JP4948057B2 - Reversible recording medium - Google Patents

Description

  The present invention relates to a reversible recording medium in which image formation and erasure can be repeated, and the image does not change even when exposed to water or a solvent.

  With the development and popularization of computer and network technologies, the amount of paper used in offices continues to increase as mass information processing and high-speed processing become possible. Even though most information is now digitized and processed electronically, it is not enough for a person to think about it simply because it is viewed on a display. In the case of printing on paper using a printer or the like.

  Paper has advantages such as ease of viewing that does not cause eyestrain, ease of handling and lightness that can be viewed anywhere without the need for a power source, and allows you to view a lot of necessary information side by side. Because it has a list, it is indispensable as a thinking environment. However, on the other hand, the large consumption of paper has created environmental problems such as depletion of forest resources and social problems such as the large generation of paper waste. Recycling to collect and recycle used paper is in progress, but even with recycled paper, the power and water required during production are not much different from paper made from new pulp, and this alone cannot solve the problem. .

  On the other hand, a reversible recording medium that can rewrite an image many times and can be used repeatedly has been proposed as a solution to the above-described problem. For example, a reversible recording material (Patent Document 1) that has a mat-like surface and is opaque when no solvent is present but is transparent when it accepts the solvent, can be finitely swollen by the solvent. There has been proposed a reversible recording material (Patent Document 2) having a solvent-receiving layer that is mainly composed of a solvent-absorbing resin and is not cloudy when no solvent is present, but is clouded when a solvent is received.

Japanese Patent Laid-Open No. 10-157280 (Claims) JP-A-10-272829 (Claims)

  Such a reversible recording material forms characters and the like by providing a difference in the refractive index between the printed portion and the non-printed portion by printing with an ink jet printer using water or alcohol as an ink. The water, alcohol, etc. evaporate and return to the original state after a certain period of time. However, with such a reversible recording material, if the recording surface is exposed to a solvent such as water or alcohol after printing, the refractive index will also change in portions other than the printing portion, and the original characters and the like can be recognized. It was causing the problem of disappearing.

  Therefore, the present invention is not intended for long-term storage, and when used as a temporary output application, even if it is exposed to water or a solvent, it does not affect the image area, and even if it is used many times, the image forming performance An object of the present invention is to provide a recording medium that does not deteriorate.

  As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention have made it possible to rewrite the recording medium repeatedly as a method for making the refractive index of the printed portion and the non-printed portion as described above which has been conventionally performed. The present invention has been found by newly finding a method using a redox reaction of a heteropolyacid or a salt thereof rather than a method using the difference.

  That is, as a member constituting the reversible recording medium, a reversible recording layer containing a heteropolyacid or a salt thereof is provided, and the heteropolyacid or a salt thereof is formed by irradiating ultraviolet rays or applying a voltage to any part where an image is to be formed. Utilizing the property that the part turns blue by the reduction reaction, and the oxidation reaction of the part starts afterwards due to the influence of oxygen molecules in the atmosphere. I found something to do.

  In addition, heteropolyacids or salts thereof that are merely immobilized to the binder component by electrostatic interaction or physical action flow out when washed with water or a solvent, but are immobilized by chemical bonds. As a result, it has been found that the heteropolyacid or its salt does not flow out even when exposed to water or a solvent. Therefore, a recording medium that does not affect the image area even when exposed to water or a solvent and does not affect the image area, and that does not deteriorate the image forming performance even when used many times. It has been found that this can be achieved, and the present invention has been achieved.

  The reversible reversible recording medium of the present invention having a reversible recording layer has a heteropolyacid or a salt thereof fixed in the reversible recording layer by a chemical bond.

  In the reversible recording medium of the present invention, a heteropolyacid or a salt thereof is fixed by a covalent bond in a reversible recording layer.

  In the reversible recording medium of the present invention, the heteropolyacid or a salt thereof has a reactive organic functional group.

  In the reversible recording medium of the present invention, the reactive organic functional group is a group having an unsaturated double bond.

  In the reversible recording medium of the present invention, a heteropolyacid or a salt thereof is modified with a hydrolyzate of a metal alkoxide.

  According to the reversible recording medium of the present invention, even when an image is formed many times, the image formation performance can be repeated without being deteriorated, and even when exposed to water or a solvent. Since the heteropolyacid or its salt does not flow out, the image can be recognized without damaging the image portion. Therefore, such a reversible recording medium is suitable not only for temporary output of meeting materials and e-mail documents in an indoor environment such as an office, but also for a guide board that presents information only for a short period in an outdoor environment. Can be used.

  Hereinafter, embodiments of the reversible recording medium of the present invention will be described.

  The reversible recording medium of the present invention has a reversible recording layer, and has a heteropolyacid or a salt thereof immobilized in the reversible recording layer by a chemical bond.

  The reversible recording layer used in the present invention refers to a layer in which image formation and erasure can be repeated, and has a heteropolyacid or a salt thereof immobilized in the reversible recording layer by a chemical bond. As described above, since the reversible recording layer has the heteropolyacid or salt thereof, the heteropolyacid or salt thereof can be colored by utilizing the reduction reaction of the heteropolyacid or salt thereof to form a desired image. can do. Further, the color development of the heteropolyacid or a salt thereof is easily lost by an oxidation reaction with oxygen molecules in the atmosphere, and can be suitably used for short-term image display.

  Further, since the reversible recording layer is formed by immobilizing a heteropoly acid or a salt thereof by a chemical bond, the heteropoly acid or a salt thereof is merely immobilized by an electrostatic interaction or a physical action. The problem of the outflow of the heteropolyacid or its salt, which has been caused when using, can be solved. Therefore, even if it is used many times, it is possible to repeatedly form and erase images without deteriorating the image forming performance, and even when exposed to water or a solvent, the image is recognized without being affected. The remarkable effect that cannot be achieved in the past is exhibited.

  Chemical bonds that immobilize the heteropolyacid or its salt in the reversible recording layer include common chemical bonds such as covalent bond, ionic bond, and coordinate bond, but it prevents the outflow of the heteropolyacid or its salt. From the viewpoint of more firmly immobilizing the heteropolyacid or a salt thereof, a covalent bond is preferable.

  In addition, the heteropolyacid or salt thereof used in the present invention is a reactive organic compound from the viewpoint of suitable chemical bonding between the heteropolyacid or salt and carrier, or between the heteropolyacid or salt in the reversible recording layer. It is preferable that it has a functional group. Examples of such reactive organic functional groups include hydroxyl group, (meth) acryl group, vinyl group, epoxy group, styryl group, (meth) acryloxy group, amino group, mercapto group, isocyanate group and the like.

  Among the functional groups described above, the (meth) acryl group, vinyl group, styryl group, and (meth) acryloxy group, which are groups having an unsaturated double bond, are general-purpose monomers having an unsaturated double bond, or The heteropolyacids or their salts can be easily chemically bonded, and the physical properties of the coating film can be adjusted well. Among these, it is particularly preferable to use a (meth) acryl group.

  As such a heteropolyacid having a reactive organic functional group or a salt thereof, as shown in the general formula (1), a heteropolyacid or salt thereof modified with a metal group having a reactive organic functional group may be used. Can be mentioned.

R _m [XY] · nH ₂ O (1)
[Wherein, R is a counter cation of a heteropolyacid or a salt thereof, X is a heteropolyanion in which a part of the skeleton constituent atoms is missing, and Y is a metal group having a reactive organic functional group. n is an integer greater than or equal to 1, m is an integer greater than or equal to 1, and is the absolute value of the negative charge determined from [XY] in the general formula (1). ]

R in the general formula (1) represents a counter cation of a heteropolyacid or a salt thereof. For example, Bu ₄ N ⁺ , Me ₂ NH ₂ ⁺ , H ⁺ , Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ^{+ and the} like can be mentioned. Among these, a heteropolyacid whose counter cation is H ⁺ is particularly preferable because it has good solubility in various solvents. In addition, by using a free acid type heteropolyacid having H ⁺ as a counter cation in this way, the antistatic property can be improved. Therefore, such a heteropolyacid is contained in a fuel cell separator. As a result, the proton transport ability of the fuel cell can be improved. Furthermore, since the free acid type heteropolyacid is known to act as a strong solid acid in the solid state, the free acid type heteropolyacid can be easily separated and regenerated by immobilizing the free acid type heteropolyacid in the carrier. It can be used as an acid catalyst.

X in the general formula (1) represents a heteropolyanion in which a part of the skeleton constituent atoms is missing. Such heteropolyanions include [P ₂ W ₁₇ O ₆₁ ] ¹⁰⁻ , [PW ₁₁ O ₃₉ ] ⁷⁻ , [γ-PW ₁₀ O ₃₆ ] ⁷⁻ , [SiW ₁₁ O ₃₉ ] ^8- , [γ -SiW ₁₀ O ₃₆ ] ^8- , [GeW ₁₁ O ₃₉ ] ^{8- and the} like.

  The heteropolyacid salt in which the skeleton constituent atoms are partially lost can be obtained by referring to known literature. For example, R.A. Contant, Inorg. Synth. 27, 104, 1990. (America).

  Y in the general formula (1) represents a metal group having a reactive organic functional group. Examples of such a metal group include a hydrolyzate or metal chloride of a metal alkoxide. Among these, it is preferable in the process for producing the modified heteropolyacid or salt thereof used in the present invention to modify the heteropolyacid or salt thereof with a hydrolyzate of metal alkoxide. Examples of the hydrolyzate of metal alkoxide include hydrolysates such as silane coupling agents, titanium coupling agents, aluminum coupling agents, and zirconium coupling agents. Among these, it is preferable to use a hydrolyzate of a silane coupling agent from the viewpoint of the variety of reactive functional groups, good handleability, and availability. Examples of the metal chloride include titanium chloride, silyl chloride, tin chloride and the like.

Specific examples of Y in the general formula (1) include {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O, {CH ₂ CHCOO (CH ₂ ) ₃ Si} ₂ O, {CH ₂ CHSi } ₂ O, {CH ₂ CHC ₆ H ₆ Si} ₂ O, {CH ₂ (O) CHCH ₂ O (CH ₂ ) ₃ Si} ₂ O, {NH ₂ (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si } ₂ O, {NH ₂ (CH ₂ ) ₃ Si} ₂ O, {SH (CH ₂ ) ₃ Si} ₂ O, {OCN (CH ₂ ) ₃ Si} ₂ O, and the like. Moreover, what changed these Si of Y into Ti, Al, and Zr is also mentioned.

  The heteropolyacid of general formula (1) or a salt thereof can be obtained, for example, by introducing a metal group having a reactive organic functional group as described above into a part of the skeleton constituting atom of the heteropolyacid or a salt thereof. Obtainable.

Specifically, a part of skeleton constituent atoms such as K ₁₀ [P ₂ W ₁₇ O ₆₁ ] separately synthesized in a solution in which a metal alkoxide having a reactive organic functional group is first dissolved in a mixture of water and alcohol. Add the stoichiometric amount of the heteropolyacid salt deficient in the above and stir. Next, the pH of the solution is adjusted to about 3 or less with hydrochloric acid. By this operation, the metal alkoxide is hydrolyzed in the reaction system, and the hydrolyzate is introduced into a part of the skeleton constituting atom of the heteropolyacid salt by a dehydration condensation reaction. A counter cation such as Me ₂ NH ₂ ⁺ is then added to the resulting solution to form a heteropolyacid salt as a precipitate. The produced precipitate can be filtered off and sufficiently dried under vacuum to obtain a modified heteropolyacid salt as a powder.

In addition, when H ⁺ having excellent solubility is selected as the counter cation, water-soluble Me ₂ NH ₂ ⁺ salt is recovered as a powder, and then the product name Amberlite 120NBA of Rohm and Haas is used. By performing cation exchange using a cation exchange resin, a modified heteropolyacid having H ⁺ as a counter cation can be produced.

  The carrier on which the heteropolyacid or salt thereof can be immobilized may be a polymer having a functional group capable of reacting with the above-described reactive organic functional group. Examples of such polymers include those having a hydroxyl group, (meth) acryl group, vinyl group, epoxy group, styryl group, (meth) acryloxy group, amino group, mercapto group, isocyanato group in the side chain. .

  In addition, if the heteropolyacid or its salt has a reactive organic functional group capable of being polymerized, it can be obtained by copolymerizing the reactive organic functional group in the heteropolyacid or its salt with a polymerizable monomer. The resulting polymer may be used as a carrier for immobilization.

  Furthermore, since the heteropolyacid or a salt thereof can be polymerized with the heteropolyacid or a salt thereof, it can be immobilized without using the carrier as described above.

  A method of immobilizing a heteropolyacid or a salt thereof with a carrier or a heteropolyacid or a salt thereof can be performed by a reaction of a reactive organic functional group. Hereinafter, a heteropolyacid having an unsaturated double bond is used. An example using an acid will be described.

  First, a three-necked flask containing a predetermined amount of a reaction solvent, a heteropolyacid having an unsaturated double bond, a general-purpose acrylic monomer and a polymerization initiator is prepared, and the inside of the reaction system is replaced with nitrogen while stirring. After purging with nitrogen, the flask is immersed in a 75 ° C. oil bath and the system is heated. The mixture is heated and stirred for 4 hours while keeping the temperature of the oil bath at 75 ° C. After 4 hours, the reaction solution is allowed to cool to room temperature, and the solution is added dropwise to a large amount of methanol to reprecipitate the polymer. After stirring overnight, the precipitate is separated and sufficiently dried by suction, whereby an acrylic polymer having a heteropolyacid immobilized by a covalent bond can be obtained.

  The acrylic polymer thus obtained is dissolved or dispersed in an appropriate solvent to prepare a coating solution, and the coating solution is prepared by a known method such as a roll coating method, a bar coating method, a spray coating method, or an air knife coating method. A reversible recording medium can be obtained by coating and drying on a support.

  Here, for example, paper, synthetic paper, polyethylene laminated paper, plastic film, or the like can be used as the support. Examples of the plastic film include polyester, polycarbonate, polypropylene, polyethylene, polyarylate, acrylic, acetylcellulose, and polyamide. And conventionally known materials such as polyimide, polyvinyl chloride, and vinylidene chloride-vinyl chloride copolymer.

  The above-mentioned support serves as a substrate for the reversible recording medium of the present invention, but serves as a temporary separator for simply forming a reversible recording layer. Also good.

  The immobilization method described above is based on a solution polymerization method, but can also be formed by a different polymerization method such as bulk polymerization.

  For example, first, an ultraviolet curable acrylic oligomer, an acrylic monomer, and a heteropolyacid having a group having an unsaturated double bond are uniformly mixed, and the photopolymerization initiator is uniformly dissolved. At this time, a solvent in which each component is dissolved may be used for viscosity adjustment.

  Next, the prepared solution is uniformly coated on a substrate such as a polyester film by the above-described conventionally known coating method, and when a diluted solvent is used, after removing the solvent by hot air drying, by irradiating with ultraviolet rays, A reversible recording layer in which the polymerization reaction is started and the heteropolyacid is directly immobilized on the substrate by a covalent bond can be formed.

  Such a mass polymerization method is preferable from the viewpoint of forming an image with high contrast because the concentration of the heteropolyacid contained in the reversible recording medium can be increased.

  The content ratio of the heteropolyacid or the salt thereof in the reversible recording layer is preferably 0.1 to 50% by weight, more preferably 0.1 to 25% by weight in the reversible recording layer. By setting the content to 0.1% by weight or more, an image with high contrast can be formed. Moreover, by setting it as 50 weight% or less, film property can be made favorable.

  The thickness of the reversible recording layer is not particularly limited, but is preferably 0.1 to 30 μm, and more preferably 1 to 10 μm. By setting the thickness to 0.1 μm or more, an image with high contrast can be formed. Moreover, it becomes favorable on a manufacturing process by setting it as 30 micrometers or less.

  The reversible recording layer used in the present invention may contain other resin in which the heteropolyacid or its salt is not immobilized within a range not impairing the object of the present invention. As such a resin, a conventionally known resin can be used.

  Further, in the reversible recording layer, an ultraviolet absorber, a dye, a pigment, a colorant, an antistatic agent, a flame retardant, an antifungal agent, a rust inhibitor, a light stabilizer, as long as the object of the present invention is not impaired. You may use additives, such as antioxidant, a plasticizer, a leveling agent, a flow regulator, an antifoamer, a dispersing agent, a crosslinking agent.

  Examples of the method for forming an image on the reversible recording medium of the present invention include a method of applying a positive or negative voltage to a desired portion where an image is to be formed, a method of irradiating ultraviolet rays, and the like. From the viewpoint, a method using ultraviolet irradiation is preferable. As a method of irradiating with ultraviolet rays, a mask plate that can form an irradiated portion and an unirradiated portion is prepared in advance to form a desired image. Then, a mask plate is disposed on the reversible recording medium, and ultraviolet rays are irradiated from above the mask plate. When irradiation is performed, the modified heteropolyacid or salt thereof present in the irradiated portion undergoes a reduction reaction, and a blue image is formed.

In the case of irradiating ultraviolet rays, an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a carbon arc, a metal halide lamp or the like is used, and a wavelength range of 100 to 400 nm, preferably 200 to 400 nm, 0.1 to 5 J / cm ² . An image can be formed by irradiating ultraviolet rays having energy.

  An image obtained by ultraviolet rays is maintained well for a certain period, but the oxidation reaction of the heteropolyacid or its salt starts by oxygen molecules in the atmosphere, and the image is usually erased in about several days. Thereafter, the image can be repeatedly formed and erased by the same method as described above.

  As described above, the reversible recording medium of the present invention has a reversible recording layer having a heteropolyacid or a salt thereof immobilized by chemical bonding, so that the image forming performance deteriorates even when images are formed many times. The image can be formed and erased repeatedly, and the image can be recognized without being eroded even when exposed to water or a solvent. Therefore, such a reversible recording medium is suitable not only for temporary output of meeting materials and e-mail documents in an indoor environment such as an office, but also for a guide board that presents information only for a short period in an outdoor environment. Can be used.

  The following examples further illustrate the present invention. “Parts” and “%” are based on weight unless otherwise specified.

[Examples 1 to 3]
1. Process for producing heteropolyacid salt modified with hydrolyzate of metal alkoxide having reactive organic functional group First, heteropolyacid salt modified with hydrolyzate of metal alkoxide having methacrylic group ((Me ₂ NH ₂ )) _A method for producing ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 6H ₂ O) will be described.

475 μL (2.0 mmol) of γ-methacryloxypropyltrimethoxysilane (CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) was added to a mixed solvent of 150 mL of methanol and 50 mL of pure water, and the literature ( R. Contant, Inorg. Synth., 27, 104, 1990) was added one-deficient Dawson-type Tungstopolyacid salt K ₁₀ [P ₂ W ₁₇ O ₆₁ ] .19H ₂ O (1 mmol). The pH was adjusted to 1.8 using 1M hydrochloric acid. After stirring for 30 minutes, unreacted powder was removed with a membrane filter, and the filtrate was concentrated to about 70 mL using a rotary evaporator. An excessive amount of 5.5 g (67 mmol) of Me ₂ NH ₂ Cl was added to the concentrate to precipitate a powder. The precipitated powder was collected with a glass filter (G4) and sufficiently dried under vacuum to obtain 3.98 g (yield: 81.6%) of the target product as a white powder.

<FT-IR {KBr disk}>
1702 (m), 1629 (br, m) [H ₂ O], 1466 (m) [Me ₂ NH ₂ ], 1412 (w), 1327 (w), 1304 (w), 1186 (m), 1088 ( s), 1039 (m), 954 (s), 922 (w), 793 (vs), 566 (w), 527 (m) cm ^-1
<31 P NMR>
{Solvent D ₂ O, 22.6 ° C, external standard 25% H ₃ PO ₄ aq. Capillary}
δ -10.3, -13.3 ppm
^<1 H NMR>
{Solvent D ₂ O, 21.3 ° C, External standard: TSP
Replacement method}
δ 0.93-0.94, 1.93, 2.01-1.05, 2.74, 4.28-4.29, 5.69, 6.15 ppm
< ^13C NMR>
{Solvent D ₂ O,
26.3 ° C, external standard: DSS substitution method}
δ 19.3, 23.2, 36.5, 69.0, 128.4, 138.0 ppm
<CHN elemental analysis>
(Me ₂ NH ₂ ) ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 6H ₂ O

From the characterization results, it can be seen that the target product was synthesized as a single species.
Using this compound as a precursor, free acid was synthesized.

2. Heteropolyacid H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ modified by hydrolyzate of metal alkoxide having a reactive organic functional group Production process of O (replacement of counter cation of heteropolyacid salt obtained in 1. above)
Above 1. Heteropolyacid salt (Me ₂ NH ₂ ) ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 6H ₂ O 0.4 g (0.082 mmol) Was dissolved in 60 mL of pure water on a hot water bath. After cooling to room temperature, the drug was passed through 100 mL of an H ⁺ charged cation exchange resin (Amberlite 120NBA: Rohm and Haas). Furthermore, 100 mL of pure water was poured, and the liquid that came out was dried using a rotary evaporator. Further, the target product was obtained as an orange-yellow powder in 0.3 g (yield: 80%) by vacuum drying.

<FT-IR {KBr disk}>
1686 (m), 1629 (br, w) [H ₂ O], 1419 (w), 1368 (w), 1306 (w), 1238 (w), 1189 (br, w), 1090 (s), 1039 (m), 957 (s), 915 (m), 805 (br, vs), 597 (w), 566 (w), 531 (m) cm ^-1
<31 P NMR>
{Solvent D ₂ O, 23.1 ° C, 25% H ₃ PO ₄ aq. Substitution}
δ -10.3, -13.3 ppm
^<1 H NMR>
{Solvent D ₂ O,
21.4 ° C, external standard: TSP substitution method}
δ 0.89-0.92, 1.91, 1.97-2.04, 4.25-4.26, 5.67, 6.13 ppm
< ^13C NMR>
{Solvent D ₂ O, 25.2 ° C, external standard: DSS substitution method}
δ 9.72, 19.4, 23.3, 69.1, 128.5-129.0, 138.1, 172.0 ppm
<Solid ²⁹ Si NMR>
{CPMAS: 40 Hz, standard: substitution method polydimethylsilane-solid (-37.0 ppm), RT}
δ-53.0 ppm
<CHN elemental analysis>
H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ O

As a result of the above characterization, it was confirmed that the target heteropoly acid H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ O was produced. confirmed.

3. Heteropoly acid H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · Process of copolymerization of 20H ₂ O and methyl methacrylate (MMA) Cooling pipe, introduction of nitrogen CH ₃ CN in a three-necked flask equipped with a tube and thermometer
30 mL was added to dissolve the heteropolyacid H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ O 2g (0.43 mmol). Further, 18 g (180 mmol) of MMA was added, and 0.04 g (0.28 mmol) of azobisisobutyronitrile as a polymerization initiator was further added and purged with nitrogen. After purging, the three-necked flask was placed in an oil bath and the internal temperature was kept at 75 ° C. for 4 hours. The solution with increased viscosity was dropped into 500 mL of MeOH, and the precipitated powder was recovered by decantation and sufficiently dried in vacuum. The target polymer was obtained as a white powder in 5.5 g (yield: 27.5%).

<FT-IR>
2994 (w), 2950 (w), 1723 (m), 1434 (m), 1386 (m), 1239 (s), 1190 (s), 1144 (s), 962 (m), 910 (m), 838 (m), 809 (m), 749 (m) cm ^{-1
_{<31 P NMR in CD 3 CN}} >
δ -9.1, -12.2 ppm
<GPC developing solvent THF>
Mn 12,083
Mw 31,326
Mw / Mn 2.59

As a result of the above characterization, a polymer in which the heteropolyacid H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ O is immobilized in the polymer is It was confirmed that it was obtained.

  3 g of the polymer produced this time was dissolved in 24 g of acetonitrile, the solution was filtered, and then applied to a polyester film (Lumirror T60: Toray Industries, Inc.) by a bar coating method to form a reversible recording layer. Got. The thicknesses of the reversible recording layers of Examples 1 to 3 were 1 μm, 2 μm, and 3 μm, respectively.

4). Reduction of heteropolyacid by UV irradiation The coating was irradiated by UV using a mask plate.
<Irradiation conditions: Fusion lamp output 100%, 3 J / cm ² irradiation>

  The reversible recording medium of the example could show a clear blue image by UV irradiation. Further, when this recording medium was left in the atmosphere for 3 days, the image could not be recognized, and a highly transparent recording medium before UV irradiation was obtained again.

  Furthermore, by repeatedly irradiating the reversible recording medium of the example with UV, display of a desired image could be repeated.

  Next, the reversible recording medium of the example irradiated with UV was immersed in an ethyl alcohol bath overnight. Thereafter, when the reversible recording medium was taken out of the bathtub and visually confirmed, it had no effect on the formed image.

  The same evaluation was performed using water instead of ethyl alcohol, but in this case, the formed image was not affected at all.

[Comparative Example 1]
A reversible recording layer of Comparative Example 1 is obtained by applying a coating liquid for a reversible recording layer having the following formulation to a polyester film (Lumirror T60: Toray Industries, Inc.) by filtration and applying a bar coating method to form a reversible recording layer having a thickness of 2 μm. It was.

<Coating liquid for reversible recording layer of Comparative Example 1>
-Heteropoly acid prepared in the examples (H ₆ [P ₂ W ₁₇ O ₆₁ {CH ₂ (CH ₃ ) CCOO (CH ₂ ) ₃ Si} ₂ O] · 20H ₂ O)
1.5 parts by weight, 13.5 parts by weight of polymethyl methacrylate, 120 parts by weight of acetonitrile

[Comparative Example 2]
A reversible recording layer of Comparative Example 2 is obtained by forming a reversible recording layer having a thickness of 2 μm by applying a coating solution for reversible recording layer of the following formulation to a polyester film (Lumirror T60: Toray Industries, Inc.) after filtration. It was.

<Coating liquid for reversible recording layer of Comparative Example 2>
・ Heteropolyacid (H ₃ [PW ₁₂ O ₄₀ ] .nH ₂ O: Wako Pure Chemical Industries, Ltd.)
1.5 parts by weight, 13.5 parts by weight of polymethyl methacrylate, 120 parts by weight of acetonitrile

  When the reversible recording medium of the comparative example obtained as described above was irradiated with UV under the same conditions as in the example, a blue image could be shown. Furthermore, when this recording medium was left in the atmosphere for 3 days, the image could not be recognized, and a highly transparent recording medium before UV irradiation was obtained again.

  Next, the UV-irradiated comparative reversible recording medium was immersed in an ethyl alcohol bath overnight. Thereafter, when the reversible recording medium was taken out of the bathtub and visually confirmed, the polymer and the non-immobilized heteropolyacid flowed out of the reversible recording layer, and the contrast of the formed image was lowered. .

  In addition, the same evaluation was performed using water instead of ethyl alcohol. In this case, the non-fixed heteropolyacid flows out from the reversible recording layer, and the contrast of the formed image is lowered. have done.

  Although the reversible recording medium of the comparative example can repeatedly form and erase images, the heteropoly acid gradually flows out of the reversible recording layer due to the influence of moisture in the atmosphere, etc. It was not suitable for the purpose to do.

Claims (5)

In a reversible reversible recording medium having a reversible recording layer, a functional group capable of reacting with a reactive organic functional group is formed in the reversible recording layer by any one of a covalent bond, an ionic bond, and a coordinate bond. A reversible recording medium comprising a heteropolyacid represented by the general formula (1) or a salt thereof immobilized on a monomer and / or a monomer .
R _m [XY] · nH ₂ O (1)
[Wherein, R is a counter cation of a heteropolyacid or a salt thereof, X is a heteropolyanion in which a part of the skeleton constituent atoms is missing, and Y is a metal group having a reactive organic functional group. n is an integer greater than or equal to 1, m is an integer greater than or equal to 1, and is the absolute value of the negative charge determined from [XY] in the general formula (1). ] In a reversible reversible recording medium having a reversible recording layer, the heteropolyacid represented by the general formula (1) or a salt thereof in the reversible recording layer is any one of a covalent bond, an ionic bond, and a coordinate bond. A reversible recording medium, which is fixed to another heteropolyacid or a salt thereof by bonding.
R _m [XY] · nH ₂ O (1)
[Wherein, R is a counter cation of a heteropolyacid or a salt thereof, X is a heteropolyanion in which a part of the skeleton constituent atoms is missing, and Y is a metal group having a reactive organic functional group. n is an integer greater than or equal to 1, m is an integer greater than or equal to 1, and is the absolute value of the negative charge determined from [XY] in the general formula (1). ] The chemical bonding, according to claim 1 or 2, wherein the reversible recording medium characterized in that it is a covalent bond. The reversible recording medium according to claim 1 or 2, wherein the reactive organic functional group is a group having an unsaturated double bond. The reversible recording medium according to claim 1 or 2, wherein the heteropolyacid or a salt thereof is modified with a hydrolyzate of a metal alkoxide.