EP0453907A1 - Elektrophotographischer Toner - Google Patents

Elektrophotographischer Toner Download PDF

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Publication number
EP0453907A1
EP0453907A1 EP91105867A EP91105867A EP0453907A1 EP 0453907 A1 EP0453907 A1 EP 0453907A1 EP 91105867 A EP91105867 A EP 91105867A EP 91105867 A EP91105867 A EP 91105867A EP 0453907 A1 EP0453907 A1 EP 0453907A1
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EP
European Patent Office
Prior art keywords
molecular
weight
electrophotographic toner
maximum value
ratio
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.)
Withdrawn
Application number
EP91105867A
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English (en)
French (fr)
Inventor
Teratani Teruaki
Shimizu 413-201 Fukumoto-Cho Yoshitake
Tsuyama Koichi
Inoue Masahide
Ishimaru Seijiro
Yabe Naruo
Nakano Tetsuya
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Kyocera Mita Industrial Co Ltd
Original Assignee
Mita Industrial Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP2098143A external-priority patent/JP2667547B2/ja
Priority claimed from JP2098142A external-priority patent/JPH03294865A/ja
Priority claimed from JP2098144A external-priority patent/JP2667548B2/ja
Priority claimed from JP2129416A external-priority patent/JPH0424649A/ja
Application filed by Mita Industrial Co Ltd filed Critical Mita Industrial Co Ltd
Publication of EP0453907A1 publication Critical patent/EP0453907A1/de
Withdrawn legal-status Critical Current

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    • 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
    • G03G9/087—Binders for toner particles
    • G03G9/08702—Binders for toner particles comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • G03G9/08726—Polymers of unsaturated acids or derivatives thereof
    • G03G9/08728—Polymers of esters
    • 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
    • G03G9/08702—Binders for toner particles comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • G03G9/08706—Polymers of alkenyl-aromatic compounds
    • G03G9/08708—Copolymers of styrene
    • G03G9/08711—Copolymers of styrene with esters of acrylic or methacrylic acid
    • 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
    • G03G9/0902—Inorganic compounds
    • G03G9/0904—Carbon black

Definitions

  • the present invention relates to an electrophotographic toner and more particularly to an electrophotographic toner to be used for image forming with the use of an electrostatic copying apparatus, a laser beam printer or the like.
  • a developer containing an electrophotographic toner is first held on the outer peripheral surface of a developing sleeve incorporating magnetic polarities, thereby to form a so-called magnetic brush. Then, the magnetic brush is brought in contact with a photoreceptor on the surface of which an electrostatic latent image is being formed, so that the electrophotographic toner in the developer electrostatically adheres 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 by fixing rollers. Thus, image forming is completed.
  • an electrophotographic toner as obtained by blending a fixing resin with a coloring agent such as carbon black, a charge controlling agent and the like and by pulverizing the blended body into particles having sizes in a predetermined range.
  • the electrophotographic toner above-mentioned may present the problem of so-called off-set such as contamination of paper at the reverse side thereof due to adhesion of toner or contamination of the fixing rollers caused by separation of the toner from paper.
  • off-set such as contamination of paper at the reverse side thereof due to adhesion of toner or contamination of the fixing rollers caused by separation of the toner from paper.
  • the fixing temperature is low, the toner image might not be satisfactorily fixed onto the paper (deterioration of fixing properties at a low temperature).
  • the deterioration of fixing properties at a low temperature occurs mainly when the molecular weight of the fixing resin contained in the electrophotographic toner is high.
  • the off-set occurs mainly when the molecular weight of the fixing resin is low.
  • the electrophotographic toner set forth in the Publication No. 16144/1981 above-mentioned contains, as a fixing resin, a polymer obtainable by synthesizing a vinyl-type monomer, or a mixture of the polymer above-mentioned, which presents a chromatogram as obtained by a gel permeation chromatography in which at least one maximum value appears in both molecular-weight ranges from 103 to 8 x 104 and from 105 to 2 x 104.
  • the electrophotographic toner set forth in the Publication No. 3644/1985 above-mentioned mainly contains a fixing resin having the following three components:
  • the high molecular-weight component is excellent in resistance to off-set, but apt to decrease the fixing properties of the electrophotographic toner.
  • the low molecular-weight component is excellent in fixing properties at a low temperature, but apt to decrease the resistance to off-set. It is therefore almost impossible to compatibly satisfy both fixing properties at a low temperature and resistance to off-set merely by jointly using both components.
  • the resin composition may be uneven or the resin cohesive force may be low. This involves the likelihood that the durability of the electrophotographic toner is lowered, causing the toner to be crushed during developing process. Further, toner which does not contribute to image forming (spent toner), may be increased in amount, thus disadvantageously accelerating the deterioration of the developer.
  • a styrene-acryl copolymer may be advantageously used as the fixing resin and, when high and low molecular-weight components are jointly used as the styrene-acryl copolymer, there may be advantageously used a great amount of a component common in both high and low molecular weight components, i.e., a component having an intermediate molecular weight.
  • a component common in both high and low molecular weight components i.e., a component having an intermediate molecular weight.
  • the resulting toner is improved in uniformity and durability with defective fixing and off-set restrained.
  • the electrophotographic toner above-mentioned, there is a possibility of the fixed image being coarse and presenting apparent fog.
  • the apparent fog refers to fog which is visually observed, even though the fog density is low when the formed image is optically measured with the use of an image analyzer or the like.
  • a toner image which is coarse or presents apparent fog above-mentioned is low in surface smoothness. Accordingly, such a toner image may not be satisfactorily fixed and readily separated from the paper due to friction.
  • the agitation of the developing device causes toner particles to receive a mechanical pressure, an impact force, frictional heat and the like, so that a toner aggregate is grown, causing the image to be grained. Further, the toner cannot be uniformly molten to lower the uniformity of the image quality. Further, the growth of toner aggregate presents the problem of a so-called blanking phenomenon.
  • the blanking refers to the phenomenon that the toner aggregate grown with repeated image forming is caught between the paper and the surface of the photoreceptor to form gaps at the time when the tomer image is transferred to the paper, so that toner particles around the toner aggregate are not transferred to the paper, thus leaving a white image.
  • the present invention is proposed with the object of providing an electrophotographic toner to be properly used in a high-speed copying apparatus or a copying apparatus provided with a fixing unit so designed as to consume less electric power.
  • the inventors of the present invention have studied other factors than the fixing resin, and found that the dispersibility of carbon black as a coloring agent with respect to the fixing resin and the relaxation time of electrophotographic toner are important factors for restraining the defective fixing or off-set above-mentioned. Based on this finding, the inventors have completed the present invention.
  • an electrophotographic toner which contains, as a fixing resin, a styrene-acrylic copolymer presenting a gel permeation chromatogram of molecular-weight distribution in which the maximum value is located in each of the ranges of not less than 1 x 105 and from 500 to 2 x 104, and which also contains, as a coloring agent, carbon black of which dibutyl phthalate oil absorption is not less than 80ml/100g, the toner presenting relaxation time of 10 to 50 ms at a frequency of 100 kHz.
  • the inventors of the present invention have studied the causes of coarse image and apaprent fog, and found that the coarse image is apt to be formed more often as the number of large-diameter coarse particles is increased and that the apparent fog is produced when such large toner particles as to be visually seen stick to the white parts of an image.
  • the inventors have further studied the particle-size distribution of the electrophotographic toner. Based on this study, the present invention was accomplished.
  • an electrophotographic toner which contains, as a fixing resin, a styrene-acrylic copolymer having the molecular-weight distribution above-mentioned, and which presents a particle-size distribution in which a volumetric median diameter D50 as measured with a coulter counter is in a range from 7 to 13 ⁇ m and in which the ratio of particles having a particle size of not less than 16 ⁇ m is not greater than 0,90% in terms of the number of particles.
  • the inventors of the present invention have studied the causes of defective image quality, decrease in image density and increase in the amount of spent toner, and found that such problems are caused by improper particle-size distribution of the electrophotographic toner.
  • the small-size particles cause the developer to be lowered in flowability and are meltingly bonded to one another to increase the amount of the spent toner. Further, since the small-size particles present small adhering areas at the time of image fixing. This decreases the image density. Further, the small-size particles themselves are light-weight and readily scattered. Accordingly, when the charge amount undergoes a change with the increase in the amount of spent toner, there is a possibility of the small-size particles being scattered, thereby producing fog.
  • the electrophotographic toner has been further studied on the particle-size distribution thereof in other viewpoint than that in the second embodiment. Based on this study, the present invention was accomplished.
  • an electrophotographic toner which contains, as a fixing resin, a styrene-acrylic copolymer having the molecular-weight distribution above-mentioned, and which presents a particle-size distribution in which a volumetric median diameter D50 as measured with a coulter counter is in a range from 7 to 13 ⁇ m and in which the ratio of a 75% residual particle size D75 to a 25% residual particle size D25 (D25/D75) is in a range from 1,3 to 1,7.
  • the inventors of the present invention have found that the toner aggregate provoking blanking is caused by the presence of those high and low molecular-weight components contained in the styrene-acrylic copolymer of which molecular weights are respectively over and below certain levels.
  • a polymer component of which molecular weight exceeds a certain level is poor in elasticity, causing the component to be readily pulverized.
  • a polymer component of which molecular weight is below a certain level is high in stickness. This causes the toner particles to be bonded to one another, or causes pulverized micro-fine particles to be bonded to the toner particles. Accordingly, when image forming is repeated, the pulverization and bonding above-mentioned proceed, so that a toner aggregate is grown.
  • the upper and lower limits in the molecular-weight distribution of the fixing resin have been further studied, and based on this study, the present invention was accomplished.
  • an electrophotographic toner which contains, as a fixing resin, a styrene-acrylic copolymer presenting a gel permeation chromatogram of molecular-weight distribution in which the maximum value appears in each of the ranges of not less than 1 x 105 and from 500 to 2 x 104, and in which a detection starting molecular weight corresponding to the upper limit of the molecular weight is not greater than 2 x 108 and a detection ending molecular weight corresponding to the lower limit of the molecular weight is not less than 300.
  • the fixing resin a styrene-acrylic copolymer having a molecular-weight distribution in which the minimum value is located between the two maximum values and in which the ratio of the total sum of the two peak areas respectively containing the two maximum values to the area of the valley part containing the minimum value and located below a common tangential line which connects the two peaks to each other, is not greater than 0,30.
  • a fixing resin a styrene-acrylic copolymer presenting a gel permeation chromatogram of molecular-weight distribution in which maximum values P H and P L are respectively located in the high molecular-weight side and the low molecular-weight side, as shown in Fig. 1.
  • the maximum value P H at the high molecular-weight side should be not less than 1 x 105. If the molecular weight of the maximum value P H is less than 1 x 105, the high molecular-weight component in the styrene-acrylic copolymer is insufficient in amount, thus failing to produce an electrophotographic toner excellent in resistance to off-set.
  • the molecular weight of the maximum value P L at the low molecular-weight side should be in a range from 500 to 2 x 104. If the molecular weight of the maximum value P L exceeds 2 x 104, the low molecular-weight component in the styrene-acrylic copolymer is insufficient in amount, thus failing to produce an electrophotographic toner excellent in fixing properties at a low temperature. On the other hand, if the molecular weight of the maximum value P L is less than 500, the styrene-acrylic copolymer is insufficient in retention, thus failing to produce an electrophotographic toner excellent in durability.
  • styrene-acrylic copolymer having a molecular-weight distribution in which the minimum value V M is located between the maximum values P H and P L , as shown in Fig. 1.
  • the molecular weight of the minimum value V M is not particularly limited to a certain value, as far as it is located between the molecular weights of both maximum values P H and P L .
  • V/P A ratio (V/P) is introduced from the following equation:
  • the ratio (V/P) represents how the curve of molecular-weight distribution of the styrene-acrylic copolymer is approximated to a quadrilateral formed by connecting both maximum values with the common tangential line l . As the ratio (V/P) is smaller, the curve is more approximated to a quadrilateral. This serves as an index which shows the amount of the intermediate molecular-weight component which lies between high and low molecular-weight components. More specifically, as the ratio (V/P) is smaller, the amount of the intermediate molecular-weight component is greater. This makes it possible to produce an electrophotographic toner having the optimum combination of fixing properties, resistance to off-set and durability.
  • the ratio (V/P) is preferably not greater than 0,30, and more preferably not greater than 0,20.
  • the (V/P) exceeds 0,30, the amount of the intermediate molecular-weight component contained in the styrene-acrylic copolymer is insufficient. This deteriorates the uniformity and durability of the electrophotographic toner, and cannot restrain defective fixing and offset.
  • styrene-acrylic copolymer having the molecular-weight distribution above-mentioned there are available three methods, i.e., a method of increasing the variance of the low molecular-weight component (molecular-weight distribution of M W /M N ), a method of increasing the variance of the high molecular-weight component (M W /M N ), and a method of increasing the variance of the high and low molecular-weight components (M W /M N ).
  • M W /M N the variance of the high molecular-weight component in view of various characteristics of electrophotographic toner.
  • the variance of the high molecular-weight component (M W /M N ) is preferably in a range from 2,7 to 3,7, and more preferably from 3,0 to 3,4.
  • the variance of the low molecular-weight component (M W /M N ) is preferably in a range from 1,5 to 2,5 and more preferably from 1,8 to 2,2.
  • M W weight average molecular weight
  • M N number average molecular weight
  • the styrene-acrylic copolymer to be used in the present invention may be produced either by tightly melting and blending a plurality of types of styrene-acrylic copolymers having different molecular-weight distributions, or by using a two-stage polymerization.
  • a styrene-acrylic copolymer (low molecular-weight component) having a molecular-weight distribution shown by a curve A and a styrene-acrylic copolymer (high molecular-weight component) having a molecular-weight distribution shown by a curve B
  • a styrene-acrylic copolymer having a molecular-weight distribution, as shown by a curve C , which is located in the range determined in the present invention.
  • a copolymer having a high molecular weight may generally be more easily produced as compared with a solution polymerization.
  • the styrene-acrylic copolymer having the molecular-weight distribution above-mentioned may be produced by a multi-stage polymerization in which the suspension polymerization or the emulsion polymerization and the solution polymerization are combined in this order or in the reverse order with the molecular weight adjusted at each stage.
  • the molecular weight or molecular-weight distribution may be adjusted by suitably selecting the type or amount of an initiator, the type of a solvent, a dispersing agent or an emulsifying agent relating to chain transfer, and the like.
  • styrene monomer there may be used vinyl-toluene, ⁇ -methylstyrene or the like, besides styrene.
  • acrylic monomer there may be used a monomer represented by the following general formula (I): [R1 is a hydrogen atom or a lower alkyl group, R2 is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, a hydroxyalkyl group, a vinylester group or an aminoalkyl group].
  • acrylic monomer represented by the general formula (I) examples include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl ⁇ -hydroxyacrylate, propyl ⁇ -hydroxyacrylate, butyl ⁇ -hydroxyacrylate, ethyl ⁇ -hydroxymethacrylate, propyl ⁇ -aminoacrylate, propyl ⁇ -N,N-diethylaminoacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and the like.
  • a styrene/methyl methacrylate/butyl acrylate copolymer may be used as the styrene-acrylic copolymer suitably used for the present invention.
  • the electrophotographic toner in accordance with the first embodiment of the present invention may be produced by blending the styrene-acrylic copolymer above-mentioned with carbon black as a coloring agent and conventional additives such as a charge controlling agent and the like.
  • the relaxation time at frequency of 100 kHz which represents the charge characteristics of the toner, is limited to a range of 10 to 50 ms . If the relaxation time is shorter than 10 ms , the electric charge of the toner sticked to the photoreceptor disappears in a short period of time. This deteriorates the transferring ability, causing the resulting image to be defective in quality.
  • An electrophotographic toner having bad charge characteristics is apt to be readily scattered in the developing unit or the like of an image forming apparatus. This may provoke contamination of paper, a blot on a formed image or the like. If the relaxation time exceeds 50 ms , the electric charge hardly gets away. This deteriorates a so-called cleaning ability, i.e., the removal of toner from the surface of the photoreceptor.
  • the electrophotographic toner of which relaxation time exceeds 50 ms is apt to readily stick to the fixing rollers and the like when the toner rubs against the fixing rollers and the like. This may provoke a defective image or contamination inside of the image forming apparatus.
  • the relaxation time may be adjusted to the range above-mentioned by suitably selecting the type and particle size of carbon black, the blending ratio and the like.
  • the carbon black its dibutyl phthalate oil absorption (as measured by the method A stipulated in JIS K 6221-1982 "Testing Methods of Carbon Black for Rubber Industry") which serves as a factor of determining the dispersibility to the fixing resin, should be not less than 80 ml/100 g, and is preferably in a range from 90 to 120 ml/100 g. If the dibutyl phthalate oil absorption of carbon black is smaller than 80 ml/100 g, the dispersibility to the styrene-acrylic copolymer is insufficient.
  • the particle size of carbon black is not limited to a specific value, but is preferably in a range from 10 to 50 nm. If the particle size exceeds 50 nm, there is a possibility of the carbon black preventing the pulverization of electrophotographic toner. If the particle size of carbon black is smaller than 10 nm, the dispersibility of carbon black with respect to the styrene-acrylic copolymer is lowered. This may induce poor durability and carrier contamination, or may present a variety of problems resulting from poor charge characteristics.
  • the blending ratio of the carbon black in the electrophotographic toner is not limited to a specific value, but is preferably in a range from 3 to 20 % by weight. If the blending ratio of carbon black is less than 3 % by weight, the relaxation time of the electrophotographic toner might exceed 50 ms dependent on the particle size and dibutyl phthalate oil absorption of the carbon black. On the other hand, if the carbon black blending ratio exceeds 20 % by weight, the relaxation time might be less than 10 ms .
  • carbon black there may be used any of various conventional carbon blacks such as furnace black, channel black, thermal, gas black, oil black, acetylene black and the like.
  • the particle size of the electrophotographic toner in accordance with the first embodiment is generally in a range from 5 to 20 ⁇ m, and preferably from 7 to 13 ⁇ m.
  • the toner in such a range may be obtained by grinding, classification, suspension polymerization or the like.
  • the electrophotographic toner in accordance with the second embodiment of the present invention contains, as the fixing resin, a styrene-acrylic copolymer having the molecular-weight distribution mentioned earlier, and presents a toner particle-size distribution in which a volumetric median diameter D50 as measured with a coulter counter is in a range from 7 to 13 ⁇ m and in which the ratio of particles with a particle size of not less than 16 ⁇ m being not greater tnan 0,90% in terms of the number of particles.
  • the volumetric median diameter D50 is limited to the range from 7 to 13 ⁇ m and the ratio of the particles having a particle size of not less than 16 ⁇ m is limited to not greater than 0,90% in terms of the number of particles.
  • the electrophotographic toner in accordance with the second embodiment above-mentioned may be produced by blending the styrene-acrylic copolymer having the molecular-weight distribution above-mentioned with a coloring agent and conventional additives such as a charge controlling agent and the like.
  • the electrophotographic toner in accordance with the third embodiment of the present invention contains, as a fixing resin, a styrene-acrylic copolymer having the molecular-weight distribution above-mentioned, and presents a toner particle-size distribution in which a volumetric median diameter D50 as measured with a coulter counter is in a range from 7 to 13 ⁇ m and in which the ratio of a 75% residual particle size D75 to a 25% residual particle size D25 (D25/D75) is in a range from 1,3 to 1,7.
  • a volumetric median diameter D50 as measured with a coulter counter is in a range from 7 to 13 ⁇ m and in which the ratio of a 75% residual particle size D75 to a 25% residual particle size D25 (D25/D75) is in a range from 1,3 to 1,7.
  • the volumetric median diameter D50 as measured with a coulter counter is smaller than 7 ⁇ m or the ratio of a 75% residual particle size D75 to a 25% residual particle size D25 (D25/D75) is smaller than 1,3, the ratio of small particles in the electrophotographic toner is increased. This provokes a decrease in image density, an increase in the amount of spent toner, fog and the like.
  • the volumetric median diameter D50 exceeds 13 ⁇ m, the ratio of large particles in the electrophotographic toner is increased, causing the image quality to be defective.
  • the ratio D25/D75 exceeds 1,7, the ratio of large particles in the electrophotographic toner is increased, causing the image quality to be defective.
  • the volumetric median diameter D50 is limited to the range of 7 to 13 ⁇ m and the ratio of the 75% residual particle size D75 to the 25% residual particle size D25 (D25/D75) is limited to the range from 1,3 to 1,7.
  • the upper limit of the 25% residual particle size D25 is preferably in a range from 11,5 to 14,0 ⁇ m dependent on the value of the median diameter D50 or the 75% residual particle size D75.
  • the lower limit of the 75% residual particle size D75 is preferably in a range from 6,0 to 10 ⁇ m dependent on the value of the median diameter D50 or the 25% residual particle size D25.
  • the electrophotographic toner in accordance with the third embodiment above-mentioned may be produced by blending the styrene-acrylic copolymer having the molecular-weight distribution above-mentioned with a coloring agent and conventional additives such as a charge controlling agent and the like.
  • the styrene-acrylic copolymer presents a molecular-weight distribution in which a detection starting molecular weight corresponding to the upper limit of the molecular-weight distribution is limited to not greater than 2 x 108 and a detection ending molecular weight corresponding to the lower limit of the molecular-weight distribution is limited to not less than 300.
  • the toner particles are apt to be readily pulverized. This does not only provoke a blanking phenomenon due to the growth of a toner aggregate, but also produces fog, variations of image quality and the like due to scattering of pulverized fine particles. If the detection ending molecular weight is smaller than 300, the toner particles are increased in adhesion. This does not only provoke a blanking phenomenon due to the growth of a toner aggregate, but also produces a granularly image. Further, the particles cannot be uniformly molten lowering the uniformity of image quality.
  • the detection starting molecular weight corresponding to the upper limit of the molecular-weight distribution is limited to not greater than 2 x 108 and the detection ending molecular weight corresponding to the lower limit of the molecular-weight distribution is limited to not less than 300.
  • the polymerization reaction sufficiently proceeds to prevent the formation of an extremely low molecular-weight component of which molecular weight is lower than 300.
  • the high molecular-weight component is polymerized under the relatively fast polymerization conditions, the polymerization reaction does not sufficiently proceed to prevent the formation of an extremely high molecular-weight component of which molecular weight exceeds 2 x 108.
  • the styrene-acrylic copolymer having the molecular-weight distribution above-mentioned there may be used a low molecular-weight component polymerized under relatively slow polymerization conditions and a high molecular-weight component polymerized under relatively fast polymerization conditions.
  • the electrophotographic toner in accordance with the fourth embodiment of the present invention has the average particle size in a range from 5 to 20 ⁇ m and preferably from 7 to 13 ⁇ m.
  • Toner having the particle size in the range above-mentioned may be obtained by grinding, classification, suspension polymerization or the like.
  • the electrophotographic toner in accordance with the fourth embodiment of the present invention may be produced by blending the styrene-acrylic copolymer having the molecular-weight distribution above-mentioned with a coloring agent and conventional additives such as a charge controlling agent and the like.
  • coloring agent to be used for producing the electrophotographic toner of each of the second to fourth embodiments of the present invention there may be used any of various conventional pigments and dyes to be used for coloring the toner.
  • Carbon black such as furnace black, channel black, thermal, gas black, oil black, acetylene black and the like, Lamp black, Aniline black.
  • Zinc white Titanium oxide, Antimony white, Zinc sulfide.
  • Red iron oxide Cadmium red, Red lead, Mercury cadmium sulfide, Permanent red 4R, Lithol red, Pyrazolone red, Watching red calcium salt, Lake red D, Brilliant carmine 6B, Eosine lake, Rhodamine lake B, Alizarine lake, Brilliant carmine 3B,
  • an extender pigment or a pigment made of a magnetic material examples include Baryte powder, barium carbonate, clay, silica, white carbon, talc, alumina white.
  • Examples of the pigment made of a magnetic material include: triiron tetroxide (Fe3O4), iron sesquioxide ( ⁇ -Fe2O3), zinc iron oxide (ZnFe2O4), yttrium iron oxide (Y3Fe5O12), cadmium iron oxide (CdFe2O4), gadolinium iron oxide (Gd3Fe5O4), copper iron oxide (CuFe2O4), lead iron oxide (PbFe12O19), neodymium iron oxide (NdFeO3), barium iron oxide (BaFe12O19), magnesium iron oxide (MgFe2O4), manganese iron oxide (MnFe2O4), lanthanum iron oxide (LaFeO3), iron powder, cobalt powder, nickel powder and the like. According to the present invention, any fine powder of these known magnetic materials may be used.
  • the electrophotographic toner may contain such a coloring agent in a ratio from 1 to 80 % by weight and preferably from 5 to 60 % by weight.
  • Examples of the charge controlling agent to be used for the electrophotographic toner in accordance with the present invention include: an oil-soluble dye such as nigrosine dye, oil black, spiron black and the like; metallic soap such as metallic naphthenate, metallic salicylate, metallic complex salicylate, metallic octylate, metallic fatty acid, metallic resinate and the like; a metal-containing monoazo dye; a pyrimidine compound; alkyl salicylic acid metal chelate and the like.
  • the electrophotographic toner may contain the charge controlling agent in a range from 0,1 to 5 % by weight.
  • an off-set preventing agent such as waxes including paraffin wax, polypropylene having a low molecular weight, polyethylene having a low molecular weight, fatty acid amide, silicone oil or the like, preferably in a ratio of 0,5 to 10 % by weight.
  • the toner particles may be coated at the surfaces thereof with a conventional surface treating agent which includes inorganic fine particles such as hydrophobic silica fine particles, carbon black or the like, resinous fine particles such as fluoroplastics particles, or the like.
  • a conventional surface treating agent which includes inorganic fine particles such as hydrophobic silica fine particles, carbon black or the like, resinous fine particles such as fluoroplastics particles, or the like.
  • the toner of the present invention may be mixed with a magnetic carrier such as ferrite, iron powder or the like to form a two-component developer adapted to be used for image forming by developing, transferring and fixing an electrostatic latent image.
  • a magnetic carrier such as ferrite, iron powder or the like
  • the relaxation time at frequency of 100 kHz was 30 ms
  • the dibutyl phthalate oil absorption of the carbon black was measured according to the method A stipulated in JIS K 6221-1982 "Testing Methods of Carbon Black for Rubber Industry" as set below.
  • Example 3 There was produced an electrophotographic toner having a volumetric median diameter of 12 ⁇ m in the same manner as in Example 3 except for the use of 12 parts by weight of carbon black of which dibutyl phthalate oil absorption was 100ml/100g and of which average particle size was 25 ⁇ m, instead of 7 parts by weight of carbon black used in Example 3.
  • the relaxation time at frequency of 100 kHz was 12 ms .
  • Example 2 There was produced an electrophotographic toner having a volumetric median diameter of 12 ⁇ m in the same manner as in Example 1 except for the use of 8 parts by weight of carbon black of which dibutyl phthalate oil absorption was 60ml/100g and of which average particle size was 24 ⁇ m, instead of 8 parts by weight of carbon black used in Example 1.
  • the relaxation time at frequency of 100 kHz was 22 ms .
  • Example 2 There was produced an electrophotographic toner having a volumetric median diameter of 12 ⁇ m in the same manner as in Example 1 except for the application of kneading conditions different from those in Example 1.
  • the relaxation time at frequency of 100 kHz was 60 ms .
  • Example 3 There was produced an electrophotographic toner having a volumetric median diameter of 12 ⁇ m in the same manner as in Example 3 except for the use of 20 parts by weight of carbon black of which dibutyl phthalate oil absorption was 100ml/100g and of which average particle size was 22 ⁇ m, instead of 7 parts by weight of carbon black used in Example 3.
  • the relaxation time at frequency of 100 kHz was 9 ms .
  • the electrophotographic toners of Comparative Examples 1 to 6 deviated from the scope of the present invention in any of the molecular-weight distribution of the styrene/methyl methacrylate/butyl acrylate copolymer, the dibutyl phthalate oil absorption of carbon black and the relaxation time at frequency of 100 kHz. It was found that the toners of such Comparative Examples were disadvantageous in any of the fixing properties at a low temperature, resistance to blocking or resistance to shock.
  • the resulting mixture was cooled, ground and classified to produce an electrophotographic toner which presented a volumetric median diameter D50 of 10,0 ⁇ m and in which the ratio of particles having a particle size of not less than 16 ⁇ m was 0,40% in terms of the number of particles.
  • a black-white document was copied with an electrophotographic copying apparatus (DC-5585 manufactured by Mita Industrial Co., Ltd.) using each of the developers above-mentioned.
  • the white portion of each image before fixed was measured with an image analyzer (QUANTIMET 900 Image Analyzer manufactured by Cambridge Instruments Co., Ltd.), thereby to obtain a histogram of the particle-size distribution of sticked toner. From each histogram thus obtained, there was obtained the ratio of particles having particle size of not less than 16 ⁇ m to all the particles sticked to the white portion (% by the number of particles).
  • Table 2 shows the results of the tests above-mentioned, together with the results of Fixing Property Test I, Test of Resistance to Blocking and Test of Resistance to Shock.
  • the axis of ordinate represens the ratio (in %) of the height of each peak with respect to the height of the top peak in a gel permeation chromatogram which is set to 100.
  • a black-white document was copied for 20 000 pieces under high-temperature and high-humidity conditions (35°C and relative humidity of 85%) with each of two electrophotographic copying apparatus having different copying speeds [DC-3255 (copying speed of 432 pieces/minute) and DC-5585 (copying speed of 455 pieces/minute), both manufactured by Mita Industrial Co., Ltd.] using each of the developers above-mentioned.
  • DC-3255 copying speed of 432 pieces/minute
  • DC-5585 copying speed of 455 pieces/minute
  • a solid-black document was copied for 20 000 pieces under high-temperature and high-humidity conditions (35°C and relative humidity of 85%) with each of two electrophotographic copying apparatus having different copying speeds [DC-3255 (copying speed of 432 pieces/minute) and DC-5585 (copying speed of 455 pieces/minute), both manufactured by Mita Industrial Co., Ltd.] using each of the developers above-mentioned.
  • DC-3255 copying speed of 432 pieces/minute
  • DC-5585 copying speed of 455 pieces/minute
  • the resultant formed image was defective in any of the characteristics above-mentioned, particularly when the electrophotographic copying apparatus having a high copying speed (DC-5585) was used.
  • the inside of the electrophotographic copying apparatus having a high copying speed (DC-5585) was checked after 20 000 copies had been taken with each of the toners above-mentioned.
  • the apparatus presented no special problem when the toner of each of Examples 16 to 18 and Comparative Example 26 was used.
  • the toner of Comparative Example 24 was used, a great amount of fine powder resulting from pulverization of the toner was observed inside of the apparatus.
  • the toner of Comparative Example 25 was used, a great amount of toner aggregate was found inside of the apparatus.
  • the fixing rollers of the apparatus were contaminated due to toner adhesion.
EP91105867A 1990-04-13 1991-04-12 Elektrophotographischer Toner Withdrawn EP0453907A1 (de)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP2098143A JP2667547B2 (ja) 1990-04-13 1990-04-13 電子写真用トナー
JP98143/90 1990-04-13
JP98142/90 1990-04-13
JP2098142A JPH03294865A (ja) 1990-04-13 1990-04-13 電子写真用トナー
JP98144/90 1990-04-13
JP2098144A JP2667548B2 (ja) 1990-04-13 1990-04-13 電子写真用トナー
JP2129416A JPH0424649A (ja) 1990-05-18 1990-05-18 トナー
JP129416/90 1990-05-18

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0655657A1 (de) * 1993-11-19 1995-05-31 Mita Industrial Co., Ltd. Toner für ein zwei-komponenten-Typ magnetisches, Entwicklungsagenz mit exellentem Spent-Widerstand
US7670744B2 (en) * 2004-03-04 2010-03-02 Panasonic Corporation Toner, method for producing toner, two component developer, and image forming apparatus
US20210033993A1 (en) * 2018-02-08 2021-02-04 Kao Corporation Toner production method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100227672B1 (ko) * 1996-12-30 1999-11-01 손욱 칼라브라운관 블랙매트릭스용 토너 및 그 제조방법

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0332212A2 (de) * 1988-03-11 1989-09-13 Mita Industrial Co., Ltd. Entwickler für latente elektrostatische Bilder

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0332212A2 (de) * 1988-03-11 1989-09-13 Mita Industrial Co., Ltd. Entwickler für latente elektrostatische Bilder

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 9 (P-811)(3357) 11 January 1989, & JP-A-63 217369 (KONICA CORP.) 09 September 1988, *
PATENT ABSTRACTS OF JAPAN vol. 14, no. 191 (P-1038)(4134) 18 April 1990, & JP-A-2 37365 (MITA INDUSTRIAL CO., LTD.) 07 February 1990, *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0655657A1 (de) * 1993-11-19 1995-05-31 Mita Industrial Co., Ltd. Toner für ein zwei-komponenten-Typ magnetisches, Entwicklungsagenz mit exellentem Spent-Widerstand
US5521045A (en) * 1993-11-19 1996-05-28 Mita Industrial Co., Ltd. Toner for a two-component-type magnetic developing agent having excellent spent resistance
US7670744B2 (en) * 2004-03-04 2010-03-02 Panasonic Corporation Toner, method for producing toner, two component developer, and image forming apparatus
US20210033993A1 (en) * 2018-02-08 2021-02-04 Kao Corporation Toner production method
US11768446B2 (en) * 2018-02-08 2023-09-26 Kao Corporation Toner production method

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