JP3482534B2 - Two-component developer and image forming method using the developer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electrostatic latent image formed in electrophotography, and more particularly, to a two-component developer and The present invention relates to an image forming method using a two-component developer. 2. Description of the Related Art In a toner obtained by adding and mixing an inorganic fine powder as a fluidizing agent to colored particles and adhering thereto, the chargeability of the inorganic fine powder affects the chargeability of the toner. [0003] The stirring time of the developer, that is, the toner residence time in the two-component developer (after the developer is replenished,
The time until the image is developed differs depending on the degree of blackening of the original, the original size, the transfer size, and the copy mode (single-sided copy: double-sided copy). For example, in the double-sided copy mode, a document having a low degree of blackening, a reduced copy, and the like, the amount of toner consumed with respect to the stirring time is reduced, and the residence time of the toner is increased. As a result, the inorganic fine powder attached to the toner supplied to the developer is subjected to stirring for a long time, and as a result, the inorganic fine powder existing on the toner surface is buried, and the chargeability of the toner is not stabilized. [0004] In the case of a toner in which an inorganic fine powder whose charge amount decreases as the residence time becomes longer, fine characters are crushed, gradation is reduced, and the inside of the apparatus is scattered by the scattered toner. On the other hand, in the case of a toner selected from inorganic fine powder whose charge amount increases as the residence time becomes longer, the density of a copied image decreases. The above phenomenon is caused by developing the electrostatic latent image formed on the electrostatic image carrier, transferring the electrostatic latent image to a transfer member, and then recovering the toner remaining on the electrostatic image carrier to remove the toner. Or, it is remarkable in the toner recycling system which is returned to the developing device and used repeatedly. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer capable of maintaining a constant charge amount without depending on the residence time of toner, and to provide a good copy image for a long time even in a toner recycling system. The present invention also provides a two-component developer improved so as to obtain and an image forming method using the two-component developer. [0008] The object of the present invention is to provide at least a toner obtained by adding and mixing an inorganic fine powder having an average particle diameter of 100 nm or less to colored particles comprising a binder resin and a colorant; A two-component developer used by mixing a carrier,
The charge amount of the colored particles and the carrier Q _a, the inorganic fine powder and the carrier charge amount Q _b is _{10 ≦ | Q a | ≦ 30} (μC / g) 1 ≦ | Q b / Q a | a ≦ 30, charge amount Q _c of the two-component developer prepared by mixing toner and carrier _{0.7 ≦ | Q c / Q a} | is in the range of ≦ 1.5, and the burial of I of inorganic fine powder to be defined by the following formula (1) is achieved by an image forming method using the two-component developer characterized in that a 0.1 ≦ I ≦ 0.5. The inventor has made various two-component developments,
It was recognized that 0.7 ≦ | Q _c / Q _a | ≦ 1.5 was required in order to obtain a stable and good image irrespective of the toner residence time. In the case of 0.7> | Q _c / Q _a |, when the residence time of the toner is long, the image density decreases. Furthermore, | Q _c / Q _a | At> 1.5, deterioration in image quality due to Re-zuke fine characters when the residence time of the toner is long, fog earth, machine contamination occurs due to scattered toner. Q _c is preferably 15 ≦ | Q _c | ≦ 30 (μC / g). In order to control the charge amount of the toner to 0.7 ≦ | Q _c / Q _a | ≦ 1.5, 10 ≦ | Q _a | ≦ 30 (μC / g) 1 ≦ | Q _b / Q _a | ≦ Must be 30. [0011] Then, 1> | So inorganic fine powder is easily detached from the toner, cause scratches on the photoreceptor _{| | Q b / Q a Q} b / Q a |> At 30, the inorganic fine powder separated from the toner Selectively adheres to the carrier and alienates the charge of the toner and the carrier, which is not preferable. | Q _b | is, 10 ≦ | preferably ≦ 500, still more preferably in the range of, 20 ≦ | | Q _b is ≦ 300 | Q _b. In the present invention, the burial degree I of the inorganic fine powder is defined by the following equation (1). [0013] At this time, it is preferable to use a mixture of developers until 0.1 ≦ I ≦ 0.5.
In this range of the burial degree, the charge amount during copying is remarkably stable. The means for controlling the degree of burial is not particularly limited, but is preferably controlled by the mixing strength, mixing time and mixing temperature. The BET specific surface area is measured using Flowsorb 2000 (manufactured by Shimadzu Corporation). In the present invention, a colored particle obtained by adding a coloring agent wax and other additives to a binder resin is used as a base particle, and an inorganic fine powder is fixed on the surface thereof to obtain a toner for developing an electrostatic image. . In the above, as the binder resin for the colored particles, a resin usually used as a binder resin for a toner can be used as it is, and specific examples thereof include a styrene resin, an acrylic resin, and a styrene-acryl resin. Base resin, polyester resin, epoxy resin and others. The glass transition point Tg of the binder resin is preferably from 50 to 100 ° C. from the viewpoints of low-temperature fixability, offset resistance, blocking resistance and durability. Here, the glass transition point Tg is determined by a differential scanning calorimetry (DS
This is a value measured based on C). Specifically, for example, in a graph measured at a heating rate of 10 ° C./min using a differential scanning calorimeter “DSC-20” (manufactured by Seiko Instruments Inc.), the extension of the base line below the glass transition point and the peak It refers to the temperature at the intersection with the tangent line indicating the maximum slope from the rising portion to the peak apex. Further, the softening point of the binder resin is 100 to 150.
C. is preferred. This softening point was determined by using a “flow tester” (manufactured by Shimadzu Corporation) while heating a 1 cm ³ sample at a heating rate of 6 ° C./min with a plunger to 20 kg / cm ^2.
And a plunger descent amount-temperature curve (softening flow curve) of the flow tester is drawn to obtain the S.
Assuming that the height of the curve is h, the temperature corresponding to h / 2 is the softening point. As a coloring agent contained as a component of the coloring particles, for example, carbon black, chrome yellow, Dupont oil red, quinoline yellow, phthalocyanine blue, malachite green oxalate and the like can be used. The amount of the colorant is usually 0.1 to 20 parts by weight based on 100 parts by weight of the binder resin. The coloring particles contain a wax together with a coloring agent to improve fixability. As this wax,
For example, waxes having a softening point of 60 to 150 ° C. according to the ring and ball method (JIS K2531) such as polyolefins such as polyethylene and polypropylene, fatty acid ester waxes, higher alcohols, paraffin waxes and bisamide waxes are preferably used. The above-mentioned colored particles may further contain an auxiliary agent or an additive for imparting and improving various properties or performances as a toner. Specific examples include a magnetic material, a cleaning improver, and a charge control agent. As the magnetic material, there can be mentioned ferromagnetic compounds such as ferrite, magnetite, iron, cobalt and nickel. The content ratio is 20 to 150 parts by weight per 100 parts by weight of the binder resin for a toner used as a magnetic toner. Specific examples of the cleaning property improver include:
Examples thereof include fatty acid metal salts, talc, stone mica, mica, molybdenum dioxide, zinc white, and soapstone. As the charge control agent, conventionally known compounds can be used, and examples thereof include nigrosine dyes and metal-containing dyes. The above-mentioned auxiliary or additive may be uniformly mixed and dispersed in advance with a binder fat by, for example, an extruder or the like, and the resulting mixture is pulverized and classified to obtain colored particles having a desired particle diameter. Further, an inorganic fine powder is added as a fluidizing agent to the toner of the present invention. Examples of the inorganic fine powder include silica fine powder, alumina, titanium oxide, barium titanate, magnesium titanate, titanium calcium oxide,
Strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride And so on,
Particularly, silica fine powder is preferable. Here, it is preferable that the average particle diameter of the primary particles is in the range of 2 to 100 nm. The content ratio of the inorganic fine particles is preferably 0.1 to 5% by weight based on the toner. For fixing the inorganic fine powder, various types of mixers such as a ball mill, a V-type mixer, especially a mixer having a rotary blade as shown in FIG. 1 are not particularly limited. Can be used effectively. The toner according to the present invention is mixed with a carrier and used as a two-component developer. As the carrier, a conventionally known carrier can be used as it is. For example, iron, nickel, ferromagnetic metals such as cobalt, alloys containing these metals, ferrite, particles of a compound of a ferromagnetic metal such as magnetite, and such particles, vinylidene fluoride-ethylene tetrafluoride copolymer , Tetrafluoroethylene, 1,1,
1-trifluoroethyl methacrylate, pentafluoro
Examples thereof include those coated with a fluorine resin such as -n-propyl methacrylate or a silicone resin. The average particle size of the carrier is preferably from 20 to 200 μm, particularly preferably from 30 to 150 μm. The toner according to the present invention is used for developing an electrostatic image formed in, for example, an electrophotographic copying machine, and the obtained toner image is usually electrostatically transferred onto a transfer material, and then heated. To obtain a final visible image. Examples <Colored particles A> Colored particles A1 100 parts by weight of styrene acrylic resin, carbon black 10
Parts by weight, melt-kneading 4 parts by weight of low molecular weight polypropylene,
After pulverization and classification, colored particles A1 having an average particle size of 8.5 μm were obtained. Colored particles A2 100 parts by weight of polyester resin, 10 parts by weight of carbon black, and 4 parts by weight of low molecular weight polypropylene were melt-kneaded, pulverized, and classified to obtain colored particles A2 having an average particle size of 8.5 μm. <Inorganic Fine Powder B> Inorganic Fine Powder B1 Inorganic fine powder B1 is obtained by treating silica having a primary particle size of 16 nm with a polysiloxane having a quaternary ammonium salt as a functional group. Inorganic Fine Powder B2 Titanium dioxide having a primary particle size of 30 nm treated with octyltrimethoxysilane is referred to as inorganic fine powder B2. Inorganic Fine Powder B3 Titanium dioxide having a primary particle diameter of 12 nm treated with dimethyldichlorosilane is referred to as inorganic fine powder B3. Inorganic Fine Powder B4 Titanium dioxide having a primary particle size of 60 nm treated with octyltrimethoxysilane is referred to as inorganic fine powder B4. Inorganic Fine Powder B5 A silica powder having a primary particle size of 90 nm treated with octyltrimethoxysilane is referred to as inorganic fine powder B5. <Carrier C> Carrier C1 10 parts by weight of 1,1,1-trifluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 60/40) was added to 100 parts by weight of a ferrite core material having an average particle size of 80 μm. Acetone solution 2
0 parts by weight was coated with a fluidized bed coating apparatus to obtain a carrier C1. Carrier C2 100 parts by weight of a ferrite core material having an average particle size of 80 μm was coated with 20 parts by weight of an acetone solution containing 10% by weight of a 1,1,1-trifluoroethyl methacrylate polymer by a fluidized bed coating apparatus. I got Carrier C3 A 10% by weight acetone solution of 1,1,1-trifluoroethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 50/50) was added to 100 parts by weight of a ferrite core material having an average particle size of 80 μm.
0 parts by weight was coated with a fluidized bed coating apparatus to obtain a carrier C3. Carrier C4 30 parts by weight of an acetone solution containing 10% by weight of a 1,1,1-trifluoroethyl methacrylate polymer was coated on 100 parts by weight of a ferrite core material having an average particle size of 80 μm using a fluidized bed coating apparatus to form a carrier C4. Obtained. Example 1 Inorganic fine powder B1 was added to colored particles A1 using a mixer shown in FIG. 1 until the burial degree I became 0.3, and a toner was produced.
This toner was mixed with the carrier C1 to obtain a two-component developer of the present invention. Example 2 An inorganic fine powder B2 was added to and mixed with the colored particles A2 by using the mixer shown in FIG. 1 until the burial degree I became 0.5 to produce a toner.
This toner was mixed with the carrier C1 to obtain a two-component developer of the present invention. Example 3 An inorganic fine powder B3 was added to and mixed with the colored particles A1 by using the mixer shown in FIG. 1 until the burial degree I became 0.10. Thus, a toner was produced.
This toner was mixed with the carrier C2 to obtain a two-component developer of the present invention. Comparative Example 1 A toner was produced by adding inorganic fine powder B4 to colored A2 using a mixer shown in FIG. 1 until the burial degree I became 0.08. This toner was mixed with the carrier C3 to obtain a two-component developer for comparison. Comparative Example 2 Inorganic fine powder B5 was added to Colored A1 and mixed with the mixer shown in FIG. 1 until the burial degree I became 0.08 to produce a toner. This toner was mixed with the carrier C4 to obtain a two-component developer for comparison. Comparative Example 3 A toner was prepared by adding the inorganic fine powder B4 to the colored particles A1 by using the mixer shown in FIG. 1 until the burial degree I became 0.06. This toner was mixed with the carrier C4 to obtain a two-component developer for comparison. Comparative Example 4 A toner was prepared by adding the inorganic fine powder B1 to the colored particles A2 using the mixer shown in FIG. 1 until the burial degree I became 0.06. This toner was mixed with the carrier C3 to obtain a two-component developer for comparison. Table 1 below shows the configurations of the examples and comparative examples, and Table 2 below shows the values of Q _a , Q _b , Q _c , | Q _b / Q _a |, | Q _c / Q _b | Show. [Table 1] [Table 2] The charge amount of the present invention is determined by the apparatus shown in FIG.
It refers to what was measured as follows. In a glass sample tube having an inner diameter of 25 mm and a height of 40 mm, the formula (2) or (3) is used so that the total amount of powder becomes 20 g.
The sample was weighed at the mixing ratio shown in the equation,
After standing for a while, the mixture is shaken with a shaker Yayoi type YS-8D (manufactured by Yayoi Co., Ltd.) for 20 minutes at a shake angle of 45 ° and 200 strokes / minute to mix. The mixed sample is put into a measuring cell in which a stainless steel mesh screen is set, and blown off with nitrogen gas at a pressure at which the internal pressure becomes 2 kg / cm ² for 6 seconds, and the charge and mass of the scattered powder are measured. Mixing ratio of colored particles A and toner and carrier C _A = 2ρ _t / (2ρ _t + Xρ _c ) × 100 (%) (2) ρ _t : specific gravity of toner or specific gravity ρ of colored particles A _c : specific gravity of carrier X: carrier particle size / toner (colored particle A) particle size Mixing ratio of inorganic fine powder B and carrier C _B = 100 × 2ρ _t / (2ρ _t + Xρ _c ) × 100 (%) (3) ρ _t : specific gravity of inorganic fine powder B ρ _c : carrier specific gravity X: carrier particle size / primary particle size of inorganic fine powder B Using a photocopier U-Bix 1112 (manufactured by Konica Corporation) (the residence time of the toner in the developer becomes longer)
Use a manuscript with a large white background (black area ratio 0.2%)
An endurance test was conducted to print 1,000 copies. Evaluation Items <Image Density> Using a Sakura Densitometer, the copy image density of a white background portion of the transfer paper was measured for a document having a reflection density of 1.3. <Background fog> The white background portion of the copied image was evaluated by visual observation. The case where no image stain was observed was evaluated as ○, and the case where image stain was observed was evaluated as x. <Generation Copy> An operation of copying a 8.0-point Mincho original at the same magnification and repeating copying with the copied image as the original was repeated, and the evaluation was made based on the number of copies within a range in which characters could be read. [Table 3] As described above, in the developer of the present invention, a stable image was obtained even when a document having many white backgrounds was repeatedly used in a copying machine employing toner recycling. According to the present invention, a two-component developer capable of maintaining a constant charge amount irrespective of the toner residence time and providing a high-quality copy image for a long time even in the toner recycling system was obtained. Further, an image forming method which provides a stable image by using the developer was obtained.

[Brief description of the drawings] FIG. 1 is a developer mixer. FIG. 2 is an apparatus for measuring a charge amount. [Explanation of symbols] 1 jacket 2 stirring blade 3 Motor 4 Lid 5 base 6 Control board 7 cylinder 8 Locking the lid 9 cylinders 10-way control unit 11 Outlet 12 Nitrogen gas inlet 13 Gas inlet 14 mesh screen 15 Faraday Cup 16 dust collector

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Makoto Kono Konica Corporation, 2970 Ishikawa-cho, Hachioji-shi, Tokyo (56) References JP-A-62-8165 (JP, A) JP-A-59-83171 (JP, A) JP-A-5-80590 (JP, A) JP-A-3-255461 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08 G03G 9 / Ten

Claims (1)

(57) [Claim 1] An electrostatic latent image formed on an electrostatic image bearing member
After the image is developed and transferred to the transfer member, it is placed on the electrostatic image carrier.
Recover remaining toner and use toner replenishing device or developing
In the image forming method to be returned to the apparatus and used repeatedly,
At least, a two-component developer in which a toner obtained by adding and mixing an inorganic fine powder having an average particle diameter of 100 nm or less to a binder resin and coloring particles made of a coloring agent, and mixing a carrier,
The charge amount of the colored particles and the carrier Q _a, the inorganic fine powder and the carrier charge amount Q _b is _{10 ≦ | Q a | ≦ 30} (μC / g) 1 ≦ | Q b / Q a | a ≦ 30, charge amount Q _c of the two-component developer prepared by mixing toner and carrier _{0.7 ≦ | Q c / Q a} | is in the range of ≦ 1.5, and buried degree I of inorganic fine powder to be defined by the following formula (1)
But especially the use of two-component developer Ru 0.1 ≦ I ≦ 0.5 der
The image forming method to be described. (Equation 1)