JPS6339050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner used for developing an electrical latent image or a magnetic latent image in electrophotography or electrostatic printing.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification, Special Publication No. 42-23910 and Special Publication No. 43
A number of methods are known, as described in Japanese Patent Application No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the photoreceptor is A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Various methods are also known for visualizing electrical latent images using toner. For example, US Patent No.
The magnetic brush method described in specification No. 2874063,
A large number of development methods are known, such as the cascade development method described in No. 2,618,552, the powder cloud method, the fur brush development method, and the liquid development method described in No. 2,221,776. Toners used in these developing methods have conventionally been fine powders in which dyes and pigments are dispersed in natural or synthetic resins. Furthermore, it is also known to use fine developing powder to which a third substance is added for various purposes.

The developed toner image is transferred and fixed onto a transfer material such as paper, if necessary.

Methods for fixing toner images include heating and melting the toner with a heater or hot roller to fuse and solidify it to the support, softening or dissolving the binder resin of the toner with an organic solvent, and fixing it to the support. A method of fixing toner on a support by pressure is known.

Toner materials are selected to be suitable for each fixing method, and toners used for a particular fixing method generally cannot be used for other fixing methods. especially,
It is almost impossible to transfer the toner used in the conventionally widely used heat fusion fixing method using a heater to a hot roller fixing method, a solvent fixing method, a pressure fixing method, or the like. Therefore, toners suitable for each fixing method are being researched and developed.

The method of fixing toner by applying pressure is based on US Patent No.
It is described in specification No. 3269626, Japanese Patent Publication No. 46-15876, etc., and is energy saving, non-polluting, copying can be done without waiting time when the copying machine is turned on, there is no risk of burning copies, and high speed. It has many advantages such as being able to be fixed and having a simple fixing device.

However, there are problems such as toner fixability and offset development to the pressure roller, and various research and developments are being carried out to improve the pressure fixing method. For example, Japanese Patent Publication No. 44-9880 describes a pressure fixing toner containing an aliphatic component and a thermoplastic resin;
No. 52-108134 describes a capsule-type pressure fixing toner containing a soft material in the core, and JP-A-48-75033 describes a block copolymer of a tenacious polymer and a soft polymer. Pressure-fixed toners using coalescence have been described.

However, it is easy to manufacture, has sufficient pressure fixing performance, does not cause any offset phenomenon to the pressure roller, and has stable development performance and fixing performance even after repeated use. No practical pressure fixing toner has been obtained that does not adhere to the surface of a photoconductor, does not aggregate or form cakes during storage, and has good storage stability.

More recently, the present applicant has proposed JP-A-54-
42141 and Japanese Patent Application Laid-open No. 18656/1983, there is a method of developing an electrostatic latent image with a one-component developer containing magnetic fine particles in the toner and using no carrier particles. The binder resin is required to have good dispersibility and adhesion with the magnetic fine particles, as well as impact resistance and fluidity of the toner. In addition, when developing by frictional charging between this one-component developer and the developing sleeve roller, insulating materials may separate due to impact or use over time, adhere to the sleeve roller due to triboelectric action, and accumulate, resulting in significant damage. One-component developers also have many problems, such as poor durability.

The present invention advantageously satisfies the above-mentioned needs, and the feature of the present invention is that 0.1 to 10 parts by weight of SnO ₂ -based fine powder is externally added to 100 parts by weight of a magnetic toner consisting of a binder and magnetic powder. The present invention relates to a one-component magnetic developer characterized by the following characteristics, and particularly relates to a magnetic developer which can completely eliminate the above-mentioned drawbacks and is effective in improving pressure fixing properties, improving environmental stability, etc. be.

Regarding the improvement of pressure fixability, magnetic toner usually contains a binder magnetic powder, and the content of this magnetic powder greatly influences the pressure fixability. In other words, if the magnetic powder content is large, triboelectricity will not occur and development will not be possible using the developing method of JP-A-18656, and the fixing properties will be extremely poor, so the magnetic powder content will be reduced to the minimum required amount. It is essential to suppress it. However, if the amount is small, "density unevenness" will occur in the image. This is because the thickness of the toner coating formed on the developing sleeve is disturbed.

That is, if the magnetic powder content is extremely low, toner with extremely high triboelectricity will be attracted to the sleeve, and the magnetic field will no longer have the ability to convey the toner on the sleeve. Therefore, there is an optimum amount of magnetic powder contained in the binder. The present invention has thus discovered a SnO ₂ -based fine powder that exhibits the effect of not causing density unevenness in images with at least a magnetic powder content (in other words, good pressure fixing properties).

At the same time, environmental stability can be improved. Toner caused by friction with the sleeve as described above usually has a high tribo amount in a low humidity atmosphere and a low amount in a high humidity atmosphere. Therefore, at low humidity, the image density (abbreviated as Dmax)
However, since the triboelectricity is high, "density unevenness" occurs in the image, and conversely, in a high humidity atmosphere, Dmax decreases.

The magnetic developer of the present invention can completely eliminate these drawbacks. In other words, the SnO ₂ -based fine powder externally mixed in the present invention acts as a tribocontrol agent and can be used in any atmospheric environment. It is presumed that it has stabilized.

Therefore, the effects of the externally added SnO ₂ -based fine powder are as follows: 1. Environmental stability is improved, and "density unevenness" in images due to low humidity does not occur, and even in high humidity.
One example is that there is no decrease in Dmax.

2. Pressure fixing properties are improved because the content of magnetic powder can be reduced.

In addition, the magnetic developer, which is a feature of the present invention, is compatible with toner.
This is where SnO ₂ -based fine powder is externally added and mixed.

When the SnO ₂ -based fine powder is added into the toner binder (in other words, added internally), the features of the present invention cannot be fully exhibited. This is because mixing with external additions can achieve a sufficient effect with a smaller amount than mixing with internal additions, and mixing with internal additions actually hinders the improvement of pressure fixing properties.

In addition, in the present invention, _{SnO 2 -}
It also includes TiO ₂ series, SnO ₂ -BaSO ₄ series, etc.

Regarding the mixing ratio of SnO ₂ -based fine powder, toner 100
Appropriately and preferably 0.1 to 10 parts by weight,
Furthermore, 0.3 to 5 parts by weight is good. That is, if it is less than 0.1 part, "density unevenness" will occur in the image, and if it is more than 10 parts, not only will the improvement in pressure fixability be inhibited, but also a decrease in Dmax will occur at high humidity.

Next, the magnetic developer of the present invention will be explained. As a binder, for example, wax, fatty acid salt, polyethylene, polypropylene fluorinated resin, ionomer resin, terpene resin, rosin, phenol-modified terpene resin, polyamide, polyester, low molecular weight polystyrene, maleic acidic phenol resin, methyl vinyl ether-maleic anhydride resin, polyvinyl pyrrolidone, chlorinated paraffin,
Petroleum resin, pentaerythritol resin, etc. can be used alone or in combination. As the magnetic powder, conventionally known magnetic materials such as metal oxides such as magnetite, Zn ferrite, and _C0 magnetite are used, and known dye/pigment charge control agents conventionally used in toners are also used. You may add a certain amount. The content of the magnetic powder is suitably 20 to 60 parts by weight, preferably 40 to 60 parts by weight, based on 100 parts by weight of the binder. After forming a toner, in addition to externally adding SnO ₂ -based fine powder, which is a feature of the present invention, fluidity improvers such as colloidal silica and cerium oxide are added as necessary.
An abrasive may be mixed as appropriate. This will be described in detail below with reference to Examples.

Example 1 Polyethylene wax (trade name manufactured by Hoechst)
PE130) 100 parts by weight Magnetic powder magnetite 50 parts by weight The above mixture was kneaded for 10 minutes using a roll mill heated to 150°C, cooled, pulverized using a jet mill, and classified into 5-25μ particles to obtain a toner. Next, 0.6 parts of hydrophobic colloidal silica (trade name R972, manufactured by Nippon Aerosil Co., Ltd.) is added to 100 parts by weight of this toner.
Part by weight, SnO ₂ -based fine powder (Mitsubishi Metals product name T-
1) 1.2 parts by weight were mixed for 30 seconds using a coffee mill (small pulverizer manufactured by Shibata Rika) to obtain a developer. Next, I placed it in an electronic copying machine (Canon NP-120) and conducted an environmental test. 15℃10% and 35℃85%RH
No decrease in Dmax was observed in this atmosphere, and no "density unevenness" occurred in the image.

As a comparative example, an environmental test was conducted in the same manner as in Example 1 using a magnetic developer to which the SnO ₂ -based fine powder of Example 1 was not externally added, and "density unevenness" occurred in the image at 15°C and 10%.

Example 2 The same treatment as in Example 1 was carried out except that the SnO ₂ fine powder in Example 1 was replaced with 0.8 part of snO ₂ -BaSO ₄ type (Mitsubishi Metals trade name T-10) fine powder. This magnetic developer was subjected to an environmental test in the same manner as in Example 1, and the Dmax was found to be max.
No decrease in image quality or occurrence of "density unevenness" was observed.

Example 3 The same treatment as in Example 1 was carried out except that the SnO ₂ -based fine powder in Example 1 was replaced with 1.0 part of SnO ₂ -TiO ₂ -based product (trade name W-10, manufactured by Mitsubishi Metals). This magnetic developer was subjected to an environmental test in the same manner as in Example 1.
% and in an atmosphere of 35°C and 85% RH, no decrease in Dmax or occurrence of "density unevenness" in images was observed.

Example 4 Styrene-butyl methacrylate-maleic anhydride resin (Seiko Chemical product name Hyros C-700)
100 parts by weight Magnetite 60 parts by weight Charge control agent 2 parts by weight The above mixture was kneaded for 10 minutes using a roll mill heated to 160°C, cooled, pulverized using a jet mill, and classified into 5 to 25μ particles to obtain a toner. . Next, to 100 parts by weight of this toner, 0.3 parts by weight of hydrophobic colloidal silica (Japan Aerosil Co., Ltd. trade name R972) 0.3 parts by weight SnO ₂ type fine powder (Mitsubishi Metals trade name T-1) 2
The weight parts were mixed for 30 seconds using a coffee mill to obtain a developer. Next, an electronic copying machine (manufactured by Canon)
NP200J) and conducted an environmental test. 15℃10
% and in an atmosphere of 35°C and 85% RH, no decrease in Dmax was observed, and no "density unevenness" occurred in the image.

As a comparative example, an environmental test was conducted in the same manner as in Example 4 using a magnetic developer to which the SnO ₂ -based fine powder of Example 4 was not externally added, and "density unevenness" occurred in the image at 15°C and 10%.

Claims (1)

[Claims] 1 Magnetic toner containing binder and magnetic powder
A one-component magnetic developer characterized in that 0.1 to 10 parts by weight of SnO ₂ -based fine powder is externally added to 100 parts by weight.