JP2002341585A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely prevent trouble such as the deterioration of image gloss caused by the deterioration of the surface roughness of an intermediate transfer body 2 circularly moving while carrying a toner image T formed by an image producing device 1 without inducing the central blanking phenomenon of the toner image T 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 the cleaning of the intermediate transfer body by a heating contact member. SOLUTION: In this image forming device equipped with a transfer fixing device 3 and a heating type cleaning device 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 image forming apparatus formed by an image forming apparatus. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a simultaneous transfer fixing method for transferring a toner image from an intermediate transfer body that carries and conveys the toner image to a recording medium and fixing the toner image at the same time.

[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. 7 is known. Such an image forming apparatus mainly includes
An image forming unit 100 for forming a toner image T based on image information on an image carrier 110 such as a photosensitive drum by an electrophotographic process (charging, image exposing, developing, etc.) and the like; An endless belt-shaped intermediate transfer body 200 carrying and circulating the toner image T to be primarily transferred after being transferred, and transferring the toner image T on the intermediate transfer body 200 to a recording medium P such as a recording sheet or an OHP sheet. The image forming apparatus mainly includes a transfer fixing device 300 that performs fixing simultaneously with the next transfer.

[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. Further, the transfer and fixing device 300 includes the intermediate transfer body 2
The heating roller 310 and the pressure roller 320 rotate while being pressed against each other while sandwiching the recording medium P. The recording medium P is introduced between the pressure roller 320 and the intermediate transfer belt 200 at a predetermined timing. And let it pass.

In this image forming apparatus, after a plurality of toner images T corresponding to image information are formed on an image carrier 110 by an image forming unit 100, the toner images T are transferred to an intermediate transfer member 200. Is primarily transferred electrostatically by a transfer unit. Subsequently, the toner image T transferred to the intermediate transfer member 200 is conveyed to the transfer fixing device 300, and is pressed against the heating roll 310 together with the recording medium P introduced between the intermediate transfer member 200 and the pressure roll 320. By being heated and pressurized by the roll 320, the toner image is secondarily transferred onto the recording medium P and is fixed at the same time. Subsequently, the recording medium P on which the toner image T has been secondarily transferred is brought into close contact with the outer peripheral surface of the intermediate transfer body 200, and is held on a belt support roll (peeling roll) 230.
Is transported to the peeling position where is present, and is peeled off from the intermediate transfer member 200 while being sufficiently cooled during that time. 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.

[0007] In order to suppress such deterioration of the image gloss, it is necessary to suppress an increase in the adhesive force of the intermediate transfer member to the toner due to discharge or heating. It is considered necessary to remove adhered substances such as toner and paper dust remaining on the transfer body 200.

Here, as a measure for suppressing an increase in the adhesion of the intermediate transfer member to the toner, a toner containing a release agent is interposed between the intermediate transfer belt and the toner. (Hereinafter, also referred to as "release agent-containing toner") is effective, and it has been confirmed by experiments of the present inventors that the deterioration of gloss can be reduced.

On the other hand, as a countermeasure for removing the deposits on the intermediate transfer body after the transfer and fixing and after the peeling of the recording paper, as shown in FIG. It is effective to install a heating-type cleaning device 400 that makes the cleaning member 410 come into contact with the transfer surface of the intermediate transfer body 200 to remove the adhered substance and clean.

However, even when the above-described toner containing a release agent is used in the image forming apparatus of the simultaneous transfer fixing type and the heating type cleaning device 400 is installed, the effect can be obtained at first, but the image can be obtained. As formation was continuously performed, it was confirmed that hollow images occurred in images such as fine lines and characters. In addition, this hollowing phenomenon is a phenomenon in which the toner images of the second color, the third color, and the like, which are superimposed and transferred after the second color, the third color, and the like, are remarkably formed at the time of forming the color image formed by multi-transferring the toner images of a plurality of colors. It has also been confirmed that there is.

The present invention has been made in view of such circumstances, and an object thereof is to utilize a simultaneous transfer fixing method involving cleaning of an intermediate transfer member by a heating contact member as exemplified above. As an image forming apparatus, the problem of deterioration of image gloss caused by deterioration of surface roughness of an intermediate transfer member that circulates and moves while carrying a toner image formed by an image forming device is induced into a toner image. It is an object of the present invention to provide an image forming apparatus which can easily and surely prevent the occurrence of an image, and can stably form a high-quality image rich in glossiness.

[0012]

Means for Solving the Problems The present inventors first investigated the cause of the above-mentioned problem, and found that the hollow phenomenon already occurred in the toner image transferred from the image forming apparatus to the intermediate transfer member. Turned out to be.

On the other hand, this hollowing phenomenon is caused by a heating type cleaning device for the intermediate transfer member using a heating contact member and a releasing agent-containing toner as a countermeasure for preventing the deterioration of the image gloss as described above. When at least one of them is not used (when the heating-type cleaning device is not provided, and when a toner containing no release agent is used, or when both are used), it is confirmed that no generation occurs.

Therefore, the state of the image forming apparatus when the heating type cleaning device was installed was examined. As a result, the recording medium after the transfer and fixing was peeled off and cooled after continuous image formation. The transfer body is heated again by the heating contact member of the heating type cleaning device, and the temperature gradually increases,
As a result, it was found that the surface temperature of the image carrier of the image forming apparatus in contact with the intermediate transfer member gradually increased (see FIG. 5). In addition, when the toner containing the release agent was examined again, the toner was so-called pulverized produced by mixing a binder resin, a colorant, a release agent, and the like, melting, kneading, cooling, and pulverizing. Toner,
It was found that the release agent was exposed on the toner surface.

[0015] From these facts, the hollowing-out phenomenon is formed on the heated image carrier by increasing the surface temperature of the image carrier via the intermediate transfer member by heating of the heating type cleaning device. Since the release agent of the toner containing the release agent forming the toner image is slightly softened, the softening of the release agent increases the cohesive force between the toners and the adhesion of the toner to the image carrier. In addition, it is presumed that the toner image portion in which the cohesive force and the adhesive force of the toner are increased is mainly generated due to the fact that the toner image portion is not transferred from the image carrier to the intermediate transfer member.

Incidentally, as a measure for preventing the occurrence of the hollow phenomenon, it is conceivable to arrange a cooling device for cooling the image carrier itself to suppress a rise in the temperature of the image carrier. Since the carrier is in contact with the intermediate transfer member in a heated state, the cooling effect cannot be expected by the cooling device as the number of image formation increases, and the environmental temperature in the device increases. Also, the cooling effect is reduced. Furthermore, the installation of the cooling device causes an increase in the size of the image forming device. As another preventive measure for the above-mentioned hollowing-out phenomenon, it is conceivable not to install the heating-type cleaning device itself. In that case, however, the rise in temperature of the intermediate transfer body and, consequently, the temperature of the image carrier is suppressed. Although effective in preventing the occurrence of a dropout phenomenon, it is impossible to prevent the above-described deterioration in image gloss.

Accordingly, the inventors of the present invention have conducted intensive studies based on such findings to achieve the above object. As a result, the inventors have found that a toner containing a release agent and having an increased temperature, etc. Performing image formation by a simultaneous transfer fixing method using a toner that does not increase the cohesive force between the toners and the adhesion of the toner to the image carrier due to the softening of the release agent even if heated. As a result, they have found that the above 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 for forming a toner image T corresponding to image information on an image carrier 1a, and a toner image T on the image carrier 1a formed by the image forming apparatus 1 The intermediate transfer member 2 that moves in a circulating manner, a transfer / fixing device 3 that simultaneously heats and pressurizes the toner image T on the intermediate transfer member 2 to transfer the toner image to the recording medium P and fixes the toner image T, An image forming apparatus comprising: a heating-type cleaning unit 4 that removes and adheres to the intermediate transfer body 2 after the recording medium P to be transferred and peeled is removed by a heated contact member 4a. As the toner constituting the toner image T, a release agent non-exposed toner obtained by dispersing the release agent inside the toner particles without exposing the release agent to the surface of the toner particles is used.

Here, the image forming apparatus 1 can form a monochrome or color toner image on the image carrier 1a in accordance with image information such as read image information of a document and input image information input from the outside. The image forming method and the like are not particularly limited as long as they are suitable. As the image carrier 1a, an endless belt-shaped or drum-shaped photoconductor, a dielectric, or the like is used. Further, the quantity of the image carrier 1a to be used may be either singular or plural. The intermediate transfer belt 2 may be in the form of an endless belt or a drum, and may be any as long as it can carry and circulate the toner image transferred from the upper image carrier 1a.

The transfer / fixing device 3 may be any device that has a function of simultaneously heating and pressing the toner image on the intermediate transfer belt 2 to transfer the toner image to a recording medium and fixing the toner image. For example,
An apparatus in which two or more rotating bodies (such as a rotating roll and a rotating belt) are arranged to be pressed against each other with the intermediate transfer 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. A dashed line with an arrow in FIG. 1 indicates a conveyance path of the recording medium P.

The heating-type cleaning means 4 may be any device capable of cleaning the transfer surface of the intermediate transfer member 2 by bringing a heated cleaning contact member 4a into contact with the heated transfer contact member 4a to remove extraneous matter such as toner. . The contact member 4 has, for example, a configuration in which a heating means for heating the adhesive layer is provided on a base material such as a roll or a blade, which is formed by coating a synthetic resin as an adhesive layer, which exhibits adhesiveness by heating. Is used.

In this image forming apparatus, the intermediate transfer member 2 is located between the transfer fixing device 3 and a separation point where the recording medium P is separated from the intermediate transfer member 2 after passing through the device 3.
Further, a cooling device for cooling the recording medium P may be provided. Further, if necessary, the toner image on the intermediate transfer body 2 may be preliminarily heated to a predetermined temperature (for example, a temperature at which the toner melts) between the image forming apparatus 1 and the transfer and fixing apparatus 3. A possible preheating means may be provided.

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 manufacturing method, the aggregating step is performed in two stages, and in the first stage (first step), 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).

[0027]

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 has four operations for forming toner images of respective color components of yellow (Y), magenta (M), cyan (C), and black (K) based on image information by electrophotography. Image unit 10Y,
10M, 10C, and 10K, and the respective image forming units 10
An intermediate transfer belt 20 to which each toner image formed by Y, 10M, 10C, and 10K is 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 belt cleaner 25 that removes and cleans adherents such as toner and paper dust remaining on the intermediate transfer belt 20 between the transfer fixing device 30 and the image forming unit 10Y. 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 is formed by forming a photosensitive layer made of an inorganic photosensitive material or an organic photosensitive material 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 driving roll 21 and a tension roll 22, which are driven to rotate by a rotary driving source (not shown), and a plurality of supporting 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-mentioned 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 belt cleaner 25 adheres a synthetic resin (eg, polyester) compatible with the toner in a film shape to the surface of the hollow metal roll, and heats and cleans the inside of the metal roll with an electric heat source. 26, and the heating and cleaning roll 26 is arranged in contact with the transfer surface of the intermediate transfer belt 20. Then, at the time of cleaning, the surface of the heating cleaning roll 26 is heated to a predetermined temperature by an electric heat source, and the synthetic resin film is used in a state of melting and showing adhesiveness.

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 fixing is used. The blower fan is configured to take in air outside the apparatus through a duct and send air to the intermediate transfer belt 20 to which the recording paper P is in close contact. 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, the driving roll 21 and the heating roll 3
A pre-heating member 40 for heating the toner image on the intermediate transfer belt 20 before the transfer and fixing to a temperature equal to or higher than the melting temperature of the toner may be disposed between the first and second transfer members. As the preheating body 40, for example, a contact plate made of a material having good thermal conductivity (for example, aluminum) that makes a curved surface contact with the inner peripheral surface of the intermediate transfer belt 20 in the section, and a contact plate of the contact plate It is possible to use an electric heating source (for example, a silicon rubber heater) which is installed on the surface opposite to the contact surface and heats.

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 for producing the toner E, it is desirable that the average particle size of the binder resin particles 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 carried out 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, for each additional mixing, dispersing the dispersion of the added resin particles and the matrix aggregated particles in a temperature range not higher than the glass transition temperature of the resin particles used in the first step. May be raised. In this case, generation of free particles can be suppressed.

In the color image forming apparatus having such a basic structure, 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, the toner image primarily transferred to the intermediate transfer belt 20 is sent to the transfer fixing device 30 as the intermediate transfer belt 20 rotates. When the preheating body 40 is installed, the preheating body 40
, The intermediate transfer belt 20 on which the primary transfer is performed
The upper toner image is heated in advance and brought into a state of being appropriately melted. The image on the intermediate transfer belt 20 is heated and pressed by the heating roll 31 and the pressure roll 32 together with the recording paper P supplied between the intermediate transfer belt 20 and the pressure roll 32 in the transfer fixing device 30. Thus, the toner image is secondarily transferred onto the recording paper P and is fixed at the same time.

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. . Further, the transfer surface of the intermediate transfer belt 20 after the recording paper P has been peeled off is cleaned by removing the attached matter by the adhesive action of the heating cleaning roll 26 of the belt cleaner 25.

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. In addition, the image is good without a hollow phenomenon.

In particular, in this image forming apparatus, a toner containing a release agent is used, and a heat cleaning roll 2 is used.
In addition to installing the belt cleaner 25 with 6
Although 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 transfer fixing device 30 and the like, the adhesive force with the toner is increased, but the glossiness is not lost as described above. The reason why an image rich in toner is obtained is considered mainly because the release agent non-exposed toner E acts as follows.

That is, as shown in FIG. 2A, since the release agent 5 of the toner E is not exposed to the surface of the toner particles but dispersed inside the toner particles, the belt cleaner 25 having the heating cleaning roll 26 is provided. Even if the temperature of the intermediate transfer belt 20 and the photosensitive drum 11 rises due to the influence of the heating action of the toner, the release agent 5 inside the particles softens due to the heating by the heated intermediate transfer belt 20 and the photosensitive drum 11 and the toner surface The release agent 5 is eluted on the toner surface only when heated and pressurized in the transfer fixing device 30 without being eluted. As a result, the toner (E) constituting the toner image is transferred to the photosensitive drum 11 or the intermediate transfer device. It is considered that the cohesive force between the toners and the adhesion of the toner to the photosensitive drum 11 are not increased by the softening of the release agent 5 when the toner is on the belt 20. In addition, the release agent is eluted on the toner surface by heating and pressurizing during transfer fixing, so that the intermediate transfer belt 2
It is considered that the release agent 5 contributing to the reduction of the toner adhesion force of 0 is ensured between the toner image and the intermediate transfer belt 20.

[0054]

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 In a flask prepared by dissolving 6 g of (Nonipol 400) and 12 g of an anionic surfactant (Neogen SC) in 550 g of ion-exchanged water, dispersing and emulsifying the mixture in a flask, and slowly mixing for 10 minutes, ion dissolving 3 g of ammonium persulfate. 50 g of exchanged water was charged, 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. Thus, a resin particle dispersion B in which anionic resin particles having an average particle size of 105 nm, a glass transition point of 53 ° C., and Mw of 550,000 were dispersed was obtained.

<Preparation of Colorant Dispersion Used in First Step> Carbon black: 50 g (Cabot Corporation: Mogal L) Nonionic surfactant: 5 g (Sanyo Chemical Co., Ltd.) Company: Nonipol 400) Ion-exchanged water: 200 g or more were mixed and dissolved, and a homogenizer (manufactured by 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 Corporation: Sanisol B50) Ion-exchanged water: 200 g The above was heated to 95 ° C. and dispersed by a homogenizer (IKA: Ultra Turrax T50), followed by a pressure discharge homogenizer. Dispersed, average particle size is 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 (Kanisha: Sanisol B50) The above components 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 in Third Step> To the dispersion prepared in the second step, 3 g of an anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added, and then a stainless steel flask was added. 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. Further, toners of other colors (Y, M, C) were formed in the same manner (different colorants).

Next, the average particle size of each of the obtained toners 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. Then, the following test image formation was performed to evaluate the occurrence state of the hollow defect phenomenon and the gloss ghost.

First, the evaluation of the state of occurrence of the hollowing-out phenomenon was carried out by first determining a single color (cyan C, magenta M, yellow Y) obtained from one color toner image as shown in FIG.
Three dots each of a test thin line image composed of a secondary color (blue B, green G, red R) obtained by superimposing color toner images and a tertiary color (black PK) obtained by superimposing three color toner images A test image is formed on recording paper P (horizontal feed A4 size paper) with a line thickness of 5 dots and 8 dots, and this thin line image is formed continuously on 500 recording papers P. went. And
At the time of forming the first, 200th, and 500th images at this time, the state of the occurrence of the hollow image of the transferred image on the intermediate transfer belt 20 before the transfer and fixing is determined (by stopping the intermediate transfer belt 20). ) Observed with a loupe and examined. Table 1 shows the results.

The conditions during the test image formation were such that the intermediate transfer belt 20 was rotated at a moving speed of 265 mm / 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. Further, the surface temperature of the heating / cleaning roll 26 of the belt cleaner 25 was set to be kept at 105 ° C. by heating.

[0067]

[Table 1]

In forming the test image, the surface temperature of the intermediate transfer belt 20 (intermediate transfer body) before entering the image forming device 11Y and the photosensitive drum 1 of each image forming device 10
1 (average) surface temperature was measured. The result is shown in FIG.

On the other hand, the evaluation regarding the gloss ghost was performed by first forming a rectangular solid image A shown in FIG. 6A continuously on 10,000 sheets of recording paper (A4 size paper fed in the horizontal direction), and then, as shown in FIG. As shown in FIG. 6, a test image was formed to form a halftone image B having a larger image area than the solid image A on the recording paper P. Then, when the image B is formed in the test image formation,
As shown in FIG. 6C, the determination was made by checking whether or not a gloss ghost C composed of an area with a changed gloss corresponding to the solid image A occurred in the area of the image B. As a result, generation of gloss ghost was hardly confirmed. The conditions for forming the tension image are the same as those for forming the test image.

As is clear from the above results, by using the release agent non-exposed toner E as in Example 1,
Even when the temperature of the photosensitive drum 11 or the intermediate transfer belt 20 rises, the thin line image does not suffer from the hollow phenomenon and the surface roughness of the intermediate transfer belt 20 does not change. Obtained.

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 the 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 prepared dispersion, 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. In addition, other colors (Y,
The toners (M, C) were formed in the same manner (different colorants).

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. The formation was performed to evaluate the state of occurrence of a hollow phenomenon and a glossiness ghost. Table 2 shows the evaluation results regarding the hollow phenomenon.

As a result, as to the evaluation of the hollow phenomenon, as apparent from the results in Table 2, the hollow occurs from the 200th sheet (especially, a secondary line or tertiary color fine line image), and 500 It was noticeable in the first sheet. Also at the time of forming a test image relating to this hollowing-out phenomenon, when the surface temperatures of the intermediate transfer belt 20 and the respective photosensitive drums 11 were measured in the same manner as in Example 1, almost the same results as in Example 1 (FIG. 5) were obtained. Obtained. Regarding the evaluation of gloss ghost, almost no occurrence of gloss ghost was confirmed.

[0078]

[Table 2]

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. Further, toners of other colors (Y, M, C) were formed in the same manner (different colorants).

Observation of the obtained toner with a transmission electron microscope revealed that a very large amount of wax-like substances were exposed on the toner surface. 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. The formation was performed to evaluate the state of occurrence of a hollow phenomenon and a glossiness ghost. Table 3 shows the evaluation results regarding the hollow phenomenon.

As a result, as to the evaluation of the hollow phenomenon, as is clear from the results in Table 3, the hollow occurs from the 200th sheet (especially, a thin line image of the secondary color or the tertiary color). It was noticeable in the first sheet. Also at the time of forming a test image relating to this hollowing-out phenomenon, when the surface temperatures of the intermediate transfer belt 20 and the respective photosensitive drums 11 were measured in the same manner as in Example 1, almost the same results as in Example 1 (FIG. 5) were obtained. Obtained. Regarding the evaluation of gloss ghost, almost no occurrence of gloss ghost was confirmed.

[0084]

[Table 3]

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.

4 parts by weight of carbon black was mixed with 100 parts by weight of the polyester resin, 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. Further, toners of other colors (Y, M, C) were formed in the same manner (different colorants).

After externally adding inorganic particles as a charge controlling 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. The formation was performed to evaluate the state of occurrence of a hollow phenomenon and a glossiness ghost. Table 4 shows the evaluation results regarding the hollow phenomenon.

As a result, as to the evaluation of the hollow phenomenon, as is clear from the results of Table 4, the first sheet was evaluated for 200 hours.
No void occurred in any of the sheets and the 500th sheet. Also at the time of forming a test image relating to this hollowing-out phenomenon, when the surface temperatures of the intermediate transfer belt 20 and the respective photosensitive drums 11 were measured in the same manner as in Example 1, almost the same results as in Example 1 (FIG. 5) were obtained. Obtained. Regarding the evaluation of the gloss ghost, the occurrence of a clear gloss ghost was confirmed. Further, when the gloss of the ghost was measured with a gloss meter, a decrease in gloss of 10 was confirmed.

[0090]

[Table 4]

[0091]

As described above, according to the image forming apparatus of the present invention, the simultaneous transfer fixing method using the toner containing the release agent and cleaning the intermediate transfer member by the heating contact member is used. Despite the use of an image forming apparatus, the problem of deterioration of image gloss due to deterioration of surface roughness of an intermediate transfer body can be easily and reliably prevented without inducing a dropout phenomenon of a toner image. As a result, it is possible to stably form a high-quality image rich in glossiness.

[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. 4 is an explanatory diagram showing a test thin line image formed at the time of forming a test image related to the evaluation of hollow spots.

FIG. 5 is a graph showing the results of measuring the surface temperatures of an intermediate transfer member and a photoreceptor during image formation on 500 recording sheets.

6A is an explanatory diagram showing an image A formed at the time of forming a test image related to glossiness ghost evaluation, FIG. 6B is an explanatory diagram showing an image B formed at the time of forming the test image, and FIG.
FIG. 3 is an explanatory diagram showing a state of occurrence of a gloss ghost.

FIG. 7 is a conceptual diagram illustrating a conventional image forming apparatus using a simultaneous transfer fixing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 1a ... Image carrier, 2 ... Intermediate transfer body, 3
Reference numeral 30: transfer fixing device, 4: heating type cleaning means, 4a: contact member, 5: release agent, 10: image forming unit (image forming device),
11 photosensitive drum (image carrier), 20 intermediate transfer belt, 25 belt cleaner (heating type cleaning means), 26
Heat cleaning roll (contact member), P: recording paper (recording medium), T: toner image, E: release agent non-exposed toner.

Continued on the front page F term (reference) 2H005 AA06 AA11 AA15 CA14 2H033 AA09 BA58 BB03 BB06 BB15 BB29 BB33 BB34 BE09 2H078 AA08 BB01 CC06 DD03 DD29 DD39 DD42 DD51 DD57 2H200 FA08 GA16 GA17 GA23 GA34 GA25 GA12 GB07 JC03 JC15 LB02 LB08 LB09 LB13 LB15 LB19 LB28 MA03

Claims (2)

[Claims] 1. An image forming apparatus for forming a toner image corresponding to image information on an image carrier, and an intermediate transfer body for carrying the toner image on the image carrier formed by the image forming apparatus and circulating and moving. A transfer and fixing device for transferring and fixing the toner image on the intermediate transfer body to a recording medium by heating and pressing, and the intermediate transfer after the recording medium on which the toner image is transferred and fixed by the transfer and fixing device is peeled off. An image forming apparatus comprising: a heating-type cleaning unit that removes and adheres to a body by a heated contact member and cleans the release agent. An image forming apparatus using a release agent non-exposed toner which is dispersed inside toner particles without being exposed. 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.