JPH0943893A - Developer and polymer particles - Google Patents

Abstract

(57) [Summary] [PROBLEM] To contain fine polymer particles capable of stably imparting chargeability to toner particles over a long period of time, and having stable fluidity and chargeability over a long period of time and having excellent development durability. To provide a developer, and to provide polymer fine particles suitable as an abrasive for toner particles and capable of giving a developer having the above-mentioned characteristics. In a developer containing toner particles and polymer fine particles, the polymer fine particles include (a) a core portion of an aromatic hydrocarbon-based polymer and a shell portion of a (meth) acrylic acid ester-based polymer. A developer having a core-shell structure formed by, and (b) manufactured by a soap-free emulsion polymerization method.
(A) The core has a core-shell structure in which the core is formed of an aromatic hydrocarbon polymer and the shell is formed of a (meth) acrylate polymer, and (b) a soap-free emulsion polymerization method. Polymer fine particles produced by.

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. The present invention also relates to polymer fine particles suitable as a toner abrasive.

[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, an electric charge is applied to the 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, toner particles have been used as organic fine particles.
A developer has been proposed in which an acrylic polymer fine powder, an acrylic / styrene copolymer fine powder, or the like having an average particle size smaller than that of the toner powder is mixed (Japanese Patent Laid-Open Publication No. 6-69242).
0-186851, JP-A-60-186852, and JP-A-60-186854). These polymer fine powders have an average particle size of 0.005 to 5 μm, preferably 0.1 to 2 μm.
It is said that cleaning defects can be prevented and the life of the developer can be extended without damaging the photoreceptor or the developing roll. However, according to the results of studies conducted by the present inventors, it has been found that the method of mixing such a polymer fine powder with the toner powder is not always satisfactory in the charge imparting ability to the developer.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is a developer in which polymer particles are mixed with toner particles, and the polymer particles are capable of stably imparting chargeability to the toner particles for a long term. It is intended to provide a developer which contains, and has excellent developing durability, which has stable fluidity and chargeability over a long period of time. Another object of the present invention is to provide polymer fine particles suitable as an abrasive for toner particles and capable of giving a developer having the above-mentioned characteristics.
The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and as a result, in a developer in which polymer particles are mixed with toner particles, the polymer particles are formed by an aromatic hydrocarbon polymer. Having a core-shell structure having a core portion (core portion) formed by the above and a shell portion (shell portion) formed by a (meth) acrylic acid ester-based polymer, and obtained by a soap-free emulsion polymerization method. Use of coalesced fine particles can provide a developer having excellent fluidity and cleaning properties, stable chargeability and fluidity for a long period of time, and having reduced image density and suppression of photoconductor fogging. I found it. 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 low humidity dependence of chargeability and have high chargeability due to the core / shell structure.
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 composed of (a) a core portion of an aromatic hydrocarbon polymer. A developer having a core-shell structure in which the shell portion is formed of a (meth) acrylic acid ester-based polymer, and (b) manufactured by a soap-free emulsion polymerization method. Will be provided.
Further, according to the present invention, (a) the core portion has a core-shell structure in which the aromatic hydrocarbon-based polymer is formed, and the shell portion is formed of a (meth) acrylic acid ester-based polymer, and (B) Polymer fine particles produced by a soap-free emulsion polymerization method are provided.

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 μ.
m, preferably 0.1 to 2 μm. (2) The core of the polymer fine particles is obtained by copolymerizing an aromatic hydrocarbon monomer and sodium or potassium styrenesulfonate with a water-soluble azo compound as a radical initiator. The developer which is (3) The proportion of sodium or potassium styrenesulfonate used is 0.01 to 20 parts by weight, preferably 0.05 to 1 per 100 parts by weight of the aromatic hydrocarbon monomer.
The developer according to item (2), which is 0 part by weight. (4) The ratio (weight ratio) of the core part and the shell part of the polymer fine particles is from 5:95 to 95: 5, preferably from 10:90.
The developer which is 90:10. (5) The mixing ratio of the polymer fine particles is 0.01 to 10 parts by weight, and preferably 0.1 to 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. (6) The developer as described above, wherein the volume average particle diameter of the toner particles is 1 to 30 μm, preferably 3 to 20 μm.

(7) The developer as described above, wherein the weight average particle diameter of the polymer fine particles is smaller than the volume average particle diameter of the toner particles. (8) The polymer fine particles having a weight average particle diameter of 0.005 to 5 μm, preferably 0.1 to 2 μm. (9) The above-mentioned polymer, wherein the core part is obtained by copolymerizing an aromatic hydrocarbon monomer and sodium or potassium styrenesulfonate with a water-soluble azo compound as a radical initiator. Combined fine particles. (10) The proportion of sodium or potassium styrenesulfonate used is 0.01 to 20 parts by weight, preferably 0.05 to 20 parts by weight, based on 100 parts by weight of the aromatic hydrocarbon monomer.
The polymer fine particles according to item (9), which is 10 parts by weight. (11) The ratio (weight ratio) of the core part and the shell part is 5: 9.
The polymer fine particles are 5 to 95: 5, preferably 10:90 to 90:10. (12) The polymer fine particles as an abrasive for toner particles.

(13) By the soap-free emulsion polymerization method,
Using a water-soluble initiator, first, an aromatic hydrocarbon-based monomer is copolymerized with sodium or potassium styrenesulfonate to a polymerization conversion rate of 90% or more, and then a (meth) acryl is added to the reaction system. An acid ester monomer is added to continue the polymerization reaction. (A) The core portion is formed of an aromatic hydrocarbon polymer, and the shell portion is formed of a (meth) acrylic acid ester polymer. And a method for producing fine polymer particles having a core-shell structure. (14) The production method as described above, wherein the water-soluble initiator is a water-soluble azo compound. (15) Add sodium or potassium styrenesulfonate to 100 parts by weight of the aromatic hydrocarbon monomer.
The said manufacturing method used in a ratio of 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight. (16) The production method as described above, wherein the monomer concentration is 3 to 50% by weight and the reaction temperature is 5 to 95 ° C. (17) The ratio (weight ratio) of the core part and the shell part is 5:
95 to 95: 5, preferably 10:90 to 90:10. (18) The weight average particle size of the polymer particles is 0.005 to 5
μm, preferably 0.1 to 2 μm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polymer fine particles used in the present invention have a specific core-shell type structure. Although the reason is not clear, the inventors of the present invention, when the polymer fine particles have a core-shell type structure and the core part and the shell part have different dielectric constants,
It was found that the charge amount of the polymer fine particles is increased, and when mixed with the toner particles, a developer having stable chargeability for a long term can be obtained. Examples of the aromatic hydrocarbon-based monomer (core monomer) used in the core portion formed from the aromatic hydrocarbon-based polymer of the polymer fine particles include styrene, p-methylstyrene, α- Methyl styrene, halogenated styrene, etc. can be mentioned. These can be used alone or in combination of two or more. Examples of the (meth) acrylic acid ester-based monomer (shell monomer) used in the shell portion formed from the (meth) acrylic acid ester-based polymer of the polymer fine particles include, for example, methyl (meth) acrylate. ,
Unsaturated (meth) acrylic acid esters such as ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate and glycidyl (meth) acrylate can be mentioned.

In the present invention, the polymer particles having a core / shell structure are produced by the soap-free emulsion polymerization method. An emulsifier is used in a usual emulsion polymerization method. That is,
In a general emulsion polymerization method, a monomer that is insoluble in water or a medium is emulsified using a surfactant (emulsifier), and is polymerized with an initiator that is soluble in a medium such as water. For example, in order to emulsify a hydrophobic monomer such as styrene in water, as the emulsifier, a sulfate of a higher alcohol, an anion activator of an alkyl sulfonate, or a nonionic activator of an alkyl ether of polyethylene oxide is used. As the initiator, water-soluble potassium persulfate, ammonium persulfate, a redox initiator or the like is used. In the soap-free emulsion polymerization method, for example, a reactive emulsifier is used, a persulfate initiator of a hydrophilic monomer is used, and an ionic or nonionic water-soluble monomer is copolymerized without using an emulsifier. The method is employed such as coagulation, coexistence of water-soluble polymer or oligomer, use of decomposing type emulsifier, or use of cross-linking type emulsifier.
These soap-free emulsion polymerization methods are well known in the art, and the present invention is not limited to a particular method.

In the present invention, it is preferable that sodium or potassium styrene sulfonate is present together with the aromatic hydrocarbon monomer in the soap-free emulsion polymerization of the aromatic hydrocarbon polymer forming the core portion. In order to ensure the colloidal stability of the particles during the polymerization by the soap-free emulsion polymerization method, some charge imparting agent is required to impart an electric repulsive force, and styrenesulfonic acid is used as this charge imparting agent. Preference is given to using sodium or potassium. Sodium or potassium styrene sulfonate is an aromatic hydrocarbon monomer 1
It is desirable to use 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, relative to 00 parts by weight. In the present invention, as the water-soluble initiator, those conventionally used can be used. Among these, a water-soluble azo catalyst is particularly preferable. Examples of the water-soluble azo catalyst include 2,2'-azobis (2-amidinopropane) dihydrochloride, 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis [2- (5 -Methyl-2-imidazolin-2-yl) propane] dihydrochloride,
2,2'-azobis [2-methyl-N- (1,1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide], 2,2'-azobis [2-methyl-N-
(2-hydroxyethyl) propionamide] and the like. As the polymerization conditions, the conditions of a normal soap-free emulsion polymerization method can be adopted. The monomer concentration is usually 3 to 50% by weight, preferably 5 to 20% by weight. The reaction temperature is usually from 5 to 95C.

In order to obtain fine polymer particles having a core / shell structure, for example, a method of polymerizing a monomer for core and then adding a monomer for shell during the reaction to form a shell polymer , The shell polymer is phase-separated during the reaction
Although there is a method of forming a shell type structure, the method of broadly selecting the monomer is a method of adding the shell monomer during the reaction of the core monomer. The method of addition is the batch addition method,
Either of the sequential addition methods may be used. In order to form a complete core-shell structure, the polymerization conversion rate of the core portion is preferably 90% or more as the timing of adding the shell monomer. The polymer fine particles obtained by the soap-free polymerization method are preferably purified by ultrafiltration, membrane filtration using a ceramics filter, centrifugation, or the like, if necessary. In order to add the polymer fine particles to the toner particles, it is preferable to carry out pulverization 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 ratio (weight ratio) of the core part and the shell part is usually 5: 95-9.
It is 5: 5, preferably 10:90 to 90:10. If the ratio is out of this range, the effect of the core-shell structure is substantially reduced, and it becomes difficult to achieve the intended purpose. Further, the aromatic hydrocarbon polymer in the core portion,
By disposing the (meth) acrylic acid ester-based polymer in the shell portion, it is possible to obtain polymer particles that are strongly negatively charged.

The polymer fine particles obtained by the present invention are (1)
Since perfect spherical particles can be obtained, (2) particles having a remarkably narrow particle size distribution can be obtained, (3) an appropriate and desired particle size can be obtained, and (4) there is no residual emulsifier,
In addition to the advantages that the chargeability is less dependent on humidity, it has a high chargeability due to the core-shell structure. 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 having excellent development durability can be obtained. When the polymer fine particles having a core-shell structure of the present invention are used as an abrasive for toner particles, the average particle size needs to be smaller than the average particle size 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.

In the developer of the present invention, polymer fine particles are usually added in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 100 parts by weight of toner particles. It can be obtained by mixing 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 known particles 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
２０20 μm. 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.

[0017]

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) Method of measuring photoconductor fog The fog toner particles on the photoconductor were sampled with a transparent adhesive tape and attached to a white paper, and the light reflectance Rf was measured. 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

[Example 1] Polymer fine particle 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, 20 g of styrene, and 0.
5 g was added and stirred. Next, this mixed solution is heated to 80 ° C.
After heating to 2,2'-azobis [2-methyl-N-
300 g of a 1% solution of (2-hydroxyethyl) propionamide] was added to the flask through a separating funnel to start the reaction. 20 g of ion-exchanged water was added to the separating funnel, and the separating funnel was washed. When the reaction was carried out for 7 hours, the polymerization conversion was measured by the gravimetric method.
Had reached. Next, 180 g of methyl methacrylate was charged into a separating funnel and added dropwise to the reaction liquid over 15 minutes. After that, when the reaction was continued for 3 hours, the reaction conversion rate reached 97%. In this way, the core
Polymer fine particles having a shell type structure were obtained. The particle size of the polymer particles was determined by the light scattering method (LPA3000 / 310 manufactured by Otsuka Electronics Co., Ltd.
0), the weight average particle diameter is 450 nm.
The number average particle size was 440 nm. The polymer particles are subjected to ultrafiltration (UF module ACV-30 manufactured by Asahi Kasei).
According to 50), purification treatment was performed until the electric conductivity of the aqueous phase reached 50 μS. After that, water was evaporated by a rotary evaporator and then dried in a vacuum dryer at 50 ° C. for one day. Then, the polymer fine particles were crushed into primary particles in a mortar. Thus, polymer particles A having a core / shell structure were prepared.

[Example 2] Polymer fine particle B 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, 60 g of styrene, and sodium styrenesulfonate were added.
5 g was added and stirred. Next, this mixed solution is heated to 80 ° C.
After heating to 2,2'-azobis [2-methyl-N-
300 g of a 1% solution of (2-hydroxyethyl) propionamide] was added to the flask through a separating funnel to start the reaction. 20 g of ion-exchanged water was added to the separating funnel, and the separating funnel was washed. When the reaction was carried out for 7 hours, the polymerization conversion was measured by the gravimetric method, and it was 97%.
Had reached. Next, 140 g of methyl methacrylate was charged into a separating funnel and added dropwise to the reaction liquid over 15 minutes. After that, when the reaction was continued for 3 hours, the reaction conversion rate reached 97%. In this way, the core
Polymer fine particles having a shell type structure were obtained. The particle size of the polymer particles was determined by the light scattering method (LPA3000 / 310 manufactured by Otsuka Electronics Co., Ltd.
0), the weight average particle size is 440 nm.
The number average particle size was 430 nm. The polymer particles are subjected to ultrafiltration (UF module ACV-30 manufactured by Asahi Kasei).
According to 50), purification treatment was performed until the electric conductivity of the aqueous phase reached 50 μS. After that, water was evaporated by a rotary evaporator and then dried in a vacuum dryer at 50 ° C. for one day. Then, the polymer fine particles were crushed into primary particles in a mortar. Thus, polymer particles B having a core / shell structure were prepared.

Example 3 In a 3 L four-necked flask equipped with a polymer fine particle C stirrer, a reflux condenser, a thermometer, and a separating funnel, 2000 g of ion-exchanged water, 100 g of styrene, and 0. 5 g was added and stirred. Then mix this mixture
After heating to 0 ° C, 2,2'-azobis [2-methyl-
N- (2-hydroxyethyl) propionamide]
% Solution 300 g was added into the flask from the separatory funnel,
The reaction was started. 20 g of ion-exchanged water was added to the separating funnel, and the separating funnel was washed. When the reaction was carried out for 7 hours, the polymerization conversion was measured by the gravimetric method, and it was found to be 96%.
Had reached. Next, 100 g of methyl methacrylate was charged into a separating funnel and added dropwise into the reaction liquid over 15 minutes. After that, when the reaction was continued for 3 hours, the reaction conversion rate reached 97%. In this way, the core
Polymer fine particles having a shell type structure were obtained. The particle size of the polymer particles was determined by the light scattering method (LPA3000 / 310 manufactured by Otsuka Electronics Co., Ltd.
0), the weight average particle diameter is 470 nm.
The number average particle size was 460 nm. The polymer particles are subjected to ultrafiltration (UF module ACV-30 manufactured by Asahi Kasei).
According to 50), purification treatment was performed until the electric conductivity of the aqueous phase reached 50 μS. After that, water was evaporated by a rotary evaporator and then dried in a vacuum dryer at 50 ° C. for one day. Then, the polymer fine particles were crushed into primary particles in a mortar. Thus, polymer particles C having a core / shell structure were prepared.

Comparative Example 1 Polymeric fine particle D To 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 and 200 g of styrene 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. After the reaction was carried out for 7 hours,
When the polymerization conversion rate was measured by a gravimetric method, it reached 98%. The particle size of the polymer particles thus obtained was determined by a light scattering method (LPA3000 / 310 manufactured by Otsuka Electronics Co., Ltd.).
0), the weight average particle diameter is 460 nm.
The number average particle size was 420 nm. The polymer particles are subjected to ultrafiltration (UF module ACV-30 manufactured by Asahi Kasei).
According to 50), purification treatment was performed until the electric conductivity of the aqueous phase reached 50 μS. 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 made of polystyrene were prepared.

[Comparative Example 2] Polymer fine particle E To 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 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 410 nm and the number average particle diameter was 400 nm. The polymer particles are subjected to ultrafiltration (UF module A manufactured by Asahi Kasei Corporation).
CV-3050), the electric conductivity of the water 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 E made of polymethylmethacrylate were prepared.

[Comparative Example 3] Polymer fine particle F To 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, 20 g of styrene, and 180 g of methyl methacrylate were added. , Stirred. Next, after heating this mixed solution to 80 ° C., 100 g of a 1% potassium persulfate (manufactured by Wako Pure Chemical Industries) solution
Was added to the flask from the separatory 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 size of the polymer particles thus obtained was determined by a light scattering method (LPA3000 / 3100 manufactured by Otsuka Electronics Co., Ltd.), and the weight average particle size was 440 nm and the number average particle form was 42.
It was 0 nm. The polymer particles were subjected to a purification treatment by ultrafiltration (UF module ACV-3050 manufactured by Asahi Kasei) until the electric conductivity of the aqueous phase reached 50 μS. 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 F were prepared.

Example 4 Developer Production Example 1 < Production of Toner Particles> 70 parts by weight of styrene, 30 parts by weight of butyl methacrylate, 8 parts by weight of carbon black (Printex 150T, manufactured by Degussa), Cr 0.5 parts by weight of a series 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 mixed solution 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 above dispersion liquid was subjected to high shear stirring by a rotor-stator type homomixer under conditions of pH 9 or higher to disperse the mixed liquid containing the monomer 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 introducing tube, and a reflux condenser, and polymerization was carried out at 65 ° C. for 4 hours with stirring. 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 toner particles thus obtained had a volume average particle size of 6.8 μm as measured by the Coulter counter method (Coulter counter TA-II manufactured by Coulter Co.). <Manufacture of developer>
The core / shell type polymer fine particles A prepared in Step 1.
3 parts by weight and 1.0 part by weight of silica fine particles hydrophobized 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 5] Production Example 2 of developer <Production of developer> Toner particles 100 obtained in Example 4
0.3 parts by weight of the polymer particles B having the core-shell structure prepared in Example 2 and 1.0 part by weight of silica particles hydrophobized with hexamethyldisilazane were added to the parts by weight, A Henschel mixer was used for mixing 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 6] Production Example 3 of developer <Production of developer> Toner particles 100 obtained in Example 4
0.3 parts by weight of the polymer particles C having the core-shell structure prepared in Example 3 and 1.0 part by weight of silica particles hydrophobized with hexamethyldisilazane were added to the parts by weight, A Henschel mixer was used for mixing 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 4 Production Example 4 of Developer <Production of Developer> Toner particles 100 obtained in Example 4
0.3 part by weight of the polymer fine particles D prepared in Comparative Example 1 was added to the weight part.
By weight, 1.0 part by weight of silica fine particles hydrophobized with hexamethyldisilazane were added and mixed with a Henschel mixer to obtain a developer. <Evaluation> Printing of 20,000 sheets was performed using the above-obtained developer with a commercially available electrophotographic printer, and there were many fogs on the photoconductor at the initial stage. It was not usable.

Comparative Example 5 Production Example 5 of Developer <Production of Developer> Toner particles 100 obtained in Example 4
0.3 parts by weight of the polymer fine particles E prepared in Comparative Example 2 is added to the weight part.
By weight, 1.0 part by weight of silica fine particles hydrophobized 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 6] Production Example 6 of developer <Production of developer> Toner particles 100 obtained in Example 4
0.3 part by weight of the polymer fine particles F prepared in Comparative Example 3 was added to the weight part.
By weight, 1.0 part by weight of silica fine particles hydrophobized with hexamethyldisilazane were added and mixed with a Henschel mixer to obtain a developer. <Evaluation> When the developer obtained above was used to print 20,000 sheets using a commercially available electrophotographic printer, the fog on the photoconductor was large from the initial stage, and when the printing was repeated, the fog further increased and used. Was not something that could withstand. The above results are collectively shown in Table 1.

[0030]

[Table 1]

[0031]

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. According to the present invention,
Provided are polymer fine particles having a core-shell type structure suitable as an abrasive for toner particles.

Claims (2)

[Claims] 1. A developer containing toner particles and polymer fine particles, wherein the polymer fine particles (a) have a core portion made of an aromatic hydrocarbon polymer and a shell portion made of a (meth) acrylic acid ester type polymer. A developer having a core-shell structure formed by coalescence and (b) manufactured by a soap-free emulsion polymerization method. 2. A core-shell structure having (a) a core portion formed of an aromatic hydrocarbon polymer and a shell portion formed of a (meth) acrylic acid ester polymer, and
(B) Polymer fine particles produced by a soap-free emulsion polymerization method.