JP3192218B2 - Image forming method and image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus for recording image information on a recording material such as paper using a toner, such as a copying machine or a printer.

[0002]

2. Description of the Related Art In a conventional image forming method and image forming apparatus, a latent image is formed on a photoreceptor by electrophotography, that is, image exposure, and the latent image is developed with a toner. A technique of electrically transferring toner and then fixing the toner has been widely adopted. A method and an apparatus for performing a primary transfer of a toner image formed on a photoreceptor to an intermediate transfer member by adhesive force, and then performing a secondary transfer with simultaneous fixing by simultaneously fusing the toner from the intermediate transfer member to a recording material such as paper. Conventionally known.

In the method and apparatus for transferring directly from a photoreceptor to a recording material, the paper and the photoreceptor do not adhere to each other due to the minute unevenness existing on the surface of the paper, causing an uneven gap to appear. And the non-uniform force acts on the toner due to the Coulomb repulsion described above, causing unevenness in density and scattering of the toner in the transferred image, and there is a problem of deteriorating the resolving power and dot reproducibility. In order to solve such a problem, an intermediate transfer system has been adopted. In this system, the intermediate transfer member is formed in a drum or belt shape and is repeatedly used.

However, in such a method and apparatus, in a portion where a toner image is transferred from a photoreceptor and a portion where a toner image is transferred to a recording material, a difference in peripheral speed, a pressure, and the like fluctuate, so that image quality is reduced. It is necessary to assemble mechanisms and driving means and a skeleton supporting them so as not to cause deterioration. Further, when heating is performed at the time of the secondary transfer, it is necessary to provide a cooling device so that the temperature of the photoconductor does not increase. For this reason, the configuration of the entire apparatus has become large-scale, energy consumption has increased, and the cost per recorded image has increased.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a copying machine, a printer, or the like employing an intermediate transfer step, which can be driven with a simple structure (without forming an intermediate transfer body in a drum or belt shape) while utilizing the advantages of intermediate transfer. An object of the present invention is to provide an image forming method and an image forming apparatus for recording image information on a recording material such as paper with toner, which has excellent resolution and sharpness without toner scattering without increasing the scale of a system and a support mechanism. And Another object is to provide an image forming apparatus capable of directly forming a recorded image on a recording material without using an intermediate transfer sheet.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a rotating toner image carrier, a latent image forming means for forming a latent image on the toner image carrier, and a toner image carrier. Developing means for developing the formed latent image with a developing device to form a toner image; first conveying means for conveying an intermediate transfer sheet from a transfer sheet supply unit; and an intermediate transfer sheet conveyed from the transfer sheet supply unit. Pressing means for pressing the toner image holding member against the toner image holding member by a pressing roller to transfer the toner image on the toner image holding member onto the intermediate transfer sheet; second conveying means for conveying a recording material from a recording material supply unit; And recording materials
The Align intermediate transfer sheet that Ru together I Weight each other
A serial Rokuzaikasane ne means, an intermediate transfer sheet and the recording material superposed sandwiched between the heat roller and the pressure roller, at the same time fixing the transfer onto the recording material the toner image from the intermediate transfer sheet by applying heat and pressure fixing in the image forming device comprising a means, the upper and the second conveying unit Symbol intermediate transfer sheet SL
Rokuzai overlapped by stopping the operation of the means to convey the transcription sheet feeding unit <br/> or et recording material, the recording material the toner image only that conveyance by the recording material by acting on said fixing means Is characterized by being fixed to

[0007] In the image forming apparatus according to claim 1, characterized in that the electrical bias was configuration indicia pressurized above <br/> KiKa圧means.

[0008]

After transferring the toner image on the photoreceptor of the image forming method and the image forming apparatus configured as described above to an endless intermediate transfer sheet, a recording material is superimposed on the intermediate transfer sheet and heat and pressure are applied. Then, the image is melt-transferred and fixed, so that an image having excellent resolution and sharpness without toner scattering can be obtained without increasing the scale of a drive system and a support mechanism. By providing a sheet detecting means in the image forming apparatus and conveying a recording material instead of the intermediate transfer sheet, an image can be formed by direct transfer.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the image forming apparatus of the present invention
A toner image holder 1 composed of a drum-shaped photoreceptor, a scorotron charger 11 for uniformly charging the surface of the photoreceptor, a laser optical system (latent image forming means) 12 for imagewise exposing the charged photoreceptor surface with laser light, Developing device (developing means) 6 having dry toner, intermediate transfer sheet (single leaf, that is, non-endless, non-drum-shaped) 2 or pressure roller (pressing means) which presses against toner image carrier 1 with recording material 4 interposed therebetween 7, a cleaning device 13 for cleaning the surface of the photoconductor, and a pair of registration rollers 8 with the toner transfer surface of the intermediate transfer sheet 2 after the transfer facing upward.
A recording material stacking section 15 for temporarily stocking and transporting a recording material 4 such as paper thereon, a heat roller 9 for applying heat and pressure to the intermediate transfer sheet 2 on which the recording material 4 overlaps, and a pressure roller 10 And a fusion transfer section (fixing means) 18 composed of Reference numeral 3 denotes a transfer sheet supply unit, 3
a is a first sheet for conveying the transfer sheet from the transfer sheet supply unit 3.
It is a transport means.

The rotating shafts are connected by a spring 19 between the toner image carrier 1 formed of a drum-shaped photoreceptor and the pressure roller 7 in order to maintain a predetermined pressure. Further, a toner image carrier 1 made of a drum-shaped photoreceptor and a pressure roller 7
Can be pressed and separated by a solenoid 20 controlled according to the sequence. Similarly, pressure contact and separation can be performed according to the sequence so that toner does not directly adhere to the surface of the pressure roller 7. The photoconductor is a drum-shaped organic photoconductor having relatively excellent pressure resistance and heat resistance. The laser optical system 12 includes a semiconductor laser, a rotating polygon mirror, an fθ lens, and the like, and a laser modulation circuit controls light emission of the semiconductor laser according to an image signal.

The developing device 6 accommodates yellow toner, magenta toner, cyan toner, and black toner, respectively, which are arranged in series in the moving direction of the photoconductor.
The developer contained in the developing device 6 is a two-component developer in which a high-resistance non-magnetic toner and a magnetic carrier are mixed. The toner has a particle size of 5 μm or less so that the resolution is high, the gradation reproducibility by the area gradation is good, and the swelling of the toner image due to the superposition is small.

In FIG. 2, the developing device 6 has a magnet 21 therein, and a non-magnetic sleeve 22 for transporting a developer to a developing area by rotating, and the non-magnetic sleeve 2 described above.
2 a developer regulating plate 1 for regulating the amount of developer conveyed on
4 and the like. The magnetic field formed on the non-magnetic sleeve 22 is changed by the movement of the internal magnet 21, and controls whether or not the developer is supplied to the developing area. During development, a magnetic field is formed on the non-magnetic sleeve 22 so that the developer is supplied, the non-magnetic sleeve 22 rotates, and at the same time, a developing bias is applied to the non-magnetic sleeve 22. Due to the electric field formed in the developing area, only the toner adheres to the photoconductor according to the electrostatic latent image on the photoconductor.

A method of developing with a one-component developer consisting only of a non-magnetic color toner can also be adopted in this apparatus. In this case, a conductive elastic body or a roller whose surface is coated with an insulating material is used instead of the sleeve containing the magnet. The toner contacts a charging member such as a blade and is charged to a charge having a predetermined polarity and an absolute value. According to this developing method, a relatively thin layer toner image having a small edge effect can be obtained, and the features of this apparatus can be utilized. The pressure roller 7 has rubber elasticity so that the intermediate transfer sheet 2 is pressed against the toner image carrier 1 formed of a drum-shaped photoreceptor with a sufficient contact width and a uniform pressure, and a transfer bias can be applied. Whether the surface is conductive
The volume resistance is configured to be low.

In FIG. 3, at the recording material overlapping portion 15, the intermediate transfer sheet 2 on which the toner image is transferred and guided and conveyed by the lower guide plate 16 is moved downward to the upper guide plate (the second conveying plate). Means) Recording material 4 guided to 17
Are positioned on the upper side, and their respective ends are stopped before the registration roller pair 8. In the stopped state, the intermediate transfer sheet 2 and the recording material 4 are not in surface contact due to the presence of the lower guide plate 16 and the upper guide plate 17. After the intermediate transfer sheet 2 and the leading end of the recording material 4 are aligned, the registration roller pair 8
Are started to rotate and are fed out of the nip in an overlapping state.

In FIG. 4, a fusion transfer section 18 is composed of a heat roller 9 and a pressure roller 10, and a nip between the heat roller 9 and the pressure roller 10 with respect to the intermediate transfer sheet 2 overlapping the recording material 4. Heat and pressure are applied by the unit 24, and the toner image on the intermediate transfer sheet 2 is transferred and fixed on the recording material 4 by heat. The heat roller 9 is formed by coating a hollow rigid roller with a heat-resistant material such as a silicone resin. A heater 23 such as a halogen lamp is provided inside the heat roller 9, and the entire roller is heated to 50 ° C. to 180 ° C. The pressure roller 10 has a rigid roller whose surface is coated with a silicone resin. The heat roller 9 and the pressure roller 10 need to send out the recording material 4 and the intermediate transfer sheet 2 without slipping. Therefore, those having a high friction coefficient are preferable. Pressure roller 1
A heater 23 may be provided on the 0 side.

Intermediate transfer sheet 2 used in this embodiment
Indicates that the surface of the recording material
It is necessary that the fluidized toner has releasability so that the toner is transferred efficiently. As a specific example, a silicon resin or a Teflon resin having a thickness of 10 to 300 μm is mainly used. Further, it is desirable that the surface of the intermediate transfer sheet 2 has irregularities smaller than the substantial minimum particle diameter of the toner in order to prevent transfer omission due to collapse of adhesion. That is, when the substantial minimum particle size of the toner is 5 μm, the unevenness of the intermediate transfer member is 5 μm or less.

Next, an image forming process in the image forming apparatus of the present invention will be described. 1. First, the toner image carrier 1 starts rotating at a constant linear velocity in the direction of the arrow in FIG. 1, and the scorotron charger 11 uniformly charges the surface of the photoreceptor on the toner image carrier 1 to reduce the surface potential to about-. Set to 800V. 2. The laser light modulated by the laser optical system 12 based on the image signal scans the surface of the photoconductor on the toner image carrier 1 to form an electrostatic latent image. The electrostatic latent image is formed such that a portion irradiated with laser light (surface potential is about -100 V) is a toner-attached portion and a non-irradiated portion (surface potential is about -800 V) is a background portion. 3. The electrostatic latent image is developed with the toner of the developing device 6. The developing bias applied to the non-magnetic sleeve 22 is -600 V
Then, reversal development is performed.

4. The intermediate transfer sheet 2 is conveyed from the transfer sheet supply unit 3 so that the toner image on the photoconductor surface on the toner image holder 1 is transferred to an appropriate position. When the leading end of the intermediate transfer sheet 2 is conveyed, the pressure roller 7 comes into pressure contact with the surface of the photoreceptor on the toner image carrier 1 at a timing such that predetermined transfer conditions are obtained. The pressure roller 7 rotates so that the linear velocity matches the surface of the photosensitive member on the toner image holding member 1. Due to the pressing force of the pressure roller 7, the surface of the photoconductor on the toner image carrier 1 and the intermediate transfer sheet 2 are
A pressure of between 0.3 kg / cm and 3.0 kg / cm is applied. The surface of the photoreceptor on the toner image carrier 1 and the intermediate transfer sheet 2 come into close contact with each other. The toner image on the photoconductor surface on the toner image holder 1 is transferred to the intermediate transfer sheet 2 by the adhesive force of the intermediate transfer sheet 2. At this time, +
A transfer bias of 0.5 kv to 5.0 kv may be applied. In this way, an electric field is formed between the surface of the photoreceptor on the toner image holder 1 and the nip portion (contact portion) of the intermediate transfer sheet 2, and the toner is accordingly sensitized on the toner image holder 1. Transfer from the body to the intermediate transfer sheet 2. Of course,
Even if the toner image has a multi-layer structure on the photoconductor on the toner image holding member 1, it can be transferred.

5. The cleaning device 13 cleans the photoconductor on the toner image carrier 1 after the transfer. 6. The intermediate transfer sheet 2 after the transfer and the recording material 4 such as paper conveyed from the recording material supply unit 5 are conveyed to the recording material overlapping unit 15 and stopped by the registration rollers 8. At this time, the intermediate transfer sheet 2 and the recording material 4 are not joined.

[7] FIG. After the intermediate transfer sheet 2 and the leading end of the recording material 4 coincide with each other, a registration roller 8 conveys the two by overlapping them. 8. The intermediate transfer sheet 2 and the recording material 4 conveyed in an overlapped manner reach a fusion transfer section 18 including a heat roller 9 and a pressure roller 10. In the fusion transfer section 18, the intermediate transfer sheet and the recording material 4 are pressed against each other at a pressure of 0.3 kg / cm to 3.0 kg / cm, and the heat of the heat roller 9 causes the toner on the intermediate transfer sheet 2 to be in a semi-molten state. It flows on the recording material 4 and penetrates into fibers of the recording material 4 such as paper. At the same time, releasability acts on the intermediate transfer sheet 2.

9. The intermediate transfer sheet that has passed through the fusion transfer section 18 is separated from the recording material 4. The toner is fixed on the recording material 4 and hardly remains on the intermediate transfer sheet 2. The toner image formed on the recording material 4 in this manner is an image excellent in resolving power and sharpness without toner scattering as occurs in corona transfer. The intermediate transfer sheet is preferably cleaned and then repeatedly used in the above process.

10. The image forming apparatus shown in FIG. 1 can also form an image by directly transferring the image to the recording material 4. In this case, the path along which the intermediate transfer sheet 2 is conveyed is
Is transported. In the transfer section 25, the pressure roller 7 is pressed against the photoconductor on the toner image holding member 1 according to the leading end of the recording material 4, and the pressure is 0.3 kg / cm to 3.0 kg / cm as described above.
cm, and a transfer bias of +0.5 kv to 5.0 kv may be applied to the pressure roller 7 in the same manner as described above. When transferring a toner image to a recording material 4 having no tackiness on the surface, it is essential to apply the transfer bias. After the transfer of the toner image, the recording material 4 passes through the recording material overlapping section 15 and enters the fusion transfer section 18. At this time, the fusion transfer section 18 functions as a heat roller type fixing device. That is, the toner is melted by the heat roller 9 and flows out into the paper fibers of the recording material 4 to be fixed. For this reason, it is necessary that the heat roller 9 in contact with the toner has sufficient releasability from the molten toner.

A method of discriminating whether the sheet conveyed to the transfer section 25 is the intermediate transfer sheet 2 or the recording material 4 and switching the sequence according to the result is desirable in the use environment of the image forming apparatus. . FIG. 5 is a flowchart in the case where the image forming process is changed according to the identification result of the sheet type. In this case, as shown in the flowchart, the detecting unit 26 is provided on the transport path before reaching the transfer unit 25, and When the transfer sheet 2 is used, 1. ~ 9. (Steps 3 to 11)
In the case of the recording material 4, the above process 10. (Step 2
The control unit may be programmed to execute the sequence of 0 to 25). As the detection means 26, an optical sensor for measuring an optical reflectance, a weight sensor for measuring a weight, an optical sensor for detecting a specific shape of the intermediate transfer sheet 2, or the like may be used. In the above sequence, the transfer conditions at the transfer unit 25 by the pressure roller 7 and the melt transfer unit 18
Can be changed. For example, when transferring from the photoreceptor to the intermediate transfer sheet 2, a transfer method depending only on the adhesiveness is used, and when transferring directly to the recording material 4, an electric bias can be used.

[0024]

Since the present invention is constructed as described above, after transferring the toner image on the photoreceptor to the intermediate transfer sheet, the recording material is superimposed on the intermediate transfer sheet and heat and pressure are applied. Since fusion transfer and fixing are performed, an image having excellent resolution and sharpness without toner scattering can be obtained without increasing the scale of a drive system and a support mechanism.
An image can be formed by direct transfer by conveying a recording material instead of an intermediate transfer sheet without any major change except for the provision of the detection means.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming unit of an image forming apparatus to which the present invention is applied.

FIG. 2 is a sectional view of a developing device of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a perspective view of a recording material overlapping portion of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a sectional view of a fusion transfer unit of the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is a flowchart of the image forming apparatus according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Toner image holding body, 2 ... Intermediate transfer sheet, 3
... Transfer sheet supply unit, 4 ... Recording material, 5 ... Recording material supply unit, 6 ... Developer, 7 ... Pressurizing roller, 8
... Registration roller, 9 ... Heat roller, 10 ...
Pressure roller, 11 Scorotron charger, 12
... Laser optical system, 13 ... Cleaning device, 1
4: developer regulating plate, 15: recording material overlapping portion, 16
... lower guide plate, 17 ... upper guide plate, 18 ...
Melt transfer unit, 19: spring, 20: solenoid,
21: magnet, 22: non-magnetic sleeve, 23 ...
・ Heater, 24 ・ ・ ・ Nip, 25 ・ ・ ・ Transfer, 2
6 ... Detection means

Claims (2)

(57) [Claims] An image forming apparatus includes: a rotating toner image carrier; a latent image forming means for forming a latent image on the toner image carrier; and a developing device developing the latent image formed on the toner image carrier to form a toner image. Developing means, a first transporting means for transporting the intermediate transfer sheet from the transfer sheet supply unit, and a toner image holder by pressing the intermediate transfer sheet transported from the transfer sheet supply unit against the toner image holder by a pressure roller and pressurizing means for transferring the toner image to the intermediate transfer sheet, and a second conveying means for conveying the recording material from the recording material supplying unit, it heavy one another by the intermediate transfer sheet and the recording material <br/> align an intermediate transfer sheet SL <br/> Rokuzaikasane it means Ru combined, the intermediate transfer sheet and the recording material superposed sandwiched between the heat roller and the pressure roller, the intermediate transfer sheet a toner image by applying heat and pressure Is fixed simultaneously with transfer from That in the image forming apparatus composed of a fixing means, the upper Symbol intermediate transfer and the second conveying unit sheet recording
And it stops the operation of the wood piled unit, or the transcription sheet feeding unit
Conveys the al recording material, an image forming apparatus which only the conveyance by the recording material, characterized in that for fixing to the recording material a toner image by acting on the fixing means. 2. The image forming apparatus according to claim 1, wherein the upper <br/> KiKa圧means image forming apparatus according to claim 1, wherein the electrical bias was configuration indicia addition to.