JPH0254439A - Optical recording medium - Google Patents

Abstract

PURPOSE:To allow reproduction without exerting influence on characteristics such as tracking performance and CN by providing a transparent layer consisting of a high-polymer compd., reflecting layer and protective layer on a recording layer consisting of an org. dye which can be made transparent by a specific treatment. CONSTITUTION:The recording layer 2 consisting of the org. dye is formed on a transparent substrate 1 and a transparent layer 3 consisting of the high-polymer compd. is provided thereon. The thickness of the layer is specified to 0.1 to 1mum. Further, the reflecting layer 4 and the protective layer 5 consisting of a UV curing resin for preventing the damage of the surface thereof are provided thereon. The recording layer 2 is decomposed by heat generation to form gaps when the recording layer 2 is irradiated with laser light. The dye of the recording layer 2 is thereby made transparent and as a result thereof the laser light generates the interference by the light passing the gaps and the light passing the transparent part around the gap parts. The signal reproducing as the change in light intensity is thus executed. Since the thickness of the transparent layer 3 is controlled to 0.1 to 1mum, the positions of the gaps are confined within the focal depth of the laser light and the characteristics such as tracking performance and CN are not affected.

Description

[Detailed description of the invention] Industrial applications The present invention relates to optical recording media.

BACKGROUND OF THE INVENTION Optical disks have been undergoing remarkable development in recent years, and as the market expands, it is expected that they will be used for a wide variety of purposes and applications.

Optical discs can be broadly divided into two types.

In other words, there are read-only optical discs and writable optical discs.The former uses a stamper on which information has been recorded in advance, and by depositing aluminum on a transparent substrate onto which the information on the stamper has been transferred by molding, a disc with the same information can be created. Tens of thousands of discs or more are manufactured, and like compact discs for music, manufacturers can produce them in large quantities at a relatively low cost even if they use expensive stampers.

However, this method cannot be applied to small-scale production, especially to personal information files, personal music discs, etc., in terms of cost performance.

A continuous write optical recording medium is a method for recording signals without using a stamper. There is a method of modulating the oscillation of laser light with a signal of information to be recorded and irradiating the recording layer with the laser light to record signals in the form of phase changes, geometric irregularities, voids, discoloration, etc.

Optical recording media using phase change are more expensive to manufacture than optical recording media using organic dyes. Conversely, in the case of an optical recording medium using an organic dye, the structure is a two-layer structure in which a protective plate is laminated onto the recording layer via a spacer to protect the organic dye recording layer. The structure is more complicated than a closed structure like this.

Therefore, closed-structure optical recording media using organic dyes have been developed, and one method is to irradiate the recording layer with laser light to decompose the substance in the recording layer and form voids. .

The invention tries to solve i! la When recording signals by forming voids and performing reproduction after making the recording layer transparent, the transparent layer facilitates the formation of voids, but its presence may reduce tracking performance or reduce the CN ratio. There is a problem in that voids must be formed without impairing these properties.

! Means for Solving IN In order to solve the above problems, the optical recording medium of the present invention has a recording layer on a transparent substrate, a transparent layer made of a polymer compound thereon, and It had a structure having a reflective layer thereon, and the thickness of the transparent layer was 0.1 to 1 μm.

Furthermore, a protective layer made of ultraviolet curing resin was provided to prevent surface damage.

Function When the recording layer is irradiated with a laser beam having a wavelength that is absorbed by the recording layer, the recording layer generates heat and decomposes, forming voids. By making the dye in the recording layer transparent, the laser light causes interference between the light passing through the gap and the light passing through the surrounding transparent dye, and signal reproduction can be performed as a change in light intensity. At this time, the laser light is focused on the surface of the reflective layer, but since the thickness of the transparent layer is controlled to 0.1 to 1 μm, the position of the gap can be kept within the focal depth of the laser, which improves tracking performance and CN. This will no longer affect characteristics such as ratio.

EXAMPLE Hereinafter, the present invention will be specifically explained using an example. 1st
1 in the figure is a transparent substrate, and glass, polycarbonate, polymethyl methacrylate, polyimide, epoxy resin, etc. can be used. A record N2 made of an organic dye is formed on a transparent substrate 1 by a spin coating method, a dipping method, or the like.

If the transparent substrate is to be eroded by a solvent during the formation of the recording layer, it is also possible to subject the transparent substrate to a solvent-resistant treatment using siloxane, SIO□, or the like. The dye used in the recording layer has absorption in the wavelength range of the semiconductor laser, and preferable examples include cyanine dyes, squarylium dyes, and phthalocyanine dyes. Hydroxyethylcellulose, nitrocellulose, polyvinylpyrrolidone,
The reflective layer 4, which can be made of polyimide, acrylamide, gelatin, polyvinyl alcohol, etc., needs to reflect 80% or more of the reproduction light, and can be made of aluminum, gold, m, platinum 1g4, or the like. Furthermore, in order to protect this reflective layer from damage, it is also possible to form a protective layer of ultraviolet curing resin or the like.

Example 1 A solution prepared by dissolving a dye represented by formula 1 in dichloroethane at a concentration of 2011 g/Id was spin-coated at 1100 Orp onto a polycarbonate transparent substrate l having a guide groove for a tracking servo manufactured by injection molding, and recording was performed. 712 was formed.

A hydroxyethyl cellulose aqueous solution with a concentration of 15 g/d was spin-coated at a rotation speed of 200 rpm to a thickness of 230 nm.
11 by vacuum evaporating aluminum on the transparent layer made of transparent N3.
On the reflective layer 4 on which the reflective layer 4 with a thickness of 00 nm has been formed, an ultraviolet curable resin is spin-coated and cured by irradiation with ultraviolet rays to maintain a thickness of about 5 μm! ! 1FJ5 was formed.

Recording was performed by irradiating this optical recording medium with light from a semiconductor laser with tracking servo applied at a linear velocity of 1.3 m/s, a recording power of 0 mw, and a frequency of 0.2 MHz. After recording, the recording layer was made transparent and the recorded signal was reproduced. The CNO ratio at this time was 47 dB.

Example 2 Instead of the transparent layer of Example 1, a gelatin aqueous solution having a concentration of 3 G/ml was spin-coated at a rotation speed of 200 rpm to prepare a transparent layer with a thickness of 560 nm.

When recording was performed under the same conditions as in Example 1 and the recorded signal was reproduced after the recording layer was made transparent, the CN ratio was 42 dB.

Comparative Example 1 Instead of the transparent layer of Comparative Example 1, a hydroxyethyl cellulose aqueous solution with a concentration of 3 (1@/d) was spin-coated at a rotational speed of 2000 rpm to produce a transparent layer with a thickness of 1.3 μm. Same as Example 1. When recording was performed under these conditions and the recorded signal was reproduced after the recording layer was made transparent, tracking servo could not be applied.When the CN ratio was measured without applying tracking servo, it was 23 dB.

Comparative Example 2 Recording was performed on an optical recording medium in which the transparent layer of Example 1 was omitted and reflective N4 was created directly on recording N2 under the same conditions as Example 1, and the recorded signal was reproduced after becoming transparent. Tokoro C
The N ratio was 23 dB.

Effects of the Invention In a recording method in which voids are formed in the recording layer, by making the dye in the recording layer transparent, the light from the semiconductor laser causes interference between the light passing through the void and the light passing through the surrounding transparent dye. , signal reproduction can be performed as a change in light intensity. At this time, the light from the semiconductor laser is focused at the point with the highest reflectance, that is, the surface of the reflective layer, and the focus position is not at a position where there is a gap, but the thickness of the transparent layer is controlled to 0.1 to 1 μm. Therefore, the position of the gap is within the depth of focus of the laser beam, and the gap can be detected. Therefore, reproduction can be performed without affecting characteristics such as tracking performance and CN ratio.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the optical recording medium of the present invention. 1...Transparent substrate, 2...Recording layer, 3.
...Transparent layer, 4...Reflection layer, 5...
...Main! ff layer. Name of agent Patent attorney Shigetaka Awano 1 person Figure 1 Sue - Toru B month 11 establishment 2, part # Shu Cao 3 - 19 B month view 4 - Anti-number layer 5 - Retention denied

Claims (1)

[Scope of Claims] A recording layer made of an organic dye that can be made transparent by a specific treatment on a transparent substrate, and a transparent layer made of a polymer compound with a thickness of 0.1 to 1 μm on top of the recording layer. It has a structure that has a reflective layer on top and a protective layer made of ultraviolet curing resin on top of it. By irradiating the recording layer with laser light with a wavelength in the absorption wavelength range of the recording layer, the irradiated part generates heat and decomposes. An optical recording medium characterized in that a void is formed in the recording layer, and reproduction is performed by the difference in refractive index between the void and the area around the void after the recording layer is made transparent.