JPS6338957A - Toner for flash fixing - Google Patents

Abstract

PURPOSE:To improve filming resistance and fixability and to obviate the generation of voids at the time of fixing by coating a toner consisting of a styrene/ acrylic resin as a base material on a toner consisting of an epoxy resin as a base material. CONSTITUTION:The toner consisting of the styrene/acrylic resin as the base material is coated on the toner consisting of the epoxy resin as the base material. The number average mol.wt. of the epoxy resin is preferably 1,000-4,000. The toner consisting of the styrene/acrylic resin as the base material preferably contains an electric charge controlling agent such as nigrosine dye and the number average mol.wt. of the styrene/acrylic resin is preferably 6,000-3,000. Since the styrene/acrylic resin having a high m.p. covers the surface of the toner prior to fixing, the toner has the excellent filming resistance. The shells of the styrene/acrylic resin are ruptured and the inside epoxy resin contributes mostly to the fixability at the time of fixing; therefore, the excellent fixability is obtd. Since the styrene/acrylic resin is slightly contained in the toner, the melt viscosity increases and the generation of voids is suppressed.

Description

[Detailed Description of the Invention] [Summary] Toner using epoxy resin as the base resin is coated with styrene-acrylic resin having high melt viscosity to prevent drum filming even during long-term printing and has good fixing properties for flash fixing. 1-ner is provided.

[Industrial application field]

The present invention relates to a toner for flash fixing, and particularly to a toner for flash fixing that does not cause filming on a photocon drum and has good fixing properties.

[Conventional technology]

Flash fixing toner, which is used for fixing using flash light, does not cause filming on the photocon drum or carrier even when printed continuously for long periods of time, and has good fixing properties on paper. Because toner is required to be of excellent quality, toner tends to stick to paper, but it is required to have good adhesion to photocon drums and carriers, and to have an excellent melting state during fixing.

Conventionally, as an electrophotographic method, the method described in U.S. Pat. An electrical latent image is formed by applying a light image to the insulating layer using various means, and then the latent image is developed and visualized using a fine powder called toner, and if necessary, it is printed on paper etc. After the toner image is transferred, it is fixed by pressure, heat, solvent vapor, light, etc. to obtain a copy.

Toners for developing these electrical latent images include:
Traditionally, colorants such as carbon black are dispersed in a binder resin made of natural or synthetic polymeric substances.
Particles pulverized to about 30 μm are used. Such toner is usually mixed with a carrier material such as iron powder or glass beads and used to develop an electrostatic latent image. When iron powder or other ferromagnetic particles are used as a carrier, the developer consisting of toner and carrier forms a magnetic brush by a magnetic roll in the developing device, and the rotation of the roll causes the magnetic brush to touch the latent image area. Development occurs when only the toner is carried and adheres to the latent image.

Toner is generally a finely powdered product in which a coloring agent such as carbon black is dispersed in a binder resin, and a low polymer polymer generally called an oligomer is often used as a binder. Oligomers have low molecular weight, low melt viscosity, and good thermal stability.
It is widely used as a binder resin for electrophotographic toner.

Incidentally, as there has recently been a demand for increased copying speed, the developer consisting of toner and carrier is stirred at high speed in the developing machine, and due to mutual friction and collision, toner is deposited on the surface of the carrier. Developing with sticky toner (toner filming) occurs, and as this progresses, the surface of the carrier is completely covered with a film of toner, and such carrier does not cause triboelectric charging even when mixed with other toners and stirred. The developing ability is completely lost.

Yet another problem is toner filming on the photocon drum, and when this occurs, printing performance is significantly reduced. The process of occurrence of toner filming on the drum can be considered as follows. Even after the transfer to paper is completed, a considerable amount of toner remains on the photocon drum.

This residual toner will cause problems in the next printing process, so
removed by a cleaning brush. At this time, the toner particles are struck onto the photocon surface by the fibers forming the cleaning brush and are fused to the photocon surface. The fusion of toner onto the surface of the photocon is undesirable because it not only reduces the photosensitivity of the photocon, but also causes an afterimage on the print. The cause of this fusion is thought to be mainly due to the adhesion of the toner to the photocon drum. Conventionally, therefore, a method has been used in which a non-adhesive component such as wax is included in the toner to impart non-adhesive properties to the toner. However, when the amount of wax added is small, the non-adhesive effect is poor, and If the amount added is too large, wax oozes out, and the wax adheres to the developer and photocon drum, resulting in a decrease in contrast and significant capri in the printed background area, which is undesirable.

[Problem that the invention seeks to solve]

If a resin with a high melting point is used as the base resin for flash fixing toner, it will be less likely to cause filming on the photocon drum and carrier filming, but it will also be difficult to melt under flash light, so there is a problem of poor fixing performance. Ta.

On the other hand, if a resin having a low melting point is used as the base resin of the toner, the fixing properties are improved, but there is a problem in that the above-mentioned filming tends to occur.

Conventionally, epoxy resins with low melt viscosity were used as base resins for toners, but the viscosity of the toners became too low during fixing, resulting in solid black printed areas appearing white on the fixed images, as shown in Figures 1A and 1B. A phenomenon of voids (holes) appeared and deteriorated printing characteristics. This void development is thought to be caused by surface tension because the viscosity is too low when the toner absorbs flash light and melts.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner for flash fixing that has excellent filming resistance and fixing properties and can suppress the generation of voids during fixing.

[Means for solving problems]

According to the present invention, the above problems are solved by a toner for flash fixing, which is characterized in that a toner based on an epoxy resin is coated with a toner based on a styrene-acrylic resin.

In the present invention, the number average molecular weight of the epoxy resin is 1000.
It is preferable that it is 4000 to 4000 from the viewpoint of fixing properties.

Further, in the present invention, the toner based on the styrene-acrylic resin preferably contains a charge control agent such as nigrosine dye, and it is preferable that the styrene-acrylic resin has a number average molecular weight of 6,000 to 3,000 to prevent filming. Preferable from the viewpoint of sex.

[Effect]

The toner of the present invention has a low melting point epoxy resin toner coated with a high melting point styrene-acrylic resin, so that the surface of the toner is coated with the high melting point styrene-acrylic resin before fixing, so it has excellent filming resistance. The styrene-acrylic resin shell breaks during fixing, and the epoxy resin inside is mostly involved in fixing, resulting in excellent fixing properties.Also, since it contains a small amount of styrene-acrylic resin, the melt viscosity increases and voids occur. can be suppressed.

〔Example〕

Examples of the present invention will be described below along with comparative examples.

Example 1 Epoxy resin (number average molecule 1t3400) (Epicron 4050, manufactured by Dainippon Ink and Chemicals) 94 parts by weight Carbon blank (Blasochvars, manufactured by Cabot) 3 parts by weight Nigrosine dye (oil blank BY).

(manufactured by Orient Chemical Co., Ltd.) 3 parts by weight The above composition was kneaded for 1 hour in a kneader heated to 100°C. The obtained kneaded material was coarsely pulverized, medium pulverized, and then finely pulverized using a jet mill.

The pulverized product was classified using a classifier to obtain toner having a particle size of 5 to 20 μm.

Next, a styrene-acrylic resin with a number average molecular weight of 19900 (
Hymer SBM-73F, manufactured by Kokaku Kasei Kogyo Co., Ltd.) and 3 parts by weight of nigrosine dye as a charge control agent based on the resin were used, and these were dissolved in methyl ethyl ketone solvent.
Using a U-speed dryer (5TREA-7, manufactured by Fuji Sangyo Co., Ltd.) in a fluidized bed, the toner was coated by a spray drying method to obtain a coated toner. A magnetic brush developer consisting of the coated toner and iron powder (EFV250, manufactured by Nippon Tetsuko Co., Ltd.) as a carrier was adjusted to a toner concentration of 4% and 5ivt%,
A printing test was conducted using an F6715D laser printer (manufactured by Fujitsu). As a result, it was confirmed that the fixing performance was good, and no drum filming was observed even after printing 200,000 sheets, and there was almost no deterioration of the printed image due to toner filming on the carrier surface, and no voids occurred in the fixed image. It was done. The results of printing characteristics for other Examples 2 to 6 and Comparative Examples 1 to 5 are shown in Table 1 below.

As shown in Table 1, the printing characteristics of this example were all good.

Margins below [Effects of the Invention] As explained above, according to the present invention, the image quality is good,
It has good toner adhesion to paper and does not cause drum filming even after printing for a long time.

Therefore, highly reliable printing is possible and the lifespan of the printer can be extended.

[Brief explanation of the drawing]

FIG. 1A is a schematic diagram showing the void phenomenon in the printed area;
Figure B is a partially enlarged sectional view of Figure 1A.

Claims (1)

[Scope of Claims] 1. A toner for flash fixing, characterized in that a toner based on an epoxy resin is coated with a toner based on a styrene-acrylic resin. 2. The number average molecular weight of the epoxy resin is 1000 to 40
00. The flash fixing toner according to claim 1, wherein the toner is 00. 3. The toner for flash fixing according to claim 1, wherein the toner based on styrene-acrylic resin contains a charge control agent. 4. The number average molecular weight of the styrene-acrylic resin is 60
2. The flash fixing toner according to claim 1, wherein the toner has a molecular weight of 0.00 to 30,000.