JP2511453B2 - Optical information recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical information recording medium having an optical recording layer covered with a protective layer.

[Prior Art] FIG. 5 shows a conventional example of an optical information recording medium. This recording medium comprises a substrate 1 such as a donut-shaped glass disc or a plastic disc, on which a metal layer such as Te, Bi, Mn or the like, and an optical recording layer 2 comprising a dye layer such as cyanine, merocyanine or phthalocyanine. The optical recording layer 2 is provided with a protective layer 3 for protecting the optical recording layer 2 from dirt and scratches.

For recording signals on these optical information recording media, the optical recording layer 2 is irradiated with a laser beam hν from the substrate 1 side to partially evaporate or sublimate the optical recording layer 2 and the pits having a diameter of about 1 μm 4 is formed. The vaporized component evaporated or sublimated from the optical recording layer 2 by the irradiation of the laser beam hν permeates the fine through holes of the porous protective layer 3 and is absorbed.

Further, at the time of reproducing the above-mentioned recording, a laser beam having a lower energy than that at the time of recording is irradiated from the pickup (not shown) through the substrate 1, and the optical recording layer 2 is reproduced by the difference in reflectance between the recording layer 2 and the pits 4. Get the signal.

[Problems to be Solved by the Invention] In such an optical information recording medium, as schematically shown in FIG. 5, the laser beam hν passing through the pit 4 during reproduction is reflected by the protective layer 3, This passes through the pit 4 again and is detected. Therefore, the difference between the amount of light detected in the pit and the amount of light detected in other parts is small,
There is a problem that the C / N of the obtained reproduction signal is small.

An object of the present invention is to solve the above problems and provide an optical information recording medium that can obtain a reproduction signal with a high C / N.

[Means for Solving the Problem] The structure of the present invention will be described with reference to the reference numerals in FIGS. 1 to 4. In this optical information recording medium, an optical recording layer 12 is formed on a substrate 11, The layer 12 is covered with a protective layer 13, and a light absorbing layer 17 for absorbing a laser beam is formed on at least a side of the protective layer 13 in contact with the optical recording layer 12.

[Operation] In the optical information recording medium according to the present invention, the optical recording layer 12 is irradiated with the laser beam hν from the pickup through the substrate 11 and passes through the pits 14 formed in the optical recording layer 12 when reading recorded data. Light is a light-absorbing layer behind it
It is absorbed by 17 and is hardly reflected to the light absorption layer 12 side. For this reason, the difference in the amount of reflected light detected in the pits 14 of the optical recording layer 12 and other portions becomes large, and a reproduction signal with high C / N can be obtained. In this respect, the reflectance of the laser beam on the light absorption layer 17 is preferably as low as possible, and specifically, the integrated reflectance is 5% or less.

[Examples] Next, examples of the present invention will be specifically described.

Example 1 3-Methyl-2- [7-, which is one of cyanine dyes
(3'-Methyl-2'-benzothiazoline) -1-3-
2-Heptatrienyl] -benzothiazole perchlorate was dissolved in 2-nitropropane at 2% by weight. This solution was applied onto a donut-shaped polymethylmethacrylate substrate 11 having an outer diameter of 120 mm and a thickness of 1.2 mm by a spinner method and dried to form an optical recording layer 12 having a thickness of about 60 nm.

Furthermore, a velvet coating film (Sumitomo 3M 2010) was gravure coated on one surface of a long polyethylene terephthalate film having a thickness of 75 μm and a width of 150 mm to provide a light absorption layer 17
Was formed and cut into a circle having a diameter of 120 mm. Then, this was placed on the recording layer 12 so that the light absorbing layer 17 faces the optical recording layer 12 side, and the inner and outer peripheral edges thereof were fixed to the substrate 11 to form the protective layer 12. Thus, an optical recording medium having the structure shown in FIGS. 1 and 2 was manufactured.

In this optical information recording medium, the light absorbing layer 17 side of the protective layer 13 is not in close contact with the optical recording layer 12, but is simply in contact with the optical recording layer 12.
It is a non-contact type. The integrated reflectance of the laser beam hν in the light absorption layer 17 was 1%.

A semiconductor laser having a wavelength of 780 nm is used as the optical information recording medium, and a laser beam hν having a linear velocity of 1.4 m / sec and a recording frequency of 500 KHz is applied to the optical recording layer 12 from the substrate 11 side to form a bit 14 on the same layer 12. And recorded. At this time, the optimum recording power of the laser beam hν measured and confirmed on the recording surface was 4.0 mW. After recording, output to the optical recording layer 12 0.3 mW
When the C / N of the recording surface was measured by irradiating the laser beam hν of No. 3 was 43 dB. The results are shown in the table below.

(Example 2) The same as Example 1 except that a paste made of carbon black and an acrylic resin was applied instead of the means for forming the light absorption layer 17 by the velvet coating film. An optical information recording medium was made according to the method and conditions. The integrated reflectance of the laser beam on the light absorption layer 17 was 4%.

Recording and reproduction were performed on the above optical recording medium in the same manner as in Example 1. The recording power was 4.0 mw.
The C / N of the reproduced signal was 40 dB. The results are shown in the table below.

(Example 3) The same 3-methyl-2- [7- (3'-methyl-2'-benzothiazoline) -1-3-5-heptatrienyl] -benzothiazole as that used in Example 1 was used as a dye. Using perchlorate, this was dissolved in 2-nitropropane at 3% by weight. Also, as the substrate 11, a diameter of 130 m
m, 1.2 mm thick polycarbonate substrate with pregroup
11 was used to form an optical recording layer 12 having a thickness of about 60 nm on one side by the same method as in Example 1 above.

Further, a non-reflective acrylic paint (made by Asahi Penn Co., Ltd.) was spray-coated on one surface of a long polyethylene terephthalate film having a thickness of 150 μm and a width of 150 mm to form a light absorption layer 17, which was cut into a circle having a diameter of 130 mm. Then, in the same manner as in the above-mentioned embodiment, the optical recording layer 12 is covered with the protective layer.
13 formed. The integrated reflectance of the laser beam hν in the light absorption layer 17 was 1%.

The same method as in Example 1 was applied to the optical recording layer 12 of the above optical information recording medium (however, the linear velocity of the laser beam was 1.4 m / sec, the recording frequency was
Bit 14 was formed at 450 KHz) and recording was performed. At this time, the optimum recording power of the laser beam hν measured and confirmed on the recording surface was 2.5 mW. After recording, the C / N of the recording surface was measured in the same manner and found to be 45 dB. The results are shown in the table below.

Example 4 A substrate 11 of the same type as in Example 3 above was used, and on this surface
Te alloy was vacuum-deposited at a film forming rate of 30 nm / min to form an optical recording layer 12 having a thickness of 45 nm.

The surface of this optical recording layer 12 is spray-coated with a velvet coating (Sumitomo 3M 2010) to form a light absorption layer 17 in advance, and then an aluminum layer 16 is applied by vacuum deposition, and an acrylic hard coating 18 is applied to protect it. Layers were formed. As a result, an optical recording medium having the structure shown in FIGS. 3 and 4 was manufactured. This optical information recording medium is a so-called contact type, in which the light absorption layer 17 side of the protective layer 13 is completely adhered to the optical recording layer 12. Incidentally, the light absorption layer 12
Had an integrated reflectance of 1.5%.

Recording and reproduction were performed on the above optical recording medium in the same manner as in Example 3. The optimum recording power at this time is 4.5 m
W, C / N of reproduced signal was 48 dB.

(Example 5) In Example 3, the alumina terephthalate film with black electrostatic flocking was used as the light absorbing layer 17 in place of the polyethylene terephthalate film forming the protective layer 12, and in Figs. 1 and 2. An optical recording medium having a structure as shown was manufactured. The integrated reflectance of the light absorption layer 12 is
It was 1.2%.

Recording and reproduction were performed on the above optical recording medium in the same manner as in Example 3. The optimum recording power at this time is 2.3 m
W, the C / N of the reproduced signal was 47 dB.

(Example 6) In Example 4, the velvet coating film forming the light absorption layer 17 was replaced with a porous non-reflective acrylic paint spray film containing titanium black and silica gel as main components. An optical recording medium having a structure as shown in FIG. 4 was manufactured. The integrated reflectance of the light absorption layer 12 was 1.8%.

Recording and reproduction were performed on the above optical recording medium in the same manner as in Example 3. The optimum recording power at this time is 5.0 m
W, the C / N of the reproduced signal was 46 dB.

Comparative Example 1 The optical recording layer 2 formed on the substrate 1 in the same manner as in Example 1 was immersed in a solution in which nitrocellulose corresponding to 3% by weight of carbon tetrachloride was dissolved. A protective layer 3 made of a porous nitrocellulose film was formed on the optical recording layer 2 to prepare an optical information recording medium as shown in FIG.

When the optical information recording medium was tested under the same method and conditions as in Example 1, the optimum recording power was 8.5 mW and the C / N of the reproduced signal was 32 dB. The results are shown in the table below.

(Comparative Example 2) An optical information recording medium was prepared in the same manner as in Example 3 except that the long polyethylene terephthalate film forming the protective layer 13 was not subjected to the antireflection treatment.

When the optical information recording medium was tested under the same method and conditions as in Example 3, the optimum recording power was 2.5 mW and the C / N of the reproduced signal was 32 dB. The results are shown in the table below.

Comparative Example 3 An optical information recording medium was prepared by using a glossy black paint instead of the non-reflective acrylic paint forming the light absorption layer 17 in the above-mentioned Example 3. In this case, the optical recording layer 12 of the protective layer 13
The integrated reflectance on the boundary layer side with was 6.2%.

When the optical information recording medium was tested under the same method and conditions as in Example 3, the optimum recording power was 2.4 mW and the C / N of the reproduced signal was 36 dB. The results are shown in the table below.

Comparative Example 4 An optical information recording medium was prepared in the same manner as in Example 6 except that titanium black was not added to the porous non-reflective acrylic paint. In this case, the integrated reflectance of the protective layer 13 on the interface layer side with the optical recording layer 12 was 10.5%.

When the optical information recording medium was tested under the same method and conditions as in Example 3, the optimum recording power was 4.5 mW and the C / N of the reproduced signal was 34 dB. The results are shown in the table below.

[Effects of the Invention] As described above, according to the present invention, most of the laser beam that has passed through the pit is absorbed by the light absorption layer 17 behind it, and the reflected laser beam passes through the pit again and is not detected. Therefore, there is an effect that a reproduction signal having a high C / N can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an optical information recording medium showing an embodiment of the present invention in an enlarged manner in the thickness direction, FIG. 2 is an enlarged view of part A of FIG. 1, and FIG. FIG. 4 shows an example of a conventional optical information recording medium, and FIG. 4 is an enlarged longitudinal sectional view of a main part of an optical information recording medium showing an embodiment in an enlarged manner in the thickness direction. It is a principal part longitudinal cross-sectional view which expanded the thickness direction. 11 ... Substrate, 12 ... Optical recording layer, 13 ... Protective layer, 17 ... Light absorbing layer

Claims (3)

(57) [Claims] 1. In an optical information recording medium in which an optical recording layer 12 is formed on a substrate 11 and the layer 12 is covered with a protective layer 13, a laser beam is provided on at least the side of the protective layer 13 in contact with the optical recording layer 12. An optical information recording medium, characterized in that a light absorbing layer (17) that absorbs is formed. 2. The optical information recording medium according to claim 1, wherein the protective layer 13 is non-adhesive to the optical recording layer 12. 3. The optical information recording medium according to claim 1, wherein the protective layer 13 is adhesive to the optical recording layer 12.