JP2007187876A - Positive charge type magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charge type magnetic toner so excellent in durability and stability that neither increase of ground stain (fog) of a white background portion nor image density lowering occurs even when repeatedly used in a copying machine, a printer or the like and that neither increase of image fog, nor lowering of transfer rate, nor in-machine scattering occurs even when the toner undergoes stress by being allowed to stand in a high temperature environment. <P>SOLUTION: The positive charge type magnetic toner is composed of toner base particles comprising at least a binder resin, a magnetic material, a charge control resin and a release agent, and an external additive, wherein the relation between the BET specific surface area (A) of the toner and the BET specific surface area (B) of a heated toner obtained by allowing the above toner to left to stand under heating at 50°C for 144 h, and then cooling it satisfy the conditional expression: [(A)-(B)]/(A)≤0.15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic toner used for developing an electrostatic latent image in electrophotography, electrostatic recording method, and electrostatic printing method. More specifically, the present invention relates to a positively chargeable magnetic toner having excellent copy quality, heat resistance and storage stability.

  Conventional methods for developing an electrostatic latent image formed on an electrostatic image bearing member such as an electrophotographic photosensitive member or an electrostatic recording member in a copying machine or a printer are roughly divided into fine toners that are electrically insulating. Two methods are known: a method using a liquid developer dispersed in a liquid (wet development method) and a method using a toner in which a colorant or magnetic powder is dispersed in a binder resin (dry development method). Yes. In the dry development method, a method using a two-component developer composed of carrier particles and a toner and a method using a one-component developer composed only of a toner are known. In many cases, the magnetic toner is usually used as a one-component developer composed only of toner.

  The toner for developing an electrostatic image used in these dry development methods usually uses a styrene resin or a polyester resin as a binder resin, kneaded with a colorant such as a dye or a pigment, cooled, and then pulverized. It is manufactured through a classification process. The particle diameter of the toner for developing an electrostatic charge image usually has an average particle diameter of about 1 to 30 μm. In the case of a magnetic toner, a magnetic material such as magnetite is further used.

By leaving these toners for developing electrostatic images in a high temperature state for a long time, the surface condition of the toner causes a change with time, the quality of the copy image is deteriorated, and the ratio of the amount of toner transferred to the transfer paper is indicated. There is a problem that the transfer rate, which is a numerical value, is reduced and the toner in the copying machine or printer is scattered. (Hereinafter, this phenomenon is referred to as a change with time of heating.)
In order to solve these problems, the particle size of the charge control agent is set to 10 μm or less, the value of the BET specific surface area of the colorant is set to 20 to 100 m ² / g, the toner base particles and the external additive are By specifying the mixing conditions, it was possible to withstand heating stress at 50 ° C. for 72 hours, and a certain effect was found. However, this problem still remains a fundamental solution to this heating aging problem. It was not. (For example, see Patent Documents 1, 2, 3, etc.)
JP 2002-116753 A JP 2002-116581 A JP, 2002-229261, A Toner together with copiers, printers, etc. is currently used globally all over the world and is distributed and moved internationally. In this transportation during transportation, it may be transported over the equator, in the tropics over the sea over several days, or it may be transported over a scorching desert area by land, and sometimes the toner for transportation is 50 It can be exposed for days at temperatures close to ℃. Similarly, the risk of being exposed to high temperatures and being left unattended in a storage place or causing a change with time of heating is lurking in many places. In view of such a transport state, there is a demand for a magnetic toner having heat resistance even better than the quality achieved in the prior art.

The problem of the present invention is that fog does not increase and image density does not decrease when it is repeatedly used for copying continuously with a copying machine or printer, and fogging increases even when subjected to aging due to standing in a high temperature environment. Thus, it is an object of the present invention to provide an excellent positively chargeable magnetic toner that is durable and stable without causing a decrease in transfer rate and without causing in-machine scattering.
In particular, the present invention is to further improve and improve the quality of the patent documents 1, 2, and 3 that have been studied previously, and to use the toner with improved quality as a positively chargeable magnetic toner.

The present inventor does not cause an increase in fog or a decrease in image density when used continuously by copying with a copying machine, a printer or the like. As a result of intensive studies to provide an excellent durable and stable toner that does not increase (transfer rate does not decrease) and does not scatter in the machine, the BET ratio of the toner before and after heating The present invention has been accomplished by finding that the above-mentioned problems can be solved by controlling the rate of change of the surface area within a specific range and further using a material satisfying specific properties.

That is, the present invention relates to the following inventions (1) to (7).
(1) A positively chargeable magnetic toner comprising toner base particles containing at least a binder resin, a magnetic material, a charge control resin, and a release agent and an external additive, wherein the BET specific surface area (A) of the toner, A positively chargeable magnetic toner characterized in that the relationship between the BET specific surface area (B) of the heated toner obtained by allowing the toner to stand by heating at 50 ° C. for 144 hours and then cooling satisfies the following conditional expression.
[(A)-(B)] / (A) ≦ 0.15 (b)
(2) The positively chargeable magnetic toner according to (1), wherein at least one of the external additives is a positively chargeable inorganic oxide.
(3) The positively chargeable magnetic toner according to (1) or (2), wherein the magnetic material has a BET specific surface area of 4 to 10 m ² / g.
(4) The positively chargeable magnetic toner according to any one of (1) to (3), wherein the binder resin has a glass transition temperature (Tg) of 60 to 68 ° C.
(5) The release agent contains two types of low molecular weight polypropylene and low molecular weight polyethylene, the content of the low molecular weight polyethylene is 10% or more and 60% or less of the content of the low molecular weight polypropylene, and The positively chargeable magnetic toner according to any one of (1) to (4), wherein the content is 0.5 to 6 parts by weight with respect to 100 parts by weight of the binder resin.
(6) The positively chargeable magnetic toner according to any one of (1) to (5), wherein the charge control resin is a styrene-amine copolymer.
(7) The positively chargeable magnetic toner according to (6), wherein the styrene-amine copolymer has an amine value of 160 to 200.

  By specifying the numerical value of the specific surface area of the toner while using a specific material, the fog increases and the image density decreases when it is used repeatedly and continuously on a copying machine or printer, and the toner component on the surface of the photoconductor Does not cause sticking, does not change over time even when exposed to high temperatures, does not increase fogging, does not cause a decrease in toner transfer rate, and has excellent durability and stability without causing in-flight scattering A positively chargeable magnetic toner could be obtained.

In the positively chargeable magnetic toner of the present invention, it is a very effective means to evaluate and determine the heat resistance and stability with time of heating, and it is an extremely effective means to manage the numerical value of the BET specific surface area of the toner. The BET specific surface area (A) of the toner and the BET specific surface area (A) of the heated toner obtained after the toner was left to stand in a hot air dryer at 50 ° C. for 144 hours and then cooled to room temperature (23 ° C.). When the relationship with B) satisfies the following conditional expression (a), a positively chargeable magnetic toner having excellent heat resistance and stability over time can be provided. In other words, this conditional expression can be said to be a numerical value indicating the reduction rate of the specific surface area due to heating at 50 ° C. for 144 hours, and a toner having excellent change with time in heating when this reduction rate is smaller than 0.15. is there.
[(A)-(B)] / (A) ≦ 0.15 (b)
Here, in Conditional Expression (A), the numerical value is larger than 0.15 when the decrease in the BET specific surface area due to heating is significant, and the external additive adhering to the toner surface is present in the toner base particles. It has been embedded in. In other words, this value is preferably as small as possible.

  Originally, in the toner, an external additive is attached to the surface of the toner base particles, and when developed, the toner base particles themselves are transferred to a transfer medium such as paper to form an image, but the external additive portion is the toner. The ratio of remaining on the electrostatic charge image carrier (photoreceptor) and being recovered is higher than that attached to the mother particles. In the development with toner, the toner base particles and the external additive are electrostatically classified here, and the external additive has a carrier effect for effectively developing the toner. It is what.

  On the other hand, if the external additive is embedded in the toner base particles, that is, if the numerical value is greater than 0.15 in the conditional expression (A), the toner base particles and the external additive are not separated. As a result, the carrier effect does not work, and as a result, fatal problems such as toner scattering and fogging on the image occur.

In this way, controlling the adhesion and mixing state of the external additive so that the conditional expression is 0.15 or less, preferably 0.11 or less, is very important for suppressing the change with time. (Here, the toner base particles refer to the state before the external additive is added to the toner.)
The measurement of the BET specific surface area of the toner, the BET specific surface area (A) of the toner, and the BET specific surface area (B) of the heated toner were calculated by the following procedure.

For measurement of the BET specific surface area, Flowsorb II Model 2300 manufactured by Micrometrics was used. (Mixed gas: Nitrogen and helium are mixed at 3: 7.) In addition, two types of specific surface area measurement values, adsorption value and desorption value, can be obtained in the measurement. The value was adopted to determine the BET specific surface area. Here, the numerical value of the specific surface area is converted into a specific surface area per unit weight (m ² / g).

  Weigh the unheated toner into the glass sample cell (genuine product) to the 8th part (about 80%), leave it in a desiccator for 24 hours, and then perform the measurement to determine the BET ratio of the unheated toner. The surface area (A) (desorption value) is obtained. The sample cell containing the sample after measurement is placed in a hot air dryer set at 50 ° C. and left to heat for 144 hours (6 days). After taking out, it cools to room temperature (23 degreeC), and obtains the BET specific surface area (B) (desorption value) of a heating toner. Further, the ratio of the numerical value [difference between (A) and (B)] of the specific surface area decreased by heating to (A) is obtained. This is a numerical value that is a reduction rate of the specific surface area due to heating. (Condition A) If this value is 0.15 or less, the change in the surface state of the toner due to heating is negligible, and the quality is not impaired. On the other hand, if the numerical value is more than 0.15, it will cause noticeable fogging and contamination due to in-flight scattering.

  That is, if the numerical value of the conditional expression is 0.15 or less, the toner surface hardly changes. On the other hand, if the numerical value exceeds 0.15, the external additive is embedded in the toner base particle surface and strongly It shows that it has adhered.

  Here, important factors for controlling the change in the surface state and specific surface area of the toner include the material used for the toner and the conditions of the toner manufacturing process (post-processing conditions). Hereinafter, materials that can be used for the positively chargeable magnetic toner of the present invention, manufacturing conditions, and the like will be described in detail.

  In the binder resin used in the positively chargeable magnetic toner of the present invention, the glass transition temperature Tg measured by a differential thermal scanning calorimeter (DSC) is preferably in the range of 60 to 68 ° C. More preferably, it is the range of 62-66 degreeC. When the temperature is lower than 60 ° C., the binder resin becomes soft and the external additive is easily embedded in the toner surface, and the reduction rate of the specific surface area, the numerical value of the formula (A) becomes 0.15 or more. As a result, the quality of the toner after heating is deteriorated. If the temperature exceeds 68 ° C., the external additive is not embedded, but the resin becomes hard and hinders fixing properties. Moreover, in this invention, it measured using DSC-60 by Shimadzu Corporation. Here, the glass transition temperature was defined as the temperature at the intersection of the DSC curve starting from the base line and the tangent line with the point at which the slope settled constant after the peak rising, respectively.

  Specific examples of the binder resin used in the positively chargeable magnetic toner of the present invention include styrene polymers, for example, styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and homopolymers of substituted products thereof. Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic copolymer, styrene-α-chloromethacrylic acid Methyl copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Indene copolymer, styrene-dimethylaminoethyla Relate copolymer, styrene-diethylaminoethyl acrylate copolymer, styrene-based copolymer such as styrene-butyl acrylate-diethylaminoethyl methacrylate copolymer, cross-linked styrene-based copolymer, etc .; polyester resin, for example, aliphatic dicarboxylic Polyester resins having monomers selected from acids, aromatic dicarboxylic acids, aromatic dialcohols, diphenols as structural units, crosslinked polyester resins, etc .; other polyvinyl chloride, phenolic resins, modified phenolic resins, maleic resins Rosin modified maleic resin, polyvinyl acetate, silicone resin, polyurethane resin, polyamide resin, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, xylene resin, aliphatic or aliphatic hydrocarbon resin, Petroleum resin etc. can be mentioned.

  Examples of the acrylic monomer used in the styrene-acrylic copolymer include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, (Meth) acrylic acid esters such as phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, and the like, and as monomers that can be used together with these, acrylonitrile, methacrylonitrile , Maleic acid half esters such as acrylamide, maleic acid, butyl maleate or diesters, vinyl esters, vinyl chloride, vinyl chloride, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl butyl ether, etc. Examples thereof include vinyl ketones such as nyl ethers, vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone.

  Examples of the crosslinking agent used for producing the above-mentioned crosslinked styrene-based polymer include compounds having two or more unsaturated bonds, specifically, for example, divinylbenzene, divinylnaphthalene and the like. Aromatic divinyl compounds; carboxylic acid esters having two or more unsaturated bonds such as ethylene glycol diacrylate and ethylene glycol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and 3 unsaturated bonds One or more compounds can be used alone or in combination. The crosslinking agent is used in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on 100 parts by weight of the binder resin.

These resins can be used alone or in combination of two or more. Of these resins, styrene-based polymers and polyester resins are preferable because they exhibit particularly excellent charging characteristics. The molecular weight distribution measured by GPC (gel permeation chromatography) (polystyrene conversion) has at least one peak in the region of ³ × 10 ³ to 5 × 10 ⁴ and at least one in the region of 10 ⁵ or more. A styrene copolymer having a peak or a shoulder, and further two or more kinds of resins, for example, a combination of the styrene resin and a styrene-acrylic copolymer or a combination of two or more kinds of styrene-acrylic copolymers. A resin composition having such a molecular weight distribution is preferred from the viewpoints of toner pulverization and fixing properties.
Examples of magnetic materials that can be used in the positively chargeable magnetic toner of the present invention include iron oxides such as magnetite, maghemite, and ferrite, or compounds of divalent metals and iron oxides, metals such as iron, cobalt, and nickel, or metals of these metals. Examples thereof include powders of alloys of metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof. These magnetic materials have an average particle diameter of 0.05 to 2.0 μm, preferably about 0.1 to 0.5 μm. The amount of the magnetic material contained in the positively chargeable magnetic toner is 100 parts by weight of the binder resin. The amount is 10 to 150 parts by weight, preferably 17 to 125 parts by weight.
Moreover, the outstanding effect can be acquired in the range whose specific surface area by BET method is 4-10 m < ² > / g. By satisfying this range, it is possible to uniformly disperse the magnetic material in the toner and to reduce the fog on the image. If the specific surface area of the magnetic material is smaller than 4 m ² / g, the coloring ability of the toner is lowered and the image density is lowered. In addition, in order to compensate for this, a large amount of a magnetic material is added, so that the fixing performance of the toner is deteriorated or desired magnetic characteristics cannot be obtained. Further, if the specific surface area of the magnetic material is larger than 10 m ² / g, the aggregated particles increase, making it difficult to disperse the magnetic material in the toner, increasing fog, generating in-machine scattering, This leads to a decrease in transfer rate, which is not preferable.
Further, if necessary, a magnetic material and a colorant can be used in combination. Examples of the colorant include carbon black, copper phthalocyanine, and iron black.

  In the positively chargeable magnetic toner of the present invention, it is preferable to use a charge control resin in that the toner is preferably compatible with the binder resin to obtain a good dispersion state, and as a result, a toner having favorable charging characteristics can be obtained. preferable. Among them, it is particularly preferable to use a charge control resin of a styrene-amine copolymer. The general formula of a styrene-amine copolymer is shown below.

Examples of the styrene-amine copolymer include a styrene / dimethylaminoethyl methacrylate copolymer and a styrene / diethylaminoethyl methacrylate copolymer.
In addition, the amine value of these styrene-amine copolymers is preferably 160 to 200 for obtaining good chargeability. If the amine value is smaller than 160, it becomes difficult to impart a good charge as a toner. On the other hand, if it is larger than 200, the compatibility with the binder resin is deteriorated, the charge amount distribution is unevenly distributed, fogging is increased as an image, and in-machine scattering may occur.

  In order to obtain good compatibility with the binder resin, the number average molecular weight of the styrene-amine copolymer is preferably in the range of 4000 to 15000. This is important for compatibility with the low molecular component of the binder resin.

アミン価の測定は、荷電制御樹脂１ｇを秤量し、トルエン２０ｍｌに溶解後、イソプロピルアルコール（ＩＰＡ）２０ｍｌ及びブロムフェノールブルー溶液を数滴加えて１／１０Ｎ塩酸ＩＰＡ溶液で滴定し、終点はブルーから黄緑色になる点とした。

To measure the amine value, weigh 1 g of charge control resin, dissolve in 20 ml of toluene, add 20 ml of isopropyl alcohol (IPA) and a few drops of bromophenol blue solution, and titrate with 1/10 N hydrochloric acid IPA solution. The point turned yellowish green.

  Moreover, the addition amount of the charge control resin is usually 0.2 to 30 parts by weight, preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the binder resin. In consideration of good dispersibility and compatibility with the binder resin, the glass transition temperature is preferably 40 to 70 ° C. and the softening temperature (Ts) is preferably 100 to 140 ° C.

  The release agent used in the positively chargeable magnetic toner of the present invention includes polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene, hydrocarbon waxes such as Fiescher-Tropsch wax, synthetic ester waxes, carnauba wax, rice A release agent selected from the group of natural ester waxes such as wax is used. Among them, it is preferable to use two types of low molecular weight polypropylene and low molecular weight polyethylene in combination. By using these two types in combination, it is possible to improve fixability (fixing strength and rubbing strength), and also improve heat resistance and stability over time. When used in a pulverized toner, the release agent serves as a pulverization point and is selectively present on the toner surface. By using these two release agents in combination, both the performance of the binder resin works. The heat resistance of the toner can be improved. The weight average molecular weight (Mw) of the low molecular weight polypropylene and the low molecular weight polyethylene is preferably in the range of 1000 to 10,000. When the weight average molecular weight (Mw) is smaller than 1000, the strength of the toner becomes weak and the external additive is easily embedded. On the other hand, when the weight average molecular weight (Mw) is larger than 10,000, the performance as a release agent is lowered, and the toner fixing property is deteriorated.

  The effect of the combination of these two types of release agents is that low molecular weight polypropylene greatly contributes to offset prevention, and low molecular weight polyethylene contributes to rubbing strength and has positive chargeability, and the toner itself has a stable positive charge. By imparting the property, it is possible to maintain a stable positive charge on the toner surface even under heat stress. However, if the amount of low molecular weight polyethylene on the toner surface becomes excessive, image unevenness is likely to occur, secondary transfer occurs, and image omission occurs.

  As a preferable use form of the release agent, the content of the low molecular weight polyethylene is 10% to 60% of the content of the low molecular weight polypropylene, and the total content of the two types (content of the release agent) Is preferably 0.5 to 6 parts by weight with respect to 100 parts by weight of the binder resin. If the content of the low molecular weight polyethylene with respect to the low molecular weight polypropylene exceeds 60%, image unevenness tends to occur, secondary transfer occurs, and image omission occurs. Moreover, when the content is less than 10%, the rubbing strength is weakened.

  Further, since it is often difficult to uniformly disperse and distribute the release agent uniformly in the resin, it is preferable to produce the toner after pulverizing the release agent to 10 μm or less.

  As described above, the content of the release agent is preferably 0.5 to 6 parts by weight with respect to 100 parts by weight of the binder resin. On the other hand, if the content of the release agent exceeds 6 parts by weight, the release agent becomes excessive, causing spent on the carrier, filming on the developing sleeve, and the like. The release agent component adheres to the photoreceptor and the quality deteriorates. On the other hand, if the amount is less than 0.5 parts by weight, the effect of adding a release agent is not seen, that is, the heat resistance of low molecular weight polypropylene and the function of improving the rubbing strength of low molecular weight polyethylene cannot be obtained.

  As the external additive used in the positively chargeable magnetic toner of the present invention, those such as a fluidizing agent, an abrasive, a conductivity imparting agent, and a lubricant can be used. Examples of the base material for the fluidizing agent used in the present invention include fine particles of inorganic oxides such as silica, alumina, titania, magnesia, amorphous silicon-aluminum co-oxide, and amorphous silicon-titanium co-oxide. Powder can be used. The fluidizing agent as an external additive has not only the purpose of imparting fluidity to the toner but also the role of imparting and controlling toner chargeability. That is, the external additive adheres to the outermost part of the toner, thereby greatly affecting the chargeability of the toner.

  If the fluidizing agent is used as it is without surface treatment, the environmental stability is impaired due to hygroscopicity, and the fluidizing agent adheres to the surface of the photosensitive drum and causes filming. There is a problem that causes defects. Regarding the problem that the environmental stability due to hygroscopicity is impaired, the fluidizing agent is affected by moisture in a high humidity environment, causing toner charge decay, causing fog on the image, and causing toner scattering in the machine End up. Therefore, it is preferable to carry out surface treatment of the particles used for the fluidizing agent so as to impart hydrophobicity. Further, by selecting the treatment agent used for the surface treatment, it is possible to control and stabilize the chargeability of the toner by imparting desired positive and negative polarities. It is necessary to select the surface treatment agent to be used. Examples of the surface treatment agent for the fluidizing agent used in the present invention include organoalkoxysilanes such as dimethyldimethoxysilane and dimethyldiethoxysilane, organochlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, octadecyltrichlorosilane, and t-butyldimethylchlorosilane. , Compounds of silazanes such as hexamethyldisilazane, and organoaminosilanes such as bis (dimethylamino) dimethylsilane can be used. Of these, aminosilane compounds are particularly preferred in the present invention. By using an aminosilane compound, it is possible to obtain good and stable positive chargeability as a toner.

  As the external additives other than the fluidizing agent used in the positively chargeable magnetic toner of the present invention, the following known additives such as a lubricant, an abrasive, and a conductivity imparting agent can be used. Examples of the lubricant include polytetrafluoroethylene and zinc stearate, and examples of the abrasive include fine powders such as strontium titanate, calcium titanate, barium titanate, calcium carbonate, chromium oxide, silicon carbide, and tungsten carbide. It is done. These abrasives have the effect of removing the toner component deposits and filming on the surface of the photosensitive drum by polishing and scraping. As the conductivity imparting agent, a metal oxide such as tin oxide can be added. However, these examples are merely examples, and what is added and mixed in the positively chargeable magnetic toner of the present invention is not limited to those specifically exemplified above.

  In the positively chargeable magnetic toner of the present invention, the above materials are premixed by a dry blender, a Henschel mixer, a ball mill or the like, and then the mixture is heated by a heat kneader such as a heat roll, kneader, uniaxial or biaxial extruder. It is preferable to manufacture by kneading and kneading the obtained kneaded product by cooling, pulverizing after cooling, and classifying to a desired particle size if necessary. The toner base particles obtained by the classification are finally added to an external additive in the post-processing step to finally become a toner. However, the method for producing the positively chargeable magnetic toner of the present invention is not limited to this kneading and pulverization method. For example, the toner constituent material is dispersed in the binder resin solution and then spray-dried or the binder is baked. It goes without saying that any method of a conventionally known method such as a method of obtaining a toner by mixing a predetermined material with a monomer to constitute the adhesion resin to form an emulsion suspension and then polymerizing it may be used.

  The toner for developing an electrostatic charge image of the present invention preferably has a volume average particle size of 3 to 35 μm, more preferably 5 to 25 μm. In the case of a small particle size toner, the particle size is about 4 to 13 μm.

  In the post-treatment step, a Henschel mixer, a super mixer, etc. are usually used. The post-processing step is an important step for controlling the surface state of the toner. The surface state of the toner changes greatly depending on the post-processing process conditions, and in order to obtain characteristics with excellent stability over time and heat resistance, mixing is usually performed at a low speed of 10 to 30 m / sec at the peripheral speed of the mixer. preferable. Here, the adhesion state of the external additive is in two states, physical adhesion and electrostatic adhesion.

  Even in the mixing step in which an external additive is added to the toner base particles and mixed, this adhesion is found to have a general correlation with the mixing speed, which is the mixing speed. By increasing the number of revolutions of the mixer, the fluidizing agent is strongly fixed in the toner base particles and further tends to be embedded inside. Also, electrostatically, the polarization of the toner base particles and the fluidizing agent increases and adheres strongly. If the fluidizing agent strongly adheres to the toner base particles, the fluidizing agent becomes assimilated on the toner base particles. As a result, the surface of the toner is covered with a fluidizing agent, and it becomes difficult to electrostatically separate the toner base particles from the fluidizing agent even during development, making it difficult to reflect the characteristics of the toner base particles. . In general, in the case of a positively chargeable toner, even if positively chargeable silica is used as a fluidizing agent, the charge of the toner becomes lower than the positive chargeability of the toner base particles, resulting in toner scattering and image fogging. It becomes a cause. Therefore, it is preferable to design the toner so that the fluidizing agent acts as a carrier for the toner base particles during development and is separated from the toner base particles. Further, if extremely weak mixing is performed, the toner base particles and the fluidizing agent cannot be sufficiently mixed, and fluidity cannot be imparted to the toner. That is, if the rotational speed is mixed at a peripheral speed exceeding 30 m / sec., The stability with time of heating deteriorates, and there is a tendency that fogging and in-machine scattering increase due to heating, and the transfer rate also decreases. 10 m / sec. At the following peripheral speeds, it is difficult to sufficiently mix the toner base particles and the external additive.

  As a final step after adding and mixing the external additive, the toner is manufactured through a sieving step for the purpose of removing foreign matters in the toner. As the type of sieve, a vibration sieve, an ultrasonic vibration sieve, a gyro shifter, or the like can be used. At that time, the mesh openings used for sieving affect the toner quality. In the present invention, it is preferable to use a sieve mesh opening of 120 to 300 μm. Furthermore, 150-210 micrometers is preferable. When the toner is manufactured using a mesh having a mesh size larger than 300 μm, coarse particles contained in the toner base particles are mixed in the toner, and aggregates of external additives are contained in the toner. The image characteristics will be adversely affected. That is, the presence of coarse toner particles and external additive aggregates in the developer causes white spots in a solid image and the occurrence of spots on a white background. On the other hand, when the toner is manufactured using a mesh having a mesh size smaller than 120 μm, the toner surface is damaged when the toner passes through the mesh and the toner surface is damaged. The external additive adhered to the toner base particles under the desired conditions in the mixing step becomes a state of being further mixed by this physical stress, and the surface state of the toner changes. This action has the same adverse effect as increasing the peripheral speed in the mixing step, and also adversely affects the image characteristics of the toner. The type of mesh is preferably a plain weave structure, and a twill weave structure can also be used, but generally has a property that coarse particles are likely to be generated. This is because the twill weave structure is more susceptible to stress due to friction and contact during passage than the plain weave structure in terms of the mesh structure.

  When the positively chargeable magnetic toner of the present invention is used as a two-component magnetic developer, a carrier is included. The carrier used together with the positively chargeable magnetic toner of the present invention may be any carrier conventionally used in a two-component dry developer, for example, a ferromagnetic metal such as iron powder or an alloy powder of a ferromagnetic metal, Preferred examples include ferrite powders, magnetite powders, and the like composed of elements such as nickel, copper, zinc, magnesium, barium, and the like, and resin carriers obtained by pulverization and classification after dispersing the magnetic substance in the binder resin. . These carriers are preferably those coated with a resin such as a styrene / methacrylate copolymer, a styrene polymer, a silicone resin, or a fluorine resin. As a method of coating the carrier with a resin, a coating resin is dissolved in a solvent, and this is applied onto the core particles by a dipping method, a spray method, a fluidized bed method, etc., dried, and then heated and applied as necessary. Any known method such as a method of curing the film can be used. The average particle diameter of the carrier is usually 15 to 200 μm, preferably 20 to 100 μm.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the embodiments of the present invention are not limited to these examples. In the following, all parts represent parts by weight.

Binder resin Styrene-butyl acrylate copolymer resin (Tg = 63 ° C.) 52.5 parts
Magnetic material Magnetite (Specific surface area 6 m ² / g) 40 parts Charge control resin (Styrene-amine copolymer: amine value 180) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 2 parts
0.5 parts of low molecular weight polyethylene wax (Mw = 3500) was blended, kneaded, pulverized and classified to obtain toner base particles having an average particle size of 10 μm. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica and 0.3 parts of tungsten carbide surface-treated with hexamethyldisilazane and aminosilane were added to a Henschel mixer. Were mixed using a vibrating sieve and sieved using a vibrating sieve to remove foreign matter, and a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 20 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

The BET specific surface area (A) of the toner obtained here is 1.57 m ² / g, and the BET specific surface area (B) of the heated toner obtained after standing by heating at 50 ° C. for 144 hours is It was 1.44 m ² / g. The value of [(A)-(B)] / (A) was 0.083.

Using the obtained positively chargeable magnetic toner, a live-action test was performed using a commercially available copy machine NP-3050 manufactured by Canon Inc. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained toner was used, the fog was as low as 0.6, the image density was stable at 1.36, and the transfer rate of the toner after 100,000 sheets was 86% even after the actual shooting of 100,000 sheets. . Also, no toner scattering was observed in the machine. Here, the transfer rate is a value obtained by calculating the difference between the toner amount (Tw) in the collection container from the consumed toner amount (Ta), determining the weight of the transferred toner, and determining the ratio with the consumed toner amount. It is expressed as
Transfer rate (%) = (Ta−Tw) / Tax 100
[Example 2]
Binder resin Styrene-butyl acrylate copolymer resin (Tg = 63 ° C.) 52 parts
Magnetic material Magnetite (Specific surface area 5 m ² / g) 40 parts Charge control resin (Styrene-amine copolymer: amine value 180) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 2.5 parts
0.5 part of low molecular weight polyethylene wax (Mw = 3500) was blended, kneaded, pulverized and classified to obtain toner base particles having an average particle size of 10 μm. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica surface-treated with hexamethyldisilazane and aminosilane, 0.3 parts of tungsten carbide, conductive After mixing 0.3 parts of tin oxide fine powder with a Henschel mixer and sieving using a vibrating sieve to remove foreign matter, a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 20 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

Further, the BET specific surface area (A) of the toner obtained here is 1.74 m ² / g, and the BET specific surface area (B) of the heated toner obtained after leaving to stand at 50 ° C. for 144 hours is It was 1.51 m ² / g. The value of [(A)-(B)] / (A) was 0.132.

Using this toner thus obtained, a live-action test was performed using a commercially available Canon Co. NP-3050. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained positively chargeable magnetic toner was used, the fog was as low as 0.7 and the image density was stable at 1.36 even after the actual copying of 100,000 sheets, and the transfer rate of the toner after 100,000 sheets was 85. %Met. Also, no toner scattering was observed in the machine.
[Example 3]
Binder resin Styrene-butyl acrylate copolymer resin (Tg = 65 ° C.) 52.5 parts
Magnetic material Magnetite (Specific surface area 6m ² / g) 40 parts Charge control resin (Styrene-amine copolymer: amine value 180) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 2.0 parts
0.5 part of low molecular weight polyethylene wax (Mw = 3500) was blended, kneaded, pulverized and classified to obtain toner base particles having an average particle size of 10 μm. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica surface-treated with hexamethyldisilazane and aminosilane, 0.3 parts of tungsten carbide, conductive 0.2 parts of tin oxide fine powder was mixed with a Henschel mixer, sieved using a vibrating sieve to remove foreign matters, and a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 20 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

The BET specific surface area (A) of the toner obtained here is 1.67 m ² / g, and the BET specific surface area (B) of the heated toner obtained after being left to stand at 50 ° C. for 144 hours is It was 1.59 m ² / g. The value of [(A)-(B)] / (A) was 0.048.

Using the obtained positively chargeable magnetic toner, a live-action test was performed using a commercially available copy machine NP-3050 manufactured by Canon Inc. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained toner was used, the fog was as low as 0.5 and the image density was stable at 1.37 even after the actual copying of 100,000 sheets, and the transfer rate of the toner after 100,000 sheets was 87%. . Also, no toner scattering was observed in the machine.
[Comparative Example 1]
Binder resin Styrene-butyl acrylate copolymer resin (Tg = 59 ° C.) 52.5 parts
Magnetic material Magnetite (Specific surface area 9 m ² / g) 40 parts Charge control resin (Styrene-amine copolymer: amine number 180) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 2.5 parts are blended and kneaded. By pulverization and classification, toner mother particles having an average particle diameter of 10 μm were obtained. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica surface-treated with hexamethyldisilazane and aminosilane, 0.3 parts of tungsten carbide, conductive After mixing 0.3 parts of tin oxide fine powder with a Henschel mixer and sieving using a vibrating sieve to remove foreign matter, a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 20 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

The BET specific surface area (A) of the toner obtained here is 1.67 m ² / g, and the BET specific surface area (B) of the heated toner obtained after being left to stand at 50 ° C. for 144 hours is It was 1.38 m ² / g. The value of [(A)-(B)] / (A) was 0.174.

Using the obtained positively chargeable magnetic toner, a live-action test was performed using a commercially available copy machine NP-3050 manufactured by Canon Inc. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained toner was used, fogging increased to 2.7 after 20,000 actual images were taken, and the image test was stopped because image smearing occurred due to scattering in the machine.
[Comparative Example 2]
Binder resin Styrene-butyl acrylate copolymer resin (Tg = 59 ° C.) 52 parts
Magnetic material Magnetite (Specific surface area 12 m ² / g) 40 parts Charge control resin (Styrene-amine copolymer: amine value 180) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 3 parts are blended, kneaded, pulverized, Classification was performed to obtain toner base particles having an average particle size of 10 μm. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica surface-treated with hexamethyldisilazane and aminosilane, 0.3 parts of tungsten carbide, conductive After mixing 0.3 parts of tin oxide fine powder with a Henschel mixer and sieving using a vibrating sieve to remove foreign matter, a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 30 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

Further, the BET specific surface area (A) of the toner obtained here is 1.72 m ² / g, and the BET specific surface area (B) of the heated toner obtained after leaving to stand at 50 ° C. for 144 hours is It was 1.35 m ² / g. The value of [(A)-(B)] / (A) was 0.198.

Using the obtained positively chargeable magnetic toner, a live-action test was performed using a commercially available copy machine NP-3050 manufactured by Canon Inc. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained toner was used, fogging increased to 3.2 after 5,000 actual images were taken, and the image test was stopped because image contamination occurred due to scattering in the machine.
[Comparative Example 3]
Binder resin Styrene-butyl acrylate copolymer resin (Tg = 59 ° C.) 52 parts
Magnetic material Magnetite (specific surface area 13 m ² / g) 40 parts Charge control resin (styrene-amine copolymer: amine number 140) 5 parts Wax Low molecular weight polypropylene wax (Mw = 4000) 3 parts are blended, kneaded, pulverized, Classification was performed to obtain toner base particles having an average particle size of 10 μm. The toner base particles, 100 parts of the toner base particles, 0.3 parts of positively charged hydrophobic silica surface-treated with hexamethyldisilazane and aminosilane, 0.3 parts of tungsten carbide, conductive After mixing 0.3 parts of tin oxide fine powder with a Henschel mixer and sieving using a vibrating sieve to remove foreign matter, a positively chargeable magnetic toner was obtained. At this time, the mixing condition of the Henschel mixer was a peripheral speed of 30 m / sec. The mesh used for the vibration sieve was 180 μm (plain weave).

Further, the BET specific surface area (A) of the toner obtained here is 1.66 m ² / g, and the BET specific surface area (B) of the heated toner obtained after leaving to stand at 50 ° C. for 144 hours is It was 1.24 m ² / g. The value of [(A)-(B)] / (A) was 0.253.

  Using the obtained positively chargeable magnetic toner, a live-action test was performed using a commercially available copy machine NP-3050 manufactured by Canon Inc. At this time, the toner was heated in a dryer (Daily Scientific Co., Ltd. DN-62 type) at 50 ° C. for 144 hours in order to promote confirmation of change with time. When the obtained positively chargeable magnetic toner was used, fogging increased to 3.6 from the beginning, and image smearing occurred due to scattering in the apparatus, so the image test was stopped.

  The positively chargeable magnetic toner of the present invention can be preferably used in an electrophotographic dry developer, a copying machine using a toner, a printer, and the like, and has excellent heat resistance and stability over time, and heat stress during transportation and storage. Thus, it is possible to provide a toner having an excellent quality that does not deteriorate even if the toner is received.

Claims (7)

A positively chargeable magnetic toner comprising toner base particles containing at least a binder resin, a magnetic material, a charge control resin, and a release agent, and an external additive, wherein the toner has a BET specific surface area (A) of 50 toner. A positively chargeable magnetic toner characterized in that the relationship with the BET specific surface area (B) of a heated toner obtained by cooling after standing at 150 ° C. for 144 hours satisfies the following conditional expression (A):
[(A)-(B)] / (A) ≦ 0.15 (b)   The positively chargeable magnetic toner according to claim 1, wherein at least one of the external additives is a positively chargeable inorganic oxide. The positively chargeable magnetic toner according to claim 1, wherein the magnetic material has a BET specific surface area of 4 to 10 m ² / g.   The positively chargeable magnetic toner according to claim 1, wherein the binder resin has a glass transition temperature (Tg) of 60 to 68 ° C.   The release agent contains two types of low molecular weight polypropylene and low molecular weight polyethylene, the content of the low molecular weight polyethylene is 10% or more and 60% or less of the content of the low molecular weight polypropylene, and the total content of the release agent is The positively chargeable magnetic toner according to claim 1, wherein the amount is 0.5 to 6 parts by weight with respect to 100 parts by weight of the binder resin.   The positively chargeable magnetic toner according to claim 1, wherein the charge control resin is a styrene-amine copolymer.   The positively chargeable magnetic toner according to claim 6, wherein the styrene-amine copolymer has an amine value of 160 to 200.