JPH038147A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disk with which the control of a thermal conductivity and refractive index is easy and which has high reliability by forming an underlying film formed of an Sn-Se material between a plastic resin substrate and a recording film provided thereon. CONSTITUTION:The underlying film 2 is formed of the Sn-Se material by a vacuum vapor deposition method on the substrate 1 made of the plastic resin. The information recording film 3 and a protective film 4 are provided on the film 2 to form the optical disk. the film 2 is formed by setting Sn and Se in two vapor deposition boats and controlling the current to be passed to the boat, by which the desired compsn. value is obtd. The thermal conductivity is controlled by controlling the Sn/Se ratio thereof, by which the temp. distribu tion of the film 3 is controlled to desired characteristics. The film 2 has a low pinhole density and further, the coefft. of thermal expansion exists between the coeffts. of thermal expansion of the metal and the substrate material and, therefore, internal stresses are relieved. the optical disk having the high reliabil ity is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to optical recording in which recording, reproduction, or erasing is performed using laser light. The present invention relates to an optical disc having an excellent protective film or base film.

[Conventional technology]

Optical recording is attracting attention as a high-density, large-capacity file memory. Currently, in addition to the practical use of write-once type optical discs that can be recorded only once, rewritable type optical discs that can be repeatedly recorded and erased any number of times are also on the verge of being put into practical use. By the way, many of the information recording materials used in rewritable reversible optical discs contain elements that are active against water and oxygen in the atmosphere, which causes corrosion and makes it impossible to ensure the reliability of the disc. This has been one of the difficulties in promoting practical application. To solve this problem, (1) improve the corrosion resistance of the information recording material itself; (2) Countermeasures have been taken, such as covering the information recording material with an effective protective film or using the above-mentioned rain sound.

In particular, when adopting the above-mentioned method of covering with a protective film, ■ the density of film defects such as pinholes is low; ■ it does not react with the information recording material; ■ the optical constants such as refractive index are appropriate;
Appropriate thermal conductivity.

All of the following conditions must be met at the same time.

Searches for materials that satisfy this condition are being actively conducted in various places, and an example of this is Japanese Patent Application Laid-open No. 195743/1983.

[The invention aims to solve a! M]

With the above-mentioned conventional technology, it is difficult to simultaneously satisfy conditions such as low defect density, non-reaction with recording materials, control of refractive index, and control of thermal conductivity, and protection for optical disks that can overcome the deterioration of disk characteristics and reliability. No membrane was found.

An object of the present invention is to provide a material that has low pinhole density, suppresses reactivity with information recording materials, and can control thermal conductivity and refractive index, thereby producing highly reliable and high-performance optical discs. Our goal is to provide the following.

[Means to solve the problem]

The above object can be achieved by using a 5n-8e type material as the FT film material. What is the system of this composition?

By controlling the S n /S a ratio, the above-mentioned characteristics required for a protective film material can be easily controlled.

To explain in more detail, the most important problem is light absorption, which is caused by containing 55% to 95% Se, which results in low light absorption (~0)) and a tB refractive index of 2 or more, which requires optical properties. It can provide suitable properties both as a base film and as a protective film material that requires stability. here,
The base film needs to have a refractive index difference of 0.4 or more from the substrate material in consideration of light interference effects. In addition, in order to improve the adhesion between the substrate and the underlying film, it is effective to heat the substrate before forming the film.

[Effect]

By controlling the S n /S s ratio, the temperature distribution on the conjunctiva during laser beam irradiation can be controlled. S
Increasing n increases the thermal conductivity, and conversely, increasing Se decreases the thermal conductivity. In other words, by keeping the composition within a range where the light absorption rate is small and controlling the composition ratio of the 5n-3e film, the thermal conductivity of the 5n-5e film can be controlled, and the temperature distribution of the information recording film can be adjusted to desired characteristics. Can be controlled.

As a result, (1) the recording/erasing characteristics of the disk are selected as desired, and (2) fluctuations in the reproduction output due to repeated recording/erasing are suppressed. (3) The first effect of controlling the shape of the recording magnetic domain can be obtained.6 Furthermore, on a substrate made of plastic resin such as polycarbonate, polysulfone, polyolefin, polymethyl methacrylate, acrylic resin, and photocurable resin, When this 5n-3e film is formed, weak chemical bonds or chemical adsorption occur between atoms in the material and atoms in the substrate material, resulting in a significant improvement in adhesive strength3. If the film is formed while being heated to an extent that does not change its quality, the above effect will be even stronger. Also.

When the ratio of Sn and Se is within the above-mentioned range, the stress inside the film and at the interfaces of each layer is low, and separation etc. are less likely to occur.

As described above, when a 5n-3e material is used as a material for a protective film or underlayer of an optical disc, it has a low pinhole density, excellent chemical stability, and a high protective effect. In addition, it is necessary to control the A'+l refractive index and film thickness of the optical disc base film, which may cause multiple interference.
It can also be easily controlled. Furthermore, by controlling the ratio of metal to chalcogenide, the thermal conductivity can be increased or decreased. Thereby, the temperature distribution of the information recording film can be controlled, the recording/erasing sensitivity of the disc can be arbitrarily set, and compatibility with the disc drive can be freely achieved. Furthermore, by providing this film, it becomes possible to dissipate heat in the direction parallel to the substrate, making it easier to cool down the information recording film, so the maximum temperature of the recording film increases as the thermal conductivity increases. There is no decrease in playback output when recording/erasing is repeated.

〔Example〕

The details of the present invention will be explained below using Examples 1 to 3.

[Example 1] FIG. 1 is a film diagram showing the cross-sectional structure of the optical disc manufactured in this example. 1 is a disk substrate. The substrate may be a plastic substrate with guide grooves or a glass substrate with guide grooves formed on the surface using the photopolymer method (2P method).
Alternatively, a glass substrate with guide grooves formed directly thereon may be used.

A 5n-8e film of the present invention was formed as a base film 2 on this substrate 1 by vacuum evaporation. First, Sn and Se were set in two deposition boats, and the tt flow flowing through each boat was controlled to obtain a film having a desired composition value. On this occasion,
When the substrate was heated to about 80° C., the composition of Sn and Se was set to 66 at % in this example. The refractive index at this time is 2.3. The l/J thickness is 750 people.

The information recording film 3 is "l'bzaF" with a thickness of 800 people.
An eelcotxNba amorphous alloy film was formed by sputtering.

Using an alloy target having the above composition, A
The discharge gas pressure was set to 5×10 −8 Torr, and the input RF vehicle power density was set to 4.2 W/cof. The magnetic and magneto-optical properties of this recording film 3 are such that the Kerr rotation angle θ is 0.
．． 34°, coercive force Ha is l OK Oe, compensation temperature Tc
omp is 70°C, and Curie degree rc is 200°C. Then, a protective film 4 using a 5n-Se alloy film was formed again by vacuum evaporation. Here, this protective film composition was prepared with arbitrary sensitivity by changing the Se content between 55 at% and 95 at%. In addition, as a comparative example, 5iO, which is widely known as a base film and protective film material, was used.
A disk using z was manufactured.

First, the relationship between the Se content of the 5n-8e film and the light absorption rate of laser light with a wavelength of 830 nm is shown in Figure 2.
When the e content is 62 at% or more, the light absorption rate is almost zero. This means that the attenuation of the laser light incident for information reading is small, and that there are few low codes of the 4f1 intensity. Therefore, when using a 5n-3e film as the base film or protective film on the laser beam incident side, it is preferable to use a film having the above composition range.

FIG. 3 shows the recording/reproducing characteristics when a 5n-8e system (S n S e2 film) was used as the underlayer and the protective film composition was varied. As the protective film 4, the atomic ratio of Sn and Se is 5.
/95.27/75 and 45155 were produced. According to FIG. 3, as the Se content increases, the minimum recording power decreases, that is,
It can be seen that the recording sensitivity has become crystalline. On the other hand, in the comparative example, the recording sensitivity was low, and the recording sensitivity could not be controlled other than by changing the protective film thickness. C/N is 1800r
When recording at 1.5T synchronization at pm, 3011foφ position, 49dB was obtained in the case of one example, whereas
In the comparative example, it was 46 dB, an improvement of 3 dB.

Furthermore, when this disk was subjected to a heat cycle test of -20°C to 60°C 50 times, peeling occurred in a comparative example in which a 5iOz base film and a protective film were formed on a plastic substrate, whereas 5n No peeling, cracking, etc. occurred in the disk using the -8e system. This is S
This is because the n-Se film has a coefficient of thermal expansion in the middle range of information recording films and relieves internal stress generated in the film.

Next, FIG. 4 shows the results of a reliability test of this disk. That is, the produced optical disc was heated to 80°C-85°C.
%RH, the change in defect rate over time was measured. First, in this example, Sn
For any protective film with a ratio of 5/95°45155 to
bit).

Both of these had a defect rate of 7X10"-6 (cases/bit) even after being left in the above environment for 2000 hours.

The increase was small. However, in the comparative example, 5X1
0-'(cases/bit) The defect rate increased approximately 10 times.

In this example, an example was shown in which the 5n-8e layer was formed by vacuum evaporation, but even if the S n -S c film is formed by sputtering or ion plating, the composition and film thickness may vary. As long as it was controlled, no difference in performance was observed depending on the manufacturing method.

[Example 2] In this example, Ar was added to the reaction residue when forming the base film.
5n-8e was sputtered using a mixed gas containing . The cross-sectional structure of the manufactured disk was the same as that of Example 1, as shown in FIG.

The disk was produced according to the procedure shown below. First, 5n-3s was placed on a substrate 1, which was made of a plastic or glass disk having guide grooves on its surface and guide grooves made of ultraviolet curable resin.
A base film 2 was formed by sputtering. A SnSez sintered target was used as the target, Ar/02 (=90/10) mixed scum was used as the discharge gas, and the discharge gas pressure was set to 1 x 10'-2 (Torr).
The input RFJ force was set to 0.7 (W/Cl11), and a film with a refractive index of 2.0 and an absorption coefficient of O1 and a film thickness of 850 mm was formed.

An information recording film 3 and a protective film 4 were formed thereon using the same method and conditions as in Example 1.

The inner diameter of this disk is 30n+n+φ, rotation speed: 240Orpm, pulse width 70nsec, period 1.5T
FIG. 5 shows the dependence of the reproduction output on the laser power when recording was performed. A comparative example is a case where 5iaN4 is used for the protective film and the base film. When the 5n-3e material of this embodiment is used, the sensitivity is increased because the thermal conductivity is lower than that of Si3N+. The C/N was also determined at 8IQ under the same conditions as in Example 1, and was C/N = 49 dB.

On the other hand, in the comparative example, the C/N was as low as 46 dB. This disk was subjected to a heat cycle test at -20 to 60°C. As a result, in the disk using the material of the present invention, no peeling or cracking occurred even after 800 repetitions or more, but in the comparative example, abrasion already occurred after about 100 repetitions. By the way, S with only Ar without oxygen
In the film prepared by sputtering nSe2, peeling occurred after about 500 N0 heat cycles.

As in this example, Ig! 1 containing reactive gases such as
By sputtering in a medium atmosphere, the surface of the substrate is clarified, and bonds are formed between the atoms on the surface of the substrate and the underlying film material.
In addition to the buffer layer effect of suppressing peeling caused by the difference in thermal expansion between the information recording layer and the substrate, the adhesive force can be increased.

Figure 6 shows the disk produced in this example at 80°C.
It shows the change in defect rate over time when left in 85°C RH. A comparative example is a case where 5iaN+ is used for the protective film and the base film. According to the results, in the case of this example, what was 5 x 1 O-6 (bits/bit) at the initial stage of disk production was 7
0-1′! There was only a slight increase (items/bit). On the other hand, in the comparative example, 6X10-B (items/bit)
An increase in the defect rate of more than one order of magnitude was observed. In this way, the 5n-8 of this example sputtered with Ar102 gas
The e-type protective film and base film have extremely high protective performance.

[Example 3] The cross-sectional structure of the optical disc manufactured in this example is similar to the schematic diagram shown in FIG. As the substrate 1, a plastic substrate having uneven guide grooves on the surface or a substrate having uneven guide grooves formed on the surface by the 22 method was used. First, a base film 2 was formed on this substrate 1 by a vacuum evaporation method. Sn and Se were set in two deposition boats, and the film composition was adjusted to a desired value by controlling the current flowing through the boats. The substrate was rotated around its axis during the deposition. The molar ratio of Sn and Se produced was O/100°20
/80, 33/67, and 55/45, and Membrane No. 4 has 750 people.

TbxsFe is formed on the base film 2 as an information recording film 3.
An RsCox7Nb2Pt,s film was formed in the same manner as in Example 1. Finally, a protective film 4 of 41,500 SiO was formed on the target by sputtering. The conditions for forming the Si*2 film were as follows: Ar was used as the discharge gas, a Si* sintered body was used as the target, the input RF power density was 4.2 W/cd, and the discharge gas pressure was 1×10 −2 Torr.

Using the disk of this example, the rotation speed was 2400 rβm and the disk was synchronized at the innermost circumference (30 mm) position for 1.5 T.

The signal was recorded with a pulse width of 70 ns, and the dependence of the reproduction output on the recording laser power was investigated, and the carrier-to-noise ratio (C
/N) was calculated. As a result, the base film composition becomes S n /
20/80 and 33 dB compared to 43 dB for discs with S e = O/100 and 55/45.
/67 had the highest C/N of 48 dB.

In addition, when we investigated the change in defect rate when these four types of disks were left at 80°C and 85% RH, it was 5X10-' (cases/bit) at the initial stage of disk production, but after 2000 hours After leaving it, Sn/5e=33/
In the case of a disk using a base film with a composition of 67.55/45, the increase is extremely small at 7 X I Q"-' (items/bit), but when Sn/5e=O/100.20/80, it is 5 X 10 -'(items/bit) and increased significantly.Like this.

When a 5n-3s base film is used, the protection performance and disk performance differ depending on the composition. Sn/Se ratio 33/6
When a base film having a rating of 7 was used, both of the above performances were satisfied at the same time and the bonding was the best.

〔Effect of the invention〕

According to the present invention, desired disk characteristics can be easily obtained because the thermal conductivity and optical constants of the base film can be freely controlled. This material also has a low pinhole density, which increases the reliability of the disk. Furthermore, the coefficient of thermal expansion of this material is intermediate between that of the metal and the substrate material, making it useful for alleviating internal stresses caused by the difference in coefficient of thermal expansion.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of an optical disk according to an embodiment of the present invention, FIG. 2 is a relationship curve between Sea degree and light absorption rate in the 5n-8e system, and FIGS. 3 and 5 are according to the present invention. Figure 4 shows the laser output dependence characteristic diagram of the playback output of the disc according to the embodiment of the invention.
Figure 6 shows the change in defect rate over time showing the corrosion resistance performance of the optical disk according to the embodiment of the present invention. 111 constant diagram. DESCRIPTION OF SYMBOLS 1...Substrate, 2... Base film, 3... Information recording film,
4...Protective film. Houki Kankyo Sendai Diagram L-zu-tka (Job W) Chapter 4 l Mosquito placement time (11 books)

Claims (1)

[Claims] 1. In an optical disk that records, reproduces, or erases information using a laser beam, a layer formed of a material consisting of Sn and Se so as to be in contact with the interface of one or both of the information recording layers. What is claimed is: 1. An optical disc characterized in that a layer is provided. 2. The composition of the material consisting of Sn and Se is 55% Se.
2. The optical disc according to claim 1, wherein the optical disc is made of a material containing at least 95 at%. 3. When the material consisting of Sn and Se is provided between the substrate and the information recording layer or on the laser beam incident side for recording, reproduction, or erasing, the refractive index of the material is in contact with the substrate material or the information recording layer. Claim 1 or Claim 1, characterized in that the material layer made of Sn and Se is formed so that the difference in refractive index between the material layer and the material of the layer in contact at the other interface is 0.4 or more. The optical disc described in item 2. 4. The material layer made of Sn and Se is formed by a thin film forming technique such as a sputtering method, a vacuum evaporation method, an ion plating method, or a chemical vapor deposition method. The optical disc according to any of paragraph 3. 5. In forming the material layer made of Sn and Se, the film thickness or composition is selected, thereby controlling the temperature distribution of the information recording film. An optical disc described in Crab. 6. The optical disc according to claim 1, wherein the material layer made of Sn and Se is formed on a resin substrate or a substrate whose outermost surface is a resin layer. 7. A claim characterized in that the resin material forming the substrate is at least one selected from the group consisting of polycarbonate, polysulfone, polyolefin, polymethyl methacrylate, acrylic resin, and photocurable resin. The optical disc according to No. 6. 8. Chemical bonds or interatomic bonds such as chemical or physical adsorption are formed between the constituent atoms of the material layer consisting of Sn and Se and the resin material forming the substrate. 7. The optical disc according to claim 6, characterized in that: 9. In forming the material layer made of Sn and Se, select the film thickness or composition, and thereby make the substrate and Sn
and Se, or a material layer consisting of Sn and Se and an information recording film, or a material layer consisting of Sn and Se, to alleviate internal stress generated between the information recording film and the substrate. An optical disc according to any one of claims 1 to 3. 10. Claim 1, wherein the material layer made of Sn and Se has a sufficiently small absorption of light that can be ignored.
The optical disc according to any one of items 1 to 3. 11. The optical disk according to claim 1, wherein the material layer made of Sn and Se is formed at a substrate temperature higher than room temperature.