JPH05274715A - Draw type optical recording medium - Google Patents

Abstract

PURPOSE:To increase the reflectivity and to form an inexpensive metallic reflection layer by providing an interference layer consisting of a prescribed material to increase the reflectivity of reproducing light from a substrate side between a recording layer and the light reflection layer. CONSTITUTION:A light transparent substrate 1 integrally molded of an injection molded resin constitutes a disk shape and pregrooves for tracking are concentrically or spirally formed on one surface. Cyanine dyestuff, etc., are incorporated as essential components into the recording layer 12 formed on the substrate 11 and are applied by a spin coating method, etc. The interference layer 13 is formed thereon to increase the reflectivity of the reproducing light from the substrate side. The light reflection layer 14 is provided on such interference layer 13 and is constituted of metals, such as Al, Ag and Cu. Au is of course usable. This layer is formed by vacuum vapor deposition, sputtering, ion plating, etc. A protective layer 15 is provided on the reflection layer 14 to protect the layers 12, 13, 14. As a result, the reflectivity is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writable write-once type optical recording medium, and more particularly to improvement of the reflectance of a write-once type optical recording medium having a recording layer and a light reflecting layer on a light transmitting substrate.

[0002]

2. Description of the Related Art Conventionally, it is generally well known that a recording film of a so-called writable write-once type optical recording medium uses an organic dye such as cyanine or phthalocyanine.

As a writing method for such a write-once type optical recording medium, a laser beam is focused on a very small area of the recording film and converted into heat energy to change the properties of the recording film (pit formation. )Is going. In order to smoothly change the properties of the recording film, the medium may have a so-called air sandwich structure in which two recording films are provided on a substrate and the recording films are arranged to face each other. It is common.

The writing laser beam used in the write-once type optical recording medium of this type is irradiated from the transparent substrate side to form light-readable pits in the recording film. The reading laser beam for reproducing the recorded data has a weaker output than that for writing, and the contrast between the portion where the pits are formed and the portion where the pits are not formed is read as an electric signal.

On the other hand, unlike the above-mentioned medium, a so-called ROM (read only memor) in which data is already recorded in advance.
There is also a y) type medium, which has been widely put to practical use in the fields of voice recording and information processing. However, this does not have a writable recording film as described above. That is, the pre-pits corresponding to the data to be reproduced are already formed by press molding on the plastic substrate, the reflective layer made of metal such as Au, Ag, Cu, Al is formed on the plastic substrate, and the protective layer is further formed thereon. Layers have been formed. A typical medium of this ROM type is a compact disc called a so-called CD. The specifications of the recording and reading signals of this CD have been standardized, and in accordance with this standard, a CD reproducing device is widely used as a compact disc player (CD player).

The writable write-once type optical recording medium is similar to a CD in that a laser beam is used, and is similar to a CD in that the form of the medium is a disk shape. Therefore, a writable medium that conforms to the CD specification standard and can be used as it is for a CD player is being actively developed.

[0007]

However, in order to obtain a high reflectance that complies with the CD standard, there is a problem that it is difficult to apply a wide variety of metal films that are inexpensive as a material for the reflective film. That is, expensive gold having an extremely high absolute reflectance (absolute reflectance of 95% or more) must be used as the material of the reflective film, and when other inexpensive aluminum Al or the like is used as the material of the reflective film. Has a problem that a predetermined reflectance cannot be obtained.

The present invention was conceived in view of the above circumstances, and an object thereof is to improve the reflectance not only from the metal film but also from the medium structure, and at a low cost, a wide variety of metal films can be produced. It is to provide a write-once type optical recording medium which can be applied.

[0009]

In order to solve the above-mentioned problems, the present invention provides a write-once type optical recording medium having a recording layer on a light-transmissive substrate and a light-reflecting layer on the recording layer, An interference layer for increasing the reflectance of reproduction light emitted from the substrate side is provided between the recording layer and the light reflection layer.

FIG. 1 is a schematic perspective view of the write-once type optical recording medium of the present invention with a part cut away. FIG. 2 shows a partially enlarged sectional view of FIG. As shown in these figures, the write-once type optical recording medium 1 of the present invention comprises a light transmissive substrate 11
The recording layer 12 is provided on the recording layer 12, the interference layer 13 is provided on the recording layer 12, and the reflection film 14 is provided on the interference layer 13.
Is laid. Usually, a protective layer 15 is further provided on the reflective film 14.

The light transmissive substrate 11 has a disk shape, and a pregroove for tracking is usually formed on one side of the substrate 11 in a concentric or spiral shape. Substrate 11 having such a pre-groove
From the viewpoint of improving productivity, it is preferable to use a so-called integrally formed injection-molded resin substrate, which is, for example, a transparent material such as polycarbonate resin (PC) or polymethylmethacrylate resin (PMMA). Formed from. Further, the substrate is not limited to the injection-molded resin substrate integrally formed, and may be a substrate formed by a so-called 2P (photo-polymer) method. The thickness of such a substrate 11 is 1.
It is about 0 to 1.5 mm.

The recording layer 12 formed on such a substrate 11 contains a dye such as a cyanine dye as a main component. As a more specific preferred example, a cyanine dye represented by the following general formula [I] or general formula [II] is used.

[0013]

[Chemical 1]

[0014]

[Chemical 2] In the above general formula [I], R ₁ and R ₂ each represent an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 3 to 5 carbon atoms. When the carbon number exceeds 8, deterioration is accelerated in the high temperature and high humidity test. In addition, there is an inconvenience that waxing occurs and handling becomes inconvenient. X ⁻ represents a counter ion, specifically ClO ₄ ⁻ , I ⁻ , Br ^−.
Etc. n represents an integer of 1 to 3.

In the above general formula [II], R ₃ and R
₄ is an alkyl group having 1 to 8 carbon atoms, preferably 3
Represents an alkyl group of ~ 5. If the carbon number exceeds 8, the same inconvenience as in the case of the above general formula [I] occurs.
X ⁻ and n have the same meanings as above.

Further, the recording layer 12 may contain a first quencher for preventing the above-mentioned cyanine dye from photodegradation. The recording layer 12 containing such a cyanine dye as a main component is applied by a conventional means such as spin coating. Recording layer 12 to be coated
Has a thickness of 30 to 900 nm, preferably 100 to 3
00 nm. If this value is less than 30 nm, the absorption will be small and the sensitivity in the wavelength region of the semiconductor laser will be lowered, resulting in an inconvenience that a signal cannot be recorded. As a result, there arises a disadvantage that the reflectance decreases.

As the solvent used for coating, various known solvents can be used, and examples thereof include diacetone alcohol, ethyl cellosolve, methyl cellosolve, isophorone, methanol and tetrafluoropropanol.

As the material of the recording layer 12, various known recording materials capable of optical recording can be used in addition to the above cyanine dye. The interference layer 13 is formed on the recording layer 12. The interference layer 13 is provided to increase the reflectance of the reproduction light emitted from the substrate side. Specifically, magnesium fluoride (MgF ₂ ) or polyvinyl alcohol is used. The former can be formed by a vacuum film forming method such as vacuum deposition, and the latter can be formed by a spin coating method. The thickness of the interference layer 13 is 0.01 to 1 μm.
It is considered as a degree.

A light reflection layer 14 is provided on the interference layer 13. The light-reflecting layer 14 is made of a metal such as Al, Ag, and Cu, and is formed by vacuum evaporation, sputtering, ion plating, or the like. Of course, A
u may be used. The thickness of the light reflection layer 14 is
It is set to about 0.02 to 2.0 μm.

The recording layer 1 is usually formed on the light reflecting layer 14.
2. A protective layer 15 is provided to protect the interference layer 13 and the light reflection layer 14. The protective layer 15 is generally formed by spin-coating an ultraviolet curable resin and applying it, and then irradiating it with ultraviolet rays to cure the coating film. In addition, epoxy resin, acrylic resin, silicone resin, urethane resin or the like is used as the material of the protective layer 15. The thickness of such a protective layer 15 is usually about 0.1 to 100 μm.

An intermediate layer for protecting the substrate 11 from the solvent may be provided between the substrate 11 and the recording layer 12.

[0022]

EXAMPLES The present invention will be further described below with reference to specific examples.
The details will be described.Experimental example 1 (present invention) First, in the general formula [I], R₁= R₂= C_FourH
₉, X^-= ClO_Four ^-, The cyanine color specified by n = 2
And R in the general formula [II]₃= R _Four= C₃
H₇, X^-= I^-, N = 2, the cyanine dye
Dissolve in ethyl cellosolve solvent,
15 on a 20mm, 1.2mm thick polycarbonate substrate
A recording layer was formed by coating to a thickness of 0 nm. Of this recording layer
80nm thick interference layer made of magnesium fluoride on top
It was vacuum evaporated. Then, Al (Al
A light-reflecting layer of 0.1 μm by vacuum deposition.
Layered to a thickness. In addition, photopoly
A protective film of a polymer is provided to prepare a medium sample 1 of the present invention.
It was

When the reflectance of this medium sample 1 of the present invention was measured by actually irradiating it with light having a wavelength of 783 nm from the substrate side, the reflectance was improved by about 15% as compared with the comparative sample having no interference layer. Experimental Example 2 (Invention) Inventive Medium Sample 2 was prepared by changing the recording layer thickness and interference layer thickness of Inventive Medium Sample 1 to 120 nm and 60 nm, respectively. Other than that, it produced like the above-mentioned medium sample 1 of this invention.

When the reflectance of this medium sample 2 of the present invention was measured by actually irradiating it with light having a wavelength of 783 nm from the substrate side, the reflectance was improved by about 20% as compared with the comparative sample having no interference layer. Experimental Example 3 (Invention) Polyvinyl alcohol was used as the material of the interference layer of the medium sample 1 of the present invention, and this was formed by spin coating. Except for this, the medium sample 3 of the present invention was manufactured in the same manner as the medium sample 1 of the present invention.

When the reflectance of the medium sample 3 of the present invention was measured by actually irradiating it with light having a wavelength of 783 nm from the substrate side, the reflectance was improved by about 10% as compared with the comparative sample having no interference layer.

[0026]

The write-once type optical recording medium of the present invention has an interference layer of a predetermined material between the recording layer and the light reflecting layer for increasing the reflectance of the reproduction light irradiated from the substrate side. Since it is provided, the reflectance can be improved and expensive gold (A
In addition to u), it is possible to apply an inexpensive and wide variety of metal reflective layers.

[Brief description of drawings]

FIG. 1 is a schematic perspective view in which a part of an optical recording medium of the present invention is cut away.

FIG. 2 is a partially enlarged sectional view of a cutout portion of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Write-once type optical recording medium 11 ... Light transmissive substrate 12 ... Recording layer 13 ... Interference layer 14 ... Light reflection layer 15 ... Protective layer

Claims (3)

[Claims] 1. A write-once type optical recording medium having a recording layer on a light-transmissive substrate and a light-reflecting layer on the recording layer, wherein the substrate side is provided between the recording layer and the light-reflecting layer. A write-once type optical recording medium having an interference layer for increasing the reflectance of reproduction light emitted from the recording medium. 2. The write-once type optical recording medium according to claim 1, wherein the interference layer contains magnesium fluoride or polyvinyl alcohol as a main component. 3. The transparent substrate has a thickness of 1.0 to
1.5 mm, the recording layer has a thickness of 30 to 900 nm, the light reflecting layer has a thickness of 0.02 to 2 μm, and the interference layer has a thickness of 0.01 to 1 μm. Is applied to a CD player, and the write-once type optical recording medium according to claim 1 or 2.