Adhesive composition and adhesive composition for forming a flat cable

Abstract

To provide an adhesive composition which has a low dielectric loss tangent, has excellent heat resistance even in one-drop use, and is also excellent in solubility to an organic solvent.SOLUTION: An adhesive composition contains a polyester-based resin containing a structural unit derived from polyvalent carboxylic acids and a structural unit derived from polyhydric alcohols, wherein the polyester-based resin satisfies all of the following requirements (A) to (D). (A): The structural unit derived from the polyvalent carboxylic acids contains 90 mol% or more of the structural unit derived from aromatic polyvalent carboxylic acids with respect to the total structural units derived from the polyvalent carboxylic acids, (B): the structural unit derived from the polyhydric alcohols contains a structural unit derived from aliphatic diols having a side chain, (C): the polyester-based resin is a crystalline polyester-based resin, and (D): a dielectric loss tangent (α) at 10 GHz is 0.01 or less (temperature of 23°C and relative humidity of 50%RH).

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition containing a polyester resin and an adhesive composition for forming a flat cable, and more specifically to an adhesive composition that has a low dielectric loss tangent, excellent heat resistance even when used in a one-component form, and excellent solubility in organic solvents. [Background technology]

[0002] Polyester resins have been used in a wide range of applications, such as films, PET bottles, fibers, toner, electrical components, adhesives, and pressure-sensitive adhesives, due to their excellent heat resistance, chemical resistance, durability, and mechanical strength. In addition, polyester resins have high polarity due to their polymer structure, and are therefore known to exhibit excellent adhesion to polar polymers such as polyester, polyvinyl chloride, polyimide, and epoxy resin, as well as to metal materials such as copper and aluminum. Taking advantage of such excellent adhesive properties, it is used as an adhesive for various applications, and recently, its application as an adhesive for flat cables used in wiring within electrical equipment has been attracting attention.

[0003] In recent years, in response to the increasing complexity of internal wiring in computers, liquid crystal displays, mobile phones, printers, automobiles, home appliances, copiers, and various other electrical devices, flat cables have come into use to reduce the labor required for wiring and prevent incorrect wiring.

[0004] The term "flat cable" generally refers to a film (including tape and sheet). An insulating film is prepared by laminating an adhesive layer on a substrate (insulating layer) of the same shape, and multiple conductors are arranged in parallel between the adhesive layers of two insulating films. The adhesive layers are then overlapped to form the conductors. The flat cable is manufactured by sandwiching the cable and heat sealing it. The cable has a structure that includes a conductor and has an insulating layer on both sides of the outside of the cable. As an adhesive used for forming a flat cable, a solvent-soluble crystalline polyester resin is used because of advantages such as high adhesiveness and high heat resistance even in one-component use (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in recent years, with the technological development of thin TVs, game devices, etc. that handle high-definition video and video data, the need for flexible flat cables that can transmit signals faster and with less loss has been increasing. For the adhesive layer used therein, in addition to conventional adhesiveness and heat resistance, low dielectric properties such as low dielectric constant and low dielectric tangent, particularly low dielectric tangent, are strongly required.

[0007] In the disclosed technology of Patent Document 1 above, it is described that by using a specific crystalline polyester resin as an adhesive, high adhesiveness and heat resistance are achieved, but the low dielectric properties are not considered and it does not meet the recent requirements.

[0008] Therefore, in view of such circumstances, an object of the present invention is to provide an adhesive composition containing a polyester-based resin having low dielectric properties, particularly low dielectric tangent, and also excellent in adhesiveness, heat resistance, and solvent solubility.

Means for Solving the Problems

[0009] However, as a result of intensive research by the present inventor in view of such circumstances, it has been found that the following adhesive composition meets the object of the present invention, and the present invention has been completed. That is, the present invention relates to an adhesive composition containing a polyester resin containing a structural unit derived from polycarboxylic acids and a structural unit derived from polyhydric alcohols, wherein the polyester resin is a polyester resin that satisfies all of the following requirements (A) to (D). (A): The structural unit derived from polycarboxylic acids contains 90 mol% or more of the structural unit derived from aromatic polycarboxylic acids with respect to the entire structural unit derived from the polycarboxylic acid component. (B): The structural unit derived from polyhydric alcohols contains a structural unit derived from aliphatic diols having side chains. (C): It is a crystalline polyester resin. (D): The dielectric loss tangent (α) at 10 GHz is 0.01 or less (temperature 23°C, relative humidity 50%RH).

[0010] As described in Patent Document 1 above, usually, although crystalline polyester resins are excellent in adhesiveness and heat resistance, generally, they have high dielectric constant and dielectric loss tangent, and it has been difficult to use them as adhesives having low dielectric characteristics required in recent years. The present inventor has studied the composition of monomers constituting the polyester resin and found a structure effective for reducing the dielectric loss tangent, resulting in an adhesive composition having a lower dielectric loss tangent than conventional crystalline polyester resins and also excellent in adhesiveness, heat resistance, and solvent solubility, thereby completing the present invention.

Effects of the Invention

[0011] The adhesive composition of the present invention forms an adhesive having a low dielectric loss tangent and excellent adhesiveness, heat resistance, and solvent solubility. In particular, such an adhesive composition is effective as an adhesive used in the production of flat cables and the like.

[0012] In the present invention, it is presumed that a low dielectric loss tangent can be achieved by containing a structural unit derived from an aromatic polycarboxylic acid and a structural unit derived from a diol having a side chain in the structure of the polyester resin used in the adhesive composition.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the configuration of the present invention will be described in detail, but these show an example of a preferred embodiment. In the present invention, the “-like” attached after the compound name is a concept that includes not only the compound but also derivatives of the compound. For example, the term “carboxylic acids” includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylates, carboxylic anhydrides, carboxylic acid halides, and carboxylic acid esters.

[0014] <Polyester resin> First, the polyester resin used in the present invention will be described. The polyester resin used in the present invention contains structural units derived from polycarboxylic acids and structural units derived from polyhydric alcohols in the molecule. Preferably, it is a polyester resin obtained by reacting polycarboxylic acids and polyhydric alcohols and forming an ester bond.

[0015] 〔Structural units derived from polycarboxylic acids〕 The content of the structural units derived from aromatic polycarboxylic acids in the polyester resin used in the present invention is 90 mol% or more based on the total structural units derived from polycarboxylic acids (requirement (A)). Such content is preferably 92 mol% or more, more preferably 95 mol% or more, particularly preferably 98 mol% or more, and most preferably 100 mol%. If the content of aromatic polycarboxylic acids is too small, the long-term durability in a wet and hot environment may deteriorate, or the dielectric loss tangent tends to increase.

[0016] The content (molar ratio) of the structural units derived from aromatic polycarboxylic acids with respect to the total polycarboxylic acids is determined from the following formula. Content of structural units derived from aromatic acids (mol%) = (Structural units derived from aromatic polycarboxylic acids (mol) / Structural units derived from polycarboxylic acids (mol)) × 100

[0017] Moreover, the content of the structural unit derived from aromatic polycarboxylic acids in the entire polyester resin is preferably 15 to 70% by weight, more preferably 20 to 65% by weight, still more preferably 25 to 60% by weight, and particularly preferably 30 to 55% by weight. When the content of the structural unit derived from aromatic polycarboxylic acids is too small, the dielectric tangent tends to increase, and when it is too large, the adhesiveness tends to be insufficient.

[0018] Examples of the structural unit derived from polycarboxylic acids include the structural unit derived from aromatic polycarboxylic acids described later; the structural unit derived from alicyclic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and its acid anhydride; and the structural unit derived from aliphatic polycarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. One or more polycarboxylic acids can be used.

[0019] Examples of the structural unit derived from the above aromatic polyvalent carboxylic acids include structural units derived from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, dimethyl isophthalate, orthophthalic acid, naphthalenedicarboxylic acid, dimethyl naphthalenedicarboxylate, biphenyldicarboxylic acid, and their derivatives (aromatic dicarboxylic acids). Further, structural units derived from aromatic oxycarboxylic acids such as p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid can be mentioned. Furthermore, the structural unit derived from a polyfunctional aromatic polyvalent carboxylic acid having three or more functional groups introduced for the purpose of imparting a branched skeleton or acid value to the polyester resin is also included in the structural unit derived from the above aromatic polyvalent carboxylic acids. Examples of the structural unit derived from a polyfunctional aromatic polyvalent carboxylic acid having three or more functional groups include structural units derived from trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride, etc.

[0020] Among these, the structural unit derived from aromatic dicarboxylic acids is preferable, more preferably the structural unit derived from terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl isophthalate, or dimethyl naphthalenedicarboxylate. From the viewpoint of low dielectric tangent, the structural unit derived from dimethyl naphthalenedicarboxylate is particularly preferable. Further, it is preferable to have a structural unit derived from terephthalic acid, more preferably 35 to 100 mol%, particularly preferably 40 to 90 mol%, and still more preferably 45 to 80 mol% based on the total structural units derived from the polyvalent carboxylic acid component. If the content of the structural unit derived from terephthalic acid is too small, the polyester resin tends to be amorphous and the heat resistance becomes insufficient. If it is too large, the crystallinity becomes too strong and the solvent solubility tends to be insufficient.

[0021] In addition, structural units derived from aromatic dicarboxylic acids having a sulfonic acid group such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5(4-sulfophenoxy)isophthalic acid, and structural units derived from aromatic dicarboxylates having a sulfonate group such as metal salts and ammonium salts thereof are preferably contained in an amount of 10 mol% or less, more preferably 5 mol% or less, particularly preferably 3 mol% or less, still more preferably 1 mol% or less, and most preferably 0 mol% based on the total amount of polycarboxylic acids from the viewpoint of the low dielectric tangent property of the polyester resin.

[0022] [Structural units derived from polyhydric alcohols] The structural units derived from polyhydric alcohols include structural units derived from aliphatic diols having a side chain (requirement (B)) from the viewpoint of reducing the dielectric tangent. Here, the side chain refers to an organic group bonded to the main chain, and the main chain refers to an organic group connecting two hydroxyl groups of the diol.

[0023] Examples of the structural units derived from aliphatic diols having a side chain include structural units derived from 1,2-propylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, dimer diol, etc. Among them, from the viewpoint of reducing the dielectric tangent, it is preferable that the carbon number of the side chain is 3 or more, more preferably 5 or more, still more preferably 7 or more. In particular, from the viewpoint of increasing the side chain content and reducing the dielectric tangent without significantly impairing the crystallinity of the polyester resin, the structural units derived from dimer diol are preferable.

[0024] Examples of the structural units derived from the above-mentioned dimer diols include structural units derived from dimer diols which are reduction products of dimer acids (mainly those having 36 to 44 carbon atoms) derived from, for example, oleic acid, linoleic acid, linolenic acid, erucic acid, etc., and structural units derived from hydrogenated products thereof. Among these, from the viewpoint of suppressing gelation during the production of polyester resins, structural units derived from hydrogenated products are preferred.

[0025] In addition, as the structural units derived from aliphatic diols having side chains, those having a primary hydroxyl group are preferred in terms of easily increasing the molecular weight of the polyester resin, and those having only a primary hydroxyl group are more preferred.

[0026] The content of the structural units derived from aliphatic diols having side chains with respect to the total polyhydric alcohols is preferably 2 to 50 mol%, more preferably 3 to 40 mol%, particularly preferably 5 to 30 mol%, and still more preferably 7 to 20 mol%. If the content of the structural units derived from aliphatic diols having side chains is too small, the low dielectric tangent property tends to be inferior, and if it is too large, the polyester resin tends to be amorphous and the heat resistance becomes insufficient.

[0027] Also, the content of the structural units derived from aliphatic diols having side chains with respect to the total polyester resin is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, particularly preferably 12 to 40% by weight, and still more preferably 15 to 30% by weight. If the content of the diol having side chains is too small, the low dielectric tangent property tends to be inferior, and if it is too large, the polyester resin tends to be amorphous and the heat resistance becomes insufficient.

[0028] Examples of the structural units derived from other polyhydric alcohols include structural units derived from bisphenol skeleton-containing monomers, aliphatic polyhydric alcohols having no side chains, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols. The structural units derived from polyhydric alcohols may contain one or more kinds.

[0029] Examples of the structural unit derived from a monomer containing a bisphenol skeleton include structural units derived from bisphenol A, bisphenol B, bisphenol E, bisphenol F, bisphenol AP, bisphenol BP, bisphenol P, bisphenol PH, bisphenol S, bisphenol Z, 4,4'-dihydroxybenzophenone, bisphenol fluorene, biphenylphenol fluorene, and their hydrogenated products, and structural units derived from glycols such as ethylene oxide adducts obtained by adding 1 to several moles of ethylene oxide or propylene oxide to the hydroxyl groups of bisphenols, and propylene oxide adducts.

[0030] Examples of the structural unit derived from an aliphatic polyhydric alcohol having no side chain include structural units derived from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, etc. Among them, from the viewpoint of facilitating crystallization of the polyester resin, it is preferable to contain a structural unit derived from 1,4-butanediol, and such a content is preferably 30 mol% or more, particularly preferably 40 mol% or more, and more preferably 50 mol% or more.

[0031] Examples of the structural unit derived from an alicyclic polyhydric alcohol include structural units derived from 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecanedimethanol, spiroglycol, etc.

[0032] Examples of the structural unit derived from an aromatic polyhydric alcohol include structural units derived from paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenyleneglycol, ethylene oxide adducts of 1,4-phenyleneglycol, etc.

[0033] In addition, structural units derived from glycols containing ether bonds such as diethylene glycol, triethylene glycol, dipropylene glycol, and further polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. preferably have a content of 20% by weight or less, more preferably 15% by weight or less, particularly preferably 10% by weight or less, still more preferably 5% by weight or less, and most preferably 0% by weight, based on the total amount of the polyester resin, from the viewpoint of low dielectric tangent.

[0034] In the present invention, from the viewpoint of low dielectric tangent, it is preferable to increase the content of aromatic rings in the structure of the polyester resin. The aromatic ring content based on the total amount of the polyester resin is preferably 5% by weight or more, more preferably 10% by weight or more, particularly preferably 15% by weight or more, still more preferably 20% by weight or more. The upper limit is usually 50% by weight.

[0035] Here, the definition and calculation method of the aromatic ring content in the present invention are as follows. The aromatic ring content is the weight ratio occupied by the atoms constituting the aromatic rings in the polyester resin. Note that for the two aromatic ring portions derived from the bisphenol skeleton, since they do not contribute to the low dielectric properties, they are not included in the aromatic ring content in the present invention. The reason why the two aromatic ring portions derived from the bisphenol skeleton do not contribute to the low dielectric tangent is not clear, but it is presumed that, for example, due to steric factors, the two aromatic rings derived from the bisphenol skeleton cannot participate in the stacking of aromatic rings.

[0036] The aromatic ring content is calculated from the composition of the polyester resin. The calculation method is as follows. Aromatic ring content = A1×(a11×m11 + a12×m12 + a13×m13···) / (x1 - y1) + A2×(a21×m21 + a22×m22 + a23×m23···) / (x2 - y2) + A3×(a31×m31 + a32×m32 + a33×m33···) / (x3 - y3)··· A: Content (wt%) of structural units derived from each monomer in the polyester resin a: Atomic weight of atoms constituting the aromatic ring in each monomer (for example, 12 for carbon, 14 for nitrogen, etc. When there are two or more kinds of atoms, it corresponds to a11, a12, a13,... in the above formula. For example, a11: carbon, a12: nitrogen, a13: oxygen.) m: Number of atoms constituting the aromatic ring in each monomer x: Molecular weight of each monomer y: Total formula weight of leaving groups in each monomer Regarding the two aromatic ring sites derived from the bisphenol skeleton, for the above reasons, they are not included as atoms constituting the aromatic ring (handled as m = 0).

[0037] In addition, oxycarboxylic acid compounds having a hydroxyl group and a carboxyl group in their molecular structure can also be used as raw material compounds for the polyester resin. Examples of such oxycarboxylic acid compounds include 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, 4,4-bis(p-hydroxyphenyl)valeric acid, and the like.

[0038] In the present invention, from the viewpoint of low dielectric loss tangent, it is preferable to increase the side chain content. The side chain content with respect to the entire polyester resin is preferably 2 wt% or more, more preferably 3 wt% or more, particularly preferably 5 wt% or more, and still more preferably 7 wt% or more from the viewpoint of low dielectric loss tangent. The upper limit is usually 50 wt%. 。

[0039] Here, the definition and calculation method of the side chain content in the present invention are as follows. The side chain content is the weight ratio occupied by the carbon atoms of the side chains derived from monomers having side chains in the polyester resin.

[0040] The side chain content is determined by calculation from the composition of the polyester resin. Such a calculation method is as follows. Side chain content = A1×12×m1 / (x1 - y1) + A2×12×m2 / (x2 - y2) + A3×12×m3 / (x3 - y3) ··· A: Content (wt%) of the structural unit derived from each monomer in the polyester resin m: Number of carbons constituting the side chain in each monomer x: Molecular weight of each monomer y: Total formula weight of the leaving groups in each monomer

[0041] For the polyester resin used in the present invention, for the purpose of introducing a branched skeleton, at least one selected from the group consisting of the content of the structural unit having an aromatic ring of a polycarboxylic acid having three or more functional groups and the content of the structural unit having an aromatic ring of a polyalcohol having three or more functional groups may be copolymerized.

[0042] In that case, examples of the content of the structural unit derived from polycarboxylic acids having three or more functional groups include structural units derived from trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride, and the like. Also, examples of the structural unit derived from polyalcohols having three or more functional groups include structural units derived from glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and the like. For the structural unit derived from polycarboxylic acids having three or more functional groups and the structural unit derived from polyalcohols having three or more functional groups, one kind or two or more kinds can be used respectively.

[0043] When using at least one selected from the group consisting of structural units derived from polycarboxylic acids having three or more functional groups and structural units derived from polyhydric alcohols having three or more functional groups for the purpose of introducing a branched skeleton, the content of the structural units derived from polycarboxylic acids having three or more functional groups with respect to the total structural units derived from polycarboxylic acids, or the content of the structural units derived from polyhydric alcohols having three or more functional groups with respect to the total structural units derived from polyhydric alcohols is preferably in the range of 0.1 to 5 mol%, more preferably 0.3 to 3 mol%, and still more preferably 0.5 to 2 mol%, respectively. If the content of both or either of them is too large, the resulting polyester resin tends to be amorphous and have insufficient heat resistance, and also tends to gel during polymerization.

[0044] [Production of Polyester Resin] The polyester resin used in the present invention can be produced by a well-known method. For example, polycarboxylic acids and polyhydric alcohols are subjected to an esterification reaction in the presence of a catalyst as necessary to obtain a prepolymer, and then polycondensation is carried out while distilling off excess glycol under reduced pressure to obtain a polyester resin.

[0045] The temperature in the esterification reaction of polycarboxylic acids and polyhydric alcohols is usually 180 to 280 °C, and the reaction time is usually 60 minutes to 8 hours.

[0046] The temperature in the polycondensation is usually 220 to 280 °C, and the reaction time is usually 20 minutes to 4 hours. Also, the polycondensation is preferably carried out under reduced pressure.

[0047] The polyester resin used in the present invention is crystalline. Here, the crystallinity can be confirmed by a differential scanning calorimeter. For example, it refers to the case where an endothermic peak due to crystal melting is observed when measured in a measurement temperature range of -70 to 260 °C and a temperature increase rate of 10 °C / min. The measurement temperature range can be appropriately changed according to the sample.

[0048] [Glass Transition Temperature (Tg) of Polyester Resin] The glass transition temperature (Tg) of the polyester resin used in the present invention is preferably -20°C or higher, more preferably -10 to 50°C, particularly preferably -5 to 40°C, still more preferably 0 to 350°C, especially preferably 5 to 30°C, and most preferably 10 to 25°C. If the glass transition temperature (Tg) is too low, the tack-free property becomes insufficient, and if the glass transition temperature (Tg) is too high, the adhesiveness and flexibility tend to become insufficient.

[0049] The method for measuring the glass transition temperature (Tg) is as follows. The glass transition temperature (Tg) can be determined by measuring using a differential scanning calorimeter. The measurement conditions are a measurement temperature range of -70 to 260°C and a temperature increase rate of 10°C / min.

[0050] 〔Melting point of polyester resin〕 The melting point of the polyester resin used in the present invention is preferably 60°C or higher, more preferably 70 to 180°C, particularly preferably 80 to 170°C, still more preferably 90 to 160°C, especially preferably 100 to 150°C. If the melting point is too low, the heat resistance becomes insufficient, and if it is too high, the solvent solubility tends to become insufficient.

[0051] The method for measuring the melting point is as follows. The melting point can be determined by measuring using a differential scanning calorimeter. The measurement conditions are a measurement temperature range of -70 to 260°C and a temperature increase rate of 10°C / min.

[0052] 〔Flow start temperature of polyester resin〕 The flow start temperature of the polyester resin used in the present invention is preferably 70°C or higher, more preferably 80 to 180°C, particularly preferably 90 to 170°C, still more preferably 100 to 160°C, especially preferably 110 to 150°C. If the flow start temperature is too low, the heat resistance becomes insufficient, and if it is too high, the solvent solubility tends to become insufficient.

[0053] The method for measuring the flow start temperature is as follows. The flow start temperature can be determined by measuring it by a temperature rising method using a flow tester. The measurement conditions are as follows: test force: 30 kg, temperature rising rate: 3 °C / min, measurement temperature range: 40 to 250 °C, die hole diameter: 1 mm.

[0054] For the polyester resin used in the present invention, it is preferable from the viewpoints of adhesiveness, heat resistance, and solvent solubility that the difference between the flow start temperature and Tg is within a predetermined range. The difference between the flow start temperature and Tg (flow start temperature - Tg) is preferably 70 °C to 160 °C, more preferably 80 °C to 150 °C, particularly preferably 90 °C to 140 °C, and still more preferably 100 °C to 130 °C. If the difference between the flow start temperature and Tg is too small, the balance between adhesiveness and heat resistance becomes insufficient, and if the difference is too large, the solvent solubility tends to be insufficient.

[0055] 〔Acid value of polyester resin〕 The acid value of the polyester resin used in the present invention is preferably 5 mgKOH / g or less, more preferably 0.2 to 4 mgKOH / g, and particularly preferably 0.5 to 3 mgKOH / g. If the acid value is too low, the adhesiveness becomes insufficient, and if it is too high, the long-term durability in a humid heat environment tends to decrease.

[0056] The definition and measurement method of the acid value are as follows. The acid value (mgKOH / g) can be determined by dissolving 1 g of the polyester resin in 30 g of a mixed solvent of toluene / methanol (for example, toluene / methanol = 9 / 1 by volume ratio) and performing neutralization titration based on JIS K0070. In the present invention, the acid value of the polyester resin is due to the carboxy group content in the resin.

[0057] 〔Ester bond concentration of polyester resin〕 The ester bond concentration of the polyester resin used in the present invention is preferably 9 mmol / g or less, more preferably 4 to 8.5 mmol / g, still more preferably 5 to 8 mmol / g, and particularly preferably 6 to 7.7 mmol / g. If the ester bond concentration is too high, the low dielectric tangent property tends to be insufficient, and the hygroscopicity increases, which also tends to cause an increase in the dielectric tangent due to moisture absorption. On the other hand, if the ester bond concentration is too low, the adhesiveness tends to be insufficient.

[0058] The definition and measurement method of the ester bond concentration are as follows. The ester bond concentration (mmol / g) refers to the number of moles of ester bonds in 1 g of the polyester resin, and can be obtained, for example, as a calculated value from the charged amounts. Such a calculation method is the value obtained by dividing the smaller number of moles of the charged amounts of polycarboxylic acids and polyhydric alcohols by the total weight of the resin. An example of the calculation formula is shown below. When the charged amounts of polycarboxylic acids and polyhydric alcohols are the same in terms of the number of moles, either of the following calculation formulas may be used. In addition, when using a monomer having both a carboxy group and a hydroxyl group, or when producing a polyester from caprolactone or the like, the calculation method will be changed as appropriate.

[0059] (When the polycarboxylic acids are less than the polyhydric alcohols) Ester group concentration (mmol / g) = [((A1 / a1 × m1 + A2 / a2 × m2 + A3 / a3 × m3 ···) / Z)] × 1000 A: Charged amount of polycarboxylic acids (g) a: Molecular weight of polycarboxylic acids m: Number of carboxylic acid groups per molecule of polycarboxylic acids Z: Final weight (g)

[0060] (When the polyhydric alcohols are less than the polycarboxylic acids) Ester group concentration (mmol / g) = [((B1 / b1 × n1 + B2 / b2 × n2 + B3 / b3 × n3 ···) / Z)] × 1000 B: Charge amount of polyhydric alcohols (g) b: Molecular weight of polyhydric alcohols n: Number of hydroxyl groups per molecule of polyhydric alcohols Z: Final weight (g)

[0061] The ester bond concentration can also be measured by a known method using NMR or the like.

[0062] In addition, the concentration of other polar groups other than ester bonds and reactive functional groups is preferably low from the viewpoints of low hygroscopicity and long-term durability in a wet heat environment. Examples of other polar groups include an amide group, an imide group, a urethane group, a urea group, an ether group, a carbonate group, and the like.

[0063] The total concentration of the amide group, imide group, urethane group, and urea group is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, particularly preferably 1 mmol / g or less, still more preferably 0.5 mmol / g or less, and most preferably 0.2 mmol / g or less. Examples of the ether group include an alkyl ether group and a phenyl ether group. From the viewpoints of low hygroscopicity and long-term durability in a wet heat environment, it is particularly preferable to lower the concentration of the alkyl ether group. The concentration of the alkyl ether group is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, particularly preferably 1.5 mmol / g or less, still more preferably 1 mmol / g or less, and most preferably 0.5 mmol / g or less. The concentration of the phenyl ether group is preferably 5 mmol / g or less, more preferably 4 mmol / g or less, particularly preferably 3 mmol / g or less, and still more preferably 2.5 mmol / g or less. The carbonate group concentration is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, particularly preferably 1 mmol / g or less, still more preferably 0.5 mmol / g or less, and most preferably 0.2 mmol / g or less.

[0064] 〔Peak top molecular weight (Mp) and weight average molecular weight (Mw) of polyester resin〕 The peak top molecular weight (Mp) of the polyester resin used in the present invention is preferably from 5,000 to 150,000, more preferably from 10,000 to 120,000, particularly preferably from 20,000 to 100,000, and still more preferably from 30,000 to 80,000. If the peak top molecular weight (Mp) is too low, the heat resistance and long-term durability in a humid heat environment tend to be insufficient, or the low dielectric tangent characteristics tend to be insufficient due to a large amount of hydroxyl groups remaining at the ends. Also, if the peak top molecular weight (Mp) is too high, the adhesiveness and solvent solubility tend to be insufficient.

[0065] The weight average molecular weight (Mw) of the polyester resin used in the present invention is preferably from 5,000 to 150,000, more preferably from 10,000 to 120,000, particularly preferably from 20,000 to 100,000, and still more preferably from 30,000 to 80,000. If the weight average molecular weight (Mw) is too low, the heat resistance and long-term durability in a humid heat environment tend to be insufficient, or the low dielectric tangent characteristics tend to be insufficient due to a large amount of hydroxyl groups remaining at the ends. Also, if the weight average molecular weight (Mw) is too high, the adhesiveness and solvent solubility tend to be insufficient.

[0066] <{ The measuring methods for the peak top molecular weight (Mp) and the weight average molecular weight (Mw) are as follows. The peak top molecular weight (Mp) and the weight average molecular weight (Mw) are measured using two columns in series (TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2×10 6 , theoretical plate number: 16,000 plates / book, filler material: styrene-divinylbenzene copolymer, filler particle size: 4 μm)) by high performance liquid chromatography (manufactured by Tosoh Corporation, "HLC-8320GPC") and can be determined by converting to standard polystyrene molecular weight.

[0067] 〔Water absorption rate (% by weight) of polyester resin〕 The water absorption rate of the polyester resin used in the present invention is preferably 2% by weight or less, more preferably 1% by weight or less, particularly preferably 0.8% by weight or less, and even more preferably 0.6% by weight or less. If the water absorption rate is too high, the wet heat durability and insulation reliability tend to decrease, and the low dielectric tangent characteristics tend to be inferior.

[0068] The method for measuring the water absorption rate is as follows. A polyester resin solution (before mixing with a curing agent) was applied onto a release film using an applicator and dried at 120°C for 10 minutes to produce a sheet with a dry film thickness of 65 μm for the polyester resin layer. This sheet was cut into a size of 7.5 cm × 11 cm, and after laminating the polyester resin layer side of the sheet onto a glass plate, the release film was peeled off. By repeating this operation 6 times, a test plate having a polyester resin layer with a thickness of 390 μm on the glass plate was obtained. The test plate thus obtained was immersed in purified water at 23°C for 24 hours, then taken out, the moisture on the surface was wiped off, and dried at 70°C for 2 hours. The weights required for each of these steps were measured, and the water absorption rate (% by weight) was calculated from the weight change according to the following formula. (c - d)×100 / (b - a) a: Weight of the glass plate alone b: Weight of the initial test plate c: Weight of the test plate immediately after taking it out of the purified water and wiping off the moisture d: Weight of the test plate after drying at 70°C for 2 hours

[0069] [Dielectric properties of the polyester resin] (Dielectric constant (Dk)) The relative dielectric constant of the polyester resin used in the present invention at a frequency of 10 GHz under an environment of 23°C and 50% RH relative humidity is preferably 3.0 or less, more preferably 2.9 or less, particularly preferably 2.8 or less, and even more preferably 2.7 or less. If the above relative dielectric constant is too high, the transmission speed when made into a flat cable tends to be inferior or the transmission loss tends to increase.

[0070] (Dissipation factor (Df)) The dielectric tangent of the polyester resin used in the present invention at a frequency of 10 GHz under the environment of a temperature of 23°C and a relative humidity of 50%RH is 0.01 or less, preferably 0.008 or less, more preferably 0.007 or less, and particularly preferably 0.0065 or less. If the above dielectric tangent is too high, the transmission loss when made into a flat cable becomes large.

[0071] The measurement methods of the relative permittivity and the dielectric tangent can be determined by the cavity resonator perturbation method using a network analyzer. In addition, when the adhesiveness of the polyester resin is strong and it is difficult to prepare a measurement sample alone, it can be measured in a state of being sanded on a film, and the dielectric properties of the polyester resin alone can also be calculated by subtracting the film component.

[0072] Thus, a polyester resin having a very small dielectric tangent compared to the conventional one used in the present invention can be obtained. And the polyester resin having a very small dielectric tangent is very useful as a raw material for the adhesive composition for flat cables because it can suppress the transmission loss in the high-frequency region.

[0073] In addition, in the present invention, it is preferable that the polyester resin is soluble in an organic solvent from the viewpoint of forming the adhesive composition described later. If the solubility in such an organic solvent is insufficient, the preparation of the adhesive composition tends to be difficult.

[0074] The above organic solvents are, for example, aromatic solvents such as toluene, xylene, solvent naphtha, and Solvesso, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and isobutyl alcohol, ester solvents such as ethyl acetate and normal butyl acetate, acetate solvents such as cellosolve acetate and methoxyacetate, halogen solvents such as dichloromethane, tetrachloroethylene, and chloroform, or a mixture of two or more of these solvents. Among them, from the viewpoint of toxicity to the human body and the like, it is preferable to use solvents other than halogen-based solvents.

[0075] <Hardening agent> The adhesive composition of the present invention has excellent heat resistance even when it contains only a polyester resin, but it may contain a hardening agent if necessary. By containing a hardening agent, a hardening agent having a functional group that reacts with a functional group in the polyester resin reacts with such a functional group and hardens, and an adhesive excellent in adhesive strength, heat resistance, and durability can be obtained. Examples of such hardening agents include compounds having a functional group that reacts with at least one of a hydroxyl group and a carboxyl group contained in a polyester resin, such as a polyisocyanate compound and a polyepoxy compound.

[0076] Examples of the polyisocyanate compound include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. Also, isocyanate adducts such as tolylene diisocyanate adduct of trimethylolpropane, hexamethylene diisocyanate adduct, and isophorone diisocyanate adduct can be mentioned. In addition, the above polyisocyanate compound can also be used when the isocyanate moiety is blocked with phenol, lactam, or the like. These isocyanate compounds may be used alone or in combination of two or more.

[0077] Examples of the polyepoxy compound include bifunctional glycidyl ether types such as bisphenol A diglycidyl ether, bisphenol S diglycidyl ether, and brominated bisphenol A diglycidyl ether; polyfunctional glycidyl ether types such as phenol novolac glycidyl ether and cresol novolac glycidyl ether; glycidyl ester types such as hexahydrophthalic acid glycidyl ester and dimer acid glycidyl ester; and alicyclic or aliphatic epoxides such as triglycidyl isocyanurate, 3,4-epoxycyclohexylmethyl carboxylate, epoxidized polybutadiene, and epoxidized soybean oil. These polyepoxy compounds can be used alone or in combination of two or more.

[0078] Furthermore, when a polyepoxy compound containing a polyepoxy compound containing a nitrogen atom (nitrogen atom-containing polyepoxy compound) is used as the polyepoxy compound, the coating film of the adhesive composition can be B-staged (semi-cured state) by heating at a relatively low temperature, and the fluidity of the B-stage film can be suppressed to improve the workability in the bonding operation. In addition, an effect of suppressing the foaming of the B-stage film can be expected, which is preferable.

[0079] Examples of the nitrogen atom-containing polyepoxy compound include glycidylamine types such as tetraglycidyl diaminodiphenylmethane, triglycidyl para-aminophenol, tetraglycidyl bisaminomethyl cyclohexanone, and N,N,N',N'-tetraglycidyl-m-xylenediamine.

[0080] When the adhesive composition of the present invention contains a polyepoxy compound, and the polyepoxy compound further contains a nitrogen-containing polyepoxy compound, the content of the nitrogen-containing polyepoxy compound is preferably 30% by weight or less, more preferably 25% by weight or less, and particularly preferably 20% by weight or less, based on the total weight of the polyepoxy compound. The content of the nitrogen-containing polyepoxy compound is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and particularly preferably 2 parts by weight or less, based on 100 parts by weight of the polyester resin. If the content of such nitrogen atom-containing polyepoxy compound is too high, the rigidity tends to be excessively high, and the adhesive properties tend to be reduced. In addition, the crosslinking reaction tends to proceed easily during storage of the adhesive sheet, and the sheet life tends to be reduced.

[0081] The equivalent weight of the epoxy group to the carboxy group is preferably 0.8 to 5, more preferably 0.9 to 3, particularly preferably 1 to 2.5, and further preferably 1.2 to 2. If the equivalent weight is too large, the adhesiveness tends to be insufficient and the low dielectric tangent characteristics tend to be poor, whereas if it is too small, the durability and heat resistance tend to be insufficient.

[0082] The equivalent weight of epoxy groups relative to carboxy groups (COOH) can be calculated from the acid value of the polyester resin and the epoxy equivalent weight (g / eq) of the blended polyepoxy compound using the following formula. Equivalent weight of epoxy to COOH = (a ÷ WPE) / (AV ÷ 56.1 ÷ 1000 × b) a: Weight (g) of polyepoxy compound used in the formulation WPE: Epoxy equivalent of polyepoxy compound (g / eq) AV: Acid value of polyester resin (mgKOH / g) b: Weight (g) of polyester resin used in the formulation

[0083] <Adhesive composition> The adhesive composition of the present invention contains at least a polyester resin, and may further contain a curing agent as necessary, and exhibits the effects of excellent low dielectric tangent characteristics, excellent adhesiveness, and excellent heat resistance.

[0084] In the adhesive composition of the present invention, a filler, a flame retardant, etc. may be blended. In that case, considering the blending of a filler, a flame retardant, etc., the content of the polyester resin of the present invention in the adhesive composition is preferably 30% by weight or more, more preferably 40 to 95% by weight, particularly preferably 50 to 90% by weight, and still more preferably 60 to 85% by weight based on the total solid content.

[0085] When the adhesive composition of the present invention contains a curing agent, the content of the curing agent is preferably 1 to 30 parts by weight, more preferably 1.5 to 20 parts by weight, particularly preferably 2 to 15 parts by weight, and still more preferably 2.5 to 10 parts by weight with respect to 100 parts by weight of the polyester resin of the present invention. If the content of the curing agent is too small, the heat resistance and durability tend to be insufficient, and if it is too large, the adhesiveness tends to be insufficient or the low dielectric tangent characteristics tend to be inferior.

[0086] A solvent may be blended in the adhesive composition of the present invention in order to appropriately adjust the viscosity of the adhesive composition and facilitate handling when forming a coating film. The solvent is used to ensure the handleability and workability in the molding of the adhesive composition, and there is no particular limitation on its usage amount.

[0087] Examples of the solvent include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate; ethers such as ethylene glycol monomethyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; alcohols such as methanol and ethanol; alkanes such as hexane and cyclohexane; aromatics such as toluene and xylene. The solvents listed above may be used alone, or two or more of them may be mixed and used in any combination and ratio.

[0088] [Other ingredients] The adhesive composition of the present invention may contain other components in addition to the components listed above to further improve its functionality, such as inorganic fillers, coupling agents such as silane coupling agents, ultraviolet protection agents, antioxidants, plasticizers, fluxes, flame retardants, colorants, dispersants, emulsifiers, elasticity reducing agents, diluents, antifoaming agents, ion trapping agents, leveling agents, and catalysts. When the adhesive composition of the present invention contains other components, the content of the other components is preferably 70% by weight or less, more preferably 0.05 to 60% by weight, particularly preferably 0.1 to 50% by weight, and even more preferably 0.2 to 40% by weight.

[0089] <Adhesive> When the adhesive composition contains a curing agent, the adhesive of the present invention can be obtained by further carrying out a curing treatment, and exhibits the effects of low dielectric loss tangent characteristics, excellent adhesiveness, and excellent heat resistance. In the present invention, "curing" means intentionally curing the adhesive composition by heat and / or light, etc., and the degree of curing can be controlled depending on the desired physical properties and application.

[0090] The method for curing the adhesive composition of the present invention when it is cured or semi-cured to form an adhesive varies depending on the components and their amounts in the adhesive composition, but typically includes heating conditions of 80 to 200°C for 1 minute to 10 hours.

[0091] When curing the adhesive composition of the present invention using a curing agent, a catalyst may be used. Examples of such catalysts include imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole; tertiary amines such as triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, 6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7; and compounds obtained by converting these tertiary amines into amine salts with phenol, octylic acid, quaternized tetraphenylborate salts, etc.; cationic catalysts such as triallylsulfonium hexafluoroantimonate and diallyliodonium hexafluoroantimonate; triphenylphosphine, etc. Among these, tertiary amines such as 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, 6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7; and compounds obtained by converting these tertiary amines into amine salts with phenol, octylic acid, quaternized tetraphenylborate salts, etc. are preferable in terms of thermosetting properties, heat resistance, adhesiveness to metals, and storage stability after compounding. The compounding amount at that time is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polyester resin. Within this range, the catalytic effect on the reaction between the polyester resin and the curing agent is further enhanced, and strong adhesive performance can be obtained.

[0092] 〔Use〕 Since the adhesive composition of the present invention is excellent in low dielectric tangent characteristics, adhesiveness, and heat resistance, it is suitable for adhesives for flat cables.

Examples

[0093] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as it does not exceed the gist thereof. In the examples, "parts" and "%" mean weight basis.

[0094] <Production of polyester resin> The compositions described in Table 1 below are the final composition ratios (resin composition ratios), and are the relative ratios (molar ratios) and weight percentages of the amounts of the respective constituent monomers of the obtained polyester resin.

[0095] (Example 1) [Production of polyester resin (A-1)] Into a reaction vessel equipped with a thermometer, a stirrer, a rectifying column, and a nitrogen inlet tube, 239.0 g (1.4385 mol) of terephthalic acid (TPA), 102.4 parts (0.6163 mol) of isophthalic acid (IPA) as polycarboxylic acids, 237.1 parts (2.6309 mol) of butane-1,4-diol (1,4BG), 51.0 parts (0.8217 mol) of ethylene glycol (EG), 130.5 parts (0.2466 mol) of dimer diol "Pripol 2033" (P2033) (manufactured by Croda) as polyhydric alcohols, and 0.1 part of tetrabutyl titanate as a catalyst were charged. The temperature was raised to 270 °C over 2.5 hours, and an esterification reaction was carried out at 270 °C for 1.5 hours. Thereafter, 0.1 part of tetrabutyl titanate was added as a catalyst, the pressure inside the system was reduced to 2.5 hPa, and a polymerization reaction was carried out over 2 hours to obtain a polyester resin (A-1).

[0096] Regarding the aromatic acid content, aromatic ring content, side chain content, ester bond concentration (mmol / g), glass transition temperature (Tg) (°C), acid value (mgKOH / g), melting point (°C), flow start temperature (°C), peak top molecular weight (Mp), weight average molecular weight (Mw), and dielectric properties, measurements were carried out according to the description in this specification. The measurement methods for other physical properties are as follows.

[0097] [Dimer diol content] It shows the content (% by weight) of dimer diol with respect to the polyester resin.

[0098] 〔Solvent Solubility〕 20 g of polyester resin, 64 g of toluene, and 16 g of methyl ethyl ketone were mixed, heated and stirred under reflux at the boiling point temperature for 3 hours, and evaluated based on the following criteria. (Evaluation Criteria) 〇: The polyester resin was completely dissolved. ×: The polyester resin was not completely dissolved and some remained as individual entities.

[0099] 〔Solution Stability〕 For those evaluated as 〇 in the above solvent solubility test, the time until solidification after standing at 23 °C after dissolution was measured and evaluated based on the following criteria. (Evaluation Criteria) ◎: Did not solidify even after standing for 24 hours or more after dissolution. 〇: Solidified between 1 hour and less than 24 hours after dissolution. △: Solidified between 0.5 hour and less than 1 hour after dissolution. ×: Solidified in less than 0.5 hour after dissolution.

[0100] <Manufacture of Adhesive Composition> Using the polyester resin obtained above, an adhesive composition was manufactured as follows.

[0101] 20 g of the polyester resin (A-1) obtained above, 64 g of toluene, and 16 g of methyl ethyl ketone were mixed, heated and stirred under reflux at the boiling point temperature for 3 hours to completely dissolve the polyester resin, thereby obtaining an adhesive composition.

[0102] <Fabrication of Laminate> The adhesive composition prepared above was applied to a 50 μm-thick PET film "Lumirror T60" (manufactured by Toray Industries, Inc.) with an applicator and then dried at 120°C for 5 minutes to form an adhesive layer with a dry thickness of 25 μm. Next, a 100 μm-thick tin-plated copper foil "SnCu-O" (manufactured by Kawasaki Rolling Co., Ltd.) was laminated to the adhesive layer surface of the adhesive-coated PET film (lamination conditions: 170°C, 0.2 MPa, feed rate 1.5 m / min), and then aged for 3 days at 23°C and 50% RH to obtain a laminate. For convenience, a laminate of PET film and tin-plated copper foil (PET film / adhesive layer / tin-plated copper foil) is referred to as PET / Sn.

[0103] [Adhesive strength] The laminate obtained above was cut into a 1 cm wide piece to be used as a test piece. The test piece was fixed to a 2 mm thick glass plate using double-sided tape, and the tensile peel strength of the test piece was measured in an 80°C environment using a peel tester (peel rate: 100 mm / min, peel angle: 180°). The evaluation criteria were as follows: (Evaluation criteria) ◎:9N / cm or more ○: 7N / cm or more and less than 9N / cm △: 5N / cm or more and less than 7N / cm ×: Less than 5N / cm

[0104] (Examples 2 and 3, Comparative Examples 1 and 2) [Production of Polyester Resins (A-2 to A-3, A'-1 to A'-2)] Polyester resins (A-2 to A-3, A'-1 to A-2) were obtained in the same manner as in A-1 except that the resin composition was changed as shown in Table 1, and then various evaluations were performed using the same methods as in Example 1.

[0105] The resin composition (structural units derived from components) and various physical properties of the obtained polyester resin are shown in Tables 1 and 2. In Table 1, the abbreviations are as follows. "TPA": Terephthalic acid "IPA": Isophthalic acid "AdA": adipic acid "SebA": Sebacic acid "EG": Ethylene glycol "NPG": Neopentyl glycol "CHDM": 1,4-cyclohexanedimethanol "1.4BG": 1,4-butanediol "1.6HG": 1,6-hexanediol "P2033": Dimer diol "Pripol 2033" (manufactured by Croda)

[0106] [Table 1]

[0107] [Table 2]

[0108] The results in Tables 1 and 2 above show that the adhesive compositions using the polyester resins (A-1) to (A-3) of Examples 1 to 3, which satisfy all of the requirements of the present invention, have excellent low dielectric tangent characteristics, solvent solubility, and adhesion at high temperatures. On the other hand, the adhesive composition using the polyester resin (A'-1) of Comparative Example 1 was inferior in low dielectric tangent characteristics and was not suitable for use as an adhesive for low-loss flat cables, which is currently required. Also, the adhesive composition using the polyester resin (A'-2) of Comparative Example 2 was inferior in low dielectric tangent characteristics, and in addition, because it was amorphous, it had poor adhesion at high temperatures and poor heat resistance. [Industrial Applicability]

[0109] The adhesive composition of the present invention is an adhesive composition containing a crystalline polyester resin, which has a low dielectric tangent and exhibits excellent adhesion, solvent solubility, and heat resistance. For example, it is effective as an adhesive used for flat cables and the like.

Claims

1. An adhesive composition containing a polyester resin containing a structural unit derived from polycarboxylic acids and a structural unit derived from polyhydric alcohols, wherein the polyester resin has a glass transition temperature (Tg) of 50°C or lower and is a polyester resin that satisfies all of the following requirements (A) to (D). The adhesive composition is characterized by this. (A): The structural unit derived from polycarboxylic acids contains 90 mol% or more of the structural unit derived from aromatic polycarboxylic acids with respect to the entire structural unit derived from the polycarboxylic acid component. (B): The structural unit derived from polyhydric alcohols contains a structural unit derived from aliphatic diols having side chains. In the structural unit derived from aliphatic diols having side chains, the aliphatic diols having side chains are dimer diols. (C): It is a crystalline polyester resin. (D): The dielectric tangent (α) of the polyester resin at 10 GHz is 0.01 or less (temperature 23°C, relative humidity 50% RH), the glass transition temperature (Tg) is -5°C or higher, and the melting point is 60°C or higher.

2. The adhesive composition according to claim 1, further characterized by containing an organic solvent.

3. The adhesive composition according to claim 2, wherein the polyester resin is dissolved in an organic solvent.

4. The adhesive composition according to any one of claims 1 to 3 is used as an adhesive interposed between a resin base material and a conductor in a flat cable. A flat cable forming adhesive composition characterized by this.

Images