JP2001040246A - Protective film for optical disk and optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk having little change in camber angles after a test at a high temperature and humidity by forming a coating film comprising a specific composition. SOLUTION: This coating film for protecting optical disks is obtained by curing a composition consisting of a bisphenol-type epoxide (meth)acrylate (A), a compound expressed by CH2=CHCOOR (R is a 6-12C alicyclic hydrocarbon residue) (B), a compound containing an ethylenic unsaturated group (C) and <=7 wt.% of an optical polymerization initiator (D) by active energy rays having <400 nm wave lengths to form a cured coating film having >=91 wt.% gel fraction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film formed by applying and curing an ultraviolet-curable coating material for an optical disk, which is excellent in the protective performance of a metal reflective film. The present invention relates to a protective film for an optical disk, characterized in that an optical disk having a small change in the warp angle after a high-temperature and high-humidity test is obtained when the optical disk is provided.

[0002]

2. Description of the Related Art In recent years, optical disks such as compact disks, write-once optical disks, magneto-optical disks, and phase-change optical disks have been widely used as information recording media. These optical disks have a structure having a metal reflective film layer formed by a sputtering method on a transparent resin substrate such as polycarbonate. Since the metal reflective film layer is generally a thin film having a thickness of 30 to 150 nm, if it is deteriorated by moisture or oxygen in the air, the reflectivity is reduced or pitting is caused, and the optical disk is hardened. This can cause read and write errors. Therefore, in order to prevent these deteriorations, it is common to provide a protective coating made of an ultraviolet curable resin. For example, a specific viscosity and surface tension as described in JP-A-3-131605 are reduced. An ultraviolet-curable resin composition for protecting a metal film of a compact disk, which has a hardness of 2H or more and has an adhesive force to an optical disk substrate and a metal reflection film, has been used.

[0003]

However, if the optical disk is required to have a small warp angle due to the recent increase in the density of the optical disk, such a resin composition for protecting a metal film cannot be used. Have been.
Therefore, attempts to reduce the warp angle of the optical disk by reducing the curing shrinkage of the protective film, for example,
As disclosed in JP-A-4-264167, in the case of a protective film made of the composition, even if the initial warp angle is small, the protective film gradually shrinks and warps when a durability test is performed under high temperature and high humidity. The corners tended to be large, and there was a problem with long-term mechanical reliability.

In recent years, from the viewpoint of cost reduction, CD-
The type of metal forming the reflective film of R (write-once optical disk) is changing from gold to silver, but silver is a metal that is very susceptible to corrosion. In the endurance test below, corrosion of the metal reflective film may occur, and it has not been practically possible at present. As described above, the object of the present invention is to provide a long-term mechanical reliability with a small warpage angle even after an endurance test under high temperature and high humidity, and it is excellent even for a metal which is susceptible to corrosion such as silver. An object of the present invention is to obtain an optical disk having an improved protection performance.

[0005]

The present inventors have studied the cause of the increase in the warp angle of an optical disk with time, which is the object of the present invention, and as a result, have found that mainly the photopolymerization initiator remaining in the protective film, Residues of the polymerization initiator and the remaining monomer monomer are considered to arise from volume shrinkage due to volatilization or decomposition and distillation, and to suppress the increase in the warpage angle over time,
Investigations were made to reduce the amount of substances that volatilize under high temperature and high humidity, and a composition for forming a protective film composed of the components (A) to (D) was found. Then, the curing reaction rate of the composition is further increased, and the insoluble 3
91% by weight of the content (gel fraction) of the two-dimensional crosslinked polymer
The present inventors have found that the above control can control the temporal increase of the warp angle of the optical disc in a durability test under high temperature and high humidity, and have reached the present invention.

That is, the present invention relates to a bisphenol type epoxy di (meth) acrylate (A), a compound (B) represented by the following general formula (I), CH ₂ ＝ CHCOOR (R is an alicyclic group having 6 to 12 carbon atoms) (Hydrocarbon residue) ... (I) A composition comprising an ethylenically unsaturated group-containing compound (C) other than the components (A) and (B) and a photopolymerization initiator (D) is subjected to activation energy having a wavelength of 400 nm or less. A protective coating for an optical disk, wherein the cured coating film obtained by curing with a wire has a gel fraction of 91% by weight or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a protective film for an optical disk and an optical disk of the present invention will be described in detail. In the present invention, bisphenol-type epoxy di (meth) acrylate (A), a compound (B) represented by the following general formula (I), and CH ₂ ＣＨCHCOOR (where R is an oil having 6 to 12 carbon atoms) are used as the protective film forming composition. (Cyclic hydrocarbon residue) (I) A composition comprising an ethylenically unsaturated group-containing compound (C) other than the components (A) and (B) and a photopolymerization initiator (D) in an amount of 7% by weight or less. There is a feature in using it.

[0008] The bisphenol type epoxy di (meth)
The acrylate (A) is not particularly limited, and any known acrylate may be used. In order to impart excellent protective film performance, a bisphenol-type epoxy resin and (meth)
It is preferable to use an epoxy di (meth) acrylate (A) which is a reactant of acrylic acid.

For application to a metal reflecting film made of a metal which is easily corroded such as silver, the total chlorine content is preferably 1500 ppm or less, more preferably 500 pp.
It is desirable to use a bisphenol-type epoxy di (meth) acrylate using a bisphenol-type epoxy resin having a molecular weight of m or less as a raw material. Here, the total chlorine content of the bisphenol-type epoxy resin refers to the chlorine content obtained by burning a sample in an oxygen stream and titrating the generated hydrogen halide with silver ions generated electrolytically. Pp quantity
Means represented by m.

The composition for forming a protective film using an epoxy di (meth) acrylate synthesized using a bisphenol-type epoxy resin having a total chlorine content exceeding 1500 ppm tends to have a high chlorine concentration in the composition. is there. Therefore, for example, protection of a metal reflective film made of a material which is easily corroded such as silver tends to have insufficient protection performance. Such a bisphenol-type epoxy resin having a total chlorine content of 1500 ppm or less is not particularly limited, and a commercially available bisphenol-type epoxy resin may be used.
Specifically, for example, in Bisphenol A type epoxy resin, Epicoat 828US manufactured by Yuka Shell Epoxy,
Epicoat YL980 and bisphenol F epoxy resin include Epicoat YL983U.

The bisphenol-type epoxy di (meth) acrylate (A) used in the present invention is obtained by a reaction of adding (meth) acrylic acid to the bisphenol-type epoxy resin, and a catalyst used in this reaction is as follows. It is preferable to use a tertiary amine. In the case of this reaction, synthesis can be generally performed using triphenylphosphine, triethylmethylammonium chloride, or the like, but phosphorus and ions contained in these catalysts tend to promote corrosion of the metal reflective film. For example, it is not preferable in view of its protection performance when applied to a metal reflection film made of a metal which is easily corroded such as silver.

In the present invention, the tertiary amine which can be used as a reaction catalyst for obtaining the bisphenol type epoxy di (meth) acrylate (A) includes, for example, triethylamine, benzyldimethylamine, p
-Dimethylaminopyridine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate and the like.

Among these, 300 nm to 450 n
When p-dimethylaminoacetophenone, p-dimethylaminobenzoic acid ethyl ester, and p-dimethylaminobenzoic acid isoamyl ester having a maximum absorption wavelength in the region of m are used, the resulting bisphenol-type epoxy di (meth) acrylate (A) Because it is contained in
When this is used as a composition for forming a protective film, it is particularly preferable because a photosensitizing effect can be imparted to the composition.

The amount of the catalyst used in the reaction for adding the (meth) acrylic acid to the bisphenol type epoxy resin is preferably 0.05 to 10% by weight, more preferably 0.1 to 10% by weight, based on the total weight of the raw materials. 1 to 5% by weight.

The reaction between the bisphenol type epoxy resin and (meth) acrylic acid to obtain the component (A) used in the present invention is carried out by the reaction of the epoxy group 1 of the bisphenol type epoxy resin.
0.9-1.0 (meth) acrylic acid to chemical equivalent
It is preferable to carry out with a chemical equivalent, more preferably 0.9
5 to 1.0 chemical equivalent. If the (meth) acrylic acid is less than 0.9 chemical equivalent to 1 chemical equivalent of the epoxy group of the bisphenol type epoxy resin, the resulting epoxy di (meth) acrylate tends to have insufficient curability. If it exceeds 0 chemical equivalent, excess (meth) acrylic acid remains, and the acid value of the obtained bisphenol-type epoxydi (meth) acrylate (A) tends to be too high, causing corrosion of the metal reflective film. There is a tendency.

The reaction temperature is preferably from 70 to 130 ° C, more preferably from 80 to 100 ° C. The reaction is performed under these conditions, and the epoxy (meth) acrylate obtained at the time when the acid value becomes 2 mgKOH / g or less is used as the component (A) of the present invention.

In the present invention, the content of the component (A) is preferably 5 to 30% by weight, more preferably 10 to 28% by weight, based on the total amount of the components (A) to (D).
When the content of the component (A) is less than 5% by weight, the obtained cured coating film of the protective film-forming composition tends to fail to impart sufficient protective performance to the metal reflective film.
If it exceeds 0% by weight, the viscosity of the composition for forming a protective film is too high, and the coating productivity tends to decrease.

In the composition for forming a protective film used in the present invention, the compound (B) represented by the following general formula (I) is used as a reactive diluent. CH ₂ ＣＨCHCOOR (R is an alicyclic hydrocarbon residue having 6 to 12 carbon atoms) (I) The compound (B) not only lowers the viscosity of the obtained protective film-forming composition, but also reduces the viscosity. It also has the purpose of improving the protective performance of the metal reflective film by improving the water resistance of the cured coating film.

Specific examples of the compound (B) include cyclohexyl acrylate, isobornyl acrylate, adamantyl acrylate, tricyclodecanyl acrylate, dicyclopentenyl acrylate and the like. Tricyclodecanyl acrylate is particularly preferred.

In the present invention, the content of the compound (B) is preferably from 5 to 30% by weight, more preferably from 10 to 28% by weight, based on the total amount of the components (A) to (D).
When the content of the component (B) is less than 5% by weight, the viscosity of the obtained composition for forming a protective film tends to be high, so that the coating productivity is reduced and the water resistance of the cured coating film is reduced. Also tend to decrease. If it exceeds 30% by weight, the UV curability of the composition for forming a protective film obtained tends to decrease.

In the composition for forming a protective film used in the present invention, an ethylenically unsaturated group-containing compound other than the above-mentioned components (A) and (B) is used for the purpose of adjusting the viscosity and ultraviolet curing performance of the composition. C) is used.

Specific examples of the ethylenically unsaturated group-containing compound (C) include, for example, trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate,
Propoxylated trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, ethoxylated glycerin tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, ditrimethylolpropanetetra (meth) ) Acrylates, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate,
Ethylene glycol di (meth) acrylate, di (meth) acrylate
Polyethylene glycol acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, di (meth) acrylic acid 1,
6-hexanediol, nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acrylate, polypropylene glycol di (meth) acrylate, di (meth) acrylate ) Polytetramethylene glycol acrylate, tricyclodecane dimethanol di (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
(Meth) acrylates such as 4-hydroxybutyl (meth) acrylate, phenoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate; polybasic acids such as phthalic acid and adipic acid; ethylene glycol ,
Polyester poly (meth) acrylates obtained by reaction with polyhydric alcohols such as hexanediol, polyethylene glycol and polytetramethylene glycol and (meth) acrylic acid or a derivative thereof; hexamethylene diisocyanate, isophorone diisocyanate,
To isocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Urethane poly (meth) acrylates obtained by reacting a (meth) acrylate having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate, caprolactone-modified 2-hydroxyethyl acrylate, and pentaerythritol triacrylate; hydroxyethoxylated bisphenol A; polybutadiene Diol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyester diol, caprolactone modified diol, polycarbonate diol, the above diisocyanate compound is added to hydroxyl groups such as spiro glycol,
The remaining isocyanate groups have hydroxyl groups such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified 2-hydroxyethyl acrylate, and pentaerythritol triacrylate. Urethane poly (meth) acrylates reacted with (meth) acrylate are exemplified. These are 1
Species or a combination of two or more can be used.

Of these, hydrophobic compounds such as trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate,
Ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth)
Acrylic ester, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hydroxypivalic acid Neopentyl glycol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like are particularly preferable.

In the present invention, the content of the component (C) is preferably in the range of 33 to 83% by weight, more preferably 50 to 75% by weight, based on the total amount of the components (A) to (D). . When the content of the component (C) is less than 33% by weight, the ultraviolet curing performance tends to decrease, and when the content of the component (C) exceeds 83% by weight, curing shrinkage during ultraviolet curing. Tends to be larger

The composition for forming a protective film used in the present invention contains a photopolymerization initiator (D) for the purpose of efficiently curing with an active energy ray having a wavelength of 400 nm or less.

Specific examples of the component (D) include, for example, benzophenone, 4,4-bis (diethylamino) benzophenone, 2,4,6-trimethylbenzophen, methylorthobenzoylbenzoate, 4-phenylbenzophenone, and t-phenylbenzophenone. Butylanthraquinone, 2-ethylanthraquinone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 1-hydroxycyclohexyl-phenylketone, benzoin methyl ether, benzoin ethyl ether, benzoin Isopropyl ether, benzoin isobutyl ether, methylbenzoyl formate and the like can be mentioned.

Further, in the present invention, known photosensitizers such as methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, amyl 4-dimethylaminobenzoate and 4-dimethylaminoacetophenone are also used as (D). It can be used as a component. These photopolymerization initiators (D)
Can be used alone or in combination of two or more.

In the present invention, the proportion of the component (D) must be in the range of 0.001 to 7% by weight, preferably 1 to 6% by weight, based on the total amount of the components (A) to (D). It is in the range of 5% by weight. The content of the component (D) is 7% by weight.
In the case where the amount exceeds the above range, the residual amount of the photopolymerization initiator and the remaining photopolymerization initiator in the protective film obtained by curing with the active energy ray are too large. The residual and unreacted photopolymerization initiator remaining are extracted, resulting in volume shrinkage of the protective coating,
It tends to cause the warpage angle of the optical disk to increase over time.

As described above, the extraction phenomenon that occurs under high temperature and high humidity tends to occur at a low speed even when the optical disk is stored at normal temperature and normal humidity for a long period of 10 years or more. If the residue is too large, it will not be extracted and volatilized at normal temperature and normal humidity, bleeds out to the surface of the coating film, and the printability tends to decrease. That is, to ensure long-term reliability and printability after long-term storage, (D)
The amount of the component used must be in the range of 0.001 to 7% by weight.

When the content of the component (D) is less than 0.001% by weight, it is difficult to obtain a curing rate in the step of providing a protective film suitable for industrial production, and it is obtained. The amount of residual monomer monomer in the protective film increases, and these residual monomer monomers are also extracted during the durability test under high temperature and high humidity, resulting in volume shrinkage of the protective film and the optical disk. It tends to cause the warpage angle to increase with time.

The composition for forming a protective film used in the present invention may further contain known additives such as a lubricant, a leveling agent, an antioxidant, a light stabilizer, an ultraviolet absorber, a polymerization inhibitor and a silane coupling agent. It may be added.

The protective coating of the present invention is characterized in that the gel composition of the cured coating obtained by curing the composition for forming a protective coating with an active energy ray having a wavelength of 400 nm or less is 91% by weight or more. There are two major features.

The inventors of the present invention have studied the cause of the increase in the warp angle of the optical disk with time, which is the subject of the present invention, and as a result, mainly found the photopolymerization initiator remaining in the protective film, the residue of the polymerization initiator and the like. The remaining monomer is considered to be caused by volume shrinkage due to volatilization or decomposition and distilling out. To suppress the increase of the warpage angle over time, studies were conducted to reduce these substances that volatilize under high temperature and high humidity. A composition for forming a protective film comprising the above components (A) to (D) was found. However, simply specifying the range of the composition was not sufficient to reliably suppress the increase in the warpage angle. The inventors of the present invention have conducted further intensive studies and found that, within the range of the composition, the gel fraction of the cured coating film of the composition cured with an active energy ray having a wavelength of 400 nm or less was 91% by weight. With the above, it has been found that it is possible to suppress a temporal increase in the warp angle of the optical disc in a durability test under high temperature and high humidity.

The protective coating of the present invention comprises the component (A)
The gel fraction of the cured coating film of the composition comprising the component (D) is 91.
% By weight or more, more preferably 93% by weight or more. Here, what is defined as "cured coating film cured with an active energy ray having a wavelength of 400 nm or less" is that light composed only of a wavelength region exceeding a wavelength of 400 nm forms the protective coating of the present invention. This is because the surface hardening of the composition hardly proceeds in the atmosphere, and it is impossible to obtain a protective film for an optical disk industrially.

If the gel fraction of the cured coating film is lower than 91% by weight, a large amount of unreacted monomers and unreacted photopolymerization initiator residues are present in the cured coating film. When a durability test is performed on an optical disc with a protective coating as a coating under high temperature and high humidity, the volume of the protective coating shrinks as a result of extraction of unreacted components, and the warpage of the optical disc over time. Change tends to increase.

Further, in order to obtain a cured film having a gel fraction of 91% by weight or more, which is the protective film of the present invention, the above-mentioned composition for forming a protective film may be cured by photopolymerization. In order to efficiently obtain the cured coating film, the irradiation amount of the ultraviolet light at the time of photopolymerization is set to 100 mw / cm ² or more under the condition that the peak illuminance on the 350 nm monitor is 100 mw / cm ² or more.
mj / cm ² or more is preferable, and the integrated light amount 200 mj under the condition that the peak illuminance is 200 mw / cm ² or more.
/ Cm ² or more is more preferable.

The optical disk of the present invention has the above-mentioned protective coating on one or both sides of the optical disk substrate.
In the present invention, the type of the optical disk is not particularly limited, and examples thereof include known optical disks such as a compact disk, a write-once optical disk, a magneto-optical disk, and a phase change optical disk. Among them, the phase-change type optical disk is particularly preferable as an optical disk having the protective coating on one or both surfaces since it is required that the change in the warp angle is particularly small.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. The warp angle in the examples means the maximum warp angle in the radial direction toward the cured coating film side.

The evaluation results in the table are shown based on the following criteria. [Protection performance] The initial C1 error average value was 5.0 frame.
es / sec, good: average C1 error after a durability test is 20 frames
In case of less than s / sec Poor: average C1 error after endurance test is 20 frames
When s / sec or more [Change in warp angle] Small: When change in warp angle is within 6 mrad Large: When change in warp angle exceeds 6 mrad [Mechanical properties] Good: When change in warp angle is within 6 mrad Bad: Change in warp angle Exceeds 6 mrad

[Synthesis Example 1] Epicoat 828US (bisphenol A type epoxy resin, epoxy equivalent 189, total chlorine content 1400 pp) manufactured by Yuka Shell Epoxy Co., Ltd.
m) 189 g, acrylic acid 72 g, hydroquinone monomethyl ether 0.39 g, ethyl p-dimethylaminobenzoate 5.2 g were charged and reacted at 95 ° C. for 16 hours,
Bisphenol A type epoxy acrylate (EA) having an acid value of 1.0 mgKOH / g was obtained.

Example 1 22 parts by weight of the epoxy acrylate (EA) obtained in Synthesis Example 1, 29 parts by weight of trimethylolpropane triacrylate, 24 parts by weight of 1,6-hexanediol diacrylate, 19 parts by weight of isobornyl acrylate , 2 parts by weight of 1-hydroxycyclohexylphenyl ketone, 2 parts by weight of benzophenone, and 2 parts by weight of ethyl p-dimethylaminobenzoate were mixed and dissolved to obtain a coating material. The above coating material is P
Painted on an ET film, using a high-pressure mercury lamp (350 mw / cm ² peak illuminance at 350 nm monitor)
Integrated light quantity 30 measured by Oak Corporation UV-350
Curing was performed with an energy amount of 0 mj / cm ² . The cured coating film (10 g) was peeled off from the PET and pulverized, and then placed in 1 L of methyl ethyl ketone and refluxed for 4 hours. After the completion of the reflux, the mixture was filtered through a filter paper 5C manufactured by Toyo Roshi Kaisha Co., Ltd. and sufficiently dried. The gel fraction was determined from the remaining weight to be 93% by weight.

Next, Panlite AD9 manufactured by Teijin Chemicals Ltd.
2,000TG injection-molded optical disk with a compact disk test signal and a diameter of 12 cm and a thickness of 1.2 mm, a sputtering device CDI manufactured by Balzers Co., Ltd.
According to -900, silver (purity 99.99%) was formed to a film thickness of 50 n.
m to obtain an optical disk having a silver reflective film on the signal recording surface. The above-mentioned coating material was applied on the reflective film using a spin coater so as to have an average film thickness of 6 μm, and was coated with a high-pressure mercury lamp (350 mw / cm ² peak illuminance on a 350 nm monitor) to obtain U-manufactured by Oak Co., Ltd.
The composition was cured with an energy amount of 300 mj / cm ² as measured by V-350. The obtained optical disk was measured at 20 ° C. and 50% R using a DLD-3000 optical disk optical property measuring device manufactured by Japan Em Corporation.
When the warp angle of the outermost circumference was measured under the H environment, the warp angle was 1 mrad. Further, when an average value of C1 errors of all tracks was measured using an optical disk error counter DX610A manufactured by Shibasoku Co., Ltd., 5 frames
/ Sec. This optical disk is heated at 80 ° C and 85% R
After leaving for 100 hours under the environmental conditions of H
Leave at 0 ° C. and 50% RH for 100 hours.
When the warp angle of the outermost circumference was measured again, the warp angle was 4 mr.
ad, and the overall evaluation was good. When the average value of the C1 errors of all the tracks was measured,
s / sec, which was good without any change from before the test.

Examples 2 to 4 and Comparative Examples 1 to 3 Each component was mixed in the composition shown in the resin composition column of Table 1 in the same manner as in Example 1 to obtain a coating material. The gel fraction of the obtained coating material was measured in the same manner as in Example 1.
Further, the obtained coating material was applied to an optical disk having a silver reflective film similar to that used in Example 1, and the optical disk obtained by curing was measured for a warp angle and a C1 error before and after a durability test. Are shown in the test result column of Table 1.

Comparative Example 4 The coating material described in Example 1 was measured with a high-pressure mercury lamp (peak illuminance 60 mw / cm ^{2 on a} 350 nm monitor, 60 mw / cm ² ), and the integrated amount of light was 70 mj / cm ^{2 as} measured by UV-350 manufactured by Oak Co., Ltd. Except for the amount of energy to be used, coating and curing on a PET film were performed in the same manner as in Example 1. Then, the result of measuring the gel fraction in the same manner as in Example 1 is shown in the test result column of Table 1. In addition, an integrated light quantity of 70 mj / m was measured with a UV-350 manufactured by Oak Co., Ltd. using a high-pressure mercury lamp (peak illuminance 60 mw / cm ^{2 on a} 350 nm monitor).
An optical disc having a cured coating film was obtained in the same manner as in Example 1, except that the composition was cured with an energy amount of cm ² . With respect to the obtained optical disc, the result of measuring the warp angle after the durability test of the optical disc in the same manner as in Example 1 is shown in the test result column of Table 1.

[0045]

[Table 1]

TMPTA: trimethylolpropane triacrylate IBXA: isobornyl acrylate TCDA: tricyclodecanyl acrylate HDDA: 1,6-hexanediol diacrylate 2HPA: 2-hydroxypropyl acrylate HCPK: 1-hydroxy-cyclohexyl phenyl ketone BNP : Benzophenone EPA: Ethyl P-dimethylaminobenzoate

Example 5 An optical disk having a cured coating film was obtained in the same manner as in Example 1 except that aluminum (JIS A6061) was used as a reflective film material of the optical disk. When the same evaluation as in Example 1 was performed for the optical disc, the initial average C1 error value was 5.0 frames.
/ Sec, the maximum warp angle in the radial direction is 1.0 mrad,
After the endurance test, the average value of the C1 error was 5.0 fr.
ames / sec, maximum warpage angle in the radial direction 4.0 mrad
And showed good protection performance and mechanical properties.

Example 6 Evaluation was performed in the same manner as in Example 1 except that gold (purity: 99.99%) was used as a reflective film material for an optical disk. The initial C1 error average value was 5.0 frames / sec. , Maximum warpage angle in the radial direction
After the durability test, the average C1 error was 5.0 frames / sec, and the maximum warpage angle in the radial direction was 4.0 mrad, indicating good protection performance and mechanical properties.

[0049]

As described above, since the protective film of the present invention has a very small warpage angle even after the durability test,
The change in mechanical properties is very small, and the metal reflective film is excellent in protection performance. Therefore, the optical disk having the protective film of the present invention is extremely useful.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 AA05 AC04 QA03 QA13 QA22 QA23 QA24 QA25 QA34 QA37 QA45 QB14 QB16 QB20 QB23 SA05 SA06 SA22 SA23 SA25 SA36 SA54 SA61 SA63 SA75 SA78 UA01 VA01 WA02 4J027 AB10 AB23 AC04 AC06 AE02 AG03 AG04 AG05 AG07 AG09 AG14 AG23 AG24 AG27 AG33 AJ08 BA07 BA08 BA19 BA20 BA24 BA26 BA27 CB10 CC05 CD05 CD08 4J038 FA012 FA132 FA251 JB03 JB06 KA04 PA17 PB08 5D029 LA04 LC21

Claims (4)

[Claims] 1. A bisphenol type epoxy di (meth) acrylate (A), a compound (B) represented by the following general formula (I), CH ₂ ＣＨCHCOOR (R is an alicyclic hydrocarbon residue having 6 to 12 carbon atoms) (I) A composition comprising an ethylenically unsaturated group-containing compound (C) other than the components (A) and (B) and a photopolymerization initiator (D) is cured with an active energy ray having a wavelength of 400 nm or less. A protective coating for an optical disk, wherein the cured coating film obtained has a gel fraction of 91% by weight or more. 2. An epoxy di (meth) acrylate obtained by reacting a bisphenol type epoxy di (meth) acrylate (A) with a bisphenol type epoxy resin having a total chlorine content of 1500 ppm or less and (meth) acrylic acid using a tertiary amine as a catalyst. 2.) An acrylate.
The protective film for an optical disc according to the above. 3. The protective coating for an optical disk according to claim 2, wherein the tertiary amine is a compound having an absorption maximum wavelength at 300 nm to 450 nm. 4. An optical disk having the protective coating according to claim 1 on one or both sides of an optical disk substrate.