Insulating materials and their manufacturing methods

Abstract

This insulating material comprises cross-linked polyethylene oxide having liquid crystal primary side chains in each repeating unit. The cross-linked polyethylene oxide satisfies the following formulas (I) and (II). a, b, and c are the storage elastic moduli of the aforementioned cross-linked polyethylene oxide at 30°C, 100°C, and 260°C, respectively. The insulating material may also be made of cross-linked polyethylene oxide.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to insulating materials and their manufacturing methods. [Previous Technology]

[0002] In various electrical / electronic circuit boards exemplified by semiconductor integrated circuits, since heat generated by the circuit is released, a metal substrate that functions as a heat sink is used, and a circuit is formed on it by a bonding agent containing an insulating material. For example, in the circuit boards disclosed in Patent Documents 1 and 2, a bonding agent containing epoxy resin as an insulating material is disposed between the metal substrate and the circuit.

[0003] 『Patent Documents』 《Patent Document 1》: International Patent Publication No. 2021 / 125258 《Patent Document 2》: International Patent Publication No. 2020 / 179693 [Summary of the Invention]

[0004] One embodiment of the present invention aims to provide an insulating material with a novel structure. Alternatively, one embodiment of the present invention aims to provide a highly thermally conductive insulating material with high thermal conductivity and high heat resistance.

[0005] One embodiment of the present invention is an insulating material. This insulating material comprises: cross-linked polyethylene oxide having liquid crystal primary side chains in each repeating unit. The cross-linked polyethylene oxide satisfies the following formulas (I) and (II). a, b, and c are the storage elastic moduli of the aforementioned cross-linked polyethylene oxide at 30°C, 100°C, and 260°C, respectively.

[0006]

[0007] One embodiment of the present invention is a method for manufacturing an insulating material comprising cross-linked polyethylene oxide. This manufacturing method includes: ring-opening copolymerization of a trifunctional or higher epoxy compound, both containing liquid crystal atoms, with a difunctional epoxy compound. The cross-linked polyethylene oxide satisfies the following formulas (I) and (II). a, b, and c are the storage elastic moduli of the aforementioned cross-linked polyethylene oxide at 30°C, 100°C, and 260°C, respectively.

[0008]

Implementation Method

[0016] The following describes the insulating material (hereinafter sometimes referred to as the insulating material) and its manufacturing method related to embodiments of the present invention. The present invention can be implemented in various forms without departing from its spirit and is not limited to the description of the embodiments exemplified below.

[0017] 1. Insulating materials

[0018] (1)Structure

[0019] This insulating material is manufactured by ring-opening copolymerization of a trifunctional or higher epoxy compound and a difunctional epoxy compound. Specifically, the trifunctional or higher epoxy compound can be selected from trifunctional and tetrafunctional epoxy compounds. Therefore, this insulating material comprises: cross-linked polyethylene oxide with a basic backbone formed by the chain polymerization of epoxy groups. Furthermore, both the trifunctional or higher epoxy compound and the difunctional epoxy compound have one or more liquid crystal atoms within their molecules. Therefore, each repeating unit of the polyethylene oxide contains side chains containing liquid crystal atoms. This insulating material may also further include fillers as an arbitrary configuration. Here, the so-called ring-opening polymerization is a polymerization mode different from addition polymerization and polycondensation, which are successive polymerizations; it is a chain polymerization of cyclic compounds through ring-opening and mutual addition to form linear polymers.

[0020] Liquid crystal originators have rigid frameworks, such as naphthalene, biphenyl, phenoxycarbonyl, azobenzene, stilbene, and tetrahydronaphthalene frameworks. However, liquid crystal originators for epoxides with three or more functionalities and difunctional epoxides are not limited to the above frameworks and can use various rigid frameworks. For example, fused aromatic ring frameworks such as anthracene, fused tetraphenyl, perylene, pyrene, phenanthrene, styrene, and argentinium frameworks can also be used. Alternatively, they can be aromatic heterocyclic frameworks in which one or more carbon atoms forming such fused aromatic rings are substituted with nitrogen, oxygen, sulfur, or other heteroatoms. For example, liquid crystal originators can also be fused aromatic heterocyclic frameworks such as quinoline, isoquinoline, benzyline, acridine, 1-naphthazine, and benzyline frameworks.

[0021] The liquid crystal origins of trifunctional or higher-functionality epoxy compounds and difunctional epoxy compounds can be different from each other or the same. When the trifunctional or higher-functionality epoxy compounds and difunctional epoxy compounds have the same liquid crystal origin, the intramolecular π-π stacking interaction between the liquid crystal origins of the trifunctional or higher-functionality epoxy compounds and the difunctional epoxy compounds in this insulating material will operate more strongly. This allows the insulating material to be endowed with high heat resistance and thermal conductivity.

[0022] Epoxy compounds with 3 or higher functionalities are generally solid at room temperature and pressure. 2-functional epoxy compounds are desirable to have a structure that allows them to exist in a liquid state at room temperature and pressure. 3-functional, 4-functional, and 2-functional epoxy compounds can be described as monomers 1a, 1b, and 2, respectively, as shown below.

[0023]

[0024] Here, M1, M2, and M refer to the liquid crystal atoms described above. In the example described above, monomers 1a and 1b, which are epoxy compounds with three or more functionalities, contain two liquid crystal atoms M1 and M2, and a difunctional epoxy compound contains one liquid crystal atom M. M1, M2, and M may be the same as each other, or at least one of them may be different from the other two. When M1, M2, and M are the same, the intermolecular forces caused by π-π stacking between M1 and M2, M1 and M, and / or M2 and M will operate strongly, thus imparting higher heat resistance and thermal conductivity to this insulating material.

[0025] L represents a single bond or a divalent linker. L is, for example, an alkyl group having 1 to 7 carbon atoms, such as an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 3 carbon atoms, or a methylene group.

[0026] This insulating material is manufactured by ring-opening polymerization in which three or more epoxy groups contained in a trifunctional or higher epoxy compound and two epoxy groups contained in a difunctional epoxy compound contribute to the process. Furthermore, the polyethylene oxide backbone obtained by ring-opening polymerization of epoxy groups is cross-linked via liquid crystal atoms M1, M2, M and oxymethylene groups to form a complex three-dimensional network. Therefore, although this insulating material cannot be described by a general formula, it contains at least a portion of the following structure. In addition, a portion of the trifunctional or higher epoxy compound may also exist in the insulating material in an epoxy group state where at least one epoxy group has not reacted during ring-opening polymerization. Similarly, a portion of the difunctional epoxy compound may also exist in the insulating material in an epoxy group state where one of its two epoxy groups has not reacted during ring-opening polymerization.

[0027]

[0028] The 3-functional epoxy compound, the 4-functional epoxy compound, and the 2-functional epoxy compound may also be monomers 3, 4, and 5 as shown in the following structural formulas, respectively. Here, R1 to R3 are substituents introduced into the naphthalene skeleton, and can be independently selected from hydrogen, alkyl, alkoxy, hydroxyl, halogen, cyano, amino, nitro, alkanecarbonyl, arylcarbonyl, alkoxycarbonyl, aryloxycarbonyl, etc. The number of carbon atoms in the alkyl group of the alkanecarbonyl and alkoxycarbonyl groups is not restricted, and is, for example, 1 or more and 6 or less. The number of carbon atoms in the arylcarbonyl and aryloxycarbonyl groups is also not restricted, and is, for example, 5 or more and 12 or less. The substitution position of R1 to R3 is also not restricted, and R1 to R3 can be introduced onto carbons selected from carbons other than the sp2 carbons already used for bonding.

[0029]

[0030] As a filler with arbitrary structure, an inorganic material with high thermal conductivity is preferred. Examples include: silicon oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide, silicon nitride, etc. The filler is contained in the insulating material in powder form. There are no restrictions on the shape, particle size, or particle size distribution of the filler. There are also no restrictions on the content of the filler, but for example, it is 70% by volume or more or 80% by volume or more relative to the insulating material. The upper limit of the filler content is 95% by volume or less. By using fillers, the thermal conductivity of the insulating material can be further improved. Furthermore, it is also acceptable for the insulating material to contain additives such as surfactants, silane coupling agents, and ion trapping materials.

[0031] (2)Characteristics

[0032] The insulating material having the structure described above exhibits high heat resistance and thermal conductivity, and its flexibility changes little over a wide temperature range. Flexibility can be evaluated by its storage modulus, and the storage modulus of this insulating material changes relatively little over a wide temperature range. This characteristic contrasts with insulating materials such as epoxy resins formed from polymers, where flexibility increases with increasing temperature, i.e., the storage modulus decreases significantly. More specifically, this insulating material satisfies the following equations (I) and (II). Here, a, b, and c are the storage moduli of this insulating material at 30°C, 100°C, and 260°C, respectively. The storage modulus can be measured according to JIS C6481 using the DMA method (Dynamic Viscoelasticity Measurement).

[0033]

[0034] As can be understood from the above formulas (I) and (II), although the storage modulus of elasticity of this insulating material also decreases with increasing temperature, the rate of decrease decreases with increasing temperature. Therefore, this insulating material can maintain a relatively high storage modulus of elasticity even at high temperatures. That is, by maintaining high rigidity even at high temperatures, it simultaneously possesses high heat resistance and high thermal conductivity (i.e., high rigidity). Therefore, when this insulating material is used as an insulating material between a metal substrate and a circuit, a high bonding force can be maintained between the circuit and the metal substrate even at high temperatures. Furthermore, since both the trifunctional and difunctional epoxy compounds that make up this insulating material contain liquid crystal atoms, the repeating units of ethylene oxide contain one or more liquid crystal atoms. Therefore, this insulating material exhibits excellent thermal conductivity and high rigidity due to the π-π stacking effect between liquid crystal atoms. Therefore, by using this insulating material, a circuit board with high heat resistance and high thermal conductivity can be provided.

[0035] 2. Manufacturing method of insulating materials

[0036] As described above, this insulating material can be manufactured by ring-opening copolymerization of a trifunctional or higher epoxy compound and a difunctional epoxy compound. To facilitate effective ring-opening copolymerization, an initiator (sometimes called a curing catalyst) can also be used. Specifically, this insulating material can be manufactured by adding an initiator to a trifunctional or higher epoxy compound and a difunctional epoxy compound and heating as needed. The heating temperature can be selected from a range of 80°C to 300°C or 150°C to 200°C, and the heating time can be appropriately selected from 1 second to 600 minutes or 1 minute to 5 minutes. At this time, fillers can also be further added. The amount of initiator, for example, relative to the total mass of the trifunctional or higher epoxy compound and the difunctional epoxy compound, can be 0.1% by weight or more and 10% by weight or more and 4% by weight. Since the initiator is bonded to the end of the polyethylene oxide in this insulating material, without the use of fillers, this insulating material can be said to be made of cross-linked polyethylene oxide obtained by ring-opening copolymerization of a trifunctional or higher epoxy compound and a difunctional epoxy compound.

[0037] There are no restrictions on the types of initiators that can be used, such as alkane oxides of alkali metals or alkaline earth metals, imidazoles, tertiary amines such as benzyl dimethylamine, diacylbicyclic compounds, phosphines such as triphenylphosphine, and phosphonium initiators. Among these, imidazoles that are less prone to termination reactions or chain transfer, have a high degree of polymerization, and can polymerize epoxides are preferred. Examples of imidazoles include, for instance, imidazole compounds with a cyano group. Specifically, examples include 1-(2-cyanoethyl)-2-methylimidazolium, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazolium, 1-(2-cyanoethyl)-2-undecylimidazolium, 1-(2-cyanoethyl)-2-isopropylimidazolium, 1-(2-cyanoethyl)-2-phenylimidazolium, and 1-(2-cyanoethyl)-2-phenyl-5-(2-cyanoethoxy)methylimidazolium.

[0038] Alternatively, complexes of boron trifluoride with amines, salts of aromatic diazo compounds with BF4, PF6, SbF6, AsF6, SnCl6, FeCl4, BiCl5, or SbCl6, diaryl monazite salts, triaryl strontium salts, or triaryl salts may also be used as initiators. Alternatively, salts of zinc, manganese, cobalt, tin, or other carboxylic acids such as naphthenic acid, stearic acid, and caprylic acid may also be used as initiators.

[0039] In a typical manufacturing method, firstly, an epoxy compound with three or more functionalities, a difunctional epoxy compound, and an initiator are mixed. When the epoxy compound with three or more functionalities and / or the difunctional epoxy compound are in a liquid state, a paste-like mixture can be obtained by mixing, and this mixture can be shaped into a desired form. To improve the formability of the mixture, a solvent may be added. Examples of solvents include: aromatic solvents such as toluene or xylene, tetrahydronaphthalene; ether solvents such as tetrahydrofuran or dimethyl ether; alcohols such as ethanol or isopropanol; acetamide solvents such as N-methylpyrrolidone or N,N-dimethylformamide, N,N-dimethylacetamide; ester solvents such as ethyl acetate, butyl acetate, hexyl acetate, ethyl 3-methoxypropionate, propylene glycol monomethyl ether ester; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, or cyclohexanone; etc. If the insulating material contains filler, the filler can be further added to the mixture. After removing the solvent from the obtained mixture as needed, the mixture is heated at room temperature or at the temperature described above for the heating time described above, thereby allowing the ring-opening polymerization of the epoxy groups to proceed, and the insulating material can be manufactured.

[0040] To obtain the insulating material of the present invention in the form of a thin film, the above-described mixture containing the solvent is coated to a desired thickness onto a support such as a polyethylene terephthalate (PET) film, and then the solvent is distilled off to obtain a precursor of the insulating material. The precursor is then heated at the temperature described above for the heating time described above. A pressure of 1 MPa to 30 MPa—preferably 5 MPa to 20 MPa—may also be applied during at least a portion of this heating time.

[0041] When using this insulating material as an insulating layer for a circuit board formed from a metal substrate and a circuit, an adhesive can be further used to improve the bonding strength between the insulating material and the metal substrate and the circuit. Examples of adhesives include thermosetting resin-based adhesives such as acrylic resin-based adhesives, carbamate resin-based adhesives, and epoxy resin-based adhesives. Epoxy resin-based adhesives are preferred. When using epoxy resin-based adhesives, a polymerization initiator containing an alkaline solution is desirable. An adhesive that can penetrate the insulating material or its precursor is preferred. Here, "adhesive penetration" means that a portion of the adhesive diffuses into the insulating material or its precursor, while simultaneously forming a discontinuous adhesive layer between the metal substrate, the circuit, and the insulating material.

[0042] The method for bonding the insulating material to a metal substrate and a circuit using an adhesive can be exemplified as follows. A mixture comprising an epoxy compound with three or more functionalities, an epoxy compound with two functionalities, a filler, and a solvent is coated onto a support such as a PET film, and the solvent is removed to obtain a precursor. After coating the precursor with an adhesive, a metal substrate is placed with the adhesive-coated surface facing each other, and heat-treated at the temperature and time described above, thereby effectively bonding the insulating material to the metal substrate. At this time, applying a pressure of 1 MPa to 30 MPa or 5 MPa to 20 MPa is also acceptable. Afterward, the support is peeled off, an adhesive is coated on the exposed surface, a circuit is placed on the adhesive, and heat-treated at the temperature and time described above, thereby effectively bonding the insulating material to the circuit. At this time, applying a pressure of 1 MPa to 30 MPa or 5 MPa to 20 MPa is also acceptable.

[0043] Therefore, in the manufacture of this insulating material, curing agents such as polyfunctional alcohols and polyfunctional phenols (e.g., curing agents with multiple phenolic groups) are not used. Thus, as shown in the examples, since the liquid crystal atoms efficiently undergo π-π stacking, and soft polyethylene oxide chains exist around the liquid crystal atoms, a structure close to that of a liquid crystal is formed. Therefore, this insulating material can be expected to exhibit a relatively high storage modulus of elasticity even at high temperatures. Therefore, this insulating material can be expected to possess both high thermal conductivity and high heat resistance.

[0044] 『Example』

[0045] In this embodiment, an insulating material related to the implementation of the present invention is prepared, and the results of evaluating its properties are described.

[0046] (1) Preparation of the sample

[0047] 10 parts by weight of the following four-functional epoxy compound 6 (manufactured by DIC Corporation), 5 parts by weight of the following two-functional epoxy compound 7 (manufactured by DIC Corporation), and 0.3 parts by weight of the initiator 8 (manufactured by Dissolve Technology Corporation) were dissolved in 100 parts by weight of cyclohexanone. Then, 23 parts by weight of boron nitride powder (HP-4012W, median diameter (D50) 12 μm) and boron nitride powder (P-40MH100, median diameter (D50) 18 μm) manufactured by JFE Mineral & Alloy Company, Ltd. were added as fillers. The obtained mixture was pulverized using a ball mill. As shown in Figure 1, this mixture 102a was coated onto a PET film 100 and heated at 120°C for 10 minutes.

[0048]

[0049] As shown in Figure 2, a copper foil 104 with a thickness of 0.5 mm is placed on a mixture 102a through a bonding agent obtained by mixing 2.5 parts by weight of the difunctional epoxy resin 9 (manufactured by DIC Corporation) and 0.1 parts by weight of the initiator 8. Then, the mixture 102a is cured into the insulating material 102 by hot pressing at a temperature of 170°C and a pressure of 25 MPa for 3 minutes, thereby bonding the insulating material 102 to the copper foil 104. Afterwards, by peeling off the PET film 100, a bond 106 containing the copper foil 104 and the insulating material 102 is obtained (see Figure 3). Two bond 106 pieces are fabricated.

[0050]

[0051] Next, the two bonding bodies 106 are joined together such that the insulating material 102 is sandwiched between two copper foils 104. The bonding is carried out using a hot press at a temperature of 170°C for 1.5 minutes, and then hot-pressed at a pressure of 12 MPa for 1.5 minutes (Figure 4). Afterwards, the copper foils 104 are dissolved using an etching solution (manufactured by Sunhayato Corp., H-20L), the remaining insulating material 102 is washed with water and dried, thereby obtaining the sample of the embodiment (thickness 0.24 mm) (Figure 5).

[0052] Excluding the use of the 2-functional epoxy compound 10 shown below instead of the 4-functional epoxy compound 6 above, and the use of the 2-functional epoxy compound 10 in the preparation of the binder, a comparative example sample was obtained by performing the same operation as in the example.

[0053]

[0054] (2) Evaluation

[0055] Thermal conductivity, storage modulus of elasticity, and heat resistance were evaluated for the samples of the Examples and Comparative Examples. Thermal conductivity was obtained by measuring the thermal conductivity in the thickness direction using a laser flash method. The storage modulus of elasticity was measured according to JIS C6481 using a dynamic viscoelasticity analysis apparatus (manufactured by TA Instruments Japan Inc.) via the DMA method (tensile mode, load 100 g, frequency 1 Hz). The storage modulus of elasticity was measured at temperatures of 30°C, 100°C, and 260°C. Heat resistance was evaluated by observing the cross-section of the sample after heating. Specifically, the sample before peeling off the copper foil 104 was treated in a solder bath at 300°C for 5 minutes, and then the copper foil 104 was removed using the method described above. The heat resistance was evaluated by observing the cross-sectional SEM images of the obtained sample. The results are shown in Table 1.

[0056] 『Table 1』 Table 1 Evaluation results of the samples from the Examples and Comparative Examples Storage elastic modulus (GPa) 30℃ 100℃ 260℃ c / a a c / b b thermal conductivity (W / mK) The occurrence of rupture Example 15.6 14.4 8.27 0.530 0.574 20.2 none Comparative example 18.1 15.5 3.00 0.166 0.194 17.7 have a Storage elastic modulus at 260°C relative to storage elastic modulus at 30°C b Storage elastic modulus at 260°C relative to storage elastic modulus at 100°C

[0057] As can be understood from Table 1, the storage modulus of elasticity of the insulating material of the embodiment at 260°C relative to the storage modulus of elasticity at 30°C (c / a) and the storage modulus of elasticity at 260°C relative to the storage modulus of elasticity at 100°C (c / b) are 0.530 and 0.574, respectively, confirming that equations (I) and (II) are satisfied. Furthermore, the c / a and c / b of the insulating material of the embodiment are larger than those of the comparative example. This indicates that the insulating material of the embodiment maintains a high storage modulus of elasticity over a wide temperature range. Furthermore, the thermal conductivity of the insulating material of the embodiment is higher than that of the comparative example, indicating that the material has high stability even at high temperatures.

[0058] SEM images of the samples from the Examples and Comparative Examples obtained in the heat resistance evaluation are shown in Figures 6 and 7, respectively. As can be understood from Figure 6, no cracking was observed in the samples from the Examples. In contrast, as shown in Figure 7, numerous cracks were observed in the samples from the Comparative Examples (refer to the arrows in the figure). As a result, it is indicated that the insulating material of the Examples has high heat resistance.

[0059] The above results indicate that this insulating material can be appropriately used as an insulator for, for example, a metal substrate having a circuit that generates a large amount of heat due to driving.

[0060] Based on the embodiments described above as embodiments of the present invention, any additions, deletions, or design changes to the constituent elements, or additions, omissions, or changes to the conditions of the processes made by those skilled in the art, are also included within the scope of the present invention, as long as they possess the essence of the present invention. Even if the effects are different from those achieved by the various embodiments described above, those that are obvious from the description in this specification or that can be easily predicted by those skilled in the art should be understood as being achieved by the present invention. [Simplified Explanation of the Diagram]

[0009] Figure 1 shows a schematic end view of the method for manufacturing the insulating material according to the embodiment.

[0010] Figure 2 shows a schematic end view of the method for manufacturing the insulating material according to the embodiment.

[0011] Figure 3 shows a schematic end view of the method for manufacturing the insulating material according to the embodiment.

[0012] Figure 4 shows a schematic end view of the method for manufacturing the insulating material according to the embodiment.

[0013] Figure 5 shows a schematic end view of the method for manufacturing the insulating material according to the embodiment.

[0014] <Figure 6> Scanning electron microscope (SEM) image of the cross-section of the insulating material of the embodiment.

[0015] 〈Fig. 7〉SEM image of the cross-section of the insulating material of the comparative example.

Claims

1. An insulating material comprising: cross-linked polyethylene oxide having liquid crystal primary side chains in each repeating unit, wherein the cross-linked polyethylene oxide satisfies the following formulas (I) and (II): a, b, and c are the storage elastic moduli of the cross-linked polyethylene oxide at 30°C, 100°C, and 260°C, respectively.

2. The insulating material as described in claim 1 is made of the aforementioned cross-linked polyethylene oxide.

3. The insulating material as claimed in claim 1, wherein the aforementioned liquid crystal matrix comprises a skeleton selected from naphthalene skeleton, biphenyl skeleton, phenoxycarbonyl skeleton, azobenzene skeleton, stilbene skeleton and tetrahydronaphthalene skeleton.

4. The insulating material as claimed in claim 3, wherein the aforementioned skeleton has substituents selected from alkyl, alkoxy, hydroxy, halogen, cyano, amino, nitro, alkoxycarbonyl, arylcarbonyl, alkoxycarbonyl and aryloxycarbonyl.

5. The insulating material as claimed in claim 1, wherein the aforementioned cross-linked polyethylene oxide is manufactured by ring-opening copolymerization of monomer 1a and monomer 2 or monomer 1b and the aforementioned monomer 2, as shown in the following general formula: M1, M2 and M are the aforementioned liquid crystal atoms, and L is a linking group selected from alkyl, oxyalkyl, carbonyl and ester groups.

6. The insulating material as claimed in claim 5, wherein the mass ratio of the aforementioned monomer 1a or the aforementioned monomer 1b to the aforementioned monomer 2 is 0.25 or more and 3 or less.

7. The insulating material as claimed in claim 5, wherein the aforementioned monomer 1b and the aforementioned monomer 2 are respectively composed of monomer 3 and monomer 4 represented by the following general formulas: R1 to R3 are independently selected from hydrogen, alkyl, alkoxy, hydroxy, halogen, cyano, amino, nitro, alkoxycarbonyl, arylcarbonyl, alkoxycarbonyl, and aryloxycarbonyl.

8. The insulating material as described in claim 1, further comprising filler.

9. A method for manufacturing an insulating material comprising cross-linked polyethylene oxide, comprising: ring-opening copolymerization of a trifunctional epoxy compound or a tetrafunctional epoxy compound and a difunctional epoxy compound, each comprising a liquid crystal element, wherein the aforementioned cross-linked polyethylene oxide satisfies the following formulas (I) and (II): a, b, and c are the storage elastic moduli of the aforementioned cross-linked polyethylene oxide at 30°C, 100°C, and 260°C, respectively.

10. A method for manufacturing an insulating material as claimed in claim 9, wherein the aforementioned liquid crystal matrix comprises a skeleton selected from naphthalene skeleton, biphenyl skeleton, phenoxycarbonyl skeleton, azobenzene skeleton, stilbene skeleton and tetrahydronaphthalene skeleton.

11. A method for manufacturing an insulating material as claimed in claim 10, wherein the aforementioned skeleton has substituents selected from alkyl, alkoxy, hydroxy, halogen, cyano, amino, nitro, alkoxycarbonyl, arylcarbonyl, alkoxycarbonyl, and aryloxycarbonyl.

12. A method for manufacturing an insulating material as claimed in claim 9, wherein the aforementioned 3-functional epoxy compound, the aforementioned 4-functional epoxy compound and the aforementioned 2-functional epoxy compound are respectively derived from monomer 1a, monomer 1b and monomer 2 represented by the following general formulas: M1, M2 and M are the aforementioned liquid crystal atoms, and L is a linking group selected from alkyl groups, oxyalkyl groups, carbonyl groups and ester groups.

13. The method for manufacturing an insulating material as claimed in claim 12, wherein the aforementioned ring-opening copolymerization is carried out under the condition that the mass ratio of the aforementioned monomer 1a or the aforementioned monomer 1b to the aforementioned monomer 2 is 0.25 or more and 3 or less.

14. The method for manufacturing an insulating material as claimed in claim 12, wherein the aforementioned monomer 1b and the aforementioned monomer 2 are respectively composed of monomer 3 and monomer 4 represented by the following general formulas: R1 to R3 are independently selected from hydrogen, alkyl, alkoxy, hydroxy, halogen, cyano, amino, nitro, alkoxycarbonyl, arylcarbonyl, alkoxycarbonyl, and aryloxycarbonyl.

15. A method for manufacturing an insulating material as claimed in claim 9, wherein the aforementioned ring-opening copolymerization is carried out in the presence of filler.

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