JP2009300699A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus using a small particle size toner having a volume average particle diameter of 5 μm to 7 μm, which can obtain high transfer efficiency and good cleaning properties, and can form an image with high image quality. Provided is an image forming apparatus having good durability of an intermediate transfer belt.
A toner image is formed on a surface of a photosensitive drum 11 by a developing device 14, and the toner image is transferred onto a recording medium via a transfer belt 25 and a transfer roller 28, and then an unfixed toner image is transferred to a fixing roller 31 and In an image forming apparatus that is fixed to a recording medium by a pressure roller 32, the film thickness of the transfer belt 25 is 40 μm to 70 μm, the linear pressure of the cleaning blade 29 is 1.8 gf / mm to 3.0 gf / mm, and the volume average A toner having a particle diameter of 5 μm to 7 μm and a shape factor SF-2 of 135 or more and less than 143 is used.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus.

  Toner that visualizes a latent image is used in various image forming processes, and as an example, it is known to be used in an electrophotographic image forming process.

  An electrophotographic image forming apparatus that forms an image based on an electrophotographic method can easily form an image having good image quality, and is widely used in a copying machine, a printer, a facsimile machine, a multifunction machine, and the like. .

  The electrophotographic image forming apparatus includes, for example, a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, a slow current unit, and a cleaning unit. The image forming apparatus is an apparatus that forms an image on a recording medium by performing a charging process, an exposure process, a developing process, a transfer process, a fixing process, a cleaning process, and a slow charging process using the photoreceptor and these means.

  In recent years, colorization technology in electrophotography has rapidly developed, and full-color image forming apparatuses have been developed and provided to the market. Generally, for color reproduction in a full-color image forming apparatus, three subtractive primary colors, yellow (Y), magenta (M), cyan (C), or black (K) are added to these three colors. Four color toners are used. As a color reproduction procedure, for each of C, M, Y, and K colors, the steps from charging, exposure, development, and transfer in the image forming process are repeated, and a plurality of color toners are formed on the recording medium. A full color image is formed by overlapping the toner images. In the final fixing step, the superimposed toner images are melted and fixed on the recording medium. According to such a procedure, the superimposed toner images are mixed by being melted, so that the color is reproduced according to the subtractive color mixing principle.

  In a transfer process in full-color image formation, a so-called intermediate transfer system is often used in which toner of each color is primarily transferred onto an intermediate transfer belt and then secondarily transferred from the intermediate transfer belt to a recording medium.

  In such an intermediate transfer type image forming apparatus, in order to achieve high image quality, the toner image is accurately obtained in each step of primary transfer and secondary transfer until the toner image carried on the photoreceptor is transferred to the recording medium. It is desired to transfer to a recording medium.

  However, reducing the particle size of the toner in order to improve the image quality is useful for forming a high-definition image. However, since the toner contains a large amount of fine powder toner, the transfer efficiency is low and a sufficient high-quality image can be obtained. Have the problem of not.

  In order to improve transfer efficiency, it is effective to reduce the thickness of the intermediate transfer belt. If the intermediate transfer belt is reduced in thickness, the transfer efficiency is improved and an image without a sticky image is formed. There is a problem that it is difficult to sufficiently clean the toner having a reduced particle size without damaging the belt.

  In order to solve such a problem, Patent Document 1 discloses that the value of the toner shape factor SF-2 is 100 or more and 140 or less, the wall thickness of the intermediate transfer belt is 40 μm or more and 300 μm or less, and the intermediate transfer belt. When the surface roughness Rz value A and the average particle diameter Dt of the toner satisfy A <Dt / 2, it is possible to repeatedly perform good cleaning, and an electrophotographic apparatus with high transfer efficiency is disclosed. .

JP 2003-156949 A

  However, in the electrophotographic apparatus disclosed in Patent Document 1, when the film thickness of the intermediate transfer belt is made thicker than 70 μm, the toner whose particle diameter is reduced to about 5 μm to 7 μm (that is, containing a lot of fine powder). Toner) cannot be transferred with high transfer efficiency, resulting in image stickiness. Further, as the cleaning means for the intermediate transfer belt, it is essential to employ a roller-shaped charge applying means for applying a charge having a polarity opposite to that of the toner at the time of primary transfer to the toner on the intermediate transfer belt, In this case, it is difficult to sufficiently clean the toner having a particle diameter of about 5 μm to 7 μm or a toner having a small particle surface irregularity (that is, a toner having a small shape factor SF-2).

  Therefore, an object of the present invention is to form a high-quality image with high transfer efficiency and good cleaning properties even in an image forming apparatus using a small particle size toner having a volume average particle diameter of 5 μm to 7 μm. It is possible to provide an image forming apparatus in which the intermediate transfer belt has good durability.

The present invention includes a photoconductor, a toner image forming unit that forms a toner image on the surface of the photoconductor, a primary transfer unit that transfers a toner image on the surface of the photoconductor onto a transfer belt, a cleaning blade that cleans the transfer belt, In an image forming apparatus comprising: a secondary transfer unit that transfers a toner image on a transfer belt to a recording medium; and a fixing unit that fixes an unfixed toner image transferred to the recording medium to the recording medium.
The transfer belt has a film thickness of 40 μm to 70 μm,
The linear pressure of the cleaning blade is 1.8 gf / mm to 3.0 gf / mm,
An image forming apparatus using a toner having a volume average particle diameter of 5 μm to 7 μm and a shape factor SF-2 of 135 or more and less than 143.

In the invention, it is preferable that the transfer belt is made of a polyimide resin.
In addition, the present invention is characterized in that a toner whose exposure amount of the release agent on the toner surface is 2.5% by weight or less of the total amount of toner is used.

  Further, the present invention is characterized in that a toner obtained by spheroidizing all or part of the pulverized toner is used.

The present invention also provides a first pulverized product and a second pulverized product having a volume average particle diameter larger than that of the first pulverized product, by pulverizing a resin composition containing at least a binder resin, a colorant, and a release agent. Crushing process to
A first classification step of classifying the first pulverized product to produce a first toner particle group;
The second pulverized product is classified after the spheronization treatment to classify the second pulverized product, or a second spheroidizing / classifying step for producing a second toner particle group having a volume average particle diameter larger than that of the first toner particle group. A second classification and spheronization step in which a second toner particle group having a volume average particle diameter larger than that of the first toner particle group is produced and then spheroidized.
A toner produced through a mixing step of mixing the first toner particle group and the second toner particle group is used.

  According to the present invention, a small particle size toner having a volume average particle size of 5 to 7 μm is useful for forming a high-definition image. However, when the transfer belt is thinned to 40 μm to 70 μm in order to improve transfer efficiency, an image without a betham is formed. Also, if the transfer belt is cleaned with a cleaning blade at a linear pressure greater than 3.0 gf / mm, the transfer belt is easily torn, so the linear pressure of the cleaning blade is reduced to less than 1.8 gf / mm and the belt is torn. To prevent.

  Further, in order to sufficiently clean the belt, the toner shape factor SF-2 is controlled to be 135 or more and less than 143, whereby an image with high image quality is formed and the durability of the transfer belt is also good. Can be realized. If a toner having a shape factor SF-2 of less than 135 is used, the transferability is improved and an image without unevenness is formed. However, it is necessary to increase the linear pressure of the belt cleaning blade, and the belt is torn.

  Further, when a toner having a shape factor SF-2 of 143 or more is used, the contact area between the toner and the transfer belt is increased, transferability is deteriorated, and betaram is likely to occur. Therefore, in the present invention, the thickness of the transfer belt is 40 μm to 70 μm, the linear pressure of the cleaning blade is 1.8 gf / mm to 3.0 gf / mm, and the toner shape factor SF-2 is 135 or more and less than 143. As a result, high transfer efficiency and good cleaning properties can be obtained, and a high-quality image can be formed, and an image forming apparatus with good transfer belt durability can be obtained.

  According to the present invention, since the transfer belt is made of a polyimide-based resin, the tensile elastic modulus is higher than that in the case of using a polycarbonate resin, and it is difficult to extend. Therefore, the mechanical durability of the transfer belt can be improved.

  Further, according to the present invention, if the exposure amount of the release agent on the toner surface is too large, the adhesion between the toner and the transfer belt is increased, the transferability is deteriorated, and the image becomes rough and uneven. Appropriateness is achieved by adjusting the amount to 2.5% by weight or less.

  Furthermore, according to the present invention, by using the toner, it is possible to realize an image forming apparatus capable of achieving both cleanability and high image quality.

  Further, according to the present invention, when a toner particle group having a small volume average particle diameter is spheroidized, it becomes difficult to clean the toner remaining on the transfer belt. By spheroidizing only the county, it is possible to realize an image forming apparatus capable of achieving both cleanability and high image quality.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is a multifunction machine having both a copying function, a printer function, and a facsimile function, and forms a full-color or monochrome image on a recording medium in accordance with transmitted image information. That is, the image forming apparatus 100 has three types of printing modes, ie, a copier mode (copying mode), a printer mode, and a facsimile mode, and an operation input from an operation unit (not shown), a personal computer, a portable terminal device, information A print mode is selected by a control unit (not shown) in response to reception of a print job from an external device using a recording storage medium or a memory device.

  The image forming apparatus 100 includes a photosensitive drum 11 that is an image carrier, an image forming unit 2, a transfer unit 3, a fixing unit 4, a recording medium supply unit 5, and a discharge unit 6. Each member constituting the image forming unit 2 and some members included in the transfer unit 3 are black (b), cyan (c), magenta (m) and yellow (y) included in the color image information. In order to correspond to image information, four each are provided. Here, each member provided by four according to each color is distinguished by attaching a subscript consisting of alphabets “b”, “c”, “m”, “y” representing each color to the same number, When referring generically, the subscripts “b”, “c”, “m”, and “y” are omitted and only numbers are used.

  The image forming unit 2 includes a charging unit 12, an exposure unit 13, a developing device 14, and a cleaning unit 15. The charging unit 12 and the exposure unit 13 function as a latent image forming unit. The charging unit 12, the developing device 14, and the cleaning unit 15 are arranged around the photosensitive drum 11 in this order. The charging unit 12 is disposed below the developing device 14 and the cleaning unit 15 in the vertical direction.

  The photosensitive drum 11 is provided with a roller-like member which is provided so as to be rotatable around an axis line by a rotation driving means (not shown), and on which an electrostatic latent image is formed. The rotation driving unit of the photosensitive drum 11 is controlled by a control unit realized by a central processing unit (abbreviated as CPU). The photosensitive drum 11 includes a conductive substrate (not shown) and a photosensitive layer (not shown) formed on the surface of the conductive substrate. The conductive substrate can take various shapes, and examples thereof include a cylindrical shape, a columnar shape, and a thin film sheet shape. Among these, a cylindrical shape is preferable. The conductive substrate is formed of a conductive material.

  As the conductive material, those commonly used in this field can be used, for example, aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, etc. A conductive layer comprising one or more of aluminum, aluminum alloy, tin oxide, gold and indium oxide on a film-like substrate such as a metal, two or more alloys thereof, a synthetic resin film, a metal film or paper And a resin composition containing conductive particles and / or a conductive polymer. As the film-like substrate used for the conductive film, a synthetic resin film is preferable, and a polyester film is particularly preferable. Moreover, as a formation method of the electroconductive layer in an electroconductive film, vapor deposition, application | coating, etc. are preferable.

  The photosensitive layer is formed, for example, by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. In that case, it is preferable to provide an undercoat layer between the conductive substrate and the charge generation layer or between the conductive substrate and the charge transport layer. By providing an undercoat layer, it is possible to smooth the surface of the photosensitive layer by covering the scratches and irregularities present on the surface of the conductive substrate, and to prevent deterioration of the chargeability of the photosensitive layer during repeated use. In addition, there is an advantage that the charging characteristics of the photosensitive layer are improved in a low temperature and / or low humidity environment. Further, it may be a laminated photoreceptor having a three-layer structure having a large durability, in which a photoreceptor surface protective layer is provided as the uppermost layer.

  The charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and contains a known binder resin, plasticizer, sensitizer and the like as necessary. As the charge generation material, those commonly used in this field can be used, for example, perylene pigments such as perylene imide and perylene acid anhydride, polycyclic quinone pigments such as quinacridone and anthraquinone, metal and metal-free phthalocyanines, and halogenated compounds. Phthalocyanine pigments such as metal-free phthalocyanine, squalium dye, azulenium dye, thiapyrylium dye, carbazole skeleton, styryl stilbene skeleton, triphenylamine skeleton, dibenzothiophene skeleton, oxadiazole skeleton, fluorenone skeleton, bis-stilbene skeleton, distyryl And azo pigments having an oxadiazole skeleton or a distyrylcarbazole skeleton.

  Among these, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing a fluorene ring and / or a fluorenone ring, bisazo pigments composed of aromatic amines, trisazo pigments, etc. have high charge generation ability and high sensitivity. Suitable for obtaining a photosensitive layer. One type of charge generating material can be used alone, or two or more types can be used in combination.

  Although the content of the charge generation material is not particularly limited, it is preferably 5 parts by weight or more and 500 parts by weight or less, more preferably 10 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the binder resin in the charge generation layer. To be elected. As the binder resin for the charge generation layer, those commonly used in this field can be used. For example, melamine resin, epoxy resin, silicon resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, polycarbonate, phenoxy Examples thereof include resins, polyvinyl butyral, polyarylate, polyamide, and polyester. Binder resin can be used individually by 1 type, or can use 2 or more types together as needed.

  The charge generation layer is prepared by dissolving or dispersing appropriate amounts of a charge generation material, a binder resin and, if necessary, a plasticizer and a sensitizer in an appropriate organic solvent capable of dissolving or dispersing these components. It can be formed by preparing a generation layer coating solution, applying the charge generation layer coating solution to the surface of the conductive substrate, and drying the surface of the conductive substrate. The film thickness of the charge generation layer thus obtained is not particularly limited, but is preferably selected from 0.05 μm to 5 μm, more preferably from 0.1 μm to 2.5 μm.

  The charge transport layer laminated on the charge generation layer has a charge transport material having the ability to accept and transport the charge generated from the charge generation material and a binder resin for the charge transport layer as essential components. Contains known antioxidants, plasticizers, sensitizers, lubricants and the like.

  As the charge transporting material, those commonly used in this field can be used. For example, poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives , Polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, Pyrazoline derivatives, phenylhydrazones, hydrazone derivatives, triphenylamine compounds, tetraphenyldiamine compounds, triphenylmethane compounds, stilbene compounds, 3-methyl-2-benzothiazo Donors such as azine compounds having a ring, fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, Examples thereof include electron-accepting substances such as tetracyanoethylene, tetracyanoquinodimethane, promanyl, chloranil, and benzoquinone.

  A charge transport material can be used individually by 1 type, or can use 2 or more types together. Although the content of the charge transport material is not particularly limited, it is preferably 10 to 300 parts by weight, more preferably 30 to 150 parts by weight, with respect to 100 parts by weight of the binder resin in the charge transport material. It is.

  As the binder resin for the charge transport layer, those commonly used in this field and capable of uniformly dispersing the charge transport material can be used. For example, polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy Examples thereof include resins, polyurethanes, polyvinyl ketones, polystyrenes, polyacrylamides, phenol resins, phenoxy resins, polysulfone resins, and copolymer resins thereof. Among these, in consideration of film formability, wear resistance of the resulting charge transport layer, electrical characteristics, etc., polycarbonate containing bisphenol Z as a monomer component (hereinafter referred to as “bisphenol Z type polycarbonate”), bisphenol Z type polycarbonate A mixture of and other polycarbonates is preferred. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The charge transport layer preferably contains an antioxidant together with the charge transport material and the binder resin for the charge transport layer. As the antioxidant, those commonly used in this field can be used, such as vitamin E, hydroquinone, hindered amine, hindered phenol, paraphenylenediamine, arylalkane and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. Can be mentioned. An antioxidant can be used individually by 1 type, or can use 2 or more types together. Although the content of the antioxidant is not particularly limited, it is selected from 0.01% by weight to 10% by weight, preferably from 0.05% by weight to 5% by weight, based on the total amount of the components constituting the charge transport layer. .

  The charge transport layer is dissolved or dispersed in a suitable organic solvent capable of dissolving or dispersing these components, such as a charge transport material, a binder resin, and if necessary, an antioxidant, a plasticizer, and a sensitizer. The charge transport layer coating liquid is prepared, the charge transport layer coating liquid is applied to the surface of the charge generation layer, and the charge generation layer surface is dried. The film thickness of the charge transport layer thus obtained is not particularly limited, but is preferably 10 μm or more and 50 μm or less, more preferably 15 μm or more and 40 μm or less.

  A photosensitive layer in which a charge generation material and a charge transport material are present can be formed in one layer. In that case, the type, content, binder resin, and other additives of the charge generation material and the charge transport material may be the same as in the case of separately forming the charge generation layer and the charge transport layer.

  In this embodiment, the photosensitive drum on which the organic photosensitive layer using the charge generation material and the charge transport material is formed as described above is used, but instead, an inorganic photosensitive layer using silicon or the like is formed. A photosensitive drum can also be used.

  The charging unit 12 faces the photoconductor drum 11 and is disposed so as to be spaced apart from the surface of the photoconductor drum 11 along the longitudinal direction of the photoconductor drum 11 with a gap radially outward. Can be charged to a predetermined polarity and potential. As the charging unit 12, a charging brush type charger, a charger type charger, a sawtooth type charger, an ion generator, or the like can be used. In the present embodiment, the charging unit 12 is provided so as to be separated from the surface of the photosensitive drum 11, but is not limited thereto. For example, a charging roller may be used as the charging unit 12, and the charging roller may be arranged so that the charging roller and the photosensitive drum are in pressure contact with each other, or a contact charging type charger such as a charging brush or a magnetic brush may be used. .

  The exposure unit 13 is arranged such that light of each color information emitted from the exposure unit 13 passes between the charging unit 12 and the developing device 14 and is irradiated on the surface of the photosensitive drum 11. The exposure unit 13 branches the image information into light of each color information of black, cyan, magenta, and yellow in the unit, and the surface of the photosensitive drum 11 charged to a uniform potential by the charging unit 12 is light of each color information. To form an electrostatic latent image on the surface. As the exposure unit 13, for example, a laser scanning unit including a laser irradiation unit and a plurality of reflection mirrors can be used. In addition, a unit in which an LED array or a liquid crystal shutter and a light source are appropriately combined may be used.

  The developing unit 14 includes a developing tank 20 and a toner hopper 21. The developing tank 20 is disposed so as to face the surface of the photosensitive drum 11, and is a container that supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 11 and develops it to form a visible toner image. It is a shaped member. The developing tank 20 accommodates toner in its internal space and accommodates a roller member such as a developing roller, a supply roller, and a stirring roller, or a screw member, and rotatably supports the developing tank 20. An opening is formed in a side surface of the developing tank 20 facing the photosensitive drum 11, and a developing roller is rotatably provided at a position facing the photosensitive drum 11 through the opening.

  The developing roller is composed of a roller-like member that supplies toner to the electrostatic latent image on the surface of the photoconductor 11 at the pressure contact portion or the closest portion with the photoconductor drum 11. When supplying the toner, a potential having a polarity opposite to the charging potential of the toner is applied to the surface of the developing roller as a developing bias voltage (hereinafter simply referred to as “developing bias”). As a result, the toner on the surface of the developing roller is smoothly supplied to the electrostatic latent image. Further, by changing the developing bias value, the amount of toner (toner adhesion amount) supplied to the electrostatic latent image can be controlled.

  The supply roller is composed of a roller-like member provided so as to be able to rotate and face the developing roller, and supplies toner to the periphery of the developing roller. The agitation roller is composed of a roller-like member provided so as to be rotationally driven so as to face the supply roller, and feeds toner newly supplied from the toner hopper 21 into the developing tank 20 to the periphery of the supply roller. The toner hopper 21 is provided so that a toner replenishing port (not shown) provided at the lower part in the vertical direction communicates with a toner receiving port (not shown) provided at the upper part in the vertical direction of the developing tank 20. The toner is replenished according to the toner consumption status of 20. Further, the toner hopper 21 may not be used, and the toner may be directly supplied from each color toner cartridge.

  The cleaning unit 15 uses the developing device 14 to transfer the toner image formed on the surface of the photosensitive drum 11 to a recording medium, and then removes the toner remaining on the surface of the photosensitive drum 11 to remove the surface of the photosensitive drum 11. Provided for cleaning. For the cleaning unit 15, for example, a plate-like member such as a cleaning blade is used. In the image forming apparatus of the present embodiment, an organic photosensitive drum is used as the photosensitive drum 11, and the surface of the organic photosensitive drum is mainly composed of a resin component, and thus is generated by corona discharge by a charging device. Deterioration of the surface of the organic photosensitive drum is likely to proceed due to the chemical action of ozone. However, the deteriorated surface portion is worn by receiving a rubbing action by the cleaning unit 15 and the gradually deteriorated surface portion is surely removed. Therefore, the problem of surface deterioration due to ozone or the like is practically solved, and the charging potential by the charging operation can be stably maintained over a long period of time. Although the cleaning unit 15 is provided in the present embodiment, the present invention is not limited to this, and the cleaning unit 15 may not be provided.

  According to the image forming unit 2, the surface of the photosensitive drum 11 that is uniformly charged by the charging unit 12 is irradiated with signal light according to image information from the exposure unit 13 to form an electrostatic latent image. Then, the toner is supplied from the developing device 14 to form a toner image. After the toner image is transferred to the intermediate transfer belt 25, the toner remaining on the surface of the photosensitive drum 11 is removed by the cleaning unit 15. This series of toner image forming operations is repeatedly executed to form an image.

  The transfer means 3 is disposed above the photosensitive drum 11 and has an intermediate transfer belt 25 having a film thickness of 40 μm to 70 μm, a driving roller 26, a driven roller 27, black (b), cyan (c), magenta ( m) and four intermediate transfer rollers 28 corresponding to the image information of yellow (y), a transfer belt cleaning unit 29, and a transfer roller 30, respectively.

  The reason why the film thickness of the intermediate transfer belt 25 is 40 μm to 70 μm is apparent from Examples 1 to 17 and Comparative Examples 1 to 8 described later, as long as the film thickness is less than 40 μm. This is because the durability of No. 25 decreases (Comparative Example 2), and when the film thickness exceeds 70 μm, the transfer efficiency is lowered and the betham is caused (Comparative Example 1). Therefore, the film thickness of the intermediate transfer belt 25 is selected from 40 μm to 70 μm, and more preferably 40 μm to 60 μm.

  The intermediate transfer belt 25 is stretched around a driving roller 26 and a driven roller 27, and is composed of an endless belt-like member that forms a loop-shaped movement path, and is driven to rotate in the direction of an arrow B. The driving roller 26 is provided so as to be rotatable around its axis by driving means (not shown), and the intermediate transfer belt 25 is driven to rotate in the direction of the arrow B by the rotational driving. The driven roller 27 is provided so as to be able to be driven and rotated by the rotational drive of the driving roller 26, and applies a constant tension to the intermediate transfer belt 25 so that the intermediate transfer belt 25 does not loosen. The intermediate transfer roller 28 is provided in pressure contact with the photosensitive drum 11 via the intermediate transfer belt 25 and capable of being driven to rotate about its axis by a driving unit (not shown). The intermediate transfer roller 28 is connected to a power source (not shown) for applying a transfer bias as described above, and has a function of transferring the toner image on the surface of the photosensitive drum 11 to the intermediate transfer belt 25.

  When the intermediate transfer belt 25 passes through the photosensitive drum 11 while being in contact with the photosensitive drum 11, an intermediate transfer roller 28 disposed on the surface of the photosensitive drum 11 is opposed to the photosensitive drum 11 via the intermediate transfer belt 25. A transfer bias having a polarity opposite to the charging polarity of the toner is applied, and the toner image formed on the surface of the photosensitive drum 11 is transferred to the intermediate transfer belt 25. In the case of a full-color image, each color toner image formed on each photoconductor drum 11 is transferred to the intermediate transfer belt 25 in an overlapping manner, thereby forming a full-color toner image.

  The transfer belt cleaning unit 29 faces the driven roller 27 via the intermediate transfer belt 25 so that the cleaning blade contacts the outer peripheral surface of the intermediate transfer belt 25 at a linear pressure of 1.8 gf / mm to 3.0 gf / mm. Provided. The toner adhering to the intermediate transfer belt 25 due to contact with the photosensitive drum 11 causes the recording medium to be contaminated. Therefore, the transfer belt cleaning unit 29 removes and collects the toner on the surface of the intermediate transfer belt 25.

  In the transfer belt cleaning unit 29, the reason why the linear pressure of the cleaning blade to the outer peripheral surface of the intermediate transfer belt 25 is 1.8 gf / mm to 3.0 gf / mm is described in Examples 1 to 17 and Comparative Example 1 described later. As apparent from ˜8, when the linear pressure is less than 1.8 gf / mm, the cleaning property of the intermediate transfer belt 25 is deteriorated (Comparative Example 3), and when the linear pressure exceeds 3.0 gf / mm, This is because the durability of the intermediate transfer belt 25 is reduced (Comparative Example 4). Therefore, the linear pressure of the cleaning blade is selected from 1.8 gf / mm to 3.0 gf / mm, and more preferably 2.0 gf / mm to 2.8 gf / mm.

  The transfer roller 30 is provided in pressure contact with the drive roller 26 via the intermediate transfer belt 25, and can be driven to rotate about an axis by a drive unit (not shown). The toner image carried on the intermediate transfer belt 25 and conveyed at the pressure contact portion between the transfer roller 30 and the driving roller 26, that is, the transfer nip portion, is transferred to a recording medium fed from a recording medium supply means 5 described later. The The recording medium carrying the toner image is fed to the fixing unit 4.

  According to the transfer unit 3, the toner image transferred from the photosensitive drum 11 to the intermediate transfer belt 25 at the pressure contact portion between the photosensitive drum 11 and the intermediate transfer roller 28 is moved in the direction of arrow B of the intermediate transfer belt 25. The sheet is conveyed to the transfer nip portion by rotation and transferred to a recording medium there.

  In the present embodiment, the intermediate transfer belt 25 is preferably made of a polyimide resin, and by using the intermediate transfer belt 25 made of a polyimide resin, the tensile elastic modulus is higher than that in the case of using a polycarbonate resin that is usually used. Therefore, the mechanical durability of the intermediate transfer belt 25 can be improved.

  The fixing unit 4 is provided downstream of the transfer unit 3 in the conveyance direction of the recording medium, and includes a fixing roller 31 and a pressure roller 32. The fixing roller 31 is rotatably provided by a driving unit (not shown), and fixes an unfixed toner image carried on the recording medium to the recording medium by heating and melting the constituent toner. A heating unit (not shown) is provided inside the fixing roller 31. The heating unit heats the fixing roller 31 so that the surface of the fixing roller 31 reaches a predetermined temperature (hereinafter also referred to as “heating temperature”). For example, a heater or a halogen lamp can be used as the heating means. The heating means is controlled by fixing condition control means described later. The control of the heating temperature by the fixing condition control means will be described in detail later.

  A temperature detection sensor (not shown) is provided near the surface of the fixing roller 31, and the temperature detection sensor detects the surface temperature of the fixing roller 31. The detection result by the temperature detection sensor is written in the storage unit of the control means described later. The pressure roller 32 is provided so as to be in pressure contact with the fixing roller 31 and is supported so as to be driven to rotate by the rotation drive of the pressure roller 32. When the toner is melted by the heat from the fixing roller 31 and the toner image is fixed on the recording medium, the pressure roller 32 presses the toner and the recording medium to assist the fixing of the toner image onto the recording medium. . The pressure contact portion between the fixing roller 31 and the pressure roller 32 constitutes a fixing nip portion.

  According to the fixing unit 4, the recording medium onto which the toner image is transferred by the transfer unit 3 is sandwiched between the fixing roller 31 and the pressure roller 32, and the toner image is recorded under heating when passing through the fixing nip portion. By being pressed against the medium, the toner image is fixed on the recording medium, and an image is formed.

  The recording medium supply unit 5 includes an automatic paper feed tray 35, a pickup roller 36, a transport roller 37, a registration roller 38, and a manual paper feed tray 39. The automatic paper feed tray 35 is a container-like member that is provided in the lower part of the image forming apparatus 100 in the vertical direction and stores a recording medium. Examples of the recording medium include plain paper, color copy paper, overhead projector sheet, and postcard.

  The pick-up roller 36 takes out the recording medium stored in the automatic paper feed tray 35 one by one and feeds it to the paper transport path S1. The conveyance roller 37 includes a pair of roller members provided so as to be in pressure contact with each other, and conveys the recording medium toward the registration roller 38. The registration roller 38 is composed of a pair of roller members provided so as to be in pressure contact with each other, and the recording medium fed from the conveyance roller 37 is transferred at a timing when the toner image carried on the intermediate transfer belt 25 is conveyed to the transfer nip portion. Synchronously, it is fed to the transfer nip.

  The manual paper feed tray 39 is a device that takes a recording medium into the image forming apparatus 100 by a manual operation, and the recording medium taken from the manual paper feed tray 39 passes through the paper conveyance path S2 by the conveyance roller 37. Then, it is fed to the registration roller 38. According to the recording medium supply means 5, the toner image carried on the intermediate transfer belt 25 is conveyed to the transfer nip portion of the recording medium supplied one by one from the automatic paper feed tray 35 or the manual paper feed tray 39. The paper is fed to the transfer nip portion in synchronization with the timing.

  The discharge unit 6 includes a conveyance roller 37, a discharge roller 40, and a discharge tray 41. The conveyance roller 37 is provided on the downstream side of the fixing nip portion in the conveyance direction of the sheet, and conveys the recording medium on which the image is fixed by the fixing unit 4 toward the discharge roller 40. The discharge roller 40 discharges the recording medium on which the image is fixed onto a discharge tray 41 that is provided vertically above the image forming apparatus 100. The discharge tray 41 stores a recording medium on which an image is fixed.

  The image forming apparatus 100 includes a control unit (not shown). For example, the control unit is provided in an upper part of the internal space of the image forming apparatus 100 and includes a storage unit, a calculation unit, and a control unit. The storage unit of the control means stores various setting values via an operation panel (not shown) arranged on the upper surface of the image forming apparatus 100, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus 100, and external Image information from the device is input. A program for operating various means is also written in the storage unit. Examples of the various means include a recording medium determination unit, an adhesion amount control unit, and a fixing condition control unit.

As the storage unit, those commonly used in this field can be used. For example, a read only memory (abbreviation ROM), a random access memory (Random)
Access Memory (abbreviated as RAM) and hard disk drive (abbreviated as HDD). As the external device, an electric / electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus 100 can be used. For example, a computer, a digital camera, a television, a video recorder , DVD recorder, HD DVD, Blu-ray disc recorder, facsimile apparatus, portable terminal apparatus and the like.

  The arithmetic unit takes out various data (image formation command, detection result, image information, etc.) written in the storage unit and programs of various means, and performs various determinations. The control unit sends a control signal to the corresponding device according to the determination result of the calculation unit, and performs operation control. The control unit and the calculation unit include a processing circuit realized by a microcomputer, a microprocessor, or the like provided with a central processing unit (abbreviated as CPU). The control means includes a main power supply together with the processing circuit described above, and the power supply supplies power not only to the control means but also to each device in the image forming apparatus 100.

<Toner>
(1) Toner Constituent Material Toner used in the image forming apparatus of the present invention is added to toner particles including a charge control agent in addition to binder resin, colorant and release agent, which are essential components, and optionally added. Containing external additives.

  The binder resin is not particularly limited as long as it is commonly used as a binder resin for toners and can be granulated in a molten state. For example, polyester resins, polystyrene, and styrene can be used. -Styrenic resins such as acrylic ester copolymer resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyurethane, and epoxy resins.

  Moreover, as the binder resin, a resin obtained by mixing a release agent with a raw material monomer mixture and performing a polymerization reaction may be used. In this case, it is preferable to contain a polyester resin. By including a polyester resin in the binder resin, it is possible to improve the dispersion state controllability of the release agent, and to obtain a toner having even better fixing properties. Further, the toner can be provided with excellent durability and transparency. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The polyester resin is not particularly limited, and known ones can be used, and examples thereof include polycondensation products of polybasic acids and polyhydric alcohols. Polybasic acids are polybasic acids and derivatives of polybasic acids, such as acid anhydrides or esterified products of polybasic acids. Polyhydric alcohols are compounds containing two or more hydroxyl groups, and include both alcohols and phenols.

  As the polybasic acids, those commonly used as monomers for polyester resins can be used, for example, aromatics such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid and naphthalenedicarboxylic acid. Examples include carboxylic acids, maleic anhydride, fumaric acid, succinic acid, and aliphatic carboxylic acids such as adipic acid. Polybasic acids may be used alone or in combination of two or more.

  As polyhydric alcohols, those commonly used as monomers of polyester resins can be used, for example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol and glycerin. And alicyclic polyhydric alcohols such as cyclohexanediol, cyclohexanedimethanol and hydrogenated bisphenol A, and aromatic diols such as bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct.

  “Bisphenol A” is 2,2-bis (p-hydroxyphenyl) propane. Examples of the ethylene oxide adduct of bisphenol A include polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane. Examples of the propylene oxide adduct of bisphenol A include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane. Polyhydric alcohols may be used alone or in combination of two or more.

  The polyester resin can be synthesized by a condensation polymerization reaction. For example, it can be synthesized by polycondensation reaction, specifically dehydration condensation reaction of polybasic acids and polyhydric alcohols in the presence of a catalyst in an organic solvent or without solvent. At this time, a demethanol polycondensation reaction may be carried out using a methyl esterified product of a polybasic acid as part of the polybasic acid.

  The polycondensation reaction between polybasic acids and polyhydric alcohols may be terminated when the acid value and softening point of the produced polyester resin reach the values in the polyester resin to be synthesized. In this polycondensation reaction, by appropriately changing the reaction conditions such as the blending ratio of polybasic acids and polyhydric alcohols and the reaction rate, for example, the content of carboxyl groups bonded to the terminal of the resulting polyester resin, and thus The acid value, softening point, and other physical properties of the resulting polyester resin can also be adjusted.

  Examples of the colorant include a yellow toner colorant, a magenta toner colorant, a cyan toner colorant, and a black toner colorant.

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15 and C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 180, C.I. I. Organic pigments such as CI Pigment Yellow 185, inorganic pigments such as yellow iron oxide and ocher, C.I. I. Nitro dyes such as Acid Yellow 1, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, and C.I. I. Examples thereof include oil-soluble dyes such as Solvent Yellow 21.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10 and C.I. I. Disperse Red 15 etc. are mentioned.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, and C.I. I. Direct Blue 86 and the like can be mentioned.

  Examples of the colorant for black toner include carbon black such as channel black, roller black, disk black, gas furnace black, oil furnace black, thermal black, and acetylene black.

  In addition to these pigments, red pigments, green pigments, and the like can be used. A colorant may be used individually by 1 type, or may use 2 or more types together. Two or more of the same color can be used, and one or more of the different colors can also be used.

  The colorant is preferably used as a masterbatch. A master batch of a colorant can be produced, for example, by kneading a resin melt and a colorant. As the resin, the same kind of resin as the toner binder resin or a resin having good compatibility with the toner binder resin is used. The use ratio of the resin and the colorant is not particularly limited, but is preferably selected from 30 parts by weight to 100 parts by weight with respect to 100 parts by weight of the synthetic resin. The master batch is used after being granulated to a particle size of about 2 mm to 3 mm, for example.

  The content of the colorant is not particularly limited, but is preferably selected from 4 parts by weight to 20 parts by weight with respect to 100 parts by weight of the binder resin. When using a masterbatch, it is preferable to adjust the usage amount of the masterbatch so that the content of the colorant in the toner falls within the above range. By using the colorant in the above-mentioned range, it is possible to form a good image having a sufficient image density, high color developability and excellent image quality.

  The release agent is not particularly limited, and known ones can be used. For example, petroleum wax such as paraffin wax and its derivative, and microcrystalline wax and its derivative, Fischer-Tropsch wax and its Derivatives, polyolefin waxes and derivatives thereof, low molecular weight polypropylene waxes and derivatives thereof, and hydrocarbon synthetic waxes such as polyolefin polymer waxes and derivatives thereof, carnauba wax and derivatives thereof, ester waxes, and the like.

  The toner of the present invention preferably contains other toner additive components such as a charge control agent in addition to the binder resin, the colorant, and the release agent. The charge control agent is added in order to impart preferable chargeability to the toner. Examples of the charge control agent include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, triphenylmethane derivatives, guanidine salts, And charge control agents for positive charge control such as amidine salts and oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and derivatives thereof And charge control agents for controlling negative charges such as metal salts (metal is chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and resin acid soaps. One charge control agent can be used alone, or two or more charge control agents can be used in combination.

  The amount of the charge control agent used is preferably selected from 0.5 parts by weight to 5 parts by weight with respect to 100 parts by weight of the binder resin, and more preferably 0.5 parts by weight with respect to 100 parts by weight of the binder resin. More than 3 parts by weight is selected. If the charge control agent is contained in an amount of more than 5 parts by weight, the carrier may be contaminated and toner scattering may occur. When the content of the charge control agent is less than 0.5 parts by weight, sufficient charging characteristics cannot be imparted to the toner. Therefore, the charge control agent is used in an amount of 0.5 to 5 parts by weight, preferably 0.5 parts by weight or more with respect to 100 parts by weight of the binder resin, as described above. 3 parts by weight or less is selected.

  The toner of the present invention is mixed with, for example, external additives responsible for functions such as powder flowability improvement, triboelectric chargeability improvement, heat resistance, long-term storage stability improvement, cleaning property improvement and photoreceptor surface wear property control. Also good. As the external additive, those commonly used in this field can be used, and examples thereof include fine silica powder, fine titanium oxide powder and fine alumina powder.

  These inorganic fine powders are used for the purpose of hydrophobizing, charging control, etc. Silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organic It is preferable that it is processed with processing agents, such as a silicon compound, 1 type can be used individually or 2 or more types can be used together. The amount of the external additive added is 1 weight with respect to 100 parts by weight of the toner particles in consideration of the charge amount necessary for the toner, the influence of the external additive on the abrasion of the photoreceptor, the environmental characteristics of the toner, and the like. Part to 10 parts by weight, more preferably 1 part to 5 parts by weight.

  The external additive preferably has a number average particle diameter of primary particles of 10 nm to 500 nm. By using an external additive having such a particle size, the effect of improving the fluidity of the toner is more easily exhibited.

(2) Toner Production Method The toner used in the image forming apparatus of the present invention includes toner particles including a charge control agent in addition to a binder resin, a colorant, and a release agent, and an organic that is added as necessary. Including fine particles and inorganic fine particles.

  The toner particles contained in the toner used in the image forming apparatus of the present invention are obtained by pulverizing at least a resin composition containing a binder resin, a colorant, and a release agent, and by using a first pulverized product and a first pulverized product. A pulverization step for producing a second pulverized product having a large volume average particle size, a first classification step for classifying the first pulverized product to produce a first toner particle group, and a classification after the second pulverized product is spheroidized. Then, the second spheroidizing / classifying step for producing a second toner particle group having a larger volume average particle diameter than the first toner particle group, or the second pulverized product is classified to obtain a volume average from the first toner particle group. The second toner particle group having a large particle diameter is manufactured through a second classification / spheronization process in which the second toner particle group is spheroidized and a mixing process in which the first toner particle group and the second toner particle group are mixed.

  FIG. 2 is a flowchart showing an example of a method for producing toner particles contained in toner used in the image forming apparatus of the present invention. The toner particle manufacturing method of the present embodiment includes a pre-mixing step (step S1) in which at least a binder resin, a colorant, and a release agent are mixed to produce a mixture, and the mixture is melt-kneaded to obtain a resin composition. A melt-kneading step for producing a melt-kneaded product (step S2), and a grinding step for pulverizing the melt-kneaded product to produce a first pulverized product and a second pulverized product having a larger volume average particle diameter than the first pulverized product. (Step S3), a first classification step (Step S4) for classifying the first pulverized product to produce a first toner particle group, a spheronization step (Step S5) for spheroidizing the second pulverized product, (2) A second classification step (step S6) for classifying the spheroidized product of the pulverized product to produce a second toner particle group having a volume average particle diameter larger than that of the first toner particle group, and the first toner particle group and the second toner Mixing process (steps for mixing particles) 7) a.

  Below, each manufacturing process of step S1-step S7 is demonstrated in detail. Note that the manufacturing process of step S4 for preparing the first toner particle group and the manufacturing process of steps S5 to S6 for manufacturing the second toner particle group may be performed simultaneously. The manufacturing process may be performed first. By shifting from step S0 to step S1, the production of the toner of this embodiment is started.

(Pre-mixing process)
In the pre-mixing step of step S1, at least a binder resin, a colorant, and a release agent are dry-mixed with a mixer to prepare a mixture. The toner particles may contain other toner additive components in addition to the binder resin, the colorant, and the release agent. Examples of other toner additive components include a charge control agent. Each of these raw materials and their use amounts are not particularly limited, and known materials can be used in general use amounts.

  A known mixer can be used for dry mixing. For example, a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.), a super mixer (trade name, manufactured by Kawata Co., Ltd.) and a mechano mill (product) Name, Okada Seiko Co., Ltd. and other Henschel type mixing devices, Ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), and Cosmo System (trade name, Kawasaki) Heavy Industries, Ltd.).

  In the present invention, the exposure amount of the release agent on the toner particle surface is preferably 2.5% by weight or less of the total amount of toner. Here, the toner particle surface refers to a region having a depth of 700 nm or less from the toner particle surface. In order to adjust the exposure amount of the release agent on the toner particle surface to an appropriate range, it is necessary to control the addition amount of the release agent in the premixing step. Specifically, in order to make the amount of the release agent on the surface of the toner particles 2.5% by weight or less, the addition amount of the release agent in the premixing step is 6.0 parts by weight with respect to 100 parts by weight of the binder resin. The following.

(Melting and kneading process)
In the melt-kneading process of step S2, the mixture prepared in the pre-mixing process is melt-kneaded to prepare a melt-kneaded product. Melting and kneading the mixture is performed by heating to a temperature not lower than the softening point of the binder resin and lower than the thermal decomposition temperature. The binder resin is melted or softened to disperse the toner raw materials other than the binder resin in the binder resin. Let

  As the kneader, known ones can be used, and for example, general kneaders such as a twin-screw extruder, a three-roller, and a lab blast mill can be used. More specifically, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), etc. Extruder, Needex (trade name, manufactured by Mitsui Mining Co., Ltd.) and other open roll type kneaders. Among these, an open roll type kneader is preferable. The toner raw material mixture may be melt-kneaded using a plurality of kneaders.

(Crushing process)
In the pulverization step of Step S3, the melt-kneaded product obtained in the melt-kneading step is cooled and solidified, and then the cooled and solidified melt-kneaded product is pulverized to obtain the first pulverized product and the first pulverized product. Also, a second pulverized product having a large volume average particle diameter is prepared.

  The cooled and solidified melt-kneaded product is first pulverized by a hammer mill or a cutter mill into coarsely pulverized products having a volume average particle size of about 100 μm to 5 mm, for example. Thereafter, the obtained coarsely pulverized product is finely pulverized into a first pulverized product having a desired volume average particle size and a second pulverized product having a desired volume average particle size.

  The coarsely pulverized product is finely pulverized by, for example, a jet crusher that uses a supersonic jet stream, or a space formed between a rotor that is a rotor that rotates at high speed and a liner that is a stator. An impact pulverizer that introduces and pulverizes a coarsely pulverized product can be used.

  The cooled and solidified melt-kneaded product may be directly pulverized by a jet pulverizer or an impact pulverizer without being coarsely pulverized by a hammer mill or a cutting mill.

(First classification process)
In the first classification step of step S4, the first toner particle group is produced by removing the excessively pulverized toner particles and the coarse toner particles from the first pulverized product obtained in the pulverization step with a classifier. Overground toner particles and coarse toner particles can be recovered and reused for the production of other toner particles.

  For the classification, a known classifier capable of removing excessively pulverized toner particles and coarse toner particles by classification by centrifugal force or classification by wind force can be used. For example, a swirling wind classifier (rotary wind classifier), etc. Can be used.

  In the first classification step, it is preferable to perform classification so that the volume average particle diameter of the toner particles obtained after the classification is 5.5 μm or more and 6.5 μm or less by appropriately adjusting the classification conditions. When the volume average particle diameter of the toner particles is less than 5.5 μm, the content of small particle diameter particles in the toner is excessively increased, so that the cleaning property may be deteriorated. When the volume average particle diameter of the toner particles exceeds 6.5 μm, the volume average particle diameter of the toner becomes too large, and there is a possibility that a high-definition image cannot be obtained. In addition, since the specific surface area of the toner particles is reduced and the charge amount of the toner is reduced, the toner is not stably supplied to the image carrier, and there is a possibility that internal contamination due to toner scattering may occur. Therefore, as described above, the volume average particle diameter of the toner particles obtained after classification is selected to be 5.5 μm or more and 6.5 μm or less.

  The classification condition to be adjusted as appropriate is, for example, the rotational speed of the classification rotor in a swirling wind classifier (rotary wind classifier).

(Spheronization process)
In the spheronization step of step S5, the second pulverized product obtained in the pulverization step is spheroidized by mechanical impact force or hot air to produce a spheroidized product of the second pulverized product. In the present embodiment, it is preferable that the first pulverized product and the first toner particle group are not spheroidized, and at least one of the second pulverized product and the second toner particle group is spheroidized.

  In general, the smaller the toner particle size, the more difficult the transfer residual toner on the image carrier is removed by the cleaning blade, so the cleaning performance decreases. The tendency for the cleaning property to decrease as the particle diameter of the toner decreases becomes more prominent as the particle shape of the toner becomes spherical and the unevenness of the particle surface decreases. Further, as the toner particle diameter increases, the unevenness of the toner particle surface increases, and the balance of physical adhesion force between the toner particles on the image carrier tends to be lost.

  The first pulverized product and the first toner particle group are not spheroidized, and at least one of the second pulverized product and the second toner particle group is spheroidized, so that toner particles having a small volume average particle diameter are obtained. As the toner particles having a large volume average particle diameter can be reduced in unevenness, good cleaning properties can be obtained as a whole. Accordingly, it is possible to obtain a toner that can form a high-definition and high-resolution high-quality image more stably over a long period of time without fogging.

  Examples of the spheroidizing method include a method of spheronizing with a mechanical impact force and a method of spheronizing with hot air, but mechanical impact that can be spheroidized with moderate unevenness. A force is preferred. In the spheroidization treatment by heat, the toner particles are fused to each other, and the release agent contained in the toner particles may bleed on the surface of the toner particles, so that the fluidity of the toner may be deteriorated.

  As the impact spheroidizing device used for the spheroidizing treatment by mechanical impact force, a commercially available device can be used, for example, Faculty (trade name, manufactured by Hosokawa Micron Corporation) or the like can be used. As the hot-air spheronizing device used for the spheronization treatment with hot air, a commercially available device can be used. For example, a surface reformer, Meteorebom (trade name, manufactured by Nippon Pneumatic Industry Co., Ltd.) Can be used.

  In the present invention, the second toner particle group may be spheroidized after the second classification step of step S6.

(Second classification process)
In the second classification step of step S6, the second toner particle group is obtained by removing excessively pulverized toner particles and coarse toner particles with a classifier from the spheroidized product of the second pulverized product obtained in the spheronization step. Make it. Over-pulverized toner particles and coarse toner particles can be recovered and used for reuse in the production of other toner particles.

  For the classification, a known classifier capable of removing excessively pulverized toner particles and coarse toner particles by classification by centrifugal force or classification by wind force can be used. For example, a swirling wind classifier (rotary wind classifier), etc. Can be used.

  In the classification step, it is preferable that the classification conditions are appropriately adjusted so that the toner particles obtained after classification have a volume average particle diameter of 7.3 μm or more and 8.3 μm or less. When the volume average particle diameter of the toner particles is less than 7.3 μm, the content of small particle diameter particles in the toner is excessively increased, so that the cleaning property may be deteriorated. If it exceeds 8.3 μm, the volume average particle diameter of the toner becomes too large, and there is a possibility that a high-definition image cannot be obtained. Further, since the specific surface area of the toner particles is reduced and the charge amount of the toner is reduced, the toner is not stably supplied to the latent image carrier, and there is a possibility that internal contamination due to toner scattering occurs.

  The classification conditions to be adjusted include, for example, the rotational speed of the classification rotor in a swirl type wind classifier (rotary type wind classifier).

  Depending on the type of apparatus used in the spheronization process, the spheronization process in step S5 and the second classification process in step S6 may be performed simultaneously, or the order may be switched.

(Mixing process)
In the mixing process of step S7, the first toner particle group produced through the first classification process of step S4 and the second toner particle group produced through the spheroidization process of step S5 and the second classification process of S6 are combined. By mixing, toner particles contained in the toner used in the image forming apparatus of the present invention are produced.

  As a mixer used in the mixing step, for example, Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.) ) Henschel type mixing equipment, ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), etc. It is done.

  In the exemplary embodiment, the second toner particle group is preferably mixed in a weight ratio range of 5 parts by weight to 120 parts by weight with respect to 100 parts by weight of the first toner particle group. When the second toner particle group is mixed at a weight ratio of less than 5 parts by weight with respect to 100 parts by weight of the first toner particle group, it is compared with the case where the second toner particle group is mixed at a weight ratio of 5 parts by weight or more. As a result, the contact area between the image carrier and the intermediate transfer medium and the toner increases, and the transfer efficiency of the toner to the recording medium decreases, so that when the image is formed using a recording medium having a rough surface, the formed image The image reproducibility deteriorates due to the occurrence of omission. In the fixing step, the gap between the toner particles becomes large, so that the thermal conductivity of the toner image is lowered and there is a possibility that good low-temperature fixability cannot be obtained. Further, the unevenness on the surface of the toner particles is not controlled, and the number of second toner particles that are difficult to make the charge distribution on the toner surface uniform is increased, so that toner scattering is likely to occur. Further, since toner particles having a small volume average particle diameter increase, fluidity may be lowered.

  When the second toner particle group is mixed at a weight ratio exceeding 120 parts by weight with respect to 100 parts by weight of the first pulverized product, it is compared with the case where the second toner particle group is mixed at a weight ratio of 120 parts by weight or less. Further, since the content of toner particles having a large volume average particle diameter increases, it becomes difficult to form a high-definition image and image reproducibility is lowered.

  By mixing the second toner particle group in a weight ratio range of 5 parts by weight to 120 parts by weight with respect to 100 parts by weight of the first toner particle group, a high-definition image with a toner having a small volume average particle diameter. Can suppress toner scattering, reduce image deterioration, have good low-temperature fixability, and have excellent fluidity, so high resolution and high resolution over a long period of time Thus, it is possible to obtain a toner that can form a high-quality image more stably.

  In the present embodiment, the second toner particle group is more preferably mixed in a weight ratio range of 5 parts by weight to 70 parts by weight with respect to 100 parts by weight of the first toner particle group. Since the second toner particle group is mixed at a weight ratio of 70 parts by weight or less with respect to 100 parts by weight of the first pulverized product, the content of toner particles having a large volume average particle diameter is further optimized. The effect of forming a high-definition image with good quality can be remarkably exhibited.

  The second toner particle group is mixed in a weight ratio range of 5 parts by weight or more and 70 parts by weight or less with respect to 100 parts by weight of the first toner particle group. A toner capable of forming a quality image more stably can be obtained.

  When the mixing step is finished, the production of toner particles contained in the toner used in the image forming apparatus of the present invention is finished.

  The toner particles obtained in this way are mixed with external additives that perform functions such as powder flowability improvement, triboelectric chargeability improvement, heat resistance, long-term storage stability improvement, cleaning property improvement and photoreceptor surface wear property control. May be. As the external additive, those commonly used in this field can be used, and examples thereof include fine silica powder, fine titanium oxide powder and fine alumina powder. These inorganic fine powders are used for the purpose of hydrophobizing, charging control, etc. Silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organic It is preferable that it is processed with processing agents, such as a silicon compound, 1 type can be used individually or 2 or more types can be used together.

  The addition amount of the external additive is 1 to 100 parts by weight of the toner particles in consideration of the charge amount necessary for the toner, the influence on the abrasion of the photoreceptor due to the addition of the external additive, the environmental characteristics of the toner, and the like. The amount is preferably 10 parts by weight, and more preferably 5 parts by weight or less. The external additive preferably has a number average particle diameter of primary particles of 10 nm to 500 nm. By using an external additive having such a particle size, the effect of improving the fluidity of the toner is more easily exhibited.

  The volume average particle diameter of the toner used in the image forming apparatus of the present invention produced as described above is selected from 5.0 μm to 7.0 μm. The content of toner particles having a number average particle diameter of 5.0 μm or less is preferably less than 40% by number of all toner particles. When the particle size distribution and number distribution of the toner satisfy this range, toner scattering can be suppressed and a high-definition and high-resolution high-quality image can be formed. If the volume average particle diameter is less than 5.0 μm, the transfer belt cleaning may be insufficient. If the volume average particle diameter is more than 7.0 μm, it is not possible to form a sufficiently high-definition solid image with no roughness and unevenness. . When the content ratio of the toner particles having a number average particle diameter of 5.0 μm or less is 40% by number or more of all the toner particles, the toner scatters due to a decrease in fluidity and the fogging due to deterioration of transfer efficiency occurs.

  The shape factor SF-2 of the toner used in the image forming apparatus of the present invention is 135 or more and less than 143. When the shape factor SF-2 representing the degree of unevenness on the surface of the toner particles satisfies this range, it is possible to form an image forming apparatus in which a high-quality image is formed and the durability of the transfer belt is also good. If a toner having a shape factor SF-2 of less than 135 is used, the transferability is improved and an image without unevenness is formed. However, it is necessary to increase the linear pressure of the belt cleaning blade, and the belt is torn. Further, when a toner having a shape factor SF-2 of 143 or more is used, the contact area between the toner and the intermediate transfer belt is increased, transferability is deteriorated, and betaram is likely to occur.

Here, the volume average particle diameter of the toner is measured by a particle size distribution measuring apparatus “Multisizer III” manufactured by Beckman Coulter, Inc. The measurement conditions are shown below.
Aperture diameter: 100 μm
Measurement particle number: 50000 count Analysis software: Coulter Multisizer AccuComp version 1.19 (manufactured by Beckman Coulter, Inc.)
Electrolyte: ISOTON-II (Beckman Coulter, Inc.)
Dispersant: Sodium alkyl ether sulfate

  In the measurement procedure, 50 ml of electrolyte solution, 20 mg of sample toner and 1 ml of dispersant are added to a beaker, a dispersion sample is prepared for 3 minutes by an ultrasonic disperser to prepare a measurement sample, and the particle size is measured. The volume particle size distribution of the sample particles is obtained from the obtained measurement results, and the volume average particle diameter of the toner is obtained from the volume particle size distribution. The toner shape factor SF-2 is a value measured according to the following method.

A metal film (Au film, film thickness 0.5 μm) is formed on the surface of the toner particles by sputtering deposition. From this metal film-coated toner, 200 to 300 samples were randomly extracted at an acceleration voltage of 5 kV and a magnification of 1000 times by a scanning electron microscope (trade name: S-570, manufactured by Hitachi, Ltd.). Take a photo. The electron micrograph data is image-analyzed by image analysis software (trade name: A image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.). Particle analysis parameters of the image analysis software “A image-kun” are: small figure removal area: 100 pixels, shrinkage separation: number of times 1; small figure: 1; number of times: 10, noise removal filter: none, shading: none, result display unit : Μm. The shape factor SF-2 is obtained from the perimeter length PERI and the graphic area AREA of the particles thus obtained by the following equation (1).
SF-2 = {(PERI) 2 / AREA} × (100 / 4π) (1)

  The shape factor SF-2 is a value represented by the above formula (1), and indicates the degree of unevenness of the surface shape of the toner particles. When the value of SF-2 is 100, the unevenness does not exist on the surface of the toner particles, and the larger the value of SF-2, the more the unevenness becomes remarkable.

(Developer)
The toner used in the image forming apparatus of the present invention can be used as it is as a one-component developer, or can be mixed with a carrier and used as a two-component developer. When used as a one-component developer, the toner is used only without using a carrier. When used as a one-component developer, a blade and a fur brush are used, and the toner is conveyed by frictional charging with a developing sleeve to adhere the toner onto the sleeve, thereby forming an image. When used as a two-component developer, the toner of the present invention is used with a carrier.

  As the carrier, a known carrier can be used. For example, a resin-coated carrier or a resin in which iron or copper, zinc, nickel, cobalt, manganese, chromium or the like alone or a composite ferrite and carrier core particles are coated with a coating material. And a resin-dispersed carrier in which magnetic particles are dispersed. As the coating material, known materials can be used, such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicon resin, polyester resin, metal compound of ditertiary butyl salicylic acid, styrenic resin, Acrylic resin, polyacid, polyvinyllar, nigrosine, aminoacrylate resin, basic dye, basic dye lake, silica fine powder, alumina fine powder, and the like.

  The resin used for the resin-dispersed carrier is not particularly limited, and examples thereof include styrene acrylic resin, polyester resin, fluorine resin, and phenol resin. Either of them is preferably selected according to the toner component, and one can be used alone, or two or more can be used in combination.

The shape of the carrier is preferably a spherical shape or a flat shape. Further, the particle size of the carrier is not particularly limited, but is preferably selected from 10 μm to 100 μm, and more preferably from 20 μm to 50 μm, considering high image quality. Furthermore, the resistivity of the carrier is preferably selected to be 10 ⁸ Ω · cm or more, and more preferably 10 ¹² Ω · cm or more. The carrier resistivity is determined by placing the carrier in a container having a cross-sectional area of 0.50 cm ² and tapping it, then applying a load of 1 kg / cm ² to the particles packed in the container and placing the load between the load and the bottom electrode. This is a value obtained by reading a current value when a voltage generating an electric field of 1000 V / cm is applied. When the resistivity is low, when a bias voltage is applied to the developing sleeve, charges are injected into the carrier, and carrier particles easily adhere to the photoreceptor. Further, breakdown of the bias voltage is likely to occur.

  The magnetization strength (maximum magnetization) of the carrier is preferably selected from 10 emu / g to 60 emu / g, more preferably from 15 emu / g to 40 emu / g. Although the magnetization strength depends on the magnetic flux density of the developing roller, if the magnetic strength is less than 10 emu / g under the general magnetic flux density conditions of the developing roller, the magnetic binding force does not work, causing the carrier scattering. There is a risk of becoming. On the other hand, if the magnetization strength exceeds 60 emu / g, it is difficult to maintain a non-contact state with the image carrier in the non-contact development in which the carrier spikes are too high. Further, in the contact development, there is a risk that a sweep is likely to appear in the toner image. Therefore, the magnetization strength (maximum magnetization) of the carrier is selected from 10 emu / g to 60 emu / g, more preferably from 15 emu / g to 40 emu / g.

The ratio of the toner and the carrier used in the two-component developer is not particularly limited and can be appropriately selected according to the type of the toner and the carrier, but an example is a resin-coated carrier (density 5 g / cm ^{2 to} 8 g / cm ² ). For example, the toner may be used so that the toner is contained in 2% to 30% by weight, preferably 2% to 20% by weight of the total amount of the developer. In the two-component developer, the carrier coverage with the toner is preferably 40% to 80%.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not particularly limited as long as it does not exceed the gist thereof.

(Melting point of release agent)
Using a product name: DSC220, manufactured by Seiko Electronics Industry Co., Ltd. Repeated twice, DSC (Differential Scanning Calorimeter) curve was measured. The temperature at the top of the endothermic peak corresponding to the melting of the DSC curve measured in the second operation was determined as the melting point of the release agent.

(Volume average particle diameter of toner particle group and toner)
To 50 ml of electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), 20 mg of toner and 1 ml of sodium alkyl ether sulfate are added, and ultrasonic waves are applied using an ultrasonic dispersing device (trade name: UH-50, manufactured by STM). A sample for measurement was prepared by dispersing for 3 minutes at a frequency of 20 kz. This sample for measurement was measured using a particle size distribution measuring device (trade name: Multisizer III, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and from the volume particle size distribution of the toner. The volume average particle diameter of the toner was determined.

(Toner shape factor SF-2)
To a 100 ml beaker, 2.0 g of toner, 1 ml of sodium alkyl ether sulfate and 50 ml of pure water were added and stirred well to prepare a toner dispersion. This toner dispersion was treated with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at an output of 50 μA for 5 minutes and further dispersed. After standing for 6 hours and removing the supernatant, 50 ml of pure water was added, and the mixture was stirred with a magnetic stirrer for 5 minutes, and then subjected to suction filtration using a membrane filter (caliber: 1 μm). The washed product on the membrane filter was vacuum-dried in a desiccator containing silica gel for about overnight.

  A metal film (Au film, film thickness 0.5 μm) was formed by sputtering deposition on the surface of the toner particles whose surface was cleaned in this way. From this metal film-coated toner, 200 to 300 samples were randomly extracted at an acceleration voltage of 5 kV and a magnification of 1000 times by a scanning electron microscope (trade name: S-570, manufactured by Hitachi, Ltd.). I took a photo. This electron micrograph data was obtained by image analysis using image analysis software (trade name: A image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.) and calculating the shape factor therefrom.

(Exposure amount of release agent on toner surface)
1 g of the toner was dispersed in 20 ml of hexane, stirred for 10 minutes with a stirrer to elute the release agent on the toner surface layer with hexane, filtered, and placed in a dryer set at 40 ° C. overnight to dry. An operation of heating 1 g of toner eluted with hexane from a temperature of 20 ° C. to 150 ° C. at a heating rate of 10 ° C. per minute and then rapidly cooling the toner from 150 ° C. to 20 ° C. was repeated twice to measure the DSC curve. The heat capacity of the release agent in the toner was calculated from the heat of fusion of the DSC curve measured in the second operation. For the untreated toner, the heat capacity was calculated in the same manner. The exposure amount of the release agent on the toner surface layer was estimated from the difference between these heat capacities.

(Example 1)
[Pre-mixing process]
Polyester resin A, 81.8 parts by weight, 12 parts by weight of a master batch (containing 40% by weight of CI Pigment Red 57: 1), paraffin wax (release agent, trade name: HNP10, manufactured by Nippon Seiki Co., Ltd.) 4.5 parts by weight of acid value = 0 mgKOH / g, melting point 75 ° C., 1.5 parts by weight of alkylsalicylic acid metal salt (charge control agent, trade name: BONTRON E-84, manufactured by Orient Chemical Co., Ltd.) using a Henschel mixer A mixture was made by mixing for 10 minutes.

[Melting and kneading process]
The mixture was melt-kneaded with an open roll type continuous kneader (trade name: MOS320-1800, manufactured by Mitsui Mining Co., Ltd.) to prepare a melt-kneaded product.

[Crushing process]
After roughly pulverizing the melt-kneaded product with a cutting mill (trade name: VM-16, manufactured by Ryoko Sangyo Co., Ltd.) to produce a coarsely pulverized product, the coarsely pulverized product is finely pulverized with a counter jet mill. 1 ground material and 2nd ground material were produced, respectively.

[First classification process]
In the first pulverized product, the excessively pulverized toner was classified and removed with a rotary classifier to prepare a first toner particle group having a volume average particle diameter of about 5.5 μm.

[Spheronization process]
The second pulverized product was spheronized using an impact spheroidizing apparatus (trade name: Faculty F-600, manufactured by Hosokawa Micron Corporation) to produce a spheroidized product of the second pulverized product.

[Second classification process]
In the spheroidized product of the second pulverized product, the excessively pulverized toner was classified and removed with a rotary classifier to prepare a second toner particle group having a volume average particle diameter of about 7.5 μm.

[Mixing process]
A toner was prepared by mixing 50 parts by weight of the second toner particle group with 100 parts by weight of the first toner particle group.

[External addition process]
100 parts by weight of toner, 2.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) as an external additive, and hydrophobic titanium (trade name: T-805, manufactured by Nippon Aerosil Co., Ltd.) The toner of Example 1 was externally added to the toner by mixing 3.8 parts by weight in total with 1.6 parts by weight with a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.). (Toner coverage by external additive: 80%) was prepared. At this time, the volume average particle diameter is 6.2 μm, and the toner shape factor SF-2 is 141. Further, the exposure amount of the release agent on the toner surface was 1.8 wt%.

[Preparation of two-component developer]
A ferrite core carrier having a volume average particle diameter of 45 μm is used as the carrier, and a V-type mixer / mixer (trade name: V-5, Tokuju Kogyo Co., Ltd.) is used so that the toner coverage on the carrier is 60%. The two-component developer containing the toner of Example 1 was prepared by mixing for 20 minutes.

[Image output]
The above two-component developer was output on Igeba paper, which is a US medium quality paper having a thickness of about 90 μm and a surface roughness Ra of 2.1 μm, using a color compound machine (trade name: MX-2700, manufactured by Sharp Corporation). At this time, the film thickness of the intermediate transfer belt 25 was 55 μm, and the cleaning blade pressure was 2.4 gf / mm.

(Example 2)
A toner of Example 2 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the film thickness of the intermediate transfer belt was 40 μm.

(Example 3)
A toner of Example 3 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the film thickness of the intermediate transfer belt was changed to 60 μm.

(Example 4)
A toner of Example 4 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the film thickness of the intermediate transfer belt was changed to 70 μm.

(Example 5)
A toner of Example 5 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 1.8 gf / mm.

(Example 6)
A toner of Example 6 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 2.0 gf / mm.

(Example 7)
A toner of Example 7 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 2.8 gf / mm.

(Example 8)
A toner of Example 8 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 3.0 gf / mm.

Example 9
A toner of Example 9 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the conditions of the pulverization step were changed to make the particle size of the toner 5.2 μm.

(Example 10)
A toner of Example 10 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the pulverization process conditions were changed to make the toner particle size 6.8 μm.

Example 11
The toner of Example 11 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the processing conditions in the spheronization process were changed and the toner shape factor SF-2 was changed to 137.

Example 12
The toner of Example 12 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the processing conditions in the spheronization process were changed and the toner shape factor SF-2 was changed to 142.

(Example 13)
A toner of Example 13 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the material of the intermediate transfer belt was polycarbonate.

(Example 14)
A toner of Example 14 and an image forming apparatus including the same were obtained in the same manner as Example 1 except that the content of the release agent was 5.3 parts by weight. The exposure amount of the release agent on the toner surface was 2.4 wt%.

(Example 15)
A toner of Example 15 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the content of the release agent was 6.0 parts by weight. The exposure amount of the release agent on the toner surface was 2.7 wt%.

(Example 16)
A toner of Example 16 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the first pulverized product was spheroidized in the same manner as the second pulverized product. The toner shape factor SF-2 was 136.

(Example 17)
The toner of Example 17 and the image forming apparatus including the same are obtained in the same manner as in Example 1 except that the second pulverized product is not spheroidized like the first pulverized product, that is, the spheronization step is not performed. It was. The toner shape factor SF-2 was 142.

(Comparative Example 1)
A toner of Comparative Example 1 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the film thickness of the intermediate transfer belt was 75 μm.

(Comparative Example 2)
A toner of Comparative Example 2 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the film thickness of the intermediate transfer belt was 35 μm.

(Comparative Example 3)
A toner of Comparative Example 3 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 1.6 gf / mm.

(Comparative Example 4)
A toner of Comparative Example 4 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the cleaning blade pressure was 3.2 gf / mm.

(Comparative Example 5)
A toner of Comparative Example 5 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the pulverization process conditions were changed and the particle size of the toner was 4.8 μm.

(Comparative Example 6)
A toner of Comparative Example 6 and an image forming apparatus including the same were obtained in the same manner as in Example 1 except that the conditions of the pulverization process were changed to change the particle diameter of the toner to 7.2 μm.

(Comparative Example 7)
The toner of Comparative Example 7 and the toner thereof were included in the same manner as in Example 1 except that the first pulverized product was spheroidized in the same manner as the second pulverized product, and the spheroidizing treatment conditions were made stronger than in Example 12. An image forming apparatus was obtained. The toner shape factor SF-2 was 134.

(Comparative Example 8)
The second pulverized product was not spheroidized similarly to the first pulverized product, that is, the spheroidizing step was not performed, and the pulverization conditions were changed to change the toner particle size to 7.3 μm. Thus, the toner of Comparative Example 8 and an image forming apparatus including the toner were obtained. The toner shape factor SF-2 was 143.

  Table 1 summarizes the physical properties of the toners obtained in Examples 1 to 17 and Comparative Examples 1 to 8 and image forming apparatuses including the toners.

  Using the toners obtained in Examples 1 to 17 and Comparative Examples 1 to 8 and the two-component developers containing the toners, the intermediate transfer belt durability, stickiness, unevenness, and cleaning properties were evaluated by the following methods.

(Intermediate transfer belt durability)
The durability of the intermediate transfer belt was subjected to the following acceleration test.
The rotation speed was idle at 300 mm / sec, and the time until a crack occurred in the intermediate transfer belt 25 was measured. The evaluation criteria in Table 2 to be described later are as follows.
◎: Time until cracking is 280 hours or more ○: Time until cracking is 250 hours or more and less than 280 hours Δ: Time until cracking is 220 hours or more and less than 250 hours ×: Time until cracking occurs Is less than 220 hours

(Solid, uneven)
For the image formed when the surface temperature of the fixing heating roller is 190 ° C., the optical reflection density of the solid image portion is measured using a spectrophotometer (trade name: X-Rite 938, manufactured by X-Rite). This was used as the image density, and a solid image was printed on the entire surface by adjusting the developing bias and the like so that the 10-point average of the image density was 1.5. Variation in image density measurement at 10 points was used as an index for evaluation of unevenness and unevenness.
A: The difference between the maximum value and the minimum value of the image density is less than 0.08. A: The difference between the maximum value and the minimum value of the image density is 0.08 or more and less than 0.10. Δ: The difference between the maximum value and the minimum value of the image density. Is 0.10 or more and less than 0.15 x: The difference between the maximum value and the minimum value of image density is 0.15 or more

(Cleanability)
A two-component developer obtained by mixing 5 parts of toner with 95 parts of a ferrite core carrier having a volume average particle diameter of 45 μm is charged into a color composite machine (trade name: MX-2700, manufactured by Sharp Corporation), and is used as an evaluation sheet. Using a domestic medium quality paper (Sharp Corporation recommended paper) MI paper with a surface roughness Ra of about 60 μm and a MI paper, a chart with a printing rate of 5% is continuously printed, and a test chart is formed after printing 30,000 sheets did. Three types of test charts were formed: a full-color image, a fine line chart, and white paper (printing rate 0%). The image defects, streaks, etc. of these three types of test charts were visually confirmed, and image evaluation was performed with 30,000 sheets. Further, when 30,000 sheets had no image defects, streaks, etc., 20,000 sheets were printed and image evaluation was performed. The evaluation criteria are as follows.
A: Very good. Even when printing 50,000 sheets, image defects, streaks, etc. do not occur in all three types of test charts.
○: Good. Image defects, streaks, etc. do not occur in all three types of test charts printed on 30,000 sheets, but image defects, streaks, etc. occur on 50,000 sheets.
Δ: Slightly good Only one type of test chart has some image defects, streaks, and the like.
×: Unusable. Image defects, streaks, etc. have occurred in one or more types of test charts.

(Comprehensive evaluation)
Evaluation was made based on the following comprehensive evaluation criteria.
A: Very good. All the evaluation results are ◎, and there is no ○, △ and ×.
○: Good. There is one ◯ in the evaluation result, and there is no △ or ×.
Δ: No problem in actual use. There is one Δ in the evaluation result, and there is no x.
X: Defect. There are one or more evaluation results.

  Table 2 shows the evaluation results and comprehensive evaluation results of the toners obtained in Examples 1 to 17 and Comparative Examples 1 to 8 and the two-component developers containing the toner.

  From the above results, as apparent from Examples 1 to 17, the film thickness of the transfer belt is 40 μm to 70 μm, the linear pressure of the cleaning blade is 1.8 gf / mm to 3.0 gf / mm, and the toner shape factor By setting SF-2 to be 135 or more and less than 143, an image forming apparatus that forms a solid image without unevenness and has excellent durability of the transfer belt even when paper having a rough surface is used can be obtained. confirmed.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 100 according to an embodiment of the present invention. 4 is a flowchart illustrating an example of a method for producing toner particles contained in toner used in the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Image formation part 3 Transfer means 4 Fixing means 5 Recording medium supply means 6 Ejection means 11 Photoconductor drum 12 Charging means 13 Exposure unit 14 Developing device 15 Cleaning unit 20 Developing tank 21 Toner hopper 25 Intermediate transfer belt 26 Drive roller 27 Driven roller 28 Intermediate transfer roller 29 Transfer belt cleaning unit 30 Transfer roller 31 Fixing roller 32 Pressure roller 35 Automatic paper feed tray 36 Pickup roller 37 Transport roller 38 Registration roller 39 Manual paper feed tray 40 Discharge roller 41 Discharge tray 100 Image forming apparatus

Claims (5)

A photosensitive member; a toner image forming unit that forms a toner image on the surface of the photosensitive member; a primary transfer unit that transfers the toner image on the surface of the photosensitive member onto the transfer belt; a cleaning blade that cleans the transfer belt; In an image forming apparatus comprising: a secondary transfer unit that transfers a toner image to a recording medium; and a fixing unit that fixes an unfixed toner image transferred to the recording medium to the recording medium.
The transfer belt has a film thickness of 40 μm to 70 μm,
The linear pressure of the cleaning blade is 1.8 gf / mm to 3.0 gf / mm,
An image forming apparatus using a toner having a volume average particle diameter of 5 μm to 7 μm and a shape factor SF-2 of 135 or more and less than 143.   The image forming apparatus according to claim 1, wherein the transfer belt is made of a polyimide resin.   3. The image forming apparatus according to claim 1, wherein a toner whose release amount on the toner surface is 2.5 wt% or less of the total amount of the toner is used.   The image forming apparatus according to claim 1, wherein a toner obtained by spheroidizing all or part of the pulverized toner is used. A pulverization step for producing a first pulverized product obtained by pulverizing a resin composition containing at least a binder resin, a colorant and a release agent, and a second pulverized product having a volume average particle size larger than that of the first pulverized product;
A first classification step of classifying the first pulverized product to produce a first toner particle group;
The second pulverized product is classified after the spheronization treatment to classify the second pulverized product, or a second spheroidizing / classifying step for producing a second toner particle group having a volume average particle diameter larger than that of the first toner particle group. A second classification and spheronization step in which a second toner particle group having a volume average particle diameter larger than that of the first toner particle group is produced and then spheroidized.
The image forming apparatus according to claim 1, wherein a toner manufactured through a mixing step of mixing the first toner particle group and the second toner particle group is used.

Images