JPH0827979B2 - Optical information recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical information recording medium that irradiates a laser beam and reproduces recorded data by the reflected light.

[Prior Art] An optical information recording medium capable of recording data by irradiating a laser beam has a recording layer including a metal layer such as Te, Bi and Mn and a dye layer such as cyanine, merocyanine and phthalocyanine. The pits are formed and the data is recorded by means such as irradiating with a laser beam to modify the recording layer by deformation, sublimation, evaporation, or the like. In an optical information recording medium having such a recording layer, a void is generally provided behind the recording layer in order to facilitate deformation, sublimation, evaporation or modification of the recording layer when forming pits. ing. Specifically, for example, a so-called air sandwich structure, in which two substrates are stacked with a space therebetween, is used.

In this optical information recording medium, the translucent substrate 1 is used.
Laser light is irradiated from the side to form pits. And
When the recorded data is reproduced, a laser beam whose power is weaker than that at the time of recording is emitted from the side of the substrate 1, and a signal is read due to the difference in reflected light between the pit and other portions.

On the other hand, a so-called ROM type optical information recording medium in which data is recorded in advance and the data cannot be written or erased thereafter has already been widely put to practical use in the information processing and audio departments. This kind of optical information recording medium does not wait for the recording layer as described above, and pits for reproducing recorded data are formed beforehand on a polycarbonate substrate by means of a press or the like, and Au, Ag A reflective layer made of a metal film such as Cu, Al or the like is formed and further covered with a protective layer.

The most typical of these ROM type optical information recording media is a compact disc, a so-called CD, which has been widely put into practical use in the audio sector and the information processing sector. The specifications of the recording and reproducing signals of this CD are the so-called CD format. A playback device that has been standardized as, and is compliant with this, is extremely widespread as a compact disc player (CD player).

[Problems to be Solved by the Invention] Since the above optical information recording medium is also a recording / reproducing means that uses the same laser light as that of a CD, it is strongly desired that the optical information recording medium conforms to the already widespread CD when reproducing.

However, a writable optical information recording medium is a CD
Has a recording layer which is not present in the present invention, and since a pit is formed in this recording layer in order to facilitate formation of the pit, a laser beam which has passed through the recording layer is not reflected. As a result, the amount of light reflected on the incident side of the laser light is greatly attenuated, so the reflectance of the laser light is lower than that of CD, and it is difficult to satisfy the above-mentioned CD format that defines the standard for so-called CD. . Therefore, in the past, CD
It was not possible to provide a writable optical information recording medium that complies with the above.

The present invention has been made to solve the above-mentioned conventional problems, has a high reflectance, and when reproducing data,
An object of the present invention is to provide a writable optical information recording medium that can obtain an output signal conforming to the CD format.

[Means for Solving the Problem] That is, in order to achieve the above-mentioned object, the gist of the means adopted in the present invention is that light that absorbs laser light directly on the translucent substrate 1 or through another layer. In an optical information recording medium having an absorption layer 2 and a light reflection layer 3 provided on the light absorption layer 2 via another layer for reflecting laser light, the light absorption layer 2 and the light reflection layer 3 An enhancement layer 6 that is transparent to the wavelength of the laser light for reproduction is formed between the light absorption layer 2 and
_Is given by the real part n _abs and the imaginary part k _abs of the complex index of refraction of, and the real part n _ehs and the imaginary part k _ehs of the complex index of the enhancement layer 6. Is 0.05 ≦ ρ ≦ 1.1, which is an optical information recording medium.

[Operation] The product of the real part n _abs of the complex refractive index of the light absorption layer 2 of the optical information recording medium and the film thickness d _abs is the optical film thickness of the light absorption layer 2, and the complex refraction of the enhancement layer 6 Real part n _ehs and film thickness
The product of d _ehs is the optical film thickness of the enhancement layer 6. The relationship between the above ρ obtained by dividing the sum of these optical film thicknesses by the wavelength λ of the laser light and the reflectance of the laser light of the optical information recording medium is as shown in FIG. It is represented by a periodic function. Here, the two curves in the same figure are for the real part n _sbs = 2.7 of the complex index of refraction of the light absorbing layer 2, but the solid line curve is the enhancement layer 6 and the complex index of When n _ehs is 1.4 for the real part, the dashed line on one side is the reflectance of the laser beam with wavelength λ = 780 nm when the value of ρ is changed by changing the film thickness without providing the enhancement layer. Shows the change.

As is clear from this graph, the solid line showing the optical information recording medium provided with the enhancement layer 6 has a considerably higher reflectance as a whole than the broken line showing the optical recording medium not provided with the enhancement layer. There is.

In the optical information recording medium shown by the broken line, in order to obtain a high reflectance of laser light of 70% or more, the light absorption layer 2
Taking into account the sensitivity of and the thermal energy stored in the same layer 2,
It is necessary to set ρ near the second peak in the figure. On the other hand, in the optical information recording medium according to the present invention shown by the solid line, the reflectance of the laser light is generally increased by the action of the enhancement layer 6, so that ρ can be set in a wide range. Specifically, of the first peak,
The thickness of the light absorption layer 2 must be very thin, ρ <
Looking into the range of 0.05, it is possible to select from the range of ρ ≦ 1.1 where the first peak to the third peak exceed the pass.

The present invention has been made on the basis of the above facts, and by the first means, the reflectance of the laser light of the optical information recording medium can be made higher than that in the case where the enhancement layer is not provided over the whole, further, By the second means, it becomes possible to make the reflectance of the laser light 70% or more in the optical information recording medium.

[Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.

An example of a schematic structure of the optical information recording medium according to the present invention,
It is shown in FIGS. In the figure, 1 is a transparent substrate, and 2 is a light absorption layer formed thereon, which absorbs the irradiated laser light to generate heat, which is melted, evaporated, sublimated, deformed or modified. Is a layer having a function of forming pits on the surface of the transparent substrate 1.

As described above, in the present invention, the light absorption layer 2 described above is used.
A dielectric layer that is transparent to the laser beam for reproduction (imaginary part of complex refractive index k _ehs = 0), that is, an enhancement layer 6 is provided on the above. The enhance layer 6 can be formed of, for example, an inorganic dielectric layer such as SiO ₂ , amorphous SiO, Si ₃ N ₄ , SiN, AlN, or ZnS, or an organic dielectric layer such as a silicon resin, as described later. The optical film thickness 6 is related to the light absorption layer 2, Is set to 0.05 ≦ ρ ≦ 1.1,
As described above, a high reflectance of not less than% can be obtained.

Reference numeral 3 denotes a light reflecting layer formed thereon for reflecting the laser light, and 4 denotes a protective layer provided on the outside thereof. Incidentally, FIG. 2 shows a state before recording with laser light, and FIG. 3 shows a state after recording, that is, the light absorption layer 2 at the time of laser light irradiation.
The surface of the substrate 1 is partially deformed by the local thermal deformation of, and the pits 5 are schematically formed.

A specific example of this optical information recording medium will be described below.

Example 1 A spiral pregroup having a width of 0.8 μm, a depth of 0.08 μm, and a pitch of 1.6 μm, formed with a thickness of 1.2 mm and an outer diameter of 120 mm.
A polycarbonate substrate 1 having a diameter of 15 mm and an inner diameter of 15 mm was molded by an injection molding method.

5.0 g of 1,1′dibutyl 3,3,3 ′, 3′tetramethyl 5,5′diethoxyindodicarbocyanine perchlorate was dissolved on the surface of the transparent substrate 1 in 10 cc of hydroxyacetone solvent, This was applied onto the above substrate 1 by spin coating to form a light absorption layer 2 having a film thickness d _abs = 70 nm. The real part n of the complex refractive index of this light absorption layer 2
_abs = 2.65 and its imaginary part k _abs = 0.04.

Further, a SiO ₂ film having a film thickness n _ehs = 50 nm is formed on the light absorption layer 2 as the enhancement layer 6 by a sputtering method, and Au and Ti having a film thickness of 50 nm are formed thereon by a vacuum deposition method. A reflective layer 3 made of a 9: 1 alloy film was formed. The real part n _ehs of the complex refractive index of the enhancement layer 6 is 1.45,
Therefore ρ = 0.33.

Then, an ultraviolet curable resin is spin-coated on the light reflection layer 3 and is irradiated with ultraviolet rays to be cured to obtain a thickness.
A protective layer 4 having a thickness of 10 μm was formed.

The optical disc thus obtained was irradiated with a semiconductor laser with a wavelength of 780 nm at a linear velocity of 1.2 m / sec and a recording power of 6.0 mW.
The signal was recorded. Then, use this optical disc as a commercially available CD
When reproduced with a player (Aurex XR-V73, wavelength of reproduced light λ = 780 nm), the reflectance of the optical disk was 79%, and a good eye pattern was obtained.

(Embodiment 2) In the embodiment 1, the enhancement layer 6 has a film thickness n.
An optical disk was manufactured in the same manner as in Example 1 except that an AlN layer having a thickness of _ehs = 40 nm was formed, and a protective layer 4 was formed on the light reflecting layer 3 with an epoxy resin layer having a thickness of 15 nm. did. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disk is 2.2, and therefore ρ = 0.35.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced with a commercially available CD player, the reflectance was 75%, and a good eye pattern was obtained.

(Example 3) In Example 1, the enhancement layer 6 has a film thickness n.
_ehs = 40 nm amorphous SiO layer was formed by the reactive sputtering method in O ₂ , the light reflection layer 3 was formed of a 9: 1 alloy film of Au and Sb, and on the light reflection layer 3. An optical disk was manufactured in the same manner as in Example 1 except that the protective layer 4 was formed on the above with a polyvinyl acetate layer having a film thickness of 15 nm. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 1.98,
Therefore ρ = 0.34.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced with a commercially available CD player, the reflectance was 75%, and a good eye pattern was obtained.

(Example 4) In Example 1, the enhancement layer 6 has a film thickness n.
_ehs = 45 nm Si ₃ N ₄ layer was formed by reactive sputtering method in N ₂ , and the light reflection layer 3 was made of 9: 1 Au and Sb.
An optical disk was manufactured in the same manner as in Example 1 except that the optical disk was formed of the alloy film having the ratio of. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 1.85, and therefore ρ = 0.34.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 76%, and a good eye pattern was obtained.

(Fifth Embodiment) In the first embodiment, the enhancement layer 6 has a film thickness n.
An optical disk was manufactured in the same manner as in Example 1 except that the ZnS layer with _ehs = 30 nm was formed by the vacuum evaporation method and the light reflecting layer 3 made of the Au film was formed by the sputtering method. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 2.31.
Therefore ρ = 0.33.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced with a commercially available CD player, the reflectance was 80%, and a good eye pattern was obtained.

(Example 6) 5.5 g of 1, 1'dibutyl 3, on the surface of the transparent substrate 1,
3,3 ', 3' tetramethyl 4,5,4 ', 5' dibenzoindodicarbocyanine perchlorate (manufactured by Japan Photosensitive Dye Research Institute, product number: NK3219) was added to diacetone alcohol 1
It was dissolved in 0 cc, and this was applied onto the above substrate 1 by a spin coating method to form a light absorption layer 2 having a film thickness d _abs = 90 nm. The real part n _abs = 2.7 of the complex refractive index of the light absorption layer 2,
Its imaginary part k _abs = 0.05.

Further, a SiO ₂ film having a film thickness n _ehs = 50 nm is formed as a enhance layer 6 on the light absorption layer 2 by a sputtering method, and a SiO ₂ film having a film thickness of 50 nm is formed on the SiO ₂ film by a sputtering method.
The reflective layer 3 made of an Au film was formed. Enhance layer 6 above
The real part n _ehs of the complex refractive index of is 1.45, so ρ =
It is 0.40.

Then, an isocyanate-curable epoxy resin was spin-coated on the light reflection layer 3 and thermally cured to form a protective layer 4 having a thickness of 5 μm.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 82%, and a good eye pattern was obtained.

(Embodiment 7) In the above Embodiment 6, the thickness n is used as the enhancement layer 6.
_ehs = 40 nm AIN layer was formed, a polybutadiene layer having a film thickness of 15 nm was interposed between the light reflection layer 3 and the protective layer 4, and the protective layer 4 was formed of an ultraviolet curable resin having a film thickness of 10 μm. An optical disc was manufactured in the same manner as in Example 6 except for the above. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 2.2, and thus ρ = 0.42.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 82%, and a good eye pattern was obtained.

(Embodiment 8) In the above-mentioned Embodiment 6, the thickness n is used as the enhancement layer 6.
_ehs = 40 nm amorphous SiO layer was formed by a reactive sputtering method in O ₂ , the light reflection layer 3 was formed by a vacuum evaporation method, and the protective layer 4 was formed by an ultraviolet curable resin having a film thickness of 10 μm. Other than the above, Example 6 above
An optical disc was manufactured in the same manner as in. The real part of the complex refractive index of the enhancement layer 6 in this optical disc
n _ehs is 1.98, so ρ = 0.41.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 82%, and a good eye pattern was obtained.

Example 9 In Example 6, the film thickness of 60 nm was formed on the transparent substrate 1.
A light absorbing layer 2 is formed on the acrylic resin layer, and a silicon resin layer having a film thickness n _ehs = 45 nm is formed as the enhancing layer 6 by spin coating.
An optical disk was manufactured in the same manner as in Example 6 except that the light reflecting layer 3 was formed by a vacuum evaporation method and the protective layer 4 was formed by an ultraviolet curable resin having a film thickness of 10 μm. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 1.47, and therefore ρ
= 0.40.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 82%, and a good eye pattern was obtained.

(Embodiment 10) In the above-mentioned Embodiment 6, the thickness n is used as the enhancement layer 6.
The ZnS layer of _ehs = 20 nm was formed, and Au was used as the light reflection layer 3.
An optical disc in the same manner as in Example 6 except that a 9: 1 alloy thin film of Ir and Ir was formed by a vacuum evaporation method, and the protective layer 4 was formed of an ultraviolet curable resin having a thickness of 10 μm. Was produced. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 2.
31 and thus ρ = 0.37.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced with a commercially available CD player, the reflectance was 73%, and a good eye pattern was obtained.

Example 11 In Example 6, the film thickness of 20 nm was formed on the transparent substrate 1.
Of the UV curable resin layer and the light absorption layer 2 formed on the UV cured resin layer of SiN having a film thickness n _ehs = 35 nm as the enhancement layer 6.
Forming a layer, forming an alloy thin film of Au: Ir at a ratio of 9: 1 as a light reflecting layer 3 by a vacuum vapor deposition method, and forming a protective layer 4 by an ultraviolet curable resin having a thickness of 10 μm An optical disc was manufactured in the same manner as in Example 6 except for the above. The real part n _ehs of the complex refractive index of the enhancement layer 6 in this optical disc is 1.82, and therefore ρ = 0.39.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced on a commercially available CD player, the reflectance was 76%, and a good eye pattern was obtained.

Comparative Example An optical disk was manufactured in the same manner as in Example 1 except that the enhancement layer 6 was not formed in Example 1 above. In this case, ρ = n _abs · d _abs /λ=0.41.

An EFM signal was recorded on the optical disc thus obtained in the same manner as in Example 1 above, and then this optical disc was recorded.
When reproduced with a commercially available CD player, the reflectance was 12% and the eye pattern was unclear.

[Effects of the Invention] As described above, according to the present invention, the reflectance of laser light is high, and particularly according to the second means, the reflectance is as high as 70% or more, and moreover, recording is performed on the light absorption layer. A writable optical information recording medium that can obtain a reproduction signal conforming to the CD format when data is reproduced can be provided.

[Brief description of drawings]

FIG. 1 is a schematic half cross-sectional perspective view showing an example of the structure of an optical information recording medium, FIG. 2 is an enlarged view of part A of FIG. 1, and FIG.
FIG. 4 is a graph showing an example of the relationship between ρ = (n _abs · d _abs + n _ehs · d _ehs ) / λ and the laser light reflectance, FIG. is there. 1 ... Substrate, 2 ... Light absorbing layer, 3 ... Reflective layer, 4 ... Protective layer, 6 ... Enhance layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Ishiguro 6-16-20 Ueno, Taito-ku, Tokyo Within Taiyo Electric Co., Ltd. (56) Reference JP 62-139149 (JP, A) JP Sho 61-273756 (JP, A) JP-A-2-33738 (JP, A)

Claims (1)

[Claims] 1. A light absorbing layer 2 which absorbs a laser beam directly or through another layer on a transparent substrate 1, and a laser beam provided on the light absorbing layer 2 through another layer. In an optical information recording medium having a light reflection layer 3 that reflects light, an enhancement layer 6 transparent to the wavelength of the reproduction laser light is formed between the light absorption layer 2 and the light reflection layer 3, It is given by the real part n _abs and imaginary part k _abs of the complex refractive index of the absorption layer 2 and the real part n _ahs and imaginary part k _ehs of the complex refractive index of the enhancement layer 6. The optical information recording medium is characterized in that 0.05 ≦ ρ ≦ 1.1.