JP6122637B2 - Insulating film and manufacturing method thereof - Google Patents

Description

  The present invention relates to an insulating film and a method for producing the same, and more specifically, an insulating film made of a thermally conductive liquid crystal polymer composition that can be suitably used to ensure insulation between heating elements or between a heating element and a heat radiating member. And a manufacturing method thereof.

  Conventionally, electronic circuit boards using an insulating material are known. A metal base circuit board known as a board having a large heat dissipation effect includes a metal board, an insulating film provided on the metal board, and a conductive foil provided on the insulating film. When such a substrate is used, part of heat generated in the electronic component reaches the metal substrate through the insulating film and is radiated from the metal substrate. Therefore, studies have been made to improve the heat dissipation effect of the metal base circuit board by improving the thermal conductivity of the insulating film. Patent Document 1 discloses a technique for producing a printed wiring board by extruding a mixture of liquid crystal polyester and a filler into a plate shape to form a flat plate, and laminating copper on the surface of the flat plate. . However, since the liquid crystal polyester used does not exhibit an isotropic phase when heated, it is necessary to extrude in a liquid crystal state, and the molecular chains of the liquid crystal polyester are remarkably oriented in the extrusion direction. For this reason, while the thermal conductivity in the in-plane direction of the flat plate is increased, the thermal conductivity in the thickness direction is decreased, which is not suitable for the insulating film of the metal base circuit described above. When an insulating film is formed using a liquid crystalline polyester that does not show an isotropic phase when heated, the liquid crystalline polyester molecular chain is also in the in-plane direction of the film in heat molding other than extrusion molding, such as press molding and injection molding. It will be oriented.

  Patent Document 2 describes that an insulating film is formed by casting a solution on a support substrate and evaporating the solvent using a solvent-soluble liquid crystal polyester. Thus, it is described that the thermal conductivity can be increased in the thickness direction by suppressing the in-plane alignment of the liquid crystal polyester as described above and causing random alignment. However, since a step of casting the solution on the support substrate and a step of removing the solvent are necessary, there are disadvantages that the number of manufacturing steps increases and the manufacturing cost increases. In Example 1 of Patent Document 2, 70% by volume of a heat conductive filler is blended in order to obtain high heat conductivity, and the thermal resistance at the interface between the metal and the insulating film tends to increase. Accordingly, in order to increase the heat conductivity in the thickness direction of the insulating film by using a smaller amount of the heat conductive filler, it is necessary to further increase the heat conductivity of the base resin.

  Further, attempts have been widely made to obtain a highly heat conductive resin composition by blending a large amount of heat conductive filler into a general-purpose thermoplastic resin. However, even when a large amount of filler is blended, it is difficult to increase the thermal conductivity in the thickness direction in particular because the thermal conductivity of the resin alone is low. In Patent Document 3, a resin composition containing a Sn—Cu alloy, a metal powder having a melting point of 400 ° C. and / or carbon fiber, a hexagonal boron nitride powder, and a magnesium oxide powder as a low melting point alloy has high thermal conductivity in the thickness direction. It is described that it has. However, since a low melting point alloy, metal powder, or carbon fiber is used, it becomes a non-insulator and cannot be used for an insulating film. Patent Document 4 or 5 describes that the anisotropy of thermal conductivity is reduced for a resin composition containing a spherical or particle-shaped thermally conductive filler and a plate-like thermally conductive filler. However, since the thermal conductivity of the base resin is low, there is a problem that it is difficult to improve the thermal conductivity in the thickness direction. Therefore, improvement of the thermal conductivity of the base resin has been demanded.

  Patent Document 6 describes that a thermoplastic resin having a specific structure exhibits high thermal conductivity as a single resin, and that the thermal conductivity of the resin composition is greatly improved by blending a thermal conductive filler. It is described in Non-patent Documents 1 to 3 that many of the described thermoplastic resins exhibit smectic liquid crystallinity when heated. However, there is no mention of using these resin compositions for insulating films.

JP 62-291195 A JP 2011-032316 A JP 2007-070587 A Special table 2011-503328 gazette JP 2012-136684 A International Publication Number WO2010 / 050202 Journal of Polymer Science Polymer Physics Edition, 21, 1119-1131 (1983) Macromolecules, 16, 1271-1279 (1983) Macromolecules, 17, 2288-2295 (1984).

  An object of this invention is to provide the insulating film which shows high heat conductivity in the thickness direction, and its manufacturing method, even if it does not mix | blend a heat conductive filler in large quantities.

As a result of intensive research to solve the above problems, an insulating film made of a liquid crystal polymer composition containing a liquid crystal polymer that exhibits an isotropic phase upon heating and a heat conductive filler has a large amount of heat conductive filler. In addition to exhibiting isotropic high thermal conductivity without blending, the inventors have found that it has excellent surface smoothness and adhesion to metal, and has led to the present invention.
That is, the present invention includes the following 1) to 13).

  1) Thickness of 500 μm comprising a liquid crystal polymer composition containing 50 to 1200 parts by weight of a spherical or granular thermally conductive filler (B1) with respect to 100 parts by weight of a liquid crystal polymer (A) that exhibits an isotropic phase upon heating. The following insulating films.

  2) The insulating film according to 1), wherein the liquid crystal polymer (A) exhibits a smectic liquid crystal phase when heated.

  3) The insulating film according to 1) or 2), wherein the liquid crystal polymer composition further contains 5 to 100 parts by weight of a flame retardant (C).

  4) The liquid crystal polymer composition further contains 20 to 200 parts by weight of a plate-like thermally conductive filler (B2), and the content ratio with the spherical or granular thermally conductive filler (B1) is in a volume ratio ( The insulating film according to any one of 1) to 3), wherein B1) / (B2) = 5/95 to 70/30.

  5) The insulating film according to any one of 1) to 4), wherein the spherical or granular thermally conductive filler (B1) is alumina, magnesium oxide having a water absorption rate of 0.5% or less, and aluminum nitride.

  6) The insulating film according to 4) or 5), wherein the plate-like thermally conductive filler (B2) is at least one selected from talc and hexagonal boron nitride.

7) The insulating film according to any one of 1) to 6), wherein the structure of the main chain of the liquid crystal polymer is mainly composed of repeating units represented by the general formula (1).
-M-Sp- . . . (1)
(In the formula, M represents a mesogenic group, and Sp represents a spacer.)
8) The insulating film according to 7), wherein the liquid crystal polymer is mainly composed of repeating units represented by the following general formula (2).
_{^{-A 1 -x-A 2 -OCO (}} CH 2) m COO- . . . (2)
(In the formula, A ¹ and A ² each independently represent a substituent selected from an aromatic group, a condensed aromatic group, an alicyclic group, and an alicyclic heterocyclic group. Bond, —O—, —S—, —CH ₂ —CH ₂ —, —C═C—, —C═C (Me) —, —C≡C—, —CO—O—, —CO—NH—. , —CH═N—, —CH═N—N═CH—, —N═N— or —N (O) ═N—, wherein m represents 2 to 20. Indicates an integer.)
9) The insulating film according to 8), wherein -A ¹ -xA ² -of the liquid crystal polymer is represented by the following general formula (3).

(In the formula, each R is independently an aliphatic hydrocarbon group, F, Cl, Br, I, CN, or NO ₂ , y is an integer of 2 to 4, and n is an integer of 0 to 4.)
10) The insulating film according to 8) or 9), wherein m of the liquid crystal polymer is at least one selected from an even number of 4 to 14.

  11) The insulating film according to any one of 1) to 10), wherein the number average molecular weight of the liquid crystal polymer is 3000 to 100,000.

  12) The method for producing an insulating film according to any one of 1) to 11), wherein the liquid crystal polymer composition is heated and pressed to a temperature at which the liquid crystal polymer becomes isotropic on a support substrate. . 13) An electronic circuit board having a metal substrate, an insulating film provided on the metal substrate, and a conductive foil for forming a wiring pattern provided on the insulating film, wherein the insulating film is 1) To 11) An electronic circuit board, which is the insulating film according to any one of the above.

  Since the insulating film of the present invention can increase the thermal conductivity in the thickness direction without blending a large amount of a thermally conductive filler, it has a large amount of resin components and is excellent in adhesion to metal, and thus is generated from an electronic component. Heat can be efficiently transferred to the metal heat radiating member. Therefore, it can be applied as a heat dissipation material for electric / electronic devices, and can contribute to miniaturization or higher performance of electric / electronic devices.

  The insulating film of the present invention is a liquid crystal polymer composition containing 50 to 1200 parts by weight of a spherical or granular heat conductive filler (B1) with respect to 100 parts by weight of the liquid crystal polymer (A) that exhibits an isotropic phase when heated. The insulating film is 500 μm or less in thickness.

The liquid crystal polymer in the present invention can be isotropic when heated. The isotropic phase refers to a state in which polymer molecular chains are randomly oriented, and refers to a state in which a dark field is obtained by microscopic observation under orthogonal polarized light.
Most of the resins exhibiting liquid crystallinity that have been put to practical use so far exhibit nematic liquid crystallinity when heated, and further decompose even if heated to a high temperature without transitioning to an isotropic phase. Therefore, since it is necessary to perform the molding process in the state of nematic liquid crystal, when a thin film such as an insulating film is molded by, for example, injection molding or press molding, the molecules are aligned in the in-plane direction of the film, and the heat conductive filling is performed. There was a problem that the thermal conductivity in the thickness direction of the liquid crystal polymer composition was not greatly improved even when the materials were blended. On the other hand, the liquid crystal polymer described in Patent Document 6 is a liquid crystal polymer exhibiting an isotropic phase when heated, and it is described that the resin alone has high thermal conductivity, and further, liquid crystal is used to increase the thermal conductivity of the resin alone. It is described that it is preferable to melt and mold the resin at the temperature of However, for the resin described in Patent Document 6, when a thin insulating film is molded in an isotropic phase state, the thermal conductivity of the resin alone is as low as that of a general-purpose polymer when the thermal conductive filler is not blended. Nevertheless, it was an unexpected discovery that the thermal conductivity of the liquid crystal polymer composition was greatly improved when a thermally conductive filler was added. Further, since the liquid crystal polymer described in Patent Document 6 mainly exhibits smectic liquid crystallinity, even if it is molded in the state of a smectic liquid crystal phase, molecular alignment in the in-plane direction of a film like a nematic liquid crystal polymer is suppressed. The insulating film has a relatively high thermal conductivity in the thickness direction. However, the present inventors have found that the thermal conductivity is higher when molding in the isotropic phase. This is because the thickness of the insulating film is smaller than the influence of the crystallinity of the liquid crystal polymer, so forming in the isotropic phase state with higher melt flowability suppresses the formation of voids in the insulating film, The influence of having been able to form a denser insulating film is considered to be greater. Since it can be molded in an isotropic phase, the molding processability is improved, so that the insulating film can have both planar smoothness and adhesion to metal in addition to high thermal conductivity.

  The liquid crystal polymer composition in the present invention is characterized by containing a spherical or granular heat conductive filler (B1). When the shape of the thermally conductive filler is spherical or granular, the thermal conductivity can be increased in the thickness direction even when the liquid crystal polymer composition is formed into a thin wall. The thermal conductivity in the thickness direction is preferably 2.0 W / (m · K) or more, more preferably 2.2 W / (m · K) or more, and 2.5 W / (m · K). More preferably, it is more preferably 3.0 W / (m · K) or more.

  The amount of the thermally conductive filler (B1) used is 50 to 1200 parts by weight, preferably 60 to 1000 parts by weight, more preferably 70 to 800 parts by weight, and most preferably 100 parts by weight based on 100 parts by weight of the liquid crystal polymer (A). -700 parts by weight. If it is less than 50 parts by weight, the thermal conductivity in the thickness direction of the insulating film is insufficient, and if it exceeds 1200 parts by weight, the molding processability is deteriorated and the dielectric breakdown strength of the insulating film is lowered.

  The average particle diameter of the heat conductive filler (B1) is preferably in the range of 1 μm to 100 μm, more preferably 2 μm to 80 μm, and particularly preferably 10 μm to 60 μm. If the thickness is less than 1 μm, the thermal conductivity of the insulating film may be insufficient, and if it exceeds 100 μm, the moldability may deteriorate. Further, the filler may be highly filled in the liquid crystal polymer by mixing fillers of different particle sizes.

  Examples of the heat conductive filler (B1) include alumina, aluminum nitride, magnesium oxide, calcium fluoride, glass beads, and hexagonal boron nitride aggregated in a spherical shape or a granular shape. However, magnesium oxide is preferable in terms of low Mohs hardness, thermal conductivity, and cost. Magnesium oxide preferably has a water absorption rate of 0.5% or less, and more preferably 0.3% or less. If it exceeds 0.5%, the liquid crystal polymer may be hydrolyzed when blended with the liquid crystal polymer, or fired during molding. For example, the water absorption can be reduced to 0.5% or less by baking magnesium oxide at a high temperature of 1900 ° C. or higher, or by surface treatment with a silane coupling agent or the like. Here, the water absorption is a mass change rate when treated for 48 hours in an atmosphere of a temperature of 85 ° C. and a relative humidity of 85%.

  In order to increase the dispersibility in the liquid crystal polymer (A) or to improve the adhesion to the liquid crystal polymer (A), such a thermally conductive filler is used as a silane coupling agent and / or an acrylic resin. It is preferable that the surface is treated with urethane resin, epoxy resin or the like.

  The thickness of the insulating film of the present invention is 500 μm or less. When the film thickness is larger than 500 μm, the thermal resistance of the insulating film increases and the heat dissipation effect of the heating element becomes insufficient. For the purpose of reducing the thermal resistance, the thickness of the insulating film is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. The lower limit of the film thickness is not particularly limited, but is usually 10 μm or more, preferably 30 μm or more, more preferably 50 μm or more for the purpose of ensuring the dielectric breakdown strength of the film.

  The liquid crystal polymer of the present invention preferably exhibits a smectic liquid crystal when heated, because the polymer molecular chains are ordered and the thermal conductivity of the polymer itself increases. A smectic liquid crystal is called a smectic layer in which molecules are arranged almost parallel to the molecular axis, and the center of gravity of the parallel connected parts is on the same plane and has a layer state substantially perpendicular to the molecular axis. It has a layer structure. It is known that smectic liquid crystals exhibit a peculiar pattern such as a batonets structure, a mosaic structure, a fan-like structure, etc. in microscopic observation under orthogonal polarization. In addition, a diffraction peak derived from the period of the smectic layer is observed from wide-angle X-ray diffraction measurement in a liquid crystal state.

The thermophysical properties of the liquid crystal polymer generally indicate a transition point T _m from the solid phase to the liquid crystal phase and a transition point T _i from the liquid crystal phase to the isotropic phase in the temperature rising process. These phase transition points can be confirmed as the peak top of the endothermic peak in the temperature rising process of DSC measurement.

In view of the use of the insulating film of the present invention for electric and electronic equipment, the above _Tm is preferably 180 ° C. or higher, more preferably 190 ° C. or higher, more preferably 200 ° C. or higher, from the viewpoint of heat resistance of the insulating film. Be. _Tm is preferably as high as possible from the viewpoint of heat resistance, but _Tm is preferably 350 ° C or less, more preferably 330 ° C or less, and more preferably 310 ° C or less from the viewpoint of moldability of the insulating film. More preferably it is.

  The crystallinity of the liquid crystal polymer (A) in the present invention at room temperature (25 ° C.) is preferably 20% or more, more preferably 40% or more, from the viewpoint of improving the thermal conductivity. % Or more is more preferable. The degree of crystallinity is obtained from the X-ray diffraction measurement by the Ruland method.

  The liquid crystal polymer (A) in the present invention preferably has a periodic higher order structure of about 10 to 70 nm such as a crystalline lamella formed by folding molecules or in a tuft shape. The structure is in close contact with the thermally conductive filler and contributes greatly to efficiently transferring heat between the thermally conductive fillers. From the viewpoint of high thermal conductivity, the period of the higher order structure is preferably longer, more preferably 20 nm or more, further preferably 30 nm or more, and most preferably 40 nm or more. The presence or absence of this periodic higher order structure and the period of the higher order structure can be confirmed by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and small angle X-ray scattering measurement (SAXS). .

  The liquid crystal polymer composition in the present invention may contain a reinforcing material such as a fibrous filler and an acicular filler. Thereby, the strength and heat resistance of the insulating film obtained from the liquid crystal polymer composition can be increased. Examples of the fibrous filler include glass fiber, carbon fiber, boron fiber, aramid fiber, and liquid crystal polyester fiber. Examples of the needle-shaped filler include wollastonite (calcium metasilicate). Potassium titanate whisker, aluminum borate whisker, zinc oxide whisker, calcium carbonate whisker and the like. Among them, as the reinforcing material, glass fibers are preferably used from the viewpoint of high strength and low cost, and needle fillers are preferably used from the viewpoint of obtaining a molded product having high surface smoothness. In particular, glass fiber, wollastonite (calcium metasilicate), potassium titanate whisker, and aluminum borate whisker can be preferably used from the viewpoint of maintaining whiteness.

  In order to enhance the dispersibility in the liquid crystal polymer (A) or to improve the adhesiveness to the liquid crystal polymer (A), such a reinforcing material is used as a silane coupling agent and / or an acrylic resin or a urethane resin. It is preferable that the surface is treated with an epoxy resin or the like.

  The content of the reinforcing material of the liquid crystal polymer composition in the present invention is in the range of 0 to 100 parts by weight, preferably 1 to 80 parts by weight, more preferably 10 to 60 parts by weight with respect to 100 parts by weight of the liquid crystal polymer (A). Is within. If it exceeds 100 parts by weight, the moldability may be lowered.

  The liquid crystal polymer composition in the present invention may contain an epoxy compound, an acid anhydride compound, and an amine compound for the purpose of increasing the adhesive strength with a metal.

  The liquid crystal polymer composition in the present invention preferably further contains 5 to 100 parts by weight of a flame retardant (C). The flame retardancy of the liquid crystal polymer composition is equivalent to V-0 in the UL-94 standard, which can be a condition adopted in electric / electronic devices that handle large currents.

  As a usage-amount of a flame retardant (C), it is more preferable that it is 7-80 weight part, It is more preferable that it is 10-60 weight part, It is further more preferable that it is 12-40 weight part. Various flame retardants (C) are known, and examples include various ones described in “Technology and Application of Polymer Flame Retardation” (P149-221) issued by CMC Chemical. However, it is not limited to these. Among these flame retardants, phosphorus flame retardants, halogen flame retardants, and inorganic flame retardants can be preferably used.

  Examples of phosphorus flame retardants include phosphate esters, halogen-containing phosphate esters, condensed phosphate esters, polyphosphates, and red phosphorus. These phosphorus flame retardants may be used alone or in combination of two or more. Specific examples of the halogen flame retardant include brominated polystyrene, brominated polyphenylene ether, brominated bisphenol type epoxy polymer, brominated styrene maleic anhydride polymer, brominated epoxy resin, brominated phenoxy resin, deca Brominated diphenyl ether, decabromobiphenyl, brominated polycarbonate, perchlorocyclopentadecane, brominated crosslinked aromatic polymer, particularly brominated polystyrene and brominated polyphenylene ether are preferred. These halogen flame retardants may be used alone or in combination of two or more. In addition, the halogen element content of these halogen flame retardants is preferably 15 to 87%.

  Specific examples of the inorganic flame retardant include aluminum hydroxide, antimony trioxide, antimony pentoxide, sodium antimonate, tin oxide, zinc oxide, iron oxide, magnesium hydroxide, calcium hydroxide, zinc borate, Examples include kaolin clay and calcium carbonate. These inorganic compounds may be treated with a silane coupler, a titanium coupler, or the like, or may be used alone or in combination of two or more.

  The liquid crystal polymer composition in the present invention further contains 20 to 200 parts by weight of a plate-like thermally conductive filler (B2), and the content ratio with the spherical or granular thermally conductive filler (B1) is in a volume ratio ( It is preferable that B1) / (B2) = 5/95 to 70/30. In order to efficiently increase the thermal conductivity in the thickness direction of the liquid crystal polymer composition, the content of the heat conductive filler (B2) is preferably 30 to 180 parts by weight, more preferably 40 to 160 parts by weight. More preferably, it is 50-140 weight part, Most preferably, it is 60-120 weight part. When the ratio of the spherical or granular thermally conductive filler (B1) is less than (B1) / (B2) = 5/95 in volume ratio, the plate-like thermally conductive filler is easily oriented in the in-plane direction. In addition, even if the total amount of the thermally conductive filler is increased, the thermal conductivity in the thickness direction may not be increased. When the ratio of the spherical or granular heat conductive filler (B1) is more than (B1) / (B2) = 70/30, the total amount of the heat conductive filler is set to increase the thermal conductivity in the thickness direction. Need to increase. When the thermally conductive fillers (B1) and (B2) are used under the conditions of (B1) / (B2) = 5/95 to 70/30, the heat conductivity of a spherical or granular material having a relatively high Mohs hardness is obtained. Since the thermal conductivity in the thickness direction can be increased while suppressing the total amount of the filler (B1), the moldability of the liquid crystal polymer composition can be further improved. A more preferable volume ratio is (B1) / (B2) = 10/90 to 65/35, and further preferably (B1) / (B2) = 20/80 to 660/40.

  Examples of the plate-like thermally conductive filler (B2) include talc, mica, hexagonal boron nitride, and alumina. The effect of improving the thermal conductivity and the liquid crystal polymer composition when blended with the liquid crystal polymer. Of these, hexagonal boron nitride is preferable because it is difficult to reduce the moldability of the material, and talc is preferable from the viewpoint of improving thermal conductivity to some extent and cost.

  The average particle diameter of the heat conductive filler (B2) is preferably 1 μm to 300 μm, more preferably 5 μm to 150 μm, and particularly preferably 10 μm to 60 μm. When the thickness is less than 1 μm, the thermal conductivity of the insulating film may be insufficient, and when it exceeds 300 μm, the moldability may be deteriorated.

  The dielectric breakdown strength of the insulating film of the present invention is preferably 15 kV / mm or more, more preferably 20 kV / mm or more, and further preferably 25 kV / mm or more. If it is less than 15 kV / mm, it may be impossible to use in electric / electronic devices that handle a large current.

The liquid crystal polymer in the present invention preferably has a main chain structure composed mainly of repeating units represented by the general formula (1).
-M-Sp- . . . (1)
(In the formula, M represents a mesogenic group, and Sp represents a spacer.)
Here, mainly means that the amount of the general formula (1) contained in the main chain of the molecular chain is 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more, based on all the structural units. And most preferably substantially 100 mol%. If it is less than 50 mol%, high thermal conductivity may not be exhibited due to disorder of the molecular structure.
The mesogenic group M contained in the liquid crystal polymer of the present invention means a rigid and highly oriented substituent. The inclusion of the mesogenic group M in the main chain is preferable because liquid crystallinity is easily exhibited during heating. The mesogenic group M corresponds to the general formula (4) in the following general formula (2) and can be preferably applied.
_{^{-A 1 -x-A 2 -OCO (}} CH 2) m COO- . . . (2)
-A ^{1 -x-A 2} -. . . (4)
(In the formula, A ¹ and A ² each independently represent a substituent selected from an aromatic group, a condensed aromatic group, an alicyclic group, and an alicyclic heterocyclic group. Bond, —O—, —S—, —CH ₂ —CH ₂ —, —C═C—, —C═C (Me) —, —C≡C—, —CO—O—, —CO—NH—. , —CH═N—, —CH═N—N═CH—, —N═N— or —N (O) ═N—, wherein m represents 2 to 20. Indicates an integer.)
Here, A ¹ and A ² each independently represent a hydrocarbon group having a benzene ring having 6 to 12 carbon atoms, a hydrocarbon group having a naphthalene ring having 10 to 20 carbon atoms, or a biphenyl structure having 12 to 24 carbon atoms. A hydrocarbon group having 3 or more benzene rings having 12 to 36 carbon atoms, a hydrocarbon group having a condensed aromatic group having 12 to 36 carbon atoms, and an alicyclic heterocyclic group having 4 to 36 carbon atoms It is preferable that it is selected from.

Specific examples of A ¹ and A ² include phenylene, biphenylene, naphthylene, anthracenylene, cyclohexyl, pyridyl, pyrimidyl, thiophenylene, and the like. These may be unsubstituted or may be a derivative having a substituent such as an aliphatic hydrocarbon group, a halogen group, a cyano group, or a nitro group. x is a bond, direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH ₂ —CH ₂ —, —C═C—, —C≡C —, —CO—, —CO—O—, —CO—NH—, —CH═N—, —CH═N—N═CH—, —N═N— or —N (O) ═N—. A divalent substituent selected from Among these, those in which the number of atoms in the main chain of x corresponding to the connector is an even number are preferable. That is, a direct bond, —CH ₂ —CH ₂ —, —C═C—, —C≡C—, —CO—O—, —CO—NH—, —CH═N—, —CH═N—N═CH A divalent substituent selected from the group of-, -N = N- or -N (O) = N- is preferred. When the number of atoms in the main chain of x is an odd number, the increase in molecular width of the mesogenic group and the flexibility due to the increase in the degree of freedom of rotation of the bond promotes a decrease in the crystallization rate, thereby reducing the thermal conductivity of the resin alone. May decrease.

  Specific examples of such preferred mesogenic groups include biphenyl, terphenyl, quarterphenyl, stilbene, diphenyl ether, 1,2-diphenylethylene, diphenylacetylene, benzophenone, phenylbenzoate, phenylbenzamide, azobenzene, azoxybenzene, 2-naphthoate. , Phenyl-2-naphthoate, and derivatives thereof, and the like, but divalent groups having a structure in which two hydrogens are removed are not limited thereto.

  More preferably, it is a mesogenic group represented by the following general formula (3). This mesogenic group is rigid and highly oriented due to its structure, and is easily available or synthesized.

(In the formula, X is independently an aliphatic hydrocarbon group, F, Cl, Br, I, CN, or NO ₂ , y is an integer of 2 to 4, and n is an integer of 0 to 4.)
In order to obtain a liquid crystal polymer composition having excellent moldability, the mesogenic group contained in the liquid crystal polymer preferably does not contain a crosslinkable substituent.

  The spacer Sp contained in the liquid crystal polymer means a flexible molecular chain and includes a bonding group with a mesogenic group. The inclusion of the spacer Sp in the main chain makes it easy for the liquid crystal polymer in the present invention to show an isotropic phase when heated, and the above-mentioned molecules are folded and about 20 to 60 nm like a crystal lamella formed in a tuft shape. It is preferable in that it is easy to form a periodic higher order structure. The number of main chain atoms of the spacer of the liquid crystal polymer is preferably 4 to 28, more preferably 6 to 24, and still more preferably 8 to 20. When the number of main chain atoms of the spacer is less than 4, the molecular structure of the liquid crystal polymer does not exhibit sufficient flexibility, the crystallinity may be lowered, and the thermal conductivity may be lowered. In some cases, the thermal conductivity may decrease. The type of atoms constituting the main chain of the spacer is not particularly limited, and any type can be used. However, it is preferably at least one atom selected from C, H, O, S, and N.

The spacer Sp corresponds to the general formula (5) in the following general formula (2), and can be preferably applied.
_{^{-A 1 -x-A 2 -OCO (}} CH 2) m COO- . . . (2)
-OCO _{(CH 2)} m COO-. . . (5)
(In the formula, A ¹ and A ² each independently represent a substituent selected from an aromatic group, a condensed aromatic group, an alicyclic group, and an alicyclic heterocyclic group. Bond, —O—, —S—, —CH ₂ —CH ₂ —, —C═C—, —C═C (Me) —, —C≡C—, —CO—O—, —CO—NH—. , —CH═N—, —CH═N—N═CH—, —N═N— or —N (O) ═N—, wherein m represents 2 to 20. Indicates an integer.)

  m is preferably an integer of 2 to 20, and more preferably an integer of 4 to 14. M is preferably an even number. In the case of an odd number, since the mesogenic group is inclined, the crystallinity may be lowered and the thermal conductivity may be lowered. In particular, m is preferably at least one selected from 8, 10, and 12 from the viewpoint that a liquid crystal polymer having excellent thermal conductivity can be obtained.

  The number average molecular weight of the present invention is high-temperature GPC using a solution prepared by dissolving polystyrene in a mixed solvent of p-chlorophenol and toluene at a volume ratio of 3: 8 so as to have a concentration of 0.25% by weight. (Viscotek: 350 HT-GPC System) is a value measured at a column temperature of 80 ° C. and a detector as a differential refractometer (RI).

  The number average molecular weight of the liquid crystal polymer in the present invention is preferably 3000 to 100,000, more preferably 3000 to 90000, and particularly preferably 3000 to 80000 in view of the upper limit. On the other hand, considering the lower limit, it is preferably 3000 to 100,000, more preferably 10,000 to 100,000, and particularly preferably 20,000 to 100,000. Further, considering the upper limit and the lower limit, it is more preferably 10,000 to 90,000, and most preferably 20,000 to 80,000. When the number average molecular weight is less than 3000, the mechanical strength of the film may be lowered, and when it is more than 100,000, the moldability may be lowered or the thermal conductivity may be lowered.

  In the liquid crystal polymer of the present invention, 10% or more of the end groups of the molecular chain are preferably sealed with a terminal blocking agent, more preferably 60% or more, more preferably 80% or more. It is more preferable that it is sealed, and it is particularly preferable that it is substantially 100% sealed. When the end-capping rate is 10% or more, the long-term heat resistance is more excellent, and the molecular weight change during heating is further suppressed.

The terminal blocking rate of the liquid crystal polymer can be determined by the following formula (6) by measuring the number of terminal functional groups sealed and non-blocked in the liquid crystal polymer. The number of each terminal group is preferably determined from the integral value of the characteristic signal corresponding to each terminal group by ¹ H-NMR in terms of accuracy and simplicity.
Terminal sealing rate (%) = [number of sealed terminal functional groups] / ([number of sealed terminal functional groups] + [number of unsealed terminal functional groups]). . . (6)

  As the end-capping agent, a monoamine having 1 to 20 carbon atoms or an aliphatic monocarboxylic acid is preferable from the viewpoint of enhancing the thermal conductivity of the liquid crystal polymer, and an aliphatic monocarboxylic acid having 1 to 20 carbon atoms is more preferable. An aliphatic monocarboxylic acid of several 10 to 20 is more preferable. Specific examples of aliphatic monocarboxylic acids include fatty acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid. Group monocarboxylic acids, and any mixtures thereof. Among these, myristic acid, palmitic acid, and stearic acid are preferable from the viewpoint of particularly improving the thermal conductivity of the liquid crystal polymer. Specific examples of monoamines include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, and any of these A mixture etc. can be mentioned. Among these, butylamine, hexylamine, octylamine, decylamine, stearylamine, and cyclohexylamine are preferable from the viewpoints of reactivity, high boiling point, stability of the capped end, and price.

  The liquid crystal polymer in the present invention may be produced by any known method. From the viewpoint that the control of the structure is simple, a method of producing by reacting a compound having reactive functional groups at both ends of the mesogenic group and a compound having reactive functional groups at both ends of the spacer is preferable. As such a reactive functional group, known groups such as a hydroxyl group, a carboxyl group, an alkoxy group, an amino group, a vinyl group, an epoxy group, and a cyano group can be used, and the conditions for reacting these are not particularly limited. From the viewpoint of ease of synthesis, a compound having a hydroxyl group at both ends of the mesogen group and a compound having a carboxyl group at both ends of the spacer, or a compound having a carboxyl group at both ends of the mesogen group and a hydroxyl group at both ends of the spacer Preferred is a production method in which a compound having a reaction is made.

  As an example of a method for producing a liquid crystal polymer comprising a compound having a hydroxyl group at both ends of a mesogenic group and a compound having a carboxyl group at both ends of a spacer, a mesogenic group having a hydroxyl group at both ends is used with a lower fatty acid such as acetic anhydride. A method in which an acetate ester is obtained individually or collectively and then subjected to a deacetic acid polycondensation reaction with a compound having a carboxyl group at both ends of the spacer in a separate reaction vessel or the same reaction vessel. The polycondensation reaction is carried out at a temperature of generally 230 to 350 ° C., preferably 250 to 330 ° C. in the presence of an inert gas such as nitrogen, at normal pressure or under reduced pressure, in the presence of substantially no solvent. ~ 5h done. When the reaction temperature is lower than 230 ° C., the reaction proceeds slowly, and when it is higher than 350 ° C., side reactions such as decomposition tend to occur. When making it react under reduced pressure, it is preferable to raise a pressure reduction degree in steps. When the pressure is rapidly reduced to a high degree of vacuum, the monomer volatilizes and the molecular weight may not be controlled. The ultimate vacuum is preferably 50 torr or less, more preferably 30 torr or less, and particularly preferably 10 torr or less. When the degree of vacuum is greater than 50 torr, the polymerization reaction may take a long time. A multi-stage reaction temperature may be employed. In some cases, the reaction product can be withdrawn in a molten state and recovered as soon as the temperature rises or when the maximum temperature is reached. The obtained liquid crystal polymer may be used as it is, or it may be subjected to solid phase polymerization in order to remove unreacted raw materials or to improve physical properties. In the case of performing solid phase polymerization, the obtained liquid crystal polymer is mechanically pulverized into particles having a particle size of 3 mm or less, preferably 1 mm or less, and in an inert gas atmosphere such as nitrogen at 100 to 350 ° C. in a solid state. It is preferable to treat for 1 to 20 hours under or under reduced pressure. If the particle size of the polymer particles is 3 mm or more, the treatment is not sufficient, and problems with physical properties are caused, which is not preferable. It is preferable to select the treatment temperature and the rate of temperature increase during solid phase polymerization so that the liquid crystal polymer particles do not cause fusion.

  Examples of the acid anhydride of the lower fatty acid used in the production of the liquid crystal polymer in the present invention include an acid anhydride of a lower fatty acid having 2 to 5 carbon atoms such as acetic anhydride, propionic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, anhydrous Examples include trichloroacetic acid, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, etc. Acetic acid, propionic anhydride, and trichloroacetic anhydride are particularly preferably used. The amount of the lower anhydride fatty acid used is 1.01 to 1.50 times equivalent, preferably 1.02 to 1.20 times equivalent to the total of hydroxyl groups of the mesogenic groups used.

  The liquid crystal polymer of the present invention may be copolymerized with other monomers to such an extent that the effect is not lost. For example, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids, aromatic diols, aromatic hydroxyamines, aromatic diamines, aromatic aminocarboxylic acids or caprolactams, caprolactones, aliphatic dicarboxylic acids, aliphatic diols, aliphatic diamines, Examples include alicyclic dicarboxylic acids, and alicyclic diols, aromatic mercaptocarboxylic acids, aromatic dithiols, and aromatic mercaptophenols.

  Specific examples of the aromatic hydroxycarboxylic acid include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-5-naphthoic acid, 2-hydroxy 7-naphthoic acid, 2-hydroxy-3-naphthoic acid, 4'-hydroxyphenyl-4-benzoic acid, 3'-hydroxyphenyl-4-benzoic acid, 4'-hydroxyphenyl-3-benzoic acid and their Examples thereof include alkyl, alkoxy, and halogen-substituted products.

  Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4′-dicarboxybiphenyl, 3 , 4′-dicarboxybiphenyl, 4,4 ″ -dicarboxyterphenyl, bis (4-carboxyphenyl) ether, bis (4-carboxyphenoxy) butane, bis (4-carboxyphenyl) ethane, bis (3- Carboxyphenyl) ether and bis (3-carboxyphenyl) ethane and the like, alkyl, alkoxy or halogen substituted products thereof.

Specific examples of the aromatic diol include, for example, pyrocatechol, hydroquinone, resorcin, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 3,3′-dihydroxybiphenyl, 3,4 ′. -Dihydroxybiphenyl, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenol ether, bis (4-hydroxyphenyl) ethane, 2,2'-dihydroxybinaphthyl, etc., and alkyl, alkoxy or halogen substituted products thereof Is mentioned.
Specific examples of the aromatic hydroxyamine include 4-aminophenol, N-methyl-4-aminophenol, 3-aminophenol, 3-methyl-4-aminophenol, 4-amino-1-naphthol, 4-amino- 4'-hydroxybiphenyl, 4-amino-4'-hydroxybiphenyl ether, 4-amino-4'-hydroxybiphenylmethane, 4-amino-4'-hydroxybiphenyl sulfide and 2,2'-diaminobinaphthyl and their alkyls , Alkoxy or halogen-substituted products.

  Specific examples of the aromatic diamine and aromatic aminocarboxylic acid include 1,4-phenylenediamine, 1,3-phenylenediamine, N-methyl-1,4-phenylenediamine, N, N′-dimethyl-1,4. -Phenylenediamine, 4,4'-diaminophenyl sulfide (thiodianiline), 4,4'-diaminobiphenyl sulfone, 2,5-diaminotoluene, 4,4'-ethylenedianiline, 4,4'-diaminobiphenoxyethane 4,4′-diaminobiphenylmethane (methylenedianiline), 4,4′-diaminobiphenyl ether (oxydianiline), 4-aminobenzoic acid, 3-aminobenzoic acid, 6-amino-2-naphthoic acid and 7-amino-2-naphthoic acid and alkyl, alkoxy or halogen substituted products thereof It is below.

  Specific examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, fumaric acid, maleic acid Etc.

  Specific examples of the aliphatic diamine include 1,2-ethylenediamine, 1,3-trimethylenediamine, 1,4-tetramethylenediamine, 1,6-hexamethylenediamine, 1,8-octanediamine, 1,9- Nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, and the like can be given.

  Specific examples of the alicyclic dicarboxylic acid, aliphatic diol and alicyclic diol include hexahydroterephthalic acid, trans-1,4-cyclohexanediol, cis-1,4-cyclohexanediol, and trans-1,4-cyclohexane. Dimethanol, cis-1,4-cyclohexanedimethanol, trans-1,3-cyclohexanediol, cis-1,2-cyclohexanediol, trans-1,3-cyclohexanedimethanol, ethylene glycol, propylene glycol, butylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, neo Such as pentyl glycol Such Jo or branched chain aliphatic diols, as well as reactive derivatives thereof.

  Specific examples of the aromatic mercaptocarboxylic acid, aromatic dithiol and aromatic mercaptophenol include 4-mercaptobenzoic acid, 2-mercapto-6-naphthoic acid, 2-mercapto-7-naphthoic acid, benzene-1,4- Dithiol, benzene-1,3-dithiol, 2,6-naphthalene-dithiol, 2,7-naphthalene-dithiol, 4-mercaptophenol, 3-mercaptophenol, 6-mercapto-2-hydroxynaphthalene, 7-mercapto-2 -Hydroxynaphthalene and the like, as well as reactive derivatives thereof.

  The liquid crystal polymer composition in the present invention includes an epoxy resin, a polyolefin resin, a bismaleimide resin, a polyimide resin, a polyether resin, a phenol resin, a silicone resin, a polycarbonate resin, and a polyamide resin as long as the effects of the present invention are not lost. Any known resin such as a polyester resin, a fluorine resin, an acrylic resin, a melamine resin, a urea resin, or a urethane resin may be contained. Specific examples of preferred resins include polycarbonate, polyethylene terephthalate, polybutylene terephthalate, liquid crystal polymer, nylon 6, nylon 6,6 and the like. The amount of these resins used is preferably in the range of 0 to 10,000 parts by weight and more preferably in the range of 1 to 800 parts by weight with respect to 100 parts by weight of the liquid crystal polymer usually contained in the liquid crystal polymer molding.

  In the liquid crystal polymer composition of the present invention, as an additive other than the resin and the filler, any other component depending on the purpose, for example, a reinforcing agent, a thickener, a release agent, a coupling agent, a flame retardant Further, flame retardants, pigments, colorants, other auxiliaries, and the like can be added as long as the effects of the present invention are not lost. The amount of these additives used is preferably in the range of 0 to 20 parts by weight and more preferably in the range of 0.1 to 15 parts by weight with respect to 100 parts by weight of the liquid crystal polymer.

  The blending method of the blend for the liquid crystal polymer is not particularly limited. For example, it can be produced by drying the above-described components, additives and the like and then melt-kneading them in a melt-kneader such as a single-screw or twin-screw extruder. Moreover, when a compounding component is a liquid, it can also manufacture by adding to a melt-kneader on the way using a liquid supply pump etc.

  The insulating film of the present invention can be molded by various resin molding methods such as injection molding, extrusion molding, press molding, and blow molding. Among these molding methods, a press molding method is preferable because it is simple. Specifically, it is preferable to heat and press the liquid crystal polymer in the present invention in an isotropic phase state in a press machine. Molding is not possible at the temperature of the crystal phase, and at the temperature of the liquid crystal phase, the molecular chains of the liquid crystal polymer are aligned in the in-plane direction, and the thermal conductivity cannot be improved in the thickness direction of the film. May be inferior. However, if the molecular chain of the liquid crystal polymer is randomly macroscopically aligned even if it is molded at the temperature of the liquid crystal phase, and there is no problem with the surface smoothness of the insulating film and adhesion to the metal, the temperature of the liquid crystal phase It is also possible to mold with. At the time of press molding, it is preferable to heat-press a suitable amount of pellets or powder of the liquid crystal polymer composition on the support substrate. However, a solution composition is prepared by dissolving the liquid crystal polymer composition in a solvent, and on the support substrate. The liquid crystal polymer composition may be supported on the support substrate by removing the solvent after casting. The solvent that can be used in this case is not particularly limited, and any other general-purpose solvent can be used as long as the solvent of phenols, halogenated fatty acids, and halogenated alcohols dissolves the liquid crystal polymer of the present invention well and contains these solvents. It can also be diluted with a solvent. Examples of phenols include phenol, 4-chlorophenol, 2,4-dichlorophenol, 3,4-dichlorophenol, 2,4,5-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6. -Trichlorophenol, pentachlorophenol, pentafluorophenol, 4-chloro-2-fluorophenol, 4-chloro-3-fluorophenol and the like. Examples of the halogenated fatty acids include trifluoroacetic acid and trichloroacetic acid. Examples of halogenated alcohols include hexafluoroisopropanol. The liquid crystal polymer in the solution composition is preferably 0.5 to 100 parts by weight, more preferably 1 to 50 parts by weight, and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the solvent. Further preferred. When the amount is less than 0.5 parts by weight, the solution viscosity is low and may not be uniformly cast on the support substrate. When the amount is 100 parts by weight or more, the liquid crystal polymer does not dissolve, or the solution viscosity is high and the workability deteriorates. Problems may arise. The solution composition is filtered through a filter as necessary, and cast on a support substrate that is usually made of resin, metal, glass, ceramics, etc., preferably flat and uniform, and then the solvent is removed. The method for removing the solvent is not particularly limited, and the solvent can be removed by evaporation of the solvent by heating, decompression, ventilation or the like. After press molding, the insulating film may be rapidly cooled and solidified, or the insulating film may be gradually cooled by gradually lowering the temperature of the press machine, but rapid solidification is preferable from the viewpoint of the molding cycle. Thus, even when a liquid crystal polymer composition containing an isotropic phase upon heating and a liquid crystal polymer composition containing a spherical or granular heat conductive filler is molded in the isotropic phase and rapidly cooled and solidified, the molecular chain of the liquid crystal polymer remains It is a feature of the present invention that it functions three-dimensionally as a heat conduction path between the heat conductive fillers and can significantly improve the heat conductivity in the thickness direction of the insulating film.

  The insulating film of the present invention has high thermal conductivity in the thickness direction. In addition, since the liquid crystal polymer composition constituting the insulating film does not require a large amount of heat conductive filler for the purpose of achieving high thermal conductivity, it has low specific gravity, good molding fluidity, and good metal adhesion. Such insulating films are used in electrical and electronic devices such as light-emitting diodes (LEDs), generators, motors, transformers, current transformers, voltage regulators, rectifiers, inverters, and chargers, especially for metal substrates and wiring. It can be suitably used for the purpose of ensuring insulation between the conductive foil for pattern formation. Further, the electronic circuit board configured as described above has high heat dissipation performance, and can contribute to further miniaturization and higher performance of the electric / electronic device.

  Next, the insulating film of the present invention will be described in more detail with reference to production examples, examples, and comparative examples, but the present invention is not limited to such examples. Unless otherwise specified, the reagents listed below were used without purification from Wako Pure Chemical Industries.

  The raw material components used for preparing the resin composition are shown below.

[Other resins]
-Polybutylene terephthalate (PBT):
NOVADURAN 5008L manufactured by Mitsubishi Engineering Plastics Co., Ltd.
-Nematic liquid crystal polymer (UENOLCP):
UENOLCP A-8100 manufactured by Ueno Pharmaceutical Co., Ltd.

[Spherical or granular thermally conductive filler (B1)]
Magnesium oxide (MgO):
RF-98 (MgO-1, no surface treatment, water absorption 0.5% or less, average particle size 50 μm) and RF-50-SC (MgO-2, no surface treatment, water absorption 0.3) manufactured by Ube Material Co., Ltd. %, Average particle size 50 μm)
Aluminum nitride (AlN):
Toyorunite FLA manufactured by Toyo Aluminum Co., Ltd., average particle size 12μm,

[Plate-like thermally conductive filler (B2)]
Boron nitride powder (BN):
PT110 (BN-1, average particle size 45 μm) manufactured by Momentive Performance Materials
·talc:
MS-KY manufactured by Nippon Talc Co., Ltd., average particle size 23 μm

[Reinforcement material]
・ Glass fiber (GF):
T187H / PL manufactured by Nippon Electric Glass Co., Ltd., fiber diameter 13 μm, number average fiber length 3.0 mm

[Flame Retardant (C)]
A mixture of brominated flame retardant and sodium antimonate, BT-Sb:
BT-93 / W: Sb = 23: 6 (weight ratio)
・ EM-Sb:
Emerald 1000: Sb = 17: 8 (weight ratio)
Brominated flame retardant:
-SAYTEX BT-93 / W (BT) manufactured by Albemarle Japan
Emerald1000 (EM) manufactured by Chemtura
・ Sodium antimonate (Sb):
SA-A manufactured by Nippon Seiko Co., Ltd.

[Evaluation method]
Number average molecular weight: A sample was prepared by dissolving the liquid crystal polymer used in the present invention in a mixed solvent of p-chlorophenol (manufactured by Tokyo Chemical Industry Co., Ltd.) and toluene in a volume ratio of 3: 8 to a concentration of 0.25% by weight. The standard material was polystyrene, and a similar sample solution was prepared. The measurement was performed using a high temperature GPC (350 HT-GPC System manufactured by Viscotek) under conditions of a column temperature of 80 ° C. and a flow rate of 1.00 mL / min. A differential refractometer (RI) was used as a detector.

Differential scanning calorimetry (DSC measurement): The temperature is raised and lowered at a rate of 10 ° C./min in the range of 50 ° C. to 320 ° C., and from the peak top of the endothermic peak at the second temperature rise of 10 ° C./min, the crystal phase The transition point (T _m ) from the liquid crystal phase to the liquid crystal phase and the transition point (T _i ) from the liquid crystal phase to the isotropic phase were determined.
Observation with an optical polarization microscope: The liquid crystal polymer (A) was heated to _Ti or higher on a hot stage, and the temperature was lowered to a temperature showing liquid crystal at 10 ° C./min, and the optical structure of the liquid crystal was observed.

Test piece molding conditions: After the obtained pellet-like liquid crystal polymer composition was dried at 120 ° C. for 4 hours using a hot air dryer, the liquid crystal polymer composition was sandwiched between two pieces of aluminum foil having a thickness of 10 μm, The sheet was pressed with a press molding machine for 2 minutes at each molding temperature to prepare a sheet composed of three layers of aluminum foil and an insulating film.
Specific gravity: measured by Archimedes method.
Specific heat: measured by DSC method.

Thermal conductivity: A sample of 10 mm in length and 10 mm in width was cut out from the above-mentioned sheet, and the thermal diffusivity in the thickness direction of the sample in the air at room temperature was measured with a laser flash method thermal diffusivity measuring device (LFA447 manufactured by NETZSCH). The thermal conductivity was calculated by the following formula from the specific gravity, specific heat, and thermal diffusivity obtained by the above method.
Thermal conductivity = thermal diffusivity × specific heat × specific gravity dielectric breakdown strength: Measured according to ASTM D149 using a test piece (2 × 100 × 100 mm).
Flame retardancy: evaluated according to UL94 standard.

[Production Example 1]
In a closed reactor equipped with a reflux condenser, a thermometer, a nitrogen introduction tube, and a stirring rod, 4,4′-dihydroxybiphenyl, dodecanedioic acid, and acetic anhydride were each in a molar ratio of 1.0: 1.0: 2. .1 was charged, and sodium acetate was used as a catalyst to react at 145 ° C. under normal pressure and nitrogen atmosphere to obtain a uniform solution, and then the temperature was raised to 250 ° C. at 2 ° C./min while acetic acid was distilled off. And stirred at 250 ° C. for 1 hour. Subsequently, while maintaining the temperature, the pressure was reduced to 10 Torr over about 40 minutes, and then the reduced pressure state was maintained. Three hours after the start of pressure reduction, the pressure was returned to normal pressure with nitrogen gas, and the produced polymer was taken out. The number average molecular weight of the obtained liquid crystal polymer was 24000, T _m was 205 ° C., T _i was 255 ° C., the end was blocked with an acetyl group, and the end blocking rate was 50%. From the observation with a polarizing microscope, a batnet structure was observed in a liquid crystal state, and it was confirmed that the liquid crystal was a smectic liquid crystal. The obtained liquid crystal polymer is defined as (A-1), and the molecular structure is shown in Table 1.

[Production Example 2]
In a closed reactor equipped with a reflux condenser, a thermometer, a nitrogen introduction tube and a stirring rod, 4,4′-dihydroxybiphenyl, tetradecanedioic acid, and acetic anhydride were each in a molar ratio of 1.0: 1.02: 2. .1 was charged, sodium acetate was used as a catalyst, and the reaction was carried out at 145 ° C. under normal pressure and nitrogen atmosphere to obtain a uniform solution, and then the temperature was raised to 260 ° C. at 2 ° C./min while distilling off acetic acid. And stirred at 260 ° C. for 1 hour. Subsequently, while maintaining the temperature, the pressure was reduced to 10 Torr over about 40 minutes, and then the reduced pressure state was maintained. Three hours after the start of pressure reduction, the pressure was returned to normal pressure with nitrogen gas, and the produced polymer was taken out. The number average molecular weight of the obtained liquid crystal polymer 32000, _{T m} is 190 ° C., _{T i} is 240 ° C., end is carboxylic acid, terminal blocking ratio was 0%. From the observation with a polarizing microscope, a batnet structure was observed in a liquid crystal state, and it was confirmed that the liquid crystal was a smectic liquid crystal. The obtained liquid crystal polymer is defined as (A-2), and the molecular structure is shown in Table 1.

[Production Example 3]
In a closed reactor equipped with a reflux condenser, a thermometer, a nitrogen introduction tube and a stirring rod, 4,4′-dihydroxybiphenyl, sebacic acid, catechol, stearic acid, and acetic anhydride were each in a molar ratio of 1: 1.01. : 0.05: 0.08: 2.2 was charged, sodium acetate was used as a catalyst, and the reaction was carried out at 145 ° C. under normal pressure and nitrogen atmosphere to obtain a uniform solution, and then acetic acid was distilled off. The temperature was raised to 240 ° C. at 2 ° C./min and stirred at 240 ° C. for 30 minutes. Furthermore, it heated up to 260 degreeC at 1 degreeC / min, and stirred at 260 degreeC for 1 hour. Subsequently, while maintaining the temperature, the pressure was reduced to 10 Torr over about 40 minutes, and then the reduced pressure state was maintained. Three hours after the start of pressure reduction, the pressure was returned to normal pressure with nitrogen gas, and the produced polymer was taken out. The number average molecular weight of the obtained liquid crystal polymer was 15000, T _m was 210 ° C., T _i was 275 ° C., the end was capped with a stearyl group, and the end capping rate was 99%. From the observation with a polarizing microscope, a batnet structure was observed in a liquid crystal state, and it was confirmed that the liquid crystal was a smectic liquid crystal. The obtained liquid crystal polymer is (A-3), and the molecular structure is shown in Table 1.

[Examples 1-5 and Comparative Examples 1-2]
After the liquid crystal polymer (A) shown in Table 1 and other resin materials are dried at 120 ° C. for 4 hours using a hot air dryer, the resin component and various blends in the amounts shown in Table 1 are mixed into the liquid crystal polymer (A). The temperature at which the liquid crystal state is obtained, in Comparative Example 1, it is extruded into a strand using a 15 mm co-rotating fully meshed twin screw extruder KZW15-45MG (manufactured by Technobell Co., Ltd.) at 260 ° C., and cut into pellets by a pelletizer. A liquid crystal polymer composition was obtained. Using the obtained liquid crystal polymer composition, the various test pieces were prepared and evaluated for various physical properties. The thickness of the insulating film was 100 μm. The results are shown in Table 2 and Table 3.

  As is clear from Tables 1 and 2, the evaluation samples using the insulating films of Examples 1 to 5 have high thermal conductivity in the thickness direction. On the other hand, the evaluation sample of Comparative Example 1 is derived from the fact that the base resin of the insulating film is a resin that does not exhibit liquid crystallinity, so that the thermal conductivity of the base resin is low, and the thermal conductivity in the thickness direction is 1.2 W / (M · K), which is about ¼ of that of Example 1 having substantially the same composition. Therefore, in order to increase the thermal conductivity to the same level as in Example 1, it is necessary to add a further thermally conductive filler. The evaluation sample of Comparative Example 2 is a resin in which the base polymer of the insulating film exhibits nematic liquid crystallinity but decomposes before exhibiting an isotropic phase even at higher temperatures, and therefore needs to be molded in a nematic liquid crystal state. . Therefore, the molecular chain of the polymer tends to be oriented in the in-plane direction at the time of press molding, and the thermal conductivity in the thickness direction of the evaluation sample becomes low. In Example 5, the molding temperature of Example 1 was changed from the isotropic phase to the liquid crystal phase. However, since the thermal conductivity is higher than that of Comparative Examples 1 and 2, the liquid crystal polymer exhibits smectic liquid crystallinity. In consideration of productivity and the like, there is no problem even if the insulating film of the present invention is manufactured in a smectic liquid crystal phase. On the other hand, since the thermal conductivity is lower than that in Example 1, it is preferable to mold in an isotropic phase from the viewpoint of thermal conductivity.

  The insulating film of the present invention has high thermal conductivity in the thickness direction and is excellent in molding processability and dielectric breakdown strength. Therefore, heat generated in electrical and electronic equipment is efficiently transferred to electrically conductive heat radiating members such as metal support boards and heat sinks, and insulation between heat generating elements or between heat generating elements and heat radiating members is ensured. It can be suitably used as an insulating film for the purpose. Among them, it can be suitably used for the purpose of ensuring insulation between the metal substrate and the conductive foil for forming the wiring pattern. This makes it possible to achieve high performance while maintaining the size or size of the electric / electronic device, and thus the industrial advantage is very large.

Claims (13)

To the liquid crystal polymer (A) 100 parts by weight of illustrating the isotropic phase when heated, Ri Do a liquid crystal polymer composition spherical or granular thermally conductive filler (B1) containing 50 to 1200 parts by weight, the liquid crystal polymer ( a) has a crystal lamellar structure, and you are randomly oriented macroscopically, thickness 500μm below the insulating film. The insulating film according to claim 1, wherein the liquid crystal polymer (A) exhibits a smectic liquid crystal phase when heated. The insulating film according to claim 1 or 2, wherein the liquid crystal polymer composition further contains 5 to 100 parts by weight of a flame retardant (C). The liquid crystal polymer composition further contains 20 to 200 parts by weight of a plate-like thermally conductive filler (B2), and the content ratio with the spherical or granular thermally conductive filler (B1) is (B1) by volume. / (B2) = 5 / 95-70 / 30. The insulating film according to claim 1. The insulating film according to any one of claims 1 to 4, wherein the spherical or granular thermally conductive filler (B1) is alumina, magnesium oxide or aluminum nitride having a water absorption of 0.5% or less. The insulating film according to claim 4 or 5, wherein the plate-like thermally conductive filler (B2) is at least one selected from talc and hexagonal boron nitride. The insulating film according to claim 1, wherein the structure of the main chain of the liquid crystal polymer is mainly composed of repeating units of the unit represented by the general formula (1).
-M-Sp-. . . (1)
(In the formula, M represents a mesogenic group, and Sp represents a spacer.) The insulating film according to claim 7, wherein the liquid crystal polymer is mainly composed of repeating units represented by the following general formula (2).
_{^{-A 1 -x-A 2 -OCO (}} CH 2) m COO-. . . (2)
(In the formula, A ¹ and A ² each independently represent a substituent selected from an aromatic group, a condensed aromatic group, an alicyclic group, and an alicyclic heterocyclic group. X each independently. Direct bond, —O—, —S—, —CH ₂ —CH ₂ —, —C═C—, —C═C (Me) —, —C≡C—, —CO—O—, —CO—NH A divalent substituent selected from the group of-, -CH = N-, -CH = N-N = CH-, -N = N- and -N (O) = N-, where m is 2 to 20. Indicates an integer.) The insulating film according to claim 8, wherein -A ¹ -xA ² -of the liquid crystal polymer is represented by the following general formula (3).

(In the formula, each R is independently an aliphatic hydrocarbon group, F, Cl, Br, I, CN, or NO ₂ , y is an integer of 2 to 4, and n is an integer of 0 to 4.) The insulating film according to claim 8 or 9, wherein m of the liquid crystal polymer is at least one selected from an even number of 4 to 14. The insulating film according to claim 1, wherein the liquid crystal polymer has a number average molecular weight of 3000 to 100,000. The method for producing an insulating film according to claim 1, wherein the liquid crystal polymer composition is heated and pressed to a temperature at which the liquid crystal polymer becomes isotropic on a support substrate. An electronic circuit board having a metal substrate, an insulating film provided on the metal substrate, and a conductive foil for forming a wiring pattern provided on the insulating film, wherein the insulating film comprises: 11. An electronic circuit board, which is the insulating film according to any one of 11 above.