Method for producing porous liquid crystal polymer and porosizing agent

Abstract

This method for producing a porous liquid crystal polymer includes a first step and a second step. In the first step, a liquid crystal polymer and a porosity-imparting agent are kneaded to prepare a composition containing the liquid crystal polymer and the porosity-imparting agent. In the second step, the porosity-imparting agent in the composition is extracted using a supercritical fluid. The mass reduction rate of the porosity-imparting agent at 230°C is 10 mass% or less.

Description

Technical Field

[0001] The present invention relates to a method for producing a porous liquid crystal polymer and a porogen.

Background Art

[0002] A method for producing a porous resin in which a porogen is extracted from a composition containing a resin and a porogen by a supercritical extraction method using supercritical carbon dioxide as an extraction solvent is known (see, for example, Patent Document 1 below). In the examples of Patent Document 1, a composition solution containing polyoxyethylene dimethyl ether as a porogen, a polyimide resin precursor as a resin, and a solvent was prepared, coated and dried to form a coating film, and then the above-mentioned polyoxyethylene dimethyl ether was extracted from the coating film by the above method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to obtain a low moisture absorption rate and a low dielectric constant, it has been proposed to use a liquid crystal polymer as a resin. In this proposal, in order to carry out the supercritical extraction method, first, a liquid crystal polymer and a porogen are kneaded to prepare a kneaded product.

[0005] However, when polyoxyethylene dimethyl ether is kneaded as a porogen, it decomposes or volatilizes during kneading, and a kneaded product containing a porogen cannot be prepared. As a result, there is a problem that a porous liquid crystal polymer cannot be produced.

[0006] The present invention provides a method for producing a porous liquid crystal polymer and a porous agent, which enable reliable kneading of the porous agent together with the liquid crystal polymer, thereby enabling reliable production of a porous liquid crystal polymer. [Means for solving the problem]

[0007] The present invention (1) includes a method for producing a porous liquid crystal polymer, comprising a first step of kneading a liquid crystal polymer and a porosizing agent to prepare a composition containing the liquid crystal polymer and the porosizing agent, and a second step of extracting the porosizing agent from the composition with a supercritical fluid, wherein the mass loss rate of the porosizing agent at 230°C is 10% by mass or less.

[0008] In this method for producing porous liquid crystal polymers, the mass loss rate of the porosizing agent at 230°C is 10% by mass or less, so the porosizing agent has excellent heat resistance. Therefore, in the first step, the porosizing agent can be reliably kneaded together with the liquid crystal polymer while suppressing decomposition or volatilization. As a result, in the second step, the porous liquid crystal polymer can be reliably produced by extracting the porosizing agent from the composition containing the porosizing agent described above.

[0009] The present invention (2) includes a method for producing a porous liquid crystal polymer as described in (1), wherein the porous agent is at least one selected from the group consisting of purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, and dicarboxylic acid anhydride derivatives.

[0010] The present invention (3) includes a method for producing a porous liquid crystal polymer according to (1) or (2), wherein the temperature of the supercritical fluid in the second step is higher than the glass transition temperature of the liquid crystal polymer.

[0011] In this method for producing porous liquid crystal polymers, the temperature of the supercritical fluid in the second step is higher than the glass transition temperature of the liquid crystal polymer, thus increasing the extraction efficiency of the supercritical fluid in the second step. Therefore, porous liquid crystal polymers with a high porosity P can be produced.

[0012] The present invention (4) includes a method for producing a porous liquid crystal polymer, wherein in the first step, a non-porous sheet made of the composition is formed, and in the second step, a porous liquid crystal polymer sheet is produced, and any one of (1) to (3) is included in the method for producing a porous liquid crystal polymer.

[0013] This method for manufacturing porous liquid crystal polymers allows for the production of thin porous liquid crystal polymer sheets.

[0014] The present invention (5) includes a method for producing a porous liquid crystal polymer according to any one of (1) to (4), wherein the first step involves kneading a hollow sphere.

[0015] In this method for producing porous liquid crystal polymers, hollow spheres are kneaded in the first step, making it possible to produce porous liquid crystal polymer sheets with high porosity.

[0016] The present invention (6) includes a method for producing a porous liquid crystal polymer in any one of (1) to (5), wherein the supercritical fluid is supercritical carbon dioxide.

[0017] In this method for producing porous liquid crystal polymers, the supercritical fluid is supercritical carbon dioxide, which allows for the low-cost production of porous liquid crystal polymers.

[0018] The present invention (7) includes a method for producing a porous liquid crystal polymer in any one of (1) to (6), wherein the second step is to produce a porous liquid crystal polymer having a porosity P of 20% or more.

[0019] This method for manufacturing porous liquid crystal polymers makes it possible to produce porous liquid crystal polymers with a low dielectric constant.

[0020] The present invention (8) includes a method for producing a porous liquid crystal polymer in any one of (1) to (7), wherein in the second step, an entrainer is blended into the supercritical fluid.

[0021] In the method for producing this porous liquid crystal polymer, in the second step, an entrainer is blended with the supercritical fluid, so that the extraction efficiency of the supercritical fluid can be increased. Therefore, a porous liquid crystal polymer with a high porosity P can be produced.

[0022] The present invention (9) includes the method for producing a porous liquid crystal polymer according to any one of (1) to (8), wherein the mass reduction rate of the porogen at 300 °C is 10% by mass or less.

[0023] The present invention (10) includes the method for producing a porous liquid crystal polymer according to any one of (1) to (9), wherein the mass reduction rate of the porogen at 350 °C is 10% by mass or less.

[0024] The present invention (11) includes the method for producing a porous liquid crystal polymer according to (2), wherein the dicarboxylic anhydride derivative contains a trifluoromethyl group.

[0025] The present invention (12) includes the method for producing a porous liquid crystal polymer according to (11), wherein the trifluoromethyl group is located at the center of the structure.

[0026] The present invention (13) includes a porogen having a mass reduction rate of 10% by mass or less at 230 °C.

[0027] The mass reduction rate of this porogen at 230 °C is 10% by mass or less. Therefore, the porogen has excellent heat resistance. Therefore, the porogen can be surely kneaded with the liquid crystal polymer while suppressing decomposition or volatilization. As a result, a porous liquid crystal polymer can be surely produced by extracting the porogen from the composition containing the above-mentioned porogen.

[0028] [[ID=2​​​​​

[0030] The present invention (16) includes a porous agent according to any one of (13) to (15), which is at least one selected from the group consisting of purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, and dicarboxylic acid anhydride derivatives.

[0031] The present invention (17) comprises a porosity agent according to (16), wherein the dicarboxylic acid anhydride derivative contains a trifluoromethyl group.

[0032] The present invention (18) comprises a porosity agent as described in (17), wherein the trifluoromethyl group is located in the center of the structure. [Effects of the Invention]

[0033] According to the method for producing porous liquid crystal polymers and the porosizing agent of the present invention, the porosizing agent can be reliably kneaded together with the liquid crystal polymer, and a porous liquid crystal polymer can be reliably obtained. [Brief explanation of the drawing]

[0034] [Figure 1] Figures 1A and 1B are process diagrams of one embodiment of the method for producing a porous liquid crystal polymer according to the present invention. Figure 1A is the first step. Figure 1B is the second step. [Figure 2] Figure 2 is a cross-sectional view of a wiring circuit board comprising a porous liquid crystal polymer sheet. [Modes for carrying out the invention]

[0035] A method for manufacturing a porous liquid crystal polymer sheet 1, which is one embodiment of the method for manufacturing a porous liquid crystal polymer of the present invention, will be described with reference to Figures 1A and 1B. This manufacturing method comprises a first step and a second step as essential steps. This manufacturing method also comprises a third step as an optional step. In this manufacturing method, for example, steps 1 to 3 are carried out in order.

[0036] <1st process> In the first step, the liquid crystal polymer and the porous agent are kneaded together to prepare the composition.

[0037] <Liquid crystal polymer> The liquid crystal polymer is not limited. The liquid crystal polymer is a liquid crystalline thermoplastic resin. Examples of liquid crystal polymers include liquid crystal polyesters, preferably aromatic liquid crystal polyesters. Liquid crystal polymers are specifically described, for example, in Japanese Patent Publication No. 2020-147670 and Japanese Patent Publication No. 2004-189867. Commercial liquid crystal polymers can be used. Examples of commercial products include UENO LCP (registered trademark, hereinafter the same) 8100 series (low melting point type, manufactured by Ueno Pharmaceutical Co., Ltd.) and UENO LCP 5000 series (high melting point type, manufactured by Ueno Pharmaceutical Co., Ltd.). Preferably, the UENO LCP 8100 series is used.

[0038] The melting point of the liquid crystal polymer is not limited. The melting point of the liquid crystal polymer is, for example, 200°C or higher, preferably 220°C or higher, more preferably 400°C or higher, and also, for example, 370°C or lower. The melting point of the liquid crystal polymer is determined by differential scanning calorimetry. In differential scanning calorimetry, the heating rate is 10°C / min, and the liquid crystal polymer is heated in a nitrogen atmosphere within a range of 25°C to 400°C. If the liquid crystal polymer is a commercially available product, the catalog value of the commercially available product can be used as is. If the melting point of the liquid crystal polymer is above the lower limit described above, the porous liquid crystal polymer sheet 1 has excellent handling and processability. If the melting point of the liquid crystal polymer is below the upper limit described above, the porous liquid crystal polymer sheet 1 has excellent heat resistance.

[0039] The glass transition temperature of a liquid crystal polymer is not limited. For example, it may be above 80°C, or below 125°C. The glass transition temperature of a liquid crystal polymer is determined by differential scanning calorimetry performed at a heating rate of 10°C / min.

[0040] <Porous agent> The porosizing agent is a component dispersed in the liquid crystal polymer to make it porous. Furthermore, the porosizing agent undergoes phase separation from the liquid crystal polymer, for example, at the kneading temperature (described later). Phase separation involves the agent not dissolving in the liquid crystal polymer and maintaining a certain shape within the kneaded mixture.

[0041] Furthermore, the mass loss rate of the porous agent at 230°C is 10% by mass or less. "230°C" is a temperature included in the kneading temperature, which will be described later.

[0042] If the mass loss rate of the porosizing agent at 230°C exceeds 10% by mass, excessive thermal decomposition will occur during the first step of kneading, and therefore, the liquid crystal polymer cannot be reliably made porous in the second step.

[0043] The mass loss rate of the porous agent at 230°C is preferably 9% or less, more preferably 7% or less, more preferably 5% or less, even more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less. The lower limit of the mass loss rate of the porous agent at 230°C is not limited. For example, the lower limit of the mass loss rate of the porous agent at 230°C is 0%.

[0044] The mass loss rate of the porous agent is measured as the mass (weight) loss rate at 230°C in thermogravimetric analysis at a heating rate of 10°C / min and scanning temperatures from 40°C to 400°C. Details of the measurement method will be described in the following examples.

[0045] The mass loss rate of the porous agent at 300°C is preferably 100% or less, more preferably 40% or less, more preferably 30% or less, more preferably 10% or less, even more preferably 6% or less, even more preferably 5% or less, even more preferably 4% or less, even more preferably 2% or less, and even more preferably 1% or less, from the viewpoint of suppressing the amount of thermal decomposition in the kneading of the first step. The lower limit of the mass loss rate of the porous agent at 300°C is, for example, 0%.

[0046] The mass loss rate of the porous agent is measured as the mass (weight) loss rate at 300°C in thermogravimetric analysis at a heating rate of 10°C / min and scanning temperatures from 40°C to 400°C. Details of the measurement method will be described in the following examples.

[0047] The mass loss rate of the porous agent at 350°C is preferably 100% or less, more preferably 90% or less, more preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, even more preferably 8% or less, even more preferably 5% or less, and even more preferably 3% or less, from the viewpoint of suppressing the amount of thermal decomposition in the first step of kneading. The lower limit of the mass loss rate of the porous agent at 350°C is, for example, 0%.

[0048] The mass loss rate of the porous agent is measured as the mass (weight) loss rate at 350°C in thermogravimetric analysis at a heating rate of 10°C / min and scanning temperatures from 40°C to 400°C. Details of the measurement method will be described in the following examples.

[0049] The type of porous agent is not limited as long as the above-mentioned mass loss rate is satisfied. Specifically, examples of porous agents include purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, acene derivatives, and dicarboxylic acid anhydride derivatives. These can be used alone or in combination.

[0050] Examples of purine derivatives include caffeine, theobromine, and theophylline-7-acetic acid. Caffeine and theobromine are particularly recommended from the viewpoint of obtaining high extraction efficiency and high porosity.

[0051] Examples of bisphenol AF derivatives include 5,5'-(1,1,1,3,3,3-hexafluoro-2,2-propanediyl)bis[2-phenyl-1H-isoindole-1,3(2H)-dione] and 2,2-bis(4-carboxyphenyl)hexafluoropropane. Examples of perfluoropolyether derivatives include perfluoropolyethers. The weight-average molecular weight (catalog value) of perfluoropolyethers is, for example, 1,000 or more and 10,000 or less. Examples of calixarene derivatives include p-tert-butylcalix[4]arene. Examples of acene derivatives include 6,13-pentacendione.

[0052] Dicarboxylic acid anhydride derivatives include, for example, compounds containing a trifluoromethyl group, preferably compounds having a trifluoromethyl group located in the center of the structure, more preferably compounds in which the density of trifluoromethyl groups differs between the center and the ends of the structure, and even more preferably compounds in which the density of trifluoromethyl groups in the center of the structure is higher than the density of trifluoromethyl groups at the ends of the structure. Specifically, examples of dicarboxylic acid anhydride derivatives include 4,4'-oxydiphthalic anhydride, 2,2'-diphenyl[5,5'-bi-1H-isoindole]-1,1',3,3'(2H,2H')-tetron, and 2,2'-[2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diyl]bis[1H-isoindole-1,3(2H)-dione], 2,2'-bis[4-(trifluoromethyl)phenyl][5,5'-bi-1H-isoindole]-1,1',3,3'(2H,2'H)-tetron, and 2,2'-[2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diyl]bis[octahydro-1,3-dioxo-1H-isoindole-5-methyl].

[0053] Furthermore, 2,2'-[2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diyl]bis[octahydro-1,3-dioxo-1H-isoindole-5-methyl] is a compound containing a trifluoromethyl group, and is an example of a dicarboxylic acid anhydride derivative in which the density of trifluoromethyl groups in the center of the structure is higher than the density of trifluoromethyl groups at the ends of the structure.

[0054] [ka]

[0055] Preferably, the porous agent includes purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, and dicarboxylic acid anhydride derivatives in which the density of trifluoromethyl groups in the central part of the structure is higher than the density of trifluoromethyl groups at the ends of the structure. If the porous agent is selected from the group consisting of purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, and dicarboxylic acid anhydride derivatives in which the density of trifluoromethyl groups in the central part of the structure is higher than the density of trifluoromethyl groups at the ends of the structure, the extraction efficiency by supercritical fluid (preferably supercritical carbon dioxide) in the second step will be increased, and thus a porous liquid crystal polymer sheet 1 having a high porosity P can be produced.

[0056] The proportion of the porous agent is not limited. The proportion of the porous agent is adjusted as appropriate to achieve the desired porosity P. Specifically, the percentage of the volume of the porous agent relative to the total volume of the liquid crystal polymer and the porous agent is, for example, 20% by volume or more, preferably 30% by volume or more, more preferably 40% by volume or more, and also, for example, 90% by volume or less, preferably 80% by volume or less, and more preferably 70% by volume or less. The percentage of the volume of the porous agent relative to the total volume of the liquid crystal polymer and the porous agent is determined by conversion using specific gravity from the percentage of the mass of the porous agent relative to the total mass of the liquid crystal polymer and the porous agent. Furthermore, the mass ratio of the porous agent to 100 parts by mass of the liquid crystal polymer is, for example, 10 parts by mass or more, preferably 50 parts by mass or more, and also, for example, 500 parts by mass or less, preferably 250 parts by mass or less.

[0057] In the first step, an additive may be further kneaded in. Examples of additives include fillers. Examples of fillers include hollow spheres. Hollow spheres include, for example, glass balloons. Hollow spheres are described, for example, in Japanese Patent Publication No. 2004-189867.

[0058] In the first step, by kneading the hollow spheres, a porous liquid crystal polymer sheet 1 with a high porosity P can be manufactured.

[0059] On the other hand, if the hollow spheres are not kneaded in the first step, the brittleness of the porous liquid crystal polymer sheet 1 can be suppressed.

[0060] The mixing temperature is not limited. For example, the mixing temperature is set to a temperature at which the amount of thermal decomposition of the porous agent described above is small. Specifically, the mixing temperature is, for example, 200°C or higher, preferably 210°C or higher, and also, for example, 350°C or lower, preferably 300°C or lower, more preferably 270°C or lower, and even more preferably 250°C or lower. Alternatively, the mixing temperature can be in the range of 230°C ± 30°C (i.e., 200°C or higher and 260°C or lower), preferably 230°C ± 20°C (i.e., 210°C or higher and 250°C or lower), more preferably 230°C ± 10°C (i.e., 220°C or higher and 240°C or lower), and even more preferably 230°C ± 5°C (i.e., 225°C or higher and 235°C or lower).

[0061] Next, in the first step, as shown in Figure 1A, the composition is formed into a sheet to produce a non-porous sheet 3. Methods for forming the composition into a sheet include, for example, pressing, extrusion, and injection. Pressing is preferred, and hot pressing is more preferred. The temperature of the hot pressing is not limited. The temperature of the hot pressing is set to a temperature at which the amount of thermal decomposition of the above-mentioned porous agent is small. Specifically, the temperature of the hot pressing is, for example, 200°C or higher and 300°C or lower. The pressing pressure is, for example, 1 MPa or higher, preferably 4 MPa or higher, and for example, 20 MPa or lower, preferably 10 MPa or lower. This yields a non-porous sheet 3 containing the liquid crystal polymer and the porous agent.

[0062] The thickness of the non-porous sheet 3 is not limited. For example, the thickness of the non-porous sheet 3 can be set to the target thickness of the porous liquid crystal polymer sheet 1.

[0063] <Second process> In the second step, the porosizing agent in the composition is extracted using a supercritical fluid. Specifically, the porosizing agent in the non-porous sheet 3 is extracted using a supercritical fluid. For example, as shown in Figure 1B, the second step uses a supercritical apparatus 10. The supercritical apparatus 10 comprises a pressure vessel 11 and a circulation device (not shown). The pressure vessel 11 is capable of circulating the supercritical fluid 15 while containing it. The circulation device circulates the supercritical fluid 15 in the pressure vessel 11. The circulation device is also provided with a recovery device. The recovery device removes the porosizing agent extracted into the supercritical fluid 15.

[0064] <Supercritical fluid 15> The type of supercritical fluid 15 is not limited. Examples of supercritical fluids 15 include supercritical carbon dioxide and supercritical nitrogen. From the viewpoint of manufacturing cost, supercritical carbon dioxide is preferred as the supercritical fluid 15.

[0065] <Entrina> An entrainer may be added to the supercritical fluid 15. The entrainer is added to the supercritical fluid 15 to increase the extraction efficiency of the porous agent by the supercritical fluid 15. The entrainer is compatible with the supercritical fluid 15 and the porous agent. Examples of entrainers include water, alcohol compounds, ketone compounds, ester compounds, aromatic compounds, long-chain alkyl compounds, and aprotic amide compounds. These can be used alone or in combination. Examples of alcohol compounds include methanol and ethanol. Examples of ketone compounds include acetone and methyl ethyl ketone. Examples of ester compounds include methyl acetate, ethyl acetate, and propyl acetate. Examples of aromatic compounds include benzene, toluene, and xylene. Examples of long-chain alkyl compounds include pentane, hexane, and heptane. Examples of aprotic amide compounds include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAC). Preferred entrainers include alcohol compounds, ester compounds, and aprotic amide compounds. The proportion of the entrainer is set as appropriate. Specifically, the entrainer flow rate is, for example, 0.1 mL / min or more, preferably 1 mL / min or more, and also, for example, 20 mL / min or less, preferably 5 mL / min or less, relative to the supercritical fluid circulation flow rate of 100 mL / min.

[0066] In the second step, the non-porous sheet 3 is placed in the pressure vessel 11. Next, the supercritical fluid 15 is introduced into the pressure vessel 11 in the supercritical device 10. Subsequently, the supercritical fluid 15 is circulated by a circulation device (not shown). Through these steps, the supercritical fluid 15 comes into contact with the non-porous sheet 3.

[0067] First, the supercritical fluid 15 on the outside of the non-porous sheet 3 is impregnated into the non-porous sheet 3. In other words, the supercritical fluid 15 penetrates into the interior of the non-porous sheet 3. Then, the supercritical fluid 15 returns to the outside of the non-porous sheet 3 while dissolving the porosizing agent. In this way, the porosizing agent in the non-porous sheet 3 is extracted by the supercritical fluid 15.

[0068] The conditions for the second step are not limited. The temperature of the supercritical fluid 15 is, for example, higher than the glass transition temperature of the liquid crystal polymer described above. Also, the temperature of the supercritical fluid 15 is, for example, at least 10°C higher, preferably at least 30°C higher, more preferably at least 50°C higher, and even more preferably 70°C higher than the glass transition temperature of the liquid crystal polymer described above. As described above, if the temperature of the supercritical fluid 15 is higher than the glass transition temperature of the liquid crystal polymer, the extraction efficiency of the supercritical fluid 15 in the second step can be increased. As a result, a porous liquid crystal polymer sheet 1 with a high porosity P can be produced. For example, 40°C or higher, preferably 75°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, particularly preferably 150°C or higher, most preferably 170°C or higher, and also, for example, 200°C or lower, preferably 190°C or lower, and more preferably 180°C or lower.

[0069] The pressure of the supercritical fluid 15 is, for example, 10 MPa or more, preferably 20 MPa or more, and also, for example, 30 MPa or less, preferably 27 MPa or less.

[0070] The extraction time is, for example, 20 minutes or more, preferably 1 hour or more, more preferably 3 hours or more, even more preferably 5 hours or more, particularly preferably 8 hours or more, most preferably 10 hours or more, and also, for example, 100 hours or less, preferably 48 hours or less, and more preferably 24 hours or less. If the extraction time is above the lower limit described above, the extraction efficiency of the supercritical fluid in the second step can be increased, and a porous liquid crystal polymer sheet 1 having a high porosity P can be produced. If the extraction time is below the upper limit described above, the cycle time can be shortened and the production efficiency can be improved.

[0071] <3rd process> In the third step, the pressure in the pressure vessel 11 is reduced while removing the supercritical fluid 15 from inside the pressure vessel 11. Specifically, the pressure in the pressure vessel 11 is returned to atmospheric pressure. The rate of pressure reduction is not limited. For example, the rate of pressure reduction is adjusted so as to suppress foaming by the supercritical fluid 15 impregnated in the non-porous sheet 3. At this time, the pressure vessel 11 may be heated. The heating temperature is the same as the temperature of the supercritical fluid in the second step, for example, 40°C or higher, preferably 75°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, particularly preferably 150°C or higher, most preferably 170°C or higher, and also, for example, 200°C or lower, preferably 190°C or lower, more preferably 180°C or lower. The heating time is, for example, 10 minutes or more and 3 hours or less.

[0072] As a result, multiple pores 2 are formed in place of the porosity-forming agent that was impregnated in the non-porous sheet 3. This produces a porous liquid crystal polymer sheet 1.

[0073] By carrying out the above-described steps 1 through 3, a porous liquid crystal polymer sheet 1 is manufactured.

[0074] <Porous liquid crystal polymer sheet 1> The porous liquid crystal polymer sheet 1 has thickness and a sheet shape. The sheet shape includes a film shape. The porous liquid crystal polymer sheet 1 extends in the planar direction. The planar direction is perpendicular to the thickness direction. The porous liquid crystal polymer sheet 1 has a large number of fine pores. Examples of the cellular structure of the porous liquid crystal polymer sheet 1 include a closed-cell structure, a continuous-cell structure, and a semi-closed / semi-continuous-cell structure. A closed-cell structure is preferred.

[0075] <Porosity P> The porosity P of the porous liquid crystal polymer sheet 1 is, for example, 1% or more, preferably 1.5% or more, more preferably 10% or more, even more preferably 20% or more, and further preferably 22% or more, 30% or more, 35% or more, 40% or more, 50% or more, or 55% or more. There is no upper limit to the porosity P of the porous liquid crystal polymer sheet 1. The upper limit of the porosity P of the porous liquid crystal polymer sheet 1 is, for example, 95%, and preferably 90% from the viewpoint of ensuring the mechanical strength of the porous liquid crystal polymer sheet 1. The porosity P of the porous liquid crystal polymer sheet 1 can be determined using a non-porous liquid crystal polymer sheet corresponding to the porous liquid crystal polymer sheet 1. Specifically, the specific gravity G1 of the porous liquid crystal polymer sheet and the specific gravity G0 of the non-porous liquid crystal polymer sheet are measured, and the porosity P of the porous liquid crystal polymer sheet 1 is determined by the following formula.

[0076] P = 100 × (1 - G1 / G0) P: Porosity P of porous liquid crystal polymer sheet 1 G1: Specific gravity of porous liquid crystal polymer sheet 1 G0: Specific gravity of non-porous liquid crystal polymer sheet

[0077] <Dielectric constant> The dielectric constant of the porous liquid crystal polymer sheet 1 at 10 GHz is preferably less than 3.10, more preferably 2.60 or less, more preferably 2.50 or less, even more preferably 2.20 or less, and even more preferably 2.10 or less, 2.00 or less, or 1.90 or less. If the dielectric constant of the porous liquid crystal polymer sheet 1 is below the above upper limit, the porous liquid crystal polymer sheet is low dielectric. The lower limit of the dielectric constant of the porous liquid crystal polymer sheet at 10 GHz is not limited. For example, the dielectric constant of the porous liquid crystal polymer sheet at 10 GHz is 1.00. The method for measuring the dielectric constant of the porous liquid crystal polymer sheet will be described in a later example.

[0078] <Dielectric loss tangent> The dielectric loss tangent of the porous liquid crystal polymer sheet 1 at 10 GHz is, for example, 0.00129 or less, preferably 0.00100 or less, more preferably 0.00080 or less, even more preferably 0.00070 or less, and particularly preferably 0.00060 or less. If the dielectric loss tangent of the porous liquid crystal polymer sheet 1 is below the upper limit described above, the porous liquid crystal polymer sheet is considered to have low dielectric properties. The lower limit of the dielectric loss tangent of the porous liquid crystal polymer sheet at 10 GHz is not limited. For example, the lower limit of the dielectric loss tangent of the porous liquid crystal polymer sheet at 10 GHz is 0.00000. The method for measuring the dielectric loss tangent of the porous liquid crystal polymer sheet will be described in a later example.

[0079] <Applications of Porous Liquid Crystal Polymer Sheet 1> The applications of the porous liquid crystal polymer sheet 1 are not limited. Examples of applications for the porous liquid crystal polymer sheet 1 include insulating layers for wiring circuit boards and antenna substrates for wireless communication.

[0080] Next, Figure 2 shows an example of a wiring circuit board that includes a porous liquid crystal polymer sheet 1 as an insulating layer.

[0081] As shown in Figure 2, the wiring circuit board 21 extends in the planar direction. The wiring circuit board 21 has a sheet shape. The wiring circuit board 21 is provided with an insulating layer 12 and a conductive layer 13 in order toward one side in the thickness direction.

[0082] The insulating layer 12 is made of the porous liquid crystal polymer sheet 1 described above.

[0083] The conductor layer 13 is in contact with one side of the insulating layer 12 in the thickness direction. The conductor layer 13 has a predetermined wiring pattern 14.

[0084] To obtain the wiring circuit board 21, for example, a laminate 16 comprising an insulating layer 12 and a conductor sheet 25 is prepared. The conductor sheet 25 is depicted by a dashed line in Figure 2. For example, a non-porous laminate (dashed line in Figure 1A) comprising the non-porous sheet 3 and the conductor sheet 25 is prepared, and the non-porous sheet 3 in the non-porous laminate is made porous using the above-described method (extraction method, foaming method) to obtain the laminate 16.

[0085] Subsequently, the conductive sheet 25 on the laminate 16 is patterned to form the conductive layer 13. For patterning, etching is used, for example.

[0086] <Effects and Effects> In the method for producing the porous liquid crystal polymer sheet 1 according to one embodiment, the mass reduction rate of the porous agent at 230°C is 10% by mass or less, so the porous agent has excellent heat resistance. Therefore, in the first step, the porous agent can be reliably kneaded together with the liquid crystal polymer while suppressing decomposition or volatilization. Therefore, in the second step, the porous liquid crystal polymer sheet 1 can be reliably produced by extracting the porous agent from the composition containing the porous agent described above.

[0087] In one embodiment of the manufacturing method, if the porosizing agent is at least one selected from the group consisting of purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, and calixarene derivatives, the extraction efficiency by supercritical fluid (preferably supercritical carbon dioxide) in the second step is increased, and as a result, a porous liquid crystal polymer sheet 1 having a high porosity P can be produced.

[0088] In one embodiment of the method for manufacturing a porous liquid crystal polymer sheet 1, if the temperature of the supercritical fluid in the second step is higher than the glass transition temperature of the liquid crystal polymer, the extraction efficiency by the supercritical fluid in the second step can be increased. As a result, a porous liquid crystal polymer having a high porosity P can be manufactured.

[0089] In one embodiment, a non-porous sheet 3 made of the composition is formed in the first step, and a thin porous liquid crystal polymer sheet 1 can be manufactured from the non-porous sheet 3 in the second step.

[0090] In one embodiment, by further kneading the hollow spheres in the first step, a porous liquid crystal polymer sheet 1 with a high porosity P can be produced.

[0091] In one embodiment of the manufacturing method, if the supercritical fluid is supercritical carbon dioxide, the porous liquid crystal polymer sheet 1 can be manufactured at low cost.

[0092] According to one embodiment of the manufacturing method, a porous liquid crystal polymer sheet 1 having a low dielectric constant can be manufactured.

[0093] In one embodiment of the manufacturing method, if the entrainer is blended with the supercritical fluid in the second step, the extraction efficiency of the supercritical fluid 15 can be increased. As a result, a porous liquid crystal polymer sheet 1 with a high porosity P can be manufactured.

[0094] The porous agent used in the above-described manufacturing method has a mass loss rate of 10% by mass or less at 230°C. Therefore, the porous agent has excellent heat resistance. As a result, the porous agent can be reliably kneaded together with the liquid crystal polymer while suppressing decomposition or volatilization. Consequently, a porous liquid crystal polymer can be reliably produced by extracting the porous agent from a composition containing the above-described porous agent.

[0095] <Variation> In the modified examples, components and processes similar to those in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted. Furthermore, the modified examples can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modified examples can be combined as appropriate.

[0096] In a modified example, the porous liquid crystal polymer may have a bulk form. That is, a non-porous bulk body is produced in the first step, and a porous liquid crystal bulk body is produced in the second and third steps. Preferably, a porous liquid crystal polymer sheet 1 is produced. This allows for the production of a thin porous liquid crystal polymer sheet 1, which can be placed in a confined space.

[0097] In a modified example, the porous liquid crystal polymer sheet 1 after the third step can be made even thinner. Methods for thinning the porous liquid crystal polymer sheet 1 include, for example, pressing, stretching, and rolling. Preferably, pressing is used, from the viewpoint of the accuracy of adjusting the thickness of the porous liquid crystal polymer sheet 1 obtained as a product.

[0098] The modified wiring circuit board comprises a conductor layer, an insulating layer, and another conductor layer, arranged sequentially toward one side in the thickness direction. The insulating layer is made of the porous liquid crystal polymer sheet described above. Each of the two conductor layers is arranged on one side and the other side in the thickness direction of the insulating layer, and has a predetermined wiring pattern. [Examples]

[0099] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited in any way to the examples and comparative examples. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the blending ratios (content ratios), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0100] First, the porous agents used are listed below. <Types of porous agents> Porousing agent 1: Caffeine (purine derivative) Porousing agent 2: Theobromine (purine derivative) Porousing agent 3: 5,5'-(1,1,1,3,3,3-hexafluoro-2,2-propanediyl)bis[2-phenyl-1H-isoindole-1,3(2H)-dione (bisphenol AF derivative) Porousing agent 4: 2,2-bis(4-carboxyphenyl)hexafluoropropane (bisphenol AF derivative) Porousing agent 5: Perfluoropolyethers with a weight-average molecular weight of 2000-9000 (perfluoropolyethers) Porousing agent 6: p-tert-butylcalix[4]allene (calixarene derivative) Porousing agent 7: 6,13-pentacendione (acene derivative) Porousing agent 8: 4,4'-oxydiphthalic anhydride (dicarboxylic acid anhydride) Porousing agent 9: Polyoxyethylene dimethyl ether (polyoxyalkylene alkyl ether) with a weight-average molecular weight of 400 Porousing agent 10: 2,2'-[2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diyl]bis[octahydro-1,3-dioxo-1H-isoindole-5-methyl](dicarboxylic acid anhydride)

[0101] <Physical properties of porous agents and liquid crystal polymers> The physical properties of the porous agent and liquid crystal polymer described below were evaluated. The evaluation results are shown in Tables 1-3.

[0102] <Mass reduction rate of the porous agent> The mass loss rates at 230°C for each of the porous materials 1 to 9 described above were measured using a thermogravimetric analyzer (model: SDT650) manufactured by T.A. Instruments Japan. The heating rate in the thermogravimetric analysis was 10°C / min, and the scanning temperature was set from 40°C to 400°C. The mass (weight) loss rates at 230°C, 300°C, and 350°C were obtained. The thermogravimetric analysis was performed under an oxygen atmosphere.

[0103] <Solubility of porous agents in supercritical carbon dioxide> 50 mg of each of the porous agents 1 through 9 was placed in an aluminum petri dish. Using an AKICO "CO2 Supercritical Fluid Experiment Apparatus," the temperature inside the pressure vessel 11 was set to 175°C and the pressure to 25 MPa, and the porous agents were extracted for 0.5 hours. The rate of mass change before and after extraction (using the following formula) was calculated to evaluate the solubility of the porous agents in supercritical carbon dioxide.

[0104] Mass change rate (%) = [Mass of porous agent before extraction - Mass of porous agent after extraction] / (Mass of porous agent before extraction) × 100

[0105] <Glass transition temperature of liquid crystal polymers> The glass transition temperature of UENO LCP A8100, a liquid crystal polymer manufactured by Ueno Pharmaceutical Co., Ltd., was determined using differential scanning calorimetry. The heating rate for differential scanning calorimetry was 10°C / min, and the liquid crystal polymer was heated in a nitrogen atmosphere. As a result, the glass transition temperature of the liquid crystal polymer (UENO LCP A8100) was found to be 100°C.

[0106] <Example 1> 1st process The composition was prepared by kneading UENO LCP A8100 (melting point 220°C, catalog value) manufactured by Ueno Pharmaceutical Co., Ltd. as a liquid crystal polymer and caffeine as a porosizing agent using a Laboplast Mill (model number: 4C150) manufactured by Toyo Seiki Co., Ltd. (Step 1, Figure 1A). The volume of the porosizing agent was 60 parts per 100 parts total volume of the liquid crystal polymer and porosizing agent. The kneading temperature was 230°C and the rotation speed was 30 min. -1 That was the case.

[0107] Next, non-porous sheets 3 with a thickness of 100-200 μm were fabricated from the kneaded material using a manual hydraulic vacuum press (model number: 11FD) manufactured by Imoto Seisakusho Co., Ltd. The press temperature was 230°C, the press pressure was 4-10 MPa, and the vacuum pressure was 0.1 MPa.

[0108] 2nd process Using an AKICO "CO2 Supercritical Fluid Experiment Apparatus," a porosizing agent was extracted from a non-porous sheet 3 using supercritical carbon dioxide as the supercritical fluid (second step, Figure 1B). In the second step, the temperature of the supercritical carbon dioxide was 175°C, the pressure of the supercritical carbon dioxide was 25 MPa, and the impregnation time (extraction time) was 1 hour.

[0109] 3rd process While removing supercritical carbon dioxide from inside the pressure vessel 11, the pressure in the pressure vessel 11 was lowered to atmospheric pressure over 30 minutes, and the temperature of the pressure vessel 11 was set to 175°C (third step).

[0110] <Examples 2 to 19> A porous liquid crystal polymer sheet 1 was manufactured using the same extraction method as in Example 1. However, the type of porosity-forming agent and the manufacturing method conditions were changed as described in Tables 1-3.

[0111] <Comparative Example 1> The same manufacturing method as in Example 1 was carried out. However, in the first step, a porosizing agent was not added. Therefore, instead of obtaining a porous liquid crystal polymer sheet 1, a non-porous sheet 3 was obtained. This was designated as the sheet for Comparative Example 1.

[0112] <Comparative Example 2> An attempt was made to produce a porous liquid crystal polymer sheet 1 using the same manufacturing method as in Example 1. However, a porosity-forming agent 9 was kneaded into the mixture.

[0113] However, in the first step, the amount of thermal decomposition of the porosizing agent was excessive, making it impossible to form a non-porous sheet 3. Therefore, the second and third steps could not be carried out, and consequently, the porous liquid crystal polymer sheet 1 could not be manufactured.

[0114] <Rating> The following aspects were evaluated for each of the porous liquid crystal polymer sheets 1 from Examples 1 to 19 and the non-porous sheet 3 of the comparative example. The results are shown in Tables 1 to 3.

[0115] <Porosity P> The specific gravity G1 of the porous liquid crystal polymer sheet 1 and the specific gravity G0 of the non-porous sheet 3, which is made of the liquid crystal polymer corresponding to the porous liquid crystal polymer sheet 1, were measured using an electronic hydrometer (model number: EW300SG) manufactured by Alpha Mirage Co., Ltd. Subsequently, the porosity P of the porous liquid crystal polymer sheet 1 was determined using the following formula.

[0116] P = 100 × (1 - G1 / G0) P: Porosity P of porous liquid crystal polymer sheet 1 G1: Specific gravity of porous liquid crystal polymer sheet 1 G0: Specific gravity of non-porous sheet 3

[0117] <Dielectric constant and dielectric loss tangent> Using the SPDR method compliant with ASTMD150, the dielectric constant and dielectric loss tangent of porous liquid crystal polymer sheet 1 and non-porous sheet 3 were measured at 10 GHz using a "10 GHz SPDR resonator" manufactured by QWED Corporation.

[0118] [Table 1]

[0119] [Table 2]

[0120] [Table 3]

[0121] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims below. [Industrial applicability]

[0122] Porousing agents are used in the production of porous liquid crystal polymers. [Explanation of Symbols]

[0123] 1. Porous liquid crystal polymer sheet 3. Non-porous sheet 15 Supercritical fluid

Claims

1. A first step involves kneading a liquid crystal polymer and a porous agent to prepare a composition containing the liquid crystal polymer and the porous agent, The composition comprises a second step of extracting the porous agent in the composition using a supercritical fluid, The mass loss rate of the porous agent at 230°C is 10% by mass or less. A method for producing a porous liquid crystal polymer, wherein the porous agent is at least one selected from the group consisting of purine derivatives, bisphenol AF derivatives, pearl fluoropolyether derivatives, calixarene derivatives, and dicarboxylic acid anhydride derivatives.

2. The method for producing a porous liquid crystal polymer according to claim 1, wherein the temperature of the supercritical fluid in the second step is higher than the glass transition temperature of the liquid crystal polymer.

3. In the first step described above, a non-porous sheet made of the composition is formed. The method for producing a porous liquid crystal polymer according to claim 1 or 2, wherein the second step is to produce a porous liquid crystal polymer sheet.

4. A method for producing a porous liquid crystal polymer according to any one of claims 1 to 3, wherein the first step involves kneading the liquid crystal polymer, the porous agent, and the hollow sphere.

5. A method for producing a porous liquid crystal polymer according to any one of claims 1 to 4, wherein the supercritical fluid is supercritical carbon dioxide.

6. The method for producing a porous liquid crystal polymer according to any one of claims 1 to 5, wherein the second step is to produce a porous liquid crystal polymer having a porosity P of 20% or more.

7. A method for producing a porous liquid crystal polymer according to any one of claims 1 to 6, wherein the second step involves blending an entrainer into the supercritical fluid.

8. A method for producing a porous liquid crystal polymer according to any one of claims 1 to 7, wherein the mass reduction rate of the porous agent at 300°C is 10% by mass or less.

9. A method for producing a porous liquid crystal polymer according to any one of claims 1 to 8, wherein the mass reduction rate of the porous agent at 350°C is 10% by mass or less.

10. A method for producing a porous liquid crystal polymer according to claim 1, wherein the dicarboxylic acid anhydride derivative contains a trifluoromethyl group.

11. A method for producing a porous liquid crystal polymer according to claim 10, wherein the trifluoromethyl group is located in the center of the structure.

Images