JP2006245065A - Method of manufacturing thermistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thermistor which can fully reduce a variation in an initial room temperature resistance value between the thermistors to be obtained. <P>SOLUTION: The method of manufacturing the thermistor includes a step of applying a paste containing a resin and conductive particle, forming resin composite layers 14 and 15 on each of a pair of metal foils 12 and 13, and obtaining a pair of laminates 16 and 17; a step of laminating the pair of the laminates 16 and 17 in the state where the resin composite layers 14 and 15 are faced to each other to obtain a laminate 18; a step of heat treating the laminate 18, and obtaining a thermistor element assembly 1 among the pair of the metal foils 12 and 13; and a step of obtaining the thermistor 10 in which the thermistor element assembly 1 is arranged between the pair of the electrodes 2 and 3 from the laminate after the heat treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a thermistor.

  A thermistor using a material composed of a polymer layer and conductive particles dispersed therein as a thermistor body is generally referred to as an organic thermistor, and its resistance value increases rapidly as the temperature rises. Those having a PTC (Positive Temperature Coefficient) characteristic may be referred to as an organic positive temperature coefficient thermistor. Such thermistors are used in devices such as overcurrent / heat protection elements, self-control heating elements, temperature sensors and the like.

As the organic thermistor, for example, a material in which a conductive particle is dispersed in an epoxy resin, which is a thermosetting resin, is used as a thermistor element (Patent Document 1). After applying a paste containing epoxy resin and conductive particles on the electrode and pasting the other electrode to the above paste, the epoxy resin in the paste is thermally cured to place the thermistor element between the pair of electrodes. A method for obtaining an improved thermistor is disclosed.
International Publication No. 2004/086421 Pamphlet

  By the way, the organic thermistor is desired to have a constant room temperature resistance value under the same manufacturing conditions.

  However, in the conventional method, the initial room temperature resistance value varies greatly among the obtained organic thermistors. Therefore, it has been required to reduce the variation in the initial room temperature resistance value.

  Accordingly, an object of the present invention is to provide a thermistor manufacturing method capable of sufficiently reducing variations in initial room temperature resistance values among the thermistors obtained.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following invention.

  That is, in the method for producing the thermistor of the present invention, a first laminate is obtained by applying a first paste containing a resin and conductive particles on a first metal foil to form a first resin composition layer. An application step, a second application step of applying a second paste containing a resin and conductive particles on the second metal foil to form a second resin composition layer to obtain a second laminate; A laminating step in which the laminated body and the second laminated body are bonded together in a state where the first resin composition layer and the second resin composition layer face each other to obtain a bonded body; A thermistor in which the thermistor body is disposed between the first electrode and the second electrode is obtained from the heat treatment step for obtaining the thermistor body between the metal foil and the second metal foil and the bonded body after the heat treatment step. And a process.

  According to this manufacturing method, it is possible to sufficiently reduce the variation in the initial room temperature resistance value between the thermistors obtained. The reason for this is not clear, but after applying the paste, the contact between the coated surface of the metal foil and the conductive particles is improved by the sedimentation of the conductive particles, and on one side of the pair of metal foils as in the past. In single-sided coating, where only the paste is applied, when one electrode is formed, air is taken in between the metal foil and the thermistor body, and the air is not released to the outside and may remain after the thermistor is completed. However, in the manufacturing method of the present invention, it is considered that air is not taken in between the metal foil and the thermistor body and does not remain after the thermistor is completed.

  In the first application step and the second application step, the resin is preferably a thermosetting resin. In this case, the variation in the initial room temperature resistance value is particularly sufficiently reduced, and the initial room temperature resistance value can be sufficiently reduced.

  According to the thermistor manufacturing method of the present invention, the variation in initial room temperature resistance value among the obtained thermistors can be sufficiently reduced, and a thermistor having a constant quality can be stably provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Thermistor)
FIG. 1 is a perspective view schematically showing a preferred embodiment of a thermistor according to the present invention. The thermistor 10 shown in FIG. 1 is provided in close contact with each electrode between a pair of electrodes 2 and 3 disposed so as to face each other, and has positive resistance-temperature characteristics. The thermistor body 1 is formed in a substantially rectangular parallelepiped shape as a whole. The thermistor 10 may be further provided with a lead (not shown) electrically connected to the electrode 2 and a lead (not shown) electrically connected to the electrode 3 as necessary. . The thermistor 10 can be suitably used as an overcurrent / heat protection element, a self-control heating element, a temperature sensor, or the like.

  The electrodes 2 and 3 are formed of a metal material that functions as an electrode of the thermistor. The material constituting the electrodes 2 and 3 is preferably made of a metal such as nickel, silver, gold, copper, or aluminum, or an alloy thereof. Furthermore, Ni is preferable from the viewpoint of low resistance of the element and relatively low cost. The thickness is preferably 1 to 100 μm, and more preferably 1 to 50 μm from the viewpoint of weight reduction of the thermistor. Further, the shape and the material of the lead are not particularly limited as long as they have electrical conductivity capable of discharging or injecting charges from the electrode 2 and the electrode 3 to the outside.

  The thermistor body 1 is formed of a cured product of a paste containing a thermosetting resin and conductive particles dispersed therein. The thermistor body 1 preferably has a thickness of 0.2 to 1.0 mm. When the thickness of the thermistor body 1 exceeds 1.0 mm, the initial room temperature resistance value tends to vary more than the thickness within the above range. Further, if the thermistor body 1 has a thickness of less than 0.2 mm, a short circuit occurs and a normal room temperature resistance value cannot be obtained as compared with the case where the thickness is within the above range.

  The thermosetting resin contains a crosslinkable resin such as an epoxy resin, a phenol resin, an unsaturated polyester resin, a urea resin, a melamine resin, a furan resin, and a polyurethane resin, and these curing agents. In addition, this hardening | curing agent may react with a crosslinkable resin etc., may comprise a part of crosslinked structure in hardened | cured material, and may act as a catalyst of hardening reaction. Alternatively, it may act as a catalyst and constitute a part of the crosslinked structure.

  As the thermosetting resin, not only the handling of the resin before curing is good, but also because the completed thermistor body 1 is excellent in heat resistance, particularly an epoxy resin and an epoxy containing the curing agent thereof. A resin composition is preferred.

  In the present invention, the epoxy resin means a resin composed of a single or plural kinds of polyepoxy compounds having a plurality of epoxy groups. Examples of the polyepoxy compound include polyglycidyl ethers of polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, catechol, resorcinol, and tetramethylbiphenyl, alkylene oxide adducts of bisphenol compounds, glycerin, and polyalkylene glycols. Examples thereof include polyglycidyl ethers of polyhydric alcohols, polyglycidyl esters of polycarboxylic acids such as phthalic acid and terephthalic acid.

  Examples of the curing agent used in combination with the epoxy resin include acid anhydrides, aliphatic polyamines, aromatic polyamines, polyamides, polyphenols, polymercaptans, tertiary amines, and Lewis acid complexes. Of these, acid anhydrides are preferred. When an acid anhydride is used, the initial room temperature resistance value of the thermistor tends to be lowered and the rate of change in resistance tends to be higher than when an amine-based curing agent such as an aliphatic polyamine is used.

  Acid anhydrides include dodecenyl succinic anhydride, methyltetrahydrophthalic anhydride, polyadipic acid anhydride, polyazeline acid anhydride, polysebacic acid anhydride, poly (ethyloctadecanedioic acid) anhydride, poly (phenylhexadecanedioic acid) Anhydrides, ethylene glycol bisanhydro trimellitate, glycerol tris anhydro trimellitate and the like.

  Other suitable specific examples of the acid anhydride include, in addition to the above, 2,4-diethylglutaric anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, succinic anhydride Acid, trimetic anhydride, pyromellitic anhydride, methyl nadic anhydride, maleic anhydride, benzophenone tetracarboxylic anhydride, endomethylenetetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, methyl Examples include cyclohexene dicarboxylic acid anhydride alkylstyrene-maleic anhydride copolymer, ethylene glycol bistrimellitate, chlorendic anhydride, and tetrabromophthalic anhydride.

  In an epoxy resin composition, the above acid anhydrides can be used alone or in combination.

  What is necessary is just to determine suitably the content rate of the hardening | curing agent in a thermosetting resin according to the kind etc. of a crosslinkable compound or a hardening | curing agent. For example, when an acid anhydride is combined with the epoxy resin as a curing agent, the equivalent ratio to the epoxy group in the epoxy resin is 0.5 to 1.5, more preferably 0.8 to 1.2. It is more preferable to contain a curing agent in a content ratio. When the equivalent ratio of the curing agent is less than 0.5 or more than 1.5 with respect to the epoxy group, the unreacted epoxy group and acid anhydride group increase, and the mechanical strength of the thermistor body decreases. Or the resistance change rate of the thermistor tends to decrease.

When the thermosetting resin is an epoxy resin composition containing an epoxy resin and a curing agent thereof, the total average molecular weight of the epoxy resin and the curing agent is preferably 300 to 1000, and preferably 300 to 650. More preferred. Thereby, hardened | cured material becomes what has moderate flexibility and the durability with respect to a heat history is further improved.

  The thermosetting resin may contain additives such as a reactive diluent and a plasticizer. As the reactive diluent, a monoepoxy compound is preferred particularly when combined with an epoxy resin. As monoepoxy compounds, n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, glycidyl methacrylate, tertiary carboxylic acid A glycidyl ester etc. are mentioned. The plasticizer is preferably a polyhydric alcohol such as polyethylene glycol or propylene glycol.

  The thermosetting resin may further contain other components, for example, thermoplastic resins, low molecular organic compounds such as waxes, fats and oils, fatty acids, and higher alcohols, if necessary. The thermoplastic resin may be dissolved in the thermosetting resin or may be dispersed in a particulate state.

  The conductive particles are not particularly limited as long as they are electrically conductive particles. For example, carbon black, graphite, metal particles of various shapes, or ceramic conductive particles can be used. Examples of the metal material of the metal particles include copper, aluminum, nickel, tungsten, molybdenum, silver, zinc, cobalt, and copper powder subjected to nickel plating. Examples of the material for the ceramic conductive particles include TiC and WC. These conductive particles can be used alone or in combination of two or more.

  As the conductive particles, metal particles are particularly preferable. When metal particles are used as the conductive particles, the resistance change rate of the thermistor can be maintained sufficiently large, and the room temperature resistance value can be further reduced. For example, it is suitable when the thermistor of the present invention is used as an overcurrent protection element. It is. Further, among the metal particles, nickel particles are particularly preferable from the viewpoint of chemical stability such as being hardly oxidized.

  The shape of the conductive particles is not particularly limited, and examples thereof include a spherical shape, a flake shape, a fiber shape, and a rod shape, and those having spike-like protrusions on the surface of the particles are preferable. By using conductive particles having spike-like protrusions, a tunnel current easily flows between adjacent particles, so that the room temperature resistance value can be further lowered while sufficiently ensuring the resistance change rate of the thermistor. Further, since the distance between the centers of the particles can be increased as compared with the spherical particles, a larger resistance change rate can be obtained. Furthermore, the variation in the room temperature resistance value of the thermistor can be reduced compared to the case where fibrous particles are used.

The conductive particles having spike-shaped protrusions may be powders in which primary particles are individually dispersed, but about 10 to 1000 primary particles are connected in a chain to form filament-shaped secondary particles. Is preferred. Further, the material is preferably a metal, and more preferably a material mainly composed of nickel. Furthermore, the conductive particles preferably have a specific surface area of 0.3 to 3.0 m ² / g and an apparent density of 3.0 g / cm ³ or less. Here, the “specific surface area” means a specific surface area determined by a nitrogen gas adsorption method based on the BET single point method.

  The average particle size of the primary particles of the conductive particles is preferably 0.1 to 7.0 μm, and more preferably 0.5 to 5.0 μm. Here, the average particle size of the primary particles is a value measured by the Fischer sub-sieving method.

Examples of commercially available conductive particles having spike-like protrusions include “INC”.
O Type 210 "," INCO Type 255 "," INCO Type 270 "," INCO Type 287 "(all are trade names, manufactured by INCO), and the like.

  The content ratio of the conductive particles in the thermistor body is preferably 5 to 90% by mass, and more preferably 60 to 80% by mass based on the whole thermistor body. When the content ratio of the conductive particles is less than 50% by mass, it tends to be difficult to obtain a low room temperature resistance value, and when it exceeds 90% by mass, it tends to be difficult to obtain a large resistance change rate.

(Thermistor manufacturing method)
Next, an embodiment of a method for manufacturing the thermistor 10 will be described. 2-6 is a figure which shows a series of manufacturing processes of the thermistor 10. FIG.

  The thermistor 10 applies a paste containing a thermosetting resin and conductive particles on a pair of metal foils 12 and 13 to form resin composition layers 14 and 15, respectively. A coating step to obtain, a laminating step of laminating the pair of laminates 16 and 17 in a state where the resin composition layers 14 and 15 face each other to obtain a laminating body 18, and a heat treatment of the laminating body 18; By a manufacturing method including a heat treatment step for obtaining the thermistor body 1 between the pair of metal foils 12 and 13 and a cutting step for obtaining the thermistor 10 by cutting the bonded body 18 after the heat treatment into a predetermined shape and size, Obtainable. That is, in the manufacturing method of the present embodiment, the first paste and the second paste are constituted by a common paste, and the first resin composition layer and the second resin composition layer are constituted by a common resin composition. In addition, the stacked body 16 corresponds to the first stacked body, and the stacked body 17 corresponds to the second stacked body.

  According to the above manufacturing method, the variation in initial room temperature resistance value among the obtained thermistors 10 can be sufficiently reduced, and a thermistor 10 having a constant quality can be obtained stably. The reason for this is not clear, but after applying the paste, the contact between the coated surface of the metal foil and the conductive particles is improved by the sedimentation of the conductive particles, and on one side of the pair of metal foils as in the past. In single-sided coating, where only the paste is applied, when one electrode is formed, air is taken in between the metal foil and the thermistor body, and the air is not released to the outside and may remain after the thermistor is completed. However, in the manufacturing method of the present invention, it is considered that air is not taken in between the metal foil and the thermistor body and does not remain after the thermistor is completed. In addition, by using a thermosetting resin as the resin contained in the paste, the initial room temperature resistance value can be sufficiently lowered in addition to the variation of the initial room temperature resistance value being sufficiently sufficiently reduced.

  The paste is obtained by mixing the above-described components, that is, a thermosetting resin and conductive particles, using various types of stirrers, dispersers, mills, and the like. At this time, in order to lower the viscosity, various organic solvents such as alcohol and acetone, and a solvent such as a reactive diluent are added to the resin composition composed of the thermosetting resin and the conductive particles. Also good. Although mixing time is not specifically limited, Usually, each component can be uniformly dissolved or dispersed by mixing for 10 to 30 minutes. Moreover, although mixing temperature is not specifically limited, What is necessary is just to be 25-80 degreeC, for example. In addition, there exists a possibility that resin may harden during mixing that mixing temperature is 100 degreeC or more. The mixed resin composition is preferably defoamed under vacuum in order to remove bubbles mixed in during mixing.

  The paste containing the resin composition is applied onto the metal foils 12 and 13, respectively, to obtain laminates 16 and 17 in which the resin composition layers 14 and 15 are formed on one side of the metal foils 12 and 13, respectively. At this time, the thicknesses of the resin composition layers 14 and 15 are preferably the same from the viewpoint of further reducing variation in resistance value. The surfaces of the metal foils 12 and 13 are preferably roughened in advance. In this case, the adhesiveness between the conductive particles in the resin composition layer 14 and the metal foil 12 and the adhesiveness between the conductive particles in the resin composition layer 15 and the metal foil 13 can be sufficiently secured, and the initial room temperature resistance. Variation in values can be further reduced.

  Subsequently, in the bonding step, the pair of laminated bodies 16 and 17 are bonded together with the resin composition layers 14 and 15 facing each other to obtain a bonded body 18. At this time, it is preferable to pressurize the whole so that the metal foils 12 and 13 and the resin composition layers 14 and 15 are in close contact with each other.

  In the heat treatment step, the bonded body 18 is heated at a predetermined temperature for a predetermined time so that the resin compositions constituting the resin composition layers 14 and 15 are sufficiently cured. What is necessary is just to set suitably the conditions of the heating at this time so that hardening may fully advance according to the kind etc. of hardening | curing agent. For example, when an acid anhydride is used as a curing agent, curing can usually proceed sufficiently by heating at 80 to 200 ° C. for 30 to 600 minutes. In addition, you may perform this heat processing process, pressing, and in this case, you may perform the said bonding process and heat processing process simultaneously or continuously.

  In the cutting step, the thermistor 10 can be obtained by cutting the bonded body 18 having the cured resin composition into a desired shape (for example, 3.6 mm × 9 mm) by punching or the like. The punching can be performed by a method usually used for obtaining a thermistor, such as a cat press.

  Furthermore, if necessary, a thermistor having a lead can be produced by bonding the lead to the surfaces of the electrode 2 and the electrode 3 made of metal foil.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, a thermosetting resin is used as the resin in the paste, but a thermoplastic resin may be used instead of the thermosetting resin. Further, the resin in the paste applied on the metal foil 12 may be a thermosetting resin, and the resin in the paste applied on the metal foil 13 may be a thermoplastic resin. The resin in the paste to be applied may be a thermoplastic resin, and the resin in the paste to be applied on the metal foil 13 may be a thermosetting resin.

  Moreover, in the said embodiment, the 1st paste and the 2nd paste are comprised with the common paste, and the 1st resin composition layer and the 2nd resin composition layer are comprised with the common resin composition. Moreover, although the laminated body 16 respond | corresponds to a 1st laminated body and the laminated body 17 respond | corresponds to a 2nd laminated body, a 1st paste and a 2nd paste may be comprised with the paste of a different composition. That is, at least one of the resin and the conductive particles may be different between the paste applied onto the metal foil 12 and the paste applied onto the metal foil 13. In addition, the paste applied on the metal foil 12 and the paste applied on the metal foil 13 may have the same resin and conductive particles, in which case the content of the conductive particles relative to the resin is different. May be.

Furthermore, although the manufacturing method of the said embodiment includes the cutting process which cuts the bonding body 18, when the metal foils 12 and 13 become the electrodes 2 and 3 of the thermistor 10 as they are, a cutting process is unnecessary. . In this case, the bonded body 18 becomes the thermistor 10.
Furthermore, in the said embodiment, the bonded body 18 is cut | judged and the thermistor 10 is obtained, However, The thermistor 10 may be obtained by a part of the bonded body 18 being hollowed out.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

Example 1
An epoxy resin (trade name, “EP-4005” manufactured by Asahi Denka Co., Ltd.) composed of a mixture of polyepoxy compounds (methyltetrahydrophthalic anhydride), an epoxy resin (trade name, “EP-4080S” manufactured by Asahi Denka Co., Ltd.), Curing agent made of acid anhydride (trade name, “B570” manufactured by Dainippon Ink and Chemicals, Inc.), curing accelerator (trade name, “PN-40J” manufactured by Ajinomoto Co., Inc.), and filaments that are conductive particles Nickel powder (trade name “Type 255 nickel powder”, manufactured by INCO, average particle size 2.2 to 2.8 μm, apparent density 0.5 to 0.65 g / cm ³ , specific surface area 0.68 m ² / g) Were mixed to prepare a resin composition.

  In the preparation of the resin composition, first, mixing is performed such that the mixing ratio (weight ratio) of the epoxy resins “EP-4005” and “EP4080S” is 70:30, and for the entire epoxy resin, A mixture containing 53% by mass of the curing agent (B570) and 1% by mass of the curing accelerator (PN-40J) was stirred using a homogenizer (Cell Master). Then, the conductive particles were added to this mixture by an amount that would be 75% by mass with respect to the entire resin composition containing the conductive particles, and then further stirred to obtain a resin composition.

  The resin composition obtained above was applied on a nickel foil to a thickness of 0.25 mm to form a resin composition layer, and a laminate was prepared. Then, another laminate having the same configuration was prepared. And a laminated body was bonded together so that a resin composition layer might face each other, the bonded body was produced, this bonded body was press-molded into a sheet form, and it hardened by heating at 130 ° C for 10 hours. The bonded body after heat treatment thus obtained was punched into a 3.6 × 9.0 mm shape with a cat press to obtain a thermistor.

(Example 2)
Example, except that the thickness of the curable resin composition applied on one nickel foil was 0.05 mm and the thickness of the curable resin composition applied on the other nickel foil was 0.45 mm The thermistor was obtained in the same manner as in 1.

(Comparative Example 1)
Example 1 except that the thickness of the curable resin composition applied on one nickel foil was 0.50 mm and the thickness of the curable resin composition applied on the other nickel foil was 0 mm. A thermistor was obtained in the same manner.

Twenty-five thermistors of Examples 1 and 2 and Comparative Example 1 were prepared as described above, and the resistance values of these thermistors were measured by a four-terminal method to obtain temperature-resistance curves. The initial room temperature resistance value of the thermistor was calculated from the obtained temperature-resistance curve. In 25 thermistors, the minimum initial room temperature resistance value (MIN room temperature resistance value), the maximum value (MAX room temperature resistance value), the difference between the maximum value and the minimum value, the average initial room temperature resistance value, and the resistance value variation rate Was calculated. The results are shown in Table 1. The resistance value variation rate is a value obtained by dividing the average initial room temperature resistance value by the difference.

  From the results shown in Table 1, it was found that according to the manufacturing methods of Example 1 and Example 2, the resistance value variation rate was remarkably reduced as compared with the manufacturing method of Comparative Example 1. In addition, from the results of Example 1 and Example 2, if the thermistor body has the same thickness, the resistance value is the same regardless of the ratio of the thickness of the resin composition layer formed on the pair of nickel foils. It was confirmed that the variation rate was obtained.

  From this result, according to the manufacturing method of this invention, it was confirmed that the dispersion | variation in an initial room temperature resistance value can fully be reduced between the obtained thermistors.

  In addition, according to Examples 1 and 2, it was confirmed that an average room temperature resistance value is also sufficiently reduced.

It is a perspective view showing typically an example of the thermistor obtained by the thermistor manufacturing method concerning the present invention. It is a figure which shows 1 process in one Embodiment of the manufacturing method of the thermistor of this invention. It is a figure which shows 1 process in one Embodiment of the manufacturing method of the thermistor of this invention. It is a figure which shows 1 process in one Embodiment of the manufacturing method of the thermistor of this invention. It is a figure which shows 1 process in one Embodiment of the manufacturing method of the thermistor of this invention. It is a figure which shows 1 process in one Embodiment of the manufacturing method of the thermistor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thermistor body, 2, 3 ... Electrode, 10 ... Thermistor, 12 ... Metal foil (first metal foil), 13 ... Metal foil (second metal foil), 14 ... Resin composition layer (first resin composition) Layer), 15 ... resin composition layer (second resin composition layer), 16 ... laminate (first laminate), 17 ... laminate (second laminate), 18 ... bonded body.

Claims (2)

A first application step of applying a first paste containing a resin and conductive particles on the first metal foil to form a first resin composition layer to obtain a first laminate;
A second coating step of applying a second paste containing a resin and conductive particles on the second metal foil to form a second resin composition layer to obtain a second laminate;
A laminating step of laminating the first laminated body and the second laminated body with the first resin composition layer and the second resin composition layer facing each other to obtain a laminated body;
Heat-treating the bonded body to obtain a thermistor body between the first metal foil and the second metal foil; and
Obtaining a thermistor in which the thermistor body is disposed between the first electrode and the second electrode from the bonded body after the heat treatment step;
A thermistor manufacturing method characterized by comprising: The thermistor manufacturing method according to claim 1, wherein the resin is a thermosetting resin in the first application step and the second application step.

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