EP0479285B1 - Toner électrophotographique - Google Patents

Toner électrophotographique Download PDF

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Publication number
EP0479285B1
EP0479285B1 EP91116862A EP91116862A EP0479285B1 EP 0479285 B1 EP0479285 B1 EP 0479285B1 EP 91116862 A EP91116862 A EP 91116862A EP 91116862 A EP91116862 A EP 91116862A EP 0479285 B1 EP0479285 B1 EP 0479285B1
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EP
European Patent Office
Prior art keywords
toner
range
weight
electrophotographic toner
electric charge
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP91116862A
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German (de)
English (en)
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EP0479285A1 (fr
Inventor
Nakano Tetsuya
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kyocera Mita Industrial Co Ltd
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Mita Industrial Co Ltd
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Priority claimed from JP2268820A external-priority patent/JP2701970B2/ja
Priority claimed from JP3052724A external-priority patent/JPH04288557A/ja
Application filed by Mita Industrial Co Ltd filed Critical Mita Industrial Co Ltd
Publication of EP0479285A1 publication Critical patent/EP0479285A1/fr
Application granted granted Critical
Publication of EP0479285B1 publication Critical patent/EP0479285B1/fr
Anticipated expiration legal-status Critical
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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
    • 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
    • G03G9/09—Colouring agents for toner particles
    • G03G9/0906—Organic dyes
    • G03G9/091—Azo dyes
    • 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
    • G03G9/09783—Organo-metallic compounds

Definitions

  • the present invention relates to an electrophotographic toner containing a specific azo-type metal complex salt as charge control agent to be used for an image forming apparatus such as an electrostatic copying apparatus, a laser printer or the like.
  • an electrostatic latent image formed on the surface of a photoreceptor by exposure to light is let come in contact with an electrophotographic developer by a developping device.
  • Toner in the electrophotographic developer is electrostatically sticked to the electrostatic latent image. This causes the electrostatic latent image to be turned into a toner image. Then, the toner image is transferred to paper from the surface of the photoreceptor and fixed on the paper, thus achieving image forming.
  • an electrophotographic toner there may be generally used toner particles containing a binder resin, a coloring agent such as carbon black or the like, an electric charge controlling agent, a release agent, a flowability imparting agent as necessary and the like.
  • an electric charge controlling agent there is generally used an azo-type metal complex salt dye (azo-type chromium dye or the like).
  • Such a complex salt dye is disclosed in EP-A-0,141,377.
  • Another azo-type metal complex salt dye for use as an electric charge controlling agent is disclosed in EP-A-0,393,479. This document is considered prior art under Article 54(3) EPC.
  • the disclosed dye comprises a metal group which may be chromium or a cobalt atom.
  • the cation may comprise a sodium or potassium ion.
  • the United States Patent US-A-4,954,409 discloses a developer comprising a toner having a colourant and a carrier having a core material.
  • the toner comprises a chromium complex salt of 0,0'-dihydroxyazo dye.
  • the complex has a cation which may be hydrogen, an alkali metal, aliphatic ammonium or a pyridinium cation.
  • the European patent application EP-A-0,291,930 discloses a toner for developing an electrostatic image comprising an azo-type metal complex salt dye.
  • the metal may scandium, venedium, manganese or zinc.
  • the cation may be hydrogen, sodium, potassium, ammonium or an organic ammonium.
  • silica fine powder particularly hydrophobic silica fine powder, is generally mixed with and dispersed in the toner particles.
  • the inventors have studied hard and paid their attention to the pH value of an azo-type metal complex salt dye used as the electric charge controlling agent.
  • the inventors have found the fact that the electric charge characteristics and humidity resistance of a toner and dispersibility of the electric charge controlling agent in the resin vary with this pH value to cause a variety of problems such as defective image (insufficient image density, fog and the like), toner scattering and the like.
  • the electric charge controlling agent is a compound represented by the following general formula (1) and presenting a pH value in a range from 3 to 5: wherein R 1 , R 2 , R 3 and R 4 may be the same as or different from one another, and each is a hydrogen atom, a halogen atom or the following group: wherein R 5 and R 6 may be the same as or different from one another, and each is an alkyl or aryl group, and R 1 , R 2 , R 3 and R 4 are not all simultaneously a hydrogen atom; Y is a Cr, Fe, Co, Zn or Ti atom; Z + is a cation selected from the group consisting of an ammonium ion and a hydrogen ion.
  • R 1 , R 2 , R 3 and R 4 may be the same as or different from one another, and each is a hydrogen atom, a halogen atom or the following group: wherein R 5 and R 6 may be the same as or different from one another, and each is an alkyl
  • toner containing carbon black as the coloring agent it is preferable to use carbon black of which pH value is in a range from 6 to 11, in addition to the use of the electric charge controlling agent having a pH in the range mentioned earlier.
  • hydrophobic silica fine powder is mixed with and dispersed in toner particles containing, as the electric charge controlling agent, the compound (1) having a pH value in a range from 3 to 5
  • the pH value of the hydrophobic silica is preferably in a range from 3.5 to 4.5.
  • the pH value above-mentioned may be measured in accordance with the method set forth in JIS K 6221. More specifically, 10 g of a sample is added to 100 ml of distilled water. The sample-water mixture is then boiled for 15 minutes and cooled to a room temperature, after which pH value is measured.
  • the compound of the general formula (1) presents a pH value in a range from 3 to 5, it can be uniformly dispersed, as the electric charge controlling agent, in the binder resin of the toner. Accordingly, the electrophotographic toner in accordance with the present invention can be stabilized in electric charge characteristics.
  • the toner is lowered in humidity resistance. If the pH value is greater than 5, the dispersibility of the compound (1) in the binder resin is defective. In both cases above-mentioned, there are caused the problems such as decrease in image density, letter dispersion, toner scattering and the like.
  • the pH value of the compound of the general formula (1) is greatly influenced by the polar group connected to this compound.
  • the polar group is an electron attractive group (e.g., a halogen atom)
  • the pH value is liable to decrease. It is therefore required to select the respective groups such that the pH value is located in the range above-mentioned.
  • Table 1 shows the relationship between the combination of the substituting groups and the pH value. It is however noted that the pH value varies with a trace amount of a by-product included in the course of production of the compound (1) or with the presence of unreacted substances, and is therefore not a definite value.
  • the coloring agent carbon black of which pH value is less than 6, the humidity resistance of the toner is not sufficient.
  • carbon black of which pH value is greater than 11 the dispersibility of the compound (1) and the carbon black in the binder resin is lowered. In both cases above-mentioned, there are caused the problems of fog, decrease in image density, letter dispersion, toner scattering and the like.
  • hydrophobic silica fine powder When hydrophobic silica fine powder is to be mixed with and dispersed in toner particles containing, as the electric charge controlling agent, the compound (1) of which pH value is in a range from 3 to 5, it is preferable to use hydrophobic silica fine powder of which pH value is in a range from 3.5 to 4.5. In this case, the electric charge characteristics are stabilized to produce stable images. More specifically, if the pH values of the compound of the general formula (1) and the hydrophobic silica fine powder are below the ranges above-mentioned, the amount of negative electric charge becomes great, causing the toner to be separated from the carrier with difficulty. This provokes the problem of decrease in image density. If both pH values exceed the ranges above-mentioned, the amount of negative electric charge becomes small, causing the toner to be insufficiently sticked to the carrier. This provokes the problem of toner scattering, fog or the like.
  • halogen atom examples include a fluorine atom, a chloride atom, a bromine atom and an iodine atom.
  • alkyl group examples include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl and hexyl groups, each having 1 to 6 carbon atoms.
  • aryl group examples include phenyl, tolyl, xylyl, biphenyl, naphthyl, antolyl and phenantolyl groups.
  • the compound (1) is used in an amount from 0.5 to 8 parts by weight, preferably from 1 to 3 parts by weight, for 100 parts by weight of binder resin. If the blending ratio of the compound (1) is smaller than the range above-mentioned, the electric charge characteristics become unstable. If the blending ratio of the compound (1) is greater than the range above-mentioned, the carrier is sticked to the toner, thereby to provoke toner scattering, fog and the like.
  • the toner is produced by a method of mixing a binder resin, a coloring agent, the compound (1) as an electric charge controlling agent, a release agent (an off-set preventive agent) and an additive such as a flowability imparting agent or the like to be used as necessary, and pulverizing the mixture into particles having a predetermined particle size.
  • the toner is produced by previously mixing and kneading the components above-mentioned uniformly with the use of a dry blender, a Henschel mixer, a ball mill or the like, uniformly melting and kneading the resultant mixture with the use of a kneading device such as a Banbury mixer, a roll, a single- or double-shaft extruding kneader or the like, cooling and grinding the resultant kneaded body, and classifying the resultant ground pieces as necessary.
  • the toner may also be produced by suspension polymerization or the like.
  • binder resin examples include styrene resins (monopolymers and copolymers containing styrene or a styrene substituent) such as polystyrene, chloro-polystyrene, poly- ⁇ -methylstyrene, a styrene-chloro-styrene copolymer, a styrene-propylene copolymer, a styrene-butadiene copolymer, a styrene-vinyl chloride copolymer, a styrene-vinyl acetate copolymer, a styrene-maleic acid copolymer, a styrene-acrylate copolymer (a styrene-methyl acrylate copolymer, a styrene-ethyl acrylate copolymer, a styrene-butyl
  • binder resin further include polyvinyl chloride, low-molecular-weight polyethylene, low-molecular-weight polypropylene, an ethylene-ethyl acrylate copolymer, polyvinyl butyral, an ethylene-vinyl acetate copolymer, rosin modified maleic acid resin, phenyl resin, epoxy resin, polyester resin, ionomer resin, polyurethane resin, silicone resin, ketone resin, xylene resin, polyamid resin and the like.
  • the examples above-mentioned may be used alone or in combination of plural types.
  • styrene resin particularly a styrene-(meth)acrylate copolymer and more particularly a styrene-methyl methacrylate-butylacrylate copolymer.
  • styrene-methyl methacrylate-butylacrylate copolymer containing 75 to 85 % by weight of styrene, 0.5 to 5 % by weight of methylmethacrylate and 10 to 20 % by weight of butylacrylate.
  • the coloring agent examples include: a black coloring agent such as carbon black (furnace black, channel black, thermal, gas black, oil black, acetylene black), lamp black, aniline black or the like; a brown coloring agent as obtained by mixing red, yellow and black coloring agents. Of these, the black coloring agent may be particularly suitably used.
  • the coloring agent may be used in an amount of 1 to 20 parts by weight and preferably 3 to 15 parts by weight for 100 parts by weights of the binder resin.
  • the release agent examples include aliphatic hydrocarbon, aliphatic metal salts, higher fatty acids, fatty esters, its partially saponified substances, silicone oil, a variety of waxes and the like.
  • a low-molecular-weight aliphatic hydrocarbon of which weight average molecular weight is from about 1,000 to about 10,000. More specifically, there is suitably used one or a combination of plural types of a low-molecular-weight polypropylene, low-molecular-weight polyethylene, paraffin wax, a low-molecular-weight olefin polymer composed of an olefin unit having 4 or more carbon atoms and the like.
  • the release agent may be used in an amount of 0.1 to 10 parts by weight and preferably from 1 to 5 parts by weight for 100 parts by weight of the binder resin.
  • the toner particles may have sizes in a range from 3 to 35 ⁇ m and preferably from 5 to 25 ⁇ m, but it is preferable that the distribution of toner particle sizes satisfies the following formula: N ⁇ -172.7C + 1.45 [wherein N is the percentage by the number of toner particles of which sizes as measured with a coulter counter exceed 16 ⁇ m, and C is surface dye density (g/g) of the toner particles]
  • the ground toner particles may be classified to remove particles having sizes greater than 16 ⁇ m, or toner particles may be ground such that the peak of the toner particle-size distribution is shifted to a smaller-size zone to reduce the content of particles having sizes greater than 16 ⁇ m.
  • silica fine powder to be mixed with and dispersed in the toner particles there may be used silica fine powder of which surface is treated with, for example, a (poly)alkyl group, a (poly)alkylsilil group, a (poly)alkylsilane or silicone oil.
  • silica fine powder of which surface has been treated with a compound having a polymethylsilil group such that the powder becomes hydrophobic.
  • Such powder is higher in hydrophobic nature than conventional silica fine powder treated with a compound having a low-molecular-weight alkyl group.
  • silica fine powder As a commercially available product of such silica fine powder, there may be mentioned "Cabosil TS720" manufactured by Cabot Co., Ltd.
  • This product is hydrophobic fumed silica fine powder, which is obtained by treating high-purity fumed silica fine powder (99.8% SiO 2 ) with an organic silicone compound, and on the surface of which a polymethylsilil group is present to increase the hydrophobic nature of the surface of the silica fine powder.
  • the particle sizes of the silica fine powder so treated as to be hydrophobic are suitably in a range from 0.01 to 0.04 ⁇ m.
  • the pH value of the hydrophobic silica fine powder varies with a variety of factors which are not always clarified. However, it is known that the surface functional group is influenced by reaction byproducts.
  • the hydrophobic silica fine powder may be added in an amount of 0.01 to 5 % by weight and preferably from 0.05 to 1 % by weight for the total amount of toner. If the amount of the hydrophobic silica fine powder is greater than the range above-mentioned, the amount of electric charge is excessive. If this amount is smaller than the range above-mentioned, the effect of improving the toner flowability cannot be expected.
  • the components above-mentioned were mixed.
  • the mixture was molten and kneaded with a double-shaft kneader, and then cooled, ground and classified to prepare toner particles having the average particle size of 10 ⁇ m.
  • Table 2 shows the substituting groups contained in the compounds (1) used, as the electric charge controlling agent, in Examples 1 to 7 and Comparative Examples 1 to 8.
  • Table 3 shows the pH values of carbon black and the compounds (1) used. Each pH value was measured in the manner that 10 g of a sample was added to 100 ml of distilled water and the sample-water mixture was then boiled for 15 minutes on a hot plate and cooled to a room temperature, after which pH value was measured with a glass electrode pH meter.
  • the pH value of the hydrophobic silica fine powder used was 4.1.
  • the moisture contents of the resultant electrophotographic toners thus obtained were measured under the condition of ambient temperature/ambient humidity (temperature : 20°C, humidity : 65%, hereinafter referred to as N/N) and under the condition of high temperature/high humidity (temperature : 35°C, humidity : 85%, hereinafter referred to as H/H), respectively, according to the Karl Fischer method.
  • Table 3 shows the results.
  • each of the electrophotographic toners was covered with and solidified by epoxy resin.
  • Each of the toners as cut with a microtome was observed with a transmission-type electro microscope.
  • the toner dispersibility was evaluated according to the following criteria:
  • Each of the electrophotographic toners was mixed with a carrier to prepare a developer having a toner density of 3%.
  • DC-7085 manufactured by Mita Industrial Co., Ltd.
  • a solid-black document was continuously copied for 150,000 pieces under the condition of ambient temperature/ambient humidity (N/N), i.e., temperature of 20°C and humidity of 65%, except that intermediate 8000 copied pieces from 16001st piece to 24000th piece were taken at temperature of 35°C and humidity of 85% (H/H).
  • N/N ambient temperature/ambient humidity
  • Every thousandth copied pieces were extracted, as samples, from 150,000 copied pieces for each of the developers and were measured as to the density values thereof with a reflection densitometer (TC-6D manufactured by Tokyo Denshoku Co., Ltd.). The averages were calculated for these samples for all the developers.
  • N/N ambient temperature/ambient humidity
  • H/H high temperature/high humidity
  • the reproduced images obtained with the use of the electrophotographic toners of Examples 1 to 7 are superior in any of image density, fog density, letter dispersion and toner scattering to the reproduced images obtained with the use of the electrophotographic toners of Comparative Examples 1 to 8.
  • the components above-mentioned were molten and kneaded with a double-shaft kneader, and then prepared as toner particles having the average toner particle size of 10 ⁇ m with a jetmil.
  • Table 4 shows the groups contained in the chromium-containing azo dye used as the electric charge controlling agent.
  • the pH value of the carbon black was 8.5.
  • Silica fine powder so treated as to be hydrophobic (particle size of 0.02 ⁇ m, pH of 3.7, Cabosil TS-720 manufactured by Cabot Co., Ltd.) was mixed with and dispersed in the toner particles thus prepared in an amount of 0.5 % by weight for the total amount of the toner particles, thus preparing a toner.
  • Toners were prepared in the same manner as in Example 1 except that there were used (i) metal-containing azo dyes which respectively contained groups shown in Table 4 and of which pH values are shown in Table 6 and (ii) hydrophobic silica fine powders of which pH values are shown in Table 6.
  • Ferrite carrier having the average particle size of 80 ⁇ m was blended with each of the toners of Examples 8 to 11 and Comparative Examples 9 to 16. Each mixture was uniformly mixed and agitated to prepare a two-component developer presenting toner density of 4%.
  • an electrophotographic copying apparatus DC-3255 manufactured by Mita Industrial Co., Ltd.
  • an original document was copied totally 80,000 pieces under different operating conditions under which a predetermined number of copied pieces were respectively taken. All the copied pieces were checked for image density, fog density, amount of electric charge and toner scattering for each of the operating conditions.
  • the density of blank portions of each reproduced image was measured and defined as fog density.
  • the amount of electric charge was measured with a blow-off electric charge measuring instrument manufactured by Toshiba Chemical Co., Ltd.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Developing Agents For Electrophotography (AREA)

Claims (7)

  1. Toner électrophotographique comprenant une résine de liaison, un agent colorant, un agent contrôlant la charge électrique et un agent de relargage, l'agent contrôlant la charge électrique étant représenté par la formule générale suivante (1):
    Figure imgb0015
     dans laquelle R1, R2, R3 et R4 peuvent être les mêmes ou différents, et chacun un atome d'hydrogène, un atome d'halogène ou le groupe suivant :
    Figure imgb0016
    dans laquelle R5 et R6 peuvent être les mêmes ou différents, et chacun un groupe alkyle ou aryle ; Y est un atome de Cr, Fe, Co, Zn ou Ti ; Z+ est un cation choisi dans le groupe composé des ions ammonium, hydrogène, potassium et sodium ;
    dans laquelle R1, R2, R3 et R4 ne sont pas tous simultanément des atomes d'hydrogène,
    dans laquelle les composants ci-dessus sont choisis de telle sorte que l'agent de contrôle de la charge a un pH dans la gamme de 3 à 5 et,
    dans laquelle R1 et R4 sont des groupes chloro et R2 et R3 sont des atomes d'hydrogène, Z+ n'est ni un sodium, ni un potassium.
  2. Toner électrophotographique selon la revendication 1, dans lequel le composé de formule générale (1) est contenu en quantité de 0,5 à 8 parties en poids pour 100 parties en poids de résine de liaison.
  3. Toner électrophotographique selon la revendication 1 ou 2, dans lequel la distribution des tailles de particules de toner est comprise dans la gamme représentée par la formule générale : N < -172,7C + 1,45
    Figure imgb0017
     dans laquelle N est le pourcentage du nombre de particules de toner dont la taille mesurée par un compteur Coulter excède 16 µm et C est la densité de pigment (g/g) en surface des particules de toner.
  4. Toner électrophotographique selon la revendication 1, 2 ou 3, dans lequel l'agent colorant est du noir de carbone dont le pH est compris entre 6 et 11.
  5. Toner électrophotographique selon l'une des revendications 1 à 4, dans lequel de la silice hydrophobe ayant un pH compris entre 3,5 et 4,5 est mélangée au toner et dispersée dans celui-ci.
  6. Toner électrophotographique selon la revendication 5, dans lequel la silice hydrophobe est une fine poudre ayant une taille de particules entre 0,01 et 0,04 µm.
  7. Toner électrophotographique selon la revendication 5, dans lequel la silice hydrophobe est contenue en quantité comprise entre 0,01 et 5 % en poids par rapport à la quantité de toutes les particules de toner.
EP91116862A 1990-10-05 1991-10-02 Toner électrophotographique Expired - Lifetime EP0479285B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP268820/90 1990-10-05
JP2268820A JP2701970B2 (ja) 1990-10-05 1990-10-05 電子写真用トナー
JP52724/91 1991-03-18
JP3052724A JPH04288557A (ja) 1991-03-18 1991-03-18 電子写真用トナー

Publications (2)

Publication Number Publication Date
EP0479285A1 EP0479285A1 (fr) 1992-04-08
EP0479285B1 true EP0479285B1 (fr) 1997-03-12

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EP91116862A Expired - Lifetime EP0479285B1 (fr) 1990-10-05 1991-10-02 Toner électrophotographique

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EP (1) EP0479285B1 (fr)
KR (1) KR950001824B1 (fr)
CA (1) CA2052571A1 (fr)
DE (1) DE69125083T2 (fr)
ES (1) ES2100916T3 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6627368B2 (en) * 1999-12-07 2003-09-30 Hodagaya Chemical Co., Ltd. Organic metal complex compound and electrostatic image developing toner using the same
DE10032138A1 (de) * 2000-07-01 2002-01-10 Clariant Gmbh Verwendung von Eisen-Azokomplexverbindungen als Ladungssteuermittel
US20050208403A1 (en) 2004-03-18 2005-09-22 Hyo Shu Toner, developer including the toner, and developing device and image forming apparatus using the toner

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0393479A2 (fr) * 1989-04-20 1990-10-24 Hodogaya Chemical Co., Ltd. Poudre de développement électrophotographique

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4954409A (en) * 1986-05-22 1990-09-04 Fuji Xerox Co., Ltd. Developer for electrophotography
US4857432A (en) * 1987-05-18 1989-08-15 Canon Kabushiki Kaisha Toner for developing electrostatic charge image
US4985328A (en) * 1988-09-22 1991-01-15 Hitachi Chemical Co., Ltd. Dry toner, dry developer and process for forming electrophotographic images

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0393479A2 (fr) * 1989-04-20 1990-10-24 Hodogaya Chemical Co., Ltd. Poudre de développement électrophotographique

Also Published As

Publication number Publication date
CA2052571A1 (fr) 1992-04-06
DE69125083D1 (de) 1997-04-17
ES2100916T3 (es) 1997-07-01
KR950001824B1 (ko) 1995-03-03
DE69125083T2 (de) 1997-10-16
KR920008541A (ko) 1992-05-28
EP0479285A1 (fr) 1992-04-08

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