JP2521178B2 - Optical recording medium disk - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an optical recording medium disc, and more particularly to a write-once optical recording medium disc compatible with compact discs.

[Prior art]

As the demand for recording various information signals at high recording density has increased, in recent years, high density recording and reproduction of information signals has been performed using information recording media made based on various constitutional principles and operation principles. For example, recording / reproducing in which an unevenness corresponding to the information signal is formed on the signal surface of the information recording medium to record the information signal, and the recorded information signal is reproduced by an optical means. The device has already been put into practical use for recording and reproducing a video signal and an audio signal. In order to meet the demand for high-density recording and reproduction in various technical fields, the recording layer of the information recording medium is irradiated with a beam whose intensity is modulated by the information signal, so that the recording layer of the information recording medium responds to the information signal. Studies have also been conducted on information recording media in which information signals are recorded by causing physical changes or chemical changes, but in recent years, it has become easier to obtain semiconductor lasers that operate stably. As a result, various optical recording media (optical discs) for high-density recording and reproduction using laser light have already been put into practical use, or research and development for practical use have been conducted. It is well known that the current situation is. That is, a recorded optical disc (playback-only optical disc) that is reproduced in large quantities from an original disc on which an information signal is recorded by a bit formed as a geometrical concave portion or a convex portion is, for example, a video disc or a compact disc. As well, it is beginning to spread to general households, 1
Optical discs (write-once optical discs) that can be additionally recorded by a user only once, erasable optical discs, and the like are being actively researched and developed for practical use in, for example, office file memories and other applications. By the way, when an information signal is reproduced from an information recording medium in which the information signal is recorded at a high density, the reproducing element or the reproducing beam is always accurately traced to the recording trace where the information signal is recorded by tracking control. It is well known that this is done, and even when reproducing the information signals recorded in high density on the information recording media of various types described above, the reproducing operation is performed under the tracking control operation. It is usually done. By the way, a compact disc known as one of the information recording media in which the information signal is recorded at a high density by the arrangement of bits corresponding to the information signal on the signal surface of the information recording medium is An information signal is recorded on the signal surface by an array of pits having a depth set in a specific relation to the wavelength, and the entire signal surface is covered with a thin film of aluminum or the like. It is specified that the reflectance of the land portion on the signal surface is 70% to 90% with respect to the light having a wavelength of 780 nm, and the wavelength of the information signal read from the signal surface of the information recording medium is The light spot of 780 nm is used. Then, when reading the information signal from the compact disc, the amount of the reflected light from the pit portion on the signal surface of the compact disc is the same as that of the reflected light from the land portion as a result of the light interference occurring at the pit portion. It is performed by utilizing the fact that the light quantity is smaller than the light quantity, and the tracking error information also uses the difference between the light quantity of the reflected light from the recording mark portion and the light quantity of the reflected light from the land portion. It is supposed to be obtained. By the way, with the spread of the compact disk mentioned above,
As an optical disc compatible with a compact disc that can be played back using a compact disc playback device, for example, additional recording of a configuration form in which a recorded area dedicated to playback and a recording area usable as a write-once optical disc are provided. -Type optical discs, or various proposals for optical discs with the entire recording area being made,
The optical disc having the recording area as described above has a structure in which a tracking guide groove is provided on the transparent substrate so that tracking control is performed even during recording. By the way, as an optical disc having compatibility with a compact disc, it is needless to say that it must satisfy the standard value regarding the reflectance among the various standards regarding reproduction defined for the compact disc. The standard value for the reflectance of compact discs is that the wavelength is 780 nm from the read side of the optical disc.
It is required to have a reflectance of 70% or more when viewed from the read side of the optical disc when the laser light of is incident on the optical disc surface. However, a reflection loss of about 8% occurs on the surface of the optical disc. Even if only the reflection loss at
%, The reflectance of the metal reflection film must be at least 80% or more.
It is well known that the disk uses an aluminum reflective film having a reflectance of 80% or more to satisfy the standard value of the above reflectance (the above reflectance is the composition of the aluminum film). Needless to say, it changes depending on the film conditions). However, in the write-once type optical disc, since recording is performed on the recording film (recording layer), the recording film absorbs energy for recording, and as described above, in the write-once type optical disc, the recording energy is reduced. For tracking control,
Since a guide groove for tracking control is provided on the transparent substrate, a light amount loss due to the incident light being diffracted by the guide groove is also added, so that the reflectance on the read side of the optical disc can be reduced. It has been conventionally difficult to make the standard value of the rate, but in recent years, in a transparent substrate having a guide groove for tracking, as disclosed in, for example, JP-A-2-42652, By applying a spin coating method to the surface of the plate where the guide groove for tracking is provided, a special dye-based recording film and a reflective film made of gold with high reflectance are laminated to produce a light with a wavelength of 780 nm. On the other hand, a write-once optical disc has been proposed in which the reflectance of the land portion on the signal surface is 70% to 90%, which is the reflectance specified by the compact disc. .

[Problems to be Solved by the Invention]

However, in the previously proposed write-once type optical disc, if a reflective film made of expensive gold is used as the metallic reflective film, the reflectance of the land portion on the signal surface is 70% with respect to light having a wavelength of 780 nm. Although a write-once optical disc that exhibits the reflectance specified by a compact disc of between 90% and 90% can be constructed, the wavelength is reduced when inexpensive aluminum or aluminum alloy is used as the metal reflection film.
It has been difficult to construct a write-once optical disc that exhibits a reflectance of 70% to 90% at the land portion on the signal surface with respect to 780 nm light, which is defined by a compact disc.

[Means for Solving the Problems]

In the present invention, the refractive index Nd is Nd = n ₁ −k ₁ i on the transparent substrate provided with the tracking guide groove and on the plate surface of the transparent substrate provided with the tracking guide groove.
With an organic dye material that absorbs an appropriate amount of recording light at, an organic dye material film having a thickness at which information is recorded in a recording state such that a predetermined signal reproduction characteristic is obtained at the time of reproduction is attached as a recording film, Further, with respect to the refractive index Nd of the recording film described above, the refractive index Ne having a relationship of | Nd |> | Ne |, n ₁ > n ₂ , k ₁ > k ₂
= N ₂ −k ₂ i is used to adhere an interference film for increasing the amount of reflected light onto the recording film described above, and further, a reflective film made of aluminum or an aluminum alloy is attached to the interference film for increasing the amount of reflected light. From the component corresponding to the portion other than the tracking guide groove on the transparent substrate by the reproducing light having a predetermined wavelength which is incident from the surface of the transparent substrate on which the tracking guide groove is not provided There is provided an optical recording medium disk, wherein the thickness of the above-mentioned interference film for enhancing reflected light amount is set so that the reflected light amount is 70% or more with respect to the incident light amount.

[Action]

On the plate surface on which the tracking guide groove is provided in the transparent substrate provided with the tracking guide groove,
A recording film made of an organic dye material that absorbs an appropriate amount of recording light,
Refractive index Nd of the organic dye material constituting the recording film in the optical recording medium disc formed by laminating the interference film for enhancing the reflected light amount and the aluminum film or the aluminum alloy film
n ₁ −k ₁ i and the refractive index N of the constituent material of the interference film for enhancing the amount of reflected light
e = n ₂ k ₂ i and | Nd |> | Ne |, n ₁ > n ₂ , k ₁ > k ₂ and the thickness of each layer is set to a predetermined value. By selecting, the portion of the transparent substrate other than the tracking guide groove by the reproducing light having a predetermined wavelength that is incident from the surface of the transparent substrate on which the tracking guide groove is not provided. The amount of light reflected from the corresponding component is 70% or more of the amount of incident light.

EXAMPLES Hereinafter, specific contents of the optical recording medium disc of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view of a part of an optical recording medium disc of the present invention, FIG. 2 is a curve diagram showing an inverse ratio characteristic of the optical recording medium disc of the present invention, and FIG.
The figure is a longitudinal cross-sectional view of a part of an optical recording medium disc used for explaining comparison of reflectances of various optical recording medium discs. In FIG. 1, reference numeral 1 denotes a transparent substrate provided with tracking guide grooves G, G ... On the plate surface of the transparent substrate 1 on which the tracking guide grooves G, G ... A recording film 2, an interference film 3 for reinforcing the amount of reflected light, and a reflective film 4 made of aluminum or an aluminum alloy are laminated. The recording film 2 has tracking grooves G, G ... In a transparent substrate 1 (for example, a transparent substrate made of polycarbonate resin) provided with tracking grooves G, G ...
On the plate surface on which is provided, an organic dye material having a refractive index Nd of Nd = n ₁ −k ₁ i and absorbing an appropriate amount of recording light is used to obtain a predetermined signal reproduction characteristic at the time of reproduction. The organic dye material film having a thickness that allows information to be recorded in a recorded state is formed by applying, for example, a spin coat method. When the solvent used in the spin coating method applied when forming the recording film 2 is such as to damage the transparent substrate 1, after forming a transparent protective thin film on the transparent substrate 1, The recording film 2 is formed on the transparent protective thin film by spin coating. Refractive index of the aforementioned organic dye material
N ₁ in Nd is the real part of the refractive index Nd, and k ₁ i is the imaginary part of the refractive index Nd of the organic dye material. As the organic dye material used for the construction of the recording film 2 described above, for example, an indolenine-based cyanine dye material such as an organic dye material of product number NK3219 manufactured by Nippon Senso Dye Co., Ltd. can be used. The refractive index Nd of the above-mentioned organic dye material is Nd = 2.3-0.05i
Is. Then, the organic dye material is dissolved in diacetone alcohol, and is formed into a film having a predetermined thickness, for example, 40 nm by spin coating to form the recording film 2 of the organic dye material film. You can In addition, the interference film 3 for enhancing the reflected light amount described above is such that | Nd |> | Ne |, n ₁ > n with respect to the refractive index Nd of the recording film 2 described above.
A material having a refractive index Ne = n ₂ −k ₂ i in the relationship of ₂ , k ₁ > k ₂ is used to form a film having a predetermined thickness on the recording film 2 by a vacuum vapor deposition method, or If the material is a material to which the spin coating method can be applied, the material can be formed by forming a film having a predetermined thickness on the recording film 2 by the spin coating method. The solvent used in the spin coating method applied when forming the reflected light amount enhancing interference film 3 is
When the recording film 2 is damaged, a transparent protective thin film is formed on the recording film 2, and then the reflected light amount enhancing interference film 3 is formed on the transparent protective thin film by spin coating. To do so. The interference film 3 for enhancing the amount of reflected light described above is formed by reproducing light having a predetermined wavelength (780 nm) which is incident from the surface of the transparent substrate 1 on which the guide grooves G for tracking are not provided. The reflected light amount enhancing interference film 3 described above is in a state in which the amount of reflected light from the constituent portion corresponding to the portion other than the tracking guide grooves G, G ... In the transparent substrate 1 is 70% or more of the incident light amount. The thickness of is determined. FIG. 2 shows an interference film 3 for increasing the amount of reflected light on the horizontal axis.
Thickness, and the vertical axis shows the wavelength of 780n on the optical recording medium disk.
The reflectance of the land portion when m reproducing light is incident is shown. N ₂ in the refractive index Ne of the material used for the structure of the interference film 3 for enhancing the amount of reflected light is the real part of the refractive index Ne,
K ₂ is the imaginary part of the refractive index Ne. As a material used for the structure of the interference film 3 for enhancing the reflected light amount, for example, guanine or bisphenol A can be used. The refractive index Ne of the above material is Ne = 1.5 (the imaginary part is zero). And the above-mentioned guanine or bisphenol A
Can be formed into a film having a thickness of, for example, 180 nm on the recording film 2 by the vacuum vapor deposition method to form the interference film 3 for increasing the reflected light amount. A thickness of 200 nm is formed on the interference film 3 for enhancing the amount of reflected light.
The aluminum reflection film 4 is formed by applying a sputtering method. Reference numeral 5 is a protective film provided on the aluminum reflection film 4 described above. FIG. 2 shows that the reflectance of the land portion when the reproducing light having a wavelength of 780 nm is incident on the optical recording medium disk of the present invention configured as described above, the interference film 3 for enhancing the reflected light amount described above.
It is a calculated value showing how it changes with the change of the film thickness, and the actually obtained reflectance is almost the same as in FIG. (The numerical values used for the calculation are as follows: the refractive index of air is 0, the refractive index of aluminum is 1.99-7.05i, the refractive index of the reflected light amount enhancing interference film 3 is Ne = 1.5 (the imaginary part is zero), and the refractive index of the recording film 2 is The refractive index of the transparent substrate 1 made of polycarbonate resin is 1.55 (the imaginary part is zero), the thickness of the aluminum reflection film 4 is 200 nm, and the thickness of the recording film 2 is 40 nm.
The thickness of the interference film 3 for enhancing the amount of reflected light is 0 to 300 nm}. Looking at the value of the reflectance which changes with the change in the film thickness of the above-described interference film 3 for enhancing the reflected light amount shown in FIG.
When a recording film 2 having a thickness of 40 nm made of an organic dye material having a refractive index Nd of 2.3-0.05i and a reflecting film 4 made of aluminum having a refractive index of 1.99-7.05i and having a thickness of 200 nm are used, a refractive index Ne When the film thickness of the reflected light amount enhancing interference film 3 made of a material having a value of 1.5 (the imaginary part is zero) is about 180 nm, it is found that the reflectance at the land portion is 85%. It can be seen that the reflectance of the land portion is 70% or more over the range of the film thickness of the light amount enhancing interference film 3 from 70 nm to 230 nm. FIG. 3 (a) is a longitudinal sectional view of a land portion of a conventional compact disc, and FIG. 3 (b) is, for example, JP-A-2-4265.
It is also disclosed in Japanese Patent Publication No. 2 that the reflectance of the land portion on the signal surface is 70% to 90% with respect to the light having a wavelength of 780 nm. Type optical disc land section,
FIG. 3 (c) is a vertical cross-sectional view of the land portion of the optical recording medium disc of the present invention. In FIG. 3, 1 has a refractive index of 1.55.
(Imaginary part is zero) Polycarbonate resin transparent substrate,
2 is a recording film made of an organic dye material having a refractive index Nd of 2.3-0.05i, 3 is an interference film for increasing the reflected light amount having a refractive index of 1.5 (the imaginary part is zero), and 4 is aluminum having a refractive index of 1.99-7.05i. And a reference numeral 6 is a gold reflective film having a refractive index of 0.149-4.654i. In the conventional compact disc shown in FIG. 3 (a), the reflectance of the reflection film 4 made of aluminum itself is 86%, but the reflectance at the land portion is 81%. Further, in the already-proposed write-once type optical disk shown in FIG. 3 (b), the reflectance of the gold reflection film 6 itself is 97%, but the reflectance at the land portion is the thickness of the recording layer. It is 74 to 84%. Then, in the optical recording medium disc of the present invention shown in FIG. 3 (c), as described above with reference to FIG. 2, the organic dye material having the refractive index Nd of 2.3-0.05i has a thickness of 40 nm. When the recording film 2 and the reflective film 4 made of aluminum having a refractive index of 1.99 to 7.05i and having a thickness of 200 nm are used, the refractive index N
When the thickness of the reflected light amount enhancing interference film 3 made of a material having e of 1.5 (the imaginary part is zero) is approximately 180 nm, the reflectance at the land portion is 85%, and the film of the light amount enhancing interference film 3 is 70 thickness
70% reflectance on the land over the nm-230 nm range
That is all. Next, a specific example of the optical recording medium disc of the present invention having a recording film containing an indolenine-based cyanine dye material as an organic dye material that absorbs an appropriate amount of recording light will be described. As the transparent substrate 1 provided with the guide grooves G, G ... For tracking, the transparent substrate 1 made of a polycarbonate resin having a diameter of 120 mm and provided with the guide grooves G, G. On the surface of the transparent substrate 1 made of the polycarbonate resin with the guide groove, on which the guide groove G is provided, an indolenine-based cyanine dye is included (additives such as quencher may be included). The dye material is dissolved in a solvent that does not attack the polycarbonate resin, for example, a cellosolve-based, ketoalcohol-based, alcohol-based, or aliphatic hydrocarbon-based solvent, and the recording film 2 having a thickness of 30 to 300 nm is formed by spin coating. To do. Next, a transparent material having a transmittance of 95% or more with respect to the reproduction light having a wavelength of 780 nm, for example, a transparent material such as adenine, guanine, quinone, etc., having a thickness of 70 to 230 nm, is used to enhance the reflected light amount. Is formed on the recording film 2 by the vacuum evaporation method. Next, a magnetron sputtering method is applied to form the aluminum reflection film 4 having a thickness of 200 nm on the interference film 3 for enhancing the amount of reflected light, and the ultraviolet reflection resin 4 is further applied to the reflection film 4 made of aluminum. To form a protective film 5 having a thickness of 5 μm. As an example, a guide groove G for tracking with a pitch of 1.6 microns is provided on a surface of the transparent substrate 1 made of a polycarbonate resin having a diameter of 120 mm on which the guide groove G is provided. A dye material containing a renin-based cyanine dye (which may include an additive such as a quencher) is dissolved in a solvent that does not attack the polycarbonate resin, for example, a cellosolve-based, keto alcohol-based, alcohol-based, or aliphatic hydrocarbon-based solvent. Then, a recording film 2 having a thickness of 50 nm is formed by a spin coating method, and then an interference film 3 for increasing the reflected light amount having a thickness of 150 nm of guanine is formed on the recording film 2 by a vacuum deposition method. Then, a magnetron sputtering method is applied to form the reflection film 4 of aluminum having a thickness of 200 nm on the interference film 3 for increasing the amount of reflected light, and In the optical recording medium disk constituted by forming the protective film 5 with a thickness of 5 μm on the reflection film 4 of minium by coating with the ultraviolet curing resin, when the light having the wavelength of 780 nm is incident through the transparent substrate 1. The reflectance in the land area was more than 75%. When the error rate was measured by performing EMF recording on the above-mentioned optical recording medium disc, the error rate was equivalent to that of a commercially available compact disc, and the reproduced signal waveform was good and satisfied the CD standard.

【The invention's effect】

As is clear from the above description, according to the present invention, a suitable amount of recording light is absorbed on the plate surface of the transparent substrate having the tracking guide groove, which has the tracking guide groove. Refractive index of the organic dye material forming the recording film in the optical recording medium disc formed by stacking the recording film of the organic dye material, the interference film for enhancing the reflected light amount, and the aluminum film or the aluminum alloy film.
Nd = n ₁ −k ₁ i and the refractive index Ne = n ₂ −k ₂ i of the constituent material of the interference film for enhancing reflected light quantity are expressed as | Nd |> | Ne |, n ₁ > n ₂ , k ₁ > k ₂ and the thickness of each of the above layers is set to a predetermined value, so that the light is incident from the surface of the transparent substrate on which the guide groove for tracking is not provided in advance. The amount of reflected light from the component corresponding to the portion other than the guide groove for tracking on the transparent substrate by the reproducing light having the specified wavelength is relative to the incident light amount.
According to the present invention, it is possible to easily provide an optical recording medium disc having compatibility with a compact disc by using a reflection film made of inexpensive aluminum or aluminum alloy. .

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a part of an optical recording medium disc of the present invention, FIG. 2 is a curve diagram showing reflectance characteristics of the optical recording medium disc of the present invention, and FIG. 3 is various optical recordings. FIG. 6 is a vertical cross-sectional view of a part of an optical recording medium disc used for explaining the comparison of the reflectances of the medium discs. 1 ... Transparent substrate provided with guide grooves G for tracking, 2 ... Recording film, 3 ... Interference film for enhancing reflected light amount, 4
... Reflective film made of aluminum or aluminum alloy, 5 ... Protective film, 6 ... Reflective film made of gold,

Front page continuation (72) Inventor Toshiki Kasai 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan (72) Koji Tsujida 3--12 Moriya-cho, Kanagawa-ku, Yokohama, Japan Victor Co., Ltd.

Claims (1)

(57) [Claims] 1. A refractive index Nd is Nd = n ₁ -k ₁ on a transparent substrate provided with a tracking guide groove and on a plate surface of the transparent substrate provided with the tracking guide groove.
Using an organic dye material that absorbs an appropriate amount of recording light at i, an organic dye material film with a thickness that allows information to be recorded in a recording state where a predetermined signal reproduction characteristic is obtained at the time of reproduction is attached as a recording film. In addition, an interference film for increasing the reflected light amount is formed by using a material having a refractive index Ne = n ₂ −k ₂ i which has a relationship of n ₁ > n ₂ and k ₁ > k ₂ with respect to the refractive index of the recording film. It adheres to the recording film described above, and further, the reflection film made of aluminum or an aluminum alloy adheres to the interference film for enhancing the reflected light amount described above, and the light is incident from the surface of the transparent substrate on which the guide groove for tracking is not provided. The amount of reflected light from the component corresponding to the portion other than the guide groove for tracking on the transparent substrate by the reproducing light having a predetermined wavelength is 70% or more with respect to the incident light amount. Recording medium disk with a thickness of interference film for enhancing reflected light quantity