JPH04298390A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium excellent in not only medium characteristics but also light resistance by containing an organic dyestuff, deterioration of which is induced by the presence of oxygen, in a recording film and constituting a light-transmitting substrate with a barrier substrate, through which oxygen does not permeate. CONSTITUTION:An optical recording medium 1 is composed of a light- transmitting substrate 11 and a recording film formed onto the substrate 11. A barrier substrate having properties, through which oxygen does not permeate, is used as the light-transmitting substrate 11, and an amorphous polyolefin resin, glass, etc., are employed. The recording film 12 formed onto the substrate 11 contains an organic dyestuff, deterioration of which is induced by the presence of oxygen, that is, a dyestuff displaying an optical reaction in the presence of oxygen and being optically deteriorated is used. To be concrete, a cyanine dyestuff having a cyanine skeleton is cited.

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 on a substrate, and a laser beam is focused from the substrate side onto a minute area of the recording film. It emits light, converts it into thermal energy, changes the properties of the recording film (forms pits) to record, and reproduces it based on the difference in the amount of reflected light from unrecorded areas. The substrates used for such media are made of polymethyl methacrylate resin, polycarbonate resin, and epoxy resin from the viewpoint of satisfying various characteristics such as: ■ transparency, ■ moldability/transferability, ■ economic efficiency, and ■ environmental resistance. etc. are commonly used. However, these resin substrates do not have oxygen barrier properties and have physical properties that allow oxygen to permeate.

On the other hand, with regard to recording films, cyanine is generally used as an organic dye. Although cyanine has excellent properties as a recording film, it has the drawback of being significantly degraded by light. 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. As a defense against such deterioration,
Conventionally, measures have been taken such as introducing a quencher into the recording film and installing a shutter to prevent more light than necessary from being applied.

[0005]

[Problem to be Solved by the Invention] However, conventional countermeasures such as introducing a quencher into the recording film or providing a structural shutter are complicated and cannot be said to be fundamental solutions. . The present invention was created under these circumstances, and its purpose is to provide an optical recording medium that not only has excellent medium characteristics but also has excellent light resistance.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an optical recording medium having a recording film on a light-transmitting substrate, in which the recording film is deteriorated by the presence of oxygen. The light-transmissive substrate contains an organic dye,
It was constructed to be a barrier substrate that does not allow oxygen to pass through.

FIG. 1 is a partial vertical cross-sectional view of the optical recording medium of the present invention.
is shown. The optical recording medium 1 of the present invention has a light-transmitting substrate 11
and a recording film 12 provided on this substrate 11. The light-transmitting substrate 11 is a barrier substrate that does not allow oxygen to pass through, and specific materials thereof include amorphous polyolefin resin (for example, ZEONEX 280 manufactured by Nippon Zeon, APO manufactured by Mitsui Petrochemicals, etc.). Glass etc. are used. Such a substrate 11 has oxygen barrier properties and can prevent oxygen from permeating. The thickness of such a substrate 11 is 1.1 to 1.5 mm.
It is considered to be a degree.

The recording film 12 provided on the substrate 11 is
The targets are those containing organic dyes that undergo deterioration in the presence of oxygen, that is, dyes that 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.

[0009]

[Chemical formula 1]

0010

[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.

[0012] On such a recording film, if necessary,
Various known metal reflective films, protective layers, etc. are laminated. Figure 1
As shown in , the protective layer 13 is made of Au, Ag, Al.
, Cu, or the like, and is provided so as to surround the upper surface and side surfaces (not shown) of the recording film 12, which prevents oxygen from permeating and is effective. Note that an intermediate layer may be provided between the substrate 11 and the recording film 12 to protect the substrate 11 from the solvent. 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.

[0013]

[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.

[0014]

EXAMPLES The present invention will be explained in more detail below by showing specific examples of the present invention. In the above general formula [II], the dyes contained in the recording film include R5 and R6.
were each a methyl group, n=2, and X=ClO4. This dye was dissolved in an ethyl cellosolve solvent (dye concentration: 25 mg/ml), and this was made into an amorphous polyolefin resin (Nippon Zeon: ZEONEX 280) with a diameter of 120 mm and a thickness of 1.2 mm.
It was coated onto a substrate to a thickness of 100 nm. A protective 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 protective film of an ultraviolet curable resin was laminated thereon to produce a sample of the present invention (sample of the present invention).

On the other hand, the substrate of the sample of the present invention was changed from an amorphous polyolefin resin to a polycarbonate substrate (
A comparative sample was prepared in the same manner as the above-mentioned sample of the present invention (comparative sample) except that Panlite (manufactured by Teijin Kasei Ltd.) was used instead. A light exposure test was conducted on these two samples under the following conditions. <Light exposure test conditions> Matsushita Electric Industrial Co., Ltd. fluorescent lamp (F
L-20SS-EX-18) and Black Light Blue (
FL-30S/BL-B) was placed at a height of 15 cm from the sample surface, and each light was irradiated onto the sample (disk) at the same time. At the start, after 410 hours, after 913 hours, and The light reflectance was measured after 1410 hours had elapsed. The results are shown in FIGS. 2 and 3. FIG. 2 shows the light exposure test results for the sample of the present invention, and FIG. 3 shows the light exposure test results for the comparative sample. The effects of the present invention are clear from the results shown in FIGS. 2 and 3. In other words, the inventive sample was able to prevent photodeterioration of the recording film and maintained its light absorption (no change in light reflectance over time), whereas the comparative sample's recording film was able to prevent light deterioration. deteriorated by
Absorption could not be maintained and the light reflectance increased over time.

[0016]

Effects of the Invention The optical recording medium of the present invention is an optical recording medium having a recording film on a light-transmissive substrate, and the recording film contains an organic dye that causes deterioration in the presence of oxygen. However, since the light-transmissive substrate is configured to be a barrier substrate that does not allow oxygen to pass through, it has the effect of not only excellent medium properties but also extremely excellent light resistance.

[Brief explanation of the drawing]

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

FIG. 2 is a graph showing the results of a light exposure test for samples of the present invention.

FIG. 3 is a graph showing the results of a light exposure test of a comparative sample.

[Explanation of symbols]

11. Light-transparent substrate 12 Recording film

Claims (2)

[Claims] 1. An optical recording medium having a recording film on a light-transmitting substrate, wherein the recording film contains an organic dye that is degraded by the presence of oxygen, and the light-transmitting substrate has a recording film disposed on a light-transmitting substrate. An optical recording medium characterized by having a barrier substrate that does not transmit light. 2. The optical recording medium according to claim 1, wherein the organic dye has a cyanine skeleton.