JP2012042730A - Development device, image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development device capable of suppressing surface contamination on a sleeve in comparison with the development device described in a patent literature 1, and further to provide an image forming device and an image forming method.SOLUTION: With respect to at least one of a plurality of magnetic poles, electrode members such as a wire electrode 410, a mesh electrode or the like are disposed in a region located in the downstream side in the developing sleeve surface movement direction where the magnetic flux density in the tangential direction is higher than the magnetic flux density in the normal direction and the magnetic flux density in the normal direction is equal to 0 or more. There is provided voltage supply means 411 for supplying voltage to the electrode members so as to form an electric field between the electrode members and a developing sleeve 403 in which toner particles on the developing sleeve 403 moves to the electrode members.

Description

  The present invention relates to a developing device, an image forming apparatus, and an image forming method.

  2. Description of the Related Art A developing device is known that uses a magnetic developer containing toner particles and magnetic carriers as magnetic particles on the surface of a developer carrying member by the magnetic force of a plurality of magnets contained in a non-magnetic sleeve and is used for development. ing. In this type of developing device, the magnetic developer forms magnetic spikes on the developer carrier by the magnetic force of the magnetism generating means. The magnetic spikes on the developer carrier are transported to the development position facing the latent image carrier while repeating the heading / falling of the heads due to the relationship between the magnetic force in the normal direction and the magnetic force in the tangential direction of the magnetism generating means. The In this type of developing device, so-called sleeve contamination occurs in which toner particles adhere to the surface of the developer carrying member and become dirty, affecting the image.

  Japanese Patent Application Laid-Open No. 2005-228561 discloses a developing device that uses an AC voltage as a developing bias to increase the frequency of the AC voltage in the inter-paper region on the latent image carrier to be higher than the frequency in the latent image forming region. Are listed. As a result, when the inter-paper area is at the development position, the adhesion of the toner particles adhering to the surface of the developer carrying member facing the inter-paper area can be weakened, and the sleeve contamination can be reduced.

  However, in Patent Document 1, there is an effect of suppressing toner adhesion only when the inter-paper area on the latent image carrier is at the development position, and sleeve contamination can not be sufficiently suppressed. In addition, since the adhesion force of the toner particles adhering to the surface of the developer carrying member is only weakened, there is a problem that sleeve contamination cannot be sufficiently suppressed.

  In the above description, a two-component developer composed of toner particles and a magnetic carrier as magnetic particles has been described. However, a similar problem occurs in a one-component developer composed of magnetic toner particles as magnetic particles.

  The present invention has been made in view of the above problems, and an object thereof is to provide a developing device, an image forming apparatus, and an image forming method capable of suppressing sleeve contamination as compared with the developing device described in Patent Document 1. It is to be.

To achieve the above object, the invention of claim 1 comprises a rotating nonmagnetic sleeve and a magnetic field generating means fixedly disposed in the nonmagnetic sleeve and having a plurality of magnetic poles, and includes at least magnetic particles. In a developing device that carries magnetic developer as magnetic spikes on the surface of the non-magnetic sleeve and supplies toner to the latent image on the latent image carrier in a development region facing the latent image carrier, the plurality of magnetic poles A region where the magnetic flux density in the tangential direction is larger than the magnetic flux density in the normal direction and the magnetic flux density in the normal direction is 0 or more with respect to at least one of the non-magnetic sleeve surface moving direction. An electrode member is disposed, and a voltage supply means is provided between the electrode member and the nonmagnetic sleeve for supplying the electrode member with a voltage for forming an electric field in which the toner particles on the nonmagnetic sleeve move to the electrode member. thing It is an feature.
According to a second aspect of the present invention, in the developing device of the first aspect, the electrode member is disposed in a region upstream of the nonmagnetic sleeve surface movement direction with respect to the peak position of the magnetic flux density in the tangential direction. To do.
According to a third aspect of the present invention, in the developing device of the first or second aspect, the absolute value of the voltage applied to the electrode member is made smaller than the absolute value of the developing bias.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the voltage applied to the electrode member is an AC voltage.
According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the electrode member has a mesh shape.
According to a sixth aspect of the present invention, there is provided an image forming apparatus having a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier. A developing device according to any one of 5 to 5 is used.
According to a seventh aspect of the present invention, there is provided an image forming method comprising: a latent image forming step for forming a latent image on the latent image carrier; and a developing step for developing the latent image on the latent image carrier using a developing means. In the method, the developing device according to any one of claims 1 to 6 is used as the developing means.

As a result of intensive studies, the present inventors have found that the toner strongly adheres to the surface of the nonmagnetic sleeve when the magnetic spike collides with the surface of the nonmagnetic sleeve. Therefore, the present invention provides a method for providing a magnetic flux density in the downstream direction of the nonmagnetic sleeve surface movement relative to at least one of the plurality of magnetic poles, the magnetic flux density in the tangential direction being greater than the magnetic flux density in the normal direction, and The electrode member was disposed in a region where the magnetic flux density in the linear direction was 0 or more. The magnetic flux density in the normal direction is the largest at the position facing the magnetic pole, and the magnetic flux density in the normal direction decreases and the magnetic flux density in the tangential direction increases as the magnetic pole moves toward the downstream side of the nonmagnetic sleeve surface movement direction. Go. When the magnetic flux density in the normal direction becomes larger than the magnetic flux density in the tangential direction, the magnetic spike on the nonmagnetic sleeve starts to fall, and when the magnetic flux density in the normal direction becomes 0, the magnetic spike becomes a nonmagnetic sleeve. collide. Therefore, the region is a region where the magnetic spike falls on the surface of the nonmagnetic sleeve. Then, the electrode member is disposed in this region, and a voltage for forming an electric field in which the toner particles on the nonmagnetic sleeve move to the electrode member between the electrode member and the nonmagnetic sleeve is supplied to the electrode member. As a result, in the case of a two-component developer composed of toner particles and magnetic carriers as magnetic particles, an electric field that moves to the electrode member is applied to the toner particles attached to the magnetic spikes that fall on the surface of the nonmagnetic sleeve. be able to. When the magnetic spike falls on the surface of the nonmagnetic sleeve by this electric field, the toner particles attached to the magnetic spike move electrostatically to the electrode member. As a result, when the magnetic spike falls to the surface of the nonmagnetic sleeve, the toner particles attached to the magnetic spike are reduced. As a result, when the magnetic spike collides with the surface of the non-magnetic sleeve, the toner adhering to the surface of the non-magnetic sleeve can be reduced, and sleeve contamination can be suppressed. The magnetic carrier that forms the magnetic spike after the collision with the non-magnetic sleeve has a charge opposite to the charged polarity of the toner due to the movement of the toner by the action of the electric field. For this reason, after the collision, when the magnetic spike moves to a region where the action of the electric field is weakened, a part of the toner adhering to the electrode reattaches to the magnetic carrier. Therefore, a decrease in the toner concentration of the developer after passing through the electrode member is suppressed.
On the other hand, in the case of a one-component developer having magnetic toner as magnetic particles, an electric field that moves to the electrode member is applied to the magnetic spike that falls on the surface of the non-magnetic sleeve, and the magnetic toner that forms the magnetic spike is applied to the electrode. It can be moved to the member. Thereby, it can suppress that a magnetic spike collides with the nonmagnetic sleeve surface, and can suppress sleeve dirt. Further, since the toner adhering to the electrode member is pushed downstream by the magnetic spikes on the upstream side in the movement direction of the nonmagnetic sleeve, the decrease in the toner amount after passing through the electrode member is suppressed.
As described above, in the present invention, the toner particles themselves can be prevented from adhering to the surface of the nonmagnetic sleeve. Therefore, like the developing device described in Patent Document 1, the toner particles are simply adhered to the surface of the nonmagnetic sleeve. As compared with a toner that reduces the adhesion of the toner particles to the non-magnetic sleeve surface, the contamination of the sleeve can be suppressed.
Furthermore, according to the present invention, it is possible to suppress the contamination of the sleeve by suppressing the adhesion of toner particles to the surface of the non-magnetic sleeve regardless of whether or not the inter-paper area on the latent image carrier is at the development position. Therefore, as in the developing device described in Japanese Patent Application Laid-Open No. H10-228707, sleeve contamination is suppressed as compared with a device that takes measures to suppress sleeve contamination only when the inter-paper area on the latent image carrier is at the development position. be able to.

  According to the present invention, as compared with the developing device described in Patent Document 1, it is possible to suppress sleeve contamination.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. Schematic configuration diagram around the developing device of the printer The figure which shows the arrangement position of the wire electrode of the developing device. FIG. 3 is a schematic configuration diagram in the vicinity of a development region. The figure which shows the magnetic flux density of the normal line direction of a magnet member, and the magnetic flux density of a tangential direction. 6 is a graph showing a change with time of toner adhering to the developing sleeve of the present embodiment and a conventional developing device. Explanatory drawing of the dynamic resistance measurement system of the magnetic particle of a developing agent. The schematic block diagram which shows the structure of the electrode in the modification 1. FIG. 10 is a schematic configuration diagram of a developing device according to Modification 2. Sectional drawing of a magnet roller. The schematic diagram of the state when magnetizing a magnet layer. The figure which shows the magnetic flux density of the perpendicular direction of a magnet roller.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic laser printer (hereinafter referred to as “printer”) as an image forming apparatus and a developing device used in the printer will be described.
First, an overall schematic configuration of the printer according to the present embodiment will be described with reference to FIG. This printer irradiates the photosensitive member 1 with a charging device 2 for uniformly charging the surface of the photosensitive member 1 around the drum-shaped photosensitive member 1 serving as a latent image carrier, and a laser beam or the like modulated based on image information. An exposure device 3 that forms a toner image by attaching a charged toner on the developing sleeve 403 to an electrostatic latent image formed on the photosensitive member 1, and a toner image that is formed on the photosensitive member 1. A transfer device 5 for transferring to a transfer paper 20 as a transfer material, a cleaning device 6 for removing toner remaining on the photoreceptor 1 after transfer, and the like are sequentially arranged. The latent image forming means for forming an electrostatic latent image on the photoreceptor 1 is constituted by the charging device 2 and the exposure device 3.
In addition, a paper feeding / conveying device (not shown) for feeding / conveying transfer paper from a paper feeding tray (not shown) and a fixing device (not shown) for fixing the toner image transferred by the transfer device 5 to the transfer paper 20 are provided. Yes.

  Note that some of the plurality of devices constituting the printer may be configured as an integrated structure (unit) that is detachable from the printer body. For example, as shown in FIG. 2, the photosensitive member 1, the charging device 2, the developing device 4, and the cleaning device 6 are configured as an image forming process unit 50 that is an integral structure so as to be detachable from the printer body. Also good.

  In the printer having the above configuration, the surface of the photosensitive member 1 rotating in the direction of the arrow a is uniformly charged by the charging device 2, and then a laser beam modulated based on image information is scanned and irradiated in the axial direction of the photosensitive member. The Thereby, an electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image formed on the photoconductor 1 is developed by attaching toner charged by the developing device 4 in the developing area A1, and becomes a toner image. On the other hand, the transfer paper 20 is fed / conveyed by a paper feeding / conveying device (not shown), and is sent / conveyed by a registration roller 7 to a transfer portion where the photosensitive member 1 and the transfer device 5 face each other at a predetermined timing. Then, the transfer device 5 applies a charge having a polarity opposite to that of the toner image on the photoconductor 1 to the transfer paper 20, whereby the toner image formed on the photoconductor 1 is transferred to the transfer paper 20. Next, the transfer paper 20 is separated from the photoreceptor 1 and sent to a fixing device (not shown), and the transfer paper 20 on which the toner image is fixed by the fixing device is output. The surface of the photoreceptor 1 after the toner image is transferred by the transfer device 5 is cleaned by the cleaning device 6, and the toner remaining on the photoreceptor 1 is removed.

  FIG. 2 is a schematic configuration diagram around the developing device of the printer. The developing device 4 used in the printer is a two-component developing type developing device that carries the toner 1 and the carrier as a two-component developer by a developing roller as a developer carrying member and develops the photosensitive member 1. is there.

  The developing roller 41 includes a non-magnetic and rotatable cylindrical developing sleeve 403 and a built-in developing sleeve 403 and four magnet members 407. Each magnet member 407 is fixedly disposed in the developing sleeve 403 so that magnetic force acts when the developer passes a predetermined location on the developing sleeve 403. The developing sleeve 403 has a diameter of φ18 [mm] and is sandblasted so that the surface roughness Rz (ten-point average roughness) falls within the range of 10 to 20 [μm]. Further, the surface layer of the developing sleeve 403 may be formed with a plurality of grooves perpendicular to the developer conveying direction in order to improve the developer conveying property.

  The magnetic poles of the magnet members 407 built in the developing sleeve 403 are arranged in the direction of rotation of the developing sleeve 403 from the restriction position by the restriction blade 404 in the N pole (N1), S pole (S1), N pole (N2), and S pole ( S2) is arranged. The arrangement of the magnetic poles of each magnet member 407 is not limited to the configuration shown in FIG. 2, and may be set to other arrangements according to the arrangement of the regulating blade 404 around the developing sleeve 403.

  Due to the magnetic force of the magnet member 407, a developer composed of toner and magnetic particles (hereinafter referred to as a carrier) is carried on the developing sleeve 403 in a brush shape. The toner in the magnetic brush on the developing sleeve 403 is mixed with a carrier to obtain a specified charge amount. The toner charge amount of the magnetic brush is preferably in the range of −10 to −40 [μC / g].

  In the present embodiment, the interval at the closest portion between the regulating blade 404 and the developing sleeve 403 is set to 300 [μm], and the magnetic pole N1 of the magnet member 407 facing the regulating blade 404 is positioned at the position facing the regulating blade 404. Further, the developing sleeve 403 is positioned at an angle of several degrees on the upstream side in the rotation direction. Thereby, the circulation flow of the developer in the casing can be easily formed.

  The regulating blade 404 is in contact with the magnetic brush so as to regulate the amount of developer formed on the developing sleeve 403 at a portion facing the developing sleeve 403 so that a predetermined amount of developer is carried and conveyed. In addition, frictional charging between the toner in the developer and the carrier is promoted.

In this embodiment, the developing sleeve 403 is rotationally driven in the counter direction at a linear speed of 300 [mm / s] with respect to the linear speed of 200 [mm / s] of the photoreceptor 1. The developing gap between the photoreceptor 1 and the developing sleeve 403 is set to 0.3 [mm]. In this printer, the toner adhesion amount was 0.45 [mg / cm ² ] in the solid portion, and the charge amount was −27 [μC / g] on average.

Next, the operation of the developing device 4 configured as described above will be described.
The developer contained in the casing is a mixture of toner and carrier, and is agitated by the rotational force of the agitating / conveying members 405 and 406 and the developing sleeve 403 and the magnetic force of the magnet member 407. The toner is charged by frictional charging with the carrier.

  On the other hand, the developer carried on the developing sleeve 403 is regulated by the regulating blade 404. Thereafter, the developer carried on the developing sleeve 403 is conveyed to the developing region by the rotation of the developing sleeve 403. Then, by the developing electric field formed by the developing bias, the electrostatic latent image on the photosensitive member 1 is selectively attached to the electrostatic latent image, and the electrostatic latent image is developed.

Next, features of the present embodiment will be described.
When the developer is conveyed by a magnet disposed inside the developing sleeve, when the magnetic brush collides with the surface of the developing sleeve, the toner adheres to the surface of the developing sleeve and the sleeve becomes dirty. In particular, when the density of the toner in the developer is relatively high, or when the adhesion between the magnetic particles in the developer and the toner is reduced, the toner tends to adhere to the surface of the developing sleeve when the magnetic brush collides. , The sleeve is likely to become dirty When such sleeve contamination occurs, a toner layer potential is generated at a portion of the developing sleeve where the toner adheres. As a result, the toner adhering portion of the developing sleeve is the same as the bias voltage becoming excessive at the time of developing, and the effective developing potential is increased and excessive toner is developed. In the developing device 4 of the present embodiment, it is intended to maintain a uniform image forming function by suppressing sleeve contamination and always maintaining a fresh surface.

  In the developing device of this embodiment, as shown in FIG. 3, wire electrodes 410-1, 410-2, 410-3, and 410-4 as electrode members are arranged in a region where the magnetic brush falls. . Each wire electrode 410-1 to 410-4 is suspended at a height of about 1 mm from the surface of the developing sleeve 403, and is disposed at a position in contact with the developer on the developing sleeve 403. The diameter of the wire electrode is 50 to 100 [μm], and the suspended tension is optimally 2 to 4 [N]. If the diameter of the wire electrode 410 is smaller than 50 [μm], the wire electrode 410 may be cut. If the diameter is larger than 100 [μm], the developer may be prevented from being conveyed. On the other hand, if the tension is weaker than 2 [N], the wire electrode 410 may be bent and come into contact with the developing sleeve or the like to be cut. On the other hand, if it is stronger than 4 [N], there is a possibility that the developer will be cut by the conveying force of the developer. Further, a voltage is applied to each wire electrode from voltage supply means 411 (see FIG. 4).

Next, the action of the wire electrode will be described by taking the wire electrode 410-2 disposed downstream in the developer transport direction as an example with respect to the S1 pole magnet member disposed in the developing nip.
FIG. 4 is a schematic configuration diagram in the vicinity of the development region.
As shown in FIG. 4, the magnetic brush on the developing sleeve 403 is raised by the S1 pole magnet member and rubs against the photoreceptor 1 at the developing nip. At this time, the toner attached to the carrier 408 is electrostatically attached to the latent image on the photoreceptor 1 by the developing bias Vb having the same polarity as the normal charging polarity (negative polarity) of the toner applied to the developing sleeve 403. After passing through the developing nip, the magnetic brush falls to the developing sleeve 403. A voltage Vel having the same polarity as the developing bias Vb and having an absolute value smaller than the developing bias Vb is applied to the wire electrode 410-2. As a result, an electric field is formed between the wire electrode 410-2 and the developing sleeve 403 so that the toner 409 attached to the carrier 408 forming the magnetic brush moves to the wire electrode 410-2. As a result, when the magnetic brush falls to the developing sleeve side with respect to the wire electrode 410-2, the toner attached to the magnetic brush by the electric field between the wire electrode 410-2 and the developing sleeve 403 is attracted to the wire electrode 410-2. It is done. As a result, the toner adhering to the magnetic brush (carrier) is electrostatically moved to the wire electrode 410-2 and detached from the magnetic brush (carrier). As a result, when the magnetic brush collides with the developing sleeve 403, since the toner hardly adheres to the magnetic brush, it is possible to suppress the toner from adhering to the developing sleeve at the time of the magnetic brush collision, and the sleeve dirt Can be suppressed. On the other hand, when the toner is separated from the carrier, the carrier has a charge opposite in polarity to the toner charging polarity. Even if the carrier is charged to a polarity opposite to the toner charging polarity, the carrier movement is bound to the surface of the developing sleeve by the magnetic flux of the magnet member 407 included in the developing sleeve 403, so that the carrier adheres to the wire electrode 410-2. There is no electrical influence. When the magnetic brush on the developing sleeve moves after the magnetic brush collides with the developing sleeve 403 and the action of the electric field between the developing sleeve and the electrode member becomes weak, the magnetic brush is held by the wire electrode 410-2. A part of the toner that has been transferred to the carrier charged to the opposite polarity to the toner charging polarity moves to the carrier again.

  The toner once attached to the surface of the developing sleeve is a toner charged to a specified polarity and value with almost no change in the charge amount distribution of the toner attached to the magnetic brush. Therefore, the toner once adhered to the surface of the developing sleeve can be attracted to the wire electrode 410-2 by the electric field between the wire electrode 410-2 and the developing sleeve 403. As a result, the toner once adhered to the sleeve surface is also electrostatically moved to the wire electrode 410-2, and the sleeve surface can be kept fresh.

  The bias Vel applied to the wire electrode 410-2 may be a bias slightly shifted to the plus side (about 20 to 30 [V]) from the developing bias Vb. Since the distance between the wire electrode 410-2 and the developing sleeve surface is about 1 [mm], an electric field of about 30 [V / mm] is formed at the maximum. Accordingly, the toner attached to the magnetic brush can be moved to the wire electrode 410-2, and the toner once attached to the sleeve surface can be attracted to the wire electrode 410-2. Incidentally, the influence on the developing electric field due to the bias applied to the wire electrode 410-2 is extremely small since it is considerably downstream from the developing region. Further, the influence can be reduced by adjusting the bias to the wire electrode 410-2 at the initial setting. However, the value of this applied voltage varies depending on the system configuration (consideration of the electric field due to the development gap and the toner charge amount range needs to be optimized), and is adjusted and set to an appropriate value.

  As shown in FIG. 5, the region in which the magnetic brush is tilted is such that the magnetic flux density Br in the normal direction is smaller than the magnetic flux density Bθ in the tangential direction on the downstream side of the developer conveyance with respect to the magnet member, and The normal direction magnetic flux degree Br is 0 or more. When the magnetic flux density in the normal direction becomes 0, the magnetic brush collides with the developing sleeve 403. Therefore, if the wire electrode 410-2 is not disposed at least on the upstream side, the effect of suppressing sleeve contamination is small. More preferably, it is on the upstream side in the developer conveyance direction from the peak position of the magnetic flux density in the tangential direction. By disposing the toner at the upstream side in the developer conveyance direction from the peak value, the toner of the magnetic brush is applied before the magnetic brush collides with the developing sleeve 403 as compared with the case where the magnetic brush is disposed at the downstream side in the developer conveyance direction from the peak value. On the other hand, the time during which the electric field can be applied can be lengthened, and the toner attached to the magnetic brush can be favorably moved to the wire electrode 410-2.

  Moreover, although the effect | action of the wire electrode 210-2 was demonstrated above, the other wire electrodes 210-1, 210-3, and 210-4 also have the same effect | action.

  FIG. 6 is a graph showing the change with time of the toner adhering to the developing sleeve of the present embodiment and the conventional developing device. Evaluation was made by passing A4 size paper and measuring the reflection density (ID) of the toner adhering to the surface of the developing sleeve. In the conventional example, the adhesion amount increased with time, whereas in the developing device of this embodiment, an increase in the adhesion amount could be suppressed. In the developing device of this embodiment, there was almost no influence on the image.

Next, the toner used in this printer will be described.
The toner used in this printer is advantageous in that the average particle size of the toner is 4 to 8 μm in order to realize a high quality image. The weight average particle size of the toner is 3 to 8 μm, more preferably 5 to 7 μm. If the weight average particle size is less than 3 μm, problems such as contamination inside the machine due to toner scattering during long-term use, image density reduction in a low-humidity environment, poor photoconductor cleaning, and the like are likely to occur, and there are concerns about the effects on the human body. When the weight average particle size exceeds 8 μm, the resolution of minute spots of 100 μm or less is not sufficient, and the image quality tends to be inferior due to many scattering to non-image areas. The weight average particle diameter and circularity of the toner can be measured using a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.).

  As the resin constituting the toner base particles, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene acrylic resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, polyethylene resin, There are silicon resin, butyral resin, terpene resin, polyol resin and the like. Examples of vinyl resins include styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and homopolymers thereof: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer. Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic copolymer Acid methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl acetate Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.

The polyester resin is composed of a dihydric alcohol as shown in the following group A and a dibasic acid salt as shown in the group B, and further a trihydric or higher alcohol as shown in the group C or What added carboxylic acid as a 3rd component may be used.
Group A: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4 butanediol, neopentyl glycol, 1,4 butenediol, 1,4-bis (hydroxymethyl) cyclohexane Bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2,2) -2,2′-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -2,2′-bis (4 -Hydroxyphenyl) propane and the like.
Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, linolenic acid, or These acid anhydrides or esters of lower alcohols.
Group C: Trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid. As the polyol resin, an alkylene oxide adduct of an epoxy resin and a dihydric phenol, or a compound having one active hydrogen in the molecule that reacts with the glycidyl ether and the epoxy group, and an active hydrogen that reacts with the epoxy resin in the molecule. There are those obtained by reacting two or more compounds.

  Examples of the pigment to be contained in the toner include the following. Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. . Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC. Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.

  These can use 1 type (s) or 2 or more types. Especially for color toners, uniform dispersion of good pigments is essential. Instead of putting pigments directly into a large amount of resin, a master batch in which pigments are once dispersed at a high concentration is prepared and diluted. The method of throwing in is used. In this case, a solvent is generally used to assist dispersibility. However, there is a problem of environment and the like, and in the present invention, water is used for dispersion. When water is used, temperature control is important so that residual moisture in the masterbatch does not become a problem.

  In the toner of this embodiment, a charge control agent is blended (internally added) inside the toner particles. The charge control agent makes it possible to control the optimum charge amount according to the development system. In particular, in this embodiment, the balance between the particle size distribution and the charge amount can be further stabilized. For controlling the toner to be positively charged, nigrosine and quaternary ammonium salts, triphenylmethane dyes, imidazole metal complexes and salts can be used alone or in combination of two or more. Further, salicylic acid metal complexes, salts, organic boron salts, calixarene compounds, and the like are used for controlling the toner to be negatively charged. Further, a release agent can be internally added to the toner in the present embodiment in order to prevent offset at the time of fixing. Release agents include natural waxes such as candelilla wax, carnauba wax, rice wax, montan wax and derivatives thereof, paraffin wax and derivatives thereof, polyolefin wax and derivatives thereof, sazol wax, low molecular weight polyethylene, and low molecular weight polypropylene. And alkyl phosphate esters. The melting point of these release agents is preferably 65 to 90 ° C. When the temperature is lower than this range, blocking during storage of the toner tends to occur, and when the temperature is higher than this range, an offset is likely to occur in a region where the fixing roller temperature is low.

  Additives may be added to the toner particles for the purpose of improving releasability and even improving dispersibility. As additives, styrene acrylic resin, polyethylene resin, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, A polyol resin etc. are mentioned, You may mix them 2 or more types. Crystalline polyester may be used as the polyester resin. It is an aliphatic polyester having crystallinity, having a sharp molecular weight distribution, and increasing the absolute amount of its low molecular weight as much as possible. This resin undergoes a crystal transition at the glass transition temperature (Tg), and at the same time, the melt viscosity suddenly decreases from the solid state and exhibits a fixing function to paper. By using this crystalline polyester resin, low-temperature fixing can be achieved without excessively reducing the Tg and molecular weight of the resin. Therefore, there is no decrease in storage stability associated with a decrease in Tg. Further, there is no excessively high gloss and offset resistance deterioration due to the low molecular weight. Therefore, the introduction of the crystalline polyester resin is very effective for improving the low-temperature fixability of the toner.

  In order to improve the fluidity, the inorganic fine powder may be adhered or fixed to the toner surface. The average particle size of the inorganic fine powder is suitably 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.

  Examples of the inorganic fine powder include Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, and Zr. Examples thereof include oxides and composite oxides. Of these, fine particles of silicon dioxide (silica), titanium dioxide (titania), and alumina are preferably used. Furthermore, it is effective to perform surface modification treatment with a hydrophobizing agent or the like. Typical examples of the hydrophobizing agent include the following. Namely, dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichloro Silane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane and the like.

  The inorganic fine powder is preferably added at a ratio of 0.1 to 2% by weight with respect to the toner. If it is less than 0.1% by weight, the effect of improving toner aggregation is poor, and if it exceeds 2% by weight, problems such as toner scattering between fine wires, contamination in the machine, scratches and abrasion of the photoreceptor tend to occur. Because there is.

  In addition, at least a charge control agent may be attached or fixed to the surface of the powder made of resin or pigment so that the powder surface shape has a small period and a large period. The average particle size is optimally as small as 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.

  In addition, other additives such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder, lubricant powders; or cerium oxide powder, silicon carbide powder, titanium, as long as they do not have a substantial adverse effect. A small amount of an abrasive such as strontium acid powder may be added as a developability improver.

  It may be a toner or a capsule toner produced by a spray drying method or the like produced without using a kneading step or a pulverizing step.

The toner resistance is adjusted by adjusting the amount of the conductive material contained and dispersed in the base resin. Examples of the carbon-based conductive material include acetyl black, oil furnace black, thermal black, carbon fiber, and graphite. Examples of the metallic conductive material include metal powders such as tin oxide (SnO ₂ ), zinc oxide (ZnO), Cu, and Ni. These are appropriately dispersed in the toner binder resin to adjust the electric resistance.

  The carrier that is a magnetic particle to be contained in the developer has a diameter of 20 to 80 [μm], more preferably 20 to 50 [μm], and contains a magnetic material such as magnetite or ferrite with a metal or resin as a core. The surface layer is coated with a material that is easily charged with a polarity opposite to that of the toner in order to efficiently apply the toner and charge by frictional charging. Examples of such a material include a material containing a silicone resin and ammonium dioxide. Styrene-acrylic resins, epoxy resins, styrene-butadiene resins, butyral resins, styrene resins, and the like may be used.

The carrier resistance is preferably in the range of 10 ⁸ to 10 ¹⁴ Ω in terms of dynamic resistance DR. Here, the measurement of the dynamic resistance DR of the carrier was performed as follows using the measuring apparatus shown in FIG. First, a rotatable sleeve 403 having a diameter of φ20 mm with a fixed magnet built in a predetermined position is set above the grounded base 200. A surface of the sleeve 403 is opposed to a counter electrode (doctor) 202 having a width W = 65 mm and a length L = 0.5 to 1 mm with a gap g = 0.9 mm. Next, the sleeve 403 starts to rotate at a rotational speed of 600 rpm (linear speed: 628 mm / sec). Then, a predetermined amount (14 g) of the carrier to be measured is held on the rotating sleeve 403, and the carrier is stirred for 10 minutes by the rotation of the sleeve 403. Next, the current IRII [A] flowing between the sleeve 403 and the counter electrode 202 is measured by the ammeter 203 without applying a voltage to the sleeve 403. Next, an applied voltage E [V] of a withstand voltage upper limit level (400 V for high-resistance silicon-coated carrier to several V for iron powder carrier) is applied to the sleeve 403 from the DC power source 204 for 5 minutes. In this embodiment, 200 V is applied. Then, the current IRQ [A] flowing between the sleeve 403 and the counter electrode 202 with the voltage E applied is measured by the ammeter 203. From these measurement results, the dynamic resistance DR [Ω] is calculated using DR = E / (I _RQ −I _RII ).

  Next, a modification of this embodiment will be described.

[Modification 1]
FIG. 8 is a schematic configuration diagram showing the structure of the electrode in the first modification.
As shown in the figure, the electrode of Modification 1 is a mesh electrode 505 having a plurality of holes, and is provided so that the mesh surface faces the sleeve surface. Further, the mesh electrode 505 is provided with a plurality of protrusions 505c extending to the surface of the developing sleeve. By disposing the plurality of protrusions 505c on the mesh electrode 505, the range in which the force of the electric field can be applied can be expanded, and the toner can be more effectively prevented from adhering to the developing sleeve 403.

  The gap between the mesh electrode 505 and the surface of the developing sleeve is 0.3 [mm]. Further, the mesh electrode 505 has a width 330 [mm] × a length 5 [mm] when the effective width of development is 320 [mm]. Further, the mesh electrode 505 may have a thickness of about 0.1 to 0.5 [mm], and it is preferable to bend the shape along the surface of the developing sleeve to maintain the gap. When the diameter of the developing sleeve 403 is 18 [mm], the developing sleeve 403 is formed with a curvature of 20 [mm].

  In Modification 1, an AC voltage is applied to the mesh electrode 505 to form an AC electric field between the developing sleeve 403 and the mesh electrode 505. Specifically, the DC equivalent to the development bias Vb and the peak-to-peak voltage of about 0.1 to 0.5 [kV] are applied to the mesh electrode 505 with respect to the DC development bias voltage applied to the development sleeve 403. Apply AC voltage. The waveform may be a sine wave or a rectangular wave, and the frequency is in the range of 1 to 5 [kHz]. This may be appropriately adjusted according to the characteristics of the toner, the characteristics of the developing sleeve 403, and the like.

  By using the mesh electrode 505 as the electrode member, it is possible to widen the region on which the electric field is applied as compared with the case of the wire electrode, and it is possible to move the toner to the electrode member satisfactorily.

  In a modification in which an AC voltage is applied to the mesh electrode 505, when the bias of the mesh electrode 505 is on the plus side of the development bias Vb, the toner attached to the carrier is detached from the carrier and attached to the mesh electrode 505. To do. When the bias of the mesh electrode 505 is on the minus side of the developing bias Vb, the toner attached to the mesh electrode 505 moves to the magnetic brush on the developing sleeve side of the mesh electrode 505, and the magnetic brush electrode member side (developing) Adhere to the opposite side of the sleeve. As described above, in the configuration in which the AC voltage is applied, when the magnetic brush collides, since the toner hardly adheres to at least the side facing the developing sleeve of the magnetic brush, the toner adheres to the developing sleeve 403. Can be suppressed. Also, the toner once attached to the developing sleeve 403 also moves to the mesh electrode side when the bias of the mesh electrode 505 is on the plus side of the developing bias, and when the bias of the mesh electrode 505 is on the minus side of the developing bias, It adheres to the electrode member side of the magnetic brush closer to the developing sleeve than the mesh electrode 505. Thereby, the toner once attached to the developing sleeve 403 can be separated from the sleeve surface, and the developing sleeve surface can be maintained in a fresh state. Further, by applying an AC voltage, the toner adhering to the developing sleeve can be removed. Thereby, even if the toner cannot be detached from the surface of the developing sleeve by the electric field, the toner layer potential of the toner attached to the developing sleeve can be reduced. As a result, it is possible to suppress an increase in the effective developing potential at the toner adhesion portion of the developing sleeve. Further, by removing electricity, it is possible to weaken the electric adsorption force between the developing sleeve and the toner, and it is possible to easily collect the toner attached to the developing sleeve due to contact with the developer.

[Modification 2]
FIG. 9 is a schematic configuration diagram of the developing device 140 according to the second modification.
The second modification is a one-component developing type developing device 140 in which the developer is composed only of magnetic toner as magnetic particles.
Even in a one-component developer using magnetic toner, when a magnetic brush formed only of magnetic toner collides with the developing sleeve 403, the toner strongly adheres to the developing sleeve 403, and there is a possibility that the sleeve becomes dirty.

  The developing device 140 according to the second modification includes a developing roller 41 as a developer carrying member that exposes a part of the peripheral surface from an opening of the developing device 140 and faces the photosensitive member 1, and a supply roller 42 as a developer supply member. And a regulating blade 43 as a developer regulating member. Further, the developing device 140 includes an agitator 44 as a developer transfer member. In the developing device 140, 100 to 200 [g] of developer is present. In the developing device, an agitator 44 with blades around the rotation shaft is disposed and rotated. As a result, the toner can be released. Although the toner particles are initially in an agglomerated state, the distance between the toners is increased by the rotation of the agitator 44, and the toner particles become fluid and easily move.

  The developing roller 41 has a non-magnetic and rotatable cylindrical developing sleeve 403 and a magnet roller 141 as a magnetic field generating means built in the developing sleeve 403. The magnet roller 141 is fixed to the apparatus, and the developing sleeve 403 is rotatably supported.

  The toner adhering to the surface of the developing sleeve so as to be rubbed by the supply roller 42 in the developing device is not in a uniform state as a layer, but after being transported on the developing sleeve 403, the regulating blade 43 passes the developer through the developer. To make contact. Therefore, the developer layer is leveled, but further electric charge is given by frictional charging with the developer. A toner charge amount of about −25 [μC / g] is obtained. The charged toner moves to the developing area by the conveyance of the developing sleeve 403.

FIG. 10 is a cross-sectional view of the magnet roller.
The magnet roller 141 included in the developing sleeve has a magnet layer 141b formed on the surface of a cored bar 141a made of metal such as SUS304 or a magnetic material (Fe). The magnet layer 141b uses a plastic magnet or a rubber magnet. Basically, a ferrite powder is dispersed in a polymer compound. The magnet layer 141b is alternately magnetized with N and S poles at a pitch of about 2 [mm] in length.

FIG. 11 is a schematic diagram of a state when magnetizing the magnet layer 141b.
As shown in the figure, by applying a current to the yoke 414, a magnetic field is generated in the yoke 414, and the magnet roller 141 is rotated and magnetized. The magnetic field generated by the magnetic permeability μ of the core metal 141a and the gap between the core metal 141a and the yoke 414 differs. In Modification 2, the material of the core bar 141a is SUS304, the diameter of the core bar is 16 [mm], the diameter of the magnet roller 141 is 20 [mm], and the distance between the magnet roller 141 and the yoke 414 is 0.8 [mm]. ], The magnetization gap is 0.05 [mm] feed (10 pole yoke 10 feed) and magnetized to obtain a magnetic flux density distribution in the normal direction as shown in FIG.

  Also in the developing device 140 according to the second modification, the magnetic toner on the developing sleeve forms a magnetic brush by the magnetic force of the magnet roller 141. When the magnetic brush is on the magnetic pole of the magnet roller 141, the magnetic brush rises and moves further to the downstream side in the developer transport direction. The magnetic brush falls down and the magnetic flux density in the normal direction is 0. By the way, the magnetic brush collides with the developing sleeve 403. Therefore, also in the developing device 140 according to the second modification, the magnetic flux density in the tangential direction is higher than the magnetic flux density in the normal direction on the downstream side in the developer transport direction from the magnetic pole, and the magnetic flux density in the normal direction is 0. An electrode member is disposed in a region upstream of the position of the developer in the developer transport direction. As a result, when the magnetic brush falls to the developing sleeve side with respect to the electrode member, the magnetic brush made of magnetic toner is attracted to the electrode member. Thereby, it is possible to suppress the magnetic toner forming the magnetic brush from electrostatically moving to the electrode member and colliding with the developing sleeve 403. Further, the electrode member is disposed at a position buried in the developer, so that the toner attached to the electrode member is pushed downstream by the toner on the upstream side in the developer transport direction. Further, when the force that attracts the magnetic toner to the developing sleeve 403 by the magnetic force is stronger than the force that electrostatically moves the magnetic toner to the electrode member due to the potential difference between the electrode member and the developing sleeve 403, the magnetic brush is used for the developing sleeve 403. Even in this case, it is possible to reduce the collision of the magnetic brush with the developing sleeve 403 by electrostatically attracting the magnetic brush to the electrode member. As a result, the magnetic toner can be prevented from strongly adhering to the developing sleeve 403 at the time of collision, and sleeve contamination can be suppressed.

  As shown in FIG. 9, in the developing device according to the second modification, an electrode member 415 is disposed downstream of the developing nip in the developer transport direction. By disposing the electrode member 415 at this position, if the amount of magnetic toner adhering to the electrode member 415 increases, it can be recovered by dropping under the developing unit under its own weight. Further, the region where the electrode member 415 is disposed is a region where the developing roller 41 is in contact with another member (a contact portion with the photosensitive member 1, a contact portion with the supply roller 42, or a contact with the regulating blade 43. Part), and can be appropriately determined according to the layout. In the configuration shown in FIG. 9, the number of electrode members 415 is one, but a plurality of electrode members 415 may be arranged.

  As described above, according to the developing device of the present embodiment, the developing sleeve 403 that is a rotating nonmagnetic sleeve, and the magnetic field generating means that is fixedly disposed in the developing sleeve and has a plurality of magnetic poles, includes at least magnetic particles. The developer is carried on the surface of the developing sleeve 403 as magnetic spikes, and toner is supplied to the latent image on the photoconductor in a developing area facing the photoconductor 1 as a latent image carrier. Further, at least one of the plurality of magnetic poles is downstream of the developing sleeve surface movement direction, the magnetic flux density in the tangential direction is larger than the magnetic flux density in the normal direction, and in the normal direction. An electrode member (wire electrode 410, mesh electrode, etc.) is disposed in a region where the magnetic flux density is 0 or more, and an electric field is formed between the electrode member and the developing sleeve 403 so that toner particles on the developing sleeve move to the electrode member. The voltage supply means 411 which supplies this voltage to an electrode member was provided. As a result, as described above, when the magnetic brush that is a magnetic brush collides with the developing sleeve 403, it is possible to suppress the toner from adhering firmly to the developing sleeve and to suppress the contamination of the sleeve.

  Further, the electrode member is arranged in a region upstream of the tangential magnetic flux density peak position in the developing sleeve surface moving direction, so that the member is moved from the tangential magnetic flux density peak position to the developing sleeve surface moving position. Compared with the case where it is arranged in the region on the downstream side in the direction, the time for applying the electric field to the magnetic brush can be lengthened, and the toner can be favorably moved to the electrode member.

  Further, by making the absolute value of the voltage applied to the electrode member smaller than the absolute value of the developing bias, an electric field for moving the toner particles on the developing sleeve to the electrode member is formed between the electrode member and the developing sleeve. be able to.

  Further, by setting the voltage applied to the electrode member to an AC voltage, it is possible to remove the toner adhering to the developing sleeve. Thereby, even if the toner cannot be detached from the surface of the developing sleeve by the electric field, the toner layer potential of the toner attached to the developing sleeve can be reduced. As a result, it is possible to suppress an increase in the effective developing potential at the toner adhesion portion of the developing sleeve. Further, by removing electricity, it is possible to weaken the electric adsorption force between the developing sleeve and the toner, and it is possible to easily collect the toner attached to the developing sleeve due to contact with the developer.

  Further, by making the electrode member a mesh-like mesh electrode, it is possible to widen the region where the electric field is applied and to move the toner to the electrode member better than when the electrode member is a wire electrode. .

  Further, according to the image forming apparatus of the present embodiment, a good image can be maintained by providing the developing device.

1: Photosensitive member 4: Developing device 41: Developing roller 42: Supply roller 43: Restricting blade 44: Agitator 140: Developing device 141: Magnet roller 141b: Magnet layer 141a: Core metal 403: Developing sleeve 404: Restricting blades 405, 406 : Stirring / conveying member 407: magnet member 408: carrier 409: toner 410: wire electrode 411: voltage supply means 415: electrode member 505: mesh electrode 505c: protrusion

JP 2003-280340 A

Claims (7)

A rotating non-magnetic sleeve;
A magnetic field generating means fixedly disposed in the non-magnetic sleeve and having a plurality of magnetic poles,
In a developing device that carries a magnetic developer containing at least magnetic particles as a magnetic spike on the surface of the non-magnetic sleeve, and supplies toner particles to a latent image on the latent image carrier in a development region facing the latent image carrier. ,
The magnetic flux density in the tangential direction is larger than the magnetic flux density in the normal direction, and the magnetic flux density in the normal direction is lower than at least one of the plurality of magnetic poles in the moving direction of the surface of the nonmagnetic sleeve. Placing electrode members in zero or more areas,
A development characterized in that a voltage supply means is provided between the electrode member and the nonmagnetic sleeve for supplying a voltage to the electrode member for forming an electric field in which the toner particles on the nonmagnetic sleeve move to the electrode member. apparatus. The developing device according to claim 1.
2. A developing apparatus according to claim 1, wherein said electrode member is arranged in a region upstream of said nonmagnetic sleeve surface movement direction with respect to a peak position of magnetic flux density in a tangential direction. The developing device according to claim 1 or 2,
A developing device characterized in that an absolute value of a voltage applied to the electrode member is smaller than an absolute value of a developing bias. The developing device according to any one of claims 1 to 3,
A developing device, wherein the voltage applied to the electrode member is an AC voltage. In the developing device according to any one of claims 1 to 4,
A developing device characterized in that the electrode member has a mesh shape. A latent image carrier for carrying a latent image;
In an image forming apparatus having a developing means for developing a latent image on the latent image carrier,
An image forming apparatus using the developing device according to claim 1 as the developing means. A latent image forming step of forming a latent image on the latent image carrier;
In an image forming method comprising a developing step of developing a latent image on a latent image carrier using a developing means,
An image forming method using the developing device according to claim 1 as the developing means.

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