JP5169081B2 - Optical recording medium, sputtering target - Google Patents

Description

The present invention relates to a write once read many (WORM) optical recording medium, and more particularly to an optical recording medium capable of performing high-density recording with a laser beam in a blue wavelength region (350 to 500 nm). optical recording medium having a sensitivity, the optical recording medium having two or more recording layers, and the optical recording medium member requiring high recording sensitivity capable of supporting the linear velocity of a wide range from low speed to high speed, as well, the optical recording about the sputtering coater rodents bets for film recording layer of the medium.

As a write-once type optical recording medium capable of high-density recording with a laser beam in a blue wavelength region (350 to 500 nm), the present inventors have disclosed metal or metalloid oxides, particularly Bi, in Patent Documents 1 to 4 and the like. It proposes the usefulness of a recording layer mainly composed of oxide. Further, Patent Document 5 and the like relating to the application of the present applicant discloses that a write-once optical recording medium using a recording layer made of Bi, B, O (oxygen) exhibits even better characteristics (hereinafter referred to as a “write-once optical recording medium”). The technology related to these applications is called in-house prior art). These in-house prior arts have been confirmed to exhibit very good recording / reproduction characteristics.
In addition to the above, in Patent Document 6, although the write-once optical recording medium having a recording layer composed mainly of Bi oxide is disclosed, it has not been studied system plus-carbon.
Patent Documents 7 to 8 disclose information recording media using a recording layer containing a metal nitride or metal carbide, but the metal nitride is the main component and records the decomposition of the metal nitride. It is based on the principle, and is not a reference of the present invention mainly composed of Bi and O (oxygen).

On the other hand, optical discs have a trend of higher density and higher speed, and conventional DVDs are also increased in density by double-layering. Yes. Even in an optical disk using a blue LD, this flow is not changed, and it is considered that the optical recording medium for high-speed recording is beginning to be developed in the direction of high-speed recording.
However, the in-house prior art does not consider high-speed recording at all. The invention of Patent Document 6 is also intended to improve recording / reproduction characteristics and reliability (reproduction stability, storage stability, etc.), and does not consider high-speed recording. Furthermore, although the material which added various elements X to bismuth oxide is examined, C is not contained in X, and the specific example which added two or more kinds of elements to bismuth oxide is also shown. Absent.

Separately, the present inventors have made sputtering for forming a recording layer mainly composed of Bi oxide of a write-once type optical recording medium capable of high-density recording with a laser beam in a blue wavelength region (350 to 500 nm). As a target, a target containing Bi and Fe was disclosed in the prior application (see Patent Document 9), and a target containing Bi and B or a target containing Bi, B and O was disclosed in Japanese Patent Application No. 2006-055120.
Sputtering is widely known as one of thin film vapor forming methods, and has been used for industrial thin film production. In the sputtering method, a target material having the same component as that of the target film is prepared. Usually, Ar (argon) gas ions generated by glow discharge are collided with the target material to strike constituent atoms of the target material. The film is formed by depositing and depositing atoms on the substrate. In particular, since oxides generally have a high melting point, methods such as vapor deposition are not preferred, and high-frequency sputtering that applies a high frequency is often used.

Sputtering has many achievements in the manufacturing process and is advantageous in terms of throughput. However, when a film made of a mixed material of two or more elements is formed, the composition of the target and the composition of the film are often not the same, and thus the target composition needs to be examined. In addition, since the structure and properties of the film are often different depending on the form of the compound constituting the target, this point needs to be studied. Further, from the viewpoint of production cost, it is necessary to further improve the film forming speed. In order to improve the film forming speed, it is necessary to input a larger electric power. In this case also, it is necessary to improve the target strength so that the target is not destroyed.
In addition to the above, Patent Document 10 discloses a method of forming a recording layer containing carbon and Bi by sputtering in a mixed gas of CH ₄ or the like and Ar using a low melting point metal target such as Bi. Is different from the present invention mainly composed of Bi and oxygen.

JP 2003-48375 A JP 2005-161831 A JP 2005-108396 A JP 2006-116948 A JP 2006-247897 A Japanese Patent No. 3802040 JP 2006-182030 A Japanese Patent No. 3810076 JP 2007-169779 A Japanese Patent No. 1480945

Optical recording media are required to have high-sensitivity recording characteristics capable of recording with low recording power from the viewpoints of the limit of laser light output, durability, power saving performance, and the like. Also, high linear velocity recording is required to improve information transfer speed as well as high density recording. In that case, recording sensitivity needs to be further improved in high linear velocity recording as compared with low linear velocity recording. In addition, for compatibility reasons, it is necessary to support the entire recording linear velocity range from low linear velocity to high linear velocity.
Accordingly, the present invention is capable of recording and reproduction by a laser beam in the blue wavelength region (350 to 500 nm), high sensitivity and optical recording media which are suitable to record a wide linear velocity range of from a low linear velocity to a high linear velocity , and it aims to provide a sputtering coater rodents bets for film recording layer of the optical recording medium.

The above problems are solved by the following inventions 1) to 10) (hereinafter referred to as the present invention 1 to 10 ).
1) On a substrate, there is a recording layer that can be recorded / reproduced by laser light of at least a blue wavelength region, and the recording layer contains Bi (bismuth) and O (oxygen) as main components, and further contains C (carbon ). An optical recording medium characterized by not containing Fe and having a C content of 1.5 to 49 atomic% of the entire recording layer .
2) The recording layer further comprises B, Li, Sn, Ge, Sr, Mg, Ba, Ca, Mo, W, Co, Si, In, Ti, Mn, Ga, Zr, Cr, Hf, K, Na, Zn 1) The optical recording according to 1), comprising at least one element X selected from Ni, Cu, Pd, Ag, P, Ta, Y, Nb, Al, V, Sb, Te, and La series elements Medium.
3) The optical recording medium according to 2), wherein the recording layer comprises Bi, B, O and C.
4 ) The optical recording medium according to any one of 1) to 3) , further comprising an upper protective layer and / or a lower protective layer adjacent to the recording layer.
5 ) The optical recording medium according to 4 ), wherein the upper protective layer and / or the lower protective layer is made of any of sulfide, oxide, nitride, carbide, or a composite thereof.
6 ) The optical recording medium according to 5 ), wherein at least one of the upper protective layer and the lower protective layer contains a sulfide.
7 ) The optical recording medium according to 6 ), wherein at least one of the upper protective layer and the lower protective layer is made of ZnS · SiO ₂ .
8 ) The optical recording medium according to any one of 4) to 7) , wherein at least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially laminated on a substrate.
9 ) The optical recording medium according to any one of 4) to 7) , wherein at least a reflective layer, an upper protective layer, a recording layer, a lower protective layer, and a cover layer are sequentially laminated on the substrate.
10 ) characterized in that it contains Bi (bismuth) and O (oxygen) as main components, further contains C (carbon ) , does not contain Fe, and the content of C is 1.5 to 49 atomic% of the whole. Sputtering target.

Hereinafter, the present invention will be described in detail.
The optical recording medium of the present invention 1 has at least a recording layer on a substrate, the recording layer contains Bi (bismuth) and O (oxygen) as main components, further contains C (carbon ) , and does not contain Fe. . Here, the main component means that the combined content (atomic%) of Bi and oxygen is the largest in the recording layer. In addition, the expression of containing Bi and oxygen is due to the fact that Bi oxide is the most common, but the recording layer may contain metal Bi in addition to Bi oxide.
It has been found that when a recording layer containing Fe is used, the optical characteristics and the like of the recording layer become unstable. The reason for this is not clear, but since Fe can take multiple valences, the oxidation state tends to be unstable, and as a result, the target becomes unstable and the composition variation of the recording layer becomes relatively large. The cause of this is considered. Variations in the optical properties occur due to the variation in composition, particularly the relatively low stability of the oxygen content. For this reason, there are adverse effects such as relatively large variations in the characteristics of the optical recording medium.
On the other hand, in the recording layer not containing Fe, the optical characteristics of the recording layer are relatively stable, and the effects of stabilizing the characteristics of the optical recording medium are significant. Actually, as shown in Example 12 which will be described later, when the light absorptance, which is one of the optical characteristics of the recording layer, was examined, when Fe was included, the variation was large, and when Fe was not included. Was found to have a small variation.

The ratio of oxygen in the recording layer is about 30 to 65 atomic%, preferably 45 to 62 atomic%, more preferably about 47 to 59 atomic%. When the amount of oxygen is large, stability is improved and recording characteristics are improved, but sensitivity is deteriorated. If the amount of oxygen is small, the sensitivity is good, but reliability such as storage stability deteriorates.
The ratio of Bi is particularly preferably in the range of 20 to 38 atomic%. Regarding the amount of Bi, since Bi and Bi oxide are responsible for recording, when Bi is decreased, it becomes difficult to form a recording mark, and the recording characteristics are deteriorated. Further, when Bi is increased, the sensitivity is improved, but reliability such as storage characteristics is deteriorated.
As described below, the proportion of C (carbon) is an 1.5 to 49 atomic%.
Thus the main component Bi and oxygen (substantially the Bi oxides), by including a small amount of carbon-containing, obtained optical recording medium of the preferred characteristics.

According to the recording principle of the present invention, it is considered that the Bi oxide Bi and oxygen are separated by laser light irradiation, and the optical characteristics are changed due to the precipitation of Bi. by including a carbon-containing, change in oxygen binding state can be controlled and the absorption rate of light change, it is possible to improve the sensitivity. In addition, since the melting point also changes, it is possible to improve the sensitivity.
Carbon is contained in the recording layer in the form of simple carbon or a compound, or a mixture thereof. As a method for inclusion in the recording layer, carbon can be introduced into the recording layer by mixing it in the target as carbon simple substance or carbide and forming a film using the target. It is also possible to introduce carbon into the recording film by mixing a gas containing carbon such as CO ₂ and CH ₄ with Ar gas and performing film formation by sputtering. Further, the recording layer may contain carbon as an organic compound.

In the present invention 2, the recording layer further comprises B, Li, Sn, Ge, Sr, Mg, Ba, Ca, Mo, W, Co, Si, In, Ti, Mn, Ga, Zr, Cr, Hf, K, Na. Zn, Ni, Cu, Pd, Ag, P, Ta, Y, Nb, Al, V, Sb, Te, and at least one element X selected from La series elements.
When these elements are contained in an amount of about 1.5 to 18 atomic%, the effect is great. Less Bi nitride is preferable, and it is more preferable that Bi nitride is almost undetectable.
A preferred form of the recording layer, Bi oxide, X oxide or Ranaru form, Bi oxide, X oxide, in the form of an X carbide.
Although the principle is not clear, since the oxidation state of the element is greatly related to the recording, it is considered to have a great relationship with the ease of oxide formation.

When the generation enthalpy indicating the ease of oxide generation is equivalent to Bi, the oxide easily releases oxygen and becomes a single element, so that the light absorption rate is improved. In addition, since the melting point changes, the sensitivity can be improved. Ge, Sn, Li, and the like are elements corresponding to this.
In addition, elements such as B, Li, Na, Mg, K, Ca, and P have the property of being easily vitrified by coexisting with bismuth oxide. The mechanism is not clear, but easiness of vitrification may be related to improved sensitivity.
In the case of elements that are relatively difficult to oxidize, such as Cu, Ag, and Pd, the oxygen itself is not so much oxidized, so that oxygen is easily taken away from Bi oxide, and the probability that Bi exists as a single metal. Becomes higher. As a result, it is considered that sensitivity is improved by the presence of elements such as Bi and Cu, Ag, and Pd as a single metal.
Since an element of La series is more easily oxidized than Bi, Bi is likely to exist as a single metal and is considered to contribute to an improvement in sensitivity.
In addition, it is possible to create an excessive state of oxygen in the film by a film forming method such as sputtering, but in this case, oxygen exists in the film in an unstable form such as entering between the lattices. Can be considered. Even in this case, the sensitivity can be improved by adding the element X, and the effect is great.

  In the third invention, the recording layer is made of Bi, B, O, and C. The preferable ratio of each element is the same as that in the case of the second aspect of the present invention. Since the carbide absorbs a large amount of light, the presence of the carbide in the recording layer makes it easier to absorb the recording light, and the sensitivity is further improved. Further, by adding B, the phenomenon that Bi is combined with oxygen or oxygen is released by recording occurs more reliably. A preferable form of the recording layer is a form composed of three kinds of compounds of Bi oxide, B oxide, and B carbide.

The following effects (1) to (3) can be considered as the effect of adding carbon.
(1) Low jitter can be realized and recording characteristics are improved. (2) Sensitivity is improved. (3) Reliability such as storage stability and reproduction light stability is improved.
It is considered that the role of carbon that brings about these effects is that the crystal phase in the recording mark is easily miniaturized, light absorption is increased, and the stability of the recording film is improved.
In the recording layer, it is considered that when bismuth oxide is phase-separated into Bi and bismuth oxide by recording, Bi and bismuth oxide are refined without agglomeration. That is, it is considered that the addition of carbon causes the crystal in the recording mark to be refined and exhibits good recording characteristics. In addition, since carbon absorbs light greatly, the light absorption of the recording layer increases, and the recording sensitivity is improved. In addition, the crystal structure of the recording mark portion is prevented from changing due to humidity, heat, and light, and reliability such as storage stability and reproduction light stability is improved.

If the amount of carbon contained is small, the above-mentioned effects cannot be obtained, and large Bi crystals may be precipitated in the recording mark, and good recording characteristics may not be obtained. If the sensitivity is poor or a large crystal is generated in the recording mark, the influence of the crystal being altered becomes large, and the reliability is likely to be lowered.
Conversely, if there is too much carbon, there will be more carbon in the recorded mark, and bismuth oxide causing contrast between the recorded and unrecorded areas will be relatively less, making it difficult to obtain contrast and recording characteristics. to degrade. In addition, light is easily absorbed, and unrecorded portions are easily changed, so that storage stability and reproduction light stability are deteriorated. In addition, carbon is agglomerated when a sputtering target is produced, and it is difficult to obtain a uniformly dispersed material, so that a black spot-like material with agglomerated carbon can be seen. With such a sputtering target, it is difficult to improve the packing density and strength, and it becomes difficult to stabilize the composition of the recording layer formed using this target.
From these viewpoints, the preferable range of the carbon content is about 1.5 to 49 atomic% of the entire recording layer.

As an example, except for using a composite target composed of Bi ₂ O ₃ and C (carbon) and changing the amount of C (atomic% relative to the entire recording layer) as shown in Table 1 to form a recording layer, A write-once type optical recording medium was prepared in the same manner as in Example 2 described later, and the reproduction light stability was examined.
The results are shown in Table 1. The reproduction light stability was evaluated in the same manner as in Example 2 by applying high-frequency superimposition at a reproduction light power of 0.6 mW and reproducing one million times, and then reducing the jitter value. The case of 20% or more was designated as “Δ”, and the case of less than 20% was designated as “◯”.
As can be seen from Table 1, when the amount of carbon is small, the stability of the recording mark portion is poor, and the stability of the recording layer by the reproduction light is deteriorated. Moreover, when there is too much carbon, the stability of an unrecorded part will be bad and reproduction light stability will deteriorate.
Further, in order to examine the density of the sputtering target, three pieces were produced under the same conditions, and the case where the average of the target filling density was 90% or more was designated as “◯”, and the case where it was less than 90% was designated as “Δ”. The results are shown in Table 1. If it is less than 90%, the target strength is relatively weak.

As another example, an implementation described later is performed except that the recording layer is formed using a composite target in which C (carbon) is added to a mixture of Bi ₂ O ₃ and B ₂ O _{3 in} a molar ratio of 8: 1. A write-once type optical recording medium was prepared in the same manner as in Example 1. Carbon was added while being changed so that the C amount shown in Table 2 (atomic% with respect to the entire recording layer) was obtained.
For these recordable optical recording media, the optimum recording power was examined in the same manner as in Example 1. The optimum recording power was examined before and after a storage test of 500 hours in an environment of a temperature of 80 ° C. and a humidity of 85%.
The results are shown in Table 2. The evaluation criteria were “◯” when the value obtained by dividing the optimum recording power by the upper limit recording power of the standard value from 1 was 0.1 or more, and “△” when the value was less than 0.1. . A value smaller than 0.1 indicates that the sensitivity is relatively poor.

  The film thickness of the recording layer is preferably set in the range of 5 to 30 nm, more preferably 5 to 20 nm. When the film thickness is less than 5 nm, it is difficult to ensure sufficient recording sensitivity even if the recording layer has an improved light absorption function at the recording / reproducing wavelength, and the film thickness exceeds 30 nm. Then, the reflectance as a write-once type optical recording medium is abruptly lowered, and the recording / reproducing characteristics are deteriorated.

The present invention 4 has an upper protective layer and / or a lower protective layer adjacent to the recording layer.
In the fifth aspect of the present invention, the protective layer is made of any of sulfide, oxide, nitride, carbide, or a composite thereof.
According to the sixth aspect of the present invention, at least one of the upper protective layer and the lower protective layer contains sulfide.
In the present invention 7 , at least one of the upper protective layer and the lower protective layer is made of ZnS · SiO ₂ .
It is preferable to provide an upper protective layer and a lower protective layer above and below the recording layer. These protective layers have a function of suppressing deformation and destruction of the recording layer and accepting melting, composition change, and diffusion of the recording layer. In addition, these protective layers are usually preferably transparent to the recording / reproducing wavelength in order to increase the reflectivity. However, in order to adjust the recording sensitivity, a certain degree of light absorption function to the recording / reproducing wavelength is provided. Is also possible. By providing such a protective layer, the contribution of deformation in the recording mark can be made much smaller than in the past, and it is possible to prevent the increase in the contribution of deformation due to the increase in recording power in high linear velocity recording. This is effective in improving the high linear velocity recording characteristics. It is also effective in improving storage stability.

The protective layer material is preferably sulfide. Although the reason is not clear, it is considered that the recording sensitivity is improved because mixing and reacting or interdiffusion of the sulfide and the recording layer material facilitates and improves the formation of recording marks and further increases the speed. Further, since many sulfides are relatively soft, it is considered that stress due to deformation of the recording layer that occurs during recording is easily relieved.
Specific examples include ZnS, CaS, SrS, BiS, GeS, or a mixture thereof, but oxides, nitrides, and the like may be further mixed.
In particular, from the viewpoint of transparency to recording / reproducing light and productivity, a material mainly composed of ZnS · SiO ₂ can be cited as a preferred example. In order to obtain a sufficient heat insulating effect, it is preferable that SiO ₂ , ZrO ₂ , Ta ₂ O ₅ , and SnO ₂ are the main components.

In addition, a relatively hard and low-reactivity material such as oxide, nitride, and carbide can be used as the protective layer material, and after the recording mark is formed, its deformation and composition change are less likely to occur. It is preferable because the heat of the layer does not cause decomposition, sublimation, cavitation or the like.
Specific examples include Al ₂ O ₃ , MgO, ZrO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , SiO ₂ , Y ₂ O ₃ , CeO ₂ , ZnO, TiO ₂ and In ₂ O ₃ . oxides of simple oxide, or composite oxide of these _{oxides; 2MgO · SiO 2, MgO ·} SiO 2, CaO · SiO 2, ZrO 2 · SiO 2, 3Al 2 O 3 · 2SiO 2, 2MgO · 2Al _{2 O 3 · 5SiO 2, Li} 2 O · Al 2 O 3 · 4SiO oxide silicate such as _2; silicon nitride, aluminum nitride, BN, nitride material such as TiN; _{SiC, B} 4 C, Carbide-based materials such as TiC, WC, and amorphous carbon; and composite compounds such as SiON, AlON, SiAlON, TiOC, and SiOC.
In addition to the above, fluorides such as MgF ₂ and CaF ₂ can be used, and borides and the like can also be used by taking advantage of the hardness and the high thermal conductivity.

Furthermore, it is also possible to use organic materials, such as a pigment | dye and resin, as a protective layer material.
The dyes include polymethine, naphthalocyanine, phthalocyanine, squarylium, croconium, pyrylium, naphthoquinone, anthraquinone (indanthrene), xanthene, triphenylmethane, azulene, tetrahydrocholine, phenanthrene , Triphenothiazine, azo, and formazan dyes, and metal complex compounds thereof.
As the resin, polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin, and the like can be used alone or in combination of two or more. It can be used by mixing.
The organic material layer can be formed by ordinary means such as vapor deposition, sputtering, CVD, and coating. When using an application method, the above organic material or the like may be dissolved in an organic solvent and applied by a conventional coating method such as spraying, roller coating, dipping, or spin coating.

  Examples of the organic solvent used in the coating method include alcohols such as methanol, ethanol and isopropanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylacetamide and N, N-dimethylformamide; dimethyl sulfoxide and the like Sulphoxides; ethers such as tetrahydrofuran, dioxane, diethyl ether, and ethylene glycol monomethyl ether; esters such as methyl acetate and ethyl acetate; aliphatic halogenated carbons such as chloroform, methylene chloride, dichloroethane, carbon tetrachloride, and trichloroethane Aromatics such as benzene, xylene, monochlorobenzene and dichlorobenzene; cellosolves such as methoxyethanol and ethoxyethanol; hexane, pentane and sucrose Hexane, and hydrocarbons such as methylcyclohexane.

The upper protective layer is a layer provided between the recording layer and the reflective layer, and mainly has a function of controlling the recording sensitivity and the reflective layer. If the thickness of the upper protective layer becomes too thin, the heat generated in the recording layer is dissipated more than necessary, so that the thickness is preferably set to 10 nm or more. Further, when the thickness of the upper protective layer is increased, the heat generated in the recording layer is difficult to be dissipated, and thermal interference between the recording marks is increased. Therefore, the thickness is preferably set to 100 nm or less.
The lower protective layer is provided to ensure the storage reliability of the recording layer. That is, the lower protective layer functions to protect the recording layer from oxygen, moisture, and other gases that pass through the substrate and the cover layer. Therefore, in order to sufficiently protect the recording layer, the film thickness is preferably 10 nm or more. However, it is preferable to set the film thickness to 100 nm or less from the viewpoint of productivity.

The present invention 8 has a layer structure in which at least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially laminated on a substrate. Thereby, it is possible to realize an optical recording medium conforming to the HD DVD-R standard, which has good sensitivity and can perform high linear velocity recording.
When a high NA lens is used to increase the density, at least a reflective layer, an upper protective layer, a recording layer, a lower protective layer, and a cover layer are sequentially stacked on the substrate as in the present invention 9. Layer structure. Thereby, it is possible to realize an optical recording medium conforming to the BD-R standard with good sensitivity and capable of high linear velocity recording.
In the above layer configuration, the upper protective layer and the lower protective layer may be made of the same material or different materials, and each protective layer may have a laminated configuration including two or more layers.
For example, the upper protective layer has a two-layer structure, a material containing sulfide is used for the layer adjacent to the recording layer, and a layer not containing sulfide is used for the layer adjacent to the reflective layer. From the viewpoint of
The write-once type optical recording medium of the present invention can be recorded and reproduced by laser light in the blue wavelength region (350 to 500 nm), but laser light with a wavelength of 450 nm or less is preferred. Note that recording and reproduction are possible even with a laser beam having a wavelength region exceeding 500 nm.

The material of the substrate and the cover layer has special thermal and mechanical characteristics, and if the recording / reproduction is performed from the substrate side (through the substrate), the material is specially limited as long as it has excellent light transmission characteristics. There is no.
Specific examples include polycarbonate, polymethyl methacrylate, amorphous polyolefin, cellulose acetate, polyethylene terephthalate and the like, and polycarbonate and amorphous polyolefin are preferred.
The thickness of the substrate varies depending on the application and is not particularly limited.
When using a lens with a high NA in order to increase the density, it is necessary to reduce the thickness of the portion through which the reproduction light is transmitted. This is due to the angle at which the disk surface deviates from the optical axis of the optical pickup as the NA increases (so-called tilt angle, proportional to the square of the product of the reciprocal of the wavelength of the light source and the numerical aperture of the objective lens). This is because an allowable amount of generated aberration is reduced, and this tilt angle is easily affected by the aberration due to the thickness of the substrate. Therefore, by providing a cover layer that is thinner than a normal substrate and performing recording and reproduction from the cover layer side, the influence of aberration on the tilt angle is made as small as possible. Thereby, it is possible to achieve a high recording density exceeding the BD-R standard.
Furthermore, when recording using near-field light, a thin layer of about several nm to several tens of nm is used as the cover layer. When this layer has a high refractive index, light does not spread and reaches the recording layer with a small spot, which is preferable for high-density recording. Moreover, since it becomes thin, it is preferable to use a material that is hard, wear-resistant, and has good sliding characteristics, and preferred examples include silicon nitride and diamond-like carbon.

For the reflective layer, for example, metals such as Al, Al—Ti, Al—In, Al—Nb, Au, Ag, and Cu, metalloids, and alloys thereof can be used. These substances may be used alone or in combination of two or more. From the viewpoint of thermal conductivity and reflectance, it is preferable to use a single metal such as Ag, Cu, Al or an alloy thereof.
Examples of the method for forming the reflective layer using these materials include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
When the reflective layer is formed of an alloy, it can be formed by a sputtering method using the alloy as a target material. In addition, a chip-on-target method (for example, forming a Cu chip on an Ag target), It can also be created by sputtering (for example, using an Ag target and a Cu target).
It is also possible to use a material other than metal by alternately stacking a low refractive index layer and a high refractive index layer to form a multilayer film and use it as a reflective layer.

The thickness of the reflective layer is preferably in the range of 20 to 200 nm, particularly preferably in the range of 30 to 160 nm. However, when the reflective layer of the present invention is applied to a multilayer optical recording medium, the lower limit of the reflective layer thickness is not limited to this. When the film thickness is less than 20 nm, there may be a problem that a desired reflectance cannot be obtained, a problem that the reflectance decreases during storage, and a problem that the recording amplitude cannot be sufficiently obtained. When the film thickness is greater than 200 nm, the film formation surface may be rough, and the reflectance may decrease. Further, it is not preferable from the viewpoint of productivity.
Further, when the reflective layer contains Ag and a material containing S is used for the protective layer, it is necessary to provide an antisulfurization layer for preventing the reaction between Ag and S between the reflective layer and the protective layer. As the material, oxides, nitrides, carbides and the like having low light absorption are preferable. Examples thereof include nitrides mainly composed of SiN, oxides such as TiO _2, and carbides such as SiC.
The film thickness of the sulfidation preventing layer is preferably about 2 to 7 nm. If it is thinner than 2 nm, there is no prevention effect due to the non-uniformity of the film, and if it is thicker than 7 nm, the reflectance and recording sensitivity are lowered.

It is preferable to form a thick environmental protection layer on the reflective layer. The material is not particularly limited as long as the reflective layer is protected from external force. Examples of the organic material include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the inorganic _{materials, SiO 2, Si 3 N 4} , MgF 2, SnO 2 and the like.
As a method for forming the environmental protection layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used. Of these, the spin coating method is preferable.
When a thermoplastic resin or a thermosetting resin is used, it is usually dissolved in an appropriate solvent, applied and dried to form a layer.
When an ultraviolet curable resin is used, the layer is usually formed by coating as it is or after dissolving in an appropriate solvent and curing by irradiation with ultraviolet rays.
As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used.
These materials may be used alone or in combination, and may be used as a multilayer film instead of a single layer.
The thickness of the environmental protection layer is generally in the range of 0.1 to 100 μm, but in the present invention, 3 to 30 μm is preferable.

The sputtering target of the present invention 10 contains Bi (bismuth) and O (oxygen) as main components, further contains C (carbon ) , and does not contain Fe.
Here, the main component means that the combined content (atomic%) of Bi and oxygen is the largest. In addition, the expression “containing Bi and oxygen” is because Bi oxide is the most common, but metal Bi may be included in addition to Bi oxide.
The reason why Fe is not contained is that a sputtering target containing Fe has a relatively low strength and may be broken during film formation. The reason is that Fe, which is relatively easily oxidized, easily forms oxides such as Fe ₂ O _3, but the thermal expansion coefficient of these oxides is relatively large (10 ⁻⁶ / ° C.). It is thought that.
On the other hand, carbon, thermal expansion coefficient of the Si C are, respectively, ^{1.5 × 10 -6 /℃,4.3×10 -6 / ℃} , those containing-carbon has a thermal expansion coefficient relatively small The durability against temperature changes during film formation is considered high.
Indeed, Bi-B-C-O target used in Example 4, but does not cause damage to the target during film, similar Bi-B-Fe-O target prepared by sintering conditions are the same The target may be damaged under the film formation conditions, and it is necessary to perform film formation by reducing the applied power during film formation from 1.2 kW to 0.8 kW. Thus, when Fe is included, productivity is adversely affected.

The proportion of oxygen in the sputtering target is about 30 to 65 atomic%, preferably 45 to 62 atomic%, more preferably about 47 to 59 atomic%. When the amount of oxygen is large, the composition of the recording layer formed is relatively stable and the recording characteristics are improved, but the recording sensitivity is deteriorated. If the amount of oxygen is small, an optical recording medium with good recording sensitivity can be produced, but the target strength tends to be relatively weak.
The ratio of Bi is particularly preferably in the range of 20 to 38 atomic%. Regarding the amount of Bi, since Bi and Bi oxide are responsible for recording, when Bi is decreased, it becomes difficult to form a recording mark, and the recording characteristics are deteriorated. Further, when Bi is increased, the sensitivity is improved, but reliability such as storage characteristics is deteriorated.
The proportion of C (carbon) is an 1.5 to 49 atomic%.
Thus the main component Bi and oxygen (substantially the Bi oxides), by including a small amount of carbon-containing, obtained optical recording medium of the preferred characteristics.
Carbon is contained in the sputtering target in the form of simple carbon or a compound, or a mixture thereof. By containing the carbide, the stability when the target is sintered is increased, and the productivity of the sputtering target is improved.

The sputtering target of the present invention further includes B, Li, Sn, Ge, Sr, Mg, Ba, Ca, Mo, W, Co, Si, In, Ti, Mn, Ga, Zr, Cr, Hf, K, Na, At least one element X selected from Zn, Ni, Cu, Pd, Ag, P, Ta, Y, Nb, Al, V, Sb, Te, and La series elements may be contained.
The effect is large when these elements X are contained in an amount of about 1.5 to 18 atomic%. Bi carbides are unstable, often less to the extent that can not be detected almost decomposed during sintering. In order to improve the target strength, the smaller one is preferable, and the smaller one is more preferable to the extent that almost no detection is possible. The preferred form, Bi oxide, X oxide or Ranaru form, Bi oxide, X oxide, form consisting of X carbide, Bi oxide, a form consisting of X carbide.
Although not clear such principles, carbide comprises sintering aid, often used as an additive for improving the strength, it is considered largely related to the target strength.
In particular, B, Si, Ti, Nb, etc. are highly effective in improving the target strength.

When the generation enthalpy indicating the ease of oxide generation is equivalent to Bi, the oxide easily releases oxygen and becomes a single element, so that the light absorption rate is improved. In addition, since the melting point changes, the sensitivity can be improved. Ge, Sn, Li, and the like are elements corresponding to this.
In addition, elements such as B, Li, Na, Mg, K, Ca, and P have the property of being easily vitrified by coexisting with bismuth oxide. The mechanism is not clear, but easiness of vitrification may be related to improved sensitivity.
In the case of elements that are relatively difficult to oxidize, such as Cu, Ag, and Pd, oxygen itself is not so much oxidized, so that oxygen is easily taken away from Bi oxide, and the probability that Bi exists as a single metal. Becomes higher. As a result, it is considered that sensitivity is improved by the presence of elements such as Bi and Cu, Ag, and Pd as a single metal.
Since an element of La series is more easily oxidized than Bi, Bi is likely to exist as a single metal and is considered to contribute to an improvement in sensitivity.

If the sputtering target of the present invention is Bi, B, consisting of O and C, for B 4 _C has a high stability, is contained in the state of B 4 _C improves target strength, a large effect. A recording layer formed using this target is more likely to absorb recording light due to the presence of carbides that absorb a large amount of light in the recording layer, and the sensitivity is further improved. Further, by adding B, the phenomenon that Bi is combined with oxygen or oxygen is released by recording occurs more reliably. Moreover, the preferable form of a target is a form which consists of three types of compounds, Bi oxide, B oxide, and B carbide.

  In the sputtering target of the present invention, the C content is 1.5 to 49 atomic% of the whole. When C is more than 1.5%, the formed recording layer is effective in improving sensitivity because carbon absorbs light. On the other hand, when the carbon content exceeds 49%, the proportion of bismuth oxide involved in recording decreases, and it becomes difficult to obtain contrast between the recorded portion and the unrecorded portion, and the recording characteristics deteriorate. Further, when the amount of carbon is excessive, it becomes difficult to produce a target, and it is difficult to improve the packing density of the target, so that it is impossible to realize a target with high productivity and high strength.

In the sputtering target of the present invention , particularly when carbon or carbide is contained, the resistivity is reduced, so that direct current sputtering is possible. Since DC sputtering is possible, the film forming cost is reduced, which is preferable.
The sputtering target of the present invention preferably has a filling density (relative density) of 90% or more. When the packing density is up to about 95%, the film forming speed and the strength of the target are improved as the packing density is improved. However, when it is about 95% or more, the strength of the target gradually decreases. Here, the packing density refers to the ratio (%) of the actually measured density to the theoretical density when the mixed raw materials are mixed at a predetermined ratio.
The sputtering target of the present invention can be produced by mixing and sintering bismuth oxide powder and carbon powder.
Also, bismuth oxide powder and powder of carbide of at least one element selected from Al, B, Ca, Cr, Hf, Mo, Nb, Si, Ta, Ti, V, W, and Zr are mixed. When sintered , carbon can be mixed with good stability. Further, since carbon has high conductivity but high reducibility, Bi oxide may be reduced during sintering. However, by mixing stable carbide, production with good reproducibility becomes possible.

Further , by sintering in a state where oxygen is blocked, in an inert atmosphere, or in vacuum, it is possible to prevent carbon from being released and escaping from the target. A sintering method such as a hot press method is effective because the mold for molding the target is made of carbon, so that the carbon is in an equilibrium state and is difficult to escape.
Further , it is effective to form a film by mixing a gas containing carbon such as hydrocarbon with Ar using a sputtering target containing Bi, B, and O. If a target containing no oxygen is used, a recording layer containing Bi and oxygen as main components cannot be obtained. In addition, when film formation is performed using a gas mixed with oxygen to supplement oxygen, the mixed hydrocarbon is oxidized to carbon dioxide and water, so that oxygen cannot be mixed.

According to the present invention, recording can be reproduced by a laser beam in the blue wavelength region (350 to 500 nm), high sensitivity and optical recording media which are suitable to record a wide linear velocity range of from a low linear velocity to a high linear velocity , and it can provide a sputtering coater rodents bets for film recording layer of the optical recording medium.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples. Further, as an example, an example using a laser beam having a wavelength of 405 nm was shown, but the recording layer of the present invention has a normal refractive index in the range of 350 to 500 nm, and a rapid change in the complex refractive index. Therefore, recording and reproduction can be performed in the same manner. That is, when the recording / reproducing wavelength changes in the range of 350 to 500 nm, the reflectivity and recording sensitivity as a write-once type optical recording medium change, but the recording principle does not change, and the same recording / reproducing is possible. .

Example 1
On a polycarbonate substrate (product name ST3000, manufactured by Teijin Bayer Polytech Co., Ltd.) having a thickness of 1.1 mm and a diameter of 120 mm having guide grooves (groove depth 21 nm, average groove width 155 nm, track pitch 0.32 μm), by sputtering, 60 nm thick AgBi alloy (Bi: 0.5 atomic%) layer, 4 nm thick SiN film, 15 nm thick ZnS · SiO ₂ (80:20 mol%) layer, 16 nm thick Bi—B—C -O layer and a 75 nm thick ZnS.SiO ₂ (80:20 mol%) layer are provided in this order, and further a 75 μm thick polycarbonate sheet (Teijin Kasei Co., Ltd.) using an ultraviolet curable resin (Nippon Kayaku DVD003). Pure Ace) was bonded to form a cover layer (light transmission layer), and a write-once type optical recording medium having a thickness of about 1.2 mm was produced.
The Bi—B—C—O layer was formed using a composite target of Bi ₂ O ₃ —B ₂ O ₃ —C (molar ratio, 8: 1: 1). Sputtering was performed in Ar gas.
Recording was performed on the write-once optical recording medium using an optical disk evaluation apparatus ODU-1000 (wavelength: 405 nm, NA: 0.85) manufactured by Pulse Tech Industry Co., Ltd.
When recording was performed at a linear velocity of 1 × (1 × speed) in accordance with the standard of a write-once Blu-ray disc (BD-R Version 1.1), a jitter value of 4.4% was obtained at an optimum recording power of 4.3 mW.
Similarly, recording was performed at 4x (linear velocity 4 times that of 1x) without changing the recording density, and the jitter value was evaluated. As a result, a jitter value of 5.5% was obtained at an optimum recording power of 6.7 mW.
These values are higher in sensitivity and lower in jitter than the write-once optical recording media of Comparative Examples 1 and 2 described later.

Example 2
The Bi-B-C-O layer was changed to a Bi-C-O layer, and the composite target for film formation was Bi ₂ O ₃ -C (molar ratio, 1: 1). A write-once optical recording medium was prepared in the same manner.
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 5.0% was obtained at an optimum recording power of 4.0 mW.
When recording was performed at a linear velocity of 4x in the same manner as in Example 1, a jitter value of 5.8% was obtained with an optimum recording power of 5.3 mW.
These values are higher in sensitivity and lower in jitter than the write-once optical recording media of Comparative Examples 1 and 2 described later.

Comparative Example 1
A write-once optical recording medium was prepared in the same manner as in Example 1 except that the Bi-B-C-O layer was changed to a Bi-O layer and the composite target for film formation was Bi ₂ O ₃ .
When this write-once type optical recording medium was recorded at linear speeds of 1x and 4x in the same manner as in Example 1, optimum conditions could not be obtained even if the recording power was changed, and the jitter value was high. Until now, low jitter values have not been obtained.

Comparative Example 2
Changing the Bi-B-C-O layer Bi-B-O layer, the film composite _{target, Bi 2 O 3 -B 2 O} 3 ( molar ratio 6: 4) except a to point, carried A write-once type optical recording medium was prepared in the same manner as in Example 1.
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 5.2% was obtained at an optimum recording power of 4.7 mW.
When recording was performed at a linear velocity of 4x in the same manner as in Example 1, a jitter value of 6.7% was obtained with an optimum recording power of 9.8 mW.

Example 3
On a polycarbonate substrate having a thickness of 0.6 mm having guide grooves (groove depth 26 nm, average groove width 200 nm, track pitch 0.4 μm), a ZnS · SiO ₂ layer (80: 80 nm) is formed by sputtering. 20 mol%), a 15 nm thick Bi—B—C—O layer, a 20 nm thick ZnS · SiO ₂ layer (80:20 mol%), an 80 nm thick AgBi alloy layer (Bi: 0.5 atomic%) ) Were sequentially laminated. The Bi—B—C—O layer was formed using a composite target of Bi ₂ O ₃ —B ₂ O ₃ —C (molar ratio, 8: 1: 1). Sputtering was performed in Ar gas.
Next, on the AgBi alloy layer, an organic protective layer having a thickness of about 5 μm made of an ultraviolet curable resin (manufactured by San Nopco Co., Ltd .: Nopco Cure 134) is provided by spin coating, and a dummy substrate having a thickness of 0.6 mm is formed thereon. Were pasted together with an ultraviolet curable resin to obtain a write-once type optical recording medium.
For this write-once optical recording medium, an optical disc evaluation apparatus ODU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. was used, and the HD DVD-R standard [DVD Specifications for High Density Recordable Disc (HD DVD-R) Version 1.0] was recorded at a linear density of 1 × (1 × speed) at a recording density.
As a result, the PRSNR value was 29.1 at the optimum recording power of 7.6 mW.
Further, when recording was performed with the recording linear velocity being 4 × (4 × speed) without changing the recording density, the PRSNR value was 20.4 at the optimum recording power of 13.4 mW.

Comparative Example 3
Changing the Bi-B-C-O layer Bi-B-O layer, the film composite _{target, Bi 2 O 3 -B 2 O} 3 ( molar ratio 6: 4) except a to point, carried A write-once optical recording medium was prepared in the same manner as in Example 3 .
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 3 , the PRSNR value was 24 at an optimum recording power of 8.8 mW.
Further, in the same manner as in Example 3 , recording was performed with the linear velocity at the time of recording being 4 × (4 × speed), and the PRSNR value was 19.8 at the optimum recording power of 17.6 mW.

Example 4
Bi ₂ O ₃ , B ₂ O ₃ and B ₄ C powder were weighed and mixed so that the molar ratio would be 76.4: 11.8: 11.8 in a state where there was no moisture adsorption, Further, after dry mixing with a ball mill for 1 hour, it was fired at 500 ° C. for 1 hour.
Thereafter, the mixture was dry-mixed with a ball mill for 1 hour, the mixed powder was pressure-molded at 150 MPa, and hot-press fired at 650 ° C. for 5 hours in the atmosphere to prepare a sputtering target. The size of the target was 200 mm in diameter and 6 mm in thickness.
This target was bonded to a backing plate made of oxygen-free copper by low melting point metal bonding to obtain a sputtering target. The packing density of this target was 84%.

Example 5
Bi ₂ O ₃ and SiC powder were weighed without moisture adsorption, mixed so that Bi ₂ O ₃ and SiC were in a molar ratio of 2: 1, and then dry-mixed for 1 hour in a ball mill. Baked at 700 ° C. for 1 hour.
Thereafter, the mixture was dry-mixed for 1 hour with a ball mill, the mixed powder was pressure-molded at 150 MPa, and hot-press fired at 750 ° C. for 5 hours in the air to prepare a sputtering target. The size of the target was 200 mm in diameter and 6 mm in thickness.
This target was bonded to a backing plate made of oxygen-free copper by low melting point metal bonding to obtain a sputtering target. The packing density of this target was 97%.

Example 6
Bi ₂ O ₃ and TiC powder were weighed without moisture adsorption, mixed so that Bi ₂ O ₃ and TiC had a molar ratio of 2: 1, and then dry-mixed for 1 hour in a ball mill. Baked at 700 ° C. for 1 hour.
Thereafter, the mixture was dry-mixed for 1 hour with a ball mill, the mixed powder was pressure-molded at 150 MPa, and hot-press fired at 750 ° C. for 5 hours in the air to prepare a sputtering target. The size of the target was 200 mm in diameter and 6 mm in thickness.
This target was bonded to a backing plate made of oxygen-free copper by low melting point metal bonding to obtain a sputtering target. The packing density of this target was 94%.

Example 7
Bi ₂ O ₃ and NbC powder were weighed without moisture adsorption, mixed so that Bi ₂ O ₃ and NbC had a molar ratio of 2: 1, and then dry-mixed for 1 hour in a ball mill. Baked at 700 ° C. for 1 hour.
Thereafter, the mixture was dry-mixed for 1 hour with a ball mill, the mixed powder was pressure-molded at 150 MPa, and hot-press fired at 750 ° C. for 5 hours in the air to prepare a sputtering target. The size of the target was 200 mm in diameter and 6 mm in thickness.
This target was bonded to a backing plate made of oxygen-free copper by low melting point metal bonding to obtain a sputtering target. The packing density of this target was 86%.

Example 8
Write-once type optical recording medium of the present invention having a thickness of about 1.2 mm in the same manner as in Example 1 except that the Bi—B—C—O layer was formed using the sputtering target prepared in Example 4. It was created.
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 4.2% was obtained at an optimum recording power of 4.5 mW.
Further, recording was performed at a linear velocity of 4x in the same manner as in Example 1, and the jitter value was evaluated. As a result, a jitter value of 5.3% was obtained at an optimum recording power of 7.1 mW.

Example 9
A write-once optical recording medium was produced in the same manner as in Example 1 except that a Bi—Si—C—O layer was formed using the sputtering target produced in Example 5 .
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 5.2% was obtained at an optimum recording power of 5.0 mW.
When recording was performed at a linear velocity of 4x in the same manner as in Example 1, a jitter value of 5.8% was obtained with an optimum recording power of 7.3 mW.

Example 10
A write-once optical recording medium was produced in the same manner as in Example 1 except that a Bi—Ti—C—O layer was formed using the sputtering target produced in Example 6 .
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 4.8% was obtained at an optimum recording power of 5.1 mW.
When recording was performed at a linear velocity of 4x in the same manner as in Example 1, a jitter value of 6.3% was obtained with an optimum recording power of 6.3 mW.

Example 11
A write-once type optical recording medium was produced in the same manner as in Example 1 except that a Bi—Nb—C—O layer was formed using the sputtering target produced in Example 7 .
When this write-once type optical recording medium was recorded at a linear velocity of 1x in the same manner as in Example 1, a jitter value of 4.5% was obtained at an optimum recording power of 4.1 mW.
Further, when recording was performed at a linear velocity of 4x in the same manner as in Example 1, a jitter value of 6.4% was obtained at an optimum recording power of 5.9 mW.

Example 12
Composition, the Bi-C-O, Bi- B-C-O, B i-Si-C-O, Bi-B-Fe-O ( control), with each sputtering target, a film in an Ar gas The recorded recording layers were compared for variations in light absorption. The wavelength of light was 405 nm, and the measured sample was a recording layer of 13 nm on a polycarbonate substrate without grooves and a ZnSSiO ₂ film formed thereon to 20 nm. Film formation was performed under the same conditions except that the time from when the film was placed in the vacuum chamber for film formation to when the recording layer was formed was randomly selected from 0 to 60 seconds. And 10 types of samples of experiment numbers 1-10 were produced for each target.
Light was incident from the surface side of the film, and the light absorption rate was measured with a photometer. Furthermore, in order to investigate the variation in the absorption rate, the absorption rate measured at each of a plurality of dates was normalized with the lowest absorption rate, and each variation was examined. Absorbance variation (%) was determined by the following equation.
Variation (%) = {(obtained absorption rate) − (smallest absorption rate)} × 100 / (most
Small absorption rate)
The result is shown in FIG. 1, the one with a large variation number indicates that the variation in the absorptance is large. There is a difference between the sample containing Fe and the sample not containing Fe, and the sample containing no Fe is more It can be seen that the variation is small.
Incidentally, those Bi-B-C-O target used in Example 4, B i-Si-C -O target are those used in Example 5, Bi-C-O target and Bi-B- The Fe—O target was prepared as follows.
<Bi-C-O target>
Bi ₂ O ₃ and C (carbon) powder were weighed and mixed so that the molar ratio was 1: 1 in a state where there was no moisture adsorption, and further dry-mixed with a ball mill for 1 hour, and then 750 Baked at 1 ° C. for 1 hour.
Thereafter, the mixture was dry-mixed for 1 hour with a ball mill, the mixed powder was pressure-molded at 150 MPa, and hot-press fired at 780 ° C. for 5 hours in the air to prepare a sputtering target. The size of the target was 200 mm in diameter and 6 mm in thickness. This target was bonded to a backing plate made of oxygen-free copper by low melting point metal bonding to obtain a sputtering target.
<Bi-B-Fe-O target>
A sputtering target was obtained in the same manner as in Example 4 except that powders of Bi ₂ O ₃ , B ₂ O ₃ and Fe ₂ O ₃ were used at a molar ratio of 65: 30: 5.

The figure which shows the evaluation result of Example 12 .

Claims (10)

On the substrate, there is a recording layer capable of recording / reproducing at least with a laser beam in a blue wavelength region, the recording layer containing Bi (bismuth) and O (oxygen) as main components, further containing C (carbon ) , Fe An optical recording medium characterized in that the C content is 1.5 to 49 atomic% of the entire recording layer .   The recording layer further comprises B, Li, Sn, Ge, Sr, Mg, Ba, Ca, Mo, W, Co, Si, In, Ti, Mn, Ga, Zr, Cr, Hf, K, Na, Zn, Ni 2. The optical recording medium according to claim 1, comprising at least one element X selected from the group consisting of Cu, Pd, Ag, P, Ta, Y, Nb, Al, V, Sb, Te, and La series elements. .   3. The optical recording medium according to claim 2, wherein the recording layer is made of Bi, B, O and C. The optical recording medium according to any one of claims 1 to 3, characterized in that an upper protective layer and / or the lower protective layer adjacent to the recording layer. 5. The optical recording medium according to claim 4 , wherein the upper protective layer and / or the lower protective layer is made of any one of sulfide, oxide, nitride, carbide, or a composite thereof. 6. The optical recording medium according to claim 5 , wherein at least one of the upper protective layer and the lower protective layer contains a sulfide. The optical recording medium according to claim 6, wherein at least one of the upper protective layer and the lower protective layer is characterized by comprising the ZnS · SiO _2. The optical recording medium according to claim 4 , wherein at least a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are sequentially laminated on the substrate. 8. The optical recording medium according to claim 4 , wherein at least a reflective layer, an upper protective layer, a recording layer, a lower protective layer, and a cover layer are sequentially laminated on the substrate. Sputtering characterized in that it contains Bi (bismuth) and O (oxygen) as main components, further contains C (carbon ) , does not contain Fe, and the C content is 1.5 to 49 atomic% of the whole. target.

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