JP7140604B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus for visualizing an electrostatic charge image.

In recent years, with the widespread use of image forming apparatuses such as copiers and printers, image forming apparatuses are required to have higher speed, longer life, and higher image quality.
As a means for achieving high image quality in image forming apparatuses, the particle size of toner is being reduced.
When the particle diameter of the toner becomes smaller, it becomes difficult for the toner to be scraped off by the cleaning blade in the cleaning process, and the cleaning failure in which the toner easily slips through the cleaning blade is likely to occur.

In addition, particles having a particle size of less than 50 nm, such as silica, are often externally added to the developer as a fluidity-imparting agent. Once these microparticles adhere, it is difficult to remove them even with a cleaning member or a bias.
As a method for improving poor cleaning, Patent Document 1 proposes a method of adding strontium titanate powder to toner particles. The strontium titanate powder used in these methods has an excellent polishing effect and is effective in preventing filming and fusion caused by adhesion of toner on the photoreceptor. It was not sufficient to remove silica adhered to the means.

JP-A-2005-338750

One aspect of the present invention is directed to providing an image forming apparatus capable of suppressing contamination of charging means and maintaining stable image characteristics at a high level.

As a result of extensive studies by the present inventors, it has been found that the following configuration is important in order to provide an image forming apparatus capable of suppressing contamination of charging means and maintaining stable image characteristics at a high level. The discovery led to the present invention.
That is, one aspect of the present invention includes an image carrier, a charging device that rotates while being in contact with the image carrier, a voltage applying device that applies only a DC voltage to the charging device, and the charged image carrier. exposure means for forming an electrostatic latent image on the surface of the image carrier; developing means for developing the electrostatic latent image formed on the surface of the image carrier using toner to form a toner image; a transfer means for transferring the toner image onto a transfer material; a cleaning member for cleaning toner remaining on the surface of the image carrier; a fixing means for fixing the toner image transferred onto the transfer material; An image forming apparatus having
The charging means is a charging roller, the outermost layer of the charging roller is composed of a particle part and a non-particle part, the 10-point average roughness Rz of the outermost layer is 1 to 20 μm, and the outermost layer is 2 Rz of the 10-point average roughness in the area of 10 μm × 10 μm range of the non-particle portion (sea portion) when quantified is 1.0 μm or less,
The toner has toner particles and strontium titanate particles and silica particles present on the surface thereof,
The strontium titanate particles are
(i) the number average particle diameter (D1T) of the primary particles is 10 nm or more and less than 95 nm;
(ii) an average circularity of 0.700 or more and 0.920 or less;
(iii) having a maximum peak (a) at a diffraction angle (2θ) of 32.00 deg or more and 32.40 deg or less in CuKα characteristic X-ray diffraction, and a half width of the maximum peak (a) of 0.23 deg or more and 0.23 deg or more; is 50 deg or less, and the intensity (Ia) of the maximum peak (a) and the maximum peak intensity (Ix) in the range of 24.00 deg or more and 28.00 deg or less of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction are as follows. satisfies the formula (1),
(iv) The sum of the contents of strontium oxide and titanium oxide when the total amount of all oxides is assumed to be 100% by mass when all the elements detected by fluorescent X-ray analysis are assumed to be contained in oxides. is 98.0% by mass or more,
The silica particles have a number average particle diameter (D1S) of primary particles of 5 nm or more and 300 nm or less,
The content of the strontium titanate particles is 20 parts by mass or more per 100 parts by mass of the silica particles ,
The image forming apparatus is characterized in that the total content of the silica particles is 8.0 parts by mass or more and 15.0 parts by mass or less with respect to 100 parts by mass of the toner particles .
(Ix)/(Ia) ≤ 0.010 Formula (1)
In another aspect of the present invention, there is provided an image carrier, charging means rotating while being in contact with the image carrier, voltage applying means for applying only a DC voltage to the charging means, and the charged image. exposure means for forming an electrostatic latent image on the surface of a carrier; and developing means for developing the electrostatic latent image formed on the surface of the image carrier with toner to form a toner image. a transfer means for transferring the toner image onto a transfer material; a cleaning member for cleaning the toner remaining on the surface of the image carrier; and a fixing means for fixing the toner image transferred onto the transfer material. , an image forming apparatus having
The charging means is a charging roller, the outermost layer of the charging roller is composed of a particle part and a non-particle part, the 10-point average roughness Rz of the outermost layer is 1 to 20 μm, and the outermost layer is 2 Rz of the 10-point average roughness in the area of 10 μm × 10 μm range of the non-particle portion (sea portion) when quantified is 1.0 μm or less,
The toner has toner particles and strontium titanate particles and silica particles present on the surface thereof,
The strontium titanate particles are
(i) the number average particle diameter (D1T) of the primary particles is 10 nm or more and less than 95 nm;
(ii) an average circularity of 0.700 or more and 0.920 or less;
(iii) having a maximum peak (a) at a diffraction angle (2θ) of 32.00 deg or more and 32.40 deg or less in CuKα characteristic X-ray diffraction, and a half width of the maximum peak (a) of 0.23 deg or more and 0.23 deg or more; is 50 deg or less, and the intensity (Ia) of the maximum peak (a) and the maximum peak intensity (Ix) in the range of 24.00 deg or more and 28.00 deg or less of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction are as follows. satisfies the formula (1),
(iv) The sum of the contents of strontium oxide and titanium oxide when the total amount of all oxides is assumed to be 100% by mass when all the elements detected by fluorescent X-ray analysis are assumed to be contained in oxides. is 98.0% by mass or more,
The silica particles have a number average particle diameter (D1S) of primary particles of 5 nm or more and 300 nm or less,
The content of the strontium titanate particles is 20 parts by mass or more per 100 parts by mass of the silica particles,
The silica particles are composed of first silica particles having a number average particle size (D1S1) of 5 nm or more and 20 nm or less and second silica particles having a number average particle size (D1S2) of 80 nm or more and 120 nm or less. is,
The relationship between the number average particle size (D1T) of the strontium titanate particles, the number average particle size (D1S1) of the first silica particles, and the number average particle size (D1S2) of the second silica particles is shown below. This image forming apparatus satisfies Expression (2) .
(Ix)/(Ia) ≤ 0.010 Formula (1)
D1S2>D1T>D1S1 Expression (2)

According to one aspect of the present invention, it is possible to provide an image forming apparatus capable of suppressing adhesion of an external additive contained in toner to a charging unit and maintaining stable image characteristics at a high level.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment; FIG. 1 is a schematic diagram of a charging roller according to an embodiment; FIG.

Embodiments for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangement of the components described in this embodiment should be changed as appropriate according to the configuration of the device to which the invention is applied and various conditions. is not limited to the following embodiments.
(Description of each part of the image forming apparatus)
FIG. 1 is a configuration diagram of an in-line (four-drum system) color image forming apparatus. The image forming apparatus includes an image forming section 1a for forming a yellow image, an image forming section 1b for forming a magenta image, an image forming section 1c for forming a cyan image, and a black image. The four image forming portions (image forming units) of the image forming portion 1d are provided. These four image forming units are arranged in a line at regular intervals.

Photosensitive drums 2a, 2b, 2c, and 2d, which are image carriers, are arranged in the image forming units 1a, 1b, 1c, and 1d, respectively. In this embodiment, the photosensitive drums 2a, 2b, 2c, and 2d are negatively charged organic photoreceptors having a photosensitive layer (not shown) on a drum substrate (not shown) made of aluminum or the like. (illustrated) rotates at a predetermined process speed.

Charging rollers 3a, 3b, 3c and 3d and developing devices 4a, 4b, 4c and 4d are arranged around the photosensitive drums 2a, 2b, 2c and 2d, respectively. The charging roller is a roller-shaped charging means that rotates in contact with the photosensitive drum and charges the photosensitive drum. A voltage applying means (not shown) for applying a DC voltage to the charging roller is connected to the charging roller.
Further, above the photosensitive drums 2a, 2b, 2c, and 2d, exposure means (hereinafter also referred to as "exposure device") 7a for forming an electrostatic latent image on the surface of the charged photosensitive drum is provided. , 7b, 7c and 7d are installed respectively. Yellow toner, cyan toner, magenta toner and black toner are accommodated in each developing means (hereinafter also referred to as "developing device") 4a, 4b, 4c and 4d, respectively. The developing device develops the electrostatic latent image formed on the surface of the photosensitive drum to form a toner image.
Around the photosensitive drums 2a, 2b, 2c and 2d are cleaning members (hereinafter also referred to as "drum cleaning devices") 6a, 6b, 6c and 6d for cleaning toner remaining on the surfaces of the photosensitive drums. are installed respectively.

A rotatable endless intermediate transfer belt 8, which is an intermediate transfer member, is installed at a position facing each image forming section. The intermediate transfer belt 8 is stretched by a drive roller 11 , a secondary transfer counter roller 12 and a tension roller 13 . A drive roller 11 to which a motor (not shown) is connected rotates (moves) the intermediate transfer belt 8 in the direction of the arrow (counterclockwise direction). The secondary transfer opposing roller 12 is in contact with the secondary transfer roller 15 via the intermediate transfer belt 8 to form a secondary transfer portion.

A belt cleaning device 16 is installed outside the intermediate transfer belt 8 to remove and collect transfer residual toner remaining on the surface of the intermediate transfer belt 8 . In addition, in the rotation direction of the intermediate transfer belt 8, on the downstream side of the secondary transfer portion where the secondary transfer counter roller 12 and the secondary transfer roller 15 are in contact, there is a heat pressure processing for fixing the toner onto the transfer material. , a fixing device 17 is installed. The fixing device 17 has a fixing roller 17a and a pressure roller 17b.

(Explanation of image forming operation)
When a controller issues a start signal for starting an image forming operation, a transfer material (recording medium) is sent out sheet by sheet from a cassette (not shown) and conveyed to registration rollers (not shown). At that time, the registration rollers (not shown) are stopped, and the leading edge of the transfer material is waiting just before the secondary transfer portion.

On the other hand, in the image forming units 1a, 1b, 1c and 1d, when the start signal is issued, the photosensitive drums 2a, 2b, 2c and 2d start rotating at a predetermined process speed. The photosensitive drums 2a, 2b, 2c and 2d are uniformly charged by charging rollers 3a, 3b, 3c and 3d, respectively. In the examples described later, it is negatively charged.

The exposure devices 7a, 7b, 7c and 7d scan and expose the respective photosensitive drums 2a, 2b, 2c and 2d with laser beams to form electrostatic latent images. The potential of the photosensitive drum was adjusted to -600 V after being charged by the charging roller and -200 V after being exposed by the exposure device (image portion). -500V. The process speed (driving speed of the photosensitive drum) was 240 mm/sec, the image forming width, which is the length in the direction perpendicular to the conveying direction, was 300 mm, the toner charge amount was about -30 μC/g, and the solid image portion on the photosensitive drum was is set to be about 0.4 mg/cm ² .

As for the order of image formation, first, in order to form a yellow image, a yellow toner is caused to adhere to the electrostatic latent image formed on the photosensitive drum 2a by the developing device 4a to visualize it as a toner image. . This yellow toner image is primarily transferred onto the rotating intermediate transfer belt 8 .

As the intermediate transfer belt 8 rotates, the area on the intermediate transfer belt 8 onto which the yellow toner image has been transferred moves toward the image forming portion 1b. Also in the image forming section 1b, the magenta toner image formed on the photosensitive drum 2b is similarly transferred onto the yellow toner image on the intermediate transfer belt 8 so as to be superimposed thereon. Subsequently, cyan and black toner images formed by the photosensitive drums 2c and 2d of the image forming units 1c and 1d are successively superimposed on the yellow and magenta toner images superimposed and transferred on the intermediate transfer belt 8 in the same manner. Together, a full-color toner image is formed on the intermediate transfer belt 8 .

Then, the transfer material is conveyed to the secondary transfer portion by registration rollers (not shown) at the timing when the leading edge of the full-color toner image formed on the intermediate transfer belt 8 is moved to the secondary transfer portion. . The full-color toner image formed on the intermediate transfer belt 8 is transferred onto the transfer material collectively by the secondary transfer roller 15 to which a secondary transfer voltage (a voltage opposite to that of the toner (positive polarity)) is applied. be transcribed. The transfer material on which the full-color toner image is formed is conveyed to the fixing device 17 . At the fixing nip formed by the fixing roller 17a and the pressure roller 17b, the full-color toner image is heated and pressurized, thermally fixed on the surface of the transfer material, and then discharged to the outside.

(Detailed description of charging roller)
The charging roller 3 will be described with reference to the cross-sectional view of FIG. First, the elastic layer 31 is formed on the outer periphery of the support 30 and the surface layer 32 is formed on the elastic layer 31 .
The outermost layer of the charging roller is composed of a particle portion and a non-particle portion. The 10-point average roughness Rz of the outermost layer is 1 to 20 μm. When the outermost layer is binarized, the non-particle portion (sea portion) has a 10-point average roughness Rz of 1.0 μm or less in an area of 10 μm×10 μm.

The support 30 is a shaft (made of steel, the surface of which is plated with nickel) that is excellent in wear resistance and bending stress. The elastic layer 31 can be made of rubber, thermoplastic elastomer, or the like, which is conventionally used as an elastic layer of a charging roller. Specifically, the following materials are mentioned. A rubber composition comprising polyurethane, silicone rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, styrene-butadiene-styrene rubber, epichlorohydrin rubber, or the like as a base rubber. Alternatively, the type of thermoplastic elastomer is not particularly limited, and one or more thermoplastic elastomers selected from general-purpose styrene-based elastomers, olefin-based elastomers, and the like can be suitably used. Solid rubber or foamed rubber may be used depending on the required elastic force.

A predetermined conductivity can be imparted to the elastic layer 31 by adding a conductivity imparting agent. The conductivity-imparting agent added to the elastic layer 31 is not particularly limited, and includes the following. Lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, modified fatty acid/dimethylethylammonium perchlorate, chlorate, hydroborofluorate, ethosulfate, bromide Cationic surfactants such as benzyl salts, quaternary ammonium salts such as benzyl halides such as benzyl chloride salts, aliphatic sulfonates, higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher Anionic surfactants such as alcohol phosphate ester salts and higher alcohol ethylene oxide addition phosphate ester salts, amphoteric ionic surfactants such as various betaines, nonionics such as higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, and polyhydric alcohol fatty acid esters antistatic agents such as antistatic agents, Li+, Na+ such as LiCF ₃ SO ₃ , NaClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl, Na+, K+ metal salts of group 1 of the periodic table, or NH Electrolytes such as ⁴⁺ salts. In addition, metal salts of Group 2 of the periodic table such as Ca ²⁺ and Ba ²⁺ such as Ca(ClO ₄ ) ₂ , and these antistatic agents contain at least one hydroxyl group, carboxyl group, primary or secondary amine Those having a group having an active hydrogen that reacts with isocyanate such as a group. Furthermore, complexes of these and polyhydric alcohols such as 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol and polyethylene glycol and derivatives thereof, or monools such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether or conductive carbon such as ketjen black EC, acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, etc., oxidation treatment Color (ink) carbon, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, metals and metal oxides such as nickel, copper, silver, germanium, polyaniline, polypyrrole, polyacetylene and the like. ^In this case ^, the amount of these conductivity ^- imparting agents to be blended is appropriately selected according to the type of composition. It is adjusted to be ⁶ Ω·cm.

Specific examples of materials forming the surface layer 32 include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, nylon resins, epoxy resins, polyvinyl acetal resins, vinylidene chloride resins, fluorine resins, and silicone resins. Both organic and water-based agents can be used. Further, the surface layer 32 may be added with a conductivity-imparting agent to impart or adjust conductivity. The conductivity-imparting agent added to the surface layer 32 is not particularly limited, and includes the following. Conductive carbon such as ketjen black EC and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, carbon for color (ink) with oxidation treatment, pyrolytic carbon, Natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium and other metals or metal oxides. Furthermore, when the electroconductivity-imparting agent is used in an organic solvent, the surface of the electroconductivity-imparting agent is preferably subjected to surface treatment such as silane coupling treatment in consideration of dispersibility. Also, the amount of the conductivity-imparting agent added can be appropriately adjusted so as to obtain a desired electrical resistance value. It is known that charging is stabilized when the electrical resistance of the surface layer 32 is basically higher than that of the elastic layer 31, and the volume resistivity is required to be 10 ³ to 10 ¹⁵ Ω·cm. is preferably 10 ⁵ to 10 ¹⁴ Ω·cm.

Particles to be added to the outermost conductive resin layer, which is the surface layer 32, include urethane particles, nylon particles, acrylic particles, and copolymer resins such as acrylic/styrene, which are insulating particles (10 ¹⁰ Ω·cm or more). can be used. In addition to these, it is also possible to use particles obtained by solidifying an inorganic material such as silica particles, titanium oxide, zinc oxide, or tin oxide with a resin. In order to improve the dispersibility, it is more preferable to perform a pretreatment such as silane coupling treatment in the same manner as the electroconductivity-imparting agent.

The method of forming the charging roller is not particularly limited, but a method of preparing a paint containing each component and applying this paint by a dipping method, a spray method, or a roll coating method to form a coating film is preferable. Used. In this case, when the outer layer is to be a plurality of layers, dipping, spraying, and roll coating may be repeated using paints for forming the respective layers.

<Description of specific manufacturing method>
A specific manufacturing method of the charging roller 3 will now be described. The manufacturing recipe described below is the recipe for the charging roller of Example 1 (charging roller No. 4 in Table 1) in Examples described later. etc. are different, but the manufacturing method itself is the same. As a general rule, "parts" means "parts by weight".
First, formation of the elastic layer 31 will be described.
The following ingredients were kneaded for 20 minutes using an open roll.
・ Epichlorohydrin rubber (trade name: Epichroma CG102, manufactured by Daiso Co., Ltd.)
100 parts Calcium carbonate 30 parts as a filler Colored grade carbon (trade name: Seast SO, manufactured by Tokai Carbon Co., Ltd.) as a reinforcing material for improving polishing 2 parts Zinc oxide 5 parts As a plasticizer 10 parts of DOP (dioctyl phthalate) 1 part of 2-mercaptobenzimidazole as an antioxidant 3 parts of perchloric acid quaternary ammonium salt represented by the following formula

Further, the following ingredients were added and kneaded for 15 minutes using an open roll.
・ Dibenzothiazyl disulfide (DM) as a vulcanization accelerator (product name: Ouchi Shinko Chemical Industry Co., Ltd. Noxcellar DM-P) 1 part ・ Tetramethylthiuram monosulfide (TS) as a vulcanization accelerator (product name: Dai Naishin Kagaku Kogyo Co., Ltd. Noxcellar TS) 0.5 parts Sulfur as a vulcanizing agent 1 part The obtained kneaded product is extruded into a cylindrical shape with a rubber extruder and then cut, and steam at a temperature of 160 ° C. is used in a vulcanizing can. for 40 minutes to obtain a primary vulcanized tube.

Next, a metal-rubber thermosetting adhesive (trade name: METALOC U-20. Co., Ltd.) was applied to the axially central portion of the cylindrical surface of the cylindrical support 30 (made of steel, the surface of which was plated with nickel). ) manufactured by Toyo Kagaku Kenkyusho) was applied, dried at a temperature of 80° C. for 30 minutes, and then dried at a temperature of 120° C. for 1 hour. This support was inserted into the primary vulcanization tube, and then secondary vulcanization and adhesive curing were performed by heating in an electric oven at a temperature of 160° C. for 2 hours to obtain an unpolished product.
After cutting off both ends of the rubber portion of this unpolished product, the rubber portion was ground with a rotary grindstone to obtain a charging roller having a conductive elastic layer with a ten-point average roughness Rz of 7 μm.

Next, the surface layer 32 was formed. 50 parts of conductive tin oxide powder (trade name: SN-100P, manufactured by Ishihara Sangyo Co., Ltd.), 450 parts of a 1% isopropyl alcohol solution of trifluoropropyltrimethoxysilane, and glass beads having an average particle diameter of 0.8 mm. 300 parts were added and dispersed on a paint shaker for 48 hours. After that, the dispersion is filtered through a 500-mesh screen, then the solution is heated in a hot water bath at 100°C while being stirred with a Nauta Mixer, alcohol is removed and dried, and a silane coupling agent is applied to the surface. A surface-treated conductive tin oxide was obtained.
Furthermore, 145 parts of lactone-modified acrylic polyol (trade name: Plaxel DC2009 (hydroxyl value: 90 KOHmg/g), manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 455 parts of methyl isobutyl ketone (MIBK) to obtain a solid content of 24.17. A mass % solution was prepared.

To 200 parts of this acrylic polyol solution, the following components were added, placed in a 450 mL mayonnaise bottle, and dispersed for 12 hours using a paint shaker while cooling.
・50 parts of the surface-treated conductive tin oxide powder ・0.01 parts of silicone oil (trade name: SH-28PA, manufactured by Dow Corning Toray Silicone Co., Ltd.) ・Fine particle silica (primary particle diameter: 0.02 μm) 1 .2 parts Crosslinked acrylic monodisperse particles Large particle size particles (trade name: Chemisnow MX-1000 (number average particle size 10 μm), manufactured by Soken Chemical Co., Ltd.) 4.5 parts Crosslinked acrylic monodisperse particles Small particle size particles (Product name: Chemisnow MX-500 (number average particle size 5 μm), manufactured by Soken Chemical Co., Ltd.) 18 parts Glass beads with a diameter of 0.8 mm 200 parts

Further, 330 parts of this dispersion was mixed with the following components, stirred in a ball mill for 1 hour, and finally the solution was filtered through a 200-mesh screen to adjust the solid content of the surface layer paint to 43% by mass. got the paint.
- Block type isocyanurate trimer of isophorone diisocyanate (IPDI) (trade name: Vestanato B1370, manufactured by Degussa Huls) 27 parts - Isocyanurate trimer of hexamethylene diisocyanate (HDI) (trade name: Duranate TPA) -B80E, manufactured by Asahi Chemical Industry Co., Ltd.) 17 parts The surface layer coating material was applied to the surface of the charging roller having the conductive elastic layer by dipping. After coating at a lifting speed of 400 mm/min, air drying for 30 minutes, reversing the axial direction, coating again at a lifting speed of 400 mm/min, air drying for 30 minutes, and drying at a temperature of 160 ° C. for 1 hour using an oven. , room temperature of 25° C. and relative humidity of 50% for 48 hours.

<Description of Method for Measuring Surface Properties of Charging Roller>
In Table 1, Rz is the ten-point average roughness specified in JIS B0601 (1994). Using a laser microscope (VK-X1000, manufactured by KEYENCE CORPORATION), a surface image of the charging roller is photographed with a 50x objective lens to obtain two-dimensional height data of an area of 273 μm in width and 204 μm in height. An automatic correction was performed for the curvature of After that, using an analysis application manufactured by Keyence Corporation, the average value of the ten-point average roughness at three points in the circumferential direction (in increments of 120° from an arbitrary point) was obtained.

Also, regarding the surface roughness of the sea portion of the surface of the charging roller, the laser microscope (VK-X1000, manufactured by KEYENCE CORPORATION) was similarly used to photograph the surface image of the charging roller with a 50-fold objective lens. Then, the curvature of the surface is automatically corrected, binarization processing is performed based on the roughness histogram peak (if there are multiple peaks, the peak value on the lower limit side is used as the reference). It was determined that the part that was Ten square regions of 10 μm wide×10 μm long were selected from the portion judged to be the sea portion, and the average value of the ten-point average roughness of these ten locations was obtained.

In addition, the influence of variations cannot be avoided only by obtaining from one image. For this reason, there are 3 positions in the longitudinal direction for each charging roller (the center, 2 cm from the left end of the roller, and 2 cm from the right end), and 3 positions in the rotational direction, for a total of 9 positions. image was taken.
Then, 10 points were selected from each image, and the average value of the 10-point average roughness of the 10 points was obtained. That is, the average value of the ten-point average roughness selected from the first image, the average value of the ten-point average roughness selected from the second image, . . . An average value of ten point average roughnesses selected from the ninth image was obtained.
Furthermore, the average value calculated from the first image, the average value calculated from the second image, ... the sum of the average values calculated from the ninth image was divided by 9 to obtain the average value of the average values. . By obtaining the average value of the average values of each image, the influence of variation was sufficiently reduced.

(toner)
The toner according to the present invention has toner particles and strontium titanate particles and silica particles present on the surfaces thereof.

(Detailed explanation about strontium titanate)
(Number average particle size of primary particles of strontium titanate)
In the present invention, the number average particle diameter (D1T) of the primary particles of strontium titanate present on the surfaces of the toner particles is characterized by being 10 nm or more and less than 95 nm.
When the number average particle size of the primary particles is 10 nm or more, the strontium titanate is effectively finely dispersed on the toner particle surfaces, and excessive charging of the toner is suppressed. When the number-average particle size of the primary particles is less than 95 nm, sufficient adhesion of strontium titanate to the toner particles can be obtained, the charge amount of the toner can be accelerated, and excessive charging of the toner can be effectively prevented. can be suppressed to Therefore, even when used in high-temperature, high-humidity or low-temperature, low-humidity environments, sleeve ghosting is less likely to occur. can be provided.

The number average particle diameter of primary particles of strontium titanate is preferably 10 nm or more and 70 nm or less, more preferably 10 nm or more and 50 nm or less. The number average particle size of the primary particles of strontium titanate can be controlled by adjusting the concentrations of the titanium raw material and the strontium raw material, the reaction temperature and the reaction time.

(Average circularity of strontium titanate particles)
In the present invention, the average circularity of the strontium titanate particles present on the surfaces of the toner particles should be 0.700 or more and 0.920 or less.
As a result, the strontium titanate particles detached from the toner near the cleaning blade can pass through the cleaning blade.
The fact that the average particle diameter of the strontium titanate particles and the average circularity of the primary particles are within the above ranges means that the particles are smaller than conventional strontium titanate particles and have rounded corners. As a result, the shape of the strontium titanate is easier to pass through the cleaning blade than the conventional strontium titanate.

In the present invention, strontium titanate has a maximum peak (a) at a diffraction angle (2θ) of 32.00 deg or more and 32.40 deg or less in CuKα characteristic X-ray diffraction, and the half width of the maximum peak (a) is It is characterized by being 0.23 deg or more and 0.50 deg or less.
The maximum peak (a) is due to the (1,1,0) plane peak of the strontium titanate crystal.

As a result of extensive studies, the inventors of the present invention have found that it is very important to control the half-value width to 0.23 deg or more and 0.50 deg or less.
In general, the half width of a diffraction peak in X-ray diffraction is related to the crystallite size of strontium titanate. One primary particle is composed of a plurality of crystallites, and the crystallite diameter is the size of each individual crystallite that constitutes the primary particle.

A diffraction peak represents an angle at which the maximum intensity is obtained in diffraction of a crystal plane. Further, the half-value width is the width represented by the difference between θ2 and θ1, where P is the maximum intensity of the diffraction peak and θ1 and θ2 are the angles on the 2θ axis that take P/2 (θ2>θ1). That is. Full width at half maximum is also called full width at half maximum. Note that the magnitude of the maximum intensity must be obtained by removing the background value.

In the present invention, crystallites refer to individual crystal grains that constitute particles, and crystallites aggregate to form particles. Crystallite size and grain size are independent. If the crystallite size of strontium titanate is small, the half-value width increases, and if the crystallite size of strontium titanate is large, the half-value width decreases.
The half width of the diffraction peak in X-ray diffraction of the strontium titanate of the present invention is 0.23 deg or more and 0.50 deg or less, which indicates that the crystallite size is smaller than that of conventional strontium titanate.

As the crystallite diameter of strontium titanate decreases, the number of grain boundaries (crystal grain boundaries) between crystallites existing in primary particles increases. Grain boundaries are considered points for trapping charges. Therefore, when the charge amount of the toner is small, the charge is likely to be trapped by the crystal grain boundaries, so that the triboelectric charge amount of the toner rises quickly. On the other hand, since the inside of the crystallite of strontium titanate easily leaks the electric charge of the toner, if the toner is excessively charged and the amount of electric charge that can be trapped by the crystal grain boundary is exceeded, the electric charge passes through the inside of the crystallite, It is believed that excessive charging of the toner can be controlled.

That is, by controlling the half-value width to 0.23 deg or more and 0.50 deg or less, it is possible to obtain the effect of speeding up the charging of the toner and suppressing the excessive charging of the toner, which could not be obtained with the conventional strontium titanate. I was able to As a result, even when a large number of images of the same pattern are printed, it is possible to keep the charging property of the toner in the printed portion and the non-printed portion of the developing sleeve uniform. Therefore, even when used in high-temperature and high-humidity environments or low-temperature and low-humidity environments, we believe that the effect of suppressing sleeve ghosts has been dramatically enhanced.

Further, when the charging rise of the toner on the developing sleeve is accelerated and the effect of suppressing excessive charging is improved, the charge amount distribution of the toner becomes sharper. If the toner has a broad charge distribution, especially if it is used for a long period of time in a high image quality may be degraded.

According to the present invention, the effects of accelerating the charging rise of the toner and suppressing excessive charging are excellent. As a result, the charge amount distribution of the toner becomes sharp, and it is possible to provide a toner with good fine line reproducibility and dot reproducibility even when used for a long period of time in a high-temperature, high-humidity environment.

In the present invention, it is important that the half width of the diffraction peak in X-ray diffraction of strontium titanate is 0.23 deg or more and 0.50 deg or less. It is preferably 0.25 deg or more and 0.45 deg or less, and more preferably 0.28 deg or more and 0.40 deg or less. Within the above range, the sleeve ghost is better even when used in a high temperature and high humidity environment or a low temperature and low humidity environment, and the fine line reproducibility of the toner is good even when used in a high temperature and high humidity environment for a long time. and good dot reproducibility.

In the present invention, the intensity (Ia) of the maximum peak (a) and the maximum peak intensity (Ix) in the range of 24.00 deg or more and 28.00 deg or less of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction are calculated by the following formula. It is important to satisfy (1).
(Ix)/(Ia) ≤ 0.010 Formula (1)
(Ix) represents the peaks of SrCO ₃ and TiO ₂ derived from the raw material of strontium titanate.

If (Ix)/(Ia) does not satisfy formula (1), it means that the purity of strontium titanate is low. For example, if SrCO ₃ and TiO ₂ derived from the raw material of strontium titanate remain as impurities, the maximum peak intensity (Ix) of these will increase and the formula (1) will not be satisfied. In this case, impurities tend to be localized at grain boundaries, and charges are not trapped at the grain boundaries and tend to leak. Therefore, the rise of charging is delayed.

On the other hand, when the formula (1) is satisfied, the purity of the strontium titanate is high and the amount of impurities localized at the grain boundaries is small, so that charges are easily trapped at the grain boundaries and charging rises quickly. As a result, even when used in a high-temperature and high-humidity environment, sleeve ghosts are less likely to occur, and fine line reproducibility and dot reproducibility are improved even when used for a long period of time in a high-temperature and high-humidity environment.
It is important that formula (1) satisfies (Ix)/(Ia)≤0.010, preferably (Ix)/(Ia)≤0.008. It is desirable that there be no (Ix) peaks derived from impurities.
(Ix)/(Ia) can be controlled by the mixing ratio of titanium raw material and strontium raw material, reaction temperature and reaction time. Furthermore, it can be controlled by acid washing the strontium titanate slurry after the reaction.

In the present invention, regarding strontium titanate, all the elements detected by fluorescent X-ray analysis are considered to be oxides, and the content of strontium oxide and titanium oxide when the total amount of all oxides is 100% by mass is It is important that it is 98.0% by mass or more.

The fact that the content is less than 98.0% by mass means that there are many impurities other than strontium titanate inside the crystal. When there are many impurities inside the crystal of strontium titanate, the impurities give strain to the crystal, and the effect increases the half-value width. In this case, although the half-value width can be increased, it is difficult to control the crystallite diameter to be small. Therefore, the rise of charging is delayed.

By setting the content of strontium oxide and titanium oxide to 98.0% by mass or more, the crystallite size of the strontium titanate particles can be controlled to be small, which has the effect of speeding up charging and suppressing excessive charging. can be made better. As a result, even when used in high-temperature, high-humidity or low-temperature, low-humidity environments, sleeve ghosts are less likely to occur, and even when used in high-temperature, high-humidity environments for long periods of time, fine line reproducibility and dot reproducibility are improved. .
The content of strontium oxide and titanium oxide is preferably 98.2% by mass or more, and although the upper limit is not particularly limited, it is preferably 100% by mass or less. The content can be controlled by refining the titanium raw material to reduce impurities.

(Specific method for producing strontium titanate)
The method for preparing strontium titanate is not particularly limited, but it is produced, for example, by the following method.
For example, strontium nitrate, strontium chloride, or the like is added to a titania sol dispersion obtained by adjusting the pH of a hydrous titanium oxide slurry obtained by hydrolyzing an aqueous titanyl sulfate solution. And after heating to reaction temperature, it can manufacture by adding aqueous alkali solution. The reaction temperature is preferably 60-100°C.

In order to control the half width of the maximum peak (a), in the step of adding the alkaline aqueous solution, the time taken to add the alkaline aqueous solution is preferably 60 minutes or less. Particles with a small crystallite size can be obtained by setting the addition rate of the alkaline aqueous solution to 60 minutes or less.
Furthermore, in the step of adding the alkaline aqueous solution, it is preferable to add while applying ultrasonic vibration in order to control the half-value width. In the reaction step, by applying ultrasonic field vibration, the deposition rate of crystals increases, and particles with a small crystallite diameter can be obtained.

In addition, it is preferable to rapidly cool the aqueous solution after the reaction by adding an alkaline aqueous solution in order to control the half-value width. As a method of quenching, for example, a method of adding pure water cooled to 10° C. or less until reaching a desired temperature can be used. By quenching, it is possible to suppress the crystallite size from increasing in the cooling step.
On the other hand, as a method of controlling the half-value width, a strong processing method (method of mechanically applying a strong force to the inorganic fine particles) may be used. As strong working, methods such as ball milling, high-pressure twisting, falling weight working, particle impact, and air shot peening can be used.

(Detailed description about silica particles)
In the present invention, the number average particle diameter (D1S) of the primary particles of the silica particles present on the surface of the toner particles is set to 5 nm or more and 300 nm or less.
When the number average particle diameter of the primary particles of silica particles present on the surface of the toner particles is 5 nm or more, the effect of scraping off the strontium titanate in the charging roller is most exhibited. By setting the number average particle diameter of the primary particles of the silica particles present on the surface of the toner particles to 300 nm or less, the silica particles form a blocking layer on the cleaning blade, and the amount of strontium titanate passing through can be controlled.

(Content of strontium titanate particles)
In the present invention, the content of strontium titanate particles is 20 parts by mass or more per 100 parts by mass of silica particles.
When the content is 20 parts by mass or more, the effect of scraping off the strontium titanate in the charging roller is exhibited.

(Total content of silica particles)
The total content of silica particles is preferably 8.0 parts by mass or more and 15.0 parts by mass or less with respect to 100 parts by mass of toner particles.
When the amount is 8.0 parts by mass or more, the silica particles form a blocking layer on the cleaning blade, and the amount of strontium titanate passing through can be controlled. is to ensure Contamination of the charging roller can be prevented by using 15.0 parts by mass or less.

(Relationship between particle size of silica particles and particle size of strontium titanate particles)
Silica particles are
first silica particles having a number average particle diameter (D1S1) of 5 nm or more and 20 nm or less;
Consists of second silica particles having a number average particle diameter (D1S2) of 80 nm or more and 120 nm or less,
The relationship between the number average particle size (D1T) of the strontium titanate particles, the number average particle size (D1S1) of the first silica particles, and the number average particle size (D1S2) of the second silica particles is shown below. It is preferable to satisfy formula (2).
D1S2>D1T>D1S1 Expression (2)

As described above, the second silica having a large particle size is preferably larger than the strontium titanate particles because it mainly contributes to the formation of the blocking layer on the cleaning blade. This allows the strontium titanate particles to pass through the cleaning blade. Furthermore, since the first silica is smaller than the strontium titanate particles, an effect of scraping off the strontium titanate particles by the charging roller is exhibited.

Silica fine particles used in the present invention include wet-process silica such as precipitation method and sol-gel method, and dry-process silica such as deflagration method and fumed method, but dry-process silica is more preferable because of ease of shape control.
Dry silica uses a silicon halogen compound or the like as a raw material. Silicon tetrachloride is used as the silicon halogen compound, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone, or a mixture of silicon tetrachloride and silanes can also be used as a raw material.

After the raw material is vaporized, it reacts with water produced as an intermediate in an oxyhydrogen flame, that is, a so-called flame hydrolysis reaction to obtain the desired silica. For example, it utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the reaction formula is as follows.
SiCl ₄ +2H ₂ +O ₂ →SiO ₂ +4HCl
An example of producing the dry silica used in the present invention will be described below.

After oxygen gas was supplied to the burner and the ignition burner was ignited, hydrogen gas was supplied to the burner to form a flame. Next, a flame hydrolysis reaction was carried out, and the produced silica powder was collected. The number average particle size and shape can be arbitrarily adjusted by appropriately changing the silicon tetrachloride flow rate, the oxygen gas supply flow rate, the hydrogen gas supply flow rate, and the retention time of silica in the flame.
As a method for crushing silica fine particles, for example, a crusher such as an atomizer (manufactured by Tokyo Atomizer Manufacturing Co., Ltd.) can be used.

(median diameter of toner)
The toner preferably has a median diameter (D50) of 3.0 μm or more and 6.0 μm or less on a number basis. The strontium titanate of the present invention exerts its effect as the particle size of the toner becomes smaller and the cleaning blade passes through more severely.

(Toner manufacturing method)
The method for producing the toner is not particularly limited except that it includes a step of fixing the strontium titanate particles and silica particles to the surface of the toner particles by a treatment using hot air or the like, and conventionally known production methods can be used. .
Here, a procedure for manufacturing toner using a pulverization method will be described.

In the raw material mixing step, a binder resin, a colorant, a wax, and, if necessary, other components such as a charge control agent are weighed in predetermined amounts as materials constituting the toner particles, and mixed.
Examples of the mixing device include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechanohybrid (manufactured by Nippon Coke Kogyo Co., Ltd.).

Next, the mixed materials are melt-kneaded to disperse wax and the like in the binder resin. In the melt-kneading step, a pressure kneader, a batch type kneader such as a Banbury mixer, or a continuous kneader can be used. A single-screw or twin-screw extruder is the mainstream because of its superiority in continuous production. For example, KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.), TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), PCM kneader (manufactured by Ikegai Co., Ltd.), twin-screw extruder (Kei · C.K.), Co-kneader (manufactured by Buss), Kneedex (manufactured by Nippon Coke Industry Co., Ltd.).
Furthermore, the resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water or the like in the cooling step.

The cooled resin composition is then pulverized to a desired particle size in a pulverization step. In the pulverization process, after coarsely pulverizing with a pulverizer such as a crusher, a hammer mill, or a feather mill, furthermore, Kryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.) or an air jet type fine pulverizer.
After that, if necessary, inertial classification Elbow Jet (Nippon Mining Co., Ltd.), centrifugal classification Turboplex (Hosokawa Micron Corporation), TSP Separator (Hosokawa Micron Corporation), Faculty (Hosokawa Micron Corporation) Toner particles are obtained by classifying using a classifier or a sieving machine such as the one manufactured by K.K.

When the weight average particle size of the toner particles is 4.0 μm or more and 8.0 μm or less, the effect of the external additive can be sufficiently obtained, which is preferable. Furthermore, the circularity of the toner particles may be increased by subjecting the particles to mechanical impact or heat treatment using hot air or the like. The average circularity is preferably 0.962 or more and 0.972 or less in order to increase the chances of charge transfer and friction between toner particles and increase the charging rising speed.
Inorganic particles and optionally other external additives are added to the toner particles and mixed (externally added). Examples of the mixing apparatus include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechanohybrid (manufactured by Nippon Coke Kogyo Co., Ltd.), each of which is preferably used.
Next, the method for measuring each physical property according to the present invention will be described.

<Method for measuring number average particle size>
The number average particle size of primary particles such as silica particles is measured using a field emission scanning electron microscope (FE-SEM) S-4700 (manufactured by Hitachi Ltd.).
The photograph was taken at a magnification of 50,000 times, and after further enlarging the photographed photograph by a factor of 2, from the obtained FE-SEM photograph image, the surface where the silica particles (primary particles) adhered to the surface of the toner particles are exposed. Measure the maximum diameter (major axis diameter) La. At the same time, the height Lb of the exposed surface is calculated.
From La and Lb, the maximum diameter of silica particles is calculated as (La2/4+Lb2)/Lb.
The same calculation is performed for 100 randomly selected silica particles (primary particles), and the number average particle diameter of the silica particles (primary particles) is obtained.

<Method for calculating average circularity>
The average circularity is measured by a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) under measurement and analysis conditions during calibration work.
The measurement principle of the flow-type particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation) is to capture a still image of flowing particles and perform image analysis. A sample added to the sample chamber is delivered to the flat sheath flow cell by a sample aspiration syringe. The sample fed into the flat sheath flow is sandwiched between the sheath fluids to form a flat flow. The sample passing through the flat sheath flow cell is irradiated with strobe light at intervals of 1/60 second, and it is possible to photograph the flowing particles as a still image. In addition, since the flow is flat, it is imaged in a focused state. A particle image is captured by a CCD camera, and the captured image is image-processed at an image processing resolution of 512×512 pixels (0.37×0.37 μm per pixel). , the projected area S, the perimeter L, and the like are measured.

Next, using the area S and the perimeter L, the equivalent circle diameter and circularity are determined. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle image, and the degree of circularity C is the value obtained by dividing the perimeter of the circle obtained from the equivalent circle diameter by the perimeter of the projected particle image. and is calculated by the following formula.
Circularity C = 2 x (π x S) 1/2/L
When the particle image is circular, the degree of circularity is 1.000. After calculating the circularity of each particle, the range of circularity from 0.200 to 1.000 is divided into 800, the arithmetic mean value of the obtained circularities is calculated, and the value is defined as the average circularity.

A specific measuring method is as follows.
First, 20 mL of ion-exchanged water from which impure solids and the like have been previously removed is placed in a glass container. As a dispersing agent, "Contaminon N" (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, Wako Pure Chemical Industries, Ltd.) was used. )) is diluted 3 times by mass with deionized water, and 0.2 mL of the diluted solution is added.
Further, 0.02 g of a measurement sample is added, and dispersion treatment is performed for 2 minutes using an ultrasonic disperser to obtain a dispersion liquid for measurement. At that time, the temperature of the dispersion liquid is appropriately cooled to 10° C. or higher and 40° C. or lower. As the ultrasonic disperser, a desktop ultrasonic cleaner disperser with an oscillation frequency of 50 kHz and an electrical output of 150 W (for example, "VS-150" (manufactured by Vervoklea Co., Ltd.)) is used. A fixed amount of deionized water is added, and 2 mL of the contaminon N is added to this water tank.

For the measurement, the flow-type particle image analyzer equipped with a standard objective lens (10x) is used, and a particle sheath "PSE-900A" (manufactured by Sysmex Corporation) is used as the sheath liquid.
A dispersion liquid prepared according to the procedure is introduced into the flow type particle image analyzer, and 3000 toner particles are counted in the HPF measurement mode and the total count mode. Then, the binarization threshold during particle analysis is set to 85%, the analysis particle diameter is limited to a circle equivalent diameter of 1.985 μm or more and less than 39.69 μm, and the average circularity of toner particles and the like is obtained.

In the measurement, automatic focus adjustment is performed using standard latex particles (for example, "RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5200A" manufactured by Duke Scientific diluted with deionized water) before starting the measurement. After that, it is preferable to perform focus adjustment every two hours from the start of measurement.
In addition, in the present embodiment, a flow-type particle image analyzer that has been calibrated by Sysmex Corporation and has received a calibration certificate issued by Sysmex Corporation is used. Except for limiting the analyzed particle size to a circle equivalent diameter of 1.985 μm or more and less than 39.69 μm, the measurement is performed under the measurement and analysis conditions when the calibration certificate was received.

<X-ray diffraction measurement>
Measurement is performed using MiniFlex600 (manufactured by Rigaku Corporation) under the following conditions.
The sample to be measured is placed on a non-reflective sample plate (manufactured by Rigaku Corporation) that does not have a diffraction peak within the measurement range, while lightly pressing the powdery inorganic fine particles (strontium titanate) flat. Once flattened, the sample plate is set in the device.

[Measurement conditions for X-ray diffraction]
Tube: Cu
Parallel beam optical system voltage: 40 kV
Current: 15mA
Start angle: 3°
End angle: 60°
Sampling width: 0.02°
Scan speed: 10.00°/min
Divergence slit: 0.625deg
Scattering slit: 8.0mm
Light receiving slit: 13.0 mm (Open)
The half-value width and peak intensity of the obtained X-ray diffraction peak are calculated using analysis software "PDXL" manufactured by Rigaku Corporation.

<Fluorescent X-ray measurement>
Fluorescent X-ray measurement of inorganic fine particles (strontium titanate or inorganic fine particles A) is performed before the surface treatment when the surface is treated with a silane coupling agent or the like.
Elements from Na to U in the inorganic fine particles are directly measured in a He atmosphere using a wavelength dispersive X-ray fluorescence spectrometer Axios advanced (manufactured by Spectris Co., Ltd.). Using the liquid sample cup attached to the device, put a PP (polypropylene) film on the bottom, add a sufficient amount of the sample, form a layer of uniform thickness on the bottom, and close the lid. Measured under the condition that the output is 2.4 kW. An FP (fundamental parameter) method is used for the analysis. At that time, it is assumed that all detected elements are oxides, and their total mass is 100% by mass. The content (% by mass) of strontium oxide (SrO) and titanium oxide (TiO ₂ ) with respect to the total mass is obtained as an oxide conversion value using software UniQuani5 (Ver. 5.49) (manufactured by Spectris Co., Ltd.).

<Method for measuring number average particle size (D1) of primary particles of inorganic fine particles>
The number average particle size of the primary particles of the external additive is measured using a transmission electron microscope (TEM) "JEM2800" (manufactured by JEOL Ltd.).
First, the measurement sample is adjusted. 1 mL of isopropanol is added to about 5 mg of the external additive, and dispersed for 5 minutes with an ultrasonic disperser (ultrasonic cleaner). Next, one drop of the above-mentioned dispersion liquid was placed on a microgrid (150 mesh) with a supporting film for TEM, and dried to prepare a measurement sample.

Next, using a transmission electron microscope (TEM), under the condition of an accelerating voltage of 200 kV, an image is acquired at a magnification (for example, 200 k to 1 M times) at which the external additive in the field of view can be sufficiently measured. The number average particle size is determined by measuring the particle size of 100 primary particles of the external additive. The particle size of the primary particles may be measured manually or using a measuring tool.

<Measurement of particle size of primary particles of inorganic fine particles on toner surface>
The particle size of the primary particles of the inorganic fine particles on the toner surface was determined by observing the inorganic fine particles on the toner surface using a scanning electron microscope (SEM) "S-4700" (manufactured by Hitachi Ltd.).
The observation magnification was appropriately adjusted according to the size of the organic-inorganic composite fine particles, but in the field of view magnified up to 200,000 times, the major diameters of 100 primary particles were measured, and the average value was taken as the number average particle diameter.

<Measurement of Median Diameter (D50) Based on the Number of Toners>
The number-based median diameter (D50) of the toner of the present invention can be determined by observation of a secondary electron image with a scanning electron microscope and subsequent image processing.
The number-based median diameter (D50) of the toner of the present invention was measured using a scanning electron microscope (SEM) S-4800 (manufactured by Hitachi Ltd.).
Specifically, the toner was fixed in a single layer on a sample stand for electron microscope observation with a carbon tape, platinum was vapor-deposited, and observation was performed under the following conditions. Observations were made after performing the flushing operation.

SignalName=SE(U, LA80)
Accelerating Voltage = 2000 Volts
Emission Current = 10000nA
Working distance = 6000um
Lens Mode = High
Condenser 1 = 5
ScanSpeed=Slow4 (40 seconds)
Magnification=50000
DataSize = 1280 x 960
ColorMode=Grayscale

The secondary electron image was obtained by adjusting the brightness to 'contrast 5, brightness -5' on the control software of the scanning electron microscope S-4800, capturing speed/accumulated number 'Slow 4 for 40 seconds', and image size 1280 x 960 pixels. A projected toner image was obtained as an 8-bit 256-gradation grayscale image. From the scale on the image, the length of 1 pixel is 0.02 μm, and the area of 1 pixel is 0.0004 μm ² .
Subsequently, using the projection image obtained by secondary electrons, the projected area circle equivalent diameter was calculated for 100 toner particles. The details of the method of selecting 100 toner particles to be analyzed will be described later.

Next, the portion of the toner particles was extracted, and the size of one extracted toner particle was counted. Specifically, first, in order to extract the toner particle clusters to be analyzed, the toner particle clusters and the background portion are separated. Select Image-Pro Plus 5.1J "Measurement" - "Count/Size". In the "Brightness range selection" of "Count/size", the brightness range was set in the range of 50 to 255, and the low-brightness carbon tape part that was reflected as the background was excluded, and the toner particle group was extracted. . When the toner particles are fixed by a method other than the carbon tape, the background does not necessarily have a low brightness area, or there is a possibility that the brightness is partially the same as that of the toner particles.

However, the boundary between the toner particles and the background can be easily distinguished from the secondary electron observation image. When extracting, in the "Count/Size" extraction option, select 4 connections, enter a smoothness of 5, check "Fill holes", and remove toner particles and other The toner particles overlapping with the toner particles of are excluded from the calculation. Next, the area and Feret diameter (average) were selected as the measurement items of "count/size", and each toner grain for image analysis was extracted with the area selection range set to 100 pixels minimum and 10000 pixels maximum. One toner particle was selected from the extracted toner particle group, and the size (number of pixels) of the portion derived from that particle was determined (ja). From the obtained ja, the projected area circle equivalent diameter _d1 was obtained using the following formula.
d1={( ₄ *ja*0.3088)/3.14}^(1/2)

Next, in Image-Pro Plus 5.1J's "Count/Size"->"Brightness Range Selection", the brightness range was set to a range of 140 to 255, and a high brightness portion on one toner grain was extracted. .
Then, each particle of the extracted particle group was subjected to the same processing until 100 toner particles were selected. When the number of toner particles in one field of view was less than 100, the same operation was repeated for the projected toner image in another field of view.
The 100 toner particles thus obtained were arranged in ascending order of projected area equivalent circle diameter, and the projected area equivalent circle diameter of the 50th toner particle was defined as the median diameter (D50) based on the number of toner particles of the present invention.

<Description of charging roller endurance test and evaluation method>
Next, the electrophotographic apparatus used for the endurance test of the charging roller and the image evaluation will be described. The electrophotographic copier used in this test was a modified full-color copier imageRUNNER ADVANCE C5500 manufactured by Canon Inc. A process cartridge station for cyan was used.

The machine is for A3 landscape output, the output speed of the recording medium is 264 mm/sec, and the image resolution is 600 dpi. The photoreceptor is a reversal development type photoreceptor drum in which an aluminum cylinder is coated with an OPC layer (Organic Photoconductor layer) and further coated with an OCL layer (overcoat layer).
The charging method of the photoreceptor is a direct current charging method (DC charging method).

The toner is obtained by externally adding fine particles of silica and fine particles of strontium titanate to pulverized toner particles having a number average particle diameter of 5.5 μm containing polyester as a binder resin and wax.
Tables 2 and 3 show the types of charging rollers and physical properties of strontium titanate used in each example and each comparative example.
For image evaluation, an image with an image ratio of 30% was output under normal temperature and low humidity (N/L: temperature 23° C./relative humidity 5%), and a continuous durability test was performed on 100,000 sheets.

The following two types of evaluation images were used.
One is developed directly with the dark potential VD formed on the surface of the photosensitive member 1 by the charging roller (hereinafter referred to as analog HT (halftone)). Specifically, the surface of the photosensitive drum is charged to about -700V as a dark potential VD, and the developing sleeve potential is set to about -720V to develop to the dark potential VD. Under these conditions, uneven charging caused by contamination of the charging roller is directly reflected in the image, so contamination can be evaluated under severe conditions.

The other used a method of image formation through normal image exposure (hereinafter referred to as digital HT (halftone)). Specifically, the surface of the photosensitive drum is charged to about -700V as a dark potential VD, and then set to about -600V as a bright potential VL by full-surface image exposure. By setting the potential of the developing sleeve to about -600 V, the light area potential is developed to VL. Both of the above images were adjusted so that reflection densities measured by X-rite were in the range of 0.3 to 0.6. The evaluation rank was judged as follows.

Rank A: Even with analog HT, charging unevenness does not appear in the image.
Rank B: Streak-like unevenness occurs in the analog HT, but does not appear in the image in the digital HT.
Rank C: Slight unevenness occurs in digital HT, but there is no practical problem.
Rank D: Unevenness and streaks can be clearly confirmed by digital HT.

<Evaluation Results of Charging Roller>
As described above, according to the present invention, in a charging device using a DC charging method such as a copying machine or a printer, when only a DC voltage is applied, contamination of the charging roller after endurance is suppressed and image defects occur. It has become possible to provide an image forming apparatus without
Tables 2 and 3 show the results of evaluating charging roller contamination in developers with different production methods, classification conditions, etc., based on the above composition and formulation.

Examples 1 to 3 and Comparative Examples 1 to 3 show the evaluation results when the conditions of the charging roller were changed. good results could not be obtained outside the range.
Examples 4 and 5 and Comparative Examples 4 and 5 show the evaluation results when the D1T of the strontium titanate particles is varied, and good results can be obtained if the D1T is within the range described in this example. However, good results could not be obtained outside the range.

Examples 6 to 7 and Comparative Examples 6 to 7 show the evaluation results when the average circularity of the strontium titanate particles was varied. Results can be obtained, but good results could not be obtained outside the range.
Examples 8 to 9 and Comparative Examples 8 to 9 show the evaluation results when changing the half width of the maximum peak of the diffraction angle (2θ) in the CuKα characteristic X-ray diffraction of strontium titanate particles. Good results can be obtained within the range of the half width of the maximum peak of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction described above, but good results cannot be obtained outside the range.

Examples 10 and 11 and Comparative Examples 10 and 11 show the evaluation results when (Ix)/(Ia) in the strontium titanate particles were changed, and the ratio of (Ix)/(Ia) described in this example. If it is within the range, good results can be obtained, but if it is outside the range, good results cannot be obtained.
Examples 12-13 and Comparative Examples 12-13 show the evaluation results when the D1S in the silica particles is changed, and if the D1S is within the range described in this example, good results can be obtained. However, good results could not be obtained outside the range.

Example 14 and Comparative Example 14 show the evaluation results when the content of strontium titanate per 100 parts by mass of silica particles is varied. Good results can be obtained if the range is high, but good results cannot be obtained outside the range.
Examples 15 and 16 show the evaluation results when the total content of silica particles was changed, and good results were obtained within the range of the total content of silica particles described in this example. .

Examples 17 and 18 show the evaluation results when varying the D1S1 of the silica particles, and good results were obtained within the range of D1S1 of the silica particles described in this example.
Examples 19 and 20 show the evaluation results when the D1S2 of the silica particles was changed, and good results were obtained within the range of D1S2 of the silica particles described in this example.
Examples 21 and 22 show the evaluation results when the median diameter of the toner was changed, and good results could be obtained within the range of the total content of the median diameter of the toner described in this example. .

1a-1d image forming units 2a-2d photosensitive drums 3a-3d charging roller 30 support 31 elastic layer 32 surface layer

Claims (3)

An image carrier, a charging means rotating while being in contact with the image carrier, a voltage applying means for applying only a DC voltage to the charging means, and an electrostatic latent image formed on the surface of the image carrier that has been charged. exposure means for forming an electrostatic latent image formed on the surface of the image carrier, developing means for developing the electrostatic latent image formed on the surface of the image carrier using toner to form a toner image, and transferring the toner image to a transfer material. An image forming apparatus comprising transfer means, a cleaning member for cleaning toner remaining on the surface of the image carrier, and a fixing means for fixing the toner image transferred to the transfer material,
The charging means is a charging roller, the outermost layer of the charging roller is composed of a particle part and a non-particle part, the 10-point average roughness Rz of the outermost layer is 1 to 20 μm, and the outermost layer is 2 Rz of the 10-point average roughness in the area of 10 μm × 10 μm range of the non-particle portion (sea portion) when quantified is 1.0 μm or less,
The toner has toner particles and strontium titanate particles and silica particles present on the surface thereof,
The strontium titanate particles are
(i) the number average particle diameter (D1T) of the primary particles is 10 nm or more and less than 95 nm;
(ii) an average circularity of 0.700 or more and 0.920 or less;
(iii) having a maximum peak (a) at a diffraction angle (2θ) of 32.00 deg or more and 32.40 deg or less in CuKα characteristic X-ray diffraction, and a half width of the maximum peak (a) of 0.23 deg or more and 0.23 deg or more; is 50 deg or less, and the intensity (Ia) of the maximum peak (a) and the maximum peak intensity (Ix) in the range of 24.00 deg or more and 28.00 deg or less of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction are as follows. satisfies the formula (1),
(iv) The sum of the contents of strontium oxide and titanium oxide when the total amount of all oxides is assumed to be 100% by mass when all the elements detected by fluorescent X-ray analysis are assumed to be contained in oxides. is 98.0% by mass or more,
The silica particles have a number average particle diameter (D1S) of primary particles of 5 nm or more and 300 nm or less,
The content of the strontium titanate particles is 20 parts by mass or more per 100 parts by mass of the silica particles ,
The image forming apparatus , wherein the total content of the silica particles is 8.0 parts by mass or more and 15.0 parts by mass or less with respect to 100 parts by mass of the toner particles .
(Ix)/(Ia) ≤ 0.010 Formula (1) An image carrier, a charging means rotating while being in contact with the image carrier, a voltage applying means for applying only a DC voltage to the charging means, and an electrostatic latent image formed on the surface of the image carrier that has been charged. exposure means for forming an electrostatic latent image formed on the surface of the image carrier, developing means for developing the electrostatic latent image formed on the surface of the image carrier using toner to form a toner image, and transferring the toner image to a transfer material. An image forming apparatus comprising transfer means, a cleaning member for cleaning toner remaining on the surface of the image carrier, and a fixing means for fixing the toner image transferred to the transfer material,
The charging means is a charging roller, the outermost layer of the charging roller is composed of a particle part and a non-particle part, the 10-point average roughness Rz of the outermost layer is 1 to 20 μm, and the outermost layer is 2 Rz of the 10-point average roughness in the area of 10 μm × 10 μm range of the non-particle portion (sea portion) when quantified is 1.0 μm or less,
The toner has toner particles and strontium titanate particles and silica particles present on the surface thereof,
The strontium titanate particles are
(i) the number average particle diameter (D1T) of the primary particles is 10 nm or more and less than 95 nm;
(ii) an average circularity of 0.700 or more and 0.920 or less;
(iii) having a maximum peak (a) at a diffraction angle (2θ) of 32.00 deg or more and 32.40 deg or less in CuKα characteristic X-ray diffraction, and a half width of the maximum peak (a) of 0.23 deg or more and 0.23 deg or more; is 50 deg or less, and the intensity (Ia) of the maximum peak (a) and the maximum peak intensity (Ix) in the range of 24.00 deg or more and 28.00 deg or less of the diffraction angle (2θ) in CuKα characteristic X-ray diffraction are as follows. satisfies the formula (1),
(iv) The sum of the contents of strontium oxide and titanium oxide when the total amount of all oxides is assumed to be 100% by mass when all the elements detected by fluorescent X-ray analysis are assumed to be contained in oxides. is 98.0% by mass or more,
The silica particles have a number average particle diameter (D1S) of primary particles of 5 nm or more and 300 nm or less,
The content of the strontium titanate particles is 20 parts by mass or more per 100 parts by mass of the silica particles,
The silica particles are composed of first silica particles having a number average particle size (D1S1) of 5 nm or more and 20 nm or less and second silica particles having a number average particle size (D1S2) of 80 nm or more and 120 nm or less. is,
The relationship between the number average particle size (D1T) of the strontium titanate particles, the number average particle size (D1S1) of the first silica particles, and the number average particle size (D1S2) of the second silica particles is shown below. An image forming apparatus that satisfies formula (2).
(Ix)/(Ia) ≤ 0.010 Formula (1)
D1S2>D1T>D1S1 Expression (2) 3. The image forming apparatus according to claim 1, wherein the toner particles have a number-based median diameter (D50) of 3.0 [mu]m or more and 6.0 [mu]m or less.

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