JP2019064089A - Epoxy resin sheet, method for producing epoxy resin sheet, and method for producing insulator and method for producing electrical device - Google Patents

Abstract

To provide an epoxy resin sheet that makes it possible to obtain an insulator having excellent thermal conductivity and a method for producing the same, and methods for producing an insulator and an electrical device using the epoxy resin sheet.SOLUTION: An epoxy resin sheet has a resin layer, and a base material in contact with at least one side of the resin layer, wherein, the side of the base material which is in contact with the resin layer has a surface free energy of 10 mJ/mor more, and the resin layer contains an epoxy resin containing an epoxy compound having a mesogen group.SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin sheet, a method of producing an epoxy resin sheet, a method of producing an insulator, and a method of producing an electrical device.

  Many of the electrical devices from power devices such as generators and motors to electronic devices such as printed wiring boards and IC chips are configured to include a conductor for conducting electricity and an insulator. As the insulator, a cured product of a thermosetting resin is widely used from the viewpoint of insulation, heat resistance, and the like.

  In recent years, the calorific value tends to increase with the miniaturization and high output of these electric devices, and the improvement of the technology to dissipate the generated heat in the insulator has become an important issue. However, since an insulator formed of a resin generally has low thermal conductivity and is poor in heat dissipation, improvement in thermal conductivity is desired.

  As an epoxy resin from which the hardened | cured material which is excellent in heat conductivity is obtained, the epoxy resin which has a mesogenic group in a molecule | numerator is proposed (for example, refer patent document 1-patent document 5). The epoxy resin having a mesogenic group has a property that molecules are stacked in the cured product to exhibit liquid crystallinity. As a result, phonon scattering is suppressed and high thermal conductivity is achieved.

Patent No. 4118691 gazette Patent No. 4619770 Patent No. 5471975 JP, 2011-84557, A JP, 2016-155985, A

Although a cured product of an epoxy resin having a mesogen group is excellent in thermal conductivity, when it is used as an insulator of an electric device, further improvement of thermal conductivity is required as described above.
An object of the present invention is to provide an epoxy resin sheet capable of obtaining an insulator excellent in thermal conductivity, a method for producing the same, and a method for producing an insulator and an electric device using the epoxy resin sheet. .

Means for solving the above problems include the following embodiments.
It has a <1> resin layer and a substrate in contact with at least one surface of the resin layer, and the surface free energy of the surface of the substrate in contact with the resin layer is 10 mJ / m ² or more, and the resin layer is The epoxy resin sheet containing the epoxy resin containing the epoxy compound which has a mesogenic group.
<2> The epoxy resin sheet according to <1>, wherein the epoxy compound having a mesogenic group has a structure in which three or more 6-membered cyclic groups are linearly linked.
The epoxy resin sheet as described in <1> or <2> which has a structural unit represented with the following general formula (I) the epoxy compound which has a <3> said mesogenic group.

[In general formula (I), R < ¹ > -R < ⁴ > shows a hydrogen atom or a C1-C3 alkyl group each independently. ]
The epoxy compound which has a <4> said mesogenic group is described in any one of <1>-<3> including the compound which has two structural units represented by the following general formula (I) in 1 molecule. Epoxy resin sheet.

[In general formula (I), R < ¹ > -R < ⁴ > shows a hydrogen atom or a C1-C3 alkyl group each independently. ]
The epoxy compound which has a <5> said mesogenic group is at least 1 structural unit selected from the group which consists of a structural unit represented by the following general formula (IA), and a structural unit represented by the following general formula (IB) The epoxy resin sheet of any one of <1>-<4> which it has.

[In general formula (IA) and general formula (IB), R ^{1 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁵ each independently has 1 to 8 carbon atoms Represents an alkyl group of n shows the integer of 0-4. ]
The epoxy resin sheet according to any one of <1> to <5>, wherein the <6> resin layer is in the A stage state.
The epoxy resin sheet of any one of <1>-<5> which is a state of the <7> above-mentioned resin layer in B stage.
The epoxy resin sheet of any one of <1>-<5> which is a state of the <8> above-mentioned resin layer of C stage.
<9> comprising a step of forming a resin layer on the substrate, the surface free energy of the surface on which the resin layer is formed of the base material is at 10 mJ / m ² or more, epoxy said resin layer having a mesogenic group The manufacturing method of the epoxy resin sheet of any one of <1>-<8> containing the epoxy resin containing a compound.
The manufacturing method of the insulator including the process of hardening the said resin layer of the epoxy resin sheet manufactured by the manufacturing method of the epoxy resin sheet as described in <10><9>.
The manufacturing method of an electric device, comprising: a step of bringing the resin layer of the epoxy resin sheet according to any one of <11><1> to <8> into contact with an insulating object.

  ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin sheet from which the insulator which is excellent in heat conductivity is obtained, its manufacturing method, the insulator using the epoxy resin sheet, and the manufacturing method of an electric equipment are provided.

Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and does not limit the present invention.
In the present disclosure, the term “step” includes, in addition to steps independent of other steps, such steps as long as the purpose of the step is achieved even if it can not be clearly distinguished from other steps. .
In the numerical value range indicated by using “to” in the present disclosure, the numerical values described before and after “to” are included as the minimum value and the maximum value, respectively.
The upper limit value or the lower limit value described in one numerical value range may be replaced with the upper limit value or the lower limit value of the other stepwise description numerical value range in the numerical value range described stepwise in the present disclosure. . In addition, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the example.
In the present disclosure, each component may contain a plurality of corresponding substances. When a plurality of substances corresponding to each component are present in the composition, the content or content of each component is the total content or content of the plurality of substances present in the composition unless otherwise specified. Means quantity.
In the present disclosure, particles corresponding to each component may contain a plurality of types. When there are a plurality of particles corresponding to each component in the composition, the particle diameter of each component means the value for the mixture of the plurality of particles present in the composition unless otherwise specified.
In the present disclosure, “epoxy compound” means a compound having an epoxy group in the molecule, and “epoxy resin” means a concept of capturing a plurality of epoxy compounds as an aggregate.

<Epoxy resin sheet>
The epoxy resin sheet of the present disclosure includes a resin layer and a substrate in contact with at least one surface of the resin layer, and the surface free energy of the surface of the substrate in contact with the resin layer is 10 mJ / m ² or more. The resin layer is an epoxy resin sheet containing an epoxy resin containing an epoxy compound having a mesogen group (hereinafter also referred to as a mesogen-containing epoxy compound).

As a result of studies by the present inventors, it was found that according to the epoxy resin sheet having the above-described configuration, an insulator having excellent thermal conductivity can be obtained. Although the reason is not necessarily clear, the orientation of the molecules of the mesogen-containing epoxy compound in the resin layer is the specific property (the surface free energy is 10 mJ / m ² or more) possessed by the surface of the substrate in contact with the resin layer. It influences the state, which is presumed to contribute to the improvement of the thermal conductivity.

  The insulator obtained by the epoxy resin sheet of the present disclosure corresponds to a cured product obtained by curing the resin layer. As a method of obtaining an insulator using the epoxy resin sheet of this indication, the method of making the resin layer side of an epoxy resin sheet contact an insulation object (conductors, such as a metal), for example, and hardening a resin layer is mentioned.

When the mesogen-containing epoxy compound is cured, the molecules tend to be oriented in a certain direction, and the heat conductivity at curing tends to be higher as the degree of orientation is higher. In the epoxy resin sheet of the present disclosure, the orientation of the molecules of the mesogen-containing epoxy compound in the resin layer is promoted by the surface of the base material having a surface free energy of 10 mJ / m ² or more and the resin layer being in contact. It is assumed that the thermal conductivity of the resulting insulator is improved.

  The epoxy resin sheet may be provided with members (protective sheet etc.) other than a base material and a resin layer as needed. Moreover, the number of the base material and the resin layer may be one or two or more, respectively. Moreover, even if the base material is disposed only on one side of the resin layer, it may be disposed on both sides. When the base materials are disposed on both sides of the resin layer, it is sufficient that at least one of the base materials satisfies the condition of the surface free energy described above. That is, the base material on the side where the insulator obtained by using the epoxy resin sheet is in contact with the object to be insulated should satisfy at least the condition of the surface free energy described above.

(Base material)
The material of the substrate is not particularly limited. For example, it can be selected from organic materials such as resins, inorganic materials such as ceramics and metals, composites of these, and the like. As resin, resin which is excellent in heat resistance, such as a polyethylene terephthalate (PET) and a polycarbonate (PC), is mentioned.

  The thickness of the substrate is not particularly limited. For example, it can be selected from the range of 10 μm to 100 μm.

The surface free energy of the surface of the base material in contact with the resin layer is not particularly limited as long as it is 10 mJ / m ² or more. From the viewpoint of thermal conductivity improvement of the resin layer, for example, is preferably 12 mJ / ^{m 2} or more, more preferably 15 mJ / ^{m 2} or more.

The upper limit of the surface free energy of the surface of the substrate in contact with the resin layer is not particularly limited. From the standpoint of facilitating the release of the substrate from the resin layer, for example, is preferably 50 mJ / ^{m 2} or less, it is more preferably 30 mJ / ^{m 2} or less, 25 mJ / ^{m 2} or less More preferable.

  The method of controlling the surface free energy of the surface of the substrate in contact with the resin layer is not particularly limited. For example, the method of surface-treating to the surface of a base material is mentioned. As a method of surface-treating to the surface of a base material, the method of providing a mold release agent on the surface of a base material, etc. are mentioned.

  In the present disclosure, the value of the surface free energy of the surface of the substrate in contact with the resin layer is the water and formamide relative to the substrate surface using an automatic contact angle meter (for example, trade name: Kyowa Interface Science Co., Ltd .: DM 500). The contact angles are respectively measured at 25 ° C. and then calculated by the Kaelble-Uy method.

(Resin layer)
The thickness of the resin layer is not particularly limited. For example, it can be selected from between 50 μm and 200 μm.

  The resin layer may be in an uncured state (A stage), a partially cured state (B stage), or a completely cured state (C stage). For definitions of A stage, B stage and C stage, refer to the provisions of JIS K6900: 1994.

  The epoxy resin sheet provided with the resin layer in the B-stage or C-stage state can be obtained, for example, by heat treatment until the resin layer is in the B-stage or C-stage state. The heat treatment may be carried out under pressure if necessary.

From the viewpoint of the handleability of the epoxy resin sheet, the resin layer is preferably in the B-stage state. When the resin layer is in the B-stage state, it is preferable that the viscosity be lowered by the temperature rise. Specifically, while the viscosity of the resin layer is 10 ⁴ Pa · s to 10 ⁵ Pa · s at normal temperature (25 ° C.), the viscosity is 100 ² Pa · s to 10 ³ Pa · s at 100 ° C. It is preferable that the viscosity is reduced. The viscosity of the resin layer is a value measured by dynamic viscoelasticity measurement (frequency 1 Hz, load 40 g, heating rate 3 ° C./min).

Although the density of the resin layer is not particularly limited, ^normally a ^{3.0g / cm 3 ~3.4g / cm 3} . Considering both flexibility and thermal conductivity, it is preferable that the density of the resin sheet is ^{3.0g / cm 3 ~3.3g / cm 3} , in 3.1g / cm ³ ~3.3g / cm 3 It is more preferable that The density of the resin layer can be adjusted, for example, by the compounding amount of the filler and the like contained in the resin layer.

  It is preferable that the resin layer forms a smectic structure described later when it is cured. If the smectic structure is formed in the cured state, the heat conductivity tends to be more excellent. The resin layer in which the smectic structure is formed in the cured state can be obtained, for example, by appropriately selecting the type of the mesogen-containing epoxy compound contained in the resin layer, the curing conditions, and the like.

(Epoxy resin)
The resin layer contains an epoxy resin containing an epoxy compound having a mesogenic group. The mesogen-containing epoxy compound contained in the epoxy resin may be one kind alone or two or more kinds.

  In the present disclosure, the mesogen group possessed by the mesogen-containing epoxy compound refers to a functional group that facilitates the development of crystallinity or liquid crystallinity in a cured product by the action of intermolecular interaction. Specifically, biphenyl group, terphenyl group, phenyl benzoate group, cyclohexyl benzoate group, azobenzene group, stilbene group, anthracene group, derivatives thereof, and groups in which these are connected by azomethine group, ester group, etc. are mentioned as a representative. Be

  From the viewpoint of improving the thermal conductivity of the insulator, the mesogen-containing epoxy compound has three or more six-membered ring groups in a straight chain in the molecule (preferably, carbon at the 1- or 4-position of each six-membered ring) It is preferred to include structures linked by atoms). Even if the 6-membered ring group is a 6-membered ring group derived from an aromatic ring represented by acenes such as benzene, pyridine, toluene and naphthalene, a 6-membered group derived from an aliphatic ring such as cyclohexane, cyclohexene and piperidine It may be a ring group. Among them, at least one of the six-membered ring groups is preferably a six-membered ring group derived from an aromatic ring, more preferably one is an aliphatic ring, and the remaining rings are all aromatic rings.

  An epoxy resin containing a mesogen-containing epoxy compound forms a higher-order structure in a cured product. Here, the higher order structure means a structure including a higher order structure in which the constituent elements are aligned to form a micro-ordered structure, and corresponds to, for example, a crystal phase and a liquid crystal phase. The presence or absence of such a higher order structure can be determined by a polarization microscope. That is, in the observation in the cross nicol state, it is possible to distinguish by the fact that interference fringes due to depolarization are observed. The higher order structure is usually present in the form of islands in the cured product to form a domain structure, and one of the islands corresponds to one higher order structure. The components themselves of this higher order structure are generally formed by covalent bonds.

  The higher order structure includes a nematic structure and a smectic structure. The nematic structure and the smectic structure are each a type of liquid crystal structure. The nematic structure is a liquid crystal structure in which the molecular long axis is oriented uniformly and has only an orientational order. On the other hand, the smectic structure is a liquid crystal structure having a layer structure, having a one-dimensional position order in addition to the alignment order. The order is higher in the smectic structure than in the nematic structure. Therefore, from the viewpoint of the thermal conductivity and the fracture toughness of the cured product, it is more preferable to form a higher order structure of the smectic structure.

  Whether or not a smectic structure is formed in the cured product of the epoxy resin can be determined by X-ray diffraction measurement of the cured product. The X-ray diffraction measurement can be performed, for example, using an X-ray diffractometer manufactured by Rigaku Corporation. When a cured product having a smectic structure is measured using a CuKα1 line and a tube voltage of 40 kV and a tube current of 20 mA, 2θ = 2 ° to 30 °, diffraction is made to a range of 2θ = 2 ° to 10 °. A peak appears.

The mesogen-containing epoxy compound contained in the epoxy resin may be in the state as it is (monomer only) or in a state (prepolymer) in which a part of the mesogen-containing epoxy compound is reacted.
Although epoxy resins containing mesogen-containing epoxy compounds tend to crystallize in general and tend to have low solubility in solvents, the crystallization can be suppressed by making part of them into a prepolymer state, so that the formability is improved. It may improve.

  As an epoxy resin in a state in which a part of the mesogen-containing epoxy compound is reacted, for example, an unreacted mesogen group-containing compound (hereinafter also referred to as an epoxy monomer) and two structural units derived from the mesogen group-containing compound The epoxy resin containing both of the epoxy compounds (it is also hereafter called a multimer compound) which it has above is mentioned. Specifically, for example, an epoxy monomer is represented by an epoxy compound having a structure represented by the following general formula (I ′ ′) (described in Japanese Patent No. 5471975), and a polymer compound represented by the following general formula (I) The epoxy resin containing both of an epoxy compound which has two or more structural units is mentioned.

In the general formula (I ′ ′), R ^{1 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, It is more preferably an atom or a methyl group, and still more preferably a hydrogen atom.
Furthermore, among R ^{1 to} R ⁴ , two to four are preferably hydrogen atoms, more preferably three or four are hydrogen atoms, and still more preferably all four are hydrogen atoms. When ^{one of} R ^{1 to} R ⁴ is an alkyl group having 1 to 3 carbon atoms, at least one of R ¹ and R ⁴ is preferably an alkyl group having 1 to 3 carbon atoms.

In the general formula (I), R ^{1 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, preferably a hydrogen atom or A methyl group is more preferable, and a hydrogen atom is more preferable.
Furthermore, among R ^{1 to} R ⁴ , two to four are preferably hydrogen atoms, more preferably three or four are hydrogen atoms, and still more preferably all four are hydrogen atoms. When ^{one of} R ^{1 to} R ⁴ is an alkyl group having 1 to 3 carbon atoms, at least one of R ¹ and R ⁴ is preferably an alkyl group having 1 to 3 carbon atoms.

  Specifically, as an epoxy compound having two or more structural units represented by General Formula (I), a group consisting of a structural unit represented by General Formula (IA) and a structural unit represented by General Formula (IB) And compounds having at least one selected from the above.

In the general formula (IA) and the general formula (IB), each of R ^{1 to} R ⁴ independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms Is preferable, a hydrogen atom or a methyl group is more preferable, and a hydrogen atom is more preferable.
Furthermore, among R ^{1 to} R ⁴ , two to four are preferably hydrogen atoms, more preferably three or four are hydrogen atoms, and still more preferably all four are hydrogen atoms. When ^{one of} R ^{1 to} R ⁴ is an alkyl group having 1 to 3 carbon atoms, at least one of R ¹ and R ⁴ is preferably an alkyl group having 1 to 3 carbon atoms.

In the general formula (IA) and the general formula (IB), each R ⁵ independently represents an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, and is preferably a methyl group More preferable. n is an integer of 0 to 4 and is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and still more preferably 0.

  In this embodiment, the structural unit represented by the general formula (IA) is a group consisting of a structural unit represented by the following general formula (IA ′) and a structural unit represented by the following general formula (IA ′ ′) The structural unit represented by the following general formula (IB ′) which is at least one selected and represented by the following general formula (IB ′) and the structural unit represented by the following general formula (IB ′ ′) The structural unit represented by the general formula (IA) is preferably a structural unit represented by the following general formula (IA ′), and is represented by the general formula (IB) More preferably, the structural unit is a structural unit represented by the following general formula (IB ′).

In the general formula (IA ′), the general formula (IB ′), the general formula (IA ′ ′) and the general formula (IB ′ ′), specific examples of R ^{1 to} R ⁵ and n are the general formula (IA) and the general formula It is the same as that of formula (IB), and the preferable range is also the same.

  Among the multimeric compounds having the above-mentioned structure, a multimeric compound having a structure represented by the general formula (IA ′) or the general formula (IB ′) is preferable. A dimer compound having these structures is likely to have a linear molecular structure. For this reason, it is considered that the stacking properties of the molecules are high and it is easier to form a higher order structure.

  The number of structural units derived from the mesogen-containing epoxy compound contained in the multimeric compound is not particularly limited, but is preferably 5 or less as an average value, and more preferably 3 or less.

  The multimeric compound may be a compound having two structural units derived from the mesogen-containing epoxy compound in one molecule (hereinafter, also referred to as “dimeric compound”). Specifically, as the dimer compound, a compound represented by the following general formula (II-A), a compound represented by the following general formula (II-B), and a compound represented by the following general formula (II-C) At least one selected from the group consisting of compounds is mentioned.

In general formula (II-A), general formula (II-B) and general formula (II-C), specific examples of R ^{1 to} R ⁵ and n are the same as in general formula (IA) and general formula (IB) The preferable range is also the same.

  Specific examples of the dimer compound include a compound represented by the following general formula (II-A ′), a compound represented by the following general formula (II-B ′), and the following general formula (II-C ′) And at least one selected from the group consisting of compounds represented by A dimer compound having these structures is likely to have a linear molecular structure. For this reason, it is considered that the stacking properties of the molecules are high and it is easier to form a higher order structure.

In the general formula (II-A ′), the general formula (II-B ′) and the following general formula (II-C ′), specific examples of R ^{1 to} R ⁵ and n have the general formula (IA) and the general formula It is the same as IB), and the preferable range is also the same.

The structure of the multimeric compound contained in the epoxy resin is the molecular weight of the structure presumed to be obtained by the reaction of the monomer (mesogen containing epoxy compound) used in the synthesis of the epoxy resin, the UV spectral detector and the mass spectral detector And the molecular weight of the target compound determined by liquid chromatography performed using a liquid chromatograph comprising
In liquid chromatography, LaChrom II C18 manufactured by Hitachi, Ltd. is used as a column for analysis, and tetrahydrofuran is used as an eluent at a flow rate of 1.0 ml / min. The UV spectrum detector detects the absorbance at a wavelength of 280 nm.
Further, in the mass spectrum detector, the ionization voltage is detected as 2700 V.
In addition, the detail about the synthesis method of epoxy resin and evaluation is mentioned later.

  From the viewpoint of reducing the crystallinity of the epoxy resin and maintaining the handleability of the epoxy resin sheet well, the epoxy resin preferably contains an epoxy monomer and a polymer compound, and the epoxy monomer and the dimer compound And more preferably.

  In the above-mentioned case, the ratio of the epoxy monomer to the multimer compound contained in the epoxy resin is not particularly limited. For example, the proportion of the multimer compound in the entire epoxy resin is preferably 15% by mass or more. On the other hand, from the viewpoint of securing a sufficient crosslink density and maintaining good thermal conductivity and heat resistance, the proportion of the multimeric compound in the entire epoxy resin is preferably 28% by mass or less.

  The ratio of the epoxy monomer or multimer compound to the entire epoxy resin can be measured, for example, by reversed phase liquid chromatography (RPLC).

  In the present disclosure, RPLC measurement uses Mightysil RP-18 from Kanto Chemical Co., Ltd. as a column, and using a gradient method, the mixing ratio (by volume) of the eluent is from acetonitrile / tetrahydrofuran / water = 20/5/75. Acetonitrile / tetrahydrofuran = 80/20 (20 minutes from the start) and then acetonitrile / tetrahydrofuran = 50/50 (35 minutes from the start) continuously. Also, the flow rate is 1.0 ml / min. In the present disclosure, the absorbance at a wavelength of 280 nm is detected, the total area of all detected peaks is set to 100, the ratio of the area in each corresponding peak is determined, and the value is the ratio of each compound to the entire epoxy resin [ % By mass].

  The epoxy resin may further contain a mesogen-containing epoxy compound and an epoxy compound other than the mesogen-containing epoxy compound. In this case, the proportion of the epoxy compound other than the mesogen-containing epoxy compound in the entire epoxy resin is preferably less than 15% by mass, more preferably 10% by mass or less, and further preferably 8% by mass or less It is particularly preferable to be substantially free of any epoxy compound other than the mesogen-containing epoxy compound.

  The epoxy equivalent of the epoxy resin is not particularly limited. For example, the epoxy equivalent measured by perchloric acid titration method is preferably 245 g / eq to 300 g / eq, and more preferably 250 g / eq to 290 g / eq. Preferably, it is more preferably 260 g / eq to 280 g / eq. When the epoxy equivalent of the epoxy resin is 245 g / eq or more, the crystallinity of the epoxy resin is suppressed to a low level, and handling properties such as flexibility when the resin layer is in the B-stage state tend to be well maintained. . On the other hand, when the epoxy equivalent of the epoxy resin is 300 g / eq or less, the crosslink density of the epoxy resin is sufficiently ensured, and good thermal conductivity and heat resistance tend to be maintained.

  The molecular weight of the epoxy resin is not particularly limited. For example, the number average molecular weight (Mn) in gel permeation chromatography (GPC) measurement is preferably 400 to 800, more preferably 450 to 750, and 500 to 500 More preferably, it is 700. If the Mn of the epoxy resin is 400 or more, the crystallinity of the epoxy resin is suppressed to a low level, and the handleability such as flexibility of the epoxy resin sheet tends to be well maintained. On the other hand, when the Mn of the epoxy resin is 800 or less, the crosslinking density of the epoxy resin is sufficiently ensured, and the thermal conductivity and the heat resistance of the insulator tend to be favorably maintained.

  GPC measurement in the present disclosure is performed using G2000HXL and 3000HXL manufactured by Tosoh Corporation as columns, using tetrahydrofuran as a mobile phase, a sample concentration of 0.2% by mass, and a flow rate of 1.0 ml / min. A calibration curve is prepared using polystyrene standard samples, and Mn is calculated by polystyrene conversion value.

  The method for obtaining the epoxy resin containing the epoxy monomer and the multimeric compound is not particularly limited. For example, it can be synthesized by dissolving an epoxy monomer, a compound having a functional group capable of reacting with the epoxy group of the epoxy monomer, and a reaction catalyst described later as required in a synthesis solvent, and stirring while heating. . Although the synthesis is possible by melting and reacting the epoxy resin monomer without using a solvent, it may be necessary to raise the temperature to a temperature at which the epoxy monomer melts. Therefore, from the viewpoint of safety, a synthesis method using a synthesis solvent is preferable.

  The synthesis solvent is not particularly limited as long as it is a solvent capable of heating to a temperature necessary for the reaction between the epoxy monomer and the compound having a functional group capable of reacting with the epoxy group of the epoxy monomer. Specifically, cyclohexanone, cyclopentanone, ethyl lactate, propylene glycol monomethyl ether, N-methyl pyrrolidone and the like can be mentioned.

  The amount of the synthesis solvent is such that the raw material can be sufficiently dissolved at the reaction temperature. Although the solubility varies depending on the type of raw material before the reaction, the type of solvent, etc., for example, it becomes a preferable range as the resin solution viscosity after synthesis if the amount of charged solid concentration becomes 20 mass% to 60 mass%. There is a tendency.

  The type of compound having a functional group capable of reacting with the epoxy group of the epoxy monomer is not particularly limited. For example, it may be a compound (dihydric phenol compound) having two hydroxyl groups on one benzene ring as a functional group capable of reacting with an epoxy group.

  Examples of dihydric phenol compounds include catechol, resorcinol, hydroquinone, and derivatives thereof. As a derivative, the compound which the C1-C8 alkyl group etc. substituted by the benzene ring of catechol, a resorcinol or hydroquinone is mentioned. The dihydric phenol compounds may be used alone or in combination of two or more.

  Among these dihydric phenol compounds, it is preferable to use resorcinol and hydroquinone from the viewpoint of improving the thermal conductivity of the insulator, and it is more preferable to use hydroquinone. Since hydroquinone is a structure in which two hydroxyl groups are substituted so as to be in a positional relationship of para position, a polymer compound obtained by reacting with an epoxy monomer tends to be a linear structure. For this reason, it is considered that the stacking properties of the molecules are high and it is easier to form a higher order structure.

  The type of reaction catalyst is not particularly limited, and an appropriate one can be selected from the viewpoint of reaction rate, reaction temperature, storage stability and the like. Specifically, imidazole compounds, organic phosphorus compounds, tertiary amines, quaternary ammonium salts and the like can be mentioned. The reaction catalyst may be used alone or in combination of two or more. Among them, organic phosphorus compounds are preferable from the viewpoint of the heat resistance of the insulator. Specific examples of the organophosphorus compounds include organic phosphine compounds; maleic anhydride, quinone compounds (1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, , 6-Dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, phenyl-1,4-benzoquinone etc.), diazophenylmethane, phenol resin And other compounds having an intramolecular polarization formed by adding a compound having a π bond, etc .; a complex of an organic phosphine compound and an organic boron compound (tetraphenyl borate, tetra-p-tolyl borate, tetra-n-butyl borate, etc.) Can be mentioned.

  Specific examples of the organic phosphine compounds include triphenylphosphine, diphenyl (p-tolyl) phosphine, tris (alkylphenyl) phosphine, tris (alkoxyphenyl) phosphine, tris (alkylalkoxyphenyl) phosphine, tris (dialkylphenyl) phosphine, Tris (trialkylphenyl) phosphine, tris (tetraalkylphenyl) phosphine, tris (dialkoxyphenyl) phosphine, tris (trialkoxyphenyl) phosphine, tris (tetraalkoxyphenyl) phosphine, trialkylphosphine, dialkyl aryl phosphine, alkyl diaryl Phosphine etc. are mentioned.

  The amount of reaction catalyst is not particularly limited. From the viewpoint of reaction rate and storage stability, it is 0.1% by mass to 1.5% by mass with respect to the total mass of the epoxy monomer and the compound having a functional group capable of reacting with the epoxy group of the epoxy monomer Preferably, 0.2% by mass to 1% by mass is more preferable.

The epoxy resin containing an epoxy monomer and a multimer compound can be synthesized using a glass flask if in a small scale, and using a stainless steel synthesis pot if in a large scale. The specific synthesis method is, for example, as follows.
First, an epoxy monomer is charged into a flask or a synthesis pot, a synthetic solvent is charged, and the temperature is raised to the reaction temperature with an oil bath or a heat medium to dissolve the epoxy monomer. A compound having a functional group capable of reacting with the epoxy group of the epoxy monomer is charged therein, and after confirming that it has been dissolved in the synthesis solvent, the reaction catalyst is charged to start the reaction. By removing the reaction solution after a predetermined time, an epoxy resin containing an epoxy monomer and a multimeric compound is obtained. In addition, the epoxy resin containing an epoxy monomer and a multimer compound is obtained at room temperature (25 ° C.) by taking out the product obtained by evaporating the synthesis solvent under reduced pressure under heating conditions in a flask or in a synthesis pot. Can be obtained in the solid state.

  The reaction temperature is not limited as long as the reaction between the epoxy group and the functional group capable of reacting with the epoxy group proceeds in the presence of the reaction catalyst, and is preferably in the range of 100 ° C. to 180 ° C., for example. More preferably, it is in the range of 100 ° C to 150 ° C. By setting the reaction temperature to 100 ° C. or more, it tends to be possible to shorten the time until the reaction is completed. On the other hand, when the reaction temperature is 180 ° C. or lower, the possibility of gelation tends to be reduced.

  The ratio of the epoxy monomer to the multimeric compound in the epoxy resin can be adjusted by changing the compounding ratio of the epoxy monomer used as the raw material and the compound having a functional group capable of reacting with the epoxy group. For example, the ratio (A / B) of the epoxy group number (A) of the epoxy monomer and the functional group number (B) of the compound having a functional group capable of reacting with the epoxy group is changed in the range of 100/100 to 100/1. Can be adjusted by

  It is preferable that A / B is in the range of 100/18 to 100/10 from the viewpoint of the handling property when the resin layer is in the B-stage state, and the heat resistance and the thermal conductivity in the cured state. . By setting A / B to 100/10 or less, a decrease in the density of crosslinking points is suppressed, and good heat resistance and thermal conductivity tend to be maintained. On the other hand, by setting A / B to 100/18 or more, the crystallinity of the epoxy resin is suppressed to be low, and the handling property tends to be well maintained when the resin layer is in the B-stage state.

(Hardening agent)
The resin layer may contain a curing agent. The curing agent is not particularly limited as long as it causes a curing reaction with the mesogen-containing epoxy resin, and can be selected from those commonly used as a curing agent. Specifically, acid anhydride curing agents, amine curing agents, phenol curing agents, mercaptan curing agents and the like can be mentioned. From the viewpoint of the heat resistance of the insulator, at least one selected from an amine curing agent and a phenol curing agent is preferable. The curing agent may be used alone or in combination of two or more.

  As the amine curing agent, from the viewpoint of the heat resistance of the insulator, an amine curing agent having an aromatic ring is preferable, and an amine curing agent having an amino group on the aromatic ring is more preferable. As an aromatic ring, a benzene ring or a naphthalene ring is preferable. From the viewpoint of curability, amine curing agents having two or more amino groups are preferred.

Specifically as an amine curing agent, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 4,4'-Diaminodiphenyl ether, 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diaminophenylbenzoate, 1,5-diaminonaphthalene, 1,3-diaminonaphthalene, 1,2- Phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 4,4'-diaminobenzanilide, 3,3'-diaminobenzanilide, trimethylene-bis-4-aminobenzoate, 1,4-diamino Naphthalene and 1,8-diaminonaphthalene are mentioned.
Among these, when using a liquid amine curing agent such as 3,3'-diethyl-4,4'-diaminodiphenylmethane, insulation excellent in adhesiveness and insulation even when the press pressure is low when producing a cured product. It tends to get a body.

  The content of the amine curing agent is not particularly limited. From the viewpoint of efficient curing reaction, the ratio of the number of equivalents of active hydrogen of amine curing agent (number of equivalents of amino group) to the number of equivalents of epoxy group of epoxy resin (number of equivalents of amino group / epoxy group The number of equivalents) is preferably 0.3 to 3.0, and more preferably 0.5 to 2.0.

  The phenol curing agent is preferably a bifunctional phenol compound such as catechol, resorcinol, hydroquinone or the like, or a phenol novolac resin in which these are linked by a methylene chain, from the viewpoint of the thermal conductivity of the insulator, and the heat resistance of the insulator From the viewpoint of properties, phenol novolac resins are more preferred.

  The content of the phenol curing agent is not particularly limited. From the viewpoint of efficient curing reaction, the ratio of the number of equivalents of active hydrogen of phenolic hydroxyl group (number of equivalents of phenolic hydroxyl group) to the number of equivalents of epoxy group of epoxy resin (number of equivalents of phenolic hydroxyl group / epoxy group The number of equivalents of is preferably 0.5 to 2, and more preferably 0.8 to 1.2.

(Curing catalyst)
The resin layer may contain a curing catalyst. When the resin layer contains a curing catalyst, the reaction between the epoxy resin and the curing agent can be promoted. The type and content of the curing catalyst are not particularly limited, and an appropriate type and content can be selected from the viewpoint of reaction rate, reaction temperature, storage stability and the like. Specific examples thereof include imidazole compounds, organic phosphorus compounds, tertiary amines, and quaternary ammonium salts. The curing catalyst may be used alone or in combination of two or more.

(Filler)
The resin layer may contain a filler. When the resin layer contains a filler, the thermal conductivity of the obtained insulator is improved. In particular, when a mesogen-containing epoxy compound is contained as an epoxy resin, a high-order structure having a high order, centering on the filler, is formed in the cured product, and the thermal conductivity of the cured product tends to be dramatically improved. See, for example, International Publication No. WO 2013/065159). It is considered that this is because the filler functions as an efficient heat conduction path in the cured product of the epoxy resin in which the high-order structure is formed.

  In a cured product of an epoxy resin containing a filler, whether or not a higher-order structure centering on the filler is formed is, for example, a polarized light microscope with the cured product (thickness: about 1 mm) sandwiched between slide glasses For example, it can judge by observing with BX51 of Olympus Corporation. At this time, an interference pattern is observed around the filler in the region where the filler is present, but no interference pattern is observed in the region where the filler is not present. From this, it can be determined whether or not a higher-order structure centered on the filler is formed in the cured product.

  The above observation is preferably performed in a state in which the analyzer is rotated by 60 ° with respect to the polarizer, not in the cross nicol state. When observed in the cross nicol state, a region where no interference pattern is observed (that is, a region where the cured product does not form a high-order structure) becomes a dark field and can not be discriminated as a filler portion. By rotating by 60 °, the area where the interference pattern is not observed disappears from the dark field, and discrimination with the filler portion becomes possible.

  The content of the filler in the resin layer is not particularly limited. From the viewpoint of the moldability of the resin layer and the handleability of the epoxy resin sheet, the content of the filler in the entire resin layer is preferably 50% by volume to 90% by volume, and from the viewpoint of the thermal conductivity of the insulator, The volume ratio is more preferably 60% by volume to 85% by volume, and from the viewpoint of thixotropy of the epoxy resin composition when the resin layer is formed using a varnish-like epoxy resin composition, 65% by volume to 78% by volume It is further preferred that

  The volume based content of the filler contained in the resin layer is measured, for example, as follows. First, the mass (Wc) of the resin layer at 25 ° C. is measured, and this is heated in air at 400 ° C. for 2 hours and then at 700 ° C. for 3 hours to decompose and burn off the resin component. Thereafter, the mass (Wf) of the remaining filler at 25 ° C. is measured. The density (df) of the filler at 25 ° C. is then determined using an electronic densitometer or a pycnometer. Next, the density (dc) of the resin layer at 25 ° C. is measured in the same manner. Next, the volume (Vc) of the resin layer and the volume (Vf) of the remaining filler are determined, and the volume ratio of the filler is calculated by dividing the volume of the remaining filler by the volume of the resin layer as shown in (Expression 1) Calculate Vr).

(Formula 1)
Vc = Wc / dc
Vf = Wf / df
Vr (%) = (Vf / Vc) × 100

Vc: volume of resin layer (cm ³ )
Wc: Mass of resin layer (g)
dc: density of resin layer (g / cm ³ )
Vf: Volume of filler (cm ³ )
Wf: mass of filler (g)
df: density of filler (g / cm ³ )
Vr: volume ratio of filler (%)

  The content by mass of the filler contained in the resin layer is not particularly limited. For example, when the entire resin layer is 100 parts by mass, the content of the filler is preferably 1 part by mass to 99 parts by mass, more preferably 50 parts by mass to 97 parts by mass, and 70 parts by mass It is further more preferable that it is -95 mass parts. When the content of the filler is in the above range, higher thermal conductivity can be achieved.

  The type of filler is not particularly limited. For example, alumina, silica, magnesium oxide, aluminum nitride, boron nitride, silicon nitride and the like can be mentioned. The fillers may be used alone or in combination of two or more.

  From the viewpoint of the thermal conductivity of the insulator, the filler is preferably nitride such as boron nitride, silicon nitride or aluminum nitride, at least one of boron nitride and aluminum nitride is more preferable, and from the viewpoint of insulation property boron nitride is preferable. More preferable.

  The type of filler contained in the resin layer can be confirmed, for example, by energy dispersive X-ray analysis (EDX).

  The filler may exhibit a particle size distribution having a single peak or may exhibit a particle size distribution having two or more peaks. From the viewpoint of the filling ratio of the filler in the resin layer, it is preferable to exhibit a particle size distribution having two or more peaks, and more preferably to exhibit a particle size distribution having three or more peaks. The filler exhibiting a particle size distribution having two or more peaks may be obtained by combining two or more fillers having different particle sizes.

  When the filler exhibits a particle size distribution having three or more peaks, the particle size distribution having three peaks exhibits a first peak in the range of 0.1 μm to 0.8 μm, and 1 μm to 8 μm It is preferred to have a second peak present in the range and a third peak present in the range 20 μm to 60 μm. In order to obtain a filler having such a particle size distribution, a first filler exhibiting an average particle diameter of 0.1 μm to 0.8 μm as small particle diameter particles, and an average particle diameter of 1 μm to 8 μm as medium particle diameter particles It is preferable to use together the 2nd filler shown and the 3rd filler which show an average particle diameter of 20 micrometers-60 micrometers as large particle diameter particle | grains.

  When the filler exhibits a particle size distribution having three or more peaks, the filling rate of the filler is further improved, and the thermal conductivity of the insulator tends to be further improved. From the viewpoint of the filling property of the filler, the average particle size of the third filler is preferably 30 μm to 50 μm, and the average particle size of the second filler is 1/15 to 1 of the average particle size of the third filler. The average particle size of the first filler is preferably 1/10 to 1/4 of the average particle size of the second filler.

  In the present disclosure, the particle size distribution of the filler refers to a volume cumulative particle size distribution measured using a laser diffraction method. Moreover, the average particle diameter of a filler means the particle diameter used as 50% of the volume cumulative particle size distribution measured using a laser diffraction method. The particle size distribution measurement using a laser diffraction method can be performed using a laser diffraction scattering particle size distribution measuring apparatus (for example, LS13 manufactured by Beckman Coulter, Inc.). The filler dispersion liquid used for the measurement is obtained, for example, by adding a filler to a 0.1 mass% sodium metaphosphate aqueous solution, ultrasonically dispersing it, and adjusting the concentration to an appropriate amount of light for the sensitivity of the device.

  When the filler includes the first filler, the second filler and the third filler described above, the third filler is preferably a nitride filler. In this case, the first filler and the second filler may be nitride fillers or other fillers, but the thermal conductivity of the insulator and the thixotropy of the varnish-like epoxy resin composition From the viewpoint of the above, it is preferable to be at least one of alumina and aluminum nitride.

  From the viewpoint of thermal conductivity, adhesion, and mechanical strength of the insulator, it is preferable to include alumina as a filler, and more preferable to include α-alumina. When alumina is included as the filler, examples of alumina include γ-alumina, θ-alumina, δ-alumina and the like, but it is preferable to include only α-alumina from the viewpoint of thermal conductivity.

  The shape of the alumina filler is preferably particulate. The shape of the alumina filler can be confirmed by a scanning electron microscope (SEM). The presence of α-alumina in the alumina filler can be confirmed by the X-ray diffraction spectrum. Specifically, according to the description of Japanese Patent No. 3759208, the presence of α-alumina can be confirmed by using a peak specific to α-alumina as an index.

  The content of α-alumina in the alumina filler is preferably 80% by volume or more of the total volume of the alumina filler from the viewpoint of thermal conductivity and fluidity, more preferably 90% by volume or more, and 100% by volume It is further preferred that As the content of α-alumina is larger, the formation of a higher-order structure by the mesogen-containing epoxy compound is promoted, and an insulator having more excellent thermal conductivity tends to be obtained. In addition, the content rate of the (alpha)-alumina in an alumina filler can be confirmed by a X-ray-diffraction spectrum.

  The ratio of the α-alumina filler to the entire filler in the resin layer is, for example, preferably 50% by volume to 90% by volume, based on 100% by volume of all the fillers, and 70% by volume to 90% by volume It is more preferable that Favorable adhesiveness with respect to the adherend (metal etc.) of an insulator is maintained as the ratio of the (alpha)-alumina filler is 50 volume% or more in the whole filler volume, and good insulation property is 90 volume% or less Tend to be maintained.

  The α-alumina filler may have a single peak when a particle size distribution curve is drawn with the particle diameter on the horizontal axis and the frequency on the vertical axis, even if it has a plurality of peaks. Good. The use of the α-alumina filler having a plurality of peaks in the particle size distribution curve tends to further improve the packing properties of the α-alumina filler and further improve the thermal conductivity of the insulator. In addition, an α-alumina filler having a plurality of peaks in the particle size distribution curve may be obtained, for example, by combining two or more fillers having different average particle sizes (D50).

  When the α-alumina filler has a single peak when the particle size distribution curve is drawn, the particle diameter at which the volume accumulation from the small particle size side of the volume cumulative particle size distribution of the α-alumina filler is 50% The average particle size (D50) is preferably 0.1 μm to 50 μm, and more preferably 0.1 μm to 30 μm from the viewpoint of thermal conductivity.

  As an example when the α-alumina filler is a combination of two types of fillers having different average particle sizes, a filler (A) having an average particle size (D50) of 10 μm to 50 μm, and an average particle size (D50) The combination of the filler (B) which is 1/2 or less of a filler (A), and is 0.1 micrometer or more and less than 10 micrometers is mentioned. In this combination, the filler (A) is 60% by volume to 90% by volume and the filler (B) is 10% by volume to 40% by volume based on the total volume of the α-alumina filler (100% by volume). Is preferred.

  As an example when the α-alumina filler is a combination of three types of fillers having different average particle sizes, an α-alumina filler (A ′) having an average particle size (D50) of 10 μm to 50 μm, and an average particle size Filler (B ') having a diameter (D50) of 1/2 or less of α-alumina filler (A') and not less than 1 μm and less than 10 μm, and an average particle diameter (D50) of α-alumina filler (B ') Combinations of α-alumina fillers (C ′) which are not more than 1⁄2) and not less than 0.1 μm and less than 1 μm. In this combination, the filler (A ′) is 30% by volume to 89% by volume, and the filler (B ′) is 10% by volume to 40% by volume, based on the total volume of the α-alumina filler (100% by volume) It is preferable that the filler (C ') is 1% by volume to 30% by volume.

  In the above combination, the average particle size of the fillers (A) and (A ′) is preferably as large as possible from the viewpoint of thermal conductivity. On the other hand, from the viewpoint of the thermal resistance of the insulator, the thinner the insulator, the better. Therefore, the average particle diameter of the fillers (A) and (A ') is preferably 10 μm to 50 μm, and more preferably 10 μm to 30 μm.

  When the filler contains boron nitride, the crystal form of boron nitride may be any of hexagonal, cubic and rhombohedral, and the particle size can be easily controlled, so that the hexagonal shape can be obtained. Crystals are preferred. In addition, two or more kinds of boron nitride having different crystal forms may be used in combination.

  From the viewpoint of the thermal conductivity of the insulator and the viscosity in the case of using a varnish-like epoxy resin composition when forming the resin layer, the nitride filler is preferably ground or agglomerated. Examples of the particle shape of the nitride filler include round, spherical and scaly shapes. The nitride filler may be aggregated particles in which these particles are aggregated. From the viewpoint of increasing the filling property of the nitride filler, it is preferable that the ratio of the major axis to the minor axis (aspect ratio) of the particles is round or spherical with 3 or less, more preferably round with an aspect ratio of 2 or less Or spherical, with spherical being more preferred. The aspect ratio of particles means the value obtained by imaging particles using an electron microscope or the like, measuring the major axis and minor axis of each particle, and calculating the arithmetic mean of the ratio of major axis to minor axis. . In the present embodiment, the major axis of the particle means the length of the circumscribed rectangle of the particle, and the minor axis of the particle means the width of the circumscribed rectangle of the particle. Further, that the particles are spherical means that the aspect ratio is 1.5 or less.

  As the nitride filler, agglomerated hexagonal boron nitride particles are preferable. Since agglomerated hexagonal boron nitride particles have many gaps, the particles are easily crushed and deformed by applying pressure to the particles. Therefore, even if the filler content is lowered to lower the viscosity of the varnish-like epoxy resin composition, it is possible to substantially increase the filler content by compressing the epoxy resin composition with a press or the like. become. From the viewpoint of the ease of formation of the heat conduction path due to the contact between the fillers having high thermal conductivity, the particle shape of the filler is more rounded or scaly than that of the sphere, and the contact points of the particles are more Although it is considered to be preferable, spherical particles are preferred in view of the filler filling property and the thixotropy and viscosity of the epoxy resin composition.

  The volume average particle size (D50) of the nitride filler is not particularly limited. It is preferably 100 μm or less from the viewpoint of moldability of the resin layer, and more preferably 20 μm to 100 μm from the viewpoints of thermal conductivity of insulator and thixotropic modification of varnish-like epoxy resin composition, and insulator It is more preferable that it is 20 micrometers-60 micrometers from an insulation viewpoint of these.

The proportion of the nitride filler in the filler is not particularly limited. In one aspect, from the viewpoint of insulation of the insulator, it is preferably 10% by volume to 100% by volume of the entire filler, and from the viewpoint of thixotropic modification of the varnish-like epoxy resin composition, 20% by volume to 90%. The volume ratio is more preferably 30% by volume to 85% by volume from the viewpoint of the thermal conductivity of the insulator.
In addition, the proportion of the nitride filler in the filler is preferably 50% by volume to 95% by volume of the entire filler in another aspect, and 60% by volume to 95% by volume from the viewpoint of the filling property. Is more preferable, and from the viewpoint of the thermal conductivity of the insulator, it is more preferably 65% by volume to 92% by volume.

  The resin layer may contain other components in addition to the above components, as necessary. Other components include solvents, elastomers, silane coupling agents, dispersants, anti-settling agents, and the like.

  When the resin layer is formed using an epoxy resin composition containing a solvent, part of the solvent may or may not remain in the resin layer. When part of the solvent remains in the resin layer, the content of the solvent is preferably 10% by mass or less of the entire resin layer. Specific examples of the solvent include methyl ethyl ketone, cyclohexanone and ethyl lactate.

  When the resin layer contains a silane coupling agent, the thermal conductivity and the insulation reliability of the insulator tend to be further improved. This can be considered, for example, because the silane coupling agent plays a role (corresponding to a binder agent) to form a covalent bond between the surface of the filler and the resin component (epoxy resin and curing agent) therearound.

  A commercially available thing may be used as a silane coupling agent. In consideration of compatibility with the resin component, reduction of heat conduction loss at the interface between the resin component and the filler, and the like, silane coupling agents having functional groups such as epoxy group, amino group, mercapto group, ureido group, hydroxyl group, etc. preferable.

  Specifically as a silane coupling agent, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane 2- (3,4-Epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Silane, 3-aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-ureidopropyltriethoxysilane and the like can be mentioned. In addition, an oligomeric silane coupling agent (for example, SC-6000KS2 manufactured by Hitachi Chemical Co., Ltd.) may be used. The silane coupling agent may be used alone or in combination of two or more.

  When the resin layer contains a silane coupling agent, the content is not particularly limited. For example, it is preferable that it is 0.01 mass%-0.1 mass% of the whole solid content of a resin layer.

  The silane coupling agent may be present in the state of covering the surface of the filler contained in the resin layer, or may be present in a portion other than the surface of the filler.

<Method of producing epoxy resin sheet>
The method for producing an epoxy resin sheet of the present disclosure includes the step of forming a resin layer on a substrate, and the surface free energy of the surface of the substrate on which the resin layer is formed is 10 mJ / m ² or more, A resin layer is a manufacturing method of an epoxy resin sheet containing an epoxy compound (mesogen containing epoxy compound) which has a mesogen group.

  The details and the preferred embodiments of the substrate and the resin layer in the above method are the same as the details and the preferred embodiment of the substrate and the resin layer in the epoxy resin sheet described above.

  The method for forming the resin layer on the substrate is not particularly limited. For example, it may be a method of applying an epoxy resin composition containing components contained in a resin layer on a substrate and performing heat treatment as necessary.

  When forming a resin layer on a base material using an epoxy resin composition, the state in particular of an epoxy resin composition is not restricted. For example, it may be varnish-like or sheet-like.

  The method for forming a resin layer on a substrate using a varnish-like epoxy resin composition is not particularly limited. Specifically, methods such as comma coating, die coating, lip coating, gravure coating and the like can be mentioned. From the viewpoint of applying the epoxy resin composition to a predetermined thickness, it is preferable to use a comma coating method in which a gap is provided and a base material is passed between them, a die coating method in which an epoxy resin composition whose flow rate is adjusted from a nozzle is applied.

The epoxy resin composition may contain a solvent for viscosity adjustment or the like.
When the epoxy resin composition contains a solvent, the viscosity at 25 ° C. of the epoxy resin composition is preferably 0.5 Pa · s to 5 Pa · s, and is 0.5 Pa · s to 4 Pa · s More preferably, the pressure is 1 Pa · s to 3 Pa · s. The viscosity of the epoxy resin composition at 25 ° C. is measured at a temperature of 25 ° C. at a shear rate of 5.0 s ⁻¹ using a rotary shear viscometer fitted with a cone plate (diameter 40 mm, cone angle 0 °). The value of
The thixotropic index at 25 ° C. of the epoxy resin composition is preferably 3 to 15, more preferably 3.5 to 10, and still more preferably 4 to 7. The thixotropic index of the epoxy resin composition was determined as follows ^: (viscosity at a shear rate of 0.5 s ⁻¹ ) / (5.0 s ⁻ ) when the viscosity was measured using a rheometer for the composition kept at 25 ° C. The viscosity at a shear rate of ¹ ). In particular, the "swinging index" is measured as shear viscosity at a temperature of 25 ° C. using a rotary shear viscometer fitted with a cone plate (diameter 40 mm, cone angle 0 °).

If necessary, after applying the epoxy resin composition on the substrate, a drying treatment may be performed to remove at least a part of the solvent contained in the epoxy resin composition.
Furthermore, heat treatment may be performed to bring the resin layer into a B-stage or C-stage state. The method of heat treatment is not particularly limited. From the viewpoint of suppressing the formation of voids (voids) in the resin layer by heat treatment, a thermal vacuum press, a hot roll laminate, and the like are preferable.

  The conditions of the heat treatment are not particularly limited. As a condition which makes a resin layer a state of B stage, the conditions which heat-press-process under reduced pressure (for example, 1 kPa) at heating temperature 80 degreeC-180 degreeC for 1 second-3 minutes are mentioned, for example. The pressure of the press at this time may be, for example, 5 MPa to 20 MPa. As a condition which makes a resin layer a state of C stage, the conditions which carry out heat press processing by 1MPa-30MPa for 1 minute-60 minutes are mentioned at heating temperature 150 ° C-250 ° C, for example.

<Method of manufacturing insulator>
The method of manufacturing an insulator according to the present disclosure is a method of manufacturing an insulator including a step of curing a resin layer of an epoxy resin sheet manufactured by the method of manufacturing an epoxy resin sheet described above.

  The insulator produced by the above method corresponds to a cured product obtained by curing the resin layer. An insulator is arrange | positioned, for example in the place which contact | connects insulation object, such as a conductor of an electric equipment. The insulator may be in contact with the base material or in a state where the base material has been removed.

  The method for curing the resin layer in the above method is not particularly limited, and can be performed by a known method.

<Method of manufacturing electrical equipment>
The method of manufacturing an electric device of the present disclosure is a method of manufacturing an electric device including the step of bringing the resin layer of the epoxy resin sheet described above into contact with an insulation target.

  The method may further comprise the step of curing the resin layer brought into contact with the object to be insulated.

  The electric apparatus manufactured by the said method has the hardened | cured material of a resin layer as an insulator. There are no particular restrictions on the type of electrical equipment and insulation target, and the place where an insulator is provided.

  In the electric device manufactured by the above method, it is preferable that the base material of the epoxy resin sheet is finally removed from the insulator. The timing of removing the base material of the epoxy resin sheet is not particularly limited. For example, even before the insulating layer of the epoxy resin sheet is brought into contact with the insulating object, the resin after the insulating layer of the epoxy resin sheet is brought into contact with the insulating object and before the resin layer is cured, It may be after curing the layer.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

(1) Synthesis of epoxy resin In a 500 mL three-necked flask, 4- {4- (2,3-epoxypropoxy) phenyl} cyclohexyl = 4- (2,3-epoxypropoxy) benzoate (epoxy equivalent weight: 212 g /) as an epoxy monomer. 50 g (0.118 mol) of eq, the following structure, synthesized by the method described in JP-A-2011-74366 was weighed, and 80 g of propylene glycol monomethyl ether was added thereto. A cooling pipe and a nitrogen introducing pipe were placed in a three-necked flask, and a stirring blade was attached so as to be immersed in a solvent. The three-necked flask was immersed in a 120 ° C. oil bath to start stirring. After confirming that the resin A was dissolved and turned into a transparent solution, hydroquinone was added as a compound having a functional group that reacts with the epoxy group of the epoxy monomer, and 0.5 g of triphenylphosphine was added as a reaction catalyst. Heating was continued at an oil bath temperature of 120 ° C. Hydroquinone was added such that the ratio (A / B) of the number of epoxy groups of the epoxy monomer (A) to the number of hydroxyl groups of the hydroquinone (B) was 100/13.
After heating is continued for 5 hours, propylene glycol monomethyl ether is distilled off from the reaction solution under reduced pressure, and the residue is cooled to room temperature (25 ° C.) to obtain an epoxy resin containing the epoxy monomer and the reaction product of the epoxy monomer and hydroquinone. Was synthesized.

  Molecular weight of the structure of the compound presumed to be obtained by the reaction between the synthesized epoxy resin and hydroquinone, and molecular weight of the target compound determined by liquid chromatography carried out using a liquid chromatograph equipped with a UV and mass spectral detector I checked against. As a result, it was confirmed that the epoxy resin contained a compound (dimeric compound) having at least one of the following structures.

The liquid chromatography was performed using LaChrom II C18 manufactured by Hitachi, Ltd. as a column, using tetrahydrofuran as an eluent and a flow rate of 1.0 ml / min.
The UV spectrum detector detected the absorbance at a wavelength of 280 nm. At this time, a peak was observed at a position of 17.4 minutes for all compounds of the following structure, and at a position of 14.9 minutes for the epoxy monomer. In the mass spectrum detector, the ionization voltage was detected as 2700 V, and the molecular weight of the compound having the following structure was 959 in a state in which one proton was added.

The solid content of the epoxy resin was measured by the heat loss method. Specifically, 1.0 g to 1.1 g of a sample is weighed in an aluminum cup and left for 30 minutes in a dryer set at a temperature of 180 ° C., based on the measurement amount before measurement and the measurement amount before heating, The solid content was 99.6% by mass as calculated by the equation.
Solid content (%) = (measured after leaving for 30 minutes / measured before heating) × 100

  The epoxy equivalent of the epoxy resin was measured by the perchloric acid titration method, and the epoxy equivalent was 275 g / eq.

  The content of the dimer compound contained in the epoxy resin and the content of the unreacted epoxy monomer were measured by reverse phase chromatography (RPLC), and the content of the compound of the dimer was 23% by mass, The epoxy monomer content was 69% by mass.

  For measurement, Mightysil RP-18 manufactured by Kanto Chemical Co., Ltd. was used as a column. Using the gradient method, the mixing ratio (by volume) of the eluents is acetonitrile / tetrahydrofuran / water = 20/5/75 to acetonitrile / tetrahydrofuran = 80/20 (20 minutes from the start), then acetonitrile / tetrahydrofuran = 50/50. The measurement was performed by continuously changing (35 minutes from the start). The flow rate was 1.0 ml / min. Absorbance at a wavelength of 280 nm is detected, the total area of all detected peaks is 100, the ratio of the area of the corresponding peak is determined, and the value is the content rate of each compound in the entire epoxy resin [mass%] did.

(2) Preparation of Epoxy Resin Composition The synthesized epoxy resin and the following materials were mixed in the ratio described in Table 1 to obtain a varnish-like epoxy resin composition.

(Filler)
Filler 1 [AA-3, alumina particles, Sumitomo Chemical Co., Ltd., D50: 3 μm]
· Filler 2 [AA-04, alumina particles, Sumitomo Chemical Co., Ltd., D50: 0.40 μm]
· Filler 3 [HP-40, boron nitride particles, Mizushima Alloy Iron Co., Ltd., D50: 40 μm, particle shape (aspect ratio): scaly aggregate (1.5), crystal form: hexagonal crystal]

(Hardening agent)
・ 4,4'-diaminodiphenyl sulfone (DDS) [Wako Pure Chemical Industries, Ltd.]

(Additive)
・ Silane coupling agent [KBM-403, 3-glycidoxypropyltriethoxysilane, Shin-Etsu Chemical Co., Ltd.]

(solvent)
・ Cyclohexanone (CHN)

(3) Preparation of Epoxy Resin Sheet The epoxy resin composition prepared above was applied onto a PET film using an applicator and then dried in a 130 ° C. box oven for 5 minutes. Two PET films in this state were produced, and they were superimposed such that the coated surfaces of the two faced each other. Next, hot pressing was performed with a vacuum press under the conditions of temperature: 150 ° C., pressure: 15 MPa, and time: 1 minute to obtain an epoxy resin sheet in which the resin layer is in a B-stage state. The epoxy resin sheet was produced using three types of PET films from which the value of the surface free energy of the surface which touches the resin layer measured by the method mentioned above differs.

(4) Curing of the resin layer The epoxy resin sheet produced above was hot pressed with a vacuum press under the conditions of temperature: 210 ° C., pressure: 15 MPa, time: 60 minutes to cure the resin layer . The thickness of the resin layer after curing was 80 μm.

(5) Evaluation of thermal conductivity A PET film is peeled off from the epoxy resin sheet which hardened the resin layer, and hardening of the resin layer is carried out using a thermal wave thermal analyzer (brand name: ai-Phase Mobile 1U of ai-Phase company). The thermal diffusivity of the object was measured. The heat conductivity of the cured product of the resin layer was determined from the product of this value, the density measured by the Archimedes method, and the specific heat measured by DSC (trade name: DSC Pyris 1 by Perkin Elmer). The results of the determined thermal conductivity are shown in Table 2 together with the surface free energy of the PET film.

Thermal conductivity λ (W / (m · K)) = α × ρ × Cp
α: Thermal diffusivity (m ² / s)
ρ: Density (kg / cm ³ )
Cp: specific heat (volume) (kJ / (kg · K))

As shown in Table 2, as the value of surface free energy of the surface in contact with the resin layer of the PET film was larger, the thermal conductivity of the cured product of the resin layer tended to be larger.
Moreover, it turned out that the hardened | cured material of the resin layer which has sufficient heat conductivity as an insulator is obtained by using the PET film whose surface free energy of the surface which touches a resin layer is 10 mJ / m < ² > or more.

Claims (11)

A resin layer and a substrate in contact with at least one surface of the resin layer, wherein surface free energy of the surface of the substrate in contact with the resin layer is 10 mJ / m ² or more, and the resin layer contains a mesogen group Epoxy resin sheet containing the epoxy resin containing the epoxy compound which it has.   The epoxy resin sheet according to claim 1, wherein the epoxy compound having a mesogen group has a structure in which three or more 6-membered ring groups are linearly linked. The epoxy resin sheet according to claim 1 or 2, wherein the epoxy compound having a mesogenic group has a structural unit represented by the following general formula (I).

[In general formula (I), R < ¹ > -R < ⁴ > shows a hydrogen atom or a C1-C3 alkyl group each independently. ] The epoxy resin according to any one of claims 1 to 3, wherein the epoxy compound having a mesogenic group contains a compound having two structural units represented by the following general formula (I) in one molecule. Sheet.

[In general formula (I), R < ¹ > -R < ⁴ > shows a hydrogen atom or a C1-C3 alkyl group each independently. ] The epoxy compound having a mesogenic group has at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (IA) and a structural unit represented by the following general formula (IB) The epoxy resin sheet according to any one of claims 1 to 4.

[In general formula (IA) and general formula (IB), R ^{1 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁵ each independently has 1 to 8 carbon atoms Represents an alkyl group of n shows the integer of 0-4. ]   The epoxy resin sheet according to any one of claims 1 to 5, wherein the resin layer is in an A-stage state.   The epoxy resin sheet according to any one of claims 1 to 5, wherein the resin layer is in a B-stage state.   The epoxy resin sheet according to any one of claims 1 to 5, wherein the resin layer is in a C-stage state. And a step of forming a resin layer on the substrate, the surface free energy of the surface of the substrate on which the resin layer is formed is 10 mJ / m ² or more, and the resin layer contains an epoxy compound having a mesogenic group The manufacturing method of the epoxy resin sheet of any one of Claims 1-8 containing an epoxy resin.   A method of manufacturing an insulator, comprising the step of curing the resin layer of the epoxy resin sheet manufactured by the method of manufacturing an epoxy resin sheet according to claim 9.   A manufacturing method of an electric appliance, comprising a step of bringing the resin layer of the epoxy resin sheet according to any one of claims 1 to 8 into contact with an insulating object.