JPH0672035A - Developing method for reversible function of functional element - Google Patents

Abstract

(57) [Summary] [Object] To provide a reversible function expressing method of a functional device based on a new principle capable of easily and rapidly transferring between a plurality of states. [Structure] Two kinds of compounds are in an interacting state and a non-interacting state, and the interacting state is a state of a regular aggregation structure formed by both compounds in cooperation with each other. In the non-acting state, a functional element in which at least one compound is aggregated or crystallized by itself is used, and reversible transition between these two states is reversibly exhibited. Method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible function expressing method for a functional device, which comprises a step of reversibly transitioning between a plurality of states having different properties.

[0002]

2. Description of the Related Art Conventionally, it has been known to use a substance having a plurality of stable states and exhibiting a phenomenon that can be arbitrarily transferred between the states by some stimulus as a reversible functional element. Examples of such a functional device include a display device that reversibly changes the arrangement of a liquid crystal compound by an electric field or heat, a reversible transition between an amorphous state and a crystalline state of an inorganic compound or an organic compound, and Like information recording elements that utilize reversible transitions between crystalline states of different types and reversible transitions between associated states of molecules, thermal reversible transitions of crystalline states, molecular alignment states, and aggregation states are performed. There is something to use. Some of these have been put into practical use and widely used, but there is room for improvement in terms of the complexity of the device configuration, the complexity of the entire system, the display, and the contrast of recorded images. Further, there are those that utilize reversible changes in molecular structure such as photochromism and electromism, but these have problems in repeatability and response speed, and have not been practically used.

On the other hand, a method utilizing a reversible reaction between two kinds of compounds has also been proposed. As such a material, there can be shown a thermochromic element which has been conventionally put to practical use as a thermosensitive recording material and which utilizes a coloring reaction between an electron-donating color-developing compound and an electron-accepting compound. Such a thermochromic element can be brought into function by heating the thermochromic element to be changed to a coloring state. Depending on the material system, the element in the colored state can be changed back to the original decolored state. However, in this case, it takes a long time to change the element in the color-developed state to the element in the decolored state again, a compound called a decoloring agent is used, and a troublesome operation using an organic solvent or water is required. However, there is a problem in that it is difficult to completely return to the original decolored state even if the element in the colored state is changed to the element in the decolored state.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems found in the prior art, and reversibly develops functional elements based on a new principle that enables easy and rapid transition between a plurality of states. The task is to provide a method.

[0005]

The present inventors have analyzed the relationship between the molecular structures of two compounds having different properties in the solid phase, the strength of the interaction, and the aggregated state of the two. The interaction is not very strong, and even if it is difficult to solidify in the state where both interact, it can be stabilized by adopting a regular aggregation structure, and on the contrary, this aggregation structure is collapsed. It has been found that by doing so, it is possible to immediately return to the state of no interaction. Further, the formation of this aggregation structure can be controlled by the molecular structure of the compound constituting the functional element, and it was found that the aggregation force of a long-chain structure such as a linear hydrocarbon chain plays an important role. It was The reversible function expressing method of the functional element according to the present invention is based on these findings. That is, according to the present invention, two types of compounds are in an interacting state and a non-interacting state, and the interacting state is a state of a regular aggregation structure formed by the two compounds in cooperation. The functional element characterized in that the non-interacting state uses a functional element in which at least one compound is independently aggregated or crystallized, and reversibly transitions between these two states. The method for reversible function expression of is provided.

Here, the regular agglomerated structure of the two kinds of compounds can be obtained by quenching from a state of heating and melting and mixing both, and by taking this state,
The interaction between the two compounds is kept stable. Also,
By collapsing this regular aggregation structure by raising the temperature, at least one of the compounds can be aggregated or crystallized independently to return to a state where no interaction occurs.

To express the function of the device in the present invention, the difference in the property between the state where two kinds of compounds interact and the state where they do not interact is utilized. The interaction here means a relatively weak bond. The formed state is shown, and for example, there is a binding state as seen in the formation of a complex by hydrogen bonding, the formation of a complex bound by charge transfer type interaction, or the formation of a complex by coordination. If a regular agglomerated structure is formed when the two types of compounds are rapidly cooled from the molten state, the interacted state is stably maintained at room temperature even if the interaction between the two compounds is weak. On the other hand, when two types of compounds having such an aggregate structure are gradually cooled from the molten state, the cohesive force between the molecules of each compound of the same type is stronger than the interaction between the two compounds. Instead, the cohesive force between the molecules of the homologous compound acts to form stable crystals of the homologous compound, and the two do not interact with each other. Therefore, the temperature of the two types of compounds that retain the interaction is first raised by the formation of a regular aggregation structure, and if this structure is destroyed, the cohesive force between the molecules of the same type compound will be increased in that state. It can be operated preferentially and can be returned to a non-interacting state. The method for reversibly expressing a functional element used in the present invention is applied to a functional element forming a complex having a relatively weak interaction as described above, and such a functional element is effective according to the present invention. Can be expressed in the function.

The method for expressing a function of the present invention comprises three factors, namely, the strength of interaction between two types of compounds, the cohesive force acting between the complexes formed by the interaction, and the cohesive force acting between molecules of the same compound. It includes the step of reversibly transitioning between two states by thermally controlling the relationship of the forces of the types.
The state where the two kinds of compounds maintain a regular aggregation structure,
This is due to the action of the cohesive force between the complexes, but this cohesive force basically also includes the action of the cohesive force acting between the compounds of the same type, and at least the two types of compounds. One of the compounds preferably has a structure having a relatively strong cohesive force or a structure that easily regularly aggregates. As such a structure, a structure in which a higher aliphatic chain such as a long hydrocarbon chain is bonded (long chain structure) can be shown. Since such a long-chain structure can change the cohesive force depending on the length of the aliphatic chain, various advantages can be obtained, for example, the temperature at which the aggregate structure of the interacted complex collapses is controlled. be able to. In addition, the part responsible for the functionality in the compound molecular structure, the cohesive force,
The parts responsible for aggregation can be designed separately, and a long-chain structure with the required length can be easily selected for the parts responsible for functionality, facilitating reversible function expression. it can.

The difference in the properties that appear in the functional element used in the present invention when two kinds of compounds having different properties interact with each other and when they do not interact with each other is, for example, absorption of light, transmission of light, scattering, refraction, and other optical properties. Crystal optical characteristics such as characteristics, birefringence and polarization characteristics, nonlinear optical characteristics such as second harmonic (SHG) characteristics, electric conductivity, electric resistance, electron or hole mobility, dielectric constant, ferroelectric Properties such as electrical properties, piezoelectricity, pyroelectricity, charging properties, thermal properties such as thermal conductivity, magnetic properties, mechanical properties, and surface physical properties such as wettability. According to the present invention, a function expression method for reversibly changing these properties thermally can be obtained.

In order to more specifically explain the present invention,
As a thermochromic functional element composed of two kinds of compounds having different properties, a thermochromic functional element composed of an electron-donating color-developing compound (color former) and an electron-accepting compound (developing agent) is taken up. A method of expressing a function of reversibly transferring a color-developed state in which a bond is formed by acting to form a chromophore and a decolored state formed by dissociation of the interaction is described below.

In a reversible functional element composed of a color former and a color developer, the state of a regular aggregation structure (interaction state) formed by the color former and the color developer in cooperation with each other indicates the color development state, On the other hand, a state in which the regular aggregation structure is disintegrated and the color-forming agent and / or the color-developing agent independently aggregates or crystallizes (a state in which they do not interact) indicates a decolored state.
In the state where the color-developing agent and the color-developing agent are melted and mixed by heating, both molecules move and come into contact with each other to form a partially interacted state, so that the element is in a color-developed state as a whole (however, The percentage of interacted molecules depends on the combination). When gradually cooled from the state of being melt-developed, the cohesive force between the developers is stronger than the interaction between the two, so the interaction is cut off during the temperature lowering process, and the developer alone crystallizes and disappears. On the other hand, when it is rapidly cooled, it is possible to form a color-forming state by jointly forming a regular aggregation structure while maintaining the interaction between the two. In the color-developed state obtained by rapid cooling, the ratio of the color-developing agent molecules that are colored in many cases is higher than the state in which the color is developed by melting. This is because the formation of the aggregated structure forms a state in which the interaction is more likely to occur. However, although the state of forming and interacting with this regular aggregation structure is stable at room temperature, the mutual binding force between the color-developing agent and the color-developing agent is originally weak, so this regular aggregation structure is present. When the element that formed the is heated to a temperature lower than the melting temperature, its regular aggregation structure collapses in the solid state, the stabilizing effect due to the aggregation structure is lost, and the developer binds to the color former. Is dissociated, and the developer alone crystallizes or agglomerates and transitions to a state in which no interaction occurs (decolored state). Moreover, the non-interacting element formed by this heating is stably maintained in its non-interacting state even when the element is cooled to room temperature.

Next, the function development of the above-described reversible thermochromic functional element will be described with reference to the drawings. FIG. 1 shows the relationship between the color density of the functional element and the temperature. In this figure, the horizontal axis represents temperature and the vertical axis represents concentration. A in the figure
Indicates an element in a decolored state at room temperature, and B indicates an element in a heated / melted state and a colored state. Further, C indicates an element that is in a colored state at room temperature. _First , when the temperature of an element that is in a color-erased state at room temperature is raised from this state, the color density rises at a temperature T ₁ at which the color-forming agent and the color-forming agent that form the element begin to mix and melt (eutectic). The element B is changed to a color-developed state. When this element B is cooled, it returns to room temperature and changes to the element C in the color-developed state while maintaining the color-developed state (the path indicated by the solid line in the figure). Next, when the temperature of the element C is raised again, the density is lowered at the temperature T ₂ and finally the element D is changed to the decolored state. When this element D is cooled and the temperature is lowered, it returns to the element A in the decolored state as it is (path indicated by a chain line in the figure). The temperature T ₁ shown in FIG. 1 is the color development start temperature of the device, and T ₂ is the color development start temperature of the device. Further, the temperature from T ₂ to T ₁ is the decoloring temperature region of the device.

As can be seen from FIG. 1, the characteristic of the reversible coloring / decoloring phenomenon exhibited by the color forming functional element is that the decoloring temperature range of the element is in a temperature region lower than the temperature at which the element melts to develop a color. That is, it is possible to erase the color by heating the element that is in a color development state at room temperature to this range. In addition, the phenomenon of color development and decolorization has excellent reversibility and can be repeatedly reproduced. Note that FIG. 1 shows a typical coloring / decoloring phenomenon of the thermochromic functional element, and the coloring start temperature and the decolorization start temperature of the element differ depending on the combination of the color former and the color developer used. Further, the concentration of the element B that is melted and develops color and the concentration of the element C that is in a color-developed state obtained by cooling the same do not necessarily match and may be different.

In order to transfer a functional element composed of a color developer and a color developing agent to a color-developed state at room temperature, it is heated to once generate a mixed and molten state, and then rapidly cooled. On the other hand, in order to transfer the color-developed element to the color-erased state at room temperature, the color-developed element is heated to a color-erasing temperature lower than the color-developing temperature to once erase the color, and then cooled. A non-reversible or scarce element used in a heat-sensitive material composed of a conventional color-developing agent and a color-developing agent does not immediately decolor when heated in a colored state. Using a device that consists of a color former and various compounds (developers) that can bring it into a colored state, we investigated the changes in the colored state when the material was once melted to develop color and then cooled. By looking at it, it was found that not only the ones that can maintain the color-developed state inevitably but also the ones that lose color as the temperature drops. It was also found that such a phenomenon greatly changes depending on the temperature lowering condition. The present inventors have changed the strength of the color developer used in the conventional heat-sensitive material, the color developer having a higher aliphatic chain bonded to the molecular structure part showing the color developability, and the color developability itself. With respect to the device containing the above-mentioned color developer, the retention characteristics of the color-developed state when the temperature was lowered were examined. In this case, as the temperature lowering condition, two conditions were used, namely, the case of slow cooling and the case of rapid cooling. The slow cooling referred to here is cooling at a cooling rate of approximately 5 ° C. or less per minute, and the rapid cooling is cooling at a rate of approximately 50 ° C. or more per second. Actually, if a color developer and a developer are melted on a glass plate on a heater and the element sandwiched between them is turned off by the heater and allowed to cool, or if the glass plate is floated in the air and allowed to cool, it will be gradually cooled, On the other hand, if it is immersed in cold water, it will be rapidly cooled. When cooling at this intermediate speed, depending on the case, the state of slow cooling and the state of rapid cooling may be mixed, or an intermediate state may be formed. The application of heat by the thermal head used for normal thermal recording is
Since the heating is for a short time, the cooling is fast and the quenching condition is reached.
Further, the structure of the device after the temperature was lowered was examined by using X-ray diffraction. Based on these measurement results, the devices are classified according to their characteristics and structural aspects, and shown in Table 1.

[0015]

[Table 1]

As can be seen from the results in Table 1, when the elements that have been heated and melted to develop color are gradually cooled and the temperature is lowered to room temperature, some elements form a colored state and some elements almost completely erase the color. is there. In all of these elements, a colored state is formed by rapid cooling from the molten colored state. Colored states formed by slow cooling or rapid cooling include those that can be stably maintained for a long period of time and those that gradually lose color over time. The X-ray diffraction measurement of the temperature-decreasing element of the element that is decolored when gradually cooled from the molten state shows that the decoloration is caused by the separated crystallization of the developer. The same applies when the color gradually disappears over time. The elements shown as classification B in Table 1 cannot form a colored state when gradually cooled, but lose color, but when rapidly cooled, a colored state is formed. In the case of the device of Class B, the structure after the rapid cooling was found from the result of X-ray diffraction to form a structure in which color formers were regularly aggregated. From these results, the elements that cannot form a colored state by slow cooling are
Since the interaction between the color developer and the color developer that compose it is relatively weak, when the temperature falls below the mixing and melting temperature of the two in the process of gradually cooling from the molten color development state, the cohesive force between the color developers acts and the color development The agent separates from the chromophore and crystallizes to disappear, but on the other hand,
It is considered that when rapidly cooled, the color former forms a regular agglomerated structure, and the agglomerated structure stabilizes the bond between the color developer and the color former to form a colored state. Therefore, if the regular agglomerated structure of the chromophore formed by the elements classified as B is caused to undergo thermal motion by increasing the temperature and then collapsed, the regular agglomerated structure of the chromophore cannot be maintained. Therefore, the developer alone crystallizes to form a decolored state.

In the following, the elements of the class B will be mainly described in comparison with the elements of other classes. In the device of Class B which forms a colored state only when a regular structure is formed by rapid cooling, the binding force between the color developing agent and the color developing agent is strong to some extent, and the cohesive force acting between the color developing bodies is also strong. If the binding force between the color developing agent and the color developing agent is not strong to some extent, an aggregated structure cannot be formed while maintaining the color developing body during quenching. When the element classified as B in the colored state is rapidly heated by quenching, the aggregated structure is maintained up to a certain temperature and the colored state is maintained, but when the temperature is exceeded, the aggregated structure collapses, and this temperature Is also the temperature at which the developer alone can exist as crystals, so that the developer immediately crystallizes and disappears. In addition, since the cohesive force between the color developers at this time is strong, the color disappears quickly.

On the other hand, the elements (A1, A2) that form a colored state when gradually cooled from the melted colored state form a colored state even when rapidly cooled, but the colored state becomes an amorphous state ( There is an element (A2) that forms a regular aggregation structure with A1). A that forms a colored state in the amorphous state
The element classified as 1 has a strong binding force between the color former and the color developer and a weak cohesive force of the color former. However, A1
In the case of the element included in, the developer having a relatively strong cohesive force does not crystallize and precipitate over time even though the coloring state after slow cooling or rapid cooling is in an amorphous state. It tends to be erased. The element of Class A2, which forms a regular aggregation structure when rapidly cooled, has a strong cohesive force of the color former, but the cohesive structure between the color developer and the color developer is stronger than that, so that the cohesive structure collapses due to temperature rise. Even if the chromophore is maintained, the ordered structure is maintained at a high temperature. In this case, the disintegration is a transition to a molten color development state, which does not lead to decolorization. In addition, even if the agglomerated structure collapses, the cohesive force between the developers is weak at that temperature, and sufficient crystallization does not occur, or it is easy to incorporate the color former into the agglomerated structure (for example, liquid crystal structure) of the developer, There are some that do not completely disappear. The former one does not substantially disappear even when the temperature is raised from the rapidly cooled color development state, but the latter one causes a certain amount of color disappearance due to the collapse of the aggregation structure, and is usable as a reversible color development element. Since the color erasing is not as complete as that of the element classified as B, the range of use is limited.

As described above, the decoloring phenomenon in the thermochromic element consisting of the color developer and the color developer is due to the strength of the bond between the color developer and the color developer, the cohesive force acting between the color formers and the color developer. It occurs due to the relative relationship between the cohesive forces acting in between. Although it is difficult to express this relationship quantitatively, those that exhibit a particularly useful reversible color development phenomenon cannot form a color development state by slow cooling from the melt color development state, but a regular aggregation structure by rapid cooling. To form a colored state. In other words, an element having such characteristics can be said to have excellent reversible thermochromic properties. In such an element, heating to a decolorization temperature lower than the melting color development temperature causes the regular agglomeration structure of the color developing material to collapse, and the cohesive force between the color developing agents is preferentially worked to crystallize the color developing agent alone. It is possible to easily and promptly form a decolored state.

The conditions for quenching and gradual cooling in the present invention are as follows:
Since it varies depending on the combination of compounds, it is difficult to clearly indicate the boundary, but as mentioned above, rapid cooling is the case of a cooling rate of about 50 ° C / sec or more, and slow cooling is a cooling rate of about 5 ° C / min or less. This is the case of speed. Speaking from the gist of the present invention, the condition when two types of compounds hold an interaction and form a regular aggregated structure is a condition of quenching, and at least one of them is crystallized or aggregated and separated. It can be said that the condition at the time of storage is the condition of slow cooling.

Next, the method for exhibiting the reversible function of the reversible thermochromic element according to the present invention will be described in more detail. Taking the phosphonic acid having a saturated hydrocarbon chain (straight chain alkyl group), which is a typical developer used for forming the reversible thermochromic element according to the present invention, as an example, the length of the long-chain structure and the formation of a coloring state. The relationship between the element and the aggregation structure of the element will be described. Phosphonic acid developer and 2- (o-chloroanilino) as color developer
-6-Dibutylaminofluorane (hereinafter abbreviated as D1) was mixed at a molar ratio of 5/1, heated and melted at 175 ° C. to produce a colored state, and a scissor element was produced on a glass plate, and 175 ° C. to about 4 ° C./min. When gradually cooled at a rate of 1, the element using phosphonic acid having a linear alkyl group having 14 to 22 carbon atoms (hereinafter abbreviated as P14 to P22) is in a substantially decolored state. When each element is rapidly cooled from 175 ° C., the element using P14 to P22 forms a colored state. Phosphonic acid P12 having an alkyl chain having 12 carbon atoms forms a colored state when rapidly cooled, but when the room temperature is high, the color disappears over time. P
The sample No. 10 once forms a colored state by both slow cooling and rapid cooling, but the coloring cannot be maintained for a long period of time, and the color disappears over time. Further, in the element using phosphonic acid P4 having an alkyl chain having a short alkyl chain of 4 carbon atoms, a colored state is formed and stably maintained by both slow cooling and rapid cooling.

When the X-ray diffraction of the element which has been rapidly cooled from the melt-colored state is measured, the diffraction patterns shown in FIGS. 2 and 3 are obtained. In the X-ray diffractions (a) to (f) of the devices using P22 to P12 shown in these figures, diffraction peaks showing a regular aggregate structure of the color former are recognized. There is a peak showing a layered structure on the low angle side of the diffraction angle of 10 ° or less,
There is a peak at 1 ° indicating aggregation of the alkyl chains. However, the element using P10 of (g) has no peak due to the agglomeration structure of the color former, and the peak of the crystal of P10 itself is observed instead, and the separation and crystallization of P10 progresses during the measurement. Indicates. The peak of the crystal of P10 becomes stronger with time. On the other hand, the element using P4 in (h) has no diffraction peak and is in an amorphous state. In addition, in the state after rapid cooling of each element, the element using P4 and P10 is in a tar-like state, and other than that, the longer the alkyl chain length is, the harder the solid film becomes.

From the above, in the element using the phosphonic acid P14 to P22, the coloring state cannot be formed by the slow cooling from the molten coloring state, and the coloring body takes the regular aggregation structure and forms and maintains the coloring state in the rapid cooling. However, it is an element classified as B described above. The element using P10 forms a colored state in both slow cooling and rapid cooling, and crystals of P10 precipitate and disappear in color over time.
The color former is in an amorphous state and is an element classified as A1. The element using P4 forms and retains a color-developed state regardless of slow cooling or rapid cooling, and the color-developing body is in an amorphous state and is an element classified into A1.

Next, regarding the devices using P14 to P22 classified into B, the change in the amount of light transmission when the film in the colored state formed by rapid cooling from the molten state is heated at a rate of 4 ° C./min. Is shown in FIG. It can be seen that the light transmission amount of each element increases from a certain temperature and the color disappears. The temperature at which the color disappears varies depending on the alkyl chain length, and the longer the temperature, the higher the temperature shifts. The change in the agglomeration structure in the temperature rising process can be detected by X-ray diffraction, for example, as shown in FIG. 5 for the element using P18 and as shown in FIG. 6 for the element using P22. In these figures, (a) shows changes on the low angle side, and (b) shows changes on the high angle side. In either case, the peak showing the layered structure on the low angle side weakens and the peak showing the aggregated structure of the alkyl chains on the high angle side strengthens as the temperature rises. In the vicinity of the color erasing temperature, the peaks showing the aggregation structure of these color formers disappear, and instead the peaks of the developer P18 or P22 alone appear, and it can be seen that the developer alone crystallizes and disappears. This change is the same for all the devices using P14 to P22, and the same change is observed for the devices composed of other developers and color formers classified in B. Therefore, the composition classified into B, that is, the coloring state cannot be formed by the slow cooling from the melted coloring state, and by the rapid cooling, the regular aggregation structure of the coloring body is formed to form the coloring state.
It can be seen that in the element to be held, the color developer is crystallized and decolored by itself due to the collapse of the aggregation structure due to the temperature rise. In particular, the collapse and crystallization of this aggregate structure may be considered as melting and rearrangement of the long-chain structure portion, and there is no system that breaks the bond between the color developer and the color developer due to such changes. It's a whole new thing.

On the other hand, the element using P4 can stably maintain the coloring state even though it is in the amorphous state. In this respect, the same applies to the case where a developer such as 2,2'-bis (p-hydroxyphenyl) propane which is used in a conventional non-reversible or poorly heat-sensitive recording medium is used. These elements are elements that fall into A1 in the above classification, and the elements in the color-developed state do not suddenly lose color even at a certain temperature.

Next, octadecylphosphonic acid (P18)
On the other hand, when a device in which 2-anilino-3-methyl-6-diethylaminofluorane (D2) is combined as a color former is examined, this device forms and maintains the color-developed state even when the melt-colored state is gradually cooled or rapidly cooled. I understand. X-ray diffraction of the rapidly cooled device shows that it has a regular aggregated structure as shown in FIG. Therefore, this element is
It is classified into. Even when the temperature of this element is increased from the color-developed state, a change in the aggregation structure as a color-developing body is recognized, but decoloring does not occur at all.

The element in which gallic acid octadecyl ester as a color developer is combined with the color-forming agent of D1 forms a color-developed state by slow cooling or rapid cooling from the melt-colored state. X-ray diffraction of the rapidly cooled element formed a regular aggregated structure as shown in FIG. 8, and this element was classified as A2 described above. 45-
At 50 ° C., decolorization occurs to some extent with the collapse of the aggregate structure of the color developing material, but at this time, the color developer does not cause clear crystallization. When the temperature is further increased, color is generated again, and a strong peak different from the initial peak of the color-developing structure appears in X-ray diffraction, and it is understood that another aggregation structure is formed and a coloring state is achieved. The element that combines P12 and D1
Decolorization occurs to some extent at 40 to 45 ° C when the temperature rises, but P
The color is not completely erased as much as the 14 / D1 element, and the temperature is 50 ° C.
As described above, the state again shifts to a color-developed state having an aggregation structure. In the case of these elements, since the cohesive force of the color developer is not sufficient and a stable coloring state is obtained in the liquid crystal state at the time of temperature rise, the decoloring is sufficiently performed unlike the elements classified as B. It won't happen.

As described above, in the thermochromic element using the color developer and the color former, the color developed state cannot be formed by gradual cooling from the melt color developed state, and when rapidly cooled, the color former has a regular agglomerated structure. What is formed to form a colored state is a good reversible thermochromic element. The method for reversible thermal color development of the device according to the present invention includes a transition step in which the color development state due to the regular aggregation structure in such a device is destroyed to crystallize the color developer alone.

The color developing agent used in the reversible thermochromic element of the present invention is basically a color developing agent capable of developing a color developing agent in a molecule as long as it can be separated and crystallized from a color developing body having an aggregate structure. From the above viewpoints, it is particularly preferable to have a long-chain structure in order to enhance or control the cohesive force between the color developers, as long as it has a structure exhibiting a function and is not limited thereto. The long-chain structure is preferably a higher aliphatic group having 12 or more carbon atoms, and if it is shorter than this, the cohesive force is often insufficient. In this case, the higher aliphatic group includes a linear or branched alkyl group or alkenyl group, and may have a substituent such as a halogen, an alkoxy group or an ester group. Specific examples of the color developer are shown below.

(A) Organic Phosphoric Acid Compound A compound represented by the following general formula (1) is preferably used. _{R 1 -PO (OH) 2 (} 1) ( provided that, R ₁ represents a number of 12 or more aliphatic group having a carbon)
Specific examples of the organic phosphoric acid compound represented by the general formula (1) include the following. Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

(B) Aliphatic carboxylic acid compound [alpha] -hydroxy fatty acids represented by the following general formula (2) are preferably used. R ₂ —CH (OH) —COOH (2) (wherein R ₂ represents an aliphatic group having 12 or more carbon atoms)
Examples of the α-hydroxyaliphatic carboxylic acid compound represented by the general formula (2) include the following. α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid,
α-Hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms, which is substituted with a halogen element, and is at least in the α-position or β-position.
Those having a halogen element in the carbon at the position are also preferably used. Specific examples of such a compound include the followings. 2-Bromohexadecanoic acid, 2-Bromoheptadecanoic acid, 2-Bromooctadecanoic acid, 2-Bromoeicosanoic acid, 2-Bromodocosanoic acid, 2-Bromotetracosanoic acid, 3-Bromooctadecanoic acid, 3-Bromoeicosanoic acid 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-
Fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-
Iodooctadecanoic acid, 3-iodohexadecanoic acid, 3
-Iodooctadecanoic acid, perfluorooctadecanoic acid and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms and having an oxo group in the carbon chain, and at least the carbon at the α-position, β-position or γ-position is oxo. The base material is also preferably used. Specific examples of such a compound include the followings. 2-oxododecanoic acid, 2-oxotetradecanoic acid, 2-oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxotetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3-oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxooctadecanoic acid, 4-oxodocosanoic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (3) is also preferably used. (However, R ₃ represents an aliphatic group having 12 or more carbon atoms,
(X represents an oxygen atom or a sulfur atom, and n represents 1 or 2.) Specific examples of the dibasic acid represented by the general formula (3) include the following. Dodecylmalic acid, tetradecylmalic acid, hexadecylmalic acid, octadecylmalic acid, eicosylmalic acid,
Docosylmalic acid, detracosylmalic acid, dodecylthiomalic acid, tetradecylthiomalic acid, hexadecylthiomalic acid, octadecylthiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyl Dithiomalic acid, tetradecyldithiomalic acid, hexadecyldithiomalic acid, octadecyldithiomalic acid, eicosyldithiomalic acid, docosyldithiomalic acid, tetracosyldithiomalic acid, etc.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (4) is also preferably used. (However, R ₄ , R ₅ , and R ₆ represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) Specific examples of the dibasic acid represented by the general formula (4) For example, the following may be mentioned. Dodecyl butanedioic acid, tridecyl butanedioic acid, tetradecyl butanedioic acid, pentadecyl butanedioic acid, octadecyl butanedioic acid, eicosyl butanedioic acid, docosyl butanedioic acid,
2,3-dihexadecylbutanedioic acid, 2,3-dioctadecylbutanedioic acid, 2-methyl-3-dodecylbutanedioic acid, 2-methyl-3-tetradecylbutanedioic acid, 2-methyl-3- Hexadecyl butanedioic acid, 2-ethyl-3-
Dodecyl butanedioic acid, 2-propyl-3-dodecyl butanedioic acid, 2-octyl-3-hexadecyl butanedioic acid,
2-tetradecyl-3-octadecyl butanedioic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (5) is also preferably used. (However, R ₇ and R ₈ represent hydrogen or an aliphatic group, and at least one of them is an aliphatic group having 12 or more carbon atoms.) Specific examples of the dibasic acid represented by the general formula (5) are as follows. , For example: Dodecylmalonic acid, tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didodecylmalonic acid,
Ditetradecylmalonic acid, dihexadecylmalonic acid, dioctadecylmalonic acid, dieicosylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, methyleicosylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, Ethyl octadecyl malonic acid, ethyl eicosyl malonic acid, ethyl docosyl malonic acid, ethyl tetracosyl malonic acid, etc.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (6) is also preferably used. (However, R ₉ represents an aliphatic group having 12 or more carbon atoms,
n represents 0 or 1, m represents 1, 2 or 3, m is 2 or 3 when n is 0, and m is 1 or 2 when n is 1) Specific examples of the dibasic acid represented by) include the following. 2-dodecyl-pentanedioic acid, 2-hexadecyl-pentanedioic acid, 2-octadecyl-pentanedioic acid, 2-eicosyl-pentanedioic acid, 2-docosyl-pentanedioic acid, 2-dodecyl-hexanedioic acid, 2- Pentadecyl-hexanedioic acid, 2-octadecyl-hexanedioic acid, 2-eicosyl-hexanedioic acid, 2-docosyl-hexanedioic acid and the like.

As the aliphatic carboxylic acid compound, a tribasic acid such as citric acid acylated with a long chain fatty acid is also preferably used. Specific examples thereof include the following.

(C) Phenol compound A compound represented by the following general formula (7) is preferably used.

[Chemical 1] (However, Y is -S-, -O-, -CONH-, or -C.
Represents OO-, R ₁₀ represents an aliphatic group having 12 or more carbon atoms, and n is an integer of 1, 2, or 3). Specific examples of the phenol compound represented by the general formula (7) include the followings. p- (dodecylthio) phenol, p- (tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (eicosylthio) phenol, p- (docosylthio) phenol, p- (tetracosyl) Ruthio) phenol, p- (dodecyloxy)
Phenol, p- (tetradecyloxy) phenol,
p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy)
Phenol, p- (docosyloxy) phenol, p-
(Tetracosyloxy) phenol, p-dodecylcarbamoylphenol, p-tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol,
p-octadecylcarbamoylphenol, p-eicosylcarbamoylphenol, p-docosylcarbamoylphenol, p-tetracosylcarbamoylphenol, hexadecyl gallate, octadecyl gallate, eicosyl gallate, docosyl gallate, Gallic acid tetracosyl ester etc.

(D) Organic phosphoric acid compound [alpha] -hydroxyalkylphosphonic acid represented by the following general formula (8) can also be preferably used. (However, R ₁₁ is an aliphatic group having ₁₁ to 29 carbon atoms)
Specific examples of the α-hydroxyalkylphosphonic acid represented by the general formula (8) include α-hydroxydodecylphosphonic acid, α-hydroxytetradecylphosphonic acid, α-
Examples thereof include hydroxyhexadecylphosphonic acid, α-hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid, α-hydroxydocosylphosphonic acid, and α-hydroxytetracosylphosphonic acid.

(E) Metal salt of mercaptoacetic acid A metal salt of an alkyl or alkenyl mercaptoacetic acid represented by the general formula (9) can also be preferably used. _{(R 12 -S-CH 2 -COO} ) 2 M (9) ( provided that, R ₁₂ represents an aliphatic group having from 10 to 18 carbon atoms, M represents tin, magnesium, zinc or copper) formula (9 Specific examples of the mercaptoacetic acid metal salt represented by the formula (1) include the following. Decyl mercapto acetate tin salt, dodecyl mercapto acetate tin salt, tetradecyl mercapto acetate tin salt, hexadecyl mercapto acetate tin salt, octadecyl mercapto acetate tin salt,
Decyl mercapto acetic acid magnesium salt, dodecyl mercapto acetic acid magnesium salt, tetradecyl mercapto acetic acid magnesium salt, hexadecyl mercapto acetic acid magnesium salt, octadecyl mercapto acetic acid magnesium salt,
Decyl mercapto acetic acid zinc salt, dodecyl mercapto acetic acid zinc salt, tetradecyl mercapto acetic acid zinc salt, hexadecyl mercapto acetic acid zinc salt, octadecyl mercapto acetic acid zinc salt, decyl mercapto acetic acid copper salt, dodecyl mercapto acetic acid copper salt, tetradecyl mercapto acetic acid copper salt , Hexadecylmercaptoacetic acid copper salt, octadecylmercaptoacetic acid copper salt and the like.

The color former in the thermochromic element has an electron donating property, and is itself a colorless or light-colored dye precursor, and is not particularly limited, and conventionally known compounds such as triphenylmethanephthalide compounds. Fluoran compounds, phenothiazine compounds, leuco auramine compounds, indinophthalide compounds and the like are used. Specific examples of the color former are shown below.

Preferred color formers for use in the present invention are compounds represented by the following general formula (10) or (11).

[Chemical 2]

[Chemical 3] (However, R ₃ represents hydrogen or an alkyl group having 1 to ₄ carbon atoms, R ₄ represents an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group or an optionally substituted phenyl group. As a substituent for the phenyl group, , .R ₆ representing an alkyl group such as a methyl group, an ethyl group, a methoxy group, .R ₅ is hydrogen alkoxy group or a halogen or the like, such as ethoxy group is indicated, an alkyl group having 1 to 2 carbon atoms, an alkoxy group or a halogen Represents hydrogen, a methyl group, halogen or an amino group which may be substituted. Examples of the substituent for the amino group include an alkyl group, an aryl group which may be substituted and an aralkyl group which may be substituted. The substituent here is an alkyl group, a halogen, an alkoxy group, or the like). Specific examples of such a color former include the following compounds.

2-anilino-3-methyl-6-diethylaminofluorane 2-anilino-3-methyl-6- (di-n-butylamino) fluorane, 2-anilino-3-methyl-6- (N
-N-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-ethylamino) fluorane, 2-anilino-3-methyl-6- (N
-N-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-diethylaminofluor Oran, 2
-(M-Trifluoromethylanilino) -3-methyl-6
-(N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-dimethylanilino) -3-methyl-
6-diethylaminofluorane, 2- (N-ethyl-p
-Toluidino) -3-methyl-6- (N-ethylanilino) fluorane, 2- (N-methyl-p-toluidino)
-3-Methyl-6- (N-propyl-p-toluidino)
Fluoran,

2-anilino-6- (Nn-hexyl-
N-ethylamino) fluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (o-bromoanilino) -6-diethylaminofluorane, 2-
(O-Chloranilino) -6-dibutylaminofluorane, 2- (o-fluoroanilino) -6-dibutylaminofluorane, 2- (m-trifluoromethylanilino)
-6-Diethylaminofluorane, 2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) ) Fluoran, 2-benzylamino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-)
2,4-Dimethylanilino) fluorane, 2-dibenzylamino-6- (N-methyl-p-toluidino) fluorane, 2-dibenzylamino-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-methylanilino) 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-methyl-anilino) fluorane, 2-dipropylamino-6- (N-ethyl-anilino) 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-dimethylanilino) fluorane, 2-amino-6- (N-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p-chloranilino) ) Fluoran, 2-amino-6
-(N-ethyl-p-chloroanilino) fluorane, 2
-Amino-6- (N-propyl-p-chloranilino)
Fluoran,

2,3-Dimethyl-6-dimethylaminofluorane, 3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane, 2-bromo-6-diethylamino Fluoran, 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-
Chlor-6-cyclohexylaminofluorane, 2-
(M-Trifluoromethylanilino) -3-chloro-6-
Diethylaminofluorane, 2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane, 1,2-benzo-6-diethylaminofluorane,
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-toluidino) fluorane, and others.

Specific examples of other color formers preferably used in the present invention are as follows. 2-anilino-3-methyl-6- (N-2-ethoxypropyl-N-
Ethylamino) fluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2
-(P-chloranilino) -6- (Nn-palmitylamino) fluorane, 2- (p-chloranilino) -6
-(Di-n-octylamino) fluorane, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (o-methoxybenzoylamino) -6-
(N-methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 2-dibenzylamino-4-methoxy-6- (N
-Methyl-P-toluidino) fluorane, 2-benzylamino-4-methyl-6- (N-ethyl-P-toluidino) fluorane, 2- (α-phenylethylamino)-
4-methyl-6-diethylaminofluorane, 2- (p
-Toluidino) -3- (t-butyl) -6- (N-methyl-p-toluidino) fluorane, 2- (o-methoxycarbonylanilino) -6-diethylaminofluorane, 2-acetylamino-6- ( N-methyl-p-toluidino) fluorane, 3-diethylamino-6- (m-
Trifluoromethylanilino) fluorane, 4-methoxy-6- (N-ethyl-p-toluidino) fluorane,
2-ethoxyethylamino-3-chloro-6-dibutylaminofluorane, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-toluidino) fluorane, 2
-(Α-phenylethylamino) -4-chloro-6-diethylaminofluorane, 2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluorane, 2-anilino-3 -Methyl-6-pyrrolidinofluorane, 2-anilino-3-chloro-6-
Pyrrolidinofluorane, 2-anilino-3-methyl-6
-(N-ethyl-N-tetrahydrofurfurylamino)
Fluorane, 2-mesidino-4 ', 5'-benzo-6-
Diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-pyrrolidinofluorane, 2- (α-naphthylamino) -3,4-benzo-
4'-Bromo-6- (N-benzyl-N-cyclohexylamino) fluorane, 2-piperidino-6-diethylaminofluorane, 2- (Nn-propyl-p-trifluoromethylanilino) -6-morpho Rinofluorane, 2- (di-Np-chlorophenyl-methylamino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinoflu Oran, 1,2-benzo-6- (N-ethyl-
Nn-octylamino) fluorane, 1,2-benzo-6-diallylaminofluorane, 1,2-benzo-6
-(N-ethoxyethyl-N-ethylamino) fluorane,

Benzoleucomethylene blue, 2- [3,
6-bis (diethylamino)]-6- (o-chloroanilino) xanthyl benzoate lactam, 2- [3,6-bis (diethylamino)]-9- (o-chloroanilino)
Lactam xanthyl benzoate, 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-
Bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3- (2 -Methoxy-
4-Dimethylaminophenyl) -3- (2-hydroxy-4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-
Methoxy-5-chlorophenyl) phthalide, 3- (2-
Hydroxy-4-dimethoxyaminophenyl) -3-
(2-Methoxy-5-chlorophenyl) phthalide, 3-
(2-hydroxy-4-dimethylaminophenyl) -3
-(2-Methoxy-5-nitrophenyl) phthalide, 3
-(2-hydroxy-4-diethylaminophenyl)-
3- (2-methoxy-5-methylphenyl) phthalide,
3- (2-methoxy-4-dimethylaminophenyl)-
3- (2-hydroxy-4-chloro-5-methoxyphenyl) phthalide, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 6'-chloro-8 '-Methoxy-benzoindolino-spiropyran, 6'-bromo-2'-methoxy-benzoindolino-spiropyran, and others.

The ratio of the color former and the developer constituting the reversible thermochromic element needs to be selected in accordance with the physical properties of the compound to be used, but the range is generally about the molar ratio of the color former 1 In contrast, the color developer is in the range of 1 to 20,
It is preferably in the range of 2 to 10. The decoloring property changes depending on the ratio of the color developer and the color developer. When the amount of the color developer is relatively large, the decolorization start temperature becomes low, and when the amount of the color developer is relatively small, the decolorization becomes sharp with respect to temperature. . Therefore, this ratio may be appropriately selected according to the use and purpose. The reversible thermochromic element used in the present invention is basically composed of the above-mentioned developer and color former, but for the purpose of improving various properties such as decoloring property and storability,
Additives that have the effect of controlling the crystallization of the developer can be included.

Next, a reversible thermosensitive recording medium using a reversible thermochromic element will be described. The recording medium in the present specification includes a display body. The reversible thermosensitive recording medium is one in which a recording layer containing the above-mentioned reversible thermochromic element is provided on a support. The support is, for example, paper, synthetic paper, a plastic film or a composite thereof, a glass plate, and the like, as long as it can hold the recording layer. The recording layer may have any form as long as the reversible thermochromic element is present. In order to take the form as a layer, as is usually done,
If necessary, a binder resin may be used to hold the device. As the binder, for example, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid esters, poly There are methacrylic acid esters, acrylic acid copolymers, maleic acid copolymers, polyvinyl alcohol, and the like. The element can be used by being encapsulated in a microcapsule. Microcapsulation of the device can be carried out by a known method such as a coacervation method, an interfacial polymerization method, an in situ polymerization method. The recording layer is formed by uniformly dispersing or dissolving the element with a binder in water or an organic solvent according to a conventionally known method, and coating and drying the element on a support. When a binder is not used, the element can be mixed and melted to form a film, and cooled to form a recording layer. The role of the binder resin in the recording layer is to maintain the state in which the reversible thermochromic elements are uniformly dispersed by repeating coloring and decoloring. In particular, since the elements often aggregate and become non-uniform when heat is applied during color development, a binder resin having high heat resistance is preferable.

The light resistance of the reversible thermosensitive recording medium can be improved by incorporating a light stabilizer in the recording layer. Examples of the light stabilizer include an ultraviolet absorber, an antioxidant, an antioxidant, a quencher for singlet oxygen, and a quencher for superoxide anion.

In order to perform recording using a recording medium using a reversible thermochromic element, the element is temporarily heated to a melting temperature or higher to bring it into a colored state. On the other hand, in order to erase the recording, the recording layer in the color-developed state is heated to the decoloring temperature below the melting temperature. The image formed on the recording medium includes one in which a color-developed image is formed on the background portion in the decolored state, and conversely, one in which a decolored image is formed on the background portion in the colored state. In both cases, when heat is applied in an image-like manner, a means such as a heating pen, a thermal head, or laser beam heating that can partially apply heat may be used. In the case of erasing the entire surface or developing the entire surface, there are methods such as contacting with a heat roller or a whole surface heater, blowing hot air, placing in a heated constant temperature bath, or irradiating with infrared rays. Of course, the entire surface may be heated with a thermal head.

The method for reversibly exhibiting the function of the functional element of the present invention has been described above by using the example of the reversible thermochromic element using the color former and the developer, but the gist of the present invention is this example. The present invention is not limited to the above, but provides a method applicable to other functional devices that reversibly take a state where two kinds of compounds interact and a state where they do not interact.

As an example of controlling an interaction different from that of the above reversible thermochromic element, an element in which a long chain alkylphosphonic acid and a long chain alkyl ester of gallic acid are combined is shown. FIG. 9 shows infrared absorption spectra of a device in which docosylphosphonic acid and octadecyl gallate were mixed at a molar ratio of 5: 1 and which was rapidly cooled from a molten state and gradually cooled.
Shown in. The absorption peak of the C = O stretching vibration of gallic acid octadecyl ester, which appears near 1700 cm ^{-1 in the} spectrum, differs greatly between rapid cooling and slow cooling, and it can be seen that there is a difference in the state of interaction with phosphonic acid molecules. . The results of infrared absorption spectrum measurement while raising the temperature of the rapidly cooled element are shown in FIG. The spectrum shows that both are mixed and melted 9
It can be seen that the temperature changes in the vicinity of 60 ° C., which is considerably lower than 3 ° C., and becomes the same state as when gradually cooled. And 70-90 ℃
The temperature of the element cooled from the temperature of 1 corresponds to the spectrum of the slowly cooled element.

On the other hand, the results of X-ray diffraction of the rapidly cooled element and the slowly cooled element are shown in FIGS. 11 and 12. The quenched elements were 1.59 °, 3.22 °, 4.84 ° and 21.1 °.
A peak indicating the formation of a regular aggregate structure is observed at °.
These diffraction peaks do not match the peaks of the individual crystals of docosylphosphonic acid and octadecyl gallate, and it can be seen that the two interact and cooperate to form a regular aggregate structure. The slowly cooled element is different from the rapidly cooled element at 1.76 °, 2.16 °, 4.00
°, 4.34 °, 6.54 °, 8.74 °, 10.94
There are diffraction peaks at °, 22.34 °, 23.94 ° and so on. All of these coincide with the peaks of a single crystal of docosylphosphonic acid. Therefore, it is understood that the slowly cooled state is a state in which dogosylphosphonic acid is crystallized alone.
FIG. 13 shows the result of X-ray diffraction measurement while raising the temperature of the rapidly cooled element. (A) shows a change on the low angle side, and (b) shows a change on the high angle side. It can be seen that in both cases, in the vicinity of 50 to 60 ° C., the aggregate structure formed due to the mutual action of the two changes to crystals of docosylphosphonic acid alone.

From the above results, even in an element composed of a combination of docosylphosphonic acid and octadecyl gallate, rapid cooling was performed to form a regular aggregation structure, and the temperature was raised to collapse the aggregation structure, It can be seen that the method of independently crystallizing the compound makes it possible to reversibly and arbitrarily take a state in which both interact and a state in which they do not interact. Such a change between two states can be functionalized, for example, as a reversible change of the nonlinear optical property, and can be said to show the effectiveness of the reversible function expressing method of the present invention. .

[0057]

EXAMPLES Next, the present invention will be described in more detail by way of examples. In the examples, parts and% are based on weight. Example 1 2- (o-chloranilino) -6-dibutylaminofluorane was used as a color former, and a thermochromic element was prepared by using phosphonic acid having a long-chain alkyl group shown in Table 2 as a developer. Created as. First, the color former and the developer were weighed so as to have a mixing ratio (molar ratio) of 1: 5, pulverized and mixed in a mortar. A 1.2 mm thick glass plate was heated to a temperature of 170 ° C. on a hot plate. On this glass plate, a small amount of the above mixture was applied and melted. The mixture developed a color upon melting and turned black. Then, a cover glass was covered on the molten mixture, the melt was spread to a uniform thickness, and immediately the whole glass plate was immersed in the prepared ice water and quenched.
Immediately after the temperature was lowered, it was taken out from the ice water and the attached water was removed to obtain a thin film-like colored element. When these 6 types of elements were cooled at a rate of 4 ° C./minute from the heated and melted state, they could not maintain the coloring state and almost disappeared.

Next, the following measurements were carried out in order to investigate the coloring and decoloring characteristics of this device. A sample heating device was installed on the sample stage of the optical microscope, and the above-described colored element sample was observed at room temperature and at the same time, the temperature was raised at a rate of 4 ° C./min. At the same time, the change in the amount of light passing through the sample from the light source of the microscope and reaching the eyepiece was measured. As a result,
It was confirmed that the device was decolored at a certain temperature and the amount of light increased at the same time, and when the temperature was further increased, the color recurred at a melting temperature. Further, the decolorization start temperature was determined from the change in the amount of transmitted light. The temperature change of the amount of transmitted light was measured for the element in the colored state using phosphonic acid having a straight chain alkyl group having 12 to 22 carbon atoms, and the results of FIG. 4 were obtained. The light transmission amount in the figure is displayed with the initial color development state being 1.0. From this figure, it can be seen that each phosphonic acid has a temperature range in which color disappears, and the decolorization start temperature shifts to the higher temperature side as the alkyl chain length increases. Table 2 shows the decolorization start temperature of each phosphonic acid. Further, the erasing rate was obtained from the density (DQ) at the time of rapid color development and the density (DE) at the time of maximum erasing. The results are shown in Table 2.
Shown in. Decoloring rate = [(DQ-DE) / DQ] × 100 (%) It is understood that the longer the alkyl chain length, the higher the decoloring rate and the better reversibility is obtained.

[0059]

[Table 2]

Example 2 Eicosylthiomalic acid was used as the color developer, and the fluoran compound shown in Table 3 was used as the color developer, with a mixing ratio of 2/1 (developing agent / color developing agent: molar ratio). A device in a colored state was prepared in the same manner as in 1. Although these elements could maintain the color development state upon rapid cooling, they almost disappeared upon slow cooling. From the X-ray diffraction, it was found that the developer and the color former jointly form a basic aggregation structure in the rapid cooling, and the developer alone crystallizes in the slow cooling. FIG. 14 shows the temperature change of the amount of transmitted light for the elements in these coloring states. In addition, Table 3 shows the decolorization start temperature obtained from this figure. It can be seen that these elements also have a clear decolorization temperature region and are reversible thermochromic elements.

[0061]

[Table 3]

Example 3 In order to prepare a recording layer containing a reversible thermochromic element composed of a developer having a long-chain structure and a color former, the composition shown in Table 4 below was used in a ball mill to prepare particles having particle sizes 1 to 1. The recording layer coating liquid was prepared by pulverizing and dispersing to 4 μm. Table 4 shows combinations of the color-developing agent and the color-developing agent used here. Each coating solution having the above composition was coated on a polyester film having a thickness of 100 μm with a wire bar and dried to prepare a reversible thermosensitive recording medium having a recording layer having a thickness of about 6.0 μm. Using a thermal tilt tester (manufactured by Toyo Seiki Seisakusho), these recording media were heated at a temperature of 130 ° C. and a pressure of 1 kg / cm ² for 1 second to bring them into contact with a heating element to develop a color, and measure the color density. did. A Macbeth densitometer RD-918 was used for the concentration measurement (all the following examples are the same). The color density of each recording material is shown in Table 5. Next, the color-developed recording medium was put into a thermostat having a decoloring temperature shown in Table 5 for about 20 seconds to be decolored, and the decoloring density was measured. Table 5 shows the decolorization density of each recording medium.
Shown in. Furthermore, when the above-described coloring operation and decoloring operation were repeated 10 times and the reversibility of coloring was examined, it was confirmed that the coloring and decoloring can be repeated for all combinations of the examples.

[0063]

[Table 4- (1)]

[0064]

[Table 4- (2)]

[0065]

[Table 4- (3)]

[0066]

[Table 4- (4)]

[0067]

[Table 4- (5)]

[0068]

[Table 4- (6)]

[0069]

[Table 4- (7)]

[0070]

[Table 5- (1)]

[0071]

[Table 5- (2)]

[0072]

[Table 5- (3)]

[0073]

[Table 5- (4)]

[0074]

[Table 5- (5)]

Example 4 A reversible thermochromic element was prepared in the same manner as in Example 1 except that the fluorane compounds shown in Table 6 were used as the color former and octadecylphosphonic acid was used as the color developer. Table 6 shows the results of determining the decolorization rate.

[0076]

[Table 6]

[0077]

The method for expressing the function of a functional element according to the present invention uses a functional element composed of two kinds of compounds having different properties, which is used between a state where both compounds interact and a state where they do not interact. Is reversibly transferred. Moreover, the interacted state is a state of a regular aggregation structure formed by both compounds in cooperation, and the non-interacted state is that at least one compound of both compounds is independent. Since it is in the aggregated or crystallized state, the function expression by the reversible transition between the states of the functional element can be caused very quickly, and the thermal means can be used as a means therefor. There is. The present invention can be applied to various fields including a thermal recording medium and a thermal display medium.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between color development and color disappearance of a reversible thermochromic element and temperature.

FIG. 2 is an X-ray diffraction diagram showing a state in which a thermochromic element is rapidly cooled from a melted and colored state.

FIG. 3 is another X-ray diffraction diagram showing a state in which the thermochromic element is rapidly cooled from the melt-colored state.

FIG. 4 is a diagram showing a state of decoloring when the temperature of the reversible thermochromic element is raised from the rapidly cooled color development state.

FIG. 5 is a diagram showing changes in X-ray diffraction when the temperature of the reversible thermochromic element is increased from the rapidly cooled color development state.

FIG. 6 is a diagram showing a change in X-ray diffraction when the temperature of a reversible thermochromic element is increased from a rapidly cooled color development state.

FIG. 7 is an X-ray diffraction diagram showing a state when the comparative element is rapidly cooled from the molten color-developed state.

FIG. 8 is an X-ray diffraction diagram showing a state when the comparative element is rapidly cooled from the molten color-developed state.

FIG. 9 is an infrared absorption spectrum diagram showing a change in the interaction state of functional elements.

FIG. 10 is a diagram showing a temperature change of an infrared absorption spectrum showing how the state of interaction changes when the temperature of a rapidly cooled element is raised.

FIG. 11: X showing regular aggregated structure formation in a quenched device
Line diffraction diagram.

FIG. 12 is an X-ray diffraction diagram showing that the gradually cooled element is in a single crystallized state.

FIG. 13 is an X-ray diffraction diagram showing a state in which the regularly aggregated structure of a rapidly cooled element is disintegrated by temperature rise and is independently crystallized.

FIG. 14 is a diagram showing a state of decoloring when the temperature of the reversible thermochromic element is raised from the rapidly cooled color development state.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaru Shimada 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Company (72) Inventor Hiroshi Goto 1-3-6 Nakamagome, Ota-ku, Tokyo Shares In Ricoh Company (72) Inventor Ichiro Sawamura 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh (72) Inventor Eiichi Kawamura 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh ( 72) Inventor Katsuji Maruyama, 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor, Hiroki Kuboyama 1-3-6, Nakamagome, Ota-ku, Tokyo (72) Invention Person Keiji Kubo 1-3-2 Honmoku Arai, Naka-ku, Yokohama-shi, Kanagawa

Claims (5)

[Claims] 1. A state in which two kinds of compounds interact with each other and a state in which they do not interact with each other, and the interacted states are:
The two compounds are in a state of a regular aggregation structure formed jointly, and the non-interacting state is obtained by using a functional element in which at least one compound is independently aggregated or crystallized. A reversible function expressing method for a functional device, which comprises reversibly transitioning between two states. 2. The functional element shows a state of a regular agglomerated structure when it is rapidly cooled after melting, while it shows a state of at least one compound alone agglomerated or crystallized when slowly cooled after melting. The reversible function expressing method for a functional device according to claim 1, wherein 3. The state of a regular agglomerate structure formed by two kinds of compounds in cooperation is formed when the two compounds are heated and melted and mixed and then rapidly cooled. Item 1. A method for reversibly exhibiting a function of the functional element according to item 1 or 2. 4. A regular agglomerated structure in which two kinds of compounds are jointly formed is heated to a temperature lower than the temperature at which both compounds are melt-mixed to collapse the regular agglomerated structure. The method for causing reversible function development of the functional element according to any one of claims 1 to 3, wherein at least one of the compounds is aggregated or crystallized by itself so as not to interact with each other. 5. The regular agglomeration structure in which two kinds of compounds retain the interaction is formed by the action of the aggregating force of the long-chain structure of at least one of the compounds. A method for reversibly exhibiting a function of the functional element according to any one of claims 1 to 4.