JP2005302269A - Optical recording medium and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a dye for a recording layer capable of high-density recording without generating noise such as jitter, low-light light such as a blue laser as well as a red laser without generating noise such as jitter. Providing a two-layer structure type optical recording medium and a method for producing the same.
First and second sets of recording composition layers are laminated on a substrate via a resin intermediate layer, and two sets of recording structures are formed by laser light irradiation from the first recording composition layer side. In an optical recording medium in which recording / reproduction is performed on each layer, the first recording constituent layer has a first dye layer and a first reflective layer adjacent thereto, and the second recording constituent layer is a second dye layer and There is a second reflective layer adjacent to this, the first reflective layer is a semi-transparent layer, and two protective layers (first protective layer, second protective layer) between the second dye layer and the resin intermediate layer And a two-layer structure type optical recording medium.
[Selection] Figure 1

Description

  The present invention relates to an optical recording medium capable of recording / reproducing information by optically changing the transmittance, reflectance, etc. of a recording material by irradiating a light beam, and a method for producing the same. Is.

Conventionally, in an optical recording medium having an organic dye thin film as a recording layer, an organic dye thin film using a phthalocyanine dye (such as Patent Document 1), a cyanine dye (such as Patent Document 2), or a phenanthrene-based film Those using dyes, naphthoquinone dyes, and the like are known.
Furthermore, write-once compact disc (CD-R) optical recording media, in which an organic dye, a metal reflective layer, and a UV resin protective layer are sequentially laminated on a substrate, require high reflectivity to satisfy the CD standard, and are therefore reproduced. It is necessary to develop an organic dye having a high refractive index in the wavelength region (770 to 830 nm) and high stability (DVD ± R, which is a write-once DVD disc, has a reproduction wavelength region of 630 to 680 nm). So far, CD-R and DVD ± R have made many proposals adopting layer structures such as cyanine dye layer / metal reflective layer, phthalocyanine dye layer / metal reflective layer, azo metal chelate dye layer / metal reflective layer, etc. (For example, there is Patent Document 3 for the one using a phthalocyanine dye, and Patent Document 4 for the one using an azo metal chelate dye). However, all of these optical recording media have one dye layer (recording layer) and a storage capacity of one dye layer.

On the other hand, in order to increase the storage capacity of one optical disk, a multiple data layer system has been proposed. In an optical disc having two or more data layers, various layers can be accessed by changing the focal point of the lens.
For example, Patent Document 5 discloses an optical disk drive system having a plurality of data layers, and the optical disk is a plurality of substrates each having a data layer spaced by an air gap, or a solid structure. One of a plurality of data layers.
In Patent Document 6, a solid structure including a plurality of data layers is employed, but each data layer is a CD type data layer.

Further, in Patent Documents 7 to 8, a recording layer having only a dye layer or a phase change film is used, and the layer configuration is not in consideration of reflectivity and compatibility with a DVD or the like. In the first embodiment, “the information layer is preferably composed of at least two or more layers. That is, in the case of a two-layer structure, for example, a structure in which a dielectric layer / recording layer is formed from the light incident side, recording layer / For example, in the case of a three-layer structure, a dielectric layer / recording layer / dielectric layer configuration from the substrate side, or a dielectric layer / For example, in the case of a four-layer structure, there is a configuration of a dielectric layer / recording layer / dielectric layer / reflective layer from the substrate side, and a first reflective layer / dielectric layer. There is a five-layer structure in which a recording layer / dielectric layer / second reflection layer are provided, and thus the recording thin film layer and the dielectric layer are provided in contact with each other, thereby preventing deterioration of the thin film during repeated recording and recording. It is possible to set a large optical change in information. " It does not take into account the case of using layers.
Further, Patent Documents 9 to 10 disclose recording media having two recording layers, all of which are recording layers made of an inorganic material.

Although there are various proposals as described above, there are only those that have not been put into practical use by repeating only the polymer layer, and those that do not consider compatibility with respect to reflectance and the like.
Further, in a write-once optical recording medium using a conventional dye as a recording material, two or more layers are provided because a metal layer is provided adjacent to the dye layer in order to increase the reflectance and record a small recording mark. A medium having a recording layer has not been realized.
Dye materials have been used since the CD generation, but in a two-layer optical recording medium, it is necessary to achieve both transmission and absorption for recording / reproducing light, which is technically difficult. Development of a technology for making multiple layers is not yet completed.
For example, in the case of an optical recording medium having a two-layer structure using a dye as a recording material, the recording structure layer on the back side tends to generate heat when viewed from the light incident side, and improvement in heat dissipation is required. However, if the thickness of the reflective layer having a high thermal conductivity is too large, there is a problem that recording sensitivity is deteriorated and jitter of recording / reproducing characteristics is deteriorated. Further, when the protective layer for adjusting the reflectance is formed so as to sandwich the recording layer, there is a problem that the film thickness is increased, the uniformity is deteriorated, and the jitter of the recording / reproducing characteristics is deteriorated.

JP 58-183296 A JP-A-57-82093 JP-A-4-226390 JP-A-4-46186 US Pat. No. 5,202,875 U.S. Pat. No. 4,450,553 International publication 00/016320 pamphlet International Publication No. 00/023990 Pamphlet JP 2001-086443 A JP 2001-10709 A

  The present invention has been made in view of the above-described circumstances, and the object thereof is not only a red laser but also a low-power light of a short wavelength such as a blue laser. An object of the present invention is to provide a two-layer structure type optical recording medium using a dye for a recording layer having good characteristics and capable of high density recording, and a method for producing the same.

The above problems are solved by the following inventions 1) to 7) (hereinafter referred to as the present inventions 1 to 7).
1) First and second recording composition layers are laminated on a substrate via a resin intermediate layer, and two sets of recording composition layers are formed by laser light irradiation from the first recording composition layer side. In an optical recording medium on which recording and reproduction are performed, the first recording constituent layer has a first dye layer and a first reflecting layer adjacent thereto, and the second recording constituent layer is a second dye layer and the first dye layer. There are adjacent second reflective layers, the first reflective layer is a translucent layer, and two protective layers (first protective layer, second protective layer) are provided between the second dye layer and the resin intermediate layer. A two-layer structure type optical recording medium comprising:
2) The two-layered optical recording medium according to 1), wherein the first and / or second reflective layer is made of Ag, Ag alloy, Au, or Al alloy.
3) The first protective layer contains at least one selected from In ₂ O ₃ , ZnO, ZrO, Ti ₂ O _3, SnO, Al ₂ O ₃ , and SiO ₂ 1) or 2) The two-layer structure type optical recording medium described.
4) The two-layer structure type optical recording medium according to any one of 1) to 3), wherein the reflectivity of the first and second recording structure layers is 15 to 30%.
5) The two-layer structure type optical recording medium according to any one of 1) to 4), wherein the thickness of the second reflective layer is 130 nm or more.
6) The two-layer structure type optical recording medium according to any one of 1) to 5), wherein the first and / or second protective layer is formed of a plurality of layers made of the same material.
7) First and second recording composition layers are laminated on a substrate via a resin intermediate layer, and the first recording composition layer has a first dye layer and a semitransparent first layer adjacent thereto. A reflective layer is provided, a second recording layer is provided with a second dye layer and a second reflective layer adjacent thereto, and two protective layers (first protection) are provided between the second dye layer and the resin intermediate layer. The first recording is characterized in that the first and / or second protective layer is divided into two or more times (a laminated structure made of the same material). A method for manufacturing a two-layer structure type optical recording medium, in which recording / reproduction is performed on two sets of recording structure layers by irradiation of laser light from the structure layer side.

Hereinafter, the present invention will be described in detail.
In a conventional layer structure in which an organic dye layer, a metal reflection layer, and a UV resin protective layer are sequentially laminated on a substrate, when Ag is used for the reflection layer, the red LD wavelength (630 to 800 nm) is obtained when the film thickness is about 100 nm. Or the blue LD wavelength (360 to 430 nm) hardly transmits light, so that it was impossible to make the recording layer into a two-layer structure.
The present invention, on the other hand, is a dye-type optical recording medium that utilizes the phenomenon of reflectance change due to perforation, deformation, or change in refractive index associated with the light absorption function of the dye layer, and is adjacent to the dye layer as in the prior art. The reflective layer is formed, but the protective layer of the second recording constitution layer is made two layers, and each has a different function. The first recording configuration layer has the same configuration as the conventional one.

  By using a dye as a recording material, it is possible to realize low jitter in high-density recording with a shortest mark length of 0.3 μm or less. However, according to the study by the present inventors, in order to realize high-density recording. When a short-wavelength laser diode (for example, a wavelength of 410 nm or less) is used, further attention needs to be paid to the quenching structure. In particular, in examining one-beam overwrite characteristics using a small focused light beam having a wavelength of 500 nm or less and a numerical aperture NA of 0.55 or more, flattening the temperature distribution in the mark width direction affects adjacent tracks. So important. Therefore, it was found that the layer structure described below is necessary. This tendency is the same in a DVR compatible optical system using an optical system with a wavelength of 350 to 420 nm and NA = 0.85.

FIG. 1 shows a cross-sectional view (schematic diagram) of a layer structure of an example of a two-layer structure type optical recording medium of the present invention.
Cover substrate 1 / first dye layer 2 / first reflective layer (translucent layer) 3 / resin intermediate layer 4 / first protective layer 5 / second protective layer 6 / second dye layer 7 / second reflective layer 8 / The first dye layer 2 and the first reflective layer (semi-transparent layer) 3 are the first recording constituent layers, and are composed of the substrate 9. The first protective layer 5, the second protective layer 6, the second dye layer 7, The two reflective layer 8 is the second recording constituent layer.
In addition to the function of protecting the dye, the second protective layer adjacent to the second dye layer has a function of adjusting recording sensitivity. Further, the first protective layer has a function of releasing heat so that the thermal deformation of the reflective layer due to the heat generation of the second dye layer during recording is reduced. With this configuration, the cooling capacity of the optical recording medium is improved, and the recording capacity in the incident direction of the laser light can be increased. In addition, since the push-pull of the groove characteristic does not become small, tracking is stabilized. Further, since the wobble signal (address signal) is also a groove characteristic, it is less likely to be deformed by heat as in the case of push-pull, so that tracking is stable and the recording / reproduction characteristic is also improved.

  Although it is not impossible to produce the medium of FIG. 1 by laminating a resin intermediate layer, a second recording constituent layer, and a substrate in this order on the first recording constituent layer, in general, the substrate is made of an inorganic film (that is, the first constituent layer) If it is laminated on (2 reflective layer), it will not stick enough. Therefore, there is a method of bonding the substrate to the inorganic film using a resin or the like, but the non-uniformity of the film thickness of the resin intermediate layer overlaps with the non-uniformity of the film thickness of the adhesive layer made of resin or the like, so Uniformity cannot be maintained, and recording / reproduction characteristics (jitter and the like) deteriorate. Therefore, in the present invention, the second recording structure layer is formed on the substrate, and the first recording structure layer is separately formed on the cover substrate. The substrate and the cover substrate are placed inside the recording structure layer. It is produced by adhering via a resin intermediate layer. According to this method, since only the influence of the film thickness unevenness (nonuniformity) of the resin intermediate layer is affected as compared with the conventional method, the film uniformity is improved.

Examples of the material of the substrate 1 include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. However, polycarbonate resins and acrylic resins which are excellent in terms of optical characteristics and cost are preferable.
The substrate 1 is usually provided with guide grooves having a pitch of 0.8 μm or less, but the grooves do not necessarily have to be geometrically rectangular or trapezoidal. An optical groove in which an object is formed may be formed.
The thickness of the substrate is changed in order to remove chromatic aberration due to the NA of the pickup of the evaluation system. Usually, when NA is about 0.6 to 0.65, a thickness of about 0.6 mm is required, and when NA = 0.85, a thickness of about 0.1 mm is required.
Examples of a method for forming a thin substrate using a transparent sheet include a method of attaching a transparent sheet via an ultraviolet curable resin or a transparent double-sided pressure-sensitive adhesive sheet. Alternatively, an ultraviolet (UV) curable resin may be applied on the protective layer and cured to form a thin substrate.
Although resin is also used for the resin intermediate layer and the adhesive layer, the UV curable resin is superior in terms of cost.

The dye material is preferably a material containing a cyanine dye, a phthalocyanine dye, a squarylium dye, an azo metal chelate dye, or the like. By using these materials, a small mark can be easily formed, and high-density recording can be handled. The dye layer is usually formed by spin coating.
The thickness of the first and second dye layers is generally preferably in the range of 30 to 150 nm. If it is thinner than 30 nm, it is difficult to obtain sufficient contrast and the modulation tends to be small. On the other hand, if it exceeds 150 nm, it becomes difficult to write a small recording mark.
In high density recording where the shortest mark length is 0.5 μm or less, the thickness of the dye layer is preferably in the range of 50 to 100 nm. If it is thinner than 50 nm, the reflectance is too low and the thickness of the dye layer tends to be non-uniform, which is not preferable. On the other hand, if it is thicker than 100 nm, the heat capacity becomes large and the recording sensitivity is deteriorated, and the edge is disturbed due to non-uniform thermal conductivity and the jitter tends to increase.
After recording, the recording mark is judged by looking at the change in reflectance due to the deformation of the dye layer by the laser, perforation, and deformation of the substrate. Usually, the difference in reflectance before and after recording is greater than 5%.

The second protective layer has a function of preventing the reaction between the second dye layer and the resin intermediate layer and adjusting the reflectance of the back layer as viewed from the light incident side. It is also effective in preventing deformation of the surface of the resin intermediate layer due to high temperature during recording.
The material of the second protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. A material having low thermal conductivity is desirable, but the standard is 1 × 10 ⁻³ pJ / (μm · N · nsec). Note that it is difficult to directly measure the thermal conductivity of such a low thermal conductivity material in a thin film state, and a guideline can be obtained from the measurement results of thermal simulation and actual recording sensitivity as an alternative to direct measurement. .

As a low thermal conductivity material that brings about favorable results, it contains 50 to 90 mol% of at least one of ZnS, ZnO, SiC, TaS ₂ and rare earth sulfide, has high transparency, and has a melting point or decomposition point of 1000 ° C. A composite dielectric containing the above heat-resistant compound is exemplified. More specifically, a composite dielectric containing 70 to 90 mol% of ZnS or ZnO, or a composite dielectric containing 60 to 90 mol% of a rare earth sulfide such as La, Ce, Nd, or Y can be given.
Examples of the heat-resistant compound material having a melting point or decomposition point of 1000 ° C. or more include Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si , Oxides such as Ge and Pb, nitrides and carbides, and fluorides such as Ca, Mg and Li.
Note that the oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have to have a stoichiometric composition, and the compositions may be controlled or mixed for controlling the refractive index and the like. .
As the second protective layer material, a mixed composition of ZnS and SiO ₂ or SiC is most preferable in consideration of the above considerations and consistency with the material constituting the second dye layer.
From the viewpoint of recording sensitivity, it is also advantageous to provide a protective layer with a layer having high transmittance and high thermal conductivity on the resin intermediate layer side.
The detailed film thickness of the second protective layer is preferably 40 to 120 nm when the wavelength of the recording laser light is 600 to 700 nm, preferably 30 to 100 nm, more preferably 40 to 80 nm when the wavelength is 350 to 600 nm.

As the first protective layer material, high transmittance and high thermal conductivity including at least one selected from In ₂ O ₃ , ZnO, ZrO, Ti ₂ O _3, SnO, Al ₂ O ₃ , and SiO ₂ Use materials. Thereby, the thermal deformation of the second reflective layer can be reduced. Preferable materials include ITO (In ₂ O ₃ + SnO) and IZO (In ₂ O ₃ + ZnO).
The detailed film thickness of the first protective layer is preferably 40 to 120 nm when the wavelength of the recording laser beam is 600 to 700 nm, preferably 30 to 100 nm, more preferably 40 to 80 nm when the wavelength is 350 to 600 nm.
In order to make the reflectivity of the first protective layer and the second protective layer comparable, and to obtain good jitter, the total film thickness of both layers is 660 nm for the wavelength of the recording laser beam, and the refractive index is 2. 2, it is necessary to be 120 nm or more (refractive index × film thickness is 260 nm or more). This is because the dye undergoes optical changes (changes in refractive index and extinction coefficient) in addition to deformation due to recording.
When a film thickness of 120 nm or more is formed at one time in one chamber of a sputtering apparatus, the film thickness is not uniform, and when the refractive index is increased to reduce the film thickness, the refractive index and the film forming rate are likely to change. . Therefore, in order to maintain the uniformity of the film thickness, it is preferable to form the film in a plurality of times in two or more chambers. That is, when the first and / or second protective layer is thick, each layer may have a laminated structure of two or more layers made of the same material. In particular, since the change is large in the RF sputtering, it is desirable to perform the DC sputtering.

In the case of FIG. 1, light absorption occurs in the second dye layer during recording, and heat is generated along with this, but the heat is higher than that of the first protective layer and is adjacent to the second dye layer. The heat is mainly radiated from the reflective layer, and at the same time, the heat is also radiated from the first protective layer having higher thermal conductivity than the second protective layer through the second protective layer. As a result, a small recording mark can be formed, and high density recording is possible. Further, when there is no first protective layer as in the prior art, deformation occurs in the second reflective layer of the recording component layer on the back side as viewed from the light incident side where heat is likely to be trapped. Can be prevented. However, the film thickness of the second reflective layer needs to be 130 nm or more. If it is less than 130 nm, even if there is a first protective layer, the deformation of the second reflective layer becomes large.
FIG. 2 shows the push-pull of the second recording constituent layer when the thickness of the second reflective layer is changed for the medium of Example 1 described later. From FIG. 2, it can be seen that when the film thickness of the second reflective layer is less than 130 nm, the groove signal rapidly deteriorates, so that 130 nm or more is necessary.
As described above, by forming the first protective layer and forming the thickness of the second reflective layer to 130 nm or more, preferably 150 nm or more, the deformation of the second reflective layer is reduced, and the groove characteristics are not deteriorated. Tracking and address can be read accurately, and recording / reproducing characteristics are also improved.

Examples of the material of the first reflective layer (semi-transparent layer) and the second reflective layer include Ag or Ag alloy, Au, Al alloy and the like, which are materials having high thermal conductivity suitable for rapid cooling. Examples of the Ag alloy include Cu, Ti, V, Ta, Nb, W, Co, Cr, Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, Pt, Mg, Zr, Mo, or Mn. What contains 2-5 atomic% is preferable. When importance is attached to stability over time, Ti and Mg are preferable as additive components.
It has been confirmed that the Ag alloy increases in volume resistivity in proportion to the additive element concentration. However, it is generally considered that the addition of impurities reduces the crystal grain size, increases the electron scattering at the grain boundaries, and decreases the thermal conductivity. Therefore, it is necessary to adjust the amount of added impurities in order to obtain the high thermal conductivity inherent to the material by increasing the crystal grain size.

Examples of the Al alloy include those containing 0.2 to 2 atomic% of Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo, or Mn. Since the volume resistivity increases in proportion to the concentration of the additive element and the hillock resistance is improved, they can be used in consideration of durability, volume resistivity, film formation rate, and the like. If the amount of added impurities is less than 0.2 atomic%, the hillock resistance is often insufficient, although it depends on the film forming conditions. On the other hand, if it exceeds 2 atomic%, it is difficult to obtain a low resistivity. When the stability over time is more important, Ta is preferable as an additive component.
Since the first reflective layer (semi-transparent layer) needs to be thin in order to transmit light, the deposition rate during film formation is slowed to eliminate film thickness non-uniformity. The film thickness is desirably 5 to 20 nm. If it is less than 5 nm, it becomes non-uniform even if the deposition rate is delayed.

As the manufacturing method of the first and second reflective layers, a sputtering method or a vacuum evaporation method is usually used. In addition to the amount of impurities in the target and the evaporation material itself, the total amount of moisture and oxygen mixed in during film formation is also included. The amount of impurities needs to be 2 atomic% or less. Therefore, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. In the case of forming a film at an ultimate vacuum lower than 10 ⁻⁴ Pa, it is desirable to prevent impurities from being taken in at a film formation rate of 1 nm / second or more, preferably 10 nm / second or more. Alternatively, when the intentional additive element is included in an amount of more than 1 atomic%, it is desirable to prevent the addition of additional impurities as much as possible by setting the film formation rate to 10 nm / second or more.

  In order to define the first and second reflective layers having high thermal conductivity exhibiting good characteristics in the present invention, it is possible to directly measure the respective thermal conductivities. It can be used and estimated. This is because a material in which electrons mainly control heat conduction or electric conduction like a metal film has a good proportional relationship between the heat conductivity and the electric conductivity. The electric resistance of the thin film is represented by a resistivity value normalized by the film thickness or the area of the measurement region. The volume resistivity and the area resistivity can be measured by a normal four-probe method and are defined by JIS N 7194. This method provides data that is much simpler and more reproducible than actually measuring the thermal conductivity of the thin film itself.

A material having a volume resistivity of 20 to 150 nΩ · m, preferably 20 to 100 nΩ · m is used for the first and second reflective layers. A layer of less than 20 nΩ · m is substantially difficult to obtain in a thin film state. Further, even when the volume resistivity is larger than 150 nΩ · m, the area resistivity can be lowered if, for example, a thick film exceeding 300 nm is used, but according to the study by the present inventors, such a high volume resistivity is obtained. Even if only the sheet resistivity was lowered with the material, a sufficient heat dissipation effect could not be obtained. This is probably because the heat capacity per unit area increases in the thick film. In addition, such a thick film takes a long time to form a film and increases the material cost, which is not preferable from the viewpoint of manufacturing cost and also deteriorates the microscopic flatness of the film surface.
Therefore, it is preferable to use a low volume resistivity material that can provide a sheet resistivity of 0.2 to 0.9Ω / □ or less at a film thickness of 300 nm or less, and most preferably 0.5Ω / □.
If the reflectance is 15 to 30%, it can be reproduced by a DVD player. Normally, the reflectivity is 18-30% in the DVD-ROM standard, but in reality, if the reflectivity is 15%, it can be reproduced by a normal DVD player. However, if it is 12% or more and less than 15%, it may or may not be reproducible, and if it is less than 12% it is not reproducible. In other words, if the reflectance is 15% or more, DVD playback compatibility is achieved. As an upper limit, if the dye recording layer (reflectance of about 50% for a recording layer medium) is made two layers, the reflectance of each layer does not reach 30%, so the upper limit is 30%, which is the same as the DVD standard. I just need it. In other words, if the reflectance is 15% or more as a two-layer medium using a dye recording layer, DVD reproduction compatibility is achieved.

  According to the present invention, not only a red laser but also a blue laser and other short output light with a short wavelength does not generate noise such as jitter, has good archival characteristics, and uses a dye capable of high density recording. A two-layered optical recording medium and a method for manufacturing the same can be provided.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
A first dye layer (squarylium dye) and a first reflective layer (Ag ₉₇ Pd ₁ Cu ₁ In ₁ ) are laminated on a polycarbonate cover substrate, while a second reflective layer (Ag ₉₇ Pd ₁ Cu _{1 is formed} on the substrate. In ₁ ), a second dye layer (squarylium dye), a second protective layer [ZnS · SiC (molar ratio 80:20)], and a first protective layer (ITO: In ₂ O ₃ , SnO) were laminated. The inorganic film was formed by sputtering, and the dye layer was formed by spin coating.
Next, the cover substrate on which the first dye layer or the like is formed and the substrate on which the second dye layer or the like is formed are bonded together via a resin intermediate layer (DVD576) so that the dye layer is inside, and the layer structure shown in FIG. A two-layer structure type optical recording medium for evaluation was produced.
The thickness of each constituent layer was controlled as follows.
Cover substrate: 0.57 mm, substrate: 0.57 mm, first dye layer: 50 nm, first reflective layer: 10 nm, resin intermediate layer: 50 μm, first protective layer: 50 nm, second protective layer: 70 nm, second dye Layer: 60 nm, second reflective layer: 170 nm

Example 2
An evaluation two-layer structure type optical recording medium was produced in the same manner as in Example 1 except that the thickness of the second reflective layer was changed to 150 nm of Au.

Example 3
A two-layer structure type optical recording medium for evaluation was produced in the same manner as in Example 1, except that the film thickness of the first reflective layer (semi-transparent layer) was changed to Al ₉₉ Ti _{1 of} 20 nm.

Example 4
A two-layer structure type optical recording medium for evaluation was produced in the same manner as in Example 1 except that the thickness of the first protective layer was changed to 50 nm of IZO (In ₂ O ₃ , ZnO).

Example 5
A two-layer type optical recording medium for evaluation was prepared in the same manner as in Example 1 except that the thickness of the first protective layer was changed to a 50 nm ZrO and Ti ₂ O ₃ mixture (molar ratio 70:30). Produced.

Example 6
Two-layer structure type optical recording medium for evaluation in exactly the same manner as in Example 1 except that the film thickness of the first protective layer was changed to a mixture of 50 nm Al ₂ O ₃ and SiO ₂ (molar ratio 50:50). Was made.

Comparative Example 1
A two-layer structure type optical recording medium for evaluation was produced in the same manner as in Example 1 except that the first protective layer was eliminated and the thickness of the second protective layer was changed to 120 nm.

Comparative Example 2
Two-layer structure light for evaluation, exactly the same as in Example 1, except that the first protective layer is eliminated, the thickness of the second protective layer is changed to 120 nm, and the thickness of the second reflective layer is changed to 80 nm. A recording medium was produced.

The evaluation two-layer structure type optical recording media produced in Examples 1-6 and Comparative Examples 1-2 were irradiated with a focused light beam using an optical system having a wavelength of 660 nm and a numerical aperture NA of 0.65, and the linear velocity: Under conditions of 3.5 m / s and 0.267 μm / bit, initial jitter (jitter), recording power (power indicating jitter minimum), and push-pull signal as groove signal characteristics were evaluated. The reflectance was also measured.
The results are shown in Tables 1 and 2.
As can be seen from the table, in Examples 1 to 6, both the initial jitter and the push-pull signal are good for the second recording configuration layer, but there is no first protective layer as in Comparative Examples 1 or 2, or When the first protective layer was not present and the second reflective layer was thin, both the initial jitter and push-pull signal were poor, the groove signal characteristics were low and the tracking characteristics were poor, and the recording / reproduction characteristics were also poor.
In addition, Examples 1 to 5 had a reflectance of 15% or more and could be reproduced by a DVD player, but Comparative Example 2 was 14.2% and could not be reproduced by a DVD player.

Example 7
A two-layered optical recording medium was produced in the same manner as in Example 1 except that the thickness of the first protective layer was changed to 120 nm.
In the middle of the process, a film was formed using only the first protective layer and compared.
When forming the first protective layer with a thickness of 120 nm, when forming 60 nm in 2 chambers (2 layers), forming 40 nm in 3 chambers (3 layers), and forming in 1 chamber (1 layer) ). The film formation rate is measured first, and the sputtering time is controlled to be 60 nm (2 chambers: total of 120 layers), 40 nm (3 chambers: total of 120 layers), and 120 nm (1 chamber: 1 layer) at that rate. did.
The film thickness was measured with ETA-RT (manufactured by Steag ETA-Optics). The measurement was performed by forming only the first protective layer on a glass substrate and blue plate tempered glass (thickness: 0.6 mm).
The results are as follows. When the film thickness was controlled in one chamber, the film thickness was shifted by about 10 nm from the set film thickness. The middle circumference is a position with a radius of 40 mm, the inner circumference is a position with a radius of 24 mm, and the outer circumference is a position with a radius of 58 mm.
(Medium circumference) (Inner circumference) (Outer circumference)
2 chambers: 119 nm 118.5 nm 117 nm
3 chambers: 121 nm 120 nm 119 nm
1 chamber: 130 nm 128 nm 126 nm
Subsequently, when the entire protective layer was measured, it was as follows.
(Medium circumference) (Inner circumference) (Outer circumference)
2 chambers: 129 nm 128.5 nm 127 nm
3 chambers: 131 nm 130 nm 129 nm
1 chamber: 140 nm 138 nm 136 nm
The film thickness of the second protective layer was as thin as 10 nm, so the film was formed almost as set.
The reflectance and jitter of the back layer as seen from the light incident direction are as follows.
2 chambers: 16.9%, jitter 7.1% (middle circumference)
3 chambers: 17.2%, jitter 6.9% (medium circumference)
1 chamber: 15.1%, jitter 11.4% (middle circumference)
When the film was formed in one chamber, the reflectivity was shifted by about 2% with respect to the set value of 17%, and the jitter was poor at 11.4%.

1 is a cross-sectional view of a layer structure showing an example of a two-layer recording layer type optical recording medium of the present invention. FIG. 6 is a diagram illustrating push-pull of a second recording configuration layer when the thickness of the second reflective layer of the medium of Example 1 is changed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cover substrate 2 1st pigment | dye layer 3 1st reflection layer (semi-transparent layer)
4 resin intermediate layer 5 first protective layer 6 second protective layer 7 second dye layer 8 second reflective layer 9 substrate 100 first recording constituent layer 200 second recording constituent layer

Claims (7)

  First and second recording composition layers are laminated on a substrate via a resin intermediate layer, and recording is performed on each of the two recording composition layers by laser light irradiation from the first recording composition layer side. In an optical recording medium on which reproduction is performed, the first recording constituent layer has a first dye layer and a first reflective layer adjacent thereto, and the second recording constituent layer is adjacent to the second dye layer Having a second reflective layer, the first reflective layer being a translucent layer, and having two protective layers (first protective layer, second protective layer) between the second dye layer and the resin intermediate layer; A two-layer structure type optical recording medium characterized by the above.   2. The two-layer structure type optical recording medium according to claim 1, wherein the first and / or second reflective layer is made of Ag, Ag alloy, Au, or Al alloy. The first protective layer contains at least one selected from In ₂ O ₃ , ZnO, ZrO, Ti ₂ O _3, SnO, Al ₂ O ₃ , and SiO ₂ . Two-layer structure type optical recording medium.   4. The two-layer structure type optical recording medium according to claim 1, wherein the reflectivity of the first and second recording structure layers is 15 to 30%.   The two-layer structure type optical recording medium according to any one of claims 1 to 4, wherein the thickness of the second reflective layer is 130 nm or more.   6. The two-layer structure type optical recording medium according to claim 1, wherein the first and / or second protective layer is formed of a plurality of layers made of the same material. A first and second recording composition layers are laminated on a substrate via a resin intermediate layer. The first recording composition layer includes a first dye layer and a semitransparent first reflective layer adjacent thereto. The second recording layer is provided with a second dye layer and a second reflective layer adjacent to the second dye layer, and two protective layers (first protective layer, between the second dye layer and the resin intermediate layer) are provided. When the second protective layer is provided, the first and / or second protective layer is formed in two or more times (a laminated structure made of the same material), and the first recording constituent layer A method for manufacturing a two-layer structure type optical recording medium, in which recording / reproduction is performed on two sets of recording structure layers by irradiation of laser light from the side.

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