Resin-metal composite comprising metal member and resin member made from composition containing electrically insulating resin

Abstract

The present invention obtains a resin-metal composite even less prone to burrs and having excellent productivity and reliability due to the excellent retention stability of the resin member. Provided are a resin-metal composite comprising a metal member and a resin member made from a composition containing an electrically insulating resin, wherein the melting point (Tm) of the electrically insulating resin in the composition as determined by differential scanning calorimetry is 300-340°C, and the half-value width of the Tm peak is 5.0-20.0°C.

Description

A resin-metal composite comprising a resin member and a metal member made from a composition containing an electrically insulating resin.

[0001] The present invention relates to a resin-metal composite comprising a resin member and a metal member, both made from a composition containing an electrically insulating resin.

[0002] Almost all electrical products utilize resin-metal composites, which consist of resin and metal components. Because resin components generally possess insulating properties, they are well-suited for coating metal components such as terminals. Among applications where high-performance resin-metal composites are in demand, and where new technologies are actively being developed in recent years, are smartphones, tablets, and wearable devices. As these devices become smaller, the integration density of components is increasing. Connectors (B2B connectors, FPC connectors, CPU sockets, etc.), one of the important applications of resin-metal composites, are becoming more complex in shape due to the increasing number of cores, and there is a growing demand for thinner walls and lower profiles.

[0003] For resin components of such ultra-small resin-metal composites with complex part shapes, liquid crystal polyester resin compositions, which offer excellent heat resistance, fluidity, and dimensional stability, are often used. For example, Patent Documents 1 to 8 show examples of liquid crystal polyester resin compositions in which the structural units constituting the liquid crystal polyester resin have been adjusted in various ways, as well as examples in which the shape and blending ratio of the inorganic fillers have been devised. All of these examples are intended for use in resin-metal composite components such as connectors.

[0004] Patent documents 1 to 4 describe liquid crystal polyester resins in which properties such as physical properties, blister resistance, and warp resistance are improved by combining four or five structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid and isophthalic acid in an appropriate ratio. Patent documents 5 and 6 propose liquid crystal polyester resin compositions in which fluidity, warp resistance, and physical properties are improved by blending plate-like fillers such as talc or mica of specific particle sizes and shapes with the liquid crystal polyester resin in an appropriate ratio. Furthermore, patent documents 7 and 8 disclose a technique for imparting properties such as blister resistance by blending liquid crystal polyester resins with different properties.

[0005] Japanese Patent Publication No. 2012-126842, Japanese Patent Publication No. 2002-179776, International Publication No. 2012 / 137636, International Publication No. 2018 / 101214, International Publication No. 2013 / 128887, Japanese Patent Publication No. 2018-109096, Japanese Patent Publication No. 2015-227404, International Publication No. 2017 / 051883

[0006] On the other hand, connectors used in next-generation smartwatches and wearable devices, for example, have complex shapes with extremely narrow terminal spacing. Therefore, even if liquid crystal polyester resins as shown in Patent Documents 1 to 8 are used, stable manufacturing is becoming difficult. Methods to improve the thin-wall fluidity of liquid crystal polyester resin compositions include lowering the molecular weight, lowering the melting point, or lowering the crystallinity. However, while these methods improve thin-wall fluidity, they also increase the likelihood of burr formation. When burrs form, they become debris that adheres to metal components in resin-metal composites, resulting in poor conductivity. Furthermore, problems arise such as the inability to insert metal components such as terminals. In addition, liquid crystal polyester resins have their structural units linked by ester bonds, and because they are highly linear and have poor molecular entanglement, in the molten state, the entanglement of molecular chains unravels, and transesterification reactions proceed, making them resins whose properties are easily altered by retention. In other words, liquid crystal polyester resins inherently have poor retention stability. Liquid crystal polyester resins given thin-walled fluidity by the aforementioned method tend to have more resin ends due to lower molecular weight, leading to frequent transesterification in the molten state and changes in properties. This causes various problems during injection molding, such as drowning and stringing, silver formation on the molded surface, and hesitation in thin-walled sections, resulting in variations in quality depending on the product shape and molding conditions. Resin-metal composites can sometimes be obtained by insert molding, where a metal component is pre-installed in the mold before injection molding. However, this type of molding results in more complex part shapes and resin flow paths, leading to problems with reduced product yield.

[0007] In other words, the present invention aims to provide a resin-metal composite that is suitable for use in applications such as small connectors and sockets having thin walls and complex shapes, and that offers excellent productivity and reliability.

[0008] As a result of diligent research to solve the above problems, the present inventors have discovered that by using a composition containing an electrically insulating resin in which the melting point (Tm) and the full width at half maximum of the Tm peak obtained from differential scanning calorimetry are within a specific range, a resin-metal composite with excellent retention stability and low burr performance can be obtained, leading to the present invention.

[0009] In other words, the present invention is as follows: (1) A resin-metal composite comprising a resin member and a metal member, wherein the melting point (Tm) of the electrical insulating resin in the composition, determined by differential scanning calorimetry, is 300 to 340°C, and the full width at half maximum of the Tm peak is 5.0 to 20.0°C: The above Tm is the endothermic peak temperature (Tm) observed when the composition containing the electrical insulating resin is heated from room temperature at a temperature increase of 20°C / min in differential scanning calorimetry. １ After the observation of Tm １ Tm is the endothermic peak temperature observed when the material is held at a temperature of +20°C for 5 minutes, then cooled to room temperature at a rate of 20°C / min, and then heated again from room temperature at a rate of 20°C / min. Furthermore, when a perpendicular line is drawn from the peak top of the obtained Tm peak to the baseline, and a straight line is drawn passing through the midpoint of the perpendicular line and parallel to the baseline, the distance between the intersection points of the Tm peak and the line is the full width at half maximum (°C). (2) The resin-metal composite according to (1), wherein the resin-metal composite is an electrical / electronic component having metal-to-metal contact points. (3) The resin-metal composite according to (1) or (2), wherein the resin member of the resin-metal composite has a plurality of metal insertion holes, and the thinnest thickness between adjacent metal insertion holes is 0.50 mm or less. (4) A resin-metal composite according to any one of (1) to (3), wherein the composition containing an electrically insulating resin has a crystallization temperature (Tc) of 290 to 325°C as determined by differential scanning calorimetry: The above Tc is the endothermic peak temperature (Tm) observed when the composition containing the electrically insulating resin is heated from room temperature at a temperature increase of 20°C / min in differential scanning calorimetry. １ After the observation of Tm １This is the exothermic peak temperature observed when the material is held at a temperature of +20°C for 5 minutes and then cooled to room temperature under a cooling condition of 20°C / min. (5) The resin-metal composite according to any one of (1) to (4), wherein the electrically insulating resin is a resin selected from polyamide resin, polyimide resin, polyphenylene sulfide resin, polyether ether ketone resin, polytetrafluoroethylene resin, and liquid crystal polyester resin. (6) The resin-metal composite according to any one of (1) to (5), wherein the electrically insulating resin is a liquid crystal polyester resin. (7) The resin-metal composite according to any one of (1) to (6), wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units. (8) A liquid crystal polyester resin (A) in which the electrically insulating resin contains 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and is a liquid crystal polyester resin that contains structural units (III) and (IV) and satisfies the following formulas (a) and (b), as described in any of (1) to (7): 5 ≤ [IV] ≤ 18 ... (a) 0 < [III] / [IV] < 1.5 ... (b) [III] and [IV] represent the content (mol%) of structural units (III) and (IV) per 100 mol% of total structural units of the liquid crystal polyester resin (A), respectively.

[0010] (9) A liquid crystal polyester resin (A) in which the electrically insulating resin contains 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and is a liquid crystal polyester resin that contains the following structural units (I) and (II), and the molar ratio of structural units (I) to (II) ([I] / [II]) is 5 to 20, as described in any of (1) to (8): [I] and [II] each represent the content (mol%) of structural units (I) and (II) per 100 mol% of total structural units of the liquid crystal polyester resin (A).

[0011] (10) The resin-metal composite according to any one of (1) to (9), wherein the composition containing the electrically insulating resin further contains an inorganic filler (B), and the inorganic filler (B) is contained in an amount of 10 to 200 parts by weight per 100 parts by weight of the electrically insulating resin. (11) The resin-metal composite according to any one of (1) to (10), wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and the composition containing the electrically insulating resin is a liquid crystal polyester resin composition containing 10 to 200 parts by weight of inorganic filler (B) per 100 parts by weight of the liquid crystal polyester resin (A).

[0012] The present invention provides a resin-metal composite with excellent productivity and reliability by using a composition containing an electrically insulating resin that exhibits high thin-wall fluidity, excellent retention stability, and a low burr generation rate. The resin-metal composite of the present invention can be suitably used in applications such as small connectors and sockets with thin walls and complex shapes, which are used in combination with resin members and metal members.

[0013] This is a schematic diagram of an example of a resin component of the resin-metal composite of the present invention. This is a schematic diagram of the endothermic peak observed when a composition containing an electrically insulating resin is heated. This is a diagram showing the stress relaxation spectrum of a composition containing an electrically insulating resin. This is a diagram showing the stress relaxation spectra of a composition containing an electrically insulating resin of the present invention and a conventional composition.

[0014] The present invention relates to a resin-metal composite comprising a resin member and a metal member made from a composition containing an electrically insulating resin. The elements constituting the resin-metal composite of the present invention will be described in detail below. Note that the melting point of the electrically insulating resin in the composition, as determined by differential scanning calorimetry, may be denoted as "Tm," the full width at half maximum (FWHM) of the melting point peak of the electrically insulating resin in the composition, as determined by differential scanning calorimetry, may be denoted as "FWHM of the Tm peak," and the crystallization temperature of the composition containing the electrically insulating resin, as determined by differential scanning calorimetry, may be denoted as "Tc."

[0015] <Electrically Insulating Resin> The electrically insulating resin used in the present invention is not limited in structure as long as it is a resin, but thermoplastic resins are preferably used from the viewpoint of moldability and recyclability. Examples of thermoplastic resins include polyester resins such as polyethylene terephthalate resin, polytrimethylene terephthalate resin, polybutylene terephthalate resin, and liquid crystal polyester resin; polyamide resins; polycarbonate resins; styrene resins; polyolefin resins such as polyethylene resin, polypropylene resin, and cycloolefin resin; polyacetal resins; polyimide resins; polyphenylene sulfide resins, polyether ether ketone resins (PEEK), polytetrafluoroethylene resins, polyvinyl chloride resins, polyetherimide resins; polyurethane resins; polyphenylene ether resins; polysulfone resins; polymethacrylate resins; and the like. Among these, from the viewpoint of obtaining a high-performance resin-metal composite with excellent heat resistance, fluidity and dimensional stability, any resin selected from polyamide resins, polyimide resins, polyphenylene sulfide resins, polyether ether ketone resins, polytetrafluoroethylene resins, and liquid crystal polyester resins is preferred as the electrically insulating resin. As the polyamide resin, polyamides using terephthalic acid as a monomer are preferred, and polyhexamethylene terephthalamide (polyamide 6T), polynonanemethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polymethylpentane terephthalamide (polyamide M5T), and modified copolymers thereof are more preferred. From the viewpoint of easily producing a dense shape with a thin minimum thickness and narrow pitch spacing, it is preferable to use a liquid crystal polyester resin, and it is more preferable to use a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acids, 10 to 40 mol% of structural units derived from aromatic diols, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acids, per 100 mol% of total structural units.

[0016] The preferred configuration and manufacturing method of the liquid crystal polyester resin (A) will be described in detail in the following sections, "Liquid Crystal Polyester Resin (A)" and "Manufacturing Method for Liquid Crystal Polyester Resin (A)".

[0017] <Liquid Crystal Polyester Resin (A)> Liquid crystal polyester resin (A), which is preferably used as an electrical insulating resin, is a polyester that forms an anisotropic molten phase. Examples of such polyester resins include polyesters composed of structural units selected to form an anisotropic molten phase from oxycarbonyl units, dioxy units, dicarbonyl units, etc., as described later.

[0018] The structural units that make up liquid crystal polyester resin (A) will be described below.

[0019] The liquid crystal polyester resin (A) preferably contains 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid as oxycarbonyl units, relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A). If the amount of structural units derived from aromatic hydroxycarboxylic acid is less than 20 mol%, the liquid crystallinity is impaired, which is undesirable because it reduces the fluidity when used in a composition. The amount of structural units derived from aromatic hydroxycarboxylic acid is preferably 25 mol% or more, and more preferably 30 mol% or more. On the other hand, if the amount of structural units derived from aromatic hydroxycarboxylic acid is more than 80 mol%, it is undesirable because it becomes difficult to control the crystallinity and melting point of the liquid crystal polyester resin (A). The amount of structural units derived from aromatic hydroxycarboxylic acid is preferably 75 mol% or less, and more preferably 65 mol% or less.

[0020] Specific examples of oxycarbonyl units include structural units derived from p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 6-hydroxy-2-naphthoic acid.

[0021] The liquid crystal polyester resin (A) preferably contains 10 to 40 mol% of structural units derived from aromatic diols as dioxy units, relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A). If the amount of structural units derived from aromatic diols is less than 10 mol%, it becomes difficult to control the crystallinity and melting point of the liquid crystal polyester resin (A), and the effects inherent to the liquid crystal polyester resin, such as physical properties and fluidity, are reduced when it is used as a resin-metal composite, which is undesirable. The amount of structural units derived from aromatic diols is preferably 12 mol% or more, and more preferably 15 mol% or more. On the other hand, if the amount of structural units derived from aromatic diols is more than 40 mol%, the liquid crystallinity is impaired, and the effects inherent to the liquid crystal polyester resin, such as physical properties and fluidity, are reduced when it is used as a resin-metal composite, which is undesirable. The amount of structural units derived from aromatic diols is preferably 37 mol% or less, and more preferably 35 mol% or less.

[0022] Examples of structural units derived from aromatic diols include those derived from 4,4'-dihydroxybiphenyl, hydroquinone, resorcinol, t-butylhydroquinone, phenylhydroquinone, chlorohydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 3,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, and 4,4'-dihydroxybenzophenone. Structural units selected from those derived from 4,4'-dihydroxybiphenyl and hydroquinone are preferred due to their excellent availability and polymerization reactivity.

[0023] The liquid crystal polyester resin (A) preferably contains 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid as dicarbonyl units, relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A). If the amount of structural units derived from aromatic dicarboxylic acid is less than 10 mol%, it becomes difficult to control the crystallinity and melting point of the liquid crystal polyester resin (A), and the effects inherent to the liquid crystal polyester resin, such as physical properties and fluidity, are reduced when it is used as a resin-metal composite, which is undesirable. The amount of structural units derived from aromatic dicarboxylic acid is preferably 12 mol% or more, and more preferably 15 mol% or more. On the other hand, if the amount of structural units derived from aromatic dicarboxylic acid is more than 40 mol%, the liquid crystallinity is impaired, and the effects inherent to the liquid crystal polyester resin, such as physical properties and fluidity, are reduced when it is used as a resin-metal composite, which is undesirable. The amount of structural units derived from aromatic dicarboxylic acid is preferably 37 mol% or less, and more preferably 35 mol% or less.

[0024] Examples of structural units derived from aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid. Structural units selected from those derived from terephthalic acid and isophthalic acid are preferred due to their excellent availability and polymerization reactivity.

[0025] Next, a more preferred configuration of the structural units constituting the liquid crystal polyester resin (A), which is preferably used as an electrical insulating resin, will be described in detail.

[0026] From the viewpoint of obtaining a composition with excellent retention stability and a low-burr resin-metal composite, the liquid crystal polyester resin (A) preferably contains the following structural units (III) and (IV) and satisfies the following formulas (a) and (b).

[0027] 5 ≤ [IV] ≤ 18 ...(a) 0 < [III] / [IV] < 1.5 ...(b) [III] and [IV] respectively represent the contents (mol%) of structural units (III) and (IV) with respect to 100 mol% of all the structural units of the liquid crystal polyester resin (A).

[0028]

[0029] The structural units (III) and (IV) are respectively a structural unit derived from 4,4'-dihydroxybiphenyl and a structural unit derived from hydroquinone.

[0030] By the content of (IV) satisfying the above formula (a), the packing property between the polymer chains of the liquid crystal polyester resin (A) is improved. As a result, it becomes easier to uniformly control the crystal structure and size, and it becomes easy to control the half-value width (°C) of the Tm peak within a preferable range described later. As a result, the residence stability and low burr property are improved. The content of (IV) with respect to 100 mol% of all the structural units of the liquid crystal polyester resin (A) is more preferably 7 mol% or more, and further preferably 10 mol% or more. Also, it is more preferably 15 mol% or less.

[0031] Further, by the molar ratio ([III] / [IV]) of the contents of the structural units (III) and (IV) satisfying the above formula (b), it becomes easy to control Tm and Tc within a preferable range described later. As a result, the residence stability and low burr property are improved. This is because by satisfying the above formula (b), the packing property between the polymer chains by the structural unit (III) is improved and it becomes easier to uniformly control the crystal structure and size. The molar ratio ([III] / [IV]) of the contents of the structural units (III) and (IV) is more preferably 0.3 or more, and further preferably 0.6 or more. ([III] / [IV]) is more preferably 1.2 or less, and further preferably 1.0 or less.

[0032] Also, the content (mol%) of the structural unit (III) derived from 4,4'-dihydroxybiphenyl in 100 mol% of all the structural units of the liquid crystal polyester resin (A) is preferably 3 mol% or more, more preferably 5 mol% or more, and even more preferably 8 mol% or more from the viewpoints of excellent residence stability and low burr property. Further, the content of the structural unit (III) is preferably 20 mol% or less, more preferably 15 mol% or less, and even more preferably 12 mol% or less.

[0033] From the viewpoints of excellent residence stability and low burr property, the liquid crystal polyester resin (A) preferably contains the following structural units (II) and (VI) and satisfies the following formulas (c) and (d).

[0034] 0.1 < [VI] < 4 ··· (c) [VI] / [II] < 1 ··· (d) [II] and [VI] respectively represent the contents (mol%) of the structural units (II) and (VI) with respect to 100 mol% of all the structural units of the liquid crystal polyester resin (A).

[0035]

[0036] Structural units (II) and (VI) are derived from 6-hydroxy-2-naphthoic acid and isophthalic acid, respectively. Structural units (II) and (VI) have a bent structure. By introducing these into the liquid crystal polyester resin (A) in the preferred ratios shown in formulas (c) and (d) above, the polymer chains become more easily intertwined while maintaining thin-wall fluidity, improving retention stability and low burriness. By setting the molar ratio of the content of structural units (VI) and (II) ([VI] / [II]) shown in formula (d) above to less than 1, it becomes easy to control the full width at half maximum (°C) of the Tm peak to the preferred range described later. This is because 6-hydroxy-2-naphthoic acid (HNA), the monomer that gives structural unit (II), is highly reactive and effectively reacts with isophthalic acid (IPA), the monomer that gives structural unit (VI), to form an oligomer. As the polymer grows from the formed oligomer, the structural units derived from IPA are efficiently incorporated near the center of the polymer chain, making it easier to form a bent structure and increasing the entanglement of polymer chains. From the viewpoint of improving retention stability and low barrier properties, the molar ratio of structural units (VI) to (II) ([VI] / [II]) is more preferably 0.8 or less, and even more preferably 0.5 or less. On the other hand, the lower limit of [VI] / [II] is not particularly limited, and may be 0.005 or more, more preferably 0.01 or more, and even more preferably 0.05 or more.

[0037] The liquid crystal polyester resin (A) is a liquid crystal polyester resin that contains the following structural units (I) to (VI) and more preferably satisfies the following formulas (e) to (j) from the viewpoint of excellent retention stability and low burr. By using such a liquid crystal polyester resin (A), it becomes easy to control the full width at half maximum (°C) of the Tm peak to the preferred range described later.

[0038] 25 ≤ [I] ≤ 75 ... (e) 1 ≤ [II] ≤ 20 ... (f) 10 ≤ [III] + [IV] ≤ 35 ... (g) 2 ≤ [V] ≤ 35 ... (h) 0.1 < [VI] < 4 ... (i) [VI] / [II] < 1 ... (j) [I] to [VI] represent the content (mol%) of structural units (I) to (VI) relative to 100 mol% of the total structural units of liquid crystal polyester resin (A).

[0039]

[0040] Structural unit (I) is a structural unit derived from p-hydroxybenzoic acid (HBA). From the viewpoint of excellent retention stability and low burriness, it is preferable that the above formula (e) is satisfied. The content (mol%) of structural unit (I) relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A) is more preferably 35 mol% or more, even more preferably 45 mol% or more, and most preferably 48 mol% or more. Furthermore, it is preferable that it be 65 mol% or less, and more preferably 55 mol% or less.

[0041] Structural unit (II) is a structural unit derived from 6-hydroxy-2-naphthoic acid (HNA). From the viewpoint of excellent retention stability and low burriness, it is preferable that the above formula (f) is satisfied. The content (mol%) of structural unit (II) relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A) is preferably 2 mol% or more, more preferably 3 mol% or more. Furthermore, it is preferably 15 mol% or less, and more preferably 10 mol% or less.

[0042] The full width at half maximum (°C) of the Tm peak can be easily controlled to the preferred range described later. From the viewpoint of excellent retention stability and low burr quality, the molar ratio of structural units (I) to (II) ([I] / [II]) is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more. On the other hand, from the viewpoint of being moldable over a wide range of molding temperatures and having low thickness dependence of fluidity, [I] / [II] is preferably 20 or less, more preferably 18 or less, and even more preferably 16 or less. By setting it within this range, it is possible to prevent HBA from preferentially polymerizing and forming regions with excessively high linearity, and the entanglement of polymer chains increases. As a result, a resin member with excellent low burr quality can be obtained.

[0043] In addition, structural units derived from m-hydroxybenzoic acid and the like can be used as oxycarbonyl units, to the extent that they do not impair the effects of the present invention.

[0044] Structural unit (III) is a structural unit derived from 4,4'-dihydroxybiphenyl. From the viewpoint of excellent retention stability and low burr, the amount of structural unit (III) is preferably 3 mol% or more, more preferably 5 mol% or more, and even more preferably 8 mol% or more, relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A). On the other hand, from the viewpoint of being moldable over a wide range of molding temperatures and having low thickness dependence of flowability, the amount of structural unit (III) is preferably 20 mol% or less, and more preferably 15 mol% or less.

[0045] It is preferable that the above formula (g) is satisfied, as it becomes easier to control Tm and Tc within the preferred range described later, and from the viewpoint of improving retention stability and low burriness. Structural units (III) and (IV) are, as described above, structural units derived from 4,4'-dihydroxybiphenyl and hydroquinone, respectively. It is more preferable that the sum of structural units (III) and (IV) is 15 mol% or more, and even more preferable that it is 20 mol% or more, with respect to 100 mol% of the total structural units of the liquid crystal polyester resin (A). It is also more preferable that it is 30 mol% or less, and even more preferable that it is 25 mol% or less.

[0046] In addition, structural units selected from aromatic diols such as resorcinol, t-butylhydroquinone, phenylhydroquinone, chlorohydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 3,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, and 4,4'-dihydroxybenzophenone; structural units derived from aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol; and structural units derived from alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol can be used as dioxy units, within a range that does not impair the effects of the present invention.

[0047] Structural unit (V) is a structural unit derived from terephthalic acid. From the viewpoint of excellent retention stability and low burriness, it is preferable that the above formula (h) is satisfied. The content (mol%) of each structural unit (V) relative to 100 mol% of the total structural units of the liquid crystal polyester resin (A) is more preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 18 mol% or more. Furthermore, 30 mol% or less is preferred, and 28 mol% or less is more preferred.

[0048] Structural unit (VI) is a structural unit derived from isophthalic acid. Details of formulas (i) and (j) are the same as those described in formulas (c) and (d).

[0049] In addition, structural units selected from the following can be used as dicarbonyl units, within limits that do not impair the effects of the present invention: structural units derived from aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; structural units derived from aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecandionic acid, and hexahydroterephthalic acid; and structural units derived from alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid.

[0050] Furthermore, in addition to the above-mentioned structural units (I) to (VI), structural units generated from p-aminobenzoic acid, p-aminophenol, etc., can be used in the liquid crystal polyester resin (A) to the extent that they do not impair the effects of the present invention.

[0051] The method for calculating the content of each structural unit constituting the liquid crystal polyester resin (A) used in the present invention is shown below. First, 2 μL of 25% methanol solution of tetramethylammonium hydroxide is added to 0.1 mg of pulverized liquid crystal polyester resin pellets to decompose the liquid crystal polyester resin into monomers. An appropriate amount of the obtained monomer solution is added to DMSO-d ６ The substance was dissolved and observed using a UNITY INOVA 500 NMR spectrometer (Varian Corporation) at a frequency of 500 MHz and at room temperature. １ 1H-NMR measurements will be performed. The composition ratio will be determined from the peak area ratio derived from each observed structural unit.

[0052] The liquid crystal polyester resin (A) preferably has a melting point (Tm(A)) of 300 to 340°C as determined by differential scanning calorimetry. This range makes it easier to control Tm to a preferred range described later. A melting point (Tm(A)) of 320 to 340°C is even more preferable. Tm(A) is the endothermic peak temperature (Tm) observed when the liquid crystal polyester resin (A) is heated from room temperature at a rate of 20°C / min in differential scanning calorimetry.１ After the observation of (A), Tm １ (A) This is the peak value of the endothermic peak observed when the sample is held at a temperature of +20°C for 5 minutes, then cooled to room temperature at a rate of 20°C / min, and then heated again from room temperature at a rate of 20°C / min.

[0053] <Method for producing liquid crystal polyester resin (A)> As a method for producing liquid crystal polyester resin (A), known polycondensation methods for polyester can be used. From the viewpoint of easily controlling the full width at half maximum (°C) of the Tm peak to a preferred range described later, and having excellent retention stability and low burriness, a "melt polymerization method" is preferred, in which a liquid crystal polyester resin consisting of structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid is reacted with acetic anhydride to acetylate the phenolic hydroxyl groups, and then deacetic acid polymerization is performed by increasing the temperature and reducing the pressure in the system to produce the liquid crystal polyester resin. In this polymerization method, the liquid crystal polyester resin is never solidified after polymerization begins, resulting in a moderately random arrangement of monomers. This suppresses the formation of excessively linear regions and reduces the occurrence of burrs. Furthermore, it prevents unreacted monomers and oligomers from solidifying and becoming insoluble. As a result, the molecular weight distribution becomes narrower, making it easier to uniformly control the crystal structure and size, and facilitating the control of the Tm peak's full width at half maximum (°C) within the preferred range described later.

[0054] On the other hand, there is also a "solid-phase polymerization method" for producing liquid crystal polyester resin, in which oligomers are extruded during melt polymerization and the molecular weight is increased by raising the temperature in the solid state (for example, the method described in Patent Document 6). However, in solid-phase polymerization, many highly reactive acetyl groups tend to remain at the polymer ends. As a result, transesterification proceeds easily in the molten state, and the structure and size of the crystals become non-uniform. Consequently, the resulting liquid crystal polyester resin begins to melt over a wide temperature range, making it difficult to control the full width at half maximum (°C) of the Tm peak, which is undesirable.

[0055] In the aforementioned "melt polymerization method," it is preferable to set the reaction time under reduced pressure to a relatively long period of 90 to 140 minutes. This makes it easier to control the full width at half maximum (°C) of the Tm peak within the preferred range described later, improving the retention stability and low burr properties of the resulting liquid crystal polyester resin. By setting the reaction time under reduced pressure within the above range, the amount of unreacted oligomers is reduced, making it easier to uniformly control the structure and size of the crystals. At the same time, the highly reactive acetyl terminus present at the ends is reduced by detachment as acetic acid, so the transesterification reaction is suppressed when the resulting liquid crystal polyester resin becomes molten inside an injection molding machine or the like. As a result, it becomes easier to uniformly control the structure and size of the crystals. The reaction time under reduced pressure is more preferably 100 to 140 minutes, and even more preferably 110 to 140 minutes.

[0056] Methods for obtaining a liquid crystal polyester resin (A) in which the structural units (I) to (VI) and other structural units are controlled to a specific content include a method (referred to as method α) in which a specific amount of monomers that give each structural unit is charged into a reactor and copolymerized, and a method (referred to as method β) in which two or more liquid crystal polyester resins with different constituent structural units and ratios are dry blended or melt-kneaded (alloyed) to adjust the content of the structural units to the desired level.

[0057] It becomes easy to control the half-width at half maximum (°C) of the Tm peak within the preferable range described later, and from the viewpoint of excellent residence stability and low burr property, the aforementioned method α is preferable. Method β is disclosed in, for example, Japanese Patent Application Laid-Open No. 2015-227404. In this method, since two or more kinds of liquid crystal polyester resins having different properties such as molecular weight and molecular weight distribution are mixed, randomization of the monomer sequence due to transesterification between polymers progresses during melt residence. Therefore, the longer the melt residence time, the more the polymer changes to a polymer having a composition different from that of the liquid crystal polyester before mixing, and at the same time, the molecular weight distribution becomes wider, so that the crystal structure and size become non-uniform. As a result, it melts in a wide temperature range, making it difficult to control the half-width at half maximum (°C) of the Tm peak, and the residence stability and low burr property deteriorate, which is not preferable. On the other hand, in the case of method α, since the randomization of the monomers is almost completed during the polymerization process, the properties of the polymer hardly change even when melt-resided.

[0058] <Composition Containing Electrically Insulating Resin> The composition containing an electrically insulating resin used in the present invention is a composition containing the resin described in detail in the aforementioned <Electrically Insulating Resin> and other components. As the other components, an inorganic filler (B) is preferable. The preferable mode of the inorganic filler (B) will be described in detail in <Inorganic Filler (B)> described later.

[0059] The melting point (Tm) of the electrically insulating resin used in the present invention by differential scanning calorimetry of the electrically insulating resin in the composition is 300 to 340 °C. When Tm is lower than 300 °C, the heat resistance and low burr property decrease. When Tm is higher than 340 °C, since it is necessary to process at a higher temperature, the properties of the resin are altered due to the progress of resin decomposition and the disappearance of entanglement, etc., resulting in a decrease in residence stability and, as a result, a decrease in low burr property. In order for the residence stability and low burr property to be more excellent, Tm is preferably 325 to 340 °C. The above Tm is the endothermic peak temperature (Tm １ ) observed when the composition containing the electrically insulating resin is heated from room temperature under the temperature rising condition of 20 °C / min in differential scanning calorimetry, and after the observation of Tm １This is the peak value of the endothermic peak observed when a sample is held at +20°C for 5 minutes, then cooled to room temperature at a rate of 20°C / min, and then heated again from room temperature at a rate of 20°C / min.

[0060] The composition containing the electrically insulating resin used in the present invention preferably has a crystallization temperature (Tc) of 290 to 325°C as measured by differential scanning calorimetry. Setting Tc within this range further improves retention stability and low burr performance. Even when the thin-wall fluidity of the composition containing the electrically insulating resin is increased to the level required in recent years, from the viewpoint of excellent retention stability and low burr performance, Tc is more preferably 290 to 320°C, and most preferably 300 to 320°C. The above Tc is the endothermic peak temperature (Tm) observed when the composition containing the electrically insulating resin is heated from room temperature at a temperature increase of 20°C / min in differential scanning calorimetry. １ After the observation of Tm １ This is the peak value (exothermic peak temperature) of the exothermic peak observed when a substance is held at a temperature of +20°C for 5 minutes and then cooled to room temperature at a rate of 20°C / min.

[0061] The composition containing the electrically insulating resin used in the present invention with a shear rate of 1000 sec at Tm + 20°C －１ The melt viscosity measured under these conditions is preferably 5.0 to 25.0 Pa·s. The temperature Tm + 20°C is a temperature that is often set as the molding temperature during injection molding, and 1000 sec －１ This shear rate is close to the shear rate applied to the resin during injection molding. By keeping the melt viscosity within this range, the thin-wall fluidity can be met at the level required in recent years. Simply lowering the melt viscosity usually improves thin-wall fluidity but reduces retention stability and low burr properties. However, with the electrically insulating resin used in this invention, it is easy to obtain an excellent resin-metal composite while maintaining retention stability and low burr properties even when the melt viscosity is lowered to the above level.

[0062] The melt viscosity is measured using a capillary rheometer conforming to JIS K 7199 standard (for example, Capillograph F-1 (orifice 0.5φ × 10 mm) (Toyo Seiki Seisakusho)), where the cylinder temperature is set to Tm + 20°C, and the electrically insulating resin dried at 150°C for 3 hours using a hot air dryer is filled and left to stand for 7 minutes, followed by a shear rate of 1000 sec. －１ This value is obtained by measuring the melt viscosity under the specified conditions. A melt viscosity of 5.0 to 20.0 Pa·s is more preferable, 5.0 to 18.0 Pa·s is even more preferable, and 5.0 to 15.0 Pa·s is most preferable.

[0063] The composition containing the electrically insulating resin used in the present invention has a Tm peak full width at half maximum (FWHM) of 5.0 to 20.0°C in differential scanning calorimetry of the electrically insulating resin within the composition. A Tm peak FWHM of 5.0 to 20.0°C indicates that the crystal structure and size of the electrically insulating resin are uniformly controlled, and that there is an appropriate level of interaction between the polymer chains and the surface of the inorganic filler. As a result, even when thin-wall fluidity is improved to the level required in recent years, retention stability and low burr performance can be achieved at a high level.

[0064] If the full width at half maximum (FWHM) of the Tm peak is greater than 20.0°C, the composition containing the electrically insulating resin can flow with less heat and over a wide temperature range, which tends to improve thin-wall fluidity. On the other hand, because the crystal structure and size are non-uniform, the mobility and reactivity of the polymer chains become uneven during melting or solidification. In injection molding, compositions containing the electrically insulating resin undergo repeated melting and solidification at high speed. If the mobility and reactivity of the polymer chains are uneven, the polymer state is unstable during melting, leading to poor retention stability, and during solidification, the proportion of polymer in a semi-molten state that does not completely solidify increases, resulting in poor low-burr properties.

[0065] If the full width at half maximum (FWHM) of the Tm peak is less than 5.0°C, the entanglement and interaction of the electrical insulating resins become too strong, resulting in reduced processability and fluidity.

[0066] To further improve retention stability and low barrier properties, the full width at half maximum is preferably 5.0 to 17.0°C, more preferably 8.0 to 15.0°C, and most preferably 10.0 to 15.0°C.

[0067] In conventional technology, it was common practice to mix two or more different polyester resins to produce liquid crystal polyester resin in order to improve the thin-wall fluidity of compositions containing electrical insulating resins. In this case, as described later, the structure and size of the crystals become non-uniform, and as a result, the composition containing the electrical insulating resin can flow with less heat and over a wide temperature range, thus improving thin-wall fluidity. On the other hand, this had the problem of deteriorating retention stability and low burr properties. Therefore, in conventional technology, it was difficult to achieve a high level of thin-wall fluidity, retention stability, and low burr properties simultaneously.

[0068] The inventors have found that the full width at half maximum (FWHM) of the Tm peak of the electrically insulating resin has a significant influence on controlling retention stability and low burr formation. Specifically, they found that in a composition containing the electrically insulating resin used in the resin-metal composite of the present invention, if the FWHM of the Tm peak of the electrically insulating resin in the composition is within the above range, retention stability and low burr formation can be achieved at a high level even when thin-wall fluidity is improved to the level required in recent years.

[0069] The method for calculating the full width at half maximum (FWHM) of the Tm peak will be explained using Figure 2, a schematic diagram of the Tm peak. A perpendicular line (8) is drawn from the peak top of the Tm peak (6) obtained by the method described above to the baseline (7). When a straight line is drawn passing through the midpoint of the perpendicular line and parallel to the baseline, the distance between the intersection point of this line and the Tm peak (6) is the FWHM (°C) (9).

[0070] The method for controlling the full width at half maximum (FWHM) of the Tm peak to a preferred range is not particularly limited, and various methods can be selected. It is preferable to use the liquid crystal polyester resin (A) as the electrical insulating resin because it makes control easier. Details are described above in <Liquid Crystal Polyester Resin (A)> and <Method for Manufacturing Liquid Crystal Polyester Resin (A)>, and in <Method for Manufacturing a Composition Including an Electrical Insulating Resin> described later, but methods 1 and 2, which are particularly useful for controlling the FWHM of the Tm peak to a preferred range, are excerpted and described below.

[0071] Method 1. Liquid crystal polyester resin (A) is used as the electrical insulating resin, and the liquid crystal polyester resin is manufactured by the "melt polymerization method" with a reaction time of 90 to 140 minutes under reduced pressure.

[0072] Method 2. A composition comprising a liquid crystal polyester resin (A) and an inorganic filler (B) is used as the composition containing the electrical insulating resin, and the composition containing the electrical insulating resin is manufactured by melt kneading. In this case, a single liquid crystal polyester resin (A) is used, without mixing two or more different liquid crystal polyester resins (A).

[0073] It is preferable to satisfy both methods 1 and 2 above, as this makes it easier to control the full width at half maximum of the Tm peak.

[0074] It is preferable that the composition containing the electrical insulating resin contains 10 to 200 parts by weight of the inorganic filler (B) per 100 parts by weight of the electrical insulating resin, from the viewpoint of easily controlling the full width at half maximum of the Tm peak to the aforementioned preferred range and having excellent retention stability and low burr properties. Furthermore, it is preferable that the electrical insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and that the composition containing the electrical insulating resin is a liquid crystal polyester resin composition containing 10 to 200 parts by weight of the inorganic filler (B) per 100 parts by weight of the liquid crystal polyester resin (A). From the viewpoint of balancing low burr properties and processability, the content of the inorganic filler (B) is more preferably 15 parts by weight or more, and even more preferably 20 parts by weight or more. Furthermore, from the viewpoint of fluidity, the content of inorganic filler (B) is preferably 120 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 50 parts by weight or less.

[0075] <Inorganic Fillers (B)> Inorganic fillers (B) are not particularly limited, but examples include fibrous, whisker-like, plate-like, powder-like, and granular fillers. Specifically, fibrous or whisker-like fillers include glass fibers; PAN-based carbon fibers and pitch-based carbon fibers; metal fibers such as stainless steel fibers, aluminum fibers and brass fibers; organic fibers such as aromatic polyamide fibers and liquid crystal polyester fibers; gypsum fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, potassium titanate whiskers, barium titanate whiskers, aluminum borate whiskers, silicon nitride whiskers, and needle-shaped titanium oxide. Plate-like fillers include mica, talc, kaolin, glass flakes, clay, molybdenum disulfide, and wollastonite. Powder-like or granular fillers include silica, glass beads, titanium oxide, zinc oxide, calcium polyphosphate, and graphite. The inorganic filler (B) described above may have its surface treated with a known coupling agent (e.g., a silane-based coupling agent, a titanate-based coupling agent, etc.) or other surface treatment agent. Furthermore, two or more types of fillers may be used in combination. It is preferable to use a plate-shaped filler, as this facilitates controlling the Tc and melt viscosity of the composition containing the electrically insulating resin within the aforementioned preferred range, and provides excellent retention stability and low burr performance. Among these, mica or talc is more preferable.

[0076] <Method for Manufacturing Compositions Containing Electrical Insulating Resins> The method for manufacturing compositions containing electrical insulating resins is not limited and can be manufactured by known methods. Examples include a dry blending method in which an inorganic filler (B) or other solid additives are blended with an electrical insulating resin, a solution blending method in which liquid additives are blended with an electrical insulating resin, a method in which an inorganic filler (B) or other additives are added during the manufacturing (polymerization) of the electrical insulating resin, and a method in which an inorganic filler (B) or other additives are melt-kneaded into an electrical insulating resin. The Tm, full width at half maximum (°C) of the Tm peak, Tc, and shear rate at 1000 sec at Tm + 20°C are also specified. －１From the viewpoint of being able to control the melt viscosity under these conditions to the aforementioned preferred range, melt kneading is preferred.

[0077] Known methods can be used for melt mixing. Applicable equipment for melt mixing includes Banbury mixers, rubber roll machines, kneaders, and single-screw or twin-screw extruders. Among these, twin-screw extruders are preferred. The melt mixing temperature is preferably in the range of Tm-10 to Tm+20°C, from the viewpoint of suppressing exchange reactions such as ester bonding, making it easy to control the full width at half maximum (°C) of the Tm peak within a suitable range, and resulting in excellent retention stability and low burr formation.

[0078] Furthermore, examples of melt-mixing methods include a method in which the electrical insulating resin, inorganic filler (B), and other additives are introduced all at once from a main feeder and mixed (bulk mixing method); a method in which the electrical insulating resin and other additives are introduced from a main feeder and mixed, and then the inorganic filler (B) and other additives are added from a side feeder and mixed (side feed method); and a method in which a composition containing a high concentration of inorganic filler (B) and other additives (master pellet) is prepared, and then the master pellet is mixed with the electrical insulating resin to the specified concentration (master pellet method).

[0079] From the viewpoint of suitably controlling the full width at half maximum (°C) of the Tm peak as described above, and improving retention stability and low burr properties, it is preferable to produce a composition containing an electrical insulating resin by melt-kneading a liquid crystal polyester resin (A) and an inorganic filler (B) as a composition containing an electrical insulating resin. In this case, it is even more preferable to use a single liquid crystal polyester resin (A) rather than using two or more different liquid crystal polyester resins (A). Different liquid crystal polyester resins here refer to "those in which the types or number of structural units constituting the liquid crystal polyester resin are different" and "those in which the types or number of structural units are the same, but the composition ratio of any of the structural units (relative to 100 mol% of all structural units of the liquid crystal polyester resin) is different by 2 mol% or more." When two or more different polyester resins (A) are mixed to produce a liquid crystal polyester resin (A), two or more liquid crystal polyester resins (A) with different properties such as molecular weight and molecular weight distribution are mixed. As a result, the molecular weight distribution broadens as transesterification progresses, and the structure and size of the crystals become non-uniform. As a result, the composition containing the electrically insulating resin begins to melt over a wide temperature range, making it difficult to control the Tm, Tc, and the full width at half maximum (°C) of the Tm peak, which is undesirable.

[0080] Compositions containing electrically insulating resins can be processed into resin components of resin-metal composites by conventional injection molding, extrusion molding, press molding, solution casting, spinning, and other melt molding methods. Examples of resin components include injection-molded products, extruded products, press-molded products, sheets, pipes; various films such as undrawn films, uniaxially oriented films, and biaxially oriented films; and various fibers such as undrawn yarns and super-drawn yarns. Injection molding is particularly preferred from the viewpoint of processability. When melt molding is performed, it is preferable to melt mold at 370°C or below, and more preferably 360°C or below, from the viewpoint of suppressing deterioration of the composition containing the electrically insulating resin and improving mechanical strength. Furthermore, temperatures above the melting point are preferable.

[0081] <Resin-Metal Composite> The resin-metal composite of the present invention comprises a resin member and a metal member, both made from a composition containing an electrically insulating resin. The resin-metal composite may further include members made from other materials. The method for compounding the resin member and the metal member is not particularly limited and includes methods such as the outsert method, in which a molded product of the composition containing the electrically insulating resin (sometimes referred to as the resin member) and a molded product of metal (sometimes referred to as the metal member) are manufactured separately and then press-fitted, or the insert method, in which the metal member is embedded in a mold when the resin member is melt-molded. Both methods can be suitably used. For example, when manufacturing a composite by the insert method, if the retention stability of the composition containing the electrically insulating resin is poor, hesitation is likely to occur at the contact site with the metal member, resulting in poor contact between the resin member and the metal member. As a result, not only is the holding power and strength of the metal member of the resin-metal composite reduced, but it also becomes difficult to ensure insulation, leading to a decrease in product reliability. The composition containing the electrically insulating resin used in the present invention has excellent retention stability, thus solving the above problems and can be suitably used in resin-metal composites comprising a resin member and a metal member. Furthermore, the composition containing the electrically insulating resin used in the present invention also exhibits excellent low burr properties. Therefore, when resin members and metal members are brought into contact with each other by outsert molding or insert molding, it is possible to prevent burrs from becoming debris and adhering to the metal members, which would impair conductivity, and to prevent burrs from blocking contact areas such as metal insertion holes.

[0082] The applications of the resin-metal composite of the present invention are not particularly limited, but it can preferably be used as an electrical or electronic component. Examples of electrical and electronic components include flexible printed circuit boards, laminated circuit boards, printed wiring boards, and three-dimensional circuit boards used in antennas for personal computers, GPS-equipped devices, mobile phones, millimeter-wave and sub-millimeter-wave radars such as collision avoidance radars, and mobile communication and electronic devices such as tablets and smartphones; lamp reflectors and lamp sockets for LEDs, small cells and microcell components for communication base stations of mobile communication terminals, antenna covers, housings, sensors, camera modules, connectors, relay cases and bases, switches, coil bobbins, and capacitors.

[0083] The resin-metal composite of the present invention is manufactured using an electrically insulating resin composition that is excellent in retention stability and low burr, so burr debris is less likely to adhere to the metal parts. For this reason, it can be preferably used in electrical and electronic components that have metal-to-metal contact points. Here, "having metal-to-metal contact points" means that the metal members of the resin-metal composite have a structure that is exposed for the purpose of contacting metal members of other components. When burrs are generated in a resin-metal composite, the burrs become debris and adhere to the metal-to-metal contact points, resulting in poor conductivity. In addition, it becomes difficult to insert the metal members. Therefore, the resin-metal composite of the present invention, which is excellent in low burr, can be preferably used in electrical and electronic components that have metal-to-metal contact points. More preferably, it can be used in connectors, sockets, coil bobbins, capacitors, camera modules, relay cases, flexible printed circuit boards, laminated circuit boards, and printed wiring boards, and most preferably in connectors or sockets.

[0084] The resin-metal composite of the present invention has a resin member having a plurality of metal insertion holes, and the thinnest thickness between adjacent metal insertion holes is preferably 0.50 mm or less, and more preferably 0.01 mm or more and 0.50 mm or less. The effects of the present invention are particularly evident in resin-metal composites having such complex and thin-walled shapes. A schematic diagram of a resin member of a resin-metal composite having such a shape is shown in Figure 1. (1) in Figure 1 is a metal insertion hole. A metal insertion hole is a hole for inserting a metal member. The shape of the metal insertion hole is not limited and can be selected as appropriate. The number of metal insertion holes may be two or more, and there is no upper limit. From the viewpoint of exhibiting the effects of the present invention, the number of metal insertion holes is preferably 10 or more, more preferably 20 or more, and most preferably 30 or more. The distance shown in (3) in Figure 1 indicates the "thinnest thickness of the resin member between adjacent metal insertion holes". Hereafter, (3) in Figure 1 may be referred to as "thinnest thickness". If there are multiple adjacent metal insertion holes, the distance between the thinnest parts is measured. From the viewpoint of achieving the effects of the present invention, the thinnest thickness is more preferably 0.40 mm or less, more preferably 0.30 mm or less, and most preferably less than 0.20 mm.

[0085] In Figure 1, (4) is the distance between the centroids of adjacent metal insertion holes, also known as the pitch distance. From the viewpoint of achieving the effects of the present invention, the pitch distance is preferably 2.0 mm or less, preferably 1.0 mm or less, more preferably 0.60 mm or less, and most preferably 0.40 mm or less. Furthermore, a pitch distance of 0.01 mm or more is preferred.

[0086] Furthermore, the material of the metal component used in the present invention is not limited, and examples include copper, silver, gold, aluminum, nickel, palladium, tin, and platinum. These may be alloys, and their surfaces may be plated.

[0087] The present invention will be described below using examples, but the present invention is not limited to these examples. Examples of the production of an electrically insulating resin are shown in the following production examples 1 to 5.

[0088] [Production Example 1] 808 parts by weight of p-hydroxybenzoic acid (HBA), 88 parts by weight of 6-hydroxy-2-naphthoic acid (HNA), 229 parts by weight of 4,4'-dihydroxybiphenyl (DHB), 161 parts by weight of hydroquinone (HQ), 428 parts by weight of terephthalic acid (TPA), 19 parts by weight of isophthalic acid (IPA), and 1278 parts by weight of acetic anhydride (1.07 equivalents of the total phenolic hydroxyl groups) were charged into a 5 L reaction vessel equipped with a stirring blade and a distillation tube. The mixture was reacted at 145°C for 120 minutes with stirring under a nitrogen gas atmosphere, and then the temperature was raised from 145°C to 360°C over 4 hours. The polymerization temperature was then maintained at 360°C, and the pressure was reduced from atmospheric pressure to 1.0 mmHg (133 Pa). Polymerization was completed when the reaction time under reduced pressure reached 120 minutes. Next, the polymer was extruded in strand form through a nozzle having a single circular discharge port with a diameter of 6 mm, and then pelletized with a cutter to obtain liquid crystal polyester resin (A-1).

[0089] [Production Example 2] Liquid crystal polyester resin (A-2) was obtained in the same manner as in Production Example 1, except that the monomer charge amounts were changed to 792 parts by weight of HBA, 88 parts by weight of HNA, 251 parts by weight of DHB, 155 parts by weight of HQ, 457 parts by weight of TPA, and 1278 parts by weight of acetic anhydride (1.07 equivalents of the total phenolic hydroxyl groups).

[0090] [Production Example 3] Liquid crystal polyester resin (A-3) was obtained in the same manner as in Production Example 1, except that the monomer amounts were changed to 970 parts by weight of HBA, 261 parts by weight of DHB, 103 parts by weight of HQ, 272 parts by weight of TPA, 117 parts by weight of IPA, and 1278 parts by weight of acetic anhydride (1.07 equivalents of the total phenolic hydroxyl groups).

[0091] [Production Example 4] 808 parts by weight of HBA, 88 parts by weight of HNA, 229 parts by weight of DHB, 161 parts by weight of HQ, 428 parts by weight of TPA, 19 parts by weight of IPA, and 1278 parts by weight of acetic anhydride (1.07 equivalents of the total phenolic hydroxyl groups) were charged into a 5 L reaction vessel equipped with a stirring blade and a distillation tube. The mixture was reacted at 145°C for 120 minutes with stirring under a nitrogen gas atmosphere, and then the temperature was raised from 145°C to 360°C over 4 hours. The polymerization temperature was then maintained at 360°C, and the pressure was reduced from atmospheric pressure to 1.0 mmHg (133 Pa). Polymerization was completed when the reaction time under reduced pressure reached 80 minutes. Next, the polymer was extruded in strand form through a nozzle with one circular discharge port of 6 mm in diameter, and pelletized with a cutter to obtain liquid crystal polyester resin (A-4).

[0092] [Production Example 5] Decamethylenediamine and equimolar salts of terephthalic acid were charged into a 5 L reaction vessel equipped with a stirring blade and a distillation tube. To this, 0.5 mol% of decamethylenediamine was added in excess relative to the total amount of decamethylenediamine, and then 300 parts by weight of water were charged for a total of 700 parts by weight of these raw materials. The reaction vessel was sealed and heated to 240°C while stirring under a nitrogen gas atmosphere. After the pressure inside the reaction vessel reached 2.0 MPa, the pressure inside the reaction vessel was maintained at 2.0 MPa and the temperature at 240°C for 120 minutes while releasing water from the system. Thereafter, the contents were discharged from the reaction vessel and vacuum dried at 100°C for 24 hours to obtain a polyamide resin oligomer. The obtained polyamide resin oligomer was pulverized and dried, and solid-phase polymerized at 240°C under reduced pressure of 50 Pa to obtain polyamide resin (polydecamethylene terephthalamide (polyamide 10T)) (C-1).

[0093] The liquid crystal polyester resin (A) obtained in manufacturing examples 1 to 4 was evaluated according to the following (1) and (2). The results are summarized in Table 1.

[0094] (1) Composition analysis of liquid crystal polyester resin (A) 0.1 mg of pulverized liquid crystal polyester resin pellets were decomposed into monomers by adding 2 μL of tetramethylammonium hydroxide 25% methanol solution. The obtained monomer solution was then mixed with an appropriate amount of DMSO-d ６ The substance was dissolved and observed using a UNITY INOVA 500 NMR spectrometer (Varian Corporation) at a frequency of 500 MHz and at room temperature. １ 1H-NMR measurements were performed. The composition ratio was determined from the area ratio of the peaks originating from each observed structural unit.

[0095] (2) Measurement of the melting point (Tm(A)) of the liquid crystal polyester resin (A) Using differential scanning calorimetry (DSC, TA-Q200 manufactured by TA Instruments Corporation), the liquid crystal polyester resin (A) was heated from room temperature under a temperature increase of 20°C / min, and the endothermic peak temperature (Tm １ After the observation of (A), Tm １ The melting point (Tm(A)) was defined as the endothermic peak temperature observed when the sample was held at +20°C for 5 minutes, cooled to room temperature at a rate of 20°C / min, and then heated again at a rate of 20°C / min.

[0096]

[0097] Next, the inorganic filler (B) used is shown below. Inorganic filler (B) (B-1) Mica manufactured by Yamaguchi Mica (AB-25S) (B-2) Milled fiber manufactured by Nippon Electric Glass (40M-10A) The above inorganic filler (B) was added to the electrically insulating resins of production examples 1 to 4 to prepare compositions containing the electrically insulating resin.

[0098] [Examples 1-3, Comparative Examples 1-3] Compositions containing electrical insulating resins were prepared using a Toshiba Machine TEM35B twin-screw extruder equipped with a side feeder. The electrical insulating resins (A-1 to A-4) obtained in each production example were fed from the hopper of the twin-screw extruder in the proportions shown in Table 2, and the inorganic filler (B) was fed from the side feeder in the proportions shown in Table 2. The mixture was melt-kneaded to form pellets. The cylinder temperature was set to the melting point of the electrical insulating resin. When mixing two or more types of electrical insulating resins, the temperature was set to the melting point of the electrical insulating resin with the higher melting point. The pellets of the obtained compositions containing electrical insulating resins were dried at 150°C for 3 hours using a hot air dryer, and the following evaluations (3) to (7) were performed. The results are shown in Table 2.

[0099] [Example 4] A composition containing an electrically insulating resin was prepared using a Toshiba Machine TEM35B twin-screw extruder equipped with a side feeder. The electrically insulating resin (C-1) obtained in Production Example 5 was fed from the hopper of the twin-screw extruder in the proportions shown in Table 2, and the inorganic filler (B) was fed from the side feeder in the proportions shown in Table 2, and the mixture was melt-kneaded to form pellets. The cylinder temperature was set to the melting point of the electrically insulating resin + 10°C. The pellets of the obtained composition containing the electrically insulating resin were vacuum-dried at 140°C for 5 hours using a vacuum heating dryer, and then evaluated according to (3) to (7) below. The results are shown in Table 2.

[0100] (3) Measurement of Tm and the full width at half maximum of the Tm peak. The measurements were performed using differential scanning calorimetry (DSC, TA-Q200, TA Instruments Inc.) under the following conditions: 10 mg of the composition containing the electrically insulating resin was heated from room temperature at a rate of 20°C / min, and the endothermic peak temperature (Tm) was measured. １ After the observation of Tm １The endothermic peak temperature observed when the sample was held at +20°C for 5 minutes, cooled to room temperature at a rate of 20°C / min, and then heated again at a rate of 20°C / min was defined as the melting point (Tm). A schematic diagram of the resulting Tm peak is shown in Figure 2. A perpendicular line (Figure 2(8)) was drawn from the peak top of the Tm peak (Figure 2(6)) to the baseline (Figure 2(7)). A straight line was drawn passing through the midpoint of the perpendicular and parallel to the baseline. The distance between the intersection points of the Tm peak (Figure 2(6)) and the perpendicular line was defined as the full width at half maximum (°C) (Figure 2(9)). In Table 2, these values ​​are listed as "Tm (°C)" and "Full width at half maximum of Tm peak (°C)," respectively.

[0101] (4) Measurement of Tc A differential scanning calorimeter (DSC, TA-Q200 manufactured by TA Instruments Inc.) was used to measure Tc under the following conditions: 10 mg of the composition containing an electrically insulating resin was heated from room temperature at a rate of 20°C / min, and the endothermic peak temperature (Tm) was measured. １ After the observation of Tm １ The crystallization temperature (Tc) was defined as the exothermic peak observed when the sample was held at +20°C for 5 minutes and then cooled to room temperature at a rate of 20°C / min. In Table 2, this is indicated as "Tc (°C)".

[0102] (5) The melt viscosity of the composition containing the electrically insulating resin was measured using a Capillograph F-1 (orifice 0.5φ × 10 mm) (Toyo Seiki Seisakusho) under the following conditions: The cylinder temperature was set to Tm + 20°C, pellets of the composition containing the electrically insulating resin were filled and left for 7 minutes, and then the shear rate was set to 1000 sec. －１ The melt viscosity was measured under the following conditions. Table 2 will list the values ​​as "Melting Viscosity (Pa·s)".

[0103] (6) Retention Stability The retention stability in the present invention is evaluated by the following method. A composition containing an electrically insulating resin was measured using a rheometer PhysicaMCR501 (rheometer manufactured by Anton Paertton) under the following conditions. In the stress relaxation mode, the gap of a parallel plate with a diameter of 25 mm was set to 1 mm, the strain to 10%, and stress relaxation measurements were performed at a temperature of Tm + 20°C until a relaxation time (τ) of 200 seconds was obtained to obtain a stress relaxation measurement spectrum. A figure showing the obtained stress relaxation spectrum is shown in Figure 3. The x axis represents the relaxation time (= t (s)), the y axis represents the shear stress (= τ (Pa)), and the x and y axes are on a logarithmic scale. The ratio (w' / v') of the absolute value of the slope (v') of the line V (Figure 3(11)) passing through the x-axis points 1 and 10 in the obtained stress relaxation spectrum (Figure 3(10)) to the absolute value of the slope (w') of the line W (Figure 3(12)) passing through the x-axis points 50 and 100 was calculated. When w' / v' is 2.00 or less, the retention stability is excellent. In Table 2, this is written as Retention Stability (w' / v'). The smaller the value, the better the retention stability. w' / v' of 1.80 or less is better, and 1.60 or less is even better. The minimum value of w' / v' is 0.

[0104] Figure 4 shows the stress relaxation spectrum of a composition containing an electrically insulating resin used in the resin-metal composite of the present invention (Figure 4(14)), and the stress relaxation spectrum of a conventional composition containing an electrically insulating resin used in resin-metal composites (Figure 4(13)). The stress relaxation spectrum of the composition containing an electrically insulating resin of the present invention (Figure 4(14)) has a (w' / v') of 2.00 or less, while the stress relaxation spectrum of a conventional composition containing an electrically insulating resin (Figure 4(13)) has a (w' / v') greater than 2.00.

[0105] Compared to the composition containing the electrically insulating resin used in the present invention, it can be seen that the applied stress in conventionally used compositions containing the electrically insulating resin decreases significantly with respect to the relaxation time (t). This indicates that the properties of conventionally used compositions containing the electrically insulating resin (viscosity, entanglement of polymers, packing properties, arrangement order of monomer compositions, etc.) tend to change depending on the residence time, indicating poor residence stability. When resin-metal composites are manufactured using such compositions containing electrically insulating resins with poor residence stability, various problems occur, such as drowning and stringing during injection molding, silver formation on the surface of the molded product, decreased insulation due to hesitation, decreased adhesion between metal and resin components, and burr formation. As is clear from Table 2, the composition containing the electrically insulating resin with excellent residence stability in this evaluation is also a material with excellent low burr properties as measured by the method described in (7) below.

[0106] (7) A composition containing a low-burr electrically insulating resin was subjected to injection molding in a TR30EHA injection molding machine (manufactured by Sodick) under the following conditions to obtain 100 connector molded products. A mold was used that could produce a connector molded product with a terminal pitch of 0.30 mm, a minimum thickness of 0.10 mm, 70 metal insertion holes, and external dimensions of 3 mm width × 1 mm height × 23 mm length. The cylinder temperature was set to the melting point of the electrically insulating resin + 30°C, the mold temperature to 130°C, the injection speed to 300 mm / s, and the peak pressure to 200 MPa. Figure 1 is a perspective view of the obtained connector molded product.

[0107] The terminal surfaces of the molded connectors were observed using a microscope (Keyence VHX-7000) to check for the presence or absence of burrs, and the burr occurrence rate was calculated. In Table 2, the "burr occurrence rate (%)" is indicated. This evaluation method is performed under harsh conditions where burrs are more likely to occur than usual. If the burr occurrence rate is 20% or less using this evaluation method, burrs will hardly occur under normal manufacturing conditions. Since the connector described in the example has a burr occurrence rate of 20% or less, if metal components such as metal terminals are attached to such a resin component to form a resin-metal composite component, a highly reliable resin-metal composite component can be obtained without the influence of burrs. When a resin component with suppressed burr generation and a metal component are brought into contact with each other by outsert molding or insert molding to form a resin-metal composite, it is possible to prevent burrs from becoming debris and adhering to the metal component, which would reduce conductivity and communication reliability, and to prevent burrs from blocking metal insertion holes and reducing product yield. Therefore, by using an electrically insulating resin with excellent properties in this regard, a superior resin-metal composite can be obtained.

[0108]

[0109] The results in Table 2 show that if Tm and the full width at half maximum of the Tm peak are within a specific range, the (w' / v') value is 2.00 or less, indicating excellent retention stability and low barrier properties.

[0110] Furthermore, comparing Comparative Example 3, which obtained a composition containing an electrically insulating resin by mixing two or more different polyester resins (A), with Examples 1 and 3, which used a single liquid crystal polyester resin (A), it can be seen that Examples 1 and 3 have superior retention stability and burr generation rate. This is because, in Comparative Example 3, mixing two or more liquid crystal polyester resins (A) with different properties such as molecular weight, molecular weight distribution, and melting point made it difficult to control the full width at half maximum (FWHM) within a specific range.

[0111] The resin-metal composite of the present invention has a low burr generation rate, making it suitable for electrical and electronic components such as connectors, relays, switches, coil bobbins, and camera modules, as well as mechanical components.

[0112] 1. Metal insertion hole 2. Resin member 3. Thinnest thickness of the resin member between adjacent metal insertion holes 4. Pitch distance 5. Gate position 6. Tm peak 7. Baseline of peak 6 8. Perpendicular line between the peak top of peak 6 and baseline 7 9. Full width at half maximum (°C) of the Tm peak 10. Stress relaxation spectrum of a composition containing an electrically insulating resin 11. Line V 12. Line W 13. Stress relaxation spectrum of a composition containing an electrically insulating resin used in conventional resin-metal composites ((w' / v') is greater than 2.00) 14. Stress relaxation spectrum of a composition containing an electrically insulating resin used in the resin-metal composite of the present invention ((w' / v') is 2.00 or less)

Claims

1. A resin-metal composite comprising a resin member and a metal member, wherein the melting point (Tm) of the electrical insulating resin in the composition, determined by differential scanning calorimetry, is 300 to 340°C, and the full width at half maximum of the Tm peak is 5.0 to 20.0°C. The above Tm is the endothermic peak temperature (Tm) observed when the composition containing the electrical insulating resin is heated from room temperature at a temperature increase of 20°C / min in differential scanning calorimetry. １ After the observation of Tm １ Tm is the endothermic peak temperature observed when a sample is held at +20°C for 5 minutes, then cooled to room temperature at a rate of 20°C / min, and then heated again from room temperature at a rate of 20°C / min. Furthermore, when a perpendicular line is drawn from the peak top of the obtained Tm peak to the baseline, and a straight line is drawn through the midpoint of the perpendicular line and parallel to the baseline, the distance between the intersection points of the two points with the Tm peak is the full width at half maximum (°C).

2. The resin-metal composite according to claim 1, wherein the resin-metal composite is an electrical / electronic component having metal-to-metal contact points.

3. The resin-metal composite according to claim 1 or claim 2, wherein the resin member of the resin-metal composite has a plurality of metal insertion holes, and the thinnest thickness between adjacent metal insertion holes is 0.50 mm or less.

4. A resin-metal composite according to claim 1 or 2, wherein the composition containing an electrically insulating resin has a crystallization temperature (Tc) of 290 to 325°C as determined by differential scanning calorimetry: The above Tc is the endothermic peak temperature (Tm) observed when the composition containing the electrically insulating resin is heated from room temperature at a temperature increase of 20°C / min in differential scanning calorimetry. １ After the observation of Tm １ This is the exothermic peak temperature observed when a substance is held at +20°C for 5 minutes and then cooled to room temperature at a rate of 20°C / min.

5. The resin-metal composite according to claim 1 or claim 2, wherein the electrically insulating resin is a resin selected from polyamide resin, polyimide resin, polyphenylene sulfide resin, polyetheretherketone resin, polytetrafluoroethylene resin, and liquid crystal polyester resin.

6. The resin-metal composite according to claim 1 or claim 2, wherein the electrically insulating resin is a liquid crystal polyester resin.

7. The resin-metal composite according to claim 1 or 2, wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, based on 100 mol% of the total structural units.

8. The resin-metal composite according to claim 1 or 2, wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and is a liquid crystal polyester resin that contains the following structural units (III) and (IV) and satisfies the following formulas (a) and (b): 5 ≤ [IV] ≤ 18 ... (a) 0 < [III] / [IV] < 1.5 ... (b) [III] and [IV] represent the content (mol%) of structural units (III) and (IV) per 100 mol% of total structural units of the liquid crystal polyester resin (A), respectively.

9. A resin-metal composite according to claim 1 or 2, wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, per 100 mol% of total structural units, and the liquid crystal polyester resin contains the following structural units (I) and (II), and the molar ratio of structural units (I) to (II) ([I] / [II]) is 5 to 20: [I] and [II] each represent the content (mol%) of structural units (I) and (II) per 100 mol% of total structural units of the liquid crystal polyester resin (A).

10. The resin-metal composite according to claim 1 or claim 2, wherein the composition comprising an electrically insulating resin further comprises an inorganic filler (B), and the inorganic filler (B) is contained in an amount of 10 to 200 parts by weight per 100 parts by weight of the electrically insulating resin.

11. The resin-metal composite according to claim 1 or 2, wherein the electrically insulating resin is a liquid crystal polyester resin (A) containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, based on 100 mol% of total structural units, and the composition containing the electrically insulating resin is a liquid crystal polyester resin composition containing 10 to 200 parts by weight of inorganic filler (B) per 100 parts by weight of liquid crystal polyester resin (A).

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