JPH08328407A - Heating device and image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the occurrence of offset in a contact heating type heating device regardless of the environment such as high humidity or low humidity. In a contact heating type heating device in which a heating member 7 and a member to be heated P are brought into contact with each other to heat-treat the member to be heated, the heating member 7 includes at least a conductive layer and a target layer formed thereon. A heating device having a release layer in contact with a heating member, and having a characteristic that the surface potential generated when an electric charge is applied to the surface of the release layer remains constant when the amount of electric charge increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact heating type heating device for bringing a heating member and a heating member into contact with each other to heat-treat the heating member, and an image forming apparatus provided with the heating device as an image heating fixing device. .

[0002]

2. Description of the Related Art Contact heating type heating devices include devices such as a heat roller type and a film heating type. For example, a copying machine, a laser beam printer, a facsimile, a micro film reader printer, an image display device, and a recording device. In an image forming apparatus such as a machine, a recording material (transfer material sheet) as an image support is formed by using a toner made of a heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. -It carries an unfixed toner image (fixed image) corresponding to the target image information formed by the transfer method or direct method on the surface of the electrofax sheet, electrostatic recording sheet, printing paper, etc. It is used as an image heat fixing device for performing heat fixing processing as a permanently fixed image on the surface of a recording material.

A heat roller type image heating and fixing device includes a heating roller as a heating member which is heated to a predetermined temperature.
A pressure roller is provided as a pressure member that has elasticity and is in pressure contact with the heating roller, and the recording material to be subjected to image fixing processing as the heated member is introduced into the pressure contact nip portion of both rollers and is nipped and conveyed. The heating roller heats and fixes the unfixed image.

The film heating type image heating and fixing device is
JP-A-63-313182 and JP-A-2-1578
No. 78 / Japanese Patent Laid-Open No. 4-44075 / No.
As disclosed in Japanese Laid-Open Patent Publication No. 204980, a heat-resistant film is sandwiched between a heat-generating member and a pressure member to form a nip portion, and the heat-resistant film is heated by the heat-generating member at the nip portion. The recording material to be image-fixed is introduced as a heated member between the heat-resistant film and the pressure member, and it moves through the nip part together with the heat-resistant film and is heated by the heat-generating member. A film is used to heat and fix an unfixed image.

[0005]

A contact heating type in which a heating member such as a heating roller or a heat-resistant film is brought into contact with a member to be heated to heat-treat the member to be heated, like the above-mentioned heating roller system or film heating system. In the heating device of
Due to the electrostatic factor, an offset occurs in which the substance on the heated member side is transferred and attached to the surface of the heating member.

In the image heating and fixing device, a toner offset occurs in which a part of the toner of the carried toner image on the recording material side as the heated member is transferred and attached to the surface of the heating member.

Therefore, it has been proposed to reduce the surface potential of the heating member by lowering the resistance of the heating roller as the heating member and the surface release layer of the heat-resistant film to prevent offset due to electrostatic factors. There is.

However, even in this case, when the recording material as a heated member to be passed through has a low resistance by absorbing moisture in a high humidity environment, the toner retained on the recording material is Transfer charges of opposite polarity leak into the low resistance release layer on the heating member side.

Therefore, the electrostatic attraction force between the recording material and the toner does not work to cause an offset, or the transfer current of the image transfer portion for transferring the toner image from the image carrier to the recording material is heated through the recording material. It flows into the low-resistance release layer of the member, and image transfer omission occurs at the image transfer portion.

When the surface release layer of the heating member is an insulating layer, the insulating surface release layer is charged with a polarity opposite to that of the toner due to friction with the recording material that has passed through the sheet in a low humidity environment. The toner on the recording material is attracted to cause an offset, or the recording material after passing through the image transfer portion is offset when the recording material is discharged by the discharging unit to separate it from the image carrier.

Therefore, an object of the present invention is to prevent the occurrence of offset in a contact heating type heating device regardless of the environment such as high humidity or low humidity.

[0012]

The present invention is a heating device and an image forming apparatus characterized by the following configurations.

(1) In a heating apparatus of a contact heating type in which a heating member and a member to be heated are brought into contact with each other to heat-treat the member to be heated, the heating member is at least a conductive layer and a member to be heated formed on the conductive layer. A heating device having a release layer in contact with a heating member, and having a characteristic that the surface potential generated when an electric charge is applied to the surface of the release layer remains constant when the amount of electric charge increases.

(2) The release layer of the heating member has a thickness of 10 μm.
The heating device according to (1), which is made of a fluororesin having a size of m or less.

(3) The heating device according to (1), wherein the release layer of the heating member contains tetrafluoroethylene resin.

(4) The heating device according to (1), characterized in that a conductive feeler is placed in the release layer of the heating member.

(5) A device for heating a heated member by introducing a heated member into the nip portion and passing the heated member through a pressing member facing the heating member to form a nip portion. The heating device according to any one of (1) to (4).

(6) The heating device according to (5), wherein the pressing member has an insulating property on the surface layer.

(7) The heating member is a heat-resistant film which is in contact with the heat-generating member and slides on one side and contacts the member to be heated on the other side. The heat-resistant film is provided on the heat-generating member. The heating device according to any one of (1) to (6), wherein the member to be heated is heated by the heat-resistant film heated by the member to be heated by moving the member to be recorded together.

(8) The heating device according to any one of (1) to (6), wherein the heating member is a heat roller.

(9) An image forming apparatus comprising the heating device according to any one of (1) to (6) as an image heating and fixing device for heating and fixing an unfixed image on a recording material. apparatus.

(10) A means for forming an image on an image carrier, a means for transferring the formed image to a recording material, and a means for discharging the recording material after the image transfer. The image forming apparatus according to (9).

[0023]

[Action]

a) The heating member has at least a conductive layer and a release layer formed thereon, which is in contact with the member to be heated, and the surface potential generated when a charge is applied to the surface of the release layer increases the charge amount. When the heating member is charged due to friction with the heated member under low humidity, the charging potential of the surface release layer of the heating member does not exceed a certain value. This is probably because the release layer is thin, and when the surface potential exceeds a certain level, the release layer microscopically causes dielectric breakdown and surface charges escape to the conductive layer. It is possible to prevent the electrostatic offset (transfer and adhesion) of the substance, and the toner offset under low humidity in the image heating and fixing device.

In addition, as in the case where the release layer is made conductive, the electric charge existing in the heated member is leaked under high humidity, and the electrostatic attraction force between the heated member and the substance on the heated member side is increased. It is also possible to prevent the occurrence of offset without the use of the toner, and it is possible to prevent the occurrence of toner offset under high humidity in the image heating and fixing device. Further, in the image forming apparatus, even when the same recording material as the member to be heated exists across the transfer section of the image forming mechanism section and the fixing nip section of the image heating and fixing apparatus, The transfer current does not flow into the release layer of the heating member through the recording material having a low resistance under high humidity to cause transfer omission.

That is, even under low humidity and high humidity, the offset (transfer adhesion) of the substance from the heated member side to the heating member side,
In the image heating and fixing device, toner offset can be prevented.

The conductive layer of the heating member may be floated without being grounded, and in this case, since the means for grounding is not required, the number of parts can be reduced.

B) Test results have shown that the release layer of the heating member is made of a fluororesin having a thickness of 10 μm or less to enhance the effect of preventing offset.

C) Since the mold release layer of the heating member contains PTFE, the film thickness can be increased and the mold releasability does not deteriorate due to wear.
Further, even if the film thickness is touched at the time of manufacturing, the offset is unlikely to occur, so that the yield at the time of manufacturing is increased.

D) By inserting a conductive feeler in the release layer of the heating member, the offset prevention property under low humidity can be improved, and the film thickness can be increased to prevent the deterioration of the release property due to abrasion. The result of the test revealed that it was possible.

E) Further, in the image forming apparatus having means for removing the charge of the recording material to separate the recording material from the image carrier after the image transfer, the charge removal on the back of the recording material is reduced by the charge removal. Even if the force of electrostatically attracting toner to the surface of the recording material is weakened, the charging potential of the surface release layer of the heating member in the image heating and fixing device does not exceed a certain value, so that the recording material side to the heating member side The amount of electric charge escaped to the heating member is small, and also in this case, toner offset to the heating member can be prevented.

F) By making the surface layer of the pressure member against the heating member insulative, the escape of charges from the heated member side to the pressure member side is prevented, and the offset prevention property under high humidity can be further improved. . Further, since it is not necessary to make the pressure member conductive, the cost of the pressure member can be reduced.

[0032]

【Example】

<Example 1> (FIGS. 1 to 4) (1) Example of image forming apparatus FIG. 1 is a schematic view of an example of an image forming apparatus. The image forming apparatus of this example is a printer or a copying machine using a transfer type electrophotographic process.

A is an image forming mechanism section, and B is an image heating and fixing device.

In the image forming mechanism section A, reference numeral 21 is a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member. It is rotationally driven in the clockwise direction indicated by the arrow at a predetermined peripheral speed (process speed). The photosensitive drum 21 is, for example, a photosensitive material layer such as OPC, amorphous Se, or amorphous Si formed on a cylindrical substrate such as aluminum or nickel.

Numeral 22 is a charging roller as a primary charging means for uniformly charging the outer peripheral surface of the rotary photosensitive drum 21 to a predetermined polarity and potential.

Image exposure 23 corresponding to the target image information is performed on the surface of the rotary photosensitive drum 21 subjected to the primary charging process by an image exposure device (laser beam scanning exposure device, document image slit exposure device, etc.) not shown. As a result, an electrostatic latent image corresponding to the exposed image is formed on the surface of the rotary photosensitive drum 21. For example, in the case of a laser printer, scanning exposure is performed by a laser beam 23 whose ON / OFF is controlled according to image information, and an electrostatic latent image is formed.

Reference numeral 24 is a developing means. The electrostatic latent image formed on the surface of the rotating photosensitive drum is developed as a toner image. As a developing method, a jumping developing method, a two-component developing method,
The FEED developing method or the like is used, and image exposure and reversal development are often used in combination.

Reference numeral 25 is a transfer charger as a transfer means. Toner is charged on the back surface of the recording material (transfer material sheet) P conveyed at a predetermined timing from a paper feeding portion (not shown) to a transfer portion between the rotary photosensitive drum 21 and the transfer charger 25 (in this example). Then, the toner image on the surface of the rotating photosensitive drum is electrostatically transferred by applying a positive charge having a polarity opposite to that of (negative).

The recording material P, which has passed through the transfer section and is in close contact with the surface of the photosensitive drum 21, is separated by the separating means and conveyed and introduced into the image heating and fixing device B as a heating device, and the toner image is heated and fixed. It is received and output as a print or copy.

In the apparatus of this embodiment, the recording material conveying path length between the transfer section of the image forming mechanism section A and the heating and fixing section of the image heating and fixing apparatus B is the same as that of the recording material fed to the apparatus. Material P
Shorter than the maximum length of. Therefore, the same recording material P may exist across the transfer section of the image forming mechanism section A and the heat fixing section of the image heat fixing apparatus B.

As means for separating the recording material P from the surface of the photosensitive drum 21, there are a separation claw type, a separation belt type, a static elimination type, a combination type thereof and the like.

Numeral 26 is a static elimination needle as a static elimination means arranged next to the transfer portion. The recording material P that has passed through the transfer portion is discharged to separate it from the surface of the rotating photosensitive drum 21.

Incidentally, the present embodiment 1 and the embodiment 2 which will be described later.
In Nos. 4 to 4, it is assumed that the recording material P is separated from the surface of the photosensitive drum 1 by a separation means other than the static elimination type.

Reference numeral 27 is a photosensitive drum cleaning means. The surface of the rotating photosensitive drum after the transfer of the toner image onto the recording material P is cleaned. The photosensitive drum 21 is cleaned and repeatedly used for image formation.

(2) Image Heating and Fixing Device B FIG. 2 is an enlarged schematic view of the image heating and fixing device B portion. The image heating and fixing device B of this example is a film heating type device using an endless belt-shaped film.

Reference numeral 1 is, for example, a ceramic heater as a heat generating member, 2 is a support for the heater, 8 is a driving roller, and 9 is a driven roller, which are arranged substantially parallel to each other.
Reference numeral 7 denotes an endless belt-shaped heat-resistant film (hereinafter referred to as a fixing film) suspended and stretched between these members. The driven roller 9 is a tension roller and is stretched without slack.

Reference numeral 10 denotes an elastic pressure roller as a pressure member, which is formed by forming a rubber elastic layer 12 of silicone rubber or the like having a good releasability on a core metal 11 of iron, stainless steel or the like.
The fixing film 7 is sandwiched between the heater 1 and the heater 1 with a contact pressure of 4 to 12 kg, for example, with a total pressure of 4 to 12 kg. A pressure contact nip portion N (fixing nip portion) having a predetermined width is formed. The core metal 11 of the pressure roller 10 is grounded to prevent noise.

The drive roller 8 is driven to rotate in the clockwise direction shown by an arrow by a drive system (not shown), so that the fixing film 7 is driven by the frictional force between the outer surface of the drive roller 8 and the inner surface of the film. The roller 9 and the heater 1 are rotationally driven in the clockwise direction indicated by an arrow at a predetermined peripheral speed, and the inner surface of the fixing film 7 in the fixing nip portion N slides in close contact with the lower surface of the heater. In the fixing nip portion N, the pressure roller 10 that is in pressure contact with the heater with the fixing film 7 interposed therebetween is driven to rotate as the fixing film 7 rotates.

In order to reduce the frictional sliding resistance between the heater 1 and the inner surface of the fixing film 7 and rotate the fixing film 7 smoothly with low torque, a heat-resistant grease is applied between the film sliding surface of the heater 1 and the inner surface of the film. It is advisable to interpose a small amount of lubricant such as.

When the heater 1 is energized, the heater generates heat and heats the fixing film 7 in the fixing nip portion. The heater 1 is temperature-controlled to a predetermined temperature.

When the fixing film 7 is rotationally driven and the heater 1 is temperature-controlled to a predetermined temperature, an image is formed between the fixing film 7 and the pressure roller 10 in the fixing nip portion N from the image forming mechanism section A side. The recording material P (paper) to be fixed is introduced by being guided by the guide 18, so that the recording material P adheres to the outer surface of the fixing film 1 and holds the fixing nip portion together with the fixing film 7. The unfixed toner image Ta is heated by the heat of the fixing film 7 that has been conveyed and heated by the heater 1 in the fixing nip portion N to become the softened / melted image Tb.

The rotating fixing film 7 has a fixing nip portion N.
When passing through the edge portion S (having a radius of curvature of about 2 mm) having a large curvature of the heater support 2, a sharp angle (refraction angle θ
Is about 45 °). Therefore, the recording material P conveyed through the fixing nip portion N while being overlapped with the fixing film 7 is curvature-separated from the outer surface of the fixing film 7 at the edge portion S and is conveyed to the discharge side. . The toner image that has been heated in the fixing nip portion N and has become a softened / melted image Tb is sufficiently cooled and solidified by the time the recording material is discharged, and is a permanent image completely fixed on the surface of the recording material P. It becomes Tc.

A) Heater 1 The heater 1 is a laterally long low-heat-capacity linear heating element whose longitudinal direction is the direction orthogonal to the moving direction of the fixing film 7. The heater 1 of this embodiment is a ceramics heater ,. Ceramic heater substrate 3 with heat resistance, insulation, and low heat capacity, for example, thickness 1 mm, width 10 mm, length 240 mm
Alumina substrate ,. An electric resistance material such as Ag / Pd (silver-palladium) or Ta ₂ N having a thickness of 10 μm and a width of 1 to 3 mm is provided along the longitudinal direction at a substantially central portion of the surface of the substrate 3 (a surface facing the fixing film 7). An electric heating resistance layer 4, which is formed by applying a linear or striped pattern by screen printing or the like ,. A surface protective layer 6 coated thereon, eg about 10 μm
m thick glass layer. The temperature measuring element 5 has a low heat capacity such as Pt or the like as a temperature measuring element 5 which is provided by coating by screen printing or the like on the substantially central portion of the back surface of the substrate 3. The temperature detecting element 5 may be configured such that a thermistor or the like having a low heat capacity is placed in contact with the heater substrate 3.

The heater 1 is fixedly supported by being mounted and held on the heater support 2. The heater support 2 has heat insulating properties, high heat resistance, and rigidity for supporting the heater 1 in a heat insulating manner with respect to the fixing device and the entire image forming apparatus.

In the case of the present example, the energization heating resistor layer 4 of the heater 1 is energized from both longitudinal ends thereof to cause the energization heating resistor layer 4 to generate heat over substantially the entire length. The heater temperature state due to this heat generation is detected by the temperature detecting element 5, and the detected temperature of the detecting element 5, that is, the temperature of the heater 1 is maintained at a predetermined fixing temperature by an energization control circuit (not shown) including a triac according to the detected temperature. The energizing power to the energizing heat-generating resistor layer 4 is controlled in such a manner.

Since such a ceramic heater 1 including the heater substrate 3 and the energization heating resistor layer 4 has a small heat capacity as a whole and is adiabatically supported by the heater support 2, the heater surface in the fixing nip portion N is the same. Since the temperature rises to a sufficiently high temperature with respect to the melting point of the toner (or the temperature at which the recording material P can be fixed to the recording material P) in a short time, there is no need for so-called standby temperature adjustment in which the heater 1 is preheated beforehand. The device can be equipped with quick start,
Energy saving can be realized and temperature rise inside the machine can be prevented.

B) Fixing Film 7 In this image heating type image fixing apparatus B, the fixing film 7 is a heating member which contacts and heats the recording material P as a heating target member. Due to a mechanical factor, a toner offset occurs in which a part of the toner of the toner image on the recording material P side is transferred and adhered to the outer surface of the fixing film 7, which is a heating member.

In this embodiment, in order to prevent the toner offset to the outer surface of the fixing film 7 regardless of the environment such as high humidity and low humidity, the fixing film 7 has the following constitution.

FIG. 3 is a schematic diagram of the layer structure of the fixing film 7 in this embodiment, which is an insulating base resin film (resin base material) 101 and a conductive layer 102 formed on the outer surface thereof.
And a release layer 103 formed on the release layer 103, the surface potential generated when a charge is applied to the surface of the release layer 103 is maintained at a constant value when the charge amount is increased. To have.

The free surface of the release layer 103 is the surface that comes into contact with the recording material P as the member to be heated, and the free surface of the base resin film 101 is the contact sliding surface for the heater 1.

.. Specifically, the insulating base resin film 101 is, for example, a heat-resistant polyimide film having a thickness of 20 to 80 μm and a volume resistance value of 10 ¹¹ Ω · cm or more.

In this embodiment, the thickness is 40 μm and the volume resistance is 1.
It is a polyimide film of 0 ¹⁴ Ω · cm.

.. The conductive layer 102 is also a primer layer for adhering the release layer 103 to the base resin film 101, and is a conductive primer layer having a surface resistance of 10 ⁷ Ω / □ or less and a thickness of 3 to 8 μm.

In this embodiment, the surface resistance is 5 × 10 ⁴ Ω / □
The following is a layer having a thickness of 4 μm.

.. The release layer 103 is made of P having excellent release properties.
It is a layer of a fluororesin such as FA (perfluoroalkoxytetrafluoroethylene) or PTFE (tetrafluoroethylene, polytetrafluoroethylene) or a silicone resin.

In this embodiment, a fluororesin made of PTFE is formed by spray coating with a thickness of 8 μm.

In this embodiment, the fixing film 7 has the conductive layer 102 grounded.

The fixing film 7 has the property that when a charge is applied to the surface of the release layer 103, the surface potential of the fixing film 7 stays at a constant value.

That is, the surface of the fixing film 7 on the release layer side (fixing film surface) is corona charger 200 as shown in FIG.
FIG. 4 shows the relationship between the voltage applied to the charger 200 and the film surface potential when the film is charged by. 15 ℃ ・ 10% R
Measured at H.

The conductive layer (conductive primer portion) 102 of the fixing film 7 is grounded, and the + electrode is applied to the corona charger 200 to approach the release layer side surface of the film 7 for 10 seconds and then 5 seconds later. A surface potential meter (TREK344) was brought close to the charged surface of the film for measurement. Measurement of surface potential starts 2
Almost no decay even after a minute.

As shown in FIG. 4, even when the voltage applied to the charger 200 is increased, the film surface potential E is 500V to 550V.
And hardly changes. It is considered that this is because the release layer 103 is thin, and when the surface potential exceeds a certain value, the release layer 103 undergoes dielectric breakdown and surface charges escape to the conductive layer 102.

When such a film 7 is used, even if the film 7 is charged due to friction between the recording material P and the film 7 under low humidity, the charging potential thereof does not exceed a certain value. The offset prevention property of the toner from the side to the outer surface of the fixing film is good.

Further, as in the case where the release layer 103 is made conductive, the transfer charges existing on the recording material P under high humidity are leaked to eliminate the electrostatic attraction force between the recording material and the toner, and offset. Even if the same recording material P exists across the transfer portion of the image forming mechanism A and the fixing nip portion of the image heating and fixing device B as shown in FIG. There is no possibility that the transfer current in the portion will flow into the release layer 103 of the fixing film 7 through the recording material P to cause transfer omission.

Since the dielectric strength increases as the thickness of the release layer 103 increases, the surface potential at the time of corona charging is, for example, about 15 μm, as the applied voltage becomes higher as shown in F of FIG. Get higher

The offset release property of the fixing film 7 and the surface potential H when the film thickness of the PTFE release layer 103 was varied were examined. Table 1 shows the results. In the evaluation of the offset prevention property, ∘ mark indicates a problem-free level, Δ mark indicates a worse level, and x mark indicates a defective level (the same applies to Tables 2 and 4 described later).

[0076]

[Table 1] That is, the thickness of the PTFE release layer 103 is 15 μm.
When m or more, the property that the surface potential does not change even if the above-mentioned electric charge is applied to the film surface is lost, and the offset prevention property is deteriorated.

Further, Table 2 shows that the material of the release layer 103 is PFA.
The results are obtained by evaluating the offset prevention property of the fixing film 7 and examining the surface potential H when the film thickness of the PFA release layer 103 is varied.

[0078]

[Table 2] That is, comparing the materials of the release layer 103 between PTFE and PFA, the comparison between Table 1 and Table 2 shows that the PTFE release layer has P
Even if the film thickness is thicker than that of the FA release layer, the above properties are exhibited and the offset prevention property is good.

This is probably because PTFE has a higher melting point than PFA and microscopic pinholes are likely to occur.

As described above, the PTFE release layer can have a large film thickness, the release property does not deteriorate due to abrasion, and the offset is less likely to occur even if the film thickness fluctuates during manufacturing, so that the manufacturing yield increases. Similar effects can be obtained by mixing PTFE in a fluororesin such as PFA.

Example 2 Even when the conductive layer 102 of the fixing film 7 in Example 1 was floated without being grounded, the same effect as in Example 1 was obtained.

In the case of float, it is considered that the potential of the conductive layer 102 becomes the same as the potential of the recording material P introduced into the fixing nip portion N. At this time, when the surface of the fixing film 7 is charged, a potential difference is generated between the film surface and the conductive layer 102, the release layer 103 undergoes dielectric breakdown, and the charge on the film surface disappears, and it is considered that the offset prevention property is good.

When the conductive layer 102 is floated,
When the release layer 103 is thick and does not have the characteristics of the film of the present invention, the anti-offset property is worse than when it is grounded, but if it has the above charging characteristics, it can be used as a float. , The number of parts for grounding can be reduced.

Example 3 Release Layer 10 of Fixing Film 7
If a conductive material (conductive feeler) such as carbon, fine metal powder, fine metal oxide powder, etc. is slightly dispersed in 3, the charging characteristics of the present invention can be obtained even if the release layer 103 is thick. is there.

When 0.3% of carbon is put in the fluororesin of PTFE / PFA = 7/3, as shown in Table 3, the charging property of the present invention is as follows: However, when 0.3% is added, the charging characteristics are maintained up to the release layer film thickness of 25 μm. The offset under low humidity has been improved accordingly. In the present invention, the film thickness can be increased and the deterioration of the releasability due to wear can be prevented.

On the other hand, when 2.0% is mixed, the film has a completely low resistance, and when the charging potential is measured by the method of FIG. 3, it is not charged at all. When this film was used, offset occurred under high humidity.

[0087]

[Table 3] <Embodiment 4> In Embodiments 1 to 3, at least the surface of the pressure roller 10 as the pressure member is preferably insulative. This is because the toner offset to the outer surface of the fixing film due to the escape of the transfer charge of the recording material P introduced into the fixing nip portion N to the pressure roller 10 side under high humidity can be better prevented.

When a fixing film having no charging property as in the present invention is used due to a large film thickness, etc., when the pressure roller 10 is made insulating, the recording material P and the film 7 are kept under low humidity. Toner offset occurs due to friction,
With the film having the charging characteristic of the present invention, the pressure roller 10 is made insulating, the offset under high humidity is improved, and the offset due to frictional charging under low humidity does not occur.
When the pressure roller 10 is made conductive, the cost is high because carbon and the like are mixed with rubber, but this is not the case.

<Embodiment 5> As in the image forming apparatus of FIG. 1, in the image forming mechanism section A, the charge eliminating means 26 is used as a means for separating the recording material P after passing the transfer portion from the surface of the photosensitive drum 21.
Is used, the transfer charge on the back of the recording material P decreases and the force of electrostatically attracting the toner to the surface of the recording material P weakens. Therefore, in the image fixing device B, the toner offset is applied to the outer surface of the fixing film 7 as a heating member. Is likely to occur.

However, when the fixing film 7 having the charging characteristic of the present invention is used, it is possible to prevent the occurrence of offset even if the charge eliminating means 26 is used.

.. Release layer 103 having a film thickness of 10 μm by adding 0.3% of carbon to PTFE / PFA = 7/3 resin
A fixing film having: A fixing film provided with a release layer 103 having a thickness of 5 μm made of PTFE, A fixing film provided with a release layer 103 having a film thickness of 30 μm by PFA; The fixing potential H and the fixing potential H of each of the fixing films provided with the release layer 103 having a PTFE / PFA = 7/3, carbon 2.0%, and a film thickness of 10 μm are as shown in FIG. The toner offset with respect to the fixing film in the image forming apparatus using the charge removing unit 26 was evaluated. The results are shown in Table 4.

The charge eliminating means 26 is a charge eliminating needle. A charge removal bias of -3 KV is applied to the charge removal needle 26 to facilitate separation of the recording material P from the photosensitive drum 21. The conductive layer 102 of the fixing film 7 is grounded. The pressure roller 10 uses insulating rubber.

[0093]

[Table 4] For the fixing film of and, the charging potential measured by the device of FIG. 3 has a constant value even if the applied voltage is increased, and the anti-offset property is good, while for the fixing film, the charging potential is high when the applied voltage is high. turn into. Offset prevention is also poor. In addition, the charging potential of the fixing film is 0 V, and the offset is bad.

The above results show that the conductive layer 102 of the fixing film
It was the same even if it was floated without grounding.

By using the film of the present invention, there is no offset, and the recording material P can be easily separated from the photosensitive drum 21.

<Sixth Embodiment> (FIG. 5) FIGS. 5A, 5B, and 5C show other structural examples of the film heating type heating device.

In the case of (a), an endless belt-shaped heat-resistant film 7 is suspended and stretched between two members, a heater 1 as a heat-generating member and a driving roller 8, so that the film 7 is driven to rotate. It is a thing.

In the case of (b), a cylindrical heat-resistant film 7 is loosely fitted on the outside of a heater support 2 having a heater 1 on the lower surface and having a substantially semi-circular cross section, and the film 7 is attached. The pressure roller 10 is brought into contact with the heater 1 so as to be opposed thereto by sandwiching. The pressure roller 10 is driven to rotate, and the film 7 is rotated while the inner surface of the film is brought into close contact with the heater 1 by the frictional force between the film 7 and the pressure roller 10 in the nip portion N to slide.

In the case of (c), a long end film wound in a roll is used as the heat-resistant film 7, and this is wound from the feeding shaft 13 via the heater 1 and the winding shaft 14.
Is configured to travel at a predetermined speed.

In the film heating type heating device having such a configuration, the heat-resistant film 7 as a heating member is also used.
Example 1 by adopting the configuration and characteristics according to the present invention
The same effect as in the case of ~ 5 can be obtained.

The heater 1 as the heat generating member is not limited to the ceramics heater as in the embodiment, but may be, for example, an induction heating type heater including a magnetic field generating means and a magnetic metal member, and the heater 1 as the heat generating member. The type and configuration of are optional. Alternatively, the heat-resistant film 7 itself serving as a heating member may be an induction heat-generating film, and the film 7 may be configured to generate heat by the magnetic field action of the magnetic field generating means.

<Embodiment 7> (FIG. 6) The present invention is not limited to a film heating type heating device, and it goes without saying that a heating roller type heating device also has the same effect.

FIG. 6 is a schematic configuration diagram of an example of a heating device of a heating roller type. As a heating member, a heating roller 15 that is heated and adjusted to a predetermined temperature and a pressurizing member that has elasticity and is in pressure contact with the heating roller. A pressure roller 10 as a member is provided, and a recording material P to be subjected to an image fixing process as a member to be heated is introduced into a pressure contact nip portion N of both rollers and is nipped and conveyed, and an unfixed image is heated by a heating roller 15. It is heated and fixed.

The heating roller 15 is a cylinder type roller base body 16 made of aluminum or the like, a release layer 17 formed on the outer peripheral surface thereof, and a halogen member as a heat generating member (heat source) inserted and arranged in the roller base body 16. It comprises a heater 18 and the like. The heating roller 15 may be heated by an induction heating method.

Even in such a heating device of the heating roller type, the same effects as those in Examples 1 to 5 can be obtained by using the heating roller 15 as a heating member having the structure and characteristics according to the present invention.

<Others> The present invention, in short, relates to a heating member contact type heating device for heating a heated member by bringing the heating member and the heated member into contact with each other regardless of the form of the contact heating member. The intended effect can be obtained by using the member having the configuration and characteristics according to the present invention.

A double-sided heating device may be used in which heating members are brought into contact with the front and back surfaces of the member to be heated, and in this case, at least one of the heating members has the structure and characteristics according to the present invention. The desired effect can be obtained.

The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but may be, for example, a device for heating a recording material carrying an image to modify the surface property (such as polishing), or an assumed attachment device. It can be widely used as a heating device for a material to be heated such as a device for heating, drying and laminating a sheet-shaped material while conveying the material.

[0109]

As described above, according to the present invention, the contact heating type heating device and the image forming apparatus provided with the heating device as the image heating and fixing device can be used in various environments such as high humidity and low humidity. Regardless, it is possible to prevent the occurrence of offset with respect to the heating member.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example of an image forming apparatus.

FIG. 2 is an enlarged model diagram of an image heating and fixing device portion.

FIG. 3 is a layer structure model diagram of a fixing film as a heating member, and an explanatory diagram of a charging characteristic measurement procedure.

FIG. 4 is a correlation graph of the voltage applied to the charger and the surface potential of the fixing film.

5 (a), (b), and (c) are other configuration diagrams of a film heating type heating device, respectively.

FIG. 6 is a schematic configuration diagram of a heating device of a heating roller system.

[Explanation of symbols]

 A image forming mechanism section B image heating and fixing device 1 heater (heating member) 2 heater support 7 fixing film (heating member) 101 base resin film 102 conductive layer (conductive primer layer) 103 release layer 10 pressure roller (additional Pressure member) N fixing nip portion P recording material (heated member) 15 heating roller (heating member)

Claims (10)

[Claims] 1. A contact heating type heating device for heating a member to be heated by bringing the heating member and the member to be heated into contact with each other, wherein the heating member is at least a conductive layer and a member to be heated which is formed thereon. A heating device having a release layer in contact with a member, and having a characteristic that the surface potential generated when an electric charge is applied to the surface of the release layer remains constant when the amount of electric charge increases. 2. The heating device according to claim 1, wherein the release layer of the heating member is made of a fluororesin having a thickness of 10 μm or less. 3. The heating device according to claim 1, wherein the release layer of the heating member contains tetrafluoroethylene resin (PTFE). 4. The heating device according to claim 1, wherein a conductive feeler is placed in the release layer of the heating member. 5. A device for heating a heated member by introducing a heated member into the nip portion and passing the heated member through a pressurizing member facing the heating member to form a nip portion. The heating device according to any one of claims 1 to 4, which is characterized. 6. The heating device according to claim 5, wherein the pressing member has an insulating property on the surface layer. 7. The heating member is a heat-resistant film, one surface of which is in sliding contact with the heat-generating member and the other surface of which is in contact with the member to be heated. The heating device according to any one of claims 1 to 6, wherein the member to be heated is heated by the heat-resistant film heated by the heat-generating member when the recording member moves together. 8. The heating device according to claim 1, wherein the heating member is a heat roller. 9. An image forming apparatus comprising the heating device according to claim 1 as an image heating fixing device for heating and fixing an unfixed image on a recording material. 10. A recording medium having means for forming an image on an image carrier, means for transferring the formed image to a recording material, and means for discharging the recording material after the image transfer. The image forming apparatus according to claim 9.