JPH0486672A - Magnetic developer,device unit and electrophotographic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention applies to magnetic developers used in electrophotography, electrostatic printing, electrostatic recording, and the like.

The present invention further provides magnetic ink symbol identification (M a g n
e t i cInk Character Re
The present invention relates to a magnetic developer suitable for printing magnetic characters used in a recognition system.

The magnetic developer of the present invention can be used in an electrophotographic image forming method.
Preferably used as a magnetic developer for visualizing a digital latent image using a reversal development method, where the latent image is expressed by a unit pixel, and each unit pixel is expressed by an on-off binary value or a finite gradation. can.

[Prior art]

2. Description of the Related Art Electrophotographic systems generally use a method in which a document image is exposed to light and a latent image carrier is exposed to the reflected light to obtain a latent image. In this method, the reflected light from the original is directly converted into an image signal, so the potential of the electrical latent image changes continuously (hereinafter referred to as an analog latent image).In contrast, recently, the reflected light from the original is converted into an electrical signal. A method has been commercialized that processes the signal and then performs exposure based on it. Compared to the analog latent image method, this method allows for easier magnification and reduction at higher magnifications, and the image signal can be taken into a computer and output together with other information. While it has a variety of uses as mentioned above,
If image signals are treated as analog, the signal amount will be enormous, so digital processing is required to divide the image into pixel units (hereinafter referred to as dots) and determine the exposure amount for each pixel.

When a latent image is digitized, each dot needs to be developed accurately compared to an analog latent image, and therefore a developer that can faithfully develop pixels at a high development rate is required.

In the case of developing a digital latent image, compared to an analog latent image, the deviation in surface potential of the latent image during latent image formation is large, and the potential difference between the developer conveying section and the latent image carrier such as a photosensitive drum is small. It is also necessary to develop the latent image area.

The developability of the developer becomes particularly important in images where images and non-images are repeated for each dot. Therefore, when a developer developed as an analog latent image developer is used in a digital latent image system, the development of each dot is insufficient, especially in the printing pattern where the image/non-image is repeated for each dot. Phenomena such as dots becoming smaller or not being developed at all occur, and the overall image density tends to be light (or characters become blurred). This becomes noticeable in a developer having a magnetic developer (hereinafter referred to as a magnetic developer).

This is thought to be because in the magnetic developer, there are portions where the magnetic material is exposed on the surface of the magnetic toner particles, and the surface area that can contribute to charging is reduced. The amount of magnetic material exposed on the surface varies depending on the amount of magnetic material contained in one magnetic toner.
The distribution of developer charge amount is wider than that of other developers. Therefore, when a magnetic developer is used in a digital latent image system, characters are likely to become blurred due to the accumulation of magnetic toner particles with a low triboelectric charge in the developer, and an improvement is desired.

Furthermore, in recent years, as image forming devices such as electrophotographic copying machines have become widespread, their uses have also expanded to a wide variety of uses. Against this background, magnetic ink symbol identification (M a g n ) has become an application field for electrophotographic printers. et icInk
Character Recognition
A character printing machine for use in a system (hereinafter simply referred to as MICR) has been devised.

The MICR system mainly prints information such as the issuing bank, amount, and account number on checks and bills using magnetic ink.
This system was devised to efficiently sort and sort items at clearinghouses using magnetic readers. Traditionally, offset printing using magnetic ink was the mainstream, but as commercial transactions using personal checks and bills became more active, small MICR character printing machines (hereinafter simply MICR) were used.
Demand for CR encoders (referred to as CR encoders) is increasing.

Until now, compact MICR encoders were mainly impact printers that applied a thermal transfer method, but most of these were single-function machines that printed only MICR characters, and were not suitable for producing general documents. It cannot be used and improvements are required.

What is desired is an electrophotographic printer that is capable of printing general documents and/or graphics, is also capable of printing Li I CR characters, and exhibits good MICRIC rates.

When applying an electrophotographic printer to a MICR encoder, if conventionally known magnetic developers are used as is, the accuracy rate (recognition rate) of magnetic reading by the MICR reader/sorter will be lower than that of MICR characters using offset printing or impact printers. Compared to printing, it is extremely low and impractical.

The number of securities printed with MICR characters is passed through the MICR reader/sorter about 10 times on average.

To perform magnetic reading, each time a sheet of paper is passed through, it is rubbed against the magnetic head at high speed. Therefore, it is necessary that the magnetic developer for printing MICR characters does not fade or fall off due to rubbing.

MICR characters are, for example, ANS (American
National Standard) x9.27-1
There is a standard called E-13B defined by 98x or JIS C62511980. The E-13B standard consists of numbers from 0 to 9 and four types of symbols, and these combinations are used to mark securities as bank coats, branch codes,
It prints the account number, amount, etc.

In order to improve the recognition rate by MICR readers and sorters, the shape and dimensions of printed MICR characters must be reproduced with high precision, and the characters can be reproduced minutely and faithfully without being crushed or cut off. This is necessary.

In order to achieve a high recognition rate when printing MICR characters using an electrophotographic printer, it is necessary to use a magnetic developer containing a specific magnetic material that exhibits magnetic properties different from those used in conventional magnetic developers. need to use.

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

In addition, it is required to exhibit good triboelectric charging properties like the magnetic developer of general electrophotographic printers, and to be uniformly coated on the developer carrier (hereinafter referred to as sleeve) of the developing machine. In order to satisfy this condition, the magnetic permeability of the magnetic material contained in the magnetic developer is also important.

In Japanese Patent Publication No. 59-7379, the ratio of major axis/minor axis is 1 to 1.
Contains cobalt-substituted triiron tetroxide powder with a residual magnetization of 1
0~20 emu/g% coercive force 150~45
0 Oe magnetic toner has been proposed, but it is difficult to uniformly apply a toner layer to the sleeve.
It has poor triboelectric charging properties, low image density (and poor sharpness).

JP-A-63-108354 proposes an insulating magnetic capsule toner containing spherical magnetic powder having a long axis/short axis ratio of 1 to 1.5 and a magnetic permeability of 3.80 to 6.00. Further, Japanese Patent No. 59-204846 proposes a magnetic toner containing fine ferromagnetic powder having a maximum magnetic permeability of 3.95 to 5.50. In this case, the image density is high, which is desirable, but improvements are required in order to meet more stringent requirements such as resolution and suitability for reversal development.

[Problem to be solved by the invention]

An object of the present invention is to provide a magnetic developer that solves the above-mentioned problems.

That is, an object of the present invention is to provide a magnetic developer with a large amount of triboelectric charge.

An object of the present invention is to provide a magnetic developer that has good fine line reproducibility and resolution and is suitable for use in developing digital latent images.

Furthermore, an object of the present invention is to use a toner that has excellent resolution, gradation, and fine line reproducibility even in an image forming apparatus that forms a latent image using a digital image signal and develops the latent image using a reversal development method. An object of the present invention is to provide a magnetic developer capable of forming images.

A further object of the present invention is to provide a magnetic developer that provides good image quality with high image density and little fog.

A further object of the present invention is to provide a magnetic developer that can be uniformly applied onto a developing sleeve, has high image density (and does not cause density unevenness).

A further object of the present invention is to provide a magnetic developer that has good interaction with the permanent magnet in the developing sleeve and can appropriately control the amount of triboelectric charge of the magnetic developer.

Still another object of the present invention is to provide a magnetic developer having a magnetic material that can be uniformly dispersed in a magnetic toner.

Furthermore, it is an object of the present invention to uniformly apply the magnetic developer on the developing sleeve, to uniformly disperse the magnetic material in the magnetic toner of the magnetic developer, and to achieve uniform magnetic properties and triboelectric charging properties. An object of the present invention is to provide a magnetic developer.

Another object of the present invention is to
ICR(M agnetic I
nk Ch a r a c t e rReco
The present invention provides a magnetic developer that exhibits an excellent recognition rate when used for printing.

Another object of the present invention is to develop a magnetic developer f that does not reduce the recognition rate even when paper is repeatedly passed through a MICR reader/sorter.
It provides:

Still another object of the present invention is to provide a magnetic developer which has excellent fine line reproducibility and resolution, and which faithfully reproduces MICR characters according to the standard even when printing MICR characters.

Still another object of the present invention is to provide a magnetic developer which provides clear images with less fog and which does not reduce the recognition rate even when MICR characters are printed.

Still another object of the present invention is to provide a magnetic developer in which MICR characters do not fall off or become blurred even when the paper is passed through a MICR reader/sorter.

[Means to solve the problem]

The present invention provides a magnetic developer having a magnetic toner containing a magnetic substance, in which the residual magnetization σr of the magnetic substance in an io, ooo Oersted magnetic field is 12≦σr≦30emu
/g, the coercive force Hc of the magnetic material in a magnetic field of 10,000 Oe is in the range of 130≦He≦300 Oe, and the magnetic permeability μ is 2.0≦μ≦4.
0, and the magnetic material is in the range of 1.2 to 2.5 g/Cm
It has a solidified apparent density of 3 and a linseed oil absorption of 5 to 30 mA/100g, and the coefficient of change of the magnetic material is expressed by the following formula = σ/
xX100 (%) (In the formula, σ indicates the standard deviation of the particle size distribution of the magnetic material, and Ma indicates the average particle diameter (μm) of the magnetic material.)
This is a magnetic developer characterized in that the change coefficient of the magnetic material calculated from 20 to 50%.

Further, the present invention is a magnetic developer characterized in that the magnetic developer is used for printing characters used in a magnetic ink symbol identification system that uses a magnetic reader to read information in magnetic characters. .

Furthermore, the present invention provides an apparatus unit in which at least a developing means and a photoreceptor are integrally supported to form a unit, and a unit is formed as a single unit that can be freely attached to and detached from the apparatus main body, and the developer held in the developing means is 10,000 Oe. The residual magnetization σr of the magnetic material in the magnetic field is 12≦σr≦30 emu
/g, the coercive force Hc of the magnetic material in a magnetic field of 10,000 Oe is in the range of 130≦H, c≦300 Oe, and the magnetic permeability μ is 2.0≦μ≦4.
0, and the magnetic material is in the range of 1, 2 to 2, 5 g
It has a solidified apparent density of / cm and a linseed oil absorption of 5 to 30 m 1/100 g, and the coefficient of change of the magnetic material is expressed by the following formula -
The change coefficient of the magnetic material calculated from σ/xX100 (%) (in the formula, σ indicates the standard deviation of the particle size distribution of the magnetic material or indicates the average particle size (μm) of the magnetic material) is 20 to 50. % of the magnetic material contained in the device unit.

Furthermore, the present invention provides an electrophotographic apparatus having a photoreceptor, a latent image forming means, a developing means for developing the formed latent image, and a transfer means for transferring the developed image onto a transfer material, in which a developer held by the developing means is provided. The residual magnetization σr of the magnetic material in a magnetic field of 10.000 Oe is 12≦σr≦3
0 e m u / g, and the coercive force Hc of the magnetic material in a magnetic field of 10,000 Oe is 130
≦Hc≦300 Oersted, magnetic permeability μ is in the range 2.0≦μ≦4.0, and the magnetic material is 1.2 to 300 Oe.
Hardened apparent density of 2.5g/crrr and 5-30ml/1
00 g of linseed oil absorption, and the variation coefficient of the magnetic material using the following formula - σ/xX100 (%) (where σ represents the standard deviation of the particle size distribution of the magnetic material, or The electrophotographic apparatus is characterized in that it is a magnetic developer having a magnetic toner containing a magnetic material whose variation coefficient calculated from .mu.m) is 20 to 50%.

[Detailed description of the invention]

The magnetic developer of the present invention contains a magnetic material having the above magnetic properties.

The magnetic developer of the present invention has improved ability to faithfully reproduce even the fine lines of the latent image formed on the photoreceptor, has excellent reproduction of halftone dots and digital-like dot latent images, and has excellent gradation. and excellent resolution.

Furthermore, the magnetic developer of the present invention exhibits a good recognition rate when printing MICR characters, and even when the paper is repeatedly passed through a MICR reader/sorter, the characters do not fade or fall off easily, resulting in good results. The recognition rate can be maintained.

The magnetic substance contained in the magnetic developer of the present invention will be explained below.

In the magnetic material according to the present invention, the residual magnetization σr is 10°0
12≦σr≦30 e in a magnetic field of 00 Oersteds
It is preferably within the range of mu/g, and more preferably within the range of 14≦σr≦28 e mu/g.

If the residual magnetization σr is less than 12 e m u / g, when printing MICR characters, the MICR
The recognition rate of the reader/sorter decreases, and when performing general printing, fine line reproducibility and gradation may deteriorate.
Since the image density is low and there is a lot of fogging, when MICR characters are printed, the recognition rate is significantly lowered, and even when ordinary printing is performed, the image quality is extremely low.

In the magnetic material according to the present invention, the coercive force Hc is 10.0
In a magnetic field of 00 Oersted, 130≦Hc≦30
It is preferably in the range of 0 Nisted, and 140≦Hc
More preferably, the range is ≦280 nisted.

If the coercive force Hc is less than 140 degrees, the image density will be high, but on the other hand, the fine line reproducibility will be poor, and when printing MICR characters, it will be difficult to uniformly coat the developing sleeve. This is undesirable because it causes a decrease in image density or uneven density.

According to studies by the present inventors, it has been found that when the magnetic material according to the present invention exhibits residual magnetization σr, the magnetic permeability μ corresponds well to the electrophotographic properties of the magnetic developer.

Furthermore, it has been found that the magnetic permeability μ corresponds well to the accuracy rate of reading by a MICR reader/sorter when MICR characters are printed.

In the magnetic material according to the present invention, the magnetic permeability μ is 2.0≦μ≦
It is preferable that the magnetic developer is in the range of 4.0, and even more preferable.Although it is possible to uniformly apply the magnetic developer on the developing sleeve, the interaction with the permanent magnet in the developing sleeve is weak, and the frictional electrification of the magnetic developer may occur. It is difficult to properly control the amount, and the toner scatters more in the image area, which is undesirable because it causes a decrease in the recognition rate when printing MICR characters.

Furthermore, if the magnetic permeability μ is less than 20, the interaction with the permanent magnet in the developing sleeve becomes too strong, and as a result, it becomes difficult to properly control the amount of triboelectric charge of the magnetic developer, resulting in image density. is low, and when MIcR characters are printed, the recognition rate decreases, making it impossible to achieve the object of the present invention.

The magnetic material used in the magnetic developer of the present invention is 1.2 to 2.
5g/c resistance, more preferably 1.3-2.0g/cm
It has a solidified apparent density of 3 and 5 to 30 m127100
g.

Preferably, it has an oil absorption of 10 to 28 ml/100 g of linseed oil.

In the present invention, the apparent solidified density (packed bulk density) of the magnetic material is determined using a powder tester manufactured by Fine Micron ■ and the container attached to the powder tester, according to the instruction manual of the powder tester. Refers to the value measured according to the procedure.

In the present invention, the linseed oil absorption amount of the magnetic material is JISK
5101-1978 (Pigment Test Methods).

In the present invention, it is preferable to use a magnetic material having a hardened apparent density of 1.2 to 2.5 g/crd. This is an impossibly large value. The magnetic material preferably used in the present invention can be prepared by crushing the magnetic material. The means used to crush the magnetic material include a mechanical crusher equipped with a high-speed rotor for crushing the powder, and a loaded roller for dispersing or crushing the powder. An example is a pressure dispersion machine equipped with the following.

When crushing aggregates of magnetic material using a mechanical crusher, the impact force from the rotor is likely to be excessively applied to the primary particles of the magnetic material, causing the primary particles themselves to be destroyed.
Fine powder of magnetic material is likely to be generated. Therefore, when a magnetic material that has been crushed using a mechanical crusher is used as a raw material for toner,
The presence of fine magnetic particles deteriorates the triboelectric charging properties of the toner. Therefore, a decrease in toner image density is likely to occur due to a decrease in the amount of triboelectric charge of the toner.

On the other hand, a pressurized dispersion machine equipped with a weighted roller such as a fret mill is preferable in terms of the efficiency of crushing the magnetic material aggregates and the suppression of the production of finely powdered magnetic material.

The tap density and oil absorption amount of the magnetic material can be understood to indirectly indicate the shape of the magnetic material, the surface condition of the magnetic material, and the amount of aggregates of the magnetic material. When the density of the solidified magnetic material is less than 1.2 g/crrf, it indicates that there are many aggregates of the magnetic material and the crushing process of the magnetic material is substantially insufficient. There is. Therefore, if a magnetic material with a density of less than 1.2 g/crrr is used, the magnetic material will not be uniformly dispersed in the binder resin. If this is done, the recognition rate will decrease, which is undesirable.

When the apparent density of the magnetic material exceeds 2.5 g/cm, the aggregates of the magnetic material are disintegrated excessively, causing the magnetic materials to stick to each other due to pressure, resulting in the formation of pellets of the magnetic material. As a result, the content of the magnetic substance differs between the individual particles of the magnetic toner, and when printing MICR characters, this also leads to a decrease in the recognition rate, which is undesirable.

Even if the oil absorption value of the magnetic material deviates from the upper and lower limits,
The same phenomenon as in the case of density tends to occur in the case of solid appearance.

The magnetic material according to the present invention has a specific surface area of 5.0 to 1 in BET specific surface area measured by a nitrogen gas adsorption method.
It is preferable that it is 3.0 rrrl'/g, and more preferably 6.0 to 10.0 rrr/g.

The BET specific surface area can be measured by the nitrogen gas adsorption method using a commercially available measuring device, for example, Autosorb 1 (manufactured by Quantum Chemicals).

According to the inventor's study, when the residual magnetization (σr) of the magnetic material according to the present invention is relatively large compared to conventional magnetic materials, the magnetic material of each magnetic material particle is It is also expected to be relatively large during property fluctuations.

On the other hand, in the case of a magnetic developer, it is known that the content of magnetic material varies depending on its particle size. In other words, this suggests that the magnetic properties of magnetic developers may vary depending on their particle size.

Therefore, in the case of a magnetic developer in which it is important to precisely titrate a certain magnetic property as in the present invention, it is necessary to control the state of existence of the magnetic substance in the binder resin. This not only simply disperses the magnetic material uniformly within the binder resin, but also
This shows that the filling condition is important.

The present inventor has determined that the filling state of the magnetic material in the binder resin is as follows:
It was found that this is strongly influenced by the particle size distribution of the magnetic material.

It has been found that the magnetic material according to the present invention achieves the above-mentioned filling state only when the coefficient of change indicating the particle size distribution thereof becomes a certain specific value.

The change coefficient of the magnetic material here is calculated from the following formula.

Variation coefficient --x 100 In the formula, X represents the average particle diameter of the magnetic material, and σ represents the standard deviation of the particle size distribution.

Furthermore, in order to improve fine line reproducibility and sharpen line images, which is the object of the present invention, in magnetic developers, one solution is to narrow the charge amount distribution.

Conventionally, it has been known that uniformly dispersing a magnetic material is an effective means for narrowing the charge amount distribution in a magnetic developer. However, when the magnetic material according to the present invention contains silicon element and aluminum element in a specific ratio on the surface and inside thereof, it is not necessarily necessary to uniformly disperse the silicon element and the aluminum element.

According to the inventor's study, in the case of the magnetic material according to the present invention, similarly to the magnetic properties, the charge amount distribution of the magnetic developer can be narrowed only when the above-mentioned change coefficient becomes a specific value. I discovered that it can be done.

In the magnetic material according to the present invention, the variation coefficient is 20 to 50%
The ratio is preferably 25% to 45%, and more preferably 25% to 45%. When the coefficient of change is less than 20%, - For boat fishing, the dispersion of the magnetic material inside the magnetic developer is
However, in the case of the magnetic material according to the present invention, according to the inventor's study, the application of the magnetic developer on the developing sleeve becomes uneven, and the homogeneity of triboelectric charging properties is reduced. However, the uniformity of the dispersion state of the magnetic material inside the magnetic developer is lost, and the magnetic properties such as residual magnetization and the homogeneity of triboelectric charging properties of the magnetic developer are lost, which is undesirable.

Furthermore, the magnetic material according to the present invention has an average particle size of 0.1 to 0.
A material having a diameter of 6 μm is used. In the present invention, the average particle size of the magnetic material is determined by taking an enlarged photograph of the sample at a magnification of 20,000 times using a scanning electron microscope and randomly measuring the long axis value of 100 to 200 particles. It is obtained by calculating the average value.

In the magnetic developer of the present invention, the amount of triboelectric charge is 5 to -0 u c/g. If the amount of triboelectric charge is less than 15 μC/g, the image density will be low, which is not preferable. Also, -20μ
c/g, the amount of charge of the toner near the sleeve on the sleeve increases due to repeated image printing (this results in so-called charge-up, which inhibits proper charging of the toner supplied there). This phenomenon occurs, and the image density gradually decreases.This phenomenon tends to occur when developing a digital latent image, which is the development of a dot latent image, and is more noticeable in the low-potential contrast reversal development method using an OPC photoreceptor. It is.

In the magnetic developer of the present invention, if the average particle size of the magnetic powder particles is less than 0.1 μm, the dispersibility of the magnetic powder particles in the binder resin will be poor, making it difficult to uniformly charge the magnetic developer. Otherwise, even if the dispersibility in the binder resin is good, the shear modulus of the magnetic developer at around the fixing temperature is significantly increased, and the constant adhesion is deteriorated.

Furthermore, if the average particle size of the magnetic powder is 0.6 μm, the dispersion into the binder resin will not be uniform, and the charging property will not be uniform, and the surface of the photoreceptor may This is not preferable as it may cause significant damage to the

The magnetic properties of the magnetic material are ``For example, V manufactured by Toei Kogyo Co., Ltd.
Refers to the value measured by SMP-1, and when measuring magnetic properties, the magnetic material is 0.1 to 0.15 g with a sensitivity of 1.
Accurately weigh the sample using a direct reading balance of about 1.5 g.
It is carried out at a temperature of around 5°C. The external magnetic field during magnetic property measurement can be set to 10.000 oersteds, and the sweep speed when drawing a hysteresis loop can be set to 10 minutes.

The magnetic toner according to the present invention has a triboelectric charge and is therefore substantially electrically insulating. Specifically, a, okg/c
It is preferable that the resistance value when a voltage of 100 V is applied under a pressure of rrr is 10+4 Ω·cm or more. The magnetic material according to the present invention is preferably 50 to 140 parts by weight (preferably 60 to 12 parts by weight) per 100 parts by weight of the binder resin.
0 parts by weight). If it is less than 50 parts by weight, the conveyance of the magnetic toner on a developer carrier such as a sleeve will be insufficient. If it exceeds 140 parts by weight, the insulation properties and heat fixing properties of the magnetic toner will deteriorate.

The magnetic material according to the present invention is produced by synthesizing by a wet method using an aqueous solution containing Fe2°, that is, ferrous sulfate as a raw material, and then oxidizing and reducing the material at a temperature of 200° C. or higher. .

The magnetic material according to the present invention is produced by synthesizing by the above-mentioned wet method, then heating and oxidizing at a temperature of 200°C or higher, and then heating and reducing.
Performed at 0 to 900°C by aerating oxidizing gas such as air,
Next, thermal reduction is preferably carried out at 250 to 550° C. by passing a reducing gas such as hydrogen and/or carbon oxide.

The amount of charge of the toner in the present invention is 1 g of toner and 200 to 3
Place 9 g of iron powder carrier of 0.00 mesh in a 50 cc polyethylene bottle, put a lid on it, shake it by hand for 20 seconds (approximately 100 times) in an environment of 23°C and 60% RH, and then add a small amount of the mixture to the apparatus shown in Figure 4. Place it in a container and apply suction at a pressure of 250 mmH20 for about 1 minute until the potential is saturated.

The saturation potential V at this time, before capacitor capacitance C1 is drawn,
The amount of charge Q was determined from the weights W1 and W2 of the subsequent containers using the following formula.

A specific method for calculating the effective relative permeability will be described below.

Effective relative permeability is defined by the following formula.

In the magnetic material according to the present invention, the magnetic permeability μ is called effective relative magnetic permeability. The measurement is performed by uniformly winding a wire around a toroidal magnetic core, applying an appropriate alternating current magnetic field, and determining the change in inductance at that time.

The specific measurement method is to add 2.5 ml of a binder resin solution to approximately 15 g of the magnetic material to be measured (after mixing, place in a ring-shaped mold and mold at a pressure of approximately 1 ton/crrr).

At this time, it is important to adjust the density of the sample so that it is constant in order to improve the reproducibility of the measured values.

Furthermore, this toroidal sample is wound with a wire several tens of turns to be used as a sample for magnetic permeability measurement, and the tuning capacitance is measured using, for example, an impedance and gain phase analyzer manufactured by Yokogawa Hewlett-Packard Corporation. be able to.

Here, Lo is the inductance of the coil when there is no magnetic material, and L is the inductance of the coil when the magnetic material is inserted. The inductance of the coil when there is no magnetic material is expressed by the following equation.

Therefore, the effective relative magnetic permeability is calculated from the following formula.

Here, μ0 is the magnetic permeability in vacuum (4πX 10-7),
A indicates the cross-sectional area of the sample, N indicates the number of turns of the coil, and ■ indicates the average magnetic path length of the sample. Therefore, by measuring the inductance when the magnetic material is inserted, the effective relative magnetic permeability can be determined.

Further, in the magnetic toner of the present invention, it is preferable to use a load control agent by blending it into the toner particles (internally adding it) or mixing it with the toner particles (externally adding it). Examples of positive charge control agents include modified products with nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, nidibutyltin oxide, dioctyltin; Diorganotin oxides such as oxide, 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.

In addition, a monopolymer of a monomer represented by -formal % formula % R2, R3: substituted or unsubstituted alkyl group (preferably 01 to C4) or a polymer of styrene, acrylic ester, methacrylic ester, etc. as described above. A copolymer with a static monomer can be used as a positive charge control agent, and in this case, these charge control agents also function as (all or part of) a binder resin.

Negative charge control agents that can be used in the present invention include:
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.

The above-mentioned charge control agent (one that does not function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is specifically 4
The thickness is preferably .mu.m or less (more preferably 3 .mu.m or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 10 parts by weight (or even 0.1 to 10 parts by weight) per 100 parts by weight of the binder resin.
．． 1 to 5 parts by weight) is preferably used.

The magnetic developer of the present invention preferably contains hydrophobic silica fine powder.

The silica fine powder referred to herein can be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Among the above-mentioned silica fine powders, those having a specific surface area due to nitrogen adsorption measured by the BET method within the range of 70 to 300 rd/g give good results. 0.2 to 1.6 parts by weight of fine silica powder per 100 parts by weight of magnetic toner, preferably 0
．． It is preferable to use 4 to 1.4 parts by weight.

When the magnetic toner of the present invention is used as a positively charged magnetic toner, positively charged silica powder is added to prevent abrasion of the toner and prevent staining of the sleeve surface. It is preferable to use fine powder because it does not impair charging stability.

As a method for obtaining positively chargeable silica fine powder, the above-mentioned untreated fine silica powder is added with at least one nitrogen atom in the side chain.
There is a method of treatment with a silicone oil having more than one organo group, a method of treatment with a nitrogen-containing silane coupling agent, or a method of treatment with both.

Further, when the magnetic toner of the present invention is used as a negatively charged magnetic toner, one having a triboelectric charge amount of 1100 μC/g to 1300 μC/g is preferably used.

If the amount of tribocharge is less than 1100 μc/g, the amount of tribocharge of the developer itself is reduced, and the humidity characteristics are deteriorated. Furthermore, if the content exceeds -300, czc/g, the memory of the developer carrier will be accelerated, and the developer will be more susceptible to deterioration of silica, which will impede the durability characteristics.

Also, if it is finer than 300 dlg, it has no effect when added to the developer, and if it is coarser than 70 rrr/g, there is a high probability that it will exist as a free substance. Prone.

The tribo value of fine silica powder is measured by the following method. That is, in an environment of temperature 23.5°C and humidity 60% RH.
0.2 g of fine silica powder left overnight and carrier iron powder (for example, EFV200/30 manufactured by Nippon Iron Powder Co., Ltd., which is not coated with resin and has a main particle size of 200 to 300 mesh)
0) 9.8g under the above environment, approximately 50c,
Mix thoroughly (hold in hand and shake up and down approximately 50 times for approximately 20 seconds) in a wide-mouth polyethylene bottle with a lid having a volume of .c.

Next, as shown in FIG. 1, approximately 0.5 g of the mixture is placed in a metal measuring container 32 with a 400-mesh screen 33 at the bottom and a metal lid 34 is placed. Measurement container 32 at this time
Weigh the entire weight and let it be W+(g).

Next, in the suction device 31 (at least the part in contact with the measurement container 32 is an insulator), suction is performed from the suction port 37 and the air volume control valve 36 is adjusted to raise the pressure of the vacuum gauge 35 to 250 mm.
Let it be Hg. In this state, suction is applied sufficiently to remove the silica. The potential of the electrometer 39 at this time is assumed to be (volt). Here, 38 is a capacitor whose capacitance is C (μF
). Also, weigh the entire measurement container after suction.
2(g). The amount of triboelectric charge of this silica (μc/
g) is calculated as shown below.

The magnetic toner of the present invention may contain additives, if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. In addition, other external additives in the magnetic developer of the present invention include lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, flowability agents such as aluminum oxide, anti-caking agents, Alternatively, there are conductivity imparting agents such as carbon black and tin oxide.

To prepare the magnetic toner for developing electrostatic images according to the present invention, magnetic powder, vinyl or non-vinyl thermoplastic resin, pigment or dye as a coloring agent, charge control agent, and other additives are used as necessary. etc. are sufficiently mixed using a mixer such as a hall mill, and then melted, kneaded, and kneaded using a heat kneader such as a heated roll, a two-der, or an extruder to make the resins compatible with each other. The insulating magnetic toner according to the present invention can be obtained by dispersing or dissolving the dye, cooling and solidifying, and then pulverizing and strictly classifying.

Further, the electrophotographic apparatus and apparatus unit of the present invention will be explained with reference to FIG.

- Charge the surface of the photoreceptor to negative polarity with a charging device (charging means) 702, and form a digital latent image by image scanning using optical image exposure (latent image forming means) 705 (slit exposure/laser beam scanning exposure); magnetic blade 7
11 and a developing sleeve 70 containing a magnet 714
The latent image is reversely developed using a one-component magnetic developer 710 held in a developing device (developing means) 709 equipped with 4. In the developing section, an alternating bias, a pulse bias, and/or a DC bias is applied between the conductive base of the photosensitive drum (photosensitive member) l and the developing sleeve 704 by a bias applying means 712. When the transfer paper P is conveyed and reaches the transfer section, the transfer paper P is charged from the back side (the opposite side to the photosensitive drum side) with a secondary charger (transfer means) 703.
A developed image (toner image) on the surface of the photosensitive drum is electrostatically transferred onto transfer paper P. The transfer paper P separated from the photosensitive drum 701 is fixed to the transfer paper P by the heated pressure roller fixing device 707.
A fixing process is performed to fix the upper toner image.

The one-component developer remaining on the photosensitive drum after the transfer process is
It is removed by a cleaning device (cleaning means) 708 having a cleaning blade. After cleaning, the photosensitive drum 701 is neutralized by erase exposure 706, and the process starting with the charging process by the negative blower 702 is repeated again.

The electrostatic image carrier (photosensitive drum) has a photosensitive layer and a conductive substrate, and moves in the direction of the arrow. A non-magnetic cylindrical developing sleeve 704 serving as a toner carrier rotates in the developing section so as to move in the same direction as the surface of the electrostatic image holder. Inside the nonmagnetic cylindrical sleeve 704, a multipolar permanent magnet (magnet roll) serving as a magnetic field generating means is arranged so as not to rotate. One-component insulating magnetic developer 71 in the developing device 709
0 is applied onto a non-magnetic cylindrical surface, and friction between the surface of the sleeve 704 and the toner particles gives the toner particles, for example, a negative triboelectric charge. Furthermore, by arranging an iron magnetic doctor blade 711 close to the cylindrical surface (with an interval of 50 μm to 500 μm) and facing one magnetic pole position of the multipolar permanent magnet, the thickness of the developer layer can be reduced (30 μm to 50 μm). 300 μm) and uniformly, a developer layer thinner than the gap between the electrostatic image carrier 1 and the toner carrier 704 in the developing section is formed so as not to be in contact with each other.

By adjusting the rotational speed of the toner carrier 704, the sleeve surface speed is substantially half the speed of the electrostatic image holding surface, or a speed close to it. Instead of iron, a permanent magnet may be used as the magnetic doctor blade 711 to form opposing magnetic poles. In the developing section, an AC bias or a pulse bias may be applied between the toner carrier 704 and the electrostatic image holding surface by the bias means 712. This AC bias has f of 200 to 4, O
It is sufficient if OOHz and V pp are 500 to 3.0 OOV.

During the transfer of toner particles in the development area, development is performed by pressure using an elastic blade made of an elastic material such as a silicone comb instead of the electrostatic force and AC bias of the electrostatic image holding surface or the magnetic doctor plate 711. The thickness of the developer layer may be regulated and the developer may be applied onto the developer carrier.

An electrophotographic apparatus is constructed by combining a plurality of components such as the above-mentioned photoreceptor, developing means, and cleaning means into an apparatus unit, and this unit is configured to be detachable from the apparatus main body. It's okay. For example, a developing means and a photoreceptor are integrally supported to form a unit,
It may be a single unit that can be attached to and detached from the main body of the apparatus, and may be configured to be detachable using guide means such as rails of the main body of the apparatus. At this time, the above device unit may be configured with a charging means and/or a cleaning means.

Furthermore, when using an electrophotographic apparatus as a copying machine, printer, etc., optical image exposure is performed using reflected light or transmitted light from a document, or by converting the document into a signal and scanning a laser beam using this signal. This is performed by driving an LED array or a liquid crystal display array.

Hereinafter, the magnetic material and magnetic developer according to the present invention will be explained with reference to production examples and examples.

Manufacture of magnetic materials [Manufacturing Example 1] Magnetic materials (1) and (2) shown in Table 1 are produced by a wet synthesis method in which ferrous sulfate is used as a raw material and an oxidation reaction is performed in an aqueous solution.
, (3) was obtained.

[Production Example 2] Magnetic materials (1), (2), (
3) was first oxidized to α-Fe203 by aerating air at 750°C for 2 hours. Next, after setting the temperature to 350°C, the substrate mixed with hydrogen gas and nitrogen scum was aerated for 3 hours, and the magnetic materials (4), (5), ( 6) was obtained.

[Example 1] The following crushing treatment was performed using the magnetic material (4) of the present invention.

Hardened apparent density 1.3g/crn', linseed oil absorption 2
8mff7100g and BET specific surface area approximately s rrt'
The magnetic material (4) with an average particle size of 0.22 μm was crushed using a fret mill to crush the aggregates of the magnetic material, and the apparent density was 1.5 g/cm. Oil absorption amount 16mjl! /100g of magnetic material was obtained. The adjusted magnetic material has a coercive force Hc of approximately 280 Oe in a magnetic field of 10,000 Oe, and a residual magnetization σr of approximately 2
3 em u / g % magnetic permeability μ was 3.0.

Magnetic material of the present invention subjected to the above crushing treatment (4) 60 parts by weight Styrene/butyl acrylate copolymer 10
0 parts by weight chromium complex of monoazo dye (negative charge control agent)
o, 5 parts by weight The above mixture was melt-kneaded with a twin-screw extruder heated to 130°C, the cooled kneaded product was coarsely ground with a hammer mill, and the coarsely ground product was pulverized with a jet mill to obtain a fine powder. The crushed powder was classified using a fixed wall type wind classifier to produce classified powder. Furthermore, the obtained classified powder is strictly classified and removed at the same time using a multi-division classifier that utilizes the Yuanda effect (elbow classifier manufactured by 8 Iron Mining Co., Ltd.) to form a black fine powder with a volume average particle size of 12.4 μm. A body (magnetic toner) was obtained. The resulting black fine powder was mixed with an iron powder carrier and then tripocharge was measured, and the result was -11.2 μc/g.
It had a value of

A magnetic developer (1) according to the present invention was obtained by adding 0.5 parts by weight of negatively chargeable silica fine powder to 100 parts by weight of the magnetic toner and mixing well.

Next, when the above-mentioned magnetic developer (1) was printed using a Canon laser beam printer LBP-8, a clear image with high image density and little fogging was obtained.

Furthermore, MICR characters were printed on 1000 sheets in accordance with the description of JIS C6251-1980. These 10
00 sheets of printed material using a commercially available MICR reader/sorter C.
When the accuracy rate (recognition rate) of magnetic reading was investigated using a machine (Model 6780 manufactured by MCR), good results were obtained, showing a recognition rate of 90% or more.

[Example 2] A magnetic developer (2) was produced in the same manner as in Example 1, except that the magnetic material (4) was used without being crushed. M.I.
When CR characters were printed and the recognition rate was evaluated in the same manner as in Example 1, the recognition rate was 91.2%, which was good.

[Example 3] The following crushing treatment using the magnetic material (5) of the present invention was performed.

The apparent hardening density is 1.3g/crr+', the linseed oil absorption is 26mj2/100g, and the BET specific surface area is approximately 7rr?
/ g 1 The magnetic material (5) with an average particle size of 0.28 μm was subjected to a crushing treatment to crush the aggregates of the magnetic material using a fret mill, and the solidified material had an apparent density of 1.6 g/crr? ,
A magnetic material with a linseed oil absorption of 19 m and a weight of 127,100 g was obtained. The adjusted magnetic material has a coercive force Hc of about 200 Oe in a magnetic field of 10,000 Oe, a residual magnetization σr of about 17 emu/g, and a magnetic permeability μ of 3.
It was 5.

Magnetic material (5) of the present invention subjected to the above crushing treatment
60 parts by weight styrene/butyl acrylate copolymer
100 parts by weight Monoazo dye chromium complex (negative charge control agent) 0.5 parts by weight Except for using the above mixture,
A magnetic developer (3) was obtained in the same manner as in Example 1. MICR characters were printed in the same manner as in Example 1 and evaluated based on the recognition rate, which was good at 92.6%.

[Example 4] A magnetic developer (4) was produced in the same manner as in Example 1, except that the magnetic material (5) was used without being crushed. MICR characters were printed in the same manner as in Example 1 and evaluated based on the recognition rate, which was good at 86.2%.

[Example 5] The following crushing treatment using the magnetic material (6) of the present invention was performed.

Appearance of hardening is density 1.3g/crrr, linseed oil absorption 2
8mA/100g and BET specific surface area approximately 7n-r/g1
The magnetic material (6) with an average particle size of 0.28 μm was crushed using a fret mill to crush the aggregates of the magnetic material, and the apparent density was 1.5 g/crrr, and it had a linseed oil absorption. A magnetic material weighing 22m f 7100g was obtained. The adjusted magnetic material had a coercive force Hc of about 160 Oe in a magnetic field of 10,000 Oe, a residual magnetization σr of about 15 e mu/gs, and a magnetic permeability μ of 3.8.

Magnetic material (6) of the present invention subjected to the above crushing treatment
60 parts by weight styrene/butyl acrylate copolymer
100 parts by weight Monoazo dye chromium complex (negative charge control agent) 0.5 parts by weight Except for using the above mixture,
A magnetic developer (5) was obtained in the same manner as in Example 1. When MICR characters were printed in the same manner as in Example 1 and the recognition rate was examined, it was found to be 89.3%, which was good.

[Example 6] A magnetic developer (6) was produced in the same manner as in Example 1, except that the magnetic material (6) was used without being crushed. M.I.
When CR characters were printed and the recognition rate was evaluated in the same manner as in Example 1, the recognition rate was 85.0%, which was good.

[Comparative Examples 1 to 2] Comparative magnetic developers (1) and (2) were prepared in the same manner as in Example 1, except that the comparative magnetic materials (1) and (2) were used without being crushed. Obtained. When MICR characters were printed and evaluated based on the recognition rate in the same manner as in Example 1, the results were clearly inferior as shown in Table 4.

〔Effect of the invention〕

The magnetic developer of the present invention has a magnetic toner containing a magnetic substance, and the residual magnetization σr of the magnetic substance in a magnetic field of 10,000 Oe is 12≦σr.
In the range of ≦30 e m u / g, 10,00
The coercive force Hc of the magnetic material in a magnetic field of 0 Oe is in the range of 130≦Hc≦300 Oe, the magnetic permeability μ is in the range of 2.0≦μ≦4.0, and the magnetic material is
1, 2~2, 5 g/crr? It has a solidified apparent density of 5 to 30 m1/100 g, and has a linseed oil absorption capacity of
And the following formula: Coefficient of change of magnetic material = σ/xX100(%) (
In the formula, σ represents the standard deviation of the particle size distribution of the magnetic material, or represents the average particle size (μm) of the magnetic material. It is an object of the present invention to provide a magnetic developer having a large amount of triboelectrification since the coefficient of change of the magnetic material calculated from the above is 20 to 50%.

An object of the present invention is to provide a magnetic developer that has good fine line reproducibility and resolution and is suitable for use in developing digital latent images.

Furthermore, in an image forming apparatus that forms a latent image using a digital image signal and develops the latent image using a reversal development method,
A magnetic developer capable of forming toner images with excellent resolution, gradation, and fine line reproducibility can be provided.

Furthermore, it is possible to provide a magnetic developer that provides good image quality with high image density and little fog.

Furthermore, the magnetic developer can be uniformly applied onto the developing sleeve, and a magnetic developer with high image density and no density unevenness can be provided.

Furthermore, it is possible to provide a magnetic developer that has good interaction with the permanent magnet in the developing sleeve and can appropriately control the amount of triboelectric charge of the magnetic developer.

Furthermore, it is possible to provide a magnetic developer having a magnetic material that can be uniformly dispersed in the magnetic toner of the magnetic developer.

Furthermore, the application of the magnetic developer on the developing sleeve becomes uniform, and the magnetic material can be uniformly dispersed in the magnetic toner of the magnetic developer, thereby providing a magnetic developer with homogeneous magnetic properties and triboelectric charging properties. can do.

Further, the magnetic developer of the present invention is a magnetic developer characterized in that it is used for printing characters used in a magnetic ink symbol identification system in which information in magnetic characters is read using a magnetic reader. , MICR (Magnetic Ink) using an electrophotographic printer
Character Recognition) It is possible to provide a magnetic developer that exhibits an excellent recognition rate when used for printing.

Furthermore, it is possible to provide a magnetic developer that does not reduce the recognition rate even when the paper is repeatedly passed through the MICR reader/sorter.

Furthermore, it is possible to provide a magnetic developer that faithfully reproduces MICR characters in accordance with the standard even when printing MICR characters with excellent fine line reproducibility and resolution.

Furthermore, it provides clear images with less fog, and -MIC
It is possible to provide a magnetic developer that does not reduce the recognition rate even when R characters are printed.

Furthermore, even if the paper is passed through the MICR reader/sorter,
It is possible to provide a magnetic developer in which ICR characters do not fall off or become blurred.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring the amount of triboelectric charge of toner in the measurement of the amount of triboelectric charge. FIG. 2 is a schematic diagram showing the electrophotographic apparatus of the present invention. 1... Photoreceptor 31... Suction device 32... Measuring container 33... Conductive screen 34... Lid 35... Vacuum gauge 36... Air volume control valve 37... Suction port 39 Capacitor 39 Electrometer 702 Charging means 703 Transfer means 705 Latent image forming means 708 Cleaning means 709 Developing means 710 Magnetic developer

Claims (4)

[Claims] (1) In a magnetic developer having a magnetic toner containing a magnetic substance, the residual magnetization σ_r of the magnetic substance in a magnetic field of 10,000 Oe is in the range of 12≦σ_r≦30 emu/g, and The coercive force Hc of the magnetic material in a magnetic field is in the range of 130≦Hc≦300 Oe, the magnetic permeability μ is in the range of 2.0≦μ≦4.0, and the magnetic material has a coercive force Hc of 1.2 to 2. It has a solidified apparent density of 5 g/cm^3 and a linseed oil absorption amount of 5 to 30 ml/100 g, and has the following formula: Coefficient of change of magnetic material = σ/@x@×100 (%) (in the formula,
σ represents the standard deviation of the particle size distribution of the magnetic material, and @x@ represents the average particle size (μm) of the magnetic material. ) A magnetic developer characterized in that the change coefficient of the magnetic material calculated from 20 to 50%. (2) The magnetic developer is used to print characters used in a magnetic ink symbol identification system that uses a magnetic reader to read information in magnetic characters. magnetic developer. (3) In an apparatus unit in which at least a developing means and a photoreceptor are integrally supported to form a single unit that can be detachably attached to the main body of the apparatus, the developer held in the developing means has a magnetic field of 10,000 oersteds. The residual magnetization σ_r of the magnetic material is in the range of 12≦σ_r≦30 emu/g, the coercive force Hc of the magnetic material in the magnetic field of 10,000 Oe is in the range of 130≦Hc≦300 Oe, and the magnetic permeability μ is in the range of 130≦Hc≦300 Oe. 2.0≦μ≦4.0, the magnetic material has a solidified apparent density of 1.2 to 2.5 g/Cm^3 and a linseed oil absorption of 5 to 30 ml/100 g,
And the following formula: Coefficient of change of magnetic material = σ/@x@×100(%) (in the formula,
σ represents the standard deviation of the particle size distribution of the magnetic material, and @x@ represents the average particle size (μm) of the magnetic material. ) A device unit characterized in that the device unit is a magnetic developer having a magnetic toner containing a magnetic material whose change coefficient calculated from 20 to 50%. (4) In an electrophotographic apparatus having a photoreceptor, a latent image forming means, a developing means for developing the formed latent image, and a transfer means for transferring the developed image onto a transfer material, the amount of developer held in the developing means is 10 ,000 oersted magnetic field, the residual magnetization σ_r of the magnetic material is 12≦σ_r≦30emu/
g, the coercive force Hc of the magnetic material in a magnetic field of 10,000 Oe is in the range of 130≦Hc≦300 Oe, the magnetic permeability μ is in the range of 2.0≦μ≦4.0, and the magnetic material is The body has a solidified apparent density of 1.2 to 2.5 g/cm^3 and a linseed oil absorption amount of 5 to 30 ml/100 g, and the coefficient of change of magnetic material = σ/@x@×100 ( %) (in the formula,
σ represents the standard deviation of the particle size distribution of the magnetic material, and x represents the average particle size (μm) of the magnetic material. ) An electrophotographic apparatus characterized in that the electrophotographic device is a magnetic developer having a magnetic toner containing a magnetic material whose change coefficient calculated from 20 to 50%.