JPH0572798A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To improve transferability and fixability by adding a solid lubricant of a specified average particle diameter. CONSTITUTION:A solid lubricant of 1-10mum average particle diameter is added to pressure fixable toner particles which are fixed by pressure on the surface of recording paper. The toner is an electric conductive magnetic one-component toner. In order to avoid remarkable rise of electric resistance while ensuring satisfactory fixability and to obtain satisfactory flowability, the solid lubricant is added in 1-10 ratio of d1 to X [d1 is the average particle diameter (mum) of the lubricant and X is the amt. (pts.wt.) of the lubricant added per 100 pts.wt. of the toner particles]. The lubricant used is not especially limited but fatty acid or a deriv. thereof which is solid at ordinary temp. is preferably used. The pref. electric resistance of the lubricant is 10<4>-10<18>OMEGA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an electrophotographic toner that is used in an image forming apparatus such as a printer or a facsimile and is pressure-fixed on a recording sheet.

[0002]

2. Description of the Related Art In electrophotography, an electrostatic latent image formed on the surface of a photoconductor, a dielectric or the like is developed into a toner image, which is then transferred and fixed on the surface of recording paper. There are various methods for fixing. For example, there are a method of melting the toner by heating, a method of applying pressure at the same time as heating, and the like. However, these methods have a problem that quick fixing is difficult because it is necessary to heat the toner. For this reason, a pressure fixing method, in which a relatively large pressure is applied during the transfer of a toner image so as to fix the toner image at the same time as the transfer without heating, has been attracting attention (JP-A-56-91243 and JP-A-63). −
135980, U.S. Pat. No. 4,877,707, etc.).

By the way, various types of toners have been used or proposed as toners used for developing electrostatic latent images in the electrophotographic system. Among them, the conductive one-component toner having a low electric resistance can be developed even if the potential of the electrostatic latent image is low. It is used when forming a latent image. However, since such a conductive one-component toner has a low charging property, the transfer method using corona discharge cannot be used, and therefore the above-mentioned pressure fixing method must be used.

However, when the pressure fixing method is used, the image density is lowered during continuous printing. The decrease in image density is remarkable especially in high-speed printing and printing of a low area occupation document. It is considered that this decrease in image density is due to poor toner peeling from the surface of the dielectric body on which the latent image is formed.

In order to improve such a decrease in image density, US Pat. No. 4,877,707 proposes that a peelable liquid such as silicone oil is contained in the toner.

However, it has been found that when such a peelable liquid is used, the reduction in the image density is improved, but the peelability from the recording paper is also improved, so that the fixing property becomes insufficient. ..

In Japanese Patent Laid-Open No. 63-135980,
A pressure transfer method using a conductive one-component toner to which 0.1 to 1.0% by weight of a fatty acid metal salt is added has been proposed. This proposal is to perform pressure transfer under high humidity environment,
When pressure transfer is performed using recording paper that has been exposed to high humidity for a long time, the conductive toner image on the image carrier (dielectric drum) is not partially or completely transferred to the recording paper. It is intended to solve the problem that defects occur. The fatty acid metal salts disclosed in the publication are only those having an average particle diameter of 0.1 μm. Further, the same publication discloses that when the amount of the fatty acid metal salt added exceeds 1.0% by weight, the fluidity and the conductivity are deteriorated and the development failure occurs.

Although the publication only discloses an example in which 10 recording papers are printed, according to the study by the present inventors, the average particle diameter disclosed in the publication is 0.1.
It was found that the fatty acid metal salt of μm cannot sufficiently improve the transfer failure during continuous printing, and that the fluidity of the toner particles is lowered. It was also found that when the amount of the fatty acid metal salt added was increased in order to improve the transfer failure during continuous printing, the electrical resistance increased as disclosed in the publication when the average particle diameter was 0.1 μm. ..

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and does not lower the fixing property of the electrophotographic toner used in the pressure fixing method, particularly the conductive magnetic one-component toner. The purpose is to improve transferability.

[0010]

These objects are achieved by the present invention described in (1) to (5) below. (1) An electrophotographic toner which is fixed on the surface of a recording paper by pressure, wherein a solid lubricant having an average particle diameter of 1 to 10 μm is externally added to the toner particles.

(2) The average particle diameter of the solid lubricant is d ₁
When the external additive amount of the solid lubricant relative to 100 parts by weight of the toner particles is x parts by weight, d ₁ / x is 1
The toner for electrophotography according to (1) above, which is 10 to 10.

(3) The toner for electrophotography according to (1) or (2) above, wherein the solid lubricant contains a fatty acid or a derivative thereof.

(4) The toner for electrophotography according to any one of (1) to (3) above, which has an electric resistance value of 10 ⁴ to 10 ⁸ Ω.

(5) The above-mentioned (1) which is a magnetic one-component toner.
The electrophotographic toner according to any one of (1) to (4).

[0015]

In the electrophotographic toner of the present invention, the solid lubricant having the above-mentioned average particle size is externally added, so that the transfer property is extremely good and the pressure fixing property is also good.

Further, if the average particle diameter of the solid lubricant and the external addition amount thereof are made to have the above relationship, an increase in electric resistance due to the external addition of the solid lubricant can be suppressed, and fluidity is not impaired. Therefore, it is suitable for a conductive one-component toner that requires low resistance.

[0017]

[Specific Structure] The specific structure of the present invention will be described in detail below. The toner for electrophotography of the present invention is a pressure fixing type toner which is fixed on the surface of a recording paper by pressure.

In the electrophotographic toner of the present invention, the toner particles have an average particle size of 1 to 10 μm, preferably 2 to 7 μm.
m solid lubricant is added externally. If the average particle size of the solid lubricant is less than the above range, the electrical resistance of the toner increases, making it difficult to obtain the characteristics of the conductive toner, and the fluidity of the toner particles decreases. When the average particle diameter of the solid lubricant exceeds the above range, the externally added solid lubricant is peeled off from the toner particle surface during pressure transfer, and the effect of improving transferability and fixability cannot be obtained.

The average particle size of the solid lubricant is preferably equal to or less than the average particle size of the toner particles, and particularly preferably 50% or less of the average particle size of the toner particles.

The addition amount of the solid lubricant is not particularly limited and may be appropriately selected according to various required characteristics such as fixability and electric resistance. In order to avoid a significant increase in resistance and to obtain good fluidity, the average particle size of the solid lubricant is set to d ₁ μm, and the external addition amount of the solid lubricant to 100 parts by weight of the toner particles is set to x parts by weight. When d ₁ / x is 1 to 10, especially 2
It is preferable to add it so that it becomes ~ 7. If d ₁ / x exceeds the above range, the effect of improving transferability and fixing property tends to be insufficient. If d ₁ / x is less than the above range, the electrical resistance increases, making it difficult to use as a conductive toner, and the fluidity also decreases.

The solid lubricant used in the present invention is not particularly limited, but it is preferable to use a fatty acid or a derivative thereof which is solid at room temperature. The fatty acid is preferably a saturated or unsaturated one having about 12 to 22 carbon atoms, and may have a straight chain or a side chain. As a derivative of fatty acid,
The metal salts and amides of the above fatty acids are preferable. In addition, various waxes containing them can be used. Among these solid lubricants, fatty acid metal salts are particularly preferable. Specifically, zinc stearate, aluminum stearate, calcium stearate, magnesium stearate, calcium laurate, zinc laurate and the like are preferable, and zinc stearate and calcium stearate are particularly preferable.

As such a solid lubricant, a commercially available one may be used as it is, but it may be pulverized if necessary so as to have the above-mentioned average particle diameter. For the pulverization, a pulverizing means for toner particles described later or the like can be used.
Examples of commercially available solid lubricants include zinc stearate 601, zinc stearate CP [Nitto Kasei Co., Ltd.], zinc stearate ZNS-P, calcium stearate CS-1 [Adeka Fine Chemicals], zinc stearate S-. Z, calcium stearate S-C
[Japanese fats and oils] and the like can be mentioned.

The external addition form of the solid lubricant may be appropriately selected from various forms such as a form in which the solid lubricant is dry-bonded to the surface of the toner particles and a form in which the solid lubricant is thermally or mechanically fixed to the surface of the toner particles. It may be a combined form.

Two or more solid lubricants may be used in combination.

The electrophotographic toner of the present invention is not particularly limited as to the other constitution as long as the above-mentioned solid lubricant is externally added thereto. That is, the electrophotographic toner of the present invention can be applied to both magnetic toner and non-magnetic toner, and can be applied to both conductive toner and insulating toner. Further, it can be applied to a one-component toner and a two-component toner using a carrier together. However, the toner of the present invention is
As described above, it is particularly suitable for the conductive magnetic one-component toner.

The toner constituent components other than the above-mentioned solid lubricant may be appropriately determined depending on the presence or absence of magnetism and the desired electric resistance value. For example, when the present invention is applied to a magnetic toner, it is preferable to have the following constitution.

The magnetic toner contains a binding resin and magnetic powder as main components.

The resin is one that can be pressure-fixed, that is,
It may be appropriately selected from those having good adhesiveness to the recording paper and being likely to undergo plastic deformation by applying pressure. As such a resin, for example, it is preferable to select from one or more kinds of ethylene-based copolymers such as paraffin wax, polyethylene, and ethylene-vinyl acetate copolymer, and particularly, polyethylene having a relatively low molecular weight and a high density. Polyethylene disclosed in, for example, US Pat. No. 4,108,653 is preferred.

Examples of commercially available polyethylene include High Wax 200P, High Wax 400P [Mitsui Petrochemical Industry Co., Ltd.], Polywax 2000 [Petrolite] and the like.

Further, in the present invention, after the transfer and fixing by pressure, the fixing may be further solidified by heating.
In this case, a styrene-based copolymer resin can also be used. The styrene copolymer resin is obtained by a copolymerization reaction of a styrene monomer and a vinyl monomer copolymerizable therewith.

In addition, polyester resin, epoxy resin, silicone resin, polystyrene resin, polyamide resin, polyurethane resin, acrylic resin, polyolefin and the like may account for 30% by weight or less of the binder resin.

The magnetic powder contained in the toner particles is not particularly limited, and metals such as iron, manganese, cobalt, nickel and chromium or alloys thereof, oxides of the above metals such as chromium oxide, iron sesquioxide, and general formulas can be used. MO / Fe ₂ O ₃
(M is Fe, Mn, Co, Ni, Mg, Zn, Cd, B
ferrites represented by one or more metals selected from the group of monovalent or divalent metals such as a and Li),
Any conventionally known magnetic material can be used. Alternatively, an amorphous magnetic alloy may be used.
As the composition of the amorphous magnetic alloy, any alloy composition such as a ferromagnetic transition metal and a semimetal, or a composition in which a small amount of other element is further added can be used. As the ferromagnetic transition metal, 1 to 3 kinds of Fe, Co, Ni, etc., especially Fe or Co as a main component, and as the semimetal, B, Si, C, P, Ge, especially B, Si as a main component And preferred ones are Fe-B-Si ternary system, Co
They are -B-Si ternary system, Fe-Co-B-Si quaternary system and the like. In addition, the content of Cr and M in these components is 10 atomic% or less.
You may add at least 1 sort (s) of n, Mo, Nb, Al, Ti, V, Sn, Zn, Cu.

The average particle size of the magnetic powder is not particularly limited,
Usually, it is preferably 0.01 to 10 μm, particularly preferably 0.05 to 3 μm. The content of the magnetic powder in the toner particles is usually about 30 to 70% by weight, and preferably about 50 to 70% by weight in the case of using the toner for ionography. If the content of the magnetic powder is less than the above range, toner scattering easily occurs in the machine, and if it exceeds the above range, the fixing property tends to be lowered.

The average particle size of the toner particles is 5 to 30 μm.
And particularly preferably 5 to 25 μm. If the average particle size is less than 5 μm, the fluidity of the developer is deteriorated, and caking of the developer and adhesion of the sleeve are likely to occur. If it exceeds 30 μm, the resolution is deteriorated and the fixing property tends to be poor. When measuring the average particle diameter of the toner particles, the volume particle diameter of the measured value is calculated by the Coulter counter method, and the 50% average particle diameter thereof is taken as the average particle diameter. In the Coulter counter method, volume standard measurement is performed using Isoton II (manufactured by Coulter Electronics Co., Ltd.) as an electrolytic solution, for example, Coulter Counter TA-II (manufactured by Coulter Electronics Co., Ltd.) having an aperture diameter of 100 μm. The particle size distribution is preferably such that 2d or more is about 5% or less, and d / 2 or less is about 5% or less, where d is the average particle size.

Various additives other than the resin and the magnetic powder may be internally added to the toner particles.

For example, as a color adjusting agent and a resistance controlling agent,
Carbon black MA-100 [Mitsubishi Kasei Kogyo Co., Ltd.], Ketjen Black EC-DJ600 [Lion Akzo Co., Ltd.], 671 Milori Blue [Dainichi Seika Kogyo Co., Ltd.], conductive titanium oxide [Titanium Kogyo Co., Ltd.] ] Inorganic or organic pigments such as] can also be internally added. These are preferably contained in 0.1 to 10 parts by weight, particularly 0.1 to 5 parts by weight, based on 100 parts by weight of the toner particles.
In particular, in the case of using a conductive toner, it is preferable to internally add carbon black, and the addition amount is preferably 1 to 5 parts by weight.

In addition to the above, a fluidity improver described later may be internally added.

If necessary, a charge control agent may be added to control the charge polarity, the charge amount, and the like. In this case, a known appropriate charge control agent may be selected according to the desired polarity, charge amount, etc., and there is no particular limitation. For example,
Examples thereof include metal complex salt azo dyes and nigrosine dyes, and these are selected according to required characteristics.
The content of such a charge control agent in the toner particles is preferably about 0.1 to 5 parts by weight. However, when the conductive toner is used, the charge control agent is not added.

A resistance adjusting agent, a color adjusting agent or a coloring agent, a fluidity improving agent and the like can be externally added to the magnetic toner particles.

Examples of these are colloidal silica,
Metal oxides such as titanium oxide, zinc oxide and alumina, inorganic fine powders such as silicon carbide, calcium carbonate, barium carbonate and calcium silicate, polymer beads such as PMMA, polyethylene, nylon, silicone resin, phenol resin, benzoguanamine resin and polyester. , Fluorine-containing organic fine powders such as polytetrafluoroethylene and polyvinylidene fluoride, resistance regulators or black pigments such as carbon black, acetylene black, channel black and aniline black, yellow pigments such as diamond light GR and vario reel yellow 1090 , Red pigments such as permanent red E5B and rhodamine 2B, blue pigments such as copper phthalocyanine and cobalt blue, green pigments such as pigment green B, and orange pigments such as pyrazolone orange. It is below.

These substances may be used alone or in combination of two or more if necessary. Further, for each substance, a titanate type, an aluminum type, a surface type hydrophobizing treatment, a surface dispersion improving treatment,
A coupling agent such as a silane-based agent, silicone oil, or other organic or inorganic treatment can be applied.

It is preferable that these external additives have a particle size of about 0.01 to 5 μm. In addition, the amount of externally added toner particles 1
The amount is preferably about 0.1 to 5 parts by weight with respect to 00 parts by weight.

When the conductive toner is used, it is preferable to externally add the resistance adjusting agent as described above.

The magnetic toner particles to which the magnetic powder is added are
Further, magnetic particles may be externally added. The magnetic particles to be added externally are preferably selected from the same as the above-mentioned magnetic powder to be added internally. In this case, the average particle diameter of the externally added magnetic particles is 0.05 of the average particle diameter of the magnetic toner particles.
More preferable results are obtained when the content is up to 20%. When the magnetic particles are externally added, the addition amount thereof is preferably 0.1 to 10 parts by weight, and particularly preferably 1 to 8 parts by weight with respect to 100 parts by weight of the toner particles. If it is less than 0.1 parts by weight, the effect of external addition is not effective, and if it exceeds 10 parts by weight, fog tends to increase and the fixing ratio tends to deteriorate.

To produce such a magnetic toner, 1
As one example, the raw material composition is thoroughly mixed in a Henschel mixer, and then kneaded in a hot melt kneader. Then, it cools, coarsely grinds with a hammer mill, and then finely grinds with a jet impact mill. Next, after removing the excess fine powder area with a wind classifier, dry mixing the solid lubricant, various external additives and magnetic particles as necessary with a Henschel mixer, and then the excess coarse powder area with a wind classifier. To obtain a toner having a predetermined particle size distribution.

Of course, other known various methods may be used.

The electrophotographic toner of the present invention may be used as a mixture with carrier particles. The carrier particle material is not particularly limited, and various soft magnetic materials such as iron, magnetite and various ferrites can be used. In this case, as the ferrite, Mg-Cu-Zn ferrite, Ni-
Any of various known compositions such as Zn ferrite and Cu-Zn ferrite can be used. These carrier particles include acrylic resin, styrene resin, and
It may have a coating of silicone resin, fluorine resin, or the like, or may contain a binder of polyester resin, styrene-acrylic resin, or the like.

When mixing the carrier particles, a Nauta mixer, a V blender or the like may be used. Further, the above-mentioned externally-added magnetic particles and certain kinds of externally-added additives may be added during this mixing.

The electrophotographic toner of the present invention is applied to pressure-fixing type electrophotography. The linear pressure applied during fixing is not particularly limited, but is usually about 20 to 50 kg / cm 2.

The developing method using the toner of the present invention is not particularly limited and various methods can be applied depending on the purpose, but it is particularly suitable for ionographic electrophotography. In the ionography system, an electrostatic latent image is formed on the surface of a dielectric material by spraying an ion stream, and this is developed with a conductive magnetic one-component toner to obtain a toner image. Then, while the recording paper is sandwiched between the dielectric and the pressure transfer roll and conveyed, the toner image is transferred onto the surface of the recording paper and fixed at the same time. In this case, the dielectric does not have to be drum-shaped, and various shapes such as a belt-shaped dielectric can be used.

When applied to ionography, the electric resistance of the conductive magnetic one-component toner is 10 ⁴ to 1
It is preferable that the 0 ⁸ Ω. The electric resistance value in this case is measured by the following method. First, the magnetic brush development system is imitated, the magnets 2 are arranged as shown in FIGS. 1 and 2, and the N pole and the S pole are opposed to each other with a gap between magnetic poles of 9.5 mm. In this case, the surface magnetic flux density of the magnetic pole is 1500 Gauss and the area of the opposing magnetic pole is 10 × 30 mm. Between the magnetic poles, parallel plate electrodes 1 and 1 are arranged with an interelectrode gap of 6.5 mm, and 500 mg of a sample is put between the electrodes and magnetically held. Then, the electric resistance when 10 V is applied is measured. The electrodes 1, 1 and the magnets 2, 2 are placed on an insulating base 3 having legs 4 made of insulating rubber. As a measuring device, for example, an insulation resistance meter (TOA SUPER MEGOHMMETER MODEL SM-10E manufactured by Toa Denpa Kogyo Co., Ltd.)
Can be used.

The electrophotographic toner of the present invention can be applied to a method of forming an electrostatic latent image on the surface of a photoconductor such as amorphous silicon or organic photoconductor (OPC) in addition to the above-mentioned ionography.

The structure of a printer, a copying machine or the like to which the electrophotographic toner of the present invention is applied may be any known structure.

[0054]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention. 33 parts by weight of polyethylene resin (Polywax 2000 made by Petrolite), ethylene-vinyl acetate resin (Sumitate MB-1 made by Sumitomo Chemical)
1) 4 parts by weight, carbon black (Mitsubishi Kasei # 4
0) 3 parts by weight, magnetic powder (made by TDK, average particle diameter 0.5 μ
60 parts by weight of (m 2 ferrite powder) were mixed with a high-speed mixer and then melt-kneaded. After cooling, pulverization and classification were carried out to obtain toner particles having an average particle diameter of 20 μm.

To the toner particles, 2 parts by weight of carbon black (# 40 manufactured by Mitsubishi Kasei) and a solid lubricant (zinc stearate manufactured by Nitto Kasei Co., Ltd. were crushed and classified) were externally added by a high speed mixer, and for electrophotography. Toner was obtained. Various toners were obtained by changing the average particle size of the solid lubricant and the external addition amount. The average particle diameter d ₁ (μm) of the externally added solid lubricant,
The addition amount x (parts by weight) and d ₁ / x with respect to 100 parts by weight of the toner particles are shown in Table 1 below.

With respect to these toners, a reduction in image density during continuous high-speed printing of a low area occupied document (image occupied area 0.5%) (1000 sheets to 5000 sheets of A4 size 60 sheets / minute) was evaluated. An ionography printer was used for printing, and the linear pressure during pressure fixing was set to 50 kg / cm 2. The image density was measured with a Macbeth densitometer RD-918S. ○, 9 when the image density was over 90% of the initial value
The case where it was 0% or less was marked with x. The results are shown in Table 1.

The fluidity of each toner was evaluated using a powder tester manufactured by Hosokawa Micron. A sieve was placed on the vibrating section in the order of # 42, # 60, and # 200.
20 g of toner was gently placed on the # 42 sieve, and the sieve was vibrated for 15 seconds with the vibration scale set to 4. The fluidity was evaluated by the amount of toner (g) remaining on the # 200 sieve. The results are shown in Table 1.

Further, the electric resistance value of each toner was measured using the above-mentioned equipment and method. The results are shown in Table 1.

[0059]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear.

That is, in toner Nos. 5 to 8 of the present invention containing a solid lubricant having an average particle diameter of 1 to 10 μm, reduction in image density during continuous high speed printing is prevented.

Further, in toner Nos. 5 to 7 in which d ₁ / x was in the range of 1 to 10, the fluidity was good, the initial density of the printed image was high, and no density unevenness was observed. But,
In toner No. 8 having d ₁ / x of less than 1, flowability is low, unevenness in density is recognized due to insufficient toner transportability, and initial density is 80% of toner Nos. 5 to 7. It was below the level.

For each toner shown in Table 1 above, the density of the printed solid image was measured with a Macbeth densitometer to evaluate the fixing rate. Scotch Mending Tape (Scotch Magic Tape 81
After attaching 0), it was gently peeled off. The image density of the solid part after peeling the tape was measured, and the fixing ratio was calculated from the following formula.

Fixing rate [%] = (solid image density after tape peeling × 100) / solid image density

As a result, it was confirmed that the toner Nos. 5 to 8 of the present invention had a fixing ratio improved by about 30 to 60% with respect to the toner No. 1.

[0066]

EFFECTS OF THE INVENTION The electrophotographic toner for pressure fixing of the present invention has good transferability and fixability because a solid lubricant having a predetermined average particle diameter is externally added.

[Brief description of drawings]

FIG. 1 is a front view of a resistance measuring device.

2 is a plan view of the resistance measuring device shown in FIG. 1. FIG.

[Explanation of symbols]

 1 electrode 2 magnet 3 base 4 leg

Claims (5)

[Claims] 1. An electrophotographic toner which is fixed on the surface of a recording paper by pressure, wherein the toner particles have an average particle diameter of 1 to 1.
An electrophotographic toner comprising a solid lubricant of 0 μm added externally. 2. The average particle diameter of the solid lubricant is d ₁ μm
Where x ₁ is an external addition amount of the solid lubricant to 100 parts by weight of the toner particles, d ₁ / x is 1 to 1
The toner for electrophotography according to claim 1, wherein the toner is 0. 3. The toner for electrophotography according to claim 1, wherein the solid lubricant contains a fatty acid or a derivative thereof. 4. The toner for electrophotography according to claim 1, which has an electric resistance value of 10 ⁴ to 10 ⁸ Ω. 5. The toner for electrophotography according to claim 1, which is a magnetic one-component toner.