JPH10207114A - Developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a developer having stable flowability and electrostatic chargeablity over a long period of time, suppressing the fogging of a photoreceptor and excellent in durability by using a (meth)acrylic ester polymer produced by a soap-free polymn. method using an alkali metallic salt of styrenesuflonic acid as fine polymer particle. SOLUTION: In a developer contg. toner particles and fine polymer particles, a (meth)acrylic ester polymer produced by a soap-free polymn. method using an alkali metallic salt of styrenesulfonic acid is used as the fine polymer particles. A (meth)acrylic ester monomer used for the fine polymer particles is, e.g. unsatd. (meth)acrylic ester such as methyl(meth)acrylate, ethyl (meth) acrylate, butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl(meth)acrylate or glycidyl (meth)acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing, and the like. The present invention relates to a developer which is charged to an electric charge, and in particular, prevents deterioration of the properties of the developer.

[0002]

2. Description of the Related Art In an electrophotographic method or an electrostatic recording method, as a developer for visualizing an electrostatic latent image, a two-component developer composed of toner particles and carrier particles and a one-component developer composed only of toner particles are used. System developers are known. Generally, in a two-component developer, a charge is applied to toner particles by frictional charging between the toner particles and carrier particles, and the electrostatic latent image is visualized by the toner particles. In a one-component developer, in the process of forming a thin layer of toner particles on a developing roll, a charge is applied to the toner particles by frictional charging between the toner particles and the developing roll, and the toner particles cause electrostatic latent. Visualizing the image.

[0003] Toner particles have excellent fluidity and stable triboelectrification, and do not cause fogging on the photoreceptor or decrease in image density for a long period of time, and enable high quality printing. Is required. If the fluidity of the toner particles is poor, cleaning failure occurs and remains on the photoreceptor, causing fogging and toner filming. Conventionally, in order to improve the fluidity of toner particles,
A developer in which various inorganic fine particles and organic fine particles such as hydrophobic silica, polytetrafluoroethylene fine particles, and polystyrene fine particles are mixed with toner particles is used.
However, conventional inorganic fine particles or organic fine particles have not sufficiently satisfied the chargeability, fluidity, print quality, and the like.

For example, silica has an average particle size of 5 to 100.
nm and the average particle size of the toner particles are very small and the hardness is high, so that the friction between the toner particles and the carrier particles or between the toner particles and the developing roll easily causes the toner particles to easily adhere to the surface of the toner particles. Embedded, resulting in
It is difficult to maintain the characteristics such as chargeability and fluidity of the developer for a long period of time. When inorganic fine particles having an average particle size of about 0.1 to 2 μm are mixed with the toner particles, the inorganic fine particles hardly embed into the toner particle surface due to friction, but are exposed to the photosensitive material by the inorganic fine particles adhered to the toner particle surface. There is a problem that the body and the surface of the developing roll are damaged, and the printing quality is deteriorated. Further, a developer in which conventionally known inorganic fine particles and organic fine particles are mixed with toner particles can prevent the toner particles from adhering to the surface of the photoreceptor and improve the cleaning property, but the frictional charging ability of the toner particles decreases. However, when the developer is used for a long period of time, there is a problem that the image density is reduced and fogging occurs.

Conventionally, organic fine particles have been used in toner powder,
A developer in which an acrylic polymer fine powder having an average particle diameter smaller than the average particle diameter of a toner powder prepared by a specific manufacturing method is mixed has been proposed (Japanese Patent Publication No. 2-3172, Japanese Patent Publication No. 4-9299). Gazette). These polymer fine powders are prepared by (1) a method using persulfate as a polymerization initiator,
(2) a method using a water-soluble polymer, or (3) a method prepared by an ordinary emulsion polymerization method, and a developer mixed with the method prevents damage to the photoconductor and the developing roll and prevents poor cleaning. It is said that the life of the developer can be extended. However, according to the results of studies by the present inventors, it has been found that the method of mixing such a polymer fine powder with a toner powder does not always provide satisfactory charging ability to a developer. That is, (1) In the method, -SO ₃ ^- it is not easy to control the amount of the charge control is difficult and also a narrow control range for the particle size.
Further, in the methods (2) and (3), the humidity dependence of the charge amount becomes large.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer comprising a mixture of toner particles and polymer fine particles, wherein the polymer particles are capable of stably imparting chargeability to the toner particles for a long period of time. An object of the present invention is to provide a developer which has stable fluidity and chargeability over a long period of time and has excellent development durability with less fogging of the photoreceptor. The present inventors have conducted intensive studies to overcome the problems of the prior art, and as a result, in a developer in which polymer particles are mixed with toner particles, an alkali metal salt of styrene sulfonic acid is used as the polymer particles. By using a (meth) acrylate polymer obtained by a soap-free polymerization method, it has excellent fluidity and cleaning properties, and also maintains stable chargeability and fluidity over a long period of time, and reduces image density. It has been found that a developer can be obtained in which deterioration and fogging of the photoreceptor are suppressed. In order to cause the polymer fine particles to act as an abrasive for the toner particles, those having an average particle size smaller than that of the toner particles are usually used. Since the polymer fine particles used in the present invention have no residual emulsifier, they have a small charge-dependent humidity dependency and have a high chargeability due to an alkali metal salt of styrenesulfonic acid. Therefore, the developer of the present invention is uniformly and strongly negatively charged, and in particular, deterioration of the properties of the developer is prevented. The present invention has been completed based on these findings.

[0007]

Thus, according to the present invention, in a developer containing toner particles and polymer fine particles, the polymer fine particles are soap-free polymerized using an alkali metal salt of styrene sulfonic acid. A (meth) acrylate polymer produced by the method described in (1).

According to the present invention, the following preferred embodiments are provided. (1) The weight average particle diameter of the polymer fine particles is 0.005 to 5
μm, preferably 0.1 to 2 μm. (2) Polymer fine particles obtained by copolymerizing a (meth) acrylate monomer and sodium or potassium styrenesulfonate with a water-soluble azo compound as a radical polymerization initiator. The developer as described above. (3) The use ratio of sodium or potassium styrene sulfonate is (meth) acrylate monomer 10
The developer according to item (2), which is used in an amount of 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, based on 0 parts by weight. (4) The mixing ratio of the polymer fine particles is 0.01 to 10 parts by weight, preferably 0.1 to 100 parts by weight, based on 100 parts by weight of the toner particles.
The developer in an amount of from 0.5 to 5 parts by weight, more preferably from 0.1 to 2 parts by weight. (5) The developer, wherein the volume average particle diameter of the toner particles is 1 to 30 μm, preferably 3 to 20 μm. (6) The developer, wherein the weight average particle diameter of the polymer fine particles is smaller than the volume average particle diameter of the toner particles.

(7) A polymer characterized in that a (meth) acrylate monomer and sodium or potassium styrenesulfonate are copolymerized by a soap-free polymerization method using a water-soluble polymerization initiator. A method for producing fine particles. (8) The above production method, wherein the water-soluble polymerization initiator is a water-soluble azo compound. (9) 0.01-20 parts by weight, preferably 0.05 parts by weight, of sodium or potassium styrenesulfonate based on 100 parts by weight of the (meth) acrylate monomer.
The above-mentioned production method used in a proportion of 10 to 10 parts by weight. (10) The above production method, wherein the reaction is carried out under the conditions of a monomer concentration of 3 to 50% by weight and a reaction temperature of 5 to 95 ° C. (11) The weight average particle diameter of the polymer fine particles is 0.005 to 5
μm, preferably 0.1 to 2 μm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Examples of the (meth) acrylate monomer used for the polymer fine particles used in the present invention include, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
Examples thereof include unsaturated (meth) acrylates such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and glycidyl (meth) acrylate.

In the present invention, other vinyl monomers can be used together with the (meth) acrylate monomer. As other vinyl monomers that can be used in the present invention, for example, styrene, vinyl toluene, α-
Styrene monomers such as methylstyrene; acrylic acid, methacrylic acid; derivatives of acrylic acid or methacrylic acid such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide; ethylene,
Ethylenically unsaturated monoolefins such as propylene and butylene; vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl Methyl ketone,
Vinyl ketones such as methyl isopropenyl ketone; nitrogen-containing vinyl compounds such as 2-vinyl pyridine, 4-vinyl pyridine, and N-vinyl pyrrolidone; These vinyl monomers may be used alone, or a plurality of vinyl monomers may be used in combination. The proportion used is usually from 0 to 50% by weight based on the total amount of the (meth) acrylate monomer.

In the present invention, polymer fine particles are produced by a soap-free polymerization method well known to those skilled in the art.

In the present invention, in soap-free polymerization,
An alkali metal salt of styrenesulfonic acid, such as sodium or potassium styrenesulfonate, is present together with the (meth) acrylate-based monomer. When performing polymerization by the soap-free polymerization method, in order to ensure the colloidal stability of the particles, in order to impart an electric repulsion,
Although some kind of charge imparting agent is required, an alkali metal salt of styrene sulfonic acid acts as the charge imparting agent.
Further, this salt is copolymerized with the (meth) acrylic acid ester-based monomer and contributes to the dispersion stabilization of the suspension. The alkali metal salt of styrene sulfonic acid is usually used in an amount of 0.01 to 100 parts by weight of the (meth) acrylate monomer.
It is desirable to use 20 parts by weight, preferably 0.05 to 10 parts by weight.

In the present invention, those conventionally used can be used as the water-soluble polymerization initiator. Among these, a water-soluble azo catalyst is particularly preferable. Examples of the water-soluble azo catalyst include, for example, 2,2′-azobis (2
-Amidinopropane) dihydrochloride, 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis [2- (5
-Methyl-2-imidazolin-2-yl) propane] 2
Hydrochloride, 2,2'-azobis [2-methyl-N- (1,
1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide] and 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]. As the polymerization conditions, the conditions of a usual soap-free polymerization method can be adopted. The monomer concentration is usually 3 to 50% by weight, preferably 5 to 2%.
0% by weight. The reaction temperature is usually from 5 to 95C.

The polymer fine particles obtained by the soap-free polymerization method are preferably purified, if necessary, by ultrafiltration, membrane filtration using a ceramic filter, or centrifugation. To add polymer particles to toner particles,
Pulverization is preferably performed as a post-treatment after the polymerization.
For that purpose, a commercially available dryer can be used. Examples of commercially available dryers include, for example, a continuous instantaneous flash dryer (flash jet dryer, manufactured by Seishin Enterprise).

The polymer fine particles obtained in the present invention are (1)
Since perfect spherical particles are obtained, (2) particles having an extremely narrow particle size distribution are obtained, (3) an appropriate and desired particle size is obtained, and (4) since there is no residual emulsifier,
There are advantages such as low humidity dependence of chargeability and (5) having a controlled charge amount by varying the amount of alkali metal styrenesulfonate. Therefore, when mixed with the toner particles, the chargeability of the toner particles can be stably maintained for a long period of time, and a developer with less fog on the photosensitive member and excellent development durability can be obtained. When the polymer fine particles of the present invention are used as an abrasive for toner particles, the average particle diameter must be smaller than the average particle diameter of the toner particles. The weight average particle diameter of the polymer fine particles is usually
It is 0.005-5 μm, preferably 0.1-2 μm. If the weight average particle size of the polymer particles is too large, the adhesion to the toner particles is weak, the polymer particles are separated from the toner particles, and the development durability of the developer tends to be insufficient. Conversely, if the weight average particle size of the polymer fine particles is too small, the chargeability of the polymer fine particles may decrease, and the durability of the developer may decrease, although the reason is not clear. The weight average particle diameter of the polymer fine particles is a value measured by a light scattering method.

The developer of the present invention contains polymer fine particles in an amount of usually 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of toner particles. It can be obtained by mixing at a ratio of 2 parts by weight. If this ratio is too small, the effect of compounding the polymer fine particles is small, and even if it is excessive, the effect is saturated. The polymer fine particles of the present invention can be used in combination with other additives such as hydrophobic silica, if desired. The toner particles are not particularly limited, and for example, ordinary particles such as those produced by a polymerization method, those produced by kneading and pulverization, and those of a core-shell type can be used. As typical toner particles, polystyrene, styrene- (meth) acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, polypropylene, etc. were used as the binder resin. Things can be mentioned. As the toner particles, those containing a colorant, a magnetic material, or the like can be used. Various additives such as paraffin and wax may be blended with the toner particles. The volume average particle diameter of the toner particles is usually 1 to 30 μm, preferably 3 to 20 μm.
It is. The reason for measuring the average particle diameter of the toner particles as the volume average particle diameter is that when the toner particles contain an additive having a large specific gravity such as magnetic powder, the weight average particle diameter may not reflect the actual average particle diameter. Because there is. The volume average particle size of the toner particles is a value measured by the Coulter counter method. The developer of the present invention can be used as a one-component developer or as a two-component developer. Further, the type of the electrophotographic developing device, the type of the photoconductor, and the cleaning method for applying the developer of the present invention are not particularly limited.

[0018]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. The evaluation method of the physical properties is as follows. (1) Measuring Method of Image Density (ID) The image density (ID) was evaluated by measuring "black solid portion" using a Macbeth reflection densitometer. (2) Method of Measuring Blow-off Charge Amount The charge amount of the polymer fine particles was determined by weighing 59.7 g of a carrier (TEFV150 / 250) manufactured by Powdertech Co., Ltd. and 0.3 g of the polymer fine particles, and forming a 200 cc SUS pot. , And triboelectrically charged at 150 rpm for 30 minutes, and blow-off was performed at a pressure of 1 kg / cm ² of nitrogen gas with a blow-off meter manufactured by Toshiba Chemical Corporation, and the charge amount was measured. (3) Measurement method of photoreceptor fog Fog toner particles on the photoreceptor were collected with a transparent adhesive tape, stuck on white paper, and measured for light reflectance Rf. On the other hand, only a transparent adhesive tape was stuck on white paper, and the light reflectance Rb was measured. The light reflectance was measured using a whiteness meter (NDW-1D manufactured by Nippon Denshoku Industries Co., Ltd.). Photoconductor fog (BG) was determined by the following equation. BG = Rb-Rf

Reference Example 1 Production of Polymer Fine Particles A In a 3 L four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a separating funnel, 2000 g of ion-exchanged water, 200 g of methyl methacrylate, and styrene sulfone 0.2 g of sodium acid was added and stirred. Next, the mixture was heated to 80 ° C., and then 2,2′-azobis [2
-Methyl-N- (2-hydroxyethyl) propionamide] (300 g) was added to the flask from a separatory funnel to start the reaction. 20 g of ion-exchanged water was added to the separating funnel, and the separating funnel was washed. At the stage when the reaction was carried out for 7 hours, the polymerization conversion was measured by a gravimetric method and found to have reached 98%. The particle size of the obtained polymer fine particles was determined by a light scattering method (LPA3 manufactured by Otsuka Electronics Co., Ltd.).
00/23100), the weight average particle diameter was 520 nm and the number average particle diameter was 500 nm. The polymer particles were subjected to ultrafiltration (UF module ACV-3050 manufactured by Asahi Kasei Corporation) to obtain an aqueous phase having an electric conductivity of 50 μm.
Purification was performed until the value reached s. Then, after evaporating water with a rotary evaporator, it was dried in a vacuum dryer at 50 ° C. for one day. Thereafter, the polymer fine particles were crushed into primary particles in a mortar to prepare polymer fine particles A.

Reference Example 2 Production of Polymer Fine Particles B Polymer fine particles were obtained in the same manner as in Reference Example 1, except that the amount of sodium styrene sulfonate was changed to 0.6 g. The particle size of the polymer fine particles was determined by a light scattering method (LPA30 manufactured by Otsuka Electronics Co., Ltd.).
00/3100), the weight average particle diameter was 420 nm and the number average particle diameter was 400 nm. The subsequent treatment and crushing were performed in the same manner as in Reference Example 1 to prepare polymer fine particles B.

Reference Example 3 Production of Polymer Fine Particles C Polymer fine particles were obtained in the same manner as in Reference Example 1, except that the amount of sodium styrene sulfonate was changed to 1.0 g. The particle size of the polymer fine particles was determined by a light scattering method (LPA30 manufactured by Otsuka Electronics Co., Ltd.).
00/3100), the weight average particle diameter was 280 nm and the number average particle diameter was 260 nm. The subsequent treatment and pulverization were performed in the same manner as in Reference Example 1 to prepare polymer fine particles C.

Reference Example 4 Production of Polymer Fine Particles D To a 3 L four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a separating funnel, 2,000 g of ion-exchanged water and 200 g of methyl methacrylate were added. And stirred.
Next, the mixture was heated to 80 ° C., and 100 g of a 1% potassium persulfate (manufactured by Wako Pure Chemical Industries) solution was added to the flask from a separating funnel to start the reaction. At the stage when the reaction was carried out for 7 hours, the polymerization conversion was measured by a gravimetric method and found to have reached 98%. The particle diameter of the polymer fine particles thus obtained was measured by a light scattering method (LPA30 manufactured by Otsuka Electronics Co., Ltd.).
00/3100), the weight average particle diameter was 400 nm and the number average particle diameter was 380 nm. The polymer particles are subjected to ultrafiltration (UF module A manufactured by Asahi Kasei Corporation).
According to CV-3050), the electric conductivity of the aqueous phase is 50 μs.
Purification treatment was performed until. Next, after evaporating water with a rotary evaporator, it was dried in a vacuum dryer at 50 ° C. for one day. Thereafter, the polymer particles were crushed into primary particles in a mortar. Thus, polymer fine particles D composed of polymethyl methacrylate were prepared.

[0023] [Reference Example 5] except that the amount of production of 1% potassium persulfate solution of the polymer particles E was 200g is to obtain a polymer fine particles in the same manner as in Reference Example 4. The particle size of the polymer fine particles was measured by a light scattering method (LPA3000 / Otsuka Electronics).
3100), the weight average particle diameter was 500.
In nm, the number average particle shape was 480 nm. The subsequent treatment and crushing were performed in the same manner as in Reference Example 4 to prepare polymer fine particles E.

Example 1 Production Example 1 of Developer < Production of Toner Particles> 70 parts by weight of styrene, 30 parts by weight of butyl methacrylate, 8 parts by weight of carbon black (trade name: PRINTEX 150T, manufactured by Degussa), Cr 0.5 parts by weight of a system dye (trade name: Bontron S-34, manufactured by Orient Chemical Industry Co., Ltd.) and 2 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) were dispersed at room temperature using a ball mill. A homogeneous mixture was obtained. The mixed solution was mixed with 350 parts of distilled water in which 5 parts by weight of calcium phosphate was finely dispersed.
To obtain a dispersion. The dispersion was subjected to high-shear stirring with a rotor-stator-type homomixer under the condition of pH 9 or more, and the mixed liquid containing the monomers was dispersed as fine droplets in the aqueous phase. Next, this aqueous dispersion was put into a 1-L four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser tube, and polymerized under stirring at 65 ° C. for 4 hours. The dispersion of the polymer thus obtained is
After sufficient acid washing and water washing, separation and drying were performed to obtain toner particles as color particles. The volume average particle diameter of the thus obtained toner particles measured by the Coulter counter method (Coulter counter TA-II manufactured by Coulter Co., Ltd.) was 6.8 μm. <Production of developer> Reference Example 1 was added to 100 parts by weight of toner particles.
0.3 parts by weight of the polymer fine particles A prepared in the above and silica fine particles subjected to a hydrophobic treatment with hexamethyldisilazane.
And 0 parts by weight, and mixed using a Henschel mixer to obtain a developer. <Evaluation> When printing was performed on 20,000 sheets using a developer obtained above with a commercially available electrophotographic printer, the printing quality was maintained from the beginning, and good results were obtained.

Example 2 Production Example 2 of Developer <Production of Developer> Toner particles 100 obtained in Example 1
The polymer fine particles B prepared in Reference Example 2 were added in an amount of 0.3 part by weight.
Parts by weight and 1.0 parts by weight of silica fine particles subjected to a hydrophobic treatment with hexamethyldisilazane were added and mixed using a Henschel mixer to obtain a developer. <Evaluation> When printing was performed on 20,000 sheets using a developer obtained above with a commercially available electrophotographic printer, the printing quality was maintained from the beginning, and good results were obtained.

Example 3 Production Example 3 of Developer <Production of Developer> Toner particles 100 obtained in Example 1
The polymer fine particles C prepared in Reference Example 3 were added in an amount of 0.3 part by weight.
Parts by weight and 1.0 parts by weight of silica fine particles subjected to a hydrophobic treatment with hexamethyldisilazane were added and mixed using a Henschel mixer to obtain a developer. <Evaluation> When printing was performed on 20,000 sheets using a developer obtained above with a commercially available electrophotographic printer, the printing quality was maintained from the beginning, and good results were obtained.

[Comparative Example 1] Production Example 4 of Developer <Production of Developer> Toner particles 100 obtained in Example 1
0.3 parts by weight of the polymer fine particles D prepared in Reference Example 4
A part by weight and 1.0 part by weight of silica fine particles subjected to a hydrophobizing treatment with hexamethyldisilazane were added and mixed with a Henschel mixer to obtain a developer. <Evaluation> When printing was performed on 20,000 sheets using a developer obtained above using a commercially available electrophotographic printer, the initial printing quality was good, but fog increased as printing was repeated.

[Comparative Example 2] Production Example 5 of Developer <Production of Developer> Toner particles 100 obtained in Example 1
To 0.3 parts by weight of the polymer fine particles E prepared in Reference Example 5,
A part by weight and 1.0 part by weight of silica fine particles subjected to a hydrophobizing treatment with hexamethyldisilazane were added and mixed with a Henschel mixer to obtain a developer. <Evaluation> When printing was performed on 20,000 sheets using a developer obtained above using a commercially available electrophotographic printer, the initial printing quality was good, but fog increased as printing was repeated. The above results are collectively shown in Table 1.

[0029]

[Table 1]

[0030]

According to the present invention, there is provided a developer which can maintain the chargeability of the developer stably for a long period of time, does not increase the fog of the photoreceptor, and has excellent development durability. The developer of the present invention contains polymer fine particles capable of stably providing chargeability to toner particles over a long period of time, and exhibits stable fluidity and chargeability over a long period of time. The developer of the present invention is less likely to damage the photoreceptor, suppresses the toner filming phenomenon, and has excellent cleaning properties.

Claims (1)

[Claims] 1. A developer containing toner particles and polymer fine particles, wherein said polymer fine particles are produced by a soap-free polymerization method using an alkali metal salt of styrene sulfonic acid. A developer characterized by being united.