JP2992710B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for preventing offset transfer and stain transfer of a fixing device in electrophotography and a means for giving gloss to a color image.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open (JP-A) No. 49-36342 discloses a fixing device for heating a toner image, particularly a fixing device via a belt. Is provided via a belt, so that the transfer material carrying the toner image is fed between the pressure roller and the belt so as to be fixed. However, not enough nip area N ₁ is obtained, to the extent that the gloss may appear at the top of the supply guaranteed without toner images of heat from the heating roller via the belt molten toner was in a situation where not made.

[0003] Although the fixing device is described which performs thermal fixing through a belt in JP-A-61-122665, is sufficient nip area N ₂ by embracing angle independent by the belt against the pressure roller The length of the transfer material is not shortened, so that a sufficient melting time cannot be obtained and the transfer material is insufficiently heated.
Eventually, the fixing property depends on the material and thickness of the transfer material, resulting in unstable heat fixing.

[0004]

SUMMARY OF THE INVENTION According to the present invention, high glossiness can be achieved without causing the offset transfer to occur even if the thermal fixability of the toner image does not depend on the material or thickness of the transfer material. An object of the present invention is to provide a fixing device capable of obtaining a high-quality color toner image.

[0005]

The object of the present invention is as follows.
This can be achieved by the configuration requirements.

(1) Include a heating roller and a peeling roller
An endless belt that has a pressure roller which presses the heating roller via the endless belt, a fixing device for fixing by heating and pressing the transfer material carrying the toner image, the heating, pressurizing圧両a first nip region N ₁ is formed by a roller及beauty endless belt, said endless belt and said 1 ≦ N ₂ / N ₁ ≦ a relationship between the second nip region N ₂ is formed by the pressure roller 3 and the fixing device being characterized in that none.

(2) The first nip region and the second nip region
Before the heating roller and the pressure roller surface to form a nip region is characterized by a soft roller rubber
The fixing device according to (1) .

(3) The first nip region and the second nip region
The heating roller and the pressure roller to form a nip region wherein characterized by having a heat source (1) or the
The fixing device according to (2) .

[0009]

1 is a side view showing a nip area of FIG. 1, a partially enlarged view of FIG. 2, a sectional side view of FIG. 3, an exploded perspective view of a cooling unit of FIG. This will be described with reference to the sectional view of the fixing roller (upper and lower), the sectional view of the layer structure of the belt in FIG. 6, and the viscosity-temperature characteristic curve of the toner in FIG.

Heating roller having a heat source heater 14 at its core
11. An endless belt 25 is wound around the separation roller 21 and the tension roller 22. And pressure roller
31 is pressed against the heating roller 11 via the belt 25. Air cooling devices 40 and 50 are provided on the upper and lower portions of the belt 25 between the pressure roller 31 and the downstream peeling roller 21 respectively.
Is arranged.

On the surfaces of the heating roller 11 and the pressure roller 31, as shown in FIG.
2,32 is pressed each other pressurized O is soft roller is formed is coated, and is easily crushed to form a 1, the nip area N ₁ sandwiching the angle theta _1, as shown in FIG. 2 . However, the rubber hardness of the pressure roller 31 is preferably larger than that of the heating roller 11.

Further, a pressure roller is provided for the heating roller 11.
The arrangement of 31 forms the holding angle θ ₂ by the endless belt 25, and the endless belt 25 forms the nip area N ₂ . The length of the nip region N ₁ is 3 to 20 mm, more preferably 3 to 10 mm, the length of the nip area N ₂ is 5 to 50 mm, more preferably it is in the 10～35Mm.

The nip ratio is preferably 1 ≦ N ₂ / N ₁ ≦ 3.

The transfer material 61 carrying the toner 62 is sandwiched between the pressure roller 31 and the belt 25 along the entrance guide 18, and an upper portion of an air cooling box 52 having a built-in fan 53 of a lower air cooling device 50. Is conveyed in a state of being in close contact with the belt 25 and a guide plate 51 provided with a louver and the endless belt 25, and is separated from the belt 25 at the peeling roller 21 by the upper and lower guides 23A and 23B. Roller pair
Recovered by 24. In the area beyond the endless belt 25 above the lower air cooling device 50, a duct 43
An upper air cooling device 40 that blows air is provided. In this way, the intermediate transfer material 61 and the toner 62 are cooled from the outside and the inside of the endless belt 25, and are easily separated and collected from the belt 25.

Further, cleaning rollers 16 and 17 are provided above the heating roller 11, and a cleaning roller 36 is similarly provided below the pressure roller 31.

Further, a discharging brush is provided immediately after being discharged from the return belt portion and the roller pair 24 near the peeling roller.
26 and 27 are provided.

A gap 56 formed between the air-cooling box 52 and the guide plate 51, a duct 41 of the upper air-cooling apparatus 40 and a heating roller
Since the endless belt 25 closer to 11 and the gap 46 are small, cooling air is blown in the direction of the heating roller 11 and the pressure roller 31 to cool the roller surfaces and reduce the heating efficiency. So that they don't end up.

The surface of the heating roller 11 and the pressure roller
Temperature detection sensors 19 and 39 are provided near the surface of 31, respectively.

As shown in FIG. 6, the endless belt 25 has a release layer 29 made of silicone rubber on a polyimide base 28.
The thickness of the polyimide layer is 25 to
The thickness is 75 μm, and the total thickness is 25 to 150 μm.

Next, the operation of the fixing device 1 configured as described above will be described.

First, the viscosity-temperature characteristic curves of the linear polyester toner and the general polyester toner shown in FIG. 7 will be described.

In this graph, the vertical axis is scaled by a common logarithmic value of viscosity in units of poise, and the horizontal axis is scaled by temperature. The linear polyester toner is indicated by a solid line, and the general polyester toner is indicated by a chain line. Both toners have a high viscosity of about 100,000 poise at around 100 ° C., that is, a glass transition state, and when the temperature exceeds 100 ° C., both toners are in a molten state. And the optimal melting state is viscosity 5000
It's about Poise. The viscosity state of the linear polyester toner is 120 ° C., which is much lower than the heating temperature of conventional polyester toners, which reaches 150 ° C.

Further, in the present invention, the endless belt 25 is interposed in comparison with a conventional fixing device in which thermal fixing is performed by a nip of only a pair of rollers by two fixing rollers. Since time can be secured, the melting temperature can be increased to a higher level than before, and the heating area can be made much wider. In this heating region, the unfixed image is sufficiently melted by a toner that can be melted at a low temperature, such as a linear polyester resin. Due to the adhesive force between the toner 62 and the transfer material 61 in the molten state and the airflow from the cooling fan 53 applied from the back surface of the transfer material, the transfer material 61 and the toner 62 are conveyed while adhering to the endless belt 25 and are transferred to the belt itself. The temperature is lowered by the temperature drop and the cooling effect of the airflow.

In this area, the toner 62 and the transfer material 61, which have been sufficiently cooled and have increased in viscosity to be in a glass dislocation state,
At the end of the endless belt 25 supported by the transport roller, the endless belt 25 is separated from the belt 25. At this time, since the toner 62 is almost in a coagulated glass dislocation state, the surface property of the belt 25 is maintained as it is, and a glossy surface close to a mirror surface is obtained. As described above, since the toner 62 solidifies after being sufficiently melted, the color reproducibility by melting and mixing a plurality of color toners is ensured, and the transparency when fixed on an OHP or the like can also be stably ensured. Here, as described above, since the surface material constituting the endless belt 25 is a material such as silicon rubber which is a release agent, since the release layer itself has elasticity as well as release properties, uniform heating and heating of the toner are performed. Pressure, and also has a damper effect between the toner 62 and the base of the endless belt 25, so that even if a toner that is easily melted at a relatively low temperature, such as a linear polyester toner, an offset state occurs at all. If it does not occur, it can be kept at a level that is very small and can be cleaned.

Further, the temperature is controlled by the contact of a sensor 19 as a temperature detecting means provided along the outer peripheral surface which does not correspond to the belt conveyance path of the fixing roller 10 on the side where the endless belt 25 is wound. As an advantage that cannot be dropped, the surface of the endless belt 25 is not damaged by the sensor 19 at all. Conversely, since the belt 25 and the toner 62 are in contact only on the front surface of the endless belt 25 and the toner does not flow to the back surface, the toner 62 does not adhere to the sensor 19 to cause detection failure.

In the case of a fixing device using the endless belt 25, the state of the upper air cooling device 40 and the lower air cooling device 50 can easily affect the temperature of the fixing portion. By controlling the heating of the heater in accordance with the reading of the sensor 39 as a means and the reading of the sensor 19, the temperature of the fixing portion can be maintained in a stable range.

[0027] Now, what is needed is length N ₁ of the nip,
This is for uniform pressing and melting, and when heated from above (inside) the endless belt 25, the toner 62 and the endless belt 25 are heated.
Melting at the interface with the substrate is guaranteed. However, if excessive heating is performed, the toner 62 spreads and the toner image is disturbed. And cooling becomes difficult.

[0028] Next is the required length N ₂ of the nip is in serves to sufficiently heat the transfer material 61 to improve the fixing property by thoroughly soak the transfer material 61 is melted toner 62 Seems to be from.

Heating on the toner side is performed in a relatively short period of time to prevent the image quality from deteriorating. Therefore, it is not necessary to apply a large pressure to the nip, and it is sufficient if the toner 62 is melted. It is important that the substrate side 25 is heated slowly to obtain sufficient toner adhesion.

The reason why the upper limit of the nip ratio N ₂ / N ₁ is suppressed to 3 is that if N ₂ is too large, the toner image is also excessively melted and the quality is lowered. If N ₂ / N ₁ is too large, the angle between the entrance side and the exit side of the transfer material 61 becomes too large. Further, N ₂ / N ₁ cannot be so large to secure a sufficient cooling area for the transfer material 61. Making it too large also hinders miniaturization of the device. Depending on the type of recording material, curling and wrinkling may occur in N ₂
Significantly as the / N ₁ increases.

Furthermore, it is desirable to avoid since the driving torque of N ₂ is made too large increases.

As described above, by setting 1 ≦ N ₂ / N ₁ ≦ 3, it is possible to stably achieve the sufficient infiltration and sufficient gloss of the toner 62 into the transfer material 61, Despite sufficient melting and gloss of the toner, offset transfer of the toner to the endless belt is eliminated, and there is practically no surface contamination on the subsequent transfer paper based on the offset transfer. We were able to. As a result, high-quality image fixing can be stably achieved. Further, the pressure roller 31 may be heated by providing a heater 34 at the center thereof, or the heater 34 may be omitted. In any case, the surface temperature detection sensor
The amount of heating may be controlled based on the information of 39.

[0033]

According to the fixing device of the present invention, high-quality image transfer without offset smear transfer and glossy bleeding, in particular, color image transfer can be performed stably without depending on the material and thickness of the transfer material. It was possible to achieve a compact and low-cost fixing device.

[Brief description of the drawings]

FIG. 1 is a side view showing a nip region in the present invention. FIG. 2 is a partially enlarged view thereof. FIG. 3 is a side sectional view of one embodiment of the present invention.
FIG. 4 is an exploded perspective view of the cooling unit of the present embodiment. FIG. 5 is a sectional view of a heating roller or a pressure roller. FIG. 6 is a sectional view of a layer structure of the endless belt. FIG. 7 shows a viscosity-temperature characteristic curve of the toner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing device 11 ... Heating roller 14, 34 ... Heater 16, 17, 36 ... Cleaning roller 18 ... Inlet guide 19, 39 ... Temperature detection sensor 21 ... Peeling roller 22 ・ ・ ・ Tension roller 23A, 23B ・ ・ ・ Vertical guide 24 ・ ・ ・ Discharge roller pair 25 ・ ・ ・ Endless belt 26,27 ・ ・ ・ Electrostatic removing brush 31 ・ ・ ・ Pressurizing roller 40,50 ・ ・ ・ Air cooling device 41 ・ ・ ・ duct 43 ・ ・ ・ fan 46,56 ・ ・ ・ gap 51 ・ ・ ・ guide plate 52 ・ ・ ・ air cooling box 53 ・ ・ ・ fan 61 ・ ・ ・ transfer material 62 ・ ・ ・ toner

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiki Yamazaki 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Shizuo Morita 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Masakazu Fukuchi 2970 Ishikawacho, Hachioji-shi, Tokyo Examiner in Konica Corporation, Makoto Ichinomiya (56) References JP-A-49-36342 (JP, A) JP-A-64-90477 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/20

Claims (3)

(57) [Claims] Has claim 1. A non <br/> end belt you containing a heat roller and the peeling roller, and a pressure roller which presses the heating roller via the endless belt, the transfer material carrying the toner image in the fixing apparatus for heating pressurized fixing, the heating, pressurizing圧両roller及beauty the first nip region N ₁ is formed by an endless belt, the endless belt and the second formed by the pressure roller fixing device being characterized in that none of the relationship between the nip area N ₂ between _{1 ≦ N 2 / N 1 ≦} 3. 2. The first nip region and a second nip region.
2. The fixing device according to claim 1 , wherein the heat roller and the pressure roller forming the tapered area are soft rollers having rubber surfaces. 3. The first nip region and the second nip region.
The heating roller and the pressure roller to form a flop region fixing device according to claim 1 or claim 2 characterized by having a heat source.