JPH01199339A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent generation of flaws and contamination from the outside and to prevent generation of pitting in a recording layer at and under a high temp. and high humidity or under the conditions equiv. thereto by using a protective layer consisting of a specific UV curing type compd. CONSTITUTION:This recording medium has the protective layer 5 consisting of the UV curing type compd. having <=0.1 (KOHmg/g) acid value. The protective layer consisting of the UV curing type compd. such as acrylic acid or acrylates having <=0.1 (KOHmg/g) acid value and contg. free acid components at the lower ratio is used as the protective layer 5 in such a manner and, therefore, the pitting of the recording layer by the deterioration in which the transition metal of the rare earth-transition metal in the recording layer 3 is ionized and dissolved by the acrylic acid and acrylates remaining in the UV curing type compd. is suppressed in the cased of using an amorphous magnetic recording layer as the recording layer 3 in particular. The increase in the bit error rate (BER) after the environmental durability test of the optical recording medium is thus prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical recording medium that can be read only or recorded, read, and erased using a light beam, and in particular has UV curing on both or one side of the medium. The present invention relates to an optical recording medium having a protective layer made of a type compound.

[Prior Art] Conventionally, in an optical recording medium, a recording layer is provided on a substrate having a preformat pattern on one surface, and a protective layer is provided to protect the recording layer. As such, plastic members are often used because they can withstand scratches and dirt attached to the surface of the optical recording medium during handling.

Ultraviolet curable compounds are used in plastic members forming such protective layers, and examples of such ultraviolet curable compounds include those disclosed in JP-A-61-123593 and JP-A-61-133067. , JP-A-61-13
As shown in JP-A No. 9961, JP-A-61-153844, etc., acrylate resin compositions are used in both cases.

[Problems to be Solved by the Invention] In the above conventional example, an a-free dielectric material layer is formed on the recording layer of an optical recording medium or on the recording layer, and a protective layer made of an ultraviolet curable compound is provided thereon. ing. That is, the recording layer may be made of a Te-based compound, a methine-based organic compound, or a Tb-based compound that records/reproduces information depending on the reflectance or polarization angle of light.
Examples include magneto-optical recording layers such as Fe and TbFeCo.

However, in such a configuration, the protective layer can achieve the purpose of protecting against scratches and dirt from the outside, but when handling optical recording media under high temperature, high humidity, or similar conditions, for example, environmental When a durability test (70° C., 90% RH, left for 2000 hours) was carried out, there was a problem in that the recording characteristics deteriorated. In particular, when a magneto-optical recording layer is used as the recording layer, there is a problem in that the pit error rate (BER) increases compared to the initial value, that is, the pitting corrosion deterioration of the recording layer increases.

The present invention was made to solve the problems of the prior art, and by using a protective layer made of a specific ultraviolet curable compound, it prevents scratches and stains from the outside, and can withstand high temperatures and high humidity. Another object of the present invention is to provide an optical recording medium in which pitting corrosion is prevented from occurring in the recording layer under similar conditions.

[Means for Solving the Problems] That is, the present invention has an acid value of 0.1 (KOHlgag)
Having a protective layer made of the following ultraviolet curable compound:
The present invention relates to an optical recording medium characterized by:

Two aspects of the present invention will be described in detail below.

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention. In FIG. 1, the optical recording medium of the present invention is as follows:
Polycarbonate resin, acrylic resin with guide grooves and preformat signals.

A dielectric layer 2 made of one or more dielectrics such as Sin, 510m, ZnS, SiC, etc. is laminated on a substrate l made of polystyrene resin, polyolefin resin, etc. by a method such as vacuum evaporation or sputtering, On top of that, as a recording layer 3, Gd-FeCo, Gd-
Tb, GdTbFe, TbFeCo, GdTbF
An amorphous magnetic recording layer such as eCo is formed, and a dielectric layer 4 similar to the dielectric layer 2 is formed on the recording layer 3,
Next, a protective layer 5 using an ultraviolet curable compound is formed.

In the present invention, the ultraviolet curable compound forming the protective layer consists of a prepolymer component (A), a monomer component (B) as a reactive diluent, and a photopolymerization initiator component (C); The usage ratio of A), (B), and (C) is (A) component: (B) component = 5-95:95-5 (
(weight ratio), a composition is used in which (C) 4 minutes is incorporated at a concentration of 0.1-10% by weight of the total amount.

(A) t, min is polyol polyacrylate (polyhydric alcohol or polyether polyacrylate), especially trifunctional or higher functional polyol polyacrylate (
pentaerythritol triacrylate, dipentaerythritol hexaacrylate, etc.), or modified polyol polyacrylate (modified polyol polyacrylate modified with polyol epoxide or lactone, or polyhydric phenol bisphenol A or bisphenol S with epoxide added. modified diol diacrylate) or polyester acrylate (
Condensation and telomerization of polyhydric alcohols, polybasic acids or their anhydrides, and acrylic acid [c
ondensation telomerization
), or urethane acrylate (manufactured by reacting a polyol such as a polyether polyol or polyester polyol with a polyisocyanate and an acrylate having a hydroxyl group), or epoxy acrylate (manufactured by reacting an epoxy compound with acrylic acid or a terminal carboxyl group). Examples include oligomers obtained by adding an acrylate having Particularly preferred is trifunctional or higher functional polyol polyacrylate which has excellent curability and high surface hardness.

For (B), acrylic acid esters of polyhydric alcohols are used, and in particular, as polyfunctional acrylic yarn weight additives, ethylene glycol diacrylate and diethylene glycol diacrylate are used.

Triethylene glycol diacrylate, polyethylene glycol diacrylate, butylene gelicol diacrylate, neopentyl glycol diacrylate, l
, 4-butanediol diacrylate, l,4-hexanediol diacrylate.

Examples include diacrylates such as pentaerythritol diacrylate, triacrylates such as pentaerythritol triacrylate, and trimethylolpropane triacrylate.

Component CB) may be one or a mixture of two or more of these.

As component (C), any known photopolymerization initiator can be used, but those with good storage stability after blending are preferred.For example, benzoin alkyl ethers such as benzoin ethyl ether and benzoin butyl ether;2. Acetophenones such as 2'-jetoxyacetophenone, 4'-phenoxy-2,2-dichloroacetophenone, 2-hydroxy-2-methylpropiophenone, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, etc. Examples include propiophenone series, benzyl methyl ketal, l-hydroxycyclohexylphenyl ketone, anthraquinone series such as 2-ethylanthraquinone and 2-chloroanthraquinone, and thioxanthone series such as 2,4-dimethylthioxanthone and Michler's ketone. One or more of these can be used as a mixture in any proportion.

An index of the content of free acid components such as acrylic acid and acrylic esters in the ultraviolet curable compound is expressed as an acid value (KOIImg/g). This was prepared by dissolving 0.6g of an ultraviolet curable compound sample and 0.3g of triethylenediamine (acid dissociation catalyst) in 40@P DMF, and
After addition of IR, 0.0% was determined by potentiometric titration. IN KOII
It was determined by titration with an isopropyl alcohol solution and using the formula below.

A: Titration amount of sample (■f) B Titration amount of blank (mj)) f: 0. Factor W of IN 011 isopropanol solution: Amount of sample collected (g) The UV-curable compound used as the protective layer of the optical recording medium of the present invention has an acid value of 0.1 (KOJI g/g).
) or less, preferably 0. O1~0.05 (KOII set
/g) is preferable. This acid value is 0.1
(011 mg/g) or less is desirable because of the acid value and the environmental durability test of optical recording media (70°C, 90% old 1.2
This was discovered in an experiment regarding the relationship between the increase in pitting corrosion of the recording layer after being left for 0.000 hours, and that if the acid value exceeds 0.1 (KO 11 mg/g), it will cause the increase in pitting corrosion of the recording layer after the environmental durability test of the medium. The occurrence of pitting corrosion deterioration of the recording layer increases, and the performance of the optical recording medium deteriorates.

The thickness of the protective layer is not particularly limited, but is usually 10 pm or less, and preferably 2IL- to 8IL-.

Further, the protective layer can be provided on either one side or both sides depending on the type of optical recording medium.

The protective layer is formed by applying an ultraviolet curable compound to a predetermined thickness by spin cord coating, spray coating, bar coater coating, dipping coating, etc., and then exposing it to light (
This can be done by curing by irradiation (mainly ultraviolet rays).

[Function] The optical recording medium related to unreleased 1J1 contains acrylic acid with an acid value of 0.1 (0.11 mg/g) or less as a protective layer,
Since a protective layer made of an ultraviolet curable compound with a low content of free 1III acid components such as cyclylic acid esters is used, especially when an amorphous magnetic recording layer is used as the recording layer, The remaining acrylic acid and acrylic esters ionize and dissolve the transition metal of the rare earth-transition metal alloy in the Q layer, which is a deterioration phenomenon that suppresses pitting corrosion of the recording layer, which improves the performance of optical recording media. Pit error rate (IIER) after environmental durability test
This seems to be able to prevent an increase in

[Examples] Hereinafter, the present invention will be further explained in JL format by showing examples.

Embodiment 1 FIG. 2 is a sectional view showing a method for producing an optical recording medium according to a first embodiment of the present invention. On a polycarbonate substrate 1 having guide grooves S and/or preformat signals, a dielectric layer 2 consisting of a SiN layer with a thickness of 800 layers is formed by a sputtering method, and then an amorphous Gd layer with a layer thickness of 400 layers is formed.
- FeCo + amorphous Tb-FeCo with a layer thickness of 400 layers, a magnetic recording layer 3a is provided, and a layer thickness of 1 layer is further provided on top of the magnetic recording layer 3a.
A dielectric layer 4 consisting of a SiN layer of 1,000 nm was deposited.

Next, as an ultraviolet curable resin, 5D-17-2A (trade name manufactured by Nippon Ink Chemical ■, acid value 0.1 (KOI1
mg/g)) on the dielectric layer 4 made of the SiN layer (rotation speed: 4000 r, p, m, , 7 seconds) to form a resin layer with a layer thickness of 5 to 1, then a UV lamp 6
(23 on the irradiated surface: JeW/cm", wavelength 365 nm
) was irradiated for 30 seconds to cure the resin layer, and an optical recording medium using this as the protective layer 5 was prepared.

Example 2 Ultraviolet curing resin 5PC-110-2 (
Product name Nippon Kayaku ■, acid value O, OS (KOH-g/
g) An optical recording medium was actually produced in the same manner as in Flow Side 1 except that )) was used.

Comparative Example 1 Ultraviolet curable resin 5D-17 (trade name manufactured by Nippon Ink Chemical Co., Ltd., acid value 0.5 (KOJI pus g/g) as a protective layer
)) An optical recording medium was prepared in the same manner as in Example 1 except that the following was used.

Comparative Example 2 Ultraviolet curing resin Aronix UV-37 as protective layer
00 (product name Nitoa Gosei Kagaku ■, acid value 0.3 (ni 01)
An optical recording medium was prepared in the same manner as in Example 1 except that 1 mg/g) ) was used.

Table 1 shows the results of the occurrence of pitting corrosion in the recording layer of the optical recording media prepared in Example 1.2 and Comparative Example 1.2 before and after the environmental durability test (70°C, 90% R11). .

Table 1 Results of occurrence of pitting corrosion before and after environmental durability test (70°C, 990% Old 1) (Note) None: No more than 5 occurrences of pitting corrosion on the entire surface under a 200x optical microscope. show.

Ant: 50 or more occurrences of pitting corrosion of l-terminus or higher are observed under an optical microscope x200.

As is clear from the results in Table 1, if an optical recording medium is prepared using an ultraviolet curable compound that satisfies the conditions of the present invention as a protective layer, the occurrence of pitting corrosion in the recording layer after the environmental durability test can be prevented. can do.

[Effects of the Invention] As described above, if an ultraviolet curable compound that satisfies the conditions of the present invention is used as a protective layer, an optical recording medium that is resistant to external scratches and stains and maintains long-term reliability can be obtained. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the optical recording medium of the present invention, and FIG. 2 is an explanatory view showing a method for producing the optical recording medium of Example 1.

Claims (1)

[Claims] An optical recording medium characterized by having a protective layer made of an ultraviolet curable compound having an acid value of 0.1 (KOHmg/g) or less.