JPH01271934A - Optical information recording medium and its production - Google Patents

Abstract

PURPOSE:To easily and inexpensively produce the optical information recording medium suitable for high-density recording by uniformly dispersing a material which is higher in melting temp., decomposing temp. or sublimation temp. than the main material of a recording layer into said layer. CONSTITUTION:An underlying layer 2 consisting of polytetrafluoroethylene is formed to about 40nm thickness by a high-frequency sputtering method on the signal pattern surface of a PC substrate 1. The recording layer 3 is then formed to about 27nm thickness by the high-frequency sputtering method on the layer 2. The sputtering conditions of this time are a tellurium-selenium-lead alloy as a target, 40W throwing power, gaseous mixture composed of argon and H2O as the gas to be introduced, 5X10<-1>Pa gaseous argon pressure, and 7XPa partial pressure of H2O. The recording layer uniformly incorporated with tellurium oxide, selenium oxide, and the oxides such as lead oxide into the tellurium-selenium-lead alloy is thus formed. The substrate is taken out into the air after the formation and is subjected to a baking treatment for about 30 minutes at 80 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium provided with a so-called perforated type recording layer.

[Conventional technology]

2. Description of the Related Art Conventionally, optical information recording media have been known in which information is recorded in the form of holes (pits) in a recording layer by irradiation with a focused radiation beam.

The mechanism of pit formation in this perforation type optical information recording medium is estimated to be approximately as follows.

First, as shown in FIG. 4(a).

When the recording layer 11 is irradiated with a radiation beam, for example a laser beam 13, focused by the objective lens 12, a recording 711
One radiation beam irradiation portion is heated by its photothermal effect, causing thermal deformation such as melting or decomposition depending on the type of recording layer material. Note that the reference numeral 14 in FIG. 1 indicates a transparent substrate, and the reference numeral 15 indicates a base layer. And Fig. 4(b)
As shown.

The hottest center evaporates, forming a pinhole 16. As a result, the balance of surface tension is broken, and as shown in FIG.
will be established. Therefore, after cooling, a mound I8 called a rim is formed around the laser beam irradiation part, as shown in FIG. 4(d).

Note that there are also research results that shrinkage occurs immediately from the melted or decomposed state without producing pinholes 16 due to the evaporation.

The inventors of the present application discovered the fact that the modulation degree of pits is significantly affected by the underlying material of the recording layer 11, and previously proposed an optical information recording medium using an organic thin film as the underlying layer 15. Here, the modulation degree of a pit is a frequency indicating the ease with which pits are formed, and the reflectance of a portion where no pit is formed is A, the reflectance of a portion where a recording layer is not formed is B, and B is the reflectance of a portion where a recording layer is not formed. When the reflectance of the pit portion opened by irradiating with a predetermined radiation power is defined as X.

(A-X) / (A-B)
No. 34, Japanese Patent Application No. 61-59437, Japanese Patent Application No. 1988-11
No. 0587, Japanese Patent Application No. 168018/1982).

[Problem to be solved by the invention]

These optical information recording media have a significantly improved modulation degree compared to optical information recording media that do not use an organic thin film as an underlayer, and can open large pits with small radiation power.

However, when an optical information recording medium having this organic underlayer is attached to a drive device equipped with a high-power radiation source and information is written, the diameter of the pits becomes too large, and when recording in a close-packed pattern, It has been found that there are problems such as insufficient resolution and a tendency to cause tracking errors due to adverse effects on tracking signals.

The present invention has been made in order to solve the problems of the prior art as described above, and it is possible to eliminate pits when irradiated with a high power radiation beam without impairing the modulation degree when irradiated with a low power radiation beam. The object of this invention is to provide an optical information recording medium suitable for high-density recording by improving the diameter.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a recording layer made of a perforated type heat mode recording material.
This recording layer is characterized in that a substance having a higher melting temperature, decomposition temperature, or sublimation temperature than that of the heat mode recording material constituting the main portion of the recording layer is uniformly dispersed.

In addition, it is possible to write 8 on the substrate by sputtering or spin coating.
A manufacturing feature is that when forming M, a substance having a melting temperature, sublimation temperature, or decomposition temperature higher than that of the heat mode recording material constituting the main part of the recording layer is mixed at the same time. be.

[Effect]

When a substance with a high melting temperature, decomposition temperature, or sublimation temperature is uniformly dispersed in the recording layer, the melting temperature, decomposition temperature, or sublimation temperature of the recording layer becomes higher than that of the heat mode recording material itself, which constitutes the main part of the recording layer. Elevated above the melting temperature or decomposition temperature or sublimation temperature. Therefore, the range of melting, decomposition, or sublimation when irradiated with a radiation beam having a Gaussian intensity distribution is limited.

Furthermore, the presence of a solid substance that does not melt, decompose, or sublimate suppresses shrinkage of the melted, decomposed, or sublimated recording layer. As a result, the pits are made smaller and the recording density is increased.

In addition, when forming the recording layer, if a substance with a melting temperature, sublimation temperature, or decomposition temperature higher than that of the heat mode recording material is mixed at the same time, the manufacturing process will not be complicated and can be carried out at low cost. be able to.

〔Example〕

First, an outline of the present invention will be explained based on FIG. 1 and FIG. 2. In the optical information recording medium shown in FIG. 1, a base layer 2 is formed on a signal pattern forming surface of a substrate 1.

A recording layer 3 is laminated on this base layer 2. - On the other hand, in the optical information recording medium shown in FIG. 2, the recording layer 3 is directly formed on the signal pattern forming surface of the substrate 1.

The substrate 1 is made of glass or polymethyl methacrylate (PMM).
A) It is made of a transparent hard material such as polycarbonate (PC) or epoxy.

On one side of the substrate 1, a signal pattern such as a pre-group 4 for guiding a radiation beam spot along a recording track and a pre-pit 5 for signal-modulating an address signal is formed in the form of an uneven shape.

The signal patterns 4 and 5 are formed by an appropriate method depending on the type of substrate material. For example, for ceramic materials such as glass, the 2P method (photocurable resin method), PMM
Injection molding is suitable for thermoplastic resins such as A and PC, and 2P method and casting method are suitable for thermosetting resins such as epoxy.

As shown in FIGS. 1 and 2, the base layer 2 is selectively formed as necessary, and is formed using any transparent material selected from organic materials and inorganic materials. can do. As an organic base layer material,
For example, organic compounds having polytetrafluoroethylene or purine derivatives as a core can be mentioned, and examples of inorganic underlayer materials include silicon oxide, silicon nitride,
Examples include silicon carbide, aluminum nitride, and zinc sulfide. However, from the viewpoint of improving the degree of modulation, it is more preferable to form the base layer 2 using an organic material.

Examples of methods for forming the base layer 2 include vacuum evaporation, sputtering, electron beam, plasma polymerization, and spin coating.
Any known thin film forming means can be used.

The main part of the recording N3 is made of a so-called perforation type heat mode recording material that forms pits in the form of holes or through holes in the radiation beam irradiation area, such as a low-melting point metal-based recording material or an organic dye-based recording material. It is formed. A substance having a melting temperature, decomposition temperature, or sublimation temperature higher than that of the heat mode recording material is uniformly dispersed in the heat mode recording material.

Recording materials based on low melting point metals include those whose main component is tellurium, to which a small amount of selenium is added, as well as indium, tin, lead, and antimony.

Examples include those to which a small amount of metal elements such as bismuth are added. Furthermore, examples of organic dye-based recording materials include cyanine and the like.

As a substance that has a higher melting temperature, decomposition temperature, or sublimation temperature than the heat mode recording material.

As long as it satisfies this temperature condition, any material such as a full bending material, a compound, or a ceramic can be used. Also, at least one selected from oxides, nitrides, and carbides of the heat mode recording material constituting the recording layer.
Different types of compounds can also be used.

As an example, tellurium oxide (TeOz ; Melting temperature is 732.6℃
), silicon oxide (SiOZ; boiling point 2230°C), germanium oxide (GeOz; melting temperature 1116°C)
, gold (Au; melting temperature 1063°C), platinum (Pt;
(melting temperature is 1770°C), etc. can be used. In addition, when using a metal as a substance with a high melting temperature, decomposition temperature, or sublimation temperature mixed in the DWJ,
In order not to impair recording stability, it is preferable to use a metal material that does not easily corrode.

As a means of forming layer B 3, spin coating is used for organic dye-based recording materials, and for other recording materials, vacuum film forming methods such as vacuum evaporation and sputtering are used. .

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

First Example A base layer of polytetrafluoroethylene with a thickness of about 40 nm (nanometers) was formed on the signal pattern surface of an injection-molded PC board by high-frequency sputtering. The sputtering conditions at this time were that the input power was 120 W, the introduced gas was pure argon, and the argon gas pressure was 5×10 −′Pa.

Next, a recording layer with a thickness of about 27 nm was formed on this underlayer by high frequency sputtering. The sputtering conditions at this time were that the target was a tellurium-selenium-lead alloy, the input power was 40 W, the introduced gas was a mixed gas of argon and HzO,
Argon gas pressure is 5X10-IPa, H20 partial pressure is 7
It is X10-4Pa.

In this way, a recording layer is formed in which oxides of tellurium oxide (TeOz, etc.), selenium oxide (SaO2, etc.), and lead oxide (PbOz, etc.) are uniformly mixed in the tellurium-selenium-lead alloy.

After forming the recording layer, the substrate was taken out into the air and subjected to beta treatment at 80°C for about 30 minutes.

Second Example A recording layer was formed on a polytetrafluoroethylene underlayer under the following sputtering conditions. Other conditions are the same as in the first embodiment.

The difference in sputtering conditions between this example and the first example is as follows:
It mainly has a high partial pressure of Hz○, the target is a tellurium-selenium-lead alloy, and the input high frequency power is 45
W, the introduced gas was a mixed gas of argon and HzO, the argon gas pressure was 5×10-'Pa, and the partial pressure of HzO was 1. lX
The pressure was set at 10-'Pa.

Third Example A recording layer was formed on a polytetrafluoroethylene underlayer under the following sputtering conditions. Other conditions are the same as those in the first and second embodiments.

The difference in sputtering conditions between this example and the first and second examples is mainly that the type of gas added to the introduced gas was changed to oxygen (02), and the target was a tellurium-selenium-lead alloy. The input high frequency power is 40W,
The introduced gas is a mixed gas of argon and Oz, the argon gas pressure is 5 x 1O-1Pa, and the partial pressure of Oz is 4X10-4P.
Adjusted to a.

Even in this way, tellurium oxide (T e O2, etc.), selenium oxide (SaO2, etc.),
A recording layer in which an oxide of lead oxide (PbOz, etc.) is uniformly mixed is formed.

<Fourth Example> The above Gm was formed on a polytetrafluoroethylene base layer under the following sputtering conditions. Other conditions are the same as in the first embodiment.

The difference in sputtering conditions between this example and the third example is as follows:
Mainly, the partial pressure of 02 is increased, the target is tellurium-selenium-lead alloy, and the input high frequency power is 45W.
, the introduced gas is a mixed gas of argon and Oz, the argon gas pressure is 5X10-'Pa, and the partial pressure of Oz is 8X10-'P.
Adjusted to a.

Fifth Example A recording layer was formed on a polytetrafluoroethylene underlayer under the following sputtering conditions. Other conditions are the same as in the first embodiment.

The difference in sputtering conditions between this example and the first to fourth examples is mainly that the type of target and the type of introduced gas were changed. e O
z) A sintered powder was used. The ratio of T e Oz to the total tellurium content in this target was approximately 2 atomic %. Other sputtering conditions were that the input high frequency power was 40 W, the introduced gas was pure argon, and the argon gas pressure was 5 xto-' Pa.

In this case, a recording layer is formed in which tellurium oxide (TeOz) is uniformly mixed in a tellurium-selenium-lead alloy.

The mixing ratio of tellurium oxide to the tellurium-selenium-lead alloy is about 2 atomic percent.

Sixth Example An organic base layer and a recording layer were sequentially laminated on the same replica substrate as in the first example by spin coating.

The base layer material is a polyvinyl alcohol solution to which ammonium dichromate is added. This solution is dropped onto the signal pattern surface of a substrate that is rotated at 4000 m", and after drying, it is irradiated with ultraviolet rays for about 1 minute to cross-link it. by about 6
A base layer with a thickness of 0 nm was formed.

Next, a solution in which about 2% by volume of platinum powder with a particle size of 10 nm or less was added to the cyanine-based organic dye was added.

The solution was dropped onto the underlayer of the substrate which was rotated at 2000 m-1, and after the entire surface of the underlayer was uniformly coated with the solution, the substrate was continued to be rotated and spin-dried to form a layer of about 60 nm. A thick recording layer was formed.

Comparative Example 1> The above sM was formed on a polytetrafluoroethylene base layer under the following sputtering conditions. Other conditions are the same as those in the first to fifth embodiments.

The target is a tellurium-selenium-lead alloy, the input high-frequency power is 40 W, the introduced gas is pure argon, and the argon gas pressure is 5×10 −1 Pa.

In this case, no oxide is mixed into the tellurium-selenium-lead alloy.

Comparative Example 2> Under the same conditions as in Example 6, a polyvinyl alcohol base layer containing ammonium dichromate and cyanine containing no high melting point powder were formed on the signal pattern of the replica substrate. A recording layer of an organic dye was formed by spin coating.

The table below shows the modulation degree of the pits created by irradiating the optical information recording media of the first to sixth embodiments with a radiation beam, and the degree of modulation of the pits formed by the heat mode recording material constituting the main part of the recording layer. Also shows a comparison of the modulation degree of pits opened by irradiating a radiation beam on a conventional optical information recording medium that is not mixed with a substance with a high melting temperature, decomposition temperature, or sublimation temperature. However, the signal writing conditions are For the optical information recording media of the first to fifth embodiments and the first comparative example, the recording frequency was 3.7 MHz, the duty ratio was 22%, the writing power was 8 mW, and the sixth embodiment For the optical information recording medium and the optical information recording medium of the second comparative example, the recording frequency was set to 3.
．． The frequency was 7 MHz, the duty ratio was 22%, and the write power was 10 mW. Further, the numerical values indicating the degree of modulation in Table 1 were determined from the ratio of the amplitude of the signal read from the write pit to the amplitude of the signal read from the sector mark pre-pits formed in advance on the substrate.

As is clear from this table, the optical information recording medium according to the present invention has a higher modulation degree than the conventional optical information recording medium used as a comparative example, has smaller pits on the recording film, and has a lower resolution. It turns out that it is expensive.

In particular, the optical information recording media of the second example and the fourth example are good, and it is more effective to improve the degree of modulation if the mixing rate of the additive substance in the recording layer is higher to some extent.

FIG. 3 shows the relationship between the strength of the write power and the diameter of the pit created for the optical information recording medium of the second example. In this graph, the horizontal axis represents the write power;
Moreover, the vertical axis indicates the diameter of the pit, and the characteristics of the second embodiment are x
The characteristics of Comparative Example 1 are indicated by . Note that the diameter of the pit was measured using a scanning electron microscope.

As is clear from this figure, the pit diameter of the optical information recording medium of the second example is not as large as that of the first comparative example even when the writing power is increased, and it is effective in improving resolution and recording density. It turns out that there is. On the other hand, when the writing power is low, pits can be formed with a diameter comparable to that of the first comparative example, and the recording sensitivity does not decrease.

Although FIG. 3 shows only the data of the second example, it has been found that the optical information recording media of the first, third, fourth, and fifth examples have similar effects. In addition, in the optical information recording medium of the second comparative example, pits with a diameter of 1.05 μm were created with a writing power of 10 mW.
In the optical information recording medium of the sixth example, the pit diameter was 0.85 μm at the same writing power, and it was found that the same effect was obtained.

Furthermore, in each of the above examples, data has been given and explained only for optical information recording media having an underlayer of polytetrafluoroethylene. It was confirmed that a similar effect was obtained when forming a .

The gist of the present invention is that a substance having a higher melting temperature, decomposition temperature, or sublimation temperature than the heat mode recording material constituting the main part of the recording layer is uniformly dispersed in the recording layer. The types of substances dispersed in the recording layer are not limited to those listed in each of the examples above, and in this case, it is presumed that similar effects will be obtained from the test results of each of the above examples. can do.

〔Effect of the invention〕

As explained above, in the optical information recording medium of the present invention, as a result of dispersing and mixing a substance with a high melting temperature, decomposition temperature, or sublimation temperature into the recording layer, the average melting temperature or decomposition temperature of the recording layer increases, and recording Since the layer becomes difficult to melt and the shrinkage of the recording layer due to surface tension is limited by the insoluble material, the diameter of the pit will not become excessively large even when a signal is written with high power. Therefore, it is possible to provide an optical information recording medium that has high recording sensitivity and is suitable for high-density recording.

Further, since a desired substance is mixed into the recording layer when forming the recording layer, the manufacturing process of the optical information recording medium does not become complicated and can be carried out at low cost.

[Brief explanation of the drawing]

1 and 2 are sectional views of essential parts showing the basic structure of the optical information recording medium according to the present invention, FIG. 3 is a graph explaining the present invention in detail, and each time in FIG. 4 is a pit formation mechanism. FIG. 12 substrates, 1a: signal pattern, 2: underlayer, 3: recording layer. Figure 1 j (Figure 2 1:

Claims (7)

[Claims] (1) In an optical information recording medium formed on one side of a substrate, a thin film layer including at least a recording layer made of a perforated type heat mode recording material, in which the main part of the recording layer is formed. An optical information recording medium characterized in that a substance having a melting temperature, decomposition temperature, or sublimation temperature higher than that of a heat mode recording material is uniformly dispersed therein. (2) In the optical information recording medium according to claim 1, at least one type of heat mode recording material selected from oxides, nitrides, and carbides forming the main part of the recording layer is contained in the recording layer. An optical information recording medium characterized by dispersing a compound. (3) In the optical information recording medium according to claim 1, the recording layer is formed from a heat mode recording material containing tellurium as a main component, and tellurium oxide is dispersed as the substance in the recording layer. Characteristic optical information recording media. (4) A method for manufacturing an optical information recording medium including a step of forming a recording layer on a substrate, characterized in that the substance is mixed at the same time when forming the recording layer on the substrate. A method for manufacturing an optical information recording medium. (5) In the method for manufacturing an optical information recording medium according to claim 4, at least one type selected from oxygen, nitrogen, and carbon is placed in a vacuum chamber containing a substrate and a target made of a desired heat mode recording material. By introducing a reactive gas containing an element of 1. A method for manufacturing an optical information recording medium, comprising forming a recording layer in which at least one kind of substance is dispersed and mixed. (6) In the method for manufacturing an optical information recording medium according to claim 4, a desired heat mode recording material and at least one kind selected from oxides, nitrides, and carbides of the heat mode recording material are placed in the vacuum chamber. By sputtering this target, a mixture of oxides, nitrides, and carbides of the heat mode recording material is deposited in the heat mode recording material onto the substrate. A method for producing an optical information recording medium, comprising forming a recording layer in which at least one selected substance is dispersed and mixed. (7) In the method for producing an optical information recording medium according to claim 4, particles made of a substance having a higher melting temperature, decomposition temperature, or sublimation temperature than that of the liquid organic dye-based heat mode recording material are mixed. and a method for manufacturing an optical information recording medium, characterized in that this mixture is spin-coated on the substrate.