JPH04340971A - Electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To improve electrification characteristics and environmental stability of a toner by incorporating such a post-treating agent which is heat treated at specified temp. to heat and condense hydroxyl groups on the surface to make the surface hydrophobic. CONSTITUTION:The toner contains such a post-treating agent the surface of which is made hydrophobic by heat treatment at 200-600 deg.C to condense hydroxyl groups on the surface. The post-treating agent is such one having hydroxyl group on its surface, and for example, silicate such as silica and alumina produced by wet or dry method, or titania, alumina calcium carbonate, barium titanate, zinc oxide, or mixture of these having 10-100mum average particle size can be used. This post-treating agent is heated preferably at 400-500 deg.C to condense OH groups on the surface and to make the surface hydrophobic. Namely, by heating and condensing, two OH groups present on the surface of silica particles, for example, are condensed while a water molecule isolates to produce an ether coupling and the surface is made hydrophobic.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to electrophotography, electrostatic recording,
The present invention relates to a toner for developing electrostatic images in electrostatic printing and the like.

0002

[Prior Art] In electrophotography, a cascade development method (United States Patent (USP) No. 2297691, USP No. 2618552) or a magnetic brush development method (USP No. 2618552) using a mixed developer of toner and carrier is used.
No. 2,832,311) or touchdown development using a developer consisting only of toner (USP No. 41).
No. 21931), non-magnetic one-component development method (USP No. 373)
No. 1146), etc., or by visualizing the electrostatic charge image by reversal development to obtain a high-quality stable image.

[0003] Toners applied to these development methods are prepared by adding a dye as a charge control agent, a pigment as a coloring agent, or a wax as a release agent to a thermoplastic resin as a binder, and then kneading, crushing, and classifying the mixture. Average particle size is 4-2
Toner particles having a diameter of 5 μm are used. Generally, inorganic fine powder such as silica, titania, or alumina is added as a post-treatment agent in order to impart fluidity to the toner and improve cleaning properties.

[0004] These post-treatment agents have high wettability with water, and as a result, humidity greatly affects the fluidity and triboelectric charging properties of the toner. In order to prevent such environmental influences, the surface of these inorganic fine powders is usually treated with a hydrophobizing agent and used as toner, which is applied to developing devices such as copying machines (for example, USP No. 3720617). , Special Public Service 1974-2
Publication No. 0344).

Silane coupling agents are generally used as these hydrophobizing agents. For example, hydroxyl groups on the surface of silica particles are made hydrophobic by reacting with silanol groups derived from a silane coupling agent. However, since coupling agents such as silane coupling agents have excellent insulating properties, toners containing post-treatment agents with a high degree of hydrophobicity are strongly affected by the coupling agents, and if continued stirring, the toner charge will increase. A charge-up development occurs in which the amount of water gradually accumulates. As described above, as the toner charge amount increases, it becomes difficult to ensure a sufficient initial density of the copied image. In addition, there are problems such as moisture adsorption and a large change in the amount of charge under the environment.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a toner having excellent charging characteristics and environmental stability.

[0007] The present invention provides a post-treatment agent for toner.
This is achieved by adding a hydrophobic treatment to the toner by heating the post-treatment agent at a constant temperature and dehydrating and condensing the surface hydroxyl groups (OH) instead of the conventional coupling treatment. be done.

[0008]

[Means for Solving the Problems] That is, the present invention relates to a toner for developing electrostatic images containing a post-processing agent which is heat-treated at a temperature of 200° C. to 600° C. to thermally condense the hydroxyl groups on the surface to make it hydrophobic.

Post-treatment agents to which the present invention can be applied include those having a hydroxyl group (-OH group) on the surface, such as silica (silicon dioxide), alumina (aluminum oxide), and silicon produced by a dry or wet method. It contains silicate such as acid aluminum, magnesium silicate, titania (titanium dioxide), alumina calcium carbonate, titanium barium, zinc oxide, etc., or a mixture thereof, and usually has an average particle size of 10 to 100 mμ.

[0010] The present invention provides the above-mentioned post-treatment agent at a temperature of 200 to 6
Heat treatment is performed at 00°C, preferably 400 to 500°C. By performing such heat treatment, the surface OH groups of the post-treatment agent are condensed and surface hydrophobization is achieved.

By heating and condensation, for example, two OH groups (Fig. 1) present on the surface of silica particles are converted into water molecules (H2
It is thought that O) is eliminated and condensed to form the ether bond shown in FIG. 2, thereby achieving hydrophobization.

[0012] If the heat treatment temperature is lower than 200°C, the surface OH groups of the post-treatment agent will condense, but will return to the original OH groups once the heating is finished, and hydrophobization will not be achieved sufficiently. Moreover, if the heat treatment temperature is higher than 600° C., reactions other than the above-mentioned dehydration condensation reaction occur, so that hydrophobization by dehydration and condensation cannot be performed.

[0013] When the post-processing agent obtained as described above is used by incorporating it into a toner, it has excellent not only fluidity and cleaning properties but also charge build-up, charge uniformity, charge stability, and environmental stability. It can be used as a toner.

In order to incorporate the surface-treated post-processing agent of the present invention into the toner, the toner and the post-processing agent are mixed and stirred in a normal ratio in a blender or mixer to uniformly apply the post-processing agent on the toner surface. A known method may be applied, such as attaching it to the surface. Further, the post-processing agent may be mixed in at the same time when the toner is kneaded to uniformly disperse it inside the toner (internal addition). When producing a toner by a polymerization method, a method can also be used in which a post-processing agent is added during polymerization so that the post-processing agent is incorporated at the same time as the toner is formed. Furthermore, it is also possible to use a method in which a post-treatment agent is fixed to the toner surface by mechanical shearing force using a hybridization system, mechanofusion system, or the like.

[0015] The toner generally comprises at least an acrylic resin,
Microparticles consisting of a binder resin such as polystyrene resin, polyester resin, styrene-acrylic copolymer resin or epoxy resin, and a colorant, which are used as a two-component together with magnetic carrier particles, and those where the toner is used as a non-magnetic single component. There are toners that contain a magnetic agent inside the toner (magnetic toner) and are used as a single component.
The post-treatment agent hydrophobized according to the present invention can be applied to any toner.

The amount of the post-processing agent added to the toner may be the amount normally used depending on whether it is used as a single component or as a two-component developer. Or, if externally added, 0.05 to the toner
It is used in amounts of ~5% by weight, preferably 0.1-2% by weight. It can also be used as a blend of one or more types. The present invention will be explained below using examples.

Example 1 Silica fine particles (AEROSIL 130; manufactured by Nippon Aerosil Co., Ltd.) were heat-treated in air at 450° C. for 24 hours.

Example 2 Alumina fine particles (Aluminum Oxide)
C; manufactured by Nippon Aerosil Co., Ltd.) was heated in air at 450° C. for 24 hours.

Example 3 Titanium oxide fine particles (titania)
Oxide P-25 (manufactured by Nippon Aerosil Co., Ltd.) was heated in air at 450°C for 24 hours.

Comparative Example 1 AEROSIL130 used in Example 1 was used as it was without heat treatment.

Comparative Example 2 Aluminum Oxide used in Example 2
C was used as it was without heat treatment.

Comparative Example 3 Titanium Oxide used in Example 3
P-25 was used as it was without heat treatment.

Comparative Example 4 AEROSIL130 used in Example 1 was treated with a silane coupling agent (dimethyldichlorosilane).

Comparative Example 5 Aluminum Oxide used in Example 2
C treated with a silane coupling agent (hexamethyldisilane) was used.

Comparative Example 6 Titanium Oxide used in Example 3
P-25 treated with a silane coupling agent (octyltrimethoxysilane) was used.

(Preparation of toner; Binder resin: Production of vinyl-modified polyester resin) Polyoxyethylene (2
)-2,2-bis(4-hydroxyphenyl)propane 68 parts by weight, isophthalic acid 16 parts by weight, terephthalic acid 1
A flask was charged with 6 parts by weight of maleic anhydride, 0.3 parts by weight of maleic anhydride, and 0.06 parts by weight of dibutyltin oxide, and the reaction was continued at 230° C. for 24 hours under a nitrogen atmosphere and then taken out. The weight average molecular weight of the obtained unsaturated polyester resin was 10,
It was 600.

50 parts by weight of this unsaturated polyester resin,
50 parts by weight of xylene was charged into a flask and dissolved. The temperature was raised until the xylene refluxed, and a solution of 13 parts by weight of styrene, 0.4 parts by weight of azobisisobutyronitrile dissolved in 2 parts by weight of methyl methacrylate was added dropwise under nitrogen atmosphere over about 30 minutes while the xylene was refluxing. . Keep warm for 3 hours after dropping.
After distilling xylene under reduced pressure, the resin was taken out, and the weight average molecular weight was 13,100, and the melt viscosity at 100°C was 6x.
A binder resin having 104 poise and a glass transition temperature of 63°C was obtained.

However, the melt viscosity is a value measured using a Shimadzu flow tester CFT-500 under the conditions of a noise diameter of 1 mm, a nozzle length of 1 mm, a load of 30 kg, and a temperature increase rate of 3° C./min.

[0029]

Part by weight: Styrene acrylic modified polyester resin obtained above
100・Organic pigment Lionol Yellow
ow FG-1310 (manufactured by Toyo Ink Manufacturing Co., Ltd.)
3. Charge control agent (Bontron E-84, manufactured by Orient Chemical Co., Ltd.) 3. The above materials were thoroughly mixed in a Henschel mixer, kneaded in a twin screw extruder, and then cooled. Coarsely grind the mixture with a feather mill,
After that, using a jet crusher and a wind classifier, the particle size of 5 to 5
Toner particles of 25 μm (average particle size 10.5 μm) were obtained.

The toner particles obtained here and the post-treatment agent obtained in each Example and Comparative Example at a ratio of 0.4% by weight to the particles were added to a 10 liter Henschel mixer (manufactured by Mitsui Miike Kako Co., Ltd.). and processed at 1000 rpm for 60 seconds.

(Evaluation) The properties (specific surface area, apparent specific gravity, degree of hydrophobicity) of the post-treatment agents obtained in each example and comparative example are shown in the table.

[0032]

[Table 1]

From Table 1, it can be seen that the degree of hydrophobicity of the post-treatment agents prepared in Examples is improved even without surface treatment with a silane coupling agent.

Next, the performance of the toner obtained by externally adding this post-treatment agent (apparent density, effective amount of post-treatment, amount of charge)
compared.

[0035]

[Table 2] In Table 2, the "effective amount of post-treatment" indicates the actual amount of the post-treatment agent attached to the toner surface, which was determined from the values of each element using fluorescent X-ray analysis means. "Charge amount" indicates the value measured by the blow-off method after charging each toner obtained above and the following carrier at a toner concentration of 8% by weight into a ball mill, stirring at 120 rpm for 5 minutes and 60 minutes. Ta. "Environmental change range" is LL (10℃, 15%) and HH (30℃
The amount of charge was measured in the same manner as the measurement of the amount of charge, except that the mixture was stirred for 60 minutes in an environment of 30%, 85%), and the difference between the two was shown.

(Preparation of carrier) Cu-Zn-Fe ferrite powder F-300 (manufactured by Powder Tech Co., Ltd., average particle size 50 μm) was used as a carrier core particle, and acrylic resin Lastrazol A-405 (Dainippon Ink Chemical Co., Ltd.) was used as a coating material. A xylene solution prepared by mixing and dissolving 80 parts by weight of (manufactured by Kogyo Co., Ltd.) and 20 parts by weight of a butylated melamine resin was coated using a spira coater. The amount of resin was 3.0% by weight. Furthermore, the obtained resin-coated carrier was cured at 140° C. for 3 hours.

From Table 2, the amount of charge could not be measured for the toners of Comparative Examples 1 to 3 due to poor charging. In Comparative Examples 4 and 5, since the toner was hydrophobized with a silane coupling agent, the initial charge amount of the toner was good, but as the stirring time became longer, the charge amount increased and the range of environmental changes was also large.

[0038] In Examples 1 to 3, both the initial charge amount and after long-term stirring showed a good charge amount, and the range of environmental change in charge was also small.

[0039]

[Effect of the invention] The toner containing the post-processing agent of the present invention is
Excellent charging characteristics, charging stability, and environmental stability.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the surface state of a post-treatment agent.

FIG. 2 is a diagram schematically showing the surface state of the post-treatment agent after heat treatment.

Claims (1)

[Claims] 1. A toner for developing an electrostatic image, which contains a post-processing agent that is heat-treated at a temperature of 200° C. to 600° C. to thermally condense hydroxyl groups on the surface to make it hydrophobic.