JP2006301269A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner excellent in transparency, fixability, and durability. <P>SOLUTION: The toner is produced by melting a source material containing a binder resin, a colorant, and a release agent, extruding the material through a die having a hole to form a thread-like kneaded material having an equivalent diameter of the toner, and cutting or pulverizing the product. The softening point T1 of the binder resin (if two or more kinds of binder resins are used, T1 represents the weighted average of them), and the softening point T2 of the toner satisfy the relation of 110°C≤T1≤150°C and 5°C≤T1-T2≤20°C. <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.

  When the toner is classified by the production method, it can be classified into a pulverized toner and a polymerized toner. The pulverized toner is obtained by melting and kneading raw materials, pulverizing with a pulverizer such as a jet mill, and classifying the pulverized toner to a desired particle size using an air classifier or the like. On the other hand, the polymerized toner is roughly classified into an emulsion polymerization method and a suspension polymerization method as its production method. The polymerized toner is grown to an arbitrary particle size by polymerization to obtain fine particles. In this case, the particle shape of the pulverized toner is indefinite, whereas the particle shape of the polymerized toner is spherical.

  As for the particle shape of the electrophotographic toner, a spherical shape is desired from the viewpoint of uniform charging and transferability. However, cleaning that removes toner remaining on the surface of the photoconductor by pressing an elastic blade against the photoconductor. When processing is performed, the spherical toner has a problem that the cleaning property is deteriorated.

  Under such circumstances, a method has been proposed in which various raw materials for toner are melted, extruded and formed into a thread-like kneaded product, and then cut or pulverized to obtain toner fine particles (for example, Patent Document 1). To 3). There is also a proposal related to an apparatus for processing toner into a cylindrical shape (see, for example, Patent Document 4).

  Such a toner production method can be expected to improve the yield and reduce the energy cost as compared with a conventional method using a mechanical pulverizer such as a jet mill. In addition, by setting the diameter of the thread-like kneaded product to a desired value, uniform particles having a narrow particle size distribution width can be obtained, and a toner having stable charging characteristics and developing characteristics can be obtained.

However, in such a toner production method, it is necessary to lower the melt viscosity in order to efficiently extrude the melt from the die. When the melt viscosity is high, clogging occurs in the die, and when the extruded melt is pulled with a roller or the like to form a thread-like kneaded product, the thread-like kneaded product is easily broken.
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)

  As described above, in a method in which various raw materials for toner are melted, extruded and formed into a thread-like kneaded product, and then cut or pulverized to obtain toner fine particles, in order to efficiently extrude the melt from a die Therefore, it is necessary to lower the melt viscosity. Therefore, it is necessary to set the melt temperature high. Specifically, it is necessary to set the melting temperature 20 to 150 ° C., preferably 80 to 120 ° C. higher than the softening point of the binder resin.

  However, at such a high melting temperature, the binder resin undergoes molecular cutting at the time of melting, causing a problem that the thermal characteristics of the toner are greatly changed, for example, the softening point of the toner is lowered. As described above, when the softening point of the toner is lowered, satisfactory fixing properties and durability may not be obtained. Further, if a binder resin having a high softening point is selected in anticipation of a decrease in the softening point of the toner, the transparency of the toner may be lowered.

  The present invention has been made under the circumstances as described above, and an object thereof is to provide an electrophotographic toner excellent in transparency, fixability and durability.

  In order to solve the above problems, the present invention melts a raw material containing a binder resin, a colorant and a release agent, and extrudes it from a die having a hole to form a thread-like kneaded material having a toner equivalent diameter, and then cuts Or a toner prepared by pulverization, wherein the softening point of the binder resin is T1 (in the case of two or more binder resins, the weighted average thereof is T1), and the softening point of the toner is T2. The toner for electrophotography is characterized by satisfying the following formula:

110 ° C ≦ T1 ≦ 150 ° C
5 ° C ≦ T1-T2 ≦ 20 ° C
In the toner for electrophotography of the present invention, desired effects can be obtained by setting the softening point T1 of the binder resin to 110 ° C. to 130 ° C. and the softening point T2 of the toner to 100 ° C. to 120 ° C. A desirable effect can also be obtained when T1 and T2 satisfy the relationship of 0.85 ≦ T2 / T1 ≦ 0.95. Furthermore, it is desirable that the electrophotographic toner of the present invention has a glass transition point of 54 ° C. or higher.

  In addition, the electrophotographic toner of the present invention preferably has a melting temperature of the raw material in the production thereof from T1 + 80 ° C. to T1 + 120 ° C. A polyester resin can be preferably used as the binder resin.

  The toner for electrophotography of the present invention configured as described above preferably has an average particle diameter of 5 to 7 μm.

  The electrophotographic toner of the present invention is configured so that the softening point of the binder resin and the difference between the softening point of the binder resin and the softening point of the toner are within a predetermined range. And durability.

  Hereinafter, an electrophotographic toner according to an embodiment of the present invention will be described.

  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 containing a binder resin, a colorant, and a release agent charged into a hopper 1 is melt-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.

  The toner for electrophotography according to an embodiment of the present invention is a columnar particle obtained by pulverizing and classifying a thread-like kneaded product as described above, and the softening point of the binder resin as described below. T1 is in a predetermined range, and the difference between T1 and the toner softening point T2 is in the predetermined range.

110 ° C ≦ T1 ≦ 150 ° C
5 ° C ≦ T1-T2 ≦ 20 ° C
Examples of the method in which the binder resin and the toner satisfy the above conditions include appropriately adjusting the type of the binder resin, the type and addition amount of the release agent to be blended in the toner, and the melting conditions. Melting conditions include melting temperature.

  The softening point T1 of the binder resin greatly affects the viscosity of the melted raw material. As the softening point T1 of the binder resin is lower, the melting temperature can be lowered, and the influence on the thermal characteristics of the toner can be suppressed. However, if T1 is less than 110 ° C., the toner fixability, durability, and storage stability are deteriorated.

The higher the T1, the higher the melting temperature and the greater the influence on the thermal properties of the toner.
If it exceeds, transparency will deteriorate.

  The binder resin may be a mixture of a plurality of types of resins. In this case, the softening point T1 is a weighted average of the softening points of the respective resins.

  The difference T1-T2 between the softening point T1 of the binder resin and the softening point T2 of the toner is 5 to 20 ° C., preferably 8 to 16 ° C. When T1-T2 is less than 5 ° C., the toner fixability deteriorates, and when it exceeds 20 ° C., the durability of the toner deteriorates.

  The ratio T1 / T2 between the softening point T1 of the binder resin and the softening point T2 of the toner is preferably 0.85 to 0.95. When T1 / T2 is less than 0.85, the durability of the toner tends to deteriorate, and when it exceeds 0.95, the toner fixing property tends to deteriorate.

  In addition, the preferable range of T1 and T2 is 110-130 degreeC for T1, and 100-120 degreeC for T2.

  The binder resin can be selected from a wide range including known ones so as to satisfy the condition of the softening point T1. 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.

  The release agent affects the viscosity of the melt and the softening point of the toner depending on the type and amount of the release agent. In order to obtain a release effect in the fixing roll, it is effective to use a release agent having a low melting point. However, if too much release agent having a low melting point is contained in a large amount, the release agent will enter the binder resin. The dispersion of the toner becomes poor, and the durability of the toner is deteriorated. A preferable content of the release agent is 5 to 20% by mass, and more preferably 5 to 10% by mass. When the content of the release agent is less than 5% by mass, it is difficult to obtain the effect of blending the release agent, and when it exceeds 20% by mass, the durability is inferior, which is not preferable.

  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.

  The melting temperature of the raw material containing the binder resin and the release agent described above is preferably the softening point T1 + 80 ° C. to T1 + 120 ° C. of the binder resin. When the melting temperature is less than T1 + 80 ° C., the viscosity of the melt-kneaded product becomes high and clogging is likely to occur in the die. .

  The columnar particles constituting the toner according to an embodiment of the present invention are not limited to a circular cylinder with a circular cross section, and may be an elliptical cross section or a rectangular column with a rectangular cross section. The average volume particle size is preferably 5 to 7 μm.

  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 apparatus and measuring method of the softening point (T1, T2), glass transition point (Tg1, Tg2), and particle diameter of the resin and toner used in each example are shown below.

Softening point (T1, T2)
Using a flow tester (CFT-500D, manufactured by Shimadzu Corporation), 1 g of sample was heated at a heating rate of 6 ° C./min. The temperature at which half of the sample has flowed out is taken as the softening point (1/2 method).

Glass transition point (Tg1, Tg2)
Using a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation), an 8 mg sample was heated at a rate of temperature increase of 10 ° C / min, cooled to 35 ° C at a rate of temperature decrease of 10 ° C / min, and then again. A second temperature increase is performed at a temperature increase rate of 10 ° C./min. In this second temperature increase, the intersection of two tangents of the curve portion obtained by the transition is taken as the glass transition point.

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
90 parts by mass of polyester resin A (softening point 148 ° C., glass transition point 75 ° C.) as a binder resin and 4 parts by mass of C.I. Pigment Red 57: 1, 1 part by weight of E-84 (trade name of salicylic acid metal complex, manufactured by Orient Chemical Co., Ltd.) as a charge control agent, and 5 parts by weight of Carnauba wax No. 1 powder as a release agent ( After being mixed using a Henschel mixer (Mitsui Mining Co., Ltd.), the mixture was melt-kneaded and extruded from a die having a hole to obtain a yarn-like kneaded product. Next, the thread-like kneaded product was pulverized and classified to produce colored fine particles. The temperature setting for melt kneading was set to the softening point of the binder resin + 100 ° C.

  The average particle diameter of the colored fine particles thus obtained was 6.7 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 obtained colored fine particles and mixed with a Henschel mixer to obtain a toner.

  This toner had a softening point of 130 ° C. and a glass transition point of 64 ° C.

Example 2
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to the polyester resin B (softening point 112 ° C., glass transition point 68 ° C.) as the binder resin. The obtained toner had a softening point of 102 ° C. and a glass transition point of 63 ° C.

Example 3
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to the polyester resin C (softening point 112 ° C., glass transition point 57 ° C.) as the binder resin. The obtained toner had a softening point of 103 ° C. and a glass transition point of 54 ° C.
Example 4
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to the polyester resin D (softening point 134 ° C., glass transition point 58 ° C.) as the binder resin. The obtained toner had a softening point of 118 ° C. and a glass transition point of 54 ° C.
Example 5
Except that 45 parts by mass of polyester resin A and 45 parts by mass of polyester resin E (softening point 100 ° C., glass transition point 55 ° C.) were used as the binder resin in the same manner as in Example 1. A toner was obtained. The obtained toner had a softening point of 114 ° C. and a glass transition point of 61 ° C.

Example 6
As in the case of Example 1, except that 45 parts by mass of polyester resin A and 45 parts by mass of polyester resin B (softening point 112 ° C., glass transition point 68 ° C.) were used as the binder resin. A toner was obtained. The obtained toner had a softening point of 119 ° C. and a glass transition point of 63 ° C.

Example 7
As in the case of Example 1, except that 45 parts by mass of polyester resin A and 45 parts by mass of polyester resin D (softening point 134 ° C., glass transition point 58 ° C.) were used as the binder resin. A toner was obtained. The obtained toner had a softening point of 126 ° C. and a glass transition point of 63 ° C.

Example 8
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to styrene acrylic resin F (softening point 125 ° C., glass transition point 60 ° C.) as the binder resin. The obtained toner had a softening point of 113 ° C. and a glass transition point of 56 ° C.
Example 9
As a binder resin, a toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to a styrene acrylic resin G (softening point 133 ° C., glass transition point 61 ° C.). The obtained toner had a softening point of 125 ° C. and a glass transition point of 57 ° C.
Comparative Example 1
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to the polyester resin E (softening point 100 ° C., glass transition point 55 ° C.) as the binder resin. The obtained toner had a softening point of 96 ° C. and a glass transition point of 51 ° C.
Comparative Example 2
A toner was obtained in the same manner as in Example 1 except that the polyester resin A was changed to the polyester resin F (softening point 158 ° C., glass transition point 70 ° C.) as the binder resin. The obtained toner had a softening point of 140 ° C. and a glass transition point of 66 ° C.
Comparative Example 3
A toner was obtained in the same manner as in Example 2, except that the temperature of the melt kneading was set to the softening point of the binder resin + 70 ° C. The obtained toner had a softening point of 108 ° C. and a glass transition point of 65 ° C.

Comparative Example 4
A toner was obtained in the same manner as in Example 4 except that the temperature of the melt kneading was set to the softening point of the binder resin + 130 ° C. The obtained toner had a softening point of 109 ° C. and a glass transition point of 52 ° C.
Conventional Example The same raw materials as used in Example 4 were mixed using a Henschel mixer, then melt-kneaded in a twin screw extruder, stretched, cooled, and roughened with a Rotoplex (Hosokawa Micron 2 mm screen). After pulverization, 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 6.7 μm to obtain colored fine particles.

  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 obtained colored fine particles and mixed with a Henschel mixer to obtain a toner. The obtained toner had a softening point of 125 ° C. and a glass transition point of 52 ° C.

  FIG. 2 is a characteristic diagram plotting T1 and (T1-T2) of the electrophotographic toners of Examples, Comparative Examples, and Conventional Examples obtained as described above. In FIG. 2, the area surrounded by a square indicates the scope of the present invention.

  Next, the following characteristics of each of the above electrophotographic toners were evaluated.

(Evaluation)
Test 1 (transparency)
The toner is mounted on a non-magnetic one-component developing device “Casio Page Prest N-5” (Casio Computer Co., Ltd .: Color Printer A4 horizontal / 29 sheets per minute), and in an ordinary environment (25 ° C., 50% RH), OHP A solid image is printed using paper, a part of the printed image is cut out, and the maximum transmittance in the wavelength range of 400 nm to 700 nm is measured using a spectrophotometer (manufactured by Shimadzu Corporation), and the transparency is evaluated. It was. The process speed was 34.1 mm / sec, and the upper roll temperature of the two upper and lower fixing rolls was in the range of 130 to 180 ° C., and optimum conditions were selected according to the toner. At that time, the set temperature of the lower roll (pressure roll) was set to the upper roll temperature of −10 ° C.

(Evaluation criteria)
A: The maximum transmittance is 80% or more, which is very good practically.

  ○: The maximum transmittance is 60% to 80%, and there is no practical problem.

  X: The maximum transmittance is less than 60%, which is problematic in practical use.

Test 2 (Fixability)
The fixing device is modified so that the temperature of the fixing device portion of the same device as that in Test 1 can be varied to be a fixing test device.

  After obtaining an unfixed image with the same apparatus as in Test Example 1, the temperature is varied every 10 ° C. in the fixing temperature range of 100 to 200 ° C. with a fixing tester, and the non-fixed image is fixed. The area was measured and taken as a low-temperature fixing property.

The process speed was 129.3 mm / sec, and the paper was XEROX-P paper A4 size (weight 64 g / m ² ).

(Evaluation criteria)
(Double-circle): A non-offset area | region is 30 degreeC or more.

  ○: The non-offset region is 20 ° C. or higher.

  X: A non-offset area | region is 20 degrees C or less.

Test 3 (durability)
Using the same device as in Test 1, under normal environment (25 ° C., 50% RH), after continuously printing 10,000 sheets of 5% printed images on plain paper (XEROX-P paper A4 size), Print an image and evaluate image degradation.

  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.

The toners according to Examples, Comparative Examples, and Conventional Examples were evaluated for the above characteristics. The results are shown in the table below.

  From the results shown in the above table, the raw material containing the binder resin, the colorant and the release agent is melted and extruded from a die having a hole to obtain a thread-like kneaded material, which is then cut and manufactured. It can be seen that the toners according to Examples 1 to 8 in which the softening points of the resin and the toner satisfy a predetermined relationship are all excellent in transparency, fixing property and durability.

  On the other hand, the toner according to Comparative Example 1 in which the softening point T1 of the binder resin is less than 110 ° C. (100 ° C.) has a softening point T2 of 96 ° C. which is sufficiently low, so that sufficient fixability and durability can be obtained. Absent. Further, the toner according to Comparative Example 2 in which the softening point T1 of the binder resin exceeds 150 ° C. (158 ° C.) has a softening point T2 as high as 140 ° C., and sufficient transparency cannot be obtained.

  Further, the toner according to Comparative Example 3 in which T1-T2 is less than 5 ° C. (4 ° C.) has insufficient fixability, and the toner according to Comparative Example 4 in which T1-T2 exceeds 20 ° C. (25 ° C.) , Durability is insufficient.

  In addition, even if the softening point of the binder resin and the toner satisfies the relationship of the present invention, it can be seen that the toner (reference example) obtained by the conventional pulverization method is inferior in durability.

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. FIG. 6 is a characteristic diagram in which T1 and (T1-T2) of electrophotographic toners of Examples, Comparative Examples, and Conventional Examples are plotted.

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 (8)

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. When the softening point of the binder resin is T1 (in the case of two or more binder resins, the weighted average thereof is T1) and the softening point of the toner is T2, the following equation is satisfied. A characteristic toner for electrophotography.
110 ° C ≦ T1 ≦ 150 ° C
5 ° C ≦ T1-T2 ≦ 20 ° C   The electrophotographic toner according to claim 1, wherein the binder resin is a polyester resin.   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 an average particle diameter is 5 to 7 µm.   The softening point T1 of the binder resin is 110 to 130 ° C, and the softening point T2 of the toner is 100 to 120 ° C. toner.   The electrophotographic toner according to claim 1, wherein the melting temperature of the raw material is T1 + 80 ° C. to T1 + 120 ° C.   The toner for electrophotography according to claim 1, wherein T1 and T2 satisfy a relationship of 0.85 ≦ T2 / T1 ≦ 0.95.   The toner for electrophotography according to any one of claims 1 to 7, wherein the glass transition point is 54 ° C or higher.

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