JPH02177138A - Optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording member capable of recording and reproducing information at high speed and high density by irradiation with laser light.

More specifically, the present invention relates to an optical recording member having a close bonding+i structure that has excellent corrosion resistance and is capable of preventing various types of thermal damage to the recording layer and inorganic protective layer caused by laser beam irradiation. It is something.

BACKGROUND OF THE INVENTION In recent years, optical disks have attracted attention as a central recording medium in the advanced information society 6-1, and are the subject of active research. There are three types of optical discs: a read-only type that can only read information, a write-once type that can record and reproduce information, and a replaceable type that can record, erase, and reproduce information. Therefore, recordable optical discs are usually constructed by bonding two identical single discs with their recording order facing each other 41.

There are two types of structures that have this kind of structure, such as those with a close bonded structure in which the entire surface is bonded at 1°, and those with a j-air bonded isostatic structure in which a substrate is glued between two single disks. Among these, the air-and-switch structure has a large number of parts and a complex structure, so it is disadvantageous compared to the adhesive bonding structure in terms of "-1" and mass production. On the other hand, those with close bonding structure have fewer parts, simple structure, and 11
) Moreover, since the recording layer and inorganic protective layer do not come into direct contact with air, it is not only advantageous in terms of cost and mass production, but also has the advantage that there is no risk of corrosion of the recording layer or inorganic protective layer. There is.

Hot melt adhesives, hot melt adhesives,
Ultraviolet curing resins, thermosetting resins, adhesive sheets, etc. are used. The properties required for the adhesive layer between these two disk veneers include (1) having sufficient adhesive strength for practical use, (2) not corroding the recording layer or inorganic protective layer, and (3) Do not deteriorate the recording characteristics (
4) Excellent mass productivity.

When two disk veneers are bonded together using a hot melt adhesive or adhesive sheet, since the entire surface is bonded, the bonding strength is sufficient for practical use, mass production is good, and there is no fear of corrosion. However, in this case, the adhesive itself is flexible and insufficient in strength to prevent deformation of the recording layer and inorganic protective layer due to laser beam heating. In rewritable optical discs,
Repeated recording and erasing causes problems such as an increase in noise and a decrease in signal-to-noise ratio (C/N ratio).

In addition, when using an ultraviolet curable resin, although there is no problem with the above-mentioned required characteristics (3) and (4), since the adhesive is sandwiched between the recording layer and the inorganic protective layer on the upper and lower sides,
Ultraviolet rays are blocked, and adhesives can only be bonded to the inner and outer peripheries of the disc, making it impossible to obtain sufficient adhesive strength. Furthermore, even if an adhesive is applied to the recording layer or inorganic protective layer, it cannot be cured. Therefore, problems arise such as being unable to prevent the recording layer and the inorganic protective layer from being deformed by heat.

Furthermore, in the method of bonding two disk veneers using thermosetting resin, the above-mentioned required characteristics (1), (
Although there are no problems with 2) and (3), they generally have a long curing time and are poor in mass productivity.

Problems to be Solved by the Invention The present invention overcomes the shortcomings of the conventional optical recording member with a close-bonding structure, has excellent corrosion resistance, and has a structure in which the recording layer and inorganic protective layer can be easily irradiated with laser light. The purpose of this invention is to provide an optical recording member having a closely bonded structure that can prevent various thermal damages caused to the optical recording member.

Means for Solving the Problems The present inventors have conducted intensive research to develop an optical recording member having a closely bonded structure having the above-mentioned preferable properties. Two disk veneers on which an inorganic protective layer and an organic protective layer are laminated are pasted together with the respective substrates facing each other via a bonding layer such as a double-sided adhesive sheet or hot melt adhesive. As a result, the inventors discovered that the object could be achieved, and based on this knowledge, they completed the present invention.

That is, the present invention provides an optical recording member capable of recording and reproducing information by irradiation with laser light, which comprises laminating an inorganic protective layer and an organic protective layer in that order on at least one side of a recording layer provided on a substrate. The present invention provides an optical recording member in which two units having such a structure are placed facing each other with the substrate facing outside and are integrated via a bonding layer.

The present invention will be explained in detail below.

The optical recording member of the present invention has two units of optical recording media,
It has a structure in which recording layers are faced and integrated,
In this unit, an inorganic protective layer is provided above and/or below a recording layer provided on a substrate, and an organic protective layer is further provided thereon.

The material of the substrate used in the unit may be selected from among those conventionally used as substrates for optical disks, such as resins such as polyethylene, polypropylene, polystyrene, polycarbonate, and polymethyl methacrylate, and glass. Among these, preferred are polycarbonate, polymethyl methacrylate, and glass, which have excellent optical properties, strong mechanical strength, and excellent dimensional stability.

In this unit, the recording layer provided on the substrate may be of a phase change type (write-once type, rewritable type), magneto-optical type (rewritable type), or dye-based type, but in particular A rewritable type that requires durability against repeated recording and erasing is preferred. As the phase change recording layer, for example, TeOx, Ta-Ge%5
n-Te-GeSBi-Te-Ge, 5b-Te-
Examples of the magneto-optical recording layer include Tb-Co1Tb-Fe-Co5Gd-Tb-Co,
Examples include those made of Nd-Dy-Tb-Fe-Co.

There is no particular restriction on the inorganic protective layer provided on at least one side of the recording layer, for example, Sin, Al2t.
Oxides such as Oi, GeO, pbo, Tie, etc., Zn
Any material can be selected and used from sulfides such as S1PbS and nitrides such as 5ilN and AffN.

In this unit, the organic protective layer provided as the uppermost layer is made of UV-curable materials such as phenol, modified phenol, epoxy, amino, polyester, acrylic, silicone, urethane, polyamide, and polyimide. Examples include mold resin and thermosetting resin. Alternatively, a two-liquid mixed epoxy resin may be used. The thickness of the organic protective layer made of these resins is preferably 5 μm or more in order to prevent deformation of the recording layer and the inorganic protective layer due to heat.

Among these resins, ultraviolet curable resins are particularly suitable in terms of mass productivity.

As a method for forming this organic protective layer on the recording layer or inorganic protective layer, for example, when an ultraviolet curable resin is used as the organic protective layer, the ultraviolet curable resin is applied by a spin cord method or the like. Thereafter, a method is used in which the resin is irradiated with ultraviolet rays of sufficient intensity to harden the resin using an ultraviolet irradiation device for a period of time until the resin reaches the required hardness. When using a thermosetting resin, it may be applied in a similar manner and then left at a temperature sufficient for curing for a period of time until the resin reaches the required hardness.

In the present invention, the unit 2 obtained in this way
The organic protective layers face each other and are integrated via a bonding layer such that the substrate is on the outside.
Hot melt adhesives and double-sided adhesive sheets are used from the viewpoint of adhesive strength and mass production.

Examples of the hot melt adhesive include ethylene-vinyl acetate copolymer (EVA), polyolefin, synthetic rubber, polyester, and polyamide. Polyolefin resins based on polyethylene and polypropylene, which have excellent low corrosion resistance, heat resistance, and thermal stability, as well as polystyrene-polybutylene block copolymers and hydrogenated polystyrene-polybutylene block copolymers. Synthetic rubber resins made into polymers are suitable.

On the other hand, the adhesive for the adhesive sheet includes, for example, rubber-based, acrylic-based, silicone-based, etc., and the sheet material includes, for example, polyester-based, polyimide-based,
Examples include polyurethane-based, polyethylene-based, polyolefin-based resin sheets, and metal sheets such as aluminum foil.

In the present invention, when an adhesive sheet is used as a bonding layer when bonding two units together, it is preferable to bond them together in a vacuum chamber. This is to prevent air bubbles from being mixed in between the adhesive sheet and the surface on which the film is formed on the optical disk substrate. Further, when using a hot melt adhesive as the bonding layer, it is preferable to apply the hot melt adhesive to the organic protective layers of two units by a roll coating method and then bond them together.

Effects of the Invention The optical recording member of the present invention has a structure in which two units are closely bonded together, and can suppress deformation of the recording layer and inorganic protective layer due to laser beam heating during recording and erasing, and is corrosion resistant. In the case of a rewritable type, an increase in noise due to repeated recording and erasing can be prevented.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Example 1 In order to confirm the effect of the present invention on an erasable optical disk using phase transformation, an optical disk was manufactured by a sputtering method.

Grooves (depth 700 mm, width 0,
Thickness 1.21 with 65μ score, pitch 1.6μm),
After forming a ZnS film to a thickness of 1000 mm by RF sputtering on a polycarbonate substrate with a diameter of 130 mm,
5b-Te-Ge ternary alloy film was deposited by DC sputtering method.
Four disks were manufactured in which a ZnS film was formed to a thickness of 2000 mm using a rough RF sputtering method.

Two of these sheets were bonded together using a hot melt adhesive with the ZnS surfaces of the uppermost layer facing each other. Comparative example 1
This is shown in Figure 4. FIG. 4 is a schematic cross-sectional view of the optical disc obtained in this way, showing two single optical discs in which an inorganic protective layer 2, a recording layer 11, and an inorganic protective layer 2' are sequentially provided on a substrate 3. A structure bonded together via an adhesive 5 is shown.

For the remaining two disks, ultraviolet curable epoxy resin was applied to the top layer of ZnS using a spin-coding method to a thickness of 10. u+
After coating i, apply ultraviolet rays at a light intensity of 500mW/cII2
The cured epoxy resin surfaces are placed opposite each other, and a double-sided adhesive film with silicone adhesive applied to both sides of the PET film is interposed between the ZnS film and the PET film. It was pasted together in a vacuum chamber to prevent it from getting in. This is shown in FIG. 1 as Example 1.

FIG. 1 is a schematic cross-sectional view of the optical disc obtained in this way, and is an optical disc in which an inorganic protective layer 2, a recording layer 11, an inorganic protective layer 2', and an organic protective layer 4 are sequentially provided on a substrate 3. It shows a structure in which two veneers are bonded together via an adhesive film 6 with adhesive 5 applied on both sides.

FIGS. 3 and 5 show changes in signal-to-noise ratio (C/N) with respect to the number of recording and erasing repetitions of the optical discs of Example 11 and Comparative Example 1, respectively. The power of the laser light required for initialization, recording, erasing, and playback was 7 mWS each.
The power output was 14mW, 711W, and 1.2TIIW.

In Comparative Example 1, noise increases and the C/N ratio decreases as the number of repetitions of recording and erasing increases, but in contrast, in Example 1, there is no increase in noise and the C/N ratio remains almost constant. It becomes. In addition, under an environment of temperature 80°C and humidity 90%,
Even after being left for 1,000 hours, it was confirmed that the optical disc of Example 1 had no pinholes and no corrosion of the recording layer or inorganic protective layer.

Example 2 In order to confirm the effect of the present invention on an erasable optical disk using magneto-optical effect, an optical disk was manufactured by a sputtering method.

Grooves (depth 700mm, width 0.0mm) are made in advance by injection molding.
Thickness 1.2+u with 65μm, pitch 1.6μm)
+.

After forming a Si3N4 film to a thickness of 800 mm on a polycarbonate substrate with a diameter of 130 mm by RF sputtering,
1,000 films of ternary B-Fe-Co alloy were formed by DC sputtering, and Si and Co were roughly formed by RF sputtering.
N.

Two disks with a film formed to a thickness of 1,000 people were manufactured. On top of these two top layer 5ixNs films, ultraviolet curable polyacrylate resin is applied to a thickness of I by spin-coding.
After applying Opm, apply ultraviolet rays at a light intensity of 500 W/cm.
The polyacrylate resin was cured by irradiation for 2 seconds, and the cured polyacrylate resin surfaces were placed facing each other and bonded together via a hot melt adhesive. This is shown in FIG. 2 as Example 2. Second
The figure is a schematic cross-sectional view of the optical disc obtained in this way, and shows an optical disc single plate 2 in which an inorganic protective layer 2, a recording layer 11, an inorganic protective layer 2', and an organic protective layer 4 are sequentially provided on a substrate 3. It shows a structure in which two sheets are bonded together with an adhesive 5 interposed therebetween.

In this optical disk, noise does not increase due to repeated recording and erasing, and the C/N ratio is constant. Also, the temperature is 80℃,
Even after being left in an environment with a humidity of 90% for 1,000 hours, no pinholes were generated, and it was confirmed that there was no corrosion of the recording layer or inorganic protective layer.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of different examples of the optical recording member of the present invention, and FIG. 4 is a schematic cross-sectional view of an example of an optical recording member with a conventional closely bonded structure, In the figure, numeral 1 is a recording layer, 2.2' is an inorganic protective layer, 3 is a substrate, 4 is an organic protective layer, 5 is an adhesive, and 6 is an adhesive film. FIG. 3 and FIG. 5 are graphs showing the relationship between the number of repetitions of recording and erasing and the C/N ratio in the optical recording members of Example 1 and Ratio 1, respectively.

Claims (1)

[Claims] 1 An optical recording member capable of recording and reproducing information by irradiation with laser light, which has a structure in which an inorganic protective layer and an organic protective layer are laminated in that order on at least one side of a recording layer provided on a substrate.2 An optical recording member made of two units facing each other with the substrate facing outside and integrated via a bonding layer.