JPH11190911A - Toner composition for developing a positively chargeable electrostatic latent image - 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. An electrostatic image developing toner comprising at least a binder resin, a magnetic substance, and silica fine particles has a charge amount of 2 to 10 μc / g when iron powder carrier particles having a particle diameter of 44 to 105 μm are used. A positively chargeable electrostatic latent image developing toner composition, wherein the charge amount of the negative charge component is 30% or less of the total charge amount.

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 toner composition for developing an electrostatic latent image 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.

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, when a magnetic toner is used, the toner itself is fused to the surface of the photoreceptor, and even when a small amount of magnetic powder is present on the surface of the photoreceptor, the characteristics of the photoreceptor are affected. It turned out that there was a problem.

The present invention provides a positively chargeable electrostatic latent image developing toner composition which solves the problem that the toner itself adheres to the filming.

[0007]

According to the present invention, there is provided a toner for developing an electrostatic image comprising at least a binder resin, a magnetic substance and fine silica particles, the charge amount when iron powder carrier particles having a particle diameter of 44 to 105 μm are used. Is 2 or more and 10 μc /
g or less, and the charge amount of the negatively charged component is 30% or less of the total charge amount.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The toner particles of the present invention have a particle diameter of 44.
The charge amount when iron powder carrier particles of up to 105 μm is used is 2 to 10 μc / g, and the charge amount of the negatively charged component is 30% or less of the total charge amount. The charge amount is more preferably 3 to 10 μc / g, and the charge amount of the negatively charged component is 25% or less of the total charge amount.

When the charge amount is less than 2 μc / g, the developing power is weak and the print density is reduced. The charge amount is 10 μc /
When the value exceeds g, the capacity becomes excessive with respect to the capacity of the photoreceptor, and the print density decreases. On the other hand, when the charge amount of the negative charge component exceeds 30% of the total charge amount, the toner of the reverse polarity component increases, and the toner adheres to the non-printed portion during development, and this toner is transferred by the transfer electric field. In the case of brush cleaning, when using a method of applying a bias while cleaning, it is difficult to transfer to the brush, so it is likely to remain on the photoconductor, and furthermore, the probability of fusing and filming on the photoconductor is high. Get higher.

As a method of measuring the charge amount, a blow pressure of 0.35 kg was measured using E-SPART manufactured by Hosokawa Micron Co., Ltd.
/ Cm 2, and the total count is 3000.

The carrier particles have a particle size of 44 to 105 μm.
After the addition of 5% by weight of toner particles to the carrier particles using iron powder carrier particles of m, the measurement was performed after stirring at 200 rpm for 5 minutes in a 100 cc polyethylene container.

The toner composition of the present invention comprises at least a binder resin, a magnetic substance and silica fine particles.

As the binder resin contained in the toner composition of the present invention, known binder resins can be used, for example, polystyrene homopolymer, styrene-isobutylene copolymer, styrene-butadiene copolymer ,
Styrene copolymers such as acrylonitrile-butadiene-styrene copolymer, styrene-acryl copolymer, styrene-methyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer, styrene-glycidyl methacrylate copolymer, polymethyl methacrylate Acrylic homopolymer or copolymer such as polyethyl methacrylate, poly nbutyl methacrylate, polyglycidyl methacrylate, polyethylene terephthalate, fumaric acid / etherified diphenyl polyester, crosslinked polyester with polyhydric alcohol and / or polycarboxylic acid, etc. And polyester resins and epoxy resins. Of these, polyester resins are preferred for reducing odor due to thermal decomposition during flash fixing.

Although not particularly limited, at least 80 mol% of the acid component of the polyester resin is composed of a phthalic dicarboxylic acid, and at least 80 mol% of the alcohol component is a bisphenol A alkylene oxide adduct. 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.

The toner composition of the present invention may contain a colorant. As the coloring agent, known coloring agents can be used, for example, furnace black,
Examples include carbon black such as acetylene black and channel black. Dispersion of carbon black in the binder resin among these colorants is important in terms of charge stability of the toner, and a dispersant can be used in combination as needed. Further, the content of carbon black is preferably 1 to 10 parts by weight based on 100 parts by weight of the toner composition. If the amount is less than 1 part by weight, the hiding power of the binder resin is insufficient, and a sufficient image density cannot be obtained. On the other hand, when the amount exceeds 10 parts by weight, it is preferable in order to increase the hiding power of the formed image and increase the image density, but on the other hand, the toner particles are excessively conductive due to the carbon black chain structure formed in the toner particles. Therefore, the insulating property is impaired, the chargeability of the toner is reduced, and as a result, the image density is reduced, and further, white background stain and toner scattering increase.

As the magnetic substance contained in the toner composition of the present invention, ferromagnetic particles are used. Specifically, iron, cobalt, magnetic metals such as nickel, alloys thereof, cobalt-added oxides, metal oxides such as chromium oxide,
Various ferrites such as Mn-Zn ferrite and Ni-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 polymers Powders such as those coated with can be used. The particle size of these magnetic powders is 0.05-1.
A range of 0 μm is preferred. Specific examples of such magnetic particles include, for example, MG-MK, MG-RF, A, MG
-SH, MG-Z, MG-WF, MG-WM, MG-W
L (manufactured by Mitsui Kinzoku Kogyo KK), MTS-005HD, M
TH-009, EPT-305, EPT-500, EP
T-1000, EPR-1000H, EPT-100
1, EPT-1002, MTO-021, EPT-L1
000, MAT-305, MAT-305HD, MAT
-222, MAT-222HD, MTA-740, MA
T-230 (all made by Toda Kogyo), KBC-100 series, KBC-200 series, KBF series KBN
-400 series (manufactured by Kanto Denka Kogyo Co., Ltd.) and the like, but are not limited thereto.

The content of these magnetic particles is preferably from 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 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. As such a substance, specifically, Bontron N-01, N manufactured by Orient Chemical Co., Ltd. as a nigrosine-based charge control agent.
-13, or those obtained by subjecting these nigrosine-based charge control agents to vacuum heat treatment. Examples of triphenylmethane-based charge control agents include C.I. I. Solvent Bl
ue66, 124, C.I. I. Pigment Blue
61, 56, 19, and 18; I. So
It is preferable to use the event blue 124. Specific examples of such triphenylmethane-based charge control agents include “Copy Blue” PR and “Br” manufactured by Hoechst.
illiant BlueBase "SM," BASF Alkali manufactured by BSF Japan
Blue "NB D 6156 D LD.

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 silica fine particles in the present invention are used as a toner fluidity improver. As the silica fine particles, in particular, silica fine particles which have been subjected to a hydrophobizing treatment are preferable in that high fluidity is reliably obtained. As the primary particle diameter of the silica fine particles, those having a diameter of 0.005 to 1.0 μm are used. When the thickness is less than 0.005 μm, the efficiency in the addition step is deteriorated, and when the thickness is 1 μm or more, the effect of improving the fluidity is insufficient. The addition amount of the silica fine particles is in the range of 0.1 to 2 parts by weight based on 100 parts by weight of the toner particles. If less than 0.1 part by weight, there is no fluidity improving effect,
If the amount is more than 2 parts by weight, the fluidity is too good, causing problems such as toner scattering.

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.

Examples of such silica fine particles include REA200, RA200SH and 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 In addition, inorganic or organic fine particles having an average particle diameter of 0.005 to 1.0 μm are optionally added. Can be added. As the inorganic fine particles, fine particles such as titanium oxide and alumina oxide can be used. Further, as the organic fine particles, resin fine particles such as polymethyl methacrylate, fluororesin, and silicone resin can be used.

The average particle size of the toner composition of the present invention is 4 to 2
It is preferably 0 μm, more preferably 6 to 12 μm. When the average particle diameter of the toner is less than 4 μm, it is difficult to produce the toner by the conventional kneading and pulverizing method, so that the product yield is remarkably reduced. . In addition, as a measuring method of a particle size, COULTER MULTISIZER (COU
(LTER Co., Ltd.) 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 composition used in the present invention can be produced by a conventionally known method. That is, after preliminarily mixing a toner composition such as a binder resin, a colorant, a charge control agent, and, if necessary,
After uniformly dispersing, melting and kneading with a screw extruder, finely pulverizing with a jet mill, and classifying with an air classifier, a desired toner composition can be obtained.

The toner composition of the present invention can be used as a two-component developer by being mixed with a carrier. It can also be used as a one-component developer for developing an electrostatic latent image. Carriers are metals such as iron, manganese, cobalt, nickel, chromium, chromium dioxide, iron sesquioxide,
It is made of a metal oxide such as ferric oxide, or a magnetic material such as ferrite. Ferrite has a general formula MFe204 (M is M
n, 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. Furthermore, magnetite fine particles,
In addition to a carrier obtained by granulating 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 or different resin as the resin contained in the toner composition 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 100 μm in order to obtain a good printing density. The carrier particle size was measured using a laser diffraction particle size distribution analyzer SALD-2000J (manufactured by Shimadzu Corporation).

The two-component developer is produced by mixing the toner composition and the carrier described above. The mixing ratio of the toner composition is usually 5 to 3 with respect to the total amount of the toner composition and the carrier.
Although it is about 0% by weight, this largely depends on the type of carrier, the charging characteristics of the toner to be 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 concentration is too high, contamination on the inside and outside of the printer due to white background stain on the image background and toner scattering becomes noticeable, so the appropriate toner mixing ratio is determined by actually performing print evaluation with a printer. You.

In the image forming method used in the toner composition of the present invention, an electrostatic latent image is formed on a photosensitive member, a toner image is formed with a developer, and the toner image is transferred onto a transfer member. An image forming method in which the toner remaining on the body is removed by a cleaning member is preferable.

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

The toner composition of the present invention is preferably used as an electrophotographic toner composition for flash fixing. Here, it is preferable that the flash fixing method averages the energy applied to the print target by attaching a light shielding plate directly below the lamp.

A typical image forming method used for the toner composition 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, using an exposure device 3 equipped with an LED array and a laser beam, the light is spatially selectively exposed according to an 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. Recording medium 6
While being transported at a constant speed, is fused and fixed by the fixing device 7.

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.

[0037]

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.) 1% 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 the medium is 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) to obtain a resin carrier having a weight average particle size of 70 µm.

Examples and Comparative Examples Toners 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; manufactured by Ikegai Co., Ltd.), and then finely ground with a jet mill pulverizer (PJM-100; manufactured by Nippon Pneumatic Industries, Ltd.). 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. In order to further improve the flowability of the toner, hydrophobic silica fine powder (manufactured by Nippon Aerosil Co., Ltd .; REA-200)
Was added to the toner in an amount of 0.4% by weight, and the mixture was mixed with a super mixer (SMV-20; manufactured by Kawata Corporation) to adjust the toner. This operation was repeated to obtain a positive chargeability as shown in Table 1. Was obtained. In each of the prototype lots, the charge amount and the ratio of the negatively charged component vary due to uncontrollable factors such as the atmosphere during manufacturing. For these toners, iron powder carrier particles having a particle diameter of 44 to 105 μm are used as carrier particles.
The charge amount and the charge amount of the negatively charged component were measured using a START analyzer.

[0042]

[Table 1] Next, these toners are blended with 10% by weight and 90% by weight of the resin carrier manufactured in Reference Example 1 to adjust a developer, and a xenon flash fixing method is adopted using the developer. An image forming method is used in which an electrostatic latent image is formed on a photoconductor, a toner image is formed with a developer, the toner image is transferred onto a transfer body, and toner remaining on the photoconductor is removed by a cleaning member. Further, an image is output by an LED printer (GP-1150HE: FIG. 1) in which the cleaning member is a cleaning brush and a negative bias is applied to the cleaning brush with respect to the toner, and the image quality is evaluated. Was. Table 2 summarizes the printing results.

[0043]

[Table 2] As described above, the prototype No. 4 having a charge amount of less than 2 has a low initial print density, and the prototype No. 3 in which the ratio of the negatively charged component exceeds 30% causes filming, resulting in black streak-like background stain on the print. Was found to occur.

[0044]

As described above, by using the toner of the present invention, the occurrence of filming in which the toner itself is fused to the surface of the photoreceptor can be solved, so that the running life of the photoreceptor can be extended.

[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

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/00 316

Claims (6)

[Claims] 1. An electrostatic image developing toner comprising at least a binder resin, a magnetic material and silica fine particles, wherein an iron powder carrier particle having a particle diameter of 44 to 105 μm has a charge amount of 2 to 10 μc / g. A positively chargeable electrostatic latent image developing toner composition, wherein the charge amount of the negative charge component is 30% or less of the total charge amount. 2. The toner composition for developing an electrostatic latent image according to claim 1, wherein the binder resin is a polyester resin. 3. The method according to claim 1, wherein the charge amount is 3 to 10 μc / g,
The toner composition for developing a positively chargeable electrostatic latent image according to claim 1, wherein the charge amount of the negative charge component is 25% or less of the total charge amount. 4. 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 the toner remaining on the photosensitive member. 2. The toner composition for developing a positively chargeable electrostatic latent image according to claim 1, wherein the toner composition is used as a developer used in an image forming method for removing by a cleaning member. 5. The toner composition for developing a positively chargeable electrostatic latent image according to claim 4, wherein the cleaning member is a cleaning brush. 6. The toner composition for developing a positively chargeable electrostatic latent image according to claim 5, wherein a negative bias is applied to the cleaning brush against the toner.