JPH05234133A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To enable high sensitivity recording and reproduction even with laser light having short wavelength by forming a layer through which light having shorter wavelength than laser light used for recording and reproduction passes hardly on a substrate. CONSTITUTION:A multicoat layer 2 is formed on the front side of a substrate 1 and a recording layer 3 on the rear side. The compsn. of the layer 2 is regulated so as to attain >15% reflectance to light having shorter wavelength than laser light used for recording and reproduction. For example, in the case of recording and reproduction with light having 680nm, materials are selected so as to ensure high reflectance and satisfactory kick-off at shorter wavelength than 680nm and the thickness of the layer 2 is regulated. Background noise due to swift light can be reduced even under indoor light and high sensitivity recording and reproduction can be carried out even with laser light having short wavelength.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical information recording medium.

[0002]

2. Description of the Related Art Optical information recording media are used in the near infrared region (780 to 830n
It has been put to practical use by using a semiconductor laser (LD) of m). In recent years, there is a growing demand for larger capacity, and there is a movement to use light of a shorter wavelength. In fact, 680 nm semiconductor lasers are being put to practical use, and SHG (Seco
nd Harmonic Generation: Second Harmonic Generation) 40
We are also trying to realize the use of light in the 0 nm range. As a result, it is possible to reduce the diameter of the recording pit and the track pitch, and the storage capacity is dramatically increased. By the way, in a system using such a large capacity medium,
Since the wavelength of the laser light is in the visible light region for recording and reproduction, when used under room light, stray light may increase background noise and reduce the C / N ratio.

As a conventional optical information recording medium, for example, Japanese Patent Application Laid-Open No. 61-208647 proposes a "security-type optical recording medium". In this publication, in order to prevent abuse and illegal use of recording / reproduction easily without disturbing recording / reproduction, a security layer that absorbs light in a wavelength range other than a specific wavelength range (especially visible light) is formed on the medium surface. It is provided. That is, the track groove information recorded on the recording medium, the track number information, and the presence or absence of recording pits are prevented from being easily observed by a magnifying means such as a microscope,
This was to prevent unauthorized use of the information by making corrections by using the information on the recording medium as reproduction or copy data. However, there is no disclosure about how to solve the problem of background noise due to stray light under room light.

[0004]

[Object] The present invention has been made in view of the above-mentioned circumstances, and a hard coat layer that reduces background noise and has a protective effect on the surface of a substrate even when used under room light or the like is provided. The present invention has been made for the purpose of providing an optical information recording medium having the same.

[0005]

In order to achieve the above object, the present invention provides (1)
In an optical information recording medium capable of recording / reproducing information using a laser beam, a substrate or a substrate surface is provided with a layer in which light having a wavelength shorter than a laser wavelength used for recording / reproducing is less likely to pass, and further, (2 ) A multi-coat is applied to the surface of the substrate so that the reflectance for the wavelength shorter than the wavelength of the laser beam used for recording and reproduction is 15% or more.
Further, (3) in (2), a transparent conductive film is used for one or more layers of the multicoat, and further,
(4) In the above (3), the transparent conductive film is made of a metal oxide containing indium, tin and zinc as main components. Hereinafter, description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an embodiment of an optical information recording medium according to the present invention, in which 1 is a substrate and 2 is a substrate.
Is a hard coat layer (multi-coat layer), and 3 is a recording layer. A multicoat layer 2 is provided on the surface of the substrate 1, and a recording layer 3 is provided on the opposite side of the substrate.
The configuration of the multi-coat layer 2 is adjusted so that the reflectance for wavelengths shorter than the wavelength used for recording / reproduction exceeds 15%. For example, when recording / reproducing is performed using light of 680 nm, the material is selected and the film thickness is adjusted so that the reflectance is high and the reflectance is high at a wavelength shorter than 680 nm. As a result, background noise due to stray light can be reduced even under room light.

2 and 3 are views showing wavelength-reflectance characteristics when a hard coat layer composed of two or four layers is provided. In this example, ITO (n =
2.0), and SiO ₂ (n = 1.46) is used as the low refractive index layer to adjust the film thickness composition to form a short wavelength cut hard coat layer. Figure 2 shows the SiO ₂ (1421
Å) / ITO (2075Å) / SiO ₂ (1421Å) / ITO
The wavelength-reflectance characteristics when four hard coat layers of (2075Å) / PC are provided are shown. As is clear from the figure, the reflectance is high in the wavelength range of 680 nm or less.

FIG. 3 shows the wavelength-reflectance characteristics when two hard coat layers are provided.
O ₂ (1421Å) / ITO (2075Å) / PC is SiO ₂
(1421Å) / ZrO ₂ (1976Å) / PC is SiO ₂ (15
63Å) / ZrO ₂ (1976Å) / PC, is SiO ₂ (1705
Four types are shown: Å) / ZrO (1976Å) / PC.
Also in this case, it is clear from the figure that the reflectance is high in the wavelength region of 680 nm or less.
In particular, when a transparent conductive film such as ITO is used, the antistatic effect is also provided, and it is possible to prevent the characteristic deterioration due to the adhesion of dust, which is more convenient. As the transparent conductive film,
_{ITO, In 2 O 3, SnO} 2, ZnO, but ZuS the like, the effect is sufficient 10 ⁹ Ω / □ or less of the membrane.
Further, by using a film having a high hardness such as SiO _{2 for} the surface layer, there is an effect of protecting the substrate surface from scratches and the like.

[0009]

As is clear from the above description, according to the present invention, by reducing the background noise due to stray light from visible light, it is possible to perform recording and reproduction with high sensitivity even with a short wavelength laser. Further, it is possible to form the hard coat layer by post-processing, and the applicable range is large.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an optical information recording medium according to the present invention.

FIG. 2 is a diagram showing wavelength-reflectance characteristics when a hard coat layer is provided.

FIG. 3 is a diagram showing wavelength-reflectance characteristics when a hard coat layer is provided.

[Explanation of symbols]

1 ... Substrate, 2 ... Hard coat layer (multi coat layer), 3
… Recording layer.

Claims (3)

[Claims] 1. An optical information recording medium capable of recording and reproducing information by using a laser beam, wherein a substrate or a surface of the substrate is provided with a layer in which light having a wavelength shorter than a laser wavelength used for recording and reproducing is difficult to transmit. A characteristic optical information recording medium. 2. The optical information recording medium according to claim 1, wherein the substrate surface is provided with a multi-coat so that the reflectance for the wavelength shorter than the wavelength of the laser light used for recording and reproduction is 15% or more. .. 3. The optical information recording medium according to claim 2, wherein a transparent conductive film is used in one or more layers of the multi coat.