JP2947562B2 - Optical recording medium - Google Patents

Description

The present invention relates to an optical recording medium capable of recording and reproducing using light such as a focused beam of a semiconductor laser, and more particularly to a computer. It is used for recording various information such as an external memory, an image, and sound.

(Prior Art) In recent years, the development of an optical recording medium capable of recording and reproducing using a focused beam of a semiconductor laser has been rapidly progressing. Recording on such an optical recording medium is performed by a method as shown in FIG.

In FIG. 3, an optical recording medium 1 having a recording layer 3 formed on a transparent substrate 2 is rotated by a rotation drive motor 4. The laser light 6 emitted from the laser light source 5 is modulated by a modulator 7, passes through an optical system 8 such as a lens or a prism, is reflected by a reflector 9, is collected by a condenser lens 10, and is formed as a minute spot. The recording layer 3 is irradiated. In this manner, information is recorded by selectively irradiating a laser beam and raising or removing a part of the recording layer 3 by the heat.

Generally, the recording layer constituting such an optical recording medium is required to have the following characteristics.

First, the recording layer of the optical recording medium that performs recording in the heat mode as described above is required to sufficiently absorb the laser light used.

To reproduce information recorded on an optical recording medium,
Since the optical recording medium is irradiated with laser light and the reflected light from the optical recording medium is read out, the recording layer needs to have a high reflectance in order to obtain a recording medium with a high C / N ratio. Similarly, since a tracking servo signal and a focus servo signal for controlling the position of the recording head are obtained from the reflected light from the optical recording medium, the recording layer is required to have a high reflectance.

Further, the life of the optical recording medium is required to be at least 10 years or more. That is, after 10 years, new information must be able to be recorded with the same sensitivity and C / N as the initial state, and already recorded information must be able to be reproduced. On the other hand, in order to improve the recording density of an optical recording medium, increasing the numerical aperture NA of an objective lens of a recording apparatus and shortening the optical wavelength of a semiconductor laser are being rapidly promoted. Of these, the light wavelength of the semiconductor laser is expected to be shortened from 830 nm, which is currently the mainstream, to about 630 nm in 10 years. In order to cope with such a tendency, it is desirable that the recording layer has relatively constant spectral absorption characteristics and spectral reflection characteristics in a light wavelength range of about 630 to 850 nm.

By the way, conventionally, many substances have been proposed as a recording layer of an optical recording medium, including a metal thin film, a composite thin film, and an organic thin film.

Among, Te alloy, Te oxide, Te-C, the metal thin film or a composite film such as Te-CS ₂ is highly generally absorbance and reflectance, yet such as light wavelength range of 630~850nm, as shown in Figure 2 , The spectral absorption characteristics and the spectral reflection characteristics are relatively constant. For this reason, the light wavelength of the light source for recording or reproduction is
Even if the wavelength is gradually shortened from 830 nm and shifted to 630 nm, there is a characteristic that sensitivity and C / N do not significantly change. However, the above-mentioned metal thin film and composite thin film have a problem in terms of toxicity. Further, low melting point metals have a disadvantage that they are very easily oxidized.

In order to compensate for such a defect, various organic recording layers have been studied.

Organic compounds for optical recording media include, for example,
As disclosed in -167140, aromatic dithiol-based metal complexes, aliphatic dithiol-based metal complexes, mercaptophenol-based metal complexes, aromatic diamine-based metal complexes, aliphatic diamine-based metal complexes, phthalocyanine derivatives, Examples thereof include cyanine dyes having a polymethine structure, merocyanine dyes, squarium dyes, dioxazine dyes, tetrahydracholine-based metal complexes, and croconic methine-based dyes. However, these dyes are generally extremely unstable with respect to reproduction light, and are oxidatively degraded or discolored, and few of them can be put to practical use.

Among the above dyes, phthalocyanine derivatives have attracted attention because of their excellent durability, and various organic recording layers have been proposed to date.

For example, JP-A-55-97033 discloses that vanadyl phthalocyanine and tin phthalocyanine are used for a recording layer. In particular, it has been reported that when vanadyl phthalocyanine is used, a dye monolayer exhibits high reflectance.
However, vanadyl phthalocyanine has low absorbance,
There is a problem that recording sensitivity is poor.

JP-A-57-82093 discloses lead phthalocyanine, and JP-A-59-67093 discloses manganese phthalocyanine. However, these have a problem that the reflectance is essentially low in the dye monolayer. Therefore, when these are used as a recording layer, it is necessary to separately provide a metal reflection film. However, the presence of such a metal reflective film complicates the configuration of the optical recording medium and causes an increase in cost. Also, the presence of the metal reflective film impairs the low thermal conductivity of the organic recording medium,
This is a cause that the recording density cannot be sufficiently improved.

Furthermore, when a cyanine dye, a phthalocyanine dye, a naphthalocyanine dye, or the like is used as a recording layer, these generally have a sharp peak in spectral absorption characteristics and spectral reflection characteristics, and have a spectral absorption characteristic in a wide wavelength range. And the spectral reflection characteristics change significantly. For this reason, as the light wavelength of the light source for recording or reproduction is shortened, the sensitivity and C / N are remarkably changed, and it is expected that recording and reproduction will be difficult.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above problems, and has high absorbance and reflectance, and has a comparative spectral absorption characteristic and spectral reflection characteristic in a light wavelength range of 630 to 850 nm. It is an object of the present invention to provide an optical recording medium in which an organic recording layer having a uniform target is provided.

[Constitution of the Invention] (Means and Actions for Solving the Problems) The optical recording medium of the present invention selectively raises or removes a part of an organic recording layer coated on a substrate by light such as laser. In an optical recording medium on which information is recorded by means such as, for example, the organic recording layer has at least two layers selected from a phthalocyanine derivative and a naphthalocyanine derivative.
Species, with an absorbance of 0.6 in the light wavelength range of 630 to 850 nm.
As described above, the reflectance is 20% or more.

In particular, it is desirable that the organic recording layer contains at least vanadyl naphthalocyanine and tertiary butyl-tin dichloride phthalocyanine.

In the present invention, it is preferable to record and reproduce signals by irradiating the organic recording layer with a light beam through a transparent substrate in order to avoid the influence of dust and scratches on the substrate. Therefore, the transparent substrate used in the present invention has a light transmittance of 85% for recording and reproducing signals.
Those having the above and having small optical anisotropy are preferable. As such a transparent substrate, plastic such as acrylic resin, polycarbonate resin, epoxy resin, and polyolefin resin, glass, and the like are preferable. Among these, plastic is particularly preferable in terms of mechanical strength, easy formation of guide grooves and address signals, and economic efficiency.

The shape of these transparent substrates may be plate-like or film-like. The thickness of the substrate is not particularly limited, but is usually 50 μm.
It is about m to 2 mm. Of course, the surface of the substrate may have irregularities such as guide grooves and address signals. Such guide grooves and address signals may be formed when the substrate is manufactured by injection molding or casting, or may be formed by applying an ultraviolet curable resin or the like on the substrate, overlapping with a stamper, and exposing with ultraviolet light. May be.

In the present invention, specific examples of the phthalocyanine derivative and the naphthalocyanine derivative used as the recording layer include those having the following exemplified central metals of the phthalocyanine skeleton or the naphthalocyanine skeleton. That is, as the central metal, a Group Ib metal such as Cu; a Group II metal such as Mg, Ca, Sr, Zn, and Cd; Al, Ga, In, and Tl
Group III metals such as; Group IV metals such as Si, Ge, Sn, Pb, and Ti; S
Group V metals such as b, V, Nb and Ta; VI such as Se, Te, Cr and W
Group metal; Group VII metal such as Mn; Fe, Co, Ni, Ru, Rh, Pd, O
Group VIII metals such as s, Ir, and Pt. Further, oxides of these metals and halides such as chlorides, bromides and iodides may be used.

These metals, metal oxides and metal halides are usually divalent, but may be a mixture of monovalent and divalent. Further, it may be a dimer via oxygen.

In the present invention, in order to form an organic recording layer composed of two or more selected from the above-mentioned phthalocyanine derivative and naphthalocyanine derivative on a substrate, for example, a vacuum deposition method may be used. In the case of this vacuum deposition, a phthalocyanine derivative or a naphthalocyanine derivative may be accommodated one by one in two or more boats.
Two or more phthalocyanine derivatives or naphthalocyanine derivatives may be accommodated in each boat.

In putting the optical recording medium of the present invention into practical use, C /
Providing an anti-reflection layer to improve N, applying a resin on the recording layer to protect the recording layer, attaching a protective sheet to the recording layer surface, and two sheets with the recording surfaces inside. For example, means such as bonding the optical recording medium may be used. When two optical recording media are to be bonded, it is desirable to provide an air gap between the recording layers and to bond them.

In the present invention, a semiconductor laser having an oscillation wavelength of 630 to 850 nm is used as a laser used for recording and reproduction. For example, when recording at 5 m / s, the laser output on the recording layer may be 4 to 12 mW. The reproduction output is about 1/10 of the recording output, and may be about 0.4 to 1.2 mW.

(Example) Hereinafter, an example of the present invention will be described.

Example 1 Vanadyl naphthalocyanine, tertiary butyl-tin dichloride phthalocyanine, and cobalt naphthalocyanine were simultaneously vacuum-deposited on a polycarbonate substrate by a resistance heating method under a vacuum of 2 × 10 ⁻⁵ Torr to form a deposited film. When the thickness of this deposited film was measured by the repeated interferometry, 98
It was 0Å.

About this vapor deposition film, the light absorbency and the reflectance were measured in the light wavelength range of 630-850 nm. The results are shown in Table 1 and illustrated in FIG.

Next, on a polycarbonate substrate with a guide groove having a diameter of 130 mm, vanadyl naphthalocyanine, tertiary butyl-tin dichloride phthalocyanine, and cobalt naphthalocyanine were simultaneously vacuum-deposited under the same conditions as above to provide an organic recording layer having a thickness of 980 mm. Then, an optical recording medium was manufactured.

This optical recording medium was subjected to a recording / reproducing test as follows.

Semiconductor laser with oscillation wavelength of 830nm (maximum output on film surface is 15m
W), using an objective lens with an NA of 0.55, and using an optical recording medium of 1800r
When recording and reproduction were performed while rotating at pm, the threshold value for recording was 5 mW, and the value at which C / N reached saturation (65 dB) was 6.7 mW.

A semiconductor laser with an oscillation wavelength of 780 nm (maximum output on the film surface is 10 m
W), using an objective lens with an NA of 0.55, and using an optical recording medium of 1800r
When recording / reproducing while rotating at pm, the threshold of recording was 4.7mW, and the value at which C / N reached saturation (66dB) was 6.7mW
Met.

A semiconductor laser with an oscillation wavelength of 670 nm (maximum output on the film surface is 4 m
When W) was used to reproduce a signal recorded with a semiconductor laser having an oscillation wavelength of 830 nm and 780 nm as described above, the C / N was 68 d
B.

When recording and reproduction were similarly performed using a He-Ne laser with an oscillation wavelength of 630 nm and an objective lens with an NA of 0.60, the saturation value of the recording was 6.8 mW, and the C / N was 66 dB.

In addition, this optical recording medium is used at 50 ° C / 85% RH, 60 ° C / 85% R
As a result of the accelerated aging test at H, 70 ° C and 85% RH, the life at room temperature was estimated to be more than 20 years.

Comparative Examples 1-3 Vanadyl naphthalocyanine (Comparative Example 1), tertiary butyl-tin dichloride phthalocyanine (Comparative Example 2), and cobalt naphthalocyanine (Comparative Example 3) were placed on a polycarbonate substrate at a vacuum of 2 × 10 ⁻⁵ Torr. Each was vacuum-deposited separately by a resistance heating method to form a 980-mm-thick deposited film.

The absorbance and reflectance of these deposited films were measured in the light wavelength range of 630 to 850 nm. Table 1 shows the results of Comparative Examples 1 and 2. FIG. 1 shows the results of Comparative Example 1. In Comparative Example 3 (cobalt naphthalocyanine), the absorbance was 0.80 and the reflectance was 2 near the maximum absorption wavelength of 660 nm.
8%, absorbance at 830 nm was 0.17, and reflectance was 12%.

Next, on a polycarbonate substrate with a guide groove having a diameter of 130 mm, vanadyl naphthalocyanine was independently vacuum-deposited to provide an organic recording layer having a thickness of 970 mm, and an optical recording medium (Comparative Example 1)
Was prepared. When a recording / reproducing test was performed on this optical recording medium, the absorbance was reduced at a wavelength of 670 nm or less, and the recording sensitivity was significantly reduced. At 830 nm, the reflectance was too small to interfere with tracking servo and focus servo.

Similarly, on a polycarbonate substrate having a guide groove having a diameter of 130 mm, tertiary butyl-tin dichloride phthalocyanine was independently vacuum-deposited to provide an organic recording layer having a thickness of 970 mm, thereby producing an optical recording medium (Comparative Example 2). When a recording / reproducing test was performed on this optical recording medium, the reflectance was as small as 20% or less at 670 nm and 630 nm.
Focus servo became difficult, and recording and reproduction became difficult.

Similarly, an organic recording layer having a thickness of 970 mm was formed on a polycarbonate substrate having a guide groove having a diameter of 130 mm by vacuum deposition of cobalt naphthalocyanine alone to prepare an optical recording medium (Comparative Example 3). When a recording / reproducing test was performed on this optical recording medium, the reflectance at 830 nm was small, which hindered tracking servo and focus servo.

As described above, when the organic recording layer is composed of a single dye, high sensitivity and stable recording / reception in the light wavelength range of 630 to 850 nm.
It turned out to be difficult to regenerate.

Example 2 Tin naphthalocyanine, tertiary butyl-tin dichloride phthalocyanine, and vanadyl naphthalocyanine were simultaneously vacuum-deposited on a polycarbonate substrate by a resistance heating method under a vacuum of 2 × 10 ⁻⁵ Torr to form a deposited film. The thickness of this deposited film was measured to be 1020 ° by a repeated interference method.

About this vapor deposition film, the light absorbency and the reflectance were measured in the light wavelength range of 630-850 nm. Table 1 shows the results.

Next, on a polycarbonate substrate with a guide groove having a diameter of 130 mm, tin naphthalocyanine, tertiary butyl-tin dichloride phthalocyanine, and vanadyl naphthalocyanine were simultaneously vacuum-deposited under the same conditions as above to provide an organic recording layer having a thickness of 980 mm. Then, an optical recording medium was manufactured.

When a recording / reproduction test was performed on this optical recording medium in the same manner as in Example 1, the recording threshold was 5.2 m at 830 nm.
W was 4.9 mW at 780 nm and 6.9 mW at 630 nm.

Comparative Example 4 An optical recording medium (Comparative Example 4) was produced by separately depositing tin naphthalocyanine under vacuum on a polycarbonate substrate having a guide groove having a diameter of 130 mm and providing a 970-mm-thick organic recording layer.
When a recording / reproducing test was performed on this optical recording medium, the absorbance was low at 670 nm and 630 nm, and the sensitivity was greatly reduced. At 830 nm, the reflectance was too small to perform tracking servo and focus servo.

[Effect of the Invention] As described in detail above, according to the optical recording medium of the present invention, 63
Even if the oscillation wavelength of the recording / reproducing semiconductor laser changes in the optical wavelength range of 0 to 850 nm, there is no significant change in sensitivity or C / N, and there is no hindrance to tracking servo and focus servo. Therefore, in the near future, even if the light wavelength of the semiconductor laser changes to achieve higher density recording, new recording can be performed in exactly the same way as in the initial state, and information already recorded can be used within the life of the medium. Can also be played. In particular, vanadyl naphthalocyanine and tert-butyl-
An optical recording medium having an organic recording layer containing tin dichloride phthalocyanine has excellent durability and extremely good recording / reproducing characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing spectral absorption characteristics and spectral reflection characteristics at 630 to 850 nm of an organic recording layer used in optical recording media of Example 1 and Comparative Example 1 of the present invention. FIG. 3 is a diagram showing spectral absorption characteristics and spectral reflection characteristics at 630 to 850 nm of a metal thin film used in a conventional optical recording medium, and FIG. 3 is a schematic configuration diagram of an optical recording device. 1 ... optical recording medium, 2 ... substrate, 3 ... recording layer, 4 ...
Rotary drive motor, 5 ... Semiconductor laser, 6 ... Laser light, 7 ... Modulator, 8 ... Optical system, 9 ... Reflector, 10 ...
…Condenser lens.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/26

Claims (2)

(57) [Claims] 1. An optical recording medium for recording information by light on an organic recording layer coated on a substrate, wherein the organic recording layer is made of at least two kinds selected from phthalocyanine derivatives and naphthalocyanine derivatives, and has a wavelength of 630 to 850 nm. An optical recording medium having an absorbance of 0.6 or more and a reflectance of 20% or more in an optical wavelength range. 2. The optical recording medium according to claim 1, wherein the organic recording layer contains at least vanadyl naphthalocyanine and tertiary butyl-tin dichloride phthalocyanine.