TW201324504A - Reflective film for optical information recording medium - Google Patents

Abstract

Provided is an extremely durable reflective film for an optical information recording medium, which naturally has excellent initial characteristics in terms of the jitter value and reflectivity of the optical information recording medium, etc., and which also has no deterioration in these characteristics when stored for a long period of time in a high-temperature, high-humidity environment, even when the thickness of the reflective film is adjusted to be thin in the range of 25 nm or less. The reflective film for an optical information recording medium of the present invention comprises an Al-base alloy including 0.5 to 10% of Si and/or 0.5 to 10% of Ge, and 0.2 to 1.0% of a metal element having a high melting point. The thickness of the reflective film is 25 nm or less.

Description

Reflective film for optical information recording media

The present invention relates to a reflective film used for an optical information recording medium that reproduces or records laser light such as a blue laser, and a sputtering target for forming a reflective film, and an optical information recording medium including the reflective film. .

The optical information recording medium (disc) is roughly classified into three types, namely, a read (reproduction) type, a record type, and a rewrite type, according to the principle of recording and reproduction. Among them, the write-once type and the rewrite type are classified into a write type.

In the optical information recording medium of the read-only type, a reflective film containing Ag, Al, Au or the like as a main component and a material for protecting data are laminated on a resin substrate such as a glass substrate or a polycarbonate. The structure of the light transmission layer (also referred to as a cover layer, a transparent intermediate layer). The light-transmitting layer is formed by applying a photo-curable resin such as an ultraviolet curable resin to the surface of the reflective film, and irradiating the laser light from the resin side or the substrate side to cure the resin. On the other hand, the write-once type and the rewritable optical information recording medium have a structure in which one or more recording layers are changed by light on the substrate, and an optical adjustment layer or a reflective layer is provided on the upper and lower sides of the recording layer. In any case, the recording signal (reproduced signal) is read by detecting the phase difference or reflection difference of the laser light irradiated on the optical information recording medium.

In Fig. 1, a representative configuration of a read-only optical information recording medium (one-layer optical disc) is displayed in a mode. As shown in Fig. 1, the optical information recording medium dedicated for reading has a sequential layer on the substrate 1 such as a transparent plastic. The structure of the reflection film 2 and the light transmission layer 3 which are mainly composed of Ag, Al, and Au are accumulated. On the substrate 1, information obtained by a combination of irregularities called land/pit is recorded, and for example, a polycarbonate substrate having a thickness of 1.1 mm and a diameter of 12 cm is used. The light transmission layer 3 is formed by, for example, bonding of light-transmitting sheets or coating/hardening of a light-transmitting resin. The reproduction of the recorded data is performed by detecting the phase difference or the reflection difference of the laser light irradiated on the optical disk.

In the first drawing, a single-layer disc in which the reflective film 2 and the light-transmitting layer 3 are formed on each of the substrates 1 on which the information obtained by the combination of the land/sink (recording data) is recorded is shown in FIG. For example, as shown in FIG. 2, a two-layer optical disc including the first information recording surface 11 and the second information recording surface 12 is also used. In detail, the two-layer optical disc of the second drawing has the first reflective film 2A laminated on the substrate 1 on which the information obtained by the combination of the land/sink (recording data) by the unevenness is recorded. The side, the first light transmission layer 3A, the second reflection film 2B (the laser light reading side), and the second light transmission layer 3B are configured to be recorded by the combination of land/sink in the first light transmission layer 3A. There are other information that is different from the substrate 1.

In order to correctly read the signal on the optical information recording medium, the reflective film must have a high reflectance, and in the case of the reflective film material as shown above, a general metal such as Au, Cu, Ag, Al or the like containing the metal as a main component alloy.

Among them, a reflective film containing Au as a main component has an advantage of being excellent in chemical stability and having little change in recording characteristics with time, but is extremely expensive. In addition, wavelengths are used in the field called Blu-ray Disk (BD). Blue laser light of 405 nm, but since the Au system has absorption at 405 nm, high reflectance cannot be obtained, and the use is limited. In addition, although the reflective film containing Cu as a main component is inexpensive, in addition to the worst chemical stability among the conventional reflective film materials, Cu also absorbs at 405 nm like Au, and thus has a blue laser. The disadvantage of low reflectivity. On the other hand, a reflective film containing Ag as a main component exhibits a very high reflectance in the practical wavelength range of 400 to 800 nm, a high reflectance at 405 nm, and good chemical stability, and thus is currently used. The blue laser light information recording medium is widely used as a reflective film material.

On the other hand, the Al-based system has a very high reflectance at a wavelength of 405 nm similarly to Ag, and is relatively inexpensive compared with Ag or Au. Therefore, it is expected to be reduced in cost. However, since Al forms an oxide film (natural oxide film) which is transparent in the atmosphere, the Al portion which contributes to the improvement of the reflectance decreases as the oxide film grows, and there are environmental conditions such as high temperature and high humidity. Reduce the reflectivity. Therefore, the film thickness of the Al-based reflective film is substantially controlled to be 35 nm or more (for example, Patent Document 1) or about 1 Å (100 nm, for example, Patent Document 2) to ensure high reflectance, and is not There is a case where it is easy to be affected by the formation of the above Al oxide film so that the reflectance is lowered, and the Al-based reflective film is used in a thin film thickness class (about 25 nm or less).

However, as shown in the above-mentioned Patent Document 1 or Patent Document 2, when the film thickness of the reflective film is increased, the transmittance of the optical information recording medium is lowered, the photocurable resin is not sufficiently cured, and the cover layer is not sufficiently cured. also In the optical information recording medium, as described above, a cover layer (transparent intermediate layer) made of a photocurable resin such as an ultraviolet curable resin is formed on the surface of the reflective film for data protection, and the ultraviolet ray is made of a resin side. Or the substrate side is incident to harden the resin. When ultraviolet rays are incident from the substrate side, the ultraviolet rays are transmitted through the reflective film formed on the substrate to harden the resin. However, in practice, it is necessary to consider the portion of the reflection due to reflection or absorption of the reflective film to harden the light-hardening resin. For high-intensity ultraviolet light transmission, optical information recording media are required to have high transmittance. Therefore, it is necessary to make the film thickness of the Al-based reflective film thin, but this is contrary to the thick film design design of the above-described Al-based reflective film.

Therefore, even if the film thickness of the reflective film is adjusted to a thickness of about 25 nm or less in order to secure a sufficiently high transmittance for curing the photo-curable resin, the reflectance required for reading, the reflectance in the state of the optical disk or Since the initial characteristics such as the jitter value are excellent, it goes without saying that it is desirable to provide a reflection film which is excellent in durability without deteriorating such characteristics even when stored under high temperature and high humidity for a long period of time.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-267366

[Patent Document 2] Japanese Patent Laid-Open No. Hei 8-241536

The present invention has been made in view of the above circumstances, and its object is to provide a A reflective film used for an optical information recording medium that performs reproduction or recording using laser light such as a blue laser, in which the film thickness of the reflective film is adjusted to a thickness of about 25 nm or less, which is a matter of the optical information recording medium. In addition, when the initial characteristics such as the transmittance, the reflectance, and the jitter value are excellent, even when stored under high temperature and high humidity for a long period of time, the characteristics are not deteriorated, and the reflective film for an optical information recording medium having excellent durability is excellent. An optical information recording medium having the reflective film; and a sputtering target used for the production of the reflective film.

The reflective film of the present invention which solves the above-described problems is mainly used in a reflective film which is used in an optical information recording medium, and the reflective film contains 0.5 to 10% of Si (unless otherwise specified, in the composition) , % means an atomic %, the same as below), and/or Ge 0.5 to 10%, and a high-melting-point metal element 0.2 to 1.0% of an Al-based alloy, and the thickness of the reflective film is 25 nm or less.

In a preferred embodiment of the present invention, when the reflective film contains 0.5 to 1.0% of Si, the thickness of the reflective film is 20 nm or less, and when the content of Si exceeds 1.0% or less, the thickness of the reflective film is Below 25nm.

In a preferred embodiment of the present invention, Ti is contained as the high melting point metal element.

In a preferred embodiment of the present invention, the high melting point metal element contains at least one selected from the group consisting of Fe, Mn, and Ta.

In a preferred embodiment of the present invention, the reflective film is used in an optical information recording medium that performs recording or reproduction by irradiating blue laser light.

In a preferred embodiment of the present invention, the reflective film has an initial reflectance of 40% or more and a transmittance at 350 nm of 8.0% or more.

In a preferred embodiment of the present invention, the reflective film has an initial reflectance of 10% or more and a transmittance at 350 nm of 15% or more.

Further, the present invention also includes an optical information recording medium including the reflective film for an optical information recording medium described in any of the above.

In a preferred embodiment of the present invention, the optical information recording medium satisfies an initial reflectance of 40% or more and a transmittance of 8.0% or more at 350 nm.

Further, the sputtering target of the present invention which solves the above-described problems is a sputtering target for forming a reflection film for an optical information recording medium described in any of the above, and has the following gist: 0.5 to 10% of Si and / or Ge 0.5 ~ 10%, and high melting point metal elements 0.2 ~ 1.0%, the residue: Al and inevitable impurities.

According to the present invention, it is possible to provide a reflective film which exhibits an appropriate transmittance and reflectance as an optical information recording medium even when the film thickness of the reflective film is as thin as about 25 nm or less, and has a low jitter value and stable regeneration at a high temperature. In the case of storage under high humidity for a long period of time, such an optical recording medium having excellent characteristics and excellent durability can be realized.

In order to impart sufficient high transmittance required for curing the photocurable resin constituting the cover layer, the inventors of the present invention display the image as an optical information recording medium even when the film thickness of the reflective film is reduced to about 25 nm or less. The reflective film in the state has an appropriate transmittance and reflectance, has a low jitter value and excellent regenerative stability, and provides a low decrease in reflectance and jitter value even when stored under high temperature and high humidity for a long period of time (that is, durability). The Al-based reflective film for optical information recording media, which is excellent in properties, is studied.

Specifically, an Al-based reflective film containing the elements (Si and/or Ge and a high melting point metal) described in Patent Document 1 is used, and Si, Ge, and high melting point are obtained as shown in Tables 1 and 2 below. The content of the metal was changed variously, and how the characteristics of the Al-based reflective film of the same composition (the elements constituting the reflective film and the same content thereof were the same) were changed. As a result, it is understood that the Al-based reflective film formed of Al-(5-40%) Si/Ge-(0.7-5%) high melting point metal described in Patent Document 1 is substantially more than about 25 nm to 100 nm. When the thickness of the Al-based reflective film is reduced to 25 nm or less, which is a target range of the present invention, Si, Ge, and high melting point are determined by the method of obtaining a desired property when the film thickness is a target. The content of the metal may not be exhibited as a desired effect. In addition, the content of Si, Ge, and high-melting-point gold which exhibits desired characteristics is changed depending on the film thickness of the reflective film, and is greatly changed by a film thickness of about 20 to 25 nm, and is also changed by the present inventors. The basic experiment can be known (more details later).

According to the above experimental results, even more basic experiments can be obtained even in the case where the film thickness of the reflective film made of the Al—(Si and/or Ge)-high melting point metal alloy is adjusted to about 25 nm or less. The content of Si, Ge, and high melting point metal of the reflective film excellent in the above characteristics was further studied in turn. As a result, it was found that the use of a reflective film made of an Al-based alloy containing 0.5 to 10% of Si, and/or 0.5 to 10% of Ge and a high-melting-point metal element of 0.2 to 1.0% can achieve the intended purpose and be completed. this invention.

The difference from the aforementioned Patent Document 1 will be described below. When the content of Si, Ge, and high melting point metal in the reflective film of the present invention is compared with the content in the reflective film of Patent Document 1, the content of Si and Ge is in Patent Document 1, Si or The Ge is similarly 5 to 40%. In contrast, in the present invention, Si is 0.5 to 10%, Ge is 0.5 to 10%, and any element is slipped to a low content side as compared with Patent Document 1. In addition, the content of the high-melting-point metal is 0.7 to 5% in the above-mentioned Patent Document 1, and is 0.2 to 1.0% in the present invention, and is still slipped to the lower content side than in Patent Document 1.

Here, when an Al—(Si and/or Ge)-high melting point metal alloy is used for the reflective film, the characteristics largely change depending on the film thickness of the reflective film, and may be No. 1 to 7 (Al-Si in Table 1 below). - The results of the experimental group of No. 14 to 18 (in the case of Al-Ge-high melting point metal alloy) of Table 2, which will be described later, are clearly known.

First, in the experimental group Nos. 1 to 7, the content of Ti belonging to the high melting point metal was prepared to be constant, and was 1.0%, and the amount of Si was kept at a minimum of 0.5% (No. 1) to a maximum of 15%. (No. 7) In the case where the amount of Si is the same, only the film thickness is changed in the range of 5 to 22 nm (these are attached with a "-" after each No. and are labeled as No. 1-1 or the like). The characteristics (initial characteristics (disc reflectance, jitter value) and rate of change (jitter value and disc reflectance) before and after the accelerated test, even at 350 nm, were measured according to the method described in the column of the examples described later. The results of the transmittance are shown in Table 1.

Similarly, in the experimental group No. 14 to No. 18, the content of Ti belonging to the high melting point metal was set to be constant at 1.0%, and the amount of Ge was kept at a minimum of 0.5% (No. 14) to a maximum of 6%. The range of (No. 18) is variously changed, and even if the amount of Ge is the same, only the film thickness is changed in the range of 5 to 30 nm (these numbers are marked with the connection number "-" after each No. .14-1, etc.). The results of these characteristics are shown in Table 2.

Among them, No. 1 to 7 (Al-Si-high melting point metal alloy) of Table 1 were examined in detail. No. 7-1 to No. 7-4 are Al-based reflective films containing Si 15% and Ti 1.0%, and the content of Si and the high-melting-point metal is included in the range of the Al-based reflective film disclosed in Patent Document 1. However, the amount of Si exceeds the upper limit (10%) of the present invention, and therefore, in the relationship with the present invention, it corresponds to a comparative example. Then, in the Al-based reflective film having the above-described composition, the film thickness is in the range of 5 μm (No. 7-1) to 30 nm (exceeding the upper limit (25 nm) of the present invention, and is formed within the film thickness specified in Patent Document 1. When the film thickness is 30 nm (No. 7-4), the properties other than the transmittance are all good, and the film thickness is reduced to 20 nm (No. 7). -3), 10 nm (No. 7-2), or even 5 nm (No. 7-1), the reflectance of the optical disk is drastically reduced. The results of these experiments are even The reflective film of the Al-Si-high-melting-point metal described in the above-mentioned Patent Document 1 is applied to the reflective film of the target film (about 25 nm or less) in the present invention as it is, and it is not possible to obtain desired characteristics. The content of the reflective film suitable for the film is individually set.

On the other hand, in Nos. 3 to 6 in which the amount of Si and the amount of Ti are controlled within the range defined by the present invention, good characteristics can be ensured even if the film thickness is changed within the range of 15 to 22 nm. In addition, it is also rigorously determined that even if the amount of Si is within the range specified in the present invention (0.5 to 10%), and the amount of Si is 1.0% or less as in No. 1 to 2, if the amount of the Al-based reflective film is The film thickness is 22 nm, and the transmittance of the optical disk cannot achieve the requirements specified in the present invention (the transmittance at 350 nm is 8.0% or more), and when the film thickness of the Al-based reflective film is 20 nm or less, Get the desired characteristics. That is, the reflective film of the Al-Si-high melting point metal specified in the present invention has a great influence on the film thickness of the element constituting the reflective film, and the characteristics may be changed accordingly, so that the light information is produced. In the case of recording a medium, it is preferred to appropriately control the film thickness in accordance with the content of each element in order to obtain desired characteristics.

The same tendency as described above was also found in the case of the Al-Ge-high melting point metal alloy of No. 14 to 18 in which Ge was substituted for Si.

When the reflective film of the present invention is used, it is possible to obtain an appropriate transmittance and an appropriate reflectance, and the jitter value is low, and it is excellent in such characteristics (that is, excellent in durability) when stored for a long period of time under high temperature and high humidity. Information recording media. The basis of each characteristic is as follows.

"Having an appropriate transmittance" in the optical information recording medium of the present invention It means that when the transmittance at 350 nm is measured by the method described in the examples below, it is 8.0% or more. A preferred transmittance is 9.0% or more. As described above, the optical information recording medium of the present invention is based on the premise that the transmittance is high, and the curing of the photocurable resin constituting the cover layer is surely performed.

Further, "having an appropriate reflectance" in the optical information recording medium of the present invention means that the initial reflectance of the disc itself is measured within a range of 40% or more when the method shown in the following examples is used. It is preferably 50% or more. On the other hand, the upper limit is not particularly limited as long as the upper limit is ensured. However, if the reflectance is too high, the jitter value tends to be high, so that it is preferably about 65% or less. More preferably less than 60%.

In the optical information recording medium of the present invention, the "low jitter value" means 6.50% or less when the initial jitter value is measured by the method described in the following embodiments. It is preferably less than 6.0%.

In the optical information recording medium of the present invention, "excellent durability" means accelerating the environment when an accelerated environmental test is carried out for 96 hours in an environment of a temperature of 80 ° C and a relative humidity of about 85% as shown in the following examples. The amount of change in reflectance and jitter value before and after the test was within ±10%.

Further, the reflective film of the present invention can be applied to various reflective films constituting an optical information recording medium. Specifically, it can be applied to the first and second reflecting films described in detail below, and the characteristics required for the respective reflecting films are different. Therefore, the preferred film thickness range of the reflecting film may be different.

In other words, the reflective film for an optical information recording medium is mainly divided into a reflective film (2 in the first drawing) used in the single-layer (one-layer) optical information recording medium of the first drawing, and the second drawing. 2-layer optical information recording medium The first reflection film (2A in the second drawing; the substrate side) and the second reflection film (2B in the second drawing; the light irradiation side) used. Among these, the single-layer optical information recording medium reflective film and the two-layer optical information recording medium first reflective film are required to have at least the same level of high reflectance and appropriate transmission as the optical information recording medium. rate. In the present specification, the term "first reflection film" is collectively referred to.

On the other hand, the second reflecting film for the two-layer optical information recording medium receives the laser light through the second information recording surface, and is required to be higher than the first reflective film in order to read the information. Transmittance. Therefore, the transmittance in the second reflection film must be higher than the value required for the first reflection film, and the reflectance in the second reflection film may be higher than that in the optical information recording medium. The required level is lower.

The characteristics required for at least the first and second reflecting films are as follows. In the present specification, the characteristics (initial reflectance and transmittance at 350 nm) of each of the reflective films are evaluated as respective characteristics of the optical information recording medium.

The first reflecting film is required to satisfy at least an initial reflectance of 40% or more as an optical information recording medium and a transmittance of 8.0% or more at 350 nm.

On the other hand, the second reflection film is required to satisfy at least an initial reflectance of 10% or more as an optical information recording medium and a transmittance of 15% or more at 350 nm.

1.About reflective film

First, the reflective film of the present invention will be described in detail. The reflective film of the present invention is formed of an Al-based alloy containing 0.5 to 10% of Si, and/or 0.5 to 10% of Ge, and 0.2 to 1.0% of a high melting point metal element, and the film thickness of the above-mentioned reflective film is 25 nm or less. Has characteristics.

In the present specification, "(containing) Si and/or Ge" means (containing) at least one of Si and Ge. Specifically, as described above, the aspect in which Si and Ge are separately contained, and the aspect in which both Si and Ge are contained is exemplified.

The elements (Si, Ge, and high melting point metal) constituting the Al-based alloy reflective film of the present invention will be described below.

Both Si and Ge have an action of suppressing a decrease in reflectance due to formation of a natural oxide film of Al. That is, Si and Ge are concentrated on the surface of the reflective film, and are preferentially oxidized instead of Al. As a result, it is presumed that the Si oxide film formed on the surface serves as a protective film, and the formation of the Al oxide film is suppressed, and the reflectance can be prevented from being lowered. The Si and Ge systems may be added singly or in combination as long as the content satisfies the following requirements.

In order to effectively exert the above effects, it is necessary to add Si of 0.5% or more and Ge of 0.5% or more. The amount of Si is preferably 1.0% or more, more preferably 3.0% or more.

On the other hand, if the Si content exceeds 10%, the absorption coefficient increases and the reflectance decreases. Therefore, in order to obtain the desired reflectance, it is necessary to increase the film thickness. When the film thickness is increased, the transmittance is reduced, and a desired value cannot be secured. A preferred Si amount is 7.0% or less. Further, when the content of Ge exceeds 10%, the reflectance decreases due to an increase in the absorption coefficient as in Si. Propensity. In addition, the large addition of Ge leads to an increase in cost. The amount of Ge is preferably 5% or less, more preferably less than 5%, still more preferably 3% or less.

In addition, since the high-melting-point metal is dispersed in the Al-based alloy film, it has an effect of suppressing a decrease in reflectance due to surface roughness due to self-granular growth of Al (roughening of Al crystal grains), whereby Durability will increase. In order to effectively exert the above effects, the content of the high melting point metal is set to 0.2% or more. It is preferably 0.3% or more, more preferably 0.5% or more. On the other hand, when the content of the high melting point metal exceeds 1.0%, the absorption coefficient increases, and the desired transmittance and reflectance cannot be ensured. Therefore, the upper limit is made 1.0%. It is preferably 0.8% or less. Here, the "content of the high-melting-point metal" means that the amount of the high-melting-point metal which is preferably selected from the group consisting of the following elements means a single amount, and when it contains two or more types, it means the total amount.

The preferred high melting point metal used in the present invention is at least one selected from the group consisting of Ti, Fe, Mn, and Ta. These may be used alone or in combination of two or more. A preferred high melting point metal is Ti.

The reflective film of the present invention contains at least one of Si and Ge in the above content and a high melting point metal, and the residual portion is Al and inevitable impurities. In terms of the above-mentioned unavoidable impurities, elements which are inevitably mixed in the production process of the reflective film are listed.

The upper limit of the film thickness of the above-mentioned reflective film is 25 nm or less. In the present invention, in order to cure the photo-curable resin, it is assumed that the film thickness is set to be thinner than that of Patent Document 1 in order to secure the photo-curable resin. The upper limit is set to 25 nm or less.

Strictly speaking, the upper limit of the film thickness of the above-mentioned reflective film differs depending on the range of the amount of Si. First, the upper limit of the film thickness of the reflective film containing 0.5% or more and 1.0% or less of Si is 20 nm or less. As shown in the later-described embodiment, when the thickness of the reflective film is 22 nm, the transmittance as an optical information recording medium is lowered. On the other hand, the upper limit of the film thickness of the reflective film containing Si exceeding 1.0% or less is 25 nm or less. As shown in the later-described embodiment, the above-mentioned reflective film containing a large amount of Si can provide a good transmittance as an optical information recording medium even when the film thickness is 22 nm. Specifically, the upper limit of the film thickness of the reflective film is appropriately changed depending on the content of Si, the high melting point metal, etc., and therefore, it may be appropriately controlled in consideration of such.

On the other hand, regarding Ge, strictly speaking, depending on the amount of Ge, the upper limit of the film thickness of the above-mentioned reflective film is different. For example, the upper limit of the film thickness of the reflective film containing Ge of about 0.5 to 5% is about 20 nm or less, preferably 18 nm or less. However, in the reflective film containing about 5% to 10% of Ge, the upper limit of the film thickness can be allowed to be 25 nm (refer to Examples described later). When the film thickness becomes too thick, the transmittance of the optical information recording medium is lowered or the jitter value is increased depending on the composition of the Al alloy. Specifically, the upper limit of the film thickness of the reflective film is also appropriately changed depending on the content of Ge, the high melting point metal, etc., and therefore, it may be appropriately controlled in consideration of such.

On the other hand, if the film thickness of the above-mentioned reflective film is too thin, the high initial reflectance (40% or more) required for the optical information recording medium cannot be ensured. The lower limit of the film thickness of the reflective film is preferably about 13 nm or more, and more preferably 15 nm or more, from the viewpoint of satisfying the above-described required characteristics of the optical information recording medium. Specifically, the recommended lower limit of the film thickness is also dependent on Si, Ge, and high melting. The content of the point metal or the like is appropriately changed, so that it can be appropriately controlled in consideration of such.

Among them, the film thickness range of the above-mentioned reflective film is set from the viewpoint of satisfying the required characteristics as an optical information recording medium. However, even if the film thickness is very thin, for example, 10 nm or even 5 nm, the reflective film of the present invention has high transmittance (refer to Tables 1 and 2), and therefore it is required to satisfy the reflective film for optical information recording media. The situation of the characteristics. As described above, since the reflectance or transmittance of the reflective film of the present invention differs greatly depending on the film thickness, it is preferable to record the light information of the reflective film in accordance with which layer. The medium and the position of the optical information recording medium are used to appropriately control the lower limit and the upper limit of the film thickness of the reflective film.

(When used as the first reflection film)

The first reflective film such as the reflective film 1 used for the one-layer (single-layer) optical information recording medium of the first embodiment and the reflective film 2A (substrate side) of the two-layer optical information recording medium of the second drawing. The first reflection film must have at least an initial reflectance and a transmittance required for the optical information recording medium (that is, an initial reflectance of 40% or more at a wavelength of 405 nm and a transmittance of 8.0% or more at a wavelength of 350 nm). ). The range of the film thickness of the first reflection film which exhibits the above characteristics is as described above.

(When used as the second reflection film)

2nd used for the 2-layer optical information recording medium of Fig. 2 The reflection film 2B (light irradiation side) is required to have a high transmittance especially for the second reflection film system, and it is necessary to satisfy an initial reflectance of 10% or more at a wavelength of 405 nm as an optical information recording medium, and a transmittance at a wavelength of 350 nm. It is 15% or more.

The film thickness of the second reflection film which satisfies the above requirements is strictly different depending on the content of each element constituting the reflection film. In particular, since the reflectance or transmittance of the optical information recording medium differs greatly depending on the content of Si or Ge, it is preferable to appropriately set an appropriate film thickness in accordance with the composition of the reflective film to obtain desired characteristics. Specifically, when an Al—Si—high melting point metal containing Si is used as the second reflective film, it is recommended to set the film thickness to about 5 μm or more and 15 nm or less. In the reflective film of the Al alloy shown in Table 1 below, when the film thickness is 18 nm, the transmittance is lowered regardless of the content of Si and the high melting point metal.

On the other hand, when a Ge-containing Al-Ge-high melting point metal is used as the second reflection film, it is recommended to set the thickness of the second reflection film to about 5 nm or more and 19 nm or less. As shown in Table 2 below, the upper limit of the film thickness which can be used as the second reflection film can be changed depending on the amount of Ge, and the transmittance is mainly changed. Further, in consideration of the balance with the durability required for the optical information recording medium, the thickness of the second reflective film is preferably about 5 to 15 nm, more preferably about 7 nm or more and 12 nm or less.

The reflective film which is the most characteristic of the present invention has been described above.

2. About optical information recording media

The present invention also includes an optical information recording medium having the above reflective film. body. The optical information recording medium includes a read-only type and a write type (recorded type or rewritten type), and the reflective film of the present invention can be applied to any of the above. Here, the read-only type means that a mark and a space having different sizes have been formed on the substrate, and a metal reflective film is irradiated to read the laser, and the light can be read out by the phase difference between the light of the mark and the spacer. Information recording media. On the other hand, the write type means that the power of the laser light is controlled to be at least three values corresponding to the respective pulses of the heating pulse, the cooling pulse, and the erasing pulse, by alternately illuminating the optical information recording medium with the aforementioned heating pulse and the foregoing A plurality of types of recording marks having different lengths formed by cooling pulses, and an optical information recording medium caused by an information recording method for recording predetermined information by forming an interval between the recording marks by irradiating the erasing pulses. There are two types of write type, such as write-once type and rewrite type.

The optical information recording medium is exemplified by CD, DVD, or BD, for example, having a wavelength of about 380 nm to 450 nm, preferably BD-R capable of recording or reproducing data by using blue laser light of about 405 nm. BD-ROM and BD-RW are specific examples.

The optical information recording medium of the present invention exhibits an appropriate transmittance and an appropriate reflectance, and has a low jitter value, and is excellent in such characteristics (i.e., excellent in durability) even when stored for a long period of time under high temperature and high humidity. The details of the above characteristics are as described above.

The optical information recording medium of the present invention is characterized in that it has a reflective film made of an Al-based alloy satisfying the above-described composition, and the configuration of the optical disk to which the reflective film is applied is not particularly limited. The reflective film of the present invention can be used, for example, as the reflective film 2 of the first drawing or the first of the second drawing. The reflective film 2A is used. Alternatively, it may be used as, for example, the second reflection film 2B of the second drawing.

Further, the other components (the type of the light transmission layer, the substrate, and the like) in the optical disk are also not particularly limited, and a normal user can be employed.

For example, in the substrate 1 of the first and second figures, a resin which is common to the substrate for a disk can be used. Specifically, for example, an ultraviolet curable resin, a polycarbonate resin, an acrylic resin or the like can be used. When considering the price or mechanical properties, etc., it is preferred to use a polycarbonate resin.

The thickness of the substrate 1 is preferably in the range of about 0.4 to 1.2 mm. Further, the depth of the pit formed on the substrate 1 is preferably in the range of about 50 to 100 nm.

The types of the light-transmitting layers 3, 3A, and 3B in the first and second figures are also not limited, and it is preferable to have a high transmittance for the laser and a small light absorptivity. For example, an ultraviolet curable resin, a polycarbonate resin, or the like can be used. The thickness of the light transmission layer is preferably about 100 μm, and is preferably about 100 μm. For a two-layer optical disk, the thickness of the first light transmission layer 3A is preferably about 25 μm, and the thickness of the second light transmission layer 3B is About 75 μm.

The reflective film of the present invention can be formed by, for example, a sputtering method, a vapor deposition method, or the like, but a sputtering method is preferred. By the sputtering method, the above alloying elements are uniformly dispersed in the Al group, so that a homogeneous film can be obtained, and stable optical characteristics or durability can be obtained.

The film formation conditions at the time of sputtering are not particularly limited, and it is preferred to use, for example, the conditions shown below.

. Substrate temperature: room temperature ~ 50 ° C

. The degree of vacuum reached: 1 × 10 ^-5 Torr or less (1 × 10 ^-3 Pa or less)

. Gas pressure at film formation: 1~4mTorr

. DC sputtering power density (DC sputtering power per unit area of target): 1.0~20W/cm ²

In order to form the reflective film of the present invention by the above sputtering method, the sputtering target to be used is composed of 0.5 to 10% of Si and contains a high melting point metal element (for example, selected from the group consisting of Ti, Fe, and Mn, And one or more elements of the group of Ta, preferably an Al-based alloy of 0.2 to 1.0% of Ti), and an Al having substantially the same composition/composition as a reflection film of a desired composition/composition It is preferable that the base alloy sputtering target can form a reflection film of a desired composition/composition without occurrence of compositional shift.

The chemical composition of the Al-based alloy of the sputtering target of the present invention is as described above, and the residual portion is Al and inevitable impurities.

The sputtering target can also be produced by any method such as a melt casting method, a powder sintering method, or a spray molding method.

The present application claims priority from Japanese Patent Application No. 2011-146019, filed on Jun. 30, 2011, and Japanese Patent Application No. 2012-120179, filed on May 25, 2012. The contents of the specification of Japanese Patent Application No. 2011-146019, filed on Jun. 30, 2011, and the Japanese Patent Application No. 2012-120179, filed on May 25, 2011, .

[Examples]

The present invention is not limited by the following examples, but the present invention is not limited by the following examples, and may be implemented by appropriately applying the modifications within the scope of the present invention. Within the technical scope of the present invention.

Example 1

In the present embodiment, each of Si, Ge, and a high melting point metal (Ti) is provided in a reflection film formed of an Al-(Si or Ge)-high melting point metal (Ti) by the following method. When the content of the element or even the film thickness of the above-mentioned reflective film is changed to the optical disk of the reflective film of various changes, it is investigated how the characteristics such as the reflectance change.

(production of CD)

First, a polycarbonate substrate (thickness 1.1 mm, gauge 0.32 μm, groove depth 25 nm) having a mark/space of 12 cm in diameter was used as a substrate, and Table 1 was formed on the above substrate by DC magnetron sputtering. An Al-based alloy film having a composition and a film thickness (residue: Al and unavoidable impurities, % of atomic %) or a pure Al film. In the formation of the above-mentioned reflective film, a composite sputtering target or an Al-based alloy sputtering target in which various pure metal wafers for alloy addition are disposed on a pure Al sputtering target is used.

Further, in the sputtering apparatus, a multi-layer sputtering apparatus capable of simultaneously discharging a plurality of targets (CS-200 manufactured by ULVAC, or SIH-S100 manufactured by ULVAC) was used. The sputtering conditions were: Ar gas flow rate: 20 sccm, Ar gas pressure: about 0.1 Pa, DC sputtering power density: 2 to 5 W/cm ² , and reaching vacuum degree: 2.0 × 10 ^-6 Torr or less.

The composition of the Al-based alloy reflective film formed as described above was determined by ICP emission spectrometry.

Then, an ultraviolet curable resin ("BRD-864" manufactured by Nippon Kayaku Co., Ltd.) was applied onto the reflective film obtained as described above by a spin coating method, and irradiated with ultraviolet rays to be hardened to form a film thickness of about 0.1 mm. Light transmission layer (cover layer). A 1-layer BD-ROM having reflective films of various compositions was fabricated as above.

(evaluation method of CD)

In the evaluation of the optical disc, a disc evaluation device ("ODU-1000" manufactured by PULSTEC Co., Ltd.) was used, and a lens having a laser center wavelength of 405 nm and an NA (opening number) of 0.85 was used.

First, the initial reflectance is calculated by using the above-described apparatus to irradiate a laser onto a magnetic track and from the return light intensity of the unrecorded portion of the optical disk.

In addition, the initial jitter value (signal evaluation) is set to 4.92 m/s for the line speed, and the read laser power is set to 0.35 mW with the reference clock: 66 MHz, and is measured using a multi-signal of 2T to 8T signals. The standard deviation of the error value of the reference clock of the 2T to 8T signal is obtained and calculated.

In the evaluation of the initial characteristics, the initial reflectance calculated as described above is 40% or more with reference to the BD-R specification value, and the initial jitter value is 6.50% or less. And excellent in regeneration stability).

(accelerated environmental test)

The BD-ROM on which the above-mentioned reflective film was formed was subjected to an accelerated environmental test (constant temperature and humidity test) maintained in an atmospheric gas atmosphere at a temperature of 80 ° C and a relative humidity of 85% for 96 hours, and the jitter after the test was measured in the same manner as described above. Value and reflectivity after the test. Then, the amount of change in the reflectance and the jitter value before and after the accelerated environmental test was evaluated to be within ±10% (excellent durability).

(Measurement of transmittance)

In the transmission rate, the linear transmittance in the thickness direction of light having a wavelength of 350 nm at room temperature was measured using a spectrophotometer (UV-3150 manufactured by Shimadzu Corporation). The transmittance at 350 nm as measured above was 8.0% or more as a pass.

These results are collectively shown in Tables 1 and 2. In the above table, the measured value (%) is described in the fields of "disc reflectance" and "transmittance at 350 nm", and the reflectance of the first reflective film is satisfied (the reflectance when measured by the following method) When the transmittance is 40% or more and the transmittance is 8% or more, and the passivation standard of the second reflecting film (the reflectance measured by the following method is 10% or more and the transmittance is 15% or more), ○, The satisfied person is marked with ×.

In addition, when the "evaluation" field is provided in the right-hand column of each table, when the comprehensive judgment is made, ○ is marked for each of the qualified standards that satisfy the first reflection film, the second reflection film, and the optical information recording medium, and the pair is not satisfied. Any one is marked with ×. example No. 1-4 and 1-5 of Table 1A mean that the optical data recording medium meets the criteria of the optical recording medium. However, since the reflectance and the transmittance satisfy the pass criteria of the first reflecting film, it is also suitable as the first reflecting film. . On the other hand, No. 1-1 to 1-3 of Table 1A means that the pass criteria of the optical information recording medium are not satisfied, but the reflectance and the transmittance satisfy the pass criteria of the second reflective film, and therefore it is suitable as the second standard. Reflective film.

Table 1A and Table 1B show the results when Al-Si-high melting point metal (Ti) was used. The examinations shown below can be carried out from these tables.

First, No. 1 to 7 show that the amount of Ti is constant, 1.0%, and the amount of Si is changed in the range of 0.5 to 15%, and the film thickness is 5 to 22 nm (5 to 30 nm in No. 7). The result when the range is changed. In the above, the optical information recording medium having the reflective film of the present invention in which the amount of Si and Ti is appropriately controlled is such that the film thickness is as small as 25 nm or less, and the reflectance and transmittance are appropriately exhibited, and the regeneration stability is excellent. And the durability is also excellent.

Strictly speaking, the upper limit of the film thickness of the reflective film which exhibits the desired characteristics of the desired optical information recording medium depending on the amount of Si can be changed. In other words, when the amount of Si is more than 1.0% and 10% or less, the upper limit of the film thickness of the reflective film is allowed to be up to 25 nm, but when the amount of Si is 0.5 to 1.0%, the upper limit of the film thickness of the reflective film is It is 20 nm or less.

In addition, it is also understood that the lower limit of the thickness of the reflective film which exhibits the desired characteristics of the desired optical information recording medium is about 13 nm or more irrespective of the amount of Si.

In addition, it has been found that when the characteristics of the reflective film are emphasized, the Al-based alloy satisfying the composition specified in the present invention greatly differs in film thickness, particularly in reflectance or transmittance, and therefore cannot be applied as the first A reflection film of the electrode film of the reflective film (having a film thickness of less than 13 nm) may be suitably used as the second reflection film. As a result of the present embodiment, when a reflective film of the Al-Si-high melting point metal of the present invention containing Si is used, the film thickness of the first reflective film can be suitably in the range of about 13 to 25 nm, which is suitable for the film. The film thickness of the second reflection film is in the range of about 5 to 15 nm.

In addition, No. 8 to 13 showed a result of changing the amount of Si to 10% and changing the amount of Ti in the range of 0.1 to 1.5% (film thickness: 20 nm). No. 9 to 12 satisfying the requirements of the present invention are excellent in all the characteristics. On the other hand, the No. 8 system having a small amount of Ti is reduced in durability (the amount of change in the jitter value before and after the acceleration test is large), and the amount of Ti is large. In No. 13, the transmittance was lowered.

Table 2A and Table 2B show the results when Al-Ge-high melting point metal (Ti) was used. When Ge is used instead of Si, the same result as Si is obtained. Specifically, the following examinations can be performed from the tables.

First, No. 14 to 18 shows that the amount of Ti is made constant, 1.0%, and the amount of Ge is changed in the range of 0.5 to 6%, and the film thickness is 5 to 25 nm (more specifically in No. 14). The result is changed within the range of 5 to 30 nm). It is understood that the optical information recording medium having the reflective film of the present invention in which the amount of Ge and Ti is appropriately controlled is such that, even if the film thickness is 25 nm or less, an appropriate transmittance and reflectance are exhibited, and regeneration and stability are exhibited. Excellent in properties and excellent in durability.

Among them, a preferable lower limit of the film thickness of the reflective film which exhibits a desired characteristic of the optical information recording medium is about 13 nm or more irrespective of the amount of Ge.

In addition, it has been found that when the characteristics of the reflective film are emphasized, the Al-based alloy satisfying the composition specified in the present invention greatly differs in film thickness, particularly in reflectance or transmittance, and therefore cannot be applied as The reflective film of the ultrathin film of the first reflective film may also be suitable as the second reflection membrane. As a result of the present embodiment, when a reflective film of the Al-Ge-high melting point metal of the present invention containing Ge is used, the film thickness of the first reflecting film can be suitably in the range of about 13 nm or more and 25 nm or less (in terms of Ge). The amount is 20 nm or less). A preferred range is about 15 nm or more and 20 nm or less (the amount of Ge is 18 nm or less). Further, the film thickness of the second reflection film is preferably in the range of about 5 nm or more and 19 nm or less (more preferably 15 nm or less).

However, in the above-mentioned system containing Ge, although the result of changing the amount of Ti was not shown, the same result as Si was confirmed.

On the other hand, in the case of No. 19, pure Al was used, but even if the film thickness was changed in the range of 10 to 40 nm, desired characteristics could not be secured.

1‧‧‧Substrate

2‧‧‧Reflective film

3‧‧‧Light transmission layer

2A‧‧‧1st reflective film

2B‧‧‧2nd reflective film

3A‧‧‧1st light transmission layer

3B‧‧‧2nd light transmission layer

11‧‧‧1st information record surface

12‧‧‧2nd information record surface

Fig. 1 is a cross-sectional view showing a main portion in the circumferential direction of a light information recording medium (one-layer optical disc) dedicated for reading in a mode.

Fig. 2 is a cross-sectional view showing a main portion in the circumferential direction of another optical information recording medium (two-layer optical disc) dedicated for reading in a mode.

1‧‧‧Substrate

2‧‧‧Reflective film

3‧‧‧Light transmission layer

Claims (10)

A reflective film for an optical information recording medium, which is used in a reflective film of an optical information recording medium, characterized in that the reflective film contains 0.5 to 10% of Si (if not specifically described, in the composition, It means that the atomic % is the same as the above, and/or the Ge is 0.5 to 10%, and the high melting point metal element is 0.2 to 1.0% of the Al-based alloy, and the thickness of the reflective film is 25 nm or less. The reflective film for an optical information recording medium according to the first aspect of the invention, wherein when the Si content is 0.5 to 1.0%, the thickness of the reflective film is 20 nm or less, and when the Si content is more than 1.0% and 10% or less, the The film thickness of the reflective film is 25 nm or less. The reflective film for an optical information recording medium according to the first aspect of the invention, wherein the high melting point metal element contains Ti. The reflective film for an optical information recording medium according to the first aspect of the invention, wherein the high melting point metal element contains at least one selected from the group consisting of Fe, Mn, and Ta. A reflective film for an optical information recording medium according to claim 1, wherein the optical information recording medium is used for recording or reproducing by irradiating blue laser light. The reflective film for an optical information recording medium according to the first aspect of the invention, wherein the initial reflectance is 40% or more, and the transmittance at 350 nm is 8.0% or more. The reflective film for an optical information recording medium according to the first aspect of the patent application, wherein the initial reflectance is 10% or more, and the transmission is at 350 nm. The rate is 15% or more. An optical information recording medium comprising the reflective film for an optical information recording medium according to any one of claims 1 to 7. The optical information recording medium of claim 8, wherein the initial reflectance is 40% or more, and the transmittance at 350 nm is 8.0% or more. A sputtering target for forming a sputtering target for a reflective film for an optical information recording medium according to any one of claims 1 to 7, characterized in that it contains Si 0.5 to 10%, and / or Ge 0.5 ~ 10%, and high melting point metal elements 0.2 ~ 1.0%, the residue: Al and inevitable impurities.