JP3035689B2 - Magnetic developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic device applied to a developing device for forming a latent image on an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric and visualizing the latent image. Related to the developer.

[0002] The present invention further provides magnetic ink symbol identification (M
acoustic Ink Character Rec
The present invention relates to a magnetic developer suitable for printing characters having magnetism used in an (authentication) system.

In the electrophotographic image forming method, the magnetic developer of the present invention is a digital latent image in which a latent image is represented by unit pixels and the unit pixels are represented by on-off binary or finite gradation. Can be preferably used as a magnetic developer for developing an image by a reversal development method.

[0004]

2. Description of the Related Art Conventionally, for example, a developing device which visualizes a latent image formed on the surface of a photosensitive drum as an electrostatic latent image carrier with a magnetic toner as a one-component developer has been used. The friction and the friction between the sleeve as the development carrier and the magnetic toner particles give the magnetic toner particles a charge of the opposite polarity to the electrostatic image charge formed on the photosensitive drum and the development reference potential, and apply the magnetic toner to the sleeve. The toner is applied to the developing area formed by the photosensitive drum and the sleeve, and the magnetic toner flies under the action of the magnetic field from the magnet fixed in the sleeve in the developing area, causing the electrostatic latent image on the photosensitive drum to fly. There is known a device for visualizing the image.

Further, in recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have also been diversified. Under such a background, magnetic ink symbol identification (Magnetic Ind.) Has been used as an application field of electrophotographic printers.
k Character Recognition Hereinafter, it is simply referred to as MICR. ) A character printing machine used in the system has been devised.

[0006] The MICR system mainly prints information such as issuing bank, amount, account number and the like on checks and bills with magnetic ink, and efficiently sorts and sorts at a clearinghouse using a magnetic reader. It is a system devised for. Conventionally, offset printing using magnetic ink has been the mainstream, but business transactions such as personal checks and bills have become active, and demand for small MICR character printing machines (hereinafter simply referred to as MICR encoders) has increased. doing.

The conventional small MICR encoder is:
Impact printers applying the thermal transfer method were the mainstream, but in this case, most single-function printers that print only MICR characters cannot be used for general documents, and improvements are required. .

An electrophotographic printer capable of printing general documents and / or graphics, printing MICR characters, and exhibiting a good MICR recognition rate is desired. When an electrophotographic printer is applied to a MICR encoder, if a conventionally known magnetic developer is used as it is, the correctness / error rate (recognition rate) of magnetic reading by a MICR reader / sorter is reduced to the case of MICR characters using offset printing or an impact printer. Is extremely low and impractical.

[0009] First, M by an electrophotographic printer
In order to achieve a high recognition rate in printing ICR characters, it is necessary to use a magnetic developer containing a specific magnetic material having magnetic properties different from those used in conventional magnetic developers. .

That is, a magnetic material showing a relatively large residual magnetization σr is required.

[0011] Similar to a magnetic developer of a general electrophotographic printer, it is required to exhibit good triboelectrification and to be uniformly coated on a developer carrier (hereinafter, referred to as a sleeve) of a developing machine. . In order to satisfy this condition, the magnetic permeability of the magnetic substance contained in the magnetic developer is also important.

JP-B-59-7379 contains cobalt-substituted iron tetroxide powder having a major axis / minor axis ratio of 1 to 5, a residual magnetization of 10 to 20 emu / g, and a coercive force of 150 to 4
Although a magnetic toner of 50 Oersted has been proposed, it is difficult to uniformly coat the toner layer on the sleeve, and it is inferior in triboelectricity, low in image density and poor in sharpness.

JP-A-63-108354 discloses an insulative magnetic capsule toner containing a spherical magnetic powder having a major axis / minor axis ratio of 1 to 1.5 and a magnetic permeability of 3.80 to 6.00. JP-A-59-204846 proposes a magnetic toner containing a ferromagnetic fine powder having a maximum magnetic permeability of 3.95 to 5.50. In this case, the image density is high, which is preferable, but improvement is required in order to meet more severe requirements such as resolution and compatibility with the reversal development method.

Further, MICR characters are, for example, ANS (A
merchant National Standard)
x9.27-198x or JIS C6251-1
There is a standard called E-13B specified in 980.
The E-13B standard consists of numbers from 0 to 9 and four types of symbols, and a bank code, a branch code, an account number, an amount, and the like are printed on securities by a combination of these.

In order to improve the recognition rate by the MICR reader / sorter, it is required that the shape and dimensions of the printed MICR characters are reproduced with high precision, and the characters are fine and faithful without being crushed or cut off. It needs to be reproduced.

In an image forming apparatus used for MICR in recent years, when a toner image formed on a photosensitive drum is electrostatically transferred to paper, a transfer device to which a bias is applied is pressed against the photosensitive drum. An apparatus configured to transfer the toner image on the photosensitive drum to the paper by passing paper serving as a transfer material between them (for example, see Japanese Patent Application Laid-Open No. 59-4666).
No. 4) has been proposed.

In such a method, the adhesion between the toner on the photosensitive drum and the photosensitive drum is enhanced, transfer to the transfer material is hindered, and the formed toner image has characters (only characters) having an outline formed. (Void characters). FIG. 1 (b)
FIG. 1D shows an example of the void. Such a phenomenon is
In addition to a defect as a general image, an error occurs in a magnetic signal in MICR printing, and the risk of leading to erroneous reading by a reader / sorter increases.

As a means for solving the problem of omission during transfer, there has been proposed a method in which 0.05 to 3 parts by weight of a fine powder treated with silicone oil or silicone varnish is contained per 100 parts by weight of toner (Japanese Patent Laid-Open No. Hei. 121462
No.).

However, it is presumed that the above-mentioned fine powder is selectively developed, but it is good at the initial stage of image formation, but when the number of copies is increased, the level of the hollow portion is reduced.

As a transfer device, there is a transfer roller as indicated by 503 in FIG. 5, but when the number of copies increases, a phenomenon occurs in which the roller surface is scraped by contact with the photosensitive drum or the transfer material, and the hollowing level decreases. I do. Further, when the fine powder treated with silicone oil or silicone varnish is added in an amount of 2 parts by weight or more, the effect is somewhat improved, but a decrease in performance during durability cannot be avoided.

Further, securities printed with MICR characters are passed through the MICR reader / sorter about 10 times on average. Each time a sheet is passed to perform magnetic reading, the sheet is rubbed at high speed with the magnetic head. Accordingly, in order to increase the recognition rate, the magnetic developer for printing MICR characters causes the print to be blurred by rubbing (hereinafter, referred to as smearing.
Fig. 2 shows the part where this occurs. ), It is necessary not to fall off.

In order to prevent the printed portion from being stained or the characters falling off due to the rubbing between the magnetic head and the printed characters, the frictional resistance between the magnetic head and the printed characters can be reduced, and the adhesion to paper can be improved. It is necessary to use a suitable magnetic developer. That is, it is important to improve the binder resin, wax, and the like. However, at present, a magnetic developer that overcomes both problems and satisfies electrophotographic characteristics has not been realized.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic developer which solves the above-mentioned problems.

That is, an object of the present invention is to provide a MICR reader / sorter having a good signal recognition rate and a good MICR reader / sorter with no missing characters even when the number of copies increases.
An object of the present invention is to provide a magnetic developer for forming a CR character.

It is a further object of the present invention to provide a magnetic developer which does not cause smearing and does not contaminate the magnetic head of the MICR reader / sorter even when paper is repeatedly passed through the MICR reader / sorter. It is in.

It is a further object of the present invention to provide a magnetic developer which forms a MICR character which has good adhesion to paper and is difficult to separate from paper.

It is a further object of the present invention to provide a magnetic developer capable of forming uniform image quality with no difference in image density between left and right even in a general printed image and capable of forming MICR characters having a good recognition rate of a MICR reader / sorter. Is to provide.

[0028]

According to the present invention, the above object is achieved by the following constitution.

That is, according to a first aspect of the present invention, there is provided a magnetic developer having at least a magnetic toner and an inorganic fine powder, wherein the magnetic toner contains a binder resin, a magnetic substance, and a wax. Is that the residual magnetization σr in a magnetic field of 10,000 Oersted is 12 ≦ σr ≦ 30 emu.
/ G, and the coercive force Hc is 130 ≦ Hc ≦ 300
Oersted range and magnetic permeability μ is 2.0 ≦ μ
≦ 4.0, and the inorganic fine powder contains 20% to 90% by weight of silicone oil or silicone varnish.
The present invention relates to a magnetic developer containing a bulk density of 0.2 to 0.8 (g / cc) and a specific surface area of 0.01 to 50 (m ² / g).

According to a second aspect of the present invention, there is provided a magnetic developer having at least a magnetic toner, wherein the magnetic toner contains a binder resin, a magnetic material, and a wax, and the magnetic material has a magnetic field of 10,000 Oersted. Magnetization σ at
r is in the range of 12 ≦ σr ≦ 30 emu / g, coercive force Hc is in the range of 130 ≦ Hc ≦ 300 Oersted, and magnetic permeability μ is in the range of 2.0 ≦ μ ≦ 4.0,
The wax has the following general formula RY [R: a hydrocarbon group having a weight average molecular weight of 3000 or less as determined by gel permeation chromatography. Y represents a hydroxyl group, a carboxyl group, an alkyl ether group, an ester group, or a sulfonyl group. And a magnetic developer.

The magnetic substances contained in the first and second magnetic developers of the present invention have common characteristics, and the characteristics will be described below.

The magnetic material used in the magnetic developer of the present invention preferably has a residual magnetization σr in the range of 12 ≦ σr ≦ 30 emu / g, more preferably 14 ≦ σr ≦ 28 emu, in a magnetic field of 10,000 Oersted. / G
It is good to be in the range of.

When the residual magnetization σr is less than 12 emu / g, when the MICR character is printed, the MIC
The recognition rate of the R reader / sorter is significantly reduced.

Further, when the residual magnetization σr exceeds 30 emu / g, the image density tends to be low and fogging is apt to occur. The image quality is easily lowered, and the image quality is extremely low even when general printing is performed.

In the magnetic material according to the present invention, the coercive force Hc
Is 130 at a magnetic field of 10,000 Oersteds.
It is preferably in the range of ≦ Hc ≦ 300 Oersted, and more preferably in the range of 140 ≦ Hc ≦ 280 Oersted.

When the coercive force Hc is less than 130 Oe, the image density is high, but the reproducibility of fine lines is inferior, and the recognition rate is lowered when MICR characters are printed. Absent. Coercive force Hc is 300
In the case where the ratio exceeds 1, it becomes difficult to uniformly apply the magnetic developer on the developing sleeve, and the image density is lowered or the density unevenness occurs, which is not preferable.

Further, it has been found that the magnetic permeability μ well corresponds to the correctness / error rate of reading by the MICR reader / sorter when printing MICR characters.

In the magnetic material according to the present invention, the magnetic permeability μ is preferably in the range of 2.0 ≦ μ ≦ 4.0, more preferably 2.5 ≦ μ ≦ 3.8. When the magnetic permeability μ exceeds 4.0, it is possible to uniformly apply the magnetic developer on the developing sleeve, but the interaction with the permanent magnet in the developing sleeve is weak, and the friction of the magnetic developer is low. It is difficult to appropriately control the charge amount, and the scattering of the toner in the image area increases. When printing MICR characters, the recognition rate is reduced, which is not preferable.

If the magnetic permeability μ is less than 2.0, the interaction with the permanent magnet in the developing sleeve becomes too strong, and as a result, the amount of triboelectric charging of the magnetic developer must be properly controlled. Becomes difficult, the image density is low, the recognition rate when printing MICR characters is reduced, and the object of the present invention cannot be achieved.

The magnetic substance used in the present invention is produced by being synthesized by an aqueous solution containing Fe ^2+, that is, a wet method using ferrous sulfate as a raw material, and then oxidized and reduced at a temperature of 200 ° C. or more. Is preferred. For more information,
After being synthesized by the above-mentioned wet method, it is manufactured by heating and oxidizing at a temperature of 200 ° C. or more, and then reducing by heating. The thermal oxidizing is performed by passing an oxidizing gas such as air at 500 to 900 ° C. , Then heat reduction, 250 ~
It is preferable to carry out the reaction at 550 ° C. while passing a reducing gas such as hydrogen and / or carbon monoxide.

In the present invention, the magnetic toner is the binder resin 1
The magnetic material is preferably used in an amount of 40 to 120 parts by weight per 100 parts by weight.
It is good to contain by weight, more preferably 50 to 110 parts by weight.

The inorganic fine powder used in the first invention of the present invention is characterized in that an inorganic compound is highly blended with silicone oil and silicone varnish.

As the inorganic compound, SiO ₂ , GeO ₂ ,
TiO ₂ , SnO ₂ , Al ₂ O ₃ , B ₂ O ₃ , P ₂ O ₅ , As ₂
Oxides such as O ₃ ; silicates, borates, phosphates, germanates, borosilicates, aluminosilicates, aluminoborates, aluminoborosilicates, tungstates, molybdates, tellurates Metal oxide salts such as salts;
And composite compounds thereof; silicon carbide, silicon nitride, amorphous carbon; and the like are used alone or in combination.

Of these, metal oxides are preferably used, and oxides of Si, Al and Ti and composite compounds are more preferable. Alternatively, a material whose surface has been previously rendered hydrophobic with a coupling agent or the like may be used.

The particle size of such an inorganic compound may be set at 0.1.
It is preferably from 001 to 20 μm, more preferably from 0.005 to 10 μm.

The specific surface area of the inorganic compound is 10 m
² / ^{g~400m 2} / g, and even more 50m ² / g~400
m ² / g, more 100m ² / g~350m ² / g are preferred. If it is less than 10 m ² / g, it becomes difficult to retain a large amount of silicone oil / varnish as particles in the range of the present invention.

The silicone oil used in the first invention has a general formula

[0048]

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R: an alkyl group having 1 to 3 carbon atoms R ': a silicone oil-modified group such as alkyl, halogen-modified alkyl, phenyl, and modified phenyl R ": an alkyl group or an alkoxy group having 1 to 3 carbon atoms Examples thereof include dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil.

In the present invention, an amino-modified silicone oil having a structure represented by the formula (I) can be used as the silicone oil.

[0051]

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(Where R ₁ and R ₆ are hydrogen, an alkyl group,
R ₂ represents an alkylene group or a phenylene group; R ₃ represents a compound having a nitrogen-containing heterocyclic ring in its structure; R ₄ and R ₅ represent a hydrogen, an alkyl group, or an aryl group . R ₂ may not be present. However, the above-mentioned alkyl group, aryl group, alkylene group and phenylene group may contain an amine or may have a substituent such as halogen as long as the chargeability is not impaired. M is a number of 1 or more, and n and k are positive numbers including 0. Here, n + k is a positive number of 1 or more. )

The most preferred structure among the above structures is one in which the number of nitrogen atoms in the side chain containing a nitrogen atom is one or two.

Examples of the nitrogen-containing unsaturated heterocycle are shown below.

[0055]

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Examples of the nitrogen-containing saturated heterocycle are shown below.

[0057]

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However, the present invention is not limited to the above compound examples, but preferably has a 5-membered or 6-membered heterocyclic ring.

As the derivatives, a hydrocarbon group, a halogen group, an amino group, a vinyl group, a mercapto group,
Derivatives into which a methacryl group, a glycidoxy group, a ureido group, etc. are introduced are exemplified.

These may be used alone or in a mixture of two or more.

The silicone varnish used in the present invention includes, for example, methyl silicone varnish, phenylmethyl silicone varnish and the like, and methyl silicone varnish is particularly preferred.

The methyl silicone varnish is a polymer composed of T ³¹ units, D ³¹ units, and M ³¹ units represented by the following structural formula, and is a three-dimensional polymer containing a large amount of T ³¹ units.

[0063]

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The methyl silicone varnish or the phenylmethyl silicone varnish is, for example, a substance having a chemical structure represented by the following structural formula (II).

[0065]

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(R ³¹ represents a methyl group or a phenyl group.)

In the above silicone varnish, in particular, T ³¹
The unit is an effective unit for imparting good thermosetting properties and forming a three-dimensional network structure. The T ³¹ unit is 10 to 90 mol% in a silicone varnish, in particular 30 to 80 mol%
Is preferably contained at a ratio of

Such a silicone varnish has a hydroxyl group at a terminal or a side chain of a molecular chain, and is cured by dehydration condensation of the hydroxyl group. Examples of the curing accelerator that can be used to accelerate this curing reaction include fatty acid salts such as zinc, lead, cobalt, and tin; amines such as triethanolamine and butylamine; and the like. Of these, amines can be particularly preferably used.

In order to make the above-mentioned silicone varnish into an amino-modified silicone varnish, the above-mentioned T ³¹ unit, D ³¹
Units, some of the methyl group or a phenyl group present in the M ³¹ unit may be replaced with a group having an amino group. Examples of the group having an amino group include those represented by the following structural formula. However, the present invention is not limited to these.

[0070]

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Known methods can be used for treating the silicone oil or silicone varnish. For example,
A method of mixing fine powder with silicone oil or silicone varnish using a mixer, a method of spraying silicone oil or silicone varnish into fine powder using a sprayer, after dissolving silicone oil or silicone varnish in a solvent And a method of mixing fine powder.

The above silicone oil or silicone varnish has a viscosity at 25 ° C. of 50 to 200,000 centistokes, and more preferably 500 to 150,000 centistokes.
00 centistoke, and more than 1,500
Those having 100,000 centistokes are more preferable, and those having 3,000 to 80,000 centistokes are preferable. If it is less than 50 centistokes, it is difficult to form a large amount of silicone oil / silicone varnish into particles, and the particles are not stable, and the image quality tends to deteriorate due to heat and mechanical stress. If it exceeds 200,000 centistokes, it tends to be difficult to form particles.

The viscosity of the silicone oil or silicone varnish was measured using a Visco Tester VT500 (manufactured by Haake). One of several viscosity sensors for VT500 is selected (arbitrary), and a measurement sample is put in a measurement cell for the sensor to measure. The viscosity (pas) indicated on the device was converted to cSt (centistokes).

The amount of silicone oil or silicone varnish in the inorganic fine powder is 20 to 90% by weight (preferably 27 to 85% by weight, more preferably 40 to 80% by weight).
% By weight). When the amount of the silicone oil or the silicone varnish is less than 20% by weight, the effect of improving the omission during transfer and the effect of improving the smearing in durability are small. When the amount exceeds 90% by weight, the silicone oil or the silicone varnish becomes difficult to be retained on the particles. ,
Excessive silicone oil or silicone varnish lowers the fluidity of the developer, causing various image quality deteriorations such as lower image density uniformity, lower image density, and fog.

[0075] Inorganic fine particles composed of a silicone oil or silicone varnish and the inorganic compound, a specific surface area of 0.01m ² / g~50m ² / g (preferably 0.0
5m ² / g~30m ² / g, more preferably 0.1 m ²
/ G to 10 m ² / g), a good effect can be obtained.
If it exceeds 50 m ² / g, the silicone oil or silicone varnish is difficult to hold as particles, causing aggregation of developer particles, and image quality is likely to deteriorate. Further, although the reason is not clear, the effect of improving the omission during transfer is reduced. If it is less than 0.01 m ² / g, the image quality deteriorates.

The specific surface area is a value calculated by the following method.

According to the BET method, nitrogen gas is adsorbed on the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics), and the specific surface area is calculated using the BET multipoint method.

The inorganic fine powder has a bulk density of 0.1 g.
/ Cc to 0.8 g / cc (preferably 0.2 g / cc to
0.7 g / cc, more preferably 0.3 g / cc or more
0.6 g / cc), a good effect can be obtained. This value relates to the method of treating the silicone oil or the silicone varnish and the amount of the silicone oil or the silicone varnish contained in the inorganic fine powder. When the bulk density is less than 0.1 g / cc, there is little effect on improving omission during transfer and smearing. When the bulk density is more than 0.8 g / cc, silicone oil or silicone varnish becomes excessive. The fluidity of the agent is remarkably reduced, and the above-described image quality deterioration is easily caused.

The bulk density was measured using a container attached to a powder tester (manufactured by Hosokawa Micron Co., Ltd.) according to the procedure described in the instruction manual, by measuring the number of grams in a 100 cm ³ container [g / cm]. ³ ].

The application amount of the particles composed of the silicone oil or the silicone varnish and the fine particles is determined according to the toner 10
0.01 to 5 parts by weight, and 0.0
It is preferably 3 to 2 parts by weight, more preferably 0.05 to 1 part by weight. If the amount is less than 0.01 part by weight, the effect of improving omission during transfer and smearing cannot be obtained. If the amount is more than 5 parts by weight, the fluidity of the developer is impaired, and the above-described image deterioration and the developer Impairs fixability.

The wax used in the first invention of the present invention comprises: (i) a low molecular weight alkylene polymer obtained by radical polymerization of alkylene under high pressure or a Ziegler catalyst under low pressure; and (ii) thermal decomposition of high molecular weight alkylene polymer. (Iii) Extraction and fractionation of a specific component from a material such as a synthetic hydrocarbon obtained by hydrogenating a distillation residue of a hydrocarbon obtained by the Age method from a synthesis gas comprising carbon monoxide and hydrogen (Iv) alcohol wax having a main chain of a completely long-chain saturated hydrocarbon which is considered to be obtained from an alkylene polymer utilizing a Ziegler catalyst (v) derived from an alcohol wax obtained in (iv) Fats with functional groups such as carboxyl, ester, ether, and sulfonyl groups It can be a hydrocarbon.

Among them, (iii), (iv), (v)
The waxes described above are particularly preferred.

The preferred range of the molecular weight distribution of the wax used in the present invention is that the number average molecular weight (Mn) is 550 to 1
200, preferably a weight average molecular weight (Mw)
Is preferably from 800 to 3000, more preferably from 900 to 2500, and further preferably Mw / Mn is at most 3 and more preferably at most 2.5. By having such a molecular weight distribution, the toner can have favorable thermal characteristics. That is, when the molecular weight is smaller than the above range, the magnetic head is susceptible to thermal effects excessively, smearing is likely to occur, and the magnetic head is easily contaminated at the same time. When the molecular weight is larger than the above range, the adhesion to paper is deteriorated, and as a result, MICR characters may be lost when the paper is passed through a MICR reader / sorter, which is not preferable.

In the present invention, the molecular weight distribution of the wax is measured by gel permeation chromatography (GPC) under the following conditions.

(GPC Measurement Conditions) Apparatus: GPC-150
C (Waters) Column: GMH-HT 30 cm 2 columns (manufactured by Tosoh Corporation) Temperature: 135 ° C Solvent: o-dichlorobenzene (0.1% ionol added) Flow rate: 1.0 ml / min Sample: 0.15% sample 0.4 ml injection

Measurement is performed under the above conditions, and the molecular weight of the sample is calculated using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample. In addition, Mark-Hou
It is calculated by converting to polyethylene using a conversion formula derived from the wink viscosity formula.

Further, the wax used in the first invention of the present invention has at least one endothermic peak in the range of 90 to 120 ° C. in a DSC curve measured by a differential scanning calorimeter. Temperature ± 9 ° C
A wax having a maximum exothermic peak at the time of temperature fall within the range of (1).

Further, the hydrocarbon wax used in the first invention is characterized in that an endothermic peak at the time of temperature rise is present preferably in the range of 90 to 120 ° C. That is, the melting of the wax in this temperature range produces a release effect, so that the MICR characters are less likely to be blurred or lost even when repeatedly passed through the MICR reader / sorter. Hard to contaminate the head.

When the endothermic peak temperature at the time of temperature rise is present only at less than 90 ° C., it indicates that the plasticizing effect due to the melting of the wax is exhibited from a low temperature and the mechanical strength of the binder resin is significantly reduced. In this case, although the releasing effect is exhibited when the paper is passed through the MICR reader / sorter, the MICR character is blurred when the MICR character is rubbed with the magnetic head of the MICR reader / sorter due to a decrease in the mechanical strength of the binder resin. And the magnetic head is contaminated at the same time, which is not preferable.

The endothermic peak at the time of the temperature rise may exist in a region exceeding 120 ° C., but when the endothermic peak temperature exists only in the region exceeding 120 ° C., the melting temperature of the wax becomes lower. In MICR printing, it is too high, and the releasability from paper is increased.
When the paper is passed through the sorter, the MICR characters are easily lost due to the rubbing with the magnetic head, and as a result, the magnetic head is easily contaminated. Here, when the endothermic peak below 90 ° C. becomes the maximum peak, the same behavior as when there is an endothermic peak only in this region, the endothermic peak may be present in this region, but in that case, It must be smaller than the endothermic peak in the range of 90 to 120 ° C.

When the temperature is lowered, the change during cooling of the wax and the state at normal temperature can be seen, and an exothermic peak accompanying the solidification, crystallization, and transition of the wax is observed. Among the exothermic peaks at the time of temperature decrease, the largest exothermic peak is an exothermic peak accompanying solidification and crystallization of wax. The presence of an endothermic peak due to melting at a temperature close to the exothermic peak temperature indicates that the wax is more homogeneous in terms of physical properties such as crystal structure and molecular weight distribution. Is preferably within 9 ° C., preferably 8 ° C.
It is within ° C. By reducing this difference, the wax has a sharp melt property, that is, it is hard at low temperatures, melts quickly at the time of melting, the melt viscosity greatly decreases, and an excellent release effect is exhibited. And MI
Even if you repeatedly pass through the CR reader / sorter,
MICR characters are less likely to be blurred or missing, and are less likely to contaminate the magnetic head of the MICR reader / sorter. The maximum exothermic peak temperature is in the range of 85 to 115 ° C, preferably 90 to 110 ° C.

In the DSC measurement in the present invention, since the exchange of heat of the toner is measured and its behavior is observed, it is necessary to measure with a high-precision internal heating input compensation type differential scanning calorimeter from the measurement principle. As such a measuring device, for example, DSC-7 manufactured by PerkinElmer can be used.

The measurement method is as described in ASTM D3418-82.
Perform according to. As the DSC curve used in the present invention, a DSC curve measured when the temperature is raised once, a pre-history is taken, and then the temperature is decreased and raised at a temperature rate of 10 ° C./min.
The definition of each temperature is defined as follows.

Endothermic peak temperature: The temperature at the peak top is defined as endothermic in the positive direction of the DSC curve.

Exothermic peak temperature: The temperature at the peak top where the negative direction of the DSC curve is exothermic.

The content of these waxes is preferably used within 20 parts by weight, more preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the binder resin. It may be used in combination with other waxes.

On the other hand, the wax used in the second invention of the present invention has the following general formula RY [R: a hydrocarbon group having a weight average molecular weight of 3,000 or less as determined by gel permeation chromatography. Y represents a hydroxyl group, a carboxyl group, an alkyl ether group, an ester group, or a sulfonyl group. ], And in combination with the above magnetic substance,
The object of the present invention can be achieved.

Specific examples of the compound include: (A) CH ₃ (CH ₂ ) _n CH ₂ OH (n = about 20 to about 20)
0) (B) CH ₃ (CH ₂ ) _n CH ₂ COOH (n = about 20 to about 200) (C) CH ₃ (CH ₂ ) _n CH ₂ OCH ₂ (CH ₂ ) _m CH
₃ (n = about 20 to about 200, m = 0 to about 100) (D) CH ₃ (CH ₂ ) _n CH ₂ COO (CH ₂ ) _m CH
₃ (n = about 20 to about 200, m = 0 to about 100) (E) CH ₃ (CH ₂ ) _n CH ₂ OSO ₃ H (n = about 20 to
About 200). These compounds are derivatives of compound (A), and the main chain is a linear saturated hydrocarbon. As long as the compound is derived from the compound (A), those other than those shown in the above examples can be used.

The magnetic developer of the second invention containing these waxes is effective in smearing resistance in terms of MICR characteristics, furthermore, has improved adhesion to paper, and can be used for reading characters with a reader / sorter. Dropouts and the like hardly occur. Further, it has the effect of improving the fluidity of the developer, and enables uniform coating of the developer on the developing sleeve, thereby obtaining a uniform image with no difference in density between left and right. Further, as described above, since the adhesion to paper is improved, the fixability is also improved. Further, an effect is also exerted on omission during image transfer.

The wax used in the second invention preferably has a content of the above compound of 60% or more, and more preferably 70% or more in the case of the compounds (A) and (B). Below this, the smearing resistance, the adhesion to paper, and the effect on omission during transfer are reduced.

In terms of molecular weight distribution, Mn is 200 to 2
000, more preferably 230 to
1,800, and Mw is preferably from 400 to 3,000, more preferably from 420 to 2,500. Further, Mw / Mn is preferably 3.0 or less, more preferably 2.5 or less.

By providing such a molecular weight distribution, it is possible to impart favorable thermal characteristics to the toner.
That is, when the molecular weight is smaller than the above range, the magnetic head is susceptible to thermal effects excessively, smearing is likely to occur, and the magnetic head is easily contaminated at the same time. When the molecular weight is larger than the above range, the adhesion to paper is deteriorated, and as a result, MICR characters may be lost when the paper is passed through a MICR reader / sorter, which is not preferable. The measurement of the molecular weight distribution of the wax used in the second invention is based on the aforementioned GP.
The measurement was performed according to the C measurement.

The content of the wax of the second invention is preferably used within 20 parts by weight with respect to 100 parts by weight of the binder resin, more preferably 0.5 to 15 parts by weight. Yes, and may be used in combination with other waxes.

The description of the present invention described below is common to the first and second inventions.

As the binder resin of the toner according to the present invention,
Styrene such as polystyrene and polyvinyltoluene and its substituted homopolymer; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene- Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic Acid ethyl copolymer,
Styrene-butyl methacrylate copolymer, styrene-
Dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-maleic acid copolymer,
Styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid Resin, rosin, modified rosin, tempel resin,
Phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can be used alone or in combination. In particular, styrene-based copolymers and polyester resins are preferred in terms of development characteristics, fixability, and the like.

In the magnetic developer of the present invention, it is preferable to use a charge control agent mixed (internally added) with toner particles or mixed (externally added) with toner particles.

Examples of the positive charge control agent usable in the present invention include denatured products such as nigrosine and fatty acid metal salts; tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate and the like. Quaternary ammonium salts;
Dibutyltin oxide, dioctyltin oxide,
Diorganotin oxides such as dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate 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.

Further, the general formula

[0109]

Embedded image

R ₁ ＨH, CH ₃ R ₂ , R ₃ : a homopolymer of a monomer represented by a substituted or unsubstituted alkyl group (preferably C ₁ -C ₄ ) or styrene or acrylate as described above And a copolymer with a polymerizable monomer such as methacrylic acid ester can be used as a positive charge control agent. In this case, these charge control agents can also act as (all or part of) a binder resin. Have.

As the negative charge controlling agent which can be used in the present invention, for example, metal complexes or salts of monoazo dyes; metal complexes or salts of salicylic acid, alkylsalicylic acid, dialkylsalicylic acid or naphthoic acid are preferably used. At this time, chromium and iron can be preferably used as the metal.

The above-mentioned charge control agent (having no function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is
Specifically, it is preferably 4 μm or less, more preferably 3 μm.
m or less is good.

At the time of internal addition to the toner, such a charge control agent is preferably used in an amount of 0.1 to 100 parts by weight of the binder resin.
It is good to use 1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight.

The magnetic developer of the present invention preferably has a second inorganic fine powder. The second inorganic fine powder is an auxiliary agent added mainly for the purpose of improving the fluidity of the magnetic developer of the present invention and maintaining good developability in any environment. The second inorganic fine powder referred to here is composed of an inorganic compound having the same composition as the inorganic fine powder described in the first invention, and particularly, an oxide fine powder of silica or titanium is preferably used.

Among them, as the second inorganic fine powder, a silica fine powder treated with a silane coupling agent and then treated with a silicone oil or a silicone varnish is more preferably used.

The conditions for treating the fine silica powder are as follows: a silane coupling reaction is carried out as a first-stage reaction to eliminate silanol groups by chemical bonding; Characterized by forming a thin film of:

The silane coupling agent used in the present invention has the general formula R _m SiY _n

[Wherein, R represents an alkoxy group or a chlorine atom, m represents an integer of 1 to 3, Y represents an alkyl group,
It represents a hydrocarbon group containing a vinyl group, a glycidoxy group or a methacryl group, and n represents an integer of 3 to 1. ] Are preferred. For example, typically, dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, hexamethyldisilazane, allylphenyldichlorosilane, benzyldimethylchlorosilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyl Triacetoxysilane,
Examples thereof include divinylchlorosilane and dimethylvinylchlorosilane.

The fine powder may be treated with a silane coupling agent by a dry process in which a vaporized silane coupling agent is reacted with a cloud of fine powder by stirring or the like, or a silane coupling agent in which the fine powder is dispersed in a solvent. The treatment can be performed by a method such as a wet method in which a ring agent is dropped and reacted. Among them, a dry treatment method is particularly preferably used, but is not limited thereto.

As the substance used for the silicone oil or silicone varnish treatment, the same substance as that used for the inorganic fine powder of the first invention may be used. The same method can be used as the treatment method. Among them, a method that hardly causes an increase in bulk density due to agglomeration of fine powder by the treatment, for example, a method using a sprayer is preferably used.
However, it is not limited to this.

The silane coupling agent may be treated in an amount of 1 to 40 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the fine powder. The treatment amount of the silicone oil or silicone varnish solid is 1 to 23 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the fine powder.

When the amount of the silane coupling agent is too small, good moisture resistance cannot be obtained, and when the amount is too large, problems such as a decrease in image density occur. If the amount of silicone oil or silicone varnish is too small, good moisture resistance and the effect of improving hollowing out cannot be obtained, while if too large, the fluidity of the developer cannot be improved.

The characteristic values of the treated silica fine powder are as follows:
The bulk density is preferably 30 to 60 (g / l), more preferably 35 to 55 (g / l), and the specific surface area by nitrogen adsorption measured by the BET method is in the range of 80 to 140 m ² / g. And more preferably 90 to 130 m ²
/ G. It is preferable to use 0.2 to 1.6 parts by weight, preferably 0.4 to 1.4 parts by weight, of silica fine powder with respect to 100 parts by weight of the magnetic toner.

Next, the image forming method and apparatus of the present invention will be described with reference to FIG.

The surface of the photoreceptor is negatively charged by a primary charger 502, and a digital latent image is formed by image scanning by exposure 505 with a laser beam.
The latent image is reversely developed with a one-component magnetic developer 510 of a developing device 509 having a developing sleeve 504 containing a magnet 11 and a magnet. In the developing section, between the conductive substrate of the photosensitive drum 501 and the developing sleeve 504, an alternating bias, a pulse bias and / or a DC bias are applied by a bias applying means 512. When the transfer paper P is conveyed and reaches the transfer section, the transfer image is charged by the voltage application means 514 from the back surface (the surface opposite to the photosensitive drum side) of the transfer paper P by the roller transfer means 502, so that the developed image on the photosensitive drum surface is formed. (Toner image) is electrostatically transferred onto the transfer paper P.
The transfer paper P separated from the photosensitive drum 501 is subjected to a fixing process to fix a toner image on the transfer paper P by a heating / pressing roller fixing device 507.

The one-component developer remaining on the photosensitive drum after the transfer step is removed by a cleaning device 508 having a cleaning blade. After the cleaning, the photosensitive drum 501 is neutralized by the erase exposure 506, and again,
The process starting from the charging process by the primary charger 502 is repeated.

The evaluation of the image quality was carried out periodically during the durability (about 5,000 sheets) and evaluated. (1) Image uniformity: The image density within one image was measured by a Macbeth reflection densitometer, and evaluated based on the difference between the maximum value and the minimum value. (2) Hollow-out: General character and MICR test paper [manufactured by Moor (US), 90 (g) on 120 (g / m ² ) thick paper
/ M ² )] to print the own line symbol (ON US). Rank 5: good (see (a), (c) of FIG. 1), rank 3: practically acceptable, rank 1: practically improper ((b) of FIG. 1,
(See (d)), ranks 4 and 2 are ranks 5 and 3, respectively.
It is an intermediate level between ranks 3 and 1.

The MICR characteristics were evaluated as follows.

(1) Adhesion: A solid black image was formed on ordinary plain paper (75 g /
m ² ) and drafting tape (width 1)
8 mm; manufactured by Sumitomo 3M Limited) as shown in FIG. 3, and a jig as shown in FIG. 4 (load: about 0.60 k)
g / cm ² ), rub it 10 times and then peel it off
Evaluation was made based on the average value of the reduction rate of image density at seven points.

(2) Smearing: JISC 6250
According to the description of -1980, printing of MICR characters
Dmax of a non-printed portion (see FIG. 2) of a sample obtained by passing the printed matter of 1,000 times through a commercially available MICR reader / sorter (model 3890 made by IBM) 20 times.
The value (the value obtained by subtracting the Dmax value of the non-paper passing white background portion) was measured with a Macbeth reflection densitometer.

(3) Magnetic signal strength: ANSI (Amer
ican National Standard In
state) X 9.27 E13 described in 1988
According to the B standard, in the clear band (magnetic printing area),
At 14 addresses, 14 self-running symbols (ON
A check sample printed with a US symbol was prepared. E1
3B MICR CALIBRATION DOCUM
MINI QUES calibrated by ENT 100%
Using T (manufactured by ZEISER), the signal intensities of the 14 own symbols were measured, and the average value was used as the signal intensity.

(4) Reader / sorter test: JIS
According to the description of C 6250-1980, a simulated sample on which MICR characters printed on a check or the like are actually printed is 10
00 sheets, and these 1000 samples are
2 in CR reader / sorter (IBM 3890 model)
The processing was performed 0 times and the number of misreads was checked. In addition, the number of samples considered to be clearly caused by the void was also investigated.

[0133]

Example 1 Binder resin 100 parts by weight Magnetic substance (Fe ₃ O ₄ ) 55 parts by weight Monoazo dye chromium complex 1 part by weight Chromium salicylate complex 2 parts by weight Wax 7 parts by weight

The binder resin in the above constituent materials is styrene-
A copolymer containing butyl acrylate-maleic acid as a main component and having a Mw of 2.2 × 10 ⁵ was used. The magnetic material is 1
The residual magnetization σr in a magnetic field of 0000 Oe is 1
8emu / g, Hc is 190 Oe, magnetic permeability μ
Is 2.5 (hereinafter referred to as a magnetic body A).

The wax is a hydrocarbon wax obtained by the Age method, having an Mw = 1260, a DSC characteristic, an endothermic peak temperature of 105 ° C., and a maximum exothermic peak temperature of 104 ° C. when the temperature is lowered (hereinafter referred to as wax A).
Called. ) Was used.

The above constituent materials were mixed and dispersed by a Henschel mixer and melt-kneaded by a twin-screw extruder.
After cooling the kneaded material, coarsely pulverized, finely pulverized by a pulverizer using a jet stream, and further classified using an air classifier,
A magnetic toner having a weight average particle size of 12 μm was obtained.

With respect to 100 parts by weight of the magnetic toner, the inorganic fine powder A of the present invention (containing 60% by weight of silicone oil,
Bulk density 0.4 g / cc, specific surface area 3.0 m ² / g)
2 parts by weight, hydrophobic silica treated with hexamethyldisilazane and then treated with silicone oil (hereinafter referred to as silica A) [bulk density 45 g / l, specific surface area 105 m ² / g]
Was added and mixed with a Henschel mixer to obtain a magnetic developer. Using the obtained magnetic developer, a general image and MICR characters were printed using LBP-EX, and the electrophotographic characteristics and MICR characteristics were evaluated. Table 1 shows the results.

Example 2 Hydrophobic silica not treated with silicone oil (hereinafter referred to as silica B) [Bulk density 40 g / l, specific surface area 11
0 m ² / g] to obtain a magnetic developer in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 3 The same constituent materials as those of Example 1 were used except for the wax, and the mixing weight ratio was the same as that of Example 1.

As for the wax, the molecular formula of a long-chain alcohol polymer having a hydroxyl group at a terminal and showing an average composition is represented by CH ₃ (CH ₂ ) ₄₈ CH ₂ OH, and the content of the compound having a hydroxyl group is about 80%, Mw = 880
In the DSC characteristics, those having an endothermic peak temperature of 98 ° C. and a maximum exothermic peak of 97 ° C. when the temperature was lowered (hereinafter referred to as wax B) were used. Thereafter, a magnetic toner having a weight average particle diameter of 12 μm was obtained by the same production method as in Example 1. Thereafter, inorganic fine powder A and silica A were externally added in the same manner as in Example 1 to obtain a magnetic developer. Evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 4 Binder resin (identical to Example 1) 100 parts by weight Magnetic substance (Fe ₃ O ₄ ) 90 parts by weight Monoazo dye chromium complex 1 part by weight Chromium salicylate complex 2 parts by weight Wax 7 parts by weight

In the above constituent materials, the magnetic substance A was used as the magnetic substance, and the wax B was used as the wax. Thereafter, a magnetic toner having a weight average particle diameter of 7 μm was obtained by the same production method as in Example 1. Hereinafter, 0.1 parts by weight of inorganic fine powder A and 1.2 parts by weight of silica A were externally added to 100 parts by weight of the toner to obtain a magnetic developer. Evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 5 The same constituent materials as those of Example 1 were used except for the wax, and the mixing weight ratio was the same as that of Example 1.

As for the wax, the molecular formula of a long-chain aliphatic hydrocarbon having a carboxyl group at a terminal and showing an average composition is represented by CH ₃ (CH ₂ ) ₄₈ CH ₂ COOH.
A compound having a carboxyl group has a content of about 80%, Mw = 910, and an endothermic peak temperature of 105 ° C. and a maximum exothermic peak of 98 ° C. at the time of temperature decrease in DSC characteristics (hereinafter referred to as wax C). Was used. Hereinafter, a magnetic developer was obtained in the same manner as in Example 1. Further, evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 6 Example 3 except that the inorganic fine powder A was not added to the magnetic toner.
A magnetic developer was obtained in the same manner as described above. Further, evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 7 Example 4 except that the inorganic fine powder A was not added to the magnetic toner.
A magnetic developer was obtained in the same manner as described above. Further, evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Example 8 Example 5 except that the inorganic fine powder A was not added to the magnetic toner.
A magnetic developer was obtained in the same manner as described above. Further, evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 0.6 parts by weight of silica B alone was added to 100 parts by weight of the magnetic toner obtained in Example 1, and mixed with a Henschel mixer to obtain a magnetic developer. Evaluation was performed in the same manner as in Example 1.
Table 1 shows the results.

Comparative Example 2 The magnetic material and the wax were changed from those in Example 1. The other raw materials and the weight composition ratio were the same as in Example 1. The magnetic material has a σr of 1 in a 10,000 Oe magnetic field.
0.5 (emu / g), Hc of 105 Oe and magnetic permeability of 5.0 (hereinafter referred to as magnetic material B)
Was used.

For wax, Mw = 4030 and D
In the SC characteristics, those having an endothermic peak temperature of 128 ° C. and a maximum exothermic peak of 113 ° C. at the time of cooling were used (hereinafter referred to as wax D). Thereafter, a magnetic developer was obtained in the same manner as in Comparative Example 1. Evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

[0151]

[Table 1]

[0152]

As described above, the first invention of the present invention provides a magnetic developer by incorporating an inorganic fine powder obtained by incorporating a large amount of silicone oil or silicone varnish into a magnetic developer. In this case, the following excellent effects can be obtained by combining with a magnetic material having specific magnetic properties.

(1) Even when the number of printed sheets increases, the MICR having a normal magnetic signal without any missing during transfer.
A magnetic developer capable of forming characters can be provided.

(2) A magnetic developer capable of suppressing the occurrence of smearing when paper is repeatedly passed through the MICR reader / sorter can be provided.

(3) Even in an image forming apparatus which forms a latent image by a digital image signal and develops the latent image by a reversal developing method, it is possible to provide a magnetic developer capable of forming an image without omission during transfer.

Further, according to the second invention of the present invention, by including a specific aliphatic hydrocarbon in the magnetic developer, the magnetic developer can be provided with preferable powder characteristics and preferable thermoplasticity. By combining with a magnetic material having magnetic properties, the following excellent effects are exhibited.

(1) It is possible to provide a magnetic developer which does not cause smearing even when paper is repeatedly passed through the MICR reader / sorter.

(2) It is possible to provide a magnetic developer that does not contaminate the magnetic head of the MICR reader / sorter even when the paper is repeatedly passed through the MICR reader / sorter.

(3) It is possible to provide a magnetic developer which has good adhesion to paper and forms MICR characters which are difficult to separate from paper.

(4) Even in a general print image, a uniform image quality can be formed with no difference in density between left and right image density, an effect of improving omission during transfer, and a MICR reader / sorter having a good recognition rate. A magnetic developer capable of forming characters can be provided.

[Brief description of the drawings]

FIG. 1 shows an example in which a general character (a) and an ON US character (c) have a good transfer state and examples in which the transfer state is poor (b) and (d).
It is the figure which showed typically.

[Figure 2] MIC with a check etc. in the leader / sorter test
It is the figure which showed typically the part where R character is printed, and the smearing occurrence part.

FIG. 3 is a diagram schematically showing a place where a drafting tape is stuck in an adhesion test.

FIG. 4 is a diagram schematically showing a jig used in an adhesion test and a state thereof.

FIG. 5 is a diagram schematically showing a specific example of an image forming method and an image forming apparatus suitable for the present invention.

[Explanation of symbols]

 Reference Signs List 501 photoconductor 502 charging means 503 transfer means 504 toner carrier 505 latent image forming means 506 erase exposure 507 heating / pressing roller fixing device 508 cleaning means 509 developing means 510 magnetic developer 511 magnetic blade 512 bias applying means 513 voltage applying means P Transfer paper

──────────────────────────────────────────────────続 き Continuation of the front page (72) Keita Nozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-5-249729 (JP, A) JP-A-6 -266166 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08-9/097

Claims (5)

(57) [Claims] 1. A magnetic developer having at least a magnetic toner and an inorganic fine powder, wherein the magnetic toner contains a binder resin, a magnetic substance, and a wax, and the magnetic substance has a residual magnetization in a magnetic field of 10,000 Oersted. σr is in the range of 12 ≦ σr ≦ 30 emu / g, coercive force Hc is in the range of 130 ≦ Hc ≦ 300 Oersted, and magnetic permeability μ is in the range of 2.0 ≦ μ ≦ 4.0. The fine powder contains 20% to 90% by weight of silicone oil or silicone varnish, and has a bulk density of 0.2 to 90%.
0.8 (g / cc) and a specific surface area of 0.01 to 50
(M ² / g). 2. In a DSC curve of the wax measured by a differential scanning calorimeter, there is at least one endothermic peak at the time of temperature increase in a temperature range of 70 to 130 ° C., and the peak temperature of the endothermic peak is ± 9 ° C. 2. The magnetic developer according to claim 1, wherein a maximum heat generation peak at the time of temperature decrease is within the range. 3. A magnetic developer having at least a magnetic toner, wherein the magnetic toner contains a binder resin, a magnetic material and a wax, and the magnetic material has a residual magnetization σr in a magnetic field of 10,000 Oersteds of 12 ≦ 12. σr ≦ 30 emu / g, coercive force Hc is 130 ≦ Hc ≦ 300 Oersted, magnetic permeability μ is 2.0 ≦ μ ≦ 4.0, and the wax has the following general formula: RY [R: a hydrocarbon group having a weight average molecular weight of 3000 or less as determined by gel permeation chromatography. Y represents a hydroxyl group, a carboxyl group, an alkyl ether group, an ester group, or a sulfonyl group. ] The magnetic developer which contains the compound which has these. 4. The surface of the magnetic toner particles further treated with a silicone oil after a silane coupling agent treatment has a bulk density of 30 to 60 (g / l) and a specific surface area of 80 to 140.
Magnetic developer according to claim 1, the second inorganic fine powder is characterized in that is supported in (m ² / g). 5. The magnetic developer according to claim 1, wherein the magnetic developer is used to print characters used in a magnetic ink symbol identification system that reads information using magnetic characters using a magnetic reader. 5. The magnetic developer according to any one of 4.