JPS6199951A - Optical recording element - Google Patents

Abstract

PURPOSE:To decrease noise level and to improve S/N and C/N by providing light absorptive layers which absorb information reading-out light between recording members and adhesive layer. CONSTITUTION:The deterioration of the S/N and C/N of an optical recording element arises from the reflection from another recording members adhered to each other, and therefore the reflection is prevented by incorporating a coloring agent which absorbs light into the adhesive layer. The noise level is thereby decreased. The absorptive layers 4, 4' incorporated therein with the coloring agent which absorbs the reading-out light are provided between the recording members 2, 2' and the adhesive layer 3 to decrease the noise level. The black coloring agent such as carbon black, iron black, graphite or aniline black is most preferable for the coloring agent. The blue coloring agent such as phthalocyanine blue, cobalt blue or ultramarine blue is also effective in addition to the above-mentioned black coloring agent in the case of using an He-Ne laser or Ar laser for the reading-out light.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to an element for optically recording and reproducing.

In particular, the present invention relates to an optical recording element in which noise increases little due to bonding of recording media.

[Background of the invention]

An element for optically recording and reproducing information is formed by forming a recording medium on a substrate, whose optical characteristics such as reflectance are changed by heat generated by a light beam such as a laser beam. For example, the recording medium may be an optically transparent substrate (eg, glass) as shown in FIG.

A recording member 2 (for example, an amorphous thin film of a chalcogen compound, tellurium, etc.) whose reflectance changes with heat is formed on a material 1 (acrylic resin, polycarbonate resin, etc.).

When a double-sided disk is used, the recording medium constructed in this manner is bonded to, for example, a similar recording medium by an adhesive layer 3 as shown in FIG. 4 to form a single-sided optical recording element.

For a detailed description of the double-sided bonding method or the structure of a double-sided optical recording element, see Japanese Patent Laid-Open No. 58-6
No. 536, Japanese Patent Application Laid-Open No. 57-66540, and Japanese Patent Application Laid-Open No. 58-45633.

However, in the optical recording element configured as shown in f:, a part of the readout incident light io during information reading passes through the recording member 2 and is transferred to the recording member 2' on the back side bonded together. Because it is reflected, the readout reflected light i
B includes a diffuse reflection component depending on the surface condition of the recording member 2 on the back side, and the noise level increases compared to the readout reflected light before bonding, resulting in an increase in S/N (signal-to-noise ratio) and C/N.
No consideration was given to the deterioration of the carrier-to-noise ratio.

[Purpose of the invention]

The purpose of the present invention is to achieve a low noise level (S/N and C/N
The object of the present invention is to provide a good optical recording element.

[Summary of the invention]

Deterioration of the S/N and C/N of an optical recording element is caused by reflection from another recording member bonded to it. Therefore, by mixing a coloring agent that absorbs light into the adhesive layer, the above reflection can be reduced. Prevent.

Noise level can be reduced. The present invention is characterized in that a light absorption layer containing a coloring agent that absorbs read light is provided between the recording member and the adhesive layer to reduce the noise level.

Pigments or dyes can be used as the coloring agent. As is clear from the above, it is important that the light absorption layer absorbs light at the wavelength of the information readout light, and for this purpose, a black coloring agent such as carbon black, iron black, graphite, or black is used. is the best, and in addition to the above-mentioned black coloring agent, blue coloring agents such as phthalocyanine blue, cobalt blue, and gunjo are also effective when a readout light such as an LCHe-Ne laser or an Ar laser is used.

The light-absorbing layer may be a synthetic resin material containing the coloring agent, an emulsion paint, a lacquer paint, or a photopolymerizable ultraviolet curable resin such as an acrylic acid ester resin. You can use the mixture.

The light-absorbing layer can also function as a protective layer to prevent scratches on the recording member and improve its durability. By using dyes such as aniline black as a coloring agent, it has a low noise level and high durability. A good optical recording element can be obtained. In addition, when a particulate colorant such as * is mixed into the light absorption layer, when the light absorption layer is provided on the recording member, the colorant particles are dispersed at the interface between the recording member and the light absorption layer. do,
The readout light may be diffusely reflected at the interface, increasing the noise level. In such a case, it is effective to provide an interfacial separation layer having a light-transmitting property between the light absorption layer and the recording member. Further, the thickness of the interface separation layer needs to be at least twice the depth of focus of the readout light. Namely.

Even if an interfacial separation layer is provided, the colorant particles will be dispersed at the interface between the interfacial separation layer and the light absorption layer, so it is necessary to suppress the increase in noise level due to diffuse reflection in this area. It is preferable to make the thickness of the layer at least twice the depth of focus of the readout light so that the readout light is not focused on the area where the diffused reflection occurs. The depth of focus j of the readout light depends on the NA of the optical lens and the wavelength λ of the readout light, and is given by l=λ/2(NA).For example, if the wavelength of the readout light is 8301, which is the wavelength of a semiconductor laser, , when NA is 0.6, the depth of focus Z is approximately 1t1m, and the thickness of the interface separation layer is 2μ.
m or more is better.

The interface separation layer is preferably made of a translucent material, and most preferably transparent, since this increases the noise level due to diffuse reflection at the interface with the recording member and within the interface separation layer. , ultraviolet curing resin, clear lacquer, etc. can be used.

Furthermore, the interfacial separation layer b can also serve as a protective film for the recording member.

[Embodiments of the invention]

The configuration of an embodiment of the present invention is shown in FIG. 1 and @2. f
In Figure a1, 1 and 1' are substrates made of optically transparent acrylic resin, 2 and 2' are recording members that are provided on the substrate 1°1' and whose reflectance changes when irradiated with laser light, and 3 is an adhesive. Layer 4.4' is a light absorbing layer according to the invention. Further, in FIG. 2, 5 and 5' are interfacial separation layers according to the present invention, and 6 and 6' are light absorption layers according to the present invention.

In the following embodiments of the present invention, 5h
A two-layer recording film having a 1cBi thin film formed on a 2Se3 thin film was used. Further, the noise level in the following examples is determined by measuring the noise level at IMIIzK by forming an optical recording element into a disk shape and rotating it at 1800 rpm using a spectrum analyzer. The wavelength of the readout light used in this measurement was 830%, and the NA of the optical lens was 0.6.

Next, an embodiment according to the present invention will be described.

Example 1 Aniline black was mixed as a coloring agent into a lacquer paint mainly composed of nitrocellulose.

A solution whose viscosity was lowered using a thinner solvent and a heptane diluent was spin-coated onto the recording member 2 using a spinner, and the solution was evaporated and dried to obtain a light-absorbing layer 4. Thereafter, another recording member obtained in the same manner was applied to the sticky hot melt adhesive 3.
By applying this with a roll coater, an optical recording element having the structure shown in FIG. 1 was obtained. Results of measuring the noise level of the optical recording element.

Compared to the case without a light absorption layer, the noise level is about 17
It decreased by dB. This is achieved by providing a light absorption layer.
Since the readout light that has passed through the recording member is absorbed by the light absorption layer, it is possible to prevent the generation of noise due to diffuse reflection from the recording member on the back side of the bonding, and the noise level has been significantly reduced.

Example 2 Black paint mixed with carbon black,
Spray or paint onto the recording material.

It was evaporated and dried to obtain a light absorption layer. Thereafter, another recording member obtained in the same manner was bonded together by applying a tacky hot melt adhesive using a roll coater to obtain an optical recording element. As a result of measuring the noise level of the optical recording element, the noise level was lowered by about 10 dB compared to the case where no light absorption layer was provided. On the other hand, when comparing the noise level of the optical recording element with the measurement result of the noise level in a state where the recording member is simply formed on the base as shown in FIG.
dB increased. This is because the light absorbing layer prevents the generation of noise due to diffuse reflection from the recording member on the back side of the bond and was able to reduce the noise level by about 10 dB, but on the other hand, 1. Compared to the noise repe k that causes IKn as shown in Figure 3.

As described above, the carbon black particles contained in the light absorption layer were dispersed at the interface between the recording member and the light absorption layer, and the read light was diffusely reflected at the interface, increasing the noise level by about 7 dB.

Example 3 As the interface separation layer 5, a transparent ultraviolet curing resin was spin-coated onto the recording member using a spinner, and cured by ultraviolet irradiation. The thickness of the interfacial separation layer is 1 μm. Thereafter, a black lacquer mixed with carbon black was applied by spraying on the interfacial separation layer, and the mixture was evaporated and dried to obtain a light-absorbing layer 6. Next, another recording member provided with an interfacial separation layer 5' and a light absorption layer 6' was coated with a hot-melt adhesive using a roll coater and bonded together to form the structure shown in Figure 2. An optical recording element was obtained. As a result of measuring the noise level of the optical recording element, the noise level was lowered by about 4 dB compared to the case without the interface separation layer.

In addition, the thickness of the interface separation layer was set to 2 μm, 10 μm, and 30 μm.
The increase in the noise level in the case of Example 4. Example 5. It is shown in Table 1 as Example 6. In Table 1, the noise level is based on the noise level in a state in which only a recording member is formed on a substrate as shown in FIG. From this, the noise level decreased as the thickness of the interfacial separation layer increased. Therefore, in order to reduce the noise level, it is preferable to form an interfacial separation layer, and more preferably the thickness of the interfacial separation layer is 2 μm or more.

This can be explained from the relationship between the depth of focus of the readout light and the thickness of the interface separation layer, as described above.

By providing a light absorption layer and an interfacial separation layer in Example 3 to Example 6 above, noise due to diffuse reflection from the recording member on the back side of the bonding and noise caused by particulate coloring agent contained in the light absorption layer can be reduced. I was able to prevent noise.

In the above embodiments, a layer mixed with a black coloring agent was used as the light absorption layer, but the layer is not limited to this, and the same effect can be obtained as long as it absorbs the readout light. Other organic dyes, organic pigments or inorganic materials can be used as the light absorbing layer.

Further, in the above embodiment, a light absorption layer was provided on each of the bonded recording members, but the same effects as in the embodiments of the present invention can be obtained even if only one of the recording members is provided with a light absorption layer. Obtainable.

In the method of mixing a light-absorbing colorant into the adhesive layer, the adhesion strength may decrease due to the colorant being mixed in. However, the present invention provides a light-absorbing layer between the adhesive layer and the recording member. , an appropriate adhesive can be selected, and a decrease in adhesive strength can be prevented.

Table g It has the effect of lowering the noise level.

[Brief explanation of drawings]

1 and fs2 are sectional views of essential parts conceptually representing an optical recording element according to an embodiment of the present invention, FIG. 3 is a sectional view of essential parts conceptually representing a recording medium, and FIG. 4 is a sectional view of two parts. FIG. 2 is a cross-sectional view of a main part conceptually showing an optical recording element obtained by bonding recording media together. 1.1...Substrate, 2.2...Recording member 3...Adhesive layer, 4,6.6...Light absorption layer 5...Interfacial separation m.

Claims (1)

[Claims] 1. In an optical recording element in which an information recording medium having a recording member formed on a substrate is bonded together with an adhesive layer, a light absorption layer for absorbing information read light is provided between the recording member and the adhesive layer. An optical recording element characterized by: