JP2002341584A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely preventing trouble such as the deterioration of image gloss caused by the deterioration of the surface roughness of an image feeding body (intermediate transfer body or the like) 2 circularly moving so as to carry and feed a toner image formed by an image producing device 1 without causing insufficiency in the fixing degree of the toner image and also to stably form a high-quality image rich in glossiness in an image forming device utilizing a transfer and fixing simultaneous system accompanied with preliminary heating. SOLUTION: In this image forming device equipped with a transfer fixing device 3 and a preliminary heating means 4, release agent non-exposing type toner E constituted by dispersing a release agent in toner particles in a state where it is not exposed to the surfaces of the toner particles is used as toner constituting the toner image T formed by the image producing device 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus typified by a printer, a copying machine, a multifunction machine or the like utilizing an electrophotographic system or the like, and more particularly, to an apparatus for carrying a toner image formed by an image forming apparatus. The present invention relates to an image forming apparatus using a simultaneous transfer fixing method in which a toner image is transferred from an image carrier such as a photoreceptor belt or an intermediate transfer belt to a recording medium and is simultaneously fixed.

[0002]

2. Description of the Related Art As an image forming apparatus utilizing this simultaneous transfer fixing method, for example, an image forming apparatus having a configuration as shown in FIG. 5 is known. Such an image forming apparatus mainly includes
An image forming unit 100 for forming a toner image based on image information on an image carrier 110 such as a photosensitive drum by an electrophotographic process (charging, image exposure, development, etc.), and the like; Endless belt-shaped intermediate transfer body 2 carrying and circulating and carrying the toner image to be primarily transferred after the transfer
00, a transfer fixing device 300 for performing a secondary transfer of the toner image on the intermediate transfer member 200 to a recording medium P such as a recording sheet or an OHP sheet and simultaneously fixing the same, and an image forming unit 10
The configuration mainly includes a heating member 400 for preliminarily heating the toner image on the intermediate transfer member 200 between the transfer fixing device 300 and the transfer fixing device 300.

[0003] Of these, the image forming unit 100 is usually
It is configured as an image forming unit capable of forming a color image. For example, one image carrier 110
Is used to sequentially form toner images of a plurality of colors on the image carrier 110, or a plurality of image carriers 110 are used to form toner images of the respective colors on the respective image carriers 110. Each is configured to form. The belt-shaped intermediate transfer member 200 includes a plurality of belt support rolls 210, 220, 230, 24 including a drive roll 210.
It is stretched at 0 or the like and rotates in the arrow direction B. The heating member 400 is provided between the image forming unit 100 and the belt supporting roll 220.
The toner image is preliminarily heated to a predetermined temperature via the intermediate transfer member 200 in this state. Further, the transfer fixing device 300 includes a heating roll 310 and a pressure roll 320 that rotate while being pressed against each other while sandwiching the intermediate transfer body 200.
The recording medium P is introduced between the pressure roll 320 and the intermediate transfer belt 200 at a predetermined timing and passed therethrough.

In this image forming apparatus, after a plurality of toner images corresponding to the image information are formed on the image carrier 110 by the image forming unit 100, the toner images are transferred to the intermediate transfer body 200. Is primary-transferred electrostatically by a container. Subsequently, the toner image transferred to the intermediate transfer member 200 is preliminarily heated when passing through the heating plate 400 and melted appropriately, and then conveyed to the transfer fixing device 300 in that state, and the intermediate transfer member By being heated and pressurized by the heating roll 310 and the pressurizing roll 320 together with the recording medium P introduced between the pressurizing roll 200 and the pressurizing roll 320, the image is secondarily transferred onto the recording medium P and fixed at the same time. continue,
The recording medium P on which the toner image has been secondarily transferred is an intermediate transfer member 2
The sheet P is conveyed to a peeling position where a belt supporting roll (peeling roll) 230 is present in a state of being in close contact with the outer peripheral surface of the intermediate transfer member 200, and is peeled from the intermediate transfer member 200 while being sufficiently cooled. As a result, the toner image is transferred and fixed onto the recording medium P in a state where the surface smoothness of the intermediate transfer body 200 is transferred as it is, and a high-quality image with a rich gloss is formed.

[0005]

By the way, in an image forming apparatus utilizing such a simultaneous transfer fixing method,
There are the following issues.

That is, as the image formation by the image forming apparatus increases from tens of thousands to hundreds of thousands of sheets in terms of the number of recording media, the surface of the intermediate transfer body 200 is discharged or discharged during the primary transfer of the toner image. The adhesive force with the toner increases due to the stress due to heating during secondary transfer or the like, and fine toner that is not transferred to the recording medium gradually remains on the intermediate transfer body 200 and the surface of the intermediate transfer body 200 has a rough surface. Will get worse. As a result, it is difficult to form a smooth toner image by the simultaneous transfer fixing method as described above, and as a result, there is a problem that the gloss of the image is deteriorated.

In order to suppress such deterioration of the image gloss, it is considered necessary to suppress an increase in the adhesion of the intermediate transfer belt to the toner due to discharge or heating. As a countermeasure, it is effective to use a toner containing a release agent (hereinafter also referred to as a “toner containing a release agent”) in order to interpose a release agent between the intermediate transfer belt and the toner. It has been confirmed by experiments of the present inventors that the deterioration of gloss can be reduced.

Accordingly, the present inventors have studied the amount of the release agent contained in the release agent-containing toner and the effect of improving the problem of the deterioration of the gloss of the image due to the deterioration of the surface roughness of the intermediate transfer member. The relationship was examined.

As a result, when the amount of the release agent contained in the toner is relatively large, the deterioration of the surface roughness of the intermediate transfer member is suppressed, and the gloss of the image is maintained. It has been found that there is a problem in that the strength is insufficient, for example, when the recording medium after transfer and fixing is bent at a certain portion of the image, a part of the toner image is missing from the recording medium.

For reference, a toner image of the same toner excessively containing the release agent is electrostatically transferred to a recording medium by a general transfer device, and then thermally fixed by a general roll nip type fixing device. As a result of the processing, there was no problem with the degree of fixing of the toner image after the fixing, and no part of the toner image was lost even when the recording medium was bent. From this fact, it was found that the problem of insufficient fixing degree when the toner having an excessive amount of the release agent was used was a problem peculiar to the image forming apparatus using the simultaneous transfer fixing method.

On the other hand, if the amount of the release agent contained in the toner is relatively small, the problem of insufficient degree of fixation of the toner image after transfer and fixing can be suppressed. It was also found that the effect of suppressing the deterioration of the surface roughness of the body was insufficient, and the problem of the deterioration of the image gloss could not be solved.

The present invention has been made in view of such circumstances, and a purpose thereof is to provide an image forming apparatus using a simultaneous transfer and fixing system with preheating as exemplified above, which is an intermediate device. Problems such as deterioration of image gloss caused by deterioration of surface roughness of an image carrying body that circulates and moves so as to carry and convey a toner image such as a transfer body can be easily achieved without causing insufficient toner image fixing degree. It is another object of the present invention to provide an image forming apparatus which can surely prevent the occurrence of an image and can stably form a high-quality image having a high glossiness.

[0013]

Means for Solving the Problems The present inventors first investigated the cause of the above problem, and found that the toner image on the image carrier was heated before reaching the transfer fixing device. It was found that the release agent contained in the release agent-containing toner was melted and covered the toner surface. In addition, when the release agent-containing toner used was examined again, the toner was produced by mixing a binder resin, a colorant, a release agent, and the like, melting, kneading, cooling, and then pulverizing. It was found that the toner was a so-called pulverized toner, and a release agent was exposed on the surface of the toner.

From these facts, in particular, the insufficient fixing degree of the toner image after the transfer and fixing is caused by the fact that the toner constituting the toner image (containing the release agent) is already in contact with the recording medium during the transfer and fixing. It is presumed that this is mainly caused by the fact that the binder resin of the toner, which contributes to the fixing degree, cannot sufficiently contact the recording medium because it is covered with the release agent.

Accordingly, the present inventors have conducted intensive studies based on such findings to achieve the above object, and as a result, while containing a release agent as a toner, the release agent was transferred and fixed. By performing image formation by the simultaneous transfer fixing method using a toner that partially intervenes between the image carrying body and the recording medium during the transfer and fixing without covering the toner surface by the previous heating, The inventors have found that the object can be achieved, and have completed the present invention.

That is, the image forming apparatus according to the present invention has the structure shown in FIG.
As shown in FIG. 1, an image forming apparatus 1 that forms a toner image in accordance with image information, and an image transport body 2 that circulates and moves so as to carry and transport a toner image T formed by the image forming apparatus 1 A transfer / fixing device 3 for transferring and simultaneously transferring the toner image T on the image carrying member 2 to the recording medium P by heating and pressing, and transferring the image between the transfer / fixing device 3 and the image forming device 1. A preheating means 4 for preliminarily heating the toner image T on the body 2, wherein the toner constituting the toner image T is a toner particle in a state where a release agent is not exposed to the surface of the toner particle. The present invention is characterized in that a release agent non-exposed toner dispersed inside is used.

Here, the image forming apparatus 1 is capable of forming a monochromatic or color toner image in accordance with image information such as read image information of a document or input image information input from the outside. The image forming method and the like are not particularly limited. For example, an image forming apparatus in which the toner image is once formed on an image carrier such as a photoreceptor and transferred to and supported on the image carrier 2, or the toner image is transported on the carrier 2
An image forming apparatus of a type in which the image forming apparatus is formed directly on the substrate can be used.

The image carrier 2 is appropriately selected mainly depending on the image forming system of the image forming apparatus 1. For example, when the image forming apparatus 1 is of a type in which a toner image is once formed on an image carrier, an endless belt-shaped or drum-shaped intermediate transfer body capable of carrying a toner image transferred from the image carrier. Is used. Further, the image forming apparatus 1 transfers the toner image to the image carrier 2.
Endless belt-shaped or drum-shaped photoreceptor capable of directly forming a toner image,
An image carrier made of a dielectric or the like is used.

The transfer-fixing device 3 may be any device that has a function of simultaneously transferring and fixing a toner image on an image carrying body to a recording medium by heating and pressing. For example, there is an apparatus in which two or more rotating bodies (such as a rotating roll and a rotating belt) are arranged so as to be pressed against each other with the image carrying body 2 sandwiched therebetween, and at least one of the rotating bodies is configured as a heating rotating body. Can be used. The recording medium P may be any as long as it can transfer and fix a toner image, and includes, for example, various types of recording paper, OHP sheets, thick paper, and the like. Further, a cooling device for cooling the image carrier and the recording medium is provided between the transfer fixing device 3 and a separation point where the recording medium P is peeled off from the image carrier 2 after passing through the device 3. Good. A dashed line with an arrow in FIG. 1 indicates a conveyance path of the recording medium P.

The preheating means 4 can preliminarily heat the toner image T on the image carrier 2 to a predetermined temperature (for example, a temperature at which the toner melts) before reaching the transfer fixing device 3. It is not particularly limited as long as it is a product.
Further, the preheating means 4 may be arranged at a portion inside the image carrier 2, at a portion outside the image carrier 2, or may be provided at both portions. Further, the preheating means 4 may be of a contact heating type or a non-contact heating type with respect to the image carrier 2, but the non-contact heating only when it is arranged at a portion outside the image carrier 2. Type.

The release agent non-exposed type toner E is shown in FIG.
a, the release agent 5 is dispersed inside the toner particles in a state where the release agent 5 is not exposed on the surface of the toner particles. As shown in FIG. It was not exposed to. FIG. 2 is a cross-sectional view of the toner particles observed using a transmission electron microscope. More specifically, the toner E contains at least a binder resin, which contains at least a binder resin, a colorant, and a release agent, and a binder resin that covers the surface of the inside of the particles. This is a toner comprising a particle surface layer portion containing no mold agent. Of these, the particle surface layer is not formed firmly by the outer shell resin like the shell part in the so-called capsule toner composed of the core part and the shell part, but is mainly formed by the binder resin in ordinary toner. Is what is done.

The toner E is manufactured by the following method. That is, at least a resin particle dispersion in which the binder resin particles are dispersed and a colorant dispersion in which the colorant is dispersed and a release agent particle dispersion in which the release agent particles are mixed are mixed, and the binder resin and the colorant are mixed. A first step of forming aggregated particles by aggregating a release agent to prepare an aggregated particle dispersion, and after the first step, at least the resin particle dispersion (the aforementioned (A colorant dispersion may be contained), and a second step of adhering at least the binder resin particles to the surface of the aggregated particles formed in the first step, and adhering in the second step. A third step of heating the adhered particles to fuse them with the aggregated particles.

That is, in this production method, the coagulation process is performed in two stages, and in the first stage (first process), an aggregate is formed by the binder resin particles, the colorant particles, and the release agent particles to temporarily stabilize the fusion. After that, in a second step (second step), at least resin particles for binding are further added, and at least the resin particles are adhered to the surface of the mother aggregated particles formed in the first step, and fused in the last step. On the other hand, this is a wet toner production method for obtaining toner particles. According to such a production method, the toner structure can be controlled, and a toner that contains a release agent but does not expose the release agent to the surface can be produced. The determination as to whether the release agent is exposed on the toner surface can be made by observing the cross section of the toner particles with a transmission electron microscope.

Incidentally, such a release agent non-exposed type toner E is prepared by an emulsion polymerization method (JP-A-63-282755, JP-A-6-250439) which is a wet toner production method.
However, since the aggregation process is one stage, the surface and the inside of the obtained toner particles have the same composition, and therefore the composition of the surface is intentionally controlled. As a result, the resulting toner is such that the release agent is exposed on the surface of the toner particles (FIG. 2B), and the release agent is dispersed inside the toner particles without being exposed on the surface of the toner particles. Cannot be produced (FIG. 2a).

[0025]

FIG. 3 shows a main part of a color image forming apparatus according to Embodiment 1 of the present invention.

This color image forming apparatus forms four images based on image information by electrophotography, and forms toner images of respective color components of yellow (Y), magenta (M), cyan (C), and black (K). Image unit 10Y,
10M, 10C, and 10K, and the respective image forming units 10
An intermediate transfer belt 20 to which respective toner images formed by Y, 10M, 10C, and 10K are transferred; a transfer fixing device 30 that transfers the toner image on the intermediate transfer belt 20 to recording paper P and simultaneously fixes the toner image; It basically comprises a preheating body 40 for preliminarily heating the toner image on the intermediate transfer belt 20 between the image forming unit 10K and the transfer fixing device 30. The one-dot chain line with an arrow in the drawing indicates the transport path of the recording paper P, and the recording paper P is supplied from a paper feeding device (not shown).

The image forming units 10Y, 10M, 10M
C and 10K are arranged side by side at predetermined intervals along the horizontal direction, and each of them has the same configuration. That is, each of the image forming units 10 includes a photosensitive drum 11 that rotates at a predetermined speed in the direction of arrow A by a rotation drive source (not shown),
Charger 12 for uniformly charging the surface of the
Image forming apparatus 1 for exposing light H corresponding to image information to the surface of photosensitive drum 11 charged with
3 and a developing roller 14 that applies a toner of a predetermined color to the electrostatic latent image on the photosensitive drum 11 formed by the latent image forming device 13.
The main parts are constituted by a developing device 14 for supplying and developing the toner image on the photosensitive drum 1 and a primary transfer device 15 for transferring the toner image on the photosensitive drum 1 to the intermediate transfer belt 20.

The photosensitive drum 11 has a photosensitive layer formed of an inorganic photosensitive material or an organic photosensitive material formed so as to be located on the outer peripheral surface of the drum. As the charger 12, a non-contact type charger such as a corona discharger, or a contact type charging device that charges a contact member such as a charging roll by contacting the photosensitive drum is used. The latent image forming apparatus 13 is configured to scan and expose light H emitted from a light source such as a semiconductor laser or a light emitting diode in a manner modulated in accordance with a processing signal of image information onto the photosensitive drum 11 via a scanning optical system. Things. When the image forming apparatus is a printer, the image information input from an externally connected device such as a personal computer and subjected to image processing is used as the image information in the latent image forming apparatus 13. When the forming apparatus is a copying machine, the image information input from the document reading apparatus and subjected to image processing is used.

As the developing device 14, a two-component developing device is usually used, but if possible, a one-component developing device may be used. Further, the developing device 14 supplies a two-component developer (toner) by a developing roller 14a which is arranged close to the developing area of the photosensitive drum 11 and is rotated by applying a developing bias, and is thus supplied with the toner of the two-component developer. Perform development. As the primary transfer device 15, a non-contact type such as a corona discharge device or a contact type using a contact member such as a transfer roll is used.

The intermediate transfer belt 20 is stretched around a drive roll 21 and a tension roll 22, which are driven to rotate by a rotary drive source (not shown), and a plurality of support rolls 23, 24, which are driven to rotate and support the belt. The tension roll 22 and the drive roll 21 are disposed so as to pass through the transfer position of the photosensitive drum 11 in each of the image forming units 10. The intermediate transfer belt 20 is maintained in a state of being stretched by applying a predetermined tension (for example, 8 kgf, about 80 mN) by the tension roll 22 and then circulating in the direction of arrow B by the drive roll 21. So that it can be rotated.

Of the above support rolls, the support rolls 23
Has a relatively small roll diameter, and the intermediate transfer belt 20 is configured to bend and move in a state of a small radius of curvature. Transfer belt 2 depending on waist strength
Used as a peeling roll that acts to peel off from zero on its own. In this example, if the roll diameter of the support roll 23 is too small, the roll is bent by the tension from the belt. Therefore, in consideration of this, a stainless roll having a roll diameter of 16 mm is used. In the drawing, reference numeral 28 denotes a peeling plate for assisting the peeling of the recording paper P from the intermediate transfer belt 20, and 29 denotes a paper transport roll pair for transporting the recording paper P.

The intermediate transfer belt 20 has a two-layer structure in which a surface layer is laminated on a belt base material to form an endless belt. The belt base material has a width of 350 mm and a thickness of 7, for example, containing carbon black.
It is a polyimide film having a thickness of about 0 μm, and is adjusted so that its volume resistivity is about 10 ¹⁰ Ωcm from the viewpoint of favorably primary transferring the toner image from the photosensitive drum 11 to the intermediate transfer belt 20 without image disturbance. ing. In addition, as this belt base material, besides, the thickness is 10 to 10.
Any material having a heat resistance of about 300 μm can be used. On the other hand, an elastic layer is used as the surface layer. This surface layer has a volume resistivity of 10 from the viewpoint of performing good primary transfer without image disturbance.
The intermediate transfer belt 2 is adjusted to be about ¹⁴ Ωcm and a toner image is interposed during transfer and fixing.
From the viewpoint of ensuring good adhesion between the recording paper P and the recording paper P, it is preferable to use a silicone copolymer. The surface layer may be formed using a fluororesin, a fluororubber, or the like. In this example, a silicone copolymer (manufactured by Toray Dow Silicone: DX35-547A) is used.
/ B) to form a surface layer having a thickness of 50 μm.

The transfer fixing device 30 includes a support roll 21
The heating roll 31 and the pressure roll 32, which are opposed to each other with the intermediate transfer belt 20 interposed therebetween and the support roll 24, constitute a main part thereof. Each of the heating roll 31 and the pressure roll 32 has a structure in which a heat-resistant elastic layer made of silicone rubber or the like is laminated on the surface of a cylindrical metal roll, and a heating source is provided inside the metal roll. 33 are provided. The heating temperature of the heating roll 31 and the pressing roll 32 at the pressure contact portion of the two rolls is the melting temperature of the toner (melting point: T
m) It is heated by the heating source 33 so as to be maintained at a temperature not lower than m). In this example, the heating roll 31 and the pressure roll 3
2 on an aluminum cylindrical roll with a thickness of 2 mm
A roll having a total outer diameter of 50 mm was formed by laminating a silicone rubber layer (having a hardness of 30 degrees), and a halogen lamp was used as the heating source 32. Also, both rolls 31,
No. 32 has a width of about 7.5 mm of its pressure contact (nip) portion,
The nip pressure was set so as to be 5.5 × 10 ⁵ Pa. Regarding the nip pressure of the two rolls 31 and 32, from the viewpoints of securing a good fixing strength and securing good running properties without causing paper wrinkles when the recording paper P passes through the nip. , 2.0 × 10 ^{5 to} 8.0 ×
It is preferable to set within the range of 10 ⁵ Pa.

The pre-heating member 40 is a structure disposed so as to be in surface contact with the inner peripheral surface of the intermediate transfer belt 20 between the driving roll 21 and the heating roll 31 of the transfer fixing device 30. . The preheating body 40 is provided on a contact plate 41 having a curved contact surface that comes into contact with the inner peripheral surface (entire width) of the intermediate transfer belt 20, and is heated on a surface opposite to the contact surface of the contact plate 41. And a heating source 42. Further, the preheating body 40 is set so as to heat the toner image on the intermediate transfer belt 20 before the transfer and fixing to a temperature higher than the melting temperature of the toner.

The contact plate 41 has a radius of curvature of about 900
A planar heater in which a belt moving direction B having a curved contact surface curved to about mm, an aluminum plate having a length of about 220 mm and a thickness of about 2 mm is used, and an electric heating element covered with silicone rubber as a heating source 42. Was used. The preheating time by the preheating plate 40 can be changed by, for example, appropriately adjusting the length of the contact heating plate 41. The contact heating plate 41 may be formed of a material other than aluminum as long as the material has good thermal conductivity. Further, it is preferable to make the heating source 42 from the sheet heater as thin as possible from the viewpoint of reducing the thermal resistance when conducting heat from the energized heating element to the contact plate 41 and enabling efficient heating. In this example, the thickness is about 1.5 mm. As the preheating body 40, for example, a ceramic heater plate or the like can also be used.

In this image forming apparatus, a cooling device 50 for cooling the intermediate transfer belt 20 and thus the toner image and the recording paper P is provided between the transfer fixing device 30 and the belt support roll 24.

In this example, as the cooling device 50, a blower fan that blows air toward the back surface of the recording paper P while being conveyed in a state of being in close contact with the intermediate transfer belt 20 during transfer and fixing is used. And by the blowing fan 50,
The air outside the apparatus is taken in through a duct, and the air is sent to the intermediate transfer belt 20 to which the recording paper P adheres. As the blowing fan, a cross flow fan (MFD930, manufactured by Oriental Motor Co., Ltd.) is used so that air can be blown uniformly in the width direction of the intermediate transfer belt 20, and the recording paper after transfer and fixing is used. The cooling control was set so that the temperature of the back surface of the paper when P reached the peeling position of the belt supporting roll 23 functioning as a peeling roll was about 70 to 80 ° C.

In this image forming apparatus, as the toner in the two-component developer used in the developing device 14, as shown in FIG. A dispersed release agent non-exposed toner E is used.

This release agent non-exposed toner E is prepared by a wet toner production method (production method) in which the above-described aggregation step is performed in two stages.
Produced by The method of manufacturing the toner E is based on the toner manufacturing method already proposed by the present applicant (Japanese Patent Laid-Open No.
-73955).

As the binder resin used in the method for producing the toner E, a binder resin having thermoplasticity is used. Examples of the binding resin include styrenes such as styrene, parachlorostyrene, and α-methylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate. Esters having a vinyl group such as ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, vinyl nitriles such as acrylonitrile and methacrylonitrile, vinyl methyl ether, vinyl isobutyl ether and the like Homopolymers of monomers such as vinyl ethers, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone, and polyolefins such as ethylene, propylene and butadiene; Copolymer or a mixture thereof obtained by combining the body two or more thereof. Further, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, non-vinyl condensation resins and the like, and mixtures of these with the vinyl resins, and vinyl-based monomers in the presence of these And a graft polymer obtained when the polymer is polymerized.

As the coloring agent, various pigments, dyes and the like can be used alone or in combination. Further, examples of the release agent include polyethylene, polypropylene, low molecular weight polyolefins such as polybutene, silicones having a softening point upon heating, oleic amide, erucamide, ricinoleamide, and stearamide. Fatty amides, carnauba wax, rice wax, candelilla wax,
Plant waxes such as wood wax, jojoba oil and the like, animal waxes such as beeswax, montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, microcrystalline wax,
Minerals, such as Fischer-Tropsch wax, petroleum-based waxes, and modified products thereof.

In the method of producing the toner E, it is desirable that the average particle size of the resin particles to be bound is 1 μm or less in both the first step and the second step. If the average particle size is larger than that, the particle size distribution of the finally obtained toner particles is widened or loose particles are generated, which tends to cause a decrease in performance and a decrease in reliability. .

The amount of the resin particle dispersion added in the second step depends on the volume fraction of the finally obtained toner particles, and may be within 50% of the volume of the toner. desirable. When this amount is 50% or more, the additional resin particles adhere to the base aggregated particles formed in the first step and do not aggregate, and newly aggregated particles are formed by the added resin particles. As a result, the composition distribution and the particle size distribution of the obtained toner particles fluctuate significantly, and desired performance cannot be obtained.

Further, the addition of the resin particle dispersion in the second step may be performed stepwise in a plurality of times or gradually and continuously. When added in this manner, the generation of fine aggregated particles due to the added resin particles can be suppressed, and the particle size distribution of the obtained toner can be sharpened. In addition, the addition of the resin particle dispersion is performed by adding the dispersion of the added resin particles and the base aggregated particles to the glass transition temperature of the resin of the resin particles to be used in the first step, for each additional mixing. May be used to raise the temperature. In this case, generation of free particles can be suppressed.

In the color image forming apparatus having such a basic configuration, a color image is formed as follows.

First, in each image forming unit 10, the photosensitive drum 11 rotating in the direction of arrow A is uniformly charged by the charger 12 so as to have a desired charging potential, and then a latent image is formed on the charged surface. Scanning exposure of light (for example, a laser beam) H corresponding to the color-separated image data from the device 13 forms an electrostatic latent image having a desired latent image potential. The toner is developed with a toner of a predetermined color component supplied from the printer 14. By repeating such an image forming process in the same manner for the four colors, toner images of four colors of yellow, magenta, cyan, and black are individually and sequentially formed on the respective photosensitive drums 11. Thereafter, the four color toner images on each photosensitive drum 11 are sequentially primary-transferred so as to be superimposed on the surface of the intermediate transfer belt 20 by the electrostatic transfer operation of the primary transfer device 15 in the primary transfer unit.

Next, when the toner image primarily transferred to the intermediate transfer belt 20 passes through the pre-heating body 40, the toner image is pre-heated by the heating action of the pre-heating body 40 and is transferred and fixed in a state of being appropriately melted. It is sent to the device 30. The fused toner image on the intermediate transfer belt 20 is transferred to the intermediate transfer belt 2 by the transfer fixing device 30.
The recording paper P is heated and pressurized by the heating roll 31 and the pressurizing roll 32 together with the recording paper P supplied between the recording paper P and the recording paper P, thereby being secondarily transferred onto the recording paper P and fixed simultaneously.

Next, the recording paper P on which the toner image has been secondarily transferred is conveyed to a peeling position where a peeling support roll 23 is present in a state of being in close contact with the outer peripheral surface of the intermediate transfer belt 20. It is cooled by the cooling body 50. By this cooling, the heated and melted toner is sufficiently coagulated and solidified to generate a strong adhesive force with the recording paper P, whereby the toner is strongly fixed on the paper surface, while the toner is easily peeled off from the intermediate transfer belt 20. Becomes Further, the cooled recording paper P is separated by its own strength from the waist strength (rigidity) of the paper itself from the intermediate transfer belt 20 which travels while running at a small radius of curvature by being supported by the small-diameter support roll 23 at the cooling position. .

Thus, a full-color image is formed on one side of the recording paper P. At this time, the image formed on the recording paper P is rich in glossiness because the image surface is transferred with the surface smoothness of the intermediate transfer belt 20 as it is. Further, the image is satisfactorily fixed on the recording paper P without causing the fixing degree to be insufficient.

In particular, in this image forming apparatus, when the intermediate transfer belt 20 is subjected to stress due to electric discharge at the time of primary transfer and heating at the time of passing through the preheating body 40 and the transfer fixing device 30, the adhesive force with the toner increases. Nevertheless, it is considered that the reason why the image having a high glossiness is obtained without insufficient fixing degree as described above is mainly because the release agent non-exposed type toner E acts as follows.

That is, as shown in FIG. 2A, since the release agent 5 of the toner E is not exposed on the surface of the toner particles but is dispersed inside the particles, At the stage heated by the heating element 40, the release agent 5 does not melt and cover the toner surface, and the release agent is eluted on the toner surface only at the stage where the transfer and fixing device 30 is heated and pressurized. At the time of the transfer fixing, it is ensured that the binder resin of the toner E contributing to the degree of fixation sufficiently contacts the recording paper P, and the release agent contributing to the reduction of the toner adhesion of the intermediate transfer belt 20. 5
Is considered to be ensured between the toner image and the intermediate transfer belt 20.

[0052]

The present invention will be further described below with reference to examples.

Example 1 First, a two-component developer containing a release agent non-exposed toner E used in the image forming apparatus of the present invention was prepared.

<Resin Particle Dispersion A Used in First Step>
Preparation of Styrene: 370 g n-butyl acrylate: 30 g Acrylic acid: 6 g Dodecanethiol: 24 g Carbon tetrabromide ... 4 g A mixture obtained by mixing and dissolving the above components was mixed with 6 g of a nonionic surfactant (Nonipol 400, manufactured by Sanyo Chemical Co., Ltd.) and 10 g of an anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Was dissolved in 550 g of ion-exchanged water in a flask, dispersed and emulsified in a flask, and while slowly mixing for 10 minutes, 50 g of ion-exchanged water in which 4 g of ammonium persulfate was dissolved was introduced to perform nitrogen substitution. Next, the contents of the flask were heated to 70 ° C. in an oil bath while stirring, and the emulsion polymerization was continued for 5 hours. Thereby, the average particle size is 155 nm, the glass transition point is 59 ° C.,
Resin particle dispersion A in which anionic resin particles having a weight average molecular weight (Mw) of 12,000 were dispersed was obtained.

<Resin Particle Dispersion B Used in the First Step>
Preparation of Styrene: 280 g n-butyl acrylate: 120 g Acrylic acid: 8 g

A mixture obtained by mixing and dissolving the above was mixed with 6 g of a nonionic surfactant (Nonipol 400) and 12 g of an anionic surfactant (Neogen SC) in 550 of ion-exchanged water.
g in a flask and dispersed and emulsified in a flask.
While slowly mixing for 3 minutes, 3 g of ammonium persulfate
50 g of ion-exchanged water in which was dissolved was added, and nitrogen replacement was performed. Next, while stirring the inside of the flask, the content was heated to 70 ° C. in an oil bath, and emulsion polymerization was continued for 5 hours. Thereby, the average particle size is 105 n.
m, a glass transition point of 53 ° C., and a resin particle dispersion B in which anionic resin particles having a Mw of 550,000 are dispersed. <Preparation of Colorant Dispersion Used in First Step> Carbon black: 50 g (Cabot: Mogal L) Nonionic surfactant: 5 g (Sanyo Chemical: Nonipol 400) ion-exchanged water 200 g

Mix and dissolve the above, and homogenize
(IKA: Ultra Turrax) for 10 minutes to obtain a colorant dispersion in which a colorant (carbon black) having an average particle size of 250 nm is dispersed. <Preparation of Release Agent Dispersion Used in First Step> Paraffin Wax 50 g (Nippon Seiro Co., Ltd .: HNP0190, melting point 85 ° C.) Cationic surfactant 5 g (Kao 200 g of ion-exchanged water is heated to 95 ° C., dispersed by a homogenizer (Ultra Turrax T50, manufactured by IKA), and then dispersed by a pressure discharge homogenizer. Having an average particle size of 55
A release agent dispersion having a release agent (wax) of 0 nm dispersed therein was obtained.

<Preparation of Aggregated Particles in First Step> Resin Particle Dispersion A: 120 g Resin Particle Dispersion B: 80 g Colorant Dispersion: 30 g Release Agent Dispersion: 40 g Cationic surfactant: 1.5 g (Kao Corporation: Sanisol B50) The above were mixed in a round stainless steel flask with a homogenizer (IKA: Ultra Turrax T50). Then, the mixture was heated to 48 ° C. while stirring the inside of the flask with an oil bath for heating. After maintaining this state at 48 ° C. for 30 minutes, the dispersion was observed with an optical microscope, and it was confirmed that aggregated particles of about 5 μm had been formed.

<Preparation of Adhered Particles in Second Step>
After slowly adding 60 g of the resin particle dispersion liquid A to the aggregated particle dispersion liquid prepared in the step 1, the temperature of the heating oil bath was raised and the temperature was kept at 50 ° C. for 1 hour. When the inside of the flask was observed with an optical microscope, it was confirmed that adhered particles having a particle size of about 5.7 μm were generated.

<Preparation of Toner by Third Step> To the dispersion prepared in the second step, 3 g of an anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen SC) was added, followed by addition of a stainless steel flask. Was sealed, heated to 105 ° C. while stirring with a magnetic seal, and maintained for 3 hours.
Then, after cooling, the reaction product in the dispersion is filtered, sufficiently washed with ion-exchanged water, and then dried,
Black (K) toner particles were obtained.

Next, the average particle size of the obtained toner was measured by a Coulter counter and found to be 5.6 μm.
When the toner was observed with a transmission electron microscope, no wax-like material was exposed on the toner surface. Finally, after externally adding inorganic particles as a charge control agent to the toner, the toner was mixed with a ferrite carrier coated with polymethyl methacrylate and having an average diameter of 50 μm to obtain a two-component developer.

<Evaluation Test> Next, the obtained two-component developer containing the release agent non-exposed toner E was used in (the developing device 14 of) the color image forming apparatus according to the first embodiment. The following test images were formed to evaluate the occurrence of gloss ghost and the degree of fixation.

In the test image formation, a rectangular solid image A shown in FIG.
After continuous formation on 000 sheets, a halftone image B including an image area wider than the solid image A was formed on the recording paper P as shown in FIG. The conditions for forming this test image are as follows.
The toner image on the intermediate transfer belt 20 before transfer and fixing was heated to its melting temperature by the preheating body 40 while rotating at a moving speed of m / sec. Further, the heating temperatures of the heating roll 31 and the pressure roll 32 in the transfer fixing device 30 were both set to 125 ° C.

The evaluation regarding the gloss ghost is as follows.
When the image B was formed in the test image formation, FIG.
As shown in FIG. 3C, a gloss ghost C composed of an area with a changed gloss corresponding to the solid image A in the area of the image B.
The test was performed by checking whether or not bleeding occurred. As a result, generation of gloss ghost was hardly confirmed.

The evaluation of the degree of fixation is performed by bending the recording paper P on which the solid image A is formed along the dotted line S shown in FIG. 4A so that the image is on the inside, and gently wiping the fold with a soft cloth. The inspection was performed by examining the state of the missing image A when the image A was lost. As a result, it was confirmed that no image (toner) was missing and a sufficient degree of fixation was obtained.

Further, the toner image on the intermediate transfer belt 20 after passing through the preheating plate 40 and before reaching the transfer fixing device 30 (toner particles thereof) was observed with a transmission electron microscope. Although it was in a molten state, it was confirmed that the release agent did not elute at the surface.

Comparative Example 1 A two-component developer containing the toner used in Comparative Example 1 was prepared as follows.

First, in this example, a toner was manufactured by a wet toner manufacturing method employing the first step and the third step in the method of manufacturing a toner performed in Example 1.

Resin Particle Dispersion A: 180 g Resin Particle Dispersion B: 80 g Colorant Dispersion: 30 g Release Agent Dispersion: 40 g Cation Surfactant: 1.5 g (Sanisol B50, manufactured by Kao Corporation) After mixing and dispersing the above components in a round stainless steel flask using a homogenizer (Ultra Turrax T50), the flask was stirred in a heating oil bath. While 50
Heated to ° C. After maintaining this state at 50 ° C. for 90 minutes, the dispersion was observed with an optical microscope and found to be about 5.8.
It was confirmed that μm aggregated particles were generated.

After adding 3 g of an anionic surfactant (Neogen SC) to the dispersion thus prepared, the stainless steel flask was sealed and heated to 105 ° C. while continuing to stir using a magnetic seal. Hold for hours. And
After cooling, the reaction product in the dispersion was filtered, sufficiently washed with ion-exchanged water, and dried to obtain black (K) toner particles.

Next, when the average particle size of the obtained toner was measured by a Coulter counter, it was 6.9 μm. Further, when this toner was observed with a transmission electron microscope, a lot of exposure of the wax-like substance to the toner surface was observed, and a state in which the wax-like substance was released was slightly confirmed. Finally, after externally adding inorganic particles as a charge controlling agent to the toner, the toner was mixed with the same ferrite carrier used in Example 1 to obtain a two-component developer.

<Evaluation Test> Next, the obtained two-component developer containing the toner was used in the color image forming apparatus according to the first embodiment in the same manner as in the first embodiment. After the formation, the occurrence of gloss ghost and the degree of fixation were evaluated.

As a result, almost no occurrence of gloss ghost was observed in the evaluation of gloss ghost. Regarding the evaluation of the fixing degree, it was confirmed that toner was missing along the fold and cracks were generated at the fold, and it was confirmed that a sufficient fixing degree was not obtained. Further, similarly to the first embodiment,
Observation of the toner image on the intermediate transfer belt 20 after passing through the preheating plate 40 and before reaching the transfer fixing device 30 revealed that
It was confirmed that the toner image was melted and the surface of the toner was covered with the release agent.

Comparative Example 2 The two-component developer used in Comparative Example 2 was prepared as follows. In this example, the toner was manufactured by a toner manufacturing method by kneading and pulverizing.

4 parts by weight of carbon black and 5 parts by weight of carnauba wax having a melting point of 85 ° C. are mixed with 100 parts by weight of a polyester resin, melted and kneaded by an extruder, cooled, and pulverized by a jet mill. did. Then, the pulverized material is classified to have a volume average diameter of 7 μm.
Of black toner was obtained.

Observation of the obtained toner with a transmission electron microscope revealed that a very large amount of wax-like substances were exposed on the surface of the toner. Next, after externally adding inorganic particles as a charge control agent to the toner, the toner was mixed with the same ferrite carrier used in Example 1 to obtain a two-component developer.

<Evaluation Test> Next, the two-component developer containing the obtained toner was used in the color image forming apparatus according to the first embodiment in the same manner as in the first embodiment. After the formation, the occurrence of gloss ghost and the degree of fixation were evaluated.

As a result, in the evaluation of gloss ghost, almost no occurrence of gloss ghost was confirmed. Regarding the evaluation of the fixing degree, it was confirmed that toner was missing along the fold and cracks were generated at the fold, and it was confirmed that a sufficient fixing degree was not obtained. Further, similarly to the first embodiment,
Observation of the toner image on the intermediate transfer belt 20 after passing through the preheating plate 40 and before reaching the transfer fixing device 30 revealed that
It was confirmed that the toner image was melted and the surface of the toner was covered with the release agent.

Comparative Example 3 A two-component developer used in Comparative Example 3 was prepared as follows. In this example, the toner was produced by a method of producing a toner by kneading and pulverizing as in Comparative Example 2.

100 parts by weight of the polyester resin was mixed with 4 parts by weight of carbon black, melted and kneaded by an extruder, cooled, and pulverized by a jet mill. Then, the pulverized product was classified to obtain a black toner having a volume average diameter of 7 μm containing no release agent.

After externally adding inorganic particles as a charge control agent to the obtained toner, it was mixed with the same ferrite carrier used in Example 1 to obtain a two-component developer.

<Evaluation Test> Next, the two-component developer containing the obtained toner was used in the color image forming apparatus according to the first embodiment in the same manner as in the first embodiment. After the formation, the occurrence of gloss ghost and the degree of fixation were evaluated.

As a result, regarding the evaluation of gloss ghost, occurrence of gloss ghost was confirmed. Also,
When the gloss of the ghost was measured with a gloss meter, a decrease in gloss of 10 was confirmed. Further, regarding the evaluation of the fixing degree, it was confirmed that there was no toner missing and a sufficient fixing degree was obtained.

[0084]

As described above, according to the image forming apparatus of the present invention, the image forming apparatus uses a toner containing a release agent and utilizes the simultaneous transfer fixing method with preheating. Nevertheless, problems such as deterioration of image gloss due to deterioration of the surface roughness of the image carrier can be easily and reliably prevented without causing insufficient fixing of the toner image. It is possible to stably form a high-quality image rich in feeling.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an image forming apparatus of the present invention.

FIG. 2A is a cross-sectional view illustrating a release agent non-exposed type toner used in the present invention, and FIG. 2B is a cross-sectional view illustrating a conventional toner in which a release agent is exposed.

FIG. 3 is a schematic diagram illustrating a main part of the image forming apparatus according to the first embodiment;

FIG. 4A shows an image A formed at the time of forming a test image.
FIG. 7B is an explanatory diagram showing an image B formed at the time of forming a test image, and FIG. 7C is an explanatory diagram showing a state of occurrence of a gloss ghost.

FIG. 5 is a conceptual diagram showing a conventional image forming apparatus using a simultaneous transfer fixing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Carrier, 3, 30 ... Transfer fixing device,
4: Preheating means, 5: Release agent, 10: Image forming unit (image forming device), 40: Preheating plate, P: Recording paper (recording medium), T: Toner image, E: Exposed release agent Type toner.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H005 AA06 AA11 CA14 2H033 AA10 AA39 AA49 BA07 BA12 BA25 BA27 BA42 BA58 BB01 BB10 BB28 BE09 2H078 AA01 BB01 CC06 DD39 DD40 DD42 DD51 DD56 2H200 GA23 GA44 GA47 GB22 GB23 GB27 GB27 GB27 GB27 GB27 GB27 JC03

Claims (2)

[Claims] An image forming apparatus that forms a toner image in accordance with image information, an image carrier that circulates to carry and transport the toner image formed by the image forming apparatus, and the image carrier A transfer and fixing device for transferring and fixing the toner image on the recording medium by heating and pressurizing the toner image, and preliminary heating the toner image on the image carrier between the transfer and fixing device and the image forming device In the image forming apparatus provided with a preliminary heating unit, a release agent non-exposed toner obtained by dispersing a release agent inside toner particles without exposing the release agent to the surface of the toner particles is used as a toner constituting the toner image. An image forming apparatus. 2. The release agent non-exposed toner contains at least a binder resin, a colorant, and a particle containing a release agent.
2. The image forming apparatus according to claim 1, wherein the toner is a toner comprising at least a binder resin and a surface layer of a particle that does not contain a release agent, so as to cover a surface inside the particle. 3.