JP2003200534A - Fluororesin laminate and method for manufacture thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-melting fluororesin laminate which shows outstanding heat resistance, low moisture absorption characteristics, high dielectric properties, high strength, low linear expansion coefficient and low shrinkage factor and is free from the anisotropy of these physical properties and further, is best-suited as a material for a circuit substrate. <P>SOLUTION: This laminate includes at least two fluororesin sheet layers containing a liquid crystal polymer orientated, in a fibrous fashion, in a heat- melting fluororesin, at least two layers of the fluororesin sheet layers showing a mutually different orientation direction of the liquid crystal polymer. In addition, the laminate is composed of an anisotropic heat-resistant resin sheet and a fluororesin sheet, or the laminate is composed of the heat-melting fluororesin sheet laminated on a woven fabric, a nonwoven fabric or a knitted cloth of the heat-melting fluororesin fiber including the liquid crystal polymer fibrously orientated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminate containing at least one sheet layer in which a liquid crystal polymer is oriented in a fibrous state in a heat-meltable fluororesin. More specifically, the present invention relates to a heat-fusible fluororesin laminate which has a small heat shrinkage and a low dielectric constant at high frequencies and is therefore suitable for circuit board applications.

[0002]

2. Description of the Related Art In the fields of electric and electronic parts, materials having excellent heat resistance, dimensional stability, low hygroscopicity, and high frequency characteristics have been demanded with the miniaturization, high performance and high density of equipment. There is. In particular, circuit boards are strongly required to have high frequency characteristics as information technology advances.

As a base material for a circuit board, a base material in which glass cloth is impregnated with an epoxy resin is mainly used, and a fluororesin copper clad laminate using a fluororesin and polytetrafluoroethylene (PTFE) powder are used. A base material in which a glass cloth is impregnated with the dispersed liquid (for example, JP 20
No. 01-171038), and a laminated body in which a PPS film is thermocompression bonded to a fibrous material containing PTFE as a main component (for example, Japanese Patent No. 3139515).

However, each of the above films and laminates has the following problems. That is, a copper-clad laminate in which glass cloth is impregnated with an epoxy resin is inferior in high frequency characteristics and moisture absorption characteristics, and warpage is often generated due to a difference in thermal expansion coefficient between the substrate and the copper foil. If exposed, plating may not be attached.
In the fluororesin copper-clad laminate, thermal stress strain easily occurs due to the difference in thermal expansion coefficient between the copper foil and the fluororesin, and defects such as peeling of the copper foil occur. Further, the fluorine-based film base material has poor adhesiveness, and there is a problem in that it is difficult to apply paste or plating during printing during circuit formation or metal foil lamination processing or through hole processing. The laminate of the PTFE fibrous material and the PPS film has a small heat shrinkage rate, but is inferior in high frequency characteristics because the PPS film having a higher dielectric constant than the fluororesin is used.

The liquid crystal polymer film has high strength,
It is expected to be used in the field of electronic parts due to its excellent heat resistance, low coefficient of thermal expansion, and high insulation, but when melt-extruded from a die, its molecules are significantly oriented in the extrusion direction,
The obtained film has anisotropy such as tensile strength and linear expansion coefficient in the longitudinal direction (MD direction, alignment direction of liquid crystal polymer) and its perpendicular direction (TD direction, direction perpendicular to the alignment direction of liquid crystal polymer). We could not obtain large and reliable electronic materials and products.

Therefore, after laminating a porous fluororesin film on both surfaces of a liquid crystal polymer film extruded in advance in a film shape, the porous fluororesin film is not melted, but under the temperature condition of melting the liquid crystal polymer film,
There has been proposed a method in which a liquid crystal polymer film is stretched biaxially to improve the anisotropy and a liquid crystal polymer film is used as a circuit board material (JP-A-10-34742). According to this proposal, the liquid crystal polymer molecules are randomly oriented in the plane direction of the laminate to eliminate the anisotropy of physical properties. However, since the liquid crystal polymer has a rigid molecular chain, slips easily between molecular chains, and there is almost no entanglement of each molecular chain, unlike the general biaxial stretching of thermoplastic resins, stretching at a temperature below the melting point is required. It is difficult to do. Further, when the temperature is higher than the melting point, the viscosity suddenly becomes very low, and the liquid flows like a liquid, and stretching cannot be performed. Therefore, it is extremely difficult to align the liquid crystal polymer completely randomly even if the liquid crystal polymer melt is sandwiched between the unmelted porous fluororesin films and stretched biaxially.

[0007]

On the other hand, the inventors of the present invention blended a heat-melting fluororesin with a liquid crystal polymer and formed the liquid crystal polymer into a fibrous state in the heat-melting fluororesin matrix to obtain a heat-melting property. It was previously proposed that the elastic modulus and linear expansion coefficient of the fluororesin be improved (Japanese Patent Laid-Open No. 2001-2001).
-088162). Further, by introducing a fluororesin having a specific functional group (hereinafter sometimes referred to as a compatibilizer), the size and dispersion state of the liquid crystal polymer dispersed phase becomes uniform during the melt mixing process of the fluororesin and the liquid crystal polymer, It has been proposed that the interfacial adhesive force between the fluororesin after molding and the fibrous liquid crystal polymer is improved (JP 2001-1814A).
63).

The present inventors have conducted further studies to find out a circuit board material which does not have the drawbacks as in the prior art by further developing this technology. As a result, they have found that a fluororesin laminate as described below has excellent properties as a circuit board material.

Therefore, an object of the present invention is to provide a fluororesin and a liquid crystal polymer having excellent heat resistance, low hygroscopicity, and high dielectric properties while having a high mechanical strength due to the liquid crystal polymer present in a fibrous state in the fluororesin matrix. It is an object of the present invention to provide a hot-melt fluororesin laminate which exhibits a low linear expansion coefficient and a low thermal shrinkage ratio and is suitable for a circuit board in which the anisotropy of these physical properties is eliminated. Another object of the present invention is to provide a hot-melt fluororesin laminate suitable for a circuit board that can be laminated with a copper foil without an adhesive by a compatibilizer and a liquid crystal polymer.

[0010]

Means for Solving the Problems That is, the present invention provides a laminate comprising a heat-meltable fluororesin layer, at least one layer of which is a fluorine-containing liquid crystal polymer in a fibrous orientation in the heat-meltable fluororesin. The present invention relates to a fluororesin laminate that is a resin sheet layer.

One of the preferred embodiments is a laminate comprising at least two fluororesin sheet layers in which a liquid crystal polymer is oriented in a fibrous state in a heat-meltable fluororesin, at least two of which are provided.
The layer is a fluororesin laminate in which the orientation directions of the fibrous liquid crystal polymer are different from each other, and particularly preferably, the orientation directions of the fibrous liquid crystal polymer are canceled by each other.

Another preferred embodiment is a woven fabric of heat-fusible fluororesin fibers, wherein the fluororesin sheet layer in which the liquid crystal polymer is fibrously oriented in the heat-fusible fluororesin contains the liquid crystal polymer oriented in fibrous form. A fluororesin laminate in which a fibrous sheet layer selected from cloth, non-woven fabric and knitted fabric is laminated with a heat-meltable fluororesin sheet layer containing no fibrous liquid crystal polymer on at least one side of the fibrous sheet. .

The liquid crystal polymer in the fluororesin sheet layer in which the liquid crystal polymer is fibrously oriented in the above heat-meltable fluororesin is preferably blended in a proportion of 0.5 to 30% by weight.

Another preferred embodiment of the present invention has a linear expansion coefficient of 6
A fluororesin laminate in which a fluororesin sheet layer in which a liquid crystal polymer is oriented in a fibrous state in a hot-melt fluororesin is laminated on at least one surface of an isotropic polymer layer having a temperature of × 10 ^-5 / ° C or less. According to this aspect, even if the orientation directions of the fibrous liquid crystal polymers in the heat-fusible fluororesin layers on both sides are the same, anisotropy does not substantially appear as a laminate, so it is necessary to consider the orientation direction. There is a manufacturing advantage that it does not exist.

The fluororesin laminate of the present invention has a heat shrinkage ratio at 250 ° C. of not more than 1.5% and a frequency of 1G.
It is preferable that the dielectric constant at Hz shows a value of 3.0 or less.

In the present invention, the heat-melting fluororesin and the liquid crystal polymer having a melting point of at least 15 ° C. higher than that of the heat-melting fluororesin are melt-mixed and then extruded to form the liquid crystal polymer in the heat-melting fluororesin. Producing a sheet oriented in a fibrous state and laminating a plurality of the obtained sheets, wherein at least two sheets are thermocompression-bonded so that the orientation directions of the fibrous liquid crystal polymer are different. A method of manufacturing a resin laminate is provided.

In the present invention, a fibrous liquid crystal polymer is contained in at least one side of a fiber sheet selected from a woven cloth, a non-woven cloth and a knitted cloth of fluororesin fibers in which a liquid crystal polymer is fibrously oriented in a heat fusible fluororesin. There is provided a method for producing a fluororesin laminate, which comprises stacking heat-fusible fluororesin sheets which are not laminated together and thermocompression-bonding them.

In the present invention, the heat-meltable fluororesin and the liquid crystal polymer having a melting point at least 15 ° C. higher than that of the heat-meltable fluororesin are melt-mixed and then extruded to form the liquid crystal polymer in the heat-meltable fluororesin. Produces a fibrous oriented sheet, at least one of the obtained sheets is superposed on at least one surface of an isotropic polymer sheet having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less, and thermocompression bonded. A method for producing a fluororesin laminate is provided.

In the present invention, the term sheet broadly means a flat product and includes all flat products such as film, woven fabric, non-woven fabric and knitted fabric.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the heat-melting fluororesin used in general molding can be used as the heat-melting fluororesin. It is preferable to use a mixture of this and a heat-meltable fluororesin used for general molding.

The heat-meltable fluororesin used for general molding is already widely known, and includes unsaturated fluorinated hydrocarbons, unsaturated fluorinated chlorinated hydrocarbons and ether group-containing unsaturated hydrocarbons. Polymers or copolymers such as
Alternatively, it is a copolymer of these unsaturated fluorinated hydrocarbons and ethylene. For example, a polymer or copolymer of a monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, perfluoro (alkyl vinyl ether), vinylidene fluoride and vinyl fluoride, or a copolymer of these monomers and ethylene. And so on.

More specifically, tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / hexafluoro. Propylene / perfluoro (alkyl vinyl ether) copolymer (EPE),
Tetrafluoroethylene / ethylene copolymer (ETF
E), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE)
And so on.

As the heat-meltable fluororesin having a functional group, a carboxylic acid group or a derivative thereof, a hydroxyl group, a nitrile group, a cyanato group, a carbamoyloxy group, a phosphonooxy group, a halophosphonooxy group, a sulfonic acid group or a group thereof. Examples thereof include a heat-meltable fluororesin containing a functional group selected from an inducing group and a sulfohalide group (hereinafter sometimes referred to as a functional group-containing fluororesin). Such a functional group-containing fluororesin has a function as a compatibilizing agent, but usually, in the heat-meltable fluororesin used for the general molding, the functional group-containing fluororesin is contained within a range not significantly impairing its properties. What was made to be used. For example, a heat-melting fluororesin as shown in the above-mentioned example used for general molding is synthesized and then introduced by adding or substituting these functional groups, or synthesis of the above-mentioned heat-melting fluororesin. It can sometimes be obtained by copolymerizing monomers having these functional groups.

Specific examples of the functional group include --COOH,
_{-CH 2 COOH, -COOCH 3, -CONH} 2, -
_{OH, -CH 2 OH, -CN,} -CH 2 O (CO) NH
_{2, -CH 2 OCN, -CH 2} OP (O) (OH) 2,
Examples thereof include groups such as —CH ₂ OP (O) Cl ₂ and —SO ₂ F. These functional groups are preferably introduced into the fluororesin by copolymerizing a fluorine-containing monomer having these functional groups during the production of the fluororesin.

Examples of the fluororesin-containing monomer suitable for copolymerization having such a functional group include, for example, the formula CF ₂ ═CF [OCF ₂ CF (CF ₃ )] _m —O—
_{(CF 2)} in n -X [wherein, m is, 0 to 3, n is, 0 to 4, X is, -COO
_{H, -CH 2 COOH, -COOCH 3} , -CH 2 O
_{H, -CN, -CH 2 O (} CO) NH 2, -CH 2 OC
_{N, -CH 2 OP (O)} (OH) 2, -CH 2 OP
_(O) Cl 2, functional group-containing fluorinated Binirue represented by -SO ₂ F, etc.] - is ether compound. The most preferable functional group-containing fluorinated vinyl ether has the formula CF ₂ ═CF—O—CF ₂ CF ₂ —SO ₂ F or the formula CF ₂ ═CF [OCF ₂ CF (CF ₃ )] O ( CF
₂ ) ₂ -Y (In the formula, Y is -SO ₂ F, -CN, -COOH, -C.
OOCH ₃ etc.) or the formula CF ₂ ═CF [OCF ₂ CF (CF ₃ )] O (CF
During _{2) 2} -CH ₂ -Z (wherein, Z is, -COOH, -OH, -OCN, OP
_{(O) (OH) 2,} -OP (O) Cl 2, -O (CO)
NH ₂ etc.) and the like.

The functional group-containing monomer is preferably copolymerized in the functional group-containing fluororesin in an amount of, for example, 0.5 to 10% by weight, particularly 1 to 5% by weight. When the content of the functional group-containing monomer in the functional group-containing fluororesin is too small, the effect as a compatibilizer is small, while when the content of the functional group-containing fluororesin is large, it is similar to the crosslinking reaction due to the strong interaction between the functional group-containing fluororesins. The reaction may occur, and the viscosity may suddenly increase, making it difficult to perform melt molding. Moreover, when the content ratio of the functional group-containing monomer increases, the heat resistance of the functional group-containing fluororesin deteriorates.

The viscosity or molecular weight of the functional group-containing fluororesin is not particularly limited, but it does not exceed the viscosity or molecular weight of the heat-meltable fluororesin for general molding containing the functional group-containing fluororesin. The same level is preferable.

The liquid crystal polymer used in the present invention is a thermoplastic resin forming a thermotropic liquid crystal, and the melting point of the liquid crystal polymer is not particularly limited as long as there is no problem in heat resistance at the melt molding temperature. However, from the viewpoint of moldability and thermal stability, the melting point of the heat-meltable fluororesin for molding is 1
It is preferable to use one having a high melting point of 5 ° C. or higher.

Examples of such liquid crystal polymers include polyesters, polyesteramides, polyesterimides and polyesterurethanes, with polyester being most preferred. A typical example of the liquid crystal polyester is a wholly aromatic polyester, and a great number are already known. For example, those derived from an aromatic dicarboxylic acid and an aromatic dihydroxy compound and / or an aromatic hydroxycarboxylic acid, and a part of them is derived from an aliphatic dicarboxylic acid, an aliphatic dihydroxy compound, an aliphatic hydroxycarboxylic acid, etc. It may be substituted with a polymerized unit. More specifically, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and 2,6-naphthalene dicarboxylic acid, hydroquinone, resorcin, 2,6-dihydroxynaphthalene, bisphenol A, aromatic dihydroxy compounds such as dihydroxydiphenyl, para. Examples thereof include those having a polymerized unit derived from an aromatic hydroxycarboxylic acid such as hydroxybenzoic acid.

In the present invention, one method for producing a fluororesin sheet in which a liquid crystal polymer is fibrously oriented in a heat fusible fluororesin is one of the above-mentioned hot-melting fluororesins for general molding and liquid crystal polymers, preferably In this method, a functional group-containing fluororesin is melt-mixed and extrusion-molded under appropriate conditions to form a sheet. In forming the fluororesin sheet, the compounding ratio of the latter functional group-containing fluororesin (compatibilizer) is slightly different depending on the kind of the functional group and the functional group content, but is 0.5 to 30% by weight of the resin raw material, Particularly, it is preferable to set the content to about 1 to 15% by weight. That is, the greater the blending ratio of the compatibilizer, the more fluororesin /
The surface tension between the liquid crystal polymers becomes low and the interfacial adhesion becomes strong, but if a too large amount is blended, a strong interaction between the compatibilizers may cause a reaction similar to the crosslinking reaction. However, it may be difficult to perform melt molding. Further, if the content ratio of the functional group-containing fluororesin is too large, the heat resistance of the fluororesin sheet will be deteriorated.

The blending ratio of the liquid crystal polymer in the resin raw material is preferably adjusted so that the liquid crystal polymer is 0.5 to 30% by weight, particularly 3 to 25% by weight. That is, if the compounding amount of the liquid crystal polymer is too small, a sufficient reinforcing effect cannot be expected. On the other hand, if the blending ratio is too high, a large amount of continuous fibrous liquid crystal polymer exists in the fluororesin matrix, and the viscosity suddenly decreases locally during the sheet extrusion process, making it impossible to form a sheet of uniform thickness. Sometimes.

The compatibilizer and the liquid crystal polymer each have an effect of improving the adhesive strength to a metal such as copper foil,
By adjusting the addition amount of each, it can be made suitable as a laminate for electric and electronic parts.

The thermomeltable fluororesin and the functional group-containing fluororesin, which are the raw materials of the fluororesin sheet of the present invention, and the thermoplastic liquid crystal polymer can be mixed by a usual melt mixing method, but an extruder is used. At that time, a higher shear rate is preferable because the size of the liquid crystal dispersed phase becomes smaller, and it is preferable to use a twin-screw extruder rather than a single-screw extruder. Further, in a sheet extrusion process using a T die or an annular die after melt mixing, in order to obtain a fibrous liquid crystal polymer having a more uniform size in the fluororesin matrix, in the melt mixed state before sheet extrusion, The particle size of the liquid crystal polymer is 30 μm or less, preferably 1 to 10 μm
It is desirable to set it to about m.

A thermoplastic liquid crystal polymer is oriented in a fibrous form from a mixture of the above-mentioned heat-meltable fluororesin for general molding and a thermoplastic liquid crystal polymer, preferably a functional group-containing fluororesin (hereinafter sometimes referred to as fluororesin mixture). In order to obtain the above-mentioned fluororesin sheet, the fluororesin mixture can be obtained by extruding the fluororesin mixture into a sheet using a T die, an annular die or the like. During this extrusion process, the particles of the liquid crystal polymer dispersed in the fluororesin matrix are transformed into fibers. In order to uniformly form the dispersed phase of the liquid crystal polymer in the fluororesin matrix during the sheet extrusion process, the extrusion temperature is preferably from the melting point of the liquid crystal polymer used to about 20 ° C. higher.

The diameter of the liquid crystal polymer existing in a fibrous state in the fluororesin matrix of the heat-meltable fluororesin sheet extruded by a T-die or the like depends on the size and melting of the liquid crystal phase dispersed in the melt mixture before extruding the sheet. It can be controlled by the draft ratio (die lip clearance / thickness of the film after removal) in the extrusion process. The smaller the size of the liquid crystal dispersed phase in the molten mixture before sheet extrusion or the faster the take-up speed, the smaller the diameter of the fibrous liquid crystal polymer. Draft ratio is 5 or more, especially 10
A range of 200 is preferred. The thickness of the extruded sheet is 10
˜1000 μm, preferably 20 to 400 μm. The fibrous liquid crystal polymer has a diameter of 30
It is preferable to set the aspect ratio to 10 μm or less, particularly 20 μm or more, as well as to 1 μm or less, particularly 1 to 10 μm.

The fluororesin laminate of the present invention is prepared by using at least one extruded sheet as described above,
Can be formed. That is, a plurality of extruded sheets in which a liquid crystal polymer is oriented in a fibrous state in a heat-meltable fluororesin can be constituted, and one or more extruded sheets and such a fibrous liquid crystal polymer are contained. It may be composed of one or more heat-fusible fluororesin sheets. Furthermore, the linear expansion coefficient of the extruded sheet other than 1 or 2 or more and the heat-meltable fluororesin is 6 × 10 ^−5.
It may be composed of one or two or more polymer layers having a temperature of / ° C or lower.

In order to manufacture the laminate of the present invention from a plurality of the above-mentioned extruded sheets, a method of laminating a plurality of these and thermocompression bonding may be adopted. In the extruded sheet, since the liquid crystal polymer is mainly oriented in the stretching direction (MD direction), M
Large anisotropy of physical properties remains in the D direction and the TD direction. Therefore, in this method, for the purpose of eliminating the anisotropy of physical properties, two extruded sheets are stacked so that the orientation directions of the liquid crystal polymers are orthogonal to each other (two-layer thermocompression bonding), or
It is preferable to employ a method of thermocompression bonding (multilayer thermocompression bonding) by laminating three or more layers while arbitrarily changing the angle.

The thermocompression bonding for producing the laminate is performed by stacking a plurality of the extruded sheets and using a heating roll, a press, a hot plate press or the like. At this time, the thickness of the laminate can be adjusted by adjusting the distance between the rolls and the press. The thermocompression bonding temperature needs to be higher than the melting point of the fluororesin and lower than the melting point of the liquid crystal polymer. When the thermocompression bonding temperature is higher than the melting point of the liquid crystal polymer, the liquid crystal polymer fibers oriented in the extruded sheet are melted and do not show a fiber structure, which is not preferable. Further, if the thermocompression bonding temperature becomes lower than the melting point of the fluororesin, it becomes impossible to perform thermocompression bonding between the extruded sheets. Therefore, the thermocompression bonding temperature depends on the types of the fluororesin and the liquid crystal polymer to be used, but the temperature is higher than or equal to the melting point of the fluororesin, preferably about 2 to 30 ° C. higher than the melting point, and 10 or more lower than the melting point of the liquid crystal polymer. Is preferred. Further, when the extruded sheets are thermocompression-bonded to each other, there are two-layer pressure-bonding and multi-layer pressure-bonding in which the orientation directions of the liquid crystal polymer fibers of three or more extruded sheets are arbitrarily changed and superposed in order. The latter is preferable from the viewpoint of shrinkage. In this multilayer pressure bonding, it is preferable to stack the extruded sheets so that the laminate as a whole exhibits isotropic properties. Furthermore, it is also possible to superimpose a heat-meltable fluororesin sheet containing no fibrous liquid crystal polymer on one or both sides of the extruded sheets that have been superposed and to perform thermocompression bonding. Further, the order of the extruded sheet and the heat-meltable fluororesin sheet may be arbitrarily changed to perform thermocompression bonding. The layered product may have a thickness of, for example, about 20 to 2000 μm, preferably about 50 to 1000 μm, although it depends on the application.

In the laminate thus obtained, the fiberized liquid crystal polymer is oriented in one direction in each extruded sheet, but the orientation is mutually in the entire laminate in which the sheets are superposed. It can be adjusted so that it is counteracted and isotropic. Therefore, the heat-fusible fluororesin laminate according to the present invention has a low linear expansion coefficient and a thermal shrinkage ratio which cannot be achieved by the conventional fluororesin sheet, and at the same time has a high tensile elastic modulus. Further, since the fluororesin having a relatively lower dielectric constant than the liquid crystal polymer is present in the matrix, the dielectric constant of the sheet becomes lower than that when a pure liquid crystal polymer sheet is used (for example, Japanese Patent Laid-Open No. 10-34742).

In the fluororesin laminate obtained by laminating the extruded sheets as described above, since liquid crystal polymer fibers are present even near the sheet surface, streaks appear in the MD direction of the sheet, resulting in uneven thickness. There is. Streaks and uneven thickness in the fluororesin sheet are extremely difficult to use as a circuit board material. In order to prevent the deterioration of the surface state due to such streaks and thickness unevenness, the temperature and pressure in the thermocompression bonding process are controlled, or one side or both sides of the fluororesin laminate is used as a general-use heat-meltable fluororesin sheet or functional sheet. It is also possible to stack the group-containing fluororesin sheets and thermocompress them to form a laminate. The heat-meltable fluororesin sheet for general molding or the functional group-containing fluororesin sheet used for such purpose may have a thickness of, for example, about 10 to 500 μm.

Further, for the purpose of improving the surface peel strength between the fluororesin laminate and the copper foil by laminating the extruded sheet as described above, a fluororesin sheet containing a functional group or a liquid crystal is provided on one side or both sides of the fluororesin laminate. A sheet made of a blend of a polymer and a fluorocarbon resin containing a functional group may be laminated and thermocompression bonded to form a laminate. The functional group-containing fluororesin sheet or the sheet made of a blend of the liquid crystal polymer and the functional group-containing fluororesin used for such purpose is, for example, 200 μm or less, preferably 100 μm or less.
It is possible to use one having a thickness of not more than μm.

The fluororesin laminate of the present invention also comprises one or more extruded sheets in which the liquid crystal polymer is oriented in a fibrous state in the heat-meltable fluororesin and the heat-meltable fluororesin. Can be composed of one or two or more polymer layers having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less. In particular, when an isotropic sheet layer such as a biaxially stretched product is used as such a polymer layer, the influence of the orientation direction of the fibrous liquid crystal polymer constituting the extruded sheet is small, and the substantially isotropic fluororesin is used. There is an advantage that a laminated body can be easily obtained.

The above polymer has a linear expansion coefficient of 6 ×.
10 ⁻⁵ / ° C. or lower, preferably 5 × 10 ⁻⁵ / ° C. or lower,
It is more preferably 3 × 10 ⁻⁵ / ° C. or less. More specifically, the liquid crystal polymer introduced as the fibrous liquid crystal polymer material, polysulfone, amorphous polyarylate, polyphenylene sulfide, polyether sulfone, polyether imide, polyamide imide, polyether ether ketone, polyimide and the like are exemplified. be able to. When such a polymer sheet layer is used, it is preferable that the heat-fusible fluororesin resin layer is arranged on both sides of the polymer sheet layer, and at least one of them is the extruded sheet layer. In this case, the thickness of the polymer sheet layer is, for example, 1
0 to 1000 μm, preferably about 20 to 400 μm, and the entire laminate has, for example, 20 to 2000 μm,
The thickness can be preferably about 50 to 1000 μm. Also in this case, the adhesive strength with the copper foil can be increased by using the extruded sheet layer as described above or by using a functional group-containing heat-fusible fluororesin.

As another method of obtaining the fluororesin laminate of the present invention, instead of using the extruded sheet in which the liquid crystal polymer is oriented in a fibrous state as described above, heat fusion containing a liquid crystal polymer oriented in a fibrous state is used. Woven woven fluororesin fiber,
There is a method of using a fiber sheet such as a non-woven fabric or a knitted fabric.
The hot melt fluororesin fiber containing the liquid crystal polymer oriented in a fibrous state can be produced by using the same raw material as the above extruded sheet and extruding into a fibrous state under similar molding conditions. . For details of this method, see JP-A-2001-88162 and JP-A-2001-18.
It is also disclosed in each publication of No. 1463. In this case, the fiber diameter is preferably about 5 to 1000 μm,
It is preferable that the fibrous liquid crystal polymer has a diameter of 30 μm or less, particularly about 1 to 10 μm, and an aspect ratio of 40 or more, preferably 80 or more. Further, as the fibrous sheet, for example, one having a thickness of 10 to 1000 μm, particularly 30 to 500 μm can be used.

The fibrous liquid crystal polymer in the heat-meltable fluororesin fiber containing the liquid crystal polymer oriented in a fibrous state is oriented in the length direction, and this is processed into a fiber sheet such as a non-woven fabric, a woven fabric or a knitted fabric. By doing so, an isotropic fiber sheet can be obtained as a whole. Further, by laminating a heat-melting fluororesin sheet for general molding or a functional group-containing fluororesin sheet on one side or both sides of such a fiber sheet, the fluororesin laminate of the present invention can be obtained.
The laminated body in this case is, for example, 20 to 2000 μm, and preferably 50 to 200, like the laminated body from the extruded sheet.
The thickness can be about 1000 μm. To manufacture a fiber sheet such as a woven fabric, a non-woven fabric, or a knitted fabric from a heat-meltable fluororesin fiber containing a fibrous liquid crystal polymer, a known technique for producing a fiber sheet from ordinary fibers is applied correspondingly. be able to.

Any layer of the fluororesin laminate of the present invention may be blended with any additive as required. Examples of such additives include antioxidants, light stabilizers, antistatic agents, optical brighteners, colorants, and metal oxides such as silica, alumina and titanium oxide; metals such as calcium carbonate and barium carbonate. Carbonate; calcium sulfate,
Metal sulfates such as barium sulfate; silicates such as talc, clay, mica and glass, inorganic fillers such as potassium titanate, calcium titanate and glass fiber, organic fillers such as carbon black, graphite and carbon fiber Materials and the like.

The fluororesin laminate of the present invention as described above has a heat shrinkage ratio at 250 ° C. of 1.5% or less,
It is possible to adjust the dielectric constant to 1.2% or less, and the dielectric constant at a frequency of 1 GHz to 3.0 or less, preferably 2.1 to 2.9, and more preferably 2.1 to 2.6. Is. Further, the difference between the heat shrinkage ratio at 250 ° C. in the longitudinal direction and that in the lateral direction can be adjusted to 10% or less, preferably substantially 0%.

[0048]

EXAMPLES The present invention will be described below with reference to examples.

<Experiment 1> Thermofusible fluororesin PFA (PFA 340 manufactured by Mitsui DuPont Fluorochemicals, melting point 308 ° C., melt flow rate (372 ° C., 5000 g
Load) 14g / 10min) and liquid crystal polymer (DuPont Z
(enite 7000, melting point 353 ° C.) is thoroughly dried, and then tetrafluoroethylene, perfluoro (propyl vinyl ether) (PPVE) and CF ₂ ═CF [O
CF ₂ CF (CF ₃ )] OCF ₂ CF ₂ CH ₂ OH 3
Melt blended with a compatibilizing agent (PPVE content 3.7% by weight, hydroxyl group-containing monomer content 1.1% by weight, melt flow rate 15 g / 10 min), which is an original copolymer, in a twin-screw extruder (resin temperature A fluororesin mixture was made. The liquid crystal polymer was added in an amount of 20% by weight and the compatibilizer was added in an amount of 2.5% by weight.

The fluororesin mixture formed into pellets is
Melted with a 30 mm single-screw extruder, T-die (lip length 20
0mm, lip clearance 2mm, die temperature 365
(° C.) was used to obtain a fluororesin sheet in which a liquid crystal polymer having a thickness of 100 μm was oriented in a fibrous shape (Sample S
1).

<Experiments 2 and 3> The mixing ratio of the liquid crystal polymer was 1
Fluororesin sheet samples S2 and S3 were obtained by the same procedure as in Experiment 1 except that the content was 0% by weight and 3% by weight. The obtained fluororesin sheet was cut at a right angle to the orientation direction of the fibrous liquid crystal polymer in liquid nitrogen to prepare a fracture surface, and an electron microscope (SE
The results observed in M) are shown in FIGS. 1 and 2.

<Examples 1 to 3> Two fluororesin sheet samples (Samples S1, S2 and S3) obtained in Experiments 1 to 3 were laminated so that the orientation directions of the fibrous liquid crystal polymers were orthogonal to each other. Hot plate press (temperature 325 ° C, pressure 3M
After thermocompression bonding at (Pa), it was cooled to produce a fluororesin laminate having a thickness of 180 μm, and samples S4, S5 and S6 were obtained.

Example 4 A fluororesin mixture obtained by melt blending a mixture having the same composition as in Experiment 3 with a twin-screw extruder was used.
Using a 0 mm single-screw extruder (L / D: 25), a pore size of 2.
A cross sheet of monofilament (diameter 80 μm), which was drawn from a spinning die with 8 mm and 6 holes at a spinning temperature of 365 ° C. with a take-off roller at a speed of 300 m / min, and a plain weave with a density of 45 (pieces / 25 mm). (Thickness 1
60 μm) was produced. Also, after making a functional group-containing PFA (compatibilizer used in Experiment 1) sheet having a thickness of 50 μm by the hot plate press used in Example 1, the functional group-containing PFA sheet was superposed on both sides of the cross sheet, After thermocompression bonding with a hot plate press (temperature 325 ° C., pressure 3 MPa), cooling was performed to impregnate the cross sheet with the functional group-containing PFA to prepare a laminate having a thickness of 230 μm, and sample S7 was obtained.

<Example 5> Two fluororesin sheets produced by the same procedure as in Experiment 2 were stacked so that the orientation directions of the fibrous liquid crystal polymer were orthogonal to each other, and then two sheets were produced by the same procedure as in Example 4. The functional group-containing PFA sheet of
A sheet / fluororesin sheet / fluororesin sheet / functional group-containing PFA sheet were laminated so as to have a laminated structure and thermocompression bonded by a hot plate press (temperature 325 ° C., pressure 3 MPa), and then cooled to a thickness of 250 μm. A fluororesin laminate was prepared and a sample S8 was obtained.

Example 6 A fluororesin mixture having the same composition as in Experiment 2 was extruded with a 30 mm single-screw extruder, and a T-die (lip length 200 mm, lip clearance 2 mm,
A die temperature of 365 ° C.) was used to obtain a fluororesin sheet in which a liquid crystal polymer having a thickness of 25 μm was oriented in a fibrous shape. The resulting fluororesin sheet sample was laminated with six sheets so that the orientation directions of the fibrous liquid crystal polymer were orthogonal to each other, and thermocompression bonded with a hot plate press (temperature 325 ° C., pressure 3 MPa), and then cooled to a thickness. A fluororesin laminate having a thickness of 150 μm was produced and a sample S9 was obtained.

<Example 7> Thickness 5 obtained by the biaxial stretching method
A thickness of 25 μm formed by the same procedure as in Example 6 above and below a 0 μm liquid crystal polymer (Zenite 7000) sheet.
After the fluororesin sheets in which the liquid crystal polymer of m is oriented in a fibrous state are superposed so that the orientation directions of the fibrous liquid crystalline polymer are in the same direction, and thermocompression bonding is performed with a hot plate press (temperature 325 ° C., pressure 3 MPa). , Cooled to a thickness of 100 μm
The laminated body of was produced and the sample S10 was obtained.

<Example 8> A 1 mm-thick laminate in which fluororesin sheets prepared in the same procedure as in Experiment 1 were laminated and a copper foil were thermocompression bonded by a hot plate press (temperature 325 ° C, pressure 3 MPa). A peel test piece was prepared.

<Example 9> A thickness of 1 mm prepared by the same procedure as in Example 8 except that the amount of the liquid crystal polymer was reduced to 10% by weight and the amount of the functional group-containing PFA was increased to 10% by weight.
The fluororesin laminate and the copper foil were thermocompression bonded with a hot plate press to prepare a peel test piece.

Example 10 A peeling test piece was prepared by thermocompression bonding a 1 mm-thick laminate having a fluororesin sheet produced by the same procedure as in Experiment 3 and a copper foil with a hot plate press.

<Reference Example 1> PFA resin (PFA 34
0) was compression-molded into a sheet with a hot plate press (temperature: 350 ° C., pressure: 6 MPa), and then cooled to a P thickness of 200 μm.
An FA sheet was prepared and a sample R1 was obtained.

<Reference Example 2> Liquid crystal polymer (Zenite
7000) was compression molded into a sheet with a hot plate press (temperature: 360 ° C.) and then cooled to produce a sheet having a thickness of 200 μm, and a sample R2 was obtained.

<Reference Example 3> PFA of Reference Example 1 (PFA3
40) A peeling test piece was prepared by thermocompression bonding a 1 mm-thick laminated body of sheets and a copper foil with a hot plate press.

The physical properties of each heat-meltable fluororesin sheet and its laminate obtained as described above were measured by the following methods, and the results are shown in Tables 1 and 2 and FIGS. 1 and 2. Samples S1 and S
2, liquid crystal polymer fibers are oriented in one direction in S3,
Since the physical properties are anisotropic, physical properties in both MD / TD directions were measured. In Samples S4 to S6 and Samples S8 to S9, the liquid crystal polymer fibers are fluororesin sheets laminated above and below and are oriented at right angles to each other, and in Sample 10, a biaxially stretched isotropic liquid crystal polymer sheet. for,
The physical properties in both MD / TD directions were measured, but no difference in the measured values in both directions was observed. The results (heat shrinkage rate, tensile elastic modulus) measured along one of the directions are shown in Table 1. Table 2 shows the peel strength test results of the peel test pieces.

(1) A heat shrinkage sheet or a laminate is placed in the MD direction and the TD direction by 100%.
Cut out into 10 mm × 10 mm and read the length in the longitudinal direction with an optical microscope. Next, the sample was put in a constant temperature bath at 250 ° C. for 30 minutes and then taken out, and the length in the longitudinal direction was similarly measured.
The heat shrinkage rate of each sample was calculated by the following formula. For the measurement, three samples were measured and the average thereof was used as the measured value. Heat shrinkage ratio = ((length before heating−length after heating) / length before heating) × 100

(2) The dielectric constant of the dielectric constant sheet or laminate was measured at a frequency of 1 GHz by the resonator method. (Measured according to JIS-C-6481.)

(3) Tensile Elastic Modulus According to JIS-K-7127, tensile speed 50 mm /
Measured in minutes.

(4) Peel Strength A PFA laminate or a fluororesin laminate and a copper foil having a thickness of 0.1 mm were thermocompression-bonded with a hot plate press (temperature 325 ° C., pressure 3 MPa) to obtain a 1 cm-wide peel test piece. The strength of the prepared test piece when peeled off at a speed of 50 mm / min by the 180 ° method according to JIS C5016 (kg
/ Cm) was measured.

[0068]

[Table 1]

[0069]

[Table 2]

From Table 1, in the fluororesin sheets S1, S2 and S3 extruded by the T-die (Experiments 1 to 3), the heat shrinkage ratio and the tensile elastic modulus are improved as the mixing ratio of the liquid crystal polymer is increased. Since the liquid crystal polymer fibers are oriented in one direction, anisotropy appears in the physical properties. Further, from FIG. 1 and FIG. 2, in the sample S2 (Experiment 2) containing 10% by weight of the liquid crystal polymer, the liquid crystal polymer oriented in a fibrous state was observed in the entire cross section of the sheet. In the sample S3 (Experiment 3), the liquid crystal polymer fibers oriented in a fibrous state were not sufficient. Therefore, the mixing ratio of the liquid crystal polymer is particularly preferably in the range of 3 to 25% by weight, though it depends on the extrusion conditions with the T die. Further, when the liquid crystal polymer is mixed with the fluororesin, the dielectric constant is slightly increased, but the sample S1 containing 20% by weight of the liquid crystal polymer is prepared.
(Experiment 1) also shows that the dielectric constant is 2.6, which is suitable for a high frequency compatible circuit board material.

In order to eliminate the anisotropy of the physical properties of the extruded fluororesin sheet sample with the T-die, two fibrous liquid crystal polymers were superposed so that the orientation directions thereof were orthogonal to each other, and thermocompression-bonded by a hot plate press. Also in the body samples (Examples 1 to 3), the thermal contraction rate and the tensile elastic modulus were improved with the increase of the mixing ratio of the liquid crystal polymer, and the anisotropy of the physical properties in the MD and TD directions was almost eliminated. From Example 1, the amount of liquid crystal polymer was 2
When it is 0% by weight or more, the heat shrinkage can be 1% or less. In addition, a sample using a fluororesin cloth sheet instead of the extruded fluororesin sheet with the T-die (Example 4) also had a heat shrinkage ratio and tensile elasticity with respect to the pure fluororesin sheet (Reference Example 1). The rate is improving.

A sample in which the fluororesin sheet and the functional group-containing PFA sheet were superposed in the order of the functional group-containing PFA sheet / fluororesin sheet / fluororesin sheet / functional group-containing PFA sheet and thermocompression bonded by a hot plate press (implementation In Example 5), since two more functional group-containing PFA sheets were thermocompression bonded to the sample obtained in Example 2, the heat shrinkage rate and the tensile elastic modulus were inferior to those in Example 2, but the dielectric properties were better. . As can be seen from FIG. 1, in a fluororesin sheet in which a liquid crystal polymer is oriented in a fibrous state, since fibers of the liquid crystal polymer are present even near the sheet surface, streaks appear in the MD direction of the sheet and uneven thickness occurs. Sometimes. Streaks and uneven thickness in the fluororesin sheet are extremely difficult to use as a circuit board material. The prescription as in Example 5 is effective for the purpose of solving the deterioration of the surface state due to such streaks and uneven thickness. Further, in Example 5, since the functional group-containing PFA sheets are laminated on both sides, improvement in peel strength from the copper foil can be expected.

The composition was the same, but two-layer thermocompression bonding (Example 2, X
In the sample in which the six fluororesin sheets in which the liquid crystal polymer is oriented in a fibrous state instead of (in the / Y direction) are orthogonal to each other (Example 6, X / Y / X / Y / X / Y direction), a laminate is obtained. Since the orientation directions were more canceled by each other as a whole, the heat shrinkage rate was lower than that in Example 2. Therefore, from the viewpoint of isotropic property of physical properties, the fluororesin laminate has 2
Multilayer laminates such as 4, 6 and 8 layers are preferred over layer laminates. Further, in the sample (Example 7) in which the fluororesin sheets in which the liquid crystal polymer is oriented in a fibrous state were thermocompression bonded to the upper and lower sides of the liquid crystal polymer sheet obtained by the biaxial stretching method (Example 7), the thermal contraction rate and elastic modulus due to the liquid crystal polymer sheet Improvement is seen.

From the peel strength test results in Table 2, the peel strength of the sample using PFA (Reference Example 3) is low, but the peel strength of the sample containing the compatibilizer and the liquid crystal polymer is improved. . Particularly in Example 9, a synergistic effect on the peel strength between the compatibilizer and the liquid crystal polymer is observed. Therefore, it is effective to increase the amount of the compatibilizer or the liquid crystal polymer so that there is no large difference in the mixing ratio, in order to improve the peel strength. Thus, the fluororesin laminate of the present invention in which the compatibilizing agent and the liquid crystal polymer are mixed with the fluororesin can be expected to have sufficient adhesive strength with the copper foil without the adhesive layer.

[0075]

According to the present invention, an isotropic fluororesin laminate can be provided. For example, in a mode in which a plurality of fluororesin sheets in which a liquid crystal polymer is oriented in a fibrous state are laminated in a hot melt fluororesin, the fibrous liquid crystal polymer is oriented in one direction in one extruded sheet. However, it is possible to stack the laminated bodies so that the orientation directions thereof are canceled by each other so as to show isotropic properties. Therefore, it is possible to provide a fluororesin laminate having a reduced linear expansion coefficient and a thermal contraction rate which cannot be achieved by a conventional fluororesin sheet, and at the same time, has an increased tensile elastic modulus and a low dielectric constant. You can

The fluororesin laminate of the present invention having such characteristics is suitable as a circuit board material. In addition to circuit boards, it can be expected to be used in the fields of insulating sheets such as transformers and motors, heat resistant sheets, prepreg base materials, and packaging materials.

[Brief description of drawings]

FIG. 1 is a micrograph of a fracture surface of a heat-meltable fluororesin sheet obtained in Experiment 2.

FIG. 2 is a micrograph of a fracture surface of the heat-meltable fluororesin sheet obtained in Experiment 3.

Continued front page    F term (reference) 4F100 AK01A AK01B AK17A AK17B                       AK17C AL05A AL05B AS00A                       AS00B AS00H BA02 BA03                       BA07 BA10A BA10C BA16                       BA22 CA23A CA23B DG01A                       DG01B DG01H DG11A DG11B                       EC032 EH171 EJ172 EJ422                       GB15 GB41 GB43 JA02A                       JA02B JA03 JA04A JA04B                       JA04C JG05 JK02 JK07                       YY00 YY00A YY00B                 4F213 AA16 AC07 AD16 AG01 AG03                       AH36 WA06 WA15 WA53 WA63                       WA84 WA90 WB01

Claims (14)

[Claims] 1. A fluororesin laminate comprising a heat-meltable fluororesin layer, at least one layer of which is a fluororesin sheet layer in which a liquid crystal polymer is fibrously oriented in a heat-meltable fluororesin. . 2. A laminate comprising two or more fluororesin sheet layers in which a liquid crystal polymer is fibrously oriented in a heat-meltable fluororesin, wherein at least two layers of the fibrous liquid crystal polymer have mutually oriented directions. Claim 1 characterized in that they are different.
The fluororesin laminate described. 3. A woven fabric, a non-woven fabric and a knit of a heat-meltable fluororesin fiber, wherein the fluororesin sheet layer in which a liquid crystal polymer is fibrously oriented in a heat-meltable fluororesin contains a liquid crystal polymer oriented in a fibrous form. The fluororesin laminate according to claim 1, which is a fiber sheet layer selected from cloth. 4. The content of the liquid crystal polymer is in the range of 0.5 to 30% by weight in the fluororesin sheet layer in which the liquid crystal polymer is fibrously oriented in the heat-meltable fluororesin. Fluorine resin laminate. 5. A heat fusible fluororesin sheet layer containing no fibrous liquid crystal polymer is laminated on at least one surface of a fluororesin sheet layer in which a liquid crystal polymer is fibrously oriented in at least one heat fusible fluororesin. Claim 1
The fluororesin laminate according to any one of claims 1 to 4. 6. The fluororesin laminate according to claim 1, wherein at least a part of the heat-fusible fluororesin is a functional group-containing fluororesin. 7. The fluororesin laminate according to claim 1, which has a polymer layer having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less in addition to the heat-meltable fluororesin layer. 8. A fluororesin sheet layer in which a liquid crystal polymer is fibrously oriented in a heat-meltable fluororesin is laminated on at least one surface of a polymer layer having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less. Item 7. A fluororesin laminate according to item 7. 9. The fluororesin laminate according to claim 7, wherein the polymer layer having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less is an isotropic layer. 10. A liquid crystal polymer in a heat-meltable fluororesin on both surfaces of a polymer layer having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less.
10. The fluororesin laminate according to claim 9, wherein the fluororesin sheet layers having a fibrous orientation are laminated, and the orientation directions of the fibrous liquid crystal polymer in the fluororesin sheet layers on both sides are the same. 11. The fluororesin laminate according to claim 1, which has a thermal shrinkage at 250 ° C. of 1.5% or less and a dielectric constant at a frequency of 1 GHz of 3.0 or less. 12. A meltable fluororesin and a liquid crystal polymer having a melting point of at least 15 ° C. higher than that of the meltable fluororesin are melt-mixed and then extruded to form a fibrous liquid crystal polymer in the meltable fluororesin. An oriented sheet is produced, and a plurality of the obtained sheets are superposed, and at least two of them are thermocompression-bonded so that the orientation directions of the fibrous liquid crystal polymer are different from each other. Alternatively, a method for producing the fluororesin laminate according to any of 4 to 6. 13. A heat-melting property in which a fibrous liquid crystal polymer is not contained on at least one surface of a fiber sheet selected from a woven fabric, a non-woven fabric or a knitted fabric of a fluororesin fiber in which a liquid crystal polymer is fibrously oriented in a heat-meltable fluororesin. The method for producing a fluororesin laminate according to claim 1 or 3 to 6, wherein fluororesin sheets are superposed and thermocompression bonded. 14. A hot melt fluororesin and a liquid crystal polymer having a melting point at least 15 ° C. higher than that of the hot melt fluororesin are melt-mixed and then extruded to form a fibrous liquid crystal polymer in the hot melt fluororesin. Characterized in that an oriented sheet is produced, at least one of the obtained sheets is superposed on at least one surface of an isotropic polymer sheet having a linear expansion coefficient of 6 × 10 ⁻⁵ / ° C. or less, and thermocompression-bonded. The method for producing the fluororesin laminate according to claim 7.