JPS6378156A - Toner fixing method - Google Patents

Abstract

PURPOSE:To enable fixing toner without generating offset by means of a simple and unexpensive apparatus by specifying inter-relationship between temperature and pressure of the pre-fixing of the toner and those of the post-fixing of the toner. CONSTITUTION:The inter-relationship between the pressure P1 and the temp. T1 of the pre-fixing of the toner and the pressure P2 and the temp. T2 of the post-fixing of the toner is specified by P1<P2 and T1>T2. The titled method lies in for example; thermally fixing the toner contg. binder resins having >=2 kinds of the different softening temps. at the temp. higher than the min. softening point temp. and lower than the max. softening point temp. among the softening temps. of each binder resins, followed by fixing it at the pressure higher than the usual thermal-fixing pressure of 7kg/cm<2> and lower pressure than the usual pressure fixing of 200kg/cm<2>, preferably at the pressure of 20-100kg/cm<2>, thereby preventing the melting of the whole binder resin, thus, preventing the generation of the offset, namely the sticking of the toner to the roller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic heat fixing method for heating and fixing toner adhered to recording paper.

[Prior Art] In electrophotography, a desired electrostatic latent image is formed on recording paper, toner is electrically attached to the electrostatic latent image for development, and then the toner is heated and transferred onto the recording paper. There is a way to make it stick. Conventionally, the electrophotographic heat fixing method that heats the toner to fix it on recording paper involves passing the recording paper on which an electrostatic latent image is formed between a pair of rollers and heating the rollers to melt the toner. Therefore, a method is adopted in which the toner is fixed on the recording paper.

However, in such an electrophotographic heat fixing method,
The molten toner adheres to the roller, causing so-called offset, which is then fixed on the recording paper that will be fixed next, causing background smudges.

Therefore, the rollers are provided with a coating layer to which toner does not easily adhere, or the rollers are coated with a liquid to which toner does not easily adhere, but these methods require the use of complicated and expensive equipment, which is not economical.

On the other hand, in order to eliminate the problem of heat fixing, a fixing method using pressure is also known, but this method also requires an extremely large amount of pressure without heating, and it is not possible to achieve sufficient fixing. Even if you can tolerate this, the fine parts of the toner image will collapse and the recording paper will become glossy due to the high pressure applied, and the equipment will also become heavier, making it more expensive and recording costs. It has many problems.

[Problems to be Solved by the Invention] It is an object of the present invention to provide a toner fixing method that eliminates the above-mentioned problems and can perform fixing without causing offset using a simple and inexpensive device. With the goal.

[Means and effects for solving the problems] According to the present invention, a toner t containing two or more types of binder resins having different softening temperatures is provided, and a toner fixing method in which the toner is fixed twice or more, wherein the pre-fixing pressure is PI, temperature TI, post-fixing pressure P2
, and temperature T2, the relationship between PI<P2 and TI>72 is provided.

The toner used in electrophotography is mainly composed of a binder made of thermoplastic resin and a colorant, and the toner is approximately 95% binder, and its aging behavior is dominated by the binder. be.

In the present invention, a toner using two or more types of binder resins with different softening temperatures is heat-fixed at a temperature not less than the lowest softening temperature and not more than the highest softening temperature among the softening temperatures of each binder resin. The pressure during heat fixing is 7 kg/
By fixing at a pressure higher than about cs+2 and lower than the pressure of 200 kg/cm2 or more that is the pressure in normal pressure fixing, preferably 20 to 100 kg/cm2, melting of the entire binder is prevented, This prevents the occurrence of so-called offset, where toner adheres to the roller. This also eliminates the problems of pressure fixing, such as deterioration in image quality and glossiness of the paper.

If you try to apply the above pressure and temperature at the same time using the same roller, you cannot actually use a normal heat fixing roller because it is weak against pressure and lacks durability, and a normal pressure fixing roller cannot be used. In other words, in the present invention, as shown in FIG. 1, the fixing is performed in two stages using separate heat rollers 3 and light pressure rollers 4. The above objective is achieved by dividing the process into two parts.

The amount of the binder resin having a softening point lower than the fixing temperature is preferably 20 to 90 parts by weight, more preferably 40 to 70 parts by weight, based on 100 parts by weight of the total binder. 20
If it is less than 90 parts by weight, it is difficult to obtain sufficient fixing properties;
If the amount exceeds the weight part, it is difficult to obtain sufficient offset resistance.

[Example] Examples will be described below. Note that the softening temperature was measured by the ring and ball method.

Toner production example 1 The above components were mixed, pulverized, and classified to obtain a volume average particle size of 8 and OI.
A toner of Lm was obtained.

The above components were mixed using an attritor at a temperature of 80°C for 4 hours to prepare a monomer composition.

254 parts by weight of the obtained monomer composition were mixed with 20 parts by weight of amine-modified silica (100 parts by weight of Aerosil 200 treated with 5 parts by weight of aminopropyltriethoxysilane) and 0.5 parts by weight of the monomer composition obtained. It was added to an aqueous medium of 1200 parts by weight of distilled water heated to 85°C containing 25 parts by weight of IN hydrochloric acid under stirring using a TK homomixer, and then heated at 10,000 ml for 15 minutes after the addition.
The mixture was dispersed and granulated by stirring at r, p, and m.

After granulation, the liquid temperature was lowered to 60°C, and 2.2' was added as a polymerization initiator.
3 parts by weight of -azobis-(2,4-dimethylvaleronitrile) and 1 part of 2'-7zobisisobutyronitrile,
5 parts by weight were added to the aqueous medium and stirred for 30 minutes. Furthermore, the stirring was changed to paddle blade stirring, and the mixture was stirred at 60°C for 10 hours to complete the polymerization.

The obtained aqueous medium containing the polymerized toner is cooled and dehydrated,
The amino-modified silica is dissolved and removed by washing with a sodium hydroxide solution, washed with water, dehydrated, and dried (classified as necessary to remove fine particulate unnecessary component particles), with a volume average particle size of 6.5. A polymerized toner of gm (measured with a Coulter counter using a 100 micron layer aperture) was obtained. The resulting polymerized toner contained approximately 100 parts by weight of paraffin wax per 100 fi weighted parts of polystyrene. Further, the obtained toner did not cause blocking even when left in an environment of 50° C. for one day. From this,
It was found that paraffin wax was encapsulated inside the polymerized toner particles.

The softening temperature (softening temperature of polystyrene) of the toner obtained by melt-kneading a toner polymerized in the same manner as in Toner Production Example 2 except that paraffin wax was not used was 155°C.
Met.

Examples 1 and 2, Comparative Examples 1 and 2.3 The toners obtained in Toner Production Examples 1 and 2 were developed using a conventional two-component development method, and the following fixation test was conducted. Note that the paper traveling speed was 300 am/sec. The results are shown in Table 1.

[Effects of the Invention] As described above, the fixing method of the present invention makes it possible to obtain good fixing performance with less occurrence of offset.

Furthermore, it has become possible to lower the fixing temperature compared to normal heat fixing methods, making it possible to save energy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a fixing device used in the present invention.

Claims (3)

[Claims] (1) A toner fixing method in which toner containing two or more binder resins with different softening temperatures is fixed twice or more, and the relationship between pre-fixing pressure P_1 and temperature T_1, post-fixing pressure P_2 and temperature T_2 However, P_1<P_2 and T_
A toner fixing method characterized in that 1>T_2. (2) Softening temperature T of the binder resin with the lowest softening temperature
The relationship between _L, the softening temperature T_H of the binder resin with the highest softening temperature, and the pre-fixing temperature T_1 is T_L<T_1<
The toner fixing method according to claim 1, which is T_H. (3) Post-fixing pressure P_2 is 20 to 100 kg/cm^2
The toner fixing method according to claim 1 or 2.