JPH03120085A - Erasable optical recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To achieve stabilization of a pigment by a method wherein a resin is principally composed of hardened substance of epoxy(meta)acrylate and/or epoxy-novolac(meta)acrylate having a specified transition temperature and an elastic modulus from a glass state to a rubber state. CONSTITUTION:A resin has a function wherein a bump generated by thermal expansion of an expansion layer (A) by radiation of laser beams is fixed in recording and fixing of the bump is allowed to be released in erasing. Then, epoxy(meta)acrylate, and epoxy-novolac acrylate are used as the resin. Further, its elastic modulus should be necessarily 80kg/mm<2> or higher, and preferably 100kg/mm<2> or higher. Furthermore, a transition temperature at which it varies from a glass state to a rubber state should be necessarily 60-150 deg.C and preferably 70-120 deg.C. Thereby, stabilization of a pigment can be achieved.

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, it relates to an optical recording medium characterized in that a reduced polymer that can be cured by actinic light such as ultraviolet rays is used as a part of the recording layer made of an organic polymer/dye, and a method for producing the same. It is something.

BACKGROUND TECHNOLOGIES AND THEIR POINTS Conventionally, many optical recording media using organic dyes have been proposed (for example, Japanese Patent Laid-Open No. 61-163891.61-268
487, 62-56191.62-122787.62
-39286 and 63-72594).

Furthermore, many optical recording media using a combination of organic dyes and organic polymers have been proposed.
-90291.63-62794 and 63-1916
(Refer to 91 issues). However, the recording principle of these recording media is based on the irreversible change in shape of the recording medium due to the heat generated when the dye absorbs light (often laser light) (in many cases, pit formation). Records were extremely difficult or impossible to erase. 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 pits once formed. Furthermore, in the case of a mixed system of a polymer and a dye, since recording is performed by forming bits by flowing deformation of the polymer, it is difficult to efficiently erase the recording pits once formed. In addition, another prior art (Japanese Unexamined Patent Publication No. 60-69846.63-1
36337.63-136338 and 63-1640
42 publications), a recordable and erasable medium is made up 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. 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 to form bumps on the expansion layer. Then, the holding layer also deforms according to this shape, but when irradiated with laser light, the holding layer is rapidly cooled and solidified, making it possible to maintain this shape. Next, when erasing the recorded bumps, laser light is irradiated with the absorption wavelength (λ2) of the dye mixed in the retention layer in advance, and the retention layer is heated above its Tg. If this is not done, it will become difficult to maintain the bump shape due to the restoring force of the expansion layer.

In the case of this dual layer medium consisting of a dye/polymer, in order to perform recording efficiently, or 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 changes. On the other hand, for efficient erasing, it is better for the retention layer to have a lower Tg. Moreover, in order to obtain an erasable medium, it is undesirable that the holding layer undergoes 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.

The inventors of the present invention conducted intensive studies to obtain a resin for the retention layer that satisfies these contradictory requirements, and found that a polymer with a specific structure has the desired thermal properties and can be irradiated with ultraviolet light in a short time. The present invention was achieved by discovering that it hardens.

Summary of the Invention The optical recording medium of the present invention comprises an expandable layer (A) consisting of a resin (P) exhibiting rubber elasticity at least at room temperature and a dye (Di), and a glassy B (high elastic state) at room temperature. , a resin that can reversibly change to a rubber state at higher temperatures (
A holding layer (B) consisting of P2) and a dye (D2) 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, the expansion layer (A) needs to expand effectively when heated by laser irradiation.

In order to efficiently erase 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. 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, urethane rubber, and silicone rubber; styrene, olefin, and urethane rubbers; Thermoplastic elastomer: Examples include amine crosslinked type, isocyanate crosslinked type, and ultraviolet crosslinked type elastomer.

The dyes D4 and D2 play the role of efficiently absorbing laser light and converting it into heat during the recording and erasing processes, respectively. Therefore, a dye having an absorption matching the oscillation wavelength range of the recording laser and the erasing laser is delivered. 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 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, in order to achieve efficient absorption properties, the dyes should be selected in two ways so that they are uniformly dispersed in each resin. Suitable pigmentation and D2
Examples include polymethine dyes such as cyanine dyes, pyrylium dyes, thiapyrylium dyes, squarylium dyes, croconium dyes, and azulenium dyes;
Examples include phthalocyanine dyes such as phthalocyanine and naphthalocyanine; dithiol metal complexes; naphthoquinone and anthraquinone dyes; triphenylmethane dyes; aminium and diimmonium dyes. Further, a plurality of these dyes may be used in combination.

In the present invention, the resin (P2
) has the function of fixing bumps generated by thermal expansion of the expansion layer (A>) by laser beam irradiation during recording, and allowing the bumps to be unfixed during erasing.

Therefore, in order to effectively perform creative purposes, the resin must be in a rubber state at high temperatures and a glass state at room temperature, that is, a resin with high elasticity. In other words, at high temperatures, the elastic modulus needs to be low in order to form bumps due to the thermal expansion of the expansion layer (A).At room temperature, the elastic modulus must be low to resist the contraction force of the expansion layer (A) and fix the bumps. A high tensile modulus is required, and it is necessary to have a tensile modulus of 80 Kg/mm2 or more, preferably 100 Kg/mm2 or more.If it is less than that, the shape of the bump cannot be maintained sufficiently, and the recording performance and recording stability will 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. From this point of view, the transition temperature is 60 to 150 °C, preferably 70 °C. ~
An example is 120°C. If it is less than this, the height of the formed bump 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. Examples of the resin P2 used in the present invention include epoxy (meth)acrylate and epoxy novolac (meth)acrylate.These resins can be crosslinked with actinic rays, heat, etc. to obtain a coating film having a desired Tge. .

Epoxy meta> acrylate is as follows - maximum: "In the formula,
Y is an alkylene group having 1 to 5 carbon atoms, R is a (meth)acryloyl group, and n is an integer of 1 to 20. Epoxy acrylate in which Y is a methylene group or a 2,2-propylene group is preferred because it has a high Tg and can improve recording characteristics without deteriorating erasing characteristics.

On the other hand, epoxy novolak acrylate has the following - maximum: % formula % "In the formula, R is <R' is a methyl group or a hydrogen atom), m is a carbon number of 1 to 2
is an integer of 0, and X is a hydrogen atom or a methyl group.

This is a compound represented by Further, acrylate is preferable because it has higher reactivity than methacrylate.

In the present invention, these compounds may be used alone or as a mixture of a plurality of them.

Further, other polyfunctional acrylates may be used in combination within a range of 30% by weight or less without impairing the spirit of the invention. This is effective in increasing the reactivity, controlling Tg, increasing the mechanical properties of the film, and increasing the compatibility with other dyes. Preferred polyfunctional (meth)acrylates include ethylene di(meth)acrylate, tetramethylene di(meth)acrylate, trimethylolpropane trimeth)acrylate, pentaerythritol tetrameth)acrylate, and dipentaerythritol hexa(meth)acrylate. ) acrylate, polyfunctional urethane acrylate.

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, glass, etc., or a film-shaped substrate made of polyester, etc. is used. The dye/resin ratio depends on the dye absorbance and film thickness, but is generally 0.05 to 0.4 (wt/wt), preferably 0.
．． 1 to 0.3 (wt/wt). The thickness of the expansion layer is generally 0.5 to 10 μm, preferably 1.0 to 5 μm.
0 μm is used, and the thickness of the holding layer is 0.1 to 3.0 μm.
m, preferably Oj to 2.0 μm. 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.

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, and butanol; chloroform, methylene chloride, etc. haloalkanes; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; glymes such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether; ethers such as tetrahydrofuran and dioquine; Mention may be made of nitromethane, acetonitrile and mixtures thereof.

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 is usually achieved by heating in the presence of a radical initiator. The initiator is not particularly limited, but generally includes azobisisobutyronitrile (AIBN), benzoyl peroxide<BPO
), cumene hydroperoxide, tert-butyl hydroperoxide 5, lauroyl peroxide, and the like. The heating temperature is generally 50 to 150°C, preferably 70 to 12°C.
0'C is adopted. If it is more than that, the substrate and dye will deteriorate, which is not preferable. The curing time is generally 5 minutes to 10 hours, preferably 10 minutes to 5 hours.

On the other hand, in the case of ultraviolet curing, ultraviolet rays are irradiated in the presence of a photoinitiator. As a photoinitiator,
Benzophenone-based initiators such as benzophenone and Michler's ketone; diketone-based initiators such as benzyl and phenylmethoxydiketone; benzoin-based initiators such as benzoin ethyl ether and benzyl dimethyl ketal; 2.
Thioxanthone initiators such as 4-diethylthioxanthone, quinone initiators such as 2-methylanthraquinone and camphorquinone, and the like are preferably used.

If necessary, it is also possible to use a promoter such as an amine promoter. As the ultraviolet light to be used, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, etc. are suitably used. Antigen power is 1mW/- to 1kW
/cfll is used. The irradiation time depends on the power of the light source and the photoreaction rate, but is performed for 1 second to 1 hour, preferably 10 seconds to 10 minutes.

Recording, reproduction, and erasing of the thus obtained two-layer medium are carried out by irradiating it with laser light from two companies. 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 nm, and the retention layer dye D2 shows absorption near 840 nm.
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 W3 tension layer mainly absorbs light and forms 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 with 780 nm laser light. Generally, the record is 5
~30mW, preferably 5-0 with a power of 7-20mW
．． Irradiate for 1 μsec. Regeneration is from 0.5 to 31'llW, preferably from 0.7 to 2. Irradiate for 5 to 0.1 μsec with a power of QmW. Erasing is from 1 to 20 mW, preferably from 3 to 12
Irradiate for 0.1 to 20 seconds with a power of mW.

According to the present invention, excellent recording and erasing characteristics can be obtained in a recording medium whose basic principle is to read changes in reflectance due to the formation and disappearance of bumps. At the same time, since film formation can be performed at low temperatures and high speeds, coating and curing can be performed without causing deterioration of the substrate or the dye used, and the cost of the media is low, which is an industrial advantage.

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

Example 1 1 p for bisphenol A type epoxy acrylate resin (hereinafter abbreviated as BP-1) represented by the following structural formula
hr of pendyldimethoxykecur (BDMK) and 1 phr of azobisisobutyronitrile <AIBN)
A chloroform solution of BP-1 added with was applied onto a glass plate to a thickness of 100 μm using a barcode method, irradiated with ultraviolet light, and then heated in an oven at 80° C. for 1 hour to cure. This thin film was peeled off from the glass plate and its tensile modulus was measured using an Instron 4302 (Instron Inc.) and found to be 176 Kg/mm at room temperature at 2.120°C.
It was 0.5Kg/mm2. Moreover, the glass transition point was 72°C.

-CH2CHCH2trOCOCH□CH208m=6 P-1 NK ester U-122A which is urethane acrylate
(Shin Nakamura Chemical Industry 9 Vermilion) to 1 (polymethine dye lR820 and 2 shown by the following structural formula of lphr)
A methyl ethyl ketone (MEK) solution of NK ester υ-122A added with phr Irgacure 907 (Ciba Geigy ■) was applied to a thickness of 3 μm on a glass substrate by the barcode method, and an expansion layer was formed by irradiating it with ultraviolet light. . A chloroform solution of BP-1 to which 10 phr of cyanine dye NK-125 (Japanese Photosensitive Dyes vA> and lphr(7) BDMK with the following structure was added to BR-1 was cast on the expanded layer, dried, and placed in a nitrogen atmosphere. A holding layer of 0.8 μm was formed by irradiating with ultraviolet light.

K-125 R820 When this two-layer medium was irradiated with a laser beam having a wavelength of 840 nm, 10 mW, and a pulse width of 5 μsec, the formation of bumps with a diameter of 1 μm was observed. This bump has a wavelength of 780 nm.
When a 7 mW laser beam was defocused and irradiated for 1 (bz seconds), the bumps did not disappear within the range of microscopic observation.

Example 2 Epoxy acrylate represented by the following structural formula (hereinafter referred to as BP)
ME of BP-2 with the addition of 1 phr of pendyldimethoxykecool (BDMK) and 1 phr of azobisisobutyronitrile (AIBN) to
Apply the K solution to a thickness of 100 mm on a glass plate using the barcode method.
μm, irradiated with ultraviolet light, and placed in an oven at 80℃ for 1 hour.
It was cured by heating for an hour. Peel this thin film from the glass plate,
The tensile modulus was measured using Instron 4302 (Instron Inc.) and found to be 149 Kg/m at room temperature.
m2.At 120°C, it was 3.2Kg/mm2. Moreover, the glass transition point was 70°C.

-0C82C) lcH20COCH=CHz1 H 3P-2 MEK solution of NK ester υ-122A with 10 phr of 1R820 and 2 phr of Irgacure 907 (Ciba Geigy @) added to NK ester U-122A <Shin Nakamura Chemical Co., Ltd. It was coated onto a glass substrate to a thickness of 3 μm using a barcode method, and an expansion layer was formed by irradiating it with ultraviolet light. 1 for BR-2
A MEK solution of BP-2 to which 0 phr of NK-125 and 1 phr of BDMK were added was cast onto the expansion layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retention layer. A wavelength of 840 nm, 10 mW, and a pulse width of 5 were applied to this two-layer medium.
When irradiated with a μ second laser beam, the formation of bumps with a diameter of 1 μm was observed. This bump has a wavelength of 780 nm,
When a 7 mW laser beam was defocused and irradiated for 10 μs, the bumps disappeared within the range of microscopic observation.

Example 3 1 phr of benzyl for bisphenol F type epoxy acrylate (hereinafter abbreviated as BP-3) having the following structural formula
A chloroform solution of BP-3 to which K dimethoxykecool (BDMK) and l phr azobisisobutyronitrile (AI BN) were added was applied onto a glass plate to a thickness of 100 μm using the barcode method, and irradiated with ultraviolet light. Then, it was cured by heating in an oven at 80°C for 1 hour. This thin film was peeled off from the glass plate and its tensile modulus was measured using an Instron 4302 (Instron Corporation).It was 102 Kg/mm at room temperature and 3.2 K at 120°C.
g/+n+++2. Also, the glass transition point is 78
It was ℃.

10CH2CHCH20COC) I=CH2H P-3 NK ester U-122A (Shin Nakamura Chemical Industry v7J)
A MEK solution of NK ester U-122A to which 10 phr of IR820 and 2 phr of Irgacure 907 (Ciba Geigy) were 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. 10 phr NK-125 and 1 phr BD for BR-3
A chloroform solution of BP-3 containing MK was cast onto the expanded layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a retaining layer. This two-layer medium has a wavelength of 840 nm and a power of 10 mW.
, the diameter is 1 when irradiated with laser light with a pulse width of 5 μs.
Formation of μm bumps was observed. This bump has wavelength 7
80nm, 7mW laser light is defocused and 10
When irradiated for microseconds, the bumps disappeared within the range of microscopic observation.

Example 4 VR77 (Showa Kobunshi ■) was used instead of BP-1 in Example 1.
), and as in Example 1, 2 consisting of an expansion layer/retention layer was used.
A layered medium was formed. This two-layer medium has a wavelength of 840 nm,
When irradiated with laser light of 10 mW and pulse width of 5 μs, the formation of bumps with a diameter of 1 μm was observed. When this bump was irradiated with a defocused laser beam of 7 mW and a wavelength of 780 nm for 10 μs, the bump disappeared within the range of microscopic observation.

Example 5 VR90 (Showa Kobunshi ■) was used instead of BP-1 in Example 1.
), and as in Example 1, 2 consisting of an expansion layer/retention layer was used.
A layered medium was formed. This two-layer medium has a wavelength of 840 nm,
When irradiated with laser light of 10 mW and pulse width of 5 μs, no bumps with a diameter of 1 μm were observed. When this bump was irradiated with a defocused laser beam of 7 mW and a wavelength of 780 nm for 10 μs, the bump disappeared within the range of microscopic observation.

Example 6 In place of BP-1 in Example 1, an epoxy novolak acrylate (hereinafter abbreviated as BP-4) having the following structure was used to form a two-layer medium consisting of an expansion layer/retention layer in the same manner as in Example 1. When this two-layer medium was irradiated with laser light having a wavelength of 840 nm, 10 mW, and a pulse width of 5 .mu.sec, the formation of bumps with a diameter of 1 .mu.m was observed. This bump has a wavelength of 780o.
When a 7 mW laser beam was defocused and irradiated for 10 μ seconds, the bumps disappeared within the range of microscopic observation.

P-4 Example 7 A naphthalocyanine dye having the following structure was used in place of N K 125 in Example 1, and a two-layer medium consisting of an expansion layer/retention layer was formed in the same manner as in Example 1.

H3 R=-3i-0-(CH2CH20-)-3C2H3H
3 In this two-layer medium, a wavelength of 840 nm, 10 mW, pulse @
When the laser beam was not irradiated for 5 μs, the formation of bumps with a diameter of 1 μm was observed. This bump has a wavelength of 78Qnm.
When a 7 mW laser beam was defocused and irradiated for 10 μs, the bumps disappeared within the range of microscopic observation.

Example 8 Chlorobrene F) 1050 (having a hydroxyl group at the end)
Denki Kagaku Kogyo Zashu) and Coronate L, a polyfunctional isocyanate, were mixed so that the amount of hydroxyl groups and the amount of isocyanate were equal, and 10 phr of IRDloo I (Sansui Kasei ■) was added, and a thickness of 3 μm was obtained using the barcode method.
The expansion layer was formed by applying the mixture to the substrate and heating it at 120° C. for 1 hour to cure it. 10 phr N for BR-1
BP supplemented with K-125 and 1 phr BDMK
A chloroform solution of -1 was cast onto the expanded layer, dried, and irradiated with ultraviolet light under a nitrogen atmosphere to form a 0.8 μm retaining layer. When this two-layer medium was irradiated with a laser beam having a wavelength of 840 nm, 10 mW, and a pulse width of 5 μs, the formation of bumps with a diameter of 1 μm was observed. This bump has a wavelength of 780n.
m, When a 7 mW laser beam was defocused and irradiated for 10 μs, the bumps did not disappear within the range of microscopic observation.

Example 9 Using ECHO-302 (Echo Resin and Laboratory Co., Ltd.) in place of BP-4 in Example 6, Example 1
A two-layer medium consisting of an expansion layer/retention layer was formed in the same manner as in Example 1.

When this two-layer medium was irradiated with a laser beam having a wavelength of 840 nm, 10 mW, and a pulse width of 5 μs, the formation of bumps with a diameter of 1 μm was observed. This bump has a wavelength of 780 cm.
When a 7 mW laser beam was defocused and irradiated for 10 μs, the bumps did not disappear within the range of microscopic observation.

Effects of the Invention According to the present invention, excellent recording and erasing characteristics can be obtained in a recording medium whose basic principle is to read changes in reflectance due to the formation and disappearance of bumps. At the same time, because the film can be formed at low temperatures and high speeds, coating and effects can be achieved without deteriorating the substrate or the pigments used, and the cost of the medium is low, which is an industrial advantage.

Procedural Amendment 1, Indication of Case Patent Application No. 56993 2, Name of Invention Erasable Optical Recording Medium and Method for Manufacturing the Same (3001 Teijin Ltd. (1) Paragraph 4 of the Specification, Line 15 of “Other State” "High condition," he corrected.

(2) On page 9, line 6 of the specification, "(meth)acrylate epoxy novolac (meth)j" is corrected to "(meth)acrylate, epoxy novolak (meth)."

(3) "Antigen" in the first line of page 14 of the specification is corrected to "light source."

(4) When a 100 μm film was prepared in the same manner as in Example 1 using “Toko Co., Ltd.” in Example 1 using “Toko Co., Ltd.” on page 22, line 7 of the specification, it was found that The elastic modulus was 140 kg/nwn2. The glass transition point was 71° C. Furthermore, the following is corrected as “Example 1.”

(5) Using [ in page 23, line 8 of the specification, Example IJ [
A 90 μm film was prepared in the same manner as in Example 1 using a 90 μm film, and the tensile modulus was 210 kg/image 2. The glass transition point was 115°C. Furthermore, it is corrected to ``Example 1''.

that's all

Claims (2)

[Claims] (1) An expansion layer (A) consisting of a resin (P_1) and a dye (D_1) that exhibits rubber elasticity at least at room temperature, and a glass state (highly elastic state) at room temperature, which is reversible to a rubber state at higher temperatures. Resin (P_2) and pigment (D_
2) in which the resin P_2 has a transition temperature from a glass state to a rubber state of 60 to 1
50°C, and (b) mainly consists of a cured product of epoxy (meth)acrylate and/or epoxy novolak (meth)acrylate, which has an elastic modulus of 80 Kg/mm^2 or more at room temperature. Erasable optical recording medium. (2) The retaining layer described in item 1 above is made of epoxy (meth)acrylate and/or epoxy novolac (meth)
1. A method for producing an erasable optical recording medium, which comprises coating a mixture containing an acrylate and a dye and then curing the medium by irradiating it with actinic light.