JPH0545927A - Thermal fixing toner - Google Patents

Abstract

PURPOSE:To provide a thermal fixing toner which prevents fogging, improves offset resistance, and gives high-quality image. CONSTITUTION:This toner contains a binder resin comprising a styrene-acryl copolymer, 1-5wt.% polypropylene having <=100O0 CPS melting viscosity at 160 deg.C (preferably, 100-5000 CPS), and arbitrary components such as a colorant, charge controlling agent, fluidity improving agent, etc., in total <=20wt.%. The styrene-acryl copolymer has the max. at 100000-500000 mol.wt. (preferably 140000-230000) in the gel-permeation chromatography and also shows the chromatographic max. at 100000-500000 mol.wt. and 10000-50000 mol.wt. during kneading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in the case of developing an electrostatic charge image formed on the surface of an image carrier by a magnetic brush method, and is used for heating and fixing which is mixed with a magnetic carrier or constitutes a magnetic developer alone. It's about toner,
In particular, the present invention relates to a heat-fixing toner which has improved anti-offset property while preventing background fog.

[0002]

2. Description of the Related Art Conventionally, as an image forming means in an electrophotographic method or an electrostatic recording method, a photoconductive substance is generally used, and after forming an electrostatic charge image on the surface of an image carrier by various means, the electrostatic charge image is formed. Is developed using toner, a toner image is transferred to a transfer material such as paper, if necessary, and fixed by heating or pressure application to obtain a copy. When developing the electrostatic image, a magnetic brush method is generally used. As a developer used in the developing means by the magnetic brush method, a magnetic carrier and a non-magnetic or weakly magnetic toner are used. Many mixed two-component developers. On the other hand, there is also a method of using a one-component developer composed of a resin and magnetic powder as the developer.

Many of the above-mentioned developers containing a toner which is easily melted by heating tend to aggregate during storage or in a copying machine, which is a drawback that so-called storability is deteriorated. On the other hand, if a resin having a high molecular weight is used as the resin constituting the toner in order to improve the storability, the fixing temperature rises, and a larger amount of heat is required at the time of fixing, which lowers the fixing property. Further, in order to improve the storability, it may be considered to add a large amount of, for example, a fluidity modifier, but like the above, the fixability is lowered, so that it is not preferable to add too much.

[0004]

To solve the above problems,
In order to achieve both fixability and storage stability, the maximum value of the chromatogram measured by gel permeation chromatography (hereinafter referred to as GPC chromatograph) is
A toner using an styrene-based copolymer that exists in both a low molecular weight region and a high molecular weight region and including an ethylene-based olefin polymer (for example, polyethylene wax) having a melt viscosity of 10 to 10 ⁶ CPS at 140 ° C. is proposed. (See, eg, US Pat. No. 4,499,168).

However, the resin having the so-called double peak as described above has a drawback that the dispersibility is low because a high viscosity component and a low viscosity component are mixed. Therefore, when such a resin is used, the background density is increased and the so-called fog phenomenon occurs. Further, the toner containing the ethylene-based olefin polymer has low offset resistance in a heat roll fixing method using an oilless type heat roll, toner adheres to the heat roll, and this toner is There is also a problem that an offset phenomenon of being transferred to paper occurs. In any case, there is a problem that the image quality is deteriorated due to the occurrence of the above-mentioned undesired phenomenon, and it is not possible to meet the demand which has become increasingly strict in recent years.

The present invention solves the above-mentioned problems existing in the prior art and provides a heat fixing toner capable of preventing background fog, improving offset resistance, and capable of forming a high quality image. With the goal.

[0007]

To achieve the above object, in the present invention, the maximum value of the chromatograph measured by gel permeation chromatography is 100,000 to 500,000 (preferably 140,000 to 230,000). ), And a binder resin comprising a styrene-acrylic copolymer having a maximum value of the above chromatograph in the range of 100,000 to 500,000 and 10,000 to 50,000, respectively, at the time of kneading, and 160 ° C. Melt viscosity at 10,000 CP
A technique of containing 1 to 5% by weight of polypropylene having S or less (preferably 100 to 5,000 CPS) and 20% by weight or less of a total of optional components such as a colorant, a charge control agent and a flow modifier. Adopted means.

In the present invention, the magnetic material fine powder is 20 to
The magnetic toner may be contained in an amount of 80% by weight. Such magnetic toner may be used alone or may be used as a mixture with a magnetic carrier.

In the present invention, if the maximum value of the GPC chromatograph is in the region where the molecular weight exceeds 500,000, the fixing temperature of the toner becomes high, which is not preferable. On the other hand, if the maximum value is in the range of less than 100,000 in molecular weight, the impact resistance and durability of the toner are deteriorated, which is inconvenient.

The maximum value of the GPC chromatograph is configured to exist in the molecular weight range of 10,000 to 50,000 depending on the setting of the kneading conditions. However, when the maximum value is in a region exceeding the molecular weight of 50,000, This is not preferable because the fixing temperature of the toner becomes high. On the other hand, if the above-mentioned maximum value is in a region where the molecular weight is less than 10,000, the fluidity of the toner is lowered and the toner easily aggregates, which is inconvenient.

Polypropylene has a viscosity of 10,000 CP
If it exceeds S, the dispersibility in the binder resin becomes poor. However, if the viscosity is too low, the offset prevention effect is reduced. If the amount added is less than 1% by weight, the desired offset resistance will deteriorate, while if it exceeds 5% by weight, the fog phenomenon will deteriorate.

In the toner of the present invention, various materials such as a colorant and a charge control agent may be used together with the above-mentioned binder resin, if necessary. As the colorant, for example, pigments or dyes such as carbon black, aniline blue, chalco oil blue, chrome yellow, quinoline yellow, DuPont oil red, malachite green oxalate, lamp black, rose bengal and nigrosine dye can be used. As the charge control agent, for example, a fatty acid-modified nigrosine dye, a triphenylmethane dye, a metal-containing azo dye, or the like can be used. Further, magnetic powder such as Fe ₃ O ₄ may be added.

If necessary, inorganic fine powder such as hydrophobic silica, alumina and titanium dioxide, resin fine powder such as polytetrafluoroethylene and polystyrene may be added to the toner of the present invention.

The addition amount of various materials other than the above-mentioned binder resin may be determined according to the electrical characteristics required for the toner, etc., but is generally 5% by weight in order to secure the fixing property.
The following is desirable.

The toner of the present invention can be manufactured by a known method such as a pulverization method, but the average particle diameter is adjusted to 5 to 15 μm from the viewpoint of image quality. The toner of the present invention is mixed with a magnetic carrier and prepared as a developer. Known magnetic carriers can be used, but from the viewpoint of image quality, magnetite and soft ferrite (Ni—Zn based, Mg—Zn based, Cu—Zn based, Ba—
A carrier containing iron oxide composed of Ni-Zn system or the like) is preferable. The average particle size of the magnetic carrier is 30
˜150 μm, and the saturation magnetization σs is preferably adjusted to 50 to 70 emu / g.

In the present invention, the toner particle size is a value measured by a Coulter counter model TA-II (manufactured by Coulter Electronics Co.), and the magnetic characteristics of the magnetic carrier are vibration sample magnetometers (VSM-manufactured by Toei Industry Co., Ltd.). III)
Is a value measured at a maximum magnetic field of 10 kOe.

Next, it is contained in the toner of the present invention.
Fe as a magnetic material fine powder should be ₃O_Four, Fe
₂O₃, Γ · Fe₂O₃, NMO ・ Fe₂O₃(However,
M is one of metals such as Ni, Cu, Mn, and Zn, or
Oxidation of two or more, one or more of n = 5-6)
An iron-based magnetic material fine powder can be used. Still above
Among the above materials, Fe is magnetic in terms of magnetic properties and hue.₃O_FourBut
desirable. The above magnetic material fine powder is evenly distributed in the toner.
Average particle size of 0.1 to 3 μm
One of degree is desirable.

Next, in the case of using a magnetic toner, if the content of the magnetic material fine powder is less than 20% by weight, the fixing property is improved, but the magnetic force of the toner is reduced, so that the developing roller of the developing roll is used in the developing area. This is inconvenient because it separates from the surface, stains the image with the background fog, and causes toner scattering. On the other hand, when the content is more than 80% by weight, the adsorption force to the surface of the developing roll becomes large, which hinders smooth transfer to the image bearing member side in the developing area, lowers the developability and inhibits the fixability in the subsequent stage. It is not preferable because

[0019]

With the above structure, the dispersibility is improved even during the kneading step during toner production, and a uniform composition can be obtained. On the other hand, after kneading, the toner has a so-called double peak molecular weight distribution, and the fixability and storage stability are improved. It is possible to achieve compatibility with both sex.

[0020]

Examples Styrene-acrylic copolymer 80 parts by weight (Fujikura Kasei TZ102) Carbon black 10 parts by weight (Mitsubishi Kasei # 50) Polypropylene 3 parts by weight (SANYO KASEI VISCOL 550P, melt viscosity at 160 ° C. 200 CPS) 2 parts by weight of charge control agent (Oil Black BY manufactured by Orient Chemical Co., Ltd.) 5 parts by weight of CaCO ₃ (NS # 2500 manufactured by Nitto Koka Kogyo Co., Ltd.) The above components were dry-mixed and kneaded with a kneader at a temperature shown in Table 1. .. The resulting mixture was solidified by cooling and then pulverized by a jet mill into particles of 20 μm or less. Next, the toner was classified through a zigzag classifier to obtain a toner having a volume average particle diameter of 10 μm. 0.5 part by weight of SiO ₂ (R972 manufactured by Nippon Aerosil Co., Ltd.) was externally added to this toner and mixed by a Henschel mixer to adhere to the surface of the toner to obtain a positively charged toner. Next, this toner and ferrite carrier (KBN-100 manufactured by Hitachi Metals, average particle size 74 to 149 μm)
To prepare a heat-fixing developer having a toner concentration of 3% by weight, and a commercially available copying machine (Sharp SF7300
Table 1 also shows the results of image evaluation using a machine.

[0021]

[Table 1]

The average molecular weight of the binder resin alone before kneading by GPC chromatography has a single peak at 21.5 × 10 ⁴ , and as shown in Table 1, it is 180 to 22.
By kneading at 0 ° C., it was confirmed that there was a peak on the low molecular weight side as well. It was also confirmed that the image quality such as image density and resolution was good, and the fixing property and anti-offset property were also excellent. It can be seen that the effect is remarkable when compared with the comparative example described below.

In the formulations of the above-mentioned examples, the average molecular weight before kneading was 22.0 × 10 as measured by GPC chromatography.
^{In 4} , the styrene-acrylic copolymer resin which does not have the maximum value on the low molecular weight side even after the kneading was used, and a toner was prepared in exactly the same manner at a kneading temperature of 200 ° C. The image formed by this toner had a density of 1.45, a resolution of 5.6 lines / mm, and was very good with no background fog, but the fixability was only 75% and the offset resistance was 185 to 220 ° C. It had a narrow offset temperature range.

Styrene-acrylic copolymer 50 parts by weight (Fujikura Kasei TZ104) Magnetite 45 parts by weight (Toda Kogyo EPT500) Polypropylene 3 parts by weight (Sanyo Chemical Co., Ltd. Viscole 330P, melt viscosity 4000 CPS at 160 ° C.) Charge control Agent 2 parts by weight (Bontron E81 manufactured by Orient Chemical Co., Ltd.) The above components were dry mixed and kneaded with a kneader at a temperature shown in Table 2. The resulting mixture was solidified by cooling and then pulverized by a jet mill into particles of 20 μm or less. Next, this pulverized powder was introduced into a hot air stream of 120 ° C. for heat treatment, and then classified by a zigzag classifier to obtain a magnetic toner having a volume average particle diameter of 10 μm. SiO in this magnetic toner
₂ 0.5 wt externally added (Nippon Aerosil Ltd. R972), were mixed in a Henschel mixer to adhere to the surface of the magnetic toner, and the magnetic toner of negative charging type. Next, 40 parts by weight of this magnetic toner and ferrite carrier (manufactured by Hitachi Metals)
KBN-100 and 60 parts by weight of an average particle size of 74 to 105 μm) were mixed to prepare a heat fixing developer, and the results of evaluation of the developed and fixed images are also shown in Table 2. The developing conditions and fixing conditions are as follows.

That is, a developing device provided with a magnet roll having a magnetic flux density of 650 G on the sleeve was provided with a cylindrical permanent magnet magnetized with 8-pole symmetry inside a sleeve made of SUS304 having an outer diameter of 31 mm. The electrostatic latent image (surface potential -600 to -400 V) on the OPC photoreceptor was reverse-developed. The distance between the photoconductor and the sleeve is 0.4 mm, the toner regulation thickness is 0.35 mm, the sleeve is rotated in the same direction as the photoconductor at 200 rpm in the developing section, and the permanent magnet is rotated in the opposite direction to 900 r.p.m. rotated at pm. The toner image obtained by development was corona-transferred to plain paper and fixed on a heat roll. The fixing was carried out by a heating roll having a surface coated with PFA resin and a pressure roll made of silicon rubber at a fixing temperature of 180 ° C. and a fixing pressure of 1.0 kg / cm as a linear pressure.

[0026]

[Table 2]

As is clear from Table 2, it was confirmed that the maximum value of the molecular weight distribution after kneading and turning into a toner has two peaks (the molecular weight of the resin alone before the turning into a toner is 14.5 × 10 ⁴⁾ even from this toner. However, the image, the fixing property, and the offset resistance were very good.

[0028]

EFFECT OF THE INVENTION Since the present invention has the constitution and operation as described above, it is possible to prevent the occurrence of fog on the ground, achieve both the fixability and the storability, and further improve the offset resistance. There is an effect that a high quality image can be formed.

Claims (2)

[Claims] 1. The maximum value of the chromatograph measured by gel permeation chromatography is 1
It is in the range of 0,000 to 500,000 (preferably 140,000 to 230,000) and has a molecular weight of 100,000 to 500,000 and 1 at the time of kneading.
A binder resin composed of a styrene-acrylic copolymer having a maximum value of the above chromatograph in the range of 10,000 to 50,000 and a melt viscosity at 160 ° C. of not more than 10,000 CPS (preferably 100 to 5,000 CPS). A heat-fixing toner containing 1 to 5% by weight of a certain polypropylene and 20% by weight or less of a total of optional components such as a colorant, a charge control agent and a flow modifier. 2. The toner for heat fixing according to claim 1, wherein the fine powder of magnetic material is contained in an amount of 20 to 80% by weight.