JP3004287B2 - Erasable optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable optical recording medium utilizing shape change upon heating. More specifically, in a recording layer comprising a polymer / dye, an optical recording medium having improved stability to repeated irradiation of erasing and reproducing light comprising a polymethine dye in which the dye is coordinated with a singlet oxygen quencher as an ion pair. It is about.

Background Art and Problems There have been proposed a large number of organic optical recording media capable of reproducing and erasing recording and being coatable. For example, JP
According to JP-A-5-5448, an erasable optical recording medium comprising a mixed system of a polymer and a dye is disclosed. In this medium, recording is based on pit formation due to flow deformation of the polymer, and erasing is based on the principle of closing the pits by re-melting the raised polymer around the pits generated during recording.
Therefore, it is difficult to completely recover the polymer once flowing out, and it is inevitable that erasure remains. This erasure residue is accumulated as recording and erasure are repeated. Therefore, high repetition durability cannot be obtained by this method. In addition, it is necessary to irradiate a laser beam of high energy in order to utilize the melting / flow deformation of the polymer for recording / erasing. As a result, the dye contained in the medium is liable to undergo photochemical deterioration and thermal deterioration, and the disadvantage of repeated use cannot be avoided from this point.

According to JP-A-57-27790 and JP-A-60-253036, an erasable optical recording medium comprising a pit-forming recording layer and an overcoat layer provided thereon is proposed. I have. In this medium, pits are formed by the flow deformation of the recording layer, and the recording is performed by the expansion of the overcoat layer.
However, since the overcoat layer has a high softening temperature, it is necessary to irradiate a laser beam having a relatively strong output for a long time at the time of erasing, as in the case of the above-mentioned recording medium, which is not practical.

According to another proposal (Japanese Patent Application Laid-Open No. 60-69846), it is composed of an expansion layer which is heated and expanded by laser beam irradiation to form a dome-shaped projection (bump), and a holding layer which holds this shape. A recordable / erasable medium has been proposed. When recording is performed on this medium, laser light irradiation is performed at the absorption wavelength (λ ₁ ) of the dye previously mixed in the expansion layer so that the expansion layer forms a bump and the holding layer can maintain this shape. I do. When erasing recorded bumps, laser light irradiation is performed at the absorption wavelength (λ ₂ ) of the dye previously mixed in the holding layer, and the holding layer is heated to a temperature equal to or higher than its glass transition temperature (Tg). It is difficult to maintain the bump shape. According to the recording method, although the shape of the medium changes during recording / erasing, it is advantageous in repetition characteristics because it does not involve flow deformation. Further, since recording / erasing involves a change in shape but does not involve a change in melting / flow of the polymer, it is not necessary to irradiate a high energy laser beam. Therefore, the dyes used are in a state where they are hardly deteriorated as compared with the pit type medium. However, it goes without saying that it is necessary to use a dye having high durability in order to obtain a medium that requires high repetition durability.

Several dyes have been proposed in the field of optical recording media exclusively for recording and reproduction from the viewpoint of durability. For example, phthalocyanine and naphthalocyanine are typical stable near-infrared dyes. On the other hand, a mixed dye in which a transition metal chelate complex is added to a near-infrared dye has also been proposed (JP-A-59-55794, JP-A-63-209890). In this system, a transition metal chelate complex is used as a singlet oxygen quencher, which is a cause of photodegradation of near-infrared dyes. However,
There are two major problems in applying these dyes to bump-forming dual-layer media. One is the problem of compatibility with the resin used. That is, in the conventional recording / reproduction-only recording medium, the compatibility with the resin was not a problem because only the dye and the complex were deposited or coated on the substrate. On the other hand, in the case of a bump-forming two-layer medium, compatibility is important because each layer is used in a mixed system with a resin. Near-infrared dyes that have been known to date have a highly conjugated molecular structure with a high molecular weight, and therefore have extremely poor solubility in general-purpose solvents and compatibility with polymer matrices. In particular, those proposed as a singlet oxygen quencher have many metal complexes and have extremely poor compatibility with organic polymers. Another problem is that of singlet oxygen scavenging (quench) capability in the polymer matrix. Generally, it is considered that dye deterioration due to singlet oxygen is based on the following mechanism.

(1) The dye absorbs light and is excited.

(2) The excited dye exchanges energy with oxygen to generate singlet oxygen.

(3) The generated singlet oxygen degrades the dye.

At this time, the singlet oxygen quencher prevents the deterioration of the dye by capturing (quenching) the generated singlet oxygen. Therefore, the quencher effect is achieved only when the reaction between the generated singlet oxygen and the quencher overcomes the competitive reaction with the dye. In a conventional recording / reproduction-only medium, a quencher molecule exists at an extremely high concentration because a matrix resin is not used. Therefore, the quench effect is expected to be extremely high. On the other hand,
In the case of a bump formation type two-layer medium, the effect is not necessarily expected because the quencher is dispersed in the matrix resin. From this point of view, by forming a complex comprising a cation of a near-infrared dye and an anion of a metal complex type singlet oxygen, the spatial distance between the singlet oxygen quencher and the dye which is a source of singlet oxygen is increased. There is also an example in which the quench effect is enhanced by keeping the quench effect close.
No.). However, as described above, near-infrared dyes and singlet oxygen are high molecular weight compounds in which a conjugated system has been developed. Therefore, the compatibility with the matrix resin used in the two-layer medium is further restricted by binding the respective ions.

The present inventors have conducted intensive studies and, as a result of using a salt composed of a cation of a polymethine dye and a metal complex anion in the bump-forming double-layer medium, without impairing the mechanical properties of the medium layer. The inventors have found that the dye can be stabilized, and have completed the present invention.

SUMMARY OF THE INVENTION The optical recording medium of the present invention comprises, at least at room temperature, an expansion layer (A) comprising a resin (P ₁ ) exhibiting rubber elasticity and a dye (D ₁ ) having absorption in the near infrared region. A holding layer (B) composed of a resin (P ₂ ) capable of reversibly changing to a rubber state at a temperature higher than the glass state (high elastic state) and a dye (D ₂ ) having absorption in the near infrared region. This is a configuration supported by a substrate.

The expansion layer (A) needs to expand effectively when heated by laser light irradiation in order to improve the recording characteristics. In order to efficiently erase the bumps generated by recording and return to the original state, high rubber elasticity is required at the time of erasing. Therefore, it is necessary that the resin (P ₁ ) has high rubber elasticity and does not undergo flow deformation by laser beam irradiation. Suitable resins include natural rubber; styrene-butadiene rubber, butadiene rubber,
Isoprene rubber, nitrile rubber, chloroprene rubber, butyl rubber, ethylene-propylene rubber, urethane rubber,
Synthetic rubbers such as silicone rubber; styrene-based, olefin-based, urethane-based thermoplastic elastomers; and amine-crosslinked, isocyanate-crosslinked, and ultraviolet-crosslinkable elastomers.

The resin (P ₂ ) used in the present invention has a role of fixing a bump (recording) generated by thermal expansion at the time of recording and releasing it at the time of erasing. Therefore, in order to perform both actions effectively, it is in a glassy state (high elasticity state) at room temperature, and at a certain higher temperature, for example, 60 to 18
The resin must be in a rubbery state at 0 ° C. Suitable resins include thermoplastic resins such as polymethyl methacrylate resin, polycarbonate resin and polyamide resin and their partially crosslinked products, epoxy resins,
Phenolic resin, melamine resin, epoxy (meth) acrylate resin, novolak (meth) acrylate resin,
A thermosetting resin (cross-linked resin) such as a polyfunctional (meth) acrylate resin (note: (meth) acrylate means acrylate and methacrylate).
Further, an epoxy resin, an epoxy (meth) acrylate resin, a novolak (meth) acrylate resin, and a polyfunctional (meth) acrylate resin may be cured by ultraviolet rays and are preferably used.

Dye D ₁ and D ₂ absorbs efficiently the laser beam in each recording process and erasing process serves to convert into heat. Therefore, a dye that matches the oscillation wavelength range of the recording laser and the erasing laser is selected. Then, it is preferable that the absorption intensities in the respective oscillation wavelength ranges do not excessively overlap so that both laser beams can be selectively absorbed. Further, a dye having an absorption peak in the near infrared is preferable since a laser currently used in the field of optical recording is a semiconductor laser. In addition, since reading uses the light reflection of the medium, it is required that the light reflectance of the holding layer be high. In this respect, the dye D ₂ preferably has a high reflectivity. Of course, for efficient absorption properties, the dyes should be selected to be uniformly dispersed in each resin.

At least _{one of the} dyes D ₁ and D ₂ used in the present invention is a salt comprising a cation of a polymethine dye and an anion of a singlet oxygen quencher (hereinafter, referred to as a complex salt).
It is. The polymethine dye, a cyanine dye,
A pyrylium-based dye, a thiapyrylium-based dye, a squarylium-based dye, a croconium-based dye, an azulenium-based dye, and the like are also included. As the singlet oxygen quencher, a compound in which one or two groups selected from SH, OH, and NH ₂ are bonded to both adjacent carbon atoms forming a C ＝ C double bond represented by the following formula: And a salt comprising a metal complex anion chelated by the above and a cation neutralizing the metal complex anion.

Examples of the compound include orthobenzenedithiols, catechols, orthophenylenediamines, orthoaminophenols, orthoaminobenzenethiols, orthomercaptophenols, and 1,2-ethylenedithiol derivatives. Ni, C as metal
Although o, Cu, Pd, and Pt are mentioned, Ni is particularly preferably used. These metal complexes may contain various substituents to increase their solubility.

Specific examples of the preferably used singlet oxygen quencher anion are as follows.

The salt composed of the dye cation and the singlet oxygen quencher anion can be easily obtained by an ion exchange reaction between the neutral salt of the corresponding dye and the quencher neutral salt.

These composite salts are added to the resin in an amount of 5 to 30 phr, preferably 10 to 25 phr. When the content of the composite salt is less than 5 phr, the recording sensitivity is reduced as the absorbance is reduced. Also,
When the content of the composite salt exceeds 30 phr, the mechanical strength of the coating film is reduced, and the recording cannot be maintained or erased sufficiently. In particular, when added to the expansive layer, if the amount is too large, the modulus of elasticity is reduced, which leads to a decrease in the CN ratio. Further, when added unnecessarily to the holding layer, the holding ability of the recording is significantly reduced.

In the present invention, at least one of the swelling layer (A) and the holding layer (B) contains a dye comprising the above-mentioned complex salt, but the dyes used in the other layers are cyanine dyes, pyrylium dyes, thiapyrylium dyes, Polymethine dyes such as squarylium dyes, croconium dyes, and azurenium dyes; phthalocyanine dyes such as phthalocyanine and naphthalocyanine; dithiol metal complexes; naphthoquinone and anthraquinone dyes; triphenylmethane dyes; aminium and diimmonium dyes Can be These dyes are also added to the resin in an amount of 5 to 30 phr, preferably 10 to 25 phr.

These dyes are mixed with a resin and then applied and cured on a substrate. As the substrate to be used, any substrate having excellent solvent resistance, optically uniform, and high surface smoothness can be used. Examples of a substrate having such characteristics include a disk-shaped substrate such as polycarbonate, polymethyl methacrylate, poly-4-methylpentene-1 resin, and glass, and a film-shaped substrate such as polyester. The film thickness of the expansion layer is generally 0.5 to 10 μm, preferably 1.0 to 5.
0 μm is used, and the thickness of the holding layer is 0.1 to 3.0 μm, preferably 0.3 to 2.0 μm. Since the recording characteristics and erasing characteristics of the recording medium are greatly affected by the degree of absorption of laser light in each layer, it is necessary to select these film thicknesses in consideration of the absorbance and concentration of the dye. Also, the reflection properties of the medium are not based solely on the surface reflection of the holding layer,
The interference effect with the reflected light of each layer also contributes. Therefore, the thicknesses of the holding layer and the expansion layer should be selected so as to maximize the interference effect.

The stacking order of the above layers may change depending on whether the target medium receives the laser beam from the laminating side or the substrate side, but the present invention is applicable to any of them.

The coating method is not particularly limited, but a spin coating method, a casting method, a bar coating method, a doctor knife method, a gravure coating method, or the like is used. Further, when a crosslinked resin is used as the resin for the expansion layer and the holding layer, curing is required. As the curing method, a thermal curing method, an ultraviolet curing method, and an electron beam irradiation method are used. In the case of thermal curing, a three-dimensional crosslinking effect is usually obtained by heating in the presence of a radical initiator. on the other hand,
In the case of the ultraviolet curing method, it is performed by irradiating ultraviolet rays in the presence of a photoinitiator.

The recording method, reproduction and erasure of the thus obtained double layer medium can be performed by irradiating two kinds of laser beams. As a laser used at that time, a helium neon laser, an argon laser, a semiconductor laser or the like is used, and a small and inexpensive semiconductor laser is more preferable. Hereinafter, the expansion layer dye D ₁ represents the absorption in the vicinity of 840 nm, retention layer dye D ₂ is described as an example media exhibiting absorption in 780nm vicinity. Recording is performed by irradiating 840 nm laser light. At this time, the expansion layer mainly absorbs light to form a bump. Reproduction irradiates weak laser light of 840nm,
This is performed by reading the difference in reflectance between the recorded portion and the unrecorded portion. Erasing is performed by irradiating 780 nm laser light. Generally, the recording is irradiated with a power of 5 to 30 mW, preferably 7 to 20 mW for 5 to 0.1 microseconds. Playback is
0.5 to 3 mW, preferably 5 to 0.1 μm with a power of 0.7 to 2.0 mW
Irradiate for 2 seconds. For erasing, irradiation is performed at a power of 1 to 20 mW, preferably 3 to 12 mW for 0.1 to 20 seconds.

According to the present invention, excellent durability can be obtained in a recording medium whose fundamental principle is to read the change in reflectance due to the formation and disappearance of bumps.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Synthesis Example 1 NK-125 (Nippon Kosaku Dyeing Co., Ltd.) 0.25g and PA1001 0.32 g of (Mitsui Toatsu Fine Co., Ltd.) was dissolved in 30 ml of N, N-dimethylformamide (DMF), kept at 80 ° C. for 4 hours, poured into cold water, the precipitate was washed with water, and dried under reduced pressure.
The obtained powder was recrystallized from a mixed solution of DMF and ethanol to obtain 0.21 g of brown crystals having a metallic luster. Elemental analysis confirmed that it was a complex salt of NK-125 cation and PA1001 anion. Yield 53%, melting point 205 ° C Elemental Analysis H C N theory 5.69 74.34 3.54 Found 5.79 73.63 3.41 Synthesis Example 2 NK-125 (Nippon Kanko Shikiso (Ltd.)) 0.25 g and PA1006
0.39 g of (Mitsui Toatsu Fine Co., Ltd.) was dissolved in 30 ml of N, N-dimethylformamide (DMF), kept at 80 ° C. for 4 hours, poured into cold water, the precipitate was washed with water, and dried under reduced pressure.
When the obtained powder was recrystallized with a mixed solution of DMF and ethanol, 0.18 g of crystals was obtained. According to the elemental analysis results, NK-1
It was confirmed that it was a complex salt of 25 cations and PA1006 anion. 40% yield, mp 205 ° C. Elemental Analysis H C N theory 3.78 53.07 3.02 Found 3.60 52.79 3.33 Synthesis Example 3 NK-125 (Nippon Kanko Shikiso (Ltd.)) 35 mg and MIR1031
(Midori Chemical Co., Ltd.) (50 mg) was dissolved in N, N-dimethylformamide (DMF) (10 ml), kept at 80 ° C. for 5 hours, poured into cold water, the precipitate was washed with water, and dried under reduced pressure. When the obtained powder was recrystallized with a mixed solution of DMF and ethanol, 6
0 mg of crystals were obtained. Elemental analysis confirmed that it was a complex salt of NK-125 cation and MIR1031 anion. 97% yield, mp 205 ° C. Elemental Analysis H C N theory 6.24 69.47 3.18 Found 5.85 65.05 2.81 Synthesis Example 4 CY-9 (manufactured by Nippon Kayaku Co., Ltd.) 0.29 g and PA1001 (Mitsui Toatsu Fine Co.) 0.32 g was dissolved in 30 ml of N, N-dimethylformamide (DMF), kept at 70 ° C. for 4 hours, poured into cold water, and the precipitate was washed with water and dried under reduced pressure. The obtained powder was recrystallized with a mixed solution of MEK and ethanol.
0.30 g of crystals were obtained. Elemental analysis confirmed that it was a complex salt of CY-9 cation and PA1001 anion. 61% yield, mp 130 to 150 ° C. Elemental Analysis H C N theory 5.73 68.78 2.86 Found 6.16 70.85 3.36 Synthesis Example 5 IR820 (manufactured by Nippon Kayaku Co., Ltd.) 0.75 g and PA1006 (Mitsui Toatsu Fine Co.) 0.78 g of methyl ethyl ketone (ME
K) After dissolving in 60 ml and keeping at 70 ° C for 3 hours, the mixture was poured into cold water, and the precipitate was washed with water and dried under reduced pressure. The resulting powder
Recrystallization from a mixed solution of MEK and ethanol yielded 0.75 g of crystals. Elemental analysis shows IR820 cation and PA100
It was confirmed that it was a complex salt of 6 anions.

Elemental Analysis H C N theory 5.10 10 against 57.14 4.68 Found 5.34 57.15 4.47 Example 1 NK ester U-122A (Shin-Nakamura Chemical Co.)
A NK ester U-122A MEK solution to which phr IR820 and 2 phr Irgacure 907 (Ciba Geigy Co., Ltd.) were added was applied on a glass substrate to a thickness of 3 μm by a bar coating method, and the expanded layer was irradiated with ultraviolet light. Was formed. 10 phr for SP4010CL-3x (Showa Polymer Co., Ltd.)
A chloroform solution of SP4010CL-3x to which a complex salt of NK-125 and PA1001 and 1 phr of benzoin ethyl ether were added was cast on the expansion layer, dried, and formed under ultraviolet light under a nitrogen atmosphere to form a holding layer. Wavelength 840nm, 10m
When a laser beam having a pulse width of 5 μsec was applied to the substrate, a bump having a diameter of 1 μm was formed. On the other hand, using a laser irradiation microscope (Nihon Kagaku Engineering Co., Ltd.)
Period 1m sec, where the wavelength at the pulse width 500n seconds 840 nm, continuous pulse irradiation and reflected light intensity of a laser beam to a non bumps portion of 2mW continuous monitoring, reduction in reflectance at ¹⁰⁶ times was hardly observed.

Example 2 An expansion layer was formed in the same manner as in Example 1. SP4010CL
NK-125 and PA at 10 phr against -3x (Showa Polymer Co., Ltd.)
A chloroform solution of SP4010CL-3x to which 1006 complex salt and 1 phr of benzoin ethyl ether were added was cast on the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a holding layer. Wavelength 840nm, 10mW, pulse width 5
Irradiation of laser light for μ seconds confirmed the formation of a bump having a diameter of 1 μm. On the other hand, using a laser irradiation microscope (Japan Science Engineering Co.), period 1m sec, where the wavelength at the pulse width 500n seconds 840 nm, a pulse irradiation and reflected light intensity of a laser beam of 2mW continuous monitoring, reflection at ¹⁰⁶ times There was almost no decrease in the rate.

Example 3 An expansion layer was formed in the same manner as in Example 1. SP4010CL
-3x (Showa Polymer Co., Ltd.) with 10 phr of NK-125 and MI
A chloroform solution of SP4010CL-3x to which a complex salt of R1031 and 1 phr of benzoin ethyl ether were added was cast on the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a holding layer. When a laser beam having a wavelength of 840 nm, 10 mW and a pulse width of 5 μs was irradiated to the two-layer medium, formation of a bump having a diameter of 1 μm was recognized. On the other hand, using a laser irradiation microscope (Japan Science Engineering Co.), period 1m sec, where the wavelength at the pulse width 500n seconds 840 nm, a pulse irradiation and reflected light intensity of a laser beam of 2mW continuous monitoring, reflection at ¹⁰⁶ times There was almost no decrease in the rate.

Example 4 The expansion layer was formed in the same manner as in Example 1. SP4010CL
NK-125 and CY at 10 phr against -3x (Showa Polymer Co., Ltd.)
A chloroform solution of SP4010CL-3x to which a complex salt of -9 and 1 phr of benzoin ethyl ether were added was cast on the expanding layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a holding layer. Wavelength 840nm, 10mW, pulse width 5
Irradiation of laser light for μ seconds confirmed the formation of a bump having a diameter of 1 μm. On the other hand, using a laser irradiation microscope (Japan Science Engineering Co.), period 1m sec, where the wavelength at the pulse width 500n seconds 840 nm, a pulse irradiation and reflected light intensity of a laser beam of 2mW continuous monitoring, reflection at ¹⁰⁶ times There was almost no decrease in the rate.

Example 5 An MEK solution of NK ester U-122A to which NK ester U-122A was added with 10 phr of a complex salt of IR820 and PA1006 and 2 phr of Irgacure 907 (Ciba Geigy Co., Ltd.) was applied on a glass substrate by bar coating. Was applied to a thickness of 3 μm, and irradiated with ultraviolet light to form an expansion layer.
10 phr of NK to SP4010CL-3x (Showa Polymer Co., Ltd.)
A chloroform solution of SP4010CL-3x added with a complex salt of -125 and PA1001 and 1 phr of benzoin ethyl ether was cast on the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a holding layer. Wavelength 840nm, 10mW,
When a laser beam with a pulse width of 5 μs is irradiated, the diameter is 1 μ
m formation of bumps was observed. On the other hand, a laser irradiation microscope (Nippon Kagaku Engineering Co., Ltd.)
1m sec, wavelength pulse width 500n seconds 840 nm, where the pulse irradiated reflected light intensity of a laser beam of 2mW continuous monitoring, reduction in reflectance at ¹⁰⁶ times was hardly observed.

Comparative Example 1 The expansion layer was formed in the same manner as in Example 1. SP4010CL
SP4010CL obtained by adding 10 phr of NK-125 and 1 phr of benzoin ethyl ether to -3x (Showa Polymer Co., Ltd.)
A −3 × chloroform solution was cast on the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a holding layer. When a laser beam having a wavelength of 840 nm, 10 mW and a pulse width of 5 μs was irradiated to the two-layer medium, formation of a bump having a diameter of 1 μm was recognized. On the other hand, using a laser irradiation microscope (Nihon Kagaku Engineering Co., Ltd.), the wavelength was 1 ms and the pulse width was 500 ns.
840 nm, 2 mW laser light was continuously pulsed to the non-bump forming part and the reflected light intensity was continuously monitored.
^{At 6} times, the reflectance dropped to 30% of the reflectance.

Effects of the Invention By using a polymethine dye in which a singlet oxygen quencher is coordinated as an ion pair in at least one of the polymer / dye expansion layer and the holding layer, the stability against repeated irradiation of erase and reproduction light is improved. Was.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kaoru Iwata 4-2-2 Asahigaoka, Hino-shi, Tokyo Teijin Limited Tokyo Research Center (56) References JP-A-63-136337 (JP, A) Japanese Patent Application Laid-Open No. Hei 2-189738 (JP, A) JP-A-60-69846 (JP, A) JP-A-60-166402 (JP, A) JP-A-60-162691 (JP, A) Int.Cl. ⁷ , DB name) B41M 5/26

Claims (3)

(57) [Claims] 1. A resin exhibiting rubber elasticity at least at room temperature (P ₁ )
Layer (A) comprising a dye (D ₁ ) having absorption in the near infrared region and a resin (P) capable of reversibly changing to a glassy state (high elasticity state) at room temperature and a rubbery state at a higher temperature. ₂ ) and a holding layer (B) comprising a dye (D ₂ ) having an absorption in the near infrared region as a recording layer on a substrate, wherein at least the expansion layer A and the holding layer B An erasable optical recording medium characterized in that the stabilized resin contains a salt from a cation of a polymethine dye and an anion of a singlet oxygen quencher as a stabilized dye in an amount of 5 to 40 phr with respect to a corresponding resin. 2. The stabilized dye according to claim 1, wherein the cation of the polymethine dye and at least one C ＝ C double bond are present, and both SH and OH are present on the carbon atom forming the double bond. ,
_2. A salt comprising a compound formed by bonding one or two kinds of groups selected from the group consisting of NH.sub.2 and NH.sub.2 and an anion of a chelate compound of a metal and 5 to 40 phr. Erasable optical recording medium. 3. The erasable optical recording medium according to claim 2, wherein said metal is Ni, Co, Cu, Mn, Pd and / or Pt.