JPS63174066A - Dry process toner - Google Patents

Abstract

PURPOSE:To speed up fixing and to prevent caking during storage by depositing an inorg. material on the outermost layer of a toner. CONSTITUTION:The inorg. material is deposited on the outermost layer of the toner having multi-layered structure. For example, the nucleus toner is dispersed into an aq. soln. of an inorg. salt (e.g.: K2CO3) in the presence of a surfactant and thereafter, said soln. is dispersed into an org. solvent (e.g.: benzene) contg. the surfactant and the soln. is emulsified by stirring. The resultant emulsion is mixed under stirring with an aq. soln. of an inorg. salt (e.g.: CaCl2) and is then filtered and dried. The toner formed with the walls of the inorg. material (e.g.: CaCO3) is then obtd. The inorg. material is stuck to the outermost layer in the stable state according to this constitution and, therefore, the efficient fixing is executed at a high speed; in addition, the caking during storage is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dry toner for electrostatic charge development used for development in electrophotography, electrostatic recording, and the like.

[Conventional technology]

In electrophotography, an electrostatic latent image formed on a photoreceptor is usually developed with resin powder containing pigment, and the resulting visible image is transferred onto transfer paper and fixed using heat, pressure, or a combination thereof. In recent years, there has been a demand for performing this fixing process at high speed and with high efficiency.

To this end, in the case of toner for pressure fixing, a substance that easily causes plastic deformation is used as the binder, and in the case of toner for heat fixing, in order to perform high-speed fixing with low power consumption, it is necessary to An effective means is to lower the softening point of the binder material and reduce its melt viscosity.

When the softening point of the binder polymer (binder resin), which is normally used as the main binding material of toner, is lowered, the fluidity tends to decrease due to caking during toner storage.
Furthermore, if the melt viscosity is lowered, image stains are more likely to occur due to an offset phenomenon.

For this reason, a device is installed to supply a release agent such as silicone oil to the heated roll to prevent offset, and the glass transition point of the main binder polymer is increased, or ultrafine inorganic powder such as silica is added to the toner surface. A method of preventing caking during storage by using it as an external additive has been proposed.

[Problem that the invention seeks to solve]

However, supplying silicone oil to the heat roll requires a supply mechanism, which inevitably increases the cost of the device and requires maintenance for oil replenishment.

If the glass transition point of the main binder polymer is set high, the softening temperature becomes high, which tends to make low-temperature fixing difficult.

In addition, in the case of pressure-fixed toner, if a material that is prone to plastic deformation is used, the fluidity deteriorates and caking tends to occur, and the toner material tends to film on the photoreceptor, which makes cleaning difficult. deteriorates, and images tend to deteriorate over time.

Therefore, an object of the present invention is to provide a dry toner that can be efficiently fixed at high speed.

Another object of the present invention is to provide a dry toner that is less prone to caking during storage.

Another object of the present invention is to provide a dry toner that has high fluidity and can form uniform images.

Another object of the present invention is to provide a dry toner that is less likely to cause filming on a photoreceptor.

Another object of the present invention is to provide a dry toner that is easy to clean.

Furthermore, another object of the present invention is to provide a dry toner that can provide stable images over a long period of time.

[Means for solving problems]

In order to solve the above-mentioned problems, multilayer structure toners, typically microcapsule type, have been proposed.

In this case, a component that can be easily melted by heat is used as the internal material,
It is common to use a material as the outermost layer material that has a high melting point and has good flowability and anti-caking properties as a toner. Usually, as the inner material, a wax or a resin with a low glass transition point (Tg) or a low molecular weight is used as a binder, and as the outermost layer material, a material with a high Tg, a high molecular weight, or a crosslinked structure is used. Binder is used.

However, unless the pressure responsiveness and thermal deformability of the outermost layer material are strictly optimized, the fixing energy often becomes high, and the functional separation of fixing properties and caking resistance is not necessarily achieved.

Furthermore, toners with poor fluidity and caking resistance have been practically improved by adding inorganic fine powders such as silica, alumina, and titania; Although the coating is almost capsule-shaped, it is not completely adhered, and due to the instability of the adhered state, the image tends to deteriorate and the caking resistance decreases over time.

As a result of extensive studies, the present inventors succeeded in directly depositing and attaching an inorganic substance to the outermost layer of a toner by utilizing a chemical reaction, and completed the present invention. That is, the present invention is a dry toner having a multilayer structure in which an inorganic substance is deposited on the outermost layer.

In the dry toner of the present invention, since an inorganic substance is precipitated and adhered to the outermost layer of the toner, it has excellent stability over time, and since an inorganic substance that is generally resistant to plastic deformation can be used, it has good caking resistance even in a thin layer state. An extremely excellent effect on fluidity can be obtained.

In order to precipitate an inorganic substance in the dry toner of the present invention, a reaction that forms a solid from a solution can be widely used.

That is, for example, in an inorganic chemical reaction in an aqueous solution represented by the following reaction formula %, a core toner is dispersed in an aqueous solution of an AlB compound, and then this is mixed with an organic solvent to emulsify it. After a water-in-oil emulsion is formed, when it is mixed with another aqueous solution and a precipitation reaction occurs on the surface of the aqueous solution droplets in the emulsion, a wall of inorganic material is formed on the toner surface.

Compounds A and B are water-soluble inorganic salts, inorganic acids, inorganic bases, etc., and the organic solvent used is one with low solubility in water.

If stirring and/or centrifugal sedimentation are performed during the reaction, the toner will be separated into an oil layer and an aqueous layer, so the multilayered toner may then be separated from the aqueous layer and dried by a conventional spray dryer method.

Incidentally, during the reaction, a surfactant may be used in combination to improve the stability of the emulsion.

Specific examples of reactions that can be used to form an inorganic wall in the outermost layer of a toner include: Potassium carbonate + calcium chloride → Calcium carbonate Sodium silicate + Calcium chloride → Calcium silicate sulfate + Sodium bicarbonate → General precipitation reactions include cobalt carbonate barium sulfide + sodium sulfate → barium sulfate barium sulfide + zinc sulfate → barium sulfate + zinc sulfide oxo zirconium chloride + sulfur → zirconium sulfate zirconium sulfate + sodium hydroxide → zirconium hydroxide. .

In addition, precipitation reactions of iron hydroxide and hydrated iron obtained by adding an alkaline solution to ferrous salts and ferric salts or oxidizing them can also be used, but are not necessarily limited to these. Most of the reactions are available.

In addition, although the reaction mode is generally the precipitate formation reaction using the above-mentioned emulsion, it is also possible to attach the A component to the toner surface using a fluidized bed or the like, then add the B component and perform the precipitate formation reaction in the gas phase. is also possible.

Furthermore, all conventional toner compositions can be used as the core particles.

The toner as a core may be produced by any method such as the cross-wire pulverization method 1, suspension polymerization method, streak rate zero dry method, melt dispersion method, and e-john method.

Furthermore, a conventionally used inorganic compound may be added to and dispersed in a multilayered toner having an inorganic substance precipitated on its surface.

〔Example〕

First, 70 parts by weight of amide wax (melting point 65°C) containing ricinoleic acid amide as a main component, 1 part of polyethylene wax
5 parts by weight of carbon black and 15 parts by weight of carbon black were mixed and pulverized to obtain a core toner with an average particle size of 10 μm (this was used as toner A).
shall be. ).

This was dispersed in a 1 mO1/l potassium carbonate aqueous solution in the presence of a surfactant, then dispersed in an inzene solution also containing a surfactant, and stirred and emulsified using a disperser to temporarily form an emulsion. This emulsion was mixed with a 0.2 mat/l calcium chloride aqueous solution with vigorous stirring, and stirring was continued for 20 minutes.

After that, the toner was separated into an oil layer and an aqueous layer using a centrifuge, and the toner was separated from the aqueous layer, washed with water, and then dried using a spray drying method. A toner with much better fluidity than Toner A was obtained. (This is referred to as toner B.)

When we conducted a caking test on Toner A (untreated) and Toner B (calcium carbonate capsule toner) at 50'C for 124 hours, we found that Toner A had a lot of agglomeration, and Toner B had almost the same amount of agglomeration as before the test. It didn't change.

A, B) Mix the toner with the iron powder carrier, and mix it with the FX3500 (
When a fixing test was conducted using a modified machine (manufactured by Fuji Xerox Co., Ltd.), both exhibited sufficient fixing at a roller temperature of 140°C.

〔Effect of the invention〕

The present invention provides a dry toner in which an inorganic substance is precipitated in the outermost layer of a toner having a multilayer structure using a chemical reaction. Because it has an inorganic substance attached to it, it can be fixed efficiently at high speed, it is less likely to cause caking during storage, it has high fluidity and can form a uniform image, and it is less likely to cause filming on the photoreceptor.
It has excellent features such as excellent cleaning properties and the ability to obtain stable images over a long period of time.

Claims (1)

[Claims] A dry toner having a multilayer structure, characterized in that an inorganic substance is precipitated in the outermost layer.