JP6098817B2 - Resin impregnated sheet - Google Patents

Description

  The present invention relates to a resin-impregnated sheet obtained by impregnating a fiber sheet with a composition containing liquid crystal polyester and an inorganic filler.

  As an insulating layer of a printed wiring board, a resin-impregnated sheet obtained by impregnating a fiber sheet with a resin has been studied. In this case, a liquid crystal polyester is preferably used because the resin has high heat resistance and low dielectric loss. It has been. In addition, in order to impart desired performance, it has been studied to impregnate a fiber sheet with an inorganic filler together with a liquid crystal polyester. For example, Patent Document 1 discloses silica, aluminum hydroxide as an inorganic filler. The use of calcium carbonate or the like is described. Patent Document 2 describes that silica, alumina, titanium oxide, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, or the like is used as the inorganic filler.

JP 2004-244621 A JP 2007-146139 A

  The conventional resin-impregnated sheet does not necessarily have sufficient thermal conductivity. Moreover, when a metal layer is formed on the surface to obtain a metal-clad laminate, the adhesion between the resin-impregnated sheet and the metal layer is not always sufficient. Then, the objective of this invention is providing the resin impregnation sheet | seat which is excellent in heat conductivity and excellent in adhesiveness with a metal layer.

  In order to achieve the above object, the present invention comprises a fiber sheet impregnated with a composition containing a liquid crystal polyester and an inorganic filler, and the proportion of the liquid crystal polyester in the composition is 10 to 50% by volume, The proportion of the inorganic filler in the composition is 50 to 90% by volume, the inorganic filler is an inorganic filler (1) having a volume average particle size of 0.1 μm or more and less than 3 μm, and a volume average particle size of 3 μm or more and 10 μm. Including the following inorganic filler (2), the proportion of the inorganic filler (1) in the composition is 20 to 70% by volume, and the proportion of the inorganic filler (2) in the composition is A resin-impregnated sheet of 5 to 40% by volume is provided.

  Moreover, as a suitable manufacturing method of the resin-impregnated sheet, the present invention includes a support and a layer of the composition (2) containing the liquid crystalline polyester, the inorganic filler, and a solvent on both sides of the fiber sheet, respectively. The laminate (1) having the resin-impregnated sheet precursor formed by placing the layer (1) in contact with the fiber sheet, heating and pressing, and impregnating the fiber sheet with the composition (2); A step (1) of obtaining a laminate (2) having a support, a step (2) of separating the resin-impregnated sheet precursor from the laminate (2), and the solvent from the resin-impregnated sheet precursor. There is provided a method for producing the resin-impregnated sheet, comprising removing (3) a resin-impregnated sheet.

  Furthermore, the present invention provides a metal-clad laminate in which a metal layer is formed on at least one surface of the resin-impregnated sheet or the laminate sheet.

  The present invention also provides a method for producing a metal-clad laminate in which a resin-impregnated sheet is obtained by the production method and a metal layer is formed on at least one surface of the resin-impregnated sheet or the laminate sheet.

  The resin-impregnated sheet of the present invention is excellent in thermal conductivity and adhesiveness with the metal layer.

  The resin-impregnated sheet of the present invention is a resin-impregnated sheet obtained by impregnating a fiber sheet with a composition containing liquid crystal polyester and an inorganic filler.

  The fiber sheet is a sheet composed of fibers, and may be a woven fabric (woven fabric), a knitted fabric, or a non-woven fabric. Since it is easy to improve property, it is preferable that it is a textile fabric.

  The fibers constituting the fiber sheet include glass fibers, alumina fibers, carbon fibers, silicon-containing ceramic fibers and other ceramic fibers; and liquid crystal polyester fibers and other polyester fibers, aramid fibers and polybenzazole fibers. An organic fiber is mentioned, You may use those 2 or more types. Among these, glass fiber is preferable, and the fiber sheet is preferably glass cloth which is a woven fabric of glass fiber.

  As glass fiber which comprises a glass fiber sheet, an alkali-containing glass fiber, an alkali free glass fiber, and a low dielectric glass fiber are preferable. Moreover, as a fiber which comprises a glass fiber sheet, fibers other than glass fiber, for example, ceramic fiber and carbon fiber, may be contained in a part thereof. Moreover, the fiber which comprises a glass fiber sheet may be surface-treated with coupling agents, such as an aminosilane coupling agent, an epoxysilane coupling agent, and a titanate coupling agent.

  As a method for producing a fiber sheet, for example, a method of obtaining a nonwoven fabric by dispersing fibers in water, adding an adhesive such as an acrylic resin as necessary, making a paper machine, and drying it, or weaving There is a method of obtaining a woven fabric using an adult machine. Examples of fiber weaving methods include plain weave, satin weave, twill weave and nanako weave.

The mass per unit area of the fiber sheet is preferably 40 g / m ² or less, more preferably 35 g / m ² or less, because the thermal conductivity of the resin-impregnated sheet is easily improved. Since it is difficult, it is preferably 15 g / m ² or more, more preferably 20 g / m ² or more.

  The thickness of the fiber sheet is preferably 40 μm or less, more preferably 35 μm or less because the thermal conductivity of the resin-impregnated sheet is likely to be improved, and preferably 15 μm or more, because the resin-impregnated sheet is difficult to thermally expand. More preferably, it is 20 μm or more.

  The weaving density of the fiber sheet is preferably 60/25 mm or more, more preferably 65/25 mm or more because the thermal conductivity of the resin-impregnated sheet is likely to improve, and the resin-impregnated sheet is difficult to thermally expand. The number is preferably 80/25 mm or less, and more preferably 75/25 mm or less.

  Commercially available fiber sheets are available from Unitika Ltd., Asahi Kasei E-Materials Corp., Nittobo Co., Ltd., and Arisawa Manufacturing Co., Ltd.

  The liquid crystal polyester contained in the composition is a polyester that exhibits liquid crystallinity in a molten state, and is preferably melted at a temperature of 450 ° C. or lower. The liquid crystal polyester may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide. The liquid crystal polyester is preferably a wholly aromatic liquid crystal polyester using only an aromatic compound as a raw material monomer.

  A typical example of the liquid crystal polyester is polymerization (polycondensation) of an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, and at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. At least one compound selected from the group consisting of aromatic dicarboxylic acids and aromatic diols, aromatic hydroxyamines and aromatic diamines, And those obtained by polymerizing a polyester such as polyethylene terephthalate and an aromatic hydroxycarboxylic acid. Here, the aromatic hydroxycarboxylic acid, the aromatic dicarboxylic acid, the aromatic diol, the aromatic hydroxyamine, and the aromatic diamine are each independently replaced with a part or all of the polymerizable derivative. Also good.

  Examples of polymerizable derivatives of a compound having a carboxyl group such as aromatic hydroxycarboxylic acid and aromatic dicarboxylic acid include those obtained by converting a carboxyl group into an alkoxycarbonyl group or an aryloxycarbonyl group (ester), carboxyl Examples include those obtained by converting a group into a haloformyl group (acid halide), and those obtained by converting a carboxyl group into an acyloxycarbonyl group (acid anhydride). Examples of polymerizable derivatives of hydroxyl group-containing compounds such as aromatic hydroxycarboxylic acids, aromatic diols and aromatic hydroxyamines include those obtained by acylating hydroxyl groups and converting them to acyloxyl groups (acylated products) ). Examples of polymerizable derivatives of amino group-containing compounds such as aromatic hydroxyamines and aromatic diamines include those obtained by acylating an amino group and converting it to an acylamino group (acylated product).

  The liquid crystalline polyester preferably has a repeating unit represented by the following formula (1) (hereinafter sometimes referred to as “repeating unit (1)”), and the repeating unit (1) and the following formula (2) A repeating unit represented (hereinafter sometimes referred to as “repeating unit (2)”) and a repeating unit represented by the following formula (3) (hereinafter sometimes referred to as “repeating unit (3)”). It is more preferable to have.

(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
⁽³⁾ -X-Ar 3 -Y-

(Ar ¹ represents a phenylene group, a naphthylene group, or a biphenylylene group. Ar ² and Ar ³ each independently represent a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4). X And Y each independently represents an oxygen atom or an imino group (—NH—), and each hydrogen atom in the group represented by Ar ¹ , Ar ² or Ar ³ independently represents a halogen atom or an alkyl group. Alternatively, it may be substituted with an aryl group.)

(4) -Ar ⁴ -Z-Ar ^5-

(Ar ⁴ and Ar ⁵ each independently represent a phenylene group or a naphthylene group. Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.)

As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group, An n-octyl group and n-decyl group are mentioned, The carbon number is 1-10 normally. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms is usually 6 to 20. . When the hydrogen atom is substituted with these groups, the number is usually 2 or less for each group represented by Ar ¹ , Ar ² or Ar ³ , and preferably 1 It is as follows.

  Examples of the alkylidene group include a methylene group, an ethylidene group, an isopropylidene group, an n-butylidene group, and a 2-ethylhexylidene group, and the number of carbon atoms is usually 1 to 10.

The repeating unit (1) is a repeating unit derived from a predetermined aromatic hydroxycarboxylic acid. As the repeating unit (1), Ar ¹ is a p-phenylene group (a repeating unit derived from p-hydroxybenzoic acid), and Ar ¹ is a 2,6-naphthylene group (6-hydroxy-2). -Repeating units derived from naphthoic acid) are preferred.

The repeating unit (2) is a repeating unit derived from a predetermined aromatic dicarboxylic acid. As the repeating unit (2), Ar ² is a p-phenylene group (repeating unit derived from terephthalic acid), Ar ² is an m-phenylene group (repeating unit derived from isophthalic acid), Ar ² Is a 2,6-naphthylene group (repeating unit derived from 2,6-naphthalenedicarboxylic acid), and Ar ² is a diphenyl ether-4,4′-diyl group (diphenyl ether- 4,4′-dicarboxylic acid-derived repeating units) are preferred.

The repeating unit (3) is a repeating unit derived from a predetermined aromatic diol, aromatic hydroxylamine or aromatic diamine. As the repeating unit (3), Ar ³ is a p-phenylene group (repeating unit derived from hydroquinone, p-aminophenol or p-phenylenediamine), and Ar ³ is a 4,4′-biphenylylene group. Those (4,4′-dihydroxybiphenyl, 4-amino-4′-hydroxybiphenyl or repeating units derived from 4,4′-diaminobiphenyl) are preferred.

  The content of the repeating unit (1) is the total amount of all repeating units (the mass equivalent amount of each repeating unit (moles by dividing the mass of each repeating unit constituting the liquid crystal polyester by the formula amount of each repeating unit). ) And the total value thereof) is usually 30 mol% or more, preferably 30 to 80 mol%, more preferably 30 to 60 mol%, still more preferably 30 to 40 mol%. The content of the repeating unit (2) is usually 35 mol% or less, preferably 10 to 35 mol%, more preferably 20 to 35 mol%, still more preferably 30 to 35 mol, based on the total amount of all repeating units. %. The content of the repeating unit (3) is usually 35 mol% or less, preferably 10 to 35 mol%, more preferably 20 to 35 mol%, still more preferably 30 to 35 mol, based on the total amount of all repeating units. %. As the content of the repeating unit (1) is increased, the heat resistance, strength and rigidity are likely to be improved. However, if the content is too large, the solubility in a solvent is likely to be lowered.

  The ratio between the content of the repeating unit (2) and the content of the repeating unit (3) is expressed as [content of repeating unit (2)] / [content of repeating unit (3)] (mol / mol). The ratio is usually 0.9 / 1 to 1 / 0.9, preferably 0.95 / 1 to 1 / 0.95, and more preferably 0.98 / 1 to 1 / 0.98.

  In addition, liquid crystalline polyester may have 2 or more types of repeating units (1)-(3) each independently. Further, the liquid crystalline polyester may have a repeating unit other than the repeating units (1) to (3), but the content thereof is usually 10 mol% or less with respect to the total amount of all repeating units, preferably 5 mol% or less.

  The liquid crystalline polyester has a repeating unit (3) in which X and / or Y is an imino group, that is, a repeating unit derived from a predetermined aromatic hydroxylamine and / or a repeating unit derived from an aromatic diamine. It is preferable that it has a solubility in a solvent, and it is more preferable that the repeating unit (3) has only those in which X and / or Y is an imino group.

  The liquid crystal polyester is preferably produced by melt polymerization of raw material monomers corresponding to the repeating units constituting the liquid crystal polyester, and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, high molecular weight liquid crystal polyester having high heat resistance, strength and rigidity can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  The liquid polyester has a flow initiation temperature of usually 250 ° C. or higher, preferably 250 ° C. to 350 ° C., more preferably 260 ° C. to 330 ° C. As the flow start temperature is higher, the heat resistance, strength, and rigidity are more likely to be improved. However, if the flow start temperature is too high, the solubility in a solvent tends to be low, and the viscosity of the liquid composition tends to be high.

The flow start temperature is also called flow temperature or flow temperature, and the temperature is raised at a rate of 4 ° C./min under a load of 9.8 MPa (100 kg / cm ² ) using a capillary rheometer while the liquid crystalline polyester is used. Is a temperature showing a viscosity of 4800 Pa · s (48000 poise) when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm, and is a measure of the molecular weight of the liquid crystalline polyester (Naide Koide, “ “Liquid Crystal Polymer—Synthesis / Molding / Application—”, CMC Co., Ltd., June 5, 1987, p. 95).

  Examples of the inorganic filler contained in the composition include magnesium oxide, silicon oxide (silica), aluminum oxide (alumina), oxides such as titanium oxide and zinc oxide, nitrides such as boron nitride and aluminum nitride, hydroxylation Examples thereof include hydroxides such as aluminum, barium titanate, strontium titanate, and oxoacid salts such as calcium carbonate, and two or more of these may be used. Of these, oxides and nitrides are preferable. As the inorganic filler, an inorganic filler having a thermal conductivity of 30 W / mK or more is preferable.

  The proportion of the liquid crystal polyester in the composition is 10 to 50% by volume, preferably 30 to 50% by volume, and the proportion of the inorganic filler in the composition is 50 to 90% by volume, preferably 50 to 70% by volume. It is. The higher the proportion of the liquid crystalline polyester in the composition and the lower the proportion of the inorganic filler, the better the adhesion between the resin-impregnated substrate and the metal foil, and the lower the proportion of the liquid crystalline polyester in the composition. The higher the ratio, the better the thermal conductivity of the resin-impregnated substrate.

  As the inorganic filler, from the viewpoint of adhesion between the resin-impregnated sheet and the metal layer, an inorganic filler (1) having a volume average particle diameter of 0.1 μm or more and less than 3 μm is used, and from the viewpoint of thermal conductivity of the resin-impregnated sheet. The inorganic filler (2) having a volume average particle size of 3 μm or more and 10 μm or less is used in combination. The volume average particle diameter of the inorganic filler (1) is preferably 0.5 to 2 μm, and the volume average particle diameter of the inorganic filler (2) is preferably 3 to 8 μm.

  The proportion of the inorganic filler (1) in the composition is 20 to 70% by volume, preferably 30 to 60% by volume, and the proportion of the inorganic filler (2) in the composition is 5 to 40% by volume, Preferably it is 10-30 volume%.

  The inorganic filler (1) is preferably an oxide, and the inorganic filler (2) is preferably a nitride.

  The composition may contain components other than the liquid crystal polyester and the inorganic filler, for example, a resin other than the liquid crystal polyester, an organic filler, and an additive. And usually 0 to 10% by volume. Examples of resins other than liquid crystal polyester include polypropylene, polyamide, polyester other than liquid crystal polyester, thermoplastic resin other than liquid crystal polyester such as polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether, polyether imide; and Thermosetting resins, such as a phenol resin, an epoxy resin, a polyimide resin, and cyanate resin, are mentioned. Examples of organic fillers include cured epoxy resins, crosslinked benzoguanamine resins, and crosslinked acrylic resins. Examples of additives include leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

  The resin-impregnated sheet of the present invention comprises a laminate (1) having a support and a layer of a composition (2) containing a liquid crystal polyester, an inorganic filler and a solvent on both sides of a fiber sheet, respectively. The laminate (2) having a resin-impregnated sheet precursor and a support obtained by impregnating the fiber sheet with the composition (2) is disposed so that the layer is in contact with the fiber sheet, and heated and pressurized. Step (1) for obtaining, Step (2) for separating the resin-impregnated sheet precursor from the laminate (2), Step (3) for obtaining a resin-impregnated sheet by removing the solvent from the resin-impregnated sheet precursor It is suitably obtained by the manufacturing method it has.

  The laminate (1) has a support and a layer of a composition (2) containing a liquid crystal polyester, an inorganic filler and a solvent.

  As a support body, a glass plate, a resin film, and metal foil are mentioned, for example. Among these, a resin film is preferably used because it is easy to heat and pressurize when producing the laminate (2) and can be easily removed from the laminate (2) by peeling. Examples of the resin film include a polyester film, a polypropylene film, a fluororesin film, a nylon film, and a polymethylpentene film, and two or more of them may be laminated and used. The resin film may be a surface treated with a silicone resin or the like.

  As a solvent contained in the composition (2), a liquid crystal polyester to be used can be dissolved, specifically, soluble at a concentration of 1% by mass or more ([resin] / [resin + solvent]) at 50 ° C. Those are appropriately selected and used.

  Examples of solvents include halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, o-dichlorobenzene; p-chlorophenol, pentachlorophenol, pentafluorophenol Halogenated phenols such as diethyl ether, tetrahydrofuran, 1,4-dioxane, etc .; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; carbonates such as ethylene carbonate and propylene carbonate; amines such as triethylamine Nitrogen-containing heteroaromatic compounds such as pyridine; nitriles such as acetonitrile and succinonitrile; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; Urea compounds such as tramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphoric acid amide and tri-n-butylphosphoric acid. It may be used.

  As the solvent, since it is low in corrosivity and easy to handle, an aprotic compound, particularly a solvent mainly comprising an aprotic compound having no halogen atom, is preferred, and the proportion of the aprotic compound in the entire solvent is: Preferably it is 50-100 mass%, More preferably, it is 70-100 mass%, More preferably, it is 90-100 mass%. As the aprotic compound, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone are preferably used because the liquid crystalline polyester is easily dissolved.

  Moreover, as a solvent, since it is easy to melt | dissolve liquid crystalline polyester, the solvent which has a compound whose dipole moment is 3-5 as a main component is preferable, and the ratio of the compound whose dipole moment which occupies for the whole solvent is 3-5 Is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 90 to 100% by mass, and a compound having a dipole moment of 3 to 5 is used as the aprotic compound. Is preferred.

  Moreover, as a solvent, since it is easy to remove, the solvent which has as a main component the compound whose boiling point in 1 atmosphere is 220 degrees C or less is preferable, and the ratio of the compound whose boiling point in 1 atmosphere in the whole solvent is 220 degrees C or less Is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 90 to 100% by mass, and a compound having a boiling point of 220 ° C. or less at 1 atm is used as the aprotic compound. It is preferable.

  Content of the solvent in a composition (2) is 5-20 mass% normally with respect to the whole composition (2), Preferably it is 8-14 mass%. When the content of the solvent in the composition (2) is too small, the fiber sheet is not easily impregnated with the composition (2), and high temperature and high pressure are required. When the content is too large, the fiber sheet is impregnated with the composition (2). At this time, the solvent in the composition (2) easily evaporates, and the resin-impregnated sheet precursor easily swells due to the vapor.

  The laminate (1) is a liquid composition comprising a liquid crystal polyester, an inorganic filler, a solvent and other components used as necessary on a support, and a coating film (applied on the support if necessary). By partially removing the solvent from the prepared liquid composition).

  Content of the liquid crystal polyester in a liquid composition is 5-60 mass% normally with respect to the total amount of liquid crystal polyester and a solvent, Preferably it is 10-50 mass%, More preferably, it is 15-45 mass%, desired It adjusts suitably so that the liquid composition of this viscosity may be obtained.

  The liquid composition can be prepared by mixing the liquid crystal polyester, the inorganic filler, the solvent, and other components used as necessary, all at once or in an appropriate order. The liquid composition is preferably prepared by dissolving liquid crystal polyester in a solvent to obtain a liquid crystal polyester solution and dispersing a filler in the liquid crystal polyester solution.

  Examples of the coating method of the liquid composition on the support include a roll coating method, a bar coating method, a screen printing method, a die coating method, and a comma coating method. You may go on.

  In this way, a coating film is formed on the support, and the solvent is partially removed from the coating as necessary to have a support and a layer of the composition (2) containing the liquid crystalline polyester, the inorganic filler and the solvent. A laminate (1) can be obtained.

  The removal of the solvent is preferably carried out by evaporating the solvent. Examples of the method include heating, decompression and ventilation, and these may be combined. Moreover, the removal of a solvent may be performed by a continuous type and may be performed by a single plate type. The removal temperature of the solvent is usually 40 to 200 ° C., and is appropriately adjusted so that the solvent content in the composition (2) is preferably 8 to 14% by mass in an appropriate time. The removal of the solvent may be performed in multiple stages. For example, after the first stage is performed at 50 to 150 ° C., preferably 80 to 120 ° C., the second stage is performed at 80 to 180 ° C., preferably 100 to 150 ° C. You may go.

  The laminate (1) thus obtained is arranged on both sides of the fiber sheet so that the layers of the composition (2) containing the liquid crystal polyester, the inorganic filler and the solvent are in contact with the fiber sheet, that is, the fiber sheet. Is sandwiched between the layers of the pair of laminates (1), and heated and pressurized to laminate the resin-impregnated sheet precursor in which the composition (2) is impregnated into the fiber sheet, and the both sides thereof. A laminate (2) having a support is obtained (step (1)).

  The heating temperature in the step (1) is preferably 100 to 180 ° C, more preferably 130 to 160 ° C. When the heating temperature is too low, the fiber sheet is not easily impregnated with the composition (2). When the heating temperature is too high, the solvent in the composition (2) is easily evaporated when the fiber sheet is impregnated with the composition (2). The resin-impregnated sheet precursor easily swells due to the vapor. Moreover, the pressurization pressure in a process (1) becomes like this. Preferably it is 0.1-1 MPa, More preferably, it is 0.3-0.7 MPa. The step (1) is preferably performed by using a roll laminator and passing the sheet between the pair of laminates (1) between a pair of heat rolls and heating and pressing.

  The resin-impregnated sheet precursor is separated from the laminate (2) thus obtained (step (2)). This separation is preferably performed by peeling the support from the laminate (2). When the support is a resin film, the separation is easy. When the support body which a laminated body (2) has is metal foil, you may remove metal foil from a laminated body (2) by an etching.

  Next, by removing the solvent from the resin-impregnated sheet precursor, a resin-impregnated sheet obtained by impregnating the fiber sheet with a composition containing liquid crystal polyester and an inorganic filler is obtained (step (3)). The removal of the solvent is preferably performed by evaporating the solvent by heating. By heating, the resin can have a high molecular weight, and the heat resistance can be further improved. The heating temperature is preferably 250 to 330 ° C, more preferably 270 to 320 ° C, and the heating time is preferably 1 to 30 hours, more preferably 1 to 10 hours. Heating is preferably performed under an atmosphere of an inert gas such as nitrogen gas.

  Since the resin-impregnated sheet thus obtained has few voids and is excellent in solder heat resistance, a plurality of the resin-impregnated sheets are laminated as necessary to form a laminated sheet, and by forming a metal layer on at least one surface thereof, A metal-clad laminate having an insulating layer with few voids and excellent solder heat resistance can be obtained. When a plurality of resin-impregnated sheets are stacked to form a laminated sheet, the plurality of resin-impregnated sheets may all be the same, or may be partially the same or all different. . The laminated sheet may be a sheet in which a plurality of resin-impregnated sheets are fused to each other by a hot press or the like.

  Examples of the material for the metal layer include copper, aluminum, and silver, and two or more of them may be used. Among these, copper and copper alloys are preferable from the viewpoint of conductivity. When the metal layers are formed on both surfaces of the resin-impregnated sheet or the laminated sheet, the materials of both metal layers may be the same or different.

  Formation of the metal layer may be performed by fusing the resin-impregnated sheet or the laminated sheet thereof to the metal foil with a hot press or the like, or may be performed by adhering to the metal foil with an adhesive, or plating. It may be performed by coating with a metal by a method or a sputtering method, or by coating with metal particles by a printing method such as a screen printing method. When a plurality of resin-impregnated sheets are laminated to form a laminated sheet and fused to the metal foil, the resin-impregnated sheets may be fused to the metal foil at the same time as the resin-impregnated sheets are fused to each other by a hot press or the like. The plating method may be an electroless plating method, an electrolytic plating method, or a combination of both. The metal layer formed by the plating method may be subjected to a heat treatment to improve its properties such as conductivity.

  The thickness of the metal layer is preferably 1 to 70 μm, more preferably 3 to 35 μm, and still more preferably 5 to 18 μm.

  The metal-clad laminate thus obtained can be used as a printed wiring board by patterning the metal layer by etching or the like and laminating a plurality of sheets as necessary.

[Measurement of flow start temperature of liquid crystalline polyester]
Using a flow tester (“CFT-500 type” manufactured by Shimadzu Corporation), about 2 g of liquid crystalline polyester was filled into a cylinder attached with a die having a nozzle having an inner diameter of 1 mm and a length of 10 mm, and 9.8 MPa (100 kg). The liquid crystalline polyester was melted while being heated at a rate of 4 ° C./min under a load of / cm ² ), extruded from a nozzle, and a temperature showing a viscosity of 4800 Pa · s (48000 poise) was measured.

[Measurement of viscosity of liquid crystal polyester solution]
Using a B-type viscometer (“TVL-20” from Toki Sangyo Co., Ltd.) The measurement was performed at a rotational speed of 20 rpm using 21 rotors.

[Measurement of volume average particle diameter of inorganic filler]
100 mg of the inorganic filler was dispersed in water and measured with a laser diffraction / scattering particle size distribution measuring device (“LA-950” manufactured by Horiba, Ltd.).

[Measurement of solvent content in composition layer of laminate (1)]
After peeling the support film from the laminate (1), separating the composition layer and measuring the mass, the solvent was completely removed by drying at 200 ° C. for 2 hours using a hot air drier. The mass was measured. It calculated | required by the following formula from the mass before and behind drying.
Solvent content (mass%) = (mass before drying−mass after drying) / mass before drying × 100

[Production of liquid crystalline polyester]
In a reactor equipped with a stirrer, a torque meter, a nitrogen gas introduction tube, a thermometer and a reflux condenser, 1976 g (10.5 mol) of 6-hydroxy-2-naphthoic acid and 1474 g (9.75 mol) of 4-hydroxyacetanilide were added. ), 1620 g (9.75 mol) of isophthalic acid and 2374 g (23.25 mol) of acetic anhydride, and after replacing the gas in the reactor with nitrogen gas, the mixture was stirred at room temperature to 150 ° C. under a nitrogen gas stream. The mixture was heated up to 15 minutes and refluxed at 150 ° C. for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150 ° C. to 300 ° C. over 2 hours and 50 minutes, held at 300 ° C. for 1 hour, and then the contents were taken out from the reactor, Cooled to room temperature. The obtained solid was pulverized with a pulverizer to obtain a powdery prepolymer. The flow initiation temperature of this prepolymer was 235 ° C. Next, the prepolymer was heated from room temperature to 223 ° C. over 6 hours under a nitrogen gas atmosphere, and held at 223 ° C. for 3 hours to cause solid-phase polymerization, and then cooled to obtain a powdery liquid crystal Polyester was obtained. The liquid crystal polyester had a flow start temperature of 270 ° C.

[Preparation of liquid crystal polyester solution]
2200 g of liquid crystal polyester was added to 7800 g of N-methyl-2-pyrrolidone (solvent) and stirred at 100 ° C. for 2 hours under a nitrogen gas atmosphere to obtain a liquid crystal polyester solution. The viscosity of this liquid crystal polyester solution was 400 cP.

[Production of Laminate (1)]
In the liquid crystal polyester solution, aluminum oxide (“AA-03” from Sumitomo Chemical Co., Ltd., volume average particle size 0.3 μm) is used as the inorganic filler (1), and boron nitride (Changsung Co., Ltd.) is used as the inorganic filler (2). ) “KBN-5” and a volume average particle diameter of 5 μm) were added to obtain a dispersion. At that time, the addition amounts of aluminum oxide and boron nitride were 43% by volume and 15% by volume, respectively, with respect to the total amount of liquid crystal polyester, aluminum oxide and boron nitride. The dispersion was defoamed by stirring for 10 minutes using a centrifugal stirring and defoaming machine, and then dried on a PET film having a thickness of 100 μm to a thickness of about 50 μm using a bar coater. Then, using a continuous hot air dryer, it is dried at 90 ° C. in the first drying path and then at 120 ° C. in the second drying path for a total of 5 minutes. A laminate (1) in which a layer of the composition (2) containing aluminum oxide, boron nitride and a solvent was formed was obtained. A laminate (1) was obtained.

[Manufacture of laminate (2)]
On both sides of a glass cloth of IPC designation 1067 (Unitika Ltd., mass per unit area 30 g / m ² , thickness 30 μm, weaving density (vertical) 69 / mm, weaving density (horizontal) 69 / mm), Each laminate (1) is placed so that its composition (2) layer is in contact with the glass cloth, and heated and pressurized by passing between a pair of hot rolls using a roll laminator, (2) was obtained. At that time, the temperature of the hot roll was 160 ° C., and the pressure was 0.5 MPa.

[Production of resin impregnated sheet]
The PET film on both sides of the laminate (2) is peeled off, the resin-impregnated sheet precursor is separated, and the solvent is removed by heat treatment at 290 ° C. for 9 hours in a nitrogen atmosphere using a hot air dryer. At the same time, the liquid crystalline polyester was polymerized to obtain a resin-impregnated sheet.

[Manufacture of copper-clad laminate]
An electrolytic copper foil (“3EC-VLP” from Mitsui Kinzoku Co., Ltd.) having a thickness of 18 μm is placed on both sides of the resin-impregnated sheet, and a temperature of 350 ° C. is used using a high-temperature vacuum press (Kitakawa Seiki Co., Ltd.). And hot pressing under a pressure of 15 MPa to obtain a copper-clad laminate.

Comparative Example 1
Copper was obtained in the same manner as in Example 1 except that boron nitride was not used when obtaining the dispersion, and the amount of aluminum oxide added was 40% by volume with respect to the total amount of liquid crystal polyester and aluminum oxide. A tension laminate was produced.

Comparative Example 2
When obtaining the dispersion liquid, copper was used in the same manner as in Example 1 except that aluminum oxide was not used and the addition amount of boron nitride was 40% by volume with respect to the total amount of liquid crystal polyester and boron nitride. A tension laminate was produced.

Comparative Example 3
Implementation was performed except that when the dispersion liquid was obtained, the addition amounts of aluminum oxide and boron nitride were 32% by volume and 8% by volume, respectively, with respect to the total amount of liquid crystal polyester, aluminum oxide and boron nitride. A copper clad laminate was produced as in Example 1.

[Thermal conductivity of resin impregnated sheet]
The copper-clad laminate is immersed in a 40 ° Baume ferric chloride aqueous solution (Kida Co., Ltd.), and the copper foil is removed by etching, followed by washing with water to obtain a resin-impregnated sheet for evaluation. Thermal conductivity was calculated from conductivity = thermal diffusivity × specific heat × density. The thermal diffusivity was measured at room temperature by a temperature wave thermal analysis method using “ai-Phase Mobile” manufactured by Eye Phase Co., Ltd. Specific heat was measured by comparison with a sapphire standard using a differential scanning calorimeter (DSC). The density was measured by the Archimedes method.

[Peel strength of copper-clad laminate]
The copper foil of the copper clad laminate was etched to form a copper foil pattern having a width of 10 mm. The copper foil pattern was peeled off at a rate of 50 mm / min in the vertical direction, and the strength at that time was measured.

Claims (8)

  The fiber sheet is impregnated with a composition containing a liquid crystal polyester and an inorganic filler, the proportion of the liquid crystal polyester in the composition is 10 to 50% by volume, and the proportion of the inorganic filler in the composition Is 50 to 90% by volume, and the inorganic filler includes an inorganic filler (1) having a volume average particle size of 0.1 μm to less than 3 μm and an inorganic filler (2) having a volume average particle size of 3 μm to 10 μm. The resin-impregnated sheet wherein the proportion of the inorganic filler (1) in the composition is 20 to 70% by volume and the proportion of the inorganic filler (2) in the composition is 5 to 40% by volume. The liquid crystalline polyester is a liquid crystalline polyester having a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2), and a repeating unit represented by the following formula (3). The resin-impregnated sheet according to 1.
(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
⁽³⁾ -X-Ar 3 -Y-
(Ar ¹ represents a phenylene group, a naphthylene group, or a biphenylylene group. Ar ² and Ar ³ each independently represent a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4). X And Y each independently represents an oxygen atom or an imino group, and each hydrogen atom in the group represented by Ar ¹ , Ar ² or Ar ³ is independently substituted with a halogen atom, an alkyl group or an aryl group. May be.)
(4) -Ar ⁴ -Z-Ar ^5-
(Ar ⁴ and Ar ⁵ each independently represent a phenylene group or a naphthylene group. Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.)   The resin-impregnated sheet according to claim 1 or 2, wherein the fiber sheet is a glass fiber sheet.   The resin-impregnated sheet according to claim 1, wherein the inorganic filler is an oxide and / or a nitride.   On both sides of the fiber sheet, a laminate (1) having a support and a layer of a composition (2) containing the liquid crystalline polyester, the inorganic filler, and a solvent is contacted with the fiber sheet. And (1) obtaining a laminate (2) having a resin-impregnated sheet precursor obtained by impregnating the fiber sheet with the composition (2) and the support by heating and pressurizing And (2) separating the resin-impregnated sheet precursor from the laminate (2), and (3) obtaining a resin-impregnated sheet by removing the solvent from the resin-impregnated sheet precursor. Item 5. A method for producing a resin-impregnated sheet according to any one of Items 1 to 4.   The production method according to claim 5, wherein the content of the solvent in (2) in the composition is 8 to 14% by mass.   A metal-clad laminate in which a metal layer is formed on at least one surface of the resin-impregnated sheet or laminate sheet according to claim 1.   A method for producing a metal-clad laminate in which a resin-impregnated sheet is obtained by the production method according to claim 5 and 6, and a metal layer is formed on at least one surface of the resin-impregnated sheet or the laminate sheet.