JP4708718B2 - Fixing device and fixing film - Google Patents

Description

The present invention relates to a fixing device and a fixing film .

  In general, electrophotographic image forming apparatuses are widely used in copying machines, laser beam printers, and the like. In the electrophotographic method, an electrostatic force is used to form an image of toner particles on a recording material such as recording paper by a transfer method or a direct method, and the toner image is recorded on the recording material by a fixing device as an image heating device. A stable image is formed by being melted and fixed thereon.

  As the fixing device, a heat roller method is widely used. Recently, a film heating system has been put into practical use.

  As the heat roller system, a pressure roller pair of a fixing roller (heating roller) and a pressure roller is a basic configuration, and the roller pair is rotated, and a fixing nip portion (heating nip portion) which is a mutual pressure contact portion of the roller pair A recording material on which an unfixed toner image to be image-fixed is formed and carried is introduced and nipped and conveyed, and the unfixed toner image is applied to the surface of the recording material by the heat of the fixing roller and the pressure of the fixing nip. It is to fix.

  As a fixing roller and a pressure roller used in this heat roller type fixing device, for example, a heat-resistant elastic layer such as silicon rubber or fluorine rubber is provided on the surface of a hollow roller such as aluminum, and toner or The outermost layer is coated with a release layer such as a coating layer of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) / PTFE (polytetrafluoroethylene) to prevent paper dust from sticking. In general, the fixing roller is heated from the inside by a halogen heater or the like to maintain the surface temperature at a predetermined fixing temperature and perform heat fixing.

  A film heating type fixing device (heating device) is disclosed in, for example, Patent Documents 1 to 4 and the like related to the earlier proposal of the present applicant. That is, a heat-resistant film (fixing film) as a flexible moving member is generally sandwiched between a ceramic heater as a heating body and an elastic pressure roller as a pressure member, and a nip portion (fixing nip portion, contact) A recording material on which an unfixed toner image to be fixed as a heated material is formed and supported between the film and the pressure roller in the nip portion, and is nipped and conveyed together with the film Thus, the unfixed toner image is heated and fixed on the surface of the recording material by heating and pressing at the nip portion.

  This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a film having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature, and the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced (saving) Power).

  The film as the flexible moving member is a cylindrical or endless belt-like film as a rotating body, and the driving method is to use a film pressure-contacted by a film guide for guiding the inner peripheral surface of the film and a pressure roller. There is a method of rotating the pressure roller by driving the pressure roller (pressure roller driving method), and conversely rotating the pressure roller by driving an endless belt-like film stretched between the driving roller and the tension roller. is there. Moreover, the film as a flexible movement member can also be set as the apparatus structure which makes it the long end member wound by the roll, and draws out and moves this through a heating body.

  In addition, as a fixing device of an image forming apparatus that performs full-color image formation, the applicant of the present application disclosed in Patent Documents 5, 6, and 7, as a configuration in which an elastic layer is formed on the film surface, OHT transparency, color reproducibility, and Proposals have been made to improve fixing properties such as uneven gloss and image roughness.

  There is also a configuration in which a heat source is also provided in the pressure roller so that the pressure roller is also heated. However, in the above conventional example, depending on conditions such as the type of recording material and the environment, an electrostatic offset phenomenon in which the toner on the recording material is electrostatically transferred to the fixing film may occur, thereby reducing the image quality. There was a thing.

  That is, depending on conditions such as the type of recording material and the environment, an electric field that causes the toner on the recording material to be attracted to the fixing film due to frictional charging between the recording material and the fixing film or due to transfer charge of the recording material may occur. The portion may be transferred onto the fixing film. The transferred toner returns to the recording material after the fixing film makes a round, and becomes a ghost on the image, degrading the image quality (electrostatic offset).

  There are two types of electrostatic offsets, and here they are classified into full-surface offsets and peeling offsets.

  In the entire surface offset, the recording material and the fixing film exchange charges with each other by frictional charging or the like, and an offset electric field is constantly generated, and the offset appears continuously over the entire image.

  On the other hand, the peeling offset is a phenomenon in which when the trailing edge of the recording material passes through the fixing device, the trailing edge of the recording material splashes and comes into strong contact with the fixing film, leaving a potential history in a straight line in the longitudinal direction of the film. Yes, it occurs on a straight line in the scanning direction on the image, so that it can be distinguished from the entire surface offset.

  In particular, as a fixing device of an image forming apparatus that performs full-color image formation, an elastic layer is formed on the film surface, so that the thickness of the entire film is increased and the capacitance is reduced by having the elastic layer. Thus, it is considered that the above-mentioned problem is likely to appear remarkably because the surface potential is increased even when the surface charge amount is the same.

Patent Documents 6 and 7 propose a heating device that can reduce surface charges by reducing the resistance of an elastic layer, thereby eliminating image bleeding and fixing defects, and at the same time improving offset.
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 Japanese Patent Laid-Open No. 10-48868 JP 2000-187407 A JP 2003-308949 A

  However, when the resistance of the elastic layer is reduced, it is necessary to consider both the hardness and the resistance reduction, and there is a limit to controlling the resistance value at a low cost.

  In some apparatuses, an insulating layer must be provided on the surface layer of the fixing film in consideration of electrical interference with transfer. That is, for example, in an image forming apparatus in which the distance between the transfer portion and the fixing portion is short, if the fixing film surface layer has a low resistance, the bias at the transfer portion escapes to the film surface by being transmitted through the surface layer of the recording material. In some cases, defects such as image defects due to insufficient transfer bias may occur.

  In particular, in a color image forming apparatus, since transfer is performed a plurality of times and transfer is performed with a high voltage, an insulating layer is often required.

  On the other hand, in some cases, the charging charge accumulated on the inner surface of the film due to frictional charging or the like due to rubbing on the inner surface of the film may cause defects such as image defects or malfunction due to noise due to leakage or the like.

  That is, in the above conventional example, an insulating material is generally used as a member of the base layer. For example, depending on the apparatus configuration, the base layer on the inner surface of the fixing film is charged by friction with a rib portion or the like. The electric field on the film surface may be affected, resulting in image defects such as electrostatic offset. In addition, when there is no path for releasing the charge accumulated in the base layer, the accumulated charge leaks irregularly, resulting in an image defect as a leak mark, or device malfunction due to noise due to the leak. In a severe case, damage or the like may occur due to leakage, and the durability (life) of the apparatus may be significantly deteriorated.

  On the other hand, by using a metal film (conductive) as a base layer, it is possible to prevent frictional charging and the like on the inner surface, but the metal film is more flexible (repetitive bending strength = durability) than the resin film. In some cases, it is inferior in terms of followability (followability to the heater surface) and the like, which is disadvantageous for downsizing and diameter reduction.

  In particular, when trying to use a thin elastic layer, the electrostatic capacity of the film becomes too large, and the amount of charge accumulated on the film surface due to peeling discharge increases. Depending on the material of the surface and conditions such as the environment, defects such as peeling offset may occur.

Accordingly, an object of the present invention is, in particular, a fixing device using a cylindrical fixing film having a resin base layer, a release layer, and a rubber layer provided between the base layer and the release layer, and The fixing film used in the fixing device is to moderately suppress both the entire surface offset and the peeling offset .

The present invention is a fixing device and a fixing film characterized by the following configurations.

(1) A cylindrical fixing film having a resin base layer, a release layer, and a rubber layer provided between the base layer and the release layer, and a heater in contact with the base layer of the fixing film; And a pressure roller that forms a fixing nip portion together with the heater via the fixing film, and the toner image is heated and fixed onto the recording material while the recording material carrying the toner image is sandwiched and conveyed in the fixing nip portion. In the fixing device
The base layer is a polyimide resin layer having a volume resistivity ρv of 1 × 10 ³ (Ω · cm) ≦ ρv ≦ 1 × 10 ⁹ (Ω · cm) due to the dispersion of a conductive substance, A fixing device, wherein the rubber layer and the release layer are insulating layers.

(2) a cylindrical fixing film having a resin base layer, a release layer, and a rubber layer provided between the base layer and the release layer, and a heater in contact with the base layer of the fixing film; And a pressure roller that forms a fixing nip portion together with the heater via the fixing film, and the toner image is heated and fixed onto the recording material while the recording material carrying the toner image is sandwiched and conveyed in the fixing nip portion. In a fixing film used for a fixing device,
The base layer is a polyimide resin layer having a volume resistivity ρv of 1 × 10 ³ (Ω · cm) ≦ ρv ≦ 1 × 10 ⁹ (Ω · cm) due to the dispersion of a conductive substance, A fixing film, wherein the rubber layer and the release layer are insulating layers.

That is, when the base layer is a medium resistance polyimide resin layer and the rubber layer and the release layer are insulating layers, both the entire surface offset and the peeling offset can be appropriately suppressed.

(1) 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 a full-color image printer using an electrophotographic process. The image forming apparatus includes an image forming unit that forms and supports an unfixed image on a recording material, and a fixing unit that heats and fixes the unfixed image on the surface of the recording material. The image forming means is a color image forming means for forming toner images of a plurality of colors on the recording material.

  Reference numeral 101 denotes an electrophotographic photosensitive drum (image bearing member) made of an organic photosensitive member or an amorphous silicon photosensitive member, which is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined process speed (peripheral speed).

  The photosensitive drum 101 is uniformly charged with a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

  Subsequently, the charging processing surface is subjected to scanning exposure processing of target image information by laser light 103 output from a laser optical box (laser scanner) 110. A laser optical box 110 outputs a laser beam 103 modulated (on / off) in accordance with a time-series electric digital pixel signal of target image information from an image signal generator such as an image reading device (not shown) to output a rotating photosensitive drum. The surface is subjected to scanning exposure, and an electrostatic latent image corresponding to target image information scanned and exposed on the surface of the rotary photosensitive drum 101 is formed by this scanning exposure. Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

In the case of full-color image formation, scanning exposure / latent image formation is performed on a first color separation component image of a target full-color image, for example, a yellow component image, and the latent image is subjected to yellow development in the four-color developing device 104. The yellow toner image (toner image) is developed by the operation of the device 104Y. The yellow toner image is transferred onto the surface of the intermediate transfer drum 105 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105. The surface of the rotary photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is cleaned by the cleaner 107 after removal of adhered residues such as transfer residual toner.

  The process cycle of charging / scanning exposure / development / primary transfer / cleaning as described above includes a second color separation component image (for example, magenta component image, magenta developer 104M is activated) of the target full-color image, a third An intermediate transfer member is sequentially executed for each color separation component image of a color component image (for example, cyan component image, cyan developing device 104C is activated) and a fourth color component image (for example, black component image, black developing device 104BK is activated). Four color toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred onto the surface of the drum 105, and a color toner image corresponding to the target full-color image is synthesized and formed.

  The intermediate transfer drum 105 has a middle-resistance elastic layer and a high-resistance surface layer on a metal drum. The intermediate transfer drum 105 is in contact with or close to the photosensitive drum 101 at the same peripheral speed as the photosensitive drum 101. And a bias potential is applied to the metal drum of the intermediate transfer drum 105 to transfer the toner image on the photosensitive drum 101 side to the surface of the intermediate transfer drum 105 by the potential difference with the photosensitive drum 101.

  The color toner image synthesized and formed on the surface of the intermediate transfer member 105 is not transferred to the secondary transfer portion T2 at the secondary transfer portion T2 which is a contact nip portion between the rotating intermediate transfer drum 105 and the transfer roller 106. The image is transferred onto the surface of the recording material P fed from the sheet feeding unit shown in the figure at a predetermined control timing. The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images sequentially from the surface of the intermediate transfer drum 105 to the recording material P side.

  The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105, introduced into the fixing device 100, subjected to heat-fixing processing of an unfixed toner image, and is subjected to non-fixing as a color image formed product. The paper is discharged onto the illustrated paper discharge tray.

  After the color toner image is transferred to the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 after removal of the adhering residue such as transfer residual toner and paper dust. The cleaner 108 is always held in a non-contact state with the intermediate transfer drum 105, and is in contact with the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Retained.

  Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and recording is performed on the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The contact state is maintained via the material P.

  A mono-color image print mode such as a monochrome image can also be executed. A double-sided image print mode or a multiple image print mode can also be executed.

  In the double-sided image print mode, the recording material P on which the first-side image has been printed exiting the fixing device 100 is turned upside down via a recirculation conveyance mechanism (not shown), and sent again to the secondary transfer unit T2 to be the second side. In response to the toner image transfer, the toner image is again introduced into the fixing device 100 and undergoes a toner image fixing process on two sides, whereby a double-sided image print is output.

  In the multiple image print mode, the recording material P on which the first image has been printed out of the fixing device 100 is sent to the secondary transfer portion T2 again without being turned upside down via a recirculation conveyance mechanism (not shown). The second toner image is transferred to the surface on which the second image has been printed, and is again introduced into the fixing device 100 and undergoes the second toner image fixing process, whereby a multiple image print is output.

(2) Fixing device 100
The fixing device 100 in this embodiment basically uses a cylindrical heat-resistant film (fixing film) as a flexible member disclosed in JP-A-4-44075 to 44083, 4-204980 to 204984, and the like. , Film heating system, pressure roller drive system (tensionless type).

  2 is a front model view of the fixing device 100 with the intermediate portion omitted, FIG. 3 is a longitudinal cross-sectional model diagram with the intermediate portion omitted, and FIG. 4 is a transverse cross-sectional model diagram.

  Reference numeral 15 denotes a heating assembly (film unit), and 19 denotes an elastic pressure roller as a pressure member, and a fixing nip portion N as a contact portion is formed by pressure contact between both of them.

1) Heating assembly 15
The heating assembly 15 includes a cylindrical or endless heat-resistant fixing film (hereinafter referred to as a film) 16 as a flexible moving member, a ceramic heater (hereinafter referred to as a heater) 17 as a heating body, and a support member. The film guide 18, the pressurizing rigid stay 20, and the annular flange member 25 as a film displacement movement restricting means are assembled.

The film 16 is composed of a polyimide resin base layer having a thickness of 20 to 100 μm, a heat resistant elastic layer (rubber layer) such as silicon rubber and fluororubber having a thickness of 50 to 500 μm as an intermediate layer, and PTFE, PFA on the outer peripheral surface thereof. A composite layer film coated with 10-30 μm of FEP or the like to form a release layer can be used. In this example, a polyimide film having a diameter of 20 mm in which silicon rubber was formed on the outer peripheral surface of the polyimide film and PTFE was coated was used. The film 16 will be described in detail later in section 4).

The heater 17 is a member having a low heat capacity and a temperature that rapidly rises upon energization, with the direction intersecting the recording material passing direction as a longitudinal direction. This heater 17 is basically composed of a substrate such as insulating ceramics such as alumina or aluminum nitride, a heat-resistant resin such as polyimide, PPS, or liquid crystal polymer, and a means such as screen printing on the substrate surface. An energization heating resistance layer made of Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N, etc., formed by coating and firing in a linear or narrow strip shape having a thickness of about 10 μm and a width of about 1 to 5 mm, and the energization An insulating layer such as a glass coat that covers the substrate surface on which the heating resistance layer is formed, and the substrate surface that is electrically connected to the energization heating resistance layer are formed, and a voltage is supplied from the feeding circuit through the feeding connector. And a surface heating type heater having a low heat capacity as a whole.

  Then, the surface of the heater 17 (the heater substrate surface side on which the energization heating resistor layer and the glass coat insulating layer are formed) is used as a film-adhering sliding surface, and the film guide 18 has a central portion on the outer surface side of the film guide 18. It is fixed and held by being fitted and exposed to the outside in the heater insertion groove formed along the length. The heater 17 is supplied with power from the AC power supply (not shown) to the energized heat generating resistor layer, and the energized heat generating resistor layer generates heat over the entire length, so that the temperature rises rapidly and steeply. The temperature rise of the heater 17 is detected by a temperature detection element (not shown) arranged on the back side of the heater, and the electric power supplied from the AC power source to the energization heating resistor layer of the heater 17 by the control circuit unit (not shown) is phase and wave number. The temperature of the heater 17 is controlled to a predetermined fixing temperature under the control of the control or the like. The temperature control configuration of the heater 17 is not limited to the above, and is based on temperature information detected by temperature detection means such as the surface temperature of the pressure roller 20 or a thermistor disposed at an arbitrary position on the inner surface of the film 16 of the nip N. In addition, the surface temperature of the film 16 required for fixing the toner image T on the recording material P at the nip portion N is set as a target set temperature, and the energization of the heater 17 to the energization heating resistance layer is maintained. The amount can also be controlled.

  The film guide 18 is a heat-resistant and heat-insulating member having a substantially semi-circular cross-sectional shape having a longitudinal direction that intersects the recording material passing direction, and is phenolic resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK. Insulating and heat-resistant materials such as resin, PES resin, PPS resin, fluororesin (PFA, PTFE, FEP, etc.), LCP (liquid crystal polymer) resin, and mixed resins thereof are used. It serves to back up the film 16, pressurize the nip N, support the heater 17, and transport stability when the film 16 rotates.

  The cylindrical film 16 is loosely fitted on a film guide 18 on which a heater 17 is fixedly supported.

  The annular flange member 25 is fitted to the end portion side of the film guide 18 to regulate the end portion of the film 16.

  The pressurizing rigid stay 20 is inserted inside the film guide 18, and both end portions thereof protrude outward from both end portions of the film guide 18.

2) Elastic pressure roller 19
An elastic pressure roller (hereinafter referred to as a pressure roller) 19 as a pressure member is a core metal 19a provided with an elastic layer 19b such as silicone rubber to reduce the hardness, and both ends of the core metal 19a are connected to the apparatus. The bearing is rotatably held between the front side and the rear side chassis side plate (not shown). In order to improve surface properties, a fluororesin layer such as PTFE, PFA, FEP or the like may be further provided on the outer periphery.

  Above the pressure roller 19, the heating assembly 15 is disposed with the lower surface side of the film guide 18 facing downward, and both ends of the pressure rigid stay 20 and spring receiving members 21 and 21 on the apparatus chassis side plate side, A pressing force is applied to the pressurizing rigid stay 20 by contracting the pressurizing springs 22 and 22 respectively. As a result, the lower surface of the film guide provided with the heater 17 and the pressure roller 19 are pressed against each other with the film 16 against the elasticity of the elastic layer 19b of the pressure roller 19, and a nip having a predetermined width as a contact portion. Part N is formed. The heater 17 exists in the nip portion N. The film 16 is backed up at the nip N by a film guide 18 and a heater 17.

  In this example, the ceramic heater 17 as the heating body and the film guide 18 that supports the ceramic heater 17 have a sliding surface that slides on the fixing film 16 as a moving member, and is a backup member that supports the fixing film 16. is there.

3) Device Operation In FIG. 4, the pressure roller 19 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the film 16 by the frictional force between the pressure roller 19 and the outer surface of the film 16 by the rotational driving of the pressure roller 19. As a result, the film 16 rotates around the film guide 18 in the clockwise direction indicated by the arrow while sliding and moving the inner surface in close contact with the lower surface of the heater 17 at the nip portion N (pressure roller driving method). The film 16 is in a rotating state having a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 19.

  In order to reduce the mutual sliding frictional force between the lower surface of the heater 17 and the inner surface of the film 16 in the nip portion N, a lubricant such as heat resistant grease is provided between the lower surface of the heater 17 and the inner surface of the film 16 in the nip portion N. Intervene.

The rotation of the pressure roller 19 is started based on the print start signal, and the heater 17 starts to heat up. When the rotation peripheral speed of the film 16 is stabilized by the rotation of the pressure roller 19 and the temperature of the heater 17 rises to a predetermined temperature, a material to be heated is interposed between the film 16 and the pressure roller 19 in the nip portion N. The recording material P carrying the toner t is introduced with the toner image carrying surface side of the film 16 side, so that the recording material P adheres closely to the lower surface of the heater 17 via the film 16 at the nip portion N. Part N moves and passes with the film 16. During the moving and passing process, the heat of the heater 17 is applied to the recording material P through the film 16 and the toner image t is heated and fixed on the surface of the recording material P. That is, the recording material is heated and pressed while the recording material is nipped and conveyed between the film 16 and the pressure roller 19. In the present embodiment, the heater 17 corresponds to the nip portion of the film sliding surface (moving member sliding surface) of the backup member. The recording material P that has passed through the nip portion N is separated from the surface of the film 16 and conveyed.

4) Fixing film 16
Fixing film as moving member includes a resin base layer, and the release layer is a cylindrical film having a rubber layer provided between the release layer and the base layer. The base layer is a polyimide resin layer in which the volume resistivity ρv is 1 × 10 ³ (Ω · cm) ≦ ρv ≦ 1 × 10 ⁹ (Ω · cm) because the conductive material is dispersed, and the rubber layer The release layer is an insulating layer. FIG. 5 is a schematic cross-sectional view showing the layer structure of the fixing film 16 in this embodiment. The fixing film 16 is characterized in that an elastic layer 2 made of a rubber elastic body and a release layer 3 are sequentially provided on a base layer 1 mainly composed of polyimide resin. The base layer 1 side is the heater sliding surface side (fixing film inner surface side), and the release layer 3 side is the pressure roller contact surface side (fixing film outer surface side).

a: Base layer 1
In order to satisfy the conditions such as thermal conductivity and mechanical strength necessary for the fixing film 16, the base layer 1 mainly composed of polyimide resin preferably has a thickness in the range of 20 to 100 μm. Furthermore, in order to improve the thermal responsiveness of the fixing film, the thermal conductivity of the polyimide film base layer is preferably 0.42 [W / m · ° C.] or more. Usually, the thermal conductivity of a polyimide resin is 0.25 [W / m · ° C.] or less, but by adding, for example, BN, AlN, or SiC as an additive to the resin material, the thermal conductivity of the base layer can be increased. It can be increased to the above range.

In addition, in order to prevent generation of charged charges due to electrostatic offset and rubbing on the inner surface, the resistance of the base layer is reduced by dispersing a conductive substance as a resistance control material. Specifically, when the volume resistivity is ρv, 1 × 10 ³ < ρv <1 × 10 ⁹ (Ω · cm: when JIS method K 6911, 100 V is applied), the surface resistivity ρs of the inner surface of the base layer is 1 × 10 ¹² (Ω / □ :: JIS method K 6911, when 100 V is applied) or less is preferable.

  If the base layer resistance value is outside the above range, the effect of preventing image defects such as electrostatic offset and the effect of preventing the generation of charged charges due to friction of ribs and the like are weakened, which is not suitable.

That is, when the volume resistivity ρv is 1 × 10 ³ (Ω · cm) or less, the electrostatic capacity of the film becomes too large, the charge amount due to peeling discharge increases, and peeling offset occurs. There is a case. Further, when the volume resistivity ρv is 1 × 10 ⁹ (Ω · cm) or more, the effect of canceling the surface charge is weakened and the effect of preventing the electrostatic offset is weakened.

Further, when the surface resistivity ρs is 1 × 10 ¹² (Ω / □) or more, the effect of preventing the generation of charged charges due to friction on the inner surface is weakened.

  Examples of the conductive material include carbon black such as ketjen black, thermal black, acetylene black, and metal particles having excellent conductivity such as graphite or copper, silver, nickel, metal powder, tin oxide, titanium oxide, indium oxide, etc. The above resistance value can be obtained by blending conductive metal oxides, materials plated with various inorganic fillers, or metal salts such as lithium, sodium, potassium and phosphorus, and complexes or complexes thereof. Can be obtained.

The content ratio (content) of the conductive substance in the base layer is preferably 0.5 to 50 wt% (% by weight) because both the strength of the film base layer and the effect of imparting conductivity are required.

b: Elastic layer 2
As the rubber elastic body constituting the elastic layer 2, a soft one having a low rubber hardness is preferable. For example, silicone rubber having a JIS-A hardness of 1 to 70 °, more preferably 5 to 40 ° can be suitably used. The thickness of the elastic layer is preferably in the range of 0.05 to 3 mm, more preferably in the range of 0.1 to 0.5 mm. If the thickness of the elastic layer is less than 0.05 mm, it is difficult to fix the film so that it is difficult to give sufficient elasticity to the film, and the OHT permeability, color reproducibility, gloss unevenness and image The improvement effect of fixing property such as improvement of roughness cannot be obtained. On the other hand, if it is thicker than 3 mm, the heat responsiveness of the fixing film is impaired.

c: Release layer 3
As a constituent material of the release layer 3, for example, a fluororesin such as PTFE, PFA, or FEP is suitable, or a mixture of two or more of them can be used as necessary. The thickness of the release layer is preferably 5 to 50 μm, more preferably 10 to 30 μm. When the thickness of the release layer is less than 5 μm, the durability is lowered, and when the thickness is more than 50 μm, the effect of providing the rubber elastic layer cannot be obtained.

  In addition, in this example, the elastic layer 2 or the release layer 3 is configured as an insulating layer, so that a problem due to interference with transfer can be prevented. In particular, in a heating device used in a color image forming apparatus, transfer is performed a plurality of times, and transfer is performed with a high voltage. Even in such a case, problems due to interference with the transfer can be prevented.

  Furthermore, by configuring the elastic layer having a relatively large film thickness as an insulating layer, the influence of scratches and the like can be reduced, and a stable effect can be obtained through durability.

  The fixing film of the present invention can be produced, for example, as follows. First, in manufacturing the polyimide film as the base layer 1, a polyimide precursor solution such as a polyamic acid solution in which thermally conductive inorganic particles and conductive fillers are dispersed on the outer surface of a mold serving as a core is uniform. It is made to adhere with a sufficient thickness, and is dried and imidized by heating to form a tubular product of a polyimide film.

  Any method may be used for attaching the polyimide precursor solution to the core with a uniform thickness. For example, a predetermined amount of the polyimide precursor solution is attached to the upper periphery of the core by a general method such as dipping or coating. After that, an outer mold having a predetermined clearance is fitted to the outside of the metal core body whose longitudinal direction is held vertically, and the outer mold is lowered by its own weight. The “coat” method and the like are particularly suitable.

  The rubber elastic body layer 2 can be provided on the surface of the tube-shaped polyimide film 1 formed as described above by a method in which LTV silicone rubber is further coated and cured, or a method in which HTV silicone rubber is press-molded. The release layer 3 can also be easily formed according to a conventional method such as dispersion coating of fluororesin. Thereafter, the tube-shaped material having a multilayer structure is separated from the core, whereby the image fixing film of the present invention is obtained.

  The polyimide precursor that can be used as a raw material for the polyimide film in the present invention is not particularly limited, and examples thereof include those obtained by reacting an aromatic diamine and an aromatic tetracarboxylic acid. Examples of aromatic tetracarboxylic acids such as 3,3′-dimethoxy-4,4′-diaminodiphenyl ether and 3,3′-diaminophenyl ether include 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Examples thereof include acid dianhydride and pyromellitic dianhydride. The reaction of these aromatic diamines with aromatic tetracarboxylic acid is carried out in an organic polar solvent such as dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone.

Example 1
As a polyimide precursor solution, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride having a viscosity of 2000 poise and aromatic diamine (4,4′-diaminophenyl ether) are used as a solvent, N-methyl- A polyimide precursor solution obtained by reacting in 2-pyrrolidone (NMP) was prepared.

Next, Si ₃ N ₄ (Shin-Etsu Chemical Co., Ltd. silicon nitride, thermal conductivity: 0.06 to 0.09 cal / cm · sec · ° C. as a thermally conductive inorganic filler having an average particle size of 0.6 μm. ) Powder was used.

  Further, ketjen black powder having an average particle size of 0.03 μm was used as the conductive filler.

10 g of the Si ₃ N ₄ powder and 20 g of Ketjen black powder are dispersed in 40 ml of NMP, and after using the ultrasonic cleaner to disperse the secondary agglomerated particles into primary particles, the polyimide precursor The solution was put into the body solution and stirred with a mixer to uniformly disperse the Si ₃ N ₄ particles. The mixing ratio of Si ₃ N ₄ and ketjen black to the solid content concentration of the polyimide precursor solution was 15 wt% and 30 wt%, respectively.

  After that, an aluminum cylindrical core body having an outer diameter of 30 mm and a length of 500 mm is immersed in the polyimide precursor solution and pulled up, and a ring-shaped outer mold having an inner diameter of 31 mm is formed from the top of the cylindrical core body. The film was dropped by its own weight, and a film of a polyimide precursor solution having a thickness of about 500 μm was cast on the outer surface of the cylindrical core.

  Thereafter, this core is heated at 120 ° C. for 40 minutes and at 200 ° C. for 15 minutes to advance the removal of the solvent and the imide conversion reaction to form a tubular polyimide film having a thickness of 60 μm serving as a base layer. (Polyimide intermediate) was formed.

  Next, after coating the surface of this polyimide tube on the core with Hs20 ° LTV silicone rubber (product name XE15-751, manufactured by Toshiba Silicone Co., Ltd.), heat treatment was performed at 120 ° C for 30 minutes to achieve a thickness of 0.2 mm. A rubber elastic layer was formed. And after spray-coating FEP dispersion (Daikin Kogyo make, brand name ND-1) as a fluororesin on the surface of the obtained rubber elastic body layer, the completion process of an imidation reaction and the baking process of a fluororesin are performed. Therefore, after performing heat treatment at 250 ° C. for 80 minutes, heat treatment was performed at 380 ° C. for 70 minutes to form a releasable surface layer having a thickness of 10 μm. Thereafter, the aluminum core was pulled out to obtain an image fixing film of the present invention having a multilayer structure.

  In addition, in order to ensure the adhesive strength between each layer, when it coats after apply | coating a primer, it will be excellent in the integrity without delamination.

Actually, when the resistivity of the film when 100 V was applied was measured with a high resistivity meter (“HIRESTA” manufactured by Mitsubishi Chemical Corporation), the surface resistivity ρs = 1 × 10 ⁷ (Ω / □), volume The resistivity ρv = 1 × 10 ⁶ (Ω · cm).

  The heat-resistant film thus produced was applied as the fixing film 16 of the fixing device of the image forming apparatus shown in FIGS. 1 and 2 to output an image. The base layer 1 of the fixing film 16 was grounded via the resistor or the diode 5 as shown in FIG. By grounding the base layer 1 through a resistor or a diode 5, charge relaxation can be easily realized. Table 1 shows the evaluation results when an image is output using the heating device of this example in a low-temperature and low-humidity environment.

  As comparative examples, the results are also shown for the base layer made of insulation and the elastic layer made of low resistance (Comparative Example 1), the base layer made of insulation, and the elastic layer made of insulation (Comparative Example 2). Moreover, the result of what used the metal film (electrical conductivity) for the base layer (comparative example 3) is also shown.

  As can be seen from Table 1, in the case of Comparative Example 2, image defects such as full surface offset and peeling offset occurred, and malfunctions due to noise occurred. In Comparative Example 1, image defects such as full surface offset and peeling offset did not occur, but operation failure due to noise occurred. In Comparative Example 3, there was no operation failure due to the entire surface offset or noise, but an image failure due to the peeling offset occurred.

  On the other hand, in Example 1, there was no occurrence of image defects such as full surface offset and peeling offset, and there was no malfunction due to noise, and a good fixed image was obtained.

Here, in Example 1 and Comparative Examples 1 to 3,
1) Charged charge on outer surface of fixing film due to peeling discharge of heated material (recording material) 2) Effect of two kinds of charged charges on image of surface of inner surface of base layer due to rubbing with ribs etc. on image etc. in FIG. This is shown schematically.

  In the case of Example 1 (FIG. 6-1), the influence of the charged charge accumulated on the outer surface of the film in 1) is mitigated by the generation of the opposite charge on the low resistance base layer, and the occurrence of image defects. Can be prevented. In addition, since the inner surface of the base layer also has a low surface resistance, the inner surface of the film is not charged, and therefore it is possible to prevent the occurrence of malfunctions such as malfunction due to noise or the like.

  On the other hand, in the case of Comparative Example 1 (FIG. 6-2), the influence of the charged charge accumulated on the outer surface of the film in 1) is alleviated by generating opposite charges on the elastic layer 2 having a low resistance. Although no defect occurred, the influence of the charged charge on the inner surface of the base layer due to rubbing against the ribs etc. in 2) could not prevent the occurrence of the charged charge, and could cause malfunction due to noise generation etc. It was seen.

  Further, in the case of Comparative Example 2 (FIG. 6-3), the image defect occurs due to the influence of the charged charge accumulated on the outer surface of 1), and the influence of the charged charge on the inner surface of the base layer of 2) causes noise. Malfunction due to the occurrence of.

  Further, in the case of Comparative Example 3 (FIGS. 6-4), the influence of the charged charges accumulated on the outer surface of the film in 1) is alleviated by the generation of opposite charges on the base layer 1 which is a metal film, and the entire surface offset The occurrence of image defects such as image defects can be prevented, and the inner surface of the film is not charged, and the occurrence of malfunctions such as malfunction due to noise can be prevented. However, since the electrostatic capacity becomes too large, the charged charge amount accumulated on the outer surface of the film in 1) is larger than in other examples, and peeling offset may occur depending on conditions.

  For example, by providing a path for grounding the inner surface of the film via a resistor or a diode and releasing a small amount of charged charges, it is possible to more effectively prevent the occurrence of problems due to noise due to leakage or the like. .

  In addition, when a conductive material is put into the elastic layer 2, since the hardness of the elastic body is increased, a large amount of the conductive material cannot be put in and it is difficult to reduce the resistance at a low cost. By reducing the resistance of the base layer 1, it is possible to easily achieve a desired resistance value while maintaining the hardness of the elastic layer 2 suitably.

  Furthermore, by using a flexible heat-resistant resin material as the material of the base layer 1, the flexibility (repetitive bending strength) and the followability (following ability to the heater surface, etc.) are improved as compared with the case of using a metal material. It is easy to obtain a good product at a low cost, and it is advantageous when the diameter is reduced.

(Example 2)
A tube-shaped polyimide film having a thickness of 50 μm serving as a base layer was formed in the same manner as in Example 1 except that an aluminum core having an outer diameter of 20 mm and a length of 400 mm was used.

  In this example, an ion conductive resistance control agent was used instead of the electronic conductive electrical resistance control material.

  That is, when using an electron conduction resistance control material that adds and disperses fillers such as carbon and metal oxides to reduce the resistance value, pay attention to dispersion unevenness and uneven surface resistance. Conditions must be taken into consideration, but when an ion conductive resistance control agent is dispersed in the precursor solution of the substrate, the resistance control agent is ionized and dispersed in the precursor solution to form a film. In addition, since the resistance control agent diffuses uniformly without being localized, a very uniform resistance value can be obtained, and the occurrence of defects due to charged charges can be prevented.

  In general, there is a problem in that the resistance value of an ion conductive resistance value control agent varies greatly depending on the temperature and humidity of the material surface. However, if it is used for a fixing film as in the present invention, the fixing temperature is increased during printing. Therefore, it can be used without being affected by temperature and humidity.

  In this example, image evaluation was performed in the same manner. As a result, there was no occurrence of image defects such as electrostatic offset and charged traces, and there was no malfunction due to noise, and a good fixed image was obtained.

(Other)
1) In the fixing device of the embodiment, the fixing film 16 is a cylindrical or endless belt-like film as a rotating body, and a driving method thereof includes a film guide for guiding the inner peripheral surface of the film and a pressure roller. The pressure-contacted film is driven and rotated by the pressure roller (pressure roller drive system), but the pressure roller is driven by driving an endless belt-like film stretched between the drive roller and tension roller. Ru can also be a device configured to rotate.

  2) The heating element 17 is not limited to a ceramic heater, and other various heaters can be used. For example, an electromagnetic induction heating member such as an iron plate may be used as the heating body 17.

1 is a schematic configuration diagram of an example of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a front model view of the fixing device according to the embodiment of the present invention with an intermediate portion omitted. It is a longitudinal cross-sectional model figure of the intermediate part omission of the apparatus. It is a cross-sectional model figure of the same apparatus. FIG. 3 is an enlarged cross-sectional model view of a fixing film. It is a schematic diagram which shows the influence of a charging charge.

Explanation of symbols

  16 .. Fixing film (flexible member), 17 .. Heater (heating body), 18 .. Film guide, 19 .. Pressing member, 20 .. Stay for pressing, 25. , N ... Fixing nip

Claims (2)

A cylindrical fixing film having a resin base layer, a release layer, and a rubber layer provided between the base layer and the release layer, a heater in contact with the base layer of the fixing film, and the fixing And a pressure roller that forms a fixing nip portion together with the heater via a film, and a fixing device that heats and fixes the toner image onto the recording material while nipping and conveying the recording material carrying the toner image at the fixing nip portion In
The base layer is a polyimide resin layer having a volume resistivity ρv of 1 × 10 ³ (Ω · cm) ≦ ρv ≦ 1 × 10 ⁹ (Ω · cm) due to the dispersion of a conductive substance, A fixing device, wherein the rubber layer and the release layer are insulating layers. A cylindrical fixing film having a resin base layer, a release layer, and a rubber layer provided between the base layer and the release layer, a heater in contact with the base layer of the fixing film, and the fixing And a pressure roller that forms a fixing nip portion together with the heater via a film, and a fixing device that heats and fixes the toner image onto the recording material while nipping and conveying the recording material carrying the toner image at the fixing nip portion In the fixing film used for
The base layer is a polyimide resin layer having a volume resistivity ρv of 1 × 10 ³ (Ω · cm) ≦ ρv ≦ 1 × 10 ⁹ (Ω · cm) due to the dispersion of a conductive substance, A fixing film, wherein the rubber layer and the release layer are insulating layers.