JP3025694B2 - Electrophotographic developer and manufacturing method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electrophotographic developer containing a toner and a magnetic carrier.

[Conventional technology]

The electrophotographic developer is composed of a toner and a carrier.
It is roughly classified into a one-component developer composed of only a component developer and a toner. 2. Description of the Related Art In an image forming apparatus using an electrophotographic method, such as a copier, a two-component developer is generally used. However, there are problems such as the inability to obtain a printed image, the short life of the developer, and the scattering of toner during copying.

Conventionally, a method of externally adding a powdery abrasive such as magnetite to the toner surface and polishing the surface of the photoreceptor drum to maintain image quality has been used, but in a usual external addition method such as stirring by a mixer, The abrasive is easily detached from the toner. For this reason, a method of embedding an abrasive in the toner surface by applying pressure (Japanese Patent Laid-Open No. 63-103264),
A method is known in which a magnetic powder is electrostatically adhered to a toner surface, and then the toner surface is thermally melted and fixed (Japanese Patent Laid-Open No. 1-108553).

However, conventionally used spherical, granular, cubic,
An octahedral magnetic material or the like hardly electrostatically adheres to the toner surface, and therefore requires a large amount of energy. If the magnetic material is sufficiently fixed on the toner surface, the magnetic material may be buried in the toner surface and the effect of the magnetic material may not be sufficiently exerted.

[Problems to be solved by the invention]

The present invention provides a toner having improved developer life and environmental dependency.
It is intended to provide a component developer.

[Means for solving the problem]

The present invention relates to a two-component developer containing a toner and a magnetic carrier, wherein an acicular magnetite having a major axis / minor axis ratio of 3 or more adheres to the surface of the toner. .

As the toner used in the present invention, an ordinary toner containing a binder resin, a colorant, a charge control agent and the like can be used.

Examples of the binder resin include styrene (co) polymers such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer; styrene-methyl acrylate copolymer Copolymers of styrene and acrylate such as styrene-ethyl acrylate copolymer and styrene-acrylic acid-n-butyl copolymer; styrene-methyl methacrylate copolymer and styrene-ethyl methacrylate copolymer Polymers, copolymers of styrene and methacrylate such as styrene-methacrylic acid-n-butyl copolymer; multi-component copolymers of styrene with acrylate and methacrylate; styrene-acrylonitrile copolymer, Styrene vinyl methyl ether copolymer, styrene butadiene copolymer Styrene vinyl methyl ketone copolymer, styrene acrylonitrile indene copolymer, copolymer of styrene and other vinyl monomers such as styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyester resin, Polyvinyl acetate polyester, polyamide resin, epoxy resin, polyvinyl butyral, polyacrylate phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, and the like can be used alone or in combination.

It is preferable that no magnetic powder be added to the toner used in the present invention, but the following magnetic powder may be added in some cases. Metals such as cobalt, iron and nickel, aluminum,
Cobalt, copper, iron, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium, other metal alloys, metal oxides such as aluminum oxide, iron oxide, nickel oxide, ferromagnetic ferrite,
Magnetite. This magnetic powder has an average particle diameter of 0.05 to 3 μm.
m is preferred.

As the colorant, for example, the following pigments or dyes can be used. Carbon black, aniline blue (CI
No.50405), Calco Oil Blue (CINo.axoec Blue)
3), Chrome Yellow (CINo. 14090), Ultramarine Blue (CINo. 77103), Dupont Oil Red (CINo. 26105), Orient Oil Red # 330 (C.
I.No.47005), methylene blue chloride (CINo.520
15), Phthalocyanine Blue (CINo. 74160), Malachite Green Oxalate (CINo. 42000), Lamp Black (CINo. 77266), Rose Bengal (CINo. 454)
35) etc.

Other charge control agents include (+) toner for nigrosine electron donating dyes, metal salts of naphthenic acid and higher fatty acids, alkoxylated amines, quaternary ammonium salts, alkyd amides, phosphorus, tungsten, molybdate lake pigments And a fluorinated activator. For the (-) toner, an electron-accepting organic complex, chlorinated paraffin, chlorinated polyester, polyester having an excess acid group, sulfonylamine of copper phthalocyanine and the like are used.

The acicular magnetite adhered to the toner surface means, for example, particles having a shape having a major axis / minor axis ratio of 3 or more. The acicular magnetite is preferably particles having a specific surface area of 10 m ² / g or more and an average particle diameter (major axis diameter) of 2 μm or less. Magnetite particles having a saturation magnetization of 80 emu / g (5 KOe) or more are preferable. The coverage of acicular magnetite on the toner surface is 0.2-20
% Is preferable.

The acicular magnetite used in the present invention is different from the generally used shapes such as spherical, granular, cubic, and octahedral, and the ratio of the major axis to the minor axis of 3 or more is applied to the toner surface. Has good adhesion. The reason why acicular magnetite has better adhesion to the toner surface than the cubic magnetic powder is because the specific surface area of the acicular magnetite is large, the contact area with the toner surface is large, and van der Waals force and toner It is considered that the adhesion force such as Coulomb force due to the charge exchange between the iron and the acicular magnetite increases. Therefore, it is desirable that the specific surface area of the acicular magnetite is large, preferably 10 m ² / g.
The above is preferred. The average size of the primary particles is preferably 2 μm or less because the size of the acicular magnetite must be uniformly attached to the toner surface. The average particle size in this case is the particle size of the long axis. If the particle size exceeds 2 μm, adhesion to the toner surface is not sufficient, and the amount of desorbed powder increases, so that the effect is not exhibited. As for the magnetic force of the acicular magnetite, a magnetite powder having a saturation magnetization of 80 emu / g (5 KOe) or more is effective because the larger the magnetic force, the smaller the addition, the more the magnetic effect can be exhibited.

The addition amount of the acicular magnetite is appropriately determined depending on the chargeability and particle size of the toner and carrier used. Since the surface area of the toner increases as the particle size of the toner decreases, the amount of acicular magnetite to be added also needs to be proportional to the surface area. If the added amount is too small, the effect is not exhibited, but the acicular magnetite has good adhesion to the toner and has little desorption, and the acicular magnetite itself has a large surface area, so that a sufficient effect can be expected even with a small amount. In addition, since the manufacturing method of fixing the toner to the toner surface as conventionally proposed is not taken, the needle magnetite is exposed on the toner surface, so it is considered that even a small amount is effective. However, if it is added too much, the amount of acicular magnetite coating the toner surface becomes too large, and the chargeability of the toner becomes insufficient, causing image deterioration. On the other hand, if the amount of addition is large, a considerable amount of energy is required to cause all the acicular magnetite to adhere to the toner surface. From these points, the coverage of the acicular magnetite on the toner surface is preferably about 0.2 to 20%.

 The coverage (f) was calculated by the following equation.

In the formula, Sm is the projected area of the magnetite (cm ² / g: the minor axis of the acicular magnetite is Ds (cm), the true specific gravity is ρm (cm ³ / g), and the acicular magnetite is roughly cylindrical. formula
Sm = 4 / π · Ds · ρm Projected area value calculated).

St is the specific surface area (cm ² /
g: The average particle diameter of the toner is Dt (c), the true specific gravity ρt (cm ³ / g)
Where St = 6 / ρt · Dt.

 C means the blending amount (wt%) of acicular magnetite.

In producing the developer of the present invention, first, a binder resin, a colorant, a charge control agent and, if desired, a magnetic powder are melted and mixed, and then pulverized and classified to prepare a toner.

Then, a mixing stirrer such as a ball mill, a V-type mixer,
Needle magnetite is adhered to the toner surface using a Nauter mixer, a super mixer, a Henschel mixer, or the like.

The mixing temperature of the toner and the acicular magnetite must be lower than the glass transition temperature of the toner. If the mixing temperature is higher than this, the effect of attaching the acicular magnetite to the toner surface may not be exhibited because the acicular magnetite is buried in the toner surface.

The fluidizer is then added and mixed. As the fluidizing agent, for example, oxides such as silica, titanium, and alumina, and polymer beads having a small particle diameter are used. It is important to add a fluidizing agent after the acicular magnetite is attached to the toner surface, and if the acicular magnetite and the fluidizing agent are added to the toner simultaneously, the selective attachment of the fluidizing agent to the acicular magnetite A phenomenon may occur and the fluidity of the toner may not be obtained.

The developer of the present invention can be obtained by mixing the toner and the magnetic carrier.

Carriers include iron powder, ferrite, magnetite,
A resin carrier or the like is used.

〔Example〕

 Parts in the following examples mean parts by weight.

Example 1. Styrene acrylic copolymer [TB-1000 (manufactured by Sanyo Kasei)] 86 parts Polypropylene wax [Viscol 660P (manufactured by Sanyo Chemical)] 3 parts Charge control agent [Bontron S34 (manufactured by Orient Chemical)] 1 Part Carbon black [PRINTEX-L (manufactured by Degussa)] 10 parts The above components are melt-kneaded, then crushed and classified, and the average particle size is determined.
A toner of 12 μ was obtained.

Acicular magnetite powder (A) Major axis = 0.8μ, minor axis = 0.1μ, major axis / minor axis = 8, specific surface area = 20m ² / g, saturation magnetization = 85emu / g (5KOe) Acicular magnetite powder for toner 0.5% by weight of (A) was added and mixed for 15 seconds with a Henschel mixer. Further, 0.3% by weight of silica (Aerosil R972) was added and mixed for 1 minute with a Henschel mixer. The coverage of the needle-like magnetite powder (A) on the toner surface of this mixture is about 2.7%.

Sm = 2.42 × 10 ⁴ cm / g, St = 4.55 × 10 ³ cm ² / g, C = 0.5%
Therefore, f = 2.7%.

A developer was prepared by mixing 97 parts of a ferrite carrier coated with a silicon resin on the surface and having an average particle diameter of 80 μm and 3 parts of the above mixture.

Commercial copying machine equipped with a selenium photoconductor (26 sheets / min., A4
When the above developer was used in a long run test, a good image was obtained even after 100,000 copies were made.
In addition, even under high temperature and high humidity environment or low temperature and low humidity environment, image degradation,
No scattering of the developer was observed.

Comparative Example 1. Example 1 except that the acicular magnetite powder (A) was not used.
A developer was prepared in the same manner as described above, and a long run test was performed. This developer showed a remarkable rise in charge under a low-temperature and low-humidity environment, and the image density was 1.4 in the initial state.
It decreased to 0.8 for 1,000 sheets. Further, in a high-temperature and high-humidity environment, the developer was scattered, and an image was stained by the developer dropped from the developer.

Comparative Example 2. An octahedral magnetite powder (B) was used in place of the acicular magnetite powder (A).
A developer was prepared in the same manner as described above.

The octahedral magnetite powder (B) used had an average particle size of 0.2 μm, a specific surface area of 7 m ² / g, and a saturation magnetization of 82 emu / g (5 KOe).

When a long run test was performed using this developer in the same manner as in Example 1, the fog in the image background portion increased. In addition, the magnetic powder was not sufficiently adhered to the toner surface, and the detached magnetic powder damaged the photoreceptor. Numerous streak-like scratches occurred in the circumferential direction of the photoconductor, affecting the copied image. Also, the life of the photoreceptor was much shorter than that of Example 1 due to these scratches.

Example 2. Styrene acrylic copolymer [TB-1000 (manufactured by Sanyo Kasei)] 80 parts Polypropylene wax [Himer 330P (manufactured by Sanyo Chemical)] 5 parts Charge control agent [Bontron E81 (manufactured by Orient Chemical)] 2 Part Carbon black [Mogal L (Cabot)] 8 parts Magnetite powder [EPT-500 (Toda Kogyo)] 5 parts The above components are melt-kneaded and then pulverized and classified to obtain a toner having an average particle diameter of 8 μm. .

2% by weight of acicular magnetite powder (A) was added to the toner and mixed for 15 seconds with a Henschel mixer, and 0.3% by weight of silica (Aerosil R972) was further added and mixed for 1 minute with a Henschel mixer. The coverage of the needle-like magnetite powder (A) on the toner surface of this mixture is about 7.1%.

A developer was prepared by mixing 96 parts of a granulated magnetite carrier whose surface was coated with an acrylic resin and having an average particle diameter of 68 μm and 4 parts of the above mixture.

A long-run test of the developer was performed using a laser beam printer of a type that recycles collected toner by a reversal developing method. As a result, a good image was obtained even when printing was performed on 40,000 sheets. Since this developer has a good charge rising characteristic, there is no practical problem even if the quality of the collected toner slightly changes.

Comparative Example 3 Example 2 except that the acicular magnetite powder (A) was not used.
A developer was prepared in the same manner as described above, and a long run test was performed. In the used laser beam printer, a large amount of fog occurred in the image background portion with an increase in the number of prints due to the deterioration of the quality of the toner reused due to the method of recycling the collected toner.

Example 3 Styrene-acrylic copolymer (TB-1000: manufactured by Sanyo Chemical Co., Ltd.) 88 parts Polypropylene wax (Viscol 550P: manufactured by Sanyo Chemical Co., Ltd.) 4 parts Charge control agent (Spiron Black TRH: manufactured by Hodogaya Chemical Co., Ltd.) 1 Part Carbon black (Black Pearl L: manufactured by Cabot Corporation) 7 parts The above-mentioned components were melt-kneaded and then pulverized and classified to obtain a toner having an average particle diameter of 6 μm.

0.1% by weight of acicular magnetite powder (A) was added to the toner and mixed for 10 seconds with a Henschel mixer. Further, 0.5% by weight of silica (Aerosil R972) was added and mixed for 15 seconds with a Henschel mixer. The coverage of the needle-like magnetite powder (A) on the toner surface of this mixture is about 0.27%.

A developer was prepared by mixing 97 parts of a ferrite carrier having an average particle diameter of 50 μm and 3 parts of the above mixture.

Reverse development laser beam printer (600DPI)
And a long-run test of the developer was performed, and a good image was obtained even after printing 20,000 sheets.

Comparative Example 4. A developer was prepared in the same manner as in Example 3 except that the octahedral magnetic powder (B) was used instead of the acicular magnetite powder (A). When a long run test was performed using this developer, a large amount of fogging occurred on the back surface of the image as the number of printed sheets increased.

Example 4. Polyester resin (Lunaper 1400: manufactured by Arakawa Chemical Co., Ltd.) 87 parts Polypropylene wax (Viscole 550P: manufactured by Sanyo Chemical Co., Ltd.) 1 part Charge control agent (Bontron E84: manufactured by Orient Chemical Co., Ltd.) 5 parts Carbon black (Black Pearl L : 7 parts The above components were melt-kneaded and then pulverized and classified to obtain a toner having an average particle size of 8 µm.

0.4% by weight of acicular magnetite powder (A) was added to the toner and mixed for 10 seconds with a Henschel mixer, and 0.4% by weight of silica (Aerosil R972) was further added and mixed for 15 seconds with a Henschel mixer. The coverage of the needle-like magnetite powder (A) on the toner surface of this mixture is about 1.42%.

A developer was prepared by mixing 95 parts of a ferrite carrier having an average particle diameter of 50 μm and 5 parts of the above mixture.

Using the same laser beam printer as in Example 3, a long-run test of the developer was performed. Even when printing was performed on 20,000 sheets, there was no problem such as fog and toner scattering.
Good images were obtained.

Comparative Example 5. 0.4% by weight of octahedral magnetite powder (B) in toner
And 0.4% by weight of silica (Aerosil R972) were added simultaneously and mixed with a Henschel mixer for 30 minutes to completely fix the magnetite powder (B) on the toner surface. The temperature of the toner at the time of mixing has risen to about 60 ° C., and this temperature is near the glass transition temperature of the toner. Therefore, when the toner is mixed, the magnetite powder (B) is buried in the toner surface. Conceivable.

A developer was prepared by mixing 95 parts of a ferrite carrier having an average particle diameter of 50 μm and 5 parts of the above mixture. Using this developer, a long run test was performed in the same manner as in Example 4.
There was a lot of fogging in the background of the image and poor fluidity of the toner, causing a problem in toner supply from the toner hopper. Furthermore, black spots due to a lump of toner were generated on the image due to a lot of soft blocking of the toner.

〔The invention's effect〕

In the developer of the present invention, the rising speed of the triboelectric charging between the toner and the carrier is increased, and the charging characteristics of the developer are improved, so that fog is greatly reduced. In many cases, the problem of toner scattering occurs in a high-speed copying machine. However, when this developer is used, the scattering is remarkably reduced as compared with a toner containing no magnetic powder. When a large number of copies are made, the image density decreases due to an increase in the charge amount or a change in the toner particle size in the developer due to the selective development. However, when this developer is used, the toner surface has low resistance. The excessive increase in charge of the toner is suppressed because the needle-like magnetite adheres, and the image density is stabilized. In particular, when the toner cleaned from the photoreceptor is collected and reused, the effect is particularly large because the fine particle toner and the toner having poor chargeability are recycled.
Further, in the case of a two-component developer, its life is determined by the state of deterioration of the carrier. The deterioration of the carrier is most affected by the spent toner, and when the amount of spent toner is increased, the chargeability is deteriorated, causing toner scattering and image deterioration in the first half. In the case of the developer of the present invention, it has been confirmed that the amount of this spent toner is very small due to the influence of acicular magnetite attached to the toner surface, and it is very likely that the spent toner tends to become spent toner due to the low resistance of the toner surface. It is considered that a toner having a high charge amount is hardly generated, and a polishing effect of polishing the attached spent toner from the carrier is also considered. Further, even when spent toner is generated, the phenomenon of scattering from the sleeve is suppressed because the toner has good charge rising characteristics and the toner has a weak magnetic force.

As described above, the toner externally added with the acicular magnetite of the present invention has extremely good mixing properties with the replenished developer,
Developers also have a long life. When conductive powder is adhered to the toner surface, for example, an excessive rise in charge in a low humidity environment can be suppressed, and a difference in development characteristics due to a difference in environmental conditions can be reduced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-108553 (JP, A) JP-A-59-191069 (JP, A) JP-A-62-112167 (JP, A) JP-A-2- 97968 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08-9/113

Claims (4)

(57) [Claims] 1. A two-component developer containing a toner and a magnetic carrier, wherein needle-like magnetite having a major axis / minor axis ratio of 3 or more is adhered to the surface of the toner. 2. The electrophotographic developer according to claim 1, wherein the coverage of acicular magnetite on the toner surface is 0.2 to 20%. 3. An acicular magnetite having an average particle size of 0.1 to 2 μm.
^2. The electrophotographic developer according to claim 1, wherein m, specific surface area is 10 m ² / g or more, and major axis / minor axis ratio is 3 or more. 4. A method for producing a developer for electrophotography, comprising adding a fluidizing agent after adhering acicular magnetite to the surface of a toner, and then mixing with a magnetic carrier.