JPH0153461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for flash fixing, and more specifically, a two-component developer particularly suitable as a developer for an electrophotographic printer that uses a fixing method using flash light, especially a high-speed electrophotographic printer. Regarding dry developer.

In electrophotographic printers (hereinafter referred to as printers), one method of fixing an image on a transfer medium is to use flash light. This method is
The toner image on the transfer medium is irradiated with the emission spectrum of xenon or halogen gas for a very short period of 0.1 to 1 millisecond to apply heat of about 200 to 300 Joules to soften the toner and fix it on the transfer medium. It is something to do.

Developers used in printers that employ the so-called flash fixing method have conventionally contained low polymerization degree components with a polymerization degree of 3 or less, in some cases as much as 10 to 20% by weight. Toners made of a mixture of a carrier and a toner made of a bisphenol A epoxy resin, such as epoxy resin, are known. The reason why the toner is made of bisphenol A-based epoxy resin is that such resin immediately softens even with a small amount of heat of about 200 to 300 Joules, making it extremely easy to fix, and that it has the same emission spectrum as xenon and halogen gas. This is because it does not decompose even when exposed to irradiation, and does not generate toxic gas or unpleasant odors. However, such conventional developers have the drawback of having a very short lifespan.

That is, in printers, prior to transfer, so-called toner development is performed in which toner is attracted to the electrostatic latent image on the latent image forming medium, but this toner development is performed when a two-component developer is used. It utilizes the electrostatic force generated by friction between toner and carrier. Therefore, it is necessary to rub the two well, but since the conventional developer described above is composed of a bisphenol A-based epoxy resin containing a large amount of low polymerization degree components, the toner is relatively soft. It is hard and highly sticky, and when it rubs against the carrier, it tends to stick to the surface, causing dirt on the carrier surface to progress at a rapid rate. This contamination of the carrier surface due to toner, or deterioration of the developer, is not a problem at low speed printing, but at print speeds of 2000
In high-speed printers that run more than 30 lines per minute (30 pages per minute for A4 size), the toner and carrier collide violently, causing rapid contamination and significantly shortening the lifespan of the developer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a flash fixing developer which solves the above-mentioned drawbacks of conventional developers, can significantly slow down the progress of contamination of the carrier surface by toner, and has a very long life.

To achieve the above object, the present invention is characterized in that the content of components having a degree of polymerization of 3 or less is 10% by weight or less, and the content of monomers is 2.5% by weight or less, preferably 1.5% by weight or less. The invention is characterized by a flash fixing developer comprising a mixture of a toner whose main component is an epoxy resin, and a magnetic carrier having a specific surface area of 100 cm ² /g or more.

Next, the flash fixing developer (hereinafter referred to as developer) of the present invention will be explained in more detail.

The developer of the present invention consists of a mixture of toner and carrier. The mixing ratio of toner and carrier ranges from about 0.5:99.5 to 50:50 by weight, and varies as the toner is consumed during use. This developer is capable of causing the toner, and therefore the developer, to hold a constant polarity of charge by friction between the toner and the carrier.

The above-mentioned toner mainly contains an epoxy resin in which the content of components having a degree of polymerization of 3 or less is 10% by weight or less and the content of monomers is 2.5% by weight or less.
In other words, it is a binder resin in which pigments such as carbon plaque and calcium carbonate, dyes such as nigrosine and organic complexes are mixed as necessary, and has an average particle diameter of about 5 to 30μ. There is. The above-mentioned binder resin may be other resin that normally constitutes the toner, such as vinyl resin, acrylic resin,
It may contain synthetic resins such as olefin resins and natural resins such as balsam, rosin, and silica resin, but even in that case, at least 50% by weight, preferably 80% by weight or more, has a degree of polymerization of 3 or less. The epoxy resin must have a component content of 10% by weight or less and a monomer content of 2.5% by weight or less. The above epoxy resin is
The content of components with a degree of polymerization of 3 or less is 10% by weight or less, and the content of monomers is 2.5% by weight or less, so the content of components with a degree of polymerization of 3 or less is 10% by weight or less. % by weight, and the monomer content is
It has a second-order transition point that is at least 2°C higher, preferably 5°C or more higher than those containing more than 2.5% by weight. In addition, the other resins mentioned above, even if
Even if the content of components with a degree of polymerization of 3 or less exceeds 10% by weight and the content of monomers exceeds 2.5% by weight, they will not be as flexible as epoxy resins. It's not a big deal, so there's no problem.

Here, epoxy resins include bisphenol A-based epoxy resins, novolac-based epoxy resins, polyphenol-based epoxy resins,
Phenol-based epoxy resins such as polyhydroxybenzene-based epoxy resins, aromatic carboxylic acid-based epoxy resins such as oxycarboxylic acid-based epoxy resins and aromatic dicarboxylic acid-based epoxy resins, vinyl polymer-based epoxy resins, and alicyclic compound-based epoxy resins. It is like resin. These epoxy resins are modified with, for example, phenolic resins, melamine resins, urea resins, xylene resins, polyester resins, polyurethane resins, silicone resins, furfural resins, polyamide resins, acrylic resins, polyvinyl chloride resins, and rubber. It may also be a so-called modified epoxy resin. All of the above epoxy resins have a tendency to easily soften during flash fixation and do not generate toxic gas or unpleasant odor, but bisphenol A-based epoxy resins have this tendency particularly. is most preferable. These epoxy resins are solid at room temperature, but at 50
Easily softens at temperatures of ~200℃. Furthermore, these epoxy resins are in an uncured state (A-stage) or in a state in which gelation has hardly occurred even if they are crosslinked (B-stage).

In the above, the polymerization degree of 3 or less and the monomer content are determined by well-known GPC (gel permeation chromatography). That is, a solution of epoxy resin, for example, tetrahydrofuran, is analyzed using an appropriate column, and the molecular weight is calibrated using the analysis result of a solution of polystyrene resin in tetrahydrofuran (standard sample) conducted under exactly the same conditions. Obtain a differential molecular weight distribution curve with the axis expressed logarithmically. On this differential molecular weight distribution curve,
Since a peak appears for each degree of polymerization, the area under the curve of the portion on the lower degree of polymerization side than that peak, including the peak corresponding to degree of polymerization 3, is S ₁ , and the total area under the curve.
Find S ₂ and calculate [(S ₁ / S ₂ ) x 100],
Determine the content of substances with a degree of polymerization of 3 or less. Exactly the same thing is done for the monomer peak to determine the monomer content.

Carriers contain metals such as iron, manganese, cobalt, nickel, and chromium, metal compounds such as chromium dioxide, iron sesquioxide, and triiron tetroxide, and MFe ₂ O ₄
(However, M is Mn, Co, Ni, Mg, Zn or Cd)
It is made of a magnetic material such as ferrite represented by , and has an average particle size of about 10 to 300μ.
A carrier made of a metal material may be coated with an oxide film to prevent its oxidation. In addition, on the above oxide film, a layer for preventing fluctuations in resistance value and controlling charging characteristics is added.
A coating made of a synthetic resin different from that of the toner, such as tetrafluoroethylene resin or acrylic resin, may be further applied.

The carrier as described above must have a specific surface area of 100 cm ² /g or more in order to increase the area contaminated by toner and extend its life.
Further, it is preferable that the shape factor is 5.5×10 ⁻² or more and less than 8.0×10 ⁻² . A more preferable specific surface area is 150 cm ² /g or more. In other words, since the toner consumed during development is replenished repeatedly, the lifespan of the developer is the lifespan of the carrier, or in other words, the time it takes for the carrier surface to become completely contaminated with toner. Become. Thus, in order to extend the life of the carrier, the area available for toner soiling may be increased or geometries that accelerate soiling may be avoided. For the former, it is sufficient to increase the specific surface area of the carrier. Regarding the latter,
The carrier can be made into a shape with few corners, and the best way to do this is to have a perfect spherical shape, but with a perfect spherical shape, the specific surface area cannot be increased unless the particle size is considerably reduced. On the contrary, it will shorten the lifespan. Further, since a perfectly spherical carrier having a small particle diameter has a small magnetic force, there is also the problem that it easily separates from the surface of the magnetic roll during toner development. Therefore, the carrier is neither perfectly spherical nor extremely angular; its shape factor is
It is preferably 5.5×10 ⁻² or more and less than 8.0×10 ⁻² .

In the above, the shape factor is defined as the projected area of each separated carrier divided by the square of its projected perimeter.
The value of 5.5×10 ^-2 or more and less than 8.0×10 ^-2 is a simple average value for a large number of carriers.

The developer of the present invention as described above can be produced, for example, as follows.

That is, a methyl ethyl ketone (MEK) solution of an epoxy resin made from bisphenol A and epichlorohydrin is poured into n-hexane, and the resulting precipitate is filtered off. MEK dissolves epoxy resins regardless of their degree of polymerization, but n-hexane is a non-solvent for those with a high degree of polymerization, so by the above fractionation procedure, components with a degree of polymerization of 3 or less can be dissolved. An epoxy resin having a content of 10% by weight or less and a content of monomers of 2.5% by weight or less can be obtained. Of course, as a non-solvent for the above fractionation operation, other solvents such as n-pentane and n-heptane, which have the property of dissolving only those with a low degree of polymerization and not those with a high degree of polymerization, like n-hexane, may be used. Straight chain aliphatic hydrocarbons and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane can be used.

Next, the content of the precipitate, that is, a component having a degree of polymerization of 3 or less, is 10% by weight or less, and
An epoxy resin with a monomer content of 2.5% by weight or less is melted, pigments, dyes, etc. are mixed in the desired ratio, kneaded well, cooled to room temperature, and coarsely pulverized.

Next, the coarsely pulverized product is pulverized and classified by air to obtain a toner having an average particle size of 5 to 30 μm.

Next, the above toner and a suitable carrier are mixed in a desired ratio to obtain the developer of the present invention.

As explained above, the developer of the present invention contains an epoxy resin in which the content of components with a degree of polymerization of 3 or less is 10% by weight or less, and the content of monomers is 2.5% by weight or less. Uses toner as the main component, and the content of components with a degree of polymerization of 3 or less is 10
This is because the toner is slightly harder and less sticky than conventional developers that use materials with a monomer content of more than 2.5% by weight and a monomer content of more than 2.5% by weight. This makes it difficult for the carrier surface to get dirty, and in combination with using a carrier with a specific surface area of 100 cm ² /g or more, it takes a longer time for the carrier surface to get dirty, which significantly extends the service life. . Moreover, the ease of fixing is almost unchanged compared to the conventional developer mentioned above.
Moreover, it does not generate toxic gases or unpleasant odors. And for the above life, the shape factor is 5.5×
If a carrier with a value of 10 ^-2 or more and less than 8.0×10 ^-2 is used, it will be further extended.

Example Bisphenol A-based epoxy resin "Epicote" 1004 manufactured by Yuka Ciel Epoxy Co., Ltd. was fractionated with n-hexane using a Soxhlet extractor. Then, the following composition was prepared using the epoxy resin after fractionation.

Bisphenol A epoxy resin after separation
...84 parts by weight Dye "Oil Black" manufactured by Orient Chemical Co., Ltd.
BY...7 parts by weight Pigment carbon black MA-100 manufactured by Mitsubishi Chemical Corporation
...7 parts by weight Dispersant "Aramide" manufactured by Lion Akzo
HT...2 parts by weight Next, the above composition was melted and kneaded at 170°C for 1 hour, cooled to room temperature to solidify, coarsely pulverized with a hammer mill, and further finely pulverized with a jet mill to reduce the average particle size. A 12μ toner was obtained.

When the molecular weight distribution of the epoxy resin in this toner was analyzed using gel permeation chromatography, a differential molecular weight distribution curve was obtained as shown by the solid line in the drawing, and from this curve it was found that the content of the epoxy resin with a degree of polymerization of 3 (molecular weight: 908) or less was obtained. The content of monomer (molecular weight 340) was found to be about 1.1% by weight. In the drawings, M is the molecular weight, and W is the content (% by weight) of the epoxy resin.

Next, Nippon Tetsuko Co., Ltd.'s Steel Carrier (average particle size: about 100μ, specific surface area: about 155cm ² /g,
Shape factor: 6.2×10 ⁻² ) were mixed so that the toner content was 7% by weight to obtain a developer.

Next, apply the above developer at a circumferential speed of the magnetic roll.
When the product was placed in a developing device set at 706 mm/sec, which corresponds to a printing speed of 10,000 lines/min, its lifespan was determined to be approximately 430 hours. The lifespan was determined as the time required for the amount of charge measured with a Faraday gauge to become 1/3 of its original value.

Comparative Example The same procedure as in the example was carried out except that the bisphenol A-based epoxy resin "Epicote" 1004 manufactured by Yuka Ciel Epoxy Co., Ltd. was used as it was without being separated.
Got toner.

When the molecular weight distribution of the epoxy resin in this toner was analyzed in the same manner as in the example, a differential molecular weight distribution curve indicated by a dotted line in the drawing was obtained, and from this curve, the content of epoxy resin with a degree of polymerization of 3 or less was approximately 12% by weight.
It was found that the monomer content was approximately 3.5% by weight.

Next, in the same manner as in the example, the developer was prepared and the lifespan was examined, and it was found to be only about 100 hours.

The developer of the present invention can be used at printing speeds of 2,000 yen, where violent collision between toner and carrier occurs.
Lines/minute (30 sheets/minute for A4 size) or more, especially 3000 lines/minute
It is particularly suitable as a developer for high-speed printers with a speed of 50 sheets per minute or more, but there is no problem in using it as a developer in low-speed printers, copying machines, facsimile machines, etc.

[Brief explanation of drawings]

The drawing shows that the content of polymerization degree of 3 or less is approximately 6.2
The differential molecular weight distribution curve (solid line) of a bisphenol A-based epoxy resin in which the monomer content is approximately 1.1% by weight, and the content of polymerization degree of 3 or less is approximately 12% by weight, The monomer content is approx.
It is a graph showing a differential molecular weight distribution curve (dotted line) of a bisphenol A-based epoxy resin having a concentration of 3.5% by weight.

Claims (1)

[Claims] 1. A toner whose main component is an epoxy resin in which the content of components with a degree of polymerization of 3 or less is 10% by weight or less and the content of monomers is 2.5% by weight or less, and a specific surface area of 100 cm ² 1. A flash fixing developer comprising a mixture with a magnetic carrier having an amount of at least /g/g.