Process for producing toner

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for producing a toner used in a process for rendering latent images visible and a recording process of toner-jet system.

2. Related Background Art

A number of methods as disclosed in U.S. Pat. No. 2,297,691, etc. are known as electrophotography. In general, using a photoconductive material, copies are obtained by forming an electrostatic image on the photosensitive member by various means, subsequently developing the latent image by the use of a toner to form a toner image, transferring the toner image to a transfer medium such as paper as occasion calls, and thereafter fixing the toner image onto the transfer medium by the action of heat, pressure or solvent vapor. As methods for developing the latent image by the use of toners or methods for fixing the toner image, a variety of methods have been proposed, and methods suited for the respective image forming processes are employed.

Toners used for such purpose have commonly been produced by melt-kneading colorants comprising dyes and/or pigments, into thermoplastic resins to effect uniform dispersion, followed by pulverization using a fine grinding mill, and the pulverized product is classified using a classifier to produce toners having the desired particle diameters.

Reasonably good toners can be produced by such a production method, but there is a certain limit, i.e., a limit to the range in which toner materials are selected. For example, colorant-dispersed resin compositions must be brittle enough to be pulverizable with ease by means of an economically feasible production apparatus. However, such colorant-dispersed resin compositions made brittle in order to meet these requirements tend to result in a broad particle size distribution of the particles formed when actually pulverized at a high speed, particularly causing a problem in that fine particles tend to become included in the particles in a relatively large proportion. Moreover, toners obtained from such highly brittle materials tend to be further pulverized or powdered when used for development in copying machines. Also, in this method, it is difficult to uniformly disperse solid fine particles of colorants or the like in the resin, and some toners cause an increase in fog, a decrease in image density and a lowering of color mixing properties or transparency of toners at the time of image formation, depending on the degree of dispersion. Accordingly, care must be taken when colorants are dispersed. Also, colorants may separate and cause rupture sections of pulverized particles, and may cause fluctuations in developing performance of toners.

Meanwhile, in order to overcome the problems of the toners produced by such pulverization, toners produced by suspension polymerization are proposed as disclosed in Japanese Patent Publication No. 36-10231, No. 43-10799 and No. 51-14895. In the process for producing toners by suspension polymerization, a polymerizable monomer, a colorant and a polymerization initiator, and also optionally a cross-linking agent, a charge control agent and other additives are uniformly dissolved or dispersed to form a polymerizable monomer composition. Thereafter, this polymerizable monomer composition is dispersed in a continuous phase, e.g., an aqueous medium, containing a dispersion stabilizer, by means of a suitable stirrer and is simultaneously subjected to polymerization to obtain toner particles having the desired particle diameters.

Since this method has no step of pulverization, the toner particles are not required to be brittle, and hence soft materials can be used, and also the step of classification can be omitted, bringing about a great cost reduction effect such as energy saving, time reduction and improvement in process yield.

Toners themselves are also required to be made multi-functional because of copying machines and printers being made in recent years to have a high quality image, to enable full-color formation and to enjoy energy saving. For example, accompanying the achievement of high image quality, it is required to make toner particles have very small particle diameter so as to be adaptable to high-resolution digital systems. Accompanying the achievement of full-color formation, it is desired to improve transparency of OHP images; and accompanying the achievement of energy saving, it is desired to make a shape of toner particles that is effective for incorporating low-softening substances in toners and for improving transfer efficiency to transfer materials so as to be adaptable to low-temperature fixing. As a means for satisfying such requirement, toners produced by polymerization are used.

Meanwhile, suspension polymerization, including toners produced by suspension polymerization, react such that the polymerization causes increases in viscosity. Such increases, which are magnified as polymerization progresses make it difficult for radicals and polymerizable monomers to move, and hence polymerizable monomer components tend to remain in a large quantity. Especially in the case of suspension polymerization toners, components having a possibility of restraining the polymerization reaction, such as dyes, pigments (in particular, carbon black), charge control agents and magnetic materials are typically present in the polymerizable monomer system in relatively large amounts in addition to the polymerizable monomers, and hence more unreacted polymerizable monomers tend to remain.

If components acting as solvents for not only polymerizable monomers, but also binder resins are present in the resulting toner particles in a large quantity, the resulting toners have a low fluidity to make image quality poor and also cause a reduction in blocking resistance. Besides the performances correlating directly with toners, such components may also cause, in addition to the phenomenon of adhesion of toner to photosensitive member (drum), a problem exhibited during deterioration of a photosensitive member, namely memory ghost and faint images, especially when organic materials are used in the photosensitive member. Further, there is a problem that the polymerizable monomer components volatilize at the time of fixing to cause a bad smell.

In order to solve such problems, it is proposed, as disclosed in Japanese Patent Application Laid-Open No. 7-92736, to reduce polymerizable monomers present in toner particles to a residue of 500 ppm or less so that image quality can be improved.

With miniaturization and personal use of copying machines, printers and so forth, the restrictions on apparatus increases; the burden to solve the above problems increases and the concern for environment is greater. Thus, the polymerizable monomers should preferably be made present in toner particles in a residue of 200 ppm or less, and more preferably in a residue of 100 ppm or less.

As a method for providing the polymerizable monomers present in toner particles in a residue of 200 ppm or less, a known means for accelerating the consumption of polymerizable monomers may be used when binder resins are produced by suspension polymerization. For example, as methods for removing unreacted polymerizable monomers, there is a method in which toner particles are washed with a highly volatile organic solvent not capable of dissolving toner binder resins but capable of dissolving polymerizable monomers and/or organic solvent components; a method in which they are washed with an acid or alkali; a method in which a foaming agent and a solvent component not capable of dissolving polymers are put into the polymer system and the resulting toner particles are made porous so that the area for the inner polymerizable monomers and/or organic solvent components to evaporate can be larger; and a method in which polymerizable monomers and/or organic solvent components are evaporated under drying conditions. The method in which polymerizable monomers and/or organic solvent components are evaporated under drying conditions is most preferred because in other methods the toner constituent components may dissolve out because of their poor encapsulation in toner particles and it is difficult to select solvents taking into account the undesired retention of the solvents in the toner.

Improvements have been made on drying toner particles after suspensions, formed upon completion of polymerization reaction, have been solid-liquid separated. For example, Japanese Patent Application Laid-Open No. 63-124055 discloses a method of drying toner particles while suspending them by gas to form a fluidized bed. Japanese Patent Application Laid-Open No. 4-311966 and No. 8-179562 also disclose a method of drying toner particles by means of a fluidized bed dryer.

The above method of drying toner particles by means of a fluidized bed dryer can dry toner particles efficiently. Since, however, the unreacted polymerizable monomers stated above commonly have a higher boiling point than water, they can not effectively be removed unless the removal of water has almost been completed. Namely, they can not effectively be removed unless, upon lapse of a constant rate period of drying, the falling-rate drying has sufficiently taken place. However, once the water has been removed, particles having chargeability like the toner particles may adhere to fluidizing chamber wall surfaces, and the particles having adhered to the fluidizing chamber wall surfaces may further come off in masses, causing problems in that the unreacted polymerizable monomers are removed non-uniformly on the whole and the toner particles are formed in a low yield.

Japanese Patent Application Laid-Open No. 6-324517 also discloses a method of instantaneously drying toner particles after a suspension formed upon completion of polymerization reaction has been solid-liquid separated or while dispersing the suspension as it is, in the form of powder particles in a hot air stream so as to be carried in parallel to the hot air stream.

This method of drying toner particles by a hot air stream enables removal of water efficiently and continuously. However, the unreacted polymerizable monomers stated above can not be substantially removed by instantaneous drying.

Japanese Patent Application Laid-Open No. 8-160662 discloses a method of drying toner particles by means of a vacuum dryer.

This drying method, however, not only requires a very long drying time in order to remove water by evaporation and thereafter further remove the unreacted polymerizable monomers but also, when the water is removed, the vacuum in the apparatus may cause toner particles to tighten and agglomerate to form a compressed state. This compressed state is formed significantly when the water content becomes 5% by weight or less, because of an abrupt increase in agglomerative force acting between particles which is caused by an increase in powder temperature. The formation of this compressed state causes toner particles to adhere or melt-adhere to, e.g., apparatus wall surfaces and agitating blades in the apparatus, so that the apparatus is inhibited from stable operation. Also, the agglomeration of toner particles causes powder lumps, so that external additives do not adhere uniformly to toner particle surfaces when externally added in a post-toner preparation step, to cause a problem in the performance required as developers.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process for producing a toner, having solved the problems discussed above.

More specifically, an object of the present invention is to provide a toner production process in which toner particles obtained directly by polymerization are dried in a good efficiency while removing unreacted polymerizable monomers uniformly.

Another object of the present invention is to provide a process for producing a toner which can form images with a high image quality, free of any faulty images otherwise caused by the remaining unreacted polymerizable monomers.

To achieve the above objects, the present invention provides a process for producing a toner, comprising the steps of;

polymerizing a polymerizable monomer composition containing at least a polymerizable monomer and a colorant, in an aqueous dispersion medium to form colored polymer particles, and thereafter washing the colored polymer particles, followed by dewatering to prepare wet colored polymer particles;

subjecting the resultant wet colored polymer particles to substantial removal of the water held by the wet colored polymer particles, by means of a dryer making use of hot air to obtain toner particles; and

drying the toner particles under reduced pressure by means of a vacuum dryer so that polymerizable monomers remaining in the toner particles come to be in a residue of 200 ppm or less.

The present invention also provides a process for producing a toner, comprising the steps of;

polymerizing a polymerizable monomer composition containing at least a polymerizable monomer and a colorant, in an aqueous dispersion medium to form colored polymer particles, and thereafter washing the colored polymer particles to prepare a slurry containing wet colored polymer particles;

subjecting the slurry containing wet colored polymer particles to substantial removal of the water held therein, by means of a dryer making use of hot air to obtain toner particles; and

drying the toner particles under reduced pressure by means of a vacuum dryer so that polymerizable monomers remaining in the toner particles come to be in a residue of 200 ppm or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic illustration showing an example of a system of an apparatus used in the present invention for instantaneously drying the drying target (wet particles or slurry) while dispersing it in the form of powder particles in a high-velocity hot air stream and forwarding them in parallel to the hot air stream.

FIG. 2

is a cross-sectional view showing an example of a vacuum dryer used in the present invention and a system of the dryer.

FIG. 3

is a cross-sectional view showing another example of a vacuum dryer used in the present invention and a system of the dryer.

FIG. 4

is a diagrammatic transverse cross-sectional view showing a fluidized bed dryer to which mechanical vibration is added, as used in Example 4.

FIG. 5

is a diagrammatic view showing cross sections of toner particles encapsulated with a low-softening substance.

FIG. 6

is a diagrammatic view of a dryer for drying toner particles while forming a fluidized bed, used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As a result of extensive studies, the present inventors have discovered that a toner from which unreacted polymerizable monomers remaining in toner particles have been removed up to a residue of 200 ppm or less can be obtained in a good efficiency by subjecting wet colored polymer particles to removal of the aqueous dispersion medium by means of a dryer making use of hot air, followed by drying by means of a vacuum dryer.

In the case of the fluidized bed dryer used in the conventional polymerization toner production process, in order to remove unreacted polymerizable monomers up to a residue of 200 ppm or less, drying must be continued also after the water has been removed up to 0.1% by weight (as water content) and, as stated previously, once the water has been removed, particles having chargeability like the toner particles may adhere to fluidizing chamber wall surfaces, and the particles having adhered to the fluidizing chamber wall surfaces may further come off in masses, to cause problems that the unreacted polymerizable monomers are removed non-uniformly on the whole, resulting in a low performance as developers and a low operability.

In the case when toner particles are dried by vacuum drying from the beginning, it takes a very long time for the drying and also the powder lumps due to the agglomeration of toner particles may occur when the water is removed. Once the powder lumps have occurred, external additives do not adhere uniformly to toner particle surfaces when externally added in a post step, to cause a problem in the performance required as developers. Also, it is difficult to remove from the interior of agglomerate powder lumps the unreacted polymerizable monomers remaining in the particles, making toner particles non-uniform to cause the problems as stated above.

The present invention will be described below in greater detail.

In the toner production process of the present invention, wet colored polymer particles obtained by polymerizing a polymerizable monomer composition or a slurry containing the wet colored polymer particles is/are used as a drying target. When the former wet colored polymer particles are used as the drying target, such wet colored polymer particles having not dried may preferably have a water content of 40% by weight or less, and more preferably 30% by weight or less, in view of fluidity required as a powder. The “water content” herein referred to is meant to be water content by weight, i.e., the proportion of water weight based on the total weight (the sum of weight of dried toner particles and weight of water), and is determined by weight loss on heating at 105° C.

The toner particles having such a water content can readily be obtained by usual means of solid-liquid separation (e.g., filtration). In order to attain such a water content, toner particles may also be subjected to preliminary drying.

In the present invention, the drying target is dried first by means of a dryer making use of hot air. This step is a step aiming at substantial removal of the water held in the drying target. The drying target may preferably be dried until its water content comes to be from 0.1 to 0.5% by weight, and more preferably from 0.1 to 0.3% by weight. In the case when the drying target is dried so that its water content comes to be from 0.1 to 0.5% by weight, the particles can be kept from agglomerating and from adhering to wall surfaces of the dryer. Moreover, the time necessary for the step making use of a vacuum dryer, taken after this step, can be shortened to enable efficient production of toners.

As the dryer making use of hot air, usable are a dryer which dries wet particles while suspending them and forming a fluidized bed, and an apparatus which dries the drying target instantaneously while dispersing it in the form of powder particles in a high-velocity hot air stream and forwarding them in parallel to the hot air stream.

The apparatus which dries wet particles while forming a fluidized bed may include an apparatus as shown in FIG.

6

. The apparatus as shown in

FIG. 6

has a cylindrical form on the whole, and is constituted of a fluidizing air blowing chamber

51

having a hot-air inlet

61

, a grating plate

52

for rectifying a gas, upper and lower fluidizing chambers

53

and

54

in which a fluidized bed of particles and gas is formed, a filter

56

for capturing the particles, and an exhaust chamber

55

having an exhaust vent

62

, which are provided along the gas flow path. The exhaust vent

62

is connected to an exhaust blower, through which the gas is drawn out.

The drying target is fed into the upper fluidizing chambers

54

through its feed opening

63

and a dried product is taken out through a take-out opening

64

of the lower fluidizing chamber

53

.

The drying carried out using this drying apparatus is operated, e.g., in the following way: The drying target particles fed into the fluidizing chamber

54

are blown up by the hot air fed from the fluidizing air blowing chamber

51

and introduced via the grating plate

52

, and are fluidized together with the gas. The drying target particles suspended inside the fluidizing chambers

53

and

54

to form a fluidized bed are uniformly mixed with the gas and are dried at the interior of this fluidized bed.

The drying target particles blown up into the upper fluidizing chamber

54

are captured by the filter

56

, where, e.g., a back-wash pulse may be applied to this filter, thus the drying target particles are brushed off to return downward.

The apparatus which dries the drying target (slurry or wet particles) instantaneously while dispersing it in the form of powder particles in a high-velocity hot air stream and forwarding them in parallel to the hot air stream may include an airborne dryer having a loop type drying pipe

2

as shown in

FIG. 1

, but not particularly limited thereto.

In the airborne dryer shown in

FIG. 1

, compressed air heated to a prescribed temperature in a hot-air-stream generator

1

is jetted out at a supersonic speed at an air stream dispersion section

3

to disperse the drying target fed from a drying target feed unit

6

. The drying target is dried in the loop type airborne drying pipe

2

instantaneously (in 0.5 to 10 seconds). A gas draw-out opening

4

is provided inside the loop type airborne drying pipe

2

, whereby the drying target is classified into a dried product and an undried product by the Coanda effect, and the dried product is separated from the air stream by a cyclone

5

and can be taken out of the system through a take-out opening

7

.

Coarse particles in the particles having come out of the drying pipe

2

may be separately classified by a classifier and may be returned to the drying target feed unit

6

so that only particles having particle size within a prescribed range are fed to the cyclone

5

to obtain the desired toner particles, whereby classification and drying can be carried out continuously. Incidentally, as the type of the drying pipe of the airborne dryer, in addition to the above loop type, any type of drying pipes may be used, including a straight pipe type, a type in which the middle barrel is enlarged in order to elongate the residence time, and a type in which swirl movement is imparted to particles to prevent them from depositing on the horizontal pipe bottom part. Particularly preferred is the airborne dryer having the loop type drying pipe as shown in FIG.

1

.

In the apparatus which dries the drying target while forwarding it in parallel to high-velocity hot air stream, compressed air heated to 40 to 150° C., and preferably 60 to 120° C., may preferably be used as the hot air stream. Heated-air temperature lower than 40° C. may result in a low drying efficiency, and that higher than 150° C. may cause melt-adhesion of toner, thus such temperatures are not preferable.

The apparatus preferably used in the present invention which dries the drying target (slurry or wet particles) instantaneously while dispersing it in the form of powder particles in a high-velocity hot air stream and forwarding them in parallel to the hot air stream may specifically include Flash Jet dryer (manufactured by Seishin Kigyo K.K.) and Flash dryer (manufactured by Hosokawa Micron K.K.)

As for the vacuum dryer used in the present invention, which is used after the aqueous dispersion medium has substantially been removed, any apparatus may be used without any particular limitations so long as it can dry colored polymer particles in the state of vacuum or reduced pressure. In the case when the polymer particles are dried using such an apparatus, polymerizable monomers remaining in the polymer particles can preferably be removed simultaneously with the water. For example, vacuum dryers embodied as shown in

FIGS. 2 and 3

as diagrammatic side views may preferably be used. In such reduced pressure (vacuum drying, a high pressure results in less volatiles and a low drying efficiency. Accordingly, the drying may preferably be carried out at 13 kPa or below.

In the present invention, the polymerizable monomers remaining in toner particles may be in a residue of 200 ppm or less, preferably 150 ppm or less, and particularly preferably 100 ppm or less.

When the drying for removing such polymerizable monomers is carried out using the vacuum dryer alone, the agglomeration of particles comes into question as stated previously. However, in the present invention, the water held by the polymer particles has first been removed by the dryer making use of hot air, and hence the particles can be kept from agglomeration.

The vacuum dryers embodied as shown in

FIGS. 2 and 3

, which are of agitation type, are described below in detail.

In the dryer shown in

FIG. 2

, drying target particles are fed into a drying vessel

32

having the shape of an inverted cone and dried there. The drying vessel

32

is provided therein with a screw type agitation member

35

connected, via a drive arm

34

, with a drive unit

33

disposed above the vessel

32

, and is so set up that the agitation member

35

circles along the inner periphery of the vessel

32

while being rotated. Thus, in the dryer shown in

FIG. 2

, the drying target particles inside the vessel

32

are repeatedly agitated and dispersed while being brought upward from the lower part, and hence the drying target particles are agitated and mixed in a good efficiency throughout the interior of the vessel

32

.

As shown in

FIG. 2

, the vessel

32

is also provided at the upper part thereof with a material feed opening

36

for feeding the drying target particles, and an exhaust vent

37

for drawing out the gas inside the vessel

32

when the inside of the vessel is evacuated and also when dried under reduced pressure while feeding the gas. Then, the material feed opening

36

is fitted with a hermetic cover

16

, and a bag filter

10

is connected with the exhaust vent

37

. At the lower part of the dryer, a take-out opening

38

for taking out a dried product is provided in the manner it is connected with a take-out valve

39

. When the inside of the vessel

32

is evacuated, the gas inside the vessel

32

is drawn out by means of a vacuum pump

28

through the exhaust vent

37

via the bag filter

10

and a cold trap

20

.

As shown in

FIG. 2

, around the drying vessel

32

, a jacket

11

is also provided which can appropriately control the internal temperature of the drying vessel

32

so as to carry out the drying at the desired temperature. For this purpose, a gap is formed between the outer wall of the drying vessel

32

and the inner wall of the jacket

11

, and the jacket

11

is provided with a steam feed opening

12

, a cooling water feed opening

13

and a steam or cooling water discharge opening

14

so that heating steam or cooling water can be passed through the gap. Then, a steam generating boiler (not shown) is connected to the steam feed opening

12

, and a cooling water pump

15

is connected to the cooling water feed opening

13

.

The drying vessel

32

is also provided with steam injection openings

17

at the upper and lower two positions of the vessel

32

, and is so set up that the materials can effectively be agitated with the injection of steam by feeding the steam in a large quantity from the lower-side steam injection opening

17

. These steam injection openings

17

are both connected to a steam generating boiler

19

via an accumulator

18

. This accumulator

18

is a means for feeding saturated or superheated steam quickly into the vessel

32

, and is indispensable for completing the heating of materials in the vessel

32

in a short time and bringing the materials to an optimum drying temperature.

As stated previously, when the inside of the vessel

32

is evacuated, the gas inside the vessel

32

is drawn out by means of the vacuum pump

28

through the exhaust vent

37

via the bag filter

10

and the cold trap

20

. As shown in

FIG. 2

, the inside of the bag filter

10

is partitioned by a partition plate

21

into upper and lower two chambers. Then, a cylindrical filter cloth

22

is hung from the partition plate

21

on its lower side. On the upper side of the partition plate

21

, an exhaust vent

23

connected to the cold trap

20

and a washing nozzle

24

is provided at the center upper position of the filter cloth

22

. The washing nozzle

24

is a means for intermittently jetting high-pressure air sent from a compressor

25

, to wash the filter cloth

22

by back pressure. An accumulator

27

is also attached between a filter

26

and the washing nozzle

24

. This accumulator

27

is provided so that any shortage of high-pressure air feed quantity on the side of the compressor

25

can be compensated to feed the high-pressure air in a constant quantity to the washing nozzle

24

in a stable state with less pressure variations, and also the flow rate and passing speed of the air passing through the filter

26

can be kept substantially constant to stabilize the effect of filtration by the filter

26

.

When dried under reduced pressure while feeding a gas, the gas is fed into the drying vessel

32

from a gas introducing opening

30

provided at the lower part of the apparatus. The drying under reduced pressure while feeding a gas can keep toner particles from blocking, which tends to occur at the lower part in the apparatus, and also the gas acts as a carrier gas for evaporating deposited water or residual polymerizable monomers from the material particle surfaces in a good efficiency. Thus, in view of an improvement of efficiency, it is preferable to feed the gas.

The gas fed into the drying vessel

32

becomes a moistened gas containing the water and residual polymerizable monomers originating from material particles, and is drawn out of the back filter

10

via the exhaust vent

23

. Then, the moistened gas thus drawn out is sent into the cold trap

20

and the liquid such as water formed by condensation is discharged as a drain from the cold trap

20

. Meanwhile, the gas component is drawn outside by means of the vacuum pump

28

connected to the cold trap

20

. To the cold trap

20

, a pump

29

for sending cooling water is connected so that the moistened gas can be cooled to effect gas-liquid separation in a good efficiency.

As for the dryer shown in

FIG. 3

, it is so set up that a ribbon blade

40

of double-helical structure is rotatable by means of a drive unit

33

provided at the upper part of a drying vessel

32

having the shape of an inverted cone. As being set up in this way, the drying target inside the vessel

32

is repeatedly agitated and dispersed while being brought upward from the lower part, and hence the drying target is agitated and mixed in a good efficiency throughout the interior of the vessel

32

. The construction of other constituents of the dryer shown in

FIG. 3

is common to that of the vacuum dryer shown in

FIG. 2

, and the description on such constituents is omitted.

The vacuum dryer preferably used in the present invention, which is used after the aqueous dispersion medium has substantially been removed, may specifically include Nauta mixer (manufactured by Hosokawa Micron K.K.), Ribocone (manufactured by Ohkawara Seisakusho K.K.) and SV mixer (manufactured by Shinko Panteck K.K.).

As the toner produced by the present invention, a toner having a smaller particle diameter is preferred in order to develop more minute latent-image dots for the achievement of high image quality. Stated specifically, preferred is a toner having a weight-average particle diameter of from 4 to 8 μm and a coefficient of variation of number distribution of 35% or less, as measured with a Coulter counter.

A toner having a weight-average particle diameter smaller than 4 μm may remain on the photosensitive member or intermediate transfer member in a large quantity as transfer residual toner because of a poor transfer efficiency to cause uneven images due to fog and faulty transfer, and is not preferable as the toner in the present invention. A toner having a weight-average particle diameter larger than 8 μm tends to cause its melt-adhesion to members, and this tends greatly when the coefficient of variation of number distribution of the toner is more than 35%.

The coefficient of variation of number distribution of the toner is calculated according to the following expression.

Coefficient of variation, (%)={(standard deviation of number distribution)/(number average particle diameter)}×100

In the toner production process of the present invention, the suspension polymerization disclosed in Japanese Patent Publication No. 36-10231 and Japanese Patent Application Laid-Open No. 59-53856 and No. 59-61842 may be used.

In the present invention, what is called seed polymerization may also preferably be used in which monomers are additionally adsorbed on polymer particles once obtained, and thereafter polymerized using a polymerization initiator.

In the present invention, from the viewpoint of fixing performance, it is necessary for the toner particles to be incorporated with a low-softening substance in a large quantity, and hence it is inevitably necessary to encapsulate the low-softening substance in shell resin. As a specific method by which the low-softening substance is encapsulated, a low-softening substance whose material polarity in an aqueous medium is smaller than the main polymerizable monomer may be used and also a small amount of resin or polymerizable monomer with a greater polarity than the main monomer may be added. Thus, toner particles having a core/shell structure wherein the low-softening substance is covered with the shell resin can be obtained. The particle size distribution and particle diameter of the toner particles may be controlled by a method in which the types and amounts of a slightly water-soluble inorganic salt and a dispersant having the action of protective colloids are changed, or by changing mechanical apparatus conditions, e.g., the conditions for agitation, such as the peripheral speed of a rotor, pass times and the shape of agitating blades, the shape of the reaction vessel, or the concentration of solid matter in the aqueous medium.

Whether or not the toner particles have he core/shell structure can be ascertained by observing cross sections of toner particles. Stated specifically, the cross sections of toner particles can be observed in the following way. Toner particles are well dispersed in a room temperature curing epoxy resin, followed by curing in an environment of temperature 40° C. for 2 days, and the cured product obtained is dyed with triruthenium tetraoxide optionally in combination with triosmium tetraoxide. Thereafter, samples are cut out in slices by means of a microtome having a diamond cutter to observe the cross sections of toner particles using a transmission electron microscope (TEM). In the present invention, it is preferable to use the triruthenium tetraoxide dyeing method in order to form a contrast between the materials by utilizing some difference in crystallinity between the low-softening substance used and the resin constituting the shell. A typical example is shown in FIG.

5

. It has been observed that toner particles produced in Examples given later have the structure wherein the low-softening substance is clearly encapsulated with the shell resin.

As the polymerizable monomer usable in the polymerization toner, it is preferable to use styrene monomers such as styrene, o-, m- or p-methylstyrene, and m- or p-ethylstyrene; acrylic or methacrylic acid ester monomers such as methyl acrylate or methacrylate, ethyl acrylate or methacrylate, propyl acrylate or methacrylate, butyl acrylate or methacrylate, octyl acrylate or methacrylate, dodecyl acrylate or methacrylate, stearyl acrylate or methacrylate, behenyl acrylate or methacrylate, 2-ethylhexyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, and diethylaminoethyl acrylate or methacrylate; and vinyl monomers such as butadiene, isoprene, cyclohexene, acrylo- or methacrylonitrile and acrylic or methacrylic acid amide. Any of these may be used alone, or usually used in the form of an appropriate mixture of monomers so mixed that the theoretical glass transition temperature (Tg) as described in a publication POLYMER HANDBOOK, 2nd Edition III, pp.139-192 (John Wiley & Sons, Inc.) ranges from 40 to 75° C. If the theoretical glass transition temperature is lower than 40° C., problems may arise in respect of storage stability or running stability of the toner. If on the other hand it is higher than 75° C., the fixing point of the toner may become higher. Especially in the case of color toners used to form full-color images, the color mixing performance of the respective color toners at the time of fixing may be unsatisfactory, resulting in a poor color reproducibility, and also OHP images may have a very poor transparency. Thus, such temperatures are not preferable in view of high image quality.

In the present invention, in order to encapsulate the low-softening substance with the shell resin, it is particularly preferable to further add a polar resin in addition to the shell resin. As the polar resin used in the present invention, copolymers of styrene with acrylic or methacrylic acid, maleic acid copolymers, saturated polyester resins and epoxy resins are preferably used. The polar resin may particularly preferably be those not containing in the molecule any unsaturated groups that may react with the shell resin and the polymerizable monomer. If a polar resin having such unsaturated groups is used, cross-linking reaction takes place between the polar resin and the polymerizable monomer that forms the shell resin layer, so that the shell resin comes to have a too high molecular weight for the toners for forming full-color images and is disadvantageous for color mixing performance of four color toners. Thus, such a resin is not preferable.

As the low-softening substance used in the present invention, it is preferable to use a compound showing a DSC (differential scanning calorimetry) main maximum peak value within a temperature range of from 40 to 90° C. as measured according to ASTM D3418-8. If the maximum peak is lower than 40° C., the low-softening substance may have a weak self-cohesive force, undesirably resulting in weak high-temperature anti-offset properties. If on the other hand the maximum peak is higher than 90° C., fixing temperature may become higher to make it difficult to smoothen the fixed-image surface appropriately. This is undesirable in view of color mixing performance. Moreover, in the case when the toner is directly produced by polymerization, if the maximum peak value is at a high temperature, the low-softening substance may precipitate mostly during granulation in the aqueous medium to hinder the reaction of suspension polymerization undesirably.

The temperature of the maximum peak value is measured using, e.g., DSC-7, manufactured by Perkin Elmer Co. The temperature at the detecting portion of the device is corrected on the basis of melting points of indium and zinc, and the calorie is corrected on the basis of heat of fusion of indium. The sample is put in a pan made of aluminum and an empty pan is set as a control, to make measurement at a rate of temperature rise of 10° C./min.

The low-softening substance may specifically include paraffin waxes, polyolefin waxes, Fischer-Tropsch waxes, amide waxes, higher fatty acids, ester waxes, and derivatives of these or grafted or blocked compounds of these, any of which may be used.

Ester waxes having at least one long-chain ester moiety having at least 10 carbon atoms as shown by the following structural formulas are particularly preferred in the present invention as being effective for the high temperature anti-offset properties without impairment of the transparency required for OHP. Structural formulas of typical compounds of specific ester waxes preferred in the present invention are shown below as General Structural Formulas (1) to (3).

Ester Wax General Structural Formula (1)

[R

1

—COO—(CH

2

)

n

&Brketclosest;

a

C&Brketopenst;(CH

2

)

m

—OCO—R

2

]

b

wherein a and b each represent an integer of 0 to 4, provided that a+b is 4; R

1

and R

2

each represent an organic group having 1 to 40 carbon atoms, provided that a difference in the number of carbon atoms between R

1

and R

2

is 10 or more; and n and m each represent an integer of 0 to 15, provided that n and m are not 0 at the same time.

Ester Wax General Structural Formula (2)

[R

1

—COO—(CH

2

)

n

&Brketclosest;

a

C&Brketopenst;(CH

2

)

m

—OH]

b

wherein a and b each represent an integer of 0 to 4, provided that a+b is 4; R

1

represents an organic group having 10 to 40 carbon atoms; and n and m each represent an integer of 0 to 15, provided that n and m are not 0 at the same time.

Ester Wax General Structural Formula (3)

wherein a and b each represent an integer of 0 to 3, provided that a+b is 3 or less; R

1

and R

2

each represent an organic group having 1 to 40 carbon atoms, provided that a difference in the number of carbon atoms between R

1

and R

2

is 10 or more; R

3

represents an organic group having 1 or more carbon atoms; and n and m each represent an integer of 0 to 15, provided that n and m are not 0 at the same time.

The ester wax preferably used in the present invention may preferably be those having a hardness of from 0.5 to 5.0. The hardness of the ester wax is a value obtained by preparing a sample having a cylindrical shape of 20 mm diameter and 5 mm thick and thereafter measuring Vickers hardness by the use of, e.g., a dynamic ultrafine hardness meter (DUH-200) manufactured by Shimadzu Corporation. As measurement conditions, a penetrator's position is moved by 10 μm under a load of 0.5 g at a loading rate of 9.67 mm/sec. Thereafter, it is kept as it is for 15 seconds, and a depression made on the sample is measured to determine Vickers hardness. If the ester wax has a hardness lower than 0.5, the fixing assembly may have a great dependence on pressure and on process speed, tending to make the achievement of high-temperature anti-offset effect insufficient. If on the other hand it has a hardness higher than 5.0, the toner may have a poor storage stability, and the wax itself may also have a weak self-cohesive force, likewise tending to result in insufficient high-temperature anti-offset properties.

As specific compounds, the ester wax may include the following compounds.

In recent years, it has become increasingly necessary to form full-color double-sided images. When such double-sided images are formed, there is a possibility that a toner image first formed on the surface of a transfer medium again passes through the heating section of a fixing assembly also when an image is next formed on the back. Thus, the high-temperature anti-offset properties of the toner must be well taken into account. For this end also, it is essential in the present invention to add the low-softening substance in a large amount. Stated specifically, the low-softening substance may preferably be added in the toner in an amount of from 5 to 40% by weight. Its addition in an amount less than 5% by weight may provide no sufficient high-temperature anti-offset properties. Moreover, the back-side images tend to show the phenomenon of offset when double-sided images are fixed. On the other hand, in an amount more than 40% by weight, the toner particles tend to coalesce one another during granulation, so that those having a broad particle size distribution tend to be produced, and are unsuitable for the present invention.

As the colorant used in the present invention, carbon black, magnetic materials, and colorants toned in black by the use of yellow, magenta and cyan colorants shown below may be used as black colorants.

As a yellow colorant, compounds typified by condensation azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds and allylamide compounds are used. Stated specifically, C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147 and 168 are preferably used.

As a magenta colorant, condensation azo compounds, diketopyropyyrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds and perylene compounds are used. Stated specifically, C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221 and 254 are particularly preferred.

As a cyan colorant, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds and basic dye lake compounds may be used. Stated specifically, C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62 and 66 may be particularly preferably used.

Any of these colorants may be used alone, in the form of a mixture, or in the state of a solid solution. The colorant used in the present invention are selected taking account of hue angle, chroma, brightness, weatherability, transparency on OHP films and dispersibility in toner particles. The colorant may preferably be added in an amount of from 1 to 20 parts by weight based on 100 parts by weight of the resin.

In the case when a magnetic material is used as the black colorant, it may preferably be used in an amount of from 40 to 150 parts by weight based on 100 parts by weight of the resin, which is different from the amount of other colorant.

As a charge control agent used in the present invention, known agents may be used. It is preferable to use charge control agents that are colorless, make toner charging speed higher and are capable of stably maintaining a constant charge quantity. Also, when direct polymerization is used in the present invention, charge control agents having no polymerization inhibitory action and being insoluble in the aqueous system are particularly preferred. As specific compounds, they may include, as negative charge control agents, metal compounds of salicylic acid, naphthoic acid or dicarboxylic acids, polymer type compounds having sulfonic acid or carboxylic acid in the side chain, boron compounds, urea compounds, silicon compounds and carixarene. As positive charge control agents, they may include quaternary ammonium salts, polymer type compounds having such a quaternary ammonium salt in the side chain, guanidine compounds, and imidazole compounds. Any of these charge control agent may preferably be used in a amount of from 0.5 to 10 parts by weight based on 100 parts by weight of the resin. In the present invention, however, the addition of the charge control agent is not essential. In the case when two-component development is employed, the triboelectric charging with a carrier may be utilized, and also in the case when non-magnetic one-component blade coating development is employed, the triboelectric charging with a blade member or sleeve member may be utilized. Hence, the charge control agent need not necessarily be contained in the toner particles.

A polymerization initiator used in the present invention may include, e.g., azo or diazo type polymerization initiators such as

2,2′-azobis-(2,4-dimethylvaleronitrile),

2,2′-azobisisobutyronitrile),

1,1′-azobis-(cyclohexane-l-carbonitrile),

2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile; and peroxide type polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide. The polymerization initiator may usually be used in an amount of from 0.5 to 20% by weight based on the weight of the polymerizable monomers, which varies depending on the intended degree of polymerization. The polymerization initiator may a little vary in type depending on the methods for polymerization, and may be used alone or in the form of a mixture, making reference to its 10-hour half-life period temperature.

In order to control the degree of polymerization, any known cross-linking agent, chain transfer agent and polymerization inhibitor may be further added.

When the suspension polymerization making use of a dispersant is utilized in the polymerization toner according to the present invention, the dispersant used may include, e.g., as inorganic oxides, tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica and alumina. As organic compounds, it may include polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose sodium salt, polyacrylic acid and salts thereof, and starch; which may be dispersed in an aqueous phase when used. Any of the dispersants may preferably be used in an amount of from 0.2 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer.

As these dispersants, those commercially available may be used as they are. In order to obtain fine particles, however, the inorganic compound may be formed in the dispersion medium. For example, in the case of tricalcium phosphate, an aqueous sodium phosphate solution and an aqueous calcium chloride solution may be mixed under high-speed agitation.

In order to make these dispersants finely dispersed, 0.001 to 0.1 parts by weight of a surface-active agent may be used in combination. This is used in order to accelerate the intended action of the dispersant. As examples thereof, it may include sodium dodecylbenzenesulfate, sodium tetradecylsulfate, sodium pentadecylsulfate, sodium octylsulfate, sodium oleate, sodium laurate, potassium stearate and calcium oleate.

In the toner production process of the present invention, the toner particles can be produced specifically by a production process as described below.

A monomer composition comprising polymerizable monomers and added therein the low-softening substance (as a release agent), the colorant, the charge control agent, the polymerization initiator and other additives, having been uniformly dissolved or dispersed by means of a homogenizer or an ultrasonic dispersion machine, is dispersed in an aqueous phase containing the dispersant, by means of a conventional stirrer, a homomixer or a homogenizer. Granulation is carried out preferably while controlling the agitation speed and time so that droplets of the monomer composition can have the desired toner particle size. After the granulation, agitation may be carried out to such an extent that the state of particles is maintained and the particles can be prevented from settling by the acton of the dispersant. The polymerization may be carried out at a polymerization temperature set at 40° C. or above, usually from 50 to 90° C. At the latter half of the polymerization, the temperature may be raised, and also the aqueous medium may be removed in part from the reaction system at the latter half of the reaction or after the reaction has been completed, in order to remove unreacted polymerizable monomers, by-products and so forth which are causative of a smell at the time of toner fixing. After the reaction has been completed, the toner particles formed are collected by washing and filtration, followed by drying. In such suspension polymerization, water may usually be used as the dispersion medium preferably in an amount of from 300 to 3,000 parts by weight based on 100 parts by weight of the polymerizable monomer composition.

The water content referred to in the present invention is, as stated previously, determined by weight loss on heating at 105° C.

The quantity of residual monomers in toner is determined using a sample prepared by dissolving 0.2 g of toner in 4 ml of tetrahydrofuran (THF) and subjecting the sample to gas chromatography (G.C.) to make measurement by the internal standard method under the following conditions.

G.C. conditions

Measuring device: Shimadzu GC-15A (with capillary)

Carrier gas: N

2

, 2 kg/cm

2

, 50 ml/min.

Split ratio: 1:60

Linear velocity: 30 mm/sec.

Column: ULBON HR-1, 50 m×0.25 mm

Amount of sample: 2 μl

Standard substance: Toluene

(1) Particle size distribution of the toner can be measured by various methods. In the present invention, it was measured with a Coulter counter.

As a measuring device, Coulter counter Model TA-II (manufactured by Coulter Electronics, Inc.) is used. An interface (manufactured by Nikkaki K.K.) that outputs number-average distribution and volume-average distribution and a personal computer CX-1 (manufactured by CANON INC.) are connected. As an electrolytic solution, an aqueous 1% NaCl solution is prepared using first-grade sodium chloride.

Measurement is made by adding as a dispersant 0.1 to 5 ml of a surface active agent, preferably alkylbenzene sulfonate, to 100 to 150 ml of the above aqueous electrolytic solution, and further adding 2 to 20 mg of a sample to be measured. The electrolytic solution in which the sample has been suspended is subjected to dispersion for about 1 minute to about 3 minutes in an ultrasonic dispersion machine. The values are determined by measuring the particle size distribution of particles of 2 to 40 μm on the basis of number, by means of the Coulter counter Model TA-II, using an aperture of 100 μm as its aperture.

EXAMPLES

The present invention will be described below in a specific manner by giving Examples.

Example 1

Into 710 parts of ion-exchanged water, 450 parts of an aqueous 0.1 mol/liter Na

3

PO

4

solution was introduced, and the mixture obtained was heated to 60° C., followed by stirring at 3,500 r.p.m. using Kuria mixer (manufactured by Emu Tekunikku K.K.). Then, 68 parts of an aqueous 1.0 mol/liter CaCl

2

solution was added thereto to obtain an aqueous medium containing Ca

3

( PO

4

)

2

.

Meanwhile, a disperse phase was prepared in the following way.

(by weight)

Styrene monomer

170

parts

n-Butyl acrylate

30

parts

Graphitized carbon black

10

parts

Saturated polyester

10

parts

Salicylic acid metal compound

3

parts

Ester wax, Compound (1)

25

parts

(DSC peak temperature: 59.4° C.;

Vickers hardness: 1.5)

(by weight)

Styrene monomer

180

parts

2-Ethylhexyl acrylate

20

parts

C.I. Pigment Blue 15:3

10

parts

Saturated polyester

10

parts

Salicylic acid metal compound

5

parts

Ester wax, Compound (1)

25

parts

Of the above formulation, 100 parts by weight of the C.I. Pigment Blue 15:3, salicylic acid metal compound and styrene monomer were dispersed for 3 hours by means of an attritor (manufactured by Mitsui Miike Engineering Corporation) to obtain a colorant dispersion. Next, the remainder of the above formulation was all added to the colorant dispersion, and these were heated to 60° C. and dissolved and mixed for 30 minutes. To the resultant mixture, 10 parts by weight of a polymerization initiator 2,2′-azobis(2,4-dimethylvaleronitrile) was added to obtain a polymerizable monomer composition.

The polymerizable monomer composition obtained was introduced into the above aqueous dispersion medium to carry out granulation for 15 minutes while maintaining the number of revolution. Thereafter, the high-speed stirrer was changed to a stirrer having propeller stirring blades and the internal temperature was raised to 80° C., where the polymerization was continued for 10 hours at 50 r.p.m. After the polymerization was completed, the slurry was cooled, and dilute hydrochloric acid was added to dissolve the Ca

3

(PO

4

)

2

. Thereafter, the slurry thus treated was filtered, and washed with water to obtain wet colored polymer particles having a water content of 23% by weight. The polymer particles thus obtained had a weight-average particle diameter of 6.5 μm.

Next, the wet colored polymer particles thus obtained, having a water content of 23% by weight, were put into a vibro-fluidized bed dryer having a vertically cylindrical shape as shown in

FIG. 4

, and then dried.

The apparatus as shown in

FIG. 4

has a cylindrical form on the whole, and is constituted of a gas inlet

72

, a grating plate

73

for rectifying a gas, a drying chamber

74

in which a fluidized bed of particles and gas is formed, a filter

75

for capturing the particles, and an exhaust vent

76

, which are provided along the gas flow path.

Two sets of vibrating motors (vibrators)

80

are also assembled to the side walls facing to each other, of the stand supporting the drying chamber at its bottom so that the whole drying chamber can be vibrated. The amplitude of vibration can be adjusted by changing the set angle between unbalance weights set on the both ends of the vibrating motors, and the number of vibration (or frequency) can arbitrarily be set by an inverter.

The drying target is fed into the drying chamber

78

through its feed opening

78

and a dried product is taken out through a take-out opening

79

of the lower fluidizing chamber.

The drying carried out using this drying apparatus is operated, e.g., in the following way: The drying target particles fed into the drying chamber

74

are suspended by the mechanical vibration applied from the vibrating motors

80

and simultaneously blown up by the hot air fed through the gas inlet

72

and introduced via the grating plate

73

, and are fluidized together with the gas. The drying target particles suspended inside the drying chamber

74

to form a fluidized bed are uniformly mixed with the gas and dried at the interior of this fluidized bed.

The drying target particles blown up to the upper part (the exhaust vent

76

side) of the drying chamber

74

are captured by the filter

75

, where, e.g., a back-wash pulse may be applied to this filter, thus the drying target particles are brushed off to return downward.

In the present Example, as drying conditions, a vibration of 25 Hz in frequency and 2.5 mm in amplitude was applied and 50° C. air was blown from the lower part at a linear velocity of 0.2 m/second. The toner particles thus primarily dried were taken out 2 hours later, where their water content was measured to find that it was 0.3% by weight. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 400 ppm. Any powder lumps caused by the agglomeration of toner particles did little occur, and the pass percentage on a sieve with a mesh of 149 μm was 94%.

Next, about 30 kg of the primarily dried toner particles obtained were dried by means of the Nauta type vacuum dryer (Model NXV-1, manufactured by Hosokawa Micron K.K.) in the same manner as in Example 1. Thus, toner particles were produced. At this stage, their water content was 0.1% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 40 ppm. The pass percentage on a sieve with a mesh of 149 μm was 93%.

A toner was prepared and images were reproduced and evaluated in the same manner as in Example 1. As a result, good results were obtained like those in Example 1. Images were also formed on OHP sheets, where images with a good transparency were obtained.

Example 5

Primarily dried toner particles were obtained in the same manner as in Example 1 except that the time for which the wet particles were dried using the fluidized bed dryer was changed to 3 hours. The water content of the toner particles was measured to find that it was 0.1% by weight. The polymerizable monomers remaining in the toner particles were in a content of 310 ppm. The pass percentage on a sieve with a mesh of 149 μm was 92%.

Next, about 30 kg of the primarily dried toner particles obtained were dried for 4 hours by means of the Nauta type vacuum dryer in the same manner as in Example 1. Thus, toner particles were produced. At this stage, their water content was 0.1% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 40 ppm. The pass percentage on a sieve with a mesh of 149 μm was 91%.

A toner was also prepared and images were reproduced and evaluated in the same manner as in Example 1. As a result, good results were obtained like those in Example 1.

Example 6

About 30 kg of the primarily dried toner particles obtained by drying with the fluidized bed dryer for 2 hours in Example 1 were dried using the Nauta type vacuum dryer under the following conditions. Jacket heating temperature: 50° C.; degree of vacuum: 2 to 5 kPa; and drying time: 3 hours while feeding nitrogen gas from the lower part at a rate of 0.5 N liter/min. At this stage, the water content was 0.1% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 30 ppm. Also, the pass percentage on a sieve with a mesh of 149 μm was 96%.

A toner was also prepared and images were reproduced and evaluated in the same manner as in Example 1. As a result, good results were obtained like those in Example 1.

Comparative Example 1

About 40 kg of the wet colored polymer particles obtained in Example 1, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the fluidized bed dryer (Model FBS-5, manufactured by Ohkawara Seisakusho K.K.). As drying conditions, 50° C. air was blown at a linear velocity of 0.4 m/second, and the toner particles were taken out 4 hours later, where their water content was measured to find that it was less than 0.1% by weight. The polymerizable monomers remaining in the toner particles were in a content of 180 ppm, but the powder lumps caused by the agglomeration of toner particles occurred, and the pass percentage on a sieve with a mesh of 149 μm was 85%. Also, a deposit of toner particles was seen on the inner wall of the dryer. This deposit of toner particles was taken out to measure its water content, which was found to be less than 0.1% by weight, and the polymerizable monomers remaining in the toner particles in the deposit were in a content of 310 ppm.

On the toner particles thus obtained, the subsequent procedure of Example 1 was repeated to obtain a toner.

Image reproduction was tested in the same manner as in Example 1. As a result, solid-area blank areas caused by poor transfer occurred after running on about 1,500 sheets, and also faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 4,500th sheet.

Comparative Example 2

The wet colored polymer particles obtained in Example 1, having a water content of 22% by weight, were dispersed over an aluminum pat, and vacuum-dried at 50° C. and a degree of vacuum of 3 kPa. The water content of the particles thus dried 2 hours later was measured to find that it was 12% by weight. The particles were further dried for 16 hours until their water content came to be 0.1% by weight or less. The toner particles obtained had agglomerated in part, and the pass percentage on a sieve with a mesh of 149 μm was 70%. Also, the polymerizable monomers remaining in the toner particles were in a content of 180 ppm.

The toner particles thus obtained were disintegrated, and the subsequent procedure of Example 1 was repeated to obtain a toner.

Images were reproduced and evaluated in the same manner as in Example 1. As a result, solid-area blank areas caused by poor transfer occurred after running on about 500th sheets.

Comparative Example 3

About 30 kg of the wet colored polymer particles obtained in Example 1, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the Nauta type vacuum dryer (Model NXV-1, manufactured by Hosokawa Micron K.K.) with a volume of 100 liters. As drying conditions, jacket heating temperature was set at 50° C. and the particles were dried for 4 hours at a degree of vacuum of 2 to 5 kPa. At this stage, the water content of the toner particles was measured to find that it was 0.3% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 520 ppm. The pass percentage on a sieve with a mesh of 149 μm was 75%.

The toner particles thus obtained were disintegrated and the subsequent procedure of Example 1 was repeated to obtain a toner. Image reproduction was tested in the same manner as in Example 1. As a result, solid-area blank areas caused by poor transfer occurred on about 1,000th sheet, and also faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 2,000th sheet.

Comparative Example 4

About 30 kg of the wet colored polymer particles obtained in Example 1, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the Nauta type vacuum dryer (Model NXV-1, manufactured by Hosokawa Micron K.K.) with a volume of 100 liters. As drying conditions, jacket heating temperature was set at 50° C., and the particles were dried for 7 hours at a degree of vacuum of 2 to 5 kPa. At this stage, the water content of the toner particles was measured to find that it was 0.1% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 190 ppm. The pass percentage on a sieve with a mesh of 149 μm was 70%.

The toner particles thus obtained were disintegrated and the subsequent procedure of Example 1 was repeated to obtain a toner. Image reproduction was tested in the same manner as in Example 1. As a result, solid-area blank areas caused by poor transfer occurred on about 500th sheet.

Comparative Example 5

About 40 kg of the wet colored polymer particles obtained in Example 1, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the fluidized bed dryer (Model FBS-5, manufactured by Ohkawara Seisakusho K.K.). As drying conditions, 50° C. air was blown at a linear velocity of 0.4 m/second, and the toner particles were taken out 6 hours later, where their water content was measured to find that it was 0.1% by weight. The polymerizable monomers remaining in the toner particles were in a content of 70 ppm, but the powder lumps caused by the agglomeration of toner particles occurred, and the pass percentage on a sieve with a mesh of 149 μm was 75%. Also, a deposit of toner particles was seen on the inner wall of the dryer. This deposit of toner particles was taken out to measure its water content, which was found to be less than 0.1% by weight, and the polymerizable monomers remaining in the toner particles in the deposit were in a content of 280 ppm.

The toner particles thus obtained were disintegrated and the subsequent procedure of Example 1 was repeated to obtain a toner.

Image reproduction was tested in the same manner as in Example 1. As a result, solid-area blank areas caused by poor transfer occurred on about 1,000th sheet, and also faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 2,000th sheet.

The results of measurement and evaluation in the foregoing Examples and Comparative Examples are shown in Table 1.

Example 7

Into 710 parts of ion-exchanged water, 450 parts of an aqueous 0.1 mol/liter Na

3

PO

4

solution was introduced, and the mixture obtained was heated to 60° C., followed by stirring at 3,500 r.p.m. using Kuria mixer (manufactured by Emu Tekunikku K.K.). Then, 68 parts of an aqueous 1.0 mol/liter CaCl

2

solution was added thereto to obtain an aqueous medium containing Ca

3

(PO

4

)

2

.

Meanwhile, a disperse phase was prepared in the following way.

(by weight)

Styrene monomer

170

parts

n-Butyl acrylate

30

parts

C.I. Pigment Red 122

10

parts

Saturated polyester

20

parts

Salicylic acid metal compound

3

parts

Ester wax, Compound (1)

25

parts

(DSC peak temperature: 59.4° C.;

Vickers hardness: 1.5)

Of the above formulation, 100 parts by weight of the C.I. Pigment Red 122, salicylic acid metal compound and styrene monomer were dispersed for 3 hours by means of an attritor (manufactured by Mitsui Miike Engineering Corporation) to obtain a colorant dispersion. Next, the remainder of the above formulation was all added to the colorant dispersion, and these were heated to 60° C. and dissolved and mixed for 30 minutes. To the resultant mixture, 10 parts by weight of a polymerization initiator 2,2′-azobis(2,4-dimethylvaleronitrile) was added to obtain a polymerizable monomer composition.

The polymerizable monomer composition obtained was introduced into the above aqueous dispersion medium to carry out granulation for 15 minutes while maintaining the number of revolution. Thereafter, the high-speed stirrer was changed to a stirrer having propeller stirring blades and the internal temperature was raised to 80° C., where the polymerization was continued for 10 hours at 50 r.p.m. After the polymerization was completed, the slurry was cooled, and dilute hydrochloric acid was added to dissolve the Ca

3

(PO

4

)

2

. Thereafter, the slurry thus treated was filtered, and washed with water to obtain wet colored polymer particles having a water content of 22% by weight. The polymer particles thus obtained had a weight-average particle diameter of 6.5 μm.

The wet colored polymer particles obtained were disintegrated and thereafter dried by means of a continuous instantaneous air dryer (Flash Jet dryer FJD-4, manufactured by Seishin Kigyo K.K.). As drying conditions, 90° C. air was blown at a linear velocity of 16.5 m/second, and the wet colored polymer particles were continuously fed at a rate of 20 kg/hr. It took 0.7 second for the drying. The water content of the toner particles thus primarily dried was measured to find that it was 0.1% by weight. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 530 ppm. Any powder lumps caused by the agglomeration of toner particles did not occur, and the pass percentage on a sieve with a mesh of 149 μm was 97%.

Next, about 30 kg of the primarily dried toner particles taken out were dried by means of the Nauta type vacuum dryer (Model NXV-1, manufactured by Hosokawa Micron K.K.) with a volume of 100 liters. As drying conditions, the jacket heating temperature was set at 50° C. and the particles were dried at a degree of vacuum of 2 to 5 kPa for 3 hours while feeding nitrogen gas from the lower part at a rate of 5.0 N liter/min. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 20 ppm. The pass percentage on a sieve with a mesh of 149 μm was 96%.

A photograph of cross sections of the toner particles thus obtained was taken. Its diagrammatic view is shown in FIG.

5

. The toner particles have the structure wherein the low-softening substance, Compound (1), is covered with the shell resin.

Coarse powder in the toner particles obtained was removed by classification. To 100 parts by weight of the toner particles from which the coarse powder was removed, 1.5 parts by weight of hydrophobic silica having a specific surface area of 200 m

2

/g as measured by the BET adsorption method was externally added to obtain a toner.

Using this toner, image reproduction was tested on a modified machine of a color laser jet printer COLOR LASER SHOT 2030, manufactured by CANON INC., in an environment of 23° C./65% RH. As a result, even in 5,000-sheet running, high-quality images were obtained, showing no change in image density between that of initial stage and that after the running and causing no blank areas. Also, any problems such as toner melt-adhesion and memory ghost did not occur on the printer's photosensitive member formed of an organic semiconductor. Double-sided images were also formed, but any offset did not occur on the both sides of transfer materials. Images were also formed on OHP sheets, where images with a good transparency were obtained.

Image reproduction was also similarly tested in an environment of 30° C./80% RH. As a result, good results were obtained similarly.

Example 8

About 30 kg of the primarily dried toner particles obtained in Example 7, dried using the continuous instantaneous air dryer, were dried for 4 hours by means of the same vacuum dryer (Model NXV-1) without feeding nitrogen gas from the lower part and under conditions of a jacket heating temperature of 50° C. and a degree of vacuum of 2 to 5 kPa. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 40 ppm. The pass percentage on a sieve with a mesh of 149 μm was 95%.

On the toner particles thus obtained, the subsequent procedure of Example 7 was repeated to obtain a toner. Also, images were reproduced and evaluated in the same manner as in Example 7. As a result, good results were obtained like those in Example 7.

Example 9

About 20 kg of the primarily dried toner particles obtained in Example 7, dried using the continuous instantaneous air dryer, were put into Ribocone vacuum dryer (Model RD-50, manufactured by Ohkawara Seisakusho K.K.) with a volume of 50 liters, and were dried for 4 hours at 50° C. and a degree of vacuum of 0.7 to 2 kPa to obtain particles. Their pass percentage on a sieve with a mesh of 149 μm was 90%. Also, the polymerizable monomers remaining in the toner particles were in a content of 80 ppm.

On the toner particles thus obtained, the subsequent procedure of Example 7 was repeated to obtain a toner. Also, images were reproduced and evaluated in the same manner as in Example 7. As a result, good results were obtained like those in Example 7.

Example 10

First, the same aqueous dispersion medium as that in Example 7 was prepared.

Meanwhile, a disperse phase was prepared in the following way.

(by weight)

Styrene monomer

180

parts

2-Ethylhexyl acrylate

20

parts

Graphitized carbon black

10

parts

Saturated polyester

10

parts

Salicylic acid metal compound

5

parts

Paraffin wax (m.p. 65° C.;

40

parts

Vickers hardness: 1.6)

Of the above formulation, 100 parts by weight of the graphitized carbon black, salicylic acid metal compound and styrene monomer were dispersed for 3 hours by means of an attritor (manufactured by Mitsui Miike Engineering Corporation) to obtain a colorant dispersion. Next, the remainder of the above formulation was all added to the colorant dispersion, and these were heated to 60° C. and dissolved and mixed for 30 minutes. To the resultant mixture, 10 parts by weight of a polymerization initiator 2,2′-azobis(2,4-dimethylvaleronitrile) was added to obtain a polymerizable monomer composition.

The polymerizable monomer composition obtained was introduced into the above aqueous dispersion medium to carry out granulation for 15 minutes while maintaining the number of revolution. Thereafter, the high-speed stirrer was changed to a stirrer having propeller stirring blades and the internal temperature was raised to 80° C., where the polymerization was continued for 10 hours at 50 r.p.m. After the polymerization was completed, the slurry was cooled, and dilute hydrochloric acid was added to dissolve the Ca

3

(PO

4

)

2

. Thereafter, the slurry thus treated was filtered, and washed with water to obtain wet colored polymer particles having a water content of 23% by weight. The polymer particles thus obtained had a weight-average particle diameter of 6.1 μm.

Next, the wet colored polymer particles thus obtained, having a water content of 23% by weight, were disintegrated and thereafter dried by means of the continuous instantaneous air dryer (Flash Jet dryer FJD-4) in the same manner as in Example 7. As drying conditions, 90° C. air was blown at a linear velocity of 16.5 m/second, and the wet colored polymer particles were continuously fed at a rate of 35 kg/hr. The water content of the toner particles thus primarily dried was measured to find that it was 0.1% by weight. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 650 ppm. Any powder lumps caused by the agglomeration of toner particles did not occur, and the pass percentage on a sieve with a mesh of 149 μm was 96%.

Next, about 30 kg of the primarily dried toner particles were dried by means of the Nauta type vacuum dryer (Model NXV-1) in the same manner as in Example 7. As drying conditions, jacket heating temperature was set at 50° C. and the particles were dried at a degree of vacuum of 2 to 5 kPa for 3 hours while feeding nitrogen gas from the lower part at a rate of 5.0 N liter/min. The polymerizable monomers remaining in the toner particles obtained were in a content of 30 ppm. The pass percentage on a sieve with a mesh of 149 μm was 96%. Also, the toner particles had a weight-average particle diameter of 6.1 μm. A photograph of cross sections of the toner particles thus obtained was taken. Its diagrammatic view is shown in FIG.

5

. The toner particles have the structure wherein the low-softening substance is covered with the shell resin.

Coarse powder in the toner particles obtained was removed by classification. To 100 parts by weight of the toner particles from which the coarse powder was removed, 1.2 parts by weight of hydrophobic silica having a specific surface area of 200 m

2

/g as measured by the BET adsorption method was externally added to obtain a toner.

Using this toner, images were reproduced and evaluated in the same manner as in Example 7. As a result, even in 5,000-sheet running, high-quality images were obtained, showing no change in image density between that of initial stage and that after the running and causing no blank areas. Also, any problems such as toner melt-adhesion and memory ghost did not occur on the printer's photosensitive member formed of an organic semiconductor.

Example 11

The slurry obtained in Example 10 after the polymerization was completed was cooled, and dilute hydrochloric acid was added to dissolve the Ca

3

(PO

4

)

2

. Thereafter, the slurry thus treated was filtered, and washed with water. The resultant colored polymer particles standing wet were mixed with water to obtain a slurry containing 25% by weight of colored polymer particles.

Next, this slurry having been washed was continuously fed to the continuous instantaneous air dryer (Flash Jet dryer FJD-4) at a rate of 5 kg/hr, and 90° C. air was blown at a linear velocity of 16.5 m/second. The water content of the toner particles thus primarily dried was measured to find that it was 0.1% by weight. At this stage, the polymerizable monomers remaining in the toner particles were in a content of 680 ppm. Any powder lumps caused by the agglomeration of toner particles did not occur, and the pass percentage on a sieve with a mesh of 149 μm was 95%.

Next, about 30 kg of the primarily dried toner particles were dried by means of the Nauta type vacuum dryer (Model NXV-1) in the same manner as in Example 10. The polymerizable monomers remaining in the toner particles obtained were in a content of 70 ppm. The pass percentage on a sieve with a mesh of 149 μm was 95%.

On the toner particles thus obtained, the subsequent procedure of Example 10 was repeated to obtain a toner. Also, images were reproduced and evaluated in the same manner as in Example 10. As a result, good results were obtained like those in Example 10.

Comparative Example 6

To 100 parts by weight of the primarily dried toner particles obtained in Example 7 using the continuous instantaneous air dryer (water content: 0.1% by weight; content of the polymerizable monomers remaining in the toner particles: 530 ppm), 1.5 parts by weight of hydrophobic silica having a specific surface area of 200 m

2

/g as measured by the BET adsorption method was externally added to obtain a toner.

Image reproduction was also tested in the same manner as in Example 7. As a result, solid-area blank areas caused by poor transfer occurred after running on about 500 sheets, and a decrease in image density was seen after running on about 2,000 sheets. Also, faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 1,500th sheet.

Comparative Example 7

About 40 kg of the wet colored polymer particles obtained in Example 7, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the fluidized bed dryer (Model FBS-5, manufactured by Ohkawara Seisakusho K.K.). As drying conditions, 50° C. air was blown at a linear velocity of 0.4 m/second, and the toner particles were taken out 4 hours later, where their water content was measured to find that it was 0.1% by weight. The polymerizable monomers remaining in the toner particles were in a content of 180 ppm, but the powder lumps caused by the agglomeration of toner particles occurred, and the pass percentage on a sieve with a mesh of 149 μm was 85%. Also, a deposit of toner particles was seen on the inner wall of the dryer. This deposit of toner particles was taken out to measure its water content, which was found to be 0.1% by weight, and the polymerizable monomers remaining in the toner particles in the deposit were in a content of 310 ppm.

On the toner particles thus obtained, the subsequent procedure of Example 7 was repeated to obtain a toner.

Image reproduction was also tested in the same manner as in Example 7. As a result, solid-area blank areas caused by poor transfer occurred after running on about 1,500 sheets, and also faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 4,500th sheet.

Comparative Example 8

About 30 kg of the wet colored polymer particles obtained in Example 7, having a water content of 22% by weight, were disintegrated and thereafter dried by means of the Nauta type vacuum dryer (Model NXV-1) with a volume of 100 liters. As drying conditions, jacket heating temperature was set at 50° C., and the particles were dried for 4 hours at a degree of vacuum of 2 to 5 kPa. At this stage, the water content of the toner particles was measured to find that it was 0.3% by weight, and the polymerizable monomers remaining in the toner particles were in a content of 290 ppm. The pass percentage on a sieve with a mesh of 149 μm was 75%.

The toner particles thus obtained were disintegrated and the subsequent procedure of Example 7 was repeated to obtain a toner.

Image reproduction was also tested in the same manner as in Example 7. As a result, solid-area blank areas caused by poor transfer occurred on about 1,000th sheet, and a decrease in image density was seen after running on about 4,000 sheets. Also, faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 3,000th sheet.

Comparative Example 9

To 100 parts by weight of the primarily dried toner particles obtained in Example 10 using the continuous instantaneous air dryer (water content: 0.1% by weight; content of the polymerizable monomers remaining in the toner particles: 650 ppm), 1.2 parts by weight of hydrophobic silica having a specific surface area of 200 m

2

/g as measured by the BET adsorption method was externally added to obtain a toner.

Image reproduction was also tested in the same manner as in Example 10. As a result, solid-area blank areas caused by poor transfer occurred after running on about 500 sheets, and a decrease in image density was seen after running on about 2,000 sheets. Also, faulty images due to the melt-adhesion of toner to photosensitive member occurred in the environment of 30° C./80% RH on about 2,000th sheet.

Data of the drying conditions and dried products of Examples and Comparative Examples are shown in Table 2.

TABLE 1

After fluidized bed drying

After vacuum drying

(primary drying)

(secondary dryinq)

Drying

Water

Monomer

Pass per-

Drying

Water

Monomer

Pass per-

time

content

residue

centage

time

content

residue

centage

(hrs)

(wt. %)

(ppm)

(wt. %)

(hrs)

(wt. %)

(ppm)

(wt %)

Remarks

Example

1

2

0.3

450

96

4

0.1

50

95

2

1.5

0.7

610

97

5

0.1

90

95

3

2

0.3

450

96

4

0.1

120

90

4

2

0.3

400

94

4

0.1

40

93

5

3

0.1

310

92

4

0.1

40

91

6

2

0.3

450

96

3

0.1

30

96

Compar-

ative

Example

4

<0.1

180

85

—

—

—

—

1

(0.1)*

(310)*

2

—

—

—

—

18

0.1

180

70

3

—

—

—

—

4

0.3

520

75

4

—

—

—

—

7

0.1

190

70

5

6

<0.1

70

75

—

—

—

—

(0.1)*

(280)*

* Value in parentheses is that in toner deposit.

(1): 5000-sheet running: OK

(2): Solid-area blank areas occurred after running on 1,500 sheets.

(3): After drying, toner particles had to be disintegrated because of partial agglomeration, and solid-area blank areas occurred after running on 500 sheets.

(4): After drying, toner particles had to be disintegrated because of partial agglomeration, and solid-area blank areas occurred after running on 1,000 sheets.

(5): Solid-area blank areas occurred after running on 1,000 sheets.

TABLE 2

Example 7

Drying target: Wet colored polymer particles with a water content of 22 wt. %

Primary drying conditions:

Hot-stream drying; hot stream: 90° C., 16.5 m/sec.; drying target: 20 kg/hr;

drying time: 0.7 seconds

Primary dried product:

Water content: 0.1 wt. %; residual monomers: 530 ppm; sieve pass percentage: 97%

Secondary drying conditions:

Vacuum drying; heating temperature: 50° C.; degree of vacuum: 2-5 kPa;

N

2

gas: 5.0 N lit/min; drying time: 3 hours

Secondary dried product:

Residual monomers: 20 ppm; sieve pass percentage: 96%

Example 8

Drying target: (the same as Example 7)

Primary drying conditions: (the same as Example 7)

Primary dried product: (the same as Example 7)

Secondary drying conditions:

Vacuum drying; heating temperature: 50° C.; degree of vacuum: 2-5 kPa;

N

2

gas: not fed; drying time: 4 hours

Secondary dried product:

Residual monomers: 40 ppm; sieve pass percentage: 95%

Example 9

Drying target: (the same as Example 7)

Primary drying conditions: (the same as Example 7)

Primary dried product: (the same as Example 7)

Secondary drying conditions:

Vacuum drying; heating temperature: 50° C.; degree of vacuum: 0.7-2 kPa;

drying time: 4 hours

Secondary dried product:

Residual monomers: 80 ppm; sieve pass percentage: 90%

Example 10

Drying target: Wet colored polymer particles with a water content of 23 wt. %

Primary drying conditions:

Hot-stream drying; hot stream: 90° C., 16.5 m/sec.; drying target: 35 kg/hr;

drying time: 0.7 seconds

Primary dried product:

Water content: 0.1 wt. %; residual monomers: 650 ppm; sieve pass percentage: 96%

Secondary drying conditions:

Vacuum drying; heating temperature: 50° C.; degree of vacuum: 2-5 kPa;

N

2

gas: 5.0 N lit/min; drying time: 3 hours

Secondary dried product:

Residual monomers: 30 ppm; sieve pass percentage: 96%

Example 11

Drying target: Slurry containing 25 wt. % of colored polymer particles

Primary drying conditions:

Hot-stream drying; hot stream: 90° C., 16.5 m/sec.; drying target: 5 kg/hr;

drying time: 0.7 seconds

Primary dried product:

Water content: 0.1 wt. %; residual monomers: 680 ppm; sieve pass percentage: 95%

Secondary drying conditions: (the same as Example 10)

Secondary dried product:

Residual monomers: 70 ppm; sieve pass percentage: 95%

Comparative Example 6

Drying target: (the same as Example 7)

Primary drying conditions: (the same as Example 7)

Primary dried product: (the same as Example 7)

Secondary drying: (none)

Comparative Example 7

Drying target: Wet colored polymer particles with a water content of 22 wt. %

Primary drying conditions:

Fluidized bed drying; air: 50° C., 0.4 m/sec.; drying time: 4 hours

Primary dried product:

Water content: 0.1 wt. %; residual monomers: 180 ppm (310 ppm in deposit);

sieve pass percentage: 85%

Secondary drying: (none)

Comparative Example 8

Drying target: (the same as Comparative Example 7)

Primary drying: (none)

Secondary drying conditions:

Vacuum drying; heating temperature: 50° C.; degree of vacuum: 2-5 kPa;

drying time: 4 hours

Secondary dried product:

Residual monomers: 290 ppm; sieve pass percentage: 75%; water content: 0.3 wt. %

Comparative Example 9

Drying target & primary drying: (the same as Comparative Example 10)

Secondary drying: (none)

Number	Date	Country	Kind
10-238056	Aug 1998	JP
10-304816	Oct 1998	JP

Number	Name	Date
5153092	Kao et al.	Oct 1992
5354640	Kanbayashi et al.	Oct 1994
5418109	Kanakura et al.	May 1995
5622802	Demizu et al.	Apr 1997
5885743	Takayanagi et al.	Mar 1999

Number	Date	Country
0 621 511	Oct 1994	EP
0 651 292	May 1995	EP
36-10231	Jul 1961	JP
43-10799	May 1968	JP
51-14895	May 1976	JP
59-053856	Mar 1984	JP
59-061842	Apr 1984	JP
63-124055	May 1988	JP
4-311966	Nov 1992	JP
6-324517	Nov 1994	JP
7-092736	Apr 1995	JP
8-160662	Jun 1996	JP
8-179562	Jul 1996	JP

Process for producing toner

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

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Abstract

Description

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Priority Claims (2)

US Referenced Citations (5)

Foreign Referenced Citations (13)