JPH01271937A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To prevent the corrosion of a thin film layer and to prolong the life of the recording medium by providing an intermediate layer consisting of a material which does not contain corrosive elements and hinders the permeation thereof between a resin substrate and the thin film layer for recording or reproducing. CONSTITUTION:The intermediate layer 2 is formed on one face of the resin substrate 1 and the recording layer or reflecting layer 3 is formed thereon. Signal patterns consisting of pregrooves 4 and prepits 5 are formed on the layers 2, 3. The layer 2 is formed of the material such as silicon nitride, silicon oxide, PE which does not contain the corrosive elements such as chlorine, sulfure fluorine and hinders the permeation of the corrosive materials. A sputtering method, vacuum deposition method, plasma polymn. method, spin coating method, etc., are used according to the kind of the material as the means for forming the layer 2. The corrosion of the thin film layer by the corrosive elements in the substrate is thereby prevented and the life of the recording medium is prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical information recording medium, and particularly to a means for preventing corrosion of a recording layer or a reflective layer formed on a substrate.

[Conventional technology]

Conventionally, optical information recording media have been known in which a thin film layer such as a reflective film or a recording film is formed on the signal pattern forming surface of a resin substrate. An aluminum reflective film is formed on the forming surface, and a protective film made of a urethane acrylate photocurable resin is further laminated on the aluminum reflective film.

In the case of the compact disc, if no anti-corrosion treatment is applied to the aluminum reflective film on the substrate, the temperature is 60°C.
When an accelerated environmental test is performed by leaving the device in an atmosphere of 90% RH, the aluminum reflective film corrodes in 200 to 300 hours, and the reflectance decreases, making it difficult to read information.

Although the above description has been made using a compact disc having an aluminum reflective film as an example, similar problems exist with all optical information recording media having a reflective layer or recording layer made of other materials.

Traditionally, it has been recognized that this type of corrosion of thin film layers is caused by water penetrating through the substrate or protective film, forming a waterproof coating on the surface of the thin film layer, or when the thin film layer is made of metal. In this case, corrosion-resistant treatment such as forming an oxide film on the metal has been proposed (Japanese Patent Laid-Open No. 62-6244).
No. 5).

Optical information recording media that have been subjected to such waterproofing or corrosion-resistant treatment have a longer lifespan than optical information recording media that have not been subjected to any such treatment.1For example, in the case of compact discs, aluminum reflective When an alumina layer is formed on the surface layer of the film, the corrosion initiation time of the aluminum reflective film is extended to about 1500 hours when an accelerated environmental test is conducted under the same conditions as above.

[Problem a that the invention seeks to solve]

However, this type of optical information recording medium is required to have a longer lifespan.

Conventional corrosion protection measures are still insufficient.

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

■The thin film layer is easily corroded in a high temperature, high humidity atmosphere, but hardly corroded in a high temperature, low humidity atmosphere.

When a glass substrate is used, the thin film layer is less likely to corrode even in a high temperature and high humidity atmosphere.

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

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

■Corrosion of thin film layers 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 estimated that the corrosion mechanism of the thin film layer is as follows.

First, corrosive elements contained in the resin substrate cause a chemical reaction with the thin film layer material. Taking the case where the corrosive element is chlorine (C, l) as an example, this chemical reaction is explained using a chemical formula as follows.

M (thin film material) + 4 C1--+MC14-+ 3
e - (1) Next, the MC14- produced by this reaction and the moisture that has entered from the outside through the protective film cause the following chemical reaction.

MC14-+ 3 Hz O → M(OH)3 +3H" +4C1-... (2) Furthermore, C1- generated by this reaction again causes the chemical reaction of formula (1) above, causing continuous corrosion. Proceed to.

Therefore, corrosion of the thin film layer can be prevented by preventing the intrusion of at least one of corrosive elements and moisture. However, resin substrates have some degree of water permeability, and it is difficult to completely prevent water permeability, and if treatments are applied to prevent this, the cost of the optical information recording medium will increase significantly. In contrast, it has been found that preventing the penetration of corrosive elements into the thin film layer can be carried out relatively simply by forming an intermediate layer between the substrate and the thin film layer.

The present invention has been made based on the above knowledge, and an object of the present invention is to prevent corrosion of the thin film layer by preventing corrosive elements from entering the thin film layer, thereby providing a long-life optical information recording medium. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention does not contain corrosive elements between the resin substrate and the thin film layer.

In addition, it is characterized by providing an intermediate layer made of a substance that prevents the permeation of corrosive elements.

As the substance that does not contain any corrosive elements and prevents the corrosive elements from permeating, a substance to which the corrosive elements cannot penetrate at all may be used, or a substance that captures the corrosive elements that have invaded and transfers them to the thin film layer. It is also possible to use a substance that prevents the movement of.

[Effect]

When the above-mentioned intermediate layer is provided between the resin substrate and the thin film layer,
Corrosive elements in the resin substrate, which are the main cause of corrosion of the thin film layer, do not invade the thin film layer, and corrosion of the thin film layer is prevented. Therefore, it is possible to provide an optical information recording medium with excellent corrosion resistance and long life.

〔Example〕

First, the schematic structure of the optical information recording medium according to the present invention will be explained.

FIG. 1 is a sectional view of a main part showing a typical example of an optical information recording medium according to the present invention, in which an intermediate layer 2 is formed on the signal pattern forming surface of a substrate 1, and a recording layer is formed on this intermediate layer 2. Alternatively, the reflective layer 3 is laminated.

The substrate 1 is made of polycarbonate (PC), for example.

It is formed from a transparent resin material such as polymethyl methacrylate (PMMA), polymethylpentene, or epoxy. On one side of the substrate 1, a signal pattern such as a pre-group 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 is formed in the form of an uneven shape. There is.

These signal patterns 4 and 5 are formed by an appropriate method depending on the type of substrate material. For example, injection molding is suitable for thermoplastic resins such as PC and PMMA, and so-called 2P method (photocurable resin method) and casting method are suitable for thermosetting resins such as epoxy.

The intermediate layer 2 is formed from a material that does not contain corrosive elements such as chlorine, sulfur, and fluorine and prevents the permeation of these corrosive elements. Specifically, silicon nitride (
Si:INx, however, 3<x<4, silicon oxide (S
tyx, where 1<x×2), styrene plasma polymer, polyethylene, polyvinyl alcohol, cellulose nitrate, acrylate ultraviolet curable resin, and the like. Furthermore, it is also possible to add a substance that easily binds to a corrosive element, such as tetrabutyltin, to these substances so that the intermediate layer 2 captures the corrosive element.

As a means for forming the intermediate layer 2, thin film forming means such as a sputtering method, a vacuum evaporation method, a plasma polymerization method, a spin coating method, etc. can be applied depending on the type of intermediate layer material.

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

In addition, for read-only optical information recording media, the six reflective layer materials in which a reflective layer is formed in place of the recording layer include:
Although any high reflectance material can be used, it is relatively inexpensive and easy to form a film, so
Aluminum is particularly preferred.

As a means for forming the recording layer 3, a spin coating method is used for organic dye-based recording materials, and a vacuum film forming method such as a vacuum evaporation method or a sputtering method is used for other recording materials.

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

<First Example> An intermediate layer made of 5i3Nx (3 < x 4) was formed on the signal pattern surface of a polycarbonate substrate by RF sputtering. The film forming conditions are as shown in Table 1.

Next, an aluminum reflective layer was laminated on the intermediate layer. The conditions for forming the aluminum reflective layer are that the purity of the aluminum ingot is 5N, and the ultimate vacuum is 6.67X10-
' Pa or less, the substrate temperature is 25° C., the film formation rate is 1 nm/sec, and the film thickness is about 1100 nm.

Finally, a protective film of urethane acrylate photocurable resin was laminated on the aluminum reflective layer.

Second Example> An intermediate layer made of 5iOx (where 1<x<1) was formed on the signal pattern surface of a polycarbonate substrate by RF sputtering. The film forming conditions are as shown in Table 2.

Thereafter, in the same manner as in the first example, an aluminum reflective layer and a protective film of a urethane acrylate photocurable resin were sequentially laminated on the intermediate layer.

Third embodiment> On the signal pattern side of a polycarbonate board.

An intermediate layer made of 5iOx (1 < x 2) was formed by electron beam evaporation. The film forming conditions are as shown in Table 3.

Thereafter, in the same manner as in the first example, an aluminum reflective layer and a protective film of a urethane acrylate photocurable resin were sequentially laminated on the intermediate layer.

<Fourth example> On the signal pattern side of the polycarbonate board.

An intermediate layer of a styrene plasma polymerized film was formed using a plasma polymerization method. The film forming conditions are as shown in Table 4.

Thereafter, in the same manner as in the first example, an aluminum reflective layer and a protective film of a urethane acrylate photocurable resin were sequentially laminated on the intermediate layer.

Fifth Example A polyethylene intermediate layer was formed on the signal pattern surface of a polycarbonate substrate by resistance heating vapor deposition. The film forming conditions are as shown in Table 5.

Thereafter, in the same manner as in the first example, an aluminum reflective layer and a protective film of a urethane acrylate photocurable resin were sequentially laminated on the intermediate layer.

(Sixth Example) On the signal pattern side of a polycarbonate board.

A base layer made of polyvinyl alcohol was formed by spin coating. A specific method for forming the base layer is as follows.

First, polyvinyl alcohol powder with a degree of polymerization of 2000 and a degree of saponification of 88.0% was prepared, and decantation with water was repeated several times to remove sodium acetate contained in the polyvinyl alcohol.

Next, water was added to this polyvinyl alcohol.

Heat to 60-80°C and stir for about 2 hours, then add 2.
5% by weight of polyvinyl alcohol was completely dissolved.

Next, about 10% by weight of ammonium dichromate based on polyvinyl alcohol was added to this aqueous solution and completely dissolved.

Further, this aqueous solution was filtered through a 0.2 μm filter to remove foreign matter, and an aqueous solution of polyvinyl alcohol and ammonium dichromate for forming the base layer was prepared.

Next, the aqueous solution of polyvinyl alcohol and ammonium dichromate was spin coated on the signal pattern surface of the substrate.

Finally, this film was irradiated with ultraviolet rays for several minutes using an ultra-high pressure mercury lamp to crosslink polyvinyl alcohol and ammonium dichromate to form a complex between the two. by this,
An intermediate layer made of the above complex was formed to a thickness of about 80 nm on the signal pattern surface of a polycarbonate substrate.

Next, an aluminum reflective layer and a protective layer of a urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first example to obtain a desired optical information recording medium.

<Seventh Example> On the signal pattern side of a polycarbonate board.

A base layer made of polyvinyl alcohol containing lead acetate was formed by a spin coating method. A specific method for forming the base layer is as follows.

First, the same aqueous solution of polyvinyl alcohol and ammonium dichromate was prepared by the method described in the sixth example.

Next, add about 5% of the polyvinyl alcohol to the aqueous solution of polyvinyl alcohol and ammonium dichromate.
% by weight of lead acetate powder was added and completely dissolved.

Next, this aqueous solution of polyvinyl alcohol, ammonium dichromate, and lead acetate was spin-coded onto the signal pattern surface of the substrate, and then ultraviolet rays were irradiated to coat it to a film thickness of about 80 mm.
An intermediate layer of 100 nm was formed.

Finally, an aluminum reflective layer and a protective layer of urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first example to obtain a desired optical information recording medium.

Eighth Example> An intermediate layer made of cellulose nitrate was formed on the signal pattern surface of a polycarbonate substrate by spin coating. A specific method for forming the intermediate layer is as follows.

First, cellulose nitrate having a molecular weight of 220,000 and containing about 30% by weight of isopropyl alcohol and methanol were prepared in a weight ratio of 5:15:985.

Next, cellulose nitrate was added to methanol and stirred for several hours to completely dissolve it.

Next, this solution was filtered, and then spin-coated onto the signal pattern surface of a polycarbonate substrate.

Finally, this thin film was air-dried to form an intermediate layer made of cellulose nitrate with a thickness of about 80 nm.

Next, an aluminum reflective layer and an S-retaining layer of urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first example to obtain a desired optical information recording medium.

Ninth Example> An intermediate layer made of cellulose nitrate containing tetrabutyltin was formed on the signal pattern surface of a polycarbonate substrate by spin coating. A specific method for forming the intermediate layer is as follows.

First, a methanol solution of cellulose nitrate identical to that described in the eighth example was prepared.

Next, about 5% by weight of tetrabutyltin based on the cellulose nitrate was added to the methanol solution of cellulose nitrate and completely dissolved.

Next, -1 This solution was filtered through a filter, and then spin-coated onto the signal pattern surface of a polycarbonate substrate.

Finally, this thin film was air-dried to form an intermediate layer made of cellulose nitrate containing tetrabutyltin and having a thickness of about 80 nm.

Next, an aluminum reflective layer and a protective layer of urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first embodiment.

A desired optical information recording medium was obtained.

10th Example> An intermediate layer made of an acrylate ultraviolet curing resin was formed on the signal pattern surface of a polycarbonate substrate by spin coating. A specific method for forming the intermediate layer is as follows.

First, an acrylate-based ultraviolet curing resin (for example, ThreeBond 30X4004, a trade name manufactured by ThreeBond) was completely dissolved in isopropyl alcohol.

Next, this solution was filtered through a filter, spin-coated onto the signal pattern surface of a polycarbonate substrate, and baked at 80° C. for several minutes to remove the solvent remaining in the film.

Finally, this thin film was irradiated with ultraviolet rays from a metal halide lamp to form an intermediate layer made of an acrylate ultraviolet curing resin with a thickness of about 1100 nm.

Next, an aluminum reflective layer and a protective layer of urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first embodiment.

A desired optical information recording medium was obtained.

11th Example> On the signal pattern side of a polycarbonate board.

An intermediate layer made of an acrylate ultraviolet curing resin containing tetrabutyltin was formed by spin coating. A specific method for forming the intermediate layer is as follows.

First, the same acrylate-based ultraviolet curing resin solution was prepared by the method explained in the tenth example.

Next, approximately 1% by weight of tetrabutyltin based on the acrylate-based ultraviolet curable resin was added to this solution and completely dissolved.

Next, in the same manner as in the first O embodiment, spin coating,
Baking and ultraviolet irradiation were performed to form an intermediate layer made of an acrylate ultraviolet curable resin containing tetrabutyltin and having a thickness of approximately 1100 nm.

Finally, an aluminum reflective layer and a protective layer of urethane acrylate photocurable resin were formed on this intermediate layer under the same conditions as in the first embodiment.

A desired optical information recording medium was obtained.

The optical information recording medium of each of the above embodiments according to the present invention.

Optical information recording media that have not been subjected to any anti-corrosion treatment
An accelerated environmental test was conducted by leaving the sample in an atmosphere of 90% RH. Figure 2 shows the results of this accelerated environmental test. The horizontal axis of this graph is the test time, and the vertical axis is the reflectance of the reflective layer. The data of the optical information recording medium according to the conventional example is indicated by a solid line, and the data of the optical information recording medium according to the conventional example is indicated by a two-dot chain line. However, the wavelength of the measurement light is 78
0nm laser, and the lines showing the measurement results are 3.
This is the average value of the same type of samples.

As is clear from this graph, the optical information recording medium without any anti-corrosion treatment on the substrate can be used for approximately 24 hours (at 60°C
In a 90% RH atmosphere, the reflectance begins to decrease significantly after 200 to 300 hours, whereas in the optical information recording medium of this example in which a preservative tactile element base film was formed on the substrate, the reflectance decreased after 2000 hours. No decrease in reflectance was observed even after the passage of time.

From the above test results, it was found that the optical information recording medium of the present invention has a remarkable effect on improving the corrosion resistance of the reflective layer.

In each of the above embodiments, a polycarbonate substrate was used as an example of the resin substrate, but similar effects can be obtained with other resin substrates such as epoxy resin, polymethyl methacrylate, polymethyl pentene, polyolefin, etc.

Further, in each of the above embodiments, an aluminum reflective layer was used as an example of a thin film layer to be corrosion-protected, but the same effect can be obtained for a heat mode recording material.

Further, in each of the above embodiments, only the influence of chlorine as a corrosive element has been described, but a similar effect also exists on the corrosion of gold JN calendar caused by, for example, sulfur and fluorine.

The gist of the present invention is that an intermediate layer is formed between the substrate and the recording layer or reflective layer using a material that does not easily transmit corrosive elements, but in addition to this, other anti-corrosion treatments may be combined. It can be done arbitrarily. Other anti-corrosion treatments include: - irradiating the substrate with energy such as oxygen plasma, sputter etching, glow discharge, electron beam, ultraviolet light, etc., - baking the substrate, and - increasing the content of corrosive elements in the substrate material. There are methods such as selecting one with a low value.

Further, in each of the above embodiments, the intermediate F32 is provided on the substrate 1.
And the reflective layer or record fiff3 is 2M! Although only the case where the present invention is laminated on I has been described, it can be applied to an optical information recording medium having any thin film structure, such as one in which a thin film is added to improve recording sensitivity, for example.

〔Effect of the invention〕

As explained above, according to the present invention, seepage of corrosive elements from a resin substrate can be prevented or significantly restricted. Therefore, even if the thin film layer is left in a high-temperature atmosphere, chemical reactions between the thin film layer and corrosive elements do not occur, or the progress of these chemical reactions is slowed down, significantly extending the life of the optical information recording medium. be able to.

[Brief explanation of the drawing]

The drawings are all for explaining the present invention, and FIG. 1 is a cross-sectional view of a main part showing a schematic structure of an optical information recording medium, and FIG. 2 is a graph explaining the present invention in detail.

Claims (5)

[Claims] (1) In 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 one side of a resin substrate, the thin film layer is formed between the resin substrate and the thin film layer. An optical information recording medium characterized in that an intermediate layer is provided that does not contain corrosive elements that corrode the layer and is made of a substance that prevents the corrosive elements from permeating. (2) The optical information recording medium according to claim 1, wherein the intermediate layer does not contain at least one corrosive element selected from chlorine, sulfur, and fluorine, and is selected from chlorine, sulfur, and fluorine. An optical information recording medium characterized in that it is formed of a substance that prevents the transmission of at least one type of corrosive element. (3) In the optical information recording medium according to claim 1, the intermediate layer is made of silicon nitride (Si_3Nx, where 3<x<
4), silicon oxide (SiOx, 1<x<2),
An optical information recording medium characterized in that it is formed using at least one substance selected from styrene plasma polymer, polyethylene, polyvinyl alcohol, cellulose nitrate, and acrylate ultraviolet curing resin. (4) In the optical information recording medium according to claim 1, at least one element that is easily bonded to the corrosive element is included in the intermediate layer.
An optical information recording medium characterized by adding various kinds of substances. (5) The optical information recording medium according to claim 4, wherein at least one of tetrabutyltin and lead acetate is added to the intermediate layer as a substance that easily combines with the corrosive element. optical information recording medium.