JPH11352729A - Binder carrier, developer containing the same, and image forming method using this developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of an uneven density and fog and deterioration of image density over a long period by incorporating a polyester resin having an acid value in a specified range and an vinylic resin having anionic functional groups. SOLUTION: The binder carrier comprises at least a magnetic powder and a polyester resin having an acid value of 17-55 KOH mg/g, preferably, 19-50, further preferably, 30-45 KOH mg/g, and the vinylic resin having the anionic functional groups, which are not especially limited, so long as they are anionic functional groups, for example, sulfonic and carboxylic group and hydroxy group and the like can be enumerated, and preferably, sulfonic acid group is used. As the toner, positively or negatively chargeable toner may be used in accordance with a charge controller to be used or a carrier to be used, but the positively chargeable toner is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier used for a two-component developer of an image forming apparatus such as a digital copying machine or a printer, and more particularly to a binder carrier obtained by dispersing a magnetic powder in a binder resin. is there.

[0002]

2. Description of the Related Art In an electrophotographic copying machine or a printer, a two-component developer composed of a toner and a magnetic carrier is used for developing an electrostatic latent image formed on an image carrier such as a photoconductor. The two-component developing method has been put to practical use.

Various carriers are known as carriers for two-component developers, such as iron powder carriers, ferrite carriers, resin-coated carriers in which these magnetic particles are coated with a resin, and binder carriers in which magnetic fine particles are dispersed in a binder resin. Have been. However, resin-coated carriers are
When transported as a magnetic brush on the developing roller, the spikes are hard, so that a smooth image cannot be obtained. Further, a toner image is disturbed by scraping, and a damage to a photoconductor is caused. In addition, the resin-coated carrier also has a problem that the life of the developer is short because the coating layer is peeled off as it is used.

[0004] A binder carrier has been attracting attention as a carrier which not only can solve the above-mentioned problems, but also can be easily reduced in particle size, has a high volume specific electric resistance, and hardly causes charge injection from a developer carrying member. I have. As the binder resin, an acrylic resin, a styrene resin, a styrene-acryl resin, a polyester resin, an epoxy resin, a fluororesin, and the like have been conventionally used alone.

[0005]

However, in a binder carrier using such a binder resin,
Although the service life is longer than that of a coated carrier, the charge control agent and post-treatment agent of the toner adhere to the surface of the carrier as it is used, causing poor charging of the carrier and causing image noise such as fog on the copied image. And the image density is reduced. Further, since the above-mentioned binder carrier has particularly poor charge rising property, there has been a problem that density unevenness, fogging, etc. occur on a copied image immediately after toner replenishment or the like. Further, when a CCA-less toner containing no charge control agent (CCA) is used, the above problem is remarkable in the conventional binder carrier, that is, a problem occurs in the charge providing ability of the binder carrier.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide an excellent charge stability and charge rising property for preventing the occurrence of density unevenness and fogging and a decrease in image density over a long period of time. It is to provide a binder carrier.

Another object of the present invention is to provide a developer and an image forming method which prevent the occurrence of density unevenness and fogging and a decrease in image density over a long period of time.

[0008]

The present invention relates to a binder carrier comprising at least magnetic powder, a polyester resin having an acid value of 17 to 55 KOH mg / g, and a vinyl resin having an anionic functional group.

The present invention also relates to a developer comprising the above-mentioned binder carrier and toner and an image forming method using the developer.

In the present invention, the use of the above-mentioned polyester resin makes it possible to rapidly charge the obtained carrier with the toner, so that the charge rising property is improved.
It is considered that fog and density unevenness can be prevented even when toner is supplied. In addition, by using a vinyl-based resin having an anionic functional group in combination, the resin acts as a strong charge point, which not only improves the charge rising property, but also causes the occurrence of density unevenness and fogging and image density over a long period of time. It is considered that the lowering can be prevented, and that the CCA-less toner containing no charge control agent is also charged favorably, thereby avoiding generation of image noise such as fog due to poor charging.

The binder carrier of the present invention has an acid value of 17
A magnetic powder is dispersed in a binder resin containing at least 55 KOH mg / g of a polyester resin and a vinyl resin having an anionic functional group.

The polyester resin used in the carrier of the present invention has an acid value of 17 to 55 KOH mg / g, preferably 1 to 55 KOH mg / g.
9-50 KOHmg / g, more preferably 30-45KO
Hmg / g. The acid value of the polyester resin is 17 KOHm
If the ratio is less than g / g, the charge rising property when the toner is positively charged is deteriorated, which causes fogging and density unevenness particularly during toner replenishment. On the other hand, the acid value is 55 KOHmg
If it exceeds / g, the toner is excessively charged in reverse during printing, causing a decrease in density.

As a method for adjusting the polyester resin to the above-mentioned acid value, any known method may be employed. For example, it is possible to adjust the kind of the acid used, the monomer ratio and the like. Adjusting the ratio is effective.

In the present invention, more preferably, it has the above-mentioned acid value, and has a glass transition point of 55 to 75 ° C., preferably 6 to 75 ° C.
0-75 ° C, softening point 90-140 ° C, preferably 10
0-135 ° C, number average molecular weight of 3,000-50,000
A polyester resin having 0, preferably 5,000 to 30,000, and a weight average molecular weight / number average molecular weight of 5 to 50, preferably 10 to 40 is used.

In the present invention, the acid value is determined by dissolving a 10 mg sample in 50 ml of toluene, and using a mixed indicator of 0.1% bromthymol blue and phenol red to pre-specify N / 10 potassium hydroxide. This is a value calculated from the consumption amount of the N / 10 potassium hydroxide / alcohol solution after titration with an alcohol solution. The glass transition point of the resin was measured using a differential scanning calorimeter (DSC-200: manufactured by Seiko Denshi Co., Ltd.) using alumina as a reference, with a 10 mg sample at a temperature rising rate of 10 ° C./min. The glass transition point was determined by measuring the shoulder value of the main endothermic peak. The softening point was measured using a flow tester (CFT-500: manufactured by Shimadzu Corporation) and the pores of the die (diameter 1 mm, length 1 m)
m), at a pressure of 20 kg / cm ² , at a heating rate of 6 ° C./min.
The temperature corresponding to 1/2 of the height from the outflow start point to the outflow end point when the sample of cm ³ was melted out was defined as the softening point.

The polyester resin that can be used in the present invention has the above characteristics, and is not particularly limited as long as it is a known polyester resin conventionally used in the production of carriers and toners. Specifically, a polyester resin obtained by polycondensing a polyhydric alcohol component and a polycarboxylic acid component by a known method can be used.

As the dihydric alcohol component of the polyhydric alcohol component, for example, polyoxypropylene (2,2)
-2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0)-
2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -polyoxyethylene (2,0)
Bisphenol A polyoxyalkylene adducts such as -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane can be used.

Further, other dihydric alcohol components include:
For example, ethylene glycol, diethylene glycol,
Triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, Diols such as 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A
And the like.

Examples of the trihydric or higher alcohol component include sorbitol, 1,2,3,6-hexane tetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol,
2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol,
2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like.

Examples of the divalent carboxylic acid component of the polyvalent carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. Succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-dodecenylsuccinic acid, n-
Examples thereof include alkenyl succinic acid such as dodecyl succinic acid or alkyl succinic acid, and anhydrides or lower alkyl esters of these acids.

The trivalent or higher carboxylic acid component includes, for example, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4 -Naphthalenetricarboxylic acid, 1,2,
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-
Methylene carboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, embol trimer acid, and anhydrides of these acids Products, lower alkyl esters and the like.

It is desirable that the above-mentioned polyester resin is used in an amount of 10 to 99% by weight, preferably 50 to 95% by weight of the binder resin. When the ratio is less than the above ratio, the charge rising property is reduced, and fogging and density unevenness are liable to occur particularly when toner is supplied. On the other hand, when the ratio is higher than the above ratio, the content ratio of the vinyl resin having an anionic functional group to be described later used together becomes too small, the charge imparting ability to the toner is reduced, and image noise such as fog is easily generated due to poor charging. Become.

The vinyl resin having an anionic functional group (hereinafter referred to as an anionic functional group-containing vinyl resin) used in the carrier of the present invention is a known resin used in the production of carriers and toners. There is no particular limitation as long as an anionic functional group is introduced into the vinyl resin.

The anionic functional group is not particularly limited as long as it is a functional group having an anionic property, and examples thereof include a sulfonic acid group, a carboxyl group and a hydroxyl group. In the present invention, it is preferable to use a vinyl resin having a sulfonic acid group.

When a vinyl resin having a sulfonic acid group is used, it is desirable that the sulfonic acid group is contained in the sulfonic acid group-containing vinyl resin in an amount of 1 to 20% by weight, preferably 2 to 15% by weight. If the amount is less than 1% by weight, the effect of the addition of the resin is not effective, that is, the charge-imparting ability of the carrier to the toner is reduced, and image noise such as fog is easily generated due to poor charging. On the other hand, if it exceeds 20% by weight, the charge amount becomes too high, and the image density decreases. The sulfonic acid group content can be measured by titration with a sodium hydroxide / alcohol solution.

When a vinyl resin having a carboxyl group is used, the acid value of the vinyl resin having a carboxyl group is 1
0-50 KOHmg / g, preferably 20-40 KOHmg
/ G is desirable. If it is less than 10 KOH mg / g, the effect of the addition of the resin is ineffective, and if it exceeds 50 KOH mg / g, the charge amount becomes too high, and the problem of insufficient image density occurs. The acid value can be measured by a method similar to the method for measuring the acid value of the polyester resin described above.

When a vinyl resin having a hydroxyl group is used, the hydroxyl value of the vinyl resin having a hydroxyl group is 10 to 100K.
OH mg / g, preferably 20-60 KOH mg / g. If it is less than 10 KOH mg / g, the effect of the addition of the resin is not effective, and if it exceeds 100 KOH mg / g, the charge amount becomes too high, and a problem such as a reduction in image density occurs. The hydroxyl value refers to the number of mg of potassium hydroxide required to neutralize acetic acid bound to an acetylated product obtained from 1 g of a sample, and is also referred to as a hydroxyl value. Specifically, the sample is heated with an excess of an acetylating agent, for example, acetic anhydride to perform acetylation, and the saponification value of the produced acetylated product is measured.

[0028]

(Equation 1) Here, A represents the saponification value after acetylation, and B represents the saponification value before acetylation.

In the present invention, more preferably, it has the above-mentioned physical properties and has a glass transition point of 50 to 75 ° C., preferably 5 to 75 ° C.
5 to 70 ° C, softening point of 90 to 145 ° C, preferably 10
0-140 ° C, number average molecular weight of 3,000-50,000
A styrene-based resin, an acrylic resin, or a styrene-acryl-based resin having a weight average molecular weight / number average molecular weight of 5 to 50, preferably 10 to 40, preferably 5,000 to 30,000, is used.

In producing the anionic functional group-containing vinyl resin, any method may be employed as long as a vinyl resin having the above-mentioned physical properties can be obtained. For example, once a vinyl-based resin is produced from a vinyl-based monomer described below by a known method, and then an anionic functional group is introduced (hereinafter, referred to as method 1). , A method of introducing an anionic functional group and polymerizing the obtained anionic functional group-containing prepolymer again with a vinyl monomer described below by a known method (hereinafter referred to as Method 2)
And a method of polymerizing a vinyl monomer described below and a monomer having an anionic functional group capable of polymerizing with the vinyl monomer by a known method (hereinafter, referred to as method 3).

In producing the sulfonic acid group-containing vinyl resin, it is preferable to employ the above method 2. In this case, a known sulfonation with sulfuric acid or the like is performed to introduce a sulfonic acid group. The sulfonic acid group content of the resulting sulfonic acid group-containing vinyl resin can be adjusted by appropriately setting the amount of sulfuric acid used and the amount of the sulfonic acid group-containing prepolymer used. When producing a carboxyl group-containing vinyl resin, it is preferable to employ the above method 3. In this case, examples of the monomer having a carboxyl group include acrylic monomers other than acrylamide among vinyl monomers described below, and styrene monomers and vinyl monomers among vinyl monomers described later as vinyl monomers polymerized therewith. Can be exemplified. The acid value of the resulting carboxyl group-containing vinyl resin can be adjusted by appropriately setting the amount of the monomer having a carboxyl group. When producing a hydroxyl group-containing vinyl resin, it is preferable to employ the above method 2. In this case, the hydroxyl value of the resulting hydroxyl group-containing vinyl resin can be adjusted by appropriately setting the amount of the hydroxyl group-containing prepolymer used.

The vinyl monomer is not particularly limited as long as it has a polymerizable unsaturated bond, and examples thereof include an acrylic monomer, a styrene monomer, and a vinyl monomer. Specifically, acrylic monomers include (meth) acrylic acid, maleic acid, itaconic acid, methyl (meth) acrylate, (meth)
Ethyl acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, amyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate,
Examples include stearyl (meth) acrylate, behenyl (meth) acrylate, and acrylamide. Examples of the styrene monomer include styrene, o, m, p-chlorostyrene, and α.
-Methylstyrene, vinyltoluene, divinylbenzene and the like, and examples of the vinyl monomer include vinyl chloride and vinyl acetate. One or more of these may be selected and used. Among these, it is preferable to use an acrylic monomer and a styrene monomer, and it is more preferable to use styrene and an alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include those having 1 to 1 carbon atoms.
8, preferably having 3 to 15 alkyl groups (meth)
It is preferred to use alkyl acrylates.

The anionic functional group-containing vinyl resin is used in an amount of 1 to 90% by weight, preferably 5 to 50% by weight, of the binder resin. If the ratio is less than the above ratio, the charge imparting ability to the toner decreases,
Fog tends to occur. On the other hand, if it is higher than the above ratio,
The toner tends to be excessively charged in the opposite direction, which tends to cause a decrease in density and uneven density.

The carrier of the present invention may contain other resins. Examples of the other resin include an epoxy resin, a fluorine resin, a polyamide resin, and the like. The content of the binder resin is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 50% by weight or less of the binder resin.

The carrier of the present invention can be prepared, for example, by mixing and kneading the above-mentioned polyester resin and an anionic functional group-containing vinyl-based resin with a magnetic powder, followed by cooling and then pulverizing and classifying to give a volume average particle size of 20 to 100 μm. Preferably 30
It can be manufactured to ８０80 μm. The content of the magnetic powder is 200 to 700 parts by weight, preferably 250 to 650 parts by weight, based on 100 parts by weight of the binder resin.
If the content of the magnetic powder is less than 200 parts by weight, desired magnetization cannot be obtained, which is likely to cause charging failure. If the content exceeds 700 parts by weight, production by melt-kneading becomes difficult.

The carrier of the present invention has a saturation magnetization of 3
0 to 60 emu / g, preferably 40 to 55 emu / g
It is desirable that This is because when the saturation magnetization of the carrier decreases, the magnetic restraining force of the carrier on the developer conveying member decreases, and the carrier easily adheres to the image carrier. Also, when the saturation magnetization of the carrier is high, the carrier is partially aggregated on the developer transport member, so that a uniform thin layer of the developer cannot be formed. This is because the reproducibility of images and high-definition images is reduced.

As the magnetic powder used for the carrier of the present invention, for example, metals such as iron, nickel and cobalt, ferrite, magnetite and the like can be used, and magnetite is particularly preferable. From the viewpoint of uniform dispersion in the binder, the average primary particle size of these magnetic fine particles is 2 μm.
m, preferably 0.1 to 1 μm.

The carrier of the present invention may contain a dispersant such as carbon black, silica, titania, and alumina. The uniform dispersibility of the magnetic powder in the binder resin can be improved by containing a dispersant. The content of the dispersant is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the binder resin.

The developer of the present invention comprises at least the above binder carrier and toner. The toner may be either positively chargeable or negatively chargeable depending on the charge control agent and / or the carrier used, but is preferably positively chargeable. This is because the above-mentioned effects by using the binder carrier of the present invention are most remarkably exhibited. That is, the developer of the present invention comprising the binder carrier and the positively chargeable toner prevents the occurrence of density unevenness and fog and reduces the image density over a long period of time, and is excellent in charge stability and charge rising property.

In the developer of the present invention, the toner may be a CCA-less toner containing no charge control agent (CCA). This is because the binder carrier has an excellent charge providing ability. Also in the developer of the present invention using such a CCA-less toner, it is possible to obtain the above-described effects that can prevent the occurrence of density unevenness and fogging and a decrease in image density for a long period of time. In addition, by using a CCA-less toner, it is possible to avoid deterioration in durability, environmental pollution, and the like due to free CCA, which have conventionally been problems.

The toner constituting the developer of the present invention uses a known toner binder resin, a coloring agent, and other desired additives such as a charge control agent and wax conventionally used in the production of toner. It can be produced by other known methods such as a kneading / pulverizing method, a suspension polymerization method, an emulsion polymerization method, an emulsion dispersion granulation method, an encapsulation method and the like. Among these production methods, the kneading / pulverization method is preferable from the viewpoint of production cost and production stability.

The kneading and pulverizing method includes a step of mixing toner particle components such as a toner binder resin and a colorant with a mixer such as a Henschel mixer, a step of melting and kneading the mixture, and a step of cooling and kneading the kneaded material roughly. A toner particle is produced by a step of pulverizing the coarsely pulverized particles and a step of classifying the obtained finely pulverized particles. The volume average particle diameter of the toner particles is preferably adjusted to 4 to 10 μm, more preferably 6 to 9 μm, from the viewpoint of high definition reproducibility of the image.

As the toner binder resin, a thermoplastic resin conventionally used as a toner binder resin, for example, a styrene resin, an acrylic resin, a styrene-acryl resin, a polyester resin or the like can be used. However, it is preferable to use a styrene-acryl resin as a binder resin of the positively chargeable toner and a polyester resin as a binder resin of the negatively chargeable toner. As the binder resin for the CCA-less toner, it is preferable to use a polyester resin or a styrene-acrylic resin.

The colorant used in the present invention is not particularly limited, and a colorant conventionally used in electrophotography can be used. As the black pigment, carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, ferrite, magnetite and the like can be used. As yellow pigments, yellow lead, zinc yellow, cadmium yellow, yellow iron oxide,
Mineral fast yellow, nickel titanium yellow,
Navels Yellow, Naphthol Yellow S, Banza Yellow G, Banza Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Reache and the like can be used.

Examples of the red pigment include red lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indaslen brilliant orange RK, benzidine orange G, indaslen brilliant orange GK, bengala, cadmium red, lead red, permanent Red 4R, Risor Red,
Pyrazolone red, watching red, lake red C, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake,
Brilliant Carmine 3B, permanent orange GT
R, Vulcan Fast Orange GG, Permanent Red F4RH, Permanent Carmine FB and the like can be used. Blue pigments include navy blue, cobalt blue, alkaline blue lake, Victoria blue lake,
Phthalocyanine blue or the like can be used. In addition, although the addition amount of these coloring agents is not particularly limited,
Usually, 1 to 100 parts by weight of toner binder resin
20 parts by weight, preferably 3 to 15 parts by weight.

Other desired additives to the toner, for example,
A charge control agent, wax and the like can be contained. As the charge control agent, a positive charge control agent can be used when the positive charge control of the toner is desired, and a negative charge control agent can be used when the negative charge control of the toner is desired. Examples of the positive charge control agent that can be used in the present invention include a nigrosine dye, a triphenylmethane compound, a quaternary ammonium salt compound, and the like. Salicylic acid metal complex as a negative charge control agent,
Examples include gold-containing azo dyes, calixarene compounds, and boron-containing compounds. In the present invention, it is preferable to use a positive charge control agent. The addition amount is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the toner binder resin. Note that no charge control agent is added to the CCA-less toner.

As the wax, low-molecular-weight polypropylene, low-molecular-weight polyethylene, carnauba wax, paraffin wax such as beeswax are preferably used. However, the wax is not compatible with the thermoplastic resin used as a binder resin of the toner, and has a high releasability. It is not particularly limited as long as it has. The amount of the toner binder resin 10
1 to 10 parts by weight to 0 parts by weight is preferred.

Since the above-mentioned carrier has an excellent charge-imparting ability, the content of the toner in the developer in the present invention can be set relatively large, and can be set at 3 to 20% by weight, preferably 5 to 15% by weight. % By weight is preferred. If the content of the toner is less than 3% by weight, a sufficient image density cannot be obtained or the toner is excessively charged. If the content is more than 20% by weight, the toner is not sufficiently charged and fogging tends to occur on the image. .

The developer of the present invention is suitably used in a developing device employing a two-component developing system. That is, in the image forming method employing the two-component developing method, when the developer of the present invention is used, it is possible to prevent the occurrence of density unevenness and fog and a reduction in image density over a long period of time.

An example of a developing device employing the two-component developing system will be described with reference to FIG. In the developing device 10, a developer 1 containing a toner T and a carrier is contained therein, and a plurality of magnetic poles N ₁ , S ₁ , N ₁ are used as a developer transport member 11 for transporting the developer ₁ . _2, S _2, N ₃
A cylindrical developing sleeve 11 provided with a magnet roller 11a having
1 is rotatably disposed so as to face the photosensitive member 2 serving as an image bearing member at an appropriate distance Ds in the developing area.

The developing sleeve 11 is rotated so as to move in the opposite direction to the photosensitive member 2, that is, in the developing region where the developing sleeve 11 and the photosensitive member 2 face each other, so that the developing sleeve 11 and the photosensitive member 2 move in the same direction. With the rotation of the developing sleeve 11, the developer 1 accommodated in the developing device 10 is conveyed toward the photoreceptor 2 in the state of a magnetic brush by the magnetic force of the magnet roller 11a.

The developing sleeve 11 is connected to a developing bias power supply 12.
Then, an AC voltage or a developing bias voltage obtained by superimposing a DC voltage on the AC voltage is applied to apply an oscillating electric field to the developing region.

At a position upstream of the developing area where the developing sleeve 11 and the photoreceptor 2 face each other in the transport direction of the developer ₁ and at a position facing the magnetic pole N1 of the magnet roller 11a, a magnetic blade is used as the regulating member 13. The magnetic blade 13a regulates the amount of the developer 1 on the developing sleeve 11 with a predetermined distance from the developing sleeve 11.

In the developing device 10, a toner container 14 for storing the toner T is provided at an upper portion thereof.
When the toner T in the developer 1 is supplied from the developing sleeve 11 to the photoreceptor 2 and development is performed, the toner concentration in the developer 1 in the developing device 10 is reduced. By rotating a toner supply roller 15 provided below, the toner T stored in the toner storage unit 14 is supplied to the developer 1 in the developing device 10.

In the developing device 10, as described above, the magnetic blade 13a provided on the upstream side in the transport direction of the developer 1 with respect to the developing region where the developing sleeve 11 and the photosensitive member 2 oppose each other. Developer 1
The developer 1 is conveyed to a developing area facing the photoreceptor 2 in a thin layer state on the developer sleeve 11,
A developing bias voltage is applied from the developing bias power supply 12 to cause an oscillating electric field to act on this developing area, so that the toner T in the developer 1 conveyed by the developing sleeve 11 is transferred from the developing sleeve 11 to the photosensitive member 2. The image is supplied to the image portion for development.

If the amount of the developer to be conveyed to the developing area by the developer conveying member is too small, the amount of toner supplied to the image carrier becomes insufficient, and an image having a sufficient image density cannot be obtained. For this reason, the gap between the developing sleeve and the magnetic blade is set to 0.1 to 1 mm, preferably 0.2 to 0.1 mm.
The distance is set to 6 mm so that the amount of the developer to be conveyed to the developing area by the developer conveying member is in the range of 0.7 to 10 mg / cm ² , preferably 1 to 7 mg / cm ² .

In the case where an oscillating electric field is applied between the developer carrying member and the image carrier in the developing area as described above in performing the development, if the oscillating electric field is weak, the carrier after the toner is released is discharged. Transfer of the carrier is poor, the counter charge remains on the carrier, and the carrier easily adheres to the image carrier. On the other hand, if the oscillating electric field is too strong, a leak occurs between the developer carrying member and the image carrier. When the distance between the developer carrying member and the image carrier in the developing area is Ds, and the peak-to-peak value of the applied AC voltage is Vp-p, the oscillation voltage (V
pp / Ds) is 2 to 6 kV / mm, preferably 3 to 5 kV / mm.
It is preferable to set Further, if the DC voltage is
It is desirable to superimpose 50-250V.

The developer of the present invention can also be effectively used in a developing device having the configuration shown in FIG. 1 and employing a toner recycling system. That is, even in an image forming method employing a two-component developing method and a toner recycling system, the use of the developer of the present invention can prevent the occurrence of density unevenness and fog and a reduction in image density over a long period of time. Post-treatment agents are usually removed from the toner collected through the toner recycling system, and the fluidity is reduced.Therefore, the probability of contact with the carrier is reduced, the triboelectricity is poor, the fog and the image density are reduced. However, since the carrier of the present invention is extremely excellent in charge stability and charge rising property as described above, even such a collected toner can be effectively charged, and the fluidity is reduced. This is because it is possible to prevent the above-mentioned problem caused by the above.

An example of a developing device employing a two-component developing system and a toner recycling system will be described with reference to FIG. FIG. 2 has the same configuration as FIG. 1 except that it has a toner recycling system. The toner recycling system refers to a system that collects residual toner on an image carrier by a known means, and conveys the collected toner to a developing device in order to use the collected toner again for development.

In FIG. 2, the residual toner on the image carrier is collected by a cleaning brush 21 in a cleaning device 20. The collected toner is conveyed into the developing device by a belt 24 attached to the roller 22 on the cleaning device side and the roller 23 on the developing device side, and is again subjected to development together with the developer 1 loaded in the developing device. Is to be offered. As described above, by employing the toner recycling system, the toner can be efficiently developed. The present invention is described in more detail by the following examples.

[0061]

EXAMPLES In the following examples, polyester resins (PES) 1 to 7 shown in Table 1 were used as polyester resins. Further, as the vinyl resin having an anionic functional group, styrene-acryl resin (St-A) shown in Table 2 is used.
c) 1 to 6 were used. In the table, AV represents an acid value, Tg represents a glass transition point, and Tm represents a softening point. The monomer types of these resins and their polymerization weight ratios are shown together.

[0062]

[Table 1]

[0063]

[Table 2]

In Table 2, the content of the anionic functional group is represented by the acid value (KOH mg / g) of the resin when the functional group is a carboxyl group, and the hydroxyl value of the resin when the functional group is a hydroxyl group. (KOH mg / g). The method for measuring the content of the functional group when the functional group is a sulfonic acid group will be described in detail below. First, add 10 mg of the sample to toluene
Dissolved in 50 ml, and mixed with 0.1N NaOH using a mixed indicator of 0.1% methyl orange and phenolphthalein.
/ Alcohol solution, and calculated from the consumption of 0.1 N NaOH / alcohol solution.

(Production of Carriers A to M) After the components shown in Table 3 were thoroughly mixed with a Henschel mixer, the mixture was melted at 180 ° C. with a vent twin-screw extruder (PCM-30; manufactured by Ikegai Iron Works Co., Ltd.). The mixture was kneaded, coarsely pulverized by a feather mill, finely pulverized by a jet pulverizer (IDS-2 type, manufactured by Nippon Pneumatic Industries, Ltd.), and an air classifier (MS-1)
After performing classification using a mold (manufactured by Hosokawa Micron Corp.), and further subjected to a heat treatment at 200 ° C. using a safusing system (SFS-2 model; manufactured by Nippon Pneumatic Industries, Ltd.). Carrier A having
~ M was obtained. In addition, magnetite RB-
BL (manufactured by Titanium Industry Co., Ltd.), magnetite EPT-100
0 (manufactured by Toda Kogyo), ferrite MFP-2 (manufactured by TDK), and carbon black # 970 (manufactured by Mitsubishi Chemical), REGAL330 (manufactured by Cabot) and M
A # 8 (manufactured by Mitsubishi Chemical Corporation) is used.

[0066]

[Table 3]

(Production of Toner a) 100 parts by weight of thermoplastic polyester resin (softening point 120 ° C., glass transition point 61 ° C.) 8 parts by weight of carbon black (Cabot Corporation: Mogal L) 8 parts by weight of low molecular weight propylene 3 parts by weight (Manufactured by Sanyo Chemical Industries, Ltd .: Viscol 550P) 5 parts by weight of positive charge control agent (manufactured by Orient Chemical Industries, Ltd .: P-51) After sufficiently mixing the above components, the mixture was melted and kneaded at 140 ° C. with a vented biaxial kneader, After cooling the kneaded product, it was coarsely pulverized by a feather mill, further finely pulverized by a jet pulverizer, and then subjected to air classification to obtain a black fine powder having a volume average particle size of 9 μm. Then, with respect to 100 parts by weight of this black fine powder, hydrophobic silica (H-20, manufactured by Hoechst Japan) is used.
00) was added thereto and treated with a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) at 1000 rpm for 1 minute to obtain a positively chargeable toner. The toner obtained here is referred to as a toner a.

(Production of Toner b) 100 parts by weight of thermoplastic polyester resin (softening point 120 ° C., glass transition point 61 ° C.) 5 parts by weight of carbon black (Cabot Corporation: Mogal L) 5 parts by weight of low molecular weight propylene 3 parts by weight (Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) A fine black powder having a volume average particle diameter of 11 μm was obtained in the same manner as in the method for producing toner a, except that the above components were used. To 100 parts by weight of this black fine powder, 0.3 parts by weight of hydrophobic silica (R972 manufactured by Nippon Aerosil Co., Ltd.) was added,
10 with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.)
The mixture was treated at 00 rpm for 1 minute to obtain a CCA-less toner.
The toner obtained here is referred to as a toner b.

Examples 1 to 16 and Comparative Examples 1 to 10 The above-mentioned carriers A to M and toners a and b were mixed in the combinations shown in Table 4 to prepare developers. The weight ratio of the toner in the developer was 5%, and the mixing was performed for 1 hour using a roll mill.

[0070]

[Table 4]

The average particle size of the carrier was measured using a Coulter Multisizer (manufactured by Coulter, Inc.).
The measurement was performed by measuring the relative weight distribution by particle size using a 0 μm aperture tube. The volume average particle diameter of the toner is 100 μm.
m with an aperture tube.

(Experimental Example 1) Examples 1 to 8 and Comparative Example 1
The developer obtained in Nos. 1 to 5 was mounted on a copying machine EP-9765 manufactured by Minolta having the configuration shown in FIG. 1 and an image having a B / W ratio of 10% under an N / N environment (25 ° C., 50%). 300,000 prints, 0 (initial), 10,000, 50,000, 100,000, 1
The following evaluation items were evaluated at the time of copying 50,000 sheets, 200,000 sheets, 250,000 sheets, and 300,000 sheets. In addition, B / W ratio 5
Printing was also performed on 0% of the images, and the following evaluation items were evaluated at 110,000, 210,000 and 310,000 copies. Tables 5 to 8 collectively show these evaluation results.
Tables 5 and 6 show Examples 1 to 8 and Comparative Examples 1 to 8.
Tables 7 and 8 show the evaluation results of the developers obtained in Examples 9 to 16 and Comparative Examples 6 to 10 for the evaluation results of the developer obtained in Example 5.

The setting conditions of the copying machine were adjusted as follows; the distance between the developing sleeve and the magnetic blade was 0.4 mm, and the amount of developer transported to the developing area by the developing sleeve was 5.0 mg / cm. ^2. Photoreceptor peripheral speed 165m
m / s, the peripheral speed of the developing sleeve is 300 mm / s, the surface potential of the portion where the toner T is supplied on the photosensitive member is 440 V, and the surface potential of the portion where the toner T is not supplied on the photosensitive member is -8.
0 V, the shortest distance between the photosensitive member and the developing sleeve at the opposing portion is 0.4 mm. In the developing region, a DC voltage of -210 V from the developing bias power source and a peak-peak value V
A rectangular wave having a peak-to-peak voltage of 1.5 kV and a frequency of 3 kHz is superimposed with an AC voltage having a duty ratio (development: recovery) of 1: 1.

Image Density The density of the solid (black solid) portion of each copied image was measured with a reflection densitometer (manufactured by Macbeth) and ranked according to the following. In addition, there is no problem in practical use above “〇”. ◎; 1.4 or more; Δ: 1.2 or more and less than 1.4; Δ; 1.0 or more and less than 1.2;

One black solid image was copied at the time of printing for each density unevenness , and the density variation within one page of the copied image was measured and ranked according to the following. In addition, there is no problem in practical use above “〇”. The densities at the four corners and the center at five points in one copy image were measured with a reflection densitometer (manufactured by Macbeth), and the variation was evaluated from the average value in%. ；: 5% or less; Δ: more than 5%, 10% or less; Δ: more than 10%, 20% or less; ×: more than 20%.

A white background portion in each copy image of fog was visually observed and ranked according to the following. ◎: fog was not generated at all; Δ: fog was slightly generated, but there was no problem in practical use; Δ: fog was generated and there was a problem in practical use; ×: fog was seriously generated, There was a practical problem.

[0077]

[Table 5]

[0078]

[Table 6]

(Experimental Example 2) The developers obtained in Examples 9 to 16 and Comparative Examples 6 to 10 were used in a copying machine EP manufactured by Minolta.
Image density, density unevenness, and fog were evaluated in the same manner as in Experimental Example 1 except that the image density was mounted on a modified version of -9765. Tables 7 and 8 show these evaluation results. The copying machine used was a copying machine EP-9 manufactured by Minolta.
This is a copying machine having the configuration shown in FIG.

[0080]

[Table 7]

[0081]

[Table 8]

[0082]

According to the present invention, it is possible to prevent the occurrence of density unevenness and fog and the reduction of image density over a long period of time. Further, even when a CCA-less toner is used or a toner recycling system is used, it is possible to prevent the occurrence of density unevenness and fog and a reduction in image density over a long period of time.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration diagram of a developing device employing a two-component developing method.

FIG. 2 is a schematic configuration diagram of a developing device that employs a toner recycling system in the device of FIG.

[Explanation of symbols]

1: developer, 2: image carrier, 10: developing device, 11: developer conveying member (developing sleeve), 11a: magnet roller, 12: developing bias power supply, 13: regulating member, 13
a: Magnetic blade, 14: Toner container, 15: Toner supply roller, 20: Cleaning device, 21: Cleaning brush, 22: Roller, 23: Roller, 24:
belt.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Yasunaga 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Tomoharu Nishikawa Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd.

Claims (7)

[Claims] At least a magnetic powder, an acid value of 17 to 55 KO.
A binder carrier comprising Hmg / g of a polyester resin and a vinyl resin having an anionic functional group. 2. The binder carrier according to claim 1, wherein the anionic functional group is a sulfonic group, a carboxyl group or a hydroxyl group. 3. A developer comprising the binder carrier according to claim 1 and a toner. 4. The developer according to claim 3, wherein the toner is positively chargeable. 5. The developer according to claim 3, wherein the toner does not contain a charge control agent. 6. An image forming method using the developer according to claim 3. 7. An image forming method using the developer according to claim 3 and employing a toner recycling system.