JP2009161638A - Crosslinkable polymer sheet, crosslinked polymer sheet, and crosslinked polymer composite sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crosslinkable polymer sheet suitable as an insulation layer for the use of an electric circuit board, and to provide a crosslinked polymer sheet obtained by crosslinking the same, and a crosslinked polymer composite sheet obtained by crosslinking on a base material. <P>SOLUTION: The crosslinkable polymer sheet includes a conjugated diene polymer and a hydrocarbon radical generator, and satisfies heat resistance, mechanical properties, and adhesiveness between a conductive layer and a polymer layer required by an electric circuit board, moreover satisfies excellent dielectric properties. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crosslinkable polymer sheet containing a conjugated diene polymer, a crosslinked polymer sheet obtained by crosslinking the polymer sheet, and a crosslinked polymer composite sheet. More specifically, the present invention relates to a crosslinked polymer sheet having excellent dielectric properties, a crosslinked polymer composite sheet, and a crosslinkable polymer sheet from which these can be obtained as an insulating layer in an electric circuit board.

  With the recent rapid advancement of science and technology centered on the electronic industry, the performance of each electronic device and the requirements for the material forming it have become very severe. In the field of high-frequency circuits, in recent years, delays and attenuation associated with higher signal speeds and higher frequencies have become problems. In general, epoxy polymers are used for core materials and interlayer insulation materials that are insulating layers in printed circuit boards. Epoxy polymers, however, have a very high dielectric loss tangent between the polymer itself and the substrate that is produced using it. It was difficult to use as an electronic material for circuits.

  In order to solve the above problem, Patent Document 1 discloses a method using polybutadiene or polyisoprene having excellent dielectric characteristics. Here, a composition containing a polybutadiene or polyisoprene, a specific organic peroxide as a curing agent, a flame retardant, and a web has a lower dielectric loss tangent after curing than an epoxy polymer or the like. It is disclosed.

  However, with further progress in science and technology in recent years and the higher frequency of electrical signals, the demand for lower dielectric loss tangents has increased, and a slight difference in dielectric loss tangent on a finer order than before has caused signal delay and attenuation. It has come to greatly affect.

On the other hand, it is common to use a sulfur compound or an organic peroxide for crosslinking polybutadiene or the like. However, in Patent Document 2, 2,3-dimethyl-2, as a radical crosslinking initiator is used for crosslinking polybutadiene. It is disclosed that 3-diphenylbutane or the like is used to form crosslinked product particles. Here, it is said that the obtained cross-linked particles can be used in the electronic industry or the like as a form in which, for example, an epoxy polymer is added to another polymer such as cross-linking with an amine. However, this document only discloses the use of cross-linked particles of polybutadiene as an additive, and does not disclose the use of a cross-linked product based on polybutadiene in the electronic industry or the like.
JP-A-8-208856 JP-A-4-154813

  According to the study of the present inventor, the polybutadiene or polyisoprene composition disclosed in the above-mentioned Patent Document 1 did not sufficiently answer the further increasing demand for dielectric loss tangent that affects the high frequency electrical conduction properties. .

  An object of the present invention is to provide a crosslinkable polymer sheet suitable as an insulating layer for use in an electric circuit board, a crosslinkable polymer sheet obtained by crosslinking it, and a crosslinkable polymer composite sheet obtained by crosslinking on a support. It is to provide.

  As a result of intensive studies, the present inventors have found that the composition of polybutadiene or polyisoprene disclosed in Patent Document 1 has heat resistance other than dielectric properties as an electric circuit board, mechanical properties, a conductor layer and a polymer layer. In order to satisfy the requirements such as adhesiveness, a polar material was used in addition to the polymer, and it was found that the excellent dielectric properties inherent to the polymer were impaired. Therefore, in the present invention, it has been found that the above problem can be solved by using a hydrocarbon radical generator in the crosslinking reaction of the conjugated diene polymer, and the present invention has been completed based on this finding.

（式中、Ｒ１、Ｒ２、Ｒ３、Ｒ’１、Ｒ’２、及びＲ’３は、それぞれ独立に水素原子、炭素数１〜１０の鎖状炭化水素基、脂環式炭化水素基、または芳香族炭化水素基を表す。）
（３）前記炭化水素ラジカル発生剤が、式（Ｂ）の構造を有する炭化水素化合物である（１）に記載の架橋可能なポリマーシート。

（式中、Ｒ４は芳香族炭化水素基を表し、Ｒ５は水素原子、または炭素数１〜１０の炭化水素基を表す。） Thus, according to the present invention,
(1) A crosslinkable polymer sheet comprising a conjugated diene polymer and a hydrocarbon radical generator.
(2) The crosslinkable polymer sheet according to (1), wherein the hydrocarbon radical generator is a hydrocarbon compound having a structure of the formula (A).

(Wherein R1, R2, R3, R′1, R′2, and R′3 each independently represent a hydrogen atom, a chain hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, or Represents an aromatic hydrocarbon group.)
(3) The crosslinkable polymer sheet according to (1), wherein the hydrocarbon radical generator is a hydrocarbon compound having a structure of the formula (B).

(In the formula, R4 represents an aromatic hydrocarbon group, and R5 represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.)

(4) A crosslinked polymer sheet obtained by crosslinking the polymer sheet according to any one of (1) to (3).
(5) A crosslinked polymer composite sheet obtained by crosslinking the polymer sheet according to any one of (1) to (3) on a support.
Is provided.

The crosslinked polymer sheet of the present invention is excellent in heat resistance, electrical insulation and dielectric properties. Furthermore, the laminated body provided with the said characteristic can be obtained by laminating | stacking a crosslinked polymer composite sheet with the polymer sheet before bridge | crosslinking.
The polymer sheet, crosslinked polymer sheet, and crosslinked polymer composite sheet of the present invention are suitable as an insulating layer material used for an electric circuit board.

  The crosslinkable polymer sheet of the present invention comprises a conjugated diene polymer and a hydrocarbon radical generator.

(Conjugated diene polymer)
The conjugated diene polymer used as an electric circuit material in the present invention is constituted essentially of a conjugated diene homopolymer, but preferably contains a conjugated diene copolymer. The ratio of the components of the conjugated diene homopolymer and the conjugated diene copolymer is usually 50% by weight or more, preferably 65% by weight or more, more preferably 80% by weight or more in the conjugated diene polymer.

The conjugated diene homopolymer is not particularly limited as long as it is a polymer obtained from a conjugated diene monomer having at least two conjugated double bonds in the molecule. For example, butadiene, isoprene, chloroprene, cyanobutadiene, pentadiene, etc. Is a polymer obtained by polymerizing Of these, butadiene and isoprene are preferable, and butadiene is more preferable.
The molecular weight of the conjugated diene homopolymer is a weight average molecular weight measured in terms of polystyrene in a tetrahydrofuran solvent using gel permeation chromatography (GPC), and is usually 500 to 50,000, preferably 1,000 to 10,000. More preferably, it is in the range of 1,000 to 5,000. A polymer having a molecular weight in such a range is often in a liquid state at room temperature, and by using this, the composition viscosity during processing is controlled, and molding into a predetermined shape becomes easy.
The structure of the conjugated diene homopolymer preferably has more vinyl group-containing side chains, and the ratio of 1,2 addition is usually 80% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more. When the ratio of 1,2 addition is in this range, it can be easily crosslinked by heating in the presence of a radical generator, and heat resistance and mechanical properties can be improved, which is preferable.

  The conjugated diene copolymer is not particularly limited as long as it is a polymer obtained by polymerization from a monomer composition comprising a conjugated diene monomer and a monomer having an aromatic ring or a heterocyclic ring in the molecule, and even if it is a random copolymer, Although it may be a copolymer, it is preferably a block copolymer. Examples of the monomer having an aromatic ring or a heterocyclic ring include a pyridyl group-containing vinyl monomer, an alkoxyl group-containing vinyl monomer, and an aromatic vinyl monomer. Of these, aromatic vinyl monomers are preferred. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, and 4-t-butyl. Examples thereof include styrene, 5-t-butyl-2-methylstyrene, N, N-dimethylaminoethylstyrene, N, N-diethylaminoethylstyrene, and the like. Among these, styrene and α-methylstyrene are particularly preferable.

These monomers having an aromatic ring or a heterocyclic ring used for polymerization of the conjugated diene copolymer may be contained alone or in combination of two or more kinds in the monomer composition.
The proportion of the conjugated diene monomer in the monomer composition used for the polymerization of the conjugated diene copolymer is usually 60% by weight or more and less than 99% by weight, preferably 70% by weight or more and less than 97% by weight, more preferably 80% by weight or more and 95% by weight. The range is less than%.
The molecular weight of the conjugated diene copolymer is a weight average molecular weight measured in terms of polystyrene by gel permeation chromatography (GPC) and tetrahydrofuran solvent, and is usually 100 to 500,000, preferably 50,000 to 300,000, more preferably. It is in the range of 100,000 to 200,000.
In the structure of the conjugated diene copolymer used in the present invention, it is preferable that there are more vinyl group-containing side chains derived from the conjugated diene monomer, and the ratio of 1,2 addition in the polymerization of the conjugated diene monomer is usually 80% by weight or more, preferably Is 90% by weight or more, more preferably 95% by weight or more. These vinyl group-containing side chains can be crosslinked by heating in the presence of a radical generator, and heat resistance and mechanical properties can be improved.

(Hydrocarbon radical generator)
The crosslinkable polymer sheet defined in the present invention contains a hydrocarbon radical generator in order to obtain a crosslinked polymer sheet by heating. The hydrocarbon radical generator is a compound that can generate radicals by heating, and consists of carbon atoms and hydrogen atoms. As the hydrocarbon radical generator, those having the structure of formula (A) or formula (B) are preferable.

式（Ａ）中の、Ｒ１、Ｒ２、Ｒ３、Ｒ’１、Ｒ’２、及びＲ’３は、それぞれ独立に水素原子、炭素数１〜１０の鎖状炭化水素基、脂環式炭化水素基、または芳香族炭化水素基を表す。Ｒ１、Ｒ２、及びＲ３の内、少なくとも１つは芳香族炭化水素基であることが好ましい。また、Ｒ’１、Ｒ’２、及びＲ’３の内、少なくとも１つは芳香族炭化水素基であることが好ましい。

In formula (A), R1, R2, R3, R′1, R′2, and R′3 each independently represent a hydrogen atom, a chain hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon. Represents a group or an aromatic hydrocarbon group. At least one of R1, R2, and R3 is preferably an aromatic hydrocarbon group. In addition, at least one of R′1, R′2, and R′3 is preferably an aromatic hydrocarbon group.

式（Ｂ）中の、Ｒ４は芳香族炭化水素基、Ｒ５は水素原子または炭素数１〜１０の炭化水素基を表す。

In the formula (B), R4 represents an aromatic hydrocarbon group, and R5 represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

  Examples of the hydrocarbon radical generator used in the present invention include 2,3-dimethyl-2,3-diphenylbutane, 2,3-diphenylbutane, 1,4-diphenylbutane, and 3,4-dimethyl-3,4. -Diphenylhexane, 1,1,2,2-tetraphenylethane, 2,2,3,3-tetraphenylbutane, 3,3,4,4-tetraphenylhexane, 1,1,2-triphenylpropane, A hydrocarbon compound represented by the formula (A) such as 1,1,2-triphenylethane;

Triphenylmethane, 1,1,1-triphenylethane, 1,1,1-triphenylpropane, 1,1,1-triphenylbutane, 1,1,1-triphenylpentane, 1,1,1- Examples thereof include hydrocarbon compounds represented by the formula (B) such as triphenyl-2-propene, 1,1,1-triphenyl-4-pentene, and 1,1,1-triphenyl-2-phenylethane.
Among these, 2,3-dimethyl-2,3-diphenylbutane and triphenylmethane are preferable.

  These hydrocarbon radical generators may be used alone or in combination of two or more. Controlling the glass transition temperature of the cross-linked polymer obtained by using two or more hydrocarbon radical generators in combination and adjusting the amount ratio thereof, and controlling the molten state at the time of heating makes it easy to form into a predetermined shape. be able to.

  The usage-amount of a hydrocarbon radical generator is 0.1-10 weight part normally with respect to 100 weight part of conjugated diene polymers, Preferably it is 0.5-5 weight part. If the amount of the hydrocarbon radical generator is small, crosslinking may be insufficient, and a crosslinked polymer having a high crosslinking density may not be obtained. When the amount of the hydrocarbon radical generator is large, there is a possibility that a crosslinked polymer having desired physical properties cannot be obtained while the crosslinking effect is saturated.

  In the present invention, the above hydrocarbon radical generator is used as a crosslinking agent. However, the polymer sheet of the present invention may contain a crosslinking agent other than the hydrocarbon radical generator as long as the effects of the present invention are not impaired. . Examples of other crosslinking agents include organic radicals, polar radical generators such as diazo compounds, epoxy compounds, isocyanate group-containing compounds, carboxyl group-containing compounds, and acid anhydride group-containing compounds.

  In the present invention, a crosslinking aid can be used to promote the crosslinking reaction by the hydrocarbon radical generator. The crosslinking aid is not particularly limited as long as it is a compound capable of radical crosslinking with a conjugated diene polymer. For example, dioxime compounds such as p-quinonedioxime; methacrylate compounds such as lauryl methacrylate and trimethylolpropane trimethacrylate; diallyl fumarate And the like; a phthalic acid compound such as diallyl phthalate; a cyanuric acid compound such as triallyl cyanurate; an imide compound such as maleimide; Although the usage-amount of a crosslinking adjuvant is not specifically limited, It is 0-20 weight part normally with respect to 100 weight part of conjugated diene polymers, Preferably it is 0-10 weight part. These crosslinking aids can be used alone, but may be used in combination of two or more.

  In addition to these, the polymer sheet of the present invention may contain a filler, a fiber reinforcing material, a silane coupling agent, a flame retardant and the like depending on the purpose of use.

(filler)
Examples of the filler include glass powder, ceramic powder, and silica.
The amount of the filler can be included in a range of usually 30 to 70% by volume, preferably 40 to 60% by volume in the polymer sheet excluding the fiber reinforcement described later.
By using ceramic powder having a high dielectric constant and silica having a low dielectric constant alone or in combination, the resulting crosslinked polymer sheet maintains a low dielectric loss tangent and a low coefficient of thermal expansion while maintaining a dielectric constant of 3 to 3. It is possible to adjust up to 10. A low dielectric constant is preferable because the propagation speed can be further increased in the high-frequency circuit board. A high dielectric constant is preferable because it can be incorporated as a passive component such as a capacitor.

(Fiber reinforcement)
Although it does not specifically limit as a fiber reinforcement, For example, it selects suitably from fibers, such as glass cloth, a glass cloth, a paper base material, a glass nonwoven fabric, and a heat resistant polyester fiber. By including such heat-stable fiber reinforcements, the mechanical strength of the crosslinked polymer sheet is improved and the coefficient of thermal expansion is reduced, so that the function as an electric circuit board is reduced due to thermal and physical impact. It can be suppressed and is preferable.

(Flame retardants)
The polymer sheet of the present invention can contain a flame retardant. Examples of the flame retardant include phosphorus flame retardants, nitrogen flame retardants, halogen flame retardants, metal hydroxides such as aluminum hydroxide, antimony compounds such as antimony trioxide, and the like. Although a flame retardant may be used independently, you may use it in combination of 2 or more types.

(Polymer sheet)
The polymer sheet of the present invention is produced by impregnating a fiber composition with a polymer composition prepared by mixing the materials listed above and drying, or applying the polymer composition onto a support and drying. can do.
The thickness of the polymer sheet of the present invention is appropriately selected according to the purpose of use, but in a sheet containing a fiber reinforcement, it is usually 0.01 to 10 mm, preferably 0.03 to 1 mm, more preferably 0.05. It is the range of -0.5mm. In the sheet | seat which does not contain a fiber reinforcement, it is 0.001-1 mm normally, Preferably it is 0.01-0.5 mm, More preferably, it is the range of 0.02-0.2 mm.

(Production of polymer sheet)
The polymer sheet of the present invention is produced by the following method. First, a conjugated diene polymer, a hydrocarbon radical generator, a solvent, a filler, and a flame retardant, which are added as necessary, are mixed to produce a polymer composition using a known mixing apparatus.
The solvent can be used to dissolve the polymer when the conjugated diene polymer is solid at room temperature. The solvent is not particularly limited as long as it is a substance that can dissolve the polymer, and examples thereof include toluene, xylene, tetrahydrofuran, N, N-dimethylformamide and the like. The mixing amount is usually 20 to 200 parts by weight, preferably 30 to 100 parts by weight, and more preferably 40 to 80 parts by weight with respect to 100 parts by weight of the solid polymer.
The mixing temperature is usually 1 minute half-life temperature or lower, preferably 10 minutes or more lower than the 1-minute half-life temperature, more preferably 30 degrees C or higher than the 1-minute half-life temperature so that the hydrocarbon radical generator does not decompose. Adjust at low temperature. The 1 minute half-life temperature refers to the temperature at which the radical generator decomposes to half the amount in 1 minute. The mixing time is not particularly limited, but is usually in the range of 1 to 60 minutes, preferably 3 to 30 minutes. When using a filler, it is preferable to continue mixing until the filler is uniformly dispersed throughout the polymer.

In the case of producing a polymer sheet containing a fiber reinforcement, a prepreg production method employed in a conventional electric circuit board can be employed. Usually, a fiber reinforcement is impregnated with the polymer composition, adjusted to a predetermined thickness, and the solvent is removed by heating to form a polymer sheet. The heating temperature is usually not higher than the 1-minute half-life temperature, preferably 10 ° C. or more lower than the 1-minute half-life temperature, more preferably 30 ° C. higher than the 1-minute half-life temperature so that the hydrocarbon radical generator does not decompose. A low temperature range is preferable. These steps may be performed on the support as necessary.
Even when the fiber reinforcing material is not included, the polymer composition can be applied on the support, and the solvent can be removed in the same manner as in the case of using the fiber reinforcing material to obtain a polymer sheet.
Examples of the support used at this time include polymer materials such as polyethylene terephthalate, polypropylene, and polyethylene, and metal materials such as iron, stainless steel, copper, aluminum, nickel, chromium, gold, and silver. The shape is desirably a metal foil or a polymer film. The thickness of these metal foils or polymer films is usually from 1 to 150 μm, preferably from 2 to 100 μm, more preferably from 3 to 75 μm, from the viewpoints of workability and electrical characteristics. The single-sided surface of these supports is preferably smooth. The other surface of the support may be subjected to a roughening treatment as necessary, such as adhesion to a crosslinked polymer sheet.

(Production of cross-linked polymer composite sheet)
The cross-linked polymer composite sheet of the present invention is produced by stacking one or more polymer sheet layers between two supports and heat-pressing the produced polymer sheet, or combining the heat press and heating in an oven. Thus, it can be obtained by crosslinking and molding.
As the support, the metal materials described above can be used.

The temperature of a hot press is 180-350 degreeC normally, Preferably it is 200-300 degreeC, More preferably, it is 220-250 degreeC. The heating time is not particularly limited, but is usually from several minutes to several hours.
Moreover, a press pressure is 0.5-20 Mpa normally, Preferably it is 3-10 Mpa. The heating press may be performed in a vacuum or a reduced pressure atmosphere.

The heating temperature in an oven is 150-250 degreeC normally, Preferably it is 170-230 degreeC. The heating time is not particularly limited, but is usually from several minutes to several hours.
Further, the inside of the oven may be an inert gas atmosphere or a reduced pressure atmosphere.

(Crosslinked polymer sheet)
The crosslinked polymer sheet of the present invention can be obtained by peeling off the support in the crosslinked polymer composite sheet. Examples of the peeling method include a method in which a metal material is chemically dissolved and removed by known etching.

  Examples and Comparative Examples are given below, but the scope of the present invention is not limited to the following Examples.

In this example, evaluation was performed according to the following method.
(Dielectric loss tangent)
The dielectric loss tangent (tan δ) at a frequency of 1 GHz was measured by a capacitance method using an impedance analyzer (manufactured by Agilent Technologies, model number E4991). The dielectric loss tangent was evaluated by the following index according to the value.
E: 0.0055 or more D: 0.0045 or more and less than 0.0055 C: 0.0035 or more and less than 0.0045 B: 0.0025 or more and less than 0.0035 A: 0.0015 or more and less than 0.0025

Example 1
Polybutadiene B3000 (manufactured by Nippon Soda Co., Ltd .; molecular weight 3000), styrene-butadiene-styrene (SBS) block polymer (Kraton D1300; manufactured by Shell), solvent xylene, silica (Minsil5; manufactured by Minco), brominated flame retardant (Saytex BT) -93WFG; manufactured by ALBEMARLE), hydrocarbon radical generator 2,3-dimethyl-2,3-diphenylbutane (Nofmer BC-90; manufactured by NOF Corporation) at a weight ratio shown in Table 1, and polymer A composition was obtained.
A glass cloth (# 1080; manufactured by Clark-Schwebel) was impregnated with the slurry, and the solvent was removed by heating to produce a crosslinkable polymer sheet.
Next, five produced polymer sheets were stacked, sandwiched between two 18 μm thick copper foils, and heated and pressed at 220 ° C. for 2 hours at 3 MPa to obtain a crosslinked polymer composite sheet.
This was cut out into a size of 20 × 20 mm, immersed in a ferric chloride solution at 40 ° C., and the copper foil on the surface was removed. The evaluation results of the produced crosslinked polymer sheet are shown in Table 1.

(Example 2)
A crosslinked polymer sheet was prepared in the same manner as in Example 1 except that 4.1 parts by weight of the hydrocarbon radical generator 2,3-dimethyl-2,3-diphenylbutane was replaced with 6.2 parts by weight of triphenylmethane. Produced. The evaluation results are shown in Table 1.

(Comparative Example 1)
A crosslinked polymer sheet was prepared in the same manner as in Example 1 except that 4.1 parts by weight of the hydrocarbon radical generator 2,3-dimethyl-2,3-diphenylbutane was replaced with 4.1 parts by weight of dicumyl peroxide. Produced. The evaluation results are shown in Table 1.

(Example 3)
A crosslinked polymer sheet was produced in the same manner as in Example 1 except that 349 parts by weight of silica Minsil5 was replaced with 443.3 parts by weight of titania (Ticon HG; manufactured by TAM). The evaluation results are shown in Table 2.

(Comparative Example 2)
A crosslinked polymer sheet was produced in the same manner as in Example 3 except that the hydrocarbon radical generator 2,3-dimethyl-2,3-diphenylbutane was replaced with dicumyl peroxide. The evaluation results are shown in Table 2.

As described above, by changing a material having a polar group to a nonpolar material having a specific function, it is possible to effectively utilize the excellent electrical properties of polybutadiene.
It is also possible to adjust the dielectric constant while satisfying the above characteristics.

Claims (5)

A crosslinkable polymer sheet comprising a conjugated diene polymer and a hydrocarbon radical generator. The crosslinkable polymer sheet according to claim 1, wherein the hydrocarbon radical generator is a hydrocarbon compound having a structure of the formula (A).

(Wherein R1, R2, R3, R′1, R′2, and R′3 each independently represent a hydrogen atom, a chain hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, or Represents an aromatic hydrocarbon group.) The crosslinkable polymer sheet according to claim 1, wherein the hydrocarbon radical generator is a hydrocarbon compound having a structure of the formula (B).

(In the formula, R4 represents an aromatic hydrocarbon group, and R5 represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.) A crosslinked polymer sheet obtained by crosslinking the polymer sheet according to claim 1. A cross-linked polymer composite sheet obtained by cross-linking the polymer sheet according to claim 1 on a support.