JPH07109664B2 - Optical recording medium and optical recording method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical recording medium for optically recording / reproducing information.

[Prior Art] As a material used for a conventional recording medium such as a credit card or a floppy disk, a magnetic material has been mainly used. Such a magnetic recording medium has an advantage that information can be written and read easily, but on the other hand, it has a problem that recorded contents can be easily tampered with and high-density recording cannot be performed. As a means for solving such problems and efficiently handling a wide variety of information,
An optical information recording method using an optical recording medium has been proposed, and an optical recording medium, a recording / reproducing system, a recording / reproducing apparatus, and the like for that purpose have been proposed.

As an optical recording medium for optically recording / reproducing information, for example, one having a recording layer in which silver particles are dispersed in a gelatin matrix has been proposed.

Further, a so-called heat mode recording material has been proposed in which the recording layer of the recording material is irradiated with an energy beam such as a laser beam in a spot shape to change the state of a part of the recording layer for recording. These recording materials are so-called DRAW [direct read after write] media that can be "read directly after writing" without the need for development processing after writing of information. Since recording is possible and additional writing is possible, it is expected that the application as a recording material for discs or cards will be expanded.

In addition, a thin film made of an organic dye whose properties can be changed by light of a relatively long wavelength is not toxic and has the advantage of being able to reduce the manufacturing cost such as film formation by coating. Extensive research has been conducted and many proposals have been made regarding the use of cards.

By the way, optical recording media currently used in offices, such as optical disks, generally have a hollow structure.
It is desirable that a portable optical recording medium, for example, an optical card, be as thin as possible, and it is preferable to adopt a contact sealing structure. However, there is a problem due to the close sealing.

For example, when the optical recording layer is made of an organic dye, depending on the material used for the adhesive layer for adhering the protective base material laminated on the optical recording layer, the optical recording layer is eroded and the recording contrast is lowered, resulting in reproduction failure. There was a possible problem.

Further, while the optical recording medium used in the office or the like is stored at constant temperature and humidity or stored in a jacket, the actual use environment of the portable optical recording medium is severe,
For example, the conditions of temperature and humidity are harsh, and there are many opportunities for bending, which causes the problem that peeling occurs in the adhesive layer.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned conventional problems, and is excellent in heat resistance and cold resistance, and does not cause peeling under high and low temperature conditions. It is intended to provide a recording medium.

Another object of the present invention is to provide an optical recording medium in which the optical recording layer is not deteriorated by an adhesive and peeling does not occur even when repeatedly bent.

[Means for Solving the Problems] That is, the first invention of the present invention is to provide an optical recording layer and a protective base material provided on a substrate and an adhesive layer for bonding the optical recording layer and the protective base material. In the optical recording medium having the above, the adhesive forming the adhesive layer is a thermoplastic adhesive containing the following compound A and / or compound B and compound C.

A: at least one copolymer selected from ethylene-acrylic acid copolymers and ethylene-acrylic acid ester copolymers.

B: Ethylene-maleic anhydride-acrylic acid terpolymer.

C: tackifier.

In addition, a second invention is a heat treatment containing the compound A and / or the compound B and the compound C for laminating the optical recording layer and the protective substrate provided on the substrate and the optical recording layer and the protective substrate. An optical recording method is characterized in that information is recorded on an optical recording medium having an adhesive layer made of a plastic adhesive by irradiating the optical recording layer with a light beam to form pits.

Hereinafter, the present invention will be described in detail.

An optical recording medium according to the present invention will be described with reference to specific examples shown in the drawings. FIG. 1 is a sectional view showing an embodiment of an optical card as an example of an optical recording medium according to the present invention.

Referring to FIG. 1, an optical card according to the present invention is provided with an optical recording layer 2 on a track groove surface of a substrate 1 having a track groove portion 5, and a protective base material 4 and an adhesive layer 3 on the optical recording layer 2. It is pasted together via.

In the present invention, the adhesive layer 3 is composed of at least one copolymer (compound A) selected from an ethylene-acrylic acid copolymer and an ethylene-acrylic acid ester copolymer and / or ethylene-maleic anhydride-acrylic acid tripolymer. It is composed of a thermoplastic adhesive containing a former copolymer (compound B) and a tackifier (compound C).

The contents of compound A and / or compound B and compound C in the thermoplastic adhesive of this adhesive layer 3 are compound A and / or
Or 60 to 90% by weight of compound B and 10 to 20% by weight of compound C
It is desirable that it be contained.

Further, the thermoplastic adhesive may contain an additive in an amount of 1 to 10% by weight.

Examples of the additive include a plasticizer, a filler for increasing or blocking resistance, improving odor, and reducing shrinkage, an antioxidant for improving thermal stability, and an elastomer for improving flexibility. Are used.

Examples of the tackifier for the compound C include, for example, terpene resins, terpene phenol resins, hydrogenated compounds thereof, petroleum resins having 5 or 9 carbon atoms, rosin resins and their derivatives, and low molecular weight rubbers. Although used, a terpene resin, a terpene phenol resin, and a hydrogenated product thereof are particularly preferable in terms of lowering the softening point.

As the thermoplastic adhesive used for adhesion of the optical recording medium, it is desirable that a low adhesion temperature, for example, a sufficient adhesive strength can be obtained at 120 ° C. or lower in view of the heat resistance of the recording layer, but it is used for the adhesive layer of the present invention. The thermoplastic adhesives used have softening points of 40-
It is particularly effective for optical recording layers of organic dyes, which have a low temperature of 60 ° C and are easily deteriorated by heat, and also have good cold resistance and adhesion to polycarbonate substrates.

Such a thermoplastic adhesive can be formed into a sheet, and the substrate provided with the optical recording layer and the protective base material can be bonded together. Alternatively, the thermoplastic adhesive may be heat-sealed on the protective base material in advance, or the protective base material with the thermoplastic adhesive and the substrate with the optical recording layer, which are bonded together via another adhesive, may be bonded together. .

The thickness of the adhesive layer is not particularly limited, but usually 5 to
200 μm, preferably 10 to 80 μm is desirable.

The optical recording layer 2 is near the wavelength of a light source used for recording and / or reproduction, for example, in a pit which is a recording portion when the wavelength of an energy beam for reproduction such as a semiconductor laser is 650 nm or more, particularly 700 to 900 nm. It is preferable that the difference between the reflectance in the unrecorded area and the reflectance in the unrecorded area is large. In addition, it is necessary to have absorption in the above wavelength range for writing. Further, it is preferable that the energy required for changing the reflectance due to the irradiation of the energy beam for recording is small.

The optical recording layer satisfying such conditions is preferably an organic dye, especially a thin film formed of a polymethine organic dye represented by the following general formula (I).

General formula (I)(R in the formula₁, R₂, R₃And R_FourAre hydrogen atom and alkyl
Group, substituted alkyl group, cyclic alkyl group, alkenyl group,
Aralkyl group, substituted aralkyl group, aryl group, substituted aralkyl group
Reel group, styryl group, substituted styryl group, heterocycle or
Represents a substituted heterocyclic group, n is 0, 1 or 2, X Is anion
Indicates a group. ) In particular, by using the adhesive of the present invention,
It has excellent recording / playback characteristics, and is susceptible to adhesives and heat.
Performance Degradation of Recording Layer Containing Easy Polymethine Organic Dye
An excellent optical recording medium can be obtained.

Further, these polymethine dyes have a large absorption coefficient in the wavelength region of about 800 nm of a semiconductor laser and have good solubility, and are preferable in the present invention. As such a polymethine dye, those disclosed in JP-A-58-219090 can be used, and the polymethine organic dye represented by the general formula (I) will be described below.

In the general formula (I), R ₁ , R ₂ , R ₃ and R ₄ are each a hydrogen atom or an alkyl group (eg, methyl group, ethyl group, n
-Propyl group, iso-propyl group, n-butyl group, sec-
Butyl group, iso-butyl group, t-butyl group, n-amyl group, t-amyl group, n-hexyl group, n-octyl group,
t-octyl group) and other alkyl groups,
For example, a substituted alkyl group (eg, 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 2-acetoxyethyl group, carboxymethyl group, 2
-Carboxyethyl group, 3-carboxypropyl group, 2
-Sulfoethyl group, 3-sulfopropyl group, 4-sulfobutyl group, 3-sulfatepropyl group, 4-sulfatebutyl group, N- (methylsulfonyl) -carbamylmethyl group, 3- (acetylsulfamyl) propyl Base,
4- (acetylsulfamyl) butyl group etc.), cyclic alkyl group (eg cyclohexyl group etc.), alkenyl group (vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group) Group, dodecynyl group, prenyl group, etc.), aralkyl group (eg, benzyl group, phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group, etc.), substituted aralkyl group (eg, carboxybenzyl group, sulfobenzyl group, hydroxy group). Benzyl group). Further, R ₁ , R ₂ , R ₃ and R ₄ are substituted or unsubstituted aryl groups (for example, phenyl group, naphthyl group, tolyl group, xylyl group, methoxyphenyl group, dimethoxyphenyl group,
Trimethoxyphenyl group, ethoxyphenyl group, dimethylaminophenyl group, diethylaminophenyl group, dipropylaminophenyl group, dibenzylaminophenyl group, diphenylaminophenyl group, etc.), substituted or unsubstituted heterocyclic group (eg, pyridyl group) , Quinolyl group,
Lepidyl group, methylpyridyl group, furyl group, thienyl group, indolyl group, pyrrole group, carbazolyl group, N-
Ethylcarbazolyl group etc.) or a substituted or unsubstituted styryl group (for example, styryl group, methoxystyryl group, dimethoxystyryl group, trimethoxystyryl group,
Ethoxystyryl group, dimethylaminostyryl group, diethylaminostyryl group, dipropylaminostyryl group,
Dibenzylaminostyryl group, diphenylaminostyryl group, 2,2-diphenylvinyl group, 2-phenyl-2-
Methyl vinyl group, 2- (dimethylaminophenyl) -2
-Phenylvinyl group, 2- (diethylaminophenyl)
-2-Phenylvinyl group, 2- (dibenzylaminophenyl) -2-phenylvinyl group, 2,2-di (diethylaminophenyl) vinyl group, 2,2-di (methoxyphenyl) vinyl group, 2,2- A di (ethoxyphenyl) vinyl group, a 2- (dimethylaminophenyl) -2-methylvinyl group, a 2- (diethylaminophenyl) -2-ethylvinyl group and the like are shown. n is 0, 1 or 2.

X Represents an anionic group, for example, chloride ion, bromide
Product ion, iodide ion, perchlorate ion, benze
Sulfonate ion, P-toluenesulfonate ion
Ion, methyl sulfate ion, ethyl sulfate ion, propionate
Sulphate ion, tetrafluoroborate ion, tet
Laphenyl borate ion, hexafluoroarsenate ion
Hexafluorophosphate ion, benzene sulfite
Phosphate ion, acetate ion, trifluoroacetate ion
Ion, propion acetate ion, benzoate ion,
Urate, succinate, malonate,
Oleate ion, stearate ion, citric acid
Salt ion, monohydrogen diphosphate ion, dihydrogen monophosphate
Ion, pentachlorostannate ion, chlorosulfone
Salt ion, fluorosulfonate ion, trifluoride
Lmethanesulfonate ion, hexafluoroantimo
Phosphate ion, molybdate ion, tungstic acid
Salt ion, titanate ion, zirconate ion, etc.
Represents the anion of.

Next, typical examples of the polymethine dye represented by the general formula (I) will be given.

These polymethine organic dyes are available from Bernard S.
Bernard S. Wildi et al. J. Am. Chem. Soc
(Journal of American Chemical Society) 80 3772 to 3777 (1958) and Etchschmitt (HS
chmidt) et al's Ann (Liebig Annalen del
Chemie) 623 204-216 or R. Wlzinger et al., Helv. Chim. Acta (Helvetica, Shimika, Actor) 24 369, etc.

In the present invention, any of the above polymethine organic dyes can be used, good solubility, further crystallization of the coating film obtained after coating drying does not occur easily, constant temperature and constant humidity environment (50 ℃ , Relative humidity 90%) As a result of examining that it is difficult to change (for example, reflectance, transmittance, crystallization, etc.),
It has been found that the polymethine dye represented by the following formula (II) of D-1 is excellent.

Formula (II) Further, in forming the optical recording layer, other dyes other than the above compounds, for example, diazulene type, azulene type, polymethine type, pyrylium type, squarylium type, croconium type,
Triphenylmethane type, xanthene type, anthraquinone type, cyanine type, phthalocyanine type, dioxazine type,
Tetrahydrocholine-based, triphenothiazine-based, phenanthrene-based, metal chelate complex-based dyes, etc., or metals and metal compounds, such as Al, Te, Bi, Sn, In, Se, Sn
It may be mixed and dispersed with O, TeO ₂ , As, Cd, or the like, or they may be laminated on the layer made of the compound represented by the general formula (I).

Further, such a dye may be contained in the binder in a dispersed state or a dissolved state. As the binder, for example, nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, acetic acid / cellulose propionate, cellulose esters such as cellulose acetate / butyrate, Cellulose ethers such as methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, polystyrene, polyvinyl chloride and the like can be used.

When an organic dye is used as the optical recording layer, the organic solvent that can be used during coating varies depending on whether it is in a dispersed state or in a dissolved state, but is generally methanol, ethanol, isopropanol, diacetone alcohol. Alcohols such as, acetone, methyl ethyl ketone, ketones such as cyclohexanone, N, N-dimethylformamide, amides such as N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide,
Ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether can be used.

As a coating method thereof, known coating methods such as dip coating, spray coating, spinner coating, bar coating, blade coating, roll coating, and curtain coating can be used.

Further, the optical recording medium of the present invention may have a structure in which an undercoat layer is provided between the optical recording layer and the substrate. The undercoat layer is
(A) improvement of adhesiveness, (b) barrier of water or gas, (C) improvement of storage stability of the optical recording layer, (d) improvement of reflectance, (e) protection of substrate from solvent, ( f) It is provided for the purpose of forming pregrooves.

For the purpose of (a), various polymer materials such as ionomer resin, amide resin, vinyl resin, natural polymer, silicone, liquid rubber and various substances such as silane coupling agent are used. It is possible,
For the purposes of (b) and (C), in addition to the above polymer materials, inorganic compounds such as SiO ₂ , MgF ₂ , SiO, TiO ₂ , ZnO, TiN, SiN,
, Metal or semi-metal, such as Zn, Cu, S, Ni, Cr, Ge, Se, C
d, Ag, Al, etc. can be used. For the purpose of (d), a metal such as Al, Ag or the like or an organic thin film having a metallic luster such as a diazulene dye or a polymethine dye can be used, and for the purposes of (e) and (f). For example, an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin or the like can be used. The thickness of the undercoat layer is 50Å to 100μ
m, preferably 200 to 30 μm.

Further, the undercoat layer may contain a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, a plasticizer and the like.

The substrate 1 is preferably transparent and has little inconvenience in optical recording / reproducing. For example, acrylic resin, polyester resin, polycarbonate resin, vinyl resin, polysulfone resin, polyimide resin, polyacetal resin, polyolefin. Resin, polyamide resin,
A cellulose derivative or the like can be used.

In the present invention, the method of forming the track groove portion 5 on the substrate 1 is, when the substrate is a thermoplastic resin, a method of thermally transferring a stamper mold by a method such as injection molding or hot press molding at a temperature equal to or higher than the melting point, Alternatively, it is carried out by a method in which a photocurable resin composition is applied onto a substrate, the stamper mold is brought into close contact with the substrate, and ultraviolet rays or the like are irradiated to optically transfer the stamper mold to cure the photocurable resin composition.

In the case of the thermal transfer method, the track groove portion and the substrate are formed in the same body, whereas in the case of the optical transfer method, the track groove portion is formed not by the same body as the substrate but by adhesion.

Alternatively, in addition to the stamper type transfer method, a resist film is formed on a transparent resin substrate having a translucent thin film of a desired thickness that can be etched, exposed through a photomask having a track groove pattern, and developed. Then, a resist pattern is formed, and the translucent thin film is etched using the resist pattern as a mask to form the track groove portion on the transparent substrate.

As the protective base material 4, any material that can be used as an ordinary protective base material can be used, and specifically, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, polymethyl methacrylate. Etc. Acrylic polymer, polystyrene, polyvinyl butyral, acetyl cellulose, styrene-butadiene copolymer, polyethylene, polypropylene, polycarbonate, epoxy, acrylonitrile-butadiene-styrene copolymer and the like are used. Depending on the case, a metal sheet of iron, stainless steel, aluminum, tin, copper, zinc or the like, synthetic paper, paper or the like can also be used. Furthermore, a laminate of the above materials can also be used. If necessary, these opaque protective base materials 4 may be subjected to a pretreatment such as corona discharge treatment, plasma treatment, or primer treatment for improving the adhesiveness.

Next, in the present invention, the heat containing the compound A and / or the compound B and the compound C for bonding the optical recording layer and the protective base material provided on the substrate and the optical recording layer and the protective base material Information can be recorded on an optical recording medium having an adhesive layer made of a plastic adhesive by irradiating the optical recording layer with a light beam to form pits.

Further, the optical recording medium of the present invention comprises an argon laser (oscillation wavelength 488 nm) and a helium-neon laser (oscillation wavelength 633n).
m), helium-cadmium laser (oscillation wavelength 442 nm)
It is also possible to record by irradiating a gas laser such as. It is also possible to record by irradiation with light having a half wavelength of laser light using an SHG element or the like, but preferably 650 nm
A method of recording by irradiation with a laser beam having an oscillation wavelength in the near infrared region such as a laser having the above wavelength, particularly a gallium-aluminum-arsenic semiconductor laser (oscillation wavelength 830 nm) is suitable. Further, the laser beam described above can be used for reading. At this time, writing and reading can be performed by lasers having the same wavelength, or lasers having different wavelengths can be performed.

[Operation] The optical recording medium of the present invention is an optical recording medium having an optical recording layer provided on a substrate, a protective base material, and an adhesive layer for bonding the optical recording layer and the protective base material to each other. The adhesive formed is compound A and / or compound B and compound C
Since it is composed of a thermoplastic adhesive containing, it has excellent adhesive strength and heat resistance without damaging the optical recording layer, and also has an adhesive layer with good cold resistance, flexibility and adhesiveness to polycarbonate. An optical recording medium can be obtained. Furthermore, sufficient adhesive strength can be obtained at a relatively low temperature.

Further, an optical card using a conventionally known metal thin film as an optical recording layer is difficult to punch in the punching process at the stage of finishing the shape of the card, and the bending durability of the obtained optical card is low. Since the metal thin film itself is rigid, the optical recording layer is easily cracked and easily cracked. On the other hand, in the present invention, the above-mentioned organic dye thin film is used as the optical recording layer, and such a defect does not occur.

[Examples] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

Example 1 As a transparent resin substrate, a polymethylmethacrylate casting plate having a thickness of 0.4 mm, a track groove width of 3 μm,
A track groove having a track pitch of 12 μm and a depth of 0.2 μm was molded by a hot press method. On the track groove surface of the molded product,
A diacetone alcohol solution (4% by weight concentration) of the polymethine dye represented by the same formula (II) as that of D-1 was applied by a bar coating method to form an optical recording layer having a thickness of 1000Å on the track groove surface. A transparent substrate was obtained.

As a protective substrate, a 0.3 mm thick polymethylmethacrylate casting plate was used, and ethylene-acrylic acid copolymer (acrylic acid content 7%, Vicat softening point 84 ° C)
60% by weight, ethylene-maleic anhydride-acrylic acid terpolymer (maleic anhydride content 3%, acrylic acid content 8%, Vicat softening point 70 ° C) 17% by weight, terpene resin
50 μm thick thermoplastic adhesive consisting of 20% by weight and 3% by weight of phenol and butyl rubber additive (softening point 43-51 ° C)
Via the above, the transparent substrate with the optical recording layer is superposed so that the optical recording layer and the adhesive are in contact with each other, and the surface is heated at 110 ° C. by pressure bonding with a hot roll to bond and punch with a hollow blade, I made an optical card of vertical 54.0mm and horizontal 85.5mm.

Example 2 As a polymethine dye, the dye shown in D-8 above was used, and an ethylene-acrylic acid copolymer (acrylic acid content
45% by weight, ethylene-maleic anhydride-acrylic acid terpolymer (maleic anhydride content 3%, acrylic acid content 10%, Vicat softening point 67)
Optical card was prepared in exactly the same manner as in Example 1 except that a thermoplastic adhesive (softening point 41 to 50 ° C.) composed of 40% by weight of hydrogenated terpene resin and 15% by weight of hydrogenated terpene resin was used.

Example 3 As a transparent resin substrate, a polymethylmethacrylate casting plate having a thickness of 0.4 mm, a track groove width of 3 μm,
A track groove having a track pitch of 12 μm and a depth of 0.2 μm was molded by a hot press method. On the track groove surface of the molded product,
A diacetone alcohol solution (4% by weight concentration) of the polymethine dye represented by the same formula (II) as that of D-1 was applied by a bar coating method to form an optical recording layer having a thickness of 1000Å on the track groove surface. A transparent substrate was obtained.

As a protective substrate, a 0.3 mm thick polymethylmethacrylate casting plate was used, and ethylene-acrylic acid copolymer (acrylic acid content 11%, Vicat softening point 74 ° C)
The above optical recording is performed through a 50 μm thick thermoplastic adhesive (softening point 46 to 58 ° C.) consisting of 70% by weight, 20% by weight of terpene resin, and 10% by weight of additives of barium sulfate, phenol and polyisobutylene. Layer the transparent substrates with layers so that the optical recording layer and the adhesive are in contact with each other, press-bond them with a hot roll with a surface temperature of 80 ° C and bond them together, then punch with a hollow blade
I made an optical card of 4.0mm and horizontal 85.5mm.

Example 4 An optical card was prepared in the same manner as in Example 3 except that a polycarbonate casting plate was used in place of the transparent resin substrate and the polymethyl methacrylate casting plate used as the protective substrate in Example 3.

Example 5 As a component of a thermoplastic adhesive (softening point 56 to 60 ° C.), ethylene-ethyl acrylate copolymer (acrylic acid content 10
%, Vicat softening point 90 ° C.) 65% by weight, ethylene-acrylic acid copolymer (acrylic acid content 6%, Vicat softening point
An optical card was prepared in the same manner as in Example 4 except that 20% by weight (86 ° C.), 10% by weight terpene phenol resin, and 5% by weight additive of titanium oxide and butyl rubber were used.

Example 6 As a component of a thermoplastic adhesive (softening point 55-60 ° C), ethylene-ethyl acrylate copolymer (ethyl acrylate content 14%, Vicat softening point 86 ° C) 75% by weight, terpene resin 15% by weight %, And an additive of barium sulfate and phenol of 10% by weight, an optical card was prepared in the same manner as in Example 4.

Comparative Example 1 Instead of the adhesive of Example 1 as a thermoplastic adhesive, a polyester-based adhesive (trade name; Chemit, manufactured by Toray Industries, Inc.)
An optical card was prepared in exactly the same manner as in Example 1 except that the above was used.

Comparative Example 2 Except that an amide-based adhesive (trade name; Daiamide, manufactured by Daicel Chemical Industries, Ltd.) was used in place of the adhesive of Example 1 as the thermoplastic adhesive, the same procedure as in Example 1 was performed. Created an optical card.

Comparative Example 3 Adhesion consisting of 70% by weight of ethylene-acrylic acid copolymer and 30% by weight of ethylene-maleic anhydride-acrylic acid terpolymer instead of the adhesive as the component of Example 1 as a thermoplastic adhesive. An optical card was prepared in exactly the same manner as in Example 1 except that the agent was used.

The optical cards produced in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated as follows.

(1) Contrast ratio Wavelength 830nm, laser power 3.5mW,
60m optical card with beam diameter 3.2μmφ and pulse width 50μs
The pits were formed by driving at a speed of m / s, recording was performed, and the contrast ratio was measured.

However, the contrast ratio is a value obtained by subtracting 1 from the ratio of the reflectance of the recorded portion to the reflectance of the unrecorded portion.

(2) Heat resistance test The obtained optical card was immersed in hot water at a temperature of 60 ° C to observe whether the adhesive layer portion was peeled off.

(3) Adhesive strength An optical card that has not been subjected to a heat resistance test is cut into a width of 25 mm, and a T-type peel test is performed to determine the adhesive strength at room temperature of 25 ° C and -5.
It was measured under the condition of ° C.

(4) Bending test Hold the short side of the untested optical card as shown in Fig. 2 (a), and bend the center of the card 250 times to the left and right, 250 times each, as shown in Fig. 2 (b). Then, the long side of the optical card was held, and similarly, the optical card was bent 250 times to the left and right until it flexed 10 mm, and it was observed whether the optical card was peeled.

The above results are shown in Table 1.

[Effects of the Invention] As described above, according to the present invention, an optical recording medium having an optical recording layer provided on a substrate, a protective base material, and an adhesive layer for bonding the optical recording layer and the protective base material together. In the above, since the adhesive forming the adhesive layer is a thermoplastic adhesive containing the compound A and / or the compound B and the compound C, the adhesive strength and heat resistance are excellent and the cold resistance is high without damaging the optical recording layer. It is possible to obtain an optical recording medium having an adhesive layer that has good adhesive strength and flexibility that does not cause peeling even when repeatedly bent and adhesiveness to polycarbonate.

Moreover, in the optical recording medium of the present invention, information can be easily recorded by irradiating the optical recording layer with a light beam to form pits.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the optical recording medium of the present invention, and FIGS. 2 (a) and 2 (b) are explanatory views showing a method of bending durability test of the optical recording medium of the present invention. Is. 1 ... Substrate, 2 ... Optical recording layer 3 ... Adhesive layer, 4 ... Protective base material 5 ... Track groove part, 6 ... Optical card

Claims (11)

[Claims] 1. In an optical recording medium having an optical recording layer provided on a substrate, a protective base material, and an adhesive layer for bonding the optical recording layer and the protective base material, the adhesive forming the adhesive layer is: An optical recording medium comprising a thermoplastic adhesive containing the compound A and / or the compound B and the compound C. A: at least one copolymer selected from ethylene-acrylic acid copolymers and ethylene-acrylic acid ester copolymers. B: Ethylene-maleic anhydride-acrylic acid terpolymer. C: tackifier. 2. The optical recording medium according to claim 1, wherein the tackifier is at least one resin selected from terpene resins, terpene phenol resins and hydrogenated products thereof. 3. The optical recording medium according to claim 1, wherein the optical recording layer is a thin film containing a polymethine organic dye. 4. The polymethine organic dye is represented by the following general formula:
The optical recording medium according to claim 3, which is a compound represented by (I).
body. General formula (I)(R in the formula₁, R₂, R₃And R_FourAre hydrogen atom and alkyl
Group, substituted alkyl group, cyclic alkyl group, alkenyl group,
Aralkyl group, substituted aralkyl group, aryl group, substituted aralkyl group
Reel group, styryl group, substituted styryl group, heterocyclic group or
Represents a substituted heterocyclic group, n is 0, 1 or 2, X Is anion
Indicates a group. ) 5. The polymethine organic dye is represented by the following formula (I
The optical recording medium according to claim 4, which is a compound represented by I). Formula (II) 6. The adhesive is compound A and / or compound B.
The optical recording medium according to claim 1, which contains 60 to 90% by weight and 10 to 20% by weight of compound C. 7. The optical recording medium according to claim 1, wherein the adhesive layer has a thickness of 5 to 200 μm. 8. The optical recording medium according to claim 1, wherein the adhesive layer has a thickness of 10 to 80 μm. 9. The optical recording medium according to claim 1, wherein the optical recording medium is a card-shaped optical recording medium. 10. The optical recording medium according to claim 1, further comprising an undercoat layer between the optical recording layer and the substrate. 11. A thermoplastic adhesive containing the following compound A and / or compound B and compound C for laminating an optical recording layer and a protective base material provided on a substrate and the optical recording layer and the protective base material. An optical recording method, wherein information is recorded on an optical recording medium having an adhesive layer made of, by irradiating the optical recording layer with a light beam to form pits. A: at least one copolymer selected from ethylene-acrylic acid copolymers and ethylene-acrylic acid ester copolymers. B: Ethylene-maleic anhydride-acrylic acid terpolymer. C: tackifier.