JP2020051881A - Oxygen indicator and oxygen indicator label - Google Patents

Abstract

To provide an oxygen indicator which can detect the presence or absence of oxygen highly sensitively and can present a high stability of discoloring meaning that the oxygen indicator is discolored in nearly the same length of time every time it is discolored and that the oxygen indicator completes discoloring in a set length of time.SOLUTION: The present invention achieves the above object by providing an oxygen indicator which sequentially includes: a base material; an oxygen indicator layer containing an oxidation-reduction coloring agent, a reduction agent, an alkalization agent, and a binder resin; a transparent acidic component barrier layer; a first adhesive layer containing an acidic component; and a transparent protective film with an oxygen transmitting property and a water vapor transmitting property.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oxygen indicator having good discoloration performance.

  Oxygen is known to cause oxidative deterioration of articles such as foods and pharmaceuticals due to its high reactivity. In order to suppress the oxidative deterioration of the article, for example, a method of vacuum packaging the oxygen absorber together with the article in a bag has been adopted. However, even with the above method, the oxygen concentration in the packaging increases due to the decrease in the capacity of the oxygen scavenger and the intrusion of oxygen from pinholes generated in the packaging material, and as a result, the oxidation of the article occurs. Deterioration may progress. Therefore, an oxygen indicator is placed in the package, and the presence or absence of oxygen in the package is managed by utilizing the discoloration function of the oxygen indicator.

  The oxygen indicator has an oxygen indicator layer containing at least a redox dye and a reducing agent. The color change function of the oxygen indicator utilizes a difference in color tone between the reduced state and the oxidized state of the redox dye.

  The oxygen indicator is required to detect the presence or absence of oxygen with high sensitivity, to have a small variation in discoloration time, and to exhibit discoloration stability in which discoloration is completed within a specified time. For example, Patent Document 1 discloses an oxygen indicator label having a barrier film having gas barrier properties, an oxygen indicator layer containing a redox dye, a reducing agent and a binder resin, and an adhesive layer in this order. It is disclosed that the configuration makes it possible to suppress a decrease in oxygen detectability due to the exudation of the dye of the oxygen indicator.

  Further, in Patent Document 2, a transparent substrate, an anchor coat layer, an oxygen indicator layer formed from an ink composition containing a redox dye, a reducing agent, a binder, water or an alcohol-based solvent, and a shielding property. An oxygen indicator having a white layer and a white layer in this order is disclosed, and it is disclosed that, by adopting the above-described laminated structure, variations in measured values in measurement by a color difference meter are reduced.

JP 2017-166970 A JP 2014-215111A

  For example, when packaging the oxygen indicator with food, it is necessary to avoid direct contact between the food and the oxygen indicator layer for food hygiene. Further, it is necessary to prevent the redox dye from being precipitated from the oxygen indicator layer due to oil contained in the food. Then, in the oxygen indicator, a transparent protective film is provided outside the oxygen indicator layer via a pressure-sensitive adhesive layer in order to prevent contact between the article and the oxygen indicator layer, deterioration of the oxygen indicator layer, and the like. At this time, when the acidic component contained in the pressure-sensitive adhesive layer bleeds out and enters the oxygen indicator layer, the redox reaction rate of the redox dye is reduced, and it is difficult to detect the presence or absence of oxygen with high sensitivity. There is a problem of becoming.

  The present invention has been made in view of the above problems, and provides an oxygen indicator capable of detecting the presence or absence of oxygen with high sensitivity and capable of showing discoloration stability in which discoloration is completed within a specified time. Its main purpose is to:

  In order to achieve the above object, the present invention provides a substrate, an oxygen indicator layer including at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin, a transparent acidic component barrier layer, and an acidic component. An oxygen indicator having a first pressure-sensitive adhesive layer and a transparent protective film having oxygen permeability and water vapor permeability in this order is provided.

  According to the present invention, since a transparent acidic component barrier layer is further disposed between the oxygen indicator layer and the first adhesive layer containing the acidic component, the acidic component bleed out from the first adhesive layer is removed. The migration to the oxygen indicator layer side can be blocked by the acidic component barrier layer. Thereby, the oxygen indicator of the present invention can maintain the redox reaction rate of the redox dye, so that the presence or absence of oxygen can be detected with high sensitivity, and the discoloration stability in which the discoloration is completed within a specified time is improved. Can be shown.

  Further, the present invention has an oxygen indicator and a second pressure-sensitive adhesive layer, and the oxygen indicator includes, from the second pressure-sensitive adhesive layer side, a substrate, a redox dye, a reducing agent, an alkalizing agent, And an oxygen indicator layer containing at least a binder resin, a transparent acidic component barrier layer, a first pressure-sensitive adhesive layer containing an acidic component, and a transparent protective film having oxygen permeability and water vapor permeability. Provide an indicator label.

  According to the present invention, an oxygen indicator capable of detecting the presence or absence of oxygen with high sensitivity and capable of indicating discoloration stability in which discoloration is completed within a specified time is easily provided at a desired position on an adherend. Can be affixed.

  ADVANTAGE OF THE INVENTION This invention has the effect that the presence or absence of oxygen can be detected with high sensitivity, and the oxygen indicator which can show the discoloration stability which completes discoloration within a prescribed time can be provided.

It is a schematic sectional view showing an example of the oxygen indicator of the present invention. It is a schematic sectional drawing which shows an example of the oxygen indicator label of this invention.

  Hereinafter, the oxygen indicator and the oxygen indicator label of the present invention will be described respectively.

A. Oxygen Indicator The oxygen indicator of the present invention comprises a substrate, an oxygen indicator layer containing at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin, a transparent acidic component barrier layer, and a first adhesive containing an acidic component. An agent layer and a transparent protective film having oxygen permeability and water vapor permeability are provided in this order.

  FIG. 1 is a schematic sectional view showing an example of the oxygen indicator of the present invention. The oxygen indicator 10 of the present invention comprises a substrate 1, an oxygen indicator layer 2 containing at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin, a transparent acidic component barrier layer 3, and a second layer containing an acidic component. 1. An adhesive layer 4 and a transparent protective film 5 having oxygen permeability and water vapor permeability are provided in this order.

  For example, an oxygen indicator layer containing methylene blue as a redox dye exhibits a reduced colorless color under deoxygenation because methylene blue is reduced to leucomethylene blue by the action of a reducing agent. On the other hand, under an oxygen atmosphere, leuco methylene blue is oxidized by surrounding oxygen to form methylene blue, thereby exhibiting a blue color.

  Since the color change from colorless to blue is remarkably expressed under alkaline conditions, an alkalinizing agent such as magnesium hydroxide is added to accelerate the oxidation reaction of the redox dye to make the oxygen indicator layer alkaline. Is made.

  In order to detect the presence or absence of oxygen in a desired space with high sensitivity, the oxidation reaction of the redox dye by the oxygen in the space needs to proceed rapidly. However, when the acidic component contained in the first pressure-sensitive adhesive layer enters the oxygen indicator layer, the transferred acidic component and the alkalizing agent react with each other dominantly, and the oxidation-reduction reaction rate of the redox dye decreases. . As a result, it becomes difficult for the oxygen indicator to detect the presence or absence of oxygen with high sensitivity, and the oxygen indicator cannot complete the discoloration within a prescribed time, resulting in poor discoloration stability.

  On the other hand, according to the present invention, since the transparent acidic component barrier layer is further disposed between the oxygen indicator layer and the first adhesive layer containing the acidic component, it bleeds out from the first adhesive layer. The migration of the acidic component to the oxygen indicator layer side can be blocked by the acidic component barrier layer. Thereby, the oxygen indicator of the present invention can maintain the redox reaction rate of the redox dye, so that the presence or absence of oxygen can be detected with high sensitivity, and the discoloration stability in which the discoloration is completed within a specified time is improved. Can be shown.

  The acidic component contained in the first pressure-sensitive adhesive layer refers to a monomer, oligomer or polymer containing at least one acidic group. Examples of the acidic group include a carboxyl group, a phosphoric acid group, a sulfonic acid group, and a phenolic hydroxyl group.

  Hereinafter, each configuration of the oxygen indicator of the present invention will be described.

1. Acidic Component Barrier Layer The acidic component barrier layer in the oxygen indicator of the present invention is a transparent layer disposed between the oxygen indicator layer and the first pressure-sensitive adhesive layer. It has a function of blocking migration to the oxygen indicator layer side.

  In the oxygen indicator of the present invention, the oxygen indicator layer is disposed on the first surface of the acidic component barrier layer. Usually, the oxygen indicator layer is disposed directly on the first surface of the acidic component barrier layer, but even if another layer is interposed between the first surface of the acidic component barrier layer and the oxygen indicator layer. Good. Further, a first pressure-sensitive adhesive layer is disposed on a second surface of the acidic component barrier layer opposite to the first surface. Usually, the first pressure-sensitive adhesive layer is disposed directly on the second surface of the acidic component barrier layer, but another layer is interposed between the second surface of the acidic component barrier layer and the first pressure-sensitive adhesive layer. It may be.

  The acidic component barrier layer has such a degree of transparency that a change in the color tone of the oxygen indicator layer can be visually recognized. The acidic component barrier layer is usually colorless.

  The acidic component barrier layer has oxygen permeability and water vapor permeability. The oxygen permeability and the water vapor permeability of the acidic component barrier layer can be the same as the oxygen permeability and the water vapor permeability of the transparent protective film described in the section of “4.

  The acidic component barrier layer is preferably neutral, and usually has a pH of 5 or more and 9 or less.

  The acidic component barrier layer is not particularly limited as long as it has the above-described desired function. Examples of such an acidic component barrier layer include a resin layer.

  Examples of the resin constituting the resin layer include a neutral resin. The neutral resin is a nonionic resin having no polar substituent which dissolves in a hydrophilic solvent. Specific examples include cellulose resins such as ethyl cellulose, ethyl hydroxyethyl cellulose, and cellulose acetyl propionate; butyral resins; polyester resins; acrylic resins; polyether resins; polyamide resins; The resin layer may include one or more of these resins.

  The resin layer may contain wax, silicon, or the like, in addition to the resin. If necessary, additives such as a slip agent, a plasticizer, a stabilizer, an antioxidant, a light stabilizer, an ultraviolet absorber, a curing agent, a crosslinking agent, a lubricant, an antistatic agent, and a filler may be included. .

  Specific examples of the resin layer include an overprint varnish layer (OP varnish layer) having a polyolefin resin.

  The acidic component barrier layer can have a thickness capable of blocking the migration of the acidic component bleed out from the first pressure-sensitive adhesive layer to the acidic indicator layer side. It can be set appropriately according to the composition and the like. When the acidic component barrier layer is a resin layer, for example, when it is an overprint varnish layer, the thickness is specifically preferably from 1.2 μm to 2.0 μm.

  The method for forming the acidic component barrier layer is not particularly limited as long as it can be directly formed on the oxygen indicator layer. When the acidic component barrier layer is a resin layer, the resin layer is, for example, using an ink prepared by dissolving or dispersing the above resin composition in an organic solvent or water, gravure printing, offset printing, letterpress printing, screen printing. It can be formed by applying it to the surface of the oxygen indicator layer by a printing method such as printing or a coating method and drying it.

2. Oxygen indicator layer The oxygen indicator layer in the oxygen indicator of the present invention contains at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin.

  The oxygen indicator layer is a layer in which a reversible change in color tone occurs with the presence or absence of oxygen, specifically, a change in oxygen concentration. Specifically, the oxygen indicator layer is in a state where the redox dye is oxidized in an environment having a high oxygen concentration, for example, in the atmosphere. The reducing dye changes from an oxidized state to a reduced state, and the color tone changes. The redox is reversible, and the reversibility is maintained until the coexisting reducing agent is consumed and depleted.

  The redox dye contained in the oxygen indicator layer is not particularly limited as long as it is a dye that can change color between an oxidized state and a reduced state, and among them, a dye that is colored in the oxidized state and colorless or pale in the reduced state is preferable. . This is because the oxygen indicator layer is colored in the oxidized state, so that it is easy to visually recognize that the oxygen concentration is high.

  Examples of such dyes include organic dyes such as thiazine dyes, indigo dyes, viologen dyes, azine dyes, and oxazine dyes, and inorganic dyes such as ferrocene dyes.

  More specifically, methylene blue, new methylene blue, neutral red, indigo carmine, acid red, safranin T, phenosafranine, capri blue, nile blue, diphenylamine, xylene cyanol, nitrodiphenylamine, ferroin, N-phenylanthranilic acid, etc. No.

  The oxygen indicator layer may include only one of these dyes, or may include two or more of these dyes. Among them, the oxygen indicator layer preferably contains methylene blue. This is because methylene blue is general-purpose and can express a color tone clearly.

  The reducing agent contained in the oxygen indicator layer is not particularly limited as long as it is a material capable of reducing the oxidized form of the redox dye. Examples of such a reducing agent include ascorbic acid or a salt thereof; erythorbic acid or a salt thereof; D-arabinose, D-erythrose, D-galactose, D-xylose, D-glucose, D-mannose, and D-fructose. , D-lactose, D-fructose and the like; stannous salts; ferrous salts and the like. The oxygen indicator layer may contain only one of these reducing agents, or may contain two or more thereof.

  As the binder resin contained in the oxygen indicator layer, a resin used for a known indicator ink can be used. Examples of such a binder resin include cellulose derivatives such as ethyl cellulose, ethyl hydroxyethyl cellulose, and cellulose acetyl propionate; butyral resin; polyester resin; acrylic resin; polyether resin; polyamide resin; The oxygen indicator layer may contain only one kind of these binder resins, or may contain two or more kinds.

  The oxygen indicator layer further contains an alkalizing agent. This is because the oxygen indicator layer can be made alkaline and the redox reaction of the redox dye can be promoted. Further, when the acidic component transferred from the first pressure-sensitive adhesive layer enters the oxygen indicator layer, the acidic component easily reacts with the hydroxyl group of the alkalizing agent, so that the effect of promoting the oxidation-reduction reaction rate by the alkalizing agent is obtained. However, in the present invention, since the acidic component barrier layer is disposed between the oxygen indicator layer and the first pressure-sensitive adhesive layer, the effect of promoting the oxidation-reduction reaction by the alkalizing agent can be sufficiently obtained. .

As the alkalizing agent contained in the oxygen indicator layer, known materials can be applied, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, calcium carbonate, sodium hydrogen carbonate, hydrogen carbonate Hydroxides such as potassium, calcium hydrogen carbonate, magnesium hydroxide, sodium acetate, potassium acetate, potassium sodium tartrate, and potassium 2-ethylhexanoate, carboxylate salts, and various salts are included.
Of these, magnesium hydroxide is preferred from the viewpoint of long-term stability. The oxygen indicator layer may contain only one kind of these alkalizing agents, or may contain two or more kinds.

  The oxygen indicator layer may include a pigment, a pigment dispersant, a leveling agent, a defoaming agent, a wax, a curing agent, a silane cup, if necessary, in addition to the above-described redox dye, reducing agent, and binder resin, and an alkalizing agent. It may contain additives such as a ring agent, a rust inhibitor, a preservative, a plasticizer, an infrared absorber, an ultraviolet absorber, a light resistance improver, a fragrance, and a flame retardant.

  The oxygen indicator layer preferably exhibits alkalinity. This is because the redox reaction rate of the redox dye can be increased. Usually, the pH of the oxygen indicator layer is 8 or more.

  The oxygen indicator layer can exhibit a desired discoloration function and have a thickness that allows the discoloration to be visually recognized, and the thickness is not particularly limited and can be appropriately set.

  The oxygen indicator layer is prepared by dissolving or dispersing the above-described ink composition containing at least the redox dye, the reducing agent, and the binder resin in an organic solvent or water to form an oxygen indicator layer-forming ink. It can be formed by applying to one surface of a base material described later and drying by a printing method such as printing, offset printing, letterpress printing, screen printing, or a coating method.

3. First pressure-sensitive adhesive layer The first pressure-sensitive adhesive layer in the oxygen indicator of the present invention is a layer containing an acidic component, and is disposed between the transparent protective film and the acidic component barrier layer.

  The first pressure-sensitive adhesive layer is acidic because it contains an acidic component. The pH of the first pressure-sensitive adhesive layer is usually 1 or more and 7 or less.

  The first pressure-sensitive adhesive layer can have a thickness capable of exhibiting sufficient adhesive strength for bonding the laminate including the oxygen indicator layer and the transparent protective film, and the thickness is not particularly limited. Can be set as appropriate.

  The first pressure-sensitive adhesive layer can be formed by applying the above-described pressure-sensitive adhesive to the surface of the acidic component barrier layer by a desired printing method or coating method, and drying the applied pressure-sensitive adhesive.

4. Transparent protective film The transparent protective film in the oxygen indicator of the present invention has oxygen permeability and water vapor permeability. The transparent protective film is disposed in direct contact with the surface of the first pressure-sensitive adhesive layer opposite to the oxygen indicator layer side.

  The transparent protective film has such transparency that the change in the color tone of the oxygen indicator layer can be visually recognized. The transparent protective film is usually colorless.

  As the transparent protective film, a thermoplastic resin film having oxygen permeability and water vapor permeability and having transparency can be used. Specific examples of the thermoplastic resin film include polyolefin films such as polyethylene and polypropylene; modified polyolefin films such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-vinyl alcohol copolymer; polystyrene, styrene A polystyrene film such as a methyl methacrylate copolymer; other polyamide films; a polyvinyl chloride film; and a thermoplastic resin film such as a polyvinylidene chloride film. The transparent protective film may be stretched or unstretched.

  The transparent protective film preferably protects the oxygen indicator layer, and preferably has a thickness capable of transmitting a sufficient amount of oxygen and water vapor for the redox reaction of the redox dye to proceed in the oxygen indicator layer, for example, , 20 μm or less, and particularly preferably 18 μm or more and 20 μm or less.

5. Substrate The substrate in the oxygen indicator of the present invention is a member arranged on the surface of the oxygen indicator layer opposite to the first pressure-sensitive adhesive layer side. Examples of the substrate include paper, synthetic paper, nonwoven fabric, synthetic resin film, transparent film having oxygen barrier properties, metal foil, and inorganic vapor-deposited film.

  The substrate can have a thickness capable of supporting the oxygen indicator layer, and the thickness is not particularly limited and can be set as appropriate.

6. Arbitrary Configuration The oxygen indicator of the present invention may have a filler layer between the substrate and the oxygen indicator layer, in addition to the above-described components. By providing a filler layer between the substrate and the oxygen indicator layer, the surface of the substrate can be flattened, and when forming the oxygen indicator layer on the substrate, an ink that forms the oxygen indicator layer This is because it is possible to prevent bleeding into the base material.

  The filler layer preferably has an acidic component barrier property. That is, in the oxygen indicator of the present invention, a first acidic component barrier layer is disposed on the surface of the oxygen indicator layer on the first pressure-sensitive adhesive layer side, and a second acidic component barrier layer is disposed on the surface of the oxygen indicator layer on the substrate side. Are preferably arranged. When the base material exhibits acidity, in addition to the function of the sealant layer described above, migration of the acidic component migrated from the base material to the oxygen indicator layer side can be blocked by the sealant layer. Because you can.

7. Uses The oxygen indicator of the present invention can be used in a long-term storage environment for articles such as foods, beverages, and medical / pharmaceutical products to control the presence or absence of oxygen in the storage environment for the articles. Specifically, it can be used for detecting the deoxidation state of a deoxidizer packaged with an article, detecting the presence or absence of breakage of a packaging material, and the like. Among them, the direct contact with the oxygen indicator layer can be prevented by the presence of the transparent protective film, and therefore, it can be suitably used as a food oxygen indicator.

B. Oxygen indicator label The oxygen indicator label of the present invention has an oxygen indicator and a second pressure-sensitive adhesive layer, and the oxygen indicator includes, from the second pressure-sensitive adhesive layer side, a substrate, a redox dye, and a reducing agent. And an oxygen indicator layer containing at least a binder resin, a transparent acidic component barrier layer, a first pressure-sensitive adhesive layer containing an acidic component, and a transparent protective film having oxygen permeability and water vapor permeability in this order.

  FIG. 2 is a schematic sectional view showing an example of the oxygen indicator label of the present invention. The oxygen indicator label 20 of the present invention has the oxygen indicator 10 and the second pressure-sensitive adhesive layer 11. Since the layer configuration of the oxygen indicator 10 shown in FIG. 2 is the same as that of the oxygen indicator 10 shown in FIG. 1, the description is omitted here.

  According to the present invention, an oxygen indicator capable of detecting the presence or absence of oxygen with high sensitivity, having a small variation in discoloration time, and capable of showing discoloration stability in which discoloration is completed within a prescribed time, an adherend. Can be easily attached to a desired position.

  Hereinafter, the oxygen indicator label of the present invention will be described for each configuration.

1. Oxygen Indicator Since the oxygen indicator in the oxygen indicator label of the present invention has been described in the above section “A. Oxygen Indicator”, the description here is omitted.

2. Second pressure-sensitive adhesive layer The second pressure-sensitive adhesive layer in the oxygen indicator label of the present invention is a member that is disposed on the substrate-side surface of the oxygen indicator and is used for attaching the oxygen indicator to an adherend. The composition of the second pressure-sensitive adhesive layer is not particularly limited, and generally includes a pressure-sensitive adhesive composition contained in the pressure-sensitive adhesive layer of the label.

3. Release Layer The oxygen indicator label of the present invention may have a release layer on the surface of the second pressure-sensitive adhesive layer opposite to the oxygen indicator side, in addition to the above-described constituent members. The release layer is a layer that is removed when the oxygen indicator label is attached to the adherend. The release layer only needs to be peelable from the second pressure-sensitive adhesive layer, and a release layer generally used for labeling can be used.

4. Uses The oxygen indicator label of the present invention is applied to a desired position in the storage environment of the article in a long-term storage environment of an article such as food, beverage, medical or pharmaceutical, and manages the presence or absence of oxygen in the storage environment. It can be used for applications. Specifically, it can be used for detecting the deoxidation state of a deoxidizer packaged with an article, detecting the presence or absence of breakage of a packaging material, and the like. Above all, since the presence of the transparent protective film can prevent direct contact between the oxygen indicator layer and the article, it can be suitably used as a food oxygen indicator label.

  Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Preparation]
Printing inks having the following compositions were prepared.

(Ink for forming sealing layer)
An ink for forming a sealing layer was prepared using the following materials.
・ Polyolefin resin 10% by mass
・ Magnesium hydroxide 30% by mass
・ Toluene 60% by mass

(Oxygen indicator layer forming ink)
An ink for forming an oxygen indicator layer was prepared using the following materials.
・ Methylene blue 0.05%
・ Phloxin B 0.03%
-7.58% of D-fructose
・ 5.73% of cellulose acetate propionate
・ Magnesium hydroxide 21.72%
・ Ethylene glycol 11.14%
・ Ethyl acetate 26.87%
・ Isopropyl alcohol 26.88%

[Example 1]
An ink for forming a sealing layer was directly printed on one surface of a 80 μm-thick YUPO paper (YUPO Corporation, trade name: FGP80), and dried to form a sealing layer. Next, an ink for forming an oxygen indicator layer was directly printed on the sealing layer, and dried to form an oxygen indicator layer.

  Subsequently, an overprint (OP) varnish (DICG, trade name: AP-1OP, composition: 10% polyolefin-based resin, 90% toluene) was printed and dried on the oxygen indicator layer to form an acidic component barrier layer having a thickness of 1%. A 2 μm OP varnish layer was formed. The thickness of the OP varnish layer was determined by measuring the thickness at five locations from a cross-sectional image taken using a scanning electron microscope (SEM), and taking the average value as the thickness of the OP varnish layer. The thickness of the OP varnish layer in Examples 2 to 3 described later was also specified by the above method.

  Next, a biaxially stretched polypropylene (OPP) film having an adhesive layer (Lintech, trade name: PP20PL Syn 7LK) having an adhesive layer was laminated on the OP varnish layer such that the adhesive layer was on the OP varnish layer side. Thus, an oxygen indicator having a laminated structure of a transparent protective film / first pressure-sensitive adhesive layer / OP varnish layer / oxygen indicator layer / filler layer / base material was obtained. Note that “/” in the above-mentioned laminated structure indicates an interface.

[Example 2]
An oxygen indicator was obtained in the same manner as in Example 1, except that an OP varnish layer having a thickness of 0.8 μm was formed as an acidic component barrier layer on the oxygen indicator layer.

[Example 3]
An oxygen indicator was obtained in the same manner as in Example 1 except that an OP varnish layer having a thickness of 0.4 μm was formed as an acidic component barrier layer on the oxygen indicator layer.

[Comparative Example 1]
An oxygen indicator was obtained in the same manner as in Example 1, except that the acidic component barrier layer (OP varnish layer) was not formed on the oxygen indicator layer.

[Evaluation]
1. Evaluation of discoloration performance Each of the oxygen indicators obtained in Examples 1 to 3 and Comparative Example 1 was exposed to oxygen to give an aerobic color (blue), and then put in a bag containing a humectant and an oxygen scavenger. The oxygen concentration inside was set to 0.01% or less. Starting from this state (0 hour), the time until the color of the sample became anaerobic (colorless) was visually measured. The measurement was carried out under the environment of a temperature of 25 ° C. and a humidity of 60% RH, using a D6500 light source as a color change measurement light source, and comparing the color with a chart as a color sample. .

  The measurements of Examples 1 to 3 and the Comparative Example were performed a plurality of times for each of them, and the ratios at which the discoloration was completed were determined, and are summarized in Table 1 below. In addition, as one measurement here, three measurements were performed as a series of measurements, and the average value was defined as one value.

  From the results in Table 1 above, the oxygen indicators of Examples 1 to 3 provided with the OP varnish layer had a shorter discoloration completion time and a lower discoloration performance than the oxygen indicators of Comparative Example 1 without the OP varnish layer. It turned out to be improved. When the oxygen indicators of Examples 1 to 3 were compared, it was found that the thicker the OP varnish layer was, the better the discoloration performance was.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Oxygen indicator layer 3 ... Acid component barrier layer 4 ... 1st adhesive layer 5 ... Transparent protective film 10 ... Oxygen indicator 11 ... 2nd adhesive layer 20 ... Oxygen indicator label

Claims (2)

A substrate,
An oxygen indicator layer containing at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin,
A transparent acidic component barrier layer,
A first pressure-sensitive adhesive layer containing an acidic component,
A transparent protective film having oxygen permeability and water vapor permeability,
, In this order. Having an oxygen indicator and a second pressure-sensitive adhesive layer,
The oxygen indicator, from the second adhesive layer side, a substrate,
An oxygen indicator layer containing at least a redox dye, a reducing agent, an alkalizing agent, and a binder resin,
A transparent acidic component barrier layer,
A first pressure-sensitive adhesive layer containing an acidic component,
A transparent protective film having oxygen permeability and water vapor permeability,
, In this order, an oxygen indicator label.

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