JPH05173357A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To provide an electrophotographic developer which enables fast fixing, has excellent offset resistance, and causes no drum filming nor carrier filming of a toner by sticking a wax having specified heat of fusion and glass transition temp. to the surface of the toner. CONSTITUTION:A wax having <=15 cal/g heat of fusion and 55-70 deg.C glass transition temp. is made to stick to the surface of a toner. This wax is a polyolefin having 110-190 deg.C softening point and <=2mum average particle diameter. As for the toner binder resin, an epoxy resin, styrene-acrylate copolymer, polyester resin, and polyurethane resin are used. It is preferable that the resin has 80-130 deg.C softening point. Further, a gold-contg. dye, fatty acid ester, or compd. containing an amino group may be added as a charge controlling agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in electrophotography. US Pat. No. 229 for electrophotography
The system described in JP-A-7691 and the like is well known, which generally applies uniform electrostatic charge to an electrostatic latent image carrier having photoconductivity by corona discharge or the like, and the electrostatic latent image is formed by various means. An electric latent image is formed by irradiating a light image on a carrier, and then the latent image is visualized by using a fine colored powder called toner, and after the toner image is transferred to paper or the like, if necessary, The printed matter is obtained by fixing with pressure, heat, light or the like.

[0002]

2. Description of the Related Art As a method of developing the toner, US Pat.
The magnetic brush developing method described in No. 39, etc. has been widely put into practical use. The magnetic brush developing method will be described in detail. A magnetic developer in which a magnetic carrier and a toner are mixed and stirred and frictionally charged to have opposite polarities is used, and the magnetic developer is held by a brush-shaped brush holding the magnetic developer on a magnet. The electrostatic latent image is developed by rubbing the surface of the electrostatic latent image carrier so that only the toner is separated and attached by an electric attraction force. Conventionally, a so-called two-component magnetic developer is used as the magnetic developer, and more specifically, magnetic powder such as iron powder, ferrite powder, magnetite powder having an average particle diameter of about 100 μm or resin coating powder of these magnetic powders is used as the carrier. As the toner, a non-magnetic insulating powder in which a colorant or the like is dispersed in a binder resin made of a natural or synthetic polymer and finely pulverized to have an average particle size of about 10 μm is commonly used.

In recent years, electrophotographic printers and copiers have tended to increase in operating speed, and the contact time between the heat roll and the toner at the fixing section in the high speed state is short, so the amount of heat supplied to the toner is small, The binder resin and wax used for the toner are required to have a low softening point. This is because if the wax has a high softening point, it will not melt in the hot roll portion, and the hot roll offset resistance effect cannot be exhibited. Further, conventionally, wax has been used as an internal additive for toner, and the amount of heat required to melt the toner is required to melt the wax. On the other hand, if the softening point is too low, filming on the photocondrum will occur and the printing characteristics will deteriorate. As described above, in order to perform fixing at high speed, a wax having a high glass transition temperature (Tg) that melts with a small amount of heat and does not cause drum filming is required. Did not exist.

The present invention has been made in view of the above-mentioned problems of the prior art, is capable of high-speed printing, has excellent hot roll offset resistance, and does not cause toner drum filming and carrier filming. It is intended to provide a developer for electrophotography.

[0005]

In order to achieve the above object, the present invention uses a wax having a heat of fusion of 15 cal / g or less and a glass transition temperature of 55 ° C to 70 ° C to clean the surface of a toner. It is fixed. That is, by fixing the toner surface with the present wax, it is possible to perform high-speed fixing, excellent offset resistance, and that toner drum filming and carrier filming do not occur, and good stability is found. It was realized.

The present invention will be described in more detail below. In order to achieve both high-speed (50 sheets / min. / A4 or more) fixing and offset resistance, it is necessary to use a wax that can be melted with a small amount of heat and exert a releasing effect. However, when a low softening point wax is used, drum filming and carrier filming of toner are likely to occur. Both the drum filming and the carrier filming are caused by friction with the toner, and therefore the toner having the low softening point wax is easily generated. Therefore, as a result of studying a wax having a high softening point and being easily melted, the present inventors found that a wax having a small heat of fusion of 15 cal / g or less and a high glass transition temperature of 55 ° C. to 70 ° C. is useful. I understood. That is, the temperature is 180 to 190 ° C. on the hot roll, and the heat of fusion of the wax is small, so that the wax on the toner surface is heated above the softening point and immediately melts to exhibit the releasing effect. Since the conventional wax has a heat of fusion of 50 to 60 cal / g, it does not melt unless a sufficient amount of heat is applied, and the releasing effect cannot be exhibited in high-speed fixing. Further, by fixing the present wax to the toner surface, a small amount of wax is added, which is effective, and when the wax is present on the toner surface, the releasing effect is further improved.

The wax has a softening point of 110 ° C. to 1
A polyolefin having an average particle size of 2 μm or less at 90 ° C. is used. The amount of wax added is 0.05-
It is set to 5 wt%. As the toner binder resin, an epoxy resin, a styrene-acrylic acid ester copolymer, a polyester resin, a polyurethane resin or the like can be considered. The softening point of the binder resin is 80 to 130 ° C. Further, as the colorant, nigrosine, azo dye or the like can be used. Furthermore, a metal-containing dye, a fatty acid ester, or a compound having an amino group may be added as a charge control agent.

In the developer used in the present invention, the toner is first spheroidized and then mixed with wax to uniformly and electrostatically adhere the wax to the toner surface, and then the toner surface is heat-melted to form a toner on the toner surface. This is achieved by fixing the wax. In the manufacturing method, first, an impact force that causes the toner to collide with the plate at a high speed is applied, and the collision energy is used to heat-melt the toner surface to make it spherical, and then a certain amount of spherical toner and wax are made at high speed. Mix and stir to deposit the wax on the toner surface. Next, the developer of the present invention is formed by applying an impact force such that the toner with the wax attached thereto collides with the plate at a high speed, and the collision energy heat-melts the toner surface to fix the wax onto the toner surface. It should be noted that when the particle diameter of the toner is within the range of 5 to 20 μm, 90
Make sure to add more than wt%. Further, 10 to 80 wt% of magnetic powder may be contained in the toner.

[0009]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 Binder: Polyester resin (softening point 115 ° C.) 94 parts by weight Dye: Bontron S-37 (Orient Chemical) 3 parts by weight Carbon: Black Pearls L (Cabot) 3 parts by weight The above composition was mixed and stirred by a ball mill, The mixture was melt-kneaded with an extruder heated to 140 ° C., cooled and solidified, coarsely pulverized by a pulverizer, and further finely pulverized by a jet mill. The obtained fine powder is classified with an air classifier for 5 to 20
A toner of μm was obtained.

Next, the obtained toner is subjected to a surface modification device (hybridization system NHS-1, Nara Machine).
And the toner was mechanically spheronized. Next, polyolefin wax (heat of fusion 15 cal / g, Tg62
C., softening point 125.degree. C., average particle size 0.2 .mu.m) 0.5 part by weight and the toner 100 parts by weight surface reforming apparatus (hybridization system NHS-1, Nara Machinery).
The wax was uniformly adhered to the toner surface.

A two-component developer obtained by combining the toner thus produced and a resin-coated ferrite powder (average particle size: 80 μm) is equipped with a thermal roll fixing system (a laser printer (125 sheets / minute A4). ) Was used for the printing test. As a result, even at a heat roll temperature of 190 ° C., good fixability and offset resistance were exhibited, and drum printing and carrier filming due to toner did not occur even after continuous printing of 100,000 sheets, and excellent printing stability was exhibited. .. Example 2 Binder: Polyester resin (softening point 115 ° C.) 52 parts by weight Dye Bontron S-37 (Orient Chemical) 3 parts by weight Carbon: Black Pearls (Cabot) 3 parts by weight Magnetic powder (EPT-1000 Toda Kogyo) 40 parts by weight The above composition was manufactured in the same manner as in Example 1 to obtain a magnetic toner, and then wax was fixed to the toner surface in the same manner as in Example 1.

Next, as a result of evaluation in the same manner as in Example 1, as in Example 1, good results were obtained. Example 3 Styrene-acrylic as a binder resin (softening point 105
A toner was manufactured in the same manner as in Example 1 except that (° C.) was used. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 4 As a wax (heat of fusion 12 cal / g, Tg 62 ° C.,
A toner was experimentally manufactured in the same manner as in Example 1 except that a polyolefin wax having a softening point of 122 ° C.) was used. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 5 As a wax (heat of fusion 10 cal / g, Tg 55 ° C.,
A toner was experimentally manufactured in the same manner as in Example 1 except that a polyolefin wax having a softening point of 112 ° C.) was used. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 6 A toner was experimentally manufactured in the same manner as in Example 1 except that a polyolefin wax having a heat of fusion of 7 cal / g, a Tg of 70 ° C. and a softening point of 125 ° C. was used as the wax. Next, Example 1
As a result of evaluation in the same manner as in Example 1, good results were obtained as in Example 1. Example 7 A toner was experimentally manufactured in the same manner as in Example 1 except that a polyolefin wax having a heat of fusion of 8 cal / g, a Tg of 70 ° C. and a softening point of 185 ° C. was used as the wax. Next, Example 1
As a result of evaluation in the same manner as in Example 1, good results were obtained as in Example 1. Example 8 Example 1 except that the amount of wax added was 3 wt%.
Toner was manufactured in the same manner as in. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 9 Example 1 except that the amount of wax added was 5 wt%.
Toner was manufactured in the same manner as in. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 10 As a wax, a polyolefin wax having a heat of fusion of 8 cal / g, a Tg of 55 ° C. and a softening point of 112 ° C. was used, and a toner was manufactured in the same manner as in Example 1 except that the softening point of the binder resin was 130 ° C. did. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 11 As a wax, a polyolefin wax having a heat of fusion of 8 cal / g, a Tg of 55 ° C. and a softening point of 112 ° C. was used, and a toner was manufactured in the same manner as in Example 1 except that the binder resin had a softening point of 80 ° C. did. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 12 A toner was experimentally manufactured in the same manner as in Example 1 except that the particle diameter of the wax was 2 μm. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 13 A toner was experimentally manufactured in the same manner as in Example 1 except that the particle diameter of the wax was 1 μm. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Example 14 In the particle size distribution of the toner, 90 is in the range of 5 to 20 μm.
A toner was experimentally manufactured in the same manner as in Example 1 except that the content was wt%. Next, as a result of evaluation in the same manner as in Example 1, Example 1
Similar good results were obtained. Example 15 A toner was experimentally manufactured in the same manner as in Example 2 in which the magnetic powder was 70 wt%. Next, as a result of evaluation as in Example 1, good results were obtained as in Example 1. Comparative Example 1 A toner was manufactured in the same manner as in Example 1 except that the wax was not fixed to the toner surface and the toner was manufactured by internal addition.
Next, as a result of evaluation in the same manner as in Example 1, the releasing effect of the wax did not appear and offset occurred. Comparative Example 2 Polyethylene wax as a wax (heat of fusion 50 ca
A toner was experimentally manufactured in the same manner as in Example 1 except that 1 / g, Tg 60 ° C., and softening point 120 ° C.) were used. Next, as a result of evaluation as in Example 1, an offset occurred. Comparative Example 3 A toner was experimentally manufactured in the same manner as in Comparative Example 1 except that a polyester resin having a softening point of 135 ° C. was used as the binder resin. Next, as a result of evaluation in the same manner as in Example 1, since the binder resin had a high softening point, offset did not occur, but defective fixing was observed. Comparative Example 4 As a wax, the characteristics are (heat of fusion 8 cal / g, Tg50
A toner was experimentally produced in the same manner as in Example 1 except that polypropylene having a temperature of 100 ° C. and a softening point of 110 ° C. was used. Next, as a result of evaluation in the same manner as in Example 1, the offset resistance effect is good, but since Tg is low, drum filming and carrier filming occur after printing about 20,000 sheets, and the printing characteristics are deteriorated. It was observed. Comparative Example 5 Properties as a wax (heat of fusion 9 cal / g, Tg 80
A toner was experimentally produced in the same manner as in Example 1 except that polypropylene having a softening point of 180 ° C.) was used. Next, as a result of evaluation in the same manner as in Example 1, the wax did not melt, offset occurred, and deterioration of printing characteristics was observed. Comparative Example 6 A wax having characteristics (heat of fusion 9 cal / g, Tg 70
A toner was experimentally manufactured in the same manner as in Example 1 except that polypropylene having a softening point of 195 ° C. and a polypropylene of 195 ° C. was used. Next, as a result of evaluation in the same manner as in Example 1, the wax did not melt, offset occurred, and deterioration of printing characteristics was observed. Comparative Example 7 A toner was experimentally manufactured in the same manner as in Example 1 except that the amount of wax added was 0.01 part by weight. Next, as a result of evaluation in the same manner as in Example 1, an offset occurred and deterioration of printing characteristics was observed. Comparative Example 8 A toner was experimentally manufactured in the same manner as in Example 1 except that the amount of wax added was 10 parts by weight. Next, as a result of evaluation in the same manner as in Example 1, the fluidity of the toner was lowered, the chargeability was also deteriorated, and the printing characteristics were poor. Comparative Example 9 A toner was experimentally manufactured in the same manner as in Example 1 except that montanic acid wax (Hoechst wax S) was used as the wax. Next, as a result of evaluation in the same manner as in Example 1, the charging characteristics were poor, and good printing characteristics were not obtained. Comparative Example 10 Example 1 except that the average particle size of the wax was 3 μm
Toner was manufactured in the same manner as in. Next, as a result of evaluation in the same manner as in Example 1, the charging characteristics became defective and the printing characteristics were deteriorated. Comparative Example 11 A toner was experimentally manufactured in the same manner as in Example 1 except that the toner was not spheroidized. Next, as a result of evaluation in the same manner as in Example 1, offset was generated because wax adhesion on the toner surface was defective. Comparative Example 12 A toner was experimentally manufactured in the same manner as in Example 1 except that the proportion of the toner entering 5 to 20 μm was 70 wt%. Next, as a result of evaluation in the same manner as in Example 1, offset was generated because wax adhesion on the toner surface was defective. Comparative Example 13 As a wax, polyethylene wax (heat of fusion: 10 ca)
A toner was experimentally manufactured in the same manner as in Example 1 except that 1 / g, Tg 56 ° C., and softening point 105 ° C.) were used. Next, as a result of evaluation in the same manner as in Example 1, the Tg of the wax was too low.
Print deterioration due to drum filming occurred. Comparative Example 14 A toner was experimentally manufactured in the same manner as in Example 1 except that a polyester resin having a softening point of 75 ° C. was used as the binder resin. Next, as a result of evaluation as in Example 1, an offset occurred because the binder resin had a low softening point. Comparative Example 15 A toner was experimentally manufactured in the same manner as in Example 2 except that the amount of the magnetic powder added was 5 wt%. Next, as a result of evaluation in the same manner as in Example 2, the function of the magnetic toner disappeared because the amount of the magnetic powder added was low. Comparative Example 16 Example 2 except that the addition amount of the magnetic powder was 85 wt%.
Toner was manufactured in the same manner as in. Next, as a result of evaluation in the same manner as in Example 2, the fixability of the toner is poor because the addition amount of the magnetic powder is large.

[0013]

As described above, according to the present invention, high-speed printing is possible, hot roll offset resistance is excellent, and toner drum filming and carrier filming do not occur.

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Claims (9)

[Claims] 1. A developer for electrophotography, characterized in that the surface of a toner is fixed by a wax having a heat of fusion of 15 cal / g or less and a glass transition temperature of 55 ° C. to 70 ° C. 2. The wax has a softening point of 110 ° C. to 190.
The developer for electrophotography according to claim 1, which is at a temperature of ° C. 3. The wax is added in an amount of 0.05-5 wt.
%, The electrophotographic developer according to claim 1. 4. The electrophotographic developer according to claim 1, wherein the wax is polyolefin. 5. The electrophotographic developer according to claim 1, wherein the wax has an average particle size of 2 μm or less. 6. The developer for electrophotography according to claim 1, wherein the toner is spheroidized. 7. The electrophotographic developer according to claim 1, wherein the toner has a particle diameter of 5 to 20 μm in an amount of 90 wt% or more. 8. The electrophotographic developer according to claim 1, wherein the binder resin used for the toner has a softening point of 80 to 130 ° C. 9. The magnetic powder in the toner is 10 to 80% by weight.
The electrophotographic developer according to claim 1, wherein the developer is contained.