JP2003173576A - Translucent reflecting layer for optical information recording medium, optical information recording medium, and sputtering target for translucent reflecting layer of optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an translucent reflecting layer for an optical information recording medium, the layer having the transmittance and the reflectance required as a translucent reflecting layer of an optical information recording medium and having favorable chemical stability such as corrosion resistance, aggregation resistance or the like, and to provide an optical information recording medium and a sputtering target for the translucent reflecting layer to be used for an optical information recording medium. <P>SOLUTION: The translucent reflecting layer for an optical information recording medium comprises an Al-based alloy containing at least one kind of element selected from a group composed of Ti, Ta and Cr by 0.2 to 3.0 at.% in total and has excellent durability. The optical information recording medium has the translucent reflecting layer for an information recording medium and the sputtering target for the translucent reflecting layer of an optical information recording medium comprises the above Ag alloy. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-transparent reflective layer for an optical information recording medium having excellent durability, an optical information recording medium, and a sputtering target for the semi-transparent reflective layer of the optical information recording medium.

[0002]

2. Description of the Related Art There are several types of optical disks,
From the viewpoint of the recording / reproducing principle, they are roughly classified into three types: read-only discs, rewritable (phase change) discs, and write-once discs.

Of these, the read-only disk basically consists of a transparent substrate such as a polycarbonate substrate and an A
A reflective layer having g, Al, Au or the like as a base material and a protective layer such as an ultraviolet curable resin are laminated. The above-mentioned read-only disc is for reproducing data by forming recording data by the concave and convex pits provided on the transparent plastic substrate and detecting the phase difference and the reflection difference of the laser light applied to the disc. .

Next, in the above-mentioned rewritable (phase change type) optical disk, the power of the laser beam and the irradiation time are controlled to form a two-phase state of a crystalline phase and an amorphous phase in the recording layer so that data is recorded. Is recorded, and data is detected (reproduced) by detecting a change in reflectance of both phases with a laser. With this recording / reproducing system, repetitive recording / reproducing is possible, and normally, repetitive recording can be performed several thousand to several hundred thousand times. As shown in FIG. 2, the basic structure of the rewritable optical disc includes a transparent plastic substrate 1, a dielectric layer 7, a recording layer 8, a dielectric layer 7, a reflective layer 4, and an ultraviolet curable resin protective layer 5. An optical disc which is formed by laminating various thin film layers and includes such a system as a CD-RW, a DVD-RAM, a DVD-RW,
DVD-RW etc. are mentioned.

In the above-mentioned write-once type optical disk, the dye of the recording layer (organic dye layer) is heated and deteriorated by the power of the laser beam to form a groove (a groove preliminarily formed on the substrate).
The data is recorded by deforming, and the data is detected (reproduced) by detecting the difference between the reflectance of the altered portion and the reflectance of the unaltered portion. FIG. 3 illustrates the basic structure of the write-once optical disc. In the figure, 1 is a transparent plastic substrate, 6 is an organic dye layer, 4 is a reflective layer, and 5 is an ultraviolet curable resin protective layer. This recording / reproducing system is characterized in that once recorded data cannot be rewritten (one-time recording and repetitive reproduction), examples of optical disks adopting such a system include CD-R and DVD-R. To be

The prior art will be described below using the above-mentioned read-only disk as a typical example. When the optical disc is composed of a single plate as shown in FIG. 1, there is a drawback that sufficient mechanical strength is not obtained and the optical disc is easily deformed. Further, in recent years, the amount of data loaded on an optical disc tends to increase with the use of large-capacity digital data represented by moving images, and an increase in the disc recording capacity is required. A laminated disk has been proposed as a means for solving such a problem. An example of the laminated disk is shown in FIG.
(In the figure, 41 and 46 are transparent substrates, 42 and 47 are information surfaces formed by pits, 43 and 48 are reflective layers, 44 and
Numeral 49 is a protective layer and numeral 45 is an adhesive layer). With such a structure, the mechanical strength of the disc can be improved and the recording capacity of the disc can be doubled. However, in order to reproduce the information recorded on the information surfaces 42 and 47, the transparent substrates 41 and 46 are used, respectively.
In the device in which the laser light must be incident via the optical head and the optical head (laser emitting means and reflected laser detecting means) is provided on only one side, the information surface 42 to the information surface 4
No information can be continuously reproduced to No. 7, the disc must be turned over as necessary, the advantage of doubling the disc capacity cannot be fully utilized, and reproduction continuity becomes a problem.

Therefore, as a disk in which the information on the information surfaces 42 and 47 can be read by the laser incident from one side, FIG. 5 (in the drawing, 41 is a transparent substrate, 42 and 47 are information surfaces, 48 is a reflective layer, and 49 is a protective layer). Layers, 50 is a semitransparent reflective layer, and 45 is an adhesive layer) have been proposed as a laminated disc having a structure as shown. With such a structure, the disk has the same mechanical strength and disk capacity as the disk shown in FIG. 4, and is recorded on different information surfaces 42 and 47 by the laser incident from one side surface (transparent substrate 41 side). The information can be continuously reproduced. In addition, in such a laminated disc, the laser beam is incident from the transparent substrate 41 side to make the information surface 4
When reproducing the information of No. 7, the incident laser is focused on the information surface 47 (which means that the laser diameter is small). At this time, a part of the incident laser is reflected by the semitransparent reflective layer 50, but since the line diameter of the laser reflected by the semitransparent reflective layer 50 is large, the information on the information surface 42 may be erroneously reproduced. Since it is not confused with the reflection laser by the reflection layer 48, the information on the information surface 47 is reproduced accurately. When reproducing the information on the information surface 42, the information surface 42
The incident laser is focused on. At this time, a part of the incident laser passes through the semitransparent reflection layer 50 and is reflected by the reflection layer 48. However, since the line diameter of the laser reflected by the reflection layer 48 is large, the information on the information surface 47 is erroneous. The information on the information surface 42 is accurately reproduced without being reproduced.

By the way, in order to reproduce the information on the information surface 47 as described above, the semitransparent reflection layer 50 must have sufficient transparency to the incident laser, but the information on the information surface 42 is reproduced. In addition, the semitransparent reflective layer 50 must have sufficient reflectivity for the incident laser. As a semi-transparent reflective layer satisfying such a condition, pure Au has hitherto been used.
Alternatively, an Au-based alloy is used. These Au-based semi-transparent reflective layers are commonly used because they have excellent chemical stability such as corrosion resistance and cohesion resistance, and have a good balance between reflectance and transmittance, but Au is expensive. Therefore, the manufacturing cost is high and it is not practical. The Au-based semi-transparent reflective layer has a reflectance for a blue laser (wavelength of about 405 nm), which is being researched and developed as a next-generation standard.
There is a limitation that it cannot be used with a blue laser because of the problem that the transmittance is significantly reduced. Therefore, there is a demand for a material that is low in cost and that also functions as a semitransparent reflection layer for blue lasers.

The present inventors have found the following as a result of investigating the respective characteristics by forming a semitransparent reflective layer using various materials in order to solve the above problems. The semitransparent reflective layer formed by sputtering pure Ag contains many defects such as atomic vacancies, and Ag diffuses and easily aggregates. Therefore, the Ag crystal grain size increases under the environmental test conditions. It will be easier. Further, since the adhesion to the substrate is not sufficient, the film deteriorates with the lapse of time, the record retention is insufficient, and it is not preferable from the viewpoint of long-term stability. Further, the pure Ag semi-transparent reflective layer is not preferable because it is accompanied by heat conduction and change, stress state, film strength, and interface property change. Further, although the alloy containing Ag as a main component exhibits a sufficiently high reflectance in the practical wavelength range of 400 to 480 nm, the corrosion resistance and the recording characteristics change with time.
It has the drawback of being inferior to the u-based reflective layer.

Although pure Cu or an alloy containing Cu as a main component is inexpensive, it is inferior in corrosion resistance (particularly oxidation resistance) and has a drawback that it has a low reflectance for a blue laser as in the case of Au. As a result, the reliability of the disk may decrease.

The pure Al semi-transparent reflection layer has a drawback that it has poor chemical stability and has a low thermal conductivity, which limits the structure and design of the disk. Therefore, it is difficult to provide the semi-transparent reflective layer with the required properties. As described above, it is difficult for any of these materials to satisfy various properties required for the semitransparent reflective layer.

If the semitransparent reflective layer does not have sufficient laser transparency, the intensity of the incident laser will be attenuated when passing through the semitransparent reflective layer 50 from the substrate 61, and the information surface will have sufficient intensity. 47 cannot be irradiated with laser, and as a result, the reflected laser from the reflective layer 48 cannot be received with sufficient intensity, and the information signal amplitude obtained from the information surface 47 becomes insufficient. As described above, in the case of the laminated disc, the reproduction of the information surface 47 depends on the transmissivity of the semitransparent reflection layer. If the transparency is increased, the information surface 4
In some cases, the reflected light intensity necessary for reproducing No. 2 may not be obtained. Moreover, in addition to the reflective and transmissive properties of the semitransparent reflective layer,
Considering the long-term storability required for optical information recording media,
If the semi-transparent reflective layer does not have excellent chemical stability such as corrosion resistance, information cannot be reproduced, and the reliability of the disc cannot be maintained.

As described above, the semi-transparent reflective layer for an optical disc includes
In order to obtain a highly reliable medium, it has reflectivity and transparency,
These required characteristics are required even though it is required to satisfy various characteristics such as chemical stability (especially oxidation resistance), adhesion to substrate, structural stability, recording characteristic stability, and low cost. A semitransparent reflective layer that satisfies all requirements has not been provided yet.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to have a transmittance and a reflectance required for a semitransparent reflective layer, as well as corrosion resistance and cohesion resistance. Another object of the present invention is to provide a semitransparent reflective layer for an optical information recording medium having good chemical stability, an optical information recording medium, and a sputtering target for a semitransparent reflective layer used in the optical information recording medium.

[0015]

Means for Solving the Problems According to the present invention capable of solving the above problems, a total of at least one element selected from the group consisting of Ti, Ta, and Cr is 0.2 to 3.0% ( A semi-transparent reflective layer for an optical information recording medium, which is excellent in durability and has the gist of being composed of an Al-based alloy containing (atomic%, the same hereinafter).

Further, an optical information recording medium provided with a semitransparent reflective layer for the optical information recording medium, and a sputtering target for the semitransparent reflective layer of the optical information recording medium composed of the Ag-based alloy are also within the scope of the present invention. Included in.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Among the various properties required for a semitransparent reflection layer for an optical information recording medium, the present inventors have particularly excellent corrosion resistance and anti-aggregation property, as well as transmission and reflection properties with respect to an incident laser. We have conducted intensive studies from the viewpoint of providing excellent materials. As an index of durability improvement in the present invention, specifically, adhesion to a disc substrate (polycarbonate substrate or the like) and other materials constituting the disc (hereinafter, may be represented by "adhesion to substrate or the like"). By improving the durability of the semi-transparent reflective layer by improving the, and as a result of suppressing the diffusion of the semi-transparent reflective layer, excellent structural stability, and finally the durability is raised, An experiment was conducted from this viewpoint.

The term "durability" in the present invention means that the semitransparent reflective layer exhibits excellent corrosion resistance and aggregation resistance over a long period of time.

The inventors of the present invention evaluated the characteristics as a semi-transparent reflective layer by forming alloy layers having various component compositions on a substrate by a sputtering method using an alloy sputtering target produced by using various elements. . as a result,
The Al-based alloy layer containing at least one element selected from the group consisting of predetermined amounts of Ti, Ta and Cr has extremely excellent cohesion resistance and corrosion resistance, and also has excellent reflectivity and transmittance. I found that. In addition, as a result of examination from the viewpoint of practicality (reflectivity, etc.) for blue lasers,
It was found that the Cu-Al alloy layer has a large absorption to a blue laser and is not practical as the Ag-based alloy layer, and that the Al-based alloy film containing the above elements (Ti, Ta, Cr) is excellent. It was

The semitransparent reflective layer for an optical information recording medium of the present invention will be described below with reference to the laminated read-only optical information recording medium illustrated in FIG. Of course, the laminated optical information recording medium to which the semitransparent reflective layer of the present invention is applicable is not limited to the illustrated example.

The laminated optical information recording medium (hereinafter sometimes referred to as an optical disk) according to the present invention comprises an information surface 42 having an information signal formed on one surface of a substrate 41 as illustrated in FIG. And a semitransparent reflection layer 5 on the information surface 42
0, adhesive layer 45, information surface 47, reflective layer 48, protective layer 47
Are sequentially formed. When reproducing the information (for example, the information surface 42) recorded on the optical disk of the present invention, if the laser is focused on the information surface (information surface 42) to be reproduced from the substrate 41 side, the other information surface (information The information signal can be accurately reproduced without erroneously reproducing the information on the surface 47). Further, by using the laminated disc, the mechanical strength is higher than that of the single-layer disc, and the information capacity can be increased.

The substrate 41 may be made of any material, and is not particularly limited as long as it is transparent to the incident laser and does not affect the laser (refraction, blocking, etc.). As a material having such characteristics, a transparent material such as a plastic substrate such as an acrylic resin (for example, polycarbonate) or a glass substrate is exemplified. The thickness of the substrate is not particularly limited as long as it does not affect the mechanical strength, incident laser, reflected laser, or the like. For example, normally, it is desirable to set it to 400 to 800 mm. Although fine irregularities called pits for recording information signals are formed on the surface (lamination surface side) of the substrate 41 (information surface 42), a groove for tracking or the like may be formed. The pit formed at 42 may be formed so that a necessary information signal can be reproduced, for example, by having a size according to the incident laser wavelength, and the specific shape is not particularly limited.

A semitransparent reflection layer 50 is formed on the information surface 42. The semitransparent reflective layer 50 of the present invention is made of Ti, Ta,
And an Al-based alloy containing 0.2 to 3.0% in total of at least one element selected from the group consisting of Cr and Cr. The translucent reflective layer 50 of the present invention using an Al-based alloy containing 0.2% or more of at least one element selected from the group consisting of Ti, Ta, and Cr has excellent cohesion resistance and durability. It has excellent characteristics such as excellent reflectance and transmittance for laser. Further, if the above-mentioned additional elements (that is, Ti, Ta, Cr) are contained by 0.5% or more,
The adhesion between the base 41 and the semitransparent reflective layer 50 is further enhanced,
It is also desirable because it improves corrosion resistance and cohesion resistance. However, if the total addition amount of the above elements exceeds 3.0%, on the contrary, the reflectance, corrosion resistance, cohesion resistance, etc. are deteriorated and the durability and various functions required by the present invention cannot be exhibited. Further, considering the balance between the reflectance and the transmittance for the blue laser, the upper limit is preferably 2.0%. When the content is less than 0.2% (including pure Al), sufficient corrosion resistance cannot be obtained, and white spots due to corrosion occur, and durability, reflectance, and transmittance required for the semitransparent reflective layer are reduced. I'm not satisfied. Incidentally, these elements may be used alone or in combination of two or more kinds.

The desired efficiency of the semitransparent reflective layer according to the present invention is preferably 70% or more, more preferably 80, when the incident laser intensity is 100% at a wavelength of 650 nm used in a general DVD. % Or more is recommended. The efficiency at a wavelength of 405 nm (blue laser) is preferably 70% or more, more preferably 80%.
The above is recommended.

The thickness of the semitransparent reflection layer may be appropriately determined according to the required characteristics, but if it is less than 5 nm, not only the reflectance is deteriorated but also agglomeration is easily caused and the semitransparent transport itself is deteriorated. It is not preferable because it may occur. On the contrary, 20n
If it is m or more, not only the transmittance decreases but also the light absorption rate may increase and the reflectance may decrease.
It is desirable to set it within the range of 20 nm.

The semitransparent reflective layer of the present invention contains the above-mentioned components, and the balance is Al, but other than the above-mentioned components as long as the optical characteristics (reflectance, transmittance) and chemical stability are not impaired. Other components may be added. For example, a noble metal such as Pd or Pt or a transition element (excluding those mentioned above) may be positively added for the purpose of imparting characteristics such as hardness improvement. Further, gas components such as O ₂ and N ₂ and the above-mentioned Al which is a melting raw material.
The base alloy may contain impurities that are contained in advance. In addition, elements that increase absorption for laser, such as Ag and Cu, have large absorption for blue laser,
It is not preferable because it is not practical in terms of reflectance and the like.

An adhesive layer 45 is formed on the semitransparent reflective layer 50. The adhesive layer is not particularly limited as long as it is a material that can transmit a laser and does not affect the laser such as refraction. Examples of such a material include materials having transparency such as an ultraviolet curable resin and an acrylic resin. Among these, after the ultraviolet curable resin is applied on the semitransparent reflective layer 50 by a spin coating method or the like, UV irradiation is recommended.

An information surface 47 is formed on one surface of the adhesive layer 45 (opposite to the semitransparent reflective layer 50). Further, a reflective layer 48 is formed on the information surface 47. Examples of the material of the reflective layer 48 include Al, Au, Ag, and a combination of these elements alone or with other elements. Examples of the composite system include Al-Ti, Ag-Ti, A.
Examples include g-Cu alloys, etc., but the decrease in reflectance is controlled within an acceptable range by appropriately adjusting the component composition and addition amount of the alloy, and durability such as adhesion and structural stability is started. A material that can achieve the various characteristics described below at a high level may be used. Among these, Ag-based alloys are preferable from the viewpoints of further excellent adhesion effect and cost while maintaining high reflection characteristics and corrosion resistance. Further, the reflective layer is preferably a thin film having a thickness of 50 to 150 nm from the viewpoint of reflectance, but may have an arbitrary thickness depending on the required conditions.

In the case of a so-called blue laser having a laser wavelength of about 405 nm, if the reflective layer is made of a material having a poor laser reflectance such as Au, the function as a disk is deteriorated, so that an Au-based alloy is not desirable. Sometimes.

A protective layer 49 is formed on the reflective layer 48. The protective layer 49 serves as the reflective layer 48 and the information surface 47.
It also has the function of protecting against corrosion and deterioration due to moisture. The material of the protective layer 49 is not particularly limited and is not particularly limited as long as it achieves the above purpose, but an ultraviolet curable resin or the like is desirable. For example, after coating the reflective layer 48 with an ultraviolet curable resin, it is irradiated with ultraviolet rays and cured. It can be a fish. Further, an antistatic agent or the like may be added according to the purpose. For example, a known antistatic agent may be mixed to form a protective layer to prevent dust and the like from adhering to the disk.

Since the laminated disk of the present invention reproduces the information on the laminated information surface by irradiating the laser from the substrate 41 side, the protective layer 49 does not need to be transparent to the laser. Therefore, a coloring material such as a dye may be mixed in the protective layer 49, or another layer may be laminated on the protective layer.

It is recommended that the semitransparent reflective layer 50 of the present invention is formed by a sputtering method. In the semi-transparent reflective layer formed by the sputtering method, non-equilibrium solid solution is possible due to vapor-phase quenching peculiar to the sputtering method. Therefore, compared with the case where the Al-based alloy layer is formed by another thin film forming method, the alloy element ( Ti, Ta, Cr) is Al
This is because they are uniformly present in the matrix, and as a result, the corrosion resistance and the adhesion are remarkably improved.

During sputtering, as a sputtering target material, A prepared by the melting / casting method was used.
It is preferable to use an l-based alloy (hereinafter, referred to as “molten Al-based alloy target material”). Since such a melted Al-based alloy target material is structurally uniform and the sputtering rate and the emission angle are uniform, an Al-based alloy layer (semi-transparent reflection layer) having a uniform composition is stably obtained. This is because a higher performance optical disc is manufactured. Incidentally, if the oxygen content of the molten Al-based alloy target material is controlled to 100 ppm or less, the semitransparent reflective layer forming rate is easily maintained constant, and the oxygen content of the semitransparent reflective layer is also reduced. It is possible to remarkably enhance the reflectance and corrosion resistance (particularly sulfidation resistance) of the semitransparent reflective layer. As the sputtering method, an ion beam sputtering method, a DC sputtering method, an RF
Examples of the sputtering method include, but are not particularly limited to.

The translucent reflective layer of the present invention and the optical disc using the translucent reflective layer of the present invention have been described above by exemplifying the case where the optical disc is for reproduction only. Excellent chemical properties such as anti-aggregation,
Moreover, since it has excellent reflectance and transmittance, it exhibits excellent durability. Therefore, as long as it is a laminated disc using the semitransparent reflective layer of the present invention, the structure and properties of the other layers are not particularly limited, and they can be appropriately combined and used according to the application. For example, a rewritable (phase change type) disc in which a recording layer, a dielectric layer, an organic dye layer and the like are provided on the information surface 47 side by using a known recording material such as a phase change material or an optical timing material, and It can also be a write-once disc.

The present invention will be described in detail below based on examples.
However, the following examples do not limit the present invention,
All changes and modifications made without departing from the spirits of the preceding and the following are included in the technical scope of the present invention.

[0036]

EXAMPLES Example 1 Various tests were conducted using a laminated optical disk manufactured by the method described below (having a structure similar to that shown in FIG. 5). A substrate 41 having a thickness of 0.6 mm and provided with the information signal on one side was prepared by an injection molding method using a stamper on which the information signal was recorded. Polycarbonate was used as the material of the substrate 41. After the substrate 41 was injection molded, the semitransparent reflective layer 50 was formed on the substrate 41. The semi-transparent reflection layer 50 was formed by using the alloy shown in Table 1 on the information signal surface by a DC magnetron sputtering device so as to have a layer thickness of 8 nm. In addition, a DC magnetron sputtering device was used on the information surface 47 on the information surface (the information surface 47 was formed on one surface of the substrate 49) of the substrate 49, which was created in the same manner as the substrate 41, using JIS Al6061 alloy as an alloy target. After the reflective layer 48 was formed by the above method, the semi-transparent reflective phase 50 and the reflective layer 48 were laminated so as to face each other with the UV curable resin 45 interposed therebetween to obtain a laminated optical disc.

An environmental test was conducted on each of the obtained optical disks, and the corrosion state and changes in laser efficiency (reflectance, transmittance, absorptance) before and after the environmental test were examined. The environmental test is 48 hours in an environment with a temperature of 80 ° and a humidity of 90%.
After standing still, the corrosion resistance (oxidation resistance) of the semitransparent reflective layer 50 was judged according to the following criteria. ◯: No cloud point is observed with the naked eye or an optical microscope (× 200). Δ: No cloudiness is observed with the naked eye, but cloudiness is observed with an optical microscope. X: A dull point is observed with the naked eye.

In order to examine the laser efficiency of each optical disk before and after the environmental test, the optical head equipped with the laser irradiation means and the focusing means and the substrate 41 were placed so as to face each other.

Table 1 shows the respective laser efficiencies when the lasers having the wavelengths of 650 nm and 405 nm are used. The reflectance (spectral reflectance), the light absorptance, and the transmittance are values when the intensity of the laser incident on the information surface 50 is 100%.
The methods for measuring reflectance, light absorption and transmittance are as follows.

The reflectance and transmittance of the incident laser were measured with a spectroscopic ellipsometer (SE850 manufactured by SenTech).

The light absorptance is a value obtained by dividing the [reflectance and transmittance] from the incident laser intensity of 100%.

[0042]

[Table 1]

As shown in Table 1, Ti, Ta, Cr
It can be seen that the semitransparent reflective layer 50 using the Al-based alloy (Nos. 4 to 9) containing an appropriate amount of S has a small decrease in reflectance and is excellent in corrosion resistance. Moreover, since the semitransparent reflection layer has a high transmittance, a laser having a sufficient intensity can be incident on the information surface 47, information on the information surfaces 42 and 47 can be accurately reproduced, and excellent reproduction characteristics are provided. At the same time, it has excellent durability.

Pure Al, pure Ag, pure Au (No. 1-3)
The semi-transparent reflective layer using is produced with white spots due to corrosion, and the reflectance is significantly reduced. Further, the transmissivity of the semitransparent reflection film layer is too low, so that a laser having a sufficient intensity cannot be incident on the information surface 47. Further, since the reflectance is small, sufficient reflected light cannot be obtained, the information on the information surfaces 42 and 47 cannot be reproduced, and the durability is poor.

Example 2 The correlation between the amount of each element added and the reflectance was investigated. Example 1
Samples on which various Al-based alloy layers (semi-transparent reflection layers) were formed were prepared by the same method as above, and the laser efficiency in the wavelength range of 650 nm was measured. The results are shown in Table 2.

[0046]

[Table 2]

[0047]

As described above, since the semitransparent reflective layer according to the present invention has a high transmittance, a laser having a sufficient intensity can be made incident on the information surface 47, and the reflectance is also high, which is sufficient. Reflected light with various intensities can be obtained. Therefore, the reproduction characteristics of the information surfaces 42 and 47 are also excellent. It also has excellent corrosion resistance and cohesion resistance, and has extremely high durability. Further, by constructing the semitransparent reflective layer as described above, A
The cost is lower than that of the u-based semitransparent reflective layer.

The sputtering target of the present invention is preferably used when the semitransparent reflective layer is formed by sputtering, and has the advantage that the composition of the semitransparent reflective layer to be formed is easily stabilized and, in addition, the adhesiveness, A semi-transparent reflective layer with excellent structural stability, reflection characteristics, and corrosion resistance can be efficiently obtained.

Since the semitransparent reflective layer of the present invention has excellent reflectance and transmittance, and also has excellent corrosion resistance and anti-aggregation property, it can record optical information such as CD-ROM and DVD-ROM. It is preferably used as a medium.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the basic structure of a read-only optical disc.

FIG. 2 is a schematic diagram showing the basic structure of a write-once optical disc.

FIG. 3 is a schematic diagram showing a basic structure of a rewritable optical disc.

FIG. 4 is a schematic diagram showing a basic structure of a bonded optical disc.

FIG. 5 is a schematic diagram showing the basic structure of a laminated optical disc (read-only).

[Explanation of symbols]

1 Transparent plastic substrate 2 Semi-transparent reflective layer 3 adhesive layer 4 Reflective layer 5 UV curable resin protective layer 6 Organic dye layer 7 Dielectric layer 8 recording layers 41,46 transparent substrate 42,47 Information side 43,48 reflective layer 44,49 Protective layer 45 Adhesive layer 50 Semi-transparent reflective layer

Claims (3)

[Claims] 1. A total of 0.2 to 3.0% of at least one element selected from the group consisting of Ti, Ta, and Cr.
A semi-transparent reflective layer for an optical information recording medium, which is excellent in durability and is composed of an Al-based alloy contained (meaning atomic%, the same applies hereinafter). 2. A sputtering target for a semitransparent reflective layer of an optical information recording medium, comprising the Al-based alloy according to claim 1. 3. An optical information recording medium provided with a semitransparent reflection layer composed of the Al-based alloy according to claim 1.