JP3241148B2 - Charger-free toner for two-component developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel two-component developer containing no charge controlling agent, and more particularly to a so-called electrophotographic method such as an electrostatic copying machine or a laser beam printer. The present invention relates to a two-component developer toner containing no charge control agent, which is suitably used in an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method, first, the surface of a photoreceptor is exposed to form an electrostatic latent image on the surface of the photoreceptor. Next, a developer is brought into contact with the surface of the photoconductor by a developing device. Then, the toner contained in the developer adheres to the electrostatic latent image, and the electrostatic latent image is visualized as a toner image. When this toner image is transferred from the photoreceptor surface to the paper surface and fixed, an image corresponding to the electrostatic latent image is completed.

As a developer, a two-component developer comprising the above toner and a carrier mainly containing magnetic particles such as iron powder and ferrite particles is generally used. The carrier has a function of applying a charge to the toner by frictional charging and, at the same time, supplying the toner to the electrostatic latent image in a state where the toner is adsorbed on the surface. The toner used in the two-component developer is generally prepared by mixing a colorant (for example, carbon), a charge control agent, a release agent (for example, wax) and the like with a binder resin. Among them, the charge control agent is used for controlling the amount of triboelectricity of the toner that controls development and transfer, and its selection is the most important in designing the toner. Such charge control agents include an electron donating substance and an electron withdrawing substance, which charge the toner positively and negatively, respectively.

[0004] However, some charge control agents conventionally used contain a heavy metal such as a chromium-containing dye.
Harmfulness matters. In addition, when a charge control agent having a nitro group in the molecule is used, ignition becomes a problem.

[0005] Furthermore, since the unit price of the charge control agent is much higher than that of the binder resin and other additives, there is a problem that the unit price of the toner is high despite the content of about several percent. On the other hand, since the charge control agent is involved in the frictional charging property of the toner, simply removing the charge control agent from the toner component lowers the image density as the number of copies increases, as indicated by A in FIG. There is a disadvantage that. This is because, as shown in FIG. 4, as the charge amount of the toner increases with an increase in the number of copies, the electrostatic attraction between the toner and the carrier increases, making it difficult for the toner to separate from the carrier. . In contrast, a normal toner containing a charge control agent has a stable charge amount and a constant image density (indicated by B in FIGS. 3 and 4).

Further, a toner containing no charge controlling agent has a drawback that the transfer efficiency is lowered and the toner is easily scattered. The transfer efficiency decreases because the charge amount of the toner increases as the number of copies increases. Further, it is considered that the toner is scattered because the toner not containing the charge control agent has a low charge amount at the beginning of copying as shown in FIG.

A main object of the present invention is to provide a two-component developer containing no charge controlling agent, which stabilizes image density and transfer efficiency, can maintain high image density and transfer efficiency, and prevents toner scattering. To provide toner. It is another object of the present invention to provide a toner for a two-component developer which does not contain a charge control agent and therefore can reduce material costs.

[0008]

The toner of the present invention is used for a two-component developer, and contains a magnetic material in an amount of 0.1 to 100 parts by weight of the binder resin.
A large-diameter powder having an average particle diameter of 0.05 to 1 μm on the surface was added in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the toner particles. No charge control agent is contained.

That is, the present inventors have conducted intensive studies to provide a toner for a two-component developer which does not contain a charge control agent. As a result, the magnetic material is contained in the above ratio in place of the charge control agent. At that time, the present inventors have obtained a new finding that the charge amount of the toner is stabilized, and as a result, the image density is improved and the scattering of the toner is significantly reduced, thereby completing the present invention. Further, the addition of the magnetic material to the toner also contributes to the improvement of the transfer efficiency.

[0010] Including a magnetic material in the toner is as follows.
Although well known as magnetic toners, magnetic toners are used in one-component developers that do not use a carrier, and the mixing ratio of magnetic materials is usually as large as 20 to 80 parts by weight. It is different from the toner of the invention. That is, in the present invention, when the content of the magnetic material exceeds 10 parts by weight, the electric resistance of the developer increases and the image density decreases, which is not preferable. On the other hand, when the content of the magnetic material is less than 0.1 parts by weight, the effect of stabilizing the toner by the magnetic material cannot be expected.

In the present invention, in addition to containing a magnetic material, an average particle diameter of 0.0
By adding a powder having a large particle size of 5 to 1 μm in a ratio of 0.05 to 5 parts by weight based on 100 parts by weight of the toner particles, the transfer efficiency and the image density are further improved. The reason why the transfer efficiency is improved will be described below with reference to FIGS. First, when a toner containing no charge controlling agent is used, the transfer efficiency decreases because the charge amount of the toner increases as the number of copies increases. That is, as shown in FIG. 2, the transfer of the toner particles 11 to the paper 10 is performed by an electrostatic force (indicated by an arrow a) for transferring the toner to the paper by corona discharge from the back side of the paper 10. However, since the image force (indicated by an arrow b) on the photoreceptor 12 that causes the toner particles 11 to be attracted to the photoreceptor 12 and the Van der Waals force (indicated by an arrow c) are superior to the electrostatic force, the toner particles It is considered that the transferability from the photoconductor 12 to the paper 10 becomes inferior. That is, when the charge amount increases to a certain amount or more,
This is because the mirror image power and Van der Waals force related to the toner charge increase.

On the other hand, as shown in FIG. 1, when the large particle size powder 14 is added to the surface of the toner particles 13, when the toner particles 13 are transferred from the photoreceptor 12 to the paper 10,
A gap s is formed between the photoconductor 12 and the toner particles 13, and the contact area between them is reduced. In this state, the mirror image force e and the van der Waals force f are smaller than the electrostatic force d due to corona discharge, so that the toner particles 13 can be easily transferred to the paper 10, and the transfer efficiency is improved.

Conventionally, colloidal silica in the form of fine powder having a particle diameter (primary particle diameter) of about 0.01 to 0.03 μm has been used as an external additive for the purpose of improving the fluidity and cleaning properties of toner particles. , Alumina, titanium oxide and the like are added to the surface of toner particles. However, in such an external additive having a small particle diameter, the gap s between the photoconductor 12 and the toner particles 13 is small, so that the contact area between the toner particles and the photoconductor is not sufficiently reduced, thereby improving the transfer efficiency. Has little effect on However, in the present invention,
In order to improve the flowability and the like, such an external additive having a small particle size may be used together with a large particle size powder.

Hereinafter, the two-component developer toner of the present invention will be described in more detail. The toner of the present invention is formed by blending a pigment and a release agent together with the magnetic material in a binder resin. As the binder resin, any conventionally used resin can be used, for example, polystyrene,
Chloropolystyrene, poly-α-methylstyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene- Acrylate copolymers (eg, styrene-
Methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer), styrene-methacrylate Copolymers (for example, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.),
Styrene-based resins such as styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylate copolymer (for example, monoweight or copolymer containing styrene or a styrene substituent), vinyl chloride resin, styrene -Vinyl acetate copolymer, rosin-modified maleic resin, phenyl resin, epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, Xylene resin, polyvinyl butyral resin and the like can be mentioned. These resins may be used alone or in combination of two or more.

Of these, styrene resins and styrene-acrylic resins are particularly preferred. Further, as the magnetic material, for example, magnetite
(Fe ₃ O ₄ ), various ferrites, maghemite (γ-Fe
Magnetic powders such as ₂ O ₃ ), CrO ₂ , and iron alloy powders.
The ferrites include, for example, zinc iron oxide (ZnFe
₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe ₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), oxide Iron lead (PbFe ₁₂ O ₁₂ ), nickel iron oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFeO ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂ O ₄ ),
Ferrite particles comprising one or more of iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (laFeO ₃ ), and the like. These magnetic materials have an average particle size of 0.05 to 5 μm.
m is preferred.

The electric resistance of the magnetic material may be high or low, and generally has a volume resistance of 1 ×.
10 ^-1 to 1 × 10 ⁹ Ω · cm, preferably 1 × 10 ¹ to 1
A material of × 10 ⁶ Ω · cm is used. Such a magnetic material is compounded in an amount of 0.1 to 10 parts by weight, preferably 0.3 to 7 parts by weight, based on 100 parts by weight of the binder resin for the above-described reason.

The coloring agent to be mixed in the binder resin includes
For example, carbon black, lamp black, chrome yellow, Hansa yellow, benzidine yellow, bethlen yellow, quinoline yellow, permanent orange G
TR, pyrazolone orange, parkan orange, watching red, permanent red, brilliant carmine 3B, brilliant carmine 6B, Dupont oil blend, pyrazolone red, lithol red, rhodamine B lake, lake red C, rose bengal, aniline blue, ultramarine Blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green, etc., or CISolvent Yellow 60, CISolvent Red 2
7, oil-soluble dyes such as CISolvent Blue 35 and the like. These colorants are used alone or in combination of two or more.

These colorants are used in an amount of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the binder resin. As the release agent (offset preventing agent), for example, aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids,
Fatty acid esters or saponified products thereof, silicone oil, various waxes and the like can be mentioned. Of these, aliphatic hydrocarbons having a weight average molecular weight of about 1,000 to 10,000 are preferred. Specifically, one or a combination of two or more of low-molecular-weight polypropylene, low-molecular-weight polyethylene, paraffin wax, a low-molecular-weight olefin polymer composed of olefin units having 4 or more carbon atoms, and silicone oil are suitable.

The release agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin. The production of toner consists of kneading, grinding,
It can be performed by a dry method by sieving or a wet method of spray granulation in the form of a dispersion, and the produced toner is adjusted to a preferable particle size range by a classification operation such as air classification. The particle size of the toner is not particularly limited and may be in a range usually used, but is generally 5 to 20 μm, preferably 6 to 12 μm.

The material of the large particle size powder added to the surface of the toner particles is not particularly limited, and various types of inorganic powders such as metal powders and resin powders can be used. Examples of the inorganic powder include magnetic powder such as magnetite, iron powder, aluminum powder, silica powder, alumina powder, and titanium oxide powder. Further, as the resin powder, for example, acrylic resin, polyester resin,
Powders of polyurethane resin, silicone resin and the like can be given.

The average particle size of the large particle size powder as a surface treating agent is 0.05 to 1 μm, and more preferably 0.1 to 0.1 μm.
It is appropriate that the thickness is about 07 to 1 μm. Further, the amount of the large particle size powder to be added is 0.0 to 100 parts by weight of the toner particles.
Suitably, it is about 5 to 5 parts by weight, more preferably about 0.1 to 4 parts by weight. When the average particle size is larger than the above range, or when the addition amount is larger than the above range, any of the large particle size powder adheres to the photoconductor drum,
On the contrary, since the polishing effect on the photosensitive drum becomes too large, white stripes in a solid black portion and black stripes in a blank paper portion of a copied image are easily generated. On the other hand, when the average particle size is smaller than the above range, or when the addition amount is smaller than the above range, the contact area between the toner and the photoreceptor does not decrease, so that the transfer efficiency is deteriorated.

A predetermined amount of the large particle size powder is mixed and dispersed with toner particles. For mixing and dispersion, for example, a Henschel mixer, a ball mill or the like can be used. In addition, when adding the above-mentioned finely powdered external additive which has been conventionally used together with the addition of the large particle size powder, the external additive is added simultaneously regardless of the order of addition with the large particle size powder. Or one of them may be added first.

The carrier used in combination with the toner of the present invention is not particularly limited, and a conventionally used carrier can be used as it is.

[0024]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The toner for a two-component developer will be described in detail.
The toner is not limited to only these examples.
No. Examples 1-4 and Comparative Examples 1-3 (To the content of magnetic material
(1) Manufacture of toner A styrene-acrylic resin was used as the binder resin.
Carbon black, paraffin wax and magnetic materials
Is a magnetite (trade name “BL-
100 ", average particle size 0.5 μm) are shown in Table 1.
And melt-kneaded with a twin-screw extruder. Then
The kneaded material is pulverized with a jet mill and air classification is performed with a classifier.
Thus, predetermined toner particles were obtained.

The toner particles have an average particle diameter of 0.001.
μm of hydrophobic silica fine particles (trade name “R-972” manufactured by Nippon Aerosil Co., Ltd.) was added at a ratio of 0.3 part by weight to 100 parts by weight of the toner particles, and 2 parts were added using a Henschel mixer.
The mixture was dispersed for minutes. Then, an acrylic resin powder having an average particle size of 0.15 μm (“NTP-
1)) was added at a ratio of 1 part by weight to 100 parts by weight of the toner particles, and mixed and dispersed with a Henschel mixer for 2 minutes to obtain a toner. (2) Evaluation test Ferrite carriers having an average particle size of 80 μm were mixed with the toners obtained in the respective Examples and Comparative Examples, and uniformly mixed by stirring to produce a two-component developer having a toner concentration of 3.5%. . Then, using an electrophotographic copying machine (trade name "DC-7085") manufactured by Mita Kogyo Co., Ltd., a total of 10,000 copies were made for each predetermined number of copies.

The original used for copying was a character original having a black area ratio of 8%, and the original sampled every predetermined number of sheets was an original having a black area ratio of 15% including a solid black part. . Each test method is as follows. (a) Measurement of Image Density (ID) The density of a solid black portion in a copy image of up to 10,000 sheets is measured using a reflection densitometer (Model TC-6D manufactured by Tokyo Denshoku Co., Ltd.) for every predetermined number of sheets. did.

(B) Toner scattering The toner scattering state in the copying machine at the end of copying 10,000 sheets was observed and evaluated according to the following criteria. ：: no toner scattering ×: toner scattering (c) Particle size The particle size of the toner was measured with a Coulter Counter (manufactured by Coulter). Note that the initial particle size shown in the table means the average particle size of the toner before copying.

(D) Transfer Efficiency The amount of toner in the toner hopper before the start of copying and the amount of toner in the toner hopper after copying 10,000 sheets are measured. Was calculated. On the other hand, the amount of toner collected in the cleaning step during the copying of 10,000 sheets was measured to obtain the amount of collected toner. Then, the toner transfer efficiency was determined from the toner consumption amount and the toner recovery amount by the following equation.

[0029]

(Equation 1)

(3) Results The results of the evaluation test are shown together with the amount of each toner used.
It is shown in Table 1.

[0031]

[Table 1]

From Table 1, it can be seen that when magnetite as a magnetic material was not added (Comparative Example 1), the image density was high at the beginning of copying, but rapidly decreased thereafter. . On the other hand, toner scattering also occurs and transfer efficiency is deteriorated. When the amount of magnetite added was excessive (Comparative Examples 2 and 3), toner scattering and transfer efficiency were good, but the image density was poor from the beginning of copying, and the copying speed was reduced thereafter.

On the other hand, in the first to fourth embodiments, the image density does not fluctuate greatly during copying of 10,000 sheets and is almost stable.
It is also good in terms of toner scattering and transfer efficiency. Examples 5 to 8 and Comparative Examples 4 and 6 (Effects of Addition of Large Particle Size Powder on Toner Surface) (1) Production of Toner Predetermined toner particles were obtained in the same manner as in Examples 1 to 4. After mixing and dispersing hydrophobic silica fine particles in the particles, an acrylic resin powder having an average particle diameter of 0.15 μm (“NTP-1” manufactured by Nippon Paint Co., Ltd.) or an average particle diameter of 0.5 μm is used as a large particle diameter powder. Of magnetite powder ("BL
-100 ") was added at various ratios shown in Table 2 to 100 parts by weight of the toner particles, and mixed and dispersed with a Henschel mixer for 2 minutes to obtain a toner. (2) Evaluation Test The image density (ID), toner scattering, initial particle size, and transfer efficiency were measured in the same manner as in Examples 1 to 4. Further, whether or not white streaks occurred in the solid black portion in the copied image was visually observed and evaluated according to the following criteria.

The case where two or more white streaks having a length of 1 mm or more were observed in the solid black area of 3 cm × 3 cm was determined to be white streaks, and the case where the number of white streaks was smaller than that was determined to be no white streaks. (3) Results The results of the above evaluation tests are shown in Table 2 together with the mixing ratio of each toner used.

[0035]

[Table 2]

From Table 2, it can be seen that the acrylic resin powder was added.
The toner of Example 5 is compared with the toner of Comparative Example 4 in which no toner is added.
Transfer efficiency and prevent toner scattering.
It can be seen that the image density can be prevented from lowering.
You. Similar results were obtained by replacing magnet powder with magnet
Obtained in the toners of Examples 6 to 8 to which
I have. On the other hand, a comparative example in which magnetite powder was excessively added
No. 6 shows good transfer efficiency and prevents toner scattering.
And the image density is stabilized, but added in excess
White spots on the black solid due to the effect of the magnetite powder
Had occurred. Example 9 and Comparative Examples 7 to 8 (Large particle size powder on the toner surface
(1) Production of Toner In the same manner as in Examples 1 to 4, predetermined toner particles were obtained.
After mixing and dispersing hydrophobic silica fine particles in the toner particles,
Various acrylic resins with different average particle sizes as powder
Powder or magnetite powder to 100 parts by weight of toner particles
To the Henschel mixer
For 2 minutes to obtain a toner.

The large particle size powder used in Example 9 was a magnetite powder having an average particle size of 0.8 μm (trade name “RB-BL” manufactured by Titanium Industry Co., Ltd.). The powder used in Comparative Example 7 was silica powder having an average particle size of 0.01 μm (trade name “R974” manufactured by Nippon Aerosil Co., Ltd.), and the powder used in Comparative Example 8 was magnetite having an average particle size of 4.0 μm. It is a powder (trade name “BL-SP” manufactured by Titanium Industry Co., Ltd.). (2) Evaluation Test In the same manner as in Examples 5 to 8, the image density (ID), toner scattering, initial particle size, transfer efficiency, and the presence or absence of white stripes on the solid black portion of the copied image were tested. . (3) Results The results of the above evaluation tests are shown in Table 3 together with the mixing ratio of each toner used and the results of Example 5 (using acrylic resin powder) and Example 7 (using magnetite powder).
Shown in

[0038]

[Table 3]

From Table 3, it can be seen that the particle size of the added powder is 0.01
In the case of μm (Comparative Example 7), it can be seen that the transfer efficiency was poor and sufficient image density was not obtained. When the particle size of the added powder was 4.0 μm (Comparative Example 8), the transfer efficiency was poor, and white stripes were observed in the solid black portion.

[0040]

As described above, the two-component developer toner of the present invention contains no charge control agent,
It is possible to stabilize the toner characteristics and prevent a decrease in image density and a decrease in transfer efficiency. Therefore, the toner of the present invention contains no charge control agent,
There is an effect that it can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining an improvement in transfer efficiency when a toner of the present invention is used.

FIG. 2 is an explanatory diagram for explaining a decrease in transfer efficiency when a toner containing no charge control agent is used.

FIG. 3 is a graph showing a change in image density depending on the presence or absence of a charge control agent.

FIG. 4 is a graph showing a change in charge amount depending on the presence or absence of a charge control agent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Paper 11 Toner particle 12 Photoconductor 13 Toner particle 14 Large particle size powder s Gap

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Arakawa 1-2-2, Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Industries Co., Ltd. (72) Inventor Kazuya Nagao 1-2-2, Tamazuki, Chuo-ku, Osaka, Osaka No. 28, Mita Kogyo Co., Ltd. (56) References JP-A-2-72373 (JP, A) JP-A-3-17660 (JP, A) JP-A-3-63660 (JP, A) JP-A-3 -256052 (JP, A) JP-A-3-257462 (JP, A) JP-A-6-19192 (JP, A) JP-A-6-19193 (JP, A) JP-A-4-68362 (JP, A) JP-A-2-22673 (JP, A) JP-A-2-101480 (JP, A) JP-A-3-200159 (JP, A) JP-A-3-231756 (JP, A) JP-A-4- 359260 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. A large-particle powder containing a magnetic material in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of a binder resin and having an average particle diameter of 0.05 to 1 μm on the surface. Toner particles 10
A two-component developer toner containing no charge control agent, wherein the toner is added in an amount of 0.05 to 5 parts by weight based on 0 part by weight.