JP4328310B2 - Reflective film for optical information recording medium and optical information recording medium - Google Patents

Description

  The present invention belongs to a technical field related to a reflective film for an optical information recording medium and an optical information recording medium.

In an optical disc manufactured by sequentially forming a reflective layer, a dielectric layer, a recording layer, a light transmission layer, etc. on a transparent plastic substrate such as polycarbonate having guide grooves and recording pits, an Ag alloy is used for the reflective layer. (For example, refer to JP 2002-15464 A, JP 2001-357559 A, JP 2004-139712 A). There are Blu-ray discs, DVD-ROMs, and HD-DVD-ROMs as optical discs using this method.
JP 2002-15464 A JP 2001-357559 A JP 2004-139712 A

  In the optical disc, smoothness is required for the reflective layer formed first on the transparent plastic substrate. In particular, in an optical information recording medium having a multi-layered recording layer, the smoothness of the reflective layer formed first affects the smoothness of the subsequently formed recording layer and the reflective layer, and affects the characteristics of the information recording medium. Therefore, high smoothness is required. In addition, since the Blu-ray system uses a laser having a wavelength of 405 nm, the reflective film is required to have a high reflectance at this wavelength. Al has high reflectivity at this wavelength, but is not smooth enough. Ag has a high reflectivity, but by alloying to improve durability, absorption near this wavelength increases, and the reflectivity decreases greatly.

  The present invention has been made paying attention to such a situation, and an object thereof is a reflection film for an optical information recording medium having excellent smoothness and reflectance, and an optical information recording medium including the reflection film. Is to provide.

  In order to achieve the above object, the present inventors have intensively studied, and as a result, completed the present invention. According to the present invention, the above object can be achieved.

  The present invention thus completed and capable of achieving the above object relates to a reflection film for an optical information recording medium and an optical information recording medium, and the optical information recording medium according to claims 1 to 3. Reflective film (reflective film for optical information recording medium according to first to third inventions), optical information recording medium according to claim 4 (optical information recording medium according to fourth invention), which has the following configuration It is a thing.

That is, the reflective film for an optical information recording medium according to claim 1 is formed of Al or Al alloy having a thickness of 5 to 100 nm on the light incident side of the first reflective film made of an Ag alloy having a thickness of 20 to 200 nm. A two-layer reflecting film provided with two reflecting films, wherein the Ag alloy contains one or more of Nd: 0.05 to 3.0 at% and Bi: 0.01 to 1.0 at%. A reflective film for an optical information recording medium, which is characterized [first invention].

  The reflective film for an optical information recording medium according to claim 2, wherein the Ag alloy contains at least 3.0 at% in total of one or more of Pd, Pt, and Au. There is [the second invention].

  The reflective film for an optical information recording medium according to claim 3, wherein the Al alloy contains one or more of Nd, Ti, Ta, and Cr in total at 4.0 at% or less. [3rd invention].

  An optical information recording medium according to claim 4 is an optical information recording medium comprising the reflective film for optical information recording medium according to any one of claims 1 to 3 [fourth invention].

  The reflective film for optical information recording media according to the present invention has excellent smoothness and reflectance. The optical information recording medium according to the present invention uses such a reflective film as the reflective film. Therefore, according to the present invention, a reflective film for an optical information recording medium having excellent smoothness and reflectance can be obtained, and an optical information recording medium having such a reflective film can be obtained.

As described above, the reflective film for an optical information recording medium according to the present invention is made of Al or Al alloy having a film thickness of 5 to 100 nm on the light incident side of the first reflective film made of an Ag alloy having a film thickness of 20 to 200 nm. A second-layer reflective film provided with the second reflective film, wherein the Ag alloy contains one or more of Nd: 0.05 to 3.0 at% and Bi: 0.01 to 1.0 at%. This is a reflective film for an optical information recording medium. Note that at% is synonymous with atomic%.

As described above, when the Ag alloy contains one or more of Nd: 0.05 to 3.0 at% (atomic%) and Bi: 0.01 to 1.0 at%, the film made of this Ag alloy The smoothness of (first reflective film) (hereinafter also referred to as Ag alloy film) is improved. That is, by adding (containing) 0.05 to 3.0 at% of Nd, it is possible to suppress a decrease in smoothness of the surface of the Ag alloy film by an endurance test [environment test (exposure test in an environment such as high temperature and high humidity)]. it can be. By adding (containing) 0.01 to 1.0 at% of Bi, corrosion of the Ag alloy film by the durability test can be suppressed. For this reason, the surface smoothness of the Ag alloy film by the durability test is reduced. Can be suppressed.

  Moreover, the reflectance and surface smoothness can be maintained at a high level by setting the film thickness of the Ag alloy film (first reflective film) to 20 to 200 nm.

  A second reflective film (hereinafter also referred to as an Al film) made of Al or an Al alloy having a film thickness of 5 to 100 nm is provided on the light incident side of such an Ag alloy film (first reflective film). Becomes excellent in smoothness. That is, the Ag alloy film is excellent in surface smoothness, and since an Al film (second reflective film) is formed on the Ag alloy film, the Al film (second reflective film) is an Ag alloy in the lower layer. Under the influence of the surface smoothness of the film (first reflective film), it becomes excellent in surface smoothness. Note that the Al film originally has a high reflectance.

  Therefore, the reflective film for an optical information recording medium according to the present invention can have excellent smoothness and reflectance. Note that the smoothness and reflectance include not only those in the initial stage (immediately after film formation) but also those after an environmental test. That is, the reflective film for an optical information recording medium according to the present invention is not only excellent in smoothness and reflectance in the initial stage (immediately after film formation), but also has a small degree of decrease due to these environmental tests. Is excellent in smoothness and reflectance (excellent in durability).

  As can be seen from the above, the reflective film for an optical information recording medium according to the present invention is an Al film that has a high reflectivity but is not sufficiently smooth on the Ag alloy film having excellent smoothness as described above. Thus, it can be said that the smoothness of the Al film is improved without impairing the reflectance inherent in the Al film, thereby providing excellent smoothness and reflectance.

  In the reflective film for optical information recording media according to the present invention, the film thickness of the Ag alloy film (first reflective film) is 20 to 200 nm. If this film thickness is less than 20 nm, light transmission is possible. When the reflectivity is increased and the reflectivity is decreased to more than 200 nm, the surface smoothness is lowered, and as a result, the surface smoothness of the Al film (second reflective film) on the Ag alloy film (first reflective film) is lowered. This is because it becomes insufficient. In order to make the reflectance and the surface smoothness higher, it is desirable that the thickness of the Ag alloy film (first reflective film) is 50 to 100 nm.

  The film thickness of the Al film (second reflection film) is 5 to 100 nm. If this film thickness is less than 5 nm, the smoothness deterioration due to the durability test cannot be suppressed, while 100 nm. If it is too high, the influence of the lower Ag alloy layer (first reflective film) will be reduced, and the smoothness of the Al film (second reflective film) will be reduced, which will be insufficient. In addition, in order to suppress the smoothness fall by such an endurance test and to make the smoothness to a higher level, the film thickness of the Al film (second reflective film) is desirably 10 to 50 nm.

  When the thickness of the Al film (second reflective film) is 5 to 100 nm, the light is reflected by the Al film, but the light that has entered the Al film reaches the Ag alloy film (first reflective film). The reflectance of the Ag alloy film is preferably higher.

In the reflective film for an optical information recording medium according to the present invention, the Ag alloy film (first reflective film) contains Nd: 0.05 to 3.0 at% , Bi: 0.01 to 1.0 at%. Made of alloy. When this Ag alloy further contains one or more of Pd, Pt, and Au in a total amount of 3.0 at% or less, the chemical stability is further improved and the corrosion resistance is improved. The deterioration of the surface smoothness of the film can be suppressed at a higher level [second invention]. Note that the effect of improving the thermal stability is small. If the total amount of one or more of Pd, Pt, and Au exceeds 3.0 at%, the surface smoothness of the reflective film is lowered in the durability test.

  The composition of the Al film (second reflective film) is not particularly limited, but if the Al film contains one or more of Nd, Ti, Ta, and Cr in a total of 4.0 at% or less, the crystal grains of the Al film are included. It can be miniaturized and higher surface smoothness can be obtained [third invention]. In order to bring this effect to a higher level, the total content of these elements should be 0.1 to 4.0 at%.

  The optical information recording medium according to the present invention comprises the reflective film for an optical information recording medium according to the present invention [fourth invention]. This optical information recording medium is excellent in the smoothness and reflectance of the reflective film. An example of an optical information recording medium according to the present invention is shown in FIG. In FIG. 1, 8 is a substrate, 7 is an Ag alloy film (first reflective film), 6 is an Al film (second reflective film), 5 is a dielectric layer, 4 is a recording layer, 3 is a dielectric layer, Reference numeral 2 denotes an adhesive layer, and 1 denotes a cover layer. The Al film (second reflective film) 6 is provided on the light incident side of the Ag alloy film (first reflective film) 7. Thus, in the reflective film for an optical information recording medium according to the present invention, the second reflective film (Al film) is provided on the light incident side of the first reflective film (Ag alloy film).

  Examples of the present invention and comparative examples will be described below. The present invention is not limited to this embodiment, and can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, all of which are within the technical scope of the present invention. include.

[Example 1]
Using a direct current power source by magnetron sputtering, a 100 nm thick Ag-Nd alloy film or Ag-Bi alloy film is formed on the polycarbonate substrate as the first reflective layer (Ag alloy film), and then opened to the atmosphere. Instead, an Al-2 at% Nd alloy film having a thickness of 30 nm was formed as the second reflective layer (Al film), thereby obtaining a two-layer reflective film. At this time, the Nd content in the Ag—Nd alloy film and the Bi content in the Ag—Bi alloy film were changed as parameters. The film formation conditions for the first reflective layer were a film formation rate of 9 nm / s and an Ar gas pressure of 0.26 Pa during sputtering. The deposition conditions for the second reflective layer were a deposition rate of 2.7 nm / s and an Ar gas pressure of 0.26 Pa. The composition of the film was confirmed by identification by ICP (inductively coupled plasma) emission analysis using a sample formed on soda lime glass by the same method as described above.

  For the two-layer reflective film (substrate: polycarbonate) thus obtained, the surface roughness was measured by AFM (atomic force microscope), and the reflectance was measured. Furthermore, after conducting a test (environmental test) for 100 hours in a high-temperature and high-humidity environment at a temperature of 80 ° C. and a humidity of 90%, the surface roughness and reflectance were measured.

  The results are shown in Table 1. From Table 1, it can be seen that the first reflective layer (Ag alloy film) contains Nd and Bi as alloy elements, thereby improving the smoothness after the formation of the reflective film (double-layer reflective film). If the Nd and Bi contents are small, there is no effect (No. 1A, No. 6A), and Nd requires addition (containment) of 0.05 at% or more, and Bi requires 0.01 at% or more. When the amount of Nd and Bi added (contained) is large, the reflectivity decreases (No.5A, No.10A). Therefore, the content of Nd and Bi is 3.0 at% or less for Nd and 1.0 at% for Bi. It turns out that it is necessary to do the following. Therefore, it was confirmed that the content of Nd and Bi in the first reflective layer (Ag alloy film) needs to be 0.05 to 3.0 at% for Nd and 0.01 to 1.0 at% for Bi. (No.2A to 4A, No.7A to 9A).

[Example 2]
Using a direct current power source by magnetron sputtering, an Ag-0.7 at% Nd-0.9 at% Cu alloy film (film thickness 100 nm) is formed as a first reflective layer (Ag alloy film) on a polycarbonate substrate, followed by Without releasing into the atmosphere, an Al-2 at% Nd alloy film was formed as the second reflective layer (Al film), thereby obtaining a two-layer reflective film. At this time, the thickness of the second reflective layer (Al-2 at% Nd alloy film) was changed as a parameter. The film formation conditions for the first reflective layer were a film formation rate of 9 nm / s and an Ar gas pressure of 0.26 Pa during sputtering. The deposition conditions for the second reflective layer were a deposition rate of 2.7 nm / s and an Ar gas pressure of 0.26 Pa. The composition of the film was confirmed by identification by ICP emission spectroscopic analysis using a sample formed on soda lime glass by the same method as described above.

  About the two-layer reflective film (substrate: polycarbonate) thus obtained, the surface roughness was measured by AFM, and the reflectance was measured. Furthermore, after conducting a test (environmental test) for 100 hours in a high-temperature and high-humidity environment at a temperature of 80 ° C. and a humidity of 90%, the surface roughness and reflectance were measured.

  On the other hand, a single-layer reflective film consisting only of an Al film [No.1B (Al film), No.3B (Al-2.0 at% Nd alloy film) in Table 2 to be described later] or a single-layer reflective film consisting only of an Ag alloy film A film [No. 2B (Ag-0.7 at% Nd-0.9 at% Cu alloy film) in Table 2 described later] was formed, and the same measurements and tests as described above were performed.

  The results are shown in Table 2. As can be seen from Table 2, a single-layer reflective film made of only an Al film has a high reflectance when it is made of a pure Al film, but its smoothness is low and insufficient (No. 1B). Compared with the Al-2.0 at% Nd alloy film, the smoothness is high but the smoothness is still insufficient (No. 3B). A single-layer reflective film (Ag-0.7 at% Nd-0.9 at% Cu alloy film) made only of an Ag alloy film is excellent in smoothness but low in reflectance and insufficient (No. 2B).

  As for the two-layer reflective film, the film thickness of the second reflective layer (Al-2at% Nd alloy film) of less than 5 nm is excellent in smoothness but low in reflectance and insufficient (No. 4B On the other hand, those with a thickness of more than 100 nm have high reflectivity, but are insufficient due to low smoothness (No. 9B). On the other hand, when the thickness of the second reflective layer (Al-2 at% Nd alloy film) is 5 to 50 nm, the film has excellent smoothness and high reflectance.

[Example 3]
In the same manner as in Example 2, an Ag-0.7 at% Nd-0.9 at% Cu alloy film is formed as a first reflective layer (Ag alloy film) on the same substrate, followed by the second reflection. As a layer (Al film), an Al-2 at% Nd alloy film (thickness 30 nm) was formed, thereby obtaining a two-layer reflective film. At this time, the film thickness of the first reflective layer (Ag-0.7 at% Nd-0.9 at% Cu alloy film) was changed as a parameter. The conditions for forming the first reflective layer and the conditions for forming the second reflective layer are the same as in Example 2.

  For the two-layer reflective film (substrate: polycarbonate) thus obtained, surface roughness and reflectance were measured by the same method as in Example 2, and the same environmental test as in Example 2 was performed. After that, the surface roughness and the reflectance were measured.

  The results are shown in Table 3. As can be seen from Table 3, when the thickness of the first reflective layer (Ag-0.7 at% Nd-0.9 at% Cu alloy film) is less than 20 nm, the smoothness is low and the reflectivity is insufficient. It is low and insufficient (No. 1C), while those having a thickness of more than 200 nm have high reflectivity but low smoothness and are insufficient (No. 6C). On the other hand, when the thickness of the first reflective layer is 20 to 200 nm, the first reflective layer has excellent smoothness and high reflectance.

[Example 4]
In the same manner as in Example 2, an Ag-0.7 at% Nd-0.9 at% Cu alloy film (film thickness: 100 nm) is formed on the same substrate as the first reflective layer (Ag alloy film). Then, as the second reflective layer (Al film), Al-2at% Nd alloy film, Al-2at% Ti alloy film, Al-2at% Ta alloy film, Al-2at% Cr alloy film, pure Al film (film) (Thickness: 30 nm for both) was formed, thereby obtaining a two-layer reflective film. At this time, the film forming conditions for the first reflective layer and the film forming conditions for the second reflective layer are the same as in Example 2.

  For the two-layer reflective film (substrate: polycarbonate) thus obtained, the surface roughness and reflectance were measured by the same method as in Example 2, and the corrosion resistance was evaluated. After conducting the same environmental test as above, the surface roughness and reflectance were measured. The results are shown in Table 4. Moreover, in order to evaluate heat resistance, after performing the heating test hold | maintained at 300 degreeC in a vacuum for 1 hour, the surface roughness and the reflectance were measured.

  As can be seen from Table 4, the second reflective layer (Al film) is an Al-2at% Nd alloy film, Al-2at compared to the case where the second reflective layer (Al film) is a pure Al film (No. 5D). % Ti alloy film, Al-2at% Ta alloy film, Al-2at% Cr alloy film (No.1D to No.4D) are excellent in smoothness immediately after film formation and smoothness after environmental test. Also, the smoothness after the heating test was excellent.

[Example 5]
In the same manner as in Example 2, an Ag-0.7 at% Nd-0.9 at% Cu alloy film, Ag-0.7 at% Nd-1.0 at is formed on the same substrate as the first reflective layer (Ag alloy film). % Pd alloy film, Ag-0.7at% Nd-1.0at% Pt alloy film, Ag-0.7at% Nd-1.0at% Au alloy film, Ag-0.7at% Nd-1.0at% Cu alloy film (film thickness: In each case, a 100 nm 2) film was formed, and subsequently an Al-2 at% Nd alloy film (film thickness: 30 nm) was formed as a second reflective layer (Al film), thereby obtaining a two-layer reflective film. At this time, the film forming conditions for the first reflective layer and the film forming conditions for the second reflective layer are the same as in Example 2.

  For the two-layer reflective film (substrate: polycarbonate) thus obtained, surface roughness and reflectance were measured by the same method as in Example 2, and the same environmental test as in Example 2 was performed. After that, the surface roughness and the reflectance were measured.

  The results are shown in Table 5. As can be seen from Table 5, when the first reflective layer (Ag alloy film) is made of the above alloy film (No. 1E to 5E), the decrease in smoothness due to the environmental test is small. This is because the first reflective layer (Ag alloy film) is made by adding Cu, Pd, Pt, and Au to Ag-0.7at% Nd to improve chemical stability and corrosion resistance. Thus, it is shown that the decrease in smoothness due to the environmental test could be suppressed at a high level.

  Since the reflective film for optical information recording media according to the present invention has excellent smoothness and reflectance, it can be suitably used as a reflective film for optical information recording media and is useful.

It is a schematic diagram which shows the example of the optical information recording medium based on this invention.

Explanation of symbols

1--cover layer, 2--adhesion layer, 3--dielectric layer, 4--recording layer, 5--dielectric layer, 6--second reflection film (Al film), 7--first reflection Film (Ag alloy film), 8--Substrate.

Claims (4)

A two-layer reflecting film in which a second reflecting film made of Al or an Al alloy having a film thickness of 5 to 100 nm is provided on the light incident side of the first reflecting film made of an Ag alloy having a film thickness of 20 to 200 nm, A reflective film for an optical information recording medium, wherein the Ag alloy contains at least one of Nd: 0.05 to 3.0 at% and Bi: 0.01 to 1.0 at%.   The reflective film for an optical information recording medium according to claim 1, wherein the Ag alloy contains a total of one or more of Pd, Pt, and Au at 3.0 at% or less.   The reflective film for an optical information recording medium according to claim 1 or 2, wherein the Al alloy contains at least 4.0 at% of Nd, Ti, Ta, and Cr in total.   An optical information recording medium comprising the reflective film for an optical information recording medium according to claim 1.

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