JPH1083576A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent peeling a substrate from a protective substrate in the peripheral part of an optical card in a cutting process by using specified two different kinds of adhesives for an adhesive layer to increase adhesion strength. SOLUTION: Adhesives (A) and (B) are used for an adhesive layer 3. The adhesive (A) is applied to cover a recording layer 5 on a transparent substrate 2, and the adhesive (B) is applied thereon. The transparent substrate 2 and a protective substrate 4 are laminated with the adhesive (B) in the peripheral part of the optical recording medium. By using the adhesive (A) as an adhesive in contact with the recording layer, deterioration of the reproducing light in the recording layer can be prevented since the adhesive (A) does not melt or deform around 130 deg.C.

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 which is excellent in durability, particularly, reproduction light deterioration and mechanical strength.

[0002]

2. Description of the Related Art In recent years, an optical recording medium for recording and / or reproducing information by light has been proposed as a means for storing a large amount of information. Conventionally, as a method using light, for example, Optical Engineering, Vo
l. 15, No. 2, March-April, 197
6, pp. 99- "Review and Analysis of Optical Recording Media (R
view and Analysis of Opt
As described in “optical recording media)”, when a light beam, for example, a laser beam is applied to a recording layer of an optical recording medium, a type that causes deformation or holes in the recording layer, a type that forms bubbles, and an optical type. There are known types that change the characteristic.

[0003] As a material used for the recording layer,
For example, low melting point metals such as Te, Bi, Sn, Sb, and In, cyanine, squalium, phthalocyanine, tetradehydrocholine, polymethine, naphthoquinone,
Dyeing / pigments (organic dyes) such as benzenedithiol nickel complex, and composite materials of these organic dyes and metals are known. In recent years, among the above recording layer materials, organic dyes are inexpensive optical recording media. Is attracting attention because it can be obtained.

That is, an organic dye recording medium can be formed as a recording layer on a substrate by a solvent coating method, and is more excellent in mass productivity than a low melting point metal compound formed by a vacuum evaporation method.

In a recording pit portion of an optical recording medium in which an organic dye is used for a recording layer, the reflectance is reduced by, for example, decolorization due to thermal decomposition of the organic dye, and the recording is performed due to the optical scattering effect due to the deformation of the recording pit portion. Since the reflected light amount of the information reproducing laser light in the pit portion changes, the recorded information can be sensed.

In recent years, optical recording media have been required to be thinner in accordance with the demand for smaller recording / reproducing devices.
According to the ISO standard, a thickness of 0.68 to 0.84 mm is required.

On the other hand, in order to reduce the influence of dust and scratches on the surface of the substrate of the optical recording medium on recording / reproduction, it is advantageous that the substrate is as thick as possible.
A thickness of about 6 mm is suitable. In addition, the protection substrate is 0.1 mm.
A thickness of about 15 to 0.4 mm is required. Therefore, in order to obtain an optical card having the above thickness, a so-called air gap structure, that is, a hollow portion having a thickness of about 0.5 to 1 mm is provided on a recording layer provided on a substrate, and a protective substrate is laminated thereon. It is difficult to adopt a suitable configuration.

Therefore, in a thin optical recording medium such as an optical card, an adhesive recording structure having a protective substrate laminated on a recording layer via an adhesive layer is employed.

However, when the adhesive layer made of an adhesive is directly in contact with a recording layer containing an organic dye (hereinafter, referred to as an organic dye recording layer), the recording layer is deteriorated by a reaction between the organic dye and the adhesive. However, there has been a problem that the C / N of information recorded on the recording layer is reduced.

In order to solve these problems, for example, Japanese Patent Laid-Open Publication No. 2-3116 discloses an optical card in which a recording layer on which an optical information pattern is recorded and an adhesive layer are laminated. An optical card in which a partition layer is provided between the optical card and the agent layer has been proposed.

[0011] The applicant of the present invention is Japanese Patent Application Laid-Open No. 1-146144.
In the publication, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer or ethylene-maleic anhydride-acrylic acid terpolymer is mainly used as an adhesive which does not easily damage the organic dye recording layer. An optical recording medium using an adhesive as a component is disclosed. However, the method of providing the partition layer shown in the above-mentioned conventional example has a drawback that the manufacturing method is complicated and the cost is increased.

Further, the above-mentioned ethylene-acrylic acid copolymer,
Ethylene-acrylate copolymer or ethylene-
An adhesive containing a maleic anhydride-acrylic acid terpolymer as a main component has little interaction with an organic dye recording layer, and is one of suitable adhesives for bonding optical recording media having excellent adhesive strength. However, the optical recording medium using this adhesive can also be used under conditions of high temperature and high humidity, for example, at 70 ° C. and RH90.
%, Or a decrease in the reflectance of the organic dye recording layer when stored for 100 hours or when a higher-power reproducing light beam is used, that is, specifically, 7%.
It is desired that the reflectance change rate under the conditions of 0 ° C. and RH 90% be suppressed to 10% or less, particularly 6% or less, and further 4% or less, and the recording layer is continuously irradiated with a high-power reproducing light beam. The time required for the reflectance to decrease by 10% from the initial value is 2
It is desired that the time is at least 00 seconds, especially at least 250 seconds, and further at least 280 seconds.

[0013]

In order to improve the above-mentioned problems, the present applicant has already disclosed in Japanese Patent Application Laid-Open No. Hei 5-198509 a recording medium using an adhesive in which the Vicat softening point of the adhesive is specified. Proposed. However, according to the present invention, the adhesion by the adhesive was 1 kg or less in a 25 mm width T-peel test. In a conventional recording medium, this degree of adhesion was sufficient.However, after bonding the substrate and the protective substrate with the above-mentioned adhesive to form a work size, like an optical card medium, cutting with a hollow blade was performed. When a step of cutting to the size of an optical card is necessary, there has been a problem that peeling occurs at the boundary between the substrate and the protective substrate on the outer peripheral portion of the optical card in the cutting step.

Therefore, a recording medium having an adhesion force of 1 kg (T-type peel test) or more has been required. However, an adhesive having an adhesion force of 1 kg or more has a low melt viscosity at a temperature of 130 ° C. and is not more than 20 × 10 ³ poises. did.

On the other hand, the present applicant has proposed an optical card using two kinds of different adhesives in Japanese Patent Application Laid-Open No. 1-98139, but the improvement of reproduction light deterioration has not been sufficiently studied.

Particularly, in recent years, a hybrid optical card in which an IC chip is embedded in a part of the optical card has been proposed. In these hybrid optical cards, when mechanically making holes in the optical card for embedding an IC chip, a problem arises in that the substrate and the protective substrate are separated by stress.

The present invention has been made to solve such a problem of the prior art. By using two kinds of specific adhesives for an adhesive layer, an adhesive force of 1 kg is obtained.
(T-type peeling test) Because of the above, the cutting process does not cause peeling between the outer peripheral substrate and the protective substrate of the optical card, and can sufficiently withstand machining for embedding an IC chip. It is an object of the present invention to provide an optical recording medium in which a recording layer is prevented from being deteriorated by an adhesive.

[0018]

That is, the present invention relates to an optical recording medium in which a transparent substrate, a recording layer, and a protective substrate are laminated on the recording layer via an adhesive layer, wherein the adhesive layer has two kinds of layers. The adhesives A and B are laminated, and the melt viscosity of the adhesive A in contact with the recording layer is 30 × 10 ³ poi at 130 ° C.
This is an optical recording medium characterized in that the melt viscosity of the adhesive B that does not contact the recording layer is not more than 20 × 10 ³ poise at 130 ° C.

In the present invention, adhesives A and B are used for the adhesive layer. The recording layer on the transparent substrate is coated with the adhesive A, and the adhesive B is provided thereon to bond the transparent substrate and the protective substrate. However, adhesives A and B include ethylene-acrylic acid copolymer, ethylene-acrylic ester copolymer,
At least one selected from an ethylene-methacrylic acid copolymer and an ethylene-methacrylic acid ester copolymer
Adhesives containing the various copolymers are preferred.

The outer peripheral portion of the optical recording medium according to the present invention is characterized in that a transparent substrate and a protective substrate are bonded via an adhesive B in order to improve the adhesion. In the recording layer used in the present invention, an organic dye is used, and a polymethine dye is particularly preferable. Further, the present invention is particularly effective when the optical recording medium of the present invention is a hybrid optical card having an IC chip and an emboss.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the optical recording medium according to the present invention. In FIG. 1, in an optical recording medium 10 of the present invention, a hard coat layer 1 is formed on a first surface outside a transparent substrate 2, and a preformat 6 is formed on a second surface inside. , A recording layer 5 is provided thereon, and the recording layer 5 includes an adhesive layer 3 including an adhesive layer A and an adhesive layer B.
Is bonded to the protective substrate 4 via the. Adhesives A and B are used for the adhesive layer 3.
The upper recording layer 5 is covered, and an adhesive B is provided thereon and adhered. The transparent substrate 2 and the protective substrate 4 are bonded to each other at the outer peripheral portion of the optical recording medium via the adhesive B.

An IC chip 9 is buried in a region of the optical recording medium 1 where the recording layer 5 is not formed, and can be used as a hybrid optical card. The recording / reproducing light 8 is irradiated from the side of the transparent substrate 2 to perform recording / reproducing.

In the present invention, the adhesives A and B are ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer and ethylene-methacrylic acid ester copolymer. Adhesive A contains at least one copolymer selected from coalescables and has a melt viscosity of 30 × 10 ³ pois at 130 ° C.
e or more, preferably 30 × 10 ^{3 to} 100 × 10 ³ po
is, more preferably 30 × 10 ³ to 80 × 10 ^3.
The adhesive B has a melt viscosity of not more than 20 × 10 ³ poise at 130 ° C., preferably 20 × 10 ^{3 at} 130 ° C.
５5 × 10 ³ poise is used.

The melt viscosity of the adhesive A at 130 ° C. is 3
It was found that when the value was 0 × 10 ³ poise or more, the deterioration of the reproduction light of the recording layer could be remarkably improved. This means that the heat generation of the recording layer by the reproduction light at the reproduction power of 0.2 mW to 0.1 mW is around 130 ° C., and the melting deformation of the adhesive by the reproduction light affects the reproduction light deterioration of the recording layer. This has been clarified in the study of the present inventors. Therefore, if the adhesive A is used as the adhesive in contact with the recording layer, there is no melting deformation of the adhesive at around 130 ° C., so that it is possible to prevent the reproduction light from deteriorating the recording layer.

However, if the temperature is more than 100 × 10 ³ poise, it is not preferable because the adhesive cannot be bonded to the recording layer at a temperature lower than the thermal deformation of the plastic substrate so that no gap is formed between the adhesive and the recording layer. Since it does not dissolve in the adhesive, voids are generated in the adhesive, and noise is generated at the time of recording / reproducing, causing an error.

On the other hand, the melt viscosity at 130 ° C. is 30 ×
If it is 10 ³ poise or more, the hot melt adhesive A bonded by the laminating process at a temperature of 100 to 130 ° C. has a large melt viscosity, so that it has poor wettability to the transparent substrate and the protective substrate, and has a strong adhesion, for example, T type 25mm
It was not possible to obtain an adhesion of 1 kg or more in isolation. According to the study by the present inventors, the melt viscosity of the adhesive was 20 × 10
It was found that a sufficient adhesion force could be obtained at ³ poise or less. Therefore, if the adhesive B is used, it has good wettability to the transparent substrate and the protective substrate, and has a strong adhesion to the transparent substrate and the protective substrate, for example, T-type 25 mm isolation 1 k
g or more can be obtained.

[0027] However, 5 × ¹⁰ 3 heat storage durability not preferable because it becomes adhesive which melts at the order of 80 ° C. becomes poise or less.

The adhesive containing a copolymer as a main component used for the above-mentioned adhesives A and B is excellent in storage durability of the recording layer. Has an excellent effect.

In the present invention, the weight average molecular weight of the copolymer contained in the adhesives A and B is about 10,000 to 1,0.
00,000, preferably 30,000-800,00
A range of 0 is preferred.

The ethylene-acrylic acid copolymer contained in the adhesives A and B is, for example, as shown in the following structural formula (II).

[0031]

Embedded image (However, a, b, and n are positive integers) The polyethylene has a structure in which a carboxyl group is randomly included in the structure, and the ethylene-acrylate copolymer is, for example, represented by the following structural formula (III) Is a copolymer of ethylene and acrylate, as shown in

[0032]

Embedded image (Where a, b, and n are positive integers, and R: CH ₃ , C ₂ H
₅ , C ₃ H ₇ ) The ethylene-methacrylic acid copolymer has a structure in which a carboxyl group is randomly contained in the molecular structure of polyethylene as shown by the following structural formula (IV).

[0033]

Embedded image (Where a, b, and n are positive integers) Further, the ethylene-methacrylate copolymer has, for example, a structure as shown by the following structural formula (V).

[0034]

Embedded image (Where a, b, and n are positive integers, and R: CH ₃ , C ₂ H
₅ , C ₃ H ₇ )

Among the above copolymers, in particular, ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methacrylic acid copolymer (EMAA) and ethylene-methacrylic acid copolymer (EMAA) Methyl methacrylate copolymer (EMMA) is preferred.

The adhesives A and B of the present invention contain at least one of the above four copolymers, and may contain a mixture of two or more thereof. Further, in the present invention, two or more different copolymers of the same type of copolymer, for example, a mixture of an ethylene-methyl methacrylate copolymer and an ethylene-ethyl methacrylate copolymer are mixed in the adhesive. May be contained.

In the present invention, the melt viscosities of the adhesives A and B are mainly determined by the following three factors: (1) acrylic acid in each of the above-mentioned copolymers contained in the adhesives A and B; Content of acrylic acid ester, methacrylic acid, methacrylic acid ester (2) Content of the copolymer in adhesives A and B (3) Additives in adhesives A and B alone or two In the present invention, the melt viscosity can be adjusted by controlling the above-mentioned elements (1) to (3), and the melt viscosity can be controlled by appropriately changing the combination. It is preferable to add no or minimize the amount of the additive in order to prevent the interaction between the recording layer and the adhesive layer.

In the present invention, the total content of the copolymer in the adhesive A is 80 to 100 wt.
%, Especially 90 to 100 wt%, and even 95 to 100 wt%
%, And the content (in terms of monomer) of acrylic acid, acrylic acid ester, methacrylic acid or methacrylic acid ester in the copolymer contained in the adhesive of the present invention is 20% by weight of the copolymer. Below, especially 8-
It is preferable that the content is 15 wt%, and more preferably 9 to 12 wt%.

In the present invention, the total content of the above copolymer in the adhesive B is 50 to 95 watts of the adhesive B.
t%, particularly preferably in the range of 70 to 90 wt%.

The content of the additive contained in the adhesive is preferably in the range of 1 to 10% by weight.

By adjusting the melt viscosity of the adhesive A to 30 × 10 ³ poise or more at 130 ° C. within the above composition range, the adhesive A can be used at high temperature and high humidity or when a higher power reproducing light beam is used. However, it is possible to obtain an optical recording medium in which the reflectance of the recording layer is less reduced and the durability is further improved.

In the present invention, the content of acrylic acid, acrylic acid ester, methacrylic acid or methacrylic acid ester in the copolymer can be calculated by quantifying the absorption of carbonyl in an infrared absorption spectrum.

In the present invention, examples of additives to be added to the adhesive layer include tackifiers and softeners. Examples of the tackifier include natural resins such as rosin, polymerized rosin, hydrogenated rosin, and rosin ester. And modified products thereof, aliphatic compounds, alicyclic compounds, aromatics, petroleum resins, terpene resins, terpene / phenol resins, hydrogenated terpene resins, cumarone resins, and the like.
For example, process oil, paraffin oil, castor oil,
Polybutene, low molecular weight polyisoprene and the like can be mentioned.
Further, an ultraviolet absorber or the like may be added to the adhesive layer of the present invention, if necessary, as long as it does not cause an interaction with the recording layer and does not change the physical properties described above.

In the present invention, the adhesive B is an adhesive having a melt viscosity of 20 × 10 ³ poise or less at 130 ° C. In order to lower the melt viscosity, the melt flow rate (JIS K6730 or ASTM D
1238) need not be increased. If the melt flow rate is increased and the melting point of the resin of the adhesive is lowered, the heat resistance deteriorates. Therefore, it is preferable to control the melt viscosity at 130 ° C. by adding an additive.

That is, in the present invention, the content of acrylic acid, acrylic acid ester, methacrylic acid, and methacrylic acid ester in the copolymer was set to 20 wt% or less as described above for the composition of the adhesives A and B. In this case, the critical surface tension of the adhesive layer becomes, for example, 30 to 37 dyn / cm, and a resin such as a polymethyl methacrylate (PMMA) substrate or a polycarbonate (PC) substrate which is usually used as an optical recording medium substrate and / or a protective substrate. Although the adhesiveness between the adhesive layer and the transparent substrate 2 and / or the protective substrate tends to slightly decrease due to poor wettability of the adhesive to the substrate, the surface modification of the adhesive film or the adhesive layer as described above. Is carried out to improve the critical surface tension, whereby a decrease in adhesion can be suppressed.

At this time, the method of surface modification is not particularly limited, and examples thereof include a corona discharge treatment, an ozone treatment, an alkali treatment, an argon plasma treatment, an oxygen plasma treatment and the like. Improve the critical surface tension of the adhesive sheet surface by performing corona discharge treatment using a corona discharge device on both surfaces immediately after extrusion molding when forming an acrylic acid copolymer adhesive film into a sheet by melt extrusion. be able to. Since the surface of both surfaces can be easily modified, the above production method using an adhesive sheet is preferable for producing an optical recording medium having excellent adhesiveness. In the present invention, the critical surface tension is measured according to JIS
This was performed according to the method of K-6768.

The adhesive B for the optical recording medium according to the present invention
As for the adhesive force required for the above, the adhesive force by a T-type peeling test when two resin sheets having a thickness of 0.4 mm are adhered with the adhesive B is preferably 1 kg / 25 mm or more.
In the present invention, the thickness of the adhesives A and B is not particularly limited, but is usually 5 to 200 μm, preferably 10 to 1 μm.
20 μm is preferred.

Next, in the present invention, when the wavelength of the light used for recording, for example, the wavelength of a light beam such as a semiconductor laser is 650 nm or more, particularly in the range of 700 to 900 nm, the recording layer 5 is used. It is preferable that the energy required to cause an optically detectable change by irradiation with a light beam is small.

Further, it is preferable that the difference in optical characteristics between the information recording portion and the non-recording portion is large with respect to the light used for reproduction. Examples of the substance used for the recording layer 5 in the present invention include anthraquinone derivatives (particularly those having an indazulene skeleton), dioxazine compounds and derivatives thereof, triphenodithiazine compounds, phenanthrene derivatives, cyanine compounds, merocyanine compounds, and pyrylium compounds. Compounds, xanthene compounds, triphenylmethane compounds, croconium dyes, azo dyes, crocones, azines, indigoids, polymethine dyes, azulene dyes, squarium dyes, cyanine dyes with polymethine chains, tetra Organic dye substances such as phenylcyanine dyes are exemplified.

In particular, in the present invention, when a polymethine dye represented by the following general formula (1) is used for a recording layer, an optical recording medium having particularly excellent durability can be obtained.

[0051]

Embedded image

(Where A, B, D and E represent a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group,
Shows a group selected from styryl and a heterocyclic group. r
₁ ', r _2' is a hydrogen atom, an alkyl group, cyclic alkyl group, an alkenyl group, a group selected from aralkyl and aryl radicals, k is 0 or 1, L is 0, 1 or 2
And X ^- represents an anion. A, B, D,
The aralkyl group, aryl group, styryl group and heterocyclic group in E, r ₁ ′ and r ₂ ′ may be substituted. )

The abbreviations in the above general formula will be described in more detail. A, B, D and E represent a hydrogen atom or an alkyl group (for example, a methyl group, an ethyl group, an n-propyl group, an is
o-propyl group, n-butyl group, sec-butyl group, i
so-butyl group, t-butyl group, n-amyl group, t-amyl group, n-hexyl group, n-octyl group, t-octyl group, etc.), and other alkyl groups, for example, substituted alkyl groups ( For example, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-acetoxyethyl, carboxymethyl, 2-carboxyethyl, 3-carboxypropyl, 2-sulfoethyl, 3-sulfoethyl Propyl group, 4-sulfobutyl group,
3-sulfatepropyl group, 4-sulfatebutyl group, N- (methylsulfonyl) -carbamylmethyl group,
Cyclic alkyl groups (for example, cyclohexyl group) such as 3- (acetylsulfamyl) propyl group and 4- (acetylsulfamyl) butyl group, alkenyl groups (vinyl group, propenyl group, butenyl group, pentenyl group, Hexenyl, heptenyl, octenyl, dodecynyl,
A aralkyl group (eg, benzyl group, phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group), a substituted aralkyl group (eg, carboxybenzyl group, sulfobenzyl group, hydroxybenzyl group, etc.), Aryl group (for example, phenyl group), substituted aryl group (for example, diethylaminophenyl group)
Is included.

R ₁ ′ and r ₂ ′ represent a hydrogen atom or an alkyl group (for example, methyl group, ethyl group, n-propyl group, is
o-propyl group, n-butyl group, sec-butyl group, i
so-butyl group, t-butyl group, n-amyl group, t-amyl group, n-hexyl group, n-octyl group, t-octyl group, etc.), and other alkyl groups such as substituted alkyl groups. (For example, 2-hydroxyethyl group, 3-
Hydroxypropyl group, 4-hydroxybutyl group, 2-
Acetoxyethyl, carboxymethyl, 2-carboxyethyl, 3-carboxypropyl, 2-sulfoethyl, 3-sulfopropyl, 4-sulfobutyl, 3-sulfopropyl, 4-sulfobutyl, N- (methylsulfonyl) -carbamylmethyl group, 3- (acetylsulfamyl) propyl group, 4-
(Acetylsulfamyl) butyl group), cyclic alkyl group (eg, cyclohexyl group), alkenyl group (vinyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, dodecynyl group, Prenyl group), aralkyl group (for example,
Benzyl group, phenethyl group, α-naphthylmethyl group, β
-Naphthylmethyl group) and substituted aralkyl groups (for example, carboxybenzyl group, sulfobenzyl group, hydroxybenzyl group, etc.).

The recording layers containing these organic dyes include:
A stabilizer such as an infrared absorbing compound may be contained for the purpose of improving light resistance. Examples of the material used as the stabilizer include, for example, JP-A-60-1
Nos. 63245 and 60-236131, or the following (VI) and (VI)
I) Substances represented by the formula are mentioned.

[0056]

Embedded image (Where R is a hydrogen atom, a lower alkyl group, X is an acid ion, and A is

[0057]

Embedded image Is shown. Here, n is an integer of 1 or 2. )

In the above formulas (VI) and (VII),
Compounds in which the substituent R is an alkoxyalkyl group (for example, a methoxyethyl group), an alkenyl group (for example, a propenyl group), an alkynyl group (for example, a propargyl group), or a cyclic alkyl group (for example, a cyclopentyl group) is This is a particularly suitable material when the recording layer is formed by wet coating because of its excellent function of stabilizing the organic dye and its excellent solubility in a solvent.

Examples of the quencher having the effect of stabilizing the organic dye include, for example, the following (VIII) to (X)
II) The metal complex represented by the formula can also be used.

[0060]

Embedded image

[0061]

Embedded image

[0062] (wherein, to no R ₁ R ₄ may be the same or different, each represents a substituted or unsubstituted alkyl group, an aryl group or an amino group, R ₅
To R ₈ may be the same or different and each represents a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl group or amino group, and M represents Ni, C
represents a transition metal selected from o, Mn, Cu, Pd and Pt. )

The content of the stabilizer and the quencher contained in the recording layer 5 is usually 5 to 5 with respect to the content of the dye.
A range of 50% by weight, preferably 10 to 30% by weight is desirable. Further, in the recording layer of the present invention, the above-mentioned organic dye, stabilizer, and quencher may be contained in a binder in a dispersed state or a dissolved state.

The binder used in the present invention includes:
For example, nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate,
Cellulose butyrate, cellulose myristate, cellulose palmitate, cellulose acetate / propionate, acetate
Cellulose esters such as cellulose butyrate, cellulose ethers such as methylcellulose, ethylcellulose, propylcellulose and butylcellulose, polystyrene, polyvinyl chloride and the like can be used.

In the case where an organic dye is formed as a recording layer by wet coating, the organic solvent that can be used for coating differs depending on whether the organic dye is in a dispersed state or a dissolved state. , Ethanol, isopropanol, alcohols such as diescent alcohol, ketones such as acetone, methyl ethyl ketone and cyclohesaquinone, N, N-dimethylformamide, N,
Amides such as N-dimethylacetamide, sulfoxides such as dimethylsulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, aliphatic halogenated compounds such as dichloromethane, dichloroethylene and trichloroethylene, and hydrocarbons can be used. .

Further, as a method of applying these coating solutions to the transparent substrate, known coating methods such as dip coating, spray coating, spinner coating, bar coating, blade coating, roll coating, curtain coating and the like can be used. It is formed.

The thickness of the recording layer is 400 to 1200 °.
The range is preferably, but it is usually preferable to set the film thickness such that the surface reflectance is maximized by the correlation between the film thickness of the recording layer and the reflectance, since an excellent C / N signal can be obtained. When a reflective layer is provided on the surface opposite to the light beam incident surface side, it is preferable to set the film thickness so as to minimize the surface reflectance of the recording layer because the recording sensitivity is improved.

As the transparent substrate 2 used in the present invention,
A transparent plastic plate such as PVC, polymethyl methacrylate, polycarbonate, polysulfone, polyolefin resin and the like can be used. In particular, polymethyl methacrylate, which has no optical refraction and is hard and is not easily damaged, is preferable. Preferably, the substrate is an optically transparent material.

Further, the protective substrate is preferably made of a plastic material that does not cause “warpage” on the entire recording medium.
PMMA, PC, PVC and the like can be used.

[0070]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A pre-groove of an optical card substrate made of polymethyl methacrylate having a thickness of 0.4 mm, a length of 80 mm and a width of 95 mm in which a stripe-shaped pre-groove having a width of 3 μm and a pitch of 12 μm was formed on one surface by casting. UV curable resin (trade name: Unidick 17-824-9, manufactured by Dainippon Ink Co., Ltd.) on the surface where no is formed
After coating to a thickness of μm, ultraviolet rays were applied to form a hard coat. Further, a polymethine dye represented by the following structural formula (1-1) and a stabilizer represented by the following structural formula (1-2) were mixed at a weight ratio of 3: 1 on the surface of the substrate on which the pregroove was formed. The recording layer thus formed was formed to a thickness of 900 ° by a solvent coating method.

Next, a 50 μm thick Cranbetter P-2200 (trade name, manufactured by Kurashiki Spinning Co., Ltd.) was cut as the adhesive A on the organic dye recording layer into a size of 33 mm and a width of 80 mm. On the recording layer. Next, a 70 μm thick cranbetter O was formed thereon as an adhesive B.
-4121 (trade name, manufactured by Kurashiki Spinning Co., Ltd.) and a protective substrate made of a PMMA plate having a thickness of 0.25 mm are further laminated,
An optical card-shaped recording medium was produced by pressing and bonding with a hot roll having a surface temperature of 130 ° C., and cutting the optical card into a size (length 54 mm, width 85.6 mm).

[0073]

Embedded image

Example 2 The substrate used in Example 1 was prepared by forming a pre-groove by a roller grooving method to a thickness of 0.4 mm and a length of 92 m.
An optical card-shaped recording medium was manufactured in the same manner as in Example 1 except that the polycarbonate substrate was changed to a polycarbonate substrate having a width of 97 mm and the protective substrate was changed to a polycarbonate substrate having a thickness of 0.3 mm.

Example 3 Adhesive A of Example 2 was replaced with Nucrel N-0903HC
(Trade name, manufactured by Mitsui Petrochemical Co., Ltd.) An optical card-shaped recording medium was prepared in the same manner as in Example 2 except that the recording medium was changed.

Example 4 Adhesive B of Example 2 was replaced with Crown Better W-4110
(Trade name, manufactured by Kurashiki Spinning Co., Ltd.) An optical card-shaped recording medium was produced in the same manner as in Example 2 except that the recording medium was changed.

Comparative Example 1 An optical card-shaped recording medium was produced in the same manner as in Example 2 except that only Cranbetter O-4121 of adhesive B (one adhesive layer) was used instead of the adhesives A and B of Example 2. Was prepared.

Comparative Example 2 An optical card-shaped recording medium was produced in the same manner as in Example 2 except that only Cranbetter P-2200 of adhesive A (one adhesive layer) was used instead of the adhesives A and B of Example 2. Was prepared.

Comparative Example 3 An optical card-shaped recording medium was produced in the same manner as in Example 3 except that only Nuclell N-0903HC (one adhesive layer) was used instead of the adhesives A and B in Example 3. did.

Comparative Example 4 An optical card-shaped recording medium was prepared in the same manner as in Example 4 except that only Crown Better W-4110 (one adhesive layer) was used as the adhesive instead of the adhesives A and B of Example 4. Produced.

Table 1 shows the measurement results of the adhesive strength and the reproduction light deterioration time of the optical card-shaped recording media of Examples 1 to 4 and Comparative Examples 1 to 4. However, the adhesive strength is 25mmT
It was measured by a mold release test. Note that the reproduction light deterioration time is the time required for the reflectance of the recording layer to decrease by 10% from the initial value when the reproduction light beam (wavelength 830 nm) is continuously irradiated to one point of the recording layer while fixing the optical card. It is.

In this embodiment, the reproduction light deterioration time when the reproduction light power was set to 0.1 mW and 0.2 mW was measured. Needless to say, the irradiation position of the reproduction light was changed at this time. Tables 2 and 3 show the physical properties of the adhesive.

[0083]

[Table 1]

[0084]

[Table 2]

[0085]

[Table 3]

(Note) P-2200: EAA ethylene-acrylic acid copolymer O-4121: EMA ethylene-methyl acrylate copolymer O-4122: EMA ethylene-methyl acrylate copolymer W-4110: EMMA ethylene- Methyl methacrylate copolymer N-0903HC: EMAA Ethylene methacrylate copolymer

[0087]

As described above, according to the present invention, since two specific adhesives are used for the adhesive layer, the adhesive force is as large as 1 kg (T-type peel test) or more. An optical recording medium in which the processing does not cause separation between the substrate at the outer peripheral portion of the optical card and the protective substrate, can sufficiently withstand machining for embedding an IC chip, and further prevents deterioration of the recording layer due to an adhesive. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an optical recording medium according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard-coat layer 2 Transparent substrate 3 Adhesive layer 4 Protective substrate 5 Recording layer 6 Preformat 8 Recording / playback light 9 IC chip 10 Optical recording medium

Claims (8)

[Claims] 1. An optical recording medium comprising a transparent substrate, a recording layer, and a protective substrate laminated on the recording layer via an adhesive layer, wherein the adhesive layer is formed by laminating two kinds of adhesives A and B. The melt viscosity of the adhesive A in contact with the recording layer is 30 × 10 ³ poise or more at 130 ° C., and the melt viscosity of the adhesive B not in contact with the recording layer is 20 × 1 at 130 ° C.
An optical recording medium characterized by having a diameter of 0 ³ poise or less. 2. The adhesive A has a melt viscosity of 30 × 10 ^{3 to} 100 × 10 ³ poise at 130 ° C.,
The melt viscosity of the adhesive B is 20 × 10 ^{3 at} 130 ° C.
2. The optical recording medium according to claim 1, wherein the optical recording medium has a density of 5 × 10 ³ poise. 3. The adhesives A and B are ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer and ethylene-acrylic acid copolymer.
2. The optical recording medium according to claim 1, comprising at least one copolymer selected from methacrylate copolymers. 4. The optical recording medium according to claim 1, wherein a substrate and a protective substrate are bonded to each other at an outer peripheral portion of the optical recording medium via an adhesive B. 5. The optical recording medium according to claim 1, wherein the optical recording medium is a hybrid optical card having an IC chip and an emboss. 6. The optical recording medium according to claim 1, wherein said recording layer contains an organic dye. 7. The optical recording medium according to claim 1, wherein the recording layer contains a polymethine dye. 8. The optical recording medium according to claim 7, wherein the recording layer contains a polymethine dye represented by the following general formula (1). Embedded image (Wherein, A, B, D and E represent a group selected from a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, a styryl and a heterocyclic group. R ₁ ′, r ₂ ′
Represents a hydrogen atom, an alkyl group, cyclic alkyl group, an alkenyl group, a group selected from aralkyl and aryl radicals, k is 0 or 1, L is 0, 1 or 2, X ^- represents an anion. Note that A, B, D, E, r ₁ ′ and r ₂
Aralkyl, aryl, styryl,
The heterocyclic group may be substituted. )