JP2005352246A - Positive charge type magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charge type magnetic toner excellent not only in offset resistance but in toner properties such as low-temperature fixability, sharp meltability, blocking resistance, charging characteristics and pulverizability and capable of forming good developed images over a prolonged period of time, without using bisphenol A or a derivative thereof as a component of a polyester resin in the toner. <P>SOLUTION: The positive charge type magnetic toner contains a binder resin, a magnetic material and a charge control agent, wherein the binder resin is a linear polyester resin which comprises an acid component consisting of (1) disproportionated rosin and (2) terephthalic acid and/or isophthalic acid and an alcohol component consisting of (3) a glycidyl ester of a tertiary fatty acid and (4) a 2-10C aliphatic diol, and has an acid value of <10 mgKOH/g and a hydroxyl value of ≤20 mgKOH/g, and wherein a BET specific surface area of the magnetic material by a nitrogen adsorption method is 3.0-9.0 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positive electrode used for developing an electrostatic charge image in an electrophotographic copying machine, a laser beam printer, an electrostatic recording apparatus or the like in which an image is formed using an electrophotographic method, an electrostatic recording method, or the like. The present invention relates to a chargeable magnetic toner.

  Conventionally, the electrophotographic method or the electrostatic recording method has been widely used as a method for obtaining a copy or recorded image in a copying machine for copying an original or a printer for outputting a computer including a personal computer or a printer for a facsimile receiving apparatus. Has been. Typical examples of the copying machine and printer using the electrophotographic method or the electrostatic recording method include an electrophotographic copying machine, a laser beam printer, a printer using a liquid crystal array, and an electrostatic printer. In the electrophotographic method or the electrostatic recording method, an electrostatic latent image (electrostatic image) is formed by various means on an electrostatic image carrier such as an electrophotographic photosensitive member or an electrostatic recording material. While developing the image with a developer, the obtained toner image is transferred to a transfer medium such as paper as necessary, and fixed by heating, pressing, heating and pressing, or solvent vapor to obtain a final toner image The toner remaining without being transferred onto the electrostatic image bearing member is removed by the cleaning means. By repeating these steps, a plurality of copies or records can be obtained sequentially.

  As a method for developing the electrostatic latent image, a method using a liquid developer in which a fine toner is dispersed in an electrically insulating liquid (wet development method), a colorant in a binder resin, and a magnetic material as necessary. A method of using dispersed powder toner together with carrier particles, a method of developing without using carrier particles using a magnetic toner in which a magnetic material is dispersed in a binder resin (dry development method), etc. are known. . Among these methods, in recent years, a dry development method using powder toner (magnetic toner, non-magnetic toner) is mainly employed.

  By the way, in recent years, electrophotographic copying machines, laser beam printers, and the like have become smaller and more personalized, and at the same time, higher speed has been required, and further reduction in energy has been required. For this reason, various attempts have been made to improve these apparatuses for forming a reliable and high-quality image with low energy over a long period of time by a mechanism as simple as possible. In addition to such improvements in the apparatus, various attempts have been made to improve the toner used for development.

  Further, as a device for fixing a toner image, a heat and pressure fixing device using a heating roller, a roll-shaped or long heat-resistant film, a so-called fixing belt is used, and a heating body and a transfer are transferred via the fixing belt. 2. Description of the Related Art A heat and pressure fixing device is widely used in which a sheet development surface is opposed and a transfer sheet is conveyed from the back while being pressed by a pressure roller to heat and fix the sheet. In the fixing method using these heat fixing devices, the heat roller or the fixing belt is in direct contact with the toner image at the time of fixing, so that the heat is efficiently transmitted to the toner, and the toner is melted quickly and smoothly with low energy. Can be done. However, since the molten toner and the heat roller or the fixing belt are in direct contact with each other at the time of fixing, a part of the melted toner is transferred and adhered to the surface of the heat roller or the fixing belt. When the transferred and adhered toner is transferred again to the transferred material when it contacts the transferred material, or when the transferred material does not exist, the transferred and transferred toner is transferred to the pressure roller and transferred to the pressure roll. There is a problem in that when the transferred object passes through the fixing device, a toner adhering to the pressure roll causes a so-called offset phenomenon such that the back surface of the transferred object becomes dirty, and the transferred object becomes dirty.

In order to prevent such a toner offset phenomenon, the surface of a conventional heat roll is formed of a releasable material such as silicone rubber or fluororesin, and a liquid having good releasability such as silicone oil is applied to the surface. Generally, the surface of a hot roll is covered with a releasable liquid film layer. According to this method, the occurrence of the offset phenomenon can be substantially prevented, but a problem arises in that a releasable liquid coating apparatus is required, and the silicone oil evaporates due to heat and contaminates the inside of the apparatus. Also, providing such a releasable liquid coating apparatus is incompatible with the downsizing of the apparatus. For this reason, the releasable liquid is not applied by a coating device, but the toner itself contains a releasable substance, the releasable substance is melted by heating during fixing, and the releasable liquid is supplied from the toner. In order to prevent the offset phenomenon, a number of waxes such as low molecular weight polyethylene, low molecular weight polypropylene, hydrocarbon waxes, natural waxes and modified waxes obtained by modifying them are proposed as such releasable substances. (For example, see Patent Documents 1 and 2).
Japanese Patent Publication No.52-3304 JP-A-60-252360

On the other hand, from the viewpoint of improving the low-temperature fixability of the toner, it is effective to lower the softening temperature (Tm) of the toner binder resin. However, in general, when Tm is lowered, the glass transition temperature (Tg) of the toner is also lowered at the same time, so that it is easy to cause so-called toner blocking in which the toner forms a lump in a storage state and toner offset at the time of fixing. This is one of the reasons why the fixing temperature cannot be lowered as expected. As a method for simultaneously satisfying this low-temperature fixability and blocking resistance or offset resistance, a method using a polyester resin having a relatively low fixing temperature even when Tm or Tg is high (for example, see Patent Document 3) has been proposed. ing. However, this method does not satisfy the low-temperature fixing property, blocking resistance, offset resistance and the like simultaneously and sufficiently. In addition, examples in which alkylene glycol and etherified diphenol are used in combination as an alcohol component of a polyester resin are also known (see, for example, Patent Documents 4 and 5), but the toner is not sufficiently pulverizable or has a low Tg. The blocking resistance of the obtained toner is not satisfactory. In addition, a dihydric alcohol is used as the alcohol component, and a non-linear cross-linked polyester resin composed of rosin, unsaturated dicarboxylic acid and other dicarboxylic acid as the acid component (see, for example, Patent Document 6), a specific alcohol component or Examples using acid components (see, for example, Patent Documents 7, 8, 9), examples using block polymers (see, for example, Patent Document 10), examples using amorphous polyester and crystalline polyester in combination (for example, Patents) A large number of polyester resins for toner binders have been proposed, such as offset resistance, low temperature fixability, sharp melt properties, blocking resistance, charging properties, pulverization properties, and transparency required as toner properties. Resins that can be used for toners that can simultaneously satisfy the properties have been developed.
JP-A-56-1952 Japanese Patent Laid-Open No. 1-226761 JP-A-1-155360 JP-A-4-70765 Japanese Patent Laid-Open No. 6-27728 Japanese Patent Laid-Open No. 9-278872 Japanese Patent Laid-Open No. 10-268558 JP 2001-324832 A JP 2002-284866 A

  As described above, attempts have been made to produce positively chargeable magnetic toners with good characteristics by using polyester resin as a binder resin for the toner. Conventionally, polyester binder resins for toner with good toner characteristics are obtained. In this case, it is generally considered that it is necessary to use bisphenol A or a derivative thereof as an alcohol component. In recent years, however, it has become clear that bisphenol A is not necessarily used from the viewpoint of environmental hormones. Development of a polyester resin for toner that is excellent in properties such as blocking resistance, charging properties, pulverization properties, and transparency, and that can form a good developed image over a long period of time, and a positively chargeable magnetic toner is desired. .

  Furthermore, the economics of toners have recently become important, and there has been a demand for provision of an inexpensive toner binder resin. However, conventional toner binders cannot always meet such requirements. It was.

  In addition, from the viewpoint of resource saving, there is a demand for a positively chargeable magnetic toner capable of forming a toner image having a high density similar to the conventional one with a small amount of toner.

  In view of such a current situation, the object of the present invention is to fix a polyester resin produced without using bisphenol A or a derivative thereof as a component of the polyester resin in the toner, a specific magnetic substance, and a charge control agent. In addition to excellent offset resistance, the toner properties such as low-temperature fixability, sharp melt resistance, blocking resistance, charging characteristics, and pulverization properties are also positive, and positively chargeable magnetism that can form good developed images over a long period of time To provide toner.

  Another object of the present invention is to provide a positively chargeable magnetic toner using an inexpensive polyester resin for toner as a binder resin.

  Another object of the present invention is to provide a positively chargeable magnetic toner capable of forming an image having the same density as that of the prior art by using a small amount.

The present invention relates to a positively chargeable magnetic toner containing at least a binder resin, a magnetic material, and a charge control agent, wherein the binder resin has acid components of (1) disproportionated rosin, (2) terephthalic acid and / or Alternatively, the isophthalic acid or alcohol component is composed of (3) a glycidyl ester of a tertiary fatty acid and (4) an aliphatic diol having 2 to 10 carbon atoms, and the acid value is less than 10 mgKOH / g and the hydroxyl value is 20 mgKOH / g. A positively chargeable magnetic toner which is a linear polyester resin as described below and has a BET specific surface area of 3.0 to 9.0 m ² / g as measured by a nitrogen adsorption method.

The present invention also relates to the above positively chargeable magnetic toner, wherein the binder resin has a true density of 1.1 to 1.3 g / cm ³ .

 The present invention also relates to the above positively chargeable magnetic toner, wherein the oil absorption of the magnetic material is 19 to 29 ml / 100 g.

The present invention also relates to the above positively chargeable magnetic toner, wherein the magnetic material has a true density of 5.20 to 5.40 g / cm ³ .

  The present invention also relates to the above positively chargeable magnetic toner, wherein the charge control agent is a nigrosine dye.

 The present invention also relates to the above positively chargeable magnetic toner, wherein the nigrosine dye is based on nigrosine.

 The present invention also relates to the above positively chargeable magnetic toner, wherein the Fe content in the nigrosine base is 1.0% or less.

  Since the positively chargeable magnetic toner of the present invention does not use bisphenol A derivatives such as bisphenol A or an ethylene oxide adduct of bisphenol A as the alcohol component of the linear polyester resin that is the binder resin of the toner, it is an environmental hormone viewpoint. Therefore, it is possible to obtain a positively chargeable magnetic toner that is environmentally friendly.

  By using this linear polyester resin, the same or higher anti-offset property, low-temperature fixing property, sharp melt property, blocking resistance, charging property, and the like, without using bisphenol A or a bisphenol A derivative, A positively chargeable magnetic toner having characteristics such as grindability and transparency can be obtained. As a result, the storage stability of the toner classified product is improved, and a good developed image can be formed over a long period from the beginning of development without causing a decrease in fluidity of the toner during development and blocking of the toner.

  Furthermore, since bisphenol A or a derivative thereof is not used in the present invention, a linear polyester resin can be manufactured at a low cost, and the true density of the resin is higher than that using bisphenol A or a derivative thereof as an alcohol component. Therefore, if the positively chargeable magnetic toner of the present invention is used, the amount of toner used per sheet can be reduced, and the copying cost can be reduced.

  Hereinafter, the present invention will be described in more detail. First, in the linear polyester resin used as the binder resin in the positively chargeable magnetic toner of the present invention, (a) the acid component is disproportionated rosin (1) and terephthalic acid and / or isophthalic acid (2), (b ) The alcohol component is composed of a glycidyl ester of a tertiary fatty acid (3) and an aliphatic diol (4) having 2 to 10 carbon atoms, and has an acid value of less than 10 mgKOH / g and a hydroxyl value of 20 mgKOH / g or less. It is necessary.

In the linear polyester resin used in the present invention, the disproportionated rosin used as the acid component of (a) may be produced by any conventionally known production method. For example, rosin is converted to Pd. A method of saponifying the reaction product by reacting at 250 to 300 ° C., 5 to 15 kg / cm ² for 2 to 6 hours in the presence of a disproportionation catalyst such as a carbon catalyst can be mentioned.
Commonly available gum rosin, tall oil rosin, and the like have a lot of abietic acid containing a conjugated double bond and are very easily oxidized. Therefore, it is preferable to disproportionate in order to prevent discoloration and alteration due to air oxidation. . Here, abietic acid is disproportionated into dehydroabietic acid and dihydroabietic acid, and is contained in the disproportionated rosin.

 On the other hand, terephthalic acid and isophthalic acid are composed of terephthalic acid, isophthalic acid and their lower alkyl esters. Examples of lower alkyl esters of terephthalic acid and isophthalic acid include, for example, dimethyl terephthalate, dimethyl isophthalate, diethyl terephthalate, diethyl isophthalate, dibutyl terephthalate, and dibutyl isophthalate. Dimethyl acid and dimethyl isophthalate are preferred. These dicarboxylic acids or lower alkyl esters thereof may be used alone or in combination of two or more.

 The molar ratio of disproportionated rosin (1) to terephthalic acid and / or isophthalic acid (2) is preferably (1) / (2) = 0.1 to 0.5. More preferably, it is 0.2-0.3. When the molar ratio of the disproportionated rosin (1) and terephthalic acid and / or isophthalic acid (2) is lower than 0.1, the fixability tends to deteriorate and fog tends to occur. If it exceeds .5, the offset resistance tends to deteriorate and the image density tends to decrease.

  As the acid component, dicarboxylic acids other than these can be used together with terephthalic acid and isophthalic acid as long as the object of the present invention is not impaired. Examples of these other dicarboxylic acids include benzene dicarboxylic acids such as phthalic acid and phthalic anhydride; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid; succinic acid substituted with an alkyl group having 16 to 18 carbon atoms. Acids; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid, glutaconic acid; cyclohexane dicarboxylic acid; naphthalenedicarboxylic acid; diphenoxyethane-2,6-dicarboxylic acid and lower monoesters of these acids; Examples include diesters and acid anhydrides. Since these dicarboxylic acids greatly affect the fixing property and blocking resistance of the toner, they are used in an appropriate amount in consideration of the required performance of the toner.

  Moreover, as an example of the glycidyl ester of the tertiary fatty acid used as an alcohol component of (b), what is represented, for example by following General formula (1) is mentioned.

(In the formula, R ¹ , R ² and R ³ represent an alkyl group.)
In the above formula, the total number of carbon atoms of R ¹ , R ² and R ^{3 and} the carbon number of these groups is not particularly limited, but neodecanoic acid glycidyl ester having a total carbon number of R ¹ + R ² + R ³ is particularly 8 preferable.

  Examples of the aliphatic diol having 2 to 10 carbon atoms include, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4 -Butanediol, 2,3-butanediol, 1,4-butenediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2-ethyl-2-methylpropane-1 , 3-diol, 2-butyl-2-ethylpropane-1,3-diol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2 , 4-Dimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,7-heptanediol, 1,8-octane Diol, 1,9-nonanediol, 1,10-decanediol, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropanoate, diethylene glycol, triethylene glycol, dipropylene glycol, etc. Is mentioned. As the aliphatic diol, neopentyl glycol and ethylene glycol are preferable from the viewpoint of reactivity with acid and glass transition temperature of the resin. These aliphatic diols may be used alone or in combination of two or more.

The molar ratio of the tertiary fatty acid glycidyl ester (3) and the aliphatic diol (4) having 2 to 10 carbon atoms is preferably (3) / (4) = 0.05 to 0.20. More preferably, it is 0.10-0.15. When the molar ratio of the tertiary fatty acid glycidyl ester (3) and the aliphatic diol (4) having 2 to 10 carbon atoms is lower than 0.05, image fog is likely to occur and exceeds 0.2. In some cases, offset resistance and blocking resistance tend to deteriorate. By using rosin glycidyl ester together with glycidyl ester of tertiary fatty acid, offset resistance and blocking resistance are improved.
It is preferable to use 5 to 30 mol% of the glycidyl ester of the tertiary fatty acid in the component (b). The molar ratio (2) / (4) of the aliphatic diol of the alcohol component (4) to the dicarboxylic acid of the component (2) of the acid component is the molar ratio (1) of the acid components (1) and (2). Although it varies depending on the value of the molar ratio (3) / (4) of / (2) and alcohol components (3) and (4), it is usually preferably 0.8 to 1.5, more preferably 0.9 to 1.1, particularly preferably 0.95 to 1.05.

The linear polyester resin used in the positively chargeable magnetic toner of the present invention having the above structure has an acid value of less than 10 mgKOH / g and a hydroxyl value of 20 mgKOH / g or less, preferably 15 mgKOH / g or less. is necessary.
On the other hand, when the acid value is 10 mgKOH / g or more, the positive chargeability of the toner is reduced, and the image density is lowered, or the fogging of the image and the in-machine scattering are increased. Further, since the hydrophilicity is further increased, the image density is lowered particularly in a high humidity environment. In the production examples of the linear polyester resin of the present invention, the acid value is 2.1 to 8.2 mgKOH / g, and the acid value is the polyester of the present invention. It is important for the resin to be less than 10 mg KOH / g.
Further, similarly, when the hydroxyl value exceeds 20 mgKOH / g, the hydrophilicity increases, so that the image density is lowered particularly in a high humidity environment. In the production examples of the linear polyester resin of the present invention, the hydroxyl value is 4.9 to 14.9 mgKOH / g, and the good results are obtained. It is important that the resin is suppressed to 20 mgKOH / g or less.

  The linear polyester resin used for the positively chargeable magnetic toner of the present invention has a softening temperature of 115 to 150 ° C., preferably 120 to 145 ° C., and a number average molecular weight of tetrahydrofuran (THF) solubles of 1,000 to 6. 2,000, preferably 2,000 to 4,000. This is because when the softening temperature is less than 115 ° C., the cohesive strength of the resin is extremely reduced, while when it exceeds 150 ° C., the melt flow and low-temperature fixability of the toner using the resin are reduced. This is because it is not suitable for a toner binder. Here, when the number average molecular weight decreases, the offset resistance of the toner tends to decrease, and when the number average molecular weight increases, the fixability tends to decrease.

The linear polyester resin used in the positively chargeable magnetic toner of the present invention is a type having a molecular weight distribution curve of two peaks composed of a specific low molecular weight condensation polymer component and a specific high molecular weight condensation polymer component. Alternatively, it may be of any type having a single molecular weight distribution curve. From the viewpoint of preventing toner aggregation, it is desirable that the glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) is 45 to 70 ° C., preferably 50 to 65 ° C. Furthermore, the true density of the resin is preferably 1.1 to 1.3 g / cm ³ . When the true density of the resin is low, the toner can be used in a small amount when an image having the same density is formed, and as a result, economical copying can be performed.

  The linear polyester resin used in the positively chargeable magnetic toner of the present invention is prepared by a known and commonly used production method using the predetermined acid component and alcohol component as raw materials. The reaction method may be transesterification or direct esterification. Any of the chemical reactions can be applied. In addition, polycondensation can be promoted by a method of increasing the reaction temperature by pressurization, a depressurization method, or a method of flowing an inert gas under normal pressure. In the above reaction, a known and commonly used reaction catalyst such as at least one metal compound selected from antimony, titanium, tin, zinc and manganese may be used to accelerate the reaction. Specific examples of the reaction catalyst include di-n-butyltin oxide, stannous oxalate, antimony trioxide, titanium tetrabutoxide, manganese acetate, and zinc acetate. The amount of these reaction catalysts added is usually preferably about 0.001 to 0.5 mol% in the resulting polyester resin.

  In the method for producing a linear polyester resin used in the positively chargeable magnetic toner of the present invention, a direct esterification method at normal pressure is one of the preferred methods among the various reactions described above. In this direct esterification method, for example, the alcohol component and the disproportionated rosin are charged all at the start of the reaction, and the temperature is raised to about 160 ° C. and then a high melting point terephthalic acid, isophthalic acid and a reaction catalyst are charged. Be taken. As the reaction catalyst, acids, alkalis, amines, metal organic acid salts and the like are effective. In addition, titanate, borate and the like are also effective. Specifically, di-n-butyltin oxide, stannous oxalate, antimony trioxide, zinc octylate, iron octylate and the like are used, and the addition amount is 0.01 to 0.1 with respect to the total acid component. A mol% is suitable. In this case, a sufficient reaction rate can be obtained even at normal pressure, but the reaction temperature can be increased by applying a pressurizing operation. The promotion of the reaction by the depressurization operation is applied in the case where almost no unreacted alcohol disappears at the end of the reaction, and the removal of the produced water out of the system is delayed. The promotion of the reaction by passing through an inert gas can be applied to any process of the reaction in such an amount that it minimizes the dissipation of alcohol out of the system. The reaction is terminated after confirming that the softening point of the resin has reached a predetermined temperature.

 The binder resin used in the positively chargeable magnetic toner of the present invention may be the above linear polyester resin alone, or two or more of the above linear polyester resins may be used in combination. Furthermore, as long as the object of the present invention can be achieved, conventional toner binder resins such as polystyrene polymers, polystyrene copolymers such as styrene-acrylic resins, and polyester resins other than the above linear polyester resins. The resin used as the above may be used together with the linear polyester resin.

Examples of magnetic materials that can be used in the positively chargeable magnetic toner of the present invention include iron oxides such as magnetite, maghematite, and ferrite, or a compound of a divalent metal and iron oxide, iron, cobalt, nickel, and the like. Powders of metals or alloys of these metals with aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium Body and mixtures thereof. Among these, magnetite (triiron tetroxide: Fe ₃ O ₄ ) is preferable. Moreover, the addition amount of 5-120 weight part with respect to 100 weight part of binder resin normally, Preferably 60-100 weight part is good.

In the positively chargeable magnetic toner of the present invention, it is important to use a magnetic material having a BET specific surface area of 3.0 to 9.0 m ² / g by a nitrogen adsorption method. More preferably, it is 4.0-8.0 m < ² > / g. By satisfying this range, the magnetic substance can be well dispersed and blended in the linear polyester resin of the present invention, and good charging characteristics and image characteristics can be obtained as a toner. If a magnetic material having a specific surface area of more than 9.0 m ² / g according to the BET method is used, the magnetic material in the vicinity of the toner surface will increase too much, and the charge amount of the toner will decrease and fog on the image will increase. In addition, there is a risk of causing toner scattering in the machine, and the quality of the copied image is deteriorated. Further, it becomes difficult to uniformly disperse and distribute the magnetic material in the binder resin. On the other hand, when a specific surface area smaller than 3.0 m ² / g is used, the particle size of the magnetic material becomes rough, and it becomes difficult to give sufficient coloring power as a toner. Further, the resistance of the toner is increased, the charge amount is excessively increased, the image is scattered, the image is crushed, and the defect of the image density is lowered.

  The oil absorption of the magnetic material used in the positively chargeable magnetic toner of the present invention is preferably in the range of 19 to 29 ml / 100 g. Within this range, the magnetic material can be uniformly dispersed in the binder resin. If the oil absorption amount of the magnetic material is smaller than 19 ml / 100 g, it becomes difficult for the binder resin to hold the magnetic material, and it is easy to fall off the binder resin, which is not preferable as a toner. On the other hand, if it is larger than 29 ml / 100 g, the magnetic substance tends to aggregate in the binder resin, resulting in poor dispersion and distribution. As a result, there is a difference between the magnetic substance content in the toner particles and the magnetic substance content in the classified fine powder. I will leave. Therefore, it becomes difficult to recycle the classified fine powder at the time of toner production.

The true density of the magnetic material used in the positively chargeable magnetic toner of the present invention is preferably in the range of 5.20 to 5.40 g / cm ³ . If it is this range, a magnetic body can be favorably disperse | distributed in binder resin. If the true density of the magnetic material exceeds 5.40 g / cm ^3, the density of the toner itself also increases, and the amount of toner used increases when forming an image. ^{On the other hand} , if it is less than 5.20 g / cm ^{3, a} problem that aggregation easily occurs in the binder resin occurs.

  The positively chargeable magnetic toner of the present invention needs to contain a charge control agent in order to maintain sufficient positive chargeability. In particular, in the case of a polyester resin, since the negative chargeability is strong, a charge control agent is necessary to give positive chargeability. Typical examples of the charge control agent include a nigrosine dye (such as a nigrosine base, a mixture obtained by modifying a nigrosine base with a resin acid, a mixture obtained by modifying a nigrosine base with a stearic acid), triphenylmethane, and the like. Dyes and their lake pigments (such as phosphotungstic acid, phosphomolybdic acid, water-soluble salts of phosphotungsten molybdic acid), quaternary ammonium salts (tributylbenzylammonium-1-hydroxy-4-naphthalenesulfone) Acid salt, tributylbenzylammonium-2-hydroxy-8-naphthalenesulfonate, triethylbenzylammonium-1-hydroxy-4-naphthalenesulfonate, tripropylbenzylammonium-1-hydroxy-4-naphthalenesulfone Salt, tripropylbenzylammonium-2-hydroxy-6-naphthalenesulfonate, trihexylbenzylammonium-1-hydroxy-4-naphthalenesulfonate, tetrabutylammonium-1-hydroxy-4-naphthalenesulfonate, tetra Octylammonium-1-hydroxy-4-naphthalenesulfonate, etc.), an organic tin oxide, an electron donating substance such as a polymer having an amino group, or a combination of two or more thereof can be used. Among these, it is preferable to use a nigrosine dye, particularly a nigrosine base.

Nigrosine base is produced by the following method. Oxidation and reaction with nitrobenzene at 160-180 ° C. in the presence of aniline, hydrochloric acid and ferric chloride to obtain crude nigrosine, then basing the crude nigrosine with aniline, water and sodium hydroxide, The precipitate is separated into nigrosine and iron hydroxide by centrifugation, the iron hydroxide precipitate is removed, the resulting liquid is further washed with water, and the liquid is dried and ground to obtain a nigrosine base. Here, it is preferable to make the base while re-adding aniline to the crude nigrosine at the time of base, in order to adjust the size of the nigrosine base, prevent agglomeration, and obtain stable chargeability.
The Fe content in the obtained nigrosine base is preferably 1.0% or less. If the Fe content is more than 1.0%, the conductivity of the nigrosine dye becomes high, and the charge holding ability is lowered. When the charge retention capability is reduced, the original function as a charge control agent is reduced, and as a result, the charge amount of the toner is reduced, which may cause problems such as an increase in fog, a decrease in image density, and scattering in the apparatus. . The Fe content is adjusted by changing the centrifugation conditions.
It is also preferable to mix the obtained nigrosine base with a resin, higher fatty acid and the like to obtain a mixture. In particular, a charge control agent that is easily dispersed in the toner can be obtained by mixing with a maleic acid resin and a xylene resin and dispersing the nigrosine base.

  The charge control agent can be used more effectively by pulverizing with a pulverizer and adjusting to a desired particle size distribution. In the present invention, a preferable particle size distribution as a charge control agent is 0.5 to 40 μm, more preferably 1 to 20 μm, as a volume average particle size by a Coulter counter. When the volume average particle diameter is larger than 40 μm, it becomes difficult to disperse the charge control agent in the binder resin, and it becomes difficult to disperse the charge control agent in the toner. In addition, the content of the charge control agent per individual particle of the toner is biased, leading to an increase in fog on the image and scattering in the apparatus. On the other hand, when a material having a volume average particle size of less than 0.5 μm is used, the dispersion in the binder resin is good, but the specific surface area of the charge control agent becomes large, and the toner is excessively charged. In some cases, the charge amount increases and the image density decreases.

  The addition amount of the charge control agent is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  The positively chargeable magnetic toner of the present invention contains a binder resin mainly composed of the above-described linear polyester resin, a magnetic material, and a charge control agent, and further includes a release agent and an external additive as necessary. Blended.

The positively chargeable magnetic toner of the present invention contains a release agent as necessary. Among these, it is preferable to use a wax having a melt viscosity at 140 ° C. of 100 mPa · s (CS) or less and an acid value of 2 mgKOH / g or less, and 0.5 to 10% by weight based on 100 parts by weight of the binder resin. Can be made.
Examples of such waxes include fatty acid esters such as polypropylene wax, polyethylene wax, paraffin wax, fatty acid amide wax, carnauba wax, and montan wax, partially saponified fatty acid ester wax, and fatty acid metal salts.
When the melt viscosity at 140 ° C. of the wax exceeds 100 mPa · s, there is a problem that the low temperature fixability is poor, and when the acid value of the wax exceeds 2 mgKOH / g, a low molecular weight substance is mixed in the wax. In many cases, this low molecular weight product is not preferable because it causes problems such as odor generation during fixing and deterioration of storage stability of the toner.
Considering good dispersion of the wax in the toner, the true density of the wax is preferably in the range of 0.8 to 1.1 g / cm ³ . In order to achieve good dispersion, it is also preferable to use a wax modified with a functional group having a polar group such as a hydroxyl group, a carboxyl group, or an ester group.

  The positively chargeable magnetic toner of the present invention may further contain known additives used in the production of the toner, such as a lubricant, a fluidity improver, an abrasive, a conductivity imparting agent, and an image peeling prevention agent, if necessary. Can be added internally or externally. Examples of these additives include polyvinylidene fluoride and zinc stearate as a lubricant, and silica, aluminum oxide, titanium oxide, silicon aluminum co-oxide produced by a dry method or a wet method as a fluidity improver. , Silicon-titanium co-oxide and those hydrophobized, etc., and abrasives include silicon nitride, cerium oxide, silicon carbide, strontium titanate, tungsten carbide, calcium carbonate and those hydrophobized. Examples of the conductivity imparting agent include tin oxide. In addition, fine powders of fluorine-containing polymers such as polyvinylidene fluoride are preferable from the viewpoints of fluidity, abrasiveness, charge stability, and the like.

  The positively chargeable magnetic toner of the present invention preferably contains hydrophobized silica as a fluidity improver, silicon aluminum cooxide, and silicon titanium cooxide fine powder as external additives. Examples of the hydrophobic treatment of these fine powders include treatment with a silane coupling agent such as silicone oil, tetramethyldisilazane, dimethyldichlorosilane, and dimethyldimethoxysilane. The amount of the hydrophobized fine powder such as silica that has been hydrophobized is 0.01 to 20 parts by weight, preferably 0.03 to 5 parts by weight, per 100 parts by weight of the toner particles.

  The weight average particle diameter of the toner particles in the positively chargeable magnetic toner of the present invention is preferably 3 to 15 μm. In particular, toner particles having a particle size of 5 μm or less are contained in 12 to 60% by number, toner particles having a particle size of 8 to 12.7 μm are contained in 1 to 33% by number, and toner particles having a particle size of 16 μm or more. Is more preferably 2.0 wt% or less, and the weight average particle diameter of the toner particles is 4 to 11 μm from the viewpoint of development characteristics. The particle size distribution measurement of the toner particles can be performed using, for example, a Coulter counter.

  The toner particles constituting the positively chargeable magnetic toner of the present invention can be manufactured using a conventionally known toner particle manufacturing method. Generally, after sufficiently premixing the binder resin, colorant, charge control agent, release agent, and the like, which are constituent materials of the toner particles as described above, with a mixer such as a dry blender, ball mill, Henschel mixer, etc. , Knead well using a heat kneader such as a hot roll, kneader, uniaxial or biaxial extruder, cool and solidify, then mechanically coarsely pulverize using a pulverizer such as a hammer mill, and then with a jet mill, etc. A method of classifying after fine pulverization is a preferable method. The classified toner particles are sufficiently mixed together with an external additive as required using a mixer such as a Henschel mixer to obtain the positively chargeable magnetic toner of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In the following, all “parts” represent parts by weight.

  The acid value, hydroxyl value, glass transition temperature (Tg), softening point, and true density of the resins in the following production examples, examples, and comparative examples are as follows.

(Acid value and hydroxyl value)
The acid value refers to the number of milligrams of potassium hydroxide necessary to neutralize the acid groups contained in 1 g of a sample. The hydroxyl value refers to the number of milligrams of potassium hydroxide necessary to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated.

(Glass-transition temperature)
The glass transition temperature is measured by using a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation) with an extension of the baseline below Tg when measured at a heating rate of 20 ° C./min, and an endothermic curve near Tg. The temperature at the intersection of tangents.

(Softening point)
The softening point was measured using an elevated flow tester (CFT-500D, manufactured by Shimadzu Corporation) with a load of 30 kg, a nozzle diameter of 1 mm, a nozzle length of 10 mm, a preheating temperature of 80 ° C. for 5 minutes, and a heating rate of 3 The temperature at the time of h / 2 when the height of the S-shaped curve in the plunger descent amount-temperature curve of the flow tester is h, when measured as ° C / min and the sample amount is 1 g.

(True density)
The true density refers to a value measured by a vapor phase substitution method using a dry automatic densimeter (Shimadzu-Micromeritics Accupic 1330 (10 cm ³ )). The measurement conditions are as follows.
Measurement gas: Helium Introduced pressure: Purge and run 19.5 psig (134.35 Kpag)
Equilibrium judgment pressure: 0.0050 psig / min (0.0345 Kpag / min)
Temperature and humidity: 23 ° C / 50% RH

(BET specific surface area)
For the measurement of the BET specific surface area by nitrogen adsorption of the magnetic material, a multi-sorb 12 manufactured by Yuasa Ionics Co., Ltd., which is a gas adsorption method (flow method), was used for the dried magnetic material sample. A nitrogen-helium mixed gas was used as the carrier gas. And the BET specific surface area was computed from the value of the desorption peak.

(Oil absorption)
The amount of oil absorption of the magnetic material is obtained by adding the boiled linseed oil dropwise to 5 g of the magnetic material sample and mixing it until the whole becomes a solid and uniform putty-like mass while mixing. It is. Oil absorption (ml / 100 g) = [boiled flax oil consumption (ml) / sample weight (g)] × 100

Resin production example 1
Polyester resin raw material alcohol component neopentyl glycol 82.1 mol%, neodecanoic acid glycidyl ester 11.2 mol%, disproportionated rosin 18.2 mol% as raw acid component, stirring device, heating device, thermometer, minute A stainless steel reaction vessel equipped with a distillation apparatus and a nitrogen gas introduction tube was charged and heated to 160 ° C. with stirring to melt the contents. After melting, 81.8 mol% of terephthalic acid and 0.03 mol% of di-n-butyltin oxide are charged as raw acid components so that the temperature at the top of the fractionator does not exceed 100 ° C. While removing the condensed water out of the system with a nitrogen gas stream, the temperature was gradually raised to 240 ° C. to carry out an esterification reaction, and the mixture was cooled to 200 ° C. when the acid value reached 5 mgKOH / g. After confirming that a predetermined softening point was reached by a flow tester, the reaction was terminated. The characteristic values of the obtained polyester resin A are shown in Table 1.
In addition, the composition amount mol% of each monomer is mol% with respect to all the acid components.

Resin production examples 2-5
Except making it the mixture ratio shown in Table 1, it carried out similarly to manufacture manufacture example 1, and obtained polyester resin B, C, D, and E. The characteristic values of the obtained polyester resin are shown in Table 1.

Resin production example 6
Polyester resin raw material alcohol component of ethylene glycol 82.2 mol%, neodecanoic acid glycidyl ester 9.1 mol%, disproportionated rosin 21.4 mol% as raw acid component, stirring device, heating device, thermometer, fractional distillation An apparatus and a stainless steel reaction vessel equipped with a nitrogen gas introduction tube were charged and heated to 160 ° C. while stirring to melt the contents. After melting, 78.6 mol% of terephthalic acid as a raw acid component and 0.03 mol% of di-n-butyltin oxide are charged so that the temperature at the top of the fractionator does not exceed 100 ° C. While the condensed water to be removed was removed from the system by a nitrogen gas stream, the temperature was gradually raised to 240 ° C. to carry out an esterification reaction, and the mixture was cooled to 200 ° C. when the acid value reached 5 mgKOH / g. After confirming that a predetermined softening point was reached by a flow tester, the reaction was terminated. The characteristic values of the obtained polyester resin F are shown in Table 1.

Comparative resin production examples 7-8
Polyester resins G and H were obtained in the same manner as in Resin Production Example 1 except that the blending ratios shown in Table 2 were used. The characteristic values of the obtained polyester resin are shown in Table 2.

Comparative resin production example 9
Polyester resin raw material alcohol component 83.6 mol% of bisphenol A ethylene oxide 2 mol adduct, neodecanoic acid glycidyl ester 10.3 mol%, disproportionated rosin 19.8 mol% as raw acid component, stirring device, heating A stainless steel reaction vessel equipped with an apparatus, a thermometer, a fractionator, and a nitrogen gas introduction tube was charged, and the temperature was raised to 160 ° C. with stirring to melt the contents. After melting, 80.2 mol% of terephthalic acid as a raw acid component and 0.03 mol% of di-n-butyltin oxide are charged so that the temperature at the top of the fractionator does not exceed 100 ° C. While the condensed water to be removed was removed from the system by a nitrogen gas stream, the temperature was gradually raised to 240 ° C. to carry out an esterification reaction, and the mixture was cooled to 200 ° C. when the acid value reached 5 mgKOH / g. After confirming that a predetermined softening point was reached by a flow tester, the reaction was terminated. The characteristic values of the obtained polyester resin I are shown in Table 2.

  “BPA-EO 2 mol adduct” in the table represents an ethylene oxide 2 mol adduct of bisphenol A.

  Table 3 shows the characteristic values of the magnetic materials studied.

(Component) (Blending amount)
Polyester resin A 54. 4 parts by weight Magnetic material 1 42.0 parts by weight Charge control agent (Nigrosine base: Fe content 0.5%: Volume average particle size 7 μm) 2.0 parts by weight Low molecular weight polypropylene (true density 0.905 g / cm ³ ) 1.6 parts by weight The above materials were uniformly mixed, then kneaded, pulverized and classified to obtain fine powder for positively chargeable toner having an average particle size of 10.4 μm. Next, 0.7 parts of silica fine powder treated with hexamethyldisilazane was mixed with 100 parts of this fine powder for toner with a Henschel mixer, and foreign matters were removed with a vibration sieve to obtain a positively chargeable magnetic toner. . At this time, the diameter of the mesh used for the vibrating sieve was 100 m in terms of the opening speed at a peripheral speed of 20 m / sec in a Henschel mixer. Here, the toner was heated under conditions of 50 ° C. and 72 hours during drying in order to promote confirmation of change over time. Using this obtained toner, a live-action test was performed using a commercially available Canon copier NP4145. After 50,000 sheets were taken, the image density was stable, fog was small, and the toner was scattered. Was also not seen.
The charge amount of the toner was measured to evaluate the chargeability, and the storage stability was also evaluated. The results are shown in Table 4.

  In addition, measurement and evaluation of charge amount, test and evaluation of storage stability, measurement of image density, measurement of fog density, and measurement and evaluation of toner consumption were performed as follows.

(Measurement and evaluation of charge amount)
The ferrite carrier particles and the toner sample were weighed at a ratio of the toner concentration of 5% by weight with respect to the whole, mixed with a ball mill or the like, and the charge amount of the toner was calculated with a blow-off charge amount measuring device. Specifically, the measurement was performed by the following method.
19.0 g of ferrite carrier core (trade name: MF-70) manufactured by Powder Tech Co., Ltd. and 1.0 g of dried toner sample were weighed into a 50 cc plastic bottle, shaken 5 times, (PLANT SKS type), and mixing was performed for 30 minutes under the condition that the number of rotations was 230 as measured (120 for the plastic bottle body).
The obtained sample after mixing was subjected to charge amount measurement using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation. At this time, the blow pressure was 1 kgf / cm ² , the maximum value was read at a measurement time of 20 seconds, and the mesh was 400 mesh. The measurement environment was 23 ° C. and 50% RH.

(Storage stability test and evaluation)
40 g of toner is sealed in a 200 ml glass container, left in a constant temperature bath at 50 ° C. for 24 hours, and then observed by checking the toner blocking property. △ was assigned to those to be treated, and × was designated to be aggregates that were not easily loosened.

(Measurement of image density)
The image density was measured using a Macbeth photometer. The concentration may be 1.35 or more.

(Measurement of fog density)
This was done by measuring the reflectance with a photovolt. 1.5% or less is a good value.

(Measurement of toner consumption)
This is expressed as the number of tonergrams consumed per 1,000 sheets in a 6% original document.

(Fixability test and evaluation)
The fixed image was rubbed with an eraser (dragonfly pencil MONO), and the value calculated by [image density after rubbing / image density before rubbing] × 100 was expressed as the fixing strength. 85% or more is a good value.

(Offset resistance test and evaluation)
The image for fixing test was continuously copied for 100 sheets, stopped for 5 minutes, then passed through 20 blank sheets, and the evaluation was made based on the state of the white paper. In the evaluation results, “O” indicates that no paper stain occurred, and “X” indicates that the paper stain occurred.

Examples 2-8
A positively chargeable magnetic toner was obtained and evaluated in the same manner as in Example 1 except that the polyester resin and magnetic material shown in Table 4 were used. For these positively chargeable magnetic toners, in the same manner as in Example 1, the charge amount, storage stability, image density (value of initial and image density after 50,000 sheets), fog (initial and fog after 50,000 sheets) Value), consumption, fixing ability, and offset resistance. The results are also shown in Table 4.

Comparative Examples 1-5
A positively chargeable magnetic toner was obtained and evaluated in the same manner as in Example 1 except that the polyester resin and magnetic material shown in Table 4 were used. For these positively chargeable magnetic toners, in the same manner as in Example 1, the charge amount, storage stability, image density (value of initial and image density after 50,000 sheets), fog (initial and fog after 50,000 sheets) Value), consumption, fixing ability, and offset resistance. The results are also shown in Table 4.

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 the binder resin in the toner does not use a bisphenol A derivative which is an environmental hormone. The toner is preferably used as an environmental countermeasure toner.

Claims (7)

In a positively chargeable magnetic toner containing at least a binder resin, a magnetic material, and a charge control agent, the binder resin has (1) disproportionated rosin and (2) terephthalic acid and / or isophthalic acid, A line in which the alcohol component is composed of (3) a glycidyl ester of a tertiary fatty acid and (4) an aliphatic diol having 2 to 10 carbon atoms, the acid value is smaller than 10 mgKOH / g, and the hydroxyl value is 20 mgKOH / g or less. And a BET specific surface area of 3.0 to 9.0 m ² / g by a nitrogen adsorption method of a magnetic substance, and a positively chargeable magnetic toner. The positively chargeable magnetic toner according to claim 1, wherein a true density of the binder resin is 1.1 to 1.3 g / cm ³ . The oil absorption amount of the magnetic material is 19 to 29 ml / 100 g.
The positively chargeable magnetic toner described. Claim true density of the magnetic material characterized in that it is a 5.20~5.40g / cm ³ 1~3
The positively chargeable magnetic toner according to any one of the above. The charge control agent is a nigrosine dye, according to any one of claims 1 to 4.
Positively chargeable magnetic toner.  The positively chargeable magnetic toner according to claim 1, wherein the nigrosine dye is a nigrosine base. The positively chargeable magnetic toner according to any one of claims 1 to 6, wherein the Ni content in the nigrosine base is 1.0% or less.