JP2022006863A - Fuser - Google Patents

Abstract

To provide a fuser which comprises a roller with an elastic layer made of a foam material and offers high print quality.SOLUTION: A fuser provided herein comprises a turning roller and an object that moves while being pressed by the roller. The roller comprises a core material and an elastic layer covering the outer periphery of the core material. The elastic layer is made of a silicon rubber sponge. A proportion of area of a sheet that actually touches the outer peripheral surface of the roller with respect to area of the sheet passing through a nip between the roller and the object is in a range of 21.5% to 25.7%, inclusive.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuser of an image forming apparatus using an electrophotographic method.

The fixing device of an image forming apparatus (for example, a copying machine, a printer) using an electrophotographic method presses and fixes the toner on the sheet against the sheet. One type of fuser has a pair of rolls (fixing roll and pressure roll) in which the toner is fixed to the sheet while the sheet passes through the nip between the rolls. The fixing roll not only pressurizes the toner on the sheet, but also melts the toner by heating, and the pressurizing roll pressurizes the toner on the sheet.

Other types of fusers have a fixing belt in place of or in addition to the fixing roll. Toner is anchored to the sheet while the sheet passes through the nip between the anchoring belt and the pressure roll. In this type, the fixing belt is pressed against the pressure roll by a fixing roll or fixing pad and melts by heating the toner. The fixing belt is reheated by a heating device and has a high temperature.

Patent Document 1 discloses that chemically foamed silicone rubber is used as the material of the elastic layer of the roll used in the fuser. As a result, the hardness of the elastic layer can be reduced to secure a wide nip width, and since the foamed silicone rubber has a low heat capacity, it is difficult to take heat from the roll or the fixing belt, and the effect of increasing the thermal efficiency can be obtained.

Japanese Unexamined Patent Publication No. 2016-80730

In order to reduce unevenness of the image printed by the image forming apparatus and improve the print quality, the nip between the rolls or the nip between the rolls and the belt is evenly applied to the entire surface of the sheet. It is preferable that the pressure is sufficiently high. When the elastic layer of the roll used in the fuser is formed from a foam material, it is desirable that high print quality can be obtained even if cells (air bubbles) are present in the elastic layer.

Therefore, the present invention provides a fuser in which the elastic layer of the roll is formed from the foamed material and high print quality can be obtained.

A fuser according to an aspect of the present invention has a rotating roll and an object that moves while being pressed against the roll. The roll has a core material and an elastic layer that covers the outer periphery of the core material. The elastic layer is made of a silicone rubber sponge. The ratio of the area where the sheet actually contacts the outer peripheral surface of the roll to the area of the sheet that has passed through the nip between the roll and the object is 21.5% or more and 25.7% or less.

In this aspect, high print quality can be obtained.

It is a schematic sectional drawing which shows an example of the fixing apparatus which concerns on embodiment of this invention. It is the schematic sectional drawing which shows the other example of the fixing apparatus which concerns on embodiment. It is the schematic sectional drawing which shows the other example of the fixing apparatus which concerns on embodiment. It is the schematic sectional drawing which shows the other example of the fixing apparatus which concerns on embodiment. It is the schematic sectional drawing which shows the other example of the fixing apparatus which concerns on embodiment. It is the schematic sectional drawing of the elastic layer of the roll which concerns on embodiment. It is an enlarged sectional view of a cell in an elastic layer. It is a figure which shows a plurality of areas referred to in the dimension measurement of a cell of a roll. It is a figure which shows the measurement test of the true contact area ratio of a sheet with respect to a roll. It is a figure which shows an example of the pattern of the sheet generated in the measurement test of the true contact area ratio. It is a figure which shows the fixing property test of a toner. It is a table which shows the details of the sample used for a test.

Hereinafter, various embodiments according to the present invention will be described with reference to the accompanying drawings. Drawing scales are not always accurate and some features may be exaggerated or omitted.

An image forming apparatus using an electrophotographic method forms an image (toner image) made of toner on a sheet of paper which is a recording medium to be conveyed. Although details of the image forming apparatus are not shown, the image forming apparatus includes a photoconductor drum and a charger, an exposure device, a developer, a transfer device, and a fuser arranged around the photoconductor drum. In the image forming apparatus, the toner is charged, so that the toner adheres to the sheet, and the sheet is conveyed to the fixing device.

As shown in FIG. 1, an example of a fuser has a movable fixing belt 1 and a rotatable pressure roll 2. The toner T is fixed to the sheet S while the sheet S passes through the nip between the fixing belt 1 and the pressure roll 2. The fixing belt 1 and the pressure roll 2 pressurize the toner T on the sheet S. The fixing belt 1 is melted by heating the toner T.

The pressure roll 2 has a core material 3, an elastic layer 4 that covers the outer periphery of the core material 3, and a mold release layer 5 that covers the outer periphery of the elastic layer 4.

The core material 3 is a hard round bar. The material of the core material 3 is not limited, but may be a metal or resin material such as iron or aluminum. The core material 3 may be hollow or solid. The figure shows a hollow core material 3.

The elastic layer 4 is a cylinder fixed to the outer peripheral surface of the core material 3 over the entire circumference, and is formed of a sponge.

The release layer 5 is a thin layer fixed to the outer peripheral surface of the elastic layer 4 over the entire circumference, and makes it easy for the pressure roll 2 to separate from the toner T fixed on the sheet S. FIG. 1 shows how a toner image is formed on one surface of the sheet S. After the toner T is fixed on one surface of the sheet S, the toner T is fixed on the other surface of the sheet S. Please note that there are times. In this case, the toner T is brought into contact with the pressure roll 2 at the nip.

The release layer 5 is formed of a synthetic resin material that is easily separated from the toner T. The material of the release layer 5 is preferably a fluororesin. Such fluororesin is, for example, perfluoroalkoxy alkane resin (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), or tetrafluoroethylene / ethylene copolymer (FEP). ETFE).

The fixing belt 1 is a cylinder in this example. A resin fixing pad 6 is arranged inside the fixing belt 1. The fixing pad 6 presses the fixing belt 1 against the pressure roll 2 to properly maintain the width of the nip between the fixing belt 1 and the pressure roll 2. At the nip, the fixing belt 1 and the pressure roll 2 are slightly deformed by mutual pressing.

A heating device 7 is arranged in the vicinity of the fixing belt 1. The heating device 7 reheats the fixing belt 1 which has been cooled by being deprived of heat by the pressure roll 2 at the nip. In the example of FIG. 1, the heating device 7 has a known electromagnetic induction heating device 7A and a magnetic field absorbing member 7B, the electromagnetic induction heating device 7A is arranged outside the fixing belt 1, and the magnetic field absorbing member 7B is the fixing belt 1. It is located inside the.

However, the type of the heating device is not limited to the example of FIG. As shown in FIG. 2, a heat generating source such as a halogen heater 8 arranged inside the fixing belt 1 may be used as the heating device.

In the example of the fixing device of FIGS. 1 and 2, the fixing pad 6 is used, but as shown in FIG. 3, a rotatable fixing roll 8 is arranged inside the fixing belt 1 instead of the fixing pad 6. You may. Like the pressure roll 2, the fixing roll 8 has a core material 3 and an elastic layer 4 that covers the outer periphery of the core material 3. In this type of fuser, the release layer 5 is not required for the fixing roll 8.

FIG. 4 shows an example of another fuser. This fuser has heating rolls 9 and 10 and a non-rotating fixing pad 6 inside the fixing belt 1. The fixing belt 1 is wound around the heating rolls 9 and 10 and the fixing pad 6 and moves. The fixing pad 6 and the pressure roll 2 pressurize the toner T on the sheet S. The fixing belt 1 is melted by heating the toner T. Each of the heating rolls 9 and 10 has a built-in heating device (for example, a halogen heater) (not shown), and the fixing belt 1 which has been cooled by being deprived of heat by the pressure roll 2 at the nip is reheated.

FIG. 5 shows an example of another fuser. This fuser has a fixing roll 11 and a pressure roll 2. Like the pressure roll 2, the fixing roll 11 has a core material 3, an elastic layer 4 that covers the outer periphery of the core material 3, and a mold release layer 5 that covers the outer periphery of the elastic layer 4. The fixing roll 11 and the pressure roll 2 pressurize the toner T on the sheet S. The fixing roll 11 has a built-in heating device (for example, a halogen heater) (not shown), and melts by heating the toner T.

The roll according to the embodiment can be used as the pressure roll 2, the fixing roll 8 and the fixing roll 11 described above. Therefore, the roll according to the embodiment has at least a core material 3 and an elastic layer 4. The roll according to the embodiment may further have a release layer 5.

On the other hand, the object that moves while being pressed against the roll according to the embodiment is, for example, the fixing belt 1. In the case of FIG. 3, both the pressure roll 2 and the fixing roll 8 are rolls, and are objects that move while being pressed against the rolls. In the case of FIG. 5, both the pressure roll 2 and the fixing roll 11 are rolls, and are objects that move while being pressed against the rolls.

The elastic layer 4 is formed of a sponge, that is, a foam, which uses silicone rubber as a main raw material. Therefore, the elastic layer 4 has a large number of cells (air bubbles) and has a low hardness, so that a wide nip width can be secured. Further, since the foamed silicone rubber has a low heat capacity, it is difficult to take heat from the roll and / or the fixing belt, and the effect of increasing the thermal efficiency can be obtained.

FIG. 6 is a schematic cross-sectional view of the elastic layer 4. The elastic layer 4 has spherical cells 18 of various sizes. In FIG. 6, the thickest solid line shows the contour of the cell 18 on the cut surface of the elastic layer 4, the thinner solid line shows the contour of the cell 18 on the plane close to the cut surface, and the thinnest solid line shows the contour of the cell 18 on the cut surface. Shows the contour of cell 18 in a plane farther from. The thick dotted line shows the outline of the cell 18 in the plane farther from the cut surface, and the thin dotted line shows the outline of the cell 18 in the plane farther from the cut surface. Each cell 18 has a shape close to a sphere. However, the shape of many cells 18 is not exactly a true sphere, but a prolate spheroid.

As shown in FIG. 7, each cell 18 has a major axis a and a minor axis b. For many cells 18, the major axis a is oriented along the thickness direction of the elastic layer 4 (the radial direction of the roll). That is, the length (major axis a) of the cell 18 along the thickness direction of the elastic layer 4 is the length along the axial direction of the roll (minor axis b) and the length along the circumferential direction of the roll (minor axis). b) Greater than. It is presumed that this is partly due to the temperature difference in the radial direction of the roll in the heating step in the production of the elastic layer 4.

As is clear from FIGS. 1 to 5, the roll is subjected to a shearing force from a component (fixing belt 1, fixing roll 11 or pressure roll 2) in contact with the roll. In addition, the roll is pressed against a component that comes into contact with the roll, so that it receives a compressive force. When the cell 18 in the elastic layer 4 has a prolate spheroidal shape, bubble rupture (damage of bubbles) is more likely to occur due to stress concentration as compared with the true spherical shape, which adversely affects the durability of the elastic layer 4. May give. Therefore, it is preferred that all cells 18 in the elastic layer 4 ideally have a true spherical shape. In other words, the aspect ratio (a / b), which is the ratio of the major axis a to the minor axis b, is preferably close to 1.0.

The preferred method for producing the roll according to the embodiment is as follows.

First, the core material 3 is prepared. The outer peripheral surface of the core material 3 is coated with a primer (adhesive).

On the other hand, silicone rubber is prepared as the main raw material of the elastic layer 4. The silicone rubber used as the main raw material is a mirable type silicone rubber.

Next, a cross-linking agent and a chemical foaming agent are mixed with the main raw material silicone rubber to obtain an elastic material. If desired, cross-linking aids, catalysts and / or colorants may be added to the elastic material.

The cross-linking agent and the cross-linking aid can be selected from the cross-linking agent and the cross-linking aid that cross-link the silicone rubber.

The chemical foaming agent can be selected from the chemical foaming agents used to make sponges from silicone rubber. For example, 1,1'-azobis (cyclohexane-1-methylcarboxylate) can be used as the chemical foaming agent. The amount of the chemical foaming agent to be blended is not limited, but for example, 2 to 12 parts by weight of the chemical foaming agent can be blended with respect to 100 parts by weight of the uncrosslinked silicone rubber.

The elastic material obtained by mixing is kneaded using, for example, a roller.

Next, the outer peripheral surface of the core material 3 is covered with an elastic material. For example, a rubber extruder can be used to coat the elastic material around the core material 3. Alternatively, a molding die may be used to coat the elastic material around the core material 3.

Next, a plasticizing process is performed. The plasticization treatment may be to leave the elastic material at an appropriate temperature (for example, room temperature) for a long time (for example, 48 hours). The plasticization treatment appropriately increases the degree of plasticity.

Next, the core material 3 and the elastic material around it may be preheated. This is because at the later stage of primary cross-linking, we want to make the temperature in the elastic material as uniform as possible and make the cell as spherical as possible. The preheating temperature is lower than the primary crosslink temperature.

Next, the elastic material around the core material 3 is primarily crosslinked and chemically foamed. This step is performed, for example, by heating the core material 3 and the elastic material around it for a certain period of time. Due to the action of the heated chemical foaming agent, a large number of cells are generated in the elastic material. Also, the primary cross-linking cures the elastic material to some extent and largely determines the shape, size, and arrangement of the numerous cells within the elastic material. For example, excessive cell growth is suppressed.

After the primary cross-linking, the secondary cross-linking of the elastic material is performed. This step is performed by heating the core material 3 and the elastic material around it at a temperature usually different from the temperature in the primary cross-linking for a longer time than the time of the primary cross-linking. Secondary cross-linking further cures the elastic material and ultimately determines the shape, size, and placement of the numerous cells within the elastic material. In addition, the secondary cross-linking removes the residue (decomposition product) of the cross-linking agent remaining in the elastic material and the siloxane having a low molecular weight. In this way, the elastic layer 4 made of sponge that covers the outer periphery of the core material 3 can be obtained from the elastic material.

In the steps of preheating, primary cross-linking and chemical foaming, and secondary cross-linking, heating devices such as, for example, electric furnaces are used.

If necessary, the elastic layer 4 is subjected to a finishing process (cutting process and / or polishing process).

When a roll having the release layer 5 as the outermost layer is manufactured, the outer periphery of the elastic layer 4 is further coated with the release layer 5.

The applicant manufactured test rolls (test rolls) in which the manufacturing process of the elastic layer 4 was different, and investigated various characteristics of these test rolls. As shown in FIG. 8, each test roll 20 has a core material 3, an elastic layer 4 made of sponge that covers the outer periphery of the core material 3, and a mold release layer 5. Hereinafter, these test rolls are referred to as samples.

Details of each sample are shown in FIG.

The composition of the material of each sample is as follows.

As the silicone rubber as the main raw material of the elastic layer 4, "RBB-6660-60" available from DuPont Toray Specialty Material Co., Ltd. (Tokyo, Japan) was used. The 100% modulus of "RBB-6660-60" at a temperature of 200 ° C. is 3.5 MPa.

In order to reduce cell damage during roll production and improve roll durability, it is desirable that the strength of the main raw material of the elastic layer 4 at the temperature in the foaming process and its vicinity is high to some extent. From this viewpoint, the 100% modulus of the silicone rubber, which is the main raw material of the elastic layer 4 at a temperature of 200 ° C., is preferably 2.0 MPa or more, and more preferably 3.1 MPa or more. From this point of view, "RBB-6660-60" is a preferred material.

In manufacturing each sample, 100 parts by weight of silicone rubber, 3 parts by weight of "C-25B" manufactured by Shin-Etsu Chemical Co., Ltd. (Tokyo, Japan), and "C" manufactured by Shin-Etsu Chemical Co., Ltd. -25A ”) by 0.5 parts by weight, chemical foaming agent (“KE-P-26” manufactured by Shin-Etsu Chemical Co., Ltd.) by 9 parts by weight, colorant (“KE-COLOR” manufactured by Shin-Etsu Chemical Co., Ltd.) ) Was added in an amount of 0.5 part by weight.

The uncrosslinked elastic material thus obtained was kneaded using a roller. Next, the elastic material was coated on the outer periphery of the core material 3 with a rubber extruder, and a plasticizing treatment was performed. The diameter of the core material 3 was 20 mm. In the plasticization treatment, the elastic material was left at room temperature for a long time. For each sample, the leaving time is as shown in FIG.

After the plasticization treatment, the plasticity of the uncrosslinked elastic material was measured. To be more precise, a test piece, which is a mass of the same elastic material, was prepared separately from the sample (the core material 3 and the elastic material coated on the outer periphery thereof), and the test piece was also subjected to a thermoplastic treatment (room temperature). Left underneath for a long time). For the measurement of the degree of plasticity, a "Williams plast meter" manufactured by Yasuda Seiki Seisakusho Co., Ltd. (Hyogo, Japan), which is a parallel plate plasticity meter, was used in accordance with JIS K6249: 2003. A load of 5.0 kgf was applied to the test piece, and the plasticity was measured 10 minutes after the load was applied. For each sample, the measured plasticity is as shown in FIG.

After this, sample 6 was preheated at 60 ° C. for 25 minutes. No preheating was performed on the other samples. If preheating is not performed, the size of the cell tends to be excessive and the aspect ratio of the cell is considered to be large. If preheating is performed properly, excessive growth of the cell is suppressed and the sphericity of the cell is increased. Conceivable. However, if the degree of plasticity after the plasticization treatment is high, the elastic material is hard and excessive growth of the cell is suppressed, so that it is not always necessary to perform preheating.

Next, the elastic material was heated together with the core material 3 to perform primary cross-linking and chemical foaming of the elastic material. For each sample, the temperature and time of the primary cross-linking and chemical foaming steps are as shown in FIG. It is considered that the primary cross-linking under appropriate conditions suppresses the excessive growth of the cell and increases the sphericity of the cell.

Further, the elastic material was secondarily crosslinked by heating the elastic material together with the core material 3 under different temperature conditions from the primary crosslinking. It is considered that the secondary cross-linking under appropriate conditions obtains an elastic material having an appropriate hardness and improves the durability of the elastic layer 4.

In this way, the elastic layer 4 made of sponge covering the outer periphery of the core material 3 was obtained.

Next, the excess portion of the elastic layer 4 was removed by cutting, and the surface of the elastic layer 4 was further polished. The inner diameter of the elastic layer 4 was 20 mm, which was the same as the diameter of the core material 3, and the length of the elastic layer 4 was 300 mm.

Next, a silicone rubber-based adhesive (“KE-1880” manufactured by Shin-Etsu Chemical Co., Ltd.) was coated on the outer peripheral surface of the elastic layer 4 with a thickness of 20 μm, and the conductivity was manufactured by Gunze Co., Ltd. (Osaka, Japan). A PFA tube (thickness 30 μm) was adhered. This PFA tube is the release layer 5.

After that, the roll was heated at 150 ° C. for 30 minutes to perform primary cross-linking of the silicone rubber-based adhesive, and the adhesive was cured to some extent. After that, the roll was heated at 100 ° C. for 4 hours to perform secondary cross-linking of the silicone rubber-based adhesive, and the adhesive was further cured. In this way, the sample was produced.

The outer diameter of the test roll 20 immediately after production was 31.82 mm to 31,92 mm.

In addition, the dimensions of the cells of the elastic layer 4 of each sample were measured. As shown in FIG. 8, the sample was cut along two planes P perpendicular to the axial direction, and a small region A on each of the two cut planes P was observed with a scanning electron microscope. The two planes P were randomly selected. The scanning electron microscope used was "SU3500" manufactured by Hitachi High-Technologies Corporation (Tokyo, Japan).

In the observation, the measurer divided each area A into eight areas a1 to a8. Areas a1 to a4 are arranged in the radial direction, and areas a5 to a8 are also arranged in the radial direction. The areas a1 to a8 are obtained by dividing the sector having a central angle θ into four equal parts in the radial direction from the inner circumference 4i of the elastic layer 4 to the outer circumference 4O. It is obtained by dividing the inner circumference 4i of 4 into four equal parts in the radial direction from the outer circumference 4O. θ is 30 degrees.

In each of the eight areas a1 to a8 on each of the two cut surfaces P, the measurer selected the three largest cells. Therefore, for each sample, the number of selected cells is 48. The measurer visually measured the major axis a and the minor axis b of each cell. Then, for each cell, the cell diameter which is the average (a + b) / 2 of the major axis a and the minor axis b was calculated, and the average cell diameter which is the average of the cell diameters of 48 cells was calculated. In addition, the average aspect ratio (a / b) of 48 cells was calculated for each sample. For each sample, the average cell diameter and the average aspect ratio are as shown in FIG.

As described above, the "average cell diameter" is the average of the cell diameters of the three largest cells in each area in a plurality of areas. The "cell diameter" is the average of the major axis a and the minor axis b for each cell. The "average aspect ratio" is the average of the aspect ratios of the three largest cells in each area in a plurality of areas.

Further, the specific gravity of the elastic layer 4 of each sample was measured using an electronic hydrometer "MD-200S" manufactured by A & D Co., Ltd. (Tokyo, Japan). The measured specific densities are shown in FIG.

Since the roll used in the fuser pressurizes the toner on the sheet, the surface condition of the roll is important. Therefore, the wave swell WCM (based on JIS _B0610 : 1987) on the outer peripheral surface of each sample was used with "SURFCOM 1400D", which is a surface roughness / contour shape measuring machine manufactured by Tokyo Seimitsu Co., Ltd. (Tokyo, Japan). Was measured. The length of the measured portion was 8 mm, the measurement speed was 3.0 mm / sec, and the cutoff value was 0.8 mm. The value of the wave swell WCM was read by the software attached to "SURFCOM _1400D ". The read roar wave swell _WCM is as shown in FIG.

Further, the sheet actually contacts the outer peripheral surface of the test roll 20 with respect to the area of the sheet that has passed through the nip between the test roll 20 and the object that moves in contact with the test roll 20 (for example, the fixing belt 1 and the fixing roll 11). The ratio of the area was measured. Since this ratio is the ratio of the area where the outer peripheral surface of each sample actually contacts the sheet when the outer peripheral surface of each sample comes into contact with the sheet, this ratio is called the "true contact area ratio".

In the measurement of the true contact area ratio, the test roll 20 (sample) shown in FIG. 9 is pressed against the tester roll 30 with a load of 256 N in a room temperature environment, and the test roll 20 and the tester roll 30 are rotated. , The pressure distribution measurement sheet PS was passed through the nip between them. Rolls 20 and 30 were not heated. As described above, the length of the elastic layer 4 was 300 mm.

The pressure distribution measurement sheet PS was a "prescale micropressure (4LW)" manufactured by FUJIFILM Corporation (Tokyo, Japan). The pressure distribution measurement sheet PS develops color when it receives a pressure higher than a certain value. FIG. 10 shows an example of the pattern of the pressure distribution measurement sheet PS generated in the measurement test of the true contact area ratio. After passing through the nip, the colored portion 32 on the pressure distribution measurement sheet PS corresponds to the portion in contact with the outer peripheral surface of the sample. After passing through the nip, the measurer photographs the pressure distribution measurement sheet PS, performs binarization processing (processing for discriminating between the colored portion 32 and the non-colored portion 33) on the captured image, and performs the pressure distribution measurement sheet. The ratio of the area of the colored portion in PS was calculated. This ratio is the true contact area ratio. The true contact area ratio of each sample is as shown in FIG.

Furthermore, a toner fixability test was performed on each sample. In the fixability test, a solid black image was printed on a paper sheet using a digital full-color multifunction device "MP C5504" of Ricoh Corporation (Tokyo, Japan). This machine had the fuser shown in FIG. 2, and each sample was used as a pressure roll 2.

In the fixability test, as shown in FIG. 11, the mending tape 36 was attached to the printed surface 35a of the paper sheet 35. The mending tape 36 was a "Scotch mending tape width 18 mm" available from 3M Japan Ltd. (Tokyo, Japan).

After that, the sheet 35 to which the mending tape 36 was attached was placed on the flat upper surface of the table 37, and the mending tape 36 and the sheet 35 were loaded with a cylindrical block 38 having a diameter of 100 mm and a width of 20 mm. Specifically, the cylindrical block 38 was rolled at a constant speed (10 mm / sec) and reciprocated once.

Next, the mending tape 36 was peeled off from the sheet 35. The peeling angle was 180 degrees and the peeling speed was 10 mm / sec.

The image density on the sheet 35 before and after the tape 36 was peeled off was measured with a reflection densitometer, and the toner fixing rate was calculated according to the following formula. The reflection densitometer was the "Macbeth RD-19" made by Amazis Holding Gezel Shaft Mitt Beschlenktel Haftung.
Toner retention rate (%) = (image density after tape peeling / image density before tape application) x 100

The results of the toner fixability test are shown in FIG. If the toner fixing rate calculated by the above formula is 90% or more, the test result is regarded as good, and if the toner fixing rate is less than 90%, the test result is regarded as bad.

As is clear from the results of FIG. 12, the results of the fixability test were good for Samples 3 to 6. According to the results of FIG. 12, it is preferable that the true contact area ratio is large. Further, in order to increase the true contact area ratio, it is preferable that the average cell diameter of a large cell is small. This indicates that if the cell is too large, the surface of the elastic layer 4 and thus the roll will be rough. Further, when the cell is small, the specific gravity of the elastic layer 4 is large.

From the results of FIG. 12, the ratio of the area where the sheet actually contacts the outer peripheral surface of the roll (true contact area ratio) to the area of the sheet that has passed through the nip is 21.5% or more and 25.7% or less. Is preferable. Further, it is preferable that the average of the cell diameters of the three cells having the largest size in each area of the elastic layer 4 in the plurality of areas is 106 μm or more and 144 μm or less. Further, it is preferable that the filter wave swell _WCM on the outer peripheral surface of the roll is 5.2 μm or more and 7.4 μm or less. Further, the specific gravity of the elastic layer 4 is preferably 0.552 or more and 0.610 or less.

Although the present invention has been illustrated and described above with reference to preferred embodiments of the present invention, those skilled in the art can change the form and details without departing from the scope of the invention described in the claims. It will be understood that there is. Such changes, modifications and modifications should be included within the scope of the invention.

1 Fixing belt (object)
2 Pressurized roll (roll, object)
3 Core material 4 Elastic layer 5 Release layer 8,11 Fixing roll (roll, object)
18 cells

Claims (5)

A fuser having a rotating roll and an object that moves while being pressed against the roll.
The roll is
With the core material
It has an elastic layer that covers the outer circumference of the core material, and has an elastic layer.
The elastic layer is made of a silicone rubber sponge.
The ratio of the area where the sheet actually contacts the outer peripheral surface of the roll to the area of the sheet that has passed through the nip between the roll and the object is 21.5% or more and 25.7% or less. Fixer. The fuser according to claim 1, wherein the elastic layer of the roll has an axial length of 300 mm, and the roll and the object are brought into contact with each other with a load of 256 N. The cell diameter of the three largest cells in each area of the elastic layer (the cell diameter is the average of the major axis and the minor axis of the cell) is characterized in that the average in a plurality of areas is 106 μm or more and 144 μm or less. The fuser according to claim 1 or 2. The fuser according to any one of claims 1 to 3, wherein the wave swell _WCM on the outer peripheral surface of the roll is 5.2 μm or more and 7.4 μm or less. The fuser according to any one of claims 1 to 4, wherein the elastic layer has a specific gravity of 0.552 or more and 0.610 or less.

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