JP2854339B2 - Developer for developing electrostatic images - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a developer for developing an electrostatic image in an image forming method such as electrophotography, electrostatic recording, and electrostatic printing.

[Prior Art] Conventionally, many electrophotographic methods are known as described in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910, and Japanese Patent Publication No. 43-24748. However, in general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the latent image is developed using a developer, and if necessary, a transfer material such as paper is used. After the image is transferred onto the photosensitive member, the image is fixed by heating, pressure, heating and pressurizing or a solvent vapor to obtain a copy, and the developer remaining on the photoreceptor without being transferred is cleaned by various methods. The process is repeated.

In recent years, such copying apparatuses have been used not only in office work copying machines for copying original manuscripts but also in printers as computer outputs or personal copying machines for individuals. Are also diverse.

As a result, smaller, lighter, faster, and more reliable devices have been strictly pursued, and machines have become simpler in various respects. As a result, the performance required for a one-component developer capable of simplifying and reducing the size of the developing device becomes higher, and if the performance of the developer cannot be improved, a better machine cannot be realized. Is coming.

However, a one-component developer generally has little chance of being charged due to friction, and has a weak charge retention because the developer particles contain magnetic powder. Therefore, there have been various problems such as insufficient image density, fogging on a white background, and unsatisfactory high-humidity characteristics.

Further, if such a developer is stored for a long period of time, the developer deteriorates with time, and the problem caused by the charging property becomes more remarkable.

The problem of the storability of the developer or deterioration over time is particularly important when using a cartridge system that integrates a photoconductor, a developing unit, a cleaning device, etc. from a maintenance-free standpoint suitable for personal use. Depending on the situation, it is presumed that the problem will become even more important in the future.

On the other hand, there have been many patents and other technical documents describing the addition of a charge control agent in order to obtain stable triboelectric charging of a developer. However, while the addition of the charge control agent contributes to the charging stability of the developer, little consideration has been given to the storage stability of the developer over a long period of time and the deterioration over time.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to maintain initial characteristics without deterioration even after long-term storage. An object of the present invention is to provide a developer for developing an electrostatic image.

Still another object is to provide a developer for developing an electrostatic charge image in which the amount of triboelectric charge between developer particles and between the developer and a developer carrier such as a sleeve is stable, and the distribution of triboelectric charge is sharp and uniform. Is to do.

Still another object is to provide a developer for developing an electrostatic image that reproduces a stable image which is not affected by changes in temperature and humidity.

It is still another object of the present invention to provide a developer for developing an electrostatic image that can maintain initial characteristics even when the developer is used continuously for a long period of time.

[Means and Actions for Solving the Problems] That is, the present invention relates to a developer for electrostatic image development having at least an inorganic fine powder and a magnetic toner containing a binder resin cross-linked by a cross-linking agent. The binder resin of the toner contains 10 to 60% by weight of a THF-insoluble component, and the THF-soluble component of the binder resin of the magnetic toner has a main peak in a region of a molecular weight of 2,000 to 10,000 in GPC, Further, the present invention relates to a developer for developing an electrostatic image, wherein the inorganic fine powder is treated with silicone oil or silicone varnish.

The developer of the present invention, having the above-described configuration, is extremely unlikely to deteriorate over long-term storage or storage.

From the above, it has been found that the developer according to the present invention always provides good image formation without impairing the initial characteristics.

The present inventors consider the reason why the developer according to the present invention exerts the above-described effects as follows. That is, since the toner contains a binder resin having a three-dimensional structure due to crosslinking, it is presumed that good charging characteristics can be maintained without deteriorating the surface properties of the toner.

That is, generally, the binder resin in the toner is subjected to various external pressures at the time of manufacturing the toner particles, and a part of the energy is stored as distortion in the internal structure of the particles. In addition, when an additive such as magnetic particles is present, defects in the microstructure such as craze cracks and microvoids are likely to occur. Generally, such a microscopic structural defect in the binder resin is mitigated by shifting to a state of low free energy due to the movement of a segment which is a unit of thermal motion of the polymer material. In particular, the mobility of the segment on the particle surface is large, and the change is manifested by development such as a decrease in the surface area of the particle within a certain time scale. At this time, if an additive such as a fluidity-imparting agent is present on or near the toner surface,
This will significantly alter the state of adhesion of the additive. The present inventors presume that the deterioration of the developer over time, such as instability of the charging characteristics and deterioration of the fluidity, is caused by such a change in the toner surface.

By the way, in the case of a negatively chargeable developer, a fluidity imparting agent exhibiting a strong negative charge such as hydrophobic colloidal silica is often added, and therefore, the additive has an effect on the triboelectric chargeability of the toner. By increasing the triboelectric charge of the toner, it contributes to maintaining good charging characteristics. Therefore, the deterioration of the surface properties of the toner as described above has a particularly large effect.

On the other hand, the addition of inorganic fine powder treated with silicone oil makes it possible to simultaneously impart fluidity and stabilize chargeability, as seen in many patents and technical documents. However, since this silicone oil treatment is a surface application type unlike through a chemical bond like a silane coupling agent treatment, oil permeates and contaminates the toner surface. Oil contamination on the toner surface not only affects the surface chargeability of the toner, but also reduces the viscosity of the contaminated portion of the binder resin and promotes an increase in segment mobility. Will be promoted.

Therefore, in order to prevent the developer from deteriorating with time, it is necessary to include a cross-linking area component in the binder resin and to minimize the change in the surface properties of the toner, especially when using inorganic fine powder treated with silicone oil. If you do, it becomes mandatory. Among them, a particularly remarkable effect is shown in preventing the negatively chargeable developer from deteriorating with time.

The binder resin composition used in the present invention is characterized in that the binder resin has a THF-insoluble content (that is, a gel component) of 10 to 60% by weight, preferably 20 to 60% by weight.

For these reasons, if the THF-insoluble content in the binder resin composition is less than 10% by weight, the use of an inorganic fine powder treated with silicone oil has little effect on the deterioration over time due to oil contamination.

On the other hand, when the THF-insoluble content exceeds 60% by weight, the compatibility of each material component constituting the toner deteriorates, uniform dispersion becomes difficult, and the effect of suppressing the change in the surface properties of the toner due to the cross-linking region component decreases. Not preferred.

On the other hand, the THF-soluble component basically affects the dispersibility of another material in a developer, and a low-molecular-weight component having a molecular weight of 10,000 or less increases compatibility between the binder resin and another material. It turned out to be mainly dependent. The THF-soluble matter has a molecular weight of 2,000 to 10,000 (preferably 2,000 to 8,000) by GPC.
It has a main peak in the region of 0). It also has a molecular weight of 10,000
The proportion of the component of 0 or less is preferably from 10 to 50% by weight, and more preferably from 20 to 39% by weight. Molecular weight 2,000-1
There is no peak in the region of 000 and there is a peak in the region with a molecular weight of less than 2,000.
Exceeding the formula (2) slightly raises a problem because the effect of preventing deterioration over time due to the crosslinking zone component decreases. There is no peak in the region having a molecular weight of 10,000 or less, and there is a peak in the region having a molecular weight of 10,000 or more. If the proportion of the component having a molecular weight of 10,000 or less is less than 10% by weight, the dispersibility of other materials constituting the toner in the toner is reduced. Decrease.

Here, the medium- and high-molecular-weight components having a molecular weight of 10,000 or more in the THF-soluble component not only serve as a joint for uniformly presenting a high-molecular-weight polymer and a low-molecular-weight polymer having a cross-linking region component, but also as a low-molecular-weight component. It is effective in preventing seepage from the developer surface. In other words, the low molecular weight polymer can be reliably trapped by the effect of entanglement of the molecular chain with the medium / high molecular weight polymer having relatively small mobility, and the change of the developer surface which is considered to be the cause of deterioration with time is minimized. It will be more certain that it is suppressed.

Further, in order to uniformly disperse the respective materials and components and to minimize the deterioration of the developer over time due to the cross-linking area component, the THF-soluble component is preferably Mw / Mn ≧ 5, and the Mw / Mn ≧ 5 or less. When this happens, the effect of preventing deterioration over time tends to decrease, which is a problem.

Here, Mw is a weight average molecular weight measured by GPC described later, and Mn is a number average molecular weight obtained by the same measurement.

The THF-insoluble component (gel component) in the present invention refers to a gel component which has been crosslinked in a resin composition and has become insoluble in a solvent. Can be used as a parameter to indicate degree. The gel component is defined as a value measured as follows.

That is, when the sample is resin only, 0.5 to 1.0 g of a fixed amount of resin is weighed (W ₁ g), and cylindrical paper (Toyo Paper No.86) is weighed.
R) and run through a Soxhlet extractor.
(Tetrahydrofuran) Extraction was performed for 6 hours using 100 to 200 ml, and the soluble components extracted by the solvent were evaporated, then dried in vacuum at 100 ° C. for several hours, and the amount of the soluble resin components was weighed (W ₂ g). It calculates according to the formula of.

Gel component content = [(W ₁ −W ₂ ) / W ₁ ] × 100 (%) When the sample is a developer, a series of extraction operations is the same as that for a resin, but for a non-magnetic developer, The weight of the pigment is subtracted from the weight of the developer sample, the weight of the developer sample minus the weight of the pigment and magnetic material (W ₃ g), and the weight of the solvent-soluble component in the developer (W ₄ g). ) Can be calculated according to the following equation.

Gel component content = [(W ₃ −W ₄ / W ₃ ) × 100 (%) The solvent-soluble component obtained by the above operation was evaporated to dryness in THF.
(Tetrahydrofuran), and after passing through a sample processing filter, used as a GPC sample.

In the present invention, a peak or / and / or a chromatogram by GPC (gel permeation chromatography) are used.
And the molecular weight of the shoulder is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40 ° C, and THF was added to the column at this temperature as a solvent.
(Tetravidrofuran) is flowed at a flow rate of 1 ml per minute, and the sample concentration is adjusted to 0.05 to 0.1% by weight. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. Standard polystyrene samples for preparing calibration curves include, for example, Pressure Chemi
Cal Co. or Toyo Soda Kogyo has a molecular weight of 6 × 1
0 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9
It is suitable to use those of × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ and at least about 10 standard polystyrene samples. An RI (refractive index) detector is used as the detector.

In order to accurately measure the molecular weight range of 10 ³ to 4 × 10 ^6, a plurality of commercially available polystyrene gel columns are preferably used. For example, μ-styrag manufactured by Waters, Inc. may be used.
el 500,10 ³ , 10 ⁴ , 10 ⁵ combination and Showa Denko shod
ex KF-80M or a combination of KF-802, 803, 804, 805, or TSKgel G1000H, G2000H, G2500H, G3000H, G manufactured by Toyo Soda
A combination of 4000H, G5000H, G6000H, G7000H, GMH is preferred.

The weight% of the binder resin having a molecular weight of 10,000 or less according to the present invention is obtained by cutting out the molecular weight of 10,000 or less in the chromatogram by GPC, calculating the weight ratio with the cutting weight having a molecular weight of 10,000 or more, and using the above-described weight% of the THF-insoluble portion, The weight% based on the binder resin is calculated.

The resin composition in the developer of the present invention contains styrenes,
Those obtained by polymerizing one or more monomers selected from acrylic acids, methacrylic acids and derivatives thereof are preferable from the viewpoint of developing characteristics and charging characteristics. Examples of monomers that can be used include styrenes such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene. Examples of acrylic acids, methacrylic acids and derivatives thereof include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-tetradecyl acrylate, and n-acrylate. Hexadecyl, lauryl acrylate, cyclohexyl acrylate,
Acrylic esters such as diethylaminoethyl acrylate, dimethylaminoethyl acrylate, and the like,
Similarly, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate,
Methacryls such as decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, and stearyl methacrylate Acid esters. In addition to the above-mentioned monomers, a small amount of other monomers as long as the object of the present invention can be achieved, such as acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, vinylcarbazole, vinylmethylether, butadiene, isoprene, maleic anhydride, Maleic acid, maleic acid monoesters, maleic acid diesters, vinyl acetate and the like may be used.

As the crosslinking agent used in the developer of the present invention, divinylbenzene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5
-Pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 20
Examples include diacrylates of 0, # 400 and # 600, dipropylene glycol diacrylate, polypropylene glycol diacrylate, polyester type diacrylate (MANDA Nippon Kayaku), and methacrylates obtained by replacing the above acrylates with methacrylate.

Pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxy, polyethoxyphenyl) as polyfunctional crosslinking agents Examples thereof include propane, diallyl phthalate, triallyl cyanurate, triallyl asocyanurate, triallyl isocyanurate, triallyl trimellitate, and diarylchlorendate.

The method for synthesizing the binder resin according to the present invention is basically preferably a method for synthesizing two or more polymers.

That is, a method in which a first polymer soluble in THF and soluble in a polymerizable monomer is dissolved in a polymerizable monomer containing a crosslinkable monomer, and the monomer is polymerized to obtain a resin composition containing a crosslinked region component. It is. In this case, since the former and the latter polymers are uniformly mixed, the crosslinking region component in the binder resin acts efficiently to minimize the change in the surface properties of the developer. This is effective for preventing deterioration over time.

The first polymer soluble in THF is preferably solution polymerization or ionic polymerization, and the second polymer for producing a component insoluble in THF is prepared under the conditions in which the first polymer is dissolved. It is preferable to synthesize by suspension polymerization or bulk polymerization in the presence of a crosslinking monomer. The first polymer is 10 parts by weight based on 100 parts by weight of the polymerizable monomer for forming the second polymer.
~ 120 (preferably 20-100 parts by weight) is preferably used.

The particle size of the fine powder used in the present invention is preferably in the range of 0.001 to 2 µ, and particularly preferably 0.005 to 0.2 µ.

As the inorganic compound used in the present invention, Group 3 and Group 4 metal oxides such as silicic acid, alumina, and titanium oxide are preferable. Particularly, fine silica powder is preferable.

Silicate fine powder preferably used in the present invention can use both a so-called dry method produced by vapor phase oxidation of a silicon halide compound or a so-called wet silica called fumed silica, but the surface and the silicate fine powder can be used. less silanol groups inside the body, and Na ₂ O, who dry silica without producing residue of SO ₃ ^2-like.

In the case of fumed silica, for example,
By using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide, a composite fine powder of silica and another metal oxide can be obtained, and these are also included.

In the silicone oil treatment of the silicic acid fine powder used in the present invention, the silicone oil is applied to the surface of the silicic acid fine powder, thereby completely covering the silanol groups and dramatically improving the moisture resistance. I do.

The silane coupling agent used in the present invention has a general formula For example, typically, dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, hexamethyldisilazane, allylphenyldichlorosilane, benzyldimethylchlorosilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane , Vinyltriacetoxysilane, divinylchlorosilane, dimethylvinylchlorosilane and the like.

The silane coupling agent treatment of the silicic acid fine powder is a dry treatment in which the silicic acid fine powder is reacted with a vaporized silane coupling agent to form a cloud by stirring or the like, or
The treatment can be carried out by a generally known method such as a wet method in which fine silica powder is dispersed in a solvent and a silane coupling agent is dropped.

The treatment amount of the silicone oil or silicone varnish solid in the present invention is based on 100 parts by weight of silicic acid fine powder.
The amount is preferably 1 to 35 parts by weight, more preferably 2 to 30 parts by weight. The reason for limiting the above treatment amount is that if the treatment amount of the silicone oil is too small, the same result as that of the treatment with the silane coupling agent alone will not be obtained, and the moisture resistance will not be improved. Cannot be obtained. On the other hand, if the silicone oil treatment amount is too large, the above-mentioned aggregates of the fine silica particles are likely to be formed, and also, since free silicone oil is formed,
When applied to a developer, drawbacks such as the inability to improve fluidity arise.

Known substances can be used as the silicone varnish for fine powder processing used in the present invention. For example, KR-251 and KR-112 manufactured by Shin-Etsu Silicone Co., Ltd. may be mentioned, but not limited thereto.

As a method of the silicone varnish treatment, the same known technique as that of the oil treatment can be used.

It is more preferable that the inorganic fine powder used in the present invention is first treated with a silane coupling agent and then treated with a silicone oil or silicone varnish.

In general, the silicone oil treatment alone requires a large amount of silicone oil to cover the surface of the inorganic fine powder, which tends to form aggregates of the inorganic fine powder during the treatment, and when applied to a developer, the fluidity of the developer may be deteriorated. It is conceivable that it is necessary to pay close attention to the processing steps of silicone oil. Therefore, in order to maintain good moisture resistance and prevent agglomeration of the silicic acid fine powder, it is better to treat the silicic acid fine powder with a silane coupling agent and then treat it with silicone oil, so that the silicone oil treatment effect is sufficient. It is possible to demonstrate.

Finally, it is desirable that the treated inorganic fine powder is hydrophobized so as to show a degree of hydrophobicity of 60% or more, more preferably 90% or more. If the degree of hydrophobicity is less than this, high-quality images cannot be obtained due to moisture adsorption of the inorganic fine powder under high humidity.

The degree of hydrophobicity of the inorganic fine powder in the present invention uses a value measured by the following method. Of course, other measurement methods can be applied with reference to the measurement method of the present invention.

100 ml of ion-exchanged water and 0.1 g of a sample are placed in a sealed stopper 200 ml separatory funnel, and shaken at 90 rpm for 10 minutes with a shaker (Tavla shaker mixer T2C type). After shaking, let stand for 10 minutes.After the silica powder layer and aqueous layer separate, collect 20-30 ml of the lower aqueous layer, place in a 10 mm cell, and ion exchange a blank without fine powder at a wavelength of 500 nm. The transmittance is measured with reference to water, and the value of the transmittance is used as the degree of hydrophobicity of the fine powder.

Further, the effect is exhibited when the application amount of these fine powders is 0.01 to 20 parts by weight with respect to 100 parts by weight of the toner, and more preferably an excellent developer is provided when 0.1 to 3 parts by weight is added. be able to. In a preferred mode of addition, the treated inorganic fine powder is preferably in a state of being attached to the surface of the developer particles.

The developer according to the present invention is a one-component developer in which a toner contains a magnetic substance. As the magnetic fine particles contained in the toner, a substance that is magnetized when placed in a magnetic field is used.
Powders of ferromagnetic metals such as iron, cobalt and nickel, or alloys and compounds such as magnetite, γ-Fe ₂ O ₃ and ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of 1 to ²⁰ m ² / g, particularly 2.5 to 12 m ² / g, and more preferably a magnetic powder having a Mohs hardness of 5 to 7 by a nitrogen adsorption method. The content of the magnetic powder is preferably from 10 to 70% by weight based on the weight of the developer.

Further, as a coloring material which can be further added to the developer according to the present invention, conventionally known carbon black, copper phthalocyanine, iron black and the like can be used.

Further, the developer of the present invention may contain a charge control agent if necessary, and JP-B-41-20153, JP-B-43-27596,
Metal complex salts of monoazo dyes described in JP-A-44-6397 and JP-A-45-26478, and nitrohumic acid and salts thereof described in JP-A-50-133338 or CI14
Facial cleansers such as 645, JP-B-55-42752, JP-B-58-4150
8, salicylic acid, naphthoic acid, dicarboxylic acid described in JP-B-58-7384, JP-B-59-7385, etc.
Examples include metal complexes such as Co, Cr, and Fe, sulfonated copper phthalocyanine pigments, styrene oligomers into which nitro groups and halogens have been introduced, and chlorinated paraffins. In particular, from the viewpoint of dispersibility, a metal complex salt of a monoazo dye, and a metal complex of salicylic acid, alkylsalicylic acid, naphthoic acid, and dicarboxylic acid are preferable. The addition amount of these charge control agents minimizes adverse effects such as a reduction in developing power and a decrease in environmental stability due to contamination of the developing sleeve surface by the charge control agents while maintaining good triboelectricity as described above. Therefore, the addition amount is preferably 0.1 to 3 parts by weight based on 100 parts by weight of the binder resin.

Other additives may be added to the developer of the present invention as long as they do not have a substantial adverse effect. Specific examples thereof include Teflon, a lubricant such as zinc stearate or a polishing agent such as cerium oxide, silicon carbide and strontium titanate, or a fluidity imparting agent such as colloidal silica and aluminum oxide, a caking inhibitor,
Alternatively, for example, there are a conductivity-imparting agent such as carbon black, zinc oxide, antimony oxide, and tin oxide, or a fixing aid such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, and various waxes, or an anti-offset agent. In addition, white fine particles and black fine particles of opposite polarity can be used in small amounts as a developing property improver.

In the production of the developer of the present invention, the constituent materials are kneaded well by a hot kneader such as a hot roll, a kneader, an extruder and the like, and then the material is obtained by mechanical pulverization and classification, or the material is added to a binder resin solution. A method of obtaining by dispersing and then spray-drying, or a method of producing a developer by mixing a monomer to form a binder resin with a predetermined material to form an emulsified suspension and then polymerizing to obtain a developer. Each method such as the method can be applied. Further, by adding an appropriate crosslink during the production of the developer, a crosslinkable region component can be contained in the developer.

As a method for developing the developer of the present invention, all known methods can be applied. For example, cascade method, magnetic brush method,
Two-component developing method such as microtoning method; powder cloud method and fur brush method; non-magnetic unicomponent developing method in which the toner is conveyed to a developing unit by being held on a developer carrier by electrostatic force and developed. And the like. In particular, it is extremely effective in a one-component developing method containing a magnetic material such as an insulating one-component developing method and a jumping developing method.

[Examples] The basic configuration and features of the present invention have been described below, but the method of the present invention will be specifically described below based on examples. However, this does not limit the embodiments of the present invention in any way. Parts mean parts by weight.

Synthesis Example 1 In 200 parts of toluene having a boiling point, 80 parts of styrene and n-
A mixed solution of 20 parts of butyl acrylate and 6 parts of benzoyl peroxide was added dropwise over 5 hours, then polymerized at a boiling point for 3 hours, and dried under vacuum to obtain a low molecular weight polymer except for toluene. Next, 70 parts of low molecular weight polymer,
A homogeneous mixture of 75 parts of styrene, 24 parts of n-butyl acrylate, 1 part of divinylbenzene, and 4 parts of benzoyl peroxide was suspended and dispersed in 300 parts of water in which 0.8 part of a partially saponified polyvinyl alcohol was dissolved. Polymerization was performed at 15 ° C. for 15 hours to obtain a pearl-shaped resin composition uniformly mixed from a high molecular weight polymer including a gel component to a low molecular weight polymer, and dried under reduced pressure to obtain a resin composition-1.

About 0.5 g of the resin composition-1 was precisely weighed and placed in a cylindrical paper (Toyo Paper No.86R, diameter 28 mm, length 100 mm), and T was used as a solvent.
Reflux once every 4 minutes using 180 ml of HF.
After Soxhlet extraction for an hour, evaporation to remove the medium in the extracted soluble components, vacuum drying was performed at 100 ° C. for 12 hours, and the amount of the soluble resin components was weighed. From the sample weight and this value, the gel component weight (degree of crosslinking) according to the above formula
I asked. Furthermore, this soluble resin component is dissolved in THF,
A sample having a concentration of 0.1% by weight was passed through a sample pretreatment filter for a non-aqueous system to obtain a GPC sample. Using Shodex KF-80M as a column for GPC measurement, it was incorporated into a 40 ° C heat chamber of a GPC measurement device (150C ALC / GPC manufactured by Waters), THF flow rate was 1 ml / min, and the test was performed under the condition of RI of 200.
GPC was measured by μ injection. As a calibration curve for molecular weight measurement, the molecular weight is 0.5 × 10 ³ , 2,35 × 10 ³ , 10.2 × 10 ³ , 35 × 1
0 ³ , 110 × 10 ³ , 200 × 10 ³ , 470 × 10 ³ , 1200 × 10 ³ , 2700 × 10 ³ ,
A THF solution of 10 points of 8420 × 10 ³ monodisperse polystyrene reference substances (manufactured by Waters) was used.

The gel component weight of the resin composition-1 was 33% by weight, the molecular weight main peak value of the eluted component was 6000, and the sub peak value was 51,000.

Synthesis Example 2 In the suspension polymerization, a pearl resin composition-2 was obtained in the same manner as in Synthesis Example 1 except that 1.4 parts of divinylbenzene and 4.5 parts of benzoyl peroxide were used as an initiator. The gel component of the resin composition has a gel component of 56% by weight, the elution component has a main peak value of 5,000, and a Jorda value of 3
1000.

Synthesis Example 3 In the suspension polymerization, all procedures were the same as in Synthesis Example 1 except that 100 parts of a low molecular weight polymer, 0.5 part of divinylbenzene, and 2 parts of t-butylperoxy-2-ethylhexanoate were used as a polymerization initiator. Thus, a pearl-shaped resin composition-3 was obtained. The gel component weight of the resin composition was 11% by weight, the main peak value of the molecular weight of the eluted component was 5000, and the shoulder value was 82000.
Met.

Synthesis Example 4 The same procedure as in Synthesis Example 1 was carried out except that in the suspension polymerization, 120 parts of a low molecular weight polymer, 0.5 part of divinylbenzene, and 2 parts of t-butylperoxy-2-ethylhexanoate were used as a polymerization initiator. Thus, a pearl-shaped resin composition-4 was obtained. The gel component weight of the resin composition was 5% by weight, the main peak value of the molecular weight of the eluted component was 5,000, and the shoulder value was 82000.
Met.

The above mixture is melt-kneaded with a biaxial extruder heated to 140 ° C., the cooled kneaded material is coarsely pulverized with a hammer mill, the coarsely pulverized material is finely pulverized with a jet mill, and the obtained finely pulverized powder is subjected to air classification. As a result, negatively-charged magnetic particle classified powder-1 (magnetic toner) having a volume average particle diameter of 12 μm was obtained.

The above components were used in the same manner as in Production Example 1 to obtain negatively-charged magnetic particle classified powder-2 (magnetic toner).

Production Example 3 Magnetic particle classification powder-3 (magnetic toner) was obtained in exactly the same manner as in Production Example 1, except that the resin composition-3 obtained in Synthesis Example 3 was used as the binder resin.

Production Example 4 A magnetic particle classification powder-4 (magnetic toner) was obtained in exactly the same manner as in Production Example 1, except that the resin composition-4 obtained in Synthesis Example 4 was used as a binder resin.

Example 1 100 parts of silica silicate fine powder Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g was mixed with 100 parts of hexamethyldisilazane (H
MDS) After processing in 20 parts, dimethyl silicone oil K
F-96 100cs (manufactured by Shin-Etsu Chemical Co., Ltd.) was treated with 10 parts diluted with a solvent, dried, and heated at about 250 ° C. to obtain a treated silica fine powder having a hydrophobicity of 99%. 0.4 part of this treated silicic acid fine powder was added to 100 parts of the magnetic particle classifying powder-1 (magnetic toner) and dry-mixed with a Heschel mixer to prepare a negatively chargeable developer.

(1) Test 1. (Actual photo test under normal temperature and humidity conditions) An electrophotographic copier "FC-5"
(Cannon) was performed using a modified machine. This modified machine uses a negatively charged organic photosensitive drum as shown in Fig. 1, the surface potential (maximum potential) when the organic photosensitive body is charged is -700V, and the photosensitive body and the developing sleeve in the developing space are The gap (Dsd) is 270 µm, the gap (Dsb) between the tip of the regulating blade and the developing sleeve (240 µm), the magnet body is fixed, the magnetic flux density on the surface of the developing sleeve is 800 Gauss, and the thickness of the developer layer on the sleeve is Was set to 80 μm, a DC bias of −1800 Vpp and a DC bias of −400 V at 1400 Hz were applied to the sleeve, and a copy image was obtained by reversal development. The following items were evaluated. The results are summarized in Table 1 below.

Image density Using "Macbeth reflection densitometer" (manufactured by Macbeth),
The relative density of a white background portion where the document density was 0.0 with respect to the copied image was measured.

Fog density The worst value of image fog was determined by using a "Macbeth reflection densitometer" (manufactured by Macbeth) to determine the relative density of a document density of 0.0 against a white background. The white background reversal density was set to 0.0.

Note that "image fog" refers to a phenomenon in which the developer scatters on a white background portion (non-image portion).

Image Quality The copied image was splattered, and the image was visually judged from the following five points: image missing, image blur, image unevenness, and sharpness. In the evaluation, "X" indicates that there is a problem in practical use, and "Δ" indicates that the test is slightly defective but at a practical level, "O" indicates that the test is good, and "◎" indicates that the test is very good. "

Note that “image scattering” refers to a phenomenon in which the developer scatters around the image, “image loss” refers to a phenomenon in which a part of the image is missing, and “image blurring” refers to the shading on the image. , And "image unevenness" refers to a phenomenon in which a difference in shading occurs in an image.

(2) Test 2 (real-life test after storage for 6 months) After the developer was prepared and stored for 6 months at room temperature and normal humidity, an actual-photo test was performed to evaluate each of the above items. Deterioration was evaluated. The results are described in the first section below.
Summarize in a table.

Example 2 Silica fine powder Aerosil # 200 100 parts was treated with a solution prepared by diluting 10 parts of dimethyl silicone oil KW-96 100cs (manufactured by Shin-Etsu Chemical Co., Ltd.) with a solvent. A treated silica fine powder having a degree of 93% was obtained. 0.6 part of this treated silicic acid fine powder was added to 100 parts of the magnetic particle classified powder-2 (magnetic toner) of Production Example 2, and dry-mixed with a Henschel mixer to prepare a developer. Evaluation and examination were conducted similarly. The results are shown in Table 1 below.

Example 3 Aerosil # 300 100 fine silica powder having a specific surface area of 300 m ² / g
30 parts of olefin-modified silicone oil KF-415 (manufactured by Shin-Etsu Chemical Co., Ltd.) was treated in the same manner as in Example 2 to obtain a treated silica fine powder having a hydrophobicity of 99%. 0.6 parts of this treated silicic acid fine powder was added to 100 parts of magnetic particle classified powder-3 (magnetic toner) of Production Example 3, and dry-mixed with a Henschel mixer to prepare a developer. Was evaluated and examined.
The results are shown in Table 1 below.

Example 4 Silica fine powder Aerosil # 200 100 parts was treated with 15 parts of fluorine-modified silicon oil FL-10 450cs (manufactured by Shin-Etsu Chemical Co., Ltd.) in the same manner as in Example 2 to give a treated silica fine powder having a hydrophobicity of 95%. Obtained. 0.8 part of the treated silicic acid fine powder was added to 100 parts of the magnetic particle classified powder-1 (magnetic toner) of Production Example 1, and dry-mixed with a Henschel mixer to prepare a developer.
Evaluation and examination were conducted in the same manner as in Example 1. The results are shown in Table 1 below.

Example 5 100 parts of silica fine powder Aerosil # 130 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 130 m ² / g, and 5 parts of α-methylstyrene-modified silicone oil KF-410 (manufactured by Shin-Etsu Chemical Co., Ltd.) were used.
To obtain a treated silica fine powder having a hydrophobicity of 94%. 1.0 part of this treated silicic acid fine powder was added to 100 parts of magnetic particle classification powder-1 (magnetic toner) of Production Example 1, and dry-mixed with a Henschel mixer to prepare a developer. Evaluation and examination were conducted similarly. The results are shown in Table 1 below.

Comparative Example 1 0.5 parts of the treated silicic acid fine powder of Example 2 was added to 100 parts of the magnetic particle classified powder-4 (magnetic toner) of Production Example 4, and dry-mixed with a Henschel mixer to prepare a developer. Evaluation and examination were conducted in the same manner as in Example 1. The results are shown in Table 1 below.

[Effects of the Invention] As described above, the present invention contains a magnetic toner containing an inorganic powder treated with a silicone oil or a silicone varnish in a developer and a binder resin crosslinked with a crosslinking agent. The binder resin has a THF insoluble content of 10 to 6
0% by weight, and the THF-soluble component of the binder resin has a main peak in a region of a molecular weight of 2,000 to 10,000 in GPC, so that it has a stable and uniform charging property,
Perform development faithful to the latent image. That is, even after long-term storage, the initial characteristics are maintained without deterioration and stable image quality is obtained. In addition, a high image density can be obtained from the beginning without rising of the image density, and a clear image without fog can be maintained even when performing the image forming process many times.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic sectional view of a developing device to which the magnetic developer of the present invention can be preferably applied. DESCRIPTION OF SYMBOLS 1 ... One component magnetic developer 2 ... Blade 3 ... Sleeve 4 ... Photosensitive drum 5 ... Fixed magnet 6 ... Bias applying means

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yukari Yuba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-1-118661 (JP, A) JP-A-63 JP-A-2-110475 (JP, A) JP-A-59-45457 (JP, A) JP-A-63-139371 (JP, A) (58) Fields investigated (Int. . ⁶ , DB name) G03G 9/08

Claims (5)

(57) [Claims] In a developer for developing an electrostatic image comprising at least an inorganic fine powder and a magnetic toner containing a binder resin cross-linked by a cross-linking agent, the binder resin of the magnetic toner has a THF insoluble content of 10%. From 60% by weight,
The THF-soluble component of the binder resin of the magnetic toner has a main peak in a region of a molecular weight of 2,000 to 10,000 in GPC, and the inorganic fine powder is treated with silicone oil or silicone varnish. Developer for developing electrostatic images. 2. The electrostatic image developing method according to claim 1, wherein the inorganic fine powder is a fine silica powder, and the fine silica powder is treated with 1 to 35 parts by weight of silicone oil or silicone varnish per 100 parts by weight. Developer. 3. The developer according to claim 1, wherein 0.01 to 20 parts by weight of an inorganic fine powder is externally added to 100 parts by weight of the magnetic toner. 4. The developer for developing an electrostatic charge image according to claim 1, wherein the binder resin is a resin crosslinked with civinylbenzene. 5. The magnetic toner is used in an amount of 10 to 70% based on the weight of the on-site agent.
The developer for developing an electrostatic charge image according to any one of claims 1 to 4, further comprising a magnetic powder in an amount of 1% by weight.