JP3376019B2 - Image forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for forming a color toner image, particularly a full color toner image, by an electrophotographic method, and more particularly to an image forming method for forming a color image fixed on both surfaces of a transfer material.

[0002]

2. Description of the Related Art Generally, a method for forming a full-color image will be described. The photosensitive drum, which is the electrostatic latent image bearing member, is uniformly charged by the primary charger, and image exposure is performed by the laser light modulated by the magenta image signal of the original to form an electrostatic latent image on the photosensitive drum. Then, the electrostatic latent image is developed by a magenta developing device which holds the magenta toner and forms a magenta toner image. Then, the magenta toner image developed on the photosensitive drum is transferred to the transferred transfer material by a transfer charger.

After the development of the electrostatic latent image, the photosensitive drum is destaticized by a destaticizing charger, cleaned by a cleaning means, and then recharged by a primary charger, and similarly a cyan toner image is obtained. Is formed and the cyan toner image is transferred to the transfer material onto which the magenta toner image has been transferred, and then, in the same manner as yellow color and black color, four color toner images are transferred to the transfer material. A full-color image is formed by fixing the transfer material having the toner images of four colors by the action of heat and pressure by a fixing roller.

The toner used in the color image forming method needs to have good melting property and color mixing property when heat is applied to it, and has a low softening point and a low melt viscosity. It is preferable to use a high toner.

By using such a sharp melt toner, it is possible to widen the color reproduction range of the copy and obtain a color copy faithful to the original image.

However, such a color toner having a high sharp melt property has a high affinity with the fixing roller and tends to be offset to the fixing roller during fixing.

Particularly in the case of a fixing device in a color image forming apparatus, since a plurality of toner layers of magenta, cyan, yellow and black are formed on a transfer material, offset tends to occur particularly easily.

Here, conventionally, in order to improve the releasing property of the toner from the fixing roller, a releasing agent such as silicone oil is applied to the fixing roller. However, in such an image forming method, the following problems have occurred.

In the existing fixing system in which a releasing agent such as oil is applied to the roller, the structure of the main body is not only complicated, but also the problem that this oil application shortens the life of the fixing roller is a problem. There is.

Further, in accordance with various copying needs in recent years, in addition to the recent ecology boom, an image forming method for forming images on both surfaces of a transfer material for the purpose of reducing paper consumption, so-called double-sided copying. The need for is increasing day by day.

Under such circumstances, in the current fixing system in which a releasing agent such as the above oil is applied to the roller, a part of the toner on the image subjected to the first fixing is offset during the second fixing. There was a great deal of expectation for further improvement of the fixing system and development of a toner excellent in offset resistance.

An example of a conventional image forming apparatus is an electrophotographic apparatus for forming a color image as shown in FIG.
This will be explained briefly.

The color electrophotographic apparatus shown in FIG. 3 includes a transfer material conveying system I provided from the right side of the apparatus main body 1 (right side of FIG. 3) to a substantially central portion of the apparatus main body, and the outline of the apparatus main body 1. A latent image forming section II provided in the central portion in the vicinity of the transfer drum 15 constituting the transfer material conveying system I;
The latent image forming section II is roughly divided into developing means, that is, a rotary developing device III.

The transfer material transport system I has the following structure. First, an opening is formed in the right wall (right side in FIG. 3) of the apparatus main body 1, and the transfer material supply trays 2 and 3 which are detachable are arranged in the opening so as to partially project outside the machine. There is. Paper feed rollers 4 and 5 are disposed substantially directly above the trays 2 and 3, and the transfer drum is a transfer means which is rotatable with respect to the paper feed rollers 4 and 5 and in the arrow A direction on the left side. A sheet feeding roller 6 and sheet feeding guides 7 and 8 are provided so as to communicate with the sheet feeding device 5. In the vicinity of the outer peripheral surface of the transfer drum 15, the contact roller 9, the gripper 10, the transfer material separating charger 1 from the upstream side to the downstream side in the rotation direction.
1 and the separation claw 12 are sequentially arranged. A transfer charger 13 and a transfer material separating charger 14 are provided on the inner peripheral side of the transfer drum 15. A transfer sheet (not shown) formed of a material such as polyvinylidene fluoride is attached to a portion of the transfer drum 15 around which the transfer material is wound, and the transfer material electrostatically adheres to the transfer sheet. It is pasted. Conveyance belt means 16 is provided on the upper right side of the transfer drum 15 close to the separation claw 12, and a fixing device 18 is provided at the end (right) end of the conveyance belt means 16 in the transfer material conveyance direction. . Further downstream of the fixing device 18 in the transport direction, the device body 1 extends outside the device body 1 and
A discharge tray 17 is detachably attached to the tray.

Next, the structure of the latent image forming section II will be described. First, a photosensitive drum 19, which is a latent image carrier that is rotatable in the direction of arrow B in FIG. 3, is arranged with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 15. Above the photosensitive drum 19 and in the vicinity of the outer peripheral surface thereof, a discharging charger 20, a cleaning unit 21, and a primary charger 23 are sequentially arranged from the upstream side to the downstream side in the rotation direction of the photosensitive drum 19, and further. Image exposure means 2 such as a laser beam scanner for forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum 19.
4 and an image exposure reflection means 25 such as a mirror.

Finally, the structure of the rotary developing device III is as follows. A rotatable housing (hereinafter referred to as “rotating body”) 26 is disposed at a position facing the outer peripheral surface of the photosensitive drum 19, and four types of developing devices are located at four circumferential positions in the rotating body 26. Mounted on the photosensitive drum 19
The electrostatic latent image formed on the outer peripheral surface of is visualized (that is, developed). The four types of developing devices are a yellow developing device 27Y, a magenta developing device 27M, a cyan developing device 27C and a black developing device 27BK, respectively.

The sequence of the entire image forming apparatus having the above-mentioned configuration will be briefly described by taking the case of the full color mode as an example. When the photosensitive drum 19 described above rotates in the direction of arrow B in FIG. 3, the photosensitive member on the photosensitive drum 19 is uniformly charged by the primary charger 23. In the apparatus of FIG. 3, the operating speed of each part (hereinafter referred to as process speed) is 160 mm / sec. When the photoconductor is uniformly charged by the primary charger 23, image exposure is performed by the laser light E modulated by the yellow image signal of the document 28, and an electrostatic latent image is formed on the photoconductor drum 19. The electrostatic latent image is developed by the yellow developing device 27Y which is fixed at the developing position in advance by the rotation of the rotating body 26.

The transfer material conveyed through the paper feed guide 7, the paper feed roller 6, and the paper feed guide 8 is held by the gripper 10 at a predetermined timing, and the contact roller 9 and the corresponding contact roller are held. It is electrostatically wound around the transfer drum 15 by means of the electrodes facing each other. The transfer drum 15 is rotating in the direction of arrow A in FIG. 3 in synchronization with the photosensitive drum 19, and the visible image developed by the yellow developing device 27Y is transferred to the outer peripheral surface of the photosensitive drum 19 and the transfer drum 1.
5 is transferred by the transfer charger 13 at a portion in contact with the outer peripheral surface of 5. The transfer drum 15 continues to rotate and prepares for the transfer of the next color (magenta in FIG. 3).

The photosensitive drum 19 is de-charged by the de-charging charger 20, is cleaned by the cleaning means 21 by a conventionally known blade method, is charged again by the primary charger 23, and is re-charged by the next magenta image signal as described above. Receive a unique image exposure. The rotary developing device rotates while the electrostatic latent image based on the magenta image signal is formed on the photosensitive drum 19 by the image exposure, and positions the magenta developing device 27M at the predetermined developing position described above. Develop magenta. Subsequently, the above-described processes are performed for cyan and black, respectively, and when the transfer of four colors is completed, the four-color image formed on the transfer material is discharged by the chargers 20 and 14. Then, the gripping of the transfer material by the gripper 10 is released, and the transfer material is separated from the transfer drum 15 by the separating claw 12 and sent to the fixing device 18 by the conveyor belt 16 and fixed by heat and pressure. The full-color print sequence is completed, and a required full-color print image is formed.

In FIG. 4, the fixing roller 29 as a fixing means is, for example, an HTV (high temperature vulcanization type) silicone rubber layer 32 on an aluminum cored bar 31 and an RTV (room temperature vulcanization type) silicone rubber layer 33 on the outside thereof. And has a thickness of 3 mm and a diameter of 60 mm.

The pressure roller 30, which is a pressure means, has an HTV silicone rubber layer 47 having a thickness of 1 mm on an aluminum cored bar 34 and an RTV silicone rubber layer 35 on the surface thereof, and has a diameter of 60 mm. There is.

The fixing roller 29 is provided with a halogen heater 36 which is a heat generating means, and the pressure roller 30 is also provided with a heater 37 in the core bar to perform heating from both sides. The thermistor 38 in contact with the pressure roller 30 detects the temperature of the pressure roller, and based on the detected temperature, the controller 39 causes the halogen heater 36,
37 is controlled so that both the temperature of the fixing roller 29 and the temperature of the pressure roller 30 are kept constant at about 170 ° C. The fixing roller 29 and the pressure roller 30 are pressed by a pressure mechanism (not shown) at a total pressure of about 40 kg.

In FIG. 4, O is an oil applying device which is a releasing agent applying means, C is a cleaning device, and C1 is a cleaning blade which removes oil and dirt from the pressure roller. The oil applying device O is a dimethyl silicone oil 41 (KF96 300c manufactured by Shin-Etsu Chemical Co., Ltd.) in an oil pan 40.
s) is passed through the oil pumping roller 42 and the oil application roller 43, and the oil application amount is regulated by the oil application amount adjusting blade 44 to apply it on the fixing roller 29.

In the cleaning device C, a non-woven fabric web 46 made of Nomex (trade name, manufactured by DuPont) is pressed against the fixing roller 29 by the pressing roller 45 for cleaning. Further, the web 46 is appropriately wound by a winding device (not shown) so that toner is not deposited on the contact portion.

The electrophotographic apparatus for forming a color image described above forms a visible image on only one side, but an apparatus capable of forming this visible image on both the front surface and the back surface of the transfer material has already been proposed. There is.

When performing a double-sided copy of a color image,
The toner image developed by the developing unit is transferred onto the transfer material by the transfer unit at the transfer unit, the unfixed toner image on the transfer material is fixed by the fixing unit, and then the sheet is ejected. The toner image developed by the developing means is transferred to the transfer section again in the reverse state and is transferred to the other surface of the transfer material, which is opposite to the surface on which the toner image is fixed, and is not yet fixed on the transfer material. The toner image of is fixed by the fixing means, and double-sided color copying is performed.

However, when the above-mentioned two-sided color copying is performed, the following problems occur.

When the first image forming operation is completed and the surface of the transfer material is heated and fixed for the first time, oil as a release agent adheres to the toner and the transfer material. Therefore, when the paper is re-fed, the toner surface (that is, the oil-adhered surface) on which the fixing is performed for the first time faces the transfer drum 15 side. Therefore, when the transfer material is wound around the transfer drum 15, the oil adhering to the toner or the transfer material is transferred onto the transfer sheet, and then the transfer material is separated from the transfer drum 15. The rotation of 15 causes the oil on the transfer drum to move to the photosensitive drum 1.
Transferred to 9.

When the oil is transferred to the photosensitive drum 19 as described above, the toner cannot be cleaned even by the cleaning device C on the photosensitive drum 19, or the toner adheres to the oil at a portion other than the desired latent image forming portion. Therefore, there is a problem in that, finally, in the subsequent copying, a dirty image with excess toner attached is formed.

[0030]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method which solves the above problems.

In the present invention, excellent offset resistance can be obtained without using oil in the fixing means at the time of fixing, or with a small amount of use, and image deterioration due to the transfer of oil to the surface of the latent image bearing member does not occur. An object of the present invention is to provide an image forming method for obtaining a double-sided color toner image which is prevented or suppressed.

[0032]

The present invention achieves the above object by the following constitutions.

The present invention transfers the color toner image formed on the electrostatic latent image carrier onto one surface of the transfer material,
The color toner image on the transfer material is heated and melted by the fixing means to fix the color toner image on the transfer material, and the electrostatic latent image carrier is provided on the other surface of the transfer material opposite to the surface on which the color toner image is fixed. The color toner image formed on the transfer material is transferred, and the color toner image on the transfer material is heated and melted by the fixing unit to fix the color toner image on the transfer material, and the full color image fixed on both sides of the transfer material is formed. In the image forming method for forming, the image forming method includes: (a) a first transfer step of transferring a first color toner image onto one surface of the transfer material; and (b) heat on both surfaces of the transfer material. A first fixing step for obtaining a first full-color image by heating and melting the first color toner image and fixing it on one surface of the transfer material by a fixing means for applying a pressure; (c) the first fixing step. 1 color image A second transfer step of transferring the second color toner image to the other surface of the transfer material on one surface; and (d) by a fixing means for applying heat and pressure to both surfaces of the transfer material. A second fixing step of heating and melting the second color toner image and fixing the second color toner image on the other surface of the transfer material to obtain a second full-color image; The color toner for forming the full-color toner image of No. 2 has toner particles directly obtained by the suspension polymerization method, and the toner particles have a surface layer portion mainly composed of a resin and the wax is The wax has a capsule structure that is encapsulated inside the toner particles, the wax has a melting point of 40 ° C. to 140 ° C., and the fixing unit includes heat generating units on both sides of the transfer material. And the first fixer In, the fixing means, and heat is applied from both sides of the transfer material,
And, the oil is not applied to the surface of the transfer material, or the amount of oil of 0.04 mg / A4 or less is applied,
After the first fixing is performed, the wax that has melted and exuded from the inside of the toner particles of the color toner forming the first full-color toner image covers at least a part of the first full-color image to form the toner. functions to prevent the offset, which is solidified by temperature decrease after the passage of the subsequent fixing means, in the second fixing step,
By the fixing means, heat is applied from both sides of the transfer material, and oil is not applied to the surface of the transfer material,
Alternatively, the amount of oil of 0.04 mg / A4 or less is applied, the second fixing is performed, and the second full-color toner image is melted and oozes out from inside the toner particles of the color toner forming the image. wax, covering at least a portion of the second full-color image functions to prevent toner offset, which solidified by temperature decrease after the passage of the subsequent fixing means, the first full-color image at least a part covered the wax is dissolved by fixing means, and characterized in that the function to prevent the toner offset at the time of the second fixing is solidified by temperature decrease after the passage of the subsequent fixing means Image forming method.

The color toner used in the present invention has toner particles directly obtained by a suspension polymerization method. In this suspension polymerization method, a polymerizable monomer and a colorant (and, if necessary, further Polymerization initiator, cross-linking agent, charge control agent and other additives) are uniformly dissolved or dispersed to form a monomer composition, and the monomer composition is mixed with a continuous phase containing a dispersion stabilizer (for example, It is dispersed in an aqueous phase) using an appropriate stirrer and simultaneously polymerized to obtain toner particles having a desired particle size.

In this suspension polymerization method, since droplets of the monomer composition are formed in a dispersion medium of water, which has a large polarity,
The component having a polar group contained in the monomer composition is likely to exist in the surface layer portion which is the interface with the aqueous phase, and the non-polar component such as wax does not exist in the surface layer portion, which is a so-called similar capsule structure. By utilizing this characteristic of the manufacturing method, it is possible to contain a wax having a low melting point which cannot be used in other manufacturing methods such as the pulverization method.

The toner obtained by the suspension polymerization method has a capsule structure in which the wax as described above is encapsulated inside the toner particles, and thus can contain a large amount of a low melting point wax without impairing the blocking resistance. A large amount of wax that melts out when the toner is heated and melted by the heat and pressure of the toner can effectively function as a release agent, and it is possible to fix the fixing roller without applying a release agent such as oil. It is possible to prevent high temperature offset.

Further, when such a toner is applied to an image forming method for double-sided fixing, it is possible to perform sufficient fixing without applying oil even when performing the second fixing.

That is, the wax dispersed in the toner layer of the transfer material exudes from the inside of the toner when the toner is heated and melted by heat or pressure when passing through the fixing roller, and the exuded wax does not expose the image surface or a part of the image surface. Therefore, even if an unfixed image is formed on the other surface of the transfer material and the roller is passed again to fix the unfixed image, the image is already fixed by the first fixing. The wax that covers the lens works effectively, and the second fixing is possible without any problems.

Further, as described above, in the fixing system which requires oil application, the fixed image once fixed is re-fed and the second image forming operation is started. The toner surface (that is, the surface to which the oil adheres) that has been fixed is wrapped around the transfer drum side, so the oil adhering to the fixed image or part of the oil transfers to the transfer sheet, Further, the problem of transfer to the photosensitive drum was inevitable, but in the present invention, the wax exuded from the inside of the toner at the time of fixing functions as a release agent as described above, and then the temperature drop after passing through the roller. As a result, it solidifies instantly, so the above problems could be greatly reduced.

That is, since the wax contained in the toner is a wax having high crystallinity such as paraffin, the wax solidifies due to the temperature decrease after passing through the roller, and the level of contamination of the transfer drum is remarkably higher than that of the conventional oil. Mitigation can be achieved.

The toner particles (polymerized toner) directly obtained by the suspension polymerization method used in the present invention will be described in detail below.

The polymerized toner used in the present invention is obtained by the following method.

Additives such as a release agent, a colorant and a charge control agent are added to the polymerizable monomer and heated until the release agent dissolves or melts and a mixer such as a homogenizer and an ultrasonic disperser. The monomer system uniformly dissolved or dispersed by
It is dispersed in an aqueous phase having the same temperature as the monomer system containing the dispersion stabilizer by a usual stirrer or a homomixer / homogenizer.

Preferably, the stirring speed and time are adjusted so that the monomer droplets have a predetermined toner particle size, generally 30 μm or less, and thereafter the particle state is maintained by the action of the dispersion stabilizer. In addition, the stirring may be performed to such an extent that sedimentation of the particles is prevented. The polymerization temperature is set to a temperature not higher than the release temperature of the release agent, and the polymerization initiator is added to carry out the polymerization. After the reaction is completed, the produced toner particles are collected by washing and filtration and dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight of the monomer system.

The polymerizable monomer that can be used in the above-mentioned polymerized toner includes styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene and p-ethylstyrene. Methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate,
Acrylic esters such as n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, Methacrylic acid n-
Methacrylic acid esters such as butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; other acrylonitrile , Other monomers such as methacrylonitrile and acrylamide.

These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other monomers, from the viewpoints of developing characteristics and durability of the toner.

The dispersion medium used in the present invention is, for example, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and its salt, starch, tricalcium phosphate, hydroxide. Aluminum, magnesium hydroxide,
A suitable stabilizer such as calcium metasilicate, barium sulfate or bentonite can be used by dispersing it in the aqueous phase. This stabilizer is based on 100 parts by weight of the polymerizable monomer,
It is preferred to use 0.2 to 20 parts by weight.

In order to finely disperse these stabilizers,
0.001-0.1 parts by weight of surfactant may be used. This is for promoting the intended action of the above dispersion stabilizer, and specific examples thereof include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, and lauric acid. Examples include sodium, potassium stearate, and calcium eulenate.

More preferably, a polymer or copolymer having a polar group is added to the monomer system as an additive for polymerization. Further, in the present invention, a polymer having a polar group, a copolymer or a monomer system to which a cyclized rubber is added is suspended in an aqueous phase in which a dispersant having an opposite charge to the polar polymer is dispersed. It is preferable to polymerize. That is, a cationic or anionic polymer contained in the monomer system, a copolymer,
Alternatively, the cyclized rubber electrostatically attracts the oppositely charged anionic or cationic dispersant dispersed in the aqueous phase on the particle surface of the toner that is in the process of polymerization, and the dispersant covers the particle surface. While preventing the particles from coalescing and stabilizing, the polar polymer added at the time of polymerization gathers on the surface layer of the particles that become the toner, forming a kind of shell-like morphology, and the resulting particles become pseudocapsules. . A relatively high molecular weight polar polymer, copolymer or cyclized rubber is used to give toner particles excellent properties such as blocking property and development abrasion resistance, while internally having a relatively low molecular weight to improve fixing properties. By polymerizing so as to contribute, a toner satisfying contradictory requirements of fixing property and blocking property can be obtained. The polar polymers, copolymers and reversely chargeable dispersants which can be used in the present invention are exemplified below. (1) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, or copolymers of styrene and unsaturated carboxylic acid ester. (2) Examples of anionic polymers include nitrile-based monomers such as acrylonitrile; halogen-containing monomers such as vinyl chloride; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; other unsaturated dibasic acids, unsaturated monomers. Examples thereof include saturated dibasic acid anhydrides, polymers of other monomers such as nitro monomers, and copolymers with styrene monomers. Cyclized rubber may be used in place of these polar polymers. (3) As the anionic dispersant, fine silica powder is preferably used, and particularly has a BET specific surface area of 200 m ² / g.
The above colloidal silica is suitable. (4) As the cationic dispersant, an aminoalkyl-modified colloidal silica (preferably having a BET specific surface area of 20) is used.
0 m ² / g or more) hydrophilic positively charged silica fine powder,
Aluminum hydroxide may be mentioned.

Such a dispersant is prepared by using the polymerizable monomer 100.
It is preferable to use 0.2 to 20 parts by weight based on parts by weight. More preferably, it is 0.3 to 15 parts by weight.

In the present invention, it is desirable to add a charge control agent to the toner material in order to control the chargeability of the toner. As these charge control agents, among known ones, those having almost no polymerization inhibitory property / water phase transfer property are used. For example, a nigrosine dye as a positive charge control agent,
Examples thereof include triphenylmethane dyes, quaternary ammonium salts, amine compounds and polyamine compounds, and negative charge control agents include metal-containing salicylic acid compounds, metal-containing monoazo dye compounds, styrene-acrylic acid copolymers, styrene. -Methacrylic acid copolymers may be mentioned.

As the colorant used in the present invention, known colorants can be used. For example, carbon black, iron black, C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Mordant Red 30, C.I.
I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Mordant Blue 7, C.I. I.
Direct Green 6, C.I. I. Basic Green 4, C.I. I. Dyes such as Basic Green 6, yellow lead,
Cadmium Yellow, Mineral Fast Yellow, Navel Yellow, Naphthol Yellow S, Hansa Yellow G, Permanent Yellow NCG, Tartrazine Lake, Molybdenum Orange, Permanent Orange GT
R, benzidine orange G, cadmium red, permanent red 4R, watching red calcium salt,
Brilliant Carmine 3B, Fast Violet B,
There are pigments such as methyl violet lake, dark blue, cobalt blue, alkali blue lake, Victoria blue lake, quinacridone, rhodamine B, phthalocyanine blue, fast sky blue, pigment green B, malachite green lake, and final yellow green G. When a toner is obtained by using the polymerization method in the present invention, it is necessary to pay attention to the polymerization inhibitory property and the water phase transfer property of the colorant, and preferably surface modification, for example,
It is better to apply a hydrophobic treatment with a substance that does not inhibit polymerization.

Examples of the wax used in the present invention include paraffin wax, polyolefin wax and modified products thereof (for example, oxides and graft-treated products), higher fatty acids and their metal salts, amide wax and ester wax. However, the present invention is not limited thereto, and a paraffin wax or an ester wax is particularly preferable from the viewpoint of the speed of solidification due to the temperature decrease after fixing.

In the present invention, the melting point of the wax used for the toner particles is preferably 30 to 150 ° C, more preferably 40 to 140 ° C. Melting point 30
If it is lower than 150C, the blocking resistance and shape retention of the toner are not sufficient, and if it is higher than 150C, the effect of releasability is not sufficient.

In the present invention, the melting point was calculated from the temperature of the maximum endothermic peak by DSC.

Heat of fusion of wax used in the present invention Δ
H is preferably 50 to 250 J / g.

Such a wax is prepared by using the polymerizable monomer 100.
The amount is preferably 0.1 to 50 parts by weight, more preferably 1 to 45 parts by weight, and further preferably 5 to 40 parts by weight. If less than 0.1 parts by weight,
When the effect of releasability is small and more than 50 parts by weight,
Manufacturing stability tends to decrease, and blocking resistance and storage stability also tend to decrease.

As the polymerization initiator, any suitable polymerization initiator, for example, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1, 1'-azobis (cyclohexane-1-
Carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo-based or diazo-based polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, Examples thereof include peroxide type polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide. As the redox initiator, the above-mentioned peroxides may be used in combination with a reducing agent of dimethylaniline, mercaptans, tertiary amines, iron (II) salt and sodium bisulfite. These polymerization initiators are preferably used to obtain a desired molecular weight, but generally, the addition amount of 0.1 to 10% by weight of the polymerizable monomer is sufficient.

The release agent, polymerization initiator and polymerization temperature in the present invention will be described in more detail.

When paraffin wax generally having a low melting point or softening point is used as a release agent, the temperature at which the release agent is precipitated from the polymerizable monomer system is low, and the polymerization temperature is also low. In such cases, redox initiator, or 2,
It is preferred to use a short half-life initiator such as 2'-azobis-4-methoxy-2,4-dimethylvaleronitrile. When a polyolefin wax having a high melting point or a high softening point is used, it is preferable to use an autoclave in order to dissolve or melt the release agent in the polymerizable monomer system. In this case, the release temperature of the release agent is relatively higher than that of paraffin wax, so that 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,
It is preferred to use a polymerizable initiator such as 2'-azobisisobutyrate.

Additives may be added to the toner of the present invention for the purpose of imparting various characteristics. From the viewpoint of durability when the additive is added to the toner, the particle size is preferably 1/10 or less of the volume average diameter of the toner particles. The particle size of the additive means the average particle size thereof obtained by observing the surface of the toner particles with an electron microscope. As the additives for imparting these characteristics, for example, the following ones are used. 1) Flowability-imparting agents: metal oxides (silicon oxide, aluminum oxide, titanium oxide), carbon black and fluorocarbon. Those subjected to a hydrophobic treatment are more preferable. 2) Abrasives: metal oxides (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide), nitrides (silicon nitride), carbides (silicon carbide) and metal salts (calcium sulfate, barium sulfate, calcium carbonate) ). 3) Lubricants: Fluororesin powder (vinylidene fluoride, polytetrafluoroethylene) and fatty acid metal salt (zinc stearate, calcium stearate). 4) Charge controllable particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide) and carbon black.

These additives may be used in the range of preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner particles. . These additives may be used alone or
You may use together two or more.

The weight average molecular weight (Mw) in the toluene-soluble content of the toner particles directly obtained by suspension polymerization used in the present invention is preferably 5,000 to 80,000.
0, more preferably 8,000 to 40,000, and the number average molecular weight (Mn) is preferably 1,000 to 2
10,000, more preferably 2,000 to 15,000
It is preferable that Mw / Mn is less than 20, and more preferably 2.0 to 10.0 from the viewpoint of color mixing property and meltability during color toner image formation.

The method for measuring the molecular weight of the color toner of the present invention is shown below.

In the present invention, the molecular weight distribution of the chromatogram by GPC using THF (tetrahydrofuran) as a solvent in the toluene-soluble portion of the toner particles is measured under the following conditions.

That is, the column is stabilized in a heat chamber at 40 ° C., THF as a solvent is caused to flow at a flow rate of 1 ml / min, and about 100 μl of a THF sample solution is injected into the column at this temperature for measurement. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value and the count number of the calibration curve prepared from several kinds of monodisperse polystyrene standard samples. As a standard polystyrene sample for preparing a calibration curve, for example, a standard polystyrene sample having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation or Showa Denko Corporation is used, and it is appropriate to use a standard polystyrene sample of at least about 10 points. is there. An RI (refractive index) detector is used as the detector. As a column, it is better to combine multiple commercially available polystyrene gel columns.
For example, shodex GPC KF-8 manufactured by Showa Denko KK
01,802,803,804,805,806,80
Combination of 7,800P and TSKge manufactured by Tosoh Corporation
lG1000H (H _XL ), G2000H (H _XL ), G3
000H (H _XL ), G4000H (H _XL ), G5000
H (H _XL ), G6000H (H _XL ), G7000H (H
_XL ) and a combination of TSKguard column.

The sample is prepared as follows. Soxhlet extract of toner particles with toluene
Put it inside, leave it for several hours, shake it well, mix well with THF (until the coalescence of the sample disappears), and leave it still for 12 hours or more. At this time, the leaving time in THF should be 24 hours or more. Then, a sample-treated filter (pore size 0.45 to 0.5 μm, for example, Maisori Disc H-25-5 manufactured by Tosoh Corp., Excicro Disc 25CR manufactured by Gelman Science Japan Co., Ltd., etc. can be used), Use as a GPC sample. The sample concentration is adjusted to 0.5 to 5 mg / ml.

The double-sided full-color image forming method of the present invention will be described below.

FIG. 1 shows an image forming apparatus for forming a double-sided full-color image using the image forming method of the present invention.

The color electrophotographic apparatus shown in FIG. 1 includes a transfer material conveying system I provided from the right side of the apparatus main body 1 (right side of FIG. 1) to a substantially central portion of the apparatus main body, and the transfer material conveying system I. A latent image forming section II provided in the central portion in the vicinity of the transfer drum 15 constituting the transfer material conveying system I;
The latent image forming section II is roughly divided into developing means, that is, a rotary developing device III.

The transfer material transport system I has the following structure. First, an opening is formed on the right wall (right side in FIG. 1) of the apparatus main body 1, and transfer material supply trays 2 and 3 that are detachably attached to the opening are provided so as to partially project outside the machine. There is. Paper feed rollers 4 and 5 are disposed substantially directly above the trays 2 and 3, and the transfer drum is a transfer means which is rotatable with respect to the paper feed rollers 4 and 5 and in the arrow A direction on the left side. A sheet feeding roller 6 and sheet feeding guides 7 and 8 are provided so as to communicate with the sheet feeding device 5. In the vicinity of the outer peripheral surface of the transfer drum 15, the contact roller 9, the gripper 10, the transfer material separating charger 1 from the upstream side to the downstream side in the rotation direction.
1 and the separation claw 12 are sequentially arranged. A transfer charger 13 and a transfer material separating charger 14 are provided on the inner peripheral side of the transfer drum 15. A transfer sheet (not shown) made of polyvinylidene fluoride is adhered to a portion of the transfer drum 15 around which the transfer material is wound, and the transfer material is electrostatically adhered to the transfer sheet. . Conveyance belt means 16 is provided on the upper right side of the transfer drum 15 in the vicinity of the separation claw 12, and a fixing device 180 is provided at the end (right) end of the conveyance belt means 16 in the transfer material conveyance direction. . A discharge tray 17 that extends to the outside of the apparatus main body 1 via the paper discharge roller 52 and is detachable from the apparatus main body 1 is disposed downstream of the fixing device 180 in the transport direction.

Below the paper discharge roller 52, a re-feed roller 50 for feeding the transfer material once placed on the paper discharge tray 17 to the latent image forming section II again is arranged, and behind the re-feed roller 50. A transport path 51 for transporting the transfer material is provided.

Next, the structure of the latent image forming section II will be described. First, a photosensitive drum 19, which is a latent image carrier that is rotatable in the direction of arrow B in FIG. 1, is arranged with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 15. Above the photosensitive drum 19 and in the vicinity of the outer peripheral surface thereof, a discharging charger 20, a cleaning unit 21, and a primary charger 23 are sequentially arranged from the upstream side to the downstream side in the rotation direction of the photosensitive drum 19, and further. Image exposure means 2 such as a laser beam scanner for forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum 19.
4 and an image exposure reflection means 25 such as a mirror.

Finally, the structure of the rotary developing device III is as follows. A rotatable housing (hereinafter referred to as “rotating body”) 26 is disposed at a position facing the outer peripheral surface of the photosensitive drum 19, and four types of developing devices are located at four circumferential positions in the rotating body 26. Mounted on the photosensitive drum 19
The electrostatic latent image formed on the outer peripheral surface of is visualized (that is, developed). The four types of developing devices are a yellow developing device 27Y, a magenta developing device 27M, a cyan developing device 27C and a black developing device 27BK, respectively.

The sequence of the entire image forming apparatus having the above-described configuration will be briefly described by taking the case of the full color mode as an example. When the photosensitive drum 19 described above rotates in the direction of arrow B in FIG. 1, the photosensitive member on the photosensitive drum 19 is uniformly charged by the primary charger 23. In the apparatus of FIG. 1, the operating speed of each part (hereinafter referred to as process speed) is 160 mm / sec. When the photoconductor is uniformly charged by the primary charger 23, image exposure is performed by the laser light E modulated by the yellow image signal of the document 28, and an electrostatic latent image is formed on the photoconductor drum 19. The electrostatic latent image is developed by the yellow developing device 27Y which is fixed at the developing position in advance by the rotation of the rotating body 26.

The transfer material conveyed through the paper feed guide 7, the paper feed roller 6, and the paper feed guide 8 is held by the gripper 10 at a predetermined timing, and is brought into contact with the contact roller 9 and the corresponding contact roller. It is electrostatically wound around the transfer drum 15 by means of the electrodes facing each other. The transfer drum 15 rotates in the direction of arrow A in FIG. 1 in synchronism with the photosensitive drum 19, and the visible image developed by the yellow developing device 27Y is transferred to the outer peripheral surface of the photosensitive drum 19 and the transfer drum 1.
5 is transferred by the transfer charger 13 at a portion in contact with the outer peripheral surface of 5. The transfer drum 15 continues to rotate and is ready for transfer of the next color (magenta in FIG. 1).

The photosensitive drum 19 is destaticized by the decharging charger 20, is cleaned by the cleaning means 21 by a conventionally known blade method, is recharged by the primary charger 23, and is recharged by the next magenta image signal as described above. Receive a unique image exposure. The rotary developing device rotates while the electrostatic latent image based on the magenta image signal is formed on the photosensitive drum 19 by the image exposure, and positions the magenta developing device 27M at the predetermined developing position described above. Develop magenta. Subsequently, the above-described processes are performed for cyan and black, respectively, and when the transfer of four colors is completed, the four-color image formed on the transfer material is discharged by the chargers 20 and 14. Then, the gripping of the transfer material by the gripper 10 is released, and the transfer material is separated from the transfer drum 15 by the separation claw 12 and sent to the fixing device 180 by the conveyor belt 16 and fixed by heat and pressure. After that, the discharge roller 5
2 to the paper output tray 17. After that, the sheet is re-fed by the re-feeding roller 50, passes through the conveyance path 51, and is conveyed again to the latent image forming unit II to form a color image on the back surface in the same manner as the front surface. Thus, the transfer material having the color image already fixed on the front surface and carrying the unfixed color toner image transferred on the back surface is conveyed to the fixing roller 29 and the pressure roller 30 by the conveyor belt means 16 and fixed. Finally, the paper is conveyed to the paper discharge tray 17 and the double-sided color copy is completed.

At this time, the fixing operation speed of the fixing device 180 is 90 mm / sec, which is slower than the process speed of the main body of 160 mm / sec. This is because when an unfixed image in which two to four layers of toner are laminated is melt-mixed, as described below, a sufficient amount of heat must be given to the toner, so fixing should be performed at a speed slower than the main body speed. Therefore, the amount of heat applied to the toner is increased.

FIG. 2 is an explanatory view showing the structure of the fixing device 180 in detail.

In FIG. 2, the fixing roller 29 as a fixing means is, for example, an HTV (high temperature vulcanization type) silicone rubber layer 32 on an aluminum cored bar 31 and an RTV (room temperature vulcanization type) silicone rubber layer 33 on the outside thereof. And has a thickness of 3 mm and a diameter of 60 mm.

The pressure roller 30 as a pressure means has, for example, a 1 mm thick HTV silicone rubber layer 47 on an aluminum cored bar 34 and an RTV silicone rubber layer 35 on the surface thereof, and the diameter is 60 mm. There is.

The fixing roller 29 is provided with a halogen heater 36 which is a heat generating means, and the pressure roller 30 is also provided with a heater 37 in the core bar to perform heating from both sides. The thermistor 38 in contact with the pressure roller 30 detects the temperature of the pressure roller, and based on the detected temperature, the controller 39 causes the halogen heater 36,
37 is controlled so that both the temperature of the fixing roller 29 and the temperature of the pressure roller 30 are kept constant at about 170 ° C. The fixing roller 29 and the pressure roller 30 are pressed by a pressure mechanism (not shown) at a total pressure of about 40 kg.

The cleaning device C uses the non-woven fabric web 46 made of Nomex (made by DuPont) for the pressing roller 4.
At 5 the roller is pressed against the fixing roller 29 for cleaning. The web 46 is appropriately taken up by a take-up device (not shown) to prevent toner from accumulating on the contact portion.

In the present invention, regarding the offset of the toner at the time of fixing, since the wax contained in the toner has a releasing action, it is most preferable that the fixing device is oilless as in the fixing device shown in FIG. Web 4 if necessary
6 is impregnated with oil, and the transfer paper is preferably 0.0
It is also possible to carry out fixing while applying an oil such as dimethyl silicone oil of 4 mg / A4 or less (application amount on the entire surface of A4 size transfer paper), and more preferably 0.02 mg / A4 or less.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited thereto.

In the examples, "parts" and "%" represent "parts by weight" and "% by weight" unless otherwise specified.

[0087]

Example 1 451 parts by weight of 0.1M Na ₃ PO ₄ aqueous solution was added to 709 parts by weight of ion-exchanged water, and the mixture was heated to 60 ° C., and then TK.
12,000 using a homomixer (made by Tokushu Kika Kogyo)
Stirred at 0 rpm. 67.7 parts by weight of 1.0 M-CaCl ₂ aqueous solution was gradually added to this, and Ca ₃ (PO ₄ )
A dispersion medium containing ₂ was obtained.

Styrene 170 parts by weight 2 Ethylhexyl acrylate 30 parts by weight Paraffin wax (mp 75 ° C.) 60 parts by weight C.I. I. Pigment Blue 15: 3 10 parts by weight Styrene-methacrylic acid-methyl methacrylate copolymer 5 parts by weight (Mw = 50,000, Mw / Mn = 2.2, acid value = 50) Di-tert-butylsalicylic acid metal compound 3 parts by weight Of the above formulation, C.I. I. Pigment Blue 15: 3, the di-tert-butylsalicylic acid metal compound and styrene were premixed using an Ebara Milder (manufactured by Ebara Corporation). Then heat all of the above formulations to 60 ° C,
It was dissolved and dispersed to obtain a monomer mixture. While maintaining the temperature at 60 ° C., 10 parts by weight of the initiator dimethyl 2,2′-azobisisobutyrate was added and dissolved to prepare a monomer composition.

The above monomer composition was added to the dispersion medium prepared in the 2 liter flask of the homomixer. 6
The monomer composition was granulated by stirring at 0 ° C. for 20 minutes at 10,000 rpm using a TK homomixer in a nitrogen atmosphere. Then, the mixture was reacted at 60 ° C. for 3 hours while stirring with a paddle stirring blade, and then polymerized at 80 ° C. for 10 hours.

After the completion of the polymerization reaction, the reaction product was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) _2, and the mixture was filtered, washed with water and dried to obtain polymerized toner (toner particles).

The particle size of the obtained toner particles was measured by a Coulter counter, and it was found that the weight average particle size was 8.2 μm and the particle size distribution was sharp. Furthermore, when the cross section of the particles was observed with a filtration electron microscope by the dyeing ultrathin section method, it was divided into a surface layer part mainly composed of styrene-acrylic resin and a central part mainly composed of wax, and a capsule structure could be confirmed. .

The weight average molecular weight (Mw) of the toner particles in the toluene-soluble content was 29,000, the number average molecular weight (Mn) was 8,000, and Mw / Mn was 3.
It was 6.

To 100 parts by weight of the obtained toner particles, 0.7 part by weight of hydrophobic silica having a specific surface area according to the BET method of 200 m ² / g was externally added to obtain a cyan toner. Cu-Zn-F whose surface was coated with a styrene-methyl methacrylate copolymer was added to 7 parts by weight of this cyan toner.
e 93 parts by weight of a ferrite carrier was mixed to obtain a blue developer.

Using this blue developer, a commercially available color copying machine (manufactured by CLC-500 Canon) was remodeled so that double-sided copying was possible, and images were printed.
The development condition was a development contrast of 320 V under the environment of 23 ° C./65%.

The fixing roller has an outer diameter of 60 mm, a phenyl HTV silicone rubber layer having a thickness of 800 μm on a core metal made of aluminum, and a one-component RTV silicone rubber layer having a thickness of 200 μm as an offset preventing layer thereon. Roller effective hardness of 80 ° (Asker
-C 1 kg weighted) was used. The pressure roller is
The outer diameter is also 60 mm, a phenyl HTV silicone rubber is formed on a core metal made of aluminum to a thickness of about 2 mm, and the surface is covered with a fluorine-based resin tube with a thickness of 50 μm. The roller effective hardness is 87 °. (As
ker-c 1 kg weighted) was used.

The fixing roller and the pressure roller as described above were installed in the image forming apparatus shown in FIG. 1, and a durability test of 5,000 sheets was conducted in a single color mode (cyan single color). The fixing temperature was 170 ° C., the fixing speed was 90 mm / sec, and fixing was performed without applying oil.

The obtained image was a color image faithfully reproducing the original chart without any offset on the front and back.

Furthermore, when the transfer sheet and the photosensitive drum were observed in detail at the end of the durability test, the effect of the present invention could be confirmed with almost no contamination by wax.

Example 2 In Example 1, a phenyl HTV silicone rubber layer having a piece rubber hardness of 33 ° (JIS-A 1 kg weighted) was formed with a thickness of 2 mm on a core metal made of aluminum as a fixing roller, and the surface thereof was further formed. Roller coated with a fluorocarbon resin tube with a thickness of 50 μm 81 ° effective hardness
(Asker-c 1kg weighted), except that
Similarly, the durability test of 5000 sheets was performed.

The obtained image was a color image faithfully reproducing the original chart without any offset on the front and back.

Comparative Example 1 Styrene-2 ethylhexyl acrylate copolymer 100 parts by weight (copolymerization weight ratio = 88: 12, Mw = 130,000, Mw / Mn = 3.5) 2 parts by weight of low molecular weight polyolefin wax (m P.130 ° C.) C.I. I. Pigment Blue 15: 3 4.5 parts by weight Di-tert-butylsalicylic acid metal compound 3 parts by weight are mixed, then melt-kneaded by a twin-screw kneading extruder, cooled, crushed by an airflow crusher, and air classifier. Classification was carried out to obtain a blue powder toner (toner particles) having a weight average diameter of about 8.5 μm. The toluene-soluble content of the toner particles was 29,500, Mn was 8,000, and Mw / Mn was 3.7. Cyan toner was obtained by externally adding 0.8 parts by weight of negatively charged colloidal silica to 100 parts by weight of this toner. A blue developer was obtained by mixing these toners and ferrite particles coated with a fluoroacrylic resin at a ratio of 8:92.

When durability was started in the same manner as in Example 1, offset occurred shortly after the durability and the durability was interrupted midway.

Comparative Example 2 A blue powder toner (as in Comparative Example 1) was prepared except that 2 parts by weight of paraffin wax (mp 75 ° C.) was used in place of the low molecular weight polyolefin wax used in Comparative Example 1. Toner particles) were obtained. The Mw in the toluene-soluble content of the toner particles was 29,800, and the Mn was 8,
000, and Mw / Mn was 3.7. When a blue developer was obtained and imaged in the same manner as in Comparative Example, an offset occurred shortly after the endurance as in Comparative Example 1, and the end of the endurance was interrupted.

Comparative Example 3 After preparing a developer in the same manner as in Comparative Example 1, the oil coating device shown in FIG. 4 was operated and the oil coating amount was 0.08 mg / A4.
Was applied while applying oil. Although no offset occurred, the image quality deteriorated severely during the durability.

Example 3 A monomer composition was prepared in the same manner as in Example 1 except that the amount of paraffin wax used was 30 parts by weight.
Polymerized toner (toner particles) was obtained in the same manner as in Example 1,
Similarly, hydrophobic silica was externally added to obtain a cyan toner.

The weight average molecular weight (Mw) of the toner particles in the toluene-soluble content was 32,000, the number average molecular weight (Mn) was 9,800, and Mw / Mn was 3.
It was 3.

A blue developer was prepared in the same manner as in Example 1 by using the obtained cyan toner, and an image was formed.

In the fixing device of the image forming apparatus used for image formation, a web made of heat-resistant fiber such as aromatic polyamide which is in contact with the surface of the fixing roller is impregnated with dimethyl silicone oil. A color toner image was fixed while applying 0.01 mg / A4 of dimethyl silicone oil, and a durability test of 5,000 sheets was conducted.

As a result, the image obtained after running had some image defects due to the contamination of the photosensitive drum with dimethyl silicone oil, but it was at a level where there was no practical problem.

Comparative Example 4 A blue developer was prepared in the same manner as in Comparative Example 1, and then the web was impregnated with dimethyl silicone oil in the same manner as in Example 3, and 0.01 mg / A4 of dimethyl silicone oil was added to the transfer material. While applying, the color toner image was fixed and a durability test was conducted. Offset occurred at the end of 500 sheets, and the durability was interrupted midway.

Example 4 C.I. used in Example 1 I. Pigment Blue 15: 3 instead of C.I. I. A polymerized toner (toner particles) was obtained in the same manner as in Example 1 except that 9 parts by weight of Pigment Red 122 was used, and hydrophobic silica was externally added in the same manner to obtain a magenta toner.

Example 1 was performed using the obtained magenta toner.
A red developer is prepared in the same manner as described in 1.
The durability test of the sheet was performed.

The obtained image was a color image faithfully reproducing the original chart without any offset on the front and back.

Furthermore, when the transfer sheet and the photosensitive drum were observed in detail at the end of the durability test, the effect of the present invention could be confirmed with almost no contamination by wax.

Example 5 The C.I. used in Example 1 was used. I. Pigment Blue 15: 3 instead of C.I. I. Pigment Yellow 17 was used in the same manner as in Example 1 to obtain a polymerized toner (toner particles), and hydrophobic silica was externally added in the same manner to obtain a yellow toner.

Example 1 was performed using the obtained yellow toner.
A yellow developer is prepared and imaged in the same manner as
The durability test of the sheet was performed.

The obtained image was a color image faithfully reproducing the original chart without any offset on the front and back.

Furthermore, when the transfer sheet and the photosensitive drum were observed in detail at the end of the durability test, the effect of the present invention could be confirmed with almost no contamination by wax.

Example 6 The C.I. used in Example 1 was used. I. Pigment Blue 15: 3, except that 12 parts by weight of commercially available carbon black was used, a polymerized toner (toner particles) was obtained in the same manner as in Example 1, and hydrophobic silica was externally added in the same manner as in Example 1. Black toner was obtained.

Example 1 was performed using the obtained black toner.
A black developer is prepared and imaged in the same manner as
The durability test of the sheet was performed.

The obtained image was a color image faithfully reproducing the original chart without any offset on the front and back.

Furthermore, when the transfer sheet and the photosensitive drum were observed in detail at the end of the durability test, the effects of the present invention could be confirmed with almost no contamination by wax.

Example 7 Each of the four colors of blue developer used in Example 1, red developer used in Example 4, yellow developer used in Example 5 and black developer used in Example 6 Example 1 except that a color toner image using four types of color toners is transferred to a transfer material using a developer and the color toner image is fixed to the transfer material by the fixing roller used in Example 2. When an image was printed and a durability test was performed under the same conditions as in 1. No offset was observed even after 3000 sheets of durability, and full-color images faithfully reproducing the original chart were obtained on both sides of the transfer material.

[0124]

According to the present invention, the color toner forming the color toner image has the toner particles directly obtained by the suspension polymerization method, and the toner particles contain the wax. Even when forming a color toner image fixed on both surfaces of a transfer paper, excellent offset resistance can be obtained without using oil in the fixing means at the time of fixing, or with a small amount, and a latent image carrier can be obtained. A double-sided color toner image is obtained in which the occurrence of image deterioration due to the transfer of oil to the surface is prevented or suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus capable of double-sided fixing.

FIG. 2 is a schematic configuration diagram for explaining the fixing device in FIG. 1 in detail.

FIG. 3 is a schematic configuration diagram of an image forming apparatus for forming a conventional general full-color image.

FIG. 4 is a schematic configuration diagram of a fixing device used in the conventional image forming apparatus of FIG.

[Explanation of symbols]

15 Transfer means (transfer drum) 19 Electrostatic latent image carrier (photosensitive drum) 29 fixing means (fixing roller) 30 Pressure means (pressure roller) 36 Heat generating means (halogen heater)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G03G 15/01 114 G03G 9/08 384 (72) Inventor Tatsuya Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koji Inaba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-4-107566 (JP, A) JP-A-4-107567 (JP, A) JP 5-127555 (JP, A) JP 5-142963 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 9/08 G03G 15/01

Claims (3)

(57) [Claims] 1. A color toner image formed on an electrostatic latent image carrier is transferred to one surface of a transfer material, and the color toner image on the transfer material is heated and melted by a fixing unit to form a color image on the transfer material. The toner image is fixed, and the color toner image formed on the electrostatic latent image carrier is transferred to the other surface of the transfer material that faces the surface on which the color toner image is fixed. An image forming method for forming a full-color image fixed on both surfaces of a transfer material by heating and melting the image by a fixing means to fix the color toner image on the transfer material, wherein the image forming method includes (a) the transfer material. First on one surface of
First transfer step of transferring the color toner image of step (b)
A first full-color image is obtained by heating and melting the first color toner image and fixing it on one surface of the transfer material by a fixing unit for applying heat and pressure to both surfaces of the transfer material. A fixing step; (c) a second transfer step of transferring a second color toner image to the other surface of a transfer material having the first color image on one surface; and (d) both surfaces of the transfer material. By the fixing means for applying heat and pressure,
A second fixing step in which the second color toner image is heated and melted and fixed on the other surface of the transfer material to obtain a second full color image; and the first full color toner image and the second full color image The color toner for forming the second full-color toner image has toner particles directly obtained by a suspension polymerization method, and the toner particles have a surface layer part mainly composed of a resin and the wax. Has a capsule structure in which toner particles are encapsulated inside the toner particles, the wax has a melting point of 40 ° C. to 140 ° C., and the fixing unit includes heat generating units on both sides of the transfer material. In the first fixing step, heat is applied from both sides of the transfer material by the fixing means, and oil is not applied to the surface of the transfer material, or 0.04 mg / A
The amount of oil of 4 or less is applied, the first fixing is performed, and the wax that has melted and exuded from inside the toner particles of the color toner forming the first full-color toner image is Which functions to prevent toner offset by covering at least a part of the full-color image, and is solidified by a temperature decrease after passing from the fixing unit. In the second fixing step, Heat is applied from both sides of the transfer material and no oil is applied to the surface of the transfer material, or 0.04 mg / A
The amount of oil of 4 or less is applied, the second fixing is performed, and the wax that has melted and exuded from the inside of the toner particles of the color toner forming the second full-color toner image is Which functions to prevent toner offset by covering at least a part of the full-color image, and is solidified by the subsequent temperature decrease after passing from the fixing unit, and covers at least a part of the first full-color image. The wax is dissolved by the fixing means, and the second
The image forming method characterized in that the function to prevent the toner offset at the time of fixing, in which solidified by temperature decrease after the passage of the subsequent fixing unit. 2. The wax contained in the toner particles contains a paraffinic wax, and the paraffinic wax is 0.1% by weight based on 100 parts by weight of the polymerizable monomer.
The image forming method according to claim 1, wherein the toner particles are contained in an amount of 1 to 50 parts by weight. 3. The wax contained in the toner particles is 5
It has a heat of fusion ΔH of 0 to 250 J / g, and the wax is contained in the toner particles in an amount of 5 to 40 parts by weight based on 100 parts by weight of the polymerizable monomer. Item 2. The image forming method according to Item 1.