Sheets, substrates for printed circuit boards, and methods for manufacturing sheets.

Abstract

The present invention relates to a sheet comprising the following components (A) and (B): (A) a fluoropolymer, and (B) a filler having an average particle size of less than 20% relative to a specified thickness of the sheet, wherein the sheet has an elongation at break of more than 150%.

Description

Technical Field

[0001] This invention relates to sheets, substrates for printed circuit boards, and methods for manufacturing sheets. Background Technology

[0002] Fluororubber is a synthetic resin with excellent heat resistance, electrical insulation, non-adhesive properties, and weather resistance. When molded into sheets, it is made into fluororesin sheets, which are widely used in chemical materials, electrical and electronic components, semiconductors, automobiles and other industries.

[0003] Due to the nature of these applications, the electrical and thermal properties of fluoropolymer sheets are sometimes insufficient. Therefore, to improve these properties, fluoropolymers are mixed with fillers (Patent Documents 1-4).

[0004] As an example of the application of synthetic resins such as fluoropolymers, it is known that they are used as release sheets due to their non-adhesive and excellent release properties. However, commonly used fluoropolymers (such as polytetrafluoroethylene (hereinafter referred to as PTFE)) have a relatively high coefficient of thermal expansion. Therefore, if used as release sheets, they have poor thermal stability and may sometimes cause problems such as dimensional differences from the object being demolded during heating. Therefore, to suppress the thermal expansion of fluoropolymer sheets such as PTFE, filler materials are mixed into the sheets. For example, Patent Document 2 shows a method for reducing the coefficient of thermal expansion of the molded sheet by using a PTFE composition in which PTFE resin and ceramic powder are mixed in a prescribed manner.

[0005] On the other hand, in fluoropolymer sheets mixed with fillers, if the film thickness is small, through holes (pinholes) are easily generated, and there is a tendency for the tensile properties of the sheet to be easily reduced.

[0006] Existing technical documents:

[0007] Patent Document 1: International Publication No. 2019 / 031071

[0008] Patent Document 2: Japanese Patent Publication No. 2022-510017

[0009] Patent Document 3: Japanese Patent No. 2557248

[0010] Patent Document 4: Japanese Patent Application Publication No. 10-17838 Summary of the Invention

[0011] In order to solve the above problems, the inventors attempted to use filler materials with smaller particle size as filler materials mixed into fluoropolymer sheets to suppress the generation of through holes (pinholes) and suppress the reduction of tensile properties, but they failed to solve these problems.

[0012] The purpose of this invention is to provide a sheet material with excellent thermal stability (low thermal expansion) and excellent tensile properties.

[0013] According to the present invention, the following sheets and the like are provided.

[0014] 1. A sheet comprising the following components (A) and (B).

[0015] (A) Fluoropolymer,

[0016] (B) A filler material with an average particle size of less than 20% relative to the specified thickness of the sheet.

[0017] The sheet has an elongation at break of more than 150%.

[0018] 2. The sheet according to claim 1, wherein the specified thickness of the sheet is 25 to 300 μm.

[0019] 3. The sheet according to 1 or 2, wherein the average particle size of the filler material is 0.1 to 10 μm.

[0020] 4. The sheet according to any one of 1 to 3, wherein the mixing ratio of the filler material is 20% to 50% by volume.

[0021] 5. The sheet according to any one of 1 to 4, wherein the fluororesin is polytetrafluoroethylene (PTFE) or modified PTFE.

[0022] 6. The sheet according to any one of 1 to 5, wherein the filler material is selected from one or more of alumina, titanium dioxide, silicon dioxide, barium sulfate, silicon carbide, boron nitride, silicon nitride, glass fiber, glass beads and mica.

[0023] 7. The sheet according to any one of 1 to 6, wherein the thermal expansion coefficient of the sheet is less than 100 ppm / ℃.

[0024] 8. The sheet according to any one of 1 to 7, wherein the number of through holes with a diameter of 50 μm or more present in the sheet is in the percentage of each 100 cm of the sheet. 2 The surface area is less than 25.

[0025] 9. A substrate for a printed circuit board, wherein it comprises the sheet material described in any one of 1 to 8.

[0026] 10. A method for manufacturing a sheet material, wherein,

[0027] include:

[0028] The process of preparing a raw material composition by mixing the following components (A') and (B);

[0029] The process of molding the above raw material composition into a cylindrical shape to form a molded body;

[0030] The process of firing the molded body; and

[0031] The process of machining the surface of the fired molded body to form a sheet.

[0032] (A') A fluoropolymer with an average particle size of 50% or less relative to the specified thickness of the sheet, and (B) A filler material with an average particle size of 20% or less relative to the specified thickness of the sheet.

[0033] 11. The method for manufacturing the sheet according to 10, wherein the specified thickness of the sheet is 25 to 300 μm.

[0034] 12. The method for manufacturing the sheet according to 10 or 11, wherein the average particle size of the fluoropolymer particles is 0.1 to 10 μm.

[0035] 13. A method for manufacturing a sheet according to any one of 10 to 12, wherein the average particle size of the filler material is 0.1 to 10 μm.

[0036] 14. A method for manufacturing a sheet according to any one of 10 to 13, wherein the mixing ratio of the filler material is 20 to 50% by volume.

[0037] 15. A method for manufacturing a sheet according to any one of 10 to 14, wherein the step of preparing the raw material composition includes: removing the solvent from a raw material-containing solution obtained by dispersing the fluoropolymer (A') with an average particle size of 50% or less relative to a specified thickness of the sheet and the filler (B) with an average particle size of 20% or less relative to a specified thickness of the sheet in a solvent.

[0038] 16. A method for manufacturing a sheet according to any one of 10 to 14, wherein the step of preparing the raw material composition is a step of dry mixing the (A') fluoropolymer with an average particle size of 50% or less relative to the specified thickness of the sheet and the (B) filler with an average particle size of 20% or less relative to the specified thickness of the sheet.

[0039] 17. A sheet material, wherein the sheet material is obtained by any one of the manufacturing methods described in 10 to 16.

[0040] According to the present invention, a sheet material with excellent thermal stability (low thermal expansion) and excellent tensile properties can be provided. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the preparation method of the raw material composition in conventional sheet manufacturing methods.

[0042] Figure 2 This is a schematic diagram illustrating the preparation method of the raw material composition in a sheet manufacturing method according to one aspect of the present invention.

[0043] Figure 3 This diagram illustrates the cutting process of cutting the outer peripheral surface of a fired molded body (blank) along its length to form a sheet.

[0044] Figure 4 This is a graph showing the results of elemental mapping analysis of the sheet material in Example 2.

[0045] Figure 5 This is a graph showing the results of the elemental mapping analysis of the sheet material in Comparative Example 1. Detailed Implementation

[0046] The following describes a sheet material and a method for manufacturing the sheet material according to one aspect of the present invention. In this specification, "x~y" represents a numerical range of "x or more and y or less". Regarding one technical matter, when there are multiple lower limit values ​​such as "x or more", or when there are multiple upper limit values ​​such as "y or less", it is possible to arbitrarily select from the upper and lower limit values ​​and combine them.

[0047] [Sheet]

[0048] One aspect of the sheet of the present invention is a sheet comprising the following components (A) and (B).

[0049] (A) Fluoropolymer,

[0050] (B) A filler material with an average particle size of less than 20% relative to the specified thickness of the sheet.

[0051] The sheet has an elongation at break of over 150%.

[0052] Sheets, regardless of their thickness, have one side that is flat and another side that is the back side, and are composed of shapes such as strips and flat sheets, including films and tapes.

[0053] The inventors have discovered that if a filler material is mixed into a sheet containing fluororesin, the thermal expansion rate of the sheet is suppressed to a low level. On the other hand, if coarse particles with a particle size close to the thickness of the target sheet are present in the raw material composition, when the molded body made of the raw material composition is cut and processed to form a thin sheet of about 100 μm, through holes (pinholes) will be generated on the sheet. The sheet is prone to breakage due to these through holes, and the tensile properties of the sheet are reduced.

[0054] Furthermore, the inventors discovered the following fact: If the particle size of the filler material 51 in the raw material composition for manufacturing the sheet differs significantly from the particle size of the fluororesin particles 50 in the raw material (see reference...), Figure 1 (a) As the mixing amount of the filler material 51 increases, in the raw material composition, the small-diameter filler material 51 penetrates into the gaps between the large-diameter fluororesin particles 50, and the filler material 51 aggregates between the fluororesin particles 50, easily forming aggregates of filler material 51 with a particle size that increases to nearly the thickness of the target sheet (see reference). Figure 1 (b) If the raw material composition containing the agglomerates is fired, the fluoropolymer particles 50 melt into a single matrix, but the agglomerates of filler material 51 remain directly. As a result, it was found that when the fired molded body is machined to form a thin sheet of about 100 μm, the agglomerates of filler material 51 are present in the molded body, thereby creating through holes (pinholes) on the sheet.

[0055] It should be noted that the so-called "cutting process" refers to... Figure 3 As shown, this refers to a method in which a blank 10, formed by compressing and molding resin powder, is rotated while a cutting edge 20 abuts against the surface of the blank 10 to continuously cut a sheet 30 thinly.

[0056] The sheet produced by this method, by incorporating filler material, has a low coefficient of thermal expansion and excellent thermal stability. Furthermore, the sheet produced by this method exhibits an elongation at break exceeding 150%, demonstrating excellent tensile properties. Therefore, the sheet produced by this method possesses high thermal stability (low thermal expansion) and high tensile properties.

[0057] The sheet produced in this manner can be made using the following raw material composition (see reference). Figure 2(b) The raw material composition is obtained by mixing filler material 51 having the particle size specified above and small-particle-size fluororesin particles 50' (which are small-particle-size to the same degree as the particle size of filler material 51) as raw materials, thereby uniformly dispersing the fluororesin particles 50' and filler material 51. By uniformly dispersing the fluororesin particles 50' and filler material 51 in the raw material composition, even when the mixing amount of filler material is increased, the phenomenon of filler material 51 penetrating into the gaps between fluororesin particles 50' and forming aggregates can be suppressed. Figure 1 (b) state). By suppressing the formation of agglomerates, the formation of through holes (pinholes) is suppressed in the sheet material obtained by machining the molded body obtained by firing the raw material composition. Therefore, the sheet material obtained by machining has high thermal stability (low thermal expansion) and high tensile properties.

[0058] A method for reducing the particle size of the fluoropolymer 50' to the same degree as that of the filler material 51 is described in detail in a method for manufacturing a sheet according to one aspect of the present invention.

[0059] (Fluoropolymer)

[0060] As a fluoropolymer, commonly used fluoropolymers can be used without particular limitation, but polytetrafluoroethylene (PTFE) is preferred. Polytetrafluoroethylene (PTFE) is a homopolymer of tetrafluoroethylene.

[0061] Alternatively, modified polytetrafluoroethylene (PTFE) can also be used as a fluoropolymer. Modified polytetrafluoroethylene (PTFE) is preferably PTFE modified with perfluoroalkyl vinyl ethers.

[0062] Examples of perfluoroalkyl vinyl ethers include the perfluoroalkyl vinyl ethers represented by the formula (1) below.

[0063]

[0064] In equation (1), R f It is a perfluoroalkyl group having 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms) or a perfluoroorganic group represented by the following formula (2).

[0065]

[0066] (In equation (2), n is an integer from 1 to 4.)

[0067] Examples of perfluoroalkyl groups with 1 to 10 carbon atoms in formula (1) include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl, with perfluoropropyl being preferred.

[0068] The fluoropolymer content in the sheet can be 50% or more by volume, 60% or more by volume, or 70% or more by volume, or it can be less than 80% by volume, less than 70% by volume, or less than 60% by volume.

[0069] If the fluoropolymer content is above the lower limit, good strength can be obtained as a sheet material.

[0070] In addition, if the fluoropolymer content is below the upper limit, the thermal expansion rate can be suppressed by the filler material contained in the sheet, resulting in excellent thermal stability.

[0071] (Filling material)

[0072] The sheet material of this method includes a filler material. Examples of such filler materials include alumina, titanium dioxide, silicon dioxide, barium sulfate, silicon carbide, boron nitride, glass fiber, glass beads, and mica.

[0073] From the viewpoint of imparting high thermal stability (low thermal expansion) to the sheet, silica, boron nitride, and alumina are preferred as filler materials. One or more of these filler materials can be used.

[0074] The filler content in the sheet is preferably 20% by volume or more, but can be 25% by volume or more, or 30% by volume or more.

[0075] In addition, the content of filler material contained in the sheet is preferably 50% by volume or less, but can be 48% by volume or less, 45% by volume or less, 40% by volume or less, or 30% by volume or less.

[0076] If the content of filler material in the sheet is above the lower limit, the thermal expansion coefficient of the sheet is suppressed to a small value, for example, below 100 ppm / ℃, and the thermal stability is excellent.

[0077] In addition, if the content of filler material in the sheet is below the upper limit, the strength of the sheet can be adequately maintained, and good workability can be obtained.

[0078] The average particle size of the filler material is 20% or less relative to the specified thickness of the sheet. If the average particle size of the filler material is within this range, it helps to suppress pinhole formation. The average particle size of the filler material relative to the specified thickness of the sheet can be 18% or less, 15% or less, 12% or less, 10% or less, 8% or less, or 5% or less. Specific film thicknesses for the sheet will be described later.

[0079] Regarding the average particle size of the filler material, it can be appropriately selected relative to the desired sheet thickness. For example, it is preferably 0.1 μm or more, but it can also be 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, or 1 μm or more. Furthermore, the average particle size of the filler material is preferably 10 μm or less, but it can also be 9 μm or less, 8 μm or less, 5 μm or less, or 3 μm or less. The average particle size of the filler material is preferably 0.1 μm or more and 10 μm or less.

[0080] By making the average particle size of the filler within the above range, the aggregation of filler particles can be suppressed, the percentage of coarse particles can be reduced, and thus the generation of through holes (pinholes) in the sheet can be suppressed, resulting in excellent tensile properties.

[0081] In this specification, the average particle size of the filler material contained in the sheet is obtained by the following method: using a scanning electron microscope (manufactured by Hitachi High Technology Co., Ltd., "SU8220") to observe the surface of the sheet in a range of 100μm x 100μm with an accelerating voltage of 5kV and a magnification of 1000x, the particle size (diameter or longest diameter) of 100 randomly selected filler material particles is measured, and their arithmetic mean is taken as the average particle size of the filler material contained in the sheet.

[0082] (Optional ingredients)

[0083] In one embodiment, the sheet may also contain optional components. These optional components are not particularly limited, and examples include flame retardants, flame retardant additives, pigments, antioxidants, reflective agents, masking agents, lubricants, processing stabilizers, plasticizers, and foaming agents.

[0084] At this point, the total content of optional components in the sheet can be less than 20% by mass, less than 10% by mass, or less than 5% by mass.

[0085] In one embodiment, for example, the sheet is composed of polytetrafluoroethylene or modified polytetrafluoroethylene and a filler material, wherein the polytetrafluoroethylene or modified polytetrafluoroethylene accounts for more than 85% by mass, more than 90% by mass, more than 95% by mass, more than 98% by mass, more than 99% by mass, more than 99.5% by mass, more than 99.9% by mass, or 100% by mass, and the filler material is selected from one or more of alumina, titanium dioxide, silicon dioxide, glass fiber, glass beads, and mica.

[0086] (Characteristics of sheet materials)

[0087] The sheet of one embodiment of the present invention has a specified thickness, preferably in the range of 25 to 300 μm. A method for manufacturing a sheet of this thickness, primarily composed of fluoropolymer and filler materials, can be described by machining. Details regarding machining and the method for manufacturing the sheet according to one embodiment of the present invention will be described later.

[0088] In addition to the aforementioned machining processes, known methods for manufacturing sheets that primarily consist of fluoropolymers and fillers include coating, extrusion molding, and calendering. However, for example, when manufacturing sheets using the coating method, the sheet thickness typically reaches its limit at 25 μm. To increase the sheet thickness, overlapping coatings are required, making the process more complex.

[0089] In addition, when sheets are manufactured using extrusion molding or calendering, the resulting sheets are typically 1 mm thick, making them relatively thick. It is difficult to obtain sheets with a thickness of 25–300 μm through extrusion molding or calendering.

[0090] The thickness of the sheet is preferably 25 μm or more, but can also be 30 μm or more, 50 μm or more, 70 μm or more, or 100 μm or more. Alternatively, the thickness of the sheet is preferably 300 μm or less, but can also be 200 μm or less, 150 μm or less, or 100 μm or less.

[0091] By making the sheet thickness 25μm or more, the strength of the sheet material can be fully maintained, and good operability can be obtained.

[0092] In addition, good flexibility can be obtained by making the sheet thickness less than 300μm.

[0093] It should be noted that in this specification, "sheet thickness" refers to the average thickness measured at any 10 points in the sheet.

[0094] In one embodiment, the elongation at break of the sheet exceeds 150%, and can be 152% or more, 200% or more, 300% or more, 350% or more, or 380% or more.

[0095] The elongation at break was determined using the method described in the examples.

[0096] In one embodiment, the thermal expansion coefficient of the sheet can be less than 100 ppm / ℃, or it can be 40 ppm / ℃ or more and 90 ppm / ℃ or less, or it can be 50 ppm / ℃ or more and 80 ppm / ℃ or less, or it can be 60 ppm / ℃ or more and 70 ppm / ℃ or less.

[0097] The coefficient of thermal expansion was determined using the method described in the examples.

[0098] In one embodiment, the number of through holes (pinholes) with a diameter of 50 μm or more present in the sheet is [amount] per 100 cm of the sheet. 2 The surface area is preferably 25 or less, more preferably 20 or less, even more preferably 15 or less, 10 or less, 5 or less, and preferably 0.

[0099] The number of through holes (pinholes) was determined using the method described in the examples.

[0100] [Substrate for Printed Circuit Boards]

[0101] One embodiment of the present invention provides a substrate for a printed circuit board comprising the sheet described above.

[0102] Due to their excellent heat resistance and insulation properties, fluoropolymers are expected to be used as heat-resistant materials such as heat-resistant insulating tapes or as printed circuit board materials. However, conventional fluoropolymer sheets manufactured by machining are prone to thermal shrinkage due to heating, resulting in poor dimensional stability and making it difficult to perform processing such as bonding with other materials.

[0103] In contrast, the sheet of one embodiment of the present invention has heat shrinkage suppressed and dimensional stability improved by uniformly dispersing filler particles in a fluororesin matrix. Compared with conventional fluororesin sheets, it has the advantages of easy processing, such as bonding with other materials.

[0104] As an example of a substrate for a printed circuit board made of a sheet material using one aspect of the present invention, a substrate obtained by laminating metal foil such as copper foil on the sheet material can be cited.

[0105] [Sheet manufacturing method]

[0106] One method for manufacturing a sheet according to the present invention includes the following steps (1) to (4):

[0107] (1) The process of preparing a raw material composition by mixing the following components (A') and (B),

[0108] (A') Fluoropolymer with an average particle size of less than 50% relative to the specified thickness of the sheet.

[0109] (B) A filler material with an average particle size of less than 20% relative to the specified thickness of the sheet;

[0110] (2) The process of molding the raw material composition into a cylindrical shape to form a molded body;

[0111] (3) The process of firing the molded body;

[0112] (4) The cutting process involves cutting the surface of the fired molded body to form a sheet.

[0113] (Step (1) Preparation of raw material composition)

[0114] As component (A'), the fluoropolymer can be the fluoropolymer of component (A) described in the above-mentioned sheet material item.

[0115] The fluororesin used as a raw material has a granular shape, and its average particle size is less than 50% of the specified thickness of the sheet, which can be appropriately selected according to the desired sheet thickness. The average particle size of the fluororesin particles is preferably 0.1 to 10 μm.

[0116] By using fluororesin particles within the aforementioned average particle size range, a raw material composition in which filler particles and fluororesin particles are uniformly dispersed can be obtained.

[0117] The average particle size of fluoropolymer particles can be greater than 0.1 μm, or greater than 0.2 μm, greater than 1 μm, or greater than 5 μm.

[0118] In addition, the average particle size of fluoropolymer particles can be less than 10 μm or less than 5 μm.

[0119] As a method to make the average particle size of the fluoropolymer particles less than 50% of the specified thickness of the sheet, preferably in the range of 0.1 to 10 μm, examples include: using a commercially available fluoropolymer particle dispersion (typically with an average particle size in the range of 0.1 to 0.5 μm) in which the fluoropolymer particles are dispersed in a solvent; or pulverizing commercially available powdered fluoropolymer particles (typically with an average particle size in the range of 200 to 600 μm) to form the above-mentioned average particle size. Details of the process for using fluoropolymer particles obtained by the above two methods will be described later.

[0120] In this specification, the average particle size of the fluoropolymer particles used in the preparation of the raw material composition can be measured using a particle size distribution measuring device (Spectris Corporation, “MS-3000”) under a wind pressure of 1 Bar.

[0121] As a filler material for component (B), the filler materials described in the item for the sheet can be used.

[0122] The filler material has a granular shape, and the preferred range of its average particle size and the rationale thereof are the same as the preferred range of the average particle size of the filler material particles and the rationale thereof as described in the section on the sheet material.

[0123] The average particle size of the filler material particles used in the preparation of the raw material composition can be determined by the same method as that used for the average particle size of fluoropolymer particles.

[0124] As one embodiment of a method for obtaining a raw material composition by mixing components (A') and (B), a method can be described as follows: after removing the solvent from a raw material solution obtained by dispersing components (A') and (B) in a solvent, a mixed powder is obtained by stirring and mixing using a stirrer with blades or the like.

[0125] As a raw material solution, for example, a solution obtained by adding component (B) to a dispersion in which fluoropolymer (e.g., PTFE) particles generated in a solvent by emulsion polymerization or the like are dispersed, and then mixing by stirring with a mixer or the like.

[0126] In this case, the fluoropolymer particles dispersed in the dispersion medium correspond to component (A') (fluoropolymer particles with an average particle size of less than 50% relative to the specified thickness of the sheet).

[0127] It should be noted that the raw material solution is not limited to the solution obtained by the above method. For example, it can also be a solution obtained by dispersing the fluoropolymer particles (component (A')) generated by emulsion polymerization or the like in other solvents to obtain a dispersion, and then adding component (B) to the dispersion.

[0128] There are no particular limitations on the solvents used in the dispersion; for example, methyl ethyl ketone and water are examples.

[0129] Regarding the amount of component (B) mixed in the dispersion, the mixing is carried out in such a way that the content of component (A') and the content of component (B) in the raw material composition obtained from the raw material solution are respectively the desired percentages. The preferred range of the content of component (A') in the raw material composition is the same as the preferred range of the content of component (A) described in the above-mentioned sheet material item. In addition, the preferred range of the content of component (B) in the raw material composition is the same as the preferred range of the content of component (B) described in the above-mentioned sheet material item.

[0130] There is no particular limitation on the stirring speed of the dispersion with added component (B), for example, it can be 100 to 800 rpm or 200 to 600 rpm.

[0131] There is no particular limitation on the stirring time of the dispersion with added component (B), for example, it can be 1 to 20 minutes or 2 to 18 minutes.

[0132] There are no particular limitations on the method for removing solvent from a raw material solution. For example, it can be carried out by precipitating components (A') and (B) contained in the raw material solution through co-precipitation or the like, thereby separating them from the raw material solution, and then drying them in a drying oven to evaporate and remove the solvent components contained in the precipitate.

[0133] When using a drying oven or similar device to dry the precipitate, the drying temperature can be, for example, 60–400°C or 80–300°C.

[0134] When mixing the dried component (A') and component (B) powders using a mixer with blades, there is no particular limitation on the mixing speed; for example, it can be 1000–6000 rpm or 2000–5000 rpm.

[0135] In addition, there is no particular limitation on the stirring time of the mixed powder obtained after drying; for example, it can be 1 to 15 minutes or 2 to 10 minutes.

[0136] As one embodiment of a method for obtaining a raw material composition by mixing component (A') (fluoropolymer particles with an average particle size of 50% or less relative to the specified thickness of the sheet) and component (B) (filler material with an average particle size of 20% or less relative to the specified thickness of the sheet), for example, a method of dry mixing of component (A') and component (B) may be used.

[0137] As a method for mixing component (A') and component (B), for example, a method can be described as follows: after crushing secondary particles formed by the aggregation of primary particles of fluororesin to obtain fluororesin (component (A')) with an average particle size of 0.1 to 10 μm, component (A') and component (B) are mixed by stirring using a stirrer with blades or the like.

[0138] There is no particular limitation on the particle size of the secondary particles of fluoropolymer; for example, it can be 100–800 μm, 130–700 μm, or 150–600 μm.

[0139] There are no particular limitations on the method for crushing secondary particles. For example, methods such as using a mixing mill, an air jet mill, or a cryogenic mill can be cited.

[0140] Components (A') and (B) are mixed in such a manner that the content of component (A') and component (B) in the raw material composition are respectively in the desired percentages. The preferred range of the content of component (A') in the raw material composition is the same as the preferred range of the content of component (A) described in the sheet material section above. Similarly, the preferred range of the content of component (B) in the raw material composition is the same as the preferred range of the content of component (B) described in the sheet material section above.

[0141] There are no particular limitations on the stirring speed of components (A') and (B) in dry mixing; for example, it can be 1000-6000 rpm or 2000-5000 rpm.

[0142] There is no particular limitation on the mixing time of component (A') and component (B) in dry mixing; for example, it can be 1 to 15 minutes or 2 to 10 minutes.

[0143] It should be noted that, in addition to components (A') and (B), optional components may be mixed into the raw material composition. As optional components, the optional components described in the sheet material section may be used.

[0144] The preferred range for the mixing amount of optional components can be set to the same range as the preferred range for the content of optional components described in the above-mentioned sheet material items.

[0145] (Process (2) Formation of the molded body)

[0146] The above-mentioned raw material composition is molded into a cylindrical shape to form a molded body. As a method for forming the molded body, for example, a method of filling the above-mentioned raw material composition into a mold and performing compression molding to form a cylindrical compression molded body can be described.

[0147] The surface pressure can be 10-100MPa, 20-60MPa, or 30-50MPa.

[0148] By compressing the raw material composition consisting of mixed components (A') and (B), a compression-molded body in which fluoropolymer particles and filler are uniformly dispersed is obtained (see reference). Figure 2 (b)).

[0149] (Process (3) Firing of the molded body)

[0150] The obtained compressed molded body is fired to obtain a blank. The firing temperature can be 100-400℃, 350-370℃, or 360-370℃.

[0151] The resulting blank is a molded body formed by the agglomeration of the raw material powder.

[0152] By firing the molded body, it becomes a state in which filler material particles are uniformly dispersed in a matrix formed by melting individual fluororesin particles in the molded body.

[0153] By firing a compressed molded body of a raw material composition containing components (A') and (B), it is possible to suppress the formation of agglomerates of filler material and obtain a good blank with fewer coarse particles.

[0154] From the viewpoint of facilitating the cutting process described later, the shape of the blank (molded body) is preferably cylindrical. When the blank (molded body) is cylindrical, the diameter of the cylinder can be, for example, 100 to 500 mm or 150 to 500 mm.

[0155] (Step (4) involves forming a sheet material through cutting)

[0156] Next, a cutting process is performed, that is, the surface of the fired molded body, i.e. the blank, is cut to form a sheet.

[0157] like Figure 3 As shown, when the blank (molded body) is a cylindrical body, the cutting edge is brought into contact with the outer peripheral surface of the fired cylindrical body along its length to cut it, thereby forming a sheet.

[0158] As described above, for blanks obtained by mixing components (A') and (B) in a raw material composition, since they are good blanks with few coarse particles of filler material, the generation of through holes (pinholes) can be suppressed by machining these blanks, resulting in sheets with excellent tensile properties.

[0159] When the blank (molded body) is a cylindrical body, it is also possible to remove 3 mm of thickness from the outer side of the outer peripheral surface, inner peripheral surface and end face of the fired cylindrical body before performing the process of cutting the outer peripheral surface of the fired cylindrical body in the length direction to form a sheet.

[0160] The machining process of cutting the outer circumferential surface of the fired cylindrical body along its length to form a sheet can be used. Figure 3 The apparatus shown is used for implementation. Regarding the thickness of the sheet obtained by cutting, it can be appropriately selected according to the intended use of the sheet; for example, it can be 25 μm or more, or 30 μm or more, 50 μm or more, 70 μm or more, or 100 μm or more. Alternatively, the thickness of the sheet obtained by cutting can be, for example, 300 μm or less, or 200 μm or less, 150 μm or less, or 100 μm or less.

[0161] exist Figure 3 In the process, the fired blank (cylindrical body) 10 is rotated and cut into sheet material 30 by the cutting edge (tool) 20.

[0162] The blank obtained through the above-mentioned processes (1) to (3) is cut to obtain a sheet of 25 to 300 μm.

[0163] The sheet material described above is suitable for use as a heat-resistant material such as heat-resistant insulating tape, a substrate for printed circuit boards, a printed circuit board, or a release sheet.

[0164] [Example]

[0165] (Preparation of the raw material composition)

[0166] Manufacturing Example 1

[0167] PTFE dispersion (PTFE particles dispersed in a solvent) and spherical silica (average particle size 1 μm) as filler are mixed in a volume ratio of PTFE particles to spherical silica of 6:4. The mixture is stirred at 300-500 rpm for 5-15 minutes to obtain a solution containing the raw materials.

[0168] While stirring the raw material solution with a mixer, ethanol is further added to the solution to cause PTFE particles and spherical silica to co-precipitate. The co-precipitate is then dried in a drying oven at 100℃~200℃ to evaporate and remove the solvent, thereby obtaining a dry powder.

[0169] The obtained dry powder was mixed with a mixer with rotating blades at a speed of 3000-4000 rpm for 0.5-1 minute to obtain a raw material composition 1 containing PTFE powder (average particle size: 0.25 μm) and spherical silica (average particle size: 1 μm).

[0170] Manufacturing Example 2

[0171] Polytetrafluoroethylene (PTFE) powder (average particle size 400 μm) was pulverized to obtain PTFE powder with an average particle size of 5 μm.

[0172] The PTFE powder with an average particle size of 5 μm obtained above and the spherical silica (average particle size of 3 μm) as a filler material are mixed in a volume ratio of PTFE powder: spherical silica = 6:4. The mixture is stirred for 3 to 7 minutes using a stirrer with rotating blades at a rotation speed of 3000 to 4000 rpm to obtain a raw material composition 2 containing PTFE powder (average particle size: 5 μm) and spherical silica (average particle size: 3 μm).

[0173] Manufacturing Example 3

[0174] PTFE powder (average particle size 400 μm) and spherical silica (average particle size 1 μm) as filler material were mixed in a volume ratio of PTFE powder: spherical silica = 6:4. The mixture was stirred for 3 to 7 minutes at a speed of 3000 to 4000 rpm using a stirrer with rotating blades to obtain a raw material composition 3 containing PTFE powder (average particle size: 400 μm) and spherical silica (average particle size: 1 μm).

[0175] Example 1

[0176] <Preparation of blanks>

[0177] 600g of raw material composition 1 was filled into a cylindrical mold and compressed from the top at a pressure of 30MPa for 3 minutes to obtain a cylindrical preform (outer diameter 67mm × inner diameter 33mm). The obtained preform was placed in a firing furnace and fired at 365℃ for 6 hours.

[0178] <Machining>

[0179] use Figure 3 The apparatus shown was used to cut the obtained cylindrical sintered body (outer diameter 67 mm × inner diameter 33 mm) at a cutting speed of 8 m / min and a target thickness of 100 μm to produce a sheet with a thickness of 100 μm.

[0180] Example 2

[0181] Raw material composition 2 was used instead of raw material composition 1, and the sheet was otherwise prepared in the same manner as in Example 1.

[0182] Comparative Example 1

[0183] Raw material composition 3 was used instead of raw material composition 1, and the sheet was otherwise prepared in the same manner as in Example 1.

[0184] Reference Example 1

[0185] Prepare PTFE sheets without filler material ("TOMBONo9001", manufactured by Nexus Corporation of Japan).

[0186] [Evaluation Method]

[0187] (Dispersion state of the filler material)

[0188] For any surface region of the sheets obtained in Example 2 and Comparative Example 1, elemental mapping analysis was performed using an energy-dispersive X-ray analysis apparatus (manufactured by Horiba Manufacturing Co., Ltd., "E-Max N") at an accelerating voltage of 15 kV.

[0189] The results of elemental mapping analysis of the sheets from Example 2 and Comparative Example 1 are shown below. Figure 4 and Figure 5 middle.

[0190] Depend on Figure 4 The results of the elemental mapping analysis shown confirm that, for the sheet obtained in Example 2, spherical silica Si (black portion) is uniformly dispersed in the PTFE resin (gray portion).

[0191] On the other hand, by Figure 5 The results of the elemental mapping analysis shown confirm that, for the sheet obtained in Comparative Example 1, there is an aggregate of Si (black part) formed by the aggregation of spherical silica Si (black part) in the PTFE resin (gray part), which produces through holes (pinholes) (the part surrounded by dashed lines) during machining.

[0192] (Number of through holes (pinholes))

[0193] The surface area of ​​100 cm² was measured at any position (e.g., at the midpoint other than the end of the long sheet in the longitudinal direction, at the center in the short side direction, or at the center of the sheet) of the sheet obtained from Examples 1-2 and Comparative Example 1. 2 The samples with through holes (pinholes) were observed under a microscope (KEYENCE Co., Ltd., "VHX-5000"), and the number of through holes (pinholes) with a longest diameter of 50 μm or more was counted. The results are shown in Table 1.

[0194] (Elongation at break)

[0195] The sheets obtained from Examples 1-2 and Comparative Example 1 were cut into specimens for measuring elongation at break, with a width of 10 mm for the test area and a chuck distance (mark distance) L0 of 22.25 mm. The sheets were stretched to break at a tensile testing machine (Shimadzu Corporation, "Ez-LX") at 23°C and 50% RH. The elongation at break was calculated using the following formula (3) based on the distance L1 (mm) between the marks at break. The results are shown in Table 1.

[0196]

[0197] (Ratio of thermal expansion)

[0198] Raw material compositions 1 to 3 were respectively filled into molds measuring 5mm in length and 5mm in width, and compressed under a molding pressure of 30MPa for 1 minute to obtain a cubic body with one side measuring 5mm. This body was then fired at 360°C for 6 hours. The thermal expansion rate (TER) of the fired body (test body for thermal expansion measurement) was measured using a thermomechanical measurement apparatus (TMA) (manufactured by TA Instruments Japan Co., Ltd., "Q400"). The TRA was measured as follows: the following load was set to 0.05N, and the measurement temperature was set from room temperature to 200°C at a heating rate of 5°C / min. The TRA was calculated based on the thermal expansion within the range of 50–150°C measured from room temperature to 200°C.

[0199] [Table 1]

[0200]

[0201] [Potential for Industrial Applications]

[0202] The sheet material of the present invention is suitable for use as a heat-resistant material such as heat-resistant insulating tape, a substrate for printed circuit boards, a printed circuit board, and a release sheet, but is not limited thereto.

[0203] The foregoing has provided several detailed descriptions of the embodiments and / or examples of the present invention. Those skilled in the art will readily make numerous modifications to these illustrative embodiments and / or examples without substantially departing from the new teachings and effects of the present invention. Therefore, these numerous modifications are also included within the scope of the present invention.

[0204] The entire contents of the documents described in this specification, as well as the contents of the applications that form the basis of this application under the Treaty of Paris, are incorporated herein by reference.

Claims

1. A sheet material, wherein, It contains the following components (A) and (B). (A) Fluoropolymer, (B) A filler material with an average particle size of less than 20% relative to the specified thickness of the sheet. The sheet has an elongation at break exceeding 150%. The specified thickness of the sheet is 25–300 μm. The average particle size of the filler material is 0.1–10 μm. The number of through-holes having a diameter of 50 μm or more present in the sheet is 25 or less per 100 cm 2 in the surface area.

2. The sheet according to claim 1, wherein, When the volume of the sheet is set to 100% by volume, the mixing ratio of the filler material is 20-50% by volume.

3. The sheet according to claim 1 or 2, wherein, The fluororesin is PTFE or modified PTFE, wherein PTFE represents polytetrafluoroethylene.

4. The sheet according to claim 1 or 2, wherein, The filler material is selected from one or more of alumina, titanium dioxide, silicon dioxide, barium sulfate, silicon carbide, boron nitride, silicon nitride, glass fiber, glass beads, and mica.

5. The sheet according to claim 1 or 2, wherein, Using a thermomechanical measuring device, with the following load set to 0.05 N, the temperature was increased at a rate of 5 °C / min, and the thermal expansion rate of the sheet was calculated to be less than 100 ppm / °C based on the thermal expansion in the range of 50–150 °C.

6. A substrate for a printed circuit board, wherein, The sheet comprising any one of claims 1 to 5.

7. A method for manufacturing a sheet material, wherein, This manufacturing method is a method for manufacturing the sheet material as described in claim 1. The manufacturing method includes: The process of preparing a raw material composition by mixing the following components (A') and (B); The process of molding the above raw material composition into a cylindrical shape to form a molded body; The process of firing the molded body; and The process of machining the surface of the fired molded body to form a sheet. in, (A') Fluoropolymer with an average particle size of less than 50% relative to the specified thickness of the sheet. (B) A filler material with an average particle size of less than 20% relative to the specified thickness of the sheet. The specified thickness of the sheet is 25–300 μm.

8. The method for manufacturing the sheet according to claim 7, wherein, The average particle size of the fluoropolymer particles is 0.1–10 μm.

9. The method for manufacturing the sheet according to claim 7 or 8, wherein, The average particle size of the filler material is 0.1–10 μm.

10. The method for manufacturing the sheet according to claim 7 or 8, wherein, The mixing ratio of the filler material is 20-50% by volume.

11. The method for manufacturing the sheet according to claim 7 or 8, wherein, The steps for preparing the raw material composition include: The step of removing the solvent from a raw material solution obtained by dispersing the fluoropolymer (A') with an average particle size of less than 50% relative to the specified thickness of the sheet and the filler material (B) with an average particle size of less than 20% relative to the specified thickness of the sheet in a solvent.

12. The method for manufacturing the sheet according to claim 7 or 8, wherein, The process for preparing the raw material composition is a process of dry mixing the fluoropolymer (A') with an average particle size of less than 50% relative to the specified thickness of the sheet and the filler (B) with an average particle size of less than 20% relative to the specified thickness of the sheet.

13. A sheet material, wherein, The sheet is obtained by the manufacturing method according to any one of claims 7 to 12.

Images