JP2006154387A - Image forming apparatus, image forming method, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus free from contamination of an electrifying roller and also free from an image defect caused by contamination in a photoreceptor and the electrifying roller arranged close to each other in a non-contact state. <P>SOLUTION: The image forming apparatus includes: at least an image carrier; the electrifying device to uniformly electrify the image carrier; an exposing device to expose the charged image carrier to form a latent image; and a developing device to develop the latent image formed on the image carrier with toner to visualize. The charging device has a charging roller placed close to the image carrier in a non-contact state. The toner comprises toner mother particles containing at least a binder resin and a colorant, and an external additive. When the toner is added to an aqueous solution containing a surfactant to be dispersed, the proportion of fee external additive released from the toner surface is 5 to 50%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to image formation on a photoreceptor that is used as a non-contact image carrier using a charging roller in forming an electrostatic latent image in an image forming apparatus such as a facsimile, a printer, and a copying machine using electrophotography. A charging member that uniformly applies a charge to a region, a toner with little liberation of an external additive when developing an electrostatic latent image, and an image forming apparatus and an image using the charging member and the toner The present invention relates to a forming method.

  In image forming apparatuses such as facsimiles, printers, and copiers that use electrophotography, various devices, such as charging, image exposure, and development, are arranged around the photosensitive member to form an electrostatic latent image on the photosensitive member. Charging is performed.

  As one means for charging the photosensitive member, a contact member (for example, a charging roller) covered with an elastic conductive member on a core metal is brought into contact with the photosensitive member, and a driving voltage is applied to the charging member. There are charging methods (see Patent Document 1, Patent Document 2, and Non-Patent Document 1).

  However, in the contact charging method, charging is performed while the charging member is in contact with the photoconductor, so that the image is uneven due to the adhering material (for example, toner or dust) adhering to the charging member, or the adhering material adhering to the photoconductor. This causes problems such as uneven wear of the photosensitive layer and shortened life of the photoreceptor.

Therefore, as a charging device that avoids the above problems, charges the photoreceptor uniformly, generates less ozone, and is less contaminated with residual toner on the image carrier, as in Patent Document 3 and Patent Document 4 There is known an image forming apparatus having a charging device in which spacers are provided at both ends of a charging member and are arranged in close contact with an image carrier.
The proximity non-contact arrangement refers to a state in which a minute gap exists between the photosensitive member and the specific range of the gap is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm.
However, even in an image forming apparatus having such a charging device, charging unevenness may occur due to contamination of the charging roller surface, and image defects such as a decrease in image density and solid image unevenness may occur. In order to maintain stable and good image quality, further improvements were necessary.
JP-A 63-149668 JP-A-1-267667 JP 2001-194868 A JP 2002-55508 A Toshiharu Nakamura: Journal of Electrophotographic Society, Vol. 30, no. 3, P.I. 312-317 (1991)

  Therefore, the present invention has been made in view of the above problems, and the problem is that the charging roller is not contaminated in the proximity and non-contact arrangement of the photoconductor and the image defect caused by the contamination occurs. An image forming apparatus and an image forming method are provided.

As a result of intensive studies by the present inventors, these problems are particularly caused when the amount of the external additive of the toner is 1 part by weight or more with respect to 100 parts by weight of the toner base particles, or the number average primary particles of the external additive. It has been revealed that the diameter is particularly remarkable when the diameter exceeds 40 nm, when a lubricant such as a fatty acid metal salt is applied on the photoreceptor, or when a release agent is contained in the toner.
Further investigations have revealed that the cause of contamination of the charging roller is mainly the adhesion of external additives, and contamination of the surface of the charging roller due to scattering from the photoreceptor is a problem.
As a result of further intensive studies on toner external additives, it was found that the above-described problems can be solved by using the following constitution.

That is, the present invention is as follows.
(1) an image carrier, a charging device that uniformly charges the image carrier, an exposure device that exposes the charged image carrier to form a latent image, and a latent image formed on the image carrier. An image forming apparatus having at least a developing device that is developed and visualized by the charging device, wherein the charging device includes a charging roller disposed in close proximity to and non-contact with the image carrier, and the toner includes at least a binder resin. A toner base particle containing a colorant and an external additive are contained, and a free external additive ratio released from the toner surface when the toner is added and dispersed in an aqueous solution containing a surfactant is 5 to 50. % Of the image forming apparatus.

(2) The image forming apparatus according to (1), wherein the external additive is a large particle size external additive having an average primary particle diameter of 90 to 300 nm.
(3) The large particle size external additive is an inorganic oxide, and the addition amount is 0.4 to 5.0 parts by weight with respect to 100 parts by weight of the toner before processing with the external additive. The image forming apparatus according to (1) or (2).

(4) The image forming apparatus according to any one of (1) to (3), wherein the external additive further contains a small particle size external additive having an average primary particle size of 8 to 80 nm. .
(5) The small particle size external additive is silica, and the addition amount is 0.01 to 7.0 parts by weight with respect to 100 parts by weight of the toner before processing with the external additive. 4) The image forming apparatus described above.
(6) The small particle size external additive is titania, and the addition amount is 0.01 to 7.0 parts by weight with respect to 100 parts by weight of the toner before processing with the external additive. 4) The image forming apparatus described above.

(7) The image forming apparatus according to any one of (1) to (6), wherein the toner contains 0.1 to 20 wt% of a release agent.
(8) The image forming apparatus according to any one of (1) to (7), wherein a fatty acid metal salt is applied on the image carrier.
(9) The toner contains toner base particles, an external additive, and a fatty acid metal salt, and the amount of the fatty acid metal salt added is 0.01 to 7.0 with respect to 100 parts by weight of the toner before processing with the external additive. The image forming apparatus according to any one of (1) to (8), wherein the image forming apparatus is a weight part.

(10) The image forming apparatus according to any one of (1) to (9), wherein the voltage applied to the charging device is a DC voltage on which an alternating voltage is superimposed.
(11) Any one of the above (1) to (10), wherein image formation is performed such that the charging device and the image carrier are in a non-contact state and have a gap of at least 10 μm to 100 μm. The image forming apparatus described in the item.

(12) an image carrier, a charging unit that uniformly charges the image carrier, an exposure unit that exposes the charged image carrier to form a latent image, and a latent image formed on the image carrier. An image forming method having at least a developing unit that develops and visualizes the image by the charging unit, wherein the charging unit includes a charging roller disposed in proximity to and non-contact with the image carrier, and the toner includes at least a binder resin. A toner base particle containing a colorant and an external additive are contained, and a free external additive ratio released from the toner surface when the toner is added and dispersed in an aqueous solution containing a surfactant is 5 to 50. %, The image forming method.

(13) A process cartridge that integrally supports at least one member selected from an image carrier, a charging unit that uniformly charges the image carrier, an exposure unit, and a developing unit, and is detachable from the image forming apparatus main body. The charging unit includes a charging roller disposed in close proximity to the image carrier, the developing unit holds toner, and the toner includes toner base particles containing at least a binder resin and a colorant and external additives. A process cartridge comprising an additive, wherein the ratio of free external additives released from the toner surface when the toner is added and dispersed in an aqueous solution containing a surfactant is 5 to 50%.

First, the method for measuring the ratio of free external additives will be described.
[1] To a 200 ml ointment bottle, add 100 ml of ion-exchanged water and 4.4 ml of 33% dry well aqueous solution (trade name dry well, manufactured by Fuji Photo Film Co., Ltd.) containing a surfactant. Add 5 g of toner, mix well by hand shaking 30 times, and let stand for 1 hour or more.
[2] After stirring by hand shaking 20 times, using an ultrasonic homogenizer (trade name homogenizer, model VCX750, CV33, manufactured by SONICS & MATERIALS Ltd.), a dial is set at an output of 30% and ultrasonic energy is applied for 1 minute.
Ultrasonic condition Vibration time: 60 seconds continuous Amplitude: 20W (30%)
Vibration start temperature: 23 ± 1.5 ° C.
[3] The dispersion is suction filtered with a filter paper (trade name: Qualitative filter paper (No. 2, 110 mm), manufactured by Advantech Toyo Co., Ltd.), washed twice with ion-exchanged water, filtered, and free additives are removed. The toner particles are dried.
[4] The amount of the toner additive before and after the removal of the additive is quantified by a fluorescent X-ray method, and the amount of the additive released is evaluated as the release rate.

The value of the additive amount of the toner before and after dispersion measured by the method of [1] to [4] in the previous item is expressed by the following formula:
Free external additive ratio = (amount of external additive before dispersion−amount of residual external additive after dispersion) / amount of external additive before dispersion × 100
The value obtained by substituting for is the free external additive rate.

  For the toner having a plurality of external additives such as titania and alumina in addition to silica, it is sufficient that the free external additive ratio satisfies the range of the free external additive ratio in at least silica. It is preferable to satisfy the range of the ratio of free external additives in all.

  In particular, the external additive added in an amount of 1 part by weight or more with respect to 100 parts by weight of the toner base particles preferably satisfies the range of the free external additive rate.

The ratio of the free external additive obtained by the above measuring method is used as an index indicating the ease with which the external additive attached to the toner is liberated.
When the ratio of the free external additive is less than 5%, the external additive is difficult to be liberated, and the external additive inhibits the generation of the dam effect when cleaning the photoreceptor, and the cleaning property deteriorates. If it exceeds 50%, the external additive is excessively liberated and the free external additive acts as a cause of the photoconductor filming, and the filming is not sufficiently reduced.
Therefore, the ratio of the free external additive is in the range of 5 to 50% in order to cope with both the filming property generated on the surface of the photosensitive member and the cleaning property for preventing the toner from slipping through the tip of the cleaning blade. To.

  When the charging device is non-contact as in the present invention, uneven charging tends to occur significantly when charging is performed only with a DC voltage. Thus, the occurrence of charging unevenness can be suppressed by applying an AC voltage superimposed on the DC voltage and guaranteeing the AC voltage.

  The gap of the charging device is preferably 10 to 100 μm. If the thickness exceeds 100 μm, the charged potential on the surface of the photoconductor may decrease, and the image quality of the output image may deteriorate, for example, the output image may be easily soiled. If the gap is smaller than 10 μm, the photosensitive member surface deposit that has not been removed by the cleaning member on the surface of the photosensitive member is ingested by the charging member, so that a part thereof is transferred to the charging member. This may cause uneven charging during charging.

  According to the image forming apparatus and method of the present invention, the image carrier and the charging roller arranged in close proximity and non-contact are free of contamination of the charging roller and no image defect caused by the contamination by the means for solving the above. This provides an effect that the image forming apparatus can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

  FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention. Here, an embodiment applied to the electrophotographic image forming apparatus 100 will be described. The image forming apparatus 100 includes yellow (hereinafter referred to as “Y”), cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), black (hereinafter referred to as “K”). An image forming apparatus (hereinafter, referred to as “tandem type”) 100 that forms a color image from four color toners. The image forming apparatus 100 includes four photoreceptors 1Y, 1C, 1M, and 1K as latent image carriers. Here, the drum-shaped photosensitive member 1 is taken as an example, but a belt-shaped photosensitive member can also be adopted. Each of the photoreceptors 1Y, 1C, 1M, and 1K is rotationally driven in the direction of the arrow in the drawing while being in contact with the intermediate transfer belt 6a that is a surface moving member.

  FIG. 2 is a schematic view showing the configuration of the process cartridge 2 in which the photoreceptor 1 is disposed. Since the configuration around each of the photoreceptors 1Y, 1C, 1M, and 1K in the process cartridges 2Y, 2C, 2M, and 2K is the same, only one process cartridge 2 is illustrated, and reference numerals Y, C, and M and K are omitted. Around the photosensitive member 1, along the surface movement direction, a developing device 5 that visualizes a latent image to form a toner image, and a neutralizing device before cleaning (hereinafter referred to as "PCL") that neutralizes the charged potential of the photosensitive member 1. 20. A lubricant application device 21 for applying a lubricant to the photosensitive member 1, a cleaning device 7 for cleaning residual toner on the photosensitive member 1, and a charging device 3 for charging the photosensitive member 1 are arranged in this order. Yes.

The configuration of the image forming apparatus 100 of the present invention will be described with reference to FIGS.
The charging device 3 charges the surface of the photoreceptor 1 to a negative polarity. The charging device 3 in the present embodiment includes a charging roller 3a as a charging member that performs a charging process by a so-called proximity charging method. That is, the charging device 3 charges the surface of the photosensitive member 1 by placing the charging roller 3a in close proximity to the surface of the photosensitive member 1 and applying a bias to the charging roller 3a. A charging bias obtained by superimposing an AC bias on a DC bias such that the absolute value of the surface potential of the photoreceptor 1 is 200 to 700 V is applied to the charging roller 3a. The charging device 3 is provided with a cleaning roller 3b for cleaning the surface of the charging roller 3a. Further, even when toner is slightly adhered, the surface of the charging roller 3a may be cleaned by the cleaning roller 3b in order to prevent charging failure such as charging unevenness by the charging roller 3a. As the charging device 3, a thin film is wound around both end portions in the axial direction on the peripheral surface of the charging roller 3 a, and this is installed so as to contact the surface of the photosensitive member 1, whereby the surface of the charging roller 3 a and the photosensitive member are arranged. It is in the state of being very close to the surface of 1 separated by the thickness of the film. As a result, contact with residual toner on the photoreceptor 1 can be reduced.

  An electrostatic latent image corresponding to each color is formed on the surface of the photoreceptor 1 charged in this manner by exposure by the exposure device 4. The exposure device 4 writes an electrostatic latent image corresponding to each color on the photoreceptor 1 based on image information corresponding to each color. The exposure apparatus 4 of the present embodiment is a laser type exposure apparatus, but other types of exposure apparatuses such as an exposure apparatus including an LED array and an image forming unit may be employed.

  In the developing device 5, a developing roller 5a as a developer carrying member is partially exposed from an opening of the casing. Here, a two-component developer composed of a toner and a carrier is used, but a one-component developer not containing a carrier may be used. The developing device 5 receives replenishment of the corresponding color toner from the toner bottle and accommodates it inside. The developing roller 5a is composed of a magnet roller as magnetic field generating means and a developing sleeve that rotates coaxially therearound. The carrier in the developer is transferred to the developing region facing the photosensitive member 1 in a state where it stands on the developing roller 5a by the magnetic force generated by the magnet roller. Here, the developing roller 5 a moves in the same direction at a linear velocity faster than the surface of the photosensitive member 1 in a region facing the photosensitive member 1 (hereinafter referred to as “developing region”). The carrier spiked on the developing roller 5a supplies the toner adhered to the carrier surface to the surface of the photosensitive member 1 and develops it while rubbing the surface of the photosensitive member 1. At this time, a developing bias of about 300 V is applied to the developing roller 5a from a power source (not shown), thereby forming a developing electric field in the developing region.

  The intermediate transfer belt 6a in the transfer device 6 is stretched around three support rollers 6b, 6c, and 6d, and is configured to endlessly move in the direction of the arrow in the figure. On the intermediate transfer belt 6a, the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred so as to overlap each other by an electrostatic transfer method. Although there is a configuration using a transfer charger in the electrostatic transfer system, a configuration using a transfer roller 6e that generates less transfer dust is adopted here. Specifically, the primary transfer rollers 6eY, 6eC, 6eM, and 6eK as the transfer devices 6 are disposed on the back surface of the portion of the intermediate transfer belt 6a that is in contact with each of the photoreceptors 1Y, 1C, 1M, and 1K. . Here, a primary transfer region is formed by the portion of the intermediate transfer belt 6 a pressed by the primary transfer roller 6 e and the photosensitive member 1. When transferring the toner images on the photoreceptors 1Y, 1C, 1M, and 1K onto the intermediate transfer belt 6a, a positive bias is applied to the primary transfer roller 6e. Accordingly, each primary transfer area (hereinafter referred to as a transfer area) is described. ) Is formed, and the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are electrostatically attached to the intermediate transfer belt 6a and transferred.

A belt cleaning device 6f is provided around the intermediate transfer belt 6a to remove toner remaining on the surface thereof. The belt cleaning device 6f is configured to collect unnecessary toner attached to the surface of the intermediate transfer belt 6a with a fur brush and a cleaning blade. The collected unnecessary toner is transported from the belt cleaning device 6f to a waste toner tank (not shown) by a transport means (not shown). The transfer belt 6a is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁶ to 10 ¹¹ Ωcm, and is a single-layer resin layer or a plurality of resins.

  Further, a transfer device 9 is arranged in the right direction of FIG. The transfer device 9 includes a transfer conveyance belt 9a and a transfer roller 9b. Here, the toner image superimposed on the intermediate transfer member 6 a is transferred onto the recording paper conveyed from the paper supply unit 10. Therefore, in the apparatus 100 of the present invention, the toner is transferred twice to form an image on the recording paper. The transfer of the transfer device 9 is performed by applying a voltage having a polarity opposite to that of the toner to the transfer roller 9b. A secondary transfer region is formed between the intermediate transfer belt 6a and the secondary transfer roller 9b, and a recording sheet as a recording member is fed into this portion at a predetermined timing. This recording paper is accommodated in a paper feed cassette 10 on the lower side of the exposure device 4 in the drawing, and is conveyed to the secondary transfer region by a pickup roller, a registration roller pair 11 and the like. Then, the toner images superimposed on the intermediate transfer belt 6a are collectively transferred onto the recording paper on the transfer conveyance belt 9a in the secondary transfer region. During the secondary transfer, a positive bias is applied to the secondary transfer roller 9b, and the toner image on the intermediate transfer belt 6a is transferred onto the recording paper by the transfer electric field formed thereby.

Here, the lubricant application device 21 includes a lubricant molded body 21b housed in a fixed case, and a brush roller 21a that contacts the lubricant molded body 21b to scrape off the lubricant and apply it to the photoreceptor 1. And a pressure spring 21c that presses the lubricant molded body 21b against the brush roller 21a. The lubricant molding 21 b is formed in a rectangular parallelepiped shape, and the brush roller 21 b has a shape extending in the axial direction of the photoreceptor 1. The lubricant molded body 21b is urged by a pressure spring 21c against the brush roller 21a so that almost all of the molded lubricant 21b can be used up. Since the molded lubricant 21b is a consumable product, its thickness decreases with time, but since it is pressurized by the pressure spring 21c, it is always in contact with the brush roller 21a.
The lubricant applying device 21 may be provided in the cleaning device 7 together with a cleaning blade 7a as a cleaning means. As a result, by rubbing the photosensitive member 1 with the brush-like roller 21a, it is possible to easily collect the toner attached to the brush by the lubricant molded body 21b or the flicker.

  Examples of the lubricant include fatty acid metal salts, silicone oils, fluororesins, and the like, and these can be used alone or in combination of two or more. In particular, fatty acid metal salts are preferred. As the fatty acid of the fatty acid metal salt, a linear hydrocarbon is preferable, for example, myristic acid, palmitic acid, stearic acid, oleic acid and the like are preferable, and stearic acid is more preferable. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, and iron. Among these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferable, and zinc stearate is most preferable.

The cleaning device 7 includes a cleaning blade 7a, a support member 7b, a toner recovery coil 7c, and a blade pressure spring 7d. The cleaning blade 7a removes the toner on the photoreceptor 1 remaining after the transfer. The support member 7b is attached to the cleaning device by being attached to the support member 7b, but the support member 7b is not particularly limited, but metal, plastic, ceramic, or the like can be used.
In the cleaning blade 7a, examples of the elastic body having a low friction coefficient include urethane elastomer, silicone elastomer, and fluorine elastomer among urethane resin, silicone resin, and fluororesin. As the cleaning blade 7a, a thermosetting urethane resin is preferable, and a urethane elastomer is particularly preferable from the viewpoints of wear resistance, ozone resistance, and contamination resistance. Elastomer includes rubber. The cleaning blade 7a preferably has a hardness (JIS-A) in the range of 65 to 85 degrees. The cleaning blade 7a preferably has a thickness of 0.8 to 3.0 mm and a protrusion amount of 3 to 15 mm. Further, as other conditions, the contact pressure, the contact angle, the amount of biting, and the like can be determined as appropriate.

  The lubricant application device 21 provided in the image forming apparatus 100 of the present invention reduces the interaction coefficient between the photoreceptor 1 and the toner by reducing the friction coefficient of the surfaces of the photoreceptor 1 and the intermediate transfer body 6a. The toner developed on the electrostatic latent image on the photoreceptor 1 can be easily separated and the transfer rate can be increased. Further, it is possible to suppress an increase in friction between the cleaning blade 7a and the photosensitive member 1 and improve the cleaning property. As described above, it is preferable that the friction coefficient of the surface of the photoreceptor 1 is set to 0.4 or less by applying a lubricant to the surface of the photoreceptor 1. The coefficient of friction can be measured using an Euler belt type measuring device.

  In the image forming apparatus 100 of the present invention, it is preferable to externally add an inorganic oxide having an average primary particle size of 90 to 300 nm to the toner used here. When the average particle size of the inorganic oxide is less than 90 nm, the inorganic oxide is buried in the toner by use over time in which the toner receives an impact force by stirring and mixing with the carrier or the toners in the developing device 5. When the average particle diameter exceeds 300 nm, the inorganic oxide easily desorbs from the toner surface, and is desorbed from the toner surface by mixing and stirring in the developing device 5 to change the toner characteristics. Will occur. The average particle size of the inorganic oxide is more preferably 90 to 150 nm.

  Further, it is preferable to contain 0.4 parts by weight or more with respect to 100 parts by weight of the toner before processing with the external additive. Since the inorganic oxide has a large particle size, the number per unit weight is small, and if it is less than 0.4 parts by weight, the number of inorganic oxides on the toner surface is small and the effect of improving the transfer rate is small. However, it does not exceed 5.0 parts by weight. If the amount exceeds 5.0 parts by weight, the amount present on the toner surface is large, and the toner surface is covered and the additive floats, causing an abnormal image.

Examples of the inorganic oxide of 90 to 300 nm of the present invention include silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, iron oxide, magnesium oxide, calcium oxide, manganese oxide, zinc oxide, strontium oxide, strontium titanate, barium oxide, Examples include cesium oxide or other inorganic oxides. Interoxide compounds such as strontium titanate and barium titanate can also be used.
Further, among these oxides, silicon oxide is preferable. In the case of silicon oxide, the color is white and it can be used for a color toner, and is highly safe. As manufacturing methods, two types of manufacturing methods have been established, and amorphous and spherical shapes can be easily produced. In the case of the amorphous form, there is a combustion type silica in which silicon tetrachloride is burned in the gas phase, and in the case of the spherical form, there is a method for producing silicon oxide by a sol-gel method in which silicon oxide is precipitated in the aqueous phase. In the sol-gel method, alkoxysilane is hydrolyzed and condensed in an aqueous solution to deposit silicon oxide. Examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetraisoproxysilane, and tetrabutoxysilane. Examples of the hydrolysis catalyst include ammonia, urea, monoamine and the like.
The inorganic oxide enters between the toner base and the image carrier or intermediate transfer member and functions as a spacer. By making the inorganic oxide spherical, the contact area can be reduced, and toner transfer can be improved.

  Furthermore, it is effective to perform a surface modification treatment with a hydrophobizing agent or the like. Typical examples of the hydrophobizing agent include the following. Dimethyldichlorosilane (DDS), trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyl Trichlorosilane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexamethyldisilazane (HMDS), hexaphenyldisilazane, hexatolyldisilazane and the like.

  The toner used here includes a pulverization method, a polymerization method (suspension polymerization, emulsion polymerization dispersion polymerization, emulsion aggregation, emulsion association, etc.), but is not limited to these production methods. As an example of the pulverization method, first, the above-mentioned resin, pigment or dye as a colorant, charge control agent, release agent, other additives, etc. are sufficiently mixed by a mixer such as a Henschel mixer, and then batch type. The constituent materials are well kneaded using a two-roll, Banbury mixer, continuous twin-screw extruder, continuous single-screw kneader, or the like, and cut after rolling and cooling. The toner kneaded product after cutting is crushed, coarsely pulverized using a hammer mill, etc., and further pulverized by a fine pulverizer or mechanical pulverizer using a jet stream, and a classifier or Coanda effect using a swirling airflow Is classified to a predetermined particle size by a classifier using Thereafter, inorganic fine particles are externally added by a mixer and mixed to obtain a toner. Moreover, an example of the polymerization method is shown. Use of a toner in which a toner composition containing at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is crosslinked and / or extended in the presence of resin fine particles in an aqueous medium. preferable.

  Further, fine particles can be added to the toner in addition to the inorganic oxide described above. Specific examples of the fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, and diatomaceous earth. And chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. In addition, polymer fine particles, such as polystyrene obtained by soap-free emulsion polymerization, suspension polymerization, and dispersion polymerization, methacrylic acid ester, acrylic acid ester copolymer, polycondensation system such as silicone, benzoguanamine, nylon, thermosetting Polymer particles made of resin may be used. Such external additives can be surface treated to increase hydrophobicity and prevent deterioration of flow characteristics and charging characteristics even under high humidity. For example, silane coupling agents, silylating agents, silane coupling agents having an alkyl fluoride group, organic titanate coupling agents, aluminum coupling agents, silicone oils, modified silicone oils and the like are preferable surface treatment agents. It is done. In particular, it is preferable to use hydrophobic silica and hydrophobic titanium oxide obtained by subjecting silica and titanium oxide to the above surface treatment. The primary particle diameter of the fine particles is preferably 8 to 80 nm, more preferably 8 to 50 nm, and particularly preferably 8 to 40 nm. The use ratio of the fine particles is preferably 0.01 to 7.0 parts by weight, particularly preferably 0.1 to 2.0 parts by weight with respect to 100 parts by weight of the toner.

As a method for containing these 90 to 300 nm inorganic oxides and fine particles, the fine particles and toner base particles are usually placed in a mixer and stirred.
As another method, the toner can be externally added in a water-based and / or alcohol-based solvent. An inorganic oxide is added to the toner dispersed in an aqueous solvent and adhered to the toner surface. Further, when this inorganic oxide has been subjected to a hydrophobization treatment, it may be dispersed after a small amount of alcohol or the like is used in combination to lower the interfacial tension to facilitate wetting. Thereafter, the solvent can be removed by heating and fixed to prevent desorption. Thereby, the inorganic oxide can be uniformly dispersed on the toner surface.
Further, when the toner and the additive are dispersed in the aqueous solvent, the additive can be dispersed more uniformly on the toner surface by adding the surfactant. Further, it is preferable to use an inorganic oxide or a surfactant having a polarity opposite to that of the toner.

Furthermore, in addition to the inorganic oxides and fine particles described above, a lubricant that can be applied to the photosensitive member and the intermediate transfer member can be added to the toner. As the lubricant to be added, it is preferable to use the same lubricant as that applied to the photosensitive member or the intermediate transfer member from the viewpoint of stabilizing the effect of the lubricant. Therefore, a fatty acid metal salt is preferable as the lubricant added to the toner. As the fatty acid of the fatty acid metal salt, a linear hydrocarbon is preferable, for example, myristic acid, palmitic acid, stearic acid, oleic acid and the like are preferable, and stearic acid is more preferable. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, and iron. Of these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferred, and zinc stearate is most preferred.
The addition amount of the fatty acid metal salt is preferably 0.01 to 7.0 parts by weight with respect to 100 parts by weight of the toner before processing with the external additive.
When the fatty acid metal salt is added, it is preferable to add it at the same time as other inorganic fine particles, or after adding the inorganic fine particles, from the viewpoint of maintaining the free external additive rate of the inorganic fine particles.

  Further, in the image forming apparatus 100 of the present invention, the image quality and transfer rate by transfer are greatly affected by the transfer voltage, current value and toner charge amount, toner surface form, toner surface external additive type, and addition amount. receive. Further, some external additives such as inorganic oxides on the toner surface are transferred together with the toner by transfer, and others are left on the photoreceptor.

FIG. 3 is a diagram schematically showing the force received by the external additive on the toner surface.
This is because the toner on the photoconductor 1 and the inorganic oxide sandwiched between the photoconductor 1 and the electrostatic force on the photoconductor 1 due to the force of the electric field generated by the transfer roller and the charge of the external additive. The image is subjected to an electrical attraction force and a physical adhesion force to the photoreceptor 1. The amount of inorganic oxide remaining is determined by the balance between these two forces. The toner and the inorganic oxide have different detachment forces depending on electrostatic force, van der Waals force, amount of the inorganic oxide pierced on the toner surface, adhesiveness on the toner surface, and the like. By controlling these forces, the amount of inorganic oxide scattered during transfer is prevented, and contamination of the charging roller is prevented. Specifically, the amount of the inorganic oxide that pierces the toner surface is controlled by the mixing strength at the time of adding the inorganic oxide, or the stirring strength in the step of externally adding to the toner in an aqueous and / or alcohol solvent. There are a method of controlling depending on the type of the surfactant, and a method of prescribing and controlling an appropriate amount of the external additive according to the toner surface. As a result of the control, it is preferable that the free external addition rate of the toner is 5 to 50%, and particularly preferably 10 to 35%.

At this time, the inorganic oxide remaining on the photoreceptor 1 reaches the cleaning device. The cleaning blade in this cleaning device is arranged in a counter manner. Compared with the trailing method, the counter method is less likely to cause a cleaning failure and less likely to cause a cleaning abnormality due to the occurrence of bounding and chatter noise. Even if the toner particles have a small particle size and are spheroidized and have low cleaning properties, the toner used in the present invention contains inorganic fine particles, thereby reducing the adhesion between the transfer residual toner and the photoreceptor 1. Therefore, it can be cleaned with a cleaning blade.
Further, when the inorganic oxide released from the toner by the transfer reaches the cleaning blade, the inorganic oxide is dammed up and stays at the tip of the cleaning blade, thereby contributing to cleaning of the toner that reaches the cleaning blade thereafter.

Here, as the toner used in the present invention, all known resins can be used.
First, as the binder resin, styrene such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene, and a substituted polymer 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 ketone copolymer Coalescence, styrene-butadiene copolymer, Styrene copolymers such as tylene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polychlorinated Vinyl, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, Aromatic petroleum resins, chlorinated paraffin, paraffin wax and the like can be mentioned, and these can be used alone or in combination.

  As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, parachlor ortho nitro Nilin Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Po Azo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Anine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

For color toners, the use of pigment-based colorants is more preferred from the viewpoint of migration of colorants to the surroundings, light resistance, chargeability, fixability, and the like. If it is a yellow toner, specifically C.I. I. Pingment Yellow 180, C.I. I. Pingment Yellow155, C.I. I. Pingment Yellow 74, C.I. I. Pingment Yellow 93 or the like is preferable in terms of safety, light resistance, and transparency. In the case of Magenta toner, specifically, C.I. I. Pingment Red 57-1, C.I. I. Pingment Red 122, C.I. I. Pingment Red 184, C.I. I. Pingment Violet 19, C.I. I. Pingment Red 269 or the like is preferable in terms of light resistance, transparency, and color. In the case of Cyan toner, specifically, C.I. I. Pingment Blue 15-1, C.I. I. Pingment Blue 15-2, C.I. I. Pingment Blue 15-3, C.I. I. Pingment Blue 16 or the like is preferable in terms of light resistance, transparency and color.
In particular, when a color pigment is used, it is preferable to use a master batch in which a resin and a pigment are dispersed at a ratio of about 5: 5 to 2: 1 in order to help disperse the pigment in the toner.
For black toner, the use of carbon black is very advantageous from the viewpoint of cost. In addition, since the color of black toner using only carbon black changes from red to yellow, the color may be adjusted by adding a complementary colorant or the like.

  The color toner of the present invention may contain a charge control agent as necessary. All known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified). Quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Nitronine-based dye Bontron 03, quaternary ammonium salt Bontron P-51, metal-containing azo dye Bontron S-34, oxynaphthoic acid metal complex E-82, salicylic acid metal complex E- 84, E-304, X-11, phenolic condensate E-89 (above, manufactured by Orient Chemical Industries), quaternary ammonium salt molybdenum complex TP-302, TP-415, salicylic acid metal complex TN -105 (above, manufactured by Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy charge PSY VP2038, triphenylmethane derivative copy blue PR, quaternary ammonium salt copy charge NEG VP2036, copy charge NX VP434 (above , Manufactured by Hoechst), LRA-901, LR-147 (Japan (Manufactured by Carlit Co., Ltd.), copper phthalocyanine, perylene, quinacridone, azo pigments, and other polymer compounds having functional groups such as sulfonic acid groups, carboxyl groups, and quaternary ammonium salts.

  The amount of charge control agent used in the present invention is determined by the toner production method including the charge control agent amount, the type of binder resin, the presence or absence of additives used as necessary, and the dispersion method. Although it is not limited uniquely, Preferably it is used in 0.1-10 weight part with respect to 100 weight part of binder resin. The range of 0.3 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the main charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the flowability of the developer is reduced, and the image density is reduced. Incurs a decline.

  The wax (release agent) used in the toner of the present invention preferably has a melting point of 40 to 120 ° C., particularly preferably 50 to 110 ° C. When the melting point of the wax is higher than 120 ° C., the fixing property at a low temperature may be insufficient. On the other hand, when the melting point is lower than 40 ° C., the offset resistance and durability may be lowered. The melting point of the wax can be obtained by differential scanning calorimetry (DSC). That is, the melting peak value when a sample of several mg is ripened at a constant temperature increase rate, for example, (10 ° C./min) is defined as the melting point.

Examples of the wax that can be used in the present invention include solid paraffin wax, microwax, rice wax, fatty acid amide wax, fatty acid wax, aliphatic monoketone, fatty acid metal salt wax, fatty acid ester wax, and partial kenne. Fatty acid ester wax, silicone varnish, higher alcohol, carnauba wax, and the like. Also, polyolefins such as low molecular weight polyethylene and polypropylene can be used. Particularly, a polyolefin having a softening point of 70 to 150 ° C. by the ring and ball method is preferable, and a polyolefin having a softening point of 120 to 150 ° C. is more preferable.
The wax is preferably contained in an amount of 0.1 to 20 wt% with respect to the toner.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited only to these examples.
Example 1
Preparation of spherical hydrophobic silica Tetramethoxysilane and aqueous ammonia were reacted at 50 ° C. to obtain spherical silica by a sol-gel method. After washing with water, without performing a drying operation, methanolization was performed, silica was dispersed in toluene, and hexamethyldisilazane (HMDS) treatment was performed to obtain [Inorganic oxide particles 1]. The inorganic oxide particles were stirred in methanol with an ultrasonic disperser, and the average particle size D ₅₀ was measured with a laser diffraction / scattering particle size distribution device.

Preparation of toner base particles (toner base 1)
Yellow, magenta, cyan, and black toner base particles having the formulations shown in Table 1 below were obtained by kneading / pulverization / classification to obtain particles having a weight average particle diameter of 7 μm.

(Toner base 2)
The yellow, magenta, cyan, and black toner base particles having the formulations shown in Table 2 below were obtained by kneading / pulverizing / classifying particles having a weight average particle diameter of 7 μm.

Mixing of external additives 100 parts by weight of [Toner Base 1] obtained above, 1.0 part of [Inorganic Oxide Particles 1], hydrophobic silica (HDK H1303, manufactured by Clariant Japan, average particle diameter D ₅₀ : 13 nm 4 parts of toner were obtained by mixing 0.5 part by weight with a Henschel mixer 20B manufactured by Mitsui Mining Co., Ltd. for 3 minutes at a rotating speed of 2500 rpm and passing through a 38 μm sieve to remove aggregates.

<Image quality evaluation machine for copied images>
The black toner obtained in Example 1 was evaluated for image quality and the like with only one black toner using the prototype shown in FIG.

(Examples 2 to 6)
In Examples 2 to 6, as shown in Table 3, the toner was prepared in the same manner as in Example 1 by changing the type of toner base, the amount of external additive, the type of external additive, and the external additive mixing conditions. Created and evaluated. In Examples 2 and 4 and 6, in addition, hydrophobic titanium oxide (MT-150AI, manufactured by Teika, average particle diameter D ₅₀ : 15 nm) was used. In Examples 5 and 6, zinc stearate (SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.) was used in addition to the above, and an apparatus for applying zinc stearate on an image carrier was improved and used.

(Comparative Examples 1 to 3)
In Comparative Examples 2 to 3, as shown in Table 3, toners were prepared and evaluated in the same manner as in Example 1 by changing the type of the toner base, the amount of the external additive, and the external additive mixing conditions. In Comparative Examples 1 and 2, in order to loosely adhere the base toner and the external additive, the amount of the external additive was increased and the mixing rotation speed was reduced. In Comparative Example 3, in order to strongly adhere the base toner and the external additive, the prescription amount of the external additive was decreased and the mixing rotation speed was increased.

(Evaluation methods)
For each of the examples and comparative examples, the cleaning property and charging roller contamination were confirmed together with the external additive release rate of each toner, and image evaluation was performed.

1. Cleanability Using the prototype shown in FIG. 1, 20,000 originals with an image area ratio of 25% were output under high temperature and high humidity (30 ° C., 90% RH) conditions, and the residual toner on the photoconductor was scotch tape. It is transferred to a white paper (manufactured by Sumitomo 3M Co., Ltd.) and measured with X-Rite 938 (manufactured by X-Rite). Were evaluated as ○, 0.010 or more and less than 0.02 as Δ, and 0.02 or more as ×.

Charging roller stains Using the prototype shown in FIG. 1, 20,000 original images with an image area ratio of 25% were output under high temperature and high humidity (30 ° C., 90% RH) conditions. The originating stain was confirmed. Good samples with no dirt were marked with ◎, those with slight dirt but no problem were marked with ○, those with slight dirt that could be used were marked with △, and those with bad dirt that could not be used.

  As can be seen from Table 4, in Examples 1 to 6, the amount of each external additive formulated is within the range of the above claims, so that the external additive liberation rate is between 5% and 50%, and the cleaning property, Good results were obtained with respect to the fouling of the charging roller. In Comparative Examples 1 to 3, the external additive liberation rate is out of this range, and there are problems with cleaning performance and charging roller contamination.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is the schematic of the process cartridge which concerns on embodiment of this invention. FIG. 3 is a diagram schematically illustrating toner sandwiched between a photoreceptor and an intermediate transfer member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Process cartridge 3 Charging apparatus 3a Charging roller 3b Cleaning roller 4 Exposure apparatus 5 Developing apparatus 5a Developing roller 5b Agitating and conveying screw 5c Doctor blade 6 Transfer apparatus 6a Intermediate transfer body 6b, 6c, 6d Support roller 6e Primary transfer roller 6f Belt cleaning device 7 Cleaning device 7a Cleaning blade 7b Support member 7c Recovery screw 7d Pressure spring 8 Fixing device 8a Heating roller 8b Pressure roller 9 Transfer conveyance device 9a Transfer conveyance belt 9b Secondary transfer roller 10 Paper feed unit 11 Registration roller 12 Paper discharge roller 20 Light emitting means (PCL)
21 Coating device 21a Brush-like roller 21b Lubricant molding 21c Pressure spring

Claims (13)

  An image carrier, a charging device that uniformly charges the image carrier, an exposure device that exposes the charged image carrier to form a latent image, and a latent image formed on the image carrier is developed with toner. An image forming apparatus having at least a developing device that is visualized in such a manner that the charging device has a charging roller disposed in close proximity to and non-contact with the image carrier, and the toner includes at least a binder resin and a colorant. It contains toner base particles and external additives, and the ratio of free external additives released from the toner surface when the toner is added and dispersed in an aqueous solution containing a surfactant is 5 to 50%. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the external additive is a large particle size external additive having an average primary particle diameter of 90 to 300 nm.   The external additive having a large particle size is an inorganic oxide, and the amount of the additive is 0.4 to 5.0 parts by weight with respect to 100 parts by weight of the toner before processing with the external additive. The image forming apparatus according to 1 or 2.   The image forming apparatus according to claim 1, wherein the external additive further contains a small particle size external additive having an average primary particle diameter of 8 to 80 nm.   5. The small particle size external additive is silica, and the addition amount is 0.01 to 7.0 parts by weight with respect to 100 parts by weight of toner before processing with the external additive. Image forming apparatus.   5. The small particle size external additive is titania, and the addition amount is 0.01 to 7.0 parts by weight with respect to 100 parts by weight of toner before processing with the external additive. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the toner contains 0.1 to 20 wt% of a release agent.   The image forming apparatus according to claim 1, wherein a fatty acid metal salt is applied on the image carrier.   The toner contains toner base particles, an external additive, and a fatty acid metal salt, and the amount of the fatty acid metal salt added is 0.01 to 7.0 parts by weight with respect to 100 parts by weight of the toner before treatment with the external additive. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the voltage applied to the charging device is a DC voltage on which an alternating voltage is superimposed.   11. The image formation according to claim 1, wherein image formation is performed such that the charging device and the image carrier are in a non-contact state and have a gap of at least 10 μm to 100 μm. apparatus.   An image carrier, a charging unit for uniformly charging the image carrier, an exposure unit for exposing the charged image carrier to form a latent image, and developing the latent image formed on the image carrier with toner. An image forming method having at least a developing unit that is visualized by the charging unit, wherein the charging unit includes a charging roller disposed in proximity to and non-contact with the image carrier, and the toner includes at least a binder resin and a colorant. It contains toner base particles and external additives, and the ratio of free external additives released from the toner surface when the toner is added and dispersed in an aqueous solution containing a surfactant is 5 to 50%. An image forming method. In the process cartridge that integrally supports at least one means selected from an image carrier and a charging unit that uniformly charges the image carrier, an exposure unit, and a development unit, and is detachable from the main body of the image forming apparatus, the charging unit The means has a charging roller arranged in close contact with the image carrier, the developing means holds toner, and the toner contains toner base particles containing at least a binder resin and a colorant and an external additive. A process cartridge characterized in that when the toner is added and dispersed in an aqueous solution containing a surfactant, the ratio of free external additives released from the toner surface is 5 to 50%.

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