JPH047196A - Optical recording medium - Google Patents

Abstract

PURPOSE:To optically record and reproduce data by providing an intermediate layer composed of a polyurethane resin and a recording reflecting layer on a dye recording layer. CONSTITUTION:A dye recording layer capable of recording and reproducing data by laser beam is provided on a substrate and an intermediate layer composed of a polyurethane resin and a recording reflecting layer are provided on the dye recording layer. The polyurethane resin, that is, oil modified polyurethane resin used as the intermediate layer is soluble in aliphatic hydrocarbon, alicyclic hydrocarbon and mixed hydrocarbon and formed as a membrane by a coating method. A metal reflecting film 4 is provided on the intermediate layer 3. As the metal used as the metal reflecting film 4, Al is pref. used. The metal reflecting film 4 is formed pref. in 50-100 nm thickness by vacuum vapor deposition or sputtering and a protective film 5 is provided on the metal reflecting film 4. As the protective film 5, an ultraviolet curable resin, a thermosetting resin or a plasma polymerization film is used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium on which information can be recorded and reproduced optically.

(Prior Art) In recent years, optical discs that use light to read out stored information have been put into practical use. This optical disc is a disc on which audio and moving images are recorded and is reproduced using semiconductor laser light, and is widely used as a compact disc (CD) or a video disc.

Further, optical discs (so-called write-once type) are being actively developed on which information is recorded and reproduced by changing optical characteristics (refractive index, extinction coefficient, phase, etc.) by laser beam irradiation.

Information is recorded by irradiating a laser beam to melt and evaporate the recording medium to create a hole, then continuously irradiates a weak laser beam that does not change the recording medium, and detects the presence or absence of a hole by the strength of the reflected light. There are also known methods in which information is recorded in an amorphous recording medium with low reflectance by irradiating it with a laser beam and heating it to cause a phase change, turning it into a crystalline state with high reflectance. .

Under such circumstances, an optical disc on which a user can record information and which can be played on a commercially available CD player has not yet been put into practical use.

The reason for this is that in order to satisfy the CD standard, the reflectance through the substrate must be 70% or more, and the recording linear velocity must be 1.
．． This is because it is necessary to satisfy conditions such as having a sufficient modulation depth at 2 to 1.4 m/s and also being able to obtain a tracking error signal of a required level.

In particular, it is contradictory to be able to record with the output of a semiconductor laser and to achieve high reflectance, and many efforts have been made to solve this problem.

By the way, it is now possible to put dye-based optical disks into practical use as they have lower thermal conductivity than metal materials, have higher recording sensitivity, are more stable, and can be manufactured using relatively inexpensive equipment, which means there is great potential for cost reduction. It's progressing. However, one of the disadvantages of dye-based materials is their low reflectance.

According to "Information Recording System Materials" (Takeda, Shinohara, Leather, Hirohashi eds., Academic Publishing Center, 1989), the refractive index n (real part of the complex refractive index) of the dye is increased to improve the reflectance of the dye thin film. However, it is stated that the reflectance can be increased to about 40% by reducing the extinction coefficient k (imaginary part of the complex refractive index).

Furthermore, it is stated that by providing an Au reflective film on the dye coating film, the disc can be played on a commercially available CD player.

(Problem to be solved by the invention) By the way, in order to satisfy the reflectance of 7096 or more of the CD standard and to ensure the light absorption rate that enables recording, it is necessary to use Au, Ag, and Pt, which have high reflectance at the semiconductor laser wavelength. A reflective film such as the following is required. Such noble metals are expensive, which is a disadvantage for their widespread use.

Furthermore, in order to increase the reflectance of the dye itself, the molecular structure of the dye must be newly designed and synthesized.

Furthermore, the reflectance can be increased by providing an inorganic interference layer with a high refractive index between the dye layer and the reflective layer, but this requires vacuum film formation, which requires equipment, processes, and costs. The disadvantage is that it takes a lot of time.

(Means for Solving the Problems) The present invention has been made in view of the above points, and includes a dye recording layer on which information can be recorded and reproduced by laser light on a substrate. The present invention provides an optical recording medium in which an intermediate layer made of polyurethane resin and a metal reflective layer are provided.

(Example) FIG. 1 is a sectional view of an optical recording medium according to the present invention.
is a substrate using a transparent substrate such as plastic (polycarbonate, acrylic, epoxy, polyolefin, etc.) or glass, which is usually used for optical discs.
is, for example, a dye recording film formed by a coating method. The pigments used here include cyanines, pyryliums, squaryliums, croconiums, and azulenes.

Pentamethines, thioindigos, anthraquinones,
Examples include organic dyes such as naphthoquinones, phthalocyanines, naphthalocyanines, porphyrins, tetrahydrocholines, dithiols, diamines, indoanilines, dioxazines, and dithiazines. Note that a base layer may be provided as necessary.

Reference numeral 3 denotes an intermediate layer, and the material used to constitute this layer is a polyurethane resin that can be applied without damaging the dye recording layer and the substrate.

Typically, polycarbonate resins used as substrates are insoluble in alcohols and aliphatic, cycloaliphatic, and mixed hydrocarbons. Therefore, when forming a dye recording layer by a coating method, an alcohol solvent is used.

Therefore, in order to coat an intermediate layer on the dye recording layer without attacking the dye recording layer and the substrate, a solvent must be selected from among aliphatic, alicyclic hydrocarbons, and mixed hydrocarbons. The polyurethane resin as the intermediate layer, more specifically, the oil-modified polyurethane resin is aliphatic,
It is soluble in alicyclic hydrocarbons and mixed hydrocarbons and can form a thin film by coating. The aliphatic hydrocarbons referred to here include pentane, isopentane, hexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, nonane, decane, dodecane, and dodecene.

It refers to cetane, cetine, etc., and the alicyclic hydrocarbons include cyclopentane, methylcyclopenkune, cyclohexane, methylcyclohexane, bicyclohexyl, tetralin, decalin, etc.

Mixed hydrocarbons are mixtures of various hydrocarbons and are broadly classified into petroleum solvents, coal tar solvents, and terpene solvents, and include industrial gasoline, petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and the like. A coating solution is prepared by dissolving the polyurethane resin with these aliphatic hydrocarbons, alicyclic hydrocarbons, mixed hydrocarbons, and the like.

Next, an intermediate layer can be obtained by applying this coating liquid onto the dye recording layer and drying it.

As a coating method, a spin code method, a spray method, a dip method, a blade coat method, etc. can be used. The thickness of the intermediate layer is in the range of 5 to 500 nm, preferably in the range of 10 to 200 nm. Furthermore, a metal reflective film 4 is provided on this intermediate layer 3. Examples of metals used for this metal reflective film 4 include Au, Ag, Cu,
AI, In, Pt.

Examples include one of Cr and Ni, or an alloy thereof.

Due to cost considerations and conventional CD manufacturing processes, it is preferable to use AI rather than precious metals. .

The metal reflective film 4 is formed by vacuum evaporation or sputtering.
It is formed to have a thickness in the range of 00 nm, preferably 50 to 10 nm. A protective film 5 is provided on this reflective film 4. As this protective film 5, ultraviolet curing resin, thermosetting resin, plasma polymerized film, etc. are used.

Example 1 A cyanine dye recording layer 2 is formed by a spin coding method on a polycarbonate resin substrate 1 on which a guide groove for tracking has been formed in a spiral shape. On top of this, the following solution was spin-coded as intermediate layer 3.

Oil-modified polyurethane resin (Bannock T manufactured by Dainippon Ink Co., Ltd.)
D-125-HD) ) 10 parts by weight, n-decane 9
0 parts by weight.

The specific method of spin code is 2000rpm
After coating at a rotational speed of , the intermediate layer 3 was dried at a temperature of 70° C. for 2 hours. Then, 60 nm of AI was provided on this intermediate layer 3 by sputtering, and this was used as a metal reflective layer 4. Furthermore, a protective layer 5 of ultraviolet curing resin was formed on this metal reflective layer 4 to produce an optical recording medium.

The reflectance of this optical recording medium is 78% (measured at a wavelength of 780 nm).
), which satisfied the CD standards.

This optical recording medium was rotated at a linear velocity of 1.4 m/s, and an intensity-modulated semiconductor laser beam (wavelength 780 nm) was used to generate an E.
When I recorded the FM signal and played it on a commercially available player, I was able to play it without any problems.

Example 2 A cyanine dye recording layer 2 is formed by a spin coding method on a polycarbonate resin substrate 1 on which a guide groove for tracking is formed in a spiral shape in advance. On top of this, the following solution was spin-coded as intermediate layer 3.

Oil-modified polyurethane resin (manufactured by Dainippon Ink Co., Ltd.) 5 parts by weight, i-octane 9
5 parts by weight.

Specifically, the spin code was coated at a rotational speed of 200 rpm and then dried at a temperature of 70'C for 2 hours to obtain an intermediate layer 3. Then, 60 nm of AI was provided on this intermediate layer 3 by sputtering, and this was applied to the metal reflective layer 4.
And so. Further, a protective layer 5 of ultraviolet curing resin was formed on the metal reflective layer 4 to produce an optical recording medium.

The reflectance of this optical recording medium is 79% (measured at a wavelength of 780 nm).
), which satisfied the CD standards.

This optical recording medium was rotated at a linear velocity of 1.4 m/s, and an intensity-modulated semiconductor laser beam (wavelength 780 nm) was used to generate an E.
When I recorded the FM signal and played it on a commercially available player, I was able to play it without any problems.

Example 3 A cyanine dye recording layer 2 was formed on a polycarbonate resin substrate 1 by a spin coding method.

On top of this, an oil-modified polyurethane resin (Parnock TD-125-HD manufactured by Dainippon Ink Co., Ltd.) was spin-coded as an intermediate layer 3 at varying concentrations. i-octane was used as the solvent.

As a specific method of spin cording, the intermediate layer 3 was obtained by coating and drying at a rotation speed of 150 rpm. This middle layer 3
On top of this, AI is applied to a thickness of 70 nm by sputtering,
This was used as the metal reflective layer 4.

The table shows the reflectance values when semiconductor laser light (wavelength 780 nm) was incident on the optical recording medium thus obtained from the substrate side.

Table As is clear from this table, the reflectance improved as the resin concentration increased. Incidentally, the reflectance when the light was incident from the At reflective layer side, which is the opposite side of the substrate 1, was 84%.

Comparative Example 1 In Example 1, the reflectance when no intermediate layer is provided is:
At 60% (measurement wavelength 780 nm), the CD standard could not be satisfied.

Comparative Example 2 A cyanine dye recording layer was formed by a spin coding method on a polycarbonate resin substrate on which a guide groove for tracking was formed in a spiral shape in advance.

The following solution was spin-coded on top of this as an intermediate layer.

Polyvinyl butyral resin (S-LEC B manufactured by Block Chemical Co., Ltd.)
M-1) 3 parts by weight, 97 parts by weight of diacetone alcohol.

According to this, the dye layer was dissolved and recording could not be performed.

(Effects of the Invention) The optical recording medium of the present invention is provided with a dye recording layer on a substrate that can record and reproduce information using a laser beam, and an intermediate layer made of polyurethane resin and a metal layer on the dye recording layer. Since a reflective layer is provided, the intermediate layer can be easily formed using a relatively inexpensive device, and the reflectance can be improved.

Moreover, according to the optical recording medium according to the present invention, an AI reflective layer can be used, so that a significant cost reduction is possible. Furthermore, a recordable optical record carrier that satisfies the CD standard can be easily formed.

Further, the optical recording medium of the present invention can be applied to improve the reflectance of not only optical discs compatible with CDs but also all optical discs, and can improve playback and tracking performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical recording medium according to the present invention. 1...Substrate, 2...Dye recording layer, 3.
...middle class. 4...Metal reflective layer, 5...Protective layer. Patent applicant: Kunio Umiki, representative of Victor Japan Co., Ltd.

Claims (1)

[Claims] An optical recording medium characterized in that a dye recording layer capable of recording and reproducing information using a laser beam is provided on a substrate, and an intermediate layer made of polyurethane resin and a metal reflective layer are provided on the dye recording layer.