JPH03120083A - Erasable optical recording medium - Google Patents

Abstract

PURPOSE:To achieve stabilization of a pigment without impairing the dynamic characteristic of a medium layer by a method wherein a salt composed of a cation of a polymethine pigment and a metallic complex anion is used as two layer media for forming bump. CONSTITUTION:A polymethine pigment wherein single oxygen quencher is coordinated as an ion pair to at least one side of an expanded layer composed of polymer/pigment and a retention layer is used. There are a cyanine pigment or the like herein as the polymethine pigment. Further, as the singlet oxygen quencher, a salt composed of a metallic complex anion which is chelated with a compound formed by binding one or two kinds of groups selected from SH, OH, and NH2 to both adjoining carbon atoms forming C=C double bond and of a cation neutralizing that, is exemplified. This composite salt is added to resin by 5-30phr, preferably by 10-25phr. Thereby, stabilization of the pigment can be achieved without impairing a dynamic characteristic of a medium layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an erasable optical recording medium that utilizes shape change upon heating. More specifically, the optical recording medium has improved stability against repeated irradiation with erasing and reproducing light, the recording layer consisting of a polymer/dye comprising a polymethine dye in which the dye is coordinated with a singlet oxygen quencher as an ion pair. It is related to.

BACKGROUND TECHNOLOGY AND PROBLEMS Conventionally, many organic optical recording media have been proposed that allow recording to be reproduced and erased and that can be coated. For example, JP-A-59
According to Japanese Patent No. 5448, an erasable optical recording medium made of a mixed system of a polymer and a dye is disclosed. In this medium, recording is based on the formation of pits due to flowing deformation of the polymer, and erasing is based on the principle of remelting the raised polymer around the pits generated during recording to close the pits. Therefore, it is difficult to completely restore the polymer once it has flowed out, and it is inevitable that a residue will be left behind. This erased residue is accumulated as recording and erasing are repeated. Therefore, high repeat durability cannot be obtained with this method. Furthermore, since recording and erasing utilize the melting and fluid deformation of the polymer, it is necessary to irradiate it with a high-energy laser beam. As a result, photochemical deterioration and thermal deterioration of the dye contained in the medium are likely to occur, and from this point as well, repeated use is unavoidably disadvantageous.

Also, JP-A-57-27790 and JP-A-60-253
According to each publication No. 036, an erasable optical recording medium comprising a pit-forming recording layer and an overcoat layer provided thereon is proposed. In this medium, recording is performed by forming pits due to flow deformation of the recording layer and expansion of the overcoat layer. However, since the overcoat layer has a high softening temperature, it is necessary to irradiate it with a relatively strong laser beam for a long time during erasing, similar to the above-mentioned recording medium, and this is not practical.

According to yet another proposal (Japanese Unexamined Patent Publication No. 60-69846), it consists of an expansion layer that is heated and expanded by laser beam irradiation to form a dome-shaped protrusion (bump), and a retention layer that maintains this shape. A recordable/erasable medium has been proposed.When recording on this medium, laser light is irradiated at the absorption wavelength (λ1) of the dye mixed in the expansion layer in advance, and the expansion layer forms bumps. In addition, when erasing recorded bumps, laser light is irradiated with the absorption wavelength (λ2) of the dye mixed in the retention layer in advance, so that the retention layer can maintain this shape. is heated above its glass transition temperature (Tg) so that it becomes difficult to maintain the bump shape.According to this recording method, the shape of the medium changes during recording and erasing, but it does not involve flow deformation. It is advantageous in terms of repeatability.Also, recording and erasing involve changes in shape but do not involve melting or fluidization of the polymer, so there is no need to irradiate high-energy laser light.Therefore, the dye used also However, in order to obtain a medium that requires a high degree of repeated durability, it goes without saying that it is necessary to use a dye that has high durability.

In the field of optical recording media for recording and reproduction, several dyes have been proposed from the viewpoint of durability. For example, phthalocyanine and naphthalocyanine are representative 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 (Japanese Patent Laid-Open No. 59-5579
4, Japanese Patent Application Laid-Open No. 63-209890). In this system, a transition metal chelate complex is used as a singlet oxygen quencher, which is a factor in the photodegradation of near-infrared dyes. However, there are two major problems in applying these dyes to bumped bilayer media. One is the problem of compatibility with the resin used. In other words, traditional records
In read-only recording media, only the dye and complex are deposited or coated on the substrate, so compatibility with the resin is not a problem.

On the other hand, in the case of a bump-forming two-layer medium, compatibility is important because both layers are used in a mixed system with a resin. Since the near-infrared dyes known so far have a highly conjugated molecular structure with a high molecular weight, they have extremely poor solubility in general-purpose solvents and very poor compatibility with polymer matrices. In particular, many of the proposed heavyt oxygen quenchers are metal complexes and have extremely poor compatibility with organic polymers. Another issue is singlet oxygen capture (quenching) in the polymer matrix.
It's a matter of ability. Generally, dye deterioration due to singlet oxygen is said to be based on the following mechanism.

(1) The dye absorbs light and is excited.

(2) Singlet oxygen is generated by the excited dye exchanging energy with oxygen.

(3) The generated - doublet oxygen deteriorates the dye.

At this time, the singlet oxygen quencher prevents its deterioration by capturing (quenching) the generated singlet oxygen.
The quencher effect occurs only when the reaction with the pigment outweighs the competitive reaction with the dye. In conventional recording/reading-only media, quencher molecules exist at extremely high concentrations because no matrix resin is used. Therefore, its quenching effect is expected to be extremely high. On the other hand,
In the case of a bump-forming two-layer medium, the quencher is dispersed in the matrix resin, so its effect cannot necessarily be expected. From this point of view, by forming a complex consisting of a near-infrared dye cation and a metal complex-type doublet oxygen anion, the spatial relationship between the dye, which is the source of doublet oxygen, and the singlet oxygen quencher can be reduced. There are also examples of attempts to increase the quenching effect by keeping the distance close.
Publication No. 2691〉. However, as mentioned above, near-infrared dyes and singlet oxygen are high molecular weight compounds with poorly developed conjugated systems. Therefore, by combining the respective ions, the compatibility with the matrix resin used in the bilayer medium is further limited.

As a result of extensive studies, the present inventors have found that by using a salt consisting of a polymethine dye cation and a metal complex anion in the bump-forming two-layer medium, the mechanical properties of the medium layer are not impaired. The present invention was completed by discovering that dyes can be stabilized.

Honkakusai fiend! The optical recording medium of the present invention comprises a resin (P1) that exhibits rubber elasticity at least at room temperature and a dye (D) that absorbs in the near-infrared region.
1), a resin (P1) that can reversibly change into a glass state (high elasticity state) at room temperature and a rubber state at higher temperatures, and a dye (P1) that has absorption in the near infrared region. A holding layer (B) consisting of D2) is supported by a substrate.

The expansion layer <A> needs to expand effectively when heated by laser beam irradiation in order to improve recording characteristics. In order to efficiently erase the bumps generated by recording and restore the original state, high rubber elasticity is required during erasing. Therefore, it is necessary that the resin (P1) exhibits high rubber elasticity and does not undergo flow deformation when irradiated with laser light. Preferably used resins include natural rubber; styrene-butadiene rubber, butadiene rubber,
Imprene rubber, nitrile rubber, taloloprene rubber, butyl rubber, ethylene-propylene rubber, urethane rubber,
Synthetic rubbers such as silicone rubber; styrene-based, olefin-based, and urethane-based thermoplastic elastomers; amine-crosslinked, isocyanate-crosslinked, and ultraviolet-crosslinked elastomers.

The resin (P1) used in the present invention has bumps generated due to thermal expansion during recording. ? #), and also plays the role of releasing it when erasing it. Therefore, in order to effectively create something, it is necessary to keep it in a glass state at room temperature (
(highly elastic state) and at a temperature higher than that, e.g. 6
The resin needs to be in a rubber state at 0 to 180°C. Suitable resins include thermoplastic resins such as polymethyl methacrylate resin, polycarbonate resin, and polyamide resin, and partially crosslinked products thereof, epoxy resins, phenolic resins, melamine resins, epoxy (meth)acrylate resins, and novolak (meth) resins. Examples include thermosetting resins (crosslinked resins) such as acrylate resins and polyfunctional (meth)acrylate resins [Note: (meth)acrylate means acrylate and methacrylate]. Furthermore, epoxy resins, epoxy meth)acrylate resins, novolak (meth)acrylate resins, and polyfunctional (meth)acrylate resins may be cured with ultraviolet light and are preferably used.

The dyes D1 and D2 play the role of efficiently absorbing laser light and converting it into heat during the recording and erasing processes, respectively. Therefore, dyes that match the oscillation wavelength range of the recording laser and the erasing laser are selected. In order to selectively absorb both laser beams, it is preferable that the absorption intensities in the respective oscillation wavelength ranges do not overlap excessively. Further, since the laser currently used in the optical recording field is a semiconductor laser, a dye having an absorption peak in the near infrared is preferred. Furthermore, since reading utilizes light reflection from the medium, the retention layer is required to have a high light reflectance. From this point of view, it is preferable that the dye D2 has a high reflectance. Of course, in order to achieve efficient absorption properties, the dye should be selected to be uniformly dispersed in each resin.

At least one of the dyes D1 and D2 used in the present invention is a salt (hereinafter referred to as a composite salt) consisting of a cation of a polymethine dye and an anion of a singlet oxygen quencher. The polymethine dyes include cyanine dyes, pyrylium dyes, thiapyrylium dyes, squarylium dyes, taloconium dyes, azulenium dyes, and the like. -As a heavyt oxygen quencher,
A metal complex anion chelated with a compound formed by bonding one or two groups separated by 3X from S) (, OH5NH2 to both adjacent carbon atoms forming a C=C double bond represented by the following formula) Examples include salts consisting of cations and cations that neutralize them.

Examples of such compounds include orthobenzenedithiols, catechols, orthophenylenediamines, orthoaminophenols, orthoaminobenzenethiols, orthomercaptophenols, and 1,2-ethylenedithiol derivatives. As a metal, Ni
, Co, Cu, Pd, Pt, but N
i is particularly preferably used. These metal complexes may contain various substituents to increase their solubility.

Specific examples of singlet oxygen quencher anions that are preferably used are as follows.

"Z is a valence of 1 or 2." The salt consisting of the dye cation and the singlet oxygen quencher anion is formed by an ion exchange reaction between the neutral salt of the corresponding dye and the quencher neutral salt. can be obtained easily.

These complex salts are added to the resin in an amount of 5 to 30 phr, preferably 10 to 25 phr. Complex salt content is 5
When the amount is less than phr, recording sensitivity decreases as absorbance decreases. Furthermore, if the composite salt content exceeds 30 phr, the mechanical strength of the coating film decreases, making it impossible to maintain or erase records satisfactorily. In particular, when added to the expansion layer, if the amount added is too high, the elastic modulus decreases, resulting in a decrease in the CN ratio. Furthermore, if more than necessary is added to the retention layer, the recording retention ability will be significantly reduced.

In the present invention, at least one of the expansion layer (A>) and the retention layer (B) contains a dye made of the above-mentioned complex salt, but the dyes used in the other layers include cyanine dyes, pyrylium dyes, thiapyrylium dyes, Examples include polymethine dyes such as squarylium dyes, croconium dyes, and azulenium dyes; phthalocyanine dyes such as phthalocyanine and naphthalocyanine; dithiol metal complexes: naphthoquinone, anthraquinone dyes; triphenylmethane dyes; aminium and diimmonium dyes. These dyes are also added to the resin at 5 to 30 phr, preferably 10 to 25 phr.

These pigments are mixed with a resin and then applied onto a substrate and cured. Any substrate can be used as long as it has excellent solvent resistance, optical uniformity, and high surface smoothness. Examples of substrates having such characteristics include disk-shaped substrates made of polycarbonate, polymethyl methacrylate, poly-4-methylpentene 1 resin, glass, and the like, and film-shaped substrates made of polyester. The thickness of the expansion layer is generally 0.5-It)ALm, preferably 1.0-5.0 μm, and the thickness of the retention layer is 0.5-It)ALm.
1 to 3.0 μm, preferably 0.3 to 2.0 μm is used. Since the recording characteristics and erasing characteristics of the recording medium are greatly influenced by the degree of laser light absorption of each layer, the thicknesses of these layers must be selected taking into consideration the absorbance and concentration of the dye. Further, the reflection characteristics of the medium are not simply based on the surface reflection of the holding layer, but also contribute to the interference effect with reflected light from each layer. Therefore, the thicknesses of the retention layer and the expansion layer should be selected to maximize the interference effect.

The lamination order of the above-mentioned layers may vary depending on whether the laser beam is incident on the target medium from the lamination processing side or from the substrate side, but the present invention is applicable to either case.

The coating method is not particularly limited, but a spin code method, a casting method, a bar code method, a doctor knife method, a gravure coating method, etc. are used. Further, when a crosslinked resin is used as the resin for the expansion layer and the retaining layer, curing is required. As the curing method, a thermosetting method, an ultraviolet curing method, and an electron beam irradiation method are used. In the case of thermosetting, three-dimensional crosslinking and curing is usually carried out by heating in the coexistence of a radical initiator. On the other hand, in the case of ultraviolet curing, ultraviolet rays are irradiated in the presence of a photoinitiator.

Recording, reproduction, and erasing of the thus obtained two-layer medium can be performed by irradiating it with two types of laser beams. The laser used in this case is a helium neon laser.
, an argon laser, a semiconductor laser, etc. are used, but a small and inexpensive semiconductor laser is more preferable. The following description will be given by taking as an example a medium in which the MA tension layer dye DI exhibits absorption near 840 nm and the retention layer dye D2 exhibits absorption near 780 nm. Recording is performed by irradiating a laser beam of 840 nm. At this time, the expansion layer mainly absorbs light to form bumps. Reproduction is performed by irradiating a weak laser beam of 840 nm and reading the difference in reflectance between the recorded area and the unrecorded area. Erasing is 780nrn
This is done by irradiating with laser light. - For boat fishing, recording is performed with a power of 5 to 30 mW, preferably 7 to 20 mW, for 5 to 0.1 microseconds. Reproduction is 0.5~3mW
, 5~O with a power of 0.7~2.0mW
Irradiate for 11 μs. For erasing, irradiation is performed with 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 based on the basic principle of reading changes in reflectance due to the formation and disappearance of bumps.

The present invention will be explained in more detail in Examples below.

Synthesis Example I Dissolved in 30 ml of NK-125 (Japan Photosensitive Color (41) Chylformamide<DMF) and added 809C
After keeping for 4 hours, the mixture was poured into cold water, and the precipitate was filtered, 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 with metallic luster. The results of elemental analysis confirmed that it was a complex salt of NK-125 cation and PAlooI anion. Yield 53%, melting point 205°C0, 25g and PAlooI Elemental analysis CN Theoretical value 5.69 74.34 3.54 Experimental value
5.79 '73.63 3.41 Synthesis Example 2 NK-125 (Japan Photosensitive Color Gel) 0.25g Oyohi PA1006 (Mitsui Toatsu Fine ■) 0.39g was mixed with N, N~dimethylformamide (DMF) After dissolving in 30 ml and keeping at 80°C for 4 hours, it was poured into cold water, and the precipitate was filtered, washed with water and dried under reduced pressure. The obtained powder was recrystallized from a mixed solution of DMF and ethanol to obtain 0.18 g of crystals. The elemental analysis results confirmed that it was a composite salt of NK-125 cation and PA1006 anion.

Yield 40%, melting point 205℃ Elemental analysis CN Theoretical value 3.78 53.07 3.02 Experimental value
3.60 52.79 3.33 Synthesis Example 3 NK-125 (B-insensitive dye 14) 35 rng Oyobi 1 ill R1031 (Midori Kagaku 0 Vermilion > 50 mg,
It was dissolved in 10 ml of N,N-dimethylformamide (DMF) and kept at 80"C for 5 hours, then poured into cold water, and the precipitate was filtered, washed with water, and dried under reduced pressure. The resulting powder was dissolved in a mixed solution of DMF and ethanol. 60 mg of crystals were obtained.

Based on the elemental analysis results, NK-125 cation and MIR10
Confirm that it is a complex salt of 31 anions. Yield 97
%, melting point 205°C Elemental analysis CN Theoretical value 6.24 69.47 3.18 Experimental value
5.85 65.05 2.81 Synthesis Example 4 CY-9 (Nippon Kajimi) 0.29g and PAlooI
Dissolve 0.32 g of <Mitsui Toatsu Fine ■) in 30 ml of N,N-dimethylfo/l/mu7'mide (DMF).
After keeping at 0'C for 4 hours, pour into cold water, filter the precipitate,
It was washed with water and dried under reduced pressure. The obtained powder was recrystallized from a mixed solution of MEK and ethanol to obtain 0.30 g of crystals. According to the elemental analysis results, CY-9 cation and PA, 10
It was confirmed that it was a complex salt of 01 anion. Yield 61
%, melting point 130-150℃ Elemental analysis CN Theoretical value 5.73 68.78 2.86 Experimental value
6.16 70.85 3j6 Synthesis Example 5 lR820 (Japanese Condiments>0.75g and PA100
6 (Mitsui Toatsu Fine ■) 0.78 g was dissolved in 60 ml of methyl ethyl ketone (MEK), kept at 70°C for 3 hours, poured into cold water, filtered the precipitate, washed with water and dried under reduced pressure.

When the obtained powder was recrystallized from a mixed solution of MEK and ethanol, 0.75 g of crystals was obtained. The elemental analysis results confirmed that it was a composite salt of 1R820 cation and PA1006 anion.

Elemental analysis CN Theoretical value 5.10 57.14 4.68 Experimental value
5.34 57.15 4.47 Example I NK ester jl-122A (NK ester U-122A with 10 phr of 1R820 and 2 phr of Irgacure 907 (Ciba Geigy) added to Shin Nakamura Kagaku (II)) MEK solution was applied to a thickness of 3 μm on a glass substrate by barcode method, and an expansion layer was formed by irradiating it with ultraviolet light.5P4010CL-
10 phr of NX-12 for 3X (Showa Kobunshi ■)
A 2 solution of 5P4010CL-3X in chloroform to which a complex salt of 5 and PAlooI and 1 phr of benzoin ethyl ether had been added was cast onto the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer. When this two-layer medium was irradiated with a laser beam having a wavelength of 840 cm2, 10 mW, and a pulse width of 5 .mu.sec, the formation of bumps with a diameter of 1 .mu.m was observed. On the other hand, using laser irradiation type W, Kagami Nihon Wagaku Engineering @), period 1. m seconds, pulse width 50
When continuous pulses of laser light with a wavelength of 840 nm and 2 mW were irradiated to the non-bump portion for 0 ns and the intensity of reflected light was continuously monitored, almost no low reflectance was observed after 106 times.

Example 2 The intumescent layer was formed in the same manner as in Example 1. 5P401
10 phr for 0CL-3K (Showa Kobunshi @)
complex salt of NK-125 and PA1006 and 1 ph
5P4010 with addition of r benzoin ethyl ether
A chloroform solution of CL-3X was cast onto the expanded layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer. Using a laser irradiation microscope (Nihon Kagaku Engineering ■), the wavelength was 840 nm with a period of m seconds and a pulse width of 50 On seconds.
When pulsed 2 mW laser light was irradiated and the reflected light intensity was continuously monitored, almost no decrease in reflectance was observed after 10' pulses.

Example 3 The intumescent layer was formed in the same manner as in Example 1. 5p401
10 phr for 0CL-3X (Showa Polymer ■)
A complex salt of NK-125 and MIR1031 and 1p
5P401 with added hr of benzoin ethyl ether
A chloroform solution of 0CL-3X was cast onto the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer.

Laser irradiation microscope (Japan Scientific Engineering (LS)
> using a period of 1 msec, a pulse width of 5000 seconds, and a wavelength of 84
When pulsed laser light of 0 nm and 2 mW was irradiated and the reflected light intensity was continuously monitored, almost no decrease in reflectance was observed after 106 times.

Example 4 The intumescent layer was formed in the same manner as in Example 1. 5P401
10 phr for 0CL-3K (Showa Kobunshi ■)
5P4010CL with the addition of a complex salt of NK-125 and CY-9 and 1 phr of benzoin ethyl ether.
- Casting a 3X chloroform solution onto the expanded layer and drying it,
A holding layer was formed by irradiating with ultraviolet light under a nitrogen atmosphere. Using a laser irradiation microscope (Nihon Kagaku Engineering ■),
Wavelength 840nm with period 1ms, pulse width 500ns,
When pulsed 2 mW laser light was irradiated and the reflected light intensity was continuously monitored, almost no decrease in reflectance was observed in the 106 concave case.

Example 5 10 phr of 1R8 for NK ester U-122A
A MEK solution of NK ester υ-122A to which a composite salt of 20 and PA1006 and 2 phr of Irgacure 907 (Ciba Geigy) was added was coated on a glass substrate to a thickness of 3 μm using the barcode method, and irradiated with ultraviolet light. An expanded layer was formed. 5P4010CL-3
10 phr of NK-125 for x (Showa Kobunshi ■)
A chloroform solution of 5P4010CL-3X to which a composite salt of and PAlool and 1 phr of benzoin ethyl ether had been added was cast onto the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer. Using a laser irradiation microscope (Nihon Kagaku Engineering@), we continuously monitored the reflected light intensity by irradiating pulses of 2 mW laser light with a wavelength of 840 nm and a pulse width of 500 ns with a period of 1 ms, and found that there was almost no decrease in reflectance after 106 times. I was not able to admit.

Comparative Example 1 The expansion layer was formed in the same manner as in Example 1. 5P401
10 phr for 0CL-3x (Showa Kobunshi ■)
A chloroform solution of 5P4010CL-3X to which 1 phr of NK-125 and 1 phr of benzoin ethyl ether had been added was cast onto the expanded layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer. This two-layer medium has a wavelength of 840
When irradiated with a laser beam of 10 mW, 5 μm pulse width, the formation of bumps with a diameter of 1 μm was observed. - Laser irradiation microscope (Nihon Kagaku Engineering■)
using a wavelength of 840 with a period of 1 ms and a pulse width of 500 ns.
When continuous pulses of laser light of 2 mW were irradiated onto the non-bump-formed portion and the reflected light intensity was continuously monitored, the reflectance decreased to 30% of the initial reflectance after 106 times.

Effects of the present invention By using a polymethine dye in which a singlet oxygen quencher is coordinated as an ion pair in at least one of the expansion layer and the retention layer consisting of a polymer/dye, stability against repeated irradiation of erase and reproduction light is improved. It was done.

1.1 Applicant Teijin Ltd.

Claims (3)

[Claims] (1) An expansion layer (A) consisting of a resin (P_1) that exhibits rubber elasticity at least at room temperature and a dye (D_1) that absorbs in the near-infrared region, and a glass state (high elasticity state) at room temperature and a higher In an optical recording medium having, as a recording layer, a retention layer (B) consisting of a resin (P_2) that can reversibly change into a rubber state at temperature and a dye (D_2) having absorption in the near-infrared region, the expansion layer A and at least one of the retaining layers B contains 5 to 40 phr of a salt from a cation of a polymethine dye and an anion of a singlet oxygen quencher as a stabilizer, based on the corresponding resin. optical recording medium. (2) As the above-mentioned stabilizer, the cation of the polymethine dye and at least one C=C double bond are used, and both of the carbon atoms forming the double bond contain SH, OH, and NH.
The erasure according to claim 1, characterized in that it contains 5 to 40 phr of a salt of a compound formed by bonding one or two groups selected from the group consisting of _2 and an anion of a chelate compound with a metal. Possible optical recording media. (3) The erasable optical recording medium according to claim 2, wherein the metal is Ni, Co, Cu, Mn, Pd and/or Pt.