JPH11184143A - Electrophotographic developer composition - Google Patents

Abstract

(57) [Problem] To provide a toner composition for developing an electrostatic latent image which does not cause filming and has a long running life. In an electrophotographic developer including at least a toner particle, an inorganic particle, and a carrier particle including a binder resin and a colorant, the charging order of the constituent particles is in the order of the carrier particle, the toner particle, and the inorganic particle. A developer composition for electrophotography, comprising:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing powder (hereinafter referred to as "toner composition") for developing an electrostatic latent image in electrophotography, and more particularly to a laser beam printer which flash-fixes a printing medium at high speed. Alternatively, the present invention relates to a developer composition for electrophotography suitable for an LED printer.

[0002]

2. Description of the Related Art Electrophotography includes a charging step of applying a uniform electrostatic charge to a photoreceptor using a photoconductive substance, an exposure step of irradiating light to form an electrostatic latent image, and a latent image. A developing step of electrostatically attaching toner to the portion, a transferring step of transferring the toner image to the toner image support, a fixing step of fixing the toner image to the toner image support by pressure, heat, flash light, or the like, and a fixing step of remaining on the photoreceptor. A cleaning step for removing the untransferred toner and a charge removing step for removing the electrostatic charge on the photoreceptor and returning it to an initial state are performed, and these steps are repeated to obtain an image.

[0003] As a toner used in such an image forming method, a toner disclosed in Japanese Patent Application No. 6-146534 has been known.

[0004]

However, as the repetitive steps are repeated, the photoreceptor may be deteriorated. In particular, there is a case where a certain substance adheres to the photoreceptor, leading to a printing defect. This is called filming, and when the substance is contained in the toner, improvement from the toner side is desired.

In particular, it has been found that, in the case of a small particle size toner, there is a problem that the silica fine particles added for improving the fluidity are fused to the surface of the photoreceptor and affect the characteristics of the photoreceptor.

The present invention provides a developer composition for electrophotography which solves the problem that filming occurs due to adhesion of silica fine particles.

[0007]

According to the present invention, there is provided an electrophotographic developer comprising at least toner particles, inorganic particles and carrier particles comprising a binder resin and a colorant.
The charging order of the constituent particles is carrier particles, toner particles,
The present invention relates to a developer for electrophotography, wherein the developer becomes higher in the order of inorganic particles.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in an electrophotographic developer comprising at least a toner particle, an inorganic particle and a carrier particle comprising a binder resin and a colorant, the charging order of the constituting particles is represented by carrier particles, It increases in the order of toner particles and inorganic particles. Here, when the charging order of the inorganic or organic particles is lower than that of the toner particles and higher than that of the carrier particles, the inorganic particles accumulate on the photoconductor and cause filming. If the inorganic particles are lower in charge order than the carrier particles, the chargeability of the toner particles in a state where the inorganic particles are adhered becomes poor, causing problems such as a decrease in print density and generation of white background stain.

[0009] The method of measuring the charging sequence is as follows.
The order can be determined by measuring the charge polarity of the inorganic particles and the carrier particles. For example, after the toner particles and the inorganic particles are frictionally charged, if the polarity of the toner particles is negative, it can be said that the inorganic particles are higher in the rank (plus side) than the toner particles. By performing such an operation also on the carrier particles, it is possible to determine the charging sequence between the three types of particles.

As a detailed method for determining the charging sequence between the particles, there is no problem as long as the method can measure the polarity. For example, 50 g of the toner particles and the inorganic or organic particles 1 are used.
g in a 100 cc polyethylene container,
After rotating at 50 rpm for 5 minutes, the polarity of the toner particles can be measured by exfoliating the inorganic particles through a wire mesh having a blow pressure of 0.2 kg / cm 2 and a sample amount of 0.2 g with a mesh of 500 using a blow-off charge meter made by Toshiba.

The compounding ratio of the toner particles of the present invention is usually about 1 to 20% by weight based on the total amount, and the inorganic particles are usually 0.1 to 2% by weight based on the toner particles.

The mixing ratio of the toner particles largely depends on the type of carrier, the charging characteristics of the toner used, and the development system. In general, the smaller the particle size of the carrier, the greater the specific surface area of the carrier. If the toner particle concentration in the developer is too low, the image density becomes too low or the carrier adheres to the photoreceptor, that is, so-called carrier over is likely to occur. on the other hand,
If the toner particle concentration is too high, contamination of the inside and outside of the printer due to white background stains on the image background and toner scattering becomes noticeable, so the appropriate toner particle mixing ratio is determined by actually performing print evaluation with a printer. You.

The amount of the inorganic or organic particles is in the range of 0.1 to 2 parts by weight based on 100 parts by weight of the toner particles. Preferably it is 0.2 to 1 part by weight. If the amount is less than 0.1 part by weight, the effect of improving the fluidity is not obtained. If the amount exceeds 2 parts by weight, the fluidity is too good, and problems such as toner scattering occur.

The inorganic particles of the present invention have an average particle size of 0.00
Inorganic fine particles of 5 to 5.0 μm. As the inorganic fine particles, fine particles such as silica, titanium oxide, and alumina oxide can be used. Among these, it is preferable to use silica fine particles.

The silica fine particles have a BET surface area of 1
00m ² / g or more, preferably 120 m ² / g or more, PH
Is preferably 8 or more. BET surface area is 100m ²
If it is less than / g, the fluidity is not sufficient, and if it is less than 8, filming tends to occur. This filming is likely to occur in an organic photoreceptor whose surface layer has a polycarbonate component. Further, the wettability to methanol is preferably 50% or more. When the wettability to methanol is less than 50%, the influence of temperature and humidity on the charge amount becomes large.

Such silica fine particles include REA200, RA200SH, RA2 manufactured by Nippon Aerosil Co., Ltd.
00H and the like, but are not limited thereto.

As a method for measuring the BET surface area, AST
According to MD3037-73, the method of measuring PH was in accordance with JIS K 6221-1982.

The method for measuring the wettability to methanol is as follows.
After collecting 0.2 g of the sample in a 100 ml beaker, 50 ml of pure water was added, and methanol was added dropwise while stirring the dispersion with a magnetic stirrer. The end point was defined as the point at which no silica fine particles were observed on the liquid surface. The wettability to methanol was calculated from the following equation.

Wettability to methanol (%) = (amount of methanol) / (50 ml + amount of methanol) × 100 As the binder resin contained in the toner particle composition of the present invention, the following binder resins may be used. For example, polystyrene homopolymer, styrene-isobutylene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-
Acrylic copolymer, styrene-methyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer,
Styrene copolymer such as styrene-glycidyl methacrylate copolymer, acrylic homopolymer or copolymer such as polymethyl methacrylate, polyethyl methacrylate, poly nbutyl methacrylate, polyglycidyl methacrylate, polyethylene terephthalate, fumaric acid / etherified diphenyl Examples include polyester-based resins, polyester-based resins such as polyesters crosslinked with a polyhydric alcohol and / or polycarboxylic acid, and epoxy-based resins. Of these, polyester resins are preferred for reducing odor due to thermal decomposition during flash fixing.

Although not particularly limited, an acid component comprising at least 80% by mole of a phthalic dicarboxylic acid in the acid component of the polyester resin and a bisphenol A alkylene oxide adduct of at least 80% by mole in the alcohol component A polyester resin obtained from an alcohol component consisting of Further, the softening point is 8 in consideration of the fixing property.
0-130 ° C, glass transition point (Tg) 55-70 ° C,
The temperature at which the melt viscosity obtained by a flow tester reaches 10,000 centipoise is preferably 90 to 135 ° C, and the molecular weight distribution of the polyester resin is such that the number average molecular weight is 2500 to 45 ° C.
The weight average molecular weight is preferably from 7000 to 130,000.

As the colorant contained in the toner particle composition of the present invention, a known colorant can be used, and examples thereof include carbon black such as furnace black, acetylene black and channel black. Dispersion of carbon black in the binder resin among these colorants is important in terms of charge stability of toner particles, and a dispersant can be used in combination as necessary. Further, the content of carbon black is determined according to the toner particle composition 1
The amount is preferably 2 to 10 parts by weight with respect to 00 parts by weight. If the amount is less than 2 parts by weight, the hiding power of the binder resin is insufficient, and a sufficient image density cannot be obtained. On the other hand, if it exceeds 10 parts by weight,
Although it is preferable to increase the hiding power of the formed image and increase the image density, on the other hand, the toner particles are excessively conductive due to the carbon black chain structure formed in the toner particles, so that insulation is impaired. As a result, the chargeability of the toner particles is reduced, and as a result, the image density is reduced, and further, white background stain and toner scattering increase.

In the toner particle composition of the present invention, a magnetic substance may be added. Ferromagnetic particles are used as the magnetic material. Specifically, iron, cobalt, magnetic metals such as nickel, their alloys, cobalt-added oxides,
Metal oxides such as chromium oxide, Mn / Zn ferrite, N
Various ferrites such as i-Zn ferrite, magnetite, hematite, etc., and those whose surfaces have been treated with surface treatment agents such as silane coupling agents, aluminum coupling agents, titanium coupling agents, and those coated with polymers, etc. Powder can be used. The particle size of these magnetic powders is preferably in the range of 0.05 to 1.0 μm. Specific examples of such magnetic particles include, for example, M
G-MK, MG-RF, A, MG-SH, MG-Z, M
G-WF, MG-WM, MG-WL (all manufactured by Mitsui Kinzoku Kogyo), MTS-005HD, MTH-009, EPT
-305, EPT-500, EPT-1000, EPR
-1000H, EPT-1001, EPT-1002
MTO-021, EPT-L1000, MAT-30
5, MAT-305HD, MAT-222, MAT-2
22HD, MTA-740, MAT-230 (all manufactured by Toda Kogyo), KBC-100 series, KBC-200
Series, KBF series KBN-400 series (Kanto Denka Kogyo KK) and the like, but are not limited to these.

The content of these magnetic particles is preferably 10 to 30 parts by weight based on 100 parts by weight of the toner composition. If the amount is less than 10 parts by weight, the adhesion of the toner to the mag roll is not sufficient, and a white background stain occurs. On the other hand, when the amount exceeds 30 parts by weight, the developability deteriorates and the print density decreases.

In the toner particle composition of the present invention, a charge control agent may be added. As the charge control agent, a known positively chargeable charge control agent can be used. Examples of such charge control agents include nigrosine-based charge control agents, triphenylmethane-based charge control agents, cationic compounds such as quaternary ammonium, basic dyes such as dyes, and metal salts of higher fatty acids (metal soaps). Etc. can be used.
Specific examples of such a substance include Bontron N-0 manufactured by Orient Chemical Co., Ltd. as a nigrosine-based charge control agent.
1, N-13, or those obtained by subjecting these nigrosine-based charge control agents to vacuum heat treatment are preferable. Examples of triphenylmethane-based charge control agents include C.I. I. Solvent
Blue 66, 124, C.I. I. Pigment B
lue61, 56, 19, 18 and the like, and C.I.
I. Preferably, Solvent Blue 124 is used. Specific examples of such a triphenylmethane-based charge control agent include “Copy Blue” P manufactured by Hoechst.
R, "Brilliant Blue Base" S
M, "BASF A" manufactured by BSF Japan
lkali Blue "NB D 6156 D L
D and the like.

As a specific example of the cationic compound such as quaternary ammonium, the anion of the quaternary ammonium salt compound is an inorganic anion containing a molybdenum or tungsten atom. Specific examples of the inorganic anion include molybdic acid, tungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid, phosphotungsten / molybdic acid, silicotungsten / molybdic acid, phosphotungsten / molybdic acid,
Examples thereof include chromium / molybdic acid, and specific examples thereof include TP-302 and 415 manufactured by Hodogaya Chemical Co., Ltd.

The charge control agent is preferably added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the toner composition.
If the amount is less than 0.1 part by weight, sufficient chargeability cannot be imparted to the toner. If the amount exceeds 5 parts by weight, the charge control agent is more expensive than other toner components, leading to an increase in cost.

The average particle size of the toner particles of the present invention is 4 to 20.
μm, more preferably 6 to 12 μm. When the average particle diameter of the toner particles is less than 4 μm, it is difficult to produce the toner particles by the conventional kneading and pulverizing method. Therefore, when the average particle diameter of the toner particles is more than 20 μm, the reproducibility of fine lines is poor. Occurs.

As a method for measuring the particle size, COULTE
The measurement was performed using an R MULTIZERZER (manufactured by COULTER) using an aperture diameter of 100 μm or 200 μm. The particle size in the present specification means a weight average particle size.

The toner particles used in the present invention can be produced by a conventionally known method. That is, a toner particle composition such as a binder resin, a colorant, a charge control agent and a dispersing aid as needed, for example, after premixing with a super mixer,
After uniformly dispersing, melting and kneading with a twin-screw extruder, finely pulverizing with a jet mill, and classifying with an air classifier, a desired toner particle composition can be obtained.

[0030] The carrier particles of the present invention comprise iron, manganese,
It is composed of metals such as cobalt, nickel and chromium, metal oxides such as chromium dioxide, iron sesquioxide and iron sesquioxide, and magnetic materials such as ferrite. Ferrite has a general formula MF
e204 (M is Mn, Co, Mg, Zn or Cu). When the carrier is made of a metal material, it is preferable to form an oxide film in order to prevent oxidation of the carrier surface. Further, in addition to a carrier obtained by granulating magnetite fine particles and ferrite fine particles, a so-called resin-type carrier in which magnetite fine particles or ferrite fine particles and a charge control agent are dispersed in a resin can also be used. Further, the same resin as the resin contained in the toner particle composition or a different resin may be coated on the surface of the carrier for the purpose of improving charging characteristics and the like.

The particle size of the carrier is generally 20 to 200 μm.
However, it is preferable to use a carrier having a small particle diameter of 20 to 60 μm in order to obtain a good printing density.

The developer of the present invention is produced by mixing toner particles, inorganic or organic fine particles and the above-mentioned carrier. The compounding ratio of the toner particles is usually about 1 to 20% by weight based on the total amount, and the inorganic or organic fine particles are usually 0.05 to 5% by weight based on the toner particles. However, this largely depends on the type of the carrier, the charging characteristics of the toner used, and the development method. Since the specific surface area of the carrier increases as the particle size of the carrier decreases, the compounding ratio of the toner can be generally increased. If the toner concentration in the developer is too low, the image density becomes low, or the carrier adheres to the photoreceptor, so-called carrier over tends to occur. On the other hand, if the toner particle concentration is too high, contamination on the inside and outside of the printer due to white background stains on the image background and toner scattering becomes noticeable, so the appropriate toner mixing ratio is determined by actually performing printing evaluation with a printer. Is done.

The image forming method used in the developer according to the present invention forms an electrostatic latent image on a photoreceptor, forms a toner image with the developer, and transfers the toner image onto a transfer member. An image forming method in which the toner remaining on the upper surface is removed by a cleaning member is preferable.

Further, the cleaning member is preferably a cleaning brush, and it is preferable that a negative bias is applied to the cleaning brush with respect to the toner.

The developer of the present invention is preferably used as an electrophotographic developer for flash fixing. here,
It is preferable that the flash fixing method averages the energy applied to a printing target by attaching a light-shielding plate directly below a lamp.

A typical image forming method used in the developer of the present invention and an outline of an electrophotographic printer (image forming apparatus) will be described with reference to FIG. In the electrophotographic printer, a toner image is formed on the photosensitive drum 1. First, the photosensitive drum 1 is uniformly charged using the charger 2. Next, LED
Using an exposure device 3 equipped with an array and a laser beam,
Exposure is performed spatially and selectively according to the image to be formed. The latent image formed on the photosensitive drum 1 is developed using a developing device 4 with a developer to form a toner image on the photosensitive drum 1. The toner image thus developed is transferred onto the recording medium 6 by the transfer charger 5. The recording medium 6 is melted and fixed by the fixing device 7 while being conveyed at a constant speed.

The toner image not transferred to the recording medium is
The toner is cleaned by the cleaning brush 8 with a negative bias applied to the toner, and is returned to the initial state.

[0038]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited thereto.

Reference Example 1 (Manufacture of standard carrier) Polyester resin ("Tuffton" TTR-2, manufactured by Kao Corporation) 24% by weight Magnetic substance (EPT-1000, manufactured by Toda Kogyo) 74% by weight Charge control agent ("Bontron" S-34: manufactured by Orient Chemical Co., Ltd.) 2% by weight Wax (LUVAX-1151: manufactured by Nippon Seiwa Co., Ltd.) 1% by weight.

After sufficiently mixing the above components, the mixture was melted and kneaded with a twin screw extruder (PCM-30; manufactured by Ikegai Co., Ltd.). After cooling the kneaded material, it is coarsely pulverized by a coarse pulverizer (UG-210KGS: manufactured by Torai Iron Works) into a 2 mmφ pass, and is medium-pulverized by a medium pulverizer (“FINE MILL” FM-300N: Nippon Pneumatic) After pulverization, classification was performed using a fine pulverizer ("Separator" DS-5UR: manufactured by Nippon Pneumatic Industries) to obtain a resin carrier having a weight average particle size of 50 µm.

Example 1 Toner particles were produced using the following components. [Toner composition] Polyester resin ("Tuffton" TTR-2, manufactured by Kao Corporation) 60% by weight Polyester resin ("Tuffton" TTR-5, manufactured by Kao Corporation) 16% by weight Magnetic substance (EPT-1000) 20% by weight Carbon black (manufactured by Cabot; "Regal" 330R) 2% by weight Nigrosine-based charge control agent ("Bontron" N-01, manufactured by Orient Chemical Co., Ltd.) 1% by weight.

After sufficiently mixing the above components, the mixture was melted and kneaded with a twin-screw extruder (PCM-30; Ikegai), and then finely pulverized with a jet mill pulverizer (PJM-100; Nippon Pneumatic). Thereafter, the powder was classified with an air classifier (A-12; manufactured by Alpine) to obtain a toner having a weight average particle size of 8 μm.

Further, the BET surface area is 130 m 2 / g,
Hydrophobic silica fine powder having a pH of 8.5 and a wettability to methanol of 55% (manufactured by Nippon Aerosil Co., Ltd .; REA-20)
0) was added to the toner in an amount of 0.4% by weight and mixed with a super mixer (SMV-20; manufactured by Kawata) to obtain a mixture of toner particles and silica fine particles. Next, 90% by weight of the resin carrier produced in Reference Example 1 was blended with 10% by weight of these mixtures to prepare a developer. Here, the chargeability of the silica fine particles to the toner is +11 μC
/ G, and the chargeability of the toner with respect to the carrier particles is +
23 μC / g, and the charging order of the constituent particles increases in the order of carrier particles, toner particles, and inorganic particles.

A xenon flash fixing method is adopted by using this developer, an electrostatic latent image is formed on a photosensitive member, a toner image is formed by the developer, and the toner image is transferred onto a transfer member. An image forming method for removing the toner remaining on the photoreceptor by a cleaning member, and further comprising an LED printer wherein the cleaning member is a cleaning brush and a negative bias is applied to the cleaning brush against the toner. (GP-1150H
E: An image was displayed in FIG. 1) and the image quality was evaluated. As a result, good printing was obtained, and printing was continued for 400,000 sheets. However, defects such as filming could not be found.

The outline of an electrophotographic printer (image forming apparatus) using the electrophotographic developer according to the present invention will be described with reference to FIG. In the electrophotographic printer, a toner image is formed on the photosensitive drum 1. First, the photosensitive drum 1 is uniformly charged using the charger 2. Next, using the exposure device 3 equipped with an LED array and a laser beam, the light is spatially and selectively exposed according to an image to be formed. The latent image formed on the photosensitive drum 1 is developed using the developing device 4 using toner to form a toner image on the photosensitive drum 1. The toner image thus developed is transferred to a recording medium 6 by a transfer charger 5.
Transfer onto While transporting the recording medium 6 at a constant speed,
Melting and fixing are performed by the fixing device 7. After the transfer of the toner image, the toner remaining on the photoreceptor is removed by a cleaning brush 8 to which a bias of -300 V is applied.

Example 2 Hydrophobic silica fine powder having a BET surface area of 145 m 2 / g, a pH of 8.5 and a wettability to methanol of 65% (manufactured by Nippon Aerosil Co., Ltd .; RA-200HS) was added to the toner at 0.4%. A developer was prepared in the same manner as in Example 1 except that the amount by weight was added. Here, the chargeability of the silica fine particles to the toner is +24 μC / g, the chargeability of the toner to the carrier particles is +23 μC / g, and the charging order of the constituent particles increases in the order of the carrier particles, the toner particles, and the inorganic particles. ing.

Using this developer, 40
Although continuous printing of 10,000 sheets was performed, no defect such as filming could be found.

Example 3 "Bontron" N manufactured by Orient Chemical Co., Ltd. as toner particles
Instead of adding 2% by weight of -01, "Bontron" N-
01 was treated at 190 ° C. under a vacuum of 0.01 MPa for 6 hours to produce toner particles in the same manner as in Example 1 except that 1% by weight of a charge control agent was added. Using the toner particles, a developer was prepared in the same manner as in Example 1. Here, the chargeability of the silica fine particles to the toner is +21 μC
/ G, and the chargeability of the toner with respect to the carrier particles is +
It is 14 μC / g, and the charging order of the constituent particles increases in the order of carrier particles, toner particles, and inorganic particles.

Using this developer, 40
Although continuous printing of 10,000 sheets was performed, no defect such as filming could be found.

Comparative Example 1 Hydrophobic silica fine powder having a BET surface area of 103 m 2 / g and a pH of 7.4 (manufactured by Nippon Hoechst; HVK-2150)
Was prepared in the same manner as in Example 3 except that 0.8% by weight of was added to the toner. Here, the chargeability of the silica fine particles to the toner is −5 μC / g, the chargeability of the toner to the carrier particles is +14 μC / g, and the charging order of the constituent particles is carrier particles, inorganic particles,
It is higher in the order of toner particles.

Using this developer, continuous printing was performed in the same manner as in Example 1. When printing was performed on 50,000 sheets, filming due to streak-like silica fine particles occurred on the photoreceptor, and printing defects occurred. I understood that.

[0052]

As described above, by using the developer for electrophotography of the present invention, the occurrence of filming due to the substance added for improving the fluidity can be solved, so that the running life of the photosensitive member can be extended. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an image forming apparatus.

[Explanation of symbols]

 1: photosensitive drum 2: charger 3: exposure device 4: developing device 5: transfer charger 6: recording medium 7: fixing device 8: cleaning brush

Claims (7)

[Claims] 1. An electrophotographic developer comprising at least toner particles, inorganic particles and carrier particles comprising at least a binder resin and a colorant, wherein the constituent particles have a charging sequence of carrier particles, toner particles and inorganic particles. An electrophotographic developer composition characterized by increasing in order. 2. The electrophotographic developer composition according to claim 1, wherein the binder resin is a polyester resin. 3. The electrophotographic developer composition according to claim 1, wherein the inorganic particles are silica fine particles. 4. BET surface area of 100 m ² / g or more, PH
4. The electrophotographic developer composition according to claim 3, wherein silica fine particles having a particle size of 8 or more are used. 5. An image forming method comprising: forming an electrostatic latent image on a photosensitive member, forming a toner image with a developer, transferring the toner image onto a transfer member, and removing toner remaining on the photosensitive member. 2. The electrophotographic developer composition according to claim 1, wherein the developer composition is used in an image forming method for removing with a cleaning member. 6. The electrophotographic developer composition according to claim 5, wherein the cleaning member is a cleaning brush. 7. The electrophotographic developer composition according to claim 6, wherein a negative bias is applied to the cleaning brush with respect to the toner.