JPH0236994A - Information recording medium - Google Patents

Abstract

PURPOSE:To manufacture an information recording medium which has a high sensitivity recording film excellent in signal quality even during high-density recording by using four elements such as tellurium, germanium, bismuth and lead, and defining their composition in an information recording medium which projects an energy beam to a recording film formed on a base and thereby recording information. CONSTITUTION:A recording film consists mainly of four elements such as tellurium(Te), germanium(Ge), bismuth(Bi) and lead(Pb). If its compositional formula is (TexGe100-x) 100-p-qBipPbq, where the percentage of Te atoms in (Te and Ge) is x, that of Bi atoms is p, and that of Pb in the film is q the composition of these elements is such that the ranges of x, p and q are 40<=x<=75, 1<=p<=20, and 1<=q<=20 respectively. If the percentage of Bi or Pb is small and outside the ranges, unfavorable phenomena such as noise increase or CNR deterioration occurs. On the other hand, if the percentage is large, the crystallization temperature is not reached. Consequently, a stable amorphous phase is not easily formed and excellent recording properties are hardly demonstrated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information recording medium, and is particularly used in optical disk devices that record information by irradiation with energy beams such as light and electron beams. The invention relates to information recording media.

[Prior art 1] In a recording method for an optical information recording medium, in a method that uses the difference in optical properties due to the phase change of the medium, for example, the difference in the fouling rate between the crystalline state and the amorphous state, the thin film of the medium itself There are advantages such as no need to change the shape of the film, no problem of contamination due to evaporated matter, and the ability to improve durability by removing the protective film. Various types of materials have been proposed, such as low oxide thin films, 3B-based thin films, and optical thin films.If the composition of these materials is selected appropriately, these materials can be used to absorb energy beams. → By changing the conditions, the amorphous phase and the crystalline phase are reversibly changed (A diagonal installation d "1-V"), the shape of the recording area (hereinafter referred to as mark) with minimal media noise. 1 with excellent) B2 characteristics with constant signal quality and clear mark edges
Customized designs are also available.

These various J, J)! ; When evaluating the performance of a medium with a single composition, the method of determining whether or not a certain standard condition of the media characteristics is to be improved is based on υ
This would be a preferable and rational method in terms of compatibility.

Regarding write-once type recording media, the draft ISO standard is at the stage where it has been finalized, and furthermore, replacement type media,
Standardize write-once CDs based on CD standards.
We are seeing a movement towards this. However, when looking at write-once media, for example, it is not easy to satisfy this draft standard.
It is not easy to develop and release a medium with excellent CNR (hereinafter referred to as CNR) or recording sensitivity.

Among them, Te-Ge thin film materials in particular can be easily made into thin film materials using well-known thin film forming techniques such as vapor deposition Yasbatta. It also has the advantage of being able to make a large difference in the defect rate (recording margin) between the amorphous and crystalline states before and after the phase change, and the characteristics can be controlled over a wide range by adding various elements. Therefore, it is one of the materials that is being actively researched, and several materials M'i+ and compositions have already been proposed.

[Problem to be solved by the invention] Le-e-Ge system (adding various elements to Δ 7J[]
Several proposals have been made to improve the characteristics, such as making them ternary or quaternary. JP-A No. 62-152786 claims that good properties can be obtained by adding various elements to Te-Ge. However, in the example, Ding 1 and Co may be added alone or both to Ding e-13e [
1, and no specific examination or disclosure has been made regarding CNR, media noise, etc., which are important for evaluating actual recording characteristics. When these thin films were actually fabricated and evaluated in accordance with the draft 130 standard, there were problems such as insufficient CNR under high-density recording conditions and a decline in signal quality due to increased noise, making it impractical. For other elements, Co, Co, or a part of Ge may be substituted with other elements, such as the metal elements, Al, and Al.

element, Ti, pb, 3b, △u, 3n, l'3i
1n etc. may be substituted, etc.). In particular, regarding 3i and Pb, even if the characteristics shown in the patent are good, the practical properties of the medium such as 1i) CNR and noise characteristics are not always good. It's a fortune telling job.

Moreover, no effective and empirical knowledge has been disclosed regarding the effects of adding 3i and PB simultaneously to form a quaternary system. Let's talk about recording film: recording sensitivity and speed are important [J1 noise characteristics] Although each has relatively excellent characteristics, the high density required for optical recording media Sufficient C at recording time and 14
It is difficult to obtain NR, and it cannot be said to be a practical shrine.

In JP-A-61-152487, Te-G
Is there a proposal to add ■, ■, V group elements to e?
The gist of it is simply that one of the above elements is added to Dye-Qe.

As an example, 7JIl is added with 3b to Engineering e-Ge.
In addition, T.
Only the effect of adding one of B11n to e-Ge is mentioned.

Furthermore, a thin film consisting of 1-e-Qe and [3i was also proposed in JP-A-62-209741,
Although this recording film allows crystallization recording with a practical high-density recording device, the CNR ratio in high-density recording is still not at a practical level.

In addition, with this composition, if the amount of Bi added is increased, the crystallization temperature will be lowered, leading to a problem in that recording reliability will be lowered.

The present invention improves this problem and adds Bj and F to Ding-e-Ge.
-'b is added at the same time and its composition is within a specific range, it is possible to produce a signal with an appropriate crystallization temperature, excellent record retention, good recording sensitivity, low noise, and a large playback width. The present invention aims to provide an information recording medium with excellent signal crystal quality also in 1).

[Means for Solving the Problems] An object of the present invention is to irradiate a recording thin film formed on a substrate 2 with an energetic beam, and to improve the optical properties of the thin film by heat generated directly or indirectly. In an information recording medium for recording information, the recording thin film is mainly made of four elements: tellurium (T' e ), germanium (Ge), bismuth (Bi) and 100% chloride (Pb), And its composition is represented by the general formula % p: "a atomic number % of Bi in the film formation q: atomic number % of Pb in the thin film If the range of x, p, q is 40≦X, each
Coupled with an information recording medium characterized in that ≦75.1≦p≦20.1≦q≦20.

The recording thin film of the present invention includes tellurium (Te), germanium (
It is mainly composed of four elements: Ge), bismuth (B i ), and lead (Pb), and it is important that its composition (J) satisfies the following compositional formula: (TeXGe100-x)100-p- qB i p
Pbqx: % number of atoms of d e in (Te and Ge) p: % number of atoms of 3i in the thin film q: % number of atoms of pb in the thin film When expressed as, the ranges of xSp and q are 40≦X, respectively.
It is necessary that ≦75.1≦p≦20.1≦q≦20.

If Pb (to Bi'') is small outside of this range, noise will increase or CNR will decrease, which is undesirable.On the other hand, if it is large, an appropriate crystallization temperature will not be obtained.
This is undesirable because it becomes difficult to form a stable amorphous phase and it becomes difficult to exhibit excellent recording characteristics as described in the present invention.

In addition, the range of S, Lll,
A range of 15 is necessarily preferred.

The thickness of the recording thin film is not particularly limited, or it may be possible, for example, to interfere with the anti-QiJ light between the front and back surfaces of the recording film (thickness interference effect that amplifies and covers the anti-1'l ratio change between the Ell crystal phase and the crystalline phase). When used, it can be set in the range of 70 to 120 nm.Also, if a fouling layer is provided on the back side of the record book 1) ψ either directly or via a diffusion prevention layer, approximately half of the thickness can be set. A similar interference effect can be expected if the film thickness is set to .

The reflective layer is Te, tB! It can be composed of a"3 and l"b as main components, and in particular, in the -general composition of record book 11 of the present invention, the total content of Qe is 1 in atomic %. From the total content of 3e and the total content of 3e →
By subtracting the amount of Te into a composition film containing Te, the strain 'W stress between it and the recording layer can be alleviated, and the occurrence of peeling and cracking can be suppressed. Even if diffusion of constituent elements occurs between the two, since they are originally components of the recording layer, deterioration of the characteristics of the recording layer can be suppressed to a minimum, which is preferable.

)j3b, 13i, 3n,
If a metal such as Δu, AI, Ti, N, Or, Pb or an alloy thereof is used for the anti-fouling layer, for example, 8u1Δ1 has a good cooling effect, Ti, Cr1J, a diffusion prevention effect, 3b
, B:, 3n, Ni, Pb, etc. are preferred on the market because of their advantages such as easy film formation and a sufficient rate of fouling.

Thickness of the fouling layer [, I, not particularly limited, 10 to 80
nIn is also preferred from a practical standpoint. The fouling layer also acts as a cooling layer to prevent excessive crystallization around the recording mark due to heat conduction, and can also be expected to have the effect of improving the quality of recording, where the mark shape is constant and the edges are clear. .

The substrates used in the present invention include polymethyl methacrylate 1 resin, polycarbonate resin 1 resin, ebogishi resin,
Polymer resins such as polyolefin resins, polyvinyl chloride resins, polyester phase 1 resins, and styrene resins, glass plates, and metal plates such as A in some cases may be used.

In order to effectively exhibit the original characteristics of the recording medium of the present invention, a protective film can be formed between the substrate and the recording thin film or on the surface of the medium, and a diffusion prevention layer can be formed between the recording layer and the reflective layer.

The protective layer may be formed by forming an inorganic film such as 5i02.7r''C or a violet tato line-cured film using a method such as vapor deposition, sputtering, or spin-row 1, or by forming an inorganic film such as 5i02.7r''C or a violet ray-cured film using a method such as evaporation, sputtering, or spin-low coating. Resin, film, glass, etc. may be bonded together or laminated.

The diffusion prevention layer is provided to suppress the diffusion of elements between the recording layer and the anti-q1 layer and prevent deterioration of characteristics.
Materials similar to the protective layer such as 2 can be used.

In addition, the protective layer and the diffusion prevention layer are /"゛,]-a,
7i and W);
A component containing silicon, oxygen, and carbon (can be composed of a component containing silicon, oxygen, and carbon. In this case, the preferred content of each component is -
Content of the above metals: 3 to 1.0%] 1%, silicon content: 5 to 30%, oxygen content: 5%
The carbon content is preferably in the range of ~70 at.% and the carbon content is in the range of 3~40 at.%.This allows good protection of the recording layer, that is, suppressing changes in film quality and performance deterioration of the recording layer, as well as protecting the recording layer. The thickness of the 3° diffusion prevention layer that can increase the adhesive strength with the four reflective layers is not particularly limited, but it is preferably 1100 nm or less because the cooling effect can be effectively utilized; if,
The influence on the μ thickness interference effect (of the recording layer) can be reduced.

These protective layers and anti-diffusion layers improve durability and moisture absorption resistance, protect the recording layer, prevent deformation due to peeling or swelling from the substrate, and prevent media from melting, evaporating, diffusing, etc.
This can be expected to prevent adverse effects such as loss of the medium, and improve the repeatability of recording and erasing when reversible changes between amorphous and crystalline states are utilized.

[Manufacturing Method] As a method for manufacturing the recording thin film of the present invention, there are various methods, but as an example, a manufacturing method using a magnetron sputtering method will be explained.

The recording medium of the present invention has a thickness of 1.2 mrT1, 3 x 30
m of Pyrex crow, or 1.2mrT1 loaf, 1
A polycarbonate (hereinafter referred to as PC) substrate with a spiral group of 3 cm diameter and 1.6 μm pitch was rotated at 10 to 150 rF) to make the composition and film thickness uniform, for example. , a preoccupation layer, a recording layer, a diffusion prevention layer, or an anti-diffusion layer, respectively [1] are laminated in order according to the conditions. The sputtering strip 1!1 uses argon gas as the sputtering gas, R "output number + ~ 1 kW, vacuum degree 8 x 10-'
This may be carried out within a condition range of about Pa-3x10-1 Pa.

The protective layer and the diffusion prevention layer may be formed by sputtering alone or simultaneously using a 5i02 or 7rC target and monitoring the thickness of the crystal resonator.

The recording layer is made of 3i, pb, le and di-(3e alloy,
While monitoring the thickness of the quartz film, simultaneous sputtering is performed to record a predetermined composition (11 records). In the part 1 (Figure) 3, materials such as [3i 2Te 3 and Te-pb alloys, etc., and a predetermined thin film composition (Te, Ge,
A four-element target of Bi, Pb) may also be used. The anti-fouling layer is made of Te, [3i, pb or their alloys, or A
U, Sb, Sn, B i , Pb, A, - "1, Nj,
Metals such as Or or alloys thereof may be formed in the same manner as the recording thin film.

Naturally, appropriate sputtering conditions are not constant depending on the equipment purchased, and it goes without saying that a recording medium may be produced under conditions other than those described above.

Other methods for producing the recording thin film of the present invention include thin film forming techniques such as vacuum evaporation and electron beam evaporation.

[Applications] The recording medium of the present invention thus obtained can be used particularly for optical disks, optical tapes, optical cards, optical floppy disks,
It has favorable characteristics as an information recording medium such as microfiche and laser 00M. however,
It goes without saying that the present invention is not limited to such applications, but is applicable to any application in which differences in optical properties are utilized for recording 1/'l.

[Measurement method] Evaluation methods used in Examples of the present invention will be explained.

■ A pair of electrodes is placed on the recording thin film fabricated on the transition temperature Nocolas substrate, and a 30Ω resistor is connected in series to one end of the electrode.A constant voltage of 5V is applied across the remaining electrode and the resistor. The voltage across the resistor is determined by 8111, and the voltage and current applied to the thin film are determined from this, and the resistance value is calculated.Next, the entire substrate is heated uniformly using a heating furnace, and the temperature controller is Measure the resistance while increasing the temperature at a rate of about 10'C/min, find the point at which the resistance changes from high to low, and define the temperature at that point as the transition temperature).

■ Composition: The recording thin film prepared on the glass substrate is coated with aqua regia, lil'1W.
It was dissolved and separated from the substrate. The content of each element in this solution was determined by high-frequency inductively coupled plasma (ICP) emission spectrometry (Seiko Electronics Co., Ltd. SPS-1100 model), and the composition ratio (atomic %) was calculated.

■ Recording/erasing' [The sample was a recording thin film formed on a group-attached optical disk substrate made of h-type PC. The evaluation device mainly consists of an optical head incorporating a semiconductor laser with a wavelength of 830 nm, a disk rotating device, and their control circuits. The optical head is controlled to focus a laser beam onto the recording thin film through a rotating disk substrate using an objective lens with a numerical aperture of 0.5, and to focus the laser beam once along a group carved on the substrate. Recording is done with a recording power of 1 to 15 mW.
Frequency is 0.2~5MHz, signal duty is 10-
The measurement was performed by dividing the value into 90%. The linear velocity was 1°2 to 12 m/sec. ○NR reproduces the recorded signal at 0°7mW and
It was determined from the R signal using a spectrum analyzer with the hunt width of KH2 and]○KH2 closed. Also, it was determined by interpolation from the noise lJ1 at the carrier frequency position and the noise values before and after it.

[Examples] The present invention will be further described in detail based on Examples.

Examples 1 to 3, Comparative Example 1 A protective layer, a recording layer, and a protective layer were sequentially formed on each of a Pyrex glass substrate and a PC substrate by a sputtering method (manufacturing method). The base was rotated an additional 40 times to make the composition and film thickness uniform. .

First, approximately 1100 nm of 8102 protective layer was formed on the substrate-1 under the vacuum condition of 5 × 1 O-1 pa, and then Bl,
Ding e, p, b and their alloys, and l-e50G e
While monitoring the No. 50 alloy using a quartz crystal film thickness,
A recording layer having a thickness of 95 nm was formed by simultaneous sputtering. Finally, a SiO2 layer with a thickness of 15Qnrrl was formed to serve as a protective layer. IPC of Examples 1 to 3 and Comparative Example 1 produced
Composition determined by emission spectrometry and recording conditions (see below)
Table 1 shows the CNR values and transition temperatures measured by changing the
Shown below.

"Recording conditions" Recording conditions 1: 5.5rn/sec, 3.7HIIz
, 25% decoty, 30KHz hand width recording condition 2: 4 m/s, 11 Z, 50% decoity, 30KHz hand width recording condition 3 3 T: 1.25 m / sec, 0.72, tiz
, 25. % Duty, 10Kl"Z Hand Width 11 T: 1.25 m/sec, 0.2KH2, 5
0% Decorty, 10 Kl-IZ Bandwidth Example 4J, High-density recording regulations 1
(Ma, Ri interval ・], 49#m) ○NR or 45 dB
The above is the recording condition 2 for low density recording (mark interval 4 μr 1
) at 55. It shows excellent recording and reproducing characteristics of more than dB. On the other hand, the comparative example shows a CNR value of 5.3 dB under recording condition 2, but does not show a CNR value of 43.dB under high-density recording condition 1. d
Il, which is as low as B and required by the draft ISO standard, is 5.
d B is not satisfied. As described above, the recording medium of the present invention can obtain sufficient high-density recording characteristics when formed into a simple three-decoy structure, which is easy and inexpensive to manufacture.

Comparison of recording conditions 3 for compact discs with variable mark length recording at low speeds and 1 core. The example has a CNR value of 3 to 7d[3 lower than the example, and especially under the high-density three-ring condition, the CN l't is 4 to 7d[3].
It is below 8dB and 50dB.

Furthermore, the crystallization temperature that affects the storage stability and consistency of the green signal described above is
However, in the comparative example, the temperature decreased at 123°C and above 20'C, and the long-term preservation of recorded information decreased significantly. I can say that I am doing it.

In all of Examples 1 to 3, when recording was performed using the recording strip 411, the noise increase due to recording was 1.5 to 2.4 dB.
It was only a very small amount.

Example 4 In the same manner as in Example 1, 11 pieces of SC2 were applied to a PC board.
00n, (-1e53Ce47) 843 i 11
Sample (A) was prepared by forming a pb5 recording layer with a thickness of 35 nm in the order of 35 nm.
+21'b A 20 nm thick anti-fouling layer with a composition of 24 was formed, and the history was 3i0. 1501 rT1 was laminated as a protective layer. In addition, sample a'41 (b) uses SiO as a diffusion prevention layer.
After forming 20 r + m of 2, the same di24Bi
A 2 Qnm anti-q old film of 52Pb24 silk was formed, and SiO2 was laminated thereon as a 15On ITI protective layer. Furthermore, sample (c) had a scattering prevention layer of 20nr of JIt.
Looking at the Tl thickness, the mol% ratio of S'i02 and Y r c is 74
:26, except that it was formed by simultaneous sputtering.

When recording and reproducing under high-density recording conditions of linear velocity 5.5 rTl/sec and 3.7M+-12, the hand width was 30K.
In H7, a CNR of 50 dB or more was obtained for all of the samples (A) to (C). Also, the increase in noise after recording was very small and was 3 dB or less.

Example 5 Sample (d) had a recording layer of (T e 55G e 45>
91B5Pb4 with a reflective layer of Ti, trial 1 (e)
～(su) is the recording layer (Te63Ge37>82B
i 6Pb'+2, the fouling layers are Au, A I ,
Sample (b) of Example 4 except that 3b, 3n, and Cr were used.
An optical recording medium with the same film thickness and layer structure was fabricated.

These optical recording media (d) to (s) are moved at a linear velocity of 5°5m/
When recording and reproducing under high-density recording conditions of 3.7 MHz and 3.7 MHz, the required CNR of 45 dB or more was obtained in both cases.

[Effects of the Invention] The recording medium according to the present invention has excellent effects as described below.

(2) An optical recording medium with high recording and reproduction signal amplitude, low medium noise, and good CNR characteristics can be obtained.

(2) An optical recording medium with good recording characteristics can be obtained with less signal amplitude reduction under high-density recording conditions.

■ Thinly comb the recording layer! By providing 11 layers,
An optical recording medium with improved CNR and good edge sharpness of recording marks can be obtained.

(2) By providing a nonconforming layer mainly composed of the elements constituting the recording layer, an optical recording medium can be obtained in which recording characteristics are not deteriorated due to diffusion between the recording layer and the reflective layer. .

■ By providing a diffusion prevention layer between the recording layer and the fouling layer, an optical recording medium with good and stable recording characteristics that is not affected by the fouling layer material can be created. An optical recording medium with excellent long-term preservation of recorded edge information can be obtained.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Claims] 1. An information recording medium in which information is recorded by irradiating a recording thin film formed on a substrate with an energy beam and changing the optical characteristics of the thin film by the heat generated directly or indirectly. , the recording thin film mainly consists of four elements, tellurium (Te), germanium (Ge), bismuth (Bi) and lead (Pb), and its composition has the general formula (TexGe100-x)100-p-qBipPbq
x: % number of Te atoms in (Te and Ge) p: % number of Bi atoms in the thin film q: % number of Pb atoms in the thin film When expressed as, the ranges of x, p, and q are each 40≦ x
An information recording medium characterized in that ≦75, 1≦p≦20, and 1≦q≦20. 2. The information recording medium according to claim 1, further comprising a reflective layer adjacent to the recording thin film. 3. The information recording medium according to claim 2, further comprising an anti-diffusion layer between the recording thin film and the reflective layer. 4. The information recording medium according to claim 2 or 3, wherein the reflective layer is mainly composed of Te, Bi, and Pb.