JPH04247336A - Optical disk - Google Patents

Abstract

PURPOSE:To lower the surface electric resistance of a coated film and to increase surface hardness by coating the photoirradiated surface of the optical disk with the coating film consisting of a specific curable resin compsn. CONSTITUTION:The coating film consisting of the curable compsn. which contains 3 to 40wt.% mono(meth)acrylate (A) of the (poly)ethylene oxide or (poly)propylene oxide expressed by formula I and an anionic surfactant (B) of 0.01 to 200wt.% of the component A and in which the total content of the components A, B is <=50wt.% of the entire part is formed on the flat surface of the polycarbonate disk. In the formula, R1, R2 denote H or methyl; (n) denotes 1 to 23. The pencil hardness of the coated film is preferably specified to and the surface resistance to <=10<14>OMEGA/sq. The compd. of formula II, etc., are usable for the component A and sodium dodecyl benzene sulfonate, etc., are usable for the component B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc on which information is recorded and reproduced using light such as a laser.

0002

2. Description of the Related Art Optical disks have attracted attention as high-density, large-capacity information recording media, and research and development are being carried out on various types of optical disks. Among these, erasable and rewritable magneto-optical disks have a wide range of applications and have high expectations for the future. For this reason, various materials and systems have been announced, and their practical application is expected.

[0003] These optical disks require antistatic treatment to prevent the adhesion of dust, etc., and usually an antistatic agent is applied to the surface of the substrate, or an antistatic agent is kneaded into the substrate. Methods such as inclusion are being used. However, the former treatment has problems with durability, and the latter has problems with moldability and light transmittance.

On the other hand, since polycarbonate resin or the like is generally used for the substrate of an optical disk, the surface hardness of the substrate is low. Therefore, to avoid surface damage, UV
It has been proposed to perform surface hardening treatment using a hardened resin or the like. However, with these UV-curable resin coatings, the resin is charged due to friction with the air while the disk is rotating, and the readout surface is often dirty due to dirt and dust, making the recording and readout signals unreliable. deteriorating sexuality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk having excellent durability and antistatic properties, and also having sufficient surface hardness. More specifically, the object is to provide an optical disk in which a coating film with low surface electrical resistance and high surface hardness is provided on a substrate.

[0006]

[Means for Solving the Problems] From the viewpoint of coating properties, the present inventors have developed a method using low-viscosity ultraviolet light (
Focused on UV) curable resin compositions. However, coating films formed by curing UV curable resin compositions generally have high surface electrical resistance and poor antistatic properties. As a result of intensive studies to solve this problem, the present inventors found that mono(meth)acrylate of oligoethylene oxide has an OH group and an alkylene oxide unit in the monomer, resulting in a cured coating film with low surface electrical resistance. We have already proposed this method (Japanese Patent Application No. 172655/1999). Since this mono(meth)acrylate of oligoethylene oxide is monofunctional, from the viewpoint of curability, it is desirable to obtain a cured coating film having a low surface resistance with as little amount as possible. The present inventors conducted extensive studies with the aim of obtaining a curable resin composition with low surface resistance and high hardness by reducing the amount of this mono(meth)acrylate as much as possible. As a result, by combining the mono(meth)acrylate of oligoethylene or propylene oxide with an anionic surfactant, the surface electrical resistance of the cured product can be significantly reduced while maintaining sufficient hardness. They discovered this and arrived at the present invention.

That is, the present invention provides that at least the light irradiation surface (reading surface) of an optical disc is formed by (A) general formula (I).

[0008]

[Formula 2] (wherein R1 and R2 are hydrogen atoms or methyl groups,
n represents an integer of 1 to 23. ) ethylene oxide or polyethylene oxide, or propylene oxide or polypropylene oxide mono(meth)acrylic acid ester is present in the curable resin composition in an amount of 3 to 40
% by weight, and (B) anionic surfactant relative to component (A).
01 to 200% by weight, and components (A) and (B)
An optical disk characterized in that it is coated with a coating film formed by curing a curable resin composition having a total amount of 50% by weight or less.

In the general formula (I), R1 and R2 represent a hydrogen atom or a methyl group, and n represents an integer of 1 to 23. n is preferably 2-20, particularly preferably 3-15. From the viewpoint of the interaction between the above-mentioned components (A) and (B), which will be described later, it is preferable that n is larger, but as n becomes larger, the compatibility decreases and the viscosity increases. applies. Examples of the mono(meth)acrylic acid ester of polyethylene oxide or polypropylene oxide represented by the general formula (I) include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate,
-Hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, diethylene glycol monomethacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, pentaethylene glycol monoacrylate, hexaethylene glycol monoacrylate, tetrapropylene glycol monomethacrylate, tetrapropylene glycol monoacrylate ,

0010

Examples include, but are not limited to, (MA-150, manufactured by Nippon Nyukazai Co., Ltd.).

The mono(meth)acrylic acid ester of polyethylene oxide or polypropylene oxide represented by the general formula (I) as component (A) of the present invention contains 3 in the composition.
-40% by weight, preferably 5-35% by weight. In addition, the anionic surfactant is 0.0% relative to component (A).
The content is preferably 0.1 to 200% by weight, and more preferably 0.1 to 100% by weight. The amounts of both are appropriately selected within this range depending on the compound used. Component (A) and component (B
) work together to impart excellent antistatic properties to the cured product. Although the reason is not clear, it is presumed that component (A) plays the role of a solid electrolyte and has a special interaction with component (B).

When the component (A) is less than 3% by weight, the component (B) is less than 3% by weight.
) is insufficient and the antistatic effect is insufficient. On the other hand, if it exceeds 40% by weight, the surface coating hardness of the optical disc coated and cured with the composition is undesirable. If the total amount of components (A) and (B) exceeds 50% by weight, curing properties will be insufficient and a coating film with sufficient hardness will not be obtained.

As the anionic surfactant of component (B), saturated or unsaturated fatty acid alkali metal salts, saturated or unsaturated aliphatic sulfonates, aromatic sulfonates which may contain substituents are used. , sulfonate salts containing ethylene oxide units, and sodium salts of sulfates containing various substituents. Specifically, sodium todecylbenzene sulfonate, sodium acyl (beef tallow) methyl taurate, sodium lauroyl methyl taurate, sodium cocoyl isetinate, α-sulfo fatty acid ester sodium salt, acid ether sodium sulfate, alkyl ether sulfonic acid. Examples include fatty acid soaps such as sodium, alkyl sulfate sodium salts, alkyl ether sulfate sodium salts, potassium oleate, and potassium coconut fatty acids. Among these, sulfonic acid salt compounds and sulfuric acid ester salt compounds are preferred from the viewpoint of the interaction.

In the present invention, generally known polymerizable monomers, polymerizable oligomers, and polymerizable prepolymers are used as the curable resin composition other than the compound of component (A). For example, bisphenol A epoxy acrylate,
Fatty acid modified epoxy acrylate, novolac epoxy acrylate, phenol novolac epoxy acrylate, polyester oligourethane acrylate, polyfunctional hydroxy compound urethane acrylate, polybutadiene acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane Tri(meth)acrylate, di(poly)alkylene glycol
aliphatic polyfunctional acrylates such as meth)acrylates,
Polyfunctional oligoester acrylates, polyfunctional polyester acrylates, acrylate modified products of phosphazene compounds, polyfunctional acrylates of isocyanuric acid, other vinyl polymerizable compounds, acrylic polymerizable compounds, etc. can be used. These polymerizable compounds may be used alone or in combination.

The curable resin composition of the present invention may be used with the addition of a radical polymerization initiator such as a photopolymerization initiator or a thermal polymerization initiator, if necessary. Examples of photopolymerization initiators include benzophenone initiators such as benzophenone and Michler's ketone, diketone initiators such as benzyl and phenylmethoxydiketone, acetophenone initiators such as acetophenone, and benzoin initiators such as benzoin ethyl ether and benzyl dimethyl ketal. , thioxanthone-based initiators such as 2,4-diethylthioxanthone, 2
- Quinone-based initiators such as methylanthraquinone and camphorquinone are preferably used. If necessary, it is also possible to use a promoter such as an amine promoter. In the case of heat curing, azobiswiss butyronitrile (AIBN), benzoyl peroxide (BPO), cumene hydroperoxide, dicumyl peroxide, ditertiary butyl peroxide, lauroyl peroxide and the like can be used. The upper limit of the amount of initiator used is limited from practical aspects such as cost, and is 1 to 10 parts by weight per 100 parts by weight of the composition.
Parts by weight are used, preferably 2 to 5 parts by weight.

The curable resin composition of the present invention may be diluted with a solvent, if necessary, in order to improve coating properties and workability. Note that when polycarbonate resin is used as a substrate, alcoholic solvents such as methanol, ethanol, and isopropanol are preferably used.

The curable resin composition of the present invention can be coated on the surface of an optical disk by a known method such as spin coating, dip coating, coating with a doctor knife, or coating with a bar coater. When coating an optical disk, the antistatic effect can be improved by also coating the side surfaces of the optical disk.

[0018] The thickness of the coating film after curing of the present invention is 1 to 30μ.
m, preferably 5 to 25 μm. 1μm
If the hardness is less than 30μ, sufficient performance will not be exhibited in terms of hardness.
If the thickness exceeds m, it is not only difficult to control the film thickness, but also the internal hardening properties are lowered, which is not preferable.

The optical disc coated with the polymerizable monomer composition is prepared using known methods and conditions using ultraviolet lamps such as low-pressure mercury lamps, medium-pressure mercury lamps, and high-pressure mercury lamps, halogen lamps, actinic light such as electron beams, or heat treatment. hardened by Among these, it is preferable to use actinic light such as an ultraviolet lamp, a halogen lamp, or an electron beam from the viewpoint of operability and productivity.

The surface resistance of the optical disc obtained by the present invention is preferably less than 1015 Ω/□, more preferably 1014 Ω/□ or less. Those having a resistance higher than this are ineffective from the viewpoint of antistatic properties. In addition, from the viewpoint of handling, the surface hardness is preferably a pencil hardness of HB or higher, and more preferably a pencil hardness of F or higher.

[0021]

Industrial Applicability According to the present invention, it is possible to provide an optical disk having highly durable antistatic properties and sufficient surface hardness.

[0022]

EXAMPLES The present invention will be explained in more detail with reference to Examples below. The invention is not limited to such embodiments.

In the example, the surface resistance (Ω/□) is J
According to IS K6911. Moreover, the pencil hardness was measured using Uni manufactured by Mitsubishi Pencil.

[0024]

[Example 1] 96% by weight of NSC-7106 from Nippon Fine Chemical Co., Ltd., an acrylic photocurable resin composition, was applied to the flat surface of a polycarbonate disk with a thickness of 1.2 mm, and Nippon Emulsifier represented by the following formula was applied. A curable composition containing 0.1 part by weight of sodium dodecylbenzenesulfonate is applied to 100 parts by weight of a composition containing 4% by weight of MA150 manufactured by Co., Ltd. to a thickness of 5 to 10 μm by spin coating. did. Subsequently, the coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a 2 Kw high-pressure mercury lamp with a length of about 27 cm.

[0025]

[Chemical 4] Regarding the hardened surface of the polycarbonate disk after curing,
Surface resistance and pencil hardness were measured. The pencil hardness was H, and the surface resistance was 9.8×10 13 Ω/□.

[0026]

[Comparative Example 1] The above-mentioned NSC-71 from Nippon Fine Chemical Co., Ltd. was applied to the flat surface of a 1.2 mm thick polycarbonate disk.
96% by weight of 06 and 4% of MA150 from Nippon Nyukazai Co., Ltd.
% by weight of the curable composition was applied by spin coating to a thickness of 5 to 10 μm. Subsequently, the coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a 2 Kw high-pressure mercury lamp with a length of about 27 cm. The surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured. The pencil hardness was H, and the surface resistance was 1.2×10 15 Ω/□.

[0027]

[Example 2] Hexafunctional urethane acrylate oligomer (
50% by weight of U1226A (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)
, 40% by weight of trimethylolpropane triacrylate, and 10% by weight of tetraethylene glycol monomethacrylate, 1 part by weight of sodium todecylbenzenesulfonate and 3 parts by weight of the photoinitiator Darocur 1173. The curable resin composition containing 50% of the curable resin composition was applied onto a 1.2 mm thick polycarbonate disk, and photocured in the same manner as described above. The surface hardness of the obtained disk was F, and the surface resistance was 3.6×1013Ω/□
Met.

[0028]

[Comparative Example 2] Hexafunctional urethane acrylate oligomer (
50% by weight of U1226A (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)
A curable resin composition containing 3 parts by weight of the photoinitiator Darocur 1173 was added to 100 parts by weight of a composition consisting of 40% by weight of trimethylolpropane triacrylate and 10% by weight of tetraethylene glycol monomethacrylate to a thickness of 1.2 mm. It was applied onto a polycarbonate disk and photocured in the same manner as above. The surface hardness of the obtained disk is F, and the surface resistance is 1.05×1015Ω/□
Met.

[0029]

[Example 3] Phosphazene hexaacrylate (U-
1000, manufactured by Idemitsu Petrochemical Co., Ltd.) and 30% by weight of tetrapropylene glycol monomethacrylate, was added sodium alkyl ether sulfonate (Avanel S74; manufactured by NOF Corporation).
A curable resin composition consisting of 0.1 parts by weight of the photoinitiator Irgacure 907 (manufactured by Ciba Geigy) and 3 parts by weight of the photoinitiator Irgacure 907 (manufactured by Ciba Geigy) was applied to the flat surface of a 1.2 mm thick polycarbonate disk in the same manner as in Example 1. Light-cured. The surface hardness of the cured coating film was H and the surface resistance was 3.5×10 12 Ω/□.

[0030]

[Example 4] Caprolactone-modified dipentaerythritol hexaacrylate (DPCA60; Nippon Kayaku Co., Ltd.)
To 100 parts by weight of a composition consisting of 60% by weight of trimethylolpropane triacrylate, 20% by weight of tetraethylene glycol monoacrylate, was added sodium lauroylmethyltaurate (Diapon L; manufactured by NOF Corporation). ) and 3 parts by weight of the photoinitiator Irgacure 907 (manufactured by Ciba Geigy) was applied onto the flat surface of a 1.2 mm thick polycarbonate disk in the same manner as in Example 1, and photocured. I let it happen. The surface hardness of the cured coating is F, and the surface resistance is 6.2×1.
It was 013Ω/□.

Claims (3)

[Claims] Claim 1: At least the light irradiation surface (reading surface) of an optical disc is formed by (A) the general formula (I) [Formula 1] (wherein R1 and R2 are hydrogen atoms or methyl groups,
n represents an integer of 1 to 23. ) ethylene oxide or polyethylene oxide, or propylene oxide or polypropylene oxide mono(meth)acrylic acid ester is present in the curable resin composition in an amount of 3 to 40
% by weight, and (B) anionic surfactant relative to component (A).
01 to 200% by weight, and components (A) and (B)
1. An optical disc characterized in that it is coated with a coating film formed by curing a curable resin composition having a total amount of not more than 50% by weight. 2. A paint film obtained by curing the curable resin composition has a pencil hardness of F or more and a surface resistance of 1014.
2. The optical disc according to claim 1, wherein the optical disc has a resistance of Ω/□ or less. 3. The optical disc according to claim 1, wherein the anionic surfactant contains a sulfonate and/or a sulfate ester salt.