JP4715307B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a facsimile, and a printer, and more particularly, an image including a cleaning member that removes untransferred residual toner on an image carrier that carries a toner image. The present invention relates to a forming apparatus.

  Conventionally, in an image forming apparatus using an electrophotographic system, the surface of an image carrier that rotates about a predetermined rotation axis is charged, and the surface of the charged image carrier is irradiated with a light beam. An electrostatic latent image corresponding to the image information is formed on the surface of the carrier, and the electrostatic latent image is developed with toner to form a toner image corresponding to the electrostatic latent image. An image is formed on a recording medium by a series of image forming processes in which the image is transferred to a transfer medium such as an intermediate transfer body and finally a toner image is fixed on a recording paper.

  In such an image forming apparatus, when foreign matters such as untransferred toner, paper powder, or discharge products generated in the charging process remain on the surface of the image carrier after the toner image is transferred to the transfer target, It is necessary to remove these residues because it causes image quality degradation.

  As a method for removing such a residue, a method for removing the residue mechanically by rubbing with the image carrier, in particular, a plate-shaped cleaning blade is disposed opposite to the peripheral surface of the image carrier to perform this cleaning. Many methods are used in which the tip of the blade is pressed against the surface of the image carrier.

  Here, the toner image transfer method includes a method in which the toner image formed on the image carrier is directly transferred to the recording paper, and a method in which the toner image formed on the image carrier is transferred to the intermediate transfer member and then intermediate. A method of transferring from a transfer body to a recording sheet is known. Among these methods, in an image forming apparatus that employs a method of directly transferring a toner image formed on an image carrier to a recording medium, the recording paper is sandwiched and conveyed between the image carrier and a transfer roll. Compared to the case where the toner image is transferred to the recording medium and the toner image is transferred to the intermediate transfer body, the cleaning blade and the image in which the paper powder released from the recording paper during transfer is opposed to the peripheral surface of the image carrier. It becomes easy to reach the position facing the carrier (that is, the tip of the cleaning blade). When the separated paper dust accumulates on the tip of the cleaning blade and the deposition proceeds further, foreign matter such as accumulated paper dust is sandwiched between the image carrier and the tip of the cleaning blade. To pass. When foreign matter is sandwiched between the image carrier and the tip of the cleaning blade, the cleaning performance of the toner by the cleaning blade is inhibited, and the image quality is deteriorated by the toner that has not been removed by the cleaning blade. was there. In addition, there has been a problem that the tip portion of the cleaning blade and the surface of the image carrier are deteriorated by paper dust sandwiched between the image carrier and the cleaning blade.

  In order to cope with such a problem, the cleaning blade is rotated by rotating the image carrier in the direction opposite to the rotation direction during the image forming process when a series of image forming processes is completed (hereinafter referred to as reverse rotation). A technique for removing foreign matter such as accumulated non-transfer residual toner has been disclosed (see, for example, Patent Document 1 and Patent Document 2).

  According to the techniques of Patent Document 1 and Patent Document 2, after one image creation process is completed, the cleaning blade disposed so that the tip portion contacts the surface of the image carrier is isolated from the image carrier. The image carrier is slightly rotated in the reverse direction. Thus, by separating the cleaning blade from the time of the image carrier during the reverse rotation of the image carrier, the tip of the cleaning blade is deflected by receiving the force in the reverse rotation direction of the image carrier due to the reverse rotation of the image carrier. Problems such as wear of the tip and elastic deterioration of the cleaning blade caused by repeating this can be avoided. However, since it is necessary to provide a mechanism for separating the cleaning blade from the position in contact with the image carrier, there is a problem that the apparatus becomes complicated and large.

  Here, in the accumulation portion of foreign matters such as untransferred residual toner at the tip of the cleaning blade, the toner is separated in particle size, and the particle size becomes finer as it approaches the tip of the cleaning blade. In such particle size separation, the closer the toner is to a spherical shape, the easier it is to arrange the shape at the tip of the cleaning blade. Since the number of contact points increases and the frictional force of each toner particle is directed in the same direction, the force received by the cleaning blade increases, the cleaning blade moves away from the contact position with the image carrier, and untransferred residual toner is cleaned. There is a problem of passing between the tip of the blade and the image carrier. In order to achieve high transfer efficiency, it is necessary to make the shape of the toner closer to a sphere. However, the closer the shape is to a sphere, the worse the cleaning performance, so there is a method to increase the linear pressure of the cleaning blade to the image carrier. Although it is conceivable, when the linear pressure is increased, a frictional force between the image carrier and the cleaning blade increases, which causes a problem that image quality is deteriorated.

  On the other hand, as a study from the developer side, a method of adding a fatty acid metal salt to a toner has also been proposed (see, for example, Patent Document 3), but this method is performed between the tip of the cleaning blade and the surface of the image carrier. It is effective in reducing the frictional force between the two, but adding a fatty acid metal salt greatly reduces the charge amount of the toner, and as a result, fog and toner scattering during development tend to occur, resulting in improved image quality. May fall.

  In addition, a method of adding higher alcohol or higher fatty acid to the toner has been proposed (for example, see Patent Document 4), and higher alcohol having 30 to 300 carbon atoms is added to suppress toner spot. Further, suppression of comet and filming on the image carrier by adding higher alcohols by various methods in cleaning blade cleaning has been studied (see, for example, Patent Document 5 and Patent Document 6).

  It is explained that higher alcohols and higher fatty acids form a lubricating film on the surface of the image carrier during cleaning with the cleaning blade, and the film suppresses filming of toner and toner constituent materials on the image carrier. Yes. However, it is disclosed in Patent Document 7 that a large amount of addition is required to form a sufficient lubricating film, and in that case, poor charging of the toner and a decrease in environmental stability newly occur.

Therefore, it has been proposed that the use of a higher alcohol or higher fatty acid used in the range of 21 to 29 facilitates the formation of a lubricating film on the image carrier with a small addition. However, in this case, the higher alcohol is easily softened and a lubricating film is easily formed, but at the same time, the contamination of the carrier of the two-component developer, the developing sleeve of the one-component developer, the charging cleaning blade, etc. becomes remarkable, and the development There is a problem that the charge retention of the agent is poor.
JP 60-49381 A JP-A-60-178478 JP 2000-89502 A JP-A-63-188158 Japanese Patent Application Laid-Open No. 6-282096 Japanese Patent Laid-Open No. 9-6049 JP 2001-42562 A

  The object of the present invention is to solve the problems in the prior art and to achieve the following problems. That is, the present invention provides an image forming apparatus and an image forming method capable of suppressing the enlargement of the apparatus main body, suppressing friction between the image carrier and the cleaning member due to the reverse rotation of the image carrier, and suppressing image quality deterioration. The purpose is to provide.

As a result of intensive studies, the present inventors have found that the above-described object can be achieved by using the following toner as well as the configuration of the image forming apparatus as described below, thereby completing the present invention. It came to.
The present invention as means for solving the problems is as follows.

  An image forming apparatus according to a first aspect of the present invention includes an image carrier that carries a toner image of toner on a surface and rotates in a predetermined direction, and a toner image carried on the surface of the image carrier to a recording medium. An image forming apparatus including a transfer unit that forms an image on the recording medium by transferring, and removes untransferred residual toner on the image carrier that is in contact with the outer peripheral surface of the image carrier. A cleaning member; and reverse rotation control means for controlling the image carrier so as to reversely rotate by a predetermined amount after the untransferred residual toner is removed by the cleaning member. The toner base particles have a shape factor SF1 of 140 or less, the external additive contains higher alcohol particles having a volume average particle diameter of 1 to 12 μm, and the toner additive particles include an external additive. It is characterized in that it comprises the toner the volume average particle diameter or less of a mother particle a higher alcohol particles above 0.15 wt% during chromatography.

  The shape factor SF1 is an average value of the shape factors of the toner base particles represented by the following formula (1).

[Formula 1]
SF1 = 100 × πML ² / 4A (1)
In the above formula (1), ML represents the absolute maximum length of each toner base particle, and A represents the projected area of each toner base particle.

  In the image forming apparatus according to the first aspect, the toner image carried on the surface of the image carrier that rotates in a predetermined direction is transferred to a recording medium by a transfer unit. The untransferred residual toner carried on the image carrier without being transferred to the recording medium by the transfer by the transfer means is removed by the cleaning member. The image carrier is controlled to rotate in reverse by the control of the reverse rotation control means after the untransferred residual toner is removed by the cleaning member.

  The reverse rotation control means is preferably configured to form an image after the toner image carried on the image carrier is transferred to the recording medium and before the rotation of the image carrier is stopped. It is rotated in the opposite direction, that is, reversely rotated. The predetermined amount by which the image carrier is reversely rotated may be a predetermined amount that can remove foreign matter accumulated at the contact position between the cleaning member and the image carrier.

  Although the untransferred residual toner accumulated on the cleaning member can be removed by the reverse rotation of the image carrier, the frictional force between the image carrier and the cleaning member increases, and the image carrier and the cleaning member However, according to the image forming apparatus of claim 1, the toner includes toner base particles and an external additive, and the toner base particles By defining the relationship between the particle size and the particle size of the higher alcohol particles, a sufficient lubricating surface is formed on the surface of the image carrier, and the cleaning member and the image carrier are increased by increasing the frictional force between the cleaning member and the image carrier. It was found that the wear of each body can be suppressed.

  Specifically, the toner comprises toner base particles and an external additive, the toner base particles have a shape factor SF1 of 140 or less, and the external additive is a higher alcohol particle having a volume average particle diameter of 1 to 12 μm. In addition, the above effect was found by including 0.15% by mass or more of the higher alcohol particles having a volume average particle size of the toner base particles equal to or less than the toner base particles.

  In order to suppress an increase in the frictional force between the image carrier and the cleaning member, it is necessary to form a lubricating surface with higher alcohol on the surface of the image carrier, but in order to form a lubricating surface, the image carrier It is necessary to efficiently supply higher alcohol particles to the contact position between the top and the cleaning member. In the accumulation portion of the untransferred residual toner at the position where the image carrier and the cleaning member are in contact with each other, the toner is separated in particle size, and the particle size becomes finer as it approaches this position. By containing 0.15% by mass or more of higher alcohol particles smaller than the volume average particle size of the mother particles, a lubricating surface can be efficiently formed on the surface of the image carrier.

  In order to exert the effect of reducing the frictional force between the cleaning member and the image carrier, it is considered necessary to increase the amount of higher alcohol particles added to the toner base particles. There is a problem that the chargeability of the image carrier decreases as the amount increases. However, as shown in the invention of claim 1, the content of higher alcohol particles smaller than the volume average particle size of the toner base particles is determined, By suppressing the total amount of alcohol particles added, the chargeability of the image carrier can be suppressed.

  Further, by setting the SF1 of the toner base particles to 140 or less, the toner base particles can be made close to a spherical shape, so that high transfer efficiency can be achieved.

  In addition, by setting the volume average particle size of the higher alcohol used as an external additive to 1 μm or more, it is deposited on the edge of the cleaning blade to form a dam without passing between the cleaning blade and the image carrier, thereby supporting the image. A lubricating surface can be efficiently formed on the body surface. In addition, by setting the volume average particle size of the higher alcohol used as the external additive to 12 μm or less, it is possible to suppress image deterioration due to uneven transfer at the time of a solid image, and it is possible to obtain a high-quality image.

  As described above, according to the image forming apparatus of the first aspect, the predetermined amount of the image carrier obtained in advance after the untransferred residual toner is removed by the cleaning member is rotated in the reverse direction, and the toner base particles and the external additive are rotated. Since the relationship between the particle size of the toner base particles and the particle size of the higher alcohol particles is defined as described above, a sufficient lubricating surface can be formed on the surface of the image carrier.

  Therefore, without providing a special mechanism for separating the cleaning member from the image carrier during reverse rotation of the image carrier, a sufficient lubrication surface is formed on the surface of the image carrier, thereby suppressing an increase in the size of the image forming apparatus main body. In addition, it is possible to suppress wear of the cleaning blade and the image carrier due to an increase in frictional force between the cleaning blade and the image carrier, and to suppress deterioration in image quality.

  Further, in the image forming apparatus according to claim 2, in the image forming apparatus according to claim 1, the higher alcohol particles have a shape factor SF1 equal to or higher than the shape factor SF1 of the toner base particles. However, it is possible to suppress slipping through the contact area between the cleaning member and the image carrier due to rolling. Therefore, a dam made of higher alcohol particles can be formed and retained at the contact position between the cleaning member and the image carrier, and a lubricating surface can be efficiently formed on the surface of the image carrier.

  According to a third aspect of the present invention, the toner may contain less than 2.5% by mass of higher alcohol particles having a volume average particle diameter equal to or larger than the toner base particles.

  Normally, resin fine particles such as higher alcohol particles do not affect the image quality because they have no coloring power as they are, but when forming an image with a large solid area, a higher particle size than the volume average particle size of the toner base particles is used. As the amount of alcohol particles increases, the distance between the recording medium and the image carrier increases in the transfer area where the toner image on the image carrier is transferred by the transfer means, and the transfer efficiency by the transfer means decreases and the image quality deteriorates. There is a problem that causes. For this reason, image quality deterioration can be suppressed by defining the addition amount of higher alcohol particles larger than the volume average particle diameter of the toner base particles.

  The image forming apparatus according to claim 4 is the image forming apparatus according to any one of claims 1 to 3, wherein the cleaning member is formed of urethane rubber, and a rebound resilience coefficient (JIS K6255) is 10 ° C. In the range of 18% or more at 40 ° C. and 70% or less at 40 ° C., the 300% modulus (JIS K6251) is 19600 kPa or more, and the tear strength (JIS K6252 no-cut angle type) is 83300 N / m or more. it can.

  Normally, when cleaning toner that is nearly spherical, it is necessary to increase the contact pressure of the cleaning member as compared to cleaning irregularly shaped toner. As a result, although the cleaning performance is improved, the frictional force between the cleaning blade and the image carrier increases, and there is a problem that the cleaning blade and the image carrier each wear and scratch. The effect is particularly prominent when paper dust released from the recording paper is sandwiched between the cleaning member and the image carrier or when the image carrier is reversely rotated. For this reason, by defining the impact resilience coefficient, 300% modulus, and tear strength of the cleaning member, it is possible to improve the resistance of the cleaning member to wear and scratches, and to suppress deterioration of the cleaning member due to friction. .

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a toner band supplied to the cleaning member at the time of non-image formation is the image carrier. A toner band forming means for forming on the body surface can be further provided.

  The higher alcohol particles for forming the lubricating surface on the image carrier are supplied to the cleaning member while being held or released by the toner base particles. The cleaning is performed depending on the pattern of the toner image carried on the image carrier. There may be a region where the amount of higher alcohol particles supplied to the member is less than the amount capable of forming a lubricating surface on the image carrier. However, the toner band forming means of the image forming apparatus according to claim 5 performs cleaning at the time of non-image formation except for the image formation in which a toner image is formed on an image carrier and the toner image is transferred to a recording medium. Since the toner band to be supplied to the member is formed on the surface of the image carrier, the lubricating surface can be efficiently formed on the entire surface of the image carrier.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects of the present invention, the image forming apparatus includes a storage unit that stores toner and is stored in the storage unit. A developer that forms a toner image on the image carrier by supplying toner to the image carrier; and a conveyance member that conveys the toner removed from the surface of the image carrier toward the storage unit. Therefore, the untransferred residual toner on the image carrier removed by the cleaning member can be effectively reused.

  The image forming method according to claim 7 suppresses an increase in size of the image forming apparatus main body, suppresses friction between the image carrier and the cleaning member due to reverse rotation of the image carrier, and reduces image quality. Can be suppressed. Specifically, a developing step for forming a toner image on the image carrier, a transfer step for transferring the toner image on the image carrier to a recording medium, and removing untransferred residual toner remaining on the image carrier. And a reverse rotation step of reversely rotating the image carrier by a predetermined amount after the untransferred residual toner is removed, wherein the toner comprises toner base particles. And an external additive, the toner base particles have a shape factor SF1 of 140 or less, the external additive contains higher alcohol particles having a volume average particle diameter of 1 to 12 μm, and the toner contains It contains 0.15% by mass or more of the higher alcohol particles having a volume average particle size of the toner base particles or less.

  As described above, according to the image forming apparatus and the image forming method of the present invention, the enlargement of the apparatus main body is suppressed, and the friction between the image carrier and the cleaning member due to the reverse rotation of the image carrier is suppressed. At the same time, it is possible to provide an image forming apparatus and an image forming method capable of suppressing image quality deterioration.

Embodiments of the present invention will be described below with reference to the drawings.

<Image forming apparatus>

  As shown in FIG. 1, an image forming apparatus 10 of the present invention includes an image carrier 12, a charger 14 for charging the surface of the image carrier 12, and image data stored in advance in a storage unit (not shown). Alternatively, an image reading device 16 that reads image data input from an external device (not shown) via a communication unit such as a network, and a light beam modulated based on the image data read by the image reading device 12. And a controller 20 that controls the exposure device 18 that emits a light beam and controls the entire image forming apparatus 10 so as to perform scanning exposure.

  The control unit 20 is connected to various devices including the above-described units constituting the image forming apparatus 10 so as to be able to exchange data and signals, and to a drive unit (not shown) for rotationally driving the image carrier 12, Connected so that signals can be exchanged.

  The image carrier 12 is rotated in a predetermined direction (in the direction of arrow A in FIG. 1) by a driving unit (not shown) during image formation processing, and in the periphery of the image carrier 12 (in the direction of arrow A in FIG. 1). ), A charger 14 for uniformly charging the image carrier 12, an exposure device 18 for scanning and exposing the charged image carrier 12, and a scanning exposure by the exposure device 18 to form the image carrier 12 on the image carrier 12. A developing unit 22 for developing an electrostatic latent image according to the image data, a transfer roll 26 for transferring a toner image formed on the image carrier 12 by development by the developing unit 22 to a recording medium 24, and a transfer roll A cleaning device 28 for removing untransferred residual toner remaining on the image carrier 12 without being transferred by the toner 26 and foreign matters such as paper dust from the recording medium from the surface of the image carrier 12, and the surface of the image carrier 12 potential Static eliminator 30 is provided to remove.

  The developing device 22 carries a toner containing portion 36, one or a plurality of agitating and conveying members 32 for agitating and conveying the toner accommodated in the accommodating portion 36, and the toner supplied by the agitating and conveying member 32. A developing roller 34 for supplying the toner carried together with the image carrier 12, a conveyance member 38 for conveying the untransferred residual toner removed from the image carrier 12 by the cleaning device 28 to the storage unit 36, and conveyance The member 40 is comprised.

In the present invention, the charging method using the charger 14 may be either a contact charging method or a non-contact charging method.
Further, as a developing method by the developing device 22, a cascade method, a magnetic brush method, or the like can be used, but is not limited to these methods.

  The image carrier 12 corresponds to the image carrier of the image forming apparatus of the present invention, the transfer roll 26 corresponds to the transfer unit of the present invention, and the cleaning blade 42 corresponds to the cleaning member of the present invention. .

  The cleaning device 28 includes a cleaning blade 42. The cleaning blade 42 is a plate-like member extending in the extending direction of the rotation axis of the image carrier 12, and is downstream of the surface of the image carrier 12 in the rotational direction (direction of arrow A in FIG. 1) from the transfer position by the transfer roll 26. The front end portion (hereinafter referred to as an edge portion) is provided in pressure contact on the side and on the upstream side in the rotational direction from the position where the static eliminator 30 is neutralized.

  When the image carrier 12 is rotated by the control of the control unit 20 (in the direction of arrow A in FIG. 1), after being neutralized by the static eliminator 30, and uniformly charged by the charger 14, the exposure device 18 converts the image data into image data. The light beam modulated accordingly is scanned and exposed on the image carrier 12 to form an electrostatic latent image corresponding to the image data on the image carrier 12. The electrostatic latent image formed on the image carrier 12 is developed by the developing device 22 and a toner image is carried on the image carrier 12. When the formation area of the toner image carried on the image carrier 12 reaches the arrangement position of the transfer roll 26 by the rotation of the image carrier 12, a voltage is applied to the transfer roll 26 (for example, a positive polarity voltage). ) When the recording medium 24 is nipped and conveyed by the image carrier 12 and the transfer roll 26, the toner image is transferred to the recording medium 24. The image forming apparatus 10 includes a fixing device 44 for fixing the toner image transferred onto the recording medium 24 to the recording medium 24, and the toner image transferred onto the recording medium 24 is recorded on the recording medium by the fixing device 44. After being fixed to 24, it is conveyed to the outside of the image forming apparatus 10.

  The image carrier 12 is rotated, and a light beam modulated in accordance with image data from the exposure device 18 is scanned and exposed on the image carrier 12 to form an electrostatic latent image. A series of steps from the development by 22 to the transfer of the toner image onto the recording medium 24 will be described as an image forming process.

  When the image carrier 12 rotates in a predetermined direction (the direction of arrow A in FIG. 1), the cleaning blade 42 is not transferred to the recording medium 24 by the transfer roll 26 and is not carried on the image carrier 12. Foreign matter such as residual toner particles and paper dust of the recording medium 24 is blocked and removed from the image carrier 12. The surface layer of the image carrier 12 is not only scraped by the cleaning blade 42 but is also polished by the untransferred residual toner particles, and the surface layer of the image carrier 12 is refreshed. Further, the external additive contained in the untransferred residual toner particles passes between the surface layer of the image carrier 12 and the edge portion of the cleaning blade 42, so that the lubricant is substituted for the lubricant by passing through an external additive, which will be described in detail later. The rubbing between the edge portions of the body 12 surface layer and the cleaning blade 42 is suitably maintained.

  The conveying member 38 and the conveying member 40 are rotatably provided in predetermined directions (see arrows B and C in the figure), respectively, and unfixed residual toner particles accommodated in the bottom of the cleaning device 28 are supplied to the developing device 22. And can be transported.

  Untransferred residual toner particles removed from the image carrier 12 by the cleaning blade 42 by the rotation of the conveying member 38 and the conveying member 40 are conveyed to the developing device 22. The untransferred residual toner particles conveyed to the developing unit 22 are agitated and conveyed together with the toner accommodated in the accommodating portion 36 and reused.

  As described above, the image forming apparatus 10 of the present invention is configured so that the untransferred residual toner particles removed from the surface of the image carrier 12 by the cleaning blade 42 can be collected and reused effectively.

<Cleaning blade>

  As a material of the cleaning blade 42 used in the image forming apparatus 10 of the present invention, a known material can be used. For example, urethane rubber, silicon rubber, fluorine rubber, chloroprene rubber, butadiene rubber, or the like can be used. Among them, it is particularly preferable to use a polyurethane elastic body because of its excellent wear resistance.

  As the polyurethane elastic body, a polyurethane synthesized through an addition reaction of an isocyanate with a polyol and various hydrogen-containing compounds is generally used. This uses a polyether polyol such as polypropylene glycol and polytetramethylene glycol as a polyol component, and a polyester polyol such as an adipate polyol, a polycaprolactam polyol, and a polycarbonate polyol, and a tolylene diisocyanate as an isocyanate component. Aromatic polyisocyanates such as 4,4′-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluidine diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate; Prepare a urethane prepolymer, add a curing agent to it, and pour it into the mold. And, after crosslinking and curing, it is prepared by aging at room temperature. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane or pentaerythritol are usually used in combination.

The cleaning blade of the present invention has a rebound resilience coefficient (JIS K6255) of 20% or more at 10 ° C. and 70% or less at 40 ° C., and a 300% modulus (JIS K6251) of 19600 kPa (200 kg / cm ² ) or more. Furthermore, it is desirable that the tear strength (angle type without cut) according to JIS K6252 is 83300 N / m (85 kg / cm) or more.

  When the impact resilience coefficient is out of the above range, the cleaning property is remarkably deteriorated. On the other hand, if the 300% modulus and the tear strength are too low, the edge of the edge of the cleaning blade that is deformed by sliding with the latent image carrier may be chipped, resulting in a decrease in durability.

The hardness (JIS A scale) in the cleaning blade of the present invention is preferably 70 or more and 85 or less. If the hardness is too low, the waist of the cleaning blade will become weak and the contact pressure will be low, and the contact area with the latent image carrier will increase, causing an increase in frictional force and a decrease in slidability, It is not preferable because the durability tends to be lowered. On the other hand, if the hardness is too high, scratches tend to occur on the surface of the latent image carrier, which is not preferable.

The cleaning blade of the present invention is generally formed into a shape that can be used as a cleaning blade for a latent image carrier in an electrophotographic apparatus. The shape is not particularly limited as long as it is a so-called cleaning blade shape in which the edge abuts the latent image carrier, but the thickness is generally selected from 1.5 to 2.5 mm, preferably It is selected from 1.8 to 2.2 mm. The free length of the cleaning blade (the length between the position where the cleaning blade is fixed in the apparatus and the position of the edge portion contacting the latent image carrier) is generally selected from 5 to 15 mm, preferably Is selected from 7 to 12 mm. The width may be appropriately set according to the axial length of the latent image carrier (specifically, the axial length of the portion of the latent image carrier where the latent image is formed).

<Reverse rotation control of image carrier>
The rotation control of the image carrier 20 executed in the control unit 20 that controls the image forming apparatus 10 will be described.

  The control unit 20 controls each part of the image forming apparatus 10 to execute the image forming process for transferring the toner image onto the recording medium 24, and then rotates the image carrier 12 during the image forming process (see FIG. 1). In the direction of arrow A).

  In the image forming apparatus 10 of the present invention, the control unit 20 determines the rotation direction of the image carrier 12 during the execution of the image forming process after the execution of the image forming process and before the rotation of the image carrier 12 is stopped. A drive unit (not shown) that drives the rotation of the image carrier 12 is controlled so as to rotate backward by a predetermined amount in the reverse direction (the direction of arrow D in FIG. 1). By controlling the drive unit, the image carrier 12 is rotated in the reverse direction.

  The amount of reverse rotation is determined in advance by an amount that can avoid foreign matters such as untransferred residual toner and paper dust sandwiched between the tip of the cleaning blade 42 and the image carrier 12. The control unit 20 controls a drive unit (not shown) so as to reversely rotate by a predetermined amount.

  Specifically, the reverse rotation amount is preferably 2 mm to 10 mm, particularly preferably 3 mm to 9 mm under the condition where the diameter of the image carrier 12 is 84 mm.

  If it is less than 2 mm, it is difficult to reliably avoid foreign matters such as paper dust sandwiched between the tip of the cleaning blade 42 and the image carrier 12. If it exceeds 10 mm, foreign matters such as paper dust sandwiched between the tip of the cleaning blade 42 and the image carrier 12 can be surely avoided, but the influence on the tip of the cleaning blade 42 is affected. May cause damage.

  Further, regarding the timing of the reverse rotation operation of the image carrier 12, the image carrier 12 may be operated every time after the end of the image forming process, or may be operated after the end of the most recent image creation process after setting a threshold, Although it may be determined as appropriate, it is preferably once every time an image of 50 A4 recording media is formed to once every time an image of 500 A4 recording media is formed. When the number of operations is increased more than once per 50 sheets, the productivity is lowered, and when the number of operations is decreased less than once per 500 sheets, the cleaning performance is deteriorated due to the influence of paper dust.

  In this way, by rotating the image carrier 12 in the direction opposite to the rotation direction at the time of executing the image forming process, it is possible to remove foreign matters accumulated on the tip of the cleaning blade 42.

<Toner band forming means>
The control unit 20 of the image forming apparatus 10 of the present invention reverses the voltage applied to the transfer roll 26 during transfer from the image carrier 12 to the recording medium 24 in the image forming process, and supplies toner to the cleaning blade 42. A toner band that controls the voltage applied to the transfer roll 26 so as to supply a large amount, and controls the exposure device 18 so that the image carrier 12 is scanned and exposed to a light beam corresponding to an image for forming a toner band The toner band forming unit 21 corresponding to the forming unit is included.

  The toner band forming unit 21 executes toner band forming processing at the time of non-image formation other than at the time of executing the image forming process.

  The toner image formed on the image carrier 12 during the toner band forming process includes higher alcohol particles, which will be described in detail later, in a length that includes the end region of the recording medium 24 in the entire longitudinal direction of the cleaning blade 42. It is essential to be supplied. Depending on the use environment, the creation interval is at least once every A4 size image is formed to once every 500 A4 size images are formed, and the rotation direction width is 1 mm to 100 mm, and the image density is 30 to 100. % Toner band is preferably formed. The toner image formed here may be a solid image, a halftone image, a line image, or the like as long as it is within the above range. The timing for creating a toner image that is not transferred is based on the premise that the toner image is created at an interval of the predetermined number, and it is also possible to change the control contents and set whether or not to control according to the temperature and humidity of the other use environment.

  Here, the non-transferred residual toner accumulated on the cleaning blade 42 can be removed by the reverse rotation of the image carrier 12, while the frictional force between the image carrier 12 and the cleaning blade 42 is caused by the reverse rotation. It is considered that the image quality deteriorates due to the wear at the contact position between the image carrier 12 and the cleaning blade 42.

  However, according to the image forming apparatus 10 of the present invention, the toner to be used includes toner base particles and an external additive, and defines the relationship between the particle size of the toner base particles and the particle size of the higher alcohol particles. This suppresses wear of the cleaning blade 42 and the image carrier 12 due to an increase in frictional force between the cleaning blade 42 and the image carrier 12 while forming a sufficient lubricating surface on the surface of the image carrier 12. It was found that image quality deterioration can be suppressed.

  Hereinafter, the toner used in the image forming apparatus 10 of the present invention will be described in detail.

<Toner>

  The toner used in the image forming apparatus of the present invention includes toner base particles and an external additive, and the toner base particles have a shape factor SF1 of 140 or less. Further, the external additive contains higher alcohol particles having a volume average particle diameter of 1 to 12 μm, and 0.15% by mass or more of the higher alcohol particles having a volume average particle diameter of the toner base particles or less in the toner.

  In order to achieve high transfer efficiency, it is necessary to bring the toner close to a spherical shape. From such a viewpoint, the toner for developing an electrostatic charge image of the present invention has a shape factor SF1 of the toner base particles of 140 or less.

  However, considering the cleaning mechanism, the following problems are likely to occur. For example, when the image carrier 12 is cleaned using the cleaning blade 42, the untransferred residual toner is blocked by the nip portion of the cleaning blade 42 to form a dam, and the toner is cleaned in the dam. Are separated, and the closer to the cleaning blade 42, the finer the particle size. Regardless of the shape of the toner, the nip portion of the cleaning blade 42 has the particle size separation as described above. However, the closer the toner is to a spherical shape, the easier the shape is aligned at the nip portion of the cleaning blade 42. The number of toner contact points per minute unit image carrier surface at the nip portion of the cleaning blade 42 is increased, and the toner friction force of each particle is directed in the same direction. The total amount of force received is quite large. As a result, the cleaning blade 42 is pushed up, or the edge of the cleaning blade 42 is chipped and the toner slips through the cleaning blade 42, resulting in poor cleaning. Therefore, when the linear pressure of the cleaning blade 42 is increased so that cleaning failure does not occur even when toner close to a spherical shape is used, the frictional force between the cleaning blade and the image carrier further increases, and the surface of the image carrier is worn. Will also be remarkable.

  For this reason, in order to clean toner that is nearly spherical, it is important to reduce the frictional force between the toner and the image carrier 12 at the nip portion of the cleaning blade 42. Usually, in order to supply higher alcohol to the surface of the cleaning blade 42 and form a lubricating surface on the surface of the image carrier 12, it is common to add the higher alcohol particles to the toner base particles. In order to exert the effect of reducing the frictional force at the nip portion of the blade 42, it is necessary to considerably increase the amount of higher alcohol particles added to the toner base particles, and as a result, the chargeability of the toner is greatly reduced. End up. In order to easily form a lubricating surface, the softening by reducing the number of molecules of higher alcohol particles can contaminate the carrier, charging sleeve, and charging cleaning blade, as described above, and the charge maintenance performance is significantly reduced. .

  However, in the image forming apparatus 10 of the present invention, by defining the relationship between the particle size of the toner base particles and the particle size of the higher alcohol particles to be added and the content of the higher alcohol particles having a predetermined particle size, the charging characteristics can be improved. It is possible to provide the image forming apparatus 10 using a toner that has no influence, forms a sufficient lubricating surface on the surface of the image carrier 12 and does not cause poor cleaning.

  That is, in order to efficiently form a higher alcohol lubrication surface on the surface of the image carrier 12, it is important to supply higher alcohol particles in the vicinity of the cleaning blade 42. The toner is dammed at the nip portion of the cleaning blade 42 to form a dam. In the dam, the toner is separated in particle diameter, and the closer the cleaning blade 42 is, the smaller the particle diameter is. By controlling the amount of higher alcohol particles having a volume average particle size of toner base particles or less, higher alcohol is efficiently selectively supplied to the tip of the cleaning blade 42, and the surface of the image carrier 12 is efficiently lubricated. By controlling the total amount added without lowering the softening point of the higher alcohol, there is no charge failure and charge retention It is obtained a good developer. At the same time, by forming a sufficient lubricating surface on the surface of the image carrier 12, the frictional force between the cleaning blade 42 and the image carrier can be reduced, and the wear of the image carrier 12 can be suppressed.

  As described above, while improving the cleaning property and improving the reliability by reducing the friction between the cleaning blade 42 and the image carrier 12, a high-quality image with high transfer efficiency is obtained without causing image quality defects such as image unevenness. It was possible to obtain an image forming apparatus and an image forming method capable of achieving this in a balanced manner.

<Toner base particles>

  The toner base particles of the toner used in the present invention are composed of a binder resin and a colorant, and include a release agent, silica, and a charge control agent as necessary. Binder resins include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Homopolymers and copolymers of vinyl ethers such as methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone; Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like. Among these, styrene-alkyl acrylate copolymers and styrene-alkyl methacrylate copolymers are particularly preferable.

  In addition, toner colorants include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, and malachite green oxa. Rate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I.

Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 can be exemplified as a representative one.

In addition, a release agent or a charge control agent may be added to the toner used in the present invention as necessary. Typical examples of the release agent include low molecular polyethylene, low molecular polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

Known charge control agents can be used, but azo metal complex compounds, metal complex compounds of salicylic acid, and resin type charge control agents containing polar groups can be used. When the toner is manufactured by a wet manufacturing method, it is preferable to use a material that is difficult to dissolve in water in terms of controlling ionic strength and reducing wastewater contamination. The toner in the present invention may be either a magnetic toner containing a magnetic material or a non-magnetic toner containing no magnetic material.

The toner base particles are produced by, for example, a kneading and pulverizing method in which a binder resin, a colorant, and if necessary, a release agent, a charge control agent and the like are kneaded, pulverized, and classified; particles obtained by a kneading and pulverizing method The shape is changed by mechanical impact force or thermal energy; the polymerizable monomer of the binder resin is emulsion-polymerized, the formed dispersion, the colorant, and if necessary, the release agent, electrification Emulsion polymerization aggregation method to obtain toner particles by mixing with a dispersion of a control agent, etc., and agglomerating and heat-fusing; a polymerizable monomer to obtain a binder resin, a colorant, and separation if necessary Suspension polymerization method in which a solution of a mold agent, a charge control agent, etc. is suspended in an aqueous solvent for polymerization; a binder resin, a colorant, and, if necessary, a solution of a mold release agent, a charge control agent, etc., in an aqueous system For example, a solution suspension method of suspending in a solvent and granulating can be used. In addition, a manufacturing method may be performed in which the toner obtained by the above method is used as a core, and agglomerated particles are further adhered and heat-fused to have a core-shell structure.

  The toner base particles produced as described above preferably have a volume average particle diameter in the range of 2 to 12 μm, and more preferably in the range of 3 to 9 μm.

  As described above, the toner base particles used in the present invention must have a pseudo-spherical shape from the viewpoint of improving developability and transfer efficiency and improving image quality. The sphericity of the toner base particles can be expressed by using the shape factor SF1 of the following formula (2), but it is essential that the average value of the coefficient SF1 of the toner base particles used in the present invention is 140 or less. It is preferable that it is the range of 115-140. A range of 120 to 140 is more preferable.

[Formula 2]
SF1 = (L ² / A) × (π / 4) × 100 (2)

  In the above formula (2), L represents the maximum length of each toner base particle, and A represents the projected area of each toner base particle. When the average value of the shape factor SF1 is larger than 140, the transfer efficiency is lowered, and the deterioration of the image quality of the print sample can be visually confirmed.

The average value of the shape factor SF1 is obtained by taking 1000 toner images magnified 250 times from an optical microscope into an image analyzer (LUZEX III, manufactured by Nireco), and determining the individual particle size based on the maximum length and projected area. Is obtained by averaging the values of SF1.

The toner base particles used in the present invention are not particularly limited by the production method as long as the shape factor SF1 and the particle size are satisfied, and a known method can be used.

<External additive>
The external additive added to the toner contains higher alcohol particles having a volume average particle diameter of 1 to 12 μm. The external additive contains 1 to 12 μm higher alcohol particles, more preferably 2 μm to 10 μm higher alcohol, and further preferably 3 μm to 9 μm higher alcohol.

The higher alcohol particles are pulverized to adjust the particle size distribution of the higher alcohol in order to adjust the content of the higher alcohol particles having a toner volume average particle size or less, or the toner volume average particle size or more. It can be adjusted by classification after pulverization.

  The amount of the higher alcohol particles added to the toner base particles may be 0.15% by mass or more of the higher alcohol particles having a volume average particle size of the toner base particles or less, and the total amount of the higher alcohol particles with respect to the toner base particles. Is not particularly specified, but is preferably 0.2% by mass or more and 2.5% by mass or less, and particularly preferably 0.25% by mass or more and 2.0% by mass or less.

The total amount of higher alcohol with respect to the toner base particles is not particularly specified. However, the content of higher alcohol having a toner volume average particle size or more is preferably 2.5% by mass or less, and more preferably 2% by mass or less.
Further, the shape factor SF1 of the higher alcohol is preferably not less than the shape factor SF1 of the toner base particles in order to obtain cleaning properties.

  This can prevent the higher alcohol particles from slipping through the contact area between the cleaning blade 42 and the image carrier 12 due to rolling. For this reason, a dam made of higher alcohol particles can be formed and retained for a long time at the contact position between the cleaning blade 42 and the image carrier 12, that is, at the tip of the cleaning blade 42. A lubricating surface can be formed efficiently.

  The carbon number of the higher alcohol can be represented using the following general formula (1). The number of carbons is not particularly defined, but higher aliphatic alcohols having 16 to 150 carbons are preferably used. More preferably, it is 20-120, More preferably, it is about 30-90.

また、トナーに添加される前記高級アルコールにさらなる滑剤粒子としてグラファイト、二硫化モリブデン、滑石、脂肪酸、脂肪族アルコール、脂肪酸金属塩等の固体潤滑剤や、ポリプロピレン、ポリエチレン、ポリブテン等の低分子量ポリオレフィン類；加熱により軟化点を有するシリコーン類；オレイン酸アミド、エルカ酸アミド、リシノール酸アミド、ステアリン酸アミド等のような脂肪族アミド類；カルナバワックス、ライスワックス、キャンデリラワックス、木ロウ、ホホバ油等のような植物系ワックス；ミツロウのような動物系ワックス；モンタンワックス、オゾケライト、セレシン、パラフィンワックス、マイクロクリスタリンワックス、フィッシャートロプシュワックス等のような鉱物、石油系ワックス；及びそれらの変性物を併用してもよい。

Further, solid lubricants such as graphite, molybdenum disulfide, talc, fatty acids, aliphatic alcohols, fatty acid metal salts, and low molecular weight polyolefins such as polypropylene, polyethylene, and polybutene as further lubricant particles to the higher alcohol added to the toner. Silicones having a softening point upon heating; aliphatic amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid amide; carnauba wax, rice wax, candelilla wax, wood wax, jojoba oil, etc. Plant waxes such as beeswax; animal waxes such as beeswax; minerals such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, and petroleum waxes; and their modifications It may be used in combination.

The external additive of the toner in the present invention contains at least a higher alcohol, and anything else may be used, but at least one of them has a primary particle size that functions such as powder flowability and charge control. A small-diameter inorganic oxide having an average particle diameter of 10 to 70 nm is preferable. Examples of the small-diameter inorganic oxide include silica, alumina, titanium oxide (titanium oxide, metatitanic acid, etc.), calcium carbonate, magnesium carbonate, calcium phosphate, carbon black, and the like.

As these inorganic oxide fine particles, known ones can be used, but in order to perform precise charge control, it is preferable to use silica and titanium oxide in combination. In particular, use of a volume average particle size of 20 to 60 nm does not affect the transparency, and provides good chargeability, environmental stability, fluidity, caking resistance, stable negative chargeability and image quality maintenance. This is preferable.
In addition, the surface treatment of the small-diameter inorganic fine particles increases the dispersibility and increases the powder flowability. Specifically, as the surface treatment, hydrophobic treatment with dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane or the like is preferably used.
The addition amount of the small-diameter inorganic oxide is preferably in the range of 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the toner base particles.

  The toner used in the present invention can be produced by mixing the toner base particles and the external additive with a Henschel mixer or a V blender. In addition, when the toner base particles are produced by a wet method, external addition can also be performed by a wet method.

<Career>
There is no restriction | limiting in particular as a carrier which can be used for the two-component developer of this invention, A well-known carrier can be used. For example, a resin-coated carrier having a resin coating layer on the surface of the core material can be exemplified. Further, a resin-dispersed carrier in which magnetic powder or the like is dispersed in a matrix resin may be used.

  Coating resins and matrix resins used for carriers include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic. Examples include acid copolymers, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins, urea resins, urethane resins, melamine resins, etc. It is not limited.

In general, the carrier preferably has an appropriate electric resistance value, and it is preferable to disperse the conductive fine powder in the resin for adjusting the resistance. Examples of the conductive fine powder include metals such as gold, silver and copper, carbon black, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, and carbon black. However, it is not limited to these.
Examples of the carrier core material include magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. However, in order to use the carrier for the magnetic brush method, a magnetic material is used. Preferably there is. The volume average particle size of the carrier core material is preferably in the range of 10 to 100 μm, and more preferably in the range of 25 to 50 μm.

  In order to coat the surface of the core material of the carrier with a resin, a method of coating the coating resin and, if necessary, various additives with a solution for forming a coating layer dissolved in an appropriate solvent is employed. The solvent is not particularly limited and may be appropriately selected in consideration of the coating resin to be used, coating suitability, and the like.

  Specific resin coating methods include a dipping method in which the powder of the carrier core material is immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the carrier core material, and a carrier core material. Examples thereof include a fluidized bed method in which a coating layer forming solution is sprayed in a state of being suspended by flowing air, and a kneader coater method in which a carrier core material and a coating layer forming solution are mixed in a kneader coater to remove the solvent.

<Developer>
The two-component developer of the present invention is produced by mixing the above-described toner and carrier. The mixing ratio (mass ratio) of the toner and the carrier in the developer is preferably in the range of toner: carrier = 1: 99 to 20:80, preferably in the range of 3:97 to 12:88. It is more preferable.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following description, “part” means “part by mass” unless otherwise specified.

-Method of measuring physical properties-
<Particle size distribution of toner base particles and external additives>
Using a particle size distribution measuring device (Multisizer: manufactured by Nikka Kisha Co., Ltd.), measurement was performed with an aperture diameter of 100 μm.

<Rebound resilience of cleaning blade>
The impact resilience of the cleaning blade is determined according to JIS K6255 vulcanized rubber physical test method. After leaving the cleaning blade in an atmosphere of each temperature (10 ° C., 23 ° C., 40 ° C.) for 2 hours, Kosei Keiki Co., Ltd. Measurements were made using a model EPH-50.

<300% modulus of cleaning blade>
The 300% modulus of the cleaning blade is measured according to JIS K6251 vulcanized rubber physical test method after leaving the cleaning blade in a normal temperature (23 ° C.) atmosphere for 2 hours and then at a normal temperature (23 ° C.) atmosphere and 300% elongation. Tensile strength was measured.

<Tearing strength of cleaning blade>
The tear strength of the cleaning blade is determined in accordance with JIS K6252 (angle type without cut) vulcanized rubber physical test method, after the cleaning blade is left in a room temperature (23 ° C.) atmosphere for 2 hours and then in a room temperature (23 ° C.) atmosphere. The maximum load until the test piece was torn apart was measured with the fixed jig, and the tear strength Tr was calculated based on the calculation formula shown in the following formula (3). .

[Formula 3]
Tr = F / t (3)

  In the above formula (3), Tr represents the tear strength (N / cm), F represents the maximum load (N), and t represents the thickness (cm) of the test portion of the test piece.

<Image density>
Measurement was performed using an image densitometer (X-Rite 404A: manufactured by X-Rite).

<Carrier volume resistivity>
A sample of the carrier was filled on the lower electrode of the cell (100 mmφ, thickness 1.0 mm), the upper electrode was set, a load of 3.43 kg was applied from above, and the thickness was measured with a dial gauge. Next, voltage was applied and the current value was read to determine the volume resistivity.

-Manufacture of toner base particles-
<Preparation of resin fine particle dispersion>
A mixture of 370 g of styrene, 30 g of n-butyl acrylate, 8 g of acrylic acid, 24 g of dodecanethiol, and 4 g of carbon tetrabromide was dissolved in 6 g of a nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Industries) and anion Ion exchange in which 4 g of ammonium persulfate is dissolved in 10 ml of a surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) dissolved in 550 g of ion exchange water in a flask and then mixed and mixed slowly for 10 minutes. 50 g of water was added. After carrying out nitrogen substitution, while stirring the inside of the flask, it was heated in an oil bath until the contents reached 70 ° C., and emulsion polymerization was continued for 5 hours. As a result, a resin fine particle dispersion was prepared in which resin particles having an average particle diameter of 152 nm, a glass transition temperature Tg of 58 ° C., and a mass average molecular weight Mw of 11700 were dispersed. The solid content concentration of this dispersion was 40% by mass.

<Preparation of colorant dispersion>
Carbon black (Mogal L: manufactured by Cabot) 60 g, nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) 6 g, and ion-exchanged water 240 g were mixed and dissolved into a homogenizer (Ultra Turrax T50: IKA). The colorant dispersant (1) was prepared by dispersing the colorant (carbon black) particles having an average particle diameter of 250 nm by dispersing with an optimizer.

<Preparation of release agent dispersion>
100 g of paraffin wax (HNP0190: manufactured by Nippon Seiwa Co., Ltd., melting point 85 ° C.), 5 g of a cationic surfactant (Sanisol B50: manufactured by Kao Corporation), and 240 g of ion-exchanged water are mixed and heated to 95 ° C. After dispersing for 10 minutes in a stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), the dispersion was performed with a pressure discharge type homogenizer, and release agent particles having an average particle diameter of 550 nm were dispersed. A release agent dispersion was prepared.

<Preparation of toner mother particles K1>
234 parts of resin fine particle dispersion, 30 parts of colorant dispersion, 40 parts of release agent dispersion, 1.9 parts of polyaluminum hydroxide (Pho2S manufactured by Asada Chemical Co., Ltd.), and 600 parts of ion-exchanged water were added to round stainless steel. After mixing and dispersing in a steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), the flask was heated to 55 ° C. with stirring in an oil bath for heating. After holding at 55 ° C. for 40 minutes, it was confirmed that aggregated particles having a volume average particle diameter D50 of 5.0 μm were produced. Further, when the temperature of the heating oil bath was raised and maintained at 56 ° C. for 2 hours, the volume average particle diameter D50 of the aggregated particles was 6.1 μm. Thereafter, 34 parts of the resin fine particle dispersion was added to the dispersion containing the aggregated particles, and then the temperature of the heating oil bath was set to 50 ° C. and held for 30 minutes. After the pH of the system is adjusted to 7.0 by adding a 1N sodium hydroxide solution to the dispersion containing the aggregated particles, the stainless steel flask is sealed, and the stirring is continued to 80 ° C. using a magnetic seal. Heated and held for 4 hours. After cooling, the reaction product is filtered off, washed four times with ion-exchanged water, and lyophilized to obtain toner base particles K1 having a volume average particle diameter D50 of 6.5 μm and an average value of shape factor SF1 of 132. Produced.

<Preparation of toner mother particles K2>
100 parts of a polyester resin (linear polyester obtained from terephthalic acid, bisphenol A ethylene oxide adduct and cyclohexanedimethanol, glass transition temperature Tg: 62 ° C., number average molecular weight Mn: 12000, mass average molecular weight Mw: 32000), A mixture of 5 parts of carbon black (Mogal L: Cabot) and 6 parts of carnauba wax was kneaded with an extruder, pulverized with a jet mill, and then classified with a wind classifier, and the volume average particle diameter D50 was 6. Toner mother particles K2 having an average value of 5 μm and a shape factor SF1 of 145 were produced.

<Adjustment of higher alcohol A1>
Commercially available higher alcohol (Toyo Petrolite Co., Ltd .: Unilin) was melt-kneaded with an extruder, and then pulverized with a jet mill. Volume average diameter D50 = 8.4 μm, 16% diameter D16 = 5.0 μm, 84% diameter D84 = 12.2 μm, GSD = 1.56, higher alcohol fine particles A1 having a shape factor SF1 = 145 were obtained. In the higher alcohol A1, the ratio of the volume average particle diameter D50 (6.5 μm) or less of the K1 and K2 toners was 30%. Moreover, carbon number of higher alcohol A1 was 57-73.

<Adjustment of higher alcohol A2>
After melt-kneading under the same conditions as the higher alcohol particles A1, the mixture is pulverized by a jet mill, and the volume average diameter D50 = 10.5 μm, 16% diameter D16 = 6.2 μm, 84% diameter D84 = 15.2 μm, GSD = 1 And higher alcohol fine particles A2 having a shape factor SF1 = 145 were obtained. In the higher alcohol A2, the ratio of the K1 and K2 toners having a volume average particle diameter D50 (6.5 μm) or less was 18%.

<Adjustment of higher alcohol A3>
After melt-kneading under the same conditions as in the higher alcohol particles A1, pulverizing with a jet mill and then classifying with an air classifier (Elbow Jet: Nitto Kogyo Co., Ltd.), volume average diameter D50 = 5.6 μm, 16% diameter D16 = 3 High alcohol fine particles A3 having a diameter of 0.8 μm, 84% diameter D84 = 7.8 μm, GSD = 1.41, and shape factor SF1 = 145 were obtained. In the higher alcohol A3, the proportion of the K1 and K2 toners having a volume average particle diameter D50 (6.5 μm) or less was 60%.

<Adjustment of higher alcohol A4>
After melt-kneading under the same conditions as the higher alcohol particles A1, the mixture is pulverized by a jet mill, and the volume average diameter D50 = 8.4 μm, 16% diameter D16 = 5.0 μm, 84% diameter D84 = 12.2 μm, GSD = 1 ., Higher alcohol fine particles A4 having a shape factor SF1 = 125 were obtained. In the higher alcohol A4, the ratio of the K1 and K2 toners having a volume average particle size D50 (6.5 μm) or less was 30%.

-Fabrication of carrier-
17 parts of toluene, 3 parts of a styrene-methacrylate copolymer (component ratio: 40/60), and 0.2 part of carbon black (R330: manufactured by Cabot) were mixed and stirred with a stirrer for 10 minutes. A dispersed coating layer forming solution was prepared. Next, this coating solution and 100 parts of ferrite particles (volume average particle size: 45 μm) are put into a vacuum degassing type kneader and stirred at 60 ° C. for 30 minutes, and then degassed by further reducing pressure while heating. The carrier was prepared by drying. This carrier had a volume resistivity of 10 ¹⁴ Ωcm when an electric field of 1000 V / cm was applied.

-Cleaning Blade In this example, three types of cleaning blades B1 to B3 having various physical properties shown in Table 1 below were used.

Example 1
The toner base particles K1: 100 parts, rutile type titanium oxide (average particle size 20 nm, n-decyltrimethoxysilane treatment) 1.0 part, silica (prepared by vapor phase oxidation method, volume average particle size 40 nm, silicone oil) Treatment) 1.5 parts, 0.5 part of the higher alcohol A1 was added, blended for 15 minutes at a peripheral speed of 30 m / s using a 5 liter Henschel mixer, and then coarse using a sieve with 45 μm openings. Particles were removed to prepare a toner. Further, 100 parts of the carrier and 8 parts of the toner were stirred with a V-blender at 40 rpm for 20 minutes and sieved with a sieve having an opening of 212 μm to prepare an electrophotographic developer. The amount of higher alcohol contained in the toner at the time of the volume average particle size of the toner base particles is 0.15 part or less, and the amount of higher alcohol contained in the toner that is greater than or equal to the volume average particle size of the toner base particles. Was 0.35 part (see Table 2).

  In the toner, the amount of higher alcohol contained in the toner, which is equal to or less than the volume average particle size of the toner base particles, is measured in advance by measuring the particle size distribution of the toner base particles and the particle size distribution of the higher alcohol using a Coulter counter or the like. From these, the content of higher alcohol having an average particle size equal to or smaller than the average particle size of the toner base particles in the toner may be calculated. The higher alcohols that are white particles may be separated by image analysis, and the respective particle size distributions may be calculated. In this example, the calculation was performed using the former method.

  A developer obtained by modifying DocuCentre 507 (Fuji Xerox Co., Ltd.) was used as the experimental machine. As shown in Table 3, B1 is used as the cleaning blade, the thickness is 2 mm, the free length is 9 mm, the setting angle is 28 °, and the pressure is 2.8 g / mm at a biting amount of 1.2 mm with respect to the surface of the image carrier 12. The image carrier 12 was contacted in the counter direction. Further, the collected toner was transported to the accommodating portion 36 of the developing unit 22 together with the lubricant particles by the transporting member shown in FIG. As shown in Table 3, the toner band is formed on the recording medium for 150 sheets of A3 size images having the entire developing region width in the axial direction of the image carrier 12 with a rotation direction width of 45 mm and an image density of 100%. Each time (in FIG. 3, “production interval sheet / time”), it was put in a non-image forming cycle (when the image forming cycle was not executed, that is, during non-image forming). The reversing operation of the image carrier 12 was performed once every time 100 A3-sized images were formed on the recording medium, just before the image carrier 12 was stopped.

  Using the image forming apparatus 10 described above, 10 sheets of A3 paper (manufactured by Kishu Fine PPC Kishu Paper Co., Ltd.) at high temperature and high humidity (28 ° C., 80% RH) and low temperature and low humidity (10 ° C., 20% RH) were used. A total of 200,000 running tests were conducted. These copy source images have an image density of 5%.

As shown in Table 4, the evaluation was performed for transfer efficiency, toner cleaning performance on the surface of the image carrier, damage to the cleaning blade, and transfer unevenness in the collected image.
As for the transfer efficiency, a 5 cm x 2 cm solid patch is developed in an environment of high temperature and high humidity (28 ° C, 80% RH), and the toner image on the surface of the image carrier is transferred using the adhesiveness of the tape surface. The mass (W1) was measured. Next, the same toner image was transferred onto the surface of paper (P paper: manufactured by Fuji Xerox Office Supply), and the weight (W2) of the transferred image was measured. From these, the transfer efficiency was determined by the following formula, and the transferability was evaluated. The criteria for the evaluation were as follows.

  Transfer efficiency (%) = (W2 / W1) × 100

[Evaluation criteria for transfer efficiency]
・ ○: Transfer efficiency is 90% or more ・ △: Transfer efficiency is 85% or more and less than 90% ・ ×: Transfer efficiency is less than 85%

The cleaning property was evaluated based on the image quality during the running test and the stress condition after the running test. Evaluation based on image quality was sensory evaluated according to the following criteria.
[Image quality evaluation criteria during running tests]
・ ○: No striped streaks ・ ×: Minor striped streaks ・ XX: Wide range of striped streaks

In addition, the evaluation by the stress condition after the running test is performed by letting the image forming apparatus after running 200,000 sheets clean the 100% untransferred image density, and the surface of the image carrier drum after the cleaning is functionalized according to the following criteria. evaluated. The criteria for the evaluation were as follows.
[Evaluation criteria based on stress conditions after running test]
・ ○: No cleaning failure occurred ・ ×: Minor cleaning failure occurred ・ XX: Cleaning failure occurred over a wide area

The damage to the tip of the cleaning blade 42 is observed with a laser microscope VK8510 (manufactured by Keyence Corporation) to see if there is any chipping or turning at the tip edge of the cleaning blade 42 that has completed the running test. Sensory evaluation was performed according to the following criteria.
[Evaluation criteria by observation during running test of cleaning blade tip]
・ ○: No big chipping ・ ×: Big chipping

The transfer unevenness was subjected to sensory evaluation based on the following criteria using a halftone image having the entire surface of A3 and an image density of 30%.
[Evaluation criteria based on image quality during transfer unevenness running test]
*: No visual unevenness. *: Visually visible unevenness. Tables 2 and 3 show the evaluation conditions, and Table 4 shows the evaluation results.

(Example 2)
Evaluation was performed in the same manner as in Example 1 except that the amount of the higher alcohol A1 added to the toner was 0.9 parts. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Example 3)
Evaluation was performed in the same manner as in Example 1 except that the amount of higher alcohol A1 added to the toner was 3.0 parts. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

Example 4
Evaluation was performed in the same manner as in Example 1 except that the higher alcohol was changed to A2 and the addition amount to the toner was changed to 0.9 part. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Example 5)
Evaluation was performed in the same manner as in Example 1 except that the amount of higher alcohol A2 added to the toner was 3.0 parts. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Example 6)
Evaluation was performed in the same manner as in Example 1 except that the higher alcohol was changed to A3 and the addition amount to the toner was changed to 0.3 part. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Example 7)
Evaluation was performed in the same manner as in Example 1 except that the amount of the higher alcohol A3 added to the toner was 0.9 parts. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Example 8)
Evaluation was performed in the same manner as in Example 1 except that the amount of the higher alcohol A3 added to the toner was 3.0 parts. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

Example 9
Evaluation was performed in the same manner as in Example 1 except that the width of the toner band in the rotational direction was 8 mm. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Comparative Example 1)
The amount of higher alcohol A1 added to the toner is 0.3 parts, the amount of higher alcohol below the volume average particle size of the toner base particles contained in the toner is 0.09 parts, and the toner base particles contained in the toner Evaluation was performed in the same manner as in Example 1 except that the amount of higher alcohol having a volume average particle size or more was changed to 0.21 part. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Comparative Example 2)
The higher alcohol is A2, the added amount to the toner is 0.5 part, the higher alcohol amount less than or equal to the volume average particle size of the toner base particles contained in the toner is 0.09 part, and the toner base contained in the toner is Evaluation was performed in the same manner as in Example 1 except that the amount of higher alcohol equal to or greater than the volume average particle diameter of the particles was 0.41 part. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Comparative Example 3)
The higher alcohol is A3, the amount added to the toner is 0.15 part, the amount of higher alcohol below the volume average particle size of the toner base particles contained in the toner is 0.09 part, and the toner base contained in the toner is Evaluation was performed in the same manner as in Example 1 except that the amount of higher alcohol equal to or larger than the volume average particle diameter of the particles was 0.06 part. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Comparative Example 4)
Evaluation was performed in the same manner as in Example 1 except that generation of the toner band was not performed and control of reverse rotation of the image carrier was not performed. The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

(Comparative Example 5)
Evaluation was performed in the same manner as in Example 1 except that the image carrier was not reversed. The evaluation conditions are shown in Table 2 and Table 3, and the evaluation results are shown in Table 4.

(Comparative Example 6)
The evaluation was performed in the same manner as in Example 1 except that the toner fine particle was changed to K2, the addition amount to the toner was changed to 0.5 part, and the shape factor SF1 of the toner base particle was changed to 145 which is 140 or more. . The evaluation conditions are shown in Tables 2 and 3, and the evaluation results are shown in Table 4.

  As is apparent from Table 4 above, Examples 1 to 9 using the image forming apparatus of the present invention have a transfer efficiency, an image quality during a running test, and a cleaning property under a stress condition after the running test as compared with Comparative Examples 1 to 6. Good results were obtained in all of the damage of the tip of the cleaning blade and the transfer unevenness.

  On the other hand, in Comparative Examples 1, 2 and 3 in which the content of higher alcohol particles having a volume average particle size equal to or less than the volume average particle size of the toner base particles is 0.15 parts or less, band-like streaks are generated in the running test, and cleaning is poor. And a large chip occurred at the tip of the cleaning blade. Further, in Comparative Example 6 in which the shape factor of the toner base particles was 140 or more, the transfer efficiency was poor. Further, when the image carrier is not rotated in the reverse direction, even if the toner used in the image forming apparatus of the present invention is used, as shown in Comparative Example 4 and Comparative Example 5, a strip-like streak is formed in the running test. Generation, poor cleaning, and large chipping at the tip of the cleaning blade.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image carrier 22 Developing device 26 Transfer roll 34 Developing roll 36 Housing part 38 Conveying member 40 Conveying member 42 Cleaning blade

Claims (7)

An image carrier that carries a toner image of toner on the surface and rotates in a predetermined direction, and a transfer unit that forms an image on the recording medium by transferring the toner image carried on the surface of the image carrier to the recording medium An image forming apparatus comprising:
A cleaning member that is in contact with the outer peripheral surface of the image carrier and removes untransferred residual toner on the image carrier;
Reverse rotation control means for controlling the image carrier so as to reversely rotate by a predetermined amount after the untransferred residual toner is removed by the cleaning member;
With
The toner includes toner base particles and an external additive,
The toner base particle has a shape factor SF1 of 140 or less,
The external additive includes higher alcohol particles having a volume average particle diameter of 1 to 12 μm and 0.15% by mass or more of the higher alcohol particles having a volume average particle diameter or less of the toner base particles in the toner. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein a shape factor SF1 of the higher alcohol particles is greater than or equal to a shape factor SF1 of the toner base particles.   3. The image forming apparatus according to claim 1, wherein the toner contains less than 2.5% by mass of higher alcohol particles having a volume average particle diameter equal to or larger than that of the toner base particles.   The cleaning member is made of urethane rubber and has a rebound resilience coefficient (JIS K6255) of 18% or more at 10 ° C., 70% or less at 40 ° C., and a 300% modulus (JIS K6251) of 19600 kPa or more. The image forming apparatus according to any one of claims 1 to 3, wherein the tear strength (JIS K6252 no-cut angle type) is 83300 N / m or more.   The image forming apparatus according to claim 1, further comprising a toner band forming unit that forms a toner band to be supplied to the cleaning member on the surface of the image carrier during non-image formation. A developing unit for forming a toner image on the image carrier by supplying the toner contained in the container to the image carrier, and a surface of the image carrier. The image forming apparatus according to claim 1, further comprising a conveying member that conveys the removed toner toward the storage unit. A developing step for forming a toner image on the image carrier, a transfer step for transferring the toner image on the image carrier to a recording medium, and a cleaning step for removing untransferred residual toner remaining on the image carrier. A reverse rotation step of reversely rotating the image carrier by a predetermined amount after the untransferred residual toner is removed, and an image forming method comprising:
The toner comprises toner mother particles and an external additive;
The toner base particle has a shape factor SF1 of 140 or less,
The external additive includes higher alcohol particles having a volume average particle diameter of 1 to 12 μm and 0.15% by mass or more of the higher alcohol particles having a volume average particle diameter or less of the toner base particles in the toner. An image forming method.

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