JPS63166046A - Optical disk - Google Patents

Abstract

PURPOSE:To improve adhesiveness and the protective performance of a recording layer and to simplify formation of said layer by laminating and forming a transparent protective film consisting of silicon oxide and transparent protective film consisting of oxynitride of specific elements on a transparent org. resin substrate. CONSTITUTION:The substrate 1 is the transparent org. resin substrate consisting of a resin such as polyolefin resin. A transparent joint layer 2 consisting of the silicon oxide is formed thereon and the transparent protective film 3 consisting of the oxynitride of at least one kind of the element selected from B, Al, Si, and In, for example, oxynitride of Si is formed on said layer 2. The recording layer 4, for example, a thin film essentially consisting of an amorphous alloy of a heavy rare earth and transition metal such as, for example, TbCo film, is formed thereon. An interference layer 5 consisting of a material similar to the material of the layer 3 and a reflection layer 6 consisting of an aluminum film are successively formed thereon. The adhesiveness of the recording layer is thereby improved and since the transparent protective film contains oxygen, the forming process is greatly simplified.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical disc, such as a laser dome, on which information is recorded, recorded, and reproduced by irradiation with a light beam.
In particular, the present invention relates to an optical disc having a structure in which a recording layer is formed on a transparent organic resin substrate.

(Prior Art) Optical disks, in which information is recorded and reproduced by irradiation with a light beam such as a laser beam, are expected to develop as high-density, non-contact, high-speed access memories. Among optical disks, recordable type ones basically consist of a substrate and a recording layer formed on the substrate.

Optical discs are used to prevent irregularities during recording or playback due to dust or dirt that adheres to the recording layer.
Since it is common to irradiate a light beam from the substrate side and detect the reflected light, the substrate is required to be transparent. Further, in order to obtain a high-speed access function, it is necessary to guide the optical beam to a predetermined position on the disk, and for this purpose, a guide group is formed on the substrate.

In this way, it is transparent and easy to form groups.
Polymethyl methacrylate, polycarbonate, epoxy, polyolefin, etc. are suitable as substrate materials that meet these requirements.

On the other hand, the material of the recording layer can be any material in principle as long as it can have two different optical states when irradiated with a light beam, and a wide range of materials have been developed or researched, including metals, semiconductors, chalcogens, and organic dyes. is being done. However, with the exception of a limited number of semi-organic and organic materials, most recording layer materials have poor adhesion to transparent organic resin substrates when used as a single layer, and also have poor oxidation resistance, making storage as memory difficult. The problem is that it has a short lifespan. For example, heavy rare earth (
Gd, Tb, Dy, Ho, etc.) and transition metals (Fe,
A thin film mainly composed of an amorphous alloy with Co (hereinafter referred to as RE
- Regarding the TM film), various multilayer film structures have been proposed, but none that comprehensively satisfies all practically important factors such as adhesion, protection performance of the recording layer (magnetic life), and ease of manufacturing. No such technology has yet been discovered.

In order to improve the adhesion between the organic resin substrate and the recording layer,
For example, the 9th Japanese Society of Applied Magnetics Academic Lecture Abstracts 29aB
It is effective to use a silicon oxide film as a bonding layer, as described in 10, 1985 and the like. In addition to the adhesion of the recording layer, a specific example of improving the magnetic lifetime is to use SiO or 5iO2 on the substrate.
A structure is known in which a bonding layer is formed, and a recording layer is formed thereon with a protective layer formed of a nitride or carbonitride film interposed therebetween (Japanese Patent Laid-Open Publication No. 1983-92459). However, to create nitride or carbonitride films,
(1) Evacuating the ultimate vacuum before film formation to about 10-7 Torr or less, (2) Increasing the purity of the target and gas, (3) Applying negative bias to the substrate during film formation, etc. This significantly impairs the ease of manufacturing.

In addition, nitrides and carbonitrides generally have good thermal conductivity and cause a large heat loss when the light beam passes through them, which increases the optimal recording power of the light beam, or in other words, reduces the recording sensitivity. There are also problems.

(Problems to be Solved by the Invention) Conventional optical discs using a nitride or carbonitride film as a protective layer have problems such as complicated manufacturing processes, high costs, and decreased recording sensitivity. Ta.

The present invention has been made in view of these problems, and provides an optical disc that has good adhesion between the substrate and the recording layer, excellent protection performance for the recording layer, is simple to manufacture, and has high recording sensitivity. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The optical disc according to the present invention comprises a transparent organic resin substrate, a transparent protective layer made of silicon oxide, and a transparent protective layer made of silicon oxide.
, In, a transparent protective layer made of an oxynitride of at least one element selected from In.

Note that the term oxynitride as used in the present invention includes a mixture of an oxide and a nitride.

(Function) The transparent bonding layer made of silicon oxide has the function of improving the closeness of the recording layer to the transparent organic resin substrate.
Further, the transparent protective layer made of oxynitride has the function of protecting the recording layer from moisture, gas, etc. that pass through the transparent A-type resin substrate.

Here, since the transparent protective layer made of oxynitride contains oxygen, it does not contain oxygen, which is required in the conventional technology where the protective layer is a nitride or carbonitride film that does not contain oxygen. This eliminates the need for manufacturing considerations, greatly simplifying the manufacturing process.

Furthermore, since the thermal conductivity deteriorates due to the inclusion of oxygen, the optimum recording power decreases, and recording sensitivity is improved.

(Embodiment) FIG. 1 is a sectional view showing the structure of an optical disc according to an embodiment of the present invention. In FIG. 1, a substrate 1 is a transparent organic resin substrate such as a polyolefin resin having an outer diameter of 130 mm, an inner diameter L of 5 mm, and a plate thickness of about 1.5 mm, on which a tracking guide group is formed. A transparent bonding layer 2 made of oxide (Styx) is formed, and on the second transparent bonding layer 2 B, Al2 + S L
A transparent protective layer 3 is formed of an oxynitride of at least one element selected from , In, for example, an oxynitride of St (SiOyNz). Then, on the transparent protective layer 3, a recording layer 4, for example, an RE-
A TM film is formed, and an interference layer 5 made of the same material as the transparent protective layer 3 and a reflective layer 6 made of an aluminum film are sequentially formed thereon.

Here, the silicon oxide constituting the transparent bonding layer 2 is Si
When expressed as Ox, the oxygen composition ratio X is 0.6≦X≦1.
It is preferable to select a value in the range of 5.

The SiOx film is formed by sputtering a SiO target with Ar gas or a Si target with Ar-02 mixed gas, and the oxygen composition ratio X changes depending on the sputtering conditions, but when X<0,6 This is undesirable because the light transmittance of the film (in other words, the light reflectance of the disk) is significantly reduced, and when x>1.5, the bonding property with the transparent organic resin substrate 1 is reduced. 0.6≦X≦1.
If it is 5, there is no problem in practical use, but more preferably it should be set to a more appropriate value depending on the field of application of the optical disc. For example, when it is applied to consumer memory where the storage environment is harsh, the optical reflection of the disc should be set. A composition range of 0, 6 ≦ A suitable composition range is 1≦X≦1.5, where X can increase the optical reflectance of the disk.

On the other hand, the oxynitride Me Oy N constituting the transparent protective layer 3
z (Me is a Ma group element or IVa group element) is M
eNitride target (BN, A)N.

S L3 N4, Ge3 N4, etc.) is sputtered with Ar gas without bias, or Me sputtered (B).

A, ff, SL, Ge, In, etc.) can be obtained by non-bias sputtering with N2Ar mixed gas.

That is, a nitride film obtained by low-temperature (substrate temperature ≦100° C.) non-bias sputtering generally incorporates oxygen due to residual impurities in the sputtering device, forming an oxynitride. The composition ratio of this oxynitride shifts from the stoichiometric composition ratio. The total amount of oxygen mixed in and the deviation from the stoichiometric composition vary depending on the purity of the target used, the pressure of the sputtering gas, the degree of vacuum before introducing the sputtering gas, etc., but at an oxygen concentration of y>0.4 or more, the recording layer This is not preferable because the protective function of Also, y+z<0.
5 is not preferable because the light transmittance decreases, and furthermore, y
+z>1.5 is not preferable because the film becomes porous and unstable. From the viewpoint of protection function, y-O is the most preferable, but it is difficult to obtain a pure nitride film of y-0 by non-bias sputtering, which imposes a small heat load on the substrate, and in practical terms, 0.05≦ y≦0.2 is appropriate from the viewpoint of both protection function and productivity.

From the viewpoint of recording sensitivity, the larger y is, the better. In other words, oxygen in the oxynitride has the effect of lowering the thermal conductivity of the transparent protective layer 3 and reducing the heat loss when the recording light beam passes through the protective layer 3, so the oxygen composition ratio y is increased. The higher the recording sensitivity, the higher the recording sensitivity. In order to keep the recording sensitivity high to a certain extent, it is appropriate that 0.2≦y≦084.

In this way, by using the SiOx film as the transparent adhesive layer 2 and the Me Oy Nz film as the transparent protective layer 3, the requirements for adhesion, protection performance of the recording layer (memory life), productivity, and recording sensitivity can be simultaneously satisfied. Moreover, if each composition ratio is selected within the above-mentioned range, more preferable results can be obtained.

Note that polymethyl methacrylate, polycarbonate, epoxy, polyolefin, etc. can be used as the material for the transparent organic resin substrate 1, but experimental results show that among these, polyolefin and epoxy have the highest adhesion properties. It was confirmed that the effect was obtained.

Further, the material of the recording layer 4 in the present invention is not particularly limited as long as it can be recorded with light, but metal-based, semiconductor-based, and chalcogen-based materials that themselves have poor adhesion to the transparent organic resin substrate 1 are used. It is particularly effective in the case of metallic materials (for example, RE-7M film) that have poor oxidation resistance by themselves.

Next, an embodiment of the method for manufacturing an optical disc according to the present invention will be described. In manufacturing the optical disk having the structure shown in FIG. 1, transparent bonding layer 2. Transparent protective layer 3. Recording layer 4.
The interference layer 52 and the reflective layer 6 were all created by non-bias magnetron sputtering according to the following procedure.

The above-described polyolefin substrate was used as the transparent organic resin substrate 1, and after installing it in a sputtering device,
Exhaust to -6 Torr and add 5N grade Ar gas to 7 Torr.
0800M was introduced, and the gas pressure was set to 5 x 10-3 Torr. In this state, 300W RFm is applied to the SiO target.
Applying force and performing sputtering for about 20 minutes, about 100
S i Ox Jli was formed on the substrate 1 as the transparent bonding layer 2 of zero stock.

Next, the gas was replaced with 1O% N2Ar mixed gas, and Y2O
A main RF power of 500 W was applied to a Si3N4 target containing 1% of S3 as a binder, and sputtering was performed for about 10 minutes.
An i Oy Nz film was formed on the transparent protective layer 2 .

Next, the gas was replaced with Ar gas and the power was applied to the substrate 1 at 300W.
of the transparent protective layer 3 for 5 minutes.
After sputter etching and cleaning the surface, a DC voltage is applied to the Tb target and the Co target to perform binary simultaneous sputtering for 40 seconds, and about 250 TbCo films (approximately 250 in stock) are deposited on the cleaned transparent protective layer 3. The recording layer 4 was formed with a composition containing more Tb than the compensation composition.

Next, the gas was replaced with a 10% N2-Ar mixed gas, and the interference layer 5 was formed to a thickness of about 1000 mm in the same manner as the transparent protective layer 3. After the gas was replaced with Ar, the A ivy layer was formed. - RF power of 300 W was applied to the target and sputtering was performed for 10 minutes to form about 1000 A reflective layers 6 to complete the series of film formation, and the optical disk was taken out of the sputtering apparatus.

The optical disc thus obtained was irradiated with a probe light with a wavelength of 830 nm from the first surface of the substrate to determine the disc reflectance R.
When we calculated the coercive force He at the rotation angle θ as much as possible,
R-20%, θ=0.8deg, He-8kOe
was gotten. Also, the recording power is 5mW.

Recording was carried out on an optical disc at a recording magnetic field of 4000e, a frequency of 1.1 MHz, and a disc rotational speed of tzoorp. When the reproduction C/N (carrier-to-noise ratio) was examined, a good value of 52 dB was obtained.

Next, this disk is JIS C5024 (1978)
After being subjected to the Z/AD acceleration cycle test specified in
When similarly evaluated, R-20%, θk -0,8d
cg.

A reproduction C/N of -52 dB, the same numerical value as in the accelerated deterioration test, was obtained, and it was confirmed that the optical disc had no deterioration at all in the Z/AD acceleration cycle test. Furthermore, the optical disc exhibited a mirror surface (the group surface was rainbow-colored) over the entire surface before and after accelerated deterioration, and there was no occurrence of peeling.

Next, in order to optimize the composition of the transparent bonding layer 2 (SiOx film), a Si target and a 5i02 target were simultaneously sputtered to form 5tox films with different X to a thickness of 1000 layers as the transparent bonding layer 2. Thereon, a transparent protective layer 3, a recording layer 4. An interference layer 5 and a reflective layer 6 were formed. Reproduction of the optical disc thus obtained C/
The results of evaluating N are shown in FIG.

As shown in FIG. 2, in the range of X<0.6, the disk reflectance was too low (R<10%) and tracking and focusing were impossible, making it inoperable. When X≧0.8, it is possible to operate with R≧15%, and the reproduction C/N increases as X increases because the disk reflectance increases, and when X≧
At 1.5, it was constant at 55 dB. When six optical disks with X≧0.6 (reproduction C/N is plotted in FIG. 2) were subjected to a Z/AD acceleration cycle test, X≧1.
The disc of No. 5 suffered significant delamination during the accelerated deterioration test, making it impossible to evaluate, whereas the disc with X≦1.5 did not exhibit delamination at least on the group surface, and
After the accelerated test, the reproduced C/N of the samples No. 1 and 5 maintained the same value as before the accelerated deterioration.

From the above experimental results, it is clear that SiOx constituting the transparent bonding layer 2
The appropriate oxygen composition ratio X is in the range of 0.6 to 1.5,
From the top of the adhesion range, the range is 0.6 to 0.9, and the reproduction C
It was found that the optimum value for /H is about 1.1 to 1.5.

Next, evaluation was performed by using SiO as the transparent bonding layer 2, using a SiOy Nz film as the transparent bonding layer 3, and changing the sputtering conditions to change y+Z. Although y and 2 vary depending on the purity and density of the target used, the purity and pressure of the sputtering gas, the residual gas of the sputtering equipment, etc., here, in order to optimize y and z, we will use a SiO target and a Si3N4 target. was adjusted by simultaneous sputtering of two elements while changing the input power ratio, and layers other than the transparent protective layer 3 were prepared according to the above example. First, a transparent protective layer 3 was created using pure A gas. In this case, SiO
Regardless of the power input to the target and the Si3N4 target, y+z was maintained at approximately 0.9, and only y changed. y
Optical disks were created by changing the values from 0.05 (sputtering only on Si3N4 target) to 0.9 (sputtering only on SiO target), and the coercive force Hc, reproduction C/N,
When we investigated the optimal recording power (the power at which the second harmonic is the lowest) and its changes over time, we found that y immediately after disc creation.
When ≦0.4, He-8kOe (Tb excess) is constant, and when y>0.4, the effective Tb composition ratio decreases as y increases, Hc increases, and decreases by changing the Kerr hysteresis loop sense. , He-6koc at y-0,9
(Co excess). Moreover, the playback C/N is y≦0.
In 4, the values were all 52 dB, but in 4, where y>o, it gradually decreased as y increased, and in y-0, 9, there was a lot of jitter, and it decreased to 45 dB. Also, the optimum recording power P is 0
．． 05≦y≦0.2, it was 5mW, but y>0.2
(that is, the recording sensitivity improved), and was 4.5 mW at l-0,4 and 4 mW at y-0,9.

After leaving these optical discs under accelerated deterioration conditions of 65°C and 95% R, H for one week, they were evaluated again.
At ≦0.2, both Hc and C/N remained the same as before accelerated deterioration, but at 0.2≦y≦0.4, the reproduced C/N was 50 dB.
(due to an increase in the amount of jitter), when y>0.4, He shifted to the side where Tb further decreased compared to before accelerated deterioration, and when y>0.6, it became an in-plane magnetized film.

This result shows that when the concentration of oxygen mixed in the transparent protective layer 3 is high (Y>0.4), a part of the recording layer 4 formed on the transparent protective layer 3 is oxidized (in the case of a TbCo film, This is because the oxidation of the interface between the transparent protective layer 3 and the recording layer 4 progresses during accelerated deterioration tests. Conceivable.

Furthermore, the optimum recording power is considered to decrease as y increases (that is, the recording sensitivity improves) because the more oxygen there is in the transparent protective layer 3, the worse the thermal conductivity of the protective layer 3 becomes.

From the above results, it is clear that S i O constituting the transparent protective layer 3
y The oxygen composition ratio y in the Nz film has a practical protective function if y≦0.4, and has an almost complete protective function if y≦0.2, so y ≦
It can be seen that 0.2 is preferable, and when higher recording sensitivity is required, the range of 0.2≦y≦0.4 is preferable.

Next, the formation of the transparent protective layer 3 was performed using A of the Si3N4 target.
When the protective function was investigated by making a disk by sputtering in r-N2 gas and increasing the N concentration in the film, it was found that y was kept at approximately 0.05.
．． 05N z, if y+z, that is, z+0.05, exceeds 1.5, there will be an excess of N, and the protective function for the recording layer 4 will be insufficient (formation of interfacial nitrides or SiON
It was found that this is thought to be due to the fact that the Z film is porous.

Next, the transparent protective layer 3 was formed using 81 targets and 5L3N.
When a disk was created by dual-component simultaneous sputtering using four targets of Ar gas, y
When z, that is, z + 0.050.05, is 0.5 or less, the attenuation of light in the transparent protective layer 3 becomes large and the disc reflectance decreases, causing tracking and
It was unable to focus and became inoperable. From these results, it was found that S i Oy Nz constituting the transparent protective layer 3
It is preferable that y and z in the film are in the range of 0.5 to 1.5.

As mentioned above, a transparent bonding layer (SiO
x film) and a transparent protective layer (Sicy Nz film) to find the optimal values of x, y, and z.
The value of z can change depending on the sputtering equipment, sputtering conditions, etc. even when the above-mentioned sputtering method is not used, that is, when a simple SiO target or Si3N4 target sputtering method is used, and the sputtered film may change unintentionally. Since contamination of oxygen and shifts from the stoichiometric composition occur, the present invention provides numerically clear boundaries to these uncertainties.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof. For example, in the example, a Si Oy Nz film was used as the Me Oy Nz film constituting the transparent protective layer, but as Me, in addition to Si, B, AI! , Ge,
Similar results were obtained using In, etc., and in short, Me was B, A, St.

It may be at least one element selected from In. Oxynitrides of elements other than these, such as Ti, Ta, V
, W, Nb, etc., y≦0.4, 0.5≦
A composition in the range of y+z≦1.5 is not suitable because the film becomes opaque and interferes with the operation of the optical disc.

In addition, in the above embodiment, a TbCo film was used as an example of the recording layer, but the recording layer material can be any RE-TM other than the TbCo film.
The present invention is effective for films, and also for RE-TM films, external metal films, semiconductor films, chalcogen films, and the like.

[Effects of the Invention] The optical disc according to the present invention includes a transparent protective layer made of silicon oxide and B on a transparent organic resin substrate.

A) It has a structure in which a transparent protective layer made of an oxynitride of at least one element selected from Si and In is laminated, and it has good adhesion to the recording layer and has excellent protection performance for the recording layer. To form a transparent protective layer made of nitride,
Compared to conventional products that use a nitride or carbonitride film as a protective layer that does not contain oxygen, the manufacturing process is simplified because there is no need for complicated manufacturing methods to prevent oxygen from being contained. , which significantly reduces manufacturing costs.

In addition, the transparent protective layer contains oxygen and has poor thermal conductivity, which can reduce the optimal recording power.
Recording sensitivity is improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an optical disc according to an embodiment of the present invention, and FIG. 2 is a reproduction C/H of the optical disc according to the embodiment.
1... Transparent organic resin substrate, 2
...Transparent bonding layer, 3...Transparent protective layer, 4...Recording layer, 5...Interference layer, 6...Reflection layer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 x (Si Ox a 1L14: L, G) Figure 2

Claims (4)

[Claims] (1) In an optical disc that records and reproduces information by irradiation with a light beam, a transparent bonding layer made of silicon oxide is provided on a transparent organic substrate, and an acid of at least one element selected from B, Al, Si, and In is used. An optical disc characterized in that a recording layer is formed with a transparent protective layer made of nitride interposed therebetween. (2) The silicon oxide constituting the transparent protective layer is SiO_
The optical disc according to claim 1, characterized in that it is represented by the compositional formula x (0.8≦x≦1.5). (3) The oxynitride constituting the transparent protective layer is MeOyNz (Me is at least one element selected from B, Al, Si, and In, y≦0.4, 0.5≦y+
The optical disc according to claim 1, characterized in that the optical disc is represented by a compositional formula of z≦1.5). (4) The optical disc according to claim 1, wherein the recording layer is made of a rare earth-transition metal amorphous alloy thin film.