JPH0719077B2 - Toner for magnetic printing - Google Patents

Description

The present invention relates to a toner used in a magnetic printing method of developing a magnetic latent image and performing flash fixing after transfer.

[Prior Art] As one of image reproducing methods, a magnetic printing method applying a magnetic recording technology has been developed and put into practical use. The magnetic printing method includes a step of writing an information signal with a magnetic head to form a magnetic latent image on a magnetic drum that is a recording medium, and a step of developing the magnetic latent image with a one-component magnetic toner.
It includes a step of transferring the toner image onto a transfer sheet, a step of fixing the transferred toner image, and a step of cleaning the magnetic toner remaining on the magnetic drum after the transfer with a blade or the like (JP-A-54-54). See 32328). This magnetic printing system has an advantage that it is not necessary to replace the photoconductor for every tens of thousands of copies unlike the electrophotographic system, and maintenance is easy.

The fixing in the magnetic printing method is performed by the hot roll fixing method, the oven fixing method, the flash fixing method or the pressure fixing method as in the electrophotographic method. Among these, the flash fixing method using the emission spectrum of Xe or halogen gas irradiates a heat amount of about 200 to 300 J in a short time of about 100 μsec, so that heat loss from the irradiation target can be efficiently heated, It has advantages such as no fire and quick start.

[Problems to be Solved by the Invention] In the above-mentioned magnetic printing method, a part of magnetic lines of force generated by energizing the magnetic head leaks from the gap portion of the magnetic head to the recording medium, and the magnetization pattern ( A latent image) is formed. Therefore, it is preferable that the space between the magnetic head and the magnetic drum is as narrow as possible, and generally, it is extremely narrow at 5 μm or less (practically about 1 μm).

However, when magnetic printing is performed using a magnetic toner capable of flash fixing as the magnetic toner, a phenomenon occurs in which the toner or the like adheres to the magnetic head. More specifically, when writing information to the magnetic drum by the magnetic head, the cleaning blade is separated from the magnetic drum, so that the toner accumulated at the tip of the blade, the fine powder of the magnetic drum surface coating material, and the paper dust are scattered, Stick to the magnetic head. Of these, the toner for flash fixing has a property of being easily melted by heat, and thus is in a state of being fused to the magnetic head and is not easily separated. Further, some toner or the like remains on the magnetic drum even if cleaning is performed with the blade. Therefore, the toner or the like adheres to the magnetic head even when the magnetic head scans the magnetic drum when writing the information signal. Thus, as the number of times the magnetic head writes the information signal increases, the amount of toner or the like attached to the magnetic head increases.

When toner or the like adheres to the magnetic head, the space between the magnetic drum and the magnetic head apparently expands, so that the magnetic latent image has a weaker force for attracting the magnetic toner, and the image density decreases.

Therefore, it is an object of the present invention to provide a magnetic printing toner which is less likely to adhere to a magnetic head and which can provide a high density image.

[Means for Solving Problems] As a result of various studies to prevent the adhesion of toner and the like to the magnetic head, the present inventors have added polyethylene wax to toner particles mainly composed of a fixing resin and magnetic powder. It was discovered that the above-mentioned object can be achieved by doing so and reached the present invention.

The magnetic printing toner of the present invention comprises an epoxy resin having an epoxy equivalent of 700 to 1000, 50 to 70% by weight of magnetic powder, and 1 to 5% by weight of polyethylene wax having a molecular weight in the range of 7,000 to 12000. The magnetic toner is suitable for the flash fixing method.

When magnetic printing is performed using a magnetic toner containing polyethylene wax, the toner temporarily adheres to the magnetic head when the information signal is written by the magnetic head as described above, but the polyethylene wax shrinks when heated and cooled. As a result, the toner hardly separates from the magnetic head and is hardly fused.

The polyethylene wax added to the toner particles is 7,000-
It has a molecular weight in the range of 12000. When the molecular weight is less than 7,000, the polyethylene wax is soft and the magnetic head is apt to be contaminated. On the other hand, when the molecular weight exceeds 12000, the polyethylene wax becomes hard and the fixability is lowered.

Such polyethylene wax is contained in the toner particles in an amount of 1 to
Add 5% by weight. If the addition amount is less than 1% by weight, the effect is insufficient, and if the addition amount exceeds 5% by weight, the fixability deteriorates.

The toner particles of the present invention contain the following fixing resin and magnetic powder as essential components.

In the flash fixing toner, an epoxy resin having a relatively low softening point is used as a fixing resin from the viewpoint of storability and fixability, and a bisphenol type epoxy resin is particularly effective. Among such epoxy resins, when the epoxy equivalent is less than 700, the resin becomes too soft and the storage stability is low, and when the epoxy equivalent exceeds 1000, the fixing property is deteriorated. Therefore, the epoxy equivalent of the epoxy resin is 70
The range is from 0 to 1000.

As the magnetic powder, particles having a particle size of about 0.1 to 3 μm, which are made of an alloy or compound containing an element exhibiting ferromagnetism such as ferrite, magnetite, and other iron, cobalt, nickel, etc., can be used. The content of magnetic powder is 50-70
A weight% range is preferred. If it is less than 50% by weight, the magnetic force of the toner is low, fog is likely to occur, and the transportability is low. On the other hand, if it exceeds 70% by weight, the fixing property is deteriorated.

In addition to the above components, the toner particles of the present invention include one type of known additive such as a fluidity modifier (eg, hydrophobic silica), a resistance modifier (eg, carbon black), and a charge control agent (eg, nigrosine dye). Alternatively, two or more kinds may be included. The content of these additives is preferably 10% by weight or less in order not to impair the fixability.

The magnetic toner of the present invention can be produced, for example, by dry-mixing the above-mentioned raw materials, heating and kneading, cooling and solidifying, pulverizing, heat-treating, and classifying.

The magnetic toner of the present invention preferably has a volume resistance of 10 ¹⁴ Ω · cm or more in order to facilitate transfer to plain paper. This volume resistance is measured by measuring several tens of mg of a sample, and filling it into an insulating cylinder made of Teflon (trade name) with an inner diameter of 3.05 mm (cross-sectional area = 0.073 cm ² ) with an improved dial gauge and applying a load of 0.1 kg, DC4KV Calculated by measuring the resistance in an electric field of / cm. The Yokogawa Hewlett-Packard insulation resistance tester (model 4329A) is used for the measurement.

Further, the magnetic toner of the present invention preferably has a charging voltage within ± 25 V in order to reduce fog. This charging voltage is measured by the device shown in FIG. In the figure, 1 is a non-magnetic sleeve, 2 is a permanent magnet member, 3 is a surface electrometer, and 4 is a probe. Specifically, the non-magnetic sleeve 1 has an outer diameter of 50 mm, the permanent magnet member 2 has an outer diameter of 46 mm and a length of 150 mm, and is 12-pole symmetrically magnetized, and the magnetic flux density on the sleeve is 1000 G. A trek 344 is used as the surface electrometer 3. After adjusting the gap g between the sleeve 1 and the tracing stylus 4 to 5 mm, 3 g of toner is supplied onto the sleeve 1 and the permanent magnet member 2 is rotated at 7000 rpm for 1 minute to measure the surface potential of the toner.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 32% by weight of bisphenol type epoxy resin (Epicoat 1004K manufactured by Shell Chemical Co., epoxy resin = 880), 2% by weight of carbon black, 65% by weight of magnetite (EPT500 manufactured by Toda Kogyo), 1% by weight of high-density polyethylene wax (molecular weight 8000) % Were dry mixed and kneaded at a temperature of 100 ° C. in Banbury. The kneaded product was cooled and solidified, then pulverized by a jet mill and classified to obtain a magnetic toner (No. 1) having an average particle size of 15 μm. The volume resistance of this toner is 1 × 10 ¹⁵ Ω · cm, and the charging voltage is −10.
It was V.

Example 2 Example 1 except that the amount of polyethylene wax added was changed.
Same conditions as above (however, the content of magnetic powder remains the same and the content of epoxy resin is changed to 100% by weight)
Then, three kinds of magnetic toners (No. 2 to 4) were manufactured. The amount of polyethylene wax added is 2% by weight for No. 2 toner, 3% by weight for No. 3 toner, and 5% by weight for No. 4 toner.
And

Example 3 A magnetic toner (No. 5) was produced under the same conditions as in Example 1 except that a high-density polyethylene wax having a molecular weight of 11000 was used.

Comparative Example 1 Under the same conditions as in Example 1 except that the amounts of polyethylene wax added were changed to 0.5% by weight and 6% by weight (however, the content of the magnetic powder was unchanged and the content of the epoxy resin was changed to be the whole). Of 100% by weight), two types of magnetic toner (N
o.6, 7) was produced.

Comparative Example 2 A magnetic toner (No. 8) was manufactured under the same conditions as in Example 1 except that a medium density polyethylene wax having a molecular weight of 4000 was used.

An image was formed under the following conditions using each of the above magnetic toners.

A magnetic drum (outer diameter 86 mm) in which a Co-Ni-P magnetic layer was formed on an aluminum alloy drum, and a Ni-P non-magnetic layer was further formed on the drum by using a peripheral speed of 18 m / sec And a magnetic latent image was formed by writing an image with the magnetic head. The magnetic head is made of Mn-Zn ferrite and the butt gap is 4 μm.
The space with the magnetic drum was about 2 μm during recording. 4 pole magnetized rubber ferrite magnet inside the aluminum sleeve (The magnetic flux density on the sleeve is 50G for the developing pole,
A magnetic latent image was developed by a developing device equipped with a magnet roll having 400 G). The developed toner image was transferred onto plain paper at a transfer voltage of 1.5 KV using a dielectric transfer roller. Fixing is done by Xe lamp fixing (condenser capacity 25
The irradiation was performed by irradiating about 600 J of energy with 0 μF, 2000 V). The magnetic drum was cleaned with a brass blade having a thickness of 50 μm and air suction.

The images were evaluated initially and after 10,000 cycles of writing. The results are shown in Table 1.

From Table 1, a magnetic toner containing 1 to 5% by weight of polyethylene wax having a molecular weight of 7,000 to 12000 (No. 1 to
When 5) is used, it can be seen that even if writing is performed frequently, the magnetic head is not contaminated, a high image density is obtained, and there is almost no decrease.

On the other hand, it can be seen that the magnetic toner (No. 6) with a small amount of polyethylene wax significantly reduces the image density, and the magnetic toner with a large amount of polyethylene wax (No. 7) has a low fixing property. It was confirmed that when the molecular weight of polyethylene wax was small (No. 8), the magnetic head was contaminated.

[Advantages of the Invention] Since the magnetic toner of the present invention contains polyethylene wax, it is possible to prevent adhesion to the magnetic head and obtain a good image.

[Brief description of drawings]

 FIG. 1 is a diagram showing a device for measuring the surface potential of toner.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication 8305-2H G03G 9/08 101 (72) Inventor Tokio Kogaji 1-7 Kugayama, Suginami-ku, Tokyo No. 41 Iwasaki Tsushin Co., Ltd. (72) Inventor Harunori Okabe 1-5-20 Kugayama, Suginami-ku, Tokyo Iwatsu Technica Co., Ltd. (56) References JP-A-58-203456 (JP, A) Kai 56-5560 (JP, A) JP-A 55-129358 (JP, A)

Claims (3)

[Claims] 1. In a toner for magnetic printing using flash fixing, an epoxy resin having an epoxy equivalent of 700 to 1000, a magnetic powder of 50 to 70% by weight, and a polyethylene wax 1 having a molecular weight of 7,000 to 12000. The toner for magnetic printing is characterized in that it is composed of particles containing 5 to 5% by weight. 2. The toner for magnetic printing according to claim 1, which has a volume resistance of 10 ¹⁴ Ω · cm or more. 3. The magnetic printing toner according to claim 1 or 2, wherein the magnetic printing toner has a charging voltage of ± 25 V or less.