JPH06332232A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To prevent the filming of a toner on the carrier, sleeve, surface of a photosensitive body, to stabilize the triboelectrifying characteristic of the toner and to improve the picture quality by sticking an acicular titanium oxide particle on the surface. CONSTITUTION:This toner contains at least a binder resin and a colorant, and the acicular titanium oxide particle is stuck on the surface. In this case, the aspect ratio of the particle is preferably controlled to >=10 and the volume resistivity to <=10OMEGAcm. Such a particle is easily stuck on the toner surface and hardly released, and hence the grinding effect, chargeability and fluidity improving effect of the titanium oxide are fully exhibited. Accordingly, when the toner is used, the excessive increase in the charge of the toner is suppressed since the titanium oxide having higher conductivity than the binder resin is stuck on the surface, and contact of the toner base particle with the carrier, sleeve, etc., is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic charge image formed by electrophotography, electrostatic printing, electrostatic recording or the like.

[0002]

2. Description of the Related Art A method for developing an electrostatic latent image with toner is roughly classified into a developing method using a two-component developer mainly composed of toner and carrier, or a developing method using a one-component developer consisting of only toner. There are various methods, and various proposals have been made regarding each developing method. The method of using a two-component developer is a method of developing an electrostatic latent image by applying an electric charge to the toner by frictional charging between the toner and the carrier. Therefore, if the mixing property of the toner and the carrier and the charging property are not good, sufficient charging property cannot be obtained, and good image quality cannot be obtained. Further, when a large number of sheets are copied, the toner is electrically attached or mechanically fused to the surface of the carrier and the surface of the carrier is changed, so that the characteristics of the developer are changed and the triboelectric charging speed becomes slow, resulting in various problems. Occur. Specifically, when the charge distribution of the developer spreads and the toner of the opposite charge is generated, the fogging phenomenon to the image background portion and the toner scattering from the developing layer become remarkable, and the characteristics of the developer change due to the selective development. The toner consumption may increase due to a decrease in image density or a decrease in charging property and an increase in image density.

Further, in the case of the one-component toner, a method of charging the toner by frictional charging between the toner and the sleeve or the charging blade is used, but a phenomenon similar to the above-mentioned phenomenon occurring on the carrier surface occurs on the sleeve. Then
After all, the developability changes. As a means for solving these problems, conventionally, powdered relatively conductive inorganic fine powder such as magnetite, carbon black, titanium oxide, alumina, or ceramics is externally added to the toner surface to coat the surface of the carrier or the sleeve. A method of maintaining the image quality by polishing or by utilizing the conductive property of these additives to leak the charge accumulated in the toner to prevent an increase in the charge amount is used.

It is known that by adhering the conductive inorganic fine powder to the surface of the toner as described above, it is possible to obtain the effect of polishing the photosensitive member, the sleeve, or the carrier, and the effect of preventing an increase in the charge amount. However, the shape of the conductive inorganic fine powder is conventionally used spherical, granular, cubic,
In the case of an octahedron or the like, it was difficult for the toner to electrostatically adhere to the toner surface, and sufficient energy was required to fix the toner on the surface. However, when these conductive inorganic fine powders are buried in the toner surface by taking a method of applying strong energy in order to sufficiently fix the conductive inorganic fine powders to the toner surface, the expected effect may not be sufficiently exhibited. There was a problem such as that. Further, when these conductive inorganic fine powders were not sufficiently adhered to the toner surface, the inorganic fine powders detached from the toner in the developing device, and similarly sufficient effects could not be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the above-mentioned conventional electrophotographic developers, and prevents the filming of toner on the carrier, sleeve, photosensitive member surface, etc. It is an object of the present invention to provide an electrophotographic developer having stable toner triboelectric charging characteristics and good image quality during copying.

[0006]

The present invention relates to a toner containing at least a binder resin and a colorant, wherein needle-shaped titanium oxide particles are adhered to the surface of the toner for electrophotography. The aspect ratio of the titanium oxide particles is preferably 10 or more, and the volume resistivity is preferably 10 Ωcm or less.

The needle-shaped titanium oxide particles adhered to the toner surface of the present invention have good adhesion to the toner surface and have the effect of being hard to be detached. Therefore, the titanium oxide itself has a polishing effect, a charging property, and a flow property. The effect of imparting sex can be fully exerted. Therefore, when this toner is used, since titanium oxide, which is relatively more conductive than the binder resin, adheres to the surface of the toner, an excessive increase in charge of the toner is suppressed and the image density is stabilized. Further, the contact between the toner mother particles and the carrier or sleeve is suppressed, and the generation of spent toner is reduced. Further, even if toner filming occurs on the carrier, sleeve, or photoreceptor, the filming substance is polished by the polishing effect of titanium oxide, so that a fresh state can be always obtained. The acicular titanium oxide of the present invention preferably has an aspect ratio of 10 or more, whereas spherical or granular titanium oxide is not preferred because of its poor adhesion to the toner surface. The diameters of the major axis and the minor axis as used herein indicate the average body area diameter measured by an image analyzer, and the aspect ratio means the ratio of the major axis to the minor axis. Needle-shaped titanium oxide having an aspect ratio of 10 or more comes into contact with the toner on the surface when a high-speed shearing force is applied to the surface of the toner and adheres to the toner, and the contact area becomes larger than when spherical particles are used. Therefore, it is considered that the adhesion is improved. Further, since it is needle-shaped, it may be embedded while being stuck in the toner.

The content of the acicular titanium oxide in the toner is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the toner mother particles. When the content of needle-shaped titanium oxide is less than 0.1 parts by weight, it is difficult to maintain the triboelectric charging characteristics of the toner in good condition and the polishing effect is not sufficient. On the other hand, if the amount is more than 2 parts by weight, there arises a problem that the charging property of the toner itself is hindered.

The acicular titanium oxide used in the present invention preferably has a volume resistivity of 10 Ωcm or less.
The volume resistivity of titanium oxide having an ordinary rutile type crystal structure is 10 ¹³ to 10 ¹⁴ Ωcm, and the volume resistivity of titanium oxide having an anatase type crystal structure is about 10 ⁸ Ωc.
m. When titanium oxide having a high volume resistivity is adhered to the surface of the toner as described above, the effect of preventing the charge amount by stirring for a long time cannot be obtained because the leakage of the charge is not sufficient. When titanium oxide having a low resistance of 10 Ωcm or less as in the present invention is used, it is possible to easily achieve an increase in the charge amount. As a means for reducing the resistance of titanium oxide, a method of surface-treating titanium oxide with a conductive layer such as SnO ₂ doped with Sb is used. The volume resistivity referred to here was measured in a state in which a cell having an electrode was filled with powder and compressed under a load of 100 kg / cm ² .

The means for adhering the acicular titanium oxide of the present invention to the toner surface can be achieved by mixing the toner and acicular titanium oxide and then agitating with a stirrer capable of imparting a high shearing force. For example, Henschel mixer, super mixer, turbulizer, hybridizer from Nara Machinery Co., Ltd., which is generally used as a surface reformer for powder, Ong mill from Hosokawa Micron,
The turbo mill manufactured by Turbo Industry Co., Ltd. can be mentioned.

As the binder resin to be contained in the toner,
Styrene resin, styrene-acrylic acid ester copolymer resin, styrene-butadiene copolymer resin, polyester resin, epoxy resin and the like can be used. Other constituent components of the toner constituting the present invention include a colorant, a charge control agent, and other additives to be blended as required, and the toner is a mixture of these materials and a binder resin in a desired blend. It is obtained by mixing in a ratio, melt-kneading, cooling, solidifying, and pulverizing and classifying. Further, it may be obtained as a so-called polymerization method toner prepared by mixing the above materials at the time of polymerizing the binder resin.

Examples of colorants include carbon black, monoazo red pigments, disazo color pigments, quinacridone magenta pigments, and anthraquinone dyes. Charge control agents include nigrosine dyes, quaternary ammonium salts, and monoazo dyes. Examples thereof include metal complex salt dyes. Other additives added as necessary include polyolefins such as polypropylene as a release agent, and hydrophobic silica and colloidal silica as a fluidizing agent.

[0013]

In the toner for electrophotography of the present invention, by attaching acicular titanium oxide to the toner surface, filming on the carrier, sleeve and photoreceptor surface is prevented and the triboelectric charging property is improved. Can be maintained.

[0014]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 Preparation of toner mother particles-Styrene-acrylic acid ester copolymer resin 100 parts (manufactured by Sanyo Chemical Co., Ltd .; trade name: TB-1000) -Polyethylene 6 parts (Hoechst trade name: PE-130) -Charge control Agent 1 part (Orient Chemical Co., Ltd. trade name; Bontron S-34) Carbon black 6.5 parts (Mitsubishi Kasei Co., Ltd. trade name; MA-100) Polypropylene 3 parts (Sanyo Chemical Co., Ltd. trade name; Viscol 660P) The above raw materials were mixed with a super mixer manufactured by Nippon Rigaku Kogyo Co., Ltd., melt-kneaded, and then pulverized and classified to obtain negatively chargeable toner mother particles having an average particle diameter of 9 μm. Thereafter, 100 parts of the toner mother particles, acicular titanium oxide manufactured by Ishihara Sangyo Co., Ltd., trade name FT-1000 (particle diameter: minor axis 0.13 μm, major axis 1.6 μm, aspect ratio: 12.9, volume specific resistance:
5-10 Ωcm) 0.2 part and hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd .; trade name: R-972) 0.3 part are adhered to the surface by a Hosokawa Micron Henschel mixer, and a gyro shifter is used to form a 200 mesh net. Sieving The electrophotographic toner of the present invention was obtained. Then, 100 parts of the carrier coated with a silicone resin and 4.5 parts of the above toner are mixed with a core material of a ferrite carrier having an average particle diameter of 60 μm and a saturation magnetization of 55 emu / g, and electrophotography using the toner of the present invention. A developer was prepared.

Example 2 Needle-shaped titanium oxide manufactured by Ishihara Sangyo Co., Ltd., trade name FT-2000
(Particle diameter: minor axis 0.21 μm, major axis 2.86 μm, aspect ratio: 13.6, volume resistivity: 5-10 Ωcm)
A toner of the present invention and a developer using the same were prepared in the same manner as in Example 1 except that was used.

COMPARATIVE EXAMPLE 1 Titanium oxide trade name MT-500B (spherical, particle diameter: about 0.035 μm, volume resistivity: 10 ¹³ Ωc)
A toner of Comparative Example and a developer using the same were prepared in the same manner as in Example 1 except that m) was used.

Comparative Example 2 MT-600B, spherical titanium oxide, trade name, manufactured by TAYCA (spherical, particle diameter: about 0.05 μm, volume resistivity: 10 ¹³ Ω)
cm) was used and a toner of Comparative Example and a developer using the same were prepared in the same manner as in Example 1.

Next, using the electrophotographic developers obtained in the above-mentioned Examples and Comparative Examples, a continuous copying test of up to 50,000 sheets was conducted with a commercially available copying machine (trade name: BD-9110 manufactured by Toshiba Corporation). The amount of triboelectrification, the image density and the background fog were measured at the initial stage and after the completion of copying of 50,000 sheets, and the results are shown in Table 1. The copied original is A4 size with a black portion of 6%, and the triboelectrification amount was measured using a blow-off triboelectrification amount measuring device manufactured by Toshiba Chemical Co.,
Image density is a reflection densitometer RD-914 manufactured by Macbeth, and ground fog is a color difference model MODEL Z-1 manufactured by Nippon Denshoku Industries Co., Ltd.
001DP was used.

[0019]

[Table 1]

As is clear from the results shown in Table 1, the electrophotographic developers of the present invention of Examples 1 and 2 have good and stable triboelectrification properties, and the initial stage after the completion of copying 50,000 sheets. An image characteristic equivalent to that of was obtained. On the other hand, in the comparative example, the image density or background fog after copying 50,000 sheets was poor. Further, desorbed particles of titanium oxide were deposited under the developing device. Further, when the surface of the photoconductor was visually observed, a slight filming phenomenon occurred.

[0021]

The toner of the present invention has excellent triboelectrification characteristics and image quality, and even when copying for a long time, the phenomenon of filming on the photosensitive member, the developing sleeve or the carrier, etc.
There is no problem in other practical characteristics.

Claims (3)

[Claims] 1. A toner for electrophotography, comprising a toner containing at least a binder resin and a colorant, wherein needle-shaped titanium oxide particles are attached to the surface. 2. The aspect ratio of the acicular titanium oxide particles is 1.
The toner for electrophotography according to claim 1, which is 0 or more. 3. The volume resistivity of acicular titanium oxide particles is 1
The toner for electrophotography according to claim 1, which has a resistance of 0 Ωcm or less.