JPH0652587A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent corrosion of a recording layer, and to hold excellent environmental durability and reliability for a long period by specifying a constructing material of a protective layer. CONSTITUTION:A first substrate 11 having a thickness of 1-100mum is adhered on a second substrate 12 through an adhesive layer 13 having an acid value of 0.5 KOHmg/g or less to form a protective layer 14. If the thickness of the substrate 11 is specified to thinner than 1mum, its mechanical strength is small and sufficient protective function cannot be obtained. If it is thicker than 100mum, a distance between a magnetic head and a recording layer is increased, and hence a sufficient recording magnetic field intensity cannot be applied. There is a correlation between the acid value of the adhesive layer and the corrosion of the recording layer. If a material having an acid value of 0.5 KOHmg/g or less is used as the adhesive layer, corrosion of the recording layer is prevented, and an optical recording medium in which reliability for a long period can be held is obtained. Further, the layer 13 may be formed of a protective adhesive sheet for the medium made of other specific adhesive composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of recording, reproducing and erasing information with a light beam.

[0002]

2. Description of the Related Art Conventionally, the following magneto-optical recording media have been typical as optical recording media. That is, on a resin substrate having a guide groove and a preformat signal, SiN, Si
O _X, ZnS, forming a dielectric film of a combination of one or more inorganic dielectrics such as SiC, GDT thereon
b, TbFe, GdTbFe, TbFeCo, GdTb
An amorphous magneto-optical recording film such as FeCo is provided, a dielectric film similar to the inorganic dielectric film is formed on the magneto-optical recording film, and an ultraviolet curable resin is applied and cured on the dielectric film to mechanically It is used as a protective film.

[0003]

However, the above conventional magneto-optical recording medium cannot maintain its stability for a long time because the recording film is corroded when it is placed in a high temperature and high humidity environment for a long time. There was a problem.

An object of the present invention is to solve the above problems and provide an optical recording medium excellent in environmental durability.

[0005]

According to the present invention for solving the above problems, a first substrate having a thickness of 1 to 100 μm is provided with a second substrate through an adhesive layer having an acid value of 0.5 kOHmg / g or less. An optical recording medium is characterized in that a protective layer is formed by being adhered thereon.

FIG. 1 is a partial sectional view showing the basic structure of the optical recording medium of the present invention. The first substrate 11 is bonded onto the second substrate 12 via the adhesive layer 13 to form the protective layer 14.

The first substrate is for protecting the recording film of the optical recording medium, and is made of polyamide type, polyester type,
It is selected from synthetic resin films such as polyamide-imide type, polypropylene type, polyethylene type, polyacetal type, polycarbonate type, polyvinyl chloride type and polyvinylidene chloride type.

The above film is used as a protective layer in the thickness range of 1 to 100 μm. Because, when the thickness is less than 1 μm, the mechanical strength is small and a sufficient protective function cannot be obtained.
This is because if the thickness is thicker than 00 μm, the distance between the magnetic head and the recording layer becomes large, so that sufficient recording magnetic field strength cannot be applied.

As a result of extensive studies on the cause of corrosion of the magneto-optical recording film of the optical recording medium, the present inventor found a large correlation between the acid value of the adhesive layer and the occurrence of corrosion. That is, by using a specific material having an acid value of 0.5 kOHmg / g or less as the adhesive layer, it is possible to provide an optical recording medium that does not cause corrosion of the magneto-optical recording film and can maintain reliability for a long period of time. In the present invention, the acid value is measured as follows.

<Measurement of Acid Value> 0.6 g of a sample and 0.3 g of triethylenediamine which is an acid dissociation catalyst are dissolved in 40 ml of DMF, and 2 ml of water is added. The acid value of the above aqueous solution was measured by a potentiometric titrator (trade name: COMITITE-7 type,
Hiranuma Sangyo Co., Ltd.) is used to titrate with 0.1N kOH of isopropanol (hereinafter referred to as IPA) solution, and the acid value is calculated by the following formula.

[0011]

[Equation 1] (In the formula, A represents a sample titer (ml), B represents a blank titer (ml), f represents a 0.1N kOHIPA solution factor, and W represents a sample weight (g).) The acid value is satisfied. The adhesive constituting the adhesive layer is a solvent-type acrylic resin, epoxy resin, polyester resin, urethane resin, ethylene-vinyl acetate copolymer (hereinafter,
It is referred to as EVA), a reactive hot melt adhesive, a polyamide resin, or the like.

The second substrate is an optical recording medium having at least an optical recording layer on a transparent substrate.

The present invention also provides a protective pressure-sensitive adhesive sheet for an optical recording medium, which comprises an adhesive layer adhered to a second substrate laminated on a first substrate, wherein the adhesive layer is (1) 50 wt. % To 80% by weight of acrylic acid ester-based monomer,
(2) Containing 1% by weight or more and 3% by weight or less of a polar acrylic monomer, (3) 5% by weight or more and 40% by weight or less of a macromonomer, and (4) having a weight average molecular weight M _w of 1.5.
× 10 ⁵ or more 2.0 × 10 ⁶ or less, (5) protective adhesive sheet and for optical recording medium, characterized in that the glass transition temperature T _g is made of the adhesive composition is 80 ° C. or less -60 ° C. or higher An optical recording medium obtained by adhering the sheet.

The present inventor has conducted extensive studies to develop a pressure-sensitive adhesive sheet having excellent blister resistance, and as a result, it has been found that the formation of blisters is caused by a trace amount of gas generated from the inside of the first substrate. I found it. Therefore, acrylic acid ester-based monomer units, polar acrylic-based monomer units,
In addition, by using a copolymer containing a macromonomer unit having a polymer chain and a polymerizable functional group at a terminal in a predetermined ratio and having a specific molecular weight and a glass transition point in the adhesive layer, Since the adhesive layer has a microphase-separated structure due to the polymer chain in the macromonomer unit incorporated as a side chain in the side chain, it is effective in absorbing and diffusing a trace amount of gas from the first substrate and preventing the formation of blisters, and is good. The present invention has been completed by discovering that it has excellent adhesiveness and adhesive holding power.

As the acrylic acid ester-based monomer, hydroxyethyl methacrylate, 2-ethylhexyl acrylate and the like are preferable.

As the polar acrylic monomer, methacryl terminated polystyrene, acrylic acid and the like are preferable.

As the macromonomer, an oligomer or polymer having a polymer chain such as butyl acrylate and a polymerizable functional group at the terminal and having a molecular weight of 500 or more is preferable.

The weight average molecular weight M _w (hereinafter referred to as M _w ) of the copolymer composed of the above compounds is 1.5 × 10 ^5.
To 2.0 × 10 ⁶ is required. Because, if it is less than 1.5 × 10 ⁵ , the adhesive holding force is low and 2.0
This is because if it exceeds × 10 ⁶ , the coating workability deteriorates.

Further, the glass transition point T _{g of the} copolymer (hereinafter,
T _g ) is required to be -60 ° C to 80 ° C. This is because if the temperature is less than -60 ° C, the adhesive strength is insufficient, and if the temperature exceeds 80 ° C, the tackiness is lowered.

The present invention also provides a protective pressure-sensitive adhesive sheet for an optical recording medium, comprising a first substrate and an adhesive layer laminated on the second substrate, wherein the adhesive layer comprises (1) natural rubber. And 100 parts by weight of one or more synthetic rubbers, (2)
5 to 80 parts by weight of an epoxy monomer composed of one kind or two or more kinds of an unsaturated glycidyl ester monomer and an unsaturated glycidyl ether monomer, and (3) a radical polymerization initiator of 0.1 to 10% by weight based on the monomer. And an adhesive composition comprising (4) a tackifier and (5) an epoxy curing agent, and a protective pressure-sensitive adhesive sheet for an optical recording medium, and an optical recording obtained by adhering the sheet. It is a medium.

As the natural rubber or synthetic rubber, one having a diene bond and retaining tack in the presence of a tackifier is used.

As the epoxy monomer, unsaturated glycidyl ester monomers such as glycidyl acrylate and glycidyl methacrylate, and unsaturated glycidyl ether monomers such as glycidyl allyl ether can be preferably used.

In the present invention, the above rubber and an epoxy monomer are graft-polymerized. At this time, 5 parts of the epoxy monomer is added to 100 parts by weight of the rubber.
80 parts by weight, 0.1 to 10% by weight, preferably 0.3 to 3.0% by weight, of a polymerization initiator is mixed with the epoxy monomer, and the mixture is polymerized while heating and stirring. When the compounding amount of the epoxy monomer is 5 parts by weight or less, a sufficient polymer cannot be obtained, and when it is 80 parts by weight or more, gelation tends to occur.

Next, a tackifier made of a rosin-based resin, a terpene-based resin, a petroleum resin such as an aliphatic, alicyclic or aromatic petroleum resin is added to the obtained graft polymer solution. This is cooled to room temperature to obtain a pressure sensitive adhesive.

An epoxy curing agent such as an aliphatic polyamine or an acid anhydride is blended with the above pressure-sensitive adhesive to obtain an adhesive composition having pressure-sensitive viscoelasticity even after completion of room temperature crosslinking.

In the adhesive layer of the present invention, the flow of the rubber elastic body is prevented by the formation of the graft polymer. Further, since the tackifier is favorably held in the network of the crosslinked structure of the epoxy resin, the tackifier can be prevented from flowing out. For this reason, even when it is placed in an environment of high temperature and high humidity for a long time, the cold flow phenomenon due to the temperature rise does not occur, and the thermal stability is excellent.

In the protective pressure-sensitive adhesive sheet and optical recording medium of the present invention, the above adhesive composition is directly coated on the first substrate,
It is characterized in that it is formed by volatilizing the solvent and crosslinking at room temperature.

The present invention also provides a protective pressure-sensitive adhesive sheet for an optical recording medium, which comprises an adhesive layer adhered to a second substrate laminated on a first substrate, wherein the adhesive layer is (1) maleic anhydride. Acid, maleic acid, fumaric acid, and one or more kinds of these mixtures in an amount of 50 mol% of all acid components.
And (2) an unsaturated polyester having one or more polyhydric alcohols having four or more carbon atoms in an amount of 50 mol% or more of all alcohol components (3)

[0029]

[Chemical 2] (Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ each independently represent an alkyl group having 1 to 8 carbon atoms), and the mixture is dissolved and mixed in one or more monomers. A protective pressure-sensitive adhesive sheet for an optical recording medium comprising the unsaturated polyester resin composition obtained, and an optical recording medium obtained by adhering the sheet.

Conventionally, an electron beam irradiation method has been used as a method for curing a liquid resin at room temperature, and an unsaturated polyester is generally used as the liquid resin. However, the unsaturated polyester resin has extremely high rigidity, so that it is apt to cause curing inhibition by oxygen, and therefore, the curing reaction ends while the unreacted polyester monomer remains.
The unreacted monomer promoted corrosion and deterioration of the recording layer under high temperature and high humidity.

In the present invention, as a result of improving the unsaturated polyester resin in view of the above problems, the above problems can be solved by curing an unsaturated polyester resin composition comprising a specific unsaturated polyester and a specific monomer. The inventors have found that they can be solved and completed the present invention.

The first substrate is selected from the above resin films, but polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyvinyl chloride copolymer, and polycarbonate are particularly preferable.

For forming the adhesive layer on the substrate, a method of applying a solvent-type adhesive and then curing it is preferable. After applying the adhesive composition onto the substrate, the adhesive composition may be coated with a release layer and then cured, or may be cured and then coated with a release layer.

The method for curing the liquid resin composition includes a method in which a conventionally known radical polymerization initiator is mixed and heated, a method in which a photopolymerization initiator is mixed and irradiated with UV light, an electron beam is irradiated, and the like. Although applicable, the method by electron beam irradiation is most suitable in the present invention.

The energy of the electron beam is not particularly limited, but from the viewpoint of the thickness of the adhesive layer and the production rate, the acceleration voltage is preferably 150 to 500 keV.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples. In this example, percentages and parts are by weight unless otherwise specified.

Example 1 An optical recording medium of the present invention having the structure shown in FIG. 1 was manufactured by the following procedure.

An 8 μm polyvinylidene chloride film was prepared as the first substrate 11, and a commercially available solvent-type acrylic resin having an acid value of 0.1 (trade name, Acrylift R-17,
Sumitomo Chemical Co., Ltd.) was applied to form the adhesive layer 13.

FIG. 2 is a partial cross-sectional view showing the structure of the second base body. This base body was manufactured by the following procedure. First, a dielectric layer 22 made of a Si ₃ N ₄ film having a film thickness of 1000Å and a magneto-optical recording layer 23 made of an amorphous TbFeCo film having a film thickness of 200Å are formed on a transparent substrate 21 on which guide grooves and signal pits are formed by a sputtering method. Then, a dielectric layer 24 made of a Si ₃ N ₄ film having a film thickness of 400 Å and a reflective layer 25 made of an Al—Cr film having a film thickness of 600 Å were sequentially formed.

On the reflective layer 25 of the second base, the first
The optical recording medium of the present invention was completed by pressure-bonding and bonding the base 11 of No. 1 through the adhesive layer 13.

Example 2 Instead of the adhesive used in Example 1, a commercially available acrylic acid-acrylic acid ester adhesive having an acid value of 0.3 (trade name Nucrel, manufactured by Mitsui DuPont Polychemical Co., Ltd.) was used. An optical recording medium of the present invention was manufactured in the same manner as in Example 1 except for the above.

Example 3 Instead of the adhesive used in Example 1, a commercially available acrylic acid-acrylic acid ester-based adhesive having an acid value of 0.5 (trade name Acryft R-15, manufactured by Sumitomo Chemical Co., Ltd.) was used. An optical recording medium of the present invention was manufactured in the same manner as in Example 1 except for the above.

Comparative Example 1 EV having an acid value of 0.8 instead of the adhesive used in Example 1
An optical recording medium was manufactured in the same manner as in Example 1 except that the A-based adhesive was used.

Comparative Example 2 As Example 1 except that a commercially available polyester adhesive (trade name: Chemit R-188, manufactured by Toray Industries, Inc.) having an acid value of 1.0 was used instead of the adhesive used in Example 1. An optical recording medium was manufactured in the same manner.

Example 4 <Environmental durability test> The optical recording media produced in Examples 1 to 3 and Comparative Examples 1 and 2 were left to stand for 2000 hours in an environment of a temperature of 80 ° C. and a relative humidity of 90%, and before and after that. The change in the bit error rate (hereinafter, referred to as BER) was examined. The BER was measured at room temperature and normal humidity for the optical recording medium before the test was started and after 2000 hours had elapsed. The results are shown in Table 1. The optical recording media of Examples 1 to 3 showed no change in BER,
From this, it can be seen that the recording layer is not corroded, but in the optical recording media of Comparative Examples 1 and 2, the BER value after 2000 hours has greatly increased, and the recording layer is corroded. I understand.

[0046]

[Table 1] Example 5 Hydroxyethyl methacrylate 80%, Aron macromonomer AN-6 (product name of Toagosei Co., Ltd.) 5
%, And methacryl-terminated polystyrene (trade name C-45
00, manufactured by Sartomer Co., Ltd.) Composition A consisting of 15%
Then, 0.5 g of azobisisobutylnitrile and 200 g of ethyl acetate were charged into a four-necked flask equipped with a reflux condenser, a nitrogen gas introduction tube, a thermometer, and stirring blades, and the temperature was raised to 80 ° C. Reacted for hours. The obtained adhesive composition had M _w of 7.0 × 10 ⁵ and T _g of 60 ° C.

The above adhesive composition was applied on a polyethylene terephthalate (hereinafter referred to as PET) film having a thickness of 6 μm to a thickness of 2 μm to prepare a protective pressure-sensitive adhesive sheet of the present invention.

The above-mentioned protective pressure-sensitive adhesive sheet was pressure-bonded onto the reflective layer of the second substrate as in Example 1 to obtain the optical recording medium of the present invention.

Example 6 Instead of the composition A used in Example 5, acrylic acid 2-
A protective pressure-sensitive adhesive sheet and an optical recording medium of the present invention were produced in the same manner as in Example 5 except that the composition B containing 75% ethylhexyl, 20% butyl acrylate, and 5% acrylic acid was used. However, M of the adhesive composition constituting the adhesive layer
_w was 7.5 × 10 ⁵ and T _g was 40 ° C.

Example 7 Instead of the composition A used in Example 5, acrylic acid 2-
A protective pressure-sensitive adhesive sheet and an optical recording medium of the present invention were produced in the same manner as in Example 5 except that the composition C containing 70% ethylhexyl, 28% butyl acrylate, and 2% acrylic acid was used. However, the M _w of the adhesive composition constituting the adhesive layer is
Was 4.0 × 10 ⁵ , and T _g was 60 ° C.

Comparative Example 3 An optical recording medium was obtained by forming a protective film made of a UV curable resin on a reflective layer of the same substrate as the second substrate used in Example 5.

Example 8 <Environmental endurance test> The environmental endurance test of the optical recording media produced in Examples 5 to 7 and Comparative Example 3 was performed in the same manner as in Example 4.
The results are shown in Table 2. The optical recording medium of the example has BER
Does not change, whereas the optical recording medium of Comparative Example 3 has 200
After the lapse of 0 hours, the BER greatly increased, and recording, reproduction and erasing became impossible.

[0053]

[Table 2] Example 9 In a four-necked flask equipped with a reflux condenser, a nitrogen gas introduction tube, a thermometer, and stirring blades, a concentrated rubber solution obtained by dissolving 30 g of natural rubber in 200 g of toluene, and 5 g of glycidyl acrylate monomer, 0.05 g of benzoyl peroxide was added, the temperature was raised to 80 ° C., and polymerization was performed for 24 hours. After cooling the obtained polymer solution to room temperature, ethylenediamine was added thereto to obtain a pressure-sensitive adhesive composition.

The above adhesive composition was applied onto a PET film having a thickness of 8 μm to complete the protective pressure-sensitive adhesive sheet of the present invention.

Next, the protective pressure-sensitive adhesive sheet was pressure-bonded onto the reflective layer of the second substrate similar to that in Example 1 to obtain the optical recording medium of the present invention.

Example 10 20 g of styrene-butadiene rubber (hereinafter referred to as SBR) and 20 g of natural rubber were kneaded in a four-necked flask equipped with a reflux condenser, a nitrogen gas introduction tube, a thermometer, and stirring blades. A concentrated rubber solution prepared by adding 200 g of toluene to the prepared rubber, 2 g of glycidyl ether monomer and 0.05 g of benzoyl peroxide were added, and the temperature was raised to 80 ° C. to 24
Polymerized for hours. A terpene resin was added to the obtained polymer solution and mixed, then cooled to room temperature, and ethylenediamine was further added to obtain a pressure-sensitive adhesive composition.

A protective pressure-sensitive adhesive sheet of the present invention and an optical recording medium were produced in the same manner as in Example 9 except that the above composition was used.

Example 11 In a four-necked flask equipped with a reflux condenser, a nitrogen gas inlet tube, a thermometer, and stirring blades, a concentrated rubber solution prepared by dissolving 20 g of natural rubber in 200 g of toluene and a glycidyl acrylate monomer were used. 2 g and 0.05 g of benzoyl peroxide were added, the temperature was raised to 80 ° C., and polymerization was performed for 24 hours. A terpene resin was added to the obtained polymer solution and mixed, then cooled to room temperature, and 0.5 g of metaxylenediamine was further added to obtain a pressure-sensitive adhesive composition.

A protective pressure-sensitive adhesive sheet of the present invention and an optical recording medium were produced in the same manner as in Example 9 except that the above composition was used.

Comparative Example 4 In a four-necked flask equipped with a reflux condenser, a nitrogen gas introduction tube, a thermometer, and stirring blades, a concentrated rubber solution prepared by dissolving 20 g of natural rubber in 200 g of toluene and a thermoplastic terpene were used. Add 20 g of resin and 0.5 g of hydroquinone, and
The temperature was raised to 0 ° C. and polymerization was carried out for 24 hours to obtain a conventionally known adhesive composition.

A protective pressure-sensitive adhesive sheet and an optical recording medium were produced in the same manner as in Example 9 except that the above composition was used.

Example 12 <Environmental durability test> The environmental durability of the optical recording media manufactured in Examples 9 to 11 and Comparative Examples 3 to 4 was examined in the same manner as in Example 4. Table 3 shows changes in BER with time. Examples 9 to 11
The optical recording medium of No. 3 did not change the BER, whereas the optical recording media of Comparative Examples 3 to 4 had a large increase in the BER value after 2000 hours, and recording, reproduction and erasing became impossible.

[0063]

[Table 3] Example 13 Maleic anhydride 8 molar equivalents, sebacic acid 2 molar equivalents, 2
A mixture of 10 molar equivalents of -ethylhexane-1,3-diol was heated and condensed to obtain unsaturated polyester A. A resin composition prepared by dissolving 100 g of this unsaturated polyester A in 0.5 mol of diethylaminoethyl methacrylate monomer was formed on a PET film of 6 μm and had a thickness of 5 μm.
Then, the protective pressure-sensitive adhesive sheet of the present invention was completed by irradiating it on a conveyor system with an electron beam generated from an accelerator (EGB) having a maximum acceleration voltage of 2 MeV.

In the same manner as in Example 1, the protective pressure sensitive adhesive sheet was pressure-bonded onto the second substrate to obtain the optical recording medium of the present invention.

Example 14 A protective pressure-sensitive adhesive sheet and an optical recording medium of the present invention were produced in the same manner as in Example 13 except that 100 g of unsaturated polyester A was dissolved and mixed in a compound consisting of 1.5 mol of diethylaminomethacrylate.

Example 15 A mixture of 3 molar equivalents of maleic anhydride, 4 molar equivalents of tetrahydrophthalic anhydride and 10 molar equivalents of 2-ethylenehexane-1,3-diol was heated and condensed to obtain an unsaturated polyester B.

A protective pressure-sensitive adhesive sheet of the present invention and an optical recording medium were produced in the same manner as in Example 13 except that the unsaturated polyester resin B was used instead of the unsaturated polyester resin A used in Example 13.

Example 16 <Environmental durability test> The environmental durability of the optical recording media produced in Examples 13 to 15 and Comparative Example 3 was examined in the same manner as in Example 4. The results are shown in Table 4. The recording medium of the present invention is BE
While R did not change, Comparative Example 3 significantly increased BER after 2000 hours.

[0069]

[Table 4]

[0070]

As described above, the acid value is 0.5 kO.
Preventing corrosion of the recording layer by adhering the protective layer of the resin film on the substrate using an adhesive layer of Hmg / g or less,
It is possible to provide a stable optical recording medium for a long period of time.

Further, by applying to the adhesive layer an adhesive composition having a specific molecular weight and a glass transition point, which is obtained by graft-polymerizing an acrylic acid-acrylic acid ester adhesive and a macromonomer, the occurrence of blisters in particular is prevented. It is possible to prevent and provide an optical recording medium that is stable over a long period of time.

Further, by applying a room temperature cross-linking type adhesive composition in which rubber and an epoxy monomer are graft-polymerized to the adhesive layer, cold flow can be particularly prevented and a stable optical recording medium can be provided for a long period of time.

By applying the improved unsaturated polyester resin composition to the adhesive layer, it is possible to prevent the inhibition of curing by oxygen and provide a stable optical recording medium for a long period of time.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the basic structure of an optical recording medium of the present invention.

FIG. 2 is a partial cross-sectional view showing one configuration example of a second base body.

[Explanation of symbols]

 11 First Substrate 12 Second Substrate 13 Adhesive Layer 14 Protective Layer 21 Transparent Substrate 22 Dielectric Layer 23 Recording Layer 24 Dielectric Layer 25 Reflective Layer

Claims (6)

[Claims] 1. A protective layer is formed by adhering a first substrate having a thickness of 1 to 100 μm on a second substrate through an adhesive layer having an acid value of 0.5 kOHmg / g or less. Optical recording medium. 2. A protective pressure-sensitive adhesive sheet for an optical recording medium, which comprises an adhesive layer adhered to a second substrate laminated on a first substrate, wherein the adhesive layer comprises (1) 50% by weight or more and 80% by weight or more. weight%
The following acrylic acid ester-based monomers, and (2) 1% by weight or more and 3% by weight or less of a polar acrylic-based monomer,
(3) 5% by weight or more and 40% by weight or less of a macromonomer, (4) a weight average molecular weight M _w of 1.5 × 10 ⁵ or more and 1.0 × 10 ⁶ or less, and (5) a glass transition point. T _g is -6
A protective pressure-sensitive adhesive sheet for an optical recording medium, comprising an adhesive composition having a temperature of 0 ° C. or higher and 80 ° C. or lower. 3. A protective pressure-sensitive adhesive sheet for an optical recording medium, which comprises an adhesive layer adhered to a second substrate laminated on a first substrate, wherein the adhesive layer comprises (1) natural rubber and synthetic rubber. Of 1
100 parts by weight of one kind or two or more kinds, 5 to 80 parts by weight of an epoxy monomer composed of (2) one or more kinds of unsaturated glycidyl ester monomer and unsaturated glycidyl ether monomer, and (3) the monomer With respect to 0.1 to 10% by weight of a radical polymerization initiator, (4)
A protective pressure-sensitive adhesive sheet for an optical recording medium, comprising an adhesive composition obtained by mixing a tackifier and (5) an epoxy curing agent. 4. The protection for an optical recording medium according to claim 3, which is formed by directly coating the adhesive composition according to claim 3 on a first substrate, volatilizing the solvent and crosslinking at room temperature. Adhesive sheet. 5. A protective pressure-sensitive adhesive sheet for an optical recording medium, comprising an adhesive layer adhered to a second substrate laminated on a first substrate, wherein the adhesive layer comprises (1) maleic anhydride and maleic acid. Acid, fumaric acid, and one or more of these mixtures in an amount of 50 mol% of the total acid component
And (2) an unsaturated polyester having one or two or more polyhydric alcohols having four or more carbon atoms in an amount of 50 mol% or more of all alcohol components. (3) The following general formula: (Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ each independently represent an alkyl group having 1 to 8 carbon atoms), and the mixture is dissolved and mixed in one or more monomers. A protective pressure-sensitive adhesive sheet for an optical recording medium, comprising the unsaturated polyester resin composition obtained. 6. An optical recording medium obtained by laminating the protective pressure-sensitive adhesive sheet according to claim 2.