JP3437375B2 - Heat 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 recording material (transfer material, transfer material, transfer material) in an image forming process unit in an image forming apparatus adopting an image forming process such as an electrophotographic method and an electrostatic recording method.
Related to a heat fixing device for thermally fixing and processing as a fixed image an unfixed toner image of intended image information formed and carried on a transfer paper or a direct recording paper (photosensitive paper, electrostatic recording paper, etc.) Is.

[0002]

2. Description of the Related Art Conventionally, as a heat fixing device, a heat roller type device or a film heating type device has been widely used.
In particular, do not supply power to the heat fixing device during standby,
A method of suppressing the power consumption as low as possible, more specifically, a so-called film heating method for fixing a toner image on a recording material via a film between a heater unit and a pressure roller is a heat fixing method. For example, JP-A-63-313182, JP-A-2-157878, and JP-A-4-440.
No. 75, Japanese Patent Laid-Open No. 4-204980, and the like.

The outline of the main part of this type of heat fixing device is as follows.
It is shown in FIG. That is, in the heat fixing device described above, a heat-resistant thin film (hereinafter, referred to as a fixing film) 43 is attached to a heating member (heater, hereinafter, referred to as a heater) 41 fixed and supported by a stay holder (support) 42. A recording material P is sandwiched together with the opposing elastic pressure roller 50, and a nip portion (fixing nip portion) N having a predetermined nip width is formed so as to be pressed by a pressing means (not shown). It was made.

Here, by energizing the heater 41, the fixing film 43 is heated and adjusted to a predetermined temperature. The fixing film 43 is an appropriate driving means (not shown).
Or by the rotating force of the pressure roller 50 described above,
In the fixing nip portion N, it is conveyed and moved in the direction of the arrow a while closely adhering to and sliding on the surface of the heater 41, and its shape is a cylindrical shape or an endless belt shape, or an end of a long roll winding. It is composed of a web-shaped member.

In this heat fixing device, the heater 41 is heated and adjusted to a predetermined temperature, and the fixing film 43 is moved to the arrow a.
In the fixing nip portion N, the recording material P on which an unfixed toner image t as a heated material is formed and carried is held between the fixing film 43 and the pressure roller 50 in the state of being conveyed and moved in the direction of. When introduced, the recording material P comes into close contact with the surface of the fixing film 43 and passes through the fixing nip portion N together with the fixing film 43, but during that time, the recording material P is nipped by the pressure roller 50 and conveyed.

In the fixing nip portion N, the recording material P,
The toner image t is heated by the heater 41 via the fixing film 43, and the toner image t is fixed on the recording material P. Then, the portion of the recording material that has passed through the fixing nip portion N is peeled off from the surface of the fixing film 43 and is conveyed to a required location.

A ceramic heater is generally used as the heater 41 as a heating member. For example, along the longitudinal direction (direction perpendicular to the drawing) of the surface of the ceramic substrate 41a (a surface facing the fixing film 43) of electric insulation, good thermal conductivity, and low heat capacity, such as alumina, along the longitudinal direction of the substrate. , Silver palladium: (Ag / Pb) .Ta ₂ N, etc., the current-generating heating resistance layer 41b is formed by means of screen printing or the like, and the surface on which the heating resistance layer 41b is formed is made of thin glass. It is covered with a protective layer 41c.

The ceramic heater 41 has a structure in which the entire heater, including the ceramic substrate 41a and the glass protective layer 41c, rapidly heats up by being energized by the energization heating resistance layer 41b to generate heat. And this heater 41
The temperature rise is detected by the temperature detecting means 44 installed on the back surface of the heater and fed back to the energization controller (not shown). The energization control unit controls power supply to the energization heating resistance layer 41b so that the heater temperature detected by the temperature detection unit 44 is maintained at a required temperature (fixing temperature). That is, the heater 41 is heated and adjusted to a predetermined fixing temperature.

In the fixing nip portion N, the fixing film 43 applies heat from the heater 41 to the recording material P as a material to be heated.
In order to efficiently give the
And, it is quite thin. The structure of the fixing film 43 will be described with reference to FIG. The fixing film 43 is composed of three layers of a film base layer 43a, a conductive primer layer 43b, and a release layer 43c.
The side is the heater side, and the release layer 43c is the pressure roller side.

The film base layer 43a is made of highly insulating polyimide, polyamideimide, PEEK or the like, has heat resistance and high elasticity, and has a thickness of about 15 to 60 μm. In addition, the film base layer 43a maintains mechanical strength such as tear strength of the entire fixing film 43.

The conductive primer layer 43b has a thickness of 2 to
It is formed of a thin layer of about 6 μm. Further, the releasable layer 43c is a toner offset preventing layer for the fixing film 43, and in order to obtain a covering effect, a fluororesin such as PFA, PTFE, FEP or the like having a good releasability is used in a thickness of 5 to 10 μm. It is formed to some extent.

Here, the thermal characteristics of the fixing film 43 are governed by the film base layer 43a having the largest thickness, and the thermal conductivity of this layer is particularly the fixing performance of the toner image on the recording material. Greatly contributes to For this reason, a filler having high thermal conductivity such as boron nitride (BN), aluminum nitride (AlN), silicon nitride (SiN), or alumina (Al ₂ O ₃ ) is mixed in the film base layer 43a. This makes it possible to more efficiently apply the heat of the heater 41 to the recording material in the fixing nip.
The shape of the filler mixed in the film base layer may be needle-like, spherical, scale-like, or the like, but it is preferable to mix the film base layer 43a with about 5 to 35% by volume. In particular, in a machine in which an image forming apparatus conveys a recording material at a high speed, the fixing performance can be improved by using a filler having high thermal conductivity or increasing the amount of filler mixed.

When the fixing film 43 is made entirely insulative, the recording material charged in the transfer portion of the image forming apparatus passes through the fixing nip portion N,
The surface potentials of the fixing film 43 and the pressure roller 50 rise, causing charge-up. Therefore, a considerable electric field may be generated between the fixing film 43 and the pressure roller 50, and toner offset may occur on the fixing film 43.

Therefore, in order to avoid this, as described above, the primer layer 43, which is an intermediate layer of the fixing film 43, is used.
The primer layer is made conductive by mixing carbon black into b. Further, the conductive primer layer 43b is electrically grounded. This prevents the fixing film 43 from being charged up and prevents toner offset.

The stay holder 42 is made of, for example, a heat-resistant plastic member, holds the heater 41, and also serves as a conveyance guide for the fixing film 43. Therefore, in order to improve the slidability with the fixing film 43, grease having high heat resistance is interposed between the fixing film 43 and the outer peripheral surface of the heater 41 or the stay holder 42.

With respect to the width direction of the recording material P, at the end portion of the fixing film 43 and the stay holder 42, a flange (not shown) fitted in the stay holder 42 is used.
The position of the fixing film 43 is regulated. In particular, when the pressure applied between the stay holder 42 and the pressure roller 50 for forming the fixing nip portion N is uneven in the width direction (that is, the longitudinal direction of the fixing film and the stay holder), Since the fixing film 43 receives a force that is brought toward one end thereof, the movement of the fixing film 43 is restricted by the flange at one end of the stay holder 42 in the longitudinal direction.

Such a thin fixing film 4 for fixing
In the film heating type heat fixing device using No. 3, the pressure roller 50 having the elastic layer 51 is pressed against the above-mentioned heater due to the high rigidity of the ceramic heater 41 as a heating member. Following the flat bottom surface of 41,
The pressure contact portion is flat and forms a fixing nip portion N having a predetermined length. By heating only the fixing nip portion N, quick start heating and fixing are realized. In addition, in order to increase the thermal conductivity of the fixing film 43 as the speed of the image forming apparatus increases, a large amount of high thermal conductivity filler is mixed.

Further, the glass protective layer 41c of the heater 41
And by suppressing the thickness of the film 43 as much as possible,
The heat generated by the energization heat generation resistance layer 41b of the heater 41 is efficiently transmitted to the fixing nip portion N.

[0019]

However, in the above-described film heating type heat fixing device, in order to improve the quick start property and heat efficiency, the fixing film 43 is used.
Since a highly heat-conductive filler is mixed in the film base layer 43a, if there is a large amount of the filler mixed, there is a problem that mechanical strength such as tear strength deteriorates.

In particular, the pressure roller 50 and the fixing film 43
When the pressing force is set high in order to secure a sufficient fixing nip width formed between the fixing holder and the stay holder, the fixing film and the stay holder are slid and rotated by the bias of the pressing force in the longitudinal direction. Since the fixing film 43 to be pushed toward the one end portion in the longitudinal direction thereof with a strong force, if the mechanical strength such as the tear strength of the fixing film 43 is weak as described above, the fixing film 43 becomes brittle and is fixed in a short durability period. Problems such as tearing of the film 43 occur.

Further, if a large amount of high thermal conductive filler is mixed in the film base layer 43a of the fixing film 43, the surface roughness of the inner and outer surfaces of the fixing film 43 becomes large, and the glass protective layer 41c of the heater 41 is increased. The heater 41 and the fixing film 43, or the fixing film 4
The contact thermal resistance between No. 3 and the recording material P increases, heat is not efficiently transferred to the recording material, and fixing failure occurs.

When the thicknesses of the glass protective layer 41c and the fixing film 43 of the heater 41 are suppressed as much as possible, the conductive portion of the heater 41 (the energization heating resistance layer 41b) and the fixing film are prevented in order to prevent dielectric breakdown. The withstand voltage between the conductive primer 43b of the intermediate layer must be sufficiently maintained, but for this purpose, the glass protective layer 41c and the polyimide of the film base layer 43a are required to have a high resistance insulating property. There is. However, in order to secure the withstand voltage to the polyimide layer of the film base layer 43a, it is necessary to make the thickness sufficiently thick to prevent the generation of small holes.

In this case, it becomes difficult to efficiently transfer the heat from the heater 41 to the fixing nip portion N, which causes problems such as defective fixing. Therefore, in the related art, the withstand voltage is satisfied by forming the glass protective layer 41c of the heater 41 having a higher thermal conductivity than the film base layer 43a with a thickness of about 60 μm. However, as the speed of the image forming apparatus increases, it is necessary to form the glass protective layer 41c thinner in order to increase the thermal efficiency.

That is, by satisfying the withstand voltage property of the film base layer 43a of the fixing film 43 and ensuring the thermal conductivity, the film heat fixing which can cope with the speeding up of the image forming apparatus can be realized. However, since the dielectric strength is dependent on the glass protective layer 41c of the heater 41, there is no fixing film 43 that satisfies both the dielectric strength and the high thermal conductivity at the same time.

The present invention has been made based on the above circumstances, and it is possible to increase the speed of an image forming apparatus by satisfying the withstand voltage of the film base layer of the fixing film and ensuring sufficient thermal conductivity. It is also an object of the present invention to provide a heat fixing device that can also be used.

[0026]

To achieve this object, in the present invention, a recording material on which an unfixed image is formed is passed through a fixing nip formed by pressing a fixing member and a pressing member against each other. As a result, in the heat fixing device for fixing the unfixed image on the recording material as a permanent image, the fixing member is composed of a heater for heating having an electric heating resistance layer and a thin film. becomes the base layer constituting the inside of a plurality of layers, in which at least one layer a, insulating filler of high thermal conductivity than the base material of the film substrate are mixed, the fill
Layer B that rubs against the heater for heating
Has a higher thermal conductivity than the at least one layer A.
Insulating filler is mixed in or mixed
It is characterized by not being.

[0027]

[0028]

Accordingly, this makes it possible to form a film having high durability, which satisfies the mechanical strength such as tear strength, in the inner layer of the fixing film base layer, and is a layer in which a large amount of outer filler is mixed. Thus, the heat from the heater can be efficiently transferred to the fixing nip side. in this case,
A small amount of heat-conducting filler or a layer that is not mixed in the inner surface of the fixing film suppresses the surface roughness of the inner peripheral surface of the fixing film to a small level, causing problems such as scraping the glass surface of the rubbing heater. This can be avoided, and since the film base layer has two layers, the frequency of occurrence of small holes in the film is reduced, so there is a high possibility that sufficient dielectric strength voltage can be obtained between the inner surface of the film and the conductive primer. Become. Accordingly, even if the glass protective layer of the heater is not required to have a withstand voltage, it is possible to sufficiently satisfy the withstand voltage between the energization heating resistance layer of the heater and the conductive primer of the fixing film. The thickness of the glass protective layer can be significantly reduced, thus improving the fixing performance.

When the base layer of the fixing film has a three-layer structure and the layer containing a large amount of the heat conductive filler is sandwiched between the layers containing a small amount of the filler or the layer not containing the filler, the film is thereby formed. Even when a large amount of high thermal conductive filler is mixed in the intermediate layer of the base layer, the surface roughness of the outer peripheral surface of the fixing film can be suppressed to a small level.
The contact thermal resistance between the outer peripheral surface of the fixing film and the recording material can be reduced, and problems such as defective fixing do not occur and heat fixing with high thermal efficiency can be performed.

Further, in the width direction of the recording material (longitudinal direction of the fixing film), at least the base layer of the fixing film is used.
Also, the mixing amount of the heat conducting filler in one layer A is different, a large amount of the heat conducting filler is mixed in the central part of the fixing film, and the heat conducting filler is small in both ends, or is not mixed, As a result, the mechanical strength such as tear strength of both ends of the fixing film becomes strong, and even when the fixing film is offset to one side in the longitudinal direction,
A long-life fixing film is formed without problems such as tearing and damage within a short durability period.

Further, with respect to the width direction of the recording material (longitudinal direction of the fixing film), only the end portion of the fixing film is
By providing a layer on the outside of the base layer, the
A large amount of heat conductive filler is mixed in at least one layer A
Even if there is a small amount of heat conductive filler, or a layer that is not mixed, is formed in the outer layer at the end,
Tear strength at both ends of the fixing film, mechanical strength such as buckling strength becomes strong, and even when the fixing film approaches one side, it is possible to avoid the problem of tearing or buckling,
Furthermore, a durable fixing film is constructed.

[0033]

DETAILED DESCRIPTION OF THE INVENTION

(First Embodiment) An embodiment according to the present invention will be described below. FIG. 1 is a configuration diagram of an image forming apparatus according to the present invention. In FIG. 1, reference numeral 1 is a photosensitive drum, and OP
A photosensitive material such as C, amorphous Se, or amorphous Si is formed on a cylindrical substrate such as aluminum or nickel.

The photosensitive drum 1 is rotated and driven in the direction of the arrow, and its surface is first uniformly charged by a charging roller 2 as a charging device, and then ON / OFF control is performed according to image information. Scanning exposure is performed by the laser beam 3 thus formed to form an electrostatic latent image. This electrostatic latent image is developed and visualized by the developing device 4. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used. In this case, image exposure and reversal developing are often used in combination.

The visualized toner image is transferred from the photosensitive drum 1 onto the recording material P conveyed at a predetermined timing by a transfer roller 5 as a transfer device. At this time, the recording material P is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5 with a constant pressure. The recording material P on which the toner image is transferred is conveyed to the fixing device 6 and fixed as a permanent image. On the other hand, transfer residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

FIG. 2 shows the structure of the heat fixing device 6 according to the present invention. In FIG. 2, the fixing member 10 is composed of the following members. Reference numeral 13 is a fixing film having a small heat capacity, and has a total thickness of 100 μm or less in order to enable quick start, and has heat resistance and thermoplasticity.
Polyimide, polyamide imide, PEEK, PES, P
It is a film having PS, PFA, PTFE, FEP, etc. as a base layer. Further, in order to construct a long-life heat fixing device, a film having a sufficient strength and an excellent durability must have a total thickness of 20 μm or more. Therefore, the total thickness of the fixing film 13 is 20 μm or more and 100 μm or more.
The following is optimal.

Further, in order to prevent offset and ensure separability of the recording material, PFA, PTFE, FE are formed on the surface layer.
A heat-resistant resin having a good releasability such as P or a silicone resin is mixed or coated alone. The details of the structure of the fixing film will be described later. Reference numeral 11 is a heating heater provided inside the fixing film 13 to melt the toner image on the recording material.
The nip part to be fixed is heated. Heating heater 11
On the surface of a highly insulating ceramic substrate such as alumina along the longitudinal direction (that is, the width direction of the recording material),
For example, Ag / Pd (silver palladium), RuO ₂ , Ta
A conductive heating member formed by applying a conductive heating resistance layer of ₂ N or the like in a linear or strip shape with a thickness of about 10 μm and a width of about 1 to 5 mm by screen printing or the like.

On the back surface of the ceramic substrate, a temperature detecting element 14 such as a thermistor is provided to detect the temperature of the ceramic substrate which has risen in response to the heat generated by the energization heating resistance layer. By appropriately controlling the duty ratio, the wave number, or the like of the voltage applied to the energization heating resistance layer from the electrode portion (not shown) at the end portion of the fixing film in accordance with the signal of the temperature detection element 14, The adjustment temperature in the fixing nip is kept substantially constant, and heating necessary for fixing the toner image on the recording material is performed.

The DC energization from the temperature detecting element 14 to the temperature control section (not shown) is achieved by the connector via the DC energization section and the DC electrode section (both not shown). In addition, a protective layer such as a thin glass coat capable of withstanding rubbing against the fixing film is provided on the surface of the energization heating resistance layer of the heating heater 11.

Further, reference numeral 12 is a heat insulating stay holder for holding the heater 11 for heating and preventing heat radiation in the direction opposite to the nip, which is made of liquid crystal polymer, phenol resin, PP.
The fixing film 13 is formed of S, PEEK, or the like, is loosely fitted to the fixing film 13 with a margin, and is rotatably arranged in the direction of the arrow. Further, since the fixing film 13 rotates while slidingly contacting the heating heater 11 and the heat insulating stay holder 12 inside, it is necessary to suppress the frictional resistance between the heating heater 11 and the heat insulating stay holder 12 and the fixing film 13 to be small. However, for this purpose, a small amount of lubricant such as heat resistant grease is interposed on the surfaces of the heater 11 for heating and the heat insulating stay holder 12. As a result, the fixing film 13 can rotate smoothly.

The pressing member 20 is composed of an elastic layer 22 formed by foaming heat resistant rubber such as silicone rubber or fluororubber or silicone rubber on the outside of the cored bar 21. In addition, a releasable layer 23 such as PFA, PTFE, FEP may be formed. Pressure member 2
0 is for forming a nip portion required for heat fixing from both ends of the fixing member 10 by a pressing means (not shown) in the longitudinal direction (width direction of the recording material). It is pressed with sufficient pressure, and the core metal 21
Through the rotation and drive means, in the direction of the arrow,
Driven.

As a result, the fixing film 13 is driven and rotated toward the outside of the stay holder 12 in the direction of the arrow in the figure. Alternatively, a driving roller (not shown) may be provided inside the fixing film 13 and the fixing roller 13 may be rotated by rotationally driving the driving roller.

Here, the fixing film 13 according to the present invention
The configuration of is shown in FIG. In the figure, reference numeral 31 is a film base layer and is composed of the following two layers. That is, reference numeral 31a is an inner layer of the film base layer 31, and polyimide, polyamideimide, PEE having insulation, heat resistance, and thermoplasticity.
It is made of K, PES, PPS, PFA, PTFE, FEP, etc., and has a thickness of 5 to 30 μm. Also, reference numeral 3
1b is an outer layer of the film base layer 31, and the same member as the inner layer 31a of the film base layer is provided with an insulating and highly thermally conductive filler, for example, boron nitride (BN), aluminum nitride (AlN), silicon nitride. A filler such as (SiN) or alumina (Al ₂ O ₃ ) has a volume ratio of 10 to 35.
%, And the thickness is about 25 to 55 μm.

On the outside of the film base layer, a conductive primer layer 32 is formed as a thin layer having a thickness of about 2 to 6 μm. Here, in the case where the fixing film 13 is made entirely insulative, the recording material charged in the transfer portion of the image forming apparatus passes through the fixing nip portion N, whereby the fixing film 13 and the pressure are applied. The surface potential of the roller 20 rises, causing charge-up. For this reason, an electric field may be generated between the fixing film 13 and the pressure roller 20 to cause an electrostatic offset in the fixing film 13. In order to avoid this, as described above, the primer layer 32, which is an intermediate layer of the fixing film 13, is made conductive by mixing carbon black or the like.

Further, the conductive primer layer 32 is electrically grounded. This prevents the fixing film 13 from being charged up and prevents electrostatic offset. Further, a releasable layer 33 is provided on the outer side, and this serves as a toner offset prevention layer for the fixing film 13. It should be noted that this is formed by coating a fluororesin such as PFA, PTFE, and FEP, which has a good releasability, to a thickness of about 5 to 10 μm.

As a method of forming each of the layers described above, dipping is performed by placing a cylindrical mold in each liquid phase such as resin varnish, or resin varnish is formed while the mold is rotating. Method of applying each liquid phase such as, or
There are combinations of these, which form each layer.

As described above, according to this embodiment, the film base layer 3
By mixing the high thermal conductive filler in the first outer layer 31b, the heat of the heater 11 can be more efficiently applied to the recording material in the fixing nip. The shape of the filler mixed in the outer layer 31b of the film base layer 31 may be needle-like, spherical, scaly, or the like, but the volume ratio of the filler to the outer layer 31b of the film base layer 31 is 10 to 35%.
It should be mixed to some extent.

Particularly, in a machine in which the image forming apparatus conveys the recording material at a high speed, the fixing performance can be enhanced by using a filler having a high thermal conductivity or increasing the amount of the filler mixed. In addition, the above-mentioned filler is not mixed in the inner layer 31a of the film base layer 31, or
A layer having high mechanical strength such as tear strength can be formed by mixing the filler having high thermal conductivity in a small amount of about 2 to 10% by volume. As a result, even if the fixing film 13 approaches one end in the longitudinal direction (width direction of the recording material) of the stay holder 12, compared to the conventional example, the endurance of the fixing film 13 until end tearing occurs. Time is greatly extended.

Further, since the amount of the filler mixed in the inner layer of the base layer of the fixing film is small or not contained, the surface roughness of the inner surface of the fixing film can be suppressed to a small level,
The amount of abrasion of the glass protective layer of the heater is extremely reduced, so that the durability performance is improved. Furthermore, since the thermal resistance of the glass protective layer surface of the heater and the inner surface of the fixing film becomes small,
It is possible to avoid problems such as poor fixing due to a decrease in heat transfer efficiency.

Further, when the film base layer 31 has a two-layer structure, the yield of non-defective films which sufficiently satisfy the withstand voltage between the inner surface of the film and the conductive primer layer, as compared with the conventional one-layer structure. Is greatly improved. This eliminates the need for satisfying the withstand voltage in the glass protective layer of the heater 11 as in the conventional case, so that the glass protective layer of the heater can be made thinner and the fixing performance can be further improved. You can

[0051]

EXAMPLES Here, in order to confirm the above effects, the following studies were conducted. As the constitution of the heat fixing device, a fixing film having an inner diameter of φ24 was used, and the following items were evaluated under the following conditions. The other members such as the heater and the pressure roller have the same configuration as the above. In addition, all fixing films had a primer layer of 4 μm, and the surface layer was coated with PTFE of 8 μm. Conventional example ... The thickness of the base layer was 50 μm, and 20% of the filler was mixed. Example: 10 μm inner layer of the base layer and 40 μm outer layer
The filler is not mixed in the inner layer, only the outer layer is 15
-30% (in 5% increments) filler was incorporated.

◎ Evaluation item (1) Fixability ... Transporting speed of recording material is 50 mm / s.
The fixing property of the toner image on the recording material was evaluated when each fixing film was used while changing the speed between 200 mm / s (200
The temperature was adjusted to a constant temperature of 0 ° C., and after 10 seconds from the start of energization of the energization heating resistance layer of the heater, fixing was started) and the surface roughness of the inner surface of the fixing film was also measured. (2) Durability: A heat fixing device was attached to the idle rotation endurance jig, the temperature was adjusted to a constant temperature of 200 ° C., idle rotation was performed at a speed of 100 mm / s, and the endurance time until the edge of the film was torn was increased. Evaluation (total pressure is 10 kgf,
(Evaluation of the case where the pressure is applied substantially uniformly and the case where the bias of the applied pressure is large in the longitudinal direction of the film.) (3) Dielectric strength ... Voltage of 1000 to 3000 V is applied for 1 minute between the conductive primer layer and the conductive primer layer, and the non-defective rate with respect to the withstand voltage is evaluated. The evaluation results are shown below. In the table, ◯ represents a level without problems, Δ represents an acceptable level, and x represents a poor level (the same applies to the tables below).

[0053]

[Table 1] From the above results, it is understood that the fixing performance is improved as the amount of the high thermal conductive filler mixed in the base layer of the fixing film is increased. In particular, the difference in the amount of filler increases as the recording material conveyance speed increases. Further, as in the conventional example, when the fixing film base layer is composed of one layer, the surface roughness of the inner surface of the fixing film is
The larger the amount of the mixed filler, the larger it becomes, and the larger the contact thermal resistance with the glass protective layer of the heater becomes, so that the improvement of the fixing performance becomes slow. Therefore, in this embodiment, although the inner layer of the film base layer having poor thermal conductivity is provided, the amount of the mixed filler is the same.
The fixing performance of No. 1 and the conventional example have become the same fixing performance.

[0054]

[Table 2] From the above results, in the case of the fixing film of the present embodiment (the fixing film having a two-layer structure of the film base layer and a small amount of the filler in the inner layer or not mixed) as compared with the conventional fixing film having a single film base layer Since the tear strength of the inner layer of the film base layer was strong, the durability was dramatically improved. In particular, in the longitudinal direction of the film (width direction of the recording material), even when the pressure applied between the pressure roller and the heater is deviated, the durability performance is improved compared to the conventional one. As a result, the life of the heat fixing device can be extended.

Further, when the glass protective layer of the heater was observed, the abrasion amount was smaller in this embodiment than in the conventional example.
It is considered that this is due to the surface roughness of the inner surface of the fixing film. The surface roughness of the inner surface of the fixing film is preferably 5 μm or less, and more preferably 4 μm or less, in order to suppress the fixing performance and the scraped amount of the glass protective layer of the heater within the allowable range.

[0056]

[Table 3] The conclusion obtained from the above results is that, compared with the conventional example, in this example, the withstand voltage between the film inner surface and the conductive primer layer as the film intermediate layer can be sufficiently secured, and the non-defective rate of the fixing film also jumps. It is improving.
This is because, when the base layer of the fixing film is formed, since the base layer to be formed is a thin film, the small holes generated in the conventional example have a poor withstand voltage as they are, whereas in the present embodiment, two base layers are formed. This is because there is a very small possibility that the small holes will overlap in the first layer and the second layer, which results in a high non-defective rate that satisfies the withstand voltage. Therefore, in the past, the glass protective layer of the heater satisfied the withstand voltage, but in the present invention, since it is possible to replace the base layer of the fixing film, it is possible to reduce the thickness of the glass protective layer of the heater, It is possible to further improve the fixing performance.

The inner layer 31 of the fixing film base layer 31
The thicknesses of a and the outer layer 31b not only greatly contribute to the tear strength, but also have a great influence on the dielectric strength and the fixing performance. That is, the inner layer 31a or the outer layer 31
When a small hole is formed in a part of b, the other layer must sufficiently satisfy the dielectric strength voltage. Therefore, each layer of the fixing film base layer is 5 μm or more, preferably,
It is necessary to have a thickness of 10 μm or more.

On the other hand, from the viewpoint of fixability, the inner layer 31a of the fixing film base layer 31 has a smaller thermal conductivity than that of the outer layer 31b, so that if the thickness is extremely thick, a problem of poor fixing occurs. Therefore, the inner layer of the fixing film base layer is 30 μm or less, preferably 25 μm.
It is recommended to keep the thickness below. Further, the total thickness of the fixing film base layer is 20 μm or more, preferably 30 μm or more, in consideration of twist, tear, buckling, etc. of the film, and is 100 μm in consideration of quick start property and fixing performance. Hereafter, it is preferably 80 μm or less. From the above, in carrying out the present invention, the thickness of the outer layer 31b is preferably about 1 to 15 times the thickness of the inner layer 31a of the fixing film base layer 31.

The outer layer 31b of the fixing film base layer 31
The amount of the high thermal conductive filler mixed in is 10% by volume or more, preferably 1% in order to secure the fixing performance.
It is better to mix 5% or more. Further, the surface roughness of the outer surface of the fixing film largely depends on the amount of the filler mixed in the outer layer 31b of the fixing film base layer 31, but since the conductive primer layer and the release layer are formed outside the film base layer, Is smoothed by smoothing. Therefore, the contact frictional resistance between the recording material and the surface of the fixing film is large, and the amount of the filler mixed is smaller than the range causing the fixing failure.
The amount of the filler mixed as described below is 35% or less, preferably 30% or less in volume ratio.

As described above, according to the present invention, the base layer of the fixing film has a two-layer structure, and the inner layer contains a small amount of a filler having a high thermal conductivity or does not contain a filler. By mixing 10 to 35% by volume of a highly thermal conductive filler into the outer layer having a thickness of about 1 to 15 times that of the inner layer, the mechanical strength such as tear strength in the inner layer of the film base layer is increased. The mechanical strength is sufficiently satisfied, and problems such as the glass protective layer of the heater being shaved can be mitigated, so long life can be achieved, and the heat transfer performance is increased by the outer layer of the film base layer to improve the fixing property. It is possible to improve. As a result, the means of the present invention is effective in the case of constructing a heat fixing device having a long service life and in the case of being incorporated in a high-speed image forming apparatus, and enhances the film heat fixing performance. (Second Embodiment) The second embodiment of the present invention will be described below. The configuration of the entire apparatus is the same as that shown in FIG. 1 showing the first embodiment, and the configuration inside the heat fixing apparatus is also the same as that shown in FIG. 2, so description of the configuration will be omitted. In this embodiment, the fixing film base layer has a three-layer structure and the surface roughness of the inner and outer surfaces of the fixing film is reduced to provide a fixing film excellent in durability and heat conductivity.

That is, the constitution of the fixing film here is as shown in FIG. 4, and since the conductive primer layer 32 and the releasable layer 33 are the same as those in the first embodiment, the description thereof will be omitted. In FIG. 4, reference numeral 34 is a base layer of the fixing film 13, and is composed of the following three layers.

The innermost layer 34a and the outermost layer 34c of the fixing film base layer 34 are made of polyimide, polyamideimide, PEEK, PES, which has insulation, heat resistance and thermoplasticity.
It is made of PPS, PFA, PTFE, FEP or the like, and is formed to have a thickness of about 5 to 15 μm. Reference numeral 34b denotes an intermediate layer of the fixing film base layer, which is formed on the same member as the innermost layer 34a and the outermost layer 34c of the film base layer and has a high thermal conductivity, such as boron nitride (B).
N), aluminum nitride (AlN), silicon nitride (Si)
N), alumina (Al ₂ O ₃ ), and other fillers having high thermal conductivity are mixed in a volume ratio of approximately 20 to 70%, and the thickness thereof is approximately 25 to 55 μm. The method of forming each layer is similar to that of the first embodiment.

As described above, when the fixing film base layer 34 is formed, the surface roughness of the inner surface of the fixing film which is in contact with the glass protective layer of the heater can be suppressed to be small. Therefore, as in the first embodiment, there is no problem such as the glass protective layer of the heater being scraped during long-term use, so that a long life can be realized and the surface roughness of the outer peripheral surface of the fixing film can be suppressed to be small. Therefore, the amount of the high thermal conductive filler mixed in the intermediate layer 34b of the fixing film base layer 34 can be significantly increased.

Therefore, by increasing the amount of the high thermal conductive filler mixed in the intermediate layer of the fixing film base layer 34,
It is possible to fix the toner image on the recording material without causing problems such as defective fixing in response to speeding up of the image forming apparatus. Further, since the surface roughness of the outer surface of the fixing film on the fixing nip side is also suppressed to be small, the contact thermal resistance with the recording material conveyed to the fixing nip also becomes small, and the heat from the heater is efficiently applied to the recording material. .

[0065]

EXAMPLES In order to confirm the above, a conventional example having a single fixing film base layer and a specific example of an embodiment of the present invention,
The fixability was compared. As the evaluation method, the amount of the high thermal conductive filler mixed in the base layer of each fixing film (in the present embodiment, the intermediate layer of the fixing film base layer) and the transport speed of the recording material are selected, The fixability of these examples was evaluated. In the conventional example, the thickness of the fixing film base layer is 50 μm, and in this example, the thickness of the innermost layer and the outermost layer of the fixing film base layer is 7 μm, respectively.
μm, and the thickness of the intermediate layer of the fixing film base layer is 36 μm
And The surface roughness of the outer peripheral surface of the fixing film was also measured. Further, other members such as the heater and the pressure roller are common to each other as in the first embodiment. The evaluation results are shown below.

[0066]

[Table 4] From the above results, it is understood that in the conventional example, the surface roughness of the outer surface of the fixing film is increased according to the amount of the filler mixed in the fixing film base layer. As a result, if the amount of filler mixed in the fixing film base layer is increased to some extent, the fixing performance can be improved. The contact thermal resistance with the material increases,
The heat cannot be transferred efficiently, causing fixing failure.

On the other hand, in the examples according to the present invention, even when the amount of the filler mixed in the intermediate layer of the fixing film base layer is significantly increased as compared with the examples in the first embodiment, the outer surface of the fixing film is The surface roughness of does not change. Therefore, even when the recording material conveyance speed is increased,
By increasing the amount of the filler mixed in the intermediate layer of the base layer of the fixing film, the heat fixing without causing the fixing failure can be easily configured. In particular, since the surface roughness of the inner and outer surfaces of the fixing film does not depend on the amount of filler to be mixed, a large amount of high thermal conductive filler can be mixed even in comparison with the examples in the first embodiment. In addition, since the fixing film base layer has a three-layer structure, the dielectric strength between the inner surface of the fixing film and the conductive primer is further improved, and the non-defective rate is improved, as compared with the examples of the first embodiment. To do. (Third Embodiment) The third embodiment of the present invention will be described below. The configuration of the entire apparatus is the same as that of FIG. 1 showing the first embodiment, and the configuration inside the heat fixing apparatus is also the same as that of FIG. 2, and therefore the description of the configuration is omitted. Here, the amount of the high thermal conductive filler mixed in the film base layer is changed in the longitudinal direction of the fixing film (width direction of the recording material).

In particular, in the constitution of the fixing film in this embodiment, as shown in FIG.
It is divided into two types of parts (13a and 13b) with respect to its longitudinal direction, and its central portion 13a and
The configuration of both end portions 13b outside the image forming area L of the recording material is as shown in FIG. Note that, in FIG. 6, the conductive primer layer 32 and the releasable layer 33 are the same as those in the first embodiment, and therefore the description thereof is omitted. In addition, the base layer 35 of the central portion 13a includes the first and second layers.
Similar to the base layer in the above embodiment, it has a layer in which a large amount of high thermal conductive filler is mixed .

On the other hand, in the fixing film base layer 36 at the end portion 13b outside the image forming area L of the recording material, the amount of the high thermal conductive filler mixed is smaller than that in the central portion 13a. In the case of forming the fixing film as described above, the following forming method is considered to be optimal. That is, this is a method in which a cylindrical mold is rotated at a constant speed, and a required amount of a resin varnish for each liquid phase is applied thereto in a required width in the longitudinal direction of the film.

As a result, the mechanical strength such as tear strength of both ends of the fixing film becomes stronger in the longitudinal direction of the fixing film, and when the fixing film is pushed toward one side in the longitudinal direction due to the pressure for fixing. However, due to the rubbing against the restricting flange (not shown), the durability time until the tearing is significantly extended. Therefore, a fixing film having a long life is formed without causing problems such as tearing and damage within a short durability time unlike the case of the tenth structure.

[0071]

EXAMPLES In order to confirm the above, some amounts of the high thermal conductive filler mixed in the film base layers at both ends of the fixing film were selected, and the same evaluation as the durability evaluation in the above-described examples was performed. That is, 10 kg at an adjusted temperature of 200 ° C. and a speed of 100 mm / s with an idle rotation durability jig.
When the test is performed with a substantially uniform pressurization by the pressing force of f and when the test is performed under the condition that the deviation of the pressurizing force is large in the longitudinal direction of the film, the durability time until the film edge tear occurs evaluated.

For comparison, the following fixing films were also evaluated. Conventional example: The film base layer has a thickness of 50 μm (one layer),
A high thermal conductive filler was mixed in a volume ratio of 20% in the longitudinal direction. Comparative Example: As shown in Example 1, the inner layer of the film base layer was 10 μm, the outer layer was 40 μm, no filler was mixed in the inner layer, and only the outer layer was 30% by volume in the longitudinal direction of the film. Of the high thermal conductive filler. Example: 5 m at both ends in the longitudinal direction of the film of the above comparative example
With respect to the m width (outside the image forming area of the recording material), the high thermal conductive filler mixed therein was set to 0 to 15% (in 5% increments). The evaluation results are shown below.

[0073]

[Table 5] From the above results, by reducing the amount of filler mixed in the film base layer at both ends of the fixing film, the tear strength at both ends of the fixing film can be increased and the durability time can be further extended. Further, since the fixing film base layer in the image forming area of the recording material has a large amount of filler, the heat from the heater can be efficiently transferred onto the recording material, and there is no problem such as defective fixing. And
Rather, in order to prevent heat from escaping from both ends of the fixing film, when the fixing film according to this embodiment is used,
Even when compared with the comparative example, it was found that the fixing property of the toner image on the recording material at both ends in the longitudinal direction of the film was good, and the fixing uniformity was good over the longitudinal direction. (Fourth Embodiment) The fourth embodiment of the present invention will be described below. The configuration of the entire apparatus is the same as that in FIG. 1, and the configuration in the heat fixing device is also the same as that in FIG. 2, and therefore description thereof will be omitted. Further, here, the film reinforcing layer is formed at both end portions (outer than the recording material conveyance region L ′) in the longitudinal direction of the fixing film.

The structure of the fixing film in this embodiment is as shown in FIG. 7, and here, the fixing film 1 is used.
The fixing film basic layer 13c formed along the longitudinal direction of 3 (the width direction of the recording material) has two film base layers shown in the first and second embodiments or a three-layer structure. It is a high thermal conductive film .

FIG. 8 shows the film structure of the portions where the film reinforcing layers 13d are formed at both ends of the fixing film. Here, the conductive primer layer 32 and the releasable layer 33 are the same as those in the first embodiment, but these layers are not present in the end portions of the fixing film where the reinforcing layer 13d is formed. May be. Here, reference numeral 35 is a film base layer, which is a layer in which a high thermal conductive filler is mixed. Further, reference numeral 37 is a film reinforcing layer, which has insulation, heat resistance, and thermoplasticity, and is polyimide, polyamideimide, PEEK, PES, PPS, PFA, PTF.
It is preferably made of E, FEP, or the like and is the same as the main component of the fixing film base layer 35. In addition, the film reinforcing layer 37
Has a thickness of about 10 to 100 μm, and has a width of about 1 to 8 mm in the longitudinal direction.

Generally, when it is desired to make the thickness of the fixing film as thin as possible with the increase in the speed of the image forming apparatus,
The strength of both ends of the fixing film becomes a problem. In particular, the tear strength decreases as the high thermal conductive filler is mixed into the film base layer. On the other hand, a film having no filler mixed therein has a low buckling strength, and when the fixing film leans toward one end in the longitudinal direction with a strong force, it is bent at the end portion of the fixing film. From the above, the thickness of the base layer of the fixing film is 20 μm or more, preferably 30 μm.
μm or more was required.

Therefore, in this embodiment, by forming the film reinforcing layer on the end portion of the fixing film, both the improvement of the tear strength and the improvement of the buckling strength can be achieved, and the fixing film having high durability can be constructed. . Further, since the thickness of the fixing film base layer in the recording material conveyance region can be reduced to about 10 μm, the heating and fixing device can be used without deteriorating the fixing performance even when the image forming apparatus is accelerated. It will be configurable.

[0078]

As described above, according to the present invention,
Heating for fixing the unfixed image on the recording material as a permanent image by passing the recording material on which the unfixed image is formed through a nip portion maintained at a predetermined temperature between the fixing member and the pressure member. In the fixing device, the fixing member includes a heater as a heating body including an electric heating resistance layer and a thin film-shaped rotating member (fixing film) that rotates while slidingly contacting the heater, while the pressing member is An elastic layer is provided so as to form a fixing nip portion required for heat fixing between the fixing member and the fixing member. Particularly, the constitution and effect of the fixing film in the present invention are as follows.

1) The base layer of the fixing film has a plurality of layers, for example
Example, if has a two-layer structure, the inner layer is a layer which thermally conductive filler is not a small amount, or is mixed, the layer of the outside, to provide a layer thermally conductive filler is heavily contaminated, the fixing film The inner layer of the base layer can sufficiently obtain mechanical strength such as tear strength and can obtain a highly durable film.The outer layer is a layer mixed with a large amount of filler to fix the heat from the heater to the fixing nip. It becomes possible to efficiently communicate to the side. In addition, a small amount of the heat conductive filler, or a layer not mixed with the inner surface of the fixing film, the surface roughness of the inner peripheral surface of the fixing film can be suppressed to a small level,
It does not cause problems such as the glass surface of the rubbing heater being scraped.

2) Further, since the film base layer is formed of two layers, the frequency of occurrence of small holes in the film is reduced, so that there is a possibility that a sufficient withstand voltage can be obtained between the inner surface of the film and the conductive primer. Get higher As a result, even if the glass protective layer of the heater is not required to have dielectric strength performance,
Since it is possible to satisfy the pressure resistance between the energization heat generation resistance layer of the heater and the conductive primer of the fixing film, the thickness of the glass protective layer of the heater can be significantly reduced, and thus the fixing can be performed. Performance is improved.

3) In addition, the base layer of the fixing film has a three-layer structure, so that a layer containing a large amount of the heat conductive filler is sandwiched between layers containing a small amount of filler or no filler. By doing so, even if a large amount of a high thermal conductive filler is mixed in the intermediate layer of the film base layer, the surface roughness of the fixing film outer peripheral surface can be suppressed to a small level, and therefore, between the fixing film outer peripheral surface and the recording material. The contact heat resistance can be reduced, problems such as defective fixing do not occur, and heat fixing with high thermal efficiency can be performed.

4) Furthermore, in the longitudinal direction of the fixing film (the width direction of the recording material), a smaller amount of the base layer of the fixing film is used.
At least one layer A has different amounts of the heat conductive filler mixed therein, and the central portion of the fixing film is a base layer having a large amount of the heat conductive filler mixed therein, and both end portions thereof have a small amount of the heat conductive filler.
Alternatively, by using a base layer that is not mixed, mechanical strength such as tear strength at both ends of the fixing film becomes strong, and when the fixing film receives pressure, even if it is offset to one side in the longitudinal direction, it is short. A long-life fixing film can be constructed without causing problems such as tearing and breaking in durability time.

Alternatively, the width direction of the recording material (fixing film
(Longitudinal direction of), only the edge of the fixing film
A layer is provided outside the rum base layer, and
A large amount of heat conductive filler is mixed in at least one layer A.
Also it is, on the outer layer of the end, by forming a layer thermally conductive filler is not a small amount, or are mixed, tear strength of both ends of the fixing film, the mechanical strength such as buckling strength strong However, even if the fixing film receives pressure and shifts in its longitudinal direction, the problem of tearing or buckling can be avoided, and a fixing film with high durability can be configured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram of a heat fixing device according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a fixing film according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a fixing film according to a second embodiment of the invention.

FIG. 5 is a configuration diagram of a fixing film according to a third embodiment of the present invention.

FIG. 6 is likewise a sectional view of a fixing film.

FIG. 7 is a configuration diagram of a fixing film according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of the end portion of the fixing film.

FIG. 9 is a configuration diagram of a main part of a heat fixing device according to a conventional example.

FIG. 10 is a sectional view of a fixing film according to a conventional example.

[Explanation of symbols]

11 Heating heater 12 Thermal insulation stay holder 13 Fixing film 20 pressure roller

Continuation of the front page (56) Reference JP-A-7-156287 (JP, A) JP-A-6-222695 (JP, A) JP-A-6-266254 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (5)

(57) [Claims] 1. An unfixed image is formed on a recording material as a permanent image by passing the recording material on which the unfixed image is formed through a fixing nip formed by pressing a fixing member and a pressure member against each other. In the heat fixing device, the fixing member is composed of a heater for heating having an electric heating resistance layer and a thin film, and the base layer constituting the innermost side of the film is composed of a plurality of layers, at least one of which is the layer a, insulating filler of the high thermal conductivity than the base material of the film substrate are mixed, the Fi
Layer B that rubs against a heater for heating among a plurality of layers of the rum base layer
Has a higher thermal conductivity than the above-mentioned at least one layer A.
Insulating filler of
A heat fixing device characterized by not being installed. 2. A heat fixing device according to claim 1, wherein the base layer of the film to be provided in the fixing member is formed of two-layer structure. 3. A base layer of the film provided in the fixing member is formed a three-layer structure, the heater and the slide
The middle of the rubbing layer B and the outermost layer farthest from the layer B
There is at least one layer A in
The outer outer layer is smaller than the at least one layer A above.
Is the high heat conductive insulating filler mixed in?
2. The heat fixing device according to claim 1, wherein the heat fixing device is not mixed . 4. The amount of the filler mixed in the at least one layer A is larger in the central portion of the recording material than in the both ends of the film in the width direction of the recording material. The heat fixing device according to claim 1, wherein the distribution of the filler is set. 5. A layer formed of the same base material as the base material of the film base layer outside the film base layer is provided at an end portion of the film in the width direction of the recording material. The heat fixing device described.