JP2005031485A - Fixing belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing belt of high durability, and to provide an image heating device of high durability and high reliability, regarding the image heating device capable of heating with low energy by using a heating body of small heat capacity. <P>SOLUTION: The fixing belt is provided with at least a mold-released layer and a metal layer constituted of nickel-electrocast, wherein the metal layer constituted of the nickel-electrocast is formed by layering two or more kinds of layers having different crystal structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing belt used in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus.

  In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format paper, etc.) in an image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process As a fixing device that heats and fixes a non-fixed image (toner image) of target image information formed and supported by a transfer method or a direct method as a permanently fixed image on a recording material surface, a heat roller type device is widely used. It was. This generally uses a heat source such as a halogen heater in the roller.

  On the other hand, in recent years, as a heating method, a method of heating a resin belt or a metal belt having a small heat capacity using a ceramic heater as a heat source has been widely proposed and implemented. That is, in the heating method, generally, a nip portion is formed by sandwiching a heat-resistant belt (fixing belt) between a ceramic heater as a heating body and a pressure roller as a pressure member, By introducing a recording material that forms and carries an unfixed toner image to be fixed between the pressure roller and nipping and conveying it together with the belt, the heat of the ceramic heater is recorded via the belt at the nip. The unfixed toner image is fixed to the surface of the recording material by heat and pressure by the heat and the pressure applied to the nip portion.

  This belt heating type fixing device can be configured as an on-demand type device using a low heat capacity member as a belt. That is, it is only necessary to energize a ceramic heater as a heat source to generate heat to a predetermined fixing temperature only when image forming of the image forming apparatus is executed, and wait time from power-on of the image forming apparatus to an image forming executable state Are short (quick start), and power consumption during standby is significantly small (power saving). FIG. 4 shows a configuration example of a belt heating type image heating and fixing apparatus. In this heating method, generally, a nip portion is formed by sandwiching a heat resistant belt (fixing belt 10) between a ceramic heater 12 as a heating body and a pressure roller 30 as a pressure member, and fixing the nip portion. The recording material P on which an unfixed toner image t to be image-fixed is formed and supported is introduced between the belt and the pressure roller, and is nipped and conveyed together with the belt, whereby the heat of the ceramic heater 12 is The recording material P is applied to the recording material P through the belt 10, and the unfixed toner image is fixed to the recording material P by heat and pressure by the heat and the pressure applied to the nip portion.

  As a belt used in such a belt heating system, a heat-resistant resin or the like is used, and a polyimide resin excellent in heat resistance and strength is used. However, when the machine is further increased in speed and durability, the resin film sometimes has insufficient strength. For this reason, it has been proposed to use a belt having a base layer made of a metal having excellent strength, such as SUS, nickel, copper, or aluminum.

  As a driving method of the fixing belt in the belt heating type fixing device, a film pressure-contacted by a film guide for guiding the inner surface of the belt and a pressure roller is driven by a rotational driving of the pressure roller (pressure roller driving method). In contrast, there is a method in which the pressure roller is driven to rotate by driving an endless belt stretched between a drive roller and a tension roller.

  As a fixing belt using a metal belt, Patent Document 2 uses a nickel fixing belt having a heater surface contact portion surface roughness of less than 0.5 μm and a thickness of about 40 μm. A nickel fixing belt having a thickness of 10 to 35 μm having a coating layer having releasability on the outer peripheral surface and a resin layer on the inner peripheral surface is exemplified.

  Patent Document 1 also discloses an induction heating method in which a metal belt is used and self-heats by an eddy current due to electromagnetic induction. That is, a heating device has been proposed in which eddy current is generated in the belt itself or a conductive member close to the belt by magnetic flux, and heat is generated by Joule heat. In this electromagnetic induction heating method, the heat generation area can be made closer to the object to be heated, so that the efficiency of energy consumption can be increased. A configuration example when the fixing belt having the configuration shown in FIG. 3 is used will be described. The magnetic cores 17a, 17b and 17c are high permeability members, and the exciting coil 18 generates alternating magnetic flux by alternating current (high frequency current) supplied from an exciting circuit (not shown). When this alternating magnetic flux acts on the metal layer 1, an eddy current is generated and the metal layer 1 generates heat. The heat heats the fixing belt 10 through the elastic layer 2 and the release layer 3, and heats the recording material P that is passed through the fixing nip N to heat and fix the toner image.

  FIG. 6 shows a model diagram of the magnetic field generating means of the image heating apparatus of FIG. The magnetic field generating means shown in FIG. 5 includes a magnetic core 17 a, power feeding units 18 a and 18 b connected to the excitation circuit 27, and the excitation coil 18. The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27 through the power feeding units 18a and 18b.

As described above, a seamless belt base material is generally used for a fixing belt member used in an image forming apparatus such as an electrophotographic image / electrostatic recording apparatus, and a seamless belt base material made of a nickel material is generally a sulfamine. Manufactured by electroforming using nickel acid or watt bath.
In this electroforming method, a mother die having a required shape is used, and after electroforming film formation is performed on the outer periphery of the mother die, the seamless belt base material is manufactured by drawing out from the mother die.

Further, as an example of a metal belt having a structure in which two or more layers are laminated, Patent Document 4 shows an example in which a matte electrodeposition layer is laminated on an inner layer formed from a bath to which a brightener is added. However, the purpose of this is to form a grain on the electroformed surface and to make the stress of the inner layer a compressive stress. Patent Document 5 shows an example in which the inner surface layer portion is nickel and the outer surface layer portion is an iron-nickel alloy. However, in such an alloy containing 55 to 65% and a large amount of iron, the internal stress of the film itself is large, and it may be difficult to form a film without a stress reducing agent. Further, when a stress reducing agent is added, the durability at a high temperature is insufficient due to the influence of a sulfur compound in the stress reducing agent, and there are cases where application to a fixing belt is difficult. In addition, this electroforming is aimed at adjusting the linear expansion coefficient and suppressing the release from the mother mold and the generation of wrinkles.
JP-A-7-114276 Japanese Patent Laid-Open No. 7-13448 JP-A-6-222695 Japanese Patent Laid-Open No. 5-17892 JP-A-6-75489

  Conventionally, in general electroformed nickel, in order to obtain a fine crystal structure and improve the strength and toughness of the material, a primary brightener containing sulfur has been added. In this case, the crystal structure is (111) plane preferred growth. The addition of the primary brightener ensures surface gloss and hardness, and has been used for decoration or sliding surfaces. However, if such a primary brightener is used in a large amount during electroforming, a large amount of sulfur, which is a decomposition product of the primary brightener, is taken into the plating layer, and if the electroformed product is heated to a high temperature, for example, 200 ° C. or higher, May precipitate at the nickel grain boundary, and a thin brittle sulfur layer may be formed at the nickel grain boundary. When such nickel grain boundaries are formed, the nickel grain boundaries become weaker under conditions where stress is repeatedly applied at high temperatures such as a fixing belt, cracks occur at the nickel grain boundaries, and the fixing belt breaks early. There was a case.

  Therefore, if the amount of the primary brightener added during electroforming is reduced, such a problem does not occur and high temperature durability can be imparted to the fixing belt. In this case, it has been found that the crystal structure of the electroformed nickel belt is (200) plane preferred growth. However, this belt has a low content of sulfur in the film, a relatively large crystal grain size, a hardness as low as Vickers hardness of 400 (load: 100 g) or less, and the strength of the electroformed nickel itself of the belt material is weak There was a need to be careful when handling it. In addition, due to the weak strength, cracks and fractures occur particularly at both ends, and it may be difficult to maintain long-term heat resistance and tensile fracture strength.

  The present invention was made to solve such problems of the prior art, and by laminating a nickel electroformed layer having high tensile strength and a high hardness nickel electroformed layer excellent in high temperature durability, An object is to achieve both the mechanical strength and high-temperature durability of a seamless belt made of nickel.

In order to achieve the above object, the present invention
(1) A fixing belt having at least a release layer and a metal layer made of nickel electroforming provided on the release layer,
A fixing belt, wherein the metal layer is laminated with two or more layers having different crystal structures.
(2) The fixing belt according to (1), wherein at least one of the two or more layers has a Vickers hardness of less than 400, and at least one of the other layers has a Vickers hardness of 400 or more.
(3) Of the two or more layers, at least one layer has a Vickers hardness of 250 or more and less than 400, and at least another layer has a Vickers hardness of 400 or more and 600 or less,
Furthermore, the total thickness of the laminated film having a Vickers hardness of 400 or more and 600 or less is 1/8 or more and 3/4 or less of the total thickness of the metal layer, The fixing according to (1) or (2), belt.
(4) The fixing belt according to any one of (1) to (3), wherein at least an elastic layer is provided between the release layer and the metal layer.
(5) The fixing belt according to (4), wherein the elastic layer includes at least one selected from the group consisting of silicone rubber, fluororubber, and fluorosilicone rubber.

  In addition, all the Vickers hardness described in this specification represents a measured value at a load of 100 g.

  In the present invention, a high-quality fixing belt having good durability and fixing properties can be provided by laminating at least two types of layers having different crystal structures on the electroformed belt base material.

  The fixing belt of the present invention is a fixing belt having at least a release layer and a metal layer made of nickel electroforming, wherein the metal layer is laminated with two or more layers having different crystal structures. . With such a layer structure, a fixing belt having high mechanical strength and high temperature durability can be obtained. “Layers having different crystal structures” means that the crystal orientation ratios I (200) / I (111) of the target layers show different values.

  The metal layer of the fixing belt of the present invention may have a multilayer laminated structure including two or more layers having different crystal structures, and may include two or more layers having the same crystal structure. For example, when two layers having different crystal structures (a first layer and a second layer) are used, at least one of the first layer and the second layer is used in two or more, and the first layer and The metal layer can be configured such that the second layers are stacked adjacent to each other. Alternatively, when three layers having different crystal structures (first to third layers) are used, at least one of the first to third layers is used in two or more layers, and layers having different crystal structures are used. The metal layer can be configured so as to be laminated adjacent to each other.

  Furthermore, it is preferable that the two or more layers having different crystal structures include two or more layers having different Vickers hardness, including a combination of a layer having a Vickers hardness of less than 400 and a layer having a Vickers hardness of 400 or more. More preferably. When a plurality of layers having a Vickers hardness of less than 400 are used, the plurality of layers may have the same or similar Vickers hardness, or two or more layers having different Vickers hardness may be included. The same applies when a plurality of layers having a Vickers hardness of 400 or more are used.

  By laminating layers having different Vickers hardnesses, a fixing belt in which the mechanical strength and high-temperature durability of the metal layer are balanced can be obtained. FIG. 5 shows a cross-sectional model view of the main part of the fixing device. Here, nickel electroforming refers to nickel formed by an electroforming process or an alloy thereof. The (200) plane preferential growth of the present invention is to preferentially grow crystals on the (200) plane parallel to the matrix surface. The crystal orientation ratio I (200) / I (111) is defined by the X-ray diffraction intensity ratio I (200) / I (111) of the (200) and (111) crystal planes. The d value of the (200) plane is 1.7619 mm and the d value of the (111) plane is 2.0345 mm.

  Conventionally, in general electroformed nickel, the crystal structure is (111) plane preferred growth. As a result, the glossiness and hardness of the surface are secured, and it has been used for decoration or sliding surfaces. In contrast, recent research has shown that electroformed nickel belts with high temperature durability are preferentially grown in the crystal structure (200) plane.

  This is based on the following principle. In general, in order to obtain a small crystal structure, a primary brightener containing sulfur as a stress reducing agent is usually added during electroforming. When the primary brightener is added, since the sulfur / nickel compound produced on the cathode surface (matrix) is a fine particle, the crystal grain size is about 1/100 or less, and gloss can be imparted to the electroformed product. The strength of the material is improved, and both material strength and toughness can be achieved. In this case, the crystal structure is (111) plane preferred growth. However, when the primary brightener is used in this way, a large amount of sulfur, which is a decomposition product of the primary brightener, is taken into the plating layer, and when the electroformed product is heated to a high temperature, for example, 200 ° C. or higher, sulfur precipitates at the nickel grain boundaries. However, a thin brittle sulfur layer may be formed at the nickel grain boundary. Under conditions where stress is repeatedly applied in a high temperature state such as a fixing belt, the nickel grain boundary becomes weak, cracks occur at the nickel grain boundary, and the fixing belt may break early. In addition, in this case, the crystal structure of the electroformed nickel tends to be microcrystals, and there may be a problem regarding the flexibility of the belt.

  For this reason, as a result of investigation by the present inventors, it was found that when the amount of primary brightener added during electroforming is reduced, the metal layer exhibits high-temperature durability and the crystal structure exhibits (200) plane priority growth. Thus, the reason why the high temperature durability of electrocast nickel with (200) plane preferred growth is superior to the high temperature durability of electroformed nickel with (111) plane preferred growth is that Sulfur and organic substances resulting from the brightener in the electrolytic bath do not eutect with the crystal growth of nickel. For this reason, even when the fixing belt is used at a high temperature for a long time, cracks in the nickel grain boundary do not occur and the high temperature durability is improved.

  However, since the fixing belt of the (200) plane priority growth has a small amount of primary brightener added, the sulfur content in the film is low and the crystal grain size is relatively large. For this reason, the hardness is as low as Vickers hardness of 400 (load: 100 g) or less, and the strength of the electroformed nickel itself of the belt material may be weak, and care must be taken in handling. In addition, due to the low strength, cracks and fractures may occur particularly at both ends, and it may be difficult to maintain long-term heat resistance.

  Hereinafter, examples in which the material strength differs depending on the surface on which crystals preferentially grow are shown. Using an example of nickel sulfamate as the electroforming liquid, an example shows the tensile fracture strength as an indicator of strength, but the crystal orientation ratio I (200) / I (111) of (111) plane preferential growth is 1. In this experiment, the electrocast nickel has a hardness of Hv500 (load: 100 g) or higher and a tensile fracture strength of 1500 MPa or higher, whereas the crystal orientation ratio I (200) / The electroformed nickel having I (111) of 40 has a hardness of Hv350 (load: 100 g) at most and a tensile fracture strength of about 1050 MPa.

  Furthermore, in our research, there is a correlation between tensile strength and hardness, and it is known that the tensile fracture strength is approximately three times the hardness although the unit is different. That is, a belt having a Vickers hardness Hv350 (load: 100 g) exhibits a value of about a tensile fracture strength of about 1050 MPa as described above. Further, the crystal orientation ratio I (200) / I (111) and the hardness are in a contradictory relationship as shown in FIG. 2, and it is difficult to secure both the tensile fracture strength and the high temperature durability with the conventional belt forming method. there were. Here, the Vickers hardness was measured by preparing a test sample (shape flat plate, size 10 mm, film thickness 30-50 μm) by the method of JIS Z2244.

  By laminating a nickel electroformed layer with high hardness and excellent tensile strength and a nickel electroformed layer with excellent high temperature durability as in the present invention, it has sufficient high temperature durability and high tensile fracture strength for easy handling. An excellent nickel electroformed belt can be supplied.

  The tensile fracture strength was determined by cutting out an array-shaped sample from nickel electroforming in accordance with the test method of JIS (JIS number Z2241) and using a tensile tester. Regarding the Vickers hardness, the hardness was determined by a micro hardness tester manufactured by AKASHI.

  Details of the present invention will be described below.

(1) Fixing belt 10
The fixing belt of the present invention will be described.
FIG. 3 is an example of a layer configuration model diagram of the fixing belt 10. The fixing belt 10 includes a metal layer 1 made of a nickel electroformed endless belt as a base layer, an elastic layer 2 laminated on the outer surface, a release layer 3 laminated on the outer surface, and an inner surface of the metal layer 1. It has a composite structure with the sliding layer 4. In the fixing belt 10, the sliding layer 4 is on the inner surface side (belt guide surface side), and the release layer 3 is on the outer surface side (pressure roller surface side). A primer layer (not shown) is provided for adhesion between the metal layer 1 and the elastic layer 2, between the elastic layer 2 and the release layer 3, or between the metal layer 1 and the sliding layer 4. May be. The primer layer may be a known one such as silicone, epoxy, or polyamideimide, and the thickness is usually about 1 to 10 μm. Alternatively, the release layer 3 may be formed directly on the metal layer 1 without forming the elastic layer 2 on the metal layer 1. In particular, in the case of heat-fixing a monochrome image in which the toner amount on the recording material is small and the unevenness of the toner layer is relatively small, such an elastic layer can be omitted.

  When this fixing belt is used for the electromagnetic induction heating method, the metal layer 1 formed of a nickel electroformed endless belt functions as a heat generating layer exhibiting electromagnetic induction heat generation. As will be described later, an eddy current is generated in the metal layer 1 due to the alternating magnetic flux acting on the metal layer 1, and the metal layer 1 generates heat. The heat heats the fixing belt 10 through the elastic layer 2 and the release layer 3, and heats the recording material passed through the fixing nip portion N to heat and fix the toner image. Further, the fixing belt 10 of the present invention may be used in a belt heating method using a ceramic heater.

a. Metal layer 1
The metal layer 1 is made of nickel or a nickel alloy, which is formed by immersing a cylindrical mold such as stainless steel in an electroforming bath and growing it on the front surface or the back surface of the mold by an electroforming process. As the nickel alloy, nickel-iron, nickel-cobalt, nickel-manganese, nickel-molybdenum, nickel-tungsten, or the like is preferably used.

In the present invention, the metal layer has a multilayer structure including two or more layers having different crystal structures, and is manufactured by an electroforming process using, for example, a matrix made of stainless steel as a cathode. As the electrolytic bath in this case, for example, a known nickel electrolytic bath such as a sulfamic acid type can be used, and additives such as a pH adjuster, a pit inhibitor, and a brightener may be appropriately added. For example, the nickel electrolyte which consists of 300-450 g / l of nickel sulfamate, 0-30 g / l of nickel chloride, and 30-45 g / l of boric acid is mentioned. Then, by controlling the concentration of the brightener to be added, the electrolytic bath temperature, the cathode current density, and the like, a nickel electroformed belt made of nickel or a nickel alloy having desired characteristics can be obtained. Although it depends on the electrolytic bath used in the electroforming process, it is usually preferable to carry out at an electrolytic bath temperature of about 45 to 60 ° C. and a cathode current density of about 1 to 20 A / dm ² . The brightener to be added is an additive called a secondary brightener containing saccharin, sodium benzenesulfonate, sodium naphthalenesulfonate, etc., a stress reducing agent / primary brightener, 2-butyne-1,4-diol, coumarin, diethyltriamine, etc. Etc. are added.

  Next, a lamination method will be described. Regarding the lamination of the layers, it is also possible to obtain a belt having a desired thickness by sequentially performing electroforming in electroforming tanks having different liquid compositions. However, if that method is used, the number of electroforming tanks is required only for the type of layer to be laminated, the laminating operation becomes complicated, and an interface is created between the laminated layers. There are problems such as the possibility of peeling.

  Here, the electroformed nickel of the present invention controls the crystal structure (crystal orientation) and hardness according to working parameters such as liquid temperature, stirring method and its strength (flow rate), current density, current shape (direct current / pulse shape). .

  Generally, electroformed nickel is a primary brightener (stress reducing agent) containing saccharin, sodium benzenesulfonate, sodium naphthalenesulfonate, etc., 2-butyne-1,4-diol, coumarin, formalin in the electrolyte. By adding a secondary brightener containing, etc., desired electroformed nickel can be obtained. Since the primary and secondary brighteners have a synergistic effect, the effect alone cannot be clarified, but the basic crystal structure is determined by the content and content ratio contained in the film. The final crystal structure (crystal orientation) / hardness can be obtained by combining the above work parameters.

  For example, when the liquid temperature of the electroforming bath is increased, the mobility of the components of the electroforming bath increases and the thickness of the diffusion layer decreases. Therefore, many components can reach the cathode. By simply raising the temperature of the electroforming bath by 5 ° C., the amount of brightener incorporated into the electroformed nickel film is greatly increased, the crystal structure is refined and the hardness is increased, and the crystal orientation ratio I (200) / I (111) becomes smaller.

  Similarly, by increasing the agitation strength, the thickness of the diffusion layer is reduced, the amount of brightener incorporated into the electroformed nickel film is increased, and the same effect as that obtained by increasing the liquid temperature can be obtained.

  It can also be controlled by adjusting the current density. The amount of electroformed nickel deposited within a unit time is directly proportional to the cathode efficiency and current density. If the cathode current density is doubled at a constant stirring intensity and temperature, the film thickness of nickel electroforming is doubled. However, since the mobility of the brightener does not increase, the amount of brightener incorporated into the unit thickness film decreases. As a result, the crystal grain size increases, the hardness decreases, and the crystal orientation ratio I (200) / I (111) increases.

  The crystal structure (crystal orientation) and hardness can also be controlled by adjusting the current waveform. In particular, when a rectangular pulse is added, the crystal structure can be controlled by the ON / OFF time length of energization and the ON / OFF ratio. For example, since the brightener component in the vicinity of the cathode is replenished when the current is turned off, the amount of brightener incorporated into the electroformed nickel film increases, the crystal structure becomes finer and the hardness increases, and the crystal orientation ratio I (200 ) / I (111) becomes smaller.

  For example, in a nickel sulfamate solution, saccharin (primary brightener) and 2-butyne 1,4-diol (secondary brightener) are used as brighteners, and the hardness / An example of the change in the crystal orientation strength ratio I (200) / I (111) is shown in FIG. It can be seen that by increasing the current density, the crystal orientation strength ratio I (200) / I (111) increases and the hardness decreases.

  This indicates that the crystal structure (crystal orientation) and hardness are determined by the brightener content ratio in the film during electroforming.

  From the above, the desired crystal structure (crystal orientation) and hardness can be obtained by controlling the operating parameters such as the liquid temperature, the stirring method and its strength (flow rate), current density, and current waveform during electroformed nickel deposition. It is possible to arbitrarily produce an electroformed nickel belt, and it is possible to form metal layers having different laminated structures by changing the operating parameters during nickel deposition. Moreover, the constituent material of each layer which comprises a metal layer may be the same as mentioned above, and may differ.

Regarding crystal orientation, X-ray diffractometer (RAD-3R type) manufactured by Rigaku Denki Co., Ltd.
Thus, the orientation plane diffraction intensity was measured, and the orientation intensity ratio I (200) / I (111) was determined therefrom.

  The thickness of the metal layer 1 is thicker than the skin depth represented by the following formula (1), and is preferably 10 μm or more. Moreover, 200 micrometers or less are preferable, 100 micrometers or less are more preferable, and 50 micrometers or less are still more preferable. The skin depth σ [m] is determined by the frequency f [Hz] of the excitation circuit, the permeability μ, and the specific resistance ρ [Ωm].

と表される。これは電磁誘導で使われる電磁波の吸収の深さを示しており、これより深いところでは電磁波の強度は１／ｅ以下になっており、逆にいうとほとんどのエネルギーはこの深さまでで吸収されている。金属層１があまりに薄いと、ほとんどの電磁エネルギーが吸収しきれなくなってきて効率が悪くなってくることがある。また、金属層１があまりに厚いと、剛性が高くなり、また、屈曲性が悪くなって回転体として使用しにくくなることがある。また、セラミックヒータを使用するベルト加熱方式に金属層を有する定着ベルトを用いる場合、金属層の厚みを上記範囲内とすることによって、熱容量を小さくしてクイックスタート性を向上させることができる。

It is expressed. This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction, and the intensity of electromagnetic waves is less than 1 / e deeper than this, and conversely most energy is absorbed up to this depth. ing. If the metal layer 1 is too thin, most of the electromagnetic energy cannot be absorbed and the efficiency may deteriorate. On the other hand, if the metal layer 1 is too thick, the rigidity becomes high, and the flexibility becomes poor, which may make it difficult to use as a rotating body. Further, when a fixing belt having a metal layer is used in a belt heating method using a ceramic heater, the heat capacity can be reduced and the quick start performance can be improved by setting the thickness of the metal layer within the above range.

  The thickness of each laminated layer is not particularly limited, but when the total thickness of the metal layer is 50 μm, the total of the layers having a Vickers hardness of 400 (load: 100 g) or more is preferably 6.3 μm or more and 39 μm or less. 19.5 μm or more and 33 μm or less is more preferable. When the thickness is within these ranges, the entire metal layer has high heat resistance, the strength of the material is high, and the effect of lamination is exhibited. Further, the two or more types of layers having different crystal structures include a combination of a layer having a Vickers hardness of 250 or more and less than 400 (load: 100 g) and a layer having a Vickers hardness of 400 or more and 600 or less (load: 100 g). Furthermore, the film thickness of the layer having a Vickers hardness (hereinafter referred to as “hardness”) of 400 or more and 600 or less (load: 100 g) (the total film thickness of the multilayer in the case of two or more layers) is the total thickness of the metal layer. When the ratio is 1/8 or more and 3/4 or less, the effect of the present invention is more effectively exhibited, which is preferable. Of the layers having different crystal structures, the Vickers hardness of one layer is more preferably 250 or more and less than 400, and further preferably 300 or more and 380 or less. The Vickers hardness of the other layer is more preferably 400 or more and 600 or less, and further preferably 450 or more and 550 or less. By laminating these layers having different hardnesses, it is possible to obtain a fixing belt in which mechanical strength and high-temperature durability are more harmonized.

  The total film thickness of the layers having a Vickers hardness of 400 or more and 600 or less is preferably 1/8 or more and 3/4 or less of the film thickness of the entire metal layer. The total film thickness of the layers having a Vickers hardness of 250 or more and less than 400 is preferably 1/4 or more and 7/8 or less, more preferably 3/8 or more and 5/8 or less than the film thickness of the entire metal layer. Is good. By making the thickness within these ranges with respect to the film thickness of the entire metal layer, a fixing belt in which mechanical strength and high-temperature durability are harmonized can be obtained. The thickness is measured by dividing the belt in the axial direction by 2 and measuring the film thickness in the axial direction at intervals of 10 mm with a HEIDENHAIN measuring instrument.

  Moreover, it is preferable to make thicker than the skin depth calculated | required from Formula (1) as the whole belt. Usually, it is 100 micrometers or less, Especially preferably, a favorable result can be obtained by setting it as about 10-50 micrometers as mentioned above.

  The number and order of layers of layers having different crystal structures are not particularly limited. As shown in FIGS. 1 (a) and 1 (b), "a layer having a hardness of 400 or more / a layer having a hardness of less than 400" is usually set from the viewpoint of workability and productivity, usually 1 to 20 sets, preferably 1 to 10 It is desirable to form in the range of about a set. Then, the layers are laminated in an odd number of layers such as “layer of hardness 400 or more / layer of hardness less than 400 / layer of hardness of 400 or more” and “layer of hardness of less than 400 / layer of hardness of 400 or more / layer of hardness of less than 400”. Also good. Further, “a layer having a hardness of 400 or more (1) / a layer having a hardness of 400 or more (2) / a layer having a hardness of less than 400” and “a layer having a hardness of less than 400 (1) / a layer having a hardness of less than 400 (2) / a hardness of 400 or more. It is also possible to adopt a form such as

b. Elastic layer 2
The elastic layer 2 may or may not be provided. By providing the elastic layer, heat transfer can be ensured by covering the heated image at the nip portion, and the restoring force of the metal layer 1 can be supplemented to reduce fatigue due to rotation and bending. Further, by providing an elastic layer, the adhesion between the surface of the fixing belt release layer and the unevenness of the unfixed toner image on the recording material can be increased, and heat can be efficiently transferred to the toner image. The fixing belt provided with the elastic layer 2 is particularly suitable for heat fixing of a color image having a large amount of unfixed toner.

  The material of the elastic layer 2 is not particularly limited, and a material having good heat resistance and good thermal conductivity may be selected. The elastic layer 2 preferably contains at least one selected from the group consisting of silicone rubber, fluorine rubber and fluorosilicone rubber, and more preferably silicone rubber.

  Silicone rubber used in the elastic layer includes polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polytrifluoropropylvinylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, and a combination of these polysiloxanes. A polymer etc. can be illustrated.

  If necessary, the elastic layer may be provided with a reinforcing filler such as dry silica, wet silica, calcium carbonate, quartz powder, zirconium silicate, clay (aluminum silicate), talc (hydrous magnesium silicate), alumina (aluminum oxide). , Bengara (iron oxide) or the like may be included in the elastic layer.

The thickness of the elastic layer 2 is preferably 10 μm or more, and more preferably 50 μm or more, because good fixed image quality can be obtained. Moreover, 1000 micrometers or less are preferable and 500 micrometers or less are more preferable. When a color image is printed, a solid image is formed over a large area on the recording material P, particularly in a photographic image. In this case, if the heating surface (release layer 3) of the fixing belt cannot be deformed into the uneven shape of the recording material or the uneven shape of the toner layer, heating unevenness occurs, and the image has a glossy portion with a large amount of heat transfer and a portion with a small amount of heat transfer. Unevenness occurs. That is, the glossiness is high at the portion where the heat transfer amount is large, and the glossiness is low at the portion where the heat transfer amount is small. Here, if the elastic layer 2 is too thin, the fixing belt cannot be deformed into the uneven shape of the recording material or the toner layer, and image gloss unevenness may occur. On the other hand, if the elastic layer 2 is too thick, the thermal resistance of the elastic layer may increase and it may be difficult to realize a quick start.
The hardness of the elastic layer 2 (JIS K 6301 (JIS-A)) is preferably 60 ° or less, and more preferably 45 ° or less, because the occurrence of uneven image gloss is sufficiently suppressed and good fixed image quality is obtained.

The thermal conductivity λ of the elastic layer 2 is preferably 2.5 × 10 ⁻¹ [W / m · K] or more, and more preferably 3.3 × 10 ⁻¹ [W / m · K] or more. Further, it is preferably 8.4 × 10 ⁻¹ [W / m · K] or less, and more preferably 6.3 × 10 ⁻¹ [W / m · K] or less. If the thermal conductivity λ is too small, the thermal resistance increases, and the temperature rise in the surface layer (release layer 3) of the fixing film may be slow. If the thermal conductivity λ is too large, the hardness may increase or the compression set may deteriorate.

  Such an elastic layer is a known method, for example, a method in which a material such as liquid silicone rubber is coated on the metal layer with a uniform thickness by means such as a blade coating method, and heat-cured, or a material such as liquid silicone rubber. May be formed by a method of injecting into a mold and vulcanizing and curing; a method of vulcanizing and curing after extrusion molding; a method of vulcanizing and curing after injection molding.

c. Release layer 3
The material of the release layer 3 is not particularly limited, and a material having good release properties and heat resistance may be selected. As the release layer 3, fluorine resin such as PFA (tetrafluoroethylene / perfluoroalkyl ether copolymer), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), silicone resin, Fluorosilicone rubber, fluororubber, and silicone rubber are preferable, and PFA is particularly preferable. If necessary, the release layer may contain carbon, tin oxide or the like in a conductive agent or the like at 10% by mass or less of the release layer.

  The thickness of the release layer 3 is preferably 1 μm or more. Moreover, 100 micrometers or less are preferable. If the release layer 3 is too thin, a portion having poor release properties may be formed due to uneven coating of the coating film, or durability may be insufficient. Also, if the release layer is too thick, heat conduction may deteriorate, especially in the case of resin-based release layers, the hardness will be high, and good heat transfer properties and fatigue relaxation due to rotation / bending, etc. The effect of the elastic layer 2 may be offset.

  Such a release layer is formed by a known method, for example, in the case of a fluororesin system, by coating, drying and baking a dispersion of fluororesin powder, or by coating and bonding a pre-tubulated material. In the case of a rubber system, it may be formed by a method of injecting a liquid material into a mold and vulcanizing and curing; a method of vulcanizing and curing after extrusion molding; a method of vulcanizing and curing after injection molding.

  Also, a tube that has been previously primed with an inner surface primer and a nickel electroformed belt that has been previously surface primed are mounted in a cylindrical mold, and liquid silicone rubber is injected between the tube and the nickel electroformed belt gap, and heated to heat the rubber. If a method of curing and bonding is used, the elastic layer and the release layer can be formed simultaneously.

d. Sliding layer 4
Although the sliding layer 4 is not an essential component of the present invention, it is preferable to provide the sliding layer 4 in order to reduce the driving torque when operating the image heating and fixing apparatus of the present invention and to take measures against wear during operation. If the sliding layer 4 is provided, the heat generated in the metal layer 1 can be insulated so as not to go to the inside of the fixing belt without excessively increasing the heat capacity of the fixing belt. As a result, the heat supply efficiency to the recording material P is improved, and the power consumption can be suppressed. In addition, the rise time can be shortened.

  The material is not particularly limited, and a material having high heat resistance, high strength, and smooth surface may be selected. The sliding layer 4 is preferably a polyimide resin or the like. If necessary, the sliding layer may contain fluorine resin powder, graphite, molybdenum disulfide, or the like as a sliding agent.

  The thickness of the sliding layer 4 is preferably 5 μm or more, and more preferably 10 μm or more. Moreover, 100 micrometers or less are preferable and 60 micrometers or less are more preferable. If the sliding layer 4 is too thin, durability may be insufficient. If the sliding layer 4 is too thick, the heat capacity of the fixing belt increases and the rise time may be longer.

  Such a sliding layer may be formed by a known method, for example, a method of coating / drying / curing a liquid material, or a method of pasting a tube formed in advance.

A nickel electroformed belt base material having a length of 250 mm, an inner diameter of 34 mm, and a thickness of 50 μm to be the metal layer 1 was produced as follows. In order to prepare a nickel electroformed belt base material, an aqueous solution bath of 450 g / l nickel sulfamate tetrahydrate, 10 g / l nickel chloride and 40 g / l boric acid was made, and then a pit inhibitor was added to 1 g / l. Thereafter, a saccharin (0.04 g / l) as the first brightener and 2-butyne-1,4-diol (0.4 g / l) as the second brightener were added in an appropriate combination. Then, electroforming was started at a bath temperature of 50 ° C. and an initial current density of 11 A / dm ^{2 using} a stainless steel matrix as a cathode, and 1/3 of the amount of electricity corresponding to the desired total film thickness of 50 μm was passed. By the way, the current density is continuously and rapidly changed to 7 A / dm ² to deposit the film to a thickness of 2/3. Thereafter, the current density was again increased to 11 A / dm ² , and the remaining 1/3 of the electroformed film was deposited. As a result of analyzing this electroformed belt, a three-layer lamination / crystal structure change was observed. Converted from the value of current density according to FIG. 2, the first and third layers from the inner surface side have a crystal orientation ratio I (200) / I (111) of around 40, a hardness of about 350 (load: 100 g), and tensile fracture strength. It is considered that a 1050 MPa precipitation layer is formed, and the second layer has a crystal orientation ratio I (200) / I (111) of around 5, a hardness of about 450 (load: 100 g), and a tensile fracture strength of 1350 MPa. It is done. Further, the tensile breaking strength of the entire belt was 1170 MPa. Then, 300 μm silicone rubber as the elastic layer 2 and 30 μm PFA tube as the release layer 3 are laminated on the electroformed belt obtained above via a primer, respectively, and the thickness of the polyimide resin layer of the sliding layer 4 becomes 15 μm. A fixing belt was produced.

  The fixing belt thus produced was mounted on an image heating fixing apparatus as shown in FIG. 5 and an idling durability test was performed. In the idling test, the pressure roller was pressed against the fixing belt with a predetermined pressure while adjusting the temperature to 220 ° C., and the fixing belt was driven to rotate by the pressure roller. As the pressure roller, a rubber roller having an outer diameter of 30 mm, in which a 3 mm thick silicone layer was coated with a 30 μm PFA tube on the outer periphery of the mandrel, was used. In this experimental example, the pressure was set to 220 N (10% increase of the normal test), the fixing nip was 8 mm × 230 mm, and the surface speed of the fixing belt was 100 mm / sec. As a result, the fixing belt of the present invention was good without deformation even after 500 hours of durability, and the end face was not broken or cracked. Further, the above fixing device was mounted on a full color LBP LASER SHOT “LBP-2040” manufactured by Canon, and the image was printed and subjected to a durability test. The endurance test for printing 100,000 sheets was performed, and there was no problem in the fixing property and it was good.

A nickel electroformed belt having a length of 250 mm, an inner diameter of 34 mm, and a thickness of 50 μm, which similarly becomes the metal layer 1, was prepared except that the rate of changing the current density was different from that in Example 1. This time, 1/10 of the total film thickness (that is, 5 μm) is electroformed at a current density of 7 A / dm ² , and then 1/10 of the total film thickness (5 μm) is electroformed at a current density of 11 A / dm ² . This operation was repeated 5 times to produce a 10-layer nickel electroformed belt (FIG. 1B). Similar to Example 1, the layer laminated at a current density of 7 A / dm ² had a crystal orientation ratio of about I (200) / I (111) 5, a hardness of about 450 (load: 100 g), and a tensile fracture strength of 1350 MPa. . As a layer laminated at a current density of 11 A / dm ² , a deposited layer having a crystal orientation ratio I (200) / I (111) of about 40, a hardness of about 350 (load: 100 g), and a tensile fracture strength of 1050 MPa was obtained. The tensile strength at break of the entire belt was 1220 MPa. Thereafter, a 300 μm silicone rubber as the elastic layer 2 and a 30 μm PFA tube as the release layer 3 were laminated via a primer, respectively, to obtain the belt of FIG. A durability test was conducted in the same manner as in Example 1. Table 1 shows the results.

  Similar to Example 1, it was found that the deformation after 500 hours of endurance was satisfactory and there was no breakage or cracking of the end face. Further, the above fixing device was mounted on a full color LBP LASER SHOT “LBP-2040” manufactured by Canon, and the image was printed and subjected to a durability test. The endurance test for printing 100,000 sheets was performed, and there was no problem in the fixing property and it was good.

[Comparative Example 1]
As the metal layer 1, a nickel electroformed belt having a length of 250 mm, an inner diameter of 34 mm, and a thickness of 50 μm was produced as follows. In order to prepare a nickel electroformed belt base material, an aqueous solution bath of 450 g / l nickel sulfamate tetrahydrate, 10 g / l nickel chloride and 40 g / l boric acid was made, and then a pit inhibitor was added to 1 g / l. Thereafter, a saccharin (0.04 g / l) as the first brightener and 2-butyne-1,4-diol (0.4 g / l) as the second brightener were added in an appropriate combination. Then, electrocasting was performed using a stainless steel matrix as a cathode at a bath temperature of 50 ° C. and a current density of 7 A / dm ² to obtain an electroformed belt having a film thickness of 50 μm. As a result of analyzing this belt, a belt having a crystal orientation ratio I (200) / I (111) 5, a hardness of 460 (load: 100 g), and a tensile fracture strength of 1360 MPa was obtained. Thereafter, 300 μm silicone rubber as the elastic layer 2 and a 30 μm PFA tube as the release layer 3 were laminated via a primer, respectively. The belt was subjected to an idling durability test under the same conditions as in Example 1.
The results are shown in Table 1.

実施例１、２と比べ結晶配向比Ｉ（２００）／Ｉ（１１１）の小さい比較例の定着ベルトは、空回転耐久１５０時間において、ベルトに割れが見られた。

The fixing belt of the comparative example having a smaller crystal orientation ratio I (200) / I (111) than that of Examples 1 and 2 showed cracks in the belt at 150 hours of idling.

Fig.1 (a) is an example of the electrocast nickel lamination method of this invention. FIG.1 (b) is a figure showing the cross section of the thickness direction of an electroformed nickel layer. It is an example of the change of the hardness and orientation ratio by the current density of the electroformed nickel of the present invention. FIG. 2 is an example of a layer configuration schematic diagram of the fixing belt of the present invention. It is an example of the schematic block diagram of an image heating apparatus. It is an example of the schematic block diagram of an image heating apparatus. 6 is a magnetic field generating means model diagram of the image heating apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal layer 2 Elastic layer 3 Release layer 4 Sliding layer 10 Fixing belt 12 Ceramic heater 12b Heat generation layer 12c Protective layers 16a, 16b, 16e made of glass or fluororesin Belt guide member 16c Belt guides 17a, 17b, 17c Magnetic core 18 Excitation coils 18a and 18b Power supply unit 19 Insulating member 22 Pressurizing rigid stay 26 Temperature detecting element (thermistor)
27 Excitation Circuit 30 Pressure Member (Pressure Roller)
30a, 30b Elastic layer 40 such as silicone rubber Slide plate M Driving means N Fixing nip portion t Toner image P Recording material 100 Image heating fixing device

Claims (5)

A fixing belt having at least a release layer and a metal layer made of nickel electroforming provided on the release layer,
A fixing belt, wherein the metal layer is laminated with two or more layers having different crystal structures.   2. The fixing belt according to claim 1, wherein at least one of the two or more layers has a Vickers hardness of less than 400 and at least one of the other layers has a Vickers hardness of 400 or more. Of the two or more layers, at least one layer has a Vickers hardness of 250 or more and less than 400, and at least another layer has a Vickers hardness of 400 or more and 600 or less,
The fixing belt according to claim 1, wherein the total thickness of the laminated films having a Vickers hardness of 400 or more and 600 or less is 1/8 or more and 3/4 or less of the total thickness of the metal layer.   The fixing belt according to claim 1, further comprising at least an elastic layer between the release layer and the metal layer.   The fixing belt according to claim 4, wherein the elastic layer includes at least one selected from the group consisting of silicone rubber, fluorine rubber, and fluorosilicone rubber.

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