JP2008008761A - Dye sensor and recording set - Google Patents

Abstract

To detect with high sensitivity to organic molecular gas.
A dye sensor that detects an organic gas that is a Bronsted base, a polymer having a strongly acidic group (a), and a cationic organic dye that is bonded to the polymer and protonated by the strongly acidic group. (C) is contained so that the molar ratio (c / a) is 1/10 to 1/25.
[Selection figure] None

Description

  The present invention relates to a dye sensor using proton transfer reaction (acidichromism) of an organic dye, and a rewritable recording set using the organic dye.

  In recent years, dye sensors that exhibit a color change in response to an organic molecular gas (volatile organic vapor; hereinafter also referred to as VOC) in which an organic compound has volatilized have been actively studied. For example, the use of vapochromism of metal complex thin films has attracted attention (see, for example, Patent Document 1).

  In addition to this metal complex thin film, there is a research report on a dye sensor for VOC using the vapochromism of an organic dye (for example, see Non-Patent Document 1). A thin film containing organic dyes has advantages such as a polymer film in which a minute amount of dyes of several mass% or less is dispersed responds to high speed and high sensitivity, is easy to process, has flexibility, is lightweight, and is low in cost. It is said that there is.

  In addition, dye sensors that use proton transfer reactions of organic dyes do not require, for example, optical equipment or electricity in addition to organic dye films, and can easily detect and recognize VOCs by color changes. Therefore, it is expected to be widely used in fields related to the presence of the target VOC, concentration change, and the like.

On the other hand, writing instruments, various inks, and ink-jet recording materials used for recording have conventionally been provided with various types and functions. However, once recorded characters and images are erased, they can be placed in the same area. Few ones have a rewritable function that can easily record multiple times.
JP 2003-64091 A IM Raimundo Jr., R. Narayanaswamy, Simultaneous determination of relative humidity and ammonia in air using an optical fiber sensor and artificial neural network Sensors and Actuators B, 74, 60-68 (2001)

  However, with respect to dye sensors that utilize proton transfer reactions of organic dyes, the actual situation is that until now various performances including sensitivity to VOC have not been fully studied.

  In addition, when recording and erasing images such as pictures and characters are repeated, a colored so-called ink liquid is usually used. For example, the ink liquid is absorbed by an absorbent core material and a capillary phenomenon is used. There are limitations such as the fact that the usage pattern is limited to a specific form, such as recording, or the surroundings are stained with ink liquid, the trace does not disappear completely, the trace remains, and the recording or erasing cannot be performed over a wide area.

  The present invention has been made in view of the above, and a dye sensor that can detect organic molecular gas (VOC) with high sensitivity, and a recording form (character width, typeface, recording area, etc.) are widely selected. It is an object of the present invention to provide a recording set that is simple to record and erase, can be erased neatly, and can repeatedly perform clear recording, and to achieve the object.

Specific means for achieving the above object are as follows.
<1> A dye sensor that detects an organic gas that is a Bronsted base,
A polymer having a strongly acidic group, and a cationic organic dye bonded to the polymer and protonated by the strongly acidic group, wherein the cationic organic dye (c) and the strongly acidic group (a) This is a dye sensor having a molar ratio (c / a) of 1/10 to 1/25.
<2> The dye sensor according to <1>, wherein the organic gas is an amine derivative.
<3> On a substrate, a polymer having a strongly acidic group, and a cationic organic dye bonded to the polymer and protonated by the strongly acidic group, the cationic organic dye (c) and the strong acid A recording material having a polymer film containing a molar ratio (c / a) of the functional group (a) of 1/30 to 1/50, and an organic substance which is a Bronsted base for the cationic organic dye. And a recording liquid for recording by changing the color of the cationic organic dye of the recording medium, and an erasing liquid for erasing the recording, containing a compound that protonates the discolored cationic organic dye. A set for recording.
<4> The recording set according to <3>, wherein the organic substance is an amine derivative, and the compound is an acid.

  According to the present invention, the dye sensor capable of detecting organic molecular gas (VOC) with high sensitivity and the selectivity of the recording form (character width, typeface, recording area, etc.) are wide, and recording and erasing are simple. It is possible to provide a recording set that can be erased neatly and can perform clear recording repeatedly.

Hereinafter, the dye sensor and the recording set of the present invention will be described in detail.
<Dye sensor>
The dye sensor of the present invention is a dye sensor that detects an organic gas that is a Brønsted (Brφnstead; hereinafter the same) base. The dye sensor binds to a polymer having a strongly acidic group and the polymer, and is protonated by the strongly acidic group. And a cationic organic dye added, and the molar ratio (c / a) of the cationic organic dye (c) and the strongly acidic group (a) is in the range of 1/10 to 1/25. is there.

  In the dye sensor of the present invention, a cationic organic dye is bound to a polymer having a strongly acidic group via the strongly acidic group, and a proton is given to the cationic organic dye from the strongly acidic group for reception. A possible range of equivalents of protons is provided. At this time, the ratio of the molar amount of the strongly acidic group in the polymer that gives protons to the molar amount of the cationic organic dye existing in an ionic bond with the strongly acidic group is within the above range, so that protons are imparted. The reactivity of the organic gas (Bronsted base) with respect to the cationic organic dye (Bronsted acid) is improved, and the detection sensitivity when detecting in response to the organic gas can be effectively increased.

In the dye sensor of the present invention, the molar ratio (c / a) between the cationic organic dye and the strongly acidic group is 1/10 to 1/25. If the molar ratio c / a exceeds 1/10, that is, the amount of the strongly acidic group with respect to the cationic organic dye is too small, the response speed is lowered, and less than 1/25, that is, with respect to the strongly acidic group. If the amount of the cationic organic dye is too small, the color change is small and judgment by visual recognition becomes difficult.
Among the molar ratio c / a, from the viewpoint of further improving the detection sensitivity, it is preferably in the range of 1/15 to 1/25.

  When determining the molar ratio (c / a) between the cationic organic dye and the strongly acidic group, for example, neutralization titration of the molar amount of the sulfo group (sulfonic acid group) of the polymer (for example, Nafion) and the molar amount of CV ( Sulfo group), measured by colorimetric determination with a spectrophotometer.

  In order to adjust the molar ratio (c / a) between the cationic organic dye and the strongly acidic group to the above range, for example, a polymer film using a desired polymer is a dye aqueous solution containing the desired cationic organic dye. After appropriately controlling the time of contact with the membrane, the method can be performed by a method of washing the cationic organic dye adhering to the membrane (for example, with pure water).

  “Polymer having strongly acidic group” is selected from known polymer compounds according to the purpose as long as it is a polymer compound having a strongly acidic group such as a sulfonic acid group in its polymer (for example, its side chain). can do. Specific examples include Nafion [for example, (trade name) Nafion (registered trademark) manufactured by Aldrich] and the like, which can be used in the form of a solution.

Among them, a polymer that can adsorb and remove organic gas in the atmosphere and can be reused thereafter is desirable in terms of functioning not only as a sensor but also as a purification material, and Nafion is preferred.
In such a case, the organic gas in the atmosphere can be adsorbed and removed for visualization.

  As the cationic organic dye, any dye compound having at least one cationic group can be selected from known dye compounds according to the purpose. Specific examples include methylene blue (MB), crystal violet (CV), flavilium (FV), safranin-O, thionine, and Nile blue.

  The ratio between the polymer having a strongly acidic group and the cationic organic dye (polymer: dye) is particularly limited if the “molar ratio of the cationic organic dye to the strongly acidic group (c / a)” is within the above range. Although there is no limitation, generally 1:10 to 1:25 is desirable, and 1:15 to 1:25 is preferable. When this ratio is within the above range, the VOC detection sensitivity is improved, and a color change that can be detected by visual recognition is obtained.

The relationship between a polymer having a strongly acidic group and a cationic organic dye will be described by taking Nafion and Crystal Violet (CV) as an example.
As shown in the following scheme, when a Nafion solution is applied to a base material (eg, a Nafion 117 solution is applied to a substrate by spin coating to a thickness of about 2 μm) to form a thin film, sulfonic acid groups ( -SO ₃ ^- H ⁺ ) exist, and when a membrane surface on which a sulfonic acid group exists is attached to a CV (DH ⁺ ) solution, CV ions are adsorbed by a cation exchange reaction. Then, the proton of the sulfonic acid group moves to the adsorbed nitrogen atom of the CV, and the CV becomes a strongly acidic state (DH ₂ ³⁺ ) to which 2 equivalents of proton is added and exhibits a light yellow color. At this time, CV is strongly ion-bonded with Nafion's —SO ₃ ^— .

  The dye sensor of the present invention was formed by first forming a polymer thin film by using a desired polymer, for example, by applying a known coating method such as a spin coating method on a cleaned substrate. The polymer thin film can be produced by bringing the polymer thin film into contact with an aqueous dye solution containing a desired cationic organic dye, followed by washing (for example with pure water) and drying.

As a method of bringing the polymer thin film into contact with the aqueous dye solution, a method of immersing the polymer thin film in the aqueous dye solution or spraying the aqueous dye solution onto the polymer thin film by spraying or showering is suitable.
The substrate is preferably washed from an alcohol such as methanol, preferably ultrasonically washed and dried from the viewpoint of uniformly providing a polymer such as Nafion to enhance detection sensitivity.

  The film thickness of the polymer thin film is not limited as long as the molar ratio (c / a) is satisfied. From the viewpoint of easy processing, flexibility, light weight, low cost, and the like. A range of 5 μm is desirable.

As shown in the following reaction formulas (1) to (2), the dye sensor of the present invention is a proton acceptor (Bronsted base) for a proton-added cationic organic dye (DH ₂ ³⁺ or DH ²⁺ ). The acting organic gas (B) is detected.

  Reaction formula (1) shows a reversible reaction when the Bronsted base is a weak base, but when the Bronsted base is a strong base, the reaction formula (1) further shifts to the reaction formula (2). After the reaction proceeds to the right and exhibits blue-violet, the reaction in the left direction in reaction formula (2) is difficult to proceed, indicating irreversibility and maintaining the color change. .

Hereinafter, detection of organic gas by the dye sensor of the present invention will be described in more detail by taking as an example the case where alcohol ROH (weak base) and amine derivative R ₃ N (strong base) are used as the organic gas as proton acceptors.

(Alcohol ROH)
When the dye sensor of the present invention is exposed to the alcohol ROH vapor, as shown in the following scheme, proton transfer from the nitrogen atom of the protonated cationic organic dye (DH ₂ ³⁺ ; trication) to the alcohol causes DH ²⁺ ( indication) and changes from yellow to green. When this dye sensor is returned to the atmosphere again, the reaction proceeds to the left and returns to yellow again, and can be used again as a dye sensor.

(Amine derivative R ₃ N)
When the dye sensor of the present invention is exposed to the vapor of the amine derivative R ₃ N, as shown in the following scheme, first, yellow to green is exhibited in the same manner as described above, and then proton transfer (the above reaction formula ( 1) to (2) in two steps) to D ⁺ (monocation), and the color changes to bright blue-violet. At this time, the reverse reaction from D ⁺ (monocation) to DH ²⁺ (dication) is difficult to proceed. When a strong Bronsted base is detected, the color change does not return even if it is returned to the atmosphere, for example. Is possible. In particular, the gas of a diluted amine derivative exhibits a bright purple color when exposed to a long period of time, and exhibits “accumulation” that does not fade even after returning to the atmosphere.
The above color reaction is not hindered by water vapor.

Examples of organic gases that are test gases include those with relatively weak bases (weak Bronsted bases) such as alcohols, ethers, aldehydes, carboxylic acids, and esters, triethylamines, various amino acids, and caffeine (1.3.7-trimethyl). Xanthine), amine derivatives such as alkylamines such as nicotine ((S) -3- (1-methylpyrrolidin-2-yl) pyridine), relatively strong bases such as ammonia, pyridine, aniline derivatives and indoles (strong) Bronsted base) can be detected.
Among these, the dye sensor of the present invention is suitable as a sensor for detecting an amine derivative because it can be detected with high sensitivity and can maintain a color change (history).

  The dye sensor of the present invention is highly sensitive, and the organic gas detection concentration may be as low as 1 ppm or less, and can be detected even at a low concentration of 0.02 ppm, for example.

  In addition, the dye sensor of the present invention can recover the color change and removal ability using an acid (for example, dilute hydrochloric acid or dilute sulfuric acid) described later. For example, the removal ability can be obtained by spraying extremely diluted sulfuric acid solution. Can be easily reused.

  The dye sensor of the present invention can detect low-concentration VOCs, for example, a sensor for detecting freshness or spoilage of food such as fish meat, a sensor for monitoring air components in a working environment or a living environment, and a gas adsorbing agent. It can be applied to a wide range of fields, such as sensor application to an amine-based gas removal device that “senses” by coloration.

<Recording set>
The recording set of the present invention comprises, on a base material, a polymer having a strongly acidic group, and a cationic organic dye bonded to the polymer and protonated with the strongly acidic group, the cationic organic dye ( a recording material having a polymer film containing c) and a molar ratio (c / a) of the strongly acidic group (a) in a ratio of 1/30 to 1/50, and a Bronsted base for the cationic organic dye A recording liquid that contains an organic substance and changes the color of the cationic organic dye of the recording medium for recording, and an erasing liquid that contains a compound that protonates the discolored cationic organic dye and erases the recording And is a rewritable recording material that can repeatedly record and erase in the same area a plurality of times.

  In the recording set of the present invention, a recording medium to be recorded is a polymer having a strongly acidic group (a), and a cationic organic dye bonded with the polymer and protonated by the strongly acidic group (C) is a constitution using a polymer film containing a molar ratio (c / a) of 1/30 to 1/50, thereby to protonated cationic organic dye (Bronsted acid) Since the reactivity of the organic substance (Bronsted base) is improved, recording with high sensitivity and high color density can be performed, recording and erasing are simple, clear erasing can be performed, and clear recording can be repeated.

  In the recording set of the present invention, the molar ratio (c / a) between the cationic organic dye and the strongly acidic group is 1/30 to 1/50. If the molar ratio c / a exceeds 1/30, that is, the amount of strongly acidic groups relative to the cationic organic dye is too small, the response speed will decrease, and less than 1/500, that is, against strongly acidic groups. If the amount of the cationic organic dye is too small, the color change is small and the color density is lowered.

~ Recorded material ~
The recording medium has at least one polymer film on the substrate, and other layers may be laminated as necessary. The polymer film includes at least one polymer having a strongly acidic group and at least one cationic organic dye, and the cationic organic dye is protonated by the strongly acidic group of the polymer.

  Further, the polymer film can be constituted by using other components such as inorganic or organic particles (for example, silica particles) and a binder component depending on the purpose and the like. For example, it can be configured as a recording medium for ink jet recording. In this case, it is preferable to use silica particles and / or a binder component.

  Examples of the inorganic or organic particles include inorganic particles such as silica particles, titanium dioxide, barium sulfate, zeolite, calcium carbonate, alumina, and zinc oxide. Organic particles include, for example, emulsion polymerization and dispersion polymerization. Examples thereof include polymer particles obtained, specifically particles such as polyethylene, polypropylene, and polystyrene.

  As the binder component, polyvinyl alcohol resins, cellulose resins, resins having an ether bond, gelatins, and the like can be used. A polyvinyl alcohol resin is preferable.

The details of the “polymer having a strongly acidic group” contained in the polymer film constituting the recording medium, the cationic organic dye, and preferred forms thereof are the same as those in the dye sensor of the present invention described above. . The relationship between the “polymer having a strongly acidic group” and the cationic organic dye and the color development mechanism are also as described above.
Moreover, about content of an inorganic or organic particle | grain and a binder component, it can select suitably in the range which does not impair the effect of this invention.

  After a desired substrate is washed, a recording medium is coated with a polymer solution containing a “polymer having a strongly acidic group” on the substrate by a known coating method such as a spin coating method. It can be produced by forming a molecular film, bringing the formed polymer film into contact with an aqueous dye solution containing a desired cationic organic dye, and then washing (for example, with pure water) and drying.

  The adjustment of the molar ratio (c / a) at this time is similar to the case of the dye sensor described above, for example, after appropriately controlling the time for contacting the polymer film with the dye aqueous solution, It can be performed by a method of washing an organic dye (for example, with pure water).

The substrate is not particularly limited and can be selected from any material and shape depending on the purpose. For example, known glass such as alkali glass, non-alkali glass, quartz glass, and plastics such as polyester are used. Or opaque paper such as recycled PET paper. Specifically, a plate material, a sheet material, a film material, artificial flowers and the like are suitable, and a plastic film, a sheet, and the like can be used in order to provide flexibility such as a glass plate or paper.
The thickness of the substrate may be selected as desired. From the viewpoint of uniformly providing a polymer film such as Nafion, it is preferable to perform cleaning with an alcohol such as methanol or ultrasonic cleaning.

  Moreover, the polymer film may be provided only on the surface on one side of the substrate, or may be provided on the surfaces on both sides.

~ Recording liquid ~
The recording liquid in the present invention contains at least one organic substance that is a Bronsted base with respect to the cationic organic dye in the polymer film of the recording medium, changes the color of the cationic organic dye, and reveals a desired image. Is to do. The recording liquid can be constituted by using other components such as a viscosity modifier as required.

  “Organic substances that are Bronsted bases” are organic compounds that can accept protons from cationic organic dyes (Bronsted acids). Examples of such organic substances include alcohols, ethers, aldehydes, carboxylic acids, esters, and amine derivatives such as alkylamines such as triethylamine and various amino acids. Nonvolatile amino acids are particularly preferable.

The “organic substance that is a Bronsted base” can be used after being dissolved in a soluble solvent, for example, an aqueous medium or an organic solvent. The aqueous medium includes water and a mixed solvent of water and water-compatible organic solvent, and an aqueous medium (particularly water) is preferable from the viewpoint of safety. The organic solvent includes methanol, ethanol, acetone and the like.
In the present invention, an aqueous solution is preferable from the viewpoint of safety during use.

  The concentration of the “organic substance that is a Bronsted base” in the recording liquid is preferably 2% to 5%.

~ Eraser ~
The erasing liquid in the present invention contains at least one compound that protonates the cationic organic dye changed in color by the recording liquid and erases the recording on the recording medium.

  The “compound capable of adding a proton to a cationic organic dye” is a compound that can be protonated again to a cationic organic dye that has been discolored by the action of an organic substance in the recording liquid. Examples of such compounds include acids such as dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid.

  The “compound capable of protonating a cationic organic dye” can be used by dissolving in a soluble solvent such as an aqueous medium or an organic solvent. Details and preferred embodiments of the aqueous medium and the organic solvent are the same as those of the recording liquid, and an aqueous solution is preferred from the viewpoint of safety during use.

  The concentration of the “compound capable of protonating a cationic organic dye” in the erasing solution is preferably from 0.1 mol / l to 1 mol / l, more preferably from 0.1 mol / l to 0.2 mol / l.

  The recording liquid and the erasing liquid can be selected in any use form, for example, absorbed in an absorbent core material having an arbitrary cross-sectional diameter or attached to a brush, and an image such as a desired picture or character is recorded. And can be erased.

  Furthermore, the recording set of the present invention can be used as an ink jet recording liquid in which a recording medium is configured for ink jet recording and a recording liquid and an erasing liquid are loaded on an ink jet head and discharged.

In the recording set of the present invention, a recording liquid prepared in accordance with the composition of the polymer film is applied on the polymer film of the recording medium of a desired size, for example, by applying it to a brush or ejecting it from a head. When an image is drawn, only an area drawn with the recording liquid is discolored and an image such as a letter or a picture can be recorded. After recording, if an erasing liquid is applied to the image portion, for example, on another brush or ejected from the head, only the applied portion is erased and the image can be erased.
In addition, after erasing, if an image is drawn with a recording liquid with or without being overlapped with an erased portion, an image having the same hue and color density as that of the first recording can be obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1 Production of Dye Sensor A commercially available polyester sheet was cut into 50 mm × 50 mm, immersed in methanol for 1 hour, washed and dried. On one surface of this polyester sheet, 1.0 ± 0.1 g of 5% Nafion 117 solution (Aldrich) is dropped, and spin coated with a spinner (K359SD-270A, Kyowa Riken) to form a thin film (Nafion thin film). ). At this time, the rotation speed and time of the spin are “the number of rotations 200 rpm. × 15 seconds” + “the number of rotations 600 rpm.times.10 seconds” + “the number of rotations 1200 rpm.times.10”. Second ".

Next, the formed Nafion thin film was dried on a hot plate at 80 ° C. for 30 minutes. The dried Nafion thin film was immersed in an aqueous dye solution (containing crystal violet (CV) at 5.0 × 10 ⁻⁴ mol / l) for 3 seconds, washed with pure water, and dried with hot air using a dryer.

Here, with respect to the amount of CV adhering to the surface of the Nafion thin film, the molar amount of the sulfonic acid group and the molar amount of CV of the Nafion thin film were determined by neutralization titration (sulfo group) and colorimetric determination with a spectrophotometer. And 1.46 × 10 ⁻⁶ mol and 8.40 × 10 ⁻⁸ mol, respectively. From these values, the molar ratio (c / a) between CV (c) and sulfonic acid group (a) was 1 / 17.4.

<Test 1>
After drying, this was cut into 25 mm × 10 mm pieces to obtain a dye sensor.
In addition, unused dye sensors should be sealed in a vial (or in a plastic bag with a chuck (made of polyethylene)) and sealed in a vial to avoid coloring due to trace amounts of ammonia and amine gases in the air. Stored at room temperature (25 ° C.).

As shown in FIG. 1, the obtained dye sensor is placed in a container with a volume of 60 cm ³ together with 2 g of raw tuna pieces and sealed, and the color change of the dye sensor over time is observed at room temperature (25 ° C.). Attempted to detect corruption. At this time, since the color of the dye sensor is changed from yellow to green due to the presence of water vapor, the color change of the dye sensor placed in the same volume container together with water vapor is referred to (25) separately from the container containing raw tuna pieces. ° C).

As a result, as shown in FIG. 1, a color change [green (dication) → purple (monocation)] starts to occur in the dye sensor in the raw tuna container in about 5 hours and turns completely purple in about 7.5 hours. did. With this color change, a rotting odor was observed.
On the other hand, the reference-side dye sensor containing wet absorbent cotton remained light green due to water vapor.

  From the above, it can be seen that the present invention can be suitably used as a simple sensor for detecting the presence / absence and progress of foods such as fish meat.

<Test 2>
Triethylamine (TEA) was introduced (concentration = 0 ppm, 0.6 ppm, 1.2 ppm, 2.9 ppm, 5.8 ppm, 12 ppm) into an approximately 1.0 L container (temperature 20 ° C., humidity 50-60% RH). Inside, the above dye sensor was put and the color change with time was observed. For the color change, the ratio of the area changed to purple with respect to the total area was visually determined, and this was used as an index for evaluating the sensitivity. The results are shown in FIG.
As shown in FIG. 2, detection was possible in a low concentration TEA atmosphere, and the sensitivity was high.

<Test 3>
The above-mentioned dye sensor was placed in a room using a chemical sample (concentration of amine and amide of about 0.03 ppm, temperature of 22 ° C.), and the color change with time was observed. As a result, as shown in FIG. 3, the color change from yellow to purple was observed after about 6 to 10 hours, and almost the entire region was changed to purple in 21 hours. The reason why the discoloration proceeds from the end is presumed to be that the gas such as amine is adsorbed and removed by the dye sensor, resulting in a density difference.
As described above, detection was possible even in an extremely low concentration atmosphere, and the sensitivity was high.

From the above, as a sensor application to the environment-friendly simple sensor for investigating and monitoring the working environment and the living environment, and the amine-based gas removal device that "senses" by coloring when gas is adsorbed It turns out that it can utilize suitably.
The dye sensor of the present invention has been confirmed to be adsorbed at an amine gas concentration of 0.02 ppm to 5% or more, and is gradually colored from an adsorbed region by an adsorption action from a low concentration to a high concentration. The end of the removal capability can be surely confirmed by the fact that the entire color gamut extends. In this case, since the above-mentioned base material can be appropriately selected, various shapes such as a film shape, a rod shape, and artificial flowers are possible. Moreover, the combination of colors is possible by selecting the color of the base material and the coloring material. Of course, the operation can be easily restarted without changing the removing device by reproducing the removing ability by spraying the extremely diluted sulfuric acid solution.

Example 2 Production of Recording Set A commercially available polyester sheet was cut into 50 mm × 50 mm, immersed in methanol for 1 hour, washed and dried. In addition to the polyester sheet, a desired appropriate opaque paper such as recycled PET paper may be used.

  1.0 ± 0.1 g of 20% Nafion 117 solution (manufactured by Aldrich) is dropped on one surface of the polyester sheet after washing and drying, and spin coated with a spinner (K359SD-270A, manufactured by Kyowa Riken). A thin film (Nafion thin film) was used. At this time, the rotation speed and time of the spin are “the number of rotations 200 rpm. × 15 seconds” + “the number of rotations 600 rpm.times.10 seconds” + “the number of rotations 1200 rpm.times.10”. Second ".

Next, the formed Nafion thin film was dried on a hot plate at 80 ° C. for 30 minutes. The dried Nafion thin film was immersed in an aqueous dye solution (containing crystal violet (CV) at 5.0 × 10 ⁻⁴ mol / l) for 60 seconds, washed with pure water, and dried with hot air using a dryer. In this way, a rewritable substrate was produced.

Here, with respect to the amount of CV adhering to the surface of the Nafion thin film, the molar amount of the sulfonic acid group and the molar amount of CV of the Nafion thin film were determined by neutralization titration (sulfo group) and colorimetric determination with a spectrophotometer. And 1.03 × 10 ⁻⁶ mol and 2.94 × 10 ⁻⁸ mol, respectively. From these values, the molar ratio (c / a) between CV (c) and sulfonic acid group (a) was 1/35.

Next, lysine (amino acid) was dissolved in a 1: 1 mixed solvent of methanol and water to prepare an approximately 3% colored liquid (recording liquid).
Separately, a 0.2 mol / l dilute hydrochloric acid aqueous solution was prepared and used as a decoloring solution (erasing solution).

When the above colored liquid was applied to a small brush and applied to the rewritable substrate obtained above, a desired picture or character could be drawn in a bright purple color. Subsequently, when the above-described decoloring solution was applied to another small brush and applied over the drawn pictures and letters, these pictures could be easily erased without any trace.
After the decolorizing liquid was dried, the coloring liquid was again applied to the erased area by applying it to the small brush, and the same vivid pictures and letters as the beginning could be drawn. Furthermore, when it was applied over another picture with a decoloring solution drawn with another small brush, it was easily erased without any traces. Thus, the image quality was not inferior even after rewriting 10 times or more.
In addition, it was confirmed that the drawn pictures and characters were not contaminated by amine gas and could be stably maintained for more than one week even when stored under air.

It is a figure which shows the test method of Test 1, and the color change of the dye sensor in Test 1. It is explanatory drawing for demonstrating the relationship between the TEA density | concentration and color change in Test 2. It is explanatory drawing for demonstrating the detection by the color change under the lean density in Test 3. FIG.

Claims (4)

A dye sensor that detects an organic gas that is a Bronsted base,
A polymer having a strongly acidic group, and a cationic organic dye bonded to the polymer and protonated by the strongly acidic group, wherein the cationic organic dye (c) and the strongly acidic group (a) A dye sensor having a molar ratio (c / a) of 1/10 to 1/25.   The dye sensor according to claim 1, wherein the organic gas is an amine derivative. On a substrate, a polymer having a strongly acidic group, and a cationic organic dye bonded to the polymer and protonated with the strongly acidic group are converted into the cationic organic dye (c) and the strongly acidic group ( a recording material having a polymer film containing a molar ratio (c / a) of 1/30 to 1/50;
A recording liquid that contains an organic substance that is a Bronsted base with respect to the cationic organic dye, and records the recording material by changing the color of the cationic organic dye of the recording medium;
An erasing solution containing a compound that protonates the discolored cationic organic dye and erasing the recording;
A set for recording.   The recording set according to claim 3, wherein the organic substance is an amine derivative, and the compound is an acid.