JP2007293287A - Indicator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an indicator which suffers less color change during storage and uniformly changes its color at any portion of the indicator in use, so that the remaining validity time can be definitely judged. <P>SOLUTION: An indicator includes a color-changing layer (A) which has a porous film having pores therein and a liquid compound retained in the pores, and a substrate layer (B) having a barrier property, which are laminated with the first adhesive layer (D); wherein the liquid compound has a vapor pressure of from 1×10<SP>-6</SP>to 5×10<SP>-3</SP>mmHg at 25°C, and the porous film contains a polyolefin resin containing 10% by weight or more of polyolefin having a molecular chain length of at least 2,850 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an indicator.

There is known an indicator (period display tool) that utilizes a phenomenon that the color of rubbed glass or water paper holding liquid on the surface changes as the liquid evaporates (see Patent Documents 1 and 2).
However, since the conventional indicator is not uniformly discolored during use, it is difficult to determine the remaining validity period, or discoloration may occur when stored for a long period of time.

Japanese Patent Laid-Open No. 57-158682 JP-A-7-281603

It is an object of the present invention to provide an indicator that can clearly determine whether or not the effective period remains, because discoloration hardly occurs during storage and uniform discoloration occurs in any part during use.

The first aspect of the present invention is that a porous film having micropores, a discoloration layer (A) containing a liquid compound retained in the micropores, and a base material layer (B) having a barrier property. An indicator that is laminated through an adhesive layer (D), wherein the liquid compound has a vapor pressure of 1 × 10 ^{−6 to} 5 × 10 ⁻³ mmHg at 25 ° C., and the porous film is It is an indicator which is a porous film formed from a polyolefin resin containing 10% by weight or more of polyolefin having a molecular chain length of 2850 nm or more.

The indicator of the present invention is unlikely to undergo discoloration during storage, and since discoloration occurs uniformly in any part during use, the remaining validity period can be clearly determined from the color.

The discoloration layer (A) in the present invention is a layer containing a porous film having fine pores and a liquid compound retained in the fine pores. The discoloration layer discolors as the liquid compound contained in the porous film evaporates and displays the remaining effective period of the indicator. Here, “changes color” means that the transparency changes.

The porous film constituting the discoloration layer (A) is a porous film formed of a polyolefin resin containing 10% by weight or more of polyolefin having a molecular chain length of 2850 nm or more. A porous film made of such a specific material is superior in strength to conventional porous films, and thus can have a large number of fine pores of a uniform size. In the indicator of the present invention, since the discoloration layer is formed of such a porous film, discoloration occurs uniformly in any part of the discoloration layer.
The polyolefin having a molecular chain length of 2850 nm or more is a polyolefin having a molecular chain length of 2850 nm or more measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. Chain-length ethylene homopolymer, copolymer of ethylene and α-olefin having 3 to 12 carbon atoms, propylene homopolymer, copolymer of propylene and α-olefin having 4 to 12 carbon atoms Etc. Since a resin composed only of polyolefin having a molecular chain length of 2850 nm or more is very difficult to form into a film shape, in the present invention, the polyolefin resin constituting the porous film of the discoloration layer has a molecular chain length of It is allowed to contain polyolefin having excellent processability, such as polyolefin of less than 2850 nm and olefinic wax, if the amount is acceptable in view of the intended purpose of the present invention. Specifically, the porous film of the color changing layer may contain 90% by weight or less of a polyolefin other than a polyolefin having a molecular chain length of 2850 nm or more. In other words, the polyolefin resin constituting the porous film needs to contain 10% by weight or more of polyolefin having a molecular chain length of 2850 nm or more. The olefin wax is a polyolefin having a weight average molecular weight of 700 to 6000, and is usually solid at 25 ° C. Examples of olefin waxes include ethylene resin waxes such as low density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), high density polyethylene, and propylene resin waxes such as polypropylene and ethylene-propylene copolymer. , Poly (4-methylpentene-1), poly (butene-1), and ethylene-vinyl acetate copolymer wax.

The molecular chain length of the polyolefin-based resin is a molecular chain length determined by GPC measurement using polystyrene as a standard substance, and is determined by the following procedure. As a mobile phase for GPC measurement, a solvent capable of dissolving both an unknown sample to be measured and standard polystyrene having a known molecular weight is used. First, GPC measurement of a plurality of types of standard polystyrene having different molecular weights is performed under predetermined measurement conditions, and the retention time of each standard polystyrene is obtained. For many polymers, it is known that the formula: molecular weight = molecular chain length × Q factor (constant) holds, and polystyrene has a Q factor of 41.3.
Therefore, the molecular chain length of each standard polystyrene is obtained using the above formula, and the retention time corresponding to the molecular chain length of each standard polystyrene is further known.
Next, GPC measurement of an unknown sample (polyolefin resin) is performed to obtain a retention time-eluting component amount curve. In the standard polystyrene GPC measurement, when the molecular chain length of the standard polystyrene that was the retention time T is L, the molecular chain length of the component that was the retention time T in the GPC measurement of the unknown sample is also regarded as L. Using this relationship, a molecular chain length-eluting component amount curve indicating the molecular chain length distribution of the unknown sample is obtained from the retention time-eluting component amount curve of the unknown sample. The content of polyolefin having a molecular chain length of 2850 nm or more in the unknown sample is a range corresponding to a molecular chain length of 2850 nm or more with respect to the value obtained by integrating the molecular chain length-elution component amount curve obtained by the above method over the entire range. It can obtain | require as a ratio of the integrated value about.

The porous film used in the present invention preferably has an average pore size of 0.06 to 0.1 μm measured using a porosimeter according to JIS K1150. The porous film preferably has a Gurley value (air permeability) measured in accordance with JIS P8117 of 100 to 250 seconds / 100 cc and a thickness of 5 to 20 μm. An indicator having a discoloration layer composed of such a porous film is particularly excellent in the uniformity of discoloration, easily determines whether or not the effective period remains, and is extremely excellent in storage stability.

The Gurley value is a value measured using a B-type densometer according to JIS P8117. When the Gurley value of the porous film is 150 seconds / 100 cc, the volume fraction of pores in the porous film is about 50% by volume. When the Gurley value is too large, the average pore diameter is large. The Gurley value depends on the thickness of the porous film. An indicator including a porous film that satisfies the requirements of the above-mentioned Gurley value and thickness as a discoloration layer is extremely excellent in discoloration uniformity. Further, the indicator needs to be able to visually recognize the base material layer through the discoloration layer during the effective period. From such a viewpoint, the thickness of the porous film constituting the discoloration layer (A) is preferably 20 μm or less, more preferably 15 μm or less.

The porous film can be produced, for example, by the method described below. Polyolefin resin containing 10.5% by weight or more of polyolefin having a molecular chain length of 2850 nm or more, 5 to 100 parts by weight of olefin wax with respect to 100 parts by weight of the resin, and a total of 100 parts by weight of the polyolefin resin and olefin wax On the other hand, a polyolefin resin composition containing 100 to 400 parts by weight of a water-soluble filler is formed into a sheet by a sheet forming method such as inflation, calendaring, T-die extrusion, or Skyf's method. The water-soluble filler is removed from the obtained sheet with an aqueous solvent, and the obtained filler-free sheet is dried. A porous film is obtained by stretching the dried sheet under stretching temperature conditions that do not block the pores generated by the removal of the filler. For stretching, a stretching machine such as a tenter can be used.

The liquid compound in the present invention is a liquid at 25 ° C. and is a method reported by Stephen F. Donovan (New method for controlling vapor pressure by the use of gas chromatography: Journal of Chromatography A. 749 (1996) 123- 129) is a compound having a vapor pressure at 25 ° C. of 1 × 10 ^{−6 to} 5 × 10 ⁻³ mmHg. When the vapor pressure of the liquid compound in the color changing layer is lower than 1 × 10 ⁻⁶ mmHg, the start of the color change is slow in a normal environment, and the color change does not occur uniformly. Further, when the vapor pressure of the liquid compound in the discoloration layer is higher than 5 × 10 ⁻³ mmHg, discoloration occurs in a very short time under a normal environment. When using an indicator, since it is usually used for several days, such a liquid compound having a high vapor pressure cannot be used. Specific examples of liquid compounds applicable to the present invention include isopropyl myristate (5.54 × 10 ⁻⁵ mmHg), methyl laurate (1.57 × 10 ⁻³ mmHg), ethyl laurate (6.85 × 10 ⁻⁴ mmHg), isopropyl palmitate (8.14 × 10 ⁻⁶ mmHg), dibutyl sebacate (2.70 × 10 ⁻⁶ mmHg), dioctyl maleate (3.13 × 10 ⁻⁶ mmHg), acetyl citrate Examples include triethyl acid (1.46 × 10 ⁻⁴ mmHg), tributyl acetylcitrate (1.27 × 10 ⁻⁶ mmHg), and the like. The pressure indicated in parentheses is the vapor pressure at 25 ° C. From the viewpoint of transparency of the discoloration layer composed of the porous film and the liquid compound, the refractive index of the liquid compound is preferably in the range of (refractive index of the porous film) ± 0.1.

The method for retaining the liquid compound in the porous film is not particularly limited, and a normal dry laminator, a printing machine such as a gravure printing machine, or the like can be used. Moreover, the method of immersing a porous film in the liquid compound put into the container, and the method of dripping a liquid compound in a porous film are applicable.

The base material layer (B) in the indicator of the present invention is a layer having a barrier property, which is laminated with the above-described discoloration layer (A) via the first adhesive layer (D). The barrier property of the layer (B) means a property of preventing the liquid compound in the discoloration layer (A) from diffusing into the layer (B), and more specifically, for example, according to ASTM D3985, the temperature of 20 The oxygen permeability measured under the conditions of ° C., relative humidity 65% RH, and film thickness 20 μm is preferably 40 cc / m ² · day · atm or less. By disposing the base material layer (B) having a barrier property on one side of the color changing layer (A), the transpiration of the liquid compound from the color changing layer (A) is unidirectional, that is, on the side opposite to the layer (B). The liquid compound can be uniformly evaporated by this. When the indicator of the present invention contains a sufficient amount of a liquid compound in the color changing layer (A), the color changing layer (A) is transparent, and the base material layer (B) is passed through the color changing layer (A). Is visible. Then, when the discoloration layer (A) becomes opaque due to the transpiration of the liquid compound and the base material layer (B) becomes invisible, it is determined that the effective period has ended. The period during which the base material layer (B) is visible through the color changing layer (A) is the effective period of the indicator.

As a base material having a barrier property constituting the layer (B), unstretched made of a material having excellent barrier properties such as ethylene / vinyl alcohol copolymer (EVOH), polyethylene naphthalate, polyacrylonitrile, polyvinyl chloride, Unstretched, uniaxially stretched from uniaxially or biaxially stretched films, materials with excellent barrier properties, polyolefins such as polyethylene and polypropylene, polyamides, and materials with relatively low barrier properties such as polyethylene terephthalate (PET) Alternatively, a film in which a layer made of a material having a relatively excellent barrier property is laminated on at least one surface of a support film such as a biaxially stretched film. Moreover, not only the film which consists of resin materials but metal films, such as aluminum foil, can also be used. The substrate is preferably a laminate in which a layer of a composition in which a layered inorganic compound is dispersed in a resin is laminated on a transparent support film. Here, the “layered inorganic compound” is an inorganic compound having a layered structure in which unit crystal layers are stacked, and examples thereof include kaolinite, montmorillonite, mica, talc, vermiculite, and the like.

Further, the substrate is preferably a film made of a resin colored with a pigment or the like, or a film on which a character or pattern is printed in a single color or multicolor on the surface on the side where the discoloration layer (A) is arranged. .

When the substrate is a laminate having a support film layer and a layer of a material having excellent barrier properties laminated on one side thereof, the barrier layer and the color changing layer (A) are formed of the first adhesive. Lamination via the layer (D) is preferable because diffusion of the liquid compound in the discoloration layer (A) to the layer (B) of the base material is effectively suppressed.

The discoloration layer (A) and the base material layer (B) are laminated via the first adhesive layer (D). As the first adhesive constituting the layer (D), an adhesive for dry lamination used in general packaging materials can be used. Examples include aliphatic polyethers, aliphatic polyesters, aromatics. Two-component adhesives such as aromatic polyethers and aromatic polyesters, and one-component adhesives such as polyethyleneimine and polybutadiene. Since the liquid compound in the color changing layer (A) also diffuses into the layer (D), the adhesive strength between the color changing layer (A) and the layer (B) may decrease with time. Therefore, it is preferable to use a two-component reactive adhesive such as an aliphatic polyester-based adhesive or an aromatic polyester-based adhesive having a high initial adhesive strength, and it is particularly preferable to use an adhesive having a high organic solvent resistance. The thickness of the layer (D) is preferably as small as possible, and is usually in the range of 0.5 to 4 μm, and preferably in the range of 0.7 to 2 μm. As a method for laminating the discoloration layer (A) and the layer (B) via the layer (D), a dry laminating method can be mentioned. In this method, a first adhesive diluted with a solvent is applied to one surface of a substrate, and the solvent is volatilized and removed, and then a discoloration layer (A) is laminated on the formed first adhesive layer. It is a method to do. After laminating the discoloration layer (A), curing may be performed as necessary.

It is preferable to hold | maintain the indicator of this invention without evaporating the liquid compound in the porous film which comprises a discoloration layer (A) from the manufacture to use start (at the time of the start of period display). Therefore, it is preferable that the layer (C) having a barrier property is laminated on the discoloration layer (A) through the second adhesive layer (E) until use is started. The second adhesive in this form is an adhesive.

As a material constituting the layer (C) having a barrier property, the same material as the material of the substrate constituting the layer (B) described above can be used. As the layer (C), it is preferable to use a laminate in which a layer of a composition in which a layered inorganic compound is dispersed in a resin is laminated on one side of a support film. When the layer (C) is composed of such a laminate, the composition layer and the discoloration layer (A) are preferably laminated via the pressure-sensitive adhesive layer (E).

The second adhesive layer (E) is peeled off together with the layer (C) when the indicator is used (that is, when the period display is started). Therefore, after peeling the layer (C) and the layer (E), it is possible to select a pressure-sensitive adhesive in which part or all of the layer (E) remains on the surface of the discoloration layer (A), so-called adhesive residue does not occur. preferable.

Examples of the pressure-sensitive adhesive constituting the layer (E) include general solvent-type acrylic pressure-sensitive adhesives and water-based emulsion-type acrylic pressure-sensitive adhesives, and have resistance to the liquid compound contained in the discoloration layer (A). An adhesive is preferably used. When a pressure-sensitive adhesive having low resistance to the liquid compound is used, the pressure-sensitive adhesive may be dissolved or swelled by the liquid compound in the discolored layer (A) and enter the pores of the porous film together with the liquid compound. In such a case, the period display performance of the indicator may be impaired. As an adhesive having resistance to a liquid compound, it is preferable to use an acrylic adhesive having a number average molecular weight (Mn) of 50,000 or more as measured by GPC using polystyrene as a standard substance, and Mn is 100,000 or more. It is more preferable to use an acrylic pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive is a pressure-sensitive adhesive mainly composed of a polymer of an acrylic acid monomer such as 2-ethylhexyl acrylate or n-butyl acrylate. In addition, the aqueous emulsion type adhesive is preferable from the viewpoint of liquid compound resistance compared to the solvent type adhesive. The aqueous emulsion type pressure-sensitive adhesive is an emulsion having a solid content of about 50% in which a resin mainly composed of an acrylic acid monomer such as 2-ethylhexyl acrylate and n-butyl acrylate is dispersed in water. Moreover, it is preferable that the thickness of a layer (E) is 1-20 micrometers.

An example of a method of laminating the color changing layer (A) and the layer (C) via the layer (E) includes a method using a dry laminator. Specifically, the method includes the following steps.
(1) A laminated film in which a porous film and a base material are laminated via a first adhesive layer (D) is fed out from a dry laminator feeding machine;
(2) A liquid compound is applied to the surface of the rolled-up laminated film by a gravure roll or the like, so that the liquid compound is impregnated in the pores of the porous film. (B) forms a laminated body laminated with the layer (D) interposed therebetween;
(3) The film made of the barrier material fed from another feeding machine of the dry laminator and the discoloration layer (A) of the laminate formed in the step (2) are pressure-bonded via an adhesive. The pressure-sensitive adhesive is usually applied to one side of a film made of the barrier material before pressure bonding with the laminate. In step (2), after applying the liquid compound, drying in an oven may be performed as necessary.

In the indicator of the present invention, the length of the display period can be adjusted by adjusting the type and amount of the liquid compound to be contained in the color changing layer (A) and the thickness of the porous film constituting the color changing layer (A). it can. Further, release paper may be laminated on the surface of the layer (B) on the side where the layer (D) is not present, with an adhesive layer interposed therebetween. In such a configuration, if the release paper is removed, an indicator can be attached to a desired place of the article via the pressure-sensitive adhesive layer.

The shape of the indicator of the present invention is not limited. When the indicator of the present invention has a layer (C) of a barrier material, if the area of the layer (C) is larger than that of the other layers, the consumer can easily peel and remove the barrier layer (C). Further, a peeling tape or the like may be provided on the layer (C).

When using the indicator of the present invention, a laminate having the same configuration as that of the indicator of the present invention except that it does not contain a liquid compound is disposed with the indicator as a comparison target so that the consumer can more clearly recognize the remaining effective period. This is a preferred embodiment.

The indicator of the present invention can be used as a device for indicating the remaining period of insect repellent effect by attaching it to an insect repellent device containing an insect repellent, insecticide, repellent and the like with an adhesive seal or string. In addition to insect repellent applications, it can be used for applications that require the remaining effective period to be displayed.

Examples are shown below, but the present invention is not limited thereto.

(1) Gurley value measurement method The Gurley value (second / 100 cc) of the porous film was measured using a B-type densometer (manufactured by Toyo Seiki Co., Ltd.) according to JIS P8117. The Gurley values were measured at 10 arbitrary locations in the porous film, and the average value thereof was taken as the Gurley value of the porous film.

(2) Measuring method of average pore diameter The average pore diameter (μm) of the porous film was measured by a mercury injection method using a porosimeter (manufactured by Shimadzu Corporation) according to JIS K1150. Measurement was made at five arbitrary locations in the porous film, and the average value of the measured values was defined as the average pore diameter of the porous film.

(3) Measurement of molecular chain length and molecular weight by GPC A gel chromatograph Alliance GPC2000 model manufactured by Waters was used. Other conditions are shown below.
Column: Tosoh Corporation TSKgel GMHHR-H (S) HT 30 cm × 2, TSKgel GMH6-HTL 30 cm × 2
Mobile phase: o-dichlorobenzene detector: differential refractometer flow rate: 1.0 mL / min column temperature: 140 ° C.
Injection volume: 500 μL
After completely dissolving 30 mg of the sample in 20 mL of o-dichlorobenzene at 145 ° C., the solution was filtered through a sintered filter having a pore size of 0.45 μm, and the filtrate was used as a feed solution. The calibration curve was prepared using 16 kinds of standard polystyrenes with known molecular weights. The Q factor of polystyrene is 41.3.

(3) Storage stability test Ten indicators having the layer (C) of the barrier material were placed in an oven adjusted to 40 ° C. When there was a color change, the number of days until the change occurred was counted, and an average number of days and an error (unit: days) were obtained. The evaluation period was 60 days.

(4) Color change test After the indicator having the layer (C) of the barrier material was stored at 40 ° C. for 10 days, the layer (C) was peeled off and further left at room temperature. The number of days until the color change occurred was counted, and an average number of days and an error (unit: days) were obtained.

(5) Total performance Storage stability test (3) When the color change does not occur for more than 60 days, and the color change test (4) has an error within ± 3 days, it has good performance as an indicator. Then, it evaluated and it displayed with the symbol "(circle)" in the table | surface which is mentioned later. Those not satisfying the above requirements were evaluated as not having sufficient performance as an indicator, and indicated by the symbol “x” in the table below.

[Example 1]
Preparation of porous film (1) 100 parts by weight of polyethylene powder (Hi-Zex Million 340M, manufactured by Mitsui Chemicals, Ltd., weight average molecular chain length 17000 nm, weight average molecular weight 3 million, melting point 136 ° C.) Wax powder 43 parts by weight (High Wax 110P, Mitsui Chemicals, Inc., weight average molecular weight 1000, melting point 110 ° C.) and calcium carbonate (Shiroishi Calcium Vigot 10, average particle diameter 0.15 μm determined by SEM) 150 parts by weight Were mixed with a Henschel mixer, and then kneaded with a biaxial kneader to obtain a composition (1). The composition (1) was rolled with a calender roll adjusted to 150 ° C. to produce a sheet (1) having a thickness of about 70 μm. The sheet (1) was immersed in an aqueous hydrochloric acid solution to remove calcium carbonate, washed with an aqueous sodium hydroxide solution, further washed with water, and dried to obtain a resin sheet. The resin sheet was transversely stretched 5 times at a stretching temperature of 100 ° C. to produce a porous film (1). The porous film (1) was wound up into a roll. The content of polyethylene having a molecular chain length of 2850 nm or more in the resin component of the porous film (1) was 28% by weight.
Production of base material Commercially available polyethylene terephthalate film coated on one side with a layer containing a plate-like inorganic-inorganic compound (manufactured by Nippon Eco Wrap Co., Ltd .; trade name: Savix YPET-G2; thickness: 12 μm) Prepared. A red ink was printed on the entire surface of the film with a gravure printer to obtain a substrate. The printed substrate was wound up into a roll.
Lamination of substrate and porous film A substrate roll was attached to a dry laminator feeder (first paper feeder), and the substrate was fed from the roll at a speed of 5 m / min. Next, an aliphatic polyester-based adhesive was applied to the coating surface of the substrate with a gravure roll, and the organic solvent for diluting the adhesive was removed in an oven at 80 ° C. to form an adhesive layer (D) having a thickness of 2 μm. Formed. Then, this base material with an adhesive layer (D) was pressure-bonded with the porous film (1) fed out from another feeding machine (second paper feeding machine) of the dry laminator. It aged at 40 degreeC for 2 days, and obtained the laminated body (1) by which the layer (B) of the base material and the porous film (1) were laminated | stacked through the adhesive bond layer (D). The laminate was wound into a roll.
Production of barrier film with pressure-sensitive adhesive layer A commercially available polyethylene terephthalate film coated with a layer containing a plate-like inorganic inorganic compound on a dry laminator feeding machine (manufactured by Nippon Eco Wrap Co., Ltd .; product) Name: Savix YPET-G2; Thickness: 12 μm) roll is attached, and an acrylic water-based emulsion type adhesive (manufactured by Ganz Kasei Co., Ltd.) is 20 μm thick on the coating surface of the film drawn out from the roll Thus, an adhesive layer (E) was formed. The barrier film with the pressure-sensitive adhesive layer (E) thus formed was wound up into a roll.
Production of indicator stock The roll of the laminate (1) was attached to the dry laminator feeding machine (first paper feeder), and the laminate (1) was fed from the roll. Isopropyl myristate (vapor pressure 5.54 × 10 ⁻⁵ mmHg at 25 ° C., liquid at room temperature) was applied to the surface of the porous film (1) of the unrolled laminate (1) with a gravure roll. The applied isopropyl myristate was retained in the pores of the porous film (1), and the discoloration layer (A) was formed. Thus, a laminate (2) in which the discoloration layer (A) and the base material layer (B) were laminated via the adhesive layer (D) was obtained. A roll of a barrier film with an adhesive layer (E) was attached from another feeder (second paper feeder) of the dry laminator. The barrier film with the pressure-sensitive adhesive layer (E) is fed out from the roll, and this and the laminate (2) are stacked and pressure-bonded so that the pressure-sensitive adhesive layer (E) and the porous film (1) are in contact with each other. . Thereby, the laminated body (3) laminated | stacked in order of barrier film layer (C) / adhesive layer (E) / discoloration layer (A) / adhesive layer (D) / base material layer (B) is obtained. It was.
Production of indicator The laminate (3) was punched into a diameter of 10 mm to form an indicator. Various evaluations were performed using the indicator. The results are shown in Table 1.

[Example 2]
An indicator was obtained in the same manner as in Example 1 except that an acrylic solvent-type adhesive was used instead of the acrylic aqueous emulsion-type adhesive. The evaluation results of the indicator are shown in Table 1.

[Example 3]
Instead of the polyethylene terephthalate film coated with the plate-like inorganic compound for the layer (C), a polyethylene terephthalate film (thickness 12 μm) and an ethylene-vinyl alcohol copolymer film (thickness 20 μm, ethylene 44 mol%) An indicator was obtained in the same manner as in Example 1 except that a laminated film (commercial product) was used and the pressure-sensitive adhesive layer (E) was formed on the layer of the ethylene-vinyl alcohol copolymer film. The evaluation results of the indicator are shown in Table 1.

[Example 4]
Example 1 was used except that an ethylene-vinyl alcohol copolymer film (thickness 20 μm, ethylene 44 mol%) was used instead of the polyethylene terephthalate film coated with the plate-like inorganic compound for the layer (B). And got an indicator. The evaluation results of the indicator are shown in Table 1.

[Comparative Example 1]
100 parts by weight of polyethylene pellets (Sumikasen-L, FS240 manufactured by Sumitomo Chemical Co., Ltd.) and 300 parts by weight of calcium carbonate were mixed with a Henschel mixer, and further kneaded with a biaxial kneader to obtain a composition (2). .
A sheet (2) having a film thickness of about 65 μm was produced in the same manner as in Example 1 except that this composition (2) was used instead of the composition (1). After removing calcium carbonate from this sheet (2) in the same manner as in Example 1, transverse stretching was performed 5 times at a stretching temperature of 90 ° C. to produce a porous film (2). The content of polyethylene having a molecular chain length of 2850 nm or more in the resin component of the porous film (2) was 1% by weight or less.
An indicator was obtained in the same manner as in Example 1 except that the porous film (2) was used instead of the porous film (1). The results of the indicator are shown in Table 2.

[Comparative Example 2]
Except for using a commercially available polyethylene porous film (3) (thickness 24 μm, average pore diameter 0.04 μm, Gurley value 420 seconds / 100 cc) instead of the porous film (1), the same as in Example 1, Got an indicator. The content of polyethylene having a molecular chain length of 2850 nm or more in the resin component of the porous film (3) was 8% by weight. The evaluation results of the indicator are shown in Table 2.

Claims (4)

The first adhesive layer comprises a porous film having micropores, a discoloration layer (A) containing a liquid compound held in the micropores, and a base material layer (B) having a barrier property. (D) is an indicator that is laminated via, the vapor pressure of the liquid compound at 25 ° C. is 1 × 10 ^{−6 to} 5 × 10 ⁻³ mmHg, and the porous film has a molecular chain length. An indicator which is a porous film formed from a polyolefin-based resin containing 10 wt% or more of a polyolefin having a thickness of 2850 nm or more. The porous film has an average pore diameter measured according to JIS K1150 of micropores of 0.06 to 0.1 μm, a Gurley value measured according to JIS P8117 of 100 to 250 seconds / 100 cc, and a thickness of 5 to 5 The indicator according to claim 1 which is 20 micrometers. The layer (C) having a barrier property is laminated on the discoloration layer (A) via the second adhesive layer (E), and the second adhesive is a pressure-sensitive adhesive. Indicator described in. The indicator according to claim 3, wherein the second adhesive is an aqueous emulsion-type pressure-sensitive adhesive, and the thickness of the layer (E) is 1 to 20 µm.