JP2005121975A - Fixing belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing belt that is fully durable, even when higher speed is demanded. <P>SOLUTION: The fixing belt includes a belt base material, in which a polymide resin layer and a metal layer are bonded together. The proportion of imide to polyimide, forming the polyimide resin layer, is set to 95% or higher; thereby, while the heat conductivity required for the fixing belt and a nip width required for fixing can be satisfied, a very long life can be ensured, even if higher speed is demanded in future . <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing belt for fixing unfixed toner on a recording medium onto the recording medium by pressure-heat fusion.

  Conventionally, a so-called heating roller system has been often used for a fixing device for an electrophotographic apparatus. However, recently, from the viewpoint of energy saving, a belt fixing method using a fixing belt has been used.

  As an example of such a belt-fixing type fixing device, a fixing device described in Japanese Patent Application Laid-Open No. 2003-57981 (Patent Document 1) will be described with reference to FIG.

FIG. 6 is a model cross-sectional view of the fixing unit U on a plane perpendicular to each roller. In this fixing unit U, heating for heating the fixing roller R ₁ and the fixing nip formed by the core bar R _C and the elastic body R _R attached to the outer periphery thereof to a temperature suitable for fixing an image or the like. fixing belt B _f is stretched between the rollers R _2.

Since the heating roller R ₂ is urged upward by a tension applying means such as a spring (not shown ₎ , an appropriate tension is applied to the fixing belt B _f . A pressure roller R ₃ is brought into contact with a portion of the fixing belt B _f located on the outer peripheral portion of the fixing roller R _{1 with} a pressure suitable for fixing an image or the like from below, and the fixing belt B _f and the pressure roller R ₃ The unfixed toner image supplied to the fixing nip portion is fixed.

  As a belt substrate for a fixing belt used in such a fixing device, a metal belt substrate made of a metal such as nickel or stainless steel, or a resin belt substrate made of a resin such as polyimide or polyamideimide is often used. Yes.

  However, considering the response to higher speeds that are expected to be required in the future, when using a metal belt base material, the flexibility is low and it is hard, so it will break easily, for durability If the thickness is increased, it is expected that the necessary nip width cannot be obtained and the function as a fixing belt cannot be exhibited.

  On the other hand, when a resin belt base material is used, higher durability is required to cope with higher speeds, and for that purpose, increasing the film thickness decreases thermal conductivity, resulting in a warm-up time. It is expected that the time will be delayed, the amount of heat supply necessary for fixing will be insufficient, or the energy consumption will increase.

  In order to compensate for both of these disadvantages, a composite belt base material in which a metal layer is provided on a resin belt such as polyimide has attracted attention. In such a composite belt substrate, the low thermal conductivity of the resin belt substrate can be solved by the metal layer, but the flexibility of the polyimide belt substrate may be impaired by the presence of the metal layer.

  In JP-A-2001-341231, in a fixing film based on a laminated film of a driven metal layer and a polyimide resin layer, in order to obtain a fixing film having excellent use durability under heating and pressure, It has been proposed to form a polyimide resin layer from a polyimide resin having an imidization rate of 70 to 93%.

However, when this technique is applied to a fixing belt generally used under a tensile load, it has been found that sufficient durability cannot be obtained when high speed operation is performed.
JP 2003-57981 A JP 2001-341231 A

  An object of the present invention is to provide a fixing belt which improves the above-mentioned conventional problems, that is, has good durability even when heat conduction is good and high speed is required. To do.

  In order to solve the above problems, a fixing belt according to the present invention is a fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, and the polyimide resin layer is formed. The polyimide to be imidized has a structure of 95% or more.

  In order to solve the above-described problem, the fixing belt of the present invention is a fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, and the thickness of the polyimide resin layer as described in claim 2. When Dp (μm) is in the range of 10 (μm) ≦ Dp ≦ 30 (μm), the thickness Dn (μm) of the metal layer satisfies 25 (μm) ≦ Dn ≦ Dp / 2 + 25 (μm). When the thickness Dp (μm) of the polyimide resin layer is in the range of 30 (μm) ≦ Dp ≦ 40 (μm), the thickness Dn (μm) of the metal layer is 25 (μm) ≦ Dn ≦ 70−. It has the structure which is the range which satisfies Dp (micrometer).

  In order to solve the above-described problem, the fixing belt of the present invention is a fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, and forming the polyimide resin layer. When the polyimide imidization ratio is 95% or more and the thickness Dp (μm) of the polyimide resin layer is in the range of 10 (μm) ≦ Dp ≦ 30 (μm), the thickness Dn ( μm) is in a range satisfying 25 (μm) ≦ Dn ≦ Dp / 2 + 25 (μm), and the thickness Dp (μm) of the polyimide resin layer is in a range of 30 (μm) ≦ Dp ≦ 40 (μm). Sometimes, the metal layer thickness Dn (μm) is in a range satisfying 25 (μm) ≦ Dn ≦ 70−Dp (μm).

  At this time, the thickness of the metal layer is 25 μm or more and 35 μm or less, the thickness of the polyimide resin layer is 20 μm or more and 30 μm or less, and the sum of the thickness of the metal layer and the thickness of the polyimide resin layer is 45 μm or more and 65 μm or less. In particular, excellent durability can be obtained.

  Since the fixing belt of the present invention can reduce the thickness of each layer while maintaining durability even at a high speed required in the future, a sufficient nip width can be secured, and at this time, a resin made of polyimide resin It has much higher thermal conductivity than a belt.

  The fixing belt of the present invention is a fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, and has a configuration in which the imidization ratio of polyimide forming the polyimide resin layer is 95% or more. .

  Here, as the metal, a metal conventionally used as a metal for a fixing belt can be used as it is. In general, nickel or a nickel alloy is used. For example, a nickel-manganese alloy proposed in Japanese Patent Laid-Open No. 7-187100 can also be used.

  Here, the shape of the fixing belt is preferably an endless sheet-like shape. Here, the endless metal layer is, for example, a known electrolytic bath capable of electrodepositing a target metal such as nickel. Can be obtained by an electroforming method using a mother die made of stainless steel or the like as a cathode.

  After separating the side end portion of the electroformed body obtained by electroforming, it is possible to obtain a metal layer having a desired shape and dimension through washing, drying, machining, etc. The hardness can be adjusted by applying a heat treatment as necessary.

  The thickness of the metal layer should be in the range of 25 to 50 μm from the viewpoint of the balance of thermal properties such as workability, thermal conductivity and heat capacity, and mechanical properties such as flexibility, dimensional stability and strength. Is preferred.

  A polyimide resin layer is formed on the inner surface of the metal layer thus obtained to obtain a belt substrate for a fixing belt. Specifically, after a polyimide precursor solution or gel (polyimide precursor varnish) is applied to the metal layer, the polyimide resin layer is formed by an imidation reaction by heat treatment so as to have a predetermined imidization rate described later. It is formed. Here, various polyimide precursor varnishes are commercially available from Toray Industries, Ube Industries, etc.

  Further, as a manufacturing method other than the above, for example, a polyimide resin layer is formed into a cylindrical shape using a cylindrical mold, and then chemical plating or chemical plating and electroplating are combined on the outer surface thereof. And a method of forming a metal layer by a plating method such as a belt base material.

  The thickness of the polyimide resin layer is in the range of 5 to 50 μm from the viewpoint of balance of thermal properties such as processability, thermal conductivity, and heat capacity, and mechanical properties such as flexibility, dimensional stability, and strength. It is preferable.

  Here, the thickness Dp (μm) of the polyimide resin layer is in the range of 10 (μm) ≦ Dp ≦ 40 (μm), and the thickness Dp (μm) of the polyimide resin layer is 10 (μm) ≦ Dp. When the range is ≦ 30 (μm), the thickness Dn (μm) of the metal layer is a range satisfying 25 (μm) ≦ Dn ≦ Dp / 2 + 25 (μm), and the thickness Dp (μm) of the polyimide resin layer ) Is in the range of 30 (μm) ≦ Dp ≦ 40 (μm), the thickness Dn (μm) of the metal layer satisfies the range of 25 (μm) ≦ Dn ≦ 70−Dp (μm) (hatched in FIG. 1) It is preferable because high durability can be obtained within the range indicated by hatching (including the boundary).

  Furthermore, the thickness Dn (μm) of the metal layer is 25 μm or more and 35 μm or less, the thickness Dp (μm) of the polyimide resin layer is 20 μm or more and 30 μm or less, and the thickness Dn of the metal layer and the thickness Dp of the polyimide resin layer Is in the range of 45 μm or more and 65 μm or less (a range indicated by cross hatching in FIG. 1 (including on the boundary line)), since particularly excellent durability is obtained.

  In this invention, it is preferable that the imidation ratio of the polyimide which forms a polyimide resin layer is 95% or more. If the imidation ratio is less than 95%, sufficient durability may not be obtained.

  Here, the imidation ratio of the present invention will be described. Polyimide is formed by a dehydration ring-closing reaction between an aromatic dianhydride and an aromatic diamine, but the imidization rate of the polyimide in the present invention is completely equal to the amount of the imide ring actually produced. It is a ratio with the amount of the imide ring.

First, since the amount of the benzene ring in the resin is unchanged before and after the reaction, the absorbance of the peak near 1510 cm ⁻¹ based on the skeleton vibration of the benzene ring in the infrared absorption spectrum by FTIR on the resin surface is used as a reference. The intensity ratio is determined by the following formula (i) from the absorbance of the peak in the vicinity of 1721 cm ⁻¹ based on the C═O vibration of imidic acid with respect to the ring peak.

  The ratio of the strength ratio obtained as described above when the same resin was heat-treated until the progress of imidization was completed was 100%, which was defined as the imidization ratio in the present invention.

  The completion of imidization in the polyimide formation was determined as follows. While maintaining the polyimide precursor varnish so that the final shape is a film shape having a thickness of 20 μm, the rate of temperature increase is 5 ° C./min, and the final heat treatment temperature is 150 ° C. to 350 ° C. every 10 ° C. As the temperature, the strength ratios defined above were examined when the heat treatment was held for 60 minutes at the final heat treatment temperature, the strength ratio of the resin that was heat-treated at a certain temperature, and the treatment temperature When the difference from the strength ratio of the resin in the heat treatment lower by 10 ° C. became 1% or less, it was determined that the imidization progress was completed.

Here, the heat treatment temperature and strength ratio of a polyimide precursor varnish (trade name: Trenys # 3000, hereinafter referred to as “varnish A” manufactured by Toray Industries, Inc. The structure of the polyimide thus obtained is shown as structural formula I below) The relationship between the absorbance at 1710 cm ⁻¹ / the absorbance at 1510 cm ⁻¹ is shown in FIG. Figure 3 the relationship between the heat treatment temperature and the intensity ratio at shown as structural formula II) shown below (absorbance at the absorbance / 1550 cm ^-1 in 1710 cm ^-1), respectively, further, the varnish a and B Table 1 shows the imidization ratio when the heat treatment is performed at 200, 220, 250, 300, and 350 ° C. In addition, these were calculated | required from the result of the measurement by an ATR reflection method using Shimadzu Corporation FT-IR4200.

  2 and 3, the horizontal axis represents the heat treatment temperature, and the vertical axis represents the intensity ratio when the intensity ratio when it is determined that the progress of imidization determined by the above method has been completed is 100%. 2 and 3 and Table 1 show only the results up to 350 ° C., but the strength ratio when varnish A or varnish B was treated at a temperature of 400 ° C. was also 100%.

  The fixing belt of the present invention has heat resistance such as silicone rubber, fluororubber, fluororesin and the like on the surface of the belt substrate formed by laminating the polyimide resin layer and the metal layer as described above, similarly to a normal fixing belt. It is formed by providing a release layer made of a non-adhesive material by a conventional method.

  Here, FIG. 4 schematically shows an example of a cross section of the fixing belt according to the present invention. In the figure, the reference numeral 1 indicates a metal layer, and a polyimide resin layer 2 is laminated on one surface (inner surface side) of the metal layer 1. The two metal layers 1 and the polyimide resin layer 1 are used to fix the fixing belt. A belt base material is formed, and PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene) is provided on the other surface (outer surface side) of the metal layer 1 of the belt base material via a silicone rubber layer 3. Layer 4 is provided.

Examples of the fixing belt of the present invention will be specifically described below.
[Preparation of belt base material (examination with varnish A)]
By electroforming, two types of nickel endless belts (metal layers) each having a width of 5 mm, a diameter of 34 mm, and only thicknesses of 30 μm and 50 μm were produced.

  Varnish A (trade name: Torenice # 3000, manufactured by Toray Industries, Inc.), which is a polyimide precursor varnish, was applied to the inside of these endless belts, and heat treatment was performed at a final heating temperature of 220 ° C. or 350 ° C. At this time, the amount of each varnish applied was adjusted, and a polyimide resin layer having a thickness different from 14 μm or 50 μm was prepared.

[Evaluation of belt substrate]
The belt base material produced above was evaluated as follows. That is, as shown in FIG. 5, a belt base material B to be evaluated is stretched between a roller Ra having a rotating shaft having a diameter of 10 mm fixed and a roller Rb having no rotating shaft fixed, and a weight of 3 kg is applied. The roller Ra was rotated at 3600 rpm while applying a load of 29.4 N to the roller Rb using the weight W and the pulley P to apply tension to the belt base material B. At this time, the durability of the belt base material B up to 400 minutes after the start of rotation was evaluated, and the presence or absence of breakage or, if broken, the durability time until breakage was investigated. The results are shown in Table 2.

  From Table 2, it can be seen that the base material in which the imidization ratio of the polyimide resin layer is 100% has a longer lifetime than the base material in which the imidization ratio is 82% under any condition. In particular, it can be seen that a belt substrate having an imidization rate of 100%, a metal layer thickness of 30 μm, and a polyimide resin layer thickness of 50 μm has a very long life.

[Examination of thickness of nickel layer and polyimide resin layer (examination in varnish A)]
Several nickel endless belts made of nickel were produced in the same manner as above, except that the electroforming conditions were changed and only the thickness was changed to 25, 30, 35, or 40 μm. At this time, an endless belt having a thickness of less than 25 μm was difficult to be processed thereafter, so that no further examination was performed.

  Varnish A was applied to the inside of each of these metal endless belts, and the final heating temperature was set to 350 ° C. to obtain a belt base material. At this time, the coating amount was changed to obtain a polyimide resin layer having a thickness of 10, 20, 30 or 40 μm.

  Regarding the life of these belt base materials, together with the results of only the nickel endless belt without the polyimide resin layer, the durability was examined in the same manner as described above.

  When the durability time is 1000 minutes or more, “◯” is assumed to be an extremely long life, and when it is 500 minutes or more and 1000 minutes or less, “Δ” is 500 Less than a minute was evaluated as “x” because the durability was insufficient. The evaluation results are shown in Table 3 together with the actual endurance time value (unit: minutes).

  From Table 3, it can be seen that the belt base material according to the present invention has superior durability compared to the metal belt base material according to the prior art.

  Here, when the thickness Dp (μm) of the polyimide resin layer is in the range of 10 (μm) ≦ Dp ≦ 30 (μm), the thickness Dn (μm) of the metal layer is 25 (μm) ≦ Dn ≦ Dp / 2 + 25. When the thickness Dp (μm) of the polyimide resin layer is in the range of 30 (μm) ≦ Dp ≦ 40 (μm), the thickness Dn (μm) of the metal layer is 25 ( (μm) ≦ Dn ≦ 70−Dp (μm), it can be seen that sufficiently high durability can be obtained in the range (the range shown by hatching in FIG. 1 (including the boundary line)).

  Furthermore, the thickness Dn (μm) of the metal layer is 25 μm or more and 35 μm or less, the thickness Dp (μm) of the polyimide resin layer is 20 μm or more and 30 μm or less, and the thickness Dn of the metal layer and the thickness Dp of the polyimide resin layer It can be seen that the lifetime is particularly long when it is in the range of 45 μm or more and 65 μm or less (the range indicated by cross hatching in FIG. 1 (including the boundary line)).

[Examination by varnish B]
As above, however, varnish B was used in place of varnish A for examination. A nickel electroformed belt having a thickness of 25 μm, 30 μm, 35 μm, or 40 μm is used, and varnish B is applied to the inner periphery thereof so that the final polyimide resin layer thickness becomes 30 μm, and the polyimide resin layer is subjected to heat treatment. A belt base material obtained by laminating a nickel layer and a polyimide resin layer with an imidization ratio of 100% was obtained. These belt base materials were subjected to the same durability test as described above. The results are shown in Table 4.

  Even when varnish B is used, when the resin layer thickness is 30 μm, sufficient durability is obtained in the range of the nickel layer thickness of 25 μm to 40 μm, and the nickel layer thickness is 25 μm. It can be seen that the lifetime is particularly long in the range of 35 μm or less.

  The fixing belt of the present invention is capable of satisfying the thermal conductivity required for the fixing belt and the nip width necessary for fixing, but having an extremely long life even under high speed conditions required in the future. It is a belt.

It is the graph which showed the range in which especially high effect is acquired in the thickness of a nickel layer, and the thickness of a polyimide resin layer. It is a figure which shows the relationship between the heat processing of varnish A, and intensity | strength ratio. It is a figure which shows the relationship between the heat processing of varnish B, and intensity ratio. FIG. 3 is a model diagram illustrating a cross section of an example of a fixing belt according to the present invention. It is a model figure which shows the evaluation apparatus used in order to evaluate a belt base material in the Example. 1 is a diagram illustrating an example of a fixing belt type fixing device described in JP-A-2003-57981.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal layer 2 Polyimide resin layer 3 Silicone rubber layer 4 PFA layer Ra, Rb Roller B Evaluated belt base material W Weight P Pulley

Claims (4)

  A fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, wherein the imidation ratio of polyimide forming the polyimide resin layer is 95% or more. A fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated,
When the thickness Dp (μm) of the polyimide resin layer is in the range of 10 (μm) ≦ Dp ≦ 30 (μm), the thickness Dn (μm) of the metal layer is 25 (μm) ≦ Dn ≦ Dp / 2 + 25 (μm )
When the thickness Dp (μm) of the polyimide resin layer is in the range of 30 (μm) ≦ Dp ≦ 40 (μm), the thickness Dn (μm) of the metal layer is 25 (μm). ≦ Dn ≦ 70−Dp (μm)
A fixing belt characterized by satisfying the requirements. A fixing belt having a belt base material in which a polyimide resin layer and a metal layer are laminated, and the imidation ratio of polyimide forming the polyimide resin layer is 95% or more, and the thickness of the polyimide resin layer When Dp (μm) is in the range of 10 (μm) ≦ Dp ≦ 30 (μm), the thickness Dn (μm) of the metal layer is 25 (μm) ≦ Dn ≦ Dp / 2 + 25 (μm)
When the thickness Dp (μm) of the polyimide resin layer is in the range of 30 (μm) ≦ Dp ≦ 40 (μm), the thickness Dn (μm) of the metal layer is 25 (μm). ≦ Dn ≦ 70−Dp (μm)
A fixing belt characterized by satisfying the requirements.   The metal layer has a thickness of 25 μm to 35 μm, the polyimide resin layer has a thickness of 20 μm to 30 μm, and the sum of the thickness of the metal layer and the polyimide resin layer is 45 μm to 65 μm. The fixing belt according to claim 3.

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