JPH04298388A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium, which has excellent light resistance and in which pit mismatching is difficult to be generated and a flow is difficult to be generated on the surface of the medium, by forming a silicon oxide film on the external surface and/or internal surface of a light-transmitting substrate. CONSTITUTION:An optical recording medium 1 is composed of a light- transmitting substrate 11, a silicon oxide film 51 formed on the external surface of the substrate 11, a silicon oxide film 55 shaped on the internal surface of the substrate 11 and a dyestuff recording film formed onto the silicon oxide film 55. The intrusion of oxygen and steam from the outside can be prevented by forming the silicon oxide film 51. Even the generation of the surface flaw of the substance 11 can be obviated. The silicon oxide film 51 is formed through a vacuum thin-film forming method such as a sputtering method, an ion plating method, etc. On the other hand, a recording film 21 is shaped onto the silicon oxide film 55 formed on the internal surface of the substance 11 in the same method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writable optical recording medium, and more particularly to an optical recording medium comprising a recording film containing an organic dye on a light-transmitting substrate.

0002

2. Description of the Related Art Optical recording media generally have a large storage capacity and have excellent features such as non-contact writing and reading, and have been actively developed. An example of such an optical recording medium is a write-once optical disk, which has a recording film containing, for example, an organic dye on a substrate. A laser beam is focused from the side, converted into thermal energy, and recorded by changing the properties of the recording film (pit formation), and reproduction is performed based on the difference in the amount of reflected light from the unrecorded area. The substrates used for such media are cost-effective,
Polycarbonate resin (PC) and polymethyl methacrylate resin (PMMA) materials are widely used.

However, such a substrate has physical properties such that it does not have oxygen barrier properties, allows oxygen to pass through it, and has low mechanical strength. On the other hand, when it comes to recording films, cyanine, phthalocyanine, etc. are generally used as organic dyes. In particular, when cyanine is used in a recording film, although cyanine has excellent properties as a recording film, it has the drawback of being extremely weak against light and easily deteriorating. That is, cyanine causes a photoreaction in the presence of oxygen, and oxygen cross-linking occurs mainly at the double bond in the methine chain, which breaks the methine chain and leads to molecular collapse.

0004

Therefore, in a medium having a recording film of a cyanine-based organic dye film on the substrate, deterioration of the recording film inevitably occurs. In addition, the above-mentioned substrate has insufficient mechanical strength, and when pits are formed during recording, thermal deformation and flow occur in the substrate, resulting in pit misalignment and an inconvenience in that a sufficient reproduced signal cannot be obtained. Furthermore, the resin substrate described above also has the disadvantage that scratches are likely to occur on the substrate surface.

The present invention was created under these circumstances, and its purpose is to provide an optical recording medium that has excellent light resistance, is less likely to cause pit misalignment, and is less likely to have scratches on its surface. There is a particular thing.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an optical recording medium having a recording film on a light-transmitting substrate.
Alternatively, a silicon oxide film is provided on the internal surface. A partial longitudinal cross-sectional view of the optical recording medium of the present invention is shown in FIG. The optical recording medium 1 of the present invention includes a light-transmissive substrate 11, a silicon oxide film 51 formed on the outer surface of the substrate 11, a silicon oxide film 55 formed on the inner surface of the substrate, and a silicon oxide film 55 formed on the inner surface of the substrate. A dye recording film 21 is provided on a silicon film 55.

From the viewpoint of improving productivity, it is preferable to use a so-called injection molded resin substrate as the light-transmitting substrate 11, and this substrate is made of a transparent resin material such as polycarbonate resin (PC) or polymethyl methacrylate resin (PMMA). formed from. Although the grooves 11a are usually formed at the same time as the substrate molding, it may also be a so-called 2P substrate in which the resin substrate and the groove forming layer are separate bodies. .

The thickness of such a substrate 11 is usually 1.1
~1.5mm. A silicon oxide film 51 is formed on the external surface (laser incident side) of the substrate 11 as described above. By providing this silicon oxide film 51, it is possible to prevent oxygen and water vapor from entering from the outside. Furthermore, it is possible to prevent surface scratches on the substrate. The silicon oxide film 51 is formed by a vacuum thin film forming method such as a sputtering method or an ion plate method.

On the other hand, the inner surface of the substrate 11 (groove 11
A silicon oxide film 55 is formed on the formation surface a). This material is formed in the same manner as the silicon oxide film 51 described above. The film thickness is approximately 100 to 150 nm. A recording film 21 is formed on the silicon oxide film 55. The recording film 21 contains various known organic dyes. The present invention particularly targets organic dyes whose deterioration is caused by the presence of oxygen, that is, dyes which exhibit a photoreaction and are photodegraded in the presence of oxygen. Specifically, cyanine dyes having a cyanine skeleton can be mentioned. More specifically, for example, cyanine dyes represented by the following general formula [I] or general formula [II] may be mentioned.

0010

[Chemical formula 1]

[0011]

[Case 2]

In the above general formulas [I] and [II], R
1 and R2 are H, Cl or CH3, respectively
and R3 to R6 each have 1 to 8 carbon atoms.
represents an alkyl group, X represents a counter ion such as ClO4, I, Br, etc., and n represents an integer of 0 to 3. The recording film 12 containing such a dye is coated, for example, by a conventional method such as a spin coating method. The thickness of the coated recording film 12 is approximately 20 to 2000 nm. Note that various known solvents are used as the solvent for coating, such as diacetone alcohol, ethyl cellosolve, methyl cellosolve, isophorone,
Examples include methanol and tetrafluoropropanol.

A light reflecting film 31 is provided on such a recording film depending on the configuration of the medium. Light reflective film 3
1 is made of metal such as Au, Ag, Cu, Al, etc.
This material is formed by various vacuum film forming methods such as vacuum evaporation, sputtering, and ion plating. The thickness of such a light reflecting film 31 is approximately 0.02 to 2.0 μm.

[0014] On such a light reflection film 31, there is usually a
A protective film 41 is provided. The protective film 41 is generally formed by spin-coating an ultraviolet curable resin and then irradiating it with ultraviolet rays to cure the coating. In addition, silicone resin, urethane resin, etc. are used as the material for the protective film 41. The thickness of such a protective film 41 is usually 0.1
It is about 100 μm.

Note that an intermediate layer may be provided between the recording film 21 and the light reflecting film 31 in order to increase light absorption and reflectance. Alternatively, a so-called air sandwich structure may be used in which two substrates provided with recording films are prepared and the recording films are opposed to each other.

[0016]

[Operation] The medium of the present invention is generally irradiated with recording light in a pulsed manner while being rotated. At this time, part of the recording film is melted and removed to form pits. The pits formed in this manner are also formed by detecting the difference in the reflected light of the read light while the medium is rotating.

[0017]

EXAMPLES The present invention will be explained in more detail below by showing specific examples of the present invention. On the laser beam incident surface side and the groove surface of a polycarbonate substrate with a thickness of 1.2 mm and a diameter of 120 mm on which a groove was integrally molded,
A silicon oxide film was formed to a thickness of 150 nm by sputtering.

A recording film was formed on the silicon oxide film formed on the groove surface of this substrate. In the above general formula [II], R5 and R6 are each a methyl group, n=2, and X=ClO as the dye contained in the recording film.
4 were used. This dye was dissolved in an ethyl cellosolve solvent (dye concentration: 25 mg/ml) and coated on a substrate to a thickness of 100 nm. A reflective film made of Au was further deposited to a thickness of 1000 angstroms by vacuum evaporation so as to cover the top and side surfaces of this recording film. Furthermore, a photopolymer protective film was formed on this to produce an optical recording medium sample of the present invention (sample of the present invention).

On the other hand, a comparative sample was prepared in the same manner as the inventive sample (comparative sample), except that the silicon oxide films formed on both sides of the substrate were removed from the inventive sample. When these two samples were subjected to a light exposure test, it was confirmed that the sample of the present invention shows extremely little change in light transmittance over time compared to the comparative sample, and is significantly superior in light resistance. Furthermore, when the shape of the actually written pits and the substrate were confirmed, it was confirmed that the sample of the present invention had very little substrate deformation and was less likely to cause pit misalignment.

[0020]

Effects of the Invention The optical recording medium of the present invention has a structure in which a silicon oxide film is provided on the outer surface and/or inner surface of the light-transmitting substrate, so it has excellent light resistance, is less likely to cause pit misalignment, This has the effect that scratches are less likely to occur on the surface of the medium.

[Brief explanation of drawings]

FIG. 1 is a partial vertical cross-sectional view of an optical recording medium of the present invention.

[Explanation of symbols]

11 Light transparent substrate 21 Recording film 51,55 Silicon oxide film

Claims (3)

[Claims] 1. An optical recording medium having a recording film on a light-transmitting substrate, characterized in that a silicon oxide film is provided on the outer surface of the light-transmitting substrate. 2. An optical recording medium having a recording film on a light-transmitting substrate, characterized in that a silicon oxide film is provided on the inner surface of the light-transmitting substrate. 3. An optical recording medium having a recording film on a light-transmitting substrate, characterized in that a silicon oxide film is provided on an outer surface and an inner surface of the light-transmitting substrate, respectively. optical recording medium.