Resistor

Abstract

[Problem] To provide a resistor having improved resistance value responsiveness to humidity. [Solution] Said problem is solved by a resistor in which a pair of electrodes are disposed on an insulating base material sheet so as to face each other with an interval therebetween, the resistor being characterized in that a moisture-sensitive material having an electrical resistance that changes in accordance with humidity is provided at least at the interval between the pair of electrodes, and the moisture-sensitive material contains a modified cellulose fine fiber in which the average fiber width is 1-20 nm and a portion of a hydroxy group of the cellulose fiber is substituted with an anionic group.

Description

Resistor

[0001] The present invention relates to a resistor.

[0002] In recent years, a technology for forming a resistor by providing electrodes on a substrate film has been attracting attention. Such resistors can be manufactured, for example, by printing conductive, fast-drying ink onto a substrate film using a roller or the like. If a plastic or other material is used for the substrate film, a thin, flexible resistor can be obtained. Because of its ease of manufacture and ability to be designed in a small size, it is expected to be used as a highly versatile product.

[0003] As a technology related to such resistors, Patent Document 1 discloses resistors containing cellulose nanofibers (also called "cellulose fine fibers"). In the resistors disclosed in this document, the cellulose fine fibers utilize the property of cellulose fine fibers to swell upon absorbing moisture, and the swelling reduces the conductivity of the entire resistor, thereby increasing the resistance value.

[0004] However, the above-mentioned documents only describe the use of cellulose fine fibers for one-sided applications.

[0005] Incidentally, in conventional resistors that can be used in humidity sensors, the moisture-sensitive material is prepared through the following laborious and time-consuming process. Specifically, equimolar amounts of N,N,N',N'-tetramethyl-1,8-diaminooctane and 1,8-dichlorooctane are first reacted in a mixed solvent of N,N'-dimethylformamide and ethanol at 60°C for as long as 240 hours. Next, the reaction product obtained from this reaction is placed in a large amount of ether to polymerize, and the resulting polymer is recovered to obtain a moisture-sensitive polymer made of 8,8-ionene chloride.

[0006] Next, a humidity-sensitive liquid is obtained by mixing the 8,8-ionene chloride with a humidity-sensitive polymer made of a water-soluble cellulose ether of hydroxypropylmethylcellulose, an additive polymer, and ion-exchanged water in an amount 42 times the weight of the humidity-sensitive polymer. An insulating substrate provided with electrodes and the like is then immersed in the humidity-sensitive liquid and dried, thereby obtaining a resistor with a humidity-sensitive material formed thereon (Patent Document 2).

[0007] Thus, the inventors believe that there is room for improvement in terms of the time and effort required to prepare the moisture-sensitive material.

[0008] JP 2022-181352 A JP 2019-66427 A

[0009] In the first place, conventional resistors containing cellulose fine fibers do not have sufficient sensitivity of resistance value to humidity changes, and it is believed that there is room for further improvement. Based on such trial and error, the inventors have decided to provide a resistor with improved responsiveness of resistance value to humidity as the problem to be solved by the present invention.

[0010] In order to solve the above problems, the present inventors first focused on the molecular structure of cellulose that constitutes cellulose microfibers. They believed that if localized portions of the cellulose molecule have more polarity, the affinity with water molecules in the atmosphere will increase, and the sensitivity to humidity will improve. Based on this idea, the following aspects of the invention were completed.

[0011] (First Aspect) A resistor comprising an insulating substrate sheet and a pair of electrodes arranged facing each other with a gap therebetween, wherein a moisture-sensitive material whose electrical resistance changes depending on humidity is provided at least in the gap between the pair of electrodes, and the moisture-sensitive material has an average fiber width of 1 to 20 nm and contains modified cellulose fine fibers in which some of the hydroxyl groups of the cellulose fibers have been substituted with anionic groups.

[0012] The resistor of the first embodiment has a moisture-sensitive material whose electrical resistance changes depending on humidity provided at least in the gap between the pair of electrodes. When moisture near the resistor adheres to the gap between the pair of electrodes, the conductivity of the moisture-sensitive material increases, resulting in a decrease in the electrical resistance of the resistor. Here, the anionic groups have excellent affinity for moisture, and the moisture-sensitive material is a resistor containing modified cellulose fine fibers substituted with anionic groups, resulting in improved sensitivity to humidity. Furthermore, the moisture-sensitive material of the resistor of the first embodiment does not require as much time and effort to prepare as the moisture-sensitive material disclosed in Patent Document 2, and can be prepared in a shorter time than conventional moisture-sensitive materials.

[0013] (Second Aspect) The resistor according to the first aspect, wherein a metal ion is bonded to the anionic group.

[0014] Since moisture near the resistor is more likely to bind to anionic groups with metal ions bonded thereto than to anionic groups with hydrogen ions bonded thereto (i.e., —OH groups), the modified cellulose fine fibers having anionic groups with metal ions bonded thereto have excellent water absorption and permeability, and therefore the resistor of this embodiment has excellent sensitivity of the resistance value to humidity.

[0015] (Third Aspect) The resistor of the first aspect, wherein the anionic group is an oxo acid group.

[0016] When the anionic groups of the modified cellulose fine fibers of this embodiment are oxo acid groups, hydrogen ions are easily released from or adsorbed to the oxo acid groups in response to changes in pH. By focusing on this property, it is possible to adjust the humidity response of the resistor by controlling the pH.

[0017] (Fourth Aspect) The resistor according to the first aspect, wherein the percentage of anionic groups to which metal ions are bonded is 5 to 100% of the total anionic groups.

[0018] If the percentage is within the above range, the modified cellulose fine fibers will have excellent water absorption and permeability.

[0019] (Fifth Aspect) The resistor according to the first aspect, wherein the anionic group is a phosphorus oxo acid group represented by the following structural formula (1): [Structural formula (1)] In the structural formula (1), a, b, m, and n are natural numbers. １ , A ２ , ..., A ｐ and at least one of A' is O － and the remainder is either R, OR, NHR, or none. R is any of a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, and derivatives thereof. α is a cation made of an organic or inorganic substance.

[0020] When the anionic group is a phosphorus oxo acid group, hydrogen ions are easily released from or adsorbed onto the oxo acid group in response to changes in pH. Therefore, for example, by increasing the pH during the production process, oxo acid groups with a larger number of bound metal ions can be easily produced.

[0021] (Sixth Aspect) The resistor of the first aspect, wherein the anionic group is a phosphite group.

[0022] The resistor of the sixth aspect has the same effect as the resistor of the fifth aspect.

[0023] (Seventh Aspect) The resistor according to the first aspect, wherein the anionic group is a polycarboxylic acid group.

[0024] When the anionic group is a polycarboxylic acid group, the carboxylic acid group is an oxo acid group, and hydrogen ions are easily released from or adsorbed onto the oxo acid group in response to changes in pH. Therefore, for example, by increasing the pH during the production process, oxo acid groups to which a larger number of metal ions are bound can be easily produced.

[0025] (Eighth Aspect) The resistor according to the first aspect, wherein the anionic group is a citric acid group.

[0026] The resistor of the eighth aspect has the same effect as the resistor of the seventh aspect.

[0027] (Ninth Aspect) The cellulose fine fibers are applied to the pair of electrodes in an amount of 0.23 to 95 g / m２ The resistor according to the first aspect is provided.

[0028] A resistor of this embodiment has high insulating properties when the humidity is low, but low insulating properties when the humidity is high, and has excellent responsiveness to humidity.

[0029] (Tenth Aspect) The resistor according to the first aspect, wherein the moisture-sensitive material is provided to cover the pair of electrodes.

[0030] The moisture-sensitive material is more likely to come into contact with moisture near the resistor, making the sensitivity response more sensitive.

[0031] (Eleventh Aspect) The resistor of the first aspect, wherein the pair of electrodes are comb-shaped electrodes, and each comb tooth of one of the pair of electrodes is positioned in a comb tooth of the other electrode, and each comb tooth of the one electrode and each comb tooth of the other electrode are alternately arranged with a gap therebetween.

[0032] The resistor of this embodiment has high insulating properties when the humidity is low, but low insulating properties when the humidity is high, resulting in a resistor with excellent response that can adapt to a wide range of humidity.

[0033] (Twelfth Aspect) The resistor of the first aspect, wherein the pair of electrodes are comb-shaped electrodes, and each of the comb teeth of one of the pair of electrodes is positioned in a comb hole of the other electrode, and the comb teeth of the one electrode and the comb teeth of the other electrode are alternately arranged with a gap therebetween, the gap being 20 to 5000 μm, the width of each of the comb teeth of the one electrode being 20 to 5000 μm, and the width of each of the comb teeth of the other electrode being 20 to 5000 μm.

[0034] The resistor of this embodiment is a more limited embodiment of the eleventh embodiment, and has the interval and width within the above ranges, so that it has high insulating properties when the humidity is low, but low insulating properties when the humidity is high, resulting in a resistor with excellent responsiveness that can handle a wide range of humidity.

[0035] (13th Aspect) The resistor according to the first aspect, wherein the base sheet is a nonwoven fabric.

[0036] With this type of resistor, the degree of wetting of the nonwoven fabric can be determined from the electrical resistance value.

[0037] According to the present invention, a resistor is obtained which has improved responsiveness of the resistance value to humidity.

[0038] Fig. 1 is a schematic diagram of a resistor of the present invention. Fig. 2 is a schematic diagram of a resistor of the present invention. Fig. 3 is a schematic diagram of a resistor of the present invention. Fig. 4 is a conceptual diagram of modified cellulose fine fibers (modified CNF) substituted with citric acid groups. The modified cellulose fine fibers (modified CNF) are substituted with citric acid groups, and the -O of the carboxyl group constituting the citric acid group is － It is a conceptual diagram showing a modified cellulose fine fiber (modified CNF) substituted with citric acid groups, in which a metal ion is bonded to the carboxyl group of the citric acid group. － FIG. 1 is a conceptual diagram showing a resistor having metal ions bonded to a group moiety. FIG. 2 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 3 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 4 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 5 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 6 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 7 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example. FIG. 8 is a graph plotting the relationship between humidity and electrical resistance value for a resistor of a test example.

[0039] Next, an embodiment of the present invention will be described. Note that this embodiment is an example of the present invention.

[0040] (Resistor) The resistor of this embodiment is a resistor comprising an insulating substrate sheet 2 and a pair of electrodes arranged facing each other with a gap therebetween, and a moisture-sensitive material whose electrical resistance changes in response to humidity is provided at least in the gap between the pair of electrodes, and the moisture-sensitive material has an average fiber width of 1 to 20 nm and contains modified cellulose fine fibers in which some of the hydroxy groups of the cellulose fibers have been substituted with anionic groups. Methods for substituting some of the hydroxy groups of the cellulose fibers with anionic groups and introducing anionic groups into the cellulose fibers include, for example, TEMPO oxidation, phosphate esterification, phosphite esterification, sulfate esterification, and polycarboxylic acid esterification. When the cellulose fine fibers are modified with anionic groups, the modified cellulose fine fibers are more likely to absorb moisture, resulting in increased humidity responsiveness and improved resistance value responsiveness.

[0041] (Raw Fiber) As the raw fiber of cellulose fiber, for example, plant-derived fiber (plant fiber), animal-derived fiber, microbial-derived fiber, etc. can be used. These fibers can be used alone or in combination as needed. However, it is preferable to use plant fiber as the raw fiber, and it is more preferable to use pulp fiber, which is a type of plant fiber. When the raw fiber is pulp fiber, it is easy to adjust the physical properties of the cellulose fine fiber (also called "CNF").

[0042] Examples of plant fibers that can be used include wood pulp made from broad-leaved trees, conifers, etc., non-wood pulp made from straw, bagasse, etc., and decomposed paper pulp (DIP) made from recycled waste paper, broke, etc. These fibers can be used alone or in combination.

[0043] Examples of wood pulp that can be used include chemical pulps such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), transverse mechanical pulp (TMP), and recycled paper pulp (DIP). These pulps can be used alone or in combination.

[0044] The hardwood kraft pulp (LKP) may be bleached hardwood kraft pulp, unbleached hardwood kraft pulp, or semi-bleached hardwood kraft pulp. The softwood kraft pulp (NKP) may be bleached softwood kraft pulp, unbleached softwood kraft pulp, or semi-bleached softwood kraft pulp. The recycled paper pulp (DIP) may be magazine recycled paper pulp (MDIP), newspaper recycled paper pulp (NDIP), corrugated paper pulp (WP), or other recycled paper pulp.

[0045] (Modification) The modified cellulose fine fibers of this embodiment are those in which some of the hydroxyl groups (—OH groups) of the cellulose fibers have been substituted with anionic groups. When the cellulose fibers are substituted with anionic groups, electrostatic repulsion (and further, bonding with metal ions) creates gaps between the cellulose fibers, which allows osmotic pressure to act effectively, making it easier to defibrate the cellulose fibers.

[0046] The amount of anionic groups introduced into cellulose fibers by substitution can be measured, for example, by two methods. One is a value evaluated based on neutralization titration using an automatic titrator. This neutralization titration method can be performed using an "AUT-801" manufactured by DKK-TOA Corporation. The other is a value evaluated based on elemental analysis. This elemental analysis can be performed using an X-Max 50 001 manufactured by Horiba, Ltd.

[0047] The amount of anionic groups introduced into the modified cellulose fine fibers is preferably 0.1 to 3.0 mmol / g, more preferably 0.2 to 2.5 mmol / g. If the amount introduced is 0.1 to 3.0 mmol / g, the moisture absorption as a moisture-sensitive material is sufficient, and there is an effect of improving the responsiveness to humidity, i.e., the responsiveness of the resistance value. In addition, since the cellulose maintains sufficient crystallinity, it is excellent in film-forming properties on the substrate sheet 2, and the cellulose fine fibers mixed in a liquid are maintained in a dispersed state without dissolving, which is preferable. The unit of the amount introduced, mmol / g, refers to the amount of anionic groups introduced (mmol) per 1 g of modified cellulose fine fibers.

[0048] The modified cellulose fine fibers substituted with anionic groups have one or more anionic groups bonded to the cellulose fibers. When the modified cellulose fine fibers are dispersed in a liquid containing metal ions, the anionic groups have a negative charge and can be (coordinated) bonded to positively charged metal ions. When the pH is low (on the acidic side), hydrogen ions are likely to bond to the anionic groups, and when the pH is high (on the alkaline side), metal ions are likely to bond to the anionic groups. For example, when the anionic group is -O － When the pH is low, － The group is likely to bond with a hydrogen ion to form an -OH group (the form shown in Figure 4), and when the pH is high, it becomes -O － The group is a metal ion (M ＋ ) is bonded to -O － ・M ＋ The anionic group is likely to take the form of a citric acid group (the form shown in Figures 5 and 6). Figures 4 to 6 show an example in which the anionic group is a citric acid group, but the anionic group is not limited to a citric acid group and may be any functional group having a negative charge. Furthermore, Figures 4 to 6 show a form in which one anionic group (citric acid group) is bonded to the cellulose fine fiber (CNF), but the present invention is not limited to this, and forms in which multiple anionic groups are bonded to the cellulose fine fiber are also included in embodiments of the present invention.

[0049] The modified cellulose fine fibers substituted with anionic groups have -O groups to which metal ions can be (coordinated) bonded per anionic group. － When the modified cellulose fine fibers substituted with anionic groups are mixed with a liquid to form a dispersion, the -O － The ratio of hydrogen ions to metal ions bound to the radical sites varies with pH.

[0050] In the anionic group-substituted modified cellulose fine fibers contained in the moisture-sensitive material 5 according to an embodiment of the present invention, the percentage of anionic groups to which metal ions are (coordinated) bonded to the total anionic groups is preferably 1 to 100%, more preferably 5 to 100%. When the percentage is 1 to 100%, the base sheet 2 is not deteriorated during the resistor manufacturing process, and the equipment such as a bar coder that applies the moisture-sensitive material 5 to the base sheet 2 is not damaged.

[0051] Examples of metal ions that bond to anionic groups include alkali metal ions and alkaline earth metal ions. Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions. Examples of alkaline earth metal ions include calcium ions.

[0052] To make cellulose fibers easier to defibrate, some of the hydroxyl groups of the cellulose fibers may be substituted with carbamate groups (carbamate modification). Carbamate modification improves the transparency and viscosity of the dispersion. In particular, when citric acid modification and carbamate modification are both performed, hydrogen bonds are weakened, making cellulose fibers easier to defibrate.

[0053] The amount of carbamate groups introduced is preferably 0.01 to 0.2 mmol per gram of cellulose fine fibers. If the amount introduced exceeds 0.2 mmol, the modification with citric acid may not proceed.

[0054] The amount of introduced carbamate groups was calculated by the Kjeldahl method.

[0055] (Fine Fibers) Cellulose fine fibers can be obtained by micronizing cellulose fibers. The average fiber diameter (width) of modified cellulose fine fibers substituted with anionic groups is preferably 1 to 20 nm, more preferably 3 to 10 nm. When the average fiber diameter is 1 nm or more, cellulose is less likely to dissolve in water, and the physical properties of the cellulose fine fibers, such as strength, rigidity, and dimensional stability, are outstanding, which is preferable. On the other hand, when the average fiber diameter is 20 nm or less, the diameter is about 1 / 10 or less of the wavelength of visible light, and therefore, when the cellulose fine fibers are dispersed in water (when formed into an aqueous dispersion), refraction and scattering of visible light are less likely to occur, resulting in sufficient light transmittance.

[0056] The fiber diameter of cellulose fine fibers is measured using an electron microscope as follows. First, 100 ml of an aqueous dispersion of cellulose fine fibers with a solid content concentration of 0.01 to 0.1% by mass is filtered through a Teflon (registered trademark) membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. Next, the sample is freeze-dried and osmium-coated to obtain a sample. This sample is observed using an electron microscope SEM image at a magnification of 5,000x, 10,000x, or 30,000x, depending on the width of the fibers constituting it. In this observation, two diagonal lines are drawn on the observed image, and three additional straight lines are arbitrarily drawn passing through the intersections of the diagonal lines. The widths of a total of 100 fibers intersecting with these three straight lines are then visually measured. The median diameter of this measurement is taken as the fiber diameter (width).

[0057] The average fiber length of the cellulose fine fibers is preferably 0.01 to 1000 μm, more preferably 0.05 to 500 μm, and particularly preferably 0.1 to 100 μm. If the average fiber length is 0.01 μm or more, a fiber network structure is easily formed and an excellent thickening effect is obtained. On the other hand, if the average fiber length is 1000 μm or less, the cellulose fine fibers are less likely to become entangled with each other, and a dispersed state is maintained, which is preferable.

[0058] The fiber length of the cellulose fine fibers is a value measured using a fiber analyzer "FS5" manufactured by Valmet.

[0059] The axial ratio (fiber length / fiber width) of the cellulose fine fibers is preferably 3 to 10,000, more preferably 10 to 1,000. When the axial ratio is 3 or more, the fibers have a fibrous shape and exhibit good viscosity when dispersed in a dispersion liquid. On the other hand, when the axial ratio is 10,000 or less, entanglement and aggregation of the fibers are less likely to occur.

[0060] The crystallinity of the cellulose fine fibers is preferably 50 to 99%, more preferably 65 to 90%. A crystallinity of 50% or more is preferable because it provides sufficient strength and heat resistance. The crystallinity can be adjusted, for example, by selecting the raw fiber, pre-treating, defibrating, etc.

[0061] The crystallinity is a value measured by X-ray diffraction in accordance with JIS-K0131 (1996) "General rules for X-ray diffraction analysis." Cellulose fine fibers have amorphous and crystalline portions, and the crystallinity refers to the percentage of the crystalline portion in the entire cellulose fine fibers.

[0062] When the concentration of the cellulose fine fibers is 1% by mass (w / w), the B-type viscosity of the aqueous dispersion is preferably 500 to 200,000 cP, more preferably 1,000 to 10,000 cP. If the B-type viscosity is 500 to 200,000 cP, the cellulose fine fibers remain sufficiently dispersed in the liquid, the moisture-sensitive material 5 does not become watery, and it does not solidify into a clay-like substance, which is preferable because it can be applied evenly to the base sheet 2 with a percoder or the like.

[0063] The B-type viscosity is a value measured for an aqueous dispersion of cellulose fine fibers with a solid content of 1% in accordance with JIS-Z8803 (2011) "Method for measuring viscosity of liquids." The B-type viscosity is the resistance torque when stirring the dispersion, and the higher the viscosity, the more energy is required for stirring.

[0064] (Example of production of modified cellulose fine fibers) An example of producing modified cellulose fine fibers by substituting a part of the hydroxy groups of cellulose fibers with anionic groups and introducing the anionic groups into the cellulose fibers will be described below. Modified cellulose fine fibers can be produced by, for example, TEMPO oxidation, phosphate esterification, phosphite esterification, sulfate esterification, polycarboxylic acid esterification, etc., and the method of producing modified cellulose fine fibers by polycarboxylic acid esterification can be carried out as follows.

[0065] (Pretreatment) Before or after the cellulose fibers are modified with various reagents such as citric acid, the cellulose fibers can be subjected to a pretreatment such as beating, if necessary. By subjecting the pulp fibers to a pretreatment before defibrating the cellulose fibers, the number of defibration steps can be significantly reduced, and the energy required for defibration can be saved.

[0066] The pretreatment of the cellulose fibers can be carried out by a physical method or a chemical method, preferably by a physical method and a chemical method. The pretreatment by a physical method and the pretreatment by a chemical method can be carried out simultaneously or separately.

[0067] As a pretreatment by a physical method, beating is preferably employed. When cellulose fibers are beaten, the cellulose fibers are cut into uniform pieces. Therefore, entanglement of the cellulose fibers with each other (prevention of aggregation) is prevented. From this viewpoint, beating is preferably carried out until the freeness of the cellulose fibers is 700 ml or less, more preferably 500 ml or less, and particularly preferably 300 ml or less.

[0068] The freeness of the cellulose fiber is a value measured in accordance with JIS P8121-2 (2012). Beating can be performed using, for example, a refiner or a beater.

[0069] Examples of pretreatments by chemical methods include hydrolysis of polysaccharides with acid (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), oxidation of polysaccharides with an oxidizing agent (oxidation treatment), and reduction of polysaccharides with a reducing agent (reduction treatment). However, as pretreatments by chemical methods, enzyme treatment is preferred, and it is more preferred to additionally carry out one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment. Below, alkali treatment is described in detail.

[0070] As a method of alkali treatment, for example, there is a method of immersing cellulose fibers in an alkali solution before introducing citric acid or the like.

[0071] The alkaline compound contained in the alkaline solution may be an inorganic alkaline compound or an organic alkaline compound. Examples of inorganic alkaline compounds include hydroxides of alkali metals or alkaline earth metals, carbonates of alkali metals or alkaline earth metals, and phosphate oxoacid salts of alkali metals or alkaline earth metals. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate. Examples of alkali metal phosphate oxoacid salts include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

[0072] Examples of organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammonium, aromatic ammonium, heterocyclic compounds, and their hydroxides, carbonates, phosphates, etc. Specific examples include ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N,N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogencarbonate, diammonium hydrogenphosphate, etc.

[0073] The solvent for the alkaline solution may be either water or an organic solvent, but is preferably a polar solvent (water, a polar organic solvent such as alcohol), and more preferably an aqueous solvent containing at least water.

[0074] The pH of the alkaline solution at 25°C is preferably 9 or higher, more preferably 10 or higher, and particularly preferably 11 to 14. When the pH is 9 or higher, the yield of cellulose fine fibers increases. However, when the pH exceeds 14, the handling of the alkaline solution decreases.

[0075] In this manufacturing method, an alkali is first added to an aqueous dispersion of cellulose fibers to adjust the pH to 9 or higher, preferably 10 or higher, and more preferably 11 or higher. The addition of the alkali causes the cellulose fibers to swell and separate, making crosslinking by adding citric acid difficult. If the pH is less than 9, the crosslinking reaction makes it difficult to defibrate the fibers, preventing them from becoming fine cellulose fibers, which may result in insufficient viscosity and transparency. However, if the alkali concentration (causticity) is 18% or higher, there is a risk of regenerated cellulose.

[0076] The alkali to be added may be, for example, sodium hydroxide, potassium hydroxide, aqueous ammonia, sodium carbonate, or the like, which can adjust the pH of the cellulose fiber dispersion to 9 to 14. However, it is preferable to use sodium hydroxide because of its high ability to swell the fibers.

[0077] (Addition of Polycarboxylic Acids, etc.) Next, at least one of a polycarboxylic acid and a metal salt of a polycarboxylic acid (reaction liquid) is added to the dispersion of cellulose fibers.

[0078] As the reactant (polycarboxylic acids or metal salts of polycarboxylic acids), for example, citric acid having three carboxylic acid groups, as well as malic acid, aconitic acid, malonic acid, succinic acid, etc. can be used.

[0079] The amount of the reactant added is preferably 1 to 20 mmol, more preferably 2 to 18 mmol, per gram of cellulose fiber. If the amount added is within this range, the degree of esterification is sufficient, and the resulting product has appropriate transparency and viscosity.

[0080] The amount of reactant introduced is measured by neutralization titration using a 0.2% by mass concentration modified cellulose fiber (dispersion) with an automatic titrator AUT-801 (DKK-TOA Corporation). The automatic titration method involves treating a 0.2% by mass concentration dispersion with ion exchange resin at a mass ratio of 10:1, followed by titration in 0.1 mL increments with 0.05 M sodium hydroxide. The measured pH is used as a dissociation curve, and two inflection points are observed. The first inflection point obtained can be designated the first inflection point, and the next inflection point can be designated the second inflection point.

[0081] Preferably, urea and / or a urea derivative (hereinafter simply referred to as "urea, etc.") is added together with, before or after, or after the addition of a reactant such as citric acid. Addition of urea, etc. breaks the hydrogen bonds between cellulose fibers, causing the fibers to swell and separate, making crosslinking by the addition of citric acid more difficult. Examples of urea, etc. that can be used include urea, thiourea, biuret, and phenylurea. These ureas or urea derivatives can be used alone or in combination. However, the use of urea is preferred.

[0082] When heated, urea or the like is decomposed into isocyanic acid and ammonia as shown in the following reaction formula (1). Isocyanic acid is highly reactive and modifies the hydroxyl groups of cellulose into carbamate groups as shown in the following reaction formula (2). Therefore, adding urea or the like to cellulose fibers promotes the introduction of carbamate groups. NH ２ —CO—NH ２ → HN=C=O+NH ３ ...(1) Cell-OH+H-N=C=O → Cell-O-CO-NH ２ …(2)

[0083] In the above reaction formula (2), Cell refers to a cellulose molecule. The amount of urea or the like added is 0.1 mmol or more, preferably 0.1 to 5.0 mmol, and more preferably 0.2 to 4.0 mmol, per 1 g of cellulose fiber. If the amount added exceeds 5.0 mmol, the effect of adding urea or the like may plateau.

[0084] When adding the various reagents, the cellulose fibers may be in a dry state, a wet state, or a dispersion state. The various reagents may be in a powder state or an aqueous solution state. However, adding the reagents in an aqueous solution state to the dry cellulose fibers is preferred because it results in a high degree of reaction uniformity.

[0085] (Heating) The cellulose fiber to which various reagents have been added is heated to promote a modification reaction with citric acid, etc. The heating temperature is preferably 110 to 200°C, more preferably 120 to 160°C. If the heating temperature is within the above range, the reaction between citric acid and pulp is promoted, and the cellulose fiber is less likely to deteriorate, and coloration and a decrease in viscosity are also less likely to occur.

[0086] The pH when heating cellulose fibers to which various reagents such as citric acid have been added is preferably 2.0 to 8.0, more preferably 3.0 to 6.0. As mentioned above, the pH of the dispersion becomes alkaline by adding an alkali such as sodium hydroxide, but becomes acidic, for example, pH 2.0 to 8.0, by adding various reagents such as citric acid. However, if the pH is less than 2.0, there is a risk of coloration. On the other hand, if the pH exceeds 8.0, citric acid will turn into trisodium citrate, which may prevent the reaction from proceeding and result in insufficient transparency and viscosity.

[0087] The cellulose fibers to which various reagents have been added are preferably heated until the cellulose fibers are dried. Specifically, the cellulose fibers are dried until the moisture content of the cellulose fibers is preferably 20% or less, more preferably 10% or less.

[0088] The reaction time of the cellulose fiber to which the various reagents have been added is, for example, 1 to 3600 seconds, preferably 10 to 1000 seconds. If the reaction time is too long, the cellulose fiber may turn yellow. On the other hand, if the reaction time is too short, the modification of the citric acid or the like may not proceed sufficiently.

[0089] As a device for heating the cellulose fibers to which various reagents have been added, for example, a hot air dryer, a kiln, a heated kneader, a paper machine, a dry pulp machine, etc. can be used.

[0090] (Washing) The cellulose fibers after the addition of the reagents are preferably washed before defibration. By washing the cellulose fibers, residual reagents such as citric acid and alkalis such as sodium hydroxide can be washed away.

[0091] The cellulose fibers can be washed using, for example, water or an organic solvent.

[0092] (Addition of Alkali Again) Next, an alkali such as sodium hydroxide is added again to the cellulose fibers to hydrolyze the cellulose fibers. This addition of alkali again breaks the crosslinks in the cellulose fibers, reducing the degree of crosslinking.

[0093] The alkali is added again so that the pH becomes 8 to 14, preferably 9 to 13. If the pH is within the above range, crosslinking is suppressed and elimination of polycarboxylic acid groups can be suppressed.

[0094] The alkali that can be used in this alkali re-addition step is the same as the alkali that was initially added. Furthermore, although the above uses the term "alkali" or "alkali treatment," the true meaning of this term is "hydrolysis." This is because, although an acidic solution may also be able to destroy crosslinks, an alkali destroys the crosslinks and promotes the hydrolysis reaction.

[0095] The amount of citric acid groups introduced is preferably 3.0 mmol or less, more preferably 2.5 mmol or less, per 1 g of cellulose fine fibers. On the other hand, the amount of citric acid groups introduced is preferably 0.1 mmol or more, more preferably 0.2 mmol or more, per 1 g of cellulose fine fibers. If the amount of citric acid groups introduced is within the above range, the moisture-sensitive material 5 will have excellent sensitivity responsiveness of electrical resistance to humidity.

[0096] The amount of citric acid groups introduced into the cellulose fine fibers is a value evaluated based on the neutralization titration method using an automatic titrator, "AUT-801" manufactured by DKK-TOA Corporation.

[0097] Here, the following remarks are made regarding the crosslinked structure and the ester structure. Before hydrolysis, the structure of citric acid-modified cellulose is a mixture of crosslinked structures and ester structures. If many crosslinked structures are present, it is thought that defibrating to a high level of transparency is difficult. In contrast, if the crosslinked structures are destroyed by hydrolysis and the ester structures become more numerous than before hydrolysis, defibration becomes easier. However, it is thought that it is difficult to destroy all of the crosslinked structures and leave only the ester structures. Incidentally, if the reagent is continued to be added, all of the crosslinked structures and ester structures are destroyed, returning to a state where defibration is difficult. Furthermore, if the crosslinked structures become more numerous, transparency does not increase because defibration is difficult, but viscosity tends to increase due to the crosslinked structures. If the ester structures become more numerous, transparency increases because defibration is easier, but viscosity tends to be lower compared to modified cellulose with many crosslinked structures.

[0098] (Addition of phosphorus oxoacids, etc.) After chemical pretreatment, cellulose fibers may be subjected to a treatment in which the cellulose fibers are substituted with phosphorus oxoacid groups. This treatment is generally carried out by adding a solution of an additive (A) containing at least one of phosphorus oxoacids and phosphorus oxoacid metal salts, the solution having a pH of less than 3, to the cellulose fibers, and then heating the solution to introduce esters of the phosphorus oxoacids into the cellulose fibers.

[0099] (Additive (A)) The additive (A) contains at least one of phosphorus oxoacids and phosphorus oxoacid metal salts. Examples of the additive (A) include phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium polyphosphate, lithium dihydrogen phosphate, trilithium phosphate, dilithium hydrogen phosphate, lithium pyrophosphate, lithium polyphosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium polyphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium polyphosphate, phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and phosphorous acid compounds such as pyrophosphorous acid. These additives can be used alone or in combination. However, it is preferable to use phosphorous acids as part or all of the phosphorus oxoacids. When phosphorous acids are used, cellulose fibers having an average fiber width of 10 nm or less are easily produced, and they can be suitably used for producing the porous ceramic of this embodiment.

[0100] When adding the additive (A), the cellulose fibers may be in a dry state, a wet state, or a slurry state. The additive (A) may be in a powder state or an aqueous solution state. However, it is preferable to add the additive (A) in an aqueous solution state to the dry cellulose fibers because this ensures a high degree of reaction uniformity.

[0101] The amount of additive (A) added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and particularly preferably 300 to 1,500 g, per kg of cellulose fiber.

[0102] (Other Additives) In addition to the additive (A), it is preferable to add a hydroxide salt, particularly sodium hydroxide, to the cellulose fibers. The hydroxide salt functions as a pH adjuster and also facilitates defibration of the cellulose fibers due to the difference in osmotic pressure.

[0103] (Heating) The heating temperature when heating the cellulose fiber to which the additive (A) has been added is preferably 100 to 210°C, more preferably 100 to 200°C, and particularly preferably 100 to 160°C. If the heating temperature is 100°C or higher, the phosphorus oxoacid ester can be introduced. However, if the heating temperature exceeds 210°C, there is a risk that the cellulose will deteriorate rapidly. Furthermore, if the heating temperature exceeds 160°C, there is a risk that the B-type viscosity of the fine fibrous cellulose will decrease.

[0104] The pH when heating the cellulose fiber to which the additive (A) has been added is preferably less than 3.0, more preferably 2.8 or less, and particularly preferably 2.5 or less. The lower the pH, the easier it is to incorporate the phosphorus oxoacid ester. However, if the pH is less than 2.1, the viscosity tends to decrease, and particularly if the pH is less than 2.0, there is a risk that the deterioration of the cellulose fiber will progress rapidly. Therefore, the pH is preferably 2.0 or more, more preferably 2.1 or more.

[0105] The cellulose fibers containing the additive (A) are preferably heated until they are dry. Specifically, the cellulose fibers are dried until the moisture content of the cellulose fibers is preferably 10% or less, more preferably 0.1% or less, and particularly preferably 0.001% or less. Of course, the cellulose fibers may be in an absolutely dry state with no moisture.

[0106] The heating time for the cellulose fiber containing the additive (A) is, for example, 1 to 1,440 minutes, preferably 10 to 180 minutes, and more preferably 30 to 120 minutes. If the heating time is too long, the introduction of the phosphorus oxoacid ester may proceed too quickly. In addition, the cellulose fiber may turn yellow.

[0107] As a device for heating the cellulose fiber to which the additive (A) has been added, for example, a hot air dryer, a kiln, a heating kneader, a paper machine, a dry pulp machine, etc. can be used.

[0108] The cellulose fine fibers obtained by defibrating the cellulose fibers into which the above-mentioned phosphorus oxoacids or the like have been introduced have, for example, an average fiber width of 1 to 20 nm, and some of the hydroxy groups of the cellulose fibers are substituted and esterified with phosphorus oxoacid groups represented by the following structural formula (1):

[0109] [Structural formula (1)]

[0110] In the structural formula (1), a, b, m, n, and p are natural numbers.

[0111] A １ , A ２ , ..., A ｐ and at least one of A' is O － and the remainder is either R, OR, NHR, or none. R is any of a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, and derivatives thereof. α is a cation made of an organic or inorganic substance.

[0112] Esters of phosphorus oxoacids are compounds in which a hydroxyl group (-OH) and an oxo group (=O) are bonded to a phosphorus atom, and the hydroxyl group provides an acidic proton. Phosphorus oxoacid esters have a high negative charge, and therefore, when an ester of phosphorus oxoacid is introduced, the repulsion between cellulose molecules becomes stronger, making it easier to defibrate cellulose fibers. As the ester of phosphorous acid to be introduced, an ester of phosphorous acid is more preferred. When phosphorous acid is introduced for esterification, some of the hydroxyl groups (-OH groups) of the cellulose fibers are substituted with the functional group shown in structural formula (2) below.

[0113] [Structural formula (2)]

[0114] In structural formula (2), α is either absent, R, or NHR. R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, or a derivative thereof. β, bonded to the oxygen atom (O) of the phosphorous group, is a hydrogen atom or a cation made of an organic or inorganic substance, particularly a hydrogen ion or an alkali metal ion, and among alkali metal ions, lithium ion, sodium ion, or potassium ion.

[0115] In cellulose fine fibers modified by the introduction of a phosphorous acid ester (also referred to as "phosphorous acid-modified cellulose fine fibers"), the β bonded to the oxygen atom (O) of the phosphorous acid group becomes a hydrogen ion and becomes a hydroxyl group (-OH) in an acid solution. On the other hand, in an alkaline solution containing alkali metal ions, phosphorous acid-modified cellulose fine fibers in which alkali metal ions are bonded to the β can be observed. Note that in a weak alkaline solution, phosphorous acid-modified cellulose fine fibers in which hydrogen ions are bonded to the β and phosphorous acid-modified cellulose fine fibers in which alkali metal ions are bonded to the β coexist.

[0116] The amount of phosphorus oxoacid ester or phosphorous acid ester introduced is preferably 0.1 mmol or more, more preferably 0.2 mmol or more, per 1 g of cellulose fine fibers. On the other hand, the amount of phosphorus oxoacid ester or phosphorous acid ester introduced is preferably 3.0 mmol or less, more preferably 2.5 mmol or less. If the amount introduced is within the above range, the moisture-sensitive material 5 will have excellent sensitivity responsiveness of electrical resistance to humidity.

[0117] The amount of phosphorus oxoacid ester introduced is a value evaluated based on elemental analysis, using an X-Max 50 001 manufactured by Horiba, Ltd.

[0118] (Defibrillation) The cellulose fibers that have been subjected to the above-mentioned chemical pretreatment and various treatments are defibrillated (fine-refining treatment). Through this defibrillation, the cellulose fibers are microfibrillated into cellulose fine fibers (cellulose nanofibers (CNF)).

[0119] When defibrating cellulose fibers, it is preferable to prepare the cellulose fibers in a slurry form. The solid content of this slurry is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and particularly preferably 1.0 to 5.0% by mass. When the solid content is within the above range, the cellulose fibers can be defibrated efficiently.

[0120] Defibration of cellulose fibers can be carried out using one or more means selected from homogenizers such as high-pressure homogenizers and high-pressure homogenizers, millstone-type friction machines such as grinders and grinders, refiners such as conical refiners and disk refiners, and various bacteria. However, defibration of cellulose fibers is preferably carried out using an apparatus or method that uses a water flow, particularly a high-pressure water flow, to refine the fibers. This apparatus or method results in extremely uniform dimensions and uniform dispersion of the resulting cellulose fine fibers. In contrast, for example, when using a grinder that grinds the fibers between rotating grindstones, it is difficult to uniformly refine the cellulose fibers, and in some cases, there is a risk that some undisintegrated fiber clumps may remain.

[0121] Grinders used to defibrate cellulose fibers include, for example, the Masscolloider manufactured by Masuko Sangyo Co., Ltd. Devices that use high-pressure water flow to pulverize fibers include, for example, Starburst (registered trademark) manufactured by Sugino Machine Co., Ltd. and Nanovater (registered trademark) manufactured by Yoshida Kikai Kogyo Co., Ltd. High-speed rotary homogenizers used to defibrate cellulose fibers include the Clearmix-11S manufactured by M Technique Co., Ltd.

[0122] As a device for defibrating using a high-pressure water stream, it is preferable to use a high-pressure homogenizer. A high-pressure homogenizer is a homogenizer capable of ejecting a cellulose fiber slurry at a pressure of, for example, 10 MPa or more, preferably 100 MPa or more. When cellulose fibers are treated with a high-pressure homogenizer, collisions between the cellulose fibers, pressure differences, microcavitation, and the like act to effectively defibrate the cellulose fibers. Therefore, the number of defibration treatments can be reduced, and the production efficiency of cellulose fine fibers can be improved.

[0123] The cellulose fibers are preferably defibrated so that the average fiber width, average fiber length, degree of crystallinity, etc. of the resulting cellulose fine fibers have the desired values ​​or evaluations described above.

[0124] (pH Adjustment) The modified cellulose fine fibers obtained by defibration can be imparted with metal ions by mixing with an aqueous solution containing a metal compound. For example, a sufficient amount of cation exchange resin is first added to the modified cellulose fine fiber dispersion under strongly acidic conditions and mixed to create modified cellulose fine fibers in which hydrogen ions are bound to the anionic groups. Next, an alkaline metal compound aqueous solution is gradually added to the modified cellulose fine fiber dispersion in which hydrogen ions are bound to the anionic groups under strongly acidic conditions and mixed to create modified cellulose fine fibers in which hydrogen ions are bound to the anionic groups, resulting in the hydrogen ions being released from the anionic groups and the metal ions being bound to the anionic groups. Here, by changing the amount of metal compound aqueous solution added and the concentration of the metal compound, the percentage of anionic groups bound to metal ions relative to the total anionic groups of the modified cellulose fine fibers can be appropriately adjusted.

[0125] Examples of metal compounds contained in the alkaline metal compound aqueous solution to be added include inorganic alkali compounds. Examples of inorganic alkali compounds include hydroxides of alkali metals or alkaline earth metals, carbonates of alkali metals or alkaline earth metals, and phosphate oxoacid salts of alkali metals or alkaline earth metals. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate. Examples of alkali metal phosphate oxoacid salts include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

[0126] (Base Sheet) The base sheet 2 is not particularly limited as long as it has insulating properties, but it is preferable that it is deformable so as to be freely curved or bendable. Examples of materials for the base sheet 2 include plastic sheets such as polyimide, polyester, polyethylene terephthalate, and polyethylene naphthalate, and nonwoven fabric sheets.

[0127] If the base sheet 2 is a plastic sheet, it should be an insulating sheet with a thickness of 50 to 500 μm. If the thickness of the base sheet 2 is 50 μm or more, the base sheet 2 can be easily wound up in a sheet conveyance test and wrinkles are less likely to occur. On the other hand, if the thickness of the base sheet 2 is 500 μm or less, resistors can be manufactured without any problems even if the sheet material is, for example, polyimide.

[0128] If the base sheet 2 is a nonwoven fabric sheet, the constituent fibers can be selected without particular limitation, for example, synthetic fibers such as polyolefins (e.g., polyethylene or polypropylene), polyesters, or polyamides (including single-component fibers and composite fibers such as core-sheath fibers), regenerated fibers (e.g., rayon or cupra), or natural fibers (e.g., cotton), or a mixture of these can also be used. To increase the flexibility of the nonwoven fabric, it is preferable to use crimped fibers as the constituent fibers. Furthermore, the constituent fibers of the nonwoven fabric can be hydrophilic fibers (including those made hydrophilic by a hydrophilizing agent), hydrophobic fibers, or water-repellent fibers (including those made water-repellent by a water-repellent agent). Nonwoven fabrics are generally classified into staple fiber nonwoven fabrics, long fiber nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, thermal bond (air-through) nonwoven fabrics, needle-punched nonwoven fabrics, point-bonded nonwoven fabrics, laminated nonwoven fabrics (including SSS nonwoven fabrics in which identical or similar nonwoven fabric layers are laminated, as well as SMS nonwoven fabrics and SMMS nonwoven fabrics in which different nonwoven fabric layers are laminated, such as spunbond layers with a meltblown layer sandwiched between them), etc., depending on the fiber length, sheet formation method, fiber bonding method, and laminated structure, and any of these nonwoven fabrics can be used. ２ Below, especially 200 g / m ２ The following are desirable: The fineness of the constituent fibers of the nonwoven fabric sheet is preferably about 1.0 to 5.0 dtex.

[0129] (Moisture-Sensitive Material) The moisture-sensitive material 5 constituting the resistor of this embodiment is formed by drying moisture-sensitive ink applied to the base sheet 2. The moisture-sensitive ink is a liquid containing water and an organic solvent, with cellulose microfibers dispersed therein. The moisture-sensitive ink may contain trace amounts of unavoidable impurities, provided that the impurities do not affect the characteristics of the resistor of the present invention. The mass ratio of water to organic solvent contained in the liquid may be, for example, 1:5 to 5:1. A concentration of cellulose microfibers contained in the liquid of 1 to 5% by mass is preferred because it provides the liquid with an appropriate viscosity, provides good wettability to the base sheet 2, allows the moisture-sensitive ink applied to the base sheet 2 to adhere firmly to the base sheet 2 without dripping or smearing, and allows the cellulose microfibers to be uniformly dispersed in the moisture-sensitive ink.

[0130] The organic solvent contained in the moisture-sensitive ink can be, for example, one or a combination of two or more selected from the group consisting of ethanol, methyl ethyl ketone, ethyl acetate, ethylene glycol monopropyl ether, and toluene, but ethanol and ethylene glycol monopropyl ether are preferred because they place less strain on the printing equipment and have good volatility.

[0131] The moisture-sensitive ink can be obtained by dispersing cellulose microfibers in the liquid, and therefore can be easily prepared, unlike the ink disclosed in Patent Document 2, which requires time and effort to prepare.

[0132] The moisture-sensitive ink can be applied to the base sheet 2 by flexographic printing, screen printing, inkjet printing, gravure printing, gravure offset printing, spin coating, dip coating, etc. Flexographic printing is particularly preferred because it allows application of a uniform ink concentration to form a thin film and also provides excellent dispersibility of cellulose fine fibers.

[0133] Flexographic printing can be performed, for example, as follows: moisture-sensitive ink is applied to a relief plate on the surface of a plate cylinder of a flexographic printing press, and the moisture-sensitive ink is then transferred to a base sheet 2 directly or via a blanket cylinder. By making the moving speed of the base sheet 2 in the machine direction MD equal to the peripheral speed of the plate cylinder, or the moving speed of the base sheet 2 in the machine direction MD equal to the peripheral speed of the blanket cylinder or the like, the moisture-sensitive ink can be applied appropriately to the base sheet 2.

[0134] The moisture-sensitive material 5 is formed as a thin film on the base sheet 2, and the thickness of the thin film formed by the moisture-sensitive material 5 may be, for example, 0.001 to 0.65 μm. The thickness of the thin film can be adjusted appropriately depending on the application of the resistor 1, but if it is within this range, it can be used for many applications, and is also preferable because the rigidity of the cellulose fine fibers themselves is not noticeable, allowing the resistor 1 to be freely curved or bent.

[0135] (Electrodes) For example, silver powder can be used as the electrodes disposed on the base sheet 2, and conductive ink dispersed in a solvent can be printed onto the base sheet 2. Printing on the base sheet 2 can be performed by, for example, flexographic printing, screen printing, inkjet printing, gravure printing, or gravure offset printing, with flexographic printing being particularly preferred. Printing on the base sheet 2 is performed on one side of the base sheet 2, but may also be performed on both sides.

[0136] (Resistor) The resistor 1 of this embodiment can be manufactured, for example, by the following procedure. First, a conductive ink is printed on a base sheet 2 to obtain a base sheet 2 on which electrodes are arranged. Next, a moisture-sensitive ink is applied to the surface of the base sheet 2 on which the electrodes are arranged so as to overlap the electrodes, and the surface is subjected to a drying process to obtain the resistor 1. The drying process is a process in which the base sheet 2 on which the moisture-sensitive ink has been applied is exposed to infrared rays with a wavelength of 700 nm to 4 mm for 0.15 seconds to 20 minutes.

[0137] In addition to the above, there is also a procedure for manufacturing the resistor 1, in which moisture-sensitive ink is first applied to the base sheet 2 and subjected to a drying process to obtain the base sheet 2 to which the moisture-sensitive material 5 is applied, and then conductive ink is printed on the surface of the base sheet 2 to which the moisture-sensitive material 5 is applied. However, the resistor 1 obtained by the procedure of printing conductive ink on the base sheet 2, applying moisture-sensitive ink, and subjecting it to a drying process has excellent responsiveness to atmospheric humidity because the moisture-sensitive material 5 is located over the electrodes.

[0138] The moisture-sensitive material 5 is provided on the base sheet 2, and is particularly provided in the gap between a pair of opposing electrodes arranged on the base sheet 2. The moisture-sensitive material 5 may be provided so as to overlap the pair of electrodes, in addition to the gap. When the pair of electrodes are comb-tooth electrodes 3 and 4, the moisture-sensitive material 5 may be provided so as to overlap the comb-tooth portion 31 consisting of the body 36 and linear comb teeth of the comb-tooth electrode 3, and the comb-tooth portion 41 consisting of the body 46 and linear comb teeth of the comb-tooth electrode 4. With the moisture-sensitive material 5 provided in this manner, when the humidity near the resistor 1 increases and moisture is adsorbed (or bonded) to the cellulose microfibers contained in the moisture-sensitive material 5, the conductivity of the resistor 1 increases and the resistance value decreases. On the other hand, when the humidity near the resistor 1 decreases and moisture adsorbed (or bonded) to the cellulose microfibers contained in the moisture-sensitive material 5 decreases, the conductivity of the resistor 1 decreases and the resistance value increases.

[0139] In particular, if the cellulose fine fibers are modified cellulose fine fibers substituted with anionic groups, the change in resistance value (impedance Z (Ω)) per unit humidity (% Rh) change becomes relatively large in an environment with a humidity of 40% Rh, and the humidity responsiveness of the resistor 1 becomes excellent.

[0140] First Embodiment Referring to Figures 1 to 3, a resistor 1 according to the present invention includes an insulating substrate sheet 2 and a pair of electrodes 3 and 4 disposed opposite each other. The substrate sheet 2 and the pair of electrodes 3 and 4 are provided with cellulose microfibers. The pair of electrodes 3 and 4 may be comb-shaped electrodes, as shown in Figure 2 (note that the moisture-sensitive material 5 containing the cellulose microfibers is omitted from Figure 2 for the purpose of illustrating the electrodes in detail). The comb-shaped electrode 3 has a body 36 extending upward from an application unit 35. A comb-shaped portion 31 is formed by a number of linear comb teeth projecting from the body 36 in a direction perpendicular to and to the right of the direction of extension of the body 36 (upward in the plane of ... The gaps (spaces) formed by the parallel arrangement of the linear comb teeth are part of the base sheet 2 and can be expressed as comb teeth 32 .

[0141] Similarly, the comb-tooth electrode 4 has a body 46 extending upward from the output portion 45 on the paper, and a number of linear comb teeth protrude from the body 46 in a direction perpendicular to and to the left of the direction of extension of the body 46 (upward on the paper), forming a comb-tooth portion 41. The linear comb teeth forming the comb-tooth portion 41 extend linearly to the left of the paper, spaced apart from each other in the vertical direction of the paper. The gaps (spaces) formed by the parallel arrangement of the linear comb teeth are part of the base sheet 2 and can also be expressed as comb teeth 42. Note that, although the illustrated application portion is located on the left side of the paper and the output portion is located on the right side of the paper, the application portion may be located on the right side of the paper and the output portion may be located on the left side of the paper.

[0142] The body portion 36 of the comb-tooth electrode 3 and the body portion 46 of the comb-tooth electrode 4 can each be linear and extend in the vertical direction of the page, and can be arranged opposite each other. Each tooth of the comb-tooth electrode 3 is located in a corresponding one of the teeth 42 of the comb-tooth electrode 4, and each tooth of the comb-tooth electrode 4 is located in a corresponding one of the teeth 32 of the comb-tooth electrode 3, so that the teeth of the comb-tooth portion 31 of the comb-tooth electrode 3 and the teeth of the comb-tooth portion 41 of the comb-tooth electrode 4 are alternately arranged at a vertical interval W2. In this case, the interval W2 can be 20 to 5000 μm, preferably 20 to 500 μm, more preferably 20 to 300 μm, and even more preferably 20 to 100 μm. Furthermore, the width of each tooth in the interdigital electrode 3 and the width of each tooth in the interdigital electrode 4 may be the same width W1, for example, 20 to 5000 μm, preferably 20 to 500 μm, more preferably 20 to 300 μm, and even more preferably 20 to 100 μm. The spacing W2 can be adjusted as appropriate, but the narrower it is, the greater the change in electrical resistance value in response to changes in humidity. Furthermore, the narrower the width W1 and the greater the number of interdigital teeth, the greater the change in electrical resistance value in response to changes in humidity. Furthermore, when the length of the width W1 and the length of the spacing W2 are close to each other (or equal), the greater the total area of ​​the areas of the interdigital teeth, the greater the change in electrical resistance value in response to changes in humidity.

[0143] The vertical spacing W2 formed between the teeth of the comb-tooth electrode 3 and the teeth of the comb-tooth electrode 4, the width W1 of each tooth of the comb-tooth electrode 3, and the width W1 of each tooth of the comb-tooth electrode 4 can be adjusted as appropriate. If the spacing W2 and the width W1 of each tooth are increased, the comb-tooth portions 31 and 41 will have coarse meshes (see FIG. 3(a)), and if the spacing W2 and the width W1 of each tooth are decreased, the comb-tooth portions 31 and 41 will have fine meshes (see FIG. 3(b)). These can be used in accordance with the application of the resistor.

[0144] The comb teeth constituting the comb tooth portion 31 of the comb-tooth electrode 3 may all have the same length, and the tips 34 of the comb teeth may be aligned in the vertical direction of the drawing. Each tip 34 of the comb teeth of the comb-tooth electrode 3 is spaced apart from the base 43 of the comb-tooth electrode 4 by a distance L2, and each tip 44 of the comb teeth of the comb-tooth electrode 4 is also spaced apart from the base 33 of the comb-tooth electrode 3 by a distance L2. The length L1 from the tip 34 of the comb tooth of the comb-tooth electrode 3 to the position on the comb tooth of the comb-tooth electrode 3 facing the tip 44 of the comb tooth of the comb-tooth electrode 4 may be, for example, 2 mm or more, and preferably 2 mm to 500 mm. In other words, the length L1 can be defined as the length of the teeth of the comb-tooth electrode 3, the length of the portion where the teeth of the comb-tooth electrode 3 and the teeth of the comb-tooth electrode 4 are alternately arranged, or the length of the teeth of the comb-tooth electrode 3 excluding the distance L2 from the base 33 of the teeth of the comb-tooth electrode 3 to the tip 44 of the teeth of the comb-tooth electrode 4. The distance L2 is preferably longer than the distance W2 in the vertical direction between the teeth of the comb-tooth electrode 3 and the teeth of the comb-tooth electrode 4. If the length L1 is 2 mm or more, the change in electrical resistance value with respect to humidity is large, which is preferable. On the other hand, the upper limit of the length L1 is not particularly limited, and it may be adjusted depending on the application of the resistor.

[0145] The cellulose fine fibers can be provided on the comb-tooth portions 31, 41 of at least one pair of electrodes by applying (printing) the moisture-sensitive material 5, and may also be provided so as to protrude from the comb-tooth portions 31, 41 in the up, down, left, and right directions of the paper surface, or may also be provided on the comb holes 32, 42 of the base sheet 2. The moisture-sensitive material 5 is, for example, a material in which the cellulose fine fibers (basis weight) are 0.23 to 95 g / m on the base sheet 2. ２ , preferably 1 to 50 g / m２ , more preferably 2 to 10 g / m ２ When the basis weight of the cellulose fine fibers is within the above range, the electrical resistance changes with changes in humidity, and the hysteresis effect (the effect in which the electrical resistance at the same humidity differs between humidification and dehumidification) can be suppressed to a low level, which is preferable.

[0146] Next, an example of the present invention will be described. (Citric Acid-Modified Cellulose Microfibers) 60 g of a 4% by mass aqueous solution of sodium hydroxide was added to 10 g of pulp to swell it (alkali treatment step). 12.2 g of citric acid and 26.8 g of water were added to the swollen pulp and mixed in a mixer for 10 minutes (reagent addition step). This was then heated and reacted at 130°C for 4 hours in a hot air dryer (drying reaction step). This was then washed until the washing filtrate became neutral, yielding citric acid-modified pulp. Water was added to the washed citric acid-modified pulp to a concentration of 1% by mass, and sodium hydroxide was added to a pH of 11.3, followed by hydrolysis for 1 hour (hydrolysis step). The hydrolyzed citric acid-modified pulp was further washed until the washing filtrate became neutral. The citric acid-modified pulp was defibrated to obtain citric acid-modified cellulose microfibers. Defibration was performed using a high-pressure homogenizer.

[0147] The obtained citric acid-modified cellulose fine fibers were dispersed in water to obtain 100 g of an aqueous cellulose fine fiber dispersion containing 1.0 mass % (based on solid content) of the cellulose fine fibers. The aqueous cellulose fine fiber dispersion was subjected to cation exchange with 10 g of a cation exchange resin ("Urbanlite HPR1024H" manufactured by Organo Corporation) to convert O of the carboxyl groups constituting the citric acid groups on the citric acid-modified cellulose fibers. － Hydrogen ions were bound to the sites to form hydrogen ion-type citric acid-modified cellulose fine fibers, and an aqueous dispersion in which the hydrogen ion-type citric acid-modified cellulose fine fibers were dispersed was obtained.

[0148] Aqueous sodium hydroxide solution was gradually added to this aqueous dispersion to convert the O of the carboxyl group constituting the citric acid group on the citric acid-modified cellulose fiber. －The hydrogen ions bound to the sites were replaced with sodium ions. By varying the amount of sodium hydroxide solution added, Samples 1 to 6 were prepared, each of which had different percentages of anionic groups bound to metal ions (also referred to as "metal ion ratio") relative to the total anionic groups in the citric acid-modified cellulose microfibers. The metal ion ratio was calculated from the relationship between the amount added and pH using an "AUT-801" analyzer manufactured by DKK-TOA Corporation.

[0149] (Phosphite-modified cellulose fine fibers) As the phosphorous-modified cellulose fine fibers, "ELLEX (registered trademark)-☆ (Star)" manufactured by Daio Paper Corporation, in which some of the hydroxyl groups of the cellulose fibers have been substituted with phosphorous groups, was used, and this was designated as Sample 7.

[0150] (Unmodified cellulose fine fibers) Mechanical pulp was used as the raw material pulp, which was defibrated without any modification treatment to obtain unmodified cellulose fine fibers, which were designated as Sample 8. Similarly, chemical pulp was used as the raw material pulp, which was defibrated without any modification treatment to obtain unmodified cellulose fine fibers, which were designated as Sample 9. Defibration was performed using a high-pressure homogenizer.

[0151] Table 1 shows the type of anionic group, the amount of anionic groups introduced into the cellulose fibers, the percentage of anionic groups to which metal ions are (coordinated) bonded (proportion of metal ions) in the total anionic groups, and the Brookfield viscosity of the prepared cellulose fine fibers or aqueous dispersions of cellulose fine fibers (samples 1 to 9).

[0152] The Brookfield viscosity was determined as a value measured for an aqueous dispersion of cellulose fine fibers with a solids concentration of 1% in accordance with JIS-Z8803 (2011) "Method for measuring viscosity of liquids" under conditions of 1 atmosphere, 20°C, M rotor, and 4.6 rpm.

[0153]

[0154] (Production of resistor) Each of the obtained cellulose fine fibers was dispersed in water to obtain an aqueous dispersion with a solids concentration of 1%. An aqueous dispersion of cellulose fine fibers, which is a moisture-sensitive material, was applied to an insulating substrate sheet printed with silver comb-shaped electrodes using a bar coater to a wet film thickness of 6.9 μm, and then dried to obtain a resistor. The aqueous dispersion of cellulose fine fibers was applied to the substrate sheet and applied to the entire portion of the comb-shaped electrodes excluding the application section 35 and the output section 45, as well as to the gaps formed between each comb tooth of one electrode 3 and each comb tooth 42 of the other electrode 4, and the gaps formed between each comb tooth of the other electrode 4 and each comb tooth 32 of the one electrode 3. A 50 μm thick PET film (product of Toyobo Co., Ltd., model number: A4360, product name: Cosmoshine) was used as the substrate sheet.

[0155] Resistors with varying comb tooth widths were prepared. Specifically, four types, first to fourth resistors, each having comb-shaped electrodes were prepared. The first resistor consisted of a pair of electrodes, with each comb tooth of one electrode (3) positioned at a corresponding tooth of the other electrode (4), and the comb teeth of the first electrode (3) and the comb teeth of the second electrode (4) alternately spaced apart. The length L1 from the tip 34 of the comb tooth of one electrode (3) to a position facing the tip 44 of the comb tooth of the second electrode (3) was the same as the length L1 from the tip 44 of the comb tooth of the second electrode (4) to a position facing the tip 34 of the comb tooth of the first electrode (3), both of which were 5 mm long. The widths of the comb teeth of the first electrode (3) and the second electrode (4) were the same, 0.5 mm. When the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 were alternately arranged with a gap therebetween, the gap was set to 0.5 mm.

[0156] The second resistor was composed of a pair of electrodes, with each comb tooth of one electrode 3 of the pair positioned at a comb tooth of the other electrode 4, and the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 arranged alternately with a gap therebetween. The length L1 from the tip 34 of the comb tooth of one electrode 3 to a position facing the tip 44 of the comb tooth of the other electrode was the same as the length L1 from the tip 44 of the comb tooth of the other electrode 4 to a position facing the tip 34 of the comb tooth of the one electrode 3 of the other electrode, both of which were 5 mm. The width of the comb tooth of the one electrode 3 and the width of the comb tooth of the other electrode 4 were the same, 0.3 mm. When the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 were arranged alternately with a gap therebetween, the gap was 0.3 mm.

[0157] The third resistor was composed of a pair of electrodes, with each comb tooth of one electrode 3 of the pair positioned at a comb tooth of the other electrode 4, and the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 arranged alternately with a gap therebetween. The length L1 from the tip 34 of the comb tooth of one electrode 3 to a position facing the tip 44 of the comb tooth of the other electrode was the same as the length L1 from the tip 44 of the comb tooth of the other electrode 4 to a position facing the tip 34 of the comb tooth of the one electrode 3 of the other electrode. The width of the comb tooth of the one electrode 3 and the width of the comb tooth of the other electrode 4 were the same, 0.2 mm. When the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 were arranged alternately with a gap therebetween, the gap was 0.2 mm.

[0158] The fourth resistor was composed of a pair of electrodes, with each comb tooth of one electrode 3 of the pair positioned in a comb hole of the other electrode 4, and the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 arranged alternately with a gap between them. The length L1 from the tip 34 of the comb tooth of one electrode 3 to a position facing the tip 44 of the comb tooth of the other electrode was the same as the length L1 from the tip 44 of the comb tooth of the other electrode 4 to a position facing the tip 34 of the comb tooth of the one electrode 3 of the other electrode. The width of the comb tooth of the one electrode 3 and the width of the comb tooth of the other electrode 4 were the same, 0.1 mm. When the comb teeth of the one electrode 3 and the comb teeth of the other electrode 4 were arranged alternately with a gap between them, the gap was 0.1 mm.

[0159] For each of the first to fourth resistors, one provided with citric acid-modified cellulose fine fibers, one provided with phosphorous acid-modified cellulose fine fibers, and one provided with unmodified cellulose fine fibers were prepared. For the one provided with citric acid-modified cellulose fine fibers, the percentage of citric acid-modified cellulose fine fibers in which sodium ions are bound to the citric acid groups (proportion of metal ions) in the total citric acid-modified cellulose fine fibers was further varied.

[0160] (Test 1) Test Examples 1 to 8 were manufactured using the first resistor described above. For each of the resistors of Test Examples 1 to 8, the electrical resistance (impedance Z (Ω)) was measured while changing the humidity. The measurement conditions were as follows. In an environment conforming to JIS-B-7920:2000 Hygrometer - Test Method, each test device was operated in a stable state, the resistor was placed in a stable environment, and the electrical resistance of the resistor was measured under conditions of increasing humidity. The measurement was performed in an environment of 20°C, by applying a voltage of 0.5 V to the application unit 35 and output unit 45 of the resistor every 35 minutes, and measuring the humidity around the resistor and the electrical resistance of the resistor. The measurement results are shown in Table 2.

[0161] (Test 2) Next, resistors of Test Examples 11 to 22 were produced in the same manner as in the production of the resistors described above. Each of the obtained cellulose fine fibers was dispersed in water to prepare aqueous dispersions (Samples 1 to 6) with a solids concentration of 1%. The aqueous dispersions of cellulose fine fibers (Samples 1 to 6) were applied to an insulating substrate sheet on which a silver comb-shaped electrode had been printed using a bar coater so as to give a wet film thickness of 6.9 μm, and then dried to obtain resistors.

[0162] The resistors were produced by adjusting the type of cellulose fine fiber dispersion, the type of resistor, the amount of anionic groups introduced, and the proportion of metal ions as shown in Table 3. The electrical resistance values ​​of the resistors of Test Examples 11 to 22 were measured while varying the humidity.

[0163] Each test device was operated in a stable state under an environment conforming to JIS-B-7920:2000 Hygrometer - Test Method, and the resistor was placed in a stable environment, and the electrical resistance of the resistor was measured under conditions of increasing and decreasing humidity. Measurements were performed in a 20°C environment, with a voltage of 0.5 V applied to the application unit 35 and output unit 45 of the resistor every 35 minutes, and the humidity around the resistor and the electrical resistance of the resistor were measured. The humidity was varied from 5% RH to 95% RH in 5% RH increments, and from 95% RH to 5% RH in 5% RH increments.

[0164]

[0165] The results are shown in Figures 7 to 12. Test Example 11 is shown in Figure 7(a), Test Example 12 in Figure 7(b), Test Example 13 in Figure 8(a), Test Example 14 in Figure 8(b), Test Example 15 in Figure 9(a), Test Example 16 in Figure 9(b), Test Example 17 in Figure 10(a), Test Example 18 in Figure 10(b), Test Example 19 in Figure 11(a), Test Example 20 in Figure 11(b), Test Example 21 in Figure 12(a), and Test Example 22 in Figure 12(b).

[0166] (Test 3) Next, resistors of Test Example 31 to Test Example 33 were manufactured in the same manner as the manufacturing of the resistor described above. Each of the cellulose fine fibers obtained above was dispersed in water, and an aqueous dispersion with a solid content of 1% was designated Sample 7, and an aqueous dispersion with a solid content of 2% was designated Samples 8 and 9. The aqueous dispersions of cellulose fine fibers (Samples 7 to 9) were applied to an insulating substrate sheet on which silver comb-shaped electrodes were printed using a bar coater so as to give a wet film thickness of 6.9 μm, and then dried to obtain resistors. Test Example 31 was manufactured using Test Example 31, which used the first resistor as the resistor. １ Test Example 31 using the second resistor as the resistor ２ Test Example 31 using a third resistor as the resistor ３ Test Example 31: Using the fourth resistor as the resistor ４ Similarly, Test Example 32 group was the same as Test Example 32, in which the first resistor was used as the resistor. １ Test Example 32: Using the second resistor as the resistor ２ Test Example 32 using a third resistor as the resistor ３ Test Example 32: Using the Fourth Resistor as the Resistor ４ Similarly, the Test Example 33 group was the same as Test Example 33, in which the first resistor was used as the resistor. １ Test Example 33 using the second resistor as the resistor ２ Test Example 33 using a third resistor as the resistor ３ Test Example 33: Using the Fourth Resistor as the Resistor ４ It was decided.

[0167] The resistors were produced by adjusting the type of cellulose fine fiber dispersion, the type of resistor, the amount of anionic groups introduced, and the proportion of metal ions as shown in Table 4. The electrical resistance values ​​of the resistors of Test Example 31 to Test Example 33 were measured while varying the humidity.

[0168] Each test device was operated in a stable state under an environment conforming to JIS-B-7920:2000 Hygrometer - Test Method, and the resistor was placed in a stable environment, and the electrical resistance of the resistor was measured under conditions of increasing and decreasing humidity. Measurements were performed in a 20°C environment, with a voltage of 0.5 V applied to the application unit 35 and output unit 45 of the resistor every 35 minutes, and the humidity around the resistor and the electrical resistance of the resistor were measured. The humidity was varied from 5% RH to 95% RH in 5% RH increments, and from 95% RH to 5% RH in 5% RH increments.

[0169]

[0170] The results are shown in Figure 13 for Test Example 31 group, Figure 14 for Test Example 32 group, and Figure 15 for Test Example 33 group.

[0171] The equipment used in the tests is as follows: The humidity and temperature were adjusted using a split-flow precision humidity supply device (SRG-1M-10L), sold by Daiichi Scientific Co., Ltd. and manufactured by Shin-ei Technology Co., Ltd., which mixes completely dry gas (0% Rh) with saturated gas (100% Rh) and generates gas with a constant relative humidity by adjusting the flow rate ratio. The high-performance low-temperature circulating constant temperature water bath (RE415S), sold by Daiichi Scientific Co., Ltd. and manufactured by LAUDA, is a device that maintains the air in the test bath at a constant temperature by using a constant temperature water flow around the test bath. The constant temperature water circulation test bath (custom-made), sold by Daiichi Scientific Co., Ltd. and manufactured by Daiichi Scientific Co., Ltd., is a test bath that houses a resistor, maintains a constant humidity and temperature for testing, and can change the humidity from 0% Rh to 100% Rh. The LCR meter (IM3523) is a device for measuring electrical resistance, sold by Asuka Electronics Co., Ltd. and manufactured by Hioki E.E. Corporation. The humidity sensor measurement system (custom-made) is manufactured and sold by Asuka Electronics Co., Ltd. and is a device that outputs the relationship between the humidity and electrical resistance of a resistor. The dew point meter (DewStar S-1) is an optical dew point hygrometer sold by Daiichi Scientific Co., Ltd. and manufactured by Shinyei Technology Co., Ltd., which calculates humidity from the air dew point and temperature.

[0172] The present invention is applicable to resistors, such as humidity sensors, carbon dioxide sensors, biosensors, and chemical sensors, and to absorbent articles such as diapers having these sensors.

[0173] Resistor 1 Base sheet 2 Electrode 3, 4 Moisture-sensitive material 5 Teeth 31, 41 Teeth 32, 42 Teeth base 33, 43 Teeth tip 34, 44 Application section 35 Body 36, 46 Output section 45 Teeth length L1 Spacing L2 Teeth width W1 Spacing W2

Claims

1. A resistor comprising an insulating substrate sheet and a pair of electrodes arranged facing each other with a gap therebetween, wherein a moisture-sensitive material whose electrical resistance changes in response to humidity is provided at least in the gap between the pair of electrodes, and wherein the moisture-sensitive material has an average fiber width of 1 to 20 nm and contains modified cellulose fine fibers in which some of the hydroxyl groups of the cellulose fibers have been substituted with anionic groups.

2. The resistor according to claim 1, wherein a metal ion is bonded to the anionic group.

3. The resistor according to claim 1, wherein the anionic group is an oxo acid group.

4. The resistor according to claim 1, wherein the percentage of anionic groups to which metal ions are bonded is 5 to 100% of the total anionic groups.

5. The resistor according to claim 1, wherein the anionic group is a phosphorus oxoacid group represented by the following structural formula (1): [Structural formula (1)] In the structural formula (1), a, b, m, and n are natural numbers. １ , A ２ , ..., A ｐ and at least one of A' is O － and the remainder is either R, OR, NHR, or none. R is any of a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, and derivatives thereof. α is a cation made of an organic or inorganic substance.

6. The resistor according to claim 1, wherein the anionic group is a phosphite group.

7. The resistor according to claim 1, wherein the anionic group is a polycarboxylic acid group.

8. The resistor according to claim 1, wherein the anionic group is a citric acid group.

9. The cellulose fine fibers are applied to the pair of electrodes in an amount of 0.23 to 95 g / m ２ The resistor of claim 1 , 10. The resistor according to claim 1, wherein the moisture-sensitive material is provided to cover the pair of electrodes.

11. A resistor according to claim 1, wherein the pair of electrodes are comb-shaped electrodes, and each of the comb teeth of one of the pair of electrodes is positioned in a comb hole of the other electrode, and each of the comb teeth of the one electrode and each of the comb teeth of the other electrode are alternately arranged with a gap therebetween.

12. The resistor according to claim 1, wherein the pair of electrodes are comb-shaped electrodes, and each of the comb teeth of one of the pair of electrodes is located in a comb hole of the other electrode, and the comb teeth of the one electrode and the comb teeth of the other electrode are alternately arranged with a gap therebetween, the gap being 20 to 5000 μm, the width of each of the comb teeth of the one electrode being 20 to 5000 μm, and the width of each of the comb teeth of the other electrode being 20 to 5000 μm.

13. The resistor according to claim 1, wherein the base sheet is a nonwoven fabric.

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