JPH0689462A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disc which is excellent in impact resistance, in which the photo-setting adhesive gives no adverse influence to an information recording layer, the adhesive is cured in a very short time without need of heeting, the cured adhesive layer is rich in flexibility and does not give deformation to the disc substrate. CONSTITUTION:An information recording layer 2 is formed on a transparent substrate 1, and the layer is placed opposite to another substrate 5 and joined with a spacer 3. The joined part of the spacer is fixed with a photo-setting adhesive 6 containing a urethaneacrylate photo-setting oligomer having a polyether bond in the backbone having above 300 molecular wt., a monofunctional acrylate photo-setting monomer containing at least one or more polymerizable ethylenical double bond in the molecule and having above 300 molecular wt. and a photophlymerization initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc used as a document file, an image file, a computer memory, and the like, and more specifically, it has an air sandwich structure for fixing a joint portion of a spacer with a photocurable adhesive having a predetermined composition. The present invention relates to an optical disc that it has.

[0002]

2. Description of the Related Art In recent years, with the rapid increase in the amount of information to be handled, information processing technology has been rapidly developed, and optical discs have been drawing attention as a means for processing and accumulating such a large amount of information.

The structure of the optical disk used for such a purpose is (1) a single plate type, (2) a disk-shaped substrate having an information recording layer formed on at least one substrate is opposed via a spacer. It can be roughly classified into three types: an air sandwich type that is adhered, and (3) a close-bonding type that is a direct bonding of a disk-shaped substrate having an information recording layer formed on at least one substrate.

Among these, the types (2) and (3) are advantageous in that they alleviate the movement of the substrate such as warpage and undulation, and protect the information recording layer, and (2) is mainly a write-once disc. (3) is used as a rewritable disc.

The write-once disc is mainly a transparent substrate 1 having guide grooves for tracking as shown in FIG.
The structure is such that the information recording layer 2 is formed on the upper side, the space 4 is provided via the spacer 3, and the protective plates 5 are provided so as to face each other.

Alternatively, as shown in FIG. 2, two transparent substrates 1 each having an information recording layer 2 formed on the upper surface thereof are provided, and a gap 4 is provided via a spacer 3, and the two transparent substrates 1 and 1 are respectively provided. It has a structure in which the information recording layers 2 and 2 are provided so as to face each other.

Here, Te-based compounds, oxides, organic dyes, etc. have been developed as recording materials, and glass, thermoplastics such as polycarbonate and acrylic resin, epoxy resin, etc., as substrate materials for optical disks. Thermosetting plastics have been developed.

In an optical disc having such an air sandwich structure, it is essential to join the substrate 1 or the protective plate 5 and the spacer 3 together.

Japanese Unexamined Patent Publication (Kokai) No. 64-67738 proposes in advance that the projections that play the role of spacers should be processed during the molding of the substrate, but there are problems such as cost and productivity. It's difficult.

Therefore, to bond the substrate 1 or the protective plate 5 to the spacer 3, an adhesive 6 such as rubber, an adhesive in which elastomers are dissolved in a solvent, an epoxy adhesive or a hot melt adhesive is used. ing.

However, in the case of an adhesive in which rubber or elastomer is dissolved in a solvent, there is a problem that it takes a long time to cure and the residual solvent affects the information recording layer.

In the case of the one-component type, most of the epoxy-based adhesives have high viscosity, and it is difficult to obtain a colorless and transparent appearance. In the case of the two-component type, complicated operations such as weighing and mixing are required. In the case of the room temperature curing type, it takes a long time to cure, and in the case of the heat curing type, the substrate is distorted by heat, so that there is a problem that the operating temperature is limited.

In the case of a hot melt adhesive, the curing is fast, but since the adhesive is used in a molten state, the heat of the molten adhesive tends to cause thermal distortion such as deformation and warpage of the disk, Furthermore, since the melt viscosity is high, it is a thin film and even,
In addition, it is difficult to apply the coating only to the area of the spacer, and therefore, there is a problem that an expensive coating machine is required.

On the other hand, many proposals have been made to use a photo-curable resin having the characteristics of one-liquid type, solvent-free and fast curing for bonding the substrate or the protective plate and the spacer (
JP-A 61-165842, 62-185264, 60-185234
Issue 61-142545, Issue 61-165840, Issue 61-190736
No. 62-6449, etc.).

[0015]

Problems to be Solved by the Invention The types of the photocurable resin are roughly classified into a radical polymerization type resin represented by an acrylate resin and a cationic polymerization type resin represented by an epoxy resin. On the other hand, a disc with an air sandwich structure has a bonding area that is much smaller than the contact type because of its structure, and is inferior in impact resistance when dropped.
The adhesive to be used is required to have flexibility and flexibility. For this reason, the hardened material as disclosed in the above-mentioned JP-A Nos. 61-165842 and 62-185264 is airy. It is not suitable as an adhesive for disks having a sandwich structure.

The above-mentioned JP-A-60-185234 and 61-142545.
No. 61-165840, No. 61-190736 and No. 62-6449 disclose proposals using urethane acrylates, but if rigid urethane acrylates are used, problems similar to the above occur. .

In the above publication, in order to increase the curing speed,
Although polyfunctional acrylate monomers and tetrahydrofurfuryl acrylate are added and heat treatment is performed before use, the addition of polyfunctional monomers certainly contributes to the improvement of the curing speed, but on the other hand, it causes an increase in curing shrinkage and causes In a special joint such as a sandwich structure, it is difficult to contribute to improving the adhesive strength.

Further, although the addition of tetrahydrofurfuryl acrylate contributes to the improvement of air-drying property, on the other hand, it has a very high skin irritation and has a drawback that it corrodes a thermoplastic substrate material such as polycarbonate or acrylic resin. However, there is a problem in that the heat treatment is very troublesome.

Further, the photo-curable resin proposed in the related art has problems such as defective writing or reading on the information recording layer, in addition to the above-mentioned problems of adhesive strength and impact resistance.

The cause of the influence on the information recording layer is that the resin surface inside which is sealed by the spacer becomes insufficiently cured due to insufficient irradiation of light or the presence of oxygen, and thus the unreacted low molecular weight monomer left behind is stored. Alternatively, the heat generated during the drive may volatilize into the disk voids and adversely affect the information recording layer.

In view of the above-mentioned problems of the prior art, the present invention provides a photocurable resin which is excellent in adhesive strength and impact resistance and does not adversely affect the information recording layer, and an optical disc having an air sandwich structure using the same. The purpose is to do.

Therefore, as a result of earnest research to solve the above problems, when a compound having a molecular weight of 300 or more is used as the composition of the photocurable adhesive, it goes without saying that the compound is not completely cured.
It has been found that even if the uncured component remains, it does not adversely affect the information recording layer, and thus a highly reliable optical disk substrate can be obtained.

[0023]

The present invention is based on the above findings, in which an information recording layer is formed on at least one transparent substrate, and the surface of the information recording layer is opposed to another substrate, and an inner peripheral spacer and an outer periphery are formed. The present invention proposes an optical disc having a sandwich structure in which the joint portion of the spacer is fixed with a photo-curable adhesive having the following composition in the optical disc having a sandwich structure bonded via a spacer.

(A) Urethane acrylate photocurable oligomer having a polyether bond in the main chain having a molecular weight of 300 or more. (B) Having at least one polymerizable ethylenic double bond in the molecule and having a molecular weight of 300 or more. Monofunctional acrylate photocurable monomer (C) photopolymerization initiator

The reason why the molecular weight of the urethane acrylate whose main chain is polyether used in the present invention is 300 or more is that if the molecular weight is 300 or more, the curing is insufficient and the uncured product remains in the void portion of the optical disk. In this case, the uncured material is hard to volatilize even if there is an external factor such as heat, and even if a part of the uncured material is volatilized, it does not adversely affect the information recording layer.

The reason why the urethane acrylate photocurable oligomer having a polyether bond in the main chain is used in the present invention is that the air sandwich structure has a small adhesive area as described above, and thus is weak against impact such as dropping. This is because the adhesive to be used is also required to have flexibility and flexibility, but among various urethane acrylates, the polyether urethane acrylate in which the polyether polyol is used as the hydroxy compound of the main chain most meets this requirement. .

Examples of the polyol component in this polyether urethane acrylate include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and bisphenol modified with polyethylene glycol, polypropylene glycol, polytetramethylene glycol or the like.

The photoreactive group of the oligomer is preferably acrylate. This is because when the molecular weight of the oligomer increases, the density of the reactive groups decreases and the crosslink density decreases, so that the curing rate decreases and the oxygen is apt to be inhibited by the oxygen in the air. That is, when the photoreactive group of the oligomer is methacrylate, the resin surface inside which is sealed with the spacer as described above causes the unreacted low molecular weight monomer to be stored during storage due to the inhibition of curing by oxygen in the air. Alternatively, it is because the heat during the drive is volatilized into the void portion of the disk and adversely affects the information recording layer.

Further, the photocurable monomer having at least one polymerizable ethylenic double bond in the molecule used in the present invention has a molecular weight of 300 or more because of the same reason as that of the above-mentioned oligomer and skin irritation is reduced. Use one.

A monofunctional acrylate is preferably used as the photocurable monomer. Here, the reason that it is monofunctional is to impart flexibility and flexibility to the cured product, and the reason that it is acrylate is the same as described for the above oligomer.

Specific examples of the monofunctional acrylate monomer having a molecular weight of 300 or more include alicyclic modified neopentyl glycol acrylate and caprolactone modified 2
-Hydroxyethyl acrylate, nonylphenoxyethyl acrylate, nonylphenoxydiethylene glycol acrylate, nonylphenoxytriethylene glycol acrylate, nonylphenoxytetraethylene glycol acrylate, nonylphenoxypolyethylene glycol acrylate, nonylphenoxypropyl acrylate, nonylphenoxydipropylene glycol acrylate, nonylphenoxytriacrylate Propylene glycol acrylate, nonylphenoxytetrapropylene glycol acrylate, nonylphenoxy polypropylene glycol acrylate, phenoxytetraethylene glycol acrylate, phenoxypentaethylene glycol acrylate, phenoxyhexaethylene glycol acrylate , Phenoxy polyethylene glycol acrylate, phenoxy tetrapropylene glycol acrylate, phenoxy pentapropylene glycol acrylate, phenoxy polypropylene glycol acrylate, methoxypentaethylene glycol acrylate, methoxyhexaethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxytetrapropylene glycol acrylate, methoxypenta Propylene glycol acrylate, methoxy polypropylene glycol acrylate,
Hexaethylene glycol monoacrylate, polyethylene glycol monoacrylate, tetrapropylene glycol monoacrylate, pentapolypropylene glycol monoacrylate, polypropylene glycol monoacrylate, stearyl acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, and the like, one of these monomers or Two or more types are provided for the resin composition.

A photopolymerization initiator is added to the adhesive composition of the present invention. Specifically as a photopolymerization initiator, for example, benzophenone, acetophenone, 2,2-diethoxyacetophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin butyl ether, tetramethyl thiuram furfide, Examples thereof include thioxanthone, chlorotoxanthone, dimethylthioxanthone, diethylthioxanthone, benzyldimethylketal, methylbenzoinformate and hydroxycyclohexylphenylketone, and one or more of these photopolymerization initiators can be used in the resin composition. To serve.

If desired, a sensitizer may be used in combination with the photopolymerization initiator.

The amount of the photopolymerization initiator added may be the amount added to the conventional photocurable resin, but if added more than necessary, unreacted substances or photodecomposition products will volatilize in the voids of the disk after curing. The photopolymerization initiator is added in an amount of 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the resin composition, since it adversely affects the information recording layer.

Here, the photopolymerization initiator volatilized from the photocurable resin composition according to the present invention by using as the photopolymerization initiator a reactive photopolymerization initiator which can be polymerized by itself and / or a polymer thereof. And the gas component resulting from the photodecomposition product can be suppressed.

Examples of such self-polymerization type photopolymerization initiators include those exemplified in JP-A-63-57038 and JP-A-2-292307, and Darocure as a commercially available product.
ZLI3331 (made by MERK) and Esacure KIP (Fratelli lamberti
(spa company) etc. are easily available.

The photocurable resin composition of the present invention contains a polymerization inhibitor such as hydroquinone monomethyl ether, benzoquinone, 2,6-ditert-butyl-p-cresol, and catechol for improving the storage stability. Also, addition of other known additives such as leveling agents, defoaming agents, colorants, fillers, adhesion promoters, silane coupling agents, etc. is not limited.

If necessary, a resin component such as a thermoplastic resin or rubber may be added within a range that does not change the characteristics of the photocurable resin composition of the present invention.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments, but the embodiments described here are merely examples of the present invention, and the present invention is not of course limited thereto.

Example 1 500cc equipped with a stirrer, thermometer, drying tube, and nitrogen introducing tube
In a 4-neck separable flask, 85 g (0.17 mol) of polyethylene glycol-modified biphenol A with a molecular weight of 500, 33.6 g (0.2 mol) of hexamethylene diisocyanate, 90 g of phenoxytetraethylene glycol acrylate, 0.5 g of hindered phenol anti-aging agent, sulfur-containing aging Inhibitor 0.
5 g and 0.03 g of hydroquinone monomethyl ether as a polymerization inhibitor were charged, and while blowing nitrogen gas, 0.02 g of dibutyltin dilaurate was added when a uniform solution was obtained, and the mixture was stirred at 80 ° C. for 3 hours. Then, 7 g (0.06 mol) of 2-hydroxyethyl acrylate was added, and the mixture was stirred at 80 ° C. for 3 hours until the absorption of isocyanate measured by infrared spectrum analysis disappeared to obtain a urethane acrylate solution.

Next, 100 g of this urethane acrylate solution
Phenoxytetraethylene glycol acrylate 15
0 g and 5 g of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator were added and stirred until homogeneous to obtain a photocurable resin composition.

Then, a solution of a cyanine dye was applied to the guide groove surface of a disk-shaped polycarbonate substrate (outer diameter: 130 mm, inner diameter 15 mm, thickness 1.2 mm) provided with guide grooves by injection molding by spin code method. Then, it was dried to form an information recording layer. After that, the photocurable resin obtained above was applied to the inner peripheral portion and the outer peripheral portion of this disc, and pressure-bonded through a spacer. 2000mJ with a high pressure mercury lamp in the crimped state
An optical disc was prepared by irradiating ultraviolet rays of / cm ² to cure the adhesive.

Example 2 500 cc equipped with stirrer, thermometer, drying tube, nitrogen introducing tube
In a four-necked separable flask, 270 g (0.09 mol) of polypropylene glycol with a molecular weight of 3000, 26.7 g (0.12 mol) of isophorone diisocyanate, 0.5 g of hindered phenolic antioxidant, 0.5 g of sulfur-containing antioxidant, hydroquinone as a polymerization inhibitor Monomethyl ether (0.05 g) was charged, and while blowing nitrogen gas, 0.02 g of dibutyltin dilaurate was added when a uniform solution was formed, and the mixture was stirred at 80 ° C. for 3 hours. Then 2-hydroxyethyl acrylate
7.5 g (0.065 mol) was added, and the mixture was stirred at 80 ° C. for 3 hours until absorption of isocyanate measured by infrared spectrum analysis disappeared to obtain a urethane acrylate solution.

Next, 100 g of this urethane acrylate solution
To the mixture, 150 g of nonylphenoxyethyl acrylate and 5 g of Darocure ZLI 3331 as a photopolymerization initiator were added and stirred until homogeneous to obtain a photocurable resin composition. Then, Example 1
An optical disc was obtained in the same manner as in.

Comparative Example 1 (when the photo-curable oligomer is not a polyether urethane acrylate) 100 g of bisphenol A-modified epoxy resin acrylate (DICLITE UE-8200 manufactured by Dainippon Ink and Chemicals, Inc.) was used as a photo-curable oligomer and phenoxytetraethylene glycol. 150 g of acrylate and 5 g of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator were added and stirred until homogeneous to obtain a photocurable resin composition.

Comparative Example 2 (The photo-curable monomer has a molecular weight of 30.
In the case of less than 0) A photocurable resin composition and an optical disc were obtained in the same manner as in Example 1 except that phenoxyethyl acrylate was used as the photocurable monomer.

Comparative Example 3 (when the photocurable monomer is a polyfunctional monomer) A photocurable resin composition and an optical disk were prepared in the same manner as in Example 1 except that tetraethylene glycol diacrylate was used as the photocurable monomer. Obtained.

The characteristics of the photocurable resins obtained in Examples 1 and 2 and Comparative Examples 1 to 3 and the performance test of the optical discs thus produced were conducted, and the results are shown in Table 1 below. Show.

[0049]

[Table 1]

Resin characteristics in Table 1 Appearance ··· Visual viscosity ··· Measured at 25 ° C, unit: cP hardness ··· Measured at 25 ° C, Shore hardness elongation・ ・ ・ Measured by punching with JIS No. 2 dumbbell type, unit:% PC / PC Shear adhesive strength ・ ・ ・ Polycarbonate shear adhesive strength, unit: Kgf / cm ²

Disk characteristics in Table 1 Impact resistance: A change in state was observed when the disk was naturally dropped onto the epoxy floor from a height of 2 m so that the disk surface was perpendicular to the floor. Cold / heat resistant cycle ・ ・ ・ -40 ℃ × 60 minutes ← → 80 ℃ × 60 minutes, 5
0 cycle humidity resistance ... 80 ℃ × 85% RH × 2000 hours

[0052]

In summary, the optical disk having the air sandwich structure according to the present invention is excellent in impact resistance because the substrate or the protective plate and the spacer are joined with a photocurable adhesive composed of an oligomer or a monomer having a large molecular weight. In addition, the reliability of the information recording layer is not adversely affected.

Since a photo-curable adhesive is used as the adhesive, the adhesive can be cured in an extremely short time without requiring heating.

Further, since urethane acrylate having a polyether bond in the main chain is used as an oligomer,
The cured adhesive layer is highly flexible and does not deform the disk substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an optical disc having an air sandwich structure.

FIG. 2 is a cross-sectional view showing another example of an optical disc having an air sandwich structure.

[Explanation of symbols]

 1 Transparent substrate with guide groove 2 Information recording layer 3 Spacer 4 Void portion 5 Transparent protective plate 6 Adhesive

Claims (2)

[Claims] 1. An optical disc having a sandwich structure in which an information recording layer is formed on at least one transparent substrate, a surface of the information recording layer is opposed to another substrate, and the optical disc is bonded via an inner peripheral spacer and an outer peripheral spacer. An optical disc having a sandwich structure, in which a joint portion of a spacer is fixed with a photo-curable adhesive having the following composition. (A) Urethane acrylate photocurable oligomer having a polyether bond in the main chain having a molecular weight of 300 or more (B) Monofunctional having a molecular weight of 300 or more having at least one polymerizable ethylenic double bond in the molecule Acrylate photocurable monomer (C) Photopolymerization initiator 2. The optical disk according to claim 1, wherein the photopolymerization initiator is a reactive photopolymerization initiator which itself can be polymerized, or a photocurable adhesive which is a polymer thereof.