JPH11143120A - Electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a toner which can be fixed at a low temp. and which can prevent blocking during storage or offset development during fixing by specifying the glass transition temp. of an outer shell layer which covers the surface of a core and specifying the glass transition temp. of the core material. SOLUTION: In this electrophotographic toner, the glass transition temp. of the outer shell layer which covers the surface of the core is 50 to 70 deg.C and the glass transition temp. of the core material is >=75 deg.C. Since the outer shell layer melts and fixes at a low temp. during fixing, the toner can be fixed with small energy and can be used for fast fixing. Further, such problems that the toner melts by heat and sticks during stored and that the surface of a copy sticks to the back surface of a copy sheet just after copying on a tray are prevented. It is preferable to use a resin for the outer shell layer, which is stable at the glass transition temp., preferably of 50 to 100 deg.C, and then rapidly melts over that temp. As for the resin for the core material, a resin which hardly deforms by heat compared to the material of the outer shell layer is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image in electrophotography or electrostatic recording.

[0002]

2. Description of the Related Art In an electrophotographic system in which a visible image is formed by developing an electric latent image with a developer, an electric latent image is formed on a photoconductor made of a photoconductive substance, and then the latent image is developed. After transferring the toner powder image to paper etc. as necessary,
A visible image is obtained by fixing by heating, pressing or the like.
By the way, in order to cope with recent technical trends of high speed and energy saving of copying machines and printers, there is a strong demand for fixing at a low temperature in an electrophotographic system.

[0003] In response to the above demands, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin or using a polyester resin having a lower softening temperature. However, the toner easily fuses (blocks) during storage, and a part of the toner easily migrates to the surface of the heating roller, resulting in a disadvantage that an offset phenomenon occurs.

To solve such a problem, Japanese Patent Laid-Open No.
JP-A-6-158340 and JP-A-58-202455 propose a technique in which a resin used for a toner is composed of a resin comprising a low molecular weight polymer component and a high molecular weight polymer component. Also, JP-A-8-22146,
Japanese Patent Application Laid-Open No. Hei 8-22147 proposes to improve the low-temperature fixability and the prevention of offset by using a crosslinked polyester resin, and proposes a microcapsule toner as a toner for pressure fixing. Furthermore, Japanese Patent Publication No. 46-15876, Japanese Patent Application Laid-Open No. 48-7503, Japanese Patent Application Laid-Open No. 48-75033, and the like propose a core material using a low melting point wax or the like. JP-A-59-148066 and JP-A-61-5635.
No. 2 and the like propose a resin in which a resin having a low glass transition temperature is used as a core material and a resin having a high melting point is used as an outer shell by an interfacial condensation method. Japanese Patent Application Laid-Open No. 63-128357 proposes a core material made of a resin having a low glass transition temperature and an outer shell made of a high melting point resin formed by a spray drying method. Also, Japanese Patent Application Laid-Open No. H4-2121
No. 69, JP-A-8-179550 and the like disclose a heat-meltable core material having a low glass transition temperature to form an outer shell by reacting an isocyanate with a compound having active hydrogen. Japanese Patent Laid-Open Publication No. H11-15064 proposes a core material having a low glass transition temperature and having an outer shell formed by an in situ polymerization method.

On the other hand, in copiers and printers, the temperature of the fixing unit is set low except when used for energy saving purposes.
In recent years, a device has been devised to set the temperature to a predetermined value only during use.
It has become necessary to shorten the time required for the toner used in these copiers and printers to reach a predetermined temperature (to make the start-up time faster) and to reduce the energy during use. For these reasons, there is a strong demand for a toner that can be fixed at a lower temperature than before, but the above-mentioned conventional toner has not satisfied these requirements.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-fixable toner which can be fixed at a low temperature and can prevent blocking during storage and offset phenomenon during fixing.

[0007]

According to the present invention, there is provided a two-layer structure comprising a core material mainly composed of a resin and a coloring agent and an outer shell layer covering the surface of the core material. The toner has a glass transition temperature of 5
An electrophotographic toner characterized by having a core transition temperature of 0 ° C. to 70 ° C. and a glass transition temperature of 75 ° C. or higher.

The electrophotographic toner of the present invention has a fixing function by melting the outer shell layer at a low temperature at the time of fixing, so that fixing can be performed with energy saving, and high-speed fixing can be performed. This prevents the cohesion and fusing, and the cohesion of the copy surface and the back surface of the copy paper on the tray immediately after copying.

The outer shell layer of the present invention has a glass transition temperature of 50 ° C.
It is composed of a resin in the range of -70 ° C. When the glass transition temperature is lower than 50 ° C., the toner is thermally melted and fused at the time of storage, or it is easy to fuse the copy back surface with the copy back surface on the tray immediately after copying, and the temperature exceeds 70 ° C. And the fixability at low temperatures becomes inferior. Further, the outer shell layer of the present invention uses a resin having a glass transition temperature of 50 ° C. to 70 ° C., preferably a resin which is stable up to 50 ° C. to 100 ° C. and melts sharply. Preferably, it is used. This is because the storability is good and energy-saving fixing becomes possible.

These materials include low molecular weight polystyrene, polyester resin, aliphatic or alicyclic hydrocarbon resin, polyol resin derived from bisphenol type epoxy resin, hydrogenated petroleum resin, rosin ester, low molecular weight polyethylene, low molecular weight Low molecular weight polyolefins such as polypropylene and polyethylene oxide, beeswax, natural waxes such as carnauba wax and montan wax, higher fatty acids such as stearic acid, palmitic acid and myristic acid, and metal salts of higher fatty acids, and higher fatty acids Other dimers, trimers and oligomers having a melting point of 70 ° C to 120 ° C, such as amides, are used. These materials can also be used as a mixture.

The core material of the present invention has a glass transition temperature of 75 ° C.
It is composed of the above resins. It is preferable that the resin used as the core material of the present invention is a resin which is less likely to be thermally deformed than the material of the outer shell layer. This is because if a material that is not easily deformed under the conditions of heating and fixing of a copying machine or a printer is used as a core material, offset phenomenon and paper wrapping that occur during fixing can be prevented.

Examples of the core material include styrene, parachlorostyrene, vinyltoluene, vinyl chloride, vinyl acetate, vinyl propionate, methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acryl Lauryl acid, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-chloroethyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, (meth) acrylic acid, vinyl methyl ether, Vinyl ethyl ether, vinyl isobutyl ether, vinyl methyl ketone, N-vinyl pyrrolidone,
N-vinylpyridine, a polymer of a monomer such as butadiene,
Or a copolymer of two or more of these monomers,
A copolymer having a crosslinked structure with a functional monomer, or a mixture thereof is exemplified. Other examples include polyester, polyurethane, polyamide, epoxy resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, and aromatic petroleum resin.

The coloring agents used in the present invention include the following. Black pigment: carbon black (oryl furnace black, channel black, lamp black, acetylene black, etc.); azine dyes such as aniline black, metal salt azo dyes, metal compounds, and composite metal compounds. Yellow pigment: Cadmium yellow, mineral fast yellow, nickel titanium yellow, navels yellow,
Naphthol Yellow S, Hansa Yellow G, Solder Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigments: molybdenum orange, permanent orange GTR, porazolone orange, balkan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK. Red pigment: Bengala, Cadmium Red, Permanent Red 4R, Risor Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. Purple pigment: Fast Violet B, Methyl Violet Lake. Blue pigment: cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue,
First Sky Blue, Indanthrene Blue BC. Green pigment: chrome green, chromium oxide, pigment green B, malachite green lake. The amount of these colorants used is 1% to 2% based on the thermoplastic resin.
About 0% is preferable.

In the present invention, a charge control agent is used to control charging. Examples of such an antistatic agent include nigrosine, an azine dye having a C 2 to C 16 noalealkyl group (Japanese Patent Publication No. 42-1627), and a basic dye (eg, CI Basic Ye).
Ilo 2 (CI. 41000) C.I. I. Basic
Yellow 3, C.I. I. Basic Red 1
(CI. 45160), C.I. I. Basic Red
9 (CI. 42500), C.I. I. BasicVi
olet 1 (CI. 42535), C.I. I. Bas
ic Violet 3 (CI. 42555), C.I.
I. Basic Violet 10 (CI.451)
70), C.I. I. Basic Violet 14
(CI. 42510), C.I. I. Basic Blu
e1 (CI. 42025), C.I. I. Basic
Blue 3 (CI. 50005), C.I. I. Bas
ic Blue 5 (C.I. 42140), C.I. I.
Basic Blue 7 (C.I. 42595),
C. I. Basic Blue 9 (CI.5201)
5), C.I. I. Basic Blue 24 (C.I.
52030), C.I. I. Basic Blue 25
(CI.52025), C.I. I. Basic Blu
e 26 (CI. 44045), C.I. I. Basic
Green 1 (CI. 42040), C.I. I. B
asic Green 4 (CI.42000),)
Lake pigments of these basic dyes, such as C.I. I. So
event Black 8 (CI. 26150),
Contains benzoylmethyl-hexadecylammonium chloride, decyltrimethyl chloride, etc., a tetra-ammonium salt, or a dialkyltin compound such as dibutyl or dioctyl, a dialkyltin borate compound, a guanidine derivative, a vinyl polymer containing an amino group, containing an amino group Polyamine resins such as condensation polymers described in JP-B-41-20153, JP-B-43-27596 and JP-B-44-27596.
No. 6397, No. 45-26478 and metal complex salts of monoazo dyes described in JP-B-55-42752, JP-B-59-7385, and salicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid. Z
Metal complexes of n, Al, Co, Cr, and Fe; sulfonated copper phthalocyanine pigments; and fluorine-based compounds described in JP-A-4-151168.

Further, in the present invention, at the time of fixing,
In order to improve the releasability of the fixing roller and the toner, a releasable substance can be added. Examples of such release materials include natural waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and oxidized polyethylene, higher fatty acids such as stearic acid, palmitic acid, and myristic acid, metal salts of higher fatty acids, and higher fatty acid amides. Etc. These can be used alone or in combination of two or more. In the present invention, low molecular weight polyethylene, low molecular weight polypropylene and carnauba wax are preferably used.

The average particle size of the core particles is about 3 to 10 μm, and the thickness of the outer shell depends on the particle size of the core particles.
About 2 μm is preferable. If it is less than 0.1 μm, the fixability is poor, and if it exceeds 2 μm, offset tends to occur.

The toner having a two-layer structure of the present invention can be prepared by a conventionally known coacervation method, in situ method, spray drying method,
It can be produced by coating on the surface of fine particles by an interfacial polymerization method or other mechanical methods, surface modification in liquid using zeta potential, and the like.

[0018]

The present invention will be described below with reference to examples.

Example 1 A mixture comprising 100 parts by weight of polystyrene (Tg: 76 ° C.), 10 parts by weight of carbon black, 5 parts by weight of low molecular weight polypropylene, and 5 parts by weight of an iron complex salt azo dye was heated and kneaded with a hot roll, pulverized and classified. Thus, core particles having a volume average particle size of 7 μm were obtained. 10 parts of the core particles are dispersed in 30 parts of methanol, and a polyol resin (Tg; 65.6, Ts; 6) derived from a bisphenol-type epoxy resin is dispersed therein.
8.3, Tf94.8) A solution of 2 parts of methanol and 10 parts of methanol was added, and about 0.2 μm
m to form a toner layer having a resin layer of a polyol resin. The glass transition temperature of the core material of this toner was 76 ° C., and the glass transition temperature of the outer shell layer was 65.6 ° C. 0.3 parts of colloidal silica was added to and mixed with 100 parts of the toner, and 3 parts of the toner was mixed with 100 parts of an iron powder carrier to prepare a two-component developer. This developer is placed in a magnetic brush developing device, and the electrostatic latent image formed on the organic photoreceptor by the usual electrophotographic method is developed. The transferred image is transferred to plain paper while applying corona discharge to silicone oil. Fixing with a fixing roller that does not supply
The image was sufficiently fixed in the range of 0 to 200 ° C., and a good image was obtained without occurrence of paper wrapping or offset phenomenon. The toner was stored in a thermostat at 50 ° C. for one week, but no fusion of the powder was observed, and the toner was excellent without toner blocking.

Example 2 40 parts of polystyrene (Tg: 76 ° C.), polyester resin (Tg: 56 ° C., Ts: 63.9 ° C., Tf 85.4)
C.) 8 parts Carbon black, 4 parts Disperse with a ball mill for 24 hours together with 2 parts of iron complex dye, then add 2 parts of carnauba wax, and add 0.9 parts of 2,2 ′ azobis (2,4 dimethylvaleronitrile). Added and dissolved. This solution was added to 150 parts of a 2% aqueous polyvinyl alcohol solution, dispersed with a homomixer for 3 minutes, transferred to a four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a condenser, and heated at 70 ° C. for 10 minutes.
Polymerized for hours. This polymerization solution was centrifuged at 1500 rpm for 8 minutes to remove the supernatant, 100 parts of water was added and dispersed by stirring, and the polymer solution was centrifuged at 1500 rpm for 8 minutes and washed. This washing operation was repeated two more times by filtration and drying to obtain a toner having an average particle diameter of 7 μm. When this toner was observed with a transmission electron microscope (10,000 times and 40,000 times), a 0.3 μm outer shell layer was formed on the surface of the core particle, and the core had a glass transition temperature of 76 ° C. It was confirmed that the glass transition temperature of the outer shell layer was 56 ° C. 0.3 part of colloidal silica was added to 100 parts of the toner,
After mixing, 3 parts of the toner was mixed with 100 parts of iron powder carrier to prepare a two-component developer. This developer was used to develop an electrostatic latent image in the same manner as in Example 1, and the transferred image was thermally fixed with a fixing roller not supplying silicone oil, and was sufficiently fixed at a fixing temperature in the range of 120 to 200 ° C. And a good black image without the occurrence of wrapping and offset phenomenon was obtained. The toner was stored in a thermostat at 50 ° C. for one week, but no fusion of the powder was observed, and the toner was excellent without toner blocking.

Example 3 In Example 2, a rosin ester (oxidation; melt viscosity at 3,150 ° C. 107) was used in place of the polyester resin.
A toner was prepared in the same manner as in Example 2 except that 2) was used. The glass transition temperature of the core material of this toner was 76 ° C., and the glass transition temperature of the outer shell layer was 58 ° C. This toner 1
Then, 0.3 part of colloidal silica was added to and mixed with 00 parts, and then 3 parts of this toner was mixed with 100 parts of iron powder carrier to form a two-component developer, and an image was formed using a digital copying machine. As a result of a fixing test in a fixing temperature range of 100 ° C. to 200 ° C., fixing was performed at 120 ° C. or higher, and a black image having excellent dot reproducibility without offset development or paper wrapping was obtained. The toner was stored in a thermostat at 50 ° C. for one week, but no fusion of the powder was observed, and the toner was excellent without toner blocking.

Example 4 In Example 1, a partially crosslinked polyester resin (Tg; 71.4 ° C., Ts; 73.
3 ° C., Tf 122.1 ° C.), and a toner was prepared in the same manner as in Example 1. The glass transition temperature of the core material of this toner was 76 ° C., and the glass transition temperature of the outer shell layer was 56 ° C. To 100 parts of this toner, 0.3 parts of colloidal silica was added and mixed, and then 3 parts of this toner was mixed with 100 parts of iron powder carrier to obtain a two-component developer, and an image was formed using a digital copying machine. As a result of performing a fixing test in a fixing temperature range of 100 ° C. to 200 ° C., fixing was performed at 120 ° C. or higher, and a black image having excellent dot reproducibility without offset development or paper wrapping was obtained. The toner was stored in a thermostat at 50 ° C. for one week, but no fusion of the powder was observed, and the toner was excellent without toner blocking.

Example 5 15 parts of styrene, 20 parts of butyl acrylate, 5 parts of acrylic acid, polyester resin (Tg; 77.4 ° C., Ts;
(73.3 ° C., Tf 122.1 ° C.) 20 parts Carbon black 4 parts, iron complex salt dye 2 parts dispersed in a ball mill for 24 hours, and then carnauba wax 2 parts were added.
2 'Asobis (2,4 dimethylvaleronitrile) 0.9
Was added and dissolved. This solution was added to 150 parts of a 2% aqueous polyvinyl alcohol solution, dispersed for 3 minutes with a homomixer, transferred to a four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a condenser, and polymerized at 70 ° C. for 10 hours. . The polymerization solution was centrifuged at 1500 rpm for 8 minutes to remove the supernatant, 100 parts of water was added, and the mixture was stirred and dispersed.
Washing was performed by centrifugation for minutes. This washing operation was repeated two more times by filtration and drying to obtain a toner having an average particle diameter of 7 μm. When this toner was observed with a transmission electron microscope (10,000 times and 40,000 times), the particle surface layer was 0.5 μm.
m, a glass transition temperature of the core material was 77 ° C., and a glass transition temperature of the outer shell layer was 58 ° C. 0.3 parts of colloidal silica was added to and mixed with 100 parts of the toner, and 3 parts of the toner was mixed with 100 parts of an iron powder carrier to prepare a two-component developer. When this developer was used to develop an electrostatic latent image in the same manner as in Example 1, and the transferred image was thermally fixed with a fixing roller not supplying silicone oil, the image was sufficiently fixed at a fixing temperature of 120 to 200 ° C. A good black image was obtained without occurrence of paper wrapping or offset phenomenon. In addition, this toner
It was stored in a thermostat at 0 ° C. for one week, but no fusion of the powder was observed, and the toner was good without toner blocking.

Example 6 10 parts of hydrogenated petroleum resin was finely ground and mixed with 100 parts of core particles prepared in the same manner as in Example 1, and the surface of the core particles was mechanically mixed with a hybridizer (manufactured by Nara Machinery Co., Ltd.). And a finely pulverized product of 10 parts of hydrogenated petroleum resin was added thereto, and then mechanically fixed to the surface to prepare a toner. The glass transition temperature of the core material of this toner was 78 ° C., and the glass transition temperature of the outer shell layer was 56 ° C. 0.3 parts of colloidal silica was added to and mixed with 100 parts of the toner, and 3 parts of the toner was mixed with 100 parts of an iron powder carrier to prepare a two-component developer. When this developer was used to develop an electrostatic latent image in the same manner as in Example 1, and the transferred image was thermally fixed with a fixing roller not supplying silicone oil, the fixing temperature was 120 to 2
The image was sufficiently fixed in the range of 00 ° C., and a good black image was obtained without occurrence of paper wrapping or offset phenomenon. The toner was stored in a thermostat at 50 ° C. for one week, but no fusion of the powder was observed, and the toner was excellent without toner blocking.

Comparative Example 1 In Example 2, a polyester resin (Tg: 56 ° C.)
Was used in the same manner as in Example 2 except that a polyester resin (Tg: 48 ° C.) was used instead of the toner. The glass transition temperature of the core material of this toner was 78 ° C., and the glass transition temperature of the outer shell layer was 48 ° C. When this toner was stored at 40 ° C. for 8 hours, blocking occurred and the toner was solidified.

Comparative Example 2 In Example 2, a polyester resin (Tg: 56 ° C.)
Was used in the same manner as in Example 2 except that a polyester resin (Tg: 75 ° C.) was used instead of the toner. The glass transition temperature of the core material of this toner was 78 ° C., and the glass transition temperature of the outer shell layer was 75 ° C. This toner did not fix in a fixing temperature range of 100 to 170 ° C. in a fixing test.

[0027]

The toner of the present invention can be fixed at a low temperature, has excellent storability, and has a high practical value without an offset phenomenon at the time of fixing and paper wrapping around a fixing roller.

Claims (1)

[Claims] 1. A toner having a two-layer structure comprising a core material mainly composed of a resin and a colorant and an outer shell layer covering the surface thereof, wherein the outer shell layer has a glass transition temperature of 50 ° C.
-70 ° C, and the glass transition temperature of the core material is 75 ° C or more.