JP2805388B2 - Magnetic toner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used for electrophotography, electrostatic recording, and the like, and particularly to an insulating magnetic toner.

[Prior Art] Conventional electrophotographic methods are disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 (U.S. Pat. No. 3,666,363) and Japanese Patent Publication No. 43-24748 (U.S. Pat. No. 4,071,3).
61)), a number of methods are known, but generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The latent image is developed with toner to form a visible image, and if necessary, a toner image is transferred to a transfer material such as paper, and then fixed by heating, pressure, etc. to obtain a copy.

Various development methods for visualizing an electrostatic latent image using toner are also known. For example, the magnetic brush method described in U.S. Pat.No. 2,874,063, the cascade development method described in U.S. Pat. No. 2,815,552 and the powder cloud method described in U.S. Pat.No. 2,221,776, fur brush development Many development methods, such as a liquid development method and a liquid development method, are known. Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method and the like using a developer mainly composed of a toner and a carrier have been widely put to practical use. All of these methods are excellent methods for obtaining a good image relatively stably, but have the common drawbacks relating to the two-component developer such as deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier.

In order to avoid such a drawback, various developing methods using a one-component developer composed of only a toner have been proposed.
Among them, many are excellent in a method using a developer composed of toner particles having magnetism.

U.S. Pat. No. 3,909,258 proposes a method of developing using an electrically conductive magnetic toner. In this technique, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and is brought into contact with an electrostatic image for development. At this time, in the developing unit, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and electric charges are guided to the toner particles from the sleeve via the conductive path. The toner particles adhere to the image area by the Coulomb force and are developed. The developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image can be transferred from a recording medium to plain paper or the like. It has the disadvantage that it is difficult to transfer electrostatically to the final support member.

As a developing method using a high-resistance magnetic toner capable of electrostatic transfer, there is a developing method using dielectric polarization of toner particles. However, such a method is disadvantageous in that the development speed is essentially low and the density of a developed image cannot be sufficiently obtained, and is practically difficult.

As another developing method using a high-resistance magnetic toner, there is a method in which toner particles are frictionally charged by friction between toner particles, friction between the toner particles and a sleeve or the like, and developed by contacting the toner particles with an electrostatic image holding member. Are known. However, these methods have disadvantages in that the number of times of contact between the toner particles and the friction member is small and triboelectric charging is likely to be insufficient, and the charged toner particles are liable to agglomerate on the sleeve due to the strong Coulomb force between the sleeve and the sleeve. And it was practically difficult.

However, Japanese Patent Application Laid-Open No. Sho 55-18656 has proposed a new developing method which eliminates the above-mentioned disadvantages. This involves applying a very thin coating of magnetic toner on a sleeve, triboelectrically charging it, and then developing it very close to the electrostatic image. This method increases the chance of contact between the sleeve and the toner by applying the magnetic toner on the sleeve very thinly, enabling sufficient triboelectric charging,
The toner is supported by magnetic force and the magnet and toner are moved relatively to solve the aggregation of toner particles and sufficiently rub against the sleeve.The toner is supported by magnetic force and this is formed into an electrostatic image. An excellent image can be obtained, for example, by preventing development of the background fog by developing the image without facing the surface.

The developing device used in such a developing method is characterized in that it can be made very small with a simple configuration. Therefore, for example, in a high-speed machine, there is room around the photoreceptor, so some developing devices of other colors are arranged, color can be changed with one touch, and laser light is used at the same time as analog light, and writing of pages and characters is copied. There is an advantage that it is easy to perform them at the same time.

However, this developing method is simple, light and small, so the toner used in this method is, on the contrary, better in image quality and durability unless the charged state is better due to environmental stability than the conventional toner. ,
Stability cannot be obtained. That is, the performance of the toner is often directly reflected in the performance of the system. Further, since copiers are moving toward higher speeds, toners must be highly satisfied with high resolution, high speed development, and high durability.

Research and development of toners have been earnestly performed to meet these demanding requirements. Among the materials used for the magnetic toner, the magnetic substance particularly has a content of 20 to 70% by weight based on the whole toner, and thus greatly affects the performance of the toner.

Here, as seen in JP-A-58-189646,
It has been shown that a magnetic toner containing a magnetic powder having an FeO content of 16 to 25% by weight can provide a high electrostatic image development efficiency and a good transfer efficiency, and a stable and sufficient image can be obtained. However, as copiers have been moving toward higher speeds in recent years, the above magnetic toners containing 16 to 25% by weight of FeO have high resolution, high speed development, and high durability. I cannot be satisfied enough. Also, when trying to apply the above magnetic toner to a high-speed machine, it becomes difficult to appropriately control the toner charge amount under a low temperature and low humidity environment,
In many cases, an excessive increase in the toner charge amount causes a decrease in image density and background stain. Further, as one of the methods for suppressing the excessive increase of the charge amount, there is a method of increasing the magnetic material. However, in this method, the fixing property tends to be deteriorated. It is only a symptomatic treatment.

Various methods and apparatuses have been developed for fixing the toner image to a sheet such as paper, which is the final step of the above-described electrophotographic method, but the most common method is a pressure roller heating method using a heat roller. is there.

In the pressure heating method using a heating roller, fixing is performed by allowing the toner image surface of the sheet to be fixed to pass through the surface of the heating roller having a surface having releasability from the toner while applying pressure. 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. And is very effective in high speed electrophotographic copiers.

In such a fixing method, use of a binder resin containing an acid component in order to improve fixability has been disclosed in JP-A-55-134861.
No. pp. 139 to 163. However, the toner using such a binder resin is susceptible to environmental fluctuations such as insufficient charging under high humidity and excessive charging under low humidity.
Further, sufficient developability such as fog and image density may not be obtained.

On the other hand, an acid anhydride has a function of improving the chargeability, and is disclosed in JP-A-59-13 as an example in which a resin containing an acid anhydride is applied.
No. 9053, JP-A-62-280758, and the like. These methods employ a method of diluting a polymer having acid anhydride units at a high density into a binder resin. With these methods,
It is necessary to uniformly disperse the acid anhydride-containing resin in the binder resin. If the resin is not dispersed well, the toner particles become non-uniformly charged, which adversely affects developability such as fogging. In these methods, the negative chargeability is high, which is not preferable for a positively chargeable toner.

Therefore, by dispersing and diluting the polymer chain in the binder resin of the acid anhydride unit by copolymerization, the problem of dispersion can be solved, and toner particles having uniform chargeability can be obtained. Examples of this are disclosed in JP-A-61-123856 and 61-123856.
There are JP-A-123857 and the like, and these toners have good fixing properties, anti-offset properties, and developability.

However, when such a toner is applied to a high-speed machine or the like under a low humidity, the toner may be excessively charged, resulting in fog and a decrease in density.

This is because the units of the acid anhydride in the binder resin used in these toners are uniformly dispersed, but the amount thereof is large.

[Problems to be Solved by the Invention] An object of the present invention is to provide a stable triboelectric charge amount between toner particles, between a toner and a toner carrier such as a sleeve, and a sharp and uniform triboelectric charge distribution. Another object of the present invention is to provide a magnetic toner capable of controlling a charge amount suitable for a developing system to be used.

It is still another object of the present invention to provide a magnetic toner capable of increasing a density difference between dots for performing development faithful to a digital latent image and sharply reproducing dot edges.

Still another object is to provide a magnetic toner that maintains its initial properties even when the toner is used continuously for a long period of time.

Still another object is to provide a magnetic toner with less fogging and reversal fog even in an image forming process including post-charging.

Still another object is to provide a magnetic toner that reproduces a stable image that is not affected by changes in temperature and humidity.

Still another object is to provide a magnetic toner having excellent storage stability that maintains initial characteristics even after long-term storage.

[Means and Actions for Solving the Problems] The present invention relates to a magnetic toner containing at least a binder resin and magnetic iron oxide, wherein the content of FeO in the magnetic iron oxide is 25 to 30% by weight; The binder resin has an acid anhydride group, and the total acid value (A) of the entire binder resin measured by hydrolyzing the acid anhydride group of the binder resin is 2 to 100 mgKOH / g. The total acid value (B) derived from the acid anhydride group is less than 6 mgKOH / g; and the total acid value (A) of the entire binder resin having the total acid value (B) derived from the acid anhydride group. [(B) / (A)] × 100
Is not more than 60%.

The object of the present invention can be achieved by the present invention because the balance between the release and accumulation of electric charges at the microscopic interface on the surface of the toner particles is balanced, and the toner particles can be uniformly charged. It is believed that there is.

The magnetic iron oxide having an FeO content of 25 to 30% by weight used in the toner of the present invention has a high blackness as a black pigment and has an effect of stabilizing the toner charge amount in order to maintain an appropriate electric resistance. It has the effect of improving the image density and improving the fog rank on the image in terms of developability.

Here, if magnetic iron oxide having an FeO content of less than 25% by weight is used for the toner, it becomes difficult to appropriately control the toner charge amount in a low-temperature and low-humidity environment, especially when considering application to a high-speed machine, and the toner charge It cannot sufficiently cope with a decrease in image density due to an excessive increase in the amount and a stain on the background.

Further, when a magnetic iron oxide having an FeO content of more than 30% by weight is used for the toner, the charge amount of the toner is reduced particularly in a high humidity environment, and the image density is reduced.

The magnetic iron oxide used in the present invention is obtained by neutralizing iron sulfate (FeSO ₄ ) with caustic soda (NaOH) to obtain Fe (OH) ₂ , adjusting the pH to 12 to 13 by alkali adjustment, oxidizing with steam and air, and slurrying magnetite. Get. By controlling the drying temperature and the drying time using a hot air dryer in the next drying step, FeO in the magnetic iron oxide can be controlled. After drying is completed, the powder is crushed to obtain magnetite powder.

Here, the measurement of FeO in the magnetic iron oxide is performed according to the following procedure. 1.000 g of magnetic iron oxide is put into a 500 ml beaker, 50 ml of deionized water is added, and 20 ml of special grade sulfuric acid is further added to completely dissolve the magnetic iron oxide.

Next, 100 ml of deionized water was added, and further MnSO ₄ , H ₂ SO ₄ and
After adding 10 ml of a mixed solution of MnSO ₄ composed of H ₃ PO ₄ (molar ratio 0.3: 2.0: 2.0) to make a total of 180 ml, 10 ml is collected and titrated with a 0.1N KMnO ₄ solution.

And FeO contained in 1.000 g of magnetic iron oxide by the following formula
(%).

Components that give an acid value include a carboxyl group and an acid anhydride group, and these functional groups have a large effect on the chargeability of the toner. For example, when there is a carboxyl group in the polymer chain, there is a weak negative charge imparting ability. However, as the density of the carboxyl group increases, the hydrophilicity increases, and the electric charge is released to the water in the air.

On the other hand, acid anhydride groups have the ability to impart negative charge, but do not have the ability to release charge. Binder resins having these functional groups are preferred for negatively charged toners because they are negatively charged,
Depending on the selection of the charge control agent, it can be used for a positively chargeable toner. In other words, if the charge-controlling ability of the charge control agent overcomes the charge-giving ability of the functional group, these functional groups will only release charge.

Therefore, the ratio of these functional groups is important for stabilizing the chargeability of the toner. That is, the carboxyl group functions to release electric charges and also to provide charging.

On the other hand, the acid anhydride group works particularly effectively only for imparting chargeability. When a large number of carboxyl groups are present, charge release is increased, the charge amount of the toner becomes insufficient, and it becomes difficult to obtain a sufficient image density. This tendency becomes remarkable under high humidity.

On the other hand, when a large number of acid anhydride groups are present, the charge amount of the toner becomes excessive and fog is increased, and this tendency is enhanced particularly under low humidity, causing a decrease in image density.

Therefore, by providing these functional groups at an appropriate ratio, it is possible to balance the application and release of the charge, stabilize the chargeability of the toner, and minimize the influence of environmental fluctuations on the chargeability. It becomes possible.

That is, charging is imparted in the presence of an acid anhydride group, and charge is released in the presence of a carboxyl group to prevent overcharging.

As described above, the binder resin used in the toner of the present invention has a specific acid value.

First, the total acid value (A) measured by hydrolyzing an acid anhydride group is 2 to 100 mgKOH / g, preferably 5 to 70 mgKOH / g.
g, more preferably 5 to 50 mgKOH / g.

If the total acid value (A) is less than 2 mgKOH / g, it is difficult to obtain good fixability in a low-temperature environment. A phenomenon occurs in which the toner is fixed and the fixing roller is contaminated by the toner. When the total acid value (A) exceeds 100 mgKOH / g, the chargeability of the toner cannot be controlled.

The total acid value (B) derived from the acid anhydride group is 6 mgKOH / g
Is less than. However, as described in a synthesis example described below,
It preferably has an acid value of 1.6 to 2.6 mg KOH / g. 6
If the amount is more than mgKOH / g, the toner is liable to be excessively charged, and the density may decrease under low humidity and fog may occur.

Further, the total acid value (B) derived from the acid anhydride group is not more than 60% (preferably 50% or less, more preferably 40% or less) of the total acid value (A) of the whole binder resin. I do. However, as described in the synthesis examples described later, the content is preferably 4.8 to 12%. If it exceeds 60%, it becomes impossible to balance the application and release of electric charge, so that the ability to apply electric charge will be prevailed and excessive charging will be likely to occur.

In addition, when an acid anhydride group is used as a constituent, the absorption peak derived from the acid anhydride (about 17
50cm around ^{-1 ~1850cm -1)} is that for which it is recognized. When the toner is present to this extent, sufficient triboelectric charging stability of the toner can be obtained.

The absorption of carbonyl of the acid anhydride appears on the higher wave number side than that of the ester acid, so that its existence can be confirmed.

Here, the toner of the present invention and FeO were measured by a charge amount distribution measuring device E-Spurt Analyzer (manufactured by Hosokawa Micron).
The distribution state of the charge amount per unit weight of the comparative toner having the same formulation as the toner of the present invention except that the content was less than 25% by weight was measured. FIG. 1 shows the measurement results. Hereinafter, the charge amount per unit weight of the magnetic toner is expressed as q / m (μc / g).

In the present invention, whether the charge amount distribution (q / m distribution) of the magnetic toner is sharp or broad is determined by:
The judgment is made based on A and B (existence width of q / m) shown in FIG. The smaller the existence width of q / m (μc / g), the sharper the charge amount distribution (q / m distribution) of the magnetic toner.

In FIG. 1, A = 28 (μc / g), B = 45 (μc / g)
The charge distribution (q / m distribution) of the toner of the present invention was much sharper than that of the comparative toner, indicating that the charge state of each toner particle was uniform.

Conventionally, in a copying machine having a mechanism in which toner is supplied from a toner hopper to a developing device in accordance with a remaining amount of toner in the developing device, a new toner is supplied from the hopper to the charged toner around the sleeve of the developing device. Is supplied, the toner charge amount becomes non-uniform, and the image density may temporarily decrease. As shown in FIG. 1, the toner of the present invention has a sharp charge amount distribution, so that the above-described temporary decrease in image density did not occur.

As the binder resin used in the magnetic toner of the present invention, a binder resin having a total acid value of 2 to 100 mgKOH / g measured by the following method among known binder resins for toner can be used.

The qualitative and quantitative determination of the functional group in the binder resin in the present invention is, for example, a method using infrared absorption spectrum, acid value measurement of JIS K-0070, hydrolysis acid value measurement (total acid value measurement) and the like. It is listed as.

For example, in the case of infrared absorption, an absorption peak derived from anhydride carbonyl appears at around 1780 cm ^-1 , so the presence of an acid anhydride is confirmed.

In the acid value measurement of JIS K-0070 (hereinafter referred to as JIS acid value), about 50% of the theoretical value of the acid anhydride is measured (the acid anhydride has an acid value as a dicarboxylic acid).

On the other hand, in the measurement of the total acid value, it is measured almost as a theoretical value. Therefore, the difference between the total acid value and the JIS acid value is about 50% of the theoretical value, and the acid anhydride is measured as a dibasic acid. Therefore, the total acid value derived from the acid anhydride per 1 g is determined.

As a specific example, when monooctyl maleate is used as the acid component, a copolymer of monooctyl maleate and maleic anhydride is first synthesized by solution polymerization. By measuring the JIS acid value and total acid value (A) of this copolymer, the total acid value (B) derived from the anhydride can be determined. When this copolymer is further dissolved in a monomer and subjected to suspension polymerization, the ring is partially opened. By measuring the JIS acid value and total acid value (A) of the binder resin thus obtained, the total acid value (B) derived from the remaining anhydride is determined, and the total acid value of the entire binder resin is determined. (A)
The ratio of the total acid value (B) derived from the anhydride in the content is determined.

In the present invention, the total acid value is determined as follows. Dissolve 2 g of sample resin in 30 ml of dioxane,
To this, pyridine 10ml, dimethylaminopyridine 20ml,
3.5 ml of water is added, and the mixture is refluxed for 4 hours while stirring. After cooling, the acid value obtained by neutralization titration with 1 / 10N KOH-THF solution using phenolphthalein as an indicator is defined as the total acid value.

Preparation of 1 / 10N KOH-THF solution is performed as follows. KOH1.5
g was dissolved in about 3 ml of water, and 200 ml of THF and 30 ml of water were added thereto, followed by stirring. Add a small amount of methanol if the solution has separated after standing, and add a small amount of water if the solution is turbid to obtain a uniform and transparent solution, and standardize with a 1 / 10N HCl standard solution.

As the toner binder resin, a known toner binder resin can be used. For example, a styrene-based copolymer of styrene such as a styrene-maleic acid ester copolymer and another vinyl-based monomer or the like can be used alone or in combination.

In the binder resin of the toner, unsaturated dibasic acids such as maleic acid, citraconic acid, dimethylmaleic acid, itaconic acid, alkenylsuccinic acid and anhydrides thereof; fumaric acid, metaconic acid, dimethylfumaric acid; , Anhydride monomers. Further, monoesters of the above unsaturated dibasic acids. Α, β-unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid and anhydrides thereof; anhydrides between the α, β-unsaturated acids and anhydrides with lower fatty acids; These anhydride monomers. Alkenyl malonic acid, alkenyl glutanic acid, alkenyl adipic acid and anhydrides and monoesters thereof. And so on.

Among these, it is particularly preferable to have a structure of a monoester of α, β-dibasic acid having a maleic acid, fumaric acid or succinic acid structure.

In the present invention, a charge control agent can be used if necessary, and a conventionally known negative or positive charge control agent is used.

Today, charge control agents known in the art include:

The following substances control the toner to be negatively charged.

For example, an organometallic complex, a chelate compound is effective and a monoazo metal complex as described above, an acetylacetone metal complex,
There are aromatic hydroxycarboxylic acids and aromatic dicarboxylic acid-based metal complexes. In addition, aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and metal salts, anhydrides and esters thereof. Phenol derivatives such as bisphenol.

The following substances control the toner to be positively charged.

Modified products such as nigrosine and fatty acid metal salts. Onium salts such as quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate, and analogs thereof such as phosphonium salts and lake pigments thereof. Triphenylmethane dyes and their lake pigments. (As the lacking agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, phenylic acid, ferrocyanide, etc.) Metal salts of higher fatty acids; dibutyltin oxide, dioctyltin oxide, Diorganotin oxides such as dicyclohexyltin oxide. Diorganotin borates such as dibutyl tin borate, dioctyl tin borate and dicyclohexyl tin borate. These can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

In the toner of the present invention, it is preferable to add fine silica powder in order to improve charging stability, developability, fluidity, and durability.

The silica fine powder used in the present invention has a specific surface area by nitrogen adsorption measured by the BET method of 30 m ² / g or more (particularly 50 to 400 m
² / g) gives good results. Toner 100
It is preferable to use 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight of silica fine powder based on parts by weight.

Also, the silica fine powder used in the present invention, if necessary,
Silicone varnish, various modified silicone varnishes, silicone oil,
It is also preferable to be treated with a treating agent such as various modified silicone oils, a silane coupling agent, a silane coupling agent having a functional group, or another organosilicon compound, or in combination with various treating agents.

As other additives, for example, abrasives such as cerium oxide, silicon carbide, and strontium titanate, among which strontium titanate is preferable. Alternatively, for example, a fluidity-imparting agent such as titanium oxide and aluminum oxide, particularly a hydrophobic agent is preferable. A small amount of an anti-caking agent or a conductivity-imparting agent such as carbon black, zinc oxide, antimony oxide, or tin oxide, or white and black fine particles of opposite polarity can also be used as a developability improver.

For the purpose of improving the releasability at the time of fixing with a hot roll, a wax-like substance such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, sazol wax, and paraffin wax is added in an amount of 0.5 to 100% by weight of the binder resin. Addition of about 10% by weight to the toner is also a preferred embodiment of the present invention.

In the magnetic toner of the present invention, metals such as iron, cobalt, and nickel or aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium,
Magnetic materials such as alloys of metals such as manganese, selenium, titanium, tungsten, and vanadium and mixtures thereof may be used in combination.

These ferromagnetic substances preferably have an average particle size of about 0.1 to 2 μm, preferably about 0.1 to 0.5 μm. The amount of the ferromagnetic substance contained in the toner is preferably about 20 to 200 parts by weight per 100 parts by weight of the resin component.
Parts by weight, particularly preferably 40 to 1 to 100 parts by weight of the resin component.
50 parts by weight is good.

In addition, the magnetic characteristics when 10 Ke is applied have a coercive force of 20 to 150 e.
Desirably, the saturation magnetization is 50 to 200 emu / g and the residual magnetization is 2 to 20 emu / g.

Colorants that can be used in the toner of the present invention include any suitable pigments or dyes. Toner colorants are well known and include pigments such as carbon black, aniline black, acetylene black, naphthol yellow, hansa yellow, rhodamine lake, alizarin lake, bengara, phthalocyanine blue, and indanthrene blue. These are used in an amount necessary and sufficient to maintain the optical density of the fixed image, and 0.1 to 20 parts by weight, preferably 2 to 10 parts by weight, per 100 parts by weight of the resin is good. A dye is further used for the same purpose. For example, there are azo dyes, anthraquinone dyes, xanthene dyes, methine dyes, etc.
The addition amount is preferably up to 20 parts by weight, preferably 0.3 to 3 parts by weight.

To prepare the toner for developing an electrostatic image according to the present invention, a binder resin, a metal salt or a metal complex, a pigment or dye as a colorant, a magnetic substance, a charge control agent as necessary, and other additives After thoroughly mixing with a mixer such as a Henschel mixer or a ball mill, melting, kneading and kneading using a hot kneading machine such as a heating roll, kneader or extruder to dissolve the metals in the resin, The toner according to the present invention can be obtained by dispersing or dissolving the compound pigments, dyes, and magnetic substances, and solidifying by cooling, followed by pulverization and classification.

Further, if necessary, desired additives are sufficiently mixed with a mixer such as a Henschel mixer to obtain the toner for developing an electrostatic image according to the present invention.

EXAMPLES Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited thereto. First, a synthesis example of the binder resin used in the present invention will be described.

Synthesis Example 1 The above compound was added dropwise to 200 parts by weight of xylene heated to the reflux temperature over 4 hours. Further, the polymerization was completed under xylene reflux (138 to 144 ° C), and xylene was removed while heating to 200 ° C under reduced pressure. The resin thus obtained is referred to as resin A.

Next, using resin A 0.12 polyvinyl alcohol partially saponified in the above mixture
170 parts by weight of water in which parts by weight are dissolved are added, and vigorously stirred.
This was a suspension dispersion. The suspension dispersion was added to a reactor filled with 50 parts by weight of water and purged with nitrogen, and a suspension polymerization reaction was performed at a reaction temperature of 80 ° C. for 8 hours. After completion of the reaction, the resultant was washed with water, dehydrated and dried to obtain a resin B.

Synthesis Example 2 Resin C was obtained in the same manner as in Synthesis Example 1 using the above compound.

Resin D was obtained in the same manner as in Synthesis Example 1 using the above mixed liquid.

Synthesis Example 3 The above compound was added dropwise to 200 parts by weight of xylene heated to the reflux temperature over 4 hours. Further, the polymerization was completed under xylene reflux (138 to 144 ° C), and xylene was removed while heating to 200 ° C under reduced pressure. The resin thus obtained is referred to as a resin E.

Synthesis Example 4 Resin F was obtained using the above compound in the same manner as in Synthesis Example 1.

Using the above mixture, Resin G was obtained in the same manner as in Synthesis Example 1.

Synthesis Example 5 The above compound was added dropwise to 200 parts by weight of xylene heated to the reflux temperature over 4 hours. Further, the polymerization was completed under xylene reflux (138 to 144 ° C), and xylene was removed while heating to 200 ° C under reduced pressure. The resin thus obtained is referred to as a resin H. The acid values of the above resins, B, D, E, G, H, are summarized in Table 1.

Hereinafter, production examples of the magnetic iron oxide used in the present invention will be described.

Production Example 14 0.8 M FeSO ₄ aqueous solution 1 in the three-necked flask of ₄
And 0.85M caustic soda aqueous solution 1
Oxidize at about 70 ° C. while blowing steam and oxygen. The obtained black powder is washed with water, and the drying temperature is 130 ° C.
After 10 minutes (initial drying condition) and drying temperature 80
C. for 2 hours (late drying conditions) to obtain a magnetic iron oxide powder containing 26.1% by weight of FeO.

Production Example 2 Initial drying conditions were 130 ° C. for 10 minutes in Production Example 1.
Except that the temperature was kept at 0 ° C. for 15 minutes and the latter drying condition was 80 ° C. for 2 hours, the same operation as in Production Example 1 was carried out.
A magnetic iron oxide powder containing 5.4% by weight was obtained.

Production Example 3 Except that drying conditions were changed to 65 ° C. and 15 hours in Production Example 1, the same operation as in Production Example 1 was carried out.
A magnetic iron oxide powder containing 1% by weight was obtained.

Production Example 4 Production was carried out in the same manner as in Production Example 1 except that the drying conditions were changed to 70 ° C. for 10 hours.
A magnetic iron oxide powder containing 2% by weight was obtained.

Comparative Production Example 1 Production was performed in the same manner as in Production Example 1 except that the drying conditions were changed to 130 ° C. and 1.5 hours.
A magnetic iron oxide powder containing 3.0% by weight was obtained.

Comparative Production Example 2 The drying conditions in Production Example 1 were changed to 75 ° C. for 18 hours,
Except that after leaving for 50 hours at 0 ° C. and then for 15 hours in an H ₂ atmosphere, the same operation as in Production Example 1 was performed,
A magnetic iron oxide powder containing 0.5% by weight was obtained.

Table 2 summarizes the drying conditions and the FeO content of each of the above production examples.

Example 1 After the above materials were mixed well in a blender, they were kneaded with a twin screw extruder set at 150 ° C. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and further classified by an air classifier to obtain a volume average particle size of 12 μm (number average). Particle size 10μ
m) A black fine powder was obtained.

0.6 parts by weight of negatively charged hydrophobic dry colloidal silica was added to 100 parts by weight of this black powder, and mixed with a Henschel mixer to obtain a negatively charged magnetic toner.

This toner is applied to a commercially available Canon copier NP-8580, and is used at normal temperature and normal humidity (23.5 ° C, 60%), low temperature and low humidity (15 ° C, 10%).
%) And high temperature and high humidity (32.5 ° C., 85%).

As shown in Table 3 below, the charge amount of the toner on the developing sleeve did not change significantly in any environment, and the image density was stable.

The image quality was not significantly changed even after 100,000 sheets were repeatedly copied, and there was no problem with the background fog and the reverse fog of the white portion due to the area designation function. Also,
The fusing roller was not contaminated by copying.

 The evaluation of fixability was performed according to the following procedure.

The fixability was evaluated by leaving the evaluation machine overnight in a low-temperature and low-humidity environment (15 ° C, 10%) and continuously copying 200 sheets from a state in which the evaluation machine and the fixing device inside the evaluation machine were completely adjusted to the low-temperature and low-humidity environment. The image was taken and the 200th copy of the copied image was used for evaluation of fixability. Evaluation of fixability is about 100 g of image reciprocating 10 times with silbon paper
Rubbing with load, image peeling, decrease in reflection density (%)
Was evaluated.

 As a result, the fixability was a density reduction rate of 5.1%.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m is 25μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Example 2 A negatively chargeable magnetic toner was obtained and evaluated in the same manner as in Example 1 except that the magnetic iron oxide of Production Example 2 was used instead of the magnetic iron oxide of Production Example 1 used in Example 1. As a result, as shown in Table 3 below, both the charge amount and the image density were stable. In addition, the image quality was not significantly changed even by repeating 100,000 copies, and there was no problem with the background fog and the reverse fog of the white blank portion by the area designation function.

Further, the fixing roller was not contaminated by copying. The fixability was a density reduction rate of 8.1%.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 28μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Example 3 Using the above materials, a negatively charged magnetic toner was obtained and evaluated in the same manner as in Example 1.

As a result, as shown in Table 3 below, both the charge amount and the image density were stable. There were no major problems with repeated copying.

There was no significant change in image quality even after repeated printing of 100,000 sheets, and there was no problem with background fog and reversal fog of white blank areas by the area designation function.

Further, the fixing roller was not contaminated by copying. The fixability was 10.1% in density reduction rate.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m is 30μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Example 4 Using the above materials, a negatively charged magnetic toner was obtained and evaluated in the same manner as in Example 1.

As a result, as shown in Table 3 below, both the charge amount and the image density were stable. There were no major problems with repeated copying.

There was no significant change in image quality even after repeated printing of 100,000 sheets, and there was no problem with background fog and reversal fog of white blank areas by the area designation function.

Further, the fixing roller was not contaminated by copying. The fixability was 9.2% in density reduction rate.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 27μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Example 5 Using the above materials, a negatively charged magnetic toner was obtained and evaluated in the same manner as in Example 1.

As a result, as shown in Table 3 below, both the charge amount and the image density were stable. There were no major problems with repeated copying.

There was no significant change in image quality even after 100,000 repeated copies, and there was no problem with background fog and reversal fog of white areas due to the area designation function.

Further, the fixing roller was not contaminated by copying. The fixability was a density reduction rate of 11.2%.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 27μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Example 6 Using the above materials, a negatively charged magnetic toner was obtained and evaluated in the same manner as in Example 1.

As a result, as shown in Table 3 below, both the charge amount and the image density were stable. There were no major problems with repeated copying.

There was no significant change in image quality even after repeated printing of 100,000 sheets, and there was no problem with background fog and reversal fog of white blank areas by the area designation function.

Further, the fixing roller was not contaminated by copying. The fixability was 9.8% in density reduction rate.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m is 25μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Comparative Example 1 A negatively-charged magnetic toner was evaluated in the same manner as in Example 1 except that the resin E was used instead of the resin B used in Example 1.

Room temperature and humidity (23.5 ° C, 60%), high temperature and high humidity (32.5 ° C 85%)
Under each environmental condition, the charge amount of the toner on the developing sleeve did not change much and the image density was stable, and the image quality did not change significantly even after 100,000 repeated copies. Inversion fogging of the part was not a problem, but repeated copying in a low-temperature and low-humidity (15 ° C, 10%) environment caused white streaks on the image from around 10,000 sheets and a decrease in image density at the same time The image density near 15,000 sheets was 1.07. Also, the toner charge amount on the sleeve around 15,000 sheets was -30.1
The charge amount was as high as μc / g, and an excessive increase in the charge amount occurred.

The fixing roller was not contaminated by copying, and the fixability was 12.1% in density reduction rate.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m is 51μc / g, and the charge amount distribution (q / m distribution)
Turned out to be broad.

Comparative Example 2 A negatively-charged magnetic toner was obtained in the same manner as in Example 1 except that the magnetic iron oxide of Comparative Production Example 1 was used instead of the magnetic iron oxide of Production Example 1 used in Example 1. The same evaluation was performed.

Under normal temperature, normal humidity, and high temperature and high humidity, the toner charge amount on the developing sleeve is not largely changed and the image density is stable even after repeated printing of 100,000 sheets. Reversal fog of white areas by the designated function was not a problem.

Further, the fixing roller was not contaminated by copying. The fixing property was a density reduction rate of 11.1%.

However, when repeated copying was performed in a low-temperature and low-humidity environment, white streaks appeared on the image from around 12,000 sheets, and the image density declined at the same time. The image density near 17,000 sheets became 1.11. Was. Further, the toner charge amount on the sleeve at around 17,000 sheets was as high as -32.5 μc / g, and an excessive increase in the charge amount occurred.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 48μc / g, and the charge amount distribution (q / m distribution)
Turned out to be broad.

Comparative Example 3 A negatively-charged magnetic toner was obtained in the same manner as in Example 1 except that the magnetic iron oxide of Comparative Production Example 2 was used instead of the magnetic iron oxide of Production Example 1 used in Example 1. The same evaluation was performed.

Under normal temperature, normal humidity and low-temperature, low-humidity environment, the toner charge amount on the developing sleeve is not largely changed and the image density is stable even after repeated copying of 100,000 sheets. Reversal fog of white areas by the designated function was not a problem.

Further, the fixing roller was not contaminated by copying. The fixing property was a density reduction rate of 9.6%.

However, when repeated copying is performed in a high-temperature and high-humidity environment, the image density is reduced from about 14,000 sheets, and the transfer efficiency of toner to paper is also reduced. The toner charge amount was −7.2 μc / g, and the toner charge amount on the sleeve was reduced.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 26μc / g, and the charge amount distribution (q / m distribution)
Turned out to be sharp.

Comparative Example 4 A negatively-charged magnetic toner was obtained in the same manner as in Example 1 except that the resin H was used in place of the resin B used in Example 1.
The same evaluation as in Example 1 was performed.

Under normal temperature, normal humidity, and high temperature and high humidity environment, the toner charge amount on the developing sleeve is not largely changed and the image density is stable even after repeated copying of 100,000 sheets. Inversion fogging of white blank areas by the area designation function was not a problem.

However, when copying was continued for 40,000 sheets in a normal temperature and normal humidity environment, the toner was fixed to the fixing roller, and development in which the fixing roller was contaminated by the toner occurred. The fixability was 31.1%, and a poor fixability was obtained.

However, when repeated copying was performed in a low-temperature and low-humidity environment, white streaks appeared on the image from around 13,000 sheets, and the image density declined simultaneously. The image density near 18,000 sheets became 1.08. Was. In addition, the toner charge amount on the sleeve at around 18,000 sheets was as high as −33.5 μc / g, and an excessive increase in the charge amount occurred.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 50μc / g, and the charge amount distribution (q / m distribution)
Turned out to be broad.

Comparative Example 5 Using the above materials, a negatively charged magnetic toner was obtained and evaluated in the same manner as in Example 1.

Under normal temperature, normal humidity, and high temperature and high humidity environment, the toner charge amount on the developing sleeve is not largely changed and the image density is stable even after repeated copying of 100,000 sheets. Inversion fogging of white blank areas by the area designation function was not a problem.

However, when copying was continued for 40,000 sheets in a normal temperature and normal humidity environment, the toner was fixed to the fixing roller, and development in which the fixing roller was contaminated by the toner occurred. The fixability was 33.8%, and a poor fixability was obtained.

However, when repeated copying was performed in a low-temperature and low-humidity environment, white streaks were generated on the image from around 8,000 sheets, and the image density was lowered at the same time. The image density near 13,000 sheets was 1.07. In addition, the toner charge amount on the sleeve at about 13,000 sheets was as high as −34.8 μc / g, and the charge amount was excessively increased.

The q / m distribution measured by the charge distribution analyzer E-Spurt Analyzer (manufactured by Hosokawa Micron) indicates that q
/ m has a width of 53μc / g, and the charge amount distribution (q / m distribution)
Turned out to be broad.

[Effects of the Invention] According to the present invention, it is possible to prevent the toner charge amount from excessively increasing in a low humidity environment, and to obtain a magnetic toner capable of maintaining an appropriate charge amount for a considerably long period of time. In particular, when applied to a high-speed copying machine, the fixing property can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the charge amount distribution of the toner of the present invention and the comparative toner.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhisa Akashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masaki Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-58-189646 (JP, A) JP-A-63-163469 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9 / 08-9/087

Claims (3)

(57) [Claims] 1. A magnetic toner containing at least a binder resin and magnetic iron oxide, wherein the content of FeO in the magnetic iron oxide is 25 to 30% by weight, and the binder resin has an acid anhydride group. The total acid value (A) of the entire binder resin measured by hydrolyzing the acid anhydride groups of the binder resin is 2 to 100 mgKOH / g, and is derived from the acid anhydride groups. The total acid value (B) is less than 6 mgKOH / g, and the ratio of the total acid value (B) derived from the acid anhydride group to the total acid value (A) of the whole binder resin [(B) / (A) ] × 100 is 6
Magnetic toner characterized by being 0% or less. (2) The total acid value (B) derived from the acid anhydride group is 1.
2. The magnetic toner according to claim 1, wherein the amount is 6 to 2.6 mgKOH / g. 3. The ratio [(B) / (B) / (B) / total acid value (A) of the entire binder resin of the total acid value (B) derived from the acid anhydride group.
3. The magnetic toner according to claim 1, wherein (A)] × 100 is 4.8 to 12%.