JP2005200542A - Adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet which has a thin and yet sufficiently strong adhesive layer, is excellent in heat resistance and fusibility and exhibits a low hygroscopicity. <P>SOLUTION: The adhesive sheet is used for bonding two sheet-like materials, composed of a laminate in which bondable fluoro resin films are laminated and fused on both the sides of a stretched porous polytetrafluoroethylene sheet. The bondable fluoro resin film is a blend of (A) a fluoro resin having an adhesive functional group, (B) a liquid crystal polymer resin and (C) a fluoro resin not having an adhesive functional group. The bondable fluoro resin film is integrated with the stretched porous polytetrafluoroethylene sheet, stretched at least in one direction and has a thickness of ≤50 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention provides an adhesive sheet used as an adhesive material having excellent heat resistance, low moisture absorption, and low dielectric properties as well as excellent weather resistance, long-term stability, and fusion property in the electric / electronic field, and bonding the adhesive sheet The present invention relates to a laminate sheet formed using materials, a surface adhesive sheet formed using the adhesive sheet, and a method for imparting adhesiveness to a sheet surface using the adhesive sheet.

In the electric / electronic field, an adhesive sheet in which a thermoplastic resin layer is formed on a sheet surface is used as an insulating adhesive material for bonding between plastic sheets or bonding between a plastic surface and a metal surface. Yes. As such an adhesive sheet, a sheet in which a thermoplastic resin layer such as polyimide, polyether amide imide, or fluororesin is formed on the surface of a liquid crystal polymer sheet or a polyimide sheet is known.
Since such an adhesive sheet is used in the electric / electronic field, the adhesive layer is excellent in heat resistance, low hygroscopicity and low dielectric properties, and excellent in heat-fusibility. is necessary. Moreover, the thickness of the adhesive layer needs to be as thin as possible within a range in which the adhesive force can be maintained at a certain level or more so that “warping” or the like does not occur when the adhesive layer is adhered to the plastic sheet.

  As a method for forming a thermoplastic resin into a thin film, a method that combines a melt film forming method such as precision T-die extrusion or inflation extrusion and post-processing such as calendering, rolling, and stretching is generally used. The obtained film needs to have a certain film thickness in order to ensure later handling. In addition, when thin film forming is advanced by these processes, pinholes are easily formed due to external factors such as extremely small foreign matter, electrostatic discharge, or scratches on the molding die. Therefore, when a homogeneous film is industrially formed by a conventional method, it has been necessary to have a film thickness exceeding about 10 μm.

  With regard to materials (including adhesive layers) used in the electrical / electronic field, it will be necessary to increase the accuracy and electrical characteristics to meet the demands for advanced information communications, as well as the structural requirements of lighter and thinner products. Although it is necessary to answer the requirements, among them, it is important to increase the signal propagation speed and the rise time (rise time) of the clock signal.

Ｋ：係数
ｃ：光速
ε：比誘電率
また、信号伝搬遅延時間は下記（２）式で表される。

Here, regarding the increase in the propagation speed and the shortening of the rise time, the signal propagation speed is expressed by the following equation (1).

K: Coefficient
c: speed of light
ε: relative dielectric constant Further, the signal propagation delay time is expressed by the following equation (2).

α_１：導体損
α_２：誘電損 As can be seen from the equations (1) and (2), in order to increase the signal propagation speed, that is, to shorten the signal propagation delay time, it is necessary to reduce the relative dielectric constant ε of the material.
Furthermore, signal attenuation in materials is known as a material property to be considered for use in the field. Here, transmission loss is raised as one element of signal attenuation. The transmission loss is represented by the sum of the conductor loss due to the resistance of the conductor and the dielectric loss depending on the dielectric characteristics of the substrate material, as shown in the following equation (3).

α ₁ : Conductor loss α ₂ : Dielectric loss

ｆ：周波数
ｔａｎδ：誘電正接 In particular, in a next-generation device using a high-frequency region, the in-substrate transmission loss mainly acts on the dielectric loss α ₂ rather than the conductor loss α ₁ , but as expressed by the following equation (4): It is known that the higher the frequency, the higher the dielectric loss. Therefore, countermeasures for increasing the frequency and capacity of information communication and reducing the dielectric loss as the frequency increases are required.

f: Frequency
tan δ: dielectric loss tangent

  As shown in the equation (4), in order to reduce the dielectric loss, it is necessary to reduce the relative dielectric constant ε and the dielectric loss tangent tan δ of the material, but the relative dielectric constant ε is a factor of 1/2 power. While contributing to the dielectric loss, the dielectric loss tangent tan δ contributes to the dielectric loss as a directly proportional factor, so it is effective to reduce the dielectric loss of the material.

Ｚ：特性インピーダンス
ｔ_１：基板厚さ
ｔ_２：導体厚さ
ｗ：ライン幅 Another element of signal attenuation is reflection due to characteristic impedance mismatch of signals propagating on circuit wiring. The characteristic impedance is expressed by the following equation (5).

Z: Characteristic impedance
t ₁ : substrate thickness
t ₂ : conductor thickness
w: Line width

As can be seen from this equation, in order to keep the characteristic impedance constant in the substrate, it is necessary to keep the substrate and conductor thickness and line width constant. Therefore, if the relative dielectric constant of the material is reduced, the line width can be increased, that is, the wiring pattern can be roughened, and extreme miniaturization in circuit processing can be avoided, which is advantageous.
In addition, since the signal energy attenuated by the dielectric loss of the substrate is released as heat, using a low dielectric loss material is also effective as a heat dissipation measure.
In addition to the above electrical characteristics, if a highly hygroscopic material is used in this field, the moisture absorbed in the material will evaporate in a high-temperature process such as solder reflow, which will adhere to the adhesive layer. In the worst case, voids (bubbles) are formed between the layers of the material, leading to defects such as peeling.
In addition, materials such as epoxy resins that are generally used as adhesives have a thermal expansion coefficient that is significantly different from copper as a signal circuit or IC as a component, so when this is used as an adhesive layer, It is easy to generate "warp" and leads to defects such as cracks on the adhesive surface in long-term use.

  From such a viewpoint, it is not a material having a relatively large relative dielectric constant, such as an epoxy resin or polyimide, or a large difference in hygroscopicity or linear expansion coefficient, and has a small relative dielectric constant and almost no hygroscopicity. Further, attention has been focused on a liquid crystal polymer resin (LCP) having an excellent feature that the thermal linear expansion coefficient can be adjusted according to copper or IC by a molecular orientation technique.

  LCP as used herein refers to a thermotropic liquid crystal polymer exhibiting liquid crystallinity in a heat-melted state, and among these, it is appropriate to use a wholly aromatic polyester having excellent heat resistance. This LCP has a rigid linear molecular structure, and as already mentioned, low relative dielectric constant, low dielectric loss tangent, high strength, high dimensional stability (controllable thermal expansion coefficient), low moisture absorption In addition to features such as (approximately 0.2%), it is possible to adhere to other materials in a self-fusing manner by taking advantage of the properties of thermoplastic resins.

However, with this LCP, simply by extruding the film using existing methods, rigid molecular chains are highly oriented in the direction of extrusion, and mechanical properties such as tensile strength in the length and width directions of the film. In addition, only anisotropic films having greatly different thermal characteristics such as a thermal linear expansion coefficient and electrical characteristics such as a relative dielectric constant can be obtained.
In order to solve this problem, Japanese Patent Application Laid-Open No. 2-88212 and Japanese Patent Application Laid-Open No. 7-186253 propose a technique for suppressing the physical property difference in the length / width direction of the film by devising an inflation die. In Japanese Patent Laid-Open No. 7-323506, a proposal is made to suppress the difference in physical properties in the length / width direction of a film by laminating an LCP film obtained by T-die extrusion with another synthetic resin film and then stretching.

However, when LCP is used, there is a weak point that the adhesive strength with other materials such as copper is not always sufficient because of its low polarity surface characteristics. This weakness is the pre-adhesion stage, known surface treatment techniques, such as physical irradiation methods such as UV irradiation, corona discharge or plasma treatment, chemical etching with chemicals, chemical methods such as application of primer or coupling agent, Even if the easy adhesion treatment is performed using the material, it is not completely eliminated, and another proposal has been made to laminate another easily adhesive resin layer as a surface layer.
Among them, as those intended for higher performance required in the field of electrical / electronic materials, for example, JP 2003-163460 A (Patent Document 1) and JP 2003-39602 A (Patent Document 2). Then, a proposal to combine a thermosetting polyphenylene ether and an LCP film is disclosed in JP-A-2003-82301 (Patent Document 3), which is a fluoropolymer having a water absorption of 0 to 0.1% and a melting point of 150 to 345 ° C. There has been proposed a material in which an adhesive layer made of is formed on at least one surface of an LCP film.

Next, description is added regarding the adhesiveness due to heat in an adhesive sheet containing a thermoplastic resin as an adhesive layer. Particularly in the circuit board manufacturing process in the field of electrical / electronic materials, the key to high performance is a multi-layered board with high integration and built-in components, which can be achieved with a simpler material structure. Materials are attracting attention. With thermosetting resin adhesive materials typified by epoxy resin, circuit copper bonding process and circuit formation patterning process can be carried out without any problem for single-layer substrates, but in the subsequent multi-layering process, Since it is not possible to laminate without using an adhesive material, it is not possible to employ a batch multi-layer process for the purpose of simplifying the process.
Specifically, this requirement is an organic material that has a low electrical property, particularly a dielectric constant and a dielectric loss tangent as dielectric properties, and has both heat resistance and heat fusion properties. In addition, sufficient strength and high dimensional accuracy can be maintained as a substrate material, and this is achieved by a material that approximates the linear expansion coefficient of copper as a circuit and IC as a component within a certain range.

Therefore, the electrical characteristics of the adhesive layer, particularly the relative dielectric constant and the dielectric loss tangent are small, more specifically, the dielectric constant is less than 3.0 and the dielectric loss tangent is less than 0.03 (both values in the 3 GHz band). In addition, the in-plane anisotropy of the characteristics is required to be small. Furthermore, in this field, since the copper foil is chemically etched for circuit formation, an adhesive layer that is resistant to chemicals (etchant) used in this process is required, and solder reflow and the like are required. A heat resistant adhesive layer that is durable even in high temperature processes is essential. Here, from the viewpoint of recent environmental measures, the use of solder with a low lead content or no lead is being promoted, but the processing temperature of such environmental measures solder is more than a dozen degrees higher than normal products. As it is known, there is an increasing demand for heat-resistant adhesive layers. At the same time, in this field, materials that easily absorb moisture due to environmental humidity during storage or use are avoided because they can cause defects such as bubbles during high-temperature processing, and can lead to reduced reliability during long-term use.
In addition, for outdoor long-term use, there are many cases where the material deteriorates due to the above-mentioned hygroscopicity or the strength decreases due to the influence of ultraviolet rays, etc., and design of material properties that fully consider these characteristics is required. It is done.
From these viewpoints, among thermoplastic resins, fluorinated resin = fluoropolymer, which has excellent heat resistance, chemical resistance, weather resistance and low dielectric properties compared to other resins, is the most suitable material for adhesive sheets. It can be said.

  However, among the fluoropolymers proposed so far, the resin formed only from polytetrafluoroethylene and perfluoromonomer typified by tetrafluoroethylene / hexafluoropropylene has sufficient adhesive strength with other materials. Not.

  On the other hand, polyvinylidene fluoride is slightly inferior in chemical resistance, and polychlorotrifluoroethylene has a problem in heat resistance.

Japanese Patent Application Laid-Open No. 2001-187833 (Patent Document 4) describes a fluoropolymer composition containing LCP as an adhesion improver and a fluoropolymer having a functional group in a certain ratio. This composition is a material system that has a high possibility of solving the above-mentioned problems, but when it is formed into a film, the contained LCP is dispersed in islands in the fluoropolymer component, and is discharged during melt extrusion. By being sheared in the direction and highly oriented in the film length direction, it shows a fine fibrous form parallel to the film extrusion direction, ie the film length direction.
LCP has the property that the tensile strength is large, the thermal expansion coefficient is small, and the relative dielectric constant is large in the oriented direction. That is, the film has anisotropy in mechanical, thermal, and electrical characteristics in the length direction and width direction, and when this is applied to the adhesive layer as it is, due to the difference in physical properties in the length / width direction of the film. Even after bonding, the product will have anisotropy of in-plane characteristics, leaving a problem.

  In addition, when the fluoropolymer composition of Patent Document 4 is formed into a film shape, in an area where the film thickness is approximately 10 μm or less, the oriented LCP present in the fiber shape and the surrounding fluoropolymer with respect to the pulling force in the width direction of the film There is a problem in handling property. Also, pinholes are easily formed at the same location.

JP 2003-163460 A JP 2003-39602 A Japanese Patent Laid-Open No. 2003-82301 JP 2001-187833 A

  The present invention relates to an adhesive sheet used as an adhesive material in the electric / electronic field, wherein an adhesive layer is provided on a sheet-like material, the adhesive layer is a thin layer, has sufficient strength, and has heat resistance. Provided is an adhesive sheet excellent in low hygroscopicity and fusion, and a laminate sheet formed using the adhesive sheet as an adhesive layer, a surface adhesive sheet formed using the adhesive sheet, and the adhesive sheet A method is provided for imparting adhesion to a sheet surface.

  According to the present invention, there are provided the following adhesive sheet, laminate sheet, sheet having an adhesive surface layer, and a method for imparting adhesiveness to the sheet surface.

(1) An adhesive sheet used for adhering two sheet-like materials, comprising a laminate in which an easy-adhesive fluororesin film is laminated and fused on both surfaces of an expanded porous polytetrafluoroethylene sheet. The fluororesin film comprises a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and the easily adhesive fluororesin An adhesive sheet, wherein the film is integrated with the stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.
(2) An adhesive sheet used for imparting adhesiveness to the surface of the sheet-like material, comprising a laminate obtained by laminating and bonding an easily adhesive fluororesin film on both surfaces of the stretched porous polytetrafluoroethylene sheet, The easily adhesive fluororesin film comprises a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and the easy adhesive An adhesive sheet characterized in that the porous fluororesin film is integrated with the stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.
(3) An adhesive sheet used for imparting adhesiveness to the surface of a sheet-like material, which is a laminate in which an easily adhesive fluororesin film is laminated and fused on one side of an expanded porous polytetrafluoroethylene sheet. The easily adhesive fluororesin film is composed of a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and The adhesive sheet is characterized in that the easily adhesive fluororesin film is integrated with the stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.
(4) A laminate sheet obtained by adhering two sheet-like materials through an adhesive sheet, the adhesive sheet comprising the adhesive sheet according to (1).
(5) The laminate sheet according to (4), wherein at least one of the two sheet-like materials is a liquid crystal polymer resin sheet.
(6) A sheet obtained by imparting adhesiveness to the surface of a sheet-like material via an adhesive sheet, wherein the adhesive sheet is composed of the adhesive sheet described in (2).
(7) The sheet according to (6), wherein the sheet-like material provided with adhesiveness through an adhesive sheet is a liquid crystal polymer resin sheet.
(8) A sheet having adhesion on the surface of the sheet-like material, the adhesive sheet according to (3) being laminated and adhered to the surface of the sheet-like material, and then the expanded porous polytetrafluoroethylene A sheet obtained by peeling and removing the sheet.
(9) The sheet according to (8), wherein the sheet-like material imparted with adhesiveness is a liquid crystal polymer resin sheet.
(10) The fused porous polytetrafluoroethylene sheet is peeled and removed after the adhesive sheet according to (3) above is fused to the surface of the sheet-like material via the easily adhesive fluororesin film. A method for imparting adhesiveness to the surface of a sheet-like material characterized by the above.

According to the present invention, a high-performance and high-quality adhesive sheet used in the electric / electronic field is provided. In this adhesive sheet, the adhesive layer has a sufficient strength while being a thin layer having a thickness of 50 μm or less. This adhesive layer has excellent fusion properties to plastic layers such as liquid crystal polymer resin layers, metal layers, and ceramic layers, as well as excellent heat resistance, low moisture absorption, low dielectric properties, weather resistance, and the like. .
By laminating and bonding the adhesive sheet of the present invention to the surface of a sheet-like material such as a plastic sheet such as a liquid crystal polymer sheet, it is excellent in heat resistance, low moisture absorption, low dielectric property, weather resistance, etc., and a film such as a pinhole A surface layer with few defects can be formed.

  Furthermore, what formed the adhesive layer (fusion layer) on the liquid crystal polymer sheet by using the adhesive sheet of the present invention is remarkably improved in adhesion to a plastic sheet, a metal foil, etc., and has a dielectric property. This is a significant improvement.

  The laminate sheet obtained by laminating the adhesive sheet of the present invention on a plastic sheet such as a liquid crystal polymer sheet can be advantageously used as an electric / electronic material such as a flexible printed board and a high-frequency compatible board.

  In the adhesive sheet of the present invention, an easily adhesive fluororesin film is laminated and integrated on both sides or one side of a stretched porous polytetrafluoroethylene (ePTFE) sheet as a support and stretched in at least one direction. It is obtained by doing.

In the ePTFE sheet after stretching in the adhesive sheet of the present invention, the thickness is 1-1000 μm, preferably 3-200 μm, more preferably 5-50 μm, and the porosity is 0-99%, preferably 10 -90%, More preferably, it is 20-80%.
In the easily adhesive fluororesin film after stretching in the adhesive sheet of the present invention, the thickness is 50 μm or less, usually 0.3 to 50 μm, preferably 1 to 10 μm, more preferably 1 to 5 μm.
When the adhesive sheet is used as an adhesive material for adhering two sheet-like materials or a fusion material for imparting fusibility to the sheet surface, the adhesive sheet may be a thin material. Preferably, the thickness of the adhesive sheet in this case is usually 1 to 150 μm, preferably 2 to 15 μm.

  The ePTFE sheet is a conventionally known one. This is, for example, after ram-extruding a sheet precursor obtained by compression molding fine particles of polytetrafluoroethylene (PTFE) together with a molding aid, in a uniaxial to biaxial direction under a temperature condition near the melting point of the PTFE. It can be obtained by stretching. This ePTFE is described in detail in, for example, Japanese Patent Publication No. 51-18991.

The easily adhesive fluororesin film comprises (i) a fluororesin (A) having an adhesive functional group, (ii) a liquid crystal polymer resin (LCP) (B), and (iii) a fluororesin having no adhesive functional group (C ) Can be obtained by forming into a film.
In the fluororesin (A) having the adhesive functional group, the adhesive functional group has a high affinity for plastics and metals (for example, copper). Such functional groups include halogen atoms such as chlorine, bromine, iodine and fluorine, groups containing halogen atoms, groups containing active hydrogen atoms, polar groups, and the like.
As the group containing a halogen atom, —SO ₂ F is preferable.
Examples of the group containing an active hydrogen _{atom, -COOH, -CH 2 OH, -CH} 2 OCONH 2, -CH 2 OPO (OH) 2 and the like.
Examples of the polar group include -CN and -OCN.
The adhesive functional group may be bonded to the main chain of the fluororesin or may be bonded to the side chain, and the bonding position is not particularly limited.

The ratio (content) of the adhesive functional group in the fluororesin (A) is not particularly limited as long as the blend has sufficient adhesiveness (fusibility) to plastics and metals. . In general, all the fluororesin contained in the blend (A), 25 to 2,500 or backbone carbon atoms 10 ⁶ per contained in (C), preferably 50 to 2000 pieces proportion.

  In the fluororesin (A) containing an adhesive functional group, the fluororesin itself can be a fluororesin having a conventionally known structure. Such a fluororesin can be a homopolymer or copolymer of tetrafluoroethylene (TFE). In this case, as a comonomer to be copolymerized with TFE, perfluoroolefin having 3 to 8 carbon atoms (such as hexafluoropropylene) or 1 to 3 carbon atoms, preferably 2 to 3 carbon atoms of an alkyl group. Perfluoro (alkyl vinyl ether) [perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether) and the like].

  The fluororesin (A) having an adhesive functional group used in the present invention can be obtained by copolymerizing a comonomer having an adhesive functional group with TFE. Examples of the comonomer in this case include those represented by the following general formula (1).

In the above formula, Y represents H or F, and Z represents an adhesive functional group or a group containing the same. In the present invention, it is preferable that Y is F and Z is —OR _f X. In this case, R _f is a perfluoroalkyl group having 2 to 20 carbon atoms, and X is an adhesive functional group or a group containing the same.

  Specific examples of the comonomer represented by the general formula (1) include the following.

  In the above formula, m = 0 to 3, n = 1 to 4, p = 1 to 2, and R is methyl or ethyl.

  Examples of the comonomer preferably used in the present invention include the following.

（式中、ＹはＳＯ_２Ｆ、ＣＮ又はＣＯＯＨである）

（式中、ＺはＯＨ、−ＯＣＮ、−ＯＣＯＮＨ_２又はＯＰＯ（ＯＨ)_２である）

(Where Y is SO ₂ F, CN or COOH)

(Wherein Z is OH, —OCN, —OCONH ₂ or OPO (OH) ₂ )

  In the copolymer of TFE and comonomer, the proportion of the comonomer is 10% by weight or less, preferably 5% by weight or less based on the copolymer. The lower limit is usually about 0.5% by weight.

  Various conventionally well-known things can be used as a fluororesin (C) which does not have an adhesive functional group. These include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF). ), Tetrafluoroethylene-ethylene copolymer (ETFE), and the like.

The liquid crystal polymer resin (LCP) (B) used in the present invention is a thermotropic type, and such LCPs include polyester-based, poly (ester amide) -based, poly (ester imide) -based, and polyazomethine-based. Are included. Preferred LCPs are those of polyester or poly (ester amide) type. The polyester-based or poly (ester amide) -based LCP preferably has an aromatic skeleton partially or entirely.
In the LCP used in the present invention, the melting point is 150 to 400 ° C, preferably 250 to 350 ° C.

  In the blend used in the present invention, the proportion of the fluororesin (A) having an adhesive functional group is usually 1 to 30% by weight, preferably 1 to 20% by weight, more preferably 3 to 15% by weight. . The ratio of LCP is usually 0.5 to 15% by weight, preferably 1 to 10% by weight. The ratio of the fluororesin (C) having no adhesive functional group is usually 55 to 98.5% by weight, preferably 70% by weight or more. The proportion of the fluororesin (C) having no adhesive functional group is 50 parts by weight or more, preferably 70 parts by weight per 100 weights of the total amount of the fluororesin (A) having the adhesive functional group and the LCP (B). More than a part.

  The blend used in the present invention is described in detail in JP-A No. 2001-187833.

The first adhesive sheet (I) according to the present invention is formed by laminating and bonding an easy-adhesive fluororesin film made of the blend on both sides of an expanded porous polytetrafluoroethylene sheet (ePTFE sheet). Manufactured by stretching in at least one direction in an integrated state.
The blend can be formed into a film by a conventionally known method (extrusion method, hot roll method, hot press method, etc.). The thickness of the film is usually 1-1000 μm, preferably 10-100 μm.

  In the adhesive sheet (I), the easily adhesive fluororesin film after stretching has a thickness of 50 μm or less, preferably 5 μm or less. The lower limit is usually about 0.3 μm.

When producing the adhesive sheet (I), the easy-adhesive fluororesin film may be laminated and adhered to both sides of the ePTFE sheet at the same time, or laminated on one side of the ePTFE sheet and then laminated on the other side. It may be adhered.
For the laminating and bonding of the easily adhesive fluororesin film to the ePTFE sheet, a conventionally known laminating and bonding method such as a continuous laminating method using a hot roll or a batch pressing method using a flat press apparatus can be used. The laminated adhesion can be performed under a pressure condition of 0.1 to 10 MPa at a temperature at which the easily adhesive fluororesin film is melted and softened, usually 250 to 350 ° C.

The laminate (laminate sheet) obtained in the laminate adhesion step is stretched in at least one direction in order to obtain an adhesive sheet. In this case, the draw ratio is a draw ratio R expressed as an area ratio, and is usually 1.2 to 100 times, preferably 5 to 30 times.
The draw ratio R is defined as follows.
R = A / B
A: Area of the film after stretching B: Area of the film before stretching

  The laminate is stretched so that the thickness of the easily adhesive fluororesin film after stretching is 50 μm or less. The thickness of the film after stretching can be adjusted by the thickness of the film before stretching and the stretching ratio. For example, when the thickness of the easily adhesive fluororesin film before stretching is 30 μm, the stretching ratio R may be set to 10 times in order to set the thickness after stretching to 3 μm. The stretching direction in this case is arbitrary, and can be only one direction (uniaxial direction), two directions (biaxial direction), or more directions (multiaxial direction).

  In the stretching step, the stretching temperature may be a temperature at which the laminate can be stretched, and is usually 150 to 400 ° C, preferably 300 to 380 ° C. The stretching speed is 1 to 100% / second, preferably 5 to 20% / second.

  In the second adhesive sheet (II) according to the present invention, an easy-adhesive fluororesin film made of the blend is laminated and adhered to one side of ePTFE so as to be peelable (removable) and integrated. In this state, it is produced by stretching in at least one direction.

In the production of the adhesive sheet (II), the easily adhesive fluororesin film is laminated and adhered to one side of the ePTFE sheet so as to be peelable (detachable). And / or a method of laminating and adhering the pressure to the ePTFE sheet, a method of laminating and adhering the film to the ePTFE sheet by reducing the adhesion area with a mold having dot-like protrusions, and the film and the ePTFE sheet. For example, a method of reducing the adhesive force between the two by interposing inorganic fine particles such as talc and SiO _{2 at the} bonding interface is applied.

  The laminate of the film and the ePTFE sheet can be stretched in the same manner as in the case of the adhesive sheet (1).

  Since the easy-adhesive fluororesin film used in the present invention contains LCP, it usually has in-plane anisotropy in its film properties. This anisotropy may be preferably eliminated or improved (reduced) depending on the application of the adhesive sheet. In the case of the present invention, this anisotropy can be eliminated or improved by adjusting the stretching direction when the laminate of the film and the ePTFE sheet is stretched. Generally, when the film is stretched, the anisotropy is eliminated by setting the stretching ratio higher in the direction orthogonal to the LCP orientation direction of the film.

Next, it demonstrates concretely about manufacture of the adhesive sheet by which the anisotropy of the easily-adhesive fluororesin film eliminated or improved.
First, an easily adhesive fluororesin composition (blend) film having a thickness of 10 μm was obtained by an existing extrusion method. In this case, pinholes and fine tearing of the film occurred in some places, and a long homogeneous film could not be obtained. Therefore, only a portion having no defect was used by visual inspection in advance.
The linear expansion coefficient of this film is -11 ppm in the film length direction and 410 ppm in the width direction. The relative dielectric constant at 12 GHz is 2.36 in the film length direction and 2.14 in the width direction. is there. Therefore, in order to improve this, the film should be stretched at a larger stretching ratio in the width direction of the film. As an example, when the above-mentioned film is laminated on both sides of ePTFE having a thickness of 20 μm and stretched 5 times in the width direction, and the thickness of the fluoropolymer composition after stretching is designed to be 2 μm, the linear expansion of the obtained stretched film The coefficient is 37 ppm in the film length direction and 80 ppm in the width direction. The relative dielectric constant at 12 GHz is 2.09 in the film length direction and 2.03 in the width direction, and the anisotropy is greatly improved.

  The first adhesive sheet (I) according to the present invention can be used as an adhesive material for bonding two sheet-like materials. Since the adhesive sheet (I) in this case has the easily adhesive fluororesin film formed on both surfaces thereof, the two sheet-like materials can be bonded with each film as an adhesive surface. In order to bond two sheet-like materials using the adhesive sheet (I), the sheet (I) is interposed between the two sheet-like materials, and the two sheet-like materials are subjected to thermocompression treatment. Can be obtained.

  The first adhesive sheet (I) according to the present invention can be used for imparting fusibility (adhesiveness) to the surface of a sheet-like material such as a plastic sheet. Since the adhesive sheet (I) in this case has an easily adhesive fluororesin film formed on both surfaces thereof, when this is laminated and adhered to one sheet-like material, the surface layer is made of an easily adhesive fluororesin film. A sheet formed on the adhesive layer can be obtained.

1 and 2 are explanatory sectional views of an adhesive sheet formed by using the first adhesive sheet (I) according to the present invention.
FIG. 1 shows an example in which the adhesive sheet (I) is laminated and adhered to one side of the sheet-like material, and FIG. 2 shows an example in which the adhesive sheet (I) is laminated and adhered to both sides of the sheet-like material.
In these drawings, 1 is an ePTFE sheet, 2 and 3 are easily adhesive fluororesin films, 4 is a sheet-like material such as a plastic sheet, and I is an adhesive sheet (I).

  The second adhesive sheet (II) according to the present invention can be used to impart fusing properties (adhesiveness) to the surface of a sheet-like material such as a plastic sheet. In this case, the adhesive sheet (II) is formed so that the easily adhesive fluororesin film can be peeled on one side thereof. When the ePTFE sheet is peeled and removed, the surface layer is peeled off. A sheet formed on an adhesive layer made of an easily adhesive fluororesin film can be obtained.

FIG. 3 shows an explanatory sectional view of a sheet formed by laminating and bonding the second adhesive sheet (II) according to the present invention to a sheet-like material such as a plastic sheet, and FIG. 4 shows the surface of the sheet-like material such as a plastic sheet. FIG. 2 is an explanatory cross-sectional view of a surface-adhesive sheet formed by removing and removing an ePTFE sheet from an adhesive sheet (II) laminated and adhered to the surface.
In these figures, 1 is an ePTFE sheet, 2 is an easily adhesive fluororesin film, 4 is a sheet-like material, and II is an adhesive sheet (II).

  When two sheet-like materials are bonded using the adhesive sheet (I) to obtain a laminate sheet, a material that can be fused by the adhesive sheet (II) is used as the sheet-like material. Such sheet-like materials include plastic sheets, metal sheets, ceramic sheets and the like. The thickness of the sheet-like material is not particularly limited, but is usually 1 to 1000 μm, particularly 10 to 100 μm. Examples of the resin forming the plastic sheet in this case include those having a melting point or softening point of 150 to 400 ° C, preferably 300 to 380 ° C. Specific examples thereof include LCP, fluororesin, PES (polyethersulfone), PEI (polyetherimide), PAI (polyamideimide), PEEK (polyetheretherketone), PAR (polyarylate), PPS (polyphenylene sulfide). Etc. A thermotropic liquid crystal polymer having a melting point of 250 ° C. or higher is preferable, and various conventionally known ones can be used. A preferable melting point is 280 ° C to 380 ° C. Examples of such a liquid crystal polymer include aromatic polyesters that are synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids, and that exhibit liquid crystallinity when melted. The first type consisting of parahydroxybenzoic acid (PHB), terephthalic acid and biphenyl (the following formula a), the second type consisting of PHB and 2,6-hydroxynaphthoic acid (the following formula b), PHB and terephthalate There is a third type (formula c) consisting of an acid and ethylene glycol.

When an LCP sheet is used as the plastic sheet, it is preferable that the LCP sheet has no anisotropy of mechanical, thermal, and electrical characteristics in the in-plane direction.
As a method for eliminating or improving (reducing) the anisotropy of the LCP sheet, for example, a method of stretching the LCP sheet can be used. In this method, the degree of orientation in the length direction of the sheet and the degree of orientation in the width direction obtained by stretching in the transverse direction can be controlled by stretching, and the X / Y CTE ratio of the resulting LCP sheet can be controlled. I can do it.
In this case, the X / Y CTE of the LCP film is preferably -5 to 21 ppm / ° C.
In addition, when the LCP sheet and the adhesive sheet are laminated and bonded, the same process as that used for the lamination and bonding of the ePTFE sheet and the easily adhesive fluororesin film can be applied. That is, the existing lamination | stacking adhesion | attachment methods, such as the continuous lamination by a hot roll, and the batch press by a plane press apparatus, can be used.
At this time, the LCP sheet can be laminated on one side or both sides. However, in the case of double-sided lamination, either a method of laminating each side or a method of laminating both sides simultaneously can be selected. The processing temperature at this time is approximately 200 to 350 ° C. at which the easily adhesive fluororesin film melts and softens, and the pressure is in the range of 0.1 to 10 Mpa.

The fluororesin used in the present invention has a melting point or softening point of 280 ° C. or higher, preferably 300 ° C. or higher. Such materials include polytetrafluoroethylene, PFA, FEP, ETFE, PVDF and the like.
Further, the sheet-like material referred to in the present invention can be a metal sheet, a ceramic sheet or the like, but the thickness of the metal sheet or ceramic sheet in this case is not particularly limited, and is 1 to 1000 μm, particularly 3 to 200 μm. Can be. Specific examples of the metal sheet include a copper film (copper foil), an aluminum film (aluminum foil), and a stainless sheet.

When two sheet-like materials are bonded using the adhesive sheet of the present invention, one sheet-like material can be a plastic sheet, and the other sheet-like material is a plastic sheet, a metal sheet, a ceramic sheet, or the like. be able to.
In the laminate sheet formed by adhering two sheet-like materials using the adhesive sheet of the present invention, the two sheet-like materials are made of metal foil such as copper foil. Since it has a formed structure, it is advantageously used as a double-sided metal-laminated flexible printed wiring board for high frequency.
In the laminate sheet formed using the adhesive sheet of the present invention, one sheet-like material made of a metal foil and the other sheet-like material made of a ceramic sheet is advantageous as a high-frequency compatible rigid wiring board. Can be used.

  When the adhesive sheet (I) according to the present invention is laminated and adhered to the surface of one sheet-like material to give adhesiveness (fusibility) to the surface of the sheet-like material, the sheet-like material is a plastic sheet. be able to. As the plastic sheet in this case, the various types described above can be used. In this case, a preferable plastic sheet is an LCP sheet, and specific examples thereof include those described above. Further, in this case, it is preferable to use an LCP sheet having no anisotropy or having little anisotropy.

When the adhesive sheet (II) according to the present invention is laminated and adhered to the surface of the sheet-like material, the ePTFE sheet is detached and removed to impart adhesiveness (fusion property) to the surface of the sheet-like material. Various materials described above can be used as the material. In this case, a preferable plastic sheet is an LCP sheet, and specific examples thereof include those described above. Further, in this case, it is preferable to use an LCP sheet having no anisotropy or having little anisotropy.
The sheet-like material can be a metal sheet, a ceramic sheet, or the like.

  When the adhesive sheet (1) or (2) is used and a sheet-like material is formed with an adhesive layer (fusion layer) on the surface, various materials can be adhered to the adhesive surface. The material in this case includes plastic, metal, ceramic and the like.

  When a plastic layer is formed by adhering plastic to the adhesive layer surface formed on the surface of the sheet-like material, the plastic layer can be formed using a plastic sheet bonding method, a plastic vapor deposition method, a plastic sputtering method, or the like. .

  When a metal layer is formed by adhering a metal to the adhesive layer surface formed on the surface of the sheet-like material, the metal layer is formed using a metal sheet bonding method, a metal vapor deposition method, a metal sputtering method, a metal plating method, or the like. Can be formed.

  In the case of forming a ceramic layer by adhering ceramic to the adhesive layer surface formed on the surface of the sheet-like material, the ceramic layer may be formed using a ceramic sheet bonding method, a ceramic vapor deposition method, a ceramic sputtering method, or the like. it can.

  As described above, when various materials are adhered to the adhesive layer surface of the sheet-like material, the adhesive layer surface made of the easily adhesive fluororesin can be in a fused state or a non-fused state.

According to the present invention, as described above, one side is made of a metal sheet or ceramic sheet, the intermediate layer is made of an insulating layer (adhesive sheet), and the other side is made of a metal (Ag, etc.) vapor deposition layer. A body sheet can be obtained, but this sheet is advantageously used as a solar cell substrate or the like.
In order to obtain a solar cell using this substrate, a silicon layer and a transparent conductive layer are formed on the metal deposition surface of the substrate.
Moreover, according to the present invention, as described above, a laminate sheet is obtained in which one side is made of a metal sheet and a ceramic sheet, the intermediate layer is made of an insulating layer (resin sheet), and the other side is made of a copper plating layer. be able to. This sheet can be advantageously used as a copper-clad printed circuit board corresponding to an ultrafine pattern.

When the adhesive sheet (1) or (2) is laminated and adhered to a plastic sheet, the plastic sheet surface and / or the highly adhesive fluororesin film surface forming the adhesive surface is subjected to an easy adhesion treatment. It can be an easily adhesive surface.
As the easy adhesion treatment, various conventionally known methods can be used. Examples of such methods include physicochemical methods such as UV irradiation, corona discharge or plasma treatment, and chemical methods such as chemical etching with chemicals and application of a primer or a coupling agent.
When laminating and bonding the adhesive sheet according to the present invention and a plastic sheet, in particular, an LCP sheet, by making the surface of the plastic sheet and / or the surface of the adhesive sheet (the surface of the easily adhesive fluororesin film) an easily adhesive surface, The adhesive strength between them can be remarkably improved.

  By using the adhesive sheet of the present invention, various products used in the electric / electronic field can be obtained. Examples of such products include sheet-like materials, such as plastic sheets having a fusible surface in which an easy-adhesive fluororesin film is laminated and bonded to one or both sides of a plastic sheet such as an LCP sheet, and sheet-like materials such as plastic sheets. A laminate sheet in which an easy-adhesive fluororesin film is laminated and adhered on one or both sides of the sheet, and a metal foil or ceramic sheet is laminated and adhered thereon, a sheet-like material, for example, an adhesive sheet (1) on one or both sides of a plastic sheet Is a plastic sheet having a fusible surface, and a sheet-like material, for example, a laminate in which an adhesive sheet (1) is laminated and adhered to one or both sides of a plastic sheet, and a metal foil or a ceramic sheet is laminated and adhered thereon Body sheet, one side of LCP sheet formed by laminating and bonding multiple LCP films On both sides, the adhesive sheet (1) is laminated and bonded and further other materials necessary (metal foil, ceramic sheet, a plastic sheet, etc.) laminate sheet or the like formed by laminating bond the are included.

  In this invention, it is preferable to use the adhesive sheet (1) which has an easily-adhesive fluororesin film on both surfaces as an adhesive sheet. Such an adhesive sheet (1) has no pinholes or very few pinholes, and can be advantageously used as an adhesive sheet in the electric / electronic field.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples.

In addition, the evaluation method of the physical property shown below is as follows.
(Peel strength)
In accordance with JIS C6481, a 180 ° peel test was conducted using Orientec Corp .: Tensilon Universal Testing Machine RTC-1210A.
One side of a peel test piece having a width of 5 mm was adhered and fixed to a support plate with a double-sided adhesive sheet, and the metal foil on the opposite side was pulled at a speed of 50 mm / min, and the peel strength was measured.
(Dielectric properties)
The dielectric constant and dielectric loss tangent of 3 GHz and 12 GHz of each film were measured using an impedance material analyzer (resonator method) (manufactured by Hewlett-Packard: HP8510T).
(Dielectric constant)
Using a molecular orientation meter (MOA-3012A manufactured by Oji Scientific Instruments), the anisotropy of the dielectric constant in the plane of a 12.58 GHz film was measured as a measurement condition.
(Linear expansion coefficient (CTE))
Using a thermomechanical analyzer (TMA100 manufactured by Seiko Denshi Kogyo Co., Ltd.), CTE anisotropy in the plane of the film was measured at a tensile load of 49 mN and a measurement range of 50 to 100 ° C. as measurement conditions.
(Film thickness)
The film thickness was measured using a dial gauge (φ10 flat type).
(Film defect)
The surface of the film was visually observed, and the presence or absence of defects such as film tears and pinholes was inspected.

Reference example 1
90 parts by weight of a thermotropic liquid crystalline polyester (Sumitomo Chemical Co., Ltd., SUMIKASUPER E6000) and 10 parts by weight of natural silica (average particle size: 3 μm, FS-15, manufactured by Denki Kagaku) were melt mixed using a twin screw extruder. At the same time, it was extruded from the strand die at its tip and formed into pellets with a pelletizer. Next, this pellet was melted in a single-screw extruder, extruded into a sheet form from a T-die at the tip of the extruder, and cooled to obtain a liquid crystal polymer sheet A having a thickness of 125 μm.
A laminated porous polytetrafluoroethylene (ePTFE) sheet (average pore diameter 0.2 μm, porosity 80%) B1 having a thickness of 40 μm is laminated on both surfaces of the liquid crystal polymer sheet A, and heated with a laminator having a pair of rolls. After the pressure bonding, it was cooled through a pair of cooling rolls. The laminate sheet thus obtained was stretched by a biaxial stretching machine, then cooled, and finally the ePTFE sheet thermocompression bonded on both surfaces was peeled off from both surfaces, and a 25 μm-thick stretched liquid crystal polymer sheet C Got.

Example 1
80% by weight of TFE (tetrafluoroethylene) -PPVE (perfluoroalkyl vinyl ether) copolymer (PFA) (PFA grade 340, manufactured by Mitsui DuPont Chemical), 10% by weight of liquid crystal polymer (LCP) (Zenite 7000, manufactured by DuPont) ), PFA containing 1.1% by weight of 9,9-dihydro-9-hydroxy-perfluoro (3,6-dioxa-5-methyl-1-nonane) (hereinafter abbreviated as EVE-OH) in the polymer unit (Mitsui・ Weigh 10% by weight (manufactured by DuPont Chemical), blend with a tumbler mixer, melt knead and pelletize with a twin-screw kneader (Technobel) (die temperature during kneading: 360 ° C.), easy-adhesive fluoro A polymer composition (blend body) D was obtained.
The pellets of the pelletized fluoropolymer composition D were extruded into a tube shape from a circular die (die / mandrel diameter 60 mm / 56 mm die / mandrel temperature 350 ° C.) through a mandrel with a single screw extruder (manufactured by NOKIA), and an inside mandrel Using a mold (inside mandrel diameter of 48 mm), a thin tube was formed and cut into a film. At this time, as shown in Japanese Patent No. 2001-181463, in order to make the liquid crystal polymer in the fluoropolymer composition D into more fibers, it was extruded under conditions of a take-up speed of 1 m / min or more.
And the 10-micrometer-thick fluoropolymer composition film (adhesive adhesive fluororesin film) E was obtained.

Next, the obtained film E was placed on both sides of a 15 μm-thick stretched porous PTFE (porosity 30%) sheet B2 using a vacuum hot press machine at a temperature of 280 ° C., a pressure of 20 kg / cm ² , and a time of 3 And a degree of vacuum of −0.098 MPa or less was laminated to obtain a three-layer laminate sheet F having a total thickness of 35 μm. The obtained laminate sheet F is subjected to a biaxial stretching machine and stretched under the conditions of a stretching temperature of 350 ° C., a stretching speed of 5% / second, and a stretching ratio of 10 times, whereby a fluoropolymer composition having a total thickness of 3.5 μm. A film laminate G (adhesive sheet (I-1)) was obtained. In addition, no visual defect was observed in the obtained film.

  In the above experiment, when the fluoropolymer composition film has anisotropy in the linear expansion coefficient or dielectric properties by biaxially stretching a laminate sheet obtained by laminating the fluoropolymer composition film and the porous PTFE sheet. Even it can be greatly improved.

Example 2
In the same manner as in Example 1, a fluoropolymer composition film (adhesive fluororesin film) H having a thickness of 20 μm was prepared, and this film H was laminated on both surfaces of a porous PTFE sheet B2 having a thickness of 15 μm. A three-layer laminate sheet I having a thickness of 55 μm was obtained.
Next, this laminate sheet I is stretched on a biaxial stretching machine under the conditions of a stretching temperature of 350 ° C., a stretching speed of 5% / second, and a stretching ratio of 15 times, whereby a fluoropolymer composition film having a total thickness of 4 μm. Laminated body J (adhesive sheet (I-2)) was obtained. In addition, no visual defect was observed in the obtained film.

Example 3
The three-layer laminate sheet F is subjected to a biaxial stretching machine and stretched as a stretching condition at a stretching temperature of 350 ° C., a stretching speed of 5%, and a stretching ratio of 5 times to obtain a fluoropolymer composition film laminate K having a total thickness of 7 μm ( An adhesive sheet (I-3) was obtained.
Next, the in-plane anisotropy of the dielectric constant and CTE in-plane anisotropy of the obtained sheet were measured.

Example 4
The three-layer laminate sheet F was subjected to a biaxial stretching machine and stretched as a stretching condition at a stretching temperature of 350 ° C., a stretching speed of 5%, and a stretching ratio of 10 times to obtain an adhesive sheet (I-4).
Next, the in-plane anisotropy of the dielectric constant and CTE in-plane anisotropy of the obtained sheet were measured.

Example 5
The three-layer laminate sheet I was subjected to a biaxial stretching machine and stretched as stretching conditions at a stretching temperature of 350 ° C., a stretching speed of 5%, and a stretching ratio of 15 times to obtain an adhesive sheet (I-5).
Next, the in-plane anisotropy of the dielectric constant and CTE in-plane anisotropy of the obtained sheet were measured.

Comparative Example 1
The in-plane anisotropy of the dielectric constant and the in-plane anisotropy of CTE in the unstretched state of the three-layer laminate film F were measured.

Comparative Example 2
The in-plane anisotropy of the dielectric constant of the fluoropolymer composition film E and the in-plane anisotropy of CTE were measured.

  The measurement results in Examples 3 to 5 and Comparative Examples 1 and 2 are shown in Table 1.

  As is apparent from Table 1, the in-plane anisotropy of the dielectric constant was observed in the films (adhesive sheets) of Examples 3 to 5 that were stretched compared to the films of Comparative Examples 1 and 2 that were not stretched. The dielectric properties were improved, and the anisotropy in the MD and TD directions of CTE could be reduced. Moreover, it becomes possible to make the thickness of a film (adhesive sheet) thinner than the comparative example by extending | stretching, Furthermore, since it is a 3 layer structure, the favorable extending | stretching product without film defects, such as a pinhole, is obtained. It has been found

Example 6
A fluoropolymer composition film laminate sheet G having an overall thickness of 3 μm is placed on a liquid crystal polymer sheet C having a thickness of 25 μm at a temperature of 320 ° C., a pressure of 20 kg / cm ² , a time of 10 minutes, and a degree of vacuum of −0.098 MPa or less. Under the conditions, heat fusion was performed with a hot press machine to obtain a laminate sheet having an overall thickness of 28 μm. The dielectric properties of the obtained laminate sheet were evaluated.
Further, an electrolytic copper foil (grade: USLP) having a thickness of 12 μm was applied to the obtained laminate sheet at a temperature of 320 ° C., a pressure of 20 kg / cm ² , a time of 10 minutes, and a vacuum degree of −0.098 MPa or less. Heat fusion was performed with a hot press machine to obtain a copper-clad laminate having a thickness of 40 μm. The peel strength between the copper foil and the substrate of the obtained copper-clad laminate was evaluated.

Comparative Example 3
As the liquid crystal polymer film, a stretched liquid crystal polymer film C having a thickness of 25 μm was used, and the dielectric properties were evaluated.
Furthermore, the electrolytic copper foil was heat-sealed with a hot press in the same manner as in Example 6 to obtain a copper-clad laminate having a thickness of 37 μm. The peel strength between the copper foil and the substrate of the obtained copper-clad laminate was evaluated.

Comparative Example 4
Polyamideimide varnish (PAI) (Toyobo: Viromax HR16NN) was diluted 4 times with N-methylpyrrolidone as a solvent, and then applied onto a stretched liquid crystal polymer C having a thickness of 25 μm with a bar coater (# 30). After coating and primary drying (temperature 170 °, time 10 minutes), secondary drying (250 ° C., 30 minutes) was performed to obtain a PAI coating film (PAI coating film thickness 3.0 μm). The dielectric properties of the obtained PAI coating film were evaluated.
Furthermore, an electrolytic copper foil (grade: USLP) having a thickness of 12 μm was applied to the obtained PAI coating film at a temperature of 330 ° C., a pressure of 20 kg / cm ² , a time of 10 minutes, and a degree of vacuum of −0.098 MPa or less. Heat fusion was performed with a hot press machine to obtain a copper-clad laminate having a thickness of 40 μm. The peel strength between the copper foil and the substrate of the obtained copper-clad laminate was evaluated.

  Table 2 shows the evaluation results of dielectric properties and peel strength in the sheets of Example 6 and Comparative Examples 3 and 4.

  As is apparent from Table 2, Example 6 in which the fluoropolymer composition film laminate sheet was laminated on the liquid crystal polymer film as compared with Comparative Examples 3 and 4 in which the fluoropolymer composition film laminate sheet was not laminated on the liquid crystal polymer film. Has improved dielectric properties and improved interlayer adhesion between the metal foil and the substrate.

Example 7
A 10 μm-thick fluoropolymer composition film (adhesive fluororesin film) E is applied to one side of a 15 μm-thick stretched porous PTFE (porosity 30%) sheet B2 by a vacuum press machine. Lamination was performed at 280 ° C., a pressure of 20 kg / cm ² , a time of 3 minutes, and a degree of vacuum of −0.098 MPa or less to obtain a two-layer laminate sheet having an overall thickness of 25 μm.

Next, this sheet was subjected to a biaxial stretching machine in the same manner as in Example 1 to obtain a fluoropolymer composition film laminate (adhesive sheet (II)) having an overall thickness of 3 μm.
This laminate was heat-sealed on a liquid crystal polymer sheet C having a thickness of 25 μm with a hot press machine at a temperature of 320 ° C., a pressure of 20 kg / cm ² , a time of 5 minutes, and a vacuum degree of −0.098 MPa or less. A laminate sheet having an overall thickness of 28 μm was obtained.

Next, the stretched porous PTFE sheet forming the surface layer was peeled and removed from the laminate sheet to obtain a surface-fusible liquid crystal polymer sheet having a surface layer made of an easily adhesive fluororesin film.
On this sheet, an electrolytic copper foil having a thickness of 12 μm was heat-sealed with a hot press under the same conditions as in Example 6 to obtain a copper-clad laminate having a thickness of 40 μm.

An explanatory sectional view of a plastic sheet laminate formed by laminating and bonding a first adhesive sheet (I) according to the present invention to one surface of a plastic sheet is shown. An explanatory sectional view of a plastic sheet laminate formed by laminating and bonding a first adhesive sheet (I) according to the present invention on both sides of a plastic sheet is shown. An explanatory sectional view of a plastic sheet laminate formed by laminating and bonding a second adhesive sheet (II) according to the present invention to one surface of a plastic sheet is shown. The stretched porous polytetrafluoroethylene sheet adhered to the adhesive sheet (II) is detached from the plastic sheet laminate formed by laminating and bonding the second adhesive sheet (II) according to the present invention to one surface of the plastic sheet. An explanatory cross-sectional view of a plastic sheet having a fusible surface formed as described above is shown.

Explanation of symbols

1, 2 Stretched porous polytetrafluoroethylene sheet 3 Adhesive fluororesin film 4 Sheet-like material

Claims (10)

  An adhesive sheet used for adhering two sheet-like materials, comprising a laminate obtained by laminating and bonding an easily adhesive fluororesin film on both surfaces of an expanded porous polytetrafluoroethylene sheet, and the easily adhesive fluororesin The film is composed of a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and the easily adhesive fluororesin film includes An adhesive sheet, which is integrated with a stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.   An adhesive sheet used for imparting adhesiveness to the surface of a sheet-like material, comprising a laminate obtained by laminating and bonding an easily adhesive fluororesin film on both surfaces of a stretched porous polytetrafluoroethylene sheet. The fluororesin film comprises a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and the easily adhesive fluororesin An adhesive sheet, wherein the film is integrated with the stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.   An adhesive sheet used for imparting adhesiveness to the surface of a sheet-like material, comprising a laminate obtained by laminating and fusing an easily adhesive fluororesin film on one side of a stretched porous polytetrafluoroethylene sheet, The easily adhesive fluororesin film comprises a blend of a fluororesin (A) having an adhesive functional group, a liquid crystal polymer resin (B), and a fluororesin (C) having no adhesive functional group, and the easy adhesive An adhesive sheet characterized in that the porous fluororesin film is integrated with the stretched porous polytetrafluoroethylene sheet and stretched in at least one direction and has a thickness of 50 μm or less.   A laminate sheet obtained by adhering two sheet-like materials through an adhesive sheet, the adhesive sheet comprising the adhesive sheet according to claim 1.   The laminate sheet according to claim 4, wherein at least one of the two sheet-like materials is a liquid crystal polymer resin sheet.   A sheet obtained by imparting adhesiveness to the surface of a sheet-like material via an adhesive sheet, the adhesive sheet comprising the adhesive sheet according to claim 2.   The sheet according to claim 6, wherein the sheet-like material imparted with adhesiveness through an adhesive sheet is a liquid crystal polymer resin sheet.   A sheet provided with adhesiveness on the surface of the sheet-like material, wherein the adhesive sheet according to claim 3 is laminated and adhered to the surface of the sheet-like material, and then the stretched porous polytetrafluoroethylene sheet is peeled and removed. The sheet | seat characterized by comprising.   The sheet according to claim 8, wherein the sheet-like material imparted with adhesiveness is a liquid crystal polymer resin sheet.   After the adhesive sheet according to claim 3 is fused to the surface of the sheet-like material via the easily adhesive fluororesin film, the stretched porous polytetrafluoroethylene sheet is peeled and removed. A method for imparting adhesiveness to the surface of a sheet-like material.

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