JPS6339051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic photographic toner, and more particularly to a microcapsule toner that can be fixed under pressure or at low heat under weak pressure.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
No. 2825314, No. 3220324, No. 3220324, No.
No. 3220831, Special Publication No. 23910 and Special Publication No. 1973
A number of methods are known, as described in Japanese Patent Application No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the photoreceptor is A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Various methods are also known for visualizing electrical latent images using toner.

For example, the magnetic brush method described in US Pat. No. 2,874,063, the cascade development method described in US Pat. No. 2,618,552, the powder cloud method described in US Pat. No. 2,221,776, and the powder cloud method described in US Pat. No. 2,895,847. A large number of development methods are known, such as the touch-down development method, the furbrush development method, and the liquid development method described in . As toners used in these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used.
Furthermore, it is also known to use fine developing powder to which a third substance is added for various purposes.

The developed toner image is transferred and fixed onto a transfer material such as paper, if necessary.

Methods for fixing toner images include a method in which the toner is heated and melted using a heater or a heated roller, and then fused and solidified on the support, a method in which the binder resin of the toner is softened or dissolved with an organic solvent and then fixed on the support, and a method in which the toner is fixed on the support by applying pressure. A method of fixing toner on a support by using a method is known.

Currently, there are many improvements in terms of high-speed copying, energy saving, and non-pollution, as well as the fact that once the copying machine is turned on, copies can be made without waiting time, there is no risk of burnt copies, and the fixing device is simple. Heat roller fixing and pressure fixing at low temperatures, which have advantages, are becoming mainstream.

The toners hitherto used in these fusing systems are woefully inadequate. This is because to fix the toner at low temperatures, it is necessary to use a material with a low melting point, but this not only poses problems in terms of blocking properties, but also causes contamination of the carrier, fusion to the metal sleeve, and exposure to light during development. Fusion to the body surface occurs.

In addition, fixing methods that use toner pressure have problems with toner fixing performance, especially when using a pressure roller, pressure is applied unevenly, resulting in differences in fixing performance depending on the location.Furthermore, during development, the carrier may be contaminated. , fusion to the metal sleeve, and fusion to the surface of the photoreceptor.

These problems cannot be solved by using toner that is finely pulverized as in the past.

Therefore, in recent years, research has been conducted on capsule toner, which is considered to be an ideal toner. This is made up of a core material and a shell material, and the core material is responsible for fixing properties, and the shell material is responsible for developing properties.The shell is broken during fixing, and the core material is fixed.

However, since the material used for the core material has improved fixing properties to the utmost, developability is sacrificed immediately.If the capsule has a thin shell, if the capsule breaks due to force such as friction during development, it will be immediately The various problems mentioned above occur conspicuously. On the other hand, if the thickness of the shell is increased to prevent the capsule from breaking during development, the capsule will not be broken by the pressure during fixing, which will cause toner fixation failure.

These problems are solved by creating capsule toners with shells of appropriate thickness. However, in reality, there is a distribution in the shell thickness of capsules, and if there is no problem with development, many capsules have thick shells that are difficult to break, resulting in poor fixation, and a capsule toner that is practically satisfactory has not yet been obtained. .

Furthermore, recently, a method has been used in which electrostatic latent images are developed using a one-component developer that contains magnetic fine particles in the toner and does not use carrier particles, but in this case, the toner binding resin contains magnetic fine particles. Dispersibility and adhesion with toner, impact resistance and fluidity of the toner are required, and it is extremely difficult to achieve both with fixing performance.

The present invention provides stable performance without the above-mentioned drawbacks by creating appropriate voids in the shell material in capsule toners used for low-temperature hot roll fixing using weak pressure or pressure fixing capsule toners. The present invention provides a capsule toner that is

The present invention has extremely good and stable fixing performance in low-temperature hot roll fixing or pressure fixing performed under weak pressure on plain paper, and furthermore, development performance and fixing performance are stable even when copying a large number of sheets. The company provides capsule toners with

Furthermore, the present invention provides a capsule toner that does not cause smearing on the carrier, developing sleeve, or photoreceptor surface.

Further, the present invention provides a capsule toner which has excellent storage stability and does not aggregate or form cakes during use or storage.

Furthermore, even when the present invention contains magnetic fine particles and is used as a magnetic toner for one-component developers or magnetic recording, it exhibits good pressure fixing properties, good magnetism, and electrostatic transferability. This is to provide a capsule toner that can be used.

Further, the present invention provides a capsule toner that has excellent durability and fluidity.

That is, the present invention provides a capsule toner in which a heat-fixable core material or a pressure-fixable core material is coated with a film material, which is characterized in that appropriate voids are provided in the capsule shell material. It is in.

The capsule toner shell is easily broken by the pressure during fixing, and is desired to be strong against friction during development. Therefore, the idea was to make the shell thick enough to withstand the friction during development, but also to make it structurally more susceptible to breakage under the pressure of fixing. In other words, if the shell is thick, it is difficult to break by itself, but the pressure applied to the shell is further dispersed throughout the shell, making it difficult to break. By concentrating the pressure on a shell in one part of the shell, shells of similar thickness become far more likely to break. A structure that concentrates pressure on a portion of the shell means creating a void or wound inside or outside. This is similar to what is generally known, for example, when you want to break a brick, block, or glass in a certain place, you make a scratch in the place you want to break beforehand and then apply force to break it.

Based on the above considerations, a microcapsule toner having voids in the capsule shell was produced, and as a result, fully satisfactory developability and sufficiently good fixing performance were obtained.

There are various ways to create the bubble-like voids, but for example, a method in which the shell material contains a foamable material and is encapsulated and then foamed near the softening point of the shell material, or a method in which the shell material is molten and foamed or Methods include mechanical foaming, foaming, and encapsulation.

The size of the voids can be examined by observing an ultrathin section of the toner using a transmission electron microscope or a high-magnification optical microscope, and the number or amount of voids can also be determined from the same observation.

The size of the void may vary, but voids that reach the core from outside the shell are not preferred. Preferably, the size is 1/5 to 2/3 of the thickness of the shell (the length in the thickness direction of the shell).

The number of voids within this range must be at least one in each shell, preferably five or more. The size and number of voids are correlated; if the void size is about 2/3 of the thickness of the shell, it is fine if there is only one void in the shell, but even if it is about 1/5 of the thickness of the shell. For example, at least 5 are required. Furthermore, in reality, shells without voids are also observed, but toner particles with shells without voids account for the entire toner.
If it is below 10%, we can expect an overall effect.

Next, in the present invention, the foaming materials that can be used are conventionally known foaming agents, such as ammonium carbonate (double salt of ammonium hydrogen carbonate and ammonium carbamate) as an inorganic foaming agent. , sodium bicarbonate, nitrourea, and as the organic blowing agent, nitroso-based, sulfohydrazide-based, and azo-based blowing agents are used as appropriate, but closed-cell organic blowing agents are particularly preferred.

Further, as the core material, it is possible to use a material that fixes at low temperatures or a material that fixes under pressure.

Substances that fix at low temperatures include thermoplastic polymers that generally have a large amount of low molecular weight, or those that are mixed with polyolefin or the like.

Substances that are fixed by applying pressure are, for example,
-9880, JP-A-48-7503, JP-A-48-78931,
Many of the fatty acids described in 49-17739, 52-108134, 48-75033, etc. can be used, but higher fatty acids (stearic acid, palmitic acid, lauric acid, etc.) are particularly preferred. , polyolefin (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polytetrafluoroethylene, etc.), low molecular weight polystyrene, epoxy resin, polyester resin (acid value 10 or less), styrene-butadiene copolymer (monomer ratio 5 to 30) :95～
70), ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenolic resin, phenol-modified terpene resin , etc.

Various resins can be used as the outer shell material, including those that are insulating and have good film-forming ability, those that have good positive or negative chargeability, and those that have good fluidity and non-agglomeration. Particularly preferred are those that do not inhibit the pressure fixing properties of the core material. For example, polymers or copolymers of styrene or substituted products thereof such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-maleic anhydride copolymer, polyester resin,
Acrylic resin, xylene, resin, polyamide resin, ionomer resin, furan resin, ketone resin, terpene resin, rosin, rosin modified pentaerythritol ester, natural resin modified phenolic resin, natural resin modified maleic acid resin, coumaron indene resin , alicyclic hydrocarbon resin, petroleum resin,
Cellulose acetate phthalate, starch graft polymer,
polyvinyl butyral, polyvinyl alcohol,
These can be used alone or in combination. In particular, styrene resins, polyester resins, ionomer resins, cellulose acetate phthalate, starch graft polymers, polyvinyl butyral, and the like having an average molecular weight of 1500 or more are preferred.

If the affinity adhesion between the core material and the shell material is poor, an intermediate adhesive layer may be provided. Further, the outer shell only needs to cover the core material and have sufficient toner properties such as chargeability and fluidity, and does not necessarily need to completely cover the core material.

Further, an appropriate amount of a charge control agent such as a metal-containing dye or nigrosine conventionally used in toners may be added to the insulating material for the outer shell. Furthermore, charge control agent fine particles can also be used in combination with the toner shell material.

In the capsule toner of the present invention, all dyes, pigments, etc. conventionally used as coloring agents for toners can be used, if necessary, and may be added to either or both of the core material and the outer shell. Furthermore, if it is desired to obtain a magnetic toner, magnetic fine particles may be added to the toner. The magnetic substance may be any material that exhibits magnetism or can be magnetized, such as fine metal powders such as iron, manganese, nickel, cobalt, and chromium, various ferrites, alloys and compounds of manganese, and other ferromagnetic alloys. Conventionally known magnetic materials can be used.
These magnetic fine particles may be added to either the core material or the shell material, but in the case of obtaining an insulating toner, it is preferable to add them to the core material.

The image obtained by the capsule toner for pressure fixing of the present invention is fixed by passing between a pair of pressure-loaded rollers, but auxiliary heating may be performed. The applied pressure is generally about 10-30Kg/cm
It is. Regarding the pressure fixing device,
12797, U.S. Patent No. 3269626, U.S. Patent No. 3612682,
It is described in the same No. 3655282, the same No. 3731358, etc.

The image obtained by the heat-fixing capsule toner of the present invention is fixed by being passed between a pair of heated rollers (150° C. or less) under a weak pressure (generally around 10 kg/cm).

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these are not intended to limit the present invention in any way. Further, all parts in the examples are parts by weight.

Example 1 A mixture consisting of 70 parts of polystyrene (D-125), 30 parts of polyethylene (PE-130), and 6 parts of carbon black (Raven 1000) was kneaded in a heated roll mill, cooled, and coarsely ground in a cutter mill. The powder was pulverized to an average size of about 15 μm using a jet mill to obtain core material particles.

Separately, a methyl methacrylate/butyl acrylate/styrene/acrylic acid copolymer emulsion (acrylic acid 3 mol%, solid content 40%) was prepared.
Five parts of benzenesulfonyl hydrazide (Neocelvon P#1000) was added as a foaming agent and thoroughly mixed and dispersed using a homomixer.

To 15 parts of this emulsion, 60 parts of the core material and 165 parts of water were added, and after being well mixed and dispersed, spray drying was performed at an inlet temperature of 140°C and an outlet temperature of 80°C, so that the surroundings of the core material particles were The emulsion-constituting copolymer was applied while foaming to form a coating layer.

The thus obtained capsule toner was mixed with 10% by weight of a carrier (resin-coated iron powder of 250 to 400 meshes) and supplied to a transfer type electronic copying machine to perform a copying test. Sufficient image density and development durability were obtained.
The adhesion of the outer shell film to the core material was also sufficient. Furthermore, when fixing was carried out using a heat fixing machine at 140° C. and a pressure of 10 kg/cm, sufficient heat fixing was achieved, and no caking was observed even when this capsule toner was left in an atmosphere at 45° C. for a long time. In order to compare with this toner, we made a toner without voids using the same materials and the same method, and performed similar image printing and fixing.
This toner did not exhibit sufficient fixing properties.

Example 2 A mixture consisting of 100 parts of polyethylene (PE130) and 60 parts of magnetic powder (magnetite particle size 0.4μ) was kneaded and ground in the same manner as in Example 1 to obtain core material particles. This softening point (Ts) was approximately 130°C.

Separately, an emulsion of methyl methacrylate-ethyl acrylate-2 ethylhexyl acrylate-styrene acrylic acid copolymer (acrylic acid 5
mol%, solid content 45%) was prepared, and 10 parts by weight of azodicarbonamide (Azobis CA) as a blowing agent was added to 100 parts by weight and mixed and dispersed using a homomixer.

To 14 parts of this emulsion, 60 parts of the core material and 165 parts of water were added, mixed and dispersed well, and then coated and dried by spray drying at an inlet temperature of 170°C and an outlet temperature of 110°C. The resin was coated with the emulsion and foamed at the same time.
When this capsule toner was subjected to a copying test, sufficient image density and development durability were obtained.
Furthermore, when pressure fixing was carried out using a pressure roller of 10 kg/cm, sufficient pressure fixing was achieved, and no caking occurred during storage.

In order to compare with this toner, a toner having no voids was prepared using similar materials and method, and the same image fixation was performed, but this toner did not exhibit sufficient fixing properties.

Example 3 Polyethylene oxide (density 0.99) 100 parts Magnetite (trade name, EPT-1000 manufactured by Toda Kogyo) 50 parts The above mixture was heated at approximately 150°C using a roll mill for 30 minutes.
After thorough kneading for a minute, a jet pulverizer was used to obtain particles with a particle size of about 3 to 10 microns. Separately, 3% of tonalium chloride fine powder (particle size maximum 0.5 microns) was dispersed in a 10% solution of styrene-butadiene copolymer (15:85wt ratio) in methyl ethyl ketone. The powder was sufficiently dispersed in this solution to form a capsule toner having a particle size of about 5 to 15 microns using a spray dryer.

Next, this magnetic capsule toner was dispersed in water and sufficiently dispersed and agitated using an ultrasonic disperser to dissolve the sodium chloride exposed on the surface of the capsule shell. This was vacuum dried in a silica gel desiccator for about 2 weeks.

Next, this magnetic capsule toner was developed and fixed using a one-component dry electronic copying machine. Fixation is done by applying pressure.
Pressure fixing is performed using two chrome-plated rigid rollers (upper and lower) of 10 kg/cm. In addition, a capsule toner without toner voids similar to the above was also prepared and compared at the same time.

As a result, the toner with voids was superior to the toner without voids in terms of fixability, and there was no difference in other aspects such as developing performance, transferability, and cleaning performance.

A transmission electron microscope observation of an ultra-thin section of this toner revealed that voids were irregularly shaped and uniformly present near the surface of the shell. However, none of the core substances were observed to be exposed.

Claims (1)

[Claims] 1. A microcapsule toner for electrostatic photography consisting of a core material and an outer shell thereof, characterized in that a synthetic resin constituting the outer shell covering the core material has voids.