JPH04340972A - Electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To improve electrification characteristics, electrification stability and environmental stability of a toner by incorporating a post-treating agent which is made hydrophobic by heating at specified temp. so that hydroxyl groups is condensed on the surface and further treating with a hydrophobe. CONSTITUTION:The post-treating agent is such one having hydroxyl groups on its surface, and for example, silicate such as silica and alumina produced by wet or dry method, titania, alumina calcium carbonate, barium titanum, zinc oxide, or mixture of these having 10-100mum average particle size can be used. This post-treating agent is heated at 200-600 deg.C, preferably at 400-500 deg.C to condense OH groups on the surface and to make the surface hydrophobic. This post-treating agent is further treated with a hydrophobe agent. Thereby, OH groups remaining on the surface even after the heat treatment couple with the hydrophobe and the surface of the post-treating agent is made further hydrophobic. The electrification characteristics and the like of the post-treating agent thus treated are not affected so much by the hydrophobe.

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 inorganic fine powders 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 a 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 (silicon dioxide) 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 agitation is continued, the toner charge will increase. A charge-up phenomenon occurs in which the amount of energy gradually accumulates. As the toner charge amount increases in this way, it becomes difficult to ensure a sufficient initial density of the copied image. In addition, there is a problem that moisture is easily adsorbed and the amount of charge changes greatly in 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. In the present invention, the post-treatment agent for toner is hydrophobized by heating the post-treatment agent at a constant temperature to dehydrate and condense the surface hydroxyl groups (-OH) before the conventional coupling treatment. This is achieved by incorporating a post-processing agent into the toner.

[0007]

[Means for Solving the Problems] That is, the present invention contains a post-treatment agent that is heated at a temperature of 200°C to 600°C to heat-condense the hydroxyl groups on the surface to make it hydrophobic, and then treated with a hydrophobizing agent to make it hydrophobic. The present invention relates to a toner for developing electrostatic images.

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 silicic acid produced by a dry or wet method. Contains aluminum, silicates such as magnesium silicate, titania (titanium dioxide), alumina calcium carbonate, titanium barium, zinc oxide, etc., or mixtures thereof, and usually has an average particle size of 10 to
Use one with a diameter of 100 mμ.

[0009] In the present invention, the above-mentioned post-treatment agent is heated to 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 thermal condensation, for example, the OH groups present on the surface of the silica particles (Figure 1), one water molecule (H2O) is detached from two OH groups and condensed, forming the ether shown in Figure 2. It is believed that surface hydrophobization is partially achieved through the formation of chemical bonds. 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 after heating, and hydrophobization will not be achieved sufficiently. Furthermore, 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.

The post-treatment agent heat-treated as described above is treated with a hydrophobizing agent. By doing this, the OH groups remaining on the surface even after the heat treatment are coupled with the hydrophobizing agent,
The surface of the post-treatment agent is further made hydrophobic. FIG. 3 illustrates a phase diagram of the surface after coupling of OH groups with dimethylchlorosilane. The surface is made hydrophobic by ether bonds generated by heat treatment and by a post-treatment agent. The surface of the post-treatment agent that has been hydrophobized in this way is only partially coupled with the hydrophobizing agent, so its charging characteristics are not strongly affected by the hydrophobizing agent, and it does not cause charge-up etc. We believe that it is effective in preventing static electricity, stabilizing static electricity, and stabilizing the environment.

On the other hand, when hydrophobization treatment is directly performed using a hydrophobizing agent without undergoing heat hydrophobization, the surface becomes as shown in FIG.
It is believed that the material is covered with a hydrophobizing agent, and its charging characteristics are strongly influenced by the hydrophobizing agent, leading to problems such as charge-up and associated environmental instability.

[0013] As the hydrophobizing agent applied to the post-treatment agent, various coupling agents such as silane type, titanate type, aluminum type and zircoaluminate type, silicone oil, etc. are used. Examples of silanes include chlorosilane, alkylsilane, alkoxysilane, and silazane.

Specifically, for example,

[Chemical formula 1]

[Case 2] etc. can be mentioned.

[0015] For titanate series, for example,

[Chemical formula 3]

[C4]

[C5] etc. can be mentioned.

[0016] For silicone oil systems, for example,

[C6]

[C7]

[Chemical formula 8] etc., but is not particularly limited.

The following method is used to treat the surface of the post-treatment agent powder using a hydrophobizing agent. First, a hydrophobizing agent alone or tetrahydrofuran (THF), toluene,
Mix and dilute with a solvent such as ethyl acetate, methyl ethyl ketone, or acetone, and thoroughly mix by dropping or spraying the diluted solution of the coupling agent while forcibly stirring the post-treatment agent powder with a blender or the like. Next, the obtained mixture is transferred to a vat or the like and placed in an oven to heat and dry. Then, stir again in a blender to thoroughly crush the mixture. In such a method, each hydrophobizing agent may be used simultaneously. In addition to such a dry method, there is also a wet treatment method in which a post-treatment agent is immersed in a solution of a hydrophobizing agent dissolved in an organic solvent, dried, and crushed.

[0018] The amount of the hydrophobizing agent to be used needs to be adjusted depending on the type of post-treatment agent and the degree of hydrophobization by heat treatment, but it is 0.1 to 5% by weight, preferably 0.1% by weight based on the post-treatment agent. ~
Use 3% by weight. If it is less than 0.1% by weight, the ratio of hydrophobization by the hydrophobizing agent will decrease and the effect cannot be expected, and if it is more than 5% by weight, the particle size will increase due to the binding of the hydrophobizing agent itself. .

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 be used in which a post-processing agent is added during polymerization and 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.

The toner to which the post-processing agent of the present invention is added is generally fine particles consisting of at least a binder resin such as acrylic resin, polystyrene resin, polyester resin, styrene-acrylic copolymer resin or epoxy resin, and a colorant, and a magnetic carrier. There are toners that are used as two components together with particles, toners that are used as a non-magnetic single component, and toners that are used as a single component that contains a magnetic agent inside the toner (magnetic toner). It can also be applied to the toner used in the method.

The amount of the post-processing agent to be added to the toner may be the amount normally used depending on whether the toner is used as a single component or as a two-component. When adding or externally adding, 0.0 to toner
It is used in an amount of 5 to 5% by weight, preferably 0.1 to 2% by weight. It can also be used as a blend of more than one type. The present invention will be explained below using examples.

[0022]

【Example】

Example 1 Silica fine particles (AEROSIL130; manufactured by Nippon Aerosil Co., Ltd.) were heated in air at 450° C. for 24 hours. Next, surface treatment was performed by a dry method using dimethyldichlorosilane at a ratio of 2.0% by weight to the heat-treated silica particles.

Example 2 Alumina fine particles (Aluminum Oxide)
C; manufactured by Nippon Aerosil Co., Ltd.) was heat-treated in the same manner as in Example 1. Next, surface treatment was performed by a dry method using hexamethyldisilane at a ratio of 1.0% by weight to the heat-treated alumina fine particles.

Example 3 Titanium oxide fine particles (titania)
Oxide P-25 (manufactured by Nippon Aerosil Co., Ltd.) was heat-treated in the same manner as in Example 1. Next, 1.0% of octyltrimethoxysilane was added to the heat-treated titanium oxide fine particles.
It was used at a ratio of 0% by weight, and surface treatment was performed by a dry method.

Comparative Example 1 The heat treatment performed in Example 1 was not performed, and only surface treatment was performed with dimethyldichlorosilane.

Comparative Example 2 The heat treatment performed in Example 2 was not performed, but only surface treatment was performed using hexamethyldisilane.

Comparative Example 3 The heat treatment performed in Example 3 was not performed, but only surface treatment was performed with octyltrimethoxysilane.

The specific surface area, apparent specific gravity, and degree of hydrophobicity of the post-treatment agents obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1.

In Table 1, the specific surface area was determined by the BET method. The degree of hydrophobicity was determined by the methanol wettability method.

[0030]

[Table 1]

Table 1 shows that the degree of hydrophobicity of silica, alumina, and titania can be increased with a small amount of hydrophobizing agent (silane coupling agent).

The post-processing agent obtained as described above was added to the toner described below, and further mixed with the carrier described below to prepare a developer, which was subjected to characteristic evaluation.

(Preparation of toner) (Binder resin: Production of vinyl-modified polyester resin) 68 parts by weight of polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane, 1 part by weight of isophthalic acid.
6 parts by weight, 16 parts by weight of terephthalic acid, 0 maleic anhydride
．． A flask was charged with 3 parts by weight 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 10,600.

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 nozzle diameter of 1 mm, a nozzle length of 1 mm, a load of 30 kg, and a temperature increase rate of 3° C./min.

[0035]

Part by weight: Ethylene acrylic modified polyester resin obtained above
100・Organic pigment Lionol Yellow FG
-1310 (manufactured by Toyo Ink Mfg. Co., Ltd.) 3. Charge control agent (Bontron E-84, manufactured by Orient Chemical Co., Ltd.) 3. The above materials were sufficiently mixed in a Henschel mixer, kneaded in a twin screw extruder, and then cooled. The mixture was coarsely pulverized using a feather mill, and then a jet pulverizer and an air classifier were used to obtain toner particles having a particle size of 5 to 25 μm (average particle size 10.5 μm).

1 kg of the obtained toner particles and 0.4% by weight of the after-treatment agent based on the toner particles were charged into a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) with a capacity of 10 liters, and treated at 1000 rpm for 60 seconds. did. After the treatment, the resulting mixture was passed through a sieve with an opening of 105 μm to remove coarse powder.

(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.

(Evaluation of Toner) The apparent density and charging characteristics of the obtained toner were evaluated and the results are summarized in Table 2. In Table 2, the apparent density was measured using a powder tester manufactured by Hosokawa Micron. "Charge amount" is the value measured by the blow-off method after charging each toner obtained above and the carrier at a toner concentration of 8% by weight into a ball mill and stirring at 120 rpm for 5 minutes and 60 minutes. . “Environmental change range” is
LL (10°C, 15%) and HH (30°C, 85%)
After stirring for 60 minutes in each environment, the amount of charge was measured, and the difference between the two was shown.

[0039]

[Table 2]

[0040] Examples 1 to 3 exhibited good charge amounts both at the initial stage and after long-term stirring, and the range of environmental changes in charge was small. In Comparative Examples 1 to 3, 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.

[0041]

[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.

FIG. 3 is a diagram schematically showing the surface state of the post-treatment agent after heat treatment and treatment with a hydrophobizing agent.

FIG. 4 is a diagram schematically showing the surface state of the post-treatment agent after treatment with a hydrophobizing agent without 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 the hydroxyl groups on the surface to make it hydrophobic, and then subjected to a hydrophobic treatment with a hydrophobizing agent.