Film, laminate, method for manufacturing laminate

Abstract

[Abstract] [Problem] To reduce manufacturing costs while maintaining the performance of a laminate that includes a polyphenylene sulfide layer and a copper layer.　[Solution] Provided are: a low-crystallinity high-adhesiveness polyphenylene sulfide film; a laminate L1 that includes a layer A1 formed from said low-crystallinity high-adhesiveness polyphenylene sulfide film, and a layer of a copper foil having low surface roughness; and a laminate L2 that includes a layer A2 formed from a crystalized substance of the low-crystallinity high-adhesiveness polyphenylene sulfide film, and a layer of a copper foil having low surface roughness.　Selected drawing: FIG. 1

Description

Technical Field

[0001] The present invention relates to a film, a laminate, and a method for manufacturing a laminate. Specifically, it relates to a novel low-crystallinity and high-adhesion polyphenylene sulfide film, a laminate having a layer made of the above low-crystallinity and high-adhesion polyphenylene sulfide film and a layer made of copper (hereinafter, "laminate L1"), a laminate obtained by subjecting the laminate L1 to heat and pressure treatment (hereinafter "laminate L2"), and a method for manufacturing the laminate L2.

Background Art

[0002] Polyphenylene sulfide (hereinafter "PPS") is known as an engineering plastic. Polyphenylene sulfide (PPS) has a structure in which 1,4-phenylene groups and sulfur are alternately repeated, and is a thermoplastic crystalline resin with excellent heat resistance. PPS has a high melting point (280°C), and in addition to exhibiting excellent mechanical strength, rigidity, and dimensional stability by filler filling or alloying, it is a high heat-resistant engineering plastic with the molding processability peculiar to thermoplastic resins, and its applications are expanding mainly as a substitute for metals and thermosetting resins. The electrical properties of PPS have attracted particular attention in recent years. The dielectric tangent, which is a measure of electrical insulation when an alternating voltage is applied, is significantly smaller than that of other engineering plastics, and PPS exhibits excellent insulation even under high temperature and high humidity conditions because it has low water absorption in addition to high heat resistance (Non-Patent Document 1).

[0003] However, because the surface of PPS film lacks reactive groups such as hydroxyl groups (-OH) and carboxyl groups (-COOH), it exhibits poor adhesion to dissimilar materials such as other thermoplastic resins, metals, and glass. Adhesives are known as a means of firmly bonding PPS film to dissimilar materials. Examples include bonding PPS film to copper foil using a polyimide adhesive (Patent Document 1) and bonding PPS film to polyolefin using an adhesive made of polyolefin grafted with specific ethylenically unsaturated monomers (Patent Document 2). However, such adhesive bonding methods have problems, such as the need for various adhesives depending on the materials to be bonded, resulting in poor versatility; increased costs associated with adhesive use; increased overall product size due to the adhesive layer; and the influence of the adhesive layer on the overall product's properties such as shape retention and strength.

[0004] Another method for firmly bonding PPS film to dissimilar materials is so-called surface roughening. In this method, the bonding surface of the PPS film is either physically treated beforehand with plasma treatment or corona discharge treatment, or chemically treated beforehand with acid or alkali (Patent Document 3). Since such surface roughening does not require a new material layer such as an adhesive layer, it is suitable for manufacturing laminates that require thin and precise structures.

[0005] In particular, laminates containing a PPS film layer and a copper foil layer are useful as materials for high-frequency circuits. In the manufacture of such laminates, typically, a pre-plasma-treated PPS film and copper foil are stacked and then pressurized at a high temperature (typically around the melting point of the PPS film: approximately 280°C or higher) to make the PPS film layer and the copper foil layer adhere to each other (Patent Document 4). However, this method tends to have high energy costs for heating and pressurizing, and moreover, the equipment that can be used at such high temperatures is limited.

[0006] In recent years, while the performance of electronic devices has been steadily increasing, there has also been a strong demand for lower costs for electronic devices and their components. Laminates containing PPS film layers and copper foil layers, which are widely used in electronic devices, require both high performance and low cost. However, since performance and manufacturing cost are inherently in a trade-off relationship, solving these challenges is not easy. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Synthetic Chemistry of High-Purity Polyphenylene Sulfide, Kenichi Koyanagi, ENEOS Technical Review Vol. 59, No. 1 (February 2017) [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-55334 [Patent Document 2] Japanese Patent Publication No. 2003-268051 [Patent Document 3] Japanese Patent Publication No. 2003-39595 [Patent Document 4] Japanese Patent Publication No. 2011-253958 [Overview of the project] [Problems that the invention aims to solve]

[0009] The inventors tackled the challenging task of reducing the manufacturing cost of a laminate containing a PPS film layer and a copper foil layer while maintaining its performance characteristics such as heat resistance, dielectric properties, and peel strength. The inventors attempted to solve this problem by re-examining the materials and manufacturing process of the laminate from a fresh perspective, without being bound by preconceived notions or conventional approaches. [Means for solving the problem]

[0010] As a result, the inventors of this invention solved this difficult problem by using PPS film as a raw material, which had not been considered in the prior art. Specifically, in this invention, a low-crystallinity PPS film is used as the sole PPS material, and a low-crystallinity, high-adhesion polyphenylene sulfide film is obtained by subjecting this PPS film to a specific hydrophilization treatment. Furthermore, in this invention, a laminate containing the above low-crystallinity, high-adhesion polyphenylene sulfide film and a specific copper foil is manufactured. Moreover, in this invention, the above laminate is subjected to pressure under relatively mild conditions that could not be used in the prior art, thereby crystallizing the above low-crystallinity, high-adhesion polyphenylene sulfide film and producing a laminate with high peel strength. In other words, this invention is as follows.

[0011] (Invention 1) A low-crystallinity, high-adhesion polyphenylene sulfide film, mainly composed of polyphenylene sulfide resin, having a crystallinity of 20% or less as measured by X-ray diffraction, and a water contact angle of 45° or less on at least one surface.

[0012] (Invention 2) A laminate (L1) comprising a layer (Layer A1) made of a low-crystallinity, high-adhesion polyphenylene sulfide film whose main component is polyphenylene sulfide resin, whose crystallinity measured by X-ray diffraction is 20% or less, and whose water contact angle of at least one surface is 45° or less, and a layer (Layer B) made of copper foil whose surface roughness (Rz) of at least one surface is 2 μm or less, wherein at least one surface of the low-crystallinity, high-adhesion polyphenylene sulfide film with a water contact angle of 45° or less is in contact with at least one surface of the copper foil with a surface roughness (Rz) of 2 μm or less.

[0013] (Invention 3) A laminate (Laminate L2) comprising a layer (Layer A2) made of a crystallized low-crystallinity, high-adhesion polyphenylene sulfide film, mainly composed of polyphenylene sulfide resin, with a crystallinity of 20% or less as measured by X-ray diffraction, and a water contact angle of 45° or less on at least one surface, and a layer (Layer B) made of copper foil with a surface roughness (Rz) of 2 μm or less on at least one surface, wherein Layer A2 and at least one surface of the copper foil with a surface roughness (Rz) of 2 μm or less are in close contact, and the peel strength measured in a 180-degree peel test between Layer A2 and Layer B is 1 N / cm or more.

[0014] (Invention 4) A product comprising the laminate (L2) of Invention 3.

[0015] (Invention 5) A method for manufacturing a laminate, comprising the following steps 1, 2, and 3: (Step 1) First, a low-crystallinity polyphenylene sulfide film is prepared, the main component of which is polyphenylene sulfide resin and the degree of crystallinity measured by X-ray diffraction is 20% or less; and second, a plasma treatment is performed on at least one surface of the low-crystallinity polyphenylene sulfide film, the step of manufacturing a low-crystallinity, high-adhesion polyphenylene sulfide film, the main component of which is polyphenylene sulfide resin and the degree of crystallinity measured by X-ray diffraction is 20% or less. (Step 2) A step of manufacturing a laminate (laminated L1) comprising a layer (layer A1) made of the low-crystallinity, high-adhesion polyphenylene sulfide film and a layer (layer B) made of copper foil having a surface roughness (Rz) of 2 μm or less on at least one side, wherein the low-crystallinity, high-adhesion polyphenylene sulfide film and the copper foil are stacked such that at least one surface of the low-crystallinity, high-adhesion polyphenylene sulfide film having a water contact angle of 45° or less is in contact with at least one surface of the copper foil having a surface roughness (Rz) of 2 μm or less. (Step 3) A step of manufacturing a laminate (laminated L2) comprising a layer (layer A2) made of a crystallized product of the low-crystallinity, high-adhesion polyphenylene sulfide film, and a layer (layer B) made of copper foil having at least one surface roughness (Rz) of 2 μm or less, wherein layer A2 and at least one surface of the copper foil having a surface roughness (Rz) of 2 μm or less are in close contact, and the peel strength measured in a 180-degree peel test between layer A2 and layer B is 1 N / cm or more, the step of heating the laminate L1 under pressure to a temperature above the crystallization temperature of the low-crystallinity, high-adhesion polyphenylene sulfide film. [Effects of the Invention]

[0016] The present invention makes it possible to manufacture a laminate containing a PPS film layer and a copper foil layer having performance equivalent to or better than conventional products at a low cost. [Brief explanation of the drawing]

[0017] [Figure 1]An example of the low-crystallinity and high-adhesion polyphenylene sulfide film of the present invention, and an example of the copper foil used in the present invention are schematically shown. [Figure 2] An example of the laminate L1 of the present invention is schematically shown. [Figure 3] An example of the laminate L2 of the present invention is schematically shown.

Mode for Carrying Out the Invention

[0018] [Low-crystallinity and high-adhesion PPS film] In the present invention, a low-crystallinity and high-adhesion polyphenylene sulfide film (hereinafter referred to as "low-crystallinity and high-adhesion PPS film") having a crystallinity of 20% or less measured by X-ray diffraction method and mainly composed of polyphenylene sulfide resin is used as a starting material, which is one of the features. The above low-crystallinity and high-adhesion PPS film can be produced by irradiating at least one surface of a low-crystallinity PPS film mainly composed of polyphenylene sulfide resin with plasma to enhance the adhesion of this surface to other material surfaces.

[0019] The X-ray diffraction method used for measuring the above crystallinity follows a conventional method. The measurement of the above water contact angle also follows a conventional method. These measurement methods have already been established and there is no difficulty for those skilled in the art to understand and reproduce. The measurement methods adopted in the examples described later are an example following a conventional method, and changes in measurement conditions and measuring instruments are allowed within a range that does not impair the measurement accuracy.

[0020] Any known linear polyphenylene sulfide resin can be used without limitation as the polyphenylene sulfide resin contained in the above-mentioned low-crystallinity PPS film. "Linear polyphenylene sulfide resin" is well known in the art as a representative type of polyphenylene sulfide (the other type is called "crosslinked polyphenylene sulfide"). The above-mentioned linear polyphenylene sulfide resin is a linear polymer substantially composed of p-phenylene sulfide units in which p-phenylene units and sulfide bond units are alternately bonded, and can contain a small amount of m-phenylene sulfide units as long as it has a substantially linear structure. Methods for producing linear polyphenylene sulfide resin are also well known, and industrially, the Phillips method, in which p-dichlorobenzene and sodium sulfide are condensed polymerized in N-methyl-2-pyrrolidone at 200°C to 250°C, and the Dow Chemical method, in which p-bromothiophenylene metal salts are self-condensed polymerized, are typical.

[0021] The proportion of polyphenylene sulfide resin in the low-crystallinity PPS film used in this invention is generally 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more. If the polyphenylene sulfide content is less than 70% by weight, the heat resistance, frequency characteristics, temperature characteristics, etc. of the laminate L2 described later will decrease. If it is less than 30% by weight, other resins or additives may be included. In terms of film molding, the polyphenylene sulfide has a melt viscosity of 1,000 to 25,000 poise (measurement conditions: temperature 300°C, shear rate 200 (seconds)). -1 ) is preferred. The preferred low-crystallinity PPS film of the present invention is an unreinforced (without reinforcing fillers) film made of a linear polyphenylene sulfide resin.

[0022] The thickness of the low-crystallinity PPS film of the present invention is not particularly limited and can be appropriately selected depending on the application of the laminate L2 described later. The thickness of the low-crystallinity PPS film of the present invention is generally 10 μm or more and 500 μm or less, preferably 15 μm or more and 300 μm or less, and more preferably 20 μm or more and 100 μm or less.

[0023] Generally available polyphenylene sulfide resin films are obtained by melt-extruding a base film of polyphenylene sulfide resin and then uniaxially or biaxially stretching it under heating, exhibiting a crystallinity of approximately 40% or more. In contrast, the low-crystallinity PPS film used in the present invention is made by forming a film from a material mainly composed of the above-mentioned polyphenylene sulfide resin under conditions that suppress the crystallinity of the polyphenylene sulfide resin. The means for suppressing crystallinity are not limited, but examples include rapidly cooling a base film obtained by melt-extruding a polyphenylene sulfide resin under unstretched conditions, remelting a commercially available polyphenylene sulfide resin film to make it amorphous, and forming a film from a polyphenylene sulfide resin copolymerized with monomers that give an amorphous structure. In terms of manufacturing cost, the first method (unstretched and rapidly cooled) is preferred. In the production of the low-crystallinity PPS film of the present invention, the crystallization of the polyphenylene sulfide resin is suppressed so that the degree of crystallinity measured by X-ray diffraction is 20% or less, preferably 15% or less, and more preferably 5% or less.

[0024] The low-crystallinity, high-adhesion PPS film of the present invention is obtained by improving the adhesion of at least one surface of the low-crystallinity PPS film to other materials, specifically by plasma-treating at least one surface of the low-crystallinity PPS film. The plasma processing apparatus and plasma treatment conditions are not limited as long as the water contact angle of at least one surface of the obtained low-crystallinity PPS film is 45° or less, preferably 35° or less. Typically, the plasma treatment involves introducing the low-crystallinity PPS film into a drum-type plasma irradiation apparatus or a flat-plate-type plasma irradiation apparatus, and irradiating at least one surface of the low-crystallinity PPS film with plasma in the apparatus. It is presumed that reactive groups such as hydroxyl groups (-OH) and carboxyl groups (-COOH) are generated on the surface by this plasma treatment. For this reason, the plasma treatment in the present invention can also be positioned as a type of hydrophilization treatment. The obtained low-crystallinity, high-adhesion PPS film exhibits high adhesion to other materials such as metals, particularly copper foil. Typically, the plasma treatment described above is performed at a low temperature that does not cause the polyphenylene sulfide resin to crystallize; therefore, the degree of crystallinity of the low-crystallinity PPS film is maintained even after plasma treatment.

[0025] The upper plasma irradiation voltage using a drum-type plasma irradiation device is generally 1.0kV to 4.0kV, preferably 1.5kV to 3.5kV, and more preferably 1.5kV to 3.0kV. Plasma treatment can be performed using other methods, such as a flat-plate type plasma irradiation device, under conditions that provide equivalent plasma irradiation intensity.

[0026] The low-crystallinity, high-adhesion PPS film of the present invention exhibits suppressed thermal shrinkage. The thermal shrinkage rate (%) in the longitudinal direction and the thermal shrinkage rate (%) in the transverse direction of the low-crystallinity, high-adhesion PPS film of the present invention, as determined by the following method, are both 1% or less, preferably 0.5% or less.

[0027] (Method for measuring thermal shrinkage rate) First, cut out a square (100mm × 100mm × 0.025mm) test piece from the sample film and measure the lengths of the four sides (two vertical sides: l1, l2 and two horizontal sides: l3, l4) (l1b, l2b, l3b, l4b). Next, heat press the test piece at 200°C under a load of 2 MPa for 10 minutes. Measure the lengths of the four sides of the test piece after heat pressing (l1a, l2a, l3a, l4a). Calculate the thermal shrinkage rate in the vertical direction (%) and the thermal shrinkage rate in the horizontal direction (%) according to the following formula. • Thermal shrinkage rate in the vertical direction (%) = ((l1b-l1a)+(l2b-l2a))÷(l1b+l2b)×100 • Lateral thermal shrinkage rate (%) = ((l3b-l3a)+(l4b-l4a))÷(l3b+l4b)×100 Using the low-crystallinity, high-adhesion PPS film and copper foil of the present invention, a laminate (hereinafter referred to as "laminated L2") containing a layer made of crystalline PPS and a layer made of copper can be manufactured at a lower manufacturing cost. Because this laminate L2 has excellent peel strength, dielectric properties, and heat resistance, it is useful as a component of capacitors, circuit boards used in various communication devices, transmission cables, and antennas.

[0028] The above-mentioned laminate L2 can be manufactured by heating and pressurizing a laminate (hereinafter referred to as "laminated L1") which includes a layer made of the above-mentioned low-crystallinity, high-adhesion PPS film (hereinafter referred to as "layer A1") and a layer made of copper (hereinafter referred to as "layer B"). The above-mentioned laminate L1 is positioned as an intermediate of the above-mentioned laminate L2.

[0029] [Laminate L1] In the present invention, a laminate (laminated L1) is manufactured by stacking the above-mentioned low-crystallinity, high-adhesion polyphenylene sulfide film and copper foil, and including a layer (layer A1) made of the above-mentioned low-crystallinity, high-adhesion polyphenylene sulfide film and a layer (layer B) made of copper foil.

[0030] It has been found that the smoother the surface of the copper foil in contact with the low-crystallinity, high-adhesion polyphenylene sulfide film, i.e., the lower its surface roughness, the better the adhesion between layer A1 and layer B. When bonding a polyphenylene sulfide film and copper foil via an adhesive, or when coating a molten polyphenylene sulfide film with copper foil, a higher surface roughness on the copper foil surface in contact with the polyphenylene sulfide film results in higher adhesive strength. Surprisingly, however, the opposite is true in this invention.

[0031] Therefore, in this invention, copper foil is used in which at least one surface roughness (Rz) is 2 μm or less, preferably at least one surface roughness (Rz) is 1.5 μm or less. The measurement of the above surface roughness (Rz) follows a conventional method. The method for measuring surface roughness (Rz) is already established and will not be difficult for those skilled in the art to understand and replicate. The measurement method adopted in the examples described later is one example of a conventional method, and changes to the measurement conditions and measuring equipment are permitted as long as the measurement accuracy is not impaired.

[0032] In the laminate L1 described above, at least one surface of the low-crystallinity, high-adhesion polyphenylene sulfide film having a water contact angle of 45° or less is in contact with at least one surface of the copper foil having a surface roughness (Rz) of 2 μm or less.

[0033] The copper foil used here can be any known copper foil, such as electrolytic copper foil or rolled copper foil, as long as its surface roughness meets the above-mentioned conditions. Furthermore, copper foil with a carrier foil or copper foil with a nickel layer can also be used. The copper foil may also be pre-treated. The thickness of the copper foil is not particularly limited, but is generally in the range of 5 μm to 50 μm, preferably 10 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0034] The number of layers A1 and B that constitute the laminate L1 is not particularly limited. The lamination method for the low-crystallinity, high-adhesion polyphenylene sulfide film and copper foil follows conventional methods. Generally, a vacuum press is used.

[0035] [Laminate L2] In the present invention, laminate L2 is further manufactured by heating laminate L1 under pressure to a temperature above the crystallization temperature of the low-crystallinity, high-adhesion polyphenylene sulfide film. The polyphenylene sulfide contained in the low-crystallinity, high-adhesion polyphenylene sulfide film crystallizes due to the heating. Therefore, laminate L2 of the present invention includes a layer (layer A2) made of crystalline material of the low-crystallinity, high-adhesion polyphenylene sulfide film, and a layer (layer B) made of copper foil having a surface roughness (Rz) of 2 μm or less on at least one side, and layer A2 and at least one surface of the copper foil having a surface roughness (Rz) of 2 μm or less are firmly adhered to each other.

[0036] The peel strength of the laminate L2 of the present invention, as measured in a 180-degree peel test, is 1 N / cm or more, preferably 4 N / cm or more. The above 180-degree peel test follows a conventional method. The measurement method for the 180-degree peel test is already established and will not be difficult for those skilled in the art to understand and replicate. The measurement method adopted in the embodiments described below is just one example of a conventional method, and changes to the measurement conditions and measuring equipment are permitted as long as the measurement accuracy is not impaired.

[0037] The manufacturing of the laminate L2 involves pressing the laminate L1 so that layer A1 and layer B are tightly packed together without any gaps, and then heating the laminate L1 to a temperature above the crystallization temperature of the low-crystallinity, high-adhesion polyphenylene sulfide film. While any suitable apparatus can be selected for this pressurizing and heating process, a vacuum press is typically used. The pressing force is not limited as long as layer A1 and layer B are tightly packed together without any gaps, but is generally between 1 MPa and 6 MPa, preferably between 2 MPa and 5 MPa. The crystallization temperature, which serves as the basis for the predetermined temperature, refers to the crystallization temperature of the polyphenylene sulfide resin, the main component of the low-crystallinity, high-adhesion polyphenylene sulfide film. The crystallization temperature of polyphenylene sulfide resin, typically linear polyphenylene sulfide resin, is in the range of 120°C to 130°C. In order to sufficiently crystallize the layer (layer A1) made of the low-crystallinity, high-adhesion polyphenylene sulfide film described above with the minimum necessary energy cost, the predetermined temperature is selected within a range of approximately 130°C to 230°C, preferably 140°C to 200°C, and more preferably 150°C to 190°C. The higher this temperature, the higher the energy cost, but the greater the crystallization that tends to be achieved.

[0038] Layer A2 differs from conventional crystalline polyphenylene sulfide layers, i.e., layers made of films commercially available as crystalline polyphenylene sulfide films, in terms of thermal history. While current analytical techniques make it difficult to express the difference between layer A2 and conventional crystalline polyphenylene sulfide layers in terms of the molecular structure or orientation of polyphenylene sulfide, it is known that differences in thermal history affect some property of most polymer compounds. Therefore, the laminate L2 having layer A2 is different from both conventional laminates consisting of a crystalline polyphenylene sulfide layer and laminates consisting of a copper layer.

[0039] The advantages of the laminate L2 of the present invention over conventional products lie in manufacturing cost and manufacturing equipment. In the manufacturing of conventional products, it was necessary to heat the crystalline polyphenylene sulfide film to a temperature near the melting point of the polyphenylene sulfide film (approximately 280°C) during the hot pressing process between the crystalline polyphenylene sulfide film and the copper foil. However, in the present invention, the hot pressing temperature is much lower. As a result, the cost of manufacturing the laminate L2 is reduced compared to conventional products, and the laminate L2 of the present invention can be manufactured even with equipment that has relatively poor heat resistance.

[0040] Using a laminate containing smoother copper foil and a polyphenylene sulfide film as a circuit board offers the advantage of reducing transmission loss. At the interface between the copper foil layer B and the crystalline polyphenylene sulfide film layer A2 constituting the laminate L2 of the present invention, the lower surface roughness of the copper foil used in the aforementioned laminate L1 is maintained. For this reason, the laminate L2 of the present invention is particularly excellent as a material for copper-clad laminates for high-frequency circuit boards.

[0041] [Product] In terms of peel strength, heat resistance, and dielectric properties, the laminate L2 of the present invention has performance equal to or better than conventional products, namely laminates obtained by laminating a crystalline polyphenylene sulfide film and copper foil. For this reason, the laminate L2 of the present invention can replace conventional products in all fields in which laminates obtained by laminating a crystalline polyphenylene sulfide film and copper foil have been applied. The laminate L2 of the present invention can be used, for example, as a component of capacitors, circuit boards used in various communication devices, circuit boards used in base stations, circuit boards used in automotive millimeter-wave radar, transmission cables, and antennas, and is particularly useful as a component for high frequencies. [Examples]

[0042] [Examples 1-10, Comparative Examples 1-10] (Materials) The following materials were used in the manufacture of the examples and comparative products of the present invention. * indicates a comparative product that deviates from the conditions of the present invention.

[0043] • Low-crystallinity PPS film (F1): An unstretched film made of linear, unreinforced PPS with 0% crystallinity, obtained by melt-extruding a film of linear polyphenylene sulfide composed of p-phenylene sulfide units and then rapidly cooling the film. Thickness: 25 μm.

[0044] • Low-crystallinity PPS film (F2): An unstretched film made of linear, unreinforced PPS with a crystallinity of 13.9%, obtained by melt-extruding a film of linear polyphenylene sulfide composed of p-phenylene sulfide units and then rapidly cooling the film. Thickness: 25 μm.

[0045] • Low-crystallinity PPS film (F3*): An unstretched film made of linear, unreinforced PPS with a crystallinity of 28.4%, obtained by melt-extruding a film of linear polyphenylene sulfide composed of p-phenylene sulfide units and then rapidly cooling the film. Thickness: 25 μm.

[0046] • Crystalline PPS film (comparative product, F4*): A commercially available linear, filler-free type of PPS film. Crystallinity approximately 50%, thickness 25 μm.

[0047] • Copper foil (M1): Rolled copper foil with a thickness of 30 μm. Surface roughness Rz: 1.2 μm • Copper foil (comparative product, M2*): Rolled copper foil with a thickness of 30 μm. Surface roughness Rz: 2.2 μm (Manufacturing of Low Crystallinity, High Adhesion Polyphenylene Sulfide Film) One side of the above PPS film was plasma-treated using a drum-type plasma irradiation device under the conditions shown in Table 1. In this way, the low crystallinity, high adhesion polyphenylene sulfide film of the present invention and its comparative product were manufactured. In Table 1, "-" indicates that no treatment was performed. The water contact angle and thermal shrinkage rate of the obtained polyphenylene sulfide film are shown in Table 1.

[0048] [Table 1]

[0049] (Manufacturing of Laminate L1) PPS film and copper foil were laminated in the combinations shown in Tables 2 and 3, such that the plasma-treated surface of the PPS film was in contact with the surface of the copper foil. Laminate L1 of the present invention and its comparative counterparts were obtained.

[0050] (Manufacturing of Laminate L2) Laminate L1 of the present invention and its comparative counterpart were placed in a vacuum press and heated under pressure under the following conditions. Thus, laminate L2 of the present invention and its comparative counterpart were obtained. The peel strength, dielectric constant, and dielectric loss tangent of the obtained laminate L2 are shown in Tables 2 and 3. • Pressurization conditions: The pressure was maintained at 4 MPa from the start to the end of heating. • Heating conditions: The temperature was raised from 70°C to 160°C in 7 minutes, and then held at 160°C for 5 minutes.

[0051] [Table 2]

[0052] [Table 3]

[0053] (Measurement Method) The crystallinity, water contact angle, surface roughness (Rz), peel strength, and thermal shrinkage rate were measured using the following method.

[0054] <Crystallization> • Measuring instrument: Horizontal X-ray diffractometer for samples Voltage: 30kV ·Current: 20mA Step width: 0.02° ·Measurement speed: 2° / min The peaks identified by XRD measurement were separated into crystalline and amorphous regions, and the degree of crystallinity was calculated from the ratio of their peak areas according to the following formula. Crystallinity = (Peak area of ​​crystalline portion) / (Total peak area) × 100 <Contact angle of water> • Measuring instrument: Contact angle and wettability measuring instrument ·Dropped water amount: 2μL • Sample size (N): 5 • Measurement method: 2 μL of distilled water was slowly dropped onto the film surface using a syringe, and the contact angle was observed and measured using a CCD camera 3 seconds after dropping. The average of the measured values ​​was adopted as the water contact angle.

[0055] <Surface roughness> • Measuring instrument: Surface roughness measuring instrument • Stylus material: Diamond ·Stylus tip radius: 5μm • Measuring force: 4mN • Low-frequency cutoff value: 8μm • High-frequency cutoff value: 2.5mm • Evaluation length: 7.5mm • Measurement interval: 1.5 μm ·Measurement speed: 0.5mm / s • Number of sections: 3 • Number of records: 5 The value of Rz (maximum height of the roughness curve), which is the sum of the maximum peak height and maximum valley depth of the roughness curve, was adopted as the surface roughness.

[0056] <Peel strength> • Measuring instrument: High-speed peel tester • Test speed: 120 mm / min • Test: A test specimen measuring 150 mm in length and 10 mm in width was cut from the laminate. The 180° peel strength (M / cm) of this specimen was measured. • Evaluation: Interlayer adhesion was evaluated in three stages based on peel strength (exceptionally good +++: 4 N / cm or more, acceptable +: 1 N / cm or more but less than 4 N / cm, poor -: less than 1 N / cm).

[0057] <Thermal shrinkage rate> A square (100mm x 100mm x 0.025mm) test specimen was cut from the film, and the lengths of its four sides (two vertical sides: l1, l2 and two horizontal sides: l3, l4) (l1b, l2b, l3b, l4b) were measured. Next, the test specimen was hot-pressed at 200°C under a load of 2 MPa for 10 minutes. The lengths of the four sides of the test specimen after hot-pressing (l1a, l2a, l3a, l4a) were measured. The thermal shrinkage rate in the vertical direction (%) and the thermal shrinkage rate in the horizontal direction (%) were calculated according to the following formula. • Thermal shrinkage rate in the vertical direction (%) = ((l1b-l1a)+(l2b-l2a))÷(l1b+l2b)×100 • Lateral thermal shrinkage rate (%) = ((l3b-l3a)+(l4b-l4a))÷(l3b+l4b)×100 (Evaluation) As shown in Table 2, the laminate L2 of the present invention (Examples 6-10) exhibits good peel strength and dielectric properties despite being obtained by hot pressing at relatively low temperatures. Comparative examples of laminate L2 using polyphenylene sulfide film whose crystallinity or water contact angle does not meet the requirements of the present invention (Comparative Examples 7-10), and comparative examples of laminate L2 where the surface roughness of the copper foil does not meet the requirements of the present invention (too high) (Comparative Examples 5 and 6), show lower peel strength between the polyphenylene sulfide layer and the copper foil layer, making them less practical.

[0058] [Examples 11-15] (Manufacturing of low-crystallinity, high-adhesion polyphenylene sulfide films) A film of linear polyphenylene sulfide consisting of p-phenylene sulfide units was melt-extruded and rapidly cooled to obtain an unoriented PPS film (F5) with 0% crystallinity. One side of this film was plasma-treated under the conditions shown in Table 4. The low-crystallinity, high-adhesion polyphenylene sulfide film PPS10 of the present invention was obtained. The properties of film PPS10 are shown in Table 4.

[0059] [Table 4]

[0060] Separately, copper foils M2 to M5, as shown in Table 5 below, were prepared.

[0061] [Table 5]

[0062] (Manufacturing of Laminate L1) A low-crystallinity, high-adhesion PPS film (PPS10) and one of the above copper foils M2 to M5 were laminated in the combinations shown in Table 6, such that the plasma-treated surface of the PPS film was in contact with the surface of the copper foil. In this way, laminate L1 of the present invention was obtained.

[0063] (Manufacturing of Laminate L2) The laminate L1 of the present invention was placed in a vacuum press and heated under pressure under the conditions shown in Table 6. Laminate L2 of the present invention was thus obtained. The peel strength, dielectric constant, and dielectric loss tangent of the obtained laminate L2 are shown in Table 6. The method for determining the peel strength is the same as in Examples 6 to 10 and Comparative Examples 5 to 10.

[0064] [Table 6]

[0065] (Evaluation) As shown in Table 6, when the low-crystallinity, high-adhesion polyphenylene sulfide film PPS10 is laminated with copper foil having a different thickness and surface roughness than M, the laminate L2 exhibits particularly high peel strength and good dielectric properties. That is, the peel strength of the laminates produced in Examples 12 to 15 far exceeds the standard value of "4 N / cm" required to be judged as "particularly good +++". Examples 11 to 15 demonstrate that the low-crystallinity, high-adhesion polyphenylene sulfide film of the present invention adheres firmly to a wide range of copper foils with at least one surface roughness (Rz) of 2 μm or less, and as a result, a useful laminate L2 can be obtained. [Industrial applicability]

[0066] The low-crystallinity, high-adhesion polyphenylene sulfide film of the present invention, the laminate L1 of the present invention comprising a layer A1 made of the low-crystallinity, high-adhesion polyphenylene sulfide film and a layer B made of copper foil, and the laminate L2 of the present invention comprising a layer A2 made of a crystalline product of the low-crystallinity, high-adhesion polyphenylene sulfide film and a copper foil layer B are useful as materials for high-performance, low-cost electrical, electronic, and communication devices. [Explanation of Symbols]

[0067] 1. Low-crystallinity, high-adhesion polyphenylene sulfide film 100 Surfaces with a water contact angle of 45° or less 101 Layer A1, made of a low-crystallinity, high-adhesion polyphenylene sulfide film 102 Layer A2 consisting of crystallized material of low-crystallinity, high-adhesion polyphenylene sulfide film 2 Copper foil 200 Surfaces with a surface roughness (Rz) of 2 μm or less 201 Layer B 3. Laminate L1 4 Laminate L2

Claims

1. A layer (Layer A1) consisting of an unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, the crystallinity measured by X-ray diffraction is 20% or less, the water contact angle of both surfaces is 45° or less, and both the longitudinal thermal shrinkage (%) and transverse thermal shrinkage (%) determined by the following thermal shrinkage measurement method are 1% or less. (Method for measuring thermal shrinkage rate) From the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, a square (100 mm × 100 mm × 0.025 mm) test specimen is cut out, and the lengths of the four sides (two vertical sides: l1, l2 and two horizontal sides: l3, l4) (l1b, l2b, l3b, l4b) are measured. Next, the test specimen is hot-pressed at 200°C under a load of 2 MPa for 10 minutes. Measure the lengths of the four sides (l1a, l2a, l3a, l4a) of the test specimen after heat pressing. Calculate the thermal shrinkage rate in the longitudinal direction (%) and the thermal shrinkage rate in the transverse direction (%) according to the following formula. • Thermal shrinkage rate in the vertical direction (%) = ((l1b - l1a) + (l2b - l2a)) ÷ (l1b + l2b) × 100 • Transverse thermal shrinkage rate (%) = ((l3b - l3a) + (l4b - l4a)) ÷ (l3b + l4b) × 100 And, It includes a layer (layer B) made of copper foil having at least one surface roughness (Rz) of 0.7 μm or more and 1.2 μm or less, Both surfaces of the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, where the water contact angle is 45° or less, are in contact with at least one surface of the above-mentioned copper foil, where the surface roughness (Rz) is 0.7 μm or more and 1.2 μm or less. Laminate (L1).

2. A layer (Layer A2) consisting of crystallized material of an unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, the crystallinity of which is measured by X-ray diffraction is 20% or less, the water contact angle of both surfaces is 45° or less, and both the longitudinal heat shrinkage rate (%) and transverse heat shrinkage rate (%) determined by the following heat shrinkage rate measurement method are 1% or less. (Method for measuring thermal shrinkage rate) From the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, a square (100 mm × 100 mm × 0.025 mm) test specimen is cut out, and the lengths of the four sides (two vertical sides: l1, l2 and two horizontal sides: l3, l4) (l1b, l2b, l3b, l4b) are measured. Next, the test specimen is hot-pressed at 200°C under a load of 2 MPa for 10 minutes. Measure the lengths of the four sides (l1a, l2a, l3a, l4a) of the test specimen after heat pressing. Calculate the thermal shrinkage rate in the longitudinal direction (%) and the thermal shrinkage rate in the transverse direction (%) according to the following formula. • Thermal shrinkage rate in the vertical direction (%) = ((l1b - l1a) + (l2b - l2a)) ÷ (l1b + l2b) × 100 • Transverse thermal shrinkage rate (%) = ((l3b - l3a) + (l4b - l4a)) ÷ (l3b + l4b) × 100 Furthermore, it includes a layer (layer B) made of copper foil having a surface roughness (Rz) of at least one side of 0.7 μm or more and 1.2 μm or less. Both surfaces of layer A2 and at least one surface of the copper foil having a surface roughness (Rz) of 0.7 μm or more and 1.2 μm or less are in close contact. The peel strength measured in the 180-degree peel test between layer A2 and layer B is 4 N / cm or more. Laminate (Laminate L2).

3. A product comprising the laminate (L2) described in Claim 2.

4. A method for manufacturing a laminate, comprising the following steps 1, 2, and 3. (Process 1) First, a low-crystallinity polyphenylene sulfide film is prepared, mainly composed of polyphenylene sulfide resin, with a crystallinity of 20% or less as measured by X-ray diffraction. Next, at least one surface of the low-crystallinity polyphenylene sulfide film is subjected to plasma treatment. A process for producing an unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, in which polyphenylene sulfide resin is the main component, the degree of crystallinity measured by X-ray diffraction is 20% or less, the water contact angle of both surfaces is 45° or less, and both the longitudinal thermal shrinkage rate (%) and transverse thermal shrinkage rate (%) determined by the following thermal shrinkage rate measurement method are 1% or less. (Method for measuring thermal shrinkage rate) From the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, a square (100 mm × 100 mm × 0.025 mm) test specimen is cut out, and the lengths of the four sides (two vertical sides: l1, l2 and two horizontal sides: l3, l4) (l1b, l2b, l3b, l4b) are measured. Next, the test specimen is hot-pressed at 200°C under a load of 2 MPa for 10 minutes. Measure the lengths of the four sides (l1a, l2a, l3a, l4a) of the test specimen after heat pressing. Calculate the thermal shrinkage rate in the longitudinal direction (%) and the thermal shrinkage rate in the transverse direction (%) according to the following formula. • Thermal shrinkage rate in the vertical direction (%) = ((l1b - l1a) + (l2b - l2a)) ÷ (l1b + l2b) × 100 • Transverse thermal shrinkage rate (%) = ((l3b - l3a) + (l4b - l4a)) ÷ (l3b + l4b) × 100 (Step 2) A process for producing a laminate (laminated L1) comprising a layer (layer A1) made of the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, and a layer (layer B) made of copper foil having a surface roughness (Rz) of 0.7 μm or more and 1.2 μm or less, A step of stacking the unoriented, low-crystallinity, high-adhesion polyphenylene sulfide film and the copper foil such that both surfaces of the unoriented, low-crystallinity, high-adhesion polyphenylene sulfide film, where the water contact angle is 45° or less, are in contact with at least one surface of the copper foil, where the surface roughness (Rz) is 0.7 μm or more and 1.2 μm or less. (Step 3) A process for manufacturing a laminate (laminated L2) comprising a layer (layer A2) made of a crystallized product of the above-mentioned unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film, and a layer (layer B) made of copper foil having at least one surface roughness (Rz) of 1.2 μm or less, wherein both surfaces of layer A2 and at least one surface of the copper foil having a surface roughness (Rz) of 0.7 μm or more and 1.2 μm or less are in close contact, and the peel strength measured in a 180-degree peel test between layer A2 and layer B is 4 N / cm or more, A step of heating the laminate L1 under pressure to a temperature in the range of 150°C to 190°C, which is above the crystallization temperature of the unstretched, low-crystallinity, high-adhesion polyphenylene sulfide film.

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