JP2002350419A - Humidity detection material, its manufacturing method and desiccant using humidity detection material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe humidity detection material having little load to an environment, capable of displaying clearly and stepwise plural kinds of changing colors corresponding to a humidity change by one humidity detection material, its manufacturing method, and an inexpensive desiccant using the humidity detection material. SOLUTION: A hygroscopic coloring substance formed by impregnating acidic material and an acid-base indicator into silica gel is laminated on paper, nonwoven fabric, a permeable film or the like, to thereby manufacture one humidity detection tape 4 for detecting prescribed humidity and discoloring stepwise to plural kinds of humidity display colors 5 corresponding to the detected humidity. This desiccant 1 is constituted by sticking in a belt-like shape the humidity detection tape 4 and a humidity display tape 7 where the humidity display colors 5 and a humidity display 6 corresponding to each humidity display color are described in parallel, on the surface of a packing material 3 filled with a desiccant body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity detecting material used for detecting and displaying humidity in a packaging container for preserving mainly foods and electric parts, a method of manufacturing the same, and a packaging container together with the humidity detecting material. The present invention relates to a desiccant which is enclosed and used for preventing moisture absorption in a packaging container.

[0002]

2. Description of the Related Art Conventionally, as a humidity detecting material used for detecting and displaying humidity and the like in a packaging container for storing, for example, food and electric parts, Japanese Patent Application Laid-Open No. 52-100379 is disclosed.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10 (1994), cobalt chloride has been widely used as a moisture-sensitive coloring agent which is impregnated with silica gel or paper. And such a humidity detection material,
It is often used enclosed in a packaging container together with a desiccant used to prevent moisture absorption in the packaging container, and determines whether the relative humidity is below the effective value and whether the desiccant is effective . In other words, cobalt chloride is blue in a dry state, but changes from violet to light red as the humidity increases, so that the effectiveness of the desiccant can be determined based on the changed color.

Further, when judging the appropriateness of the humidity in the packaging container in addition to the effectiveness of the desiccant, a plurality of kinds of changed colors corresponding to the relative humidity are required. Therefore, in the related art, in order to use the changed color as the humidity display color, using a humidity detecting material having a plurality of display spots and display lines in which the concentration of the cobalt chloride solution is different depending on the predetermined humidity to be detected. I have.

[0004]

However, in the above-mentioned conventional example, cobalt chloride used as a humidity detecting material is an element essential for the human body, but is a substance which is also suggested to be carcinogenic, and is not necessarily safe. Absent.

[0005] Further, when the concentration of cobalt chloride is different, the changed color, which changes color from blue to violet or light red, is not clear, and the changed color is different in a plurality of display spots and display lines having different densities. Appears, making it difficult to determine the changed color, and there is a problem that a clear display corresponding to a change in humidity cannot be made.

Accordingly, the present invention solves the above-mentioned problems, and a plurality of changed colors corresponding to changes in humidity can be clearly and stepwise displayed on a single humidity detecting material, and the humidity detecting material is safe and has a small load on the environment. And a method for producing the same, and a desiccant using the humidity detecting material.

[0007]

In order to achieve the above-mentioned object, the humidity detecting material of the present invention detects a predetermined humidity and changes its color stepwise to a plurality of humidity indicating colors corresponding to the detected humidity. In addition, a moisture-sensitive color product in which silica gel is impregnated with an acidic substance and an acid-base indicator is formed in a granular or sheet form.

In the humidity detecting material of the present invention, the porous silica gel is a moisture-sensitive coloring material in which pores are impregnated with an acidic substance and an acid-base indicator, for example, when sealed in a packaging container. The water vapor in the air absorbs moisture, and the amount of moisture absorption that changes with a change in humidity appears as the concentration of the acidic substance impregnated in the pores, and the color of the acid-base indicator changes stepwise according to the pH. Then, the changed color indicates the humidity state in the packaging container to the outside as a plurality of types of humidity display colors that have detected the predetermined humidity. Therefore, a plurality of humidities can be visually identified from the outside with one humidity detecting material.
In addition, since the humidity is displayed using the color change of the acid-base indicator, the humidity display color is clearer than that of cobalt chloride, and its distinction can be made accurately and easily, and it is safe and environmentally friendly. Less is.

In the above-mentioned humidity detecting material, the moisture-sensitive coloring material is
If a powder obtained by impregnating an acidic substance and an acid-base indicator into silica gel particles having a particle size of 200 μm or less is mixed with a resin agent, the acidic substance or the acid-base indicator impregnated into the silica gel particles is immobilized with the resin agent. Since such leakage can be prevented, safety is further improved, which is preferable.

[0010] Further, solid paraffin,
When a polyethylene resin, a polypropylene resin, an ionomer resin, or the like is used, a stable color change can be obtained without a reaction with silica gel or an interaction with an acid-base indicator. As described above, a resin material having relatively low moisture permeability disperses a powdery moisture-sensitive coloring material in the resin material and stretches the film during film formation, or rapidly evaporates the solvent to form a thin film. This is preferable because a sharp color change can be obtained.

Further, if the moisture-sensitive coloring material is stretched to form a moisture-permeable microporous film and this is used as a sheet-like humidity detecting material, it can be used alone as a waterproof microporous film for disposable diapers, for example. It is suitable because it can be used as a part and that part can function as a stuffiness detection material.

Further, the above-mentioned moisture-sensitive coloring material is laminated on paper, a nonwoven fabric, a breathable film or the like by coating or printing, and this is used as a sheet-like humidity detecting material. By sticking on a nonwoven fabric or converting a moisture-sensitive coloring material into an ink and printing it on a breathable film, leakage of an acidic substance or an acid-base indicator can be prevented as described above. Silica gel fine powder is generally available on the market (“Sunsphere” manufactured by Dokai Chemical Co., Ltd., “Microid” series manufactured by Toyo Chemical Co., Ltd., etc.). Since a particle size of 3 μm or less is easily available, a humidity detecting material can be easily and inexpensively manufactured. For silk printing, it is possible to make an ink even if the particles are large, but as the particle size increases, the amount of moisture-sensitive coloring increases to obtain a constant color change of the acid-base indicator. Need to be
If the particles have a size of 00 μm or more, they cannot be formed into a thin film. In addition, by covering the surface of the laminated moisture-sensitive coloring material with a perforated film, it is possible to prevent the stored articles from directly touching the mixture while maintaining the moisture absorption property, making the humidity detecting material safer and more environmentally friendly. Can be reduced. It is preferable that the perforated film is made transparent so that a plurality of types of humidity indicating colors of the humidity detecting material accompanying the color change of the acid-base indicator can be visually observed from the outside.

In the above humidity detecting material, if an edible blue No. 1 (brilliant blue FCF and its aluminum lake) or an edible green No. 3 (fast green FCF and its aluminum lake) is used as the acid-base indicator, it is recognized as a food additive. It is safe and has a low environmental impact because it is a color component that has been given. In addition, with one indicator, the color changes stepwise from orange to yellow, green, and blue-green in the case of green No. 3, for example. Since the color changes, the changed color is clear and the determination is easy and accurate.

In order to achieve the above object, the method for producing a humidity detecting material according to the present invention detects a predetermined humidity and gradually changes the color to a plurality of humidity indicating colors corresponding to the detected humidity. To form a powder by impregnating an acidic substance and an acid-base indicator into a powder, and forming a moisture-sensitive coloring material mixed with a resin agent in the powder into a granular or sheet form to produce a humidity detecting material, The humidity display color is adjusted by changing the impregnation concentration of the substance.

According to the method for producing a humidity detecting material of the present invention,
In a silica gel having the above-mentioned porous material and having a certain moisture absorbing performance, the pH is determined by the impregnation amount of the acidic substance into its pores. By displacing the corresponding color change of the acid-base indicator, the hue of the humidity display color on the humidity detecting material can be adjusted. Then, it is preferable to select an appropriate acid-base indicator that can obtain a clear color change according to the impregnation concentration of the acidic substance. In the process of producing silica gel, it is also possible to adjust the amount of moisture absorption by obtaining silica gel (JIS Z-701) having different moisture absorption performance by changing the concentration of the sulfuric acid solution and the concentration of the sodium silicate solution. is there. When the same acidic substance, acid-base indicator, and silica gel are used, the humidity display color shifts to the high humidity side when the hydrogen ion concentration is increased, and shifts to the low humidity side when the hydrogen ion concentration is decreased. .

In order to achieve the above object, the desiccant of the present invention is a sheet in which the humidity detecting material is a humidity detecting tape formed into a single tape, and the desiccant is formed of a packaging material filled with a desiccant body. On the surface, the humidity detection tape and a humidity display tape on which a plurality of types of humidity display colors when the humidity detection tape detects a predetermined humidity and changes color and a humidity display corresponding to each humidity display color are written in a strip shape. Characterized in that it is affixed to

According to the desiccant of the present invention, a humidity detecting tape is affixed to the surface of the packaging material filled with the desiccant main body, and a humidity indication corresponding to the humidity indicating color of the humidity detecting tape is also written. Since the humidity indicator tape is also attached, the work efficiency is higher and the equipment cost can be reduced compared to a humidity detection material sealed in a packaging container separately from the desiccant, so the product is inexpensive. Can be provided. In addition, unlike cobalt chloride, a humidity detection material that is safe and has a low environmental impact is used, so that the desiccant can be used with confidence, and of course, the humidity detection tape has a clear humidity display color, and the corresponding humidity display Since it is directly attached to the desiccant together with the humidity indicating tape having the desiccant, it is possible to easily and accurately determine whether the humidity in the packaging container is properly maintained by the desiccant in addition to the effectiveness of the desiccant. .

In the above desiccant, the humidity detecting tape and the humidity indicating tape are integrated into a single band, and the band tape is attached to two opposing seal edges on the periphery of the packaging material. With this configuration, the humidity detection portion and the humidity display color can be easily compared with each other, so that the determination can be made easier. In addition, the manufacturing cost can be suppressed by, for example, matching the sending direction of the manufacturing machine, and the product can be provided at lower cost. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below by taking a desiccant using a humidity detecting material shown in FIGS. 1 to 3 as an example. FIG. 1 is a plan view showing the desiccant of the present embodiment, FIG. 2 is a cross-sectional view thereof, and FIG.

As shown in FIGS. 1 and 2, the desiccant 1
On the surface of the packaging material 3 filled with the desiccant body 2, a humidity detecting tape 4 as a sheet-like humidity detecting material, and a plurality of types when the humidity detecting tape 4 detects a predetermined humidity and changes its color stepwise. Humidity display tape 7 on which a humidity display color 5 and four levels of humidity display 6 corresponding to 10% RH to 40% RH corresponding to each humidity display color 5 are written, and two opposing sides of the periphery of the packaging material 3 Is affixed in a band shape as one band-shaped tape 9 up to the seal edge. The humidity display 6 may be described on each humidity display color 5.

The humidity detecting tape 4 is composed mainly of a moisture-sensitive color product obtained by impregnating silica gel with an acidic substance such as sulfuric acid and an acid-base indicator such as Food Blue No. 1 and Food Green No. 3, as a main component. A resin agent is mixed to form a shape. As shown in FIG. 3, a plastic film 8 such as polyethylene is adhered to the back surface of the humidity detecting tape 4, and the surface of the plastic film 8 (the contact surface with the packaging material 3) is slightly melted by heat. The heat seal layer 8a is attached to the surface of the packaging material 3 by thermal lamination.

Since the humidity detecting tape 4 is shown in a sheet-like completed state, the humidity-sensitive coloring materials (silica gel, acidic substance, acid-base indicator, resin agent) and the base material The resulting paper, nonwoven fabric and breathable film are not shown.

As the drying material main body 2, silica gel, calcium chloride or the like is used, and as the packaging material 3, water-resistant oil-resistant paper, another plastic film having water vapor permeability, or a laminated film thereof is used.

In addition to the sheet-shaped humidity detecting tape 4 described above, the humidity detecting material may be constituted by a granular single substance that does not require a base material such as a resin agent or a nonwoven fabric as in Example 5 described later. In such a case, it is preferable that the desiccant is enclosed in a transparent packaging material 3 so that the changed color of the granular humidity detecting material can be visually observed from the outside together with the granular silica gel used as the desiccant main body 2.

When the sheet-like humidity detecting tape 4 is formed as in the present embodiment, silica gel particles having a size of 200 μm or less are used, and the particles are impregnated with an acidic substance and an acid-base indicator. A moisture-sensitive coloring material, which is mixed with a resin agent appropriately selected in consideration of the purpose and the period of use and thinned as in Example 2 to be described later or made into an ink as in Example 3, is formed on paper, nonwoven fabric, Laminated on a breathable film or the like.

The desiccant 1 is enclosed in a packaging container (not shown), and a humidity detecting tape 4 formed of a sheet of a moisture-sensitive coloring material.
However, the humidity in the packaging container is detected and displayed. Specifically, silica gel, which is a porous material, impregnates the pores with an acidic substance and an acid-base indicator to absorb water vapor in the air in the packaging container, and the amount of moisture absorption that changes with humidity changes is acidic. It appears as the concentration of a substance, and the acid-base indicator changes its color according to its pH. The changed color indicates the humidity state in the packaging container and the effectiveness of the desiccant 1 to the outside as a plurality of humidity display colors 5 that have detected a predetermined humidity.

In the present embodiment, when the amount of impregnation of the pores with the acidic substance is changed based on the moisture absorption performance of the silica gel, the impregnation concentration of the acidic substance changes, and the coloration of the acid-base indicator corresponding to a predetermined humidity is changed. By displacing the change, the hue of the humidity display color 5 can be adjusted. Then, it is preferable to select an appropriate acid-base indicator so that the changed color becomes clear according to the impregnation concentration of the acidic substance.

Examples of the acidic substance include sulfuric acid, inorganic acids such as phosphoric acid, and organic acids such as oxalic acid, citric acid, and sulfonic acid. A list of acid-base indicators and the corresponding pH and color change is shown in Table 1 below.

[0029]

[Table 1] When solid paraffin, polyethylene resin, polypropylene resin, ionomer resin, or the like is used as the resin agent, a stable color change can be obtained without a reaction with silica gel or an interaction with an acid-base indicator. In this way, the resin material having a relatively small moisture permeability disperses the powdery moisture-sensitive coloring material in the resin material and stretches it during film formation,
By thinning the solvent by rapid volatilization, etc.,
A sharp color change can be obtained. Note that resin agents such as polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polyvinyl acetate, polyacryl methacrylate, polyvinyl chloride, and nylon having polar groups such as a hydroxyl group and an amide group have a large moisture permeability but an interaction with an acid-base indicator. Therefore, it is not suitable for long-term use type humidity detecting materials.

The sticking direction of the humidity detecting tape 4 and the humidity indicating tape 7 is set to coincide with the sending direction of an automatic filling and packaging machine for filling the desiccant body 2 into the packaging material 3, and the sticking range is the desiccant 1 Up to the edge of the seal portion 1a at the peripheral portion. Therefore, since the humidity detecting tape 4 and the humidity indicating tape 7 are continuously attached in a belt shape in parallel with the sending direction of the packaging material 3 sent out in a tape shape, the desiccant body 2 is filled and the heel seal is applied. Then, if the connected seal portion 1a is cut, the band-shaped tape 9 (the humidity detecting tape 4) is cut.
And the desiccant 1 with the humidity indicating tape 7) can be manufactured, so that the working efficiency is good and the cost can be reduced. In the present embodiment, an example of the desiccant manufactured by the four-side seal type automatic packaging and filling machine is shown, but a three-side seal type may be used. When this is shown in FIG. 1, the folded part is located at the right end.

Further, by forming the above-mentioned moisture-sensitive coloring matter into a thin film and applying it on a nonwoven fabric or by making it into an ink and printing it on a breathable film, it is possible to use an acidic substance or an acid-base indicator impregnated in silica gel. Leakage can be prevented. By covering the surface of the humidity detecting tape 4 formed by laminating the moisture-sensitive coloring materials with the perforated film 10 through the air layer 11 as shown in FIG. Can be prevented from directly touching the mixture while keeping the humidity, the humidity detecting tape 4 and the desiccant 1 can be made safer and have less environmental load. In addition,
It is preferable that the perforated film 10 be transparent so that a plurality of types of humidity indicating colors of the humidity detecting tape 4 accompanying the color change of the acid-base indicator can be visually observed from the outside.

Next, the experimental results of this embodiment are shown in Examples 1 to 3.
This will be described in Section 5. The sheet-like humidity detecting material used for the desiccant 1 will be described in Examples 1 to 3, the film-like humidity detecting material will be described in Example 4, and the granular humidity detecting material will be described in Example 5.

Example 1 0.2 g of silica gel having an average pore diameter of 12 μm (“Sunsphere” manufactured by Dokai Chemical Industry Co., Ltd.) was added.
250 ml of 2N (specified concentration) sulfuric acid aqueous solution and food blue 3
No. 0.06 g, shaken for 24 hours, filtered,
Drying was carried out at a temperature of not more than 05 ° C. to obtain finely divided moisture-sensitive colored powder.
This powder exhibited yellow at 0% RH, yellow-green at 30% RH, green at 50% RH, and blue at 70% RH, and it was confirmed that the changed color changed stepwise with the change of humidity. . 100 g of paraffin (melting point: 60 to 62)
C.) while heating to obtain a moisture-sensitive colored product. This moisture-sensitive colored product was applied to the surface of a polyester nonwoven fabric to prepare a sheet-shaped humidity detecting material. When the humidity detection sheet was left in each humidity atmosphere, the color changed sharply, and a clear humidity display color corresponding to a predetermined humidity was obtained.

Example 2 A 0.02N benzenesulfonic acid aqueous solution 25 was added to 20 g of silica gel having an average pore diameter of 3 μm.
After adding 0 ml and 10 mg of methyl violet, the mixture was shaken for 3 hours, filtered, and dried at 80 ° C. or lower to obtain finely particulate moisture-sensitive colored powder. This powder is yellow at a humidity of 20% RH or less, light green at 30% RH, green at 40% RH, 60% RH
It exhibited a blue color at H and a purple color at 80% RH, and it was confirmed that the changed color changed stepwise as the humidity changed. This powder was mixed with Daicel Chemical polyamide powder resin 350-P2M at 25% to obtain a moisture-sensitive colored product. 30 g of non-woven fabric was applied to this moisture-sensitive colored product using a spraying apparatus capable of adjusting the spraying amount.
/ M2 ("Elves" manufactured by Unitika Ltd.)
As disclosed in JP-A-79545, the powder is spread by passing the powder-dispersed surface in contact with a heat roll heated to a surface having a good releasability and a surface temperature higher than the melting point of the powder. A sheet-like humidity detecting material was prepared by sandwiching and fixing a powdery moisture-sensitive coloring material with the polyethylene layer of a transparent film obtained by laminating a perforated polyester film and a polyethylene film facing the nonwoven fabric. When the humidity detection sheet was left in each humidity atmosphere, the color changed sharply, and a clear humidity display color corresponding to a predetermined humidity was obtained.

(Example 3) A 20% silica gel having an average pore diameter of 12.2 µm was mixed with a sulfuric acid aqueous solution having a 0.02 normal concentration in 250 g.
ml, calcium chloride 1g and methyl violet 10m
g, and the mixture was shaken for 3 hours, then filtered and dried at 80 ° C. or lower to obtain fine particulate moisture-sensitive colored powder. This powder exhibits yellow at a humidity of 5% RH or less, green at 10% RH, blue at 20% RH, and purple at 30% RH. did. Polyvinylpyrrolidone solution (20%) dissolved in methyl alcohol
0.5 g of moisture-sensitive coloring powder was mixed with 25 ml to obtain a silk printing ink (moisture-sensitive coloring material). This printing ink was printed on a breathable film (NF sheet manufactured by Tokuyama Corporation) to prepare a sheet-shaped humidity detecting material. When the humidity detection sheet was left in each humidity atmosphere, the color changed sharply, and a clear humidity display color corresponding to a predetermined humidity was obtained.

Example 4 To 20 kg of silica gel having an average pore diameter of 3 μm, 250 l of a 0.2N sulfuric acid aqueous solution and 60 g of Food Green No. 3 were added, and the mixture was shaken for 24 hours and then filtered.
Drying was performed at a temperature of not more than ℃ to obtain fine particles of moisture-sensitive colored powder. This powder was kneaded with 50 kg of a melted low-density polyethylene resin, and a 60 μm extruded film was obtained from a slit, followed by stretching to produce a 35 μm moisture-permeable microporous film (humidity detecting material). When this was used as a part of a waterproof microporous film for disposable diapers, it was shown that it could be used as a stuffiness detection material.

Example 5 20 g of a spherical silica hydrogel having a diameter of 5 mmφ (water content: 80%) manufactured from sulfuric acid and sodium silicate, 50 ml of 0.02N sulfuric acid aqueous solution, and 1 mg of brilliant green were shaken for 2 hours and then gently at 60 ° C. After drying, a granular humidity detecting silica gel having a diameter of 2.5 mmφ was obtained. This humidity detecting material has a relative humidity of 10
It showed yellow at% RH, green at 20% RH, and blue at 50% RH, and it was confirmed that the changed color changed stepwise with the change of humidity. With the same composition, a sulfuric acid aqueous solution was prepared at 0.2 N, yellow at 43% RH or less, 60% RH
At 85% RH. Further similarly,
When prepared with 0.11N sulfuric acid, yellow color was exhibited at 5% RH or less, yellowish green at 10% RH, and blue at 43% RH.

[0038]

As described above, according to the present invention, when it is granular, it is a moisture-sensitive coloring substance in which silica gel is impregnated with an acidic substance and an acid-base indicator. In the state where the mixed moisture-sensitive coloring material is laminated on paper, nonwoven fabric, breathable film, etc., it is clearly displayed with multiple types of humidity display colors that gradually change color in response to changes in humidity, making it easy to distinguish between them. It is possible to provide a humidity detecting material that is safe and has a low impact on the environment. Then, if the sheet-shaped humidity detecting material is further taped and affixed to the desiccant, the effectiveness of the desiccant and the appropriate humidity in the packaging container can be easily and accurately determined by a plurality of types of humidity indication colors. And a desiccant can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is an enlarged sectional view of a main part showing a modification of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Desiccant 2 Desiccant main body 3 Packaging material 4 Humidity detection tape 5 Humidity display color 6 Humidity display 7 Humidity display tape 9 Strip tape 10 Perforated film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seigo Yoshida 2-2-1-15 Toyoshin, Higashi-Yodogawa-ku, Osaka F-term in Oe Chemical Industry Co., Ltd. (reference) 2G042 AA01 BB01 CA01 CB01 DA08 FA01 FA12 FA19 FB07 FC03 FC07 GA04 HA07

Claims (9)

[Claims] 1. A method of detecting a predetermined humidity, and changing the humidity to a plurality of types of humidity display colors corresponding to the detected humidity in a stepwise manner.
A humidity detecting material, characterized in that a moisture-sensitive colored substance obtained by impregnating silica gel with an acidic substance and an acid-base indicator is formed in a granular or sheet form. 2. The humidity sensing material according to claim 1, wherein the moisture-sensitive coloring material is a mixture of a resin material and powder obtained by impregnating an acidic substance and an acid-base indicator into silica gel particles of 200 μm or less. 3. The humidity detecting material according to claim 2, wherein the resin agent is any of solid paraffin, polyethylene resin, polypropylene resin, and ionomer resin. 4. The humidity detecting material according to claim 2, wherein the sheet-shaped humidity detecting material is a moisture-permeable microporous film obtained by stretching a moisture-sensitive coloring material. 5. The sheet-like humidity detecting material is obtained by laminating a moisture-sensitive coloring material on paper, nonwoven fabric, a breathable film, or the like by coating or printing, and covering the surface with a perforated film. 2. The humidity detecting material according to 2 or 3. 6. The humidity detecting material according to claim 1, wherein the acid-base indicator is edible blue No. 1 or edible green No. 3 of a food additive. 7. A method of detecting a predetermined humidity and changing the color in a stepwise manner to a plurality of types of humidity display colors corresponding to the detected humidity.
Silica gel is impregnated with an acidic substance and an acid-base indicator to form a powder, and a moisture-sensitive coloring material mixed with a resin agent is formed into a granular or sheet-like form on the powder to produce a humidity detecting material.
A method for producing a humidity detecting material, wherein the humidity display color is adjusted by changing the impregnation concentration of the acidic substance. 8. The packaging material in which the sheet-like humidity detection material according to any one of claims 1 to 6 is a humidity detection tape formed in a single tape shape, and is filled with a desiccant body. The surface of the above, the humidity detection tape, the humidity detection tape is a humidity display tape in which a plurality of types of humidity display colors when the humidity detection tape detects and changes color and a humidity display corresponding to each humidity display color are described. A desiccant characterized by being applied in a belt shape. 9. The humidity detecting tape and the humidity indicating tape are one.
9. The desiccant according to claim 8, wherein the desiccant is integrated into a band shape of a book, and the band-shaped tape is affixed to two opposing seal edges on the periphery of the packaging material.