JPH0439066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-fixable dry toner for electrostatic charge development, which is used to develop an electrical latent image in electrophotography or electrostatic recording.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
specification, Japanese Patent Publication No. 42-23910, and Japanese Patent Publication No. 1973
Many methods are known, as described in Japanese Patent 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 After developing the latent image using toner and transferring the toner image to a transfer material such as paper as necessary, a copy is obtained which is fixed by heating, pressure, solvent vapor, or the like.

Various methods and devices have been developed for the above-mentioned final step, which is the step of fixing the toner image on a sheet such as paper. The most common method at present is the compression heating method using a heated roller.

In the press-heating method using a hot roller, fixing is performed by passing the toner image surface of the sheet to be fixed under pressure on the surface of a hot roller whose surface is made of a material that has releasability to the toner. . In this method, the surface of the heated roller and the toner image on the fixing sheet come into contact with each other under pressure.
It has extremely good thermal efficiency when fusing a toner image onto a sheet to be fixed, allows rapid fixing, and is very effective in high-speed electrophotographic copying machines. However, in the above method, since the heated roller surface and the toner image contact each other under pressure in a molten state, a part of the toner image adheres to and transfers to the fixing roller surface, and this is transferred again to the above-mentioned sheet to be fixed. One of the essential conditions for the heated roller fixing method is to prevent toner from adhering to the surface of the heat fixing roller, which may cause a so-called offset phenomenon and stain the sheet to be fixed.

Conventionally, in order to prevent toner from adhering to the fixing roller surface, for example, the roller surface is made of a material that has excellent releasability for toner, such as silicone rubber or fluorine-based resin, and the surface is also coated with anti-offset and roller surface coatings. In order to prevent fatigue, the surface of the roller is coated with a thin film of a liquid with good mold releasability, such as silicone oil. However, although this method is extremely effective in preventing toner offset, the offset prevention liquid evaporates due to heating, giving the user an unpleasant odor, and requires a device to supply the offset prevention liquid. Therefore, there are problems such as a complicated fixing device. Therefore, it is not desirable to prevent offset by supplying an offset-preventing liquid, but rather the development of a toner with high offset resistance over a wide fixing temperature range is currently desired.

As described in Japanese Patent Publication No. 51-23354, such an offset phenomenon tends to occur when a low molecular weight resin is used. Therefore, as described in the same publication, a method for preventing the offset phenomenon by using a crosslinked resin has been proposed. The inventors of the present invention have investigated and found that simply creating a crosslinked resin is not necessarily satisfactory. In particular, when the degree of crosslinking is increased, the dispersion of pigments and the like into the binder resin deteriorates, the pigments and the like are exposed on the toner surface, the development characteristics of the toner deteriorates, and the fixing temperature also rises.

In addition, in the case of magnetic toner, there are problems such as an increase in fixing temperature and poor offset resistance.While it is certainly effective to crosslink gel the binder resin to prevent offset, it is necessary to provide sufficient offset resistance. It has the fatal flaw that the fixation point becomes too high.

Furthermore, since the oil crisis, energy saving has been required in various fields, and product development in office machines is also largely moving in this direction. Pressure fixing type copiers, which can significantly reduce power consumption, have started to appear on the market, but they still do not account for the majority of users, except for low-speed, low-end machines with insufficient fixing performance and poor image quality. do not have.

Currently, there is a strong demand for energy saving in the heat roller method, which is the most popular type of heat fixing method.
There is a need for a copying machine that uses less power and has faster fusing capabilities. To this end, it is necessary to develop a toner that can be melted and fixed at a lower temperature, has no offset, and has good blocking resistance, which does not cause the toner particles to coagulate and solidify during long-term storage.

Recently, polyester-based and epoxy-based resins have attracted attention as materials that are compatible with low-temperature fixing, and in particular, several patents have been disclosed regarding toners using carboxyl group-containing polymers or polyester-based toners. According to these reports and experiments conducted by the present inventors, it is true that toners containing polyester resin as the main binder can have a lower fixing temperature than other materials, but have a problem with offset properties. However, JP-A No. 56-94362, No. 56-116041, story 56-
As seen in Publication No. 166651, a method has been discovered to improve offset properties by adding a polyvalent metal compound to cause a type of crosslinking and gelation with the metal, and is approaching practical application. However, this reaction that imparts crosslinking properties is carried out in a state where the solids are made meltable by heating, and is greatly affected by the chance of association during kneading, and the type, amount, reaction conditions, etc. of the metal compound are extremely delicate, and this control is extremely difficult. It is difficult to maintain a constant dispersibility of various materials and a constant degree of crosslinking. Furthermore, relatively simple kneading machines such as extruders and kneaders that have been widely used in the production of dry toner and have a large processing capacity are insufficient, and it is highly anticipated that production costs will rise, as existing equipment will no longer be usable.

Therefore, in order to commercialize toners whose main binder resin is polyester or carboxyl group-containing polymers, which are superior in terms of low-temperature fixing, crosslinking with metals must be done not during hot kneading but when cold. It is thought that the important point will be whether or not it can be done.

In addition, to improve the offset properties, charging properties, and anti-blocking properties of the original toner, it is sufficient to modify only the surface, or to modify the necessary amount sequentially from the surface toward the core. The basic technical idea of the present invention is that there is no need to use a film that has been stained for a long time, and when it was carried out based on this idea, the results were almost as expected. A toner with good overall properties, good stability and stable chargeability was obtained.

That is, an object of the present invention is to provide a method for producing a toner for hot roller fixing which can be sufficiently fixed at a lower temperature and has good offset resistance.

A further object of the present invention is to provide a method for producing a toner with excellent blocking resistance that does not cause phenomena such as agglomerated cakes even when left in a relatively high-temperature environment for a long period of time. .

A further object of the present invention is to provide a method for producing a toner for hot roller fixing that has good chargeability and always shows stable chargeability during use, and provides clear and fog-free images.

A further object of the present invention is to provide a method for producing a toner for hot roller fixing that has excellent fluidity, does not cause aggregation, and has excellent impact resistance.

A further object of the present invention is to provide a method for producing a toner for thermal roller fixing that causes less deposits on the surface of a toner holding member or photoreceptor.

A further object of the present invention is to provide a method for producing a magnetic toner that, when used as a magnetic developer, exhibits good and uniform magnetism and can be fixed by a hot roller.

Specifically, the present invention provides a heat fixing dry toner having a carboxyl group-containing polymer as the main binder resin, using a compound selected from the group consisting of NaOH, KOH, ammonia, sodium phosphate, sodium carbonate, and sodium acetate. 1. A method for producing a dry toner for heat fixing, which comprises modifying the surface of the toner particles by immersing the toner in a basic aqueous solution containing the above dry toner.

Although the details of the physicochemical mechanism of the present invention are unknown, it is predicted that the acidic groups on the toner surface, that is, the carboxyl groups, and the basic component will react to form a salt, and also that the necessary and sufficient immersion time will be provided. This metal ion enters the toner and connects the carboxyl groups with each other, causing a type of crosslinking, which is thought to improve the offset resistance in the same way as when a decomposable metal compound is added and mixed under heat. It is also believed that by containing more of these metals on the toner surface, blocking resistance can be improved without raising the fixing temperature.

Various types of carboxyl group-containing polymers can be used in the present invention, such as polymers obtained by copolymerization of carboxyl group-containing vinyl monomers with other vinyl monomers, and polymers obtained by ionic polymerization of vinyl monomers by blowing carbon dioxide gas into them. Polymers obtained by partially oxidizing polymers having unsaturated double bonds in the main chain or side chains, polymers obtained by hydrolyzing polymers having ester bonds in side chains, etc. are used. be done.

Further, as the main component of the preformed unit of the carboxyl group-containing polymer a, for example, the following carboxyl group-containing vinyl monomer and other vinyl monomer components can be mentioned.

Carboxyl group-containing vinyl monomers acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, isocrotonic acid, β-methylcrotonic acid, maleic acid, fumaric acid, itaconic acid, vinyl acetic acid, angelic acid, tiglic acid, 4
- Vinyl monomers such as pentenoic acid, citraconic acid, mesaconic acid, glutaconic acid, α- or β-dihydromuconic acid, alkyl esters, halogenated alkyl esters, alkoxyalkyl esters, aralkyl esters, alkenyl esters derived from the above unsaturated carboxylic acids, Aminoalkyl esters, amides and nitriles: aliphatic monoolefins such as ethylene, propylene, butyne, isobutylene;
Vinyl chloride, vinyl bromide, vinyl iodide, 1,2
- halogenated aliphatic olefins such as dichloroethylene, 1,2-dibromoethylene, 1,2-diiodoethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride; 1,3 -butadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene, 2,
Conjugated diene aliphatic diolefins such as 3-dimethyl-1,3-butadiene, 2,4-hexadiene, and 3-methyl-2,4-hexadiene; styrene, alkyl groups of styrene, halogen atoms, nitro groups, alkoxyl groups, Nuclear substitutes such as acyl groups.

As the basic aqueous solution used in the present invention, existing industrially available solutions at low cost are sufficient;
NaOH, KOH, ammonia, sodium phosphate, soda carbonate or sodium acetate are preferably used.

All known dyes and pigments can be used as the coloring material used in the toner together with the binder of the present invention, such as carbon black, iron black,
Examples include, but are not limited to, metallic salt dyes, red iron, phthalocyanine blue, and chrome yellow. Further, as carriers used in toner, iron powder, nickel powder, glass beads, and those whose surfaces are treated with resin or the like are used. Additionally, known thermoplastic resins such as polyester resins, urethane resins, epoxy resins, ethylene-ethyl acrylate resins, phenolic resins, styrene-butadiene resins, xylene resins, and petitral resins other than those of the present invention may be used within a range that does not impair the performance of the present invention. etc. may be used by mixing or metamorphosing. It is preferable that the amount of the known thermoplastic resin added to the toner binder does not exceed 20% by weight.

Moreover, when the developing powder used in the present invention is used as a magnetic developing powder, magnetic powder is contained. Magnetic powders include ferromagnetic elements and alloys and compounds containing these elements, including alloys and compounds of iron such as magnetite and hematite ferrite, cobalt, nickel, manganese, and other ferromagnetic alloys. There is a known substance. The magnetic powder is preferably contained in an amount of 10 to 70% by weight, preferably 15 to 50% by weight, based on the weight of the developing powder.

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but these are not intended to limit the present invention in any way. Note that all parts used are parts by weight.

Example 1 Styrene/butadiene/acrylic acid (75/20/
5) 100 parts Ternary copolymer Average molecular weight 200,000 Magnetic powder (EPT-1000, manufactured by Toda Kogyo) 60 parts Alloy dye 2 parts Low molecular weight polyethylene (molecular weight 3000) 2 parts After mixing the above materials, knead with a roll mill and hammer. After coarsely pulverizing with a mill, finely pulverizing with a supersonic jet mill, and classifying fine powder and coarse powder with an air classifier, a powder for dry type developer having a size of 5 to 20 μm was obtained.

100 g of the developer powder obtained above was added to an aqueous solution of caustic soda having a pH of 12, and after immersion for 10 hours, it was neutralized with hydrochloric acid, the liquid was removed, and the mixture was thoroughly washed with a sufficient amount of water and dried.

After adding and mixing 0.3 parts of hydrophobic colloidal silica to 100 parts of this dry powder, a commercially available copying machine (NP-280J,
A continuous image printing test of 10,000 sheets of A3 size was conducted using a Canon (manufactured by Canon).

As a result, a very clear and good image with no background fog was obtained, and this was maintained until the end of the test.

Furthermore, after the test was completed, the fuser was disassembled and the degree of dirt on the rollers and the amount of dirt and offset material on the cleaning blade for removing offset material were examined. There were no problems whatsoever.

In addition, a small amount of the obtained developer was placed in a container and left in a constant temperature bath kept at 50℃ for 24 hours.The properties of the powder were examined, and it was found that the toner remained in an extremely fluid state without any problems. No blocking phenomenon due to agglomeration or adhesion between the two was observed.

Comparative Example 1 In the continuous image printing test, which was conducted in the same manner as in Example 1 except for the step of immersion in a basic aqueous solution, clear and good image quality was obtained at the beginning, but gradually Offset images due to offset during fixing began to appear mainly in the form of lines on the copy, and the test had to be discontinued.

Furthermore, when the fixing device was disassembled after the interruption, the rollers were stained with toner in many places, and the cleaning blade was covered with mountains of offset toner, making it completely unusable.

In addition, the storage stability of the toner was examined in the same manner as in Example 1. After being left at 50°C for 24 hours, the toner was found to have lumps and clumps in some places, which were thought to be due to aggregation and fusion of the toner, and some of the toners were pressed with fingers. Some of them did not disintegrate easily, and their blocking resistance was poor.

Example 2 A test was carried out in exactly the same manner as in Example 1, except that ammonia water with a pH of 9.5 was used instead of a caustic soda aqueous solution as the basic aqueous solution in Example 1. Excellent results almost the same as in Example 1. was gotten.

Comparative Example 2 The same procedure as in Example 2 was carried out except for the step of immersing in a basic aqueous solution, and the test results were almost the same as in Comparative Example 1.

Example 3 Instead of using 100 parts of the styrene/butadiene/acrylic acid terpolymer in Example 1, a styrene/butyl acrylate/monobutyl maleic acid (75/15/10) terpolymer (average molecular weight 200 000)
A developing powder was obtained by the same procedure as in Example 1 using 100 parts, and tested, and the results were almost the same as in Example 1.

Example 4 Example 3 was carried out in the same manner as in Example 3, except that caustic potash with a pH of 12 was used instead of caustic soda with a pH of 12 as the basic aqueous solution, and extremely excellent results as described in Example 1 were obtained. Obtained.

Comparative Example 3 Instead of using 100 parts of the styrene/butadiene/acrylic acid ternary copolymer in Example 3, 100 parts of the styrene/butyl acrylate (75/25) copolymer was used.
A developing powder was obtained in the same manner as in Example 3 using
The test result was almost the same as that of Comparative Example 1.

Example 5 In Example 1, instead of using 100 parts of the styrene/butadiene/acrylic acid ternary copolymer in Example 1, 100 parts of oxidized polyethylene (Mitsui Hiwax 1105A, manufactured by Mitsui Petrochemical) with an acid value of 60 was used. Similar results were obtained as in Example 1.

Comparative Example 4 When the same procedure as in Example 5 was carried out except for the step of immersing in a basic aqueous solution, the results were almost the same as in Comparative Example 1.

Example 6 Styrene/butadiene/acrylic acid (75/20/
5) 100 parts Ternary copolymer Average molecular weight 200,000 Metal-containing dye 2 parts Low molecular weight polyethylene (molecular weight 3000) 2 parts After mixing the above materials, knead with a roll mill, coarsely crush with a hammer mill, and then finely crush with a supersonic jet mill to average. A powder for development with a particle size of 8 μm was obtained.

Add 100% of this developing powder to a PH12 caustic soda aqueous solution.
After soaking for 10 hours, the mixture was neutralized with hydrochloric acid, the liquid was removed, and the mixture was thoroughly washed with a sufficient amount of water and dried.

10 parts of this dry powder and carrier iron powder (trade name,
A developer was prepared by mixing 90 parts of EFV250/400 (manufactured by Nippon Tetsuko Co., Ltd.). This developer was applied to a commercially available plain paper copying machine (product name NP-5000, manufactured by Canon) and a continuous copying test of 10,000 sheets of A3 size paper was conducted.

As a result, an extremely clear image with no background blur was obtained, and this image was maintained until the end of the test.

Further, after the test was completed, the fixing device was disassembled and the degree of dirt on the rollers was examined.The rollers were found to be hardly dirty and pose no problem in practical use.

In addition, a small amount of the obtained dry powder was placed in a container and left in a constant temperature bath kept at 50°C for 24 hours.The properties of the powder were then examined, and it was found that it remained fluid with no problems and was used as a toner. No blocking phenomenon due to agglomeration or adhesion between the two was observed.

Comparative Example 5 In the image reproduction test of 10,000 sheets of A3 size paper, which was carried out in exactly the same manner as in Example 6 except for the step of immersing it in a basic aqueous solution, there were very clear background fogs etc. at the beginning. Although a high-quality image was obtained, the offset phenomenon became noticeable midway through, and an offset image appeared on the transfer paper, and the back side of the transfer paper was also smudged, so the test had to be discontinued.

Also, after the interruption, I disassembled the fuser and checked how dirty the rollers were, but the fuser roller, back-up roller,
Almost all of the heat supply rollers were black and dirty and in poor condition.

In addition, a small amount of the obtained developing powder (without carrier) was placed in a container and left in a constant temperature bath kept at 50°C for 24 hours, and the properties of the powder were examined.
There were clumps of adhesion here and there, and some of them were so hard that they wouldn't fall apart even when pressed slightly with a finger, making them unsuitable for practical use.

Claims (1)

[Claims] 1. A dry toner for heat fixing whose main binder resin is a carboxyl group-containing polymer is immersed in a basic aqueous solution containing a compound selected from the group consisting of NaOH, KOH, ammonia, sodium phosphate, sodium carbonate, and sodium acetate. A method for producing a dry toner for heat fixing, characterized in that the surface of the toner particles of the dry toner for heat fixation is modified.