JP2001296689A - Magnetic single-component developer and method for developing with single-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic single-component developer, which hardly causes image defects such as development ghost and fog, which is free from decrease in the image density or irregular image density, even in a high temperature and high humidity environment, which has satisfactory transfer property and fixing property and good low temperature fixing property and which can form stable images over a long time. SOLUTION: In the magnetic single-component developer, containing a toner containing at least a binder resin and a magnetic material, the binder resin is a polyester resin having 1 to 20 hydroxyl group value and the magnetic material is prepared by allowing 1 to 10 pts.wt. of carbon black for adsorption with respect to the surface of 100 pts.wt. of a magnetic material before adsorption of the carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic one-component developer used in electrophotography or electrostatic recording and containing a binder resin and a magnetic material, and a one-component developer developing method.

[0002]

2. Description of the Related Art In recent years, dry development methods in electrostatic copying have been widely used in fields for personal users such as printers and facsimile machines, and the demand for further downsizing and weight reduction of apparatuses has been increased. ing. Accordingly, an image forming method has been improved. The two-component developing method is the most widely used developing method.However, since toner adheres to the carrier surface to deteriorate the toner or consumes only the toner, the toner concentration in the developer is reduced. The mixing ratio with the carrier must be kept constant so that the ratio does not decrease, and therefore there is a disadvantage that the developing device becomes large.

On the other hand, the one-component developing system does not have the above-mentioned disadvantages and has advantages such as miniaturization of the apparatus, and is becoming the mainstream of the developing system in the field of small office environments and personal users. The one-component developing system is roughly classified into a non-magnetic one-component developing system and a magnetic one-component developing system.
The former is suitable for colorization, but since the force carried on the developer carrier mainly depends on the amount of charge of the developer, problems such as fog and in-machine contamination are likely to occur. Has not become mainstream. on the other hand,
Although the latter does not have these problems, a common problem of the one-component developing method is that a developing ghost is more likely to occur as compared with the two-component developing method.

[0004] Various attempts have been made to improve the development ghost for some time. JP-A-1-276174
In Japanese Patent Application Laid-Open Publication No. H11-146, a technique is disclosed in which a developing resin ghost is provided with a conductive and surface lubricating resin layer made of phenol resin and carbon to suppress development ghost. Also, JP-A-7-28151 discloses that
A method has been proposed in which a coating containing Mo, H, and O is provided on a base material of a developer carrier to suppress generation of a development ghost. According to these methods, charge-up of the developer can be suppressed, and generation of a development ghost can be prevented. However, the use of a developer carrier having such a configuration can prevent the occurrence of development ghosts, but the developer carrier itself has a low charging ability, so that the charge level of the developer is particularly low in a high-temperature and high-humidity environment. This causes problems such as a decrease in image density and uneven image density.

In the magnetic one-component developing system, a magnetic substance such as magnetite is generally used as a coloring agent for the developer, and carbon black is further used in combination with the developer for the purpose of increasing the coloring power of the developer. It is also known. In the former case, the image density cannot be obtained if the added amount of the magnetic substance is too small, so that the image density can be increased by increasing the added amount. Problems such as defects occur.
On the other hand, the latter is advantageous in suppressing development ghosts due to the conductivity of carbon black, but it is difficult to control the dispersion of the carbon black in the toner because it has a small particle size compared to magnetic materials. In particular, when the dispersion is poor, there is a problem that the transfer resistance is poor due to a local decrease in the electric resistance of the toner.

Further, from the viewpoints of higher printing speed and ecology in recent years, a magnetic one-component developer using a polyester resin which is advantageous in low-temperature fixing property has been proposed. However, in general, the dispersibility of the magnetic substance in the polyester resin is poor, and in addition, when the developer material such as the binder resin or the magnetic substance is mixed as a pre-process of the kneading step, the surface of the magnetic substance may be disturbed. Materials with high resistance are likely to be electrostatically charged due to friction between powders and easily cause electrostatic agglomeration and the like. Image defects such as fog are likely to occur.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention is less likely to cause image defects such as development ghosts and fogging, does not cause a decrease in image density or uneven image density even under a high-temperature and high-humidity environment, and has good transferability and fixability. It is an object of the present invention to provide a magnetic one-component developer and a one-component developer developing method which have good low-temperature fixability and can form a stable image for a long period of time.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the use of a specific polyester resin and a specific magnetic material makes it possible to use a magnetic material for a polyester resin which is advantageous for low-temperature fixability. The inventors have found that a magnetic one-component developer capable of solving the above-mentioned problems can be obtained by overcoming the problem of poor internal dispersibility, and have completed the present invention. The means for solving the above problems are as follows. That is, <1> in a magnetic one-component developer including a toner containing at least a binder resin and a magnetic material, the binder resin is:
It is a polyester resin having a hydroxyl value of 1 to 20 (hereinafter, referred to as “specific polyester resin”), and the magnetic substance is a magnetic substance before adsorbing carbon black (hereinafter, “magnetic substance before adsorption”). The magnetic material is a magnetic material obtained by adsorbing 1 to 10 parts by weight of carbon black on the surface with respect to 100 parts by weight (hereinafter, referred to as “magnetic material after adsorption”). It is a one-component developer. <2> A one-component developer developing method for forming a layer of a one-component developer on a developer carrier, negatively charging the developer, and developing a latent image on the latent image carrier by an electric field, wherein the one-component developer is A one-component developer developing method, wherein the developer is the magnetic one-component developer according to <1>.

[0009] Further, means for solving the above problems include:
The following embodiments are preferred. That is, <3> the THF insoluble content derived from the binder resin of the magnetic one-component developer is 0.1 to 20% by weight, and the binder resin has an MI (melt index value) of 1 to 15 g / 10 min, glass transition temperature is 50-70 ° C., peak soluble molecular weight of THF is 300
The magnetic one-component developer according to <1>, wherein the developer is 0 to 7000 and the acid value is 3 to 20. <4> The magnetic material before adsorption has an average primary particle diameter of 0.1
The magnetic one-component developer according to the above <1> or <3>, which has a diameter of from 0.3 to 0.3 μm. <5> The above <1>, <3> containing a polyolefin
And the magnetic one-component developer according to any one of <4> and <4>.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. -Magnetic one-component developer-The magnetic one-component developer of the present invention contains at least a toner, and further contains an external additive as needed.

[Toner] The toner contains at least a binder resin and a magnetic substance, and further contains other components as necessary.

(Magnetic Material) The magnetic material is a magnetic material after the adsorption obtained by adsorbing 1 to 10 parts by weight of carbon black on the surface with respect to 100 parts by weight of the magnetic material before the adsorption. The reason why the magnetic one-component developer of the present invention does not cause a development ghost, and particularly a decrease in image density and uneven image density even under a high-temperature and high-humidity environment, is that the magnetic substance after adsorption has a conductive property on the surface. Because the carbon black is adsorbed, the charge exchange property between the toner particles is promoted, so that the development ghost is hardly generated, and in the toner particles, the magnetic particles after the adsorption are dispersed in the unit of particle size. Since the aggregation of carbon black does not occur and the electrical resistance of the toner particles themselves is maintained at a certain level, poor transfer hardly occurs. In addition, since the blackness of carbon black increases the coloring power of the developer, a high image density can be maintained, and further, the magnetic substance content in the toner can be reduced by using this coloring power. As a result, it is considered that transferability and fixing property are advantageous.

Further, the magnetic one-component developer of the present invention develops despite the use of a polyester resin having excellent low-temperature fixability as a binder resin but poor dispersibility in a magnetic substance. The reason why image defects such as ghost and fog do not occur is that the specific polyester resin and the magnetic material after the adsorption are used in combination. Among them, the effect of using the magnetic substance after the adsorption is that since conductive carbon black is adsorbed on the surface, the material of the developer such as a binder resin or a magnetic substance is mixed as a step before the kneading step. Also, when the magnetic material surface after the adsorption is relatively low in resistance, even if the magnetic material after the adsorption is electrostatically charged due to friction between the powders, the charge exchange property of the surface is good. Therefore, it is considered that electrostatic aggregation and the like hardly occur, and as a result, the magnetic substance after the adsorption is uniformly dispersed in the binder resin, and image defects such as development ghost and fog are less likely to occur. On the other hand, the effect of using the specific polyester resin will be described later.

The amount of carbon black adsorbed on the surface of the magnetic material before the adsorption is 1 to 10 parts by weight, preferably 2 to 7 parts by weight, based on 100 parts by weight of the magnetic material before the adsorption. When the amount of the carbon black is less than 1 part by weight, the amount of the carbon black adhering to the surface of the magnetic material before the adsorption is not sufficient, and the electric resistance is not sufficiently reduced, and the effect of suppressing the development ghost is insufficient. Would. On the other hand, when the amount of the carbon black exceeds 10 parts by weight, the amount of the carbon black adhering to the surface of the magnetic substance before the adsorption is too large, so that the carbon black is easily released, and the carbon black is easily removed into the binder resin. Since carbon black is dispersed with agglomeration, transferability is deteriorated.

As the magnetic material before the adsorption, a conventionally known magnetic material can be used. For example, metals such as iron, cobalt and nickel and alloys thereof, Fe ₃ O ₄ , γ-Fe
₂ O ₃ , metal oxides such as cobalt-added iron oxide, Mn-Zn
Various ferrites such as ferrite and Ni-Zn ferrite, magnetite, hematite and the like can be mentioned.

The average primary particle diameter of the magnetic material before adsorption is as follows:
It is preferably 0.1 to 0.3 μm. When the average primary particle diameter of the magnetic material before the adsorption is less than 0.1 μm, the magnetic material is easily aggregated, and it is difficult to uniformly disperse the magnetic material in the binder resin. May occur. As a result, the developer having a small amount of the magnetic material is more likely to fly due to reduced binding force due to the magnetic force of the developer carrier,
Image defects such as fog tend to occur. On the other hand, when the average primary particle size exceeds 0.3 μm, dispersion in the binder resin is poor, and in addition, image defects such as scattering may occur.

As the carbon black, conventionally known carbon blacks can be used. For example, commercially available furnace black, channel black, acetylene black and the like can be used.

The average primary particle diameter of the carbon black is preferably 5 to 50 nm, more preferably 15 to 35 nm. If the average primary particle size is less than 5 nm, it becomes difficult to handle the material at the time of adsorption with a magnetic material, while if the average primary particle size exceeds 50 nm, the contact area ratio between carbon black and the magnetic material decreases. Further, as a result, the adsorptivity of both is inferior, which is not preferable.

As a method of adsorbing carbon black on the surface of the magnetic material before the adsorption, the surface of the magnetic material before the adsorption is bonded by performing a treatment with a known coupling agent such as a silane coupling agent. After the layer is provided, the surface of the magnetic material before adsorption can be uniformly coated with carbon black by a method such as attaching carbon black using a dry stirring device or the like. Examples of the silane coupling agent include alkoxysilanes such as methyltriethoxysilane and dimethyldimethoxysilane. In order to form the adhesive layer, for example, a solution in which the above silane coupling agent is dissolved in a known organic solvent (for example, an alcohol such as ethanol or methanol) can be used. The content of the coupling agent in this solution can be appropriately selected according to the type of the coupling agent and the type of the organic solvent.

The magnetic material after adsorption used in the toner is preferably contained in the toner in the range of 30 to 70% by weight, more preferably in the range of 35 to 65% by weight. When the content of the magnetic substance after the adsorption is 30
When the content is less than the weight percentage, the binding force of the developer due to the magnetic force of the developer carrying member is reduced, so that the developer easily flies, which may cause image defects such as fog. On the other hand, if it exceeds 70% by weight, the reproducibility of the image density may decrease.

(Binder Resin) The binder resin of the toner includes:
A polyester resin having a hydroxyl value of 1 to 20 is used. The polyester resin basically comprises a polycarboxylic acid and a polyol component. As the polycarboxylic acid component, divalent carboxylic acids and, if necessary, trivalent or higher carboxylic acids are used. Specific examples of the divalent carboxylic acids include aliphatic carboxylic acids such as maleic acid, fumaric acid succinic acid, adipic acid, malonic acid, sebacic acid, mesaconic acid, dodecenyl (anhydride) succinic acid, and anhydrides thereof. And lower alkyl esters, phthalic acid, isophthalic acid, terephthalic acid, toluenedicarboxylic acid, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid and their anhydrides and lower alkyl esters, and having 4 to 35 carbon atoms in the side chain.
Alkyl or alkenyl (anhydride) succinic acid {dodecenyl (anhydrous) succinic acid, pentadodecenyl (anhydride) succinic acid} having a hydrocarbon group of the following, and anhydrides and lower alkyl esters thereof. Among them, maleic anhydride, fumaric acid, isophthalic acid, terephthalic acid, dimethyl terephthalate, and n-dodecenyl succinic anhydride are preferred, and maleic anhydride and fumaric acid are preferred because of their high reactivity. Acids and terephthalic acid are preferable because they increase the glass transition temperature (Tg) of the polyester, contribute to blocking resistance, reduce the dependence of the toner charge amount on temperature and humidity, and suppress toner sticking to the toner fixing member.

Specific examples of the trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, 1,2,4-
Cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,2,2
7,8-octanetetracarboxylic acid, and anhydrides and lower alkyl esters thereof. When these are used, trimellitic acid and anhydrides and lower alkyl esters thereof have an effect of increasing the Tg of the resin, and are preferable from the viewpoints of cost and imparting offset resistance. The polycarboxylic acid component may be used alone or in combination with a trivalent or higher carboxylic acid.

On the other hand, as the divalent polyol, ethylene glycol, 1,2-propylene glycol, 1,3
-Propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,
C2-C12 alkylene glycols such as 5-pentanediol and 1,6-hexanediol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; C6-C30 such as 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.
Alicyclic diols, bisphenols such as bisphenol A, bisphenol F and bisphenol S, and adducts of bisphenols with 2 to 8 mol of alkylene oxides. Of these, alkylene glycols having 2 to 12 carbon atoms and adducts of 2 to 8 mol of alkylene oxides of bisphenols are preferable, and adducts of 2 to 8 mol of alkylene oxides of bisphenols are more preferable, and ethylene oxide to propylene oxide 2 of bisphenols are particularly preferable. A 4 mol adduct is preferred.

The polyols having 3 or more valences include sorbitol, 1,2,3,6-hexanetetrol, 1,4-
Sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butane C3-20 aliphatic polyhydric alcohols such as triol, trimethylolethane and trimethylolpropane; C6-20 aromatic polyhydric alcohols such as 1,3,5-trihydroxylmethylbenzene; And alkylene oxide adducts. Of these, aliphatic polyhydric alcohols having 3 to 20 carbon atoms are preferred.

The polyester resin used in the present invention has a hydroxyl value of 1 to 20. If the hydroxyl value exceeds 20, the dependence of the charge amount of the toner on the temperature and humidity increases, and the fixation of the toner to the toner fixing member is deteriorated. On the other hand, when the hydroxyl value is less than 1, the low-temperature fixability of the toner deteriorates. The industrial limit of the normal polyesterification reaction is that the hydroxyl value is about 30, but by changing a part of the dicarboxylic acid to a dicarboxylic acid alkyl ester, a part of the hydroxyl group located at the terminal of the polyester becomes an alkyl carboxylate. It becomes an ester and can reduce the hydroxyl group concentration. Preferably, the hydroxyl value is 1 to
Fifteen.

The acid value of the polyester resin is 3 to 2
0 is preferable, and 5 to 15 is more preferable. If the acid value is less than 3, the charge amount of the toner may decrease. On the other hand, if the acid value exceeds 20, the temperature-humidity dependence of the toner charge amount may increase. . In the present invention, the acid value and the hydroxyl value of the polyester resin are J
It is a value measured according to the method specified in ISK0070. When the sample did not dissolve, a solvent such as dioxane or tetrahydrofuran was used as the solvent.

THF in the polyester resin
The peak molecular weight of the (tetrahydrofuran) soluble component is 30.
00-7000 is preferable and 4000-6000 is more preferable. When the peak molecular weight is less than 3,000, the high-temperature fixability is deteriorated, and offset tends to occur. On the other hand, if the peak molecular weight exceeds 7000, the low-temperature fixability may deteriorate and the pulverizability of the toner may deteriorate. In the present invention, the peak molecular weight of the THF-soluble component in the polyester resin is a value measured by gel permeation chromatography (GPC).

The Tg (glass transition temperature) of the polyester resin is preferably from 50 to 70 ° C., more preferably from 55 to 65 ° C. When the Tg is lower than 50 ° C., the cohesiveness and powder fluidity of the toner may be deteriorated. On the other hand, if the Tg exceeds 70 ° C., the low-temperature fixability and the pulverizability may deteriorate. In the present invention, the glass transition temperature of the polyester resin is ASTM D341.
It is a value measured according to the method specified in 8-82 (DSC method).

The polyester resin preferably has an MI (melt index value) of 1 to 15 g / 10 min, more preferably 1 to 10 g / 10 min. If the MI is less than 1 g / 10 min, the low-temperature fixability and the pulverizability may deteriorate, while if the MI exceeds 15 g / 10 min, the high-temperature fixability may deteriorate,
Offset is likely to occur. In the present invention, the melt index value of the polyester resin is AST
It is a value measured according to the method specified in MD1238 and JISK6760. Although the MI itself changes depending on the measurement conditions, in the present invention, the load = 49 N, 1
The measurement was performed at 50 ° C.

In the magnetic one-component developer of the present invention, the THF-insoluble content derived from the binder resin is preferably from 0.1 to 20% by weight, more preferably from 0.3 to 15% by weight. When the THF-insoluble content is less than 0.1% by weight, high-temperature fixability may be deteriorated. On the other hand, when the THF-insoluble content exceeds 20% by weight, low-temperature fixability and crushability may be deteriorated. . In the present invention, the method for measuring the THF-insoluble content derived from the binder resin of the magnetic one-component developer is as follows. That is, 0.5 g of the sample and TH were placed in an Erlenmeyer flask.
After adding 50 ml of F and heating and stirring with a hotting stirrer for 3 hours, a glass filter filled with celite is attached to a suction bottle, the solution is filtered, and substances attached to the flask are wiped off using a filter paper. Thereafter, the glass filter and the filter paper were dried at 80 ° C. in a vacuum drier, and the value obtained by dividing the weight difference between the glass filter and the filter paper before and after drying by the original sample weight and further multiplying 100 times by the THF-insoluble matter ( %).

(Other Components) In the toner, a release agent may be added as the other components in order to improve the offset resistance. The release agent is preferably a paraffin having 8 or more carbon atoms, polyolefin, or the like. For example, paraffin wax, paraffin latex, microcrystalline wax, or the like, or polypropylene can be used. The amount of the release agent added is preferably 0.3 to 15% by weight based on the toner. If the amount is less than 0.3% by weight, the releasability of the toner may be reduced. On the other hand, if the amount exceeds 15% by weight, the chargeability and developability of the toner may be reduced. The thermal storage stability of the toner may decrease.

The toner is used for charge control or the like.
Various substances can be added as the other components. Specifically, a high molecular acid such as a fluorosurfactant, salicylic acid, an iron dye such as an iron complex, a chromium dye such as a chromium complex, or a copolymer containing maleic acid as a monomer component. Quaternary ammonium salts, azine dyes such as nigrosine, etc.
It can be added in the range of 0% by weight.

The toner can be produced by any known method, but it is particularly preferable to use a pulverization method. That is, a method is preferred in which a binder resin, a magnetic material, and the like are melt-kneaded using a hot kneader, cooled, pulverized and classified to obtain a toner. The toner has a volume average particle size of 5
To 8 μm, more preferably 5.5 to 7.0 μm.
m is good from the viewpoint of balance between image quality and developer consumption per sheet. If the volume average particle size is less than 5 μm, the image density may be reduced or fogging may occur, while if it is more than 8 μm, the graininess may be deteriorated.

[External additives] The magnetic one-component developer of the present invention comprises:
For the toner, durability of toner particles as required,
For the purpose of improving fluidity or cleaning properties, inorganic fine powders such as silica and titania, organic fine powders such as fatty acids or their derivatives and metal salts, and resin fine powders such as a fluororesin, an acrylic resin or a styrene resin. Can be added as the external additive. The average primary particle diameter of the external additive is preferably 5 to 100 nm. In the case of the inorganic fine powder, the surface of the particle may be subjected to a hydrophobic treatment. The amount of the external additive is preferably 1 to 3 parts by weight based on 100 parts by weight of the toner. When the amount is less than 1 part by weight, it is difficult to quickly and uniformly charge the toner. On the other hand, when the amount is more than 3 parts by weight,
The external additive tends to adhere to the photoreceptor and cause problems such as comet and filming.

-One-Component Developer Developing Method- In the one-component developer developing method of the present invention, the magnetic one-component developer of the present invention having the above-described structure is formed into a layer on a developer carrying member, and is negatively charged. This is a method of developing a latent image on a latent image carrier using an electric field. The one-component developer developing method of the present invention includes a step of contacting or bringing a developer carrier and a latent image carrier into contact with each other and bringing the magnetic one-component developer and the latent image carrier into contact with each other, so that the latent image carrier is A contact type method for developing a latent image on the latent image carrier may be used, or a non-contact type method for developing a latent image on a latent image carrier by flying a magnetic one-component developer in a non-contact manner may be used. Is preferred. When developing a latent image on a latent image carrier with an electric field, it is particularly preferable to use an alternating electric field.

In the one-component developer developing method of the present invention, a method of forming a layer of a magnetic one-component developer on a developer carrier is provided.
The method of negatively charging, the method of applying an electric field, and the like are not particularly limited, and can be performed by a conventionally known method.

[0037]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. still,
The particle size of the magnetic one-component developer was determined using a particle size analyzer TA-II manufactured by Coulter Counter Co., Ltd. with an aperture diameter of 100 μm.
m.

[Preparation of Magnetic Material a] Magnetite particles having an average primary particle diameter of 0.22 μm were added to a solution obtained by mixing 1 part by weight of methyltriethoxysilane and 2 parts by weight of ethanol.
Then, 00 parts by weight were added and mixed with stirring for 90 minutes. Next, while gradually adding 4 parts by weight of carbon black (MA100B, manufactured by Mitsubishi Chemical Corporation, average primary particle size: 22 nm), stirring and mixing for 90 minutes, the magnetic material a in which carbon black was adsorbed on the surface of magnetite particles was used. Was prepared.

(Example 1) [Preparation of magnetic one-component developer] Binder resin: 43.0 parts by weight of polyester resin A Alcohol component: propylene oxide adduct of bisphenol A Acid component: terephthalic acid Melt index (MI) : 6g / 10min Glass transition temperature (Tg): 58 ° C Peak molecular weight of THF-soluble component: 5800 Acid value: 7.2 Hydroxyl value: 8.7 THF-insoluble component: 28% by weight-Magnetic substance: Magnetic substance a 52. 0 parts by weight-Negatively chargeable charge control agent: 1.5 parts by weight (Fe-containing azo dye, trade name: T77, manufactured by Hodogaya Chemical Industry Co., Ltd.)-Polypropylene wax: 3.5 parts by weight (trade name: 660P, The above materials are dry-stirred and mixed with a Henschel mixer,
This was heat-kneaded with an extruder at a set temperature of 140 ° C. After cooling, coarse pulverization and fine pulverization were performed to obtain a pulverized product having a volume average particle size of 5.8 μm. The pulverized product was further classified to obtain a classified product having a volume average particle size of 6.4 μm, 4 μm or less: 24% by number. To 100 parts by weight of the obtained classified product, 1.2 parts by weight of dimethyl silicone oil-treated silica having an average primary particle diameter of 12 nm, and 0.3 parts by weight of titanium oxide having an average primary particle diameter of 50 nm were externally added using a Henschel mixer. A magnetic one-component developer was prepared. The THF insoluble content derived from the binder resin of the obtained magnetic one-component developer was 5.4% by weight.

[Image Formation] Using the obtained magnetic one-component developer, Laser Press 43 manufactured by Fuji Xerox Co., Ltd.
00, image formation was performed under the following conditions. Development bias (AC) = 1.8 kVp-p (frequency 2.
0 kHz) developing bias _{(DC) = - 300V V High} = -420V, V Low = -120V image bearing member: organophotoreceptor latent image bearing member, a developer carrying member spacing = 250 [mu] m using a polycarbonate surface layer binder

<Evaluation> The evaluation environment was 28 ° C./85% RH.
Was set to a high temperature and high humidity environment, and 10 ° C./15% RH was set to a low temperature and low humidity environment, and an image sample was collected. The evaluation was performed on the initial image quality in each environment. <Image Density> Comparative evaluation was performed using values measured by an X-rite densitometer. <Density unevenness> For solid images after printing 5 blank sheets,
The difference between the maximum value and the minimum value when measuring the image density at five points was compared and evaluated. ：: density difference less than 0.05 △: density difference 0.05 or more and less than 0.1 ×: density difference 0.1 or more

<Development ghost> The image density difference between the first solid image portion and the next solid image portion formed after this solid image portion and corresponding to the first solid image portion was evaluated. . ：: density difference less than 0.05 △: density difference 0.05 or more and less than 0.1 ×: density difference 0.1 or more

<Transferability> The untransferred image remaining on the photoconductor when the machine was forcibly stopped immediately after the solid image transfer step was transferred by tape, and the X-write of the portion pasted on plain paper was performed.
The concentration measured by the densitometer was compared and evaluated. ：: less than 0.20 △: 0.20 or more and less than 0.25 ×: 0.25 or more

<Minimum Fixing Temperature> Evaluation was performed by changing the fixing temperature using a modified copy machine Laser Press 4300 manufactured by Fuji Xerox Co., Ltd. Evaluation is based on a basis weight of 80 g / cm ²
The solid image fixed on the paper was folded in two, and the trace at the fold was visually evaluated for grade. The temperature at which the level reached an allowable level was defined as the minimum fixing temperature. Note that the minimum fixing temperature is 1
If it is 90 ° C. or lower, there is no practical problem.

(Embodiment 2) In Embodiment 1, the magnetic material a
A magnetic one-component developer was prepared in the same manner as in Example 1, except that the amount of carbon black adsorbed was changed from 4 parts by weight to 1 part by weight during the production of The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

(Embodiment 3) In Embodiment 1, the magnetic material a
A magnetic one-component developer was produced in the same manner as in Example 1, except that the amount of carbon black adsorbed was changed from 4 parts by weight to 10 parts by weight during the production of The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

(Embodiment 4) In Embodiment 1, the magnetic material a
A magnetic one-component developer was prepared in the same manner as in Example 1 except that magnetite particles having an average primary particle diameter of 0.15 μm were used instead of magnetite particles having an average primary particle diameter of 0.22 μm during the production of . The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

Fifth Embodiment In the first embodiment, the magnetic material a
A magnetic one-component developer was prepared in the same manner as in Example 1, except that magnetite particles having an average primary particle diameter of 0.29 μm were used instead of magnetite particles having an average primary particle diameter of 0.22 μm in the production. . The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

(Embodiment 6) In Embodiment 1, the magnetic material a
Was prepared in the same manner as in Example 1 except that the addition amount of the resin was 40 parts by weight and the addition amount of the polyester resin A was 60 parts by weight. The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

Comparative Example 1 In Example 1, the magnetic material a
Instead of using a magnetic material not subjected to surface treatment with carbon black, a magnetic one-component developer was prepared in the same manner as in Example 1. The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

Comparative Example 2 In Example 1, the magnetic material a
A magnetic one-component developer was prepared in the same manner as in Example 1, except that the amount of carbon black adsorbed was changed from 4 parts by weight to 15 parts by weight. The obtained magnetic one-component developer was evaluated in the same manner as in Example 1.

Comparative Example 3 A magnetic one-component developer was prepared in the same manner as in Example 1, except that the following polyester resin B was used instead of the polyester resin A. The obtained magnetic one-component developer was evaluated in the same manner as in Example 1. The THF-insoluble content derived from the binder resin of the magnetic one-component developer was 8.3% by weight. Binder resin: Polyester resin B Alcohol component: propylene oxide adduct of bisphenol A Acid component: terephthalic acid Melt index (MI): 8 g / 10 min Glass transition temperature (Tg): 62 ° C. Peak molecular weight of THF soluble component: 6000 Acid value: 7.6 Hydroxyl value: 27.2 THF-insoluble: 27% by weight

[0053]

[Table 1]

From the results shown in Table 1, it can be seen that the use of the magnetic one-component developer of Examples 1 to 6 of the present invention has excellent characteristics in both a high-temperature, high-humidity environment and a low-temperature, low-humidity environment. On the other hand, in Comparative Example 1 using a magnetic material not subjected to surface treatment with carbon black, it can be seen that density unevenness occurs. In Comparative Example 2 in which the amount of adsorption by the carbon black was out of the specified range of the present invention, the development ghost and transferability in a high-temperature and high-humidity environment were not sufficient.
Furthermore, in Comparative Example 3 using a polyester resin having a hydroxyl value outside the range specified in the present invention, a satisfactory result was not obtained as a whole.

[0055]

According to the present invention, image defects such as development ghosts and fog are unlikely to occur, and even under a high-temperature and high-humidity environment, the image density does not decrease and the image density unevenness does not occur. Good, low-temperature fixability is also good,
A magnetic one-component developer and a one-component developer developing method capable of forming a stable image over a long period of time can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsu Torigoe 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Tomohiro Takeda 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. Inventor Shinpei Takagi 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. A magnetic one-component developer including a toner containing at least a binder resin and a magnetic material, wherein the binder resin is a polyester resin having a hydroxyl value of 1 to 20, and the magnetic material is a carbon-based resin. A magnetic one-component developer comprising a magnetic material obtained by adsorbing 1 to 10 parts by weight of carbon black on the surface with respect to 100 parts by weight of a magnetic material before black is adsorbed. 2. A one-component developer developing method of forming a layer of a one-component developer on a developer carrier, charging the developer negatively, and developing a latent image on the latent image carrier by an electric field, A one-component developer developing method, wherein the one-component developer is the magnetic one-component developer according to claim 1.