JPS597097B2 - Dry developer for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in dry developers used in dry development of electrophotography.

Thermoplastic electrical detection powder (toner) as a dry developer for electrophotography
and dimethylpolysiloxane, petroleum oil, on the magnetic particle surface.
A carrier consisting of a fatty acid ester of polyglycol ether and a carrier in which an adhesive such as animal oil is dispersed (Special Publication Act 4)
2-5592) is known.

Although this dry developer has the effect of preventing background stains and improving image density, after development, magnetic particles adhere to the image area, resulting in a change in the composition of the developer within the device, that is, a decrease in magnetic particles. However, there is a drawback that developing performance is deteriorated. Moreover, the magnetic particles attached to the image area are easily detached from the image area along with the surrounding toner due to an external impact, so that the image is easily damaged. The present invention eliminates the above-mentioned drawbacks, and provides a dry developer for electrophotography with excellent developability, in which the composition does not change even after repeated development, and the carrier does not separate even when subjected to external impact. It is something to do. Such a developer consists of a toner whose main component is resin and a carrier whose magnetic particle surfaces are coated with polybutene having a viscosity of 1,500 to 6,000 cps.

The toner used in the present invention may be one used in general electrophotographic dry developers.

Therefore, the composition of the toner is styrene resin such as polystyrene,
Thermoplastic resins such as chroman~indesi resin, rosin, and epoxy resin and chromogen black ETOO (C, I,
Haruka 14645), Solvent Black 3 (C, I, Mu2
6150), carbon black, and other colorants. The method for producing such toner is the same as in the past, by mixing the above-mentioned materials, heating and kneading them with a heated roll mill, etc., cooling them and crushing them, and then crushing the coarse particles again with a jet mill, etc., to reduce the particle size to 5 to 5. Adjust to a range of about 20μ. The polybutene-coated carrier has a particle size of 100 to 300 mesh (150 to 5
0 μ) magnetic particles and 0.05 to 1
It is obtained by heating and mixing % by weight of polybutene in a ball mill and then cooling.

The polybutene used here has a viscosity of 1500 to 6000.
cps1 preferably should be in the range of 1700-2500 cps. If it is outside this range, the purpose of the present invention cannot be achieved and therefore it is not used. Examples of the magnetic particles include iron powder (reduced iron powder or electrolytic iron powder with a Fe content of 99% or more), magnetite, cobalt, nickel, ferrite, or alloys thereof.

The effects of the present invention will be explained with reference to the drawings.

Figure 1 is a curve diagram showing the relationship between the number of development cycles and image density when the developer of the present invention and the comparative developer are applied to a zinc oxide-resin dispersion photosensitive paper, and Figure 2 is a curve diagram showing the relationship between the number of development cycles and image density. It is a curve diagram showing the relationship between the relative adhesion amount of iron powder adhering to. As shown in Figure 1, in the product of the present invention shown by curve 1, there is almost no change in image density even if the number of development increases;
In the case of the comparative product (in which SEA3O lubricating oil was used instead of polybutene in the present invention), the image density significantly decreased as the number of development increases. Furthermore, in FIG. 2, the relative adhesion amount of iron powder on the image area is small in the case of the product of the present invention, and remains approximately constant K regardless of the number of times of development.
In the case of comparative products, the change is large and the change tends to be significant, especially when the number of times of development is large. Note that the data in FIG. 1 was measured under the conditions of 10° C. and 30% RH. In addition, the data in Figure 2 was measured without replenishing or stirring the developer, and the relative adhesion amount of iron powder is determined by the K of fluorescent X-rays.
It was determined as a count number using alpha rays. As can be seen from the above results, the developer of the present invention has extremely stable developability.

Examples are shown below.

Example 1 Iron powder with a particle size of 60 to 100μ, 99.9 parts by weight was mixed with a viscosity of 17
The mixture was mixed with 0.1 part by weight of polybutene of 0.00 cps by heating to 40° C. in a ball mill, and then cooled to prepare a carrier.

On the other hand, 95 parts by weight of polystyrene, 5 parts by weight of nigrosine, and 5 parts by weight of carbon black were kneaded in a heated roll mill, heated to 130°C, cooled, and coarsely crushed. A 20μ toner was obtained. Next, 5 parts by weight of this toner was mixed with 95 parts by weight of the polybutene-coated carrier to obtain a dry developer for electrophotography. Next, a commercially available zinc oxide/resin dispersion photosensitive paper was charged and imagewise exposed using a conventional method to form an electrostatic latent image, and this was magnetically developed using the developer, resulting in an image density of 2.32.
An image (by Maghes densitometer) was formed.

The same developing method was repeated over 30 times, but the image density remained almost constant as shown by curve 1 in FIG.

Further, the relative adhesion amount of iron powder on the image was small as shown in curve 1 in FIG. 2, and the relative adhesion amount of iron powder did not increase even if this developing operation was repeated 60 times or more. On the other hand, in the case of the comparative dry developer prepared using SEA3O lubricating oil instead of polybutene in this example, the image density was good at the time of initial development, but when the development operation was repeated, the curve in Figure 1 As shown in Figure 2, there was a significant decrease. Furthermore, the relative adhesion amount of iron powder on the image was larger than that of the product of the present invention, as shown by curve 2 in FIG. 2, and it was observed that it tended to increase as the number of times of development increased. Example 2 Example 1 except that polybutene with a viscosity of 3500 cps was used.
A dry developer for electrophotography was prepared in exactly the same manner as described above.

Images were formed and tested using the same copying method as in Example 1, and similarly good results were obtained.

[Brief explanation of drawings]

Figure 1 is a diagram of the relationship between the number of times of development and image density when the developer of the present invention and the developer for comparison are applied to zinc oxide photosensitive paper, and Figure 2 is a diagram of the relationship between the number of times of development and the relative adhesion amount of iron powder on the image. This is a relationship diagram. 1...Developer of the present invention, 2...Developer for comparison.

Claims (1)

[Claims] 1. A dry developer for electrophotography consisting of a toner whose main component is a resin and a carrier whose magnetic particle surface is coated with polybutene having a viscosity of 1,500 to 6,000 cps.