Electromagnetic wave shielding material

Abstract

The problem of the present invention is to provide an electromagnetic wave shielding means that can easily be applied to a target and that has a broad shielding band for radio waves, and the inventor of the present invention discovered that it is possible to address the abovementioned problem by providing an electromagnetic wave shielding material for which PEDOT-pTS (poly(3,4-ethylene-dioxythiophene)-p-toluenesulfonate) or PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate) is adhered to all or a portion of a base.

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave shielding means, and more specifically, to an electromagnetic wave shielding material, an electromagnetic wave shielding body using the same, and a method for attenuating electromagnetic waves. [Background technology]

[0002] In recent years, electromagnetic waves have been increasingly used as an information and communication medium in various aspects.

[0003] For example, electromagnetic waves in the 40-75 GHz frequency range, defined as the V-band (the standard name given by IEEE), are used in millimeter-wave radar and are applied to collision prevention systems for automobiles, etc. As mobile phones and Internet communication networks are gradually upgraded, this band is expected to be actively utilized as a frequency band capable of higher capacity and faster transmission and reception.

[0004] When using such electromagnetic waves, it is important to eliminate unnecessary electromagnetic waves that cause noise as much as possible in order to prevent misidentification and improve sensitivity, and various electromagnetic wave shields have been provided that block electromagnetic waves by absorbing or reflecting them.

[0005] For example, the technology of Patent Document 1 relates to an electromagnetic wave absorber having a bandwidth of 2 GHz or more in the frequency band of 60 to 90 GHz.

[0006] Furthermore, PEDOT-pTS (poly(3,4-ethylene-dioxythiophene)-p-toluenesulfonate), which is related to the present invention, is known to have high conductive performance among conductive polymers. However, the types of substrates to which PEDOT-pTS can be attached are limited. The present inventors have invented an invention using silk as a substrate to which PEDOT-pTS can be attached, and have already filed patent applications (Patent Document 2, Patent Document 3).

[0007] In addition, PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate) is also known as a conductive polymer having predetermined performance (Patent Document 4, Patent Document 5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-98367 A [Patent Document 2] WO2016 / 148249 International Publication Pamphlet [Patent Document 3] WO2016 / 031872 International Publication Pamphlet [Patent Document 4] International Publication WO2013 / 073673 International Publication Pamphlet [Patent Document 5] JP 2014-108134 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0009] The technology of Patent Document 1 expands the bandwidth of electromagnetic wave absorption in the frequency band of 60-90 GHz, but requires the construction of a three-layer structure consisting of a dielectric layer, a resistive layer, and a conductive layer. There are clear peaks in the absorbed electromagnetic wave wavelength that differ depending on the thickness and material of the dielectric layer of the electromagnetic wave absorber, and it was necessary to establish standards and combinations corresponding to specific purposes of use. [Means for solving the problem]

[0010] In the process of examining the properties of the conductive polymer PEDOT-pTS, the present inventor discovered that by attaching it to a fiber material, a conductive hybrid material with an electrical resistance of several hundred to 1 kΩ can be obtained, and that it can be used as a flexible material that can be freely deformed. Surprisingly, the material has electromagnetic wave shielding properties over a wide bandwidth, specifically, in the range of microwaves (UHF) to millimeter waves (SHF), which is at least 1-60 GHz. Specifically, it has been revealed that a material to which the conductive polymer is attached has electromagnetic wave absorption ability for electromagnetic waves of 1 GHz or more, and can provide a predetermined electromagnetic wave shielding without a large peak up to at least about 60 GHz, particularly if it is 8 GHz or more. Moreover, even without providing a complex structure such as a layered structure with other materials or a pyramidal structure, the above-mentioned attached material itself has electromagnetic wave shielding ability for radio waves over a wide bandwidth, and further, by simply stacking the attached materials together, it is possible to enhance the electromagnetic wave shielding ability. When the adhesive materials are laminated, it is preferable to sandwich an insulating material such as a base material, film, or paper that does not have a conductor between the adhesive materials.

[0011] The present invention provides an electromagnetic wave shielding material (hereinafter also referred to as the electromagnetic wave shielding material of the present invention) in which PEDOT-pTS (poly(3,4-ethylenedioxythiophene)-p-toluenesulfonate) or PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate) is attached to all or a part of a substrate. Electromagnetic wave shielding is a concept that includes both electromagnetic wave absorption and electromagnetic wave reflection, but the main electromagnetic wave shielding means of the electromagnetic wave shielding material of the present invention is electromagnetic wave absorption.

[0012] The material of the substrate is not particularly limited as long as it is a material to which PEDOT-pTS or PEDOT-PSS can be attached, and examples thereof include substrates containing one or more of polyester, polyamide, polyurethane, sericin-coated synthetic fibers of these, paper, and silk. At least substrates containing paper, silk, or polyester have been found to be suitable, but are not limited to these. Furthermore, it is even more preferable that the above-mentioned "substrate containing paper" is Japanese paper.

[0013] The substrate may be a sheet in which no "mesh" (gaps) are visible to the naked eye at a clear viewing distance, but is preferably a "fabric", and examples of the fabric include knitted fabric, woven fabric, braided fabric, net, etc., with knitted fabric, woven fabric, or net-like fabric being particularly preferred, knitted fabric or woven fabric being extremely preferred, and knitted fabric being most preferred. This is presumably the reason why knitted fabrics are preferably made of a continuous single thread in principle.

[0014] As described above, the range of frequencies that can be absorbed by the electromagnetic wave shielding material of the present invention is a wide range of at least 1-60 GHz, from microwaves (UHF) to millimeter waves (SHF) (included in radio waves), and the electromagnetic wave shielding material of the present invention is characterized in that it exhibits electromagnetic wave shielding ability including any region selected from this range, and at least if the frequency range is 8-60 GHz, it is possible to achieve the specified electromagnetic wave shielding without any large peaks.

[0015] The present invention provides an electromagnetic wave shielding body (hereinafter, also referred to as the electromagnetic wave shielding body of the present invention) containing the electromagnetic wave shielding material of the present invention. The electromagnetic wave shielding body of the present invention may contain non-essential parts other than the electromagnetic wave shielding material of the present invention. The non-essential parts include a conductive material, an insulating material, a dielectric material, a conductive connector, a cover material for covering the electromagnetic wave shielding material of the present invention, an adhesive material for attaching the electromagnetic wave shielding material to another object, a cushioning material or a filler material for protecting the electromagnetic wave shielding material, etc.

[0016] The present invention further provides a method for attenuating electromagnetic waves (hereinafter also referred to as the electromagnetic wave attenuation method of the present invention), which comprises exposing a substrate having PEDOT-pTS (poly(3,4-ethylenedioxythiophene)-p-toluenesulfonate) or PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate) adhered to any or a part of the substrate to electromagnetic waves, thereby attenuating the electromagnetic waves. Effect of the Invention

[0017] INDUSTRIAL APPLICABILITY The present invention provides an electromagnetic wave shielding material capable of absorbing and shielding a wide range of electromagnetic waves in the radio wave region, an electromagnetic wave shielding body including the same, and a method for attenuating electromagnetic waves using the electromagnetic wave shielding material. [Brief description of the drawings]

[0018] [Figure 1 (1)] FIG. 1 is a simple diagram of the measurement system used in the present embodiment. [Figure 1 (2)] 1 shows an overview of the measurement system used in this embodiment in a 1-10 GHz measurement environment. [Figure 1 (3)] 1 shows an overview of the measurement system used in this embodiment in a 40-60 GHz measurement environment. [Diagram 2] 1 is a diagram showing the results of an investigation into the electromagnetic wave shielding characteristics of 1-10 GHz. [Diagram 3] 1 is a diagram showing the results of an investigation into the electromagnetic wave shielding characteristics of 40-60 GHz. [Figure 4] 1 is a schematic diagram showing the test system for electromagnetic shielding test 2(1) using a motion sensor. [Diagram 5] 13 is a graph showing the results of electromagnetic wave shielding test 2(1) using a motion sensor. [Figure 6] 13 is a graph showing the test system for electromagnetic shielding test 2(2) using a motion / distance sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 1. Base material The substrate used in the electromagnetic wave shielding material of the present invention is not particularly limited, but is preferably a "substrate containing paper". The "substrate containing paper" may be a "substrate made of paper" or may be a "substrate in which paper and materials other than paper are mixed". An example of a "substrate in which paper and materials other than paper are mixed" is a case in which fibers other than paper are present among the constituent fibers combined by twisting a paper thread. In addition, when the substrate is a fabric, the paper thread may be combined with other types of thread to form a fabric, i.e., a knitted fabric, a woven fabric, etc. The content of paper in the "substrate containing paper" is 10% by mass or more of paper relative to the entire substrate, and may be 100% by mass. In particular, when emphasizing the presence of paper, 20% by mass or more is preferable.

[0020] Thus, the "paper" which is the main material of the base material of the electromagnetic wave shielding material of the present invention is manufactured by agglutinating plant fibers and, if necessary, other fibers, and the manufacturing method thereof is known. The basic method is to obtain plant fibers by beating or the like, disperse them in water, etc., and then comb and dry them to manufacture the paper. Examples of plant fibers include seed hair fibers such as cotton; bast fibers such as flax, hemp, jute, paper mulberry, mitsumata, and gampi; coniferous fibers such as spruce, fir, pine, and larch; broad-leaved fibers such as poplar, birch, beech, willow, eucalyptus, and elm; leaf fibers such as abaca (Manila hemp); rice straw, wheat straw, and other grass fibers; and esparto, reed, bamboo, bamboo grass, and kumazasa. Examples of other fibers include polyamide fibers such as nylon, polyester fibers such as PET, acrylic fibers, aramid fibers, polyurethane fibers, carbon fibers, and glass fibers, which are added as components of the paper depending on the properties of the fibers. In addition, components that are normally contained in paper other than fibers, such as fillers such as talc, clay, calcium carbonate, titanium dioxide, and glue, are also defined as components of paper in the present invention. The above-mentioned "materials other than paper" calculated by mass in the "paper-containing substrate" separately from paper are "materials that are externally combined" with the "paper that is integrally formed" and are different from the "components contained inside the paper that is integrally formed". In some cases, it may be preferable to make the paper flame-retardant by adding glass fibers or the like. For example, when used for shielding electromagnetic waves from automobile radar, etc., it is preferable that the paper has flame retardancy that can withstand heat generated by absorbing electromagnetic waves and the heat of the automobile itself. An example of such a technology is the flame-retardant paper described in JP 2013-2003 A (flame-retardant paper containing a predetermined amount of cellulose fiber, glass fiber, aluminum hydroxide powder, and guanidine phosphate flame retardant).

[0021] Among the "papers" that are the main materials of the substrate of the electromagnetic wave shielding material of the present invention, Japanese paper is preferred in that it has excellent moisture absorption as a material to be used, and furthermore, the constituent fibers are long and the state of entanglement between the fibers is moderate, so that it has excellent adhesion to PEDOT-pTS or PEDOT-PSS. The Japanese paper of the present invention is paper that essentially has bast fibers as its constituent fibers. Originally, Japanese paper is paper made by hand using bast fibers (mentioned above) as a raw material and kneading (plant mucus), but in the present invention, paper made by machine kneading is also included in the "Japanese paper" of the present invention. In addition, paper that is a mixture of bast fibers and plant-based components other than kneading, such as chemical substances that replace kneading, or other plant-based components, such as Kumazasa fibers, is also included in the "Japanese paper" of the present invention.

[0022] Paper yarns for knitted or woven fabrics can be produced by shredding and slitting already-produced paper sheets, and twisting the slit paper. When twisting, it is possible to intertwine fibers or yarns other than paper, such as silk, rayon, cotton yarn, etc., and it is also possible to use other types of yarn as the core material, but it is necessary that the paper is exposed on at least the entire or part of the yarn surface.

[0023] The thickness of the paper thread is not particularly limited and can be selected as needed within the range of about 0.1 μm to 3 mm, but is usually about 1 μm to 1 mm.

[0024] For example, when PEDOT-pTS is selected as the conductive polymer, materials other than the "substrate containing paper" include silk, polyester fibers such as PET (polyethylene terephthalate) fibers, polyamide (nylon) fibers, polyurethane fibers, etc. Also, it may be coated with sericin, a component of silk (JP Patent Publication 2003-171874).

[0025] The silk may be raw silk, or may have been subjected to "degumming", a process for removing impurities including sericin. Degumming methods include soap degumming, alkali degumming, soap-alkali degumming, enzyme degumming, high-temperature / high-pressure degumming, and acid degumming, and any of these methods can be used. In addition, it is also possible to use blended twisted yarns of silk and other fibers, such as silk-acetate blended twisted yarns, silk-nylon blended twisted yarns, silk-polyester blended twisted yarns, and silk-polyurethane blended fibers, and the combinations of blends are not limited to these. In addition to ordinary domestic silk, wild silk, and natural silk from spiders and bees, it is also possible to use silk obtained using genetic engineering technology, such as "glowing silk" obtained from silkworms into which a gene encoding a fluorescent protein has been incorporated.

[0026] The material to be coated with sericin in the sericin-coated yarn may be polyamide fiber such as nylon, polyester fiber such as PET, acrylic fiber, aramid fiber, polyurethane fiber, carbon fiber, or other synthetic fiber; vegetable fiber such as cotton, hemp, jute, or other animal fiber such as silk, wool, collagen fiber, or other mixed fiber. The polyester fiber may be PET (polyethylene terephthalate) fiber, PEN (polyethylene naphthalate) fiber, PTT (polytrimethylene terephthalate) fiber, PBT (polybutylene terephthalate) fiber, or other fiber. The polyester yarn to which stretchability has been imparted may be in the form of a filament yarn (long fiber) or a yarn that has been subjected to a spinning process. As described above, it may be used as a blended yarn in which it is combined with other fibers. The polyamide fiber may be made into a yarn to which stretchability has been imparted using nylon 6, nylon 6,6, nylon 11, nylon 12, or other fiber, and may be used as a blended yarn in which it is combined with other fibers, as described above.

[0027] On the other hand, when PEDOT-PSS is selected, the material of the fiber or thread other than paper is not particularly limited as long as it is made of a polymer, and for example, synthetic fiber, vegetable fiber, animal fiber, etc. may be used. It may be made of a single material, or a mixture.

[0028] Examples of the synthetic fibers include nylon fibers, polyester fibers, acrylic fibers, aramid fibers, polyurethane fibers, carbon fibers, etc. Examples of the vegetable fibers include cotton, hemp, jute, etc. Examples of the animal fibers include silk, wool, collagen, elastic fibers constituting animal tissues, etc.

[0029] The thickness of the threads other than the paper threads is not particularly limited and can be selected as needed within the range of about 1 μm to 3 mm, but is usually about 10 μm to 1 mm.

[0030] The fabric made of paper yarn, which is one embodiment of the electromagnetic wave shielding material of the present invention, is a fabric based on the above-mentioned paper yarn to which PEDOT-pTS or PEDOT-PSS is attached, and the type of fabric is preferably a knitted fabric or woven fabric, and most preferably a knitted fabric, as described above.

[0031] The knitted or woven fabric may be a single layer or multiple layers. Even if it is a single layer, it is possible to provide overlapping of yarns in the thickness direction depending on the knitting or weaving method.

[0032] A knitted fabric is basically a fabric made of a single thread, and is made of continuous loops of thread (stitches) formed by successively hooking threads onto the loops of thread. Unlike woven fabrics, warp and weft threads are not used. As described above, the fact that the constituent thread is, in principle, a single thread is presumably one of the reasons why knitted fabrics are suitable as the base material in the present invention.

[0033] The knitted fabric used in the present invention is not particularly limited, and may be made by any knitting method, such as machine knitting (using a flat knitting machine, warp knitting machine, circular knitting machine, tricot knitting machine, raschel knitting machine, Milanese knitting machine, rib knitting machine, interlock knitting machine, etc.), knitting, crochet knitting, afghan knitting, etc. The knitting structure is not limited, and examples thereof include plain knit, pique knit, elastic knit, pearl knit, tuck knit, transfer knit, one rib knit, both rib knit, double side knit, swing knit, pelerine knit, floating knit, pile knit, plating knit, rope knit, intarsia, wrap knit, non-run structure, chain knit, single tricot knit, single cord knit, single atlas knit, double stitch knit, single satin knit, single velvet knit, plain tricot knit, double atlas knit, double cord knit, half tricot knit, reverse half, queens cord knit, satin tricot knit, double tricot knit, velvet knit, shell knit, knop knit, tapestry knit, warp insertion knit, marquise, drop plate structure, net knit, Milanese knit, warp and weft insertion knit, and weft insertion knit.

[0034] Woven fabrics are fabrics made by combining warp threads with weft threads. The weave of the woven fabric used in the present invention is not particularly limited. For example, it can be used as the three basic weaves of plain weave, twill weave, and satin weave. Furthermore, it may be a modified weave in which the three basic weaves are changed or combined, or it may be a single special weave or a figured weave. Furthermore, it may be a multi-layered weave such as a warp double weave, a weft double weave, a warp double weave, a pile weave, a towel weave, or a woven weave.

[0035] Woven fabrics are fabrics made by combining warp threads. The weave of the woven fabric used in the present invention is not particularly limited. For example, it can be used as the three basic weaves of plain weave, twill weave, and satin weave. Furthermore, it may be a modified weave in which the three basic weaves are changed or combined, or it may be a single special weave or a figured weave. Furthermore, it may be a multi-layered fabric such as a warp double fabric, a weft double fabric, a warp double fabric, a pile fabric, a towel fabric, or a woven fabric. As described above, the multi-layered fabric can have overlapping threads in the thickness direction.

[0036] In general, compared to knitted fabrics, woven fabrics have warp and weft threads that hook together and pull on each other to maintain the two-dimensional balance of the fabric, and there are originally many points of contact between the threads.

[0037] It is preferable that the stitches or weave are uniform in order to obtain equal absorption of electromagnetic waves over the entire surface, but it is also possible to provide closed stitches (selvedge) on the outer edge of the knitted or woven fabric as necessary, for example to prevent fraying of the thread. Also, the frequency or size of the stitches or weave can be adjusted in order to obtain appropriate sensitivity to electromagnetic waves.

[0038] The size of the stitches is not particularly limited, and even fine stitches that cannot be easily seen with the naked eye at a clear viewing distance are acceptable, but usually, 100-5 stitches and 100-5 rows (1 mm in stitch size) are required for a 10 cm width. 2 -4cm 2 ) degree.

[0039] The size of the weave is not particularly limited, and even fine weave that cannot be easily confirmed by the naked eye at a clear viewing distance is acceptable, but normally the size of the weave is 0.2 mm 2 -2mm 2 That's about it.

[0040] 2. Attachment of PEDOT-pTS to the substrate PEDOT-pTS (poly(3,4-ethylenedioxythiophene)-p-toluenesulfonate) is a conductive polymer formed by polymerizing pTS (p-toluenesulfonate) and EDOT (3,4-ethylenedioxythiophene). For example, as a first attachment method, attachment by contact of an organic solvent solution containing an oxidizing component and pTS and a mixture of EDOT to a substrate (mainly a sheet-like substrate or a filamentous substrate) is performed by dipping or printing, etc., and then a polymerization acceleration treatment is applied to the contact portion to perform the attachment of PEDOT-pTS (the method disclosed in Patent Document 2 or a modified method thereof). As a second attachment method, (a) an attachment step of attaching a pTS solution containing an oxidizing component and pTS to a substrate (mainly a sheet-like substrate or a filamentous substrate), (b) further attaching EDOT to the substrate to which the oxidizing component and pTS have been attached in the attachment step (a), and allowing the polymerization reaction to proceed to generate PEDOT-pTS therein, whereby the attachment of PEDOT-pTS can be performed (second attachment method: the method disclosed in Patent Document 3).

[0041] <The first attachment method of PEDOT-pTS> In the first attachment method, by mixing the pTS solution and EDOT, the polymerization reaction of EDOT proceeds in the pTS-EDOT mixture, and PEDOT-pTS, which is a polymer, is formed. This polymerization reaction follows the following formula, and the polymerization rate increases with an increase in temperature. If stored at a low temperature at the refrigerator level, the polymerization rate can be reduced, contributing to ensuring the time of the attachment step. Fe is exemplified as the oxidizing component 3+ but is not limited thereto.

[0042]

Chemical formula

[0043] In the first attachment method, "after" means that the polymerization promotion treatment is performed at a timing "after the same time" related to the timing when the pTS-EDOT mixed solution contacts the substrate. Specifically, the two timings may be virtually simultaneous, or the polymerization promotion treatment may be performed with a time lag from the timing when the pTS-EDOT mixed solution contacts the substrate. In addition, for example, the "after" in the first attachment method also includes a mode in which the polymerization promotion treatment is continuously performed on the substrate while the pTS-EDOT mixed solution is contacted thereon, with substantially no time lag. The mixing ratio of the pTS solution and EDOT in the first attachment method is pTS solution:EDOT=10:1-100:1, preferably 20:1-40:1, by volume.

[0044] pTS is known as a paratoluenesulfonic acid compound (salt or ester with paratoluenesulfonic acid (tosylic acid)), and is commercially available. The organic solvent that can be the solvent of the pTS solution is capable of dissolving pTS and oxidized components, and preferably has good compatibility with aqueous solvents. Specific examples include monovalent lower alcohols having 1 to 6 carbon atoms, specifically methanol, ethanol, propyl alcohol, isopropyl alcohol, butanol, pentanol, and hexanol. The carbon atom skeleton constituting these monovalent lower alcohols may be linear, branched, or cyclic, and may be used alone or in combination of two or more. In addition, they may be appropriately diluted with water before use. Among these, monovalent lower alcohols having 1 to 4 carbon atoms, specifically methanol, ethanol, propyl alcohol, isopropyl alcohol, and butanol, are suitable as organic solvents for the pTS solution.

[0045] The oxidizing component contained in the pTS solution is not particularly limited as long as it is capable of activating the polymerization reaction to PEDOT-pTS in the pTS-EDOT mixed solution, and examples thereof include transition elements and halogens.

[0046] Examples of transition elements include first transition elements such as iron, titanium, chromium, manganese, cobalt, nickel, and zinc; second transition elements such as molybdenum, silver, zirconium, and cadmium; and third transition elements such as cerium, platinum, and gold. These transition elements may be used as simple metals or as metal salts. Among these, it is preferable to use first transition elements such as iron and zinc.

[0047] The content of the oxidizing component in the pTS solution varies depending on the type of oxidizing component used, and is not particularly limited as long as it is an amount that can activate the above polymerization reaction. For example, ferric ions (Fe 3+ ), the content of ferric chloride in the solution is preferably 1 to 10% by mass, and particularly preferably 3 to 7% by mass. If the content is too high, the polymerization reaction proceeds quickly but it becomes difficult to remove the iron in a later step, whereas if the content is too low, the polymerization reaction proceeds slowly.

[0048] The content of pTS acting as a dopant in the pTS solution is preferably 0.1-10% by mass, more preferably 0.15-7% by mass, particularly preferably 1-6% by mass, and most preferably 2-5% by mass, based on the solution.

[0049] EDOT is known as 3,4-ethylenedioxythiophene and is commercially available. EDOT is liquid at room temperature and water-soluble, and can be used by diluting it appropriately in an aqueous solvent such as water.

[0050] Other components can be added to the pTS solution as necessary, as long as they do not quantitatively or qualitatively impair the effects of the present invention, such as by not substantially impairing the adhesion of the pTS-EDOT mixed solution to the substrate and the conductive performance of the finished conductive material.

[0051] Examples of the other components include one or more of glycerol, polyethylene glycol-polypropylene glycol polymer, ethylene glycol, sorbitol, sphingosine, and phosphatidylcholine, and preferably glycerol, polyethylene glycol-polypropylene glycol polymer, and sorbitol.

[0052] Other examples include cationic surfactants such as quaternary alkyl ammonium salts and alkyl pyridinium halides; anionic surfactants such as alkyl sulfates, alkyl benzene sulfonates, alkyl sulfosuccinates, and fatty acid salts; nonionic surfactants such as polyoxyethylene and polyoxyethylene alkyl ethers; natural polysaccharides such as chitosan, chitin, glucose, and aminoglycan; sugar alcohols, dimethyl sulfoxide, and the like.

[0053] At room temperature, the gelation of the liquid proceeds due to the polymerization reaction in the pTS-EDOT mixed liquid. For this reason, it is preferable to carry out a step of removing the excess gelling polymer attached to the substrate after contact with the mixed liquid. For example, the substrate separated from the mixed liquid can be removed by physical means such as vibration, air blowing, or contact with a roller. If the step of removing the excess gelling polymer is not carried out after the polymerization reaction, there is a restriction that the substrate and the mixed liquid should be contacted for a short time after the preparation of the mixed liquid, and that the contact should be carried out for a short time after the preparation of the mixed liquid. Specifically, the adhesion by the contact should be completed within 5 minutes, more preferably within 1 minute, after the preparation of the pTS-EDOT mixed liquid. When the step of removing the excess gelling polymer is carried out, there is virtually no time restriction on the adhesion step by contact even at room temperature, and it is possible to sufficiently adhere PEDOT-pTS to the substrate by taking an adhesion step time of preferably 10 minutes or more, more preferably 15 minutes or more after the preparation of the pTS-EDOT mixed liquid. Even if the adhesion process is carried out for 40 minutes or more, the progress of gelation means that no adhesion promoting effect commensurate with the long process time is observed.

[0054] In the first adhesion method, adhesion by contact is preferably performed by dripping, spraying, immersion, transfer, or coating.

[0055] The polymerization promotion treatment in the first adhesion method includes a heat treatment, such as (α) contact of the polymerization promotion part with a heat sink at 50-90°C, (β) contact with hot air set to heat the polymerization promotion part to 50-90°C, or (γ) contact with a heated atmosphere at 50-90°C in a thermostatic bath or the like.

[0056] The contact with the heat sink at 50-90° C. in the above (α) is preferably performed for a heating time of 3-10 minutes, more preferably 3-6 minutes, and most preferably 4-6 minutes.

[0057] When the polymerization promotion part (β) is contact with hot air set to 50-90° C., the time is preferably 3-10 minutes, and particularly preferably 4-6 minutes.

[0058] When the heating atmosphere is set to 50-90° C. as in (γ) above, the heating time is preferably 3-10 minutes, and particularly preferably 4-6 minutes.

[0059] After the heat treatment, the substrate is removed from the solution and washed preferably with water, more preferably with distilled water or deionized water, and then dried in a thermostatic chamber, with hot or warm air, in the sun, or the like.

[0060] Furthermore, for example, in the first adhesion method, the adhered portion of the pTS-EDOT mixed liquid that comes into contact with the substrate can be made into a drawing design on a part of the substrate surface, thereby making use of the feature of the first adhesion method that the adhered portion is less likely to bleed. A drawing design is different from a simple one-sided adhesion, and includes simple figures such as circles and triangles, various depictions such as animal and plant drawings and portraits, letters, patterns, and the like.

[0061] When performing the first adhesion method, mask treatment or spray coating can be carried out to more precisely create a drawing design, especially on a substrate. Mask treatment may involve covering in advance the parts where the conductive polymer is not to be adhered with a mask. In this mask treatment mode, in the first adhesion method, before the pTS-EDOT mixture adheres to the substrate by contact, after performing mask treatment on the parts except the planned adhesion location, contact with the mixture is made at least at the planned adhesion location, and after further performing a polymerization acceleration treatment, the above mask is removed.

[0062] Specific examples of mask treatment include, for example, applying a resist paste or beeswax as a masking agent. Examples of resist paste include starch pastes such as rice bran paste, corn starch paste, sweet potato starch paste, etc.; rubber paste; seaweed paste such as nori; and various other types of paste. As the resist paste, starch paste is preferred. The concentration of the resist paste during use (paste powder mass / water mass) is not particularly limited, but is generally 3 - 5 mass%. The removal of the resist paste can be carried out by washing with water. Beeswax, which is wax derived from a honeycomb, is also preferred. During use, it is usually directly heated and melted for use. Also, the removal of beeswax is carried out by melting it again by heating.

[0063] <The second adhesion method of PEDOT-pTS> In the second adhesion method, first, an oxidation component and pTS as a dopant are dissolved in an organic solvent solution, and the substrate is immersed in the organic solvent solution (pTS solution).

[0064] The organic solvent that can be a solvent for pTS and the oxidation component contained therein are the same as the "organic solvent and oxidation component of the pTS solution in the first adhesion method" described above. Also, the "other components" that can be contained in the pTS solution are the same as the "other components in the pTS solution in the first adhesion method" described above.

[0065] The content of the oxidation component in the pTS solution varies depending on the type of oxidation component used, and is not particularly limited as long as it can activate the above polymerization reaction. For example, ferric ion (Fe 3+), the amount of ferric chloride in the pTS solution is preferably 1-10% by mass, and more preferably 3-7% by mass. If the content is too high, the polymerization reaction proceeds quickly, but it becomes difficult to remove the iron in a later step, and if the content is too low, the polymerization reaction proceeds slowly.

[0066] The content of pTS acting as a dopant in the pTS solution is preferably 0.1-10% by mass, more preferably 0.15-7% by mass, particularly preferably 1-6% by mass, and most preferably 2-5% by mass, based on the solution.

[0067] In the second adhesion method, the monomer EDOT is then added to the PTS solution in which the substrate is immersed, and the substrate is then heated at 50-100° C., preferably for 10-60 minutes, more preferably for 10-40 minutes at 50-80° C., and most preferably for 10-30 minutes at 60-80° C. After heating, the substrate is removed from the solution, washed preferably with water, more preferably with distilled water or deionized water, and then dried in a thermostatic bath, with hot or warm air, in the sun, or the like.

[0068] The ratio of the amount of the pTS solution to the amount of EDOT used in this step is pTS solution:EDOT=10:1 to 100:1, preferably 20:1 to 40:1, by volume.

[0069] 3. Attachment of PEDOT-PSS to the substrate PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate) can be attached by a so-called electrolytic polymerization method, in which a substrate is immersed in a conductive solution containing PEDOT-PSS, and the substrate is vertically pulled up from the conductive solution while running between electrodes and current is applied to electrochemically polymerize and fix the PEDOT-PSS attached to the substrate (Patent Document 4). Alternatively, PEDOT-PSS can be attached by attaching a resin composition obtained by mixing PEDOT-PSS and a binder resin to a thread to which stretchability has been imparted, and solidifying or polymerizing the resin by drying, heating, heating, or the like (Patent Document 5). Alternatively, the substrate can be made conductive by adsorbing a water-soluble / solvent dispersion in which finely divided PEDOT-PSS (average particle size is about 10 microns) is dispersed in a solution / solvent to the substrate. EXAMPLES

[0070] [sample] As the base material for the conductive material of the present invention, two types of stretchable fabric (50 cm x 50 cm) were obtained, made of 240 denier (22 count) Japanese paper yarn (double yarn with loose twist for the upper twist) and piqué knit (a loose knit base material with a mesh width of 3111 μm and a tight knit base material with a mesh width of 1783 μm). One is a "loose knit base material" with a mesh width of 3111 μm, and the other is a "tight knit base material" with a mesh width of 1783 μm.

[0071] In addition, silk cloth with a weave width of 620 μm (plain weave silk fabric made from silk threads that had been enzymatically refined with a proteolytic enzyme: 50 cm×50 cm) was obtained.

[0072] The pTS solution used was a butanol solution containing the transition metal iron (III) ion and pTS (CLEVIOS CB 40 V2 manufactured by Heraeus, approximately 4% by mass as iron (III) p-toluenesulfonate; "CLEVIOS" is a registered trademark). The EDOT solution used was an aqueous solution of EDOT (CLEVIOS MV2 manufactured by Heraeus, approximately 98.5% by mass of EDOT; "CLEVIOS" is a registered trademark).

[0073] A mixed solution was prepared by mixing EDOT with the pTS solution and cooled to about 4°C, and the substrate was immersed in the mixed solution at room temperature for 20 minutes. The immersed substrate was then removed from the mixed solution, suspended by clipping two points on one side, and exposed to the wind (strong wind) of an electric fan for 5-10 minutes to vibrate the substrate with the wind while drying, and then rubbed with a roller to remove excess gelled polymer that had adhered to the substrate by these steps.

[0074] Next, the substrate from which the gelled polymer had been removed was placed in a thermostatic bath at 70°C and heated for 5 minutes to polymerize into PEDOT-pTS. The polymerized substrate was then washed twice with water and then dried at 90°C to obtain two types of "knitted paper fabrics with PEDOT-pTS attached." These are also called "sparsely knitted substrates" and "tightly knitted substrates," respectively. Substrates with silk fabric attached were also obtained. These are also called "silk substrates." These were used as samples.

[0075] [Electromagnetic shielding test 1] 1. Measurement of electromagnetic shielding effect In the "free space method" in which the absorption and shielding amounts of the electromagnetic waves under test are measured non-destructively and non-contactingly on the attached substrate as a sample, two horn antennas are placed facing each other so that the polarization planes coincide, and a sample is inserted between the two horn antennas, and the "shielding amount of the electromagnetic waves under test" is calculated by a network analyzer (VNA) as "(the transmission amount of the electromagnetic waves under test when there is no sample) - (the transmission amount of the electromagnetic waves under test when there is a sample)". A schematic diagram of this measurement system is shown in Figure 1 (1)-(3). Figure 1 (1) is a simple sketch of the measurement system. The horn antennas on the transmitting and receiving sides were placed at predetermined positions facing the sample (sheet-shaped electromagnetic wave shielding material) fixed and installed surrounded by a radio wave absorber so as to fill the calculated first Fresnel zone cross section, and the specified electromagnetic waves were transmitted and received, and the shielding amount of the electromagnetic waves was calculated according to the above formula. The angle between the sample surface and the horn antenna (the electromagnetic wave irradiation direction and the reception direction) was basically orthogonal (90 degrees).

[0076] The electromagnetic waves selected for testing were (1) 1-10 GHz and (2) 40-60 GHz.

[0077] (1) Measurement environment and results for 1-10 GHz An overview of this measurement system is shown in Figure 1 (2). The black structure in front is an ultra-high frequency electromagnetic wave absorber with a pyramidal structural unit. A window is provided in the center, and the sample surface is aligned parallel to the window surface, and the sample is placed near the window.

[0078] The vector network analyzer (VNA) used was a Keysight Field Microwave Analyzer N9916A, and calibration was performed at the input end of the antenna. The horn antenna used was a Schwarzbeck Mess Electronik, BBHA9120B, with the sample-antenna distance (D) of 2300 mm (>2208 mm in far-field condition) and the vertical direction (90 degrees), the sample size was 50 cm x 50 cm, and there was one sample for each. The results are shown in Figure 2. The horizontal axis of Figure 2 is the measurement frequency (GHz), and the vertical axis is the shielding effect (dB) of the measured electromagnetic wave. As shown in Figure 2, a substantial electromagnetic shielding effect was observed in the paper yarn knitted fabrics (sparsely knitted substrate and densely knitted substrate), and was slight in the densest silk substrate. The electromagnetic shielding effect of the paper yarn knitted fabric increased steadily from 1 to 8 GHz, and a tendency to flatten out beyond that was observed.

[0079] (2) Measurement environment and results for 40-60 GHz An overview of this measurement system is shown in Figure 1(3). The basic method is similar to that shown in Figure 1(2).

[0080] The vector network analyzer (VNA) used was Rohda & Schwarz ZVA67 (-67GHz), and the horn antenna was SAGE,MN:SAR-2309-19-52 (40-60GHz). The sample-antenna distance (D) was 500mm (>460mm in far-field condition) and vertical (90 degrees). The sample size was 50cm x 50cm, and there was one sample for each. The results are shown in Figure 2 (40-60GHz). These results, along with the results of Figure 2 above, show that the paper yarn fabric has good and stable frequency shielding characteristics of about 5-8db from 10GHz to at least 60GHz.

[0081] When two or more samples were stacked so that they were not electrically connected to each other, the electromagnetic shielding performance improved according to the number of stacked sheets. Furthermore, when the electromagnetic wave irradiation angle from the horn antenna was set to 45 degrees, the electromagnetic shielding performance was best for the same number of substrates.

[0082] 2. Electrical resistance measurement The electrical resistance of the above paper yarn knitted fabrics (loosely knitted and tightly knitted) was measured by cutting five 5cm pieces of yarn from each sample fabric, and bundling all five together, since a single piece alone would not be able to make stable contact with the tester terminal. In order to stabilize the fibers and measure in a straight state, measurements were taken with adhesive tape attached to a flat plate along the length of the yarn. Each measurement was carried out three times. The tester used was a FLUKE115 True RMS Multimeter.

[0083] As a result of the above measurements, the electrical resistance value of the loosely knitted substrate was 29±5.3 kΩ (5.8 kΩ per yarn), and the electrical resistance value of the tightly knitted substrate was 116±16 kΩ (23.2 kΩ per yarn).

[0084] [Electromagnetic shielding test 2] Based on the results of the above electromagnetic wave shielding test 1, the electromagnetic wave shielding effect of the above substrate in the frequency band of 10-40 GHz, where an electromagnetic wave shielding effect of about 5 dB is expected, was confirmed using a motion sensor (near 10 GHz) and a motion / distance sensor (near 24 GHz).

[0085] (1) Test using a motion sensor (around 10 GHz) The test system using a moving object sensor to examine the electromagnetic wave blocking effect around 10 GHz is as shown in Figure 4. The above-mentioned sample 2 (loosely knitted base material) was fixed to one end of a cylindrical body 1, the outside and inside of which were covered with aluminum foil, near the opening of that end, at a position perpendicular to the central longitudinal axis of the cylindrical body 1 as the basic position, and a moving object sensor 3 was fixed near the other end so that the emitted electromagnetic wave was emitted in the central longitudinal axial direction of the cylindrical body 1. Three lengths of the cylindrical body 1 were used: 100 mm, 150 mm, and 200 mm, and these were treated as the "distance of the sample from the sensor."

[0086] A DS-XDMA (Asakusa Giken Co., Ltd.) was used as a motion sensor. The frequency of the emitted electromagnetic waves was 10.525 GHz. The sample was moved up and down or left and right in parallel with the opening surface of the cylindrical body, and the shielding rate (%) of the above electromagnetic waves was calculated using the difference in intensity between the emitted and received waves as a parameter. The results are shown in Figure 5. This confirmed the electromagnetic shielding effect at the above electromagnetic wave frequency (near 10 GHz) from any distance. The shielding effect was greater when the distance from the sensor was greater because the intensity of the emitted electromagnetic waves when they came into contact with the sample was weaker. Based on this, the electromagnetic shielding effect of the sample at the relevant frequency was 6-8 (dB). It was also confirmed that the shielding effect was further increased when the sample was stacked with a non-conductive base material such as paper or an insulator such as an insulating film sandwiched between them.

[0087] (2) Test using a motion / distance sensor (near 24 GHz) The test system using a motion / distance sensor to examine the electromagnetic wave blocking effect around 24 GHz is as shown in Figure 6. The above-mentioned sample 20 (loosely knitted substrate) was placed close to the electromagnetic wave transmission point of the motion / distance sensor 30 so as to block the electromagnetic wave perpendicular to the central traveling direction of the transmitted electromagnetic wave, and the motion / distance sensor detected the electromagnetic wave reflected from a concrete wall 40 located 6 m away.

[0088] The motion and distance sensor used was (NJR4233D1: New Japan Radio Co., Ltd.). The frequency of the emitted electromagnetic waves was 24.05-24.25GHz. The detection method used was FMCW (frequency continuous modulation), which transmits radio waves modulated so that the frequency increases linearly over time. The shielding effect was evaluated using the detection sensitivity of the distance measurement as an index. As a result, the electromagnetic wave shielding effect of the sample at the relevant frequency was 5.4-6.7 (dB).

[0089] The above sample 20 was replaced with a loosely knitted base material (washi paper thread) and knitted fabric made of silk thread (silk thread was a piqué knitted fabric made of "3 out of 21" threads: size 50cm x 50cm, mesh size finer than the above densely knitted base material) was used. A "test using a motion / distance sensor" similar to that described above was conducted to examine the electromagnetic shielding effect in the vicinity of 24GHz. The electromagnetic shielding effect was confirmed to be greater than that of the system using the loosely knitted base material described above.

[0090] Similarly, instead of the loosely knitted base material (washi paper yarn) of sample 20, a knitted fabric made of polyester yarn (the mesh is dense, and it is difficult to visually check the mesh from 50 cm away: size is 50 cm x 50 cm) was used, and a similar "test using a motion / distance sensor" was conducted to examine the electromagnetic wave shielding effect in the vicinity of 24 GHz. Although it was inferior to the system using the loosely knitted material described above, it was confirmed that the electromagnetic wave shielding effect was not negligible.

[0091] Thus, in addition to the above-mentioned electromagnetic wave shielding test 1, electromagnetic wave shielding test 2 confirmed the excellent electromagnetic wave shielding effect of the electromagnetic wave shielding material of the present invention in the radio wave range for multiple types of materials and knitted fabrics with various stitch sizes.

Claims

1. An electromagnetic wave shielding material having PEDOT-pTS (poly(3,4-ethylene-dioxythiophene)-p-toluenesulfonate) attached to all or part of a substrate.

2. 2. The electromagnetic wave shielding material according to claim 1, wherein the substrate comprises one or more of polyester, polyamide, polyurethane, sericin-coated synthetic fibers of these fibers, paper, and silk.

3. 2. The electromagnetic wave shielding material according to claim 1, wherein the substrate is a substrate containing paper, silk, or polyester.

4. The electromagnetic wave shielding material according to claim 3 , wherein the paper is Japanese paper.

5. The electromagnetic wave shielding material according to any one of claims 1 to 4, wherein the substrate is a fabric.

6. The electromagnetic wave shielding material according to claim 5 , wherein the fabric is a knitted fabric or a woven fabric.

7. 7. The electromagnetic wave shielding material according to claim 1, wherein the frequency range of the electromagnetic waves to be shielded includes any range selected from 1 to 60 GHz.

8. An electromagnetic wave shielding body comprising the electromagnetic wave shielding material according to any one of claims 1 to 7.

9. A method for attenuating electromagnetic waves, comprising exposing a substrate having PEDOT-pTS (poly(3,4-ethylene-dioxythiophene)-p-toluenesulfonate) adhered to all or part of the substrate to electromagnetic waves, thereby attenuating the electromagnetic waves.

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