Water-based ink composition for oxygen detection and oxygen detection agent using same

Abstract

The present invention provides a water-based ink composition for oxygen detection having excellent visibility and color-change responsiveness, and an oxygen detection agent using the same. A water-based ink composition for oxygen detection according to the present invention contains a first dye that reversibly changes in color tone between an oxidized state and a reduced state, a reducing agent, a magnesium compound, granulated silica, and a binder component. The water-based ink composition for oxygen detection according to the present invention preferably further contains sodium carbonate. An oxygen detection agent according to the present invention comprises a base material and an oxygen detection layer formed on the base material and containing the water-based ink composition for oxygen detection.

Description

Aqueous ink composition for oxygen detection and oxygen indicator using the same

[0001] The present invention relates to an aqueous ink composition for oxygen detection that allows changes in the amount of oxygen in an atmosphere to be visually indicated by a change in color, and an oxygen indicator using the same.

[0002] When storing food, pharmaceuticals, and other similar products, oxygen in the surrounding atmosphere oxidizes them, degrading their quality. Therefore, to prevent quality deterioration during storage, food and pharmaceuticals are placed in containers or packaging with an oxygen absorber and sealed. The oxygen absorber absorbs the oxygen inside the container or packaging, preserving the food and pharmaceuticals in an oxygen-free state (referring to a state with an oxygen concentration of 0.1% or less).

[0003] In recent years, it has become common practice to enclose an oxygen indicator along with an oxygen absorber inside containers and packaging, allowing for the detection of oxygen presence or absence within the container. The oxygen indicator makes it possible to visually confirm the presence or absence of oxygen inside the sealed container by changing its color. Users can easily confirm whether food, pharmaceuticals, etc., are stored in an oxygen-free state based on the color change exhibited by the oxygen indicator.

[0004] This type of oxygen indicator generally consists of a reducing agent, a basic substance, and a redox dye that exhibits different colors in oxidized and reduced states. The reducing agent is used to maintain the redox dye in a reduced state when the atmosphere is deoxygenated. In this way, oxygen indicators detect oxygen by utilizing the mechanism in which the redox dye, maintained in a reduced state, is oxidized by oxygen in the atmosphere, causing a change in color.

[0005] Patent Document 1 describes an oxygen indicator comprising an aqueous solution of an oxygen indicator containing reducing sugars, a basic substance, and a redox dye that is reduced by the reducing sugars, supported on a carrier, characterized in that the reducing sugars include a monosaccharide as a first component and a reducing trisaccharide as a second component. Patent Document 2 describes an ink composition for an oxygen indicator, characterized in that it comprises synthetic silica supporting an aqueous solution of an oxygen indicator containing reducing sugars, an alkali metal compound, and a redox dye that is reduced by the reducing sugars, and an aqueous resin solution, and an oxygen indicator characterized by being formed by printing this ink composition for an oxygen indicator onto a printing medium. Patent Document 3 describes an oxygen indicator, characterized in that a binder layer containing magnesium hydroxide and a binder, and an oxygen detection layer containing a redox dye that changes color depending on the presence or absence of oxygen in the atmosphere are laminated on a substrate in that order from the substrate side.

[0006] Japanese Patent Publication No. 2011-95020, Japanese Patent Publication No. 2012-207059, Japanese Patent Publication No. 2018-128391

[0007] The oxygen indicators described in Patent Documents 1 to 3 did not always exhibit sufficient visibility of color changes and color change responsiveness in response to changes in the amount of oxygen in the atmosphere. Furthermore, there were limited aqueous ink compositions for oxygen detection that could be coated or printed on the surface of hydrophobic resin substrates, and there was a need for the development of an aqueous ink composition for oxygen detection with excellent visibility and color change responsiveness.

[0008] Therefore, the present invention aims to provide an aqueous ink composition for oxygen detection that has excellent visibility and color change responsiveness, and an oxygen detection agent using the same.

[0009] As a result of diligent research into the above-mentioned problems, the present inventors have found that by including a first dye whose color tone reversibly changes between oxidation and reduction states, a reducing agent, a magnesium compound, granulated silica, and a binder component, an aqueous ink composition for oxygen detection with excellent visibility and color change responsiveness can be obtained.

[0010] In other words, the present invention provides an aqueous ink composition for oxygen detection comprising a first dye whose color tone reversibly changes between an oxidized state and a reduced state, a reducing agent, a magnesium compound, granulated silica, and a binder component.

[0011] In the water-based ink composition for oxygen detection according to the present invention, the granulated silica volume average particle size D ５０ However, it is preferable that the particle size is between 3 μm and 30 μm.

[0012] In the water-based ink composition for oxygen detection according to the present invention, the BET specific surface area of ​​the granulated silica is 100 m². ２ / g or more 500m ２ It is preferable that the amount is less than or equal to / g.

[0013] In the water-based ink composition for oxygen detection according to the present invention, it is preferable that the peak pore size of the granulated silica is 0.1 μm or more and 1.0 μm or less.

[0014] In the water-based ink composition for oxygen detection according to the present invention, the magnesium compound is preferably magnesium hydroxide.

[0015] In the water-based ink composition for oxygen detection according to the present invention, the reducing agent is preferably a reducing sugar. More preferably, the reducing sugar is D-mannose, D-glucose, D-fructose, D-erythrose, or D-althrose.

[0016] In the water-based ink composition for oxygen detection according to the present invention, the binder component is preferably polyvinyl alcohol.

[0017] The water-based ink composition for oxygen detection according to the present invention preferably further contains a second dye different from the first dye.

[0018] The water-based ink composition for oxygen detection according to the present invention preferably further contains sodium carbonate.

[0019] Furthermore, the present invention provides an oxygen detection agent having a substrate and an oxygen detection layer formed on the substrate, the oxygen detection agent comprising the aforementioned water-based ink composition for oxygen detection.

[0020] In the oxygen indicator according to the present invention, the material of the base material is preferably a polyolefin, a halogenated polyolefin, a vinyl carboxylate polymer, an aromatic vinyl polymer, a polyester, or a polyamide.

[0021] In the oxygen indicator according to the present invention, the oxygen permeability coefficient of the base material is 1×10 －１５ cm ３ (STP) cm / (cm ２ ·s·Pa) or more.

[0022] In the oxygen indicator according to the present invention, the thickness of the oxygen sensing layer is preferably 3 μm or more and 100 μm or less.

[0023] The oxygen indicator according to the present invention preferably further has a protective layer covering the oxygen sensing layer.

[0024] According to the present invention, it is possible to provide an aqueous ink composition for oxygen sensing that is excellent in visibility and color change responsiveness, and an oxygen indicator using the same.

[0025] These are diagrams showing the configuration of the oxygen indicator according to one embodiment of the present invention, where (a) is a schematic plan view and (b) is a schematic cross-sectional view. These are diagrams showing the configuration of the oxygen indicator according to one embodiment of the present invention, where (a) is a schematic plan view and (b) is a schematic cross-sectional view. This is a schematic plan view showing the configuration of the oxygen indicator according to one embodiment of the present invention.

[0026] Hereinafter, preferred embodiments of the aqueous ink composition for oxygen sensing and the oxygen indicator using the same according to the present invention will be described.

[0027] 1. Aqueous Ink Composition for Oxygen Sensing The aqueous ink composition for oxygen sensing according to one embodiment of the present invention includes a first dye that reversibly changes color tone between an oxidized state and a reduced state, a reducing agent, a magnesium compound, granulated silica, and a binder component. It is preferable that the aqueous ink composition for oxygen sensing further contains a second dye that does not change color tone between the oxidized state and the reduced state. Such an aqueous ink composition for oxygen sensing makes it possible to detect the presence or absence of oxygen in the atmosphere and changes in the amount thereof, as the first dye changes its color tone in response to changes in the amount of oxygen in the atmosphere, and is particularly excellent in visibility and color change responsiveness.

[0028] (1) Pigments (First pigment, second pigment) The first pigment is a component (redox pigment) that reversibly changes its color tone between the oxidized and reduced states. That is, when oxygen comes into contact with the first pigment in the reduced state, the first pigment becomes oxidized and its color tone changes. Therefore, the presence or absence of oxygen in the atmosphere and changes in its amount can be detected by the change in color tone. Specific examples of the first pigment include methylene blue, new methylene blue, phenosafranin, Rouss violet, and methylene green. For example, methylene blue is colorless in the reduced state (leucomethylene blue) and blue in the oxidized state.

[0029] The amount of the first dye used is not particularly limited as long as it is within a range that can detect a change in the color tone of the water-based ink composition for oxygen detection containing the first dye. However, it is preferably 0.01% by weight or more and 0.10% by weight or less, and more preferably 0.02% by weight or more and 0.07% by weight or less, based on 100% by weight of the water-based ink composition for oxygen detection.

[0030] In particular, when a colorless dye such as methylene blue is used as the first dye, it is preferable to use a second dye different from the first dye in combination to make it easier to determine the change in color tone. Specific examples of the second dye include food coloring, safranin T, and phenosafranin. These are all red dyes and components whose color tone does not change between the oxidized and reduced states.

[0031] When using the second dye, there are no particular restrictions on the amount used, as long as it is within a range that makes it easy to detect changes in the color tone of the water-based ink composition for oxygen detection containing the first dye. However, generally, the amount used should be less than the amount used for the first dye, preferably 0.0005% by weight or more and 0.0050% by weight or less, and more preferably 0.0010% by weight or more and 0.0030% by weight or less, based on 100% by weight of the water-based ink composition for oxygen detection.

[0032] For example, if methylene blue is used as the first dye and a red dye is used as the second dye, the water-based ink composition for oxygen detection will change color as follows. First, in an oxygen-free atmosphere, methylene blue is reduced to a reduced state (leucomethylene blue) by a reducing agent described later and is colorless. At this time, the water-based ink composition for oxygen detection will be red due to the second dye. On the other hand, in an oxygenated atmosphere, methylene blue becomes oxidized and turns blue, so the water-based ink composition for oxygen detection will be purple to blue. Thus, when using a first dye that is colorless in the reduced state, adding a second dye to the water-based ink composition for oxygen detection in addition to the first dye makes the change in color of the water-based ink composition in response to changes in the amount of oxygen in the atmosphere more vivid and makes it easier to judge the change in color.

[0033] (2) Reducing agent The reducing agent is a component for maintaining the first dye in a reduced state in an oxygen-free atmosphere. For example, reducing sugars can be used as the reducing agent. Specific examples of reducing sugars include reducing monosaccharides such as D-mannose, D-glucose, D-fructose, D-erythrose, and D-althrose; reducing disaccharides such as maltose and lactose; and reducing trisaccharides such as maltotriose, cerotriose, manninotriose, and vanose. Among these, reducing monosaccharides are particularly preferred from the viewpoint of high reactivity and high reducing power for the first dye, and D-glucose is even more preferred. High-purity D-glucose (for example, 99% purity or higher) products can be obtained cheaply and easily on the market. In addition to reducing sugars, ascorbic acid and the like can also be used as the reducing agent.

[0034] The amount of reducing agent used is not particularly limited as long as it can maintain the first dye in a reduced state, but it is preferably 0.5% to 5.0% by weight, and more preferably 1.0% to 3.0% by weight, based on 100% by weight of the water-based ink composition for oxygen detection.

[0035] (3) Magnesium Compounds Magnesium compounds are alkaline components used to make the water-based ink composition for oxygen detection alkaline. For example, when cyclic reducing sugars are used as reducing agents, they do not act as reducing agents under acidic and neutral conditions, but act as reducing agents under alkaline conditions. Therefore, the water-based ink composition for oxygen detection needs to contain a basic substance (alkaline agent), and in the present invention, magnesium compounds are used as such basic substances. Because magnesium compounds have low solubility in water, a cloudy water-based ink composition for oxygen detection can be obtained, which not only improves the visibility of the oxygen detection layer formed thereon, but also increases the viscosity appropriately, making it suitable for coating or printing the water-based ink composition for oxygen detection. Specific examples of magnesium compounds include magnesium hydroxide and magnesium carbonate. Among these, magnesium hydroxide is preferred because it tends to increase viscosity more easily.

[0036] The amount of magnesium compound used is not particularly limited as long as it can make the water-based ink composition for oxygen detection alkaline, but it is preferably 2% to 20% by weight, and more preferably 5% to 15% by weight, based on 100% by weight of the water-based ink composition for oxygen detection.

[0037] Furthermore, the water-based ink composition for oxygen detection may contain alkali metal hydroxides or carbonates such as sodium and potassium as basic substances other than magnesium compounds. In particular, it is preferable to use alkali metal carbonates such as sodium carbonate and potassium carbonate, but it is also possible to use alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

[0038] When using basic substances other than magnesium compounds, the amount used is preferably less than the amount of magnesium compounds used, from the viewpoint of allowing the magnesium compounds to exert their effects. It is preferably 0.01% to 1.00% by weight, more preferably 0.05% to 0.50% by weight, and even more preferably 0.10% to 0.30% by weight, based on 100% by weight of the water-based ink composition for oxygen detection.

[0039] In particular, the water-based ink composition for oxygen detection preferably contains sodium carbonate. Since sodium carbonate exhibits stronger alkalinity than magnesium compounds, using it in combination with magnesium compounds allows the reducing agent to act more effectively, resulting in a faster color change in the water-based ink composition for oxygen detection.

[0040] Furthermore, oxygen indicators are sometimes used by sealing them in the packaging of containers holding food, and in such cases, when the food is heat-sterilized, the oxygen indicator is also heated. Many of the dyes used in oxygen indicators decompose and change color when heated, and reducing agents (reducing sugars) turn brown when heated, so there was a problem that oxygen indicators could not retain their original color after heating. However, with an aqueous ink composition for oxygen detection containing magnesium compounds such as magnesium hydroxide and sodium carbonate, the synergistic effect of the magnesium compound and sodium carbonate can suppress the thermal decomposition and discoloration of the dye and the browning of the reducing agent. As a result, the oxygen indicator can retain its original color even after exposure to high temperatures, the rate of color change is maintained, and the number of color change cycles is increased. In this respect as well, it is preferable for the aqueous ink composition for oxygen detection to contain sodium carbonate, and the preferred amount of sodium carbonate to use in that case is the same as the amount used when using basic substances other than magnesium compounds as described above.

[0041] (4) Granulated Silica Granulated silica is obtained by granulating powdery silica with a small particle diameter into a granular form. An oxygen detection layer formed from an oxygen-detecting water-based ink composition mixed with ungranulated silica of small particle diameter tends to transmit light, resulting in reduced visibility. Since ungranulated silica with a large particle diameter has few pores, an oxygen detection layer formed from an oxygen-detecting water-based ink composition mixed with such silica takes a long time for the atmosphere to penetrate into its interior and cause discoloration. In contrast, since granulated silica has a large particle diameter and moderately large pores, the oxygen detection layer formed from the oxygen-detecting water-based ink composition mixed with granulated silica is less likely to transmit light, improving visibility, and the atmosphere easily penetrates into the interior, resulting in faster discoloration. Specific examples of granulated silica include CARPLEX #67, #80, and #101 (all are trade names manufactured by DSL Japan). Since granulated silica is porous, easily absorbs moisture, and has water retention capacity, thermal decomposition / discoloration of the dye due to sodium carbonate and browning of the reducing agent are more easily suppressed, increasing the number of color change cycles.

[0042] Volume average particle diameter D of granulated silica ５０ is preferably 3 μm or more and 30 μm or less. When the volume average particle diameter D of granulated silica ５０ is 3 μm or more, light does not transmit when used as an oxygen detector, so the L value of the oxygen detector increases. Therefore, the dye contained in the oxygen-detecting water-based ink composition develops a vivid color, improving the visibility of the oxygen detector. When the volume average particle diameter D of granulated silica ５０ is 30 μm or less, even if the granulated silica is cracked into small pieces during the preparation of the oxygen-detecting water-based ink composition, a sufficient size is secured to prevent light transmission, and when formed into an oxygen detector, unevenness formed by the porous silica particles allows air to exist on the surface of the oxygen detector. Therefore, the color change speed of the oxygen detector can be increased. The volume average particle diameter D of granulated silica ５０ is more preferably 8 μm or more and 20 μm or less. The volume average particle diameter D of granulated silica ５０ can be measured by a laser diffraction / scattering method based on JIS Z8825.

[0043] The BET specific surface area of ​​granulated silica is 100 m². ２ / g or more 500m ２ It is preferable that the amount is less than or equal to / g. The BET specific surface area of ​​the granulated silica is 100 m². ２ A value of 1 / g or higher indicates that the granulated silica contains pores of sufficient size, allowing air to enter and exit through these pores, resulting in a faster color change when used as an oxygen indicator. The BET specific surface area of ​​the granulated silica is 500 m². ２ If the amount is less than / g, and even if the binder component partially clogs the pores, the effect on the color change rate can be minimized. The BET specific surface area of ​​granulated silica is 220 m². ２ / g or more 350m ２ It is more preferable that the amount is less than or equal to / g. The BET specific surface area of ​​granulated silica can be measured according to JIS R1626.

[0044] The peak pore size of the granulated silica is preferably 0.1 μm or more and 1.0 μm or less. If the peak pore size of the granulated silica is 0.1 μm or more, the water, which is the solvent of the water-based ink composition for oxygen detection, is less likely to be absorbed, so the viscosity of the water-based ink composition for oxygen detection does not increase easily, and streaking on the coated surface can be suppressed when used as an oxygen detection agent. If the peak pore size of the granulated silica is 1.0 μm or less, the binder component does not easily clog the pores, and sufficient flow can be made through the pores, so the color change speed when used as an oxygen detection agent can be increased. The peak pore size of the granulated silica is more preferably 0.2 μm or more and 0.5 μm or less. The peak pore size of the granulated silica can be determined by the method described in the examples below.

[0045] The amount of granulated silica used is preferably 2% by weight or more and 20% by weight or less, and more preferably 5% by weight or more and 15% by weight or less, based on 100% by weight of the water-based ink composition for oxygen detection.

[0046] (5) Binder component The binder component is a component that enhances the adhesion between the substrate and the oxygen detection layer in an oxygen detection agent in which an oxygen detection layer containing an oxygen detection water-based ink composition is formed on a substrate. Preferably, it also has the function of retaining water in the oxygen detection water-based ink composition. As the binder component, for example, a water-soluble resin used as a binder for water-based inks can be used. Specific examples of binder components include water-based polyurethane resin, water-based acrylic resin, water-based polyester resin, and polyvinyl alcohol. Among these, polyvinyl alcohol is preferred because it takes on a water-containing gel-like structure, making it difficult for water to escape, thus enabling stable reduction by the reducing agent over a long period of time. Furthermore, polyvinyl alcohol has the property of holding water and has water-retaining capacity, so the thermal decomposition and discoloration of the dye by sodium carbonate and the browning of the reducing agent are more easily suppressed. In addition, because the chemical structure of polyvinyl alcohol is similar to that of the reducing agent (reducing sugars), it has the effect of further suppressing the browning of the reducing agent.

[0047] The amount of binder component used is not particularly limited as long as it is within a range that can improve the adhesion between the substrate and the oxygen detection layer, but it is preferably 1% to 10% by weight, and more preferably 3% to 7% by weight, based on 100% by weight of the water-based ink composition for oxygen detection.

[0048] (6) Other water-based ink compositions for oxygen detection are obtained by mixing the above components with water as a solvent. However, in addition to the above components, the composition may also include, for example, a curing agent, an antifoaming agent, a thickening agent, etc., in order to impart the necessary properties for a water-based ink composition for coating and printing.

[0049] (7) Preparation Method The water-based ink composition for oxygen detection contains the above components, but there are no particular restrictions on the preparation method. For example, the water-based ink composition for oxygen detection can be easily prepared by a method including the following steps: (a) The first dye and water are stirred and mixed in the required proportions to obtain the first dye solution. (b) The second dye, reducing agent and water are stirred and mixed in the required proportions to obtain the second dye solution. (c) The PVA aqueous solution, water, granulated silica, magnesium compound, the first dye solution and the second dye solution are mixed in the required proportions, and the mixture is dispersed and mixed using a rotating-orbit type mixer (manufactured by Shinky Co., Ltd., product name: Awatori Rentaro) to obtain the water-based ink composition for oxygen detection. Note that the water-based ink composition for oxygen detection has high viscosity and may not disperse and mix well with a normal stirrer, and it is preferable to use a rotating-orbit type mixer in order to minimize contamination by impurities and foreign substances other than the water-based ink composition for oxygen detection by not including stirring blades. If the viscosity of the water-based ink composition for oxygen detection becomes too high, granulated silica or magnesium compounds may be added and dispersed / mixed in several stages.

[0050] 2. Oxygen Indicator The oxygen indicator 10 according to one embodiment of the present invention has a substrate 1 and an oxygen detection layer 2 formed on the substrate 1, as shown in Figure 1. The oxygen detection layer 2 contains the aforementioned water-based ink composition for oxygen detection. This oxygen indicator 10 makes it possible to detect the presence or absence of oxygen in the atmosphere and changes in its amount by having the oxygen detection layer change its color tone in response to changes in the amount of oxygen in the atmosphere inside a container or packaging containing food, pharmaceuticals, etc.

[0051] (1) The base material 1 forms the oxygen detection agent 10 by forming an oxygen detection layer 2 on its surface. The base material 1 can be a paper base material, a resin base material, etc., and its shape is not particularly limited. The base material 1 can also be a packaging material molded into various shapes such as a film, a bag, or a container. The aforementioned water-based ink composition for oxygen detection can form the oxygen detection layer 2 by coating or printing it on the surface of the base material 1. Therefore, if a packaging material is used as the base material 1, the packaging material itself can be used as the oxygen detection agent 10, and the oxygen detection agent 10 can be made more compact.

[0052] Examples of materials for the base material 1 include polyolefins such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP); halogenated polyolefins such as polyvinyl chloride (PVC); vinyl carboxylate polymers such as polyvinyl acetate (PVAc); aromatic vinyl polymers such as polystyrene (PS); polyesters such as polyethylene terephthalate (PET); and polyamides such as nylon (NY). Specific examples of the film-like base material 1 include films formed from the above materials. The film-like base material 1 may be an unoriented film, or a uniaxially oriented or biaxially oriented film. For example, a polypropylene film-like base material 1 may be an unoriented polypropylene (OPP) film or a biaxially oriented polypropylene (CPP) film. The film-like base material 1 may be a single-layer film, or a laminated film formed by laminating films of different materials. Specific examples of laminated films include two-layer films such as OPP / CPP, OPP / LDPE, PET / LDPE, and PET / CPP, as well as three-layer or more films such as PET / OPP / LDPE, PET / CPP / LDPE, and PET / CPP / OPP / LDPE.

[0053] The substrate 1 may be opaque, such as a paper substrate, but it is preferable that it be transparent, such as a transparent resin substrate. That is, it is preferable that light passes through the substrate 1 so that the other side is visible. By using a transparent substrate 1, the color change of the oxygen detection layer 2 can be observed from the back side (the side of the substrate 1 opposite to the side on which the oxygen detection layer 2 is formed). In addition, the side of the substrate 1 on which the oxygen detection layer 2 is provided may be hydrophobic (because the water-based ink composition for oxygen detection contains a binder component), or it may be treated to be hydrophilic.

[0054] It is preferable that the substrate 1 is oxygen permeable. By using an oxygen-permeable substrate 1, even if the area around the oxygen detection layer 2 is sealed to isolate it from the outside world, as described later, oxygen in the atmosphere can permeate into the interior through the substrate 1, making it possible to detect the presence or absence of oxygen in the atmosphere and changes in its amount. From the above, the oxygen permeability coefficient of the substrate 1 is 1 × 10⁻⁶.－１５ or more (cm ３ (STP)cm / (cm ２ It is preferable that the oxygen permeability coefficient of the substrate 1 is 1 × 10⁻⁶. －１２ Below (cm ３ (STP)cm / (cm ２ It is ・s・Pa)).

[0055] The thickness of the substrate 1 is not particularly limited as long as the oxygen detection agent 10, which has an oxygen detection layer 2 formed on the surface of the substrate 1, can perform the desired function. However, it is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. If the thickness of the substrate 1 is the same when the periphery of the oxygen detection layer 2 is sealed, the higher the oxygen permeability of the substrate 1, the faster the color change of the oxygen detection layer 2 will be. Also, even if the substrate 1 is made of the same material, the thinner it is, the better the oxygen permeability. Therefore, when the periphery of the oxygen detection layer 2 is sealed, the thinner the substrate 1, the faster the color change of the oxygen detection layer 2 will be.

[0056] (2) Oxygen detection layer 2 The oxygen detection layer 2 contains the aforementioned water-based ink composition for oxygen detection. Such an oxygen detection layer 2 allows for the detection of the presence or absence of oxygen in the atmosphere and changes in its amount by having the first dye contained in the water-based ink composition for oxygen detection change its color tone in response to changes in the amount of oxygen in the atmosphere, and is particularly excellent in visibility and color change response. The oxygen detection layer 2 may consist only of the aforementioned water-based ink composition for oxygen detection, or it may contain other components as long as they do not impair its function.

[0057] The thickness of the oxygen detection layer 2 (after drying) is preferably 3 μm or more and 100 μm or less. If the thickness of the oxygen detection layer 2 is 3 μm or more, the water can be evaporated without deformation or elongation of the substrate during the drying process after coating with the water-based ink composition for oxygen detection having an oxygen detection function, thereby obtaining an oxygen detection agent. If the thickness of the oxygen detection layer 2 is 100 μm or less, the resin film that serves as the substrate can permeate oxygen, so the oxygen detection function can be exhibited even when all four sides of the printed oxygen detection area are sealed. The thickness of the oxygen detection layer 2 is more preferably 10 μm or more and 40 μm or less. The thickness of the oxygen detection layer 2 can be measured, for example, by embedding the oxygen detection agent in resin and photographing the cross-section with an FE-SEM.

[0058] The surface roughness Ra of the oxygen detection layer 2 is preferably 3 μm or more and 30 μm or less. If the surface roughness Ra of the oxygen detection layer 2 is 3 μm or more, the color change of the oxygen detection layer 2 will be sufficiently fast. If the surface roughness Ra of the oxygen detection layer 2 is 30 μm or less, blurring of the oxygen detection layer 2 will be less likely to occur. The surface roughness Ra of the oxygen detection layer 2 is more preferably 5 μm or more and 20 μm or less. The surface roughness Ra of the oxygen detection layer 2 can be measured, for example, by forming an oxygen detection layer by coating a black sheet with an oxygen detection water-based ink composition under the same conditions and measuring it using a laser microscope.

[0059] (3) Other Layers The oxygen detection agent 10 may also have layers other than the base material 1 and the oxygen detection layer 2. For example, the oxygen detection agent 10 may have a protective layer 3 (other than the base material 1 and the oxygen detection layer 2) on the upper side of the oxygen detection layer 2. The area around the oxygen detection layer 2 (outer circumference of the base material 1 and the protective layer 3) may be sealed to block it from the outside world by forming a completely sealed area 4 as shown in Figure 2, or it may be sealed to a partially sealed area 4 as shown in Figure 3. By completely sealing the area around the oxygen detection layer 2, the oxygen detection layer 2 can be prevented from being affected even if it comes into contact with the contents of the package (e.g., food) or the components contained therein (e.g., water) in the package containing the oxygen detection agent 10. Even if the area around the oxygen detection layer 2 is completely sealed, it is still possible to detect the presence or absence of oxygen in the atmosphere and changes in its amount by using an oxygen-permeable base material 1. Furthermore, by partially sealing the area around the oxygen detection layer 2, the air (oxygen) inside the package can be intentionally brought into contact with the oxygen detection layer 2, thereby increasing the rate of color change.

[0060] The sealing region 4 may be formed by sealing the base material 1 and the protective layer 3 with an adhesive, or by sealing the base material 1 and the protective layer 3 by thermocompression or ultrasonic bonding; in either case, known methods can be used. Width W of the sealing region 4 ４ For example, it can be 3 to 10 mm.

[0061] A general-purpose resin film can be used as the material for forming the protective layer 3. Due to its availability, the same resin film as the aforementioned film-like substrate 1 can be used. However, it is preferable to use an oxygen-permeable resin film for forming the protective layer 3, as this allows the oxygen concentration around the oxygen indicator to be more easily reflected inside the oxygen indicator. Depending on the location where the oxygen indicator is installed (attached), a material with gas barrier properties may be used to slightly reduce the sensitivity to the effect of oxygen concentration.

[0062] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0063] <Example 1-1> (1) Preparation of water-based ink composition First, a blue aqueous solution was prepared by mixing 4.2 g of methylene blue as the first dye with 95.8 g of water. Next, a red aqueous solution was prepared by mixing 0.04 g of food coloring (Food Red No. 106) as the second dye with 38.4 g of glucose (D-glucose) as a reducing agent with 57.9 g of water. Then, 0.25 g of the blue aqueous solution and 1.00 g of the red aqueous solution were mixed with magnesium hydroxide (BET specific surface area: 48 m²). ２ 2.5 g of ( / g) and CARPLEX #101 (DSL. Japan product name, volume average particle size D) as granulated silica. ５０ :10.0μm, BET specific surface area: 260m ２ A water-based ink composition was obtained by adding 2.5 g of (1 / g), 12 g of a 10 wt% aqueous solution of polyvinyl alcohol (Denka, product name: Denka Popal) as a binder, and 7 g of water to a disposable cup and stirring and mixing for 2 minutes at a rotation speed of 1000 rpm using a rotation-and-revolution mixer (Thinky, product name: Awatori Rentaro). The peak pore size of the granulated silica (the most frequent pore size with a pore size of 3 μm or less to eliminate the effect of interparticle voids) was measured using a mercury porosimeter (Anton Paar, product name: PoreMaster) and was found to be 0.23 μm. The viscosity of the obtained water-based ink composition was measured using an E-type viscometer (Toki Sangyo, product name: RE-85U) and was found to be 120 Pa·s. The preparation conditions and results of the water-based ink composition are shown in Tables 1 and 2.

[0064] (2) Formation of oxygen detection film (film-like oxygen detection agent) Using a test coater (manufactured by Matsuo Sangyo, product name: K303S Multi Coater) equipped with a gravure roll set so that the coating thickness (wet) of the oxygen detection film (film-like oxygen detection agent) is 60 μm, a polyester film (thickness: 16 μm, oxygen permeability coefficient: 1.1 × 10) is used as the base material. －１３ cm ３ (STP)cm / (cm ２A water-based ink composition was applied to a sPa (s) surface at a coating speed of 1 m / min. The gravure roll used had a diameter of 60 mm and multiple test patterns with a length of 10 mm, a width of 7 mm, and a depth of 125 μm were engraved on it. The printing speed at this time was 1 m / min. After applying the water-based ink composition, the polyester film was removed from the test coater and dried at room temperature on a flat surface for 2 hours to obtain an oxygen-detecting film with an oxygen-detecting layer formed on the substrate. The thickness of the oxygen-detecting layer (after drying) in the obtained oxygen-detecting film was 24.3 μm, and the surface roughness Ra was 10.56 μm. The thickness of the oxygen-detecting layer (after drying) was determined by embedding the oxygen-detecting film in resin, photographing the cross-section with FE-SEM, measuring the thickness of the oxygen-detecting layer at 5 points perpendicular to the substrate surface, and taking the average value. Furthermore, the surface roughness Ra of the oxygen detection layer was measured using a laser microscope after forming the oxygen detection layer by coating a 0.5 mm thick black vinyl chloride sheet with a water-based ink composition under the same conditions. The formation conditions and results of the oxygen detection film are shown in Table 2.

[0065] (3) Evaluation 1: Blurring of the oxygen detection layer The presence or absence of blurring of the oxygen detection layer in the obtained oxygen detection film was visually checked. Note that if blurring is present in the oxygen detection layer, the visibility of the oxygen detection layer will decrease. The results are shown in Table 2. ○: None △: Slightly present ×: Heavily blurred and uneven

[0066] (4) Evaluation 2: Color change test The obtained oxygen detection film was cut into 20 mm squares and placed in a transparent bag made of oxygen-impermeable film (OP) together with an oxygen absorber with an oxygen indicator (Wonder Keep Takahagi, product name: Wonder Keep ALP), and sealed with a sealer. After that, it was left at room temperature (25°C), and it was confirmed that the oxygen concentration inside the bag had decreased completely (become an oxygen-free state) due to the effect of the oxygen absorber with the oxygen indicator by checking the oxygen indicator attached to the oxygen absorber. Then, using a colorimeter, the Lab value of the oxygen detection film was measured five times from different locations on the sealed bag, and the average value was taken as the Lab value of the oxygen-free state. As a guideline for the oxygen-free state, the Lab value of the oxygen indicator attached to the oxygen absorber was considered to be within the following ranges: L: 62 to 78 a: 21 to 41 b: -17 to -6

[0067] Subsequently, the oxygen-detecting film was removed from the sealed bag and exposed to the atmosphere. It was then left at room temperature (25°C), and the Lab value of the oxygen-detecting film was measured every two minutes using a colorimeter. The Lab value was measured five times at different locations when the change in L, a, and b values ​​all fell within 0.5. The average value was defined as the Lab value for an aerobic state. The time required for this change was defined as the color change time from an anaerobic state to an aerobic state. As a guideline for an aerobic state, the Lab value of the oxygen-detecting agent attached to the oxygen absorber was considered to be within the following ranges: L: 55-69, a: 2-13, b: -35--18.

[0068] Subsequently, the oxygen detection film was placed again in a transparent bag made of oxygen-impermeable film (OP) along with an oxygen absorber with an oxygen indicator, and sealed with a heat sealer. The bag was then left at room temperature (25°C) to confirm that the oxygen concentration inside the bag had decreased completely (become an oxygen-free state) due to the effect of the oxygen absorber with the oxygen indicator, using the oxygen indicator attached to the oxygen absorber. Then, using a colorimeter, the Lab value of the oxygen detection film was measured five times from different locations on the sealed bag, and the average value was taken as the Lab value of the oxygen-free state after one cycle. The time required for this change was taken as the color change time from oxygen-rich state to oxygen-free state.

[0069] The above procedure was repeated, and the Lab values ​​of the oxygen detection film were measured in anaerobic and aerobic conditions during the 5th and 10th cycles. The results are shown in Tables 3 and 4.

[0070] <Example 1-2> The procedure was carried out in the same manner as in Example 1-1, except that a gravure roll with multiple patterns of 10 mm in length, 7 mm in width, and 50 μm in depth was engraved as the test pattern, and the coating thickness (wet) of the water-based ink composition was set to 24 μm. The conditions and results are shown in Tables 1 to 4.

[0071] <Example 1-3> The procedure was carried out in the same manner as in Example 1-1, except that a gravure roll with multiple patterns of 10 mm in length, 7 mm in width, and 125 μm in depth was engraved as the test pattern, and the coating thickness of the water-based ink composition was set to 80 μm (wet). The conditions and results are shown in Tables 1 to 4.

[0072] <Example 1-4> The procedure was carried out in the same manner as in Example 1-1, except that the amount of granulated silica used was 1.5 g. The conditions and results are shown in Tables 1 to 4.

[0073] <Example 1-5> The procedure was carried out in the same manner as in Example 1-1, except that the amount of granulated silica used was 3.5 g. The conditions and results are shown in Tables 1 to 4.

[0074] <Example 1-6> The procedure was carried out in the same manner as in Example 1-1, except that the amount of magnesium hydroxide used was 1.5 g. The conditions and results are shown in Tables 1 to 4.

[0075] <Example 1-7> The procedure was carried out in the same manner as in Example 1-1, except that the amount of magnesium hydroxide used was 3.5 g. The conditions and results are shown in Tables 1 to 4.

[0076] <Example 1-8> The procedure was carried out in the same manner as in Example 1-1, except that the amount of water used was 3.5 g. The conditions and results are shown in Tables 1 to 4.

[0077] <Example 1-9> The procedure was carried out in the same manner as in Example 1-1, except that the amount of water used was 10.5 g. The conditions and results are shown in Tables 1 to 4.

[0078] <Examples 1-10> As granulated silica, CARPLEX #67 (product name of DSL Japan, volume average particle size D ５０ :11.5μm, BET specific surface area: 380m ２ The procedure was carried out in the same manner as in Example 1-1, except that the amount of 1 / g was used. The conditions and results are shown in Tables 1 to 4.

[0079] <Example 1-11> As granulated silica, CARPLEX #80 (product name of DSL Japan, volume average particle size D ５０ : 15.0μm, BET specific surface area: 200m ２ The procedure was carried out in the same manner as in Example 1-1, except that the amount of 1 / g was used. The conditions and results are shown in Tables 1 to 4.

[0080] <Examples 1-12> Low-density polyethylene film as base material (thickness: 16 μm, oxygen permeability coefficient: 2.3 × 10⁻⁶) －１２ cm ３ (STP)cm / (cm ２ Except for using sPa), the procedure was carried out in the same manner as in Example 1-1. The conditions and results are shown in Tables 1 to 4.

[0081] <Example 1-13> Magnesium carbonate instead of magnesium hydroxide (BET specific surface area: 102 m²) ２ The procedure was carried out in the same manner as in Example 1-1, except that the amount of 1 / g was used. The conditions and results are shown in Tables 1 to 4.

[0082] <Comparative Example 1-1> The procedure was the same as in Example 1-1, except that no reducing agent was added to the red aqueous solution. However, in the color change test (1st cycle), no color change was observed when the oxygen detection film was changed from an oxygen-rich state to an oxygen-free state, so no further evaluation was performed. The conditions and results are shown in Tables 1 to 4.

[0083] <Comparative Example 1-2> The procedure was carried out in the same manner as in Example 1-1, except that granulated silica was not added. The conditions and results are shown in Tables 1 to 4.

[0084] <Comparative Example 1-3> The procedure was the same as in Example 1-1, except that magnesium hydroxide was not added. However, in the color change test (1st cycle), no color change was observed when the oxygen detection film was changed from an oxygen-free state to an oxygen-rich state, so no further evaluation was performed. The conditions and results are shown in Tables 1 to 4.

[0085] <Comparative Example 1-4> The procedure was the same as in Example 1-1, except that a 10% by weight aqueous solution of polyvinyl alcohol was not added. However, since an oxygen detection layer could not be formed even after coating the substrate with the water-based ink composition, the oxygen detection film was not evaluated. The conditions and results are shown in Tables 1 to 4.

[0086] <Comparative Example 1-5> Instead of 2.5 g of granulated silica, mesoporous silica (Sigma-Aldrich, trade name: SBA-15, volume average particle size D) was used. ５０ :80μm, BET specific surface area: 730m ２ The volume-average particle size D (per g) is classified by sieving. ５０ The procedure was carried out in the same manner as in Example 1-1, except that 2.5 g of a 15.0 μm particle was added and 10.5 g of water was used. The conditions and results are shown in Tables 1 to 4.

[0087] <Comparative Example 1-6> Instead of 2.5 g of granulated silica, AEROSIL200 (product name of Nippon Aerosil, volume average particle size D), which is ungranulated silica, was used. ５０ :0.012μm, BET specific surface area: 200m ２ The procedure was carried out in the same manner as in Example 1-1, except that 1.5 g of ( / g) was added and the amount of water used when preparing the water-based ink composition was 35 g. The conditions and results are shown in Tables 1 to 4.

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[0092] <Example 2-1> (1) Preparation of water-based ink composition and formation of oxygen detection film 7.125 g of the blue aqueous solution prepared in Example 1-1, 28.5 g of the red aqueous solution prepared in Example 1-1, 0.93 g of sodium carbonate, 37.5 g of magnesium hydroxide used in Example 1-1, 37.5 g of granulated silica used in Example 1-1, 180 g of a 10% by weight aqueous solution of polyvinyl alcohol used in Example 1-1, and 105 g of water were placed in a disposable cup and stirred and mixed in the same manner as in Example 1-1 to obtain a water-based ink composition. Then, using the obtained water-based ink composition, an oxygen detection film was obtained in the same manner as in Example 1-1. The amount of each component added is shown in Table 5.

[0093] (2) Evaluation 1: Color change test (before heat treatment) The Lab values ​​of the obtained oxygen detection film were measured in the same manner as in Example 1-1, under oxygen-free and oxygen-containing conditions at room temperature (25°C). The results are shown in Table 5.

[0094] (3) Evaluation 2: Color change test (after heat treatment) The oxygen detection film after Evaluation 1 was subjected to heat treatment at 80°C for 60 minutes or 120°C for 15 minutes. Then, the oxygen detection film after heat treatment was subjected to a color change test up to the 5th cycle in the same manner as in Example 1-1. Furthermore, the same treatment as the color change test was continued up to the 10th cycle, and the number of cycles at which color change occurred was confirmed. The results are shown in Tables 6-7.

[0095] <Example 2-2> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 8.55 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0096] <Example 2-3> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 14.25 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0097] <Example 2-4> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 5.7 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0098] <Example 2-5> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 9.975 g, the amount of red aqueous solution used was 39.9 g, the amount of sodium carbonate used was 1.30 g, and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0099] <Example 2-6> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 14.25 g, the amount of red aqueous solution used was 57 g, the amount of sodium carbonate used was 1.85 g, and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0100] <Example 2-7> The procedure was carried out in the same manner as in Example 2-1, except that the amount of blue aqueous solution used was 4.275 g, the amount of red aqueous solution used was 17.1 g, the amount of sodium carbonate used was 0.56 g, and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0101] <Example 2-8> The procedure was carried out in the same manner as in Example 2-1, except that the amount of magnesium hydroxide used was 60 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0102] <Example 2-9> The procedure was carried out in the same manner as in Example 2-1, except that the amount of magnesium hydroxide used was 75 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0103] <Example 2-10> The procedure was carried out in the same manner as in Example 2-1, except that the amount of magnesium hydroxide used was 15 g and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

[0104] <Example 2-11> The procedure was carried out in the same manner as in Example 2-1, except that sodium carbonate was not added. The amount of each component added and the results are shown in Tables 5 to 7.

[0105] <Comparative Example 2-1> The procedure was the same as in Example 2-1, except that no blue aqueous solution was added and the amount of water used was 52.5 g. However, in the color change test before heat treatment and the color change test after heat treatment (1st cycle), no color change was observed when the oxygen detection film was changed from an oxygen-free state to an oxygen-rich state, so no further evaluation was performed. The amount of each component added and the results are shown in Tables 5 to 7.

[0106] <Comparative Example 2-2> The procedure was the same as in Example 2-1, except that the blue aqueous solution, red aqueous solution, and sodium carbonate were not added, and the amount of water used was 52.5 g. However, in the color change test before heat treatment and the color change test after heat treatment (1st cycle), no color change was observed even when the oxygen detection film was changed from an oxygen-free state to an oxygen-rich state, so no further evaluation was performed. The amount of each component added and the results are shown in Tables 5 to 7.

[0107] <Comparative Example 2-3> The procedure was the same as in Example 2-1, except that magnesium hydroxide was not added and the amount of water used was 52.5 g. However, in the color change test (1st cycle) after heat treatment at 120°C for 15 minutes, no color change was observed when the oxygen detection film was changed from an oxygen-free state to an oxygen-rich state, so no further evaluation was performed. The amount of each component added and the results are shown in Tables 5 to 7.

[0108] <Comparative Example 2-4> The procedure was carried out in the same manner as in Example 2-1, except that silica was not added and the amount of water used was 52.5 g. The amount of each component added and the results are shown in Tables 5 to 7.

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[0112] 1. Substrate 2. Oxygen detection layer 3. Protective layer 4. Sealing area 10. Oxygen detection agent W ４ Seal width

Claims

1. An aqueous ink composition for oxygen detection comprising a first dye whose color tone reversibly changes between oxidized and reduced states, a reducing agent, a magnesium compound, granulated silica, and a binder component.

2. Volume-average particle size D of the granulated silica ５０ The aqueous ink composition for oxygen detection according to claim 1, wherein the particle size is 3 μm or more and 30 μm or less.

3. The BET specific surface area of ​​the granulated silica is 100 m². ２ / g or more 500m ２ The water-based ink composition for oxygen detection according to claim 1, wherein the amount is less than or equal to / g.

4. The water-based ink composition for oxygen detection according to claim 1, wherein the peak pore size of the granulated silica is 0.1 μm or more and 1.0 μm or less.

5. The aqueous ink composition for oxygen detection according to claim 1, wherein the magnesium compound is magnesium hydroxide.

6. The aqueous ink composition for oxygen detection according to claim 1, wherein the reducing agent is a reducing sugar.

7. The aqueous ink composition for oxygen detection according to claim 6, wherein the reducing sugar is D-mannose, D-glucose, D-fructose, D-erythrose, or D-althrose.

8. The water-based ink composition for oxygen detection according to claim 1, wherein the binder component is polyvinyl alcohol.

9. The water-based ink composition for oxygen detection according to claim 1, further comprising a second dye different from the first dye.

10. The aqueous ink composition for oxygen detection according to claim 1, further comprising sodium carbonate.

11. An oxygen detection agent comprising a substrate and an oxygen detection layer formed on the substrate, the oxygen detection layer comprising the water-based ink composition for oxygen detection described in any one of claims 1 to 10.

12. The oxygen indicator according to claim 11, wherein the material of the base material is a polyolefin, a halogenated polyolefin, a vinyl carboxylate polymer, an aromatic vinyl polymer, a polyester, or a polyamide.

13. The oxygen permeability coefficient of the substrate is 1 × 10 －１５ cm ３ (STP)cm / (cm ２ The oxygen indicator according to claim 11, wherein the oxygen level is s・Pa or higher.

14. The oxygen detection agent according to claim 11, wherein the thickness of the oxygen detection layer is 3 μm or more and 100 μm or less.

15. The oxygen detection agent according to claim 11, further comprising a protective layer covering the oxygen detection layer.

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