JPH0729205A - Optical recording medium - Google Patents

Abstract

PURPOSE:To inhibit the cracking of a protective layer and a reflecting layer and the mass transfer of a recording film even after repeated recording and erasing with laser light and to improve repetitive characteristics. CONSTITUTION:A recording layer 9 causing an optical change when irradiated with laser light is formed in fine recesses 13 in a glass disk substrate 1 and a GeTe film 10 whose reflectance is equal or close to that of the recording layer 9 is formed on the surface of the recording layer 9. The mass transfer of the recording film caused by making the recording film repeatedly crystalline and amorphous by irradiation with laser light is inhibited and the repetitive recording-erasing characteristics of the resulting optical recording medium are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium used in an optical recording device or the like.

[0002]

2. Description of the Related Art In recent years, the recording density of information has been increased, and an optical recording medium using a laser is capable of large-capacity recording, and an optical head and an optical recording medium are non-contact unlike a hard disk drive. Therefore, the optical recording medium is highly promising as a large-capacity recording medium because it has little damage and has high reliability.

An optical recording medium capable of high density recording includes a read-only type, a write-once type in which information can be written only once, and a recording / writing type.
There are three rewritable types that can be erased.

The basic structure of these optical recording media comprises a disk-shaped transparent substrate made of plastic, glass or the like, and a laminated thin film provided on the transparent substrate.

In a read-only type optical recording medium, reflective films Al and Au are formed on a polycarbonate substrate on which irregularities are formed, a laser is focused and irradiated from the substrate side, and light is returned from the reflective film. The reflected light intensity of is detected.

The write-once type optical recording medium can record information only once and is mainly used as a document / still image file.

The write-once type optical recording medium has several types of recording methods. A perforated type which records information by making holes by sublimation by heat of a laser, and an optical constant of a crystalline state and an amorphous state of a recording film. There are a phase change type that uses a difference in reflectance due to a change, a bubble type that forms bubbles by a laser, and a type that uses an organic dye. Write-once optical discs are irreversible in these reactions.
It can be recorded only once, but can be played back as many times as desired.

As a recording method of a rewritable optical recording medium,
The recording film is heated by laser irradiation, and the heated portion reverses the direction of magnetization by an external magnetic field to form a recording pit and recording is performed. For reproduction, there are magneto-optical recording utilizing the Kerr effect of the recording film, optical mode recording utilizing reversible change of two states having different absorption spectra using light, and phase change recording.

FIG. 10 is a structural diagram of a disk of a conventional optical recording medium. The phase change recording is performed as shown in FIG.
The glass disk substrate 1 has a first dielectric film 2, a recording film 3,
It has a structure in which a second dielectric film 4, a reflective film 5, and a UV curable resin 6 as a protective layer are sequentially laminated. As a recording method, the laser 7 from the laser light source 7a is used as shown in FIG. 11, and the glass disk substrate 1 of the optical recording medium 8 shown in FIG.
When the laser beam 7 is focused and irradiated from the side and the optical recording medium 8 is irradiated with the laser 7 with the recording power, the recording film 3 in the irradiated portion is melted and rapidly cooled to become amorphous. When the optical recording medium 8 is irradiated with the erasing power of the laser 7, the recording film 3 is heated to a temperature at which it can be crystallized, so that the recording film 3 becomes a crystalline state.
Reproduction is performed by using a laser power lower than the recording / erasing power and utilizing the difference in optical constants due to the phase transition between amorphous and crystalline.

The optical recording medium 8 (hereinafter referred to as a phase change disk) shown in FIG. 10 can be overwritten by a single beam, and the optical system can be simplified. .

[0011]

However, in the phase-change optical disk, the recording film 3 is melted by laser irradiation and rapidly cooled to form an amorphous material which is a recording mark. A defect may occur in the thin film of the recording film 3 formed on the disk substrate 1. The cause of the defect in the thin film of the recording film 3 is a crack generated in the UV curable resin 6 or the reflective film 5 as a protective layer, a mass transfer of the recording film 3, and the like. There was a problem of deterioration.

FIG. 12 shows the repetitive recording / erasing characteristics of the conventional phase change optical disk. The number of error bits increases as the number of repetitive recording / erasing by laser increases (10 ³ or more). I understand that.

Further, the conventional optical recording medium has a four-layer structure in which a first dielectric film 2, a recording film 3, a second dielectric film 4 and a reflective film 5 are sequentially laminated as shown in FIG. However, there is a problem that the manufacturing process of the optical recording medium becomes complicated.

Therefore, the present invention solves the above-mentioned conventional problems, suppresses the mass transfer of the recording film, has good recording / erasing repetitive characteristics, simplifies the manufacturing process, and is excellent in mass productivity. The purpose is to provide a recording medium.

[0015]

In order to achieve the above object, the first aspect of the present invention is to provide a recording layer having a fine recess on a substrate, and an optical change caused by irradiating the recess with a laser. And a film having a reflectance equal to or close to the reflectance of the recording layer on the surface of the recording layer.

Secondly, the substrate has a minute concave portion, and the concave portion has a recording layer in which an optical change is generated by irradiating the concave portion with a laser, and a heat insulating layer is provided on the surface of the recording layer. In addition, a film having a reflectance equal to or close to the reflectance of the recording layer is further provided on the heat insulating layer.

[0017]

According to the present invention, by forming the recording layer in the fine recesses on the substrate, the crystal of the recording film due to laser irradiation,
It is possible to suppress the occurrence of mass transfer of the recording film caused by the repeated amorphization, and to improve the repeating characteristics of the optical recording medium.

Further, since the structure of the optical recording medium can be simplified from the conventional four-layer structure to the two-layer structure or the three-layer structure by the above means, the manufacturing process is simplified and the optical recording medium is excellent in mass productivity. Can be provided.

[0019]

EXAMPLES Examples of the present invention will be described below.

Polycarbonate, acrylic resin, epoxy resin, glass or the like is used as the substrate of the optical recording medium.

In the method for producing an optical recording medium, first, a glass master is coated with a photosensitizer, exposed by a laser and developed to form fine recesses. Nickel electroforming is performed on this master, and the stamper is formed by peeling and washing.

The substrate described above is placed on this stamper, and a photopolymer resin is filled and cured to form fine recesses on the optical recording medium.

A recording layer is formed on the substrate having the fine recesses, and a film having a reflectance equal to or close to the reflectance of the recording layer is formed on the recording layer, or on the recording layer. A heat insulating layer is formed, and a film having a reflectance equal to or close to the reflectance of the recording layer is further formed thereon.

As the material of the recording layer, a material which reversibly changes its phase between crystalline and amorphous is selected. As such a material, Ge--Te, Ge--Sb--Te, Ge--Te-- S, Ge
-Se-Sb, In-Sb-Te, Ge-As-Se, In-T
e, Se-Te, Se-As, In-Sb, etc.

As the material of the heat insulating layer, ZnS.SiO ₂ ,
There are Ta ₂ O ₅ , SiO ₂ , SiN, ZnS and the like.

As a material having a reflectance close to that of the recording layer of the semiconductor laser used and having a melting point higher than that of the recording layer, there is GeTe for Ge-Sb-Te.

The thin film is formed by vacuum vapor deposition, electron beam vapor deposition, ion plating, plasma CVD, light C
It can be formed by a VD method, a sputtering method, or the like.

The sputtering method using Ar gas is suitable for forming the thin film, but depending on the material, (Ar + N ₂ ) gas,
Sputtering with (Ar + H ₂ ) gas, N ₂ gas, and H ₂ gas is suitable.

After forming a recording film or the like on the disc, a UV curable resin is used as an overcoat. The UV curable resin is coated with a spin coater.

After forming a thin film on the substrate and coating the UV curable resin, the thin films are laminated so as to face each other inward. A hot melt type adhesive is well known as an adhesive used when laminating optical recording media.

An optical recording medium is manufactured through the above manufacturing process. A lubricant or an antistatic agent may be applied on the surface of the optical recording medium that has been laminated.

The optical recording medium of the present invention will be specifically described below.

(Embodiment 1) As shown in FIG. 1, the structure of the optical recording medium of the embodiment 1 is such that a glass disk substrate 1 having a diameter of 86 mm is used.
Ge-Sb-Te is used as the recording layer 9 in the recess 13 formed above.
And the laser wavelength of the recording layer Ge-Sb-Te is formed on it.
Recording layer 9 in which a GeTe film 10 having a reflectance close to that at 30 nm is formed and a UV curable resin 6 is laminated thereon
And the GeTe film 10 have a two-layer structure.

At this time, the lubricant 11 or the antistatic agent 12 may be applied to the surface of the glass disk substrate 1.

The width of the recesses 13 on the glass disk substrate 1 is 0.1 μm and the depth is 250 Å, and many recesses 13 are uniformly formed on the glass disk substrate 1.

Next, a method of manufacturing the optical recording medium will be described with reference to FIGS. As shown in FIG. 2, a glass master disk 15 whose surface has been polished is washed and dried, and a photoresist film 16 as a recording material is coated thereon with a film thickness of 250 Å. The coated glass master 15 enhances the adhesion between the glass master 15 and the photoresist film 16 by baking.

Next, the glass master 15 coated with the photoresist film 16 is exposed by the laser 7 modulated by the laser light source 7a as shown in FIG. 3, and after the exposure, the photoresist film 16 is removed. As shown in FIG. 4, a recess 13 having a width of 0.1 μm and a depth of 250 Å is formed on the glass master disk 15.

A glass stamper 15 having a large number of minute recesses 13 formed thereon is electroformed with nickel, and is peeled off and washed to form a stamper.

The glass disk substrate 1 having a diameter of 86 mm is placed on this stamper, and the photopolymer resin 17 is filled or applied between the stamper and the glass disk substrate 1 as shown in FIG. The existing resin is hardened by the reaction at the optical bridge end. Then, when the glass disk substrate 1 and the cured photopolymer resin 17 are peeled off, as shown in FIG.
As shown in FIG. 3, fine recesses 13 are formed on the glass disk substrate 1.

The glass disk substrate 1 thus prepared is placed in a vacuum sputtering apparatus and the chamber is evacuated to a high vacuum. Next, Ar gas was introduced into the chamber,
A Ge—Sb—Te target is sputtered to form a 350 Å recording layer 9 on the glass disk substrate 1. next,
This recording layer 9 is dry-etched to remove the recording layer 9 by 10
0Å Dry etching. As a result, the recording layer 9 is formed only in the concave portion 13 on the glass disk substrate 1.

Next, a GeTe film 10 having a reflectance close to that of the recording layer 9 at a laser wavelength of 830 nm and having a melting point higher than that of the recording film is sputtered on the recording layer 9 to form a thin film of 50 nm. To form. After that, the UV curable resin 6 is coated with a spin coater. The surface of the glass disk substrate 1 may be coated with the lubricant 11 or the antistatic agent 12.

Next, the optical recording medium was tested for repetitive recording / erasing characteristics.

As a test method, the linear velocity of the disk is 10 m.
Signals were written using a semiconductor laser at / s.
The wavelength of the semiconductor laser used was λ = 830 nm, and the error bit number of the optical recording medium was measured as a repetitive characteristic. FIG. 7 shows the recording / recording of the optical recording medium according to the first embodiment of the present invention.
The erasing repetition characteristics are shown, and it can be seen that the number of error bits is significantly reduced as compared with the recording / erasing repetition characteristics of the conventional optical recording medium shown in FIG.

That is, as shown in FIG. 12, the number of error bits increases from the number of repetitions of 10 ³ or more in the conventional optical recording medium, whereas in Example 1 of the present invention in FIG. 7, fine recesses are formed on the glass disk substrate 1. 13 is provided, and the recording layer 9 is provided in the recess 13.
Is formed and has a reflectivity close to the reflectivity of the recording layer 9, by forming a GeTe film 10 having a melting point higher than the melting point of the recording film, the number of error bits in the repeat count ¹⁰⁷ times Little increase is seen.

(Embodiment 2) As shown in FIG. 8, the construction of the optical recording medium of the present embodiment 2 is such that Ge-Sb-T as the recording layer 9 is formed as the recording layer 9 in the recess 13 formed on the glass disk substrate 1 having a diameter of 86 mm.
e is formed, ZnS.SiO ₂ is formed as a heat insulating layer 14 thereon, and Ge-Sb-Te as a recording layer 9 is further formed thereon.
Of the GeTe film 10 having a reflectance close to that at the laser wavelength of 830 nm, and a UV curable resin 6 is laminated thereon to form a three-layer structure of a recording layer 9, a heat insulating layer 14, and a GeTe film 10. There is. At this time, the lubricant 11 or the antistatic agent 12 may be applied to the surface of the glass disk substrate 1.

The recesses 13 on the glass disk substrate 1 have a width of 0.1 μm and a depth of 250 Å, and a large number of recesses 13 are uniformly formed on the glass disk substrate 1.

Next, a method of manufacturing the optical recording medium will be described. The recording layer 9 is formed only in the concave portion 13 of the glass disk substrate 1.
The process up to the step of forming is similar to that of the first embodiment. Here, as the heat insulating layer 14 according to this embodiment, 100% ZnS.SiO ₂ is used.
A film of nm is formed to block heat from laser irradiation. On the heat insulating layer 14, a GeTe film 10 having a reflectance close to that of the recording layer at a laser wavelength of 830 nm is sputtered to form a 50 nm thin film. After that, the UV curable resin 6 is coated with a spin coater. The surface of the glass disk substrate 1 may be coated with the lubricant 11 or the antistatic agent 12.

Next, the same recording / erasing repetitive characteristic test as in Example 1 was conducted on this optical recording medium. The result is shown in FIG.

As shown in FIG. 9, a minute concave portion 13 is formed on the glass disk substrate 1, a recording layer 9 is formed in the concave portion 13, and the recording layer 9 and the reflectance of the recording layer 9 close to the reflectance at a laser wavelength of 830 nm. Between the GeTe film 10 and the heat insulating layer (ZnS
・ By having SiO ₂ ) 14, the number of repetitions is greater than that of the conventional recording / erasing repetition characteristics of the optical recording medium shown in FIG.
No increase in the number of error bits was observed even after 10 ⁷ times, showing excellent repeatability.

[0050]

As described above, the optical recording medium of the present invention has a fine concave portion on the substrate of the optical recording medium, and a recording layer which causes an optical change by irradiating the concave portion with a laser. Having a film having a reflectance equal to or close to the reflectance of the recording layer on the surface of the recording layer, or having a minute concave portion on the substrate of the optical recording medium, and laser in the concave portion. By having a recording layer that undergoes an optical change by irradiation, having a heat insulating layer on the surface of this recording layer, and further having a film having a reflectance equal to or close to the reflectance of the heat insulating layer. In addition, mass transfer of the recording film due to repeated recording / erasing due to laser irradiation is suppressed, the repeatability is excellent, and the disk structure can be simplified as compared with conventional optical recording media. Recording medium It is possible to provide a.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an optical recording medium of Example 1 of the present invention.

FIG. 2 is a diagram in which a photoresist film is applied to a glass master in the manufacturing process of the present embodiment.

FIG. 3 is a diagram in which a photoresist film applied to a glass master in the manufacturing process of this example is exposed by a laser.

FIG. 4 is a diagram showing a recess formed in a glass master in the manufacturing process of the present embodiment.

FIG. 5 is a diagram in which a substrate is placed on a stamper and filled with a photopolymer resin in the manufacturing process of the present embodiment.

FIG. 6 is a diagram showing a recess formed on a substrate in a manufacturing process of this embodiment.

FIG. 7 is a diagram showing repetitive recording / erasing characteristics of the optical recording medium according to the first embodiment of the present invention.

FIG. 8 is a diagram showing the structure of an optical recording medium of Example 2 of the present invention.

FIG. 9 is a diagram showing repetitive recording / erasing characteristics of an optical recording medium according to a second embodiment of the present invention.

FIG. 10 is a structural diagram of a disk of a conventional optical recording medium.

11 is a schematic diagram showing a recording method of the optical recording medium of FIG.

FIG. 12 is a diagram showing recording / erasing repetition characteristics of a conventional optical recording medium.

[Explanation of symbols]

1 ... Glass disk substrate, 6 ... UV curable resin, 7 ...
Laser, 8 ... Optical recording medium, 9 ... Recording layer, 10 ... Film having a reflectance close to that of the recording layer (GeTe film), 11 ... Lubricant, 12 ... Antistatic agent, 13 ... Recess, 14 ... Heat insulation layer,
15… Glass master, 16… Photoresist film, 17… Photopolymer resin.

Claims (2)

[Claims] 1. A substrate is provided with a minute concave portion, and the concave portion has a recording layer that undergoes an optical change when irradiated with a laser, and has the same reflectance as the recording layer on the surface of the recording layer. Or an optical recording medium having a film having a reflectance close to that. 2. A substrate is provided with a minute concave portion, a recording layer having an optical change caused by irradiating the concave portion with a laser, and a heat insulating layer on the surface of the recording layer. An optical recording medium comprising a film having a reflectance on the heat insulating layer which is equal to or close to the reflectance of the recording layer.