means-
The transfer step is a step of transferring the visible image onto a recording medium. After the primary transfer of the visible image onto the intermediate transfer member using an intermediate transfer member, the visible image is transferred onto the recording medium. A primary transfer step of forming a composite transfer image by transferring a visible image onto an intermediate transfer body using two or more colors, preferably full color toner as the toner, and a composite transfer image; A mode including a secondary transfer step of transferring the transfer image onto the recording medium is more preferable.
The transfer can be performed, for example, by charging the latent electrostatic image bearing member (photoconductor) of the visible image using a transfer charger, and can be performed by the transfer unit. The transfer means includes a primary transfer means for transferring a visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. Embodiments are preferred.
The intermediate transfer member is not particularly limited and may be appropriately selected from known transfer members according to the purpose. For example, a transfer belt and the like are preferable.

The volume resistivity of the intermediate transfer member is preferably adjusted to a range of 10 ⁷ to 10 ¹⁴ Ωcm. When the volume resistivity of the intermediate transfer member is less than 10 ⁷ Ωcm, charge leakage may occur and the transfer efficiency tends to decrease. When the volume resistivity exceeds 10 ¹⁴ Ωcm, after the transfer, Residual charges are likely to be generated, and a static eliminator may be required.

  The material of the intermediate transfer member is not particularly limited and can be appropriately selected from known materials according to the purpose. For example, (1) a material having a high Young's modulus (tensile elastic modulus) is used as a single-layer belt. PC (polycarbonate), PVDF (polyvinylidene fluoride), PAT (polyalkylene terephthalate), PC (polycarbonate) / PAT (polyalkylene terephthalate) blend material, ETFE (ethylene tetrafluoroethylene copolymer) / PC blend material, ETFE / PAT blend material, PC / PAT blend material, carbon black-dispersed thermosetting polyimide, and the like. These single-layer belts having a high Young's modulus have the advantage that the amount of deformation with respect to stress during image formation is small, and registration is not likely to occur particularly during color image formation. (2) A belt having a two- to three-layer structure in which a belt having a high Young's modulus is used as a base layer and a surface layer or an intermediate layer is provided on the outer periphery of the belt. Therefore, the line image has a performance capable of preventing the line image from being lost. (3) Belts having a relatively low Young's modulus using rubber and elastomer, and these belts have an advantage that line images are hardly lost due to their softness. In addition, the belt width is made larger than that of the drive roll and the tension roll, and the elasticity of the belt ear protruding from the roll is used to prevent meandering, so that a low cost can be realized without the need for ribs or meandering prevention devices. .

The resistance value adjusting conductive agent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metal powders such as carbon black, graphite, aluminum, and nickel, tin oxide, titanium oxide, antimony oxide, and oxidation. Conductive metal oxides such as indium, potassium titanate, antimony oxide-tin oxide composite oxide (ATO), indium oxide-tin oxide composite oxide (ITO), and the conductive metal oxides are barium sulfate and magnesium silicate. Further, it may be coated with insulating fine particles such as calcium carbonate.
As the surface layer material, a surface layer is required to prevent contamination of the photoreceptor with an elastic material and to reduce surface friction resistance to the surface of the transfer belt to improve cleaning property and secondary transfer property. For example, materials that use one or a combination of two or more of polyurethane, polyester, epoxy resin, etc. to reduce surface energy and increase lubricity, such as fluororesin, fluorine compound, fluorocarbon, titanium dioxide, silicon carbide, etc. These powders and particles can be used by dispersing one type or two or more types or a combination of particles having different particle sizes. Further, it is also possible to use a material having a reduced surface energy by forming a fluorine-rich layer on the surface by heat treatment, such as a fluorine-based rubber material.
The manufacturing method of the belt is not limited. For example, a centrifugal molding method in which a material is poured into a rotating cylindrical mold to form a belt, a spray coating method in which a liquid paint is sprayed to form a film, and a cylindrical mold. These include the dipping method in which the material is dipped in the material solution, the casting method in which it is injected into the inner mold and the outer mold, the method in which the compound is wound around a cylindrical mold and vulcanized and polished. It is not limited and it is common to manufacture a belt combining several manufacturing methods.

The transfer means (the primary transfer means and the secondary transfer means) is a transfer for peeling and charging the visible image formed on the electrostatic latent image carrier (photoconductor) to the recording medium side. It is preferable to have at least a vessel. There may be one transfer means or two or more transfer means.
Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.
The recording medium is typically plain paper, but is not particularly limited as long as it can transfer an unfixed image after development, and can be appropriately selected according to the purpose. PET for OHP A base or the like can also be used.

The fixing step is a step of fixing the visible image transferred to the recording medium using a fixing device, and may be performed each time the toner of each color is transferred to the recording medium, or for the toner of each color. You may perform this simultaneously in the state which laminated | stacked this.
There is no restriction | limiting in particular as said fixing device, Although it can select suitably according to the objective, A well-known heating-pressing means is suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt.
The heating in the heating and pressing means is usually preferably 80 to 200 ° C.
In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

The neutralization step is a step of performing neutralization by applying a neutralization bias to the electrostatic latent image carrier, and can be suitably performed by a neutralization unit.
The neutralization means is not particularly limited, and may be appropriately selected from known neutralizers as long as it can apply a neutralization bias to the electrostatic latent image carrier. Preferably mentioned.

The cleaning step is a step of removing the electrophotographic toner remaining on the electrostatic latent image carrier, and can be suitably performed by a cleaning unit.
The cleaning means is not particularly limited as long as it can remove the electrophotographic toner remaining on the electrostatic latent image carrier, and can be appropriately selected from known cleaners. Suitable examples include brush cleaners, electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.

The recycling step is a step of recycling the electrophotographic toner removed by the cleaning step to the developing unit, and can be suitably performed by the recycling unit.
There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.

The control means is a process for controlling the respective steps, and can be suitably performed by the control means.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

Here, FIG. 3 is a schematic configuration diagram showing an example of the image forming apparatus of the present invention. In FIG. 3, there are a charging device 22 for charging the drum surface, an exposure device 23 for forming a latent image on the charging surface, and a drum surface around a photosensitive drum 21 which is an electrostatic latent image carrier. A developing device 24 for forming a toner image by attaching charged toner to the latent image of the toner, a transfer device 25 for transferring the toner image on the formed drum onto the recording medium 26, and a fixing device for fixing the toner on the recording medium. 27, a cleaning device 30 for removing and collecting the residual toner on the drum, and a static eliminating device 31 for removing the residual potential on the drum are arranged in this order.
First, the surface of the photosensitive drum 21 is uniformly charged by the charging roller 22. In the example of FIG. 3, the photosensitive drum 21 is charged using a charging roller, but corona charging such as corotron or scorotron may be used. Note that charging using a charging roller has an advantage of less ozone generation than when corona charging is used.

The charged photosensitive drum 21 is irradiated with a laser beam 23 according to image information, and an electrostatic latent image is formed. It is also possible to control the charging conditions and exposure conditions by detecting the charging potential and exposure part on the photosensitive drum 21 with a potential sensor.
Next, the developing device 24 forms a toner image on the photosensitive drum 21 on which the electrostatic latent image is formed.
Here, FIG. 4 shows a configuration example when the developing device 24 is a two-component developing device using a two-component developer composed of toner and carrier. In this example, the developer is stirred and conveyed by the screw 41 and supplied to the developing sleeve 42. The developer supplied to the developing sleeve 42 is regulated by the doctor blade 43, and the amount of developer supplied is controlled by a doctor gap that is the distance between the doctor blade 43 and the developing sleeve 42. If the doctor gap is too small, the developer amount is too small and the image density becomes insufficient. Conversely, if the doctor gap is too large, the developer amount is excessively supplied and carrier adhesion occurs on the photosensitive drum 21. Problems arise. The developing sleeve 42 is provided with a magnet that forms a magnetic field so that the developer is sprinkled on the peripheral surface, and the developer is placed on the developing sleeve 42 so as to follow a normal magnetic field line emitted from the magnet. A magnetic brush is formed with a chain.

The developing sleeve 42 and the photosensitive drum 21 are arranged so as to be close to each other with a certain gap (developing gap) therebetween, and a developing region is formed in a portion facing both. The developing sleeve 42 is formed of a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape, and is rotated by a rotation drive mechanism (not shown). The magnetic brush is transferred to the developing area by the rotation of the developing sleeve 42. A developing voltage is applied to the developing sleeve 42 from a developing power source (not shown), and the toner on the magnetic brush is separated from the carrier by the developing electric field formed between the developing sleeve 42 and the photosensitive drum 21, and the photosensitive drum 21. It is developed on the upper electrostatic latent image. An alternating current may be superimposed on the development voltage. The development gap can be set to 0.5 to 1.5 mm when the developer particle size is about 5 to 30 times and the developer particle size is 50 μm. If it is wider than this, it is difficult to obtain a desired image density.
Further, the doctor gap needs to be the same as or slightly larger than the development gap. The drum diameter and drum linear speed of the photosensitive drum 21 and the sleeve diameter and sleeve linear speed of the developing sleeve 42 are determined by restrictions such as the copying speed and the size of the apparatus. The ratio of the sleeve linear velocity to the drum linear velocity is preferably 1.1 or more in order to obtain a necessary image density. It is also possible to control the process conditions by installing a sensor at a position after development and detecting the toner adhesion amount from the optical reflectance.
In FIG. 4, a two-component developing device is used as the developing device. However, the present invention is not limited to the two-component developing device, and the toner thin layer formed on the developing sleeve is applied to the photosensitive member by an electric field. A one-component developing device for developing may be used.

The toner image formed on the photosensitive drum 21 is conveyed to a transfer nip where the photosensitive drum 21 and the recording medium 26 are in contact with each other. A transfer voltage having a polarity opposite to that of toner is applied to a roller 25 that contacts a recording medium 26 conveyed from a paper feed tray (not shown) by a transfer power source (not shown). The toner image formed on the photosensitive drum 21 is transferred onto the recording medium 26 by the transfer electric field acting on the recording medium 26.
The recording medium 26 on which the unfixed toner image is placed is fixed on the recording medium 26 by applying constant heat and pressure to the recording medium 26 by the fixing roller 28 and the pressure roller 29. In order to keep the fixing temperature constant, a thermistor (not shown) is in contact with the fixing roller 28 to control the temperature of the fixing roller 28. A fixing method using a fixing roller has high thermal efficiency, excellent safety, can be miniaturized, and has a wide range of applications from low speed to high speed.
The toner remaining on the photosensitive drum 21 is removed by the cleaning device 30, but a cleaning blade may be used as the cleaning device, and a cleaning roller, a cleaning brush, or the like may be used in combination. Further, the cleaning efficiency can be increased by applying a voltage having a polarity opposite to that of the toner to these cleaning members.

  FIG. 5 is a schematic configuration diagram showing an example of a color image forming apparatus of the present invention. In the color image forming apparatus 51, a charging device 51b, an exposure device 51c, a developing device 51d, a transfer device 51e, a cleaning device 51f, and a charge eliminating device 51g are arranged around the photosensitive drum 51a. The image formed by the yellow toner is transferred onto the intermediate transfer belt 55 by the transfer device 51e, and the toner remaining on the photosensitive drum 51a is removed by the cleaning device 51f. Similarly, images of magenta toner, cyan toner, and black toner are formed on the intermediate transfer belt 55 by the devices 52 to 54. The color image on the intermediate transfer belt 55 is transferred onto the recording medium 57 by the transfer device 56, and the toner remaining on the intermediate transfer belt 55 is removed by the cleaning device 58. The color image formed on the recording medium 57 is fixed by a fixing device (not shown). The order in which the color images are formed is not specified and may be formed in any order.

The present invention is characterized in that, in the example of the image forming apparatus as described above, the toner transfer efficiency is high, image defects such as “collapse” do not occur, and a stable image can be obtained even after long-term use. It is said.
When the image forming apparatus as shown in FIGS. 3 and 5 is used for a long time, the external additive coated on the surface of the toner that is not consumed but mechanically stressed in the developing device is embedded in the toner. Or separation from the toner, the contact between the toner mother particles and the other members and between the toner mother particles increases, and the contact area increases, so that the adhesion between the toner and the other members and between the toners increases. When the toner adhesion force increases, the toner cannot be separated from the photoconductor by the Coulomb force generated by the transfer electric field, and the transfer rate decreases. In addition, when a toner layer formed of a toner having a high adhesion force is compressed by a pressure at the time of transfer, the toner adhesion force, particularly non-electrostatic properties such as van der Waals force and liquid cross-linking force that do not depend on toner charging. Adhesive force increases, toner aggregation occurs, and voids are likely to occur.

  Therefore, in the present invention, by using an external additive having a large particle size that is difficult to be embedded in the toner, an increase in the toner adhesion force against mechanical stress is suppressed, and the non-electrostatic adhesion force is controlled within an appropriate range. The occurrence of “missing” is suppressed, the transfer efficiency is high even when used for a long period of time, and image defects such as “missing” are prevented from occurring. Japanese Patent Application Laid-Open No. 2000-66441 etc. defines the range of non-electrostatic adhesion force between the toner and the photoconductor, but the non-electrostatic adhesion force is proportional to the toner particle size, and the Coulomb force due to the transfer electric field. The size of the toner depends on the toner particle size, and therefore, the range of non-electrostatic adhesion that is difficult to cause “collapse” varies depending on the toner particle size. JP 2001-318485 A, JP 2001-255777 A, etc. define the range of the proportional coefficient in the toner particle size dependence of non-electrostatic adhesion force, and even for small particle size toners. Applicable. However, the non-electrostatic adhesion force depends on the particle size of the external additive, and the patent does not specify the relationship between the non-electrostatic adhesion force and the external additive particle size. In the case of using an additive, the relationship between the non-electrostatic adhesion force and “missing” has not been sufficiently studied.

  Measure the average value F of the non-electrostatic adhesion force between the toner and the photoconductor using the centrifugal separation method for the toners with various particle sizes and external additives coated on the toner base particles of various particle sizes. did. As a result, the non-electrostatic adhesion force F is proportional to the volume average particle diameter Dt of the toner, and the proportionality coefficient α increases as the average particle diameter Da of the external additive increases. In addition, the proportionality coefficient α depends on the material of the external additive and the coverage of the external additive, decreases with an increase in the coverage of the external additive, and tends to be saturated at a certain external additive coverage. The external additive coverage means the ratio of the area of the part where the external additive is adhered to the surface area of one toner particle, and can be measured by image analysis of an electron micrograph of the toner.

  As a result of the evaluation of “blank” by the image forming apparatus shown in FIG. 3 with respect to the toner for which the non-electrostatic adhesion force was measured, not only the proportionality coefficient α is likely to cause “blank”, Depending on the average particle diameter Da of the external additive, the larger the α / Da, the more likely to be “collapse”. The reason why the occurrence of “collapse” depends on the average particle diameter Da of the external additive is that the non-electrostatic adhesion between the toner and other members and between the toners increases due to the compression of the toner layer. It is conceivable that the ratio varies depending on Da.

Therefore, in the present invention, a large particle size external additive having an average particle diameter Da of 100 to 300 nm is used, and F corresponding to the proportionality coefficient α is a value obtained by dividing the product of Dt and Da [F / (Dt × Da)] needs to be 7.5 × 10 ⁴ (N / m ² ) or less, and preferably 7 × 10 ⁴ (N / m ² ) or less. By satisfying this, even if the image forming apparatus is used for a long period of time, image defects such as “missing” do not occur, and good image quality can be obtained.
When [F / (Dt × Da)] exceeds 7.5 × 10 ⁴ (N / m ² ), image defects such as “missing” and transfer rate may occur when the image forming apparatus is used for a long time. Decrease may occur.
In the toner layer, toners repel each other electrostatically, but the toner is constrained in the toner layer by non-electrostatic adhesion between the toners. For this reason, if the non-electrostatic adhesion force between the toners is too small, the toner is easily separated from the toner layer, and the separated toner adheres to the periphery of the image, so that “image blur” tends to occur. As a result of evaluating the “image blur” with respect to the toner whose non-electrostatic adhesion was measured, it was found that [F / (Dt × Da)] was 2.0 × 10 ⁴ (N / m ² ) or more, It was found that “smear” is less likely to occur.
Also, when forming a color image, if the transferability varies depending on the color, good image quality cannot be obtained. Therefore, the toner of each color satisfies the condition [F / (Dt × Da)]. Need to be satisfied.

Next, a method for measuring the non-electrostatic adhesion force between the toner and the photoreceptor by the centrifugal separation method will be described.
As a method for measuring the non-electrostatic adhesion force of the toner, a method for estimating a force necessary for separating the toner from an object to which the toner is adhered is generally used. As a method for separating the toner, for example, a method using centrifugal force, vibration, impact, air pressure, electric field, magnetic field or the like is known. Among these, a method using centrifugal force is particularly preferable as a method for measuring the adhesion force between the toner and the photosensitive member because it is easy to quantify and has high measurement accuracy.

  Hereinafter, a method for measuring toner adhesion by centrifugation will be described. The centrifugation method is IS & T NIP7th p. 200 (1991) and the like are known.

1 and 2 are diagrams illustrating an example of a measurement cell and a centrifugal separator of a toner adhesion measuring apparatus.
FIG. 1 is an explanatory diagram of a measurement cell of the toner adhesion measuring apparatus. In FIG. 1, reference numeral 1 denotes a measurement cell. The measurement cell 1 has a sample substrate 2 having a sample surface 2a to which toner is adhered, and a receiving substrate 3 having an adhesion surface 3a to which toner separated from the sample substrate 2 is adhered. And a spacer 4 provided between the sample surface 2 a of the sample substrate 2 and the attachment surface 3 a of the receiving substrate 3. FIG. 2 is a partial cross-sectional view of the centrifugal separator.
In FIG. 2, reference numeral 5 denotes a centrifugal separator, and the centrifugal separator 5 includes a rotor 6 that rotates the measurement cell 1 and a holding member 7. The rotor 6 has a hole-shaped cross section perpendicular to the rotation center axis 9 of the rotor 6 and has a sample setting portion 8 for setting the holding member 7. The holding member 7 includes a rod-like portion 7a, a cell holding portion 7b provided on the rod-like portion 7a for holding the measurement cell 1, a hole portion 7c for pushing the measurement cell 1 out of the cell holding portion 7b, and the rod-like portion 7a as a sample installation portion. 8 is provided with an installation fixing portion 7d to be fixed to 8. The cell holding unit 7b is configured such that when the measurement cell 1 is installed, the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor.

Here, a method for measuring the non-electrostatic adhesion force between the toner and the photoreceptor using the above apparatus will be described.
First, a photoconductor is directly formed on the sample substrate 2 or a part of the photoconductor is cut out and attached to the sample substrate 2 with an adhesive. Next, uncharged toner is deposited on the photoreceptor (sample surface 2 a) on the sample substrate 2.
Next, as shown in FIG. 1, the measurement cell 1 is configured using the sample substrate 2, the receiving substrate 3, and the spacer 4. The cell holding of the holding member 7 is performed so that the sample substrate 2 is positioned between the receiving substrate 3 and the rotation center axis 9 of the rotor 6 when the holding cell 7 is placed on the sample setting portion 8 of the rotor 6. It installs in the part 7b. The holding member 7 is installed on the sample installation unit 8 of the rotor 6 so that the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor. The centrifugal separator 5 is operated to rotate the rotor 6 at a constant rotational speed. The toner adhering to the sample substrate 2 receives a centrifugal force corresponding to the rotational speed, and when the centrifugal force received by the toner is larger than the adhesive force between the toner and the sample surface 2a, the toner is separated from the sample surface 2a, It adheres to 3a.

Here, the centrifugal force Fc received by the toner is obtained from the following formula 2 using the toner mass m, the rotational speed f (rpm) of the rotor, and the distance r from the central axis of the rotor to the toner adhesion surface of the sample substrate. .
<Formula 2>
Fc = m × r × (2πf / 60) ²

Further, the toner mass m is obtained from the following Equation 3 using the true specific gravity ρ of the toner and the equivalent circle diameter d.
<Formula 3>
m = (π / 6) × ρ × d ³

Further, from the above formulas 2 and 3, the centrifugal force Fc received by the toner can be obtained from the following formula 4.
<Formula 4>
^{Fc = (π 3/5400)} × ρ × d 3 × r × f 2

Next, after completion of the centrifugation, the holding member 7 is taken out from the sample setting portion 8 of the rotor 6, and the measurement cell 1 is taken out from the cell holding portion 7 b of the holding member 7. The receiving substrate 3 is replaced, the measurement cell 1 is installed on the holding member 7, the holding member 7 is installed on the rotor 6, and the rotor 6 is rotated at a higher rotational speed than the previous time. The centrifugal force received by the toner becomes larger than the previous time, and the toner having a large adhesion force separates from the sample surface 2a and adheres to the adhesion surface 3a. By performing the same operation by changing the set rotational speed of the centrifugal separator from a low rotational speed to a high rotational speed, the toner on the sample surface 2a is changed according to the magnitude relationship between the centrifugal force and the adhesive force received at each rotational speed. Moves to the attachment surface 3a.
After centrifuging for all the set rotational speeds, the particle size of the toner adhering to the adhesion surface 3a of the receiving substrate 3 at each rotational speed is measured. The toner particle size is measured by observing the toner on the adhesion surface 3a with an optical microscope, inputting the image of the adhesion surface to the image processing device through a CCD camera, and measuring the particle size of each toner using the image processing device. Can do. Since the adhesion force of the toner separated at a certain rotational speed is smaller than the centrifugal force at the rotational speed at which the toner is separated and larger than the centrifugal force at the rotational speed before separation, the centrifugal force of the two is calculated by the above equation 1. The average value was defined as toner adhesion. The average value F of the toner adhesion can be obtained from F = 10 ^A by calculating the arithmetic average value A for the common logarithm of the adhesion of each toner.

  According to the image forming apparatus and the image forming method of the present invention, by satisfying the condition of [F / (Dt × Da)], the transfer efficiency is high, and there is no image defect such as “missing”, and long Even if it is used for a period, a good image can be obtained stably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to the following Example.

Example 1
<Preparation of Toner A>
-Production of graft carbon black-
Add three parts by weight of styrene monomer, 20 parts by weight of carbon black (MA100, manufactured by Mitsubishi Kasei Co., Ltd.) and 0.5 parts by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator. In a 500 ml four-necked separable flask equipped with a condenser, a gas inlet tube, and a thermometer, the mixture was stirred for 30 minutes at room temperature under a nitrogen stream, and oxygen in the flask was replaced with nitrogen. Then, it stirred at 60 rpm in a 70 degreeC hot water bath for 6 hours, and produced graft carbon black.

Next, a mixture having the following composition was dispersed with a ball mill for 10 hours. After dissolving 1 part by mass of 2,2′-azobisisobutyronitrile and sodium nitrite respectively in the obtained dispersion, it was added to 250 parts by mass of a 2% by weight aqueous solution of polyvinyl alcohol, and TK homomixer ( A suspension was obtained by stirring at 8,000 rpm for 10 minutes.
Styrene monomer: 50 parts by mass n-butyl methacrylate: 14.5 parts by mass 1,3-butanediol dimethacrylate: 0.5 parts by mass t-butylacrylamide sulfonic acid: 3 parts by mass-Low molecular weight polyethylene (Mitsui Petrochemical Co., Ltd., Mitsui High Wax 210P) ... 2 parts by mass-Graft carbon black ... 30 parts by mass

Next, the obtained suspension was placed in a 500 ml four-necked separable flask equipped with a three-one motor-driven stirring blade, a cooler, a gas introduction tube, and a thermometer, and stirred at room temperature under a nitrogen stream. The oxygen inside was replaced with nitrogen. Subsequently, it stirred at 100 rpm in a 70 degreeC hot water bath for 5 to 8 hours, polymerization was completed, and the suspension polymerization particle | grains were produced. 100 parts by mass of these particles are re-dispersed in a water / methanol = 1/1 (mass ratio) mixed solution so as to have a solid content of 30% by mass, and H ₄ N (CH ₂ ) ₅ CH═C (C 3 parts by mass of ₂ F ₅ ) ₂ was added, and after stirring, filtered and dried to prepare polymer particles A.
With respect to the obtained polymer particles A, the volume average particle diameter was measured as follows and the average value of the shape factor SF1 was 112.

[Measurement of volume average particle diameter Dt]
The volume average particle diameter was measured by a Coulter counter method. Examples of the measuring device for the particle size distribution of the toner particles by the Coulter counter method include Coulter Counter Multisizer and Multisizer IIe (both manufactured by Coulter). The measurement method will be described below.
First, 0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. Here, the electrolytic solution is prepared by preparing a 1% by mass NaCl aqueous solution using primary sodium chloride, and ISOTON-II (manufactured by Coulter, Inc.) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the volume average particle diameter of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 .35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to less than 12.70 μm; 12.70 to less than 16.00 μm; 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm. The particle size values of each channel are 2.24 μm; 2.83 μm; 3.56 μm; 4.49 μm; 5.66 μm; 7.13 μm; 8.98 μm; 11.31 μm; 14.25 μm; 22.63 μm; 28.51 μm; 35.92 μm were used.

[Measurement of average value of shape factor SF1]
The average value of the shape factor SF1 is determined by depositing toner on an observation substrate for an electron microscope, coating the observation substrate on which the toner is adhered with gold, and observing the toner with a scanning electron microscope (manufactured by Hitachi, Ltd., S-4500). Then, the projected area and the maximum length of the toner were obtained using image processing software (Image Cyber Pro, manufactured by Media Cybernetics), and SF1 was calculated by the following Equation 1. SF1 was measured for 100 or more toners, and the average value of SF1 was obtained.
<Formula 1>
SF1 = 100 × (maximum length) ² × π / (area × 4)

  Next, the silica A having an average particle diameter of 120 nm subjected to the hydrophobization treatment is loosened (stirring by a mixer or the like), blended so as to be 4% by mass with respect to the polymer particles A, and stepwise using a Henschel mixer. The toner A was produced by performing a stirring and mixing process (in which the rotational speed was increased stepwise from 500 to 2,000 rpm).

(Measurement of external additive coverage)
The obtained toner A is adhered to an observation substrate for an electron microscope, the observation substrate to which the toner A is adhered is coated with gold, and the toner A is observed with a scanning electron microscope (manufactured by Hitachi, Ltd., S-4500). The area where the external additive is attached is measured using image processing software (Media Cybernetics, Image-Pro Plus), and the area where the external additive is attached to the toner surface area. The ratio of the area was calculated to determine the external additive coverage. The external additive coverage is represented by an average value measured for 10 toners. In the toner A of Example 1, the toner adhered uniformly to the surface of the toner base particles, the difference in coverage between toners was small, and the average value of the external additive coverage of toner A was 19.3%.
The average particle diameter Da of the external additive was determined by measuring the particle diameter of each external additive adhering to the toner surface and calculating the average value when measuring the external additive coverage.

-Production of developer-
The two-component developer of Example 1 was mixed by mixing toner A and carrier A (carrier used by Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner A was 5% by mass. Produced.

<Preparation of electrostatic latent image carrier (photoconductor)>
-Formation of charge generation layer-
0.4 parts by mass of a bisazo pigment represented by the following structural formula (A) together with 4 parts by mass of a 5% by weight tetrahydrofuran solution of butyral resin (ESREC BL-S, manufactured by Sekisui Chemical Co., Ltd.) and 7.6 parts by mass of tetrahydrofuran Ball milling was performed, and after milling, tetrahydrofuran was added to dilute to 2% by mass to prepare a coating solution for a charge generation layer.
The obtained charge generation layer coating solution was applied by an immersion method onto an aluminum drum A having a diameter of 90 mm that had been roughened by cutting and dried to form a charge generation layer having a thickness of 1 μm.

-Formation of charge transport layer-
Next, 6.0 parts by mass of a hole transport material represented by the following structural formula (B) and 9.0 parts by mass of cyclohexylidene bisphenol polycarbonate (Z Polyca, manufactured by Teijin Chemicals Ltd., TS2050) as a photoreceptor binder resin. Part was dissolved in 67 parts by mass of tetrahydrofuran to prepare a charge transport layer coating solution.
The obtained charge transport layer coating solution was applied onto the charge generation layer by a dipping method and dried to form a charge transport layer having a thickness of 20 μm.
Thus, the photosensitive drum of Example 1 was produced. As a result of measuring the surface shape of the obtained photosensitive drum of Example 1 using a stylus type surface shape measuring device DEKTAK manufactured by Nippon Vacuum Technology Co., Ltd., the average value of the period of surface irregularities was 470 μm, and the volume of the toner The average particle size was about 90 times as large as 5.2 μm.

<Measurement of non-electrostatic adhesion force and F / (Dt × Da)>
Next, the non-electrostatic adhesion force between the toner A of Example 1 and the photoreceptor was measured using a centrifugal separation method.
First, the photoconductor drum of Example 1 was cut out into a disk shape having a diameter of 7 mm, and attached to a sample substrate having a diameter of 8 mm used for centrifugation using an adhesive. Uncharged toner A was adhered onto the photoreceptor by compressed air, and the non-electrostatic adhesion force F between the toner and the photoreceptor was measured using a centrifugal separation method to obtain F / (Dt × Da). In addition, the apparatus and measurement conditions used for the measurement of nonelectrostatic adhesion force are as follows.
[Device and measurement conditions]
Centrifugal separator: CP100α manufactured by Hitachi Koki Co., Ltd. (maximum rotational speed: 100,000 rpm, maximum acceleration: 800,000 g)
・ Rotor: Angle rotor P100AT manufactured by Hitachi Koki Co., Ltd.
Image processing device: Digital Hyper II Image HyperII
Sample substrate and receiving substrate: a disk with a diameter of 8 mm and a thickness of 1.5 mm, and the material is aluminum. Spacer: a ring with an outer diameter of 8 mm, an inner diameter of 5.2 mm, and a thickness of 1 mm, and the material is aluminum. It is a cylinder with a diameter of 13 mm and a length of 59 mm, and the material is a distance from the central axis of the aluminum rotor to the toner adhesion surface of the sample substrate: 64.5 mm
・ Setting speed f: 1,000 rpm, 1,600 rpm, 2,200 rpm, 2,700 rpm, 3,200 rpm, 5,000 rpm, 7,100 rpm, 8,700 rpm, 10,000 rpm, 15,800 rpm, 22,400 rpm, 31,600 rpm, 50,000 rpm, 70,700 rpm, 86,600 rpm, 100,000 rpm

<Image formation>
Using the developer and photoconductor of Example 1 on a color copier (Ricoh Co., Ltd., Imagio Color 4000), after the initial image after changing the developer and continuous copying of 50,000 sheets, transfer in primary transfer Rate measurement and evaluation of hollow images were performed.
In a color copying machine (Imagio Color 4000, manufactured by Ricoh Co., Ltd.), a two-component development system is used for development, and an intermediate transfer belt system is used for transfer. This color copying machine (Imagio Color 4000, manufactured by Ricoh Co., Ltd.) was modified so that the image forming process can be stopped at an arbitrary timing by an external signal. Also, the lubricant application mechanism on the photosensitive drum was removed.

-Measurement of transfer rate-
The solid image is developed on the photosensitive drum, the image forming process is stopped in the middle of the primary transfer, the photosensitive drum unit and the transfer belt unit are taken out from the copying machine, and the toner mass per unit area developed on the photosensitive member (M / A) _PC and the toner mass per unit area (M / A) _T transferred onto the transfer belt were measured by the sack-in method, and the transfer rate was calculated from the following Equation 5. In the sack-in method, the toner adhering to the photoreceptor is sucked by a vacuum pump or the like, the mass M of the sucked toner is measured, and the transfer rate is obtained from the suction area A of the toner.
<Formula 5>
Transfer rate = 100 × (M / A) _T / (M / A) _PC

-Image evaluation-
In the image evaluation, a single color image in which characters and photographs were mixed was used to evaluate the occurrence of a hollow image lacking a part of the image and the graininess. Four-stage evaluation samples for hollow out and graininess are prepared, images are observed visually and by a CCD microscope camera (manufactured by KEYENCE, Hypermicroscope), and compared with the evaluation samples, and evaluated in the following four stages. did.
〔Evaluation criteria〕
4: No problem 3: Almost no problem 2: Some problem 1: Problem

<Result>
F / (Dt × Da) of Example 1 is 6.13 × 10 ⁴ (N / m ² ), and the initial value and the value after continuous copying of 50,000 sheets when the developer and photoconductor of Example 1 are used. The evaluation of void and graininess is 4, the initial transfer rate is 97.5%, the transfer rate after continuous copying of 50,000 sheets is 95.4%, and a stable and good image can be obtained even after long-term use. Obtained. The results are shown in Tables 1 and 2.

(Example 2)
In Example 1, the polymer particles A were stirred and mixed with a Henschel mixer in the same manner as in Example 1 except that silica A having a hydrophobized average particle size of 120 nm was blended so as to be 7% by mass. Toner B was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner B was 31%.
Next, the two-component development of Example 2 is performed by mixing toner B and carrier A (carrier used by Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner B is 5% by mass. An agent was prepared.
Further, in the same manner as in Example 1, measurement of non-electrostatic adhesion force, transfer rate measurement, and image evaluation were performed.
F / (Dt × Da) of Example 2 is 5.25 × 10 ⁴ (N / m ² ), and the initial and 50,000 sheets when the developer of Example 2 and the photoreceptor of Example 1 are used. Evaluation of hollowness and graininess after continuous copying is 4, initial transfer rate is 98.3%, transfer rate after continuous copying of 50,000 sheets is 96.8%, stable even after long-term use A good image was obtained. The results are shown in Tables 1 and 2.

(Example 3)
In Example 1, the polymer particles A were stirred and mixed with a Henschel mixer in the same manner as in Example 1 except that the silica B having a hydrophobized average particle diameter of 200 nm was blended so as to be 8% by mass. Toner C was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage was 17.2%. The two-component developer of Example 3 is mixed by mixing toner C and carrier A (carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner C is 5% by mass. Produced.
Next, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 3 was 5.95 × 10 ⁴ ( N / m ² ), and evaluation of void and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 3 and the photoreceptor of Example 1 is 4, and the initial transfer rate is The transfer rate after continuous copying of 97.1% and 50,000 sheets was 95.9%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

Example 4
In Example 1, the polymer particles A were stirred and mixed with a Henschel mixer in the same manner as in Example 1 except that the silica A having a hydrophobized average particle diameter of 120 nm was blended to 3% by mass. Toner D was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner D was 15.3%.
Next, with respect to toner D, silica C having an average particle diameter of 14 nm subjected to hydrophobic treatment was blended so as to be 1% by mass of the toner amount, and stirred and mixed with a Henschel mixer to prepare toner E.
Next, the toner E and the carrier A (the carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) are mixed so that the ratio of the toner E is 5% by mass, and the two components of Example 4 are mixed. A developer was prepared.
Next, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 4 was 4.45 × 10 ^4. (N / m ² ), and evaluation of void and graininess after initial and 50,000-sheet continuous copying when the developer of Example 4 and the photoreceptor of Example 1 were used. 98.9%, the transfer rate after continuous copying of 50,000 sheets was 95.8%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Comparative Example 1)
In Example 1, the polymer particles A were stirred and mixed with a Henschel mixer in the same manner as in Example 1 except that the silica A having a hydrophobized average particle diameter of 120 nm was blended so as to be 0.5% by mass. The toner F was processed.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner F was 3.7%.
Next, the two-component development of Comparative Example 1 is performed by mixing the toner F and carrier A (the carrier used in Rigoh Co., Ltd., Imagio Color 4000) so that the ratio of the toner F is 5 mass%. An agent was prepared.
In addition, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Comparative Example 1 was 8.13 × 10 ⁴ ( N / m ² ), and the evaluation of initial void and graininess in the case of using the developer of Comparative Example 1 and the photoreceptor of Example 1 is the void and graininess after continuous copying of 50,000 sheets. The evaluation was 1, the initial transfer rate was 91.2%, the transfer rate after continuous copying of 50,000 sheets was 82.1%, and the transfer rate and image quality were lowered by long-term use. The results are shown in Tables 1 and 2.

(Example 5)
In Example 1, the volume average particle size is 6.7 μm and the shape factor SF1 is the same as in Example 1 except that the rotation speed of the TK homomixer (manufactured by Tokushu Kika Co., Ltd.) is 5000 rpm in the polymerization step. Polymerized particles B having an average value of 117 were obtained.
The obtained polymer particles B were stirred and mixed with a Henschel mixer in the same manner as in Example 1, except that silica A having a hydrophobized average particle size of 120 nm was blended to 3.5% by mass. Toner G was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner G was 22.4%.
Next, the two-component development of Example 5 is performed by mixing toner G and carrier A (carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner G is 5% by mass. An agent was prepared.
In addition, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 5 was 5.54 × 10 ⁴ ( N / m ² ), and evaluation of voids and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 5 and the photoreceptor of Example 1 is 4, and the initial transfer rate is The transfer rate after continuous copying of 97.9% and 50,000 sheets was 96.1%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Example 6)
In Example 5, the polymer particle B was stirred and mixed with a Henschel mixer in the same manner as in Example 5 except that the silica A having a hydrophobized average particle size of 120 nm was blended so as to be 6.5% by mass. The toner H was processed.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner H was 33.8%.
Next, the two-component development of Example 6 is performed by mixing toner H and carrier A (carrier used by Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner H is 5 mass%. An agent was prepared.
In addition, as in Example 1, measurement of non-electrostatic adhesive force, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 6 was 3.73 × 10 ⁴ ( N / m ² ), and evaluation of voids and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 6 and the photoreceptor of Example 1 is 4, and the initial transfer rate is The transfer rate after continuous copying of 98.7% and 50,000 sheets was 97.1%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Example 7)
In Example 5, the polymer particles B were stirred and mixed with a Henschel mixer in the same manner as in Example 5 except that the silica B having a hydrophobized average particle diameter of 200 nm was blended so as to be 9% by mass. Toner I was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of Toner I was 45.3%.
Next, the two-component development of Example 7 is carried out by mixing toner I and carrier A (carrier used by Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner I is 5% by mass. An agent was prepared.
In addition, as in Example 1, measurement of non-electrostatic adhesive force, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 7 was 2.86 × 10 ⁴ ( N / m ² ), and evaluation of void and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 7 and the photoreceptor of Example 1 is 4, and the initial transfer rate is The transfer rate after continuous copying of 99.2% and 50,000 sheets was 97.8%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Example 8)
In Example 1, the volume average particle size is 4.2 μm, and the shape factor SF1 is the same as in Example 1 except that the number of rotations of the TK homomixer (manufactured by Tokushu Kika Co., Ltd.) is 10,000 rpm in the polymerization step. Polymerized particles C having an average value of 109 were obtained.
The obtained polymer particles C were stirred and mixed with a Henschel mixer in the same manner as in Example 1, except that silica A having a hydrophobized average particle diameter of 120 nm was blended so as to be 4.5% by mass. Toner J was prepared.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner J was 17.0%.
Next, toner J and carrier A (the carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) are mixed so that the ratio of toner J is 5% by mass, and the two-component development of Example 8 is performed. An agent was prepared.
Next, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Example 8 was 6.35 × 10 ^4. (N / m ² ), and evaluation of void and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 8 and the photoreceptor of Example 1 was 4, and the initial transfer rate 96.8%, the transfer rate after continuous copying of 50,000 sheets was 94.5%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Comparative Example 2)
In Example 8, the polymer particles C were stirred and mixed using a Henschel mixer in the same manner as in Example 8 except that the silica A having a hydrophobized average particle diameter of 120 nm was blended so as to be 1% by mass. The toner K was processed.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner K was 5.3%.
Next, the two-component development of Comparative Example 2 is carried out by mixing toner K and carrier A (carrier used by Imagio Color 4000, manufactured by Ricoh Co., Ltd.) so that the ratio of toner K is 5% by mass. An agent was prepared.
Further, in the same manner as in Example 1, measurement of non-electrostatic adhesive force, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) in Comparative Example 2 was 7.88 × 10 ⁴ (N / M ² ), and the evaluation of the initial void and graininess when using the developer of Comparative Example 2 and the photoreceptor of Example 1 is that of the void and graininess after continuous copying of 350,000 sheets. The evaluation was 2, the initial transfer rate was 92.6%, the transfer rate after continuous copying of 50,000 sheets was 85.7%, and the transfer rate and image quality were lowered by long-term use. The results are shown in Tables 1 and 2.

Example 9
A mixture having the following composition was sufficiently stirred and mixed in a Henschel mixer, then heated and melted at a temperature of 130 to 140 ° C. for 30 minutes using a roll mill, cooled to room temperature, and the kneaded product obtained using a hammer mill was 1 mm. Roughly pulverized to ˜2 mm and finely pulverized with a jet mill to produce amorphous particles A having a volume average particle size of 5.9 μm and an average value of shape factor SF1 of 142.
-Polyester resin (mass average molecular weight = 250,000) ... 80 parts by mass-Styrene-methyl methacrylate copolymer ... 20 parts by mass-Rice wax (acid value 15) ... 5 parts by mass-Carbon black ( Mitsubishi Chemical Industries, Ltd., # 44) ... 8 parts by mass-Metal-containing monoazo dye ... 3 parts by mass

Next, 4.0% by mass of hydrophobized silica A having an average particle diameter of 120 nm was blended with the obtained amorphous particles A, and the mixture was stirred and mixed using a Henschel mixer to prepare toner L.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner L was 11.0%.
Next, the toner L was agitated and mixed with a Henschel mixer in the same manner as in Example 1 except that silica C having an average particle size of 14 nm that had been subjected to a hydrophobic treatment was blended so as to be 1% by mass. Was made.
Next, the toner M and carrier A (the carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) are mixed so that the ratio of the toner M is 5% by mass, and the two components of Example 9 are mixed. A developer was prepared.
In addition, as a result of measuring the non-electrostatic adhesion force, the transfer rate measurement, and the image evaluation in the same manner as in Example 1, F / (Dt × Da) of Example 9 is 5.63 × 10 ⁴ ( N / m ² ), and evaluation of void and graininess after initial and 50,000-sheet continuous copying when using the developer of Example 9 and the photoreceptor of Example 1 is 4, and the initial transfer rate is The transfer rate after continuous copying of 96.1% and 50,000 sheets was 94.1%, and a stable and good image was obtained even after long-term use. The results are shown in Tables 1 and 2.

(Comparative Example 3)
In Example 9, the amorphous particles A were mixed with stirring by a Henschel mixer in the same manner as in Example 9 except that the silica A having a hydrophobized average particle diameter of 120 nm was blended so as to be 1.2% by mass. The toner N was processed.
Further, when the external additive coverage was measured in the same manner as in Example 1, the average value of the external additive coverage of the toner N was 4.2%.
Next, the toner N and the carrier A (the carrier used in Imagio Color 4000, manufactured by Ricoh Co., Ltd.) are mixed so that the ratio of the toner N is 5% by mass, and the two components of Comparative Example 3 are mixed. A developer was prepared.
Further, as in Example 1, measurement of non-electrostatic adhesion, transfer rate measurement, and image evaluation were performed. As a result, F / (Dt × Da) of Comparative Example 3 was 8.0 × 10 ⁴ (N / M ² ), and the evaluation of the initial void and graininess when using the developer of Comparative Example 3 and the photoreceptor of Example 1 is that of the void and graininess after continuous copying of 50,000 sheets. The evaluation was 1, the initial transfer rate was 87.8%, the transfer rate after continuous copying of 50,000 sheets was 78.2%, and the transfer rate and image quality were lowered by long-term use. The results are shown in Tables 1 and 2.

(Example 10)
A photosensitive drum of Example 10 was produced in the same manner as in Example 1 by using another aluminum drum B in which the cutting rough surface treatment conditions of the aluminum drum were changed instead of the photosensitive member in Example 1. .
As in Example 1, the surface shape of the photosensitive drum of Example 10 was measured using a stylus type surface shape measuring device DEKTAK manufactured by Nippon Vacuum Technology Co., Ltd. As a result, the average value of the surface irregularities was 47 μm. In other words, the volume average particle size of toner A was about 9 times as large as 5.2 μm.
Using the toner A, the two-component developer of Example 1, and the photoreceptor of Example 10, the non-electrostatic adhesion measurement, the transfer rate measurement, and the image evaluation were performed in the same manner as in Example 1.
F / (Dt × Da) of Example 10 is 6.28 × 10 ⁴ (N / m ² ). The initial value and 50,000 sheets when the developer of Example 1 and the photoreceptor of Example 10 are used. The evaluation of voids after continuous copying was 4, the evaluation of graininess was 3, the initial transfer rate was 97.9%, and the transfer rate after continuous copying of 50,000 sheets was 96.3%. Also, a stable and good image was obtained. The results are shown in Tables 1 and 2.

(Example 11)
A photosensitive drum of Example 11 was produced in the same manner as in Example 1 by using another aluminum drum C in which the cutting rough surface treatment conditions of the aluminum drum were changed instead of the photosensitive member in Example 1. .
As in Example 1, the surface shape of the photosensitive drum of Example 11 was measured using a stylus type surface shape measuring device DEKTAK manufactured by Nippon Vacuum Technology Co., Ltd. As a result, the average value of the period of surface irregularities was 27 μm. In other words, the volume average particle diameter of the toner G was about 4 times as large as 6.7 μm.
Using the toner G, the two-component developer of Example 5, and the photoreceptor of Example 11, the non-electrostatic adhesion measurement, the transfer rate measurement, and the image evaluation were performed in the same manner as in Example 1.
F / (Dt × Da) in Example 11 is 5.67 × 10 ⁴ (N / m ² ). The initial value and 50,000 sheets when the developer in Example 5 and the photoreceptor in Example 11 are used. The evaluation of voids after continuous copying was 4, the evaluation of graininess was 3, the initial transfer rate was 97.4%, and the transfer rate after continuous copying of 50,000 sheets was 95.9%. Also, a stable and good image was obtained. The results are shown in Tables 1 and 2.

  The image forming apparatus and the image forming method of the present invention are high in transfer efficiency, do not cause image defects such as “cold”, and can stably obtain a good image even when used for a long period of time. Widely used in full-color image forming apparatuses such as electrostatic copying machines and full-color laser beam printers, electrostatic recording and electrostatic printing.

FIG. 1 is an explanatory diagram of a measurement cell in the powder adhesion measuring apparatus of the present invention. FIG. 2 is a partial cross-sectional side view of the centrifugal separator of the powder adhesion measuring apparatus of the present invention. FIG. 3 is a schematic configuration diagram showing an example of the image forming apparatus of the present invention. FIG. 4 is a schematic configuration diagram showing an example of the developing device of the present invention. FIG. 5 is a schematic configuration diagram showing another example of the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement cell 2 Sample substrate 2a Sample surface 3 Receiving substrate 3a Adhesion surface 4 Spacer 5 Centrifugal device 6 Rotor 7 Holding member 7a Rod-shaped part 7b Cell holding part 7c Hole part 7d Installation fixing part 8 Sample installation part 9 Rotation center axis 21 Photosensitive Body drum 22 Charging device 23 Exposure device 24 Developing device 25 Transfer device 26 Recording medium 27 Fixing device 28 Fixing roller 29 Pressure roller 30 Cleaning device 31 Static eliminating device 41 Screw 42 Developing sleeve 43 Doctor blade 51 Yellow image forming device 51a Photosensitive drum 51b Charging device 51c Exposure device 51d Development device 51e Transfer device 51f Cleaning device 51g Static elimination device 52 Magenta image forming device 53 Cyan image forming device 54 Black image forming device 55 Intermediate transfer belt 56 Transfer device 57 Recording medium 5 Cleaning device

Claims (13)

An electrostatic latent image carrier, electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and developing the electrostatic latent image with toner to form a toner image In an image forming apparatus having at least developing means and transfer means for transferring the toner image to a recording medium,
The surface of the toner is coated with an external additive containing fine particles having an average particle diameter Da of 100 to 300 nm, and an average value F of non-electrostatic adhesion force between the toner and the electrostatic latent image carrier. Is divided by the product of the volume average particle diameter Dt of the toner and the average particle diameter Da of the external additive [F / (Dt × Da)] is 7.5 × 10 ⁴ N / m ² or less. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the image forming apparatus is of a tandem type in which a plurality of image forming elements each having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit are arranged.   An intermediate transfer body on which a toner image formed on the electrostatic latent image carrier is primarily transferred, and a secondary transfer means for secondary transfer of the toner image carried on the intermediate transfer body to a recording medium The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 1, wherein the toner has a volume average particle diameter Dt of 2 to 7 μm.   The image forming apparatus according to any one of claims 1 to 4, wherein an average value of the toner shape factor SF1 is 100 to 130.   The image forming apparatus according to claim 1, wherein the toner is a polymerized toner produced by a polymerization method.   The average value of the ratio of the area (external additive coverage) of the portion where the external additive having an average particle diameter Da of 100 to 300 nm adhered to the surface area of one toner particle is 5 to 90%. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein the external additive is at least one selected from hydrophobized silica, hydrophobized titanium, and hydrophobized alumina.   9. The image forming apparatus according to claim 1, wherein the average value Sm of the surface irregularities of the electrostatic latent image carrier and the volume average particle diameter Dt of the toner satisfy the following expression: Sm ≧ 10 Dt. An electrostatic latent image forming step for forming an electrostatic latent image on the electrostatic latent image carrier, a developing step for developing the electrostatic latent image with toner to form a toner image, and recording the toner image In an image forming method including at least a transfer step of transferring to a medium,
The surface of the toner is coated with an external additive containing fine particles having an average particle diameter Da of 100 to 300 nm, and an average value F of non-electrostatic adhesion force between the toner and the electrostatic latent image carrier. Is divided by the product of the volume average particle diameter Dt of the toner and the average particle diameter Da of the external additive [F / (Dt × Da)] is 7.5 × 10 ⁴ N / m ² or less. An image forming method characterized by that.   The image forming apparatus according to claim 10, wherein an image forming apparatus of a tandem type in which a plurality of image forming elements having at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, and a transfer unit are arranged is used. Method.   In the transfer step, an intermediate transfer body on which the toner image formed on the electrostatic latent image carrier is primarily transferred, and secondary transfer means for secondary transfer of the toner image carried on the intermediate transfer body to a recording medium The image forming method according to claim 10, wherein: 13. The image forming method according to claim 11, wherein the average value Sm of the surface irregularities of the electrostatic latent image carrier and the volume average particle diameter Dt of the toner satisfy the following expression: Sm ≧ 10 Dt.