JPH0437587A - Two-layer type organic light recording medium using crosslinked polycarbonate as record-holding layer and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a light recording medium having an excellent holding layer resin by constituting the holding layer resin in the manner of having specific elastic modulus and glass-transition temperature and crosslinking polycarbonate having unsaturated hydrocarbon radical. CONSTITUTION:This light recording medium is formed by supporting an expansion layer A composed of resin P1 indicating a rubber elasticity at least at room temperature and pigment D1 and a holding layer B composed of resin P2 reversibly changeable to a glass state at room temperature and to a rubbery state at a temperature higher than the former and pigment D2 on a substrate. The holding layer resin P2 has 50kg/mm<2> or more elastic modulus at room temperature and 60-150 deg.C glass-transition temperature and crosslinks polycarbonate having unsaturated hydrocarbon radical. A two-layer medium forming the holding layer of polycarbonate indicates not only excellent bump-forming properties but also excellent erasing properties. The medium stands the repetition of recording and erasing because of causing no irreversible deformation accompanying the flow of the medium. Also, the medium can conduct coating and hardening without causing deterioration of substrate and pigments to be used because of enabling film-making at low temperature and high speed.

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 and a method for manufacturing the same. More specifically, the present invention relates to an optical recording medium characterized in that a crosslinkable polymer is used in a recording layer made of an organic polymer/dye, and a method for producing the same.

Background technology and its problems Many optical recording media using organic dyes have been proposed (for example, Japanese Patent Laid-Open No. 61-163891.61268).
487, 62-56191. 62-122787.6
2-39286.6372594 publications). Also, I have it! Many optical recording media using a combination of dyes and organic polymers have also been proposed (for example, Japanese Patent Application Laid-Open No. 62-90
291.63-62794゜63-191691). However, the recording principle of these recording media is that the dye absorbs light (often laser light) and the heat generated causes an irreversible change in the shape of the recording medium (in many cases,
(bit formation), making it extremely difficult or impossible to erase the records. That is, in the case of a dye-only medium, since recording is performed by forming bits accompanied by vaporization and dispersion of the dye, it is impossible to erase the bits once formed. Furthermore, in the case of a mixed system of a polymer and a dye, since recording is performed by forming bits accompanied by flow deformation of the polymer, it is difficult to efficiently erase the recorded bits once formed. In addition, another conventional technique (JP-A-60-69846.63-136337.
63-136338. 63164042 publications)
proposes a recording/erasable medium comprising 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.

When recording on this medium, laser light is irradiated with the absorption wavelength (λ1) of the dye mixed in the expansion layer in advance, so that the expansion layer forms a bump and the retention layer maintains this shape. do. In addition, when erasing recorded bumps, laser light is irradiated at the absorption wavelength (λ2) of the dye mixed in the retention layer in advance, and the retention layer is
It is heated to such an extent that it becomes difficult to maintain the bump shape.

In the case of this dual layer medium consisting of a dye/polymer, in order to perform recording efficiently, in other words to make the bump as high as possible, the Tg of the polymer in the retention layer should be made as high as possible. This is because the holding layer becomes a glass state when the degree of thermal expansion is high. On the other hand, in order to perform erasing efficiently, it is better for the retention layer to have a lower Tg.

Moreover, in order to obtain an erasable medium, it is not preferable that the holding layer undergo irreversible deformation due to laser beam irradiation, that is, flow deformation of the polymer. From this point of view, three-dimensionally crosslinked polymers are preferable as the resin for the holding layer. However, in order to laminate crosslinked polymers, a post-coating curing process is generally required, and industrially it is necessary to perform this curing in a short period of time. This becomes an essential requirement for continuous coating on film substrates.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide an optical recording medium having an excellent resin for a holding layer and a method for manufacturing the same.

The present inventors conducted intensive studies to obtain a resin for the retaining layer that satisfies the above-mentioned contradictory requirements, and found that a polycarbonate crosslinked product with a specific structure has the desired thermal properties, and that The present invention was achieved by discovering that it cures in a short time.

The present invention has the following features: (1) An expansion layer (△) consisting of a resin (P1) that exhibits rubber elasticity at least at room temperature and a dye (D+) on a substrate, and a layer that is reversible to a glass state at room temperature and to a rubber state at a higher temperature. In an optical recording medium that supports a retention layer (B) consisting of a resin (P1) that can change depending on the temperature and a dye (D1), the retention layer resin P2 (1) has an elastic modulus of 50 kg/kg at room temperature. mm2 or more,
(2) a glass transition temperature of 60 to 150°C,
(3) An erasable two-layer organic optical recording medium characterized by being made of crosslinked polycarbonate having unsaturated hydrocarbon groups.

The present invention also includes a method for producing the above-mentioned optical recording medium, characterized in that polycarbonate is coated on the expansion layer (A) and then subjected to ultraviolet light irradiation or heat treatment.

The optical recording medium of the present invention includes an expandable layer (A) consisting of a resin (P1) exhibiting rubber elasticity at least at room temperature and a dye (D1), and a reversible layer (A) that is in a glass state at room temperature and in a rubber state at a higher temperature. Variable resin (P1) and dye (D,!
') is supported by a substrate.

Note that the relationship between the expansion layer (A>) and the holding layer (B) with respect to the substrate can be changed as appropriate depending on the direction of laser incidence.

In order to improve the recording properties, it is necessary for the expansion layer (A) to expand effectively when heated by laser irradiation. 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 due to laser beam irradiation. Suitable resins include natural rubber; synthetic rubbers such as styrene-butadiene rubber, butadiene rubber, isoprene rubber, nitrile rubber, chloroprene rubber, butyl rubber, ethylene-propylene rubber, utarene rubber, and silicone rubber; styrene-based, olefin-based, and urethane rubbers; thermoplastic elastomer; amine crosslinked type,
Examples include incyanate crosslinking type and ultraviolet crosslinking type elastomers.

The dyes D1 and Dl play the role of efficiently absorbing laser light and converting it into heat during the recording process and the erasing process, respectively. Therefore, a dye is selected that matches the oscillation wavelength range of the recording laser and the erasing laser. 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. In addition, since the lasers currently used in the optical recording field are semiconductor lasers, dyes with an absorption peak in the near infrared are preferable, and in order to use light reflection on the medium surface for reading, the retention layer Since a high light reflectance is required, the holding 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, for efficient absorption properties, the dyes should be selected to be uniformly dispersed in the respective resin. Suitable dyes D1 and Dl include cyanine dyes such as polymethine dyes, biryllium dyes, thiapyrylium dyes, squarylium dyes, croconium dyes, and azulenium dyes; phthalocyanine dyes such as phthalocyanine and naphthalocyanine; dithiol metals. Complexes: naphthoquinone, anthraquinone-based dyes; nitriphenylmethane-based dyes; aminium and diimmonium-based dyes.

In the present invention, the resin (P1
) fixes the bumps generated by thermal expansion during recording,
It has the function of releasing the hump fixation when erasing.

Therefore, in order to efficiently perform the self-function, it is preferable that the elastic modulus is low because it turns into a rubber state at high temperatures and forms bumps due to thermal expansion of the expansion layer (A>.The elastic modulus at high temperatures is ' 1/10 or less of the value at g temperature, preferably 1/
It is suitable that it is 2o or less. At room temperature, the expansion layer (A
) A high tensile elastic modulus is required in order to fix the bump against the contraction force of 50 to 9/mm2 or more, preferably 80 to 9/mm2 or more.
If it exceeds 0.001 (9/-), the elastic modulus at high temperature becomes a value of 8, making erasing difficult. If it is less than 50/9/-, the shape of the bumps cannot be maintained sufficiently, and the recording characteristics and recording stability deteriorate. In addition, for efficient recording and erasing, the temperature at which the glass state changes to the rubber state (glass transition temperature Tg) is also important.
60 to 150°C, preferably 70 to 120°C. If it is less than this, the height of the bumps formed will be low, which is unfavorable in terms of recording characteristics, and also unfavorable in terms of recording stability. If the amount is more than this, an erased residue will remain during erasing, which is undesirable.

The resin P2 used in the present invention is a crosslinked polycarbonate obtained by crosslinking polycarbonate containing an unsaturated hydrocarbon group in the molecule by photo or thermal reaction. Such a crosslinked polycarbonate body itself not only has a Tg suitable for the recording medium holding layer, but also can form a strong and uniform coating film. In addition, it is also possible to insolubilize by crosslinking. The degree of insolubilization is 10% by weight of the dissolved portion in a good solvent such as dichloromethane.
It is preferably less than or equal to 5% by weight, more preferably 5% by weight.
It is as follows.

Polycarbonates suitably used in the present invention include:
Examples include polyh-bonnets containing at least 10 mol% or more of the following formula 1] and/or [I[1].

Suitable examples of the unsaturated hydrocarbon group used for R1 in the polycarbonate unit [I] include vinyl group, allyl group, 10
benyl group, isopropenyl group, 3-butenyl group, 1,3-
Examples include butadienyl group and 1,3-pentagenyl group. In addition to the unsaturated hydrocarbon group or hydrogen atom used for R1, R2 includes an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms. used. R1 and R2 may be the same unsaturated hydrocarbon group. Preferred alkyl groups include methyl, ethyl, propyl, isopropyl, isobutyl, and cycloalkyl groups include cyclopentyl and cyclohexyl.

Further, examples of the aryl group include a phenyl group, tolyl group, xylyl group, and naphthyl group.

Ar+ and Ar2 are the same or different phenylene groups which may be substituted with halogen and/or alkyl groups. Preferred are p-phenylene and Akebono-phenylene groups. In addition, as the halogen, bromine, chlorine, etc. are preferably used, and as the alkyl group, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group,
Isobutyl group, terciselybutyl group, etc. are preferably used.

On the other hand, preferred examples of the unsaturated hydrocarbon group used for R3 in the polycarbonate unit [II], including the bonded carbon atoms, are 2-cyclopentene-1,1-diyl, 2-cyclohexene 1.1 -diyl, 2,4-cyclohexadiene-1,1-diyl, 3,5.5-trimethyl-2-cyclohexene-1,1-diyl, and the like. Further, Ar 3 and Ar4 are the same or Ha Tatsumi, and the phenylene group used for ArΔr2 is used.

In the polycarbonate used in the present invention,
The structural units other than the intermediate ones represented by the formulas [I] and [n] are not particularly limited, but are generally represented by the following formula [11
1], [■], [V] and [VI] are preferably used.

R4 -Ar　　9　-0 〇－ Area Ar.

-O- [V] [VI] Among R4 and R5, suitably used alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, isobutyl group, etc., and cycloalkyl groups include cyclopentyl group, Examples include cyclohexyl group. Further, examples of the aryl group include a phenyl group, tolyl group, xylyl group, and naphthyl group. Ars~
Preferable examples of A'11 include p-phenylene and -1-phenylene groups.Also, examples of halogen include bromine,
Chlorine is preferably used, and the alkyl group includes a methyl group,
Ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, etc. are preferably used. Moreover, suitable examples of X include a phenylene group, a cyclohexylene group, -05--802-, and the like.

In the polycarbonate used in the present invention, the constituents represented by the formulas [I] and/or [II] are present in a proportion of at least 10% by mole, preferably 20% by mole or more, based on the total polycarbonate. If it is less than 1011%, the degree of crosslinking will be insufficient, which is not preferable. The selection and proportion of these structures are determined based on the compatibility of polycarbonate with dyes, compatibility with crosslinking agents, solubility in solvents, photocrosslinkability, thermal properties including Tg of the crosslinked product, mechanical properties, etc. It should be selected with consideration. In the present invention, these structural intermediates may be used alone, a copolymer using a plurality of them, or a mixture thereof may be used.

The polycarbonate used in the present invention can be obtained by a conventionally well-known reaction (see Nikkan Kogyo Shimbun, Plastic Materials Course [5], Polycarbonate, pages 9 to 14). An example of a polycarbonate consisting of the structural unit represented by the formula [I] is shown below.

(1) Reaction using phosgene represented by the following formula Reaction using bischloroformate - [Ar+ C-Ar20 C-0]n +nHcj
(3) Reaction using carbonic acid diester Among these production methods, the reaction using phosgene is most preferably used because the resulting polycarbonate has excellent transparency and can be produced at low cost.

The crosslinking reaction of the polycarbonate of the present invention can be carried out thermally or by a photochemical reaction. The thermal crosslinking reaction is easily achieved by heating the resin in the presence of a radical initiator, adding a crosslinking agent if necessary. As a radical initiator, 50-100℃
It is preferable from the viewpoint of the process that the half-life is 1 to 10 hours. Specific examples include peroxides such as benzoyl peroxide, peroxide, t-butyl peroxybivalate, octanoyl peroxide, lauroyl peroxide, acetyl peroxide, and cyclohexanone peroxide, and azobisisobutyronitrile. and azo compounds such as azobisisovaleronitrile. The amount used is 0.1 to 10% by weight, preferably 0.5 to 5% by weight based on the polycarbonate.
Weight%.

Moreover, a crosslinking agent can also be used. As a crosslinking agent,
Diallyl compounds such as diallyl phthalate, diallylamine hydrochloride, and diallyl ether, and polyfunctional acrylates such as trimethylolpropane triacrylate, 2-hydroxyethyl dimethacrylate, and pentaerythritol tetraacrylate are preferably used. These crosslinking agents are used in amounts of 3.0 to 30% based on polycarbonate.
, preferably 5.0 to 20% by weight. When the polycarbonate of the present invention is subjected to a thermal crosslinking reaction, the
It is carried out at a temperature of 0 to 200°C, preferably 70 to 150°C. 70
If the temperature is below 0.degree. C., the thermosetting reaction will not proceed sufficiently, which is not preferable. Moreover, it is not preferable to use tso'cg because it causes deterioration of the substrate and dye. Curing time is generally 5 minutes to 1
It is carried out for 0 hours, preferably in the range of 10 minutes to 5 hours.

When the crosslinking reaction of the polycarbonate of the present invention is carried out by irradiation with ultraviolet rays, it is preferably carried out by irradiating ultraviolet rays after coating in the coexistence of a crosslinking agent in addition to a photoradical initiator. Crosslinking agents suitably used in the present invention include (1) polyallyl compounds, (2) polyfunctional acrylates, (3) polymercaptans, and (4) polyfunctional azide compounds.

Suitable examples of the polyallyl compound include diallyl compounds such as diallyl phthalate, diallylamine hydrochloride, and diallyl ether. Examples of polyfunctional acrylates include trimethylolpropane 1-7 acrylate;
Representative examples include ethylene glycol dimethacrylate and pentaerythritol tetraacrylate. Polymercaptans include pentaerythritol tetra (3-mercaptoproonate) and 1,
Examples include 4-dimercaptohexane. As the polyfunctional azide compound, aromatic azide having relatively good thermal stability is preferably used. Preferred polyfunctional azides include 4,4'-diazidobenzalacetone, 2,6-di(4'-azidobenzal)cyclohexanone, and 2,6-di(4'-azidobenzal)-4-methylcyclohexanone. , di[4-(4'-azidophenyl)butadienyl 1 ketone, 4,4'-diazidochalcone, 4,4'-diazitosderbene-2,2'-disulfonic acid, and the like. These crosslinking agents are used in an amount of 1 to 50% by weight, preferably 3 to 30% by weight, based on the polycarbonate. Among these crosslinking agents, the coexistence of a photopolymerization initiator is preferred in the ultraviolet crosslinking reaction of polyallyl compounds, polyfunctional acrylates, and polymercaptans. Suitable photopolymerization initiators include benzophenone compounds such as benzophenone and Michler's ketone, diketone compounds such as pencil and phenylmethoxydiketone, benzoin compounds such as benzoin ethyl ether and benzyl dimethyl ketal, and 2,4-diethylthioxanthone. Quinone compounds such as thioxanthone compounds, 2-methylanthraquinone, and camphorquinone are preferably used. Although it depends on the type of crosslinking agent, these initiators are generally 0.
1 to 20% by weight, preferably 1 to 10% by weight is used.

Moreover, it is also possible to use an ultraviolet crosslinking reaction accelerator (for example, N,N-diethylaminobenzene derivative) in addition to the above-mentioned initiator, if necessary.

As the irradiation source used for the photocuring reaction, a mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, etc. are suitably used. The power of the light source is 1TIL W/tyi
, ~1 kW/cj are used. The irradiation time depends on the power of the light source and the photoreaction speed, but it ranges from 1 second to 1 hour.
It is preferably carried out for 10 seconds to 10 minutes.

These resins used in the present invention are mixed with a pigment and then applied onto a substrate and cured. The substrate used is not particularly limited, but generally a disk-shaped substrate made of polycarbonate, polymethyl methacrylate, poly-4-methylpentene-1, glass, or the like, or a film-shaped substrate made of polyester or the like is used.

The weight ratio of dye/resin depends on the absorbance of the dye and the film thickness, but is generally 0.05 to 0.4, preferably 0.1 to 0.4.
It is 0.3.

The thickness of the expansion layer is generally 0.5 to 10 μm, preferably 1.0 to 5.0 μm, and the thickness of the retention layer is 0.5 to 10 μm.
1 to 3.0 μm, preferably 0.3 to 2.0 μm is used.

There are no particular limitations on the coating method, but spin code method, casting method,
Barcode method, doctor knife method, gravure coating method, etc. are used. Suitable solvents used in this case include: aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methanol, ethanol, butanol; chloroform, methylene chloride, etc. Haloalkanes such as; esters such as ethyl acetate and butyl acetate; acetone, methyl ethyl ketone; ketones such as methyl isobutyl ketone and cyclohexanone; glymes such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether; ethers such as tetrahydrofuran and dioquine , nitromethane, acetonitrile and mixtures thereof.

Recording, reproduction, and erasing of the thus obtained two-layer medium are performed by irradiating it with two types of laser beams. The laser used in this case may be a helium neon laser, an argon laser, a semiconductor laser, etc., but a small and inexpensive semiconductor laser is more preferable. Hereinafter, the expansion layer dye D1 shows absorption near 840 nl, and the retention layer dye D2 shows absorption near 840 nl.
This will be explained by taking as an example a medium that exhibits absorption in the vicinity of 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 performed by irradiating 780 nll of laser light.

By design, the recording is 5-30 mW, preferably 7-20 mW.
Irradiate with a power of W for 20 to 0.1 μsec. Playback is 0.5
It is performed with a power of ~3 mW, preferably 0.7-2.0 TrLW. Erasing is from 1 to 20 mW, preferably from 3 to 1
Irradiate for 0.1-20 μsec with a power of 2 mW.

Effects of the Invention The two-layer medium having polycarbonate as a retention layer obtained according to the present invention not only exhibits excellent bump-forming properties, in other words, recording properties, but also exhibits excellent erasing properties. Recording is performed in order to prevent irreversible deformation due to the flow of the medium.
Can withstand repeated erasures.

Furthermore, according to the present invention, since film formation can be performed at low temperatures and high speeds, coating and curing can be performed without deteriorating the substrate or the dye used, and there are also industrial advantages in that the media cost is low. are doing.

Hereinafter, the present invention will be explained in more detail according to examples. However, the present invention is not limited to this.

Example 1 Urethane acrylate U~12 as expansion layer resin P1
2A (Shin Nakamura Chemical) was used, and Irgacure 907 (Chiba) was added to this resin as a photopolymerization initiator.
A coating solution was prepared by adding 3 parts by weight of Polymethine dye TR-820 (Nippon Kayaku) as a dye for an 830 nm semiconductor laser, and using methyl ethyl ketone as a solvent. After coating the obtained solution on a glass substrate to a film thickness of 3 to 4 μm and drying,
80W/cm high pressure mercury lamp light under nitrogen atmosphere
Ultraviolet light curing was performed by irradiating for minutes. Next, 3-butenyl and methyl group-substituted p, p' shown in the following formula C
Polycarbonate copolymer obtained from -methylidene bisphenol and p,p'-cyclohexylidene bisphenol (molar ratio = 1,71) PC-1) 100
Parts by weight, 10 parts by weight of cyanine dye (NK-125゜Japan Photosensitive Color), 10 parts by weight of pentaerythritol tetra (3-mercaptopropionate) and 10 parts by weight of Irgacure 907.1 parts by weight were dissolved in chloroform to give 10% by weight of boron. A homogeneous solution of was obtained. This solution was applied onto the above-mentioned expansion layer to a thickness of 1 μm, and then dried at 80° C. for 10 minutes. Thereafter, the film was cured by irradiating it with high-pressure mercury lamp light having an irradiation energy of 80 W/CIi for 10 minutes while the film was left standing.

When the resulting two-layered medium was irradiated with a semiconductor laser beam with an oscillation wavelength of 830 nm and a leading output of 107yLW,
Formation of clear bumps with a diameter of 1.4 μm was observed on the surface of the medium. Subsequently, when this recording spot was irradiated with a 7TrLW semiconductor laser beam having a beam diameter of 5 μm and an oscillation wavelength of 780 r+n for 5 μ seconds, the bumps mentioned above had disappeared to such an extent that they could not be confirmed by microscopic observation. From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

Further, while rotating the obtained medium at a linear velocity of 2 m/s, a laser beam having an oscillation wavelength of 840 nII and an intensity of 10 mW was applied for 50 minutes.
When irradiated with a cycle of MHz (duty ratio 50), a clear bump with a width of 1.2 μm was formed on the medium, and the CN ratio was 55 dB. Subsequently, when this recording bump was continuously irradiated with a 7 mW semiconductor laser beam having an oscillation wavelength of 780 rv, the bump disappeared. After repeating this dynamic evaluation recording/erasing test 1000 times, the C/N ratio hardly decreased.

Example 2 In Example 1, 3-butenyl and methyl group-substituted p, p represented by the following formula % were used instead of PC-1 as the retention layer.
A two-layer medium was similarly obtained using a polycarbonate homopolymer (PC-2') made from '-methylidene bisphenol.

When the thus obtained two-layered medium was irradiated with semiconductor laser light with an oscillation wavelength of 830 nm and a leading output of 10 TrLW for 1 μs, the formation of clear bumps with a diameter of 1.4 μm was observed on the medium surface. . When this recording spot was subsequently irradiated with a 7771W semiconductor laser beam having a beam diameter of 5 μm and an oscillation wavelength of 780 nm for 10 μs, the bumps had disappeared to such an extent that they could not be confirmed by microscopic observation. From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

In addition, while rotating the obtained medium at a linear velocity of 2 m/s, a laser beam with an oscillation wavelength of 840 nm and an intensity of 10 mW was applied for 5 minutes.
During cyclic irradiation with a frequency of MHz < duty ratio 50), a clear bump with a width of 1.2 μm was formed on the medium, and the CN ratio was 50 dB. Subsequently, when this recording bump was continuously irradiated with a 7TrLW semiconductor laser beam having an oscillation wavelength of 780 nm, the bump disappeared.

Example 3 Instead of using urethane acrylate tJ-122A alone as the expansion layer in Example 1, urethane acrylate oligomer (U-12A) with a polyfunctional crosslinking component was used.
26A, Shin Nakamura Chemical) using a 4-bilayer weight ratio mixture,
A two-layer medium was similarly prepared.

When the thus obtained two-layer medium was irradiated with a semiconductor laser beam having an oscillation wavelength of 83 Or+m and a leading output of 10 mW for 1 μs, the formation of a clear bump with a diameter of 1.6 μm was observed on the medium surface. Subsequently, when this recording spot was irradiated with a 7 mW semiconductor laser beam having a beam diameter of 5 μm and an oscillation wavelength of 780 nm for 10 μs, the bumps had disappeared to such an extent that they could not be confirmed by microscopic observation.

From this result, it was found that the above recording medium can be used as an optical information recording medium that allows recording and erasing. In addition, as a result of a dynamic test conducted in the same manner as in Example 1, 55 d
A high C/Nlt of 3 was obtained.

Example 4 In Example 1, pentaerythritol tetra(3-
A bilayer media was similarly made using trimethylolpropane triacrylate instead of using mercaptopropionate.

This medium had an oscillation wavelength of 830 nn+ as in Example 1.

When irradiated with a recording laser beam with an intensity of 10TrLW,
Clear bump formation was observed. Subsequently, on this recording spot, a 7 m beam with a beam system of 5 μm and an oscillation wavelength of 780 nm was placed.
When irradiated with W semiconductor laser light for 6 microseconds, the bumps mentioned above were confirmed by microscopic observation and disappeared to such an extent that they could not be seen. From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

Example 5 In Example 1, 3-butenyl and methyl substituted p, p'- represented by the following formula % were used instead of PC-1 as the retention layer.
Polycarbonate copolymer (P) obtained from methylidene bisphenol and bisphenol A (molar ratio: 1/1)
A two-layer medium was similarly obtained using C-3). When the thus obtained two-layered medium was irradiated with semiconductor laser light with an oscillation wavelength of 830 rv and a leading output of 10 mW for 1 μs, a clear bump with a diameter of 1.4 μm was observed on the medium surface.
The formation of was observed.

Subsequently, when this distribution spot was irradiated with a 7 mW semiconductor laser beam having a beam diameter of 5 μ and an oscillation wavelength of 780 na+ for 10 μ seconds, the bumps had disappeared to such an extent that they could not be confirmed by microscopic observation. From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

Further, while rotating the obtained medium at a linear velocity of 2 m/sec, a laser with an oscillation wavelength of 840 nm and an intensity of 10 mW was heated at 5 MHz (duty ratio 50) nocyc/l/
As a result, a clear bump with a width of 1.2 μm was formed on the medium, and the C/N ratio was 55 dB. Subsequently, when this recording bump was continuously irradiated with a 7rrLW semiconductor laser beam having an oscillation wavelength of 780 nm, the bump disappeared. In addition, this recording/erasing test
Although the test was repeated 00 times, no significant decrease in the C/N ratio was observed.

Example 6 In Example 1, PC-1 was replaced with vinyl-substituted rl, D'-methylidene bisphenol and p, p'-cyclohexylidene bisphenol (molar ratio Nia/3) as the retention layer according to the following formula. A further medium was similarly obtained using a polycarbonate copolymer (PC-4) obtained from PC-4.

When the thus obtained two-layered medium was irradiated with a semiconductor laser beam having an oscillation wavelength of 830 nm and a leading output power of 10 mW for 1 μs, the formation of clear bumps with a diameter of 1.4 μm was observed on the medium surface. . Subsequently, a 7 m beam with a beam diameter of 5 μm and an oscillation wavelength of 780 nm was placed on this recording spot.
When irradiated with W semiconductor laser light for 10 microseconds, the bumps mentioned above had completely disappeared to the extent that they could not be confirmed by microscopic observation. From this result, it was found that the above recording medium can be used as an optical information recording medium that allows recording and erasing. Also,
While rotating the obtained medium at a linear velocity of 2 m/sec, a 5 MH laser with an oscillation wavelength of 840 nl and an intensity of 10 mW was applied
When irradiated with a cycle of Z (duty ratio 50), a clear bump with a width of 1.2 μm was formed on the medium, and the C
/N ratio was 57 dB. Subsequently, when this recording bump was continuously irradiated with a 7 mW semiconductor laser beam having an oscillation wavelength of 780 nm, the bump disappeared.

Example 7 In Example 1, 1), +1'-(2-cyclohexecolidene)bisphenol, and bisphenol-A (molar ratio Nia/
3) Polycarbonate copolymer (PC-5
A two-layer medium was obtained in the same manner. A dynamic test was performed on the two-layer medium thus obtained under the same conditions as in Example 1, and a C/N ratio of 48 dB was obtained.

Claims (4)

[Claims] (1) On the substrate, there is an expansion layer (A) consisting of a resin (P_1) that exhibits rubber elasticity at least at room temperature and a dye (D_1), which changes reversibly into a glass state at room temperature and into a rubber state at higher temperatures. In an optical recording medium formed by supporting a retention layer (B) consisting of a resin (P_2) and a dye (D_2), the retention layer resin P_2 (1) has an elastic modulus of 50 Kg/mm^2 or more at room temperature; and (2) a glass transition temperature of 60 to 150°C, (
3) An erasable two-layer organic optical recording medium characterized by being made of crosslinked polycarbonate having unsaturated hydrocarbon groups. (2) The polycarbonate crosslinked product has the following general formula [I]▲
There are mathematical formulas, chemical formulas, tables, etc. ▼...[I] In the formula [I], R_1 is a monovalent unsaturated hydrocarbon group with 2 to 8 carbon atoms, and R_2 is the unsaturated hydrocarbon group used for R_1. group, a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and A
r_1 and Ar_2 are the same or different and are phenylene groups optionally substituted with a halogen atom and/or an alkyl group. 2. The erasable two-layer organic optical recording medium according to claim 1, wherein the erasable two-layer organic optical recording medium is a crosslinked polycarbonate containing at least 10 mol% of units represented by (3) The polycarbonate crosslinked product has the following general formula [II] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ... [II] In formula [II], R_3 is a divalent unsaturated hydrocarbon having 4 to 10 carbon atoms Ar_3 and Ar_4 are the same or different and are phenylene groups optionally substituted with a halogen atom and/or an alkyl group. 2. The erasable two-layer organic optical recording medium according to claim 1, wherein the erasable two-layer organic optical recording medium is a crosslinked polycarbonate containing at least 10 mol% of units represented by (4) The method for producing an erasable optical recording medium according to any one of claims 1 to 3, wherein the polycarbonate is coated on the expansion layer (A) and then subjected to ultraviolet light irradiation or heat treatment.