JP2000222789A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase adhesion property between a transparent resin substrate and a transparent dielectric layer and to obtain a higher Kerr rotation enhancement effect by successively laminating an optical recording layer and a reflection layer on a transparent resin substrate, and forming a transparent dielectric layer consisting of SiaCbOcNd on at least one interface of the optical recording layer. SOLUTION: A first transparent dielectric layer 2 and a second transparent dielectric layer 4 consists of SiaCbOcNd (wherein a=37 to 47 atom.%, b=3 to 9 atom.%, c=6 to 18 atom.% and d=26 to 54 atom.%, satisfying a+b+c+d=100 atom.%). By mixing a rather small proportion of C and O to Si in this structure, the production of SiNx can be suppressed, and C, O on the surface of the transparent resin substrate and Si, C, O in the transparent dielectric layer make covalent bonds to improve the adhesion property. The first transparent dielectric layer 2 and the second transparent dielectric layer 4 are formed by using a target essentially comprising Si and by a reactive sputtering method in a mixture gas of CO2 and N2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped transparent resin substrate on which a phase-change type optical recording layer, a magneto-optical recording layer and the like are provided. The present invention relates to an optical recording medium for reproducing information by an effect.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical recording medium, which is a kind of optical recording medium, is composed of sialon (amorphous film of Si, Al, O, N), Si on a disk-shaped transparent resin substrate made of plastic or the like. ₃ N ₄ , SiO _2, etc., first transparent dielectric layer, T
bFe, TbFeCo, GdFeCo, GdTbFeC
o, etc., at least one magneto-optical recording layer, a second transparent dielectric layer having the same composition as the first transparent dielectric layer, Al,
There have been proposed ones comprising a reflective layer made of Au, Pt, Al-Ti alloy or the like.

[0003] The first and second transparent dielectric layers are used when the reproducing light incident on the magneto-optical recording layer is reflected by the magneto-optical recording layer and the direction of polarization of the reflected light is rotated by the Kerr effect. Multiply-reflecting the reflected light on the second transparent dielectric layer to increase the Kerr rotation angle and improve the C / N ratio, etc.
It is provided to enhance the so-called car rotation angle enhancement effect. The first and second transparent dielectric layers are provided for the purpose of protecting the magneto-optical recording layer which is easily corroded by oxidation and preventing oxidation.

In such a magneto-optical recording medium, for example, in what was deposited enhance film of silicon nitride on the substrate, the composition formula of the enhancing film is Si _x N _y
O _z (A atomic% <x <49 atomic% and A is 10x + y = 4
X value satisfying 87, 37 atomic% <y <57 atomic%, 0
Atomic% <z <18 atomic%) and the refractive index is 2.0
It has been proposed that an enhanced film having a low pinhole density and internal stress and a good adhesion to a substrate can be obtained when the ratio is 2.15 to 2.15 (conventional example 1: Japanese Patent No. 268).
No. 8505).

[0005] Further, as a conventional example 2, in the case where an amorphous metal perpendicular magnetization film and a light-transmitting non-magnetic material layer are laminated on a plastic substrate, the light-transmitting non-magnetic material layer is 33 to 65 atomic%.
By forming the light-transmitting nonmagnetic layer with a plastic substrate, the adhesion of the light-transmitting nonmagnetic layer to the plastic substrate is increased, the antireflection effect on laser light is increased, and the output during reproduction and recording is increased. It is known (see JP-A-62-157346).

As a third conventional example, at least one of H, F, C, N, and O selected on one or both surfaces of the magnetic layer.
It is known that by providing an amorphous Si layer containing at least 50 at% of a certain element as a Kerr rotation angle increasing layer, the light absorption rate of the amorphous Si layer is reduced and the Kerr rotation angle is increased (Japanese Patent Application Laid-Open No. 60-1985). 163247).

[0007]

However, in the above-mentioned conventional example 1, oxygen in the enhanced film easily penetrates into the adjacent magnetic layer, and the magnetic layer is oxidized to deteriorate the characteristics such as the C / N ratio. Was.

Further, in Conventional Example 2, a film is formed by a sputtering method using a silicon carbide target in a hydrocarbon gas. However, hydrogen is mixed into the light-transmitting nonmagnetic layer, and as a result, Although the light absorption coefficient was reduced, the refractive index was lowered by hydrogen, so that a high Kerr rotation angle enhancement effect could not be obtained.

In the conventional example 3, when H is mixed, the refractive index is reduced by H, so that a high Kerr rotation angle enhancement effect cannot be obtained, and when F is mixed, it causes corrosion of the magnetic layer. Further, when C is mixed, the refractive index decreases to near 1.5, so that the Kerr rotation angle enhancement effect cannot be obtained. When O is mixed, the oxidation of the magnetic layer is promoted when the O content increases. You. When N is mixed, there is a problem that the adhesiveness is deteriorated.
There is no mention of what combination and composition ratio of C, N, O, etc. to Si can solve the above problems.

Accordingly, the present invention has been completed in view of the above circumstances, and has as its object the purpose of achieving high adhesion between a transparent resin substrate and a transparent dielectric layer, achieving a high Kerr rotation angle enhancement effect, and improving optical performance. Another object is to make the magnetic recording layer effective for preventing oxidation.

[0011]

The optical recording medium of the present invention comprises:
An optical recording medium sequentially laminated between the optical recording layer and a reflective layer on the transparent resin substrate, Si _a at least one interface of the optical recording layer _{C b O c N d (a} = 37~47at ( atoms)
%, B = 3 to 9 at%, c = 6 to 18 at%, d = 26
(At +54 at%, a + b + c + d = 100 at%).

According to the present invention, the generation of SiN _x is suppressed by mixing a relatively small amount of C and O into Si, and C and O on the surface of the transparent resin substrate and Si in the transparent dielectric layer are mixed. , C, and O are covalently bonded, and the adhesion is improved. Further, since the transparent dielectric layer of the present invention has a high refractive index, a high Kerr rotation angle enhancement effect can be obtained.

In the present invention, preferably, in the transparent dielectric layer, the ratio of carbon atoms existing as single atoms is C1, the ratio of carbon atoms singly bonded to oxygen is C2, and the ratio of carbon atoms existing as carbon dioxide is Is C3, C1 =
0-20 at%, C2 = 80-100 at%, C3 = 0
２０20 at%, C1 + C2 + C3 = 100 at%.

According to the above configuration, the adhesion between the transparent resin substrate and the transparent dielectric layer, the C / N ratio, and the Kerr rotation angle are further improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical recording medium of the present invention will be described below. FIG. 1 is a partial sectional view of a magneto-optical recording medium M according to the present invention. In FIG. 1, reference numeral 1 denotes a transparent resin substrate (hereinafter abbreviated as a substrate) made of plastic such as polycarbonate, polyacetal, and polymethyl methacrylate; One transparent dielectric layer, 3 is Cr, Fe, Co, Ni, Cu
And transition metal elements such as Nd, Sm, Gd, Tb, Dy, H
amorphous alloys with rare earth elements such as o, for example, TbFe, T
a magneto-optical recording layer comprising at least one magnetic layer such as bFeCo, GdFeCo, GdTbFeCo, 4 a second transparent dielectric layer comprising the same as the first transparent dielectric layer 2,
Reference numeral 5 denotes a reflection layer made of Al, Au, Pt, an Al—Ti alloy, or the like. The first and second transparent dielectric layers 2 and 4 may be provided on at least one interface of the magneto-optical recording layer 3.

The first transparent dielectric layer 2 and the second transparent dielectric layer 4 of the present _{invention, Si a C b O c N} d (a = 37~47at
(Atomic)%, b = 3 to 9 at%, c = 6 to 18 at%,
d = 26 to 54 at%, a + b + c + d = 100 at
%).

When a is less than 37 at%, the C / N ratio decreases due to a decrease in the refractive index, and when a exceeds 47 at%, the internal stress in the first transparent dielectric layer 2 and the second transparent dielectric layer 4 increases. The transparent resin substrate 1 is easily warped. When b is less than 3 at%, the adhesion to the transparent resin substrate 1 is reduced, and when b is more than 9 at%, the C / N ratio is reduced due to a decrease in the refractive index.

When c is less than 6 at%, the adhesion to the transparent resin substrate 1 is reduced, and when c exceeds 18 at%, the magneto-optical recording layer 3 is oxidized and the C / N ratio is lowered. For d, 2
If it is less than 6 at%, the internal stress in the first transparent dielectric layer 2 and the second transparent dielectric layer 4 increases, and the transparent resin substrate 1 is easily warped. If it exceeds 54 at%, the C / N ratio decreases due to a decrease in the refractive index. I do.

The first transparent dielectric layer 2 and the second transparent dielectric layer 4 preferably have a thickness of 100 to 1000 °,
If it is less than Å, the first transparent dielectric layer 2 becomes too thin and the substrate 1
Corrosion resistance is degraded by water and oxygen passing through. 1000
If Å is exceeded, the reflectance of the entire medium M becomes too high, and the loss of incident laser light increases, so that a high-power laser light source is required.

The first transparent dielectric layer 2 and the second transparent dielectric layer 4 of the present invention are formed as follows. A film is formed by a reactive sputtering method in a mixed gas of CO ₂ and N ₂ using a target containing Si as a main component. In this case, DC (direct current) sputtering with a high film-forming rate is preferable, and a target mainly composed of conductive Si instead of an insulator such as SiC is preferable as a target material, and oxidation is promoted as an atmosphere gas. A mixed gas of CO ₂ and N ₂ is preferred over an oxygen gas. CO ₂
In the plasma generated during the film formation, the the O ₂ dissociates less, therefore the magnetic layer is it is hardly oxidized.

Further, the substrate 1 and the first by using CO _2, although the adhesion is improved between the second transparent dielectric layers 2 and 4, it C surface of the substrate 1, the O and SiCON C, and O By a covalent bond. That is, 2 = O = C = O
The CO ₂ bonded by two bonds (double bonded) becomes two radicals between C and O in the plasma and becomes a radical state as shown in FIG. O and S
It is considered that the adhesiveness is enhanced by penetrating and covalently bonding between C and O of iCON.

In the present invention, for the first transparent dielectric layer 2 and the second transparent dielectric layer 4, the ratio of carbon atoms existing as single atoms is C1, and the ratio of carbon atoms which are single-bonded to oxygen is C1.
2. Assuming that the ratio of carbon atoms existing as carbon dioxide is C3, C1 = 0 to 20 at% and C2 = 80 to 100 at.
%, C3 = 0 to 20 at%, C1 + C2 + C3 = 100
It is preferably at%.

If C1 exceeds 20 at%, the amount of dissociated oxygen increases, oxidizing the magneto-optical recording layer 3 and deteriorating the C / N ratio. When C3 exceeds 20 at%, the ratio of direct covalent bonding between Si and N increases, so that Si, C, O in the first transparent dielectric layer 2 and the second transparent dielectric layer 4 and C, C,
The rate at which O is covalently bonded decreases, and the adhesiveness deteriorates. C
2 is less than 80 at%, the carbon and oxygen atoms are bonded by one bond, that is, the number of radical carbon and oxygen atoms is reduced, and C, O and the first transparent dielectric layer of the substrate 1 are reduced. The ratio of covalent bonding between Si, C, and O of the second and second transparent dielectric layers 4 is reduced, and the adhesion is deteriorated.

C1, C2 and C3 can be measured by X-ray photoelectron spectroscopy (so-called ESCA).

In the above embodiment, the case where the magneto-optical recording layer 3 has one layer has been described. However, the present invention can be applied to a case where the magneto-optical recording layer 3 has two or more layers. For example, from the substrate 1 side, a recording layer, a recording auxiliary layer, a control layer, and an initialization layer
Basically, the temperature increases from room temperature to the Curie temperature of the control layer, the Curie temperature of the recording layer, the Curie temperature of the recording auxiliary layer, and the Curie temperature of the initialization layer, and the coercive force of the recording layer is the largest at room temperature. Then, direct overwriting (rewriting by overwriting) may be possible because the coercive force is larger in the order of the recording auxiliary layer, the control layer, and the initialization layer. In the case of such a direct overwrite-capable device, since the number of magnetic layers is large, each magnetic layer is thin and their functional roles are different, protection against oxidation prevention is extremely important, and the transparent dielectric layer of the present invention is It is effective as a protective layer.

In the above-mentioned direct overwrite-capable recording medium, an exchange coupling force adjusting layer for controlling the exchange coupling force between the recording layer and the recording auxiliary layer at room temperature by losing the magnetization at room temperature or becoming horizontal magnetization is provided. It may be provided between the recording layer and the recording auxiliary layer. Also, between the substrate 1 and the recording layer,
A read-only read layer may be provided to increase the C / N ratio.

Further, conventionally, a magneto-optical recording layer 3,
Although the laser beam for reproduction was incident on the back surface side of the substrate 1 by laminating the reflective layer 5 in this order, the present invention laminates the reflective layer 5 and the magneto-optical recording layer 3 on the substrate 1 in this order. The present invention can also be applied to a case where a reproduction laser beam is incident from the magneto-optical recording layer 3 side. In this case, the thickness of the first transparent dielectric layer 2 and the second transparent dielectric layer 4 is preferably from 100 to 400 °, and if it is less than 100 °, the first transparent dielectric layer 2 becomes too thin and the corrosion resistance deteriorates. 4
If it exceeds 00 °, the heat generated by the incident laser light is unlikely to radiate, and the laser light output becomes relatively large from the optimum value, and as a result, the C / N ratio and the like deteriorate.

In the present invention, each layer such as the magneto-optical recording layer 3 is laminated on both surfaces of the substrate 1 (in this case, the reflective layer 5 and the magneto-optical recording layer 3 are laminated in this order), or each layer is laminated on one surface. The recording density may be doubled by attaching two substrates 1 together.

In the above embodiment, the magneto-optical recording medium has been described, but the present invention is not limited to GeTe, GeSbTe.
The present invention can also be applied to an optical recording medium having a phase-change type optical recording layer that can be changed into a crystalline state and an amorphous state by such temperatures. Also,
The present invention is not limited to the phase change type, and the present invention can be applied as long as an optical recording layer and a reflective layer capable of optically recording and reproducing information are formed on a transparent resin substrate.

Thus, according to the present invention, a substrate having a high adhesion between the substrate and the transparent dielectric layer, a high Kerr rotation angle enhancement effect can be obtained, and a material effective for preventing oxidation of the magneto-optical recording layer can be obtained. It has the function and effect.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0032]

Embodiments of the present invention will be described below.

(Embodiment) The magneto-optical recording medium M of FIG. 1 was constructed as follows. The substrate 1 disc-shaped made of polycarbonate and baked at about 100 ° C., was placed in a DC sputtering apparatus stationary opposed type, evacuated to a predetermined degree of vacuum, Si on one main surface of the substrate 1 _a C _b O _c the first transparent dielectric layer 2 having a thickness of 400Å consist _{N d, Gd 12 Dy 18 Fe} 70
Thickness 300Å consisting magneto-optical recording layer 3, Si _a C _b O
_c N second transparent dielectric layer having a thickness of 300Å consist _d 4, A
The reflective layers having a thickness of 1000 ° were sequentially formed. In such a magneto-optical recording medium M, the adhesiveness when the composition of the first and second transparent dielectric layers 2 and 4 is changed, the C / N ratio during reproduction, the refractive index n, the Kerr rotation angle (θk ) Are shown in Table 1.

[0034]

[Table 1]

In Table 1, C1 to C3 are measured by the ESCA method, and θk is measured by a Kerr rotation angle measuring device. To explain the ESCA method specifically,
And the inside of the measuring device to vacuum every sample of Si _a C _b O _c N _d solid, photoelectron kinetic energy generated by the photoelectric effect measured when irradiated with X-rays in the sample, determine the binding energy of the photoelectrons , The constituent elements of the sample from its binding energy spectrum position and peak intensity,
It is possible to know the content of the constituent elements and the state of chemical bonding of the constituent elements.

The adhesion was evaluated by peeling or bubbles on the first transparent dielectric layer 2 or the second transparent dielectric layer 4 after the device was placed in an atmosphere at 80 ° C. and a relative humidity of 90% for 500 hours. In the case where peeling or air bubbles were generated, the area obtained by subtracting the area occupied by the peeling or air bubbles in a unit area (10 mm × 10 mm) was indicated by%.

According to the NO. In 1-3, the atmosphere gas at the time of film formation was CO ₂ , and the composition ratio of C and O was 1: 2, indicating that the bond between C and O in CO ₂ was not separated. I have. On the other hand, NO. In 7-18, C
The composition ratio of O and O is set to CO ₂ and O ₂ as the atmosphere gas at the time of film formation, and the mixing ratio is adjusted.
The chip was mounted and controlled.

As shown in Table 1, the NO. 1-7
Shows high values in all of the adhesiveness, C / N ratio, refractive index n, and θk. 8 to 25, adhesion, C / N
One or more parameters of the ratio, refractive index n, and θk deteriorated.

In particular, NO. 1,
NO.4, 5 and C1 exceeding 20 at%. No. 10 when compared with NO. In the case of No. 10, the C / N ratio was deteriorated. In addition, the NO. NO.1, 2, 3, and C3 exceeding 20 at%. 9 and N
O. In No. 9, the adhesion deteriorated. And C2 is 80a
NO. N in which 1,6 and C2 are less than 80 at%
O. No. 8 in comparison with NO. In the case of No. 8, the adhesion deteriorated.

Further, when Si exceeds 47 at% and N is 26 a
NO. 20 and Si is 47 at% and N is 26
at% of NO. Compared with NO. In the case of No. 20, the substrate 1 was deformed by the internal stress, and the adhesion was deteriorated.

NO. In which O exceeds 18 at%. 25
And O. of 18 at% NO. 7 in comparison with NO.
In No. 25, the magneto-optical recording layer 3 was oxidized and the C / N ratio deteriorated.

When C. is less than 3 at%, NO. 22 and C are 9
NO. 23 and N at 6 at% C
O. Compared with NO. In the case of NO. In No. 23, n decreased and C / N ratio deteriorated.

NO.3 containing less than 37 at% of Si and more than 54 at% of N. 21 and Si is 37 at% and N is 54
at% of NO. No. 3 in comparison with NO. In the case of No. 21, the C / N ratio was lowered.

When NO is less than 6 at%. 24 and O 6
at% of NO. No. 3 in comparison with NO. 24 exhibited poor adhesion.

[0045]

According to the present invention, at least one interface of the optical recording layer _{Si a C b O c N d} (a = 37~47at%, b
= 3-9at%, c = 6-18at%, d = 26-54
At%, a + b + c + d = 100 at%), a relatively small amount of C and O is mixed with Si to suppress generation of SiN _x .
Also, C, O on the surface of the transparent resin substrate and S,
Since i, C, and O are covalently bonded, the adhesion is improved. Further, since the transparent dielectric layer of the present invention has a high refractive index, a high Kerr rotation angle enhancement effect is obtained, and as a result, the C / N ratio and the Kerr rotation angle are improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a magneto-optical recording medium M of the present invention.

FIG. 2 is a molecular structural formula of carbon and oxygen bonded in a radical state.

[Explanation of symbols]

 1: transparent resin substrate 2: first transparent dielectric layer 3: magneto-optical recording layer 4: second transparent dielectric layer 5: reflective layer

Claims (2)

[Claims] 1. A optical recording medium formed by laminating an optical recording layer and a reflective layer on the transparent resin substrate, Si _a at least one interface of the optical recording layer _{C b O c N d (a} = 37~47at
(Atomic)%, b = 3 to 9 at%, c = 6 to 18 at%,
d = 26 to 54 at%, a + b + c + d = 100 at
%) Provided with a transparent dielectric layer comprising: 2. In the transparent dielectric layer, the ratio of carbon atoms present as single atoms is C1, the ratio of carbon atoms singly bonded to oxygen is C2, and the ratio of carbon atoms present as carbon dioxide is C3. C1 = 0-20at%, C2 = 80-
100at%, C3 = 0-20at%, C1 + C2 + C
2. The optical recording medium according to claim 1, wherein 3 = 100 at%.