JP4943133B2 - Reversible thermosensitive coloring composition and reversible thermosensitive recording medium using the same - Google Patents

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. That is, the problem is that the sensitivity for color development is low.

  On the other hand, phenol compounds having a relatively low melting point have been proposed as the phenol compounds described in Patent Document 12. However, although the color development sensitivity of recording media using these compounds is good, the image storage stability is poor, and the practicality is low. 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. Improvement of heat resistant storage stability is desired.

  Further, Patent Document 15 (Japanese Patent Laid-Open No. 2000-141901) and Patent Document 16 (Japanese Patent Laid-Open No. 2005-11279) 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 low color development sensitivity, poor storage stability of image areas, or problems with decoloring properties.

Furthermore, in order to increase the added value, it is desired to realize a recording medium compatible with a thermal head overwrite that simultaneously performs printing and erasing in order to support rewriting with a small-sized and energy-saving printer. In addition to the good color development and erasability, high color development sensitivity, and heat-resistant storage properties that have been required, high-speed erasability that can be erased by heating in a short time with a thermal head is essential. there were.
In order to realize these, a coloring / decoloring control agent and a decoloring accelerator aimed at improving decoloring property and image stability have been studied. Patent Document 17 (Japanese Patent Laid-Open No. 9-48175) ), Patent Document 18 (Japanese Patent Laid-Open No. 9-290563), Patent Document 19 (Japanese Patent Laid-Open No. 11-70731), and the like, the erasability is improved, and a heat stamp or the like There was almost no unerased residue due to, and in particular, by using the long-chain alkyl compound described in Patent Document 17, the erasability was improved and the color image was stabilized. Furthermore, as described in Patent Document 20, as a decoloring accelerator, fatty acids, waxes, higher alcohols, phosphoric acid, benzoic acid, phthalic acid or various esters of oxyacid, silicone oil, liquid crystalline compounds, Surfactants and fatty acid saturated hydrocarbons having 10 or more carbon atoms are disclosed. In these recording media, there is a problem that there are many unerased parts in high-speed erasing such as thermal head erasing, and there is still room for examination.

Further, Patent Documents 21 to 26 propose an ionic salt decolorization accelerator. The combination of the developer and the quaternary ammonium salt or alkylene oxide described in Patent Document 21 (Japanese Patent Application Laid-Open No. 8-108627) can provide a good contrast, but the image has low heat storage stability and is not practical. Absent. Patent Document 22 (Japanese Patent Laid-Open No. 9-300820) discloses an onium salt, Patent Document 23 (Japanese Patent Laid-Open No. 10-44607) discloses a quaternary ammonium salt having a heteroaromatic ring, and Patent Document 24 (Japanese Patent Laid-Open No. 2000-263946). JP-A 2000-313171 discloses a combination of a decoloring accelerator having a polar site (for example, an onium salt or a quaternary ammonium salt having a heteroaromatic ring) with a specific developer. ), Patent Document 26 (Japanese Patent Application Laid-Open No. 2001-47749) describes a combination of a quaternary ammonium salt and a specific developer. When these ionic salt decoloring accelerators are used, erasing is possible over a wide temperature range, and good contrast is obtained during color development and decolorization. Therefore, there is a problem that the heat-resistant storability of the image is poor under further high-temperature conditions (for example, heat-resistant storability at 60 ° C.).
A compound having a basic group such as an amine group together with an acidic group such as a carboxyl group or a sulfo group described in Patent Document 27 (JP-A-7-285270), Patent Document 28 (JP-A-7-285271) The amine compounds described have been proposed as a decoloring palpation agent, but these are also impractical because of their large problems in high-speed erasability and heat-resistant storage stability of images.
As described above, although the practical level has been reached, an excellent reversible thermosensitive recording material having good color developability, erasability, high color development sensitivity, and high-speed erasability has not yet been reported.

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 Utility Model Publication 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 2005-11279 A Japanese Patent Laid-Open No. 9-48175 Japanese Patent Laid-Open No. 9-290563 Japanese Patent Laid-Open No. 11-70731 Japanese Patent Laid-Open No. 5-294663 JP-A-8-108627 Japanese Patent Laid-Open No. 9-300820 Japanese Patent Laid-Open No. 10-44607 JP 2000-263946 A JP 2000-313171 A JP 2001-47749 A JP-A-7-285270 JP 7-285271 A

  An object of the present invention is to provide a reversible thermosensitive composition and a reversible thermosensitive recording medium having high color development and decoloring properties, high-speed erasability, heat-resistant storage properties, high sensitivity properties, little background coloration, and high visibility. Is to provide.

In the color erasing process of the reversible color erasing phenomenon of such a color developer and developer composition, the present inventors have developed a color developer and a leuco dye having a long-chain aliphatic group that forms a colored state. Various studies have been carried out on the assumption that the intermolecular cohesive force of the color development / decoloration control agent or the decolorization accelerator and the intermolecular interaction exerted on each other are important. Among the studies, the inventors have focused on ionic compounds and have studied the influence of them on the color development process and the color erasing process. As a result of various investigations, when a compound having a Zwitter ion whose total charge in the molecule is 0 is used as a coloring / decoloring control agent, high erasability and high heat resistance are achieved while having high coloring properties. It was discovered that a highly practical reversible thermosensitive composition and a reversible thermosensitive recording medium capable of ensuring storage stability were obtained.
In addition, it has a high color developing and decoloring characteristics and high speed erasability by combining a developer having a high color developing sensitivity and a heat resistant storage stability of 60 ° C. or higher with a compound having a Zwitter ion by having a hydrocarbon group having 23 or more carbon atoms. It was found that a reversible thermosensitive composition and a reversible thermosensitive recording medium having both heat-resistant storage stability and high sensitivity characteristics can be obtained. In addition, it has been newly found that these reversible thermosensitive compositions and reversible thermosensitive recording media have a background density lower than that of the conventional one and a good contrast between the background and the colored portion. One of the causes of background coloration is known to develop in the decolored state due to the interaction between the active developer's phenolic part (acidic part) and the leuco dye. Cause. However, due to electrostatic interaction between the polar part of the compound having Zwitter ion and the phenol part of the specific developer, a complex of the developer and the compound having Zwitter ion may be formed in the erased state. It became clear. This reason is based on experiments of X-ray structural analysis and thermal analysis. That is, it is considered that the compound having the Zwitter ion was able to reduce the fog of the background by quenching the active phenolic site of the specific developer.

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 thermochromic composition, a reversible thermosensitive coloring composition comprising a phenol compound represented by the following formula (1) as the electron-accepting compound and a compound having a Zwitter ion as a coloring and decoloring control agent: object;

（式中、ｌは１から３の整数、ｍは２３以上の整数を示す。）」、
（２）「電子供与性呈色性化合物と電子受容性化合物を用い、加熱温度および／又は加熱後の冷却速度の違いにより、相対的に発色した状態と消色した状態を形成しうる可逆性感熱発色組成物において、該電子受容性化合物として下記式（１）で表わされるフェノール化合物を用いるとともに、発色消色制御剤としてＺｗｉｔｔｅｒイオンを有する化合物の陽イオンがＮ^＋であり、且つ、陰イオンがＯ⁻、ＣＯＯ⁻、ＳＯ_３ ⁻基の単独、又は、複数個の組み合わせであることを特徴とする前記第（１）項に記載の可逆性感熱発色組成物；

(Wherein, l represents an integer of 1 to 3, and m represents an integer of 23 or more)],
(2) “A reversible feeling that uses an electron-donating color-forming compound and an electron-accepting compound to form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. In the thermochromic composition, a phenol compound represented by the following formula (1) is used as the electron-accepting compound, and the cation of the compound having a Zwitter ion as the color-decoloring control agent is N ⁺ and an anion Is a reversible thermosensitive coloring composition as described in the above item (1), wherein is a single or a combination of O ⁻ , COO ⁻ and SO ₃ ^— groups;

（式中、ｌは１から３の整数、ｍは２３以上の整数を示す。）」、
（３）「電子供与性呈色性化合物と電子受容性化合物を用い、加熱温度および／又は加熱後の冷却速度の違いにより、相対的に発色した状態と消色した状態を形成しうる可逆性感熱発色組成物において、該電子受容性化合物として下記式（１）で表わされるフェノール化合物を用いるとともに、発色消色制御剤として下記式（２）で示されるＺｗｉｔｔｅｒイオンを有する化合物を少なくとも含有することを特徴とする可逆性感熱発色組成物；

(Wherein, l represents an integer of 1 to 3, and m represents an integer of 23 or more)],
(3) “Reversible sensation using an electron-donating color-forming compound and an electron-accepting compound to form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. In the thermochromic composition, a phenolic compound represented by the following formula (1) is used as the electron-accepting compound, and at least a compound having a Zwitter ion represented by the following formula (2) is used as a coloring and decoloring control agent. reversible heat sensitive color developing composition you wherein;

(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_２、及びＲ_３は互いに同じであっても異なっていても良い炭素数１から２２の飽和または不飽和炭化水素基、または下記式（３）の構造を有する基で、Ｒ_１、Ｒ_２、及びＲ_３は互いに結合して、環を形成していても良い。Ｒ_４は水酸基を有しても良い炭素数１から１８の飽和、不飽和炭化水素基を示す。Ａ⁻はアニオンであり、Ｏ⁻、ＣＯＯ⁻、ＳＯ_３ ⁻のいずれかを示す。

(Wherein R ₁ , R ₂ , and R ₃ may be the same or different from each other, a saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms, or a group having the structure of the following formula (3) R ₁ , R ₂ and R ₃ may be bonded to each other to form a ring, and R ₄ represents a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms which may have a hydroxyl group. A ⁻ is an anion and represents any one of O ⁻ , COO ⁻ , and SO ₃ ^— .

Ｒ_５は炭素数１から２２の飽和または不飽和炭化水素基を示す。Ｒ_６は２価の炭素数１〜１８の飽和または不飽和炭化水素基を示す。Ｘはカルバモイル基、アミド基、尿素基、ジアシルヒドラジン基、エーテル基、エステル基からなる基を示し、ｎは１から３の整数を示し、ｎが２以上の場合はＲ_６、Ｘは同一であっても異なっていても良い。）」、
（４）「支持体上に前記第（１）項乃至第（３）項のいずれかに記載の可逆性感熱組成物を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 hydrocarbon group having 1 to 22 carbon atoms. R ₆ represents a divalent saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms. X represents a group consisting of a carbamoyl group, an amide group, a urea group, a diacylhydrazine group, an ether group, and an ester group, n represents an integer of 1 to 3, and when n is 2 or more, R ₆ and X are the same It can be different. ) ",
(4) “A reversible thermosensitive recording medium comprising a recording layer comprising the reversible thermosensitive composition according to any one of (1) to (3)” above a support.

  The reversible thermosensitive composition or reversible thermosensitive recording medium of the present invention has high color erasing characteristics, high-speed erasability, heat resistant storage stability, high sensitivity characteristics, and has low visibility and high visibility. It has an extremely excellent effect.

The present invention is described in detail below.
The reversible thermosensitive recording medium 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 melted state is a state in which the developer and the color former are in contact with each other and 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 in which molecules of at least one component (for example, developer molecules) of the developer and the color former are aggregated to form a domain or crystallize, and color is formed by aggregation or crystallization. It is considered that the agent and the developer are separated and stabilized. 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.

In the recording medium of the present invention, the stability of the image density increases as the aggregation structure in the color development state is stable, and the crystallization of the developer occurs faster from the aggregation structure during color development in the decoloring process. It is considered that erasability can be obtained. For this reason, as a color-decoloring / controlling agent, stabilization of the color-developing state and improvement of erasability have been studied by introducing a hydrogen-bonding associating group into a molecular structure having a long-chain alkyl.
The color erasing control agents reported as such prior art satisfy the static erasure using a thermal stamp and the high speed erasing characteristics using a thermal head, while the color developing characteristics and storability are mostly deteriorated. There are no reports that practically satisfy all of the color development characteristics, the color erasing characteristics, the high speed erasability, and the heat storage stability.

In the reversible thermosensitive composition and reversible thermosensitive recording medium of the present invention, when having a Zwitter ion in the molecular structure of the color-decoloration controlling agent, it has high color developability and high speed and good erasability and heat-resistant storage stability. It was discovered that it can be secured. Here, the compound having a Zwitter ion described in the present invention is a structure in which both ions of a cation (positive charge) and an anion (negative charge) coexist through a covalent bond, or an N-oxide structure without a covalent bond. A compound having a structure having a bipolar structure in which a negative charge such as (N ⁺ -O ⁻ ) comes on an electronegative atom such as oxygen (O), and the total charge of one molecule is 0 A cation or anion such as a cationic compound represented by a quaternary ammonium salt or an anionic compound represented by a sulfonium salt is ion-bonded to a counter ion and the apparent charge is zero. In addition to ionic compounds, in addition, compounds with carboxyl and amino groups, such as aminocarboxylic acids, which are covalently bonded compounds that are not ionized It is also very different from (specifically, for example, amino acids).

  As described in Japanese Patent Application No. 2006-1228829, a compound having a Zwitter ion structure has a cation and an anion, and the electric dipole from the fact that the centers of gravity of positive and negative charges do not coincide with each other. Is present. This electric dipole plays an extremely important role in the color developing and decoloring characteristics. Such a color development / decoloration controlling agent is considered to act as follows.

That is, the leuco dye which is an electron donating compound is in a decolored state, for example, in the case of a fluorane compound, in a compound structure having an amino group site substituted on a dibenzoxazole ring and a lactone ring-closing site (phthalide compound, azaphthalide compound The same applies to the case), but there is no bias of electric charge and there is no electric dipole. However, in the colored state, the leuco dye, which is an electron-donating compound, interacts with an electron-accepting compound (developer) to form a molecule. In this state, the electric charge is biased and the electric dipole is present (the lactone ring is opened into a quinoid type and has an electron donating site and a sparse amino group site). The same applies to phthalide compounds and azaphthalide compounds. However, each molecule has a dipole, but the static coloring state is an agglomerated structure, so they cancel each other out, and the electric dipole moment that indicates the strength and direction of the dipole of the entire system is 0. On the other hand, a structural change occurs when changing from a colored state to a decolored state. As the structure changes, the aggregated structure of the colored state collapses and the symmetry of the entire system is instantaneously disrupted, and an electric dipole moment is induced. At this moment, the induced dipole derived from the electron-donating compound (leuco dye) in the colored state and the dipole of the color-decoloring control agent produced intermolecular cohesion due to the induced dipole-dipole interaction. As a result, it is considered that the intermolecular distance between the electron-accepting compound and the electron-donating compound is increased to promote decolorization.
For the above reasons, a reversible thermosensitive composition or reversible thermosensitive recording medium having high color development characteristics, high-speed erasability and high heat resistance characteristics is obtained by using these compounds having Zwitter ions.

Furthermore, as described in Japanese Patent Application No. 2006-061885, it has been found that by using a specific phenol developer, both good storage stability and high color development sensitivity can be achieved. This is because the stability of the coloring state is remarkably improved by increasing the number of carbon atoms of the alkyl group as the long-chain aliphatic hydrocarbon group. When the carbon number of the alkyl group is 22 or less for image storability at 60 ° C., which is required in the industrial field, which is used as a logistics tag or process instruction sheet, which requires higher image stability than in the office field However, the color development state at 60 ° C. is remarkably improved and a high image retention rate can be obtained by using 23 or more. I can do it now.
This is because the decolorization start temperature from the colored state depends on the chain length of the alkyl group, and in the case of 22 carbon atoms, the decolorization start temperature is 60 ° C. or less, but by setting it to 23 or more, the decoloration start temperature This is because the temperature becomes 60 ° C. or higher, and a dramatic change appears in the image storage stability at 60 ° C.
In addition, it has been clarified that even when the alkyl chain length is increased, the melting point of the compound is almost constant and does not increase, and the melting point is not increased to cause a decrease in color development sensitivity.
In this way, by using a specific developer having an alkyl group having 23 or more carbon atoms, the color can be sufficiently erased by a short heating at the color erasing temperature even though the color development state is stable. In addition, a material excellent in high-speed erasability can be obtained.

Various studies have been made from the above background, and by combining a specific developer having a hydrocarbon group having 23 or more carbon atoms with a compound having a Zwitter ion, high color-decoloring properties, high-speed erasability, heat-resistant storage It has been found that an excellent reversible thermosensitive composition and a reversible thermosensitive recording medium that have both high performance and high sensitivity characteristics can be obtained. In general, there is a concern about a decrease in color density, a decrease in heat-resistant storage stability, a decrease in erasability, and the like by combining a control agent with a developer, but in the case of this combination, these adverse effects were not found.
Even better, it has been newly found that these reversible thermosensitive compositions and reversible thermosensitive recording media have a background density lower than that of the prior art and a good contrast between the background and the color development site.

One of the causes of background coloration is known to develop in the decolored state due to the interaction between the active developer's phenolic part (acidic part) and the leuco dye. Cause. However, due to electrostatic interaction between the polar part of the compound having Zwitter ion and the phenol part of the specific developer, a complex of the developer and the compound having Zwitter ion may be formed in the erased state. It became clear based on experiments of X-ray structural analysis and thermal analysis. It is considered that the compound having Zwitter ion was able to reduce the fog of the background by quenching the active phenolic site of the specific developer.
Such a reversible thermosensitive coloring composition or reversible thermosensitive recording medium having a high color erasing property, high-speed erasability, heat-resistant storage property, and high sensitivity property, and with little coloring of the background is a compound having a Zwitter ion. It can be obtained only from a combination with a specific phenol compound.

  Here, 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 are good and the utility is high.

  Specific examples of the compound having a Zwitter ion used in the present invention are listed below, but the present invention is not limited thereto.

なお、式中の記号ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｄ’、ｄ”、ｅ’は整数であり、好ましくは１から３０の整数である。加えて、分子中に同一の記号がある場合は同じでも異なっていてもよい。
本発明に特に好ましい構造として以下の構造が挙げられる。

The symbols a, b, c, d, e, f, g, d ′, d ″, e ′ in the formula are integers, preferably integers of 1 to 30. In addition, they are the same in the molecule. May be the same or different.
The following structures may be mentioned as particularly preferred structures for the present invention.

（式中、Ｒ_１、Ｒ_２、及びＲ_３は互いに同じであっても異なっていても良い炭素数１から２２の飽和または不飽和炭化水素基、または下記式（３）の構造を有する基で、Ｒ_１、Ｒ_２、及びＲ_３は互いに結合して、環を形成していても良い。Ｒ_４は水酸基を有しても良い炭素数１から１８の飽和、不飽和炭化水素基を示す。Ａ⁻はアニオンであり、Ｏ⁻、ＣＯＯ⁻、ＳＯ_３ ⁻のいずれかを示す。

(Wherein R ₁ , R ₂ , and R ₃ may be the same or different from each other, a saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms, or a group having the structure of the following formula (3) R ₁ , R ₂ and R ₃ may be bonded to each other to form a ring, and R ₄ represents a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms which may have a hydroxyl group. A ⁻ is an anion and represents any one of O ⁻ , COO ⁻ , and SO ₃ ^— .

Ｒ_５は炭素数１から２２の飽和または不飽和炭化水素基を示す。Ｒ_６は２価の炭素数１〜１８の飽和または不飽和炭化水素基を示す。Ｘはカルバモイル基、アミド基、尿素基、ジアシルヒドラジン基、エーテル基、エステル基からなる基を示し、ｎは１から３の整数を示し、ｎが２以上の場合はＲ_６、Ｘは同一であっても異なっていても良い。）

R ₅ represents a saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms. R ₆ represents a divalent saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms. X represents a group consisting of a carbamoyl group, an amide group, a urea group, a diacylhydrazine group, an ether group, and an ester group, n represents an integer of 1 to 3, and when n is 2 or more, R ₆ and X are the same It can be different. )

  Although an example of said preferable structure is shown, these specific examples do not limit this invention at all.

  The compound having Zwitter ions used in the present invention is used in a proportion of 0.1 to 50% by weight with respect to the developer. When the amount is less than 0.1% by weight, a sufficient effect cannot be obtained, and when it exceeds 50% by weight, the color density is lowered, which is not preferable. More preferably, 0.1% by weight to 30% by weight is particularly preferably used. Moreover, the compound which has Zwitter ion may be used independently, and may be used in multiple combination.

  As a coating liquid preparation method for incorporating the material used in the present invention into the reversible thermosensitive recording layer, each material is dissolved in a solvent alone or dispersed in a dispersion, and then mixed. The method of dissolving in a solvent or dispersing in a dispersion medium, the method of heating and dissolving each material to homogenize and then cooling, and the method of dissolving in a solvent or dispersing in a dispersion medium, etc., are not particularly limited. . If necessary, a dispersing agent may be used during dispersion.

As the leuco dye used in the reversible thermosensitive recording layer, one or more of those generally used for this type of reversible thermosensitive recording medium can be used. For example, phthalide compounds, azaphthalide compounds, fluorane compounds It is a known dye precursor. Examples of these compounds are leuco dyes described in JP-A-5-124360, JP-A-6-210594, JP-A-10-230680 and the like.
Of these, particularly preferred examples include 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-ethyl-p-) Toluidino) fluoran, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- ( - ethyl-2-methylindole-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, and the like.

  Examples of the developer used in the recording layer include, as representative examples, developers described in JP-A-5-124360, JP-A-6-210554, JP-A-10-95175, and the like. is there. The developer used here is a structure having a color developing ability for developing a leuco dye in the molecule, such as a phenolic hydroxyl group, a carboxylic acid group, or a phosphate group, and a structure that controls the cohesion between molecules, such as a long It is a compound having one or more structures in which chain hydrocarbon groups are linked. The linking moiety may be via a divalent or higher valent linking group containing a hetero atom, and the same linking group and / or aromatic group may be contained in the long-chain hydrocarbon group. Specific examples of such a reversible developer are disclosed in, for example, JP-A-9-290563, JP-A-11-188969, and JP-A-11-99749, in addition to the above-mentioned publications. Among these developers, particularly preferred examples include N- (4-hydroxyphenyl) -N′-octadecylurea, N- [11- (p-hydroxyphenoxy) undecano-N′-n-decanohydrazide. N- [3- (p-hydroxyphenyl) propiono] -N′-n-docosanohydrazide and the like are used.

  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 and 500 (KOHmg / g) or less. When the hydroxyl value is 500 (KOHmg / g) or more, the decoloring property is lowered due to the influence of the remaining hydroxyl group, and the mechanical strength is lowered, and the repeated durability is impaired. 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.

  Furthermore, according to the present invention, the recording layer contains a different color-decoloration control agent having a linear hydrocarbon group, a hydrogen bond group such as an amide group or a urea group, and the like together with the developer and the leuco dye. 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. The amount of the different color-decoloring / controlling agent used is preferably 150 parts by weight or less, more preferably 100 parts by weight or less per 100 parts by weight of the color-decoloring / controlling agent (compound having Zwitter ions) in the present invention. Yes, more preferably 50 parts by weight or less.

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 thereof include propyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, etc. Among them, 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 from about several μm to about several mm is used.
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.

The reversible thermosensitive recording label of the present invention is one in which an adhesive layer or a pressure-sensitive adhesive layer is provided on the surface opposite to the surface of the support constituting the reversible thermosensitive recording medium described above.
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.
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, silicone resins and the like, but are not limited thereto.

The reversible thermosensitive recording medium of the present invention is an information display produced by combining at least a thermosensitive layer constituting the reversible thermosensitive recording medium as a reversible display unit and a member (information storage unit) having an information storage function. It can be used as a memory member.
Next, the information display storage member will be described.
The members having the information storage unit and the reversible display unit can be roughly classified into the following three items.
(1) A part of a member having an information storage function is used as a support for a reversible thermosensitive recording medium, and a thermosensitive layer is directly formed thereon.
(2) The support surface of a reversible thermosensitive recording medium having a thermosensitive layer formed on a support, which is separately formed, on a member having an information storage function.
(3) The reversible thermosensitive recording label bonded to a member having an information storage function via an adhesive layer or an adhesive layer.
In these cases (1), (2), and (3), it is necessary to set the functions of the information storage unit and the reversible display unit so that the functions of the information storage unit are set. The position can be arbitrarily selected according to the purpose, and it can be provided on the surface of the reversible thermosensitive recording medium opposite to the surface on which the thermosensitive layer is provided, between the support and the thermosensitive layer, or on the thermosensitive layer. It can also be provided in a part of

The member having the information storage function is not particularly limited, and a general card, disk, disk cartridge, or tape cassette can be used.
Examples of these include thick cards such as IC cards and optical cards, flexible disks, magneto-optical recording disks (MD), disk cartridges with built-in disks that can rewrite storage information, such as DVD-RAM, CD-RWs, etc. Examples thereof include a disc that does not use a disc cartridge, a write-once disc such as a CD-R, an optical information recording medium (CD-RW) that uses a phase-change storage material, and a video tape cassette.

  The information display storage member having both the reversible display function and the information storage function will be described in the case of a card, for example, by displaying a part of the information stored in the information storage unit on the reversible thermosensitive recording layer. The owner or the like can confirm information by looking at the card without a special device, and the convenience is greatly improved compared to a card to which the reversible thermosensitive recording medium is not applied.

The information storage unit is not particularly limited as long as it can store necessary information. For example, magnetic recording, contact IC, non-contact IC, or optical memory is useful.
The magnetic recording layer is formed by coating the support using a commonly used metal compound such as iron oxide or barium ferrite and a resin such as vinyl chloride, urethane or nylon, or without using a resin. It forms by methods, such as vapor deposition and sputtering, using the said metal compound. Further, the reversible thermosensitive recording layer in the reversible thermosensitive recording medium used for display can also be used as a storage unit in a manner such as a barcode or a two-dimensional code.
In addition, as an example of using the reversible thermosensitive recording label of (3) above, when the reversible thermosensitive recording layer is difficult to apply as a support, such as a vinyl chloride card with a magnetic stripe, An adhesive layer or a pressure-sensitive adhesive layer can be provided on the entire surface or a part thereof.
By doing so, the convenience of this medium can be improved, such as being able to display a part of the information stored in the magnetism.
The reversible thermosensitive recording label provided with the adhesive layer or the pressure-sensitive adhesive layer is applicable not only to the above-described magnetic PVC card but also to a thick card such as an IC card or an optical card.

Further, the reversible thermosensitive recording label can be used in place of a display label on a disk cartridge having a built-in disk capable of rewriting storage information such as a flexible disk, MD, DVD-RAM and the like.
Further, in the case of a disc that does not use a disc cartridge such as a CD-RW, a reversible thermosensitive recording label can be directly attached to the disc, or a reversible thermosensitive recording layer can be provided directly on the disc. By doing so, it is possible to apply to applications such as automatically changing display contents in accordance with changes in the stored contents.

The reversible thermosensitive recording label of the present invention can also be displayed by rewriting a part of the stored information added to the CD-R by sticking the reversible thermosensitive recording label on a write-once disc such as a CD-R.
Further, it may be used as a display label for a video tape cassette.
As a method of providing a thermoreversible recording function on a thick card, a disc cartridge, and a disc, in addition to the method of applying the reversible thermosensitive recording label, a method of directly applying a reversible thermosensitive recording layer on them, There is a method of forming a reversible thermosensitive recording layer on the support and transferring the thermosensitive recording layer onto a thick card, a disc cartridge, or a disc.
When transferring, an adhesive layer such as a hot melt type or an adhesive layer may be provided on the reversible thermosensitive recording layer.
When attaching a reversible thermosensitive recording label or providing a reversible thermosensitive recording layer on a rigid object such as a thick card, disk, disk cartridge, tape cassette, etc., improve the contact with the thermal head. In order to form an image uniformly, it is preferable to provide a cushioning layer or sheet between the rigid substrate and the label or the reversible thermosensitive recording layer.

  The present invention further provides an image processing method, wherein the reversible thermosensitive recording medium, the member having the information storage unit or the label is used to form and / or erase an image by heating.

For image formation, an image recording means such as a thermal head, a laser or the like that can partially heat the medium on the image is used. For erasing the image, an image erasing means such as a hot stamp, a ceramic heater, a heat roller, hot air, a thermal head, or a laser is used.
Among the erasing means, heating by a ceramic heater, thermal head, or laser is preferably used. When a ceramic heater is used, the apparatus can be reduced in size, energy can be saved, and stable. The erased state is obtained, and an image with good contrast is obtained.
The set temperature of the ceramic heater is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and even more preferably 115 ° C. or higher.
Further, by using a thermal head as the image erasing means, it is possible to further reduce the size of the entire apparatus, to reduce power consumption, and to realize a battery-driven handy type apparatus. If a single thermal head is used for both forming and erasing, the size can be further reduced.
When forming and erasing with a single thermal head, once the previous image has been erased, a new image may be formed again. The energy is changed for each image, and the previous image is erased at one time. It is also possible to use an overwrite method that forms the film.
In the overwrite method, the time required for forming and erasing is reduced, and the recording speed is increased.
In addition, when rewriting is performed by heating with a laser, rewriting can be performed in a non-contact manner with the recording medium, and in other methods, deterioration occurs due to friction during contact with the heating medium as well as heating during rewriting. As a result, the deterioration of the recording medium is less than when the surface of the recording medium is damaged, and the rewriting can be performed many times.
In the case of using a card having a reversible thermosensitive recording layer and an information storage unit, the above device includes means for reading and rewriting the memory of the information storage unit.

  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.

[Creation of thermal recording layer]
Developer: 4 parts Color development / decoloration control agent: 0.4 parts Acrylic polyol resin: 9 parts (LR503 manufactured by Mitsubishi Rayon Co., Ltd., solid content concentration 50% solution)
Methyl ethyl ketone: 70 parts The above composition was pulverized and dispersed to a mean 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.
A thermal recording layer coating solution having the above composition was applied to white PET having a thickness of 100 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 acrylic resin (GS-1015 manufactured by Toagosei Co., Ltd.) ): 0.5 part Methyl ethyl ketone: 10 parts The above composition was thoroughly 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. A reversible thermosensitive recording medium using the reversible thermosensitive coloring composition of the invention was prepared.

  The color development / decoloration control agents (compounds represented by symbols A-1 to A-7) used in the examples are shown in Table 4, and the developers (compounds represented by B-1 to B-5) are shown. The color development / decoloration control agents (compounds represented by C-1 to C-5) used in Comparative Examples and shown in Table 5 are shown in Table 6, and the developers (compounds represented by D-1 to D-5). Is shown in Table 7.

(Test 1) Color development characteristics The reversible thermosensitive recording media of Examples and Comparative Examples produced as described above were subjected to a voltage of 0.5 V in a range of 13 V to 21 V under a pulse width of 2 msec using a thermal printing simulator manufactured by B.COM. Printing was performed with. The print image density was measured using a Macbeth densitometer RD914, and the highest density was defined as the maximum color density. Table 8 shows combinations and color development characteristics of the reversible thermosensitive recording media of Examples and Comparative Examples.
Furthermore, a sensory test was performed by printing a character pattern on a reversible thermosensitive recording medium. The results are shown in Table 10.
<Criteria>
◎: Can be clearly read ○: Can be read △: Slightly unclear ×: Unclear

(Test 2) Decoloring characteristics After printing at a printing voltage giving the maximum voltage color density with a thermal printing apparatus manufactured by Becom as in Test 1, it was 1 Kgf / cm ² , 0.5 using a thermal inclination tester manufactured by Toyo Seiki Co., Ltd. After heating for 2 seconds, the residual density after erasure (image density after erasure−background density) was measured in the same manner as in Test 1. The printing voltage was selected under appropriate conditions according to the color development sensitivity of the recording medium. The results are shown in Table 8.
Further, a sensory test was performed after a character pattern was printed on a reversible thermosensitive recording medium and erased with a thermal tilt tester. The results are shown in Table 10.
<Criteria>
◎: Unerased residue is not visible ○: Unerased residue is almost invisible △: Unerased residue is somewhat visible ×: Unerased residue is visible

(Test 3) High-speed erasability test In the same manner as in Test 1, the reversible thermosensitive recording media of Examples and Comparative Examples were printed with a voltage that gives the maximum color density with a thermal printing device manufactured by BCOM, and then printed on the printed image. The image was erased again with an energy of 0.5V in the condition of 9V to 17V, the image density of the most decolored portion was measured in the same manner as in Test 1, and the thermal head erasure rate was calculated from the following formula to obtain high-speed erasure characteristics. . The results are shown in Table 8.
Thermal head erasure rate (%) = (1− (image density after erasure−background density) / (image density before erasure−background density)) × 100
Furthermore, a sensory test was conducted on the high-speed erasing characteristics when a character pattern was printed on a reversible thermosensitive recording medium and erased with a thermal head. The results are shown in Table 10.
<Criteria>
◎: Very good ○: Good △: Somewhat unclear ×: Unclear

(Test 4) Heat-resistant storage stability test A printed image obtained in the same manner as in Test 2 was stored under dry conditions at 60 ° C 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 to obtain heat resistant storage stability. The results are shown in Table 8.
Image retention (%) = (image density after storage−background density after storage) / (image density before storage−background density before storage) × 100
Further, a sensory test was performed on an image which was printed on a reversible thermosensitive recording medium with a character pattern and stored at 60 ° C. for 24 hours. The results are shown in Table 10.
<Criteria>
◎: Can be clearly read ○: Can be read △: Slightly unclear ×: Unclear

(Test 5) Coloring sensitivity characteristics Printing was performed at the voltage shown in Table 9 under the condition of a pulse width of 2 msec using a thermal printing simulator manufactured by BCOM. The color density was measured using a Macbeth densitometer RD914. The results are shown in Table 9.
Further, a sensory test was performed on the color development sensitivity when a character pattern was printed at a voltage of 16V. The results are shown in Table 10.
<Criteria>
◎: Can be clearly read ○: Can be read △: Slightly unclear ×: Unclear

(Test 6) Measurement of background density The background density of the non-printed part of the reversible thermosensitive recording medium was measured using a Macbeth densitometer RD914. The results are shown in Table 9.
Furthermore, a sensory test of the background concentration was performed. The results are shown in Table 10.
<Criteria>
◎: White ○: Almost white △: Slightly brown ×: Brown

  Furthermore, as a comprehensive evaluation of the sensory test, a sample satisfying all the requirements was rated as ◯, and a sample that did not satisfy any requirement was marked as ×.

As shown in Table 8, the reversible thermosensitive recording medium of the present invention has high color developability and erasability, and also has high erasability of 90% or more in terms of erasability by a thermal head, The heat resistant storage stability is also maintained at 80% or more. In addition, regarding the color development sensitivity in Table 9, it can be seen that printing can be performed with high sensitivity as compared with Comparative Examples 9 and 10 using different developers. In addition, it can be seen that the coloring of the background is also reduced and a high contrast is obtained.
As can be seen from the above results and the sensory test of Table 10, the reversible thermosensitive composition or reversible thermosensitive recording medium of the present invention has high color erasing properties, high-speed erasability, heat-resistant storage properties, and high sensitivity properties. In addition, the background is less colored and has high visibility.

It is a figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention. It is a figure which shows the example which stuck the reversible thermosensitive recording label on the disk cartridge of MD. It is a figure which shows the example which stuck the reversible thermosensitive recording label on CD-RW. It is a figure which shows the example used as a display label of a videotape cassette. It is a figure which shows the example of the image processing apparatus of this invention. It is a figure which shows the other example of the image processing apparatus of this invention.

Explanation of symbols

11 Conveying roller 12 Magnetic head 13 Ceramic heater 14 Thermal head 21 Conveying roller 22 Conveying roller 23 Thermal head

Claims (2)

A reversible thermosensitive coloring composition 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 method, a phenol compound represented by the following formula (1) is used as the electron-accepting compound, and at least a compound having a Zwitter ion represented by the following formula (2) is contained as a color-decoloration controlling agent. A reversible thermosensitive coloring composition.

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

(Wherein R ₁ , R ₂ , and R ₃ may be the same or different from each other, a saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms, or a group having the structure of the following formula (3) R ₁ , R ₂ and R ₃ may be bonded to each other to form a ring, and R ₄ represents a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms which may have a hydroxyl group. shown .A- is an anion, O-, COO-, SO ₃ - represents any.

R ₅ represents a saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms. R ₆ represents a divalent saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms. X represents a group consisting of a carbamoyl group, an amide group, a urea group, a diacylhydrazine group, an ether group, and an ester group, n represents an integer of 1 to 3, and when n is 2 or more, R ₆ and X are the same It can be different. ) Reversible thermosensitive recording medium, characterized in that a recording layer on a support having a reversible thermosensitive composition according to claim 1.

Images