JP2003162125A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the secondary transfer efficiency of an image forming apparatus using an intermediate transfer body and to prevent the adverse effects of transparent toner (minute particles) adopted to improve the secondary transferring efficiency. <P>SOLUTION: In the image forming apparatus using the intermediate transfer body, an image forming unit forming an image with the transparent toner and color toner is provided and the transparent toner is reused. <P>COPYRIGHT: (C)2003,JPO

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 which employs an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art In the conventional electrophotographic technique, a toner image formed on an image carrier is transferred to a recording material or the like, and the toner image is fixed to the recording material by heat or pressure to obtain a recorded image. The transfer residual toner remaining on the image carrier after transferring the toner image is generally collected and discarded.

FIG. 10 shows a general image forming apparatus using an intermediate transfer member for explaining a conventional example. A charging step of uniformly charging the surface of the photosensitive drum, which is the first image carrier, an exposure step for forming a latent image on the charged surface of the image carrier, a developing step of attaching toner to the electrostatic latent image, First transfer step for transferring the toner image to the intermediate transfer body which is the second image carrier, second transfer step for transferring the toner image from the second image carrier onto the recording material, toner on the recording material P A fixing step of fixing the toner on the recording material P by heat and pressure, and a first step of collecting the transfer residual toner after the first transfer step on the first image carrier.
Cleaning step and a second cleaning step of collecting the transfer residual toner after the second transfer step on the second image carrier, and the collected first and second transfer residual toner images are It is transported to the toner collection container and is regularly discarded.

[0004]

In such an apparatus, the capacity of the recovery container is determined by the transfer residual toner amount (for a certain image density) and the number of regular replacement of the recovery container. , Requires a large space. Techniques for reusing recovered toner to improve this are disclosed in Japanese Patent Laid-Open No. 54-121133 and Japanese Patent Laid-Open No. 54-121133.
As described in JP-A-109842 and the like, which is actually performed, the transfer residual toner generated after the second transfer process described in the above-mentioned conventional example has a color mixture and is difficult to reuse.

In the second transfer step in which images of a plurality of colors are multi-transferred onto the intermediate transfer member and then the full-color toner images on the intermediate transfer member are collectively transferred onto the recording material, the temperature and humidity environment and The transfer efficiency greatly changes depending on the amount of toner deposited on the image carrier, and therefore the image quality is affected.

Particularly, after the primary transfer, an image is formed on the second image bearing member with toner of four colors of yellow, magenta, cyan and black, for example. These are
If the charge amount is almost the same, the transfer is relatively uniform. However, if there is a large difference in the charge amount of the toner for each color, the transfer efficiency also varies, and image defects are generated. Give birth. Further, since the charge density of the toner differs depending on the image density, the density gradation is affected.

In order to solve the above problems, it is realized by setting the transfer efficiency to almost 100% under all the above conditions.

As a technique for making the transfer efficiency 100%, an electrostatic latent image is formed on an image carrier described in Japanese Patent Laid-Open No. 01-134485, and a colorless transparent toner is adhered to the latent image, and then the latent image is formed. The colored toner is overlaid and developed. It is described that by doing this, almost 100% of the color toner is transferred. However, since the transparent toner is developed on the latent image on the photoconductor and then the colored toner is developed, a large development contrast is required to secure sufficient gradation, and the transparent toner and the colored toner are combined. If the balance of developing efficiency is different, large image defects are caused.

Further, in Japanese Unexamined Patent Publication No. 09-212010 and Japanese Unexamined Patent Publication No. 2000-259011, fine particles having a particle size smaller than the toner particle size are attached almost uniformly on the photosensitive member or the intermediate transfer member. , Increasing transfer efficiency and eliminating the cleaning step. However, the latent image may be disturbed due to exposure after coating the fine particles on the photoconductor. Further, in the configuration in which the fine particles are attached almost uniformly on the intermediate transfer member, since the fine particles having different physical properties from the toner are partially applied except for the image, they are attached to the secondary transfer roller which is the second transfer step. The image may be disturbed due to image defects caused by the above, or fine particles remaining on the intermediate transfer member may be transferred onto the photosensitive drum and filmed on the surface of the photosensitive drum. Further, in the case of an image forming apparatus that does not have a cleaning unit on the photosensitive drum, fine particles different from the toner component existing in the developing device increase as the durability progresses, which causes toner scattering and "fogging" image generation. Sometimes.

In view of the above, the object of the present invention is that the fine particles formed in the lowermost layer of the colored toner formed on the image carrier adhere to the photosensitive drum, the intermediate transfer belt or the like and are formed into a film or into a developing device. To prevent the image deterioration caused by the mixing of the fine particles, to minimize the waste toner, and to improve the secondary transfer efficiency to the recording material, thereby significantly reducing the toner consumption amount.

[0011]

An image forming apparatus for achieving the above object is characterized as follows.

A first image carrier for forming an electrostatic latent image on the surface and a plurality of developing devices for selectively adhering toner to the image carrier to visualize the latent image are visualized by the toner. In an image forming apparatus having a first transfer device for transferring the formed toner image to a second image carrier and a second transfer device for transferring the toner image on the second image carrier to a recording sheet, At least one of the toner images is a colorless and transparent transparent toner, and the transparent toner is image-formed on the lowermost layer of the toner image formed on the second image carrier.

The image signal of the transparent toner is determined according to the image signal of the colored toner for forming an image.

The transparent toner image collecting means on the second image carrier is provided downstream of the moving direction of the second image carrier of the second transfer device, and the transparent toner collected by the collecting means is transparent toner. It is characterized in that it has a carrying means for carrying to the above-mentioned developing device for use.

A charging means for charging the transparent toner to a polarity opposite to the polarity at the time of image formation is provided downstream of the moving direction of the second image carrier of the second transfer device and upstream of the first transfer device. It is characterized by

A feature is that the maximum amount of the transparent toner per unit area is controlled by each mode.

The above mode depends on the type of recording material.

The above-mentioned mode is characterized in that it is an environmental mode which is switched depending on temperature, humidity or both.

It is characterized in that it has means for detecting the amount of colored toner contained in the recovered transparent toner, and the means for recovering the transparent toner is made variable according to a predetermined signal value.

[0020]

Based on the above construction, it is possible to secure the improvement of the releasing property of the colored toner by the transparent toner from the intermediate transfer member, and the harmful effect of the transparent toner can be minimized. Reduction and improvement of image quality can be achieved.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a sectional view of an image forming apparatus for explaining the first embodiment.

An endless intermediate transfer belt 81 running in the direction of arrow X is arranged in the main body of the image forming apparatus. The intermediate transfer belt 81 is made of a dielectric resin such as polycarbonate, polyethylene terephthalate resin film, polyvinylidene fluoride resin film, or polyimide film. In this embodiment,
In order to realize the elimination of the charge removal mechanism of the intermediate transfer belt 81 and to satisfy the high durability, the volume resistivity is 1 × 10 ⁸ to 1 × 10.
A conductive polyimide having a conductive carbon black dispersion of ¹² Ω · cm and a thickness of 50 to 150 μm is used. Volume resistivity is R834 manufactured by Advantest Corporation as a measuring instrument.
It is a value when a voltage of 100 V is applied for 10 seconds using a probe having a main electrode outer diameter of φ50 and a guard electrode inner diameter of φ70 according to JIS-K6911 method.

Above the intermediate transfer belt 81, five image forming portions Pa, Pb, Pc, P having substantially the same structure are provided.
d and Pt are arranged in series. The configuration of the image forming unit Pa will be described as an example. The image forming portion Pa includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1a that is rotatably arranged. Around the photosensitive drum 1a, process devices such as a primary charger 22a and a developing device 23a are arranged. Other image forming units Pb, Pc, P
d and Pt have the same configuration as that of the image forming portion Pa, and only the photosensitive drums 1b, 1c, and 1d are shown in FIG. These image forming units 1a, 1b, 1
The difference between c, 1d, and 1t is that each forms a toner image of each color of magenta, cyan, yellow, and black, and a transparent toner image.

A magenta toner, a cyan toner, a yellow toner, a black toner, and a transparent toner are stored in the developing units arranged in the respective image forming sections.

First, when the original is read, magenta, cyan,
The image signal based on the yellow and black components is determined. Then, the image signal for forming the transparent toner is determined according to the image signal value. In this embodiment, the amount of transparent toner is determined according to the integration of image signal values. FIG. 2 shows the relationship between the amount of transparent toner applied and the transfer efficiency for each amount of applied colored toner. From this figure, it can be seen that the required transparent toner amount differs depending on the applied amount of the colored toner. Further, the secondary transfer efficiency can be improved by forming the transparent toner on the intermediate transfer belt. However, if the transparent toner is formed on the intermediate transfer belt 81 more than necessary, the color toner located downstream is transferred to the photosensitive drums 1 (1a-1).
In the primary transfer portion for transferring from t) to the intermediate transfer belt, the transparent toner is re-transferred to the photosensitive drum, so that the transparent toner is mixed more than necessary in the multi-color developing devices 3 (3a to 3d), etc. This is an obstacle to stable image formation. Therefore, it suffices to form the transparent toner only on the lowermost layer on the intermediate transfer belt 81 on which the colored toner image is formed, and to perform only the necessary amount. Further, it is more effective to change the maximum amount of the transparent toner per unit area for each color in order of the colored toner image-formed on the intermediate transfer belt 81 in consideration of some re-transfer of the transparent toner. Is.

Preferably, the secondary transfer efficiency is different depending on the type of recording material P and the image forming environment such as temperature and humidity, so that it is transparent depending on the type of recording material P and the signal value of the temperature and humidity sensor (not shown). It goes without saying that the adverse effect of the transparent toner can be minimized by making the maximum amount of toner per unit area variable.

When the image signal for forming the transparent toner is determined, the image signal of the transparent toner component is projected onto the photosensitive drum 1t via a polygon mirror (not shown) or the like to form an electrostatic latent image. Then, the transparent toner is supplied from the developing device to form a transparent toner image on the photosensitive drum. When this transparent toner image arrives at the transfer site where the photosensitive drum 1t and the intermediate transfer body 81 are in contact with the rotation of the photosensitive drum 1t, the first transfer bias applied by the first transfer member 4t causes The transparent toner image is transferred to the intermediate transfer body 81. When the intermediate transfer member 81 carrying the transparent toner image is conveyed to the image forming portion, by this time, the magenta toner image formed on the photosensitive drum 1a in the image forming portion by the same method as described above, Transferred onto the transparent toner image.

Next, the image forming portion for the colored toner image will be described. Basically, it is the same as the image formation of the transparent toner image. An image signal of magenta component color is projected onto the photosensitive drum 1a via a polygon mirror (not shown) or the like to form an electrostatic latent image, on which magenta toner is supplied from the developing unit to form an electrostatic latent image on the magenta image. It becomes a toner image. This toner image is transferred to the photosensitive drum 1 as the photosensitive drum 1a rotates.
When the magnetic transfer sheet a reaches the transfer portion where the a and the intermediate transfer body 81 come into contact with each other, the magenta toner image is formed on the intermediate transfer body 81 by the first transfer bias applied by the first transfer member 4a. Transferred onto the toner.
When the intermediate transfer body 81 carrying the transparent toner image and the magenta toner image is conveyed to the image forming section,
In the image forming section, the photosensitive drum 1 is processed in the same manner as described above
The cyan toner image formed on b is transferred onto the magenta toner image.

At each transfer portion, after the yellow toner image and the black toner image are superposed and transferred onto the above-mentioned toner image, by this time, the recording material P taken out from the paper feed cassette 60 reaches the transfer portion. , Transfer member 40
The four color toner images are transferred onto the recording material P by the transfer bias applied to the recording material P. At this time, since the lowermost layer of the toner image formed on the intermediate transfer belt 81 has the transparent toner, the releasability of the colored toner from the intermediate transfer belt 81 is improved, and the colored toner image is almost 100%. %
Transcribed. The transparent toner remaining on the intermediate transfer belt as the transfer residue is collected by the cleaning blade 30 disposed downstream of the secondary transfer by the cleaning blade, and is collected by the cleaning unit 3t of the transparent toner via the conveying path 31 and re-collected. Used.

The recording material P is then conveyed to the fixing section.
The fixing section has a step of fixing the toner on the recording material P by heat and pressure.

As the toner used in the present invention, both the transparent toner and the colored toner are transferred at the primary transfer portion in order to correspond to the image forming apparatus of the present embodiment which does not have the cleaning means on the photosensitive drum. A highly efficient spherical toner having a volume average particle diameter of 7.5 μm is used.
A method of measuring the volume average particle diameter will be briefly described. A Coulter Counter TA-II type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) for outputting number distribution, volume distribution, number average and volume average are connected. Then, the electrolyte is 1% Na using primary sodium chloride.
Adjust the Cl aqueous solution. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, is added in an amount of 0.1 to 5 ml as a dispersant in 100 to 150 ml of the electric field aqueous solution.
In addition, 0.5 to 50 mg, preferably 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the Coulter Counter TA-II type is used to form an aperture 10
The volume average particle size is obtained by measuring the particle size distribution of particles having a particle size of 2 to 40 μ using a 0 μ aperture. The spherical toner used in the present embodiment will be described in detail. A capsule obtained by suspension polymerization, which is divided into a surface layer portion mainly containing styrene-acrylic resin containing paraffin wax and a core mainly containing paraffin wax. The structured polymerized toner is adopted as both a transparent toner and a colored toner. Further, in these toners, a charge control agent is preferably added to the toner for the purpose of controlling chargeability. As the charge control agent, among the known charge control agents, those having almost no polymerization inhibitory property and water phase transfer property can be used. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, amine compounds and polyamine compounds, and negative charge control agents include, for example, metal-containing salicylic acid compounds and metal-containing monoazo compounds. Examples thereof include dye compounds, styrene-acrylic acid copolymers, and styrene-methacrylic acid copolymers. In this embodiment, a di-tert-butylsalicylic acid metal compound, which is a negative charge control agent, is added. The difference between the transparent toner and the colored toner is the presence or absence of the colorant. The reason is that even when the transparent toner is mixed in the developing device for the colored toner, the effect is kept to a minimum. The other toner may be a pulverized toner, an emulsion polymerization toner, or a toner obtained by a dispersion polymerization method, an interfacial polymerization method, or the like. A detailed description of the manufacturing method is omitted because it is a commonly known toner manufacturing method. It is common to add known external additives to the obtained toner for the purpose of imparting various characteristics. From the viewpoint of the durability of the toner, the external additive is preferably 1/10 or less of the volume average particle diameter of the toner particles (the measuring method is outlined above). The particle diameter of the external additive means the average particle diameter of the toner particles obtained by observing the surface of the toner particles with an electron microscope. The external additives include the following. First,
Metal oxides (silicon oxide, aluminum oxide, titanium oxide), carbon black, and carbon fluoride for the purpose of improving the fluidity of the toner. It is more preferable that these have been subjected to a hydrophobic treatment. Next, metal oxides (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitrides (silicon nitride, etc.) for the purpose of polishing the filming of toner and external additives on the drum surface. , Carbides (silicon carbide, etc.), metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.). Further, as a releasing agent for releasing toner from a toner image bearing member such as a photosensitive drum or an intermediate transfer member or a lubricant for lowering a friction coefficient μ between a rubber blade cleaning the toner image bearing member and the surface of the toner image bearing member, Fluorine-based resin powder (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salt (zinc stearate, calcium stearate, etc.). In addition, a metal oxide (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.) as charge control particles may be externally added for the purpose of controlling the chargeability of the toner. These external additives are used as toner particles 10
The amount is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 0 parts by weight. By using a plurality of these external additives in combination, it is possible to realize optimization of each image forming process such as development characteristics, transfer characteristics and fixing characteristics. The external additive used in this embodiment has a particle size of about 10-4.
0.7 parts by weight of silicon oxide fine particles of 0 nm was used with respect to 100 parts by weight of the toner, and 0.7 parts by weight of titanium oxide particles with a particle diameter of 5 to 30 nm was used with respect to 100 parts by weight of the toner.
It is desirable that the basic structures of the applied transparent toner and the base of the colored toner, the external additive, and the like be made common. This is because it is difficult to completely eliminate the re-transfer phenomenon in which the toner image once transferred to the intermediate transfer body returns to the photosensitive drum again at the downstream primary transfer section in each station. In the case of an image forming apparatus that does not have a cleaning unit on the photosensitive drum, such as a form, it will be collected by a developing device, and if even a small amount of upstream toner is mixed, it is not the same toner type, This will greatly affect the developability.

As described above, in the present embodiment, in the image forming apparatus which employs the intermediate transfer member, the image forming signal of the colored toner is fed back to the image forming signal of the transparent toner, and the image forming signal of the colored toner is obtained. Depending on,
By determining the image forming signal of the transparent toner, it is possible to minimize the harmful effects of the transparent toner and to make the secondary transfer efficiency almost 100%.

(Second Embodiment) FIG. 3 shows an image forming apparatus according to the second embodiment.

An unusual case of this letter paper is that it is an image forming apparatus having one photosensitive drum and one intermediate transfer member. This embodiment is characterized in that one photosensitive drum is provided with a rotatable developing unit 3. As a developing unit, a transparent toner unit, a magenta unit, a cyan unit, a yellow unit, and a black toner unit are provided. When the original image is read, the image signal of each color is determined. The image signal forming the transparent toner is determined according to the image signal of each color.

In accordance with the above-mentioned image signal, the image formation of each color is performed similarly to the first embodiment, and the image formation is performed on the intermediate transfer member. First, the charging device 2 uniformly charges the photosensitive drum 1. After reading the original, the image signal value of each color (magenta, cyan, yellow, black) is determined.
The image signal value of the transparent toner image is determined according to the image signal. An image signal of a transparent toner image is first exposed on the uniformly charged drum to form a latent image on the photosensitive drum 1. Thereafter, the rotary developing device 3 is rotationally moved to a position for developing the transparent toner, and develops the transparent toner in the developing process. The transparent toner developed on the photosensitive drum 1 is transferred onto the intermediate transfer body 81 at the primary transfer portion 4. Next, when the image formation of the transparent toner is completed, the image formation of the colored toner is performed.

After the transparent toner is transferred to the intermediate transfer body 81, the photosensitive drum 1 is uniformly charged to a desired voltage by the charging device 2 again, and then the image signal of the magenta component is exposed to the photosensitive drum. Being a latent image. At this time, in the present embodiment, since the polymerized toner (spherical toner) is adopted, the transfer efficiency of almost 100% can be realized, so that almost no residual toner remains on the drum, and the latent image is formed by exposure. The impact is small. When the latent image of the magenta component is completed, the developing process is started and the toner image of the magenta toner is developed on the photosensitive drum, similarly to the image forming process of the transparent toner. The toner image developed on the photosensitive drum is image-formed on the transparent toner image formed on the intermediate transfer member 81 by the primary transfer unit 4.

Then, cyan toner, yellow toner,
The black toner image is formed on the intermediate transfer body 81. When the four-color toner image + transparent toner image is formed, the secondary transfer process is subsequently performed. In the secondary transfer process, the toner on the intermediate transfer member is fed from the paper feeding unit, adjusted in timing by the registration roller, and adjusted in the secondary transfer portion so that the image and the recording material match. Images are transferred at once. At this time, since the transparent toner is present in the lowermost layer of the image formed on the intermediate transfer body 81, almost 100% of the colored toner is transferred onto the recording material. The transparent toner remains on the intermediate transfer member, and the transparent toner is collected and reused by the cleaning unit.

As described above, the image forming apparatus including the intermediate transfer belt as in the present embodiment can be applied to an image forming apparatus having one photosensitive drum.

(Third Embodiment) The basic structure is the same as that of the above embodiment. In this embodiment, the intermediate transfer belt 81
It is characterized in that the transparent toner remaining above is charged on the downstream side of the secondary transfer portion, oppositely to that at the time of image formation, returned to the photosensitive drum again at the primary transfer portion, and collected by the transparent toner developing device. . By doing so, the cleaning means by the rubber blade on the intermediate transfer member can be removed, and the transfer residual toner collecting and conveying means can be deleted, so that the space can be significantly reduced, It also leads to cost reduction.

FIG. 4 is a schematic sectional view for explaining the image forming apparatus of this embodiment. The image forming process is the same as that of the first embodiment and will not be described below. The intermediate transfer member cleaning process after the secondary transfer portion, which is a feature of this embodiment, will be described. The transparent toner t2 remaining on the intermediate transfer belt 81 after passing through the secondary transfer portion
Is recharged by the transparent toner recharging means 33. The transfer residual toner has a wide charging profile having a peak at -3 μC / g and almost no polarity.
Therefore, in this state, when the transparent toner reaches the primary transfer portion, the transparent toner is hardly transferred to the photosensitive drum. Therefore, in the present embodiment, the charging roller 33 is adopted as the recharging means, a DC voltage is applied to an alternating voltage of a rectangular wave having a frequency of 2 kHz, a voltage Vpp = 2 kV, and 80% Duty, and a differential current constant of +20 to 40 μA is applied. The current is controlled to charge the toner to the positive polarity. By doing so, when the output of normal image formation, + 500V, is applied to the primary transfer unit in the primary transfer unit 4t, the transparent toner t1 for normal image formation is negatively charged, and therefore the intermediate transfer from the photosensitive drum 1 is performed. Since the secondary transfer residual transparent toner t2 on the intermediate transfer belt 81 is positively charged to the transfer belt 81, it is transferred from the intermediate transfer belt 81 to the photosensitive drum 1. The transparent toner t2 transferred to the photosensitive drum is once collected by the brush charging unit 2 (FIG. 5). After that, the toner is discharged onto the photosensitive drum 1 by a transparent toner discharging sequence which is facilitated separately from the image forming process, and is collected by the developing device 3. Specifically, the brush charging means 2 is normally an AC voltage Vpp = 1.5 kV and a SIN wave having a frequency of 2 kHz, and a DC output of -700 V (environment,
The photosensitive drum is uniformly charged by outputting (variable depending on durability, etc.), but in the transparent toner discharge sequence, the photosensitive drum is once charged to −700 V (FIG. 6), and the developing process and the transfer process are performed. When the charged portion on the photosensitive drum comes to the charged portion again without performing
By mainly turning off DC and DC, the transparent toner attached to the brush charging unit flies due to the potential difference between the photosensitive drum and the brush charging unit (FIG. 7), and is discharged to the photosensitive drum. By exposing the photosensitive drum with the exposure device, the potential of the photosensitive drum becomes about -100V. The discharged toner is transferred to the developing device A by the developing means.
By turning off the C output and setting the DC output to an output smaller than the surface potential of the photosensitive drum, specifically -500 V, the positively charged toner is developed due to the potential difference between the surface of the photosensitive drum and the sleeve of the developing device. It moves in the direction of the apparatus and is collected by the developing device (FIG. 8). The toner in the developing device 3 which is negatively charged is electrically attached to the magnetic brush formed on the surface of the sleeve in the developing device, and the potential difference generated by the DC output alone is sufficient for the photosensitive drum 1.
Never fly to. By carrying out such a collecting process, it is possible to remove the collecting means using a generally known rubber blade and the toner conveying means after collecting,
A large space reduction and cost reduction can be realized.

(Fourth Embodiment) FIG. 9 is a schematic sectional view of an image forming apparatus for explaining the fourth embodiment. The present embodiment is characterized in that a detection unit 34 for detecting the coloring amount of the remaining transparent toner on the intermediate transfer belt is provided downstream of the intermediate transfer belt 81 in the rotation direction of the secondary transfer unit. By doing so, when the recording material P is stopped in the middle of image formation due to poor conveyance of the recording material P, an error signal of another detection signal, or the like, the colored toner and the transparent toner exist on the intermediate transfer belt. Further, due to secondary transfer failure or the like, a large amount of colored toner may be mixed with the transparent toner in the secondary transfer residue accidentally. In the event of an accident as described above, the detection means 34 is provided so as not to mix colored toner in the transparent toner image forming portion, and when the detection signal exceeds a predetermined value, a dedicated The transparent toner containing the colored toner is collected by the toner collecting means.

As described above, since the colored toner on the intermediate transfer belt which has been accidentally generated can be collected, a stable image can be obtained for a long period of time.

[0043]

As described above, in an image forming apparatus that employs an intermediate transfer member, it is possible to ensure an improvement in the releasability of the colored toner by the transparent toner from the intermediate transfer member, and to minimize the adverse effects of the transparent toner. In addition to being able to stop, it is possible to reduce waste coloring toner and consumption coloring toner and improve image quality.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming apparatus for explaining a first embodiment of the present invention.

FIG. 2 shows the amount of toner adhesion and transfer efficiency.

FIG. 3 is a sectional view of an image forming apparatus for explaining a second embodiment of the present invention.

FIG. 4 is a sectional view of an image forming apparatus for explaining a third embodiment of the present invention.

FIG. 5 is a first diagram illustrating a step of returning the transparent toner to the developing device according to the third embodiment of the invention.

FIG. 6 is a second diagram illustrating a step of returning the transparent toner to the developing device according to the third embodiment of the invention.

FIG. 7 is a third diagram illustrating a step of returning the transparent toner to the developing device according to the third embodiment of the invention.

FIG. 8 is a fourth diagram illustrating the step of returning the transparent toner to the developing device according to the third embodiment of the invention.

FIG. 9 is a sectional view of an image forming apparatus for explaining a fourth embodiment of the present invention.

FIG. 10 is a cross-sectional view of an image forming apparatus illustrating a conventional example.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d, 1t Photosensitive drum 2a, 2b, 2c, 2d, 2t charging device 3a, 3b, 3c, 3d, 3t developing device 4, 4a, 4b, 4c, 4d, 4t Primary transfer roller 24 backup roller 25 drive roller 26 Tension roller 33 Transparent toner recharger 34 Colored toner amount detection sensor included in transparent toner 40 Secondary transfer roller 81 Intermediate transfer belt P recording material t1 transparent toner for image formation t2 Toner after recharging of transparent toner

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA11 DA14 DC02 DD03 DD05                       DE07 EA02 EB04 EC06                 2H030 AA00 AB02 AD01 AD03 AD11                       AD16 BB24 BB42 BB63 BB71                 2H200 FA05 GA10 GA12 GA23 GA34                       GA47 HA02 HB12 HB22 JA02                       JC03 JC07 JC11 JC12 JC15                       LB02 LB09 LB13 LB17 LB39                       LB40 MA04 MA20 PA10 PB01                       PB25 PB27 PB28

Claims (8)

[Claims] 1. A first image carrier that forms an electrostatic latent image on the surface, and a plurality of developing devices that selectively attach toner to the image carrier to visualize the latent image. In an image forming apparatus having a first transfer device for transferring the imaged toner image to a second image carrier and a second transfer device for transferring the toner image on the second image carrier to a recording sheet. An image forming apparatus characterized in that at least one of the toner images is a colorless and transparent transparent toner, and the transparent toner is imaged on the lowermost layer of the toner image formed on the second image carrier. . 2. The image forming apparatus according to claim 1, wherein the image signal of the transparent toner is determined according to the image signal of the colored toner for forming an image. 3. A transparent toner image collecting means on the second image carrier is provided downstream of the moving direction of the second image carrier of the second transfer device, and the transparent toner collected by the collecting means is provided. The image forming apparatus according to claim 1, further comprising a conveying unit that conveys the transparent toner to the developing device. 4. A charging unit for charging the transparent toner to a polarity opposite to the polarity at the time of image formation, downstream of the moving direction of the second image carrier of the second transfer device and upstream of the first transfer device. The image forming apparatus according to claim 3, further comprising: 5. The image forming apparatus according to claim 1, wherein the maximum amount of transparent toner deposited per unit area is controlled in each mode. 6. The image forming apparatus according to claim 5, wherein the mode depends on the type of recording material. 7. The image forming apparatus according to claim 5, wherein the mode is an environmental mode that is switched depending on temperature, humidity, or both. 8. A means for detecting the amount of colored toner contained in the transparent toner of the recovered toner, wherein the means for recovering the transparent toner is made variable according to a predetermined signal value. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: