JPS6280668A - Developer for electrophotography - Google Patents

Abstract

PURPOSE:To shorten the time for heat fixing and to lower the temp. of heat fixing by flocculating primary particles having a specific grain size to form flocs having a specific grain size, thereby upgrading the sharpness of recorded characters and drawings. CONSTITUTION:35wt% Polyester resin, 55wt% tri-iron tetroxide and 10wt% carbon black as a pigment are mixed and the mixture is kneaded at 150 deg.C and is cooled to solidify. The cooled mixture is crushed by a hammer mill and is put into a ball mill made of Ni. After water is added to the powder, Ni balls are put therein and the powder is subjected to wet grinding. A soln. of a PE glycol is added to such suspension and the mixing is further continued for about 5 hours; thereafter, the suspension is subjected to drying, bonding the flocculating by a spray dryer. The dried powder is classified by spray classification to 3-15mum flocs.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in copying machines and recording machines, such as electronic copying machines, laser recording printers, and optical printers, that utilize electrophotography, and is applicable to paper, plastic, etc. The present invention relates to an electrophotographic developer for forming visible images such as characters and drawings on a recording medium.

Conventional technology As shown in Japanese Patent Publication No. 58-40182 and Japanese Patent Application Laid-open No. 55-126266, conventional developers are made by mixing thermoplastic resins, magnetic powders, pigments, etc. and then heating to thermally solidify the mixture. After that, it is crushed to a size of 3 to 20 μm. Additionally, there is also a developer that is subsequently surface-treated to become spheroidal.

Problems to be Solved by the Invention However, the developers produced by these methods have the following problems.

The size of the 30 particles varies widely, ranging from 3 to 20 μm.

b, and the average particle diameter is 10 to 15 μm.

Due to the factor a, the formed characters become unclear and are generally developed in a blurred state. This is because the particle size and variation are large, and the number of particles existing in that area and the thickness of the toner when developed are naturally different between areas developed with large particles and areas developed with small particles. It's for a reason. Regarding factor b, in the step of thermal fixing after development, the fixing speed is less than 70 mm/sec due to the large particle size of the developer, which makes it impossible to increase the speed and also increases the temperature of thermal fixing. This is due to the following reasons.

When it comes to particles with large and small particle sizes, the smaller the particle size, the larger the surface energy. In other words, it is easy to react. Also,
The phenomenon of heat fixation is that the developer particles, especially the thermoplastic resin part in the developer particles, melt as the temperature rises and fuse or adhere to the paper fibers, etc., and the developer particles also melt with each other. This is a process that ends with fusing. Therefore, the smaller the particle size, the better this phenomenon will be.

Means for Solving the Problems In the present invention, primary particles having a particle size of 0.3 to 1.0 μm are aggregated to form an aggregate having a particle size of 3 to 15 μm.

Effect: By using the above means, the clarity of recorded characters and drawings can be increased, and it is also possible to shorten the heat fixing time and lower the heat fixing temperature.

Example An embodiment of the present invention will be described below.

<Example 1> 35 wt% polyester resin and 55 wt% triiron tetroxide
and carbon black Lowt% as a pigment,
Next, the mixture was kneaded at 150°C, cooled, and solidified. next,
This was coarsely pulverized with a hammer mill, then placed in a Ni ball mill, water was added, and a Ni pole was placed there for wet pulverization. After 200 hours had elapsed, about 10 cc of the black suspended liquid was taken out and applied to a particle size distribution analyzer, and the particle size was 1 μm or less. Furthermore, even when measured using an electron microscope, no diameter of 1 μm or more was observed, and most of the diameters were about 0.6 μm. A polyethylene glycol solution was added to this suspension, and mixing was continued for about 5 hours. Thereafter, this suspension was dried and coagulated using a spray dryer. Furthermore, this was classified into aggregates of 3 to 15 μm by spray classification. In this way, an electrophotographic developer of the present invention was prepared.

Next, this developer was placed in a copying machine, and three types of line widths, 1 mm, 0.5 mm, and 0.2 mm, were drawn on a square with 4 lines on each side, and the sharpness was compared with that of a conventional developer. The comparison method was determined by the linearity of a line drawn using a 50x microscope.

As a result, the developer of the present invention was superior.

Further, regarding the heat fixing time and temperature, similar shapes were copied and the heat fixing time and temperature were varied. The heat fixing time was determined by the speed of the heater roll, and the temperature was determined by the temperature of the heater roll.

Then, the evaluation was performed by rubbing a plastic eraser on the shape with a load of 100 g/cJ.
After repeating the test several times, judgment was made based on the dirt on the eraser. If the fixing is insufficient, the developer particles will detach and the eraser and the rubber at the detached portion will turn black. the result,
The heat fixing speed was more than twice that of conventional developers at the same temperature. Furthermore, the temperature could be reduced by 20°C. It could also be used in laser printers and optical printers. Therefore, we investigated the relationship between the particle size of aggregates and the sharpness of lines under a microscope. 3-1
Using a developer with an aggregated particle size of 5 μm and a developer with an aggregated particle size of 15 to 25 μm, characters and drawings were printed using a copying machine, and it was clear that the cases with 3 to 15 μm were clearer. Met. Moreover, when the thickness is less than 3 μm, the fluidity decreases and rotational fluidization by the magnetic roll becomes poor.

According to the above results, a particle size of 3 to 15 μm is favorable.

In addition, to produce secondary particles, after coarsely pulverizing with a hammer mill,
Similar results were obtained using a jet mill for particles of 1 μm or less. The primary particles obtained by pulverization with a jet mill were suspended in a polyethylene glycol solution, and then aggregated with a spray dryer to obtain a developer. However, the yield of primary particles in the jet mill was worse than that in the wet method.

FIG. 1 is a diagram showing the structure of the developer of the present invention. Here, 1 is a magnetic powder, 2 is a pigment, 3 is a thermoplastic resin, and 4 is a binding flocculant.

Similar results were obtained using a polyacrylic binder as the binding flocculant. The polyacrylic binder needs to be water-soluble.

<Example 2> Using the same method as in Example 1, the composition range was investigated. Thermoplastic resins have a pale color, so it is necessary to add pigments to make them darker. In addition, the magnetic powder has a reddish-black color tone, although it is not as strong as that of the pigment. Therefore, we added 50% of magnetic powder.
The effect of adding a pigment was investigated with the amount constant at 0 wt%. The results are shown in Table-1.

Table-1 Also, Table-1 shows the case when the magnetic powder is kept constant at 60wt%.
Shown in 2.

Table 2 Density was determined by visually observing the color tone of characters when printed using a copying machine. There is almost no difference in color tone between 5 wt % and 20 wt %, and even if 18 wt % or more of pigment is added, there is no effect and it lacks economic advantage. Carbon black was used as the pigment. Similar results were obtained using nigrosine.

The relationship between the content of magnetic powder in the developer and the clarity of characters during development was investigated. - Development conditions for the developer.

In order to maintain this level, a magnetic roll with a sleeve is used as shown in Figure 2, and the magnetic roll is rotated at 140 Orpm, and the sleeve is rotated in the same direction at 15 Orpm, and the interval between the doctor blades for regulating the developer is adjusted. 0
．． The diameter was set to 4 mm.

Table 3 shows the results when the pigment content was constant at 5 wt%. In FIG. 2, 5 is a doctor blade, 6 is a sleeve, 7 is a magnet roll, and 8 is a developer.

Table 3 In addition, Table 4 shows the case where the pigment was kept constant at 15 wt%.

Table 4 As shown above, when the content of magnetic powder is low, the sharpness deteriorates because the magnetic force of the developer becomes weak due to the low content of magnetic powder, and it also scatters slightly to the side. It is thought that this is because of this. The developer, which is attracted by the amount of charge on the electrostatic latent image and the electric force induced by it, is fixed by magnetic force, but if the magnetic force is weak, it will be attracted to the less charged latent image, and during development. The sharpness deteriorates.

From the above results, it can be seen that a minimum amount of magnetic powder of 50 wt% is required.

Next, the degree of heat fixation was investigated depending on the content of thermoplastic resin. The results are shown in Table-5. The evaluation was performed using the method of evaluating using an eraser in Example 1. The conditions were a heat roll speed of 140 ma/sec and a heat roll temperature of 150°C. 5 wt pigment
Table 5 shows the percentage.

Table-5 Further, Table 6 shows the case where the pigment was 15 wt%.

Table-6 Thermoplastic resins include polyester and polyamide.

The tests were conducted on polystyrene, polyethylene, styrene-acrylic copolymer, and ethylene-vinyl acetate copolymer. Similar results were obtained in all cases.

From the above results, it can be seen that 5 wt% or more of the pigment is required, and 50 wt% or more of the magnetic powder is required. Further, the thermoplastic resin is required to be at least 35 wt%. Therefore, from the experimental results, thermoplastic resin 35 to 45 w
t%, magnetic powder 50-60wt%, pigment 5-15w
t% is the composition ratio of the present invention.

Furthermore, the amount of binding flocculant added was investigated. A solution of polyethylene glycol was added to the primary particles of the above composition, and the agglomerated particle size of the developer was aggregated using a spray dryer, and the state of solidification at a temperature of 50° C. was investigated.

Regarding the particle size of the aggregate, the particle size of 90% or more of the particles was defined as the average particle size.

FIG. 3 shows the results of investigating the relationship between the addition rate of the binding flocculant and the average particle size.

Additionally, the addition rate and solidification status at 50°C were investigated.

Solidification means that particles of the developer react with each other and combine to form large aggregates. The results are shown in Table-7.

Agglomeration was examined by determining whether the particles remained agglomerated even after 4000 hours at a temperature of 50°C.

Table 7 From the above results, it is found that 1 to 3 wt% of the binding flocculant is good.

In addition, Mn-ZU ferrite and iron powder were used as the magnetic powder in addition to triiron tetroxide, but similar results were obtained.

The magnetic powder is a soft magnetic material, and any powder may be used as long as the developer has a certain magnetic permeability.

<Example 3> To prepare an anodic developer, 1 wt% of a nigrosine-based electron-donating dye was added as a charge control agent to the aggregate of the present invention, and 1 w of colloidal silica was added as a fluidizing agent.
t%, 1 fluorine surfactant as a cleaning agent
wt% was added. Then, mixing was performed. As a result of copying using this, clear copies were made.

In addition, the above charge control agent was added at 3 wt%, and the fluidizing agent was added at 3 wt%.
As a result of adding 3 wt% of the cleaning agent, similar clear copies could be made.

Furthermore, a copper phthalocyanine compound was added as a charge control agent to obtain a negative polarity developer. The ratio is the same as in the case of the charge control agent added to the anodic developer.

As a result, it acted as a good negative polarity developer and good copying was possible.

It could also be used satisfactorily as a developer for laser printers and optical printers.

Effects of the Invention By using the electrophotographic developer of the present invention, clear copying or recording can be performed, and the heat fixing speed can be increased to 7 cm.
/sec, making it possible to reduce the heat fixing temperature to 5°C.

Therefore, it is possible to realize faster recording or copying.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the electrophotographic developer of the present invention,
FIG. 2 is a cross-sectional view for explaining the relationship between the developer and the magnet roll, and FIG. 3 is a diagram showing the relationship between the addition rate of the binding flocculant and the average particle system of the aggregates. 1...Magnetic powder 2...Pigment 3
... Thermoplastic resin 4... Name of agent for binding flocculant Patent attorney Toshio Nakao and one other person f-7 or 1 powder pot 4, --jit Jtlh No. 3 1 go counterfeit sword B q (w
t z) Procedural amendment February 77, 1988 1 Indication of the case 1985 Patent Application No. 222212 2 Name of the invention Electrophotographic developer 3 Relationship with the person making the amendment Patent application Colonel Osaka 1006 Kadoma, Fukadoma City
'(582) Representative of Matsushita Electric Industrial Co., Ltd.
Toshihiko Yamashita 4 Agent 571 Address Matsushita Electric Industrial Co., Ltd., 1006 Oaza Kadoma, Kadoma City, Osaka Name (,5971) Patent attorney Toshio Tsuchinakao (and 1 other person) [Contact information Telephone (Tokyo) 437-1121 Tokyo Legal Affairs Branch 15 Column 6 for Detailed Explanation of the Invention in the Specification Subject to Amendment Contents of Amendment (1) Table 7 on page 12 of the specification will be amended as follows. "Table-7

Claims (4)

[Claims] (1) From an aggregate of primary particles composed of a mixture of a thermoplastic resin with a specific resistance of 10^1^2 Ωcm or more, magnetic powder of triiron tetroxide, and pigments mainly containing carbon black and nigrosine. and the primary particle has a particle size of 0.3μ
m to 1 μm, and the aggregate is an aggregate obtained by aggregating the primary particles using polyethylene glycol or a polyacrylic binder as a binding flocculant, and the particle size of the aggregate is 3 μm to 15 μm. An electrophotographic developer. (2) For electrophotography according to claim 1, wherein the thermoplastic resin is any one of polyester, polyamide, polystyrene, polyethylene, styrene-acrylic copolymer, and ethylene-vinyl acetate copolymer. developer. (3) Magnetic powder 50~60wt%, thermoplastic resin 35~
45 wt% of pigment, 5 to 15 wt% of pigment, and 1 to 3 wt% of a binding and aggregating agent. (4) Charge control agent 1-3 wt%, fluidizing agent 1-3 wt%
2. The electrophotographic developer according to claim 1, wherein 1 to 3 wt% of a cleaning agent is added.