Molded body, circuit board, and modification method

Abstract

To achieve both adhesion to another material such as metal and electric characteristics inherent to a fluorine resin.SOLUTION: A molding made of a fluorine resin has such an element composition on a surface, which is specified by X-ray photoelectron spectroscopy with carbon, oxygen, fluorine, and sodium as detection objects, in which a limit of the total of carbon and oxygen is 100 atom% or less, carbon is 60 atom% or more and 80 atom% or less and oxygen is 10 atom% or more and 25 atom% or less, and a content of oxygen at a position of a depth from the surface which is specified by X-ray photoelectron spectroscopy with carbon, oxygen, fluorine, and sodium as detection objects of 200 nm is 0 atom% or more and 12 atom% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluororesin molded article, a circuit board including the fluororesin molded article, and a method for modifying the surface of the fluororesin molded article. [Background technology]

[0002] Circuit boards are widely used in the field of electronic devices. In particular, circuit boards used in communication devices are desirably made of an insulator with a small dielectric constant and dielectric loss tangent to achieve high-speed, low-loss communication.

[0003] Fluorine resins are a typical example of a material with a small dielectric constant and dielectric loss tangent. However, since fluororesins have poor adhesion to other materials, including metals, in order to manufacture circuit boards that use fluororesins as insulators, it is necessary to perform a treatment to impart adhesiveness to the surface of the fluororesin. For example, Japanese Patent Laid-Open Publication No. 2006-128443 (Patent Document 1) discloses a method of imparting adhesiveness to the surface of a fluororesin molded body by treating it with a metal sodium-naphthalene complex solution.

[0004] Furthermore, substrate materials that combine fluororesin and inorganic materials are also widely used in this field, as exemplified by the substrate material manufactured by impregnating glass cloth with fluororesin, as disclosed in JP 2008-12683 A (Patent Document 2). In this case, the inorganic material portion is responsible for adhesiveness to metal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-128443 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-12683 [Non-patent literature]

[0006] [Non-Patent Document 1] Peng Lei et. al., Org. Lett. 2018, 20, 12, 3439-3442 Summary of the Invention [Problem to be solved by the invention]

[0007] However, surface modification techniques using a metallic sodium-naphthalene complex solution modify not only the surface area that contributes to adhesiveness but also the area deep below the surface, which can result in the loss of the electrical properties inherent to the fluororesin. Furthermore, substrate materials manufactured by impregnating glass cloth with fluororesin contain glass material, which has inferior electrical properties compared to fluororesin, making it difficult to improve their electrical properties.

[0008] Therefore, there is a demand for fluororesin molded articles that have both adhesive properties to other materials such as metals and the electrical properties inherent to fluororesins, and there is also a demand for circuit boards that include such molded articles. [Means for solving the problem]

[0009] The first molded article according to the present invention is a molded article made of a fluororesin, and the elemental composition at the surface, as determined by X-ray photoelectron spectroscopy using carbon, oxygen, fluorine, and sodium as the detection targets, is 60 atomic % or more and 80 atomic % or less of carbon and 10 atomic % or more and 25 atomic % or less of oxygen, with the sum of carbon and oxygen being limited to 100 atomic % or less, and the oxygen content at a position 200 nm deep from the surface, as determined by X-ray photoelectron spectroscopy using carbon, oxygen, fluorine, and sodium as the detection targets, is 0 atomic % or more and 12 atomic % or less. In Raman spectroscopy, the Raman shift was 1050 cm -1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 A peak is detected in at least one of the following areas: It is characterized by:

[0010] The second molded article according to the present invention is a molded article made of a fluororesin, and the elemental composition on the surface, as determined by X-ray photoelectron spectroscopy detecting carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being limited to 100 atomic % or less, and the Raman shift is 1050 cm or less in Raman spectroscopy. -1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 The peak is detected in at least one of the following regions:

[0011] A third molded article according to the present invention is a molded article made of a fluororesin, and the elemental composition of the surface, as determined by X-ray photoelectron spectroscopy detecting carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon and 10 atomic % or more and 25 atomic % or less of oxygen, with the sum of carbon and oxygen being 100 atomic % or less, and the developed area ratio (Sdr) of the interface, as measured in accordance with ISO 25178, is 0.02 or more and 0.1 or less. In Raman spectroscopy, the Raman shift was 1050 cm -1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 A peak is detected in at least one of the following areas: It is characterized by:

[0012] Further, a circuit board according to the present invention is a circuit board including a molded body made of a fluororesin, The molded body, The elemental composition at the surface of the molded body, as determined by X-ray photoelectron spectroscopy using carbon, oxygen, fluorine, and sodium as the detection targets, is 60 atomic % or more and 80 atomic % or less of carbon and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being 100 atomic % or less, and the oxygen content at a position 200 nm deep from the surface of the molded body, as determined by X-ray photoelectron spectroscopy using carbon, oxygen, fluorine, and sodium as the detection targets, is 0 atomic % or more and 12 atomic % or less. In Raman spectroscopy, the Raman shift was 1050 cm-1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 A peak is detected in at least one of the following regions: It is characterized by:

[0013] These features provide a molded article in which only the outermost surface portion that contributes to adhesiveness is modified, and a circuit board including the molded article, which can achieve both adhesiveness to other materials such as metals and the electrical properties inherent to fluororesin. Furthermore, the reaction required to develop adhesiveness progresses particularly sufficiently on the surface of the molded article, so that good adhesiveness can be developed.

[0014] The modification method according to the present invention is a method for modifying the surface of a molded body made of a fluororesin, and includes a first step of contacting an electron donor with the surface of the molded body, and a second step of contacting a ketone compound with the surface of the molded body after the first step, wherein the electron donor includes a dispersion in which metallic sodium is dispersed in a solvent, and at least one compound selected from the group consisting of 1,3-dialkyl-2-imidazolidinone and crown ether.

[0015] According to these configurations, only the outermost surface portion that contributes to adhesiveness can be modified, so that the molded article obtained by modification can have both adhesiveness to other materials such as metals and the electrical properties that the fluororesin inherently possesses.

[0016] Preferred embodiments of the present invention will be described below, but the scope of the present invention is not limited to the preferred embodiments described below.

[0017] In one embodiment, the molded body according to the present invention preferably has a fluorine content of 30 atomic % or more and 67 atomic % or less at a depth of 200 nm from the surface, as determined by X-ray photoelectron spectroscopy that detects carbon, oxygen, fluorine, and sodium.

[0018] According to this configuration, the electrical properties inherent to the fluororesin are further maintained, and even better electrical properties can be achieved.

[0019] In one embodiment, the molded article according to the present invention has a Raman shift of 1050 cm -1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 Preferably, a peak is detected in at least one of the following regions:

[0020] In this configuration, the reaction required to develop adhesiveness progresses particularly sufficiently in the surface portion of the molded article, so that even better adhesiveness can be developed.

[0021] In one aspect of the molded article according to the present invention, the fluororesin preferably contains 95 mol % or more of tetrafluoroethylene units.

[0022] In this configuration, the molded body is formed mainly from a fluororesin that has particularly good electrical properties among fluororesins, and therefore, even better electrical properties can be achieved.

[0023] In one embodiment, the molded article according to the present invention preferably has an interface developed area ratio (Sdr) measured in accordance with ISO 25178 of 0.02 or more and 0.1 or less.

[0024] According to this configuration, since no more modification than necessary is carried out, the electrical properties inherent to the fluororesin are further maintained, and even better electrical properties can be exhibited.

[0025] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments, which is given with reference to the drawings. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing a Raman spectrum according to an example. [Figure 2] FIG. 10 is a diagram showing a Raman spectrum according to a comparative example. [Figure 3]1 is an SEM image according to an example. [Figure 4] 10 is an SEM image according to a comparative example. [Figure 5] FIG. 10 is a diagram showing the measurement results of the transmission loss of a copper-plated modified sheet. DETAILED DESCRIPTION OF THE INVENTION

[0027] Embodiments of the molded body, circuit board, and modification method according to the present invention will be described with reference to the drawings. Below, an example in which a fluororesin sheet was modified to obtain a surface-modified sheet, and an example in which a circuit board was manufactured using the modified sheet as a substrate will be described. The sheet is an example of the molded body.

[0028] [Modification method] First, we will explain the modification method for modifying a fluororesin sheet to obtain a surface-modified sheet. Hereinafter, for the sake of distinction, the sheet before the modification treatment will be referred to as an "unmodified sheet," and the surface-modified sheet will be referred to as a "modified sheet." Furthermore, the term "sheet" refers to a molded product having a thickness that is significantly smaller than its surface extent. The thickness of the sheet is not particularly limited, but can be, for example, 10 μm or more and 2000 μm or less.

[0029] (Unmodified sheet composition) The unmodified sheet is a sheet made of a conventional fluororesin. Fluororesin is a resin material containing fluorine-containing monomers as polymerization units. The fluororesin in this embodiment may be, but is not limited to, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or a mixture thereof. However, among the fluororesins listed above, it is preferable to use perfluorofluororesins (PTFE, FEP, and PFA), which exhibit particularly good high-frequency characteristics.

[0030] However, the fluororesin preferably contains 95 mol% or more of tetrafluoroethylene units, more preferably 97 mol% or more. Fluororesins that meet this condition are typically PTFE and PFA, with PTFE being more preferred. PTFE may be a so-called homo-PTFE containing only tetrafluoroethylene as a polymer unit, or a so-called modified PTFE containing polymer units other than tetrafluoroethylene. The content of tetrafluoroethylene units in a fluororesin can be determined by nuclear magnetic resonance (melt) analysis. 19 F NMR or solid state 19 It can be quantified by F NMR or infrared spectroscopy (IR).

[0031] The melting point of the fluororesin is preferably 300°C or higher, and more preferably 320°C or higher. The melting point of the fluororesin can be determined, for example, by differential scanning calorimetry (DSC measurement). The measurement conditions for DSC measurement follow the industrial standards for each fluororesin (ASTM D4894, ASTM D2116, ASTM D3307, etc.).

[0032] Unmodified sheets can be produced by known methods such as cutting, compression molding, and extrusion. For example, PTFE sheets can be obtained by compression molding a PTFE material into a block, followed by sintering the resulting billet, and then cutting the resulting billet. For example, PFA sheets can be obtained by extrusion molding using a T-die.

[0033] (Procedure for modification method) The modification method according to this embodiment includes a first step of contacting the surface of an unmodified sheet with an electron donor, and a second step of contacting the surface of the sheet after the first step with a ketone compound. Through the first and second steps, fluorine atoms present on the surface of the unmodified sheet are substituted with oxygen-containing functional groups.

[0034] (1) First step The first step is to contact the surface of the unmodified sheet with an electron donor, which is a mixture containing a dispersion of metallic sodium in a solvent (hereinafter referred to as "SD," where SD is an abbreviation for sodium dispersion) and at least one compound selected from the group consisting of 1,3-dialkyl-2-imidazolidinone and crown ether.

[0035] SD is a dispersion of sodium in the form of fine particles (i.e., a solid) in a dispersion medium, or in the form of minute droplets (i.e., a liquid) in a dispersion medium, where the sodium may be pure metallic sodium or an alloy containing metallic sodium.

[0036] The average particle size of sodium (fine particles or droplets) in SD is preferably less than 100 μm, more preferably less than 50 μm, even more preferably less than 30 μm, even more preferably less than 10 μm, and particularly preferably less than 5 μm. The average particle size is expressed as the diameter of a sphere having the same projected area as that obtained by image analysis of a micrograph.

[0037] The content of metallic sodium in SD is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass. The content of metallic sodium may be calculated from the mass ratio of metallic sodium to dispersion solvent used in producing SD, or may be determined by a method in which the obtained SD is added to an excess amount of water to form an aqueous sodium hydroxide solution, and the amount of metallic sodium in SD is determined based on the concentration of the aqueous sodium hydroxide solution determined by neutralization titration.

[0038] Any known solvent can be used as the dispersion solvent, as long as it can disperse sodium (fine particles or droplets) and does not inhibit the reactions occurring in the first and second steps of this embodiment. Dispersion solvents that meet these requirements include solvents known in the art, such as paraffinic solvents (normal paraffinic solvents and cycloparaffinic solvents), aromatic solvents, and heterocyclic solvents. Examples of normal paraffinic solvents include, but are not limited to, normal pentane, normal hexane, normal heptane, normal octane, normal nonane, and normal decane. Examples of cycloparaffinic solvents include, but are not limited to, cyclopentane. Examples of ether solvents include, but are not limited to, tetrahydrofuran, cyclopentyl methyl ether, and 2-methyltetrahydropyrene. Examples of aromatic solvents include, but are not limited to, benzene, toluene, and xylene. Examples of amine solvents include, but are not limited to, ethylenediamine. Examples of heterocyclic solvents include, but are not limited to, tetrahydrothiophene. These solvents may be used alone or as a mixed solvent of two or more of them.

[0039] As a specific method for producing SD, known methods can be adopted. For example, JP 2007-197787 A discloses a method in which metallic sodium (liquid) heated to a temperature equal to or higher than the melting point and a paraffinic solvent are mixed sequentially in a primary dispersion device and a secondary dispersion device.

[0040] The primary dispersion device can be, for example, a stirrer equipped with paddle blades or disk turbine blades, and the stirrer is provided with a jacket through which synthetic heat transfer oil can be circulated. The stirrer is operated with synthetic heat transfer oil at 105 to 140°C circulating through the jacket, to obtain a primary dispersion in which metallic sodium is dispersed in a paraffin-based solvent. The average particle size of sodium in the primary dispersion is, for example, 20 μm or less.

[0041] The secondary dispersion device may be, for example, a device having a rotor and a stator. Both the rotor and the stator are provided with blades, and shear force generated between the rotor blades and the stator blades as the rotor rotates is applied to the object to be treated. When the primary dispersion is supplied to the secondary dispersion device and the secondary dispersion device is operated, a secondary dispersion in which the dispersed particle size of metallic sodium is smaller than that of the primary dispersion is obtained. This secondary dispersion is used as the SD.

[0042] Furthermore, the electron donor according to this embodiment contains, in addition to SD, at least one compound (hereinafter referred to as "predetermined compound") selected from the group consisting of 1,3-dialkyl-2-imidazolidinone and crown ether.

[0043] 1,3-Dialkyl-2-imidazolidinone is a compound represented by the following formula (1). [ka]

[0044] In formula (1), R 1 and R 2 are the same or different alkyl groups. More specifically, R 1 and R 2 can be a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, etc. For example, R 1 and R 2 are both methyl groups, the compound of formula (1) is 1,3-dimethyl-2-imidazolidinone (DMI), and R 1 and R 2 are both ethyl groups, the compound of formula (1) is 1,3-diethyl-2-imidazolidinone (DEI).

[0045] In formula (1), R 1 and R 2is preferably selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. 1 and R 2 It is more preferable that at least one of R is a methyl group or an ethyl group. 1 and R 2 More preferably, both of are methyl groups or ethyl groups.

[0046] The 1,3-dialkyl-2-imidazolidinone used in the first step may be commercially available or may be produced by a method known in the art. For example, it may be obtained by the reaction of N,N'-dialkylethylenediamine having the corresponding alkyl group with phosgene (Equation (2)), or by the reaction of ethyleneurea with an alkyl iodide (Equation (3)). However, in the latter case, two alkyl groups R on the nitrogen atom are present. 1 The same result is obtained. [ka] [ka]

[0047] The crown ether used in the first step may be commercially available or may be produced by a method known in the art, and more specifically, the crown ether may be, but is not limited to, 18-crown-6, 15-crown-5, 12-crown-4, etc.

[0048] In the electron donor according to this embodiment, the ratio between SD and the predetermined compound is not particularly limited, but for example, the molar ratio between sodium and the predetermined compound may be 1:1 to 1:60.

[0049] The electron donor according to this embodiment may contain a dilution solvent in addition to the SD and the predetermined compound. The dilution solvent may be the same as or different from the dispersion solvent for the SD.

[0050] The electron donor according to this embodiment preferably contains an ether-based solvent. This is because when the electron donor contains an ether-based solvent, the active species serving as the electron donor are more easily dispersed uniformly in the ether-based solvent. Examples of ether-based solvents include, but are not limited to, tetrahydrofuran, cyclopentyl methyl ether, and 2-methyltetrahydropyrene. However, tetrahydrofuran is particularly preferred. There are typically two methods for providing an electron donor containing an ether-based solvent. The first example is a method using SD as a raw material, with an ether-based solvent as the dispersion solvent. The second example is a method in which an ether-based solvent is added as a diluent to SD and 1,3-dialkyl-2-imidazolidinone. These methods are preferred because they allow the entire electron donor to be obtained as a single-phase liquid.

[0051] The electron donor according to this embodiment may also contain additives such as a surfactant and an antioxidant.

[0052] The electron donor according to this embodiment can be obtained by mixing SD and a predetermined compound in a reaction vessel and stirring the mixture. Other components, such as a dilution solvent, may also be added to the reaction vessel. Known methods can be used for stirring, including, for example, a method using a magnetic stirrer or a stirring device with stirring blades.

[0053] When SD and a specific compound (e.g., DMI) are mixed and stirred, the solution in the reaction vessel turns blue. The reason for this is unclear, but one hypothesis is that metallic sodium (Na) reacts with the cation Na + and anion Na - It is thought that separate chemical species are generated. Among these chemical species, the anion Na - are active species that act as electron donors. These species are unstable, but in this system, certain compounds can convert the cation Na + is stabilized, and the anion Na -This prevents recombination with the active species, the anion Na - It is believed that this can exist stably at room temperature. It should be noted that the solution turns blue when the alkali metal separates into cations and anions, as reported in Peng Lei et al., Org. Lett. 2018, 20, 12, 3439-3442 (Non-Patent Document 1).

[0054] Based on the above hypothesis, the blue color of the solution in the reaction vessel is considered to indicate the generation of an electron donor. Therefore, the electron donor used in the first step can be obtained by mixing SD and a predetermined compound in a reaction vessel and stirring until the solution turns blue.

[0055] That is, a given compound contains the cation Na + Any Lewis base having coordination ability to the compound (I) may be used. The present inventors have confirmed that the effects of the present invention are actually exhibited when the Lewis base is at least one compound (predetermined compound) selected from the group consisting of 1,3-dialkyl-2-imidazolidinone and crown ether, and have completed the present invention. However, it is expected that the same effects as those obtained when the predetermined compound is used will also be obtained when other Lewis bases are used.

[0056] The electron donor prepared as described above can be brought into contact with the surface of an unmodified sheet by a known method, such as applying a solution of the electron donor to the surface of the unmodified sheet, spraying the solution of the electron donor onto the surface of the unmodified sheet, or immersing the unmodified sheet in a solution of the electron donor.

[0057] When an electron donor is brought into contact with the surface of an unmodified sheet, fluorine atoms (e.g., derived from tetrafluoroethylene units) contained in the main chain of the fluororesin are abstracted from the main chain to generate radicals. An example in which the specified compound is DMI is shown in formula (4). This radical functions as a reaction site in the subsequent second step. [ka]

[0058] The time (first reaction time) for contacting the electron donor with the surface of the unmodified sheet is not particularly limited, but can be, for example, 10 seconds or more and 20 minutes or less. When the first reaction time is 10 seconds or more, the reaction of formula (4) tends to proceed sufficiently. Furthermore, when the first reaction time is 20 minutes or less, it is preferable because it is easy to avoid unnecessary reactions caused by sodium. The first reaction time is more preferably 30 seconds or more, and even more preferably 60 seconds or more. Furthermore, the first reaction time is more preferably 10 minutes or less.

[0059] The temperature (first reaction temperature) when the electron donor is brought into contact with the surface of the unmodified sheet is not particularly limited, but may be, for example, -20°C or higher and 40°C or lower. A first reaction temperature of 0°C or higher is preferred in terms of cooling efficiency. A first reaction temperature of 40°C or lower is also preferred in terms of reactivity. The first reaction temperature is more preferably 0°C or higher, and even more preferably 15°C or higher. The first reaction temperature is more preferably 35°C or lower, and even more preferably 25°C or lower.

[0060] (2)Second process The second step is a step of contacting the surface of the sheet after the first step with a ketone compound.

[0061] Examples of the ketone compound to be subjected to the second step include, but are not limited to, acetone, methyl ethyl ketone, etc. Furthermore, the ketone compound may be a single ketone compound or a mixture of multiple types of ketone compounds. The ketone compound to be subjected to the second step preferably contains acetone, and more preferably is acetone alone.

[0062] In the second step, the sheet surface can be brought into contact with a ketone compound by a known method, for example, by immersing the sheet after the first step in a ketone compound.

[0063] When a ketone compound is brought into contact with the surface of the sheet after the first step, the radical generated by the reaction of formula (4) acts as a nucleophile and adds to the carbon of the carbonyl group of the ketone compound. The alkoxide anion generated at this time is protonated, ultimately producing a functional group having a hydroxyl group. In this way, the fluororesin after the first step reacts with the ketone compound, and a functional group having a hydroxyl group is introduced into the fluororesin. An example when the ketone compound is acetone is shown in formula (5). [ka]

[0064] The time for which the ketone compound is brought into contact with the surface of the sheet after the first step (second reaction time) is not particularly limited, but can be, for example, 10 seconds or more and 30 minutes or less. If the second reaction time is 10 seconds or more, the reaction of formula (5) is likely to proceed sufficiently. Furthermore, if the second reaction time is 30 minutes or less, it is preferable from the viewpoint of productivity. The second reaction time is more preferably 30 seconds or more, and even more preferably 1 minute or more. Furthermore, the second reaction time is more preferably 20 minutes or less, and even more preferably 10 minutes or less. Note that it is preferable to make the reaction time of the second step longer than the reaction time of the first step in order to ensure that the reaction proceeds reliably.

[0065] The temperature (second reaction temperature) at which the ketone compound is brought into contact with the surface of the sheet after the first step is not particularly limited, but may be, for example, -20°C or higher and 30°C or lower. A second reaction temperature of -25°C or higher is preferred in terms of cooling efficiency. A second reaction temperature of 30°C or lower is also preferred in terms of productivity. The second reaction temperature is more preferably 0°C or higher, and even more preferably 10°C or higher. The second reaction temperature is more preferably 25°C or lower, and even more preferably 20°C or lower.

[0066] The surface of the modified sheet that has undergone the first and second steps at least partially contains the structure of formula (6). Note that formula (6) shows an example in which the ketone compound is acetone, similar to formula (5). [ka]

[0067] The functional group produced by the reaction of formula (5) exhibits adhesiveness to mating materials such as metals because the hydroxyl group can form hydrogen bonds. Therefore, when the surface of the modified sheet contains the structure of formula (6), the surface has adhesiveness. In this way, adhesiveness can be imparted to fluororesin, which does not have adhesiveness before modification, through the first and second steps.

[0068] [Configuration of modified sheet] Next, the structure of the modified sheet (one embodiment of the molded article according to the present invention) obtained by the above-mentioned modification method will be described. The modified sheet according to this embodiment is a sheet made of fluororesin, and functional groups derived from ketone compounds are introduced into the fluororesin that constitutes its surface. The thickness of the modified sheet is the same as that of the unmodified sheet used as the starting material, and can be, for example, 10 μm or more and 2000 μm or less.

[0069] The modified sheet according to this embodiment has an elemental composition on the surface, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium. The carbon content is 60 atomic % to 80 atomic % and the oxygen content is 10 atomic % to 25 atomic %, with the sum of carbon and oxygen being 100 atomic % or less. The remainder, other than carbon and oxygen, may include fluorine derived from the unmodified fluororesin and sodium derived from SD. The oxygen content on the surface of the modified sheet is higher than the normal oxygen content in unmodified fluororesin. This is due to the substitution of fluorine atoms with functional groups having hydroxyl groups by the reactions of formulas (4) and (5).

[0070] The elemental composition of the surface of the modified sheet was measured by X-ray photoelectron spectroscopy using, for example, a scanning X-ray photoelectron spectrometer PHI5000 VersaProbeII manufactured by Alvac-Phi, equipped with an argon gas cluster ion gun (Ar +The X-ray source used is an X-ray source (AlKα 1486.6 eV, 10 keV, cluster size 2500 atoms, raster range 3 mm x 3 mm). Measurement conditions include, for example, a take-off angle of ±20° and a take-off angle of 90°. Detection of carbon, oxygen, fluorine, and sodium can be achieved by narrow-scan analysis, which measures the binding energy range in which peaks attributed to these elements appear.

[0071] An oxygen content of 10 atomic % or more on the surface of the modified sheet means that the surface of the modified sheet is sufficiently modified, resulting in a modified sheet that is easily adhered to mating materials such as metals. An oxygen content of 25 atomic % or less on the surface of the modified sheet means that excessive modification has not occurred, resulting in a modified sheet that is easily able to exhibit the electrical properties and heat resistance of unmodified fluororesin. The oxygen content of the surface of the modified sheet is preferably 15 atomic % or more, and more preferably 20 atomic % or more. The oxygen content of the surface of the modified sheet is preferably 25 atomic % or less.

[0072] When the fluorine content on the surface of the modified sheet is 5 atomic % or less, it can be said that the surface of the modified sheet is sufficiently modified. In this case, a modified sheet that is easily adhered to a mating material such as a metal can be obtained, which is preferable. The fluorine content on the surface of the modified sheet is not particularly limited and may be 0 atomic % or more (above the detection limit). The fluorine content on the surface of the modified sheet is more preferably 5 atomic % or less, and even more preferably 3 atomic % or less.

[0073] The sodium detected on the surface of the modified sheet is due to the SD used in the modification treatment. The upper limit of the sodium content can be, for example, 10 atomic %. Note that it is not necessary for sodium to remain (below the detection limit).

[0074] The modified sheet according to this embodiment has an oxygen atom content of 0 atomic % or more and 12 atomic % or less at a depth of 200 nm from the surface (hereinafter referred to as the "predetermined depth"), as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium. An oxygen atom content of 12 atomic % or less at a predetermined depth indirectly means that excessive modification has not occurred, and a sheet is obtained that is likely to exhibit the electrical properties, heat resistance, and other properties of unmodified fluororesin. The oxygen content at the predetermined depth is preferably 12 atomic % or less, and more preferably 10 atomic % or less. Furthermore, the oxygen content at the predetermined depth is preferably 2 atomic % or more, and more preferably 5 atomic % or more.

[0075] The elemental composition at a predetermined depth from the surface of the modified sheet can be measured by adjusting the combination of output and sputtering time when measuring the elemental composition by X-ray photoelectron spectroscopy. For example, the elemental composition at a depth of 200 nm from the surface can be measured under the same measurement conditions as above for identifying the elemental composition at the surface of the modified sheet, except that the sputtering time is changed to 6 minutes. The basis for the idea that the elemental composition can be measured at a depth of 200 nm from the surface by setting the sputtering time to 6 minutes is that the theoretical sputtering rate of polystyrene is 33.75 nm per minute, and multiplying this by 6 minutes to one significant digit gives 200 nm (2 × 10 2 The goal is to achieve a saturation of 100 nm.

[0076] The modified sheet according to this embodiment preferably has a fluorine content at a predetermined depth, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium, of 30 atomic % or more and 67 atomic % or less. A fluorine content of 30 atomic % or more at a predetermined depth directly indicates that excessive modification has not occurred, resulting in a modified sheet that is more likely to exhibit the electrical properties and heat resistance of unmodified fluororesin. The fluorine content at a predetermined depth is more preferably 60 atomic % or less, and even more preferably 50 atomic % or less. Furthermore, the fluorine content at a predetermined depth is more preferably 35 atomic % or more, and even more preferably 40 atomic % or more.

[0077] The modified sheet according to this embodiment preferably has a carbon content at a predetermined depth, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium, of 30 atomic % or more and 60 atomic % or less.

[0078] The modified sheet according to this embodiment has a Raman shift of 1050 cm -1 More than 1150cm -1 The following region and Raman shift 1450cm -1 More than 1550cm -1 It is preferable that a peak is detected in at least one of the following regions, and more preferable that a peak is detected in both regions: Raman shift 1050 cm -1 More than 1150cm -1 Peaks in the following region (e.g., 1110 cm -1 ) is attributed to the carbon-carbon single bond (formula (7)) sandwiched between carbon-carbon double bonds in the polymer main chain of the fluororesin. Also, the Raman shift of 1450 cm -1 More than 1550cm -1 Peaks in the following region (e.g., 1495 cm -1) is attributed to the carbon-carbon double bond (formula (8)) sandwiched between carbon-carbon single bonds in the polymer main chain of the fluororesin. Thus, the detection of a peak attributed to a partial structure containing a double bond means that the sheet surface has been sufficiently modified. [ka]

[0079] Furthermore, the modified sheet according to this embodiment has a Raman shift of 1900 cm -1 More than 2000cm -1 It is preferable that no peaks are detected in the region of Raman shift 1900cm -1 More than 2000cm -1 region (for example, 1920 cm -1 ) is attributed to partial structures containing hydrogen atoms (=CH-, =CH2). The presence of these partial structures indicates excessive modification and loss of excessive fluorine atoms.

[0080] The Raman spectrum analysis can be carried out, for example, using a LabRAM HR Evolution manufactured by HORIBA under the measurement conditions of an excitation wavelength of 458 nm or 633 nm, 600 diffraction grating lines, and a 100x objective lens.

[0081] In addition, the modified sheet according to this embodiment preferably has an interface developed area ratio (Sdr) of 0.1 or less, as measured in accordance with ISO 25178. The lower limit of the interface developed area ratio (Sdr) is not particularly limited, but for example, the interface developed area ratio (Sdr) can be 0.02 or more. The modified sheet according to this embodiment preferably has a peak surface arithmetic mean surface (Spc) of 10,000 or less, as measured in accordance with ISO 25178. The lower limit of the peak surface arithmetic mean surface (Spc) is not particularly limited, but for example, the peak surface arithmetic mean surface (Spc) can be 3,000 or more. The interface developed area ratio (Sdr) and the peak surface arithmetic mean surface (Spc) are both parameters that represent so-called surface roughness, and the fact that these parameters are in the above ranges indicates that the surface of the modified sheet has a relatively high level of smoothness.

[0082] [Circuit board configuration] Next, the configuration of the circuit board according to this embodiment will be described. In the circuit board according to this embodiment, copper wiring is formed on the surface of the above-mentioned modifying sheet.

[0083] The circuit board according to this embodiment can be manufactured by a method known in the art, except for using the modified sheet as a material. That is, a modified sheet with copper plating on its surface can be used as a material, and a conventional method for manufacturing a circuit board can be applied.

[0084] As described above, functional groups derived from ketone compounds are introduced onto the surface of the modified sheet, and the hydroxyl groups of these functional groups interact with copper atoms to exhibit good adhesion to copper. Because fluororesins are materials that are difficult to adhere to other materials, including metals, it has traditionally been difficult to plate fluororesins with copper. However, the modified sheet obtained by applying the above-mentioned modification method can be plated with copper with sufficient strength for practical use.

[0085] Furthermore, in the modified sheet obtained by applying the above-mentioned modification method, only the surface portion that contributes to adhesiveness is modified to a minimum, so the good high-frequency characteristics (low dielectric constant and low dielectric loss tangent) inherent to fluororesin are maintained at a high level. Therefore, when a circuit board manufactured using the modified sheet as a material is used in a high-frequency device, high-speed, low-loss communication can be achieved.

[0086] Other Embodiments Regarding other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects and that the scope of the present invention is not limited thereby. Those skilled in the art will easily understand that appropriate modifications are possible without departing from the spirit of the present invention. Therefore, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention. [Example]

[0087] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0088] [Test 1: Elemental composition at the surface and at a specified depth] The elemental composition of the modified sheet prepared under the conditions shown below was measured at the surface and at a predetermined depth (200 nm from the surface).

[0089] (Common conditions) As the untreated sheet, a PTFE sheet having a width of 210 mm, a length of 297 mm, and a thickness of 1 mm was used. When SD was used, the SD had an average particle size of sodium of 10 μm or less and a metallic sodium content of 25 to 26 mass %. When a ketone compound was used, acetone was used. Both the first and second steps were carried out at room temperature. Note that the preparation conditions and the measurement conditions of the elemental composition for each example that are not specifically mentioned were the same as those in the above embodiment.

[0090] Example 1 A modified sheet was prepared using an electron donor containing SD and DMI (Na:DMI = 1:6). The first reaction time was 1 minute, and the second reaction time was 10 minutes. In the modified sheet of Example 1, the elemental composition at the surface was measured using carbon, fluorine, oxygen, nitrogen, sodium, calcium, and silica as detection targets. The measured values ​​were carbon 72.0 atomic%, oxygen 23.7 atomic%, fluorine 0.0 atomic% (below detection limit), sodium 3.4 atomic%, nitrogen 0.9 atomic%, calcium 0.0 atomic% (below detection limit), and Si 0.0 atomic% (below detection limit). Meanwhile, the measured values ​​of the elemental composition at a depth of 200 nm from the surface were carbon 48.1 atomic%, oxygen 7.3 atomic%, fluorine 42.5 atomic%, sodium 0.0 atomic% (below detection limit), nitrogen 1.7 atomic%, calcium 0.4 atomic%, and Si 0.0 atomic% (below detection limit). When this calculation is limited to the four elements carbon, fluorine, oxygen, and sodium, the elemental composition at the surface is 72.3 atomic % carbon, 0.0 atomic % fluorine, 23.9 atomic % oxygen, and 3.4 atomic % sodium. The elemental composition at a depth of 200 nm from the surface is 49.1 atomic % carbon, 43.4 atomic % fluorine, 7.5 atomic % oxygen, and 0.0 atomic % sodium (below the detection limit). Since similar values ​​were obtained when measuring only carbon, fluorine, oxygen, and sodium, the following XPS measurements were performed focusing on carbon, fluorine, oxygen, and sodium. Note that the totals in the following examples and comparative examples do not equal 100 atomic % due to rounding to the nearest significant digit.

[0091] Example 2 A modified sheet was prepared using an electron donor containing SD and crown ether (Na:crown ether = 1:1). The first reaction time was 1 minute, and the second reaction time was 10 minutes. The modified sheet of Example 2 had an elemental composition at the surface of 61.5 atomic percent carbon, 21.9 atomic percent oxygen, 12.3 atomic percent fluorine, and 4.2 atomic percent sodium. The elemental composition at a depth of 200 nm from the surface was 36.3 atomic percent carbon, 2.1 atomic percent oxygen, 60.7 atomic percent fluorine, and 0.9 atomic percent sodium.

[0092] (Comparative Example 1) A commercially available modified sheet was used as Comparative Example 1. The modified sheet of Comparative Example 1 was obtained by contacting the surface of an unmodified sheet with a solution containing sodium and naphthalene, and then washing the surface with water. In the modified sheet of Comparative Example 1, the elemental composition at the surface was 71.8 atomic % carbon, 22.8 atomic % oxygen, 5.1 atomic % fluorine, and 0.4 atomic % sodium. In addition, the elemental composition at a depth of 200 nm from the surface was 64.5 atomic % carbon, 16.5 atomic % oxygen, 19.0 atomic % fluorine, and 0.1 atomic % sodium.

[0093] (Comparative Example 2) A commercially available modified sheet was used as Comparative Example 2. The modified sheet of Comparative Example 2 was obtained by contacting the surface of an unmodified sheet with a solution containing sodium and ammonia, and then washing the surface with water. The modified sheet of Comparative Example 2 had an elemental composition at the surface of 67.9 atomic percent carbon, 29.2 atomic percent oxygen, 1.9 atomic percent fluorine, and 0.8 atomic percent sodium. The elemental composition at a depth of 200 nm from the surface was 68.4 atomic percent carbon, 22.8 atomic percent oxygen, 6.1 atomic percent fluorine, and 2.7 atomic percent sodium.

[0094] [Test 2: Raman Spectroscopic Analysis] Raman spectrum analysis was performed on the surface of the modified sheet of Example 1. The excitation wavelength was 633 nm, and the other measurement conditions were the same as those in the above embodiment. Figure 1 shows the measurement results for Example 1 (top row) and the measurement results for the unmodified sheet (bottom row). In Example 1, the Raman shift was 1110 cm -1 Peak P1 and Raman shift 1495 cm -1 These peaks are not observed in the unmodified sheet.

[0095] Similarly, Raman spectroscopy was performed on the modified sheets of Comparative Examples 1 and 2 using an excitation wavelength of 633 nm. Figure 2 shows the measurement results for Comparative Example 1 (top row), Comparative Example 2 (middle row), and the measurement results for the unmodified sheet (bottom row). For the modified sheets of Comparative Examples 1 and 2, the Raman shift was 1110 cm -1 Peak and Raman shift 1495cm -1 No peaks were observed.

[0096] [Test 3: Measurement of dielectric properties] The relative permittivity and dielectric loss tangent of the modified sheets of each example and comparative example, as well as the unmodified sheet, were measured by a cavity resonator perturbation method in accordance with IEC 62810. The measurement frequency was 10 GHz, and the test environment was a room temperature of 23±1°C and a humidity of 50±5% RH.

[0097] (sample) Example 1 was prepared in Test 1. Comparative Example 1 was the same commercially available product as used in Test 1. Comparative Example 3 was RO3003 manufactured by Rogers Corporation with the copper foil removed. RO3003 manufactured by Rogers Corporation is a substrate material in which a composite material of PTFE and ceramic filler is copper-plated.

[0098] (Measurement results) The measurement results for each example are shown in Table 1. The modified sheet of Example 1 exhibited dielectric properties that could be evaluated as being equivalent to those of the unmodified sheet. It was shown that the modification method of Example 1 makes it difficult for the dielectric properties inherent to the fluororesin to be impaired.

[0099] On the other hand, the modified sheet of Comparative Example 2 had a larger dielectric loss tangent than the unmodified sheet. It can be said that the modification method of Comparative Example 2 impaired the dielectric properties of the fluororesin. Furthermore, Comparative Example 3 had a higher relative dielectric constant than the unmodified sheet. This is due to the inclusion of a ceramic filler in Comparative Example 3.

[0100] Table 1: Dielectric properties [Table 1]

[0101] [Test 4: Measurement of surface roughness] The surface roughness of the modified sheets of Examples 1 and 2 prepared in Test 1, the modified sheets of Comparative Examples 1 and 2 used in Test 1, and the unmodified sheet was measured according to ISO 25178. A Keyence Vk-X3000 was used as the measuring device, and the developed area ratio (Sdr) of the interface and the arithmetic mean surface area (Spc) of the peak surface were measured under the conditions of a 150x objective lens and a half laser scanning range. For each sample, measurements were taken at two locations on the sheet surface, and the average value was used as the measurement result for that sample. For Example 1 and Comparative Example 1, surface observations were also performed using a scanning electron microscope (SEM).

[0102] (Measurement results) The measurement results (Sdr and Spc) for each example are shown in Table 2. SEM images of Example 1 and Comparative Example 1 are shown in Figures 3 and 4. For both Sdr and Spc, lower measurement values ​​were obtained in Examples 1 and 2 than in Comparative Examples 1 and 2. Furthermore, when comparing the SEM images of Example 1 and Comparative Example 1, it was confirmed that the modified sheet of Example 1 had a smoother surface than the modified sheet of Comparative Example 1. From the above, it was shown that the modification method of the Example is a modification method that is less likely to impair the smoothness of the sheet surface than the modification method of the Comparative Example.

[0103] Table 2: Surface roughness [Table 2]

[0104] [Test 5: Measurement of adhesion strength] The modified sheets of the examples and comparative examples were copper plated under the same conditions, and then the adhesive strength between the modified sheet and copper was measured in accordance with JIS C 6481.

[0105] Examples 3 to 11 A modified sheet was prepared using an electron donor containing SD and DMI (Na:DMI=1:6). For each of Examples 3 to 11, the first treatment time and the second treatment time were as shown in Table 2 below.

[0106] (Comparative Examples 1 and 2) Comparative Examples 1 and 2 are the same commercially available products as those used in Test 1.

[0107] (Measurement results) In all of Examples 3 to 11, the adhesive strength was higher than in Comparative Examples 1 and 2. It was shown that the fluororesin can be provided with good adhesion to copper by the modification method of Example 1. In Examples 3 to 11, copper could be adhered to form a circuit, but in Comparative Examples 1 and 2, the adhesion strength was low and a circuit could not be formed.

[0108] Table 3: Adhesion strength [Table 3]

[0109] [Test 6: Measurement of transmission loss] A 0.1 mm thick PTFE sheet was used as the untreated sheet. The SD was the same as in Test 1. Modified sheets were prepared using SD and an electron donor containing DMI (Na:DMI = 1:6). The first reaction time was 1 minute, and the second reaction time was 10 minutes. After copper plating, a microstrip line with a characteristic impedance of 50 Ω was formed on each of two samples: a 13 mm wide, 25 mm long sample and a 13 mm wide, 225 mm long sample. Transmission loss was measured by VNA measurement (thru-line de-embedding). The 13 mm wide, 25 mm long sample was used as a thru line for de-embedding to cancel fixture loss, while the 13 mm wide, 225 mm long sample was used as the measurement line. The thru line measurement results were de-embedding based on the measurement line results, and the resulting measurements over a 200 mm length are shown in Figure 5.

[0110] As shown in Fig. 5, the transmission loss in this example was about -3 dB at 60 GHz. Considering that the transmission loss at 60 GHz when using conventional circuit board materials (for example, RO3003 manufactured by Rogers Corporation, Vecstar (registered trademark) FCCL series manufactured by Kuraray, etc.) is about -10 to -7 dB, it is clear that this example improves the transmission loss. [Industrial Applicability]

[0111] The present invention can be used, for example, in circuit boards for high-frequency devices. [Explanation of symbols]

[0112] P1 Raman shift 1100cm -1 Peak (Example) P2 Raman shift 1495cm -1 Peak (Example)

Claims

1. A molded body made of fluororesin, The elemental composition of the surface, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon, and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being limited to 100 atomic % or less; the oxygen content at a position 200 nm deep from the surface, as determined by X-ray photoelectron spectroscopy targeting carbon, oxygen, fluorine, and sodium, is 0 atomic % or more and 12 atomic % or less; A molded article in which a peak is detected in at least one of the Raman shift regions of 1050 cm −1 to 1150 cm −1 and the Raman shift region of 1450 cm −1 to 1550 cm −1 in Raman spectrum analysis.

2. 2. The molded body according to claim 1, wherein the fluorine content at a depth of 200 nm from the surface, as determined by X-ray photoelectron spectroscopy detecting carbon, oxygen, fluorine, and sodium, is 30 atomic % or more and 67 atomic % or less.

3. 3. The molded article according to claim 1, wherein the fluororesin contains 95 mol % or more of tetrafluoroethylene units.

4. The molded article according to any one of claims 1 to 3, wherein the developed area ratio (Sdr) of the interface measured in accordance with ISO 25178 is 0.02 or more and 0.1 or less.

5. A molded body made of fluororesin, The elemental composition of the surface, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon, and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being limited to 100 atomic % or less; In Raman spectroscopy, the Raman shift was 1050 cm －１ 1150cm or more －１ The following region and Raman shift 1450 cm －１ More than 1550cm －１ A molded article in which a peak is detected in at least one of the following regions:

6. A molded body made of fluororesin, The elemental composition of the surface, as determined by X-ray photoelectron spectroscopy, which detects carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon, and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being limited to 100 atomic % or less; The developed area ratio (Sdr) of the interface measured in accordance with ISO 25178 is 0.02 or more and 0.1 or less, A molded article in which a peak is detected in at least one of the Raman shift regions of 1050 cm −1 to 1150 cm −1 and the Raman shift region of 1450 cm −1 to 1550 cm −1 in Raman spectrum analysis.

7. A circuit board including a molded body made of a fluororesin, The molded body, The elemental composition of the surface of the molded body, as determined by X-ray photoelectron spectroscopy detecting carbon, oxygen, fluorine, and sodium, is 60 atomic % or more and 80 atomic % or less of carbon and 10 atomic % or more and 25 atomic % or less of oxygen, with the total of carbon and oxygen being 100 atomic % or less; the oxygen content at a position 200 nm deep from the surface of the molded body, as determined by X-ray photoelectron spectroscopy detecting carbon, oxygen, fluorine, and sodium, is 0 atomic % or more and 12 atomic % or less; In Raman spectroscopy, a peak is detected in at least one of a Raman shift region of 1050 cm −1 to 1150 cm −1 and a Raman shift region of 1450 cm −1 to 1550 cm −1 . Circuit board.

8. A method for modifying the surface of a fluororesin molded body, comprising: a first step of contacting an electron donor with the surface of the molded body; a second step of contacting a ketone compound with the surface of the molded body after the first step, The method for modifying a substrate, wherein the electron donor comprises a dispersion of metallic sodium dispersed in a solvent, and at least one compound selected from the group consisting of 1,3-dialkyl-2-imidazolidinone and crown ether.

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