Polybenzoxazole resin, resin film and method for producing resin

Abstract

To provide a polybenzoxazole resin capable of forming a resin film having long-term heat resistance, repeated heat resistance and excellent dielectric properties only by a relatively low-temperature baking process and to provide a method for producing the same.SOLUTION: There is provided a polybenzoxazole resin having a repeating unit represented by the following general formula. X1 represents a tetravalent aromatic group independently for each repeating unit, N and O bonded to X1 forms a pair, N and O of each pair are bonded to adjacent carbons on the same aromatic ring, X2 is a divalent organic group independently for each repeating unit, at least a portion of X2 is a residue X2d corresponding to a structure excluding a carboxyl group of a dimer acid and the X1 and an oxazole bond are bonded together to form two oxazole rings.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polybenzoxazole resin, a resin film, and a method for producing the resin. [Background technology]

[0002] Polybenzoxazole resins are considered useful as alternatives to polyimides, which are widely used as protective films and insulating films for electronic components in the semiconductor-related and other microelectronics fields due to their excellent heat resistance, low moisture absorption, electrical insulation, and low dielectric properties. However, like polyimide resins, they have problems such as poor flexibility due to their rigidity, poor usability due to their high glass transition temperature, and poor solubility in commonly used organic solvents with high volatility.

[0003] To address these issues, attempts have been made to introduce a highly flexible molecular skeleton structure to reduce rigidity and a high glass transition temperature, thereby improving flexibility and varnish applicability. For example, Patent Document 1 proposes using not only bisaminophenol compounds and aromatic dicarboxylic acid chlorides, which are used as synthetic raw materials for polybenzoxazole resins, but also dimer diamine as a raw material, and copolymerizing the amide bond formed between the dimer diamine and the aromatic dicarboxylic acid chloride to obtain an amide group-containing polybenzoxazole resin, thereby improving varnish applicability. Patent Document 2 also proposes a similar method of copolymerizing a flexible diamine residue structure derived from dimer diamine or polyether diamine with a polybenzoxazole structure via an amide bond to improve flexibility, thereby utilizing the wide usable temperature range for cleaning sheets for substrate processing equipment.

[0004] On the other hand, polybenzoxazole resin is usually synthesized on a part by applying a solution of its precursor, polyhydroxyamide, and then subjecting it to a thermal ring-closing reaction (oxazolization reaction) at high temperatures. However, this requires high temperatures of over 300°C and prolonged heating, which poses a particular problem in that it is often inapplicable to some manufacturing processes. While it is possible to avoid the high-temperature treatment by performing the thermal ring-closing reaction during the polymerization reaction of the polybenzoxazole resin, this would still require synthesis at extremely high temperatures, making it extremely difficult to achieve in terms of the synthesis process. In both Patent Documents 1 and 2, the coating varnish used is polyhydroxyamide, which is a polybenzoxazole resin precursor before the ring-closing reaction, as in the prior art. Therefore, a baking step at high temperature is also essential to obtain a polybenzoxazole resin film. Furthermore, since the linking structure between the dimer diamine and the aromatic dicarboxylic acid chloride is a highly polar amide bond, the excellent low dielectric properties that the polybenzoxazole resin should inherently possess are impaired. In this case, the more the amount of dimer diamine residue introduced, the greater the amount of amide bond, which is associated with a decrease in not only the low dielectric properties but also the solvent solubility, and therefore there is an inherent limit to the amount of dimer diamine residue that can be introduced, presenting a difficult-to-solve trade-off problem. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2023 / 228815 [Patent Document 2] Japanese Patent Publication No. 2023-62865 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above background, and aims to provide a polybenzoxazole resin that can form a resin film having long-term heat resistance, repeated heat resistance, and excellent dielectric properties by a baking step at a relatively low temperature, and to provide a method for producing the same. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the problems of the present invention can be solved in the following aspects. The present invention has been completed based on the findings. The polybenzoxazole resin of the present invention has a repeating unit represented by the following general formula (1). [ka] ···(1) (X 1 represents a tetravalent aromatic group for each repeating unit, and X 1 The N and O bonded to form pairs, and each pair of N and O is bonded to adjacent carbon atoms on the same aromatic ring, and X 2 are each independently a divalent organic group for each repeating unit, and X 2 At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. 2 d, and X 1 and oxazole bonds are linked together to form two oxazole rings.

[0008] One embodiment of the polybenzoxazole resin in the present invention is 1 is a structure represented by the following general formula (2). [ka] ···(2) (In formula (2), X 3-CH2-, -O-, -S-, -SO-, -SO2-, -SO2NH-, -CO-, -COO-, -NHCO-, -NHCONH-, -C(CF3)2-, -CF2-, -C(CH 3)2-, -CH(CH3)-, -C(C2H5)(CH3)-, -C(C6H5)(CH3)-, -Si(R7)2-, -O-Si(R8)2-O-, -Si(R9)2-O-Si(R 10 )2-, and -(CH2) i -Si(R 11 )2-O-Si(R 12 )2-(CH2) i - (where i represents an integer of 0 to 6), or a structure represented by any of the following chemical formulas (3) to (7), or a direct bond. [ka] ···(3) [ka] ···(4) [ka] ···(5) [ka] ···(6) [ka] ···(7) (In formula (2), R1~R 12 are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or -(CF2) b -CF3 or -O-(CF2) b -CF3 (wherein b represents an integer of 0 to 5).

[0009] One embodiment of the polybenzoxazole resin of the present invention is a polybenzoxazole resin comprising X 2 When the total is 100 mol%, X 2 It contains 40 to 100 mol % of d.

[0010] The resin film of the present invention contains the polybenzoxazole resin.

[0011] The method for producing a polybenzoxazole resin in the present invention includes a step of reacting a compound represented by the following general formula (8) with a compound represented by the following general formula (9). [ka] ···(8) (X 1 represents a tetravalent aromatic group for each repeating unit, and X 1 The N and O bonded to form pairs, with each pair of N and O bonded to adjacent carbons on the same aromatic ring. [ka] ···(9) (In formula (9), X 2 are each independently a divalent organic group for each repeating unit, and X 2 d and X 4 H, OH, Cl, Br, I, OR 13 and an organic group represented by the following formula (10), 13 represents a hydrocarbon group having 3 or less carbon atoms or a phenyl group. [ka] ···(10) [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a polybenzoxazole resin that can form a resin film having long-term heat resistance, repeated heat resistance, and excellent dielectric properties by only a baking step at a relatively low temperature, and a method for producing the same. The polybenzoxazole resin of the present invention can be suitably used for producing protective films and insulating films for electronic parts in the semiconductor-related field, as well as laminate sheets, sealing materials, and prepregs for electronic substrates. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. Needless to say, other embodiments are also included within the scope of the present invention as long as they are consistent with the spirit of the present invention. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the range of the lower and upper limits. Furthermore, in this specification, "film" and "sheet" are synonymous and are not distinguished by thickness. Furthermore, unless otherwise noted, the various components appearing in this specification may be used independently, either singly or in combination of two or more types. The numerical values ​​described in this specification refer to values ​​obtained by the methods described in the Examples below.

[0014] <Polybenzoxazole resin> The polybenzoxazole resin of the present invention has a repeating unit represented by the following general formula (1). [ka] ···(1) In general formula (1), X 1 represents a tetravalent aromatic group for each repeating unit, and X 1 The N and O bonded to form pairs, and each pair of N and O is bonded to adjacent carbon atoms on the same aromatic ring, and X 2 are each independently a divalent organic group for each repeating unit, and X 2 At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. 2 d, and X 1and oxazole bonds are bonded to each other to form two oxazole rings. 2 d is not particularly limited as long as it corresponds to the structure of a dimer of any unsaturated aliphatic carboxylic acid belonging to the dimer acid group described below or a hydrogenated product thereof, excluding the carboxy group.

[0015] The polybenzoxazole resin of the present invention, having the above structure, is a ring-closed benzoxazole resin that is soluble in common solvents, and the resin film obtained therefrom by a baking process at a relatively low temperature has long-term heat resistance, repeated heat resistance, and excellent dielectric properties. 2 The structure in which d is directly bonded to the carbon of the oxazole ring moderately suppresses the interaction between the benzoxazole rings in the varnish state, and the resin as a whole has large molecular chain mobility and free volume, which is thought to contribute to improved solvent solubility. 2 The fact that d is directly bonded to the carbon of the oxazole ring of the benzoxazole structure is considered to be extremely advantageous in terms of achieving a low dielectric constant and dielectric loss tangent, since it does not involve a polarized structure that would deteriorate the dielectric properties. It is also presumed that the absence of a structure that is likely to be the starting point for thermal decomposition leads to improved heat resistance. 2 The fact that d is directly bonded to the oxazole ring carbon of the benzoxazole structure is thought to improve the molecular chain mobility around the hydroxyamide structure, which is the precursor structure of the benzoxazole structure, during the synthesis stage, and thereby effectively promote the ring-closing reaction of the benzoxazole ring at a lower temperature than in conventional polybenzoxazole resins.

[0016] residue X 2 It is particularly preferable that d contains at least one of the structures represented by the following general formula (11), the following general formula (12), and the following general formula (13), since this makes it possible to achieve a higher level of solubility, heat resistance, and dielectric properties. residue X 2d may be any one of the structures represented by the following general formula (11), the following general formula (12), and the following general formula (13), or may contain two or more types, for example, including both structures of the following general formula (11) and the following general formula (12). [ka] ···(11) [ka] ···(12) In formula (11) and formula (12), a, b, c, and d each independently represent an integer of 1 or greater, and satisfy 5≦a+b≦17 and 4≦c+d≦16. The dashed lines represent carbon-carbon single bonds or carbon-carbon double bonds. [ka] ···(13) In formula (13), e, f, g, and h each independently represent an integer of 1 or greater, and satisfy the conditions 6≦e+f≦18 and 8≦g+h≦20. The dashed lines represent carbon-carbon single bonds or carbon-carbon double bonds.

[0017] X 1 Regarding the above, it is preferable that the structure be represented by the following general formula (2), in that higher long-term heat resistance and heat cycle resistance can be exhibited. [ka] ···(2) (In formula (2), X 3-CH2-, -O-, -S-, -SO-, -SO2-, -SO2NH-, -CO-, -COO-, -NHCO-, -NHCONH-, -C(CF3)2-, -CF2-, -C(CH 3)2-, -CH(CH3)-, -C(C2H5)(CH3)-, -C(C6H5)(CH3)-, -Si(R7)2-, -O-Si(R8)2-O-, -Si(R9)2-O-Si(R 10 )2-, and -(CH2) i -Si(R 11 )2-O-Si(R 12 )2-(CH2) i - (where i represents an integer of 0 to 6), or a structure represented by any one of chemical formulas (3) to (7), or a direct bond. [ka] ···(3) [ka] ···(4) [ka] ···(5) [ka] ···(6) [ka] ···(7) (In formula (2), R1~R 12 are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or -(CF2) b -CF3 or -O-(CF2) b -CF3 (wherein b represents an integer of 0 to 5).

[0018] X constituting the polybenzoxazole resin of the present invention2 Residue X when the total is 100 mol% 2 The content of d is preferably 40 to 100 mol %, more preferably 50 to 100 mol %. 2 The content of d within this range is particularly preferable in that extremely excellent dielectric properties, repeated heat resistance, and long-term heat resistance can be exhibited.

[0019] The method for producing the polybenzoxazole resin of the present invention is not particularly limited, but preferably includes a step of reacting a bisaminophenol compound represented by the following general formula (8) with a dicarboxylic acid or dicarboxylic acid derivative compound represented by the following general formula (9). [ka] ···(8) (X 1 represents a tetravalent aromatic group for each repeating unit, and X 1 The N and O bonded to form pairs, with each pair of N and O bonded to adjacent carbons on the same aromatic ring. [ka] ···(9) (In formula (9), X 2 are each independently a divalent organic group for each repeating unit, and X 2 At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. 2 d and X 4 H, OH, Cl, Br, I, OR 13 and an organic group represented by the following formula (10), 13 represents a hydrocarbon group having 3 or less carbon atoms or a phenyl group. [ka] ···(10)

[0020] In the reaction of a bisaminophenol compound represented by general formula (8) with a dicarboxylic acid or dicarboxylic acid derivative compound represented by general formula (9), the amino group of the bisaminophenol compound reacts with the carboxy group, formyl group, ester group, haloacyl group, or amide group of the dicarboxylic acid derivative compound to form an amide bond (an imino bond in the case of an amino group and a formyl group), resulting in polymerization of the main chain in the first step. In the second step, the resulting amide group (or imino group) and the adjacent phenolic hydroxyl group undergo a dehydration ring-closing reaction to form an oxazole ring. This is a two-step reaction in total, which allows the production of a polybenzoxazole resin.

[0021] The bisaminophenol compound is not particularly limited as long as it is a compound represented by the general formula (8), but X 1 It is more preferable that the bisaminophenol compound has a structure represented by the general formula (2). Specific examples of such bisaminophenol compounds include aromatic diaminophenols such as bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(3-amino-4-hydroxyphenyl)sulfone, bis(3-amino-4-hydroxyphenyl)propane, bis(3-amino-4-hydroxyphenyl)methylene, bis(3-amino-4-hydroxyphenyl)ether, bis(3-amino-4-hydroxy)biphenyl, bis(3-amino-4-hydroxyphenyl)fluorene, and 2,2'-dihydroxybenzidine. Furthermore, within the scope of the structure represented by the general formula (8), a substituent may be introduced at any position of these compounds.

[0022] The dicarboxylic acid or dicarboxylic acid derivative compound is not particularly limited as long as it is a dicarboxylic acid or dicarboxylic acid derivative compound represented by the general formula (9). 2 At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. 2 d is contained as an essential ingredient. X 2Specific examples of the dicarboxylic acid or dicarboxylic acid derivative compound having d include dimer acid or a derivative obtained by converting the carboxy group of the dimer acid to another functional group.

[0023] Here, the term "dimer acid" refers to a dimer of an unsaturated aliphatic carboxylic acid or its hydrogenated product. For example, dimer acids can be obtained by dimerizing natural fatty acids such as soybean oil fatty acids, tall oil fatty acids, and rapeseed oil fatty acids, or unsaturated fatty acids such as linoleic acid, linoleic acid, oleic acid, erucic acid, myristoleic acid, palmitoleic acid, sapienic acid, elaidic acid, stearic acid, vaccenic acid, gadoleic acid, eicosenoic acid, brassidic acid, nervonic acid, eicosadienoic acid, docosadienoic acid, pinolenic acid, eleostearic acid, mead acid, dihomo-γ-linolenic acid, eicosatrienoic acid, stearidonic acid, arachidonic acid, eicosatetraenoic acid, cetoleic acid, adrenic acid, bosseopentaenoic acid, osbondo acid, sardine acid, tetracosapentaenoic acid, eicosapentaenoic acid, docosahexaenoic acid, and herring acid. The unsaturated bonds may be hydrogenated as necessary to reduce the degree of unsaturation. Dimer acids with reduced unsaturation are advantageous in terms of oxidation resistance (particularly coloration at high temperatures) and suppression of gelation during synthesis.

[0024] The dimer acid is preferably a compound having 20 to 60 carbon atoms, more preferably a compound having 24 to 56 carbon atoms, even more preferably a compound having 28 to 48 carbon atoms, and even more preferably a compound having 36 to 44 carbon atoms, in terms of achieving both high solubility and low dielectric properties. Dicarboxylic acid compounds having a branched structure (general formula 11 or 12) obtained by Diels-Alder reaction of a fatty acid are also preferred. The branched structure is preferably an aliphatic chain or a cyclic structure, more preferably a cyclic structure, in terms of achieving higher heat resistance. The cyclic structure is preferably one or more aromatic rings or an alicyclic structure, more preferably an alicyclic structure. When there are two cyclic structures, the two rings may be independent or continuous. One or more dimer acid compounds can be used. The alicyclic structure may have one or more double bonds within the ring, or may have no double bonds.

[0025] Commercially available dimer acids include, for example, "Pripol 1004," "Pripol 1006," "Pripol 1009," "Pripol 1013," "Pripol 1015," "Pripol 1017," "Pripol 1022," "Pripol 1025," and "Pripol 1040" manufactured by Cargill Japan; and "Empol 1008," "Empol 1012," "Empol 1016," "Empol 1026," "Empol 1028," "Empol 1043," "Empol 1061," and "Empol 1062" manufactured by BASF Japan. Among these, "Pripol 1009," which has 36 carbon atoms, is used to easily obtain polybenzoxazole resins that exhibit excellent thermal cycling properties while maintaining adhesion to metals. Furthermore, "Pripol 1004," which has 44 carbon atoms, is used to easily obtain polybenzoxazole resins that exhibit excellent solvent solubility and flexibility.

[0026] The dicarboxylic acid is X 2 At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. 2 d as an essential ingredient, X 2 As X 2 It is also possible to use one that does not have d. 2 X without d 2 The dibasic acid compound is not particularly limited as long as it is a dibasic acid compound other than dimer acid, and specific examples thereof include aromatic dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and 4,4'-biphenyldicarboxylic acid; aliphatic dibasic acids such as oxalic acid, malonic acid, methylmalonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, malic acid, tartaric acid, thiomalic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, and diglycolic acid; and alicyclic dibasic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid.

[0027] When the dimer acid or other dibasic acid is used, it is also preferable to use an equimolar amount of a condensing agent such as dicyclohexylcarbodiimide or diisopropylcarbodiimide to accelerate the main chain polymerization reaction in the first stage.

[0028] Dicarboxylic acid derivative compounds include X 2 Dicarboxylic acids (dimer acids) with d and X 2 For each dicarboxylic acid not having d, it is preferable to use dicarbaldehydes in which the carboxy group is reduced to a formyl group, acid halides in which the OH in the carboxy group is replaced with a halogen element such as Cl, Br, or I, diesters in which methoxy, ethoxy, isopropoxy, or phenoxy groups are used, and dicarboimidazoles in which the dicarboxylic acid is amide with imidazole. The use of these dicarboxylic acid derivative compounds is preferred in that, depending on the synthesis conditions, the first-stage main chain polymerization reaction can be accelerated, enabling synthesis at a lower polymerization temperature and in a shorter time, making it easier to obtain a resin with a high degree of polymerization.

[0029] A method for converting the carboxy group of a dicarboxylic acid into an ester group includes, for example, dehydration condensation of the dicarboxylic acid with an alcohol such as methanol, ethanol, isopropyl alcohol, or phenol in the presence of an acid catalyst such as sulfuric acid. A method for converting the carboxy group of a dicarboxylic acid into a formyl group includes, for example, reduction of a diester synthesized from the dicarboxylic acid with DIBAL-H (diisobutylaluminum hydride). A method for converting the carboxy group of a dicarboxylic acid into an acyl halide group includes, for example, reaction of the dicarboxylic acid with thionyl chloride to form a dibasic acid chloride. A method for converting the carboxy group of a dicarboxylic acid into a carboimidazole group includes, for example, reaction of the dicarboxylic acid with carbonyldiimidazole to decarboxylate the dicarboxylic acid.

[0030] When an acid halide is used as the dicarboxylic acid derivative compound, it is preferable to use a base such as pyridine in combination to capture the acid halide that is eliminated by the reaction and smoothly promote the reaction, and to carry out the reaction at a low temperature of about −78° C. to proceed with the reaction without side reactions.

[0031] The weight-average molecular weight of the polybenzoxazole resin in the present invention is preferably in the range of 10,000 to 150,000. A weight-average molecular weight in this range is particularly preferred in that better film-forming properties and low dielectric properties can be obtained.

[0032] The glass transition temperature of the polybenzoxazole resin of the present invention is not particularly limited, but a suitable range is -20 to 140°C. A glass transition temperature in this range is particularly preferred in that a resin film having high flexibility and toughness and low elasticity can be obtained. The method for measuring the glass transition temperature is described in the Examples section.

[0033] Although there is no particular limitation on the functional group value of the polybenzoxazole resin in the present invention, the amine value, phenolic hydroxyl value, and acid value are each preferably 0 to 30 mgKOH / g, more preferably 0 to 23 mgKOH / g. Having the functional group value in this range is preferred in that better low dielectric properties can be obtained.

[0034] <Resin film> The resin film of the present invention contains the polybenzoxazole resin. The method for producing the resin film is not particularly limited, but examples thereof include a method in which the polybenzoxazole resin is dissolved in an arbitrary solvent to prepare a solution, and the solution is coated and then the solvent is removed to obtain the resin film.

[0035] The solvent used to coat the polybenzoxazole resin of the present invention to obtain a resin film is not particularly limited as long as it can stably dissolve the polybenzoxazole resin of the present invention, but a general-purpose solvent other than N-methylpyrrolidone (NMP) is preferred. Using a solvent other than NMP is advantageous from the viewpoints of low health hazards and reducing residual solvent during drying. Furthermore, a solvent with a boiling point of 60 to 180°C is particularly preferred from the viewpoint of further reducing residual solvent during drying. Specific examples of suitable solvents include ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, cyclohexanone, cyclopentanone, methyl ethyl ketone, cyclopentyl methyl ether, toluene, and anisole.

[0036] The method for forming a resin film from the polybenzoxazole resin of the present invention can be any known or commonly used method suitable for the purpose. When the benzoxazole resin of the present invention is dissolved in a solvent, a coating solution (varnish) of the present composition containing the solvent is applied to one side of a release-treated resin film (hereinafter referred to as a release substrate), and the liquid medium, such as an organic solvent, is removed and dried, for example, at 40 to 150°C, to obtain a coated sheet having a resin film. Laminating another release film on the surface of the resulting coated sheet produces a laminate sheet, which is a coated sheet with double-sided release films. Laminating both sides with release films prevents surface contamination of the resin film. The resin film can be isolated by peeling off the release film. The two release films can be the same or different types. Using release films with different release properties allows for varying levels of release force, making it easier to peel them in order. Alternatively, a laminate sheet having a resin film can be obtained by applying the coating solution to a substrate other than the release substrate. When the benzoxazole resin of the present invention is in the form of a powder or a lumpy solid, a thick resin film may be formed by injecting the molten benzoxazole resin into a mold at a temperature equal to or higher than the flow-initiation temperature of the benzoxazole resin using any melt molding method such as transfer molding.

[0037] The materials for the release substrate and other substrates can be selected from a wide range of materials, including those that do not have high heat resistance, due to the characteristic of the present invention that a polybenzoxazole resin film can be obtained by heat treatment at a relatively low temperature. Examples include resin materials such as polyimide film, polyethylene film, polycarbonate, polyethylene, polyester (including PET (polyethylene terephthalate) and PEN (polyethylene naphthalate)), liquid crystal polymers, phenolic resins, and aramid resins; metal materials such as copper, aluminum, and stainless steel; inorganic materials such as ITO, glass, silicon, and silicon carbide; and composite materials containing any combination of these. Furthermore, as mentioned above, using a resin material film with a release treatment on its surface is preferable because it allows easy handling and allows for the formation of a polybenzoxazole resin film by peeling off the substrate after coating and drying.

[0038] When obtaining the resin film of the present invention, the coating liquid (varnish) containing the benzoxazole resin and a solvent can be applied by any known method, such as comma coating, knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure printing, flexographic printing, screen printing, dip coating, spray coating, spin coating, etc. The thickness of the resin film after drying is preferably 5 to 500 μm, more preferably 10 to 100 μm, in order to ensure sufficient performance and adhesiveness as a protective layer and from the standpoint of ease of handling.

[0039] The polybenzoxazole resin of the present invention can be used alone or in combination with two or more types of resins, regardless of whether they are the same or different. Fillers, curing agents, and curing accelerators may also be used in combination. The polybenzoxazole resin of the present invention not only has low dielectric properties but also excellent electrical insulation properties. Therefore, a resin film or cured film with excellent insulation properties can be provided by using the resin alone or, if necessary, in combination with a filler, curing agent, and curing accelerator. Such a resin film or cured film can be suitably used, for example, as an insulating layer-forming material on a circuit board such as a high-frequency circuit (including a coverlay layer of a printed wiring board, an interlayer insulating layer of a built-up board, a bonding sheet, etc.). [Example]

[0040] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" are based on mass.

[0041] (i) Measurement of weight average molecular weight (Mw) Mw was measured using a Showa Denko GPC (gel permeation chromatography) "GPC-101." The mobile phase was THF (tetrahydrofuran), and the stationary phase column was two "KF-805L" (Showa Denko: GPC column: 8 mm ID x 300 mm size) connected in series. The sample concentration was 1% by mass, the flow rate was 1.0 mL / min, the pressure was 3.8 MPa, and the column temperature was 40°C. Mw was determined in polystyrene equivalent terms. Data analysis was performed using the manufacturer's built-in software to calculate the calibration curve, molecular weight, and peak area, and Mw was calculated for the retention time range of 17.9 to 30.0 minutes.

[0042] (ii) Measurement of phenolic hydroxyl value The phenolic hydroxyl value was measured in accordance with JIS K0070. The phenolic hydroxyl value is expressed as the amount (mg) of potassium hydroxide required to neutralize the acetic acid bonded to the phenolic hydroxyl groups when the phenolic hydroxyl groups contained in 1 g of polybenzoxazole resin are acetylated. The phenolic hydroxyl value of polybenzoxazole resin was calculated taking into account the acid value, as shown in the following formula. Specifically, approximately 1 g of sample (polybenzoxazole resin) was precisely weighed into a stoppered Erlenmeyer flask and dissolved in 100 mL of cyclohexanone solvent. Exactly 5 mL of the acetylating agent (a solution prepared by dissolving 25 g of acetic anhydride in pyridine to a volume of 100 mL) was then added and stirred for approximately 1 hour. Phenolphthalein test solution was added as an indicator. The solution was then titrated with 0.5 N alcoholic potassium hydroxide solution until it turned a pale pink color. The endpoint was when the indicator retained its pale pink color for 30 seconds. The phenolic hydroxyl value was calculated by the following formula. Phenolic hydroxyl value (mgKOH / g) = [{(ba) × F × 28.05} / S] - D however, S: Amount of sample collected (g) a: Consumption of 0.5N alcoholic potassium hydroxide solution (mL) b: Amount of 0.5N alcoholic potassium hydroxide solution consumed in the blank experiment (mL) F: Potency of 0.5N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g) The value of b can be determined by titrating 5 mL of the acetylating agent (a solution of 25 g of acetic anhydride dissolved in pyridine to a volume of 100 mL) with 0.5 N alcoholic potassium hydroxide solution.

[0043] (iii) Amine value determination Approximately 1 g of sample (polybenzoxazole resin) was precisely weighed and placed in a stoppered Erlenmeyer flask, and 100 mL of cyclohexanone solvent was added for dissolution. Two or three drops of an indicator, prepared separately by mixing 0.20 g of Methyl Orange in 50 mL of distilled water with 0.28 g of Xylene Cyanol FF in 50 mL of methanol, were added. The solution was then titrated with 0.1 N alcoholic hydrochloric acid until it turned blue-gray. The endpoint was when the indicator retained its blue-gray color for 30 seconds. The amine value was calculated using the following formula: Amine number (mgKOH / g) = (5.611 x a x F) / S however, S: Amount of sample collected (g) a: Amount of 0.1N alcoholic hydrochloric acid solution consumed (mL) F: Potency of 0.1N alcoholic hydrochloric acid solution

[0044] (iv) Acid value measurement The acid value was measured in accordance with JIS K0070. Approximately 1 g of sample (polybenzoxazole resin) was precisely weighed and placed in a stoppered Erlenmeyer flask, and 100 mL of cyclohexanone solvent was added to dissolve it. Phenolphthalein test solution was added as an indicator, and the solution was titrated with 0.1 N alcoholic potassium hydroxide solution. The endpoint was when the indicator retained a pale pink color for 30 seconds. The acid value was calculated using the following formula. Acid value (mgKOH / g)=(5.611×a×F) / S however, S: Amount of sample collected (g) a: Amount of 0.1N alcoholic potassium hydroxide solution consumed (mL) F: Potency of 0.1N alcoholic potassium hydroxide solution

[0045] (v) Measurement of glass transition temperature Measurement specimens cut out to a size of 5 mm x 30 mm from each of the resin films described below were cooled to -40°C, then heated to 300°C at a rate of 10°C / min using a dynamic viscoelasticity measuring device "DVA200" (manufactured by IT Measurement Control Co., Ltd.), and the viscoelasticity was measured at an oscillation frequency of 10 Hz. The storage modulus was determined from the obtained viscoelastic curve, and the loss tangent (tanδ) was calculated from the loss modulus at each temperature. These were plotted, and the maximum point of the tanδ curve was calculated. If there are multiple maximum points, the highest temperature value was taken as the tanδ peak of the cured product.

[0046] [Synthesis Example 1] <Synthesis of dimer acid dichloride (DC2)> In a 1 L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge device, and reflux condenser, 2.0 g of 1,3-dimethyl-2-imidazolidinone (DMI) was added to 100.0 g of dimer acid (DC1, PRIPOL 1009 manufactured by Cargill Japan, acid value: 194 mg KOH / g) while introducing nitrogen gas. 42.4 g of thionyl chloride was added dropwise at 40 °C over 3 hours. The reaction was then continued for 1 hour while the dissolved acidic gases (sulfur dioxide and hydrogen chloride) were distilled off under reduced pressure at 30 kPa and 40 °C. Further, thionyl chloride was distilled off at 5 kPa and 40 °C for 3 hours, yielding dimer acid dichloride (DC2) as a concentrated residue.

[0047] [Synthesis Example 2] <Synthesis of dimer acid diisopropyl ester (DC3)> A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge system, and reflux condenser was charged with 200.0 g of dimer acid (DC1, PRIPOL 1009, Cargill Japan, acid value: 194 mg KOH / g), 83.1 g of isopropyl alcohol, and 0.66 g of paratoluenesulfonic acid monohydrate under nitrogen gas. The mixture was refluxed for 10 hours. The remaining isopropyl alcohol was removed by distillation using a Dean-Stark trap. The cooled reaction mixture was then purified by adding 500 g of 1% aqueous sodium hydroxide and 500 g of toluene. The organic layer was washed three times with water, dried over anhydrous sodium sulfate, and filtered. Finally, the toluene was removed by distillation under reduced pressure to obtain diisopropyl dimer acid (DC3).

[0048] [Synthesis Example 3] <Synthesis of dimer dicarbaldehyde (DC4)> In a 1 mL separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge system, reflux condenser, and cryocooler, 68.46 g of dimer acid diisopropyl ester (DC3) obtained in Synthesis Example 2 was dissolved in 68.46 g of toluene and cooled to -78 °C while introducing nitrogen gas. 15.45 g of DIBAL (68.7 mL as a 1.5 M solution in toluene) was added to the flask while cooling. The resulting mixture was stirred at -78 °C for 1 hour and then warmed to room temperature over an additional 2 hours. The reaction was quenched by slowly adding 500 mL of 5 M ammonium chloride solution. The organic layer was separated, washed twice with water, dried over anhydrous sodium sulfate, and filtered. Finally, the toluene was removed by distillation under reduced pressure to obtain dimer dicarbaldehyde (DC4).

[0049] [Synthesis Example 4] <Synthesis of dicarboimidazole dimer acid (DC5)> A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with 35.67 g of 1,1'-carbonyldiimidazole and 178 g of γ-butyrolactone while introducing nitrogen gas. A solution of 57.85 g of dimer acid (PRIPOL 1009, manufactured by Cargill Japan, acid value: 194 mg KOH / g) dissolved in 131 g of γ-butyrolactone was added dropwise from the dropping funnel over 15 minutes. The solvent was concentrated under reduced pressure at 70 °C. The concentration was stopped when the distillate reached 195 g. The mixture was cooled to below 10 °C under a nitrogen stream, and 195 g of acetone was added dropwise. The precipitate was filtered. The precipitate was washed with 50 g of isopropanol and dried under reduced pressure at 65 °C to obtain dicarboimidazole dimer acid (DC5).

[0050] [Synthesis Example 5] <Synthesis of 1,1'-(4,4'-oxybenzoyl)diimidazole (DC8)> A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with 35.17 g of 1,1'-carbonyldiimidazole and 178 g of γ-butyrolactone while introducing nitrogen gas. A solution of 25.04 g of 4,4'-dicarboxydiphenyl ether in 131 g of γ-butyrolactone was added dropwise from the dropping funnel over 15 minutes. The solvent was concentrated under reduced pressure at 70°C. When the distillate reached 195 g, the concentration was stopped. The mixture was cooled to below 10°C under a nitrogen stream, and 195 g of acetone was added dropwise. The precipitate was filtered. The precipitate was washed with 50 g of isopropanol and dried under reduced pressure at 65°C to obtain 1,1'-(4,4'-oxydibenzoyl)diimidazole (DC8).

[0051] <Synthesis of polybenzoxazole resin> [Example 1] A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with nitrogen gas. 200.0 g of γ-butyrolactone as a solvent and 117.9 g of dimer acid (DC1, PRIPOL 1009, Cargill Japan) were added, and 42.1 g of N,N'-dicyclohexylcarbodiimide as a condensing agent was added and stirred at room temperature until homogeneous. 82.1 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) was added with stirring, and the mixture was stirred at room temperature for another 10 hours. The temperature was then raised to 220°C and the ring-closing dehydration reaction was carried out for 20 hours. Water was removed from the system using a Dean-Stark trap during the ring-closing dehydration reaction. The precipitated dicyclohexylurea by-product was filtered from this solution to obtain a varnish of polybenzoxazole resin P1.

[0052] [Example 2] A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with 200.0 g of γ-butyrolactone as a solvent, 119.8 g of the dimer acid dichloride (DC2) obtained in Synthesis Example 1, and 15.7 g of pyridine. 80.2 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) was added with stirring. After stirring at room temperature for 10 hours, the reaction solution was poured into 2 L of water for reprecipitation. The precipitated solid was washed with ion-exchanged water and methanol and dried at 120 °C for 3 hours. γ-butyrolactone was added again to dissolve the solids to a concentration of 50%. This solution was poured into a 1-L separable flask with the same specifications as above, heated to 220 °C, and allowed to undergo a ring-closing dehydration reaction for 20 hours while removing water from the system using a Dean-Stark trap, yielding a varnish of polybenzoxazole resin P2.

[0053] [Example 3] A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge system, and reflux condenser was charged with 200.0 g of γ-butyrolactone as a solvent and 123.4 g of the diisopropyl dimerate (DC3) obtained in Synthesis Example 2. The mixture was stirred at room temperature until homogeneous. 76.6 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) was added with stirring. The mixture was heated to 190°C and stirred for 10 hours. The temperature was then further increased to 220°C. The ring-closing dehydration reaction was carried out for 20 hours while removing water and isopropyl alcohol from the system using a Dean-Stark trap, yielding a varnish of polybenzoxazole resin P3.

[0054] [Example 4] A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge system, and reflux condenser was charged with 200.0 g of γ-butyrolactone as a solvent and 113.9 g of dimer dicarbaldehyde (DC4) obtained in Synthesis Example 3. The mixture was stirred at room temperature until homogeneous. 86.1 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) was added with stirring. After stirring at room temperature for 10 hours, the mixture was heated to 220°C and subjected to a ring-closing dehydration reaction for 20 hours while removing water from the system using a Dean-Stark trap, yielding a varnish of polybenzoxazole resin P4.

[0055] [Example 5] A 1-L separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge system, and reflux condenser was charged with 200.0 g of γ-butyrolactone as a solvent and 124.6 g of dimer dicarboimidazole (DC5) obtained in Synthesis Example 4. The mixture was stirred at room temperature until homogeneous. 75.5 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) was added with stirring. The mixture was heated to 85°C and stirred for 10 hours. The temperature was then further raised to 220°C. The ring-closing dehydration reaction was carried out for 20 hours while removing water and imidazole from the system using a Dean-Stark trap, yielding a varnish of polybenzoxazole resin P5.

[0056] [Comparative Example 1] A 500 mL separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with 234.67 g of N-methylpyrrolidone (NMP) and 22.93 g of 1,1'-(4,4'-oxybenzoyl)diimidazole (DC8) as solvents while introducing nitrogen gas. The mixture was stirred at 60 °C to dissolve the solids. Then, 1.09 g of meta-aminophenol (MAP) was added along with 5 g of NMP, and the mixture was heated to 85 °C and reacted for 15 minutes. Then, 8.04 g of PRIAMINE 1075 and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1) were added along with 29.67 g of NMP (20 g), and the mixture was further reacted at 85 °C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature and poured into 3 L of water. The resulting white precipitate was collected by filtration, washed with ion-exchanged water, and dried at 50 °C for 3 weeks. The resulting powder was then dissolved in NMP to a solids concentration of 50%. This solution was placed in a 500 mL separable flask with the same specifications as above, heated to 220 °C, and the ring-closing dehydration reaction was carried out for 20 hours while removing water from the system using a Dean-Stark trap. However, the ring-closing dehydration reaction hardly progressed, so the reaction was terminated and a varnish of polybenzoxazole resin precursor N1 was obtained.

[0057] Comparative Example 2 A 500 mL separable flask equipped with an oil bath, stirrer, thermometer, nitrogen purge unit, and reflux condenser was charged with 24.0 g of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AF1), 16.0 g of pyridine, and 100 g of NMP. While introducing nitrogen gas, the mixture was stirred to dissolve the solids. Then, 15.0 g of trimethylchlorosilane was added dropwise over 10 minutes and stirred at room temperature for 60 minutes. 4.0 g of PRIAMINE 1075 was added and stirred for 3 minutes. Then, 22.0 g of 4,4'-oxybis(benzoyl chloride) was slowly added over 30 minutes and stirred at room temperature for 2 hours. After the reaction was completed, the reaction solution was cooled to room temperature, poured into 3 L of water, and the resulting white precipitate was collected by filtration, washed with ion-exchanged water, and dried at 50 °C for 3 weeks. The resulting powder was then dissolved again in NMP to a solids concentration of 50%. This solution was placed in a 500 mL separable flask with the same specifications as above, and the temperature was further increased to 220 °C. The ring-closing dehydration reaction was carried out for 20 hours while removing water from the system using a Dean-Stark trap. However, the ring-closing dehydration reaction hardly progressed, so the reaction was terminated and a varnish of polybenzoxazole resin precursor N2 was obtained.

[0058] [Examples 6 to 19, Comparative Examples 3 to 4] Varnishes of polybenzoxazole resins P6 to P19 and N3 to N4 were obtained in the same manner as in Examples 1 to 5 as shown in Tables 1 to 3, except that the monomers and blending amounts were changed as shown in Tables 1 to 3. (Example 6 and Comparative Example 3 were examined in the same manner as in Example 2, Example 8 in the same manner as in Example 5, and the other examples were examined in the same manner as in Example 1.) DC2, DC3, DC4, DC5, and DC8 below were those obtained in Synthesis Examples 1 to 5, and the others were commercially available products that were used as they were without further purification.

[0059] The abbreviations for the monomers in Tables 1 to 3 are shown below. AF1: 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane AF2: 2,2-bis(3-amino-4-hydroxyphenyl)propane AF3: Bis(3-amino-4-hydroxyphenyl) sulfone AF4: 9,9-bis(3-amino-4-hydroxyphenyl)fluorene AF5: 4,6-diaminoresorcinol dihydrochloride AF6: 3,3'-diamino-4,4'-dihydroxybiphenyl DC1: Dimer acid (Cargill Japan PRIPOL 1009, acid value: 194 mg KOH / g) DC2: Dimer acid dichloride DC3: Dimer acid diisopropyl ester DC4: Dimer dicarbaldehyde DC5: Dimer dicarboimidazole DC6: 4,4'-oxybis(benzoyl chloride) DC7: 4,4'-dicarboxydiphenyl ether DC8: 1,1'-(4,4'-oxybenzoyl)diimidazole DC9: Isophthalic acid DA1: Dimer diamine (PRIAMINE 1075, manufactured by Cargill Japan, amine value: 205 mg KOH / g) DCC: N,N'-dicyclohexylcarbodiimide PYR: Pyridine MAP: Meta-aminophenol GBL: gamma-butyrolactone NMP: N-methylpyrrolidone TCS: Trimethylchlorosilane

[0060] Tables 1 to 3 show the blending amounts (parts by mass), the phenolic hydroxyl group (PhOH) value, amine value, acid value, glass transition temperature, and X of the obtained polybenzoxazole resin. 2 X relative to 100 mol% 2 d indicates the mole percentage of the residue. 2 X relative to 100 mol% 2 The mole % value of the d residue was calculated from the amounts of raw materials used in the synthesis of the polybenzoxazole resin.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] <Solvent solubility> The varnishes of Examples 1 to 19 and Comparative Examples 1 to 4 were poured into 2 L of water and reprecipitated. The precipitated solid was washed with ion-exchanged water and methanol and dried at 120°C for 3 hours to obtain a solid of each resin. 10 g of each of these resin solids was placed in two 70 mL mayonnaise bottles, and toluene and cyclohexanone were added to each individually to adjust the solid concentration to 50%, followed by heating at 80°C for 3 hours. These varnishes were cooled to 25°C, and the time from inverting the bottle until the varnish came into contact with the lid was measured to confirm their fluidity. The appearance was also observed, and the solubility was evaluated according to the following criteria. ○: The time from turning the mayonnaise bottle upside down until the varnish comes into contact with the lid side (opposite side of the bottle) is less than 1 minute (high fluidity), and the appearance is clear and completely dissolved (good). ×: The time it takes for the varnish to come into contact with the lid (opposite side of the bottle) after the mayonnaise bottle is turned upside down is 1 minute or more (poor fluidity), and there is turbidity or insoluble matter, indicating poor solubility (unusable)

[0065] <Low-temperature formation of polybenzoxazole resin film> The solid resins of Examples 1 to 19 and Comparative Examples 1 to 4 obtained in the same manner as in the above α. Investigation of Solvent Solubility were dissolved in DMF-d7 solvent to a solid content of 10%, and the solid content was measured by FT-NMR (JEOL ECS-400, 400 MHz). 1 H-NMR measurement was performed. The C- 1The oxazole ring closure rate was calculated from the ratio of the peak integrated area of ​​the amide (before ring closure) to that of the oxazole (after ring closure) with respect to the H peak, and the ability to form a polybenzoxazole resin film using only a low-temperature baking process (low-temperature formability of polybenzoxazole resin film) was evaluated according to the following criteria. ○: The ring closure rate is high at 90% or more, and polybenzoxazole resin films can be formed using only a relatively low-temperature baking process (good). ×: The cyclization rate is low, less than 90%, and a baking step at high temperature is required to close the hydroxyamide structure, so that a polybenzoxazole resin film cannot be formed by a baking step at a relatively low temperature alone (unusable, poor).

[0066] (Creating a resin film) A toluene solution with a solids concentration of 50% obtained from the varnishes of Examples 1 to 19 and Comparative Examples 1 to 4 in the solvent solubility verification (the original varnish was used for those that were insoluble in toluene) was uniformly coated onto a polyester film that had been subjected to a release treatment using a blade coater so that the film thickness after drying would be 50 μm, and the film was dried for 15 minutes at 120° C. After drying, the polyester film was peeled off to obtain each resin film.

[0067] <Dielectric properties> (dielectric constant) Three test pieces, each 10 mm wide and 65 mm long, were cut out from the resin films prepared from the varnishes of Examples 1 to 19 and Comparative Examples 1 to 4 and placed in a dielectric constant measuring device "ADMS01Oc" manufactured by AET Corporation. The dielectric constants were determined by the cavity resonator method at a measurement temperature of 23°C and a measurement frequency of 10 GHz and evaluated according to the following criteria. ◎: Dielectric constant less than 2.5 (very good) ○: Dielectric constant 2.5 or more and less than 2.6 (good) △: Dielectric constant 2.6 or more and less than 2.7 (usable) ×: Dielectric constant 2.7 or more (unusable)

[0068] (dielectric tangent) Three test pieces, each 10 mm wide and 65 mm long, were cut out from the resin films prepared from the varnishes of Examples 1 to 19 and Comparative Examples 1 to 4 and placed in an ADMS01Oc relative permittivity measuring device manufactured by AET Corporation. The dielectric loss tangents at a measurement temperature of 23°C and a measurement frequency of 10 GHz were determined using a cavity resonator method and evaluated according to the following criteria. ◎: Dielectric tangent less than 0.002 (very good) ○: Dielectric loss tangent 0.002 or more and less than 0.003 (good) △: Dielectric loss tangent 0.003 or more and less than 0.005 (usable) ×: Dielectric tangent 0.005 or more (unusable)

[0069] <Heat cycle test> Each of the resin films for evaluation in Examples 1 to 19 and Comparative Examples 1 to 4 was placed in a thermal shock device ("TSE-11-A", manufactured by Espec Corporation) and subjected to 2000 cycles of alternating exposure under the following conditions: high temperature exposure: 125°C, 15 minutes; low temperature exposure: -50°C, 15 minutes. Next, the change in 5% weight decomposition temperature in an air atmosphere was measured for each resin film before and after the heat cycle test using a TGDTA220 (Seiko Instruments Inc., simultaneous thermogravimetry and differential thermal analyzer). Using an aluminum open sample pan, the test was carried out under the following conditions: 5 mg of resin film, air flow rate 200 mL / min, starting temperature 25°C, and heating rate 10°C / min up to 550°C. The weight change was calculated using the following formula, with the temperature plotted on the horizontal axis and the weight change plotted on the vertical axis, and the temperature at which a 5% weight loss occurred was determined as the 5% weight loss temperature. Weight change (%) = Weight at each temperature (g) / Weight of cured material before measurement (g) × 100 The resistance to the heat cycle test was evaluated based on the difference in the 5% weight loss temperature before and after the heat cycle test, according to the following evaluation criteria. ◎: Decrease less than 5°C (very good) ○: Decrease of 5°C or more, less than 10°C (good) △: Decrease in temperature by 10°C or more and less than 20°C (usable) ×: Decreased width of 20℃ or more. (Unavailable)

[0070] <Long-term heat resistance test> Each resin film for evaluation in Examples 1 to 19 and Comparative Examples 1 to 4 was stored in a hot air oven under an air atmosphere at 250°C for 1000 hours. The 5% weight loss temperature of each resin film was calculated by thermogravimetric measurement using a TGDTA220 (Seiko Instruments Inc., simultaneous thermogravimetry and differential thermal analyzer) under the same conditions as the heat cycle test. Heat resistance was evaluated based on the difference in 5% weight loss temperature before and after the storage test, according to the following evaluation criteria. ◎: Decrease less than 5°C (very good) ○: Decrease of 5°C or more, less than 10°C (good) △: Decrease in temperature by 10°C or more and less than 20°C (usable) ×: Decreased width of 20℃ or more. (Unavailable)

[0071] X 2 As a result, the residue X corresponds to the structure of the dimer acid excluding the carboxyl group. 2 As shown in Comparative Examples 1 to 4, resins lacking d exhibited poor solubility in commonly used organic solvents, which are advantageous in terms of economy and volatility. Furthermore, the rate of oxazole ring closure during solution synthesis was extremely low, resulting in the resin essentially remaining as a precursor to polybenzoxazole resin. Therefore, when subjected to a baking process at a relatively low temperature that does not damage the device, the resins exhibited poor long-term heat resistance and poor resistance to heat cycle tests, which simulate multiple heating processes. Furthermore, the dielectric properties, such as the dielectric constant and dissipation factor, were also clearly poor. This was no exception even for Comparative Examples 1 and 2, which had a structure in which residues equivalent to the structure of dimer acid without the carboxyl group were linked by amide bonds from diamine raw materials. On the other hand, in Examples 1 to 19 according to the present invention, polybenzoxazole resins with sufficiently high ring closure rates could be synthesized even by solution synthesis. This is because X introduced from the carboxylic acid raw material 2We speculate that the high molecular mobility of the d residues increases the overall mobility of the polybenzoxazole resin during synthesis, favoring the progress of the ring-closure reaction occurring in its immediate vicinity. As a result, polybenzoxazole resin films could be formed using only a relatively low-temperature baking process that would not damage the device. Furthermore, we confirmed that the resin films exhibited excellent long-term heat resistance, heat cycle test resistance, and dielectric properties.

Claims

1. A polybenzoxazole resin having a repeating unit represented by the following general formula (1): 【Chemical 1】 ・・・（１） (X １ each independently represents a tetravalent aromatic group for each repeating unit; X １ The N and O bonded to X form pairs, and the N and O of each pair are bonded to adjacent carbon atoms on the same aromatic ring. ２ are each independently a divalent organic group for each repeating unit, and X ２ At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. ２ d, and X １ and oxazole bonds are linked together to form two oxazole rings.)

2. X １ The polybenzoxazole resin according to claim 1, wherein R is a group represented by the following general formula (2): 【Chemistry 2】 ・・・（２） (In formula (2), X ３ is -CH ２ -, -O-, -S-, -SO-, -SO ２ -, -SO ２ NH-, -CO-, -COO-, -NHCO-, -NHCONH-, -C(CF ３ ) ２ -, -CF ２ -, -C(CH ３ ) ２ -, -CH(CH ３ ) -, -C(C ２ H ５ ) (CH ３ ) -, -C(C ６ H ５ ) (CH ３ ) -, -Si(R ７ ) ２ -, -O-Si(R ８ ) ２ —O—, —Si(R ９ ) ２ —O—Si(R 1０ ) ２ -, and -(CH ２ ) ｉ -Si(R １１ ) ２ —O—Si(R １２ ) ２ - (CH ２ ) ｉ -(i represents an integer of 0 to 6), or a structure represented by any of the following chemical formulas (3) to (7), or a direct bond. 【Chemistry 3】 ・・・（３） 【Chemistry 4】 ・・・（４） 【Chemistry 5】 ・・・（５） 【Chemistry 6】 ・・・（６） 【Chemistry 7】 ・・・（７） (In formula (2), R １ ~R １２ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or -(CF ２ ) ｂ -CF ３ Or -O-(CF ２ ) ｂ -CF ３ (b represents an integer of 0 to 5.)

3. X constituting the polybenzoxazole resin ２ When the total is 100 mol%, X ２ 2. The polybenzoxazole resin according to claim 1, wherein d is 40 to 100 mol %.

4. A resin film comprising the polybenzoxazole resin according to any one of claims 1 to 3.

5. A method for producing the polybenzoxazole resin according to any one of claims 1 to 3, characterized by reacting a compound represented by the following general formula (8) with a compound represented by the following general formula (9): 【Chemistry 8】 ・・・（８） (X １ each independently represents a tetravalent aromatic group for each repeating unit; X １ The N and O bonded to form pairs, and each pair of N and O is bonded to adjacent carbon atoms on the same aromatic ring. 【Chemistry 9】 ・・・（９） (In formula (9), X ２ are each independently a divalent organic group for each repeating unit, and X ２ At least a part of the residue X corresponds to the structure of the dimer acid excluding the carboxy group. ２ d and X ４ is H, OH, Cl, Br, I, OR １３ and an organic group represented by the following formula (10), １３ represents a hydrocarbon group having 3 or less carbon atoms or a phenyl group. 【Chemistry 10】 ・・・（１０）

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