JP2001134019A - Developer, method of producing the same and method of forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-component developer with small initial fluctuation in the charge amount of the toner and excellent in the durability which shows stable electrification characteristics for a long time. SOLUTION: The developer is prepared by mixing a toner and a resin-coated carrier and satisfies the relation of formula (1):1<(a/b)<1.4 and formula (2):5<(t/s)<50, wherein a is the charge amount of the toner when the core material constituting the carrier and the toner are mixed, b is the charge amount of the toner when the carrier and the toner are mixed, s is the amount of the exposed core material of the carrier before mixed with the toner, and t is the amount of the exposed core material of the carrier after mixed with the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a developer used for developing an electrostatic image in electrophotography and the like, a method for producing the same, and an image forming method.

[0002]

2. Description of the Related Art In a developer obtained by mixing a toner and a carrier, fluctuations in the toner charge amount in the early stage of image formation and fluctuations in the image density due to the initial fluctuations in the toner charge amount are small. What can stabilize is desired. In response to such a request, a resin-coated carrier obtained through a step of removing free resin has been proposed as a carrier constituting a developer (Japanese Patent Application Laid-Open No. H6-1994).
No. 59519).

[0003]

However, in the case of a developer composed of a conventionally known carrier, including the resin-coated carrier described in the above-mentioned publication, the charging characteristics (toner charge amount) are reduced due to so-called toner spent. In addition, the charging characteristic (toner charge amount) is also reduced by exfoliating the resin coating layer of the carrier and partially exposing the surface of the core material. Then, a decrease in the charging characteristics causes a decrease in image density and a decrease in image quality. As described above, in the conventionally known two-component type developer, the charging characteristics (and, consequently, the image density and image quality) decrease with time due to the peeling of the toner spent and the resin coating layer. It does not have the property.

The present invention has been made based on the above circumstances. A first object of the present invention is to provide a two-component developer having a small initial variation of the toner charge amount and exhibiting stable charging characteristics over a long period of time and having excellent durability. . A second object of the present invention is to provide a method of manufacturing a developer that can reliably manufacture a developer having a small initial variation in the toner charge amount and excellent durability. A third object of the present invention is to provide an image forming method capable of stably forming a high-density and high-quality image from an initial stage for a long period of time.

[0005]

The developer of the present invention is a developer obtained by mixing a toner and a resin-coated carrier, wherein a core material constituting the carrier and the toner are mixed. When the toner charge amount is a, the toner charge amount when the carrier and the toner are mixed is b, the carrier core material exposure amount before mixing with the toner is s, and the toner after mixing with the toner is When the core material exposure amount of the carrier is t, the following formulas (1) and (2) are satisfied.

[0006]

Equation (1): 1 <(a / b) <1.4 Equation (2): 5 <(t / s) <50

[0007] In the developer of the present invention, it is preferable that the coating resin constituting the carrier is a silicone resin containing an aminosilane coupling agent. Also,
Preferably, the binder resin constituting the toner is a polyester resin.

[0008] The production method of the present invention is a method for producing a developer, which comprises a step of mixing a toner and a resin-coated carrier, wherein the core material constituting the carrier is mixed with the toner. The charge amount is a, the toner charge amount when the carrier and the toner are mixed is b, the core material exposure amount of the carrier before mixing with the toner is s, and the carrier core is mixed with the toner. When the material exposure amount is t, a toner and a carrier satisfying the condition of the following formula (1) are mixed until the condition of the formula (2) is satisfied.

[0009]

Equation (1): 1 <(a / b) <1.4 Equation (2): 5 <(t / s) <50

The image forming method of the present invention is characterized in that the developer of the present invention is charged into a developing device and an image is formed after preliminary stirring.

[0011]

[1] Since the toner charge amount a when the core material constituting the carrier and the toner are mixed is larger than the toner charge amount b when the carrier and the toner are mixed,
When the resin coating layer of the carrier is peeled off and the surface of the core material is partially exposed, the charging characteristics are improved (the toner charge amount is increased). For this reason, a decrease in toner charge due to toner spent due to repeated image formation and an increase in toner charge due to peeling of the resin coating layer (exposure of the core material surface) occur in parallel. Then, the toner charge amount ratio (a /
By setting b) to be greater than 1 and less than 1.4, the amount of decrease in toner charge due to toner spent and the amount of increase in toner charge due to exposure of the core material surface become substantially equal. A stable toner charge amount is obtained over a long period of time, and the durability as a developer is significantly improved.

[2] The ratio (t / t) of the core material exposure amount t of the carrier (carrier constituting the developer) after mixing with the toner to the core material exposure amount s of the carrier before being mixed with the toner. s) is greater than 5 and 5
By setting it to less than 0, the durability as a developer can be improved, and the initial fluctuation (increase) of the charge amount can be reliably suppressed.

[3] When the coating resin constituting the carrier is a silicone resin containing an aminosilane coupling agent, the charge amount of the toner can be stabilized for a long time, and the humidity dependency of the charge is reduced. Therefore, a stable image can be formed.

[4] Since the binder resin constituting the toner is a polyester resin, it is possible to suppress the initial fluctuation of the toner charge amount after the replacement of the developer.

[5] By preliminarily stirring the developer charged in the developing device and then forming an image, the toner charge amount and the conveyance amount of the developing roll during image formation can be stabilized. As a result, The image density can be stabilized.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. <Developer> The developer of the present invention is obtained by mixing a toner and a resin-coated carrier.

<Toner> The toner used to obtain the developer of the present invention is not particularly limited.
A conventionally known toner (pulverized) containing at least a binder resin and a colorant and, if necessary, an internal additive such as a release agent and a charge control agent and / or an external additive such as inorganic fine particles. Toner and polymerized toner). As the average particle size of such a toner,
The volume average particle diameter is preferably 4 to 10 μm.

Here, as the binder resin constituting the toner, for example, a styrene resin, an acrylic resin, a styrene-acryl resin, a polyester resin and the like can be cited. Of these, the toner after replacement of the developer is used. A polyester resin is preferred from the viewpoint of suppressing the initial fluctuation of the charge amount.

The colorant constituting the toner is not particularly limited. For example, carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride Phthalocyanine blue, malachite green oxalate, rose bengal and the like.

Examples of the release agent internally added as required include low molecular weight polypropylene, low molecular weight polyethylene, polyolefins such as ethylene-propylene copolymer, microcrystalline wax, carnauba wax, sasol wax, paraffin Waxes such as wax and amide wax can be mentioned.

Examples of the charge control agent internally added as required include azo metal complexes, salicylic acid metal complexes, and calixarene compounds as negatively chargeable ones, and nigrosine as positively chargeable ones. Dyes and quaternary ammonium salt compounds.

Examples of the inorganic fine particles which are externally added as required include inorganic oxide particles such as silica, titanium oxide and aluminum oxide. It is preferable that these inorganic fine particles have been subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent, or the like.

<Carrier> The carrier used to obtain the developer of the present invention is a resin-coated carrier having a core material surface coated with a resin. The average particle size of the carrier is preferably 60 to 120 μm in terms of volume average particle size.

In this carrier, the charge amount of the toner when the core material constituting the carrier and the toner are mixed is represented by a, and the charge amount of the toner when the carrier (the resin-coated carrier) is mixed with the toner is represented by b. , The ratio (a / b) of the toner charge amount is larger than 1 and 1.4.
And preferably 1.05 to 1.35.

When the ratio (a / b) of the toner charge amount is 1 or less, the toner charge amount decreases due to peeling of the resin coating layer (exposure of the core material surface) by repeating image formation. Along with the decrease in the toner charge amount due to the toner spent, the image density and the image quality are reduced (deteriorated) over time. On the other hand, the toner charge amount ratio (a /
When b) is 1.4 or more, the toner charge amount is excessively increased due to the exposure of the surface of the core material, and the toner charge amount becomes unstable, so that the developer sufficiently exhibits durability. Can not.

In order to make the toner charge ratio (a / b) greater than 1 and less than 1.4, the composition of the core material,
It is necessary to appropriately select the surface shape and the resin composition. Also,
The value of the toner charge amount a can be adjusted by subjecting the core material to airflow classification to remove impurities on the surface and fine powder adhering to the surface.

The toner charge amount a (the charge amount by mixing with the core material) and the toner charge amount b (the charge amount by mixing with the carrier) are measured as in the following (1) and (2).

(1) Mixing with core material or carrier: 20
1 g of the toner and 19 g of the core material or the carrier are placed in a glass screw bottle of ml and mixed and stirred for 20 minutes in an environment at a temperature of 20 ° C. and a relative humidity of 50%.

(2) Measurement of charge amount of toner: Measured by a known blow-off method. Specifically, a developer (a mixture of a toner and a core material or a carrier) is placed in a metal measurement cell having a stainless mesh having an opening of 40 μm on one end side, and the other end face of the measurement cell is placed. Blow pressure 2.0 kg / cm ² (0.196 MPa)
By ejecting nitrogen gas for 6 seconds, a part of the toner is discharged, and the amount of change (Q) in the amount of charge and the amount of change in the mass (amount of the discharged toner) in the measuring cell are measured.
(M) to toner charge (Q / M) [unit: μC / g]
Ask for. Here, the blow rate (toner discharge rate) is 2
0 to 60%. That is, when 1 g of a developer having a toner concentration of 5% is placed in the measurement cell, the measurement is performed under the condition that 10 to 30 mg of the toner is blown.

Further, in this carrier, the exposed amount of the core of the carrier before mixing with the toner is s, and the core of the carrier (the carrier constituting the developer of the present invention) after mixing with the toner. Assuming that the exposure amount is t, the ratio of the core material exposure amount (t / s) is larger than 5;
And it is set as less than 50, Preferably it is 10-20.

When the ratio (t / s) of the exposed amount of the core material is 5 or less, the charge is accumulated in the carrier by repeating the image formation. Image density is reduced. On the other hand, when the ratio (t / s) of the exposed amount of the core material is 50 or more, the charge amount is significantly reduced by leaving the developer unattended, which causes problems such as fogging and crushed characters in a formed image.

Here, the “exposure amount of the core material of the carrier” before and after mixing with the toner is measured as follows. The concentration (c ₁ ) of the metal element (eg, iron) most contained in the core material is measured by ESCA. Then, the concentration (c _2s ) of the metal element on the carrier surface before mixing with the toner is measured by ESCA, and (c _2s /
Let c ₁ ) be the amount of exposed core material. Further, the concentration (c _2t ) of the metal element on the carrier surface after mixing with the toner is _expressed by E
It is measured by SCA, and (c _2t / c ₁ ) is defined as the core material exposure amount. The amount of exposure of the core material after mixing with the toner (c _2t
/ C ₁ ) is measured after washing and separating the toner from the developer (mixed system). And the ratio of the core material exposure amount (t / s) "
Is calculated from the amount of exposed core material of the carrier before mixing with the toner (s = c ₂ s / c ₁ ) and the amount of exposed core material of the carrier after mixing with the toner (t = c _2t / c ₁ ). (T / s = c _2t / c _2s ).

Examples of the core material constituting the carrier include conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead.

Examples of the coating resin constituting the carrier include olefin resins, styrene resins, styrene-acryl resins, silicone resins, ester resins, and fluorine-containing polymer resins. Among these, a silicone resin containing an aminosilane coupling agent is preferable from the viewpoints of abrasion resistance, stain resistance, and charging stability.

<Production Method of Developer> The production method of the present invention includes a step of mixing the toner and the carrier. That is, the toner and the carrier satisfying the condition of the above formula (1) are mixed until the condition of the above formula (2) is satisfied.

Here, examples of the mixing device used when mixing the toner and the carrier include a V-type mixer and a double cone type mixer. In addition, before mixing the toner and the carrier, if necessary, only the carrier may be agitated by the mixing device. Further, the carrier may be agitated (pre-processed) with a vibration mill, a Henschel mixer, or the like, and then the carrier and the toner may be mixed.

By controlling the mixing conditions of the toner and the carrier, the pretreatment conditions, and the like, the ratio (t / s) of the exposed amount of the core material can be made larger than 5 and smaller than 50. The toner concentration in the developer thus obtained is, for example, 3 to 7% by weight.

<Image Forming Method> In the image forming method of the present invention, a developer (the developer of the present invention) satisfying the above formulas (1) and (2) is charged into a developing device, and after pre-stirring, an image is formed. Is formed. By performing the preliminary stirring of the developer, the exposure amount of the core material of the carrier is increased to some extent, and as a result, the initial fluctuation (increase) of the toner charge amount can be suppressed.

Here, the preliminary stirring can be performed by driving the stirring blade or the developing roll of the developing device for 1 to 10 minutes.

Assuming that the exposed amount of the core of the carrier constituting the developer after the preliminary stirring is u, the ratio of the exposed amount of the core (u / s)
Is preferably 10 to 50.

[0041]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Carrier Production Example> [Carrier 1] Manganese / strontium ferrite particles having a volume average particle size of 70 μm are sucked into an air current having a wind speed of 2.2 m / sec, collected by a cyclone, and adhered to the surface of the ferrite particles. The ferrite fine powder having a particle diameter of 1 μm or less was removed to obtain a carrier core material. Silicone resin "SR-2411" (manufactured by Dow Corning Toray Silicone Co., Ltd., solid content concentration 20% by weight) and N-phenyl-γ-aminopropylmethyltrimethoxysilane in a ratio of 8% by weight based on the solid content (Aminosilane coupling agent), and the resulting mixture was dissolved in toluene to prepare a coating solution. Using a fluidized bed coating apparatus, the coating liquid is coated on the surface of the carrier core material at a ratio of 0.5% by weight with respect to the carrier core material, and then baked at 200 ° C. for 2 hours, After cooling, the carrier 1 was obtained by treating with a vibration mill for 5 minutes.

[Carrier 2] The carrier 2 was manufactured in the same manner as in the production example of the carrier 1 except that a stirring process (peripheral speed of the stirring blades: 4 m / sec) was performed by a horizontal rotating blade type stirring device instead of the process by the vibration mill. I got

[Carrier 3] Carrier 3 was obtained in the same manner as in Production Example of Carrier 1, except that no aminosilane coupling agent was used when preparing the coating solution.

[Carrier 4] Instead of manganese / strontium ferrite particles, copper /
Using zinc ferrite particles and styrene /
Carrier 4 was prepared in the same manner as in Production Example 1 of Carrier 1, except that a methyl methacrylate copolymer (copolymerization ratio = 6: 4, glass transition point = 102 ° C.) was used, and the coating amount on the core material was changed to 1% by weight. I got

[Carrier 5] Production example of carrier 3 except that magnetite particles having a volume average particle diameter of 100 μm were used instead of manganese / strontium ferrite particles, and the cyclone treatment of the core material and the vibration mill treatment of the carrier were not performed. Carrier 5 was obtained in the same manner as described above.

[Carrier 6] Nickel / zinc ferrite particles having a volume average particle diameter of 120 μm were used in place of the manganese / strontium ferrite particles, and the carrier 3 was prepared except that the core material was not subjected to cyclone treatment and the carrier was not subjected to vibration mill treatment. Carrier 6 was obtained in the same manner as in Production Example 1.

[Carrier 7] Carrier 7 was obtained in the same manner as in Production Example of Carrier 3, except that the cyclone treatment of the core material and the vibration mill treatment of the carrier were not performed.

<Toner Production Example> [Toner 1] 100 parts by weight of a polyester resin, 12 parts by weight of carbon black, 1 part by weight of an iron complex of a monoazo dye, and low-molecular-weight polypropylene "Biscol 660P"
After mixing with 2 parts by weight (manufactured by Sanyo Kasei Co., Ltd.) using a Henschel mixer, the mixture was melt-kneaded using a twin-screw kneading extruder set at 110 ° C. The obtained kneaded material was cooled, coarsely pulverized by a hammer mill, finely pulverized by an air-flow type pulverizer equipped with a rotor, and classified by an air classifier to give a color with a volume average particle size of 9.5 μm. Particle A was obtained. 100 parts by weight of the obtained colored particles A and 0.6 parts by weight of the hydrophobic silica fine particles were mixed with a Henschel mixer for 20 minutes at a rotation speed at which the peripheral speed of the stirring blade was 30 m / sec, to thereby prepare toner 1. Obtained.

[Toner 2] Styrene / n-butyl acrylate copolymer (Mw = 111,000, Mn = 4.0)
00, Mw / Mn = 28) 100 parts by weight, 10 parts by weight of carbon black, 1 part by weight of a chromium complex of a monoazo dye, and low-molecular-weight polypropylene "Biscol 660P"
After mixing with 5 parts by weight (manufactured by Sanyo Chemical Co., Ltd.) using a Henschel mixer, the mixture was melt-kneaded using a twin-screw kneading extruder set at 110 ° C. The obtained kneaded material was cooled, coarsely pulverized by a hammer mill, finely pulverized by an air-flow type pulverizer equipped with a rotor, and classified by an air classifier to give a color with a volume average particle size of 9.5 μm. Particle B was obtained. 100 parts by weight of the obtained colored particles B and 0.6 parts by weight of the hydrophobic silica fine particles were mixed with a Henschel mixer for 20 minutes at a rotation speed at which the peripheral speed of the stirring blade was 30 m / sec, to thereby form toner 2. Obtained.

[Toner 3] 65 parts by weight of a polyester resin and a styrene / n-butyl acrylate copolymer (Mw
= 111,000, Mn = 4,000, Mw / Mn = 2
8) 35 parts by weight, 10 parts by weight of carbon black, 1 part by weight of a chromium complex of a monoazo dye, and 5 parts by weight of low-molecular-weight polypropylene "Biscol 660P" (manufactured by Sanyo Chemical Co., Ltd.) were mixed with a Henschel mixer. The mixture was melt-kneaded using a twin-screw kneading extruder set at a temperature of ° C. The obtained kneaded material was cooled, coarsely pulverized by a hammer mill, finely pulverized by an air-flow type pulverizer equipped with a rotor, and classified by an air classifier to give a color with a volume average particle size of 9.5 μm. Particle C was obtained. 100 parts by weight of the obtained colored particles C and 0.6 parts by weight of the hydrophobic silica fine particles were mixed with a Henschel mixer for 20 minutes at a rotation speed at which the peripheral speed of the stirring blade was 30 m / sec, to thereby form toner 3. Obtained.

<Examples 1 to 4 and Comparative Examples 1 to 3> According to Table 1 below, the ratio of each of the carriers 1 to 7 and each of the toners 1 to 3 was such that the toner concentration was 5% by weight. To prepare a developer of the present invention and a developer for comparison. For each of the thus obtained developers, the ratio of the toner charge amount (a / b) and the ratio of the core material exposure amount (t / s) were measured. Table 1 shows the results.
Shown in

Here, the ratio (t / s) of the core material exposure amount is
Core material using "ESCA 1000" (manufactured by Shimadzu Corporation)
Iron concentration (c₁), Before mixing with toner
Iron concentration on carrier surface (c_2s), After mixing with toner
(C) _2t) And s (s = s
c_2s/ C₁) And t (t = c_2t/ C₁)
I did. The carrier surface after mixing with the toner
Iron concentration (c_2tIn the measurement of), the developer is fixed with a magnet,
Was washed with a surfactant and dried.

[0054]

[Table 1]

<Actual Photo Test> Each of the developers obtained in Examples 1 to 4 and Comparative Examples 1 to 3 was left in an environment at a temperature of 30 ° C. and a relative humidity of 80% for 60 days from the production date. The degree of the initial variation of the charge amount was evaluated by performing a real-photograph test for forming a copied image under normal temperature and normal humidity (temperature: 20 ° C., relative humidity: 50%). The image density in each of the samples was measured, and the developer life was measured.

The evaluation method and evaluation criteria are as follows. Initial fluctuation of charge amount: The difference between the charge amount at the initial stage of image formation and the charge amount at 10,000 times formation was measured. Here, the case where the difference in charge amount is less than 2 μC / g is “「 ”,
/ G, “△”, 4-8 μC / g, and “×”, exceeding 8 μC / g.

Image density: For each of the initial image and the image formed 10,000 times, the relative reflection density with respect to white paper was measured using a reflection densitometer “RD-917” (manufactured by Macbeth).

Developer life: The number of image formations (the number of prints) when the fog density became 0.05 or more was measured.

Here, a digital copier “7065” manufactured by Konica Corporation was used as the image forming apparatus. An organic photoreceptor was used as the photoreceptor, and a method of cleaning the transfer residual toner on the photoreceptor surface with a blade was adopted. The developing conditions were set as follows.

Photoconductor surface potential = -750 V DC bias = -600 V developing gap = 0.8 mm developer layer regulating plate gap = 1.0 mm developer pre-stirring time = 5 minutes

[0061]

[Table 2]

[0062]

The developer of the present invention has a small initial fluctuation of the toner charge amount, can exhibit stable charging characteristics over a long period of time, and has excellent durability. Further, even after being left as it is, an image defect such as fog does not occur in the formed image. According to the production method of the present invention,
It is possible to reliably produce a developer having a small initial variation of the toner charge amount and excellent durability. According to the image forming method of the present invention, a high-density and high-quality image can be stably formed over a long period of time from the initial stage.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiyasu Matsumoto 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H005 AA01 AB10 BA02 BA06 BA07 CA08 CA12 CA26 CA28 EA01 EA07 FA01

Claims (5)

[Claims] 1. A developer obtained by mixing a toner and a resin-coated carrier, wherein a charge amount of the toner when a core material constituting the carrier and the toner are mixed is a, When the charge amount of the toner when mixed with the toner is b, the exposed amount of the core material of the carrier before mixing with the toner is s, and the exposed amount of the core material of the carrier after mixing with the toner is t And a developer satisfying the following formulas (1) and (2). Equation (1): 1 <(a / b) <1.4 Equation (2): 5 <(t / s) <50 2. The developer according to claim 1, wherein the coating resin constituting the carrier is a silicone resin containing an aminosilane coupling agent. 3. The developer according to claim 1, wherein the binder resin constituting the toner is a polyester resin. 4. A method for producing a developer, comprising a step of mixing a toner and a resin-coated carrier, wherein a toner charge amount when a core material constituting the carrier and the toner are mixed is a, The charge amount of the toner when the carrier and the toner are mixed is b, the exposure amount of the core material of the carrier before mixing with the toner is s, and the exposure amount of the core material of the carrier after mixing with the toner is t. Wherein a toner and a carrier satisfying the condition of the following formula (1) are mixed until the condition of the formula (2) is satisfied. Equation (1): 1 <(a / b) <1.4 Equation (2): 5 <(t / s) <50 5. An image forming method comprising: charging the developer according to claim 1 into a developing device; and forming an image after preliminary stirring.