JPH0410249A - Information recording carrier - Google Patents

Abstract

PURPOSE:To lower the water absorptivity of the substrate of the recording carrier and to prevent the oxidation and corrosion of a recording film by forming the substrate of a UV curing resin compsn. chiefly composed of a resin having a methacryloyl group at the terminal. CONSTITUTION:The substrate of the recording medium formed with a recording layer and a protective layer on the resin substrate is formed of the cured matter of the resin having the methacryloyl group at the terminal, for example, the UV curing resin compsn. contg. trimethyl propane trimethacrylate as the substantial material. The water absorptivity of the substrate is lowered by using the resin of the constitutional formula having the methacryloyl group at the terminal as the chief material in such a manner. The moisture in the substrate is lessened in this way and the oxidation and corrosion of the recording film are prevented. The process at the time of production is shortened and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a disc-shaped or card-shaped information recording carrier for recording or reproducing information signals.

(Prior Art) In recent years, information recording media have progressed to higher density and larger capacity. Optical disks and magneto-optical disks are typical media. A method for forming tracking grooves and address detection pits on these disks is a method of injection molding thermoplastic resin using a mold called a stamper with grooves and pits on the surface (injection method). Oh, it's transparent! Line curing resin (2
There is a method of curing P@fat) (2P method). Although the injection molding method is superior in terms of mass production of media, the 2P method is said to be superior in terms of faithfully transferring the shape of the grooves or pits of the stamper.

As an improved means of the 2P method, for example, JP-A-55-1
A method of manufacturing a transparent plate and a 2P layer integrally, as in Japanese Patent No. 60338, has also been proposed. That is, 2P resin is injected into a mold with a space equivalent to the size of the disk, and is cured by irradiating it with ultraviolet rays from at least one direction.
The method is to take it out. At this time, a stamper is provided on one side of the mold, and pits are formed on one side of the molded substrate. It is said that substrates made using this method exhibit superior properties in weather resistance tests compared to the conventional 2P method.

Discs produced by this method are disclosed in Japanese Patent Application Laid-Open No. 6226658.
No. 62-226101, JP-A-63
This method has also been proposed in Japanese Patent No.-23238. It is stated that these substrates are effective in increasing the number of erasable/recordable times, improving optical anisotropy, and improving durability under high temperature and high humidity conditions, compared to conventional substrates.

(Problems to be Solved by the Invention) The recording and reproducing characteristics of optical disks and magneto-optical disks are determined by the film quality of the recording layer. This recording layer is mainly formed on a substrate by a sputtering method, but it is well known that the film quality of the recording layer changes depending on the sputtering conditions even if the same sputtering target is used. For example, in the case of a magneto-optical disk, the Kerr rotation angle of a magneto-optical film serving as a recording layer changes depending on the state of gas released from the substrate in a sputtering chamber. This is because the rare earth elements contained in the magneto-optical film are subjected to I'8 by the gas emitted from the substrate, and if the substrate contains a lot of moisture, the amount of emitted debris increases and the magneto-optical properties tend to deteriorate. .

Furthermore, it is also known that pinholes occur during formation of a magneto-optical film if a large amount of gas is released. It is well known that even in the case of optical discs, moisture in the substrate poses a problem during the manufacturing process.

Attempts to reduce the amount of gas emitted from the substrate, that is, to remove moisture from the substrate, include evacuating the substrate for a long time before forming the recording layer, baking it below its melting point, etc., but it is not possible to use both methods in combination. It is common practice to degas efficiently by

However, such pretreatment is time consuming and is not a practical means in production.

Furthermore, if we consider the conditions in which the product is used by the user, depending on the environment in which it is used, moisture may be absorbed from the substrate side, accelerating oxidation and S corrosion of the recording layer, which may limit the lifespan of the disk. was.

For the above reasons, it has been desired to develop a resin substrate with low water absorption.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems. In an information recording carrier consisting of 28 layers whose optical or magnetic state changes depending on the temperature and a protective layer formed on the recording layer, the substrate is made of an ultraviolet curing resin containing as a main ingredient a resin having a methacryloyl group at the end. The present invention provides an information recording carrier characterized by being made of a cured composition.

(Example) Generally, information recording carriers such as optical disks and magneto-optical disks include a substrate made of resin, and are formed on this substrate, and the optical or magnetic state changes by applying laser light or a magnetic field. It is well known that the recording layer consists of a recording layer and a protective layer formed on the recording layer. Therefore, in this embodiment, only the improved portion of the substrate will be described.

Note that this substrate is prepared by mixing a main material (reactive diluent, sensitive unsaturated resin, etc.) and a photopolymerization initiator and curing the mixture.

[Example] A mold having a space of 130 m+ in diameter with a spacing of 1.2 mm was prepared. One side of the mold was coated with a nickel stamper, and the opposite side was coated with a silicone-based mold release agent, and a fired glass plate was provided. In this mold, 100 parts of THPTH^ (trimethylpropane trimethacrylate) as the main ingredient and Darocur 1173 (2-hydroxy-2-
A resin composition containing 0.3 parts by weight of methyl-1-phenylpropan-1-one (manufactured by Merck Japan Co., Ltd.) was injected, and ultraviolet rays were irradiated from the glass plate side using a 120 W/cm high-pressure mercury lamp. It was irradiated for 60 seconds. The substrate cured by this irradiation was taken out from the mold, and its water absorption rate was measured using a known method.

[Comparative example] The same mold as in the example was prepared, and 100 parts by weight of THPTA (trimethylpropane triacrylate) as the main ingredient,
A resin composition containing 0.3 parts by weight of Darocur 1173 as a photopolymerization initiator was injected, and 120t4/cm was added.
Ultraviolet rays are emitted from the glass plate side using a high-pressure mercury lamp.
I wanted to irradiate for 0 seconds, but the irradiation device was equipped with a neutral density filter). The substrate cured by this irradiation was taken out from the mold, and its water absorption rate was measured using a known method.

Table 1 shows the results of the water absorption rates of the substrates in the above Examples and Comparative Examples. In addition, THP used as the main agent
The structural formulas of THA and THPTA are shown in Table 2.

(Margin below) Table 1 As can be understood from Table 1, when comparing the Example and the Comparative Example, the substrate of the Example has a much lower water absorption rate than the substrate of the Comparative Example. When considering the reason for this together with the structural formula of the base material shown in Table 2, it is speculated that a factor significantly related to the water absorption rate of the substrate is the terminus of the base material's structural formula. can.

That is, in the examples, a resin (THPTHA) having a methacryloyl group (indicated by a dashed-dotted line) at the end was used as the main ingredient, while in the comparative example, a resin (THPTHA) having an acryloyl group (indicated by a two-dot chain line) at the end TMPTA
”) was used as the main ingredient.

Therefore, it can be easily understood that in order to reduce the water absorption rate of the substrate, a resin having a structural formula having a methacryloyl group at the end may be used as the main ingredient.

In this way, by using a substrate with a low water absorption rate, it is possible to reduce the amount of moisture in the substrate, thereby shortening the evacuation time of the recording film forming apparatus, and increasing the productivity of information recording carriers. improves.

Further, moisture absorption of the substrate after manufacturing is reduced, and even after the recording film is formed, oxidation and corrosion of the recording film that occurs from the substrate side can be minimized, and the life of the disk can be extended.

Furthermore, from the above results, the base material of the substrate in this example is not limited to THPTHA, but may also be other resins having methacryloyl groups as terminal groups, such as 16-hexanediol dimethacrylate and 1,10-decanediol dimethacrylate. Needless to say.

In addition, methacrylate 2P resin has a lower viscosity and less skin irritation than acrylate, so it has the advantage of superior workability.

In the above examples and comparative examples, 2-hydroxy-2-methyl-1=phenylpropan-1-one (Darocur 1173) was used as a photopolymerization initiator, but the invention is not limited to this, and benzyl, Benzoin, benzophenone, 4-methoxybenzophenone, benzyl dimethyl ketal, benzoin ethyl ether, benzoin isopropyl ether, myrrhaz ketone, anthraquinone, 2-methylanthraquinone, acetophenone,
αα dichloro-4-phenoxy-acetophenone, p
Similar results can be obtained with -tertbutyltrichloroacetophenone, methyloxobenzoylbenzoate, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and the like. Furthermore, an amine compound may be added to promote curing.

In addition, although the embodiments have been explained using disk-shaped information recording carriers such as optical disks and magneto-optical disks, it goes without saying that the same applies to card-shaped information recording carriers having the same structure. .

(Effects of the Invention) As described above, in the information recording medium of the present invention, the following effects can be obtained.

- Since a resin having a methacryloyl group at the end is used as the main ingredient in the substrate serving as a constituent part, the water absorption rate of the substrate can be reduced. This has the great effect of providing favorable conditions during the production of the information recording carrier, especially when forming the recording layer on the substrate.

Another advantage is that oxidation and g-erosion of the recording layer generated from the side of the substrate after the production of the information recording carrier can be minimized.

Patent applicant: Victor Japan Co., Ltd. Representative Kunio Kakiki

Claims (1)

[Scope of Claims] A substrate made of a cured ultraviolet curable resin, a recording layer formed on the substrate and whose optical or magnetic state changes upon application of laser light or a magnetic field, and a recording layer formed on the recording layer. An information recording carrier comprising a protective layer comprising a protective layer, wherein the substrate is made by curing an ultraviolet curable resin composition containing as a main ingredient a resin having a methacryloyl group at the end.