JP2647426B2 - Optical information recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly, to a means for preventing corrosion of a recording layer or a reflective layer formed on a substrate.

[Conventional technology]

2. Description of the Related Art Conventionally, there has been known an optical information recording medium in which a thin film layer such as a reflective film or a recording film is formed on a signal pattern forming surface of a resin substrate. For example, taking a compact disk as an example, an aluminum reflective film is formed on a signal pattern forming surface of a polycarbonate substrate, and a protective film made of a urethane acrylate-based photocurable resin is laminated on the aluminum reflective film. Have been.

In the case of the compact disk, if no corrosion protection treatment is performed on the aluminum reflective film on the substrate, 60 ° C. ×
When an accelerated environmental test is performed in an atmosphere of 90% RH, the aluminum reflective film is corroded in 200 to 300 hours, and the reflectance is reduced, making it difficult to read information.

As described above, the compact disk having an aluminum reflecting mirror has been described as an example. However, the same problem occurs in all optical information recording media having a reflective layer or a recording layer made of another substance.

Conventionally, it has been recognized that the corrosion of this type of thin film layer is caused by water penetrating through a substrate or a protective film, and a waterproof film is formed on the surface of the thin film layer, or the thin film layer is made of metal. In this case, a corrosion-resistant treatment such as forming an oxide film of the metal has been proposed (Japanese Patent Laid-Open No. 62-62445).
issue).

An optical information recording medium that has been subjected to such a waterproofing or corrosion-resistant treatment has a longer life expectancy than an optical information recording medium that has not been subjected to any such treatment. For example, in the case of a compact disk, if an alumina layer is formed on the surface of the aluminum reflective film, when the accelerated environment test is performed under the same conditions as described above, the corrosion start time of the aluminum reflective film is extended to about 1500 hours. .

[Problems to be solved by the invention]

However, this type of optical information recording medium is required to have a longer life, and conventional anticorrosion means are still insufficient.

As a result of the research, the present applicant has learned the following facts regarding the corrosion of the thin film layer.

The thin film layer is easily corroded in a high-temperature and high-humidity atmosphere, and hardly corrodes in a high-temperature and low-humidity atmosphere. However, when a glass substrate is used, the thin film layer does not easily corrode even in a high-temperature and high-humidity atmosphere.

As a result of the analysis, it was confirmed that the corroded thin film layer was converted to hydroxide.

Corrosive elements such as chlorine, sulfur, and fluorine are detected from the corroded thin film layer.

Corrosion of the thin film layer occurs from the interface with the substrate.

Corrosive elements such as chlorine, sulfur, and fluorine are detected in the resin substrate.

From these facts, it is assumed that the corrosion mechanism of the thin film layer is as follows.

First, the corrosive element contained in the resin substrate causes a chemical reaction with the thin film layer material. This chemical reaction is described by a chemical formula in the case where the corrosive element is chlorine (Cl) as an example.
It is as follows.

M (thin film _{^{material) + 4Cl - → MCl 4 -}} + 3e - ...... (1) Next, MCl ₄ in which I connexion produced in this reaction ^- a moisture invading from the outside cause the following chemical reaction through the protective film.

MCl ₄ ⁻ +3 HzO → M (OH) ₃ + 3H ⁺ + 4Cl ⁻ (2) Further, Cl ⁻ generated by this reaction again causes the chemical reaction of the above-mentioned formula (1), and corrosion is continuously caused. proceed.

Therefore, corrosion of the thin film layer can be prevented by preventing at least one of the corrosive element and moisture from entering. However, the resinous substrate has some water permeability, and it is difficult to completely stop the resinous substrate. If such a process is performed, the cost of the optical information recording medium is greatly increased. In contrast, it has been found that preventing corrosive elements from entering the thin film layer can be relatively easily implemented by baking the substrate.

The present invention has been made on the basis of this finding, and prevents corrosion of a thin film layer by preventing intrusion of corrosive elements into the thin film layer, thereby providing a long-life optical information recording medium. It is intended to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an optical information recording medium comprising a thin film layer including at least one of a recording layer and a reflective layer on a signal pattern forming surface of a resin substrate. As the resin substrate, a polycarbonate substrate subjected to baking at a temperature of 60 ° C. to 110 ° C. for 30 minutes to 5 hours by external heating after substrate molding was used.

This baking treatment can be performed in a vacuum or in air.

[Action]

The reason why the baking treatment of the substrate containing the corrosive element makes the recording layer or the reflective layer less likely to corrode has not yet been sufficiently elucidated. As a matter of fact, the surface of the substrate has been modified to make it difficult for corrosive elements to pass through,
This is presumed to be because the reaction between the corrosive element in the substrate and the recording layer material or the reflective layer material is suppressed. Thank you
A long-life optical information recording medium having excellent corrosion resistance can be provided.

〔Example〕

First, a schematic configuration of the optical information recording medium according to the present invention will be described.

FIG. 1 is a cross-sectional view of a principal part showing a typical example of an optical information recording medium according to the present invention. A recording layer or a reflective layer 3 is laminated on a signal pattern forming surface of a substrate 1.

The substrate 1 is formed of, for example, polycarbonate (PC). On one surface of the substrate 1, signal patterns such as a pre-groove 4 for guiding a recording / reproducing radiation beam (for example, a laser beam) along a recording track and a pre-pit 5 for modulating an address signal are formed in an uneven shape. ing.

The baking conditions can be appropriately set as required. However, if the temperature is too low and the time is short, the anticorrosion effect is small. If the processing is too high and the time is long, the substrate 1 itself or the signal patterns 4 and 5 are not used. Is deformed,
If the mass productivity deteriorates, problems may occur.
It is preferable to adjust the baking time to a range of 30 minutes to 5 hours. In this case, the baking process can be performed in a vacuum or in the air.

The recording layer 3 can be formed with any known heat mode recording material.

For a read-only optical information recording medium, a reflective layer is formed instead of the recording layer. As the material of the reflective layer, any high-reflectance substance can be used, but aluminum is particularly preferable because it is relatively inexpensive and the film formation is simple.

As a method of forming the recording layer 3, a spin coating method is adopted for an organic dye-based recording material, and a vacuum film forming method such as a vacuum evaporation method or a sputter method is adopted for other recording materials.

Hereinafter, specific examples of the present invention will be described, and effects of the present invention will be referred to.

First, a polycarbonate substrate having a signal pattern transferred to one side is housed in a vacuum chamber, and the inside of the vacuum chamber is 6.67 × 10 ^-4.
After evacuation to Pa, the substrate heater is turned on and the substrate is
The temperature was raised to 80 ° C. and maintained for 2 hours.

Next, while the substrate was kept at 80 ° C., an aluminum reflective film was formed on the signal pattern surface of the substrate. The film forming conditions of the aluminum reflective film are as follows: the purity of the aluminum ingot is 5N, the ultimate vacuum degree is 6.67 × 10 ^-3 Pa, the film forming speed is 1 nm / sec,
The film thickness was 100 nm.

After the formation of the aluminum reflective film, the substrate heater was turned off and the substrate was allowed to cool in a vacuum chamber for about one hour, and then the vacuum chamber was returned to normal pressure and the substrate was taken out.

Finally, a protective film of a urethane acrylate-based photocurable resin was laminated on the aluminum reflective film formed as described above to obtain a desired optical information recording medium.

The optical information recording medium thus manufactured and the optical information recording medium which had not been subjected to any anticorrosion treatment prior to the formation of the aluminum reflective film were each three examples at 60 ° C. × 90.
The sample was left in an atmosphere of% RH, and an accelerated environment test was performed. Second
The figure shows the results of this accelerated environment test. The horizontal axis of this graph indicates the test time, and the vertical axis indicates the reflectivity of the reflective layer. The data of the recording medium is indicated by a two-dot chain line. However, the wavelength of the measurement light is
Using a 780 nm laser, the line showing the measurement results shows the average value of three samples of the same type.

As is clear from this graph, the reflectance of the optical information recording medium in which the substrate has not been subjected to the baking treatment decreases rapidly between 200 and 300 hours, and becomes 15% after 3000 hours. On the other hand, in the optical information recording medium of this example in which the substrate was heated in a vacuum, the reflectance did not decrease at all even after about 3000 hours. When an accelerated environment test was performed on the optical information recording medium of this example under the conditions of 80 ° C. × 90% RH, a decrease in reflectance was observed after about 750 hours.

In the above-described embodiment, a polycarbonate substrate is described as an example of the resin substrate. Was.

In the above embodiment, the aluminum reflective layer was described as an example of the thin film layer to be corroded. However, the same effect was obtained with the heat mode recording material.

Furthermore, when the substrate was baked in the air and when the heating conditions were changed, almost the same effects as in the case of the above embodiment were obtained.

The gist of the present invention resides in the use of a resin substrate subjected to a baking process. In addition to this, it is possible to arbitrarily combine other anticorrosion processes. Other anticorrosion treatments include irradiating the substrate with energy such as oxygen plasma, sputter, glow discharge, electron beam, ultraviolet light,
Means are to form an intermediate layer between the substrate and the recording layer or the reflective layer with a material that does not easily transmit corrosive elements, or to select a substrate material that originally has a low content of corrosive elements. is there.

〔The invention's effect〕

As described above, according to the present invention, exudation of corrosive elements from a polycarbonate substrate can be prevented or significantly restricted. Therefore, the chemical reaction between the thin film layer and the corrosive element does not occur even when the thin film layer is left in a high-temperature and high-humidity atmosphere, or the progress of these chemical reactions slows down, and the life of the optical information recording medium is significantly shortened. Can be extended. Further, since the polycarbonate substrate is baked at a temperature of 60 ° C. to 110 ° C., the signal pattern formed on the surface of the substrate is not deformed, and excellent recording / reproducing characteristics are maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part showing a schematic configuration of an optical information recording medium according to the present invention, and FIG. 2 is a graph illustrating the effect of the present invention. 1 ... substrate, 3 ... recording layer or reflective layer, 4 ... pregroove, 5 ... prepit.

Claims (3)

(57) [Claims] An optical information recording medium in which a thin film layer including at least one of a recording layer and a reflective layer is formed on a signal pattern forming surface of a resin substrate. An optical information recording medium using a polycarbonate substrate which has been subjected to a baking treatment at a temperature of up to 110 ° C. for 30 minutes to 5 hours. 2. The optical information recording medium according to claim 1, wherein
An optical information recording medium, wherein the substrate is baked in a vacuum. 3. The optical information recording medium according to claim 1, wherein
An optical information recording medium, wherein the substrate is baked in air.