JP2728550B2 - Positively chargeable magnetic toner - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a toner for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, etc., and more particularly to a toner obtained by a pulverization method. The present invention relates to a positively chargeable magnetic toner for an electrostatic image suitable for fixing with a heat roller.

(Prior Art) Conventionally, many electrophotographic methods are known from U.S. Pat. No. 2,297,691, JP-B-42-23910 and JP-B-43-24748. Forms an electrical latent image on a photoreceptor by various means using a photoconductive substance, and then develops the latent image with toner, and if necessary, forms a toner image on a transfer material such as paper. After the transfer, the toner is fixed by heating, pressurizing or solvent vapor to obtain a copy, and the toner remaining on the photoreceptor without being transferred is cleaned by various methods, and the above steps are repeated. .

In recent years, such copying apparatuses have begun to be used not only as office work copying machines for copying original manuscripts, but also as printers as personal computer outputs or personal copies for individuals.

For this reason, smaller, lighter, faster, and more reliable devices have been strictly pursued, and machines have been constructed with simpler elements in various respects.
As a result, the performance required of the toner becomes higher,
If the performance of the toner cannot be improved, a better machine cannot be realized.

For example, various methods and apparatuses have been developed for a process of fixing a toner image on a sheet such as paper, but the most common method at present is a pressure heating method using a heat roller.

The pressure bonding heating method using a heating roller fixes the toner by allowing the toner image surface of the sheet to be fixed to pass through the surface of the heating roller formed of a material having a releasing property with respect to the toner under pressure. is there. In this method, since the surface of the heat roller and the toner image of the sheet to be fixed come into contact with each other under pressure, the thermal efficiency at the time of fusing the toner image onto the sheet to be fixed is extremely good, and the fixing can be performed quickly. It is very effective in high speed electrophotographic copying machines. However, in the above method, since the surface of the heat roller and the toner image come into contact with each other under pressure in a molten state, a part of the toner image adheres to and transfers to the surface of the fixing roller, and is transferred again to the next sheet to be fixed. A so-called offset phenomenon occurs, and the sheet to be fixed may be stained. Preventing toner from adhering to the surface of the heat fixing roller is one of the essential conditions of the heat roller fixing method.

Conventionally, for the purpose of preventing toner from adhering to the surface of the fixing roller, for example, the roller surface is formed of a material having excellent releasability from the toner, such as silicone rubber or a fluorine-based resin, and furthermore, the surface of the roller is prevented from being offset and the surface of the roller is prevented. In order to prevent the fatigue of the roller, the surface of the roller is coated with a thin film of a liquid having good releasability such as silicone oil. However, this method is extremely effective in preventing the offset of the toner, but has a problem that the fixing device becomes complicated because a device for supplying the liquid for preventing the offset is required. .

This is in the opposite direction to miniaturization and weight reduction, and moreover, silicone oil and the like may evaporate due to heat and contaminate the inside of the machine. Therefore, instead of using a silicone oil supply device, instead of supplying the anti-offset liquid from the toner during heating, a method of adding a release agent such as low molecular weight polyethylene or low molecular weight polypropylene to the toner has been proposed. Proposed. If a large amount of such an additive is added in order to obtain a sufficient effect, filming on the photoreceptor or contamination of the surface of the toner carrier such as a carrier or a sleeve will deteriorate the image and pose a practical problem. Therefore, a small amount of release agent is added to the toner to such an extent that the image is not deteriorated, and a small amount of release oil is supplied or the offset toner is cleaned by a take-up type device using a member such as a web. It has been practiced to use devices together.

However, in view of recent demands for miniaturization, weight reduction, and high reliability, it is necessary and preferable to remove even these auxiliary devices. Therefore, further improvement in performance such as toner fixing and offset is desired.

As a technique relating to improvement of toner fixing / offset, for example, Japanese Patent Publication No. 51-23354 discloses a toner using a crosslinked polymer as a binder resin;
JP-A-8340 discloses a toner comprising a low-molecular-weight polymer and a high-molecular-weight polymer, and JP-A-58-86558 discloses a toner comprising a low-molecular-weight polymer and an insoluble high-molecular-weight polymer as disclosed in JP-A-58-86558. No. 166958, number average molecular weight (Mn) 500 to 1,500
A toner comprising a resin component obtained by polymerization in the presence of low molecular weight poly-α-methylstyrene
In the molecular weight distribution by GPC to 14 discloses, molecular weight 10 ³ to
Toners and the like containing a binder resin having at least one maximum value in each region of 8 × 10 ⁴ and a molecular weight of 10 ⁵ to 2 × 10 ⁶ have been proposed. These proposals have an effect on the high-temperature offset related to the thermal properties of the toner, for example, the physical properties such as the melt viscoelasticity of the toner, but have no effect on the electrostatic offset generated by the electrostatic adhesion. Further, an improvement in offset resistance has been desired.

An outline of the mechanism of the occurrence of the electrostatic offset will be described below.

As described above, the surface of the pressure-bonding heating member for the toner image is generally formed of low surface energy silicone rubber or fluorine resin in consideration of the releasability of the toner. The surface material of the pressure-bonding heating member exhibits negative charging property during the pressure-bonding process of the toner image support. For this reason, when a positively chargeable toner is used, an electrostatic adhesion acts between the toner and the negatively chargeable pressure-applying and heating member surface, and the positively chargeable toner on the toner image support causes the pressure-applying heat-applying member. Adheres and transfers to the surface. This phenomenon is considered to be the mechanism of the electrostatic offset. Therefore, this phenomenon tends to be remarkable when there is a machine for applying a positive charge to the toner after the development in the image forming process and before the transfer in order to improve the transferability of the toner. Further, even when the toner is bulky mounted on the toner image support to obtain a high image density, the electrostatic offset phenomenon easily occurs.

As a countermeasure against this electrostatic offset phenomenon, it is conceivable to provide a means for controlling the charge of the toner image support before or during fixing, but this is contrary to the downsizing and weight saving of the image forming apparatus and increases the cost. Therefore, it is preferable to improve with a toner.

Further, as a countermeasure against the electrostatic offset phenomenon, there is a means for providing a device for supplying a releasable oil to the heat fixing roller or a device for cleaning the offset toner by a winding type device using a member such as a web. Also, in consideration of miniaturization, weight reduction, increase in cost, improvement in reliability, and the like of the image forming apparatus, it is desirable that the image forming apparatus be improved with toner.

In contrast, JP-A-55-134861 and JP-A-56-13661
No. 65147 discloses toners using a binder resin having an acid value, and although these are expected to have some effect on the electrostatic offset phenomenon, when they are used as positively chargeable magnetic toners, In addition, since the binder resin having an acid value exhibits negative chargeability, many problems remain in the chargeability and durability of the toner.

In general, as a one-component magnetic toner used in dry electrophotography, a fine powder in which magnetite, a charge control agent, a lubricant, and the like are dispersed in a binder resin composed of a natural or synthetic resin has been used.

Examples of the positive charge control agent contained in such a one-component magnetic toner include a quaternary ammonium compound and an organic dye, particularly a basic dye and a salt thereof. Nigrosine base and nigrosine dye are common positive charge control agents. Often used as. These are usually added to a thermoplastic resin, melt-dispersed by heating, finely pulverized, and adjusted to an appropriate particle size as required, before use.

However, when these positive charge control agents are used in a magnetic toner containing a binder resin having an acid value as a main component, not only the electrostatic offset resistance is insufficient, but also mechanical shock, friction, temperature and humidity conditions. A phenomenon in which charge controllability changes due to a change or the like is likely to occur.

(Problems to be Solved by the Invention) An object of the present invention is to provide a positively chargeable magnetic toner which has solved the above-mentioned problems. The objects of the present invention are listed below.

An object of the present invention is to provide a positively chargeable magnetic toner having excellent resistance to electrostatic offset.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a positively chargeable magnetic toner having excellent resistance to electrostatic offset even in a hot roller fixing method in which oil is not applied.

An object of the present invention is to provide a positively chargeable magnetic toner having good positive chargeability.

Another object of the present invention is to provide a positively chargeable magnetic toner that always provides high-quality and stable images without being affected by the environment such as temperature and humidity.

Another object of the present invention is to make the dispersion of the magnetic substance, lubricant and the like in the resin good, have excellent durability, and always provide a stable image free from fogging and scattering even when used continuously for a long time. It is to provide a magnetic toner.

It is another object of the present invention to provide a positively chargeable magnetic toner that constantly stably frictionally charges and maintains a high density without contaminating a frictional charging member such as a developing sleeve.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention applies a pressure-adhesion heating member having a surface formed of silicone rubber or a fluorine-based resin and not coated with oil to a toner image formed on a toner image support formed of a positively chargeable magnetic toner. A positively-chargeable magnetic toner for use in an image forming method having a fixing step of heating and fixing the toner image to a toner image support by contacting the toner image, wherein the positively-chargeable magnetic toner is a magnetic material, and has an acid value of 1 to 3. A charge controlling agent comprising: a quaternary ammonium salt; a metal salt of a fatty acid having a metal content of 2.0 to 4.5% by weight and a melting point of 110 to 145 ° C. And the charge controllability of each of the quaternary ammonium salt and the fatty acid metal salt is a triboelectric charge amount with respect to iron powder, and the following relationship T _c ≧ T _b ≧ T _a [T _a ; as a charge control agent Contains only quaternary ammonium salts Charge amount of magnetic toner (μc / g) T _b ; charge amount of magnetic toner containing only fatty acid metal salt as charge control agent (μc / g) T _c ; quaternary ammonium salt and fatty acid metal salt as charge control agent And the content of the quaternary ammonium salt and the fatty acid metal salt in the magnetic toner has the following relationship: 0.4 ≦ W _q + W _p ≦ 2 0.2 ≦ W _p / W _q ≦ 1 [W _q ; quaternary ammonium salt content (% by weight) W _p ; fatty acid metal salt content (% by weight)] is there.

(Action) In the positively chargeable magnetic toner of the present invention, a binder resin having an acid value of 1 to 20 is used, and a quaternary ammonium salt and a fatty acid metal salt (metal content of 2.0
(4.5% by weight, melting point: 110 ° C to 145 ° C) at a specific ratio to prevent the occurrence of electrostatic offset and to improve the dispersion of the magnetic substance and lubricant in the binder resin, The inventors have found that a toner excellent in chargeability and durability can be obtained, and have completed the present invention. As a result, no electrostatic offset occurs even in the hot roller fixing method that does not apply oil, and the image density is high in any environment, fine line reproducibility, excellent gradation, fog-free, clear and high image quality Images can be obtained over a long period of time.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The positively chargeable toner of the present invention contains, as main components, a magnetic substance, a binder resin having an acid value of 1 to 20, and the following specific charge control agent.

First, the quaternary ammonium salt and the fatty acid metal salt contained as the charge control agent have a charge controllability based on a triboelectric charge amount against iron powder, and T _c ≧ T _b ≧ T _a [T _a ; charge amount of the toner containing _{(μc / g), T b} ; charge amount of the toner containing only fatty acid metal salt ([mu] c /
g), T _c ; the charge amount (μc / g) of the toner containing both the quaternary ammonium salt and the fatty acid metal salt], and the charge controllability of the fatty acid metal salt is equivalent to the charge of the quaternary ammonium salt used in combination. It is characterized in that the charge controllability is equal to or higher than the controllability, and the charge controllability when used together due to the synergistic effect of both is equal to or higher than that when used alone.

In contrast, T _a> T charge under low temperature and low humidity when used together in _b becomes too high, prone to uneven development and density mouse or the like.

In addition, when T _b > T _c and T _a > T _c , there is not much effect of the combined use.
In particular, the concentration is lowered when left under high temperature and high humidity.

Here, the charge amount of the positively chargeable toner is 6.0 μc / g or more.
Preferably it is less than 15.0 μc / g.

In the positively chargeable toner of the present invention, the content of the quaternary ammonium salt and the fatty acid metal salt in the toner is 0.4 ≦ W _q + W _p ≦ 2 and 0.2 ≦ W _p / W _q ≦ 1 [W _q ; 4 Quaternary ammonium salt content (% by weight), W _p ; fatty acid metal salt content (% by weight)].

If W _q + W _p <0.4, offset is likely to occur, and the charging is too low, the density is low, the durability is insufficient, and the dispersion is liable to occur, which causes fogging.

When W _q + W _p > 2, contamination of the charging member such as the developing sleeve is likely to occur. Further, W _p / W _q <At 0.2, easily offset occurs and results in decrease in density under high temperature and high humidity, W _P / W _q> becomes the 1 fluidity deteriorated image with much fog.

Further, each of W _P and W _q is preferably is between 0.1 to 2.0 wt%.

Further, the metal content of the fatty acid metal salt used in the positively chargeable toner of the present invention is preferably 2.0% by weight to 4.5% by weight. If it is less than 2.0% by weight, the density tends to decrease under high temperature and high humidity, and the fluidity of the toner is poor. On the other hand, 4.5
If the amount exceeds 10% by weight, the combined effect with the quaternary ammonium salt is not sufficient.

The melting point of the fatty acid metal salt is preferably 110 ° C to 145 ° C. If the temperature is less than 110 ° C., the melt viscosity at the time of kneading the toner is too low, resulting in a toner having poor dispersion and poor fluidity,
A slippage occurs with the kneading machine, and the dispersion of the magnetic substance and the lubricant is also deteriorated, resulting in an image with much fog. If the temperature exceeds 145 ° C., the melting at the time of kneading the toner is not sufficient, and the poor dispersion is likely to occur.

Fatty acid metal salts satisfying the above physical properties include those having 10 carbon atoms.
Good combinations of up to 20 fatty acids with metals such as Al and Mg are preferred, with aluminum stearate being particularly preferred.

The content of the magnetic substance in the positively chargeable toner of the present invention is 20 to 150 parts by weight, preferably 40 to 120 parts by weight, based on 100 parts by weight of the binder resin component.

The quaternary ammonium salt used in the present invention includes those represented by the following general formula (I) or (II).

In the above general formula, R ₁ , R ₂ , R ₃ , and R ₄ represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an aryl group which may have an aromatic ring as a substituent, and an alkyl group CH- (CH ₂ ) _N- Ar,
n = 1 to 5, Ar = aryl group｝.

R ₅ is an alkyl group having 1 to 30 carbon atoms, an alkyl group
(CH ₂ ) _n- Ar, n = 1 to 5, Ar = aryl group｝.

R ₆ represents an alkyl group having 1 to 10 carbon atoms, and the substituent may be plural.

A ^- represents an anion. Examples of anions include halo ions, sulfate ions, nitrate ions, borate ions, phosphate ions, organic sulfate ions, organic sulfonate ions, organic phosphate ions, polyacid ions, heteropolyacid ions, carboxylate ions, and tetrafluoroborate. is there.

 Specifically, there are the following.

Usually, as a method for incorporating a quaternary ammonium salt and a fatty acid metal salt, which are charge control agents, into the toner during kneading, there are a method in which the toner is contained in the toner and a method in which the toner is externally added. Is not added during kneading, the effect of the present invention cannot be obtained. That is, in the method of externally adding the toner to the surface of the toner later, the density is significantly reduced.

The binder used in the toner of the present invention has an acid value of 1 to 1.
20 is a binder resin.

When the acid value of the binder resin used in the present invention is less than 1, offset tends to occur, and when the acid value is more than 20, the chargeability is lowered and environmental stability is problematic.

As the binder resin having an acid value of 1 to 20 used in the present invention, acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, dimethylmaleic acid and their acid anhydrides and / or partial esters thereof as monomer units Preferred are monomers having a compound, copolymers of these with olefin or vinyl monomers, polyesters and rosin-modified resins having a carboxyl group at the terminal or side chain, and olefin oxides.

The method for adjusting the binder resin having an acid value of 1 to 20 used in the present invention varies depending on the resin, but a polymerization method such as a bulk polymerization conventionally known for a vinyl copolymer containing acrylic acid or methacrylic acid is conventionally used. The acid value can be adjusted by changing the monomer ratio or by changing the degree of esterification.

On the other hand, in a condensation resin such as polyester, in addition to changing the ratio of diol and dicarboxylic acid, as the polymerization proceeds, the ratio of terminal carboxyl groups decreases,
The acid value can be adjusted by adjusting the degree of polymerization.

In addition, if the temperature is raised to a temperature close to the melting point of an olefin resin, particularly polyethylene, oxidation occurs more quickly in air than in water in which air is well dissolved, and a polyethylene oxide can be obtained. The oxidation reaction may be advanced while proceeding.

In the present invention, as a method for measuring the oxidation, Japanese Industrial Standards
The test is performed according to JIS K 0076-66 “Test method for acid value of chemical products”.

The binder resin having the above acid value can be used alone as a binder resin for a toner. The binder resin having an acid value may be used in an amount of 30% by weight or more, more preferably 50% by weight or more, based on all the binder resins in the toner. Have been.

When the amount of the binder resin having an acid value is less than 30% by weight with respect to all the binder resins in the toner, the offset resistance is poor.

In the magnetic toner according to the present invention, various additives may be added internally or externally as necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight per 100 parts by weight of the binder resin may be used. Other additives include strontium titanate, barium titanate, cerium oxide, abrasives such as silicon carbide, for example, colloidal silica, a fluidity imparting agent such as aluminum oxide or a caking inhibitor, for example, carbon black, tin oxide And the like.

Further, for the purpose of improving the releasability at the time of hot roll fixing, a wax-like substance such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, sasol wax, paraffin wax, etc. The addition of about 5% by weight of the toner is also a preferred embodiment of the present invention.

Further, the toner of the present invention contains a magnetic material.Examples of the magnetic material contained in the toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite; Fe, Co, Metals such as Ni, or these metals and Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd,
Examples include alloys with metals such as Ca, Mn, Se, Ti, W, and V, and mixtures thereof.

These ferromagnetic materials preferably have an average particle size of about 0.1 to 1 μm, preferably about 0.1 to 0.5 μm. The amount contained in the magnetic toner is 3 parts per 100 parts by weight of the resin component.
0 to 120 parts by weight, preferably 40 parts per 100 parts by weight of the resin component
110110 parts by weight.

In order to prepare the positively chargeable magnetic toner according to the present invention, the magnetic powder, the binder resin, the charge control agent, and, if necessary, the pigment or dye as a colorant and other additives are sufficiently mixed by a mixer such as a ball mill. And then the heating roll,
Using a heat kneader such as a kneader or extruder, melt or knead and knead the resin to disperse or disperse the resins, disperse or melt the pigment or dye.After cooling and solidifying, pulverize and strictly classify. The positively-chargeable magnetic toner according to the present invention can be obtained.

The toner of the present invention may be internally or externally mixed with silica fine powder, but is preferably externally added and mixed.

As the silica fine powder, any of silica fine powders produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a silica fine powder obtained by a dry method.

Here, the dry method is a method for producing silica fine powder generated by vapor phase oxidation of a silicon halide. For example, in a method utilizing the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen-hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl Also, in this manufacturing process, by using another metal halide compound such as aluminum chloride or titanium chloride together with the silicon halide compound, composite fine powder of silica and other metal-containing complex can be obtained. It is also possible to obtain bodies, including them.

Commercially available silica fine powder produced by vapor phase oxidation of a silicon halide used in the present invention includes, for example, those commercially available under the following trade names.

Aerosil 130 (Nippon Aerosil) 200 300 380 OX50 TT600 MOX80 MOX170 COX84 Ca-O-Si M-5 (CABOTO Co.) MS-7 MS-75 HS-5 EH-5 Vacker HDK N20 V15 (Vakker Chem GMBH) N20E T-30 T-40 DC fine silica (Dow Corning Co.) Furansol (Franzil) On the other hand, the method for producing the silica fine powder used in the present invention by a wet method is known in the art. Method can be used. For example, there is a method of decomposing sodium silicate with an acid as shown in the general reaction formula below.

Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl In addition, decomposition of sodium silicate by ammonium salts or alkali salts, formation of alkaline earth metal silicate from sodium silicate and decomposition by acid Silicic acid, sodium silicate solution with ion exchange resin, silicic acid, natural silicic acid or natural silicate.

As the silica fine powder here, anhydrous silicon dioxide (colloidal silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate can be used.

Commercially available fine silica powder synthesized by the wet method includes, for example, those commercially available under the following trade names.

Carplex Shionogi Pharmaceutical Nip Seal Nippon Silica Tokusil, Fine Seal Tokuyama Soda Vita Seal Shiki Taki, Shirunex Mizusawa Chemical Starsil Kamijima Chemical Himejir Ehime Pharmaceutical Syloid Fuji Devison Chemical Hi-Sil Pittsburgh Plate Glass.Co. (Pittsburgh Plate Glass) Durosil Ultorasil Fiillstoff-Gesellschaft Marquart Manosil Hardman and Holden Hoesch Chemische Fabrik Hoesch K-G Hiemische Fabrik -Hesh) Sil-Stone (Sil-Stone) Stoner Rubber Co. (Staller Rubber) Nalco (Narco) Nalco Chem. Co. (Narco Chemical) Quso (Kuso) Philadelphia Quartz Co. ( Illadelphia Quartz Imsil Illinois Minerals Co. Calcium Silikat Calcium Silikat Chemische Fabrik Hoesch.K-G Calm (Carzil) Phil) Imperial Chemical Industries.Ltd. (Imperial Chemical Industries) Microcal (Microcal) Joseph Crosfiels & Sons.Ltd. (Joseph Crossfield and Sands) Vulkasil (Burkazir) Farbenfabriken Bryer.A.-G. Tufknit Durham Chemicals. Ltd. (Dulham Chemicals) Silmos Shiraishi Kogyo Co., Ltd. Star Rex Ehime Pharmaceutical Fricosil Multi-wood fertilizer Of the above silica fine powder, BET method Specific surface area by the boss was nitrogen adsorption in the range of 30 m ² / g or more (especially 50 to 400 m ² / g) gives good results. 0.01 to 8 parts by weight of silica fine powder, preferably 100 parts by weight of magnetic toner, preferably
It is preferable to use 0.1 to 5 parts by weight.

The silica fine powder used in the present invention may be a silane coupling agent, a silicone oil, a treating agent that reacts or physically adsorbs with silica fine powder such as an organic silicon compound or the like for the purpose of hydrophobicity, if necessary. Various treatment agents may be used in combination. Such treating agents include, for example, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane , Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyl Dimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3- Diphenyltetramethyldisiloxane and 2 to 2 per molecule
For example, dimethylpolysiloxane having 12 siloxane units and each containing a hydroxyl group bonded to Si as one of the units located at the terminal may be used. These are used in one kind or in a mixture of two or more kinds.

Further, the silica fine powder used in the present invention, in addition,
It may be treated with a silicone oil having an organo group having at least one nitrogen atom in the side chain or a nitrogen-containing silane coupling agent, and treated with the above-mentioned treating agent which reacts or physically adsorbs with silica fine powder.

As the silicone oil having a nitrogen atom in the side chain used for treating the silica fine powder, a silicone oil having at least a partial structure represented by the following formula can be used.

(Wherein, R ₁ represents a hydrogen atom, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represent a hydrogen atom, an alkyl group or an aryl group, ₅ represents a nitrogen-containing heterocyclic group). The alkyl group, aryl group, alkylene group, or phenylene group may have an organo group having a nitrogen atom, or may have a substituent such as halogen.

Further, the nitrogen-containing silane coupling agent used in the present invention,
It generally has a structure represented by the following formula.

R _m -Si-Y _n (R represents an alkoxy group or a halogen, Y represents an organo group having at least one amino group or a nitrogen atom, m and n is an integer of 1 to 3 m + n = The organo group having at least one nitrogen atom is, for example, an amino group having an organic group as a substituent or a group having a nitrogen-containing heterocyclic group. Examples of the nitrogen-containing heterocyclic group include an unsaturated heterocyclic group and a saturated heterocyclic group, and each of them can be used. As the unsaturated heterocyclic group,
For example, the following are exemplified.

Examples of the saturated heterocyclic group include the following.

The heterocyclic group used in the present invention is preferably a 5- or 6-membered ring in consideration of stability.

Examples of such treating agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-
γ-propylphenylamine, trimethoxysilyl-γ
And nitrogen-containing heterocycles having the above-mentioned structure. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine and trimethoxysilyl-γ-propylmonocyclic. Holin, trimethoxysilyl-γ-propylimidazole and the like.

In the toner of the present invention, a fine powder of a fluorine-containing polymer may be added internally or externally. As the fluorine-containing polymer powder, for example, it is preferable to add a fine powder of polytetrafluoroethylene, polyvinylidene fluoride or the like and a tetrafluoroethylene-vinylidene fluoride copolymer. In particular, polyvinylidene fluoride fine powder is preferred in terms of fluidity and abrasiveness. The amount added to the toner is preferably 0.01 to 2.0% by weight, particularly preferably 0.02 to 1.0% by weight.

In particular, in magnetic toner in which silica fine powder and the above fine powder are combined and externally added, the reason is not clear, but stabilizes the state of silica attached to the toner, for example, the attached silica is released from the toner. As a result, the effect on toner friction and sleeve fouling does not decrease, and the charging stability can be further increased.

In the measurement of the triboelectric charge amount in the present invention, the temperature / humidity was 2
Under an environment of 3.5 ° C / 60%, the test substance is mixed with an iron powder carrier having a particle size of 200/300 mesh (Nihon Iron Powder EFV200 / 300) at a ratio of 2/98, and 0.5 to 1.5 g of this mixture is added. The method is based on a method of precisely weighing and suctioning a metal 400 mesh screen connected to an electrometer with a pressure of 25 cmH ₂ O, and obtaining the amount of charge per unit weight from the amount of the test substance sucked at that time and the amount of charge.

Further, the order of the charge amount in the present invention is not changed by a conventionally known blow-off measuring method.

This order is more evident in the black fine powder before silica addition and mixing.

The toner of the present invention is preferably applied to an image forming method of developing a latent image while flying toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoconductor.
That is, the magnetic toner is provided with a triboelectric charge mainly by contact with the surface of the sleeve, and is applied in a thin layer on the surface of the sleeve. The thickness of the thin layer of the magnetic toner is formed to be smaller than the gap between the photosensitive member and the sleeve in the developing area. When developing the latent image on the photoconductor, it is preferable to fly the magnetic toner having triboelectric charge from the sleeve to the photoconductor while applying an alternating electric field between the photoconductor and the sleeve.

Examples of the alternating electric field include a pulse electric field, an AC bias, and a synergistic AC and DC bias.

(Examples) Next, the present invention will be described more specifically with reference to examples, but these do not limit the present invention at all. or,
Parts in Examples are parts by weight.

Example 1 Styrene / n-butyl acrylate / n-maleic acid
-Butyl / divinylbenzene copolymer (copolymerization weight ratio of 75
/23.5/0.8/0.7, acid value 2.5, Mw 380,000) 100 parts Low molecular weight polyethylene 4 parts Magnetic iron oxide 70 parts 0.5 parts of aluminum stearate (melting point: 120 ° C, metal content: 3.4%)
After kneading with an extruder set at 0 ° C, cooling, coarse pulverization with a cutter mill, fine pulverization with a jet mill using a jet stream, classification with an air classifier, and an average particle size of 12
A black fine powder of μm was obtained. An amino-modified silicone oil (viscosity of 10 at 25 ° C.) was added to 100 parts of the obtained black fine powder.
0.4 parts of positively charged hydrophobic dry silica (BET200m ^{2 /} g) treated with 0 cp, amine equivalent 800) and spherical particles with an average particle size of 0.2 μm
0.2 parts of PVDF particles were added and mixed with a Henschel mixer to obtain a positively chargeable toner of the present invention.

An electrophotographic copier is used as a heat roller fixing device, comprising a pair of a heating roller having a fluororesin coating and a fixing roller, without using an anti-offset liquid, and removing a fixing roller cleaning mechanism. A copy test of 20,000 sheets was performed by incorporating the printer in an NP-5540 (40 sheets / minute, manufactured by Canon Inc.). During the test, no offset on the image was seen, very good and no staining of the metering roller was observed.
Further, the image density was always 1.3 or more, no fog was observed in the background portion and the reversal portion, and scattering was small.

Also, good results were obtained in a copy test of 20,000 sheets under environmental conditions of 15 ° C./10% humidity and 32.5 ° C./85%, respectively.

Example 2 Instead of the binder resin having an acid value of 2.5 used in Example 1, styrene / n-butyl acrylate / maleic acid-
n-butyl / divinylbenzene copolymer (copolymer weight ratio
75 / 19.3 / 5 / 0.7, acid value 15, Mw 360,000), except that a binder resin was used. The temperature was 23.5 ° C / 60% humidity, 32.5 ° C / 85% and As a result of image output of 20,000 sheets under each environment at 15 ° C./10%, no offset was always generated, and no stain on the fixing roller was observed. Further, the image density was always 1.25 or more, fog was not observed, and scattering was small.

Comparative Example 1 The binder resin was changed to a styrene / n-butyl acrylate / n-butyl maleate / divinylbenzene copolymer (copolymer weight ratio: 75 / 24.1 / 0.2 / 0.7, acid value: 0.6, Mw: 370,000). Except for the above, the same procedure as in Example 1 was carried out. As a result, an offset was generated on the image, and the fixing roller was stained.

Comparative Example 2 The binder resin was changed to a styrene / n-butyl acrylate / n-butyl maleate / divinylbenzene copolymer (copolymer weight ratio 75/13 / 11.3 / 0.7, acid value 35, Mw 340,000). Except for the above, the temperature was 23.5 ° C.
Image density may fall below 1.20 through 20,000 images output in each environment of 60% humidity / 15% / 10%
In particular, it decreased to 0.8 in an environment of 32.5 ° C / 85%.

Example 3 Styrene / n-butyl acrylate / n-maleic acid
Butyl / divinylbenzene copolymer (copolymerization ratio 73.1 / 23.
9/3 / 0.4, acid value 10, Mw 240,000) 100 parts Low molecular weight propylene-ethylene copolymer 4 parts Magnetic iron oxide 60 parts 0.5 part of magnesium stearate (melting point: 145 ° C., metal content: 4.5%)
Image output of 20,000 sheets under environmental conditions of 23.5 ° C / 60% humidity, 32.5 ° C / 85% and 15 ° C / 10% results in very good images without any offset on the image at all times And no staining of the fixing roller was observed. Further, the image density was always 1.3 or more, fog was not recognized, and scattering was small.

Example 4 The procedure of Example 1 was repeated, except that the aluminum stearate was changed to aluminum stearate having a melting point of 140 ° C. and a metal content of 4.0% by weight.
2,0% under each environment of 32.5 ℃ / 85% and 15 ℃ / 10%
As a result of image formation on 00 sheets, the offset resistance was as good as in Example 1, and the image density was always 1.3 or more, no fogging was observed, and scattering was small.

Example 5 Quaternary ammonium salt A copy test was conducted in the same manner as in Example 1 except that the temperature was changed to 23.5 ° C./60% humidity, 32.5 ° C./85% and 15%.
As a result of image output of 20,000 sheets under each environment at 10 ° C./10%, the anti-offset property was as good as in Example 1, the image density was always 1.3 or more, no fog was observed, and no scattering occurred. There were few.

Comparative Example 3 An image was formed in the same manner as in Example 1 except that aluminum stearate was not used. As a result, an offset was easily generated on the image, and the fixing roller was stained. Further, the image density is as low as 1.0 to 1.2, and may be 1.0 or less in an environment of 32.5 ° C./85%. Further, under an environment of 15 ° C./10%, the concentration was 1.1 to 1.2. Further, when image formation was performed without replenishing toner, the density was particularly reduced, and the image density was reduced to about 0.6.

Comparative Example 4 In Example 1, no quaternary ammonium salt was used,
Except that the amount of aluminum stearate was 1.0 part,
When performed in the same manner, although the offset resistance was good, the image density was lower than that of Comparative Example 1 by 0.8 to 1.0.
Only images with poor fog and a lot of fog were obtained.

Comparative Example 5 The same procedure was followed as in Example 1, except that two parts of a nigrosine dye were used instead of the quaternary ammonium salt and aluminum stearate. Was done. The image density was 1.3 or more at the initial stage, but the density slightly decreased to about 1.1 to 1.2 as the number of durable sheets advanced, but the fog was good. However, at 15 ° C./10%, although the image density was 1.3 at the beginning, the density gradually decreased with much scattering, and the image became rough below 0.9.

Comparative Example 6 In Example 1, the amount of the quaternary ammonium salt was 0.5
And the amount of aluminum stearate was changed to 1.0 part, the offset resistance was as good as in Example 1. However, the image density under 15 ° C./10% environment was as follows: The density gradually decreased, and the image became rougher than 1.0.

Comparative Example 7 In Example 1, the amount of aluminum stearate was
When the same method was used except that the amount was 0.15 parts, a slight offset was generated on the image. 23.5 ℃ / 6
Under 0%, 15 ℃ / 10% environment, through 20,000 images
Although an image density of 1.25 or more was obtained, in an environment of 32.5 ° C./85%, the image density may be lower than 1.20, and particularly decreased to 1.0 after standing overnight.

Comparative Example 8 In Example 1, the amount of the quaternary ammonium salt was 3.0
And the amount of aluminum stearate was changed to 1.5 parts, the same method was carried out. However, the shear caused by slippage during kneading of the toner was not sufficient.

When this toner was imaged, the anti-offset property was as good as in Example 1. However, the image density was initially 1.
Although it was as high as 40, it was reduced to 1.10 with 20,000 images taken out, and there were many fogs.

When the developing sleeve was cleaned with a solvent and an image was formed, the image density was restored to 1.35, and it was found that the sleeve was contaminated.

Comparative Example 9 The procedure of Example 1 was repeated, except that zinc stearate (melting point: 123 ° C., metal content: 10.5% by weight) was used instead of aluminum stearate. The offset resistance was the same as in Example 1. Although the image density was good, the image density was stable through the output of 20,000 sheets, but 1.15
The image was as low as 1.20 and slightly fogged.

Comparative Example 10 In Example 1, the melting point of aluminum stearate was changed to
When the same procedure was carried out except that the temperature was changed to 160 ° C. and the metal content was 5.0% by weight, the dispersion of aluminum stearate was poor, and a slight but offset on one image occurred.
Although the image density was as high as 1.40, black spots occurred.
In addition, after standing overnight at 32.5 ° C./85%, the concentration decreased by 1.05.

 Table 1 below shows the respective triboelectric charges.

(Effects of the Invention) As described above, the toner of the present invention is excellent in offset resistance and charging stability, and can provide high-quality images for a long period of time.

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Claims (3)

(57) [Claims] 1. A press-fit heating member having a surface formed of silicone rubber or a fluorine-based resin and not coated with oil is brought into contact with a toner image on a toner image support formed of a positively chargeable magnetic toner. A positively-chargeable magnetic toner used in an image forming method having a fixing step of heating and fixing the toner image on a toner image support, wherein the positively-chargeable magnetic toner is a magnetic material, an acid value of 1 to 20. A binder resin and a charge control agent, wherein the charge control agent has a quaternary ammonium salt and a metal content.
A fatty acid metal salt having a melting point of 110 to 145 ° C., wherein the charge controllability of each of the quaternary ammonium salt and the fatty acid metal salt is a triboelectric charge amount with respect to iron powder. And the following relationship: T _c ≧ T _b ≧ T _a [T _a ; Charge amount of magnetic toner containing only quaternary ammonium salt as charge control agent (μc / g) T _b ; Only fatty acid metal salt as charge control agent Charge of magnetic toner contained (μc / g) T _c ; charge of magnetic toner containing both quaternary ammonium salt and fatty acid metal salt as charge control agent (μc / g)] The content of the quaternary ammonium salt and the fatty acid metal salt in the toner has the following relationship: 0.4 ≦ W _q + W _p ≦ 2 0.2 ≦ W _p / W _q ≦ 1 [W _q ; content of quaternary ammonium salt (% by weight) W _p ; fatty acid metal salt content (% by weight)]. 2. The positively chargeable magnetic toner according to claim 1, further comprising silica fine powder and fluorine-containing polymer fine powder. 3. The positively chargeable magnetic toner according to claim 2, wherein the silica fine powder is a positively charged hydrophobic silica fine powder.