JP6004659B2 - Method for producing resin sheet with conductive layer - Google Patents

Description

  The present invention relates to a method for producing a resin sheet and a method for producing a resin sheet with a conductive layer.

  Liquid crystalline polyester has been studied as a material for an insulating layer of a printed wiring board because of its high heat resistance and strength, and low hygroscopicity and dielectric loss. As a specific form, a material obtained by processing liquid crystal polyester into a sheet or film (hereinafter sometimes referred to as a resin sheet) is used as a material for a printed wiring board.

  As a method for producing such a resin sheet, a method using a liquid composition containing a liquid crystal polyester having a specific structure and a solvent has been studied. For example, Patent Document 1 discloses a method for producing a resin sheet by casting the liquid composition on a support substrate, removing the solvent, and performing heat treatment. The resin sheet produced in this way has a high insulating property and a low dielectric loss tangent, and thus is suitably used for, for example, a printed wiring board.

International Publication No. 09/64121

  However, the above method still has room for improvement from the viewpoint of producing a stable quality resin sheet. For example, the resin sheet produced by the above method may be colored due to the color of the sheet depending on the production conditions. Further, depending on the manufacturing conditions, the adhesion strength with the metal thin film (conductive layer) constituting the wiring pattern of the printed wiring board is lowered, and there is a risk of problems such as peeling of the conductive layer and disconnection of the wiring pattern.

  This invention is made | formed in view of such a situation, Comprising: Self-coloring and the manufacturing method of the resin sheet which can suppress at least any one of the fall of adhesive strength with a conductive layer are provided. For the purpose. Another object of the present invention is to provide a method for producing a resin sheet with a conductive layer, which can suppress at least one of coloring of the resin sheet and a decrease in adhesion strength between the resin sheet and the conductive layer.

  As a result of intensive studies to achieve the above object, the present inventors have completed the present invention.

That is, the present invention includes a step of impregnating a fiber sheet with a liquid composition containing liquid crystal polyester and an organic solvent for dissolving the liquid crystal polyester, and forming the sheet into a sheet, and removing the organic solvent from the formed sheet Forming a temporary molded body, and heat-treating the temporary molded body in an environment with an oxygen concentration of less than 0.05% by volume under a temperature condition of 240 ° C. or higher and lower than the thermal decomposition temperature of the liquid crystalline polyester, A method for producing a resin sheet is provided.

  In the present invention, the fiber sheet is preferably a glass cloth.

In the present invention, the liquid crystal polyester has 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). A polyester is desirable.
(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.)

  In the present invention, the liquid crystalline polyester contains 30 to 80 mol% of the repeating unit represented by the formula (1) with respect to the total amount of all repeating units constituting the above-described formula (2). It is desirable to have 10 to 35 mol% of the repeating unit represented by the formula (3) and 10 to 35 mol% of the repeating unit represented by the formula (3).

  In the present invention, in the repeating unit represented by the formula (3), either one or both of X and Y is preferably an imino group.

  In the present invention, the heat treatment temperature is desirably 260 ° C. or higher and 320 ° C. or lower.

  In the present invention, the heat treatment time is desirably 1 hour or more and 30 hours or less.

  In the present invention, the liquid composition preferably includes an inorganic filler having a thermal conductivity of 10 W / m · K or more.

The present invention also provides a temporary molded body obtained by removing the organic solvent from a sheet obtained by molding a liquid composition containing liquid crystalline polyester and an organic solvent for dissolving the liquid crystalline polyester into a sheet, and the temporary molded body A step of forming a temporary molded body with a conductive layer having a conductive layer laminated on one or both sides of the conductive layer, 240 ° C. or higher in an environment having an oxygen concentration of less than 0.05% by volume, and have a, a step of heat treatment at a temperature lower than the thermal decomposition temperature of said liquid crystal polyester, sheet forming the conductive layer with the preformed body includes the steps of forming the liquid composition into a sheet, molded a step of forming the organic solvent was removed preformed body from the preformed body and laminating a conductive layer on one or both sides of, the manufacturing method of the resin sheet with the conductive layer and having a Subjected to.

  In the present invention, the liquid composition preferably includes an inorganic filler having a thermal conductivity of 10 W / m · K or more.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the resin sheet which can suppress at least any one of own coloring and the fall of adhesive strength with a conductive layer can be provided.

  Hereinafter, the manufacturing method of the resin sheet which concerns on embodiment of this invention is demonstrated.

  The terms “sheet” and “sheet shape” used in the specification include those having a very thin film thickness to a thick thickness. Moreover, about a shape, not only the flat thing which has a breadth of a surface direction but a bottle-like container form etc. are contained.

(Liquid crystal polyester)
The liquid crystalline polyester used in the present embodiment is a liquid crystalline 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)”). And more preferably.
(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 is independently 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 an n-decyl group are mentioned, The carbon number becomes like this. Preferably it is 1-10. 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 carbon number thereof is preferably 6-20. is there. When the hydrogen atom is substituted with these groups, the number is independently preferably 2 or less for each group represented by Ar ¹ , Ar ² or Ar ³ , more preferably One.

  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 carbon number thereof is preferably 1-10.

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 (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 (a repeating unit derived from terephthalic acid), Ar ² is an m-phenylene group (a repeating unit derived from isophthalic acid), Ar ² Is a 2,6-naphthylene group (a 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 (a 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 preferably 30 mol% or more, more preferably 30 mol% or more and 80 mol% or less, still more preferably 30 mol% or more and 60 mol% or less, and even more preferably 30 mol%. It is mol% or more and 40 mol% or less.

  Similarly, the content of the repeating unit (2) is preferably 35 mol% or less, more preferably 10 mol% or more and 35 mol% or less, further preferably 20 mol% or more 35 with respect to the total amount of all repeating units. The mol% or less, more preferably 30 mol% or more and 35 mol% or less.

  Similarly, the content of the repeating unit (3) is preferably 35 mol% or less, more preferably 10 mol% or more and 35 mol% or less, further preferably 20 mol% or more 35 with respect to the total amount of all repeating units. The mol% or less, more preferably 30 mol% or more and 35 mol% or less.

  As the content of the repeating unit (1) increases, the heat resistance, the strength and the rigidity are easily improved. However, when the content is too large, the solubility in a solvent tends to be low.

  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 preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and still 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. The liquid crystalline polyester may have a repeating unit other than the repeating units (1) to (3), but the content thereof is preferably 10 mol% or less, based on the total amount of all repeating units. Preferably it is 5 mol% or less.

  The liquid crystalline polyester has, as the repeating unit (3), one or both of X and Y are imino groups, that is, a repeating unit derived from a predetermined aromatic hydroxylamine and an aromatic diamine. It is preferable to have one or both of the repeating unit derived from it, since the solubility in a solvent is excellent, and as the repeating unit (3), one or both of X and Y are imino groups It is more preferable to have only.

  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 crystal polyester has a flow initiation temperature of preferably 250 ° C. or higher, more preferably 250 ° C. or higher and 350 ° C. or lower, and further preferably 260 ° C. or higher and 330 ° C. or lower. 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 described later tends to be high.

The flow start temperature is also called the flow temperature or flow temperature, and the liquid crystal polyester is heated at a rate of 4 ° C./min under a load of 9.8 MPa (100 kgf / cm ² ) using a capillary rheometer. 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).

(Liquid composition containing liquid crystal polyester)
The liquid crystal polyester-containing liquid composition (liquid composition) used in the method for producing the resin sheet of the present embodiment contains an organic solvent in addition to the liquid crystal polyester as described above. As the organic solvent, those that can dissolve the liquid crystal polyester used, specifically those that can be dissolved at a concentration of 1% by mass or more at 50 ° C. ([liquid crystal polyester] / [liquid crystal polyester + organic solvent]) are appropriately used. Select and use.

  Examples of organic solvents include halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, o-dichlorobenzene; p-chlorophenol, pentachlorophenol, pentafluoro Halogenated phenols such as phenol; Ethers such as diethyl ether, tetrahydrofuran and 1,4-dioxane; Ketones such as acetone and cyclohexanone; Esters such as ethyl acetate and γ-butyrolactone; Carbonates such as ethylene carbonate and propylene carbonate; Triethylamine and the like Amines; Nitrogen-containing heterocyclic aromatic compounds such as pyridine; Nitriles such as acetonitrile and succinonitrile; Ami such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone System solvents (organic solvents having an amide bond), urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and hexamethylphosphoric acid amide and tri-n-butylphosphoric acid A phosphorus compound is mentioned. Two or more organic solvents may be used in combination.

  As the organic solvent, an aprotic compound, particularly a solvent containing an aprotic compound having no halogen atom as a main component is preferable because it has low corrosivity and is easy to handle. The proportion of the aprotic compound in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and still more preferably 90% by mass to 100% by mass. Moreover, as the aprotic compound, an amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone or the like is preferably used because a liquid crystalline polyester is easily dissolved. It is more preferable to use an amide-based solvent that does not have any of

  Moreover, as an organic solvent, since it is easy to melt | dissolve liquid crystalline polyester, the solvent which has as a main component the compound whose dipole moment is 3-5 is preferable. The proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and still more preferably 90% by mass to 100% by mass. % Or less. In the present invention, it is particularly preferable to use a compound having a dipole moment of 3 to 5 (unit: Debye) as the aprotic compound.

  Examples of the aprotic compound having a dipole moment of 3 to 5 include dimethyl sulfoxide (dipole moment: 4.1 debye), N, N-dimethylacetamide (3.7 debye), N, N -Dimethylformamide (3.9 debye) and N-methylpyrrolidone (4.1 debye) can be exemplified.

  Moreover, as an organic 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 boiling point in 1 atmosphere which occupies the whole solvent of the compound which is 220 degrees C or less The ratio is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and still more preferably 90% by mass to 100% by mass, and the aprotic compound is 1 atmosphere. It is preferable to use a compound having a boiling point of 220 ° C. or lower.

  N, N-dimethylacetamide (boiling point: 160 ° C.) N, N-dimethylformamide (153 ° C.) can be exemplified as a compound that is an aprotic compound and has a boiling point of 220 ° C. or less at 1 atm. .

  The content of the liquid crystal polyester in the liquid crystal polyester-containing liquid composition is preferably 5% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 50% by mass or less, with respect to the total amount of the liquid crystal polyester and the organic solvent. More preferably, it is 15 mass% or more and 45 mass% or less, and it adjusts suitably so that the liquid composition of desired viscosity may be obtained.

  The liquid crystal polyester-containing liquid composition may contain one or more components such as a filler, an additive, and a resin other than the liquid crystal polyester as long as the effects of the present invention are not impaired.

  Examples of fillers include silica, alumina, titanium oxide, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, boron nitride, aluminum nitride, magnesium oxide, zinc oxide, and other inorganic fillers; and cured epoxy resins And organic fillers such as a crosslinked benzoguanamine resin and a crosslinked acrylic resin, and the content thereof is preferably 0% by volume or more and 80% by volume or less with respect to the total of the liquid crystal polyester and the inorganic filler.

  In the case where the liquid crystal polyester-containing liquid composition of the present embodiment is used as a material for an electronic substrate (heat radiating substrate) excellent in heat dissipation, an inorganic filler is preferable among these fillers because it exhibits high thermal conductivity. Furthermore, an inorganic filler having a thermal conductivity of 10 W / m · K or more is more preferable because sufficient heat dissipation can be ensured when a heat dissipation substrate is manufactured. Examples of the inorganic filler having a thermal conductivity of 10 W / m · K or more include alumina, strontium titanate, boron nitride, aluminum nitride, magnesium oxide, and zinc oxide.

  Examples of the additive include a leveling agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, a flame retardant, and a colorant, and the content thereof is preferably 0 part by mass with respect to 100 parts by mass of the liquid crystalline polyester. The amount is 5 parts by mass or less.

  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, a cyanate resin, are mentioned, The content is preferably 0 to 20 parts by mass with respect to 100 parts by mass of the liquid crystalline polyester.

  A liquid composition can be prepared by mixing liquid crystal polyester, a solvent, and other components used as necessary in a batch or in an appropriate order. When using a filler as another component, it is preferable to prepare by dissolving liquid crystal polyester in a solvent to obtain a liquid crystal polyester solution, and then dispersing the filler in the liquid crystal polyester solution.

(Production method of resin sheet)
The method for producing a resin sheet of the present embodiment includes a step of impregnating a fiber sheet with the liquid crystal polyester-containing liquid composition described above to form a sheet, and an organic solvent is removed from the formed liquid composition to form a temporary molded body. And a step of heat-treating the temporary molded body in an environment having an oxygen concentration of less than 0.05% by volume.

(Fiber sheet)
As a fiber sheet used in the present embodiment, a sheet constituted by using inorganic fibers such as glass fibers, carbon fibers, ceramic fibers, and organic fibers such as aromatic polyamide fibers, polyimide fibers, polyzenzazole fibers, or liquid crystal polymer fibers. Is mentioned. The organic fiber preferably has heat resistance that does not melt at the above heat treatment temperature. Two or more kinds of these fibers may be used in combination. Of these, glass fiber is preferable. Examples of glass fibers include alkali-containing glass fibers, alkali-free glass fibers, and low dielectric glass fibers.

  The fiber sheet may be a woven fabric (woven fabric), a knitted fabric, or a non-woven fabric, but it is a woven fabric because the dimensional stability of the resin-impregnated sheet is easily improved. Is preferred. Examples of weaving methods include plain weaving, satin weaving, twill weaving and nanako weaving. The weaving density of the woven fabric is preferably 10 to 100/25 mm.

The thickness of the fiber sheet is preferably 10 μm or more and 200 μm or less, and preferably 10 μm or more and 180 μm or less. The mass per unit area of the fiber sheet is preferably 10 g / m ² or more and 300 g / m ² or less.

  In addition, the fiber sheet is preliminarily silane coupling agent, aminosilane coupling agent, epoxysilane coupling agent, titanate coupling agent so as to improve the adhesion to the liquid crystal polyester contained in the liquid composition to be impregnated. It may be surface-treated with a coupling agent such as

  As a method for producing a fiber sheet composed of these fibers, the fibers forming the fiber sheet are dispersed in water, and if necessary, a paste such as an acrylic resin is added, and after making with a paper machine, drying is performed. The method of obtaining a nonwoven fabric by this and the method of using a well-known weaving machine can be mentioned.

  Moreover, it is also possible to use a glass cloth as a fiber sheet which can be easily obtained from the market. Various glass cloths are commercially available as insulating impregnation base materials for electronic components, and can be obtained from Asahi Sebel, Nittobo, Arisawa Seisakusho, etc. In addition, in a commercially available glass cloth, the thing of suitable thickness is 1035, 1078, 2116, 7628 etc. by IPC name.

(Manufacture of resin sheets)
As a method of impregnating the fiber sheet with the liquid composition, a method of typically preparing a dipping tank charged with the liquid composition and impregnating the fiber sheet into the dipping tank can be shown. In such a method, the amount of the liquid crystal polyester adhering to the fiber sheet is the liquid crystal polyester content of the liquid composition used, the conditions for impregnating the fiber sheet into the dipping bath, and the excess liquid composition adhering to the fiber sheet. It can be adjusted by controlling the conditions to be removed.

  Examples of “conditions for impregnating the fiber sheet in the immersion tank” include, for example, the time of immersion in the immersion tank and the speed at which the fiber sheet impregnated with the liquid composition is pulled up. In addition, as “conditions for removing the excess liquid composition adhering to the fiber sheet”, for example, the excess liquid composition is removed by squeezing the fiber sheet impregnated with the liquid composition through a pair of rolls. In this case, an interval between the rolls can be mentioned.

  Thus, the fiber sheet impregnated with the liquid composition can produce a fiber sheet containing liquid crystal polyester (corresponding to the “temporary molded product” in the present invention) by removing the solvent. The method for removing the solvent is not particularly limited, but it is preferable to remove the solvent by evaporating it from the viewpoint of easy operation. When removing such a solvent, it is preferable to promote evaporation of the solvent by heating, decompressing, ventilating, or a combination thereof.

  Moreover, in the manufacturing method of the resin sheet of this embodiment, after removing a solvent, it heat-processes further. According to such heat treatment, the liquid crystalline polyester contained in the temporary molded body can be increased in molecular weight, and the heat resistance and mechanical strength can be improved.

  The conditions relating to this heat treatment are a treatment temperature of 240 ° C. or higher and lower than the thermal decomposition temperature of the liquid crystal polyester used, and a treatment time of 1 hour or more and 30 hours or less. If the treatment temperature is lower than 240 ° C., the intended liquid crystal polyester will not have a high molecular weight (polymerization reaction). In addition, when the treatment temperature is higher than the thermal decomposition temperature of the liquid crystal polyester, the liquid crystal polyester used is naturally decomposed and a desired resin sheet cannot be obtained.

  The thermal decomposition temperature of the liquid crystal polyester was JIS K7120, and the 5% weight reduction temperature when the temperature was raised at 5 ° C./min in a nitrogen atmosphere was defined as the thermal decomposition temperature.

  From the viewpoint of obtaining a resin sheet having better heat resistance, the heat treatment is preferably performed at a processing temperature of 250 ° C. or higher, more preferably a processing temperature of 260 ° C. or higher and 320 ° C. or lower. It is a range.

  Moreover, it is preferable from the point of productivity that the processing time of heat processing is 1 hour or more and 10 hours or less.

  In the resin sheet manufacturing method of the present embodiment, such heat treatment is performed in an atmosphere having an oxygen concentration of less than 500 ppm (0.05% by volume). Thereby, the oxidation of the liquid crystalline polyester during the heat treatment can be suppressed, and deterioration of physical properties can be prevented. The oxygen concentration at the start of the heat treatment step is preferably less than 100 ppm (0.01% by volume), more preferably less than 50 ppm (0.005% by volume). Theoretically, when the oxygen concentration becomes 0 ppm (0% by volume), no oxidative deterioration occurs, so the lower limit of the oxygen concentration at the start of the heat treatment step is “0 ppm”.

  Such a processing environment having an oxygen concentration can be prepared, for example, by replacing the inside of a processing furnace in which heat treatment is performed with an inert gas. As the inert gas, a rare gas such as nitrogen, helium, or argon can be used.

  Specifically, when replacing the inside of the processing furnace with nitrogen, the replacement can be performed by extruding and discharging the air in the processing furnace while introducing nitrogen into the processing furnace. Further, the replacement may be performed by repeating the operation of introducing nitrogen after degassing the inside of the processing furnace in advance. These replacement operations may be performed while operating the processing furnace (for example, while heating the processing furnace to 100 ° C.). Then, the oxygen concentration in the processing furnace is measured, and after confirming that the oxygen concentration has become a desired value or less by the replacement operation with nitrogen, the processing furnace is heated to the above-described heat treatment temperature to perform the heat treatment. .

  According to the above manufacturing method, coloring during heat treatment is suppressed, and a resin sheet having a good appearance can be obtained.

  Moreover, the resin sheet obtained in this way is laminated | stacked as needed, and after forming a conductive layer, such as a metal thin film, in at least one surface, the resin sheet with a conductive layer (resin sheet with a conductive layer) Can be obtained.

(Resin sheet with conductive layer)
The conductive layer may be formed by laminating a metal foil by bonding with an adhesive, fusing by hot pressing, or by coating metal particles by a plating method, a screen printing method, a sputtering method, or the like. May be. Examples of the metal constituting the metal foil or metal particle include copper, aluminum, and silver, but copper is preferably used from the viewpoint of conductivity and cost.

  In the case of forming a resin sheet with a conductive layer, a plurality of resin sheets may be bonded together by hot pressing and multilayered. In particular, in the case where one resin sheet (one layer) is insufficient in rigidity as a base material, it is preferable to obtain rigidity by multilayering. In such a case, a resin sheet on which a conductive layer is formed in advance and a resin sheet on which a conductive layer is not formed may be laminated. A conductive layer is formed on a resin sheet that has been previously multilayered as described above. May be.

  The temperature of the hot press at the time of multilayering the resin sheet is preferably 300 ° C. or higher and 360 ° C. or lower, more preferably 320 ° C. or higher and 340 ° C. or lower. The press pressure is preferably 1 MPa or more and 20 MPa or less, more preferably 3 MPa or more and 10 MPa or less. Further, the pressing time is preferably 5 minutes or more and 60 minutes or less, more preferably 10 minutes or more and 50 minutes or less. When performing pressing, it is preferable to reduce the pressure environment to 5 kPa or less and to perform under reduced pressure. By performing press working under reduced pressure, oxidative deterioration of the resin sheet during press working can be suppressed.

  As for the resin sheet with a conductive layer obtained as mentioned above, the deterioration at the time of the heat processing at the time of resin sheet preparation is suppressed. Therefore, peeling between the resin sheet and the conductive layer hardly occurs. Therefore, the obtained resin sheet with a conductive layer is formed into a circuit layer by forming a predetermined wiring pattern on the conductive layer, and by laminating a plurality of sheets as necessary, the wiring pattern is hardly peeled off or disconnected, and the reliability is improved. A high printed wiring board can be obtained.

  In the present embodiment, the resin sheet containing the fiber sheet is manufactured by impregnating the fiber sheet with the liquid composition. However, the present invention is not limited to this. For example, a resin composition is obtained by casting a liquid composition on a support, removing the solvent from the cast to obtain a temporary molded body, and then performing a heat treatment in an environment having an oxygen concentration of less than 500 ppm as described above. May be manufactured.

  In the present embodiment, the resin sheet with a conductive layer is formed by forming a conductive layer on at least one surface of the resin sheet after manufacturing the resin sheet using the liquid composition as a forming material. Not limited to this.

  That is, first, a temporary molded body obtained by removing the organic solvent from a sheet obtained by molding a liquid composition containing liquid crystalline polyester and an organic solvent that dissolves the liquid crystalline polyester into a sheet, and one side of the temporary molded body Or a conductive layer with a conductive layer laminated on both surfaces, and then forming the temporary molded body with a conductive layer in an environment having an oxygen concentration of less than 0.05% by volume and at least 240 ° C. and the liquid crystal By conducting a heat treatment under a temperature condition lower than the thermal decomposition temperature of the polyester, a resin sheet with a conductive layer can be formed without isolating the resin sheet as in the above embodiment.

  In this case, as a method of forming a temporary molded body with a conductive layer, first, after creating the temporary molded body in the present embodiment, a conductive layer is laminated on one or both surfaces of the temporary molded body, and the conductive layer is attached. The method of forming a temporary molded object is mentioned.

  In the present embodiment, a fiber sheet containing liquid crystal polyester is used as a temporary molded body, but a conductive layer is laminated on one or both sides of the temporary molded body, for example, by the following method regardless of the presence or absence of the fiber sheet. Thus, a temporary molded body with a conductive layer can be formed.

  That is, a liquid composition is first cast on a support, a temporary molded body is formed on the support, a metal foil is laminated on the surface of the temporary molded body, and the support, the temporary molded body, and the metal foil are laminated. Forms a first laminated body laminated in this order. Thereafter, the first laminate is passed between a pair of heat rolls to apply heat and pressure to bond the temporary molded body and the metal foil together.

  Next, after peeling the support from the first laminate, a metal foil is laminated on the surface of the exposed temporary molded body, and the second laminated body in which the metal foil, the temporary molded body, and the metal foil are laminated in this order. By forming this and passing the second laminate between a pair of heat rolls, the target temporary molded body with a conductive layer can be formed by applying heat and pressure.

  Second, for example, by applying the liquid composition to the surface of the metal foil, the liquid composition is formed into a sheet shape on the surface of the metal foil, and the solvent is removed to form a temporary molded body on the metal foil. The method of forming and forming the temporary molding with a conductive layer which uses metal foil as a conductive layer is mentioned. In this case, a conductive layer may be further formed on the surface of the temporary molded body formed on the metal foil, and a temporary molded body with a conductive layer in which conductive layers are provided on both surfaces of the temporary molded body may be formed.

  As a method for forming a conductive layer on the surface of the temporary molded body, a metal foil may be adhered with an adhesive, or metal particles may be coated by a plating method, a screen printing method, a sputtering method, or the like. Good. Examples of the metal constituting the metal foil or metal particle include copper, aluminum, and silver, but copper is preferably used from the viewpoint of conductivity and cost. Moreover, when bonding metal foil with an adhesive agent, if necessary, heat and pressure are applied by passing the temporary molded body to which the metal foil is bonded between a pair of hot rolls. And may be fused.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Measurement of flow start temperature of liquid crystalline polyester]
The flow start temperature of the liquid crystal polyester was measured using a flow tester (manufactured by Shimadzu Corporation, CFT-500 type). About 2 g of liquid crystalline polyester was filled in a cylinder equipped with a die having a nozzle having an inner diameter of 1 mm and a length of 10 mm, and the temperature was increased at a rate of 4 ° C./min under a load of 9.8 MPa (100 kgf / cm ² ). The liquid crystal polyester was melted and extruded from a nozzle, and a temperature showing a viscosity of 4800 Pa · s (48000 poise) was measured as a flow start temperature.

[Production of liquid crystalline polyester]
To a reactor equipped with a stirrer having a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 1976 g (10.5 mol) of 6-hydroxy-2-naphthoic acid and 1474 g (9.75) of 4-hydroxyacetanilide were added. Mol), 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 from 150 to 150 with stirring under a nitrogen gas stream. The temperature was raised to 15 ° C. over 15 minutes and refluxed at 150 ° C. for 3 hours.

  Subsequently, while distilling off acetic acid by-produced during the reflux 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 from the reactor. The contents were removed and 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.

  Subsequently, the prepolymer was pulverized into a powder form, spread on a metal tray, and placed in a hot air dryer (IPHH-201M, manufactured by Espec Corp.). Under a nitrogen atmosphere, the temperature was raised from room temperature to 223 ° C. over 6 hours and held at 223 ° C. for 3 hours to solid-phase polymerize and then cool to obtain a powdery liquid crystalline polyester. The liquid crystal polyester had a flow start temperature of 270 ° C.

[Creation of liquid composition]
22 parts by mass of the above liquid crystalline polyester was dried at 120 ° C. for 2 hours in a ventilated oven, then added to 78 parts by mass of N, N-dimethylacetamide, heated at 100 ° C. for 2 hours in a nitrogen atmosphere, and then cooled. A liquid crystal polyester-containing liquid composition (hereinafter sometimes referred to as a liquid composition) was obtained.

Example 1
[Manufacture of resin sheets]
Glass cloth (Arisawa Manufacturing Co., Ltd., thickness 96 μm, IPC name 2116) was used as the fiber sheet, and after impregnating the liquid composition with this, the solvent was evaporated at 160 ° C. using a hot air dryer, A fiber sheet (temporary molded product) containing liquid crystal polyester was obtained.

  The obtained temporary compact was placed in a hot air dryer (IPHH-201M, manufactured by ESPEC Corporation), and nitrogen at a purity of 99.999% was introduced at 40 L / min from the nitrogen inlet of the dryer at room temperature. However, the oxygen concentration in the storage was set to less than 0.05% by volume (less than 500 ppm) by overflowing from the discharge port and performing nitrogen replacement in the storage over 30 minutes. The oxygen concentration in the hot air dryer was measured using an oxygen concentration meter LC-300 manufactured by Toray Engineering Co., Ltd.

  Thereafter, the temperature in the hot air dryer was raised to 290 ° C., held for 3 hours, and then allowed to cool to obtain a resin sheet. Visual evaluation was performed about coloring of the obtained resin sheet.

[Production of resin sheet with copper foil]
Copper foil (Mitsui Metals Co., Ltd., 3EC-VLP, thickness 18 μm) is arranged on both surfaces of the obtained resin sheet, and 340 ° C. using a high-temperature vacuum press machine (VH1-1765 manufactured by Kitagawa Seiki Co., Ltd.). Was pressed at a pressure of 5 MPa for 30 minutes to obtain a resin sheet with copper foil to which a double-sided copper foil was attached.

[Peel strength measurement (adhesion strength measurement)]
A 10 mm wide peel test piece was cut out from the obtained resin sheet with copper foil. And about this test piece, 90 degree convex point average test force at the time of peeling copper foil (Shimadzu Corporation autograph AG-5000D, 50 mm / min peeling speed) is measured, and a resin sheet and copper foil are measured. The adhesion strength was measured.

(Comparative Example 1)
Comparative Example 1 was performed in the same manner as in Example 1 except that the heat treatment during the production of the resin sheet was performed in air.

(Example 2)
The above liquid composition is applied to copper foil (Mitsui Metals, Inc., 3EC-VLP, thickness 18 μm), dried at 60 ° C. for 120 minutes, and an intermediate of a resin sheet with copper foil (temporary molded body 1 with a conductive layer) ) At this time, coating was performed so that the resin thickness after drying was 20 μm.

  The obtained temporary molded body 1 with a conductive layer was placed in a hot air dryer (IPHH-201M, manufactured by Espec Corp.), and 30 L of 99.999% nitrogen was supplied from the nitrogen inlet of the hot air dryer at room temperature. While being introduced at a rate of / min, it was allowed to overflow from the discharge port, and nitrogen substitution in the hot air dryer was performed for 120 minutes. After confirming that the oxygen concentration in the hot air dryer was 0.01 vol% (100 ppm), the temperature increase was started.

  Thereafter, the temperature in the hot-air dryer was raised to 290 ° C., held for 3 hours, and then allowed to cool to obtain a resin sheet with copper foil in which a copper foil was attached to one side of the resin sheet.

(Comparative Example 2)
Except that nitrogen having a purity of 99.9% was introduced at a rate of 10 L / min during the heat treatment of Example 2, the same procedure as in Example 2 was performed to replace the nitrogen in the hot air dryer. At this time, the oxygen concentration in the hot air dryer was 2.7% by volume (27000 ppm). Thereafter, a resin sheet with a copper foil in which a copper foil was attached to one surface of the resin sheet was obtained by the same operation as in Example 2.

(Example 3)
Aluminum oxide (alumina) (manufactured by Sumitomo Chemical Co., Ltd., “AA-5”, thermal conductivity 38 W / mK) is added to the liquid composition, and a centrifugal stirring deaerator (AR-500, manufactured by Shinky Corporation) is added. ) For 5 minutes to prepare a dispersion. Here, the filling amount of aluminum oxide was 50% by volume with respect to the total of the liquid crystal polyester and aluminum oxide.

  The obtained dispersion was applied to a copper foil (Fukuda Metal Co., Ltd., CF-T8G-UN-35, thickness 35 μm), dried at 120 ° C. for 10 minutes, and an intermediate (conductive layer) of a resin sheet with copper foil An attached temporary molded body 2) was obtained. At this time, coating was performed so that the resin thickness after drying was 100 μm.

  A heat treatment was performed in the same manner as in Example 2 except that the temporary molded body 2 with a conductive layer was used to obtain a resin sheet with a copper foil in which a copper foil was attached to one side of the resin sheet.

(Comparative Example 3)
Except that nitrogen having a purity of 99.9% was introduced at a rate of 10 L / min during the heat treatment of Example 3, the same procedure as in Example 3 was performed to replace the nitrogen in the hot air dryer. At this time, the oxygen concentration in the hot air dryer was 2.7% by volume (27000 ppm). Then, the resin sheet with a copper foil by which copper foil was attached to the single side | surface of the resin sheet was obtained by the same operation as Example 3.

  About Examples 1-3 and Comparative Examples 1-3, the result of the adhesion strength of the resin sheet and copper foil in each resin sheet with a copper foil is shown in Table 1 below.

As a result of the measurement, the resin sheet obtained in Example 1 was suppressed from being colored without the liquid crystal polyester being oxidized as compared with the resin sheet obtained in Comparative Example 1.
Moreover, the adhesive strength of the resin sheet with copper foil produced using the resin sheet obtained in Example 1 is compared with the adhesive strength of the resin sheet with copper foil produced using the resin sheet obtained in Comparative Example 1. It was excellent.

Compared with the resin sheet with a copper foil obtained in Comparative Example 2, the resin sheet with a copper foil obtained in Example 2 was inhibited from being colored and the coloring was suppressed.
Further, the adhesion strength of the resin sheet with copper foil obtained in Example 2 was superior to the adhesion strength of the resin sheet with copper foil obtained in Comparative Example 2.

Compared with the resin sheet with a copper foil obtained in Comparative Example 3, the resin sheet with a copper foil obtained in Example 3 was suppressed from being colored without being oxidized.
Moreover, the adhesion strength of the resin sheet with copper foil obtained in Example 3 was superior to the adhesion strength of the resin sheet with copper foil obtained in Comparative Example 3.
From these results, the usefulness of the present invention was confirmed.

Claims (8)

  A temporary molded body obtained by removing the organic solvent from a sheet obtained by molding a liquid composition containing liquid crystalline polyester and an organic solvent for dissolving the liquid crystalline polyester into a sheet, and laminated on one side or both sides of the temporary molded body Forming a temporary molded body with a conductive layer having a conductive layer,
  Heat-treating the temporary molded body with a conductive layer in an environment having an oxygen concentration of less than 0.05% by volume under a temperature condition of 240 ° C. or more and less than the thermal decomposition temperature of the liquid crystal polyester,
  The step of forming the temporary molded body with a conductive layer includes the step of forming the liquid composition into a sheet,
  Removing the organic solvent from the molded sheet to form a temporary molded body;
  And a step of laminating a conductive layer on one side or both sides of the temporary molded body. A method for producing a resin sheet with a conductive layer, comprising: The liquid crystal polyester is a liquid crystal 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). method for producing a conductive layer with a resin sheet according to claim 1, wherein.
(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 liquid crystalline polyester has a repeating unit represented by the formula (1) of 30 mol% or more and 80 mol% or less, and a repeating unit represented by the formula (2), based on the total amount of all repeating units constituting the liquid crystal polyester. 3. The method for producing a resin sheet with a conductive layer according to claim 2 , wherein the unit is 10 mol% or more and 35 mol% or less, and the repeating unit represented by the formula (3) is 10 mol% or more and 35 mol% or less. . In the repeating unit represented by the formula (3), either one or both of X and Y is, the production method of the conductive layer with a resin sheet according to claim 2 or 3, characterized in that an imino group. The method for producing a resin sheet with a conductive layer according to any one of claims 1 to 4 , wherein the heat treatment temperature is 260 ° C or higher and 320 ° C or lower. The method for producing a resin sheet with a conductive layer according to any one of claims 1 to 5 , wherein the heat treatment time is 1 hour or more and 30 hours or less. The said liquid composition contains the inorganic filler whose heat conductivity is 10 W / m * K or more, The manufacturing method of the resin sheet with a conductive layer of any one of Claim 1 to 6 characterized by the above-mentioned. The said liquid composition contains the inorganic filler whose heat conductivity is 10 W / m * K or more, The manufacturing method of the resin sheet with a conductive layer of any one of Claim 1 to 7 characterized by the above-mentioned.