JPS63102049A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To improve resistance to heat and moisture by providing a thin recording film layer which is changed in state by photoirradiation and a reflection layer contg. tellurium, palladium and oxygen on a substrate. CONSTITUTION:The reflection layer 2 consisting of Te, Pd, and O is provided on the substrate 1 and a dielectric layer 3 is provided thereon; further, the thin recording film layer 4 is provided thereon to constitute an optical information recording medium. An information signal is recorded or reproduced by projecting laser light 7 to such medium. The reflection layer consisting of Te, Pd and O is formed by using a vapor deposition device which permits vapor deposition with 3 sources and deposits TeO2, Te and Pd by evaporation from the respective sources. Te and PdTe exist dispersedly in the matrix consisting of TeO2 of the Te, Pd and O films obt. in such a manner and since TeO2 acts to suppress the oxidation of Te and PdTe is an extremely stable compd. and is hardly oxidizable, the thin film having the good moisture resistance as a whole is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information recording medium that records and reproduces information at high speed and with high density using light, heat, and the like.

BACKGROUND OF THE INVENTION When laser light is converged by a lens system, a small light spot with a diameter on the order of the wavelength of the light can be created. Therefore, it is possible to create a light spot with high energy density per unit area even from a light source with a small output.

Optical information recording media utilize this for recording and reproducing information.

Hereinafter referred to as "optical recording medium" or simply "medium"3"-
” states.

The basic structure of an optical recording medium is that a recording thin film layer whose state changes in some way by laser spot light irradiation is provided on a substrate with a flat surface. The following methods are used to record and reproduce signals. That is, the medium is rotated by a rotating means such as a motor, and laser light is focused and irradiated onto the recording thin film surface of the medium by a lens system. The recording thin film absorbs the laser light and increases its temperature. When the output of the laser beam is increased above a certain threshold, the state of the recording thin film changes and information is recorded. This threshold value is a quantity that depends on the characteristics of the recording thin film itself, the thermal characteristics of the base material, the relative speed of the disk to the light spot, etc.

The recorded information is obtained by irradiating the recording section with a laser beam spot with an output sufficiently lower than the threshold value, and some optical characteristics such as the transmitted light intensity, reflected light intensity, or their polarization direction are different between the recorded section and the unrecorded section. Detect and play.

Therefore, materials and structures that change state with small laser powers and exhibit large optical changes are available. As a countermeasure to this problem, there is a recording medium structure called a tri-layer structure (Tri-1 ager 5 structure) proposed by RCA, USA. (Bell and Spong (B)
ELL and Spong), IEEE Journal of Quantum Electronics
ics), Vol QE-1a ni 7 Ju
ly 197s).

In addition to the recording thin film layer, this structure has a metal reflective layer sandwiched between transparent dielectric layers, and utilizes the interference effect of light to increase light absorption efficiency and achieve large changes in reflectance. .

Further, even if the recording thin film is thin, absorption efficiency can be ensured, and a recording medium with high absorption energy per unit volume of the recording layer and high sensitivity can be obtained.

Problems to be Solved by the Invention Although the three-layer optical recording medium has the above-mentioned advantages, it also has the following problems.

Since a metal with high thermal conductivity is used for the reflective layer, the absorbed heat escapes to the reflective layer and prevents the temperature of the recording thin film layer from rising, which limits the sensitivity.

6 The vane or the metal reflective layer oxidizes over time and the reflectance changes, causing recording sensitivity, reflectance changes, etc. to deteriorate over time. Noise also increases. As a result, the life of the entire medium is short.

Means for Solving the Problems A recording thin film layer whose state changes upon irradiation with light and a reflective layer made of tellurium (Te), palladium (Pa) and oxygen are provided on a substrate.

Effects According to the present invention, a reflective layer can be formed using a material with low thermal conductivity, and a thermally efficient three-layer optical recording medium can be obtained.

Further, the reflective layer has good heat resistance and moisture resistance, and can improve the life of the recording medium.

Example As shown in FIG. 1, Te, Pd, O
A reflective layer 2 is provided, a dielectric layer 3 is provided thereon,
Further, a recording thin film layer 4 is provided thereon to form an optical information recording medium. A laser beam 7 is irradiated onto this medium to record or reproduce information signals.

s'<-'' The reflective layer made of Te, Pd, and O used in the present invention will be described below.

Chemically, the material with this composition consists of T e O2, Te, and PdTe, and is considered to be a mixture thereof. There are several methods that can be considered to form such a material, but a typical one is to use a vapor deposition machine capable of three-source vapor deposition to deposit T e O from each source.
2. Deposit T e p P d. In addition, when using a two-source source, Pd is evaporated from one source, and metal powder that has the effect of partially reducing T e O2 and T e O2f, such as A$, Cu, Fe, Cr, etc., is mixed from the other source. Ta
O2 and Te f are simultaneously deposited, and TaO2°Te is deposited on the substrate.
, forming a mixture of Pd. In addition, when using a single source source, T e O2 when using the above two source source
Pd is also mixed in the source on the side where Te and Te are evaporated,
It is also possible to perform p-evaporation from T e 02 , T e , P d f 1 sources.

The Te, Pd, O film made in this way is T eO2
Te and PdTe are distributed in a matrix consisting of 7
Since PdTe is present as PdTe and has a function of suppressing the oxidation of Te, and PdTe is a very stable compound and is difficult to oxidize, a thin film with good moisture resistance can be obtained as a whole.

Furthermore, the optical constants (refractive index and extinction coefficient k) of the film can take large values due to Te and PdTe, and sufficient reflectance can be obtained as a reflective layer.

Furthermore, it is expected that T e O2, which is an oxide, lowers the thermal conductivity of the film and suppresses heat escaping to the reflective layer during recording.

The characteristics described above depend on the composition ratio of each component.

The amount of T e O2 and the amount of PdTe affect the moisture resistance, and the amount of Te mainly contributes to the optical constant. The thermal conductivity is related to the ratio of TaO2, Te, and PdTe.

In the present invention, the content of oxygen O is 20 to 60 atm % based on the total of Te, O, and Pd, but if it is less than 2 O atm %, the moisture resistance will be poor, and if it exceeds 60 atm %, the optical constant will be low. As a result, it no longer functions as a reflective layer.

Te is an essential component of the reflective layer within the scope of the present invention.

A particularly preferable composition for Pd is 8 to 3 Pd.
5 atm%, and oxygen is 30-55 atm%.

Next, data on composition dependence of reflective layer properties will be shown.

Using an electron beam evaporator capable of three-source evaporation, the sample was evaporated from T e O 2 , T e , and P df sources onto a glass substrate (18 x 18 x t 0.2 M) mounted on a holder rotating at 150 rpm. Created by Vapor deposition was performed at a vacuum level of 1×1σ5 Torr or less, and the thickness of the thin film was 40 nm. The deposition rate from each source was varied in order to adjust the ratio of the number of Te, O, and Pd atoms in the recording thin film.

Elemental analysis results by Auger electron spectroscopy (hereinafter abbreviated as AES) of various optical discs created by the above method,
Table 1 shows the reflectance of the sample film (wavelength: 830 nm; a reflectance of 50 or more is evaluated as ○) and the results of the moisture resistance test. The moisture resistance test was carried out by leaving the sample at 50°C and 90% RH. ○ indicates that some changes were observed, and △ indicates that crystallization progressed and a black pattern was observed, or that the transmittance increased due to oxidation of Te in the film.

(No/Bottom (White) 10''-No Table 1 11'-/゛As is clear from Table 1, a Te, O, Pd-based thin film with a reflectance of 50% or more and good moisture resistance. The composition (6 or more in overall evaluation) is 5 to 40 atm % of Pd and 20 to 60 atm % of oxygen.

A more preferable composition (○ in overall evaluation) has Pd of 8-3
5 atm%, ○ij 30-55 atm%.

From the optical constants of Te34042Pd24 composition in Figure 3,
It shows the results of calculating the film thickness dependence of reflectance when formed on a glass substrate. For comparison, Au(O, 2+5.
04i) and A# (2, os+7.15i) are also shown. As shown in Figure 3, the thickness of the Te, O, and Pd films is 20 mm.
A reflectance of 40 coefficient or more can be obtained at a film thickness of 70 nm or more.
The reflectance is saturated above nm.

Considering thermal effects, the thinner the film thickness, the better, so it can be said that the range of film thickness useful as a reflective layer is 20 to 70 nm.

Au and Al each have a saturation reflectance of 97.

Although it is large at 86 mm, the thermal effect is large and the film thickness is 20 mm.
A value in the vicinity of nm (reflectance of 73% and 77%, respectively) gives rather good results.

In Figure 4 T @ s 4042 P d 24 f 4
Data on changes in reflectance of a sample provided on a 0 nm glass substrate in an atmosphere of 50° C. and 80° C. is shown. A u (2
0nm) +Al (20nm) data are also shown for comparison.

Al is oxidized and its reflectance is halved in 10 days, but Te, O
, Pd film and Au film showed no change for 40 days.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an optical information recording member according to the present invention.

1 is a substrate, and metal 2 is, for example, aluminum.

copper etc., glass such as quartz, pyrex, soda glass etc., or resin 2 such as ABS resin.

polystyrene, acrylic, polycarbonate, vinyl chloride, etc.
Further, as the transparent film, acetate, Teflon, polyester, etc. can be used. Among them, polycarbonate,
When using acrylic plates, etc., transparency is excellent,
This is effective when optically reproducing a formed signal image.

The reflective layer 13''-2 is made of Te, Pd, and O, and is formed on the substrate 1 by vapor deposition, sputtering, etc. as described above.

Reference numeral 3 denotes a layer made of a dielectric material, and any material that forms a homogeneous thin film can be used as the dielectric material.

S 102, T z○2. Oxides such as ZnO and MCl0, carbides such as SiC, nitrides such as SiN and BN, ZnS, and CdS.

Sulfides such as PbS or composites thereof can be used.

The dielectric layer 2 is formed on the reflective layer 2 by vapor deposition or sputtering depending on the material.

For the 4Vi recording layer, a thin film material that can be deformed or have its optical constants changed by laser beam irradiation can be used.

As for those using deformation, Bi, Te, metal thin films containing these as main components, and compound thin films containing Tef are known. Further, as substances whose optical constants change, there are amorphous alkogenides.

T, e l ” ekInitially, Te [As, S,
Si, Se.

Examples are known in which Sb, Bi, etc. are added.

As another embodiment, the one shown in FIG.
−′ is present. In this method, a dielectric layer 5, a recording layer 4, a dielectric layer 3, a reflective layer 2 made of Te, Pd, and O are provided on a substrate 1 in the same manner as described above, and a protective layer 6 made of resin or the like is further provided. It is something. A laser beam for recording and reproduction is made incident through the entire substrate 1. This structure is a practical structure because it protects the recording film from dust and scratches from the outside, but a perforated type cannot be used as the recording film.

Center: Cypress: Transparent polymethyl methacrylate PMMA substrate (tl
, 2) A 100 nm thick ZnS film was formed as a recording layer (Te65G2
A thin film of oSe15)7oSb3° was formed by a four-source electron beam evaporation method, and then ZnS f
It was formed by the sputtering method in the same way as the 170 nm layer. Furthermore, T l
It s 4042Pd24 to form a reflective layer and further PM
MA plate (tl, 2)' was adhered with UV curable resin to form a protective layer. Similar structure with Au and A as reflective layers
A 15" film deposited using the all-electron beam method was also prepared (the film thickness was 20 nm for both Au and Al).
m).

Recording and reproducing experiments were conducted using this sample [NAo, 5] objective lens to converge semiconductor laser light with a wavelength of 830 nm. FIG. 5 shows data on recording power and reflectance change. The change in reflectance was calculated by measuring the amount of reflected light before and after recording using a reproduction light power of 1 mW. As shown in Figure 5, when a Te, O, Pd film is used for the reflective layer, the recording power is 2 m.
It changes with W and is A-4? It was confirmed that the sensitivity was better than that using Au for the reflective layer. Also, when the recording power is increased, the saturation reflectance change value is Au, A/
It can be said that the contribution to the change in reflectance is almost the same as when Au and Al are used for the reflective layer, and the characteristics are comparable to those of Au and Al.

Effects of the Invention The optical information recording medium of the present invention has higher recording sensitivity, better moisture resistance, and longer life than conventional examples.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an optical information recording medium in one embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing another embodiment of the present invention, and FIG. A graph comparing the film thickness dependence of the reflectance of the reflective layer used in the example, Figure 4 is a graph comparing the sensitivity characteristics of the optical information recording medium in the example of the present invention and a conventional example, Figure 5 is a graph comparing the sensitivity characteristics of the optical information recording medium in the example of the present invention and the conventional example It is a graph comparing the moisture resistance of the reflective layer used and the reflective layer used in the conventional example. 1...Substrate, 2...Reflection layer, 3, 5...
. . . dielectric layer, 4 . . . recording layer, 6 . . . protective layer, 7 . . . recording/reproduction source. Name of agent: Patent attorney Toshio Nakao and one other person
Mourning Figure 4 Garden, N time (B) Figure 4 θ 246,9/θ Lelini Buff-(77?W)

Claims (5)

[Claims] (1) An optical information recording medium comprising, on a substrate, at least a recording thin film layer whose state changes upon irradiation with light and a reflective layer containing tellurium (Te), palladium (Pd), and oxygen (O). . (2) The composition of the reflective layer is P relative to the sum of Te, O, and Pd.
d is 5 to 40 atm% and oxygen (O) is 20 to 60 atm%
2. The optical information recording medium according to claim 1, wherein the optical information recording medium has a content of m%. (3) The optical information recording medium according to claim 1, wherein the thickness of the reflective layer is 20 nm≦t≦70 nm. (4) A reflective layer made of Te, Pd, and O is provided on the substrate,
2. The optical information recording medium according to claim 1, further comprising a dielectric layer provided thereon, and further provided thereon a recording layer whose state changes upon irradiation with light. (5) providing a layer made of a first dielectric on a transparent substrate;
A recording layer whose state changes by light irradiation is provided on the first dielectric layer, a second dielectric layer is provided on the recording layer, and Te, Pd, O, etc. are further provided on the second dielectric layer. 2. The optical information recording medium according to claim 1, further comprising a reflective layer consisting of: