JP2006276477A - Fixing film and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a recording material from slipping, to keep fixing property and to prevent a film damage upon film fixing. <P>SOLUTION: The fixing film 26 comprises at least a base layer 26a made of a resin composition and a surface layer 26c made of a resin composition and functions to fix an image on a recording material. The fixing film 26 is characterized in that: the resin in the base layer 26a contains a first filler F1 having a higher thermal conductivity than that of the resin and a second filler F2 having a lower surface energy than that of the resin; and the content (a) vol% of the first filler F1 and the content (b) vol% of the second filler F2 satisfy the expressions of a≥2b and 5≤a+2b≤80. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing film and a fixing device for fixing an image formed on a recording material by image forming means such as an electrostatic recording method and an electrophotographic method.

  Conventionally, in an electrostatic recording apparatus or an electrophotographic apparatus, fixing of a toner image formed on a recording material is performed by a heating roller including a heating element such as a halogen lamp and a pressure roller having an elastic layer. Generally, the recording material is nipped and conveyed.

  However, recently, a film heating type heating device (film fixing) has been put into practical use in order to realize power saving and a reduction in time from the start of energization to the energizing heating body to the temperature at which fixing is possible.

  Film fixing includes a fixedly supported heating body (ceramic heater) and a heat-resistant fixing film (also referred to as a fixing belt, hereinafter referred to as a film) that is conveyed while being pressed against the heating body. A toner unit formed on the recording material by applying the heat of the heating body to the recording material through a film. It fixes the image.

  In such film fixing, the buckling strength is secured by the outer diameter and thickness of the film to such an extent that the film does not buckle due to the biasing force caused by the driving of the film, and the shifting control is omitted, and A system in which the film is driven to the film guide by press-fitting to the film guide, and the film is driven by applying pressure roller driving to press contact with the film guide, and the recording material is conveyed by driving the pressure roller. Has been put to practical use.

  In order to further improve the fixing performance, as described in Patent Document 1, it has been proposed to add a filler having higher thermal conductivity than the heat resistant base resin to the base layer of the film.

  Further, as described in Patent Document 2, by adding a filler having a surface energy smaller than that of a heat-resistant base resin such as fluorine resin to the heat-resistant base resin, sliding resistance is reduced, and the recording material conveyance speed is reduced. Has been proposed to be stable.

Patent Document 3 discloses that a film having excellent heat resistance, mechanical strength, releasability, and thermal conductivity is mainly composed of a thermosetting polyimide resin, and fluorine resin particles are dispersed on the surface. In addition, it has been proposed to contain thermally conductive powder.
JP-A-7-110632 JP 2001-056615 A Japanese Patent Laid-Open No. 11-156971

  However, in the case of Patent Document 1, an increase in sliding resistance due to the durability of the sliding portion between the film guide and the film inner surface, an increase in sliding resistance due to a temperature rise due to heating, and water vapor generated from the recording material during pressurization is pressurized. A phenomenon that the conveyance speed of the recording material or film is delayed with respect to the peripheral speed of the pressure roller due to, for example, a decrease in frictional driving force of the pressure roller due to adhesion to the roller surface. In spite of the rotation at the peripheral speed of the recording material, the conveyance of the recording material is delayed from a predetermined speed, resulting in a paper jam (JAM), or the film is delayed from the conveying speed of the recording material. There is a case where the toner image shifts to the downstream side in the transport direction and the image is disturbed, so-called slip problem occurs.

  In the case of Patent Document 2, if the filler having higher thermal conductivity than the heat resistant resin is not present in the heat resistant base resin, the heat conductivity is inferior, and the fixing performance may be deteriorated.

  And if patent document 3 adds both a filler with higher heat conductivity than heat-resistant resin and a filler whose surface energy is smaller than heat-resistant resin, both fixing performance and anti-slip can be achieved, but the total amount of filler to be added If the amount exceeds a predetermined amount, the tear strength of the film may be reduced, and film breakage may occur. In addition, the strength reduction rate due to the addition of a filler with a surface energy smaller than that of the heat resistant resin is greater than the strength reduction rate due to the addition of a filler having higher thermal conductivity than the heat resistant resin. Depending on the ratio, film breakage may occur.

  It is an object of the present invention to achieve prevention of slip of a recording material, securing of fixability, and prevention of film breakage in film fixing.

  A typical configuration of the fixing film according to the present invention for attaining the above object has at least a base layer formed of a resin composition and a surface layer formed of a resin composition, on a recording material. In the fixing film for fixing the image, the base layer resin contains a first filler having a higher thermal conductivity than the resin and a second filler having a surface energy lower than that of the resin, and the first filler contains When the amount is a volume% (vol%) and the content of the second filler is b volume%, the following formulas are satisfied: a ≧ 2b and 5 ≦ a + 2b ≦ 80.

  Since the heat conduction from the heating element to the toner on the recording paper is improved, the fixing performance is improved, and the frictional resistance between the surface of the heater sliding with the fixing film and the sliding surface of the film guide can be reduced. Paper slip can be prevented.

  Furthermore, by controlling the total of the thermally conductive filler and the slidable filler to be added, it is possible to prevent breakage due to a decrease in the strength of the film.

  That is, two of the first filler and the second filler are added to the base layer, and the ratio (volume%) and the total amount of both fillers in that case are preferably changed as the fixing film. As a result of studying the condition range where the characteristics can be obtained, the ratio of the added amount of both fillers and the total amount are regulated as described above to prevent the recording material from slipping, improve the fixing performance, and cause no film breakage. The present invention has been completed by finding that a fixing film and a fixing device using the same can be provided.

  According to the fixing film of the present invention, the heat conduction from the heating body to the image on the recording material is improved, the fixing performance is improved, and the surface of the heating body that slides on the fixing film, and the film guide sliding surface Since the frictional resistance can be reduced, the recording material can be prevented from slipping. Furthermore, the damage by the strength reduction of a film can be prevented by controlling the sum total of the 1st filler which is heat conductivity to add, and the 2nd filler which is slidability.

<Example of image forming apparatus>
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic laser printer.

  An image signal to be printed is input to a control unit (not shown) of the printer from an external host device (not shown) such as a personal computer. With the input as a trigger, at a predetermined control timing, the photosensitive drum 1 as an image carrier is rotationally driven by a drive system (not shown) in a clockwise direction indicated by an arrow at a predetermined peripheral speed, in this example, a peripheral speed of 140 mm / sec. .

  On the other hand, the first sheet feeding roller 8 is driven at a predetermined sheet feeding timing, and the sheet-like recording material P stacked and accommodated in the sheet feeding cassette 7 is separated and fed one by one and passes through the sheet path 9. To the registration roller 10. Alternatively, the second sheet feeding roller 12 is driven at a predetermined sheet feeding timing, and the sheet-like recording material P placed on the multi-tray 11 corresponding to a general-purpose sheet size is separated and fed one by one. 13 is conveyed to the registration roller 10. The registration roller 10 receives the leading end of the fed recording material P and corrects the skew of the recording material, and is a contact portion between the photosensitive drum 1 and the transfer roller 5 at a predetermined control timing. It is conveyed to the transfer nip at a speed of 140 mm / second, which is the same as the peripheral speed of the photosensitive drum 1. Reference numeral 14 denotes a first paper sensor (top sensor) including a photo sensor and a flapper, which is disposed in the vicinity of the recording material outlet side of the registration roller 10. The first paper sensor 14 detects the passage of the leading and trailing ends of the recording material P conveyed by the registration roller 10, determines the timing of laser scanning exposure for the photosensitive drum 1, and the recording material for the input image size. The authenticity of the length in the transport direction is determined.

  The photosensitive drum 1 is formed by forming an organic photosensitive layer on a grounded aluminum drum, and rotates when a charging bias is applied from a bias power source (not shown) to the core of the charging roller 2 brought into contact therewith. The peripheral surface of the photosensitive drum is uniformly charged to a predetermined polarity and potential. In this example, the photosensitive drum 1 is charged to a negative polarity. Laser scanning exposure L is performed on the charging surface of the photosensitive drum 1 by the laser scanner 3. The laser scanner 3 is composed of a semiconductor laser, a lens, a polygon mirror, a motor, and the like, and a DC controller as a control unit (not shown) performs polygon rotation and laser modulation in accordance with the image signal. The charged surface of the drum 1 is subjected to scanning exposure L. As a result, an electrostatic latent image corresponding to the scanning exposure pattern is formed on the photosensitive drum surface.

  The electrostatic latent image is reversely developed as a toner image by the developing device 4. The developing device 4 is composed of a negative-polarity one-component magnetic toner, a developing magnet, a developing sleeve, and the like. A developing bias is applied from a bias power source (not shown) to perform reverse development of the electrostatic latent image.

  Then, the toner image formed on the photosensitive drum 1 is transferred to the surface of the recording material P which is introduced into the transfer nip portion and is nipped and conveyed. The transfer roller 5 is electrostatically transferred onto the recording material P by applying a positive bias from a bias power source (not shown).

  The recording material P that has passed through the transfer nip is separated from the surface of the photosensitive drum 1 and introduced into the fixing device 16 from the sheet path 15. The surface of the photosensitive drum after separation of the recording material is wiped off by a cleaning blade 6 and cleaned by removing residual contaminants such as transfer residual toner and paper dust, and repeatedly used for image formation.

  The recording material P introduced into the fixing device 16 is subjected to a toner image fixing process by heating and pressing as described later. Then, the sheet passes through the sheet path 18 and is output as a print on the discharge tray 20 by the discharge roller 19.

  Reference numeral 17 denotes a second paper sensor (paper discharge sensor) disposed on the downstream side of the fixing nip portion of the fixing device 16. The conveyance state of the recording material P in the printer is monitored by the CPU in the DC controller by signals from the first paper sensor 14 and the second paper sensor 17. Even if the recording material P is sent to the transfer nip portion by the first paper sensor 14, the leading and trailing edges of the recording material P are not detected by the second paper sensor 17 within an appropriate time. As JAM (paper jam), the energization of the printer motor, the high voltage transformer, the energizing heating element of the fixing heating device 16 and the like is cut off.

<Fixing device 16>
FIG. 2 is a schematic cross-sectional view of the main part of a fixing device (hereinafter referred to as a fixing device) 16. The fixing device 16 is a so-called tensionless type heating device using a film heating method or a pressure member driving method.

  Here, in the following description, the longitudinal direction of the apparatus constituent member is a direction parallel to the direction orthogonal to the recording material conveyance direction in the recording material conveyance path surface. Further, the width or width direction (short direction) is a dimension in the recording material conveyance direction or a parallel direction. Alternatively, the upstream side and the downstream side are the upstream side and the downstream side in the recording material conveyance direction.

  21 is a heater unit as a heating member, and 22 is an elastic pressure roller as a pressure member. The heater unit 21 and the pressure roller are held at both ends in the longitudinal direction (perpendicular to the drawing) between the front and back side plates of the fixing device frame (not shown), and arranged in parallel vertically. In addition, the fixing nip portion N is formed with a predetermined width in the recording material direction by pressing with a predetermined pressing force.

  In the heater unit 21, reference numeral 23 denotes a substantially semicircular saddle-shaped film guide having a transverse cross section, which is a heat-resistant resin molding member such as PPS or liquid crystal polymer. The film guide 23 is a horizontally long member having a longitudinal direction in the drawing as a longitudinal direction, and a heating body 24 is fitted and held in a slot provided along the longitudinal direction on the lower surface thereof. Reference numeral 25 denotes a reinforcing sheet metal having an inverted U-shaped cross section disposed inside the film guide 23. Reference numeral 26 denotes a cylindrical fixing film having flexibility, and is loosely fitted to the assembly of the film guide 23, the heating body 24, and the reinforcing sheet metal 25. The fixing film 26 is a film in which a fluororesin layer such as PTFE or PFA is formed on a cylindrical polyimide resin. More specifically, on the surface of a cylindrical polyimide film (base layer) having a thickness of 60 μm, an intermediate layer (primer layer) made of fluororesin and carbon, and a fluororesin made of PTFE, PFA, etc. as a release layer (surface layer) A film in which a layer is formed. The fixing film 26 will be described in detail later.

  The pressure roller 22 is formed by covering a metal core 27 made of aluminum, iron, or the like with an elastic layer 28 made of silicone rubber, fluorine rubber, or the like, a PFA tube, or the like to form a release layer 29. The pressure roller 22 is configured to rotatably support both longitudinal end portions of the cored bar 27 between a front side plate and a back side plate of the fixing device frame via a bearing member.

  Then, the heating unit 24 and the pressure roller 22 are fixed by bringing the heater unit 21 and the pressure roller 22 into a pressure state by a pressure unit (not shown) against the elasticity of the elastic layer 28 of the pressure roller. A fixing nip portion N having a predetermined width necessary for heat fixing is formed by pressing the film 26 therebetween. The reinforcing sheet metal 25 prevents the film guide 23 and the heating body 24 from being deformed by the applied pressure. The fixing film 26 is backed up by the heating body 24 and the film guide 23 at the fixing nip N.

  The pressure roller 22 is rotationally driven by the driving means M in a counterclockwise direction indicated by an arrow, which is the recording material conveyance direction, at a predetermined peripheral speed (pressure member drive type). As the pressure roller 22 is driven to rotate, a rotational force acts on the cylindrical fixing film 26 by a frictional force in the fixing nip N between the pressure roller 22 and the outer surface of the fixing film 26, and the fixing film 26 is Around the outer periphery of the film guide 23, the inner surface of the fixing film in the fixing nip portion N rotates in a clockwise direction indicated by an arrow while sliding in close contact with the downward surface of the heating body 24 and the film guide 23. Sliding grease (not shown) is applied between the inner surface of the fixing film 26 and the film guide 23 to keep the fixing film 26 slidable. Further, the rotation stability of the fixing film 26 is maintained by the film guide 23.

  In the state where the fixing film 26 is rotated by the rotation driving of the pressure roller 22 and the heating body is heated to a predetermined target temperature by energizing the heating body 24 as will be described later, the fixing nip portion The recording material P carrying the unfixed toner image t is introduced between the N fixing film 26 and the pressure roller 22 while being guided by the entrance guide 30, and the toner image carrying surface is brought into close contact with the outer surface of the fixing film 26. By passing through the fixing nip N together with the fixing film 26, the heat of the heating body 24 is applied to the recording material P through the fixing film 26, and the unfixed toner image t is heated and fixed on the surface of the recording material P. The The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 26 by the curvature, guided to the exit guide 31 and discharged and conveyed.

In this embodiment, a ceramic heater (hereinafter referred to as a heater) is used as the heating body 24. FIG. 3 is an explanatory diagram of the configuration of the heater 24 used and the energization system. The heater 24 of this example is formed by screen-printing two energization heating elements 24c and 24e made of silver alloy on the surface of an insulating substrate 24a made of a ceramic material such as Al ₂ O ₃ or AlN. . And it coats glass, a fluororesin, etc. as a protective layer 24g on it. A thermistor TH as a temperature detecting element is bonded to the surface of the insulating substrate 24a opposite to the surface where the energization heating elements 24c and 24e are formed. The surface on the protective layer 24g side of the heater 24 is the heater surface side on which the inner surface of the fixing film 26 is in close contact and slides. The heater 24 is held by being fitted into a slot of the film guide 23 with the surface side exposed downward.

  Further, the heater 24 is energized to the energization heating elements 24c and 24e from the AC energization control circuit (triac) 41, so that the temperature of the heater 24 is quickly raised by the heat generated by the energization heating elements. That is, the heater 24 is supplied with power through the path of the feeding electrode 24b → the first energizing heating element 24c → the connecting electrode 24d → the second energizing heating element 24e → the feeding electrode 24f, and the energizing heating elements 24c and 24e generate heat. The temperature state of the heater 24 is detected by the thermistor TH. The output of the thermistor TH is A / D converted by an A / D converter 43 and taken into a control circuit (DC controller having a CPU) 42. The control circuit (CPU) 42 controls the energization power to the energization heating elements 24c and 24e of the heater 24 by performing phase control, wave number control, etc. on the AC voltage supplied from the AC energization control circuit 41 to the heater 24 based on the information. Thus, the temperature of the heater 24 is controlled to a predetermined fixing temperature. In this embodiment, the control temperature (fixing temperature) of the heater 24 at the time of paper feeding is 200 ° C.

<Fixing film 26>
The fixing film 26 will be described in detail. FIG. 4 is a cross-sectional view showing the layer structure of the fixing film 26. The fixing film 26 has a three-layer structure including a base layer 26a, an intermediate layer 26b, and a surface layer 26c, and has flexibility as a whole. The base layer 26 a is a base film of the fixing film 26, and its surface comes into contact with the heater 24 and the film guide 23 and slides. The surface layer 26c is a release layer, and the pressure roller 22 and the recording material P are in contact with the surface at the fixing nip portion. The intermediate layer 26b is a primer layer (adhesive layer) that joins the base layer 26a and the surface layer 26c.

  The base layer 26a is formed of a resin composition containing a heat resistant resin, a first filler F1 having a higher thermal conductivity than the heat resistant resin, and a second filler F2 having a lower surface energy than the heat resistant resin. The surface layer 26c is formed of a resin composition containing a fluororesin and a conductive third filler F3. And the intermediate | middle layer 26b is formed with the resin composition containing the electroconductive 3rd filler F3.

1) Base layer 26a
The base layer 26a of the fixing film 26 is formed of a resin composition in which a first filler F1 having higher thermal conductivity than the heat resistant resin and a second filler F2 having lower surface energy than the heat resistant resin are contained in a heat resistant resin such as polyimide. This improves the thermal conductivity and slidability.

  The thickness of the base layer is usually 10 to 70 μm, preferably 30 to 60 μm.

  Examples of the heat-resistant resin used for the base layer include polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polyphenylene sulfide, polyetheretherketone, polyethersulfone, polyetherimide, and liquid crystal polymer. Among these heat resistant resins, polyimide and polyamideimide are particularly preferable. This resin layer ensures insulation of the fixing film. Since the single layer of these resins has low thermal conductivity, a filler having higher thermal conductivity than the heat-resistant resin is contained.

  Examples of the first filler F1 having higher thermal conductivity than the heat resistant resin include boron nitride (BN), alumina, silicon carbide, potassium titanate, aluminum nitride, mica, silica, titanium oxide, talc, calcium carbonate, and the like. The mixture of 2 or more types can be mentioned. Among these, boron nitride, alumina, silicon carbide, and aluminum nitride are preferable.

  The content of the first filler F1 in the base layer 26a is usually 4 to 40% by volume, preferably 15 to 30% by volume. Within this range, it is possible to improve the thermal conductivity and rigidity while ensuring substantially the same level of flexibility as the resin single layer. When the content is less than 4% by volume, a sufficient effect of improving the thermal conductivity cannot be obtained. Conversely, when the content exceeds 40% by volume, the flexibility is insufficient, and the fixing device is used as a fixing film. In some cases, the film tends to crack in a relatively short period of time.

  Moreover, the average particle diameter of the 1st filler F1 is 0.5-15 micrometers, Preferably it is 1-10 micrometers. Heat-resistant resins, especially polyimide and polyamideimide, are generally formed using a varnish in which a solvent is added to a resin (including a precursor such as polyamide acid), but a film-like product is formed using a varnish containing a filler. When molded, irregularities are likely to occur on the surface. In order to obtain a belt having a thin base layer having a good surface state with few irregularities, the average particle diameter of the first filler F1 needs to be in the above range. If the average particle diameter exceeds 15 μm, the film tends to be uneven, and if it is less than 0.5 μm, the effect of improving the thermal conductivity is small, and the film tends to be uneven due to aggregation of the filler. If the unevenness of the base layer is large, the unevenness of the surface layer of the fixing film also becomes large, the adhesiveness with the toner is deteriorated, and the fixing property is lowered.

  The shape of the first filler F1 may be any of a spherical shape, a scale shape (flat plate shape), and a fibrous shape. Of these, the flat plate shape filler provides a smooth film with few irregularities and a spherical filler. Since higher rigidity is obtained than in the case of, it is particularly preferable. Therefore, as the first filler F1, boron nitride having a flat plate shape and high thermal conductivity and insulation is particularly suitable.

  The second filler F2 having a surface energy smaller than that of the heat-resistant resin is a fluororesin powder such as polytetrafluoroethylene powder, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer powder, tetrafluoroethylene-hexafluoro. One or more of propylene polymer powders can be used, and the powder diameter is 0.01 to 20 μm, preferably 0.1 to 10 μm for uniform dispersion.

  By adding the second filler F2, the friction coefficient (according to JIS K7218) of the inner peripheral surface of the fixing film is set to 0.3 or less, preferably 0.2 or less, more preferably 0.15 or less.

  The amount of the second filler F2 added to the base layer 26a is usually 2 to 20% by volume, preferably 5 to 10% by volume. If it is less than 2% by volume, it is difficult to achieve a friction coefficient of 0.3 or less, and if it exceeds 20% by volume, it tends to break due to shear stress generated by sliding contact.

  In the present invention, regarding the contents of both the first filler F1 and the second filler F2 in the base layer 26a, the content of the first filler F1 having higher thermal conductivity than the heat resistant resin is a volume%, and the surface energy is higher than that of the heat resistant resin. When the content of the small first filler F2 filler is b volume%, it is characterized in that the formulas of a ≧ 2b and 5 ≦ a + 2b ≦ 80 are satisfied.

  That is, the inventor shall add two of the first filler F1 and the second filler F to the base layer 26a, and variously change the ratio and the total amount of both fillers F1 and F2 in that case. As a result of studying the range of conditions for obtaining preferable characteristics as a fixing film, the ratio of the added amount of both fillers F1 and F2 and the total amount are regulated as described above to prevent the recording material from slipping and fixing performance. The present invention has been completed by discovering that it is possible to provide a fixing film that improves the resistance and does not cause film breakage, and a fixing device using the same.

2) Surface layer 26c
The surface layer 26c of the fixing film 26 is formed of a resin composition containing a fluorine resin and a conductive third filler F3.

  The thickness of the surface layer 26c is 1-30 micrometers normally, Preferably it is 5-15 micrometers.

  By using a fluororesin, releasability is ensured and a conductive filler is contained, thereby imparting conductivity to the surface layer 26c and preventing offset due to charging.

  As the fluorine resin, those having particularly excellent heat resistance are preferable so that the fixing film 26 can be continuously used at a high temperature of about 200 ° C., and examples thereof include tetrafluoroethylene resin (PTFE) and tetrafluoroethylene-par. Examples thereof include fluoroalkoxyethylene copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).

  The conductive third filler F3 is not particularly limited, and examples thereof include carbon black such as ketjen black and metal powder such as aluminum. The average particle diameter of the third filler F3 is preferably 0.5 μm or less in order to obtain stable and uniform conductivity.

The content of the third filler F3 in the surface layer 26c is usually about 0.1 to 5% by volume. However, when the conductivity of the surface layer 26c is increased to a certain level or more, when the toner on the recording material comes into contact with the surface layer 26c, the charge of the toner flows to the surface layer 26c, and between the recording material and the toner. The suction power of is lost. For this reason, it is desirable that the surface resistivity of the surface layer 26c be 1 × 10 ¹² to 1 × 10 ¹⁵ Ω / □ to achieve both the antistatic effect and the toner charge leakage prevention.

3) Intermediate layer 26b
The intermediate layer 26b of the fixing film 26 is formed of a resin composition containing an adhesive resin and a conductive third filler F3 on both the base layer 26a and the surface layer 26c.

  The thickness of the intermediate layer is usually 0.1 to 20 μm, preferably 1 to 10 μm.

  Similarly to the surface layer 26c, the intermediate layer 26b is made of a resin containing a conductive filler. Further, an intermediate layer exposed portion a is provided at the end of the fixing film, and the conductive sliding electrode member 44 is provided in the intermediate layer exposed portion a. By grounding through the fixing film 26, a shielding effect against frictional charging of the inner surface of the fixing film 26 and an antistatic effect of the outer surface are provided, and offset is prevented. That is, in order to prevent the offset, the conductivity of the fixing film may be increased. However, since the inner surface of the film in contact with the heater 24 needs to be insulative, the intermediate layer 26b and the surface layer 26c contain a conductive filler. Accordingly, a shielding effect against charging on the inner surface of the fixing film and an antistatic effect on the outer surface of the fixing film are provided, and offset is prevented.

  The resin constituting the intermediate layer 26c is not particularly limited, but for example, a mixture of a fluorine resin and a polyamideimide, a mixture of a fluorine resin and a polyethersulfone, and the like are preferable in terms of adhesiveness.

  As the conductive third filler F3 contained in the intermediate layer 26c, the same conductive third filler F3 contained in the surface layer 26c can be used.

The content of the conductive filler is usually about 0.5 to 10% by volume, preferably about 1 to 5% by volume. The surface resistivity of the intermediate layer is preferably 1 × 10 ⁶ Ω / □ or less, and it is preferable to sufficiently increase the conductivity. This effectively improves the shielding effect against the charging of the inner surface of the fixing film and the antistatic effect on the outer surface. Obtainable.

  In order to produce the fixing film 26 having the three-layer structure 26a, 26b, and 26c as described above, for example, a varnish that forms the base layer 26a on a cylindrical mold (heat-resistant resin and thermal conductivity more than that of the heat-resistant resin). The resin composition (the base layer 26a and the surface layer 26c) which forms the intermediate layer 26b after applying the first filler F1 having a higher surface area and the second filler F2 having a surface energy smaller than that of the heat resistant resin and applying the solvent. A resin composition (resin composition containing an adhesive resin and a conductive third filler F3) is applied to both of the resin layers, dried, and then further dried to form a resin composition (fluorine resin and A liquid containing a resin composition containing the conductive third filler F3) is applied and dried, and then polyimide, fluorine resin, or the like may be fired.

  The fixing film 26 is generally adjusted to have a total thickness of 20 to 110 μm and a thermal conductivity of 1.0 w / m · K or more.

<Examples and comparative examples>
Examples and the like specifically showing the configuration and effects of the present invention will be described below.

[Example 1]
The fixing film 26 of Example 1 was prepared as follows.

1) Base layer 26a
Polyimide varnish as heat-resistant resin (product of Ube Industries, product number U-varnish-S), as first filler F1, boron nitride having an average particle size of 1.5 μm (product number UHP-S1 manufactured by Showa Denko) and second PTFE powder is added as filler F2, and after stirring for 60 minutes with a stirrer, vacuum degassing is performed, and the first filler F1 having higher thermal conductivity than the polyimide resin and the varnish containing the second filler F2 having a lower surface energy than the polyimide resin Was prepared.

  The addition amount of the first filler F1 was adjusted to 10% by volume after varnish curing, and the addition amount of the second filler F2 having a surface energy smaller than that of the polyimide resin was adjusted to 5% by volume after varnish curing. That is, when the content of the first filler F1 is a volume% and the content of the second filler F2 is b volume%, the above a ≧ 2b and 5 ≦ a + 2b ≦ 80 are satisfied.

This varnish was adhered to a fixed thickness by dipping on a cylindrical mold. Subsequently, the solvent was removed by stepwise heating at 100 to 200 ° C. Thereby, the base layer 26a is formed on the cylindrical mold.
Is formed. However, the polyimide resin is in an unfired state.

2) Intermediate layer 26b
An intermediate layer (primer layer) containing 3% by volume of conductive carbon black as a conductive third filler F3 in a dispersion made of a mixture of polyamideimide, PTFE, PFA, etc. (product number 855-003, manufactured by DuPont Japan Limited). ) Was prepared.

  Then, the intermediate layer 26b made of the above resin composition was formed by dipping on the base layer 26a formed on the cylindrical mold as described above.

3) Surface layer 26c
A resin composition for a surface layer was prepared by blending 0.7% by volume of conductive carbon black as a conductive third filler F3 in a fluororesin dispersion (product number 855-405, manufactured by DuPont Japan Limited).

  And the surface layer 26c by said resin composition was formed by dipping on the base layer 26a + intermediate | middle layer 26b formed on the cylindrical metal mold | die as mentioned above.

  Thereafter, after firing polyimide, fluorine resin, and the like of each layer, the mold was pulled out to obtain a fixing film 26 having a three-layer structure 26a, 26b, and 26c.

The thicknesses of the layers 26a, 26b, and 26c were 50 μm for the base layer 26a, 5 μm for the intermediate layer 26b, and 10 μm for the surface layer 26c. Moreover, the surface resistivity of the intermediate layer 26b was 5 × 10 ⁵ Ω / □, and the surface resistivity of the surface layer 26c was 7 × 10 ¹³ Ω / □.

[Example 2]
Except that the first filler F1 having higher thermal conductivity than the polyimide resin is contained in the base layer 26b at 30% by volume after varnish curing, and the second filler F2 having a surface energy smaller than that of the polyimide resin is set at 15% by volume after varnish curing. A fixing film 26 was prepared using the same material and manufacturing method as in Example 1.

  That is, in the case of the fixing film of Example 2 as well, for the base layer 26a, when the content of the first filler F1 is a volume% and the content of the second filler F2 is b volume%, a ≧ 2b and 5 ≦ a + 2b ≦ 80 is satisfied.

[Comparative Example 1]
A fixing film was prepared by the same material and manufacturing method as in Example 1 except that the base layer 26a did not contain the first filler F1 having higher thermal conductivity than the polyimide resin.

[Comparative Example 2]
A fixing belt was produced by the same material and manufacturing method as in Example 1 except that the base layer 26a did not contain the second filler F2 having a surface energy smaller than that of the polyimide resin.

[Comparative Example 3]
Example 1 except that the base layer 26a contains 50% by volume of the first filler F1 having higher thermal conductivity than the polyimide resin after varnish curing, and 20% by volume of the second filler F2 having a surface energy smaller than that of the polyimide resin after varnish curing. A fixing film was prepared using the same material and production method as described above.

  That is, in the case of the fixing film of Comparative Example 3, with respect to the base layer 26a, the expression of the first filler F1 is satisfied, but the expression of 5 ≦ a + 2b ≦ 80 is not satisfied.

  The following characteristics of the fixing films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were examined.

a: Thermal conductivity Measured with a rapid thermal conductivity meter Chemtherm QTM-D3 manufactured by Kyoto Electronics Industry Co., Ltd.

b: Fixing performance When A4 size paper is left in an environment of 15 ° C. and 999 sheets are continuously copied at an environment temperature of 15 ° C. at 30 sheets / minute, a solid black image is rubbed with a predetermined paper for a specified number of times. Was measured with a reflection densitometer and used as a fixing ability index by the rate of decrease in density (standard: 20% or less).

c: Friction coefficient (film inner peripheral surface)
According to JIS K 7218, the friction coefficient was measured using an EFM-III-F manufactured by Toyo Baldwin.

d: Slip 100 black sheets of A3 size paper were passed intermittently in an environment of 30 ° C. and 80% RH, and the occurrence of JAM was examined.

e: Tear strength Tear strength was measured by a trouser tear method at a test speed of 10 mm / min, and converted into thickness.

f: Actual machine durability test Attach a fixing film to the fixing device 16 of the copying machine that passes 30 sheets of A4 size paper per minute, actually pass the paper, count the number of passed paper, and use it as the fixing film. It was visually observed whether there were any abnormalities such as cracks.

  The above evaluation results are shown in Table 1.

  As shown in Table 1, the fixing films obtained in Example 1 and Example 2 were excellent in thermal conductivity, had sufficient durability, and did not cause recording material slip.

  In Comparative Example 1, since the first filler F1 having higher thermal conductivity than the base resin was not added to the base layer 26a, the thermal conductivity effect could not be obtained, and the fixability could not satisfy the standard.

  In Comparative Example 2, since the second filler F2 having a surface energy smaller than that of the heat resistant resin was not added to the base layer 26a, the friction coefficient could not be reduced, and JAM due to slip occurred.

  In Comparative Example 3, when the content of the first filler F1 having higher thermal conductivity than the base resin is a volume% and the content of the filler having a surface energy smaller than that of the heat resistant resin is b volume%, a ≧ 2b and a + 2b Was over 80%, the tear strength was reduced, and breakage occurred when the paper was passed through the actual machine. That is, when the total amount of filler added exceeds a predetermined amount, the tear strength decreases regardless of the filler ratio to be added.

1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment. FIG. 3 is a schematic configuration diagram of a main part of a fixing device. Explanatory drawing of the structure of a used heating body (ceramic heater), and an electricity supply control system. The schematic diagram which shows the layer structure of a fixing film.

Explanation of symbols

  1 .... Organic photosensitive drum, 2 .... Charging member, 4 .... Developer, 7 .... Paper cassette, 16 .... Fixing device, 21..Heater unit, 22..Pressure roller, 23..Film guide, 24..Heating body (ceramic heater), 26..Fixing film, 26a..Base layer, 26b..Intermediate layer (primer layer), 26c..Surface layer, TH..Thermistor, 42..Control circuit (CPU)

Claims (12)

In a fixing film having at least a base layer formed of a resin composition and a surface layer formed of a resin composition, and fixing an image on a recording material,
In the resin of the base layer, a first filler having higher thermal conductivity than the resin and a second filler having a surface energy smaller than that of the resin are contained, and the content of the first filler is a volume%, and the second filler. A fixing film characterized by satisfying the formulas of a ≧ 2b and 5 ≦ a + 2b ≦ 80 when the content of is b volume%.   2. The fixing film according to claim 1, wherein the surface layer contains a fluorine resin and a conductive filler.   The fixing film according to claim 1, wherein the resin of the base layer is polyimide.   The fixing film according to claim 1, wherein the content of the first filler is 4 to 40% by volume.   The fixing film according to claim 1, wherein the first filler is boron nitride.   The fixing film according to claim 1, wherein the content of the second filler is 2 to 20% by volume.   The fixing film according to claim 1, wherein the second filler is a fluorine resin.   8. The method according to claim 1, further comprising an intermediate layer formed of a resin composition between the base layer and the surface layer, wherein the intermediate layer contains a conductive filler. The fixing film according to any one of the above.   The fixing film according to claim 1, wherein the total thickness is 20 to 110 μm.   The fixing film according to claim 1, wherein the thermal conductivity is 1.0 w / m · K or more.   The fixing film according to claim 1, wherein a coefficient of friction (specified in JISK7218) is 0.3 or less. A recording material carrying an image at the nip portion is sandwiched and conveyed, having a heating body, a film that slides with the heating body, and a rotary pressure member that forms a nip with the heating body via the film In a fixing device for fixing an image on a recording material by heat from the heating body via the film,
The fixing device according to claim 1, wherein the film is the fixing film according to claim 1.