JP2000321922A - Method and device for fixing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save electric power by surely fixing at low temperature even kneaded and pulverized toner fixed at high temperature being the surface temperature 150 to 190 deg.C in a fixing roller. SOLUTION: By as preliminary heating part 2, the toner of transfer paper 4 on which unfixed toner is transferred and at least the surface of the paper 4 are preliminarily heated to temperature which is equal to or over the softening point of the toner and which is not over the (boiling point of water+20) deg.C. By a heating and pressuring part 3, the toner of the paper 4 on which the unfixed toner is transferred and at least the surface of the paper 4 is heated and pressured so that the temperature thereof do not become under the softening point of the toner. Thus, the unfixed toner is fixed on the paper 4 by preliminarily heating and heating and pressuring the paper 4 so that water content evaporating from the paper 4 including water content becomes equal to or under 50% of the water content of the paper 4 on which a fixing action is not executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in a copying machine, a printer, and a facsimile machine using an electrophotographic system.

[0002]

2. Description of the Related Art In recent years, environmental issues have become important, and energy saving has been progressing in image forming apparatuses such as copiers and printers. In an electrophotographic image forming apparatus, since a toner image electrostatically transferred from a photoreceptor to transfer paper or the like easily peels off, the toner image transferred to a recording material such as transfer paper is heated or heated. It is pressed and fixed on the recording material.
In considering the energy saving of the image forming apparatus, what cannot be ignored is the power saving of the fixing device for fixing the toner on the recording material. To reduce the power consumption of the fixing device during standby of the image forming apparatus, the heat capacity can be reduced by reducing the thickness of the heating roller, and the film heating method using a low-heat-capacity heating element and a fixing film can be used to speed up the start-up to reduce standby. A fixing device that does not sometimes perform heating has been proposed.

Further, the lower the fixing temperature of the fixing device, the greater the power saving effect, and a fixing device which reduces power consumption during standby and fixing by low-temperature fixing is disclosed in Japanese Patent Laid-Open No. 5-107.
965 and JP-A-10-161451. The fixing device disclosed in JP-A-5-107965 heats at least one surface of a recording material having a toner image formed by using a toner whose surface melts in a temperature range of 50 ° C. to 120 ° C. Then, while the surface of the toner is in a softened state, the toner image is fixed on a recording material at a low temperature of 120 ° C. by passing between a pressure roller and a fixing roller having a release layer, thereby reducing power consumption. We are trying to reduce it. Further, the fixing device disclosed in JP-A-10-161451 has a volume average particle diameter of 5 μm to 9 μm,
A toner having a particle size distribution of 1 μm or more and a particle size distribution of 5% or less and a melting start temperature of 60 ° C. to 105 ° C. is used.
By using a heat roller fixing device having a temperature of 90 ° C. or less, the toner having a small particle diameter is fixed at a low temperature to obtain a sufficient fixing strength, thereby saving power.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
The fixing device disclosed in Japanese Patent Application Laid-Open No.
This is an apparatus applicable when using a toner that melts in a temperature range of from about 120 ° C. to about 120 ° C.
The fixing device disclosed in Japanese Patent Application Laid-Open Publication No. H10-209,837 is a device which can be applied when a toner containing a toner having a large particle diameter of 20 μm or more is used, and any fixing device has a fixing roller surface temperature of 150 to 190 which is generally used at present. It cannot be applied to kneaded and crushed toner which has been fixed at a high temperature of ℃, and it has been difficult to fix the kneaded and crushed toner which has been fixed at a high temperature at a low temperature.

According to the present invention, there is provided a fixing method and a fixing apparatus which can improve power consumption by reliably fixing a kneaded and crushed toner, which has been conventionally fixed at a high temperature of 150 to 190 ° C. at a low temperature, to a low temperature. The purpose is to provide.

[0006]

According to the fixing method of the present invention, the temperature of the image forming material of the image carrier to which the unfixed image is transferred and at least the surface temperature of the image carrier are set to a temperature not lower than the softening point of the image forming material. In the fixing method of fixing the unfixed image-forming substance to the surface of the image-holding member by heating and pressurizing the image-forming substance in a state where the temperature does not fall below the softening point of the image-forming substance, the evaporation of moisture from the image carrier containing moisture The temperature and time for preheating and heating and pressing are adjusted so that the amount is 50% or less of the water content of the image carrier before fixing.

The temperature of the image forming material of the image carrier to which the unfixed image forming material has been transferred and the temperature of at least the surface of the image carrier is higher than the softening point of the image forming material (the boiling point of water + 20).
After preheating to a temperature not exceeding ℃, it is preferable to fix the unfixed image-forming substance to the surface of the image-bearing member by applying a pressure not lower than the softening point of the image-forming substance.

Further, the fixing device according to the present invention has a preheating section and a heating / pressing section, and the preheating section includes an image forming material and an image holding member of an image holding member onto which an unfixed image forming material is transferred. Preheating at least the surface temperature to a temperature above the softening point of the imaging substance and not exceeding (boiling point of water + 20) ° C.,
The heating and pressing unit has a temperature of at least the surface of the image forming material and the image holding body of the image holding body onto which the unfixed image forming material is transferred,
The method is characterized in that an unfixed image forming substance is fixed on the surface of the image holding member by applying pressure so as not to fall below the softening point of the image forming substance.

It is preferable to use an infrared heating system or a flash heating system for the preheating unit and to use a heating roller having a low heat capacity for the heating and pressing unit.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fixing device according to the present invention has a preheating section, a heating / pressing section, and a recording material transport section for transporting a transfer sheet. The preheating unit is, for example, of an infrared heating type, and is provided to face the surface of the transfer paper conveyed by the recording material conveyance unit having the toner image. The heating and pressing unit has a heating roller with a low heat capacity, such as a thin roller with a halogen lamp inside and a surface heating roller with a resistance heating element on the surface, and a pressure roller provided opposite the heating roller. The preheating unit is provided downstream of the preheating unit and downstream of the transfer paper conveyance path and close to the preheating unit.

When the fixing device heats and fixes the unfixed toner transferred to the transfer paper by the developing device of the image forming apparatus, the unfixed toner image on the surface of the transfer paper being conveyed by the recording material conveyance section is fixed. Is preheated in a preheating section at a temperature at which the surface temperature of the toner image and the transfer paper exceeds the softening point of the toner to soften the unfixed toner. The transfer paper having the softened toner is sent to the heating and pressurizing unit, and the unfixed toner image is fixed on the transfer paper by applying pressure without falling below the softening point of the toner.

[0012]

FIG. 1 is a block diagram of one embodiment of the present invention.
As shown in FIG. 1, a fixing device 1 of an image forming apparatus such as an electrophotographic copying machine has a preheating unit 2, a heating / pressing unit 3, and a recording material conveying unit 5 for conveying a transfer sheet 4. The preheating unit 2 employs a fast rising infrared heating method or a flash heating method having an infrared reflecting mirror, and is provided to face the surface of the transfer paper 4 transported by the recording material transport unit 5 having the toner image 6. I have. The heating / pressing unit 3 includes a heating roller 7 having a low heat capacity such as a thin roller provided with a halogen lamp therein or a surface heating roller provided with a resistance heating element on the surface, and a pressing roller provided opposite the heating roller 7. 8 and
The preheating unit 2 is provided on the downstream side of the transfer path of the transfer paper 4 and close to the preheating unit 2. As the heating / pressing unit 3, a heating / pressing method using a low heat capacity fixing film may be used. As a heating and pressurizing method using a low heat capacity fixing film, there are a method in which a low heat capacity heating element is brought into contact with the inner periphery, and a method in which a metal layer is provided at least on one layer of the film to generate heat by electromagnetic induction.

In order to prevent the toner 6 from offsetting, the outermost surface layer of the heating roller 7 and the fixing film which is in contact with the toner is made of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or tetrafluoroethylene-ethylene copolymer. Fluorinated compounds such as coalesced (ETFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV) and the like Desirably, it is made of resin.

The toner 6 is formed of a resin component, a colorant, a polarity control agent, and the like, which are conventionally used generally.
The resin component is a thermoplastic resin such as a styrene resin, an acrylic resin, a methacrylic resin, a styrene-acrylic copolymer, a polyester resin, an epoxy resin, a thermosetting resin, or a mixture of two or more of these resins. And the like. These resins generally have a glass transition point of 55 to 70 ° C. and a softening point of 60 to 140 ° C. The toner 6 used in the fixing device 1 has a softening point of (the boiling point of water + 20) ° C. or less.

When the unfixed toner 6a transferred to the transfer paper 4 is heated and fixed by the developing device of the image forming apparatus in the fixing device 1 configured as described above, the unfixed toner 6a is conveyed by the recording material conveying section 5 to be conveyed. The unfixed toner 6a on the surface of the transfer paper 4 is heated by the preheating unit 2 to soften the unfixed toner 6a. The transfer paper 4 having the softened toner 6b is heated and pressed
And is fixed by heat and pressure. When the unfixed toner 6 a is fixed to the transfer paper 4 by the fixing device 1, the pre-heating unit 2
And the temperature of the heating and pressurizing unit 3 is changed so that the toner 6
FIG. 2 shows the result of evaluating the fixing property of the toner 6 by measuring the fixing rate by the clock meter method and transferring the toner. FIG. 2 shows a change in the fixing rate (%) with respect to the temperature of the toner 6 and the transfer paper 4 at the time of fixing, that is, the toner / transfer paper temperature. As shown in FIG. 2, when the temperature of the toner 6 and the transfer paper 4 at the time of fixing was changed, it was found that there was a temperature Tx at which the fixing rate sharply increased. It was also found that the temperature Tx also changed when the type of the toner was changed. As a result of examining the temperature Tx, it was confirmed that the temperature Tx showed a good match with the softening point T1 of the toner 6. The softening point T1 mentioned here is determined by measuring the toner sample in the cylinder by heating the sample at 1 ° C./min under a load of 10 kg / cm ² by a plunger using a Koka type flow tester (Shimadzu Corporation). ³ is 0.5mm in diameter and 1 in length
When the plunger is extruded from the nozzle, the plunger gradually descends, the sample is compressed, the gap in the cylinder disappears, and the stroke of the plunger does not fluctuate clearly as shown in FIG. The temperature at which a transparent body or phase is formed. Further, the melting start temperature T2 of the toner 6 is such that the sample becomes a uniform transparent body or phase under the above conditions and the plunger position does not fluctuate clearly, and then the plunger descends again and the stroke starts to change. When is the temperature.

Therefore, when the fixing device 1 heats and fixes the unfixed toner 6a transferred to the transfer paper 4 by the developing device of the image forming apparatus, the pre-heating unit 2 applies the unfixed toner 6a and the transfer paper 4 to the toner. The toner 6 b is heated to a temperature equal to or higher than the softening point T 1, and the softened toner 6 b is pressed by the heating / pressing unit 3 so as not to fall below the softening point Tx, and is fixed to the transfer paper 4. As described above, the unfixed toner 6a and the transfer paper 4 are heated to a temperature equal to or higher than the softening point T1 of the toner 6 by the preheating unit 2, and the toner 6
Since the heating is performed to such an extent that the temperature does not decrease, the power consumption of the heating / pressing unit 3 can be reduced. Also, the preheating unit 2
By using an infrared heating method or the like which has a fast rise, it is possible to save power during standby without requiring preheating as in a generally used heat roller method.

For example, the fixing device of a copying machine (Ricoh; trade name: Spiro 7000) using ordinary plain paper is removed, and the unfixed toner image 6a is transferred using the toner 6 having a softening point T1 of 76 ° C. Paper 4 was made. The transfer paper 4 was passed through the fixing device 1 to fix the toner 6 thereon. Here, a polyimide film is used as the transport belt 9 of the recording material transport section 5, a halogen lamp is used as the preliminary heating section 2, and the heating length is set to 80 mm.
Temperature of the toner 6b and the transfer paper 4 at the outlet of the softening point T
Preheating was performed to 100 ° C., which is higher than 76 ° C. which is 1. Here, the toner 6 at the outlet of the preheating unit 2
b and the temperature of the transfer paper 4 were measured with a radiation thermometer. Then, a silicon rubber layer and a tetrafluorothiene layer were provided on an aluminum tube having a thickness of 1 mm as a heating roller 7 of the heating / pressing unit 3,
A set temperature of the heating roller 7 was set to 80 ° C. which was higher than the softening point T1 of 76 ° C., and a fixing speed was set to 150 mm / sec. As a result of performing this fixing by continuously passing 20 sheets of A4 horizontal plain paper, it was possible to obtain a good fixed image without fixing defects such as offset.

For comparison, the temperature of the toner 6b and the transfer paper 4 at the outlet of the preheating unit 3 is set to 70 ° C., which is lower than the softening point of 76 ° C., and fixing is performed under the same conditions as above. And when the set temperature of the heating roller 7 of the heating and pressing unit 3 is set to a temperature 6 lower than 76 ° C. which is the softening point T1.
In both cases where the fixing was performed at 5 ° C. and the other conditions were exactly the same as those described above, cold offset occurred and fixing failure occurred.

The energy required for the temperature rise of the toner 6, the temperature rise of the transfer paper 4, and the evaporation of the moisture in the transfer paper 6 among the thermal energy consumed at the time of fixing is the ratio of the toner image on the transfer paper 4. When fixing is performed at 120 ° C. at 6%, the ratio is approximately 1:50 to 50, and a large amount of energy is consumed for evaporating the moisture in the transfer paper 4. Therefore, the smaller the water evaporation from the transfer paper 4, the higher the power saving effect.
When the amount of water evaporated from the water is 50% or more, the power saving effect is reduced. In order to make the amount of evaporation of water from the transfer paper 4 containing water equal to or less than 50% of the water content of the transfer paper 4 before fixing,
It is possible by adjusting the temperature and time of the preheating unit 2 and the heating and pressing unit 3. As a result of measuring the relationship between the temperature of the transfer paper 4 and the moisture content of the transfer paper 4, it was found that the evaporation of water became active at about (the boiling point of water +20) ° C. This is because a part of the water in the transfer paper 6 is hydrogen-bonded to the cellulose of the paper fiber, or is bonded to water molecules hydrogen-bonded to the cellulose by van der Waals force. It is considered that it is more difficult to evaporate. Therefore, the temperature for preheating in the preheating unit 2 and the temperature for heating in the heating and pressurizing unit 3 are set to a temperature lower than (boiling point of water + 20) ° C. to reduce evaporation of moisture in the transfer paper 4 during fixing. Thus, the amount of evaporation can be suppressed to 50% or less.

For example, in the same manner as described above, a copying machine using ordinary plain paper (Ricoh; product name: Spirio 7000)
And the toner 6 having a softening point T1 of 80 ° C.
To form a transfer sheet 4 onto which the unfixed toner image 6a has been transferred, and the transfer sheet 4 is passed through the fixing device 1 so that the toner 6
Was established. Assuming that the heating length of the preheating unit 2 is 100 mm, the toner 6 b and the transfer paper 4 at the outlet of the preheating unit 2 are
Was preheated to a temperature of 105 ° C., and the toner 6 b was fixed on the transfer paper 4 at a fixing speed of 150 mm / sec by the heating / pressing unit 3 having the heating roller 7 at a set temperature of 80 ° C. As a result of performing this fixing by continuously passing 20 sheets of A4 horizontal plain paper, it was possible to obtain a good fixed image without fixing defects such as offset. Also, the transfer paper 4 before and after fixing is used.
As a result of the measurement of the water content, the amount of water evaporation due to fixing was less than 50% of the water contained in the transfer paper 4 before fixing.

For comparison, fixing was performed under exactly the same conditions as above except that preheating was performed so that the temperature of the toner 6b and the transfer paper 4 at the outlet of the preheating unit 2 became 125 ° C. As a result, the fixability was good. However, the amount of water evaporation from the transfer paper 4 in the preheating unit 2 was large, and 50% or more of the water contained in the transfer paper 4 before fixing was evaporated. When a large amount of water evaporates in this manner, the temperature drop on the surface of the transfer paper 4 is large, and the input power for maintaining the temperature on the surface of the transfer paper 4 must be increased.

In the above embodiment, the case where the surface of the transfer paper 4 on which the toner 6 is transferred, on which the toner 6 is present, is directly pre-heated by the pre-heating unit 2 has been described. However, as shown in FIG. The back surface of the transfer paper 4 may be preheated by a preheating unit 2 such as a heater.

[0023]

As described above, according to the present invention, the temperature of the image forming material of the image carrier to which the unfixed image is transferred and the temperature of at least the surface of the image carrier are preheated to a temperature higher than the softening point of the image forming material. After fixing the unfixed image-forming substance on the surface of the image carrier by applying heat and pressure in a state where the softening point of the image-forming substance does not fall below the softening point, the amount of evaporation of moisture from the image carrier containing moisture is determined before fixing. Since the water content of the image bearing member is set to 50% or less, it is possible to reliably fix the toner at a low temperature and save power.

Further, after preliminarily heating the temperature of the image forming material of the image carrier to which the unfixed image forming material has been transferred and the temperature of at least the surface of the image carrier to a temperature exceeding the softening point of the image forming material, The unfixed image-forming substance is applied to the surface of the image-holder by applying pressure while the temperature of at least the surface of the image-forming substance of the image-holding body onto which the image-forming substance has been transferred and the softening point of the image-forming substance does not fall below the softening point. Since the fixing is performed, even a commonly used kneaded and crushed toner that has been fixed at a high temperature can be reliably fixed at a low temperature to save power.

Further, since the preheating is performed at a temperature not lower than the softening point of the image forming substance and not exceeding (the boiling point of water + 20) ° C. during preheating, the amount of water evaporating from the image holding member during fixing is reduced. Power consumption can be reduced.

Further, by using an infrared heating system or a flash heating system for the preheating unit and using a heating roller having a low heat capacity for the heating and pressing unit, the rise time from the standby time can be shortened, and the power consumption can be reduced. Can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a change characteristic diagram of a fixing rate with respect to a temperature of a toner and a transfer sheet during fixing.

FIG. 3 is a graph showing softening and melting characteristics of a toner.

FIG. 4 is a configuration diagram of another embodiment.

[Explanation of symbols]

1; fixing device; 2; preheating section; 3; heating / pressing section; 4;
Transfer paper, 5: recording material transport section, 6: toner image, 7: heating roller, 8: pressure roller.

Claims (4)

[Claims] An image forming material of an image carrier to which an unfixed image has been transferred and at least the surface of the image carrier are preheated to a temperature higher than the softening point of the image forming material, and then the softening point of the image forming material is obtained. In the fixing method of fixing the unfixed image forming substance to the surface of the image holding member by heating and pressing under a pressure not lower than the value, the evaporation amount of the water from the image holding member containing the water is determined based on the water content of the image holding member before fixing. A fixing method characterized by adjusting the temperature and time for preheating and heating / pressing so as to be 50% or less. 2. A fixing method for fixing an unfixed image on a surface of an image carrier by heating and pressing, wherein the temperature of at least the surface of the image forming material of the image carrier and the surface of the image carrier on which the unfixed image forming material is transferred. Is preheated to a temperature not lower than (the boiling point of water + 20) ° C. at a temperature equal to or higher than the softening point of the image forming substance, and then pressurized so as not to fall below the softening point of the image forming substance to remove the unfixed image forming substance. A fixing method characterized by fixing on a surface of a holding member. 3. A preheating section having a preheating section and a heating / pressing section, wherein the preheating section forms an image of the image forming material of the image carrier to which the unfixed image forming material has been transferred and the temperature of at least the surface of the image carrier. Preheating is performed at a temperature not lower than (softening point of water + 20) ° C. at a temperature not lower than the softening point of the substance, and the heating and pressurizing unit is an image forming substance and an image holding body of the image holding body onto which the unfixed image forming substance is transferred. A fixing device for fixing an unfixed image-forming substance to the surface of an image carrier by applying pressure in a state where at least the surface temperature does not fall below the softening point of the image-forming substance. 4. The fixing device according to claim 3, wherein an infrared heating method or a flash heating method is used for the preliminary heating section, and a heating roller having a low heat capacity is used for the heating / pressing section.