JP7571438B2 - Phenoxy resin, thermosetting resin composition and uses thereof - Google Patents

Description

The present invention relates to a novel phenoxy resin, a thermosetting resin composition, and uses thereof.

So far, various developments have been made in heat dissipation and insulation materials. For example, the technology described in Patent Document 1 is known as this type of technology. Patent Document 1 describes a thermosetting resin composition that uses bisphenol A type epoxy resin, a phenolic hardener, and boron nitride particles as a thermally conductive filler as a heat dissipation and insulation material for electrical and electronic devices (Table 1 of Patent Document 1).

Patent Document 2 describes an encapsulating resin composition containing a biphenyl-type epoxy resin represented by a specific general formula.

Patent Document 3 discloses an epoxy resin composition containing an epoxy resin and a curing agent. The document describes an epoxy resin composition containing an epoxy resin having a bisphenylene structure and bis(4-hydroxyphenyl)terephthalate as a curing agent, and a cured product of the composition (e.g., Example 2).

JP 2015-193504 A JP 2019-151691 A JP 2013-237860 A

However, the epoxy resins described in Patent Documents 1 and 3 leave room for improvement in terms of thermal conductivity. Patent Document 2 does not mention thermal conductivity.

After much research, the inventors discovered that high thermal conductivity can be achieved by using a new phenoxy resin with a specific structure, and thus completed the present invention.

（一般式（１）中、Ｒ^１～Ｒ^４はそれぞれ独立して、水素原子、ハロゲン原子、水酸基、アミノ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、またはアリル基を示す。Ｑ^１～Ｑ^３は、それぞれ独立して、水素原子、炭素数１～６のアルキル基、または炭素数１～６のアルコキシ基を示す。複数存在するＱ^１、複数存在するＱ^２または複数存在するＱ^３は同一でも異なっていてもよい。＊は結合手を示す。） According to the present invention,
There is provided a phenoxy resin comprising a repeating unit represented by the following general formula (1):

(In general formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group. Q ¹ to Q ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. A plurality of Q ^{1 s} , a plurality of Q ^{2 s} , or a plurality of Q ^{3 s} may be the same or different. * represents a bond.)

According to the present invention,
A thermosetting resin composition is provided that includes the phenoxy resin.

According to the present invention,
The thermosetting resin composition is formed into a film to provide a resin sheet.

According to the present invention,
There is provided a resin substrate comprising a cured product of the thermosetting resin composition.

According to the present invention,
A metal layer;
A resin layer laminated on at least one surface of the metal layer,
There is provided a circuit board, wherein the resin layer is made of a cured product of the thermosetting resin composition.

（一般式（ａ）中、Ｒ^１～Ｒ^４はそれぞれ独立して、水素原子、ハロゲン原子、水酸基、アミノ基、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、またはアリル基を示す。）
で表される２官能エポキシ化合物（ａ）と、一般式（ｂ）：

（一般式（ｂ）中、Ｑ^１～Ｑ^３はそれぞれ独立して、水素原子、炭素数１～６のアルキル基、または炭素数１～６のアルコキシ基を示す。）
で表される２官能フェノール化合物（ｂ）と、を反応させる、下記一般式（１）で表される繰り返し単位を含むフェノキシ樹脂の製造方法が提供される。 According to the present invention,
The following general formula (a):

(In general formula (a), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group.)
and a bifunctional epoxy compound (a) represented by the general formula (b):

(In formula (b), Q ¹ to Q ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.)
The present invention provides a method for producing a phenoxy resin containing a repeating unit represented by the following general formula (1), which comprises reacting a bifunctional phenol compound (b) represented by the following general formula (1):

The present invention provides a phenoxy resin with high thermal conductivity, and a thermosetting resin composition using the same.

1 is a cross-sectional view showing a configuration of a metal base substrate according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In all drawings, similar components are given similar reference symbols and descriptions are omitted where appropriate. In addition, "~" indicates "above" to "below" unless otherwise specified.

[Phenoxy resin (A)]
The phenoxy resin (A) of the present embodiment contains a repeating unit represented by the following general formula (1): By having this structure, the phenoxy resin (A) has excellent thermal conductivity.

In general formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group.

From the viewpoint of the effects of the present invention, R ¹ to R ⁴ are preferably an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group, more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably an alkyl group having 1 to 3 carbon atoms.

Q ¹ to Q ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. A plurality of Q ^{1 s} , a plurality of Q ^{2 s} , or a plurality of Q ^{3 s} may be the same or different.
In view of the effects of the present invention, Q ¹ to Q ³ are preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.
* indicates a bond.

The phenoxy resin (A) of the present embodiment is not particularly limited as long as it contains the repeating unit, and various structures can be adopted. For example, a phenoxy resin represented by the following general formula (2) can be mentioned.
A phenoxy resin having this structure has excellent thermal conductivity.

In the general formula (2), R ¹ to R ⁴ and Q ¹ to Q ³ have the same meanings as in the general formula (1). When there are multiple R ¹ to R ⁴ , they may be the same or different, and when there are multiple Q ¹ to Q ³ , they may be the same or different. n is an average value of 1 to 50, preferably 5 to 20.

The weight average molecular weight (Mw) of the phenoxy resin (A) is, for example, 2,000 or more and 20,000 or less, preferably 2,500 or more and 15,000 or less, and more preferably 3,000 to 10,000. Mw is a value measured by gel permeation chromatography and converted using a standard polystyrene calibration curve. By setting Mw within the above range, the thermal conductivity of the phenoxy resin (A) can be further improved.

In this embodiment, the weight average molecular weight of the phenoxy resin can be measured by obtaining a molecular weight distribution curve using GPC (Gel Permeation Chromatography). The weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity (PDI: Mw/Mn) of the phenoxy resin (A) are calculated using polystyrene-equivalent values obtained from a calibration curve of standard polystyrene (PS) obtained by GPC measurement.
The measurement conditions for GPC are, for example, as follows.
Gel permeation chromatography device HLC-8320GPC manufactured by Tosoh Corporation
Column: TSK-GEL GMH, G2000H, Super HM-M manufactured by Tosoh Corporation
Detector: RI detector for liquid chromatography Measurement temperature: 40°C
Solvent: THF
Sample concentration: 2.0 mg/ml

The dispersity (Mw/Mn) of the phenoxy resin (A) is, for example, 2.0 or more and 10.0 or less, preferably 2.5 or more and 9.0 or less, and more preferably 3.0 or more and 8.0 or less. By setting the dispersity within the above range, the thermal conductivity and fluidity of the phenoxy resin (A) can be further improved.

The phenoxy resin (A) may contain a low molecular weight phenoxy resin having a weight average molecular weight (Mw) of 1000 or less. When the phenoxy resin (A) contains a low molecular weight phenoxy resin, the low molecular weight phenoxy resin is, for example, 5% to 60% and preferably 5% to 50% in terms of the total area of the components corresponding to a weight average molecular weight Mw of 1,000 or less, which accounts for 100% of the total area of the entire molecular weight distribution obtained by GPC measurement. The phenoxy resin (A) containing the low molecular weight phenoxy resin in the above amount range has improved fluidity and excellent handleability. Therefore, for example, the processing stability is improved when the phenoxy resin (A) is processed into the form of a sheet or film.

From the viewpoint of the effects of the present invention, the epoxy equivalent of the phenoxy resin (A) is 300 g/eq or more and 6,000 g/eq or less, preferably 350 g/eq or more and 5,000 g/eq or less, and more preferably 400 g/eq or more and 4,500 g/eq or less.

The melt viscosity of the phenoxy resin (A) at 180°C is 50 mPa·s or less, preferably 30 mPa·s or less. This provides excellent moldability and excellent processing stability when the phenoxy resin (A) is processed into a sheet or film.

The phenoxy resin (A) of this embodiment has the above-mentioned configuration, and thus the thermal conductivity of the cured product can be improved. The thermal conductivity of the cured product of the phenoxy resin (A) is, for example, 0.3 W/(m·K) or more, preferably 0.35 W/(m·K) or more, and more preferably 0.4 W/(m·K) or more.

[Method for producing phenoxy resin (A)]
The phenoxy resin (A) containing a repeating unit represented by general formula (1) of the present embodiment can be synthesized by reacting a bifunctional epoxy compound (a) represented by general formula (a) with a bifunctional phenol compound (b) represented by general formula (b).

In formula (a), R ¹ to R ⁴ have the same meanings as in formula (1), and in formula (b) and Q ¹ to Q ³ have the same meanings as in formula (1).
The above reaction can be carried out in the absence of a solvent or in the presence of a reaction solvent using a reaction catalyst.

As the reaction solvent, aprotic organic solvents such as methyl ethyl ketone, dioxane, tetrahydrofuran, acetophenone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, sulfolane, propylene glycol monomethyl ether, and cyclohexanone can be suitably used. By using a reaction solvent, the initial viscosity can be reduced, and the reactivity of the monomer can be improved.

As the reaction catalyst, a conventionally known polymerization catalyst can be used, and alkali metal hydroxides, tertiary amine compounds, quaternary ammonium compounds, tertiary phosphine compounds, quaternary phosphonium compounds, and imidazole compounds are preferably used.

Specifically, a bifunctional epoxy compound (a), a bifunctional phenol compound (b), a reaction catalyst, and, if necessary, a reaction solvent are added and melt-mixed under stirring. The heating temperature during melt-mixing is about 100 to 120°C, the mixing time is about 30 minutes to 2 hours, and the reaction pressure is normal pressure.

After melt mixing, the mixed solution is heated and the polymerization reaction is carried out at a specified reaction temperature under reduced or normal pressure. The reaction temperature is about 140 to 180°C, the reaction time is about 2 to 15 hours, and the reaction pressure is about 1 to 760 Torr.

After the reaction is complete, it is possible to obtain the resin dissolved in a suitable solvent by performing solvent replacement or the like. In addition, the phenoxy resin (A) obtained by the solvent reaction can also be obtained as a solvent-free solid resin by performing a solvent removal process using an evaporator or the like.

In the above synthesis method, the reaction conditions, such as the amount of starting material used, reaction temperature, and reaction time, can be appropriately selected to adjust the degree of polymerization, thereby obtaining a phenoxy resin (A) having the desired weight average molecular weight.

The phenoxy resin (A) of this embodiment can be obtained as a mixture containing impurities such as ionic impurities and low molecular weight components. When the phenoxy resin contains these components, it can also be called a phenoxy resin composition.

The phenoxy resin (A) can be obtained by purifying the crude phenoxy resin (phenoxy resin composition) containing impurities obtained after synthesis. By setting the allowable values of impurities as described below, it is possible to obtain a desired phenoxy resin composition and reduce the purification load. Furthermore, by containing a predetermined amount of impurities, a predetermined effect can be obtained.
In this specification, the phenoxy resin (A) can be defined as containing impurities such as ionic impurities and low molecular weight components, but not containing a solvent.

From the viewpoint of insulating properties, the phenoxy resin (A) of this embodiment can contain ionic impurities in an amount of 1,500 ppm or less, preferably 1,300 ppm or less, and more preferably 1,200 ppm or less.

Examples of the ionic impurities include ^F- , Cl- ^, _NO2- ^{, Br- ,} _NO3- ^, _PO43- ^, _SO42- , (COO) _22- , _CH3COO- ^, and ^HCOO- .
The ionic impurity concentration can be measured, for example, as follows. First, the phenoxy resin (A) is weighed into a container, and ultrapure water is added and the container is sealed. Next, hot water extraction is performed by heat treatment at a temperature of 125° C. for 20 hours using a thermostatic bath. Next, the phenoxy resin (A) and the like are removed from the solution obtained by hot water extraction by centrifugation, filtration, etc. to prepare a test liquid. Next, the ionic impurity content in the test liquid is measured using an ion chromatography analyzer by a calibration curve method using a standard solution. The ionic impurity content relative to the phenoxy resin (A) used to prepare the test liquid was taken as the ionic impurity concentration.

The ionic impurities may include hydrolyzable chlorine.
From the viewpoint of insulating properties, the phenoxy resin (A) of the present embodiment may contain ionic impurities including hydrolyzable chlorine in the above-mentioned amount.
The hydrolyzable chlorine concentration can be measured, for example, as follows.
First, phenoxy resin (A), an acetone-methanol mixed solution, and a methanol solution of CH ₃ ONa are mixed, and BTB solution is added as an indicator. Next, nitric acid is added until the solution turns yellow, and the above indicator is further added. Potentiometric titration is performed on this solution using an automatic titrator (using a silver electrode) with an aqueous silver nitrate solution to determine the amount of hydrolyzable chlorine. The amount of hydrolyzable chlorine relative to phenoxy resin (A) is taken as the hydrolyzable chlorine concentration.

The low molecular weight component contained in the phenoxy resin (A) of this embodiment is a component having a weight average molecular weight Mw of 1,000 or less.
The low molecular weight component may contain at least one of the monomer components (C) (bifunctional epoxy compound (a), bifunctional phenol compound (b)) contained in the phenoxy resin (A) and a low molecular weight component (B) having Mw of 1k or less and not including the monomer component (C). The low molecular weight component (B) may be composed of one or more polymers of the monomer components (C).

By reducing the amount of low molecular weight components contained in the phenoxy resin (A), the thermal conductivity can be further increased, and the fluidity of the phenoxy resin (A) can be improved.

The peak area corresponding to the low molecular weight components (B+C) in the phenoxy resin (A) with Mw of 1k or less is calculated from the ratio of the total area of components with a weight average molecular weight Mw of 1,000 or less to the total area of the entire molecular weight distribution (100%), based on data on molecular weight obtained, for example, by GPC measurement.

This low molecular weight component (B+C) with Mw of 1k or less includes monomer component (C) and low molecular weight component (B) with Mw of 1,000 or less that does not contain monomer component (C).

The total peak area of 100% is defined as the sum of the peak areas of the phenoxy resin (A), the monomer component (C), and the low molecular weight component (B) having an Mw of 1,000 or less and not including the monomer component (C).

The peak area of the low molecular weight components (B+C) can be 10% or less, preferably 7% or less. This can further improve the thermal conductivity of the phenoxy resin (A).

In addition, in the molecular weight distribution of the phenoxy resin (A) obtained by GPC measurement, the peak area of the low molecular weight component (B) with Mw of 1,000 or less can be 7% or less, preferably 5% or less, relative to the total peak area of 100%. This can further improve the thermal conductivity of the phenoxy resin (A).

The low molecular weight component (B) with Mw of 1,000 or less does not contain monomer component (C). The peak area ratio of this low molecular weight component (B) with Mw of 1,000 or less represents the content ratio of low-molecular weight components (low molecular weight polymer components) contained in the low molecular weight component.

In the molecular weight distribution of the phenoxy resin (A) measured by GPC, the peak area of the monomer component (C) relative to the total peak area of 100% can be 3% or less, preferably 2% or less, thereby further improving the thermal conductivity of the phenoxy resin (A).
Furthermore, the melting point and melt viscosity of the phenoxy resin (A) can be adjusted by the molecular weight of the phenoxy resin (A) and the amount of the low molecular weight component.

In this embodiment, for example, by appropriately selecting the type and amount of each component contained in the phenoxy resin (A), the preparation method of the phenoxy resin (A), etc., it is possible to control the peak area of the low molecular weight components (B + C) in the phenoxy resin (A), the peak area of the low molecular weight component (B), and the Mw and Mw/Mn of the phenoxy resin (A). Among these, for example, appropriately selecting the synthesis conditions of the phenoxy resin (A), such as the reaction temperature, reaction time, and removal of monomers, is cited as an element for setting the peak area of the low molecular weight components (B + C) in the phenoxy resin (A), the peak area of the low molecular weight component (B), and the Mw and Mw/Mn of the phenoxy resin (A) to the desired numerical range.

Hereinafter, a resin material using the phenoxy resin (A) of this embodiment will be described.
The resin material of this embodiment includes a phenoxy resin (A) or a phenoxy resin composition. The content can be appropriately adjusted based on various applications and other blending components. For example, the content of the phenoxy resin (A) in the thermosetting resin composition used for the heat dissipation insulating material is, for example, 1% by mass to 70% by mass, preferably 2% by mass to 50% by mass, and more preferably 3% by mass to 45% by mass, based on the non-volatile components (100% by mass) of the thermosetting resin composition not including a filler.

Here, the term "filler" includes ordinary fillers such as a thermally conductive filler, an inorganic filler, or an organic filler, which will be described later. That is, a thermosetting resin composition that does not contain a filler is composed of resin components other than a filler, and includes, as the resin components, for example, a thermosetting resin and a phenoxy resin.
It also refers to the non-volatile content (100 mass%) in the thermosetting resin composition, and refers to the remainder excluding solvents such as water and solvents.

(Thermosetting resin)
The thermosetting resin composition of the present embodiment contains the phenoxy resin (A) and may further contain a thermosetting resin other than the phenoxy resin (A).
Examples of the thermosetting resin include epoxy resin, polyimide resin, benzoxazine resin, unsaturated polyester resin, phenol resin, melamine resin, silicone resin, cyanate resin, bismaleimide resin, acrylic resin, phenol derivatives, and derivatives thereof. As the thermosetting resin, a monomer, oligomer, or polymer having two or more reactive functional groups in one molecule can be used, and the molecular weight or molecular structure is not particularly limited. These may be used alone or in combination of two or more.

(Hardening agent)
The thermosetting resin composition of the present embodiment may contain a curing agent as necessary.
The curing agent is selected depending on the type of thermosetting resin, and is not particularly limited as long as it reacts with the thermosetting resin.

Examples of the curing agent include phenolic resin curing agents, amine curing agents, acid anhydride curing agents, mercaptan curing agents, etc. These may be used alone or in combination of two or more.

(Cure Accelerator)
The thermosetting resin composition may contain a curing accelerator as necessary.
The type and amount of the curing accelerator are not particularly limited, but an appropriate one can be selected from the viewpoints of reaction rate, reaction temperature, storage property, and the like.

Examples of the curing accelerator include imidazoles, organic phosphorus compounds, tertiary amines, phenolic compounds, organic acids, and the like. These may be used alone or in combination of two or more. Among these, from the viewpoint of improving heat resistance, it is preferable to use nitrogen atom-containing compounds such as imidazoles.

(Thermal conductive filler)
The thermosetting resin composition of the present embodiment may contain a thermally conductive filler.
The thermally conductive filler may contain, for example, highly thermally conductive inorganic particles having a thermal conductivity of 20 W/m·K or more. The highly thermally conductive inorganic particles may contain, for example, at least one selected from alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide. These may be used alone or in combination of two or more.

The thermally conductive filler may contain boron nitride in the form of monodisperse particles, agglomerated particles, or a mixture thereof, of scaly boron nitride. The scaly boron nitride may be granulated. By using agglomerated particles of scaly boron nitride, the thermal conductivity can be further increased. The agglomerated particles may be sintered particles or non-sintered particles.

(Silane coupling agent)
The thermosetting resin composition of the present embodiment may contain a silane coupling agent.
This can improve the compatibility of the thermally conductive filler in the thermosetting resin composition. The coupling agent may be added to the thermosetting resin composition, or may be used by treating the surface of the thermally conductive filler.

The thermosetting resin composition of the present embodiment may contain other components in addition to the above-mentioned components. Examples of the other components include an antioxidant and a leveling agent.
The thermosetting resin composition of the present embodiment can be produced, for example, by the following method.

A resin varnish (a varnish-like thermosetting resin composition) can be prepared by dissolving, mixing, and stirring each of the above components in a solvent. This mixing can be performed using various mixers such as ultrasonic dispersion, high-pressure collision dispersion, high-speed rotation dispersion, bead mill, high-speed shear dispersion, and rotation-revolution dispersion.

The above solvents are not particularly limited, but include acetone, methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, ethylene glycol, cellosolve-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone.

(Thermal conductive resin sheet)
The resin sheet of the present embodiment is obtained by forming the thermosetting resin composition into a film.
The thermally conductive resin sheet of the present embodiment includes a carrier substrate and a resin layer (resin sheet) formed on the carrier substrate and made of the thermosetting resin composition of the present embodiment.

The thermally conductive resin sheet can be obtained, for example, by applying a varnish-like thermosetting resin composition onto a carrier substrate to obtain a coating film (resin layer) and then carrying out a solvent removal process. The solvent content in the resin sheet can be 10% by weight or less based on the entire thermosetting resin composition. For example, the solvent removal process can be carried out under conditions of 80°C to 200°C and 1 minute to 30 minutes.

In this embodiment, the carrier substrate may be, for example, a polymer film or a metal foil. Examples of the polymer film include, but are not limited to, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, release papers such as silicone sheets, and heat-resistant thermoplastic resin sheets such as fluorine-based resins and polyimide resins. Examples of the metal foil include, but are not limited to, copper and/or copper-based alloys, aluminum and/or aluminum-based alloys, iron and/or iron-based alloys, silver and/or silver-based alloys, gold and gold-based alloys, zinc and zinc-based alloys, nickel and nickel-based alloys, and tin and tin-based alloys.

(Resin substrate)
The resin substrate of the present embodiment includes an insulating layer made of the cured product of the thermosetting resin composition. This resin substrate can be used as a material for a printed circuit board on which electronic components such as LEDs and power modules are mounted.

(Metal base board (circuit board))
The metal base substrate (circuit substrate) of this embodiment includes a metal layer and a resin layer made of a cured product of the thermosetting resin composition laminated on at least one surface of the metal layer.
As an example of this embodiment, a metal base substrate 100 will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing an example of the configuration of a metal base substrate 100. As shown in FIG.

As shown in FIG. 1, the metal base substrate 100 can include a metal substrate 101, an insulating layer 102 provided on the metal substrate 101, and a metal layer 103 provided on the insulating layer 102. The insulating layer 102 can be made of one selected from the group consisting of a resin layer made of the above-mentioned thermosetting resin composition, a cured product of the thermosetting resin composition, and a laminate. Each of these resin layers and laminates may be made of a thermosetting resin composition in a B-stage state before the circuit processing of the metal layer 103, and may be a cured product obtained by curing the resin composition after the circuit processing.

The metal layer 103 is provided on the insulating layer 102 and is processed into a circuit. Examples of metals constituting the metal layer 103 include one or more selected from copper, copper alloys, aluminum, aluminum alloys, nickel, iron, tin, and the like. Among these, the metal layer 103 is preferably a copper layer or an aluminum layer, and is particularly preferably a copper layer. By using copper or aluminum, the circuit processability of the metal layer 103 can be improved. The metal layer 103 may be a metal foil available in a plate form, or a metal foil available in a roll form.

The lower limit of the thickness of the metal layer 103 is, for example, 0.01 mm or more, and preferably 0.035 mm or more, so that the metal layer 103 can be applied to applications requiring a high current.
The upper limit of the thickness of the metal layer 103 is, for example, 10.0 mm or less, and preferably 5 mm or less. If the thickness is less than this value, the circuit processability can be improved, and the substrate as a whole can be made thinner.

The metal substrate 101 has the role of dissipating heat accumulated in the metal base substrate 100. The metal substrate 101 is not particularly limited as long as it is a heat-dissipating metal substrate, but may be, for example, a copper substrate, a copper alloy substrate, an aluminum substrate, or an aluminum alloy substrate, with a copper substrate or an aluminum substrate being preferred, and a copper substrate being more preferred. By using a copper substrate or an aluminum substrate, the heat dissipation properties of the metal substrate 101 can be improved.

The thickness of the metal substrate 101 can be appropriately set as long as the object of the present invention is not impaired.
The upper limit of the thickness of the metal substrate 101 is, for example, 20.0 mm or less, and preferably 5.0 mm or less. By using a metal substrate 101 having a thickness of this value or less, the workability of the metal base substrate 100 in the outer shaping, cutting, and the like can be improved.

The lower limit of the thickness of the metal substrate 101 is, for example, 0.01 mm or more, and preferably 0.6 mm or more. By using a metal substrate 101 with a thickness of this value or more, the heat dissipation properties of the metal base substrate 100 as a whole can be improved.

In this embodiment, the metal base substrate 100 can be used for various substrate applications, but because it has excellent thermal conductivity and heat resistance, it can be used as a printed circuit board that uses LEDs and power modules.

The metal base substrate 100 can have a metal layer 103 that has been circuitized by etching or the like into a pattern. In this metal base substrate 100, a solder resist (not shown) may be formed on the outermost layer, and connection electrodes may be exposed so that electronic components can be mounted by exposure and development.

The above describes embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted as long as they do not impair the effects of the present invention.

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these. The raw materials used in the examples are as follows.

(Epoxy Compound)
Tetramethylbiphenyl type epoxy resin represented by the following formula (3) (product name: YX4000, bifunctional epoxy compound, having a mesogen structure, manufactured by Mitsubishi Chemical Corporation)

(Phenol compounds)
・1,4-phenylene bis(4-hydroxybenzoate) represented by the following formula (4) obtained by the following synthesis method
20 g (0.145 mol) of 4-hydroxybenzoic acid, 7.7 g (0.07 mol) of hydroquinone, 0.25 g (0.014 mol) of sodium toluenesulfonate, and 300 g of toluene were added to a 500 mL four-neck flask equipped with a stirrer, a temperature sensor, and a reflux condenser, and the mixture was heated to 90° C. under a nitrogen stream and stirred for 10 hours. After stirring was completed, the reaction liquid was cooled to room temperature and reduced in pressure to 10 hPa, and then gradually heated to 70° C. to distill off the toluene.

<Synthesis of phenoxy resin (A)>
Example 1
62 parts by weight of the epoxy compound represented by the above formula (3), 31 parts by weight of the phenol compound represented by the above formula (4), 0.05 parts by weight of triphenylphosphine (TPP), and 7 parts by weight of a solvent (cyclohexanone) were dropped into a reactor and melt-mixed at 100°C to 110°C for 1 hour. The mixture was then heated to 170°C, and reacted while removing the solvent under reduced pressure at that temperature. It was confirmed by GPC that the molecular weight was the target, and the reaction was stopped to obtain a phenoxy resin represented by the following chemical formula. The reaction was carried out for 12 hours. After the reaction, 100 parts by weight of cyclohexanone was added to the resin to dissolve the resin and cooled to room temperature. After cooling, the resin was purified by a reprecipitation method using methanol to obtain 100 parts by weight of a phenoxy resin represented by the following formula (5) (the average value of the number of repeating units n in the chemical formula is 11). It was inferred that the target polymer was produced because the peak of the low molecular weight component decreased and the peak of the high molecular weight component increased in the GPC chart.

(Comparative Example 1)
As the phenoxy resin, a linear phenoxy resin: a bisphenol A type phenoxy resin (having no mesogen structure, manufactured by Mitsubishi Chemical Corporation, YP-55) represented by the following formula (6) was used.

The physical properties of the phenoxy resins in the examples and comparative examples were measured by the following methods.
(Molecular weight, dispersity, and peak area)
The measurement conditions for GPC are as follows.
- Gel permeation chromatography device HLC-8320GPC manufactured by Tosoh Corporation
Column: TSK-GEL GMH, G2000H, Super HM-M manufactured by Tosoh Corporation
Detector: RI detector for liquid chromatography Measurement temperature: 40°C
Solvent: THF
Sample concentration: 2.0 mg/mL Weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity index (PDI: Mw/Mn) were calculated using polystyrene-equivalent values obtained from a calibration curve of standard polystyrene (PS) obtained by GPC measurement.
Based on the data on molecular weight obtained by the above GPC measurement, the area ratio (%) of the peak area corresponding to the low molecular weight phenoxy resin having Mw of 1k or less contained in the entire phenoxy resin to be measured was calculated when the total area of the molecular weight distribution obtained by the GPC measurement was taken as 100%. The results are shown in Table 1.

(Thermal Conductivity)
- Preparation of resin molded body 100 parts by weight of each phenoxy resin of Example 1 or Comparative Example 1 was mixed with 2 parts by weight of catalyst (2-methylimidazole) and set in a mold coated with a release agent, and compression molded at 180°C for 30 minutes to obtain a resin molded body with a diameter of 10 mm and a thickness of 1 mm. Then, curing was performed in an oven at 180°C for 180 minutes to obtain a resin molded body (a sample for measuring thermal conductivity).

Measurement of thermal conductivity of resin molded body From the obtained resin molded body, a test piece was processed to a diameter of 10 mm and a thickness of 1 mm for thickness direction measurement. Next, the thermal diffusion coefficient (α) in the thickness direction of the plate-shaped test piece was measured by the laser flash method using a Xe flash analyzer TD-1RTV manufactured by ULVAC. The measurement was performed under the condition of air atmosphere and 25°C.
The thermal conductivity of the resin molded body was calculated from the measured values of the thermal diffusion coefficient (α), specific heat (Cp), and density (ρ) according to the following formula. The results are shown in Table 1.
Thermal conductivity [W/m・K] = α [m ² /s] × Cp [J/kg・K] × ρ [g/cm ³ ]

The phenoxy resin of the embodiment showed superior thermal conductivity compared to the comparative example. Such a novel phenoxy resin can be used as a resin material, and can be suitably used as a heat dissipation insulating material such as a heat dissipation insulating substrate or sheet.

100 Metal base substrate 101 Metal substrate 102 Insulating layer 103 Metal layer

Claims (13)

A phenoxy resin comprising a repeating unit represented by the following general formula (1):
A phenoxy resin having a thermal conductivity of 0.3 W/(m·K) or more after curing.

(In general formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group. Q ¹ to Q ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. A plurality of Q ¹ to Q ³ may be the same or different. * represents a bond.) The phenoxy resin according to claim 1, represented by the following general formula (2):

(In the general formula (2), R ¹ to R ⁴ and Q ¹ to Q ³ have the same meanings as in the general formula (1). When multiple R ¹ to R ⁴ are present, they may be the same or different, and when multiple Q ¹ to Q ³ are present, they may be the same or different. n is an average number of 1 to 50.) The phenoxy resin according to claim 1 or 2, having a weight average molecular weight of 2,000 or more and 20,000 or less. The phenoxy resin according to any one of claims 1 to 3, having a polydispersity PDI (Mw/Mn) of 2.0 or more and 10.0 or less. Contains a low molecular weight phenoxy resin represented by general formula (1) having a weight average molecular weight of 1,000 or less,
The phenoxy resin according to any one of claims 1 to 4 , wherein in a molecular weight distribution of the phenoxy resin obtained by gel permeation chromatography, a peak area of the low molecular weight phenoxy resin is 5% or more and 60% or less with respect to a total peak area of 100%. A thermosetting resin composition comprising the phenoxy resin according to any one of claims 1 to 5 . The thermosetting resin composition according to claim 6 , further comprising a thermally conductive filler. The thermosetting resin composition according to claim 6 or 7 , further comprising a solvent. A resin sheet obtained by forming the thermosetting resin composition according to any one of claims 6 to 8 into a film. A resin substrate comprising a cured product of the thermosetting resin composition according to any one of claims 6 to 8 . A metal layer;
A resin layer laminated on at least one surface of the metal layer,
A circuit board, wherein the resin layer is made of a cured product of the thermosetting resin composition according to any one of claims 6 to 8 . The following general formula (a):

(In general formula (a), R ¹ to R ⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an allyl group.)
and a bifunctional epoxy compound (a) represented by the general formula (b):

(In formula (b), Q ¹ to Q ³ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.)
A phenoxy resin containing a repeating unit represented by the following general formula (1), which is reacted with a bifunctional phenol compound (b) represented by the following general formula (1) :
A method for producing a phenoxy resin, wherein the thermal conductivity of a cured product of the phenoxy resin is 0.3 W/(m·K) or more .

(In formula (1), R ¹ to R ⁴ have the same meaning as in formula (a), and Q ¹ to Q ³ have the same meaning as in formula (b). * indicates a bond.) The method for producing a phenoxy resin according to claim 12 , wherein the phenoxy resin is represented by the following general formula (2):

(In the general formula (2), R ¹ to R ⁴ and Q ¹ to Q ³ have the same meanings as in the general formula (1). When multiple R ¹ to R ⁴ are present, they may be the same or different, and when multiple Q ¹ to Q ³ are present, they may be the same or different. n is an average number of 1 to 50.)

Images