JP2018021180A - Epoxy resin composition, heat conduction material precursor, b stage sheet, prepreg, heat conduction material, laminate, metal substrate and printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition having excellent thermal conductivity when becoming a cured product, and a heat conduction material precursor, a B stage sheet, a prepreg, a heat conduction material, a laminate, a metal substrate and a printed wiring board.SOLUTION: An epoxy resin composition has: a boron nitride particle with an oxygen atom concentration on its surface being 1.5 at% or more; a bisphenol type liquid crystalline epoxy monomer obtained from a structure in which two phenols are linked together with a linking group such as -N=N-, -HC=CH-, -HC=N-, an optionally substituted divalent aromatic group or divalent alicyclic group, and the like; and a curing agent. The substitution may occur with a plurality of groups of at least one selected from C1-C8 aliphatic hydrocarbon groups, aliphatic alkoxy groups, halogens, cyano groups, nitro groups or acetyl groups.SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin composition, a heat conductive material precursor, a B stage sheet, a prepreg, a heat conductive material, a laminate, a metal substrate, and a printed wiring board.

  In recent years, with the increase in energy density due to the downsizing of electronic devices, the amount of heat generated per unit volume tends to increase. Therefore, high thermal conductivity is required for insulating materials constituting electronic devices. In addition, an epoxy resin is widely used as an insulating material from the viewpoint of high withstand voltage and easy molding. As a method for increasing the thermal conductivity of an epoxy resin, for example, Patent Document 1 describes that it is effective to use a liquid crystalline epoxy resin obtained by polymerizing a resin composition containing a monomer having a highly oriented mesogenic group. Has been.

  Furthermore, in order to increase the thermal conductivity of the epoxy resin, a method of adding an insulating filler having a high thermal conductivity and an insulating property is generally used. Examples of the insulating filler having high thermal conductivity include boron nitride particles, aluminum nitride, and alumina.

JP-A-11-323162

However, when inorganic nitride particles such as boron nitride and aluminum nitride are combined with a liquid crystalline epoxy resin, the orientation of the liquid crystalline epoxy resin is inhibited by the inorganic nitride particles, and the thermal conductivity may be lowered.
Therefore, the object of the present invention is to provide an epoxy resin composition, a heat conductive material precursor, a B stage sheet, a prepreg, a heat conductive material, a laminated board, a metal board, and a printed wiring board that have excellent thermal conductivity when cured. It is to provide.

The present invention is as follows.
<1> An epoxy resin composition comprising boron nitride particles having a surface oxygen atom concentration of 1.5 at% or more, a liquid crystalline epoxy monomer represented by the following general formula (1), and a curing agent.

  In the general formula (1), X represents a single bond or a linking group composed of at least one selected from the group (I) consisting of a divalent group represented by the following chemical formula. Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an aliphatic alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. Indicates. n independently represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12.

<2> The epoxy resin composition according to <1>, wherein the content of the boron nitride particles is 20% by mass to 95% by mass in the total solid content.

<3> The epoxy resin composition according to <1> or <2>, wherein the boron nitride particles are irradiated with 100 mJ / cm ² or more of light including ultraviolet rays having a wavelength of 150 nm to 400 nm.

<4> The above <1> or <2>, wherein the boron nitride particles are heat-treated at 60 ° C. to 400 ° C. for 1 minute or longer and irradiated with light containing ultraviolet rays having a wavelength of 150 nm to 400 nm for 100 mJ / cm ² or more. The epoxy resin composition as described.

<5> The epoxy resin composition according to any one of <1> to <4>, wherein the epoxy resin composition does not contain alumina particles or contains alumina particles, and the content of the alumina particles is 70% by mass or less.

<6> The epoxy resin composition according to <5>, wherein the alumina particles are irradiated with light containing ultraviolet rays having a wavelength of 150 nm to 400 nm in an amount of 100 mJ / cm ² or more.

<7> A heat conductive material precursor that is a semi-cured product of the epoxy resin composition according to any one of <1> to <6>.

<8> The heat-curing material precursor according to <7>, wherein the semi-cured product has a periodic structure with a period of 2 nm to 3 nm.

<9> A B-stage sheet, which is a sheet-like semi-cured product of the epoxy resin composition according to any one of <1> to <6>.

<10> The B-stage sheet according to <9>, wherein the sheet-like semi-cured product of the epoxy resin composition has a periodic structure having a period of 2 nm to 3 nm.

The prepreg which has a <11> fiber base material and the semi-hardened | cured material of the epoxy resin composition of any one of said <1>-<6> impregnated in the said fiber base material.

<12> A heat conductive material which is a cured product of the epoxy resin composition according to any one of <1> to <6>.

<13> The heat conductive material according to claim 12, wherein the cured product of the epoxy resin composition has a periodic structure having a period of 2 nm to 3 nm.

<14> A substrate,
The resin layer comprised from the epoxy resin composition of any one of said <1>-<6> provided on the said adherend, B stage as described in said <9> or <10> A cured layer of at least one resin-containing layer selected from the group consisting of a sheet and the prepreg according to <11>,
A laminate having

<15> Metal foil,
A metal plate,
In the resin layer comprised from the resin composition of any one of said <1>-<6> arrange | positioned between the said metal foil and the said metal plate, <9> or <10> A cured layer of at least one resin-containing layer selected from the group consisting of the B-stage sheet described above and the prepreg described in <11>,
A metal substrate.

<16> a wiring layer;
A metal plate,
<9> or <10>, the resin layer comprising the epoxy resin composition according to any one of <1> to <6>, which is disposed between the wiring layer and the metal plate. A cured layer of at least one resin-containing layer selected from the group consisting of the B stage sheet described in <11> and the prepreg described in <11>,
A printed wiring board having:

  According to the present invention, there are provided an epoxy resin composition, a heat conductive material precursor, a B stage sheet, a prepreg, a heat conductive material, a laminate, a metal substrate, and a printed wiring board that have excellent thermal conductivity when cured. can do.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. .
In the present specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
Further, in the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. means.

<Epoxy resin composition>
The epoxy resin composition of the present invention comprises boron nitride particles having a surface oxygen atom concentration of 1.5 at% or more and a liquid crystalline epoxy monomer represented by the following general formula (1) (hereinafter simply referred to as “liquid crystalline epoxy monomer”). And a curing agent. The surface in the present invention is a region having a depth of 5 nm or less from the extreme surface. In particular, in the present invention, the surface is a range within the depth limit detected under the measurement conditions of an X-ray photoelectron spectrometer (XPS).

  In the general formula (1), X represents a single bond or a linking group composed of at least one selected from the group (I) consisting of a divalent group represented by the following chemical formula. Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an aliphatic alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. Indicates. n represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12.

  In the divalent group represented by the above chemical formula, the connecting direction of the bond may be any.

  It is considered that the orientation of the liquid crystalline epoxy monomer on the surface of the boron nitride particles is enhanced by setting the oxygen atom concentration on the surface of the boron nitride particles to 1.5 at% or more. As a result, when the epoxy resin composition of the present invention is cured, the orientation of the liquid crystalline epoxy resin that is a polymer of the liquid crystalline epoxy monomer is suppressed from being inhibited by the boron nitride particles, and the epoxy resin composition It is considered that the thermal conductivity of the cured product is improved. Hereinafter, the components of the epoxy resin composition will be described in detail.

(Boron nitride particles)
The boron nitride particles in the present invention have a surface oxygen atom concentration of 1.5 at% or more.
In general, the surface energy of boron nitride particles is small, and the boron nitride particles tend not to have excellent dispersibility in epoxy resin. Therefore, the present inventors have studied to increase the surface energy of the boron nitride particles in order to improve the dispersibility of the boron nitride particles in the epoxy resin. When the oxygen atom concentration on the surface of the boron nitride particles is 1.5 at% or more in the process of earnest examination, the surface energy of the boron nitride particles can be improved, and the liquid crystal in the epoxy resin composition containing the boron nitride particles It was derived that the orientation of the curable epoxy monomer and further the orientation of the liquid crystalline epoxy resin in the cured product of the epoxy resin composition were improved. This can be considered as follows.

  Boron nitride particles originally have a high affinity for nonpolar compounds such as n-hexadecane, n-tetradecane, n-dodecane, n-undecane, n-decane, n-nonane, and n-octane, and are hydrophobic. It has a low affinity for polar compounds such as water, diiodomethane, tetrabromoethane, tetrachloroethane, glycerin, formamide, etc. and poor hydrophilicity. Here, since the epoxy group of the liquid crystalline epoxy monomer is a hydrophilic group, in order to enhance the orientation of the liquid crystalline epoxy monomer, the surface of the boron nitride particles is appropriately made hydrophilic so that the boron nitride particles and the liquid crystal It is considered effective to improve the affinity with the functional epoxy monomer. It is considered that an appropriate hydrophilic state of the boron nitride particles that is effective in improving the orientation of the liquid crystalline epoxy monomer is an oxygen atom concentration of 1.5 at% or more on the surface of the boron nitride particles.

  As described above, when the oxygen atom concentration on the surface of the boron nitride particles is 1.5 at% or more, the alignment of the liquid crystalline epoxy monomer is hardly inhibited. Therefore, the orientation of the liquid crystalline epoxy resin derived from the liquid crystalline epoxy monomer and the curing agent contained in the semi-cured product and cured product of the epoxy resin composition of the present invention is also less likely to be inhibited by the boron nitride particles. The thermal conductivity of the cured product of the composition is improved.

  From the viewpoint of increasing the orientation of the liquid crystalline epoxy monomer, the oxygen atom concentration on the surface of the boron nitride particles is more preferably 2 at% or more. This is presumably because the surface energy of the boron nitride particles is increased by increasing the oxygen atom concentration on the surface of the boron nitride particles, and the orientation of the liquid crystalline epoxy monomer is improved. In addition, from the viewpoint of suppressing the oxygen atom concentration on the surface of the boron nitride particles from being excessively high and the oxide layer itself on the surface of the boron nitride particles to become a thermal resistance to reduce the thermal conductivity, the oxygen atom concentration on the surface of the boron nitride particles is suppressed. Is preferably 5 at% or less.

  On the other hand, the boron nitride particles preferably have a low oxygen atom concentration. If the oxygen atom concentration inside the boron nitride particles is high, the oxygen atoms may become defects in the crystal lattice of boron nitride, which may hinder thermal conduction.

  The oxygen atom concentration on the surface of the boron nitride particles in the present invention is measured as follows. That is, boron nitride particles are measured with an X-ray photoelectron spectrometer (XPS) (manufactured by Shimadzu / KRATOS: AXIS-HS) at a scanning speed of 20 eV / min (0.1 eV step). As detailed measurement conditions, monochrome Al (tube voltage: 15 kV, tube current: 15 mA) was used as the X-ray source, the lens conditions were HYBRID (analysis area: 600 μm × 1000 μm), and the resolution was Pass Energy 40. To do. The peak area values of oxygen, nitrogen, boron, and carbon obtained by measurement are corrected with the sensitivity coefficient of each element. By obtaining the corrected ratio of oxygen to the total amount of oxygen, nitrogen, boron and carbon, the oxygen atom concentration on the surface of the boron nitride particles can be measured.

  Specifically, the method of correcting the peak area values of oxygen, nitrogen, boron, and carbon obtained by measurement with the sensitivity coefficient of each element is as follows. For oxygen, a peak area value of 528 eV to 537 eV is obtained. Divided by a sensitivity factor of 0.780 for oxygen, for nitrogen, the peak area value from 395 eV to 402 eV, divided by a sensitivity factor of 0.477 for nitrogen, and for boron, a peak area value of 188 eV to 194 eV Is divided by a sensitivity coefficient of 0.159 for boron, and for carbon, the peak area value from 282 eV to 289 eV is divided by a sensitivity coefficient of 0.282 for carbon.

  The boron nitride particles may be any of single crystal particles, single crystal aggregate particles, polycrystal particles, polycrystal aggregate particles, and the like. The crystal structure of the boron nitride particles may be any of hexagonal, cubic and wurtzite type. From the viewpoint of use as a filler of a heat conductive material, hexagonal crystals are preferable.

  The volume average particle diameter of the boron nitride particles is preferably 0.01 μm to 1 mm from the viewpoint of use as a filler of the heat conductive material, and is 0.1 μm to 100 μm from the viewpoint of highly filling the boron nitride particles. It is more preferable.

The volume average particle diameter of the boron nitride particles is measured using a laser diffraction method. The laser diffraction method can be performed using a laser diffraction scattering particle size distribution measuring apparatus (for example, LS230 manufactured by Beckman Coulter, Inc.).
The volume average particle diameter of the boron nitride particles in the epoxy resin composition is measured using a laser diffraction / scattering particle size distribution measuring device after extracting the boron nitride particles from the epoxy resin composition. Specifically, boron nitride particles are extracted from the epoxy resin composition using an organic solvent, nitric acid, aqua regia, etc., and sufficiently dispersed with an ultrasonic disperser or the like to prepare a dispersion. When the volume cumulative distribution curve is drawn from the small diameter side with a laser diffraction / scattering particle size distribution measuring device, the particle diameter (D50) of 50% is obtained as the volume average particle diameter. The volume average particle diameter of the boron nitride particles contained in the can be measured.

  The boron nitride particles are not particularly limited as long as the surface oxygen atom concentration is 1.5 at% or more, and are formed by any manufacturing method such as a direct nitriding method, a reductive nitriding method, or a gas phase reaction method. May be.

In general, the oxygen atom concentration on the surface of the boron nitride particles is less than 1.5 at%. Therefore, as a method of setting the oxygen atom concentration on the surface of the boron nitride particles to 1.5 at% or more, a method of heating the boron nitride particles at 900 ° C. or higher, a method of irradiating with ultraviolet rays, a method of ozone treatment, or an O ₂ plasma treatment. Examples thereof include a method, a method of performing atmospheric pressure plasma treatment, and a method of treating chromic acid. Among them, the method of irradiating ultraviolet rays can efficiently form a hydrophilic portion on the surface of the boron nitride particles without increasing the oxygen atom concentration inside the boron nitride particles, and has an affinity for the polar group of the epoxy resin. Can be improved. On the other hand, if it is attempted to increase the oxygen atom concentration on the surface of the boron nitride particles only by heating the boron nitride particles at a high temperature, the oxygen atom concentration may increase up to the inside of the boron nitride particles. Conductivity may be reduced.

  As described above, by irradiating the boron nitride particles with ultraviolet rays, a part of the hydrophobic surface becomes hydrophilic, and the oxygen atom concentration on the surface can be effectively increased to 1.5 at% or more. For irradiation of the boron nitride particles with ultraviolet rays, for example, an ultraviolet irradiation treatment technique and an ultraviolet irradiation apparatus that are used in manufacturing techniques of various chemical products can be used. Examples of the ultraviolet irradiation device include a high pressure mercury lamp, a low pressure mercury lamp, a deuterium lamp, a metal halide lamp, a xenon lamp, and a halogen lamp.

  The ultraviolet rays used for irradiation preferably include light including an ultraviolet region having a wavelength of 150 nm to 400 nm, and may include light of other wavelengths. From the viewpoint of decomposing organic impurities on the surface of the boron nitride particles, it is preferable to include light having a wavelength of 150 nm to 400 nm, and from the viewpoint of activation of the surface of the boron nitride particles, light having a wavelength of 150 nm to 300 nm is included. It is more preferable.

The irradiation intensity is not particularly limited as the ultraviolet irradiation condition, but it is preferably 0.5 mW / cm ² or more. With this irradiation intensity, the intended effect tends to be more fully exhibited. Moreover, it is preferable that it is 100 mW / cm < ² > or less. With this irradiation intensity, there is a tendency that damage to boron nitride particles due to ultraviolet irradiation can be further suppressed. A preferred range of the irradiation intensity was ^{0.5mW / cm 2 ~100mW / cm 2} , more preferably ^{a 1mW / cm 2 ~20mW / cm 2} .

  The irradiation time is preferably 10 seconds or longer in order to exhibit the intended effect more fully. Moreover, it is preferable to set it as 30 minutes or less from a viewpoint of suppressing the damage of the boron nitride particle by ultraviolet irradiation. A suitable range of irradiation time is 10 seconds to 30 minutes.

The amount of irradiation ultraviolet rays is defined by irradiation intensity (mW / cm ² ) × irradiation time (seconds), and is preferably 100 mJ / cm ² or more from the viewpoint of fully exhibiting the intended effect. more preferably from the viewpoint of improved affinity of the non-polar liquid is 1000 mJ / cm ² or more, still more preferably 5000 mJ / cm ² or more, and particularly preferably 10000 mJ / cm ² or more. Moreover, it is preferable that it is 50000 mJ / cm < ² > or less from a viewpoint of suppressing the damage of the boron nitride particle by ultraviolet irradiation more. A preferred range of the irradiation amount of ultraviolet rays is less than ^{100mJ / cm 2 ~50000mJ / cm 2} , more preferably not more than ^{1000mJ / cm 2 ~50000mJ / cm 2} , more preferably 5000mJ ^/ cm 2 ~50000mJ ^/ cm ² or less, even more preferably less ^{10000mJ / cm 2 ~50000mJ / cm 2} .
In addition, ultraviolet irradiation intensity | strength is prescribed | regulated by the method described in the Example mentioned later.

In the ultraviolet irradiation treatment, for example, it is preferable to irradiate boron nitride particles with light containing ultraviolet rays having a wavelength of 150 nm to 400 nm at 100 mJ / cm ² or more.

When irradiating the boron nitride particles with ultraviolet rays, it is preferable to irradiate the entire boron nitride particles with ultraviolet rays as uniformly as possible. Examples of a method for making the irradiation uniform include a method of irradiating ultraviolet rays while stirring boron nitride particles. For the stirring of boron nitride particles at the time of ultraviolet irradiation, a method that does not use a stirring device, such as a stirring rod, a spatula, a method of stirring with a spoon, a method of stirring a container containing boron nitride particles, and the like, Any of the methods using a stirring device such as a vibration mixer, a ribbon mixer, a paddle mixer, or the like can be applied during the ultraviolet irradiation. From the viewpoint of uniform mixing, a stirrer is preferably used, and specifically, a stirrer such as a paddle type mixer is preferably used.
Moreover, although there is no restriction | limiting in an ultraviolet irradiation atmosphere, From a viewpoint of the improvement of the oxygen atom density | concentration on the surface of a boron nitride particle, it is preferable in oxygen presence or ozone presence.

  Further, from the viewpoint of improving the effect of ultraviolet irradiation on the boron nitride particles, the boron nitride particles are preferably heat-treated. In the heat treatment, the boron nitride particles are preferably heated to 60 ° C. to 400 ° C., and more preferably 100 ° C. to 400 ° C. from the viewpoint of removing moisture. And it is still more preferable to heat at 200 to 400 degreeC from a viewpoint of removing the organic deposit | attachment of the surface of a boron nitride particle more effectively. By removing extraneous deposits such as moisture and organic deposits on the surface of the boron nitride particles as described above, an improvement in the effect of ultraviolet irradiation on the boron nitride particles can be expected.

  The heat treatment time of the boron nitride particles is preferably 1 minute or more from the viewpoint of further improving the effect of ultraviolet irradiation to the boron nitride particles, and more preferably 5 minutes or more and 120 minutes or less from the viewpoint of moisture removal. Preferably, it is 10 minutes or more and 120 minutes or less from the viewpoint of removal of organic deposits.

  The heat treatment of the boron nitride particles can be performed by a general method. In the heat treatment, it is possible to use a general heating apparatus that is used in the manufacturing technology of various chemical products such as a hot plate, a thermostatic bath, an electric furnace, and a baking furnace.

  The reason why the orientation of the liquid crystalline epoxy resin can be improved by irradiating the boron nitride particles with ultraviolet rays can be considered as follows. It is considered that the oxygen atom concentration on the surface of the boron nitride particles itself is increased by the ultraviolet irradiation treatment, and B—O bonds are generated. Furthermore, it is considered that B—OH (hydroxyl group) is generated at the terminal portion where the B—O bond is generated together with the generation of the B—O bond. As a result, the hydrophilicity of the surface of the boron nitride particles is improved. Therefore, the affinity between the epoxy group of the liquid crystalline epoxy monomer and the boron nitride particles is improved, and the orientation of the liquid crystalline epoxy resin is improved.

  In the ultraviolet irradiation process, the temperature inside the processing apparatus may rise. For example, when processing is started at room temperature, the maximum temperature may be close to 60 ° C. However, even if the boron nitride particles are simply heated to 60 ° C., the inhibition of the alignment of the liquid crystalline epoxy resin is not suppressed in the composition containing the liquid crystalline epoxy monomer. Therefore, it is thought that the effect of ultraviolet irradiation is not due to temperature rise.

  Further, the heat treatment of boron nitride particles may be performed together with the ultraviolet irradiation treatment, or may be performed prior to the ultraviolet irradiation treatment.

  The boron nitride particles having a surface oxygen atom concentration of 1.5 at% or more contained in the epoxy resin composition of the present invention have an alignment property of the liquid crystalline epoxy monomer as compared with boron nitride particles not satisfying this condition. To improve the orientation of the liquid crystalline epoxy resin.

Although there is no restriction | limiting in particular as a content rate of the boron nitride particle in the epoxy resin composition of this invention, it is 20 mass%-95 mass% in the total solid which comprises an epoxy resin composition from a viewpoint of viscosity adjustment. From the viewpoint of thermal conductivity, it is more preferably 30% by mass to 90% by mass, and further preferably 50% by mass to 85% by mass.
In addition, solid content in a resin composition means the residue which removed the volatile component from the component which comprises a resin composition.

(Liquid crystal epoxy monomer)
The epoxy resin composition of this invention contains the liquid crystalline epoxy monomer represented by following General formula (1).

  In the general formula (1), X represents a single bond or a linking group composed of at least one selected from the group (I) consisting of a divalent group represented by the following chemical formula. Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an aliphatic alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. Indicates. n independently represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12.

  The liquid crystalline epoxy monomer in the present invention is a monomer having a so-called mesogenic group. When a liquid crystalline epoxy monomer forms a cured product together with a curing agent, a mesogenic group (biphenyl group, terphenyl group, terphenyl analog group, anthracene group, a group in which these are connected by an azomethine group or an ester group in the cured product. Etc.), a higher order structure (also referred to as a periodic structure) is formed. Here, the higher order structure (periodic structure) means a state in which molecules are oriented and aligned after the epoxy resin composition is cured. For example, a crystal structure or a liquid crystal structure is present in the cured product. The presence of such a crystal structure or liquid crystal structure can be directly confirmed by, for example, observation with a polarizing microscope under crossed Nicols or X-ray scattering. In addition, the presence of the elastic modulus of storage can be confirmed indirectly by a small change in temperature.

  In the semi-cured product and cured product of the epoxy resin composition of the present invention, the length of one cycle in the periodic structure is preferably 2 nm to 3 nm. When the length of one cycle is 2 nm to 3 nm, higher thermal conductivity can be exhibited.

  The length of the one period is a semi-cured product or a cured product of the epoxy resin composition measured under the following conditions using a wide-angle X-ray diffractometer (for example, RINT2500HL manufactured by Rigaku), and the diffraction angle obtained thereby is calculated as follows: It is obtained by conversion according to the following Bragg equation.

(Measurement condition)
・ X-ray source: Cu
・ X-ray output: 50 kV, 250 mA
-Divergence slit (DS): 1.0 degree-Scattering slit (SS): 1.0 degree-Receiving slit (RS): 0.3 mm
・ Scanning speed: 1.0 degree / min

    2 dsin θ = nλ

  Here, d is the length of one period, θ is the diffraction angle, n is the reflection order, and λ is the X-ray wavelength (0.15406 nm).

  In the cured product of the epoxy resin composition of the present invention, high thermal conductivity can be achieved. For example, this can be considered as follows. That is, the liquid crystalline epoxy monomer represented by the general formula (1) in the molecule forms a cured product together with the curing agent, thereby forming a highly ordered higher-order structure derived from a mesogenic group in the cured product. be able to. For this reason, it is considered that scattering of phonon conduction, which is a heat conductive medium in the insulating resin, can be suppressed, and thereby high thermal conductivity can be achieved. In general, the presence of the filler hinders formation of a highly ordered higher-order structure by the liquid crystalline epoxy resin. However, if boron nitride particles having a surface oxygen atom concentration of 1.5 at% or more are used as fillers, inhibition of alignment of the liquid crystalline epoxy resin is suppressed. As a result, it can be considered that the thermal conductivity is improved.

  Y in the general formula (1) is each independently an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an aliphatic alkoxy group having 1 to 4 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a cyano group. , A nitro group, or an acetyl group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, or a chlorine atom is more preferable, and a methyl group or an ethyl group is still more preferable.

  N in the general formula (1) is preferably an integer of 0 to 2, and more preferably 0 or 1. k is preferably an integer of 0 to 3, and more preferably 0 or 1. m is preferably an integer of 0 to 4, and more preferably 0 or 1. l is preferably an integer of 0 to 4, and more preferably 0 or 1.

  X in the general formula (1) is preferably a linking group composed of at least one selected from the group (II) consisting of a divalent group represented by the following chemical formula.

As the liquid crystalline epoxy monomer represented by the general formula (1), the temperature range in which the liquid crystal phase is expressed is 25 ° C. or more, the orientation of the liquid crystalline epoxy resin is improved, and the heat conduction when the cured product is obtained. From the viewpoint of improving the properties, 1- (3-methyl-4-oxiranylmethoxyphenyl) -4- (4-oxiranylmethoxyphenyl) -1-cyclohexene, 1- (3-methyl-4-oxira Nylmethoxyphenyl) -4- (4-oxiranylmethoxyphenyl) benzene, 2-methyl-1,4-phenylene-bis {4- (2,3-epoxypropoxy) benzoate}, or 4- {4- ( 2,3-epoxypropoxy) phenyl} cyclohexyl-4- (2,3-epoxypropoxy) benzoate and the like, and preferably 1- (3-methyl-4-oxiranylmethoxyphenyl) ) -4- (4-oxiranylmethoxy-phenyl) -1-cyclohexene is more preferable.
A liquid crystalline epoxy monomer may be used by a single type, or may be used by 2 or more types.

  The liquid crystalline epoxy monomer represented by the general formula (1) can be produced by a known method, and described in Japanese Patent No. 4619770, Japanese Patent Application Laid-Open No. 2011-98952, Japanese Patent Application Laid-Open No. 2011-74366, and the like. Can be referred to.

  The liquid crystalline epoxy monomer in the epoxy resin composition may be partially polymerized with a curing agent or the like to form a prepolymer. Liquid crystalline epoxy monomers are generally easy to crystallize and many have low solubility in a solvent, but crystallization can be suppressed by partial polymerization. For this reason, if prepolymerized, moldability may be improved.

  The content of the liquid crystalline epoxy monomer is preferably 3% by volume to 30% by volume in the total volume of the total solid content of the epoxy resin composition from the viewpoints of moldability, adhesiveness, and thermal conductivity. It is more preferable that the volume is 25% by volume.

  In the present specification, the volume-based content of the liquid crystalline epoxy monomer with respect to the total solid content is a value determined by the following formula.

  Content (volume%) of liquid crystalline epoxy monomer with respect to the total solid content = {(Bw / Bd) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd) + (Dw / Dd))} × 100

Here, each variable is as follows.
Aw: Mass composition ratio (% by mass) of boron nitride particles
Bw: Mass composition ratio of liquid crystalline epoxy monomer (mass%)
Cw: mass composition ratio (% by mass) of curing agent
Dw: mass composition ratio (% by mass) of other optional components (excluding solvent)
Ad: Specific gravity of boron nitride particles Bd: Specific gravity of liquid crystalline epoxy monomer Cd: Specific gravity of curing agent Dd: Specific gravity of other optional components (excluding solvent)

(Curing agent)
Examples of the curing agent in the present invention include amine curing agents, acid anhydride curing agents, phenol curing agents, polymercaptan curing agents, polyaminoamide curing agents, isocyanate curing agents, and block isocyanate curing agents. It is done. Of these, amine-based curing agents are preferred.

  Content of the said hardening | curing agent can be suitably set in consideration of the kind of hardening | curing agent to mix | blend and the physical property of the said liquid crystalline epoxy monomer. Specifically, the content of the curing agent is preferably such that the chemical equivalent of the curing agent is 0.005 to 5 equivalents relative to 1 mol of the epoxy group in the liquid crystalline epoxy monomer, and 0.01 to 3 equivalents. More preferably, it is more preferably 0.5 equivalent to 1.5 equivalent. When the content of the curing agent is 0.005 equivalent or more with respect to 1 mol of the epoxy group, the curing rate of the liquid crystalline epoxy monomer is more excellent. Moreover, when it is 5 equivalents or less, the curing reaction can be suppressed more appropriately.

  Here, the chemical equivalent represents the number of moles of active hydrogen of amine with respect to 1 mole of epoxy group, for example, when an amine-based curing agent is used as the curing agent.

(Other ingredients)
The epoxy resin composition of the present invention may contain a solvent for dissolving the epoxy resin or the curing agent when the epoxy resin or the curing agent is solid, and for reducing the viscosity when the epoxy resin or the curing agent is liquid.
Examples of the solvent include acetone, isobutyl alcohol, isopropyl alcohol, isopentyl alcohol, ethyl ether, ethylene glycol monoethyl ether, xylene, cresol, chlorobenzene, isobutyl acetate, isopropyl acetate, isopentyl acetate, ethyl acetate, methyl acetate, cyclohexanol, Cyclohexanone, 1,4-dioxane, dichloromethane, styrene, tetrachloroethylene, tetrahydrafuran, toluene, normal hexane, 1-butanol, 2-butanol, methanol, methyl isobutyl ketone, methyl ethyl ketone, methyl cyclohexanol, methyl cyclohexanone, chloroform, tetrachloride Organic solvents that are commonly used in the manufacturing technology of various chemical products such as carbon and 1,2-dichloroethane It is possible to use.

  Moreover, the epoxy resin composition of this invention can contain suitably ceramic particles other than boron nitride particles, a coupling agent, a dispersing agent, an elastomer, etc. Examples of the ceramic particles include alumina particles, silica particles, magnesium oxide particles, aluminum nitride particles, and silicon nitride particles. As ceramic particles other than boron nitride particles, alumina particles are preferable. The epoxy resin composition of the present invention may or may not contain alumina particles. When the epoxy resin composition of the present invention contains alumina particles, the content of alumina particles is preferably 0% by mass to 70% by mass with respect to the total amount of boron nitride particles and alumina particles, and 0% by mass. It is more preferable that it is% -50 mass%.

  The volume average particle diameter of the alumina particles is preferably 0.01 μm to 1 mm from the viewpoint of use as a filler of a heat conductive material, and is preferably 0.1 μm to 100 μm from the viewpoint of highly filling the alumina particles. More preferred.

When the alumina particles are used in combination, it is preferable to increase the oxygen atom concentration on the surface of the alumina particles. Examples of the method include the same methods as the boron nitride particles, and among them, the method of irradiating with ultraviolet rays is preferable. The conditions of ultraviolet irradiation in the alumina particles are the same as in the case of boron nitride particles. Specifically, in the ultraviolet irradiation treatment on the alumina particles, for example, it is preferable to irradiate light including ultraviolet rays having a wavelength of 150 nm to 400 nm at 100 mJ / cm ² or more.

  Further, like the boron nitride particles, the alumina particles are preferably heat-treated from the viewpoint of improving the effect of ultraviolet irradiation on the alumina particles. The heat treatment conditions (heating temperature and heating time) for the alumina particles are the same as for the boron nitride particles.

  The alumina particles and boron nitride particles may be collectively subjected to ultraviolet irradiation treatment and / or heat treatment. If the surface treatment conditions (ultraviolet irradiation conditions and / or heating conditions) of the particles are the same, the surface oxygen atom concentration when the boron nitride particles are surface treated alone and the mixed particles of boron nitride and alumina particles are surface treated. The oxygen atom concentration on the surface of the boron nitride particles is considered to be equal.

  In addition, when boron nitride particles and alumina particles are used in combination, the epoxy resin composition, or a semi-cured product or a cured product of the epoxy resin composition is heated to thermally decompose the resin, and then the boron nitride is removed. Particles and alumina particles are classified, and the obtained boron nitride particles can be measured by XPS to estimate the oxygen atom concentration on the surface of the boron nitride particles.

(Use)
In the epoxy resin composition of the present invention, since the oxygen atom concentration on the surface of the boron nitride particles is 1.5 at% or more, the orientation of the liquid crystalline epoxy monomer is improved. As a result, the epoxy resin composition is semi-cured and cured. The thing is excellent in thermal conductivity. Accordingly, the epoxy resin composition of the present invention can be suitably used as a heat conductive material for heat-generating electronic components (for example, IC (Integrated Circuit) chips or printed wiring boards) of various electric and electronic devices. Specific examples of the heat conductive material include a heat conductive material precursor, a B stage sheet, a prepreg, a heat conductive material, a laminated board, a metal substrate, and a printed wiring board.

<Heat conductive material precursor>
The heat conductive material precursor of the present invention is a semi-cured product of the epoxy resin composition. Thereby, it is excellent in handleability and can comprise the heat conductive material which has the outstanding heat conductivity.
As the heat conductive material precursor, a B stage sheet which is a sheet-like semi-cured product of the epoxy resin composition, and a semi-cured product of the epoxy resin composition impregnated in a fiber base material and the fiber base material And a prepreg having the following.

  As described above, the semi-cured product of the epoxy resin composition of the present invention preferably has a period length of 2 nm to 3 nm in the periodic structure. When the length of one cycle is 2 nm to 3 nm, higher thermal conductivity can be exhibited.

<B stage sheet>
The B stage sheet of the present invention is a semi-cured product of the sheet-like product of the epoxy resin composition of the present invention. The B stage sheet of the present invention is obtained by molding the epoxy resin composition into a sheet shape and semi-curing it. Since the B stage sheet includes the epoxy resin composition, the thermal conductivity after curing is excellent. Here, semi-curing refers to a state generally referred to as a B-stage state, where the viscosity at room temperature (25 ° C.) is 10 ⁴ Pa · s to 10 ⁵ Pa · s, whereas the viscosity at 100 ° C. It means a state in which the viscosity decreases to 10 ² Pa · s to 10 ³ Pa · s. The B stage is defined in JIS K 6900: 1994. The viscosity can be measured with a torsional dynamic viscoelasticity measuring device or the like.

  The B stage sheet of the present invention can be produced, for example, by applying the epoxy resin composition on the support, drying it to produce a resin sheet, and semi-curing it. With respect to the application method and the drying method of the epoxy resin composition, a method that is usually used can be appropriately selected without particular limitation. Specifically, a comma coater, a die coater, a dip, etc. are mentioned as a coating method.

  As the drying method, a box-type hot air dryer can be used for batch processing, and a multistage hot air dryer can be used for continuous processing with a coating machine. There is no particular limitation on the heating conditions for drying, and when using a hot air dryer, heating with hot air in a temperature range lower than the boiling point of the solvent is used from the viewpoint of preventing the epoxy resin composition from swelling. It is preferable to include the process of processing.

  There is no restriction | limiting in particular as the method of semi-hardening, The method used normally can be selected suitably, For example, the said epoxy resin composition is semi-hardened by heat-processing. There is no particular limitation on the heat treatment method for semi-curing.

The temperature range for the semi-curing can be appropriately selected according to the epoxy resin constituting the epoxy resin composition. From the viewpoint of the strength of the B stage sheet, it is preferable to proceed the curing reaction slightly by heat treatment, and the temperature range of the heat treatment is preferably 80 ° C to 180 ° C, and more preferably 100 ° C to 160 ° C. Further, the time for the heat treatment for semi-curing is not particularly limited, but can be appropriately selected from the viewpoint of the curing speed of the resin of the B stage sheet, the fluidity and the adhesiveness of the resin, and is from 1 minute to 30 minutes. Heating is preferably performed within minutes, and more preferably within 1 minute and within 10 minutes.
Pressurization may be applied during the heat treatment for semi-curing, and the pressurization conditions are not particularly limited. Usually, it is in the range of 0.5 MPa to 15 MPa, preferably in the range of 1 MPa to 10 MPa. Moreover, a vacuum press is used suitably for a heating and pressurizing process.

  The thickness of the B stage sheet can be appropriately selected according to the purpose, and can be, for example, 50 μm to 500 μm. From the viewpoint of thermal conductivity, electrical insulation, and flexibility, the thickness is 80 μm to 300 μm. Preferably there is. Moreover, it can also produce by heat-pressing, laminating | stacking the resin sheet of 2 or more layers (The sheet-like material of an epoxy resin composition, and the thing before a hardening process).

  The B stage sheet preferably has a length of one cycle of 2 nm to 3 nm. When the length of one cycle is 2 nm to 3 nm, higher thermal conductivity can be exhibited.

<Prepreg>
The prepreg of the present invention has a fiber base material and a semi-cured product of the epoxy resin composition impregnated in the fiber base material. The prepreg is configured to have other layers such as a protective film as necessary. The semi-cured product of the epoxy resin composition is excellent in thermal conductivity by containing the boron nitride particles according to the present invention.

  The fiber base material constituting the prepreg is not particularly limited as long as it is used when producing a metal foil-clad laminate or a multilayer printed wiring board. Specifically, a fiber substrate such as a woven fabric or a nonwoven fabric is usually used. However, in the case of a fiber with extremely clogged eyes, the boron nitride particles may be clogged and impregnation may be difficult. Therefore, the opening is preferably set to 5 times or more the volume average particle diameter of the boron nitride particles.

  The material of the fiber base material is inorganic fiber such as glass, alumina, boron, silica alumina glass, silica glass, tyrano, silicon carbide, silicon nitride, zirconia; aramid, polyetheretherketone, polyetherimide, polyethersulfone Organic fibers such as carbon and cellulose; and mixed papers thereof. Of these, glass fiber woven fabric is particularly preferably used. As a result, it is possible to obtain a flexible printed wiring board having flexibility. Furthermore, it becomes possible to reduce the dimensional change of the printed wiring board accompanying the temperature, moisture absorption, etc. in the manufacturing process.

  The thickness of the fiber substrate is not particularly limited, but is preferably 30 μm or less from the viewpoint of imparting better flexibility, and more preferably 15 μm or less from the viewpoint of impregnation. Although the minimum of the thickness of a fiber base material is not restrict | limited in particular, Usually, it is about 5 micrometers.

  In the prepreg, the impregnation ratio of the epoxy resin composition is preferably 50% by mass to 99.9% by mass with respect to the total mass of the fiber base material and the liquid crystalline epoxy resin composition.

  The prepreg can be produced by impregnating a fiber base material with an epoxy resin composition prepared in the same manner as described above, and removing the solvent by heating at 80 ° C to 180 ° C. The solvent residual ratio in the prepreg is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and further preferably 0.7% by mass or less.

  The solvent residual rate is determined from the change in mass before and after drying when the prepreg is cut into 40 mm square and dried in a thermostat preheated to 190 ° C. for 2 hours.

  The drying time for removing the solvent by heating is not particularly limited. Moreover, there is no restriction | limiting in particular in the method of impregnating a fiber base material with an epoxy resin composition, For example, the method of apply | coating with a coating machine can be mentioned. Specifically, a vertical coating method in which a fiber base material is pulled through an epoxy resin composition, a horizontal coating method in which an epoxy resin composition is coated on a support film and then impregnated by pressing the fiber base material, etc. From the viewpoint of suppressing the uneven distribution of the thermally conductive filler in the fiber base material, the horizontal coating method is suitable.

  In the prepreg, the epoxy resin composition impregnated in the fiber base material is semi-cured and is in a B-stage state. The B stage state in the prepreg is the same as the B stage state in the B stage sheet, and the same conditions can be applied to the B stage method.

  The prepreg may be used after the surface has been smoothed before being laminated or pasted by heat and pressure treatment using a press, a roll laminator or the like. The method for the heat and pressure treatment is the same as the method mentioned for the B stage sheet. Moreover, the conditions of the heating temperature, the degree of vacuum, and the pressing pressure in the heat and pressure treatment of the prepreg are the same as the conditions mentioned in the heat treatment and pressure treatment of the B stage sheet.

The thickness of the prepreg can be appropriately selected depending on the purpose. For example, it can be 50 μm or more and 500 μm or less, and preferably 60 μm or more and 300 μm or less from the viewpoint of thermal conductivity and flexibility.
The prepreg can also be produced by laminating two or more prepregs and hot pressing.

<Heat conduction material>
The heat conductive material of the present invention is a cured product of the epoxy resin composition. Specific examples of the heat conductive material include a laminated board, a metal board, a printed wiring board, and the like that are configured by having a cured product of the epoxy resin composition. It has excellent thermal conductivity by containing a cured product of the liquid crystalline epoxy monomer represented by the general formula (1) and the boron nitride particles.

  As described above, the cured product of the epoxy resin composition of the present invention preferably has a period length of 2 nm to 3 nm in the periodic structure. When the length of one cycle is 2 nm to 3 nm, higher thermal conductivity can be exhibited.

<Laminated plate>
The laminated board in this invention has an adherend and the hardened layer arrange | positioned on the said adherend. The cured layer is a cured layer of at least one resin-containing layer selected from the group consisting of a resin layer composed of the epoxy resin composition, the B stage sheet, and the prepreg. By having the hardened layer formed from the epoxy resin composition, a laminated board having excellent thermal conductivity is obtained.

Examples of the adherend include a metal foil and a metal plate. The adherend may be attached to only one side of the cured layer or may be attached to both sides.
In the said laminated board, the form which has the cured layer of any one resin content layer of the said resin layer, the said B stage sheet, or the said prepreg as a cured layer may be sufficient, and it has laminated | stacked two or more layers. Form may be sufficient. In the case of having two or more cured layers, any of a form having two or more resin layers, a form having two or more B stage sheets, and a form having two or more prepregs may be used. Furthermore, you may have in combination any 2 or more of the said resin layer, the said B stage sheet | seat, and the said prepreg.

  The laminated board in the present invention is, for example, formed by applying the epoxy resin composition on an adherend to form a resin layer, and heating and pressurizing the resin layer to cure the resin layer. Obtained by close contact. Alternatively, a laminate of the resin sheet, the B-stage sheet, or the prepreg is prepared on the adherend, and the resin sheet, the B-stage sheet, or the prepreg is cured by heating and pressurizing the adherend. It is obtained by sticking to the material.

  The curing method for curing the resin layer (resin sheet), the B stage sheet, and the prepreg is not particularly limited. For example, heat treatment and pressure treatment are preferable. The heating temperature in the heating and pressure treatment is not particularly limited. Usually, it is the range of 100 to 250 degreeC, Preferably it is the range of 130 to 230 degreeC. Moreover, the pressurization conditions in a heating and pressurizing process are not specifically limited. Usually, it is in the range of 1 MPa to 10 MPa, preferably in the range of 1 MPa to 5 MPa. Moreover, a vacuum press is used suitably for a heating and pressurizing process.

The thickness of the laminate is preferably 500 μm or less, and more preferably 100 μm to 300 μm. When the thickness is 500 μm or less, the flexibility is excellent, and the occurrence of cracks during bending is suppressed, and when the thickness is 300 μm or less, the tendency is further improved. Further, when the thickness is 100 μm or more, the workability is excellent.
The thickness of a laminated board means the average value when arbitrary five places are measured with a micrometer.

<Metal substrate>
The metal substrate includes a metal foil, a metal plate, and a hardened layer disposed between the metal foil and the metal plate. The cured layer is a cured layer of at least one resin-containing layer selected from the group consisting of a resin layer composed of the epoxy resin composition, the B stage sheet, and the prepreg. By having the hardened layer formed from the epoxy resin composition, a laminated board having excellent thermal conductivity is obtained.

  The metal foil is not particularly limited, and can be appropriately selected from commonly used metal foils. Specifically, gold foil, copper foil, aluminum foil, etc. can be mentioned, and copper foil is generally used. As thickness of the said metal foil, 1 micrometer-200 micrometers are mentioned, A suitable thickness can be selected according to the electric power etc. to be used.

  Further, as the metal foil, nickel, nickel-phosphorus, nickel-tin alloy, nickel-iron alloy, lead, lead-tin alloy or the like is used as an intermediate layer, and a copper layer of 0.5 μm to 15 μm and 10 μm to A composite foil having a three-layer structure provided with a 150 μm copper layer, or a two-layer structure composite foil in which aluminum and a copper foil are combined can also be used.

  The metal plate is preferably made of a metal material having a high thermal conductivity and a large heat capacity. Specific examples include copper, aluminum, iron, alloys used for lead frames, and the like.

The plate | board thickness of the said metal plate can be suitably selected according to a use. For example, the material of the metal plate can be selected according to the purpose, such as aluminum when priority is given to weight reduction or workability, and copper when priority is given to thermal conductivity.
The thickness of the metal plate is not particularly limited. From the viewpoint of workability, the thickness of the metal plate is preferably 0.5 mm or more and 5 mm or less.

  Moreover, it is preferable that the said metal plate is cut | disconnected to the size to be used, after producing a larger size than necessary and mounting an electronic component from a viewpoint of improving productivity. Therefore, it is desirable that the metal plate used for the metal substrate is excellent in cutting workability.

  When aluminum is used as the metal plate, aluminum or an alloy mainly composed of aluminum can be selected as the material. Many types of aluminum or alloys containing aluminum as a main component are available depending on the chemical composition and heat treatment conditions. Among them, it is preferable to select a type having high workability such as easy cutting and excellent strength.

<Printed wiring board>
The printed wiring board of this invention has a wiring layer, the said metal plate, and the hardening layer arrange | positioned between the said wiring layer and the said metal plate. The cured layer is a cured layer of at least one resin-containing layer selected from the group consisting of a resin layer composed of the epoxy resin composition, the B stage sheet, and the prepreg. By having a hardened layer formed from the epoxy resin composition, a printed wiring board having excellent thermal conductivity is obtained.
The wiring layer can be manufactured by circuit processing the metal foil on the metal substrate described above. An ordinary photolithography method can be applied to the circuit processing of the metal foil.

  Preferable embodiments of the printed wiring board include, for example, the same printed wiring board as described in paragraph No. 0064 of JP2009-214525A and paragraph Nos. 0056 to 0059 of JP2009-275086A. be able to.

When the epoxy resin composition of the present invention is cured to obtain a cured product, the oxygen atom concentration on the surface of the boron nitride particles contained therein can be measured as follows.
The cured product is heated at 600 ° C. for 30 minutes in the atmosphere to decompose a resin component such as an epoxy resin and take out boron nitride particles. With respect to the obtained boron nitride particles, the oxygen atom concentration on the surface can be measured by the method described above.

  In the above, the resin content of the cured product is decomposed and the oxygen atom concentration on the surface of the boron nitride particles is measured, but “before adding to the epoxy resin composition; in the epoxy resin composition; or curing of the epoxy resin composition” It is considered that there is almost no difference between “the oxygen atom concentration on the surface of the boron nitride particles in the product” and “the oxygen atom concentration on the surface of the boron nitride particles after decomposing the resin content of the cured product”. This is because the temperature at which boron nitride is oxidized is 900 ° C. or higher, and it is considered that there is no difference in oxygen atom concentration even when boron nitride particles are heated at 600 ° C.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

Example 1
Using a desktop light surface treatment device (Sen Special Light Source Co., Ltd. device name: Photo Surface Processor PL21-200) on boron nitride particles (Mizushima Alloy Iron Co., Ltd., trade name: HP-40) having a volume average particle size of 40 μm. The mixture was irradiated with UV light for 10 minutes with a 200 W low-pressure mercury lamp while stirring.

  The irradiation intensity of ultraviolet rays was obtained as an average irradiation intensity of 254 nm light by measuring the light amount of 254 nm light with an ultraviolet integrating light meter (USHIO UIT-150). More specifically, the ultraviolet intensity meter was put in the surface treatment apparatus, the irradiation intensity was measured, and the value displayed on the meter was recorded every 10 seconds. Thereafter, the sum of the recorded values was divided by the ultraviolet irradiation time to obtain the average irradiation intensity.

  The boron nitride particles irradiated with ultraviolet rays were measured with an X-ray photoelectron spectrometer (XPS) (manufactured by Shimadzu / KRATOS: AXIS-HS) at a scanning speed of 20 eV / min (0.1 eV step). As detailed measurement conditions, monochrome Al (tube voltage: 15 kV, tube current: 15 mA) was used as the X-ray source, the lens conditions were HYBRID (analysis area; 600 μm × 1000 μm), and the resolution was Pass Energy 40. It was measured. The peak area values of oxygen, nitrogen, boron, and carbon obtained by measurement were corrected with the sensitivity coefficient of each element. The oxygen atom concentration on the surface of the boron nitride particles was measured by obtaining the corrected ratio of oxygen to the total amount of oxygen, nitrogen, boron and carbon. The oxygen atom concentration on the surface was 2.5 at%.

  Specifically, the method of correcting the peak area values of oxygen, nitrogen, boron, and carbon obtained by measurement with the sensitivity coefficient of each element is as follows. For oxygen, a peak area value of 528 eV to 537 eV is obtained. Divided by a sensitivity factor of 0.780 for oxygen, for nitrogen, the peak area value from 395 eV to 402 eV, divided by a sensitivity factor of 0.477 for nitrogen, and for boron, a peak area value of 188 eV to 194 eV Was divided by a sensitivity coefficient of 0.159 for boron, and for carbon, the peak area value from 282 eV to 289 eV was divided by a sensitivity coefficient of 0.278 for carbon.

  Boron nitride particles irradiated with ultraviolet rays, liquid crystalline epoxy resin (1- (3-methyl-4-oxiranimethoxyphenyl) -4- (oxiranylmethoxyphenyl) -1-cyclohexene, represented by the general formula (1) A liquid crystal epoxy monomer (hereinafter also referred to as “resin 1”), a curing agent (1,5-diaminonaphthalene), and a solvent (cyclohexanone) were added to prepare an epoxy resin composition. The compounding amounts of the liquid crystalline epoxy monomer and the curing agent were adjusted so that the molar ratio of the active hydrogen of the amine of the curing agent to the epoxy group of the liquid crystalline epoxy monomer was 1: 1. Moreover, the addition amount of boron nitride was adjusted so that the boron nitride content rate in the epoxy resin composition after hardening might be 60 mass%.

  The prepared epoxy resin composition was coated on a polyethylene terephthalate (PET) film having a thickness of 75 μm at a thickness of 300 μm, and then the epoxy resin composition was sandwiched between the PET films and vacuumed at 140 ° C., 1 MPa for 2 minutes. A B stage sheet was obtained by pressing.

The diffraction angle derived from the periodic structure of the obtained B-stage sheet, which is a semi-cured product, was measured with a wide-angle X-ray diffractometer (RINT 2500HL manufactured by Rigaku). As detailed measurement conditions, Cu is used as the X-ray source, the X-ray output is 50 kV, 250 mA, the divergence slit (DS) is 1.0 degree, and the scattering slit (SS) is 1.0 degree. The slit (RS) was 0.3 mm, and the scanning speed was 1.0 degree / min.
The measured diffraction angle was converted into the length of one period by the following Bragg equation.

    2 dsin θ = nλ

  Here, d is the length of one period, θ is the diffraction angle, n is the reflection order, and λ is the X-ray wavelength (0.15406 nm).

  The PET film on both sides of the obtained B-stage sheet is peeled off. Instead, it is sandwiched between copper foils with a roughened surface (made by Furukawa Electric Co., Ltd., trade name: GTS), and vacuum-pressed at 160 ° C. to be crimped to the copper foil. It was. This was further cured by heating at 140 ° C. for 2 hours and further at 190 ° C. for 2 hours to obtain a sheet-like copper press-cured cured product.

  The copper foil on both sides of the obtained copper pressure-cured cured product was removed by acid etching using a mixed solution of 200 g / L ammonium persulfate and 5 ml / L sulfuric acid to obtain a sheet-shaped epoxy resin cured product.

  The obtained sheet-like cured epoxy resin was cut into a 1 cm square and used as a test piece for measuring the thermal diffusivity. Using a flash method apparatus (manufactured by Bruker, NETZSCH, nanoflash LFA447), the thermal diffusivity of the cut specimen was measured, and this was multiplied by the density measured by the Archimedes method and the specific heat measured by the DSC method to obtain a thickness. The thermal conductivity in the direction was determined.

  The diffraction angle derived from the periodic structure of the obtained sheet-like cured epoxy resin was measured in the same manner as in the case of the B stage sheet.

  In order to measure the oxygen atom concentration on the surface of the boron nitride particles contained in the cured epoxy resin, the resin content was decomposed by heating at 600 ° C. for 30 minutes in the air. Thereafter, the oxygen atom concentration on the surface of the remaining boron nitride particles was measured with an X-ray photoelectron spectrometer (manufactured by Shimadzu / KRATOS: AXIS-HS) at a scanning speed of 20 eV / min (0.1 eV step). The obtained results are shown in Table 1.

  As detailed measurement conditions, monochrome Al (tube voltage: 15 kV, tube current: 15 mA) was used as the X-ray source, the lens conditions were HYBRID (analysis area: 600 × 1000 μm), and the resolution was Pass Energy 40. did.

(Example 2)
In Example 1, the boron nitride particles were treated in the same manner except that the ultraviolet irradiation time was 20 minutes. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Example 3)
In Example 1, the boron nitride particles were treated in the same manner except that the ultraviolet irradiation time was 30 minutes. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

Example 4
In Example 3, as a pretreatment for the ultraviolet irradiation treatment, the boron nitride particles were treated in the same manner except that the heat treatment was performed in a thermostatic bath at 150 ° C. for 10 minutes. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Example 5)
In Example 4, the boron nitride particles were treated in the same manner except that the heat treatment temperature was 250 ° C. Using the treated boron nitride particles, a cured epoxy resin was produced in the same manner as in Example 1, and the length of one cycle and the thermal conductivity were determined.

(Example 6)
In Example 5, the boron nitride particles were treated in the same manner except that the heat treatment time was 30 minutes. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Example 7)
In Example 1, after adding alumina particles having a volume average particle diameter of 0.4 μm (trade name: AA04) to boron nitride particles having a volume average particle diameter of 40 μm, ultraviolet irradiation is performed in the same manner as in Example 1. The epoxy resin composition was obtained in the same manner except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass. . Using the obtained epoxy resin composition, a B stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Example 8)
In Example 2, after adding alumina particles having a volume average particle diameter of 0.4 μm (trade name: AA04) to boron nitride particles having a volume average particle diameter of 40 μm, ultraviolet irradiation was performed in the same manner as in Example 2. The epoxy resin composition was obtained in the same manner except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass. . Using the obtained epoxy resin composition, a B stage sheet and a cured epoxy resin were prepared in the same manner as in Example 2, and the length of one cycle and the thermal conductivity were determined.

Example 9
In Example 3, after adding alumina particles (Sumitomo Chemical Co., Ltd., trade name: AA04) having a volume average particle diameter of 0.4 μm to boron nitride particles having a volume average particle diameter of 40 μm, ultraviolet irradiation was performed in the same manner as in Example 3. The epoxy resin composition was obtained in the same manner except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass. . Using the obtained epoxy resin composition, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 3, and the length of one cycle and the thermal conductivity were determined.

(Example 10)
In Example 4, after adding alumina particles having a volume average particle size of 0.4 μm (trade name: AA04) to boron nitride particles having a volume average particle size of 40 μm, heat treatment is performed in the same manner as in Example 4. The epoxy resin composition was prepared in the same manner as above except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass after UV irradiation. Obtained. Using the obtained epoxy resin composition, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 4, and the length of one cycle and the thermal conductivity were determined.

(Example 11)
In Example 5, after adding alumina particles having a volume average particle size of 0.4 μm (trade name: AA04) to boron nitride particles having a volume average particle size of 40 μm, heat treatment is performed in the same manner as in Example 5. The epoxy resin composition was prepared in the same manner as above except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass after UV irradiation. Obtained. Using the obtained epoxy resin composition, a B stage sheet and a cured epoxy resin were prepared in the same manner as in Example 5, and the length of one cycle and the thermal conductivity were determined.

(Example 12)
In Example 6, after adding alumina particles having a volume average particle diameter of 0.4 μm (trade name: AA04) to boron nitride particles having a volume average particle diameter of 40 μm, heat treatment is performed in the same manner as in Example 6. The epoxy resin composition was prepared in the same manner as above except that the epoxy resin composition was prepared so that the boron nitride content in the cured resin was 60% by mass and the alumina particle content was 20% by mass after UV irradiation. Obtained. Using the obtained epoxy resin composition, a B-stage sheet and a cured epoxy resin were produced in the same manner as in Example 6, and the length and thermal conductivity of one cycle were determined.

(Comparative Example 1)
In Example 6, a liquid crystalline epoxy resin (1- (3-methyl-4-oxiranimethoxyphenyl) -4- (oxiranimethoxyphenyl) -1-cyclohexene was replaced with an epoxy monomer (Mitsubishi Chemical: jER828, general formula ( A B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 6 except that the difference was changed to 1), which was different from 1), and the length and thermal conductivity of one cycle were determined in the same manner as in Example 1. .

(Comparative Example 2)
Without treating the boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Comparative Example 3)
In Example 1, the boron nitride particles were treated in the same manner except that the ultraviolet irradiation time was 6 seconds. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Comparative Example 4)
The boron nitride particles were heat-treated in a constant temperature bath at 150 ° C. for 10 minutes. Using the treated boron nitride particles, a B-stage sheet and a cured epoxy resin were prepared in the same manner as in Example 1, and the length and thermal conductivity of one cycle were determined.

(Comparative Example 5)
B stage sheet and cured epoxy resin were prepared in the same manner as in Example 7 without heating treatment and ultraviolet irradiation treatment of boron nitride particles and alumina particles, and the length and thermal conductivity of one cycle were obtained.

(Comparative Example 6)
In Example 7, the particles were treated in the same manner except that the ultraviolet irradiation time of boron nitride particles and alumina particles was set to 6 seconds. A B stage sheet and a cured epoxy resin were prepared in the same manner as in Example 7, and the length and thermal conductivity of one cycle were determined.

(Comparative Example 7)
In Example 7, a B-stage sheet and a cured epoxy resin were prepared in the same manner except that heat treatment was performed for 10 minutes in a thermostatic bath at 150 ° C. instead of ultraviolet irradiation, and the length and thermal conductivity of one cycle were determined. .

From Table 1, since the epoxy monomer of Comparative Example 1 is not liquid crystalline, the periodic structure is not confirmed, whereas in Examples 1 to 6, the cured epoxy resin has a periodic structure of 2.5 nm per period, It can be seen that the thermal conductivity is high.
In Comparative Examples 2 to 4, and further Comparative Examples 5 to 7 using boron nitride particles having a surface oxygen atom concentration of less than 1.5 at%, no periodic structure was confirmed. And when Examples 1-12 are compared with Comparative Examples 2-7, any Example of Examples 1-12 has higher thermal conductivity than any Comparative Example of Comparative Examples 2-7. Therefore, it can be seen that when boron nitride particles having a surface oxygen atom concentration of less than 1.5 at% are present, the liquid crystalline epoxy resin does not form a periodic structure, so that the thermal conductivity is lowered.

Claims (16)

An epoxy resin composition comprising boron nitride particles having a surface oxygen atom concentration of 1.5 at% or more, a liquid crystalline epoxy monomer represented by the following general formula (1), and a curing agent.


[In General Formula (1), X represents a linking group composed of at least one selected from the group (I) consisting of a single bond or a divalent group represented by the following chemical formula. Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an aliphatic alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. Indicates. n independently represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12. ]

  The epoxy resin composition according to claim 1, wherein the content of the boron nitride particles is 20% by mass to 95% by mass in the total solid content. 3. The epoxy resin composition according to claim 1, wherein the boron nitride particles are irradiated with 100 mJ / cm ² or more of light including ultraviolet rays having a wavelength of 150 nm to 400 nm. 3. The epoxy resin according to claim 1, wherein the boron nitride particles are heat-treated at 60 ° C. to 400 ° C. for 1 minute or longer and irradiated with light containing ultraviolet rays having a wavelength of 150 nm to 400 nm for 100 mJ / cm ² or more. Composition.   The epoxy resin composition according to any one of claims 1 to 4, wherein the epoxy resin composition does not contain alumina particles or contains alumina particles, and the content of the alumina particles is 70% by mass or less. The epoxy resin composition according to claim 5, wherein the alumina particles are irradiated with light containing ultraviolet rays having a wavelength of 150 nm to 400 nm at 100 mJ / cm ² or more.   The heat conductive material precursor which is a semi-hardened | cured material of the epoxy resin composition of any one of Claims 1-6.   The heat conductive material precursor according to claim 7, wherein the semi-cured product has a periodic structure having a length of one cycle of 2 nm to 3 nm.   The B stage sheet | seat which is a sheet-like semicured material of the epoxy resin composition of any one of Claims 1-6.   The B-stage sheet according to claim 9, wherein the sheet-like semi-cured product of the epoxy resin composition has a periodic structure having a period of 2 nm to 3 nm.   The prepreg which has a fiber base material and the semi-hardened | cured material of the epoxy resin composition of any one of Claims 1-6 impregnated in the said fiber base material.   The heat conductive material which is a hardened | cured material of the epoxy resin composition of any one of Claims 1-6.   The thermally conductive material according to claim 12, wherein the cured product of the epoxy resin composition has a periodic structure having a length of one cycle of 2 nm to 3 nm. A substrate,
The resin layer comprised from the epoxy resin composition of any one of Claims 1-6 provided on the said adherend, The B stage sheet | seat of Claim 9 or Claim 10, And a cured layer of at least one resin-containing layer selected from the group consisting of the prepreg according to claim 11;
A laminate having Metal foil,
A metal plate,
The resin layer comprised from the epoxy resin composition of any one of Claims 1-6 arrange | positioned between the said metal foil and the said metal plate, Claim 9 or Claim 10. A cured layer of at least one resin-containing layer selected from the group consisting of the B stage sheet of claim 11 and the prepreg according to claim 11;
A metal substrate. A wiring layer;
A metal plate,
The resin layer comprised from the epoxy resin composition of any one of Claims 1-6 arrange | positioned between the said wiring layer and the said metal plate, Claim 9 or Claim 10. A cured layer of at least one resin-containing layer selected from the group consisting of the B stage sheet of claim 11 and the prepreg according to claim 11;
A printed wiring board having: