JPH0219861A - Fixing method for full color electrophotography - Google Patents

Abstract

PURPOSE:To fix toner which possesses excellent color reproducibility, color mixing ability and transparency by using a specific polymerized toner and permitting a crosslinking component to be present in the binder of the toner which forms the top and the second layers of transfer medium. CONSTITUTION:The title method utilizes the polymerized toner which is obtained by suspension polymerizing a polymerized toner which contains at least a colorant corresponding to wax and each color as toner in an aqueous medium, and permitting the crosslinking component to be present in the binder of the toner forming the top and the second layers on the transfer medium. The color mixing ability and the transparency are improved by permitting the wax, which sufficiently melts at the fixing temperature or under and operates as a good heat conductive material, to be contained in the toner, and offset is prevented by permitting the crosslinking component to be present in the binder of the top layer toner. Thus, the fixed image which excels in the color mixing ability and the transparency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner fixing method used for visualizing an electrical latent image in electrophotography, electrostatic photography, or the like.

[Prior Art] In recent years, there has been a rapid shift from monochrome copying to full-color copying in copying machines, and two-color copying machines and full-color copying machines are being widely studied and put into practical use.

Color image formation by full-color electrophotography generally requires 3
It reproduces all colors using toner of three primary colors: yellow, magenta, and cyan.

The method involves first passing light from the original through a color-separating light transmitting filter that has a complementary color to the toner color to form an electrostatic latent image on the photoconductive layer.Then, through a development and transfer process, the toner is transferred to the support. Then, the above-mentioned steps are performed several times in sequence, and the toners are superimposed on the same support while registering, and a final full-color image is obtained by one fixation.

For example, the present inventor has published Japanese Patent Application Publication No. 59-2E! As proposed in Japanese Patent No. 757, etc., a color toner kit consisting of three types of toners of three primary colors is used as a full-color toner.

However, while these combinations are relatively balanced for color reproduction, their electrophotographic properties are
There are still points that need to be improved in terms of charging properties other than storage stability and durability when copying with green leaves.

Furthermore, in the above proposal, in order to obtain black by superimposing three colors of toner, subtle differences in tone between these three colors and differences in superposition during constant development and transfer are reflected in the black tone. The complexity of color matching of each color toner during the process and the development-transfer process and fixing process of the copying process must be highly accurate, which naturally complicates the process and causes an increase in costs.

Also, Japanese Patent Application Laid-Open No. 53-138234 and U.S. Patent No. 4.
There are many applications for monochromatic color toners such as No. 518゜672, but for full color, the color balance of at least three colors, preferably four colors, must be achieved in harmony, and only one color can be used. There is no point in discussing reproducibility or electrophotographic characteristics.

In principle, if we have the three primary colors of yellow, magenta, and cyan, it should be possible to reproduce almost all colors using the subtractive color mixing method, which is why full-color reproductions currently on the market The machine is configured to use three primary color toners superimposed on each other. Ideally, this would make it possible to achieve all colors in all density ranges, but in reality, there are still many improvements to be made in terms of the spectral reflection characteristics of toner, color mixing properties when toners are superimposed, and loss of saturation due to subtractive color mixing. It has a certain point.

After intensive research to improve these problems, the applicant has
By using a new black toner for inking in addition to the three primary color toners, it has a wide range of color reproducibility and is easy to develop,
We have achieved a full color toner kit that exhibits particularly favorable characteristics in the fixing process.

Generally, in a full-color toner kit, in order to obtain excellent color reproducibility, color mixing properties, and transparency, it is necessary that the toner particles be almost completely melted during fixing to the extent that the shape of the toner particles cannot be discerned. As a solution,
Examples include increasing the fixing temperature, decreasing the fixing speed, and increasing the contact surface of the fixing roller. However, there is a limit to increasing the fusing temperature, considering the thermal deterioration of the fusing roller and the increase in energy costs. Undesirable. Therefore, it is necessary to take measures to ensure sufficient heat transfer by increasing the contact area between the image and the fixing roller.
In order to increase the contact area of the fusing roller, it is necessary to increase the ease with which the roller can be elastically deformed, but this requires thickening the rubber layer of the roller, which weakens its strength against heat and prevents fusing. This results in a shortened roller life. On the other hand, as a result of sufficient melting, high-temperature offset occurs, making it necessary to apply a release agent such as oil to the roller.Moreover, the application of this oil promotes a shortening of the lifespan of the fusing roller. This is causing a vicious cycle.

The above-mentioned problem also applies to the aforementioned four-color toner kit invented by the present applicant, and is a major problem to be improved.

On the other hand, a suspension polymerization method has been proposed as a method for producing toner (Japanese Patent Publication No. 3B-10231). In this suspension polymerization method, polymerizable monomers and colorants (and, if necessary, polymerization initiators, crosslinking agents, charge control agents, and other additives) are uniformly dissolved or dispersed to form a monomer composition. After that, this monomer composition was mixed into a continuous phase containing a dispersion stabilizer (
For example, toner particles having a desired particle size are obtained by dispersing the toner particles in an aqueous phase (for example, an aqueous phase) using a suitable stirrer and simultaneously carrying out a polymerization reaction.

In this suspension polymerization method, droplets of the monomer composition are generated in water, which is a highly polar dispersion medium. It has a so-called pseudocapsule structure in which it tends to exist in a certain surface layer and non-polar components do not exist in the surface layer. Utilizing this characteristic of the manufacturing method, it is possible to contain waxes with low melting points that cannot be used in the pulverization method.

By incorporating this low-melting-point wax, the toner produced by the polymerization method can achieve both contradictory properties of blocking resistance and low-temperature fixing.

In other words, since the low melting point wax is included, the thermal conductivity in the toner is improved due to the wax that melts at low temperature without reducing the anti-blocking performance.
As a result, low temperature fixing becomes possible. More preferably, since the wax melted during fixing also acts as a release agent, it is possible to prevent high-temperature offset without applying a release agent such as oil to the fixing roller.

[Problems to be Solved by the Invention] However, even with the above-mentioned polymerized toner having advantageous performance during fixing, when multiple development is performed in full color and a multiple transfer image is obtained, the thickness of the toner layer becomes monochromatic. It is several times more expensive than color toner, so like crushed toner,
Hot offset occurs under fixing conditions that sufficiently melt the toner, making it difficult to simultaneously achieve the characteristics of not needing to apply a release agent and the requirements of obtaining excellent color reproducibility, color mixing, and transparency as a full-color toner. Met.

An object of the present invention is to provide a toner fixing method having excellent color reproducibility, color mixing properties, and transparency.

A further object of the present invention is to provide a fixing method that can prevent offset without applying a release agent to the fixing roller.

A further object of the present invention is to provide a fixing method that can extend the life of the fixing roller.

[Means and effects for solving the problem] The object of the present invention is to color separate an original image, form a latent image for each color, develop it with primary color and black toners corresponding to the color separation filter, and visualize it. In a full-color electrophotographic copying device that sequentially transfers each color image onto a transfer member to obtain a multicolor image, the toner contains at least wax and a coloring material corresponding to each color. Using a polymerized toner obtained by subjecting a polymerizable monomer system to a suspension JWJ polymerization in an aqueous medium, on a transfer medium,
This is achieved by a full-color electrophotographic fixing method in which a crosslinking component is present in the binder of the toner forming the top layer and the second layer.

The present invention will be explained in detail below.

The present inventors have arrived at the present invention by paying attention to the fact that a polymerized toner has a pseudocapsule structure with respect to wax, and that a low melting point wax can be added without impairing blocking performance.

In other words, in order to apply full-color polymerized toner that extends the life of the fixing roller, it is necessary to ensure sufficient color mixing and transparency after fixing the multiple transfer image, and to avoid applying oil as a release agent. It was also required that no offset occur.

Therefore, by incorporating wax into the toner, which melts sufficiently below the fixing temperature and acts as a good heat transfer material,
In addition to improving color mixing properties and transparency, the presence of a crosslinking component in the binder of the upper layer toner prevents offset.

As a result, a fixed image with excellent color mixing properties and transparency could be obtained. The term "upper layer" as used herein refers to the uppermost layer or second layer in a multiple transfer image, that is, the third or fourth color in four-color multiple development.

Generally, in a full-color electrophotographic copying apparatus, in order to fix a thick toner layer in full color and impart transparency, the fixing temperature and fixing pressure are set so that the toner is sufficiently melted and colors are mixed. Therefore, in heavy and double transfer images, the toner layer that forms the image is thin, so the fixing pressure on the toner is low, but the thermal energy given to the toner is sufficient, so melting and color mixing are performed sufficiently, while the fixing roller Since the contact pressure between the toner and the toner is low, the encapsulated wax alone provides sufficient mold releasability. However, in multiple images, the toner layer becomes thicker, so the fixing pressure becomes higher. As a result, the contact pressure between the fixing roller and the toner increases, and the encapsulated wax alone does not provide sufficient release properties, resulting in offset.

The crosslinking component in the binder of the toner according to the present invention is produced by adding a crosslinking agent to the monomer composition during polymerization. If the amount of crosslinking agent added is too small, properties such as blocking resistance and durability will be poor, and offset will be difficult to prevent.
Color toner has poor color mixing and transparency, making it difficult to fix.

Therefore, the amount added is preferably 0.001 to 2 parts by weight per 100 parts by weight of the polymerizable monomer. Examples of the types of crosslinking agents include divinylbenzene, divinylnaphthalene, divinyl ether, divinyl sulfone, and diethylene glycol dichloromethane. Methacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexane gelicold dimethacrylate, neopentyl glycol Dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2.2'-bis(4-
methacryloxyjethoxyphenyl)propane, 2.2
'-bis(4-acryloxyjethoxyphenyl)propane, trimethylolpropane trimethacrylate 1/-t,
Common crosslinking agents such as trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, dibromneopentylglycol dimethacrylate, and diallyl phthalate can be used as appropriate.

In the present invention, wax is added and the wax acts as a conductive substance during fixing, thereby facilitating the melting of the toner and improving color mixing properties and transparency.

The added wax does not exist in the surface layer, and there is a binder resin that has higher thermal strength than the added wax, so if the toner environment is below the melting point of the wax, blocking will not occur. When the melting point is exceeded, the wax becomes liquid and leaches to the surface layer, causing fusion. Considering the temperature environment inside the copying machine, the melting point of the wax is preferably 55°C or higher, and when producing toner by FJ or % polymerization, additives such as wax should be uniformly dissolved or dispersed in the monomer system. If the melting point of the wax is too high, it will not dissolve uniformly in the wax. Than this,
As the wax that can be added, paraffin hydrocarbons having a melting point in the range of 55 to 70°C are preferably used. For example, as paraffin wax, there are products manufactured by Nippon Oil Co., Ltd. and Nippon Seiro Co., Ltd., and as branched paraffin waxes, there are microcrystalline wax (manufactured by Nippon Seiro Co., Ltd.) and microwax (manufactured by Nippon Seiro Co., Ltd.).

The amount of wax added is preferably 1 to 6 parts by weight per 100 parts by weight of the polymerizable monomer.

The polymerized toner used in the present invention can be obtained by the following method. In other words, a monomer system in which wax, colorant, polymerization initiator, and other additives are added to a polymerizable monomer and uniformly dissolved or dispersed using an ultrasonic dispersion machine, homogenizer, etc., and a suspension stabilizer. The mixture is dispersed in the aqueous phase (ie, continuous phase) using a conventional stirrer, homomixer, homogenizer, etc. Preferably, the stirring speed and time are adjusted so that the IN body droplets have the desired toner particle size, generally a size of 301AI11 or less, and then the stirring is continued so that the particle size is maintained approximately in that state due to the action of the dispersion stabilizer. The polymerization temperature should be set to a temperature of 40°C or higher, generally 50 to 90°C. After the reaction is completed, the generated toner particles are washed and filtered. Collect and dry. In the suspension polymerization method, 300 to 300 parts of water is usually added to 100 parts by weight of upper
Preferably, 3000 parts by weight are used as dispersion medium.

Polymerizable monomers that can be applied to the toner of the present invention include:
Styrene, 0-methylstyrene, W-methylstyrene,
Styrene and its derivatives such as p-methylstyrene, p-methoxystyrene, p-ethylstyrene; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
Methacrylic acid esters such as n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, acrylic ugly stearyl.

Acrylic acid esters such as 2-chloroethyl acrylate and phenyl acrylate; acrylonitrile and methacriconitrile. Examples include vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylamide.

These monomers can be used alone or in combination. Among the above-mentioned seven monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other monomers as a polymerizable monomer in terms of the development characteristics and durability of the toner.

In addition, it is more preferable to polymerize the monomer by adding a polymer or copolymer having a polar group as an additive during the polymerization of the monomer. It is preferable to suspend and polymerize a polymerizable monomer system containing a copolymer or a cyclized rubber in an aqueous phase in which the polar polymer and a dispersant with an opposite charge are dispersed. The cationic or anionic polymer, copolymer or cyclized rubber contained in the polymer system becomes a toner during polymerization with the oppositely charged 7-ionic or cationic dispersant dispersed in the aqueous phase. They attract each other electrostatically on the particle surface, and the dispersant covers the particle surface, which prevents the particles from coalescing and stabilizes them. At the same time, the polar polymer added during polymerization collects on the surface layer of the particles that become the toner, creating a kind of shell. The resulting particles become pseudo-capsules. A relatively high molecular weight polar polymer, copolymer or cyclized rubber is used to give toner particles excellent blocking properties and development abrasion resistance, while a relatively low molecular weight internal material improves fixing properties. Polar polymers (including polar copolymers) that can be used in the present invention and reverse loading Examples of the dispersant are shown below.

Examples of the (+) cationic polymer include polymers of nitrogen-containing monomers such as dimethylamine ethyl methacrylate and diethylaminoethyl acrylate, or copolymers of styrene, unsaturated carboxylic acid esters, etc., and the nitrogen-containing @mer. .

(i?) Anionic polymers include nitrile monomers such as acrylonitrile, vinyl chloride and other monomers, unsaturated carboxylic acids such as acrylic acid, unsaturated dibasic acids, unsaturated diprotic acids, etc. There are anhydrides of basic acids and polymers of nitro monomers.

(City) As an anionic dispersant, Aerosil 1200
There are colloidal silicas such as Rei 300.1380 (manufactured by Nippon Aerosil Co., Ltd.).

(iv) Examples of the cationic dispersant include aluminum oxide, fine wood-philic positively chargeable silica powder such as aminoalkyl-modified colloidal silica, and the like. Cyclized rubber may be used instead of the polar polymer.

Such a dispersant is preferably used in an amount of 0.2 to 20 parts by weight, more preferably 0.2 to 20 parts by weight, based on 100 parts by weight of the polymerizable monomer.
It is 3 to 15 parts by weight.

On the other hand, as the charge control substance to be added as necessary, commonly known ones are used. For example, nigrosine, azine dyes containing an alkyl group having 2 to 16 carbon atoms, metal complex salts of monoazo dyes, salicylic acid, dialkyl Metal complex salts of salicylic acid and the like are used.

As the polymerization initiator, any suitable polymerization initiator such as 2,2'-7zobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, l,1'- Azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2
, 4-dimethylvaleronitrile, and other azo or diazo polymerization initiators such as azobisisobutyronitrile (AIBN); benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, cumene hydroperoxide, 2.4 −
Examples include peroxide-based polymerization initiators such as dichloryl benzoyl peroxide and lauroyl peroxide.

Generally, about 0.5 to 10% of the polymerization initiator based on the weight of the polymerizable monomer is sufficient.

Further, the fluidity modifier may be mixed (externally added) with the toner particles and used. Examples of fluidity modifiers include colloidal silica, fatty acid metal salts, and fine Teflon powder. In addition, fillers such as calcium carbonate and finely powdered silica are added for the purpose of increasing the volume.
It may be blended into the toner in a range of 5 to 20% by weight.

To fix the unfixed image carrying the polymerized toner obtained in the above manner, an ordinary heating/pressure roller is used, but preferably an area pressure of 3 to 6 kg/
It is preferable to pass through a heat fixing roller having a pressure of c+*2, and the fixing temperature at this time is 120°C to 200°C.
The fixing speed is preferably in the range of 20 to 100 mm#ec.

The area pressure of the fixing roller is a value obtained by dividing the total pressure applied to the roller by the contact area between the fixing roller and the fixing medium.

[Example] A detailed explanation will be given below based on examples.

All parts are by weight.

Examples 1 to 3 A monomer composition uniformly dissolved or dispersed according to the formulation shown below was subjected to suspension polymerization in a dispersion medium system in which a suspension stabilizer was dispersed in water to produce yellow, cyan, and magenta. , black toners of four colors were obtained.

〈Prescription〉 (blank below) Use these four color toners with Canon Color Laser Copier 1
Multiple development was carried out in the order of macenta, cyan yellow, and blank, and the resulting unfixed image was passed between fluorine-containing fixing rollers under the fixing conditions shown in Table 1 to obtain a fixed image. No offset was observed in the resulting image. Furthermore, the image on the carrier had excellent transparency.

Comparative Example The same experiment was carried out using toners obtained in the same manner as in Example except that the amounts of crosslinking agents in four color toners were changed to the proportions shown in Table 1, and fixed images were obtained.

An offset phenomenon was observed in the obtained image.

[Effects of the Invention] As described below, according to the present invention, excellent images without offset can be obtained.

Claims (1)

[Claims] The original image is color separated, latent images are formed for each color, developed with primary color and black toners compatible with the color separation filter, and the visualized color images are sequentially overlaid and transferred onto a transfer member to create a multicolor image. After obtaining the toner, a polymerizable monomer system containing at least wax and a colorant corresponding to each color is suspended and polymerized in an aqueous medium in a full-color electrophotographic copying machine that fixes the toner using a heating and pressure roller. 1. A method for fixing full-color electrophotography, using a polymerized toner obtained by the above method, and including a crosslinking component present in the binder of the toner forming the uppermost layer and second layer on a transfer medium.