JP2002025113A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium excellent in accuracy of thickness, having high accuracy of reproduction of signals, excellent also in various durabilities, having high reliability and easily producible with high accuracy. SOLUTION: The recording medium is obtained by joining a transparent resin substrate and another transparent resin substrate or a transparent resin sheet with a filmlike photo-curable adhesive based on a (meth)acrylic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium, such as a digital video disk, for recording information such as large-capacity characters, sounds, and moving images by digital signals.

[0002]

2. Description of the Related Art In manufacturing an optical disk or the like using a single transparent resin substrate, a liquid ultraviolet curable resin adhesive is applied to a recording layer as a protective layer, and then light is applied to the recording layer. A method of irradiating photopolymerized and cured has been proposed. However, the method using a liquid ultraviolet curable adhesive has the following disadvantages.

That is, since the ultraviolet curable resin adhesive is in a liquid state, it is difficult to control the thickness of the protective layer uniformly. In particular, since this recording medium is a method of reading by irradiating reproduction light from one side, extremely precise control of the thickness of the adhesive layer in the circumferential direction on the micron order is required, but in the case of a liquid ultraviolet curable resin, Since a liquid is applied while rotating a resin disk on a rotary table at a high speed, a spin coating method is used, so that when the liquid spreads due to centrifugal force, a ripple occurs and it is difficult to obtain a desired film thickness accuracy. In addition, the adhesive strength with the transparent resin substrate is low, and there is a problem in durability. Therefore, an adhesive free of such a problem has been desired. In addition, although a disk originally has warpage, an EVA-based adhesive has a low elasticity and cannot suppress warpage, and an adhesive having a high elasticity to suppress warpage has been desired.

SUMMARY OF THE INVENTION The present invention has been made in response to the above-mentioned demands, and has as its object to provide a recording medium which can be manufactured with high accuracy and has high reliability.

[0005]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies in order to achieve the above object, and as a result, as a coat layer for protecting the transparent resin substrate and the recording layer, one sheet was used. Transparent resin substrate or transparent resin sheet, (meta)
By bonding using a film-shaped photocurable adhesive containing an acrylic resin as a main component, defects such as those in the ultraviolet curable resin adhesive can be eliminated, and a highly reliable recording medium can be obtained. And that such a recording medium can be manufactured easily and with high precision.

That is, the present invention provides the following recording medium. Claim 1: A recording medium comprising a transparent resin substrate and a transparent resin substrate or a transparent resin sheet joined by a film-shaped photocurable adhesive mainly composed of (meth) acrylic resin. In a preferred embodiment, the transparent resin substrate is a digital video disk substrate having a reflective layer. Claim 3: The photocurable adhesive is a (meth) acrylic resin 1
3. The recording medium according to claim 1, wherein 0.1 to 10 parts by weight of a photosensitizer and 10 to 300 parts by weight of a photopolymerizable oligomer are added to 00 parts by weight. Claim 4: The photocurable adhesive is a (meth) acrylic resin 1
4. The recording according to claim 1, wherein at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound is added in an amount of 10 to 200 parts by weight with respect to 00 parts by weight. Medium. Claim 5: The photocurable adhesive is a (meth) acrylic resin 1
The silane coupling agent is used in an amount of 0.01 to 100 parts by weight.
5. The composition according to claim 1, wherein 5 parts by weight are added.
The recording medium according to any one of the preceding claims. In a preferred embodiment, the total thickness of the transparent resin substrate and the photocurable adhesive layer or the total thickness of the transparent resin substrate, the photocurable adhesive layer and the transparent resin sheet is 1 to 10,000 μm. The recording medium according to the above.

According to the present invention, the thickness of the recording protection layer can be easily and accurately formed because the film thickness accuracy can be precisely controlled and provided, and this can be seen in the case of an ultraviolet curable resin adhesive. Bonding is possible without any protrusion from the edge. The bonding with the transparent resin substrate is performed by a simple method such as a pressure roll or a simple press.
After temporary compression bonding at 100 ° C, it can be cured by light at room temperature for 1 to 10 seconds, and the laminated body is less likely to shift or peel due to the self-adhesive force peculiar to the present adhesive, so that it can be handled freely up to light curing. Has features.

Hereinafter, the present invention will be described in more detail.
As described above, the recording medium of the present invention is formed by joining a transparent resin substrate and a transparent resin substrate or a transparent resin sheet with a film-shaped photocurable adhesive containing (meth) acrylic resin as a main component. is there.

In this case, the recording medium of the present invention has a structure in which a transparent resin substrate and a transparent resin sheet are joined by the above-mentioned photocurable adhesive (see FIG. 1, FIG. 1 shows a transparent resin substrate 1 having a reflective layer 2). 2 shows a configuration in which a transparent resin film 3 is bonded by an adhesive layer 4), and a configuration using a transparent resin substrate 1 instead of the transparent resin film 3 (see FIG. 2).

Here, as the transparent resin substrate forming the recording medium, a transparent organic resin having a glass transition temperature of 50 ° C. or more is preferable. As such a transparent resin substrate, polyethylene terephthalate, polycyclohexylene terephthalate, polyethylene Polyester resin such as naphthalate, nylon 46, modified nylon 6T, nylon M
XD6, polyamide resins such as polyphthalamide, ketone resins such as polyphenylene sulfide and polythioether sulfone, sulfone resins such as polysulfone and polyether sulfone, as well as polyether nitrile, polyarylate, polyether imide, A transparent resin substrate mainly containing an organic resin such as polyamide imide, polycarbonate, polymethyl methacrylate, triacetyl cellulose, polystyrene, or polyvinyl chloride can be used. Particularly, among these, polycarbonate, polymethyl methacrylate, polyvinyl chloride, polystyrene, and polyethylene terephthalate are preferably used in terms of transferability and birefringence. If necessary, an opaque resin substrate or a metal substrate can be used instead of the transparent resin substrate.

On the other hand, also as the transparent resin sheet, a transparent organic resin having a glass transition temperature of 50 ° C. or more is preferable. As such a transparent resin sheet, the same organic resin as that exemplified for the transparent resin substrate is used. Can be Note that a recording layer can be provided on the transparent resin sheet.

The (meth) acrylic resin (acrylic resin, methacrylic resin) which is the main component of the adhesive layer used in the recording medium of the present invention is a homopolymer or copolymer of alkyl acrylate such as methyl acrylate or methyl acrylate, or alkyl methacrylate. And those obtained by copolymerizing these monomers and other acrylates and methacrylates capable of obtaining a transparent polymer copolymerizable therewith. In particular, polymethyl methacrylate is desirable from the viewpoint of reactivity during photocuring, durability after curing, and transparency.

The photosensitizer added for curing the adhesive used in the recording medium of the present invention may be prepared under the following conditions:
The selection is made in consideration of the film forming temperature, curing (bonding) conditions, storage stability of the adhesive, and the like, but a radical photopolymerization initiator is preferably used.

Among the radical photopolymerization initiators, hydrogen abstraction initiators include benzophenone, methyl orthobenzoylbenzoate, 4-benzoyl-4'-methyldiphenylsulfide, isopropylthioxanthone, diethylthioxanthone, and ethyl-4- (diethylamino).
-Benzoate and the like are used. Among radical photopolymerization initiators, examples of intramolecular cleavage initiators include benzoin ether and benzyldimethyl ketal, and α-hydroxyalkylphenones include 2-hydroxy-2-methyl-1-phenylpropan-1-one, -Hydroxycyclohexyl phenyl ketone, alkyl phenyl glyoxylate, diethoxy acetophenone and the like can be used. Furthermore, as an α-aminoalkylphenone type,
Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 and the like; Phosphine oxide or the like is used.

As the photosensitizer, one of these can be used alone, or two or more can be used as a mixture. The amount of the photosensitizer is 0.1 to 100 parts by weight of the (meth) acrylic resin. 10 to 10 parts by weight is sufficient.

Further, the adhesive of the present invention may be provided with tackiness,
A photopolymerizable oligomer can be blended for imparting curability. As such a photopolymerizable oligomer,
Epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, polyol polyacrylate, modified polyether acrylate, melamine acrylate, polybutadiene acrylate, and the like can be used. In particular, urethane acrylate is preferably used in terms of toughness. The amount is
10 to 30 with respect to 100 parts by weight of (meth) acrylic resin
0 parts by weight, especially 50 to 150 parts by weight.

Further, the present invention is intended to improve or control the physical properties (mechanical strength, optical properties, adhesiveness, heat resistance, heat and moisture resistance, weather resistance, crosslinking speed) of the photocurable adhesive of the present invention. In the above, an acryloxy group, methacryloxy group or allyl group-containing compound can be added.

As the compound used for this purpose, acrylic acid or methacrylic acid derivatives, for example, esters and amides thereof are most common. In this case, as an ester residue, in addition to an alkyl group such as methyl, ethyl, dodecyl, stearyl, lauryl, a cyclohexyl group, a tetrahydrofurfuryl group, an aminoethyl group,
-Hydroethyl group, 3-hydroxypropyl group, 3-chloro-2-hydroxypropyl group and the like. Esters of acrylic acid or methacrylic acid with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, and pentaerythritol are also used. A typical amide is acrylamide. Examples of the allyl group-containing compound include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, diallyl maleate, and the like. One or a mixture of two or more of these are (meth) 10 to 100 parts by weight of acrylic resin
It is used in an amount of 200 parts by weight, preferably 30 to 150 parts by weight. If the amount is less than 10 parts by weight, the effect of improving heat resistance and mechanical strength may be reduced, and 200 parts by weight may be reduced.
When the amount is more than the weight part, the workability and the film forming property at the time of preparing the adhesive may be reduced.

Further, a silane coupling agent can be added to the adhesive of the present invention as an adhesion promoter. Examples of the silane coupling agent include vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane,
γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl)
Ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more. The amount of the silane coupling agent to be added is usually 0.01 to 5 parts by weight based on 100 parts by weight of the (meth) acrylic resin.

Further, an epoxy group-containing compound can be similarly added to the adhesive of the present invention for the purpose of improving adhesiveness. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate; neopentyl glycol diglycidyl ether;
1,6-hexanediol diglycidyl ether; acrylic glycidyl ether; 2-ethylhexyl glycidyl ether; phenyl glycidyl ether; phenol glycidyl ether; pt-butylphenyl glycidyl ether; adipic acid diglycidyl ester; o-phthalic acid diglycidyl ester Glycidyl methacrylate; butyl glycidyl ether and the like. Also,
Similar effects can be obtained by adding an oligomer having an epoxy group and having a molecular weight of hundreds to thousands or a polymer having a weight average molecular weight of thousands to hundreds of thousands. The amount of these epoxy group-containing compounds added is (meth) acrylic resin 1
0.1 to 20 parts by weight relative to 00 parts by weight is sufficient, and at least one of the epoxy group-containing compounds can be added alone or in combination.

A hydrocarbon resin can be added to the adhesive of the present invention for the purpose of improving processability such as processability and lamination and reducing cure shrinkage. In this case, the hydrocarbon resin to be added may be either a natural resin or a synthetic resin. Rosin, rosin derivatives, and terpene resins are preferably used in the natural resin system. For rosin, gum-based resins, tall oil-based resins, and wood-based resins can be used. As the rosin derivative, rosin obtained by hydrogenation, heterogeneization, polymerization, esterification, and metal salification can be used. Α-pinene in terpene resins,
In addition to terpene resins such as β-pinene, terpene phenol resins can be used. Also, dammar, corval, and shellac may be used as other natural resins. On the other hand, in the case of synthetic resins, petroleum resins, phenol resins, and xylene resins are preferably used. As the petroleum resin, aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin, copolymer petroleum resin, hydrogenated petroleum resin, pure monomer petroleum resin, and cumarone indene resin can be used. As the phenolic resin, an alkylphenol resin and a modified phenol resin can be used. As the xylene-based resin, a xylene resin or a modified xylene resin can be used.

The amount of the hydrocarbon resin to be added is appropriately selected, but is preferably 1 to 100 parts by weight of the (meth) acrylic resin.
The amount is preferably 200 parts by weight, more preferably 1 to 150 parts by weight.

In addition to the above additives, the photocurable adhesive of the present invention may contain a small amount of an ultraviolet absorber, an antioxidant, a dye, a processing aid and the like. In some cases, additives such as silica gel, calcium carbonate, silicon copolymer fine particles and the like may be contained in a small amount.

The photocurable adhesive of the present invention is obtained by uniformly mixing (meth) acrylic resin and the above-mentioned additives, kneading them with an extruder, a roll, or the like, and then calendering, rolling, T-die extrusion, inflation, etc. The film can be formed into a predetermined shape by the film forming method described above. A more preferred method of forming a photocurable adhesive of the present invention is to uniformly mix and dissolve each component in a good solvent, and apply this solution to a separator precisely coated with silicone or a fluororesin by flow coating or roll coating. A gravure roll method, a Myrbar method, a lip die coating method, and the like, and a solvent is dried to form a film.

When forming a film, blocking is prevented.
Embossing may be performed to facilitate degassing during pressure bonding with the base material (transparent resin substrate). As a method of embossing, a known method can be adopted, and for example, there is embossing roll molding or the like. In the case of the solution coating method, the emboss can be transferred by applying the composition on an embossed film (paper) having a releasing property. The average roughness (Ra) of the emboss is 50 μm or less, more preferably 0.01 to 50 μm, and still more preferably 0.1 to 20 μm.
It is preferable to form irregularities, whereby air can easily escape from the bonding surface with the device, and complicated irregularities on the device surface can be filled. If it is smaller than 0.01 μm, poor degassing tends to occur, and if it is larger than 50 μm, irregularities may remain during temporary press bonding.

Here, the thickness of the transparent resin substrate and the transparent resin sheet is 1 to 10,000 μm, especially 100 to 5,000 μm.
Desirably, it is 0 μm. If the thickness is less than 1 μm, the support becomes weak. On the other hand, if the thickness is more than 10,000 μm, the thickness of the recording medium increases, which may cause problems in storage of the recording medium, assembly, and the like.

The thickness of the adhesive layer is 1 to 1,000 μm.
m, particularly preferably 5 to 500 μm. 1 μm
If the thickness is smaller, the sealing property is inferior, and there are cases where the irregularities of the transparent resin substrate cannot be completely filled. On the other hand, if the thickness is more than 1,000 μm, the thickness of the recording medium increases, which may cause problems in storage of the recording medium, assembly, and the like.

The total thickness of the transparent resin substrate, the transparent resin sheet and the adhesive layer is preferably 1 to 10,000 μm, particularly preferably 100 to 5,000 μm.

When the photocurable adhesive of the present invention is cured, many light sources that emit light in the ultraviolet to visible range can be used as the light source. For example, ultrahigh pressure, high pressure, low pressure mercury lamps, chemical lamps, xenon lamps, halogen lamps , A mercury halogen lamp, a carbon arc lamp, an incandescent lamp, a laser beam and the like. The irradiation time cannot be determined unconditionally depending on the type of lamp and the intensity of the light source, but is about several tens of seconds to several tens of minutes.

Further, in order to promote curing, the laminate was previously
It may be heated to 0 to 80 ° C. and irradiated with ultraviolet rays.

The method for producing a recording medium according to the present invention will be illustrated below, but is not necessarily limited to these methods, and any method may be used as long as the object of the present invention can be achieved. .

First, the transparent resin melt is poured into a metal plate (stamper) on which the signal surface has been transferred, and is solidified. A reflection layer made of a metal film is formed on the transparent resin substrate. In advance,
The photocurable adhesive film formed on the transparent resin sheet is transferred to the signal surface side of the transparent resin substrate. After that, they are collectively light-cured through a large or continuous light (UV) irradiation device. At this time, heat may be applied at 30 to 80 ° C. to accelerate the curing. After joining, the transparent resin sheet is punched out in the same shape as the recording layer. Thereafter, since the transparent resin sheet used for the recording medium of the present invention can accurately form the recording surface protective layer at a predetermined thickness, it is possible to provide a recording medium free from errors when reading recording signals.

[0033]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples and Comparative Examples The following components were uniformly mixed and dissolved in ethyl acetate to prepare an ethyl acetate solution having a solute concentration of 30%. This solution was applied on a polycarbonate sheet using a reverse roll coater to prepare a photocurable adhesive film having a dry thickness of 100 ± 1 μm. Methacrylic resin (polymethyl methacrylate) 100 parts by weight U-4HA [urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)] 100 parts by weight A-TMPT (trimethylolpropane triacrylate) 60 parts by weight Irgacure 819 [bis (2,4,6) -Trimethylbenzo 2 parts by weight yl) -phenylphosphine oxide (manufactured by Ciba)]

A signal surface was previously transferred to one surface of a polycarbonate transparent resin substrate, and a 1.1 mm thick transparent resin substrate provided with a dielectric material on the signal surface side was prepared. The photocurable adhesive film was transferred to the signal side of the transparent resin substrate. Next, after irradiating the laminate under a high-pressure mercury lamp of 3 kW for 1 minute, the curing of the photocurable adhesive film was completed, and the polycarbonate sheet protruding from the recording medium was punched out to remove the recording medium of the present invention. Obtained.

It was confirmed that the thickness deviation of the cured recording medium was extremely high, that is, ± 3.0 μm or less, that is, the thickness deviation was satisfactory for reproducing a recorded signal.

On the other hand, as a comparative example, a commercially available photocurable adhesive (trade name: Photobond: manufactured by Sunrise Sansei Co., Ltd.) was used to form a film having a target film thickness of 30 μm by spin coating. The thickness deviation after the irradiation with the high-pressure mercury lamp for 1 minute was ± 6.5 μm, which was inferior in thickness accuracy.

Further, a reliability test was performed on each of the recording media of the example and the comparative example. Table 1 shows the results. The evaluation items of the reliability test include heat resistance (85 ° C. × 1,000).
0 hours), wet heat durability (60 ° C., 90% RH × 1,000)
0 hours), endurance test (-30 ° C x 6 hours)
(50 cycles of 70 ° C. × 6 hours). As a criterion, after the test was completed, the presence or absence of adhesive peeling, warpage, deviation, and the like was visually observed.

[0039]

[Table 1]

In the recording medium of the example using the above-mentioned composition, no abnormality was observed in each of the above reliability tests, and it was confirmed that a recording medium having excellent reliability was obtained.

[0041]

The recording medium of the present invention has excellent plate thickness accuracy,
It has a high signal reproduction accuracy, is excellent in various durability, has high reliability, and can be easily manufactured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment (single-sided reading type digital video disk) of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent resin substrate 2 Reflective layer 3 Transparent resin film 4 Adhesive layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuhiro Morimura 3-1-1, Ogawa-Higashi-cho, Kodaira-shi, Tokyo F-term in Bridgestone Corporation (reference) 5D029 LA04 LB01 LB13 LB17 LC21 MA43

Claims (6)

[Claims] 1. A recording medium comprising a transparent resin substrate and a transparent resin substrate or a transparent resin sheet joined by a film-shaped photocurable adhesive containing (meth) acrylic resin as a main component. 2. The recording medium according to claim 1, wherein the transparent resin substrate is a digital video disk substrate having a reflective layer. 3. A photocurable adhesive comprising 0.1 to 10 parts by weight of a photosensitizer and 10 to 300 parts by weight of a photopolymerizable oligomer based on 100 parts by weight of a (meth) acrylic resin. 3. The recording medium according to claim 1, wherein: 4. A photo-curable adhesive comprising 10 to 200 parts by weight of at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound with respect to 100 parts by weight of a (meth) acrylic resin. The recording medium according to claim 1, wherein the recording medium comprises: 5. A photo-curable adhesive containing 0.0 parts of a silane coupling agent per 100 parts by weight of a (meth) acrylic resin.
5. The recording medium according to claim 1, wherein the recording medium is added in an amount of 1 to 5 parts by weight. 6. The total thickness of the transparent resin substrate and the photocurable adhesive layer or the total thickness of the transparent resin substrate, the photocurable adhesive layer and the transparent resin sheet is 1 to 10,000 μm. 6. The recording medium according to 6.