Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/083—Magnetic toner particles
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/083—Magnetic toner particles
  • G03G9/0835—Magnetic parameters of the magnetic components
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/087—Binders for toner particles
  • G03G9/08742—Binders for toner particles comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/08755—Polyesters
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/097—Plasticisers; Charge controlling agents
  • G03G9/09708—Inorganic compounds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/097—Plasticisers; Charge controlling agents
  • G03G9/09708—Inorganic compounds
  • G03G9/09716—Inorganic compounds treated with organic compounds

Definitions

• the present invention relates to a toner and a developer for use in an image forming apparatus equipped with an amorphous silicon photoreceptor. More particularly, it relates to a toner and a developer which can ensure an image development without uncontrolled toner attraction, fogging, toner scattering and blurring even under high humidity.
• an amorphous silicon photoreceptor is noted as an electrophotograhic photoreceptor, which has high surface hardness and high durability, and is useful for high speed copying.
• the amorphous silicon photoreceptor has a relatively low surface potential, which makes it difficult to obtain a high quality copy image.
• the amorphous silicon photoreceptor has the problem of "blurring". Specifically, when the surface of the amorphous photoreceptor is subject to oxidization by ozone generated, for example, in the process of coloring particles being charged, an oxidation layer occurs on the surface of the photoreceptor.
• the oxidation layer is likely to adsorb moisture from the air, and consequently disturb an electrostatic latent image formed on the photoreceptor.
• a developed toner image has a so-called "blurring". Blurring decrease the image quality. In the case that the blurred image includes characters, there is a likelihood that characters cannot be recognized.
• JP-A-278661/1996 proposes an image forming method in which a specific resin-coated carrier and toner are used for an amorphous silicon photoreceptor. With this method, however, blurring cannot be prevented satisfactorily and, under high humidity environment, the chargeability of toner is reduced to cause fog and toner scattering in some cases.
• a toner comprises coloring particles each including a main particle, particles made of a hydrophobic silica and attached on a surface of the main particle, and magnetic particles attached on a surface of the main particle.
• the main particle includes coloring elements and a binder resin containing a polyester resin having an acid value of not less than 20 for binding coloring elements.
• Primary particles of the hydrophobic silica particles have a mean particle size of from 7 to 20 nm.
• Primary particles of the magnetic particles have a mean particle size of from 100 to 1000 nm.
• a developer comprises carrying particles and the above-mentioned coloring particles.
• the inventive toner and developer effectively prevents blurring, which is liable to occur in a photoreceptor including amorphous silicon, and assures formation of a high quality image free from fog under high humidity.
• the problems attributed to high humidity are solved by adding to the surface of main particles, which include a coloring agent and a binder resin, a hydrophobic silica whose primary particles have a mean particle size of from 7 to 20 nm. This is because of the fact that the surface of the hydrophobic silica is generally negatively charged, adding the hydrophobic silica to the surface of the toner can increase chargeability of the toner.
• the surface treatment for the toner with the hydrophobic silica enables to suppress the chargeability of the toner from decreasing under high humidity.
• the components included in the toner of the present invention will be described as below.
• Polyester resin used in the present invention is usually obtained by condensation polymerization of polyhydric carboxylic acids and polyhydric alcohols.
• polybasic carboxylic acids used in the polyester resin are aromatic polyhydric carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1,2,4-benzene tricarboxylic acid, 2,5,7-naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid and pyromellitic acid; fatty dicarboxylic acids such as maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid and glutaconic acid; alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid and cyclohexene dicarboxylic acid; anhydrides of these carboxylic acids; and lower alkyl esters. These can be used solely or in a combination of two or more kinds.
• degree of crosslinking depends upon the total amount of components of the alcohol having more than three hydroxyl groups and the carboxylic acid having more than three carboxyl groups, a desired degree of crosslinking is obtainable by adjusting the amounts of such components. It is usually preferable that the components are present in the amount of not more than 15 mol percent.
• polyhydric alcohols used in the polyester resin are alkylene glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, neopentyl glycol, 1,5-pentane glycol and 1,6-hexane glycol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; fatty polyhydric alcohols such as 1,4-cyclohexane dimethanol and hydrogenerated bisphenol A; bisphenols such as bisphenol A, bisphenol F and bisphenol S; and alkylene oxides of bisphenols. These may be used solely or in a combination of two or more kinds.
• alkylene glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,
• the polyester resin used in the present invention is resins with an acid value of not less than 20.
• Such resins is made from alcohol monomers and carboxylic acid monomers whose amounts are in a specified proportion so that the rate of carboxylic groups contained carboxylic acid monomers to hydroxyl groups contained alcohol monomers is more than one. Specifically, the rate is preferably 1.1 to 1.5.
• the acid value of the polyester resin is preferably not less than 35, and its upper limit is preferably 70.
• monobasic carboxylic acid and monohydric alcohol may be used as required in the present invention.
• monobasic carboxylic acid are benzoic acid, paraoxy benzoic acid, toluene carboxylic acid, salicylic acid, acetic acid, propionic acid and stearic acid.
• monohydric alcohol examples of the monohydric alcohol are benzil alcohol, toluene-4-methanol and cyclohexane methanol.
• the polyester resin used in the present invention is prepared by using the above materials in the usual way. For instance, alcohol compositions and acid compositions are placed in a reactor in predetermined amounts and, while an inert gas, e.g., nitrogen, is blown into the reactor, they are allowed to react at temperatures between 150 and 190 °C in the presence of a catalyst. Low molecular compounds by-produced in the course of the reaction is successively removed outside of the system. Thereafter, the reaction is accelerated by raising the reaction temperature to between 210 and 250 °C, to obtain the desired polyester resin.
• the reaction can be conducted at atmospheric pressure, under reduced pressure, or high pressure. After a conversion of 50 to 90 % is reached, however, the reaction is preferably conducted under reduced pressure of not more than 200 mmHg.
• the catalyst examples include metals such as tin, titanium, antimony, manganese, nickel, zinc, lead, iron, magnesium, calcium and germanium; metals thereof; and compounds containing these metals.
• the glass transition temperature of the above polyester resin is preferably from 45 to 90 °C. If a toner contains the resin whose glass transition temperature is below 45 °C, the toner is likely to solidify in a toner cartridge or developing machines. On the other hand, if a toner contains the resin whose glass transition temperature is above 90 °C, the fixability of the toner to a transfer material is likely to be insufficient.
• polyester resin used in the present invention if necessary, other resins may be jointly used as a binder resin, to such an extent that the effect of the present invention is not inhibited.
• the toner according to the present invention can be prepared by a number of methods which are well known in the art, such as pulverization classification method, melt granulating method, spray granulating method, and polymerization method.
• pulverization classification method for example, the above binder resin is premixed together with toner compositions which comprises a coloring agent, a charge control agent and a mold releasing agent, in a mixer such as Henschel's mixer, and the mixture is kneaded with a kneading machine, e.g., a biaxial extruder. The obtained kneaded composition is then cooled, pulverized and, if necessary, classified, to prepare main particles.
• a kneading machine e.g., a biaxial extruder
• the coloring agent incorporated in the polyester resin there are black pigments such as acetylene black, lamp black and aniline black; yellow pigments such as chrome yellow, zinc chromate, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, naples yellow, naphthol yellow S.
• black pigments such as acetylene black, lamp black and aniline black
• yellow pigments such as chrome yellow, zinc chromate, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, naples yellow, naphthol yellow S.
• Olefin resin has a number average molecular weight (Mn) of from 1000 to 10000, particularly from 2000 to 6000.
• Mn number average molecular weight
• examples of the olefin resin are polypropylene, polyethylene and propylene-ethylene copolymer. Especially preferred is polypropylene.
• charge control agent any charge control agents normally used can be used.
• charge control agent of positively charged type are nigrosine dye, fatty acid modified nigrosine dye, carboxyl group containing fatty acid modified nigrosine dye, quaternary ammonium salt, amine compounds and organic metallic compounds.
• charge control agent of negatively charged type are metallic complex dye and salicylic acid derivatives.
• the main particle has a median size from 5 to 15 ⁇ m, particularly from 7 to 12 ⁇ m, in terms of measurement of a Coulter counter.
• a hydrophobic silica and magnetic powder are added, to prepare coloring particles.
• the added silica prevents aggregation of coloring particles and increases chargeability of coloring particles by the negatively-charged surface of the silica.
• the added magnetic powder decreases the resistance of coloring particles, which results in an increased image density, and decreases the magnetic power of the coloring particles, which results in a decreased amount of coloring particles scattered in an image forming apparatus.
• the primary particles of the hydrophobic silica has a mean particle size of from 7 to 20 nm. Below 7 nm, the coloring particles having such hydrophobic silica are likely to aggregate, i.e., a dispersibility of the toner is decreased. Above 20 nm, the coloring particles are likely to have a decreased chargeability under high humidity. More suitable mean particle size of the primary particle of the hydrophobic silica is from 7 to 16 nm. In the present invention, the mean particle size of the primary particle of the hydrophobic silicon was measured with microscopy.
• hydrophobic silica fine powder of silicon dioxide in which the silicon atom on the surface is silanol group is allowed to react with a compound, so that a hydrophobic group is bonded to the silicon atom on the surface of the silicon dioxide particles, via an oxygen atom.
• Examples of the above compound are octyltrichlor silane, decyltrichlor silane, nonyltrichlor silane, 4-isopropylphenyl- trichlor silane, 4-tert-buthylphenyl trichlor silane, dimethylchlor silane, dipentyldichlor silane, dihexyldichlor silane, dioctyldichlor silane, dinonyldichlor silane, deciledichlor silane, didodecyldichlor silane, 4-tert-buthylphenyloctyldichlor silane, dioctyldichlor silane, didecenyldichlor silane, dinonenyldichlor silane, di-2-ethylhexyldichlor silane, di-3,3-dimethyl pentyldichlor silane, trimethylchlor silane, trihexylchlor silane, trioctylch
• hydrophobic silicas preferred is one having on its surface polydimethyl siloxane group.
• polydimethyl siloxane group enables to provide the coloring particles an improved chargeability under high humidity.
• the hydrophobic silica is preferably present in an amount of from 0.1 to 2 wt% per main particle. If an amount of hydrophobic silica added to main particles is below 0.1 wt%, the obtained coloring particles are likely to have a decreased chargeability On the other hand, if an amount of hydrophobic silica added to main particles is above 2 wt%, a larger part of the silica is likely to separate from the surface of the coloring particles to adhere to a photoreceptor surface, resulting in a so-called photoreceptor filming.
• the primary particles of the magnetic powder used in the present invention preferably have a mean particle diameter of from 100 to 1000 nm. If the diameter of the magnetic particles is below 100 nm, the magnetic particles have a decreased abrasive property in the aspect of removing an oxidation layer on the surface of an amorphous silicon photoreceptor drum, resulting in a blurring. If the diameter of the magnetic particles is above 1000 nm, the magnetic particles are likely to adhere to the surface of the photoreceptor drum, resulting in black spots. In addition, magnetic particles having such large diameter hinder contact of coloring particles with carrying particles or the other coloring particles to decrease the charging of coloring particles. Furthermore, magnetic particles having such large diameter increase an amount of toner present in a developer.
• More suitable mean particle size is from 300 to 800 nm.
• the mean particle size of the primary particle of the magnetic powder was measured with microscopy.
• black spots means the following phenomenon: coloring particles are fused to the surface of a photoreceptor; other coloring particles easily adhere on the fused coloring particles; and such other particles are transferred on a paper sheet as black spots.
• toner scattering means coloring particles with poor chargeability scattered within an image forming apparatus by the centrifugal force exerted on a rotating magnetic brush. The presence of the scattered coloring particles on a path through which a transfer paper sheet is conveyed is likely to cause contamination of the rear face of the transfer paper.
• uncontrolled toner attraction means the following phenomenon: when a toner image is developed by poor charged coloring particles, coloring particles near to a charging brush are liable to be attracted to the charging brush.
• the magnetic powder is preferably present in an amount of from 0.1 to 10 wt% per main particle. Below 0.1 wt%, it is likely to cause a decreased image density, toner scattering and blurring. Above 10 wt%, such larger amount of the magnetic powder hinder contact of coloring particles with carrying particles or the other coloring particles to decrease the charging of coloring particles, and also it increases the amount of toner present in a developer. These decreased chargeability and the excessive amount of the toner cause an uncontrolled toner attraction, toner scattering, a decreased image quality, and a decreased fixability.
• Examples of the above magnetic powder are triiron tetroxide (Fe 3 O 4 ), diiron trioxide ( ⁇ -Fe 2 O 3 ), iron oxide zinc (ZnFe 3 O 4 ), iron oxide yttrium (Y 3 Fe 5 O 12 ), iron oxide cadmium (CdFe 2 O 4 ), iron oxide gadolinium (Gd 3 Fe 5 O 12 ), iron oxide copper (CuFe 2 O 4 ), iron oxide lead (PbFe 12 O 19 ), iron oxide nickel (NiFe 2 O 4 ), iron oxide neodymium (NdFeO 3 ), iron oxide barium (BaFe 12 O 19 ), iron oxide magnesium (MgFe 2 O 4 ), iron oxide manganese (MnFe 2 O 4 ), iron oxide lanthan (LaFeO 3 ), iron powder (Fe), cobalt powder (Co), and nickel powder (Ni).
• Particularly suitable magnetic powder is fine particles of triiron tetroxide (magnetite). Suitable
• the surface of magnetic powder is preferably coated with, for example, a long chain aliphatic compound, in terms of dispersibility and the adhesive properties to the surface of coloring particles.
• a long chain aliphatic compound examples include stearic acid, oleic acid, palmitic acid, hexanoic acid, linoleic acid, ricinoleic acid, fatty dicarboxylic acid having 10 to 22 carbon atoms, and hydroxy containing compounds of these acids, and salts which are composed of a combination of these acids and zinc, magnesium, calcium, cadmium, lead, iron, nickel, cobalt, copper, or aluminum.
• the strength of magnetization is preferably from 30 to 80 emu/g, when the external magnetic field is 1000 Oe.
• modifiers can be added to the coloring particles of the present invention, if necessary.
• hydrophobic silica and magnetic powder In the case of adding the hydrophobic silica and magnetic powder to the surface of main particles, it is preferable to premix them closely, and add the mixture to main particles, and then mix all the components so sufficiently as to disperse the silica and magnetic powder in the main particles uniformly.
• any well-known mixing apparatuses can be employed, such as Henschel's mixer, V-shape mixer, Tumbler's mixer, and Hybritizer.
• the toner of the present invention can be used as it is, as a one-component developer.
• magnetic powder is incorporated into the main particles to prepare a magnetic toner.
• the toner may be mixed with a carrier so as to be used as a two-component developer.
• a toner is preferably present in an amount of from 2 to 20 wt% to the total weight of the developer. Below 2 wt%, the obtained image by using such a developer has too low image density. Above 20 wt%, toner scattering and fog are liable to occur due to the excessive amount of the toner.
• carrier for the two-component developer there may be iron powder carrier, ferrite carrier, magnetite carrier. Also, it may be appreciated to use these carriers coated with a suitable resin. Developer containing a resin-coated carrier can give excellent high quality and a prolonged life to a developed image. No special limitations are imposed upon the form of carrier, and it may be in the form of flat, sponge, coin, ball, sphere, etc.
• a toner according to the present invention is applicable to any fixing methods such as heat roll fixing with/without oil, flash fixing and oven fixing, and it is applicable to both cleaning methods of fur brush method and blade method.
• a toner according to the present invention is more advantageous when it is used in combination with an amorphous silicon photoreceptor.
• applications of the toner is not limited thereto.
• a photoreceptor suitable for the toner of the present invention there are, for example, one which has a photosensitive layer containing amorphous silicon, amorphous silicon germanium or amorphous silicon tin; these amorphous ones incorporated by carbon, nitrogen and oxygen atoms; and these amorphous ones doped with an element of the group III a or Va in periodic law table.
• the toner of the present invention is used in image forming apparatus, it is suitably used for high speed type ones which can copy not less than 50 paper sheets of longitudinal A4 size, per minute.
• Material Resins A to C were prepared as shown in Table 1. More specifically, Material Resin A was prepared as follows. Dibutyl tin oxide as a polymerization catalyst was added into a mixture of 9.6 mol % of ethylene glycol and 17.8 mol % of neopentyl glycol as fatty alcohol, 19.7 mol % of polyoxypropylene-(2,2)-2,2-bis(4-hydroxyphenyl) propane as an aromatic alcohol, 46.4 mol % of terephthalic acid as a carboxylic acid, and 6.5 mol % of absolute 1,2,4-benzene tricarboxylic acid. This mixture was then placed in a four-mouth flask. To the flask, a stirrer, a condenser, a thermometer, and a gas conduit pipe were attached and then placed in a mantle heater.
• Material Resins B and C were prepared in the same manner as Material Resin A . Specific prescription and the characteristic features of the resulting resin are given in Table 1.
• Fatty series alcohol Resin A Resin B Resin C Ethylene glycol 9.6 14.8 16.2 Neopentyl glycol 17.8 18.9 19.5
• Aromatic series alcohol Polyoxypropylene-(2,2)-2,2-bis(4-hydroxyphenyl) propane 19.7 20.4 21.1
• Polyester resin A 100 parts of Polyester resin A as a binder resin, 10 parts of carbon black "Morgal L” (manufactured by Cabot Corp.) as a coloring agent, 5 parts of "Biscall 550P” (manufactured by Sanyo Kasei Industries Ltd.) as a mold releasing agent, were all placed in a Henschel's mixer and then mixed. This mixture was subjected to melt kneading by a biaxial extruder and then cooled by a drum flaker. Subsequently, this was roughly pulverized by a hammer mill, finely pulverized by a jet mill, and classified by a pneumatic classifier, to obtain main particles having a mean particle size of 9.0 micron.
• hydrophobic silica "TG308F” having on its surface polydimethyl siloxane (manufactured by Cabot Corp.) and 0.5 wt% of magnetite whose primary particle has a mean particle size of 700 nm, were added to main particles and mixed with high speed stirring.
• the density of a black solid area of the initially copied image was measured on a reflection density meter (Model #TC-6D, Tokyo Denshoku Co., Ltd.). The obtained value was employed as image density.
• a fog density was obtained by measuring the density of a blank portion of the paper sheet bearing a copy image by a reflection density meter (Model #TC-6D, Tokyo Denshoku Co., Ltd.).
• the fog density is usually required to be below 0.005.
• a 0.2 g of a sample developer was placed in a Faraday cage and nitrogen was sprayed for 30 seconds at a pressure of 1 kg/cm 2 , to measure chargeability of the toner contained the sample developer by using a Blow-Off Charge Measuring Device (manufactured by Toshiba Chemical corp.). The measurement was performed under an ordinary condition (temperature: 20°C, humidity: 60%) and under high humidity condition (temperature: 35°C, humidity: 85%).
• Toner was prepared in the same manner as in Example 1, except for the use of Polyester resin B as a binder resin. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of hydrophobic silica "R812S” having on its surface polydimethyl siloxane (manufactured by Nippon Aerosil Co., Ltd.), as a finishing agent. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of hydrophobic silica "R972" having on its surface polydimethyl siloxane (Nippon Aerosil Co. Ltd.), as a surface treatment agent. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of magnetite whose primary particle has a mean particle size of 100 nm. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of magnetite whose primary particle has a mean particle size of 1000 nm. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of Polyester resin C as a binder resin. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of magnetite whose primary particle has a mean particle size of 60 nm. The same evaluations were made and the results are given in Table 2.
• Toner was prepared in the same manner as in Example 1, except for the use of magnetite whose primary particle has a mean particle size of 1300 nm. The same evaluations were made and the results are given in Table 2.
• Examples 1 to 6 gave good results in all the evaluation items of image density, fog density, black spots, uncontrolled toner attraction, blurring, toner scattering, and chargeability of toner.
• Comparative Example 3 in which the primary particle of magnetite had a mean particle size of 1300 nm that exceeds 1000 nm, good results were given in image density, fog density and blurring, hit particle size of the magnetite was too large and thus the magnetite was liable to separate from the surface of the main particles. This caused black spots, as well as uncontrolled toner attraction and toner scattering.

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• Physics & Mathematics (AREA)
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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Developing Agents For Electrophotography (AREA)

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Citations (6)

• 1998
  • 1998-07-21 JP JP20562498A patent/JP2000039739A/ja active Pending
• 1999
  • 1999-07-20 EP EP99114087A patent/EP0974870A1/de not_active Withdrawn

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