JP3185072B2 - Manufacturing method of carrier for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carrier for an electrostatic image, that is, a carrier constituting an electrostatic image developer together with a toner.

[0002]

2. Description of the Related Art Conventionally, in electrophotography, a method of developing an electrostatic latent image using toner is roughly classified into a method using a so-called two-component developer in which a small amount of toner is dispersed in a medium called a carrier, There is a method using a so-called one-component developer in which toner is used alone without using a carrier.

[0003] The present invention relates to a two-component developer comprising a toner and a carrier among the above-mentioned developers. The carrier constituting the two-component developer is roughly classified into a conductive carrier and an insulating carrier, and as the conductive carrier, usually oxidized or unoxidized iron powder is used, and the iron powder carrier is used as a component. The developer has a drawback that the triboelectric charging property with respect to the toner is unstable and that a visible image formed by the developer is fogged.

That is, the toner adheres and accumulates (spent toner) on the surface of the iron powder carrier particles with the use of the developer, so that the electric resistance of the carrier particles increases, the bias current decreases, and triboelectric charging occurs. As a result, the image density of the visible image formed decreases, and fog increases. Therefore, if the copying operation is continuously performed by an electronic copying apparatus using a developer containing an iron powder carrier, the developer deteriorates in a small number of times, so that it is necessary to replace the developer at an early stage, resulting in a high cost. It will be.

[0005] A typical example of an insulating carrier is a carrier obtained by uniformly covering the surface of a carrier core material made of a ferromagnetic material such as iron, nickel, or ferrite with an insulating resin. In the developer using this carrier, toner particles are less likely to fuse to the carrier surface than in the case of the conductive carrier, and at the same time, it is easy to control the triboelectric charging property between the toner and the carrier, and the durability is high. This is advantageous in that it is particularly suitable for high-speed electronic copiers in that it has excellent service life and a long service life.

However, in this insulating carrier, a coating layer covering the surface of the carrier core material is uniform and a desired size and a charged state of polarity can be stably obtained by friction with a specific toner used with the carrier. Is required. That is, if the surface of the resin-coated carrier is non-uniform, the frictional charging between the toner and the carrier becomes unstable, and as a result, the image quality of a visible image obtained after copying is reduced.

Therefore, for the purpose of making the carrier surface after resin coating uniform, attempts have been made to smooth the surface layer of the carrier core itself and then coat the resin with the resin. However, according to this method, although the carrier surface is made uniform, the adhesion between the carrier core material and the coating resin becomes unstable, and the usable coating resin is limited to only a resin having good adhesion. If the amount of the coating resin is increased to further increase the coating strength, the carrier itself is strongly charged to the opposite polarity to the toner particles due to the insulating property of the coating resin, and the problem of carrier adhesion to the background portion is reduced. Will happen.

This tendency is remarkable in a non-magnetic color toner having no leak site in the toner itself. In particular, when a toner containing colorant-containing resin particles using a polyester binder having a high chargeability is used as a toner, the length is further increased. This is a problem especially at low humidity.

As a countermeasure, improvement directions have been studied from both the carrier side and the toner side (particularly, external additives of the toner).

On the toner side, addition of conductive powder has been attempted for the purpose of preventing excessive charging.
When the conductive powder is added, the charge amount is significantly reduced under high temperature and high humidity, causing adverse effects such as uneven image density and fogging. In addition, since the conductive powder is generally colored, it adversely affects the color of the color toner ( In particular, when viewed with transmitted light from an OHP sheet or the like, the problem is more pronounced).

On the carrier side, it has been proposed to disperse, for example, conductive carbon black or the like in a coating resin and coat the carrier with a purpose of eliminating carrier adhesion caused by the carrier itself being strongly charged. However, a stable coating state has not always been achieved so far, and new problems such as fog due to liberation of carbon black and the like due to long-term use have occurred.

As described above, there is a close relationship between the surface of the carrier core material and the characteristics of the resin coating.

To date, methods for applying a resin to a carrier core material have been disclosed in JP-A-55-47164 and JP-A-55-47164.
These are disclosed in, for example, JP-A-7-94754 and JP-A-60-227271.

Among these methods, a method of coating with an organic solvent is widely used at present because of its excellent production stability and excellent adhesion to a core material.

An example of heating the carrier core material to a temperature of Tg or more in resin coating is disclosed in JP-A-60-227271, and the durability is improved.

However, in the above-mentioned example, the adhesion is improved using a silane-based coupling agent, and the coating is heated to Tg or more after coating. It is.

An example using a titanium-based coupling agent is disclosed in Japanese Patent Application Laid-Open No. 60-221767. When these coupling agents are used, the resin for coating greatly changes over time, and the coating conditions, especially Due to slight differences in coating time, fluctuations in physical properties after coating become large, not only is it difficult to supply the carrier stably, but also the charge amount tends to decrease under high humidity, which causes environmental fluctuations. There is. Further, the cost is high, which is not practically desirable.

[0018]

SUMMARY OF THE INVENTION The main object of the present invention is to provide an electrophotographic carrier which has been improved in the above-mentioned conventional drawbacks, particularly in chargeability, uniformity of charge distribution, mechanical strength, and adhesion to a core. To provide.

It is another object of the present invention to provide an electrophotographic carrier having excellent stability of resin coating and excellent quality stability.

It is another object of the present invention to provide a long-life electrophotographic carrier having a stable developing ability, in which toner is less likely to be spent on the surface of carrier particles.

[0021]

In view of this situation, the present inventors have conducted various studies and studies to improve the above-mentioned conventional disadvantages. As a result, the present inventors have found that the Tg (glass transition point) of the coating resin is high. In contrast, it has been found that it is effective to control the temperature of the resin solution used when performing resin coating on the carrier core material,
The present invention has been completed.

That is, the feature of the present invention is that a styrene monomer, an addition-polymerizable unsaturated aliphatic monocarboxylic acid, an addition-polymerizable unsaturated aliphatic dicarboxylic acid, and the addition-polymerizable unsaturated carboxylic acid and an alcohol A monomer selected from the group consisting of the esterified products of the above, or a polymer of two or more types, as a resin for coating the carrier core material, and a resin of 0.05 to 5.00% by weight based on the weight of the carrier core material. In the resin adhering step of coating the core material, a resin coating solution having a temperature in the range of Tg ≦ Temperature of the resin coating solution ≦ Tg + 40 ° C. (Tg represents a glass transition point of the coating resin) is used. A method for producing an electrophotographic carrier.

In the present invention, the reason why the adhesion is improved by heating the carrier coating resin solution to Tg or more is not necessarily clear, but generally, the more the coating resin is diluted with the solvent, the lower the solution viscosity becomes. It is thought that the wettability of the resin on the surface of the core material is improved. However, by heating the resin to a temperature equal to or higher than the Tg of the resin, the viscosity can be reduced without increasing the amount of the solvent, and the wettability to the core material is improved. It is thought that this is for efficient improvement.

The solution temperature in the present invention may be in the range of “resin Tg” to “resin Tg + 40 ° C.”, but a solution close to “resin Tg + 40 ° C.” in terms of image fineness is more preferable. It is excellent. It is presumed that the reason for this is that the higher the temperature, the lower the viscosity of the coating resin solution, the more stable the adhesiveness, the more uniform the coating, and the smoother the charging of the toner.

If the temperature is equal to or higher than Tg, the resin coating is stabilized, but the temperature is preferably up to “Tg of coating resin + 40 ° C.”. The reason is that "T
When the temperature exceeds (g + 40 ° C.), the resin is softened, and adhesion (coalescence) of the resin-coated carrier particles is likely to occur. Therefore, when the coalesced particles are separated, the resin is easily released. It is.

Therefore, according to the present invention, the resin is not melted and coagulated, and the carrier core material can be stably coated with the resin.

The glass transition point (Tg) of the resin for resin coating used is desirably 55 ° C. to 140 ° C.

The reason why the Tg is within the above range is that a carrier coating resin having a Tg lower than 55 ° C. is excellent in adhesion to the core material, but causes toner adhesion (spent) to the carrier. This is problematic in that the degree of softening of the resin is insufficient, particularly under high temperature conditions, the fluidity of the carrier alone is deteriorated, and the charge providing ability is reduced.

On the other hand, at Tg higher than 55 ° C., Tg
As g increases, the resistance to toner adhesion improves,
Adhesion to the core material decreases. Particularly, in the case of a resin having a temperature exceeding 140 ° C., the adhesion becomes extremely weak, and even if the resin is heated to a temperature of Tg or more, the resin is peeled off from the core material or cracks occur.

Therefore, the coating resin of the present invention has a Tg of 5
The temperature is 5 to 140 ° C, preferably 60 to 120 ° C.

When a coating resin heated to a temperature higher than the glass transition point is used, the adhesion is improved. However, it is desirable that the coating be performed at a temperature in the resin coating apparatus equal to or higher than the glass transition point.

However, if the temperature is too high, the same adhesion (coalescence) of the carrier particles as in the case of heating the resin solution.
Therefore, it is preferable to perform resin coating at substantially the same temperature as the resin solution.

The reason why a good result can be obtained when the resin coating is performed at a temperature higher than the glass transition point is not necessarily clear, but the affinity between the resin and the carrier core material is increased by heating the resin at a temperature higher than the glass transition point. It can be seen as a reason.

Resin adhered below the glass transition point remains strained in view of its polymer properties, but by continuing to heat above the glass transition point, stress relaxation is promoted, and distortion is corrected. This is presumed to be due to the fact that the resin coating becomes tough and the cracking resistance and peeling resistance are improved.

Since the effect of reducing the stress is small if it is applied as a heat treatment (curing treatment) after baking, which is a subsequent step after the adhesion, the stress is alleviated almost simultaneously with the adhesion of the resin to the core material. Things are considered important.

In the present invention, the number average molecular weight of the resin for resin coating is preferably in the range of 10,000 to 200,000.

That is, when a material having a number average molecular weight of more than 200,000 is used, the adhesion to the core material is poor and the rise of charge is slow, so that the charge amount during running is reduced, and as a result, fog is generated early. In addition, this causes undesirable contamination inside the machine. On the other hand, if the number average molecular weight is less than 10,000, peeling due to internal destruction of the coating layer is remarkable, which causes a short life of the carrier and the developer, which is not preferable.

As described above, the number average molecular weight of the coating resin in the present invention is from 10,000 to 200,000, preferably from 20,000 to 150,000.

Further, the molecular weight distribution of the resin is also important,
In the present invention, for stable adhesion of the resin to the core material,
The weight average molecular weight is at least twice as large as the number average molecular weight 1
It is desirable to have a value of less than twice.

Although the reason is not yet clear, when the weight average molecular weight is less than twice the number average molecular weight, the molecular weight distribution is sharp, but the adhesion to the core material during coating tends to be weak. In the case where the weight average molecular weight exceeds 12 times the number average molecular weight, the adhesion to the core material is sufficient, but the carrier is liable to be contaminated with the toner, and the carrier surface after printing has been printed. A large amount of toner is attached, and the triboelectric charge tends to decrease.

Further, in order to make the present invention even more effective, 50% of the residual monomer is contained in the coating resin with respect to the resin solid content.
It is good to make it contain -3000 ppm.

The amount of the residual monomer is suitably from 50 to 3000 ppm based on the solid content of the resin, and it has been found that the higher the Tg, the better the results. This is because the resin has a configuration in which a decrease in adhesion due to an increase in Tg of the resin is compensated for by the presence of a residual monomer.

However, it has been found that it is difficult to suppress deterioration during printing for a resin having a Tg of more than 140 ° C. even if a residual monomer is present in the resin.

The reason why the carrier coated with a resin containing a certain amount of the residual monomer in the resin is extremely effective in stabilizing the charge is not clear, but it is probably unclear that the residual monomer may be mixed between the polymer and the core material when the resin is coated. The slight presence between them increases the wettability of the polymer to the surface of the core material, and the polymer can be more uniformly attached than when no monomer is present. The amount of the monomer can be determined using gas chromatography or the like.

The following components can be used as the polymer component used in the present invention.

That is, alkylstyrenes such as styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, octylstyrene, fluorostyrene, chlorostyrene, Bromostyrene, dibromostyrene, halogenated styrenes such as iodostyrene, styrene monomers such as nitrostyrene, acetylstyrene, methoxystyrene; acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, α-methylcrotonic acid, α-ethyl crotonic acid, isocrotonic acid, tiglic acid, addition-polymerizable unsaturated aliphatic monocarboxylic acids such as ungeric acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, Saconic acid, glutaconic acid, addition-polymerizable unsaturated aliphatic dicarboxylic acids such as dihydromuconic acid; the above-mentioned addition-polymerizable unsaturated carboxylic acids and alcohols, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, Alkyl alcohols such as heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, and hexadecyl alcohol; halogenated alkyl alcohols obtained by partially halogenating these alkyl alcohols; methoxyethyl alcohol; ethoxyethyl alcohol; ethoxyethoxyethyl alcohol , Methoxypropyl alcohol, alkoxyalkyl alcohols such as ethoxypropyl alcohol, benzyl alcohol, Esters with aralkyl alcohols such as phenylethyl alcohol and phenylpropyl alcohol, alkenyl alcohols such as allyl alcohol and crotonyl alcohol, especially alkyl acrylate, alkyl methacrylate, alkyl fumarate, alkyl maleate and the like Are preferred examples; amides and nitriles derived from the addition-polymerizable unsaturated carboxylic acids; aliphatic monoolefins such as ethylene, propylene, butene, and isobutylene; vinyl chloride, vinyl bromide,
Vinyl iodide, 1,2-dichloroethylene, 1,2-dibromoethylene, 1,2-diiodoethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride, fluoride Halogenated aliphatic olefins such as vinylidene; 1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene;
Conjugated diene-based aliphatic diolefins such as 2,4-hexadiene and 3-methyl-2,4-hexadiene; 2-vinylpyridine, 4-vinylpyridine, 2-vinyl-6-methylpyridine, 2-vinyl-5- Methylpyridine, 4-
Butenylpyridine, 4-pentylpyridine, N-vinylpiperidine, 4-vinylpiperidine, N-vinyldihydropyridine, N-vinylpyrrole, 2-vinylpyrrole, N-vinylpyrroline, N-vinylpyrrolidine, 2-
Vinylpyrrolidine, N-vinyl-2-pyrrolidone, N-
Nitrogen-containing vinyl monomers such as vinyl-2-piperidone and N-vinylcarbazole can be exemplified. These can be used alone or in combination of two or more.

The coating amount of the coating resin according to the present invention with respect to the carrier core material is such that the resin solid content is 0.05% by weight to 5% by weight, preferably 0.2% by weight to 5% by weight. 0.0
If the content is less than 5% by weight, the effect of coating the carrier core material with the resin is not sufficient, and the coating amount exceeding 5% by weight has little meaning, and the production means is limited and the cost is increased, which is not preferable.

As the carrier core material used in the present invention, those usually used may be used. For example, as a material of the magnetic particles as the carrier core material, 98% or more of Cu—Zn—Fe (metal composition ratio (5 to 20): (5
To 20): Ferrite particles having a composition of (30 to 80)) are preferable for facilitating surface uniformity and stabilizing the charging ability, but are not particularly limited, and may be flat, spongy, or the like.
Iron oxide powder of various shapes such as coin shape, spherical shape, true spherical shape, copper,
Use of ferrite containing one or more of manganese, cobalt, nickel, zinc, tin, magnesium, lead, strontium, barium, lithium, etc., and particles made of a mixture of various resins and magnetic powders, etc. Can be.

The solvent used in the present invention is not particularly limited as long as it can dissolve or swell the resin for coat coating, but it is necessary to select a solvent whose boiling point is higher than the temperature at the time of resin coating. is there. Generally, ketones, alcohols, toluene, acetates, and the like are widely used, and those having a boiling point higher than the Tg of the resin are appropriately selected depending on the apparatus conditions and the like.

In the present invention, methyl ethyl ketone, methanol, ethyl acetate and the like can be used, but preferably, toluene, methyl isobutyl ketone, butyl acetate, ethylene monoethyl ether, acyl acetate, butyl alcohol and the like having a higher boiling point are used. Preferably, xylene, mesitylene, 2-ethylbutanol, methylcyclohexanone and the like are used.

The resin coating apparatus used in the present invention is not particularly limited, and various methods can be used.

For example, there is a method in which a solution obtained by dissolving a coating resin in an organic solvent is sprayed onto a suspended powdery core material using a fluidized bed apparatus or the like, and dried. Further, there is a method in which a coating resin, an organic solvent, and a powdery core material are mixed and spray-dried using a spray dryer.

As another method, a method of mixing a coating resin, an organic solvent, and a powdery core material and heating and stirring and drying the mixture, or a method of mixing a resin solution in which a coating material is dissolved in an organic solvent with a powdery core material, Materials, and the mixture was gradually added and dispersed in an aqueous solution with stirring to form a suspended state.
There is a method of coating the surface of the powdery core material with the coating material by heating to evaporate the organic solvent, but the method is not particularly limited.

In each of the methods, a method of drying and baking at a high temperature after coating can be used. In these methods, the high-temperature baking treatment is preferably performed at about 80 to 240 ° C. from the viewpoint of removing residual monomers and increasing the adhesion strength between the core material and the copolymer layer.

The carrier of the present invention thus obtained is mixed with a toner and used as a magnetic brush developer for developing an electrostatic latent image.

As the toner, any toner usually used in electrophotography, in which a colorant is dispersed in a final resin, can be used, and is not particularly limited.

When a two-component developer is prepared by mixing with the toner according to the present invention, the mixing ratio is from 1.0% by weight to 12% by weight, preferably from 2% by weight to 9% by weight, as the toner concentration in the developer. Good results are usually obtained with a percentage by weight. When the toner concentration is less than 1.0% by weight, the image density is low and cannot be used practically. When the toner concentration is more than 12% by weight, fog and scattering in the machine are increased, and the service life of the developer is shortened.

Hereinafter, the measuring method in the present invention will be described. (1) Measurement method of triboelectric charge amount The measurement method will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view of an apparatus for measuring a triboelectric charge amount of a toner. First, 50 g of a mixture of a toner and a carrier whose weight ratio is to be measured and having a weight ratio of 1:19 is placed in a polyethylene bottle having a capacity of 50 to 1000 ml in a metal measuring container 2 having a 500-mesh screen 3 at the bottom. , 30 times and 500 times by hand, and about 0.5 to 0.9 g of the mixture (developer) is put therein, and the metal lid 4 is closed. At this time, the weight of the entire measurement container 2 is weighed and W ₁
(G). Next, in the suction device 1 (at least the portion in contact with the measurement container 2 is an insulator), the air is sucked from the suction port 7 and the air volume control valve 6 is adjusted to adjust the pressure of the vacuum gauge 5 to 250 mmA.
q. In this state, suction is sufficiently performed, preferably for about 2 minutes, to remove the toner by suction. The potential of the electrometer 9 at this time is set to V (volt). Here, reference numeral 8 denotes a capacitor, whose capacity is C (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). The triboelectric charge (μc / g) of this toner is calculated as in the following equation.

Amount of triboelectric charge of toner (μc / g) = (C ×
V) / (W ₁ -W ₂ ) (2) Method of quantifying residual monomer in resin Resin by gas chromatography (Shimadzu GC-15A).
As a standard component, the monomer used to obtain the polymer (eg, methyl methacrylate) is used.

The resin to be measured is taken in acetone containing DMF, left in an ultrasonic cleaner for 30 minutes, filtered, injected, and the column is determined by an internal standard method using DB-1 of J & W.
Measure. (3) Molecular weight distribution measurement method The molecular weight distribution was measured using GPC (High Performance Liquid Chromatograph 150C manufactured by Waters), and the column was Shodex GPC KF-801,8 manufactured by Showa Denko KK
02,803,804,805,806,807,80
A combination of 0P was used. The sample concentration was 5
It was adjusted to be mg / ml.

In the present invention, GP using THF as a solvent
The molecular weight distribution of the chromatogram by C (gel permeation chromatography) is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) was passed through the column at this temperature as a solvent at a flow rate of 1 ml per minute, and about 100 μl of a THF sample solution was injected. Measure. 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 kinds of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, one having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation or Showa Denko KK is used.
It is appropriate to use about 0 standard polystyrene samples. An RI (refractive index) detector is used as the detector.
As the column, a plurality of commercially available polystyrene gel columns are preferably combined. For example, Shodex GPC KF-801, 802, 80 manufactured by Showa Denko KK
3,804,805,806,807,800P or TSKgel G1000H manufactured by Tosoh Corporation
(H _XL ), G2000H (H _XL ), G3000H
(H _XL ), G4000H (H _XL ), G5000H
(H _XL ), G6000H (H _XL ), G7000H
(H _XL ) and TSKguardcolumn.

A sample is prepared as follows.

The sample is placed in THF, left for several hours, shaken sufficiently, mixed well with THF (until the sample is no longer united), and allowed to stand for 12 hours or more. At this time, TH
The time of leaving in F is set to 24 hours or more. Then, a sample processing filter (pore size 0.45 to
0.5 μm, for example, Myshoridisk H-25
5 The product passed through Tosoh Co., Ltd., and can be used as a sample of GPC. The sample concentration is
The resin component is adjusted to be 0.5 to 5 mg / ml. (4) Method of measuring Tg of resin In the present invention, Tg is measured using a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by PerkinElmer).

The measurement sample is 5 to 20 mg, preferably 10
Weigh the mg precisely.

This is put in an aluminum pan, and an empty aluminum pan is used as a reference. First, the following operation is performed for the purpose of deleting the previous history. Room temperature to 200 in N ₂ atmosphere
The temperature is raised to 10 ° C at 10 ° C / min and kept at 200 ° C for 10 minutes. Thereafter, the mixture is rapidly cooled, the temperature is lowered to 10 ° C, and the temperature is kept at 10 ° C for 10 minutes. Then, at a heating rate of 10 ° C./min, 2
Raise the temperature to 00 ° C. In this heating process, the temperature is 40 to 10
An endothermic peak of the main peak in the range of 0 ° C. is obtained.

The intersection between the line of the middle point of the pace line before and after the endothermic peak appears and the differential heat curve is defined as the glass transition temperature Tg in the present invention (see FIG. 2).

[0069]

Embodiments of the present invention will be described below.

1. Synthesis Example A of Carrier Coating Resin Methyl methacrylate / butyl acrylate (75: 2
5) Using a monomer, perform solution polymerization (initiator: azobisisobutyronitrile 0.5%) in a toluene solution, Tg = 66 ° C., number average molecular weight (hereinafter abbreviated as Mn) 8
10,000, weight average molecular weight (hereinafter abbreviated as Mw) 250,000, Mw /
A resin solution with Mn = 3.1 and residual monomer of 1600 ppm was obtained. This resin solution was further diluted with toluene to obtain a resin solution A having a solid content of 10%.

2. Synthesis Example B Methyl methacrylate / butyl acrylate (75: 2
5) Using a monomer, perform solution polymerization in a xylene solution, Tg = 64 ° C., Mn = 70,000, Mw = 250,000, Mw
/Mn=3.6 to obtain a resin solution having a residual monomer content of 2200 ppm. This resin solution was further diluted with xylene to obtain a resin solution B having a solid content of 10%.

3. Synthesis Example C Using methyl methacrylate / styrene (60:40) monomer, solution polymerization was performed in a xylene solution, and Tg
= 108 ° C, Mn = 40,000, Mw = 200,000, Mw / Mn =
A resin solution of 5.0 and a residual monomer of 600 ppm was obtained.
The resin solution was further diluted with xylene to obtain a solid content of 10%.
Resin solution C was obtained.

Example 1 Using a resin solution B heated to 100 ° C., and using a Spira coater manufactured by Okada Seiko Co., Ltd., Cu having an average particle size of 45 μm was used.
-Applied to spherical ferrite of Zn-Fe composition. The temperature in the apparatus during coating was 100 ° C., which was the same as the temperature of the resin solution.

Dry at 100 ° C. for 1 hour, and dry at 150 ° C.
After baking for 1 hour, a resin-coated carrier was obtained.

The resin coating amount of the obtained carrier was 0.55
% By weight.

On the other hand, 4 parts by weight of a polyester resin phthalocyanine pigment obtained by condensing 100 parts by weight of propoxylated bisphenol and fumaric acid and 4 parts by weight of a chromium complex of di-tert-butylsalicylic acid were sufficiently premixed with a Henschel mixer. The mixture was melt-kneaded by a twin-screw extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified to obtain a negatively triboelectrically charging cyan powder having a weight average particle size of 8.3 μm.

100 parts by weight of the above colored powder, 0.5 part by weight of silica fine powder hydrophobized with hexamethyldisilazane, and 0.3 part by weight of hydrophilic alumina were mixed to obtain a cyan toner. This cyan toner and the aforementioned carrier are
/ N (23 ° C./60%) and mixed at a toner concentration of 5% to prepare a developer.

Table 1 shows the results obtained by using a color copying machine CLC-500 (manufactured by Canon) to produce 30,000 images at 23 ° C./60% using an original document having an image area ratio of 50%. Was. From Table 1, it can be seen that the above-mentioned developer has a small variation in the printing durability test and is very good.

The following comparative examples and examples are also shown in Table 1.

Here, the evaluation of the fog was performed using a REFLECOMETER MODEL TC-6D manufactured by Tokyo Denshoku Co., Ltd.
S, and for cyan toner images,
It was calculated from the following equation using an r filter. The smaller the value, the less fog.

Fog reflectance (%) = reflectance of standard paper (%)-reflectance of non-image portion of sample (%) Example 2 A resin solution A heated to 70 ° C. was used.
After drying at 75 ° C. for 1 hour to remove the solvent,
Baking treatment was performed at 50 ° C. for 1 hour to obtain a resin-coated carrier.

Using this carrier, image formation was performed in the same manner as in Example 1. As a result, good results were obtained, but the fineness of the image was slightly inferior to Example 1.

Example 3 Example 1 was used in which a resin solution B was heated to 70 ° C.
The solvent was removed by drying at 75 ° C. for 1.5 hours in the same manner as described above, followed by baking treatment at 150 ° C. for 1 hour to obtain a resin-coated carrier. When an image was formed using this carrier in the same manner as in Example 1, good results were obtained. However,
Comparison of the fineness of the image by visual inspection was slightly inferior to Example 1.

Example 4 A resin solution C heated to 120 ° C. was used.
Except for removing the solvent by drying at a temperature of 0.5 ° C. for 0.5 hour, the obtained carrier was imaged in the same manner as in Example 1, and good results were obtained.

Example 5 A carrier was obtained in the same manner as in Example 1 except that a fluidized-bed dryer as another apparatus was used as a resin coating apparatus. Good results were obtained. .

Example 6 A carrier was obtained in the same manner as in Example 4 except that a fluidized bed dryer was used as another resin coating apparatus, and good results were obtained. Was.

Comparative Example 1 An image was formed using the obtained carrier in the same manner as in Example 1 except that the temperature of the resin solution B for carrier coating was set to 50 ° C. In comparison with Examples 1 to 6, the fineness of the image tended to be worse with the number of copies, and the fog increased.

Comparative Example 2 A carrier was produced in the same manner as in Example 1 except that the temperature of the resin solution B for carrier coating was set to 125 ° C., and adhesion of the particles to the carrier after the baking treatment (coalescence). Was seen a lot. After crushing and sieving, image output was performed using this carrier. The ground fog was large from the beginning and did not decrease even after copying 5,000 sheets. Therefore, the evaluation was stopped halfway.

Comparative Example 3 An image was formed using the carrier obtained in the same manner as in Example 4 except that the temperature of the resin solution C for carrier coating was set to 70 ° C., and the fineness of the image was initially low. Although it was somewhat bad, fog increased with the number of copies and the quality of the image also deteriorated.

Comparative Example 4 An image was formed using the carrier obtained in the same manner as in Example 5 except that the temperature of the resin solution B for carrier coating was changed to 50 ° C. Bad
The image quality further decreased with the number of copies.

Comparative Example 5 A carrier was obtained in the same manner as in Example 5 except that the temperature of the resin solution B for carrier coating was set at 125 ° C. Was seen a lot. After crushing and sieving, image formation was carried out using this carrier. As a result, fog in the initial image was large and no reduction in fog was observed even after copying 5,000 sheets. Therefore, the evaluation was stopped.

[0092]

[Table 1]

[0093]

According to the present invention, by performing coating using a resin solution having a temperature in a specific range with respect to the Tg of the resin for coating the carrier, stable resin coating can be performed, and the chargeability of the carrier can be stabilized. High quality images can be obtained.

Further, the adhesion between the core material of the carrier and the coating is excellent, the mechanical strength is high, and the contamination by the toner based on the coating is suppressed, so that the life of the carrier is long. Agent can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of a toner.

FIG. 2 is an explanatory diagram of a glass transition temperature in the present invention.

Continuation of front page (56) References JP-A-5-216284 (JP, A) JP-A-5-80590 (JP, A) JP-A-4-350668 (JP, A) JP-A-5-216286 (JP) JP-A-5-188650 (JP, A) JP-A-56-113146 (JP, A) JP-A-3-269546 (JP, A) JP-A-2-7073 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/113

Claims (2)

(57) [Claims] 1. Styrene monomer, addition polymerizable unsaturated
Aliphatic monocarboxylic acid, addition-polymerizable unsaturated aliphatic dical
Bonic acid and the addition polymerizable unsaturated carboxylic acid and alcohol
Of a monomer selected from the group consisting of
A single or two or more polymers are coated on a carrier core material.
Used as resin , 0.05 to the weight of carrier core material
In the resin adhering step of coating the core material with 5.00% by weight of resin, the temperature is in the range of Tg ≦ Temperature of resin coating solution ≦ Tg + 40 ° C. (Tg represents a glass transition point of the coating resin). A method for producing an electrophotographic carrier, comprising using a resin coating solution. 2. The glass transition point of the coating resin is 55 to 1
The method for producing an electrophotographic carrier according to claim 1, wherein the temperature is 40 ° C.