JP2005070579A - Rewritable optical memory material using change in fluorescence by photoirradiation or heat treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material capable of realizing recording of high density information by multiple recording. <P>SOLUTION: The optical memory material is obtained by incorporating rare earth ions into a polymer having a carbonyl group in a backbone or a side chain of the polymer, increases a degree of fluorescence in accordance with a quantity of applied light, and is restored to the initial state by heat treatment. The optical memory material is particularly a polymer film obtained by dissolving a polymer having a carbonyl group in a backbone or a side chain of the polymer and a compound of a rare earth element forming an ion of the rare earth element in a solvent which dissolves at least the two components and by incorporating the above rare earth ions into the above polymer formed from the resulting solution; is fine polymer particles containing the above rare earth ions formed in a particle diameter of 5-10,000 nm by injecting the solution into a bad solvent for at least the above two components; and is a fine particle film formed from the above fine particles; or is a bulk molded article from the above fine particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has an optical memory material in which ions of an element belonging to a rare earth element, particularly an element belonging to a lanthanoid, are contained in a polymer having a carbonyl group, and an optical memory characteristic produced using a solution of the rare earth element ion and the polymer. Rare earth ion-containing polymer film, or formed from a solution containing the rare earth ion-containing polymer fine particles having optical memory characteristics with a particle size of 5 nm to 10000 nm manufactured by reprecipitation by injecting the solution into a poor solvent. The present invention relates to the rare earth ion-containing polymer fine particle film. The polymer film, fine particle, or fine particle film has an increased fluorescence intensity as the product of light irradiation energy, in other words, irradiation intensity × irradiation time increases, and the fluorescence intensity decreases to the initial state as the heat treatment temperature increases. It can be used as a rewritable optical memory material utilizing the change in fluorescence.

  With the development of the information society in recent years, a recording material capable of high-density and high-speed processing of information has been demanded. By developing a recording medium capable of shortening the light wavelength used for recording, the above-mentioned short Although the recording density has been improved by narrowing the pit width due to the wavelength, multiple recording that can record several bits per pit instead of the conventional one-bit recording when achieving higher density has been achieved. Material is desired. Further, from the viewpoint of environmentally friendly technology requirements, a material having rewritable characteristics in addition to the recording characteristics is desired.

Shinya MAENOSONO, Ceco Danov DUSHKIN, Soichiro SAITA and Yukio YAMAGUCHI, `` Optical Memory Media Based on Excitation-Time Dependent Luminescence from a Thin Film of Semiconductor Nanocrystals '' Japanese Journal of Applied Physics 39, 4006-4012 (2000). Masayuki Nogami, `` Room temperature persistent spectral hole burning of Eu3 + ions doped in sol-gel derived glasses '' Journal of Luminescence 98, 289-294 (2002). Nobuhiko Umezu, Tsunenori Asatsuma, Yoshihiro Takemoto, Masahiko kaneko `` Multi-wavelength recording at room temperature by gated persistent spectral hole burning in SrFCl0.5Br0.5: Sm2 + '' Journal of Luminescence 64, 195-199 (1995).

In Non-Patent Document 1, dimethylcadmiumu, seleniumu-tri-butylphosphine solution was added to tri-octylphosphine oxide, and the resulting solution was maintained at 300 ° C. CdSe fine particles capped with 430 nm and 15 mW of laser light increase in fluorescence intensity and saturate in about 500 minutes to show 7 times the initial fluorescence intensity. It is described that the strength is almost stable for 500 hours or more. However, there is no description regarding the extinction of fluorescence.
Non-Patent Document 2 describes the excitation spectrum of Eu ³⁺ by irradiating an aluminosilicate glass containing Eu ³⁺ ions produced by the sol-gel method with 300 W at −196 ° C. (77 K) for 30 minutes and a rhodamine 6G laser having a spot size of 1 mm. In addition, it is described that holes are generated in the same manner, and that X-ray irradiation at room temperature generates holes in the same way and raises the temperature, thereby reducing the depth of the holes. It is proposed to record several bits. In Non-Patent Document 3, SrFCl _0.5 Br _0.5 powder containing Sm ²⁺ ions is irradiated with a multi-wavelength dye laser ranging from 688 nm to 693 nm to generate a large number of holes in the excitation spectrum of Sm ^2+. It is described that wavelength multiplex recording is performed, and high-density recording is possible. However, in both cases, the hole depth is shallow and broad, and the threshold value is ambiguous.
This cannot be said to be a satisfactory recording material in room temperature recording characteristics and high resolution characteristics required for recording materials in the information society. Moreover, it cannot be said that it is sufficient from the viewpoint of ease of production of the recording material.

The present invention provides an optical recording material that is stable at room temperature, can perform multi-bit multiplex recording for one pit, and is rewritable, and utilizes a change in fluorescence characteristics due to light irradiation. That is.
The present inventors determined that ions of elements belonging to rare earths, particularly elements belonging to lanthanoids, contained in a polymer having a carbonyl group, for example, an imide group, a carboxyl group or an ester group thereof, depend on the amount of light irradiation, that is, irradiation light intensity × irradiation time. As a result, it was found that the fluorescence intensity of rare earth ions was enhanced, and in particular, it was enhanced up to 400 times in the polyimide system, and the emission intensity characteristics after light irradiation was stopped were stable for several months at room temperature. By providing a threshold value, high density recording is possible. In addition, the fluorescence intensity was erased by returning to the initial state by heat treatment using the flexible structure of the polymer. Furthermore, after the fluorescence was erased, it was found that the fluorescence intensity was increased again by light re-irradiation depending on the amount of light irradiation. Since the optical recording is possible not only in the film but also in the form of fine particles having a size of 5 nm, it has been found that high-resolution recording is possible and has solved the above-mentioned problems.

According to the first aspect of the present invention, (1) the fluorescence intensity increases corresponding to the amount of irradiation light in which a rare earth ion is contained in a polymer having a carbonyl group in the main chain or side chain of the polymer, and the initial state can be recovered by heat treatment. Optical memory material. Preferably, (2) the optical memory material according to (1) or (3) the carbonyl group, wherein the polymer having the carbonyl group is a polyimide obtained by a reaction of a tetracarboxylic acid or a dianhydride thereof and a diamine. The optical memory material according to (2) above, wherein the polymer having a carboxyl group or ester group thereof in the side chain is more preferred, (4) a polymer having a carboxyl group or ester group in the side chain Is an optical memory material as described in (3) above, which is obtained by addition polymerization of an ethylenically unsaturated group.
More preferably, (5) the optical memory material according to (1), (2), (3) or (4), wherein the rare earth is selected from elements having an element number of 58 to 70.

  In the second aspect of the present invention, the optical memory material is prepared by dissolving a polymer having a carbonyl group in the main chain or side chain of the polymer and the rare earth element compound that generates rare earth ions in a solvent that dissolves at least the two components. A polymer film in which the rare earth ions are contained in the polymer formed from the solution, a polymer having a carbonyl group in the main chain or side chain of the polymer, and a rare earth element compound that generates rare earth ions, Dissolve two components in a solvent that dissolves, and inject the solution into at least the two component poor solvents, and form the rare earth ion-containing polymer fine particles having a particle diameter of 5 nm to 10,000 nm, or the main chain or side chain of the polymer. The polymer having a carbonyl group and the rare earth element compound that generates rare earth ions are at least The particle size having optical memory characteristics in which the rare earth ions are contained in the polymer by dissolving the two components in a solvent that dissolves the two components and injecting the solution into at least the two component poor solvents is 5 nm to 10,000 nm. It is a fine particle film or a bulk molded body of the rare earth ion-containing polymer formed from a solution containing polymer fine particles by producing polymer fine particles.

  As an effect of the invention, as a high-density recording material using rare earth ions, a high-density recording (memory) material in which the emission intensity is divided into a plurality of threshold regions and independent information recording is possible in each of the intensity regions. Similar to the case where the known rare earth ion is contained in the glass material, but is realized by using a polymer that is easy to process, and that the characteristics such as recording are presumed to be caused by a phenomenon different from the known one. It can be mentioned that the company has provided a completely new optical memory material.

A. It is important that the material constituting the rare earth ions exists in a polymer material having a carbonyl group, forms different coordination states by light irradiation, and stably maintains the state at room temperature. The rare earth element that generates the coordination state is selected from elements belonging to lanthanoids, preferably elements having an atomic number of 58 to 70, and more preferably Eu, Tb, Gd, and Ce. Recording corresponding to multiple transitions having specific fluorescence peak wavelengths and different fluorescence intensity enhancements is possible.
B. It is important for the polymer material to stably hold the rare earth ions in the coordination state at room temperature. The coordination bond state between the rare earth element ions and oxygen and the rare earth element ion-O maintain the multiple coordination bond state. Therefore, in the present invention, a polymer having a carbonyl group in the main chain or side chain of the polymer is used as a preferable one.
If we make an electronic theory related to the coordination bond state, the HOMO and LUMO energy gaps of the polymer and the ground state of the rare earth ion and the excitation are realized in order to realize the energy transfer between the polymer and the rare earth element ion. It is important that the energy gap of the state corresponds to the above conditions.
B-1. As a preferred polymer, first, polyimide can be mentioned.
Examples of tetracarboxylic acid or dianhydride thereof include 3,3′-4,4′-benzophenonetetracarboxylic acid (BTDA), 3,3′-4,4′-tetracarboxybiphenyl, 2,2- (3, 4-Dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane and dianhydrides thereof can be exemplified.
B-2. The diamine that reacts with the tetracarboxylic acid or its dianhydride to form a polyimide precursor polyamic acid and then forms a polyimide by subsequent imidization or the like includes 4,4'-diaminodiphenyl ether, 4,4'- Bis (4-aminophenoxy) biphenyl, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-diaminobenzene, 4,4′-methylenebis (methyl) Cyclohexylamine), 4,4′-methylenebis (ethylcyclohexylamine), and the like.
B-3. Examples of the other polymer include addition polymers of monomers having an ethylenically unsaturated bond having a carboxyl group or an ester group in the side chain, such as polyacrylic acid and polymethyl methacrylate (PMMA).

C. The particle size is important from the viewpoint of effective use of recording light. The polymer and the rare earth element compound are dissolved to prepare a solution in which the rare earth element is present as ions, and the solution is injected into the two-component poor solvent to produce fine particles. Particles in which ions of the rare earth element having a diameter of 5 nm are uniformly dispersed can be obtained.
D. Method for Producing Recording Material In the production of the optical memory material, 1 to 10% by weight of a rare earth salt is blended with respect to a polymer having a carbonyl group in the main chain or side chain of the polymer, and the polymer is 0.1 to 15%. A polymer solution in which the polymer is dissolved in a solvent at a concentration of% by weight, preferably a polar solvent in order to allow the rare earth salt to exist as ions in the solution, is known as means for forming a polymer film, such as spin coating, dip coating, and casting. Or a rare earth salt-containing polymer film, or the polymer solution is made of an aliphatic solvent (decalin, hexane) alicyclic solvent (cyclohexane), an aromatic solvent (benzene, toluene), CS ₂ and is selected from a mixture of two or more of these, the particle size by injecting into a poor solvent having a controlled temperature of -20 ° C. to 60 ° C. To produce a polymer particle is Nm～10000nm,
By applying the same means as the polymer film forming means to the obtained polymer fine particle dispersion liquid, or by electrodeposition, a rare earth salt-containing polymer fine particle film is prepared.

Examples of the polar solvent include acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, acetonitrile, alcohols (methanol, ethanol, isopropanol, etc.), N, N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone (NMP), and the like. .
For the production of optical memory materials using polyimide as a polymer material, it is preferable to use a polyamic acid (also referred to as an amic acid), which is a precursor of polyimide, and then physically or chemically imidize the film or fine particles after production. .

E. The rare earth salt-containing polymer film or the rare earth salt-containing polymer fine particle film prepared by the production method includes the B. Fluorescence intensity of rare earth ions depending on the irradiation light amount by irradiating light having a wavelength corresponding to the coordinated bonding state of the polymer having a carbonyl group, a rare earth element ion and oxygen, for example, light having a wavelength of 254 nm or 304 nm Can be recorded stably at room temperature. In addition, the fluorescence intensity can be reduced or eliminated in a state corresponding to the treatment temperature by performing a heat treatment below the glass transition point of the rare earth salt-containing polymer.
F. Preferably, the rare earth salt used in the production of the optical memory material is Eu ³⁺ or Tb ³⁺ chloride salt, nitrate salt, cyanide compound or the like. A method for producing a multi-bit recordable material using the enhancement of the fluorescence property in the film, wherein the polymer is polyimide, polyacrylic acid, or polymethyl methacrylate (PMMA).

Example 1 will be described.
Polyamic acid (average molecular weight) obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4-diaminodiphenyl ether : 122955) was dissolved in acetone to a concentration of 0.7% by weight. Eu (NO ₃ ) ₃ was added thereto so that the blending amount of Eu ³⁺ was 1% by weight, 5% by weight, 10% by weight / polyamic acid with respect to the dissolved polyamic acid. An acetone solution of (NO ₃ ) ₃ was prepared. Next, 0.01 ml of the solution was cast on a 20 × 10 mm quartz plate, spin-coated or dip-coated at 3000 rpm, and dried to prepare a Eu ^{3 +} -containing polyamide film. This was held at 350 ° C. for 2 hours to complete the thermal imidization to obtain an Eu ³⁺ containing polyimide film. In order to investigate the optical recording characteristics of the prepared Eu ³⁺ containing polyimide film, when UV light was used to irradiate light with a wavelength of 254 nm of 6 W, the fluorescence intensity attributed to Eu ³⁺ increased with the increase of the irradiation time. The results are shown in FIG. The saturation strength was the largest for 5% by weight of Eu ^{3 +} -containing polyimide fine particles, which was about 400 times that before UV irradiation. When the Eu ^{3 +} -containing polyimide fine particle film with saturated fluorescence intensity was subjected to a heat treatment for 5 minutes, the fluorescence intensity decreased as the heat treatment temperature increased and disappeared completely at 200 ° C. The results are shown in FIG. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced. The results are shown in FIG.
From this, it was found that the Eu ^{3 +} -containing polyimide fine particle film is useful as a writable and reproducible optical memory material.

Polyamic acid (average molecular weight) obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4-diaminodiphenyl ether : 122955) was dissolved in NMP to a concentration of 0.7% by weight. To this, Tb (NO ₃ ) ₃ was added so that the blending amount of Tb ³⁺ with respect to the dissolved polyamic acid was 5% by mass / polyamic acid to prepare an NMP solution of polyamic acid-Tb (NO ₃ ) _3. did. Next, 0.01 ml of the solution was cast on a 20 × 10 mm quartz plate, spin-coated or dip-coated at 3000 rpm, and dried to prepare a Tb ^{3 +} -containing polyamide film. After performing thermal imidization by holding this at 350 ° C. for 2 hours and irradiating with 6 W wavelength 254 nm light using a UV lamp, the fluorescence intensity attributed to Tb ³⁺ increases with an increase in the irradiation time, Saturated in about 15 hours. The results are shown in FIG. When the Tb ^{3 +} -containing polyimide fine particle film with saturated fluorescence intensity was subjected to a heat treatment for 5 minutes, the fluorescence intensity decreased as the heat treatment temperature increased and disappeared completely at 200 ° C. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced.
From this, it was found that the Tb ³⁺ containing polyimide fine particle film is useful as an optical memory material capable of writing and reproducing.

Polyamic acid (average molecular weight) obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4-diaminodiphenyl ether : 122955) was dissolved in acetone to a concentration of 0.7% by weight. Eu (NO ₃ ) ₃ was added thereto so that the blending amount of Eu ³⁺ with respect to the dissolved polyamic acid was 5% by mass / polyamic acid to prepare an acetone solution of polyamic acid-Eu (NO ₃ ) _3. did. Next, 0.01 ml of the solution was cast on a 20 × 10 mm quartz plate, spin-coated or dip-coated at 3000 rpm, and dried to prepare a Eu ^{3 +} -containing polyamide film. This was held at 350 ° C. for 2 hours to complete the thermal imidization to obtain an Eu ³⁺ containing polyimide film. In order to investigate the optical recording characteristics of the prepared Eu ³⁺ containing polyimide film, when UV light was used to irradiate light with a wavelength of 6 W of 304 nm, the fluorescence intensity attributed to Eu ³⁺ increased with an increase in the irradiation time, When a heat treatment for 5 minutes was performed on the Eu ³⁺ containing polyimide film in which the fluorescence intensity was saturated in about 24 hours, the fluorescence intensity decreased with the increase of the heat treatment temperature and disappeared completely at 200 ° C. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced.
From this, it was found that the Eu ³⁺ containing polyimide film is useful as an optical memory material capable of writing and reproducing.

Polyamic acid obtained by polymerization of 3,3 ′, 4,4′-tetracarboxybiphenyl dianhydride and 1,4-diaminobenzene was dissolved in NMP to a concentration of 1% by weight. Eu (NO ₃ ) ₃ or Tb (NO ₃ ) ₃ or Sm (so that the blending amount of Eu ³⁺ or Tb ³⁺ or Sm ³⁺ or Er ³⁺ with respect to the dissolved polyamic acid is 5% by mass / polyamic acid. NO ₃ ) ₃ or Er (NO ₃ ) ₃ is added to form polyamic acid-Eu (NO ₃ ) ₃ , polyamic acid-Tb (NO ₃ ) ₃ , polyamic acid-Sm (NO ₃ ) ₃ , and polyamic acid- A solution of Er (NO ₃ ) ₃ was prepared. 0.01 ml of the solution was cast on a 20 × 10 mm quartz plate, spin-coated or dip-coated at 3000 rpm, and then dried to obtain a Eu ^{3 +} -containing polyamic acid film. In order to investigate the optical recording characteristics of the produced Eu ^{3 +} -containing polyamide film, when irradiating light with a wavelength of 254 nm of 6 W using a UV lamp, the fluorescence intensity attributed to Eu ³⁺ increases with an increase in the irradiation time, and about The fluorescence intensity was saturated in 3 hours. The result of the Eu ³⁺ containing polyamide film is shown in FIG. When the Eu ³⁺ containing polyamic acid film with saturated fluorescence intensity was subjected to a heat treatment at 200 ° C. for 5 minutes, it completely disappeared. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced. In the polyamide film containing Tb ³⁺ or Sm ³⁺ or Er ³⁺ , the same characteristics as in the case of Eu ³⁺ were developed.

Polyacrylic acid (molecular weight: 450,000) was dissolved in NMP to a concentration of 1% by weight. Eu (NO ₃ ) ₃ was added thereto so that the blending amount of Eu ³⁺ with respect to the dissolved polyacrylic acid was 5% by weight / polyacrylic acid to prepare a polyacrylic acid-Eu (NO ₃ ) ₃ solution. An Eu ^{3 +} -containing polyacrylic acid film was prepared by casting 0.01 ml of the solution on a 20 × 10 mm quartz plate, spin coating or dip coating at 3000 rpm, and drying. In order to investigate the optical recording characteristics of the prepared Eu ^{3 +} -containing polyacrylic acid film, when a 6 W wavelength 254 nm light was irradiated using a UV lamp, the fluorescence intensity attributed to Eu ³⁺ increased as the irradiation time increased. In about 24 hours, the fluorescence intensity was saturated. The results are shown in FIG. When the Eu ³⁺ containing polyimide film with saturated fluorescence intensity was subjected to a heat treatment for 5 minutes, the fluorescence intensity decreased as the heat treatment temperature increased and disappeared completely at 140 ° C. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced.

Polymethyl methacrylate (PMMA) (molecular weight: 350,000) was dissolved in NMP to a concentration of 1% by weight. A solution was prepared so that the blending amount of Eu ³⁺ was 5 wt% / PMMA with respect to the polymethyl methacrylate dissolved therein. Next, 0.01 ml of the solution was cast on a 20 × 10 mm quartz plate, spin-coated or dip-coated at 3000 rpm, and dried to prepare a Eu ^{3 +} -containing PMMA film. In order to investigate the optical recording characteristics of the produced Eu ^{3 +} -containing PMMA film, irradiation with 6 W wavelength 254 nm light using a UV lamp increases the fluorescence intensity attributed to Eu ³⁺ as the irradiation time increases, The fluorescence intensity was saturated in 24 hours. When the Eu ³⁺ containing PMMA film with saturated fluorescence intensity was subjected to a heat treatment for 5 minutes, the fluorescence intensity decreased as the heat treatment temperature increased, and disappeared completely at 160 ° C. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced.

Polyacrylic acid (average molecular weight: 450,000) was dissolved in NMP to a concentration of 1% by weight. Eu (NO ₃ ) ₃ was added thereto so that the blending amount of Eu ³⁺ with respect to the dissolved polyacrylic acid was 5% by weight / polyacrylic acid to prepare a polyacrylic acid-Eu (NO ₃ ) ₃ solution. Eu ^{3 +} -containing polyacrylic acid fine particles are obtained by injecting 0.1 ml of the above solution into 10 ml of cyclohexane (acridic: containing 0.1% by weight) using a microsyringe under stirring conditions of 1500 rpm at room temperature. It was. The results observed with a scanning electron microscope (SEM) are shown in FIG. The Eu ^{3 +} -containing polyacrylic acid fine particles were dried by the casting method or electrodeposition (fine particle concentration of dispersion: 0.1 to 1 wt%, applied voltage: 10 to 1000 V / cm ⁻¹ ). .2 g was put into a molding machine having a diameter of 3 mm and pressed to prepare a bulk molded body. Next, in order to investigate the optical recording characteristics of the produced film, when the Eu ^{3 +} -containing polyacrylic acid film is irradiated with light having a wavelength of 254 nm of 6 W using a UV lamp, it is attributed to Eu ³⁺ as the irradiation time increases. The fluorescence intensity increased, and the fluorescence intensity was saturated in about 24 hours. When the Eu ³⁺ containing polyimide film with saturated fluorescence intensity was subjected to a heat treatment for 5 minutes, the fluorescence intensity decreased as the heat treatment temperature increased and disappeared completely at 140 ° C. When UV light was further irradiated after the fluorescence was erased, the fluorescence intensity was enhanced.

  As described above, the rare earth element ion-containing polymer material has enhanced fluorescence intensity corresponding to the amount of irradiation light, and its characteristics are stably maintained at room temperature conditions, so that it can be used as an optical recording material, and The optical recording can be used as a rewritable recording material because multiple recording can be performed by dividing the threshold value, and the optical recording can be restored to the initial state by means such as heating.

Fluorescence spectrum of the Eu ³⁺ containing polyimide film obtained in Example 1 when irradiated with a UV lamp for various times Fluorescence spectra when heat-treated at various temperatures for the Eu ³⁺ containing polyimide film obtained in Example 1 Fluorescence spectrum of the Eu ^{3 +} -containing polyimide film obtained in Example 1 after heat treatment at 200 ° C. and irradiation with a UV lamp for various times. Fluorescence spectrum of the Tb ^{3 +} -containing polyimide film obtained in Example 2 when irradiated with a UV lamp for various times Fluorescence spectrum of the Eu ^{3 +} -containing polyamic acid film obtained in Example 5 when irradiated with a UV lamp for various times Fluorescence spectrum of the Eu ^{3 +} -containing polyacrylic acid film obtained in Example 6 when irradiated with a UV lamp for various times SEM photograph of Eu ^{3 +} -containing polyacrylic acid fine particles obtained in Example 8

Claims (6)

An optical memory material whose fluorescence intensity is enhanced in response to the amount of irradiation light in which a rare earth ion is contained in a polymer having a carbonyl group in the main chain or side chain of the polymer, and which is restored to a state corresponding to the processing temperature by heat treatment. 2. The optical memory material according to claim 1, wherein the polymer having a carbonyl group is a polyimide obtained by a reaction of tetracarboxylic acid or a dianhydride thereof and a diamine. The optical memory material according to claim 1, wherein the polymer having a carbonyl group is a polymer having a carboxyl group or an ester group thereof in a side chain. The optical memory material according to claim 3, wherein the polymer having a carboxyl group or an ester group thereof in the side chain is obtained by addition polymerization of an ethylenically unsaturated group. The optical memory material according to claim 1, 2, 3, or 4, wherein the rare earth is selected from elements having an atomic number of 58 to 70. The optical memory material is formed from the solution by dissolving a polymer having a carbonyl group in the main chain or side chain of the polymer and the rare earth element compound that generates rare earth ions in a solvent that dissolves at least the two components. A polymer film containing the rare earth ions in a polymer, the rare earth ion-containing polymer fine particles having a particle diameter of 5 nm to 10,000 nm formed by injecting the solution into at least the two poor solvents, and fine particles formed from the fine particles An optical memory material which is a film or a bulk molded body from the fine particles.

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