JP2001270248A - Optical multiple-recording glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a recording density by the same precision or the same mechanism by realizing a recording method by ternary or higher system, not by binary system with the radiation of laser beams, and also, eliminate shortcomings such that the materials for a conventional recording method at the time of the manufacture require a large-scale vacuum-depositing device or spattering device, and the reduction of the manufacturing cost and the increase of the productivity are difficult. SOLUTION: For this sheet-form or film-form optical multiple-recording glass, to glass of TeO2:90 to 65 mol.%-Na2O:10 to 20 mol.% composition, an oxide of transition metals (Co, Fe, Cr, Ni) is added by 0.1 to 5 mol.%. In addition, when either one kind or more of Al2O3, GeO2, TiO2 are contained by not more than 15 mol.%, the sensitivity of the optical recording is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass for optical multiplex recording.

[0002]

2. Description of the Related Art Conventionally, optical recording materials employ a system utilizing crystallization of glass (phase change type), a system in which a magnetic substance is recorded with light and read by a magnetic head (magneto-optical type), and additional recording is not possible. There is a compact disc system. A recordable recording medium is one in which glass or a magnetic thin film layer is formed on a disk-shaped base by vapor deposition, etc., and the glass crystallized by laser light irradiation is vitrified, or laser light irradiation is used. Recording is performed by forming fine magnetic domains. The compact disc is recorded by deforming the disc-shaped base itself by laser beam heating.

[0003]

In the conventional recording method,
In order to read the record, the change in the intensity of the reflected light of the laser beam irradiation or the change in the intensity of the magnetization read by the magnetic head is calculated by two times.
They are read as decimal numbers (on-off). If a recording system of not a binary system but a ternary system or more can be realized by laser beam irradiation, the recording density can be improved with the same accuracy and mechanism. In addition, the conventional recording method requires a large-scale vacuum vapor deposition apparatus or a sputtering apparatus during production, and thus has difficulty in reducing the production cost and improving the productivity.

[0004]

According to the present invention, a glass material containing tellurium dioxide as a main component is used as a material suitable for a recording system utilizing a change in refractive index due to the thermal history of glass, unlike the conventional recording system. To provide. That is, the present invention _is, TeO 2: 90 to 65 mol% -Na ₂ O:
Glass having a composition of 10 to 20 mol% and a transition metal (C
This is a plate-like and film-like glass for optical multiplex recording to which 0.1 to 5 mol% of an oxide of (o, Fe, Cr, Ni) is added. Further, the present invention is the above-mentioned glass for optical multiplex recording, further comprising 15 mol% or less of any one or more of Al ₂ O ₃ , GeO ₂ and TiO _2.

[0005] TeO ₂ and Na ₂ O components are necessary to form a stable glass, and the transition metals (Co, Fe,
An oxide of (Cr, Ni) is a component for adjusting the light absorption efficiency. As for TeO ₂ and Na ₂ O, a stable glass can be obtained within the above composition range. Otherwise, it is difficult to make glass. Transition metals (Co, Fe, C
The range of 0.1 to 5 mol% of the oxide of (r, Ni) is an amount sufficient to adjust the light absorption efficiency. Further, further additions degrade the thermal properties of the glass.

The components of Al ₂ O ₃ , GeO ₂ and TiO ₂ are components necessary for improving the sensitivity of optical recording. The addition of these components has the effect of adjusting the specific heat of the glass to a value suitable for optical recording. If these components are not more than 15 mol%, it is difficult to produce glass.

The glass of the present invention can be manufactured by a general glass manufacturing method, and the current glass manufacturing equipment can be used as it is. That is, an oxide or the like as a raw material is mixed at a predetermined ratio, melted at a temperature of 900 ° C. to 1000 ° C., and a melt is poured out into a mold or the like to manufacture.

[0008] The glass of the present invention writes a record by changing the refractive index of the irradiated portion by irradiating the surface with a laser beam of which intensity and irradiation time are controlled, and has a refractive index of at least five levels. Can record different states.

The reading is performed by irradiating a linearly polarized laser beam (having a lower intensity than that at the time of recording) and grasping it as a change in the refractive index by analyzing the polarization. The information to be read is
Since the data is not binary data as in the conventional system but data in the ternary system or higher, the recording density is higher than that of the conventional system. FIG. 1 shows a difference in recording density due to a difference in recording method at that time.
Further, at the time of erasing, the recording portion is heated to a certain temperature by laser beam irradiation.

FIG. 2 shows the relationship between the thermal history and the refractive index of glass as an operating principle. In general, glass undergoes a structural change from a solid state to a liquid state (supercooled liquid) upon heating and the opposite structural change upon cooling, at the glass transition temperature region. This transition phenomenon is also called a second-order phase transition, and is a transition phenomenon between a liquid state in which constituent atoms of glass can move and a solid state in which the atoms are difficult to move, and is therefore one of relaxation phenomena. In other words, a phenomenon in which the glass state (the liquid state to be solidified) reaches depending on the cooling rate at the time of cooling back to the solid (glass) after heating to the glass transition temperature or higher again.

The temperature of a supercooled liquid corresponding to the state of glass solidified by the above phenomenon is called a virtual temperature. Generally, glass formed by slow cooling (very slow cooling) has a glass transition temperature almost equal to this. Is equivalent to The state of the glass after cooling differs depending on the magnitude of the cooling rate, and as a result, the refractive index of the glass also differs. That is, by changing the cooling rate, glass having various refractive indexes can be produced from one glass. Therefore, if spot heating / cooling using femtosecond laser light is used, small glass islands (recording dots) having different physical properties can be formed on a uniform glass surface, and can finally be used for information recording.

[0012]

EXAMPLE The composition was 76.5 by a usual glass manufacturing technique.
TeO ₂ -13.5Na ₂ O-10Al ₂ O ₃ (mol%)
To obtain a thin glass sheet to which 2 mol% of CoO was added. FIG. 3 shows the change in the refractive index of a glass having this composition due to irradiation with a femtosecond laser. Femtosecond laser light (wavelength: 800 nm, pulse width: 100 fs, beam energy: 660 μJ, oscillation frequency: 1 kHz, beam diameter: 5 mmφ) is condensed by a lens, and irradiated for 2 ms (2 pulses) under a condition slightly shifted from the focal point. About 500
0.18 (μm diameter) refractive index difference (wavelength: 632.8 nm)
Are obtained.

The diameter of the irradiation beam, that is, the diameter of the recording spot can be adjusted by shifting the focal point. The refractive index distribution diagram of the example is an ellipsometer (ellipsometer)
It is measured by the following. At least a refractive index difference of 0.
Since a difference of about 15 can be detected, 10 steps can be performed as a gradation step as a recording refractive index. Therefore, at least five or more recording steps can be obtained in consideration of prevention of overlap.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a difference in recording density due to a difference in a recording method (advancing system).

FIG. 2 is a diagram showing the relationship between the thermal history and the refractive index of glass.

FIG. 3 is a diagram illustrating a change in refractive index due to irradiation of a femtosecond laser in an example.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G11B 7/24 522 B41M 5/26 X (72) Inventor Masayuki Yamane 2-12-1 Ookayama, Meguro-ku, Tokyo Tokyo Kogyo F-term (Reference) 2F111 EA48 FA33 FB05 FB14 FB25 4G062 AA18 BB11 CC10 DA01 DA10 DB01 DB02 DB03 DB04 DC01 DD01 DE01 DF01 EA01 EB04 EC01 ED01 EE01 EF01 EG01 FA01 FA04 FB01 FB01 FB01 FB01 FB01 FB01 FB01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GB01 GC01 GD06 GD07 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 MM29 MM10

Claims (2)

[Claims] 1. TeO ₂ : 90-65 mol% -Na ₂ O:
Glass having a composition of 10 to 20 mol% and a transition metal (C
Plate-like and film-like optical multiplex recording glass to which 0.1 to 5 mol% of an oxide of (o, Fe, Cr, Ni) is added. _2. The glass for optical multiplex recording according to claim 1, wherein at least one of Al ₂ O ₃ , GeO ₂ , and TiO ₂ is contained in an amount of 15 mol% or less.