JP2022145063A - Capsule toner, method for manufacturing the same and two component developer including capsule toner - Google Patents

Abstract

To provide a capsule toner capable of reducing the separation of an external additive, suppressing reduction in transferability and deterioration in image quality by carrier contamination and providing stable image quality over a long term; a method for manufacturing the same; and a two component developer including the capsule toner.SOLUTION: A capsule toner is constituted of at least toner base particles including a binder resin, a colorant and a release agent, a coating layer coating the toner base particle surface and formed of resin fine particles and an external additive externally added to the coating layer surface. The resin constituting the coating layer has a first peak (P1) in a mass average molecular weight Mw of 3000-5000 and a second peak (P2) in a mass average molecular weight Mw of 50000-500000 in average molecular distribution by a gel permeation chromatography, and the peak intensity ratio P1/P2 of the first peak to the second peak is 0.2-3.0.SELECTED DRAWING: Figure 1

Description

The present invention relates to a capsule toner, a method for producing the same, and a two-component developer containing the same. More specifically, the present invention provides a capsule toner capable of reducing the detachment of an external additive, suppressing deterioration of image quality due to deterioration of transferability and carrier contamination, and providing stable image quality over a long period of time, and a method for producing the same. It relates to a two-component developer containing it.

In recent years, with the remarkable development of OA equipment, image forming apparatuses such as copiers, printers, and facsimile machines using an electrophotographic method have become widely used.
2. Description of the Related Art An image forming apparatus that forms an image using an electrophotographic method generally comprises a photoreceptor, charging means for charging the surface of the photoreceptor, and irradiating the surface of the photoreceptor in a charged state with signal light corresponding to image information. An exposure means for forming an electrostatic latent image, a developing means for forming a toner image by supplying toner in a developer to the electrostatic latent image formed on the surface of the photoreceptor, and a toner image formed on the surface of the photoreceptor. onto a recording medium, a fixing means for fixing the transferred toner image on the recording medium to form an image, and a cleaning blade to scrape off residual toner on the surface of the photoreceptor after the toner image is transferred. A cleaning means for cleaning the surface of the photoreceptor is provided.

In such an image forming apparatus, a one-component developer containing toner or a two-component developer containing toner and carrier is used as a developer for developing an electrostatic latent image to form an image.
In a two-component developer, the carrier provides the functions of agitating, conveying, and charging the toner. Unlike a one-component developer, the toner itself does not need to have the function of a carrier, and the toner and carrier functions are separated. Therefore, the controllability is improved as compared with the one-component developer containing only the toner alone, and high-quality images can be easily obtained.
The carrier has two basic functions: a function of stably charging the toner to a desired charge amount and a function of transporting the toner to the photoreceptor. The carrier is agitated in the developing tank, transported onto the mag roller, forms a magnetic brush, passes through the regulating blade, returns to the developing tank, and is used repeatedly.

Various techniques have been proposed in order to provide stable image quality over a long period of time in response to the speedup, energy saving, and full-color electrophotography.
For example, in order to achieve both low-temperature fixability and heat resistance of the toner, there is a technology for capsule toner that provides a coating layer (shell layer) made of high-melting-point, high-molecular-weight resin particles on low-melting-point toner base particles. Proposed.

Japanese Patent Application Laid-Open No. 2018-197811 (Patent Document 1) discloses an electrostatic latent image developing toner containing a plurality of toner particles each having toner base particles and an external additive adhering to the surfaces of the toner base particles, The toner base particles comprise a core and a shell layer covering the surface thereof, the shell layer having a thickness of 50 nm or more and 200 nm or less, preferably 120 nm or more and 200 nm or less. The indentation hardness is 250 MPa or more and 980 MPa or less, the storage elastic modulus of the toner at a temperature of 90° C. is 1.0×10 ³ Pa or more and 1.0×10 ⁵ Pa or less, and the temperature is 23° C. and the humidity is 50% RH. The ratio σQ/σD of the standard deviation σQ of the number-based charge distribution of the toner to the standard deviation σD of the volume-based particle size distribution of the toner measured after continuous printing of 100,000 sheets with a printing rate of 8% under the environment is An electrostatic latent image developing toner (capsule toner) is disclosed in which the shell layer contains an acrylic resin having a number average molecular weight of 0.05 to 0.20 and a number average molecular weight of 25000 to 95000. It is said that this toner has excellent low-temperature fixability and can maintain a sharp charge amount distribution even in continuous printing to continuously form high-quality images.

Further, Japanese Patent Application Laid-Open No. 2006-084839 (Patent Document 2) discloses a toner for developing an electrostatic latent image containing at least a binder resin, a colorant and a release agent, wherein the release agent is contained in an amount of 10 to 40 by mass. %, and the weight average molecular weight (Mw) measured by gel permeation chromatography (gel permeation chromatography: GPC) of the tetrahydrofuran (THF) soluble portion of the toner is 200,000 to 1,000,000. An electrostatic latent image having a peak (P1) and having an intensity ratio (P/P1) of 0.05 or less between the maximum peak (P1) and any other peak (P) within the range of Mw≧5000 A developer toner is disclosed. This toner is said to be excellent in releasability during fixing even when a fixing roll not coated with a resin having high release properties is used, and excellent in shape controllability during toner production.

Further, Japanese Patent Application Laid-Open No. 2015-152758 (Patent Document 3) discloses a toner for developing an electrostatic latent image containing a plurality of toner particles, wherein the toner particles are anionic toner cores and cationic particles formed on the surface thereof. The shell layer is composed of a resin containing a thermosetting resin, the toner core contains a polyester resin as a binder resin, the polyester resin has a main peak and a sub-peak in its molecular weight distribution, and the main An electrostatic latent image developing toner having a peak in the range of 3.0×10 ³ to 1.0×10 ⁴ and a sub-peak in the range of 3.0×10 ⁵ to 1.8×10 ⁶ . (capsule toner). This toner is said to be excellent in heat-resistant storage stability and low-temperature fixability, and capable of suppressing the occurrence of offset at high temperatures.

Further, Japanese Patent Application Laid-Open No. 2011-017864 (Patent Document 4) describes a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a release agent, and an aqueous system in which a dispersion stabilizer is dispersed. Suspended in a medium, mixed with fine resin particles when the polymerization conversion rate of the polymerizable monomer in the aqueous medium reaches 50.0% or more, and then polymerized the polymerizable monomer. wherein the resin constituting the resin fine particles has a mass average molecular weight (Mw) of 3,000 or more and 100,000 or less as measured by GPC, and the toner particles constitute the resin fine particles. A toner (capsule toner) coated with is disclosed. This toner is said to have excellent low-temperature fixability, sufficient heat-resistant storage stability, and excellent durability due to high adhesion between the core particles and the coating layer.

JP 2018-197811 A JP 2006-084839 A JP 2015-152758 A JP 2011-017864 A

However, in the prior art described above, since the coating layer made of a high-molecular-weight resin has a high resin hardness, the adhesion strength of the external additive to the toner surface tends to decrease. When the surface of the toner deteriorates, the external additive is detached, and image quality deteriorates due to deterioration in transferability and carrier contamination.
Further, Patent Documents 1, 3 and 4 do not disclose that the resin constituting the coating layer has first and second peaks in the weight average molecular weight measured by GPC. Further, Patent Document 2 discloses that the resin constituting the toner has two peaks in the mass-average molecular weight (Mw) measured by GPC. do not have.

Accordingly, the present invention provides a capsule toner capable of reducing the detachment of an external additive, suppressing deterioration of image quality due to deterioration of transferability and carrier contamination, and providing stable image quality over a long period of time, a method for producing the same, and the same. An object of the present invention is to provide a two-component developer containing

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that by using a specific resin for the coating layer of the capsule toner, the detachment of the external additive is reduced, resulting in deterioration of transferability and carrier contamination. The inventors have found that deterioration of image quality is suppressed and stable image quality can be provided over a long period of time, and have completed the present invention.

Thus, according to the present invention, toner base particles containing a binder resin, a colorant and a release agent, a coating layer formed from fine resin particles covering the surfaces of the toner base particles, and an outer layer on the surface of the coating layer. The capsule toner is composed of at least an added external additive, and the resin constituting the coating layer has a first peak ( P1) and a second peak (P2) in the range of mass average molecular weight Mw of 50,000 to 500,000, and a peak intensity ratio P1/P2 of 0.2 to 3.0. provided.

Further, according to the present invention, in the method for producing the capsule toner described above, the composite particles containing the toner base particles and the resin fine particles forming the coating layer are circulated in an annular flow path at a flow rate of 30 m/s or more. Provided is a method for producing a capsule toner, comprising a step of dispersing the toner in an air stream and obtaining the capsule toner by mechanical treatment with a rotary agitator provided in the middle of the flow path.

Further, according to the present invention, there is provided a two-component developer comprising the above capsule toner and carrier.

According to the present invention, a toner and a two-component developer containing the same can reduce the detachment of an external additive, suppress the deterioration of image quality due to deterioration of transferability and carrier contamination, and provide stable image quality over a long period of time. can be provided.
As shown in FIG. 1, the resin B forming the coating layer of the capsule toner of the present invention differs from the conventional resin A in the average molecular distribution by gel permeation chromatography with the first peak (P1) and the second peak. Having a peak (P2) and having P1 makes the coating layer soft and can maintain the adhesive strength of the external additive, and having P2 suppresses deterioration in image quality due to deterioration in transferability and carrier contamination. It is considered possible.
The inventors of the present invention have found that the capsulated toner using a resin containing only P1 causes deterioration in image quality due to deterioration in transferability and carrier contamination, and the capsulated toner using a resin containing only P2 has a hard coating layer, It is confirmed that drug withdrawal occurs.

The capsule toner of the present invention exhibits the above effects more when it satisfies any one of the following conditions (1) to (5).
(1) The fine resin particles forming the coating layer have a glass transition point Tg of 55 to 90°C.
(2) The fine resin particles forming the coating layer have a volume average particle diameter of 0.10 to 0.50 μm.
(3) The toner base particles have a glass transition point Tg of 40 to 55°C.
(4) The external additive is one or more inorganic particles containing at least silica particles having an average primary particle diameter of 100 nm or more.
(5) When the capsule toner is dispersed in water at an ultrasonic intensity of 150 W for 3 minutes, the number ratio of silica particles having a primary particle diameter of 100 nm or more is less than 30%.

FIG. 2 is a view showing the molecular weight distribution by GPC of fine resin particles forming the coating layer of the capsule toner of the present invention. 1 is a schematic cross-sectional view of a capsule toner of the present invention; FIG. FIG. 3 is a diagram showing a manufacturing flow of the capsule toner of the present invention; 1 is a front view showing a schematic configuration of a rotary stirring device used in the method for producing a capsule toner according to the present invention; FIG. FIG. 5 is a schematic cross-sectional view taken along a cutting plane line A200-A200 in the rotary stirring device of FIG. 4;

(1) Capsule Toner The capsule toner of the present invention comprises toner base particles containing a binder resin, a colorant and a release agent, a coating layer formed of fine resin particles covering the surface of the toner base particles, and the coating. A capsule toner comprising at least an external additive externally added to a layer surface,
In the average molecular distribution by gel permeation chromatography, the resin constituting the coating layer has a first peak (P1) in the range of mass average molecular weight Mw 3000 to 5000 and a second peak in the range of mass average molecular weight Mw 50000 to 500000 ( P2) and their peak intensity ratio P1/P2 is 0.2 to 3.0.
FIG. 2 is a schematic cross-sectional view of the capsule toner 100 of the present invention, in which toner mother particles (core toner) 101 are covered with a coating layer (shell layer) 102 formed of fine resin particles. Figure numbers 103 and 104 indicate the colorant and release agent, respectively.
Hereinafter, (1) the configuration and physical properties that characterize the capsule toner of the present invention and its basic configuration will be described, (2) its manufacturing method, and (3) a two-component developer containing it will be described.

[Toner base particles]
The toner base particles contain at least a binder resin, a colorant and a release agent.
[Binder resin]
As the binder resin for the toner base particles of the present invention, resins commonly used in the relevant technical field can be used.
A styrene-acrylic copolymer resin can be used as the binder resin. For example, monomers that can be used as resin raw materials include styrene derivatives such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, and 2,4-dimethylstyrene. , acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, Acrylics such as ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, and dimethylamino methacrylate Acid derivatives and methacrylic acid derivatives can be exemplified.
Furthermore, vinyl monomers such as maleic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid monophenyl ester, maleic acid monoallyl ester, and divinylbenzene may be used as resin raw materials.

The binder resin preferably has a glass transition point Tg of 40-55°C.
If the glass transition point Tg of the binder resin is less than 40° C., the capsule toner particles are likely to thermally aggregate to cause blocking within the image forming apparatus, resulting in image defects (fogging) and reduced storage stability. There is On the other hand, when the glass transition point of the binder resin exceeds 55° C., the low-temperature fixability is impaired, and image defects (offset) may occur.
Although the capsule toner of the present invention has a coating layer, it is difficult to completely cover the toner. Therefore, if the glass transition point Tg of the binder resin is low, blocking is likely to occur.
The preferred binder resin has a glass transition point Tg of 42 to 53°C, more preferably 45 to 50°C.

[Coloring agent]
As the colorant for the toner base particles of the present invention, various types and colors of organic and inorganic pigments and dyes commonly used in the field of electrophotography can be used, for example, black, white, yellow, orange, Red, purple, blue and green colorants are included.

Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite and magnetite.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

Examples of yellow colorants include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, and benzidine. Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138 and the like.

Examples of orange colorants include red chrome, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43 and the like.

Examples of red colorants include red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, resole red, pyrazolone red, watching red, calcium salts, lake red C, lake red D, and brilliant carmine 6B. , eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B, C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48:1, C.I. I. Pigment Red 53:1, C.I. I. Pigment Red 57:1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 222 and the like.

Examples of purple colorants include manganese purple, fast violet B, and methyl violet lake.

Blue colorants include, for example, Prussian Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-Free Phthalocyanine Blue, Partially Chlorinated Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15:2, C.I. I. Pigment Blue 15:3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60 and the like.
Examples of green colorants include chrome green, chromium oxide, picment green B, micalite green lake, final yellow green G, C.I. I. Pigment Green 7 and the like.

In the present invention, one of the above colorants may be used alone or two may be used in combination, and the combination may be of different colors or of the same color.
Also, two or more kinds of colorants may be formed into composite particles and used.
Composite particles can be produced, for example, by adding an appropriate amount of water, a lower alcohol, or the like to two or more colorants, granulating the mixture with a general granulator such as a high-speed mill, and drying.
Furthermore, in order to uniformly disperse the colorant in the binder resin, it may be used in the form of a masterbatch.
The composite particles and masterbatch are incorporated into the toner composition during dry mixing.

The amount of the coloring agent to be added is not particularly limited, but is preferably 3 to 15 parts by weight, particularly preferably 5 to 12 parts by weight, based on 100 parts by weight of the binder resin.
If the blending amount of the colorant is within the above range, an image having a high image density and very good image quality can be formed without impairing various physical properties of the toner.

[Release agent]
As the mold release agent, a mold release agent commonly used in the art can be used, for example, petroleum waxes such as paraffin wax, microcrystalline wax, and derivatives thereof; Fischer-Tropsch wax, polyolefin wax (polyethylene wax, Polypropylene wax, etc.), low molecular weight polypropylene wax and polyolefin polymer waxes (such as low molecular weight polyethylene wax) and their derivatives; carnauba wax, rice wax and candelilla wax and their derivatives, Japan wax animal waxes such as beeswax and spermaceti; oil-based synthetic waxes such as fatty acid amides and phenolic fatty acid esters; long-chain carboxylic acids and their derivatives; long-chain alcohols and their derivatives; silicone polymers; Fatty acid etc. are mentioned.
The above derivatives include oxides, block copolymers of vinyl-based monomers and wax, and graft-modified products of vinyl-based monomers and wax.
In the present invention, one of the release agents described above may be used alone, or two or more thereof may be used in combination.

The release agent particles preferably have a melting point of 70 to 110°C and an onset temperature of 60 to 100°C in order to exhibit the excellent effects of the present invention. More preferably, the melting point is 70-95°C and the onset temperature is 60-85°C.
Here, the “onset temperature” means a straight line obtained by extending the base line on the lower temperature side than the endothermic peak corresponding to melting to the higher temperature side in the DSC curve, and the curve from the rising part of the peak to the apex. It means the temperature at the point of intersection with the tangent drawn at the maximum point. A specific measuring method thereof will be described in detail in Examples.
When the melting point and onset temperature of the release agent particles are within the above ranges, images having high image density and excellent image quality can be formed without impairing various physical properties of the toner. .

Although the amount of the release agent to be added is not particularly limited, it is preferably 2.0 to 6.0 parts by weight with respect to 100 parts by weight of the binder resin. When the amount of the release agent is within the above range, it is possible to form an image having a high image density and excellent image quality without impairing various physical properties of the toner.
If the amount of the release agent added is less than 2.0 parts, the release agent is difficult to seep out during fixing of the capsule toner, and high-temperature offset may occur. On the other hand, if the amount of the release agent added exceeds 6.0 parts, the release agent may be exposed on the surface of the toner base particles, and the fluidity of the toner base particles may be deteriorated.

[Charge control agent]
A charge control agent may be added to the toner base particles, if necessary. As the charge control agent, charge control agents for positive charge control and negative charge control commonly used in this field can be used.
As charge control agents for positive charge control, for example, quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, amidine salts and the like can be used.
Charge control agents for negative charge control include metal-containing azo compounds, azo complex dyes, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), organic bentonite compounds, and boron compounds. can.
The amount of the charge control agent to be used is not particularly limited and can be appropriately selected from a wide range.

The volume average particle size of the toner base particles is preferably 4 to 8 μm. By reducing the volume average particle diameter to within this range, high-definition images can be stably formed over a long period of time, high image density can be obtained even with a small adhesion amount, and toner consumption can be reduced. also occur.
If the volume average particle diameter of the toner base particles is less than 4 μm, high charging and low fluidity may occur. If the toner becomes highly charged and less fluid, it becomes impossible to stably supply the toner to the photoreceptor, and background fogging and a decrease in image density may occur. On the other hand, when the volume average particle diameter of the toner base particles exceeds 8 μm, the layer thickness of the formed image becomes large and the graininess of the image is remarkable, so that a high-definition image may not be obtained, and the specific surface area is reduced. Otherwise, the amount of charge on the toner becomes small, and the toner is not stably supplied to the photoreceptor, which may cause contamination inside the machine due to toner scattering.

[Coating layer]
The coating layer is formed of fine resin particles on the outside of the toner base particles.
The fine resin particles are preferably made of an acrylic resin.
As the acrylic resin, a resin obtained by polymerizing or copolymerizing a single monomer or a plurality of monomers containing at least an acrylic monomer or a methacrylic monomer can be used.
Examples of acrylic monomers that can be used include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, octyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate. .
Examples of methacrylic monomers include methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, methacrylic acid 2 - Acrylic and methacrylic acid derivatives such as ethylhexyl, phenyl methacrylate, dimethylamino methacrylate can be used.
Monomers that can be used in addition to acrylic and methacrylic monomers include styrene such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, and 2,4-dimethylstyrene. Derivatives can be used.

In the average molecular distribution by gel permeation chromatography, the resin constituting the coating layer of the capsule toner of the present invention has a first peak (P1) in the range of weight average molecular weight Mw 3000 to 5000 and a weight average molecular weight Mw in the range of 50000 to 500000. It has a second peak (P2) and their peak intensity ratio P1/P2 is 0.2 to 3.0.
By having the first peak (P1), the coating layer is soft, the adhesion strength of the external additive can be maintained, and the detachment of the external additive can be reduced. It is possible to suppress deterioration of image quality due to deterioration and carrier contamination.
If the peak intensity ratio P1/P2 is less than 0.2, the coating layer becomes hard and the external additive may not adhere strongly. On the other hand, when the peak intensity ratio P1/P2 exceeds 3.0, the coating layer becomes soft, and image quality may deteriorate due to deterioration in transferability and carrier contamination.
A preferable peak intensity ratio P1/P2 is 0.5 to 2.5, more preferably 1.0 to 2.0.

The fine resin particles preferably have a glass transition point Tg of 55 to 90°C.
If the glass transition point Tg is less than 55° C., the toners may thermally aggregate in the developing tank, blocking may occur, and image defects (fogging) may occur. That is, since the coating layer is thin, if the glass transition point Tg is low, heat is transferred to the toner base particle (core) portion, and blocking is likely to occur. On the other hand, when the glass transition point Tg exceeds 90° C., the low-temperature fixability is impaired, and image defects (offset) may occur. Since the coating layer is a thin layer, heat is easily conducted in the fixing process, the glass transition point Tg is high, and fixing is possible even at 55 to 90°C.
The glass transition point Tg of the fine resin particles is preferably 60 to 80°C, more preferably 65 to 75°C.

The fine resin particles preferably have a volume average particle diameter of 0.10 to 0.50 μm.
If the volume average particle size is less than 0.1 μm, the coating layer will be too thin, and sufficient heat resistance may not be obtained. On the other hand, when the volume average particle size exceeds 0.5 μm, the coating layer becomes too thick, and sufficient low-temperature fixability may not be obtained.
The volume average particle diameter of the fine resin particles is preferably 0.15 to 0.4 μm, more preferably 0.2 to 0.3 μm.

The amount of fine resin particles in the coating layer is preferably 3 to 15 parts by mass with respect to 100 parts by mass of toner base particles.
If the amount of the fine resin particles is less than 3 parts by mass based on 100 parts by mass of the toner base particles, the coating layer becomes too thin, and sufficient heat resistance may not be obtained. On the other hand, if the amount of the fine resin particles exceeds 15 parts by mass based on 100 parts by mass of the toner base particles, the coating layer becomes too thick, and sufficient low-temperature fixability may not be obtained.
Preferably, the amount of fine resin particles is 4 to 12 parts by mass, more preferably 5 to 10 parts by mass, per 100 parts by mass of toner base particles.

[External Additive]
As the external additive, hydrophobized fumed silica, colloidal silica, silica-polymer composite fine particles, etc. having a primary particle size of about 7 to 300 nm can be used. In particular, since silica particles having a primary particle size in the range of 70 to 300 nm have a large particle size, they exhibit a spacer effect and can suppress adhesion and aggregation between toner particles.
Metal oxides such as alumina particles, titania particles, and magnetite may also be used for chargeability control and polishing effects.
In the capsule toner of the present invention, the external additive is preferably one or more inorganic particles containing at least silica particles having an average primary particle size of 100 nm or more.
If the average primary particle size of the external additive is too large, the thermal conductivity of the toner may be lowered, and the upper limit is about 300 nm.

When the capsule toner is subjected to dispersion treatment in water at an ultrasonic intensity of 150 W for 3 minutes, it is preferable that the number ratio of silica particles having a primary particle diameter of 100 nm or more liberated is less than 30%.
This number ratio is a guideline indicating the state of adhesion between the toner base particles and the external additive. However, stable transfer performance can be maintained over a long period of time, and contamination of the carrier by the external additive can be suppressed, so stable image quality can be provided.
This test method will be described in detail in Examples.

(2) Capsule Toner Production Method In the capsule toner production method of the present invention, composite particles containing toner base particles and resin fine particles forming a coating layer are placed in an air current circulating in an annular flow path at a flow rate of 30 m/s or more. and a step of mechanically processing a rotating agitating unit provided in the flow path to obtain a capsule toner.
Specifically, in the method for producing the capsule toner of the present invention, for example, as shown in FIG.
Toner base particles obtained by mixing, melting and kneading toner materials containing at least a binder resin, a colorant and a release agent to obtain a kneaded product, and then cooling, solidifying and pulverizing the obtained kneaded product to obtain toner base particles. manufacturing step (S1),
resin fine particle preparation step (S2) for obtaining an emulsion of resin fine particles;
A microparticle dispersion containing at least the toner base particles, the emulsion of the resin microparticles, and a charge control agent that is a water-soluble metal salt is stirred and mixed, and then stirred under reduced pressure to remove the liquid, thereby removing the toner base particles. a composite particle forming step (S3) for obtaining composite particles having the fine resin particles and the charge control agent uniformly adhered to the surface thereof;
a capsule particle forming step (S4) of stirring and mixing the composite particles to form a film of the composite particles on the surface of the toner base particles to obtain capsule particles having a coating layer formed thereon; and the capsule particles and the external additive. are stirred and mixed to obtain a capsule toner (S5).
including.
Hereinafter, each step will be described, more specifically, in Examples, but the present invention is not limited to these.

[Toner base particle preparation step: S1]
In this step S1, toner base particles are produced.
Examples of the method for producing the toner base particles include a dry method such as a kneading pulverization method and a wet method such as a suspension polymerization method, an emulsion aggregation method, a dispersion polymerization method, a dissolution suspension method, and a melt emulsification method.
A method for producing toner base particles by a kneading pulverization method will be described below.
In the production of toner base particles by the pulverization method, raw materials for toner base particles containing a binder resin, a colorant and other additives are dry-mixed in a mixer and then melt-kneaded in a kneader to obtain a melt-kneaded product. .
Next, the resulting melt-kneaded product is solidified by cooling, and the solidified product is pulverized with a pulverizer to obtain a fine pulverized product. After that, toner base particles are obtained by performing particle size adjustment such as classification as necessary.

A known mixer can be used, and examples thereof include Henschel Mixer (trade name, manufactured by Nippon Coke Kogyo Co., Ltd.) and Super Mixer (trade name, manufactured by Kawata Co., Ltd.).
As a kneader, a known one can be used, for example, PCM-65/87, PCM-30 (both are trade names, manufactured by Ikegai Co., Ltd.) and other twin-screw kneaders, Kneedex (trade name, Nippon Coke Kogyo Co., Ltd.) and other open roll kneaders can be mentioned.
Examples of the pulverizer include a counter jet mill AFG (trade name, manufactured by Hosokawa Micron Corporation) that pulverizes using a supersonic jet stream.
Examples of the classifier include rotary classifier TSP Separator (trade name, manufactured by Hosokawa Micron Corporation).

The volume average particle diameter of the toner base particles is preferably about 4.0 to 8.0 μm.
Although the glass transition point and softening point of the toner base particles depend on the type of resin used, they are preferably about 40 to 55° C. and about 90 to 130° C., respectively.

[Resin fine particle preparation step: S2]
Examples of methods for preparing resin fine particles include a method of emulsifying and dispersing a resin, which is a raw material of resin fine particles, using a homogenizer or the like, and a method of polymerizing a monomer by emulsion polymerization or soap-free emulsion polymerization.
The fine resin particles are preferably prepared as an emulsion with a solids content of 30% by weight (water content of 70% by weight).
The volume average particle size of the fine resin particles (primary particles) must be sufficiently smaller than the average particle size of the toner base particles, preferably 0.10 to 0.50 μm, more preferably 0.1 to 0.2 μm. is more preferable.
When the resin fine particles (primary particles) have a volume average particle diameter of 0.10 to 0.50 μm, a coating layer (resin coating layer) having a suitable thickness can be formed on the surface of the toner base particles.
The softening temperature of the resin used as the resin fine particle raw material is preferably higher than the glass transition temperature of the binder resin contained in the toner base particles, and more preferably 55° C. or higher.
As a result, it is possible to prevent fusion between toner particles during storage of the capsule toner produced by the method of the present embodiment. Thereby, the storage stability of the capsule toner can be improved.

[Composite particle forming step: S3]
In step S3, the surfaces of the toner base particles are coated with fine resin particles to form composite particles. That is, by applying mechanical energy, the fine resin particles are fixed to the surface of the toner base particles to form a coating layer.
As a method for forming composite particles, for example, toner base particles and a fine resin particle emulsion are put into a Henschel mixer vacuum drying system (trade name: FM20C, manufactured by Nippon Coke Kogyo Co., Ltd.), and the tips of the stirring blades are mixed. A method of reducing the pressure in the mixer tank while stirring at a peripheral speed of 10 to 30 m/sec can be used.
Composite particles dried to a moisture content of less than 1% by weight can be obtained by mixing and drying under reduced pressure.
The mixing ratio of the toner base particles and the fine resin particles is preferably such that the surfaces of the toner base particles are completely and thinly coated with the fine resin particles. The ratio is 3 to 15 parts by weight.
If the blending ratio of the fine resin particles is less than 3 parts by weight, it may be difficult to sufficiently coat the toner base particles, resulting in insufficient storage stability. On the other hand, if the blending ratio of the fine resin particles exceeds 15 parts by weight, the amount of the coating is excessive, making it difficult to reduce the thickness of the coating layer and possibly deteriorating the low-temperature fixability.

[Capsule particle forming step: S4]
In this step S4, a mechanical impact force is applied to the composite particles to form a film of the fine resin particles on the surface of the toner base particles to form capsule particles.
FIG. 4 is a front view showing a schematic configuration of a rotary stirring device used in the manufacturing method of the capsule toner of the present invention, and FIG. 5 is a schematic cross-sectional view of the rotary stirring device taken along the line A200-A200 in FIG. .
In this step S4, for example, the capsule toner manufacturing apparatus 201 shown in FIG. A coating layer (resin coating layer) is formed on the toner base particles by the impact force.
A capsule toner manufacturing apparatus 201 is a rotary stirring device, and includes a powder flow path 202, a rotary stirring means 203 (rotary stirring section), a temperature adjusting jacket (not shown), a powder charging section 206, and a powder collecting section. 207.

The rotary stirring means 203 and the powder flow path 202 constitute circulation means.
The powder flow path 202 is composed of a stirring section 208 and a powder flow-through section 209. The stirring section 208 is a cylindrical container-like member having an internal space.
Openings 210 and 211 are formed in the stirring section 208, which is a rotating stirring chamber, and the opening 210 includes the surface 208a of the stirring section 208 at a substantially central portion of the surface 208a on one side in the axial direction of the stirring section 208. It is formed so as to penetrate the side wall in the thickness direction.
Further, the opening 211 is formed so as to pass through the side wall including the side surface 208b of the stirring portion 208 in the thickness direction on the side surface 208b perpendicular to the axial one-side surface 208a of the stirring portion 208 .
The powder flow-through portion 209, which is a circulation pipe, has one end connected to the opening portion 210 and the other end connected to the opening portion 211, thereby forming an internal space of the stirring portion 208 and an internal space of the powder flow-through portion 209. are communicated with each other to form a powder flow path 202 .
Composite particles and gas flow through this powder channel 202 . The powder flow path 202 is provided so that the powder flow direction, which is the direction in which the composite particles flow, is constant.

The rotary stirring means 203 includes a rotating shaft member 212 , a disk-shaped rotating disk 213 and a plurality of stirring blades 214 .
Rotating shaft member 212 has a through hole formed in surface 208c on the other side in the axial direction of stirring unit 208 so as to pass through the side wall including surface 208c in the thickness direction. 205, and is a cylindrical rod-shaped member that is rotated around the axis by a motor (not shown).
The rotating disk 213 is a disk-shaped member that is supported by the rotating shaft member 212 so that its axis coincides with the axis of the rotating shaft member 212 and rotates as the rotating shaft member 212 rotates.
A plurality of stirring blades 214 are supported by the peripheral portion of the rotating disk 213 and rotate as the rotating disk 213 rotates.

In this step S4, the peripheral speed of the outermost circumference of the rotary stirring means 203 is preferably set to 30 m/sec or more, more preferably 50 m/sec or more.
The outermost periphery of the rotary stirring means 203 is the portion 203a of the rotary stirring means 203 that is the longest from the axis of the rotary shaft member 212 in the direction perpendicular to the direction in which the rotary shaft member 212 of the rotary stirring means 203 extends.
By setting the peripheral speed at the outermost periphery of the rotary stirring means 203 at the time of rotation to 30 m/sec or more, the composite particles circulate in the annular flow channel (powder flow channel 202) at a flow speed of 30 m/s or more. It can be dispersed in an air stream.
This allows the composite particles to flow in isolation. If the peripheral speed at the outermost periphery is less than 30 m/sec, it is difficult to cause the composite particles to flow in isolation, making it difficult to uniformly coat the toner base particles 101 with a resin film.
A temperature adjusting jacket (not shown), which is a temperature adjusting means, is provided on at least a part of the outside of the powder flow path 202, and a cooling medium or a heating medium is passed through the space inside the jacket, and the inside of the powder flow path 202 and the rotary stirring means are provided. 203 is adjusted to a predetermined temperature.
This makes it possible to control the temperature inside the powder passage and outside the rotary stirring means to be below the temperature at which the toner base particles 101 and the fine resin particles are not softened and deformed.

[External addition step: S5]
In step S5, in order to impart fluidity and a spacer effect to the capsule toner particles, the capsule toner particles and the external additive are mixed in a mixer to adhere the external additive to the surfaces of the capsule toner particles.

A known mixer can be used, and examples thereof include Henschel Mixer (trade name, manufactured by Nippon Coke Kogyo Co., Ltd.) and Super Mixer (trade name, manufactured by Kawata Co., Ltd.).
Although the amount of the external additive to be added is not particularly limited, it is preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the toner base particles.

(3) Two-component developer The two-component developer of the present invention is characterized by containing the capsule toner of the present invention and a carrier.
[Career]
As the carrier, a carrier commonly used in the technical field can be used. For example, a resin coating in which the surfaces of single or composite ferrite particles made of iron, copper, zinc, nickel, cobalt, manganese, chromium, etc. are coated with a coating substance. A carrier, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin, or the like can be used.

As the coating substance, substances commonly used in the art can be used, for example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicon resin, polyester resin, metal compound of ditertiarybutylsalicylic acid. , styrene resins, acrylic resins, polyamides, polyvinyl butyral, nigrosine, aminoacrylate resins, basic dyes, lakes of basic dyes, fine silica powder, fine alumina powder, and the like.
The resin used for the resin-dispersed carrier is not particularly limited, but examples thereof include styrene-acrylic resin, polyester resin, fluororesin, and phenol resin.
The resins used in the coating material and the resin-dispersed carrier may be used singly or in combination of two or more, and are preferably selected according to the toner components.

The shape of the carrier is not particularly limited, but spherical and flat shapes are preferred.
The particle size of the carrier is not particularly limited, but is preferably 10 to 100 μm, more preferably 20 to 50 μm, in consideration of high image quality.

The volume resistivity of the carrier was measured by placing the carrier particles in a container with a cross-sectional area of 0.50 cm ² and tapping them, applying a load of 1 kg/cm ² to the particles packed in the container, and measuring the volume resistivity between the load and the bottom electrode. It is a value obtained from a current value when a voltage that generates an electric field of 1000 V/cm is applied. If the volume resistivity is low, the carrier will be charged when a bias voltage is applied to the developing sleeve, and the carrier particles will easily adhere to the photoreceptor. Also, bias voltage breakdown is likely to occur. A preferable volume resistivity of the carrier is 1.0×10 ⁹ to 1.0×10 ¹³ (Ω·cm).

The magnetization strength (maximum magnetization) of the carrier is preferably 10-60 emu/g, more preferably 15-40 emu/g. Under general magnetic flux density conditions of a developing roller, if the magnetic flux density is less than 10 emu/g, the magnetic binding force does not work, which may cause carrier scattering. On the other hand, when the magnetization intensity exceeds 60 emu/g, the carrier bristles become too high in non-contact development, making it difficult to maintain the non-contact state between the image carrier and the toner. Eyes may become more visible.

The mixing ratio of the toner and carrier in the two-component developer is not particularly limited, and can be appropriately selected according to the types of toner and carrier. For example, when mixed with a resin-coated carrier (density of 5 to 8 g/cm ² ), the toner should be contained in an amount of 2 to 30% by weight, preferably 2 to 20% by weight, based on the total developer amount. Further, the coverage of the carrier with the toner is preferably 40 to 80% by mass.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
The obtained capsule toners and their intermediate products were measured and evaluated by the following methods.

[Glass transition temperature (Tg) of binder resin/toner base particles/fine resin particles]
Using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., model: DSC220), according to Japanese Industrial Standards (JIS) K7121-1987, 1 g of a sample is heated at a temperature increase rate of 10 ° C. per minute to perform DSC (Differential Scanning Calorimetry). : differential scanning calorimetry) curves were measured.
A straight line obtained by extending the base line on the high temperature side of the endothermic peak corresponding to the glass transition of the obtained DSC curve to the low temperature side, and a point where the slope of the curve from the rising part of the peak to the top of the peak is maximized is drawn. The glass transition point (Tg: °C) was obtained from the intersection with the tangent line.

[Softening point (Tm) of binder resin/toner base particles/fine resin particles]
Using a flow property evaluation device (manufactured by Shimadzu Corporation, model: flow tester CFT-100C), 1 g of a sample was heated at a temperature increase rate of 6°C per minute, and a load of 20 kgf/cm ² (9.8 × 10 ⁵ Pa) was applied. The sample was allowed to flow out through a die (nozzle diameter 1 mm, length 1 mm). The temperature at which the outflow of the sample started was defined as the outflow start temperature (Tfb: °C), and the temperature at which half of the sample flowed out was defined as the softening point (Tm: °C).

[Volume Average Particle Size of Toner Base Particles/Capsule Toner Particles]
To 50 mL of electrolytic solution (manufactured by Beckman Coulter, Inc., trade name: ISOTON-II), 20 mg of sample and 1 mL of sodium alkyl ether sulfate are added, and an ultrasonic disperser (manufactured by AS ONE Corporation, model: desktop dual-frequency ultrasonic wave Dispersion treatment was performed for 3 minutes at a frequency of 20 kHz using a washer VS-D100) to obtain a sample for measurement.
The resulting measurement sample was measured using a particle size distribution analyzer (manufactured by Beckman Coulter, Inc., model: Multisizer 3) under the conditions of an aperture diameter of 100 µm and the number of particles to be measured: 50,000 counts. A volume average particle diameter (μm) was obtained from the particle size distribution.

[Volume average particle diameter of fine resin particles]
The volume average particle diameter of the fine resin particles is measured twice using a dynamic light scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., model: Nanotrac wave series), and the average value is obtained. rice field.
As measurement conditions, the measurement time was 30 seconds, the sample particle refractive index was 1.49, the dispersion medium was water, and the dispersion medium refractive index was 1.33. The volume particle size distribution of the measurement sample was measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution was 50% was calculated as the volume average particle size (μm) of the fine resin particles.

[Molecular Weight Distribution of Resin Fine Particles]
After freeze-drying the resin fine particle emulsion using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: small freeze dryer FDS type), tetrahydrofuran was added so that the dry resin fine particles became 0.25% by weight. (THF), 200 μL of the sample was injected into a GPC device (manufactured by Tosoh Corporation, model: HLC-8220GPC), and a molecular weight distribution curve was obtained at a temperature of 40°C. The molecular weight distribution was obtained from the obtained molecular weight distribution curve. A molecular weight calibration curve was prepared using standard polystyrene.

(Example 1)
[Toner Base Particle Preparation Process]
A solution consisting of 74 parts by mass of styrene, 26 parts by mass of n-butyl acrylate, and 80 parts by mass of xylene solvent was filled, and di-t-butyl was added to a 5 L reaction vessel maintained at an internal temperature of 180°C and an internal pressure of 6 kg/cm ² . 20 parts by mass of a xylene solution in which 1.5 parts by mass of peroxide was uniformly dissolved was continuously supplied at 750 mL/hour to polymerize the monomers to obtain a solution of styrene-acrylic resin.
Thereafter, the obtained solution is flushed into a vessel at a temperature of 90° C. and a pressure of 10 mmHg to distill off the solvent, etc., and then the obtained styrene acrylic resin is roughly pulverized using a coarse pulverizer to obtain 1 mm chips of styrene. An acrylic resin was obtained.

5 parts by mass of carbon black (manufactured by Mitsubishi Chemical Corporation, trade name: MA-100) and a release agent (melting point 95 ° C., manufactured by Nippon Seiro Co., Ltd., product Name: Fischer-Tropsch wax FNP0090) 4 parts by mass together with styrene-acrylic resin chips are put into a high-performance fluidized mixer (total capacity: 20 L, manufactured by Nippon Coke Kogyo Co., Ltd., model: Henschel mixer vacuum drying system FM20C), After stirring and mixing for 5 minutes at a peripheral speed of 40 m / sec at the tip of the stirring blade, a twin-screw extruder (manufactured by Ikegai Co., Ltd., model: PCM-30) is used to set the cylinder temperature to 100 ° C. and the barrel rotation speed to 250 rpm. and a raw material feed rate of 10 kg/hour to obtain a melt-kneaded product.

After cooling the resulting melt-kneaded product with a cooling belt, it was coarsely pulverized with a speed mill having a screen with a diameter of 2 mm, and a fluidized bed opposed jet mill (manufactured by Hosokawa Micron Corporation, model: counter jet mill AFG) and a rotary (Centrifugal force type airflow) type classifier (manufactured by Hosokawa Micron Corporation, model: TSP separator) is used to finely pulverize and classify, resulting in a volume average particle diameter of 6.7 μm, a glass transition point of 48 ° C., and a softening point of 120. 5.0 kg of toner base particles C-1 having a temperature of 10° C. were obtained (see S1 in FIG. 3).

[Resin fine particle preparation step]
A reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube and a cooling tube was charged with 168 parts by mass of deionized water, heated to 80° C., and added with 252 parts by mass of deionized water and 65 parts by mass of styrene. , 27 parts by mass of n-butyl acrylate and 8 parts by mass of acrylic acid (pre-emulsion), 1 part by mass of ammonium peroxodisulfate, 0.2 parts by mass of n-dodecyl mercaptan and 62 parts by mass of deionized water. At the same time, 56 parts by mass of an aqueous initiator solution was added dropwise over 110 minutes. After that, the reaction was terminated by further stirring for 60 minutes, so that the glass transition point was 72° C., the softening point was 145° C., the mass average molecular weight (Mw) was 3100, the first peak (P1), and the second peak was 52,000 ( P2), their peak intensity ratio P1/P2 was 0.2, and 2.0 kg of an emulsion (solid content: 30% by mass) of almost monodisperse fine resin particles having an average particle diameter of 0.2 µm was obtained (Fig. 3 S2).

[Composite Particle Forming Step]
100 parts by mass of toner base particles and 7 parts by weight of fine resin particles (toner base particles in the state of emulsion) are placed in a high-performance fluid mixer (total capacity: 20 L, model: Henschel mixer vacuum drying system FM20C, manufactured by Nippon Coke Kogyo Co., Ltd.). Particles (core particles) 23 parts by mass per 100 parts by mass) were added (see A in FIG. 2), stirring and mixing was started at a peripheral speed of 15 m / second at the tip of the stirring blade, and stirred for 5 minutes. After that, the inside of the mixer tank was evacuated to a degree of vacuum of 0.01 MPa. Stirring was carried out under reduced pressure until the water content was 0.3 parts by mass or less, and 3.0 kg of composite particles were obtained in which the fine resin particles and the charge control agent were uniformly adhered to the surface of the toner base particles (S3 in FIG. 3). reference).
The moisture content of the composite particles was measured using an infrared moisture meter (model: FD-720, manufactured by Kett Science Laboratory Co., Ltd.). 10 g of the sample to be measured was set on a sample dish, and the moisture content was defined as the moisture content when the amount of change in moisture during 30 seconds at a drying temperature of 120° C. became 0.05% or less.

[Capsule Particle Forming Step]
0.6 kg of the obtained composite particles are put into a hybridization system (manufactured by Nara Machinery Co., Ltd., model: NHS-3 type), and the peripheral speed at the outermost periphery of the rotary stirring means is set to 50 m / s for 10 By stirring and mixing for a minute, the fine resin particles formed a film on the surface of the toner base particles, and this operation was repeated several times to obtain 2.0 kg of capsule toner (see S4 in FIG. 3, and FIGS. 4 and 5). .

[External addition process]
100 parts by mass of the obtained capsule toner and 1 part by mass of hydrophobic silica fine particles (average particle size of primary particles: 12 nm) as an external additive were mixed in a mixer (total capacity: 20 L, manufactured by Nippon Coke Kogyo Co., Ltd., model: : Henschel mixer), and stirred and mixed for 3 minutes at a peripheral speed of the rotating shaft member of 30 m/sec to obtain 2.0 kg of capsule toner (T1) of Example 1 (see S5 in FIG. 3).

[Preparation of two-component developer]
Capsule toner T1 and resin-coated carrier were weighed so that the toner concentration was 7.0% (toner/carrier = 1/13.3), and a V-type mixer (manufactured by Tokuju Kosakusho Co., Ltd., model: V-5) was used. 2 kg of a two-component developer was obtained by stirring and mixing for 20 minutes at .

(Examples 2-20 and Comparative Examples 1-11)
Instead of the resin S-1 constituting the coating layer, it has a molecular weight distribution (peak intensities P1 and P2 and a peak intensity ratio P1/P2), a glass transition point Tg and a volume average particle size shown in Tables 1 and 2, respectively. Capsule toners and two-component developers of Examples 2 to 20 and Comparative Examples 1 to 11 were obtained in the same manner as in Example 1 except that resins S-2 to S-31 were used.

(Examples 21-24)
In place of the resin S-1 constituting the coating layer, a resin S- having a molecular weight distribution (peak intensities P1 and P2 and a peak intensity ratio P1/P2), a glass transition point Tg and a volume average particle size shown in Table 2, respectively. Capsule toners and two-component developers of Examples 21 to 24 were obtained in the same manner as in Example 1 except that 32 to S-35 were used.

(Examples 25-28)
In place of the resin S-1 constituting the coating layer, a resin S- having a molecular weight distribution (peak intensities P1 and P2 and a peak intensity ratio P1/P2), a glass transition point Tg and a volume average particle size shown in Table 2, respectively. Capsule toners and two-component developers of Examples 25 to 28 were obtained in the same manner as in Example 1 except that 36 to S-39 were used.

(Examples 29-32)
In the same manner as in Example 19, except that resins C-2 to C-5 each having a glass transition point Tg shown in Table 2 were used instead of the binder resin C-1 constituting the toner base particles. Capsule toners and two-component developers of Examples 29-32 were obtained.

[evaluation]
Fixability of capsule toners and two-component developers prepared in Examples 1 to 26 and Comparative Examples 1 to 17 using a test copier modified from a digital copier (manufactured by Sharp Corporation, model: MX-M6071). (offset), image sticking (developing roller image sticking), transferability, blocking and silica liberation rate were evaluated.

[Evaluation 1: Fixability (offset)]
A two-component developer is filled in the developing unit of the above-mentioned commercially available copier, and a rectangular solid image of 20 mm long and 50 mm wide is formed on a recording medium (trade name: PPC paper SF-4AM3, manufactured by Sharp Corporation). A sample image was made as an unfused image. At this time, the amount of toner adhering to the solid image portion was adjusted to 0.5 mg/cm ² .
Next, a fixed image was formed using an external fixing device using the fixing section of the copying machine. The fixing process speed was set to 250 mm/sec, and the temperature of the fixing belt was increased from 150 to 220° C. in 10° C. increments. High-temperature offset and low-temperature offset refer to toner not being fixed on the recording paper during fixing, and toner re-adhering to the recording paper after the fixing belt completes one turn while remaining adhered to the fixing belt.

Furthermore, on the fixed image sample with the fixing belt at a temperature of 150° C., the surface of the image was rubbed back and forth three times with a sand eraser with a load of 1 kg on the Gakushin fastness tester, and the optical reflection density (image Density) was measured with a reflection densitometer (manufactured by Macbeth), and the fixing rate (%) was calculated by the following formula.
Fixing rate (%)=[(image density after rubbing)/(image density before rubbing)]×100
Based on the results of the fixed non-offset area and the fixing rate, the fixability was evaluated according to the following criteria.
A: No offset on an image sample of 150 to 220°C and a fixation rate of 80% or more ◯: No offset on an image sample of 150 to 220°C and a fixation rate of 60% to less than 80% △: 150 to 220 No offset on the image sample at 150°C and less than 60% fixing rate ×: Offset occurred on the image sample at 150 to 220°C

[Evaluation 2: Burn-in (developing roller burn-in)]
The two-component developer was charged into the developing unit of the commercial copier, and 1,000 sheets of a document with a coverage rate of 25% were continuously printed on A4 size recording paper, and then a solid black image was output on one sheet. This cycle was repeated to continuously print a total of 100,000 copies of a document with a printing rate of 25%, and the image quality of a solid black image was confirmed.
When images with a high coverage rate are continuously output, the toner and fine resin particles fuse onto the developing roller, increasing the resistance of the developing roller and destabilizing the electric field between the developing roller and the photoreceptor drum, resulting in a solid black image. Image unevenness occurs on the image.
Therefore, after printing 50,000 sheets and after printing 100,000 sheets, the developer on the surface of the developing roller was removed by air blow, and the surface condition of the developing roller was visually observed.

Furthermore, the presence or absence of image defects on the solid black image due to deterioration of the surface properties of the developing roller was checked, and image sticking was evaluated according to the following criteria.
A: No image defects after printing 100,000 sheets, and the surface of the developing roller is glossy. , and the surface of the developing roller is glossy. △: Image defects occur after printing 100,000 sheets, and the surface of the developing roller is dull, and 50,000 sheets are printed. There is no image defect, and the surface of the developing roller is glossy. ×: Image defects occur after printing 50,000 sheets, and the surface of the developing roller is not glossy.

[Evaluation 3: Transferability]
The two-component developer was charged into the developing unit of the above-mentioned commercially available copier, and 10,000 sheets (200 sets of 50 sheets in succession) were printed on A4 size recording paper with a coverage rate of 1%.
After that, print an evaluation chart (a chart that can be used to evaluate characters, lines, and solid areas), check for voids in characters and lines, and rough solid areas. was evaluated according to the criteria of
◎: Neither voids nor coarseness occurs 〇: Either voids or roughness occurs, but it is at a level that cannot be determined visually, and can be determined with an optical microscope (300x magnification) △: voids and coarseness occurs, but it is a level that cannot be visually determined and can be determined with an optical microscope (magnification of 300 times) ×: voids and roughness that can be visually determined

[Evaluation 4: Blocking]
The two-component developer was charged into the developing unit of the above-mentioned commercial copier, and 30,000 sheets (600 sets of 50 sheets in succession) of originals with a coverage rate of 1% were printed on A4 size recording paper. At that time, it was confirmed whether or not blocking occurred due to aggregation of toner in the developing unit, and the blocking was evaluated according to the following criteria.
◎: No blocking occurred ○: Blocking occurred at 20,000 to less than 30,000 sheets △: Blocking occurred at 10,000 to less than 20,000 sheets ×: Blocking occurred at less than 10,000 sheets

[Evaluation 5: Free rate of silica (primary particle diameter 100 nm or more)]
3 g of capsule toner was weighed into a 100 mL beaker, wetted with 60 ml of a 0.2% aqueous solution of polyoxyethylphenyl ether, and thoroughly stirred. After that, an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, model: US-150E) was used to insert a probe so that the liquid level was 70 ml. The ultrasonic energy was adjusted to 150 W, and ultrasonic waves were applied for 3 minutes. After standing for several hours, the supernatant was removed, 50 ml of pure water was added to the precipitate, and the mixture was stirred for 5 minutes. Next, the sufficiently washed sediment (capsule toner) was subjected to suction filtration using a membrane filter with a pore size of 1 μm, and then vacuum-dried overnight to sufficiently remove moisture.
Twenty capsule toners before and after the treatment were each observed with a scanning electron microscope (SEM), the number of silica particles having a primary particle diameter of 100 nm or more present on the toner surface was measured, and the silica liberation rate was calculated. rate was evaluated according to the following criteria.
◎: Silica liberation rate is less than 20% ○: Silica liberation rate is 20% or more and less than 25% △: Silica liberation rate is 25% or more and less than 30% ×: Silica liberation rate is 30% or more

[Comprehensive evaluation]
The evaluation results of evaluations 1 to 5 are scored as 3 points for "◎", 2 points for "○", 1 point for "△", and 0 points for "×". was comprehensively evaluated on the basis of
◎: 12 points (very good)
○: 11 points (good)
△: 10 points (actually usable)
×: Less than 10 points or including “×” in any evaluation (cannot be used in practice)
Tables 1 and 2 show the main constituent materials and physical properties of the produced capsule toner, as well as the results of measurement and evaluation.

Tables 1 and 2 show the following.
(1) The capsulated toners of the present invention (Examples 1 to 26) exhibit less external additive detachment than conventional toners (Comparative Examples 1 to 17), resulting in poor image quality due to deterioration in transferability and carrier contamination. (2) In the capsule toner of Comparative Example 1, since the peak P1 on the low molecular weight side of GPC of the resin fine particles is low, image sticking occurs, and the image quality is stable over a long period of time. The capsulated toner of No. 2 has a high peak P1, so that the adhesion of the external additive is weak and the transferability is poor. The capsulated toner of Comparative Example 4 has a high peak P2, so the adhesion of the external additive is weak and the transferability is poor. Since the ratio P1/P2 of the peak P1 on the low molecular weight side and the peak P2 on the high molecular weight side of GPC is low, image sticking occurs. (5) In the capsule toners of Comparative Examples 7 and 9, since the molecular weight of the fine resin particles was low, the coating layer was soft and seizure occurred. Since the toner has a high molecular weight resin fine particle, the coating layer is hard and transferability is poor.

P1 first peak P2 second peak 100 capsule toner 101 toner base particles (core toner)
102 Coating layer (shell layer)
103 Colorant 104 Release agent

201 Rotary stirrer (filming device)
202 powder flow path 203 rotary stirring means (rotary stirring section)
203a A portion of the rotary stirring means 203 that is the longest from the axis of the rotating shaft member 212 205 Through hole 206 Powder input section 207 Powder recovery section 208 Stirring section 208a One surface of the stirring section 208 in the axial direction 208b Stirring section 208 208c The surface of the stirring part 208 on the other side in the axial direction 209 Powder flowing parts 210, 211 Opening 212 Rotating shaft member 213 Disk-shaped rotating disk 214 A plurality of stirring blades A200 Cutting face line

Claims (8)

A toner base particle containing a binder resin, a colorant, and a release agent, a coating layer formed from fine resin particles covering the surface of the toner base particle, and an external additive externally added to the surface of the coating layer. A capsule toner comprising at least
In the average molecular distribution by gel permeation chromatography, the resin constituting the coating layer has a first peak (P1) in the range of mass average molecular weight Mw 3000 to 5000 and a second peak in the range of mass average molecular weight Mw 50000 to 500000 ( P2) and their peak intensity ratio P1/P2 is 0.2 to 3.0. 2. The capsule toner according to claim 1, wherein the fine resin particles forming the coating layer have a glass transition point Tg of 55 to 90.degree. 3. The capsule toner according to claim 1, wherein the fine resin particles forming the coating layer have a volume average particle diameter of 0.10 to 0.50 μm. The capsule toner according to any one of claims 1 to 3, wherein the toner base particles have a glass transition point Tg of 40 to 55°C. The capsule toner according to any one of claims 1 to 4, wherein the external additive is one or more inorganic particles containing at least silica particles having an average primary particle size of 100 nm or more. 6. The number ratio of silica particles having a primary particle diameter of 100 nm or more that is liberated when the capsule toner is dispersed in water for 3 minutes at an ultrasonic intensity of 150 W is less than 30%. Capsule toner according to one. A method for producing a capsule toner according to any one of claims 1 to 6,
The composite particles containing the toner base particles and the resin fine particles forming the coating layer are dispersed in an air flow circulating in an annular flow path at a flow rate of 30 m/s or more, and a rotating agitating section provided in the middle of the flow path. A method for producing a capsule toner, comprising a step of obtaining the capsule toner by mechanical treatment. A two-component developer comprising the capsule toner according to any one of claims 1 to 6 and a carrier.

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