Water discoloring indicator

Abstract

To provide a water discoloring indicator that can discriminate whether adhesion of water has occurred previously and that offers enhanced precision in detecting water adhesion from a rear surface of the indicator having a feature of discriminating whether water adheres at present time.SOLUTION: On a substrate 2 of a water discoloring indicator 1, there are provided: a porous layer 3 that is formed by fixing a low refractive index pigment to a binder resin in a dispersive condition, is opaque in a non-liquid absorbent condition, and gets transparent in a liquid absorbent condition; and a water-soluble resin layer 4 which is incorporated in part of the porous layer and is disposed in a coexistent condition. In the non-liquid absorbent condition, part of the porous layer including the water-soluble resin layer exhibits higher light transmissivity than the other part of the porous layer not including the water-soluble resin layer. The water discoloring indicator has a through hole 5 that passes through an upper surface of the porous layer to a lower surface of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water-color-changing indicator, and more particularly to a water-color-changing indicator that can be visually recognized as exhibiting a different appearance from that in a dry state when a water-containing medium is attached thereto. [Background technology]

[0002] Conventionally, a water-discoloring indicator has been disclosed that has a porous layer on a support, in which a low refractive index pigment is dispersed and fixed in a binder resin, and that is opaque when not absorbing liquid and becomes transparent when absorbing liquid, and a water-soluble resin layer that coexists with the porous layer and is embedded in part of the porous layer, and that has the function of determining whether water has adhered thereto in the past and whether water is currently adhered thereto (see, for example, Patent Document 1). The water-color changing indicator is disclosed to use a water-permeable support such as fabric or a film with holes, and can also detect water adhering to the lower surface (back surface) of the support. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-113588 Summary of the Invention [Problem to be solved by the invention]

[0004] To provide a water-color-changing indicator that can determine whether water has adhered in the past and has a function of determining whether water is currently adhering, and has improved accuracy in detecting adhesion of water from the back surface of the indicator. [Means for solving the problem]

[0005] The present invention requires a water-colorable indicator comprising a support, a porous layer on which a low refractive index pigment is dispersed and fixed in a binder resin, the porous layer being opaque in a non-liquid-absorbing state and becoming transparent in a liquid-absorbing state, and a water-soluble resin layer coexisting within a portion of the porous layer, the porous layer in the portion where the water-soluble resin layer is provided being more translucent in the non-liquid-absorbing state than the porous layer in the portion where the water-soluble resin layer is not provided, and a through hole communicating from the upper surface of the porous layer to the lower surface of the support. Furthermore, a plurality of the through holes are provided, and the area of ​​each through hole is 0.008 to 20 mm 2 the ratio of the area occupied by the through holes to the total area of ​​the porous layer and the water-soluble resin layer is 0.1 to 80%; 2 The area ratio of the through holes to the four sides is 1 to 50%, the area where the porous layer is provided and the area where the water-soluble resin layer is provided are each provided with through holes, the area ratio of the through holes to the total area of ​​the porous layer where the water-soluble resin layer is not provided is 0.1 to 80%, and the area ratio of the through holes to the total area of ​​the porous layer where the water-soluble resin layer is provided is 0.1 to 80%, the support is made of a water-impermeable material, and a non-abrasive layer is formed under the support, in which a low refractive index pigment is fixed in a dispersed state in a binder resin. The film comprises a porous layer that is opaque in a liquid-absorbing state and becomes transparent in a liquid-absorbing state, and a water-soluble resin layer that is present in a part of the porous layer and coexists with the porous layer, and the porous layer in the part where the water-soluble resin layer is provided in a non-liquid-absorbing state has higher light transmittance than the porous layer in the part where the water-soluble resin layer is not provided, and has through holes that communicate from the upper surface of the porous layer on the support to the lower surface of the porous layer below the support, an adhesive layer provided in the bottom layer and through holes that communicate from the upper surface of the porous layer to the lower surface of the adhesive layer, and the adhesive layer is formed from a water-insoluble resin. [Effects of the Invention]

[0006] The present invention can provide a water-color-changing indicator that is highly convenient and has improved accuracy in detecting water adhesion from the back surface of the indicator, which can determine whether water has adhered to it in the past and has the function of determining whether water is currently adhering to it. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory vertical cross-sectional view of one embodiment of a water-color changing indicator of the present invention. [Figure 2] FIG. 2 is an explanatory vertical cross-sectional view of another embodiment of the water-color changing indicator of the present invention. [Figure 3] FIG. 2 is an explanatory vertical cross-sectional view of another embodiment of the water-color changing indicator of the present invention. [Figure 4] FIG. 2 is an explanatory vertical cross-sectional view of another embodiment of the water-color changing indicator of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention is a water-discoloring indicator comprising a support, a porous layer on which a low refractive index pigment is dispersed and fixed in a binder resin, the porous layer being opaque when not absorbing liquid and becoming transparent when absorbing liquid, and a water-soluble resin layer coexisting within a portion of the porous layer, with through holes provided that connect the upper surface of the porous layer to the lower surface of the support. In the water-color-changing indicator, when it is not absorbing liquid, the porous layer in the area where the water-soluble resin layer is provided is more translucent than the porous layer in the area where the water-soluble resin layer is not provided, so that the underlying layer can be seen from the area where the water-soluble resin layer is provided, and various images can be seen.

[0009] The support is not particularly limited, and examples thereof include paper, synthetic paper, fabrics such as woven fabrics, knitted fabrics, braided fabrics, and nonwoven fabrics, natural or synthetic leather, plastics, glass, ceramics, metals, wood, and stone, with synthetic paper and plastics being preferred. The shape of the support may be either flat or three-dimensional. The support is made of a water-impermeable material, so that it maintains its strength as a support even after the formation of the through-holes, and also has excellent strength as an indicator, and can also satisfy the strength requirements for repeated application (re-adhesion and re-peeling) of an indicator provided with an adhesive layer, which will be described later. The support may be a support itself that is colored, or a support having a non-color-changing colored layer provided thereon. Examples of the colorant that colors the support or the colorant contained in the non-discoloring colored layer include general dyes, fluorescent dyes, and colored pigments. Of these, examples of colored pigments include general pigments, fluorescent pigments, metal powders, and transparent metallic luster pigments (pearl pigments) in which a core substance such as mica, alumina, or glass is coated with titanium oxide.

[0010] The porous layer is a layer in which a low refractive index pigment is fixed together with a binder resin in a dispersed state, and is a layer whose transparency differs between a dry state and a liquid-absorbing state. The refractive index of the low refractive index pigment is in the range of 1.4 to 1.8, and exhibits good transparency when it absorbs water. Examples of the low refractive index pigment include silicic acid and its salts, baryte powder, barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, talc, alumina, alumina white, and magnesium carbonate, with silicic acid and its salts being preferred. Examples of the salt of silicic acid include aluminum silicate, potassium aluminum silicate, sodium aluminum silicate, calcium aluminum silicate, potassium silicate, calcium silicate, sodium calcium silicate, sodium silicate, magnesium silicate, and potassium magnesium silicate. Two or more of the low refractive index pigments can also be used in combination. The particle size of the low refractive index pigment is not particularly limited, but a particle size of 0.03 to 10.0 μm is preferably used. A preferred example of a low refractive index pigment is silica. The silicic acid may be silicic acid produced by a dry method, but silicic acid produced by a wet method (hereinafter referred to as wet-method silicic acid) is particularly effective. To explain this point, silicic acid is produced as amorphous silicic acid, and depending on the production method, it can be broadly divided into dry-method silicic acid (hereinafter referred to as dry-method silicic acid) which uses a gas-phase reaction such as thermal decomposition of silicon halide such as silicon tetrachloride, and wet-method silicic acid which uses a liquid-phase reaction such as decomposition with an acid such as sodium silicate. Dry-method silicic acid and wet-method silicic acid have different structures; the dry-method silicic acid forms a three-dimensional structure in which silicic acid is tightly bonded, while wet-method silicic acid has a so-called two-dimensional structure in which silicic acid is condensed to form a long molecular arrangement. Therefore, since the molecular structure is coarser than that of the dry process silica, when wet process silica is applied to a porous layer, it is presumed that the system has better diffused reflection of light in a dry state than a system using dry process silica, and therefore has greater hiding power in the normal state. Furthermore, since the porous layer is capable of absorbing water and liquids containing water, wet-process silica has more hydroxyl groups present as silanol groups on the particle surface than dry-process silica, and is therefore more hydrophilic, making it suitable for use. In order to adjust the hiding power of the porous layer in its normal state and the transparency in its liquid-absorbed state, other general-purpose low refractive index pigments may be used in combination with the wet-process silica.

[0011] The low refractive index pigment in the porous layer depends on properties such as particle size, specific surface area, and oil absorption, but in order to satisfy both hiding power in a normal state and transparency in a liquid-absorbed state, the coating amount is set to 1 to 30 g / m 2 It is preferable that the density is 5 to 20 g / m. 2 1g / m 2 If the density is less than 30 g / m, it is difficult to obtain sufficient hiding power under normal conditions. 2 If the thickness exceeds this value, it is difficult to obtain sufficient transparency when absorbing liquid. The low refractive index pigment is dispersed in a vehicle containing a binder resin as a binding agent, and after being applied to a support, the volatile components are dried to form a porous layer. Examples of the binder resin include urethane resins, nylon resins, vinyl acetate resins, acrylic ester resins, acrylic ester copolymer resins, acrylic polyol resins, vinyl chloride-vinyl acetate copolymer resins, maleic acid resins, polyester resins, styrene resins, styrene copolymer resins, polyethylene resins, polycarbonate resins, epoxy resins, styrene-butadiene copolymer resins, acrylonitrile-butadiene copolymer resins, methyl methacrylate-butadiene copolymer resins, butadiene resins, chloroprene resins, melamine resins, and emulsions of each of the above resins, casein, starch, cellulose derivatives, polyvinyl alcohol, urea resins, and phenolic resins. The mixing ratio of the low refractive index pigment to the binder resin depends on the type and properties of the low refractive index pigment, but is preferably 0.5 to 2 parts by mass, more preferably 0.8 to 1.5 parts by mass, of binder resin solids per part by mass of the low refractive index pigment. If the binder resin solids per part by mass of the low refractive index pigment is less than 0.5 parts by mass, it is difficult to obtain a practical coating strength for the porous layer, and if it exceeds 2 parts by mass, water penetration into the porous layer is impaired. The porous layer has a smaller binder resin to colorant ratio than a general coating film, making it difficult to obtain sufficient film strength. Therefore, in order to improve abrasion resistance, it is effective to use a nylon resin or a urethane resin among the binder resins. The urethane resins include polyester urethane resins, polycarbonate urethane resins, polyether urethane resins, etc., and two or more of them can be used in combination. Also usable are urethane emulsion resins in which the resins are emulsified and dispersed in water, and colloidal dispersion (ionomer) urethane resins in which the ionic urethane resin (urethane ionomer) itself emulsifies without the need for an emulsifier due to the ionic groups of the urethane resin itself, and is dissolved or dispersed in water. The urethane resin may be either an aqueous urethane resin or an oil-based urethane resin, but in the present invention, an aqueous urethane resin, particularly a urethane emulsion resin or a colloidal dispersion type urethane resin, is preferably used. The urethane-based resin can be used alone, or can be used in combination with other binder resins depending on the type of support and the performance required for the film. When a binder resin other than a urethane-based resin is used in combination, in order to obtain practical film strength, it is preferable that the urethane-based resin be contained in the binder resin of the porous layer in an amount of 30% or more in terms of solid mass ratio. Among the binder resins, if the binder resin is crosslinkable, the strength of the film can be further improved by adding an optional crosslinking agent to crosslink the binder resin. The binder resins have different affinities with water, and by combining these, it is possible to adjust the time and degree of penetration into the porous layer and the rate of drying after penetration. Furthermore, the adjustment can be controlled by adding a dispersant or surfactant as appropriate.

[0012] The porous layer can be formed on a support by preparing a liquid composition containing a low refractive index pigment and applying the composition to a printing method such as screen printing, offset printing, gravure printing, coater printing, pad printing, or transfer printing, or by brush coating, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, or dip coating. The porous layer may be in the form of a circle, oval, square, rectangle, or the like, or may be in the form of various letters, symbols, figures, patterns, or images of people, animals, plants, fruits, food products, vehicles, buildings, celestial bodies, or the like.

[0013] The water-soluble resin layer that is present in and coexists with the porous layer will now be described. Examples of the water-soluble resin contained in the water-soluble resin layer include polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol, water-soluble acrylic resin, water-soluble nylon resin, sodium alginate, propylene glycol alginate, gum arabic, casein, sodium caseinate, guar gum, gelatin, dextrin, starch, modified starch, reduced starch syrup, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethylhydroxyethyl cellulose, carboxymethyl ethyl cellulose, and other cellulose and cellulose derivatives and salts thereof.

[0014] When water adheres to the water-soluble resin layer, the water-soluble resin dissolves into the surrounding area, and the porous layer in the area where the water-soluble resin layer is provided changes from a highly translucent state in a non-liquid-absorbing state to a low translucency state due to the dissolution of the water-soluble resin, reducing the ability to see the underlying layer from the area where the water-soluble resin layer is provided.This state is maintained even when the porous layer returns to a non-liquid-absorbing state, making it possible to determine whether water has adhered to the porous layer in the past. Furthermore, the porous layer in the area where the water-soluble resin layer is not provided has the repeating function of concealing the underlying layer when in a non-liquid absorbing state, and becoming transparent when in a liquid absorbing state, allowing the underlying layer to be seen, making it possible to distinguish between a state where water is attached and a state where water is not attached. The water-soluble resin layer is excellent in storage stability in the initial state by using a resin that is in a solid state at 25°C, preferably at 30°C, and more preferably at 35°C. It is preferable to use a transparent resin as the resin used in the water-soluble resin layer, since it does not contaminate the surroundings or cause contamination due to the resin adhering thereto. The use of the water-soluble resin provides excellent elution and diffusibility upon contact with water, but the use of the water-soluble resin in combination with a water-insoluble resin can improve the preservation of the initial state under high humidity conditions. When the water-soluble resin and the water-insoluble resin are used in combination, the water-soluble resin and the water-insoluble resin are preferably used in a mass ratio of 95:5 to 10:90, more preferably 95:10 to 20:80. If the mass ratio of the water-soluble resin is low, it becomes difficult to visually recognize the change in state before and after water is applied, and the function as an indicator tends to be reduced.

[0015] The water-soluble resin layer is formed by preparing a liquid composition containing a water-soluble resin and using the same method as for forming the porous layer. The solvent for the liquid composition may be water, a mixture of water and a water-soluble organic solvent, or a solvent. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, and xylene, saturated hydrocarbons such as hexane, cyclohexane, and octane, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, halogenated hydrocarbons such as chloroform and trichloroethane, and petroleum solvents such as mineral spirits and petroleum ether. The liquid composition may contain, if necessary, a thickener, a dispersant, a pH adjuster, a preservative or antifungal agent, an antioxidant, and the like.

[0016] Examples of the water-soluble resin layer include various characters, symbols, figures, patterns, as well as shapes of people, animals, plants, fruits, food products, vehicles, buildings, celestial bodies, etc. The patterns may be independent discontinuous patterns such as polka dots, or partially connected continuous patterns such as a lattice pattern. The area ratio of the portion of the porous layer where the water-soluble resin layer is formed to the portion where the water-soluble resin layer is not formed is not particularly limited, but it is preferably 1 cm 2 By setting the ratio to 0.1:99.9 to 30:70, preferably 1:99 to 20:80 per unit area, a visually visible image of a suitable size can be provided over the entire surface of the porous layer, improving the texture of the water-colorable indicator in a dry state and allowing a clear visual change between the non-liquid absorbing state and the liquid absorbing state.

[0017] The water-color changing indicator has through-holes that communicate from the upper surface of the porous layer to the lower surface of the support. By providing the through holes, water adhering to the underside of the support efficiently adheres to the porous layer and the water-soluble resin layer through the through holes. Therefore, when water adheres to the porous layer, it becomes transparent, allowing the lower layer (support) to be seen, and when water adheres to the water-soluble resin layer, the effect of being able to see the lower layer (support) in a dry state is reduced, and this state is maintained even when the support becomes non-absorbent (dry). The through-hole may be a single hole, but it is preferable to provide a plurality of holes. When a plurality of through holes are provided, the area of ​​each through hole is 0.008 to 20 mm 2 , preferably 0.2 to 7 mm 2 , more preferably 0.8 to 7 mm 2 0.008mm 2 Less than or equal to 20mm 2 If the thickness exceeds this value, it becomes difficult to exhibit the function of allowing water to permeate through the through-holes. The area ratio of the through holes to the total area of ​​the porous layer and the water-soluble resin layer is 0.1 to 80%, preferably 0.5 to 70%, and more preferably 1 to 60%, so that both the water permeability function and the discoloration function of the porous layer and the water-soluble resin layer can be satisfied. Furthermore, the area ratio of the through holes to the total area of ​​the porous layer in the areas where the water-soluble resin layer is not provided is 0.1 to 80%, preferably 0.5 to 70%, more preferably 1 to 60%, and the area ratio of the through holes to the total area of ​​the porous layer in the areas where the water-soluble resin layer is provided is 0.1 to 80%, preferably 0.5 to 70%, more preferably 1 to 60%, thereby achieving both water permeability and a clear discoloration function of the porous layer and the water-soluble resin layer. In addition, the porous layer and the water-soluble resin layer may be measured at any position within 1 cm 2 When the area ratio of the through holes to the total area of ​​the four sides is 1 to 50%, preferably 2 to 40%, and more preferably 3 to 30%, good water permeability and color-changing properties of the porous layer and the water-soluble resin layer can be exhibited. If it is less than 1%, the water permeability is poor and it is difficult to exhibit the function as an indicator, and if it exceeds 50%, the areas of the porous layer and the water-soluble resin layer become so small that it is difficult to visually recognize the change in appearance. The color-changing function becomes poor. The through holes are preferably formed in the areas where the porous layer is provided and in the areas where the water-soluble resin layer is provided, because this allows the function of determining whether water has adhered in the past to be realized, and at the same time, the function of determining whether water is currently adhered can be realized efficiently. The shape of the through holes is not particularly limited, and examples thereof include circles, ellipses, polygons such as triangles and rectangles, various shapes such as stars, and various geometric patterns.

[0018] Under the support on which the porous layer and water-soluble resin layer are provided, a porous layer in which the same low refractive index pigment as above is dispersed and fixed in a binder resin, and which is opaque in a non-liquid-absorbing state and becomes transparent in a liquid-absorbing state, and a water-soluble resin layer is provided within a part of the porous layer and coexists therewith, and in a non-liquid-absorbing state, the porous layer in the part where the water-soluble resin layer is provided has higher light transmittance than the porous layer in the part where the water-soluble resin layer is not provided, and by providing through holes that connect from the upper surface of the porous layer on the support to the lower surface of the porous layer below the support, it is possible to obtain an indicator that can determine from both the front and back whether water has previously adhered to the indicator, and that has the function of determining whether water is currently adhered to the indicator. The water-color changing indicator can be easily adhered to an object by providing an adhesive layer as the bottom layer. The adhesive layer has through holes that connect the upper surface of the porous layer to the lower surface of the adhesive layer, so that water adhering to the lower surface of the adhesive layer efficiently adheres to the porous layer and the water-soluble resin layer through the through holes. The adhesive layer is formed from an adhesive mainly composed of a general-purpose acrylic resin, a urethane resin, a styrene-butadiene copolymer, a vinyl ether copolymer, natural rubber, etc., and by using a water-insoluble resin, it is possible to obtain an indicator that is less likely to come off due to water adhesion when attached to an object and can be firmly attached. Furthermore, the indicator can be easily peeled off from the object (removable) and can be re-adhered to the object (re-adhesive), thereby satisfying the practicality of repeated use. Furthermore, a release layer such as release paper may be provided on the surface of the adhesive layer (underside of the adhesive layer) for convenience during use.

[0019] The water-discoloring indicator can be produced by forming a porous layer and a water-soluble resin layer on a support by printing or the like, and if necessary, forming an adhesive layer, or an adhesive layer and a release layer, on the side of the support opposite to the side on which the porous layer and water-soluble resin layer are formed, and then drilling a hole that penetrates from the top surface of the porous layer to the bottom layer. The water-color changing indicator can also be produced by drilling holes that extend from the support side to the porous layer.

[0020] The water-coloring indicator can be attached to an article, cut to the desired size and shape and attached to an article, or can be used in practical use as a tape by wrapping the water-coloring indicator around the surface of a core made of paper or the like. By making it into the tape form, it is easy to carry, there is no need to provide a release layer, which promotes resource conservation, and it can be cut to an appropriate size and attached depending on the length of the object, making it suitable for use on items of various shapes and sizes.

[0021] The water-colorable indicator can be attached to objects such as pipes, plumbing, and tanks to detect water leaks, as well as to detect wetness of beverages such as juice, wetness of electronic devices, liquid leaks, and urine in disposable diapers. [Example]

[0022] Examples of the present invention will be described below. In the examples, "parts" means "parts by mass." Example 1 (see Figure 1) A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to print solid images on the entire surface of a blue polyethylene terephthalate film used as a support 2 using a 100-mesh screen. The ink was then dried and cured at 60°C for 30 minutes to form a porous layer 3. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 50.0 parts of polyvinylpyrrolidone resin (trade name: Sokalan K-17, manufactured by BASF) and 50.0 parts of water, and the ink was dried and cured at 50°C for 30 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 0.03 mm 2 5cm circular through hole 2 478 pieces were placed per unit to obtain water-color changing indicator 1. In addition, 1 cm at any position in the porous layer 2 The area occupied by the through holes was 15% of the total area.

[0023] When the back surface (underside of the support) of the water-discoloring indicator was attached to a pipe and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a blue dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the support through the through holes, the polyvinylpyrrolidone resin is dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the blue color of the support to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color because the polyvinylpyrrolidone resin has dissolved and diffused into the porous layer, and since the appearance is different from before water is attached, it is possible to determine that water has been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the blue color was visible, and the state of water attachment could be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0024] Example 2 (see Figure 1) A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to print solidly on the entire surface of a red polyethylene film used as a support 2 using a 100-mesh screen. The ink was then dried and cured at 130°C for 5 minutes to form a porous layer 3. Next, a dot pattern with a diameter of 3 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 50.0 parts of polyethylene glycol resin (trade name: PEG4000, manufactured by Sanyo Chemical Industries, Ltd.) and 50.0 parts of water, and the print was dried and cured at 100°C for 5 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 0.07 mm 2 oval through hole 5 x 1cm 2 142 pieces were placed per unit to obtain water-color changing indicators. In addition, 1 cm at any position in the porous layer 2 The area occupied by the through holes was 10% of the total area on all four sides.

[0025] When the back surface (underside of the support) of the water-discoloring indicator was fixed to the joint of a pipe using a cable tie and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a red dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the support through the through holes, the polyethylene glycol resin of the water-soluble resin layer dissolves into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the red color of the support to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the polyethylene glycol resin dissolves into the porous layer and diffuses, causing the dot pattern to disappear or become lighter in color and become visible.Since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the red color was visually recognized, and the state of water attachment could be visually recognized repeatedly. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0026] Example 3 (see Figure 1) A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to print solidly on the entire surface of a green polyethylene terephthalate film used as a support 2 using a 100-mesh screen. The ink was then dried and cured at 130°C for 5 minutes to form a porous layer 3. Next, a dot pattern with a diameter of 5 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 25.0 parts of polyvinylpyrrolidone resin (trade name: Sokaran K-17, manufactured by BASF), 55.6 parts of acrylic ester resin emulsion (trade name: Movinyl 966A, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solids content 45%), and 19.4 parts of water. The ink was then dried and cured at 100°C for 5 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 0.2 mm 2 Square through hole 5cm x 1cm 2 51 pieces were placed per unit to obtain water-color changing indicators. In addition, 1 cm at any position in the porous layer 2 The area occupied by the through holes was 10% of the total area on all four sides.

[0027] When the back surface (underside of the support) of the water-discoloring indicator was attached to the seat of a chair and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a green dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the support through the through-holes, the polyvinylpyrrolidone resin of the water-soluble resin layer is dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the green color of the support to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color because the polyvinylpyrrolidone resin has dissolved and diffused into the porous layer, and since the appearance is different from before water is attached, it is possible to determine that water has been attached in the past. When water was again attached to the water-colorable indicator, the porous layer became transparent due to liquid absorption, and the green color of the support was visible, and the state of water attachment could be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0028] Example 4 (see Figure 2) A colored layer 6 was formed on the surface of a polyethylene terephthalate film used as the support 2 by solid printing using blue printing ink. Next, on the colored layer, a screen printing ink consisting of a mixture of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to perform solid printing over the entire surface using a 100-mesh screen, and the ink was dried and cured at 130°C for 5 minutes to form a porous layer 3. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 50.0 parts of polyethylene glycol resin (trade name: PEG4000, manufactured by Sanyo Chemical Industries, Ltd.), 11.1 parts of acrylic ester resin emulsion (trade name: Movinyl 966A, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content 45%), and 38.9 parts of water. The ink was then dried and cured at 100°C for 5 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 0.008 mm 2 Heart-shaped through hole 5cm x 1cm 2 383 pieces were placed per unit to obtain water-color changing indicators. In addition, 1 cm at any position in the porous layer 2 The area occupied by the through holes was 3% of the total area.

[0029] When the back surface (underside of the support) of the water-discoloring indicator was fixed to the joint of a pipe using a cable tie and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a blue dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the support through the through holes, the polyethylene glycol resin of the water-soluble resin layer dissolves into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the blue color of the colored layer to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the polyethylene glycol resin dissolves into the porous layer and diffuses, causing the dot pattern to disappear or become lighter in color and become visible.Since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer became transparent due to liquid absorption, and the blue color of the colored layer became visible, allowing the state of water attachment to be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0030] Example 5 A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to print solid images on the surface of a blue polyethylene terephthalate film support using a 100-mesh screen. The ink was then dried and cured at 130°C for 5 minutes to form a porous layer. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 25.0 parts of polyvinylpyrrolidone resin (trade name: Sokalan K-17, manufactured by BASF), 25.0 parts of polyethylene glycol resin (trade name: PEG4000, manufactured by Sanyo Chemical Industries, Ltd.), and 50.0 parts of water. The ink was then dried and cured at 100°C for 5 minutes to form a translucent water-soluble resin layer embedded in part of the porous layer. Next, a water-insoluble adhesive layer made of an acrylic resin was provided on the back surface of the support. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the adhesive layer is 1.8 mm 2 A circular through hole of 1cm 2 Three pieces were placed per unit to obtain water-color changing indicators. In addition, 1 cm at any position in the porous layer 2 The area ratio of the through holes to the total area on all four sides was 5.3%.

[0031] When the adhesive layer side of the water-discoloring indicator was attached to a pipe joint and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a blue dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the adhesive layer through the through holes, the polyvinylpyrrolidone resin and polyethylene glycol resin of the water-soluble resin layer are dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the blue color of the support to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color and becomes visible because the polyvinylpyrrolidone resin and polyethylene glycol resin have dissolved and diffused into the porous layer, and since the appearance is different from before water is attached, it is possible to determine that water has been attached in the past. When water was again attached to the water-colorable indicator, the porous layer became transparent due to liquid absorption, and the blue color of the colored layer became visible, allowing the state of water attachment to be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0032] Example 6 (see Figure 3) A colored layer 6 was formed on the surface of a polyethylene terephthalate film used as the support 2 by solid printing using red printing ink. Next, the colored layer was solid-printed over the entire surface with a screen printing ink composed of a mixture of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent, and the ink was dried and cured at 80°C for 5 minutes to form a porous layer 3. Next, a grid pattern was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 30 parts of polyvinyl alcohol resin (trade name: Gohsenol KL-03, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 70 parts of water, and the resulting ink was dried and cured at 60°C for 30 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. Next, a water-insoluble adhesive layer 7 made of an acrylic resin was provided on the back surface of the support. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the adhesive layer is 0.8 mm 2 5cm circular through hole 2 Thirteen pieces were placed per box to obtain water-color changing indicators. In addition, 1 cm at any position in the porous layer 2 The area ratio of the through holes to the total area on all four sides was 10.2%.

[0033] When the back surface (underside of the adhesive layer) of the water-discoloring indicator was attached to a mobile phone for practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, revealing a red checkered pattern. However, when water adhered to the water-soluble resin layer from the underside of the adhesive layer through the through-holes, the polyvinyl alcohol resin of the water-soluble resin layer dissolved into the surrounding area, and the porous layer became transparent due to liquid absorption, revealing the red color of the colored layer in the areas where water had adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the checkered pattern disappears or becomes lighter in color because the polyvinyl alcohol resin has dissolved and diffused into the porous layer, and since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the red color was visually recognized, and the state of water attachment could be visually recognized repeatedly. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0034] Example 7 A blue water-resistant screen printing ink was solid-printed on the entire surface of a white synthetic paper substrate to form a colored layer. Next, a screen printing ink composed of a mixture of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was solid-printed on the entire surface of the colored layer, and the mixture was dried and cured at 80°C for 5 minutes to form a porous layer. Next, a star pattern was printed on the porous layer using an 80-mesh screen printing ink containing 25.0 parts of hydroxypropyl cellulose resin (trade name: HPC-L, manufactured by Nippon Soda Co., Ltd.) and 75.0 parts of water, and the resulting ink was dried and cured at 60°C for 30 minutes to form a translucent water-soluble resin layer embedded in part of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 3.1 mm 2 A circular through hole of 1cm 2 Two indicators were placed per unit to obtain water-color-changing indicators. In addition, 1 cm at any position in the porous layer 2 The area ratio of the through holes to the total area on all four sides was 6.3%.

[0035] When the back surface (underside of the support) of the water-discoloring indicator was attached to a pipe and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was observed, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a blue star pattern being visible.However, when water adheres to the water-soluble resin layer from the underside of the support through the through holes, the hydroxypropyl cellulose resin of the water-soluble resin layer is dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the blue color of the colored layer to be visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the star pattern disappears or becomes lighter in color because the hydroxypropyl cellulose resin has dissolved and diffused into the porous layer, and since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the blue color was visible, and the state of water attachment could be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0036] Example 8 A water-resistant and water-permeable heart-patterned colored layer was formed on the surface of a white polyethylene terephthalate film support using blue printing ink. Then, a screen printing ink consisting of 15 parts wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts water, 0.5 parts silicone antifoaming agent, 3 parts thickener for water-based inks, 1 part ethylene glycol, and 3 parts isocyanate crosslinking agent was used to print the entire surface of the colored layer using a 100-mesh screen. The ink was then dried and cured at 130°C for 5 minutes to form a porous layer. Next, a star pattern was printed on the porous layer using a 100-mesh screen printing ink containing 25.0 parts of polyvinylpyrrolidone resin (trade name: Sokalan K-17, manufactured by BASF), 55.6 parts of acrylic ester resin emulsion (trade name: Movinyl 966A, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solids content 45%), and 19.4 parts of water, so that the star pattern was positioned above the heart pattern of the colored layer.The star pattern was then dried and cured at 110°C for 5 minutes to form a translucent water-soluble resin layer embedded in part of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 12.6 mm 2 A circular through hole of 1cm 2 One water-color indicator was provided per sample. In addition, 1 cm at any position in the porous layer 2 The area ratio of the through holes to the total area on all four sides was 12.6%.

[0037] When the back surface (support surface) of the water-discoloring indicator was attached to a disposable diaper for practical use, in the normal state (non-water-absorbent state), the porous layer was white, and the transparent resin layer partially embedded in the porous layer made the porous layer transparent, revealing a blue star pattern. However, when urine adheres to the water-soluble resin layer from the underside of the support through the through holes, the polyvinylpyrrolidone resin of the water-soluble resin layer is dissolved into the surrounding area, and the porous layer absorbs the liquid and becomes transparent, revealing a blue heart pattern in the area where the urine has adhered. The indicator shows the above appearance when urine is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the polyethylene glycol resin dissolves into the porous layer and diffuses, causing the star pattern to disappear or become lighter in color and become visible.Since the appearance is different from before urine was attached, it was possible to determine that urine had been attached in the past. When urine adheres to the back side of the water-colorable indicator again, the porous layer becomes transparent due to liquid absorption, and a blue heart pattern becomes visible. The state of urine adhesion can be repeatedly visually confirmed, making it useful as an indicator for detecting the presence or absence of urine leakage. Furthermore, even if a large amount of urine adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0038] Example 9 A colored layer was formed on the surface of a polyethylene terephthalate film support by solid printing using red printing ink. Next, the colored layer was solid-printed over the entire surface with a screen printing ink composed of a mixture of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent, and the resulting ink was dried and cured at 80°C for 5 minutes to form a porous layer. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 30 parts of polyvinyl alcohol resin (trade name: Gohsenol KL-03, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 70 parts of water, and the ink was dried and cured at 60°C for 30 minutes to form a water-soluble resin layer with translucency that was embedded in part of the porous layer. Next, a water-insoluble adhesive layer made of an acrylic resin was provided on the back surface of the support, and a release paper (releasing layer) was provided on the lower surface of the water-insoluble adhesive layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the release paper is 2 mm 2A single rectangular (0.1 mm x 20 mm) through-hole was drilled to obtain a water-color changing indicator. The area ratio of the through holes to the total area of ​​the porous layer and the water-soluble resin layer was 0.2%.

[0039] After peeling the release paper from the water-discoloring indicator, the underside of the adhesive layer was attached to a pipe joint for practical use. In the normal state (non-water-absorbing state), the porous layer was white, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, revealing a red dot pattern. However, when water adheres to the water-soluble resin layer from the underside of the adhesive layer through the through holes, the polyvinyl alcohol resin of the water-soluble resin layer is dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, revealing the red color of the colored layer in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color because the polyvinyl alcohol resin has dissolved and diffused into the porous layer, and since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the red color was visually recognized, and the state of water attachment could be visually recognized repeatedly. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0040] Example 10 A colored layer was formed on the surface of a polyethylene terephthalate film support by solid printing using red printing ink. Next, the colored layer was solid-printed over the entire surface with a screen printing ink composed of a mixture of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent, and the resulting ink was dried and cured at 80°C for 5 minutes to form a porous layer. Next, a grid pattern was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 30 parts of polyvinyl alcohol resin (trade name: Gohsenol KL-03, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 70 parts of water, and the resulting ink was dried and cured at 60°C for 30 minutes to form a translucent water-soluble resin layer embedded in part of the porous layer. Next, a water-insoluble adhesive layer made of an acrylic resin was provided on the back surface of the support, and a release paper (releasing layer) was provided on the lower surface of the water-insoluble adhesive layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the release paper is 3 mm 2 A water-color changing indicator was obtained by drilling 100 circular through-holes of 100 mm in diameter. The area ratio of the through holes to the total area of ​​the porous layer and the water-soluble resin layer was 75%.

[0041] After peeling the release paper from the water-discoloring indicator, the underside of the adhesive layer was attached to the seat of a chair for practical use. In the normal state (non-water-absorbing state), the porous layer was white, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, revealing a red lattice pattern. However, when water adhered to the water-soluble resin layer from the underside of the adhesive layer through the through-holes, the polyvinyl alcohol resin of the water-soluble resin layer dissolved into the surrounding area, and the porous layer became transparent due to liquid absorption, revealing the red color of the colored layer in the areas where water had adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the grid pattern disappears or becomes lighter in color because the polyvinyl alcohol resin has dissolved and diffused into the porous layer, and since the appearance is different from before water was attached, it was possible to determine that water had been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the red color was visually recognized, and the state of water attachment could be visually recognized repeatedly. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0042] Example 11 A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solids content 30%), 40 parts of water, 0.5 parts of silicone-based antifoaming agent, 3 parts of thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of isocyanate-based crosslinking agent was used to print solid images on the surface of a blue polyethylene terephthalate film support using a 100-mesh screen. The ink was then dried and cured at 60°C for 30 minutes to form a porous layer. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 50.0 parts of polyvinylpyrrolidone resin (trade name: Sokalan K-17, manufactured by BASF) and 50.0 parts of water, and the ink was dried and cured at 50°C for 30 minutes to form a translucent water-soluble resin layer contained within a portion of the porous layer. The area of ​​the holes from the upper surface of the porous layer and the water-soluble resin layer to the lower surface of the support is 0.03 mm 2 A circular through hole of 1cm 2 A total of 478 water-color indicators were prepared. In addition, 1 cm at any position in the porous layer 2The area ratio of the through holes to the four sides was 15%, the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was not provided was 12%, and the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was provided was 30%.

[0043] When the back surface (underside of the support) of the water-discoloring indicator was attached to a pipe and put into practical use, in the normal state (non-water-absorbing state), the white color of the porous layer was visible, and the transparent resin layer partially contained within the porous layer made the porous layer transparent, resulting in a blue dot pattern.However, when water adheres to the water-soluble resin layer from the underside of the support through the through holes, the polyvinylpyrrolidone resin is dissolved into the surrounding area, and the porous layer becomes transparent due to liquid absorption, allowing the blue color of the support to be clearly visible in the areas where water has adhered. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color because the polyvinylpyrrolidone resin has dissolved and diffused into the porous layer, and since the appearance is different from before water is attached, it is possible to determine that water has been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the blue color was visible, and the state of water attachment could be repeatedly visually confirmed. Furthermore, even if a large amount of water adhered to the indicator and flowed out around it, the water-soluble resin was transparent and did not become dirty.

[0044] Example 12 (see Figure 4) A screen printing ink composed of 15 parts of wet-process fine particle silica (trade name: Nipsil E-220, manufactured by Nippon Silica Kogyo Co., Ltd.), 45 parts of urethane emulsion (trade name: Hydran AP-10, manufactured by Dainippon Ink and Chemicals, Inc., solid content 30%), 40 parts of water, 0.5 parts of a silicone-based antifoaming agent, 3 parts of a thickener for water-based inks, 1 part of ethylene glycol, and 3 parts of an isocyanate-based crosslinking agent was used to print solid images on the entire surface of a blue polyethylene terephthalate film used as a support 2 using a 100-mesh screen. The ink was then dried and cured at 60°C for 30 minutes to form a porous layer 3. Next, a dot pattern with a diameter of 2 mm was printed on the porous layer using a 100-mesh screen with a screen printing ink containing 50.0 parts of polyvinylpyrrolidone resin (trade name: Sokalan K-17, manufactured by BASF) and 50.0 parts of water, and the ink was dried and cured at 50°C for 30 minutes to form a water-soluble resin layer 4 having translucency and contained within a portion of the porous layer. Next, the same porous layer 3 and water-soluble resin layer 4 as above were formed on the back surface of the support. The area of ​​the holes is 0.03 mm from the upper surface of the porous layer and the water-soluble resin layer on the support to the lower surface of the porous layer and the water-soluble resin layer under the support. 2 5cm circular through hole 2 478 pieces were placed per unit to obtain water-color changing indicator 1. In addition, the surface porous layer is 2 The area ratio of the through holes to the four sides was 15%, the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was not provided was 12%, and the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was provided was 30%. The area ratio of the through holes on the back surface, the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was not provided, and the area ratio of the through holes to the total area of ​​the porous layer in areas where the water-soluble resin layer was provided were similar to those on the front surface.

[0045] When the water-discoloring indicator was placed closely to the side of the inside of a transparent case and put into practical use, in its normal state (non-water-absorbing state), the white color was due to the porous layer, and the transparent resin layer partially embedded in the porous layer made the porous layer transparent, resulting in a blue dot pattern that could be seen from the outside and inside of the case. When a beverage container is placed inside the case and water leaks from the container and adheres to the water-soluble resin layer on the inside, the polyvinylpyrrolidone resin dissolves into the surrounding area, the porous layer absorbs the liquid and becomes transparent, and the blue color of the support is clearly visible in the areas where water has adhered. Furthermore, when water adhered to the water-soluble resin layer on the outer surface through the through holes, the polyvinylpyrrolidone resin dissolved into the surrounding area, and the porous layer became transparent by absorbing the liquid, so that the blue color of the support was clearly visible in the areas where water was adhered, and this state could be seen from the inside and outside of the case. The indicator shows the above appearance when water is attached, but when the porous layer dries, it returns to its original white state, and in the water-soluble resin layer in the area where water is attached, the dot pattern disappears or becomes lighter in color because the polyvinylpyrrolidone resin has dissolved and diffused into the porous layer, and since the appearance is different from before water is attached, it is possible to determine that water has been attached in the past. When water was again attached to the water-colorable indicator, the porous layer absorbed the liquid and became transparent, and the blue color was visible, and the state of water attachment could be repeatedly visually confirmed. Furthermore, even if a large amount of water adheres to the indicator and flows out around it, the inside of the case does not get dirty because the water-soluble resin is transparent. [Explanation of symbols]

[0046] 1. Water color indicator 2 Support 3 Porous layer 4 Water-soluble resin layer 5 through holes 6 Colored layer 7 Adhesive layer

Claims

1. A water-colorable indicator comprising a support, a porous layer on which a low refractive index pigment is dispersed and fixed in a binder resin, the porous layer being opaque in a non-liquid-absorbing state and becoming transparent in a liquid-absorbing state, and a water-soluble resin layer coexisting within a portion of the porous layer, the porous layer in the portion where the water-soluble resin layer is provided being more translucent in the non-liquid-absorbing state than the porous layer in the portion where the water-soluble resin layer is not provided, and a through hole communicating from the upper surface of the porous layer to the lower surface of the support.

2. A plurality of the through holes are provided, and the area of ​​each through hole is 0.008 to 20 mm ２ 2. The water-color changing indicator according to claim 1, wherein

3. 3. The water-colorable indicator according to claim 1, wherein the ratio of the area occupied by the through-holes to the total area of ​​the porous layer and the water-soluble resin layer is 0.1 to 80%.

4. 1 cm at any position of the porous layer and the water-soluble resin layer ２ 3. The water-color-changing indicator according to claim 1, wherein the area occupied by the through holes is 1 to 50% of the total area of ​​the four sides.

5. 3. The water-colorable indicator according to claim 1, wherein the porous layer and the water-soluble resin layer have through-holes.

6. A water-color indicator according to claim 1 or 2, wherein the area occupied by the through holes is 0.1 to 80% of the total area of ​​the porous layer in areas where the water-soluble resin layer is not provided, and the area occupied by the through holes is 0.1 to 80% of the total area of ​​the porous layer in areas where the water-soluble resin layer is provided.

7. 3. The water-colorable indicator according to claim 1, wherein the support is made of a water-impermeable material.

8. A water-color indicator as described in claim 1 or 2, which comprises a porous layer under the support, in which a low refractive index pigment is dispersed and fixed in a binder resin, and which is opaque in a non-liquid-absorbing state and becomes transparent in a liquid-absorbing state, and a water-soluble resin layer which is present within a part of the porous layer and coexists with the porous layer, and in which the porous layer in the part where the water-soluble resin layer is provided in a non-liquid-absorbing state has higher light translucency than the porous layer in the part where the water-soluble resin layer is not provided, and which has a through hole connecting from the upper surface of the porous layer on the support to the lower surface of the porous layer below the support.

9. 3. The water-color indicator according to claim 1, wherein an adhesive layer is provided as the bottom layer, and through-holes are provided that communicate from the upper surface of the porous layer to the lower surface of the adhesive layer.

10. 10. The water-colorable indicator according to claim 9, wherein the adhesive layer is formed from a water-insoluble resin.

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