JP2010125839A - Reversible thermal recording material and reversible thermal recording member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible thermal recording material 1 which can maintain a clear recorded image even when used for a long period of time under a severe environment. <P>SOLUTION: The reversible thermal recording material 1 can be produced by successively laminating a reversible thermal recording layer 3 and a gas barrier layer 4 on a support 2 and further providing a primer layer 8 for improving adhesion between the gas barrier layer 4 and a protective layer 5 therebetween. The reversible thermal recording layer 3 is composed of a reversible thermosensitive composition comprising a mixture composed of an electron donative colorable compound which changes a coloring state according to the difference of heating temperature and/or cooling speed after heating, and an electron acceptive compound. The gas barrier layer 4 comprises at least one kind of gas barrier resin chosen from a group composed of a poly(vinyl alcohol) polymer and an ethylene-vinyl alcohol copolymer, and an inorganic lamellar compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reversible thermosensitive recording material and a reversible thermosensitive recording member.

  Thermosensitive recording materials using a color development 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 output paper for facsimiles, word processors, scientific measuring instruments, etc., and as a commuter pass for transportation, magnetic cards such as various prepaid cards and point cards, IC cards and IC tags. Has been. In particular, recently, from the viewpoint of environmental problems, waste problems, etc., development of cards, tags, labels, and the like using reversible thermosensitive recording materials that can be rewritten any number of times has attracted attention.

  The principle of reversible coloring and decoloring of the reversible thermosensitive recording material will be briefly described. A general reversible thermosensitive recording material is obtained by mixing and dispersing the above color former and developer in a binder such as a thermoplastic resin on the surface of a film-like, sheet-like or plate-like support such as paper or plastic card. A heat-sensitive recording layer is formed from the above composition. In the composition containing the color former and the developer contained in the heat-sensitive recording layer, color development does not occur when the color former and the developer are simply mixed in a solid state. However, when the composition is heated to a high temperature, the entire composition is in a molten state, and the color former and the developer contained in the composition react to develop color. When the molten composition is decooled, the color former and the developer are dissociated around the melting temperature, and are individually aggregated or crystallized and decolored. And the state will be made into a frozen state by solidification of the thermoplastic resin etc. which are binders. However, when the colored composition that has developed color is rapidly cooled, before the dissociation between the color former and the developer occurs, the thermoplastic resin solidifies, and the reaction product of the color developer and the developer develops color. Some of them remain frozen and solidify. If you choose a composition that has a suitable melting temperature and freezing temperature and that consists of a combination of two compounds that cause such a phenomenon and a binder, you can choose between coloring and decoloring by adjusting the cooling rate after heating and melting. In, each state of coloring and decoloring can be kept frozen.

  FIG. 6 is a graph showing the temporal change in color development and decoloration with respect to the temperature change of the above-mentioned thermosensitive recording material. In FIG. 6, the horizontal axis represents time, and the vertical axis represents temperature. T1 represents the melting color reaction temperature of the color former and the developer, and T2 represents the temperature at which the composition of the color developer and the developer and the binder is solidified in a frozen state. That is, in the temperature range between T1 and T2, the reaction product of the color former and the developer in the colored composition dissociates into the color former and the developer, and aggregates or crystallizes, respectively. be able to. However, a certain amount of reaction time is required for the reaction product to dissociate and aggregate or crystallize.

In the graph of FIG. 6, the composition that was initially in the state (a) (development state) at room temperature is heated to a temperature T1. The composition is melted during a time it becomes the temperature T1 t _1, keeping it colored state (b). After the temperature T2 over t ₂ hours slowly cooled it returns to room temperature. Time t ₂ is, since the reaction product which has been colored by melting is at least time to aggregation or crystallization dissociate the color former and the developer, before the composition is frozen and solidified The reaction product is dissociated and frozen in the decolored state (c) at room temperature.

When the decolored composition is heated again to a molten state (d), the color former and developer in the composition melt and react to develop color. The composition was rapidly cooled in a short time t _4, it remains as it is if the normal temperature, the composition was color becomes normal temperature in a state in which the reaction molecular state is frozen (e).

Furthermore, dissociation of the compositions of the state (e) and melting temperature T1 and T2, the crystallization temperature region, the previously exposed long time t _5, the reaction product is dissociated into the color former and the developer In some cases, they may be agglomerated or crystallized to be decolored. Also in this case, the composition remains in a decolored state (g) when returned to room temperature. By utilizing such a phase change of the composition, the composition can be colored or decolored by controlling heating, cooling temperature, cooling rate, and the like. In the graph, the interval between T1 and T2 is schematically shown, but a composition having a temperature interval of about several degrees C. to 10 ° C. is actually selected.

  In Patent Document 1, an organic phosphoric acid compound having a long-chain aliphatic hydrocarbon group, an aliphatic carboxylic acid compound, or a phenol compound is used as a color developer, and these are combined with a leuco dye that is a color former and reversible thermosensitive. A coloring composition and a reversible thermosensitive recording material using the same for a recording layer have been proposed. This reversible thermosensitive recording material can easily perform color development and decoloration by adjusting the heating conditions, and can stably maintain the color development and decoloration at room temperature. It is possible to repeat.

  In principle, the reversible thermosensitive recording material only needs to have a thermosensitive recording layer capable of repeating the above-described coloring and decoloring. However, in the reversible thermosensitive recording material disclosed in Patent Document 1, the leuco dye used in the reversible thermosensitive recording layer has a colored portion fading or a non-colored portion (erased portion) by light exposure. ) May change color and whiteness may be impaired. In particular, many leuco dyes used as color formers are liable to cause a radical reaction with oxygen when activated by light. The fading or discoloration of reversible thermosensitive recording materials is thought to involve a small amount of oxygen, and when a leuco dye and oxygen undergo a radical reaction, the colored thermosensitive recording layer may fade or fade. In addition, the heat-sensitive recording layer that has been decolored may develop a color such as yellowing.

  As a method for improving the discoloration of the color-developing part and the discoloration of the non-color-developed part as described above, in Patent Document 2 and Patent Document 3, a heat-sensitive recording layer made of a leuco dye that is relatively resistant to light exposure is used. There has been proposed a reversible thermosensitive recording material coated with a gas barrier layer made of molecular resin. Further, Patent Document 4, Patent Document 5 and Patent Document 6 propose that an antioxidant such as α-tocopherol and vitamins is added to a gas barrier layer made of a polymer resin. By these improved methods, there was an improvement effect in preventing fading of the color image and ensuring the whiteness of the background. However, when used as a reversible thermosensitive recording material for a long period of time and repeated heating and cooling for recording erasing, damage is accumulated in the gas barrier polymer film, and the gas barrier layer that has been coated peels off, resulting in a gas barrier. The problem that the function might be lost appeared.

As a method for improving the peeling of the gas barrier layer, in Patent Document 7, Patent Document 8 and Patent Document 9, an adhesive layer made of a water-soluble resin or the like is installed between the thermal recording layer and the gas barrier layer, or a specific method is used. It has been proposed to improve the properties of the adhesive surface by adding an adhesive to the gas barrier layer, and a relatively good improvement effect has been observed.
Japanese Patent No. 2981558 Japanese Patent No. 3501430 Japanese Patent No. 3504035 Japanese Patent No. 3549131 Japanese Patent No. 3596706 JP-A-6-1066 Japanese Patent Laid-Open No. 9-175024 JP 2006-82252 A JP 2006-88445 A

  As described above, the reversible thermosensitive recording material is generally provided with a gas barrier layer for blocking oxygen. As the gas barrier layer, a synthetic polymer resin having a general gas barrier function is formed. Among them, polyvinyl alcohol (PVA) resin is flexible and non-charged, and is a gas barrier in a dry state. It has the characteristic that the property is excellent. However, PVA resin has a high affinity with moisture, and when it is used as a gas barrier film, the gas barrier function is highly dependent on humidity. Under high humidity conditions, the gas barrier property is remarkably deteriorated or the gas barrier film is peeled off. May end up. When the gas barrier film is peeled off, not only the gas barrier property is remarkably deteriorated, but also the peeled portion becomes a reflecting surface and appears to be whitened, and the recorded image may be concealed.

  In order to solve the hygroscopicity of such PVA resin, it is known that the hydroxyl group of PVA is water-resistant by chemical modification such as acetalization, but even if the water resistance of PVA is realized, the gas barrier expression mechanism of PVA As a result, the hydrogen bonding force of the hydroxyl group is lowered, and the original gas barrier property is impaired. In addition, the ethylene-vinyl alcohol (EVOH) copolymer, which is a material having a gas barrier function, has better water resistance than PVA, but its hydrogen bond strength is inferior to that of PVA. The gas barrier property is not sufficiently secured.

  In this way, even under long-term use under high humidity conditions and in an environment exposed to fluorescent light or sunlight, the recorded image is faded, the background is yellowed, the gas barrier layer is peeled off, the gas barrier layer A reversible thermosensitive recording material that can record and erase clear recorded images for a long time without causing delamination of layers has not been found so far.

  In view of the above-described problems, an object of the present invention is to provide a reversible thermosensitive recording material and a reversible thermosensitive recording member that can maintain a clear recorded image even when used for a long time in a severe environment.

  In the reversible thermosensitive recording material of the present invention, as shown in the schematic cross-sectional view of FIG. 1, at least a reversible thermosensitive recording layer, a gas barrier layer, a primer layer, and a protective layer are sequentially laminated on a support. Has a structure. The primer layer is a layer for improving the adhesion and adhesion between the gas barrier layer and the protective layer, and may contain a thermosetting resin (1), particularly a thermosetting resin obtained by crosslinking a polyvinyl butyral resin with an isocyanate. preferable.

  The reversible thermosensitive recording material of the present invention is a schematic cross-sectional view of FIG. 2 in addition to a reversible thermosensitive recording layer (sometimes abbreviated as a thermosensitive recording layer or recording layer), a gas barrier layer, a primer layer and a protective layer. As shown, an intermediate layer or an anchor layer can be provided between the heat-sensitive recording layer and the gas barrier layer. The intermediate layer is an ultraviolet absorbing layer, the anchor layer has an effect of improving the adhesion between the intermediate layer and the gas barrier layer, and the ultraviolet absorbing layer prevents ultraviolet light from entering the thermal recording layer, Deterioration due to ultraviolet rays can be prevented.

  In addition, an undercoat layer can be provided that improves the adhesion and heat insulation between the heat-sensitive recording layer and the support. Since the undercoat layer has an effect of improving the adhesion and adhesion between adjacent layers, it is preferable to select a material having excellent affinity and adhesion with the adjacent layers. The reversible thermosensitive recording material of the present invention shown in the schematic cross-sectional view of FIG. 3 has an undercoat layer, a reversible thermosensitive recording layer, an anchor layer, a gas barrier layer, a primer layer, and a protective layer sequentially laminated on the surface of the support. Has been. The reversible thermosensitive recording material of the present invention shown in the schematic cross-sectional view of FIG. 4 is formed on the surface of the support in the order of an undercoat layer, a reversible thermosensitive recording layer, an ultraviolet absorbing layer, an anchor layer, a gas barrier layer, and a primer. A layer and a protective layer are laminated.

  The support in the reversible thermosensitive recording material of the present invention may be any support as long as it can support the thermosensitive recording layer, but usually a resin sheet or film such as PET is used. The support preferably has a thickness capable of protecting the reversible thermosensitive recording layer from oxygen and moisture. For example, in the case of a PET film, the thickness may be 10 μm or more, preferably 30 μm or more, particularly preferably 50 μm or more.

  The heat-sensitive recording layer is composed of a composition containing a mixture of an electron-donating color-forming compound and an electron-accepting compound whose color development state changes depending on the heating temperature and / or the cooling rate after heating. The electron-donating color-forming compound is usually a leuco dye that is a color former, and the electron-accepting compound is a developer that causes the leuco dye to develop a color. The heat-sensitive recording material of the present invention is reversible in color development and decoloration, and can develop and decolor depending on temperature. Usually, the composition contains a resin as a binder, and changes in color development and decoloration of the color former due to melting and solidification of the resin or freezing.

  The reversible thermosensitive recording material of the present invention includes a gas barrier layer that prevents oxygen in the outside air from entering the thermosensitive recording layer. The color formers and developers used in the heat-sensitive recording layer are easily affected by light, and if a radical reaction with oxygen occurs in a state activated by light, the colored heat-sensitive recording layer may be decolored. The thermosensitive recording layer that has faded or has been decolored may develop a color such as yellowing.

  The gas barrier layer contains at least one gas barrier resin selected from the group consisting of a polyvinyl alcohol polymer and an ethylene-vinyl alcohol copolymer, and an inorganic layered compound. The gas barrier resin may be a polyvinyl alcohol polymer having gas barrier properties, but may be an ethylene-vinyl alcohol copolymer having not only gas barrier properties but also moisture resistance, or a composition of a gas barrier resin containing these.

  The gas barrier layer contains an inorganic layered compound. Since the inorganic layered compound has a higher gas barrier property than the gas barrier resin and is oriented in the layer direction of the gas barrier layer in the gas barrier resin, the gas barrier property of the gas barrier layer can be improved. As the inorganic layered compound, any compound having moisture resistance may be used, and examples thereof include a smectite group such as montmorillonite, a kaolinite group, an antigolite group, a vermiculite group, and a mica group.

  The gas barrier layer in the present invention may further contain an oxazoline compound. The oxazoline compound has good compatibility with the polyvinyl alcohol polymer and the ethylene-vinyl alcohol copolymer, and is excellent in affinity and adhesiveness with the inorganic layered compound. For this reason, the adhesion between the gas barrier resin containing the polyvinyl alcohol polymer and the ethylene-vinyl alcohol copolymer and the inorganic layered compound is improved, the temperature rise and fall for color development and decoloration are repeated, and the temperature and humidity are high. Peeling of the gas barrier layer in the environment can be prevented. In a reversible thermosensitive recording material using a composition of a gas barrier resin and an inorganic layered compound that does not contain an oxazoline compound, the gas barrier layer and the boundary between the gas barrier layer and the boundary of the gas barrier layer can be used by repeatedly increasing and decreasing the temperature or using it in a high temperature and high humidity environment. Therefore, peeling at the interface of the inorganic layered compound may occur. The content of the oxazoline-based compound in the gas barrier layer is preferably 2 to 65% by mass.

  In general, since the support is a relatively thick film or sheet, it has a sufficient oxygen blocking function and moisture blocking function. When the support is not equipped with an oxygen blocking function or a moisture blocking function, the support side may be covered with a gas barrier layer, but the gas barrier layer is usually laminated on the opposite side of the support with the thermosensitive recording layer in between. It only has to be.

  The primer layer in the present invention can improve the adhesion between the gas barrier layer and the protective layer. In order to exhibit gas barrier properties, the gas barrier layer contains a polyvinyl alcohol polymer or ethylene-vinyl alcohol copolymer having a relatively high affinity with moisture, and further contains an inorganic layered compound. On the other hand, the protective layer needs to have strength, wear resistance, heat distortion resistance, and the like. For this reason, there is a limit to the material constituting each layer, and the adhesion between the layers may not be sufficient. The primer layer is composed of a material having good adhesion to both the gas barrier layer and the protective layer, and a thermosetting resin (1), in particular, a thermosetting resin obtained by crosslinking a polyvinyl butyral resin with an isocyanate is a suitable material. . Since this thermosetting resin (1) strongly bonds between the gas barrier layer and the protective layer, one of the precursors (for example, polyvinyl butyral resin and isocyanate) before the thermosetting reaction is used. It is preferable to apply to a layer, for example, a gas barrier layer, and then heat cure. The primer layer is preferably 0.1 to 3 μm thick.

  The anchor layer in the present invention preferably contains a thermosetting resin (2) like a reaction product of an ester polyol resin and an isocyanate. Since this thermosetting resin (2) firmly adheres between the heat-sensitive recording layer and the gas barrier layer, one of the thermosetting resins (2 in the state of a precursor (e.g., ester polyol resin and isocyanate) before thermosetting). It is preferably applied to a layer (for example, a heat-sensitive recording layer) and thermally cured.

  In the case of an anchor layer containing a reaction product of an ester polyol resin and an isocyanate, the mass ratio of the isocyanate and the ester polyol resin is preferably 10: 100 to 150: 100. Moreover, it is preferable that an anchor layer shall be 0.1-10 micrometers in thickness. When the layer thickness is thinner than 0.1 μm, the adhesive force is not sufficient. Also, if the layer thickness is thicker than 10 μm, the adhesion effect does not increase, but there is an effect of increasing the thickness of the reversible thermosensitive recording material, the thermal conductivity of the reversible thermosensitive recording material is deteriorated, and the flexibility is reduced. Or lose.

  A magnetic recording layer or an IC chip can be provided around the support of the reversible thermosensitive recording material of the present invention, on the back surface, inside, or the like. If an IC chip is provided together with the reversible thermosensitive recording material of the present invention, it can also be used as an IC card or IC tag. Further, if a magnetic recording layer is provided together with the reversible thermosensitive recording material of the present invention, it can be used as a magnetic card. In addition, a reversible thermosensitive recording material can be produced on both sides of one support, or an adhesive layer or the like can be provided on the opposite side of the support.

  The reversible thermosensitive recording member of the present invention has an information storage unit and a reversible display unit, the reversible display unit includes the reversible thermosensitive recording material of the present invention, and other members as necessary. It has.

  By providing (integrating) the reversible display unit capable of reversible display and the information storage unit on the same card, and displaying a part of the stored information of the information storage unit on the reversible display unit, the card holder or the like Even if there is no special device, you can check information just by looking at the card, which is very convenient. Further, when the contents of the information storage unit are rewritten, the reversible thermosensitive recording member can be used repeatedly many times by rewriting the display of the reversible display unit.

The members having the information storage unit and the reversible display unit can be roughly classified into the following two members.
(1) A member having an information recording portion is used as a support for a reversible thermosensitive recording material, and a thermosensitive recording layer is directly formed.
(2) A member having an information recording portion and a support surface of a reversible thermosensitive recording member which is separately formed and has a thermosensitive recording layer on the support.
In these cases (1) and (2), 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 and the reversible display unit can be exhibited. The thermal recording member can be provided on the surface of the support opposite to the surface on which the thermal recording layer is provided, or between the support and the thermal recording layer, or on a part of the thermal recording layer.

  The information storage unit is not particularly limited in type or number, and for example, a magnetic thermosensitive recording layer, a magnetic stripe, an IC memory, an optical memory, an RF-ID tag, a hologram, or the like is preferably used. In particular, in a sheet medium having a size larger than the card size, an IC memory and an RF-ID tag are preferably used. The RF-ID tag includes an IC chip and an antenna connected to the IC chip.

  ADVANTAGE OF THE INVENTION According to this invention, the reversible thermosensitive recording material and reversible thermosensitive recording member which can maintain a clear recorded image even if used for a long period of time in a severe environment can be provided.

The reversible thermosensitive recording material of the present invention will be specifically described by the following embodiments. Note that the present invention is not limited to these embodiments.
[Embodiment 1]
The structure of the reversible thermosensitive recording material (1) of Embodiment 1 of the present invention is shown in FIG. FIG. 1 is a partial cross-sectional view schematically showing a reversible thermosensitive recording material (1) of the present invention. In this reversible thermosensitive recording material (1), a thermosensitive recording layer 3, a gas barrier layer 4, a primer layer 8, and a protective layer 5 are laminated on the surface of a sheet-like support 2 in this order.

  The heat-sensitive recording layer 3 has a lower surface laminated on a support 2 having a sufficient gas barrier property, and the upper surface is covered with a gas barrier layer 4 so that both surfaces are not in direct contact with outside air. In principle, the reversible thermosensitive recording material only needs to have a layer made of a thermosensitive recording material that can repeat color development and decoloration. However, the color former and the developer used in the heat-sensitive recording layer 3 are easily affected by light, and particularly easily cause a radical reaction with oxygen when activated by light. When a radical reaction occurs, the heat-sensitive recording layer 3 that has been colored may be decolored or faded, and the heat-sensitive recording layer 3 that has been decolored may develop a color such as yellowing. The gas barrier layer 4 is for preventing oxygen in the outside air from entering the thermosensitive recording layer 3. The primer layer 8 improves the adhesion between the gas barrier layer 4 and a protective layer 5 described later, and has an effect of preventing the interlayer between the gas barrier layer 4 and the protective layer 5. When the protective layer 5 is recorded on the reversible thermosensitive recording material (1), the surface of the gas barrier layer 4 and the thermosensitive recording layer 3 is deformed due to the heat and pressure of the thermal head when printing is performed using the thermal head. Prevents so-called dents. The protective layer 5 preferably has a function of protecting the surface of the reversible thermosensitive recording material from mechanical stress, moisture, and the like. Hereinafter, the support 2, the thermal recording layer 3, the gas barrier layer 4, the primer layer 8, and the protective layer 5 will be described in detail.

[Support]
In the reversible thermosensitive recording material of the present invention, a thermosensitive recording layer containing a composition having a reversible thermosensitive recording function as a main component is provided on a support. Examples of the support include paper, resin film, PET film, synthetic paper, metal foil, glass, or a composite of these, and any support that can hold the recording layer may be used. Those having a thickness as required can be used alone or bonded together. These supports may have a magnetic recording layer or an IC chip on the same surface, the opposite surface, or the inside of the reversible thermosensitive recording layer. As the thickness of the support, a support having an arbitrary thickness from about several μm to about several mm is used. When the heat-sensitive recording layer is self-supporting, the use of a support can be omitted. In addition, it is preferable that a normal support has an oxygen barrier property and a moisture barrier property, but if the oxygen barrier property and the moisture barrier property of the support are insufficient, the support may be covered with a gas barrier layer. .

[Reversible thermosensitive recording layer]
The reversible heat-sensitive recording layer of the reversible heat-sensitive recording material of the present invention (sometimes abbreviated as a heat-sensitive recording layer) is basically a composition in which a color former and a developer are dispersed in a binder resin. It is a thin film layer. If necessary, an additive for improving or controlling the coating characteristics and coloring / decoloring characteristics of the thermosensitive recording layer can be used in the composition. These additives include, for example, control agents, surfactants, conductive agents, fillers, antioxidants, light stabilizers, color stabilizers and the like.

(Coloring agent)
The color former used in the present invention is an electron-donating color-forming compound, and examples thereof include colorless or light-colored dye precursors (leuco dyes), such as fluorane compounds, triphenylmethane phthalide compounds, azaphthalide compounds. , Phenothiazine-based compounds, leucooramine-based compounds, indolinophthalide-based compounds, and the like can be used without particular limitation.

  Specific examples of such color formers include, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di (n-butylamino) as fluorane compounds and azaphthalide compounds. ) 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- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3- Methyl-6-diethylaminofluorane, 2- (m-trichloromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) Luolan, 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- Rifluoromethylanilino) 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-methyl) Dole-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, and the like.

  As the color former used in the present invention, a conventionally known leuco dye can be used in addition to the fluoran compound and the azaphthalide compound. Specific examples of leuco dyes include 2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p- Toluidino) fluorane, 2-benzylamino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-2,4-dimethylanilino) fluorane, 2- Benzylamino-6- (N-methyl-p-toluidino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (di-p-methylbenzylamino) -6- (N -Ethyl-p-toluidino) fluorane, 2- (α-phenylethylamino) -6- (N-ethyl-p-toluidino) fluorane, 2-methylamino-6- (N-methylani C) fluorane, 2-methylamino-6- (N-ethylanilino) fluorane, 2-methylamino-6- (N-propylanilino) fluorane, 2-ethylamino-6- (N-methyl-p-toluidino) Fluorane, 2-methylamino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-ethylamino-6- (N-ethyl-2,4-dimethylanilino) fluorane, 2-dimethylamino -6- (N-methylanilino) fluorane, 2-dimethylamino-6- (N-ethylanilino) fluorane, 2-diethylamino-6- (N-methyl-p-toluidino) fluorane, 2-diethylamino-6- (N- Ethyl-p-toluidino) fluorane, 2-dipropylamino-6- (N-methylanilino) fluorane, 2-dipropyla Mino-6- (N-ethylanilino) fluorane, 2-amino-6- (N-methylanilino) fluorane, 2-amino-6- (N-ethylanilino) fluorane, 2-amino-6- (N-propylanilino) Fluorane, 2-amino-6- (N-methyl-p-toluidino) fluorane, 2-amino-6- (N-ethyl-p-toluidino) fluorane, 2-amino-6- (N-propyl-p-toluidino) ) Fluorane, 2-amino-6- (N-methyl-p-ethylanilino) fluorane, 2-amino-6- (N-ethyl-p-ethylanilino) fluorane, 2-amino-6- (N-propyl-p-) Ethylanilino) fluorane, 2-amino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-ethyl-2,4- Methylanilino) fluorane, 2-amino-6- (N-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p-chloroanilino) fluorane, 2-amino-6- (N -Ethyl-p-chloroanilino) fluorane, 2-amino-6- (N-propyl-p-chloroanilino) fluorane, 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluorane, 1,2- Benzo-6-dibutylaminofluorane, 1,2-benzo-6- (N-methyl-N-cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-N-toluidino) fluorane, etc. It is done. These leuco dyes can be used alone or in combination.

  Usually, the average particle size of the leuco dye is preferably 0.05 μm or more and 0.7 μm or less, more preferably 0.1 μm or more and 0.5 μm or less, and further preferably 0.1 μm or more and 0.3 μm or less. When the average particle diameter of the leuco dye is in the above range, the color development characteristics of the thermosensitive recording layer can be improved. The leuco dye can be dispersed while adjusting the average particle diameter in the range of 0.05 μm or more and 0.7 μm or less by adding a dispersant and / or a surfactant as necessary. The dispersant and / or surfactant may be contained in an amount of 5% or more and 20% or less with respect to the leuco dye. As the dispersing device, a ball mill, an attritor, a sand mill, a high-pressure jet mill, or the like can be used. A method using a medium such as a ball is preferable for fine particle formation and dispersion. A zirconia medium having a diameter of 0.5 mm or less is used from the beginning, or a zirconia medium having a diameter of 0.5 mm to 1.0 mm is used. Finely pulverizing and then dispersing using zirconia media having a diameter of 0.5 mm or less can produce fine particles. The average particle size of the compound particles constituting the leuco dye and the developer described later in the present invention is determined by laser analysis / scattering method (for example, Microtrack HRA9320-X100 type, Horiba LA920 type, Lazentec FBRM device, etc. ) Is the average particle size measured.

(Developer)
The developer used in the heat-sensitive recording layer of the reversible heat-sensitive recording material of the present invention is an electron-accepting compound, and any compound can be used as long as it has a function of developing the color former. Conventionally known developers include organic phosphoric acid compounds, aliphatic carboxylic acid compounds, phenolic compounds, metal salts of mercaptoacetic acid, and phosphoric acid esters. These may be selected in combination with the color former described above in consideration of the melting point, the color development performance, and the like.

  As the developer used in the reversible thermosensitive recording layer in the present invention, a compound represented by the following general formula (1) is preferably used from the viewpoint of color density and erasing characteristics.

（式中、ｌは０〜２の自然数、ｍは０または１、ｎは１〜３の整数を示し、Ｘ，ＹはＮ原子またはＯ原子を含む２価の基を表わす。また、Ｒ_１は置換基を有していてもよい炭素数２以上の脂肪族炭化水素基を表わし、Ｒ_２は炭素数１以上の脂肪族炭化水素基を表わす。）
前記一般式（１）において、脂肪族炭化水素基は直鎖でも分枝していてもよく、不飽和結合を有していてもよい。炭化水素基につく置換基としては、水酸基、ハロゲン原子、アルコキシ基等がある。Ｒ_１、Ｒ_２の炭素の和が７以下では発色の安定性や消色性が低下するため、炭素数は８以上が好ましく、１１以上であることが更に好ましい。上記脂肪族炭化水素基Ｒ_１の好ましい例としては以下に示すものが挙げられる。

(In the formula, l represents a natural number of 0 to 2, m represents 0 or 1, n represents an integer of 1 to 3, X and Y represent a divalent group containing an N atom or an O atom, and R _1. Represents an optionally substituted aliphatic hydrocarbon group having 2 or more carbon atoms, and R ₂ represents an aliphatic hydrocarbon group having 1 or more carbon atoms.)
In the general formula (1), the aliphatic hydrocarbon group may be linear or branched and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen atom, and an alkoxy group. When the sum of the carbons of R ₁ and R ₂ is 7 or less, the stability of color development and the decoloring property are lowered. Therefore, the number of carbons is preferably 8 or more, and more preferably 11 or more. Preferred examples of the aliphatic hydrocarbon group R ₁ include the following.

なお、式中のｑ、ｑ'、ｑ"、ｑ'"は、それぞれ前記Ｒ_１、Ｒ_２の炭素数を満足する整数を表わす。Ｒ_１は、これらの中でも−（ＣＨ_２）ｑ−であることが特に好ましい。

In the formula, q, q ′, q ″, and q ′ ″ represent integers that satisfy the carbon numbers of R ₁ and R ₂ , respectively. Among these, R ₁ is particularly preferably — (CH ₂ ) q—.

Preferred examples of the aliphatic hydrocarbon group R ₂ include the following.

なお、式中のｑ、ｑ'、ｑ"、ｑ'"は前記と同じである。Ｒ_２は、これらの中でも−（ＣＨ_２）ｑ−ＣＨ_３であることが特に好ましい。

In the formula, q, q ′, q ″, and q ′ ″ are the same as described above. Among these, R _{2 is} particularly preferably — (CH ₂ ) q—CH ₃ .

  X and Y represent a divalent group containing an N atom or an O atom, preferably

で表わされる基を少なくとも１個以上有する２価の基を表わす。その例としては、以下示すものが挙げられる。

Represents a divalent group having at least one group represented by the formula: The following are mentioned as the example.

これらのうち、特に好ましい基は次に示すものである。

Of these, particularly preferred groups are as follows.

  Specific examples of the compound represented by the general formula (1) include the following. However, the developer in the present invention is not limited to these.

式中、ｒは２以上の整数、ｓは１以上の整数を表わす。

In the formula, r represents an integer of 2 or more, and s represents an integer of 1 or more.

  The average particle diameter of the developer is 0.1 μm or more and 2.5 μm or less, preferably 0.5 μm or more and 2.0 μm or less. If the average particle diameter of the developer is in the range of 0.1 μm or more and 2.5 μm or less, the color development characteristics can be improved when used as the developer for the heat-sensitive recording material of the present invention. Further, when the average particle diameter is in the range of 0.5 μm or more and 2.0 μm or less, the above-mentioned color development characteristic improving effect is particularly remarkable.

  The appropriate ratio of the color former to the color developer varies depending on the combination of the compounds used, but the developer is generally in the range of 0.1 to 20 with respect to the color developer 1 in molar ratio, preferably 0. In the range of 2-10. 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. The color former and the developer can be used in a microcapsule. The ratio of the color developing component to the resin in the reversible thermosensitive recording layer is preferably 0.1 to 10 with respect to the color developing component 1, and if it is less than this, the heat intensity of the reversible thermosensitive recording layer is insufficient, and the ratio is higher. Is problematic because the color density is lowered.

  The developer can be dispersed while adjusting the average particle size in the range of 0.05 μm or more and 0.7 μm or less by adding a dispersant and / or a surfactant together with the leuco dye as necessary. The dispersant and / or surfactant may be contained in an amount of 5% or more and 20% or less with respect to the leuco dye. As the disperser, a ball mill, an attritor, a sand mill, a high-pressure jet mill, or the like can be used. A method using a medium such as a ball is preferable for fine particle formation and dispersion. A zirconia medium having a diameter of 0.5 mm or less is used from the beginning, or a zirconia medium having a diameter of 0.5 mm to 1.0 mm is used. Finely pulverizing and then dispersing using zirconia media having a diameter of 0.5 mm or less can produce fine particles.

(Binder resin)
The role of the binder resin used in the formation of the reversible thermosensitive recording layer in the present invention is to keep each material of the composition uniformly dispersed without being displaced by the application of heat for recording and erasing. Examples of the binder resin include polyvinyl chloride, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate, Examples include polymethacrylic acid esters, acrylic acid copolymers, maleic acid copolymers, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, and starches. As these binder resins, it is preferable to use resins having high heat resistance. In order to improve the heat resistance of the binder resin, for example, a binder resin crosslinked with heat, ultraviolet rays, electron beams, a crosslinking agent, or the like may be used.

  As the binder resin before crosslinking used in the present invention, specifically, an acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate, cellulose acetate butyrate and the like Resin having a reactive group, or a resin obtained by copolymerizing a monomer having a group that reacts with a crosslinking agent and another monomer, and the like. The binder resin in the present invention is a combination of these resins and a crosslinking agent. It is not limited to the obtained crosslinked resin.

  Acrylic polyol resins have different characteristics depending on the structure, and hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA) as hydroxyl monomers. ), 2-hydroxybutyl monoacrylate (2-HBA), 1,4-hydroxybutyl monoacrylate (1-HBA), etc. are used. 2-Hydroxyethyl methacrylate is preferably used because of its good resistance and durability.

  Examples of the crosslinking agent include conventionally known isocyanates, amines, phenols, and epoxy compounds. Among these, an isocyanate type crosslinking agent is 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. Examples of the isocyanate monomer forming the modified product include 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), etc. It is not limited to these compounds.

  Further, a catalyst may be used 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. The total amount of the crosslinking agent may or may not undergo a crosslinking reaction. That is, an unreacted crosslinking agent may be present. Since this type of cross-linking reaction proceeds over time, the presence of an unreacted cross-linking agent does not indicate that the cross-linking reaction has not proceeded at all, but an unreacted cross-linking 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 in the solute may be analyzed. Therefore, if the presence of the polymer in the solute cannot be confirmed, it can be said that the polymer is in a non-crosslinked state, and can be distinguished from the non-crosslinked polymer. Here, this can be expressed as a gel fraction.

  The gel fraction refers to the ratio of gel formation when a resin solute in a solvent loses its independent mobility due to interaction and assembles into an individualized state (gel). The resin preferably has a gel fraction of 30% or more, more preferably 50% or more, still more preferably 70% or more, and particularly preferably 80% or more. If the gel fraction is small, the durability will be reduced repeatedly. Therefore, in order to improve the gel fraction, a curable resin that is cured by heat, UV, EB or the like may be mixed in the resin, or the resin itself may be crosslinked. .

As a gel fraction measurement method, the membrane is peeled off from the support and the initial weight of the membrane is measured, and then the membrane is placed in a 400 mesh wire net and immersed in a solvent in which the resin before crosslinking is soluble for 24 hours. Then vacuum dry and measure the weight after drying.
The gel fraction calculation is performed according to the following formula.
Gel fraction (%) = [weight after drying (g) / initial weight (g)] × 100

  When the gel fraction is calculated by this calculation, the calculation is performed excluding the weight of organic low molecular weight substance particles other than the resin component in the heat sensitive layer. At this time, when the weight of the organic low molecular weight substance is not known in advance, the weight ratio is obtained from the area ratio per unit area and the specific gravity of the resin and the low molecular weight organic substance by cross-sectional observation such as TEM and SEM. The gel fraction value may be calculated by calculating the molecular weight weight.

  In the case of the above measurement, a reversible thermosensitive recording layer is provided on the support and another layer such as a protective layer is laminated thereon, or other layers are provided between the support and the thermosensitive layer. As described above, first, the thickness of the reversible thermosensitive recording layer and other layers is examined by cross-sectional observation such as TEM and SEM, and the surface of the other layers is shaved off. The reversible thermosensitive recording layer surface is exposed, and the reversible thermosensitive recording layer is peeled off, and the gel fraction measurement is performed in the same manner as in the measurement method.

  In this method, when there is an ultraviolet curable resin or the like in the upper layer of the reversible thermosensitive recording layer, in order to prevent the mixing of these layers as much as possible, the thickness of these layers is reduced and the surface of the reversible thermosensitive recording layer is slightly It is necessary to prevent the influence on the shaving gel fraction value.

(Control agent)
In the present invention, the control agent used for the reversible thermosensitive recording layer is preferably a compound containing an amide group, a urethane group, a urea group, a ketone group, a diacyl hydrazide group or the like as a partial structure from the viewpoint of color density and erasing properties. Among these, compounds having an amide group, a secondary amide group, and a urethane group are particularly preferable, and specific examples include the following.

（式中、ｎ，ｎ'，ｎ"，ｎ'"，ｎ""は０〜２１の整数を示す。ただし全てが５以下であることはない。）

(In the formula, n, n ′, n ″, n ′ ″, and n ″ ”represent integers of 0 to 21; however, all are not 5 or less.)

_{C 11 H 23 CONHC 12 H 25} , C 15 H 31 CONHC 16 H 33, C 17 H 35 CONHC 18 H 37, C 17 H 35 CONHC 18 H 35, C 21 H 41 CONHC 18 H 37, C 15 H 31 CONHC ₁₈ H ₃₇ , C ₁₇ H ₃₅ CONHCH ₂ HNOCC ₁₇ H ₃₅ , C ₁₁ H ₂₃ CONHCH ₂ HNOCC ₁₁ H ₂₃ , C ₇ H ₁₅ CONHC ₂ H ₄ HNOCC ₁₇ H ₃₅ , C ₉ H ₁₉ CONHC ₂ H ₄ HNOCC ₉ H ₁₉ , C ₁₁ H ₂₃ CONHC ₂ H ₄ HNOCC ₁₁ H ₂₃ , C ₁₇ H ₃₅ CONHC ₂ H ₄ HNOCC ₁₇ H ₃₅ , (CH ₃ ) ₂ CHC ₁₄ H ₃₅ CONHC ₂ H ₄ HNOCC ₁₄ H ₃₅ (CH ₃ ) ₂ , C _{1 H 43 CONHC 2 H 4 HNOCC} 21 H 43, C 17 H 35 CONHC 6 H 12 HNOCC 17 H 35, C 21 H 43 CONHC 6 H 12 HNOCC 21 H 43, C 17 H 33 CONHCH 2 HNOCC 17 H 33, C ₁₇ H ₃₃ CONHC ₂ H ₄ HNOCC ₁₇ H ₃₃ , C ₂₁ H ₄₁ CONHC ₂ H ₄ HNOCC ₂₁ H ₄₁ , C ₁₇ H ₃₃ CONHC ₆ H ₁₂ HNOCC ₁₇ H ₃₃ , C ₈ H ₁₇ NHCOC ₂ H ₄ CONHC ₁₈ H _{37 , C 10 H 21 NHCOC 2 H} 4 CONHC 10 H 21, C 12 H 25 NHCOC 2 H 4 CONHC 12 H 25, C 18 H 37 NHCOC 2 H 4 CONHC 18 H 37, C 21 H 43 NHOCC 2 H _{CONHC 21 H 43, C 18 H} 37 NHOCC 6 H 12 CONHC 18 H 37, C 18 H 35 NHCOC 4 H 8 CONHC 18 H 35, C 18 H 35 NHCOC 8 H 16 CONHC 18 H 35, C 12 H 25 OCONHC 18 H ₃₇ , C ₁₃ H ₂₇ OCONHC ₁₈ H ₃₇ , C ₁₆ H ₃₃ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ OCONHC ₁₈ H ₃₇ , C ₂₁ H ₄₃ OCONHC ₁₈ H ₃₇ , C ₁₂ H ₂₅ OCONHC ₁₆ H ₃₃ , C _{13 H 27 OCONHC 16 H 33, C} 16 H 33 OCONHC 16 H 33, C 18 H 37 OCONHC 16 H 33, C 21 H 43 OCONHC 16 H 33, C 12 H 25 OCONHC 14 H 29, C 13 _{27 OCONHC 14 H 29, C 16} H 33 OCONHC 14 H 29, C 18 H 37 OCONHC 14 H 29, C 22 H 45 OCONHC 14 H 29, C 12 H 25 OCONHC 12 H 37, C 13 H 27 OCONHC 12 H 37 C ₁₆ H ₃₃ OCONHC ₁₂ H ₃₇ , C ₁₈ H ₃₇ OCONHC ₁₂ H ₃₇ , C ₂₁ H ₄₃ OCONHC ₁₂ H ₃₇ , C ₂₂ H ₄₅ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC ₂ H ₄ OCONHC ₁₈ H ₃₇ , _{C 18 H 37 NHCOOC 3 H 6} OCONHC 18 H 37, C 18 H 37 NHCOOC 4 H 8 OCONHC 18 H 37, C 18 H 37 NHCOOC 6 H 12 OCONHC 18 H 37, C 18 H _{7 NHCOOC 8 H 16 OCONHC 18 H} 37, C 18 H 37 NHCOOC 2 H 4 OC 2 H 4 OCONHC 18 H 37, C 18 H 37 NHCOOC 3 H 6 OC 3 H 6 OCONHC 18 H 37, C 18 H 37 NHCOOC 12 H ₂₄ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC ₂ H ₄ OC ₂ H ₄ OC ₂ H ₄ OCONHC ₁₈ H ₃₇ , C ₁₆ H ₃₃ NHCOOC ₂ H ₄ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₃ H ₆ OCN ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₄ H ₈ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₆ H ₁₂ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₈ H ₁₆ OCONHC ₁₆ H _{33 , C 18 H 37 OCOHNC 6 H} 12 NHCOOC 18 H 37, C 16 H 33 OCOHNC 6 H 12 NHCOOC 16 H 33, C 14 H 29 OCOHNC 6 H 12 NHCOOC 14 H 29, C 12 H 25 OCOHNC 6 H 12 NHCOOC 12 H ₂₅ , C ₁₀ H ₂₁ OCOHNC ₆ H ₁₂ NHCOOC ₁₀ H ₂₁ , C ₈ H ₁₇ OCOHNC ₆ H ₁₂ NHCOOC ₈ H ₁₇

これらの制御剤は、単独でも複数でも使用することが出来る。

These control agents can be used alone or in combination.

  The proportion of the color erasure accelerator as the control agent is preferably 0.1% by weight to 300% by weight, more preferably 3% by weight to 100% by weight with respect to the developer. The control agent may be uniformly mixed with the color former and the developer when they are mixed.

(Reversible thermosensitive recording layer composition)
The heat-sensitive recording layer in the present invention is composed of a composition in which a color former and a developer are finely and uniformly dispersed in a binder resin. The color former and the developer may form particles individually, but more preferably form a dispersed state as composite particles. This can be achieved by melting or dissolving the color former and developer. Such a composition for a reversible thermosensitive recording layer is a support in which each material is dispersed or dissolved in a solvent and then mixed, or a mixed solution in which each material is mixed and dispersed or dissolved in a solvent. Can be applied on top. The color former and the developer can be used in a microcapsule.

  The thermosensitive recording layer composition is a coating liquid prepared by uniformly mixing and dispersing a mixture of a color former, a developer, various additives, a curing agent, a resin in a crosslinked state, a coating solvent, and the like. . Specific examples of the solvent used for preparing the coating liquid include water; alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl Glycol ether acetates such as acetate; Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and ethylene carbonate; Aromatic hydrocarbons such as benzene, toluene, and xylene; Hexane, heptane, iso-octane Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl Examples include pyrrolidones such as -2-pyrrolidone.

  The coating liquid can be prepared using a known coating liquid dispersing apparatus such as a paint shaker, a ball mill, an attritor, a three-roll mill, a keddy mill, a sand mill, a dyno mill, or a colloid mill. Moreover, each material may be disperse | distributed in a solvent using the said coating-liquid dispersion | distribution apparatus, and each may be disperse | distributed and mixed in a solvent individually. Further, it may be dissolved by heating and precipitated by rapid cooling or cooling.

(Formation of reversible thermosensitive recording layer)
In order to form the heat-sensitive recording layer on the support, a conventionally known method may be used. For example, the above-mentioned heat-sensitive recording layer composition may be applied on the support and dried. There are no particular restrictions on the coating method for the reversible thermosensitive recording layer composition, blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, and gravure coating. Conventionally known methods such as kiss coating, reverse roll coating, dip coating, and die coating can be used.

  After applying the coating solution for the thermosensitive recording layer composition, drying and, if necessary, curing treatment for complete crosslinking of the binder resin are performed. The drying and curing treatment may be heat-treated using a thermostatic bath or the like at a relatively high temperature for a short time or at a relatively low temperature for a long time. As specific conditions for the curing reaction, it is preferable to heat from about 1 minute to 150 hours under a temperature condition of about 30 ° C. to 130 ° C. in terms of reactivity. More preferably, heating is performed for about 2 minutes to 120 hours under a temperature condition of 40 ° C to 100 ° C. In general, since industrial production places importance on productivity, it is difficult to spend time until the crosslinking is sufficiently completed. Therefore, a crosslinking step may be provided separately from the drying step. As a condition for the crosslinking step, it is preferable to heat at a temperature of 40 ° C. to 100 ° C. for about 2 minutes to 120 hours.

  The thickness of the heat-sensitive recording layer in the present invention varies depending on the type of color former and developer, but is preferably in the range of 1 to 20 μm, more preferably 3 to 15 μm. If it is thinner than this, the contrast at the time of color development often becomes incomplete, and if it is thick, the thermal sensitivity of the thermal recording layer as a thermal recording material is lowered, which is not preferable.

[Gas barrier layer]
The gas barrier layer in the present invention contains a gas barrier resin, an inorganic layered compound, and preferably an oxazoline compound. The gas barrier layer has a function of covering the heat-sensitive recording layer, preventing oxygen from entering the heat-sensitive recording layer, and preventing the heat-sensitive recording layer from being faded or discolored by reaction with the color former or the developer. In particular, it is necessary to further improve the gas barrier properties of the gas barrier layer as the period of use of the reversible thermosensitive recording material becomes longer. By preventing oxygen from entering the heat-sensitive recording layer, the reversible heat-sensitive recording material (1) has excellent light resistance and does not fade or discolor for a long time.

  Although the thickness of a gas barrier layer changes with oxygen permeation characteristics of a gas barrier layer, the range of 0.1-20 micrometers is preferable and the range of 0.3-10 micrometers is more preferable. If the thickness of the gas barrier layer is less than 0.1 μm, the oxygen barrier property and the moisture barrier property are often incomplete, and if it is more than 20 μm, the sensitivity of the recording layer to a heating head as a heat-sensitive recording material decreases. It is not preferable.

(Gas barrier resin)
The gas barrier resin used in the present invention is preferably a resin having a high visible light transmittance. These gas barrier resins may be selected depending on the application, oxygen permeability, transparency, mixing characteristics with the inorganic layered compound, adhesion to the heat-sensitive recording layer, moisture resistance, ease of coating, and the like.

  Among the gas barrier resins, the polyvinyl alcohol polymer may be any of polyvinyl alcohol and derivatives or modified products thereof, and these may be used alone or in combination of two or more. As said polyvinyl alcohol-type polymer, Preferably a polymerization degree is 100-5000, More preferably, it is 500-3000, Moreover, a saponification degree becomes like this. Preferably it is 60 mol% or more, More preferably, it is 75 mol% or more. Examples of the polyvinyl alcohol derivative include polyvinyl alcohol derivatives in which up to about 40 mol% of the hydroxyl group is acetalized. Examples of the modified polyvinyl alcohol include carboxyl group-containing monomers and amino group-containing monomers. Examples thereof include modified polyvinyl alcohol obtained by copolymerizing monomers and the like.

  Polyvinyl alcohol polymers have the advantage of extremely high gas barrier properties in the dry state, but the degree of decrease in gas barrier properties under high humidity is higher than that of ethylene-vinyl alcohol copolymers. When used under humidity, it is preferable to increase the content of the inorganic layered compound described later when forming the gas barrier layer.

  As the ethylene-vinyl alcohol copolymer used as the gas barrier resin, those obtained by saponifying the ethylene-vinyl acetate copolymer can be suitably used. Specific examples of the gas barrier resin obtained by saponifying an ethylene-vinyl acetate copolymer include those obtained by saponifying an ethylene-vinyl acetate copolymer obtained by copolymerizing ethylene and vinyl acetate, and And ethylene and vinyl acetate, and those obtained by saponifying an ethylene-vinyl acetate copolymer obtained by copolymerizing other monomers. As a material for providing the gas barrier layer, the ethylene ratio in the monomer before copolymerization of the ethylene-vinyl acetate copolymer is preferably 20 to 60 mol%. When the ethylene ratio is less than 20 mol%, the gas barrier property under high humidity is lowered, whereas when the ethylene ratio exceeds 60 mol%, the gas barrier property tends to be lowered.

  The ethylene-vinyl acetate copolymer preferably has a vinyl acetate component having a saponification degree of 95 mol% or more, and if it is less than 95 mol%, gas barrier properties and oil resistance tend to be insufficient. It is more preferable that the ethylene-vinyl acetate copolymer is reduced in molecular weight by treatment with a peroxide or the like because the dissolution stability in a solvent is improved.

(Inorganic layered compound)
The inorganic layered compound is not particularly limited as long as it is an inorganic layered compound, but an inorganic layered compound that swells and cleaves in the dispersion medium is preferably used, and kaolinite group, antigolite group, smectite group, vermiculite group, Examples include minerals such as the mica group. For example, kaolinite group having a 1: 1 structure of phyllosilicate, antigolite group belonging to jamonite group, smectite group, hydrated silicate mineral vermiculite group, mica group, etc. can be used depending on the number of interlayer cations. . More specifically, kaolinite, nacrite, dickite, halloysite, hydrous halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, beidellite, saponite, hectorite, soconite, stevensite, tetrasilic mica, sodium teniolite , Muscovite, margarite, talc, vermiculite, phlogopite, xanthophyllite, chlorite and the like. These may be natural products or synthetic products of swellable viscosity minerals. Also, scaly silica can be used. These may be used alone or in combination of two or more. Among these, montmorillonite and mica are preferable from the viewpoint of gas barrier performance when used as a gas barrier layer.

  When the inorganic layered compound is a natural product, since the size after dispersion in the gas barrier resin is relatively large, it is easy to ensure the gas barrier function. On the other hand, the inorganic metal ions contained in a trace amount as an impurity are included in the recording material of the present invention. During image formation, application of heat energy may cause oxidative degradation of the gas barrier layer and the like, and may form colored components. This phenomenon, when the original formed image of the recording material of the present invention is erased, is visually recognized as unerased, and the image quality is significantly impaired. In order to eliminate this inconvenience, it is preferable to prevent oxidative deterioration due to impurity inorganic metal ions by adding an alkali metal or an alkaline earth metal when mixing the inorganic layered compound which is a natural product and the gas barrier resin.

  When the inorganic layered compound is a synthetic product of a swellable viscosity mineral, the above-mentioned impurities are hardly mixed, so there is no inconvenience in image quality, but the particle size is reduced during the synthesis process of the inorganic layered compound. As a result, the gas passage length becomes short, and there is a possibility that a desired gas barrier property cannot be expressed. In the present invention, both inorganic and synthetic inorganic layered compounds can be used, but a suitable gas barrier can be obtained by determining the mixing ratio of the gas barrier resin / inorganic layered compound while accurately grasping the characteristics of the substance used. It is a thing that acquires characteristics. Examples of the synthetic product include synthetic mica, natural mica, and mica subjected to physical or chemical treatment.

  In the gas barrier layer, the mass ratio of the gas barrier resin to the inorganic stratiform compound is such that the gas barrier resin / inorganic stratiform compound is in the range of 30/70 to 99/1, preferably in the range of 30/70 to 50/50. Is desirable. When the mass ratio of the inorganic layered compound is reduced, sufficient gas barrier properties are deteriorated. On the other hand, when the amount is too large, the coating strength and adhesion to other layers are insufficient and peeling or transparency is impaired. Therefore, it is not preferable as a heat-sensitive recording material. Partial delamination in the gas barrier layer tends to cause whitening of the reversible thermosensitive recording material.

  In the gas barrier layer, the inorganic stratiform compound is preferably dispersed in parallel along the layer direction of the gas barrier layer. FIG. 5 schematically shows a cross-sectional view of the gas barrier layer 4 in the reversible thermosensitive recording material of the present invention. When the inorganic layered compound 11 is dispersed in a solvent or gas barrier resin dispersion and formed as a thin gas barrier layer, the inorganic layered compound 11 has a property of being easily arranged flat in the layer direction in the gas barrier resin 10 as shown in FIG. As described above, when the inorganic layered compounds 11 are arranged in layers along the layer direction in the gas barrier layer 4, gas molecules such as oxygen and water vapor gas pass through the inorganic layered compound 11 when attempting to permeate from the top to the bottom of the gas barrier layer. It will avoid and penetrate. Then, the path through which the gas molecules permeate the gas barrier layer becomes very long compared to the vertical distance of the cross section of the gas barrier layer 4. Since the gas barrier resin 10 that forms the gas barrier layer 4 inherently has a gas barrier property, if the permeation path becomes longer, the gas barrier property of the gas barrier layer is improved in proportion thereto.

  As described above, by dispersing the inorganic layered compound 11 in the gas barrier layer, particularly in parallel along the layer direction, the moisture barrier property is improved in addition to the oxygen barrier property of the gas barrier layer. In particular, gas barrier resins with excellent oxygen barrier properties, such as polyvinyl alcohol, have moisture absorption properties, and oxygen barrier properties were not sufficient in high humidity environments, but inorganic layered compounds were added to these gas barrier resins. As a result, the gas barrier layer 11 can exhibit excellent oxygen barrier properties not only in a low humidity environment but also in a high humidity environment. Further, deterioration of the gas barrier resin due to moisture absorption can be prevented, and peeling between the gas barrier layer and the thermosensitive recording layer can also be prevented.

  The shape of the inorganic layered compound is a plate having a length and a width of 5 to 5000 nm, particularly 10 to 3000 nm, and a thickness of about 1/10 to 1 / 10,000, preferably about 1/50 to 1/5000. Are preferred. If the shape of the inorganic layered compound is too large, uneven mixing in the gas barrier layer is likely to occur, it is difficult to mix uniformly, and a thin film is difficult to form. If the inorganic layered compound is too small or the thickness ratio is too large, the inorganic layered compound becomes difficult to disperse in the gas barrier layer in parallel with the gas barrier layer, resulting in poor gas barrier properties.

(Oxazoline compounds)
The inorganic layered compound has a very good effect on oxygen and moisture barrier properties of the gas barrier layer. However, the gas barrier resin and the inorganic layered compound are different from each other, and the affinity and adhesiveness are not always excellent. Rather, combinations of gas barrier resins and inorganic layered compounds that are excellent in affinity and adhesion are limited. Even if the gas barrier resin and the inorganic layered compound are suitable for the respective required performance, it is not preferable if the affinity and adhesiveness of both are not excellent. The oxazoline-based compound has an effect of improving the affinity and adhesion between the gas barrier resin and the inorganic layered compound. If FIG. 5 is referred, the adhesiveness in the interface 12 of the gas barrier resin 10 and the inorganic layered compound 11 will improve. If peeling occurs at the interface 12 between the gas barrier resin 10 and the inorganic layered compound 11, it may be observed as whitening from the surface of the reversible thermosensitive recording material.

  The oxazoline-based compound may be any compound as long as it has an effect of improving the affinity and adhesion between the gas barrier resin and the inorganic layered compound. For example, 2-methyl-2-oxazoline, 2-ethyl -2-oxazoline, 2-isopropyl-2-oxazoline, 2-n-propyl-2-oxazoline, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-isopropenyl-2- Examples thereof include oxazoline and 2-isopropenyl-4-methyl-2-oxazoline, and commercially available products include Epocross (manufactured by Nippon Shokubai Co., Ltd.). What is necessary is just to select a suitable thing for these oxazoline type compounds by the combination of gas barrier resin and an inorganic layered compound.

  The content of the oxazoline-based compound in the gas barrier layer is 2 to 65% by mass, preferably 9 to 65% by mass, and particularly preferably 9 to 20% by mass. If the content of the oxazoline-based compound is 2% by mass or less, the peeling prevention effect in long-term use may not be sufficient. Further, when the content of the oxazoline compound is 65% by mass or more, the content of the gas barrier resin in the gas barrier layer is relatively lowered, the gas barrier property is lowered, and the lightness deterioration of the decolored portion of the reversible thermosensitive recording material. May happen.

(Adhesion improver)
Since the gas barrier layer contains an inorganic stratiform compound, an adhesion improver for improving the adhesion with an adjacent layer such as a heat-sensitive recording layer or a protective layer may be added. A silane coupling agent, a titanium coupling agent, an isocyanate compound, an aziridine as necessary so as to withstand repeated formation and erasure of recorded images, which is a basic characteristic of the recording material of the present invention, that is, repeated heating and cooling. One or more adhesion improvers for adjacent layers such as compounds can be added.

  Examples of the silane coupling agent used in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, vinyltriacetoxysilane, Alkoxysilanes having a vinyl group such as 3-propyltrimethoxysilane methacrylate, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Alkoxysilanes having an epoxy group such as silane, 3-aminopropyltriethoxysilane, 3-N- (2-aminoethyl) aminopropyltrimethoxysilane, 3-N- (2-aminoethyl) aminopropylmethyldimethoxysilane, etc. The amino A ureido group such as an alkoxysilane having a group and / or an imino group, an isocyanate alkoxysilane such as triethoxysilylpropyl isocyanate, an alkoxysilane having a mercapto group such as γ-mercaptopropyltrimethoxysilane, and a γ-ureidopropyltriethoxysilane. The alkoxysilane which has can be mentioned. Among these specific exemplary compounds, the trialkoxysilane compound having an amino group or a mercapto group rapidly reacts with an organic residue adjacent to the gas barrier layer, and the alkyl group of the trialkoxysilyl group is a methyl group. It is preferable because the chemical reaction with the inorganic layered compound in the gas barrier layer reacts quickly.

  Examples of the aziridine compound used in the present invention include trimethylolpropane tris (3-aziridinylpropionate), trimethylolpropane tris [3- (2-methyl-aziridinyl) -propionate], trimethylolpropane tris ( 2-aziridinyl butyrate), tris (1-aziridinyl) phosphine oxide, pentaerythritol tris-3- (1-aziridinylpropionate), pentaerythritol tetrakis-3- (1-aziridinylpropionate) ), 1,6-bis (1-aziridinocarbamoyl) hexamethylenediamine and the like.

  Examples of the isocyanate compound used in the present invention include the following. For example, hydrogenated TDI, hydrogenated XDI, hydrogenated MDI, aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), and derivatives thereof. In addition to trifunctional or higher functional polyisocyanates such as molds, isocyanurate types, and adduct types, various isocyanate-containing oligomers, aliphatic isocyanate compounds such as polymers, phenylene diisocyanate (PDI), toluene diisocyanate (TDI), naphthalene diisocyanate ( NDI), aromatic diisocyanates such as 4,4′-diisocyanate diphenylmethane (MDI), and derivatives thereof such as burette type, isocyanurate type, adduct type, etc. Other potential more polyisocyanates, various oligomers containing isocyanate, aromatic isocyanate compounds such as polymers. In order to form a gas barrier layer, the gas barrier coating composition basically contains water as a solvent because it is used together with a water-soluble polymer, so that the reaction with water is suppressed and cured after film formation. Preferably proceeds. Therefore, a self-emulsifying type polyisocyanate compound that is present in a water-dispersed state by introducing a hydrophilic group into the skeleton of the isocyanate compound is more preferable. Furthermore, it is more preferable to introduce a hydrophobic group because the reaction with water before film formation can be further suppressed.

  The carbodiimide compound used in the present invention is preferably a water-dispersed emulsion type as described above. The carbodiimide compound is hydrophilized by chain-extending by a urethanization reaction between an isocyanate-terminated carbodiimide compound and a polyol compound, and further a hydrophilic oligomer at the molecular end is modified with a hydrophilic oligomer, which has a balance between stability and crosslinkability. It is good and can be preferably used in the present invention.

(Method for forming gas barrier layer)
The method for forming the gas barrier layer in the present invention may be any method as long as it can be applied to the reversible thermosensitive recording layer or the like, but on the reversible thermosensitive recording layer, at least a gas barrier resin and an inorganic layered compound, preferably an oxazoline series A gas barrier resin mixed solution containing a compound and a solvent, an additive, or the like is applied and dried by heating. As a coating method of the gas barrier resin mixture, a usual coating method such as a roll coating method using a gravure cylinder, a doctor knife method, an air knife / nozzle coating method, a bar coating method, a spray coating method, a dip coating method, etc. These coating methods may be combined. In the gas barrier layer, the inorganic stratiform compound is preferably dispersed in parallel along the gas barrier layer. In that respect, when the gas barrier layer is formed by the above-described coating method, the inorganic layered compound is likely to be dispersed in parallel along the gas barrier layer.

When forming the gas barrier layer by the above-described coating method, as a method for producing a gas barrier resin mixture for coating, for example,
(1) An inorganic layered compound (which may be previously swollen and cleaved in a dispersion medium such as water) is added to and mixed with a solution in which a gas barrier resin and an oxazoline compound are dissolved in a solvent, and a stirrer or dispersion A method of dispersing an inorganic layered compound using an apparatus,
(2) After the inorganic layered compound is swollen and cleaved in a dispersion medium such as water, a stirrer or a dispersing device is used, and further, the inorganic layered compound is cleaved and dispersed in a dispersion liquid (dispersion solution) with gas barrier properties. Examples thereof include a method of adding and mixing a solution in which a resin and an oxazoline compound are dissolved in a solvent. When the inorganic layered compound is a natural product, a compound containing an alkali metal ion or alkaline earth metal ion such as magnesium hydroxide or calcium hydroxide may be added to the mixed solution. preferable.

  As the solvent for the gas barrier resin and the oxazoline compound, both an aqueous and non-aqueous solvent capable of dissolving the polyvinyl alcohol polymer and / or the ethylene-vinyl alcohol copolymer and the oxazoline compound can be used. It is preferable to use water that is not harmful to the environment.

  In addition, when an ethylene-vinyl alcohol copolymer is used as a gas barrier resin, a mixture of a terminal-modified ethylene-vinyl alcohol copolymer that has been reduced in molecular weight by treatment with a peroxide or the like, and water and a lower alcohol. It is preferable to constitute the gas barrier resin solution using a solvent. In this case, 50 to 85% by mass of water and a lower alcohol having 2 to 4 carbon atoms such as ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert When a mixed solvent containing 15 to 50% by mass of at least one kind such as butyl alcohol is used, the solubility of the ethylene-vinyl alcohol copolymer is improved, and it is also preferable for maintaining an appropriate solid content. If the content of the lower alcohol in the mixed solvent exceeds 50% by mass, cleavage will be insufficient when an inorganic layered compound described later is dispersed. Of the lower alcohols having 2 to 4 carbon atoms, n-propyl alcohol and iso-propyl alcohol are preferably used.

  The stirrer or dispersion device for forming the gas barrier resin mixed liquid is not particularly limited as long as it is a normal stirrer or dispersion device, and the inorganic layered compound can be uniformly dispersed in the dispersion using these. However, from the viewpoint of obtaining a transparent and stable inorganic layered compound dispersion, it is preferable to use a high-pressure disperser, an ultrasonic disperser or the like. Examples of the high-pressure disperser include a nanomizer (trade name, manufactured by Nanomizer), a microfluidizer (trade name, manufactured by Microfridex), an optimizer (trade name, manufactured by Sugino Machine), and DeBee (trade name, Bee). And Niro Soabi homogenizer (trade name, Niro Soabi) and the like. It is preferable to carry out dispersion treatment at 1 to 100 MPa as the pressure condition of these high-pressure dispersers. When the pressure condition exceeds 100 MPa, the inorganic stratiform compound is likely to be crushed and too fine, and the gas passage length is shortened, so that the target gas barrier property may be lowered. Conversely, if the pressure condition is less than 1 MPa, there may be a problem that the dispersion of the inorganic layered compound does not proceed or that a huge amount of time is required for the dispersion.

  Silane coupling agent, isocyanate compound, aziridine compound and carbodiimide compound, which are adhesion improvers added to improve the adhesion between the gas barrier layer and its adjacent layer, are added after the dispersion adjustment of the gas barrier resin and the inorganic layered compound. May be. By forming the gas barrier layer in this manner, the gas barrier property of the reversible thermosensitive recording material is remarkably improved, and the resistance to peeling due to the influence of moisture and the like is also improved.

(Primer layer)
The primer layer 8 is a layer for improving the adhesion and adhesion between the barrier layer 4 and the protective layer 5 and is formed of a thermosetting resin (1) having a strong affinity with the barrier layer 4 and the protective layer 5. A thermosetting resin layer is preferably used. The thermosetting resin layer may be cured after the mixed composition of the thermosetting resin (1) precursor and the curing agent (crosslinking agent) before curing is applied to the barrier layer 4.

  Specific combinations of thermosetting resin (1) precursor and curing agent include polyvinyl butyral resin and isocyanate, acrylic polyol resin and isocyanate, polyester polyol resin and isocyanate, polyurethane polyol resin and isocyanate, phenoxy resin and isocyanate, A combination of polyvinyl butyral resin and isocyanate is exemplified. Among them, a combination of a polyvinyl butyral resin and an isocyanate that acts as a curing agent (crosslinking agent) is preferable.

  Examples of the isocyanate include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), paraphenylene diisocyanate (PPDI), and tetramethylxylylene diisocyanate. (TMXDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate (LDI), isopropylidenebis (4-cyclohexylisocyanate) (IPC), cyclohexyl diisocyanate (CHDI), tolidine And diisocyanate (TODI).

  The thickness of the primer layer 8 is preferably 0.1 to 3 μm, and more preferably 0.2 to 2 μm. If the thickness of the primer layer 8 is less than 0.1 μm, the adhesion between the barrier layer 4 and the protective layer 5 may not be exhibited sufficiently. If the thickness of the primer layer 8 is greater than 3 μm, the adhesion between the barrier layer 4 and the protective layer 5 cannot be further improved, but the layer thickness of the reversible thermosensitive recording material may be increased.

[Protective layer]
A protective layer is provided on the outermost surface of the reversible thermosensitive recording material, that is, on the outside of the gas barrier layer. As a material for the protective layer (thickness of 0.1 to 10 μm), a resin curable by heat, ultraviolet rays, electron beams (described in JP-A No. 02-566) or the like is preferably used.

  Among these, it is desirable to use a resin curable by ultraviolet rays. Examples of resins that can be cured with ultraviolet rays or electron beams include urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, vinyl, unsaturated polyester oligomers, various monofunctional, polyfunctional acrylates, methacrylates, and vinyl. Monomers such as esters, ethylene derivatives, and allyl compounds are listed. In the case of crosslinking using ultraviolet rays, a photopolymerization initiator or a photopolymerization accelerator may be used. In the case of crosslinking by heat, a thermosetting resin using an isocyanate compound as a crosslinking agent, for example, acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, polyvinyl butyral resin, cellulose acetate propionate, cellulose A resin having a group that reacts with a crosslinking agent, such as acetate butyrate, or a resin obtained by copolymerizing a monomer having a group that reacts with a crosslinking agent and another monomer may be used.

  The protective layer can contain an organic or inorganic filler ultraviolet absorber, a lubricant, a color pigment, and the like. Specific examples of inorganic fillers include carbonates, silicates, metal oxides, sulfate compounds, and specific examples of organic fillers include silicone resins, cellulose resins, epoxy resins, nylon resins, phenol resins, polyurethanes. Examples include resins, urea resins, melamine resins, polyester resins, polycarbonate resins, styrene resins, acrylic resins, polyethylene resins, formaldehyde resins, polymethyl methacrylate resins, and the like. Specific examples of the ultraviolet absorber include compounds having a salicylate structure, a cyanoacrylate structure, a benzotriazole structure, a benzophenone structure, and the like. Specific examples of the lubricant include synthetic waxes, vegetable waxes, animal waxes, higher alcohols, higher fatty acids, higher fatty acid esters, amides and the like. However, this embodiment is not limited to these compounds.

[Embodiment 2]
In the heat-sensitive recording material (2) of Embodiment 2 of the present invention, as shown in FIG. 2, the difference from the heat-sensitive recording material (1) is that between the heat-sensitive recording layer 3 and the gas barrier layer 4, the heat-sensitive recording material. An anchor layer (intermediate layer) 6 is provided for the purpose of improving the adhesion between the layer 3 and the gas barrier layer 4 and further improving the repeatability of color development and decoloration. Only this difference will be described for the heat-sensitive recording material (2). Others may be as described for the heat-sensitive recording material (1) of the first embodiment.

  The anchor layer 6 of the present invention has a first purpose of strengthening the bond between the heat-sensitive recording layer 3 and the gas barrier layer 4 and has a reversible feeling during coating or during use or storage of the reversible heat-sensitive recording material. A material that does not change the characteristics of the thermal recording material is selected.

  The method for forming the anchor layer 6 of the present invention includes a normal coating method and a laminating method without particular limitation. The thickness of the anchor layer 6 is not particularly limited, but is preferably 0.1 to 10 μm, and particularly preferably 0.1 to 3 μm. If the thickness of the anchor layer 6 is less than 0.1 μm, the adhesiveness is insufficient, and if it is more than 10 μm, the thermal sensitivity of the recording layer decreases, which is not preferable.

  When providing a gas barrier layer on a reversible thermosensitive recording layer, first, an anchor agent containing a thermosetting resin (2) is applied on the reversible thermosensitive recording layer to form one or more anchor layers. After that, a gas barrier layer is formed. Anchor layer improves adhesion between reversible thermosensitive recording layer and gas barrier layer, prevents alteration of reversible thermosensitive recording layer by applying gas barrier layer, transfers additives contained in gas barrier layer to reversible thermosensitive recording layer, or reversible A function of preventing the additive contained in the heat-sensitive recording layer from shifting to the gas barrier layer can be provided.

  The anchor agent can be classified into an adhesive agent and an anchor agent in a narrow sense. Examples of adhesives include isocyanate-based, urethane-based, and acrylic-based various laminating adhesives, and narrowly-defined anchoring agents include titanium-based, isocyanate-based, imine-based, and polybutadiene-based laminates. An anchor coating agent can be mentioned. Note that these adhesives and narrowly-defined anchoring agents may contain an adhesive property-modifying material such as a crosslinking agent.

  As the solvent used for the coating liquid of the anchor layer, the dispersion apparatus of the coating liquid, the binder, the coating method, the drying / curing method, etc., a known coating method used for the reversible thermosensitive recording layer or gas barrier layer may be used. it can.

[Embodiment 3]
The reversible thermosensitive recording material (3) of the present invention according to Embodiment 3 is shown in FIG. In the reversible thermosensitive recording material (3) shown in FIG. 3, an undercoat layer 7 having a high heat insulating property is laminated between the thermosensitive recording layer 3 and the support 2 of the reversible thermosensitive recording material (2) shown in FIG. Has been.

  The undercoat layer 7 in the reversible thermosensitive recording material (3) prevents heat transfer to the support 2 side when heat is applied to the thermosensitive recording layer 3 to melt the color former or developer. The heating efficiency of the recording layer 3 can be increased, and adverse effects on the material and the like due to the temperature rise of the support 2 can be avoided. If the heating efficiency of the heat-sensitive recording layer 3 is increased, the amount of heat for melting the color former and the developer is small, and the melting time is also shortened. Therefore, color development and decoloration can be achieved in a short time with a small heating head or heating roller. Is possible. Further, if the support 2 does not reach a high temperature, the range of material selection for the support is widened, and it is not necessary to take measures against high temperatures of electronic components such as magnetic recording materials and ICs that may be mounted on the support. Further, even when the back side of the support 2 becomes high during production or use of the reversible thermosensitive recording material, the influence of heat on the thermosensitive recording layer 3 side can be reduced.

  The undercoat layer 7 is preferably formed of a material having good adhesion to the support 2 and the thermosensitive recording layer 3. The undercoat layer 7 is preferably a foamed layer in order to enhance the heat insulating effect. In the formation of the foam layer, an undercoat layer precursor may be formed on the support 2 like a urethane material and foamed to form the undercoat layer 7. Alternatively, the undercoat layer 7 may be formed on the support 2 by mixing hollow particles such as inorganic or organic foam beads and a binder resin as an undercoat layer raw material. By providing the hollow particle-containing layer as an undercoat layer between the thermosensitive coloring layer and the support, high heat insulating properties can be obtained, and adhesion with the head can be improved, and the coloring sensitivity and sensitivity speed can be improved.

  As the hollow particles, fine hollow particles containing a thermoplastic resin as a shell and containing air or other gas inside can be used, and a preferable average particle diameter of the hollow particles is 0.4 μm or more and 10 μm or less. When the average particle diameter (particle outer diameter) is smaller than 0.4 μm, there is a problem in production such as it is difficult to obtain a desired hollow ratio, and conversely, those larger than 10 μm are coated on the support. At this time, scratch-like streaks are easily formed, and the smoothness of the surface of the heat-sensitive recording material after coating and drying is lowered. Therefore, the adhesion with the thermal head is lowered during image formation, and the sensitivity improvement effect is lowered. For the same reason, it is preferable that the hollow particles have a particle size within the above range and a small particle size distribution.

  Further, the hollow particles preferably have a hollow ratio of 30% to 98%, more preferably 70% to 98%, and particularly preferably 90% to 98%. When the hollow ratio of the hollow particles increases, the thickness of the wall material decreases, and when the wall material decreases, the strength against pressure or the like becomes weak and is easily broken. On the other hand, if the wall material is simply hardened to give strength, it tends to become brittle and is easily broken by bending. Therefore, the wall material of the hollow particles needs to have a balance between hardness and flexibility, and acrylonitrile resin and methacrylonitrile resin are listed as preferable wall materials having both hardness and flexibility. Specific examples of hollow particles preferably used in the present invention are described in JP-A-2005-19974.

In addition, the hollow rate said here is ratio of the outer diameter of a hollow particle, and an internal diameter, and is represented by a following formula. The hollow ratio of the hollow particles is calculated from the inner diameter and outer diameter in the same direction for each particle observed in a micrograph of the hollow particles, and is calculated by the following equation.
Hollow ratio (%) = [(inner diameter of hollow particle) / (outer diameter of hollow particle)] × 100
In the measurement of the hollow ratio in the present invention, it is calculated as the number average of the hollow ratios of the hollow particles dispersed so as to be spread on an area of at least 100 microns square. In addition, the measuring method of the particle diameter of a hollow particle is based on the laser method similarly to the measuring method of the above-mentioned leuco dye.

  A known resin can be used in combination for the material of the undercoat layer 7. Examples of these are styrene / butadiene copolymer, which is a hydrophobic resin, latex of styrene / butadiene / acrylic ester copolymer, vinyl acetate, vinyl acetate / acrylic acid copolymer, styrene / acrylic ester copolymer, Examples thereof include emulsions such as acrylic ester resins and polyurethane resins. In addition, various modified polyvinyl alcohols such as fully saponified polyvinyl alcohol, carboxyl modified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, silyl modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, which are water-soluble resins. Is mentioned. In addition to the hollow particles and the binder, auxiliary coating components commonly used in heat-sensitive recording materials such as fillers, heat-fusible components, surfactants, and the like can be used for the undercoat layer 7 as necessary. .

  Furthermore, it is also preferable to add a pigment material containing white or black to the undercoat layer 7. If the undercoat layer 6 is colored as the base color of the heat-sensitive recording layer 3, there is no restriction on the color of the support 2 on the heat-sensitive recording layer 3 side.

[Embodiment 4]
FIG. 4 shows a reversible thermosensitive recording material (4) of the present invention in Embodiment 4. In the reversible thermosensitive recording material (4) shown in FIG. 3, an ultraviolet ray that protects the thermosensitive recording layer 3 from ultraviolet rays between the thermosensitive recording layer 3 and the anchor layer 6 of the reversible thermosensitive recording material (3) shown in FIG. An absorption layer is laminated.

(UV absorbing layer)
The material of the heat-sensitive recording layer, particularly the color former and developer, deteriorates and changes color or fades when exposed to ultraviolet rays for a long period of time, or does not cause a sufficient color reaction. For this reason, it is preferable to protect the heat-sensitive recording layer from being exposed to unnecessary ultraviolet rays. In the reversible thermosensitive recording material (4), an ultraviolet absorbing layer 9 is provided between the thermosensitive recording layer 3 and the anchor layer 6. The ultraviolet absorption layer 9 only needs to be formed of a material that absorbs ultraviolet rays. For example, a resin for the anchor layer 6 to which a filler having ultraviolet absorption performance is added may be used. There are inorganic fillers and organic fillers as fillers. Calcium carbonate, magnesium carbonate, anhydrous silicic acid, hydrous silicic acid, hydrous aluminum silicate, hydrous calcium silicate, alumina, iron oxide, calcium oxide, magnesium oxide , Chromium oxide, manganese oxide, silica, talc, mica, and the like. Examples of organic fillers include silicone resin, cellulose resin, epoxy resin, nylon resin, phenol resin, polyurethane resin, urea resin, melamine resin, polyester resin, polycarbonate resin, styrene, polystyrene, polystyrene / isoprene, styrene vinylbenzene, and other styrene series Examples thereof include resins, acrylic resins such as vinylidene chloride acrylic, acrylic urethane, and ethylene acrylic, polyethylene resins, formaldehyde resins such as benzoguanamine formaldehyde, melamine formaldehyde, polymethyl methacrylate resins, and vinyl chloride resins. The filler can be used alone, but two or more kinds may be contained. Examples of the shape include a spherical shape, a granular shape, a plate shape, and a needle shape.

  The filler content in the ultraviolet absorbing layer 9 is preferably 5 to 50% by volume in terms of volume fraction. The thickness of the ultraviolet absorbing layer 9 is preferably in the range of 0.1 to 20 μm. When the thickness of the ultraviolet absorbing layer 9 is thinner than 0.1 μm, the ultraviolet absorption may be insufficient, and when it is thicker than 20 μm, the thermal conductivity of the ultraviolet absorbing layer may be lowered.

(Additive)
Various additives can be used in the reversible thermosensitive recording material of the present invention as required. These additives include, for example, dispersants, surfactants, conductive agents, fillers, lubricants, antioxidants, light stabilizers, ultraviolet absorbers, color stabilizers, decolorization accelerators, fillers, and the like. .

  The reversible thermosensitive recording layer 3, the anchor layer 6 and the gas barrier layer 4 may be added with other fillers each having an ultraviolet absorption performance or no ultraviolet shielding performance. Examples include the fillers listed. In the present invention, the filler can be used alone, but two or more kinds may be included. Examples of the shape include a spherical shape, a granular shape, a plate shape, and a needle shape. The filler content in the gas barrier layer 4 is preferably 5 to 50% by volume in terms of volume fraction.

  A lubricant may be added to each of the reversible thermosensitive recording layer 3, the anchor layer 6, and the gas barrier layer 4. Specific examples of the lubricant include synthetic waxes such as ester wax, paraffin wax, and polyethylene wax: hardened castor oil, etc. Plant waxes: animal waxes such as hydrogenated beef tallow oil: higher alcohols such as stearyl alcohol and behenyl alcohol: higher fatty acids such as margaric acid, lauric acid, mystynolic acid, palmitic acid, stearic acid, behenic acid, and fumenic acid Class: Higher fatty acid esters such as fatty acid esters of sorbitan: amides such as stearic acid amide, oleic acid amide, lauric acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, and methylol stearic acid amide. The content of the lubricant in each layer is preferably 0.1 to 95%, more preferably 1 to 75% in terms of volume fraction.

[Embodiment 5]
(Form of reversible thermosensitive recording material)
The reversible thermosensitive recording material of the present invention may be attached to another medium via an adhesive layer or the like. Alternatively, a back coat layer is provided on one side (back side) of a support such as a PET film, a release layer used for a thermal transfer ribbon on the opposite side of the back coat layer, a reversible thermosensitive recording layer on the release layer, and further on the surface A resin layer that can be transferred to paper, a resin film, a PET film, or the like may be provided and transferred using a thermal transfer printer. The reversible thermosensitive recording material of the present invention may be processed into a sheet shape or a card shape, and the shape can be processed into an arbitrary shape, and printing processing on the front and back surfaces of the reversible thermosensitive recording material is possible. Can be applied. The reversible thermosensitive recording material processed into a card shape can be a magnetic card or IC card by mounting a magnetic layer or IC chip. Further, the reversible thermosensitive recording material of the present invention may be a reversible thermosensitive recording material on both sides, or an irreversible thermosensitive recording layer may be used in combination, and the color tone of each recording layer may be the same or different. good.

(Image formation and erasure on reversible thermosensitive recording materials)
Image forming and erasing methods on the reversible thermosensitive recording material of the present invention include conventional color forming methods and decoloring methods on reversible thermosensitive recording materials such as thermal pens, thermal heads, and laser heating depending on the purpose of use. Is available.

  FIG. 7 and FIG. 8 show examples of color development and decoloration methods for specific reversible thermosensitive recording materials. In the coloring method, as in the example shown in FIG. 7, a heating head 15 having a small area such as a thermal head of a dot printer is pressed against the surface of the reversible thermosensitive recording material 1 that is not colored. Since the reversible thermosensitive recording layer 3, the barrier layer 4, and the protective layer 5 are thin, the heated portion 13 of the reversible thermosensitive recording layer 3 is immediately heated and reaches the melting point of the color former or the like constituting the thermosensitive recording layer 3. Then, the color former and developer of the heated portion 13 facing the heating head 15 of the reversible thermosensitive recording layer 3 melt and react to develop color. Therefore, if the heating head 15 is removed from the surface of the reversible thermosensitive recording material 1, the heated portion 10 of the reversible thermosensitive recording material 1 is sufficiently small so that it can be quickly cooled. Then, the heated portion 13 is frozen while being colored.

  Also in the decoloring method, as described above, the surface of the reversible thermosensitive recording material 1 is first heated to melt the heated region of the reversible thermosensitive recording layer 3. However, it is preferable to heat a relatively wide area with a heating roller 18, for example, as shown in FIG. When the heated area of the reversible thermosensitive recording layer 3 is melted, the heating roller 18 is rolled to move the heated area. Then, the heated area once melted and colored is cooled relatively slowly. In the meantime, the color former and developer in the reversible thermosensitive recording layer 3 are dissociated and aggregated or crystallized, respectively. For this reason, the reversible thermosensitive recording layer 3 is decolored and then cooled to room temperature to be frozen. Although this decoloring method also heats the non-colored portion, such decoloring method is convenient because generally the decoloring can be performed by decoloring the entire reversible thermosensitive recording material. In FIG. 8, if the heating roller 19 rolls to the left along the direction of the arrow in the figure, the unheated portion 16 that has developed color of the thermal recording layer 3 is heated and removed by the movement of the heating roller 18. As a result, the decoloring region 17 is obtained.

[Example]
The present invention will be described in further detail with reference to examples. Unless otherwise indicated, the following parts and% are all based on mass. In addition, this invention is not limited to the following Example at all.
Example 1
(Preparation of thermoreversible recording medium)
-Support-
As a support, a 125 μm thick white turbid polyester film (manufactured by Teijin DuPont Co., Ltd., Tetron film U2L98W) was used.

-Formation of undercoat layer-
30 parts by mass of a styrene-butadiene copolymer (manufactured by Nippon A & L Co., Ltd., PA-9159), 12 parts by mass of a polyvinyl alcohol resin (manufactured by Kuraray Co., Ltd., Poval PVA103), hollow particles (manufactured by Matsumoto Yushi Co., Ltd., Microsphere) R-300) 20 parts by mass and water 40 parts by mass were added and stirred for about 1 hour until a uniform state was obtained to prepare an undercoat layer coating solution. The obtained undercoat layer coating solution was applied onto the support with a wire bar and dried by heating at 80 ° C. for 2 minutes to form an undercoat layer having a thickness of 20 μm.

-Formation of thermal recording layer-
3 parts by weight of a developer represented by the following structural formula, 1 part by weight of a dialkylurea (manufactured by Nippon Kasei Co., Ltd., Haclean SB), 9 parts by weight of an acrylic polyol 50% by weight solution (manufactured by Mitsubishi Rayon Co., Ltd., LR327), and 70 parts by mass of methyl ethyl ketone was pulverized with a ball mill so that the average particle size was about 1 μm to prepare a dispersion.

次に、この粉砕した顕色剤を含む分散液に、２−アニリノ−３−メチル−６ジブチルアミノフルオラン１質量部、及びイソシアネート（日本ポリウレタン株式会社製、コロネートＨＬ）３質量部を加え、良く撹拌させて感熱層用塗布液を得た。得られた感熱層用塗布液を前記アンダーコート層上にワイヤーバーを用いて塗布し、１００℃にて２分間乾燥後、６０℃にて２４時間キュアを行って膜厚約１１μｍの感熱層を形成した。

Next, 1 part by mass of 2-anilino-3-methyl-6dibutylaminofluorane and 3 parts by mass of isocyanate (manufactured by Nippon Polyurethane Co., Ltd., Coronate HL) are added to the dispersion containing the crushed developer. It was made to stir well and the coating liquid for heat sensitive layers was obtained. The obtained heat-sensitive layer coating solution was applied onto the undercoat layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours to form a heat-sensitive layer having a thickness of about 11 μm. Formed.

-Formation of UV absorbing layer-
Ultraviolet-absorbing polymer 40% by mass solution (manufactured by Nippon Shokubai Co., Ltd., UV-A11, hydroxyl value: 39) 20 parts by mass, isocyanate compound (Mitsui Takeda Polyurethane Co., Ltd., D-110N) 2 parts by mass, and methyl ethyl ketone (MEK) ) A composition comprising 18 parts by mass was sufficiently stirred with a ball mill to prepare a coating solution for an ultraviolet absorbing layer having an ultraviolet absorbing function. The obtained coating solution for ultraviolet absorbing layer was applied on the heat sensitive layer using a wire bar, dried at 90 ° C. for 1 minute, and then allowed to stand at room temperature for 24 hours to form an ultraviolet absorbing layer of about 2 μm. Formed.

-Formation of anchor layer-
15 parts by mass of polyester polyol resin (Mitsui Chemicals Polyurethane Co., Ltd., Takelac A-3210) and 10 parts by mass of isocyanate compound (Mitsui Chemicals Polyurethane Co., Ltd., Takenate A-3070) are mixed with 125 parts by mass of ethyl acetate. Thus, an anchor layer coating solution was obtained. The obtained coating solution for anchor layer was applied onto the ultraviolet absorbing layer using a wire bar and dried at 80 ° C. for 1 minute to form an anchor layer having a thickness of about 0.7 μm.

-Formation of gas barrier layer-
(1) Preparation of ethylene-vinyl alcohol copolymer solution Ethylene-vinyl alcohol copolymer (Nippon Synthetic Chemical Industry Co., Ltd.) was added to 60 parts by mass of a mixed solvent containing 50% purified water and 50% iso-propyl alcohol (IPA). Manufactured by Soarnol D-2908, hereinafter abbreviated as EVOH.) Add 30 parts by mass, add 10 parts of hydrogen peroxide having a concentration of 30%, and heat to 80 ° C. with stirring. The reaction was performed for about 2 hours. Thereafter, the mixture was cooled and catalase was added to 3000 ppm to remove residual hydrogen peroxide, and an almost transparent ethylene-vinyl alcohol copolymer solution having a solid content of 30% was obtained.

(2) Preparation of inorganic layered compound dispersion 5 parts by weight of natural montmorillonite (Kunimine Kogyo Co., Ltd., Kunipia F), which is an inorganic layered compound, is added to 95 parts by weight of purified water while stirring, and further 1 part of magnesium hydroxide Was sufficiently dispersed with a high-speed stirrer. Thereafter, the mixture was kept at 40 ° C. for 1 day to obtain an inorganic layered compound dispersion having a solid content of 5%.

(3) Preparation of gas barrier coating solution and formation of gas barrier layer 2.1 parts by mass of the ethylene-vinyl alcohol copolymer solution prepared in (1) was added to 60 parts by mass of a mixed solvent of 50% purified water and 50% IPA. The mixture was sufficiently stirred and mixed. Further, 37.9 parts of the inorganic layered compound dispersion prepared in (2) was added while stirring the solution at high speed. Cations were removed by adding 3 parts by mass of cation exchange resin particles to 100 parts by mass of this mixed solution, and stirring for 1 hour at a stirring speed at which crushing of the ion exchange resin particles did not occur. Thereafter, only the cation exchange resin was filtered off with a strainer. The obtained mixed solution was further subjected to a dispersion treatment at a pressure of 50 MPa in a high-pressure dispersion apparatus, and then filtered through a 300 mesh filter, and an ethylene-vinyl alcohol copolymer solution having a solid content of 5% and an inorganic layered compound dispersion liquid. (EVOH / inorganic layered compound = 25 parts / 75 parts) was obtained. While stirring 10 parts by mass of the obtained mixed solution, 0.2 part by mass (0 as an oxazoline compound) of an oxazoline-based compound solution (oxazoline-based compound 40% by mass, Nippon Shokubai Co., Ltd., Epocros WS-500). .08 parts by mass) and 0.2 part by mass of an oxazoline-based compound (Epocross WS-500, manufactured by Nippon Shokubai Co., Ltd.) was added to obtain a coating solution for gas barrier layer. The obtained gas barrier layer coating solution was applied onto the anchor layer using a wire bar and dried at 80 ° C. for 1 minute to form a gas barrier layer having a thickness of about 0.5 μm.

-Formation of primer layer-
Mixing 50 parts by mass of a mixed solution of methyl ethyl ketone, isopropyl alcohol, and ethyl acetate with 50 parts by mass of a polyvinyl butyral resin (BL-1) manufactured by Sekisui Chemical Co., Ltd. and 3 parts by mass of an isocyanate compound (Samiata Rx, Lamiol R). A primer layer coating solution was obtained. The obtained primer layer coating solution was applied onto the gas barrier layer using a wire bar and dried at 80 ° C. for 1 minute to form a gas barrier layer having a thickness of about 0.3 μm.

-Formation of protective layer-
3 parts by mass of pentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD DPHA), 3 parts by mass of urethane acrylate oligomer (manufactured by Negami Kogyo Co., Ltd., Art Resin UN-3320HA), acrylic ester of dipentaerythritol caprolactone ( Nippon Kayaku Co., Ltd., KAYARAD DPCA-120) 3 parts by mass, silica (Mizusawa Chemical Industries, P-526) 1 part, photopolymerization initiator (Ciba Geigy Japan, Irgacure 184) 0.5 part by mass Then, 0.001 part of a lubricant (ST102PA manufactured by Toray Dow Co., Ltd.) and 11 parts by weight of isopropyl alcohol were added, and the mixture was well stirred by a ball mill and dispersed to an average particle size of about 3 μm to prepare a coating solution for a protective layer. . The obtained coating solution for the protective layer was applied with a wire bar, heated and dried at 90 ° C. for 1 minute, then irradiated with an 80 W / cm ultraviolet lamp for crosslinking, and then cured at 70 ° C. for 24 hours. A protective layer of about 4 μm was formed.

  Thus, the reversible thermosensitive recording material of Example 1 was produced. This reversible thermosensitive recording material corresponds to the reversible thermosensitive recording material (4) of Embodiment 4 shown in FIG.

(Example 2)
A reversible thermosensitive recording material of Example 2 was produced in the same manner as in Example 1 except that the primer layer thickness was changed from 0.3 μm to 0.5 μm in the primer layer formation of Example 1.

(Example 3)
A reversible thermosensitive recording material of Example 3 was produced in the same manner as in Example 1 except that the primer layer thickness was changed from 0.3 μm to 0.7 μm in the primer layer formation of Example 1.

Example 4
A reversible thermosensitive recording material of Example 4 was produced in the same manner as in Example 1 except that the primer layer formation in Example 1 was changed from 0.3 μm to 1.0 μm.

(Example 5)
In the primer layer formation of Example 1, the reversible feeling of Example 5 was the same as Example 1 except that 50 parts by mass of polyvinyl butyral resin was changed to 50 parts by mass of acrylic polyol resin (LR327, manufactured by Mitsubishi Rayon Co., Ltd.). A thermal recording material was prepared.

(Example 6)
In the primer layer formation of Example 1, in the same manner as in Example 1 except that 50 parts by mass of polyvinyl butyral resin was changed to 50 parts by mass of vinyl chloride-vinyl acetate copolymer (manufactured by Nissin Chemical Co., Ltd., TA0), A reversible thermosensitive recording material of Example 6 was produced.

(Comparative Example 1)
A reversible thermosensitive recording material of Comparative Example 1 was produced in the same manner as in Example 1 except that the formation of the primer layer in Example 1 was omitted.

(Comparative Example 2)
A reversible thermosensitive recording material of Comparative Example 2 was produced in the same manner as in Example 1 except that the formation of the anchor layer, gas barrier layer, and primer layer was omitted in Example 1.

(Evaluation of reversible thermosensitive recording materials)
The produced thermoreversible recording media of Examples 1 to 6 and Comparative Examples 1 and 2 were repeatedly subjected to a print erasure test and a light resistance test as follows.

−Repeat print erasure test−
Printing and erasing of the reversible thermosensitive recording material was repeated 300 times with a card printer (R-28000, manufactured by Panasonic Communications). As printing and erasing conditions, the printing energy was 0.57 mJ / dot, the erasing temperature was 130 ° C., and the conveyance speed was 56 mm / sec. The printing state on the surface of the reversible thermosensitive recording material was observed visually at the time of repeating 10 times, 100 times, and 300 times, and evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1.
◯: Level at which the developed state of the image area and the decolored state of the erased part are good and coating film peeling is not observed Δ: Level at which the coloring and decoloring state is good but coating film peeling is slightly observed x: Level at which the color image is concealed, whitened, and film peeling occurs

-Light resistance test-
After printing on a reversible thermosensitive recording material with a card printer (R-28000, manufactured by Panasonic Communications) (printing energy is 0.57 mJ / dot, transport speed is 56 mm / sec), light irradiation with a xenon lamp (irradiation degree 120,000 Lx, 48 hours, temperature 30 ° C., humidity 70%, an artificial solar device manufactured by Celic). After exposure, the same card printer was used for erasing and printing (rewriting) tests. The printing conditions were an erasing temperature of 130 ° C., a conveyance speed of 56 mm / sec, and a printing energy of 0.57 mJ / dot. The image density, background density, and erasing density of the image on the reversible thermosensitive recording material were measured with X-RITE 918 and judged based on the following evaluation criteria. The evaluation results are shown in Table 2.
◎: Density difference between erased part and background part 0.05 or less ○: Density difference between erased part and background part 0.10 or less △: Density difference between erased part and background part 0.30 or less ×: between erased part and background part Concentration difference exceeds 0.30

  As can be seen from the results shown in Table 2, the reversible thermosensitive recording materials having the gas barrier layers of Examples 1 to 6 and Comparative Example 1 have sufficient weather resistance under high humidity conditions. However, the reversible thermosensitive recording material having no gas barrier layer of Comparative Example 2 does not have sufficient weather resistance under high humidity conditions.

  On the other hand, as shown in Table 1, the reversible thermosensitive recording materials of Examples 1 to 6 can ensure durability even in the repeated print erasure test, but the reversible thermosensitive recording material provided with the gas barrier layer is The durability against repeated printing erasure may be inferior. When the primer layer is not provided as in the reversible thermosensitive recording material of Comparative Example 1, delamination phenomenon and whitening phenomenon occur, and 300 times printing erasure is repeated. It became unusable even in the test. In addition, the primer layer is excellent when it is formed of a thermosetting resin obtained by curing a polyvinyl butyral resin with an isocyanate, and the primer layer has a thickness of 0.5 to 1.0 μm (Examples 2 to 4). Good results.

Cross-sectional schematic diagram of reversible thermosensitive recording material (1) of the present invention Schematic cross section of reversible thermosensitive recording material (2) of the present invention Cross-sectional schematic diagram of reversible thermosensitive recording material (3) of the present invention Cross-sectional schematic diagram of reversible thermosensitive recording material (4) of the present invention Cross section of gas barrier layer Illustration of coloring and decoloring of reversible thermosensitive recording material Illustration of coloring method Illustration of erasing method

Explanation of symbols

1: Reversible thermosensitive recording material 2: Support 3: Reversible thermosensitive recording layer (thermal recording layer)
4: Gas barrier layer 5: Protective layer 6: Anchor layer 7: Undercoat layer 8: Primer layer 9: Ultraviolet absorbing layer 10: Gas barrier resin 11: Inorganic layered compound 12: Interface 13: Heated part 14: Unheated part 15 : Heating head 16: Unheated part 17: Decoloring part 18: Heating roller

Claims (11)

On the support,
A reversible thermosensitive recording layer comprising a reversible thermosensitive composition comprising a mixture of an electron-donating color-forming compound and an electron-accepting compound whose color development state changes depending on the heating temperature and / or the cooling rate after heating;
A gas barrier layer comprising at least one gas barrier resin selected from the group consisting of a polyvinyl alcohol polymer and an ethylene-vinyl alcohol copolymer, and an inorganic layered compound;
A reversible thermosensitive recording material in which a protective layer for protecting the gas barrier layer is sequentially laminated,
A reversible thermosensitive recording material comprising a primer layer between the gas barrier layer and the protective layer for improving adhesion between the gas barrier layer and the protective layer.   The reversible thermosensitive recording material according to claim 1, wherein the primer layer contains a thermosetting resin (1).   The reversible thermosensitive recording material according to claim 2, wherein the thermosetting resin (1) contains a reaction product of a polyvinyl butyral resin and an isocyanate.   The anchor layer for improving the adhesion between the reversible thermosensitive recording layer and the gas barrier layer is provided between the reversible thermosensitive recording layer and the gas barrier layer. A reversible thermosensitive recording material according to 1.   The reversible thermosensitive recording material according to claim 4, wherein the anchor layer contains a thermosetting resin (2).   The reversible thermosensitive recording material according to claim 5, wherein the thermosetting resin (2) contains a reaction product of an ester polyol resin and an isocyanate.   The reversible thermosensitive recording material according to any one of claims 4 to 6, wherein the anchor layer has a thickness of 0.1 to 10 µm.   The reversible thermosensitive recording material according to claim 6 or 7, wherein the mass ratio of the isocyanate to the ester polyol resin is in the range of 10: 100 to 150: 100.   The reversible thermosensitive recording material according to any one of claims 1 to 8, further comprising an undercoat layer between the support and the reversible thermosensitive recording layer.   An reversible thermosensitive recording member comprising an information storage unit and a reversible display unit, wherein the reversible display unit comprises the reversible thermosensitive recording material according to claim 1.   The information storage unit includes at least one selected from a magnetic thermosensitive recording layer, a magnetic stripe, an IC memory, an optical memory, a hologram, an RF-ID tag card, a disk, a disk cartridge, and a tape cassette. Item 11. The reversible thermosensitive recording member according to Item 10.

Images