JP3417180B2 - Electrophotographic toner and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrophotography containing a binder resin, a colorant and a release agent for developing an electrostatic latent image and a magnetic latent image in electrophotography, electrostatic recording and the like. And a method for manufacturing the same.

[0002]

2. Description of the Related Art An electrophotographic toner is obtained by melt-kneading a binder resin, a colorant, a release agent and, if necessary, a charge control agent, cooling and solidifying, and then pulverizing and classifying. Furthermore, if necessary, a mixing process for adhering and fixing a fluidity-imparting agent, a charge control agent, a cleaning aid, a transfer aid, etc. on the toner surface and a sieving process for removing coarse powder are further provided. . In addition, after the sieving process or the like, a spheroidizing process may be provided in order to reduce the adhesive force of the toner, that is, to improve the powder fluidity, the developing property, and the transfer property.

In the toner, it is indispensable that the colorant, the release agent, the charge control agent and the like components are uniformly and finely dispersed in the binder resin. Due to the recent demand for full color and high image quality. Therefore, the higher dispersion has been required. The mixing degree and dispersibility of the colorant and the release agent inside the toner are almost determined in the melt-kneading step in the production of the toner. The dispersibility is the most important and essential parameter that affects the quality of the toner such as fluidity, chargeability, fixability, and interaction with the photoconductor.

For example, if the above-mentioned constituents are unevenly distributed in the binder resin due to poor dispersion or uniform dispersion but a large dispersion unit, a coloring agent, a release agent, and a charging agent are formed in the pulverizing step after melt-kneading. Since the toner is pulverized while the control agent and the like are unevenly distributed or the dispersion unit is large, a toner having a non-uniform composition is produced. Further, when the dispersion is remarkably poor, particles having only a single component or particles having a composition uneven distribution are mixed in the toner, which causes broadening of the charge distribution and further reverse polarity. Further, since the toner is pulverized in the state of being exposed or released on the surface of the toner, the powder fluidity of the toner is remarkably reduced, which causes filming on the photoconductor.

When the unevenly distributed particles are a releasing agent, not only the charging property is remarkably different but also the particles are not transferred inside the copying machine. Therefore, the particles are rubbed by a cleaning blade to form film on the photosensitive member, the developing roller and the charging plate. Rubbing between them causes fibrous scratches on the developing roll. In addition, if the dispersion is very poor, the release agent is exposed to the toner surface a lot, which deteriorates the powder fluidity, reproduces a low concentration due to a toner dispensing defect, and further causes an admix defect (existing inside the developing machine). (Additional defects such as poor mixing between the developer and the additional toner and poor charging) occur, causing toner spillage and stains inside the machine.

When the unevenly distributed particles are colorants, not only the charge distribution becomes very broad, but also admix failure occurs, causing fog and stains inside the machine. In addition, in the case of color toner, not only the saturation is lowered, but also the desired color tone is not obtained, and the transparency is deteriorated. In full color, color reproducibility and graininess are fatal image quality defects. Furthermore, when the colorant is magnetic powder, free magnetic powder is generated from the aggregate of magnetic powder and the uneven distribution of magnetic powder, which damages the surface of the photoconductor in the copying machine and holds it on the developer carrier. However, there is a risk of causing defects such as uneven density gradually.

Recently, high quality, high reliability, and high speed have become the mainstream in all copying machines and printers.
Demands for toners include reduction in particle size and sharpening of particle size distribution. When the toner has a smaller particle size, it is required that the dispersion unit of each component, the uniformity, and the particle size distribution are further superior to those of the conventional toner.

As a kneading device for dispersing these colorants and release agents in the binder resin, a screw, a rotor,
A Banbury mixer, a pressure kneader, and an extruder having one or more rotary shafts such as rolls are used, but from the viewpoint of improving continuous productivity such as high productivity and cost reduction, a continuous screw type kneader (Extruder) is mainly used.

Usually, a continuous screw type kneader used for producing toner is a combination of a feed screw section for feeding raw materials and a kneading section for mainly kneading, and two screw shafts are provided. A cylindrical inner wall called a barrel or a chamber surrounds the inner wall of the inner wall. The heating / cooling barrel can be heated / cooled with a heater, water, oil, etc., and the chamber dedicated to cooling can be cooled with water, etc.

The continuous screw type kneader usually has two screws, and some of them rotate in the same direction and some of them rotate in different directions. In particular, when a colorant or a release agent is highly dispersed, a high shear can be applied, so that a raw material self-heating type melt kneader equipped with a cooling chamber and a counter-rotating screw is preferably used. In a device using a co-rotating screw, the viscosity of the raw material becomes too low, so that a high shear cannot be given and high dispersion cannot be achieved.

As a method of increasing the viscosity of the raw materials to obtain a high shear, there is a method of adding water during kneading (Japanese Patent Laid-Open No. 6-58242).
1-50624). According to this method, the resin temperature during kneading is about 10 to 60 ° F (about 5.6 to 33.
3 ° C.), and dispersion can be improved. However, even if this method is adopted, it is possible to sufficiently improve the dispersibility of raw materials simply by adding water, as compared with a raw material self-heating type melt-kneader equipped with a cooling chamber and a counter-rotating screw. I can't.

In a raw material self-heating type melt-kneader equipped with a cooling chamber and a counter-rotating screw, a toner raw material is supplied from a feed port and sent to a kneading section by a feed screw. The kneading part is composed of a feeding blade that tries to send the raw material to the discharge side and a returning blade that tries to return the raw material.The kneading part is caused by the pressure for the returning and the shearing force in the clearance part of the kneading screw and the chamber. Receives a high share, undergoes self-heating, melting, kneading, and is then discharged.

The kneading temperature at this time has a great influence on the dispersion quality of the colorant and the release agent in the toner. If the kneading temperature is high, the viscosity of the raw material becomes too low to apply sufficient shear. As a result, both the colorant and the release agent have large dispersion units, and if the kneading temperature is too low, the wettability of the binder resin deteriorates, and the colorant and the release agent cannot be sufficiently wetted. As a result, the aggregate is discharged from the kneader as it is or in a state of being unevenly distributed in the binder resin. Therefore, even in the raw material self-heating type melt-kneader equipped with the cooling chamber and the counter-rotating screw, the optimum kneading temperature should be maintained in order to obtain high dispersion and to obtain the target dispersion unit. Need to be kneaded.

For adjusting the kneading temperature, conventionally, the screw rotation speed, the kneading time of raw materials, the supply amount, the cooling water amount, the cooling temperature, the amount of water added at the time of kneading, etc. are used. The conventional toner can obtain high dispersibility which cannot be obtained by other kneaders by performing the above adjustment using a raw material self-heating type melt kneader equipped with a cooling chamber and a counter-rotating screw. it can. However, it is not possible to disperse the colorant up to the vicinity of the primary particles, and there is a limit to the dispersion unit in the release agent.

As described above, according to the conventional method, it is still difficult to uniformly finely disperse the release agent that can be applied to the toner having a small particle diameter and to finely disperse the colorant and the like (especially to the vicinity of the primary particles). It is in. Furthermore, when these kneading qualities are developed in a kneader having a large scale, the dispersion becomes more difficult. In the current situation, when the kneading machine is scaled up, even if the desired characteristics are obtained on a small scale, the characteristics cannot be obtained on a large scale.

In particular, due to the recent demands for full color and high image quality, it is desired that the dispersion of the colorant exists in a state closer to that of primary particles. On the other hand, since the particle size of the colorant is smaller and the dispersible colorant is beginning to be used,
When using these raw materials, even a small-scale kneader capable of relatively obtaining a high dispersion cannot disperse up to primary particles, and dispersion in a large-scale kneader is more difficult.

In an attempt to improve the dispersibility by using these raw materials, it has been attempted to use a flushing colorant, knead a masterbatch, or add a dispersant. However, it causes problems such as deterioration in quality, soaring raw materials, and soaring production costs. As described above, in the melt-kneading step, particularly in the conventional kneading techniques, it is necessary to disperse the hardly-dispersion type coloring agent to the vicinity of the primary particles, and further to scale up to improve the productivity. I am in a difficult situation.

[0018]

Therefore, the present invention solves the above-mentioned drawbacks and a method for producing an electrophotographic toner capable of uniformly and finely dispersing a colorant and a release agent in a binder resin. Is to provide. Further, this method is a method that enables application to a large-scale kneading machine for the purpose of high productivity, which is considered difficult at present. Furthermore, the present invention provides a coloring agent, a release agent,
By uniformly and finely dispersing all of the charge control agent and the like, it is intended to provide an electrophotographic toner in which an image having a stable density can be obtained and which does not hinder the photoreceptor.

[0019]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have made possible the solution by adopting the following configuration. (1) In a method of producing a toner for electrophotography by melt-kneading a binder resin and a colorant, kneading having a plurality of kneading screws rotating in different directions and having a means for cooling the chamber inner wall The amount of heat exchange from the inner wall of the chamber to the molten raw material per unit weight is 4.2 × 10
^A method for producing an electrophotographic toner, which comprises melt-kneading by adjusting to ^{5 to} 12.6 × 10 ⁵ J / kg.

(2) The method for producing an electrophotographic toner according to (1) above, wherein the kneading screw comprises a feed blade and a return blade. (3) The clearance between the kneading screw of the kneading machine and the inner wall of the chamber is adjusted within a range of 2.0 to 4.8 mm, and water is added within a range of 0.1 to 7.0 wt% with respect to the kneading supply amount. The method for producing an electrophotographic toner according to (1) or (2) above, wherein the heat exchange amount is adjusted by adding the toner.

(4) The length M of the kneading screw consisting of the raw material conveying part and the kneading part in the kneading machine, the length L of the kneading part, and the diameter D of the kneading part.
, L = 0.4M to 0.7M, and L / D = 3
(1) or (2), which has a relationship of
Alternatively, the method for producing the electrophotographic toner according to (3).

(5) Between the crest (radius of the maximum diameter part) and the antinode (radius of the minimum diameter part) of the blade of the kneading screw of the kneader, the crest: antinode = 1: 0.50 to 0.75 The method for producing an electrophotographic toner according to any one of the above items (1) to (4), which has a relationship. (See Figure 4)

(6) The kneading machine is adjusted so that the shear rate γ defined below falls within the range of 200 to 1200, and the shear strain S defined below is 5000 to 5,000.
The method for producing a toner for electrophotography according to any one of the above (1) to (5), characterized in that the toner is adjusted to fall within the range of 30,000. γ = (π · D · N) / h × 60 (where D is the diameter of the kneading portion, N is the rotation speed of the kneading screw, and h is the clearance between the kneading screw and the inner wall of the chamber) S = γ × H (In the formula, H is the kneading time)

(7) An electrophotographic toner manufactured by the manufacturing method described in any one of (1) to (6) above.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall explanatory view of a raw material self-heating type kneader equipped with a counter-rotating screw used in the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG. It is a figure for demonstrating the relationship between a kneading screw and a chamber. The kneading screw consists of a screw part that conveys the raw material, and a kneading part that mainly mixes the raw material with a strong shearing force.The kneading part feeds the raw material to the discharge side and the raw material. It consists of return vanes that try to return, and they are surrounded by a cylindrical inner wall called a chamber. In the kneading machine of FIG. 1, two kneading screws are used in combination, and they are rotated in opposite directions. There is a gap between the tip of the screw of the kneading portion and the inner wall of the chamber, which is called a tip clearance portion. In addition, the inside of the chamber has a structure in which water, brine cooling water, or the like flows, so that the melted raw material can be cooled.

As shown in FIG. 1, the toner raw material is fed from the feed port and sent to the kneading section by the feed screw, and is melted by self-heating due to the strong pressure of the return blade and the strong shearing force of the rotation of the screw. It The melted raw material is further subjected to strong shearing due to rotation of the screw in the tip clearance portion in the latter half of the feeding blade to the returning blade portion, so that the colorant, the release agent and the like are uniformly and finely dispersed. The temperature of the kneading resin at this time is
It is kept constant by heat generated by shearing and heat absorption from the chamber and screw. The present inventors have found that this kneading resin temperature, particularly the amount of heat absorbed from the chamber, has a great influence on the dispersion of the colorant and the release agent, and completed the present invention.

The kneading resin temperature is preferably in the range of + 20 ° C. to + 100 ° C. with respect to the melting temperature of the binder resin. When the melting temperature of the binder resin is lower than + 20 ° C., the viscosity of the resin is too high, and the coloring agent and the release agent are difficult to wet, resulting in insufficient dispersion. On the other hand, when the temperature is higher than the melting temperature of the binder resin + 100 ° C., the viscosity of the resin becomes too low, and thus the kneading shearing force is hard to be applied, the coloring agent and the release agent do not disperse, and the resin itself decomposes. May cause Further, when adjusting the temperature of the kneaded product in the next step, the operation of cooling to the desired temperature becomes uneconomical.

When the amount of heat absorbed from the chamber is replaced with the amount of heat exchange per unit weight of the raw materials to be kneaded, 4.2 ×
It has been found that the dispersion of the colorant and the release agent is particularly good by adjusting the range of 10 ^{5 to} 12.6 × 10 ⁵ J / kg. As described above, by adjusting the amount of heat absorbed from the chamber, it is possible to maintain the viscosity of the binder resin at an appropriately high level, and to provide a sufficient share to disperse the colorant and the release agent to the vicinity of the primary particles. You can When the endothermic amount is outside the above range, the above dispersion cannot be provided. It is presumed that the heat exchange amount is large because, considering a minute portion in the tip clearance portion, the resin viscosity of that portion becomes large and stronger shear is applied.

The heat exchange amount Q per kg of the raw material is the difference between the temperature of the refrigerant supply port and the temperature of the discharge port, the specific heat of the refrigerant, the specific gravity,
The flow rate and the amount of raw material supplied can be measured and calculated from the following formula. Q = C × W × ρ × Δt × (1 / H) where C: refrigerant specific heat [g / kg ° C.] W: refrigerant flow rate [m ³ / hr] ρ: refrigerant specific gravity [kg / m ³ ] Δt: Temperature difference between the inlet and outlet of the chamber [° C] H: Raw material supply [kg / hr]

In the present invention, it has been found that it is effective to adjust the tip clearance and the amount of water added for lowering the temperature of the kneading resin with respect to the amount of heat exchange from the chamber. That is, the tip clearance between the inner wall of the chamber and the kneading screw portion used in the present invention is 2.0.
It is suitable to be in the range of ˜4.8 mm, preferably 2.4 to 4.2 mm. 2.0mm tip clearance
When the value is small, the resin temperature becomes too high, and a feed neck easily occurs. Further, if it is larger than 4.8 mm, it is not possible to bring it into the above range of the heat exchange amount even if the screw rotation speed, the kneading time, the added water amount, the flow rate and the temperature of the chamber cooling water are changed. Tip clearance is 4.
When it is larger than 8 mm, the stirring power of the screw inside the kneading machine decreases, and the contact probability between the resin to be kneaded and the inner wall of the chamber decreases, so that the resin near the inner wall does not sufficiently exchange heat and the resin temperature rises. Therefore, it is estimated that the viscosity of the resin in the tip clearance portion becomes low and a strong shear cannot be applied.

This tip clearance has the same meaning as in the above not only when the diameter of the kneading screw is increased but also when the kneading machine is scaled up. Usually, when a kneader with a large scale is used, the tip clearance is also enlarged proportionately, but such clearance cannot be adjusted to the range of the heat exchange amount of the chamber.

In the present invention, it is preferable to add water during kneading to lower the kneading resin temperature by utilizing latent heat of vaporization. The amount of water added varies to some extent depending on the temperature of the kneading resin, the dispersion unit of the colorant and the release agent, but is 0.1 to 7.0 wt%, preferably 0.3 to 3.0 w with respect to the kneading supply amount.
A range of t% is suitable. If the amount of added water exceeds 7.0 wt%, it will not be completely evaporated and will remain as water particles in the slab after kneading, so adhesion, sticking, and conveyance problems will occur during the crushing process during kneading and further during the crushing process. However, since the amount of water vapor also increases inside the kneading machine, the apparent viscosity of the resin decreases and it becomes impossible to apply a strong shear force. In addition, it becomes difficult to exhaust the water vapor, and the water is returned to the supply side, which easily causes a feed neck. If it is less than 0.1 wt%, the effect of adding water cannot be obtained. The effect of this water addition is to lower the temperature of the kneading resin by the latent heat of vaporization, improve the stirring power of the resin, smooth the heat exchange between the resin and the chamber, and obtain a sufficient share in the minute portion of the tip clearance part. It is speculated that it can be given.

The diameter D of the kneading screw is generally determined by the production scale. The length L of the kneading portion is L = 0.4 with respect to the total screw length M in order to give a sufficient shearing force to the kneading resin and disperse it.
It is necessary to select in the range of M to 0.7M. If it exceeds 0.7M, the length of the raw material feed screw part will become shorter,
The ability to feed the raw material to the kneading section is insufficient, which causes clogging of the supply section, that is, a feed neck, which is not preferable.
On the other hand, if it is less than 0.4 M, the shearing time becomes short and the desired high dispersion cannot be obtained.

Further, the ratio L / D of the length L of the kneading portion of the kneading screw and the diameter D of the kneading screw is appropriately in the range of 3-8, preferably 4-6. If the L / D is less than 3, the kneading time becomes too short, and if the L / D is more than 8, a feed neck is likely to occur. The kneading part is composed of a feed vane and a return vane, and when the feed vane has a length ratio of 1, the return vane has an appropriate range of 0.5 to 2.0.
In particular, the range of 0.75 to 1.5 is more preferable.

The kneading screw used in the present invention is suitably a two-blade or three-blade screw, but the ratio of the length from the center of the ridge of the wing to the center of the abdomen is such that if the ridge is 1, the abdomen is The range of 0.3 to 0.8, especially 0.5 to 0.75 is effective for the dispersion of the colorant up to the vicinity of the primary particles.

In the present invention, the shear rate γ (sec ⁻¹ ) at the time of kneading defined by the following formula is 200 <γ <1200.
It is desirable to adjust it so that it falls within the range. γ = (π · D · N) / (h × 60) [wherein, D is the diameter (mm) of the kneading screw,
N is the rotation speed of the screw (rpm), h is the tip clearance between the kneading screw and the inner wall of the chamber (m
means m). ]

In the kneading of the present invention, it is preferable to adjust the shear strain S defined by the following formula so as to be in the range of 5000 <S <30000, preferably 7000 <S <18000. S = γ × H [In the formula, H means a kneading time (sec), and means a residence time of the raw material in the kneading screw part. ]

Further, it is preferable that a vent port is provided in front of the kneading portion to remove air in the toner raw material to increase the filling rate. By this air bleeding, shearing at the kneading portion can be performed more effectively, and a feed neck can be prevented.

The present invention can be applied to both one-component toner and two-component toner. As the binder resin for the toner, a thermoplastic resin usually used for toner can be used. Specifically, styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isobutylene, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl esters such as vinyl butyrate, and methyl (meth) acrylate. , Ethyl (meth) acrylate, butyl (meth) acrylate, dodecyl (meth) acrylate, octyl (meth) acrylate, (meth)
Α-methylene aliphatic monocarboxylic acid esters such as phenyl acrylate, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether,
Examples thereof include vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone, and homopolymers or copolymers thereof.

Particularly, typical binder resins include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene. -Maleic anhydride copolymer, polyethylene, polypropylene, etc. can be mentioned. further,
Examples thereof include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and paraffin wax.

As the binder resin as described above, one having a structure and a molecular weight such that the melting temperature is in the range of 80 to 150 ° C. is suitable. In particular, styrene / acrylic resins and polyester resins are preferably and positively used.
The melting temperature is 1 × the melt viscosity on the apparent viscosity curve.
It means the temperature at 10 ⁴ Pas. The measurement of melt viscosity is
Using a Shimadzu CFT-500F flow tester, a temperature apparent viscosity curve was determined under the following conditions. Temperature rising rate 3.0 ° C / min Start temperature 80.0 ° C Ultimate temperature 150.0 ° C Measurement interval 3.0 seconds Preheating time 300.0 seconds Cylinder pressure 10.0 kgf / cm ² Die hole diameter 1.0 mm Die length 1.0 mm

As the release agent, paraffins having 8 or more carbon atoms, polyolefins and the like are preferable, and examples thereof include paraffin wax, paraffin latex, microcrystalline wax, low molecular weight polypropylene and low molecular weight polyethylene, which may be used alone or It can be used in combination. The range of the softening point of the release agent is 110 to 1
It is 50 ° C. In the present invention, when two or more releasing agents are used, it is preferable to adjust and set the temperature for the releasing agent having the lowest softening point. The softening point was measured by the JISK2207 softening point test method (ring and ball method).

Examples of the colorant for the toner of the present invention include known colorants such as carbon black, phthalocyanine copper-based cyan colorant, azo-based yellow colorant, azo-based magenta colorant, and quinacridone-based magenta colorant. it can. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate,
Lamp Black, Rose Bengal, CI Pigment Red 48: 1, CI Pigment Red 12: 2, CI Pigment Red 57: 1, CI Pigment Yellow 97, CI Pigment Yellow 12, CI Pigment Blue 15: 1, CI Pigment Blue 15: 3 Etc. can be mentioned.

When used as a magnetic toner,
All or part of the above coloring agent can be replaced with magnetic powder. Examples of the magnetic powder include simple metals such as iron, cobalt and nickel and alloys thereof, Fe ₃ O ₄ , γFe ₂ O ₃ , metal oxides such as cobalt-added iron oxide, Mn-Zn ferrite and Ni-Zn ferrite. What is formed of ferrite is used.

The suitable amount of the magnetic powder used is 20 to 80 wt%, preferably 40 to 60 wt%. Also,
The average particle size of the magnetic powder is suitably in the range of 0.05 to 0.5 μm. Incidentally, in order to impart chargeability and dispersibility, it is also possible to use those subjected to a surface treatment with a titanate coupling agent or a silane coupling agent, but in the present invention, a magnetic powder having no surface treatment is more effective. Is larger.

If necessary, a fluorine-containing surfactant, a salicylic acid metal complex, a metal-containing dye such as an azo metal compound, a polymer acid such as a copolymer containing maleic acid as a monomer component, and a quaternary compound. An azo dye such as ammonium salt or nigrosine may be added.

In the present invention, the above-mentioned binder resin, colorant, release agent and, if necessary, charge control agent are premixed in a mixer,
After kneading by the above kneading method, it is crushed and classified through steps such as rolling, cooling, crushing and crushing. Rolling is usually in the rubber industry,
A roll type roll used in the toner industry is used, and a roll type roll that can be cooled with cooling water, water, brine or the like is used from the viewpoint of adhesion and dispersion. Although the thickness of the rolled slab varies depending on the production scale, the roll gap and the like are generally adjusted to be 1 to 20 mm.

Cooling of the kneading slab includes a type of applying cooling air, a type of immersing in cooling water, a type of sandwiching a rolled slab with a belt, and a type of cooling the upper and lower surfaces of the belt with cooling water or the like. The belt type cooling type is widely used especially from the viewpoint of dispersion of the release agent. For crushing, a jet crusher, a mechanical crusher or the like can be used, but the type thereof does not matter. It is also possible to use an internal collision mechanism or a coarse powder classifier that constitutes a closed circuit. In the classification step, a centrifugal classifier or an inertial classifier can be used. The size of the particles is adjusted by pulverization and classification so as to have a volume average particle size of 3 to 15 μm.

In the toner of the present invention, after classification, an inorganic fine powder such as titania, silica or alumina is used to improve the fluidity characteristics.
It can be added and mixed for the purpose of charge control and improvement of development transferability. The surface of the above-mentioned silica, titania or the like can be treated with a silane coupling agent, a surfactant, a quaternary ammonium salt or the like. Further, if necessary, a substance for improving charge exchange such as carbon black or tin oxide can be used. It is also possible to improve the transfer / developing property by using silica, titania or the like having a large particle size.

Further, if necessary, a cleaning aid such as polystyrene fine particles, polymethylmethacrylate fine particles and polyvinylidene fluoride fine particles may be added.
As the mixer used, all known mixers can be used, and examples thereof include a V-type blender, a Henschel mixer, and a Loedige mixer. Further, the toner of the present invention may be provided with a sieving step for the purpose of removing coarse particles, if necessary. Examples of the sieving machine used include a gyro shifter, an electric sieving machine, and a high bolter.

The toner of the present invention can be used as a magnetic one-component developer containing magnetic powder or as a magnetic two-component developer using a carrier. Alternatively, it can be used as a non-magnetic one-component developer using a colorant or as a non-magnetic two-component developer using a carrier without containing magnetic powder. When used as a two-component developer, as a carrier, iron powder, glass beads, ferrite powder, nickel powder, magnetite powder, or those coated with a resin, resin and a charge control agent are magnetic materials. It is also possible to use a resin dispersion type carrier by kneading and pulverizing and classifying.

[0052]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. [Example 1] Binder resin (styrene / n-butyl acrylate copolymer, copolymerization ratio 85/15, Mw = 130,000, Tg = 60 ° C, melting temperature = 108 ° C) 84 parts by weight carbon black (primary particles Diameter = 0.02 μm) 10 parts by weight Release agent A (polypropylene wax, softening point = 146 ° C.) 5 parts by weight Release agent B (polyethylene wax, softening point = 134 ° C.) 1 part by weight

The above composition was kneaded under the conditions shown in Table 1 using a chamber-cooling type kneading screw counter-rotating raw material self-heating type continuous kneader. The temperature of the kneaded material at the discharge port was 133 ° C., and the amount of heat exchange with the chamber per unit weight of raw material was 9.3 × 10 ⁵ J
It was / kg. The obtained kneaded product was rolled and cooled by a water-cooling type cooling conveyor, and then pulverized and classified to obtain toner particles having a volume average particle size of about 9 μm. As external additives to the toner particles, 0.5% of hexamethyldisilazane-treated silica having an average particle diameter of 16 nm and 0.4% of polymethylmethacrylate resin having an average particle diameter of 0.3 μm are added to the toner weight. Was added and mixed with a 5-liter Henschel mixer (manufactured by Mitsui Miike Koki Co., Ltd.) for 10 minutes to obtain a toner of Example 1. The particle size distribution was measured by Coulter Multisizer II manufactured by Coulter Electronics.

[Examples 2 to 6] and [Comparative Examples 1 to 5] Using the same toner composition as in Example 1, kneading was carried out under the kneading machine and kneading conditions shown in Table 1, and pulverization was carried out under the same conditions as in Example 1. , Classified, mixed and toners of Examples 2 to 6, and Comparative Examples 1 to 5
Toner was obtained.

[0055]

[Table 1]

[Embodiment 7]   Binder resin (polyester resin, Mw = 130,000, Tg = 60 ° C,             Melting temperature = 108 ° C) 83 parts by weight   Colorant (P.I.Blue 15: 3, primary particle size = 0.05 μm) 8 parts by weight   Release agent (polyethylene wax, softening point = 140 ° C) 5 parts by weight

After the above composition was mixed and stirred with a 75 liter Henschel mixer, the chamber cooling type kneading screw counter-rotating raw material self-heating continuous kneader was used under the conditions shown in Table 2. Kneaded The obtained kneaded product was rolled and cooled by a water-cooling type cooling conveyor, and then pulverized and classified to obtain toner particles having a volume average particle size of about 7 μm. 0.8% of isobutyltrimethoxysilane-treated titania having an average particle diameter of 30 nm is added to the toner particles as an external additive, and the mixture is added to a 5 liter Henschel mixer (Mitsui Miike Koki Co., Ltd.) for 10 minutes. The toners of Example 7 were obtained by mixing and further sieving with a vibration type sieving machine.

[Examples 8 to 9] and [Comparative Examples 6 to 8] Using the same toner composition as in Example 7, kneading was performed under the kneading machine and kneading conditions shown in Table 2, and pulverization was performed under the same conditions as in Example 7. , Classified, mixed and toners of Examples 8 to 9 and Comparative Examples 6 to 8
Toner was obtained.

[Comparative Example 9] The same toner composition as in Example 1 was used, and a continuous screw extruder having a twin screw and rotating in the same direction (manufactured by Toshiba Machine Co., Ltd., TEM-
No. 35) was used, and the other conditions were kneaded under the kneading conditions shown in Table 2 and pulverized, classified and mixed under the same conditions as in Example 1 to obtain a toner of Comparative Example 9.

[Comparative Examples 10 to 11] The same toner composition as in Example 7 was used, the same continuous screw extruder as in Comparative Example 9 (TEM-35 manufactured by Toshiba Machine Co., Ltd.) was used, and other conditions are shown in Table 2. The toners of Comparative Examples 10 to 11 were obtained by kneading under the same kneading conditions as shown in (1) and pulverizing, classifying and mixing under the same conditions as in Example 7.

[0061]

[Table 2]

(Preparation of Developer) A silicone resin corresponding to 0.8% by weight of a ferrite core having an average particle diameter of 50 μm was kneaded with a kneader to obtain a coated carrier. 93 parts by weight of this carrier and Examples 1 to 9 and Comparative Examples 1 to 1
7 parts by weight of the toner obtained in 1 were mixed with a V blender to prepare a developer.

(Toner Colorant Dispersion Test) The slab after the toner kneading is 0.3 μm with a cutter such as Mictorome.
The sample was cut into pieces having a thickness of about 5 times and photographed with a transmission electron microscope at a magnification of 5000. The area% of the aggregate of the colorant in the range of 20 cm × 40 cm was measured by an image analyzer having a visual field of 40 μm × 80 μm. Here, as the aggregate, particles having a particle diameter of 0.05 μm or more were counted. The measurement results are shown in Tables 3 and 4. Those having a small amount of agglomerates and an area% value of 2.5% or less were determined to be dispersed up to near the primary dispersion diameter.

(Measurement of toner release agent dispersion diameter (μm))
The slab after kneading the toner is cut into a thickness of about 0.2 μm with a cutter such as Mictorome, and is cut with a transmission electron microscope.
A 000 times photograph was taken, and the particle size (equivalent circle diameter converted from the area) of the release agent in the range of 20 cm × 40 cm was measured with an image analyzer having a visual field of 40 μm × 80 μm. Here, as the release agent, those having a particle size of 0.05 μm or more were counted. The measurement results are shown in Tables 3 and 4. Those having a circle equivalent diameter value of 0.5 μm or less were determined as good dispersion.

(Test for Charging Characteristics of Developer) The developer prepared as described above was used as an A-Color manufactured by Fuji Xerox Co., Ltd.
After applying 635 M / C and copying 200,000 sheets, the charge amount of the developer and its distribution were measured using a charge distribution measuring device. The measurement results are shown in Tables 3 and 4.

(Image quality test, photoreceptor surface observation) The developer prepared as described above was used as an A-Col manufactured by Fuji Xerox Co., Ltd.
An image quality test was conducted by copying 200,000 sheets using or635M / C. In the image quality test, the image density after copying 200,000 sheets and the degree of fog in the background portion were evaluated. As the image density, a Macbeth densitometer was used. In the table, 1.0GS indicates that the original document whose density is 1.0 was used.

The evaluation criteria of the fog in the background part are as follows: ⊚: no fog, ○: almost no fog, Δ: slight fog, ×: fog, xx: extremely bad fog . Further, the surface of the photoconductor after copying 20,000 sheets was observed, and the scratches on the photoconductor due to the adhesion of the developer were visually evaluated. ⊚ indicates that the photoreceptor surface is very good, ∘ indicates that it is good, and x indicates that the surface condition is poor.

[0068]

[Table 3]

[0069]

[Table 4]

(Evaluation Results) The toners obtained in Examples 1 to 9 satisfying the kneading conditions of the present invention have a small area% of the colorant dispersion and a small dispersion diameter of the release agent, and the developer has a charge amount of Since the charge distribution is high and the charge distribution is narrow, it is possible to obtain a good image without damaging the surface of the photoconductor, keeping the image density high, and free from the background portion in the actual machine characteristics. On the other hand, in the toners of Comparative Examples 1 to 11, the area% of the colorant dispersion and the dispersion diameter of the release agent are both large, and these developers have a low charge amount and a wide charge distribution. A low-quality image having a low density and having a gutter in the background portion was formed. Further, many scratches were generated on the surface of the photoconductor.

[0071]

According to the present invention, by adopting the above-mentioned constitution, the viscosity of the raw material can be kept moderately high in the kneading step of toner production, and a strong stirring force of the raw material can be imparted. Reliably disperses the release agent,
It can be miniaturized, and as a result, a high charge amount can be maintained, the charge distribution can be sharpened, high image density can be maintained for a long time, and good image quality without background fog can be obtained. Now you can get stable. Further, the developer according to the present invention can provide an excellent developer which does not hinder the photoreceptor. further,
The transparency in full color is further improved because the dispersed area of the colorant can be reduced.

[Brief description of drawings]

FIG. 1 is an overall explanatory view of a raw material self-heating type kneader equipped with two different-direction rotating screws used in the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is an explanatory diagram showing a relationship between a kneading screw and a chamber.

FIG. 4 is an explanatory diagram of a screw showing a relationship between a crest (radius of a maximum diameter portion) and an antinode (radius of a minimum diameter portion) of a kneading screw of a kneading machine used in the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-269765 (JP, A) JP-A-5-72806 (JP, A) JP-A-58-24406 (JP, A) Actual Kaihei 2- 76020 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (3)

(57) [Claims] 1. A method for producing an electrophotographic toner by melt-kneading a binder resin and a colorant, comprising a plurality of kneading screws rotating in different directions, and means for cooling the inner wall of the chamber. The amount of heat exchange per unit weight of molten raw material from the inner wall of the chamber is
A method for producing a toner for electrophotography, which comprises adjusting to 4.2 × 10 ^{5 to} 12.6 × 10 ⁵ J / kg and melt-kneading. 2. The clearance between the kneading screw of the kneading machine and the inner wall of the chamber is adjusted within a range of 2.0 to 4.8 mm, and 0.1 to 7.0 of water is added to the kneading supply amount.
2. The method for producing an electrophotographic toner according to claim 1, wherein the heat exchange amount is adjusted by adding it in the range of wt%. 3. An electrophotographic toner manufactured by the manufacturing method according to claim 1.