Molded body and method for manufacturing a molded body

Abstract

A molded body comprising a liquid crystalline polymer powder and optionally a resin, the liquid crystalline polymer powder comprising fibrous particles composed of a liquid crystalline polymer, the fibrous particles composed of a liquid crystalline polymer having an average diameter of 2 μm or less, the resin having heat resistance, the resin being a thermoplastic resin or a thermosetting resin.

Description

Technical Field

[0001] This invention relates to molded articles and methods for manufacturing molded articles. Background Technology

[0002] Compared with existing substrate materials such as polyimide resin and epoxy resin, liquid crystal polymers (LCPs) have lower dielectric constant and dielectric loss, and also have extremely low water absorption rate, resulting in less change in dielectric properties due to water absorption. Therefore, they are used as circuit boards.

[0003] In addition, glass bismaleimide substrates and glass epoxy boards, which incorporate glass fibers as reinforcing fibers in bismaleimide resins and epoxy resins, are also used as rigid substrate materials for circuit boards. Here, if LCP is fiberized, it becomes a fiber with high rigidity equivalent to glass fiber in the fiber axis; therefore, LCP fibers can also replace glass fibers as reinforcing fibers. Compared to glass, LCP has excellent dielectric properties, resulting in circuit boards with superior high-frequency characteristics.

[0004] In order to use LCP to fabricate circuit boards, it has been proposed to use composite materials, porous bodies, etc., obtained by impregnation or other methods to combine resins such as thermoplastic resins and thermosetting resins with fabrics, non-woven fabrics, fiber sheets, etc. made of LCP fibers (Patent Documents 1 to 7).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-260228

[0008] Patent Document 2: Japanese Patent Application Publication No. 2003-218485

[0009] Patent Document 3: Japanese Patent Application Publication No. 2012-224692

[0010] Patent Document 4: Japanese Patent Application Publication No. 2006-319324

[0011] Patent Document 5: Japanese Patent Application Publication No. 2007-118528

[0012] Patent Document 6: Japanese Patent Application Publication No. 2007-169422

[0013] Patent Document 7: Japanese Patent Application Publication No. 2006-1959 Summary of the Invention

[0014] However, when using composite materials and porous materials obtained by the above-mentioned compounding method to make circuit boards, problems arise such as the inability to produce only sheet-like shapes, weak strength, and large undulations and unevenness.

[0015] Furthermore, when these composite materials and porous bodies are stacked in multiple layers, the resin bonds between the layers, but the LCP fibers do not bond to each other, thus failing to achieve sufficient interlayer bonding strength. Especially in the case of porous bodies, if the interlayer bonding is attempted using a hot press for heating and pressurization, the resin in the porous body softens, the internal pores collapse, and the desired properties are not obtained. Therefore, an additional adhesive is required for interlayer bonding.

[0016] In view of the above-mentioned problems, the present disclosure aims to provide a molded article that uses finely fibrous LCP, which has high strength and excellent interlayer bonding strength.

[0017] The molded body disclosed herein is a molded body comprising liquid crystal polymer powder and optionally comprising resin.

[0018] The aforementioned liquid crystal polymer powder comprises fibrous particles composed of liquid crystal polymers.

[0019] The average diameter of the fibrous particles composed of the above-mentioned liquid crystal polymer is less than 2 μm.

[0020] The above-mentioned resin has heat resistance.

[0021] The above-mentioned resin is a thermoplastic resin or a thermosetting resin.

[0022] According to this disclosure, it is possible to provide a molded article that uses finely fibrous LCP, which has high strength and excellent interlayer bonding strength. Attached Figure Description

[0023] Figure 1 These are SEM images obtained by photographing the surface of the molded body in Example 2.

[0024] Figure 2 It is an optical microscope photograph obtained by taking a cross-section of the molded body in Example 2.

[0025] Figure 3 These are SEM images obtained by photographing the surface of the molded body in Example 3.

[0026] Figure 4 It is an optical microscope photograph obtained by taking a cross-section of the molded body in Example 3.

[0027] Figure 5 The photograph is taken by forming the molded body in Example 3 into a film and then photographing it.

[0028] Figure 6 The photograph is a film obtained by taking a picture of the molded body in Comparative Example 5.

[0029] Figure 7The photograph was taken from the flexible printed circuit board in Example 4.

[0030] Figure 8 This is an example of a flowchart illustrating the manufacturing process of a molded body according to an embodiment.

[0031] Figure 9 This is another example of a flowchart illustrating the manufacturing process of a molded body according to an embodiment. Detailed Implementation

[0032] The following describes embodiments of the present disclosure, but the present disclosure is not limited thereto.

[0033] <Molded Body>

[0034] One embodiment of the molded body disclosed herein includes liquid crystal polymer powder (LCP powder), the LCP powder comprising fibrous particles (liquid crystal polymer fibers: LCP fibers) composed of liquid crystal polymers, the average diameter of the LCP fibers being 2 μm or less. Additionally, the molded body optionally includes a resin, the resin being a thermoplastic resin or a thermosetting resin.

[0035] (Liquid crystal polymer powder)

[0036] There are no particular limitations on what constitutes a liquid crystal polymer; for example, thermotropic liquid crystal polymers can be cited. Examples of thermotropic liquid crystal polymers include aromatic polyesters synthesized primarily from monomers such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids, which exhibit liquid crystal properties when melted.

[0037] Liquid crystal polymer molecules have a negative coefficient of linear expansion (CTE) along the molecular axis and a positive CTE in the radial direction of the molecular axis.

[0038] The liquid crystal polymer preferably does not have amide bonds. Examples of thermotropic liquid crystal polymers without amide bonds include, for example, a copolymer of p-hydroxybenzoic acid, terephthalic acid and dihydroxybiphenyl (a copolymer of p-hydroxybenzoic acid and ethylene terephthalate) with a high melting point and low CTE, which is called a type 1 liquid crystal polymer, or a copolymer of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid with a melting point between type 1 and type 2 liquid crystal polymers, which is called a type 1.5 (or type 3) liquid crystal polymer.

[0039] The LCP fibers contained in LCP powder are not particularly limited as long as they contain fibrous portions. The fibrous portions can be linear or branched, etc.

[0040] The average diameter of the LCP fibers is 2 μm or less, preferably 1 μm or less. Furthermore, the average aspect ratio of the LCP fibers is preferably 10 to 500, more preferably 10 to 300.

[0041] It should be noted that the average diameter and average aspect ratio of LCP fibers were determined by the following methods.

[0042] LCP powder, consisting of LCP fibers, which is the subject of the test, is dispersed in ethanol to prepare a slurry containing 0.01% by mass of LCP powder. The slurry is prepared with a water content of less than 1% by mass. Then, 5–10 μL of this slurry is dropped onto a glass slide, and the slide is allowed to dry naturally. By allowing the slurry to dry naturally, LCP powder is deposited on the glass slide.

[0043] Next, a designated area of ​​LCP powder disposed on a glass slide was observed using a scanning electron microscope (SEM), thereby acquiring image data of more than 100 particles (LCP fibers) constituting the LCP powder. It should be noted that the number of image data points (more than 100) was determined based on the size of each LCP particle. Furthermore, to suppress omissions or measurement errors in image data acquisition for each LCP particle, the SEM magnification was appropriately changed to 500x, 3000x, or 10000x while acquiring the aforementioned image data.

[0044] Next, using the image data obtained above, the longitudinal and width dimensions of each LCP fiber were measured.

[0045] The direction of the straight line connecting the two ends of the longest path in an LCP fiber captured by the aforementioned image data, from one end through approximately the center of the particle to the end on the opposite side of that end, is defined as the long-side direction. Then, the length of the straight line connecting the two ends of the longest path is measured as the long-side direction dimension.

[0046] In addition, the particle size in a direction orthogonal to the long side direction was measured at three different locations along the aforementioned long side direction of a single LCP powder particle. The average value of the dimensions measured at these three locations was taken as the width direction dimension (fiber diameter) of each LCP powder particle.

[0047] Then, the ratio of the longitudinal dimension to the fiber diameter (longitudinal dimension / fiber diameter) is calculated as the aspect ratio of the LCP fiber.

[0048] Then, the average fiber diameter measured from 100 LCP fibers was taken as the average diameter.

[0049] In addition, the average aspect ratio of 100 LCP fibers was used as the mean aspect ratio.

[0050] It should be noted that the aforementioned fibrous particles can be contained in LCP powder in the form of aggregates formed by the aggregation of fibrous particles.

[0051] Furthermore, the aforementioned fibrous particles tend to have the axial direction of the LCP molecules constituting the fibrous particles aligned with the long side direction of the fibrous particles. This is believed to be because, during the manufacturing of LCP powder, the multiple structural domains formed by the bundles of LCP molecules break down from each other, thereby causing the axial direction of the LCP molecules to align along the long side direction of the fibrous particles.

[0052] In LCP powder, the content (number ratio) of particles other than fibrous particles (substantially unfibrillated block particles) is preferably 20% or less. For example, when LCP powder is placed on a plane, particles with a maximum height of 10 μm or less are fibrous particles, and particles with a maximum height of more than 10 μm are block particles.

[0053] The D50 (average particle size) value of LCP powder, determined by particle size measurement using a particle size distribution measuring device based on laser diffraction scattering, is preferably 13 μm or less.

[0054] (resin)

[0055] The molded article of this embodiment arbitrarily contains resin, but preferably contains resin. The resin is heat-resistant and is either a thermosetting resin or a thermoplastic resin. The type of resin can be selected appropriately.

[0056] Examples of heat-resistant thermosetting resins include epoxy resins, bismaleimide resins, phenolic resins, unsaturated polyester resins, alkyd resins, and polyurethanes. Epoxy resins and bismaleimide resins are preferred as heat-resistant thermosetting resins.

[0057] Examples of heat-resistant thermoplastic resins include polyimide resins, polyarylates, liquid crystal polymers, polyamide-imide resins, polyether-imide resins, cyclic olefin polymers, polybenzimidazole resins, and syndiotactic polystyrene. Solvent-soluble thermoplastic resins are preferred, such as solvent-soluble polyimide resins, solvent-soluble liquid crystal polymers, polyarylates, polyamide-imide resins, polyether-imide resins, cyclic olefin polymers, polybenzimidazole resins, and syndiotactic polystyrene.

[0058] (Additives)

[0059] The molded body of this embodiment may include additives. By including additives in the molded body, the molded body can be endowed with the functions possessed by the additives, such as flame retardancy, thermal conductivity, high dielectric constant, low dielectric constant, strong magnetism, etc. In addition, the strength of the molded body can also be improved, for example. Examples of additives include inorganic fillers, metal powders, and organic fillers.

[0060] (other)

[0061] The molded article of this embodiment may include, for example, a curing agent and a curing accelerator, to the extent that it does not impair the purpose of this disclosure.

[0062] (Effect)

[0063] The molded body of this embodiment has high strength because the LCP fibers are bonded together. Furthermore, when the molded bodies are stacked, the LCP fibers in different layers are bonded to each other between layers, resulting in a molded body with excellent interlayer bonding strength. It should be noted that since the LCP fibers in the molded body of this embodiment are bonded together by heating, an adhesive for bonding the LCP fibers is not required.

[0064] <Method for manufacturing molded parts>

[0065] The following describes each step of the manufacturing method of the molded body according to this embodiment.

[0066] [Method for manufacturing molded articles using thermosetting resins]

[0067] like Figure 8 As shown, as an example of the manufacturing method of the molded body in this embodiment, it includes a dispersion process (S1), a compounding process (S2), a first heating process (S3), and a second heating process (S4).

[0068] First, the method for producing the LCP powder used in the dispersion step (S1) will be described in detail. This LCP powder can be produced, for example, by sequentially performing the following coarse grinding step, fine grinding step, coarse particle removal step, and fiberization step.

[0069] Examples of the shapes of LCP raw materials used to produce LCP powder include uniaxially oriented particles, biaxially oriented films, and powdered LCP. The LCP constituting the LCP raw material is the same as the LCP constituting the aforementioned LCP fibers.

[0070] (Coarse grinding process)

[0071] In the coarse grinding process, the LCP raw material is coarsely ground. For example, the LCP raw material is coarsely ground using a milling machine. The size of the coarsely ground LCP particles is not particularly limited, as long as they can be used as raw materials for the micro-grinding process described later. The maximum particle size of the coarsely ground LCP particles is, for example, 3 mm or less.

[0072] It should be noted that a coarse grinding process is not necessarily required. For example, if the LCP raw material can be used as a raw material for the micro-grinding process, then the LCP raw material can be used directly as a raw material for the micro-grinding process.

[0073] (Micro-pulverization process)

[0074] In the micronization process, the LCP raw material (after the coarse grinding process) is pulverized in a state of dispersion in liquid nitrogen to obtain granular micronized liquid crystal polymer (micronized LCP).

[0075] In the micronization process, it is preferable to use a medium to pulverize the LCP raw material dispersed in liquid nitrogen. The medium is, for example, beads. From the viewpoint of handling liquid nitrogen, a bead mill, which has fewer technical problems, is preferred in the micronization process of this embodiment. For example, the "LNM-08" liquid nitrogen bead mill manufactured by IMEX Corporation can be cited as an example of an apparatus suitable for the micronization process.

[0076] The granular micronized LCP obtained through the micronization process preferably has a D50 of 50 μm or less, as measured by a particle size distribution measuring device based on laser diffraction scattering. This prevents the granular micronized LCP from clogging the nozzle during the fiberization process described below.

[0077] (Coarse particle removal process)

[0078] Next, in the coarse particle removal step, coarse particles are removed from the granular micronized LCP obtained in the above-mentioned micronization step. For example, by sieving the granular micronized LCP through a sieve, the granular micronized LCP that passes through the sieve is obtained, and the granular LCP that remains on the sieve is removed, thereby removing the coarse particles contained in the granular micronized LCP. The type of sieve can be appropriately selected; for example, a sieve with a mesh size of 53 μm can be used. It should be noted that the coarse particle removal step is not necessarily required.

[0079] (Fiberization process)

[0080] Next, in the fiberization process, the granular LCP is pulverized using a wet high-pressure crushing device to obtain LCP powder. In the fiberization process, the micronized LCP is first dispersed in a dispersion medium used in the fiberization process. The dispersed micronized LCP may not have coarse particles removed, but it is preferable to remove them. Examples of dispersion media used in the fiberization process include water, ethanol, methanol, isopropanol, toluene, benzene, xylene, phenol, acetone, methyl ethyl ketone, diethyl ether, dimethyl ether, hexane, or mixtures thereof.

[0081] Then, the micronized LCP, in a state of dispersion medium used in the fiberization process, i.e., a paste or slurry-like micronized LCP, is passed through a nozzle under high pressure. By passing through the nozzle at high pressure, the shear force or impact energy generated by the high-speed flow within the nozzle acts on the LCP, breaking down the granular micronized LCP and thereby fiberizing the LCP to obtain LCP powder composed of fine LCP fibers. From the viewpoint of providing high shear force or high impact energy, it is preferable to minimize the nozzle diameter as much as possible to prevent clogging of the micronized LCP in the nozzle. Since the granular micronized LCP has a small particle size, the nozzle diameter of the wet high-pressure crushing device used in the fiberization process can be reduced. For example, the nozzle diameter is 0.2 mm or less.

[0082] As explained above, multiple microcracks are formed in the granular micro-pulverized LCP. Therefore, by pressurizing in a wet high-pressure crushing device, the dispersion medium penetrates into the interior of the micro-pulverized LCP through these microcracks. Then, when the paste-like or slurry-like micro-pulverized LCP passes through a nozzle under normal pressure, the dispersion medium that has penetrated into the interior of the micro-pulverized LCP expands within a short time. Through the expansion of the dispersion medium that has penetrated into the interior of the micro-pulverized LCP, it causes destruction from within the micro-pulverized LCP. Therefore, fiberization proceeds to the interior of the micro-pulverized LCP, and the LCP molecules are separated into unidirectionally arranged structural domain units. Thus, in the fiberization process of this embodiment, by defibrating the granular micro-pulverized LCP obtained in the micro-pulverization process of this embodiment, an LCP powder with a lower content of blocky particles and composed of fine LCP fibers can be obtained compared to the LCP powder obtained by crushing granular LCP obtained by conventional cryogenic pulverization methods.

[0083] It should be noted that in the fiberization process of this embodiment, LCP powder can be obtained by crushing the micronized LCP multiple times using a wet high-pressure crushing device. However, from the viewpoint of manufacturing efficiency, it is preferable to crush the LCP multiple times using a wet high-pressure crushing device, for example, less than 5 times.

[0084] (Dispersed process: S1)

[0085] In the dispersion step, the initial step in the method of manufacturing the molded body, a liquid mixture is prepared by dispersing the LCP powder prepared above in a solution obtained by dissolving the resin in a solvent. In addition, there are cases where thermosetting resins are in a liquid state before curing, and there are cases where it is not necessary to dissolve the thermosetting resin in a solvent to form a coating film. However, since the fiber orientation can be achieved by utilizing the volume reduction caused by drying, it is preferable to dissolve the thermosetting resin in a solvent.

[0086] As a solvent used in the dispersion process, any solvent that can dissolve the resin but not the LCP powder is acceptable. Examples include acetone, N-methyl-2-pyrrolidone (NMP), toluene, methyl ethyl ketone (MEK), N,N-dimethylacetamide (DMAC), ethyl acetate, benzene, and chloroform.

[0087] For example, the mixing ratio of LCP powder and resin can be 1:99 to 75:25 by volume.

[0088] Furthermore, when manufacturing molded articles containing additives, the additives are added in this step to obtain a mixture of liquid LCP powder, resin, and additives. The mixing ratio of the additives relative to the mixture is preferably 50% by volume or less.

[0089] It should be noted that when the molded body contains a curing agent and a curing accelerator, these are also mixed in this process. The mixing ratio of the curing agent and the curing accelerator is appropriately adjusted to the extent that it does not impair the purpose of this disclosure.

[0090] (Combination process: S2)

[0091] Next, in the compounding process, the liquid mixture is dried to form a composite of LCP fibers and resin. In one embodiment of the invention, the compounding process includes, for example, a coating process and a drying process. It should be noted that, in the following description, the composite of LCP fibers and resin is sometimes simply referred to as a "composite".

[0092] In the coating process, a liquid mixture is applied to a substrate. Here, "substrate" refers to the material or support material used to coat the liquid mixture, such as metal foils like copper foil, polyimide films, PTFE films, or composite sheets made of reinforcing materials like glass fiber fabric and heat-resistant resins that do not easily bond with resins.

[0093] Next, the liquid mixture coated on the substrate is heated and dried through a drying process, thereby vaporizing the solvent. Through the above heating and drying, a composite is formed on the substrate.

[0094] Furthermore, during the drying process, the overall thickness of the liquid mixture gradually decreases as the solvent is slowly removed from the liquid mixture. Therefore, the thickness of the composite is thinner than the overall thickness of the liquid mixture formed on the product.

[0095] Furthermore, as the overall thickness of the liquid mixture gradually decreases during drying, the orientation of the long side of the fibrous particles in the LCP powder changes. Specifically, among the fibrous particles, those with their long side orientation in the overall thickness direction of the liquid mixture are tilted so that their long side orientation faces inward toward the main surface of the substrate. Therefore, the long side orientation of the fibrous particles in the formed composite exhibits anisotropy.

[0096] In the above-described composite process, after further coating the composite formed on the substrate by the drying process with a liquid mixture, it is dried, thereby vaporizing the solvent. Thus, the coating and drying processes can be repeatedly performed in the above-described composite process. This allows for the acquisition of a composite with the desired weight per unit area. Furthermore, by repeatedly performing the coating and drying processes, a mixture in which the mixing ratios of LCP powder, resin, and additives are varied in each coating process can be used. This allows for the acquisition of a composite that can form a molded article with desired properties.

[0097] Next, after the drying process, a further heat treatment can be performed to bring the thermosetting resin to a semi-cured state (the so-called stage B). The conditions for forming the semi-cured state (heating temperature and holding time) vary depending on the curing characteristics of the thermosetting resin used, but it is preferable to perform the treatment at a lower temperature than the first heating process described later.

[0098] (First heating process: S3)

[0099] Next, the intermediate is obtained by heating the composite in the first heating process.

[0100] The heating temperature in the first heating step varies depending on the combination of thermosetting resin, curing agent, catalyst, etc., used, but it is carried out within a range where cross-linking is sufficient and abnormal heating due to over-reaction does not occur. Furthermore, the heating temperature in the first heating step is preferably lower than the heating temperature in the second heating step, which will be described later.

[0101] The holding time in the first heating process only needs to be the time for the cross-linking reaction to proceed fully, for example, it can be more than 5 minutes or more than 15 minutes.

[0102] Furthermore, pressure can be applied simultaneously with heating in the first heating step. When manufacturing a laminated molded body, pressure is applied simultaneously with heating in the first heating step. The pressure is preferably 10 MPa or less. This is because the LCP resin melts and flows when the pressure exceeds 10 MPa. Additionally, to ensure sufficient bonding of the LCP fibers between the molded bodies, the pressure is preferably 1 MPa or more.

[0103] It should be noted that when applying pressure using a press, a polyimide film, a PTFE film, or a composite sheet made of reinforcing materials such as glass fiber fabric and heat-resistant resin that is not easily bonded to LCP can be sandwiched between the press and the composite as a release film.

[0104] (Second heating process: S4)

[0105] Next, in the second heating step, the intermediate is heated to obtain the molded body. Furthermore, heating can be performed in an inert gas atmosphere during the second heating step. This operation further improves the strength of the molded body.

[0106] The heating temperature in the second heating process is within the range of -60°C to -5°C, which is the melting point of the LCP powder. When the heating temperature is below -60°C, the adhesion between the LCP fibers is weak, making it impossible to obtain a molded body with practical strength. When the heating temperature is above -5°C, the LCP fibers soften and deform, thus failing to maintain the molded body. The preferred heating temperature is within the range of -50°C to -10°C, more preferably within the range of -40°C to -20°C, which is the melting point of the LCP powder.

[0107] There are no particular restrictions on the holding time in the second heating process; for example, it can be 5 minutes or more, or 15 minutes or more. Alternatively, from the perspective of creating a stronger molded body through prolonged holding, it can be 30 minutes or more, or even 60 minutes or more.

[0108] (Other processes)

[0109] If necessary, the substrate bonded to the molded body can be removed by etching or other methods. This yields a molded body without a bonded substrate. Furthermore, when using copper foil as the substrate, wiring patterns can be obtained by partially removing the copper foil.

[0110] Furthermore, when the molded bodies are stacked, the surfaces in contact with other molded bodies can be plasma-treated after the substrate is removed. This removes the resin from the surface portion of the LCP fibers of the coated molded body, allowing the LCP fibers of the stacked molded bodies to bond together and promoting the fusion of the LCP fibers.

[0111] [Method for manufacturing molded articles using thermoplastic resin as resin]

[0112] like Figure 9 As shown, as an example of the method for manufacturing the molded body according to this embodiment, it includes a dispersion step (S1), a compounding step (S2), and a heating step (S3). It should be noted that the method for producing LCP powder and other steps are the same as described above [the method for manufacturing the molded body using a thermosetting resin as the resin], and therefore descriptions are omitted. Furthermore, in the dispersion step (S1) and the compounding step (S2), the "liquid mixture" described above is replaced with "paste-like mixture".

[0113] (Heating process: S3)

[0114] In the heating process, the composite is heated to obtain a molded body. Furthermore, heating can be performed in a non-reactive gas atmosphere during this process. This operation further improves the strength of the molded body.

[0115] The heating temperature in the heating process is within the range of -60°C to -5°C, which is the melting point of the LCP powder. When the heating temperature is below -60°C, the adhesion between the LCP fibers is weak, making it impossible to obtain a molded body with practical strength. When the heating temperature is above -5°C, the LCP fibers soften and deform, thus failing to maintain the molded body. The preferred heating temperature is within the range of -50°C to -10°C, more preferably within the range of -40°C to -20°C, which is the melting point of the LCP powder.

[0116] There are no particular restrictions on the holding time during the heating process; for example, it can be 5 minutes or more, or 15 minutes or more. Alternatively, from the perspective of creating a stronger molded body through prolonged holding, it can be 30 minutes or more, or even 60 minutes or more.

[0117] Furthermore, pressure can be applied simultaneously with heating during the heating process. In the case of manufacturing laminated molded articles, pressure is applied simultaneously with heating during the heating process. The pressure is preferably 10 MPa or less. This is because the LCP resin melts and flows when the pressure exceeds 10 MPa. Additionally, to ensure sufficient bonding of the LCP fibers between the molded articles, the pressure is preferably 1 MPa or more.

[0118] It should be noted that when applying pressure using a press, a polyimide film, a PTFE film, or a composite sheet made of reinforcing materials such as glass fiber fabric and heat-resistant resin that is not easily bonded to LCP can be sandwiched between the press and the composite as a release film.

[0119] (Resin removal process: S5)

[0120] When a solvent-soluble thermoplastic resin is used as the resin, at least a portion of the solvent-soluble thermoplastic resin can be removed from the molded article. This results in a molded article in which the removed resin portion is porous.

[0121] Resin removal can be achieved, for example, by solvent treatment after heating the molded article to remove solvent-soluble thermoplastic resins. The heating temperature is preferably within a range where the solvent used will not rapidly vaporize. The solvent is preferably one that dissolves only the thermoplastic resin and not the LCP powder.

[0122] Example

[0123] The following examples illustrate the present disclosure in more detail, but the present disclosure is not limited thereto.

[0124] Experiment 1

[0125] <Example 1>

[0126] (Manufacturing of liquid crystal polymer powder)

[0127] In Example 1, uniaxially oriented LCP particles (cylindrical particles with a diameter of 3-4 mm and a melting point of 315°C) were first prepared as the LCP raw material. The LCP was a copolymer of p-hydroxybenzoic acid and 4,6-hydroxynaphthoic acid.

[0128] The LCP raw material was coarsely ground using a milling machine (IKA, MF10). The coarsely ground LCP was obtained by passing the coarsely ground LCP through a 3mm diameter screen located at the outlet of the milling machine.

[0129] Next, the coarsely ground LCP was micronized using a liquid nitrogen bead mill (IMEX, LNM-08, container capacity: 0.8L). Specifically, 500 mL of media and 30 g of coarsely ground LCP were added to the container and milled at 2000 rpm for 120 minutes. Zirconia (ZrO2) beads with a diameter of 5 mm were used as the media. It should be noted that the micronized LCP was wet-milled in the liquid nitrogen bead mill while dispersed in liquid nitrogen. Thus, by pulverizing the coarsely ground LCP using a liquid nitrogen bead mill, granular micronized LCP was obtained.

[0130] The particle size of the micronized LCP was determined. In the particle size determination, the micronized LCP dispersed in the dispersion medium was subjected to ultrasonic treatment for 10 seconds, and then the particle size was measured using a particle size distribution measuring device based on laser diffraction scattering (Horiba Manufacturing Co., Ltd., LA-950). It should be noted that Ekinen (registered trademark, JAPAN ALCOHOL TRADING Co., Ltd.) was used as the dispersion medium, with ethanol as the main solvent. The measured D50 value of the micronized LCP was 23 μm.

[0131] Next, the dispersion of micronized LCP in Ekinen was sieved using a 53 μm mesh sieve to remove coarse particles contained in the micronized LCP, and the micronized LCP that passed through the sieve was recovered. The yield of micronized LCP obtained by removing these coarse particles was 85% by mass.

[0132] Next, the micronized LCP, from which coarse particles were removed, was dispersed in a 20% (w / w) aqueous ethanol solution. Using a wet high-pressure crushing apparatus, the ethanol slurry containing the micronized LCP was repeatedly crushed five times under a nozzle diameter of 0.2 mm and a pressure of 200 MPa, thereby achieving fiberization. A high-pressure disperser (Nanovator, manufactured by Yoshida Machinery Kogyo Co., Ltd.) was used as the wet high-pressure crushing apparatus. LCP powder was obtained by drying the ethanol slurry containing the micronized LCP using a spray dryer. The average diameter of 100 LCP fibers contained in the LCP powder was measured to be 0.8 μm.

[0133] (Manufacturing of molded parts)

[0134] Prepare bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, JER828) as the resin (thermosetting resin) and prepare imidazole-based curing agent (Mitsubishi Chemical Corporation, EMI24) as the curing agent.

[0135] The above-described resin and curing agent were dissolved in acetone as a solvent to obtain a first mixture. The mixing ratio of resin, curing agent, and solvent was 10:0.2:89.8 by mass. The LCP powder obtained above was mixed into the first mixture to obtain a second mixture. The mixing ratio of the above-described resin to LCP powder in the second mixture was 9:1 by volume.

[0136] Next, the second mixture was coated onto the surface of an unroughened electrolytic copper foil (manufactured by Furukawa Electric Industries, Ltd., FO-WS-12) with a thickness of 12 μm using a 0.1 mm thick metal plate. Then, the electrolytic copper foil coated with the second mixture was heated in a hot air oven at 150°C for 60 minutes to vaporize the acetone used as a solvent, thereby drying the second mixture on the electrolytic copper foil. The resin was then cured to obtain a cured body. The copper foil integrated with the cured body was completely removed using ferric chloride to obtain a composite of LCP fibers forming the core and the cured thermosetting resin (first composite).

[0137] Next, using the same metal plate, the second mixture was coated onto the roughened surface of a 12 μm thick electrolytic copper foil (manufactured by Furukawa Electric Industries, Ltd., FWJ-WS-12). Then, the electrolytic copper foil coated with the second mixture was heated in a hot air oven at 120°C for 5 minutes to vaporize the acetone used as a solvent, thereby drying the second mixture on the electrolytic copper foil, and then allowing the resin to semi-cur. As a result, a composite (second composite) of thin LCP fibers and resin that becomes solid at room temperature after semi-curing was formed on the electrolytic copper foil.

[0138] Next, plasma treatment was performed on the side of the first composite with the electrolytic copper foil removed and the side of the second composite opposite to the electrolytic copper foil side using a plasma treatment apparatus (Samco Corporation, Plasma Cleaner PC-300). Argon was used as the treatment gas for 5 minutes at a flow rate of 10 sccm and an output of 250 W.

[0139] Next, the first and second composites, which underwent the aforementioned plasma treatment, were heated and pressed using a vacuum high-temperature pressure apparatus (manufactured by Kitagawa Seiki Co., Ltd., KVHC). Specifically, firstly, the plasma-treated surfaces of the first and second composites were brought into contact with each other, and then a release film was laminated on the side of the first composite opposite to the side of the second composite to obtain a laminate. A polyimide film (manufactured by DU PONT-TORAY, Kapton 100H, thickness: 25 μm) was used as the release film. Then, the laminate was placed in the vacuum high-temperature pressure apparatus and pressed together with electrolytic copper foil at a temperature of 150°C and a pressing pressure of 2 MPa for 20 minutes. After the heating and pressing was completed, the release film was removed, resulting in an intermediate formed on the electrolytic copper foil.

[0140] The aforementioned intermediate was placed in a stainless steel tank and heated in a hot air reactive oven (Koyo Thermo System Co., Ltd., inactive gas oven INH-21CD). Specifically, it was heated at 270°C for 15 minutes under a nitrogen flow. This yielded the molded body of Example 1.

[0141] <Example 2>

[0142] In Example 2, a solvent-soluble polyimide resin (PI Technical Research Institute Co., Ltd., Q-AD-X0516, solid content 10% by mass) was used as the resin (thermoplastic resin).

[0143] The above-described resin and the same LCP powder as in Example 1 were dissolved in NMP as a solvent to obtain a paste-like mixture with a solid content of 8% by volume. The mixing ratio of the above-described resin to LCP powder in the mixture was 9:1 by volume.

[0144] Next, using a 0.4 mm thick metal plate, a paste-like mixture was coated onto the surface of the same unroughened electrolytic copper foil as the first composite in Example 1. Then, the electrolytic copper foil coated with the paste-like mixture was dried by heating it in a hot air oven at 150°C for 15 minutes to vaporize the NMP solvent. Thus, a composite was formed on the electrolytic copper foil.

[0145] Prepare two of the above-described composites and remove the electrolytic copper foil using the same method as in Example 1. Then, use the same plasma treatment apparatus as in Example 1 to perform plasma treatment on the side of one composite where the electrolytic copper foil has been removed and on the side of the other composite opposite to the side where the electrolytic copper foil has been removed, under the same conditions.

[0146] Each composite that underwent the plasma treatment described above was heated and pressed using the same vacuum high-temperature pressure apparatus as in Example 1. Specifically, firstly, the composites were stacked with the plasma-treated surfaces in contact with each other. Then, a release film was stacked on the side of each composite opposite to the plasma-treated surface, i.e., the surface of the stacked composites that is in contact with the pressure plate of the vacuum high-temperature pressure apparatus, to obtain a laminate. A PTFE machined film (thickness: 50 μm) was used as the release film. Next, the laminate was placed in the vacuum high-temperature pressure apparatus and pressed at a temperature of 280°C and a pressing pressure of 6 MPa for 20 minutes. After the heating and pressing was completed, the release film was removed. Thus, the molded body of Example 2 was obtained.

[0147] <Comparative Example 1>

[0148] In Comparative Example 1, the heating process using a hot air inert oven as in Example 1 was not performed. That is, the intermediate of Example 1 is equivalent to the molded body of Comparative Example 1.

[0149] <Comparative Example 2>

[0150] In Comparative Example 2, the temperature of the vacuum high-temperature pressure device in Example 2 was set to 250°C. Otherwise, the molded body of Comparative Example 2 was obtained in the same manner as in Example 2.

[0151] <Comparative Example 3>

[0152] In Comparative Example 3, a commercially available meltblown nonwoven fabric was impregnated in the first mixture used in Example 1. Otherwise, the molded body of Comparative Example 3 was obtained in the same manner as in Example 1.

[0153] <Comparative Example 4>

[0154] In Comparative Example 4, the same resin as in Example 2 and the same meltblown nonwoven fabric as in Comparative Example 3 were impregnated with NMP. Otherwise, the molded article of Comparative Example 4 was obtained in the same manner as in Example 2.

[0155] [Observation of the molded object]

[0156] The molded bodies from Examples 1-2 and Comparative Examples 1-4 were immersed in NMP for 3 minutes. As a result, in the molded bodies of Examples 1-2, although the resin swelled, no peeling of the laminated surfaces of the molded bodies was observed. In addition, SEM observation of the cross-section of the molded bodies confirmed that the LCP fibers were fused together, including the laminated surfaces.

[0157] On the other hand, in the molded bodies of Comparative Examples 1 to 4, resin swelling was confirmed, and the laminated surfaces of the molded bodies also peeled off. In addition, by observing the cross-section of the molded bodies using SEM, it was confirmed that the LCP fibers, including the laminated surfaces, were not sufficiently fused or not fused together.

[0158] It should be explained that Figure 1 This is an SEM image of the surface of the molded body in Example 2. According to... Figure 1 This allows us to confirm that the surface undulations and unevenness of the molded object are minimal. Additionally, Figure 2 This is a SEM image of the cross-section of the molded body in Example 2 before NMP processing. According to... Figure 2 This allows us to confirm the bonding of the molded parts.

[0159] Experiment 2

[0160] <Example 3>

[0161] Prepare the molded body of Example 2. Immerse the molded body in a tank filled with NMP and heat it with a heating plate at 130°C for 5 minutes to completely remove the resin, thereby obtaining the molded body of Example 3.

[0162] <Comparative Example 5>

[0163] Prepare the molded body of Comparative Example 2. Completely remove the resin by performing the same treatment as in Example 3 to obtain the laminate of Comparative Example 5.

[0164] [Observation of the molded object]

[0165] In Example 3, even after completely removing the resin, no peeling or breakage of the laminated surfaces of the molded article was observed (see Example 3). Figure 4 and 5 Furthermore, in Comparative Example 5, by completely removing the resin, not only did the laminated surfaces of the molded article peel off, but it also broke apart into fragments (see [reference]). Figure 6 ).

[0166] It should be explained that Figure 3 This is an SEM image of the surface of the laminate in Example 3. According to... Figure 3 It can be confirmed that although the LCP fibers are tightly bonded to each other, there are spaces between the LCP fibers, forming a porous structure.

[0167] Furthermore, the dielectric constant of the molded body of Example 3 was measured according to JIS R 1641 and IEC 63185. The results showed an effective dielectric constant of 2.0 and a dielectric loss tangent of 0.006 for the 30 GHz band. This is because the effective dielectric constant of the LCP fiber used as the raw material is 3.0 and the dielectric loss tangent is 0.001, while the effective dielectric constant of air is 1.0 and the dielectric loss tangent is 0. Therefore, the effective dielectric constant of air is the intermediate value between LCP fiber and air, resulting in a significant improvement in electrical properties.

[0168] Experiment 3

[0169] <Example 4>

[0170] Prepare four composites of Example 2. A wiring pattern is formed on the copper foil of the composite using a subtractive method, and then filled with conductive paste. After filling, a four-layer flexible printed circuit (FPC) substrate is fabricated using the same vacuum high-temperature pressure apparatus as in Example 1, at a temperature of 280°C and a pressing pressure of 4 MPa for 20 minutes.

[0171] The FPC substrate was immersed in NMP filled with a tank and heated with a heating plate at 130°C for 60 minutes to completely remove the resin, thereby obtaining the FPC substrate of Example 4.

[0172] [Observation of FPC substrates]

[0173] In Example 4, even after completely removing the resin, no peeling of the FPC substrate's laminated surfaces was confirmed, and no electrode peeling was also confirmed (see Example 4). Figure 7 ).

[0174] Experiment 4

[0175] <Example 5>

[0176] In Example 5, PTFE powder (average particle size: 4 μm) was prepared as an additive.

[0177] The PTFE powder, the same resin as in Example 2, and the same LCP powder as in Example 1 were dissolved in NMP as a solvent to obtain a paste-like mixture with a solid content of 8% by volume. The mixing ratio of PTFE powder, resin, and LCP powder in the mixture was 2:2:1 by volume. Otherwise, the molded article of Example 5 was obtained in the same manner as in Example 2.

[0178] [Determination of moisture content]

[0179] The moisture content of each molded body was determined for Example 5 and Example 2 described above. Specifically, each molded body was immersed in water at 20°C for 24 hours, and the moisture content of each molded body was quickly determined using the Karl Fischer method after wiping off the surface moisture. It should be noted that the n number for each molded body is 3, and the values ​​described below are their average values.

[0180] As a result, the moisture content of Example 2 was 1.8% by mass, and the moisture content of Example 5 was 0.8% by mass. Thus, it was confirmed that by adding PTFE as an additive, the moisture content of the molded article can be reduced.

[0181] In the description of the above embodiments, there are combinable configurations that can be combined with each other.

[0182] It should be considered that all aspects of the embodiments and implementations disclosed herein are merely illustrative and not restrictive. The scope of the invention is not limited to the foregoing description, but is indicated by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

Claims

1. A molded article comprising liquid crystal polymer powder and optionally resin, The liquid crystal polymer powder comprises fibrous particles composed of liquid crystal polymers. The average diameter of the fibrous particles composed of the liquid crystal polymer is less than 1 μm. The fibrous particles composed of the liquid crystal polymer contain unfibrillated blocky particles. The bulk particles are aggregates with a maximum height greater than 10 μm when placed on a plane. The content of the blocky particles is less than 20%. The resin is heat resistant. The resin is a thermoplastic resin or a thermosetting resin.

2. The molded body according to claim 1, wherein, Further includes additives.

3. A method for manufacturing a molded article, which is the method for manufacturing a molded article according to claim 1. The resin is a thermosetting resin. The method for manufacturing the molded article includes: The dispersion process involves dispersing liquid crystal polymer powder in a solution obtained by dissolving the thermosetting resin in a solvent to obtain a liquid mixture. The compounding process involves drying the mixture to form a composite. The first heating step involves heating the composite to obtain an intermediate, and The second heating process involves further heating the intermediate to obtain the molded body; The heating temperature in the second heating process is in the range of -60°C to -5°C, which is the melting point of the liquid crystal polymer powder.

4. A method for manufacturing a molded article, which is the method for manufacturing a molded article according to claim 1. The resin is a thermoplastic resin. The method for manufacturing the molded article includes: The dispersion process involves dispersing liquid crystal polymer powder in a solution obtained by dissolving the thermoplastic resin in a solvent to obtain a paste-like mixture. The compounding process involves drying the mixture to form a composite, and The heating process involves heating the composite to obtain a molded body. The heating temperature in the heating process is in the range of -60℃ to -5℃, which is the melting point of the liquid crystal polymer powder.

5. The method for manufacturing a molded article according to claim 4, wherein, The thermoplastic resin is a solvent-soluble thermoplastic resin. The method for manufacturing the molded article further includes: The resin removal process removes at least a portion of the solvent-soluble thermoplastic resin from the molded body.

6. The method for manufacturing the molded article according to any one of claims 3 to 5, wherein, Additives are further added during the dispersion process.

7. The method for manufacturing the molded article according to any one of claims 3 to 5, wherein, The composite process includes a coating process in which the mixture is applied to a substrate.

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