JPS62219245A - Optical information recording disk - Google Patents

Abstract

PURPOSE:To obviate the deterioration of a CN ratio with lapse of time by providing a light transmittable thermal impact relieving layer which is better in heat resistance than a disk substrate, is lower in m.p. or decomposition temp. and lower in heat conductivity than a recording layer between the disk substrate and the recording layer. CONSTITUTION:The thermal impact relieving layer 3 is formed of the light transmittable material which is better in the heat resistance than the disk substrate 1 and is lower in the m.p. or decomposition temp. and is lower in the heat conductivity than the recording layer. The thermal impact relieving layer 3 is preferably formed of at least one kind of org. material selected from a polytetrafluoroethylene, guanine, hydrocarbon film by a plasma polymn. method, PE, and methyl chloride if the disk substrate 1 is formed of a PMMA or PC or epoxy and the recording layer 4 is formed of a low melting metal essentially consisting of Te.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical information recording disk, such as a compact disk, a video disk, and an optical disk memory for computers, on which information is recorded and reproduced by irradiation with a light beam. .

[Prior art Fig. 2 is a partially cut-away enlarged sectional view showing an example of this type of optical information recording disk, in which a pregroove 12 corresponding to a tracking signal and a pregroove 12 corresponding to an address signal are formed on one side of a disk substrate 11. Pre-pits 13 are transferred, and a recording layer 14 made of a heat mode recording material is provided on the transfer surface of the pre-grooves 12 and pre-pits 13.

The pre-pits 13 are formed on the pre-grooves 12, and each (11
No. 7 is now read out.

When recording information on the above optical information recording disk, a tracking laser beam is incident along the pre-groove 12 and pre-pit 13 from the disk substrate 11 side, and the intensity of reflected light from the recording layer 14 is detected. Tracking information and address information are detected by and.

A recording laser beam modulated by a predetermined information signal is irradiated onto predetermined tracks and sectors, and the recording layer 14 is
By causing thermal deformation such as melting, evaporation, and contraction, information is recorded in the form of pits. When reading information recorded on the optical information recording disk, a reproducing laser beam is incident along the pregroove 12 from the disk substrate 11 side, and the intensity of reflected light from the recording layer 14 is detected. By this, the information signal is detected while tracking information and address information are being detected.

In recent years, disc substrate materials applied to this type of optical information recording disc have: (1) high productivity;

Can be manufactured cheaply. Shun) It is lightweight and does not get damaged.

PMMA (
Molded polymer materials such as polymethyl methacrylate (polymethyl methacrylate), PC (polycarbonate), and epoxy are becoming mainstream.

However, since these polymer materials have relatively low heat resistance, when repeatedly irradiated with a laser beam for reproduction, the pre-grooves 12 and pre-pits 1 transferred to the disk substrate 11 are damaged.
The shape of 3 gradually deforms.

It has been pointed out that there is a problem in that the contrast of the intensity of reflected light read from the portion decreases with the passage of time, resulting in a decrease in the CN ratio.

Conventionally, thermal deformation of the disk substrate 11 during recording has been prevented, and the disk substrate 11 around the recording pit formation area has been
In order to prevent the swelling of the pits and the resulting disturbance of the shape of the pits, and to perform recording with a high CN ratio, a layer is provided between the disk substrate 11 and the recording layer 14 that has a heat resistance higher than the temperature during recording. .

and a material with low thermal conductivity and a heat insulating effect, such as Ss.
, Cu S e or As containing 40 atomic % or more of S
An information recording medium provided with a light-transmitting heat insulating layer made of a substance such as zSe3 is known (Japanese Patent Laid-Open No. 57-189356).
).

[Problem that the invention seeks to solve]

However, according to research by the inventors of the present application, the heat resistance of the underlayer of the recording layer 14 has a significant influence on the recording sensitivity, and thermal deformation of the recording layer 14 is caused by the thermal deformation of the underlayer fFj (disk substrate 11). It has been found that the recording sensitivity of the recording layer 14 is significantly reduced if thermal deformation is promoted, that is, if the underlayer does not undergo any thermal deformation at all. For example, when a recording layer is formed directly on a glass disk substrate, P
The recording sensitivity is significantly lower than when the recording layer is directly formed on the MMAm disk substrate.

Therefore, as in the above-mentioned known example, if a heat insulating layer is formed between the disk substrate 11 and the recording layer 14 that does not cause any thermal deformation due to the temperature during recording, thermal deformation of the disk a removal 11 can be prevented. This can prevent deterioration of the CN ratio, but on the other hand, the recording sensitivity is significantly lowered and the recording power has to be increased, which is a problem.

[Means for solving problems]

In this way, in order to prevent the concavo-convex pattern transferred to the disk substrate from being thermally deformed even when repeatedly irradiated with a reproduction laser beam and to improve recording sensitivity, at least the concavo-convex pattern transfer surface of the disk substrate must be protected.

It needs to be formed of a material that has higher heat resistance than the disk substrate and melts or decomposes at a lower temperature than the melting temperature of the recording layer.

The present invention was made based on the above findings, and
Between the disk substrate and the recording layer, there is a light-transmissive thermal shock mitigation layer made of a material that has better heat resistance than the disk substrate, has a lower melting point or decomposition temperature than the recording layer, and has lower thermal conductivity. It is characterized by having the following.

〔Example〕

First, an outline of the present invention will be explained based on FIG. 1st
The figure is a cross-sectional view schematically showing an optical information recording disk according to the present invention, in which 1 is a disk substrate, 2 is a concavo-convex pattern,
3 is r! ! % impact relaxation layer, 4 indicates a recording layer. The disk substrate 1 is formed into a disk shape of a predetermined diameter with a central hole 1a in the center using a polymeric material such as PMMA, PC, or epoxy. Ru. On one side of this disk substrate 1, a concavo-convex pattern 2 such as a pre-groove corresponding to tracking information and a pre-pit corresponding to an address signal is transferred. The disk substrate 1 can be manufactured by any molding method depending on the material, but PMMA is used.

Injection molding is suitable for PC, and casting is suitable for epoxy.

The recording layer 4 is formed of a low melting point metal such as Te or an alloy containing 1°e as a main component. This recording WI4 can be formed by vacuum evaporation, sputtering,
Any known thin film forming means can be used, such as the fltlt-beam method and the plasma polymerization method.

Thermal impact relaxation layer 3 is formed of a light-transmissive material that has better heat resistance than the disk substrate 1, has a lower melting point or decomposition temperature than the recording layer 4, and has a lower thermal conductivity. Be it.

However, noise from the optical system and S/N as a system
Considering the ratio, the higher the reproduction laser power, the better. For example, when a semiconductor laser with a wavelength of 830 nm is used, a laser power of 1 mW or more is required.

Repeatedly irradiate with a reproducing laser having such power,
In order to prevent thermal deformation of the disk substrate 1 even in the case of

It is necessary to provide a thermal WRIJI sum layer 3 having heat resistance of 110° C. or higher. Further, the lower the thermal conductivity, the better the recording sensitivity can be, and in practical terms, it needs to be 5 W/mK or less.

Specifically, when the disk substrate is made of PMMA, PC, or epoxy, and the recording layer is made of a low melting point metal containing Ta as a main component, the thermal shock mitigation layer is made of polytetrafluoroethylene, Guanine, hydrocarbon film made by plasma polymerization method.

Preferably, it is formed from at least one organic material selected from polyethylene and methyl chloride.

Table 1 lists examples of disk substrate materials, recording materials, and thermal shock mitigation layer materials that can be applied to the optical information recording disk of the present invention, and lists their melting points or decomposition temperatures.

Shows heat distortion temperature and thermal conductivity.

Table 1 As a means for forming this thermal mva relaxation layer 3, any known thin film forming means such as vacuum evaporation, sputtering, plasma polymerization, etc. can be used.

Hereinafter, specific examples of the present invention will be shown, and the effects of the present invention will be discussed.

1st to 5th Examples 50 people (first example), 100 people (second example), and 2
00 people (3rd example), 400 people (4th example), 80 people
Five disk substrates 1 were prepared in which a polytetrafluoroethylene thermal ms relaxation layer 3 having a thickness of 0 A (fifth example) was formed by sputtering. The sputtering conditions at this time were that the argon gas pressure was 7X10''Pa and the RF power was 60W.Next, a sputtering process was performed on the polytetrafluoroethylene thermal shock qB relaxation layer 3 of these disk substrates l. A recording layer 4 made of a T e Se alloy with a thickness of 300 mm was formed using the following sputtering conditions.

Argon gas pressure is 6X10-'Pa, discharge power is 40W
Met.

6th Example A 300 mm thick guanine hot plate I was applied to one side of an injection molded PC@ disk substrate l using a resistance heating vacuum deposition method.
I! A relaxed M3 was formed. The degree of vacuum at this time is 10-
Then, the guanine thermal shock mitigation layer 3 was coated with 300 ml under the same conditions as in the first example.
Record of human thickness by T e S e alloy M! j4 was formed.

- Seventh Example A thermal shock mitigation layer 3 made of a hydrocarbon plasma polymerized film having a thickness of 300 mm was formed on one side of an injection-molded PC disk substrate 1 by a plasma polymerization method. In forming the above hydrocarbon plasma polymerized film, the CH4 gas pressure in the plasma polymerization apparatus was maintained at 7 x 10 Pa, and 120 W RF
'i! applied force.

Next, the above-mentioned hydrocarbon thermal shock 11! A T layer with a thickness of 300λ was formed on the relaxation layer 3 under the same conditions as in the first embodiment.
A recording layer 4 was formed using an e SE alloy.

Table 2 shows the laser power that causes a signal fluctuation of ±10% when the optical information recording disks of the first to seventh embodiments are repeatedly reproduced for 10 hours. Compare with a conventional product that does not. However, the wavelength of the reproduction laser beam applied to the five tests was 830 nm.
It is.

Table 2 As shown in Table 2, all of the optical information recording disks of this example, except for the one of the first example, had a thermal IJ7! Compared to conventional products that do not have a relaxation layer.

Signal level ±10 after 10 hours of repeated playback
% fluctuating laser power is increasing.

It can be seen that the effect of preventing thermal deformation of the uneven pattern is improved. Among these thermal shock buffering layers, hydrocarbon plasma polymerized films are the best and the following.

It can be seen that the effectiveness is highest in the order of vacuum deposition of guanine and sputtering of polytetrafluoroethylene. Furthermore, from a comparison of the first to fifth embodiments, when polytetrafluoroethylene is applied to the thermal shock mitigation layer 3, it is found that the thicker the thermal shock mitigation layer 3 is, the more effective the thermal shock mitigation effect is. It turned out that.

In order to improve the S/N ratio of the reproduced signal, the higher the reproduction laser power is, the more preferable it is, and it is preferably at least 1 mW. From this, polytetrafluoroethylene is heated to I! When applied to the relaxation layer 3, it is preferable to form the heat*@relaxation M3 to a thickness of 200 Å or more.

Next, one invention product and heat Wr 11! ! An example of a change in the waveform of a read signal and a read signal level after repeated reproduction for 10 hours is shown for a conventional product in which a Japanese layer is not formed, to further clarify the heat deformation resistance of the present invention.

FIG. 2(a) shows an optical information recording disk of the sixth embodiment.

That is, a vacuum-deposited guanine film is formed as a thermal shock mitigation layer on a PC disk substrate, and T e
SM of optical information recording disk with S e recording layer formed
FIG.
) is a waveform chart showing a readout waveform read out from the SM section after irradiating the optical information recording disk with a 1.5mW reproducing laser beam for 10 hours. Also, the third
Figure (a) shows T e S e directly on the PC disk board.
FIG. 3(b) is a waveform diagram showing the readout waveform from the SM section of the optical information recording disk on which a recording layer is formed, and FIG. FIG. 3 is a waveform diagram showing a readout waveform read out from the SM section after the above operation.

As shown in FIGS. 2(a) and 2(b), in the optical information recording disk according to the sixth embodiment of the present invention, even after being irradiated with a 1.5 mW reproducing laser beam for 10 hours, reading from the SM portion is still not possible. Almost no change is seen in the waveform.On the other hand, as shown in Section 31A(a)(b), thermal PM
! ! ! ! In a conventional optical information recording disk in which a relaxation layer is not formed, the readout waveform of the reproducing laser beam irradiation diameter (Fig. 3(a)) is different from the readout waveform before the reproducing laser beam irradiation (Fig. 3(a)). b)) Significant disturbances were observed in the optical information recording disk of the present invention on which a thermal shock mitigation layer was formed, indicating that the thermal deformation resistance of the disk substrate against repeated irradiation with a reproduction laser beam was improved. I understand.

FIG. 4 is a graph showing the change over time in the signal level ratio when a 1.5 mW reproduction laser beam is irradiated onto the optical information recording disk of the sixth embodiment (thermal I17 shock absorbing layer made of guanine). Figure 5 shows Ta directly on the PC disk board.
ke recording layer is formed on the optical information recording disk.
It is a graph showing the change over time in the signal level ratio when a W reproduction laser beam is irradiated. In these graphs, the O mark is the information signal level ratio from the recording layer, the X mark is the tracking signal level ratio from the pregroove, and the Δ mark is the SM
The O mark indicates the read signal level ratio from the VFO section.

Here, the signal level ratio refers to the ratio of the signal level to be measured to the initial signal level, that is.

The closer the signal level ratio is to 1, the smaller the change in signal level will be.

As is clear from these graphs, 1.6″A of the present invention
In the optical information recording disk according to the embodiment, even after being irradiated with a 1.5 mW reproduction laser beam for 10 hours, the change in signal level ratio was within ±5% at most.
In an optical information recording disk in which a thermal shock mitigation layer is not formed, there is a change in signal level ratio of 15 to 25% under similar conditions, and such an optical information recording disk according to the second embodiment of the present invention It can be seen that the disk substrate has improved thermal deformation resistance against repeated irradiation with a reproducing laser beam.

FIGS. 6 and 7 show the modulation degree of pits created by irradiating the optical information recording disks of the first to seventh embodiments with a laser beam, and the heat mt fRl.
Conventional optical information v! where i'lU sum layer 3 is not formed layer 3! ,
A comparison of the degree of modulation of pits created by irradiating a recording disk with a laser beam is shown. However, a recording laser beam with a wavelength of 830 nm was used, and the disk was rotated at 1200 rpm. In this graph, the horizontal axis indicates recording laser power (film surface power), and the R axis indicates modulation degree. Here, the modulation degree of the pit is
The size of the pit, that is, the frequency that indicates the ease with which the pit opens, is A, the reflectance of the part where no pit is formed, and the reflectance &B of the part where no recording film is formed, and irradiation with a predetermined laser power. If the reflectance of the pit portion where rA is set by
).

As you can see from this picture, it's hot! ! The optical information recording disk of the present invention on which relaxed M3 is formed is a hot hit! !
It can be seen that the degree of modulation with respect to a constant laser power is large compared to the conventional product in which the relaxation layer 3 is not formed, and pits are easily formed. In addition, among the products of the present invention, the third, fourth, and fifth embodiments each have a heat-impacted gRa sum layer made of polytetrafluoroethylene sputtered to a thickness of 200 Å or more.
It was found that the optical information recording disks of Examples were particularly excellent, and pits were more likely to open in the following order: disks using Gunian's vacuum-deposited film and disks using hydrocarbon plasma polymerized film. Furthermore, the difference in the degree of modulation for each laser power is larger for a laser beam with a lower power.1 Normally, the power on the recording film surface is 6 mW to 8 mW, which is installed in a disk drive that drives this type of optical information recording disk.
) was found to be particularly effective for lasers.

The gist of the present invention is to provide a light-transmitting heat-transmitting material between the disc substrate and the recording layer, which is made of a material that has better heat resistance than the disc substrate, has a lower melting point or decomposition temperature than the recording layer, and has a lower thermal conductivity. Shock aS! However, the material constituting the thermal shock mitigation layer is not limited to those listed in the above embodiments.

〔Effect of the invention〕

As explained above, the optical information recording disk of the present invention has the following features:
Between the disk substrate and the recording layer is a light-transmitting heat layer 11j made of a material that has better heat resistance than the disk substrate, has a lower melting point or decomposition temperature, and has lower thermal conductivity than the recording layer.
f! ! Since the relaxation layer is provided, the heat during irradiation with the reproduction laser beam is difficult to be transferred to the uneven pattern forming surface of the disk substrate, and the uneven pattern transferred to the disk substrate is thermally deformed, causing the CN ratio to decrease over time. Never deteriorates.

Also, this passion! Since the Ia sum layer was made of a material that melts or decomposes at a temperature lower than the melting temperature of the recording layer, it does not promote thermal deformation of the recording layer when irradiated with a recording laser beam and reduce recording sensitivity. do not have.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing the optical information recording disk according to the present invention, and FIGS. 2(a) and 2(b) are waveform diagrams showing the heat deformation resistance of the optical information recording disk according to the present invention. Of these, FIG. 2(a) is a waveform diagram showing the readout signal waveform from the SM section before irradiation with the reproduction laser beam;
b) is a waveform diagram showing the read signal waveform from the SM section after irradiation with a 1.5 mW reproduction laser beam for 10 hours. Figure 3 (a) and (b) show the heat [r! ! ! FIG. 3A is a waveform diagram showing the thermal deformation resistance of an optical information recording disk in which a relaxation layer is not formed, of which FIG. , FIG. 3(b) is a waveform diagram showing the readout signal waveform from the SM section after 10 hours of irradiation with a 1.5mW reproduction laser beam, and FIG. 4 is a waveform diagram showing the signal readout from the optical information recording disk of the present invention. A graph showing an example of a change in level ratio over time. FIG. 5 is a graph showing changes over time in the signal level ratio read from an optical information recording disk on which a thermal shock mitigation layer is not formed, and FIGS. 6 and 7 are graphs showing optical information recording disks according to the present invention and known examples. A graph showing a comparison of modulation degrees of optical information recording disks, and FIG. 8 is an enlarged sectional view showing an example of a conventionally known optical information recording disk. 1: disk substrate, 2: uneven pattern, 3: thermal shock ffi
Relaxation layer, 4: Recording layer Fig. 1 Disc substrate 2) Concave and convex pattern 3 Thermal shock 1 42 Recording layer interval/min Encircle interval/min (%) Teacher Oka Fig. 7 Procedure [l Regular belt (voluntary) May IO date, 1985

Claims (5)

[Claims] (1) Optical information obtained by forming a recording layer made of a heat mode recording material on the surface of a disk substrate on which a concavo-convex pattern is formed, such as a pre-groove corresponding to tracking information and a pre-bit corresponding to an address signal. In the recording disk, a light transmitting material is provided between the disk substrate and the recording layer, and is made of a material that has better heat resistance than the disk substrate, has a lower melting point or decomposition temperature than the recording layer, and has a lower thermal conductivity. 1. An optical information recording disk characterized by being provided with a thermal shock mitigation layer. (2) In the optical information recording disk according to claim 1, the thermal shock mitigation layer has a heat resistance of 110° C. or higher;
An optical information recording disk characterized in that it is formed from a material having a thermal conductivity of W/mK or less. (3) In the optical information recording disk according to claims 1 and 2, the disk substrate is made of PMMA, PC, or epoxy, and the recording layer is made of an alloy containing Te as a main component. 1. An optical information recording disk characterized in that the impact relaxation layer is formed from at least one organic material selected from polytetrafluoroethylene, guanine, a hydrocarbon film produced by plasma polymerization, polyethylene, and methyl chloride. (4) In the optical information recording disk according to claims 1 to 3, the thermal shock mitigation layer is formed by a thin film forming method selected from vacuum evaporation, sputtering, and plasma polymerization. An optical information recording disc characterized by: (5) An optical information recording disk according to claims 1 to 3, characterized in that the thickness of the thermal shock mitigation layer is 200 Å or more.