JP2007296653A - Reversible thermal coloring composition and reversible thermal recording medium using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible thermal coloring composition and a reversible thermal recording medium which make coloring properties and erasability compatible and are also excellent in the shelf stability of a colored image and which have good coloring sensitivity and excellent high-speed erasability. <P>SOLUTION: In the reversible thermal recording medium having a reversible thermal recording layer which uses an electron-donating color-developable compound and an electron-accepting compound and is capable of relatively forming a colored state and a color-erased state, according to a difference in heating temperature and/or a cooling speed after heating, the reversible thermal coloring composition uses a phenolic compound as the electron-accepting compound and also a quaternary ammonium salt compound as a coloring and color-erasure control agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention uses a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound, and can control the formation of a color image and erase it by controlling thermal energy. The present invention relates to a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium.

  2. Description of the Related Art Conventionally, heat-sensitive recording media using a color developing reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. With the progress of OA, it is widely used as an output sheet for facsimiles, word processors, scientific measuring instruments, etc., and recently as a magnetic thermal card such as prepaid cards and point cards. However, these conventional recording media that have been put to practical use are being reviewed for recycling and reduced usage due to environmental problems. However, since they are irreversible colors, once recorded images are erased. It cannot be used repeatedly, and the area of the recordable part is limited because new information is added to the part where no image is recorded. Therefore, the actual situation is that the amount of information to be recorded is reduced or the card is remade when the recording area runs out. Therefore, it has been desired to develop a reversible thermosensitive recording medium that can be rewritten any number of times, against the background of the dust problem and forest destruction problem that have been actively discussed in recent years.

  By the way, various reversible thermosensitive recording media have been proposed from these requirements. For example, polymer-type reversible thermosensitive recording media using physical changes such as transparency and white turbidity have been disclosed (Patent Document 1: Japanese Patent Laid-Open No. 63-107584, Patent Document 2: Japanese Patent Laid-Open No. 4-78573). See the official gazette). In addition, a dye-type reversible thermosensitive recording medium utilizing a chemical change has been newly proposed. Specifically, a combination of gallic acid and phloroglucinol is used as a developer (see, for example, Patent Document 3: JP-A-60-193691), and phenolphthalein, thymolphthalein, etc. (For example, see Japanese Patent Application Laid-Open No. 61-237684), and a recording layer containing a homogeneous solution of a color former, a developer and a carboxylic acid ester (for example, Patent Document 5). : JP-A-62-138556, Patent Document 6: JP-A-62-138568, Patent Document 7: JP-A-62-140881), ascorbic acid derivative used as a developer ( For example, Patent Document 8: Japanese Patent Laid-Open No. 63-173684), and a bis (hydroxyphenyl) acetic acid or a salt of gallic acid and a higher aliphatic amine is used as a developer. Things (e.g., Patent Document 9: JP-A 2-188293 and JP-Patent Document 10: see Japanese Patent Laid-Open No. 2-188294) have been disclosed.

  Furthermore, the present inventors previously used an organic phosphate compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer in Patent Document 11 (Japanese Patent Laid-Open No. 5-124360). By combining this with the leuco dye that is a color former, color development and decoloration can be easily performed under heating and cooling conditions, and the color development state and color erasure state can be stably maintained at room temperature. In addition, a reversible thermosensitive coloring composition capable of repeating coloring and decoloring and a reversible thermosensitive recording medium using the same for the recording layer have been proposed. After that, it has been proposed to use a phenolic compound having a long chain aliphatic hydrocarbon group having a specific structure (see, for example, Patent Document 12: Japanese Patent Application Laid-Open No. 6-210954).

  However, the recording medium using such a material has problems such as a slow erasing speed and a long time for rewriting, insufficient erasing, or low thermal stability of a color image. Therefore, the present inventors further use the phenolic compounds described in Patent Document 13 (Japanese Patent Laid-Open No. 10-95175) and Patent Document 14 (Japanese Patent Laid-Open No. 10-67177), so that the contrast between coloring and decoloring is improved. It has proposed a recording medium that is high, can be erased at high speed, and has excellent color stability in the image area. The recording medium using this phenolic compound can be erased by a heating member such as a hot stamp, a heat roller, or a ceramic heater, and has excellent practicality.

However, many of the phenolic compounds of Patent Documents 13 and 14 have a high melting point, and it is necessary to heat them to a high temperature during color development and decoloring, and it is necessary to apply high energy.
To apply high energy, it is necessary to apply a pulse for a long time during recording, so the writing speed is slow, and since the temperature is high, damage to the recording medium is large and dents are easily generated. There has been a problem that the power source of the apparatus becomes large and the rewriting apparatus becomes large.

  On the other hand, phenol compounds having a relatively low melting point have been proposed as the phenol compounds described in Patent Document 12, but recording media using these compounds have good color development sensitivity but poor image storage stability and practicality. It was low. Further, Patent Document 12 discloses a phenol compound having a long-chain alkyl group having 22 carbon atoms and a urea group. Although the recording medium using this compound is excellent in color development sensitivity, color density, and decoloration density, it has poor storage stability in the image area, and the image density is greatly reduced in a storage test at 60 ° C. usually required for these recording media. It was not practical.

Further, Patent Document 15 (Japanese Patent Laid-Open No. 2000-141901) and Patent Document 16 (Japanese Patent Laid-Open No. 2005-1127) propose specific phenol compounds having a long-chain alkyl group having 23 or more carbon atoms. . However, recording media using these compounds are not practical because they have problems such as low color development sensitivity, poor image area storage stability, or slow decoloration speed and are not suitable for high-speed erasure. It was.
Further, for the purpose of improving the decoloring characteristics, a specific compound is used as a decoloring accelerator in Patent Document 17 (Japanese Patent Laid-Open No. 2002-52826) and Patent Document 18 (Japanese Patent Laid-Open No. 2002-52833). However, even when these compounds are used, the high-speed erasability by the thermal head is not satisfactory. Patent Document 19 (Japanese Patent Laid-Open No. 8-108267) and Patent Document 20 (Japanese Patent Laid-Open No. 2000-313171) propose using a specific developer and a quaternary ammonium salt compound in combination. However, the combination of the developer and the quaternary ammonium salt compound described in Patent Document 19 has good high-speed erasability, but is poor in storage stability of a color image and is not practical. On the other hand, the combination of the developer and the quaternary ammonium salt compound described in Patent Document 20 has good stability of the color image, but the energy required for color development and decoloration is large, and high-speed rewriting is not possible. It was difficult.

JP 63-107584 A JP-A-4-78573 Japanese Patent Laid-Open No. 60-193691 Japanese Patent Laid-Open No. Sho 61-237684 JP-A-62-138556 JP-A-62-138568 JP-A-62-140881 Japanese Patent Laid-Open No. 63-173684 JP-A-2-188293 JP-A-2-188294 JP-A-5-124360 Japanese Patent Laid-Open No. 6-210954 JP-A-10-95175 JP-A-10-67177 JP 2000-141901 A JP 2005-1127 A JP 2002-52826 A JP 2002-52833 A JP-A-8-108267 JP 2000-313171 A

  An object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium that have both color developability and erasability and are excellent in storage stability of color images. Another object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium which are excellent in high-speed erasability and also excellent in storage stability of color images.

The inventors of the present invention conducted various studies on the color development sensitivity, high-speed erasability and storage stability of the image area, and found that it was largely due to the combination of the color development / decoloration control agent used in combination with the developer compound. . In particular, the characteristics of the developer are particularly important, and the basic color development and decoloring phenomenon and storage stability depend greatly on the type and structure of the developer compound.
Therefore, first, the developer was repeatedly investigated. In the reversible coloring and decoloring phenomenon of such a color former and developer composition, there is a balance between the ability of the developer having a long chain aliphatic group to develop color and the cohesion between molecules. It was important, and it was considered necessary to lower the melting point of the developer in order to further improve the color development sensitivity, and compounds with various structures were studied. As a result, by using a specific phenol compound into which a long-chain alkyl group having 23 or more carbon atoms and a urea group are introduced as a developer, high color development sensitivity and storage stability of an image area which are not found in a conventionally known developer. It was also found that the erasability can be increased. Furthermore, it has been found that the use of a specific quaternary ammonium salt results in even faster erasability.

Therefore, the above problem is solved by the present invention described below.
(1) “Reversible sensation that can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating, using an electron-donating color-forming compound and an electron-accepting compound. In a reversible thermosensitive recording medium having a thermal recording layer, a phenol compound represented by the following formula (1) is used as the electron-accepting compound, and a quaternary ammonium represented by the following formula (2) is used as a coloring / decoloring control agent. A reversible thermosensitive coloring composition characterized by using a salt compound.

（式中、ｌは１から３の整数を示し、ｍは２３以上の整数を示す。）

(In the formula, l represents an integer of 1 to 3, and m represents an integer of 23 or more.)

（式中、Ｒ_１〜Ｒ_３はそれぞれ独立に、炭素数１から２４の飽和または不飽和の炭化水素基であって、うち２つの炭化水素基は互いに結合して環を形成してもよい。Ｒ_４は炭素数６から２４の飽和または不飽和の脂肪族炭化水素基、または下記（３）の構造の一価の基である。ｐは１または２を表わす。Ａ⁻はアニオンを示し、ｑおよびｒは電荷を０にする整数を示す。

(Wherein R _{1 to} R ₃ are each independently a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and two of these hydrocarbon groups may be bonded to each other to form a ring. R ₄ is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms or a monovalent group having the structure of the following (3), p represents 1 or 2, and A ⁻ represents an anion. , Q and r are integers that make the electric charge zero.

Ｒ_５は炭素数１から２４の飽和または不飽和の１価の炭化水素基、Ｒ_６は炭素数１から１２の飽和または不飽和の２価の炭化水素基を示し、Ｒ_５またはＲ_６の少なくとも１つは炭素数６から２４の飽和または不飽和の脂肪族炭化水素基である。ＸはＯ、Ｃ＝Ｏ、ＮＨ、Ｓ、ＳＯ_２の単独または組合せからなる基を示し、ｎは１から４の整数を示す。なお、ｎが２以上のときにくり返されるＲ_６は同一であっても、異なっていてもよい。）」、
（２）「支持体上に前記第（１）項に記載の可逆性発色組成物を含有する記録層を設けたことを特徴とする可逆性感熱記録媒体」

R ₅ represents a saturated or unsaturated monovalent hydrocarbon group having 1 to 24 carbon atoms, R ₆ represents a saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms, and R ₅ or R ₆ At least one is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms. X represents a group composed of O, C═O, NH, S, SO ₂ alone or in combination, and n represents an integer of 1 to 4. Note that R ₆ repeated when n is 2 or more may be the same or different. ) ",
(2) “Reversible thermosensitive recording medium characterized in that a recording layer containing the reversible coloring composition according to (1) above is provided on a support”

  The reversible thermosensitive recording medium of the present invention has excellent color development sensitivity, excellent high-speed erasability, and excellent reproducibility recording with excellent practical storage stability of color images. Play.

The present invention is described in detail below.
The reversible thermosensitive recording medium using the phenolic compound of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. This basic coloring / decoloring phenomenon will be described.

FIG. 1 shows the relationship between the color density of this recording medium and the temperature. Introduction gradually heated the recording medium in the decolored state (A), leuco dye and the developer are mixed melt at temperatures T ₁ begins to melt, coloring occurs a molten color developed state (B). When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a fixed color state (C) is obtained. Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, the color disappears during the temperature decrease, and the same color disappearance state (A) or rapid color development state (C ) A relatively low concentration state is formed. On the other hand, rapidly cooled colored state (C) is again raised gradually and discoloring occurs at a lower temperature T ₂ than the coloring temperature (E from D), returns the beginning when the temperature decreases from here to the same decolored state (A). The actual color development temperature and decoloration temperature vary depending on the combination of the developer and color former used. Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.

  In the recording medium of the present invention, the colored state (C) obtained by quenching from the molten state is a state in which the developer and the color former are in contact with each other and are mixed in a state of color development, which is a solid state. Is often formed. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of this aggregated structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state where molecules of at least one component of the developer and the color developer are aggregated to form a domain or crystallize, and the color developer and the developer are separated by aggregation or crystallization. Is considered to be in a stable state. In many cases, in the present invention, more complete color erasure occurs due to phase separation of the two and crystallization of the developer. In both the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

The color developer in the present invention includes, as an important basic skeleton that imparts color developability and decolorability, a phenol group that is a color development site, a hydrogen bonding association group that controls the structure, and a long-chain aliphatic hydrocarbon group. It is made up.
Until now, efforts have been made to balance the phenolic group, which is the coloring site, with the hydrogen-bonding associative group that is dominant in the structure. The reason is that it has been considered that the stability of the color development state becomes more stable as the aggregation structure of the developer and the color developer is more stable. Therefore, it has been studied so far to introduce one or more hydrogen bonding associative groups into the developer molecular structure. However, as the hydrogen bonds between the developer molecules become stronger and the number of hydrogen bonds increases, the developer has a high melting point, the color development start temperature increases, and the sensitivity characteristics of the recording medium deteriorate. There was a problem. Therefore, the present inventors have focused on long-chain aliphatic hydrocarbon groups that are considered to be another factor governing the structure, and the types of hydrogen-bonding associative groups that greatly contribute to color development and erasability. Various studies were also conducted. As a result, it was found that a high color density and erasability can be obtained by using a urea group as the hydrogen bonding associative group. Therefore, we focused on examining the balance of the length of the aliphatic hydrocarbons.
As a result, it was found that the stability of the colored state is remarkably improved by increasing the number of carbon atoms of the alkyl group as the long-chain aliphatic hydrocarbon group. In particular, when the alkyl group has 22 or less carbon atoms for image storage stability required in the industrial field or the like used as a distribution tag or process instruction sheet, which requires higher image stability than in the office field. Although the stability of the color development state was poor and there was a fatal problem in the storage stability of the image area, a high image retention rate can be obtained by using 23 or more.
This is presumably because the decoloration start temperature from the color development state depends on the chain length of the alkyl group, and a dramatic change appears in the image storage stability.
Moreover, even when the alkyl chain length is increased as in the present invention, the melting point of the compound is surprisingly constant and does not increase, and it does not increase the melting point causing a decrease in color development sensitivity. It became clear.
Furthermore, these developer compounds having an alkyl group having 23 or more carbon atoms are sufficiently decolored by heating in a short time at the decoloring temperature in spite of the stable color development state, and high-speed erasability. It is also excellent.
Furthermore, by adding a specific quaternary ammonium salt compound as a color-decoloring / controlling agent, high-speed erasability is further improved without deteriorating the storage stability of the image, and extremely short like thermal head erasure. It was found that the erasability by heating with time was remarkably improved. The reason for this is not clear, but the quaternary ammonium salt used in the present invention is present in the image area (colored state) without affecting the aggregate structure formed by the developer and leuco dye used in the present invention. However, in the decoloring process, it is considered that the compound can rapidly interact with the developer and / or leuco dye, and expresses high-speed erasability.
These results are the first to be clarified by the present invention, and these findings make it possible to develop a highly practical reversible thermosensitive recording medium having high sensitivity, heat-resistant storage, and excellent high-speed erasability. Fabrication is now possible.

  The phenol compound used as the developer in the present invention is represented by the following formula (1).

ここで、本発明において、ｌは１から３の整数を示しｍは２３以上の整数を示し、これらを例示すると、下記式（４）から（１０）の構造式を有するものが挙げられる。

Here, in the present invention, l represents an integer of 1 to 3, m represents an integer of 23 or more, and examples thereof include those having the structural formulas of the following formulas (4) to (10).

Of the compounds represented by the structural formulas (4) to (10), compounds having the structural formula (4) are preferably used as those having excellent coloring / decoloring properties.
Here, as m becomes longer, the color density, decoloration density, and stability of the color image are improved, so that a longer recording medium can provide a better recording medium. However, if the chain length is long, the raw material is expensive and difficult to obtain, which causes problems in practicality. Therefore, the chain length is preferably 23 to 35, and the color density, decoloration density, The recording medium characteristics such as image stability and high-speed erasability are good and practical.

  Although the phenol compound used by this invention is illustrated below, it is not limited to this at all.

Such a phenol compound can be obtained, for example, by a coupling reaction with p-aminophenol via a long-chain aliphatic isocyanate derived from a long-chain aliphatic amine, or from an acid chloride from a long-chain fatty acid or a fatty acid ester. Then, azidation, via an isocyanate, is obtained by a coupling reaction with p-aminophenol. Usually, after completion of the condensation reaction with p-aminophenol, the temperature is returned to room temperature or further cooled, a hydrophilic organic solvent solution of an acid such as hydrochloric acid is added, the precipitate is filtered off, washed and dried, and then an appropriate solvent is added. Use to recrystallize. When both the hydroxyl group and the amino group are present, the urethane bond formation reaction and the coupling reaction become competitive, but in the case of p-aminophenol, the electron donating property of the hydroxyl group is reduced due to the resonance structure of the benzene ring. Therefore, the condensation reaction proceeds predominantly, and the phenol compound can be obtained with high selectivity. The phenol compound used in the present invention is not limited to this synthesis method.
Below, the synthesis example of the said phenol compound is shown.

(Synthesis Example 1) Synthesis example of a developer represented by the following structural formula

反応容器にトルエン２００ｍＬとリグノセリン酸１３．３ｇを加え、さらに塩化チオニルを８．６ｇ加え、８時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム３．５ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに２時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール３．５ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１５．２ｇ、収率は８９％であった。

To the reaction vessel, 200 mL of toluene and 13.3 g of lignoceric acid were added, 8.6 g of thionyl chloride was further added, and the mixture was heated to reflux for 8 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 100 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 3.5 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 2 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that generation of nitrogen was completed and an isocyanate compound was formed, 3.5 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 15.2 g, and the yield was 89%.

(Synthesis example 2) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン１００ｍＬとペンタコサン酸５．４ｇを加え、さらに塩化チオニルを３．４ｇ加え、６時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１５０ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム１．４ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール１．５ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量５．８ｇ、収率は８４％であった。

To the reaction vessel, 100 mL of toluene and 5.4 g of pentacosanoic acid were added, 3.4 g of thionyl chloride was further added, and the mixture was heated to reflux for 6 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 150 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 1.4 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1 hour. The obtained reaction solution was extracted with toluene, washed, dried with magnesium sulfate, transferred to the reaction solution, and heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 1.5 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 5.8 g, and the yield was 84%.

(Synthesis example 3) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン２５０ｍＬとセロチン酸１２．０ｇを加え、さらに塩化チオニルを７．２ｇ加え、さらに数滴のＤＭＦを加え、８時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム２．９ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに３時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール３．３ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１１．４ｇ、収率は７５％であった。

To the reaction vessel, 250 mL of toluene and 12.0 g of serotic acid were added, 7.2 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 8 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 100 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 2.9 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 3 hours. The obtained reaction solution was extracted with toluene, washed, dried with magnesium sulfate, transferred to the reaction solution, and heated at an internal temperature of 80 ° C. After confirming that generation of nitrogen was completed and an isocyanate compound was formed, 3.3 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 11.4 g, and the yield was 75%.

(Synthesis example 4) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン５０ｍＬとメリシン酸２．０ｇを加え、さらに塩化チオニルを１．１ｇ加え、さらに数滴のＤＭＦを加え、３時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１０ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム０．４３ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間半攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール０．４８ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量２．３５ｇ、収率は９５％であった。

To the reaction vessel, 50 mL of toluene and 2.0 g of mellic acid were added, 1.1 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 3 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 10 mL of acetone was added and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 0.43 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1.5 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 0.48 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 2.35 g, and the yield was 95%.

(Synthesis example 5) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン３５０ｍＬとモンタン酸１０．５ｇを加え、さらに塩化チオニルを５．９ｇ加え、さらに数滴のＤＭＦを加え、５時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン３００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム２．４ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール２．７ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１１．９ｇ、収率は９１％であった。

To the reaction vessel, 350 mL of toluene and 10.5 g of montanic acid were added, 5.9 g of thionyl chloride was further added, and a few drops of DMF were added, followed by heating under reflux for 5 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 300 mL of acetone was added and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 2.4 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1 hour. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 2.7 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 11.9 g and the yield was 91%.

(Synthesis example 6) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン２００ｍＬとドトリアコンタン酸４．５ｇを加え、さらに塩化チオニルを２．３ｇ加え、さらに数滴のＤＭＦを加え、７時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン２００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム０．９１ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに３時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール１．０２ｇを加え、２時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量５．２ｇ、収率は９５％であった。

To the reaction vessel, 200 mL of toluene and 4.5 g of dotriacontanoic acid were added, 2.3 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 7 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. 200 mL of acetone was added to the resulting acid chloride compound and stirred with ice cooling. An aqueous solution in which 0.91 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 3 hours. The obtained reaction solution was extracted with toluene, washed, dried with magnesium sulfate, transferred to the reaction solution, and heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 1.02 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 2 hours, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 5.2 g and the yield was 95%.

(Synthesis example 7) Synthesis example of developer expressed by the following structural formula

反応容器にトルエン２００ｍＬとテトラトリアコンタン酸４．６ｇを加え、さらに塩化チオニルを２．２ｇ加え、さらに数滴のＤＭＦを加え、７時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン２００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム０．８８ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに３時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール０．９９ｇを加え、２時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量５．１ｇ、収率は９２％であった。

To the reaction vessel, 200 mL of toluene and 4.6 g of tetratriacontanoic acid were added, 2.2 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 7 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. 200 mL of acetone was added to the resulting acid chloride compound and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 0.88 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 3 hours. The obtained reaction solution was extracted with toluene, washed, dried with magnesium sulfate, transferred to the reaction solution, and heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 0.99 g of p-aminophenol was added to the reaction solution, heated and stirred for 2 hours, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 5.1 g, and the yield was 92%.

(Synthesis Example 8) Synthesis Example of a developer represented by the following structural formula

反応容器にトルエン２００ｍＬとヘキサトリアコンタン酸５．１ｇを加え、さらに塩化チオニルを２．２ｇ加え、さらに数滴のＤＭＦを加え、７時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン２００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム０．９３ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに３時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール１．０４ｇを加え、２時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量５．９ｇ、収率は９７％であった。

To the reaction vessel, 200 mL of toluene and 5.1 g of hexatriacontanoic acid were added, 2.2 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 7 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. 200 mL of acetone was added to the resulting acid chloride compound and stirred with ice cooling. An aqueous solution in which 0.93 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 3 hours. The obtained reaction solution was extracted with toluene, washed, dried with magnesium sulfate, transferred to the reaction solution, and heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 1.04 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 2 hours, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 5.9 g, and the yield was 97%.

  For identification of these compounds, mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. In addition, the infrared absorption spectra of the compounds of Synthesis Examples 1 to 5 are shown in FIGS. In addition, the vibrations derived from the same urea group are also observed in Synthesis Examples 6 to 8. From these results, it was confirmed that the target compound shown in the structural formula was obtained.

  Next, as a quaternary ammonium salt used as a color-decoloring / controlling agent in the present invention, those represented by the following formula (2) are used.

式中、Ｒ_１〜Ｒ_３はそれぞれ独立に、炭素数１から２４の飽和または不飽和の炭化水素基であって、うち２つの炭化水素基は互いに結合して環を形成してもよい。Ｒ_４は炭素数６から２４の飽和または不飽和の脂肪族炭化水素基、または下記（３）の構造の一価の基である。ｐは１または２を表わす。Ａ⁻はアニオンを示し、ｑおよびｒは電荷を０にする整数を示す。
Ｒ_１〜Ｒ_３で示される炭素数１から２４までの飽和または不飽和の炭化水素基としては、分岐してもよいアルキル基およびアルケニル基、アラルキル基、アリール基を示し、さらに、これらの基がアルキル基、アラルキル基によって置換されていても良い。また、お互いに結合して環を形成しても良い。なかでも、炭素数１から１８の脂肪族炭化水素基がとくに好ましく用いられる。
Ｒ_４で示される炭素数６から２４の飽和または不飽和の脂肪族炭化水素基としては、ｐが１の場合にはアルキル基、アルケニル基、アルキニル基、ｐが２の場合にはアルキレン基、アルケニレン基、アルキニレン基を示し、これらの基がさらにアルキル基、アラルキル基によって置換されていても良い。
Ａはカウンターアニオンを示し、ハロゲン、置換スルホネート、置換ホスフェート、置換ボレートが挙げられ、とくに好ましくはハロゲンまたは置換スルホネートが挙げられる。
また、Ｒ_１からＲ_３は下記（３）の構造の一価の基であってもよい。

In the formula, R _{1 to} R ₃ are each independently a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and two of the hydrocarbon groups may be bonded to each other to form a ring. R ₄ is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms, or a monovalent group having the following structure (3). p represents 1 or 2; A ⁻ represents an anion, and q and r are integers that make the electric charge zero.
Examples of the saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms represented by R _{1 to} R ₃ include a branched alkyl group, an alkenyl group, an aralkyl group, and an aryl group. May be substituted with an alkyl group or an aralkyl group. Further, they may be bonded to each other to form a ring. Of these, an aliphatic hydrocarbon group having 1 to 18 carbon atoms is particularly preferably used.
As the saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms represented by R ₄ , an alkyl group, an alkenyl group, an alkynyl group when p is 1, an alkylene group when p is 2, An alkenylene group and an alkynylene group are shown, and these groups may be further substituted with an alkyl group or an aralkyl group.
A represents a counter anion, and examples thereof include halogen, substituted sulfonate, substituted phosphate, and substituted borate, and particularly preferably halogen or substituted sulfonate.
R ₁ to R ₃ may be a monovalent group having the structure (3) below.

Ｒ_５は炭素数１から２４の炭化水素基であって、Ｒ_１からＲ_３と同様な基が挙げられる、Ｒ_６は炭素数１から１２の２価の炭化水素基を示し、アルキレン基、アラルキレン基、アリーレン基が挙げられる。ここで、Ｒ_５またはＲ_６の少なくとも１つは炭素数６から２４の飽和または不飽和の脂肪族炭化水素基であって、その例としてはＲ_５の場合にはアルキル基、アルケニル基、アルキニル基、Ｒ_６の場合にはアルキレン基、アルケニレン基、アルキニレン基を示し、これらの基がさらにアルキル基、アラルキル基によって置換されていても良い。
また、ＸはＯ、Ｃ＝Ｏ、ＮＨ、Ｓ、ＳＯ_２の単独または組み合わせからなる会合基を示し、エーテル基、エステル基、アシル基、アミノ基、アミド基、ウレタン基、尿素基などの他、下記の構造を示す。

R ₅ is a hydrocarbon group having 1 to 24 carbon atoms, and examples thereof include the same groups as R ₁ to R ₃ , R ₆ represents a divalent hydrocarbon group having 1 to 12 carbon atoms, an alkylene group, Aralkylene group and arylene group may be mentioned. Here, at least one of R ₅ or R ₆ is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms, and examples thereof include an alkyl group, an alkenyl group, and an alkynyl group in the case of R _5. In the case of the group R _6, an alkylene group, an alkenylene group or an alkynylene group is shown, and these groups may be further substituted with an alkyl group or an aralkyl group.
X represents an associating group consisting of O, C═O, NH, S, SO ₂ alone or in combination, such as ether group, ester group, acyl group, amino group, amide group, urethane group, urea group, etc. The following structure is shown.

またさらに、ｎは１から４の整数を示す。なお、ｎが２以上のときにくり返されるＲ_６は同一であっても、異なっていてもよい。

Furthermore, n represents an integer of 1 to 4. Incidentally, R ₆ where n is repeated when 2 or more may be the same or different.

  The quaternary ammonium salt used as the color development / decoloration control agent in the present invention is used in an amount of 0.1 to 50% by weight, preferably 1 to 40% by weight, particularly preferably 3 to 30%, based on the developer. % By weight.

  Although the quaternary ammonium salt used as a coloring / decoloring control agent in the present invention is exemplified below, the present invention is not limited thereto.

In addition, the leuco dyes used in the present invention can be used alone or in combination, and are known dye precursors such as phthalide compounds, azaphthalide compounds, and fluorane compounds.
Specific examples of the leuco dye used in the present invention include the following.
2-anilino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6-di (n-butylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-sec-butyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane,
2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluorane,
2- (3-toluidino) -3-methyl-6-diethylaminofluorane 2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trichloromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2- (2,4-dimethylanilino) -3-methyl-6-diethylaminofluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-ethylanilino) fluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluorane,
2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane,
2- (o-chloroanilino) -6-diethylaminofluorane,
2- (o-chloroanilino) -6-dibutylaminofluorane,
2- (m-trifluoromethylanilino) -6-diethylaminofluorane,
2,3-dimethyl-6-dimethylaminofluorane,
3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-chloro-6-diethylaminofluorane,
2-bromo-6-diethylaminofluorane,
2-chloro-6-dipropylaminofluorane,
3-chloro-6-cyclohexylaminofluorane,
3-bromo-6-cyclohexylaminofluorane,
2-chloro-6- (N-ethyl-N-isoamylamino) fluorane,
2-chloro-3-methyl-6-diethylaminofluorane,
2-anilino-3-chloro-6-diethylaminofluorane,
2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluorane,
2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluorane,
2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane,
1,2-benzo-6-diethylaminofluorane,
3-diethylamino-6- (m-trifluoromethylanilino) fluorane,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-amyl-N-methylaminophenyl) -4-azaphthalide,
3- (1-methyl-2-methylindol-3-yl) -3- (2-hexyloxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
Etc.

  The appropriate range of the ratio of the leuco dye and the developer varies depending on the combination of the compounds to be used, but the developer is generally in the range of 0.1 to 20 with respect to the color former 1 in molar ratio, preferably 0. The range is from 2 to 10. If the amount of the developer is less or more than this range, the density of the colored state is lowered, which causes a problem. In addition, the leuco dye and the developer can be used in a microcapsule.

  In the present invention, examples of the binder resin used for forming the reversible thermosensitive recording layer together with the leuco dye and the developer include polyvinyl chloride, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, and styrene-based copolymer. Polymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid copolymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, Examples include carboxymethyl cellulose and starches. The role of these binder resins is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be crosslinked with heat, ultraviolet light, electron beam, or the like.

  Specific examples of the crosslinked resin used in the present invention include acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate, and cellulose acetate butyrate. A resin having a reactive group, or a resin obtained by copolymerization of a monomer having a group reactive with a crosslinking agent and another monomer may be used, but the present invention is not limited to these compounds.

  Further, in the present invention, a resin having a hydroxyl value of 70 (KOHmg / g) or more is preferably contained (initially used). Examples of the resin having a hydroxyl value of 70 (KOHmg / g) or more include acrylic polyol resins and polyester polyols. Resins, polyurethane polyol resins, and the like are used, and acrylic polyol resins are preferably used because they have particularly good color stability and good decoloring properties. The hydroxyl value is 70 (KOHmg / g) or more, particularly preferably 90 (KOHmg / g) or more. The magnitude of the hydroxyl value affects the crosslink density and thus affects the chemical resistance and physical properties of the coating film. The present inventors have found that durability, coating film surface hardness, and crack resistance are improved when the hydroxyl value is 70 (KOHmg / g) or more. Whether or not the resin is a reversible thermosensitive recording material using a resin having a hydroxyl value of 70 (KOHmg / g) or more can be confirmed by analyzing the amount of residual hydroxyl groups and the amount of ether bonds.

  In addition, acrylic polyol resins have different characteristics depending on the structure. Hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate ( HPMA), 2-hydroxybutyl monoacrylate (2-HBA), 1,4-hydroxybutyl monoacrylate (1-HBA), etc. are used, but it is particularly preferable to use a monomer having a primary hydroxyl group. Since the crack resistance and durability are good, 2-hydroxyethyl methacrylate is preferably used.

  Examples of the curing agent used in the present invention include conventionally known isocyanates, amines, phenols, and epoxy compounds. Of these, isocyanate curing agents are preferably used. The isocyanate compound used here is selected from known modified urethane monomers, allophanate modified, isocyanurate modified, burette modified, carbodiimide modified, blocked isocyanate and the like. The isocyanate monomer that forms the modified product includes tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), paraphenylene diisocyanate ( PPDI), tetramethylxylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate (LDI), isopropylidenebis (4-cyclohexylisocyanate) (IPC) ), Cyclohexyl diisocyanate (CHDI), tolidine diisocyanate (TODI) and the like. It is not limited to the compounds.

  Furthermore, you may use the catalyst used for this kind of reaction as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diaza-bicyclo [2,2,2] octane, and metal compounds such as organic tin compounds. Further, the total amount of the curing agent may or may not undergo a crosslinking reaction. That is, an unreacted curing agent may be present. Since this type of crosslinking reaction proceeds over time, the presence of an unreacted curing agent does not indicate that the crosslinking reaction has progressed at all, but an unreacted curing agent is detected. However, this does not mean that there is no resin in a crosslinked state. Further, as a method for distinguishing whether the polymer in the present invention is in a crosslinked state or in a non-crosslinked state, it can be distinguished by immersing the coating film in a highly soluble solvent. That is, since the polymer in the non-crosslinked state dissolves in the solvent and does not remain in the solute, the presence or absence of the polymer structure of the solute may be analyzed.

  According to the present invention, in addition to the developer and the leuco dye, a coloring / decoloring control agent having a linear hydrocarbon group, a hydrogen bond group such as an amide group or a urea group, and the like is included in the recording layer. As a result, the storage stability of the color image is good, and the erasability at the time of erasing is also improved to obtain good erasability.

  Further, according to the present invention, a protective layer containing a resin in a crosslinked state can be provided on the reversible thermosensitive recording layer. As the resin used for the protective layer, the same thermosetting resin, ultraviolet curable resin, and electron beam curable resin as those used for the recording layer are used.

  As the resin used in the protective layer, an ultraviolet absorbing polymer having an ultraviolet absorbing group in the molecular structure is particularly preferably used.

  As the ultraviolet absorbing polymer, a monomer having an ultraviolet absorbing group and a polymer having a monomer having a crosslinkable functional group are preferably used. As the monomer having an ultraviolet absorbing group, (2 '-Hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-ω-butyl- A monomer having a benzotriazole skeleton such as 5′-methylphenyl) -5-chlorobenzotriazole is particularly preferably used.

  Examples of the monomer containing a functional group include 2-isopropenyl-2-oxazoline, 2-aziridinylethyl (meth) acrylate, methacrylic acid, glycidyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxyl Examples include propyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate, among which hydroxylethyl (meth) ) Acrylate, hydroxylpropyl (meth) acrylate and the like are particularly preferably used.

  Furthermore, in order to increase the strength of the coating film and improve heat resistance, the following monomers may be copolymerized with a copolymer of a monomer containing an ultraviolet absorbing group and a monomer containing a functional group. For example, monomer groups such as styrene, styrene-butadiene, styrene-isobutylene, ethylene vinyl acetate, vinyl acetate, methacrylonitrile, vinyl alcohol, vinyl pyrrolidone, acrylonitrile, methacrylonitrile; acrylic acid, methyl (meth) acrylate, ethyl (meth ) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) ) Acrylate, lauryl tridecyl (meth) acrylate, tridecyl (meth) acrylate, cetyl stearyl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylic acid ester groups not containing functional groups such as cyclohexyl (meth) acrylate and benzyl (meth) acrylate; ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene Glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentacontahector ethylene glycol (meth) acrylate, butylene di (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, penta Decaethylene glycol di (meth) acrylate, phthalic acid diethylene glycol di (meth) acrylate, etc. have two or more polymerizable double bonds in one molecule Although it is mentioned from a monomer group etc., it is not particularly limited, among them, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Particularly preferred is t-butyl (meth) acrylate. Moreover, 2 or more types can also be used together as needed.

  From the above, specific preferred examples of the polymer having an ultraviolet absorption structure used in the present invention include 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole and 2-hydroxy methacrylate. Examples include a copolymer composed of ethyl and styrene, and a copolymer composed of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2-hydroxypropyl methacrylate and methyl methacrylate. Is not to be done.

Furthermore, according to the present invention, the protective layer can contain inorganic fine particles having ultraviolet absorbing ability.
The inorganic pigment used in the present invention is arbitrary as long as it has an average particle size of 0.1 μm or less. Examples of such inorganic pigments include zinc oxide, indium oxide, alumina, silica, zirconium oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide, Manganese oxide, tantalum oxide, niobium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite, nickel ferrite, cobalt ferrite, barium titanate, metal oxides such as potassium titanate and complex oxides thereof, zinc sulfide, Metal sulfides such as barium sulfate or sulfate compounds, titanium carbide, silicon carbide, molybdenum carbide, tungsten carbide, metal carbides such as tantalum carbide, aluminum nitride, silicon nitride, boron nitride, nitride Rukoniumu, vanadium nitride, titanium nitride, niobium nitride, and metal nitrides such as gallium nitride.

Among these, a pigment having an absorption edge in a wavelength region of 400 nm or less is particularly preferable.
Such a pigment includes a pigment (A) having an absorption edge in the ultraviolet UV-A region, that is, an ultraviolet UV-A region having a wavelength of 320 to 400 nm, and an inorganic pigment having an absorption edge on the shorter wavelength side than the ultraviolet UV-A region ( B) can be classified into two groups. In the present invention, the inorganic pigment (A) or the inorganic pigment (B) can be used alone, but the effect of the present invention becomes more remarkable by using the inorganic pigment (A) and the inorganic pigment (B) in combination. When the inorganic pigment (A) or the inorganic pigment (B) is used alone, these pigments can be contained in either the intermediate layer or the protective layer.
In the case where the inorganic pigment (A) and the inorganic pigment (B) are used in combination, these pigments can be simultaneously contained in the intermediate layer or the protective layer, but the inorganic pigment (A) and the inorganic pigment (B) are included in the intermediate layer. And can be contained separately in the protective layer. In this case, when the inorganic pigment (A) is contained in the intermediate layer and the inorganic pigment (B) is contained in the protective layer, the effect of the present invention is more remarkably exhibited.

Specific examples of the inorganic pigment (A) include zinc sulfide, titanium oxide, indium oxide, cerium oxide, tin oxide, molybdenum oxide, zinc oxide, and gallium nitride.
Specific examples of the inorganic pigment (B) include silica, alumina, silica-alumina, antimony oxide, magnesium oxide, zirconium oxide, barium oxide, calcium oxide, strontium oxide, silicon nitride, aluminum nitride, boron nitride, and barium sulfate. Can be mentioned.

  Further, in the present invention, inorganic / organic fillers, lubricants and the like used for this type of recording medium may be used in the protective layer.

The support for the reversible thermosensitive recording medium of the present invention is paper, resin film, PET film, synthetic paper, metal foil, glass or a composite thereof, and the like, as long as it can hold the thermosensitive recording layer. Moreover, the thing of the thickness as needed can be used individually or by bonding. That is, it is preferably 60 to 150 μm, and a support having an arbitrary thickness is used from about several μm to several mm.
Moreover, when providing the said under layer on these support bodies, crack generation | occurrence | production prevention and generation | occurrence | production of a burr | flash are improved by providing through an contact bonding layer.
The adhesive layer can be formed by the same coating method as that for each of the above layers.

When the reversible thermosensitive recording medium of the present invention is a reversible thermosensitive recording label, an adhesive layer or a pressure-sensitive adhesive is formed on the surface opposite to the surface of the support constituting the reversible thermosensitive recording medium described above. A layer is provided.
This reversible thermosensitive recording label includes an adhesive layer or a pressure-sensitive adhesive layer (non-peeling paper type), and a release paper attached under the adhesive layer or pressure-sensitive adhesive layer (peeling paper type). As a material constituting the adhesive layer, a hot melt type material is usually used. Therefore, the reversible thermosensitive recording medium of the present invention may be in the form of a laminate of such a reversible thermosensitive recording label and a substrate.
Commonly used materials can be used for the adhesive layer or the pressure-sensitive adhesive layer.
For example, urea resin, melamine resin, phenol resin, epoxy resin, vinyl acetate resin, vinyl acetate-acrylic copolymer, ethylene-vinyl acetate copolymer, acrylic resin, polyvinyl ether resin, vinyl chloride-vinyl acetate Copolymer, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin resin, polyvinyl butyral resin, acrylic ester copolymer, methacrylic ester copolymer, natural rubber , Cyanoacrylate resins, silicon resins, and the like, but are not limited thereto.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the text, “part” or “%” is based on weight unless otherwise specified.

Example 1
[Creation of thermal recording layer]
4 parts of developer expressed by the following structural formula

下記の構造式で表わされる発色消色制御剤 ０．２部

0.2 parts of coloring / decoloring control agent represented by the following structural formula

アクリルポリオール樹脂
（三菱レイヨン社製ＬＲ５０３、固形分濃度５０％溶液） ９部
メチルエチルケトン ７０部
上記組成物をボールミルを用いて平均粒径約１μｍまで粉砕分散した。得られた分散液に２−アニリノ−３−メチル−６−ジブチルアミノフルオラン１．５部、日本ポリウレタン社製コロネートＨＬ（アダクト型ヘキサメチレンジイソシアネート７５％酢酸エチル溶液）２部を加え、良く攪拌し感熱記録層塗布液を調製した。
上記組成の感熱記録層塗布液を、厚さ１８８μｍの白ＰＥＴにワイヤーバーを用い塗布し、１００℃２分で乾燥した後、６０℃２４時間加熱して、膜厚約１１．０μｍの記録層を設けた。

Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd., 50% solid content solution) 9 parts Methyl ethyl ketone 70 parts The above composition was pulverized and dispersed to an average particle size of about 1 µm using a ball mill. To the obtained dispersion, 1.5 parts of 2-anilino-3-methyl-6-dibutylaminofluorane and 2 parts of Coronate HL (adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. are added and stirred well. A thermal recording layer coating solution was prepared.
The thermal recording layer coating solution having the above composition was applied to white PET having a thickness of 188 μm using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to form a recording layer having a thickness of about 11.0 μm. Was provided.

[Create protection layer]
40% solution of UV-absorbing polymer (UV-G300 manufactured by Nippon Shokubai Co., Ltd.) 10 parts Isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate HX) 1.4 parts Silicone-based acrylic resin (GS-1015 manufactured by Toagosei Co., Ltd.) 0 .5 parts Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating solution.
A protective layer coating solution having the above composition is applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to provide a protective layer having a thickness of about 3.5 μm. The reversible thermosensitive recording medium of the invention was produced.

(Example 2)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer used in Example 1.
・ Developer

(Example 3)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound was used in place of the developer and color development / decoloration controlling agent used in Example 1.
・ Developer

・発色消色制御剤

・ Coloring / decoloring control agent

Example 4
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer and color development / decoloration control agent used in Example 1.
・ Developer

・発色消色制御剤

・ Coloring / decoloring control agent

(Example 5)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer and color development / decoloration control agent used in Example 1.
・ Developer

・発色消色制御剤

・ Coloring / decoloring control agent

(Example 6)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer and color development / decoloration control agent used in Example 1.
・ Developer

・発色消色制御剤

・ Coloring / decoloring control agent

(Comparative Example 1)
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the coloring / decoloring controlling agent used in Example 1 was not used.

(Comparative Example 2)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer used in Example 1.

(Comparative Example 3)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer used in Example 1.

(Comparative Example 4)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer used in Example 1.

(Comparative Example 5)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used instead of the developer used in Example 1.

(Comparative Example 6)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used in place of the color development / decoloration controlling agent used in Example 1.

(Comparative Example 7)
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compounds were used in place of the color development / decoloration controlling agent used in Example 1.

The reversible thermosensitive recording medium produced as described above was tested as follows.
Test 1: Color development characteristics Printing was carried out on the reversible thermosensitive recording media produced in Examples 1 to 6 and Comparative Examples 4 and 5 using the thermal printing simulator manufactured by B.COM with the voltage shown in Table 2 under the condition of a pulse width of 2 msec. I did it. The color density and background density were measured using a Macbeth densitometer RD914. The results are shown in Table 2.

Test 2: Thermal head decoloring characteristics (high-speed erasability)
After printing on the reversible thermosensitive recording media produced in Examples 1 to 6 and Comparative Examples 1, 2, 3, and 6 with the voltage shown in Table 3, using a thermal printing apparatus manufactured by Becom, on the printed image The image was erased again in 0.5V increments under the conditions of 9V to 17V, the image density before erasure and the image density of the most decolored portion were measured in the same manner as in Test 1, and the thermal head erasure rate was calculated from the following formula. . The results are shown in Table 3.
Thermal head erasure rate (%) = (1− (image density after erasure−background density) / (image density before erasure−background density)) × 100

Test 3: Image heat resistant storage stability Printed images printed on the reversible thermosensitive recording media produced in Examples 1 to 6 and Comparative Examples 2, 3, 5, and 7 in the same manner as in Test 2 were stored at 50 ° C. under dry conditions for 24 hours. . After measuring the density before and after storage in the same manner as in Test 1, the image retention rate was calculated by the following formula. The results are shown in Table 4.
Image heat resistance retention rate (%) = (image density after storage−background density after storage) / (image density before storage−background density before storage) × 100

From these results, as shown in Table 2, the embodiment of the present invention has a high density at low energy, and a remarkable difference appears in the color development sensitivity.
Further, as shown in Table 3, it can be seen that the examples of the present invention have good decoloring characteristics and high-speed erasure suitability.
Further, as shown in Table 4, the examples show high image heat resistant storage stability.
As is clear from the above results, a specific compound having an alkyl group having 23 or more carbon atoms and a urea group was used as the developer, and a specific quaternary ammonium salt compound was used as the color-decoloration controlling agent. It can be seen that the reversible thermosensitive recording medium of the present invention has high color development sensitivity, good high-speed erasability, and is extremely practical with excellent image storage stability.

It is a figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention. It is a positive ion peak profile observed when using the time-of-flight secondary ion mass spectrometer for the compound used in the present invention. It is a negative ion peak profile observed when using the time-of-flight secondary ion mass spectrometer for the compound used in the present invention. 2 is an infrared absorption spectrum of a compound used in the present invention synthesized in Synthesis Example 1. 2 is an infrared absorption spectrum of a compound used in the present invention synthesized in Synthesis Example 2. 4 is an infrared absorption spectrum of a compound used in the present invention synthesized in Synthesis Example 3. 4 is an infrared absorption spectrum of a compound used in the present invention synthesized in Synthesis Example 4. 7 is an infrared absorption spectrum of a compound used in the present invention synthesized in Synthesis Example 5.

Claims (2)

A reversible thermosensitive recording layer that uses an electron-donating color-forming compound and an electron-accepting compound and can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. In the reversible thermosensitive recording medium, a phenol compound represented by the following formula (1) is used as the electron-accepting compound, and a quaternary ammonium salt compound represented by the following formula (2) is used as the color-decoloration controlling agent. A reversible thermosensitive coloring composition characterized by the above.

(In the formula, l represents an integer of 1 to 3, and m represents an integer of 23 or more.)

(Wherein R _{1 to} R ₃ are each independently a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and two of these hydrocarbon groups may be bonded to each other to form a ring. R ₄ is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms or a monovalent group having the structure of the following (3), p represents 1 or 2, and A ⁻ represents an anion. , Q and r are integers that make the electric charge zero.

R ₅ represents a saturated or unsaturated monovalent hydrocarbon group having 1 to 24 carbon atoms, R ₆ represents a saturated or unsaturated divalent hydrocarbon group having 1 to 12 carbon atoms, and R ₅ or R ₆ At least one is a saturated or unsaturated aliphatic hydrocarbon group having 6 to 24 carbon atoms. X represents a group composed of O, C═O, NH, S, SO ₂ alone or in combination, and n represents an integer of 1 to 4. Note that R ₆ repeated when n is 2 or more may be the same or different. ) A reversible thermosensitive recording medium comprising a recording layer containing the reversible coloring composition according to claim 1 on a support.

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