JP2006293159A - Toner for electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for electrophotography whose particle size can be made small, whose durability can be high, and in which no oil can be used. <P>SOLUTION: The toner is manufactured as in follows steps: raw materials including a binder resin, a colorant and a release agent are melted and extruded from a pierced die to form a filiform kneaded body, having a diameter equivalent to that of the toner and the filiform kneaded body is cut or pulverized, wherein the content of the release agent is 5-20 mass% and the melting temperature is regulated to be in the range of (T+40°C) to (T+140°C), wherein T is the softening point (°C) of the release agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner composed of columnar particles.

  Recent electrophotographic technology has high demands for high image quality, high speed, and ecology. The characteristics required for toners used in such electrophotographic technology include a reduction in particle size for high image quality, an improvement in toner durability and low-temperature fixability for high speed, and silicone applied to a metering roll as an ecological measure. One example is the abolition of use of release agents such as oil, that is, oil-less.

  In order to achieve oil-less operation, it is effective to contain a large amount of wax in the toner. However, by increasing the amount of wax, in the pulverized toner, the wax tends to segregate at the pulverization interface. In addition, the durability such as in-machine contamination and fusion of toner deteriorates. Wax segregation also affects image quality degradation.

  As the toner has a smaller particle size (5 to 7 μm), the specific surface area of the toner particles increases, so that the tendency of wax segregation increases. Further, the reduction in toner particle size increases the pulverization energy and increases the cost.

  Conventionally, polyethylene or polypropylene having a melting point of about 100 to 130 ° C. has been used as a release agent internally added to the toner. However, in order to satisfy low temperature fixing and oilless characteristics, the melting point is 100 ° C. or less. It is effective to use a release agent having a low melting point. However, the low-melting-point wax is liable to cause problems in terms of durability as compared with polyethylene and polypropylene.

  On the other hand, compared with pulverized toner, polymerized toner is very advantageous for reducing particle size and adding high concentration of wax, but it has a narrow range of material selection and uses polyester resin suitable for color toner. There are problems such as being unable to do so. In addition, there is a drawback that a large capital investment is required.

  As described above, it is very difficult for conventional pulverized toners to simultaneously achieve the reduction in particle size, high durability, and oilless required for toners.

As a method for efficiently producing toner particles, several methods have been proposed in which raw materials are melted, extruded from a die having a hole, and the resulting kneaded material is cut to produce fine particles (for example, patents). References 1-3). There is also a proposal related to an apparatus for processing toner into a cylindrical shape (see, for example, Patent Document 4).
JP-A-61-20050 JP-A-6-138704 ("Summary", Fig. 1) Japanese Patent Laid-Open No. 2004-332130 (“Summary”, FIG. 1) Japanese Utility Model Publication No. 6-29632 ("Summary", Fig. 1)

  However, none of these proposals are out of the scope of ideas, and are still far from practical use, and no example of actually producing cylindrical toner has been known so far.

  An object of the present invention is to provide an electrophotographic toner that is made under the circumstances as described above, and that enables a reduction in particle size, high durability, and oil-less operation.

  As a result of repeated tests, the toner obtained by a method in which a raw material is melted at a predetermined temperature, extruded from a die having a hole, and a thread-like kneaded material is cut to produce fine particles is conventionally used. It was found that the release agent can be increased without impairing the durability as compared with the toner obtained by the method of kneading and pulverizing with the above twin screw extruder.

  The reason why the toner obtained by the method of cutting or pulverizing the thread-like kneaded material melted at the predetermined temperature does not lose its durability even when the release agent is increased is that the toner melted at the predetermined temperature. When the raw material is formed into a thread shape, the release agent tends to gather at the center of the fiber, and the release agent is not unevenly distributed on the particle surface, which is considered to improve durability.

  As a result, it has become possible to obtain a toner that simultaneously achieves particle size reduction, high durability, and oillessness, which has been difficult in the past.

  That is, in the present invention, a raw material containing a binder resin, a colorant, and a release agent is melted, extruded from a die having a hole, a thread-like kneaded material having a toner equivalent diameter is formed, and then cut or pulverized. In the produced toner, the content of the release agent is 5 to 20% by mass, and the melting temperature is (T + 40 ° C.) to (T + 140 ° C.) when the softening point of the binder resin is T ° C. An electrophotographic toner is provided.

  In the electrophotographic toner of the present invention, a release agent having a melting point of 70 to 100 ° C. can be used. Carnauba wax can be used as such a release agent.

  A binder resin having a softening point of 110 to 150 ° C. can be used. Polyester can be used as such a binder resin.

  The toner for electrophotography of the present invention desirably has an average particle diameter of 5 to 7 μm.

  The electrophotographic toner of the present invention described above controls the elastic developing roller for carrying and transporting the toner on the electrostatic latent image, and the thickness of the toner formed in a thin layer on the elastic developing roller. The toner layer regulating member is used for a developing device in which the toner conveying speed by the elastic developing roller is 100 mm / second or more, and an excellent effect can be exhibited.

  The toner for electrophotography of the present invention was produced by melting a raw material containing a binder resin, a colorant and a release agent, and extruding from a die having a hole to obtain a thread-like kneaded material, followed by cutting. Since the content of the release agent and the melting temperature of the raw material are set within a predetermined range, it is possible to simultaneously achieve the reduction in particle size, high durability, and oilless, which has been difficult in the past. It has become possible.

  The electrophotographic toner according to the embodiment of the present invention will be described below.

  FIG. 1 is a view schematically showing an apparatus for producing a thread-like kneaded material for obtaining an electrophotographic toner according to an embodiment of the present invention. In FIG. 1, a raw material 2 charged into a hopper 1 is melted and kneaded by an extruder 3 and supplied to a die 4. The die 4 includes a spinning port 4a and a hot air discharge port 4b. The melt-kneaded material 5 supplied to the die 4 is discharged from the spinning port 4a together with the hot air from the hot air discharge port 4b, and as a result, a thread-like kneaded material 6 is formed.

  The inner diameter of the die 4 is, for example, 100 μm, and the diameter of the thread-like kneaded product 6 can be adjusted to 6 to 7 μm by changing the raw material supply amount, the discharge pressure, and the hot air temperature.

  At the outlet of the die 4, by blowing cold air to the thread-like kneaded product 6, the thread-like kneaded product 6 can be stably obtained without fusing the thread-like kneaded product.

  Next, the thread-like kneaded material obtained in this way is transported by the conveyor 7, cut or pulverized by a cutting machine or pulverizer (not shown), and further classified, and the electrophotographic toner according to one embodiment of the present invention. Is obtained. In the pulverization, the thread-like kneaded product already has a cross-sectional diameter corresponding to the toner particle diameter, so that the pulverization energy can be suppressed lower than that in the case of producing a normal pulverized toner. Moreover, there is little generation | occurrence | production of a fine powder and a yield and productivity improve.

  In some cases, the classification step can be omitted.

  As described above, the electrophotographic toner according to an embodiment of the present invention is columnar particles obtained by pulverizing and classifying the thread-like kneaded product, and the content of the release agent and the melting temperature of the raw material are set. It is characterized by being limited to a predetermined value. That is, the content of the release agent is set to 5 to 20% by mass, and the melting temperature of the raw material is set to (T + 40 ° C.) to (T + 140 ° C.), preferably (T + 60 ° C.) to (T + 120 ° C.). The temperature is raised to a temperature sufficiently higher than the softening point T ° C. of the resin to lower the melt viscosity of the raw material.

  This temperature is higher than the melting temperature in the kneading step of the conventional pulverized toner. For this reason, molecular cutting of the resin by raising the melting temperature becomes a problem, but this problem can be prevented by selecting a material having a low softening point. Therefore, the parameters of softening point and melt viscosity are important items when selecting materials.

  When the melting temperature of the raw material is less than (T + 40 ° C.), it is difficult to make a toner, and when it exceeds (T + 140 ° C.), it is difficult to make oilless, which is not preferable.

  Moreover, content of a mold release agent is 5-20 mass%, Preferably it is 5-10 mass%. If the content of the release agent is less than 5% by mass, it becomes difficult to make it oilless, and if it exceeds 20% by mass, the durability is inferior, which is not preferable.

  The columnar particles are not limited to a circular cylinder having a circular cross section, and may be an elliptical cross section or a rectangular column having a rectangular cross section.

  The binder resin can be selected from a wide range including known ones. Specific examples include styrene resins such as polystyrene, styrene-acrylic acid ester copolymers, styrene-methacrylic acid copolymers, and styrene-butadiene copolymers, saturated polyester resins, unsaturated polyester resins, and epoxy resins. Phenolic resin, coumarone resin, xylene resin, vinyl chloride resin, polyolefin resin and the like can be exemplified, and two or more of these resins may be used in combination. Of these resins, polyester resins are preferred.

 The amount of the binder resin in the final toner is preferably 50 to 95% by mass.

  Examples of the mold release agent include low polar ones such as low molecular weight polyethylene, low molecular weight polypropylene, and paraffin, and high polar ones such as carnauba wax and ester. In addition, the emulsion type carboxyl group-modified polyolefin is modified to have a carboxyl group with an olefin unit such as ethylene, propylene, butene-1, pentene-1, etc. as a skeleton, and at least a part of the carboxyl group is made of ammonia or amine. It is also possible to use neutralized polyethylene wax, polypropylene wax or the like. Of these waxes, carnauba wax is preferred.

  Examples of the present invention and comparative examples will be shown below to describe the effects of the present invention more specifically. In addition, the measuring device and measuring method of the softening point and glass transition point of the resin used in each example, and the particle diameter of particle | grains are shown below.

Softening point Using a flow tester (CFT-500D, manufactured by Shimadzu Corporation), a sample of 1 g was heated at a heating rate of 6 ° C./min, a 20 kg load was applied, and a sample from a direct nozzle of 1 mm in length and 1 mm in length was used. The temperature at which half of the sample flows out is taken as the softening point (1/2 method).

Particle Size A small amount of sample, purified water, and a surfactant are placed in a beaker, dispersed with an ultrasonic cleaner, and the volume average particle size is measured with Multisizer II (Coulter). The aperture was 100 μm and the count was 50,000.

Example 1
As an internal additive, a colorant C.I. I Pigment Red 57: 1 4% by mass, charge control agent E-84 (salicylic acid-based metal complex: manufactured by Orient Chemical Co., Ltd.) 1 part by weight, release agent “Carnauba wax No. 1 powder” (imported by Kato Yoko Co., Ltd.) A polyester resin having a softening point of 137 ° C. in an amount of 5% by mass and 100 parts by mass as a binder resin was mixed with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.).

  This mixture was melt-kneaded with a kneader having a preset temperature of 200 ° C., extruded from a die having holes, made into a thread-like kneaded product, and then cut to produce colored fine particles. The average particle diameter of the obtained colored fine particles was 6.6 μm.

  As an external additive, 2 parts by mass of “R972” (manufactured by Nippon Aerosil Co., Ltd .: hydrophobic silica) was added to 100 parts by mass of the resulting colored fine particles and mixed with a Henschel mixer to obtain an electrophotographic toner.

Example 2
An electrophotographic toner was obtained in the same manner as in Example 1 except that 10% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Example 3
An electrophotographic toner was obtained in the same manner as in Example 1 except that 20% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Example 4
For electrophotography in the same manner as in Example 1, except that 5% by mass of Fischer-Tropsch wax “Paraflint C77” (imported by Kato Yoko Co., Ltd.) was used in place of “Carnauba wax No. 1 powder” as a release agent. A toner was obtained.

Example 5
An electrophotographic toner was obtained in the same manner as in Example 1 except that 5% by mass of polypropylene wax “NP055” (manufactured by Mitsui Chemicals, Inc.) was used instead of “Carnauba Wax No. 1 Powder” as a release agent. .

Example 6
An electrophotographic toner was obtained in the same manner as in Example 1 except that a die having a large-diameter hole was used and the average particle diameter was 9.0 μm.

Example 7
An electrophotographic toner was obtained in the same manner as in Example 2 except that the kneading machine was set to 180 ° C. (resin softening point + 43 ° C.).

Example 8
An electrophotographic toner was obtained in the same manner as in Example 2 except that the kneading machine was set at 260 ° C. (resin softening point + 123 ° C.).

Comparative Example 1
The same raw materials as in Example 1 were mixed with a Henschel mixer, melt-kneaded with a twin screw extruder, stretched, cooled, and coarsely pulverized with a Rotoplex 2 mm screen (Hosokawa Micron). Next, the mixture was finely pulverized with a collision type pulverizer and classified with an air classifier so that the average particle diameter of the toner was 6.6 μm to obtain colored fine particles.

  The set temperature of the kneader was 150 ° C.

  As an external additive, 2 parts by mass of “R972” (manufactured by Nippon Aerosil Co., Ltd .: hydrophobic silica) was added to 100 parts by mass of the resulting colored fine particles and mixed with a Henschel mixer to obtain an electrophotographic toner.

Comparative Example 2
An electrophotographic toner was obtained in the same manner as in Comparative Example 1 except that 3% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Comparative Example 3
An electrophotographic toner was obtained in the same manner as in Comparative Example 1 except that 2% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Comparative Example 4
For electrophotography in the same manner as in Comparative Example 1, except that 5% by mass of Fischer-Tropsch wax “Paraflint C77” (imported by Kato Yoko Co., Ltd.) was used instead of “Carnauba wax No. 1 powder” as a release agent. A toner was obtained.

Comparative Example 5
An electrophotographic toner was obtained in the same manner as in Comparative Example 1 except that a die having a large diameter hole was used and the average particle diameter was 9.0 μm.

Comparative Example 6
An electrophotographic toner was obtained in the same manner as in Comparative Example 1 except that the kneading was performed at a preset temperature of 200 ° C.

Comparative Example 7
An electrophotographic toner was obtained in the same manner as in Example 1 except that 3% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Comparative Example 8
An electrophotographic toner was obtained in the same manner as in Example 1 except that 25% by mass of “Carnauba wax No. 1 powder” was used as a release agent.

Comparative Example 9
An attempt was made to obtain an electrophotographic toner in the same manner as in Example 2 except that the kneading machine was set at a set temperature of 150 ° C. (resin softening point + 13 ° C.), but the set temperature was too low. In addition, it was not possible to extrude from the die, and toner could not be formed.

Comparative Example 10
An electrophotographic toner was obtained in the same manner as in Example 2 except that the kneading machine was set at 280 ° C. (resin softening point + 143 ° C.).

  The following characteristics of the electrophotographic toners of Examples and Comparative Examples obtained as described above were evaluated.

(Evaluation)
Test 1 (Durability)
A non-magnetic one-component developing device “Casio Page Prest N-5” (manufactured by Casio Computer Co., Ltd .: Color Printer A4, 29 sheets per minute) was loaded with toner and under normal environment (25 ° C., 50% RH) Then, after continuously printing 10,000 sheets of 5% printed images on plain paper (XEROX-P paper A4 size), solid images are printed and image degradation is evaluated.

  At the same time, the doctor blade is removed and the fused state of the toner on the blade is observed.

(Evaluation criteria)
A: No image deterioration is observed, and no toner fusion on the doctor blade is confirmed.

  ○: No image deterioration is observed and there is no practical problem, but toner fusion is observed on the doctor blade.

  X: Image deterioration is observed and there is a problem in practical use. Toner fusion occurred on the doctor blade.

Test 2 (low temperature fixability)
The fixing device of the same apparatus as in Test 1 is modified so that the temperature of the fixing unit can be varied to obtain a fixing tester.

  After obtaining an unfixed image using the same apparatus as in Test 1, the temperature is varied every 10 ° C. within a fixing temperature range of 130 to 200 ° C. with a fixing tester to fix the unfixed image. Is measured as a low-temperature fixing property.

  The fixing temperature here is the set temperature of the upper roll (the heat roll that contacts the toner) of the two upper and lower fixing rolls, and the set temperature of the lower roll (pressure roll) is set to the upper roll of −20 ° C. It was.

The image pattern was solid printing, and the paper was XEROX-P paper A4 size (weight 64 g / m ² ).

(Evaluation criteria)
A: The minimum fixing temperature is less than 140 ° C.

  ○: The minimum fixing temperature is 140 ° C. or higher and lower than 150 ° C.

  X: The minimum fixing temperature is 150 ° C. or higher.

Test 3 (oilless characteristics)
Using the same device as in Test 1, remove the oil application roller from the fixing unit.

  A4 size paper (Xerox-P paper) is used, and a solid image is printed to determine the fixability.

  The process speed is 129.3 mm / sec and the fixing temperature is 150 ° C.

(Evaluation criteria)
A: No offset is generated.

  ○: Occurrence of offset is slight, and there is no practical problem.

  X: Level where occurrence of offset is recognized and problematic in practice.

Test 4 (high quality)
The toner was mounted on a non-magnetic one-component developing device “Casio Page Prest N-5” (manufactured by Casio Computer Co., Ltd .: Color Printer A4, 29 sheets per minute, under normal environment (25 ° C., 50% RH). After 10,000 sheets of 5% print images are continuously printed on plain paper (XEROX-P paper A4 size), halftone images are printed, and image uniformity is evaluated.

(Evaluation criteria)
A: Uniform halftone image without density unevenness.

  ○: Although there is some uneven density, there is no practical problem.

  X: Level in which density unevenness is observed and is problematic in practical use.

The toners according to Examples and Comparative Examples were evaluated for the above characteristics. The results are shown in the table below. In the table, “ΔT” indicates (setting temperature of the kneader—softening point of the binder resin), “Carnauba” of the wax type is Carnauba wax No. 1 powder (melting point 83 ° C.), and “FT” is Fischer-Tropsch Wax (melting point 78 ° C.), “PP” indicates polypropylene wax (melting point 136 ° C.).

  From the results shown in the above table, a raw material containing a binder resin, a colorant, and a release agent is melted, extruded from a die having a hole, and a thread-like kneaded material is obtained and then cut, and then released. It can be seen that the toners according to Examples 1 to 8 in which the content of the agent amount and the melting temperature are set in predetermined ranges satisfy all of durability, low-temperature fixability, oillessness, and image quality.

  On the other hand, in the toners according to Comparative Examples 1 to 6 obtained by the conventional method of pulverizing after biaxial extrusion, the durability was exceeded when the amount of the release agent was 3% by mass or more (Comparative Examples 1, 2, 4 to 6). It is found that the oil-less property is inferior when the amount is less than 2% by mass (Comparative Example 3).

  Further, from the comparison between Examples 4 and 5 and Comparative Example 4, good characteristics were obtained in Examples 4 and 5 even if the type of the release agent was changed, but in Comparative Example 4, the durability was inferior. Yes. From the comparison between Example 6 and Comparative Example 5, although the toner according to Example 6 has good characteristics even when the particle size of the toner is increased to 9.0 μm, the conventional manufacturing method according to Comparative Example 5 is obtained. The toner produced by is inferior in durability.

  From the comparison between Examples 1 to 3, 7 and 8 and Comparative Examples 7 to 9, even when the same production method by cutting the thread-like kneaded material was used, the amount of the release agent was less than 5% by mass (Comparative Example 7 ) Is inferior in oil-less characteristics, and if it exceeds 20% by mass (Comparative Example 8), the durability is inferior. It can be seen that at 280 ° C. exceeding (T + 140 ° C.), the oilless characteristics are poor in (Comparative Example 10).

1 schematically shows an apparatus for producing a thread-like kneaded material for obtaining an electrophotographic toner according to an embodiment of the present invention. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Hopper, 2 ... Raw material, 3 ... Extruder, 4 ... Die, 4a ... Spinning port, 4b ... Hot-air discharge port, 5 ... Melt kneaded material, 6. ..Knitted material, 7 ... conveyor.

Claims (7)

  A toner prepared by melting a raw material containing a binder resin, a colorant and a release agent, extruding from a die having a hole, forming a thread-like kneaded material having a toner equivalent diameter, and then cutting or grinding. The content of the release agent is 5 to 20% by mass, and when the softening point of the binder resin is T ° C., the melting temperature is (T + 40 ° C.) to (T + 140 ° C.). An electrophotographic toner.   The toner for electrophotography according to claim 1, wherein the releasing agent has a melting point of 70 to 100 ° C.   3. The electrophotographic toner according to claim 1, wherein the release agent is carnauba wax.   The toner for electrophotography according to any one of claims 1 to 3, wherein the softening point of the binder resin is 110 to 150 ° C.   The electrophotographic toner according to claim 1, wherein the binder resin is polyester.   6. The toner for electrophotography according to claim 1, wherein the average particle diameter is 5 to 7 [mu] m.   An elastic developing roller for carrying and transporting the toner on the electrostatic latent image; and a toner layer regulating member for regulating the thickness of the toner formed in a thin layer on the elastic developing roller, the elastic developing The toner for electrophotography according to any one of claims 1 to 6, wherein the toner is used in a developing device in which a conveying speed of the toner by a roller is 100 mm / second or more.

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